Regulating zinc nucleation and growth with low-surface-tension electrolytes for practical aqueous zinc metal batteries

Domain: chemistry
Published: 2026-01-14
Editorial outcome: minor_revision

Abstract
Rechargeable zinc metal batteries are promising for large-scale energy storage due to their low cost and high safety, but their development is seriously hindered by the dendritic growth and side reactions of zinc metal anodes. To address this challenge, we report here that rational design of low-surface-tension electrolytes can enable dense nucleation and fine-grained growth of zinc. This low-surface-tension strategy leads to high stability of the solid-electrolyte interface, dendrite-free morphology and suppressed side reactions. Therefore, zinc metal anodes achieve a high average Coulombic efficiency of 99.72% over a lifespan of 8400 hours at 1 mA cm−2/1 mAh cm−2. Even at harsh electrochemical conditions of 10 mA cm−2/10 mAh cm−2, the lifespans of zinc metal anodes exceed 2200 and 300 hours at 17% and 85% depth of discharge, respectively—over 20-fold and 150-fold improvements compared with those using conventional electrolytes (2 mol kg−1 zinc trifluoromethanesulfonate with 1.5 wt% zinc acetate dihydrate). A 1.27 Ah pouch cell is demonstrated to showcase the practicability of this strategy. This work uncovers the critical role of electrolyte’s surface tension for advanced zinc metal anodes, and offers a potentially cost-effective and sustainable pathway toward commercially viable rechargeable zinc metal batteries.

Introduction
The rapidly expanding markets for electric vehicles, portable electronics, and grid storage have fueled the remarkable commercial success of lithium-ion batteries1,2. However, the high costs, safety concerns, and uneven geographical distribution of raw materials, such as lithium and cobalt, underscore the increasing need for the development of complementary energy storage solutions3,4. In this context, rechargeable zinc metal batteries (RZMBs) present a more economically viable option due to their lower cost5, enhanced safety6, and greater abundance of zinc (Zn) in the Earth’s crust7. Besides, the use of low-toxicity aqueous electrolytes in RZMBs also mitigates environmental risks associated with battery production and disposal, enhancing their sustainability. However, the commercialization of RZMBs is still hindered by Zn metal anodes (ZMAs)-related challenges, including uncontrolled dendritic growth and severe interfacial side reactions, leading to the poor stability and reversibility of ZMAs in practical scenarios8,9.

To meet commercial targets, ZMAs should exhibit an ideal Coulombic efficiency (CE) of 100% under demanding conditions: an anode loading of 5 mAh cm−2 with 80% Zn utilization per cycle and a fast-charging rate of 2C (10 mA cm−2)10. However, these harsh electrochemical conditions—characterized by high areal capacities (≥5 mAh cm−2), high current densities (≥10 mA cm−2), and high depth of discharge (DOD; ≥80%)—often lead to premature failure of the ZMAs11–13. During Zn plating, both Zn2+ and the electric field tend to concentrate at the protuberances with high surface energy14,15, a phenomenon known as the tip effect. In particular, when plating Zn under high current densities, high fluxes of Zn2+ concentrate on such tips and rapidly deposit, leading to the rapid soaring of big protrusions, especially upon a high areal capacity16. Additionally, high DOD incurs a great volume change of ZMAs, leading to pulverization of Zn foil and the formation of dead Zn12,14. The resulting Zn dendrite and pulverization compromise the integrity of the solid electrolyte interphase (SEI), exposing fresh Zn continuously to the aqueous electrolyte and intensifying side reactions, e.g., Zn corrosion and hydrogen evolution. Collectively, these factors reduce Zn reversibility and limit the calendar life in practical RZMB applications.

Significant efforts have been devoted to addressing these challenges, including the development of artificial protective layers on Zn17–21, three-dimensional (3D) Zn hosts22–26, and surface modification of plating substrates13,27,28. However, the large volume changes and potential pulverization during Zn plating/stripping can compromise the long-term stability of protective layers over time20,29, while 3D frameworks often incorporate a high proportion of inactive materials, reducing overall energy density. Furthermore, modification of plating substrates, while effective, often entails complex procedures and additional energy consumption. Electrolyte engineering—such as concentrated5,30,31, water-organic hybrid32–35, or additive-containing electrolytes36–38—has shown promise in improving ZMAs’ reversibility and stability. However, these approaches often introduce new challenges, such as higher cost and elevated flammability31,39. Moreover, most of these approaches are often evaluated under moderate electrochemical conditions (e.g., small current densities), and very small DODs (e.g., below 1%)10. These limitations underscore the need for a balanced strategy that effectively mitigates dendrite growth and side reactions at a practical level while maintaining cost-effectiveness, safety, and energy density to advance RZMB commercialization.

Notably, the electrodeposition of Zn—encompassing both nucleation and growth processes—occurs directly at the electrolyte/Zn interface. This makes the electrolyte surface tension (σ) a particularly relevant parameter, as it significantly influences interfacial properties and should impact the deposition behavior of Zn. However, a fundamental and quantitative understanding of how σ governs Zn nucleation and growth remains lacking. Traditional electrolyte design has primarily focused on suppressing water activity by using high organic solvent content (>55 vol%)34,40 or modifying the adsorption layer on Zn through functional additives in electrolytes41,42. While these approaches have shown some improvement, they have not established σ as a targeted design parameter, nor have they provided quantitative relationships between σ and deposition outcomes. Furthermore, the impact of σ on battery performance under practical conditions (high current, high capacity, high DOD, Ah-level pouch cells) and its overall effects on dendrite suppression, SEI stabilization, and side reaction mitigation remain insufficiently explored.

In this work, we report a low-σ electrolyte strategy that rationally tunes the Zn nucleation and growth behaviors for the high-performance practical RZMBs. Unlike previous studies that overlooked the significance of σ, we conduct a fundamental analysis of how electrolyte σ influences Zn electrodeposition behavior. Specifically, we establish a quantitative theoretical framework based on classical nucleation theory, identifying σ as the key parameter controlling both nucleation energy barrier (nucleation process) and growth resistance (growth process). This low-σ design fundamentally alters sparse nucleation/coarse-grained growth into dense nucleation/fine-grained growth, even under harsh electrochemical conditions. Experimental and computational studies reveal that low-σ electrolytes promote uniform Zn deposition, stabilize the SEI, and suppress side reactions. These synergistic effects yield highly stable and reversible ZMAs: a high 99.72% average CE over a lifespan of 8400 hours (350 days) at 1 mA cm−2/1 mAh cm−2, and high stability exceeding 2200 (17% DOD) and 300 hours (85% DOD) at harsh electrochemical conditions (10 mA cm−2/10 mAh cm−2). The practical viability of our approach is further demonstrated in a 1.27 Ah pouch cell that operates under a lean electrolyte condition and a low N/P ratio. Our work establishes quantitative relationships between σ and Zn electrodeposition behavior, and demonstrates highly stable ZMAs in low-σ electrolytes even under harsh electrochemical conditions. These findings highlight σ as a crucial yet previously overlooked electrolyte property, introducing it as a design criterion of electrolytes for high-performance practical RZMBs.

Results
Theory of σ-governed Zn nucleation and growth
By combining classical nucleation theory with electroplating dynamics, we establish electrolyte’s σ as the governing parameter for Zn electrodeposition, controlling both nucleation (Step I) and growth (Step II). Typically, the nucleation process in liquid systems can be categorized into homogeneous nucleation and heterogeneous nucleation43,44, depending on whether a substrate is involved (Supplementary Fig. 1). During Zn electroplating on a copper (Cu) substrate (Fig. 1a), Zn undergoes heterogeneous nucleation, where the change of Gibbs energy ΔGhet can be expressed as:

ΔGhet = f(θ) × ΔGhom = f(θ)(ΔGS + ΔGV) (1)

where ΔGhom is the change of Gibbs energy during homogeneous nucleation, and f(θ) is a constant (0 ≤ f(θ) ≤ 1) determined by the contact angle (θ) between the Zn nucleus and substrate. ΔGS and ΔGV refer to surface energy and volume energy, respectively. Note that ΔGS (>0) represents the energy input required to form a solid surface during nucleation. This energy also needs to be overcome in the subsequent growth processes. In contrast, ΔGV (<0) reflects the energy released during the transition of Zn2+(aq) to Zn(s) under a negative bias voltage Δφ (vs. Zn2+/Zn) (Fig. 1a, Supplementary Fig. 2).

In the nucleation stage (Step I), the nucleation energy barrier (ΔG*het), which is the maximum ΔG required to form a stable nucleus, can be expressed as (Supplementary Fig. 3):

ΔG*het = f(θ) × ΔG*hom = f(θ) × 16πM2σ3 / 3n2ρ2F2Δφ2 (2)

and the corresponding critical nuclei radius (r) (Supplementary Fig. 4), can be expressed as:

r = 2Mσ / FρΔφ (3)

where M is the molar mass of Zn; n is the mole of electrons transferred per mole of Zn; ρ is the density of Zn; F is the Faraday constant; Δφ (vs. Zn2+/Zn) is the negative bias voltage during the electroplating process. Detailed derivations of these equations can be found in Supplementary Note 1.

As such, the effect of σ on Zn nucleation can be quantified in Eqs. 2 and 3, and is summarized in Fig. 1b. Specifically, the energy barrier of Zn nucleation is proportional to σ3 (Eq. 2), indicating that reducing σ lowers the energy barrier and accelerates the nucleation process. Additionally, a lower σ also diminishes the critical nuclei radius (Eq. 3), resulting in smaller nuclei. Thus, a low-σ electrolyte is expected to promote denser and finer Zn nuclei compared to those in higher-σ counterparts, fostering a nuclei-rich growth mode.

In the growth stage (Step II), the ratio of two opposing terms (−ΔGS/ΔGV) should be minimized to enhance the thermodynamic favorability of Zn growth. Therefore, the radius of Zn particles (R) during growth can be expressed as:

R = 2M / nFρΔφ × 1 / (−ΔGS/ΔGV) × σ (4)

Therefore, in high-σ electrolytes, Zn grows from fewer nuclei, forming large particles to reduce −ΔGS/ΔGV. These large particles readily evolve into big protrusions under a high plated capacity, raising short-circuit risks. Conversely, for the same −ΔGS/ΔGV, low-σ electrolytes reduce growth resistance—that is, the surface energy per unit area, equivalent to the electrolyte surface tension σ—yielding smaller, denser particles (Supplementary Note 1).

Importantly, it should be noted that the difference of particle size in high-σ electrolyte (R High σ) and low-σ electrolyte (R Low σ) is very little when the plated capacity is low (Fig. 1c). However, it amplifies sharply at the high plated capacity (Fig. 1c). This disparity highlights the critical role of σ on the growth of Zn, especially under high areal capacities that are required in practical applications of RZABs.

Collectively, σ governs both Zn nucleation (Step I) and growth (Step II), as summarized in Fig. 1d. Low-σ electrolytes enable (i) facile and dense nucleation (Step I), (ii) smaller nuclei size (Step I), and (iii) fine-grained growth even under high areal capacities (Step II).

Guided by the theoretical prediction that identifies σ as the governing parameter, we engineered low-σ electrolytes. This was achieved by incorporating solvents with low polarity—and consequently low dielectric constants (ε)—into a reference aqueous electrolyte (Fig. 1e, f). The high σ of aqueous electrolytes typically arises from strong dipole-dipole interactions between water molecules, specifically the H2O-H2O hydrogen bonds. By adding low-polarity solvents with weaker intermolecular attractions, we aim to disrupt these strong dipole-dipole networks and consequently lower σ. It enables us to probe the effect of σ as the primary variable. The σ of the reference electrolyte (2 mol kg−1 zinc trifluoromethanesulfonate in water with 1.5 wt% zinc acetate dihydrate) decreases upon the addition of solvents with lower ε, including ethylene glycol (EG), triethyl phosphate (TEP), dimethoxyethane (DME), bis(2-methoxyethyl) ether (G2), and tetraethyleneglycol dimethyl ether (G4) (Fig. 1e, f). Electrolytes containing G4, G2, DME, and TEP exhibit lower σ compared to electrolytes containing EG, because of their lower ε values. Particularly, TEP enables the lowest σ due to its minimal ε and non-linear molecular structure (Fig. 1f). The addition of only 5 vol% TEP (denoted as 5% TEP) significantly reduces the σ to 55% of the reference electrolyte, while further increasing the TEP content to 10, 30, and 50 vol% results in only marginal additional reductions (Fig. 1f). The variation trend of σ aligns well with that of the contact angles as shown in Supplementary Fig. 5.

The nucleation energy barriers in electrolytes with different contents of TEP were also calculated and compared under a fixed bias voltage of 0.1 V based on Eq. 2. As shown in Fig. 1g, 5% TEP dramatically lowers the nucleation energy barrier to 2 × 10−22 J, which is only 17% of that in the reference electrolyte. However, further increasing TEP content leads to a substantial decline in electrolyte ionic conductivity, yet a negligible reduction in the nucleation energy barrier. Thus, the addition of merely 5 vol% TEP can effectively lower both the σ (to 55% of the reference electrolyte) and the nucleation energy barrier (to 17% of that in the reference electrolyte) without significantly compromising the ionic conductivity (still up to 90% of that of the reference electrolyte). Therefore, 5% TEP was selected for subsequent studies to achieve an optimal balance between low σ and high ionic conductivity.

Dense nucleation and fine-grained growth of Zn in low-σ electrolytes
To evaluate the impact of σ on the nucleation and growth of Zn, we examined the morphologies of Zn deposits on Cu foil. σ of the reference electrolyte (denoted as 0% Addi) and the 5% TEP are 68.2 and 37.8 mN m−1, respectively. Compared to 0% Addi, 5% TEP exhibits a slightly wider electrochemical stability window (2.55 V) but lower ionic conductivity (Supplementary Fig. 6). Zn||Cu half cells in these two electrolytes were assembled in a custom-made setup (Supplementary Fig. 7), with a 1 cm distance between Zn and Cu electrodes to allow the observation of morphological changes at high plating capacities.

As shown in Fig. 2a, Zn deposits in the high-σ electrolyte of 0% Addi exhibit sparse nuclei, resulting in large Zn protrusions during growth. At the beginning (3 minutes) of electroplating with a high current density of 10 mA cm−2, the Zn deposits appear as widely spaced large islands. Extending the plating duration to 30 minutes produces prominent Zn protrusions. After 2 hours, these protrusions further develop into larger, porous dendrites (Fig. 2b). This morphological evolution decreases the inter-electrode spacing and elevates the discharge plateau (Supplementary Figs. 8 and 9). In striking contrast, Zn deposits in the low-σ electrolyte of 5% TEP exhibit dense nucleation and compact growth. The initial 3 minutes of plating yield uniformly distributed small islands (Fig. 2c), indicating the high density of small nuclei. Even after 5 hours of plating, the Zn deposits still maintain a dense, fine-grained morphology. Cross-sectional analysis also reveals a smooth, dendrite-free layer in 5% TEP (Fig. 2d). TEP’s ability to enable dense, uniform Zn deposition is further validated across various current densities in coin cells (Supplementary Fig. 10).

For quantitative comparison, we measured the root-mean-square (RMS) roughness of Zn deposits. The 0% Addi samples shows obvious capacity-dependent roughness escalation, rapidly growing from 6.7 to 434 μm when the plating capacity increases from 5 to 50 mAh cm−2 (Figs. 2e, f, and Supplementary Fig. 11a). In stark contrast, 5% TEP maintains low RMS roughness at ~5 μm (Fig. 2g, h and Supplementary Fig. 11b), reaching only 5.2 μm at 50 mAh cm−2—a 98.8% reduction compared to 434 μm in 0% Addi. These dramatic differences confirm that high-σ electrolytes promote sparse nucleation and uneven growth, leading to rapidly escalating surface roughness with capacity. Conversely, low-σ electrolytes enable dense nucleation and uniform plating, maintaining a consistently smooth surface even at high capacities.

Finite element simulations of the deposition behavior correlate well with the experimental results, demonstrating stark contrasts in deposition behavior between high- and low-σ electrolytes. As shown in Fig. 2i, j, the initial modeling exhibits sparse and large nuclei on Cu foil in 0% Addi, whereas dense and small Zn nuclei in 5% TEP. Under the external electric field, Zn2+ fluxes flow to Zn nuclei along the trajectories of current vectors (Supplementary Fig. 12). As the simulation progresses, Zn2+ keeps accumulating at these sparse nuclei, resulting in large protrusions in 0% Addi (Fig. 2i and Supplementary Fig. 13). In contrast, the dense Zn nuclei in 5% TEP promote more uniform Zn deposition (Fig. 2j and Supplementary Fig. 13), diminishing the inhomogeneity of Zn growth.

Notably, we found that σ also regulates the orientation of crystalline facets of Zn deposits. In comparison to the (101) facet, the (002) facet of Zn not only contributes to the lateral growth of Zn but also exhibit high resistance to Zn corrosion and hydrogen evolution45–47. In 0% Addi, Zn deposits are dominated by the (101) facet, and the (002)/(101) intensity ratio is below 0.27 (Fig. 2k). In contrast, Zn deposits in 5% TEP show a significant enhancement in the (002) crystal plane, and the (002)/(101) intensity ratio rises from 0.22 to 1.18 as plating time extends from 30 minutes to 5 hours (Fig. 2l). The preferential growth of the (002) plane in 5% TEP also facilitates the high stability and reversibility of ZMAs as demonstrated in the later part.

Importantly, the favorable regulation of Zn nucleation and growth is versatile across a range of low-σ electrolytes. To compare the density of Zn nuclei in different electrolytes, we quantify the projected areas of Zn deposits on Cu after 3 minutes of electroplating at 10 mA cm−2 (Fig. 2m and Supplementary Fig. 14). The projected area—defined as the two-dimensional footprint of Zn deposits—serves as an indicator for nuclei density, with larger areas indicating higher nuclei density. Low-σ electrolytes, including 5% TEP, 5% G2, 5% G4, 5% DME, and 30% DME, exhibit much larger projected areas (35.2%, 36.5%, 36.5%, 25.1%, and 27.2%, respectively) than high-σ electrolytes (18.3% in 0% Addi, 12.7% in 5% EG, and 13.3% in 30% EG), indicating dense nucleation process. For the subsequent growth process, we analyze the RMS roughness of Zn deposits in different electrolytes, with smaller roughness values indicating smaller particles of Zn. After 5 hours of electroplating (Fig. 2n and Supplementary Figs. 15 and 16), Zn deposits in low-σ electrolytes show significantly lower RMS roughness, being 5.2 μm for 5% TEP, 16.7 μm for 5% G4, 25 μm for 5% G2, 30 μm for 30% DME, to 34.5 μm for 5% DME—less than 10% of that in 0% Addi (434 μm), indicating finer grains in low-σ electrolytes. Additionally, Zn deposits in these low-σ electrolytes also exhibit a higher proportion of the (002) crystal plane. The (002)/(101) intensity ratio reaches 2.61 in 5% DME, 3.83 in 5% G2, 4.97 in 30% DME, and 9.49 in 5% G4 (Supplementary Fig. 17). These results highlight the universality of this strategy with good potential for extensive applications.

Stable SEI and suppressed side reactions in low-σ electrolytes
The dense nucleation and fine-grained growth enabled by the low-σ electrolyte enhance the SEI stability, effectively suppressing side reactions even under harsh electrochemical conditions. The SEI chemistry of deeply cycled Zn (10 mA cm−2/10 mAh cm−2 for 10 cycles) in 0% Addi and 5% TEP was studied using X-ray photoelectron spectroscopy (XPS). The O 1s spectra of deeply cycled Zn show characteristic peaks of Zn(OH)2-related product at ~531.0 eV and ZnCO3-related product at ~532.1 eV48,49 (Fig. 3a and Supplementary Fig. 18). The former is derived from the byproducts of Zn corrosion in aqueous electrolyte48,49, while the latter is attributed to the effective SEI component derived from Zn(Ac)2 in electrolytes31,49. In 0% Addi, ZnCO3-related product remains below 40% at all depths, while Zn(OH)2-related product reaches as high as ~40% after 150 seconds of sputtering (Fig. 3b). In sharp contrast, 5% TEP enables high ZnCO3 content of over 60% and low Zn(OH)2 content below 20% at all depths. This beneficial SEI composition is also consistent across other low-σ electrolytes (5% G2, 5% G4, and 30% DME) (Supplementary Fig. 19).

Time-of-flight mass spectrometry (TOF-MS) further confirms the suppressed Zn corrosion and robust SEI in low-σ electrolytes. We characterized the deeply cycled ZMAs by tracking ZnO− (byproducts of Zn corrosion) along with F− and S− fragments (byproducts of Zn(OTf)2 decomposition) as functions of sputtering depth (Fig. 3c). The signals of ZnO−, F− and S− are strong and intensify with detection depth, indicating a thick byproducts layer caused by the corrosion of continuously exposed fresh Zn in 0% Addi. In contrast, these signals are significantly weaker in 5% TEP and diminish with detection depth, manifesting the suppressed Zn corrosion and electrolyte decomposition (Supplementary Fig. 20). The TOF-MS results align well with the XPS depth profiling at extended sputtering durations (Supplementary Fig. 21).

Differential electrochemical mass spectrometry (DEMS) demonstrates the suppressed hydrogen evolution reaction (HER) in low-σ electrolytes. In 0% Addi, the net H2 evolution in the pre-cycled symmetric Zn||Zn cell peaks at 8.3 nmol min−1 and then continues to fluctuate around 7.5 nmol min−1 when the cell is charged/discharged at 5 mA cm−2/5 mAh cm−2 (Fig. 3d). In contrast, the H2 evolution in 5% TEP is significantly suppressed, showing only an initial peak at only 1.8 nmol min−1, and then gradually declining to close to zero. Similar suppression can also be observed at harsher conditions, i.e., 10 mA cm−2/10 mAh cm−2 (Supplementary Fig. 22). Severe HER generates OH− ions that corrode Zn, forming various zinc hydroxide hydrates. Consistent with this, XRD patterns of deeply cycled Zn show prominent zinc hydroxide hydrate peaks50,51 in 0% Addi, while no such impurities are detected in low-σ electrolytes (5% TEP, 5% G2, 5% G4, and 30% DME) (Supplementary Fig. 23).

The suppressed side reactions on Zn are also supported by the electrochemical analysis. Arrhenius analysis of the Zn/electrolyte interface (Fig. 3e, Supplementary Fig. 24, and Supplementary Table 1) reveals a significantly lowered Zn2+ transport resistance (ZTR) through the SEI in 5% TEP (62.4 kJ mol−1) than that in 0% Addi (74.2 kJ mol−1). The high ZTR indicates a thick by-product-covered surface on Zn in 0% Addi, impeding Zn2+ transport. Additionally, Tafel plots of pre-cycled ZMA show a more positive potential and a lower current, also confirming the reduced corrosion and HER in 5% TEP (Supplementary Fig. 25).

Figure 3f and g illustrates the impact of σ on SEI during Zn stripping/plating under harsh electrochemical conditions. Due to the sparse nucleation and coarse-grained growth, high-σ electrolytes lead to the formation of dendrites and coarse Zn particles, which mechanically fracture the SEI, persistently exposing fresh Zn into electrolytes and accelerating Zn corrosion and HER (Fig. 3f). In contrast, low-σ electrolytes facilitate dendrite-free Zn deposition and a stable SEI, attributed to the dense nucleation and fine-grained growth, which shields fresh Zn from electrolyte-induced side reactions (Fig. 3g). Operando imaging of planar Zn||Cu cells (Supplementary Figs. 26 and 27) support this distinction: high-σ electrolytes produce porous, dendritic Zn deposits (Fig. 3h), while low-σ electrolytes yield compact, homogeneous Zn layers (Fig. 3i). Notably, such dendrite-free and dense interface persists in 5% TEP even under harsher electrochemical conditions (45 mA cm−2, 22.5 mAh cm−2; Supplementary Movies 1 and 2).

Mechanism of TEP-induced reduction of electrolyte’s σ
Instead of entering the primary solvation shell of Zn2+, TEP disrupts the hydrogen-bonding framework, particularly at the Zn/electrolyte interface, thereby reducing the σ of electrolytes. The Zn K-edge X-ray absorption near-edge structure (XANES) spectra of 0% Addi and 5% TEP overlap completely (Fig. 4a), suggesting the almost identical electronic structure of Zn2+ in both electrolytes. The Fourier transformation of extended X-ray absorption fine structure (EXAFS, Fig. 4b) reveals a peak at ~1.60 Å, corresponding to the Zn-O bond length in [Zn(H2O)x]2+33,52. This result remains consistent even when the TEP content is increased to 30 vol% (Supplementary Fig. 28), suggesting that TEP does not alter the primary solvation shell of Zn2+. These findings align with the radial distribution function (RDF) of 5% TEP (Fig. 4c). The absence of TEP in the primary solvation shell indicates TEP is electrochemically stable against reductive decomposition during Zn plating. This is further supported by the lack of phosphorus species in the XPS spectra of deeply cycled Zn and the absence of parasitic currents in the LSV measurements (Supplementary Fig. 29). Therefore, the robust SEI does not originate from the reductive decomposition of TEP but instead results from the favorable regulation of Zn nucleation and growth in low-σ electrolytes. Furthermore, it also rationalizes the significantly improved stability and reversibility of ZMAs despite the trace TEP added, as TEP is not consumed during cycling.

Since σ in aqueous media generally originates from the dipole-dipole interactions (H2O-H2O hydrogen bonds) at interfaces53, we propose that TEP reduces σ by regulating Zn/electrolyte interfacial H2O-H2O interactions. As shown in Fig. 4d, e, and Supplementary Data 1, the average number of H2O-H2O hydrogen bonds as a function of distance from the Zn electrode was calculated from the trajectories of all molecules in 20 ns (sampled every 0.2 ns). As shown in Fig. 4f, the number of H2O-H2O hydrogen bonds exhibits a maximum at 0.2 nm from the Zn surface and decreases to a minimum at 0.4 nm for both electrolytes. The decrease is due to the lower density of water molecules between the electric double layer and the bulk electrolyte. Beyond 0.4 nm, the number of H2O-H2O hydrogen bonds remains stable up to 2 nm. Notably, the addition of 5 vol% TEP significantly reduces the number of H2O-H2O hydrogen bonds at the interface (0.2 nm) compared to 0% Addi. As shown in Fig. 4g, the H2O-H2O hydrogen bonds at the interface (0.2 nm), close interface (0–2 nm), and throughout the overall electrolyte are reduced by 30%, 10%, and 6%, respectively, when comparing 5% TEP to 0% Addi. Raman spectroscopy further confirms this interfacial disruption (Supplementary Fig. 30) by showing a shift of the ~3238 cm−1 peak to higher wavenumbers and a decrease in relative intensity. The primary mechanism of disruption is the adsorption of TEP molecules at the Zn/electrolyte interface (Supplementary Fig. 31), which disrupts the water network, reduces dipole-dipole interactions, and lowers σ.

Electrochemical stability and reversibility of ZMAs
We evaluated the electrochemical stability of ZMAs using symmetric Zn||Zn cells under harsh electrochemical conditions. Zn||Zn symmetric cells in 5% TEP operate stably across 2700 hours at 5 mA cm−2/5 mAh cm−2 (Fig. 5a). In sharp contrast, cells in 0% Addi undergo rapid short-circuiting after only 150 hours. Under more demanding conditions (10 mA cm−2/10 mAh cm−2, 17% DOD), Zn||Zn cells in 5% TEP sustain stable operation for 2216 hours, while cells in 0% Addi fail within 110 hours (Fig. 5b). 5% TEP, therefore, extends the cycle life of Zn||Zn cells by 18-fold at 5 mA cm−2/5 mAh cm−2 and 20-fold at 10 mA cm−2/10 mAh cm−2 compared to 0% Addi. This enhanced stability is maintained under moderate cycling conditions (2 mA cm−2/2 mAh cm−2) (Supplementary Fig. 32).

Even at harsher electrochemical conditions of 85% DOD and 10 mA cm−2/10 mAh cm−2, Zn@Cu||Zn@Cu symmetric cells in 5% TEP demonstrate stable operation for 300 hours—150 times longer than in 0% Addi (Fig. 5c). The enhanced stability of ZMAs is not limited to 5% TEP: Zn plating/stripping in other low-σ electrolytes (e.g., 5% G2, 5% G4, and 30% DME) all exhibit improved cycle life compared to the reference electrolyte (Supplementary Fig. 33).

Notably, ZMAs show high reversibility in a long cycle life. The Zn||Cu asymmetric cell in 5% TEP sustains stably for 4200 cycles at 1 mA cm−2/1 mAh cm−2 (Supplementary Fig. 34). It achieves a high average CE of 99.72% over a lifespan of 8400 hours (350 days, Fig. 5d). This result shows improvement compared to other approaches, which typically exhibit average CE of 97.5–99.6% over short lifespans of 200–4000 hours19,27,31,54–61 (Fig. 5e and Supplementary Table 2). In sharp contrast, Zn||Cu cells in 0% Addi fail after 260 cycles, accompanied with abnormal long charging plateaus (Supplementary Fig. 34). Note that a minor yet observable CE fluctuation occurs between cycles 400–1400 in 5% TEP. This behavior, stemming from slight side reactions on the Cu current collector under low current density (Supplementary Figs. 35 and 36), does not compromise the overall stability of Zn plating/stripping in 5% TEP. Even at ten-fold higher current density and capacity (10 mA cm−2/10 mAh cm−2), Zn||Cu asymmetric cells in 5% TEP still maintain stable cycling for 230 cycles, exhibiting highly repeated profiles and a high average CE of 99.2% (Supplementary Fig. 37).

We further compare the current densities, areal capacities, cumulative plated capacities, and CE of ZMAs in 5% TEP to other reported approaches5,27,54,62–76 in Fig. 5f and Supplementary Table 3. Our strategy enables high stability and reversibility of ZMAs, with cumulative plated capacities of 6.75 Ah cm−2 (5 mA cm−2/5 mAh cm−2), 11.07 Ah cm−2 (10 mA cm−2/10 mAh cm−2) and CE of 99.72%, showing improvement compared to most reported values. Critically, this performance is achieved without compromising safety or cost-effectiveness, establishing the low-σ electrolyte strategy as a promising paradigm for highly stable and reversible ZMAs.

Electrochemical performance of full cells
Full cells incorporating Zn negative electrodes and high-loading NVO positive electrodes were evaluated. In 5% TEP, Zn||NVO batteries (NVO: ~17 mg cm−2) achieve high capacities of over 350 mAh g−1 at 5 mA cm−2 and 230 mAh g−1 at 34 mA cm−2, corresponding to high areal capacities of 6.1 and 4 mAh cm−2, respectively (Fig. 6a and Supplementary Table 4). When further increasing NVO mass loading to an industry-level of ~34 mg cm−2, Zn||NVO batteries still exhibit a high areal capacity of 12.6 mAh cm−2 at 5 mA cm−2 and 6.2 mAh cm−2 at 68 mA cm−2 (Supplementary Fig. 38 and Supplementary Table 4). The Zn||NVO batteries (NVO: ~17 mg cm−2) in 5% TEP exhibit stable cycling for 3000 cycles at 34 mA cm−2, with an average capacity of 194 mAh g−1. It presents a significant improvement over those in 0% Addi, which suffers from substantial degradation since the 200th cycle (Fig. 6b).

To assess the feasibility of low-σ electrolyte, the N/P ratio was further decreased to 1.9 by using a NVO positive electrode (~17 mg cm−2) with a capacity of 6.1 mAh cm−2 and a thin ZMA (20 μm) with a capacity of 11.7 mAh cm−2. At a high operating current density of 34 mA cm−2, the low N/P ratio cell in 5% TEP still delivers an average capacity of 166 mAh g−1 (2.8 mAh cm−2) for 2000 cycles with an average CE of 99.97% and a slow capacity decay of 0.03% per cycle (Fig. 6c). In comparison, the low N/P ratio cell in 0% Addi cell decays rapidly in 500 cycles, ascribed to the depletion of Zn metal. These pronounced differences demonstrate the superior reversibility of ZMAs in 5% TEP electrolyte, resulting from effective suppression of both dendritic growth and side reactions.

To assess the practical application and scalability of our strategy, we fabricated a single-layer pouch cell (3 cm × 4 cm) with a total capacity of 77 mAh at a low N/P ratio of 2.8. The cell demonstrates excellent rate capability, achieving areal capacities of 6.4, 5.5, and 4.2 mAh cm−2 at high current densities of 5, 10, and 18 mA cm−2 respectively (Fig. 6d). The Zn||NVO pouch cell in 5% TEP maintains 85% capacity retention over 500 cycles at 5 mA cm−2, validating the scalability of our low-σ electrolyte strategy.

In addition, a 1.27 Ah pouch cell, measuring 10.2 cm in length and 9.2 cm in width, was fabricated based on a bipolar configuration (Fig. 6e, f). It employs a limited amount of ZMA (40 μm, 23.4 mAh cm−2, N/P=3.3:1), a NVO positive electrode (7 mAh cm−2), and a lean electrolyte condition (5% TEP: 11.3 g Ah−1) (Supplementary Table 5, Supplementary Fig. 39). The pouch cell was first galvanostatically cycled at a low specific current of 60 mA g−1 (delivering an energy density of ~68 Wh L−1, Supplementary Fig. 40, Supplementary Note 2), and then cycled at a high specific current of 139 mA g−1. The cell maintains stable cycling for 120 cycles, after which it shows a high capacity retention of 84% (relative to the 6th cycle at 139 mA g−1) and an average CE exceeding 99.9% (Fig. 6g).

Methods
Chemicals
Zinc trifluoromethanesulfonate (Zn(OTf)2, 98%), zinc acetate dihydrate (Zn(Ac)2·2H2O, 99.995%), and tetraethylene glycol dimethyl ether (G4, ≥99%) were purchased from Macklin. Ethylene glycol (EG, anhydrous, ≥99.8%) and triethyl phosphate (TEP, ≥99.8%) were purchased from Sigma-Aldrich. Dimethoxyethane (DME) and bis(2-methoxyethyl) ether (G2, ≥99.5%) were purchased from Aladdin.

Preparation of electrolytes
To prepare the reference electrolyte of 0% Addi, 2 mol kg−1 Zn(OTf)2 was dissolved in deionized water, followed by the addition of Zn(Ac)2·2H2O salt as a SEI-forming additive with a weight ratio of 1.5 wt%. To prepare 5% TEP electrolyte, 5 vol% DI water in the reference electrolyte was replaced with 5 vol% of TEP. Similarly, 5 vol% or 30 vol% of DI water in the reference electrolyte was replaced with equivalent volumes of EG, DME, G2, and G4 to prepare 5% EG, 30% EG, 5% DME, 5% DME, 5% G2, and 5% G4. The surface tension of the electrolytes was measured using the tensiometer of SDC350KS.

Characterizations
Zn||Cu cells containing 3.5 mL of 0% Addi or 5% TEP electrolyte were assembled in a custom-made setup (Supplementary Fig. 7) with a fixed distance of 1 cm between the Zn and Cu electrodes to prevent short circuits under high areal capacities. Zn electroplating on Cu was performed in this setup at a current density of 10 mA cm−2 for durations of 3 minutes, 30 minutes, 1 hour, and 5 hours. After electroplating, the cells were disassembled to retrieve the Zn-deposited Cu electrodes. These electrodes were rinsed with deionized water to remove residual electrolytes before the following characterization. Scanning electron microscopy (SEM) images were acquired using a Tescan VEGA3 instrument with a beam voltage of 20 kV. X-ray diffraction (XRD) patterns were recorded using a Rigaku SmartLab diffractometer with Cu Kα radiation. Data were collected in a continuous scan mode over a 2θ range of 30° to 50° with a scan speed of 5° per minute and a step size of 0.02°. The surface roughness of Zn deposits was measured using a laser scanning confocal microscope (KEYENCE VK-X200).

After cycling at 10 mA cm−2/10 mAh cm−2 for 10 cycles, the Zn||Zn coin cells were disassembled to retrieve the cycled electrodes. These electrodes were rinsed with deionized water to remove residual electrolytes before X-ray photoelectron spectroscopy (XPS) characterization. XPS was performed using a Thermo Fisher Scientific Nexsa spectrometer with an Al Kα X-ray source, operating at a beam energy of 12 keV. Time-of-flight secondary ion mass spectrometry (TOF-SIMS, TOF-SIMS5, Germany) was employed to analyze the SEI composition as a function of depth. Sample preparation followed the same protocol as for XPS analysis. Depth profiling was conducted using a 1 keV Cs+ sputter ion beam for material removal, with analysis performed in negative ion mode over an area of 50 × 50 μm−2. The pre-cycled Zn electrodes (10 cycles in Zn||Zn coin cells at 10 mA cm−2/10 mAh cm−2) were reassembled into Zn||Zn cells, and in situ hydrogen gas evolution during charging and discharging at 5 or 10 mA cm−2 was monitored using a differential electrochemical mass spectrometry (DEMS) system (Ling Lu Instruments) with a helium carrier gas flow rate of 0.7 mL min−1. After stabilizing the baseline with helium gas-blowing, the pre-cycled Zn||Zn cells were subjected to galvanostatic charging/discharging. The net H2 release was determined by subtracting the baseline.

The X-ray absorption spectra of 0% Addi, 5% TEP, and 30% TEP were collected from the Hard X-ray micro-analysis (HXMA) at the Canadian light source (CLS). The samples were measured in a liquid cell equipped with an open window sealed by Kapton tape, giving a total thickness of approximately 5 mm. The incident photon energy was calibrated using a Zn foil, with E0 set to 9659 eV, and the spectra were collected over an energy range of 9459–10207 eV (12k). Data were acquired in fluorescence yield mode using a 32-element Ge detector. All XAS data were analyzed with the Athena software77, and the EXAFS data were processed using the Artemis program. A linear function was subtracted from the pre-edge region, then the edge jump was normalized using Athena software. The k2-weighted χ(k) data were Fourier transformed after applying a Hanning window function.

Computational study
Finite element simulations. To elucidate the dynamics of Zn electrodeposition, three-dimensional finite element simulations were performed using the COMSOL Multiphysics 5.6 software28. We employed the tertiary current distribution to model the electrochemical processes. The simulation accounted for electrode morphology evolution during plating/stripping via the Deformed Geometry module. Ion transport under the applied electric field was governed by the Nernst-Planck equation, while electrode kinetics were described by the Butler-Volmer equation at the relevant boundaries. All simulation parameters are provided in Supplementary Table 6. Molecular dynamics (MD) simulations The MD were conducted with GROMACS (version 2021.3)78,79. Initial molecular geometries were optimized using ORCA, and the simulation boxes were constructed with Packmol80. The optimized potentials for liquid simulations all-atom (OPLS-AA) force field81 was applied, with atomic charges derived via the RESP2 method in Multiwfn82. Following energy minimization, systems were equilibrated for 1 ns under NPT ensemble conditions using the Berendsen barostat. Production runs (20 ns) were then performed in the NPT ensemble at 300 K with a 1 fs timestep, employing the V-rescale thermostat (τT=1 ps) and Parrinello-Rahman barostat (τP=2 ps) for temperature and pressure control, respectively. Hydrogen bond analysis was performed using built-in GROMACS tools. To simulate the variation of H2O-H2O hydrogen bonds at the Zn(001)/electrolyte interface in 5% TEP, the Zn/electrolyte interface is modeled by adding 1675 H2O molecules, 9 TEP molecules, 64 Zn2+, 120 OTf− and 8 Ac− into a box above the Zn slab. The Zn slab model contains 4 layers of Zn(001) plane with an orthogonal supercell of 8√3*16. The area of the Zn/electrolyte interface is 3.62 nm × 4.18 nm. The electrolyte layer with a thickness of 4 nm was placed above the Zn slab, and the total thickness of the simulated box was 4.93 nm. For the 0% Addi electrolyte, the 9 TEP molecules were removed while keeping all other components unchanged. Hydrogen bonds in the simulation were defined by an OH distance of less than 3.5 Å and the angle of H-O-O less than 30°.

Electrodes fabrications
We prepared the NaV3O8·1.5H2O (NVO) powder through the following steps. 3.0 g commercial V2O5 powder (Sigma-Aldrich, ≥99.9%) was mixed with 100 mL NaCl aqueous solution (2 mol kg−1) under vigorous stirring at 25 ± 2 °C. After 96 hours, the product was centrifuged, washed with deionized water and ethanol, and freeze-dried for 24 h. The as-prepared NVO powder was mixed with multi-walled carbon nanotubes (conductive agent, Canrd, ≥99%) and polytetrafluoroethylene (binder, Canrd, 60 wt% dispersion in water) in an agate mortar at a mass ratio of 6:2:2 with deionized water (solvent-to-solid ratio of 1.1:1) to form a homogeneous, dough-like mixture. The mixture was then rolled on a Ti mesh (100 mesh, ≥99.9%, 270 μm, 28.9 mg cm−2) with a roller to get single-coated NVO electrodes. The electrode was dried at 60 °C for 72 hours. After drying, the electrode sheet was cut into rectangles using a precision cutter. The dimensions were 3 cm × 4 cm for the single-layer pouch cell and 9 cm × 10 cm for the 1.27 Ah pouch cell. The mass loading of NVO is ~17 mg cm−2 and the thickness of NVO is ~420 μm. The same methods were followed to prepare the NVO electrodes with a mass loading of ~34 mg cm−2.

Pouch cell assembling
The 1.27 Ah pouch cell was constructed with a bipolar structure (Fig. 6e) with two Zn foils (9 cm × 10 cm × 40 μm, >99.999%, MTI Corporation) clamped in the middle sharing one Ti foil current collector (9 cm × 10 cm × 10 μm, >99.99%, MTI Corporation) and two pieces of NVO electrodes (9 cm × 10 cm × 420 μm) on both sides separated by the glass fiber (9.2 cm × 10.2 cm × 240 μm, Whatman). The optical images and detailed parameters of these components are seen in Supplementary Figs. 39 and 40, and Supplementary Table 5. 5% TEP was used as the electrolyte. An Al packaging bag was used to accommodate the cell. The two positive electrode tabs and one negative electrode tab were bonded to the Al packaging films by the adhesive polymer tape (MTI Corporation) via hot pressing. The pouch cell bag was filled with 5% TEP electrolyte and left standing overnight to ensure complete wetting of the NVO electrodes. Subsequently, the bag was sealed under vacuum using the automated vacuum sealing machine (Shine Ye Corporation), with a final 10 mL (14.4 g) of 5% TEP loaded into the pouch cell, equivalent to an electrolyte-to-capacity ratio of 11.3 g Ah−1. All the assembling procedures were completed in the atmosphere at 25 ± 2 °C. The pouch cell was tested under an external pressure of ~0.1 MPa. The calculation of the energy density of this Ah-level pouch cell can be found in Supplementary Note 2. The single-layer pouch cell was assembled with one piece of NVO electrode (3 cm × 4 cm × 420 μm) and one piece of ZMA (3 cm × 4 cm × 30 μm), with glass fiber separated in the middle (3.2 cm × 4.2 cm × 240 μm).

Electrochemical measurement
Galvanostatic charge and discharge tests. The galvanostatic cycling of Zn||Zn and Zn||Cu cells (Fig. 5a–d) and Zn||NVO cells (Fig. 6a–c) were performed in CR2032-coin cells (SS304) using glass fiber separator and 120 μL electrolyte. For Zn||Zn symmetric and Zn||Cu (≥99.99%, 20 μm, MTI Corporation) asymmetric cells, a 100 μm thick Zn foil was used. Before use, Zn foil was polished by soft backing sponges (3M, USA) and then rinsed with ethanol to remove surface oxides or impurities. Electrodes were punched into disks with a diameter of 12 mm for the coin cell assembly. Zn||Zn symmetric cells were evaluated at 5 mA cm−2/5 mAh cm−2 and 10 mA cm−2/10 mAh cm−2. Zn||Cu asymmetric cells were evaluated at 1 mA cm−2/1 mAh cm−2 with the cut-off voltage at 0.5 V. Symmetric Zn@Cu||Zn@Cu cells for 85% DOD testing were prepared as follows. First, 11.76 mAh cm−2 of Zn (equivalent to 10 mAh cm−2 at 85% DOD) was pre-deposited onto Cu disks (12 mm diameter) at 10 mA cm−2 in Zn||Cu coin cells. These Zn@Cu electrodes were then retrieved and assembled into symmetric Zn@Cu||Zn@Cu cells, which were evaluated at 10 mA cm−2 and 10 mAh cm−2. For Zn||NVO cells, the Zn foil thickness was 100 μm for cells with a N/P ratio of 9.6 and 20 μm for cells with a N/P ratio of 1.9. Electrodes were punched into disks with a diameter of 8 mm for the coin cell assembly. The Zn||NVO cell was first discharged to 0.2 V and then charged to 1.6 V at different current densities.

Arrhenius analysis of the Zn/electrolyte interface was performed using Zn||Zn symmetric cells. First, a stable SEI was pre-formed by galvanostatic cycling at 5 mA−2 and 5 mAh cm−2 for 10 cycles. Subsequently, electrochemical impedance spectroscopy (EIS) was conducted under potentiostatic mode at the open-circuit potential (0 V vs. OCV) after resting at OCV for 30 min. The impedance spectra were acquired with a perturbation amplitude of 5 mV over a frequency range from 100 kHz to 10 mHz with a total of 41 measurement points. This EIS protocol was repeated at 5 different temperatures (20, 30, 40, 50, and 60 °C) to obtain the temperature-dependent resistance for the Arrhenius plot. Tafel plots (Supplementary Fig. 25) were performed in a typical three-electrode system with the EC-Lab electrochemical workstation (Biologic VMP3, France), where pre-cycled Zn foil (10 cycles in Zn||Zn cells at 10 mA cm−2/10 mAh cm−2) acted as the working electrode, graphite rod as the counter electrode, and Ag/AgCl as the reference electrode. The Tafel plots were tested at a scan rate of 2 mV s−1 and a potential of ± 0.3 V vs. open-circuit potential. The exchange current densities were calculated by fitting Tafel plots in the voltage range from −30 to 30 mV vs. Zn2+/Zn.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "In this study, the authors reveal the critical role of electrolyte surface tension (σ) in governing Zn nucleation and growth through comprehensive theoretical analysis and experimental validation. Specifically, low-σ electrolytes facilitate dense nucleation and fine-grained growth of Zn, even under harsh electrochemical conditions, owing to the reduced nucleation energy barrier and growth resistance. This optimized Zn electroplating behavior enables not only dendrite-free growth but also promotes the formation of a robust SEI, effectively suppressing side reactions on Zn metal anodes. This work reports an effective low-σ strategy to enhance the stability and reversibility of Zn metal anodes at a practical level, advancing the commercialization of zinc metal batteries. Moreover, this work underscores electrolyte`s σ as a vital consideration in future electrolyte design for advanced metal electrodes. We believe this study will attract broad interest from the research community. Therefore, we recommend the publication of this manuscript after a minor revision. Below are a few questions for the authors to address:\nThe study of Zn nucleation and growth from an energy perspective is interesting. To enhance understanding, could the authors provide further clarification on the terms of \"∆\" \"G\" _\"S\" (surface energy) and \"∆\" \"G\" _\"V\" (volume energy)? Specifically, how do these two energy components collectively determine the nucleation energy barrier of Zn?\nThe authors illustrate how the electrolyte σ affects the Zn nucleation and growth. During the nucleation process, σ affects the nucleation energy barrier and the critical nuclei radius. For the growth part, σ is linked to the growth resistance. Could the authors provide more information about the growth resistance?\nIn Fig. 1d, the surface roughness of Zn is mentioned. It is an important parameter to estimate the surface smoothness of Zn deposits and is related to the propensity for dendritic growth. Please explain more in the main text the relationship between the particle size of Zn, plated capacities, and surface roughness of Zn deposits.\nBesides σ, we noticed that the factor of f (θ), which is related to the contact angle between the Zn nucleus and substrate, also affects the nucleation energy barrier during the nucleation process. We are interested in how this parameter would potentially affect the nucleation process. Please give more information.\nSome important refs may be cited to enrich reference part of the revised manuscript, such as, Electrochem. Energy Rev. 2023, 6(1), 5; Electrochem. Energy Rev. 2023, 6, 33.\nIn the morphology characterization, custom-made cells are adopted to do the Zn plating/stripping, and the as-obtained Zn@Cu electrodes were collected for the subsequent SEM testing. Regarding the experimental configuration, would the dense Zn deposition morphology be maintained if the experiments are conducted in conventional coin cells employing glass fiber separators? Furthermore, it would be valuable to understand how the deposition morphology might evolve when employing lower current densities (e.g., 2-5 mA cm−2) in coin cells.\nIn Fig. 6g, the manuscript states a capacity retention of 84% but does not specify the cycle number to which this value corresponds. Please specify it.", "reviewer_2": "The manuscript ascribes its central contribution to a “low surface tension electrolyte strategy,” contending that trace amounts of low polarity co solvents (e.g., 5 vol % TEP) reduce σ and thereby yield uniform Zn deposition. However, the evidence provided does not convincingly identify σ as the dominant mechanistic driver. Figure 1f shows that the surface tension of electrolytes containing 5 vol % EG, G4, or G2 converges within a narrow 50-55 mN m-1 window (only a ~5 mN m-1 spread) ─ yet Figure S12 reveals strikingly different plating morphologies, with EG still producing coarse porous deposits while G4 and G2 generate compact layers. Such modest σ variations are unlikely to account for the dramatic performance divergence. A more coherent explanation is supplied by the cosolvents’ low dielectric constants: low ε co solvents are known to feature weak solvation effect, suppress water activity, and foster dense deposition in “so called weakly solvating aqueous electrolytes”. Indeed, the authors’ own RDF analysis shows that TEP scarcely enters the primary Zn2+ solvation shell, a hallmark of weak solvation. This low ε weak solvation paradigm has already been validated in some reports over the past two years as an effective means of regulating Zn growth. Consequently, the present work appears to repackage an established mechanism under a new σ centric narrative, offering only an incremental variation in additive identity rather than a substantive conceptual advance. Therefore, the claimed innovation is insufficient to meet the novelty threshold of this journal.\nIn addition, there are several other issues as follows:\nFigure 1f shows no meaningful change in bulk ionic conductivity upon adding 5 vol % TEP, yet Figure 5 and S22 reveal a pronounced change in Zn||Zn overpotential that the other additives in Figure S23 do not produce; please explain this discrepancy.\nWhy are G2 and G4 evaluated at 5 vol % while EG and DME are assessed at 30 vol %, rather than at identical additive loadings? Please provide comparative results at the same concentration for all co‑solvents.\nFundamental electrolyte information, such as the complete electrochemical stability window and ionic conductivity as a function of temperature, should be reported.\nFigure 5d shows substantial fluctuations in coulombic efficiency; please explain the underlying cause and enlarge the y axis (e.g., 80-120 %) so that the variations are clearly visible.", "reviewer_3": "This work reports a low-surface-tension electrolyte design for rechargeable Zn metal batteries that enables dense nucleation, fine-grained growth, and stable solid-electrolyte interfaces, resulting in dendrite-free morphology and suppressed side reactions. This approach achieves a high Coulombic efficiency and significant lifespan improvements under harsh conditions compared to conventional electrolytes, demonstrating practicality in an Ah-level pouch cell and offering a cost-effective pathway for commercially viable batteries. It is recommended to publish in Nature Communications after proper revision addressing the following issues:\n1. The authors highlight the importance of surface tension; however, it is expected to see more characterization on surface tension, such as contact angle comparison.\n2. The stability of the electrolyte additive may need to be further verified by experiment. If the additive molecule is involved in the SEI formation, then the optimized concentration of the additive may need to be reconsidered.\n3. The authors should provide an in-depth analysis on the mechanism of the additive molecule; for example, is there any adsorption behavior that could be monitored during cycling?\n4. The authors can provide XPS spectra of O1s of Zn in 5% TEP after 10 plating/stripping cycles at 10 mA cm−2/10 mAh cm−2, after 500 s and 1000 s sputtering time to have a better understanding of the environmental change.\n5. The insets in Figure 3c showing time-of-flight mass spectrometry figures are relatively hard to distinguish. The authors can consider putting an enlarged figure in the revised SI.\n6. In Figure 4a, the authors claim that TEP disrupts the hydrogen-bonding framework, particularly at the Zn/electrolyte interface. It would be better to support this conclusion with other supporting experimental data related to hydrogen bonding.\n7. The authors should provide an enlarged figure for the starting 0-50 cycles comparison of the CE testing to have a better understanding of the initial zinc deposition difference.\n8. The authors should provide detailed characterization, such as XPS and XRD, for the cycled zinc anode in different electrolytes to further support their conclusion that \"the low-σ electrolyte enhances the SEI stability, effectively suppressing side reactions even under harsh electrochemical conditions.\""}, "author_response": "Response letter to reviewers\nWe would like to express our sincere appreciation for the reviewers’ time and valuable\ncomments. We have revised the manuscript according to these comments with additional\nexperiments and discussions. The detailed point-to-point responses are listed below. In our\nresponses, the reviewer’s comments are shown in black, our responses are provided in blue,\nand the texts added in the manuscript and Supplementary Information (SI) are highlighted in\nred.\nReviewer #1\nIn this study, the authors reveal the critical role of electrolyte surface tension (σ) in\ngoverning Zn nucleation and growth through comprehensive theoretical analysis and\nexperimental validation. Specifically, low-σ electrolytes facilitate dense nucleation and\nfine-grained growth of Zn, even under harsh electrochemical conditions, owing to the\nreduced nucleation energy barrier and growth resistance. This optimized Zn\nelectroplating behavior enables not only dendrite-free growth but also promotes the\nformation of a robust SEI, effectively suppressing side reactions on Zn metal anodes. This\nwork reports an effective low-σ strategy to enhance the stability and reversibility of Zn\nmetal anodes at a practical level, advancing the commercialization of zinc metal batteries.\nMoreover, this work underscores electrolyte`s σ as a vital consideration in future\nelectrolyte design for advanced metal electrodes. We believe this study will attract broad\ninterest from the research community. Therefore, we recommend the publication of this\nmanuscript after a minor revision. Below are a few questions for the authors to address:\nResponse: We sincerely thank the reviewer for their positive and professional evaluation of our\nwork. We have revised the manuscript point-by-point according to your comments.\n1. The study of Zn nucleation and growth from an energy perspective is interesting. To\nenhance understanding, could the authors provide further clarification on the terms of \"∆\"\n\"G\" _\"S\" (surface energy) and \"∆\" \"G\" _\"V\" (volume energy)? Specifically, how do these\ntwo energy components collectively determine the nucleation energy barrier of Zn?\nResponse: We sincerely thank the reviewer for this comment. Based on the classical nucleation\ntheory, the change of Gibbs energy (∆G ) of a nucleus during the heterogeneous nucleation\nhet\ncan be expressed as:\n∆G = 𝑓(𝜃)(∆G +∆G ) (1)\nhet S V\nFor a spherical zinc nucleus with a radius of x, Equation (1) can be rewritten as:\n∆G = 𝑓(𝜃)(4πσx2 + 4πnFρ∆φ x3) (2)\nhet\n3M\nIn Equations 1 and 2, f(θ) is a constant determined by the contact angle (θ) between the Zn\nnucleus and substrate. The first term within the parenthesis is the surface energy ∆G . ∆G is\nS S\nalways a positive value. Its profile with x extends in quadrant I (Supplementary Fig. 3). It refers\nto the energy that has to be supplied to form a solid surface during the nucleation process. Note\nthat this energy also needs to be overcome in the subsequent growth processes. The second term\nwithin the parenthesis is the volume energy ∆G , which is the change of free energy in the\nV\nelectrochemical plating of Zn under a negative bias voltage ∆φ (vs. Zn2+/Zn), accompanied\nby the phase transition from Zn2+ (aq) to Zn (s). It is a negative value when the voltage bias ∆φ\nis negative. Its profile with x extends in quadrant IV. It refers to the energy that is released.\nTherefore, the sum of these two competing terms, ∆G , shows a maximum value of ∆𝐺∗\nhet ℎ𝑒𝑡\n(Supplementary Fig. 3). It is the energy barrier that must be overcome for a stable nucleation\nprocess with the expression of Equation (3).\n∆G∗ =\n𝑓(𝜃)16πM2\nσ3 (3)\nhet 3n2ρ2F2∆φ2\nThe following texts in red are added to the manuscript to explain it further (page 6).\n“Note that ∆G (> 0) represents the energy input required to form a solid surface during\nS\nnucleation. This energy also needs to be overcome in the subsequent growth processes. In\ncontrast, ∆G (< 0) reflects the energy release during the transition of Zn2+ (aq) to Zn (s) under\nV\na negative bias voltage ∆φ (vs. Zn2+/Zn) (Fig. 1a, Supplementary Fig. 2).”\n2. The authors illustrate how the electrolyte σ affects the Zn nucleation and growth. During\nthe nucleation process, σ affects the nucleation energy barrier and the critical nuclei radius.\nFor the growth part, σ is linked to the growth resistance. Could the authors provide more\ninformation about the growth resistance?\nResponse: We sincerely thank the reviewer for this comment. During the electrodeposition of\nZn, the surface energy ∆G is always a positive value (as demonstrated in Fig. 1a in the\nS\nmanuscript and Supplementary Fig. 3 in SI). It refers to the energy that has to be supplied to\nform a solid surface during the nucleation process. Note that this energy also needs to be\novercome in the subsequent growth processes. Therefore, the growth resistance can be\nquantified by the surface energy per unit area, which is equivalent to the electrolyte surface\ntension, σ (Equation 4).\nGrowth resistance =\n∆GS\n= σ (4)\n4πR2\nTherefore, in high-σ electrolytes, the growth resistance is high, while in low-σ electrolytes, the\ngrowth resistance is low.\nThe following texts in red are added to the manuscript to explain it further (page 7).\n“Conversely, for the same −ΔG /ΔG , low-σ electrolytes reduce growth resistance—that\nS V\nis, the surface energy per unit area, equivalent to the electrolyte surface tension σ—yielding\nsmaller, denser particles (Supplementary Note 1).”\n3. In Fig. 1d, the surface roughness of Zn is mentioned. It is an important parameter to\nestimate the surface smoothness of Zn deposits and is related to the propensity for dendritic\ngrowth. Please explain more in the main text the relationship between the particle size of\nZn, plated capacities, and surface roughness of Zn deposits.\nResponse: We sincerely thank the reviewer for this insightful comment. The surface roughness\nof the Zn plating layer is indeed a critical parameter, as it is related to the propensity for\ndendritic growth. The relationship between particle size, plated capacity, and surface roughness\ncan be explained as follows: in high-σ electrolytes, the formation of sparse and large zinc nuclei,\ncoupled with high growth resistance, leads to preferential zinc deposition onto these limited\nsites. This results in the formation of large Zn particles. These large particles stack unevenly,\ncreating a coarse surface with high roughness. This roughness is further amplified with\nincreasing plated capacity, as deposition continues to focus on these pre-existing protrusions.\nConversely, in low-σ electrolytes, the high density of small zinc nuclei and low growth\nresistance enable uniform zinc deposition across the numerous available sites. This results in\nsmall particle sizes that form a dense, smooth layer with low inherent roughness. Furthermore,\nthis homogeneous morphology remains stable even at high plated capacities, effectively\nmaintaining a low surface roughness.\nThe following texts are added to the revised manuscript to explain it further (page 9).\n“These dramatic differences confirm that high-σ electrolytes promote sparse nucleation and\nuneven growth, leading to rapidly escalating surface roughness with capacity. Conversely, low-\nσ electrolytes enable dense nucleation and uniform plating, maintaining a consistently smooth\nsurface even at high capacities.”\n4. Besides σ, we noticed that the factor of f (θ), which is related to the contact angle between\nthe Zn nucleus and substrate, also affects the nucleation energy barrier during the\nnucleation process. We are interested in how this parameter would potentially affect the\nnucleation process. Please give more information.\nResponse: We sincerely thank the reviewer for this insightful comment. The reviewer is\nabsolutely correct. According to classical nucleation theory, the nucleation energy barrier\n(∆𝐺∗ ) is indeed also governed by f(θ), which is a function of the contact angle (θ) between\nℎ𝑒𝑡\nthe Zn nucleus and the substrate. The relationship is given by:\n𝑓(𝜃) = 1 (2−3cos𝜃 +cos3𝜃) (5)\nin a lower value of f(θ), thereby reducing the overall nucleation energy barrier ∆𝐺∗\nℎ𝑒𝑡\n(Equation 2 in the manuscript). Consequently, designing substrates with high zincophilicity is\nalso a fundamental strategy to promote uniform Zn nucleation. This is exemplified by the work\nof Yang et al., who employed a zincophilic Cu-In alloy interface to significantly reduce the Zn\nnucleation overpotential and guide uniform Zn deposition (Nat. Commun. 15, 9455, (2024)).\nSimilar enhancements have been achieved using functional layers such as Au, which leverage\nthe high zincophilicity to lower the nucleation energy barrier and facilitate dendrite-free Zn\ndeposition (Adv. Mater 36, 2308592, (2024)).\nThe following texts are added to the revised SI to explain f (θ) further.\n“f(θ) is the contact factor related to the contact angle (θ) between the Zn nucleus and the\nsubstrate. This parameter can be expressed as Equation 2 and is a material-dependent constant\nfor a given substrate, ranging from 0 to 1. Specifically, substrates with higher zincophilicity\nexhibit a smaller contact angle θ, which in turn yields a smaller f(θ) value. In this work, the\nsubstrate is Cu; therefore, f(θ) is treated as a constant.\n𝑓(𝜃) = 1 (2−3cos𝜃 +cos3𝜃) (2).”\n4\n5. Some important refs may be cited to enrich reference part of the revised manuscript, such\nas, Electrochem. Energy Rev. 2023, 6(1), 5; Electrochem. Energy Rev. 2023, 6, 33.\nResponse: We thank the reviewer for this excellent suggestion. The recommended review\narticles are highly relevant and authoritative. Their inclusion can enrich the introduction part\nby providing a comprehensive background on the challenges of Zn metal anodes and the latest\nadvances in 3D host cathode design, respectively. We have now cited them as references 15\n(Electrochem. Energy Rev. 2023, 6, 33) and 26 (Electrochem. Energy Rev. 2023, 6(1)) in the\nrevised manuscript.\n6. In the morphology characterization, custom-made cells are adopted to do the Zn\nplating/stripping, and the as-obtained Zn@Cu electrodes were collected for the subsequent\nSEM testing. Regarding the experimental configuration, would the dense Zn deposition\nmorphology be maintained if the experiments are conducted in conventional coin cells\nemploying glass fiber separators? Furthermore, it would be valuable to understand how the\ndeposition morphology might evolve when employing lower current densities (e.g., 2-5\nmA cm−2) in coin cells.\nResponse: We thank the reviewer for their comment. Yes, the dense Zn deposition morphology\nis maintained if the experiments are conducted in conventional coin cells employing glass fiber\nseparators. Supplementary Fig. 10a presents the discharge curves of Zn||Cu asymmetric coin\ncells and corresponding optical images of retrieved Cu electrodes after 60 and 1030 seconds of\nplating. The results demonstrate a stark contrast. In 5% TEP, the Cu electrode is fully covered\nby a dense Zn layer after 1030s of plating at 10 mA cm−2. In sharp contrast, 0% Addi produces\nsparse Zn deposition that fails to achieve complete substrate coverage. This clear difference\nconfirms that the dense nucleation and growth behavior induced by TEP is an intrinsic property\nof the electrolyte and not a consequence of the experimental setup.\nBesides, we further investigated deposition at 2 and 5 mA cm−2 after 60 seconds of plating.\nThe optical images in Supplementary Fig. 10b show that Zn deposits in 5% TEP remain\nconsistently denser compared to those in 0% Addi at lower current densities. This confirms that\nthe beneficial effect of TEP in promoting dense Zn nucleation and growth is effective across a\nrange of current densities.\nSupplementary Fig. 10 a, Discharge curves of Zn||Cu asymmetric coin cells at 10 mA cm−2.\nInsets: corresponding optical images of retrieved Cu electrodes after 60 and 1030 seconds of\nplating. b, Zn deposits in 5% TEP and 0% Addi at lower current densities.\nThis figure is added as Supplementary Fig. 10 in the revised SI. The following texts are\nadded to the revised manuscript to explain it further (page 9).\n“TEP's ability to enable dense, uniform Zn deposition is further validated across various\nareal currents in coin cells (Supplementary Fig. 10).”\n7. In Fig. 6g, the manuscript states a capacity retention of 84% but does not specify the cycle\nnumber to which this value corresponds. Please specify it.\nResponse: We thank the reviewer for their comment. The following texts are added in the\nrevised manuscript to specify the cycle number to which this value corresponds (page 19).\n“The cell maintains stable cycling for 120 cycles, after which it shows a high capacity\nretention of 84% (relative to the 6th cycle at 139 mA g−1) and an average CE exceeding 99.9%\n(Fig. 6g).”\nReviewer #2\nThe manuscript ascribes its central contribution to a “low surface tension electrolyte\nstrategy,” contending that trace amounts of low polarity co solvents (e.g., 5 vol % TEP)\nreduce σ and thereby yield uniform Zn deposition. However, the evidence provided does\nnot convincingly identify σ as the dominant mechanistic driver. Figure 1f shows that the\nsurface tension of electrolytes containing 5 vol % EG, G4, or G2 converges within a\nnarrow 50-55 mN m-1 window (only a ~5 mN m-1 spread) ─ yet Figure S12 reveals\nstrikingly different plating morphologies, with EG still producing coarse porous deposits\nwhile G4 and G2 generate compact layers. Such modest σ variations are unlikely to\naccount for the dramatic performance divergence.\nResponse: We sincerely thank the reviewer for this comment. The reviewer points out that the\nsurface tension (σ) values of electrolytes of 5vol% G4, 5vol% G2, and 30 vol% EG fall within\na narrow range (50–55 mN m−1), yet the corresponding Zn morphologies at a high capacity (50\nmAh cm−2) differ significantly (Supplementary Fig. S15b–d in the revised SI). This observation\nis indeed crucial, and we appreciate the opportunity to clarify the underlying mechanism. The\neffect of σ on the final Zn morphology is not a simple linear relationship; rather, it arises from\nthe combined influence of σ on both the nucleation and growth processes. Moreover, the extent\nof σ's impact during the growth process varies substantially with the plated capacity. Below, we\naddress this point from both theoretical and experimental aspects.\nTheoretical Aspect: The influence of σ on Zn electrodeposition is fundamentally nonlinear.\nσ governs the nucleation energy barrier and the size of the nuclei in the nucleation process, as\nwell as the particle size in the subsequent growth process. Specifically, in the nucleation process,\nthe nucleation energy barrier (∆𝐺∗ ) is proportional to the cube of the surface tension (σ3), as\nℎ𝑒𝑡\ndescribed by Equation 2 and Fig. 1b in our manuscript. Thus, even a small reduction in σ can\nsubstantially decrease the energy barrier for nucleation, leading to a higher density of nucleation\nsites (as supported by Fig. 2a in our manuscript and Supplementary Fig. S14 in the SI).\nMoreover, a lower σ reduces the critical nucleus radius (Equation 3 and Fig. 1b), promoting the\nformation of finer initial nuclei. In the subsequent growth process, lower σ also helps maintain\nsmaller Zn particle sizes by reducing the growth resistance (Equation 4 in the manuscript and\nEquation 15 in the SI). This effect is especially amplified under high plated capacities (Fig. 1c\nin our manuscript), where prolonged growth exacerbates differences in morphology—as clearly\nobserved in Supplementary Fig. S15b–d.\nExperimental Aspect: The strikingly different morphologies shown in Supplementary Fig.\nS15b–d are obtained at a high areal capacity of 50 mAh cm−2. Under such harsh plating\nconditions, the cumulative effect of σ on nucleation and growth is markedly amplified. As such,\neven modest differences in σ (e.g., ~5 mN m−1) translate into visibly distinct deposit structures.\nThis result aligns well with our theoretical inference that the influence of σ on particle size\nbecomes more pronounced under high plated capacity (Fig. 1c).\nTo further validate this argument, we conducted additional experiments at a lower plated\ncapacity of 10 mAh cm−2. As expected, the differences in particle size among electrolytes with\nEG, G4, and G2 are much less pronounced at these low capacities (Fig. R1). This capacity-\ndependent effect reinforces the critical role of σ in governing deposition uniformity, especially\nunder harsh electrochemical conditions.\nIn summary, we acknowledge that the absolute variation in σ is small, but its nonlinear\nimpact—coupled with the high plated capacity—explains the dramatic divergence in\nmorphology.\nFig. R1 SEM images of Zn deposits at 10 mA cm−2 in 30% EG (a, b), 5% G2 (c,d), and 5%G4\n(e,f) after a plating time of 1 hour (a, c, e) or a plating time of 5 hours (b, d, f).\nA more coherent explanation is supplied by the cosolvents’ low dielectric constants: low ε\nco solvents are known to feature weak solvation effect, suppress water activity, and foster\ndense deposition in “so called weakly solvating aqueous electrolytes”. Indeed, the authors’\nown RDF analysis shows that TEP scarcely enters the primary Zn2+ solvation shell, a\nhallmark of weak solvation. This low ε weak solvation paradigm has already been\nvalidated in some reports over the past two years as an effective means of regulating Zn\ngrowth. Consequently, the present work appears to repackage an established mechanism\nunder a new σ centric narrative, offering only an incremental variation in additive identity\nrather than a substantive conceptual advance. Therefore, the claimed innovation is\ninsufficient to meet the novelty threshold of this journal.\nResponse: We sincerely thank the reviewer for their comment, which allows us to further\nclarify the conceptual advance of our work. We fully agree that low-ε cosolvents can suppress\nwater activity, but this effect is typically concentration-dependent. Our work introduces\nelectrolyte σ as a previously overlooked, fundamental parameter that governs Zn deposition, a\nconcept distinct from the weak-solvation paradigm. We address the reviewer's concern in three\nkey aspects:\nFirst, indeed, low-ε cosolvents can effectively suppress water activity—but this generally\nrequires high cosolvent concentrations (typically >50 vol%). For instance, seminal works by\nGuo et al. (Energy Environ. Sci. 17, 4569-4581, (2024)) and Zhi et al. (Nat. Commun. 14, 1828,\n(2023)) employed 60 vol% G2 and 57 vol% sulfolane, respectively, to achieve this. In stark\ncontrast, our strategy employs only 5 vol% TEP, a concentration too low to bind or constrain\n95 vol% water. Instead, this trace amount of additive does reduce the electrolyte's σ dramatically\n(Fig.1f), which directly regulates Zn nucleation and growth (Fig. 2, Supplementary Fig. 14, 15,\n26, 27).\nSecond, the core of our work is to reveal how σ governs both nucleation and growth\nprocesses. While previous studies focused on solvation, they did not even mention or\ninvestigate the critical role of σ. In our work, we provide a comprehensive theoretical\nframework, derived from classical nucleation theory, that quantitatively establishes σ as the key\nparameter controlling both the nucleation energy barrier and growth resistance. This is a\nsubstantial conceptual advance, offering a new design dimension for electrolytes beyond\nsolvation chemistry.\nThird, to decisively decouple the effect of low ε from that of σ, we prepared low-σ\nelectrolytes using surfactants. The results are unequivocal: both surfactant-containing\nelectrolytes, despite not being low-ε cosolvents, yielded identical outcomes—dense nucleation\nand compact Zn growth (Fig. R2, R3).\nSpecifically, we selected a cationic surfactant, tetrabutylammonium chloride ((Bu N)Cl),\n4\nand a non-ionic surfactant, triton x-100, for their short carbon chains and high aqueous\ncompatibility. Two electrolytes were formulated by adding 0.2 wt% of each surfactant to the\nbaseline solution, denoted as 0.2 wt% (Bu N)Cl and 0.2 wt% triton x-100, respectively. The\n4\naddition of these surfactants significantly reduced the surface tension to 31.2 mN m−1 and\n33.5 mN m−1, respectively.\nRemarkably, both surfactant-containing electrolytes induce similar dense nucleation and\ncompact growth of Zn as observed in our low-σ 5% TEP electrolyte. At the beginning (3\nminutes) of electroplating with a high current density of 10 mA cm−2, the Zn deposits fully\ncovered Cu foils, indicating the high density of Zn nuclei in these two electrolytes (Fig. R2a–\n2c; Fig. R3a–3c). Extending the plating duration to 30 minutes, 1hour, 3 hours, and 5 hours,\ncorresponding to areal capacities of 5, 10, 30, and 50 mAh cm−2, respectively, the Zn deposits\nstill maintain a dense, fine-grained morphology (Fig. R2d–2g; Fig. R3d–3g). Besides, both\nelectrolytes maintain low RMS roughness across all plated capacities, reaching only ~10.1 μm\nfor 0.2 wt% (Bu N)Cl (Fig. R2h, 2i) and ~10.5 μm for 0.2 wt% triton x-100 (Fig. R3h, 3i) even\n4\nat 50 mAh cm−2—more than 97% reduction compared to 434 μm in 0% Addi. This evidence\nconfirms that the dense nucleation and growth are a direct result of reduced σ, independent of\nthe solvent's ε.\nFig. R2. Characterization of Zn deposits in low-σ electrolytes of 0.2 wt% (Bu N)Cl. a–g,\n4\n3 minutes (a–c), 30 minutes (d), 1 hour (e), 3 hours (f), and 5 hours (g). b, the EDX\nmapping of Zn under a scale bar the same as (a). c, the enlarged view of (a). h, the LSCM image\nof Zn deposits at 10 mA cm−2/50 mAh cm−2. i, RMS roughness of Zn deposits with plated\ncapacities of 5, 10, 30, and 50 mAh cm−2 at a current density of 10 mA cm−2.\nFig. R3. Characterization of Zn deposits in low-σ electrolytes of 0.2 wt% triton x-100. a–\ng, Top views of Zn deposits at 10 mA cm−2 in low-σ electrolyte of 0.2 wt% triton x-100 after\nplating 3 minutes (a–c), 30 minutes (d), 1 hour (e), 3 hours (f), and 5 hours (g). b, the EDX\nmapping of Zn under a scale bar the same as (a). c, the enlarged view of (a). h, the LSCM image\nof Zn deposits at 10 mA cm−2/50 mAh cm−2. i, RMS roughness of Zn deposits with plated\ncapacities of 5, 10, 30, and 50 mAh cm−2 at a current density of 10 mA cm−2.\nIn addition, there are several other issues as follows:\n1. Figure 1f shows no meaningful change in bulk ionic conductivity upon adding 5 vol % TEP,\nyet Figure 5 and S22 reveal a pronounced change in Zn||Zn overpotential that the other\nadditives in Figure S23 do not produce; please explain this discrepancy.\nResponse: We appreciate the reviewer’s comment. Our results show that the high\noverpotentials are due to a combined effect of reduced ionic conductivity and lowered σ. To\ncompare overpotentials clearly, we analyzed stabilized voltage profiles during specific cycling\nwindows: 120–160 h at 5 mA cm−2 (Fig. R4a) and 70–110 h at 10 mA cm−2 (Fig. R4b). In these\nwindows, the cells in 0% Addi began to experience short circuits, while cells in low-σ\nelectrolytes exhibited stabilized, repeatable voltage profiles. At 5 mA cm−2, the overpotentials\nincrease in the order: 0% Addi < 5% G2 ≈ 5% G4 < 30% DME < 5% TEP. At 10 mA cm−2, the\norder is: 0% Addi < 5% G2 < 5% G4 < 5% TEP < 30% DME. It indicates that 5% TEP and 30%\nDME consistently exhibit the highest overpotentials.\nThe high overpotentials can be attributed to two main factors: First, the ionic conductivity\nof low-σ electrolytes is lower than that of 0% Addi (Fig. R4c), which slows Zn2+ mass transport\nand increases overpotential. Second, the σ of 5% TEP shows the most substantial reduction,\nreaching only 55% of 0% Addi (Fig. R4d). MD simulations (Fig. R4e) and Raman spectroscopy\n(Supplementary Fig. 30) confirm that TEP molecules disrupt the interfacial hydrogen-bonding\nnetwork of water molecules. This disruption simultaneously lowers σ and impedes Zn2+\ntransport at the interface. Consequently, the lowest σ of 5% TEP compromises interfacial\nkinetics and results in the slowest Zn2+ transport at the electrode/electrolyte interface,\nexplaining its higher overpotential compared to 5% G2 and 5% G4 at both current densities.\nAdditionally, 30% DME has both low σ and low bulk ionic conductivity (16.72 mS cm−1).\nAt the high current density of 10 mA cm−2, which demands a high Zn2+ flux, the combined\neffect of these two factors results in the highest observed overpotential at 10 mA cm−2.\nFig. R4 a, b, Voltage profiles of Zn||Zn symmetric cells at 5 mA cm−2/5 mAh cm−2 in the\nwindow of 120–160 hours (a) or at 10 mA cm−2/10 mAh cm−2 in the window of 70–110 hours\n(b). Ionic conductivity (c) and σ (d) of electrolytes. e, Average numbers of H O-H O hydrogen\n2 2\nbonds (H-bonds) as a function of the distance to the Zn surface.\n2. Why are G2 and G4 evaluated at 5 vol % while EG and DME are assessed at 30 vol %,\nrather than at identical additive loadings? Please provide comparative results at the same\nconcentration for all co‑solvents.\nResponse: We thank the reviewer for this comment. The primary reason for evaluating G2 and\nG4 at 5 vol% while testing EG at 30 vol% was to emphasize that even at high concentrations\n(30 vol%), high-polarity solvents of EG still result in sparse nucleation and coarse Zn deposits.\nTo directly address the reviewer’s request and provide a consistent comparison, we have\nnow included additional morphological and crystallographic data for both EG and DME at 5\nvol%. Our results show that at the beginning (3 minutes) of electroplating with a high current\ndensity of 10 mA cm−2, the Zn deposits in the high-σ electrolyte of 5% EG appear as widely\nspaced islands (Fig. R5a). Extending the plating duration to 5 hours produces prominent Zn\nprotrusions (Fig. R5b). In contrast, the initial 3 minutes of plating in the low-σ electrolyte of 5%\nDME yields dense small islands (Fig. R5c), indicating the high density of small nuclei. Even\nafter 5 hours of plating, the Zn deposits still maintain a dense, smooth morphology (Fig. R5d).\nAdditionally, deposits from 5% EG are dominated by the (101) plane, with a (002)/(101)\nintensity ratio below 0.38 (Fig. R5e). In contrast, Zn deposited in 5% DME shows a strong (002)\npreferential orientation, with the (002)/(101) ratio increasing from 0.48 to 2.61 as plating time\nextends from 30 minutes to 5 hours (Fig. R5f).\nFig. R5 a–d, SEM images of Zn deposits at 10 mA cm−2 in high-σ electrolyte of 5% EG (a, b)\nand low-σ electrolyte of 5% DME (c, d). e, f, XRD patterns of Zn deposits after 30 minutes,\n1 hour, and 5 hours of electroplating at 10 mA cm−2 in 5% EG (e) and 5% DME (f).\nFig. R5a, 5c are added as Supplementary Fig. 14a and 14e in the revised SI; Fig. R5b, 5d\nare now Supplementary Fig. 15a and 15e; and Fig. R5e, 5f are included as Supplementary Fig.\n17a and 17e. The projected areas of Zn deposits on Cu in 5% EG and 5% DME (Fig. R5a, 5c)\nare quantified, with values of 12.7% for 5% EG and 25.1% for 5% DME included in Fig. 2m.\nThe following changes in red have been made in the revised manuscript (page 10).\n“Low-σ electrolytes, including 5% TEP, 5% G2, 5% G4, 5% DME, and 30% DME, exhibit\nmuch larger projected areas (35.2%, 36.5%, 36.5%, 25.1%, and 27.2%, respectively) than high-\nσ electrolytes (18.3% in 0% Addi, 12.7% in 5% EG, and 13.3% in 30% EG), indicating dense\nnucleation process.”\n“The (002)/(101) intensity ratio reaches 2.61 in 5% DME, 3.83 in 5% G2, 4.97 in 30%\nDME, and 9.49 in 5% G4 (Supplementary Fig. 17).”\nFig. 2 Characterization of Zn deposits in high- and low-σ electrolytes. a–d, Top (a, c) and\ncross-sectional (b, d) views of Zn deposits at 10 mA cm−2 in high-σ electrolyte of 0% Addi (a,\nb) or low-σ electrolyte of 5% TEP (c, d). e–h, RMS roughness of Zn deposits with plated\ncapacities of 5, 10, 30, and 50 mAh cm−2 at a current density of 10 mA cm−2 (e, g) and the\nLSCM images of Zn deposits at 10 mA cm−2/50 mAh cm−2 (f, h) in 0% Addi (e, f) and 5% TEP\n(g, h). i, j, The finite element simulation of the post-nucleation growth of Zn in different\nelectrolytes. k, l, XRD patterns of Zn deposits after 30 minutes, 1 hour, and 5 hours of\nelectroplating at 10 mA cm−2 in 0% Addi (i) and 5% TEP (j). m, Projected area of Zn deposits\nafter 3 minutes of plating at 10 mA cm−2 in electrolytes with different σ. n, RMS roughness of\nZn surfaces after 5 hours of plating at 10 mA cm−2 in electrolytes with different σ. (Page 8)\n3. Fundamental electrolyte information, such as the complete electrochemical stability\nwindow and ionic conductivity as a function of temperature, should be reported.\nResponse: We thank the reviewer for this suggestion. In response, we have measured the\nelectrochemical stability window and temperature-dependent ionic conductivity for both 0%\nAddi and 5% TEP. The results indicate that the 5% TEP electrolyte exhibits a slightly wider\nelectrochemical stability window of 2.55 V, compared to 2.51 V for 0% Addi (Supplementary\nFig. 6a). Furthermore, the onset potential for Zn plating is shifted cathodically from −0.08 V in\n0% Addi to −0.12 V in 5% TEP. Additionally, the ionic conductivity of both electrolytes\nincreases over the temperature range of 10 to 50 °C (Supplementary Fig. 6b). The 5% TEP\nelectrolyte shows a lower ionic conductivity than the 0% Addi electrolyte across the entire\ntemperature range, which can be attributed to the TEP added.\nSupplementary Fig. 6. Electrochemical stability window (a) and ionic conductivity across the\ntemperature window of 10–50 °C (b) of 0% Addi and 5% TEP. The electrochemical window is\ncalculated based on potentials at the currents of ± 0.1 mA cm−2.\nThis figure is added as Supplementary Fig. 6 in the revised SI. The following texts are\nadded to the revised manuscript to discuss it further (page 8).\n“Compared to 0% Addi, 5% TEP exhibits a slightly wider electrochemical stability window\n(2.55 V) but lower ionic conductivity (Supplementary Fig. 6).”\n4. Figure 5d shows substantial fluctuations in coulombic efficiency; please explain the\nunderlying cause and enlarge the y axis (e.g., 80-120 %) so that the variations are clearly\nvisible.\nResponse: We thank the reviewer for their comment. In response, we have adjusted the y-axis\nrange to 80–120% in Supplementary Fig. 35a to visualize the CE variations. Our results show\nCE fluctuations for both 0% Addi and 5% TEP electrolytes, occurring during cycles 43–260\nand 400–1,400, respectively. The corresponding regions have been magnified, and the\ncharge/discharge profiles are compared in Supplementary Fig. 35b–e.\nFor 5% TEP, the CE increases steadily over the first 25 cycles and remains stable in the\nsubsequent 250 cycles. In contrast, the 0% Addi cell exhibits CE fluctuations beginning at the\n43rd cycle, ultimately leading to failure after 260 cycles (Supplementary Fig. 35b). Notably, a\nnew and irreversible charging plateau emerges near 0.26 V around the 40th cycle in the 0%\nAddi cell. This plateau intensifies and elongates over the following 100 cycles, ultimately\ntriggering cell failure (keep charging of 268th cycle) (Supplementary Fig. 35c). This plateau—\nabsent during the initial period of stable CE—coincides with the onset of CE fluctuations. We\ninfer that this plateau reflects side reactions on the Cu current collector, which interfere with\nstable Zn plating/stripping, leading to CE fluctuations and eventual cell failure in 0% Addi.\nA similar plateau is also observed in 5% TEP, although it emerges later (around the 400th\ncycle) (Supplementary Fig. 35d). Besides, this plateau gradually attenuates between cycles\n1,200–1,400 and vanishes entirely after the 1,500th cycle. Consequently, the charge profiles\nbeyond the 1,500th cycle revert to that of the 200th cycle, coupled with the recovery of a stable\nCE. These results demonstrate that, unlike 0% Addi, 5% TEP effectively suppresses side\nreactions on the Cu current collector, enabling stable Zn plating/stripping.\nAlthough CE fluctuations are observed for the 5% TEP cell between 400–1,400 cycles, the\nvast majority of CE values (in 400–1,400 cycles) remain within a narrow range of 96.7% to\n103.3%, with only 1% of cycles exceeding 105% and 0.2% of cycles falling below 95%\n(Supplementary Fig. 35e). Besides, the high total cycle number (4,205 cycles) and condensed\nx-axis scaling in Fig. 5d visually amplify these minor deviations.\nFinally, we note that the side-reaction plateau disappears at high current density (10 mA\ncm−2; Supplementary Fig. 36a) or when using Ti current collectors (Supplementary Fig. 36b),\nconfirming its origin from Cu-specific side reactions under low currents (1 mA cm−2).\nTherefore, testing at low current density on Cu provides a stringent assessment of Zn\nplating/stripping. Despite minor CE fluctuations, our results accurately reflect the true Zn\nplating/stripping behavior in 5% TEP and highlight its advantages over 0% Addi in stabilizing\nZn plating/stripping.\nSupplementary Fig. 35 a, CE of Zn||Cu cells tested at 1 mA cm−2 and 1 mAh cm−2, with the\ny-axis enlarged to the range of 80–120%. b, Enlarged view of CE during cycles 1–269 for cells\nin 0% Addi and 5% TEP. c, Representative charge/discharge profiles at selected cycles in 0%\nAddi. d, Representative charge/discharge profiles at selected cycles in 5% TEP. Panels in c and\nd marked with a black spade symbol (♠) indicate cycles with notable CE fluctuation. e, Enlarged\nview of CE during cycles 400–1,400 for cells in 5% TEP.\nSupplementary Fig. 36 a, Charge/discharge profiles of Zn||Cu cells in 5% TEP tested at 10\nmA cm−2 and 10 mAh cm−2. b, Charge/discharge profiles of Zn||Ti cells in 5% TEP tested at 1\nmA cm−2 and 1 mAh cm−2.\nThese figures are added as Supplementary Figs. 35 and 36, respectively, in the revised SI,\nwith the following discussion included.\n“Enlarging the y-axis to 80–120% reveals CE fluctuations for both 0% Addi and 5% TEP\nelectrolytes during cycles 43–260 and 400–1,400, respectively (Supplementary Fig. 35a). For\n5% TEP, CE increases steadily over the first 25 cycles and remains stable for the next 250 cycles.\nIn contrast, the 0% Addi cell shows CE fluctuations starting at cycle 43, leading to failure after\n260 cycles (Supplementary Fig. 35b). An irreversible charging plateau near 0.26 V emerges\naround the 40th cycle, intensifying over the next 100 cycles and ultimately causing failure\n(Supplementary Fig. 35c). This plateau, absent during the initial stable CE period, suggests side\nreactions on the Cu current collector, disrupting stable Zn plating/stripping.\nA similar plateau appears in 5% TEP but emerges later, around the 400th cycle\n(Supplementary Fig. 35d). It gradually diminishes between cycles 1,200–1,400 and disappears\nafter the 1500th cycle, with charge profiles reverting to those of the 200th cycle and stable CE\nrecovery. This indicates that 5% TEP effectively suppresses side reactions on Cu, enabling\nstable Zn plating/stripping. The majority of CE values during cycles 400–1,400 remain within\n96.7% to 103.3%, with only 1% exceeding 105% and 0.2% falling below 95% (Supplementary\nFig. 35e).\nFinally, the side-reaction plateau disappears at high current density (10 mA cm−2;\nSupplementary Fig. 36a) or with Ti current collectors (Supplementary Fig. 36b), confirming its\norigin from Cu-specific side reactions under low currents (1 mA cm−2). Therefore, testing at\nlow current density on Cu provides a stringent assessment of Zn plating/stripping. Despite\nminor CE fluctuations, our results accurately reflect the true Zn plating/stripping behavior in 5%\nTEP and highlight its advantages over 0% Addi in stabilizing Zn plating/stripping.”\nThe following texts are added to the revised manuscript to explain it further (page 7).\n“Note that a minor yet observable CE fluctuation occurs between cycles 400–1400 in 5%\nTEP. This behavior, stemming from slight side reactions on the Cu current collector under low\ncurrent density (Supplementary Fig. 35 and 36), does not compromise the overall stability of\nZn plating/stripping in 5% TEP.”\nReviewer #3\nThis work reports a low-surface-tension electrolyte design for rechargeable Zn metal\nbatteries that enables dense nucleation, fine-grained growth, and stable solid-electrolyte\ninterfaces, resulting in dendrite-free morphology and suppressed side reactions. This\napproach achieves a high Coulombic efficiency and significant lifespan improvements\nunder harsh conditions compared to conventional electrolytes, demonstrating practicality\nin an Ah-level pouch cell and offering a cost-effective pathway for commercially viable\nbatteries. It is recommended to publish in Nature Communications after proper revision\naddressing the following issues:\nResponse: Thank you for your positive evaluation of our work. We have revised the manuscript\npoint-by-point according to your comments.\n1) The authors highlight the importance of surface tension; however, it is expected to see more\ncharacterization on surface tension, such as contact angle comparison.\nResponse: We thank the reviewer for their comment. To further characterize surface tension,\ncontact angle (CA) measurements were performed on Zn foil for various electrolytes\n(Supplementary Fig. 5). The results indicate a significant CA reduction upon introducing low-\npolarity solvents (Supplementary Fig. 5a–d). Specifically, the CA decreases from ~85.7° for 0%\nAddi to ~48.9° for 5% TEP. Further increase in TEP concentration (10–50 vol%) results in\nmarginal CA reductions, yielding CAs of ~47.3°, ~43.8°, and 37.9° (Supplementary Fig. 5a).\nSimilar reductions are observed in electrolytes with other low-polarity solvents (G2, G4, DME;\nSupplementary Fig. 5b–d). In contrast, electrolytes containing the high-polarity solvent EG\nconsistently exhibit high CAs (70.0°–76.6°) (Supplementary Fig. 5e). Overall, the CA trends\nare consistent with the surface tension behavior shown in Fig. 1f.\nSupplementary Fig. 5 The contact angles of electrolytes with varying concentrations of low-\npolarity (a–d) or high-polarity (e) solvents on Zn foil.\nThis figure is added as Supplementary Fig. 5 in the revised SI, with the following texts\nincluded.\n“Contact angle (CA) measurements were performed on Zn foil for various electrolytes\n(Supplementary Fig. 5). The results indicate a significant CA reduction upon introducing low-\npolarity solvents (Supplementary Fig. 5a–5d). Specifically, the CA decreases from ~85.7° for\n0% Addi to ~48.9° for 5% TEP. Further increase in TEP concentration (10–50%) results in\nmarginal CA reductions, yielding CAs of ~47.3°, ~43.8°, and 37.9° (Supplementary Fig. 5a).\nSimilar reductions are observed with other low-polarity solvents (G2, G4, DME;\nSupplementary Fig. 5b–d). In contrast, electrolytes containing the high-polarity solvent EG\nconsistently exhibit high CAs (70.0°–76.6°) (Supplementary Fig. 5e). Overall, the CA trends\nare consistent with the surface tension behavior shown in Fig. 1f.”\nThe following texts are added to the revised manuscript to explain this phenomenon further\n(page 7).\n“The variation trend of σ aligns well with that of the contact angles as shown in\nSupplementary Fig. 5.”\n2) The stability of the electrolyte additive may need to be further verified by experiment. If\nthe additive molecule is involved in the SEI formation, then the optimized concentration of\nthe additive may need to be reconsidered.\nResponse: We thank the reviewer for their comment. To further verify the stability of TEP, we\nconducted XPS tests of deeply cycled Zn and linear sweep voltammetry (LSV) tests of Zn||Ti\ncells. XPS reveals no P 2p peaks between 127–138 eV after 10 or 100 cycles at 10 mA cm−2/10\nmAh cm−2 (Supplementary Fig. 29a), indicating an absence of phosphorus-containing\ndecomposition products. Similarly, LSV at 0.5 mV s−1 shows only Zn plating currents at −0.10\nV, with no other reductive features between 0.7 and −0.1 V (vs. Zn2+/Zn; Supplementary Fig.\n29b). These results confirm that TEP is not reduced on Zn.\nThis electrochemical stability is attributed to the absence of TEP in the primary solvation\nshell of Zn2+, as revealed by XAS and MD simulations (Fig. 4a–4c). Therefore, the high stability\nof Zn originates not from the reductive decomposition of TEP but instead from the favorable\nregulation of Zn nucleation and growth in low-σ electrolytes.\nSupplementary Fig. 29 a, XPS P 2p spectra of deeply cycled Zn after 10 or 100 cycles at 10\nmA cm−2/10 mAh cm−2. b, LSV curves of Zn||Ti cells in 0% Addi and 5% TEP at a slow scan\nrate of 0.5 mV s−1.\nThis figure is added as Supplementary Fig. 29 in the revised SI, with the following texts\nincluded.\n“XPS reveals no P 2p peaks between 127–138 eV after 10 or 100 cycles at 10 mA cm−2/10\nmAh cm−2 (Supplementary Fig. 29a), indicating an absence of phosphorus-containing\ndecomposition products. Similarly, LSV at 0.5 mV s−1 shows only Zn plating currents at −0.10\nV, with no other reductive features between 0.7 and −0.1 V (vs. Zn2+/Zn; Supplementary Fig.\n29b). These results confirm that TEP is not reduced on Zn. This electrochemical stability is\nattributed to the absence of TEP in the primary solvation shell of Zn2+, as revealed by XAS and\nMD simulations (Fig. 4a–4c). Therefore, the high stability of Zn originates not from the\nreductive decomposition of TEP, but instead from the favorable regulation of Zn nucleation and\ngrowth in low-σ electrolytes.”\nThe following texts are added to the revised manuscript to explain this phenomenon further\n(pages 14–15).\n“The absence of TEP in the primary solvation shell indicates TEP is electrochemically\nstable against reductive decomposition during Zn plating. This is further supported by the lack\nof phosphorus species in the XPS spectra of deeply cycled Zn and the absence of parasitic\ncurrents in the LSV measurements (Supplementary Fig. 29).”\n3) The authors should provide an in-depth analysis on the mechanism of the additive molecule;\nfor example, is there any adsorption behavior that could be monitored during cycling?\nResponse: We thank the reviewer for their comment. To further investigate the adsorption\nbehavior of TEP, we analyzed the TEP molecular distribution from the MD simulations. The\nelectrolyte box, situated between two Zn slabs with dimensions of 3.62 nm × 4.18 nm × 4 nm\n(width), shows that TEP molecules are not only present in the bulk region (center of the\nelectrolyte box) but also exhibit a significantly higher density near the Zn/electrolyte interfaces,\nindicating surface enrichment (Supplementary Fig. 31a). This interfacial accumulation of TEP\nis also supported by Raman spectroscopy, which detects TEP signals at the Zn/5% TEP interface\n(Supplementary Fig. 31b). Similarly, Raman spectra of interfaces with other low-σ\nelectrolytes—Zn/5% G2, Zn/5% G4, and Zn/30% DME—also show signals corresponding to\nG2, G4, and DME, confirming their enrichment at Zn surfaces (Supplementary Fig. 31c–e).\nThis adsorption of low-polarity molecules helps disrupt the interfacial hydrogen-bonding\nframework among water molecules (Fig. 4f, 4g), thereby facilitating a lower σ.\nSupplementary Fig. 31 a, Distribution of TEP molecules in the electrolyte box from the MD\nsimulation. Raman spectra of pure TEP and Zn/5% TEP interface (b), pure G2 and Zn/5% G2\ninterface (c), pure G4 and Zn/5% G4 interface (d), as well as pure DME and Zn/30% DME\ninterface (e). The laser excitation wavelength is 785 nm. The laser is focused on the electrolyte\nregion near the Zn surface to obtain spectra at the Zn/electrolyte interfaces.\nThis figure is added as Supplementary Fig. 31 in the revised SI, with the following texts\nincluded.\n“To further investigate the adsorption behavior of TEP, we analyzed the TEP molecular\ndistribution from the MD simulations. The electrolyte box, situated between two Zn slabs with\ndimensions of 3.62 nm × 4.18 nm × 4 nm (width), shows that TEP molecules are not only\npresent in the bulk region (center of the electrolyte box) but also exhibit a significantly higher\ndensity near the Zn/electrolyte interfaces, indicating surface enrichment (Supplementary Fig.\n31a). This interfacial accumulation of TEP is also supported by Raman spectroscopy, which\ndetects TEP signals at the Zn/5% TEP interface (Supplementary Fig. 31b). Similarly, Raman\nspectra of interfaces with other low-σ electrolytes—Zn/5% G2, Zn/5% G4, and Zn/30%\nDME—also show signals corresponding to G2, G4, and DME, confirming their enrichment at\nZn surfaces (Supplementary Fig. 31c–31e). This adsorption of low-polarity molecules helps\ndisrupt the interfacial hydrogen-bonding framework among water molecules (Fig. 4f, 4g),\nthereby facilitating a lower σ.”\nThe following texts are added to the revised manuscript to explain this phenomenon further\n(page 15).\n“The primary mechanism of disruption is the adsorption of TEP molecules at the\nZn/electrolyte interface (Supplementary Fig. 31), which disrupts the water network, reduces\ndipole-dipole interactions, and lowers σ.”\n4) The authors can provide XPS spectra of O1s of Zn in 5% TEP after 10 plating/stripping\ncycles at 10 mA cm−2/10 mAh cm−2, after 500 s and 1000 s sputtering time to have a better\nunderstanding of the environmental change.\nResponse: We thank the reviewer for this insightful suggestion. To gain deeper insight into the\ncompositional evolution within the interphase, we performed XPS depth profiling of deeply\ncycled Zn (10 cycles at 10 mA cm−2/10 mAh cm−2) with sputtering durations of 500 and 1000\nseconds. As shown in Fig. R13, the O 1s for the 0% Addi sample exhibits a strong signal even\nafter 1000 s of sputtering, with Zn(OH) -related species accounting for more than 40%. This\n2\nsuggests the presence of a thick, hydroxide-rich byproduct layer. In contrast, the O 1s signal for\nthe 5% TEP sample attenuates with sputtering time and maintains a high proportion of ZnCO -\n3\nrelated components (> 60%). This indicates a thinner and more robust interphase layer. These\nfindings are consistent with the TOF-MS results (Fig. 3c), both confirming that the low-σ\nelectrolyte effectively mitigates parasitic reactions and promotes the formation of a more robust\nand stable interphase.\nSupplementary Fig. 21 XPS spectra of O1s of deeply cycled Zn (10 cycles, at\n10 mA cm−2/10 mAh cm−2) in 0% Addi (a–c) and 5% TEP (e–g) with sputtering durations of\n500s and 1000s, respectively. d, h, Composition of ZnCO - and Zn(OH) -related components\n3 2\non Zn after various durations of Ar+ sputtering.\nThis figure is added as Supplementary Fig. 21 in the revised SI, with the following texts\nincluded.\n“We also performed XPS depth profiling of deeply cycled Zn (10 cycles at 10 mA cm−2/10\nmAh cm−2) with sputtering durations of 500 and 1000 seconds. As shown in Supplementary Fig.\n21, the O 1s for the 0% Addi sample exhibits a strong signal even after 1000 s of sputtering,\nwith Zn(OH) -related species accounting for more than 40%. This suggests the presence of a\n2\nthick, hydroxide-rich byproduct layer. In contrast, the O 1s signal for the 5% TEP sample\nattenuates with sputtering time and maintains a high proportion of ZnCO -related components\n3\n(> 60%). This indicates a thinner and more robust interphase layer. These findings are consistent\nwith the TOF-MS results (Fig. 3c), both confirming that the low-σ electrolyte effectively\nmitigates parasitic reactions and promotes the formation of a more robust and stable interphase.”\nThe following texts are added to the revised manuscript to explain this phenomenon further\n(page 12).\n“The TOF-MS results align well with the XPS depth profiling at extended sputtering\ndurations (Supplementary Fig. 21).”\n5) The insets in Figure 3c showing time-of-flight mass spectrometry figures are relatively hard\nto distinguish. The authors can consider putting an enlarged figure in the revised SI.\nResponse: We thank the reviewer for their comment. To make the insets of Fig. 3c clearer, we\nput the enlarged version of the insets in the revised SI as Supplementary Fig. 20.\nSupplementary Fig. 20. Depth profiles of ZnO−, F−, and S− fragment ions in the TOF-MS of\ndeeply cycled Zn in 0% Addi and 5% TEP.\n6) In Figure 4a, the authors claim that TEP disrupts the hydrogen-bonding framework,\nparticularly at the Zn/electrolyte interface. It would be better to support this conclusion with\nother supporting experimental data related to hydrogen bonding.\nResponse: We appreciate the reviewer’s insightful suggestion. To provide direct evidence of\nhydrogen-bonding disruption at the interface, we conducted Raman tests using a 532 nm\nexcitation laser focused on the Zn/electrolyte interface. The broad O-H stretching band (3000–\n3800 cm−1) was deconvoluted to analyze the hydrogen-bonding environment. The results show\nthat Peak I (~3238 cm−1) in 5% TEP shifts to higher wavenumbers (Supplementary Fig. 30a)\nand exhibits a reduction in peak area proportion (Supplementary Fig. 30b). These changes\nindicate a weakened hydrogen-bonding effect among water molecules near the Zn surface,\nconsistent with our MD simulation results (Fig. 4f, 4g).\nSupplementary Fig. 30 a, Raman spectra of 0% Addi and 5% TEP in the region of 3000–3800\ncm−1. b, Comparison of Peak I proportion in 0% Addi and 5% TEP.\nThis figure is added as Supplementary Fig. 30 in the revised SI, with the following texts\nincluded.\n“We also conducted Raman tests with a 532 nm excitation laser focused on the\nZn/electrolyte interface to probe the interfacial hydrogen bonding environment. The broad O-\nH stretching band (3000–3800 cm−1) was deconvoluted to analyze the hydrogen-bonding\nenvironment. The results show that Peak I (~3238 cm−1) in 5% TEP shifts to higher\nwavenumbers (Supplementary Fig. 30a) and exhibits a reduction in peak area proportion\nSupplementary Fig. 30b). These changes indicate a weakened hydrogen-bonding effect among\nwater molecules near the Zn surface, consistent with our MD simulation results (Fig. 4f, 4g).”\nThe following texts are added to the revised manuscript to explain this phenomenon further\n(page 15).\n“Raman spectroscopy further confirms this interfacial disruption (Supplementary Fig. 30)\nby showing a shift of the ~3238 cm−1 peak to higher wavenumbers and a decrease in relative\nintensity.”\n7) The authors should provide an enlarged figure for the starting 0-50 cycles comparison of\nthe CE testing to have a better understanding of the initial zinc deposition difference.\nResponse: We thank the reviewer for the comment. To make a better understanding of the initial\nZn deposition difference, we provided an enlarged figure for CE in the starting 0-150th cycles\nwith an inset of the 0-50th cycles (Supplementary Fig. 34d). Our results show that the Zn||Cu\ncell in 5% TEP exhibits a higher initial CE of 93.88%, compared to only 89.51% for the cell in\n0% Addi. The CE increases gradually in the first 40 cycles for both electrolytes. However, from\nthe 40th to 150th cycles, the CE in 5% TEP remains stable while that in 0% Addi fluctuates\nbetween 94.81% and 114.02%. This indicates that Zn plating/stripping on Cu is significantly\nmore stable in 5% TEP than in 0% Addi.\nZn||Cu; 1mA cm-2/1mAh cm-2\n115\n114\n%113 0% Addi 0% Addi\ny\n/\n100\nc\nn\ne\nci 105\neffi\n95\n100\nm\nbi\nc\nE\n/\n%\n95\no 90 C 90\nul\n85\no\nC 0 10 20 30 40 50\nCycle ID\n85\n0 50 100 150\nCycle ID\nSupplementary Fig. 34 d Comparison of CE in the initial 150 cycles. The inset shows an\nenlarged view of the first 50 cycles.\nThis figure is added as Supplementary Fig. 34d in the revised SI, with the following texts\nincluded.\n“As shown in Supplementary Fig. 34d, the Zn||Cu cell in 5% TEP exhibits a higher initial\nCE of 93.88%, compared to only 89.51% for the cell in 0% Addi. The CE increases gradually\nin the first 40 cycles for both electrolytes. However, from the 40th to 150th cycles, the CE in\n5% TEP remains stable while that in 0% Addi fluctuates between 94.81% and 114.02%. This\nindicates that Zn plating/stripping on Cu is significantly more stable in 5% TEP than in 0%\nAddi.”\n8) The authors should provide detailed characterization, such as XPS and XRD, for the cycled\nzinc anode in different electrolytes to further support their conclusion that \"the low-σ\nelectrolyte enhances the SEI stability, effectively suppressing side reactions even under\nharsh electrochemical conditions.\"\nResponse: We thank the reviewer for their comment. To further investigate SEI stability and\nside reactions on Zn in other low-σ electrolytes, we performed XPS analysis of deeply cycled\nZn (10 mA cm−2/10 mAh cm−2for 10 cycles) in these electrolytes. Supplementary Fig. 19 shows\nthat the O 1s spectra consistently exhibit low Zn(OH) -related content (< 20%) and high\n3 2\ncontent originates from Zn corrosion byproducts, while ZnCO -related content is an effective\n2\nfor 5% TEP, indicating a similarly robust and intact SEI in these low-σ electrolytes. Additionally,\nXRD patterns of deeply cycled Zn reveal no detectable impurities in low-σ electrolytes (5%\nTEP, 5% G2, 5% G4, and 30% DME), unlike Zn in the 0% Addi, where the impurities of zinc\nhydroxide hydrates (Energy Environ. Sci. 16, 1662-1675, (2023); Angew. Chem.-Int. Edit. 60,\n13035-13041, (2021)) are prominent (Supplementary Fig. 20). This result further confirms the\neffective suppression of Zn corrosion in the low-σ electrolytes.\nSupplementary Fig. 19 XPS spectra of O1s of Zn in 5% G2 (a–c), 5% G4 (e–g), and 30%\nDME (i–k) after 10 plating/stripping cycles at 10 mA cm−2/10 mAh cm−2. d, h, l,\nComposition of ZnCO - and Zn(OH) -related components on Zn after various durations of Ar+\n3 2\nsputtering.\nSupplementary Fig. 23 XRD patterns of fresh Zn and deeply cycled Zn (10 cycles at 10 mA\ncm−2/10 mAh cm−2) in 0% Addi, 5% TEP, 5% G2, 5% G4, and 30% DME. The diamond\nsymbols (♢) in the 0% Addi panel mark the diffraction peaks corresponding to zinc hydroxide\nhydrate impurities.\nThese figures are added as Supplementary Fig. 19 and 23, respectively, in the revised SI.\nThe text discussing Supplementary Fig. 19 is included beneath it.\n“To further investigate SEI stability and side reactions on Zn in other low-σ electrolytes (5%\nG2, 5% G4, and 30% DME), we performed XPS analysis of deeply cycled Zn (10 mA cm−2/10\nmAh cm−2for 10 cycles) in these electrolytes. The O 1s spectra consistently show low Zn(OH) -\n2\nrelated content (< 20%) and high ZnCO -related content (> 60%) at all sputtering depths\n3\n(Supplementary Fig. 19). These results align well with those for 5% TEP, indicating a similarly\nrobust and intact SEI in these low-σ electrolytes.”\nThe following texts are added to the revised manuscript to explain this phenomenon further\n(page 12).\n“This beneficial SEI composition is also consistent across other low-σ electrolytes (5% G2,\n5% G4, and 30% DME) (Supplementary Fig. 19).”\n“Severe HER generates OH⁻ ions that corrode Zn, forming various zinc hydroxide hydrates.\nConsistent with this, XRD patterns of deeply cycled Zn show prominent zinc hydroxide hydrate\npeaks (Energy Environ. Sci. 16, 1662-1675, (2023); Angew. Chem.-Int. Edit. 60, 13035-13041,\n(2021)) in 0% Addi, while no such impurities are detected in low-σ electrolytes (5% TEP, 5%\nG2, 5% G4, and 30% DME) (Supplementary Fig. 23).”"}, {"round": 2, "reviewer_comments": {"reviewer_2": "The revision is good.", "reviewer_3": "The revised manuscript has addressed the previously raised concerns, demonstrating significant improvements. However, the revision version requires further clarification regarding the role of the low dielectric constant solvent, specifically whether the low dielectric constant or low surface tension is the primary factor driving the results. As the core of this research hinges on the properties of the surface tension, the originality of this work should be more strongly highlighted in the introduction. Clearly state how this study advances beyond existing literature, particularly in the context of the surface tension properties investigated, to underscore its novel contributions to the field."}, "author_response": "Response letter to reviewers\nWe would like to express our sincere appreciation for the reviewers’ time and valuable\ncomments. We have revised the manuscript according to these comments with additional\ndiscussions. The detailed point-to-point responses are listed below. In our responses, the\nreviewer’s comments are shown in black, our responses are provided in blue, and the texts\nadded in the manuscript are highlighted in red.\nReviewer #1 (Remarks to the Author):\nAccept\nResponse: We sincerely thank the reviewer for their acceptance and positive feedback on our\nwork.\nReviewer #2 (Remarks to the Author):\nThe revision is good.\nResponse: We are grateful to the reviewer for their positive assessment of our revised\nmanuscript.\nReviewer #3 (Remarks to the Author):\nThe revised manuscript has addressed the previously raised concerns, demonstrating\nsignificant improvements. However, the revision version requires further clarification\nregarding the role of the low dielectric constant solvent, specifically whether the low\ndielectric constant or low surface tension is the primary factor driving the results. As the\ncore of this research hinges on the properties of the surface tension, the originality of this\nwork should be more strongly highlighted in the introduction. Clearly state how this study\nadvances beyond existing literature, particularly in the context of the surface tension\nproperties investigated, to underscore its novel contributions to the field.\nResponse: We sincerely thank the reviewer for their positive feedback and for raising these\ncritical points, which have helped us further strengthen the clarity and impact of our manuscript.\nTo clarify our work, we further summarize it according to the following flow: motivation,\nidea, methods, performance achieved, and significance.\nMotivation\nMitigating dendrite growth and side reactions of Zn at a practical level is a persistent challenge.\nTo date, various strategies have been reported to suppress these anode-related challenges,\nincluding anode engineering (e.g., artificial protective layers on Zn, three-dimensional (3D) Zn\nhosts, surface modification of plating substrates), as well as electrolyte design (e.g.,\nconcentrated-salt electrolytes, organic-water hybrid electrolytes). However, most of these\napproaches often work under moderate electrochemical conditions (i.e., small areal currents\nand capacities) and very small depth of discharge (DOD, e.g., below 1%). Moreover, these\nstrategies would compromise the overall energy density, safety, and cost of batteries. To address\nthese issues, it is essential to come up with a balanced strategy that effectively mitigates dendrite\ngrowth and side reactions at a practical level (i.e., high areal current, high areal capacity, and\nhigh DOD) while maintaining cost-effectiveness, safety, and energy density.\nNotably, the electrodeposition of Zn—encompassing both nucleation and growth processes—\noccurs directly at the electrolyte/Zn interface. This makes the electrolyte σ a particularly\nrelevant parameter, as it significantly influences interfacial properties and should impact\ndeposition behavior of Zn. However, a fundamental and quantitative understanding of how σ\ngoverns Zn nucleation and growth remains lacking. Traditional electrolyte design has primarily\nfocused on suppressing water activity by using high organic solvent content (> 55 vol.%) or\nmodifying the adsorption layer on Zn through functional additives in electrolytes. While these\napproaches have shown some improvement, they have not established σ as a targeted design\nparameter, nor have they provided quantitative relationships between σ and deposition\noutcomes. Furthermore, the impact of σ on battery performance under practical conditions (high\ncurrent, high capacity, high DOD, Ah-level pouch cells) and its overall effects on dendrite\nsuppression, SEI stabilization, and side reaction mitigation remain insufficiently explored.\nIdea / methods / Performance\nHerein, our study introduces a low-σ electrolyte strategy that enables dense Zn nucleation and\nfine-grained growth, even under harsh electrochemical conditions. Unlike all previous studies\nthat overlooked the significance of σ, we establish a quantitative theoretical framework based\non classical nucleation theory, demonstrating σ as the key parameter governing both nucleation\nenergy barrier (nucleation process) and growth resistance (growth process). The low-σ\nelectrolyte is achieved by adding only trace amounts (5 vol.%) of low-polarity TEP into the\nreference electrolyte [2m Zn(OTf)2 in water with 1.5 wt.% zinc acetate dihydrate]. Low-\npolarity solvents, characterized by their low ε, can effectively break the strong dipole-dipole\ninteraction networks between water molecules, thereby lowering σ. Our result shows that the\naddition of merely 5 vol.% TEP can effectively lower both the σ (to 55% of the reference\nelectrolyte) and the nucleation energy barrier (to 17% of that in the reference electrolyte)\nwithout significantly compromising the ionic conductivity (still up to 90% of that of the\nreference electrolyte). The as-obtained low-σ electrolyte fundamentally transforms sparse\nnucleation/coarse-grained growth into dense nucleation/fine-grained growth. In addition to TEP,\nthis regulated nucleation and growth behavior is universally observed in other low-σ\nelectrolytes, achieved by adding merely 5 vol.% of other low-polarity solvents (e.g., G2, G4,\nand DME).\nThis regulated nucleation and growth mode in low-σ electrolytes enables dendrite-free plating,\nstabilizes the SEI, and suppresses side reactions even under harsh electrochemical conditions.\nConsequently, ZMAs in low-σ electrolytes achieve a high average CE of 99.72% at 1 mA\ncm−2/1 mAh cm−2 over a record lifespan of 8,400 hours (350 days)—a 2- to 40-fold\nimprovement over previous benchmarks (typically 97.5–99.6% over 200–4,000 hours). Even\nunder harsh electrochemical conditions, e.g., 10 mA cm−2/10 mAh cm−2, ZMAs still exhibit\nsignificantly extended lifespans of 2,200 hours (at 17% DOD) and 300 hours (at 85% DOD),\nrepresenting 20-fold and 150-fold improvements over conventional electrolytes, respectively.\nBesides, Ah-level pouch cells operating under lean electrolyte (11.4 g Ah−1) and low N/P ratios\n(3.3) also demonstrate the practical viability of this strategy.\nSignificance\nOur work establishes quantitative relationships between σ and Zn electrodeposition behavior,\nand demonstrates highly stable ZMAs in low-σ electrolytes even under harsh electrochemical\nconditions. These findings highlight σ as a crucial yet previously overlooked electrolyte\nproperty, introducing it as a new design criterion of electrolytes for high-performance practical\nRZMBs. Besides, low-σ electrolytes, achieved by the addition of merely 5 vol.% of low-\npolarity solvents, provides a cost-effective, scalable pathway toward commercially viable\nRZMBs without compromising safety or energy density. The principles developed here could\npotentially be extended to other metal anode systems, such as Li and Na metal anodes.\nWe have carefully addressed the Reviewer’s comments as follows:\n1. Further clarification of the role of the low-ε solvents and highlighting the low σ is the\nprimary factor driving the results\nTo further clarify the role of the low-ε solvents and highlight the low σ is the primary factor\ndriving the results, we have revised the relevant text in the Introduction (Page 4, Paragraph 5)\nand Results (Page 7, Paragraph 8; Page 8, Paragraph 9) sections:\n“In this work, we report a low-σ electrolyte strategy that rationally tunes the Zn nucleation and\ngrowth behaviors for the high-performance practical RZMBs. Unlike previous studies that\noverlooked the significance of σ, we conduct a fundamental analysis of how electrolyte σ\ninfluences Zn electrodeposition behavior. Specifically, we establish a quantitative theoretical\nframework based on classical nucleation theory, identifying σ as the key parameter controlling\nboth nucleation energy barrier (nucleation process) and growth resistance (growth process).\nThis low-σ design fundamentally alters sparse nucleation/coarse-grained growth into dense\nnucleation/fine-grained growth, even under harsh electrochemical conditions.” (Introduction,\nPage 4, Paragraph 5)\n“Guided by the theoretical prediction that identifies σ as the governing parameter, we\nengineered low-σ electrolytes. This was achieved by incorporating solvents with low polarity—\nand consequently low dielectric constants (ε)—into a reference aqueous electrolyte (Fig. 1e, f).\nThe high σ of aqueous electrolytes typically arises from strong dipole-dipole interactions\nbetween water molecules, specifically the H O-H O hydrogen bonds. By adding low-polarity\n2 2\nsolvents with weaker intermolecular attractions, we aim to disrupt these strong dipole-dipole\nnetworks and consequently lower σ. It enables us to probe the effect of σ as the primary variable.”\n(Results, Page 7, Paragraph 8)\n“Thus, the addition of merely 5 vol.% TEP can effectively lower both the σ (to 55% of the\nreference electrolyte) and the nucleation energy barrier (to 17% of that in the reference\nelectrolyte) without significantly compromising the ionic conductivity (still up to 90% of that\nof the reference electrolyte). Therefore, 5% TEP was selected for subsequent studies to achieve\nan optimal balance between low σ and high ionic conductivity.” (Results, Page 8, Paragraph\n9)\n2. Highlighting the originality of our work and stating the advancement beyond existing\nliterature\nTo better highlight the originality of our approach and clearly state the advancement of our\nwork beyond existing literature, we have strengthened the Introduction with the addition of a\nnew paragraph (Page 4, Paragraph 4) and re-organized the significance of our work (Page 4,\nParagraph 5).\n“Notably, the electrodeposition of Zn—encompassing both nucleation and growth processes—\noccurs directly at the electrolyte/Zn interface. This makes the electrolyte σ a particularly\nrelevant parameter, as it significantly influences interfacial properties and should impact\ndeposition behavior of Zn. However, a fundamental and quantitative understanding of how σ\ngoverns Zn nucleation and growth remains lacking. Traditional electrolyte design has primarily\nfocused on suppressing water activity by using high organic solvent content (> 55 vol.%) [Nat.\nCommun. 14, 1828, (2023). Energy Environ. Sci. 17, 4569-4581, (2024).] or modifying the\nadsorption layer on Zn through functional additives in electrolytes [Angew. Chem.-Int. Edit. 64,\ne202512032, (2025). Adv. Funct. Mater., 2500780, (2025).]. While these approaches have\nshown some improvement, they have not established σ as a targeted design parameter, nor have\nthey provided quantitative relationships between σ and deposition outcomes. Furthermore, the\nimpact of σ on battery performance under practical conditions (high current, high capacity, high\nDOD, Ah-level pouch cells) and its overall effects on dendrite suppression, SEI stabilization,\nand side reaction mitigation remain insufficiently explored.” (Introduction, Page 4, Paragraph\n4)\n“Our work establishes quantitative relationships between σ and Zn electrodeposition behavior,\nand demonstrates highly stable ZMAs in low-σ electrolytes even under harsh electrochemical\nconditions. These findings highlight σ as a crucial yet previously overlooked electrolyte\nproperty, introducing it as a new design criterion of electrolytes for high-performance practical\nRZMBs.” (Introduction, Page 4, Paragraph 5)"}]

Decision letter