Effective Li₃AlF₆ Surface Coating for High-Voltage Lithium-Ion Battery Operation

Enhancing the energy density of high-voltage lithium-ion battery cathodes is challenging. Cathode surface coating can effectively suppress the irreversible side reactions occurring at the cathode/electrolyte interface. Recent high-throughput theoretical studies have demonstrated the potential of a ternary lithium fluoride, β-Li3AlF6, as a coating agent owing to its high anodic limit, sufficient stability against various cathode materials, and sufficient Li+-ion conductivity. This study improves the cathode performance by the surface coating of β-Li3AlF6 on LiNi0.5Mn1.5O4 and LiCoO2 cathodes using a simple sol–gel calcination process. β-Li3AlF6-coated LiNi0.5Mn1.5O4 shows superior cycle performance, with a capacity retention of 98.2% and a coulombic efficiency of 99% at the 100th cycle. Further, β-Li3AlF6-coated LiCoO2 can be cycled at a high voltage of 4.5 V with a capacity retention of 95% at the 100th cycle. These results demonstrate the potential of β-Li3AlF6 as a high-voltage cathode coating agent.