Controlling electrolyte solvent components to enhance cycle life of LCO/C low-temperature 18650 batteries
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.
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