Promoting OH⁻ Adsorption and Diffusion Enables Ultrahigh Capacity and Rate Capability of Nickel Sulfide Cathode for Aqueous Alkaline Zn‐Based Batteries

Abstract Aqueous alkaline Zn‐based batteries (AAZBs) possess great promise for large‐scale applications thanks to their higher discharging plateau and unique reaction mechanism. However, the capacity and rate capability of Ni‐based cathodes are still unsatisfactory due to their insufficient OH⁻ adsorption and diffusion ability. Herein, heterostructured Ni₃S₂/Ni(OH)₂ nanosheets with outstanding electrochemical performance are synthesized via a facile chemical etching strategy. The heterostructured Ni₃S₂/Ni(OH)₂ nanosheet cathode shows significantly increased capacity and rate capability due to its boosted OH⁻ adsorption and diffusion ability compared to Ni₃S₂. Consequently, the assembled Zn//Ni₃S₂/Ni(OH)₂ cell can deliver an ultrahigh capacity of 2.26 mAh cm⁻², an excellent rate performance (0.91 mAh cm⁻² at 100 mA cm⁻²) and a satisfying cycling stability (1.01 mAh cm⁻² at 20 mA cm⁻² after 500 cycles). Moreover, a prominent energy density of 3.86 mWh cm⁻² is obtained, which exceeds the majority of recently reported AAZBs. This work is expected to provide a new modification direction for developing high‐performance nickel sulfide cathode for AAZBs.