Abstract: Lithium ion battery is widely used in energy storage field because of its advantages of high energy density, low self discharge rate, long cycle life and large output power. However, due to its intrinsic instability, more and more accidents occur frequently in energy storage. From the point of view of thermal runaway and fire propagation, this paper explores the mechanism of thermal runaway. Based on the characteristics of thermal runaway such as gas generation composition and content, expansion force, surface temperature and voltage-drop, the existing early warning (external) methods are summarized. On this basis, the development idea of early warning (external) of battery thermal runaway in the future is proposed, which provides ideas for early monitoring and early warning of thermal runaway of lithium battery.

Key words: lithium-ion batteries, thermal runaway, thermal runaway characteristic parameters, early warning