ZnCo2O4 Architecture for Fast Na+ Diffusion and Stable Sodium-Ion Storage

Abstract

Herein, we report spinel ZnCo2O4 (ZCO) as a promising anode material for sodium-ion batteries (SIBs), synthesized via a scalable one-pot hydrothermal method followed by annealing. The resulting cubic spinel phase self-assembles into a three-dimensional urchin-like architecture that offers abundant electroactive sites for sodium storage. X-ray photoelectron spectroscopy confirmed the coexistence of Zn, Co, and O species, while high-resolution transmission electron microscopy and selected area electron diffraction analyses revealed crystalline domains with preferred orientation along the (311) plane, consistent with X-ray diffraction results. When evaluated in CR2032 half-cells, this architecture delivers a high initial discharge capacity of 494.8 mAh/g at 0.02 C, good rate capability (74.82% retention at 0.1 C), and stable cycling with 68.98% retention after 200 cycles at 5 C, along with nearly 100% Coulombic efficiency. Ex situ structural and morphological analyses after cycling confirmed the robustness of the 3D architecture, which effectively accommodates volume changes during sodiation/desodiation while facilitating rapid Na+ diffusion. These results highlight the well-engineered ZCO architecture as a robust and high-performance anode for advanced SIBs. © 2026 Wiley-VCH GmbH.