Effect of linear carboxylic ester on low temperature performance of LiMn2O4–graphite cells

Abstract 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 LiMn 2 O 4 –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 5 C 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 LiPF 6 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.