High temperature and high rate lithium-ion batteries with boron nitride nanotubes coated polypropylene separators

Safety of lithium-ion batteries (LIBs) is a current serious and challenging issue threating large-scale energy storage application as well as every day usage of mobile devices. Initial overheating of the cell is one of the factors responsible for the failure of LIB safety, which is caused by short circuit under high temperature and high current environment. As separator is the main component to prevent short circuit, thermal stability of the separator is crucial in this regard. In this study, boron nitride nanotubes (BNNTs) are synthesized and used for the first time as a new type of high performance inorganic nanomaterials to prevent short-circuit. We provide a new configuration strategy for the modification of conventional polyolefin separator by simply incorporation of appropriately engineered long and fine BNNTs without blocking the porous channels of the conventional separator for Li+ ion diffusion. This new BNNT separator exhibits improved thermal stability up to 150 degrees C, ensuring the safe operation of LIB cells at elevated temperatures. The high rate capability of the cell with BNNT separator is also improved dramatically due to absorb extra heat and spread it through BNNTs during the cycling process. The BNNTs demonstrate an exciting new nanomaterials in improving thermal stability of the polyolefin separator by protecting thermal shrinkage at high temperature and high current operation, which eventually prevent battery short-circuit.