Journal of Power Sources, Vol.216, 273-280, 2012
Safe positive temperature coefficient composite cathode for lithium ion battery
Ethylene vinyl acetate (EVA) based positive temperature coefficient (PTC) material with a transition temperature (T-c) of 90 degrees C is proposed and successfully fabricated in this study. It is further introduced into LiFePO4 cathode by directly mixing it with LiFePO4 powder, binder and conductive carbon or sandwiching it between the current collector and LiFePO4 electrode membrane. Thus obtained LiFePO4/PTC composite electrodes both show a self-current-limiting effect at 90 degrees C. The electrochemical properties of the LiFePO4/PTC composite electrodes are determined in terms of galvanostatic charging/discharging, cyclic voltammograms and electrochemical impedance spectroscopy measurements. Comparing with bare LiFePO4 electrode, both LiFePO4/PTC composite electrodes show no degradation in cycling stability, rate capability and electrochemical kinetic property at room temperature. The results indicate that the proposed LiFePO4/PTC composite electrode with the suitable T-c of 90 degrees C can effectively prevent thermal runaway before the occurrence of side reactions and better protect lithium ion battery during the abnormal temperature increasing. (c) 2012 Elsevier B.V All rights reserved.
Keywords:Positive temperature coefficient;Ethylene vinyl acetate;Self-current-limiting effect;Safety;Lithium ion battery