From room temperature to harsh temperature applications: Fundamentals and perspectives on electrolytes in zinc metal batteries

Aqueous Zinc-Ion Batteries with Boosted Stability and Kinetics under a Wide Temperature Range

Sustainable aqueous zinc ion batteries (AZIBs) necessitate a wide operational temperature range to ensure practicability, yet achieving this often compromises either reaction kinetics at low temperatures or cycling stability at high temperatures. Here we present an electrolyte design that balances this trade-off, enhancing the stability and kinetics of AZIBs across -60 to 60 °C. Our approach incorporates silk fibroin as a multifunctional additive into ZnCl2-based "water-in-salt" electrolyte, which modifies both electrolyte structure and electrode interphase. Specifically, Zn||Zn half-cells with this electrolyte realize low hysteresis (180 mV at 1 mA cm-2) at -60 °C, and stable operation (200 hours at 2 mA cm-2) at 60 °C. This electrolyte is compatible with both inorganic and organic cathode materials. Remarkably, an ampere-hour-level Zn||V2O5 ⋅ nH2O pouch cell with this electrolyte achieves an energy density of ∼72 W h L-1 with minimal capacity decay after 50 cycles at 0.5 A g-1. Furthermore, the pouch cell stably cycles across -60 to 60 °C. This strategy provides a powerful solution to the challenges of aqueous metal-ion batteries at extreme temperatures.

SiO2 Nanoparticles-Induced Antifreezing Hydrogel Electrolyte Enables Zn-I2 Batteries with Complete and Reversible Four-Electron-Transfer Mechanisms at Low Temperatures

Four-electron-transfer aqueous zinc-iodine batteries hold significant promise for large-scale energy storage due to their high specific capacities. However, achieving four-electron-transfer mechanisms under subzero temperatures remains challenging due to freezing point limitations of conventional aqueous electrolytes and sluggish reaction kinetics. Herein, an antifreezing hydrogel electrolyte (HC-SiO2) is developed through the spontaneous gelation of a high-concentration electrolyte (1 m Zn(OAc)2 + 21 m LiCl, HC) with SiO2 nanoparticles, enabling low-temperature operation of quasi-solid-state Zn-I2 batteries with complete and reversible four-electron-transfer processes. Abundant interactions between dispersed SiO2 nanoparticles and cations enlarge ion-pair distances, reducing close ion-pair formation and lowering the freezing temperature (-60.7 °C). Furthermore, the quasi-solid-state hydrogel electrolyte combines advantages of reduced water activity and disrupted hydrogen-bond networks, effectively suppressing I+ hydrolysis while inhibiting ice nucleation. Additionally, the utilization of low-concentration Zn(OAc)2 combined with high-concentration LiCl increases availability of free Cl- by mitigating strong ionic interaction in conventional ZnCl2-based concentrated electrolytes, thereby enhancing reaction kinetics of the I2/I+ conversion. Benefiting from synergistic manipulation of ionic interaction, water activity, and Cl- activity, the HC-SiO2 hydrogel achieves a high capacity of 490.9 mAh g-1 and durable lifespan exceeding 11,000 cycles at -20 °C. These findings offer valuable insights for advancing practical low-temperature Zn-I2 batteries.

Probing Kinetics Beyond Tafel Unlocks Highly Accurate Exchange Currents for Aqueous Zinc Metal Batteries

Understanding the kinetics of zinc electrodeposition on current collectors is crucial for improving aqueous zinc-metal battery (AZMB) performance, yet it remains largely unexplored. A major challenge within the field is the inconsistent reporting of kinetic parameters, particularly the exchange current density (j0), which is essential for accurately modeling and simulating zinc electrodeposition reactions. In this study, fast scan voltammetry on tungsten ultramicroelectrodes (UMEs) is employed to decouple mass transfer effects and isolate charge transfer kinetics. This results show that while zinc electrodeposition is a two-electron process, the rate-limiting step involves a one-electron transfer, validated through Butler-Volmer and Marcus-Hush models. This work also identifies significant limitations of Tafel analysis for certain zinc electrolytes systemsl, as their kinetically quasi-reversible/irreversible nature prevents the existence of a true Tafel regime (±118 mV kinetic regime). For such systems, the Allen-Hickling approach is proposed as a more accurate method for probing zinc electrodeposition kinetics. We report j0 values for ZnSO4 (0.20 A/cm2), Zn(OTf)2 (0.42 A/cm2), and ZnCl2 (0.46 A/cm2) and provide clear guidelines for precise kinetic analysis based on the width of the kinetic regime. Finally, the impact of accurate kinetic parameter measurements on coin cell performance is demonstrated, revealing that lower accurately determined j0 values correlate with improved long-term cycling stability, following the trend ZnSO4 > Zn(OTf)2 > ZnCl2, aligning with predictions from Sands' model. This work provides the first systematic kinetic investigation of counter anions in aqueous zinc-metal batteries, offering critical insights into how electrolyte composition influences charge transfer kinetics. These findings advance our fundamental understanding of AZMB kinetics and offer a framework for optimizing electrolyte compositions and electrode designs to enhance battery performance and durability.

Engineering electro-crystallization orientation and surface activation in wide-temperature zinc ion supercapacitors

Matching the capacity of the anode and cathode is essential for maximizing electrochemical cell performance. This study presents two strategies to balance the electrode utilization in zinc ion supercapacitors, by decreasing dendritic loss in the zinc anode while increasing the capacity of the activated carbon cathode. The anode current collector was modified with copper nanoparticles to direct zinc plating orientation and minimize dendrite formation, improving the Coulombic efficiency and cycle life. The cathode was activated by an electrolyte reaction to increase its porosity and gravimetric capacity. The full cell delivered a specific energy of 192 ± 0.56 Wh kg-1 at a specific power of 1.4 kW kg-1, maintaining 84% capacity after 50,000 full charge-discharge cycles up to 2 V. With a cumulative capacity of 19.8 Ah cm-2 surpassing zinc ion batteries, this device design is particularly promising for high-endurance applications, including un-interruptible power supplies and energy-harvesting systems that demand frequent cycling.

Robust Piezoelectric-Derived Bilayer Solid Electrolyte Interphase for Zn Anodes Operating from -60 to 60 °C

Research on the reversibility and long-term cycling stability of zinc-ion batteries (ZIBs) over a wide temperature range remains limited. One major challenge with gel electrolytes is ensuring the interface stability with Zn metal anodes under varying conditions. In this study, we introduce a multicomponent gel electrolyte that effectively addresses the interface stability challenges associated with Zn anodes under high current densities and wide temperature ranges. This advanced electrolyte is synthesized via the polymerization of poly(VDF-TrFE-CTFE) within a polyimide fiber network, which enables hydrogen-free and dendrite-free Zn deposition/stripping over 4350 h at 1 mA cm-2, even over 1500 h from -60 to 60 °C, even sustaining 20 mA cm-2 operation. Fluorine-rich components promote a self-adaptive bilayer solid electrolyte interphase (SEI) comprising an ultrathin amorphous outer layer and an inorganic/organic inner layer (ZnF2-ZnS-ZnO-ZnCO3), synergistically suppressing side reactions and guiding uniform Zn deposition via piezoelectric effects. Consequently, all-solid-state ZIBs paired with an iodine cathode achieve cycling stability: 36,500 cycles at 5 A g-1 (30 °C) and 1500 cycles at -30 °C, setting benchmarks for extreme-condition performance. This work advances interfacial engineering for high-rate, wide-temperature ZIBs through a rational electrolyte design and SEI modulation.

Progress in Developing Polymer Electrolytes for Advanced Zn Batteries

Aqueous Zn batteries (ZBs) are promising candidates for large-scale energy storage, considering their intrinsically safe features, competitive cost, and environmental friendliness. However, the fascinating metallic Zn anode is subjected to severe issues, such as dendrite growth, hydrogen evolution, and corrosion. Additionally, traditional aqueous electrolytes' narrow electrochemical windows and temperature ranges further hinder the practical application of ZBs. Solid-state electrolytes, including solid polymer electrolytes and hydrogel electrolytes, offer distinct paths to mitigate these issues and simultaneously endow the ZBs with customizable functions such as flexibility, self-healing, anti-freezing, and regulated Zn deposition, etc, due to their tuneable structures. This review summarizes the latest progress in developing polymer electrolytes for ZBs, focusing on modifying the ionic conductivity, interfacial compatibility, Zn anode stability, electrochemical stability windows, and improving the environmental adaptability under harsh conditions. Although some achievements are obtained, many critical challenges still exist, and it is hoped to offer guidance for future research, accelerating the development and application of polymer electrolytes.

Fatty acid methyl ester ethoxylate additive for enhancing high-temperature aqueous zinc-ion battery performance

Aqueous zinc-ion batteries (AZIBs) have attracted significant attention due to their high theoretical capacity, low cost, and excellent safety. Nevertheless, their practical applications are hindered by challenges such as electrolyte decomposition, Zn corrosion/passivation, and dendrite growth, which become more severe under high-temperature conditions. To address these issues, innovative electrolyte design has become a key strategy. In this study, we propose a simple and effective electrolyte modification strategy by introducing fatty acid methyl ester ethoxylate (FMEE) as an additive. FMEE functions as both a solvation structure regulator and a water cluster stabilizer, effectively suppressing side reactions and promoting the formation of a robust solid electrolyte interphase enriched with ZnS and ZnF2. This significantly improves the interfacial chemical stability of the Zn anode. As a result, the Zn anode achieves an extended cycling lifespan of up to 3000 h at 1 mA cm-2 and 1 mAh cm-2. Furthermore, the Zn-V2O5 full cell using the FMEE-modified electrolyte exhibits an excellent rate performance and long-term cycling stability. Notably, the cell maintains a superior electrochemical performance even at 60 °C, demonstrating remarkable thermal stability. This study offers a new strategy for developing high-performance, temperature-tolerant AZIBs.

Targeted Docking of Localized Hydrogen Bond for Efficient and Reversible Zinc-Ion Batteries

Hydrogen bond (HB) chemistry, a pivotal feature of aqueous zinc-ion batteries, modulates electrochemical processes through weak electrostatic interactions among water molecules. However, significant challenges persist, including sluggish desolvation kinetics and inescapable parasitic reactions at the electrolyte-electrode interface, associated with high water activity and strong Zn2+-solvent coordination. Herein, a targeted localized HB docking mechanism is activated by the polyhydroxy hexitol-based electrolyte, optimizing Zn2+ solvation structures via dipole interaction and reconstructing interfacial HB networks through preferential parallel adsorption. By combining in situ spectroscopic characterizations with theoretical calculations, we elucidate the dynamic evolution of localized HB networks, which enhance Zn2+ deposition kinetics and homogeneity, suppress water-induced side reactions, and mitigate vanadium framework collapse. Our findings support that the targeted HB docking strategy facilitates fast interfacial ion transport kinetics and enables high reversibility, with a substantially prolonged symmetric cell lifespan exceeding 5000 h. This work markedly advances the efficient and reversible zinc-based batteries.

Möbius Solvation Structure for Zinc-Ion Batteries

Zinc-ion batteries (ZIBs) have promising prospects in energy storage field, but the water molecules in aqueous electrolytes significantly compromise the stability of the anode and cathode interfaces and hinder the low-temperature performance. Herein, water-in-oil type Möbius polarity topological solvation composed of oil, water, and amphiphilic salt are first-ever pioneered, forming the surfactant-free microemulsion electrolyte (SFMEE). This water-in-oil type Möbius solvation structure, characterized by its distinct inner and outer layers and a polarity inversion feature, successfully connects the non-polar phase with the polar phase, eliminating the need for surfactants to reduce costs and system complexity. The amphiphilic anion of salt creates a polarity singularity and stabilizes the polarity-reversed encapsulation. The outer oil layer disrupts the cohesive polarity network of water and constructs a polarity-reversed cage to restrict water. A series of SFMEE combinations are investigated and then directly applied to ZIBs, confirming excellent universality and durability of this design. The Zn||NVO (NaV₃O₈·1.5H₂O) cells using SFMEE can stably cycle for 4000 cycles with a capacity of 125 mAh g-1 and 86.8% capacity retention. This discovery of Möbius solvation structure unlock unprecedented levels of electrolyte design and illuminate the development of next-generation high-performance energy storage systems.

Building Powerful Zinc-Ion Hybrid Capacitors by an Energy Drink-Inspired Strategy

Numerous modification strategies have been proposed to enhance the performance of the Zn anode and carbon cathode in aqueous zinc-ion hybrid capacitors (ZIHCs). However, one efficient strategy to modify both the anode and cathode is still lacking. Herein, taurine (Tau), the key ingredient of energy drinks, is used as the electrolyte additive and carbon precursor for ZIHCs simultaneously. As the electrolyte additive, Tau achieves the preferential growth of Zn (002) plane by preferentially adsorbing on other crystal planes. Moreover, Tau accelerates Zn2+ transference kinetics by regulating the Zn2+ solvation structure and constructs a functional solid electrolyte interphase layer, enabling suppressed hydrogen evolution, inhibited corrosion reaction, and dendrite-free deposition. The Zn//Zn cells using the Tau-modified·ZnSO4 electrolyte (Tau-ZSO) can stably work for 1000 h at 76.95% depth of discharge at room temperature and 5200 h at -10 °C. Meanwhile, the taurine-derived carbon (Tau-C) exhibits N, S heteroatom doping, hierarchical porous structure, and high specific surface area, which contributes to a high cathode capacity. By using the Tau-C cathode, limited Zn anode (10 µm), and the Tau-ZSO electrolyte, the assembled ZIHCs demonstrate reduced polarization and high discharge capacities (119.4 mA h g-1 under 3 A g-1 at room temperature and 80.0 mA h g-1 under 1 A g-1 at -10 °C) with high energy density of 101.1 Wh kg-1 and long lifetime (operating stably over 2000 cycles).

Aqueous Biphasic Electrolyte Enabling Self-Adaptation of Mutually Exclusive Electrolyte Requirements for a Zn Anode and a Cathode

Aqueous Zn-based batteries, the coupling of a zinc anode and a cathode in aqueous electrolytes, are promising for large-scale energy storage. However, the preference of these two electrodes in aqueous zinc sulfate electrolytes with different concentrations exhibits inherent contradictions, which are enhanced rapidly at increased temperatures, impeding their sustainable applications. Herein, we took a zinc metal anode and a vanadium-based cathode as an example and developed an aqueous biphasic electrolyte (ABE) that utilized the distinct ion concentration contrast characteristics between the two phases to simultaneously fulfill the mutually exclusive environmental requirements for cathodes and anodes. The ABE substantially improved the stability of the full battery, which demonstrated a stable cycling performance for up to 1000 cycles at a current density of 5 A g-1 at an increased temperature of 60 °C. A battery prototype with high-voltage output and energy expandability was also developed, providing a promising model for future large-scale applications of ABEs.

Fundamentals, Advances and Perspectives in Designing Eutectic Electrolytes for Zinc-Ion Secondary Batteries

Zinc-ion secondary batteries have been competitive candidates since the "post-lithium-ion" era for grid-scale energy storage, owing to their plausible security, high theoretical capacity, plentiful resources, and environment friendliness. However, many encumbrances like notorious parasitic reactions and Zn dendrite growth hinder the development of zinc-ion secondary batteries remarkably. Faced with these challenges, eutectic electrolytes have aroused notable attention by virtue of feasible synthesis and high tunability. This review discusses the definition and advanced functionalities of eutectic electrolytes in detail and divides them into nonaqueous, aqueous, and solid-state eutectic electrolytes with regard to the state and component of electrolytes. In particular, the corresponding chemistry concerning solvation structure regulation, electric double layer (EDL) structure, solid-electrolyte interface (SEI) and charge/ion transport mechanism is systematically elucidated for a deeper understanding of eutectic electrolytes. Moreover, the remaining limitations and further development of eutectic electrolytes are discussed for advanced electrolyte design and extended applications.

Water-Deficient Interface Induced via Hydrated Eutectic Electrolyte with Restrictive Water to Achieve High-Performance Aqueous Zinc Metal Batteries

The development of aqueous zinc metal batteries (AZMBs) is hampered by dendrites and side reactions induced by reactive H2O. In this study, a hydrated eutectic electrolyte with restrictive water consisting of zinc trifluoromethanesulfonate (Zn(OTf)2), 1,3-propanediol (PDO), and water is developed to improve the stability of the anode/electrolyte interface in AZMBs via the formation of a water-deficient interface. Additionally, PDO participates in the Zn2+ solvation structure and inhibits the movement of water molecules. PDO also preferentially adsorbs along the Zn (100) plane, thereby inducing the formation of the organic/inorganic SEI layer that enables the cycle life of a Zn//Zn symmetric cell to reach 3000 h at 1 mA cm-2 and 1 mAh cm-2. Further, interfacial modulation by the eutectic electrolyte improves the cycling stability of Zn//V2O5 and Zn//VO2 cells. Particularly, the specific capacity of a Zn//V2O5 cell with the eutectic electrolyte is 1.7 times that of a cell with the 2M Zn(OTf)2 electrolyte, with a capacity retention of 93% after 100 cycles at 0.5 A g-1. This study provides a new perspective on the electrolyte modification strategies for AZMBs, highlighting the potential of PDO-8 electrolyte in developing aqueous energy storage devices with excellent cycling stability.

How the Kinetic Balance Between Charge-Transfer and Mass-Transfer Influences Zinc Anode Stability: An Ultramicroelectrode Study

Aqueous zinc-metal batteries (AZMBs) represent a promising frontier in battery technology, offering sustainable and safe alternatives to traditional non-aqueous batteries. Despite their potential, understanding the kinetics of zinc electrodeposition-a critical factor in AZMB performance-remains underexplored. Utilizing voltammetry on ultramicroelectrodes, we investigate how scan rate influences key processes of nucleation and growth during Zn2+ electrodeposition. The findings highlight the efficacy of the Butler-Volmer formulation in capturing electron-transfer kinetics, contrasting with complex electron transfer kinetic models used for non-aqueous battery chemistries. We clearly demonstrate that there is a strong dependence of scan rate on the measured value of kinetic parameters (exchange current). To accurately probe the charge transfer kinetics, it is essential to apply fast scan voltammetry to decouple the influence of mass transfer, ensuring that the measured current is independent of the scan rate. Furthermore, by studying a model electrolyte additive, the intricate balance between charge transfer and mass transfer dynamics is unveiled, and this information is crucial for enhancing the stability of zinc metal anodes. These insights pave the way for developing advanced electrolyte and current collector formulations, promising enhanced cyclability and sustainability in zinc metal batteries.

Delocalized Electron Engineering of MXene-Immobilized Atomic Catalysts toward Fast Desolvation and Dendritic Inhibition for Low-Temperature Zn Metal Batteries

Rechargeable low-temperature aqueous zinc metal batteries (LT-AZMBs) are considered as a competitive candidate for next-generation energy storage systems owing to increased safety and low cost. Unfortunately, sluggish desolvation kinetics of hydrated [Zn(H2O)x]2+ and inhomogeneous ion flux cause detrimental hydrogen evolution reactions (HER) and Zn dendrite growth. Herein, the atomic iron well-implanted onto MXene via defect capture (SAFe@MXene) has been initially proposed to modulate Zn plating. The SAFe@MXene serves as kinetic promoters to enhance interfacial desolvation of [Zn(H2O)x]2+ to prevent HER and uniformizes Zn2+ flux for smooth deposition, as confirmed by theoretical simulation, Raman and electrochemical tests. Consequently, under 0 °C, the SAFe@MXene-modulated Zn electrodes deliver long-term stability of 800 h with lower overpotentials even at 5 mA cm-2 or higher plating/stripping capacity. The full cell with a MnO2 cathode stabilizes a high capacity-retention of nearly 100% after 1000 cycles at 1 A g-1, suggesting great promise for high-performance LT-AZMBs.

A parts-per-million scale electrolyte additive for durable aqueous zinc batteries

Zinc-ion batteries have demonstrated promising potential for future energy storage, whereas drawbacks, including dendrite growth, hydrogen evolution reaction, and localized deposition, heavily hinder their development for practical applications. Herein, unlike elaborated structural design and electrolyte excogitation, we introduce an effective parts-per-million (ppm)-scale electrolyte additive, phosphonoglycolic acid (PPGA), to overcome the intrinsic issues of zinc negative electrode in mild acidic aqueous electrolytes. Profiting from absorbed PPGA on zinc surface and its beneficial interaction with hydrogen bonds of adjacent water molecules, stable symmetric stripping/plating of zinc in aqueous ZnSO4 electrolyte at around 25 oC was achieved, procuring 362 and 350 days of operation at 1 mA cm-2, 1 mAh cm-2 and 10 mA cm-2, 1 mAh cm-2, respectively. As a proof-of-concept, an Ah-level Zn||Zn0.25V2O5·nH2O pouch cell examined the validity of PPGA and sustained 250 cycles at 0.2 A g-1 and around 25 oC without capacity loss. The Zn||Br2 redox flow battery demonstrated an operation of over 800 h at 40 mA cm-2, 20 mAh cm-2 with an average coulombic efficiency of 98%, which is attributed to restrained dendrite growth and side effects. This work is believed to open up new ways forward for knowledge of electrolyte additive engineering.

Tailoring the Solvation of Aqueous Zinc Electrolytes by Balancing Kosmotropic and Chaotropic Ions

Aqueous zinc (Zn) batteries (AZBs) have emerged as a highly promising concept for grid-scale electrochemical energy storage due to the prospects of high safety, low cost, and competitive energy density. However, the commonly employed electrolytes, at ca. 0.5-2 M salt concentration, significantly limit the cycling stability due to the uncontrolled hydrogen evolution reaction (HER). This originates from the plentiful access of free water molecules that become hydrolyzed. As a remedy, highly concentrated electrolytes, ca. 10 m and higher, have been suggested by means of altering the local solvation, promoting Zn2+-anion rather than Zn2+-H2O coordination, but this renders high viscosity electrolytes with reduced ion transport. Here, by balancing a combination of kosmotropic and chaotropic ions, specifically acetate (Ac) and guanidinium (Gua), it is possible to tailor their strong and weak coordination with water, respectively. This strategy results in a weakly solvated electrolyte with improved ion transport properties alongside stabilization of the Zn metal anode. Furthermore, our electrolyte also enhances the cathode stability, rendering an overall increase in the battery lifetime and performance. Hence, this electrolyte design strategy can be applied to the development of a new generation of AZBs.

Weakly Solvating Cyclic Ether-Based Deep Eutectic Electrolytes for Stable High-Temperature Lithium Metal Batteries

Deep eutectic electrolytes (DEE) have emerged as an innovative approach to address the instability and safety issues of lithium metal batteries at elevated temperatures. However, in practice, there is often an undesirable incompatibility between the eutectic mixture and electrodes, and also an insufficient reduction stability of DEE due to the increased Li+ concentration. Herein, we designed a new DEE by utilizing weakly solvating tetrahydropyran (THP) solvent. Due to the high reduction resistance of THP and concentrated lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), this DEE demonstrates enhanced compatibility with Li metal anode and high temperature tolerance with LiMn2O4 cathode. The Li||LiMn2O4 cell (1.6 mAh cm-2) shows a high capacity retention of 96.02 % after 600 cycles at room temperature. More importantly, this Li||LiMn2O4 cell achieves a remarkable high-temperature performance with a high capacity retention of 91.72 % after 120 cycles and low self-discharge after storage for 240 hours at a high temperature of 55 °C, which is critical for LiMn2O4 cathode. Overall, this electrolyte design provides an alternative pathway for the development of DEEs for high-temperature and high-voltage lithium metal batteries, which can also be expanded to other batteries.

Dissolution, solvation and diffusion in low-temperature zinc electrolyte design

Aqueous zinc-based batteries have garnered the attention of the electrochemical energy storage community, but they suffer from electrolytes freezing and sluggish kinetics in cold environments. In this Review, we discuss the key parameters necessary for designing anti-freezing aqueous zinc electrolytes. We start with the fundamentals related to different zinc salts and their dissolution and solvation behaviours, by highlighting the effects of anions and additives on salt solubility, ion diffusion and freezing points. We then focus on the complex structures and energetics of cation-anion-solvent interaction. We also evaluate the prevailing strategies to improve the performance of electrolytes at low temperatures, with a discussion on the kinetics of plating and stripping of zinc anodes and charge storage in various cathode materials. Furthermore, we consider the current challenges and envisage future research directions in cold-resistant aqueous electrolyte formulations for zinc batteries.

Advances in polysaccharide-based conductive hydrogel for flexible electronics

Polysaccharides, being the most abundant natural polymers, play a pivotal role in the development of hydrogel materials. Polysaccharide-based conductive hydrogels have found extensive applications in flexible electronics due to their excellent conductivity and biocompatibility. This review highlights recent advancements in this area, starting with an overview of polysaccharide materials such as chitosan, cellulose, starch, cyclodextrin, alginate, hyaluronic acid, and agarose. It then explores different classifications of conductive hydrogels: ionic conductive, electronic conductive, and ionic-electronic composite types. The review also covers key characteristics of these hydrogels, including mechanical properties, self-healing, adhesion, structural color, antibacterial, responsiveness, biocompatibility and anti-swelling. Representative applications, such as flexible sensors, triboelectric nanogenerators, supercapacitors, and flexible electronic wound dressings, are summarized. Finally, the review addresses current challenges and provides guidance for future research, aiming to advance the field of polysaccharide-based conductive hydrogels in flexible electronics.

Ternary Eutectic Electrolyte for Flexible Wide-Temperature Zinc-Ion Batteries from -20 °C to 70 °C

Aqueous Zn-ion batteries (ZIBs) have attracted attention for grid applications due to their cost-effectiveness and high security. However, their lifespan decreases at high temperatures due to declining interfacial stability and increased side reactions. To address these challenges, a ternary deep eutectic solvent-based flexible electrolyte, comprised of Zn(ClO4)2 ⋅ 6H2O, butanedinitrile (BD), and LiCl in an amphoteric polymer matrix, was developed to enable wide-temperature ZIBs working from -20 °C to 70 °C. The interactions among BD, Li+, and zinc hydrate alongside the amphoteric groups on the polyelectrolyte matrix could effectively suppress the interfacial side reactions and Zn dendrites formation. Consequently, the symmetric Zn cell demonstrates exceptional stability across a wide-temperature range, with the ability to survive up to 2780 hours (1 mA cm-2) at 50 °C. Furthermore, the flexible Zn||PANI battery can operate stably over 1000 cycles at 50 °C, boasting an initial specific capacity of 124.8 mAh g-1 and capacity retention rate of 87.9 % (3 A g-1). This work presents an effective strategy for designing high-stability energy storage devices with excellent security features that can function reliably across diverse temperature conditions.

"Anchoring Capture" Effect Mimicking Proline in Hardy Deep-Sea Fish to Stabilize the Zinc Anode with Lower Operating Temperature

The low plating/stripping efficiency of zinc anodes, dendrite growth, and high freezing points of aqueous solutions hinder the practical application of aqueous zinc-ion batteries. This paper proposes a zwitterionic permeable network solid-state electrolyte based on the "anchor-capture" effect to address these problems by incorporating proline (Pro, a biological antifreeze agent) into the electrolyte. Extensive validation tests, Quantum Chemistry (QC) calculations, Molecular Dynamics (MD) Simulations, and ab initio molecular dynamics simulations consistently indicate that the amino groups in proline adsorb onto the Zn metal surface, stabilizing the zinc anode-electrolyte interface, suppressing side reactions from water decomposition, and homogenizing zinc-ion flux. This electrolyte demonstrates excellent reversibility in Zn-Mn2O3 cells and Zn-Zn half-cells, achieving a high coulombic efficiency of over 99.4% across 2000 cycles in Zn-Mn2O3 full cells, and delivering a discharge-specific capacity of 175.2 mAh g-1 at -35 °C and 1 A g-1. Additionally, an appropriate concentration of proline lowers the electrolyte's freezing point to -45 °C through the network's solid-state effect, ensuring the stable operation of the solid-state battery at -35 °C. This innovative concept of network solid-state electrolytes injects new vitality into the development of multifunctional solid-state electrolytes.

Functional Hydrogels for Aqueous Zinc-Based Batteries: Progress and Perspectives

Aqueous zinc batteries (AZBs) hold great potential for green grid-scale energy storage due to their affordability, resource abundance, safety, and environmental friendliness. However, their practical deployment is hindered by challenges related to the electrode, electrolyte, and interface. Functional hydrogels offer a promising solution to address such challenges owing to their broad electrochemical window, tunable structures, and pressure-responsive mechanical properties. In this review, the key properties that functional hydrogels must possess for advancing AZBs, including mechanical strength, ionic conductivity, swelling behavior, and degradability, from a perspective of the full life cycle of hydrogels in AZBs are summarized. Current modification strategies aimed at enhancing these properties and improving AZB performance are also explored. The challenges and design considerations for integrating functional hydrogels with electrodes and interface are discussed. In the end, the limitations and future directions for hydrogels to bridge the gap between academia and industries for the successful deployment of AZBs are discussed.

Challenges and Prospects of Low-Temperature Rechargeable Batteries: Electrolytes, Interfaces, and Electrodes

Rechargeable batteries have been indispensable for various portable devices, electric vehicles, and energy storage stations. The operation of rechargeable batteries at low temperatures has been challenging due to increasing electrolyte viscosity and rising electrode resistance, which lead to sluggish ion transfer and large voltage hysteresis. Advanced electrolyte design and feasible electrode engineering to achieve desirable performance at low temperatures are crucial for the practical application of rechargeable batteries. Herein, the failure mechanism of the batteries at low temperature is discussed in detail from atomic perspectives, and deep insights on the solvent-solvent, solvent-ion, and ion-ion interactions in the electrolytes at low temperatures are provided. The evolution of electrode interfaces is discussed in detail. The electrochemical reactions of the electrodes at low temperatures are elucidated, and the approaches to accelerate the internal ion diffusion kinetics of the electrodes are highlighted. This review aims to deepen the understanding of the working mechanism of low-temperature batteries at the atomic scale to shed light on the future development of low-temperature rechargeable batteries.

Inducing preferential intercalation of Zn2+ in MnO2 with abundant oxygen defects for high-performance aqueous zinc-ion batteries

Unfavorable proton intercalation leading to the generation and shedding of side reaction products is still a major challenge for the performance of manganese-based aqueous zinc-ion batteries (AZIBs). In this study, we present a porous oxygen-deficient MnO2 (Od-MnO2) synthesized through n-butyllithium reduction treatment to induce preferential Zn2+ intercalation, thereby effectively mitigating the adverse consequences of proton intercalation for high-performance AZIBs. Remarkably, Od-MnO2 as a cathode material for AZIBs exhibits a specific capacity of 341 mA h g-1 at 0.1 A g-1 and 139 mA h g-1 at 5 A g-1, and outstanding long-term stability with a capacity retention of 85.4% for over 1200 cycles at 1 A g-1. Moreover, the Zn/Od-MnO2 pouch cell displays decent durability with a capacity retention of ∼90% for over 200 cycles at 1C. Our study opens new opportunities for the rational design of high-performance cathode materials by regulating the electronic structure and optimizing the energy storage process for rechargeable AZIBs.

Unraveling the Anionic Redox Chemistry in Aqueous Zinc-MnO2 Batteries

Activating anionic redox reaction (ARR) has attracted a great interest in Li/Na-ion batteries owing to the fascinating extra-capacity at high operating voltages. However, ARR has rarely been reported in aqueous zinc-ion batteries (AZIBs) and its possibility in the popular MnO2-based cathodes has not been explored. Herein, the novel manganese deficient MnO2 micro-nano spheres with interlayer "Ca2+-pillars" (CaMnO-140) are prepared via a low-temperature (140 °C) hydrothermal method, where the Mn vacancies can trigger ARR by creating non-bonding O 2p states, the pre-intercalated Ca2+ can reinforce the layered structure and suppress the lattice oxygen release by forming Ca-O configurations. The tailored CaMnO-140 cathode demonstrates an unprecedentedly high rate capability (485.4 mAh g-1 at 0.1 A g-1 with 154.5 mAh g-1 at 10 A g-1) and a marvelous long-term cycling durability (90.6 % capacity retention over 5000 cycles) in AZIBs. The reversible oxygen redox chemistry accompanied by CF3SO3 - (from the electrolyte) uptake/release, and the manganese redox accompanied by H+/Zn2+ co-insertion/extraction, are elucidated by advanced synchrotron characterizations and theoretical computations. Finally, pouch-type CaMnO-140//Zn batteries manifest bright application prospects with high energy, long life, wide-temperature adaptability, and high operating safety. This study provides new perspectives for developing high-energy cathodes for AZIBs by initiating anionic redox chemistry.

Modulating Interfacial Zn2+ Desolvation and Transport Kinetics through Coordination Interaction toward Stable Anodes in Aqueous Zn-Ion Batteries

Aqueous Zn-ion batteries (AZIBs) are promising candidates for grid-scale energy-storage applications, but uneven Zn2+ flux distribution and undesirable water-related interfacial side reactions seriously hinder their practical application. Herein, a strategy of regulating the coordination interaction between Zn2+ and artificial interphase layers (AILs) to modulate the interfacial Zn2+ desolvation/transport behaviors and relieve side reactions for building stable Zn anodes is proposed. By selectively choosing appropriate polymers with different functional groups, it is shown that compared with the strong interaction offered by aryl groups in polystyrene-based AILs, cyano groups in polyacrylonitrile (PAN)-based AILs provide a moderate coordination interaction with Zn2+, which not only accelerates interfacial Zn2+desolvation kinetics but also enables efficient Zn2+ transport within AILs. Moreover, the Zn2+ transport kinetics of PAN-based AILs can be further enhanced with the incorporation of an ionic conductor, zinc phosphate (ZP). Because of these advantages, the Zn anodes decorated with the hybrid AILs composed of PAN and ZP can steadily operate for >2000 h at 0.2 mA cm-2 and >350 h at a high current density of 10 mA cm-2. This work provides a valuable guideline for selective design of AILs at the molecular level for durable AZIBs.

Solute-solvent dual engineering toward versatile electrolyte for high-voltage aqueous zinc-based energy storage devices

Manufacturing cost-effective electrolytes featuring high (electro)chemical stability, high Zn anode reversibility, good ionic conductivity, and environmental benignity is highly desired for rechargeable aqueous zinc-based energy storage devices but remains a great challenge. Herein, a solute-solvent dual engineering strategy using lithium bis(trifluoromethane)sulfonimide (LiTFSI) and inexpensive poly(ethylene glycol) (PEG, M n = 200) as a coadditive with an optimized ratio accomplished an all-round performance enhancement of electrolytes. Due to the synergistic inhibition of water activity and Zn2+ solvation structure reorganization by LiTFSI-PEG, as well as a stable F-rich interfacial layer and PEG adsorption on the Zn anode surface, dendrite-free Zn plating/stripping at nearly 100% Coulombic efficiency and stable cycling performance over 2000 h at 0.5 mA cm-2 was achieved. Importantly, the integrated Zn-ion hybrid supercapacitors are endowed with a wide voltage window of 0-2.2 V, superb cycling stability up to 10,000 cycles, and excellent temperature adaptability from -40 °C to 50 °C. The highest cutoff voltage reached 2.1 V in Zn//LiMn2O4 and Zn//VOPO4 full cells with a stable lifespan over 500 cycles. This work provides a promising strategy for the development of aqueous electrolytes with excellent comprehensive properties for zinc-based energy storage.

Achieving dendrite-free growth of Zn anode by electrodepositing on zincophilic gold-furnished mesh for aqueous zinc-ion batteries

Here, we report a gold-furnished mesh as the current collector for Zn electrodeposition, which is used as the anode in aqueous zinc-ion batteries. The anode exhibits excellent cycling performance without obvious dendrite growth, and the full cell shows an outstanding specific capacity and long-term durability, surpassing those of bare Zn.

Organic Cations Texture Zinc Metal Anodes for Deep Cycling Aqueous Zinc Batteries

Manipulating the crystallographic orientation of zinc (Zn) metal to expose more (002) planes is promising to stabilize Zn anodes in aqueous electrolytes. However, there remain challenges involving the non-epitaxial electrodeposition of highly (002) textured Zn metal and the maintenance of (002) texture under deep cycling conditions. Herein, a novel organic imidazolium cations-assisted non-epitaxial electrodeposition strategy to texture electrodeposited Zn metals is developed. Taking the 1-butyl-3-methylimidazolium cation (Bmim+) as a paradigm additive, the as-prepared Zn film ((002)-Zn) manifests a compact structure and a highly (002) texture without containing (100) signal. Mechanistic studies reveal that Bmim+ featuring oriented adsorption on the Zn-(002) plane can reduce the growth rate of (002) plane to render the final exposure of (002) texture, and homogenize Zn nucleation and suppress H2 evolution to enable the compact electrodeposition. In addition, the formulated Bmim+-containing ZnSO4 electrolyte effectively sustains the (002) texture even under deep cycling conditions. Consequently, the combination of (002) texture and Bmim+-containing electrolyte endows the (002)-Zn electrode with superior cycling stability over 350 h under 20 mAh cm-2 with 72.6% depth-of-discharge, and assures the stable operation of full Zn batteries with both coin-type and pouch-type configurations, significantly outperforming the (002)-Zn and commercial Zn-based batteries in Bmim+-free electrolytes.

Recent advances in zinc-ion dehydration strategies for optimized Zn-metal batteries

Aqueous Zn-metal batteries have attracted increasing interest for large-scale energy storage owing to their outstanding merits in terms of safety, cost and production. However, they constantly suffer from inadequate energy density and poor cycling stability due to the presence of zinc ions in the fully hydrated solvation state. Thus, designing the dehydrated solvation structure of zinc ions can effectively address the current drawbacks of aqueous Zn-metal batteries. In this case, considering the lack of studies focused on strategies for the dehydration of zinc ions, herein, we present a systematic and comprehensive review to deepen the understanding of zinc-ion solvation regulation. Two fundamental design principles of component regulation and pre-desolvation are summarized in terms of solvation environment formation and interfacial desolvation behavior. Subsequently, specific strategy based distinct principles are carefully discussed, including preparation methods, working mechanisms, analysis approaches and performance improvements. Finally, we present a general summary of the issues addressed using zinc-ion dehydration strategies, and four critical aspects to promote zinc-ion solvation regulation are presented as an outlook, involving updating (de)solvation theories, revealing interfacial evolution, enhancing analysis techniques and developing functional materials. We believe that this review will not only stimulate more creativity in optimizing aqueous electrolytes but also provide valuable insights into designing other battery systems.

Anion Additive Integrated Electric Double Layer and Solvation Shell for Aqueous Zinc Ion Battery

Aqueous zinc ion batteries (AZIBs) show great potential in large-scale energy storage systems. However, the inferior cycling life due to water-induced parasitic reactions and uncontrollable dendrites growth impede their application. Electrolyte optimization via the use of additives is a promising strategy to enhance the stability of AZIBs. Nevertheless, the mechanism of optimal multifunctional additive strategy requires further exploration. Herein, sodium dodecyl benzene sulfonate (SDBS) is proposed as a dual-functional additive in ZnSO4 electrolyte. Benefiting from the additive, both side reactions and zinc dendrites growth are significantly inhibited. Further, a synchrotron radiational spectroscopic study is employed to investigate SDB- adjusted electric double layer (EDL) near the Zn surface and the optimized solvation sheath of Zn2+. First-principles calculations verify the firm adsorption of SDB-, and restriction of random diffusion of Zn2+ on the Zn surface. In particular, the SDBS additive endows Zn||Zn symmetric cells with a 1035 h ultra-stable plating/stripping at 0.2 mA cm-2. This work not only provides a promising design strategy by dual-functional electrolyte additives for high stable AZIBs, but also exhibits the prospect of synchrotron radiation spectroscopy analysis on surface EDL and Zn2+ solvation shell optimization.

N-Decorated Main-Group MgAl2O4 Spinel: Unlocking Exceptional Oxygen Reduction Activity for Zn-Air Batteries

The development of economical and efficient oxygen reduction reaction (ORR) catalysts is crucial to accelerate the widespread application rhythm of aqueous rechargeable zinc-air batteries (ZABs). Here, a strategy is reported that the modification of the binding energy for reaction intermediates by the axial N-group converts the inactive spinel MgAl2O4 into the active motif of MgAl2O4-N. It is found that the introduction of N species can effectively optimize the electronic configuration of MgAl2O4, thereby significantly reducing the adsorption strength of *OH and boosting the reaction process. This main-group MgAl2O4-N catalyst exhibits a high ORR activity in a broad pH range from acidic and alkaline environments. The aqueous ZABs assembled with MgAl2O4-N shows a peak power density of 158.5 mW cm-2, the long-term cyclability over 2000 h and the high stability in the temperature range from -10 to 50 °C, outperforming the commercial Pt/C in terms of activity and stability. This work not only serves as a significant candidate for the robust ORR electrocatalysts of aqueous ZABs, but also paves a new route for the effective reutilization of waste Mg alloys.

Zigzag Hopping Site Embedded Covalent Organic Frameworks Coating for Zn Anode

Precise design and tuning of Zn hopping/transfer sites with deeper understanding of the dendrite-formation mechanism is vital in artificial anode protective coating for aqueous Zn-ion batteries (AZIBs). Here, we probe into the role of anode-coating interfaces by designing a series of anhydride-based covalent organic frameworks (i.e., PI-DP-COF and PI-DT-COF) with specifically designed zigzag hopping sites and zincophilic anhydride groups that can serve as desired platforms to investigate the related Zn2+ hopping/transfer behaviours as well as the interfacial interaction. Combining theoretical calculations with experiments, the ABC stacking models of these COFs endow the structures with specific zigzag sites along the 1D channel that can accelerate Zn2+ transfer kinetics, lower surface-energy, homogenize ion-distribution or electric-filed. Attributed to these superiorities, thus-obtained optimal PI-DT-COF cells offer excellent cycling lifespan in both symmetric-cell (2000 cycles at 60 mA cm-2) and full-cell (1600 cycles at 2 A g-1), outperforming almost all the reported porous crystalline materials.

Lamellar Nanoporous Metal/Intermetallic Compound Heterostructure Regulating Dendrite-Free Zinc Electrodeposition for Wide-Temperature Aqueous Zinc-Ion Battery

Aqueous zinc-ion batteries are attractive post-lithium battery technologies for grid-scale energy storage because of their inherent safety, low cost and high theoretical capacity. However, their practical implementation in wide-temperature surroundings persistently confronts irregular zinc electrodeposits and parasitic side reactions on metal anode, which leads to poor rechargeability, low Coulombic efficiency and short lifespan. Here, this work reports lamellar nanoporous Cu/Al2Cu heterostructure electrode as a promising anode host material to regulate high-efficiency and dendrite-free zinc electrodeposition and stripping for wide-temperatures aqueous zinc-ion batteries. In this unique electrode, the interconnective Cu/Al2Cu heterostructure ligaments not only facilitate fast electron transfer but work as highly zincophilic sites for zinc nucleation and deposition by virtue of local galvanic couples while the interpenetrative lamellar channels serving as mass transport pathways. As a result, it exhibits exceptional zinc plating/stripping behaviors in aqueous hybrid electrolyte of diethylene glycol dimethyl ether and zinc trifluoromethanesulfonate at wide temperatures ranging from 25 to -30 °C, with ultralow voltage polarizations at various current densities and ultralong lifespan of >4000 h. The outstanding electrochemical properties enlist full cell of zinc-ion batteries constructed with nanoporous Cu/Al2Cu and ZnxV2O5/C to maintain high capacity and excellent stability for >5000 cycles at 25 and -30 °C.

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).

Chelating Additive Regulating Zn-Ion Solvation Chemistry for Highly Efficient Aqueous Zinc-Metal Battery

Aqueous zinc-metal batteries (AZMBs) usually suffered from poor reversibility and limited lifespan because of serious water induced side-reactions, hydrogen evolution reactions (HER) and rampant zinc (Zn) dendrite growth. Reducing the content of water molecules within Zn-ion solvation sheaths can effectively suppress those inherent defects of AZMBs. In this work, we originally discovered that the two carbonyl groups of N-Acetyl-ϵ-caprolactam (N-ac) chelating ligand can serve as dual solvation sites to coordinate with Zn2+, thereby minimizing water molecules within Zn-ion solvation sheaths, and greatly inhibit water-induced side-reactions and HER. Moreover, the N-ac chelating additive can form a unique physical barrier interface on Zn surface, preventing the harmful contacting with water. In addition, the preferential adsorption of N-ac on Zn (002) facets can promote highly reversible and dendrite-free Zn2+ deposition. As a result, Zn//Cu half-cell within N-ac added electrolyte delivered ultra-high 99.89 % Coulombic efficiency during 8000 cycles. Zn//Zn symmetric cells also demonstrated unprecedented long life of more than 9800 hours (over one year). Aqueous Zn//ZnV6O16 ⋅ 8H2O (Zn//ZVO) full-cell preserved 78 % capacity even after ultra-long 2000 cycles. A more practical pouch-cell was also obtained (90.2 % capacity after 100 cycles). This method offers a promising strategy for accelerating the development of highly efficient AZMBs.

Zn-based batteries for sustainable energy storage: strategies and mechanisms

Batteries play a pivotal role in various electrochemical energy storage systems, functioning as essential components to enhance energy utilization efficiency and expedite the realization of energy and environmental sustainability. Zn-based batteries have attracted increasing attention as a promising alternative to lithium-ion batteries owing to their cost effectiveness, enhanced intrinsic safety, and favorable electrochemical performance. In this context, substantial endeavors have been dedicated to crafting and advancing high-performance Zn-based batteries. However, some challenges, including limited discharging capacity, low operating voltage, low energy density, short cycle life, and complicated energy storage mechanism, need to be addressed in order to render large-scale practical applications. In this review, we comprehensively present recent advances in designing high-performance Zn-based batteries and in elucidating energy storage mechanisms. First, various redox mechanisms in Zn-based batteries are systematically summarized, including insertion-type, conversion-type, coordination-type, and catalysis-type mechanisms. Subsequently, the design strategies aiming at enhancing the electrochemical performance of Zn-based batteries are underscored, focusing on several aspects, including output voltage, capacity, energy density, and cycle life. Finally, challenges and future prospects of Zn-based batteries are discussed.

Gel polymer electrolytes for rechargeable batteries toward wide-temperature applications

Rechargeable batteries, typically represented by lithium-ion batteries, have taken a huge leap in energy density over the last two decades. However, they still face material/chemical challenges in ensuring safety and long service life at temperatures beyond the optimum range, primarily due to the chemical/electrochemical instabilities of conventional liquid electrolytes against aggressive electrode reactions and temperature variation. In this regard, a gel polymer electrolyte (GPE) with its liquid components immobilized and stabilized by a solid matrix, capable of retaining almost all the advantageous natures of the liquid electrolytes and circumventing the interfacial issues that exist in the all-solid-state electrolytes, is of great significance to realize rechargeable batteries with extended working temperature range. We begin this review with the main challenges faced in the development of GPEs, based on extensive literature research and our practical experience. Then, a significant section is dedicated to the requirements and design principles of GPEs for wide-temperature applications, with special attention paid to the feasibility, cost, and environmental impact. Next, the research progress of GPEs is thoroughly reviewed according to the strategies applied. In the end, we outline some prospects of GPEs related to innovations in material sciences, advanced characterizations, artificial intelligence, and environmental impact analysis, hoping to spark new research activities that ultimately bring us a step closer to realizing wide-temperature rechargeable batteries.

Improvement of surface stability of Zn anode by a cost-effective ErCl3 additive for realizing high-performance aqueous zinc-ion batteries

Rechargeable aqueous-zinc ion batteries (AZIB) have notable benefits in terms of high safety and low cost. Nevertheless, the challenges, such as dendrite growth, zinc anode corrosion, and hydrogen evolution reaction, impede its practical implementation. Hence, this study proposes the introduction of an economical ErCl3 electrolyte additive to stabilize the Zn anode surface and address the aforementioned issues. The introduced Er3+ will cover the raised zinc dendrite surface and weaken the "tip effect" on the surface of the zinc anode via the "electrostatic shielding" effect. Simultaneously, the introduced Cl- can reduce the polarization of the zinc anode. Due to the synergistic effect of Er3+ and Cl-, the zinc anode corrosion, dendrite growth and hydrogen evolution have been efficiently inhibited. As a result, the Zn||Zn-symmetric battery using ErCl3 additive can stably cycle for 1100 h at 1 mA cm-2, 1 mAh cm-2, and exhibit a high average coulomb efficiency (99.2 %). Meanwhile, Zn||MnO2 full battery based on ErCl3-added electrolyte also demonstrates a high reversible capacity of 157.1 mAh/g after 500 cycles. Obviously, the capacity decay rate of the full battery is also improved, only 0.113 % per cycle. This study offers a straightforward and economically efficient method for stabilizing the zinc anode and realizing high-performance AZIBs.

Electrolytes Design for Extending the Temperature Adaptability of Lithium-Ion Batteries: from Fundamentals to Strategies

With the continuously growing demand for wide-range applications, lithium-ion batteries (LIBs) are increasingly required to work under conditions that deviate from room temperature (RT). However, commercial electrolytes exhibit low thermal stability at high temperatures (HT) and poor dynamic properties at low temperatures (LT), hindering the operation of LIBs under extreme conditions. The bottleneck restricting the practical applications of LIBs has promoted researchers to pay more attention to developing a series of innovative electrolytes. This review primarily covers the design of electrolytes for LIBs from a temperature adaptability perspective. First, the fundamentals of electrolytes concerning temperature, including donor number (DN), dielectric constant, viscosity, conductivity, ionic transport, and theoretical calculations are elaborated. Second, prototypical examples, such as lithium salts, solvent structures, additives, and interfacial layers in both liquid and solid electrolytes, are presented to explain how these factors can affect the electrochemical behavior of LIBs at high or low temperatures. Meanwhile, the principles and limitations of electrolyte design are discussed under the corresponding temperature conditions. Finally, a summary and outlook regarding electrolytes design to extend the temperature adaptability of LIBs are proposed.

Insight into Sulfur-Containing Zwitter-Molecule Boosting Zn Anode: from Electrolytes to Electrodes

Numerous organic electrolytes additives have been reported to improve Zn anode performance in aqueous Zn metal batteries (AZMBs). However, the modification mechanism needs to be further revealed in consideration of different environments for electrolytes and electrodes during the charge-discharge process. Herein, sulfur-containing zwitter-molecule (methionine, Met) is used as an additive for ZnSO4 electrolytes. In electrolytes, Met reduces the H2O coordination number and facilitates the desolvation process by virtue of functional groups (─COOH, ─NH2, C─S─C), accelerating Zn2+ transference kinetics and decreasing the amount of active water. On electrodes, Met prefers to adsorb on Zn (002) plane and further transforms into a zincophilic protective layer containing C─SOx─C through an in situ electrochemical oxidization, suppressing H2 evolution/corrosion reactions and guiding dendrite-free Zn deposition. By using Met-containing ZnSO4 electrolytes, the Zn//Zn cells show superior cycling performance under 30 mA cm-2/30 mA h cm-2. Moreover, the full cells Zn//NH4V4O10 full cells using the modified electrolytes exhibit good performance at temperatures from -8 to 60 °C. Notably, a high energy density of 105.30 W h kg-1 can be delivered using a low N/P ratio of 1.2, showing a promising prospect of Met electrolytes additives for practical use.

Zinc ion Batteries: Bridging the Gap from Academia to Industry for Grid-Scale Energy Storage

Zinc ion batteries (ZIBs) exhibit significant promise in the next generation of grid-scale energy storage systems owing to their safety, relatively high volumetric energy density, and low production cost. Despite substantial advancements in ZIBs, a comprehensive evaluation of critical parameters impacting their practical energy density (Epractical) and calendar life is lacking. Hence, we suggest using formulation-based study as a scientific tool to accurately calculate the cell-level energy density and predict the cycling life of ZIBs. By combining all key battery parameters, such as the capacity ratio of negative to positive electrode (N/P), into one formula, we assess their impact on Epractical. When all parameters are optimized, we urge to achieve the theoretical capacity for a high Epractical. Furthermore, we propose a formulation that correlates the N/P and Coulombic efficiency of ZIBs for predicting their calendar life. Finally, we offer a comprehensive overview of current advancements in ZIBs, covering cathode and anode, along with practical evaluations. This Minireview outlines specific goals, suggests future research directions, and sketches prospects for designing efficient and high-performing ZIBs. It aims at bridging the gap from academia to industry for grid-scale energy storage.

Dynamic Thermostable Cellulosic Triboelectric Materials from Multilevel-Non-Covalent Interactions

Triboelectric materials present great potential for harvesting huge amounts of dispersed energy, and converting them directly into useful electricity, a process that generates power more sustainably. Triboelectric nanogenerators (TENGs) have emerged as a technology to power electronics and sensors, and it is expected to solve the problem of energy harvesting and self-powered sensing from extreme environments. In this paper, a high-temperature-resistant triboelectric material is designed based on multilevel non-covalent bonding interactions, which achieves an ultra-high surface charge density of 192 µC m-2 at high temperatures. TENGs based on the triboelectric material exhibit more than an order of magnitude higher power output (2750 mW m-2 at 200 °C) than the existing devices at high temperatures. These remarkable properties are achieved based on enthalpy-driven molecular assembly in highly unbonded states. Thus, the material maintains bond strength and ultra-high surface charge density in entropy-dominated high-temperature environments. This molecular design concept points out a promising direction for the preparation of polymers with excellent triboelectric properties.

Modified Ion Migration via Multi-Ion Competitive Transportation for Stable Aqueous Zn Metal Batteries

The application of metal batteries is seriously affected by active ions transport and deposition stability during operation. This article takes water-based Zn metal electrodes as an example to analyze the factors that affect ion distribution and the impact of ion distribution on electrodeposition morphology through electrochemical model simulation calculation, in situ observation and electrochemical experiment: 1) high concentration will reduce the concentration polarization and the overpotential; 2) The passage of active ions through channels are facilitated by small anion (Cl-) rather than bigger one (SO4 2-), which means small deposition overpotential; 3) The transportability-reaction properties of cations (Zn2+, Li+, Na+ and H+) depends on their concentration, solvent coordination structure, and the energy changes during redox reactions. Based on the diffusion and reaction properties, a Li+ coupled Zn2+ electrolyte is designed to achieve the rapid transportation of doped ions to cover uneven growth sites and maintain a stable interface for the steady deposition of active Zn2+, guiding the interface design for high stability metal batteries in addition to the traditional addition of organic solvents.

A Hydrogel Electrolyte toward a Flexible Zinc-Ion Battery and Multifunctional Health Monitoring Electronics

The compact design of an environmentally adaptive battery and effectors forms the foundation for wearable electronics capable of time-resolved, long-term signal monitoring. Herein, we present a one-body strategy that utilizes a hydrogel as the ionic conductive medium for both flexible aqueous zinc-ion batteries and wearable strain sensors. The poly(vinyl alcohol) hydrogel network incorporates nano-SiO2 and cellulose nanofibers (referred to as PSC) in an ethylene glycol/water mixed solvent, balancing the mechanical properties (tensile strength of 6 MPa) and ionic diffusivity at -20 °C (2 orders of magnitude higher than 2 M ZnCl2 electrolyte). Meanwhile, cathode lattice breathing during the solvated Zn2+ intercalation and dendritic Zn protrusion at the anode interface are mitigated. Besides the robust cyclability of the Zn∥PSC∥V2O5 prototype within a wide temperature range (from -20 to 80 °C), this microdevice seamlessly integrates a zinc-ion battery with a strain sensor, enabling precise monitoring of the muscle response during dynamic body movement. By employing transmission-mode operando XRD, the self-powered sensor accurately documents the real-time phasic evolution of the layered cathode and synchronized strain change induced by Zn deposition, which presents a feasible solution of health monitoring by the miniaturized electronics.

For Zinc Metal Batteries, How Many Electrons go to Hydrogen Evolution? An Electrochemical Mass Spectrometry Study

Despite the advantages of aqueous zinc (Zn) metal batteries (AZMB) like high specific capacity (820 mAh g-1 and 5,854 mAh cm-3 ), low redox potential (-0.76 V vs. the standard hydrogen electrode), low cost, water compatibility, and safety, the development of practically relevant batteries is plagued by several issues like unwanted hydrogen evolution reaction (HER), corrosion of Zn substrate (insulating ZnO, Zn(OH)2 , Zn(SO4 )x (OH)y , Zn(ClO4 )x (OH)y etc. passivation layer), and dendrite growth. Controlling and suppressing HER activity strongly correlates with the long-term cyclability of AZMBs. Therefore, a precise quantitative technique is needed to monitor the real-time dynamics of hydrogen evolution during Zn electrodeposition. In this study, we quantify hydrogen evolution using in situ electrochemical mass spectrometry (ECMS). This methodology enables us to determine a correction factor for the faradaic efficiency of this system with unmatched precision. For instance, during the electrodeposition of zinc on a copper substrate at a current density of 1.5 mA/cm2 for 600 seconds, 0.3 % of the total charge is attributed to HER, while the rest contributes to zinc electrodeposition. At first glance, this may seem like a small fraction, but it can be detrimental to the long-term cycling performance of AZMBs. Furthermore, our results provide insights into the correlation between HER and the porous morphology of the electrodeposited zinc, unravelling the presence of trapped H2 and Zn corrosion during the charging process. Overall, this study sets a platform to accurately determine the faradaic efficiency of Zn electrodeposition and provides a powerful tool for evaluating electrolyte additives, salts, and electrode modifications aimed at enhancing long-term stability and suppressing the HER in aqueous Zn batteries.

Asymmetric Anion Zinc Salt Derived Solid Electrolyte Interphase Enabled Long-Lifespan Aqueous Zinc Bromine Batteries

Organic additives with high-reduction potentials are generally applied in aqueous electrolytes to stabilize the Zn anode, while compromise safety and environmental compatibility. Highly concentrated water-in-salt electrolytes have been proposed to realize the high reversibility of Zn plating/stripping; however, their high cost and viscosity hinder their practical applications. Therefore, exploring low-concentration Zn salts, that can be used directly to stabilize Zn anodes, is of primary importance. Herein, we developed an asymmetric anion group, bi(difluoromethanesulfonyl)(trifluoromethanesulfonyl)imide (DFTFSI- )-based novel zinc salt, Zn(DFTFSI)2 , to obtain a high ionic conductivity and a highly stable dendrite-free Zn anode. Experimental tests and theoretical calculations verified that DFTFSI- in the Zn2+ solvation sheath and inner Helmholtz plane would be preferentially reduced to construct layer-structured SEI films, inhibiting hydrogen evolution and side reactions. Consequently, the Zn| | ${||}$ Zn symmetric cell with 1M Zn(DFTFSI)2 aqueous electrolyte delivers an ultralong cycle life for >2500 h outperforming many other conventional Zn salt electrolytes. The Zn| | ${||}$ Br2 battery also exhibits a long lifespan over 1200 cycles at ~99.8 % Coulombic efficiency with a high capacity retention of 92.5 %. Furthermore, this outstanding performance translates well to a high-areal-capacity Zn| | ${||}$ Br2 battery (~5.6 mAh ⋅ cm-2 ), cycling over 320 cycles with 95.3 % initial capacity retained.

Recent Advances in Low‐Temperature Liquid Electrolyte for Supercapacitors

As one of the key components of supercapacitors, electrolyte is intensively investigated to promote the fast development of the energy supply system under extremely cold conditions. However, high freezing point and sluggish ion transport kinetics for routine electrolytes hinder the application of supercapacitors at low temperatures. Resultantly, the liquid electrolyte should be oriented to reduce the freezing point, accompanied by other superior characteristics, such as large ionic conductivity, low viscosity and outstanding chemical stability. In this review, the intrinsically physical parameters and microscopic structure of low-temperature electrolytes are discussed thoroughly, then the previously reported strategies that are used to address the associated issues are summarized subsequently from the aspects of aqueous and non-aqueous electrolytes (organic electrolyte and ionic liquid electrolyte). In addition, some advanced spectroscopy techniques and theoretical simulation to better decouple the solvation structure of electrolytes and reveal the link between the key physical parameters and microscopic structure are briefly presented. Finally, the further improvement direction is put forward to provide a reference and guidance for the follow-up research.

Diagnosing the Electrostatic Shielding Mechanism for Dendrite Suppression in Aqueous Zinc Batteries

Aqueous zinc electrolytes offer the potential for cheaper rechargeable batteries due to their safe compatibility with the high capacity metal anode; yet, they are stymied by irregular zinc deposition and consequent dendrite growth. Suppressing dendrite formation by tailoring the electrolyte is a proven approach from lithium batteries; yet, the underlying mechanistic understanding that guides such tailoring does not necessarily directly translate from one system to the other. Here, it is shown that the electrostatic shielding mechanism, a fundamental concept in electrolyte engineering for stable metal anodes, has different consequences for the plating morphology in aqueous zinc batteries. Operando electrochemical transmission electron microscopy is used to directly observe the zinc nucleation and growth under different electrolyte compositions and reveal that electrostatic shielding additive suppresses dendrites by inhibiting secondary zinc nucleation along the (100) edges of existing primary deposits and encouraging preferential deposition on the (002) faces, leading to a dense and block-like zinc morphology. The strong influence of the crystallography of Zn on the electrostatic shielding mechanism is further confirmed with Zn||Ti cells and density functional theory modeling. This work demonstrates the importance of considering the unique aspects of the aqueous zinc battery system when using concepts from other battery chemistries.