Quasi-Solid-State “Water-in-Swelling-Clay” Electrolytes Enabling Ultrastable Aqueous Zinc-Ion Batteries

The poor reversibility of Zn metal anodes arising from water-induced parasitic reactions poses a significant challenge to the practical applications of aqueous zinc-ion batteries (AZIBs). Herein, a novel quasi-solid-state water-in-swelling-clay electrolyte (WiSCE) containing zinc sulfate and swelling clay bentonite (BT) is designed to enable highly reversible Zn metal anodes. AZIB full 2 cells based on the WiSCE exhibit excellent cyclic stability at various current densities, long shelf life, low self-discharge rate, and outstanding high-temperature adaptability. Particularly, the capacity of WiSCE-based AZIB full cells retains 90.47% after 200 cycles at 0.1 A/g, 96.64% after 2000 cycles at 1 A/g, and 88.29% after 5000 cycles at 3 A/g. Detailed density functional theory calculations show that strong hydrogen-bonds are formed between BT and water molecules in the WiSCE. Thus, water molecules are strongly confined by BT particularly within the interlayers, which significantly inhibits water-induced side reactions and thus greatly improves cyclic stability. Compared to the state-of-the-art water-in-salt electrolyte, the WiSCE can provide a significantly higher capacity at the full-cell level with a substantially reduced cost, which is promising for the design of next-generation high-performance AZIBs. This work provides a new direction for developing cost-competitive AZIBs as alternatives in grid-scale energy storage.