Self-Extinguishing Lithium Ion Batteries Based on Internally Embedded Fire-Extinguishing Microcapsules with Temperature-Responsiveness.

User safety is one of the most critical issues for the successful implementation of lithium ion batteries (LIBs) in electric vehicles and their further expansion in large-scale energy storage systems. Herein, we propose a novel approach to realize self-extinguishing capability of LIBs for effective safety improvement by integrating temperature-responsive microcapsules containing a fire-extinguishing agent. The microcapsules are designed to release an extinguisher agent upon increased internal temperature of an LIB, resulting in rapid heat absorption through an in situ endothermic reaction and suppression of further temperature rise and undesirable thermal runaway. In a standard nail penetration test, the temperature rise is reduced by 74% without compromising electrochemical performances. It is anticipated that on the strengths of excellent scalability, simplicity, and cost-effectiveness, this novel strategy can be extensively applied to various high energy-density devices to ensure human safety.