Engineering thin 3D Li-composite foil negative electrodes with high mechanical toughness

Domain: chemistry
Published: 2026-02-04
Editorial outcome: major_revision

Abstract
Current three-dimensional lithium negative electrodes are plagued by inherent trade-offs among mechanical robustness, thin processability, and electrochemical performance. Here, we engineer a free-standing Li-composite foil negative electrodes by integrating a lithiophilic Li-Zn alloy with a Li3N-enriched carbon nanotube network. The Li-Zn alloy strengthens tensile resistance and regulates lithium deposition, while the Li3N-enriched carbon nanotube network reinforces mechanical toughness, achieving a rupture toughness of 1.3×10⁶ J/m³, a 12-fold enhancement over bare lithium. This property enables the fabrication of thin negative electrodes (<10 μm) that resist pulverization during deep Li plating/stripping. In cells with LiNi0.8Co0.1Mn0.1O2 positive electrodes, the composite negative electrode facilitates extended cyclability (>500 cycles in coin cells at 1C, 92% retention after 300 cycles in Ah-grade pouch cells at 0.5C) and sustain high-rate operation (10C). An 8.5 Ah pouch cell demonstrates a practical specific energy of 553 Wh kg−1 at cell level when tested at 0.1C. This work presents a design strategy for realizing high-energy, long-cycle-life lithium metal batteries.

Introduction
Lithium metal has been regarded as the holy grail of the negative electrode for next-generation high-specific-energy batteries because of its high capacity (3860 mAh g−1) and the lowest electrochemical potential (−3.04 V vs. standard hydrogen electrode)1–5. However, dendritic growth, low coulombic efficiency (CE) and severe volume fluctuations during cycling critically impede the practical implementation of lithium metal batteries (LMBs)6–9. Current strategies focus on electrolyte optimization10–13, artificial interphase engineering14–18, and solid-state electrolyte design19–21. Though these approaches demonstrated effectiveness in suppressing dendrite propagation22–25, the volume fluctuations problems in planar lithium configurations remain as a critical barrier to practical implementation26,27.

Infiltrating lithium into a three-dimensional (3D) host to construct composite lithium negative electrodes, a strategy pioneered by our group, has emerged as a promising approach to mitigate the challenges associated with volumetric changes. The 3D framework facilitates a homogeneous electric field distribution, thereby promoting uniform lithium deposition and mitigating the expansion during cycling28. This innovation has spurred extensive research into metallic (e.g., Cu and Ni)29–31 and carbon-based 3D composite lithium negative electrodes32–34. Despite their advantages, the fabrication and processing of 3D Li-composite negative electrodes remain formidable challenges35,36. The carbon-based hosts suffer from poor lithophilicity, which inhibits complete lithium infiltration and results in undesirable inhomogeneity within the composite. Additionally, integrating a highly conductive ionic network within the 3D carbon architecture remains a critical challenge, restricting high-rate performance for these 3D Li–C negative electrodes. More importantly, the practical development of thin lithium metal negative electrodes (e.g., <50 μm) is essential to achieve a favorable negative-to-positive (N/P) ratio compatible with commercial positive electrodes. However, the fabrication of thin 3D Li–C negative electrodes remains hindered by processing limitations and inherent brittleness, further complicating their viability for large-scale implementation (Supplementary Fig. 1)37,38. Recent studies have explored an alternative approach of 3D Li-alloy foil negative electrodes via the reaction of molten lithium with metals or metal compounds at elevated temperatures. The incorporation of Li xMy (M=Zn, Sn, Mg, etc.) alloy phases enhances the processability of this strategy. These alloy phases not only function as mechanical pillars, but also serve as lithophilic active sites that regulate lithium deposition (Supplementary Fig. 1)39,40. Nevertheless, the discontinuous alloy foil networks are prone to fracture during prolonged cycling, particularly in lithium-limited systems. Under these conditions, lithium depletion triggers dealloying-driven electrode pulverization, ultimately accelerating battery failure41,42. To mitigate this, 3D Li-alloy negative electrodes are often co-rolled with Cu or stainless-steel substrates, though at the expense of gravimetric capacity43,44.

These unresolved challenges expose the fundamental dilemma in the design of 3D Li-composite negative electrode, which fails to simultaneously satisfy six critical requirements: (i) rapid ion/electron transport, (ii) scalable processing, (iii) mechanical toughness, (iv) minimal volume variation, (v) high specific energy, and (vi) structure integrity. Despite recent progress, the simultaneous optimization of these interdependent properties remains a pivotal scientific challenge that hinders the commercial realization of LMBs.

Herein, we present a 3D Li-composite foil negative electrode (LZNC) that achieves simultaneous multidimensional performance enhancement through synergistically integrating Li–Zn alloy with Li3N-enriched carbon nanotubes (Li3N-CNTs). The Li–Zn alloy provides intrinsic ductility, effectively accommodating cyclic strain while regulating lithium nucleation. The Li3N-CNTs network acts as a mechanically durable scaffold, preserving structural integrity even under prolonged cycling or deep delithiation. This hierarchical integration results in a tensile strength of 23.9 MPa and a rupture toughness of 1.3×106 J/m3, approximately 1200% enhancement compared to bare Li, enabling the fabrication of thin composite foil negative electrodes (<10 μm). This thin yet robust 50 μm-thick LZNC foil delivers a high gravimetric specific capacity (1800 mAh g−1) and a high volumetric capacity (1915 mAh cm−3), improving those 3D Li–C or Li-alloy composite negative electrodes. In addition, coin full cells pairing thin LZNC with LiNi0.8Co0.1Mn0.1O2 (NCM811) show stable cycling over 500 cycles and maintain good rate capability. LZNC||NCM811 pouch cells demonstrate long-term performance under practical testing conditions (300 cycles with 92% capacity retention). A practical 8.5 Ah prototype LMBs pouch cell was constructed, demonstrating a high specific energy of 553 Wh kg−1 at the cell-level, including the weight of the pouch packaging (aluminum-plastic film and tabs).

Results
The fabrication procedure for the LZNC negative electrode is illustrated in Fig. 1a. First, molten lithium was reacted with Zn3N2 (mass ratio: 2:1) at 400°C under an Ar atmosphere. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirm the uniform dispersion of Zn3N2 (Supplementary Figs. 2–4). Upon a thorough stirring, a redox chemical reaction between metallic Li and Zn3N2 occurs, yielding a hybrid matrix (LZN) comprising Li–Zn alloy and Li3N. Notably, the in situ produced Li3N, a fast ionic conductor, facilitates rapid lithium-ion transport throughout the 3D framework, as corroborated by X-ray diffraction (XRD) (Supplementary Fig. 5, Supplementary Table 1). Density functional theory (DFT)-derived ternary-phase diagrams further validated the thermodynamic stability of LZNC at ambient conditions (Supplementary Fig. 6). To reinforce structural integrity and flexibility, CNTs were integrated into LZN, serving as bridging scaffolds. Unlike conventional systems where lithiophobic CNTs resist homogeneous dispersion, the LZN enables spontaneous CNTs wetting. This enhanced compatibility arises from Li3N enrichment on CNTs surfaces during annealing, a mechanism detailed in subsequent sections. The Zn3N2-to-CNTs ratio was systematically optimized to balance mechanical robustness and ionic conductivity (Supplementary Fig. 7).

The freestanding LZNC foil negative electrode was fabricated through ambient cooling of a molten Li–Zn₃N₂ precursor, followed by roll-pressing under dry air. In the development of LMBs, thin lithium negative electrodes (<20 μm) are essential for realizing high-specific-energy cells with minimized N/P ratios. Conventional fabrication of large-area or thin lithium foils, however, is challenged by their intrinsic limitations of high viscosity and insufficient mechanical strength. Addressing this, our LZNC design enables scalable production of thin foil negative electrodes (<20 μm). We further conducted complementary tensile tests on these foils to evaluate their mechanical properties (Fig. 1b, Supplementary Fig. S8). Quantitatively, the LZN composite exhibits a ~200% increase in tensile strength over the LZ baseline, an effect we ascribe to conventional second-phase reinforcement by the inorganic Li3N particles. The Li–Zn-CNTs (LZC) composite shows an even greater strength enhancement of ~320%. Furthermore, we calculated the toughness, defined as the energy absorbed prior to fracture (integral under the stress-strain curve), for each material. While LZN shows a ~100% increase over LZ, LZC achieves ~240% enhancement. The synergistic combination of both components in the LZNC composite yields the highest toughness value (1.3×106 J/m3, 300% enhancement to LZ). These data demonstrate that the CNTs network serves as the principal mechanical reinforcement, drastically improving both tensile strength and toughness by acting as a resilient scaffold that bridges Li–Zn domains, inhibits crack propagation, and effectively redistributes mechanical stress.

Atomic force microscopy (AFM) adhesion measurements further validate the enhanced mechanical processability of LZNC foil (Supplementary Fig. 9). By modulating roller spacing during fabrication, the LZNC foil thickness can be precisely tailored from 8 to 100 μm, enabling tunable areal capacities ranging from 1.5 to 19.15 mAh cm−2 (Fig. 1c, Supplementary Fig. 10). The thin LZNC foils (8 μm) retain structural integrity under mechanical stressors such as bending, stretching, and folding, exhibiting no detectable cracks, pinholes, or defects (Fig. 1d, Supplementary Figs. 11, 12). This high mechanical resilience, coupled with flexibility, renders LZNC a promising negative electrode for operation under mechanical conditions. Furthermore, the composite foil demonstrates scalability, as evidenced by its successful processing into smooth, large-area foils (80 cm2, 40 μm thickness; Fig. 1d), highlighting its viability for industrial-scale negative electrode production in next-generation LMBs. The actual specific capacity of LZNC negative electrode was determined by electrochemical charging to 1 V (vs. Li⁺/Li), revealing gravimetric and volumetric capacities of 1800 mAh g−1 and 1915 mAh cm−3, respectively. The main components of LZNC composite materials are shown in Supplementary Table 2. The theoretical specific capacity is 1842 mAh g−1, which is very close to the actual value, demonstrating high utilization of active lithium. The negative electrode demonstrated remarkably limited thickness variation (3.6%) upon complete lithium stripping (Fig. 1e), confirming its minimized volumetric change. Compared with prior studies on Li–C or Li-alloy 3D negative electrodes, the LZNC architecture provides higher gravimetric and volumetric capacities while also allowing for thin-electrode fabrication (Fig. 1f). To comprehensively evaluate the multifunctional advantages of LZNC, we conducted a comparative analysis against conventional lithium, Li–C, and Li-alloy negative electrodes using a six-parameter radar chart framework. This analysis quantified performance across critical metrics: ion/electron transport, mechanical toughness, processability, volumetric deformation, gravimetric specific energy, and structural durability. The LZNC design synergistically integrates the structural advantages of Li–C and Li-alloy systems through a ternary-phase LZNC framework that suppresses volume fluctuations, enabling rapid charge transfer, and delivering robust mechanical resilience/scalability, thereby addressing the intrinsic brittleness of Li-alloys and processing limitations of Li–C to reconcile specific energy, structural integrity, and manufacturability trade-offs.

The structural and compositional evolution of the LZNC was thoroughly investigated. XRD results (Fig. 2a) confirm the complete conversion of Zn3N2 into Li–Zn alloy and Li3N during chemical reduction, as evidenced by the disappearance of Zn3N2 diffraction peaks and the emergence of characteristic LiZn, Li3N, and metallic Li phases. Meanwhile, the lithiation of CNTs during thermal processing is evidenced by a 2theta downshift and intensity reduction of their (002) diffraction peak (Supplementary Fig. 13). Detailed XRD and X-ray photoelectron spectroscopy (XPS) analyses further confirm the formation of lithium-intercalated carbon (LiCx). The (002) peak shifts from 25.92° to 23.85°, corresponding to an interlayer expansion from 3.57 to 3.73 Å, characteristic of Li insertion into graphitic layers. The relatively weak diffraction intensity originates from the low crystallinity of the lithiated carbon compared with the metallic phases. Moreover, the appearance of a Li–C bonding signal at 282.9 eV in the C 1s XPS spectrum provides direct chemical evidence for LiCx formation. Ex situ SEM observation (Supplementary Fig. 14) further reveal that the CNTs retain their tubular and interconnected morphology after lithiation, confirming that Li intercalation expands the lattice while preserving the robust fibrous framework. XPS validates these phase transformations, with distinct N 1s (398.9 eV) and Zn 2p (1044.4/1021.4 eV) binding energies corresponding to Li3N and LiZn alloy formation (Supplementary Fig. 15). The structural and compositional evolution of the LZNC was further elucidated using SEM, energy-dispersive X-ray spectroscopy (EDS), and X-ray microscopy (XRM). Top-view SEM images of the LZNC foil reveal that the LiZn exhibits an island-like morphology (~1 μm), while the CNTs form an interwoven network that bridges adjacent alloy clusters. Cross-sectional SEM and EDS analysis demonstrate that Li–Zn alloy particles, CNTs, and Li3N are uniformly dispersed throughout the foils (Supplementary Figs. 16, 17).

XRM further validates the presence of an interconnected 3D alloy-CNTs framework embedded in the lithium matrix (Fig. 2b, Supplementary Fig. 18). Even after complete lithium stripping, Zn particles remain interconnected with CNTs, maintaining good structural integrity (Fig. 2c–f). Intriguingly, the signals of N element almost overlap with those of C element in EDS mappings (Fig. 2e, f), suggesting strong interfacial coupling between Li3N and the CNTs. This is further corroborated by TEM, which shows Li3N crystallites preferentially enriched on CNTs surfaces with a lattice spacing of 0.32 nm, corresponding to the (111) plane (Fig. 2g). Molecular dynamics (MD) simulations were performed to investigate the dynamic evolution of the compositional distribution during the synthesis of LZNC. It reveals that during the thermal fusion process, N and Zn atoms are uniformly dispersed (Supplementary Fig. 19). After annealing, N atoms migrate preferentially to CNTs interfaces due to electronic structure mismatches between metallic and inorganic phases, while Zn atoms maintain homogeneous dispersion (Fig. 2h–j). This self-evolving architecture, where CNTs-bound Li3N enhances ion transport kinetics within the LZNC. Further computational details are provided in Supplementary Data 1.

To gain a comprehensive understanding of the Li plating/stripping mechanism on the LZNC negative electrode, we employed a series of in situ and quasi-in situ characterizations. Operando optical microscopy (Supplementary Fig. 20) provides direct visualization of Li deposition and stripping at 1 mA cm−2 with a capacity of 2 mAh cm−2. The LZNC electrode retains a continuous and intact 3D skeleton throughout Li stripping, and subsequent Li plating occurs homogeneously within the scaffold without dendrite formation. In contrast, both Li–Zn alloy and bare Li electrodes exhibit evident structural degradation during stripping, including cracking and loosening of the framework, and irregular, dendritic Li deposition during plating. To further elucidate the structural and phase evolution during Li stripping and plating, in situ XRD measurements were conducted on the LZNC negative electrode. Figure 3a shows the in situ XRD profiles of LZNC during the first Li plating/stripping. Electrochemical testing was performed at a current density of 0.1 mA cm−2, with delithiation first at a cut-off voltage of 1 V and then lithiation at a cut-off capacity of 3 mAh cm−2. The XRD pattern shows that the peak strength and peak position of Li3N remain unchanged throughout the Li stripping/plating process, indicating its electrochemical stability upon cycling. During Li stripping, the peak intensity of lithium gradually diminishes without peak shifts. Towards the end of the Li stripping (charge to ~0.15 V), the voltage gradually rises while the peak intensity of LiZn diminishes, accompanied by the emergence of the peak of Zn. This indicates that LZNC undergoes a sequential Li-stripping and de-alloying mechanism during delithiation. This interface evolution is further corroborated by quasi-in situ XPS analysis (Fig. 3b), which reveal that the characteristic signals of Li3N and metallic Zn remain essentially unchanged at different delithiation states, confirming the chemical robustness of the interface and supporting the in situ XRD observations. In situ Distribution of Relaxation Times (DRT) (Fig. 3c, Supplementary Fig. 21) reveal that the interfacial resistance of LZNC gradually decreases and stabilizes, indicating efficient charge transfer and a persistent interface, while Li–Zn exhibits large fluctuations due to framework collapse and dendritic deposition. Ex situ SEM and optical microscopy of Li–Zn and LZNC negative electrodes at 25% and 75% delithiation were characterized (Fig. 3e, f, Supplementary Fig. 22). It reveals that the Li–Zn negative electrode suffers rapid structural collapse and electrode pulverization at 25% Li removal, whereas LZNC retains 3D framework integrity even at 75% delithiation. To further verify the structural reversibility after complete delithiation, ex situ SEM and EDS mapping were performed on an LZNC sample charged to 1.0 V (vs. Li⁺/Li). The results (Supplementary Fig. 23) show a continuous, interwoven network in which Zn domains display an island-like morphology uniformly distributed within the CNTs matrix, without any signs of cracking or disintegration. This structural integrity was further confirmed by XRM (Fig. 3d, Supplementary Fig. 24), revealing that even after 100% Li stripping, the 3D Zn-CNTs network remains intact, accompanied by the formation of numerous pores within the delithiated scaffold. These interconnected voids accommodate subsequent lithium deposition, while CNTs reinforcement ensures mechanical coherence, rendering the LZNC negative electrode highly resistant to pulverization upon long-term cycling. We further investigated the structural and morphological evolution of lithium plating at 0.5 mA cm−2 on a 25% delithiated bare Li and LZNC negative electrodes. The electrochemical profiles showed that both the nucleation overpotential and deposition overpotential of the LZNC negative electrode were markedly lower than those of bare Li, suggesting that the Li–Zn alloy, acting as lithophilic sites, promotes a and flat lithium deposition (Fig. 3g). SEM images reveal a rough and dendritic surface observed for the Li foil negative electrode, in sharp contrast with a planar and dendrite-free surface for the LZNC negative electrode (Supplementary Fig. 25). Upon increasing the current density to 2 mA cm−2, the lithium deposition on the LZNC negative electrode maintains an orderly pattern (Supplementary Fig. 26).

The electrochemical performance of the LZNC foil negative electrode was first evaluated in symmetric cells. Figure 4a, b presents the voltage-time plots for bare Li, Li–Zn, LZN, Li-CNTs (LC), and LZNC symmetric cells, each with 50 μm thickness, at 1 mA cm−2 with a capacity of 1 mAh cm−2. The results show that the LZNC foil negative electrode delivers a remarkably stable Li plating/stripping performance over 1200 h with a small voltage hysteresis of ~8 mV (Supplementary Fig. 27). By contrast, the bare Li and Li–Zn electrodes experience a quick short-circuiting, accompanied by hysteresis increase to around 100 mV within 600 and 900 h, respectively. As for LZN and LC symmetric cells, although the cycle life was extended compared to bare Li, their voltage hysteresis significantly increased upon Li plating/stripping (>50 mV), accompanied by non-smooth voltage profiles indicative of unstable interfacial kinetics. Even when the current density and areal capacity are increased to 5 mA cm−2 and 5 mAh cm−2, the LZNC symmetric cell can undergo stable Li plating/stripping for over 500 h (Supplementary Fig. 28). The rate performance of the symmetric cells was evaluated at various current densities ranging from 0.5 to 10 mA cm−2 (Fig. 4c). As the current density increases, the bare Li cell exhibited significant voltage fluctuations, suggesting the formation of an unstable interface on the bare Li negative electrode. A sudden voltage drop is observed at 7 mA cm−2, which indicates the occurrence of a short circuit, which could be induced by the penetration of Li dendrites. In contrast, LZNC cells maintain stable Li plating/stripping with low voltage hysteresis (<62 mV at 10 mA cm−2; Fig. 4d). The low overpotentials of the LZNC electrode indicate a reduced energy barrier for Li nucleation/plating, which facilitates a more homogenous and planar Li deposition. The favorable electrochemical performance under high current densities indicate the potential of LZNC negative electrodes applied under more practical conditions.

The kinetic properties of the LZNC foil electrode were further validated by the exchange current density (i0) result derived from the Tafel plots (Fig. 4e, Supplementary Fig. 29). The i0 of the LZNC foil electrode is 0.089 mA cm−2, significantly higher than that of the bare Li electrode (0.011 mA cm−2). Furthermore, as illustrated in Fig. S29, LZN foil exhibits a significant enhancement (0.0716 mA cm−2) compared to the baseline LZ alloy (0.0131 mA cm−2). In contrast, the LZC composite demonstrates only a marginal improvement (0.0161 mA cm−2). The LZNC composite achieves the highest exchange current density (0.0887 mA cm−2), which we attribute to the formation of an interwoven Li3N-CNTs network that facilitates ion and electron transport.

To elucidate the kinetics of the LZNC electrode, electrochemical impedance spectroscopy (EIS) measurements were conducted on symmetric cells at different Li plating/stripping stages under 1 mA cm−2 and 1 mAh cm−2. The high-frequency semicircle in the EIS data correspond to the interfacial resistance (Rs), indicating lithium-ion diffusion within the solid electrolyte interphase (SEI) layer, while the low-frequency semicircle represents the charge transfer resistance (Rct) at the electrode/electrolyte interface, reflecting the electrochemical interfacial kinetics. As shown in Fig. 4f, g, both Rs and Rct of the LZNC electrode remain markedly lower than those of bare Li throughout Li plating/stripping, demonstrating a more stable and conductive interface. The total impedance of LZNC decreases initially and then stabilizes upon prolonged Li plating/stripping, suggesting progressive interfacial optimization and the formation of a robust conductive network (Supplementary Fig. 30). In contrast, the impedance of bare Li increases significantly upon Li plating/stripping, indicative of growing polarization and interfacial degradation. The activation energy (Ea) was calculated from the fitted profile of 1000/T and ln T/Rs (Supplementary Fig. 31). The details of the references are shown in Supplementary Table 5, Supplementary Fig. 32. LZNC negative electrode presents a significantly lower Ea (54.8 kJ mol−1) compared to the bare Li (72.5 kJ mol−1), indicating the fast Li-ion diffusion through the 3D interior interface of the LZNC foil. The enhanced kinetics can be ascribed to the interconnected and mechanically robust 3D conductive framework composed of LiZn, CNTs, and Li3N, which facilitates rapid electron and ionic transport.

Post-mortem characterizations were then performed on the cycled electrodes to elucidate the electrochemical stability of the LZNC negative electrode. Top-sectional SEM images of the bare Li after Li plating/stripping at 1 mA cm−2 and 1 mAh cm−2 for 100 h revealed a porous surface structure with obvious cracks, suggesting inhomogeneous and dendritic lithium deposition (Fig. 5a). These cracks originated from the bare Li foil, which had poor mechanical strength and can hardly withstand significant strain during repeated lithium plating and stripping. This can lead to the disruption of the electronic pathway between the active material and the collector, ultimately causing irreversible capacity loss. In sharp contrast, the surface of LZNC after Li plating/stripping remains smooth and flat (Fig. 5b). From the cross-view SEM images (Fig. 5c), a huge crack was found between the fresh Li-deposition layer and the underneath unreacted Li electrode, which accounts for the large polarization and poor Li plating/stripping stability of bare Li. By contrast, LZNC foil preserved good structure integrity after Li plating/stripping without notable structural damage, indicating uniform and compact Li deposition (Fig. 5d). The structure of LZNC is stabilized by its pulverization-resistant characteristic, which allows it to preserve the original 3D ionic and electronic conductive framework even after the metallic Li is completely stripped.

In-depth X-ray photoelectron spectroscopy (XPS) measurements were conducted on the negative electrodes after Li plating/stripping to investigate their interfacial evolution. As shown in Fig. 5e, Supplementary Figs. 33, 34, a strong signal of carbon-containing organic compounds derived from the decomposition of solvent was detected on the bare Li surface. In contrast, the peak signal intensity of the C 1s spectra on the LZNC surface was relatively weak (Supplementary Fig. 35). With increasing etching depth, the carbon signal decreased significantly, while the peak signal intensities of nitrogen (N) and zinc (Zn) remained almost constant (Fig. 5f–h). This indicates that the interface compositions on the surface and within the LZNC are dominated by inorganics. Furthermore, ex situ XPS at different Li plating/stripping stages (Supplementary Figs. 36, 37) reveals a dynamic interfacial evolution, verifying a gradual enrichment of inorganic species, mainly Li3N, accompanied by a reduction of organic components. The appearance of a characteristic C–N peak after extended Li plating/stripping confirms the continuous enrichment of Li3N on the CNTs surface, leading to the formation of a stable inorganic-rich SEI that ensures efficient Li⁺ transport and mechanical robustness at the interface. AFM measurements (Supplementary Fig. 38) were further conducted to probe the mechanical evolution of the electrode interface during Li plating/stripping. The surface modulus of the LZNC electrode gradually increases with prolonged Li plating/stripping and remains consistently higher than that of bare lithium metal, reflecting a mechanically reinforced interface (Fig. 5i). This enhancement correlates well with the XPS results, which indicate the progressive enrichment of inorganic species within the interphase. The formation of this inorganic-rich layer effectively strengthens the mechanical integrity, suppresses lithium dendrite penetration, and preserves interfacial stability. Consequently, even after 300 cycles, the LZNC electrode maintains a smooth and compact surface morphology, indicative of uniform and dense lithium deposition (Supplementary Fig. 39). In contrast, bare Li electrodes after Li plating/stripping exhibit pronounced surface roughening, irregular dendritic growth, and significant accumulation of electrochemically isolated lithium. TOF-SIMS analyses (Fig. 5j–l) further confirm a homogeneous 3D distribution of Li, N, and Zn species within the LZNC electrode, validating the formation of a stable inorganic framework that ensures favorable ion transport and long-term dendrite suppression.

The potential application of the LZNC foil negative electrode was further evaluated in full cells by pairing it with the LiNi0.8Co0.1Mn0.1O2 (NCM811) positive electrode. The cells are evaluated at a current rate of 1C (1C=200 mA g−1) in a LiTFSI-containing commercial ester electrolyte with an N/P ratio of 4. In addition, a full cell using the same NCM811 positive electrode and 50-μm-thick bare Li negative electrode (Li||NCM811) was also assembled for comparison. As shown in Fig. 6a, the LZNC||NCM811 cell exhibits a long lifespan over 500 cycles, with an average CE above 99.9% throughout the cycling. By contrast, the Li||NCM811 exhibits rapid capacity decay after only 100 cycles (retention below 50%), with a lower CE < 80%. The low CE could be attributed to the rapid active-Li loss resulting from the formation of Li dendrites or dead Li (i.e., Li metal regions which are electronically disconnected from the current collector), therefore leading to a fast cyclic deterioration. From the discharge/charge voltage profile at different cycles displayed in Fig. 6b, Supplementary Fig. 40, the LZNC||NCM811 full cell exhibits lower potential hysteresis in both the charge and discharge processes compared with the full cell using a bare Li negative electrode, indicative of the better kinetics for LZNC. The high-rate capability of full cells was further evaluated. As shown in Fig. 6c, d, LZNC||NCM811 cell delivers much higher discharge specific capacities at current rates ranging from 0.1 to 10C (1.0C=200 mA g−1), compared with Li||NCM811 cell. Even under a high rate of 10C, the cell still delivers a high capacity of 117.7 mAh g−1, which is much higher than that of the Li||NCM811 cell (53.1 mAh g−1). The high-rate performance of the LZNC||NCM811 cell can be attributed to the fast ion/electron transfer and enhanced kinetics within the LZNC negative electrode.

Moreover, to demonstrate the broad applicability of the LZNC negative electrode, we extended its use beyond conventional lithium-containing positive electrodes to lithium-free systems such as Li–S batteries, which exhibit stable cycling over 200 cycles at 0.5C (1.0C=1675 mA g−1), highlighting its compatibility and interfacial stability across diverse battery chemistries (Supplementary Fig. 41).

More practical and harsh conditions were tested to verify the practicality and implementation of the LZNC foil negative electrode. The mass loading of the NCM811 positive electrode was further increased to 15 mg cm−2 (areal capacity: 3 mAh cm−2) to couple with LZNC and bare Li negative electrode. As shown in Supplementary Fig. 42, Li||NCM811 encounters a cliff-jumping capacity decay at 100 cycles (capacity retention below 60%), indicative of a rapid lithium depletion arising from inhomogeneous Li plating/stripping. By contrast, LZNC||NCM811 demonstrates a remarkably prolonged cycle life over 180 cycles at 0.3C, with a capacity retention above 90%. Even while the areal capacity increased to 4 mAh cm−2, LZNC||NCM811 demonstrates stable cycling over 120 cycles at 0.3C, with 90% capacity retention (Supplementary Fig. 43).

A laminated pouch cell was constructed by coupling a high-loading NCM811 positive electrode (8 mAh cm−2) with a free-standing LZNC negative electrode (80 μm thickness) under stringent conditions, including a low N/P ratio (1.9) and minimal electrolyte usage (1.5 g Ah−1). (Fig. 6e, Supplementary Fig. 44). Detailed cell parameters are summarized in Supplementary Table 6. The LZNC||NCM811 pouch cell delivers cycling stability with 91.7% capacity retention after 300 cycles at 0.5C (Fig. 6f). The galvanostatic charge/discharge profiles demonstrate minimal voltage polarization with high reversibility (Supplementary Fig. 45). To further assess electrode stability under realistic operating conditions, in situ cell swelling measurements were performed on LZNC||NCM811 pouch cells (Supplementary Fig. 46). The cell exhibits markedly smaller thickness fluctuations than Li||NCM811, evidencing uniform Li stripping/plating and structural robustness of the LZNC framework. To systematically elucidate the practical advantages of LZNC negative electrodes, we conducted a comparative analysis of recent pouch cell studies, focusing on three critical metrics of cycling stability, cycle life, and normalized total negative electrode specific capacity (NSC). The NSC, defined as NSC = (mass negative electrode + mass current collector) * N=P, quantifies the effective capacity contribution of the Li negative electrode to cell-level specific energy by taking into account both the negative electrode/collector mass and the N/P ratio. Unlike conventional lithium-ion batteries, LMBs typically require an N/P > 1 configuration to offset irreversible lithium losses caused by their inherently low CE (<99%). Though this strategy enhances cycling stability, it compromises specific energy due to excessive lithium loading. The NSC metric thus provides a more holistic evaluation of the role of the Li negative electrode in full-cell performance. As illustrated in Fig. 6g, the LZNC-based pouch cell achieves an NSC of 947 mAh g−1, along with a prolonged cycle life. We also assembled 1 Ah LZNC|S pouch cells (employed a conventional DOL/DME-based electrolyte) with an areal capacity of 4.8 mAh cm−2 (3 mg cm−2), which exhibit stable cycling over 60 cycles (Supplementary Fig. 41). To further validate its practical viability, an 8.5 Ah pouch cell was fabricated, demonstrating a gravimetric specific energy of 553 Wh kg−1 at cell-level, including the weight of the pouch packaging (aluminum-plastic film and tabs). (Supplementary Fig. 47, Supplementary Table 8). The improvement in both specific-energy and cycle life verifies the effectiveness and potential of LZNC foil negative electrode for high-specific-energy, long-lifespan LMBs.

Methods
Fabrication of Li–Zn, LC, LZN, and LZNC Composite Negative electrode
The Li–Zn (LZ) compound was synthesized by melting metallic lithium and zinc foils (Alfa, 99.98%) at a molar ratio of 20:1. The Li-CNTs (LC) composite was prepared by mixing metallic lithium with CNTs powder (XFM08, XFNANO) at a weight ratio of 4:1. The LZN compound was obtained by melting metallic lithium with Zn3N2 powders (Alfa, 99%) at a molar ratio of 60:1. All smelting reactions were carried out in an Ar-protected melting setup. To prepare LZC and LZNC, CNTs powder was added to the LZ and LZN slurries, respectively, at a mass ratio of 20%. All heating reactions described above were performed in an Ar-filled glovebox (H2O and O2 < 0.1 ppm) using a melting furnace (KSL-1100X-SV-RM, Hefei Kejing Materials Technology, Ltd.) at 350°C for 3 h, during which the melt was continuously stirred using a mechanical stirring paddle to ensure homogeneous mixing. The LZNC foil was directly employed as the negative electrode for cell assembly. Based on the precursor mass ratio (Li:Zn3N2:CNTs=2:1:0.6), the expected reaction products include Li3N, LiZn, excess Li, and CNTs. Assuming complete reaction between Li and Zn3N2, the masses of the products can be determined from their stoichiometry and molar masses. The resulting composite contains approximately 8.7 wt% Li3N and 16.7 wt% CNTs, giving a total Li3N-CNTs fraction of ~25.4 wt% in the LZNC composite. After the reaction was completed, the melt was cooled to room temperature (25°C). The solidified composite was then repeatedly rolled into foils using a rolling machine (MSK-HRP-1A, Hefei Kejing Materials Technology, Ltd.) in a dry room (relative humidity ~5%).

Preparation of positive electrodes and fabrication of Li metal batteries
Electrochemical performances were evaluated in 2032-type coin cells. All the coin cells were fabricated in the Ar-filled glovebox with water and oxygen concentration less than 0.1 ppm. Celgard 2500 polypropylene membranes were used as separators. All bare Li electrodes were prepared using 500 μm-thick Li foil. Sulfur (analytical reagent, Sigma-Aldrich) was combined with carbon nanotubes (CNTs, Nanjing XFNANO Materials) at a weight ratio of ~7:3. The mixture was transferred into a glass container, evacuated, and then heated at 155°C for 20 h to achieve uniform dispersion. To prepare positive electrodes for Li–S coin cells, the sulfur-CNTs composites were blended with Super P conductive carbon and poly(vinylidene fluoride) (PVDF) binder at an 8:1:1 weight ratio, using N-methyl-2-pyrrolidone (NMP) as the solvent. The resulting slurry was uniformly applied onto carbon-coated aluminum foil and dried under vacuum at 60°C for 24 h. Circular electrodes with a diameter of 10 mm were then punched from the coated foil for coin cell assembly. The procedure was adapted and modified from previously reported methods45. Two different areal capacities of LiNi0.8Co0.1Mn0.1O2 (NCM811) positive electrodes were prepared. Low areal capacity of NCM811 positive electrodes were used to probe the cycling stability of the negative electrodes. The NCM811 positive electrode slurry was prepared by mixing NCM811, Super P and PVDF in NMP with a mass ratio of 80:10:10. The areal loading of the NCM811 positive electrode was about 5.4 mg cm−2. High areal capacity (3 and 4 mAh cm−2) NCM811 positive electrodes were used to probe the application of negative electrodes in practical systems. NCM811, super P, and PVDF were mixed in a weight ratio of 96.8:1.9:1.9, and the active material loading was 15 and 20 mg cm−2. The LiNi0.98Co0.01Mn0.01O2 positive electrode slurry was prepared by mixing LiNi0.98Co0.01Mn0.01O2, Super P and PVDF (polyvinylidene difluoride) in NMP (N-methyl-2-pyrrolidone) with a mass ratio of 98.1:1:0.9. The obtained slurries were cast on carbon-coated aluminum foil and dried at 80°C for 12 h. The positive electrodes for coin cells were tailored into slices with a diameter of 10 mm. The thickness of the LZNC foil was adjusted to match the areal loading of the positive electrodes: for 1 mAh cm−2 cathodes, a 20 μm-thick foil was used; for 3 mAh cm−2 cathodes, a 100 μm-thick foil was employed; for 4 mAh cm−2 cathodes, a 70 μm-thick foil was employed. For pouch cell assemblies, an 80 μm-thick foil was used, while symmetric cell tests were conducted with a 100 μm-thick foil. For liquid electrolyte cells, 80 μL ether-based electrolyte without any additives [1.0 M bis(trifluoromethane)sulfonimide lithium (LiTFSI, 99.0%, Sigma-Aldrich) dissolved in 1,3-Dioxolane (DOL, 99%, Alfa)/Dimethoxyethane (DME, 99%, Alfa) (1:1, by volume) containing 1% LiNO3 (99.98%, Alfa)] was employed in symmetric cells and Li–S cells, and 80 μL commercial carbonate electrolytes [1.0 M lithium hexafluorophosphate (LiPF6, 98%, Alfa) dissolved in ethylene carbonate (EC, 99%, Alfa)/ diethyl carbonate (DEC, 99%, Alfa) (1:1, by volume) containing 5% fluoroethylene carbonate (FEC, 98%, Alfa)] was applied for NCM811 full coin cells. LZNC||NCM811 and LZNC||LiNi0.98Co0.01Mn0.01O2 pouch cells were assembled with an 80-μm-thick LZNC composite foil and an LHCE [lithium bis(fluorosulfonyl)imide (LiFSI, 99.0%, Sigma-Aldrich), DME, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether (TTE, Macklin, 99.5%) were mixed in a molar ratio of 1:1:3] electrolyte mass loading of 1.5 g Ah−1. The pouch cell was tested under a pressure of 0.2 MPa after being filled with electrolyte and sealed following the standard procedure. Additional details for the pouch cells can be found in Tables S6 and S8.

Ex situ sample preparation and handling
After cycling, the cells were disassembled inside an Ar-filled glovebox (H2O and O2 < 0.1 ppm). The metallic lithium or LZNC electrodes were carefully extracted, and residual lithium salts on the surface were removed by rinsing with DME. To maintain an inert atmosphere during subsequent characterization, the electrodes were transferred and mounted using dedicated protective holders or molds, ensuring that exposure to air or moisture was minimized. All manipulations were performed under controlled Ar conditions, and the average glovebox temperature was 25.0°C.

Characterizations
Particle size distribution is done by Nanoparticle Size and Zeta Potential Analyzer (Malvern, ZS90). The crystalline structure was analyzed by X-ray diffraction (Rigaku SmartLab) with Cu Kα radiation over the 2θ angles from 10° to 80° (step size: 0.02, scan speed: 2°/min). Tensile tests were conducted on a Universal Tensile Testing Machine (INSTRON 3365). Morphology characterization was carried out by Scanning electron microscopy (SEM, JEOL 8100) at 10 kV and transmission electron microscopy (TEM, JEM-2100F) with an accelerating voltage of 200 kV. 3D X-ray microscopy (ZEISS Xradia 510 Versa, Microscopy Customer Center Beijing) was utilized to obtain 3D images with a high resolution. In situ analysis of thickness expansion behavior was conducted using an In Situ Cell Swelling Analyzer (IEST, SWE2110). The measurements were performed on 1 Ah LZNC||NCM811 and Li||NCM811 pouch cells during 0.5C charge-discharge cycling under a constant pressure of 0.2 MPa. Operando Optical Microscopy is performed using Leica optical microscopes. The adhesion of Li and microstructure of the Li surface after cycling were examined by using an atomic force microscope (AFM, Bruker DIMENSION ICON with a Nanoscope V controller) in an Ar-filled glove box with the AFM tip (Bruker Corp., k=26 N m−1, f0=300 kHz) at a constant loading rate of 400 nm s−1. The data of X-ray photoelectron spectroscopy (XPS) were collected through 150 W monochromatic Al Kα radiation (hν=1486.6 eV) with different etch depths, and the base pressure was about 3×10−9 mbar. The charge offset was applied by correcting the hydrocarbon C 1s peak at 284.8 eV (Axis supra, Kratos Analytical Ltd.). Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF-MS) analyses were carried out using a Bruker UltrafleXtreme instrument. The composition and spatial distribution of ions on the anode surface, as well as in the depth-sputtered regions, were examined via Time-of-Flight secondary ion mass spectrometry (ToF-SIMS, ToF-SIMS 5, ION-ToF GmbH, Münster, Germany). The ToF-SIMS system employed a 30 keV Bi+ primary ion beam in combination with a 2 keV Cs+ sputter beam, and an electron flood gun was applied for charge compensation. The experimental setup follows previously reported procedures46. The in situ X-ray diffraction patterns of all samples were collected using an X-ray diffractometer (D8 Bruker Advance) with Cu Kα radiation (λ=1.5418 Å) in the scan range (2θ) of 10~100°. The samples for ex-SEM, ex-XPS, and AFM were obtained by disassembling the after-cycling batteries in an Ar-filled glove box without being exposed to air.

Electrochemical measurements
For each electrochemical experiment, at least five cells were tested, and the data shown in the figures represent a representative cell. To evaluate Li plating/stripping performance, Li symmetric cells were tested under various areal current densities (1, 3, and 5 mA cm−2) and areal capacities (1, 3 and 5 mAh cm−2). In addition, the symmetric cells were first cycled under a low current density for 3 cycles to stabilize the SEI, with the cutoff capacity set the same as that used in the subsequent regular cycling. Charge-discharge tests were conducted with voltage ranging from 1.75–2.55 V for the Li||S pouch cell (1C=1600 mA g−1), 2.8-4.3 V for the Li||NCM811 (1C=200 mA g−1) coin cells, 2.8–4.4 V for the Li||NCM811 pouch cell (1C=200 mA g−1) and 2.5–4.5 V for the LZNC||LiNi0.98Co0.01Mn0.01O2 pouch cell. Tafel plots were measured at voltage range from −0.2 to 0.2 V (versus Li/Li+) in Li symmetric cells with a scan rate of 1 mV s−1 and then managed for linear fitting. The Electrochemical impedance spectroscopy (EIS) measurements were performed on a Princeton PARSTAT MC 1000 multichannel electrochemical workstation over a frequency range of 0.1 Hz to 1 MHz with an amplitude of 10 mV at 25°C. A total of 71 data points were collected. The measurements were carried out in potentiostatic mode after the cells were allowed to rest for 5 min at open-circuit voltage prior to the EIS scan. The activation energy (Ea) of Li+ ions through SEI can be acquired via temperature-dependent EIS of the symmetrical cells from 293 to 333 K. Li+ ion transportation is a thermally activated process, and it is suitable for the classical Arrhenius equation:

1/Rs = A exp(-Ea / RT) (1)

where T is the absolute temperature, Rs is the impendence of Li+ across the SEI film, A is the pre-exponential constant, and R is the standard gas constant. According to the equivalent circuit, Rs was extracted at medium frequencies. ln(T/Rs) vs 1000/T can be well fitted by linear relationships. Ea values can be obtained by Ea = -R×slope (kJ mol−1). Except for variable-temperature impedance testing, all electrochemical tests were conducted at room temperature (25°C) inside a temperature-controlled test chamber.

Computation detail
The ternary phase diagram of the Li–Zn-N system was generated via density functional theory (DFT) calculations based on thermodynamic analysis. It was performed via the pymatgen Python package, including the Materials project database47. It uses DFT as implemented in the Vienna Ab Initio Simulation Package (VASP) software48 to evaluate properties of compounds. In Materials Project, A phase diagram module is a calculation of the thermodynamic phase equilibria of multicomponent systems49–52. Therefore, when using the Materials Project to construct phase diagrams, there is no need to provide data files containing the atomic coordinates of optimized computational models, as would be required for standard VASP calculations. This greatly accelerates the computation and application of material properties. Moreover, the workflow for phase diagram construction in this work is illustrated in Fig. S48 to facilitate a clearer understanding of the above description.

Molecular dynamics (MD) model system: The simulation box had dimensions of 34.36 Å×39.89 Å×38.48 Å. Periodic boundary conditions were used in all three directions.

MD simulations: Molecular dynamics (MD) simulations were conducted using the LAMMPS package. Visualization of the simulation trajectories was performed with VMD software. The system was modeled using an all-atom CVFF force field, with a cut-off distance of 10 Å applied to all short-range van der Waals interactions. Long-range electrostatic interactions were calculated using the particle–particle particle–mesh (PPPM) method. For each system, five independent simulations with different initial velocity distributions were carried out, and all reported quantities represent averages over these runs. Simulations were performed in the canonical ensemble (NVT) at 648 K, with temperature controlled via the Nose–Hoover thermostat. The integration time step was set to 1 fs, and data were recorded every 1 ps. Each simulation was run for a total of 1 ns to ensure adequate sampling of the system behavior. The simulation protocol was adapted from standard MD procedures reported in the literature46.

Data availability
The authors declare that all data supporting the findings of this study are available within the paper and its supplementary information files. All raw data generated during the current study are available from the corresponding authors upon request. Source data are provided with this paper.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "This work presents an innovative free-standing composite-foil anode featurin toughness reinforced 3D architecture through integration of Li-Zn alloy and Li₃N-enriched CNTs. The design constitutes a strategic resolution to the persistent trade-offs among mechanical robustness, manufacturing feasibility, and charge-transfer kinetics in lithium metal anodes. Critically, the exceptional fracture toughness of foil anode effectively mitigates structural degradation in ultrathin 3D configurations during deep-delithiation cycles. The demonstration over 300 stable cycles, coupled with a high energy density of 553 Wh kg⁻¹ in Ah-scale pouch cells, provides compelling evidence of its practical viability. This study presents foundational design principles for next-generation ultrathin 3D composite lithium anodes, making a significant contribution to the field of lithium metal batteries. Due to its rigorous investigation and innovative approach, I believe this work will generate broad interest within both academic and industrial communities. Therefore, I recommend its publication in Nature Communications. To further enhance the clarity and impact of the manuscript, I suggest addressing the following revisions.\n1. In Figure 4a, what is the overpotential of the LZNC electrode at 1 mA cm-2?\n2. Was the rate test in Figure 6c conducted under temperature-controlled conditions? If so, please specify the temperature, as it could influence high-rate performance.\n3. What is the mass ratio of the Li₃N-CNTs in the LZNC composite? This information would help clarify their role in reinforcing the mechanical property of the ternary composite.\n4. Which component or structural feature of the LZNC architecture primarily contributes to the enhancement in toughness? Additionally, in Figure 4e, could the authors elaborate on the physical significance of the exchange current density?\n5. What is the theoretical gravimetric specific capacity of the LZNC composite anode, and does it match with the tested value?\n6. Others: When drawing EIS diagrams (such as Figure 4f and S23-24), it is best to keep the length of the x-axis and y-axis consistent, that is, square; There are missing spaces between some units and numbers, such as in the Computation detail section and Figure 3f-h; Some abbreviations are not given their full names when they first appear, such as SEI; In the vertical axis units of images 3e, 6b, 6d, and S32-33, there is an additional symbol after V;", "reviewer_2": "The manuscript presents the engineering of a three-dimensionalLi-composite foil anode (LZNC), combining Li-Zn alloy with Li3N-enriched carbon nanotubes (CNTs). The authors report enhanced mechanical toughness, excellent tensile strength, and high rupture toughness enabling ultra-thin anodes. The LZNC anode demonstrates superior electrochemical stability, minimal volume fluctuation during cycling. However, I believe this manuscript is not yet suitable for publication in its current form. Below are my constructive comments:\n1. It is still required to clarify the precise roles of Li3N and CNTs in enhancing mechanical properties and conductivity, supported by explicit experimental evidence.\n2. There is limited rigorous benchmarking against current state-of-the-art 3D composite anodes, essential for substantiating the claimed advantages.\n3. It would be better to provide a deeper analysis of long-term electrochemical stability, specifically detailing the mechanism of Li deposition and interface evolution with quantitative in-depth characterization.\n4. The electrochemical and structural characterizations, while extensive, still lack critical in-situ insights into the structural dynamics during actual battery operation conditions.\n5. Post-mortem characterization of the cycled electrodes is necessary to support claims regarding durability and interfacial stability.", "reviewer_3": "The three-dimensional lithium metal composite anode (LZNC) proposed in this study aims to resolve the contradictions between mechanical toughness, processability, structural integrity, and electrochemical performance of ultrathin lithium metal anodes by synergistically integrating Li-Zn alloy with Li3N-enriched carbon nanotubes (Li3N-CNTs). However, there are some unclear points in this manuscript, with a few flaws in the experimental data. Furthermore, the innovative aspects of this research have not been fully explored. Based on these considerations, major revisions are required before its publication in Nature Communications.\n1. As can be seen from Figure 1a, the authors added CNTs during the smelting process. Then, at high temperatures, why did CNTs not react with Li to form Li-Cx? If Li-Cx was formed, would it change the fibrous structure of CNTs? If the fibrous structure of CNTs were not changed, more intuitive morphological structure characterization should be provided.\n2. As mentioned by the authors in Figure 3a, \"the voltage gradually rises while the peak intensity of LiZn diminishes, accompanied by the emergence of the peak of Zn\". It is crucial to clarify whether this dealloying process is reversible, which is highly relevant to the structural integrity of the 3D framework during lithium deposition/stripping with large areal capacities.\n3. According to Figure 6f and Figure S33, it can be concluded that the assembled pouch cell has a capacity of 7.6 Ah and a mass of 0.058 kg. The median voltage of NCM811 is generally 3.8 V, and based on this calculation, the overall energy density is only 497.9 Wh/kg. However, the data calculated in the manuscript is 553 Wh/kg. A reasonable explanation should be provided.\n4. The LZNC lithium-containing composite prepared in this manuscript exhibits good cycling performance when matched with the lithium-containing NCM811 cathode. However, it remains unclear whether it has been matched with other cathodes, such as fabricating Li||S pouch cells to test its cycling performance with lithium-free cathodes.\n5. In Figure 1c, the scale bars for the 8 μm thickness test are misaligned. Please carefully check and correct this.\n6. In Figure S22, for the LZNC symmetric cell, the polarization voltage increases significantly at around 150 h of cycling and then decreases slowly. It is necessary to clarify the underlying mechanism for this phenomenon.\n7. In Figure 4c, it is suggested that different current densities should be distinguished, and the corresponding current density values should be indicated.\n8. Concerning Figures 6a and 6f, it is recommended that the corresponding N/P ratios and cathode loadings be labeled in the figures to ensure data completeness.\n9. Figure 2a presents the XRD data of the LZNC composite, but there is an absence of peaks corresponding to lithiated carbon nanotubes. A reasonable explanation for this should be provided."}, "author_response": "Detailed lists of our point-by-point responses to the comments from the three reviewers\nare listed below.\nFor Reviewer #1\nGeneral Comments: This work presents an innovative free-standing composite-foil\nanode featuring toughness reinforced 3D architecture through integration of Li-Zn alloy\nand Li₃N-enriched CNTs. The design constitutes a strategic resolution to the persistent\ntrade-offs among mechanical robustness, manufacturing feasibility, and charge-transfer\nkinetics in lithium metal anodes. Critically, the exceptional fracture toughness of foil\nanode effectively mitigates structural degradation in ultrathin 3D configurations during\ndeep-delithiation cycles. The demonstration over 300 stable cycles, coupled with a high\nenergy density of 553 W h kg-1 in Ah-scale pouch cells, provides compelling evidence\nof its practical viability. This study presents foundational design principles for next-\ngeneration ultrathin 3D composite lithium anodes, making a significant contribution to\nthe field of lithium metal batteries. Due to its rigorous investigation and innovative\napproach, I believe this work will generate broad interest within both academic and\nindustrial communities. Therefore, I recommend its publication in Nature\nCommunications. To further enhance the clarity and impact of the manuscript, I suggest\naddressing the following revisions.\nResponse to General Comments: We sincerely thank the reviewer for the encouraging\nevaluation of our work and for the thoughtful suggestions. We are pleased that the\nreviewer recognizes the novelty, practicality, and significance of our LZNC composite\nanode design. To further improve the clarity and quality of the manuscript, we have\ncarefully addressed all the comments and revised the text and figures accordingly.\nPlease find our point-by-point responses below.\nComment (1): In Figure 4a, what is the overpotential of the LZNC electrode at 1 mA\ncm-2.\nResponses to Comment 1: We appreciate the reviewer’s attention to the overpotential,\nas it is a key parameter reflecting the interfacial kinetics and electrochemical stability\nof the electrode. As shown in Figure R1, under the condition of 1 mA cm-2-1 mA h cm-\n1\n2, the LZNC anode exhibits an overpotential of ~ 8 mV during the stable cycling stage,\nreflecting the highly stable electrode/electrolyte interface. In the revised manuscript,\nwe have included more discussion in Supplementary materials to clarify the point (Text\nof Fig. S27) and updated the manuscript accordingly (Page 9-10).\nFig. R1. Voltage profiles of LZNC symmetric cell under 1 mA cm-2- 1 mA h cm-2\nconditions\nComment (2): Was the rate test in Figure 6c conducted under temperature-controlled\nconditions? If so, please specify the temperature, as it could influence high-rate\nperformance.\nResponses to Comment 2: We appreciate the reviewer’s thoughtful question\nregarding the testing conditions, as temperature can significantly influence the rate\nperformance and interfacial behavior of lithium metal anodes. We confirm that all rate\nperformance measurements shown in Fig. 6c were conducted at room temperature\n(approximately 25 °C), without any external heating or cooling applied. This further\nvalidates the practicality of our design under standard operating conditions.\nIn the revised manuscript, we have added further explanations to the manuscript\n(Page 19).\nComment (3): What is the mass ratio of the Li N-CNTs in the LZNC composite? This\n3\ninformation would help clarify their role in reinforcing the mechanical property of the\nternary composite.\nResponses to Comment 3: Thank you for this important question. Based on the\nprecursor mass ratio (Li: Zn N : CNTs = 2: 1: 0.6), the expected reaction products are\n3 2\nLi N, LiZn, excess Li, and CNTs. Assuming complete reaction between Li and Zn N ,\n3 3 2\n2\nthe mass of each product can be determined from their stoichiometry and molar masses.\nThe resulting composite mass fractions are approximately 8.7% for Li N and 16.7% for\nreinforces the toughness and structural integrity of LZNC.\nIn the revised manuscript, we have included more discussion in Supplementary\nmaterials to clarify the point (Text of Table. S2) and updated the manuscript accordingly\n(Page 17).\nTable R1. Mass fractions of the components in the LZNC composite.\nComponent Mass Fraction (%) Role\nDeposition site\nLiZn 26.9%\nSecond phase reinforcement\nLi N 8.7% Ionic transfer highway\nCNTs 16.7%\n3D interwoven matrix\nExcess Li 47.7% Electrochemically active material\nComment (4): Which component or structural feature of the LZNC architecture\nprimarily contributes to the enhancement in toughness? Additionally, in Figure 4e,\ncould the authors elaborate on the physical significance of the exchange current density?\nResponses to Comment 4: Thank you for this insightful question. The remarkable\nenhancement in toughness of the LZNC composite primarily arises from the synergistic\neffect between the Li-Zn alloy and the Li N-CNTs network. To better demonstrate the\n3\ncontribution of each component to the mechanical properties of LZNC, we further\nconducted complementary tensile tests on these foils to evaluate their mechanical\nproperties. As shown in Figs. R2 and R3, the Li-Zn alloy provides high tensile strength\nand resistance to fracture, while the Li N-CNTs network contributes mechanical\n3\ntoughness and structural flexibility. Together, these components form a robust 3D\nframework that effectively resists crack propagation and pulverization during cycling.\nRegarding the exchange current density shown in Figure 4e, it reflects the intrinsic\n3\ninterfacial reaction kinetics between the electrode and electrolyte. Physically, it defines\nthe rate of lithium redox reactions at equilibrium, and thus governs how rapidly the\nsystem can respond to applied current. A higher exchange current density corresponds\nto faster interfacial charge-transfer kinetics, enabling lower overpotentials under\npractical current densities. Therefore, the elevated exchange current density observed\nin the LZNC anode highlights its favorable reaction kinetics.\nIn the revised manuscript, we have updated figures (Text of Figs. 1b and S8) and\nincluded more discussion (Page 4).\nFig. R2. Tensile stress-displacement profiles of Li, Li-Zn, LZN, LZC and the LZNC\nfoil, with the integrated area beneath the stress-strain curve (shaded region) quantifying\nits fracture toughness.\nFig. R3. Columnar Comparison Chart of Tensile Strength and Toughness for Li, LZ,\nComment (5): What is the theoretical gravimetric specific capacity of the LZNC\ncomposite anode, and does it match with the tested value?\nResponses to Comment 5: Thank you for raising this important question. Based on the\nprecursor ratio and assuming complete reaction, the major components in the LZNC\ncomposite are LiZn (26.9 wt%), Li N (8.7 wt%), CNTs (16.7 wt%), and excess metallic\nto the reversible capacity. Given the theoretical specific capacity of lithium (3860 mAh\ng⁻¹), the overall theoretical gravimetric specific capacity of the LZNC composite can\nbe calculated as:\nCapacity = 47.7% × 3860 mA h g-1 = 1842 mA h g-1\nThis value matches well with the experimental results shown in Fig. 1e, where a\nreversible capacity of approximately 1800 mA h g-1 is achieved at a current density of\n0.5 mA cm-2. The close agreement between theoretical and experimental values\nconfirms the high utilization of the Li within the LZNC composite.\nIn the revised manuscript, we have included more discussion in Supplementary\nmaterials to clarify the point (Text of Table. S2) and updated the manuscript accordingly\n(Page 4).\nComment (6): Others: When drawing EIS diagrams (such as Figure 4f and S23-24), it\nis best to keep the length of the x-axis and y-axis consistent, that is, square; There are\nmissing spaces between some units and numbers, such as in the Computation detail\nsection and Figure 3f-h; Some abbreviations are not given their full names when they\nfirst appear, such as SEI; In the vertical axis units of images 3e, 6b, 6d, and S32-33,\nthere is an additional symbol after V;\nResponses to Comment 5: We sincerely thank the reviewer for the careful checking of\nfigures and formatting details. Following the suggestion, we have revised the\nElectrochemical Impedance Spectroscopy (EIS) diagrams (Figs. 4f and S23-24) to keep\nthe x- and y-axis lengths consistent (square format). We have also carefully checked the\nmanuscript and corrected all spacing issues between numbers and units in the\nabbreviations are given in full at their first appearance.\nFor the vertical axis labels in Figures 3e, 6b, 6d, and S32-33, the redundant\nsymbols after “V” have been removed. With regard to the reviewer’s comment on\n“Figure 3f-h,” we could not locate these subfigures in our manuscript and believe the\nreviewer may be referring to Figures 5f-h. We have carefully re-examined Figures 5f-h\nand corrected the unit formatting issues accordingly.\nTo make the corrections clear, the revised figures are provided in the response\nletter as Figs. R4-R8. We greatly appreciate the reviewer’s attention to detail, which\nhas helped us significantly improve the overall quality and readability of the manuscript.\nWe have carefully checked all figures to avoid similar issues in the revised version.\nIn the revised manuscript, we have made the corresponding modifications.\nFig. R4. Nyquist plots of bare Li and LZNC symmetric cells after 20 cycles.\nFig. R5. Nyquist plots of bare Li and LZNC symmetric cells before cycling.\n293K, b) 303K, c) 313K, d) 323K, e) 333K.\nFig. R7. XPS depth profile of f) C 1s, g) Zn 2p, and h) N 1s of LZNC anode after cycled\nfor 50 cycles.\nplating at 0.5 mA cm–2/6 mA h cm−2. b) the corresponding voltage profiles of\nNCM811||Li and NCM811||LZNC coin-type full cells at 1C. c) Voltage profiles of\nNCM811||LZNC full cells at different rates. d) The corresponding voltage profiles of\nNCM811||Li full cells. e) Voltage profiles of the NCM811||LZNC pouch cell. f) Voltage\nprofiles of the 8.5 Ah LiNi Co Mn O ||LZNC pouch cell.\n0.98 0.01 0.01 2\nGeneral Comments: The manuscript presents the engineering of a three-dimensional\nLi-composite foil anode (LZNC), combining Li-Zn alloy with Li N-enriched carbon\n3\nnanotubes (CNTs). The authors report enhanced mechanical toughness, excellent\ntensile strength, and high rupture toughness enabling ultra-thin anodes. The LZNC\nanode demonstrates superior electrochemical stability, minimal volume fluctuation\nduring cycling. However, I believe this manuscript is not yet suitable for publication in\nits current form. Below are my constructive comments:\nResponse to General Comments: Thank you for your positive comments on our\nmanuscript. We have carefully considered each of the reviewer’s constructive\nsuggestions, which have helped us significantly improve the clarity and depth of our\nmanuscript. In the revised version, we have addressed all the raised concerns point-by-\npoint, clarified key technical aspects, and revised the relevant sections accordingly.\nComment (1): It is still required to clarify the precise roles of Li N and CNTs in\n3\nenhancing mechanical properties and conductivity, supported by explicit experimental\nevidence.\nResponses to Comment 1:\nWe thank the reviewer for this insightful comment. To unequivocally decouple the\nrespective contributions of Li N and CNTs to the performance of the LZNC composite,\n3\nwe systematically prepared and characterized a series of foil anodes with controlled\ncompositions, which are bare Li, Li-Zn (LZ), Li-Zn-CNTs (LZC), Li-Zn- Li N (LZN),\n3\nand Li-Zn- Li N -CNTs (LZNC) composites.\nfoil anodes to probe their electrochemical reaction kinetics. The exchange current\ndensity, derived from Tafel measurements (Fig. R9), shows that the LZN foil exhibits a\nsignificant enhancement (0.0716 mA cm-2) compared to the baseline LZ alloy (0.0131\nmA cm-2). In contrast, the LZC composite demonstrates only a marginal improvement\n(0.0161 mA cm-2). The LZNC composite achieves the highest exchange current density\n(0.0887 mA cm-2), which we attribute to the formation of an interwoven Li N-CNTs\n3\n9\nnetwork that facilitates fast ion and electron transport. This result highlights that the\nLi N phase is the primary contributor to the superior ionic conductivity, consistent with\n3\nits known high intrinsic Li+ ion conductivity and its role in establishing percolating ion-\nconduction pathways.\nWe further conducted complementary tensile tests on these foils to evaluate their\nmechanical properties (Figs. R10, R11). Quantitatively, the LZN composite exhibits a\n~200% increase in tensile strength over the LZ baseline, an effect we ascribe to the\nsecond-phase reinforcement by the inorganic Li N particles. Notably, the LZC\n3\ncomposite shows an even greater strength enhancement of ~320%. Furthermore, we\ncalculated the toughness, defined as the energy absorbed prior to fracture (the integral\nunder the stress-strain curve, shown in Fig. R11), for each material. While LZN (6.4 ×\n~240% enhancement (11 × 105 J/m3). The synergistic combination of both components\nin the LZNC composite yields the highest toughness value (13 × 105 J/m3), representing\na 300% enhancement relative to LZ. These data demonstrate that the CNTs network\nserves as the principal mechanical reinforcement, drastically improving both tensile\nstrength and toughness by acting as a resilient scaffold that bridges Li-Zn domains,\ninhibits crack propagation, and effectively redistributes mechanical stress.\nIn summary, these complementary experimental analyses clearly delineate the\ndistinct roles of each component wherein Li N is paramount for enhancing\n3\nelectrochemical kinetics, while CNTs are dominant in imparting mechanical resilience.\nCritically, our one-step melt-infusion strategy to obtain LZNC achieves intimate\ninterfacial coupling between Li N and CNTs. This integration of LZNC facilitates a\n3\nsynergistic effect, enabling simultaneous and balanced improvements in\nionic/electronic transport and structural robustness that both higher than that of either\ncomponent alone. These findings eluminate the exclusive role of Li N and CNTs on the\nanode.\nIn the revised manuscript, we have updated figures (Text of Figs. 1b, 4e, S8 and\nFig. R9. Tafel plots of bare Li, Li-Zn, LZN, LZC and LZNC and symmetric cells.\nFig. R10. Tensile stress-displacement profiles of Li, Li-Zn, LZN, LZC and the LZNC\nfoil, with the integrated area beneath the stress-strain curve (shaded region) quantifying\nits fracture toughness.\nFig. R11. Columnar Comparison Chart of Tensile Strength and Toughness for Li, LZ,\nComment (2): There is limited rigorous benchmarking against current state-of-the-art\n3D composite anodes, essential for substantiating the claimed advantages.\nResponses to Comment 2: We appreciate the reviewer’s insightful suggestion. To\nrigorously benchmark the advantages of our LZNC composite anode, we have\nconducted a comprehensive comparative analysis against current state-of-the-art 3D\ncomposite anodes, evaluating both the intrinsic material properties and the resulting\nfull-cell performance.\nFrom a materials perspective, Figure R12 and Table R2 provide a systematic\ncomparison of gravimetric capacity, volumetric capacity, and electrode thickness for\nstate-of-the-art alloy-based and carbon-based 3D Li-composite anodes. As summarized,\nlightweight carbon-based 3D composites typically achieve high gravimetric capacity,\nhowever, their low tap density and the inherent brittleness of many carbon frameworks\noften limit their volumetric capacity and processability, presenting a significant barrier\nto fabricating ultra-thin, Li-excess anodes for high-energy-density batteries. On the\nother hand, alloy skeletons facilitate high volumetric utilization but invariably sacrifice\ngravimetric capacity due to their heavier mass. Furthermore, these alloys often suffer\nfrom structural instability during cycling due to their discontinuous frameworks. In\ncontrast, our LZNC architecture synergistically integrates a Li-Zn alloy with a Li N-\n3\nenriched CNTs network. This unique design simultaneously achieves both high\ngravimetric (1800 mA h g-1) and volumetric capacity (1915 mA h cm-3), overcoming\nthe traditional trade-off between these metrics. Critically, as shown in Figure R10, the\nLZNC composite exhibits the highest tensile strength (23.9 MPa) and toughness (13 ×\n105J/m3). This pronounced mechanical robustness enables the fabrication of ultra-thin\nlithium composite foils suitable for high-energy-density systems.\nreported 3D Li-C and 3D Li-alloy anodes. Note that the circumferential area inversely\ncorrelates with the thickness of the composite anodes.[1-14] Detailed parameters are\nprovided in Supplementary Table 2.\nTable R2. Comparison of volume and gravimetric specific capacity for reported\ncomposite anode.\nFrom the full-cell performance perspective, to evaluate its performance under\npractical cell-level conditions, we benchmarked our pouch cells against current state-\nof-the-art systems (Figure R13 and Table R3). To facilitate a fair and comprehensive\n13\nassessment, we introduced a new evaluation parameter, the normalized anode-specific\ncapacity (NSC). The NSC, defined as 𝑁𝑆𝐶 =\n𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦𝑎𝑛𝑜𝑑𝑒\n,\n(𝑚𝑎𝑠𝑠𝑎𝑛𝑜𝑑𝑒+𝑚𝑎𝑠𝑠\ncurrent collector\n)×𝑁/𝑃\nincorporates the influence of both the current collector and the N/P ratio, thereby\nenabling a direct and equitable comparison of the anode’s effective capacity\ncontribution within full-cell configurations. Unlike conventional lithium-ion batteries,\nLMBs typically require an N/P > 1 configuration to offset irreversible lithium losses\ncaused by their inherently low Coulombic efficiency (<99%). Though this strategy\nenhances cycling stability, it compromises energy density due to excessive lithium\nloading. The NSC metric thus provides a more holistic evaluation of the role of Li anode\nin full-cell performance. As illustrated in Fig. 6g, the LZNC-based pouch cell\noutperforms previously reported systems, achieving a record-high NSC of 947 mA h g-\n1, as well as prolonged cycle life and an outstanding per-cycle capacity retention of\n99.94%. In contrast to prior studies that frequently emphasize either high (anode)\ncapacity or long cycle life in isolation, the LZNC anode delivers both simultaneously\nunder realistic pouch-cell conditions, benchmarking favorably against the most\nadvanced Li-metal systems reported.\nIn the revised manuscript, we have included more discussion in the text and\nSupplementary materials to clarify the point (Text of Figs. 1f and 6g, Tables S3 and S6).\nFig. R13. Comparison of normalized total anode specific capacity versus working cycle\nlife in the previously reported Li-metal pouch cells. Note that the circumferential area\n14\ninversely correlates with the capacity decay rate of the batteries.[15-22] Detailed\nparameters are provided in Supplementary Table 5.\nTable R3. Comparison of cycling performance for previously reported pouch cells.\n(Total specific capacity of anode incorporates the influence of both the current\ncollector and the N/P ratio, thereby enabling a direct and equitable comparison of the\nanode’s effective capacity contribution within full-cell configurations.)\nComment (3): It would be better to provide a deeper analysis of long-term\nelectrochemical stability, specifically detailing the mechanism of Li deposition and\ninterface evolution with quantitative in-depth characterization.\nResponses to Comment 3: We sincerely appreciate the reviewer’s insightful suggestion.\nTo elucidate the relationship between cycling durability and structural/interface\nevolution, we have conducted a series of in situ, post-mortem characterizations on the\nelectrochemical process of LZNC anode and bare Li anode upon the long-term cycling\ncomplemented by systematic, quantitative analysis.\n15\n1) In Situ Visualization of Li Deposition/Stripping Behavior of LZNC\nIn situ optical microscopy observations of symmetric cells (Fig. R14) provide\ndirect visual evidence of the lithium deposition and stripping behaviors between the\nLZNC, bare Li, and Li-Zn electrodes. Electrochemical testing was performed at a\ncurrent density of 1 mA cm-2, with an areal capacity of 2 mA h cm-2, the LZNC electrode\ndemonstrates exceptional structural integrity without fracture or pulverization. This\npreserved 3D conductive framework subsequently guides uniform lithium replating,\nresulting in dense, homogeneous Li deposition devoid of dendritic morphologies.\nConversely, control electrodes comprising bare Li and Li-Zn alloy suffer from severe\nstructural degradation during stripping, characterized by the formation of numerous\nvoids and a progressively looser, more porous architecture. This structure degradation\ninduces irregular, localized lithium nucleation upon subsequent plating, with formation\nof dendrite or mossy Li.\nFig. 14. The in situ optical observations of Li stripping/plating processes on Li, Li-Zn\nand LZNC electrodes at a current density of 1 mA cm -2.\n2) Post-Cycling Structural Characterization of LZNC\nvarious stages (50, 100, and 300 cycles; Fig. R15) reveals a fundamental divergence in\nmorphological evolution between the LZNC and bare lithium electrodes. The LZNC\nelectrode maintains a remarkably compact and uniform surface morphology throughout\nextended cycling, with no evidence of cracking, pulverization, or dendritic formation.\nThis structural preservation indicates exceptionally homogeneous lithium deposition\nand stripping, facilitated by the stable conductive scaffold. In contrast, the bare lithium\nelectrode undergoes severe and progressive structural degradation from 50 to 300\ncycles, developing a rough surface dominated by porous, mossy lithium deposits. In\naddition, a substantial crack between a top layer of freshly deposited lithium and the\nunderlying unreacted lithium metal was observed for bare Li after 300 cycles. This\nmicrostructural failure blocks ionic and electronic pathways, directly accounting for the\nincreasing polarization and eventual cell failure observed in electrochemical data.\nCross-sectional SEM images further confirm the preservation of the integrated bulk\nframework of LZNC without structural collapse, whereas bare lithium exhibits\nsignificant structural degradation, characterized by massive cracks and the\naccumulation of inactive (dead) lithium.\nThe exceptional structural stability of the LZNC electrode stems from its unique\nresistance to pulverization, which enables the preservation of the original 3D ionic and\nelectronic conductive framework even after complete stripping of the metallic lithium,\nas verified by X-ray microscopy (XRM) results (Fig. R16).\nFig. R15. SEM images of LZNC and Li foil surfaces at different cycle stages.\nslices detected by XRM.\n3) Quantitative Analysis of Interfacial Kinetics and Degradation of Anodes\nEIS (Figs. R17 and R18) provides quantitative insight into the interfacial\nevolution and kinetics of the LZNC electrode during extended cycling (Figs. R14 and\nR15). Comparative measurements were conducted using both LZNC and pure lithium\nanodes cycled under identical conditions (1 mA cm-2, 1 mA h cm-2) over 20, 40, 60, 80\nand 100 cycles. The LZNC composite consistently exhibits significantly lower\ninterfacial (R ) and charge-transfer resistance (R ) compared to bare lithium throughout\ns ct\ncycling, indicating the stabilization of the electrode-electrolyte interface and highly\nefficient ionic transport. Notably, the interfacial resistance (R and R ) of LZNC\ns ct\ndecreases during the initial activation and subsequently stabilizes, indicating the\nformation of a robust and rapid ionic-transfer conductive interface. In contrast, the bare\nLi electrode showed a sharp increase in both R and R after approximately 80 cycles,\ns ct\nfollowing initial activation period. This rapid impedance increase is directly attributed\nto severe structural degradation and repeated solid electrolyte interphase (SEI) fracture.\nFig. R17. Nyquist plots of LZNC and Li foil at different cycle stages.\nCT s\nLZNC and Li foil at different cycle stages.\n4) Chemical Composition and Evolution of the Anode Interface\nTo elucidate the chemical composition and its dynamic evolution at the interface,\nwe further performed ex situ X-ray photoelectron spectroscopy (XPS) on those cycled\nLZNC anodes (Figs. R19-R20). The spectra confirm the persistent presence of both\nLi N and Li-Zn phases at the electrode interface throughout extended cycling. The\n3\nhighly ionic conductive Li N facilitates rapid Li⁺ transport, while the lithiophilic Li-Zn\n3\nalloy serves as a homogenous nucleation site, which facilitate to guide uniform Li\ndeposition. Quantitative deconvolution of the XPS spectra reveals a pronounced\nevolution in SEI composition with cycling. We observe a progressive enrichment of\ninorganic species, predominantly Li N, accompanied by a decrease of organic species.\ncycles confirms the continuous enrichment of Li N on the CNTs surface during the\n3\ncycling process. This compositional evolution indicates the formation of a stable,\ninorganic-dominated SEI, which enhances both interfacial ion-transport kinetics and\nmechanical stability.\nFig. R20. Comparison of atomic percentages on the surface of LZNC anodes at\ndifferent cycle stages from XPS measurement results.\n5) Mechanical Properties of the Anode Interface\nAtomic force microscopy (AFM) measurements (Figs. R21 and R22) provide\nquantitative insight into the mechanical evolution of the electrode interface. The surface\nmodulus of the LZNC electrode increases with progressive cycling, which consistently\nhigher than that of bare lithium throughout extended operation. This mechanical\nenhancement is directly correlated with the formation of an inorganic-rich interphase,\nas confirmed by XPS analysis. Such mechanical reinforcement is critical for inhibiting\nlithium dendrite penetration and preserve structure stability. Consequently, even after\n300 cycles, the LZNC electrode maintains an exceptionally smooth surface morphology,\nindicative of uniform, dense lithium deposition (refer to Figs. R15 and R21). In contrast,\ncycled bare lithium electrodes exhibit severe surface roughening, characterized by\nirregular dendrites and a substantial accumulation of electrochemically isolated (dead)\nlithium. This pronounced divergence in interfacial integrity and morphological stability\nhighlights the essential role of a mechanically robust, inorganic-stabilized interphase in\nachieving long-term cycling performance.\nIn conclusion, this comprehensive suite of experimental techniques, including in\nsitu morphological monitoring, ex situ SEM, EIS, XPS analysis, and AFM\ncharacterization, provides a comprehensive mechanistic understanding of the\nexceptional long-term performance of LZNC anode. The superior cycling stability\noriginates from the synergistic combination of structural integrity, maintained by the\nhighly-toughness scaffold, and electrochemical interface stability, enabled by the\n20\ninorganic-enriched and mechanical robustness. These properties work in concert to\nensure dense, dendrite-free lithium plating/stripping behavior, ultimately enabling\nremarkable cycle life under practical operating conditions.\nIn the revised manuscript, we have updated figures (Text of Figs. 4f, 4g, 5i, S20,\nS24, S30, S36, S37 and S38) and included more discussion (Page 7, 10, 12 and 13).\nFig. R21. AFM modulus of LZNC and Li foil at different cycle stages.\nFig. R22. Comparison of AFM modulus values for LZNC and Li foil at different cycle\nstages.\nComment (4): The electrochemical and structural characterizations, while extensive,\nstill lack critical in-situ insights into the structural dynamics during actual battery\noperation conditions.\nResponses to Comment 4: We sincerely thank the reviewer for this insightful comment.\nWe fully agree that in situ and operando characterizations are indispensable for\nelucidating the dynamic structural and interfacial evolution of battery materials under\noperating conditions. In response to this point, our revised manuscript now incorporates\na series of complementary operando and quasi-in situ techniques designed to provide a\n21\nholistic, real-time view of the (de)lithiation mechanisms within the LZNC composite\nanode.\n1) Operando Optical Microscopy\nThis technique provides direct, real-time visualization of Li deposition and\nstripping dynamics. As shown in Fig. R12, during the Li stripping at 1 mA cm-2 with a\ncapacity of 2 mA h cm-2, the LZNC electrode maintains a continuous, intact three-\ndimensional skeleton. In contrast, both the LiZn alloy and bare Li electrodes exhibit\nsevere structural degradation, characterized by observable cracking looser and more\nloosen architecture. Upon subsequent Li plating, lithium is homogeneously deposited\nwithin the robust LZNC scaffold, with no evidence of dendritic growth. Conversely,\nlithium deposition on the Li-Zn and bare Li electrodes is highly irregular and occurs\npredominantly on the surface, accompanied by extensive dendrite formation.\n2) Operando X-ray Diffraction (XRD)\nTo dynamically probe the crystallographic phase evolution, we conducted\noperando XRD on the LZNC electrode during galvanostatic cycling at 0.1 mA cm-2\n(Fig. R23). It reveals a stepwise delithiation mechanism. The process initiates with the\nremoval of free metallic Li, followed by the partial dealloying of the Li-Zn alloy, with\nCNTs framework remains structurally intact throughout the process. Upon Li plating,\nthe Li-Zn alloying reaction occurs initially, followed by the uniform deposition of\nmetallic lithium within the matrix. This result highlights the chemical reversibility and\nstructural robustness of the composite.\nFig. R23. In-situ XRD analysis and schematic illustration of the Li stripping and plating\nprocesses of LZNC anode\n3) Operando EIS\nresistance during cycling at 0.5 mA cm-2 with a fixed capacity of 5 mA h cm-2 (Fig.\nR24). For LZNC batteries, the interfacial resistance (R ) gradually decreases throughout\ns\nplating/stripping cycles, indicative of a persistent stabilized SEI and highly efficient\ncharge transfer within the 3D framework. In contrast, the LiZn electrode exhibits\nsignificant and erratic fluctuations in impedance, which could be attributed to repetitive\nSEI fracture resulting from the mechanical collapse of the framework and uncontrolled\ndendritic lithium deposition, as conclusively verified by post-mortem SEM analysis.\nNoteworthily, the impedance for LiZn remained consistently higher than that of LZNC\nthroughout the entire process.\nFig. R24. In-situ Distribution of Relaxation Times (DRT) analysis of the Li stripping\nand plating processes of Li-Zn and LZNC anode.\n4) Quasi-In Situ XPS\nThe exceptional long-term cyclability of LZNC is fundamentally facilitated by the\nchemical and electrochemical stability of its interfacial components. To quantitatively\nprobe this, we performed quasi-in situ XPS analysis on LZNC electrode at various Li\nstripping states (cut-off voltages of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0 V;\nFig. R25). The high-resolution spectra reveals that the characteristic signal of Li N and\n3\nmetallic Zn (Li-Zn) remain essentially unchanged in both binding energy and peak\nintensity. This demonstrates the exceptional chemical stability of the interface of LZNC\nthroughout the electrochemical cycling process.\nof LZNC anodes.\n5) In-situ analysis of thickness expansion behavior in pouch cells\nTo further probe the structural dynamics of the anodes under practical operating\nconditions, we conducted in-situ thickness variation measurements using in-situ cell\nswelling analyzer employing bare Li and LZNC anodes paired with NCM811 cathodes.\nDetailed experimental conditions are provided in the Supporting Information. This\nmeasurement enables direct and quantitative assessment of electrode volume evolution\nduring repeated lithium deposition and stripping processes. As shown in Figure R26,\nthe NCM811||LZNC pouch cell exhibits a significantly lower thickness fluctuation\nthroughout cycling compared to the NCM811||Li cell. The reduced thickness\nvariation indicates a highly uniform, reversible lithium deposition/stripping process\nwithin the LZNC framework. This behavior demonstrates that the 3D conductive and\nmechanically robust LZNC matrix can effectively accommodate the strain induced by\nlithium depositions/stripping and mitigate localized volume expansion. These\nobservations collectively highlight that the LZNC anode enables more homogeneous\nelectrochemical reactions and enhanced structural integrity in practical full-cell\nconfigurations, supporting its practical applicability in high-energy-density lithium\nmetal batteries.\ncharging and discharging process.\nIn conclusion, these multi-modal operando analyses provide a comprehensive\ninvestigation of the LZNC anode upon battery operation. It reveals that the LZNC\ncomposite facilitates uniform lithium deposition, maintains mechanical integrity of its\n3D host, and promotes the formation of a stable, low-impedance interface, thereby\naccounting for its superior electrochemical performance.\nIn the revised manuscript, we have updated figures (Text of Figs. 3a, 3b, 3c, S20,\nS21 and S46) and included more discussion (Page 7 and 14).\nComment (5): Post-mortem characterization of the cycled electrodes is necessary to\nsupport claims regarding durability and interfacial stability.\nResponses to Comment 5: We sincerely thank the reviewer for this valuable suggestion.\nWe fully agree that systematic post-mortem characterization is essential to substantiate\nthe claimed durability and interfacial stability of the LZNC composite anode. In\nresponse, we have conducted a comprehensive multi-technique analysis of cycled\nelectrodes to provide conclusive evidence of structural and interfacial robustness.\n1) Structural Integrity and Morphological Stability\nTo investigate the evolution of structural and morphological of LZNC upon\ncycling, we performed complementary Optical microscopy, XRM, and SEM analysis on\nthe cycled electrodes (Fig. R27).\nOptical microscopy performed at various depths of delithiation (25% and 75%;\nFig. R27a-d) demonstrates that the LZNC electrode maintains its structural integrity\neven under deep stripping conditions, whereas a control Li-Zn alloy suffers rapid\n25\nfracture and pulverization. XRM corroborates these findings, revealing the preservation\nof a continuous 3D Zn-CNTs network even after complete delithiation (100%\ndelithiation). This structural resilience originates from the inherent mechanical\nrobustness of the composite architecture, ensuring electrode integrity under practical\ncycling conditions. Post-cycling SEM characterization of the LZNC anode after 300\ncycles (Fig. R27) reveals a compact and uniform surface morphology with no evidence\nof cracking, pulverization, or dendritic growth. Cross-sectional images further confirm\nthe preservation of the integrated bulk framework without structural collapse, whereas\nbare lithium exhibits significant structural degradation, characterized by massive cracks\nand the accumulation of inactive (dead) lithium. We also conducted ex situ SEM\ncharacterization of LZNC and bare Li cycled at different cycling stages, which confirms\nLZNC maintains a remarkably compact and uniform morphology throughout extended\ncycling, whereas bare lithium undergoes severe and progressive structural degradation\n(refer to Response to Comment 3, Fig. R15).\nFig. R27. a-d) Digital photograph of Li-Zn and LZNC stripped 25% and 75% free Li.\ne-h) 3D microstructural analysis of LZNC after Li stripping and corresponding x-y\n26\nslices detected by XRM. i-l) SEM images of the surface and cross-section of LZNC\nafter 300 cycles.\n2) Interfacial Chemistry and Mechanical Properties\nTo investigate the evolution of interfacial chemistry and mechanical properties, we\nperformed XPS in-depth profiling, AFM mapping, and Time-of-flight secondary ion\nmass spectrometry analysis on the cycled electrodes (Fig. R28).\nXPS depth profiling of cycled LZNC electrodes revealed a distinct contrast with\nbare lithium. A strong signal from carbon-containing organic compounds, derived from\nelectrolyte solvent decomposition, was detected on the bare Li surface (Figs. R28a-d).\nIn contrast, the LZNC surface exhibited a relatively weak C 1s signal (Figs. R28a-d).\nFurthermore, with increasing etching depth, the carbon signal decreased significantly\nwhile the intensities of nitrogen (N) and zinc (Zn) remained constant (Figs. 5f-h),\nindicating that the interface is dominated by inorganic species both at the surface and\nwithin the bulk.\nEx situ XPS analysis at different cycling stages confirmed the persistent presence\nof both Li N and Li-Zn phases at the electrode interface. Quantitative spectral\n3\ndeconvolution revealed a dynamic evolution in SEI composition, characterized by a\nprogressive enrichment of inorganic species (predominantly Li N, refer to Response to\n3\nby the emergence of a characteristic C-N peak after 200 cycles.\nThe mechanical implications of this inorganic-rich interphase were validated by\nAFM mapping. The LZNC electrode exhibited a substantially higher surface modulus\n(13.6 GPa) compared to bare lithium (387 MPa). This mechanical superiority was\nmaintained throughout extended cycling (refer to Response to Comment 3, Figs. R21-\n22), with the LZNC's surface modulus increasing progressively, a trend directly\ncorrelated with the inorganic species enrichment observed via XPS.\nTOF-SIMS data provided 3D compositional validation (Figs. R28i-k),\ndemonstrating a homogeneous and stable distribution of key inorganic species (Li, N,\nZn). This confirms the formation of a stable, dendrite-suppressing interface with\n27\nfavorable ion-transport properties.\nFig. R28. a) Comparison of atomic percentage on the surface of bare Li and LZNC\nanodes from in-depth XPS measurements. XPS depth profile of b) C 1s, c) Zn 2p, and\nd) N 1s of LZNC anode after cycled for 50 cycles. AFM modulus and morphology\ncomparison of SEI for e, g) bare Li and f, h) LZNC anodes after cycled for 50 cycles.\ni-k) TOF-SIMS analysis of the LZNC anode after 300 cycles.\n3) Charge-Transfer Kinetics and Interfacial Stability\nTo investigate the charge-transfer kinetics and the interfacial stability upon cycling,\nwe performed EIS analysis and Tafel measurements on the cycled electrodes.\nEIS analysis confirms that the LZNC electrode exhibits lower and stable\ninterfacial (R ) and charge-transfer resistance (R ) throughout extended cycling,\ns ct\nindicating minimal degradation and rapid interfacial kinetics (refer to Response to\nComment 3, Figs. R17 and R18). Tafel measurements on batteries after multiple cycles\nreveal a notably higher exchange current density for LZNC (0.0887 mA cm-2) compared\n28\nto Li-Zn (0.0131 mA cm-2) and bare lithium (0.011 mA cm-2), attributable to the\nbiphasic Li N-CNTs network that facilitates concurrent ion and electron transport (refer\n3\nto Response to Comment 1, Fig. R9).\nThese post-mortem findings are fully consistent with the in situ and operando\ncharacterizations detailed in Response to Comment 4. These comprehensive post-\nmortem analysis presented herein robustly supports the conclusion that the LZNC\ncomposite exhibits superior structural and interfacial durability under practical, long-\nterm cycling conditions.\nIn the revised manuscript, we have updated figures (Text of Figs. 5, S22, S24 and\nS36) and included more discussion (Page 7 and 12).\nGeneral Comments: The three-dimensional lithium metal composite anode (LZNC)\nproposed in this study aims to resolve the contradictions between mechanical toughness,\nprocessability, structural integrity, and electrochemical performance of ultrathin\nlithium metal anodes by synergistically integrating Li-Zn alloy with Li N-enriched\n3\ncarbon nanotubes (Li N-CNTs). However, there are some unclear points in this\n3\nmanuscript, with a few flaws in the experimental data. Furthermore, the innovative\naspects of this research have not been fully explored. Based on these considerations,\nmajor revisions are required before its publication in Nature Communications.\nResponse to General Comments: We sincerely thank the reviewer for their\ncomprehensive assessment and valuable suggestions. In response to the general\ncomments, we have thoroughly revised the manuscript to strengthen the clarity, depth,\nand novelty of our work. The core innovation of this study lies not merely in the\ncombination of materials, but in the rational multi-scale design of a nanocomposite foil\n(LZNC) that introduces a toughness-dominated paradigm for ultra-thin lithium metal\nanodes. By synergistically integrating a lithiophilic Li-Zn alloy phase with a Li N-\n3\nenriched carbon nanotube (Li N-CNTs) network, the LZNC anode simultaneously\n3\naddresses the critical trade-offs among mechanical robustness, processability, structural\nintegrity, and electrochemical performance that have long hindered conventional anode\ndesigns. The superiority of this approach is unambiguously demonstrated through three\nkey advances as follows.\n1) A Shift in Mechanical Design of Foil Anodes: from Strength to Toughness\nConventional lithium composite anodes predominantly emphasize enhancing\nmechanical strength (defined as the maximum stress before fracture). In this work, we\nintroduce and prioritize high toughness, the energy absorbed per unit volume before\nfracture (J/m3), as a critical design metric for freestanding lithium anode foils. This is\nachieved through a hierarchical architecture in which the dispersed Li-Zn intermetallic\nphase serves as a strengthening component, while the interwoven, elastic Li₃N-CNT\nnetwork provides exceptional ductility and crack-bridging capability. This synergistic\n30\neffect endows the LZNC foil with a tensile strength of 23.9 MPa and a remarkable\nrupture toughness of 1.3 × 106 J/m3, representing an approximately 12-fold\nimprovement over bare lithium (Fig. R29). As a result, the LZNC anode can be\nprocessed into ultra-thin foils (~8 μm) to increase cell-level specific energy. Moreover,\nthe high toughness enables the foil to intrinsically resist crack propagation and\nstructural pulverization even under deep stripping conditions, ensuring long-term\ncycling stability under demanding operational scenarios.\nFigure R29. a) Tensile stress-displacement profiles of Li, Li-Zn, LZN, LZC and the\nLZNC foil, with the integrated area beneath the stress-strain curve (shaded region)\nquantifying its fracture toughness. b) Columnar Comparison Chart of Tensile Strength\nand Toughness for Li, Li-Zn, LZN, LZC, and LZNC.\n2) Reconciliation of Ultra-Thin Processability with High Gravimetric and\nVolumetric Capacity\nThe pursuit of high-energy-density batteries necessitates the development of ultra-\nthin, lithium-less anodes to minimize the use of metallic lithium. However, the\nfabrication of ultrathin Li anodes presents a fundamental challenge. Pure lithium metal\nis difficult to roll thinly due to its high viscosity and low mechanical strength, while\nmany 3D host-based composites (e.g., Li-C) exhibit brittleness and low volumetric\ncapacity owing to excessive porosity (Table R2, Fig. R30). Although alloy foils (e.g.,\nLi-Mg, Li-Al) can be processed thinly, they typically lack a continuous supporting\nmatrix and suffer from structural pulverization upon dealloying, often requiring heavy\ncurrent collectors that severely compromise gravimetric capacity. Our LZNC anode\novercomes these limitations. Its inherent ductility and toughness enable the fabrication\n31\nof current-collector-free foils below 8 μm. Crucially, the dense composite structure\ndelivers a high gravimetric capacity of 1800 mA h g-1 and an exceptional volumetric\ncapacity of 1915 mA h cm-3, substantially exceeding most reported Li-C and Li-alloy\ncomposites (Table R2, Fig. R30).\nFig. R30. Comparison of volumetric/gravimetric specific capacity of the previously\nreported 3D Li-C and 3D Li-alloy anodes. Note that the circumferential area inversely\ncorrelates with the thickness of the composite anodes.[1-14] Detailed parameters are\nprovided in Supplementary Table 2.\nTable R2. Comparison of volume and gravimetric specific capacity for reported\ncomposite anode.\n3) Simultaneous Realization of Long Cycle Life and High Energy Density in\nThe ultimate validation of an anode lies in its performance in full-cells under\npractical conditions, where achieving both long cycle life and high energy density\nremains particularly challenging. The mechanical robustness and continuous\nion/electron-conducting network of the LZNC anode enable superior comprehensive\nfull-cell performance. To ensure a fair comparison with state-of-the-art systems, we\nintroduce a standardized anode specific capacity metric (defined as 𝑁𝑆𝐶 =\n𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦𝑎𝑛𝑜𝑑𝑒\n),\nwhich normalizes effective capacity by\n(𝑚𝑎𝑠𝑠𝑎𝑛𝑜𝑑𝑒+𝑚𝑎𝑠𝑠\ncurrent collector\n)×𝑁/𝑃\naccounting for the mass of any integrated current collector and the N/P ratio.\nUnder this rigorous assessment, the NCM811||LZNC pouch cell outperforms\npreviously reported systems, achieving a record-high NSC of 947 mA h g-1, as well as\nprolonged cycle life and an outstanding per-cycle capacity retention of 99.94%. In\ncontrast to prior studies that frequently emphasize either high (anode) capacity or long\ncycle life in isolation, the LZNC anode delivers both simultaneously under realistic\npouch-cell conditions, benchmarking favorably against the most advanced Li-metal\nsystems reported (Table R3, Fig. R31). Furthermore, an 8.5 Ah pouch cell demonstrates\na practical energy density of 553 W h kg-1, confirming its high-specific-energy potential.\nFig. R33. Comparison of normalized total anode specific capacity versus working cycle\nlife in the previously reported Li-metal pouch cells. Note that the circumferential area\n33\ninversely correlates with the capacity decay rate of the batteries. [15-22] Detailed\nparameters are provided in Supplementary Table 5.\nTable R3. Comparison of cycling performance for previously reported pouch cells.\n(Total specific capacity of anode refers to the ratio of the capacity of the cell exerted\nin cycling to the mass of the complete anode including the collector.)\nFigure R32. The radar chart displays the key performance characteristics of Li, Li-C,\nLi-alloy, and LZNC.\nIn summary, this work moves beyond conventional approaches focused on\nisolated properties by pioneering a multi-dimensional design framework that\n34\nsynergistically optimizes mechanical, dynamic, and processing characteristics. The\nLZNC foil represents an integrated anode architecture that simultaneously achieves\nrapid ion/electron transport, scalable processability, mechanical toughness, and high\nvolumetric/gravimetric capacity. We contend that the design principles established\nherein provide a new pathway for developing high-energy, long-cycle-life lithium\nmetal batteries. In the revised manuscript, we have re-structured the Abstract,\nIntroduction, and Conclusion to clearly highlight these innovations.\nComment (1): As can be seen from Figure 1a, the authors added CNTs during the\nsmelting process. Then, at high temperatures, why did CNTs not react with Li to form\nLi-C ? If Li-C was formed, would it change the fibrous structure of CNTs? If the\nx x\nfibrous structure of CNTs were not changed, more intuitive morphological structure\ncharacterization should be provided.\nResponses to Comment 1: We appreciate the reviewer’s insightful questions\nconcerning the chemical and structural stability of CNTs upon exposure to molten\nlithium. Our comprehensive characterizations confirm that lithiation of CNTs does\noccur, but through a well-defined, modest intercalation mechanism that preserves the\nessential fibrous morphology of the CNTs.\nThe formation of lithium-intercalated carbon (LiC ) is unequivocally\nx\ndemonstrated through XRD and XPS analysis. The (002) diffraction peak,\ncorresponding to the graphitic stacking in pristine CNTs, shifts from 25.92° to 23.85°\nafter composite fabrication. [25,26] This signifies an expansion of the interlayer spacing\nfrom approximately 3.57 Å to 3.73 Å, a hallmark of lithium intercalation into the\ngraphitic layers. [27,28] Consistent with this, prior research by Shao et al. [29] illustrated\nthe lithiation of graphite coatings by molten lithium in solid electrolyte, identifying\nstructural defects, voids, and CNTs ends as preferential nucleation points for the\nreaction. This finding is consistent with observations over other graphite-based\nmaterials. [30] The reason for the relatively weak scattering intensity is attributed to their\nlow crystallinity of the carbonaceous materials compared to the highly crystalline\nmetal/alloy phases present in the LZNC. Furthermore, the carbon spectrum from XPS\n35\nresult of the LZNC composite reveals a new peak at 282.9 eV, which we assign to Li-\nC bonds (Fig. R33), providing direct chemical evidence for the formation of lithiated-\nCNTs.\nCritically, this intercalation process does not compromise the structural integrity\nof the CNT network. To directly assess morphology, we performed ex-situ SEM on a\npartially delithiated LZNC sample (electrochemically charged to 0.1 V vs. Li⁺/Li to\nremove free lithium metal while retaining the lithiated CNTs framework). The result\n(Fig. R34) clearly shows that the CNTs maintain their original tubular morphology and\nform a continuous, interwoven network without collapse or fracture. Furthermore,\nCNTs are widely utilized as host materials for lithium metal anodes due to their 3D\ninterconnected network, and prior reports have consistently shown that lithiated CNTs\nretain their original tubular morphology, which aligns with our experimental\nobservations. [31] Therefore, while the CNTs are indeed lithiated to form LiCₓ, this\nprocess is fundamentally an intercalation reaction that expands the lattice but crucially\nmaintains the continuous, fibrous scaffold.\nIn the revised manuscript, we have included more discussion in the text and\nSupplementary materials to clarify the point (Text of Figs. S13 and S14) and updated the\nmanuscript accordingly (Page 6).\nFig. R33. a) XRD pattern of LZNC. b) XRD patterns of pristine CNTs and LZNC,\nshowing an enlarged view of the region corresponding to the dashed rectangle in (a). c)\nXPS spectra of C 1s of the LZNC composite.\nthat removes free lithium metal while preserving the lithium-intercalated carbon\nnanotube framework.\nComment (2): As mentioned by the authors in Figure 3a, \"the voltage gradually rises\nwhile the peak intensity of LiZn diminishes, accompanied by the emergence of the peak\nof Zn\". It is crucial to clarify whether this dealloying process is reversible, which is\nhighly relevant to the structural integrity of the 3D framework during lithium\ndeposition/stripping with large areal capacities.\nResponses to Comment 2: We thank the reviewer for raising this critical point\nregarding the reversibility of the dealloying process, which is indeed fundamental to\nthe structural and functional integrity of the 3D framework during cycling. Our in-situ\nXRD data (Fig. 3a) provides direct evidence for the complete reversibility of this\nprocess. As shown in Fig. 3a, a Zn diffraction peak emerges with the diminishment of\nthe LiZn peak intensity during delithiation, while during subsequent lithiation, the Zn\nsignal vanishes as the LiZn reflection recovers, which confirms the complete\nreversibility of the dealloying process. Notably, the LiZn peaks exhibit no cumulative\nbroadening upon cycling, indicating the structure stability of the alloy framework\nwithout structural degradation. To further corroborate the morphological reversibility\nand structural integrity of the dealloyed framework, we performed ex-situ SEM and\nEDS mapping on a sample charged to 1.0 V (vs. Li+/Li), a potential at which delithiation\nis complete. These analyses reveal a continuous, interwoven network where Zn\ndomains exhibit an island-like morphology percolated by CNTs matrix, with no\nevidence of structural fragmentation or cracking (Fig. R35). This morphological\nintegrity was further confirmed by XRM (Fig. R36), which visually affirms that the Zn\n37\nparticles remain interconnected and well-anchored by the CNTs network after complete\nlithium stripping.\nThe stability of this 3D framework enables excellent cycling performance of\nLZNC-based full-cells under practical conditions. To demonstrate this, we paired the\nLZNC anode with a high-loading LiNi Co Mn O (NCM811) cathode (areal\n0.8 0.1 0.1 2\ncapacity: 4 mA h cm-2) at a low N/P ratio of 1.9. The full cell retained 92% of its\ncapacity after 300 cycles at 0.5C, highlighting the exceptional structural reversibility of\nthe LZNC composite even under demanding cycling conditions.\nIn the revised manuscript, we have included more discussion in the text and\nSupplementary materials to clarify the point (Text of Figs. 3d and S23) and updated the\nmanuscript accordingly (Page 7).\nFig. R35. SEM image and corresponding EDS mapping of LZNC after complete de-\nlithiation.\nFig. R36. X-ray CT reconstruction of the fully delithiated LZNC anode.\nComment (3): According to Figure 6f and Figure S33, it can be concluded that the\n38\nassembled pouch cell has a capacity of 7.6 Ah and a mass of 0.058 kg. The median\nvoltage of NCM811 is generally 3.8 V, and based on this calculation, the overall energy\ndensity is only 497.9 Wh/kg. However, the data calculated in the manuscript is 553\nWh/kg. A reasonable explanation should be provided.\nResponses to Comment 3: We thank the reviewer for their meticulous examination of\nour energy density calculation. The discrepancy arises from the use of standard LiNi\n0.\nCo Mn O (NCM811) parameters in the reviewer’s estimation, whereas our pouch\n8 0.1 0.1 2\ncell utilizes a LiNi Co Mn O cathode with much higher nickel content. This\n0.98 0.01 0.01 2\ncathode chemistry operates within a wider voltage window (2.5- 4.5 V), leveraging its\nhigh-voltage phase characteristics to deliver a higher average discharge voltage and\ngreater specific capacity than conventional NCM811.\nImportantly, the capacity of 7.6 Ah mentioned in the manuscript was a preliminary\nestimated value based on the theoretical specific capacity of LiNi Co Mn O\n0.98 0.01 0.01 2\ncathode materials and the designed electrode loading before cell testing. This estimated\nvalue deviates from the actual measured value. The actual measured discharge capacity\nof the assembled pouch cell, as shown in the capacity-voltage profile (Fig. R37),\nreaches 8.5 Ah. More critically, the energy-voltage curve (obtained from the testing\nsoftware) yields a total energy output of 32.36 Wh. Given the total cell mass of 58.35\ng, the specific energy of this pouch cell is calculated to be of 553 Wh kg⁻¹. To avoid\nmisunderstanding, we have corrected the estimated pouch cell capacity to the\nexperimentally measured value (8.5 Ah) in the revised manuscript.\nTo ensure transparency and facilitate comparison, we have provided a detailed\nsummary of the pouch cell configuration, including areal capacity, electrode loadings,\nactive material utilization, and total mass, in Table R4. This allows for direct\nverification of both the practically measured capacity and the resulting specific energy.\nIn the revised manuscript, we have included more discussion in the Supplementary\nmaterials to clarify the point (Text of Fig. S47 and Table S7).\nthe 8.5 Ah LiNi Co Mn O ||LZNC pouch cell.\n0.98 0.01 0.01 2\nTable R4. Parameters of the 8.5A h LiNi Co Mn O ||LZNC pouch cell.\n0.98 0.01 0.01 2\nComposition Parameter Value\nAreal capacity (mA h cm-2) 11.8\nNi98 Cathode Mass loading (mg cm-2) 27.5\nStacked number of layers 15\nAreal capacity (mA h cm-2) 14.87\nLZNC Anode Thickness (μm) 80\nStacked number of layers 16\nSeparator Areal weight (mg cm-2) 1\nAl Foil Thickness (μm) 12\nElectrolyte Volumes (g) 11.4\nEnergy (W h) 32.2924\nCell Mass (g) 58.35\nGravimetric Energy Density (Wh kg-1) 553.43\nComment (4): The LZNC lithium-containing composite prepared in this manuscript\nexhibits good cycling performance when matched with the lithium-containing\nNCM811 cathode. However, it remains unclear whether it has been matched with other\ncathodes, such as fabricating Li||S pouch cells to test its cycling performance with\nlithium-free cathodes.\nResponses to Comment 4: Thank you for this insightful comment. To evaluate the\ncompatibility of the LZNC anode with lithium-free cathodes, we assembled LZNC||S\ncoin cells and Ah-level LZNC||S pouch cells. The pouch cell utilized a conventional\nCNT-S composite cathode (70% sulfur content, obtained by integrating sulfur and\nCNTs at 155 °C for 20 h) with an areal capacity of 4.8 mA h cm-2, and employed a\nconventional DOL/DME-based electrolyte (1 M LiTFSI). As shown in Fig. R38, the\nLZNC||S coin cell exhibited stable cycling over 200 cycles at 0.5C, while the Ah-level\npouch cell achieved 60 stable cycles at 0.1C. It should be noted that the cycling stability\n40\nof lithium-sulfur batteries is not solely influenced by the anode, but is significantly\ninfluenced by the dissolution of polysulfides at the cathode. Future work will focus on\noptimizing both the sulfur–carbon composite cathode and the electrolyte to further\nimprove cycling performance. These results confirm that the LZNC anode also delivers\nexcellent performance when paired with a lithium-free cathode, highlighting the\nuniversal stability of this composite anode.\nIn the revised manuscript, we have included more discussion in the text and\nSupplementary materials to clarify the point (Text of Fig. S41) and updated the\nmanuscript accordingly (Page 14 and 16).\nFig. R38. Cycling performance and the corresponding voltage profiles of LZNC||S\ncoin-type full cell and pouch cell.\nComment (5): In Figure 1c, the scale bars for the 8 µm thickness test are misaligned.\nPlease carefully check and correct this.\nResponses to Comment 5: We thank the reviewer for identifying this oversight. The\nscale bars in Figure 1c corresponding to the 8 µm thickness have been carefully\nrealigned and corrected in the revised manuscript.\nComment (6): In Figure S22, for the LZNC symmetric cell, the polarization voltage\nincreases significantly at around 150 h of cycling and then decreases slowly. It is\nnecessary to clarify the underlying mechanism for this phenomenon\nResponses to Comment 6: Thank you for pointing out this observation. The transient\nincrease in polarization voltage around 150 h in the LZNC symmetric cell is likely\nattributed to slight ambient temperature variations or sporadic, localized micro-short\ncircuits during cycling, both of which can temporarily influence ionic transport and\ninterfacial kinetics. To rigorously exclude such potential artifacts, we repeated the\ncycling test under stringent, controlled conditions. The resulting data (Fig. R40) show\na consistently stable polarization profile, confirming that these transient fluctuations do\nnot affect the overall long-term electrochemical stability or the low-polarization\ncharacteristic of the LZNC symmetric cells.\nIn the revised manuscript, we have updated the latest data in the supplementary\nmaterials (Text of Fig. S28).\nFig. R40. Voltage profile of symmetric cell with LZNC under 5 mA cm-2 with a\ncapacity of 5 mA h cm-2.\ndistinguished, and the corresponding current density values should be indicated.\nResponses to Comment 7: We thank the reviewer for this suggestion. The current\ndensity values have been clearly indicated on Figure 4c to distinguish the different rates,\nwhich helps to enhance the clarity of the presentation (see updated Fig. 4c).\nFig. R41. Rate performances of bare Li and LZNC symmetric cells at the current\ndensities from 0.5 to 10 mA cm-2 with 1mA h cm-2.\nComment (8): Concerning Figures 6a and 6f, it is recommended that the corresponding\nN/P ratios and cathode loadings be labeled in the figures to ensure data completeness.\nResponses to Comment 8: We thank the reviewer for this valuable suggestion. In\nresponse, we have updated Figures 6a and 6f to explicitly include the corresponding\nN/P ratios and cathode areal loadings, which ensures all critical parameters are\nexplicitly stated for clarity (see updated Fig. 6a and 6f).\nFig. R42. a) Cycling performance of NCM811||Li and NCM811||LZNC coin-type full\n43\ncells at 1C. b) Cycling performance of NCM811||LZNC pouch cells at 0.5C.\nComment (9): Figure 2a presents the XRD data of the LZNC composite, but there is an\nabsence of peaks corresponding to lithiated carbon nanotubes. A reasonable\nexplanation for this should be provided.\nResponses to Comment 9: We thank the reviewer for this insightful observation. The\nabsence of distinct lithiated carbon nanotube (LiCₓ) diffraction peaks in the XRD\npattern of the LZNC composite (Figure 2a) can be attributed to its low crystallinity,\nwherein the relatively weak scattering signal from the carbonaceous component is\nmasked by the dominating scattering intensity from the highly crystalline metallic and\nalloy phases within the composite.\nAs detailed in our Response to Comment 1, LiC is indeed formed, as confirmed\nx\nby XPS and the characteristic shift of the (002) graphite peak. However, its XRD\nsignals are broad and weak due to the disordered structure and nanoscale dimensions\nof the CNTs, which result in low intensity. This is consistent with reports in the\nliterature, such as that by Tilmann et al. 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Increasing the Pressure-Free Stripping Capacity of the Lithium\nMetal Anode in Solid-State-Batteries by Carbon Nanotubes. Adv. Energy Mater. 12,\n2201125 (2022).\n47"}, {"round": 2, "reviewer_comments": {"reviewer_1": "The manuscript has been thoroughly revised in accordance with all comments, and I believe it now meets all requirements for publication.", "reviewer_2": "The manuscript has been revised accordingly. There is no more comment.", "reviewer_3": "The authors have addressed the concerns, and it can be published at this stage."}, "author_response": ""}]

Decision letter