Coating effect of Al₂O₃ on ZnMn₂O₄ anode surface for lithium-ion batteries

Zinc manganese oxide (ZnMn₂O₄), exhibiting a clustered spherical structure, is synthesized using a low-temperature coprecipitation method. Following this, a coating of nano-sized Al₂O₃ is applied via a wet chemical technique. The resultant materials—designated as ZnMn₂O₄ (ZMO) and Al₂O₃—coated ZnMn₂O₄ (ZMO-AlO)-undergo characterization using X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. Scanning electron microscopy reveals that both ZMO and ZMO-AlO retain their clustered spherical morphologies. Furthermore, XPS and TEM confirm the presence of an Al₂O₃ layer on the ZMO-AlO sample. In terms of electrochemical performance, a significant improvement is observed. Specifically, the Al₂O₃ coating enhances the initial discharge capacity of ZMO-AlO to 1228 mAh·g⁻¹, compared to the 1140 mAh·g⁻¹ capacity of the unmodified ZMO material. During the second charging and discharging cycle, the ZMO-AlO samples demonstrate specific capacities of 763 and 788 mAh·g⁻¹, respectively, achieving a coulombic efficiency of 96.8%. By contrast, the ZMO samples show specific capacities of 760 and 715 mAh·g⁻¹, respectively, with a slightly lower coulombic efficiency of 94.1%. When evaluating the electrochemical lithium storage performance of ZMO and ZMO-AlO at a current density of 100 mA·g⁻¹, it becomes evident that the Al₂O₃-modified ZnMn₂O₄ (ZMO-AlO) offers superior performance compared to the unmodified ZMO.