Safe positive temperature coefficient composite cathode for lithium ion battery

Abstract

Ethylene vinyl acetate (EVA) based positive temperature coefficient (PTC) material with a transition temperature (Tc) of 90 °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 °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 Tc of 90 °C can effectively prevent thermal runaway before the occurrence of side reactions and better protect lithium ion battery during the abnormal temperature increasing.