A temperature-sensitive poly(3-octylpyrrole)/carbon composite as a conductive matrix of cathodes for building safer Li-ion batteries

The thermal runaway is now recognized to be a main cause for the unsafety of Li-ion batteries, which poses a serious concern for large scale electric vehicles and energy storage applications. To address this issue, we propose in this work a new positive-temperature-coefficient (PTC) material, poly(3-Octylpyrrole):poly(styrenesulfonate) (P3OPy:PSS)/carbon composite, and use it as conductive matrix of cathode to enhance thermal stability of Li-ion batteries. The electrochemical and safety evaluations reveal that the such-fabricated graphite/LiCoO2 full pouch cells exhibit not only improved electrochemical performances compared to the conventional cells at ambient temperature conditions, but also a reliable thermal-switching function at an elevated temperature of ≥ 120 °C, demonstrating a strong tolerance to overcharge, thermal impact and short-circuiting. Such a thermal stable mechanism originates from the PTC effect of the cathode matrix, which turns the conductive network into an insulating state under thermally abusive conditions and therefore terminates the charge/discharge reactions, thus protecting the cell from thermal runaway. This work provides a new strategy and electrode design for constructing safer LIBs. In addition, the materials and fabrication technique of the thermal stable cathode is facile and also fully compatible with the present industrial manufacture process, making it convenient for use in practical LIBs.