Liquid-Phase Integrated Surface Modification to Construct Stable Interfaces and Superior Performance of High-Voltage LiNi0.5Mn1.5O4 Cathode Materials

Spinel LiNi0.5Mn1.5O4 (LNMO) is regarded as the next potential generation of highly competitive cathode material for high-energy-density lithium-ion batteries due to its cobalt-free and high energy density merits. Nevertheless, the unstable surface structure and severe side reactions during cycling lead to poor electrochemical stability, limiting its commercial-scale development. Herein, a comprehensive strategy of high ionic conductivity CeF3 (CF) coating and Ce doping was achieved on an LNMO surface by a liquid-phase method to enhance its interfacial stability and electrochemical properties. The results show that the capacity retention of 1 wt %-CF-modified LNMO is 87.01% after 400 cycles at 1C and room temperature and is 83.98% after 200 cycles at 55 °C. The assembled 1 wt %-coated LNMO/Li4Ti5O12 full cell exhibited an initial discharge capacity of 99.0 mAh g–1 and capacity retention of 90.1% for 100 cycles at 0.5C. Further studies revealed that the CeF3 layer alleviated the dissolution of transition-metal ions and the side reaction between the LNMO surface and electrolyte, resulting in better structural stability, and superficial Ce doping induced an increase in Mn3+ to improve the electronic conductivity. More importantly, the CeF3 modification effectively improves its electrochemical kinetic behavior, and the fast Li+ diffusion and ideal pseudocapacitance behavior make the 1 wt %-CF electrode have optimal performance.