Construction And Application Research In Zinc Metal Battery Of Multiple Cross-linked Hydrogel Electrolytes

Zinc metal batteries（ZMBs）are prospected to be one of the most promising candidates for large-scale energy storage systems,owing to their intrinsic properties of low cost,non-flammability and high theoretical capacity(820 m Ah g^-1).Nonetheless,the commercialization of ZMBs is severely hampered by the issues of Zn dendrite and parasitic reactions,which is caused by the thermodynamically instability of Zn metal in neutral and mildly acid electrolytes.Although the strategy of hydrogel electrolyte can alleviate these problems to some extent,unfortunately,ZMBs still cannot achieve long cycling stability at high depths of discharge（DOD）due to the inhomogeneity of deposition/exfoliation at the electrode-electrolyte interface.Based on these,this paper aims to design and develop a novel hydrogel electrolyte with multiple cross-linked networks to achieve dendrite-free and long-lifespan zinc metal anode.And using multi-scale characterization and theoretical simulation calculations to explore its mechanism of regulating the uniform deposition at the electrode-electrolyte interface.The details of this paper are as follows:1.A double-network hydrogel electrolyte（BC-PAAm）consisting of bacterial cellulose nanofibers and polyacrylamide is prepared via a soaking-free method to protect the zinc anode.Due to the abundant hydroxyl groups in BC and the cross-linked structure of the double-network,the BC-PAAm hydrogel electrolyte shows high ionic conductivity(18.1 m S cm^-1),excellent tensile strength（255 KPa）and good elasticity（1310%）.In addition,the BC-PAAm alleviates the corrosion and dendrite growth to some extent,effectively improving the cycling reversibility of the Zn anode.Thus,the BC-PAAm based Zn//Cu half-cells exhibit a high coulomb efficiency of 99.2%at a current density of 1 m A cm^-2,and the Zn//Zn symmetric cells at 0.5 m A cm^-2/0.5 m Ah cm^-2exhibit a life-span of 4000 h with significantly improved cycling stability.2.A novel polyacrylamide/graphene oxide/agarose（PGA）hydrogel electrolyte with a unique multiple cross-linked network is designed,enabling ultra-long lifespan and dendrite-free Zn metal anode.The synergetic integration of GO nanosheets and double network structure endows PGA hydrogel electrolyte with a high ionic conductivity of 22.5 m S cm^-1 and excellent mechanical performance（0.794 MPa）.Besides,the PGA with abundant hydrophilic groups and stable three-dimensional（3D）network structure effectively constrains Zn²⁺ions diffusion laterally along the Zn surface,which simultaneously prohibits water-induced corrosion that significantly enhance Zn anode reversibility.Theoretical simulations and experiments efficiently reveal that the PGA is capable of optimizing de-solvation kinetics and harmonizing Zn²⁺flux at the electrolyte–electrode interface,ensuring uniform Zn deposition behavior.Consequently,an ultra-long lifespan of 7800 h is achieved in the symmetric cell with PGA.Even at a high Zn utilization of 42.7%,it still delivers a stable cycling over 1100 h with a much lower voltage polarization.Additionally,the PGA-based flexible cells exhibit good cycling performance under different bending angles and can still operate normally under harsh operating conditions such as shearing and puncturing,proving its high safety for practical applications.