Constructing aqueous rechargeable Zn//Co battery with hierarchical structural cobalt phosphate octahydrate for high-performance energy storage

Abstract

It is still a strong desire to develop aqueous rechargeable zinc-cobalt batteries with high energy density, power density and excellent stability. Cobalt phosphate hydrate electrodes are prepared in situ on nickel foam by one-step hydrothermal method. By adjusting the urea content in the preparation process, the electrode materials are transformed from micron-sheet cobalt phosphate tetrahydrate to weakly crystallized cobalt phosphate octahydrate (CP-3) with hierarchical structure of nanoneedles loading on micron-sheet. The CP-3 sample has a larger specific surface area, rich micropore-mesoporous pore distribution, better electrical conductivity and wider crystal plane spacing, which can better expose the reactive site, accelerate the electrochemical reaction kinetics process and improve the structural stability of the electrode. Under the same test conditions, compared with CP-650//Zn battery composed of anhydrous cobalt phosphate (CP-650), CP-3//Zn battery shows higher energy density (2.08 mWh/cm2 vs. 0.86 mWh/cm2), peak power density (96.34 mW/cm2 vs. 70.74 mW/cm2) and better capacity retention rate (86.15% vs. 60% after 3000 cycles). The corresponding quasi-solid CP-3//Zn battery also shows high area capacity and good cycle stability, which can light up a red LED indicator. This work paves a foundation road for the development of high performance zinc-cobalt battery based on cobalt phosphate.