Constructing Nanoparticle-Integrated CoWO₄ Microflakes as a Promising Cathode Material for Aqueous Zinc-Ion Batteries

Exploring a satisfactory cathode material for aqueous zinc-ion batteries (AZIBs) represents a critical advancement toward sustainable, safe, and cost-effective energy storage solutions. In this study, cobalt tungstate (CoWO₄) hierarchical microflakes are successfully fabricated via a facile, scalable chemical precipitation-calcination strategy with the aid of hydrazine. The structural evolution is systematically investigated through calcination at 400-700 °C. When assembled by CoWO₄/Zn batteries, a redox couple at approximately 1.4/1.7 V appears on the cyclic voltammetry profiles. The hierarchical microflakes demonstrate impressive zinc-ion storage performance compared to their microrod counterparts. Specifically, the optimized architecture delivers enhanced initial discharge capacity (177.6 mAh g^-1), exceptional cycling stability (92.9% capacity retention with reference to the 50th after 1000 cycles) at 0.1 A g^-1, improved rate capability (73.7 mAh g^-1 at 2 A g^-1), and a faster zinc-ion diffusion coefficient (9.85 × 10^-13 cm² s^-1). This is attributed to the enlarged active surface area and optimized ion transport pathways. This study not only presents the first demonstration of Zn/CoWO₄ half-cell performance in an aqueous electrolyte but also establishes a viable strategy for designing hierarchical transition-metal tungstate architectures for advanced energy storage applications.