Novel Core–Shell PS-co-PBA@SiO2 Nanoparticles Coated on PP Separator as “Thermal Shutdown Switch” for High Safety Lithium-Ion Batteries

Thermal runaway is a hazardous behavior of lithium-ion batteries under extreme conditions and is mainly cause for restraint of its commercial applications in development of high-power and high-rate lithium-ion batteries. In this paper, a new dual-functions coating layer fabricated from polystyrene-poly(butyl acrylate) copolymer encapsulated silica nanoparticles as “thermal shutdown switch” with a reasonable shutdown temperature of ≈80 °C is designed and coated on polypropylene separator. The shell polymer owing to its self-adhesion upon glass transition temperature ( T g ) can retard off the Li + conduction between the electrodes, thus prevents cell from thermal runaway, the core nanoparticles protect the separator from significantly thermal shrinkage when the cell temperature keeps going up. Moreover, the coated separator has no negative affection on the normal electrochemical performance of the batteries, thereby implying that this coating layer provides a simple and effective approach to control the safety of commercial lithium-ion batteries by internal self-protecting.