Low temperature performance of LiFePO4 cathode material for Li-ion batteries

Here we report the unusual low temperature (LT) capacity retention of LiFePO4, which is superior to its room temperature (RT) counterpart. In particular, the initial LT discharging capacity of LiFePO4 at -20 degrees C was only half of the RT capacity, but its average capacity fade for the first 40 cycles was only one fourth to one fifth of the RT value, which makes the capacity at -20 degrees C exceed the RT capacity after less than 20 cycles. It is suggested from the impedance and capacity analyses that the much milder degradation of the surface and the bulk, respectively, during the LT cycling might be responsible for the stable LT operation. (C) 2013 Published by Elsevier B.V.