Low Temperature Performance of the Li[Li_0.2Co_0.4Mn_0.4]O₂ Cathode Material in Different Electrolytes

The Li[Li_0.2Co_0.4Mn_0.4]O₂ cathode material is prepared by sol–gel method. The extraction Li⁺ ions from the transition metal layer are only 40%, and the initial discharge capacity is 155 mAh g^-1 in the electrolyte of EC:DMC:EMC = 1:1:8 at -20 °C. Moreover, it exhibits excellent capacity retention of 96.32% after thirty cycles. Cyclic voltammetry shows the material reacts insufficiently at the low temperature. The inactive Mn⁴⁺ ions suppress the dissolution of manganese and the Jahn–Teller distortion of the material lattice, both of which lead to a better cycling performance than that at room temperature. In addition, the low melting point of EMC enhances the mobility of the traditional commercial electrolyte (EC:DMC = 1:1) at -20 °C. Thus, the material shows the lower charge transfer resistance after 30 cycles and improved rate ability when the EMC is introduced.