Novel Charging-Optimized Cathode for a Fast and High-Capacity Zinc-Ion Battery

Abstract

Rechargeable aqueous zinc-ion battery (ZIB) is one of attractive candidates for large-scale energy storage. Its further application relies on the exploitation of high-capacity cathode and the understanding of intrinsic energy storage mechanism. Herein, we report a novel layered K2V3O8 cathode material for ZIB, adopting a strategy of charging firstly to extract part of K-ions from vanadate in initial few cycles, which creates more electrochemical active sites and lowers charge transfer resistance of ZIB system. As results, a considerable specific capacity of 302.8 mAh g-1 at 0.1 A g-1 is achieved, as well as remarkable cycling stability (92.3% capacity retention at 4 A g-1 for 2000 cycles) and good rate capability. Besides, the energy storage mechanism was studied by in-situ X-ray diffraction, in-situ Raman spectra, X-ray photoelectron spectroscopy and inductively coupled plasma. An irreversible K-ions deintercalation in the first charge process is proved. It is believed that this novel ZIB's cathode material and the optimizing strategy will shine lights on developing next-generation large-scale energy storage devices.