One-time sintering process to synthesize ZrO 2 -coated LiMn 2 O 4 materials for lithium-ion batteries.

Herein, different amounts of ZrO 2 -coated LiMn 2 O 4 materials are successfully prepared by one-time sintering ZrO 2 -coated Mn 3 O 4 and Li 2 CO 3 . Scanning and transmission electron microscopy results confirm that the ZrO 2 coating layer on the surface of Mn 3 O 4 can still be maintained on the surface of the final LiMn 2 O 4 particles even after long-term high-temperature heat-treatment. Three key factors to realize ZrO 2 -coated LiMn 2 O 4 materials via the one-time sintering process are as follows: (i) the Mn 3 O 4 precursor is coated by ZrO 2 in advance; (ii) the ionic radius of Zr 4+ is much larger than those of Mn 3+ and Mn 4+ ; (iii) the pre-calcination temperature is set in the reaction temperature range between Li 2 CO 3 and Mn 3 O 4 and lower than that between Li 2 CO 3 and ZrO 2 . The 3 wt% ZrO 2 -coated LiMn 2 O 4 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 ZrO 2 -coated LiMn 2 O 4 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.