Tri‐Sites Element Doping with Eu─Al─F Toward Stable High‐Voltage LiCoO 2

Abstract LiCoO 2 (LCO), as the dominating cathode material for lithium‐ion batteries, still cannot satisfy the growing demand for higher energy density required by advanced consumer electronic devices. Increasing the charging cut‐off voltage can significantly improve the capacity of LCO, but it would face structural and interfacial degradation at high voltages, ultimately causing severe capacity fading. Herein, a tri‐sites multi‐element doping strategy with Eu─Al─F is proposed for high‐voltage LCO. At a cut‐off voltage of 4.55 V, the modified LCO cathode exhibits an initial discharge capacity of 205 mAh g −1 and maintains over 80% capacity retention after 250 cycles. The tri‐sites co‐doping strategy put forward in this study can better integrate the inhibitory effect of different doping sites on irreversible H3/H1‐3 phase transitions, oxygen loss, internal stress accumulation, and planar gliding, shedding light on improving the cyclic stability of high‐voltage LCO.