Effect of linear carboxylic ester on low temperature performance of LiMn_2O_4-graphite cells

线性羧酸酯对锰酸锂-石墨电池低温性能的影响(英文)

To improve the low-temperature performances of Li-ion cells, three types of linear carboxylic ester-based electrolyte, such as EC/EMC/EA（1：1：2, mass ratio）, EC/EMC/EP（1：1：2, mass ratio） and EC/EMC/EB（1：1：2, mass ratio）, were prepared to substitute for industrial electrolyte（EC/EMC/DMC）. Then, 18650-type Li Mn2O4-graphite cells（nominal capacity of 1150 mA ·h） were assembled and studied. Results show that the cells containing three types of electrolyte are able to undertake 5C discharging current with above 93% capacity retention at-20 °C. Electrochemical impedance spectra show that the discharge capacity fading of Li-ion cells at low temperature is mainly ascribed to the charge transfer resistance increasing with temperature decreasing. In comparison, the cells containing electrolyte of 1.0 mol/L LiPF6 in EC/EMC/EA（1：1：2, mass ratio） have the highest capacity retention of 90% at-40 °C and 44.41% at-60 °C, due to its lowest charge-transfer resistance.

以线性羧酸酯EA、EP和EB分别替代工业用1.0 mol/L LiPF6 EC/EMC/DMC(1:1:1,质量比)电解液中的DMC,配制了1.0 mol/L LiPF6 EC/EMC/EA(1:1:2,质量比)、1.0 mol/L LiPF6 EC/EMC/EP(1:1:2,质量比)和1.0mol/L Li PF6 EC/EMC/EB(1:1:2,质量比)3种包含线性羧酸酯的电解液,采用18650全电池研究线性羧酸酯作为电解液溶剂组元对锰酸锂-石墨电池低温性能的影响。结果表明,采用3种包含线性羧酸酯的电解液,电池在-20°C、5C倍率下放电容量保持率均大于93%,而采用工业用电解液时,电池无法在-20°C、5C倍率下放电。电化学阻抗谱分析表明,在低温下电池放电容量和放电能量衰减的主要原因是电荷转移阻抗随温度的降低而增大。在3种含线性羧酸酯的电解液中,使用1.0 mol/L LiPF6 EC/EMC/EA(1:1:2,质量比)电解液的电池因具有最低的电荷转移阻抗,表现出最好的电化学性能,在-40°C下放电容量保持率大于90%,在-60°C下放电容量保持率大于44.41%。