Engineering Sulfur Vacancies of Ni₃S₂ Nanosheets as a Binder-Free Cathode for an Aqueous Rechargeable Ni-Zn Battery

The development of an efficient metal sulfide cathode is of great importance and an ongoing challenge for the practical application of an aqueous rechargeable Ni-Zn battery. Herein, Ni3S2 nanosheets with abundant sulfur vacancies (r-Ni3S2) have been successfully prepared via hydrothermal reaction and surface engineering, which are further employed as the binder-free cathode of the aqueous Ni-Zn battery. Benefitting from the features of substantially improved electrical conductivity, low band gap, abundant active sites, and good intrinsic capacity, the r-Ni3S2 electrode delivers an impressive reversible specific capacitance (1621.6 F g–1 at 0.2 A g–1) and extraordinary rate capability (62.1% retention under 8 A g–1). Moreover, the aqueous rechargeable r-Ni3S2//Zn battery exhibits a remarkable specific capacity (240.8 mAh g–1 at 1 A g–1) and preeminent cycling durability (only 8.4% decay after 3000 cycles). Besides, a glorious energy density of 419.6 Wh kg–1 together with a peak power density of 1.84 kW kg–1 could be achieved, surpassing a significant percentage of the reported Ni-Zn batteries. The results reveal that the r-Ni3S2 cathode with abundant sulfur vacancies and the adopted facile approach possesses huge promotion potential for Ni-Zn batteries and is promising to numerous electronics and electric vehicle applications in the future.