State-of-charge mediated short-term low-temperature calendar aging impacts the cycling stability of Ni-rich cathodes in pouch full cells

Both calendar aging and cycling aging significantly affect the practical performance and service life of lithium-ion batteries (LIBs), especially for high-nickel cathodes used in high-energy-density applications. However, limited research has been conducted on how calendar aging influences subsequent cycling performance. This study addresses the gap by examining the effects of state-of-charge (SoC) during short-term low-temperature storage on both calendar aging and cycling degradation in LIBs with high-nickel cathodes. The findings demonstrate that high SoC storage accelerates calendar aging by causing structural degradation at the cathode-electrolyte interface (CEI), leading to phase transitions and increased mechanical stress. However, these conditions also enhance cycling stability by promoting surface reconstruction of the high-nickel cathode, which reduces lattice strain and mitigates detrimental phase transformations. The surface reconstruction improves lithium-ion diffusion and stabilizes the crystal structure, resulting in less mechanical degradation during cycling. Conversely, low SoC storage leads to reduced structural degradation during calendar aging, but the lack of an inert protective layer on the cathode surface causes lattice strain and phase transitions during lithium intercalation, resulting in microcracks that compromise the cathode structure. Concurrently, transition metal dissolution, migration, and deposition accelerate anode degradation by promoting interfacial reactions, which exacerbate solid electrolyte interphase (SEI) formation and degradation, and consume reversible lithium ions. Storage is a critical process in the lifecycle of LIBs in electric vehicles (EVs), necessitating the development of advanced battery management strategies tailored to the SoC-dependent stabilities of active materials. These results emphasize the complex relationship between calendar and cycling aging, providing important insights into optimizing high-energy-density cathodes with long durability.