Distinct electrolyte salt and additive adaptation in LFP and LMFP cathodes

LMFP is a promising alternative to LFP cathode due to its higher operating voltage and energy density. However, Mn incorporation introduces additional degradation pathways associated with structural instability and transition-metal dissolution. Despite this, electrolyte formulations developed for LFP are often applied directly to LMFP systems. Here, the effects of identical electrolyte salt and additive chemistries are systematically investigated and compared in LFP and LMFP, and insights are provided into the distinct impacts of similar electrolytes on their degradation mechanisms. Chemical and electrochemical characterizations reveal that, although the conventional LiPF 6 + VC electrolyte provides reasonable durability in LFP cells, LiDFOB without additives enhances the electrode–electrolyte interphase and improves capacity retention for both cathode chemistries, with a more pronounced effect in LMFP. Postmortem analyses indicate that the degradation differences between LFP and LMFP primarily originate from interfacial instability and transition-metal dissolution rather than cathode particle fracture. These results show that electrolytes designed for LFP cathodes cannot necessarily be extended to LMFP systems without considering their distinct structural, interfacial, and phase-evolution behavior. This work establishes electrolyte salt chemistry as a critical parameter governing the long-term stability of LMFP cathodes and highlights the importance of cathode-specific electrolyte engineering strategies for next-generation olivine-based LIBs.