Enhancing High-Temperature and High-Voltage Performances of Single-Crystal LiNi_0.5Co_0.2Mn_0.3O₂ Cathodes through a LiBO₂/LiAlO₂ Dual-Modification Strategy

The limited lithium-ion diffusion and depressed cathode/electrolyte interface stability greatly deteriorate the cycling and rate performance of lithium-ion batteries, especially when they are operated at elevated temperatures (≥50 °C) and/or high charge cutoff voltages (>4.4 V vs Li/Li+). Herein, we proposed a demand-oriented surface coating strategy by introducing multifunctional LiBO2/LiAlO2 layers onto the surface of LiNi0.5Co0.2Mn0.3O2 (NCM) single crystals, in which the middle LiAlO2 layer is designed to ensure intimate contact with NCM to prevent the direct contact between the cathode and electrolyte and thus strengthen the cathode surface structure. The outmost LiBO2 is expected to serve as an isolation layer to improve the Li+ transportation and solid electrolyte interface stability. LiBO2/LiAlO2 (BA-NCM)- and LiBO2 (B-NCM)-coated NCM were demonstrated and systematically studied by several experimental techniques. Benefiting from the demand-oriented coating strategy, BA-NCM shows the much-improved rate and cycling performances as compared with B-NCM and bare NCM at both 25 and 55 °C. Especially, when operated at 55 °C, the capacity retention of BA-NCM after 500 cycles at 1 C is as high as 66.3%, while it is 26.9% for B-NCM.