Unravel the influences of Ni substitution on Co-based electrodes for rechargeable alkaline Zn–Co batteries

The performance of Zn–Co batteries is hindered by some critical issues, such as the low electric conductivity and poor valence-change ability, restricting the utilization of the active material. This study aims at improving the electrochemical performance of the battery via substituting Ni on the Co₃O₄ electrode. A novel multiple self-assembled nanowire-nanosheet structure is constructed with the substitution of 10% Ni, the high electric conductivity and decent valence change-ability push the electrode to the top-tier among the reported Zn–Co batteries, including the high capacity of 272 mAh g⁻¹, high energy density of 448 Wh kg⁻¹, and excellent rate performance with a capacity retention ratio of 72.5% after even 40-fold increase of the current density. In terms of the cycle stability, it can operate well with a capacity retention ratio of 85.3% before the 1000th cycle, while dramatically decay in the subsequent cycles. More importantly, to illuminate the role of Ni substitution on the capacity decay, a systematic investigation on the Ni substituted Co₃O₄ electrode is conducted for the first time. The capacity decay mechanism is proposed as the decreased low valence species, microstructure collapse, and irreversible phase transition with an increase of the Ni substitution ratio. This work offers insights to develop high-performance and durable electrodes for Zn–Co batteries.