Lattice Modulation on Air-Stable Fe-Based Prelithiation Materials with High Capacity via Triggering Anionic Redox Activity

Li5FeO4 (LFO) is a leading candidate for cathode prelithiation due to its ability to engage in both anionic and cationic redox processes, offering substantial capacity potential. However, the practical implementation of LFO is hampered by incomplete delithiation and susceptibility to air-induced degradation, which together constrain its effectiveness in lithium compensation. In this study, we propose a lattice modulation strategy that incorporates cobalt substitution at the iron sites of LFO, resulting in the novel compound Li5.5Fe0.5Co0.5O4 (LFCO), which enhances both the anionic redox activity and the air stability of the material. We demonstrate that the incorporation of Co2+ ions facilitates the reversible oxidation of lattice oxygen species from O2– to intermediate O2n– and ultimately to O2, thereby augmenting the overall redox capacity. LFCO exhibits superior electrochemical performance with specific capacities of 860.1 mAh g–1 at 0.1C and 580.0 mAh g–1 at 1C, compared to 681.5 and 351.8 mAh g–1 for LFO. Furthermore, LFCO maintains a high capacity of 520.8 mAh g–1 after exposure to 20% relative humidity for 4 days. Integration of LFCO into graphite∥NCM811 pouch cells results in 89.6% capacity retention at 0.5C over 200 cycles, underscoring the potential of this material in developing next-generation energy-dense lithium-ion batteries.