"Two Birds with One Stone": F Doping Ni-Co Hydroxide as High-Performance Cathode Material for Aqueous Zn Batteries.

Abstract

Cathode materials have impeded the development of aqueous Zn batteries (AZBs) for a long time due to their low capacity and poor cycling stability. Here, a “two birds with one stone” strategy is devised to optimize the Ni–Co hydroxide cathode material (NCH) for AZBs, which plays an essential role in both composition adjustment and morphology majorization. The F-doped Ni–Co hydroxide (FNCH) exhibits a unique nanoarray structure consisting of the 2D flake-like unit, furnishing abundant active sites for the redox reaction. A series of analyses prove that FNCH delivers improved electrical conductivity and enhanced electrochemical activity. Contributing to the unique morphology and adjusted characteristics, FNCH presents a higher discharge-specific capacity, more advantageous rate capability and competitive cycling stability than NCH. As a result, an aqueous Zn battery assembled with a FNCH cathode and Zn anode exhibits a high capacity of 0.23 mAh cm−2 at 1 mA cm−2, and retains 0.10 mAh cm−2 at 10 mA cm−2. More importantly, the FNCH–Zn battery demonstrates no capacity decay after 3000 cycles with a conspicuous capacity of 0.15 mAh cm−2 at 8 mA cm−2, indicating a superior cycling performance. This work provides a facile approach to develop high-performance cathodes for aqueous Zn batteries.