Building thermally stable Li-ion batteries using a temperature-responsive cathode

Lithium ion batteries have now been used as a power source for electric vehicles; however, their safety still remains a serious concern as the accidents reported increase with the rapid increase of electric vehicles in transportation markets. To address this issue, we describe herein a novel temperature-responsive cathode by coating an ultra-thin layer of poly(3-octylthiophene) (P3OT) with a thickness less than 1 μm in between the Al substrate and cathode-active LiCoO₂ layer to form a sandwiched Al/P3OT/LiCoO₂ cathode (LCO-PTC). This LCO-PTC cathode demonstrates almost the same electrochemical performance as the conventional LiCoO₂ cathode at ambient temperature but a strong PTC behavior to switch off the cell reaction in a high temperature range of 90-100 °C, thus protecting the cell from thermal runaway. Because of its easy fabrication, cost effectiveness and particularly good compatibility with the current battery technology, this new type of PTC electrode can be conveniently extended to other Li-insertion cathodes for building safer Li-ion batteries.