Enhancing Lithium-Ion Battery Performance: Systematic Investigation into the Effects of Li₅FeO₄ Supplementation

As a lithium-supplementing agent, Li₅FeO₄ (LFO) is typically utilized to provide an additional lithium source for mitigating significant initial capacity loss, particularly when employing Si-based anodes. However, systematic investigations into the impact of LFO incorporation on the performance of cathode materials, as well as the determination of an optimal LFO loading amount, are still lacking. Herein, we first synthesize a high-capacity LFO (781.9 mA h g^-1) and assemble batteries using this LFO in conjunction with ultrahigh nickel ternary cathode material (NCM92). We then systematically investigate the effects of LFO incorporation on both the cathode material and overall battery performance. The results indicate that the inclusion of LFO enhances the initial discharge capacity of the full cell from 190.7 mA h g^-1 to 226.2 mA h g^-1. Moreover, the addition of LFO to the cathode can facilitate smoother lithium-ion migration, mitigate the polarization phenomenon, and reduce the electrochemical potential difference of the high-nickel cathode materials during the H2-H3 phase transition. Besides, it is discovered that the discrepancy between the theoretical and actual loading amounts of LFO is likely due to the involvement of some lithium ions in the formation of the solid electrolyte interface (SEI) film. Failure analyses confirm that the incorporation of LFO does not lead to the deposition of transition metal elements on the separator or anode. This study provides robust support for the potential of LFO in practical applications and validates its positive contributions to battery performance.