Hierarchical Micro‐Nano Sheet Arrays of Nickel–Cobalt Double Hydroxides for High‐Rate Ni–Zn Batteries

Abstract

The rational design of nickel-based cathodes with highly ordered micro-nano hierarchical architectures by a facile process is fantastic but challenging to achieve for high-capacity and high-rate Ni-Zn batteries. Herein, a one-step etching-deposition-growth process is demonstrated to prepare hierarchical micro-nano sheet arrays for Ni-Zn batteries with outstanding performance and high rate. The fabrication process is conducted at room temperature without any need of heating and stirring, and the as-grown nickel-cobalt double hydroxide (NiCo-DH) supported on conductive nickel substrate is endowed with a unique 3D hierarchical architecture of micro-nano sheet arrays, which empower the effective exposure of active materials, easy electrolyte access, fast ion diffusion, and rapid electron transfer. Benefiting from these merits in combination, the NiCo-DH electrode delivers a high specific capacity of 303.6 mAh g^-1 and outstanding rate performance (80% retention after 20-fold current increase), which outperforms the electrodes made of single Ni(OH)₂ and Co(OH)₂, and other similar materials. The NiCo-DH electrode, when employed as the cathode for a Ni-Zn battery, demonstrates a high specific capacity of 329 mAh g^-1. Moreover, the NiCo-DH//Zn battery also exhibits high electrochemical energy conversion efficiency, excellent rate capability (62% retention after 30-fold current increase), ultrafast charge characteristics, and strong tolerance to the high-speed conversion reaction.