Highly-reversible and recyclable zinc metal batteries achieved by inorganic/organic hybrid separators with finely tunable hydrophilic–hydrophobic balance

Abstract

Aqueous batteries based on zinc metal anodes show great potential in scalable energy storage due to their high specific energy, intrinsic safety and low cost. However, they are currently burdened by the limited cycling stability, which originates from the poor reversibility of zinc anodes especially under the condition of high Zn utilization. To resolve these obstacles, we designed a new inorganic/organic hybrid separator, simplified as P/FS-Z, consisting of a hydrophobic PTFE matrix, a hydrophilic fumed silica filler, and Zn salt via a unique wet-rolling method. Through finely balancing its hydrophilicity and hydrophobicity, the P/FS-Z separator exhibits more balanced mass transfer capability and controllable interface reaction benefiting from three aspects of regulation: desolvation of Zn²⁺, pH of the electrolyte, and hydrophobicity/hydrophilicity of the interface. The newly developed P/FS-Z separators exhibit an ultrahigh accumulative deposition capacity of Zn of up to 12 000 mA h cm⁻², and a record long-term cycling life of 700 h at 80% Zn DOD. More impressively, the P/FS-Z separator is totally recyclable due to its intrinsically high mechanical strength and electrochemical stability. Besides, high-specific-energy and flexible pouch cells under practical conditions are demonstrated for energy-storage and wearable devices, respectively. This report provides both theoretical and experimental guidelines for the research and practical application of separators for aqueous metal batteries.