A self-accelerating hydroxide nanoarray cathode for fast-charging Ni–Zn batteries

The development of high-rate cathode materials is critical for realizing fast-charging battery technologies. However, the existing electrodes inevitably undergo compositional and structural changes during battery cycling, which generally lead to material failure and battery performance degradation. In this study, we proactively harnessed such physical changes to design a cathode material with self-accelerating characteristics, enabling stable fast-charging Ni-Zn batteries. Specifically, a ternary NiMnZn hydroxide nanoarray cathode was fabricated and tested. During cycling of the Ni–Zn battery at 5 C, its discharge capacity increased from 169.6 to 225.7 mAh g−1 over the first 50 cycles, subsequently achieving stable charge–discharge for 500 cycles (capacity retention: 92.29%, Coulombic efficiency: 99.99%). In contrast, the NiMn hydroxide cathode retained only 39.03% of its initial capacity after 200 cycles with a Coulombic efficiency of 99.53% under the same test conditions. The self-accelerating characteristic of NiMnZn hydroxide cathode arose from the spontaneous dissolution of the Zn component during cycling, which generated oxygen vacancies and reduced the valence states of Ni/Mn active species. In situ electrochemical impedance spectroscopy studies revealed that the spontaneous dissolution of Zn component enhanced the electrical conductivity of the cathode and reduced its charge transfer resistance, thereby triggering the self-accelerating behavior of such a fast-charging Ni–Zn battery cathode.