Air-Stable Li 6 CoO 4 @Li 5 FeO 4 Pre-Lithiation Reagent in Cathode Enabling High Performance Lithium-Ion Batteries

Li 5 FeO 4 , as a high-capacity built-in pre-lithiation reagent, has attracted wide interest due to its attractive characteristics, such as extremely higher capacity and energy density, low cost, and environmental friendliness. However, the preparation technology of high-stability Li 5 FeO 4 remains a great challenge. Here, we report a highly air-stable Li 5 FeO 4 cathode pre-lithiation reagent by the solid-phase method. The Li 5 FeO 4 is coated with Li 6 CoO 4 (Li 6 CoO 4 @Li 5 FeO 4, referred to as LCO@LFO), which can effectively improve the stability of Li 5 FeO 4 materials under ambient atmosphere and significantly enhance the electrochemical performance. The material possesses an initial charge capacity of 518.8mAh g −1 when charged to 4.5 V and exhibits good air-filled capacity retention. Besides, the LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) full-cell with 5 wt% LCO@LFO additive has an initial discharging capacity of 205 mAh g −1 in the charge and discharge interval of 2.0 V–4.5 V (vs Li + /Li), respectively, higher than the initial discharging capacity of 166.5 mAh g −1 of pure NCM811. The reversible specific capacity of the NCM811 with LCO@LFO cathode in the full cell can be increased by 8.8%, which is equivalent to a 14.35% increase in energy density. Our research report opens a door for the commercial application of LCO@LFO, a high-stability cathode composite pre-lithiation reagent.