The dendritic issue in aqueous zinc‐ion batteries (ZBs) using neutral/mild electrolytes has remained an intensive controversy for a long time: some researchers assert that dendrites severely exist while others claim great cycling stability without any protection. This issue is clarified by investigating charge/discharge‐condition‐dependent formation of Zn dendrites. Lifespan degradation (120 to 1.2 h) and voltage hysteresis deterioration (134 to 380 mV) are observed with increased current densities due to the formation of Zn dendrites (edge size: 0.69–4.37 µm). In addition, the capacity is also found to remarkably affect the appearance of the dendrites as well. Therefore, at small current densities or loading mass, Zn dendrites might not be an issue, while the large conditions may rapidly ruin batteries. Based on this discovery, a first‐in‐class electrohealing methodology is developed to eliminate already‐formed dendrites, generating extremely prolonged lifespans by 410% at 7.5 mA cm–2 and 516% at 10 mA cm–2. Morphological analysis reveals that vertically aligned Zn dendrites with sharp tips gradually become passivated and finally generate a smooth surface. This developed electrohealing strategy may promote research on metal dendrites in various batteries evolving from passive prevention to active elimination, rescuing in‐service batteries in situ to achieve elongated lifetime.

Working voltage substantially limits the practical applications of batteries. This review emphasizes on the voltage issue of aqueous metal-ion batteries.

No abstract

safety, and low cost. [1][2][3][4][5] However, the strong electrostatic interaction with host materials originating from divalent chemistry leads to low output voltage, poor reversibility, and especially sluggish kinetics. Various cathode materials have been developed to navigate these challenges. Currently, the most studied cathode active materials are manganesebased [6][7][8][9] and vanadium-based [10][11][12][13] composites. Nonetheless, relative low operating voltage and poor rate performance remains as issues. To reach the operating voltage of electronic devices, multiple batteries must be connected in series. This practice increases the volume of battery and causes energy loss. Furthermore, poor rate capability limits application of Zn-ion batteries in high-power appliances.The Prussian blue analogues (PBAs) possessing a 3D open framework with large interstitial sites, [4][5][6][7][8][9][10][11][12][13][14][15][16] are considered as a promising host material for reversible Zn-ion intercalation/deintercalation with fast charge/discharge properties and high operational voltage, which is ascribed to its ideal crystal structure and desirable electrochemical properties. [17] Recently, hexacyanometallates with a typical formula of A x M′[M″(CN) 6 ] y ⋅nH 2 O (simply denoted as M′/M″ PBA) are investigated as cathode active materials for aqueous batteries including Li-, Na-, Mg-, Ca-, and Zn-ion batteries, where the A Herein, a two-species redox reaction of Co(II)/Co(III) and Fe(II)/Fe(III) incorporated in cobalt hexacyanoferrate (CoFe(CN) 6 ) is proposed as a breakthrough to achieve jointly high-capacity and high-voltage aqueous Zn-ion battery. The Zn/CoFe(CN) 6 battery provides a highly operational voltage plateau of 1.75 V (vs metallic Zn) and a high capacity of 173.4 mAh g −1 at current density of 0.3 A g −1 , taking advantage of the two-species redox reaction of Co(II)/Co(III) and Fe(II)/Fe(III) couples.Even under extremely fast charge/discharge rate of 6 A g −1 , the battery delivers a sufficiently high discharge capacity of 109.5 mAh g −1 with its 3D opened structure framework. This is the highest capacity delivered among all the batteries using Prussian blue analogs (PBAs) cathode up to now. Furthermore, Zn/CoFe(CN) 6 battery achieves an excellent cycling performance of 2200 cycles without any capacity decay at coulombic efficiency of nearly 100%. One further step, a sol-gel transition strategy for hydrogel electrolyte is developed to construct high-performance flexible cable-type battery. With the strategy, the active materials can adequately contact with electrolyte, resulting in improved electrochemical performance (≈18.73% capacity increase) and mechanical robustness of the solid-state device. It is believed that this study optimizes electrodes by incorporating multi redox reaction species for high-voltage and high-capacity batteries.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.

Current aqueous Zn batteries (ZBs) seriously suffer from dendrite issues caused by rough electrode surfaces. Despite significant efforts in prolonging lifespan of these batteries, little effort has been devoted to dendrite elimination in commercial‐grade cathode loading mass. Instead, demonstrations have only been done at the laboratory level (≤2 mg cm−2). Additionally, new dilemmas regarding change of the proton‐storage behavior and interface pulverization have emerged in turn. Herein, hydrogen‐substituted graphdiyne (HsGDY), with sub‐ångström level ion tunnels and robust chemical stability, is designed as an artificial interface layer to address these issues. This strategy prolongs the symmetric cell lifespan to >2400 h (100 days), which is 37 times larger than without protection (63 h). The simulation of dual fields reveals that HsGDY can redistribute the Zn2+ concentration field by spatially forcing Zn2+ to deviate from the irregular electric field. During practical use, the as‐assembled full batteries deliver a long lifespan 50 000 cycles and remain stable even at a commercial‐grade cathode loading mass of up to 22.95 mg cm−2. This HsGDY‐protection methodology represents great progress in Zn dendrite protection and demonstrates enormous potential in metal batteries.