调控电解液溶剂组分实现 LCO/C 低温 18650 电池循环寿命显著提升

The cycle life of low-temperature 18650 batteries has always been a key factor that limited their development. To achieve a balance between a long cycle life and low-temperature performance, the effects of different electrolytes on rate performance, high- and low-temperature discharge performance, charge retention capacity, cycle life, low-temperature cycle performance, and EIS were compared and analyzed by adjusting the components of the electrolyte solvent. The results demonstrated that the design of the electrolyte composition had a significant impact on the performance of the battery. By partially replacing the carbonate esters and the short-chain carboxylic esters with long, linear carboxylic esters having a low melting point, impressive low-temperature performance as well as high-temperature stability were achieved, which illustrated that EP and PP play an important role in the cyclic stability of the LCO/C electrode system. The solvent component EC+EP+PP (mass ratio 2∶ 5∶ 3) exhibited the best comprehensive performance. The developed LTB battery maintained a discharge capacity retention of 99.86% at 5C and a discharge capacity retention of 92.84% at −40 ℃ and 1C. After 1000 cycles, the low-temperature discharge capacity at −40 ℃ and 1C was still 90% of the initial low-temperature discharge capacity. At room temperature, the cycling retention rate reached 85% after 1500 cycles; at a low temperature of −10 ℃, the cycling retention rate was 82.4% after 500 cycles.