Coating effect of Al2O3 on ZnMn2O4 cathode surface for lithium ion batteries

Zinc manganate (ZnMn 2 O 4 ) with cluster spherical structure is prepared by low temperature coprecipitation method, and then coated with nano-sized Al 2 O 3 via a wet chemical process. The as-prepared ZnMn 2 O 4 (ZMO), Al 2 O 3 -coated ZnMn 2 O 4 (ZMO-AlO) are characterized by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. The scanning electron microscopy shows both the ZMO and ZMO-AlO form cluster spherical structure. X-ray photoelectron spectroscopy confrms that ZMO-AlO covered with a layer of Al 2 O 3 particles. The ZMO and ZMO-AlO exhibit improved electrochemical performance. The initial discharge capacity is enhanced to 1228 mAh·g − 1 after the Al 2 O 3 coating compared to the ZMO material that has an initial discharge capacity of 1140 mAh·g − 1 . During the second charging and discharging process, the specific capacities of ZMO-AlO samples were 763 and 788 mAh·g − 1 respectively, with a coulombic efficiency of 96.8%. The charge-discharge specific capacities of ZMO samples are 760 and 715 mAh·g − 1 respectively, with a coulombic efficiency of 94.1%. By comparing the first and second charge discharge performance of ZMO and ZMO-AlO at a current density of 100 mA·g − 1 , it can be found that ZnMn 2 O 4 modified by Al 2 O 3 coating has better electrochemical lithium storage performance.