Surface Structure and High-Voltage Charging/Discharging Performance of Low-Content Zr-Oxide-Coated LiNi1/3Co1/3Mn1/3O2

The surface structures, high-voltage charging/discharging performances, and Li-ion transfer at the electrode/electrolyte interface of LiNi1/3Co1/3Mn1/3O2 coated with small amounts of Zr oxide by the sol-gel method were investigated. Island-like ZrO2 grains as well as grain-free (sea-like) zones were observed on the surfaces of the coated LiNi1/3Co1/3Mn1/3O2 samples. The ratio of the area of these sea-like zones to the total surface area of the LiNi1/3Co1/3Mn1/3O2 sample increased from 44 to 85% when the Zr oxide content was decreased from 1.0 to 0.125 wt%. A compound oxide phase containing Zr, Ni, Co, and Mn was formed uniformly on the sea-like zones; the depth of this phase was approximately 2 nm. The initial discharge capacities of the coated LiNi1/3Co1/3Mn1/3O2 samples were equal to that of bare LiNi1/3Co1/3Mn1/3O2. Further, the cycling performances of the coated LiNi1/3Co1/3Mn1/3O2 samples were significantly higher, as were their discharge capacities and discharge voltages, while their charge-transfer resistances (Rct) were lower. It was also found that the coated LiNi1/3Co1/3Mn1/3O2 samples had lower activation energies (Ea) for charge transfer than the bare LiNi1/3Co1/3Mn1/3O2. Thus, it can be surmised that the area and structure of the sea-like zones determined the Rct and Ea values and cycling performances of the coated LiNi1/3Co1/3Mn1/3O2 samples. (C) 2015 The Electrochemical Society.