Cluster level entropy enhancement in neutral acetate electrolytes enables economical and durable zinc air batteries

Domain: physics
Published: 2026-01-15
Editorial outcome: minor_revision

Abstract
Neutral zinc–air batteries provide a viable alternative to alkaline systems by avoiding salt creep and carbonate passivation. Among candidate electrolytes, acetate-based formulations are particularly attractive for their low cost, sustainability, and compatibility with ambient-air operation. However, their widespread adoption is limited by a trade-off between two concentration regimes. Dilute electrolytes trigger side reactions and lack ionic strength, while concentrated ones suffer from kinetic limitations due to contact ion pair clustering. Here, we propose a cluster-level entropy enhancement strategy that optimizes the mesoscopic configuration of the electrolyte by disrupting large clusters in concentrated acetate electrolytes. This entropy enhancement improves zinc ion diffusivity and kinetics, mitigates interfacial concentration gradients, and maintains local ionic strength for fast electrochemical reactions, as evidenced by various synchrotron X-ray techniques and theoretical simulations. Consequently, the zinc–air batteries in neutral electrolyte deliver over 1800 hours at 0.1 mA cm-2 (1 mAh cm-2, 61.4% round-trip efficiency) and 500 hours at 1 mA cm-2 (12 mAh cm-2, 51.2% round-trip efficiency) in ambient air. This study extends the application of sustainable acetate electrolytes in neutral zinc–air batteries and illustrates a mesoscopic tuning approach applicable to aqueous energy systems with metal electrodes and concentrated solvents.

Introduction
Rechargeable zinc–air batteries offer high theoretical energy density, low cost, and intrinsic safety, making them attractive for next-generation energy storage1,2. Over the past decade, much effort has focused on improving air electrode reversibility via four-electron oxygen evolution and reduction (OER/ORR) reactions3,4. Indeed, substantial progress has been made in the development of high-activity, low-cost catalysts applied to the positive electrode5,6. Our previous studies have contributed to this field, proposing dynamic catalysis7, surface reconstruction strategies8, and electrode/electrolyte structure engineering9. However, commercialization of zinc–air batteries remains hindered by persistent challenges10,11. A primary barrier lies in the use of concentrated alkaline electrolytes to support ORR/OER reactions12, which induce dendrite growth and passivation, severely limiting reversibility13. Moreover, exposure to CO2 in ambient air forms insoluble carbonates on the positive electrode, blocking pores and degrading performance14,15. Thus, designing electrolytes with adaptive local environments is essential for enabling long-term zinc–air battery operation.

To address these issues, various strategies involving additives or alternative aqueous electrolytes have been explored to suppress undesired reactions. For example, zinc acetate has been used as a sustainable additive to enhance zinc electrode stability by partially replacing hydroxide coordination, thus suppressing ZnO formation while preserving ionic strength16,17. Desipite this, reversibility remains limited in alkaline environments due to unresolved side reactions and corrosion18,19. Neutral electrolytes offer greater chemical stability and reduced corrosion burden20,21. Recently, cost-effective zinc acetate has been investigated as a standalone electrolyte system for neutral zinc–air batteries22. Particularly, dilute solutions offer high ionic mobility and suppress dead-zinc formation (Fig. 1a, gray spot in the dilute region). Nonetheless, like most reported diluted electrolytes, the high content of active water led to poor interfacial stability and side reactions. A recent study23 demonstrated that supporting salts or hydrotropic agents can overcome solubility limits and create a Zn2+-rich local environment, enabling prolonged Zn stripping/plating. Yet, as will be extensively discussed in this study, we find that intrinsic contact ion pairs (CIPs) in acetate electrolytes tend to aggregate into large ion clusters in high-concentration regions. While these clusters offer some stabilization, they severely impair overall electrolyte kinetics (Fig. 1a, marked by the gray spot in the concentrated region), posing a critical limitation for multi-electron systems like Zinc-air batteries. Although the sustainable and cost-effective zinc acetate electrolyte holds great potential for enabling neutral zinc–air batteries and avoiding harsh alkaline conditions, its practical application remains challenging due to current technological limitations24.

Recent advances in solvation engineering of aqueous electrolytes have deepened the understanding of Zn2+ coordination and opened alternative avenues to design electrolytes with tailored structures and interfacial dynamics25–27. Since the first report in 202328, entropy-tuned electrolytes have gained growing attention as their compositional complexity offers promising routes to enhance ionic conductivity, solubility, and interfacial stability, particularly in concentrated systems where sluggish ion transport and unstable electrode reactions remain critical challenges29. In aqueous systems, entropy-regulation strategies typically involve the introduction of multiple functional components to manipulate solvation structures and interfacial behaviors30. Representative approaches include incorporating mixed cations or anions to tune solvation shells and modulate electric double layer31,32, co-solvents to weaken hydrogen-bond networks33, and solvated additives to suppress side reactions and regulate solid electrolyte interphase chemistry34. Despite the significant progress, the inclusion of compositionally diverse species raises additional concerns over side reactions, increased cost, and dubious electrolyte stability, underscoring the need for alternative entropy-regulation with improved structural simplicity and reliability35.

Herein, we propose a cluster-level entropy-enhancement strategy that leverages the intrinsic solvophobicity of large ion clusters. Unlike multi-salt/additive “high-entropy” systems that rely on compositional complexity, our approach tunes configurational entropy at the mesoscopic level by regulating ion-cluster configuration in a bi-salt electrolyte. Specifically, by introducing non-aqueous structural disruptors into the system, these molecules (such as DMC, which serves as a model disruptor in this study) weakly interact with and perturb large ion clusters into smaller, more dispersed units with greater configurational freedom. This structural transition increases the system’s entropy, reducing ion association, enhancing Zn2+ transport, and improving overall electrolyte dynamics. Consequently, it effectively overcomes the trade-off between electrolyte kinetics and electrochemical stability even at high acetate salt concentrations (Fig. 1a yellow spot on the red line). This entropy-enhanced zinc acetate electrolyte, featuring a smaller ion cluster, effectively mitigates concentration gradients near the electrode and enables rapid electrochemical interfacial reactions. Combined with the ZnO positive electrode chemistry, the resulting Zn-air battery delivers over 1800 h of stable cycling at 0.1 mA cm−2 and 400 h at 1 mA cm−2 in ambient air, showing competitive performance compared with recent acetate-based and other neutral zinc–air batteries. Beyond extended lifespan, our neutral zinc acetate electrolyte demonstrates favorable attributes in affordability, sustainability, safety, and kinetics compared with systems such as 6 M KOH and 3 M Zn(OTF)2. This work presents a cost-effective and sustainable electrolyte for zinc-air battery systems. Its applicability across multiple carbonate solvents suggests that the cluster-level entropy tuning strategy can be applied to electrolyte design in various metal–based aqueous batteries.

Results
Entropy-enhanced strategy for concentrated zinc acetate electrolyte
To systematically elucidate the entropy enhancement strategy for breaking the performance trade-offs, three types of electrolytes, dilute, concentrated, and an entropy-enhanced acetate system, were prepared and investigated. Dilute electrolyte was prepared via a regular dissociation process as illustrated in Fig. S1, consisting of 1 M Zn(AC)2 and 1 M NaAC bi-salt electrolyte (denoted as 1Zn1Na). However, even in dilute conditions, Zn2+ and AC− (acetate anion) readily form intrinsic CIPs due to strong bidentate coordination. These CIPs hinder further concentration increases since they spontaneously aggregate through hydrophobic interactions between the –CH3 groups on acetate (Fig. S2)36,37. To reach higher concentrations and overcome solubility limits, excess NaAC was introduced as a supporting salt to enhance Zn(AC)2 dissociation (Fig. 1b). This method macroscopically results in a homogeneous solution resembling the dilute system. However, CIPs persist at the mesoscopic scale and tend to aggregate into large ion clusters, exhibiting liquid–liquid phase separation (LLPS) like protein aggregation in aqueous media38,39. This mesoscale phase instability significantly hinders ion mobility and the practical usability of the concentrated system. Our entropy-enhancement strategy addresses this issue by exploiting the inherent solvophobicity of clustered ionic domains in concentrated electrolytes. By introducing dimethyl carbonate (DMC) as a structural disruptive agent which weakly interacts with Zn2+ and embeds into ion clusters via outer-sphere contacts, large CIP clusters are broken into smaller, more mobile aggregates with greater configurational entropy (Fig. 1c), thereby improving electrolyte homogeneity and ion transport.

We first optimized the concentrated electrolyte composition by adjusting the Zn(AC)2/NaAC molar ratio and the water content (R). As evaluated and discussed in Fig. S3a, b, a Zn2+:Na+:H2O ratio of 1:3:10 (denoted as ZN3A5·10H2O, where Z represents Zn2+, N represents Na+, A represents AC−) was identified as an optimal balance, considering Zn2+ concentration, viscosity, ionic conductivity, and pH, thereby providing a sustainable neutral electrolyte. Despite favorable properties, the ZN3A5·10H2O contains large ion clusters and lacks long-term kinetic stability. Rheological measurements reveal a high viscosity of ~37.5 mPas, nearly 10 times that of the dilute 1Zn1Na system (~3.7 mPas), along with pronounced shear-thickening behavior at high shear rates (10–100 s−1) (Fig. 1d). These observations suggest that external environmental stress accelerate the coalescence of CIPs into larger aggregates and even salt precipitation by overcoming ionic shielding (inset image in Fig. 1d), thereby sharply increasing viscosity. Similar behavior was observed at higher Zn2+ concentrations (Fig. S4), where the onset of phase separation shifts to lower shear rates, indicating widespread cluster formation.

In our entropy-enhanced electrolyte, ZN3A5·10H2O-EE, the introduced DMC interacts with the hydrophobic tails of AC−, disrupting CIP–CIP interactions and preventing the clustering phenomenon. As a result, viscosity drops from 37.5 to 12.3 mPas, and the system exhibits enhanced dynamic stability even under high shear (>100 s−1). Additionally, the incorporation of organic molecules into the electrolyte structure expands the operational window and introduces interphase chemistry at the metal electrode interface. Moreover, DMC modulates the extended solvation structure of Zn2+, improving electrolyte kinetics by optimizing solvation strength and the local electrochemical environment. This enhancement improves ion cluster transport in the bulk electrolyte and facilitates interfacial charge transfer (Fig. 1e), thereby mitigating concentration gradients and promoting uniform diffusion, as detailed in the following section.

The Zn2+ local environment variation in the ion cluster
The entropy-driven disruption of ion clusters was initially examined using isothermal titration calorimetry (ITC), a sensitive method for probing molecular interactions40. As shown in Fig. 2a, the setup includes a sample cell containing the target electrolyte and a reference cell with a buffer for heat detection. By incrementally injecting DMC into different electrolytes, we derived the system’s ΔS and ΔG based on variations in enthalpy (ΔH). Initially, DMC was injected into water and 1Zn1Na for comparison (Fig. S5a, b). They showed similar thermal responses (dQ/dt < 0 after stabilized) due to the immiscibility between water and DMC, primarily reflecting interfacial effects rather than molecular interactions. In contrast, sequential DMC injection into concentrated ZN3A5·10H2O produced distinct, consistent endothermic peaks (dQ/dt > 0, Fig. 2b), reflecting significant heat absorption and enabling quantitative thermodynamic analysis of microenvironmental changes. As shown in Fig. 2c and Table S1, these peaks arise from partial disruption of CIP clusters by DMC, weakening ionic associations and increasing configurational entropy (ΔS = 43.4 cal mol−1 K−1), reducing ion cluster size and promoting structural disorder within the electrolyte. Despite requiring energy to overcome intra-cluster interactions (ΔH = +3.85 kcal mol−1), the process is entropy-driven and thermodynamically favorable (ΔG = −9.17 kcal mol−1). These findings indicate that DMC mediates distinct interactions with the disrupted clusters, leading to a more disordered yet stable microenvironment that benefits battery performance. Moreover, the consistent thermodynamic behavior observed in other carbonate-based systems (Figs. S6–S8) supports the broader applicability of this entropy modulation strategy in Zn-based electrolytes.

To further reveal entropy-enhanced effects on local Zn2+ coordination and mesoscopic structure, Raman spectroscopy was employed to probe Zn2+–AC− contact ion pair (CIP) coordination. As shown in Fig. 2d, no peaks appear in the low-frequency region (<500 cm−1), indicating suppression of the Zn2+-(H2O)6 vibration (~390 cm−1) across all electrolyte systems41. This effect helps reduce water-involved side reactions, including the hydrogen evolution reaction during the desolvation at the negative electrode/electrolyte interface42. The C–C stretching vibration serves as probe for understanding the complexation between Zn2+ and acetate CIPs43,44. In 1 M Zn(AC)2, the ν(C–C) peak appears near 948 cm−1, characteristic of bidentate ion pairing (BIP) between Zn2+ and AC− due to strong coulombic interaction. With NaAC as a supporting salt, the peaks in 1Zn1Na and ZN3A5·10H2O exhibit significant blue shifts to near 942 cm−1, indicating an increased presence of monodentate contact ion pairs (MIP) in the electrolyte systems45. This shift arises because fully dissociated Na⁺ and AC− ions elevate the overall ionic strength of the electrolyte, enhancing the ionic shielding effect. Consequently, the coordination strength between Zn2+ and Ac− decreases, and one coordination site of AC− is released from the Zn2+—AC− CIPs. The peak in ZN3A5·10H2O-EE shifts slightly to a lower wavenumber than that in ZN3A5·10H2O, while maintaining the MIP state of the electrolyte system. It’s worth mentioning that at excessive NaAC concentrations, the system shifts toward a solvent-shared ion pair (SSIP) state, with a shoulder at ~910 cm−1 indicating free acetate anion in ZN10A12·20H2O system. While it increases the overall ionic conductivity of the electrolytes, the hydrolysis of NaAC raises pH and viscosity, hindering the reversibility of Zinc stripping/plating.

The regulation of electrolyte configuration via entropy tuning also modulates water activity, as shown by changes in O–H vibrations (3000–3750 cm−1)46,47. The peak of strong hydrogen bond water (at 3253 cm−1) can be clearly observed in 1 M Zn(AC)2 since the BIP state of acetate anion exposes the hydrophobic –CH3 groups. Water molecules will form 4-coordinate hydrogen-bonded water (4-HBW) and polyhedral cages of tetrahedrally hydrogen-bonded water molecules surround –CH3 groups, showing high activity and inducing the side reaction at the negative electrode interface48. The intensity of 4-HBW decreases with increasing Zn2+ concentration. Correspondingly, the higher content of bonded water (3410 cm−1) can be attributed to the in-phase vibrations of water molecules captured by the –C=O groups of the acetate anion. In particular, the addition of DMC further disrupts water-water interactions, thereby increasing the thermodynamic stability of ZN3A5·10H2O-EE and expanding the water splitting window up to 2.53 V (Fig. S9)49.

The configuration change in CIP was further examined via attenuated total reflectance-infrared spectroscopy (ATR-IR), which sensitively detects polar vibrations, especially carboxyl group modes (ν(COO−)s, ν(COO−)a)50. The defined Δν (the difference in the wavenumber, Δν = ν(COO−)a - ν(COO−)s), serves as an indicator of the acetate coordination mode. As illustrated in Fig. 2e, the two bands observed at 1450 cm−1 and 1536 cm−1 are assigned to the symmetry ν(COO−)s and asymmetry ν(COO−)a, respectively, in solid Zn(AC)2·2H2O as in ref. 51. The Δν increases upon NaAC addition (Δν1Zn1Na > Δν1M Zn(AC)2), consistent with Raman trends. This confirms that the bonding strength between acetate anions and Zn2+ decreases across the sequence (ZN3A5·10H2O-EE > ZN3A5·10H2O > 1Zn1Na > 1M Zn(AC)2), facilitating cluster disintegration and mesoscale homogeneity.

Various synchrotron-based X-ray techniques and MD simulations were utilized to reveal the structural configuration around Zn2+ in electrolyte systems. Zn K-edge X-ray absorption spectroscopy (XAS) was conducted on dilute 1Zn1Na, concentrated ZN3A5·10H2O, and Entropy-enhanced ZN3A5·10H2O-EE electrolytes (Fig. 3a). The X-ray absorption near-edge structure (XANES) spectra highlight energy level differences among the four electrolyte systems, reflecting distinct local chemical environments around Zn2+. The absorption edge shifts to lower energy levels in the order of ZN3A5·10H2O < 1Zn1Na < 1M Zn(AC)2, suggesting reduced Zn–O electron transfer and a weakened Zn2+–AC− interaction. Notably, the entropy-enhanced process does not introduce additional inner solvation structures around Zn2+, as evidenced by the minimal change in edge energy in XANES between ZN3A5·10H2O-EE and ZN3A5·10H2O (inset image of Fig. 3a)52. This indicates that DMC does not directly participate in the inner solvation shell around Zn2+ or alter its oxidation state. Instead, it resides outside the primary coordination sphere and perturbs the outer solvation structure through weak solvophobic and dielectric interactions, which destabilize CIP networks and facilitate cluster fragmentation53.

Fourier-transformed extended X-ray absorption fine structure illustrated the solvation shell variation around Zn2+ (Fig. 3b). In all electrolytes, the dominant Zn–O peak indicates solvation is primarily confined to the first coordination shell. Zn–O bond lengths increase from 1.84 Å in 1 M Zn(AC)2 to 1.89 Å and 1.93 Å in 1Zn1Na and ZN3A5·10H2O, respectively, indicating weakened Zn2+–AC− coordination. This result aligns with Raman and ATR-IR data, confirming a coordination shift from BIP to MIP. Notably, the addition of DMC shortens the Zn–O bond to 1.90 Å in ZN3A5·10H2O-EE and decreases peak intensity. The observed spectral change reflects a partial reorganization of the Zn2+ coordination environment, not through direct Zn–DMC coordination, but rather due to the suppression of long-range ion-cluster interactions and the partial collapse of the extended solvation shell. DMC molecules embedded within the ion clusters facilitate this compaction, leading to reinforced Zn–O interactions and the formation of smaller, more dynamic clusters while preserving the MIP coordination state.

The extended solvation and ion cluster structures, especially smaller ion clusters in ZN3A5·10H2O-EE, were further characterized and proved in the synchrotron-based high-energy (55 keV) X-ray scattering data S(q). Similar to X-ray diffraction (XRD) for crystalline materials, S(q) reveal short-range structural correlations in liquid electrolytes, particularly those related to mesoscopic ion clustering54,55. As shown in Fig. 3c, only a broad peak appears for the 1Zn1Na electrolyte for high scattering vector (Q) value around 10 Å−1. This indicates the absence of a network structure in the local electrolyte environment, and that the detected configuration mainly reflects atomic packing distances, likely arising from CIPs between Zn2+ and AC, as previously discussed in Raman and EXAFS. In contrast, ZN3A5·10H2O and ZN3A5·10H2O-EE exhibit pronounced S(q) signals in the low-Q region (0.4–1.9 Å−1) and medium-Q region (2–5 Å−1), indicating the formation of mesoscopic ion clusters in electrolyte systems. Moreover, ZNA·10H2O-EE shows a slight increase in Q value and a reduced S(q) intensity compared to ZN3A5·10H2O, suggesting that the entropy-enhancement process with DMC not only reduces the size of ion clusters but also increases the proportion of denser clusters, thereby lowering viscosity and improving ionic conductivity in electrolyte. These findings are further supported by molecular dynamics (MD) simulations (Fig. 3d, e). Simulation snapshots confirm that Zn2+ is primarily coordinated by acetate via monodentate ion pairs (MIP) rather than BIP structures. Besides, a distinction cluster structure composed of interconnected CIP units is observed in Fig. 3e. Notably, DMC molecules (highlighted by the gray arrow) insert into the centers of large clusters and fragment larger aggregates into smaller units, as confirmed by surface mesh analysis.

To further validate ion cluster rearrangement, we compared the experimental pair distribution function (PDF, G(r)) with simulated radial distribution functions (RDF, g(r)) from MD (Supplementary Data 1). As shown in the PDF data (top panel of Fig. 3f), the ZN3A5·10H2O-EE electrolyte exhibits several additional peaks beyond the typical Zn–O distances (1.8–2 Å), located at approximately 2.3–2.9 Å, 2.5–3.0 Å, 2.7–3.5 Å, and 4.3–5.8 Å, compared to ZN3A5·10H2O. These longer distances are significantly larger than those typical inner-shell solvation and can be attributed to Zn2+ weak interactions with DMC molecules as verified by the RDF data from MD simulation (bottom panel of Fig. 3f), specifically Zn2+–O (carbonyl oxygen in DMC, whose structure is shown in Fig. S10), Zn2+–C (esterified carbonyl carbon in DMC), Zn2+–O (ether oxygen in DMC), and Zn2+–H (methyl hydrogen in DMC). Additionally, Fig. S11 offers macroscopic evidence of DMC integration into the concentrated electrolyte. Unlike the dilute 1Zn1Na electrolyte, which remains immiscible with DMC, ZN3A5·10H2O-EE shows complete miscibility, forming a clear and homogeneous solution after entropy enhancement.

The ion clusters, carried by water, form hydrodynamic entities that govern electrolyte diffusivity as described by the Stokes–Einstein equation:

D = kBT / 6πηR (1)

Where kB is the Boltzmann constant, T is the temperature, η is the viscosity, and R represents the hydrodynamic radius. The inverse relationship between diffusivity (D) and hydrodynamic radius (R) was verified by dynamic light scattering56. As shown in Fig. S12, near the 1.6 M solubility limit, Zn(AC)2 forms either small clusters (~0.83 nm) fully hydrated by water, or large stacked clusters (~295.8 nm) dominated by BIP-state CIPs and hydrated sheaths. In contrast, no hydrodynamic clusters are detected in 1Zn1Na, as the dilute environment and complete dissociation of NaAC prevent cluster formation. The main peak for ZN3A5·10H2O appears at 10.1 nm and shifts to 2.01 nm in ZN3A5·10H2O-EE and is consistent with X-ray scattering results, confirming that entropy-driven cluster disruption reduces hydrodynamic radius and enhances ion diffusivity. This, in turn, effectively mitigates the concentration gradient near the electrode, enabling smoother and faster interfacial chemistry57.

Stripping/plating reversibility and electrolyte
The reversibility of asymmetric Zn||Cu cells was evaluated at 0.5 mA cm−2 with 2 h cycling (Fig. 4a). Overall, the average coulombic efficiency (CE) increased with Zn2+ concentration. 1 M Zn(AC)2 and 1Zn1Na exhibited CE values of ~96.5% and ~98.2%, respectively, but both failed within 100–200 cycles due to dendrite growth and side reactions. In contrast, the concentrated ZN3A5·10H2O electrolyte extends cycling life beyond 300 cycles with CE ~99.1%, benefiting from higher Zn2+ content and reduced water activity. Remarkably, entropy-enhanced ZN3A5·10H2O-EE delivered 600 stable cycles with CE up to 99.7% and minimal voltage hysteresis (Fig. 4b), reflecting suppressed dead-zinc formation and H2 evolution as further confirmed by gas chromatography (Fig. S10). Corrosion resistance was further assessed via Tafel polarization (Fig. S14). Compared with 1Zn1Na and ZN3A5·10H2O, ZN3A5·10H2O-EE exhibited a lower corrosion current density and more positive electrode potential, indicating reduced side reactions and alleviated corrosion rate of the zinc negative electrode.

The Zn2+ transference number, an important parameter indicating electrolyte diffusivity, is defined as the fraction of the total current carried by Zn2+ and reflects its electro-mobility. This can be calculated via the sand’s time as follows58:

t+ = I0ΔV / IsΔV0 (2)

Where I0 and Is are the initial and stable state current, respectively ΔV is the polarization applied potential, R0 and Rs are the resistance before and after polarization, respectively. As shown in Figs. 4c and S15, the entropy-enhanced ZN3A5·10H2O-EE, with smaller ion clusters and higher ionic conductivity, leads to a significant increase in Zn2+ transference number from 0.235 in ZN3A5·10H2O to 0.537.

The enhanced electrolyte stability is further demonstrated by the Zn||Zn symmetric cell (Fig. 4d). Compared to the concentrated ZN3A5·10H2O electrolyte system where polarization gradually increases with operation, the platform overpotential of ZN3A5·10H2O-EE remains constant at 1 mA cm−2 for over 2000 h without any soft short-circuit phenomena (inset Fig. 4d), accumulating over 2 Ah cm−2 capacity. Even under high current density and high areal capacity conditions, the ZN3A5·10H2O-EE electrolyte maintains promising electrochemical stability (Fig. S16). In comparison, the 1Zn1Na and ZN3A5·10H2O cells fail after ~200 h and ~800 h, respectively, due to inferior Zn2+ transport and unstable interfacial environments. In ZN3A5·10H2O, continuous Zn plating/stripping promotes CIP aggregation and clustering, which impairs mass transfer and desolvation kinetics. This is reflected in the increasing electrolyte resistance Rs over time (Fig. S17a). Specifically, ZN3A5·10H2O-EE maintains a low and stable Rs (13.7∼26.3 Ω) from the 10th to 500th cycle, whereas Rs in ZN3A5·10H2O increases from 30.2 to 181.1 Ω, indicating cluster-induced viscosity buildup. Charge-transfer resistance (Rct) further reflects interfacial stability. Rct in ZN3A5·10H2O rises from 409 to 1055 Ω over 500 cycles, while ZN3A5·10H2O-EE exhibits only a slight increase in Rct (Fig. S17b), suggesting stable electrochemical reactions at the interface. DRT analysis (Fig. S18) further reveal that interfacial ion clusters are not merely inherited from the bulk electrolyte but are dynamically formed during cycling as an extension of the solvation process where multiple solvated Zn2+ species further aggregate through shared anions or overlapping coordination shells beyond the primary solvation59. The incorporation of DMC into the ion-cluster environment in ZN3A5·10H2O-EE facilitates rapid desolvation and reduces cluster size, thereby mitigating interfacial concentration gradients. This results in a consistently low nucleation overpotential of ~34 mV even after 2000 h. For comparison, ZN3A5·10H2O starts at ~45 mV, rising above 100 mV after 700 h.

The nucleation and growth behavior of Zn negative electrode was further investigated using chronoamperometry (CA, Fig. 4e). The dilute 1Zn1Na electrolyte exhibits an increasing current trend over a 600 s deposition process, similar to the previously reported 2D diffusion model of Zn2+ ions, leading to an uncontrolled growth of porous Zn dendrites. ZN3A5·10H2O partially suppresses 2D diffusion at the cost of reducing the absolute current but still exhibits persistent interfacial instability. In sharp contrast, the ZN3A5·10H2O-EE electrolyte suppresses planar diffusion and quickly achieves stable 3D diffusion, indicating more nucleation sites and a dense zinc plating layer due to the disparate clustering behavior and diffusivities. These trends are also confirmed by scanning electron microscopy (SEM). In dilute 1Zn1Na (Fig. 4f), Zn deposits show flake-like, loosely stacked morphologies typical of 2D growth. ZN3A5·10H2O (Fig. 4g) exhibits denser Zn deposition but with large protrusions and rough surfaces due to limited bulk and interfacial diffusion. In sharp contrast, ZN3A5·10H2O-EE (Fig. 4h) delivers a uniform and compact Zn layer, free from dendritic or protrusive features, highlighting the advantage of entropy-tuned electrolyte environments.

To resolve the spatial-temporal evolution of zinc plating beyond conventional surface-level observations, we developed an operando projection X-ray microscopy (PXM) platform enabling real-time 2D/3D morphological imaging. As shown in Fig. 5a, the setup uses high-flux synchrotron X-rays focused on a zinc electrode housed in a custom cell. A Fresnel zone plate serves as the objective lens, and images are recorded on a CCD detector (The detailed experimental setup is provided in Fig. S19). After 5 plating/stripping cycles, significant differences in Zn growth behavior were observed between electrolytes. Phase-contrast imaging based on grayscale gradients enables clear differentiation of dense versus porous Zn morphologies. In the concentrated ZN3A5·10H2O electrolyte, the deposited Zn layer grows rapidly, exhibiting rough surfaces with obvious dendritic protrusions (Fig. 5b). This behavior is attributed to large ion clusters, which restrict Zn²⁺ diffusivity and create local concentration gradients near the interface. In contrast, the entropy-enhanced ZN3A5·10H2O-EE electrolyte exhibits stable and uniform Zn deposition as shown in Fig. 5c, with a much smoother surface and no visible protrusions or dendritic features.

3D profiling of early-stage nucleation further reveals these microstructural differences. In ZN3A5·10H2O, the initial Zn nuclei are relatively large (20–25 μm, Fig. 5d1), and subsequent growth results in a porous, uneven morphology. The restricted ion transport caused by large clusters leads to rapid Zn2+ accumulation near the deposition interface, forming high local concentration gradients and rough particle surfaces. As plating proceeds (Fig. 5d2, d3), polarization intensifies, further obstructing diffusion pathways and triggering tip-enhanced dendrite growth. This results in the formation of secondary dendrites along the edges of primary spines, producing gaps between original and newly formed nuclei. These voids contribute to a highly porous structure, as illustrated in the 3D phase-contrast profile (Fig. 5d4). By contrast, in ZN3A5·10H2O-EE, the initial nuclei are significantly smaller (5–10 μm, Fig. 5e1). The presence of disrupted ion clusters enhances ionic conductivity and suppresses concentration gradients, leading to more uniform Zn2+ distribution and dense, compact particle growth (Fig. 5e2–e4). Together, these observations demonstrate that the entropy-enhanced electrolyte enables more controlled Zn nucleation and plating by modulating both interfacial deposition behavior and bulk-phase ion transport. Compared to ZN3A5·10H2O, ZN3A5·10H2O-EE exhibits reduced concentration polarization and more uniform interfacial current distribution, effectively mitigating dendrite formation and promoting stable zinc deposition.

To validate these effects, multiphysics modeling based on a modified Li model was used to simulate the electrolyte–interface behavior60. The relationship between concentration gradient and local current density is illustrated in the extended Butler–Volmer equation as follows:

j = j0 [ C / C* exp(αc zFη / RT) - exp(-αa zFη / RT) ] (3)

where j signifies the current density, j0 is the exchange current density, C is the local Zn concentration at the electrode–electrolyte interface, C* is the reference Zn concentration in electrolytes, αc and αa are the cathodic and anodic charge-transfer coefficients, z is the number of electrons and η is the overpotential. As shown in Fig. S20, Zn2+ depletion at 1 mA cm−2 induces a sharp concentration gradient near deposited zinc in the concentrated ZN3A5·10H2O electrolyte. In contrast, ZN3A5·10H2O-EE exhibits a much milder gradient due to differences in key electrochemical parameters such as ion transference numbers, zinc ion concentrations, and ionic conductivities (Detailed data in Table S5). These differences in cluster kinetics induce a substantial difference in current density acting on zinc nuclei. As reflected in Fig. S21, the heterogeneous current density in concentrated ZN3A5·10H2O induces Zn2+ preferential deposition, leading to dendritic morphological evolution. Conversely, the ZN3A5·10H2O-EE electrolyte enables dense and uniform growth, contributing to extended device lifespan.

Zinc-air battery operated in ambient air
Conventional alkaline electrolytes (e.g., 6 M KOH) offer high ionic conductivity and kinetic stability, supporting efficient ORR/OER in Zn–air batteries. However, in ambient air, they suffer from salt creep, passivation, and poor reversibility, limiting cycle life and charge/discharge efficiency. In comparison, neutral electrolytes are CO2-tolerant and better suited for long-term use. The reaction mechanism depends on the specific neutral electrolyte system employed1. Here, a ZnO2-based two-electron reaction, compatible with acetate electrolytes, was adopted to support full-cell operation, as expressed in Eq. 4 and Eq. 561.

Positive electrode: Zn2+ + O2 + 2e− = ZnO2 (4)

Negative electrode: Zn2+ + 2e− = Zn (5)

Rate capability was evaluated using the ZN3A5·10H2O-EE electrolyte (Fig. 6a). From 0.1 to 2 mA cm−2, the cell exhibits minor polarization. At 5 mA cm⁻², increased overpotential is observed, likely limited by the catalytic activity of the carbon-based air positive electrode. Nonetheless, the performance remains competitive compared to recently reported neutral systems, with high round-trip efficiency and significantly reduced costs (Table S7 and Fig. S22).

To confirm the Zn||ZnO2 reaction reversibility, we monitored pH using a Swagelok cell (Fig. S23). In ZN3A5·10H2O-EE, pH remains stable at 6.8–7.4 over multiple cycles (Fig. S24a), indicating OH− is not involved in the reaction. In contrast, the ZN3A5·10H2O electrolyte exhibits irreversible pH drift (Fig. S24b), pointing to side reactions. Ex situ XRD was performed to identify reaction products after 5th discharging/charging process. As shown in Fig. S24c, the characteristic peak confirms the formation of ZnO2 discharge products at the positive electrode, which disappear upon charging in the ZN3A5·10H2O-EE electrolyte. At the negative electrode, ZN3A5·10H2O-EE promotes compact Zn deposition, reflected in a high I002/I101 peak ratio (Fig. 6b). This effect is attributed to steric repulsion in Zn2+–Ac− ion pairs near the interface, which guides tight metal packing supported by previous studies62. Additionally, no side products at negative electrode were detected in ZN3A5·10H2O-EE electrolyte. In contrast, concentrated ZN3A5·10H2O forms zinc hydroxyacetate, while 1Zn1Na leads to zinc hydroxycarbonate byproducts, both tied to sluggish desolvation, cathodic OH⁻ accumulation, as well as subsequent reactions with acetate anions in the electrolyte63.

These electrochemical and interfacial advantages translate directly to discharge behavior under ambient air. The ZN3A5·10H2O-EE cell delivers a stable discharge plateau at ~1.0 V for over 100 h (Fig. 6c), with an areal capacity of 58.3 mAh cm−2 and a specific capacity of 710.6 mAh g−1, corresponding to 87.4% zinc utilization (inset, right). Replacing the Zn foil with electrochemically deposited Zn on a Ti substrate (Fig. S25, fixed areal capacity of 12 mAh cm−2) enables a higher Zn utilization of 94.1% with higher current density. In comparison, the ZN3A5·10H2O system achieves only 52% utilization. When replacing the carbon catalytic materials with a developed FeCo-based dynamic catalyst from our group featuring hollow nanostructures (Fig. S26), the discharge voltage further increases and the Zn utilization reaches 94.3% (Fig. S27), demonstrating the compatibility of the electrolyte with advanced catalysts.

The prepared ZN3A5·10H2O-EE can support stable operation of the neutral zinc-air cell for over 1800 h in ambient air, rather than pure O2, at a low current density of 0.1 mA cm−2 with a 10-h charging/discharging period (Fig. 6d). Maintaining the same charging/discharging capacity at ten times higher current density (Fig. S28) enables zinc-air battery operation for over 400 h, demonstrating robust stability and reversibility. Even at higher practical areal capacities (e.g., 12 mAh cm−2, Fig. S29), the entropy-enhanced electrolyte maintains stable electrochemical performance comparable to that observed at lower capacities, confirming its robustness under more demanding scenarios. Compared to other reported non-alkaline zinc-air battery systems (Fig. 6e and Tables S6, S7), our system demonstrates comparable in accumulated capacity, round-trip efficiency, and lifespan, even rivaling alkaline systems with significantly better battery life at both low and high current densities. To facilitate a direct comparison, Table 1 summarizes key metrics of representative non-alkaline neutral electrolytes for Zn–air battery systems, further demonstrating the favorable performance of our entropy-enhanced system under ambient conditions. Beyond the enhanced bulk ion transport from smaller clusters in ZN3A5·10H2O-EE, interfacial chemistry also plays a critical role in performance, as detailed in Figs. S30 and S31. Employing ZN3A5·10H2O-EE as a neutral electrolyte forms a hydrophobic organic interphase that promotes reaction kinetics and suppresses side reactions. By contrast, dense ion clustering in its LLPS state in ZN3A5·10H2O electrolyte promotes severe side reactions, including ZnCO3 formation induced by CO2 ingress. This disparity impacts not only the long-term stability and cycle life but also the continuous discharge rate and overall power output (Fig. S32).

In addition to its competitive performance among neutral electrolyte systems, our work emphasizes a holistic approach to sustainability and practicality in Zn-air battery design. To illustrate this, we compare three representative electrolyte systems, as shown in Fig. 6f: the conventional 6 M KOH, the organic salt 3 M Zn(OTf)2, and our proposed entropy-enhanced ZN3A5·10H2O-EE electrolyte system. The evaluation is based on five key criteria: affordability, sustainability, lifetime, safety, and kinetics, for which detailed calculations are provided in Supplementary Note 1. While 6 M KOH offers low cost and high conductivity, its corrosivity and short cycle limit practical use. Alternative 3 M Zn(OTf)2 electrolytes reported recently improved stability but at the expense of high cost and poor environmental compatibility. In contrast, our ZN3A5·10H2O-EE electrolyte integrates low volatility, cost-effectiveness, and environmental sustainability with high zinc utilization, long cycle life, and reliable reversibility. Thanks to reduced water activity, ZN3A5·10H2O-EE exhibits ultra low volatility in ambient air, significantly mitigating electrolyte loss. Additionally, as DMC is incorporated into the CIPs ion cluster network rather than existing as a free solvent, its volatility and environmental exposure are effectively suppressed (Fig. S33). This structural confinement helps maintain the electrolyte configuration and ion transport characteristics over extended use. Finally, a prototype square cell (Fig. S34) delivered 60 mAh at 10 mA, operating below 2 V during charge and ~1 V during discharge—matching lab-scale performance and demonstrating promise for practical scale-up.

Methods
Electrolyte preparation
All chemicals were purchased from Sigma-Aldrich and used directly for electrolyte preparation without further purification. The chemicals included anhydrous zinc acetate (Zn(CH3COO)2, Zn(AC)2, >99%), anhydrous sodium acetate (NaCH3COO, NaAC, >99%), DMC (anhydrous, >99%), hydrogen peroxide solution (30% w/w in water), cobalt nitrate hexahydrate (reagent grade, 98%), and iron nitrate (ACS reagent, >98%). Zinc foil (99.9%, 100 μm and 50 μm), stainless steel mesh (500 mesh), Nickel mesh (99.9%, 500 mesh, pore size 50 μm), titanium foil (20 μm), copper foil (20 μm), coin cell case (CR2032) and glass fiber filter paper (GF/B, Whatman) were purchased from Cyber Electrochemical Materials Network.

Three types of electrolytes were prepared: dilute, concentrated, and entropy enhanced. Zn(AC)2 and NaAC were dissolved in Milli-Q water at 40 °C and stirred for 1 h before storage at 23 ± 1 °C and an ambient relative humidity of ~40%. The dilute electrolyte (1Zn1Na) contained 1 mol L−1 Zn(AC)2 and 1 mol L−1 NaAC. For the concentrated electrolyte ZN3A5·10H2O consisted of Zn(AC)2, NaAC, and H2O at a molar ratio of 1:3:10, corresponding to Zn2+:Na+:CH3COO−:H2O = 1:3:5:10. In this notation, Z = Zn2+, N = Na+, A = acetate, and H2O = water. For entropy-enhanced electrolyte, the ZN3A5·10H2O was first deoxygenated by N2 purging to prevent DMC degradation, followed by stepwise addition of 200 µL DMC in four aliquots (50 µL each) at 40 °C. After each addition, the solution was stirred until clear. Elevated temperature facilitated disruption of large ion clusters and reorganization of CIPs. The final ZN3A5·10H2O-EE electrolyte was obtained after cooling to room temperature (23 ± 1 °C). Detailed molar ratios of all formulations are listed in Table S1.

Electrode preparation
Commercial zinc foil with a thickness of 50 μm was ultrasonically cleaned in a mixed solution of ethanol and acetone for 20 min. After wiping with a dust-free cloth, it was allowed to air dry. The treated zinc foil was then cut into 15 mm diameter disks and used as zinc anodes in various types of cells. The air positive electrode for the acetate-based neutral Zn–air battery was fabricated by mixing 0.7 g Vulcan XC-72R (CABOT), 0.2 g synthesized ZnO2, and 0.1 g PTFE binder with 3 mL isopropanol (Sigma-Aldrich) in a mortar to form a homogeneous paste. The mass ratio of ZnO2: carbon black: PTFE is 20:70:10. The mixture was pressed onto hydrophobic carbon paper (Fuel Cell Store), followed by drying at 40 °C to evaporate the isopropanol.

ZnO2 powder was synthesized based on a reported method with slight modifications. Briefly, 3 g zinc acetate was dissolved in 50 mL water at 40 °C under stirring (300 rpm), followed by dropwise addition of 10 mL 30 wt% H2O2. The mixture was stirred overnight at 40 °C, filtered, rinsed with water, and vacuum-dried at 70 °C. FeCo-based hollow catalysts were synthesized following a modified reported procedure. Briefly, 0.1 mmol cobalt nitrate was dissolved in 8 mL glycerol and 40 mL isopropanol, stirred at 600 rpm for 40 min, transferred to a 100 mL Teflon-lined autoclave, and heated at 180 °C for 6 h. After cooling, the precipitate was collected by centrifugation, washed with ethanol, and dried at 60 °C. In the cation-carving step, 0.2 g of the Co precursor was ultrasonically dispersed in 20 mL anhydrous ethanol, then mixed with 0.2 mmol FeSO4·7H2O dissolved in 100 mL ethanol–water (1:1) under N2. The combined solution was stirred at 5000 rpm for 10 min under N2 bubbling, and the resulting pink powder was collected by centrifugation (7000 rpm) and washed with ethanol. Subsequently, during ammonization, the precursor was polymer-coated with dopamine hydrochloride in 0.01 M Tris buffer (pH ~8.5, material-to-dopamine ratio 2:1), stirred at 500 rpm for 5 h, and then calcined at high temperature.

Electrochemical measurements
Unless otherwise specified, all cell assembly was conducted under ambient laboratory conditions (23 ± 2 °C, 40–60% RH), with no additional humidity control applied. Zn||Zn symmetric and Zn||Cu asymmetric cells were assembled in CR2032 coin-type cells using different acetate-based electrolytes and glass fiber (Whatman GF/B) separators with 120 μL electrolyte. The dimensions of all electrodes we used in coin-type cells are circular with a diameter of 12 mm. The glass fiber separators we used were 16 mm in diameter and 675 μm in thickness. A cut-off potential of 0.9 V (vs. Zn/Zn2+) was applied for the Zn||Cu based CE measurement, and the CE for Zn||Cu is calculated as the ratio of discharge capacity divided by the charge capacity in the preceding charge cycle. Linear sweep voltammetry (LSV) and Tafel plots were recorded using a Biologic VSP-300 workstation in a three-electrode configuration (vs. Ag/AgCl). For Tafel measurements, LSV was performed at a scan rate of 0.2 mV s−1 from +0.2 V to -0.2 V. The corrosion current density (jcorr) was extracted by linear fitting of the Tafel region and determining the intercept at the open-circuit potential (OCV = 0 V). Electrochemical impedance spectroscopy (EIS) measurements were conducted using a Bio-Logic VMP3 workstation. EIS spectra were recorded from Zn||Zn symmetric cells in potentiostatic mode, with a sinusoidal perturbation amplitude of 10 mV over the frequency range of 100 kHz–10 mHz. Prior to each measurement, the cells were stabilized at open-circuit potential for 20 min. Neutral Zn–air battery performance was evaluated using two types of cells: 1. Lab-scale configuration: A Swagelok-type three-neck cell (Fig. S23) was used for pH monitoring, galvanostatic discharge tests, and long-term cycling. Glass fiber B was used as the separator. The cell was assembled by stacking Zn foil and a pre-fabricated air positive electrode, operated under ambient air conditions. A cut-off capacity of 1, 5 and 12 mAh cm−2 were applied for the Swagelok-type zinc–air battery in the manuscript. The areal capacity for the lab-scale cell was calculated based on the geometric area of the positive electrode (1.13 cm2). The mass loading of the ZnO2 for neutral Zn-air battery is from 3.5 mg cm−2 to 21.4 mg cm−2 based on the capacity requirement (1 mAh cm−2 or 12 mAh cm−2) for measurement. 2. Prototype configuration: For large-area testing (Fig. S34), a pouch-like configuration was adopted. Zn foil (5 × 5 cm2) and the coated side of the air positive electrode (mass loading ≈ 21.4 mg cm−2) were placed face-to-face, separated by a glass fiber B membrane. The back side of the air positive electrode was exposed to ambient air through a channel in the casing. Nickel mesh (500 mesh, pore size 50 μm) was used as the current collector for the air positive electrode. A cut-off capacity of 60 mAh was applied for the square type of zinc–air battery. The areal capacity for the square cell (Fig. S34) was calculated based on the cell geometry (5 × 5 cm2). Both the coin cells and the prismatic (square) Zinc-air cells were tested in the wet lab without specific air convection. The testing environment was maintained at 23 ± 1 °C and an ambient relative humidity of ~40%.

Zinc utilization calculation
The Zinc utilization calculation was calculated based on the ratio between the experimentally discharged capacity (mAh) and the theoretical capacity of the consumed Zn metal, using the following equation:

Zn utilization (%) = Q discharge / (n Zn × 820) × 100% (S1)

Where Q is the total discharge capacity in mAh which collected from the experiment, n is the number of moles of Zn involved in the reaction, based on the Zn mass, F is the Faraday constat (96485 C mol−1), z is the electron transfer in the reaction, the factor 3.6 utilized in the equation is converted from the total charge from the coulombs (C) to milliampere-hours (mAh), as 1 mAh = 0.001 Ah * 3600 = 3.6 C. In our example, a 100 μm Zn foil was used as the negative electrode in a Swagelok-type cell. The initial Zn mass was calculated based on the tested area (1.13 cm−2) and foil thickness (100 μm). Assuming complete utilization of the active Zn and a theoretical specific capacity of 820 mAh g−1, we obtained a zinc utilization of 87.4 and 52% for ZN3A5·10H2O-EE and ZN3A5·10H2O in our system. All the specific capacity was calculated by considering only the mass of the Zn plate used. Additionally, the power density was calculated based on the geometric area of the positive electrode (1.13 cm2).

Characterization
Rheology and thermodynamics. Electrolyte viscosity was measured using a Malvern Kinexus Ultra+ rheometer in rotational mode. A solvent trap was employed to minimize evaporation during measurement. ITC was performed to evaluate thermodynamic parameters using a one-site binding model. From the titration curves, key values including the association constant (Ka), enthalpy change (ΔH), entropy change (ΔS), free energy change (ΔG), and binding stoichiometry (N) were extracted. The molar ratio was calculated based on the concentrations of DMC (ligand) and concentrated electrolyte (aptamer equivalent).

Microscopy and spectroscopy. Morphology and energy-dispersive X-ray spectroscopy (EDS) were analyzed via field-emission SEM (Ultra-Plus FESEM, 20 kV). XRD patterns were collected using a Rigaku Ultima IV (Cu Kα radiation), and Raman spectra were obtained with a WITec alpha300R confocal Raman microscope (532 nm laser). X-ray photoelectron spectroscopy (XPS) was performed using a PHI 5000 VersaProbe III. Surface etching was conducted via Ar+ sputtering to reveal bulk chemical composition, and all spectra were calibrated to the C 1s peak at 284.8 eV. Cells were opened under ambient air, after which the residual separator and electrolyte were carefully removed. The electrodes were rinsed with deionized water to clean the surface prior to the ex situ SEM, XPS, and XRD measurement.

Synchrotron-based techniques. Scattering profiles and PDF analyses were conducted at the Brockhouse XRD and Scattering Beamline (BXDS-WHE) of the Canadian Light Source, using a transmission geometry and high-energy wiggler source. XAS, including XANES and EXAFS, was carried out at the HXMA beamline (061D) using a superconducting wiggler source with Si(111) monochromator and Rh-coated mirrors. Operando PXM (as shown in Fig. 5) was performed at the BMIT-BM beamline using a filtered white beam. Zn plating dynamics were resolved via absorption contrast and analyzed using Fiji software, with the electrolyte manually set as the reference background (lowest absorption).

MD simulation
Force fields details. Force fields (FFs) for acetate and DMC were generated through wavefunction calculations using ORCA-v5.0 at the B3LYP/def2-TZVP level. Partial charges were subsequently determined using Multiwfn, and the FF parameters were extracted using AMBER Tools GAFF. The SPC/E water-FF was applied for water molecules, while Zn2+ and Na+ ions were parameterized based on calculated optimized hydration free energies. Non-bonded interactions were modeled with cut-off distances set to 9 Å and 10 Å, with the Lorentz–Berthelot combining rules used for non-bonded interactions. Long-range Coulombic interactions were addressed using the particle-particle, particle-mesh method with a precision of 0.0001.

Simulation and MD analysis protocol
The electrolyte system was constructed using the Moltemplate package with a composition ratio of (Zn: Na: acetate: H2O: DMC = 1:3:5:10:0.5), incorporating 1110 water molecules. MD simulations were performed using the large-scale atomic/molecular parallel simulator package. The SHAKE algorithm was employed to constraint the behavior of water molecules. In the simulations, a Verlet integrator with a timestep of 1.0 femtosecond (fs) was utilized. The Nose–Hoover thermostat and barostat were employed, with damping factors for temperature and pressure set to 102 fs and 105 fs, respectively.

The electrolyte structure was analysis by the RDF by following equation.

g(r) = dN(r) / ρπ4r2dr

where N(r) is the atom number in the spherical shell, ρ is the number density of the whole system, and r is the distance from molecules.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "In this article the authors have demonstrated a nice approach on designing neutral electrolyte for Zn-air battery and propose a cluster-level entropy-enhancement strategy that leverages the intrinsic solvophobicity of large ion clusters. The authors are requested to address the following minor comments.\n1. The authors have strategically used dimethyl carbonate (DMC) as a disruptive agent, to improve the electrolyte homogeneity and ion transport via generating more mobile aggregates with greater configurational entropy. Can this method be applicable while using other carbonate-based system to achieve the same phenomenon? Thus, the authors are requested to demonstrate whether this method can be used as a universal approach to modulate the entropy of Zn-based electrolytes.\n2. In all the PXRD data the authors are suggested to incorporate the standard JCPDS CARD No.\n3. The authors are advised to fit the EIS data presented throughout the manuscript and additionally, they are requested to provide a detailed explanation for the change in EIS behavior observed in Figure S13 across the two figures.\n4. Do the authors calculate the round-trip voltaic efficiency (RTVE) on the basis of working capacity? If not why? Authors should also include this.\n5. The authors have tested the data and correlated it with various physicochemical characterizations. However, for the Zn- based system, the authors are requested to retest all data at ≥12 mAh cm-2 areal capacity and correlate the results with electrochemical performance at lower areal capacities. A comparison of the specific capacity at high areal capacity is also recommended.\n6. Is there any enhancement in the Power density and Rate capability, when used with an air cathode? Please include the performance.\n7. Authors are requested to include the EIS-DRT analysis for the clearer representation of cluster formation.\n8. Authors are requested to mention the FWHM and area % calculation from XPS analysis.", "reviewer_2": "This manuscript presents an entropy enhancement strategy for improving the performance of neutral zinc–air batteries (ZABs) using concentrated zinc acetate electrolytes. The authors introduce dimethyl carbonate (DMC) as a molecular \"disruptor\" that breaks up contact ion pair (CIP) clusters, thereby increasing configurational entropy, improving Zn2+ diffusivity, and enhancing interfacial electrochemical kinetics.\nThe work is supported by robust experimental validation (including in situ synchrotron X-ray techniques, electrochemical testing, and molecular dynamics simulations). It demonstrates improved electrochemical performance, over 1800 hours of operation at 0.1 mA/cm2 and 400 hours at 1 mA/cm2 in ambient air.\nMajor Issues\nReproducibility:\nWhile the experimental section is well-described in general electrolyte formulation and cell design, critical details such as the exact composition and preparation protocol for ZN3A5 10H2O-EE and the operando PXM setup require clarification for reproducibility. The authors should provide a concise but detailed composition table and preparation procedure (including the DMC amount, solvent ratios, and any pre-treatment) in the Methods or Supporting Information.\nComparative Benchmarking:\nWhile the manuscript claims better performance than other acetate-based and neutral systems, a quantitative benchmark table (including key metrics like electrolyte composition, CE, lifetime, current density, and voltage efficiency) is missing from the main text. It is suggested that a comparative table be included in the main text for quick and transparent comparison.\nClarity on the Role of DMC:\nThe manuscript states that DMC does not coordinate directly with Zn2+ but plays a disruptive role. However, RDF data suggest weak interactions with Zn2+. This point should be clarified and concisely summarized.\nEnvironmental Impact of DMC:\nDMC is cited as a sustainable \"catfish disruptor,\" but its environmental toxicity and volatility are not addressed. This weakens the sustainability argument. The authors should briefly mention the environmental safety and volatility considerations of DMC in the Discussion section.\nGrammar and Style:\nSeveral grammatical issues and awkward phrases are present. A professional language edit is recommended to improve readability and polish.\nFigures:\nSome insets and labels in several figures are too small or cluttered, making them difficult to interpret. It is suggested to improve font size and clarity in figure insets and ensure consistency in color coding and legend design.\nData Presentation:\nThe authors mention ~87% zinc utilization, but the method for calculating this is not provided. The authors must add a clear explanation or formula for how zinc utilization was calculated.\nCitations:\nRecent works on entropy tuning and aqueous battery electrolytes are not cited. These would contextualize the contribution more strongly. The authors must expand the literature discussion slightly in the Introduction and Discussion sections.\nRemaining Issues to Address\nClarify exact electrolyte formulations and preparation protocols.\nInclude a benchmarking table in the main manuscript for transparency.\nReframe and clarify DMC's interaction mechanism.\nImprove grammar and figure legibility.\nDiscuss the environmental impact of DMC and sustainability more critically."}, "author_response": "Response to the referees: NCOMMS-25-27080\nNote 1: Nomenclature for the figures: The notation for the figures used in this document\nis in agreement with the description used in the main text or the supporting information\nBlue fonts- responses to the reviewers\nBlue fonts with yellow highlights- responses to the reviewers’ comments and added to the\nrevised manuscript, either in the main text or the supporting information\nNote 2:\n Response to reviewer 1: Page 2-20\n Response to reviewer 2: Page 21-33\n[... Author response text truncated for brevity as per instructions to parse the provided text ...]"}, {"round": 2, "reviewer_comments": {"reviewer_1": "The authors have addressed all the comments raised by me. The manuscript may now be accepted.", "reviewer_2": "This manuscript presents a novel strategy for improving the performance and longevity of neutral zinc–air batteries using cluster-level entropy enhancement in acetate-based electrolytes. By introducing dimethyl carbonate (DMC) as a structural \"disruptor\" to break up contact ion pair (CIP) clusters, the authors report improved Zn²⁺ transport, reduced interfacial resistance, and dendrite suppression. The work is validated using an extensive array of techniques, including in situ synchrotron X-ray analysis, operando X-ray microscopy, and molecular dynamics simulations. The authors demonstrate battery performance exceeding 1800 hours at low current and 400 hours at higher current in ambient air, which is a significant advance in neutral aqueous Zn–air systems.\nMajor Issues\n1. Benchmarking vs. Existing Systems\nThe manuscript positions its electrolyte as superior to others (KOH, Zn(OTF)₂, etc.) based on cost, sustainability, and performance. However, economic and environmental claims (e.g., biodegradability, volatility of DMC) should be supported by quantitative life-cycle data or citations. The radar plot (Fig. 6f) lacks transparency on how metrics were assigned.\nAdd a more detailed explanation or table (referenced from Supplementary Note 1) justifying the criteria and values assigned in the radar chart.\n2. Reproducibility & Generalization\nWhile the study is comprehensive, the reproducibility of electrolyte formulation across different labs or scales is unclear.\nParticularly, how sensitive is the performance to small variations in Zn2+/Na+/H2O ratios or DMC content?\nAdd a supplementary experiment or discussion on formulation tolerance and reproducibility to help future researchers apply this technique.\n3. Electrochemical Mechanism Confirmation\nThe cathode reaction is proposed to involve ZnO2, yet evidence for ZnO2 as the discharge product relies mainly on ex-situ XRD. Complementary techniques such as XPS, FTIR, or in situ DEMS could strengthen this claim.\nProvide additional characterization (or acknowledge as a limitation) to conclusively confirm the full-cell reaction mechanism and ZnO2 reversibility.\n4. Environmental Safety of DMC\nWhile DMC is portrayed as safe, its long-term chemical stability in electrochemical environments (especially under continuous cycling and exposure to O₂) is not addressed.\nInclude any stability assessments or degradation studies for DMC under battery operation, or acknowledge as a potential direction for future work.\nMinor Issues\n1. Terminology Clarification\nThe term \"catfish disruptor\" is used creatively but is not standard scientific language.\nUse a more technical description and relegate metaphors to figure captions or discussions for clarity.\n2. Typographical and Unit Consistency\nStandardize all units and symbols according to IUPAC or journal style.\n3. Supporting Information Navigation\nThe referencing of supplemental figures (e.g., S3a/S3b, S10, S24) is somewhat disjointed in the main text. In a few cases, interpretation relies heavily on figures not visible to readers of the main article.\nWhere key claims depend on supplementary data, include summary panels or descriptors in the main text or figures."}, "author_response": ""}]

Decision letter