High hydrophilic/zincophilic interpenetrating double-network hydrogel electrolyte constructing stable organic-inorganic anode interface toward nickel–zinc batteries

Abstract

Nickel–zinc batteries are attracting growing interest due to flame-retardant properties, high discharge voltage and attractive power density. However, the interface side reactions, dendrite growth and redistribution of the highly soluble [Zn(OH)₄]²⁻ on the electrode surface result in the degradation of the zinc anode. Herein, an interpenetrating polymer network hydrogel (denoted as IPN–Alg) is prepared by introducing alginate and a stable organic–inorganic interface is successfully constructed in situ on the zinc anode. The high hydrophilicity and zincophilicity of IPN–Alg hydrogel electrolyte provide the inherent advantages in reducing the amounts of free water to suppress the side reactions and being preferentially adsorbed on the zinc anode to construct a water-poor interface. Moreover, due to the topological entanglement in the interpenetrating structures, the IPN–Alg hydrogel electrolyte exhibits excellent mechanical strength. Combining with the in situ formation of the inorganic protective layer of Ca(Zn(OH)₃)₂·2H₂O, the robust organic–inorganic interface layer can effectively inhibit the dendrite growth and reduce the diffusion and redistribution of [Zn(OH)₄]²⁻. Hence, the Zn||Zn symmetric cell and nickel–zinc pouch battery based on IPN–Alg hydrogel electrolyte demonstrate ultralong cycling life of more than 800 h at 2 mA cm⁻² and 1100 h (563 cycles) at 4 C, 40% DOD (depth of discharge), respectively.