Insights for understanding multiscale degradation of LiFePO4 cathodes

Lithium-ion batteries (LIBs) based on olivine LiFePO4 (LFP) offer long cycle/calendar life and good safety, making them one of the dominant batteries in energy storage stations and electric vehicles, especially in China. Yet scientists have a weak understanding of LFP cathode degradation, which restricts the further development of LFP materials and batteries. Here, we critically review reports on LFP cathode degradation with respect to different electric parameters (including C-rates, storage, and long cycling), mechanical stresses, and thermal fields. The detailed chemical and physical aspects of degradation mechanisms at various scales (i.e., from atomic to devices) and their causes are comprehensively summarized, and discussions of related concerns are provided in each section. We close with a systematic overview of LFP degradation research and mediation strategies, suggesting future directions for developing robust, safe LFP batteries with long cycle life.