Cycle performance improvement of Li-rich layered cathode material Li[Li_(0.2)Mn_(0.54)Ni_(0.13)Co_(0.13)]O_2 by ZrO_2 coating

摘要

Lithium-rich layered cathode material Li[Li_(0.2)Mn_(0.54)Ni_(0.13)Co_(0.13)]O_2 with sphericalmorphology is prepared via coprecipitation method followed by high-temperature treatment and surface coated with a uniform nano-layer of ZrO_2 by controlled-hydrolysis of Zirconium(IV) Propoxide. The results show that Li[Li_(0.2)Mn_(0.54)Ni_(0.13)Co_(0.13)]O_2 with a well-ordered layered structure consists of small and homogenous primary particles ranging from 100 nm to 200 nm.The ZrO_2 layer with nano-sized particles is coated uniformly on the matrix particle surface. A notable improvement of the cathode coated by ZrO_2 is obtained in cycle performance from charge-discharge cycling tests in the range of 2.0-4.8 V, and the optimum amount of ZrO_2 coating which maximizes the capacity retention is 1 wt.%. A high initial discharge capacity of 253.1 mAh/g at 0.1C is obtained for the 1 wt.% ZrO_2-coated sample, and it maintains a capacity of 207.3 mAh/g after 50 cycles at 0.5C and a capacity of 235.3 mAh/g after 50 cycles at 0.2C. The improved cycling performance of ZrO_2-coated Li[Li_(0.2)Mn_(0.54)Ni_(0.13)Co_(0.13)]O_2 is attributed to the decrease of electrolyte decomposition reactions and the alleviation of the impedance due to the existence of ZrO_2 coating layer.