Achieving synergetic anion-cation redox chemistry in freestanding amorphous vanadium oxysulfide cathodes toward ultrafast and stable aqueous zinc-ion batteries

Flexible aqueous zinc-ion batteries (AZIBs) with high safety and low cost hold great promise for potential applications in wearable electronics, but the strong electrostatic interaction between Zn2+ and crystalline structures, and the traditional cathodes with single cationic redox center remain stumbling blocks to developing high-performance AZIBs. Herein, freestanding amorphous vanadium oxysulfide (AVSO) cathodes with abundant defects and auxiliary anionic redox centers are developed via in situ anodic oxidation strategy. The well-designed amorphous AVSO cathodes demonstrate numerous Zn2+ isotropic pathways and rapid reaction kinetics, performing a high reversible capacity of 538.7 mAhg-1 and high-rate capability (237.8 mAhg-1@40Ag-1). Experimental results and theoretical simulations reveal that vanadium cations serve as the main redox centers while sulfur anions in AVSO cathode as the supporting redox centers to compensate local electron-transfer ability of active sites. Significantly, the amorphous structure with sulfur chemistry can tolerate volumetric change upon Zn2+/H+ insertion and weaken electrostatic interaction between Zn2+ and host materials. Consequently, the AVSO composites display alleviated structural degradation and exceptional long-term cyclability (89.8% retention after 20 000 cycles at 40 Ag-1). This work can be generally extended to various freestanding amorphous cathode materials of multiple redox reactions, inspiring development of designing ultrafast and long-life wearable AZIBs.R.P. and F.C. contributed equally to this work. This work was supported by the National Key R&D Program of China (No. 2020YFB2007402), the Natural Science Foundation of Jiangsu Province (No. BK20220288), and the National Natural Science Foundation of China (No. 12174050 and 12234005), and the Fundamental Research Funds for the Central Universities