Impact of surface coating on electrochemical and thermal behaviors of a Li-rich Li1.2Ni0.16Mn0.56Co0.08O2 cathode

Abstract

Lithium-rich layered oxide materials are considered as potential cathode materials for future high-performance lithium-ion batteries (LIBs) owing to their high operating voltage and relatively high specific capacity. However, perceptible issues such as poor rate performance, poor capacity retention, and voltage degradation during cycling need to be improved before the successful commercialization of the material. In this report, zirconia coated Li_1.2Ni_0.16Mn_0.56Co_0.08O₂ (NMC) (where ZrO₂ = 1.0, 1.5 and 2.0 wt%) materials are synthesized using a sol–gel assisted ball milling approach. A comparison of structural, morphological and electrochemical properties is examined to elucidate the promising role of ZrO₂ coating on the performance of the NMC cathode. A uniform and homogeneous ZrO₂ coating is observed on the surface of NMC particles as evident by TEM elemental mapping images. The ZrO₂ coated NMCs exhibit significantly improved electrochemical performance at a higher C-rate as compared to pristine material. 1.5% ZrO₂ coated NMC demonstrates better cycling stability (95% capacity retention) than pristine NMC (77% capacity retention) after 50 cycles. All ZrO₂ coated NMC materials demonstrated improved thermal stability compared to pristine material. The difference in onset temperature of 2 wt% ZrO₂ coated and pristine NMC is 20 °C. The improved electrochemical performance of ZrO₂ coated NMC can be attributed to the stabilization of its surface structure due to the presence of ZrO₂.