A novel mechanism for suppressing cycling degradation of lithium-ion batteries under medium-to-high C-rates

Conventional understanding suggests that the cycle life of lithium-ion batteries generally decreases significantly with increasing charge rate. However, performance testing of 18,650 cells from three manufacturers revealed an anomalous behavior: the cycle life of Cell A was substantially longer at 4C (≈1000 cycles) and 6C (≈800 cycles) compared with 1C (≈300 cycles) and 2C (≈350 cycles). Further investigation indicated that the capacity fade of current commercial ternary lithium-ion batteries is mainly concentrated in the anode region, while the cathode material maintains relatively high structural stability. High-rate cycling was found to promote an increase in LiF content within the SEI film, leading to a higher proportion of inorganic components and a reduction in organic components. The incorporation of Zr into the anode significantly enhanced this effect and reduced the content of intermediate products such as LiPO₂F₂, effectively suppressing further electrolyte decomposition and interfacial side reactions. This stabilization of graphite particles contributed to prolonged cycle life. Based on these results, an indicator and threshold for characterizing the comprehensive mechanical performance of the SEI film were proposed, thereby elucidating the structural evolution of the SEI film on Zr-doped graphite anodes under high-rate conditions. These findings provide new insights into suppressing lithium dendrites and extending the cycle life of lithium-ion batteries under high charge–discharge rates.