Positive temperature coefficient materials for intelligent overload protection in the new energy era

Since the discovery of positive temperature coefficient resistive (PTCR) materials, they have been widely used in electric/electronic thermistor devices for overload protection. The rapid growth of new energy devices and power electronics, such as lithium or thermal batteries, has aroused tremendous attention and released the demand for high-performance PTCR. The present review provides an in-depth analysis of the PTCR theory, properties, and fabrication techniques from room-temperature to high-temperature, encompassing polymers and metal oxides. The metal oxide-based PTCR ceramics encompass established materials like BaTiO₃ and newly developed materials like ZnO and Bismuth layered-structured ceramics. The article elucidates the limitations of said materials and the different approaches employed to overcome them. However, there is still a gap between the application of the high-temperature PTCR devices and high-temperature PTCR materials/theories, including their materials system, doping-induced PTCR effect, manufacturing techniques, and potential applications. The work is believed to provide invaluable guidance to research on PTCR materials and call on exploring advanced PTCR effects in novel material systems.