Construction of Vertical 2D Open Hierarchical NiCoSx Nanosheet Arrays for High-Performance Alkaline Zinc Batteries

Alkaline nickel zinc batteries feature high safety, low cost and eco-friendly characteristics, making them highly promising for large-scale energy storage deployment. However, their practical application is severely constrained by the cathode’s electrical conductivity, available active sites, and cycling stability. Herein, vertical 2D hierarchical flake-like NiCoSx arrays were in situ grown on nickel foam (NF) via a facile alkali-free solvothermal and in situ sulfidation approach. This highly interconnected and open porous flaky structure significantly shortens the ion diffusion pathways, exposes abundant redox-active sites, and accelerates electron transport, imparting excellent rate performance and superior long-cycle stability to the material. The optimized NiCoSx/NF electrode achieves a high specific capacity of 323 mAh g−1 at 0.5 A g−1, along with excellent capacity retention capability. Assembled with a commercial Zn anode, the NiCoSx/NF//Zn full battery delivers 124 mAh g−1 at 3 A g−1, and maintains 112.5% of the initial capacity after 500 cyclic tests. Moreover, the assembled NiCoSx/NF//Zn full cell possesses a high energy density of 615.2 Wh kg−1 along with a power density of 38.6 kW kg−1 (based on the mass of positive electrode active materials). This unique vertical 2D open hierarchical structure plays a crucial role in enhancing the electrochemical performance of cobalt sulfide cathodes and provides valuable insights for the design of high-performance alkaline zinc-based battery electrodes.