The Influences of Surface Coating Layers on the Properties of Layered/Spinel Heterostructured Li-Rich Cathode Material

摘要

Layered/spinel heterostructured Li-rich material is prepared by controlling the conditions of a solvothermal method to obtain precursor and the subsequent high temperature solid phase reaction, and then, 3 wt % LiF, 3 wt % Li2TiO3, and 3 wt % Li3PO4 are coated on the surface of the layered/spinel heterostructured Li-rich oxide by a wet chemical method. The influences of different lithium salt coating layers on the layered/spinel heterostructured material are investigated by transmission electron microscopy, galvanostatic charge/discharge tests, and electrochemical impedance spectroscopy. It can be seen that after coating a Li salt layer, the initial charge-discharge efficiency, cycle, and rate performance are obviously improved. Especially, the sample coated with Li3PO4 shows an optimum result in improving the rate capability of layered/spinel heterostructured Li-rich material and effectively inhibiting the side reaction between the layered/spinel heterostructured Li-rich material and organic electrolyte as well as maintaining the structural stability of the material. Therefore, the layered/spinel heterostructured Li-rich material coated with Li3PO4 has the highest rate capability of 148.2 mAh g(-1) at 10 C, the best cycle ability with capacity retention of 85.3% cycling 200 times at 0.5 C, and improved initial Coulombic efficiency of 88.3%.