One-time sintering process to synthesize ZrO₂-coated LiMn₂O₄ materials for lithium-ion batteries

Herein, different amounts of ZrO₂-coated LiMn₂O₄ materials are successfully prepared by one-time sintering ZrO₂-coated Mn₃O₄ and Li₂CO₃. Scanning and transmission electron microscopy results confirm that the ZrO₂ coating layer on the surface of Mn₃O₄ can still be maintained on the surface of the final LiMn₂O₄ particles even after long-term high-temperature heat-treatment. Three key factors to realize ZrO₂-coated LiMn₂O₄ materials via the one-time sintering process are as follows: (i) the Mn₃O₄ precursor is coated by ZrO₂ in advance; (ii) the ionic radius of Zr⁴⁺ is much larger than those of Mn³⁺ and Mn⁴⁺; (iii) the pre-calcination temperature is set in the reaction temperature range between Li₂CO₃ and Mn₃O₄ and lower than that between Li₂CO₃ and ZrO₂. The 3 wt% ZrO₂-coated LiMn₂O₄ material exhibits excellent electrochemical properties with an initial specific discharge capacity of 118.8 mA h g^-1 and the capacity retention of 90.1% after 400 cycles at 25 °C and 88.9% after 150 cycles at 55 °C. Compared with the conventional coating method, the one-time sintering process to synthesize ZrO₂-coated LiMn₂O₄ materials is very simple, low-cost, environmentally friendly, and easy to scale up for large-scale industrial production, which also provides a valuable reference for preparing other coating-type cathode materials for lithium-ion batteries.