Binding properties of sulfur to enable solvent-free fabrication of high-performance polymer-free sulfur-carbon positive electrodes

Domain: neuroscience
Published: 2026-02-04
Editorial outcome: minor_revision

Abstract
The development of a scalable, cost-effective and environmentally benign manufacturing of binder-free sulfur positive electrodes can make substantial advance for lithium-sulfur (Li||S) batteries as sustainable competitors to lithium-ion systems. Here we show a solvent- and binder-free method to fabricate sulfur-carbon composite electrodes directly on aluminum foil via thermal-assisted dry pressing. A key finding is the role of sulfur as a structural binder, where its softening, distribution, and adhesion properties enable the formation of mechanically robust electrodes without polymer binders. Systematic experimental characterizations and computational modeling reveal the underlying mechanisms governing electrodes formation and electrochemical performance. The developed binder-free positive electrodes achieve a reversible capacity of 932 mAh g⁻¹ after 500 cycles at 1.0 C rate; for comparison, conventional slurry-cast positive electrodes containing 10 wt.% binder deliver lower capacity under the same electrochemical test conditions. This scalable process has the potential to reduce fabrication costs by a factor of 2.1 while eliminating hazardous solvents and binders, offering a sustainable and cost-effective approach to advancing Li||S battery technology.

Introduction
The relentless pursuit of advanced energy storage systems stands at the forefront of modern scientific inquiry, driven by the urgent need for sustainable, efficient, and high-energy density solutions. Among the various contenders, lithium-sulfur (Li||S) batteries have gained significant attention due to their high theoretical specific energy (2600 Wh kg−1) and cost-effectiveness, primarily attributed to the abundance of sulfur, used as a positive electrode active material1,2. Despite the problematic issues associated with poor electronic conductivity of sulfur, soluble lithium polysulfide (Li-PS) intermediates such as Li-PS shuttling3 and repeated changes in the porous structure of sulfur positive electrodes4, diminishing cycling stability of Li||S batteries, significant progress in enhancing the performance of Li||S batteries accomplished by researchers have positioned Li||S batteries to be one of promising future energy storage options5–8.

Li||S batteries typically employ the conventional slurry casting method to fabricate a sulfur positive electrodes with the incorporation of polymer binders (about 10 wt.% in general)9. The slurry casting process requires a processing solvent, typically N-Methyl-2-Pyrrolidone (NMP) to dissolve the binder and disperse the solid constituents uniformly. However, the use of solvent introduces environmental challenges and increases production costs due to the energy-intensive solvent evaporation and vapor recovery process, thereby undermining the sustainability and economic viability of Li||S batteries10,11. Note that the electrode manufacturing process is the most energy-intensive part of battery manufacturing12, with the wet-slurry coating, drying, and NMP solvent recovery making up ~50% of total electrode manufacturing costs13,14. The drying step accounts for about 39% of energy consumption, releasing ~1000 kg CO2-equivalent emissions for every 10 kWh of batteries produced15,16. Eliminating the NMP recovery system could yield substantial benefits for battery manufacturing facilities, such as reducing capital costs by up to $6 million and saving 16.5% in areal footprint for a gigafactory producing GWh-level batteries17. As shown in Table S1, the estimated manufacturing cost of our dry process approach ($38.4 per kg of sulfur in the positive electrodes) is less than half the cost of a slurry-cast sulfur positive electrodes ($80.91 per kg of sulfur in the positive electrodes).

Although aqueous binders such as styrene–butadiene rubber-carboxymethylcellulose18 and polyacrylic acid19 can partially mitigate the environmental and economic impacts of electrode fabrication process, they introduce other challenges. For instance, aqueous binders often lead to electrode cracking during the slurry drying process20, and leave residual water in positive electrodes. This residual water is challenging to remove through vacuum drying at the elevated temperature (typically 120–150°C for conventional non-sulfur electrodes) due to low melting point of sulfur, which negatively impacts the performance of Li||S batteries20. Recent reviews have highlighted growing interest in dry-fabrication of sulfur positive electrodes for Li||S batteries as a means to improve manufacturing efficiency and interface control21–24. Moreover, although the role of binders is crucial in enhancing the mechanical durability of electrode films, binders increase the resistance in positive electrodes as they are generally electronic and ionic insulators25. Efforts to eliminate binders from sulfur positive electrodes have explored the use of three-dimensional porous carbon structure26–29 and metal foam30,31 as current collectors. However, prior binder-free strategies often rely on specialized or nonstandard current collectors that are incompatible with scalable manufacturing methods such as roll-to-roll coating, ultimately increasing production costs. In some cases, high-temperature melt-infiltration of sulfur into carbon substrates is also required29, adding to process complexity and material expenses. Moreover, these approaches typically involve rigid or pre-structured porous carbon architectures where precise control over bulk porosity is difficult to achieve. These limitations make it challenging to implement such methods in high-throughput, cost-sensitive manufacturing environments, thereby restricting their scalability.

Building on this background, our research introduces a polymer binder- and solvent-free method for fabricating sulfur-carbon (S-C) composite positive electrodes using a conventional aluminum (Al) foil current collector. In this approach, sulfur serves a dual function as both the active material and an inherent binder, eliminating the need for conventional binders. By removing binders and processing solvents, our process provides an environmentally friendly, cost-effective alternative for electrode fabrication. The method is based on dry powder formation on Al foil followed by roll-pressing, both of which are compatible with continuous processing and allow control over key processing parameters such as areal loading and electrode porosity, highlighting its potential for scalable and tunable manufacturing. We conducted a comprehensive analysis of the structural, compositional, and electrochemical properties of the binder-free S-C composite positive electrodes using advanced techniques such as X-ray imaging, and in situ optical microscopy (OM). Our findings reveal the mechanisms driving the improved electrochemical performance, including structural features of binder-free sulfur positive electrodes that boost electrochemical activity. This study demonstrates significantly enhanced electrochemical performance using inexpensive commercial porous carbon as a sulfur host in S-C composites, comparable to previous reports that relied on more expensive or complexly synthesized S-C composite active materials and conventional slurry-cast electrodes containing ~10 wt.% polymer binder. The binder-free S-C electrodes achieve a reversible capacity of 932 mAh g−1 after 500 cycles, which is among the higher values reported in Table S2. These insights pave the way for more sustainable manufacturing practices for high-performance Li||S batteries.

Results
Results and discussion
Thermally-assisted consolidation of elemental sulfur
Substituting sulfur for a polymer binder in binder-free sulfur electrodes requires sulfur particles to bind together effectively. Given a low melting temperature of sulfur (112–120°C)32, there is potential for partial sulfur powder sintering or densification to occur at relatively low temperatures, facilitating the direct lamination of the sulfur powder bed under controlled temperature and pressure conditions. To investigate the thermal characteristics of sulfur, operando X-ray diffraction (XRD) was conducted, showing thermal lattice expansion (diffraction peak shifting to lower angle) above 60°C (Figs. 1a and S1 and Table S3). Powder rheology tests of elemental sulfur at room temperature (RT, 25°C) and 80°C (Fig. 1b and Table S4) revealed increased softening and interparticle bonding of sulfur particles at higher temperatures33,34. Scanning electron microscopy (SEM) images (Fig. 1c−f) visualize that as the sulfur powder bed (SEM image of sulfur raw powder is shown in Fig. S2) roll-pressed at various temperatures (RT, 40, 60, and 80°C). At RT and 40°C (Fig. 1c, d), the sulfur particles retain their original granular structure with visible inter-particle gaps, indicating minimal particle deformation or contact. As the temperature increases to 60°C (Fig. 1e), the particles begin to show signs of localized deformation and slightly improved inter-particle contact, though some void spaces persist. Notably, at 80°C (Fig. 1f), the sulfur powder bed undergoes significant morphological transformation. The particles exhibit pronounced deformation and a substantial reduction in inter-particle voids, resulting in a highly compact and smooth surface texture. This densification indicates a critical threshold where thermal softening, combined with applied pressure, facilitates extensive surface diffusion or solid-state sintering. The substantial contrast between 60 and 80°C highlights the temperature-dependent consolidation mechanism, suggesting that 80°C induces sufficient particle plasticity to promote extensive particle reorganization and bonding, even without sulfur melting.

To understand the pronounced morphological transformation observed at 80°C, the thermal compression behavior of elemental sulfur particles under conditions mimicking the roll-pressing process was simulated. The initial height of the powder bed (h i) of 50 mm, P=50 MPa, and t=1.0 s at RT (25°C for the simulation) and 80°C (Fig. 1g−j). The simulation provides insights into particle-level deformation and densification under thermal and mechanical stresses, illustrating how elevated temperatures influence sulfur particle rearrangement, deformation, and packing efficiency. Note that the simulation is designed for qualitative insights into bulk deformation and densification during powder compaction. To balance accuracy and efficiency, we used millimeter-scale particles, which capture bulk mechanical responses acceptable computational cost, whereas a quantitative comparison with experimental data would require micrometer-scale particles that account for adhesive forces. At RT, the particles exhibited elastic and plastic deformation, with a final height (h f) of 24.7 mm, yielding a compaction ratio (h i /h f) of 2.1. The porosity is 53.2%, estimated as the ratio of empty space to particle volume. At 80°C, plastic deformation becomes more prominent due to reduced stiffness and increased Poisson’s ratio (ν), resulting in h f of 15.5 mm, a compaction ratio of 3.1, and porosity of 38.6%. Figure 1j compares the number of particles undergoing plastic deformation at RT and 80°C. The final particle diameter (d f) is calculated from the minor axial length. At RT, most particles showed moderate deformation, with an average d f of 4.0 ± 0.5 mm and a 5–10% variation in d i due to higher stiffness at low temperatures. At 80°C, d f decreased by 20−30%, averaging 3.0 ± 0.7 mm, confirming that sulfur particles exhibited ductile plastic deformation, forming a dense powder bed at higher temperatures. To achieve similar compactness of sulfur powder bed between RT and 80°C, approximately four times higher pressure is needed at RT (Fig. S3). This behavior forms the basis of our next section on heat- and pressure-assisted compression of S-C composites, where the role of sulfur in achieving high-density, cohesive electrode structures will be further explored.

Polymer binder-free S-C composite electrode fabrication
The cohesive nature of sulfur at elevated temperatures, as previously demonstrated, enhances the mechanical integrity of the compressed powder bed. Consequently, when thermally assisted compression effectively facilitates the distribution of sulfur within the S-C composite powder bed, enabling inter-particle bonding, the fabrication of S-C composite electrodes through solvent-free processes without the need for a polymer binder becomes feasible. Conventional designs of S-C composites generally focus on confining sulfur in nanosized carbon pores to prevent sulfur agglomerates, which helps reduce resistance and mitigate the Li-PS shuttling effect35. Our approach, however, combines nano-confined sulfur within porous carbon with micron-sized sulfur particles embedded in S-C secondary particles to facilitate polymer binder-free electrode fabrication. A two-step melt diffusion method was used to synthesize the S-C composite with Ketjen black as the carbon host, and the powder was ground and sieved for uniformity.

SEM (Fig. 2a) with energy-dispersive spectroscopy (EDS) elemental mapping (Fig. S4), bright field transmission electron microscopy (TEM, Fig. S5), high-angle annular dark-field (HAADF, Fig. 2b), and energy loss spectroscopy (EELS) mapping (Fig. 2c) images in the synthesized S-C composites reveal a highly porous morphology, typical of Ketjen black, with sulfur likely confined within the porous structure. The HAADF and EELS image provides further insight into the internal structure of the composite, confirming the hybrid structure where nano-confined sulfur coexists with micron-sized sulfur in S-C composite secondary particles. XRD (Fig. S6) shows crystalline α-sulfur (JCPDS 08-0247) in the composite, and to further investigate local structural features, including non-crystalline sulfur, we performed pair distribution function (PDF) analysis for elemental sulfur and S-C composite (Fig. S7). Compared to elemental sulfur, the S-C composite exhibited broadened features in I(Q) and S(Q)36,37, along with diminished long-range correlations in G(r)38,39, indicating the presence of amorphous sulfur domains. The preservation of nearest-neighbor S–S distances further suggests that local sulfur bonding is retained despite structural disorder induced by confinement within the porous carbon matrix. Sulfur content in S-C composite of ~70 wt.% was confirmed by thermogravimetric analysis (TGA, Fig. S8). From the integrated peak areas of XRD patterns shown in Fig. S9, the crystalline sulfur fraction in the S-C composite was estimated to be approximately 44 wt.% of the total composite, corresponding to about 63% of the total sulfur content. This partial amorphization suggests effective sulfur dispersion and confinement within the carbon matrix. The particle size distribution and morphology analysis of the S-C composite (Fig. S10 and Table S6) indicates that most of the particles fall within the size range of 30.4 µm and their morphology is relatively well-rounded (circularity of 0.896), which is advantageous for uniform formation of S-C composite powder bed. SEM (Fig. 2d, e) shows a 266% larger flattened area in particles compressed at 80°C compared to RT (186%), indicating greater compressibility, corresponding to rheological data of S-C composite (Fig. 2f and Table S7), confirming improved cohesion at higher temperatures. Higher-magnification SEM images (Fig. S11) show that RT-pressed samples exhibit uneven sulfur distribution with particles remaining outside aggregates, while 80°C-pressed samples exhibit more uniform morphology and sulfur distribution.

Using the developed S-C composite containing both nano-confined and micron-sized sulfur, a polymer binder-free S-C electrode was fabricated through a solvent-free manufacturing process. In this approach, the S-C composite powder bed was directly deposited onto a carbon-coated Al foil current collector and laminated via thermally assisted compression. A heat-roll press enables precise pressure control by adjusting the gap, roll temperature, and feeding speed. This process, illustrated in Fig. 2g, uses elevated temperatures to soften sulfur in S-C composites, promoting powder bed consolidation and inter-particle bonding. Micron-sized sulfur serves as a natural binder, while both micron-sized and nano-confined sulfur function as active materials. This dual role eliminates the need for additional binders or conductive agents, facilitating the formation of a binder-free S-C composite network. The heat-roll pressing of a Ketjen black powder bed under identical compression conditions fails to form a mechanically stable film on the Al current collector (Fig. S12a). In contrast, the sulfur–Ketjen Black mixture formed a coherent film, highlighting the critical role of sulfur as a binder (Fig. S12b).

In this work, positive electrodes with an areal sulfur loading of 3 mg cm−2 and porosity of 51–56% were prepared at 80°C (referred to as 80°C-pressed), with another set prepared at RT (referred to as RT-pressed) for comparison (Table S8). Due to the higher stiffness of S-C composite at RT, a narrower roll press gap was used for RT-compression process. The XRD patterns (Fig. 3a) of the RT-pressed and 80°C-pressed electrodes show structural changes with distinct peak differences, indicating better structural reorganization and compaction at 80°C. The compression at RT leads to some structural disorder of α-sulfur phase, as evidenced by peak broadening, but lacks the more pronounced crystallographic changes (i.e., peak shifting) seen at 80°C. The shift and associated peak shape distortion of α-sulfur in 80°C-pressed electrodes suggest thermomechanical strain or local lattice distortion within α-sulfur, likely facilitating improved particle–particle cohesion and mechanical integrity in the composite electrode. Peel force measurements (Fig. S13) confirm that 80°C-pressed electrodes exhibit enhanced mechanical stability over the RT-pressed electrodes.

To gain deeper insight into the process, a structural analysis of the RT-pressed and 80°C-pressed electrodes was performed using X-ray micro-computed tomography (µ-CT), SEM, and OM with surface profilometry. Despite the fact that RT-pressed and 80°C-pressed electrodes have approximately the same bulk porosity, the X-ray µ-CT results in Fig. 3b (RT) and 3e (80°C) reveal key differences: the RT-pressed electrode shows a non-uniform void structure with more complex pore pathways (tortuosity: 3.14), while the 80°C-pressed electrode has a more uniform structure with direct pore pathways (tortuosity: 2.79). The reduction in tortuosity is expected to facilitate more efficient Li-ion migration by shortening diffusion paths, which can contribute to improved rate capability and electrochemical uniformity during cycling. Top and cross-sectional view SEM images and porosity distribution analysis by X-ray µ-CT of the RT-pressed (Fig. 3c, d) and 80°C-pressed electrodes (Fig. 3f, g) indicate uniform porosity for the 80°C-pressed electrode, while the RT-pressed electrode has lower porosity at the top and bottom. SEM and OM with surface profilometry results (Figs. 3c, f and S14 and Table S8) reveal the 80°C-pressed electrode has a higher surface void fraction (49%) and greater roughness (S pc of 1612.7 mm−1) compared to the RT-pressed electrode (40% void fraction, S pc of 1192.0 mm⁻¹). Although the S-C composite deforms and compresses more effectively at 80°C than at RT, the 80°C-pressed electrode exhibits a rougher surface, interestingly. This difference arises from how pressure is distributed to achieve the same bulk porosity (51–56%) at varying temperatures. At RT, higher pressure was given to the powder bed to address the higher stiffness of the S-C composite particles, resulting in higher pressure concentrated at the top and bottom of the powder bed. This uneven pressure leads to smoother surfaces but non-uniform porous structures, as seen in cross-sectional images and X-ray µ-CT. In contrast, at 80°C, the S-C composite compresses more uniformly due to increased compressibility, requiring lower pressure for the same porosity, creating a rougher surface and more consistent porous structure. This effect becomes more pronounced as the areal mass loading increases from 1 to 5 mg cm−2 (Table S8 and Figs. S15−S17). At low loadings, pressure transfers more uniformly throughout the powder bed, but with higher loadings, thicker beds show greater inhomogeneity, especially at RT, leading to a more non-uniform structure.

X-ray µ-CT analysis results of the slurry-cast S-C composite electrodes (Fig. S18) reveal significant differences between binder-based and binder-free S-C composite electrodes, particularly in terms of tortuosity and structural integrity. The slurry-cast electrodes display a more tortuous pore network with pronounced microscale defects than the RT and 80°C-pressed electrodes, as evident from the top-view SEM and OM and surface topology analysis (Fig. S19 and Table S9) and the 3D reconstructed X-ray µ-CT images (Fig. S18). High-speed camera observations reveal that the electrolyte absorptivity of the electrodes differs significantly between the binder-free and slurry-cast S-C composite electrodes. The binder-free electrodes display more rapid and uniform electrolyte absorption, with contact angles of 17° and 14° after 0.02 s for RT-pressed and 80°C-pressed samples, respectively, compared to 23° for the slurry-cast S-C composite electrode. This enhanced wettability is attributed to their more homogeneous porosity and structural integrity (Fig. S20). This faster absorptivity ensures improved wetting of the electrode and enhanced ion transport pathways, which could contribute to the enhancement in the electrochemical performance of the binder-free electrodes. In contrast, the binder-containing slurry-cast electrodes, with their more tortuous pore network and the presence of a polymer binder, exhibits lower and less uniform electrolyte absorption, leading to poorer wetting. After 2 s, the RT-pressed electrode shows surface swelling and irregularity (Fig. S20), indicating localized expansion and reduced mechanical stability. In contrast, the 80°C-pressed and slurry-cast electrodes maintain flat, intact surfaces, suggesting better structural resilience. These findings, in conjunction with the X-ray µ-CT and SEM observations, emphasize the critical role that microstructural uniformity and electrolyte accessibility play in the overall performance of S-C composite electrodes.

Electrochemical tests
The electrochemical performance of the S-C composite positive electrodes (3 mg cm−²) was systematically evaluated through a series of tests, including rate capability, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge-discharge cycling. While pouch cells are important for assessing practical energy metrics40–42, coin cells were used to enable controlled evaluation of the intrinsic properties of the sulfur positive electrodes developed in this work. The rate capability test (Figs. 4a and S21) demonstrates that the 80°C-pressed electrodes exhibit higher rate performance across a wider range of C-rates with specific capacities of approximately from 1300 to 600 mAh g−1 from 0.05 to 1.0°C, respectively, whereas the RT-pressed electrodes (70 wt.% sulfur) show a dramatic reduction in capacity as the C-rate increases, particularly above 0.5°C rate. The cycling tests (Fig. 4b) validate these improvements, with the 80°C-pressed electrodes retaining significantly more capacity over 200 cycles compared to the RT-pressed electrodes, which decayed after 60 cycles. The slurry-cast electrode containing a polymer binder prepared for comparison (3 mg cm−², 58 wt.% sulfur) showed even worse cycle performance and rate performance with rapid capacity decay and early failure than both binder-free positive electrodes. The inset chart in Fig. 4b shows that the slurry-cast electrode exhibited a specific capacity of only 627 mAh g ⁻¹ (based on the mass of the electrode film vs. 896 mAh g ⁻¹ for 80°C-pressed electrodes) during the initial cycle. This performance declined substantially by the 90th cycle, decreasing to 320 mAh g ⁻¹. A gradual decline in Coulombic efficiency was observed during extended cycling (Fig. 4b), particularly in the RT-pressed and slurry-cast samples, indicating increasing interfacial resistance. Figure 4c−e highlight the more stable voltage profile of the 80°C-pressed electrodes with lower charge and discharge overpotentials, compared to the RT-pressed electrodes. The CV results (Fig. 4f−h) align with previous findings, showing sharper and more distinct redox peaks for the 80°C-pressed electrodes, indicating better electrochemical reversibility and more efficient sulfur redox reactions. EIS analysis performed at the charged state after 30 cycles (Fig. 4i−k and Table S10) revealed distinct trends for each electrode type. The 80°C-pressed electrodes maintained low impedance, while both the RT-pressed and slurry-cast electrodes exhibited showed clear increases in ohmic resistance (R s). The rise in R s for the RT-pressed electrode suggests compromised structural integrity, likely due to mechanical degradation during cycling43–45, whereas the thermally compressed 80°C-pressed electrode retained a stable architecture. Similarly, the increase in R s for the slurry-cast electrode is consistent with previous reports that conventional slurry processing can lead to solvent-induced inhomogeneity and poor interfacial stability issues46–48. The 80°C-pressed electrodes was further evaluated in a single-layer pouch cell (1.5×1.5 cm2, 3 mg cm−2, Fig. S22), which delivered an initial capacity of 1000 mAh g−1 and maintained 897 mAh g−1 after 30 cycles, demonstrating the applicability of the binder-free S-C electrodes to a more practical cell form factor and consistent electrochemical behavior with the corresponding coin-cell results.

In the cycling tests (Fig. 4l) conducted at a lower mass loading of 1 mg cm−2, both the binder-free positive electrodes demonstrated stable cyclability at 1C. However, the 80°C-pressed electrodes sustained a higher capacity of approximately 1000 mAh g−1 over 500 cycles. In contrast, the slurry-cast positive electrode failed after 400 cycles, despite showing slightly low charge and discharge overpotentials across various C-rates, comparable to those of the binder-free positive electrodes (Fig. S23). The improved performance of the binder-free positive electrodes highlights the limitations of conventional slurry casting processes in achieving the necessary structural and electrochemical stability, as demonstrated by the underperformance of the slurry-cast S-C composite positive electrodes compared to both the RT- and 80°C-pressed electrodes. This is also featured at a higher mass loading of 5 mg cm−2 (Fig. S24) as well. While consistently delivering higher capacities across all C-rates in the rate performance test and at 0.1°C during cycling, the 80°C-pressed electrodes (5 mg cm−2) exhibited Coulombic efficiency values slightly above 100%, likely due to delayed activation of isolated sulfur domains within the sulfur positive electrodes, unlike the consistently lower Coulombic efficiency observed in the RT-pressed and slurry-cast S-C positive electrodes. EIS analysis for the 1 and 5 mg cm−2 electrodes revealed trends consistent with those observed at 3 mg cm−2, reinforcing the generality of the impedance behavior across various loadings (Figs. S23 and S24 and Table S10). The electrochemical analyses reveal that the S-C composite positive electrodes pressed at 80°C exhibit significantly enhanced performance compared to those pressed at RT. This improvement can be directly attributed to the optimized microstructure achieved during compression at elevated temperatures, as demonstrated in the previous characterization results. The more uniform porosity distribution, low tortuosity, and enhanced structural integrity of the 80°C-pressed electrodes facilitate efficient ion transport and electron conduction, resulting in reduced polarization and improved electrochemical kinetics49,50. In contrast, the RT-pressed electrodes suffer from inhomogeneous compression and lower porosity at the electrode surface, which impedes their overall performance. These findings are further supported by the structural differences observed, where the more uniform compression of the 80°C-pressed electrodes leads to better contact between the active material and the conductive matrix. The enhanced structural and compositional uniformity at higher processing temperatures results in lower interfacial resistance, attributed to improved adhesion between the active materials and the current collector, as well as better particle-to-particle contact within the positive electrode. This uniform microstructure contributes to improved cycling stability, minimizing electrode degradation, sulfur loss, and active material disconnection during repeated charge-discharge cycles. In contrast, the RT-pressed electrodes exhibit faster capacity fading due to their less stable and inhomogeneous structure.

In situ and ex situ characterizations
In situ OM conducted during the initial discharge provides complementary insights into the dynamic behavior of the positive electrodes (Fig. 5 and Supplemental Movies 1 and 2). At the onset of lithiation, both the RT-pressed and 80°C-pressed electrodes exhibit the formation of Li-PS, indicated by the color change of the electrolyte to light orange. As discharge progresses, both positive electrodes undergo volume expansion due to sulfur lithiation, accompanied by a darkening of the electrolyte color, reflecting an increased concentration of Li-PS51. Due to the spacer-free design of the in situ OM cell, the larger interelectrode gap results in higher polarization than in conventional coin cells. While no evidence of particle detachment was observed, the volume expansion behavior differed significantly between the two electrodes. During the initial 10% depth of discharge (DOD), the RT-pressed electrodes exhibit localized and uneven volume changes, with specific regions of the electrode expanding disproportionately, resulting in uneven mechanical deformation (Fig. 5b). In contrast, the 80°C-pressed electrodes display a more uniform volume expansion across the electrode, consistent with improved structural cohesion and more uniform sulfur distribution in the 80°C-pressed electrodes. Comparative OM images during both discharge and charge at various DOD and states of charge, as shown in Fig. S25, further clarify these differences. The fully charged positive electrode pressed at 80°C exhibits a uniform reformation of sulfur from Li-PS, returning to its original microstructure. Conversely, the RT-pressed electrode shows a sulfur structure largely confined within the carbon matrix, resulting from microstructural deformation.

Ex situ SEM images of positive electrodes after cycling (Fig. 5c, d) further confirm these observations, revealing clear differences in the mechanical stability and surface morphology of the RT- and 80°C-pressed samples. The RT-pressed electrodes display significant surface cracking and delamination after 5 cycles, indicating mechanical degradation caused by repeated volume expansion and contraction during Li-S redox reactions. Conversely, the 80°C-pressed electrodes maintain a crack-free surface, with no signs of delamination or particle separation, even after the same number of cycles. Additional ex situ SEM images collected at ~40% DOD at the initial discharge process reveal that the 80°C-pressed electrodes retain structural cohesion during early electrochemical cycling (Fig. S26). This observation, together with prior findings that sulfur conversion does not occur uniformly across the electrode52, suggests that partially unreacted sulfur and early-stage Li2Sx species can coexist, allowing localized structural retention during the formation of discharge products. Importantly, the observations suggest that the initial mechanical integrity provided by heat-pressing plays a critical role in mitigating the potential structural weakening associated with the solid–liquid–solid transition of sulfur during cycling. Although polysulfide formation and subsequent sulfur precipitation inherently involve relocation of active material, the 80°C-pressed electrode preserves a cohesive framework that accommodates these transformations without particle detachment or severe cracking, as confirmed by ex situ SEM. S||Li2S cell testing (Fig. S27) in which a lithiated positive electrode (Li2S-containing) was paired with a fresh S/C positive electrode further confirmed enhanced reversibility in 80°C-pressed electrodes, which exhibited lower charge polarization and more stable cycling behavior compared to RT-pressed samples, consistent with improved structural integrity and Li2S distribution. This indicates that effective thermomechanical compression, by promoting structural uniformity, not only ensures intimate interparticle contact at the outset but also helps preserve the electrode architecture throughout repeated Li-S redox cycles, as summarized in Fig. 5e, f. These collective findings of ex situ SEM and S||Li2S symmetric cell test highlight that the improved morphological integrity of the 80°C-pressed electrodes not only supports structural robustness but also accommodates the chemo-mechanical stresses induced by repeated sulfur redox cycling. Given that sulfur serves both as the active material and a structural binder in this solvent- and binder-free system, its homogeneous distribution within the carbon matrix is particularly critical. The resulting uniform composite architecture enhances interparticle cohesion and mitigates fracture propagation during solid–liquid–solid transitions. This structural coherence is essential to maintaining continuous electron and ion transport pathways, preventing the detachment of active material, and ultimately enabling prolonged cycling stability. The findings presented here provide valuable insights into the relationship between processing conditions, structural integrity, and electrochemical performance, offering a practical framework for designing next-generation sulfur-based energy storage systems.

Methods
Characterization of elemental sulfur
Operando XRD measurements during heating were performed using a STADI P STOE dual-transmission diffractometer equipped with an Ag Kα source (λ=0.55941 Å, 40 kV, 40 mA). Data were collected with a step size of 0.015° and a dwell time of 15.81 s per step to investigate the thermal behavior of elemental sulfur (sulfur nanopowder, 99.99%, Skyspring). At each temperature, diffraction patterns were acquired for 10 min total, consisting of two 5 min scans at successive detector positions. To investigate particle deformation and densification, a powder bed of elemental sulfur was deposited onto Al current collectors and compressed using a heat-roll press (Wellcos, WCRP-1015HG) at various temperatures. The compression pressure applied to the sulfur powder bed was kept consistent across all samples by maintaining a fixed gap between the rolls and the roll rotation speed. SEM analysis (Auriga Zeiss) was performed on the compressed powder bed to examine the structural changes resulting from the thermal and mechanical treatments. Powder rheological properties were evaluated using a powder shear cell tester (TA Instruments, Discovery HR-20). Over 20 mL of powder was loaded into a stainless steel cylindrical cell (28 mm diameter). The assembly was then heated to the target temperature—either RT or 80°C—at a ramp rate of 3°C min−1. Upon reaching the set temperature, the powder was equilibrated for 5 min to ensure thermal uniformity throughout the sample. A pre-consolidation pressure of 9 kPa was applied to condition the powder bed and achieve a uniform packing state. Excess powder was removed after consolidation, resulting in an exact sample volume of 18 mL for shear testing. The sample was then subjected to a constant shear rate (0.001 rad s−1) under fixed normal stress until shear failure occurred53. The normal stress was systematically decreased to 7, 6, 5, 4, and 3 kPa in successive cycles, following instrument protocols. A yield locus was constructed by plotting the steady-state shear stress versus normal stress, and a linear fit was applied. Using Mohr’s circle analysis, the unconfined yield strength (UYS) and the major principal stress (MPS) were extracted: (1) The first Mohr’s circle was constructed with one point at the origin (0,0) and a second point tangent to the yield locus; its x-axis intersection yields the UYS. (2) The second Mohr’s circle used the pre-shear point and a tangent to the yield locus; its x-axis intersection defines the MPS54–56. The flow function (FF) of the powder was calculated using the UYS and MPS values, as expressed in Eq. (1) shown below.

FF= MPS / UYS (1)

Computation modeling for thermal compression behavior of elemental sulfur
The roll-pressing of sulfur powder bed is modeled using ANSYS Workbench, a commercial software package that integrates ROCKY and Mechanical modules, which implements both discrete element model (DEM) and finite element model (FEM). The objective of the model is to qualitatively understand how temperature changes in the roll-pressing process affect the sizes and shapes of particles in the resulting hot-rolled sintered film. To simplify the modeling process, the actual roll-pressing process was represented as the compaction of sulfur particles in a die compressed by a rigid punch. First, DEM was used to randomly pack sulfur particles in the simulation domain, which was then imported into the FEM for the compaction simulation. The computational domain, which measures 50×50×50 mm3, contains polygonal sulfur powder particles modeled as sphero-polygons with 12 vertices, an initial equivalent sphere diameter, d i=5 mm, and vertical/horizontal aspect ratio of 1. This sphero-polygon representation captures the irregular, faceted geometry of actual particles while enabling computation of inter-particle contact mechanics and packing behavior. The simulation domain was sized to include at least ten sulfur particles with a representative diameter of ~5 mm in each spatial direction, ensuring statistically meaningful assessment of bulk powder behavior. The initial height of the powder bed, hi, is 50 mm. Each powder particle is independent and deformable, with a friction coefficient of 0.2, determined by the Coulomb friction model. The contact between neighboring particles is modeled by the Bond model, similar to the works of Gimenez et al.57 and Potyondy & Cundall58. In the Bond model, a massless cylindrical bond entity is attached to a pair of neighboring particles, exerting elastic and viscous forces and moments on the particles as a reaction to deformations caused by their relative motion. An external load higher than the specified tensile and shear strengths may break the bonds. The bond model parameters used in the simulation include a maximum elongation of 1 mm, a damping ratio of 0.25, a distance factor of 0.1, normal and tangential stiffness per unit area of 100 kNm−³, tensile and shear stress limits of 10 kPa, and a bond activation time of 0.1 s. These values were selected to approximate the mechanical behavior of loosely agglomerated particles and to enable realistic fracture and rearrangement during compaction. These Bond model parameters were chosen to represent the general inter-particle mechanics of ductile porous powders, but since they are not material-specific, they cannot be used for direct quantitative comparison with experimental data. In the FEM, a free-fall displacement boundary condition is imposed on the rigid punch, along with an additional force factor that controls the applied pressure, P. As the punch moves downward, it interacts with the particles in the top-most layer, transmitting forces downward to neighboring particles in each layer. As the powder particles are compressed and undergo elasto-plastic deformation, the punch monotonously moves downward for the prescribed punch time, resulting in a final powder bed height, hf. To simulate the powder compaction at RT (25°C) and 80°C, the appropriate mechanical properties, i.e., Young’s modulus, E, and Poisson’s ratio, ν, are defined. Due to the limited data for sulfur particles at various temperatures, we assume E=10 GPa59 and v=0.2 at 25°C. Most crystalline materials possess v in the range of 0.2–0.3 at 25°C60. At 80°C, we assume E=5 GPa and v=0.3, based on the linear model for the temperature dependence of Young’s modulus61. During pressing, relative density, defined as the volume ratio of particles to the die, varies across three stages. As the punch starts to press, particles rearrange their positions to fill large gaps, resulting in rapid increase in relative density. Next, the positions of particles become interlocked, and the rate of increase in relative density slows down. The particles start undergoing plastic deformation, and the gaps are filled by large-scale plastic deformations. Finally, a dense state is formed, and the relative density no longer increases. Among the three stages, plastic deformation is most influenced by the temperature change.

Synthesis and characterization of S-C composites
The S-C composite was synthesized via a conventional melt diffusion process. Initially, sulfur nanopowder and Ketjen black EC-600JD (MSE Supplies) were combined in a 75:25 weight ratio and mixed using a mortar and pestle. The S-C mixture was transferred to an alumina crucible and placed in a tube furnace (Lindberg/Blue M Mini-Mite, Thermo) to heat-treat the mixture at 155°C for 10 h under an argon (Ar) atmosphere to enable the melt diffusion of sulfur into the porous carbon matrix. After natural cooling, the resulting S-C composite was ground using a mortar and pestle, reloaded into the crucible, and subjected to a second heat treatment at 155°C for 5 h under Ar atmosphere. After cooling, the final composite was retrieved from the crucible and passed through a 500-mesh (30 µm) ultrasonic sieve (UP200st, Hielscher) operating at 40 W to ensure uniform particle size distribution. The sulfur content in the S-C composite was 70 wt.%, confirmed by TGA testing conditions.

The morphology of the synthesized S-C composite was analyzed using SEM (Auriga Zeiss) with an electron acceleration voltage of 5 keV and a working distance of 5 mm, along with EDS elemental mapping (Oxford Instrument) and TEM (ARM200F, JEOL), accompanied by scanning TEM (STEM) with EDS elemental mapping (Oxford Instrument) and HAADF imaging. Sulfur content in the S-C composite was determined by TGA (TG92 Setaram) at the ramping rate of 5°C min−1 under Helium gas. The crystal structure of the S-C composite was scanned between 10 and 70 2θ degree using Cu-Kα source XRD (PANalytical Aeris Malvern, λ=1.54060 Å, 40 kV, 15 mA) with a step size of 0.01° and a dwell time of 200 s per step. PDF measurements were performed using a STOE STADI 60P transmission X-ray diffractometer equipped with an Ag Kα source (λ=0.55941 Å; 40 kV, 40 mA) and a curved Ge (111) monochromator. Diffraction patterns were collected in Debye–Scherrer geometry using four stationary MYTHEN2 R 1K silicon strip detectors covering a 2θ range of 2°–140° (Q max=21 Å−1). Samples were sealed in spinning borosilicate glass capillaries (0.50 mm outer diameter, 10 µm wall thickness) to minimize preferred orientation and enhance statistical averaging. Each sample was measured for 24 h, and background scattering was subtracted using data from an identically measured empty capillary. The 1D diffraction patterns were processed with PDFgetX3 to yield the background-subtracted intensity I(Q), structure function S(Q), reduced function F(Q), and real-space PDF G(r)39,62. To evaluate the amorphous sulfur content in the S-C composites, a calibration series of crystalline S-C (S cryst-C) samples was prepared by mechanically mixing sulfur and Ketjen black at weight ratios of 90:10 (90S cryst), 70:30 (70S cryst), 50:50 (50S cryst), and 40:60 (40S cryst) without any heat treatment. All S cryst-C mixtures were pre-weighed to maintain a constant carbon mass on the sample holder. For reference, pure crystalline sulfur (100S cryst), Ketjen black, and the synthesized S-C composites were also analyzed. XRD was performed using a PANalytical Aeris diffractometer with a Cu-Kα source (λ=1.5406 Å), scanning from 20° to 33° 2θ with a step size of 0.01° and a dwell time of 200 s per step. The integrated intensities of the sulfur (222), (026), and (040) reflections were obtained and used to construct calibration curves of integrated peak area versus crystalline sulfur content. Linear regression yielded R2 values higher than 0.95 for all peaks, indicating strong linearity. The relative crystalline sulfur content of the S-C composite was then determined by extrapolation from the regression model, and the amorphous sulfur fraction was estimated by subtracting the crystalline contribution from the total sulfur content. This analytical approach follows methodologies established in prior XRD-based phase quantification studies63,64. Particle size and morphology analysis were done by particle size analyzer (Morphologi G3 SE Malvern) at the magnification of ×20 and ×50. To observe the particle deformation behaviors of the S-C composite at different temperatures, the S-C composite particles were dispersed onto poly(vinylidene fluoride)-coated Al foil. First, a PVDF-coated Al foil was prepared by casting a PVDF (Kureha 9300; Molecular weight: >1.0×106 g mol−1) solution in NMP (50 mg mL−1). The solution was cast onto Al foil (Wellcos, thickness: 20 µm) with a blade gap of 100 µm, followed by partial drying process in a fume hood at 25°C for 3 h. Before the solution is completely dried. Subsequently, the S-C composite powder was uniformly dispersed onto the partially dried PVDF film. The samples were then dried overnight in the fume hood, followed by vacuum drying at 50°C for 12 h. SEM images were acquired prior to calendaring. Subsequent to the initial SEM imaging, the S-C composite on the Al foil underwent calendaring processes at both RT and 80°C, with the heat-roll press gap remaining consistent in both instances. The compressed particles were subsequently subjected to SEM imaging once again to analyze their deformation characteristics resulting from the calendaring process. The same shear cell-based method described above was employed to characterize the rheological behavior of the S-C composite powder under identical testing conditions.

Solvent- and binder-free S-C composite positive electrode preparation and characterization
S-C composite powder was carefully loaded into a stainless steel window measuring 4×5 cm², which is positioned on carbon-coated Al foil (Wellcos, thickness: 20 µm) to create a 4×5 cm² powder bed. The heat-roll press was meticulously preheated to the specific target temperature for a duration of 10 min to ensure consistent and uniform heating throughout the material. The gap between the rolls was then precisely adjusted to align with the desired areal mass loading and processing temperature, guaranteeing the maintenance of a constant bulk porosity. The roller speed was carefully set at 10 cm min−1 to achieve the desired lamination process. Following the lamination, electrodes were accurately punched into circular discs using a hand operated punching tool (WC-H125), preparing them for subsequent electrochemical testing within 2032 coin cells (Wellcos). A simple mixture of S (70 wt.%) and Ketjen black (30 wt.%) using a mortar and pestle method was also prepared to compare the physical properties of electrodes. This mixture was compressed under conditions identical to those of the heat-roll press method.

The crystallographic structure of the S-C composite positive electrodes was characterized by XRD using a Cu-Kα radiation source (PANalytical Aeris, Malvern; λ=1.54060 Å, 40 kV, 15 mA). For the peel test, RT- and 80°C-pressed S-C composite electrodes were attached to a glass slide using glue (Super Glue, 15187). The uncoated side of the current collector was facing the slide glass. Then, adhesive tape (3M Scotch® 600) was firmly attached to the top surface of each electrode. A tensile test machine (AEL-A-100, Wenzhou Tripod Instrument Manufacturing Co., Ltd.) with a 50 N load cell was used to conduct the peel test. The tensile tester was used to peel the tape and separate the S-C composite electrode film from the current collector measuring peel force at a speed of 50 µm s−1.

The bulk porosity of the electrode is estimated by calculating the ratio between the theoretical densities of sulfur and carbon and the measured density of the fabricated electrodes. To analyze surface voids, the brightness of each image was adjusted to a grayscale range of 62–302, and the images were converted to 8-bit format to analyze surface voids. A manual contrast threshold adjustment was applied to each image to clearly distinguish the voids from filled areas. The percentage of voids present was then calculated by quantifying the surface voids through area analysis. The surface roughness of the material was analyzed using a Surface Profiler (VK-X3000 3D Keyence). This analysis was conducted in optical and laser mode at a magnification of ×50, while scanning an area of 200×300 µm. The data obtained from the scan was then processed using the VK-X3000 software to perform a detailed analysis of the surface topology.

The 3D microstructure of the prepared RT- and 80°C-pressed S-C composite electrodes and slurry-cast S-C composite electrodes were characterized using X-ray μ-CT (Skyscan Bruker). The imaging was conducted at 50 kV and 200 µA with a 4k resolution and no filter applied. A total of 3600 2D projections were captured over a full 360° rotation of the sample, with an exposure time of 9.25 s for each projection. The 3D-CT images were reconstructed using VGSTUDIO MAX (Volume Graphics) from a series of acquired 2D X-ray projection images. The 3D models were analyzed and visualized using Avizo software (Thermo Fisher). To prepare cross-sectional SEM images of RT- and 80°C-pressed S-C composite electrodes, the electrodes were vertically embedded in carbon black-infused epoxy (Allied Materials). After curing overnight, the embedded samples were ground and polished using a polishing wheel. The mechanically polished samples were then further polished using ion milling (Clean Mill Ion Polisher, Thermo Fisher) at 5 kV for 5 h under cryogenic conditions.

To evaluate the wetting properties of the electrode, a precise 7 µL droplet of electrolyte was carefully deposited onto the electrode surface using a micropipette. The entire spreading process was recorded at 1000 frames per second using a high-speed camera to capture the detailed dynamics of the droplet. Subsequently, the contact angle formed by the droplet on the electrode surface was analyzed from the exported images to precisely evaluate and understand the wetting behavior of the electrode.

Electrochemical test
All electrochemical tests were performed at 25°C. Each electrochemical condition was tested using multiple independent cells (typically n=2–3, depending on the experiment), and consistent trends were observed; the data shown are representative of typical performance. 2032-type coin cells made of stainless steel (Wellcos) were assembled in an Ar-purged glove box. The cells consisted of lithium foil (120 µm, Honjo Metal) negative electrode, S-C composite positive electrode (single-side coated), a carbon-coated Celgard 2400 (carbon coating: 6 µm and 0.06 mg cm−2; Celgard: 25 µm and 1.7 mg cm−2), and an electrolyte composed of a 1:1 mixture of Dioxolane (DOL, 99.8%, Sigma-Aldrich) and Dimethoxyethane (DME, 99.5+ %, Sigma-Aldrich), containing 1 M Lithium bis(trifluoromethanesulfonyl) imide (LiTFSI, 99.95 % trace metal basis, Sigma-Aldrich) and 3 wt.% lithium nitrate (LiNO₃, 99+%, Strem). Before use, the salts were dried under vacuum in the glove box antechamber at 50°C for 12 h and then immediately transferred into an Ar-filled glove box. The solvents were dried over molecular sieves (4 Å, Wisesorb) for 48 h prior to use. The electrolyte-to-sulfur ratio (E/S) was set to 10 for 1 mg cm−2 electrodes, 7 for 3 mg cm−2, and 5 for 5 mg cm−2 electrodes. For single-layer pouch cells, the 80°C-pressed electrode (1.5×1.5 cm2, 3 mg cm−2) was assembled together with the carbon-coated Celgard 2400, Li metal negative electrode (120 µm, Honjo Metal), and the same electrolyte with the E/S ratio of 7 as in the coin cells. Negative to positive (N/P) ratio of the single-layer pouch cell is 4.9. An Al tab (MTI Corporation) was ultrasonically welded onto the as-prepared positive electrode. Li metal was laminated onto a nickel mesh (MTI Corporation) with a pre-welded nickel tab (MTI Corporation). After stacking the electrodes with the carbon-coated separator, the stack was placed in an aluminum-laminated pouch (Wellcos), and the electrolyte was injected using a micropipette in an Ar-filled glovebox to ensure complete wetting of the electrodes and separator. The pouch was then hermetically heat-sealed. No external pressure was applied during cycling.

For comparison with the binder-free S-C composite positive electrodes with an areal sulfur loading of 3 mg cm−2 (70 wt.% sulfur), a S-C composite positive electrode was also prepared using the conventional slurry casting process with a polymer binder. A mixture of S-C composite, Super P (99+%, Timcal), and LA133 (MSE Supply) binder, at a weight ratio of 83:10:7 (58.1 wt.% active sulfur), was blended using a centrifuge mixer (Thinky ARE-310) with water as the solvent at a solid-to-liquid ratio of 100 mg mL−1 for 1 h. The slurry was cast onto carbon-coated Al foil (Wellcos, thickness: 20 µm) with a doctor blade (BYK instrument), air-dried overnight in a fume hood, and subsequently vacuum-dried at 50°C for 12 h. Lithium metal foil was punched into 15 mm diameter disks inside an Ar-filled glove box and used immediately as the negative electrode. Galvanostatic charge-discharge cycling and rate performance were tested within a cell voltage window of 1.7–2.7 V using an Arbin LBT Series battery tester, with the cells placed in a multi-zone temperature chamber (Arbin MZTC) maintained at 25°C. 1C rate corresponds to 1675 mA g −1 (based on sulfur mass) in the positive electrode. CV measurements were performed using a potentiostat (BioLogic VMP) within a cell voltage range of 1.7–2.7 V with scan rates of 0.05 and 0.1 mV s−1. EIS was conducted from 1 MHz to 10 mHz using a 5 mV stimulus on before and fully discharged cells after 30 galvanostatic charge-discharge cycles.

S||Li2S symmetric cells were fabricated as follows. Since both electrodes are based on S-C composites and thus lack a native lithium source, the lithiated positive electrode was prepared by fully discharging a Li||S cell to convert sulfur into Li2S prior to assembly. First, Li||S cells were assembled using RT-pressed or 80°C-pressed electrodes (3 mg cm−2 areal sulfur loading) and Li metal negative electrodes, with the same electrolyte composition used throughout this study. The cells were discharged at 0.05°C to 1.7 V to convert sulfur to Li2S, electrochemically, after which the discharged cells were disassembled in an Ar-filled glove box to recover the lithiated positive electrodes. A symmetric cell was then assembled using the collected Li2S positive electrode as the positive electrode and a fresh S-C positive electrode (identical in mass loading and fabrication condition) as the negative electrode. The symmetric cells were rested for 24 h before galvanostatic cycling at 0.2°C between −1 V and 1 V, using a 2-h cutoff for both charge and discharge steps.

In situ OM and Ex situ SEM analysis
In situ OM analysis was performed to examine the dynamic behavior of the positive electrodes. Customized optical cells, each featuring a 3 mm diameter hole, were sealed with a transparent glass window to enable direct observation of the electrode under light irradiation. These optical cells contained side-by-side S-C composite electrodes (3 mg cm−2) and lithium foil (thickness: 350 µm, Wellcos), filled with a 1 M LiTFSI and 3 wt.% LiNO3 solution in a 1:1 mixture of DOL/DME. Galvanostatic charge-discharge tests were conducted at 0.1°C within a cell voltage range of 1.8–2.7 V using a WonATech battery tester at 25°C. All optical cells were assembled in an Ar-filled glove box. In situ OM analysis was carried out with an LV150N optical microscope (Nikon) equipped with a ×50 magnifying lens. Ex situ SEM was performed on electrodes obtained at approximately 40% DOD during the initial discharge at a C/20 (target capacity: 520 mAh g−1, based on a discharge capacity of 1300 mAh g−1). Cells were disassembled inside an Ar-filled glove box immediately after reaching the targeted discharge capacity. The recovered positive electrodes were gently rinsed with anhydrous DOL/DME mixture solution to remove residual electrolyte and lithium salts, followed by vacuum drying at RT for 2 h. After drying, the electrodes were mounted on SEM stubs inside the Ar-filled glove box, placed in a sealed glass vial (Parafilm-sealed), and transported to the SEM facility using a double zip-bag to minimize air exposure prior to loading. For cycled electrodes, ex situ SEM samples were collected from cells at the fully charged status after five charge-discharge cycles at 0.2°C within 1.7–2.7 V. Sample preparation was identical to that described above. Surface morphology was examined using a field-emission scanning electron microscope (Auriga Zeiss) operated at 5 kV accelerating voltage.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "The contribution by An et al reports on the preparation of S cathode for LiS batteries based on powder processing without\npolymer binder. The sulfur is used as binder in this case.\nOverall the contribution is timely and well written\nThe materials are well characterized by various methods including SEM, XRD etc. and electrochemical characterization is\nextensive.\nA major question is the stability after cycling as the binder Sulfur is consumed and should transform to Li2S. Post mortem\nanalyses could be more comprehensive in this sense to shine light on this aspect.\nThe crystallographic analysis of sulfur is not so clear. The authors should state which modifications of sulfur are formed in\nthe electrode (alpha, beta etc. ). The peak shift is not explained well. What is the origin? This seems to be an artefact. It is\nrecommended to measure with a NIST Si internal standard to confirm the peak shift.\nMoreover, the amount of amorphous sulfur should be quantified.\nL 214: “Improving transport” is a vague statement\nL243 “faster absorptivity” is very qualitative: provide numbers on wetting behavior like contact angle.\nIt would be good to also analyze electrode swelling after electrolyte wetting vs. dry electrode. KB electrodes significantly\nexpand typically with DME/DOL.\nL287: cycling behavior. This probably reflects more the instability of Li anode than cathode. A better way to monitor cathode\ncycling stability alone is to work with symmetric cathode cells.\nL303: RT-pressed cells are a poor benchmark. Its easy to outperform a bad standard. Refer to literature and a standard\nelectrode with PTFE binder to compare in fair way.\nFig 4: low loading in cathode makes it easy to get high cycling stability. Only 1 mg/cm2 and E/S = 10!\nThis will never give a high specific energy. E/S < 3 needed and at least 3 mg/cm2. Please also provide data for higher\nloading and lower E/S. Pouch cell data would be better. Limitations of coin cells are well documented in literature but not\ncited.\nMethods: wavelength of Ag radiation should be given and also mentioned in XRD figure for clarification.\nReferences:\nCritical references (reviews) on Dry processing as well as LiS batteries are missing! Literature too narrow.", "reviewer_2": "Summary: This Research Paper NCOMMS-25-41503, entitled “Unveiling sulfur as a binder for high-performance polymer-\nfree sulfur-carbon cathodes via solvent-free fabrication,” reports a novel, scalable, and environmentally friendly method for\nfabricating binder- and solvent-free sulfur–carbon composite cathodes for lithium–sulfur cells via thermal-assisted dry\npressing directly onto aluminum foil. By using sulfur’s intrinsic softening and adhesive properties, the process eliminates the\nneed for polymeric binders and toxic solvents. Thus, the heat-roll pressed cathode simplifies the electrode fabrication and\nachieves a high reversible capacity of 932 mAh g⁻¹ over 500 cycles at a 1C rate. The use of low-cost commercial porous\ncarbon further enhances the practical relevance of the approach, which also reduces production costs by more than 50%.\n[General Comment]: This research reports the novel fabrication design and optimization for lithium–sulfur battery cathodes\nwith comprehensive analysis and study. The following minor revisions are suggested to further improve the clarity and\nimpact of the work.\nAdditional Comments:\n(1) For the fundamental concept, sulfur would be served as both the active material and the binder in the heat-roll pressed\ncathode. During cycling sulfur becomes liquid-state polysulfides, this solid-liquid conversion would weaken the electrode\nstructure. Moreover, polysulfides would convert to sulfur and sulfide during charge and discharge. The relocation and\nreformation of solid-state active material during cycling do not have heat and pressure to support the stability of the heat-roll\npressed cathode. These concerns can be discussed.\n[Suggestion] Please consider having a discussion on the cathode stability during polysulfide formation and its\nnucleation toward sulfur and sulfide.\n(2) In the electrochemical analysis, the discharge/charge efficiency of the heat-roll pressed cathode would decrease during\ncycling and would decrease to less than 90%. However, 5 mg cm-2 cathode shows the discharge/charge efficiency of over\n100%. These issues are suggested to be addressed and discussed. With this concern, discharge/charge efficiency is\nsuggested to be reported in all electrochemical analysis, including cycling and rate performances.\n[Suggestion] Please address the issues of discharge/charge efficiency, including the missing data, the decrease in\nelectrochemical efficiency, and the efficiency of over 100%.\n(3) In the electrochemical analysis, the electrochemical impedance analysis of the heat-roll pressed cathode is suggested to\nbe analyzed with an equivalent circuit model to support the corresponding discussion. The raw experimental data and the\nfitting data are suggested to be reported together as experimental data points and the fitting curves.\n[Suggestion] Please analyze the impedance data.\n(4) The heat-roll pressed cathode is reported with the sulfur loadings of 1 to 5 mg cm-2. The cell-fabrication parameters of 5\nmg cm-2 cathode cannot be found in the manuscript. The corresponding sulfur loading and content and the related\nelectrolyte-to-sulfur ratio are suggested to be reported together for a reference and for a comparison. The amount of lithium is\nsuggested to be reported.\n[Suggestion] Please report on the necessary cell-fabrication parameters.\n(5) After reviewing the introduction and references, it is suggested to provide a more comprehensive literature survey.\nSeveral recent studies have reported cathode fabrication methods involving heat and pressing treatments, many of which\nare closely related to the present work. Incorporating a discussion of these studies could help position this research within\nthe current landscape and highlight its novelty.\n[Suggestion] Please consider expanding the introduction and discussion sections to include recent advances in cathode\ndesign using thermal and pressure-assisted treatments.", "reviewer_3": "This manuscript presents a solvent- and binder-free approach for fabricating sulfur-carbon composite cathodes via thermally\nassisted dry-pressing, leveraging sulfur’s softening behavior to serve as an intrinsic binder. The experimental work is well\nexecuted and supported by structural characterizations, in-situ observations, and mechanical simulations. The study\naddresses a practical and timely issue in green and scalable manufacturing of Li–S batteries, achieving long cycle life and\ncompetitive capacity metrics. However, the conceptual novelty of the work is limited. The central idea is largely based on the\nwell-known thermal softening behavior of sulfur and does not introduce fundamentally new mechanisms in materials design\nor electrochemistry. Moreover, the role of sulfur as a persistent structural binder under cycling conditions is not convincingly\ndemonstrated. The manuscript also lacks a clear differentiation from existing binder-free cathode strategies. In its current\nform, the work does not meet the originality and mechanistic depth expected for publication in Nature Communications.\nComments\nComment 1. The manuscript lacks experimental or theoretical validation that sulfur retains binding capability after being\nconverted into soluble polysulfides.\nComment 2. While ex-situ images demonstrate morphological integrity, they do not adequately explain how the electrode\nresists internal fracture or delamination under repeated volume changes.\nComment 3. Comparison with prior binder-free strategies is insufficient. Previous studies using melt-infiltration, porous\ncarbons, or 3D scaffolds have pursued similar goals.\nComment 4. There is no quantitative modeling or correlation to electrochemical performance metrics such as impedance,\ndiffusion kinetics, or polarization behavior. This weakens the causal link between electrode structure and performance.\nComment 5. The manuscript emphasizes the industrial potential of the method but omits key details such as roll-to-roll\nprocess compatibility, throughput, or large-area uniformity. More discussion or preliminary validation would be necessary.\nComment 6. The SEM image in Figure 2 is difficult to interpret. It is recommended to include both a magnified view and a\nlower-magnification overview to aid in visual comprehension of the particle morphology and packing behavior.", "reviewer_4": "This work presents a new way to fabricate solvent-free Li/S batteries with reduced fabrication costs and improved\nperformance. The work is interesting and well written. However, to be accepted by Nature Communications, the following\nissues should be considered.\n1. Figure 1 b, clarify the procedure you used to characterise the powder rheology – usually this is performed by shear cell, or\nFT4.\n2. Line 125, clarify if you are using 50 mm powder bed - This seems strange to describe the thin electrode behaviour.\n3. Figure 1 g-j,\n(1) Are you using ROCKY to quantify the particle deformation? please clarify if FEM approach is used in ROCKY module, if\nyes, can you extract the pressure acting on the punch? to calibrate your simulation results.\n(2) need to specify the simulation parameters and calibration procedure of bond model used for the simulation.\n(3) the spherical particle approximation may not be suitable to describe sulphur particles.\n(4) Line 407-408, where did you find the general relationships of particle property and temperature.\nIn general, this part needs more experimental/theoretical support to make sure your finding sound enough!\n4. Figure 4, will the compressing level significantly affect the battery performance?\n5. By using the CT-scan microstructures, do the authors need to add some transport/electrochemical simulation results to\nindicate the mesoscale effect on the electrochemical property?\nMinor errors\n1. Table S1, ‘kg’ should be deleted for the amount of elemental sulfur."}, "author_response": "Responses to Reviewers’ Comments\nResponses to the reviewer's comments:\nIn the following pages, we have provided detailed and complete responses to the reviewer's\ncomments and observations made to the manuscript (Research Article, No. NCOMMS-25-41503)\nentitled, \"Unveiling Sulfur as a Binder for High-Performance Polymer-Free Sulfur-Carbon\nCathodes via Solvent-Free Fabrication\". The revised or newly added contents have been\nhighlighted in yellow in both the revised Manuscript and Supplementary Information. These\nchanges are also marked in yellow in this response to the reviewers' comments.\nReviewer #1\nOverall comment: The contribution by An et al reports on the preparation of S cathode for Li/S\nbatteries based on powder processing without polymer binder. The sulfur is used as binder in this\ncase. Overall the contribution is timely and well written. The materials are well characterized by\nvarious methods including SEM, XRD etc. and electrochemical characterization is extensive. A\nmajor question is the stability after cycling as the binder Sulfur is consumed and should transform\nto Li S. Post mortem analyses could be more comprehensive in this sense to shine light on this\n2\naspect.\nResponse: We greatly appreciate the reviewer for positive comments. We hope that our\nrevisions have addressed the reviewer’s concerns. Point-to-point replies to the reviewer’s\ncomments are listed below.\nComment 1-1: The crystallographic analysis of sulfur is not so clear. The authors should state\nwhich modifications of sulfur are formed in the electrode (alpha, beta etc.). The peak shift is not\nexplained well. What is the origin? This seems to be an artefact. It is recommended to measure\nwith a NIST Si internal standard to confirm the peak shift. Moreover, the amount of amorphous\nsulfur should be quantified.\nResponse: We appreciate the reviewer’s feedback regarding the crystallographic analysis of\nsulfur. In our study, the diffraction peaks observed in all samples match well with the JCPDS\ncard No. 08-0247, which corresponds to orthorhombic α-sulfur (S )—the thermodynamically\n8\nstable allotrope at ambient conditions. To address concerns about peak alignment, we used the\ndiffraction peak of the carbon-coated Al substrate (marked with green diamonds in Fig. 3a) as\nan internal reference to align the patterns, rather than a standard Si, given the binder-free\nelectrode configuration. The observed slight shift of the (222) peak upon pressing at 80 °C\ncompared to that of RT-pressed cathodes is attributed to thermomechanical strain or local\ndistortion within the α-sulfur lattice during compression. To clarify this point, the following\nstatements have been revised or newly added in the revised manuscript.\n- In Result and Discussion section of the revised Manuscript:\nXRD (Fig. S6) shows crystalline α-sulfur (JCPDS 08-0247) in the composite,\n- In Result and Discussion section of the revised Manuscript:\nThe shift and associated peak shape distortion of α-sulfur in 80 °C-pressed cathodes suggest\nthermomechanical strain or local lattice distortion within α-sulfur, likely facilitating\nimproved particle–particle cohesion and mechanical integrity in the composite electrode.\nTo further investigate the structural state of sulfur in the S–C composite, we performed\nlaboratory-based total scattering measurements and pair distribution function (PDF) analysis\n(Fig. S7). While direct quantification is still challenging due to the confinement of sulfur within\nthe porous carbon matrix, we made efforts to investigate the presence of non-crystalline sulfur.\nThe broadened features in I(Q) and S(Q), along with the attenuation of long-range correlations\nin G(r), clearly indicate partial amorphization of sulfur within the composite. Although this\nmethod does not allow precise quantification of amorphous content, it supports the existence\nof amorphous sulfur domains confined within the porous host. The following statements and\nreferences have been incorporated into the revised manuscript, and the corresponding PDF\nresults and discussion have been included in the revised Supplementary Information.\n- In Results and Discussion section of the revised Manuscript:\nand to further investigate local structural features including non-crystalline sulfur, we\nperformed pair distribution function (PDF) analysis for elemental sulfur and S-C composite\n(Fig. S7). Compared to elemental sulfur, the S–C composite exhibited broadened features\nin I(Q) and S(Q),[36,37] along with diminished long-range correlations in G(r),[38,39]\nindicating the presence of amorphous sulfur domains. The preservation of nearest-neighbor\nS–S distances further suggests that local sulfur bonding is retained despite structural\ndisorder induced by confinement within the porous carbon matrix.\n- In References section of the revised Manuscript:\n36. Zhang, L. et al. Chanin breakage in the supercooled liquid-liquid transition and re-\nentry of the λ-transition in sulfur. Sci. Rep. 8, 4558 (2018).\n37. Winter, R., Egelstaff, P. A., Pilgrim, W.-C. & Howells, W. The structural properties\nof liquid, solid and amorphous sulphur. J. Phys.: Condens. Matter 2, SA215–SA218\n(1990).\n38. Shiotani, S. et al. Pair distribution function analysis of sulfide glassy electrolytes for\nall-solid-state batteries: Understanding the improvement of ionic conductivity under\nannealing condition. Sci. Rep. 7, 6972 (2017).\n[39] Yamaguchi, H. et al. Local structure of amorphous sulfur in carbon-sulfur\ncomposites for all-solid-state lithium-sulfur batteries. Commun. Chem. 8, 10 (2025).\n- In Methods section of the revised manuscript:\nPDF measurements were performed using a STOE STADI 60 P transmission X-ray\ndiffractometer equipped with an Ag Kα source (λ = 0.55941 Å; 40 kV, 40 mA) and a\n1\ncurved Ge(111) monochromator. Diffraction patterns were collected in Debye–Scherrer\ngeometry using four stationary MYTHEN2 R 1K silicon strip detectors covering a 2θ range\nof 2°–140° (Qₘₐₓ = 21 Å-1). Samples were sealed in spinning borosilicate glass capillaries\n(0.50 mm outer diameter, 10 µm wall thickness) to minimize preferred orientation and\nenhance statistical averaging. Each sample was measured for 24 h, and background\nscattering was subtracted using data from an identically measured empty capillary. The 1D\ndiffraction patterns were processed with PDFgetX3 to yield the background-subtracted\nintensity I(Q), structure function S(Q), reduced function F(Q), and real-space pair\ndistribution function G(r). [39,62]\n- In References section of the revised Manuscript:\n39. Yamaguchi, H. et al. Local structure of amorphous sulfur in carbon-sulfur composites\nfor all-solid-state lithium-sulfur batteries. Commun. Chem. 8, 10 (2025).\n62. Juhás, P., Davis, T., Farrow, C. L. & Billinge, S. J. L. PDFgetX3: a rapid and highly\nautomatable program for processing powder diffraction data into total scattering pair\ndistribution functions. J. Appl. Cryst. 46, 560−566 (2013)\n- In the revised Supplementary Information:\nFigure S7 Pair distribution function analysis comparing elemental sulfur (black) and the\nsynthesized S–C composite (red): a) background-subtracted scattering intensity I(Q), b)\ntotal scattering structure function S(Q), c) reduced structure function F(Q), d) real-space\npair distribution function G(r).\n- In the revised Supplementary Information:\nThe diffraction profiles of the melt-diffused S/C composite exhibit broadened features in\nI(Q) and S(Q) relative to the sharp Bragg peaks observed in elemental sulfur, particularly\naround q ≈ 1.7 Å⁻¹. This broadening signifies partial amorphization of sulfur as it diffuses\ninto the porous carbon framework. Further evidence is provided by the real-space pair\ndistribution function, G(r), where the melt-diffused sample displays a notable attenuation\nof long-range correlations beyond ~5 Å, in contrast to the extended order seen in elemental\nsulfur. Nevertheless, the characteristic nearest-neighbor S–S distances at 2.1 Å, 3.4 Å, and\n4.5 Å are preserved, indicating the local S–S bonding is maintained. Additionally, a minor\ndistance at 1.4 Å appears exclusively in the melt-diffused sample, which is attributed to the\ncarbon framework in the S-C composite. These results collectively confirm the presence of\namorphous sulfur domains formed through melt infiltration and confinement within the\nporous carbon matrix.\nComment 1-2: “Improving transport” is a vague statement.\nResponse: We appreciate the reviewer’s comment regarding the need to clarify the phrase\n“improving transport.” We have revised the text to specify that the reduction in tortuosity\nobserved in the 80 °C-pressed cathode is expected to facilitate Li-ion migration by providing\nmore direct ion pathways and minimizing diffusion resistance. The following statement have\nbeen added to the revised manuscript.\n- In Results and Discussion section of the revised Manuscript:\nThe reduction in tortuosity is expected to facilitate more efficient Li-ion migration by\nshortening diffusion paths, which can contribute to improved rate capability and\nelectrochemical uniformity during cycling.\nComment 1-3: “faster absorptivity” is very qualitative: provide numbers on wetting behavior like\ncontact angle. It would be good to also analyze electrode swelling after electrolyte wetting vs. dry\nelectrode. KB electrodes significantly expand typically with DME/DOL.\nResponse: Thank you for the valuable comments. We appreciate the reviewer’s careful reading\nand constructive suggestions, which helped improve the clarity and scientific rigor of the\nmanuscript. In response to the comment, we have revised the relevant sentence to provide\nadditional detail and quantitative context. The revised statement has been incorporated into the\nmanuscript, and the wetting test images after 2 s have been updated in the revised\nSupplementary Information.\n- In Results and Discussion section of the revised Manuscript:\nThe binder-free cathodes display more rapid and uniform electrolyte absorption, with\ncontact angles of 17° and 14° after 0.02 s for RT-pressed and 80 °C-pressed samples,\nrespectively, compared to 23° for the slurry-cast S–C composite cathode. This enhanced\nwettability is attributed to their more homogeneous porosity and structural integrity (Fig.\nS19).\n- In Result and Discussion section of the revised Manuscript:\nAfter 2 s, the RT-pressed electrode shows surface swelling and irregularity (Fig. S19),\nindicating localized expansion and reduced mechanical stability. In contrast, the 80 °C-\npressed and slurry-cast electrodes maintain flat, intact surfaces, suggesting better structural\nresilience.\n- In the revised Supplementary Information:\nFigure S19. Electrolyte wetting experiment on the a) RT-pressed, b) 80 °C-pressed, and c)\nslurry-cast S-C composite cathodes using a high-speed camera.\nComment 1-4: Cycling behavior. This probably reflects more the instability of Li anode than\ncathode. A better way to monitor cathode cycling stability alone is to work with symmetric cathode\ncells.\nResponse: We agree with the reviewer that conventional Li/S cell cycling can obscure cathode-\nspecific behavior due to concurrent instability of the Li metal anode. To address this, we\nperformed galvanostatic cycling of S/Li S symmetric cells, in which a lithiated cathode (Li S-\n2 2\ncontaining) was paired with a fresh S/C cathode under identical electrolyte and cell\nconfiguration conditions (Fig. S24). Since both electrodes are based on S/C composites and\nthus lack a native lithium source, the lithiated cathode was prepared by fully discharging a Li/S\ncell to convert sulfur into Li S prior to assembly. This configuration isolates cathode behavior\n2\nby eliminating the influence of a Li-metal anode. To address this, we performed galvanostatic\ncycling of S/Li S cells in which a lithiated cathode (Li S-containing) was paired with a fresh\n2 2\nS/C cathode under identical electrolyte and cell configuration conditions (Fig. S24). This\nconfiguration isolates cathode-side phenomena by removing contributions from Li metal. The\nsymmetric cell results reveal a clear distinction between RT-pressed and 80 °C-pressed\nelectrodes. The RT-pressed electrode shows high initial charge overpotentials and premature\ndischarge cutoff, indicating sluggish Li S oxidation and limited reversibility. In contrast, the\n2\n80 °C-pressed electrode exhibits low charge polarization from the first cycle and progressive\nimprovement in discharge behavior, suggesting enhanced electrochemical reversibility. These\nresults are consistent with the superior structural cohesion, improved interparticle connectivity,\nand more uniform Li S distribution previously observed in the 80 °C-pressed samples. The\n2\nfollowing statements and figures have been added in the revised manuscript and supplementary\ninformation, respectively.\n- In Results and Discussion section of the revised Manuscript:\nS/Li S cell testing (Fig. S24) in which a lithiated cathode (Li S-containing) was paired with\n2 2\na fresh S/C cathode further confirmed enhanced reversibility in 80 °C-pressed cathodes,\nwhich exhibited lower charge polarization and more stable cycling behavior compared to\nRT-pressed samples, consistent with improved structural integrity and Li S distribution.\n2\n- In Methods section of the revised Manuscript:\nS/Li S symmetric cells were fabricated as follows. Since both electrodes are based on S/C\n2\ncomposites and thus lack a native lithium source, the lithiated cathode was prepared by\nfully discharging a Li/S cell to convert sulfur into Li S, electrochemically, after\n2\nwhich the discharged cells were disassembled in an Ar-filled glovebox to recover the\nlithiated cathodes. A new symmetric cell was then assembled using the collected Li S\n2\ncathode as the positive electrode and a fresh S/C cathode (identical in mass loading and\nfabrication condition) as the negative electrode. The symmetric cells were rested for 24 h\nbefore galvanostatic cycling at 0.2 C (1 C = 1675 mAh g⁻¹) between −1 V and 1 V, using a\n2-hour cutoff for both charge and discharge steps.\nFigure S24. Galvanostatic cycling profiles of S-Li S symmetric cells in which a lithiated\n2\ncathode (Li S-containing) was paired with a fresh S/C cathode. Tests were conducted at\n2\n0.2 C (1 C = 1675 mAh g⁻¹) within −1 V to 1 V, with a 2 h cutoff per step.\nComment 1-5: RT-pressed cells are a poor benchmark. It’s easy to outperform a bad standard.\nRefer to literature and a standard electrode with PTFE binder to compare in fair way.\nResponse: We appreciate the reviewer’s comment regarding the use of RT-pressed cathodes as\na benchmark. Our intent in including the RT-pressed cathode was not to serve as a low baseline\nfor performance comparison, but rather to evaluate the impact of processing temperature—an\nimportant parameter in solvent-free electrode fabrication—on electrode structure and\nelectrochemical properties. The contrast between RT- and 80 °C-pressed electrodes allows us\nto systematically investigate how thermomechanical effects during compression influence\nporosity, tortuosity, interfacial contact, and ultimately cell performance.\nTo ensure fair and meaningful comparison with state-of-the-art sulfur cathodes, we\npreviously compiled a summary of recent literature in Table S2 in the original manuscript,\nwhich includes key electrochemical performance metrics (initial capacity, cycling stability,\nsulfur loading, binder type, etc.). Our composite cathode shows competitive or superior cycling\nstability across a range of sulfur loadings (1, 3, and 5 mg cm-2) and E/S ratios, even without\nusing polymeric binders. As the reviewer correctly pointed out, however, PTFE-based\nelectrodes—which are particularly relevant for dry-processing—were previously missing from\nthis comparison table. We have now added representative PTFE-based sulfur cathode studies\nto Table S2 to more comprehensively contextualize our results. These additions help to further\nvalidate the strong performance of our binder-free, solvent-free processed electrodes relative\nto both slurry-cast and dry-processed counterparts. The following articles have been cited in\nTable S2 in the revised Supplementary Information.\n- In Supporting Reference section of the revised Supplementary Information:\n[S15] Hu, J.-K. et al. Dry electrode technology for scalable and flexible high-energy sulfur\ncathodes in all-solid -state lithium-sulfur batteries. J. Energy Chem. 71, 612–618 (2022).\n[S16] Fiedler, M. et al. Mechanistic insights into the cycling behavior of sulfur dry-film\ncathodes. Adv. Sustainable Syst. 7, 2200439 (2023).\n[S17] Sul, H., Lee, D. & Manthiram, A. High-loading lithium-sulfur batteries with solvent-\nfree dry-electrode processing. Small 20, 2400728 (2024).\nComment 1-6: low loading in cathode makes it easy to get high cycling stability. Only 1 mg/cm2\nand E/S = 10! This will never give a high specific energy. E/S < 3 needed and at least 3 mg/cm2.\nPlease also provide data for higher loading and lower E/S. Pouch cell data would be better.\nLimitations of coin cells are well documented in literature but not cited.\nResponse: We thank the reviewer for highlighting the limitations of low-loading electrodes\nand high electrolyte-to-sulfur (E/S) ratios in Li/S cells. We fully agree that achieving practically\nrelevant specific energy requires high sulfur loading (>3 mg cm-2) and low E/S ratios\nS\n(<3 μL mg-1). In this study, in addition to 1 and 3 mg cm-2 cathodes with E/S ratio of 7 and 5,\nS\nrespectively, (Figure 4) we also evaluated higher-loading electrodes (5 mg cm-2) with E/S\nS\nratios of 5, as presented and Fig. S21 of the revised manuscript (Figures are shown below). The\n80 °C-pressed cathodes with those areal loadings demonstrated cycling stability over 200\ncycles and 50 cycles for the 3 mg cm-2 and 5 mg cm-2 electrodes, respectively. While the E/S\nratios are not as low as those referenced in the reviewer’s comment, we believe the presented\ndata support the feasibility and stability of our composite electrode design under more\npractically relevant conditions. Low-loading cathodes were employed during early-stage\nevaluation to enable more uniform sulfur distribution, improved electrolyte wetting, and\nenhanced reaction kinetics, which facilitate the assessment of intrinsic material properties of\ncathodes.\nFigure S21. Electrochemical performance of the slurry cast S-C composite cathodes with areal\nmass loading of 5 mg cm². a) Rate capability test results, b) cycle performance comparison,\nS\nvoltage profiles of c) RT-pressed, d) 80 °C-pressed, and e) slurry-cast S-C composite cathodes at\nvarious C-rate (1 C = 1675 mAh g 1) and Nyquist plot of f) RT-pressed, g) 80 °C-pressed, and\nS\nh) slurry-cast S-C composite cathodes, measured at the fully charged state before and after 50\ncharge-discharge cycling.\n- In Methods section of the revised Manuscript:\nThe electrolyte-to-sulfur ratio (E/S) was set to 10 for 1 mgS cm-2 electrodes, 7 for 3 mgS\ncm-2 and 5 for 5 mgS cm-2 electrodes.\nResponse: Regarding the use of coin cells, we agree that pouch cells provide more realistic\nsystem-level information, especially for evaluating E/S ratios, mechanical constraints, and\npractical energy density. This has been addressed in the revised manuscript, where we now cite\nprior literature that discusses the limitations of coin cells in practical relevance studies. The\nfollowing sentences have been added, and research articles have been cited in the revised\nmanuscript.\n- In Results and Discussion section of the revised Manuscript:\nWhile pouch cells are important for assessing practical energy metrics,[40−42] coin cells\nwere used to enable controlled evaluation of the intrinsic properties of the newly developed\nsulfur cathodes in this work.\n- In References section of the revised Manuscript:\n40. Xing, C., Chen, H. & Zhang, S. Powering 10-Ah-level Li-S pouch cell via a smart\n“skin”. Matter 5, 2523–2525 (2022).\n41. Das, S. et al. Optimization of the form factors of advanced Li-S pouch cells. Small\n20, 2311850 (2024).\n42. Yari, S., Reis, A. C., Pang, Q. & Safari, M. Performance benchmarking and analysis\nof lithium-sulfur batteries for next-generation cell design. Nat. Commun. 16, 5473 (2025).\nComment 1-7: Wavelength of Ag radiation should be given and also mentioned in XRD figure for\nclarification.\nResponse: We appreciate the reviewer’s comment regarding the missing information. The\nwavelength of XRD sources have been added in the revised manuscript.\n- In Methods section of the revised Manuscript:\nOperando XRD (STADI P STOE Dual Transmission, Ag-Kα source, λ = 0.55941 Å, 40 kV,\n40 mA) for heating was conducted to study the thermal behavior of elemental sulfur (sulfur\nnano-powder, Skyspring).\n- In Results and Discussion section of the revised Manuscript:\nThe crystal structure of the S-C composite was scanned between 10 and 70 2θ degree using\nCu-Kα source XRD (PANalytical Aeris Malvern, λ = 1.54060 Å, 40kV, 15mA).\n- In Results and Discussion section of the revised Manuscript:\nThe crystallographic structure of the S–C composite cathodes were characterized by XRD\nusing a Cu Kα radiation source (PANalytical Aeris, Malvern; λ = 1.54060 Å, 40kV, 15mA).\nComment 1-8: Critical references (reviews) on Dry processing as well as Li/S batteries are\nmissing! Literature is too narrow.\nResponse: We thank the reviewer for pointing out the limited scope of the literature citations\nrelated to dry processing and Li/S battery development. In response, we have revised the\nManuscript and Supplementary Information to include additional review articles that\nsummarize recent progress and ongoing challenges in both areas. The following sentences have\nbeen added and research articles on dry processing of sulfur cathode have been cited in the\nrevised manuscript.\n- In Results and Discussion section of the revised Manuscript:\nRecent reviews have highlighted growing interest in dry-fabrication of sulfur cathodes for\nLi/S batteries to improve manufacturing efficiency and interface control.[21−24]\n- In References section of the revised Manuscript:\n21. Kim, N.-Y. et al. Material challenges facing scalable dry-processable battery\nelectrodes. ACS Energy Lett. 9, 5688–5703 (2024).\n22. Jin, W. et al. Advancements in dry electrode technologies: Towards sustainable and\nefficient battery manufacturing. ChemElectroChem 11, e202400288 (2024).\n23. Hong, T. H., Kim, D. J., Ko, S. M. & Lee, J. T. Solvent-free dry-process for\ndeveloping high-performance lithium-sulfur batteries. Korean J. Chem. Eng. 42, 1475–\n1490 (2025).\n24. Park, J. et al. Sustainable and cost-effective electrode manufacturing for advanced\nlithium batteries: the roll-to-roll dry coating process. Chem. Sci. 16, 6598–6619 (2025).\nThank you very much for the valuable comments. Your comments significantly improved the\nquality of the manuscript.\nReviewer #2\nOverall comment: This Research Paper NCOMMS-25-41503, entitled “Unveiling sulfur as a binder for high-performance polymer-free sulfur-carbon cathodes via solvent-free fabrication,”\nreports a novel, scalable, and environmentally friendly method for fabricating binder- and solvent-\nfree sulfur–carbon composite cathodes for lithium–sulfur cells via thermal-assisted dry pressing\ndirectly onto aluminum foil. By using sulfur’s intrinsic softening and adhesive properties, the\nprocess eliminates the need for polymeric binders and toxic solvents. Thus, the heat-roll pressed\ncathode simplifies the electrode fabrication and achieves a high reversible capacity of 932 mAh\ng⁻¹ over 500 cycles at a 1C rate. The use of low-cost commercial porous carbon further enhances\nthe practical relevance of the approach, which also reduces production costs by more than 50%.\nThis research reports the novel fabrication design and optimization for lithium–sulfur battery\ncathodes with comprehensive analysis and study. The following minor revisions are suggested to\nfurther improve the clarity and impact of the work.\nResponse: We sincerely thank the reviewer for the constructive and encouraging feedback. We\nhave carefully revised the manuscript in response to the comments, and we hope that our\nrevisions satisfactorily address all concerns. Point-by-point responses to each comment are\nprovided below.\nComment 2-1: For the fundamental concept, sulfur would be served as both the active material\nand the binder in the heat-roll pressed cathode. During cycling sulfur becomes liquid-state\npolysulfides, this solid-liquid conversion would weaken the electrode structure. Moreover,\npolysulfides would convert to sulfur and sulfide during charge and discharge. The relocation and\nreformation of solid-state active material during cycling do not have heat and pressure to support\nthe stability of the heat-roll pressed cathode. These concerns can be discussed. [Suggestion] Please\nconsider having a discussion on the cathode stability during polysulfide formation and its\nnucleation toward sulfur and sulfide.\nResponse: We thank the reviewer for raising an important point regarding the structural\nstability of the cathode during the solid–liquid–solid transitions associated with polysulfide\nformation and sulfur re-nucleation. We fully agree that these conversion reactions pose a\nsignificant challenge for maintaining electrode stability, especially in binder- and solvent-free\nconfigurations. To address this, we have revised the manuscript to include a discussion on how\nthermomechanical compression at 80 °C enhances the structural robustness of the cathode and\nmitigates degradation during cycling. In response, we have added a discussion to the revised\nmanuscript highlighting how thermomechanical compression (via 80 °C pressing) contributes\nto maintaining electrode integrity throughout cycling.\nIn addition, to further examine whether sulfur retains its mechanical binding functionality\neven after partial conversion to soluble species, we conducted ex-situ SEM imaging at 40%\ndepth of discharge (DOD). The following sentence has been added in the revised manuscript.\nThese data indicate that the 80 °C-pressed electrodes maintain structural cohesion even at the\nearly stages of electrochemical cycling, while RT-pressed electrodes exhibit surface irregularity\nand local fracture. As highlighted in literature such as Wujcik et al. [J. Electrochem. Soc. 164,\nA18-A27 (2017)], sulfur conversion reactions do not proceed uniformly across the entire\nelectrode. Heterogeneous distribution of Li S and Li S species, along with residual elemental\n2 2 2\nsulfur and soluble polysulfides, may coexist during intermediate cycling stages. This spatial\nheterogeneity could allow certain domains of the electrode to retain solid-state binding\ncapability, thereby preserving local structural integrity even in the absence of conventional\nbinders. We emphasize that while the current experimental results support the hypothesis that\nthermomechanically compressed sulfur can retain binding functionality during partial\nconversion, a complete mechanistic understanding of the solid–liquid–solid transitions and\ntheir spatial distribution within the electrode remains an open question. Further investigation—\npotentially involving in situ or operando characterization techniques combined with mesoscale\nmodeling—will be required to fully elucidate the mechanisms by which structural cohesion is\npreserved during cycling. The following statement and literature have been added in the revised\nManuscript and the ex-situ SEM images of S-C cathodes at 40 % DOD have been added in the\nrevised Supplementary Information.\n- In Results and Discussion section of the revised Manuscript:\nAdditional ex-situ SEM images collected at ~40% depth of discharge at the initial discharge\nprocess reveal that the 80 °C-pressed cathodes retain structural cohesion during early\nelectrochemical cycling (Fig. S23). This observation, together with prior findings that\nsulfur conversion does not occur uniformly across the electrode,[52] suggests that partially\nunreacted sulfur and early-stage Li Sₓ species can coexist, allowing localized structural\n2\nretention during the formation of discharge products. Importantly, the observations suggest\nthat the initial mechanical integrity provided by heat-pressing plays a critical role in\nmitigating the potential structural weakening associated with the electrochemical solid–\nliquid–solid transition of sulfur during cycling. Although polysulfide formation and\nsubsequent sulfur precipitation inherently involve relocation of active material, the 80 °C-\npressed cathode preserves a cohesive framework that accommodates these transformations\nwithout particle detachment or severe cracking, as confirmed by ex-situ SEM. S/Li S cell\n2\ntesting (Fig. S24) in which a lithiated cathode (Li S-containing) was paired with a fresh\nexhibited lower charge polarization and more stable cycling behavior compared to RT-\npressed samples, consistent with improved structural integrity and Li S distribution.\nnot only ensures intimate interparticle contact at the outset but also helps preserve the\nelectrode architecture throughout repeated Li/S redox cycles, as summarized in Fig. 5e and\n5f.\n- In Methods section of the revised Manuscript:\nEx-situ SEM was performed on electrodes obtained at approximately 40% DOD during the\ninitial discharge cycle or after five charge-discharge cycles. For 40 % DOD cathode, coin-\ntype half-cells were disassembled inside an Ar-filled glove box after reaching the targeted\ndischarge capacity. The cathodes were gently rinsed with anhydrous DOL/DME mixture\nsolution to remove residual electrolyte and lithium salts, followed by vacuum drying at RT\nfor 2 hours. Surface morphology was examined using a field-emission scanning electron\nmicroscope (Auriga Zeiss) operated at 5 kV accelerating voltage.\n- In Reference section of the revised Manuscript:\n52. Wujcik, K. H. et al. In situ X-ray absorption spectroscopy studies of discharge\nreactions in a thick cathode of a lithium sulfur battery. J. Electrochem. Soc. 164, A18–A27\n(2017).\n- In the revised Supplementary Information:\nFigure S23. Ex-situ SEM images of S-C cathodes collected at 40% depth of discharge at\nthe initial discharge process. (a) RT-pressed cathode, (b) 80 oC-pressed cathode.\nComment 2-2: In the electrochemical analysis, the discharge/charge efficiency of the heat-roll\npressed cathode would decrease during cycling and would decrease to less than 90%. However, 5\nmg cm-2 cathode shows the discharge/charge efficiency of over 100%. These issues are suggested\nto be addressed and discussed. With this concern, discharge/charge efficiency is suggested to be\nreported in all electrochemical analysis, including cycling and rate performances. [Suggestion]\nPlease address the issues of discharge/charge efficiency, including the missing data, the decrease\nin electrochemical efficiency, and the efficiency of over 100%.\nResponse: We thank the reviewer for the insightful comment regarding the discharge/charge\nefficiency of the cathodes and the suggestion to report it consistently across all electrochemical\nanalyses. As the reviewer mentioned, the Coulombic efficiency values exceeding 100%, mainly\nobserved in the 80 °C-pressed cathodes with high sulfur loading (5 mg cm-2), are not found in\nthe RT-pressed or slurry-cast counterparts. This phenomenon could be attributed to the distinct\nstructural and electrochemical characteristics of the 80 °C-pressed electrodes. Their compact\nand well-connected microstructure enables more complete sulfur conversion, resulting in\nhigher discharge capacities. In contrast, the RT-pressed and slurry-cast electrodes exhibit poor\nparticle interconnectivity and structural heterogeneity, which limit sulfur utilization. Moreover,\nthe uniform architecture of the 80 °C-pressed cathodes may permit delayed activation of\nelectrochemically isolated sulfur domains, gradually accessed over cycling and contributing to\napparent Coulombic efficiency values above 100%. Following statements have been added to\nthe revised manuscript and Coulombic efficiency data of the rate performance test results have\nbeen added to Fig. 4 and Figs. S20 and S21.\n- In Results and Discussion section of the revised Manuscript:\nA gradual decline in Coulombic efficiency was observed during extended cycling (Fig. 4b),\nparticularly in the RT-pressed and slurry-cast samples, indicating increasing interfacial\nresistance.\n- In Results and Discussion section of the revised Manuscript:\nWhile consistently delivering higher capacities across all C-rates in the rate performance\ntest and at 0.1 C during cycling, the 80 °C-pressed cathodes (5 mg cm⁻²) exhibited\nCoulombic efficiency values exceeding 100%, likely due to delayed activation of isolated\nsulfur domains within the sulfur cathodes, unlike the consistently lower Coulombic\nefficiency observed in the RT-pressed and slurry-cast S-C cathodes. Notably, EIS analysis\nfor the 1 and 5 mg cm-2 electrodes revealed trends consistent with those observed at\n3 mg cm-2, reinforcing the generality of the impedance behavior across various loadings\n(Fig. S20, S21, Table S9).\n- In the revised Manuscript:\nFigure 4. Electrochemical performance of RT-pressed and 80 °C-pressed S-C composite\ncathodes. a) Rate capability test results and galvanostatic charge-discharge cycling results of the\nRT- and 80 °C-pressed, and slurry cast S-C composite cathodes b) areal mass loading of 3 mg\nS\ncm⁻² at 0.2 C. Voltage profiles of c) RT-pressed, d) 80 °C-pressed, and e) slurry-cast S-C\ncomposite cathodes (1 C = 1675 mA gS⁻1). CV results of the f) RT-pressed, g) 80 °C-pressed h)\nslurry-cast S-C composite cathodes. Nyquist plot of i) RT-pressed, j) 80 °C-pressed, and k)\nslurry-cast S-C composite cathodes, measured at the fully charged state before and after 30\ncharge-discharge cycling and l) equivalent circuit model. Galvanostatic charge-discharge cycling\nresults of the RT- and 80 °C-pressed, and slurry cast S-C composite cathodes m) areal mass\nloading of 1 mg cm-2 at 1.0 C.\nS\n- In the revised Supplementary Information:\nFigure S20. Electrochemical performance of the slurry cast S-C composite cathodes with\nareal mass loading of 1 mg cm². a) Rate capability test results, voltage profiles of b) RT-\nS\npressed, c) 80 °C-pressed, and d) slurry-cast S-C composite cathodes at various C-rate (1\nC = 1675 mAh g 1) and Nyquist plot of e) RT-pressed, f) 80 °C-pressed, and g) slurry-\nS\ncast S-C composite cathodes, measured at the fully charged state before and after 30\ncharge-discharge cycling.\nFigure S21. Electrochemical performance of the slurry cast S-C composite cathodes with\nareal mass loading of 5 mg cm². a) Rate capability test results, b) cycle performance\nS\ncomparison, voltage profiles of c) RT-pressed, d) 80 °C-pressed, and e) slurry-cast S-C\ncomposite cathodes at various C-rate (1 C = 1675 mAh g 1) and Nyquist plot of f) RT-\nS\npressed, g) 80 °C-pressed, and h) slurry-cast S-C composite cathodes, measured at the\nfully charged state before and after 50 charge-discharge cycling.\nComment 2-3: In the electrochemical analysis, the electrochemical impedance analysis of the\nheat-roll pressed cathode is suggested to be analyzed with an equivalent circuit model to support\nthe corresponding discussion. The raw experimental data and the fitting data are suggested to be\nreported together as experimental data points and the fitting curves. [Suggestion] Please analyze\nthe impedance data.\nResponse: We thank the reviewer for pointing out the lack of detailed analysis of the\nelectrochemical impedance data. In response, we have revised the manuscript to include a\ncomprehensive impedance fitting analysis based on an equivalent circuit model. The revised\nversion presents both the experimental Nyquist plots and the corresponding fitted curves to\nsupport the interpretation more rigorously. In addition, the fitted values for each circuit element,\nalong with the complete EIS fitting plots, have been provided in Table S9 in the updated\nSupplementary Information.\n- In Results and Discussion section of the revised Manuscript:\nEIS analysis performed at the charged state after 30 cycles (Figs. 4i4k and Table S9) revealed\ndistinct trends for each electrode type. The 80 °C-pressed cathode maintained low impedance,\nwhile both the RT-pressed and slurry-cast electrodes exhibited notable increases in ohmic\nresistance (R ). The rise in R for the RT-pressed electrode suggests compromised structural\ns s\nintegrity, likely due to mechanical degradation during cycling,[43–45] whereas the thermally\ncompressed 80 °C-pressed electrode retained a stable architecture. Similarly, the increase in R\ns\nfor the slurry-cast electrode is consistent with previous reports that conventional slurry\nprocessing can lead to solvent-induced inhomogeneity and poor interfacial stability issues.[46–\n48]\n- In Results and Discussion section of the revised Manuscript:\nNotably, EIS analysis for the 1 and 5 mg cm-2 electrodes revealed trends consistent with those\nobserved at 3 mg cm-2, reinforcing the generality of the impedance behavior across various\nloadings (Figs. S20 and S21, Table S9).\n- In Results and Discussion section of the revised Manuscript:\nFigure 4. Electrochemical performance of RT-pressed and 80 °C-pressed S-C composite\ncathodes. a) Rate capability test results and galvanostatic charge-discharge cycling results of the\nRT- and 80 °C-pressed, and slurry cast S-C composite cathodes b) areal mass loading of 3 mg\nS\ncm⁻² at 0.2 C. Voltage profiles of c) RT-pressed, d) 80 °C-pressed, and e) slurry-cast S-C\ncomposite cathodes (1 C = 1675 mA gS⁻1). CV results of the f) RT-pressed, g) 80 °C-pressed h)\nslurry-cast S-C composite cathodes. Nyquist plot of i) RT-pressed, j) 80 °C-pressed, and k)\nslurry-cast S-C composite cathodes before and after 30 charge-discharge cycling and l) equivalent circuit model. Galvanostatic charge-discharge cycling results of the RT- and 80 °C-\npressed, and slurry cast S-C composite cathodes m) areal mass loading of 1 mg cm⁻² at 1.0 C.\nS\n- In References section the revised Manuscript:\n45. Lateef, S. et al. Understanding the effects of binder dissolution dynamics on the chemistry\nand performance of lithium-sulfur batteries. EES Batteries, 1, 947−963 (2025).\n46. Horst, M. et al. A binder-free dry coating process for high sulfur loading cathodes of Li-S\nbatteries: A proof-of-concept. J. Power Sources 587, 233675 (2023).\n47. Fiedler, M. et al. Mechanistic insights into the cycling behavior of sulfur dry-film\ncathodes. Adv. Sustainable Syst. 7, 2200439 (2023).\n48. Sul, H., Lee, D. & Manthiram, A. High-loading lithium-sulfur batteries with solvent-free\ndry-electrode processing. Small 20, 2400728 (2024)\n- In the revised Supplementary Information:\nFigure S20. Electrochemical performance of the slurry cast S-C composite cathodes with areal\nmass loading of 1 mg cm². a) Rate capability test results, voltage profiles of b) RT-pressed, c)\nS\n80 °C-pressed, and d) slurry-cast S-C composite cathodes at various C-rate (1 C = 1675 mAh\ng 1) and Nyquist plot of e) RT-pressed, f) 80 °C-pressed, and g) slurry-cast S-C composite\nS\ncathodes, measured at the fully charged state before and after 30 charge-discharge cycling.\nFigure S21. Electrochemical performance of the slurry cast S-C composite cathodes with areal\nmass loading of 5 mg cm². a) Rate capability test results, b) cycle performance comparison,\nS\nvoltage profiles of c) RT-pressed, d) 80 °C-pressed, and e) slurry-cast S-C composite cathodes at\nvarious C-rate (1 C = 1675 mAh g 1) and Nyquist plot of f) RT-pressed, g) 80 °C-pressed, and\nh) slurry-cast S-C composite cathodes, measured at the fully charged state before and after 50\ncharge-discharge cycling.\nTable S9. Fitted parameters extracted from the equivalent circuit model shown in Fig. 4l,\ncorresponding to the Nyquist plots in Fig. 4i–k, Fig. S20e–g, and Fig. S21f–h.\nAreal mass\nW (Ω\no\nCathodes (mg cm2) R (Ω) CPE (µF) R (Ω) CPE (F) R (Ω)\nS s f f ct ct s−1/2)\n& Cell state\n1.0, before 1.99 2.04 59.32 4.22 × 10−2 3.10 70.2\nRT- 1.0, after 1.25 9.17 46.3 1.17 × 10−2 12.1 17.5\npressed 3.0, before 4.16 2.11 33.0 1.64 × 10−1 12.1 35.4\n3.0, after 42.1 1.73 24.7 7.16 × 10−4 21.5 3.61\n5.0, before 2.47 2.28 37.3 3.45 × 10−2 3.68 11.0\n5.0, after 19.5 3.14 22.4 3.60 × 10−1 44.1 10.9\n1.0, before 2.08 2.08 44.7 9.53 × 10−3 0.16 35.7\n1.0, after 2.26 2.31 14.5 3.99 × 10−4 1.97 3.70\n80 °C- 3.0, before 2.25 3.82 30.6 1.48 × 10−2 1.08 21.48\npressed 3.0, after 5.24 3.35 8.40 3.32 × 10−6 8.47 2.23\n5.0, before 1.24 2.51 36.6 7.56 × 10−3 7.13 21.7\n5.0, after 16.5 2.78 20.9 1.75 × 10−4 35.26 2.53\n1.0, before 7.90 1.99 60.1 3.88 × 10−2 3.64 8.48\n1.0, after 19.4 1.95 110.2 3.00 × 10−2 64.2 9.31\nSlurry- 3.0, before 5.76 3.37 34.5 1.20 × 10−4 7.13 1.70\ncast 3.0, after 45.41 2.37 35.1 9.20 × 10−4 2.64 7.86\n5.0, before 8.83 2.92 28.6 3.66 × 10−2 8.98 10.1\n5.0, after 49.6 2.81 48.5 6.14 × 10−2 36.41 3.11\nComment 2-4: The heat-roll pressed cathode is reported with the sulfur loadings of 1 to 5 mg cm-\n2. The cell-fabrication parameters of 5 mg cm-2 cathode cannot be found in the manuscript. The\ncorresponding sulfur loading and content and the related electrolyte-to-sulfur ratio are suggested\nto be reported together for a reference and for a comparison. The amount of lithium is suggested\nto be reported. [Suggestion] Please report on the necessary cell-fabrication parameters.\nResponse: Thank you for pointing this out. We would like to clarify that the use of lithium foil\nwith a thickness of 120 µm, as stated in the Experimental Section of the original manuscript,\napplies to all cells regardless of sulfur mass loading. In the revised manuscript, we have\nadditionally updated the following sentence (highlighted in yellow) to include the E/S ratio for\nthe 5 mg S cm⁻² electrode, which was previously omitted.\n- In Method section of the revised manuscript:\nThe electrolyte-to-sulfur ratio (E/S) was set to 10 for 1 mgS cm-2 electrodes, 7 for 3 mgS\ncm-2 and 5 for 5 mgS cm-2 electrodes.\nComment 2-5: After reviewing the introduction and references, it is suggested to provide a more\ncomprehensive literature survey. Several recent studies have reported cathode fabrication methods\ninvolving heat and pressing treatments, many of which are closely related to the present work.\nIncorporating a discussion of these studies could help position this research within the current\nlandscape and highlight its novelty. [Suggestion] Please consider expanding the introduction and\ndiscussion sections to include recent advances in cathode design using thermal and pressure-\nassisted treatments.\nResponse: We appreciate the reviewer’s insightful suggestion to expand the introduction and\ndiscussion with additional literature references on dry processing techniques and recent\nadvances in Li/S batteries. In response, we have revised the manuscript to include several\nrecent review articles that provide a comprehensive overview of current progress and\nremaining challenges in these areas. Furthermore, we have added citations to recent original\nresearch studies on dry-coated sulfur cathodes to contextualize our findings within the broader\nfield. These additions are reflected in the updated manuscript.\n- In the Reference section of the revised manuscript:\n21. Kim, N.-Y. et al. Material challenges facing scalable dry-processable battery\nelectrodes. ACS Energy Lett. 9, 5688–5703 (2024).\n22. Jin, W. et al. Advancements in dry electrode technologies: Towards sustainable and\nefficient battery manufacturing. ChemElectroChem 11, e202400288 (2024).\n23. Hong, T. H., Kim, D. J., Ko, S. M. & Lee, J. T. Solvent-free dry-process for\ndeveloping high-performance lithium-sulfur batteries. Korean J. Chem. Eng. 42, 1475–\n1490 (2025).\n24. Park, J. et al. Sustainable and cost-effective electrode manufacturing for advanced\nlithium batteries: the roll-to-roll dry coating process. Chem. Sci. 16, 6598–6619 (2025).\n- In the revised Supplementary Information\n[S14] Horst, M. et al. A binder-free dry coating process for high sulfur loading cathodes\nof Li-S batteries: A proof-of-concept. J. Power Sources 587, 233675 (2023)\n[S15] Hu, J.-K. et al. Dry electrode technology for scalable and flexible high-energy sulfur\ncathodes in all-solid -state lithium-sulfur batteries. J. Energy Chem. 71, 612–618 (2022).\n[S16] Fiedler, M. et al. Mechanistic insights into the cycling behavior of sulfur dry-film\ncathodes. Adv. Sustainable Syst. 7, 2200439 (2023).\n[S17] Sul, H., Lee, D. & Manthiram, A. High-loading lithium-sulfur batteries with solvent-\nfree dry-electrode processing. Small 20, 2400728 (2024).\nThank you very much for the valuable comments. Your comments significantly improved the\nquality of the manuscript.\nReviewer #3\nOverall comment: This manuscript presents a solvent- and binder-free approach for fabricating\nsulfur-carbon composite cathodes via thermally assisted dry-pressing, leveraging sulfur’s\nsoftening behavior to serve as an intrinsic binder. The experimental work is well executed and\nsupported by structural characterizations, in-situ observations, and mechanical simulations. The\nstudy addresses a practical and timely issue in green and scalable manufacturing of Li–S batteries,\nachieving long cycle life and competitive capacity metrics. However, the conceptual novelty of\nthe work is limited. The central idea is largely based on the well-known thermal softening behavior\nof sulfur and does not introduce fundamentally new mechanisms in materials design or\nelectrochemistry. Moreover, the role of sulfur as a persistent structural binder under cycling\nconditions is not convincingly demonstrated. The manuscript also lacks a clear differentiation from\nexisting binder-free cathode strategies. In its current form, the work does not meet the originality\nand mechanistic depth expected for publication in Nature Communications.\nResponse: We sincerely thank the reviewer for the thoughtful and constructive feedback. We\nhave carefully addressed all comments and revised the manuscript accordingly. We hope that\nthe revisions meet the reviewer’s expectations. Point-by-point responses to each comment are\nprovided below.\nComment 3-1: The manuscript lacks experimental or theoretical validation that sulfur retains\nbinding capability after being converted into soluble polysulfides.\nResponse: We thank the reviewer for this important comment. To address it, we performed ex-\nsitu SEM imaging on electrodes at 40% depth of discharge (DOD), as shown in the revised\nSupplementary Fig. S23. These images demonstrate that the 80 °C-pressed electrodes retain a\nmechanically cohesive framework during the early stages of electrochemical cycling, while the\nRT-pressed counterparts already exhibit signs of surface deformation and localized cracking.\nWe suggest that not all sulfur in the electrode undergoes electrochemical conversion\nsimultaneously. As discussed in the literature, including [Wujcik et al. J. Electrochem. Soc.,\n164, A18 (2017)], electrochemical and chemical reactions may proceed heterogeneously across\nthe electrode, with some regions forming solid Li S or Li S while other areas still contain\n2 2 2\nunreacted sulfur or soluble polysulfides. This spatial nonuniformity helps explain the\ncoexistence of partially converted sulfur species and maintained structural integrity in localized\ndomains, as captured in our SEM observations. We have revised the manuscript to include this\nnew data and discussion. The added content has been highlighted in yellow in the revised\nversion.\n- In Results and Discussion section of the revised Manuscript:\nAdditional ex-situ SEM images collected at ~40% depth of discharge at the initial discharge\nprocess reveal that the 80 °C-pressed cathodes retain structural cohesion during early\nelectrochemical cycling (Fig. S23). This observation, together with prior findings that\nsulfur conversion does not occur uniformly across the electrode,[52] suggests that partially\nunreacted sulfur and early-stage Li Sₓ species can coexist, allowing localized structural\n2\nretention during the formation of discharge products. Importantly, the observations suggest\nthat the initial mechanical integrity provided by heat-pressing plays a critical role in\nmitigating the potential structural weakening associated with the solid–liquid–solid\ntransition of sulfur during cycling. Although polysulfide formation and subsequent sulfur\nprecipitation inherently involve relocation of active material, the 80 °C-pressed cathode\npreserves a cohesive framework that accommodates these transformations without particle\ndetachment or severe cracking, as confirmed by ex-situ SEM.\n- In the revised Supplementary Information:\nFigure S23. Ex-situ SEM images of S-C cathodes collected at ~40% depth of discharge at\nthe initial discharge process. (a) RT-pressed cathode, (b) 80 oC-pressed cathode.\n- In Reference section of the revised Manuscript:\n52. Wujcik, K. H. et al. In situ X-ray absorption spectroscopy studies of discharge reactions\nin a thick cathode of a lithium sulfur battery. J. Electrochem. Soc. 164, A18–A27 (2017).\n- In Methods section of the revised Manuscript:\nEx-situ SEM was performed on electrodes obtained at approximately 40% DOD during the\ninitial discharge cycle or after five charge-discharge cycles. For 40 % DOD cathode, coin-\ntype half-cells were disassembled inside an Ar-filled glove box after reaching the targeted\ndischarge capacity. The cathodes were gently rinsed with anhydrous DOL/DME mixture\nsolution to remove residual electrolyte and lithium salts, followed by vacuum drying at RT\nfor 2 hours. Surface morphology was examined using a field-emission scanning electron\nmicroscope (Auriga Zeiss) operated at 5 kV accelerating voltage.\nComment 3-2: While ex-situ images demonstrate morphological integrity, they do not adequately\nexplain how the electrode resists internal fracture or delamination under repeated volume changes.\nResponse: We thank the reviewer for this insightful comment. In response, we have revised\nthe manuscript to further elaborate on the mechanisms by which the 80 °C-pressed cathodes\nresist internal fracture and delamination during repeated volume changes. A discussion\naddressing these points has been added to the revised manuscript.\n- In Results and Discussion section of the revised Manuscript:\nThese collective findings of ex-situ SEM and S/Li S symmetric cell test highlight that the\n2\nimproved morphological integrity of the 80 °C-pressed cathodes not only supports\nstructural robustness but also accommodates the chemo-mechanical stresses induced by\nrepeated sulfur redox cycling. Given that sulfur serves both as the active material and a\nstructural binder in this solvent- and binder-free system, its homogeneous distribution\nwithin the carbon matrix is particularly critical. The resulting uniform composite\narchitecture enhances interparticle cohesion and mitigates fracture propagation during\nsolid–liquid–solid transitions. This structural coherence is essential to maintaining\ncontinuous electron and ion transport pathways, preventing the detachment of active\nmaterial, and ultimately enabling prolonged cycling stability.\nComment 3-3: Comparison with prior binder-free strategies is insufficient. Previous studies using\nmelt-infiltration, porous carbons, or 3D scaffolds have pursued similar goals.\nResponse: We thank the reviewer for the valuable suggestion. To better contextualize our\napproach, we have revised the manuscript to emphasize the differences between our method\nand previous binder-free strategies that utilize melt-infiltration, porous carbon frameworks, or\n3D scaffolds. Specifically, we highlight that many prior approaches rely on nonstandard current\ncollectors and processing methods that are not compatible with scalable manufacturing, such\nas roll-to-roll coating, and often involve high-temperature or complex fabrication steps that\nincrease production costs. In contrast, our method employs a conventional aluminum foil\ncurrent collector and requires no solvents or binders, offering a more practical and cost-\neffective future direction toward scalable Li–S battery manufacturing. The following statement\nhas been added to the revised manuscript to reflect this comparison.\n- In Introduction section of the revised Manuscript:\nHowever, prior binder-free strategies often rely on specialized or nonstandard current\ncollectors that are incompatible with scalable manufacturing methods such as roll-to-roll\ncoating, ultimately increasing production costs. In some cases, high-temperature melt-\ninfiltration of sulfur into carbon substrates is also required,[29] adding to process\ncomplexity and material expenses. Moreover, these approaches typically involve rigid or\npre-structured porous carbon architectures where precise control over bulk porosity is\ndifficult to achieve. These limitations make it challenging to implement such methods in\nhigh-throughput, cost-sensitive manufacturing environments, thereby restricting their\nscalability.\n- In Reference section of the revised Manuscript:\n29. Um, K. et al. Janus architecture host electrode for mitigating lithium-ion polarization\nin high-energy-density Li-S full cells. Energy Environ. Sci. 17, 9112–9121 (2024).\nComment 3-4: There is no quantitative modeling or correlation to electrochemical performance\nmetrics such as impedance, diffusion kinetics, or polarization behavior. This weakens the causal\nlink between electrode structure and performance.\nResponse: We appreciate the comment pointing out the need for deeper interpretation of the\nimpedance data. We have revised the manuscript to include a comprehensive impedance fitting\nanalysis based on an equivalent circuit model. The revised version presents both the\nexperimental Nyquist plots and the corresponding fitted curves to support the interpretation\nmore rigorously. In addition, the fitted values for each circuit element, along with the complete\nEIS fitting plots, have been provided in Table S9 in the updated Supplementary Information.\n- In Results and Discussion section of the revised Manuscript:\nEIS analysis performed at the charged state after 30 cycles (Fig. 4i4k and Table S9) revealed\ndistinct trends for each electrode type. The 80 °C-pressed cathode maintained low impedance,\nwhile both the RT-pressed and slurry-cast electrodes exhibited notable increases in ohmic\nresistance (R ). The rise in R for the RT-pressed electrode suggests compromised structural\ns s\nintegrity, likely due to mechanical degradation during cycling,[43–45] whereas the thermally\ncompressed 80 °C-pressed electrode retained a stable architecture. Similarly, the increase in R\ns\nfor the slurry-cast electrode is consistent with previous reports that conventional slurry\nprocessing can lead to solvent-induced inhomogeneity and poor interfacial stability issues.[46–\n48]\n- In Results and Discussion section of the revised Manuscript:\nNotably, EIS analysis for the 1 and 5 mg cm-2 electrodes revealed trends consistent with those\nobserved at 3 mg cm-2, reinforcing the generality of the impedance behavior across various\nloadings (Fig. S20, S21, Table S9).\n- In the revised Supplementary Information:\nTable S9. Fitted parameters extracted from the equivalent circuit model shown in Fig. 4l,\ncorresponding to the Nyquist plots in Fig. 4i–k, Fig. S20e–g, and Fig. S21f–h.\nAreal mass\nW (Ω\no\nCathodes (mg cm2) R (Ω) CPE (µF) R (Ω) CPE (F) R (Ω)\nS s f f ct ct s−1/2)\n& Cell state\n1.0, before 1.99 2.04 59.32 4.22 × 10−2 3.10 70.2\n1.0, after 1.25 9.17 46.3 1.17 × 10−2 12.1 17.5\nRT- 3.0, before 4.16 2.11 33.0 1.64 × 10−1 12.1 35.4\npressed 3.0, after 42.1 1.73 24.7 7.16 × 10−4 21.5 3.61\n5.0, before 2.47 2.28 37.3 3.45 × 10−2 3.68 11.0\n5.0, after 19.5 3.14 22.4 3.60 × 10−1 44.1 10.9\n1.0, before 2.08 2.08 44.7 9.53 × 10−3 0.16 35.7\n80 °C- 1.0, after 2.26 2.31 14.5 3.99 × 10−4 1.97 3.70\npressed 3.0, before 2.25 3.82 30.6 1.48 × 10−2 1.08 21.48\n3.0, after 5.24 3.35 8.40 3.32 × 10−6 8.47 2.23\n5.0, before 1.24 2.51 36.6 7.56 × 10−3 7.13 21.7\n5.0, after 16.5 2.78 20.9 1.75 × 10−4 35.26 2.53\n1.0, before 7.90 1.99 60.1 3.88 × 10−2 3.64 8.48\n1.0, after 19.4 1.95 110.2 3.00 × 10−2 64.2 9.31\nSlurry- 3.0, before 5.76 3.37 34.5 1.20 × 10−4 7.13 1.70\ncast 3.0, after 45.41 2.37 35.1 9.20 × 10−4 2.64 7.86\n5.0, before 8.83 2.92 28.6 3.66 × 10−2 8.98 10.1\n5.0, after 49.6 2.81 48.5 6.14 × 10−2 36.41 3.11\nComment 3-5: The manuscript emphasizes the industrial potential of the method but omits key\ndetails such as roll-to-roll process compatibility, throughput, or large-area uniformity. More\ndiscussion or preliminary validation would be necessary.\nResponse: We thank the reviewer for emphasizing the importance of validating the industrial\nrelevance of the proposed method. As noted in our response to Comment 3-3, we have clarified\nin the revised manuscript that our binder- and solvent-free process is fully compatible with\nconventional aluminum foil current collectors and roll press-based fabrication, making it\ninherently transferable to industrial roll-to-roll platforms and well-suited for scalable\nproduction in the future. Furthermore, the manuscript demonstrates that the process allows\ncontrol over bulk porosity by adjusting the roll-gap for different pressing temperature, which\nserves as a key processing variable. Such tunable control over electrode porosity is not readily\nachievable in the previously mentioned approaches, particularly those based on three-\ndimensional porous carbon substrates, where the inherent structural rigidity and irregular\nmorphology limit precise control over electrode densification and pore structure. This\ncapability enables meaningful comparison of electrodes fabricated under different thermal\nconditions and underscores the tunability and scalability of the method. The following\nstatement has been added to the revised manuscript to reflect this comparison.\n- In Introduction section of the revised Manuscript:\nThe method is based on dry powder formation on Al foil followed by roll-pressing, both of\nwhich are compatible with continuous processing and allow control over key processing\nparameters such as areal loading and electrode porosity, highlighting its potential for\nscalable and tunable manufacturing.\nComment 3-6: The SEM image in Figure 2 is difficult to interpret. It is recommended to include\nboth a magnified view and a lower-magnification overview to aid in visual comprehension of the\nparticle morphology and packing behavior.\nResponse: We appreciate the reviewer’s helpful suggestion. In response, higher-magnification\nSEM images have been added to the Supplementary Information (Fig. S10) to better illustrate\nparticle morphology and packing characteristics. These images provide clearer contrast\nbetween the surface structure of the RT- and 80 °C-pressed composites and support the\nstructural discussion in the main text. The following statement has been added to the revised\nmanuscript and the higher magnification images have been added to the supplementary\ninformation.\n- In Results and Discussion section of the revised Manuscript:\nHigher-magnification SEM images (Fig. S10) show that RT-pressed samples exhibit\nuneven sulfur distribution with particles remaining outside aggregates, while 80 °C-pressed\nsamples exhibit more uniform morphology and sulfur distribution.\n- In the revised Supplementary Information:\nFigure S10. High magnification SEM images of S-C composite after the compression at a)\nRT and b) 80 °C.\nThank you very much for the valuable comments. Your comments significantly improved the\nquality of the manuscript.\nReviewer #4\nOverall comment: This work presents a new way to fabricate solvent-free Li/S batteries with\nreduced fabrication costs and improved performance. The work is interesting and well written.\nHowever, to be accepted by Nature Communications, the following issues should be considered.\nResponse: We sincerely thank the reviewer for the positive and encouraging feedback on our\nmanuscript. In response to the concerns raised, we have carefully revised the manuscript and\naddressed each point in detail. We hope that these revisions sufficiently clarify the issues and\nstrengthen the manuscript. Point-by-point responses are provided below.\nComment 4-1: Figure 1 b, clarify the procedure you used to characterize the powder rheology –\nusually this is performed by shear cell, or FT4.\nResponse: We thank the reviewer for the comment. A clarifying statement describing the shear\ncell-based method used for the elemental sulfur and S–C composite powder rheology test has\nbeen added to the revised manuscript.\n- In Method section of the revised Manuscript:\nPowder rheological properties were evaluated using a powder shear cell tester (TA\nInstruments, Discovery HR-20). Over 20 mL of powder was loaded into a stainless steel\ncylindrical cell (28 mm diameter). The assembly was then heated to the target\ntemperature—either RT or 80 °C—at a ramp rate of 3 °C min-1. Upon reaching the set\ntemperature, the powder was equilibrated for 5 minutes to ensure thermal uniformity\nthroughout the sample. A pre-consolidation pressure of 9 kPa was applied to condition the\npowder bed and achieve a uniform packing state. Excess powder was removed after\nconsolidation, resulting in an exact sample volume of 18 mL for shear testing. The sample\nwas then subjected to a constant shear rate (0.001 rad s-1) under fixed normal stress until\nshear failure occurred.[53] The normal stress was systematically decreased to 7, 6, 5, 4, and\n3 kPa in successive cycles, following instrument protocols. A yield locus was constructed\nby plotting the steady-state shear stress versus normal stress, and a linear fit was applied.\nUsing Mohr’s circle analysis, the unconfined yield strength (UYS) and the major principal\nstress (MPS) were extracted: (1) The first Mohr’s circle was constructed with one point at\nthe origin (0,0) and a second point tangent to the yield locus; its x-axis intersection yields\nthe UYS. (2) The second Mohr’s circle used the pre-shear point and a tangent to the yield\nlocus; its x-axis intersection defines the MPS[54−56] The flow function (FF) of the powder\nwas calculated using the UYS and MPS values, as expressed in Equation shown below.\n𝑀𝑃𝑆\n𝐹𝐹 =\n𝑈𝑌𝑆\n- In Methods section of the revised Manuscript:\nThe same shear cell-based method described above was employed to characterize the\nrheological behavior of the S–C composite powder under identical testing conditions.\n- In References section of the revised Manuscript:\n53. Krantz, M., Zhang, H. & Zhu, J. Characterization of powder flow: Static and dynamic\ntesting. Powder Technol. 194, 239–245 (2009).\n54. Rhodes, M. Storage and flow of powders-hopper design. In introduction to particle\ntechnology 2nd edn 265−292 (John Wiley & Sons, Chichester, 2008)\nhttps://doi.org/10.1002/9780470727102.ch10.\n55. Guerin, E. et al. Rheological characterization of pharmaceutical powders using tap\ntesting, shear cell and mercury porosimeter. Int. J. Pharm. 189, 91–103 (1999).\n56. Macri, D. et al. Characterization of the bulk flow properties of industrial powders\nfrom shear tests. Processes 8, 540 (2020).\nComment 4-2: Line 125, clarify if you are using 50 mm powder bed - This seems strange to\ndescribe the thin electrode behaviour.\nResponse: We thank the reviewer for the comment. The 50 mm powder bed mentioned in the\nmanuscript refers to a parameter used in the sulfur powder simulation and is not related to the\nphysical thickness of any fabricated electrode. This simulation domain size was selected to\nensure that at least ten sulfur particles with a representative diameter of ~5 mm could be\nincluded in each spatial direction, thereby allowing for statistically meaningful assessment of\nbulk powder behavior. The purpose of this simulation was to examine the intrinsic\nmorphological response and packing characteristics of elemental sulfur under idealized\nconditions, rather than to replicate the geometry of thin-film electrodes. The following\nstatement has been to the revised manuscript.\n- In Methods section of the revised Manuscript:\nThe simulation domain was sized to include at least ten sulfur particles with a representative\ndiameter of ~5 μm in each spatial direction, ensuring statistically meaningful assessment of\nbulk powder behavior.\nComment 4-3: 3. Figure 1 g-j, (1) Are you using ROCKY to quantify the particle deformation?\nplease clarify if FEM approach is used in ROCKY module, if yes, can you extract the pressure\nacting on the punch? to calibrate your simulation results. (2) need to specify the simulation\nparameters and calibration procedure of bond model used for the simulation. (3) the spherical\nparticle approximation may not be suitable to describe sulphur particles. (4) Line 407-408, where\ndid you find the general relationships of particle property and temperature. In general, this part\nneeds more experimental/theoretical support to make sure your finding sound enough!\nResponse: Thank you for your valuable feedback on our manuscript.\n(1) We clarify that ROCKY was not employed for this purpose. The primary objective of our\nsimulation was to qualitatively evaluate the influence of material properties at room\ntemperature (RT) and 80°C on the compactness of the powder bed, as observed in our\nexperimental results (see Fig. 1c and Fig. 1f). Given the unavailability of material properties\nrequired for compaction simulations at various temperatures, this approach was the most\npractical and effective choice for our study. Regarding the simulation methodology, we utilized\nANSYS Workbench, which integrates both ROCKY and Mechanical modules. The finite\nelement method (FEM) was applied exclusively within the Mechanical module, not within\nROCKY. As the focus of our study was qualitative analysis rather than quantitative comparison,\nwe did not pursue calibration of the simulation results or extraction of specific parameters such\nas the pressure acting on the punch. To clarify this, we revised the statement in the manuscript.\n- In Results and Discussion section of the revised Manuscript:\nThe simulation provides insights into particle-level deformation and densification under\nthermal and mechanical stresses, illustrating how elevated temperatures influence sulfur\nparticle rearrangement, deformation, and packing efficiency. Noted that the simulation is\ndesigned for qualitative insights rather than quantitative comparison with experimental data.\n- In Methods section of the revised Manuscript: The roll-pressing of sulfur powder bed is\nmodeled using ANSYS Workbench, a commercial software package that integrates ROCKY\nand Mechanical modules,\n(2) In this study, we employed the cohesive bond model available in ANSYS Rocky to simulate\ninterparticle forces during the compaction of sulfur powder. The model parameters were\nselected to represent the weakly cohesive and brittle nature of sulfur particles. Considering the\nsulfur particle diameter in the model (d = 5mm), a maximum elongation of 1 mm was specified,\ni\nallowing bond breakage when significant separation occurs between particles. The damping\nratio was set to 0.25 to account for energy dissipation and enhance numerical stability. A\ndistance factor of 0.1 was used to ensure that bonds form only between closely packed particles,\nmimicking realistic particle contact conditions. The normal and tangential stiffness per unit\narea were both set to 100 kN/m3 to provide moderate resistance to deformation while\nmaintaining computational efficiency. The tensile and shear stress limits were each set to 10\nkPa, reflecting the low bonding strength typical of sulfur powder. Additionally, a bond\nactivation time of 0.1 seconds was specified to allow particle rearrangement before bond\nformation, representing delayed cohesion during compaction. These values were chosen to\napproximate the mechanical behavior of loosely agglomerated particles and allow for realistic\nfracture and rearrangement during compaction. While no universally accepted bond model\nparameters exist for sulfur powder, the selected values fall within commonly reported ranges\nfor weakly cohesive granular materials and provide a practical basis for capturing the essential\nmechanics of sulfur particle compaction. Further refinement and validation can be performed\nby calibrating against experimental data such as stress-strain response or final compact density.\nWe did not perform a calibration of the bond model, as it was not essential for the primary\nobjective of this simulation. The goal was to investigate how different material properties at\nRT and 80 °C influence the compactness of the powder bed, as qualitatively observed in our\ncompaction experiments (see Fig. 1c and Fig. 1f). While we acknowledge that a quantitative\nanalysis and a detailed comparison between simulation and experimental results would require\ncalibration of the bond model, such an effort was beyond the scope of the present study. To\nclarify this, we revised statement relevant to this in the revised manuscript.\n- In Results and Discussion section of the revised Manuscript: To understand the pronounced\nmorphological transformation observed at 80 °C, the thermal compression behavior of\nelemental sulfur particles under conditions mimicking the roll-pressing process was\nsimulated.\n- In Methods section of the revised Manuscript: The objective of the model is to qualitatively\nunderstand how temperature changes in the roll-pressing process affect the sizes and shapes\nof particles in the resulting hot-rolled sintered film.\n- In Methods section of the revised Manuscript: The bond model parameters used in the\nsimulation include a maximum elongation of 1 mm, a damping ratio of 0.25, a distance\nfactor of 0.1, normal and tangential stiffness per unit area of 100 kN/m³, tensile and shear\nstress limits of 10 kPa, and a bond activation time of 0.1 seconds. These values were\nselected to approximate the mechanical behavior of loosely agglomerated particles and to\nenable realistic fracture and rearrangement during compaction.\n(3) To represent sulfur particle’s geometry, this study modeled the particles as sphero-polygons\nwith 12 vertices to capture irregular, faceted particle geometries and to allow the computation\nof inter-particle contact mechanics and packing behavior. To clarify this, the relevant statement\nhas been revised in the revised manuscript.\n- In Method section of the revised Manuscript:\nThe computational domain, which measures 50 × 50 × 50 mm³, contains polygonal sulfur\npowder particles modeled as sphero-polygons with 12 vertices, an initial equivalent spherical\ndiameter 𝑑𝑖 = 5 mm, and a vertical-to-horizontal aspect ratio of 1. This sphero-polygon\nrepresentation captures the irregular, faceted geometry of actual particles while enabling\ncomputation of inter-particle contact mechanics and packing behavior.\n(4) Due to the lack of experimentally measured temperature-dependent mechanical properties\nfor sulfur particles, we adopted a simplified linear model for the temperature dependence of\nYoung’s modulus, which is commonly applicable to crystalline solids below their phase\ntransition temperatures [Courtney, T. H. \"Mechanical Behavior of Materials.\" 2nd ed.,\nMcGraw-Hill, 2000. ISBN: 978-0070132658]. The relationship is given by E/E = [1-a(T/T )],\n0 m\nwhere E is the modulus at a temperature T, E is the modulus at 0 K, T is the melting point,\n0 m\nand a is a material-specific temperature coefficient. For many crystalline solids, a is on the\norder of 0.5 [Courtney, T. H. \"Mechanical Behavior of Materials.\" 2nd ed., McGraw-Hill, 2000.\nISBN: 978-0070132658]. In this study, we assumed a higher value of a =1 considering the\nparticle-form of materials and to ensure a significantly reduced modulus at 80°C. With these\nassumptions, the linear model yielded estimated modulus of approximately 5 GPa. The slightly\noverestimated temperature coefficient led to a notable difference in particle compaction\nbehavior compared to simulations at 25°C, aligning with our experimental observations. The\nstatement relevant to this discussion has been revised and the literature has been cited in the\nrevised manuscript.\n- In Methods section of the revised Manuscript:\nDue to the limited data for sulfur particles at various temperatures, we assume E =10 GPa [59]\nand v = 0.2 at 25 °C. Most crystalline materials possess v in the range of 0.2 to 0.3 at 25 °C.\n[60] At 80 °C, we assume E = 5 GPa and v = 0.3, based on the linear model for the temperature\ndependence of Young’s modulus. [61]\n- In References section of the revised Manuscript:\n61. Courtney, T. H. Mechanical behavior of materials (Waveland Press, 2000)\nComment 4-4: Figure 4, will the compressing level significantly affect the battery performance?\nResponse: We thank the reviewer for the comment. In this work, the bulk porosity was\ndeliberately set to approximately 55%, a level previously shown to provide an optimal balance\nbetween electrolyte accessibility and ionic/electronic transport in sulfur cathodes. This choice\naligns with earlier findings, including previous study published in Nature Communications\n[Kang et al., Nat. Commun. 10, 3366 (2019)], which demonstrated that cathode porosity\ncritically influences sulfur utilization and long-term cycling stability. Beyond porosity, the\ntortuosity of the electrode structure plays a key role in governing ion transport and reaction\nhomogeneity. Lower tortuosity has been shown to enhance Li⁺ diffusion and promote more\nuniform electrochemical reactions, ultimately improving sulfur utilization and rate\nperformance [Fu et al., Adv. Energy Mater. 13, 2300602 (2023)]. The thermomechanical\npressing strategy employed here is expected to reduce tortuosity through uniform densification\nand improved structural alignment, potentially contributing to the enhanced cycling\nperformance observed for the 80 °C-pressed cathodes. The following articles have been newly\ncited in the revised manuscript.\n- In References section of the revised Manuscript:\n49. Fu, Y. et al. Understanding of low-porosity sulfur electrode for high-energy lithium-\nsulfur batteries. Adv. Energy Mater. 13, 2203386 (2023).\n50. Kang, N. et al. Cathode porosity is a missing key parameter to optimize lithium-sulfur\nbattery energy density. Nat. Commun. 10, 4597 (2019).\nComment 4-5: By using the CT-scan microstructures, do the authors need to add some\ntransport/electrochemical simulation results to indicate the mesoscale effect on the electrochemical\nproperty?\nResponse: We appreciate the reviewer’s insightful suggestion. We fully agree that mesoscale\ntransport or electrochemical modeling could offer valuable insights into structure–property\nrelationships. However, the present study is deliberately focused on experimentally validating\na scalable, binder-free fabrication strategy, complemented by comprehensive structural and\nelectrochemical characterization across multiple length scales. While transport simulations\nwere not included in this work, we believe that the integration of such simulations with\nstructural and electrochemical analyses will further strengthen the understanding of how\nelectrode architecture governs performance. We anticipate that extending this work to include\nmultiscale modeling using experimentally derived microstructures will be a promising\ndirection for future studies to elucidate transport limitations and guide rational electrode design.\nComment 4-6: Table S1, ‘kg’ should be deleted for the amount of elemental sulfur.\nResponse: We thank the reviewer for pointing out the typo. The unit “kg” has been removed\nfrom Table S1 in the revised manuscript.\nThank you very much for the valuable comments. Your comments significantly improved the\nquality of the manuscript.\nResponses to Reviewers’ Comments\nResponses to the reviewer's comments:\nIn the following pages, we have provided detailed and complete responses to the reviewer's\ncomments and observations made to the manuscript (Research Article, No. NCOMMS-25-41503A)\nentitled, \"Unveiling Sulfur as a Binder for High-Performance Polymer-Free Sulfur-Carbon\nCathodes via Solvent-Free Fabrication\". The revised or newly added contents have been\nhighlighted in yellow in the revised Manuscript. These changes are also marked in yellow in this\nresponse to the reviewers' comments.\nReviewer #1\nOverall comment: The authors have added new data. However in some cases, only literature was\nadded. Symmetrical cathode tests are added which is valuable.\nResponse: We greatly appreciate the reviewer for positive comments. We hope that our\nrevisions have addressed the reviewer’s concerns. Point-to-point replies to the reviewer’s\ncomments are listed below.\nComment 1-1: Amorphous content: PDF only gives limited insight. Normally, amorphous content\nis determined with internal intensity standard.\nResponse: We appreciate the reviewer’s feedback regarding the crystallographic analysis of\nsulfur. We performed an internal intensity standard approach by preparing a series of crystalline\nsulfur-Ketjen Black (S-C) reference mixtures with known sulfur ratios to calibrate the\ndiffraction intensity. The integrated intensities of the sulfur (222), (026), and (040) reflections\nexhibited strong linearity (R2 > 0.97) with crystalline sulfur content. Using this calibration,\nthe S-C composite was found to contain ~44 wt.% crystalline sulfur in the total composite.\nGiven that the composite contains ~70 wt.% total sulfur (based on TGA results), this corresponds\nto approximately 63 % of the sulfur existing in a crystalline form, while the remaining ~37 % is\namorphous or poorly crystalline. The following statement, figures and table have been added\nto the revised Manuscript and Supplementary Information.\n- In Results and Discussion section of the revised Manuscript:\nFrom the integrated peak areas of XRD patterns shown in Fig. S9, the crystalline sulfur\nfraction in the S-C composite was estimated to be approximately 44 wt.% of the total\ncomposite, corresponding to about 63 % of the total sulfur content. This partial\namorphization suggests effective sulfur dispersion and confinement within the carbon\nmatrix.\n- In Methods section of the revised Manuscript:\nTo evaluate the amorphous sulfur content in the sulfur–carbon (S–C) composites, a\ncalibration series of crystalline S-C (S -C) samples was prepared by mechanically\ncryst\nmixing sulfur and Ketjen black at weight ratios of 90:10 (90Scryst), 70:30 (70S ), 50:50\ncryst\n(50S ) and 40: 60 (40S ) without any heat treatment. All S -C mixtures were pre-\ncryst cryst cryst\nweighed to maintain a constant carbon mass on the sample holder. For reference, pure\ncrystalline sulfur (100S ), Ketjen black, and the synthesized S-C composites were also\ncryst\nanalyzed. XRD was performed using a PANalytical Aeris diffractometer with a Cu-Kα\nsource (λ = 1.5406 Å), scanning from 20° to 33° 2θ with a step size of 0.01°and a dwell\ntime of 200 s per step. The integrated intensities of the sulfur (222), (026), and (040)\nreflections were obtained and used to construct calibration curves of integrated peak area\nversus crystalline sulfur content. Linear regression yielded R2 values exceeding 0.95 for all\npeaks, indicating strong linearity. The relative crystalline sulfur content of the S–C\ncomposite was then determined by extrapolation from the regression model, and the\namorphous sulfur fraction was estimated by subtracting the crystalline contribution from\nthe total sulfur content. This analytical approach follows methodologies established in prior\nXRD-based phase quantification studies [63,64].\n- In the revised Supplementary Information:\nFigure S9. (a) XRD patterns of reference crystalline sulfur, crystalline sulfur–carbon\nmixtures (S –C) with varying sulfur ratios and the synthesized S–C composite. Major\ncryst\nsulfur reflections are labeled. (b) Linear regression of integrated peak areas for the (222),\n(026), and (040) reflections versus the crystalline sulfur content, yielding R2 values of 0.97–\n0.99. The estimated crystalline sulfur fraction in the S–C composite (highlighted region) is\napproximately 44 wt.%. XRD Peak integration results are summarized in Table S5.\n- In the revised Supplementary Information:\nTable S5. XRD Peak integration results of S -C and the S-C composites\ncryst\n(222) (026) (040)\nSample FWHM Integrated FWHM Integrated FWHM Integrated\n(°) area (a.u.) (°) area (a.u.) (°) area (a.u.)\n100S 0.16 16148 0.16 8367 0.16 6662\ncryst\n90S -C 0.16 12835 0.16 6178 0.16 5174\ncryst\n70S -C 0.16 8312 0.16 4554 0.16 3402\ncryst\n50S -C 0.16 4203 0.16 2210 0.16 1935\ncryst\n40S -C 0.16 2882 0.16 1193 0.16 1590\ncryst\nS-C 0.17 3210 0.17 1433 0.17 1354\nComment 1-2: Benchmark: The authors should measure a benchmark electrode with liquid\nelectrolyte for comparison themselves. A solid state battery is not a proper benchmark.\nResponse: Thank you for the valuable comments. We agree that a solid-state battery study is\nnot an appropriate benchmark for our work. Accordingly, we have removed the all-solid-state\nreference and added two literature benchmarks that are directly comparable to our system,\nreporting 3D-printed or dry-cast electrodes tested with liquid electrolytes. Despite the higher\nactive material content and the absence of binder in our electrodes, our system demonstrates\nsuperior electrochemical performance. The updated benchmarking details are provided in the\nrevised Supplementary Information with slight reorder of the reference list.\n- In the revised Supplementary Information:\n[S13] Gao, X. et al. Toward a remarkable Li-S battery via 3D printing. Nano Energy 56,\n595−603 (2019).\n[S14] Um, K. et al. Janus architecture host electrode for mitigating lithium-ion\npolarization in high-energy-density Li-S full cells. Energy Environ. Sci. 17, 9112–9121\n(2024).\n[S15] Horst, M. et al. A binder-free dry coating process for high sulfur loading cathodes\nof Li-S batteries: A proof-of-concept. J. Power Sources 587, 233675 (2023).\n[S16] Sul, H., Lee, D. & Manthiram, A. High-loading lithium-sulfur batteries with\nsolvent-free dry-electrode processing. Small 20, 2400728 (2024).\n[S17] Kim, D.J. et al. Solvent-free dry-process enabling high-areal loading selenium-\ndoped SPAN cathodes toward practical lithium-sulfur batteries. Small 21, 2503037\n(2025).\nComment 1-3: The authors should provide pouch cell data, not only refer to literature data.\nResponse: Thank you for the valuable suggestion. Following your advice, we fabricated pouch\ncells using our binder-free, dry-cast S-C cathode and evaluated the performance. The pouch\ncell delivered good cycling performance, demonstrating that our electrode has promising\npotential in a more practical format beyond coin cells. We have included the full pouch-cell\nprocedures and data in the Supplementary information (Fig. S21) and noted these results in the\nrevised manuscript. We appreciate the reviewer’s guidance, which strengthened the manuscript.\n- In Results and Discussion section of the revised Manuscript:\nThe 80 °C-pressed cathode was further evaluated in a pouch cell (1.5 × 1.5 cm2, 3 mg cm-2,\nS\nFig. S21), which delivered an initial capacity of 1000 mAh g-1 and maintained 897 mAh\ng-1 after 30 cycles, demonstrating the applicability of the binder-free S-C cathodes to a more\npractical cell form factor and consistent electrochemical behavior with the corresponding\ncoin-cell results.\n- In Experimental section of the revised Manuscript:\nFor pouch cells, the 80 °C-pressed cathode (1.5 × 1.5 cm2, 3 mg cm−2) was assembled\nS\ntogether with the carbon-coated Celgard 2400, Li metal anode, and the same electrolyte as\nin the coin cells.\n- In the revised Supplementary Information:\nFigure S21. Charge discharge cycling performance of the pouch cell using 80 °C-pressed S-C\ncomposite cathode (1.5 × 1.5 cm2, 3 mg cm−2) at 0.3 C.\nS\nThank you very much for the valuable comments. Your comments significantly improved the\nquality of the manuscript.\nReviewer #2\nOverall comment: The paper's quality has improved significantly since its revision. By\nincorporating all the suggestions, the authors produced a revised manuscript that is now\nrecommended for publication.\nResponse: We again sincerely thank the reviewer for the constructive and encouraging\nfeedback. We believe the manuscript has been improved substantially after the revision.\nThank you very much for the valuable comments. Your comments significantly improved the\nquality of the manuscript.\nReviewer #3\nOverall comment: The authors have carefully addressed the earlier concerns by adding new\nexperimental data (ex-situ SEM, EIS fitting, high-magnification SEM) and expanding the\ndiscussion on structural stability, binder-free comparisons, and scalability. While the conceptual\nnovelty is incremental, the study provides a practical and well-supported approach toward solvent-\nand binder-free Li–S cathodes, with convincing experimental validation.\nResponse: We again sincerely thank the reviewer for the constructive and encouraging\nfeedback. We believe the manuscript has been improved substantially after the revision.\nThank you very much for the valuable comments. Your comments significantly improved the\nquality of the manuscript.\nReviewer #4\nOverall comment: The revisions are substantial, however the following two questions need to be\nanswered:\nResponse: We sincerely thank the reviewer for the positive and encouraging feedback on our\nmanuscript. In response to the concerns raised, we have carefully revised the manuscript and\naddressed each point in detail. We hope that these revisions sufficiently clarify the issues and\nstrengthen the manuscript. Point-by-point responses are provided below.\nComment 4-1: Clarify if you are using 5 μm or 5 mm particles in the powder bed simulation, from\npowder technology viewpoint, because of adhesive force difference, the bulk powder behavior\ncould be totally different.\nResponse: We sincerely apologize for the typographical error in the manuscript. The particle\ndiameter used in our powder bed punch simulations was indeed 5 mm, not 5μm which was\nstated in the Method/Computation modeling for thermal compression behavior of elemental\nsulfur section. We have corrected this typo in the revised manuscript to ensure consistency and\naccuracy. We concur with the reviewer's expert insight that particle size is a critical factor\ninfluencing the bulk powder behavior, particularly due to the dominance of adhesive forces at\nthe microscale. This is a crucial point in powder technology. However, we wish to clarify the\nprimary objective of our current study. The purpose of our finite element method (FEM)\nsimulations using ANSYS was to gain qualitative insights into the bulk morphological\ntransformation of the powder bed during compaction. Our model was not intended for a direct\nquantitative comparison with experimental data.\nAs noted, our simulation employed the Bond model, which considers elastic and viscous\nforces and moments as a reaction to inter-particle deformations. While the model is capable of\ncapturing a range of contact behaviors, its application at the mesoscale (5 mm) inherently\nfocuses on the macroscopic mechanical response to compression rather than the adhesive-\ndominant behavior at the true particle scale of the experimental sulfur (<30μm). At the scale of\nour simulation, the adhesive forces are negligible compared to the applied compressive forces,\nso our model effectively captures the bulk behavior governed by contact mechanics and particle\nrearrangement. The use of a larger, mesoscale particle size in our simulation was a necessary\nsimplification to make the computational model tractable. Simulating the true particle scale\nwith the Bond model would be computationally prohibitive for a model of this size, and it is a\ncommon practice to use a representative elementary volume (REV) or a larger, simplified\nparticle size to study macroscopic behavior. To justify the choice of millimeter-scale particle\nsize in our simulation, now we added the following text in the Results and Discussion section.\n- In Results and Discussion section of the revised Manuscript:\nNote that the simulation is designed for qualitative insights into bulk deformation and\ndensification during powder compaction. To balance accuracy and efficiency, we used\nmillimeter-scale particles, which capture bulk mechanical responses acceptable\ncomputational cost, whereas a quantitative comparison with experimental data would\nrequire micrometer-scale particles that account for adhesive forces.\n- In Methods section of the revised Manuscript:\nThe simulation domain was sized to include at least ten sulfur particles with a\nrepresentative diameter of ~5 mm in each spatial direction, ensuring statistically\nmeaningful assessment of bulk powder behavior.\nComment 4-2: Are you using the same bond parameters in the bond model to model the powder\ncompaction behaviour of RT and 80 °C? If this is the case, can you justify what material you need\nto describle use bond model in your compaction simulation? is it reasonable to use same baon\nparameters under same conditions?\nResponse: We thank the reviewer for the comment. We confirm that we used the same bond\nparameters in the Bond model for our simulations at both room temperature and 80°C. This\nchoice was deliberate and is justified by the primary purpose of our study, which is to gain\nqualitative insights into the bulk deformation and densification behavior during powder\ncompaction. In our simulation, the Bond model parameters were used to describe the inter-\nparticle mechanical behavior of the material under compressive loading. We did not use these\nparameters to describe a specific material; rather, they were selected to capture the general\ncompaction behavior of a ductile, porous powder bed. The focus was on the macroscopic\nresponse to applied pressure and the resulting morphological changes. The difference in\ncompaction behavior between RT and 80°C was captured by changing the Young's modulus\nand Poisson's ratio—the primary material inputs to the simulation—while keeping the bond\nparameters constant. This approach allowed us to isolate and study the effect of temperature\non the material's bulk mechanical response, which is the main objective of our study. To justify\nthe choice of Bond model parameters that are not specific to a certain material, now we added\nthe following text in the Methods section.\n- In Methods section of the revised Manuscript:\nThese Bond model parameters were chosen to represent the general inter-particle\nmechanics of ductile porous powders, but since they are not material-specific, they cannot\nbe used for direct quantitative comparison with experimental data.\nThank you very much for the valuable comments. Your comments significantly improved the\nquality of the manuscript."}]

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