Investigation the Degradation Mechanisms of Lithium-Ion Batteries under Low-Temperature High-Rate Cycling

Low-temperature high-rate cycling leads to accelerated performance degradation of lithium-ion batteries, which seriously hampers the large-scale popularization of electric vehicles. To clarify the battery degradation characteristics and mechanisms, this work conducts an in-depth investigation on the commercial lithium-ion batteries with 37 A h during the long-term cycling under low-temperature high-rate charging. The battery capacity displays the decelerating degradation trend during the long-term cycling, and the battery capacity recovery rate is as high as 80–90%. Furthermore, it is interesting that the constant current discharge capacity exhibits jumping behavior at around 120th cycle during the discharge process. By postmortem characterization analysis, it is found that lithium plating is the primary degradation mechanism. Lithium plating exhibits nonuniformity and displays a decelerating trend in the later stage. In view of the lower temperature, the plated lithium can better retain the reaction activity, which results in a higher capacity recovery rate. Besides, lithium plating increases the internal polarization, which makes the constant current discharge capacity jump when lithium plating reaches a certain level. The findings can provide certain references for battery optimization.