The electrochemical properties of Li[Li 0.2 Co 0.4 Mn 0.4 ]O 2 were studied at room temperature and −20°C. EIS study showed that the electrochemical kinetics of the first charge was more sluggish than subsequent cycles, which became even worse at −20°C. This made it difficult for the material to achieve a sufficient oxygen loss reaction at low temperature. XPS analysis showed that almost all of the Mn 4+ ions in the material were activated at room temperature, whereas only a few of them were activated at −20°C. As a result, the material showed a high discharge capacity of 246 mAh g− 1 at room temperature, comparing to the 155 mAh g −1 at −20°C. However, the inactive Mn 4+ ions in the electrode suppressed the dissolution of manganese and the Jahn–Teller distortion of the material lattice, both of which resulted in excellent cycle life at low temperature.