Polymer Molecules Adsorption-Induced Zincophilic-Hydrophobic Protective Layer Enables Highly Stable Zn Metal Anodes

Nickel silicate nanotubes modifying the surface of Zn anode tuning the uniform zinc deposition for high-performance Zn metal battery

Among many new types of ion batteries, aqueous Zn-ion batteries (AZIBs) have gained more and more interest because of their unique characteristics such as abundant metal Zn reserves and high capacity. Herein, a nickel silicate nanotube (NSO) is synthesized for protecting Zn metal anode by the surface modification strategy (NSO-Zn). On the one hand, the pores generated by the stacking of NSO nanotubes uniformly guide the deposition of Zn2+ on Zn plate, which greatly reduces the risk of the battery's short-circuit due to the dendrite growth puncturing the diaphragm. On the other hand, the hydrophilic nature of NSO is more conducive to the penetration of electrolyte. Thanks to the inherent material and structural properties of NSO nanotubes, the symmetric cells prepared with NSO-Zn electrodes have a long cycle life of more than 2500 h at 1 mA·cm-2. Finite element simulations of the electrical field and Zn2+ intensity demonstrate that the NSO-Zn electrodes can well reduce the local current density resulting in homogenizing electric field distribution. The present study not only provides a facile and large-grid synthesis of NSO nanotubes, but also demonstrates that NSO nanotubes can protect high-reversible zinc metal anodes and guide the uniform zinc deposition for long-cycle AZIBs.

Insights into Dendrite Regulation by Polymer Hydrogels for Aqueous Batteries

Aqueous batteries, renowned for their high capacity, safety, and low cost, have emerged as promising candidates for next-generation, sustainable energy storage. However, their large-scale application is hindered by challenges, such as dendrite formation and side reactions at the anode. Hydrogel electrolytes, which integrate the advantages of liquid and solid phases, exhibit superior ionic conductivity and interfacial compatibility, giving them potential to suppress dendrite evolution. This Perspective first briefly introduces the fundamentals underlying dendrite formation and the unique features of hydrogels. It then identifies the key role of water and polymer networks in inhibiting dendrite formation, highlighting their regulation of water activity, ion transport, and electrode kinetics. By elucidating the principles of hydrogels in dendrite suppression, this work aims to provide valuable insights to advance the implementation of aqueous batteries incorporating polymer hydrogels.

Unlocking the Potential of Aqueous Zinc-Ion Batteries: Hybrid SEI Construction through Bifunctional Regulator-Assisted Electrolyte Engineering

Aqueous zinc-ion batteries (AZIBs) represent promising candidates for energy storage devices, because of their inherent high safety and cost efficiency. However, challenges such as uneven zinc ion deposition during electrochemical reduction and anode interface side reactions pose significant obstacles to their advancement and practical deployment. Herein, a medium-concentration aqueous electrolyte combined with a bifunctional regulator (aspartame) is developed to address these issues. Practical validation experiments and theoretical calculations demonstrate that the medium-concentration Zn(OTf)2 aqueous electrolyte containing Aspartame can form a robust hybrid solid electrolyte interface (SEI) containing ZnF2 and ZnS by simultaneously modulating the Zn2+ solvation structure and optimizing the metal-molecule interface, thereby enabling dense Zn deposition. It achieves dendrite-free Zn plating and stripping and excellent Zn reversibility. Significantly, the Zn||V2O5 full cell exhibits an average capacity of 240 mAh g-1 over 8000 cycles at 5 A g-1. This work provides new insight into solvation and interface design for high-performance AZIBs.

Synergistic Anion-Cation Chemistry Enables Highly Stable Zn Metal Anodes

Engineering aqueous electrolytes with an ionic liquid (IL) for the zinc (Zn) metal anode has been reported to enhance the electrochemical performances of the Zn metal batteries (ZMBs). Despite these advancements, the effects of IL and the mechanisms involving their anions and cations have been scarcely investigated. Here, we introduce a novel electrolyte design strategy that synergizes anion-cation chemistry using a halogen-based IL and elucidates the underlying mechanism. The strongly and preferentially adsorbed halogen anions guide the formation of a water-poor electrical double layer (EDL) by imidazole-based cations, resulting in the formation of a halide-rich inorganic interphase. This synergistic interaction significantly mitigates Zn anode corrosion at the anode-electrolyte interface, while the halide-rich interphase promotes dense Zn deposition. Consequently, the battery exhibits superior performance, including high reversibility (99.74%) and an ultralong cycle life (20,000 cycles). This synergistic anion-cation chemistry strategy combines the traditional single solid electrolyte interphase and the classic EDL mechanism, substantially enhancing the electrochemical performance of ZMBs.

Highly Reversible Aqueous Zinc-Ion Batteries via Multifunctional Hydrogen-Bond-Rich Dulcitol at Lower Temperature

Aqueous zinc-ion batteries (AZIBs) are considered one of the most promising next-generation energy storage devices due to cost-effectiveness and high safety. However, the uncontrolled dendrite growth and the intolerance against low temperatures hinder the application of AZIBs. Herein, hydrogen-bonding-rich dulcitol (DOL) is introduced into the ZnSO4, which reshaped the hydrogen-bond network in the electrolyte and optimized the solvation sheath structure, effectively reducing the amount of active water molecules and inhibiting hydrogen evolution and the parasitic reaction at the zinc anode. In addition, higher adsorption energy DOL preferentially adsorbs on the surface of the zinc anode, guiding the uniform deposition of Zn2+ and inhibiting the formation of dendrites. DOL also enhances the interaction between free and free water and improves the resistance to freeze of the electrolyte. Consequently, the Zn//Zn symmetric cells assembled with DOL are extremely stable cycled for 2000 h at 2 mA cm-2. The NH4V4O10 (NVO)//Zn full cell showed more excellent specific capacity of 183.07 mAh g-1 after 800 cycles. Even at the low temperature of -10 °C, the cell still maintains 155.95 mAh g-1 capacity after 600 cycles. This work provides a new strategy for the subsequent study of AZIBs with high stability at low temperatures.

Active Water Optimization in Different Electrolyte Systems for Stable Zinc Anodes

Zinc (Zn) metal, with abundant resources, intrinsic safety, and environmental benignity, presents an attractive prospect as a novel electrode material. However, many substantial challenges remain in realizing the widespread application of aqueous Zn-ion batteries (AZIBs) technologies. These encompass significant material corrosion challenges (This can lead to battery failure in an unloaded state.), hydrogen evolution reactions, pronounced dendrite growth at the anode interface, and a constrained electrochemical stability window. Consequently, these factors contribute to diminished battery lifespan and energy efficiency while restricting high-voltage performance. Although numerous reviews have addressed the potential of electrode and separator design to mitigate these issues to some extent, the inherent reactivity of water remains the fundamental source of these challenges, underscoring the necessity for precise regulation of active water molecules within the electrolyte. In this review, the failure mechanism of AZIBs (unloaded and in charge and discharge state) is analyzed, and the optimization strategy and working principle of water in the electrolyte are reviewed, aiming to provide insights for effectively controlling the corrosion process and hydrogen evolution reaction, further controlling dendrite formation, and expanding the range of electrochemical stability. Furthermore, it outlines the challenges to promote its practical application and future development pathways.

Spatial Confinement and Induced Deposition of ZnHCF in 3D Structure for Ultrahigh-Rate and Dendrite-Free Zn Anodes

Aqueous Zn-metal batteries (AZBs) are thought as highly prospective candidates for large-scale energy-storage systems because of their abundant natural resources, low cost, high safety, and environmentally friendly. Nevertheless, the key problems of AZBs are the uncontrollable zinc dendrites growth and water-induced erosion faced by zinc anodes. Therefore, reducing the hydrophilicity of zinc anode and introducing the zincophilic sites are the availably strategy. Herein, 3D highly-conductive host is developed to inhibit Zn dendrites growth, which have a porous structure consisting of graphene and carbon nanotubes embedded with a zincophilic nucleation sites of Zn Prussian blue analogs (ZnHCF@3D-GC). The inner ZnHCF possess minimized nucleation barriers, which can serve as favorable nucleation sites, and 3D host provide a buffer interspace to allow for even more high-capacity Zn plating. Additionally, density functional theory results show that ZnHCF exhibits a strong Zn binding energy and high adsorption energy of Zn (002) plane, which can guide Zn horizontal deposition in the 3D host. As a result, the assembled symmetrical cell is able to stabilize 900 cycles at an ultrahigh current density of 100 mA cm-2. Zn-ZnHCF@3D-GC//MnO2 and Zn-ZnHCF@3D-GC//ZnHCF full cells can be stably cycled 1000 cycles at 2.0 A g-1.

Green Polymer Derived Multifunctional Layer Achieving Oriented Diffusion and Controllable Deposition of Zn2+ for Ultra-Durable Zinc-Ion Hybrid Supercapacitors

Rampant dendrite growth and severe parasitic reactions at the electrode/electrolyte interface significantly limit the cycle life of aqueous zinc ion hybrid supercapacitors (ZHSCs). In this study, sodium lignosulfonate (SLS) as one green polymer was introduced into ZnSO4 electrolyte to construct a multifunctional layer on the surface of Zn plates. Experimental analyses and theoretical calculations show that the presence of the SLS layer, rich in oxygen-containing functional groups (-SO3-), can not only modulate the structure of the electric double layer (EDL) to suppress interfacial side reactions caused by free H2O and SO42-, but also promote (101)-oriented deposition by selectively controlling the deposition behavior of Zn2+ through specific adsorption on different crystalline surfaces. The optimized electrolyte allows stable Zn//Zn symmetric cells to achieve a cumulative plating capacity exceeding 4 Ah cm-2 at a high areal capacity of 5 mAh cm-2, and stable cycling for more than 1000 cycles with an excellent average Coulombic efficiency of 99.34% in Zn//Cu asymmetric cells. The Zn//AC ZHSC exhibits ultralong cycling stability of over 40,000 cycles in the optimized electrolyte, with a capacity decay rate as low as 0.000285% per cycle.

Weak H-Bond Interface Environment for Stable Aqueous Zinc Batteries

Hydrogen evolution reaction and Zn dendrite growth, originating from high water activity and the adverse competition between the electrochemical kinetics and mass transfer, are the main constraints for the commercial applications of the aqueous zinc-based batteries. Herein, a weak H-bond interface with a suspension electrolyte is developed by adding TiO2 nanoparticles into the electrolytes. Owing to the strong polarity of Ti-O bonds in TiO2, abundant hydroxyl functional groups are formed between the TiO2[110] active surface and aqueous environment, which can produce a weak H-bond interface by disrupting the initial H-bond networks between the water molecules, thereby accelerating the mass transfer of Zn2+ and reducing the water activity. In consequence, the Zn||Zn symmetrical cells display reversible Zn plating/stripping behaviors with a high Coulombic efficiency of 99.7% over 700 cycles. Moreover, the TiO2-based suspension strategy is also applicable to other zinc salt systems and exhibits fast plating/stripping behaviors. The suspension electrolyte enables long-term full cells, including Zn||PANI hybrid capacitors and Zn||ZnVO full batteries.

Solvation structure regulation of zinc ions with nitrogen-heterocyclic additives for advanced batteries

Zinc-based battery performance is often hindered by side reactions, such as dendrite growth and hydrogen evolution, which are closely linked to the desolvation of hydrated zinc ions. This study demonstrates that the coordination microenvironment of zinc ions can be effectively regulated using poly-nitrogen heterocyclic compounds as electrolyte additives. With the composite electrolyte, the zinc electrode achieves reversible recycling for approximately 4000 h at a low nucleation overpotential (∼29 mV), demonstrating exceptional cycling stability. The solvation structure of hydrated zinc ions and chemical properties of zinc were regulated, thereby inhibiting side reactions to enhance cycling stability. Important insights into regulating the solvation structure of zinc ions and improving the reversible deposition process at the zinc-solution interface would offer valuable guidance to fabricate advanced zinc ion batteries.

Regulating Zn Deposition via Honeycomb-like Covalent Organic Frameworks for Stable Zn Metal Anodes

The irreversible chemistry of the Zn anode, attributed to parasitic reactions and the growth of zinc dendrites, is the bottleneck in the commercialization of aqueous zinc-ion batteries. Herein, an efficient strategy via constructing an organic protective layer configured with a honeycomb-like globular-covalent organic framework (G-COF) was constructed to enhance the interfacial stability of Zn anodes. Theoretical analyses disclose that the methoxy and imine groups in G-COF have more negative adsorption energy and electrostatic potential distribution, favorable Zn2+ adsorption, and diffusion. Experimental results demonstrate that G-COF effectively protects the Zn anode from dendrite formation and surface corrosion, leading to a stable and homogeneous Zn2+ deposition. Notably, the G-COF@Zn||G-COF@Zn symmetric cell obtained high stability for over 1650 h under 3 mA cm-2 for 1 mA h cm-2. Full cells assembled with the δ-MnO2 cathode and G-COF@Zn anode demonstrates exceptional rate capability and consistent cycling over 1000 cycles at a current density of 1 A g-1, achieving a specific capacity of 217 mA h g-1. Our work provides novel insight into interfacial regulation of Zn anodes for the implementation of practical aqueous zinc-ion batteries with long-term cycling characteristics.

Bidirectional pH Buffer Effect Facilitates High-Reversible Aqueous Zinc Ion Batteries

Aqueous zinc ion batteries (AZIBs) stand out from the crowd of energy storage equipment for their superior energy density, enhanced safety features, and affordability. However, the notorious side reaction in the zinc anode and the dissolution of the cathode materials led to poor cycling stability has hindered their further development. Herein, ammonium salicylate (AS) is a bidirectional electrolyte additive to promote prolonged stable cycles in AZIBs. NH4 + and C6H4OHCOO- collaboratively stabilize the pH at the interface of the electrolyte/electrode and guide the homogeneous deposition of Zn2+ at the zinc anode. The higher adsorption energy of NH4 + compared to H2O on the Zn (002) crystal plane mitigates the side reactions on the anode surface. Moreover, NH4 + is similarly adsorbed on the cathode surface, maintaining the stability of the electrode. C6H4OHCOO- and Zn2+ are co-intercalation/deintercalation during the cycling process, contributing to the higher electrochemical performance of the full cell. As a result, with the presence of AS additive, the Zn//Zn symmetric cells achieved 700 h of highly reversible cycling at 5 mA cm-2. In addition, the assembled NH4V4O10(NVO)//Zn coin and pouch batteries achieved higher capacity and higher cycle lifetime, demonstrating the practicality of the AS electrolyte additive.

Regulation of Zn2+ Solvation Configuration in Aqueous Batteries via Selenium-Substituted Crown Ether Engineering

The efficient utilization of the metallic Zn in rechargeable aqueous Zn-ion batteries (RAZBs) struggle to suffer from parasitic Zn dendrite formation, hydrogen evolution reactions as well as severe interfacial degradation at high areal capacity loadings. This study thus proposes to employ the modified crown ether as an aqueous electrolyte additive to regulate the Zn2+ desolvation kinetic and facilitates the horizontally oriented (002) deposition of Zn, extending the lifespan of both the symmetric cell and full cell models. Specifically, zincophilic cyano and hydrophobic selenium atoms are incorporated into the crown ether supramolecule to enhance Zn2+ coordination and desolvation capability. The addition of 4-cyanobenzo-21-crown-7-selenium at a low concentration of 0.5 wt.% effectively mitigates hydrogen evolution and Zn corrosion caused by water, promoting the oriented deposition of Zn2+. The Zn||V2O5 full cell prototype, assembled with the areal capacity loadings of 2 mAh cm-2 and N/P ratio of 2.95, exhibits negligible capacity fading at 2.0A g-1 for 300 cycles, highlighting the commercial feasibility of supramolecular macrocycles additive for practical RAZBs applications.

Multifunctional Self-Assembled Bio-Interfacial Layers for High-Performance Zinc Metal Anodes

Rechargeable aqueous zinc-ion (Zn-ion) batteries are widely regarded as important candidates for next-generation energy storage systems for low-cost renewable energy storage. However, the development of Zn-ion batteries is currently facing significant challenges due to uncontrollable Zn dendrite growth and severe parasitic reactions on Zn metal anodes. Herein, we report an effective strategy to improve the performance of aqueous Zn-ion batteries by leveraging the self-assembly of bovine serum albumin (BSA) into a bilayer configuration on Zn metal anodes. BSA's hydrophilic and hydrophobic fragments form unique and intelligent ion channels, which regulate the migration of Zn ions and facilitate their desolvation process, significantly diminishing parasitic reactions on Zn anodes and leading to a uniform Zn deposition along the Zn (002) plane. Notably, the Zn||Zn symmetric cell with BSA as the electrolyte additive demonstrated a stable cycling performance for up to 2400 hours at a high current density of 10 mA cm-2. This work demonstrates the pivotal role of self-assembled protein bilayer structures in improving the durability of Zn anodes in aqueous Zn-ion batteries.

Manipulation of Zn Deposition Behavior to Achieve High-Rate Aqueous Zinc Batteries via High Valence Zirconium Ions

Aqueous zinc ion batteries are excellent energy storage devices with high safety and low cost. However, the corrosion reaction and zinc dendrite formation occurring on the surface of zinc anodes are hindering their further development. To solve the problems, zirconium acetate (ZA) was used as an electrolyte additive in the ZnSO4 electrolyte. Attributing to the higher electro-positivity of Zr4+ than Zn2+, these high valence metal cations preferentially adsorb onto the surface of metallic zinc, shielding parasitic reactions between zinc and electrolyte, reshaping the electric field distribution, and directing preferential homogeneous deposition of Zn-ions on the Zn (002) crystal plane. Furthermore, the adsorption of Zr4+ on the Zn metal after electrochemical cycles can enhance the energy barrier of zinc atom diffusion, resulting in high resistance of corrosion and manipulation of the Zn2+ nucleation configuration. Attributing to these properties, the Zn//Zn symmetric cell with an electrolyte additive of ZA was able to cycle for 400 h under an extremely high current density of 40 mA cm-2 with an area capacity of 2 mAh cm-2. Meanwhile, the MnO2//Zn coin cell still had 81.7 mAh g-1 (85% retention of capacity) after 850 cycles under a current density of 1 A g-1.

Decoupling "Cling-Cover-Capture" Triple Effects on Stable Zn Anode/Electrolyte Interface

The electrochemical performance of the Zn anode in a water-based electrolyte is influenced by the Zn anode/electrolyte interface. In the present work, a distinctive interfacial chemistry is enabled by introducing synergistic "cling-cover-capture" effects of different components in aspartame (APM) molecule, which can be described in detail as clinging to the surface of Zn anode by incompletely coordinated nitrogen and oxygen atoms in the main chain, covering the surface by the benzene rings and capturing Zn2+ by the side chains. Benefiting from its triple effects, this steady anode/electrolyte interface homogenizes Zn2+ flux and excludes interfacial active water, thus effectively suppressing both dendrite growth and side reactions. Consequently, the stability and reversibility of Zn anode experience an enhancement, leading to a long cycle lifespan of 5100 h at 1 mA cm-2 and 1 mA h cm-2, and an average Coulombic efficiency of 99.73% at 1 mA cm-2 and 0.5 mA h cm-2 over 1600 cycles. The improved rate capability and cycling durability of Zn||NH4V4O10 full cells further confirm the important role of APM in stabilizing the Zn anode.

Electrolyte Additive Molecule Disassembly to Reveal the Roles of Individual Groups in Zn Electrode Stabilities in Aqueous Batteries

Zn metal anodes experience dendritic growth and hydrogen evolution reactions (HER) in aqueous batteries. Herein, we propose an interface regulation strategy with a trace (1.4 × 10-4 mol kg-1) all-in-one epicatechin (EC) electrolyte additive to solve the above issues and reveal the roles of individual functional groups. By the disassembly of EC into simple molecules combined with entire molecule investigations, we show that phenol and ether sites preferentially anchor on the Zn surface, while the hydroxyl group pointing outward enters Zn2+ solvation shells at the interface. It modifies the following desolvation path, which not only enables uniform deposition with the thermodynamically favored plate morphology but also inhibits HER. With these synergistic effects of trace EC additive, the lifespan of symmetric cells extends to 8.5 times that of the baseline ZnSO4 electrolyte. The capacity retention of Zn//MnO2 full batteries with N/P = 3 also increases from 59.1 to 85.6% after 500 cycles.

Tailoring the Whole Deposition Process from Hydrated Zn2+ to Zn0 for Stable and Reversible Zn Anode

The practical application of aqueous zinc-ion batteries (ZIBs) indeed faces challenges primarily attributed to the inherent side reactions and dendrite growth associated with the Zn anode. In the present work, N-Methylmethanesulfonamide (NMS) is introduced to optimize the transfer, desolvation, and reduction of Zn2+, achieving highly stable and reversible Zn plating/stripping. The NMS molecule can substitute one H2O molecule in the solvation structure of hydrated Zn2+ and be preferentially chemisorbed on the Zn surface to protect Zn anode against corrosion and hydrogen evolution reaction (HER), thereby suppressing byproducts formation. Additionally, a robust N-rich organic and inorganic (ZnS and ZnCO3) hybrid solid electrolyte interphase is in situ generated on Zn anode due to the decomposition of NMS, resulting in enhanced Zn2+ transport kinetics and uniform Zn2+ deposition. Consequently, aqueous cells with the NMS achieve a long lifespan of 2300 h at 1 mA cm-2 and 1 mAh cm-2, high cumulative plated capacity of 3.25 Ah cm-2, and excellent reversibility with an average coulombic efficiency (CE) of 99.7 % over 800 cycles.

Facilitating Oriented Dense Deposition: Utilizing Crystal Plane End-Capping Reagent to Construct Dendrite-Free and Highly Corrosion-Resistant (100) Crystal Plane Zinc Anode

Dendrite growth and corrosion issues have significantly hindered the usability of Zn anodes, which further restricts the development of aqueous zinc-ion batteries (AZIBs). In this study, a zinc-philic and hydrophobic Zn (100) crystal plane end-capping reagent (ECR) is introduced into the electrolyte to address these challenges in AZIBs. Specifically, under the mediation of 100-ECR, the electroplated Zn configures oriented dense deposition of (100) crystal plane texture, which slows down the formation of dendrites. Furthermore, owing to the high corrosion resistance of the (100) crystal plane and the hydrophobic protective interface formed by the adsorbed ECR on the electrode surface, the Zn anode demonstrates enhanced reversibility and higher Coulombic efficiency in the modified electrolyte. Consequently, superior electrochemical performance is achieved through this novel crystal plane control strategy and interface protection technology. The Zn//VO2 cells based on the modified electrolyte maintained a high-capacity retention of ≈80.6% after 1350 cycles, corresponding to a low-capacity loss rate of only 0.014% per cycle. This study underscores the importance of deposition uniformity and corrosion resistance of crystal planes over their type. And through crystal plane engineering, a high-quality (100) crystal plane is constructed, thereby expanding the range of options for viable Zn anodes.

Stabilizing zinc anodes via engineering the active sites and pore structure of functional composite layers

Functional composite layers composed of an amino-functionalized zirconium 1,4-dicarboxybenzene metal-organic framework were constructed on zinc anodes to mitigate the interface disturbances in aqueous batteries. These layers enable robust Zn2+ adsorption and homogenized Zn2+ transport and deposition kinetics, facilitating achieving high stability in a symmetric cell (3500 h) and a full cell (35 000 cycles, 96.7%).

Enhancing Reversibility and Stability of Mg Metal Anodes: High-Exposure (002) Facets and Nanosheet Arrays for Superior Mg Plating/Stripping

Magnesium metal batteries (MMBs), recognized as promising contenders for post-lithium battery technologies, face challenges such as uneven magnesium (Mg) plating and stripping behaviors, leading to uncontrollable dendrite growth and irreversible structural damage. Herein, we have developed a Mg foil featuring prominently exposed (002) facets and an architecture of nanosheet arrays (termed (002)-Mg), created through a one-step acid etching method. Specifically, the prominent exposure of Mg (002) facets, known for their inherently low surface and adsorption energies with Mg atoms, not only facilitates smooth nucleation and dense deposition but also significantly mitigates side reactions on the Mg anode. Moreover, the nanosheet arrays on the surface evenly distribute the electric field and Mg ion flux, enhancing Mg ion transfer kinetics. As a result, the fabricated (002)-Mg electrodes exhibit unprecedented long-cycle performance, lasting over 6000 h (>8 months) at a current density of 3 mA cm-2 for a capacity of 3 mAh cm-2. Furthermore, the corresponding pouch cells equipped with various electrolytes and cathodes demonstrate remarkable capacity and cycling stability, highlighting the superior electrochemical compatibility of the (002)-Mg electrode. This study provides new insights into the advancement of durable MMBs by modifying the crystal structure and morphology of Mg.

Switching Hydrophobic Interface with Ionic Valves for Reversible Zinc Batteries

Developing hydrophobic interface has proven effective in addressing dendrite growth and side reactions during zinc (Zn) plating in aqueous Zn batteries. However, this solution inadvertently impedes the solvation of Zn2+ with H2O and subsequent ionic transport during Zn stripping, leading to insufficient reversibility. Herein, an adaptive hydrophobic interface that can be switched "on" and "off" by ionic valves to accommodate the varying demands for interfacial H2O during both the Zn plating and stripping processes, is proposed. This concept is validated using octyltrimethyl ammonium bromide (C8TAB) as the ionic valve, which can initiatively establish and remove a hydrophobic interface in response to distinct electric-field directions during Zn plating and stripping, respectively. Consequently, the Zn anode exhibits an extended cycling life of over 2500 h with a high Coulombic efficiency of ≈99.8%. The full cells also show impressive capacity retention of over 85% after 1 000 cycles at 5 A g-1. These findings provide a new insight into interface design for aqueous metal batteries.

In Situ Self-Reconfiguration Induced Multifunctional Triple-Gradient Artificial Interfacial Layer toward Long-Life Zn-Metal Anodes

Aqueous Zn-ion batteries featuring with intrinsic safety and low cost are highly desirable for large-scale energy storage, but the unstable Zn-metal anode resulting from uncontrollable dendrite growth and grievous hydrogen evolution reaction (HER) shortens their cycle life. Herein, a feasible in situ self-reconfiguration strategy is developed to generate triple-gradient poly(diallyldimethylammonium) bis(trifluoromethanesulfonyl)imide (PDDA-TFSI)-Zn5(OH)8Cl2·H2O-Sn (PT-ZHC-Sn) artificial layer. The resulting triple-gradient interface consists of the spherical top layer PT with cation confinement and H2O inhibition, the dense intermediate layer ZHC nanosheet with Zn2+ conduction and electron shielding, and the bottom layer Znophilic Sn metal. The well-designed triple-gradient artificial interfacial layer synergistically facilitates rapid Zn2+ diffusion to regulate uniform Zn deposition and accelerates the desolvation process while suppressing HER. Consequently, the PT-ZHC-Sn@Zn symmetric cell achieves an ultralong lifespan over 6500 h at 0.5 mA cm-2 for 0.5 mAh cm-2. Furthermore, a full battery coupling with MnO2 cathode exhibits a 17.2% increase in capacity retention compared with bare Zn anode after 1000 cycles. The in situ self-reconfiguration strategy is also applied to prepare triple-gradient PT-ZHC-In, and the assembled Zn//Cu cell operates steadily for over 8400 h while maintaining Coulombic efficiency of 99.6%. This work paves the way to designing multicomponent gradient interface for stable Zn-metal anodes.

Low-Cost Aqueous Electrolyte with MBA Additives for Uniform and Stable Zinc Deposition

Aqueous zinc ion batteries (AZIBs) are attracting increasing research interest due to their intrinsic safety, low cost, and scalability. However, the issues including hydrogen evolution, interface corrosion, and zinc dendrites at anodes have seriously limited the development of aqueous zinc ion batteries. Here, N,N-methylenebis(acrylamide) (MBA) additives with -CONH- groups are introduced to form hydrogen bonds with water and suppress H2O activity, inhibiting the occurrence of hydrogen evolution and corrosion reactions at the interface. In situ optical microscopy demonstrates that the MBA additive promotes the uniform deposition of Zn2+ and then suppresses the dendrite growth on the zinc anode. Therefore, Zn//Ti asymmetric batteries demonstrate a high plating/stripping efficiency of 99.5%, while Zn//Zn symmetric batteries display an excellent cycle stability for more than 1000 h. The Zn//MnO2 full cells exhibit remarkable cycling stability for 700 cycles in aqueous electrolytes with MBA additives. The additive engineering via MBA achieved the dendrite-free Zn anodes and stable full batteries, which is favorable for advanced AZIBs in practical applications.

Dynamic Molecular Interphases Regulated by Trace Dual Electrolyte Additives for Ultralong-Lifespan and Dendrite-Free Zinc Metal Anode

Metallic zinc is a promising anode material for rechargeable aqueous multivalent metal-ion batteries due to its high capacity and low cost. However, the practical use is always beset by severe dendrite growth and parasitic side reactions occurring at anode/electrolyte interface. Here we demonstrate dynamic molecular interphases caused by trace dual electrolyte additives of D-mannose and sodium lignosulfonate for ultralong-lifespan and dendrite-free zinc anode. Triggered by plating and stripping electric fields, the D-mannose and lignosulfonate species are alternately and reversibly (de-)adsorbed on Zn metal, respectively, to accelerate Zn2+ transportation for uniform Zn nucleation and deposition and inhibit side reactions for high Coulombic efficiency. As a result, Zn anode in such dual-additive electrolyte exhibits highly reversible and dendrite-free Zn stripping/plating behaviors for >6400 hours at 1 mA cm-2, which enables long-term cycling stability of Zn||ZnxMnO2 full cell for more than 2000 cycles.

Multifunctionalized Supramolecular Cyclodextrin Additives Boosting the Durability of Aqueous Zinc-Ion Batteries

The poor cycling stability of aqueous zinc-ion batteries hinders their application in large-scale energy storage due to uncontrollable dendrite growth and harmful hydrogen evolution reactions. Here, we designed and synthesized an electrolyte additive, N-methylimidazolium-β-cyclodextrin p-toluenesulfonate (NMI-CDOTS). The cations of NMI-CD+ are more easily adsorbed on the abrupt Zn surface to regulate the deposition of Zn2+ and reduce dendrite generation under the combined action of the unique cavity structure with abundant hydroxyl groups and the electrostatic force. Meanwhile, p-toluenesulfonate (OTS-) is able to change the Zn2+ solvation structure and suppress the hydrogen evolution reaction by the strong interaction of Zn2+ and OTS-. Benefiting from the synergistic role of NMI-CD+ and OTS-, the Zn||Zn symmetric cell exhibits superior cycling performance as high as 3800 h under 1 mA cm-2 and 1 mA h cm-2. The Zn||V2O5 full battery also shows a high specific capacity (198.3 mA h g-1) under 2.0 A g-1 even after 1500 cycles, and its Coulomb efficiency is nearly 100% during the charging and discharging procedure. These multifunctional composite strategies open up possibilities for the commercial application of aqueous zinc-ion batteries.