Engineering Fluorine-rich Double Protective Layer on Zn Anode for Highly Reversible Aqueous Zinc-ion Batteries

The high thermodynamic instability and side reactions of Zn-metal anode (ZMA), especially at high current densities, greatly impede the commercialization of aqueous zinc-ion batteries (AZIBs). Herein, a fluorine-rich double protective layer strategy is proposed to obtain the high reversibility of AZIBs through the introduction of a versatile tetradecafluorononane-1,9-diol (TDFND) additive in aqueous electrolyte. TDFND molecule with large adsorption energy (−1.51 eV) preferentially absorbs on the Zn anode surface to form a Zn(OR)₂⁻ (R=−CH₂−(CF₂)₇−CH₂−) cross-linking complex network, which balances space electric field and controls the Zn²⁺ ion flux, thus enabling the uniform and compact deposition of Zn (002) crystal planes. Meanwhile, TDFND with low Lowest unoccupied molecular orbital (LUMO, 0.10 eV) energy level is priorly decomposed to regulate the interfacial chemistry of ZMA by building a ZnF₂-rich solid electrode/electrolyte interface (SEI) layer. It is found that a 14 nm-thick SEI layer delivers excellent structural integrity to suppress parasitic reactions by blocking the direct contact of active water and ZMA. Consequently, the Zn electrode exhibits a superior cycling life over 430 h at 10 mA cm⁻² and a high average Coulombic efficiency of 99.8 % at 5 mA cm⁻². Furthermore, a 68 mAh pouch cell delivers 80.3 % capacity retention for 1000 cycles.     

Amphoteric Cellulose-Based Double-Network Hydrogel Electrolyte Toward Ultra-Stable Zn Anode

Zinc (Zn) metal anode suffers from uncontrollable Zn dendrites and parasitic side reactions at the interface, which restrict the practical application of aqueous rechargeable zinc batteries (ARZBs). Herein, an amphoteric cellulose-based double-network is introduced as hydrogel electrolyte to overcome these obstacles. On one hand, the amphoteric groups build anion/cation transport channels to regulate electro-deposition behavior on Zn (002) crystal plane enabled by homogenizing Zn²⁺ ions flux. On the other hand, the strong bonding between negatively charged carboxyl groups and Zn²⁺ ions promote the desolvation process of [Zn(H₂O)₆]²⁺ to eliminate side reactions. Based on the above two functions, the hydrogel electrolyte enables an ultra-stable cycling with a cumulative capacity of 7 Ah cm⁻² at 20 mA cm⁻²/20 mAh cm⁻² for Zn||Zn cell. This work provides significant concepts for developing hydrogel electrolytes to realize stable anode for high-performance ARZBs.     

Boosting Zn Anode Utilization by Trace Iodine Ions in Organic-Water Hybrid Electrolytes through Formation of Anion-rich Adsorbing Layers

Aqueous Zn batteries are attracting extensive attentions, but their application is still hindered by H₂O-induced Zn-corrosion and hydrogen evolution reactions. Addition of organic solvents into aqueous electrolytes to limit the H₂O activity is a promising solution, but at the cost of greatly reduced Zn anode kinetics. Here we propose a simple strategy for this challenge by adding 50 mM iodine ions into an organic-water (1,2-dimethoxyethane (DME)+water) hybrid electrolyte, which enables the electrolyte simultaneously owns the advantages of low H₂O activity and accelerated Zn kinetics. We demonstrate that the DME breaks the H₂O hydrogen-bond network and exclude H₂O from Zn²⁺ solvation shell. And the I⁻ is firmly adsorbed on the Zn anode, reducing the Zn²⁺ de-solvation barrier from 74.33 kJ mol⁻¹ to 32.26 kJ mol⁻¹ and inducing homogeneous nucleation behavior. With such electrolyte, the Zn//Zn symmetric cell exhibits a record high cycling lifetime (14.5 months) and achieves high Zn anode utilization (75.5 %). In particular, the Zn//VS₂@SS full cell with the optimized electrolyte stably cycles for 170 cycles at a low N : P ratio (3.64). Even with the cathode mass-loading of 16.7 mg cm⁻², the full cell maintains the areal capacity of 0.96 mAh cm⁻² after 1600 cycles.     

Steric-hindrance Effect Tuned Ion Solvation Enabling High Performance Aqueous Zinc Ion Batteries

Despite many additives have been reported for aqueous zinc ion batteries, steric-hindrance effect of additives and its correlation with Zn²⁺ solvation structure have been rarely reported. Herein, large-sized sucrose biomolecule is selected as a paradigm additive, and steric-hindrance electrolytes (STEs) are developed to investigate the steric-hindrance effect for solvation structure regulation. Sucrose molecules do not participate in Zn²⁺ solvation shell, but significantly homogenize the distribution of solvated Zn²⁺ and enlarge Zn²⁺ solvation shell with weakened Zn²⁺−H₂O interaction due to the steric-hindrance effect. More importantly, STEs afford the water-shielding electric double layer and in situ construct the organic and inorganic hybrid solid electrolyte interface, which effectively boost Zn anode reversibility. Remarkably, Zn//NVO battery presents high capacity of 3.9 mAh ⋅ cm⁻² with long cycling stability for over 650 cycles at lean electrolyte of 4.5 μL ⋅ mg⁻¹ and low N/P ratio of 1.5, and the stable operation at wide temperature (−20 °C~+40 °C).     

Synergistic Modulation of In-Situ Hybrid Interface Construction and pH Buffering Enabled Ultra-Stable Zinc Anode at High Current Density and Areal Capacity

In aqueous electrolytes, the uncontrollable interfacial evolution caused by a series of factors such as pH variation and unregulated Zn²⁺ diffusion would usually result in the rapid failure of metallic Zn anode. Considering the high correlation among various triggers that induce the anode deterioration, a synergistic modulation strategy based on electrolyte modification is developed. Benefitting from the unique pH buffer mechanism of the electrolyte additive and its capability to in situ construct a zincophilic solid interface, this synergistic effect can comprehensively manage the thermodynamic and kinetic properties of Zn anode by inhibiting the pH variation and parasitic side reactions, accelerating de-solvation of hydrated Zn²⁺, and regulating the diffusion behavior of Zn²⁺ to realize uniform Zn deposition. Thus, the modified Zn anode can achieve an impressive lifespan at ultra-high current density and areal capacity, operating stably for 609 and 209 hours at 20 mA cm⁻², 20 mAh cm⁻² and 40 mA cm⁻², 20 mAh cm⁻², respectively. Based on this exceptional performance, high loading Zn||NH₄V₄O₁₀ batteries can achieve excellent cycle stability and rate performance. Compared with those previously reported single pH buffer strategies, the synergistic modulation concept is expected to provide a new approach for highly stable Zn anode in aqueous zinc-ion batteries.     

Triple-function Hydrated Eutectic Electrolyte for Enhanced Aqueous Zinc Batteries

Aqueous rechargeable zinc-ion batteries (ARZBs) are impeded by the mutual problems of unstable cathode, electrolyte parasitic reactions, and dendritic growth of zinc (Zn) anode. Herein, a triple-functional strategy by introducing the tetramethylene sulfone (TMS) to form a hydrated eutectic electrolyte is reported to ameliorate these issues. The activity of H₂O is inhibited by reconstructing hydrogen bonds due to the strong interaction between TMS and H₂O. Meanwhile, the preferentially adsorbed TMS on the Zn surface increases the thickness of double electric layer (EDL) structure, which provides a shielding buffer layer to suppress dendrite growth. Interestingly, TMS modulates the primary solvation shell of Zn²⁺ ultimately to achieve a novel solvent co-intercalation ((Zn-TMS)²⁺) mechanism, and the intercalated TMS works as a “pillar” that provides more zincophilic sites and stabilizes the structure of cathode (NH₄V₄O₁₀, (NVO)). Consequently, the Zn||NVO battery exhibits a remarkably high specific capacity of 515.6 mAh g⁻¹ at a low current density of 0.2 A g⁻¹ for over 40 days. This multi-functional electrolytes and solvent co-intercalation mechanism will significantly propel the practical development of aqueous batteries.     

Non-concentrated aqueous electrolytes with organic solvent additives for stable zinc batteries

Rechargeable aqueous zinc batteries (RAZBs) are promising for large-scale energy storage because of their superiority in addressing cost and safety concerns. However, their practical realization is hampered by issues including dendrite growth, poor reversibility and low coulombic efficiency (CE) of Zn anodes due to parasitic reactions. Here, we report a non-concentrated aqueous electrolyte composed of 2 m zinc trifluoromethanesulfonate (Zn(OTf)₂) and the organic dimethyl carbonate (DMC) additive to stabilize the Zn electrochemistry. Unlike the case in conventional aqueous electrolytes featuring typical Zn[H₂O]₆²⁺ solvation, a solvation sheath of Zn²⁺ with the co-participation of the DMC solvent and OTf⁻ anion is found in the formulated H₂O + DMC electrolyte, which contributes to the formation of a robust ZnF₂ and ZnCO₃-rich interphase on Zn. The resultant Zn anode exhibits a high average CE of Zn plating/stripping (99.8% at an areal capacity of 2.5 mA h cm⁻²) and dendrite-free cycling over 1000 cycles. Furthermore, the H₂O + DMC electrolytes sustain stable operation of RAZBs pairing Zn anodes with diverse cathode materials such as vanadium pentoxide, manganese dioxide, and zinc hexacyanoferrate. Rational electrolyte design with organic solvent additives would promote building better aqueous batteries.

Involvement of dimethyl carbonate and trifluoromethanesulfonate anions in a hybrid aqueous electrolyte enables the formation of a new Zn²⁺-solvation structure and a ZnF₂–ZnCO₃-rich interphase that stabilizes the Zn battery chemistry.     

Polycation-Regulated Electrolyte and Interfacial Electric Fields for Stable Zinc Metal Batteries

Zn metal as one of promising anode materials for aqueous batteries but suffers from disreputable dendrite growth, grievous hydrogen evolution and corrosion. Here, a polycation additive, polydiallyl dimethylammonium chloride (PDD), is introduced to achieve long-term and highly reversible Zn plating/stripping. Specifically, the PDD can simultaneously regulate the electric fields of electrolyte and Zn/electrolyte interface to improve Zn²⁺ migration behaviors and guide dominant Zn (002) deposition, which is veritably detected by Zeta potential, Kelvin probe force microscopy and scanning electrochemical microscopy. Moreover, PDD also creates a positive charge-rich protective outer layer and a N-rich hybrid inner layer, which accelerates the Zn²⁺ desolvation during plating process and blocks the direct contact between water molecules and Zn anode. Thereby, the reversibility and long-term stability of Zn anodes are substantially improved, as certified by a higher average coulombic efficiency of 99.7 % for Zn||Cu cells and 22 times longer life for Zn||Zn cells compared with that of PDD-free electrolyte.     

Coordinating zincophilic sites and a solvation shell for a dendrite-free Zn anode under the synergistic effects of polyacrylonitrile and dimethyl sulfoxide

The advantages of aqueous zinc-ion batteries (AZIBs) are largely offset by the dendrite growth on the Zn anode, which is induced by the heterogeneous electrical field and limited ion transport of the Zn anode–electrolyte interface during plating and stripping. Here, we propose a dimethyl sulfoxide (DMSO)–H₂O hybrid electrolyte containing polyacrylonitrile (PAN) additives (PAN–DMSO–H₂O) to improve the electrical field and ion transport of the Zn anode, which can thus effectively inhibit dendrite growth. Experimental characterization and theoretical calculations show that PAN preferentially adsorbs on the Zn anode surface and provides abundant zincophilic sites after its solubilization by the DMSO, enabling a balanced electric field and lateral Zn plating. DMSO regulates the solvation structure of the Zn²⁺ ions and strongly bonds to H₂O, which concurrently reduces side reactions and enhances the ion transport. Thanks to the synergistic effects of PAN and DMSO, the Zn anode presents a dendrite-free surface during plating/stripping. Moreover, Zn–Zn symmetric and Zn–NaV₃O₈·1.5H₂O full batteries with this PAN–DMSO–H₂O electrolyte achieve enhanced coulombic efficiency and cycling stability compared to those with a pristine aqueous electrolyte. The results reported herein will inspire other electrolyte designs for high-performance AZIBs.

In order to improve the critical issues of Zn dendritic in zinc-ion batterie, we investigate herein a hybrid electrolyte with PAN-DMSO-H₂O. With the synergistic effects of PAN and DMSO, a uniform, smooth and dendrite-free Zn anode could be obtained.     

Hydrophobic Organic-Electrolyte-Protected Zinc Anodes for Aqueous Zinc Batteries

Aqueous Zn batteries are promising energy-storage devices. However, their lifespan is limited by irreversible Zn anodes owing to water decomposition and Zn dendrite growth. Here, we separate aqueous electrolyte from Zn anode by coating a thin MOF layer on anode and filling the pores of MOF with hydrophobic Zn(TFSI)₂-tris(2,2,2-trifluoroethyl)phosphate (TFEP) organic electrolyte that is immiscible with aqueous Zn(TFSI)₂–H₂O bulk electrolyte. The MOF encapsulated Zn(TFSI)₂-TFEP forms a ZnF₂-Zn₃(PO₄)₂ solid electrolyte interphase (SEI) preventing Zn dendrite and water decomposition. The Zn(TFSI)₂-TFEP@MOF electrolyte protected Zn anode enables a Zn||Ti cell to achieve a high average Coulombic efficiency of 99.1 % for 350 cycles. The highly reversible Zn anode brings a high energy density of 210 Wh kg⁻¹ (of cathode and anode mass) and a low capacity decay rate of 0.0047 % per cycle over 600 cycles in a Zn||MnO₂ full cell with a low capacity ratio of Zn:MnO₂ at 2:1.     

In-Situ Integration of a Hydrophobic and Fast-Zn2+-Conductive Inorganic Interphase to Stabilize Zn Metal Anodes

The irreversible issues of Zn anode stemming from dendrite growth and water-induced erosion have severely hindered the commercialization of rechargeable aqueous Zn batteries. Herein, a hydrophobic and fast-Zn²⁺-conductive zinc hexacyanoferrate (HB-ZnHCF) interphase layer is in situ integrated on Zn by a rapid room-temperature wet-chemistry method to address these dilemmas. Different from currently proposed hydrophilic inorganic cases, the hydrophobic and compact HB-ZnHCF interphase effectively prevents the access of water molecules to Zn surface, thus avoiding H₂ evolution and Zn corrosion. Moreover, the HB-ZnHCF with large internal ion channels, strong zincophilicity, and high Zn²⁺ transference number (0.86) permits fast Zn²⁺ transport and enables smooth Zn deposition. Remarkably, the resultant HB-ZnHCF@Zn electrode delivers unprecedented reversibility with 99.88 % Coulombic efficiency over 3000 cycles, realizes long-term cycling over 5800 h (>8 months, 1 mA cm⁻²) and 1000 h (10 mA cm⁻²), and assures the stable operation of full Zn battery with both coin- and pouch-type configurations.     

Modulating Cation Migration and Deposition with Xylitol Additive and Oriented Reconstruction of Hydrogen Bonds for Stable Zinc Anodes

Highly reversible plating/stripping in aqueous electrolytes is one of the critical processes determining the performance of Zn-ion batteries, but it is severely impeded by the parasitic side reaction and dendrite growth. Herein, a novel electrolyte engineering strategy is first proposed based on the usage of 100 mM xylitol additive, which inhibits hydrogen evolution reaction and accelerates cations migration by expelling active H₂O molecules and weakening electrostatic interaction through oriented reconstruction of hydrogen bonds. Concomitantly, xylitol molecules are preferentially adsorbed by Zn surface, which provides a shielding buffer layer to retard the sedimentation and suppress the planar diffusion of Zn²⁺ ions. Zn²⁺ transference number and cycling lifespan of Zn ∥ Zn cells have been significantly elevated, overwhelmingly larger than bare ZnSO₄. The cell coupled with a NaV₃O₈ cathode still behaves much better than the additive-free device in terms of capacity retention.     

Bio-Inspired Trace Hydroxyl-Rich Electrolyte Additives for High-Rate and Stable Zn-Ion Batteries at Low Temperatures

High-rate and stable Zn-ion batteries working at low temperatures are highly desirable for practical applications, but are challenged by sluggish kinetics and severe corrosion. Herein, inspired by frost-resistant plants, we report trace hydroxyl-rich electrolyte additives that implement a dual remodeling effect for high-performance low-temperature Zn-ion batteries. The additive with high Zn absorbability not only remodels Zn²⁺ primary solvent shell by alternating H₂O molecules, but also forms a shielding layer thus remodeling the Zn surface, which effectively enhances fast Zn²⁺ de-solvation reaction kinetics and prohibits Zn anode corrosion. Taking trace α-D-glucose (αDG) as a demonstration, the electrolyte obtains a low freezing point of −55.3 °C, and the Zn//Zn cell can stably cycle for 2000 h at 5 mA cm⁻² under −25 °C, with a high cumulative capacity of 5000 mAh cm⁻². A full battery that stably operates for 10000 cycles at −50 °C is also demonstrated.     

The Construction of Anion-Induced Solvation Structures in Low-concentration Electrolyte for Stable Zinc Anodes

Aqueous zinc-ion batteries (ZIBs) are promising large-scale energy storage devices because of their low cost and high safety. However, owing to the high activity of H₂O molecules in electrolytes, hydrogen evolution reaction and side reactions usually take place on Zn anodes. Herein, additive-free PCA−Zn electrolyte with capacity of suppressing the activity of free and solvated H₂O molecules was designed by selecting the cationophilic and solventophilic anions. In such electrolyte, contact ion-pairs and solvent-shared ion-pairs were achieved even at low concentration, where PCA⁻ anions coordinate with Zn²⁺ and bond with solvated H₂O molecules. Simultaneously, PCA⁻ anions also induce the construction of H-bonds between free H₂O molecules and them. Therefore, the activity of free and solvated H₂O molecules is effectively restrained. Furthermore, since PCA⁻ anions possess a strong affinity with metal Zn, they can also adsorb on Zn anode surface to protect Zn anode from the direct contact of H₂O molecules, inhibiting the occurrence of water-triggered side reactions. As a result, plating/stripping behavior of Zn anodes is highly reversible and the coulombic efficiency can reach to 99.43 % in PCA−Zn electrolyte. To illustrate the feasibility of PCA−Zn electrolyte, the Zn||PANI full batteries were assembled based on PCA−Zn electrolyte and exhibited enhanced cycling performance.     

Zinc–Organic Battery with a Wide Operation‐Temperature Window from −70 to 150 °C

Aqueous zinc (Zn) batteries have been considered as promising candidates for grid‐scale energy storage. However, their cycle stability is generally limited by the structure collapse of cathode materials and dendrite formation coupled with undesired hydrogen evolution on the Zn anode. Herein we propose a zinc–organic battery with a phenanthrenequinone macrocyclic trimer (PQ‐MCT) cathode, a zinc‐foil anode, and a non‐aqueous electrolyte of a N,N‐dimethylformamide (DMF) solution containing Zn²⁺. The non‐aqueous nature of the system and the formation of a Zn²⁺–DMF complex can efficiently eliminate undesired hydrogen evolution and dendrite growth on the Zn anode, respectively. Furthermore, the organic cathode can store Zn²⁺ ions through a reversible coordination reaction with fast kinetics. Therefore, this battery can be cycled 20 000 times with negligible capacity fading. Surprisingly, this battery can even be operated in a wide temperature range from ?70 to 150 °C.     

Dynamic Zn/Electrolyte Interphase and Enhanced Cation Transfer of Sol Electrolyte for All-Climate Aqueous Zinc Metal Batteries

Zn metal as one of the promising anodes of aqueous batteries possesses notable advantages, but it faces severe challenges from severe side reactions and notorious dendrite growth. Here, ultrathin nanosheets of α-zirconium phosphate (ZrP) are explored as an electrolyte additive. The nanosheets not only create a dynamic and reversible interphase on Zn but also promote the Zn²⁺ transportation in the electrolyte, especially in the outer Helmholtz plane near ZrP. Benefited from the enhanced kinetics and dynamic interphase, the pouch cells of Zn||LiMn₂O₄ using this electrolyte remarkably improve electrochemical performance under harsh conditions, i.e. Zn powders as the Zn anode, high mass loading, and wide temperatures. The results expand the materials available for this dynamic interphase, provide an insightful understanding of the enhanced charge transfer in the electrolyte, and realize the combination of dynamic interphase and enhanced kinetics for all-climate performance.     

A Janus Separator based on Cation Exchange Resin and Fe Nanoparticles-decorated Single-wall Carbon Nanotubes with Triply Synergistic Effects for High-areal Capacity Zn−I2 Batteries

Zn−I₂ batteries stand out in the family of aqueous Zn-metal batteries (AZMBs) due to their low-cost and immanent safety. However, Zn dendrite growth, polyiodide shuttle effect and sluggish I₂ redox kinetics result in dramatically capacity decay of Zn−I₂ batteries. Herein, a Janus separator composed of functional layers on anode/cathode sides is designed to resolve these issues simultaneously. The cathode layer of Fe nanoparticles-decorated single-wall carbon nanotubes can effectively anchor polyiodide and catalyze the redox kinetics of iodine species, while the anode layer of cation exchange resin rich in −SO₃⁻ groups is beneficial to attract Zn²⁺ ions and repel detrimental SO₄²⁻/polyiodide, improving the stability of cathode/anode interfaces synergistically. Consequently, the Janus separator endows outstanding cycling stability of symmetrical cells and high-areal-capacity Zn−I₂ batteries with a lifespan over 2500 h and a high-areal capacity of 3.6 mAh cm⁻².     

High ionic conductive protection layer on Zn metal anode for enhanced aqueous zinc-ion batteries

Aqueous zinc-ion batteries (ZIBs) has been regarded as a promising energy storage system for large-scale application due to the advantages of low cost and high safety. However, the growth of Zn dendrite, hydrogen evolution and passivation issues induce the poor electrochemical performance of ZIBs. Herein, a Na₃Zr₂Si₂PO₁₂ (NZSP) protection layer with high ionic conductivity of 2.94 mS/cm on Zn metal anode was fabricated by drop casting approach. The protection layer prevents Zn dendrites formation, hydrogen evolution as well as passivation, and facilitates a fast Zn²⁺ transport. As a result, the symmetric cells based on NZSP-coated Zn show a stable cycling over 1360 h at 0.5 mA/cm² with 0.5 mAh/cm² and 1000 h even at a high current density of 5 mA/cm² with 2 mAh/cm². Moreover, the full cells combined with V₂O₅-based cathode displays high capacities and high rate capability. This work offers a facile and effective approach to stabilizing Zn metal anode for enhanced ZIBs.     

海藻酸钠-羧甲基纤维素钠凝胶涂层对锌负极稳定性的影响

通过一种绿色、自交联策略,基于海藻酸钠(SA)和羧甲基纤维素钠(CMC)中羧基对Zn²⁺的离子缔合作用,利用旋涂法在锌电极表面原位构建了具有孔结构的柔性 SA+CMC 凝胶涂层(Zn@SA+CMC)。涂层中富含羟基,羟基的强吸附效应能够使涂层与锌电极紧密结合,减少界面处的副反应。柔性涂层不仅能适应锌电镀过程中的体积变化,还表现出较好的亲锌性,更低的成核过电压,更高的离子电导率,有利于Zn²⁺均匀沉积,有效抑制了锌枝晶的生成。因此,Zn@SA+CMC对称电池能稳定运行890h(3 mA·cm^-2);Zn@SA+CMC||MnO₂全电池表现出优越的倍率和循环性能。     

Highly Stable Aqueous Zinc‐Ion Storage Using a Layered Calcium Vanadium Oxide Bronze Cathode

Cost‐effective aqueous rechargeable batteries are attractive alternatives to non‐aqueous cells for stationary grid energy storage. Among different aqueous cells, zinc‐ion batteries (ZIBs), based on Zn²⁺ intercalation chemistry, stand out as they can employ high‐capacity Zn metal as the anode material. Herein, we report a layered calcium vanadium oxide bronze as the cathode material for aqueous Zn batteries. For the storage of the Zn²⁺ ions in the aqueous electrolyte, we demonstrate that the calcium‐based bronze structure can deliver a high capacity of 340 mA h g^?1 at 0.2 C, good rate capability, and very long cycling life (96 % retention after 3000 cycles at 80 C). Further, we investigate the Zn²⁺ storage mechanism, and the corresponding electrochemical kinetics in this bronze cathode. Finally, we show that our Zn cell delivers an energy density of 267 W h kg^?1 at a power density of 53.4 W kg^?1.