Studies on rate capability of lithium-ion cells at low temperatures

The discharge capability of lithium-ion cells was characterized at 20, 0 and -20 °C. The cell discharge capability decreases rapidly with the decrease in the temperature. The impedance associated with the electrodes increases about 50 times from 20 to -20 °C for C-LiCoO 2 cell, and appears to be one of the main reasons for the dramatic decrease in the cell discharge capability at low temperature. The conductivity of the electrolyte seems not to be responsible for the very poor cell discharge capability at -20 °C since the conductivity of the electrolyte decreases only about 2.3 times from 20 to -20 °C. On the basis of this study, it appears that minimizing the electrode impedance is the most effective way to enhance the cell discharge capability at low temperature.