The mechanism principle of lithium-ion battery thermal runaway

Thermal runaway refers to the monomer accumulator battery exothermic chain reaction, which causes a sharp change since the battery temperature rise rate of overheating, fire and explosion phenomenon. Thermal Runaway Propagation refers to the inside of the battery pack or system monomer battery or accumulator cell thermal runaway, and trigger the battery in the system or other parts of the adjacent battery thermal runaway phenomenon.(Qouted from “the electric bus safety technical conditions ")

Battery in the process of thermal runaway, the chemical reaction between the material decomposed under different temperature and material heat release is the primary cause of battery burning explosion. The roughly description process is as follows:

Due to internal short circuit, external heating, or self when large current charge and discharge batteries, the battery internal temperature rise to about 90 ~ 100 ℃, lithium LiPF6 starts to break down, and the SEI film on the surface of the electrode materials decompose, and gives off heat which makes the battery temperature to rise to about 110 ~ 120 ℃.As the cathode of solid electrolyte interface film was damaged, losing protection and very lively LiC6 exothermic reaction with the solvent and adhesives, further pushing up to 150 ℃ temperature of the battery.In this  temperature, a new intense exothermic reacts, such as electrolyte decomposition in great quantities, generate PF5, then PF5 further catalytic decomposition reaction of organic solvent, etc.

Within 150 ~ 200 ℃, and the battery in polyolefin diaphragm thermal contraction or molten, lead to large area of short circuit batteries, intense heat that makes the battery temperature rise further, and accelerate the internal chemical reaction.Battery temperature rise to 180 ~ 300 ℃, the further start charging battery anode materials intense decomposition reaction occurs, the electrolyte severe oxidation reaction, release a large amount of heat, high temperature and large amounts of gas, in the end,burning blast in the battery.

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