ZnCo ₂ O ₄ Architecture for Fast Na ⁺ Diffusion and Stable Sodium‐Ion Storage

Herein, we report spinel ZnCo ₂ O ₄ (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.