Three reasons for the burning and explosion of lithium batteries

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The lithium battery we use every day is closely related to our daily life. Lithium battery has become one of the main power sources for portable electronic products such as mobile communications, notebook computers, etc. due to its high specific energy, high working voltage, small size and light weight. . However, lithium-ion batteries are at risk of explosion due to improper use during charging and discharging.

Especially under abusive conditions (such as heat, overcharge, short circuit, vibration, extrusion, etc.), the battery will burn, explode and even be injured. Therefore, it is of great significance to study the explosion mechanism of lithium-ion batteries to improve the safety of lithium-ion batteries.

There are three reasons for battery combustion and explosion in lithium batteries:

1. Three reasons for the combustion and explosion of lithium batteries - heat

When the lithium-ion battery is heated, the reactions inside the battery are like a reaction chain, and each reaction promotes each other and proceeds in sequence. First, the decomposition of the SEI film releases heat and heats the battery, which promotes the reaction between the negative electrode and the solvent to release more heat, resulting in the reaction between the negative electrode and the binder and the decomposition of the solvent. Then the positive electrode begins to undergo thermal decomposition reaction, releasing a large amount of heat and gas. , which will eventually cause the battery to burn or explode.

2. Three major reasons for lithium battery burning and explosion - overcharging

In the early stage of lithium-ion battery charging, part of the electrical energy is converted into heat energy when the current passes through the battery, and ohmic polarization also generates part of the heat, but the surface temperature of the battery rises very slowly; when the battery reaches a fully charged state, the continuous intercalation reaction of lithium ions changes. The deposition of lithium metal on the surface of the negative electrode, the solvent is oxidized (the heat released by the oxidation reaction of the solvent caused by overcharging is much higher than the heat released by the reaction between lithium ions and the solvent in the reversible state) The heat released heats the battery; When the temperature of the battery increases, the reaction of metal lithium and the solvent, and the reaction of lithium intercalation carbon and the solvent occur one after another, and the heat is out of control. At the same time, the decomposition of the solvent and the reaction between the binder and the lithium metal occur.

3. Three reasons for the combustion and explosion of lithium batteries - short circuit

Short circuits, needle sticks, and shocks pose roughly the same harm to lithium-ion batteries. During a short circuit, a large amount of heat is generated when the current passes through the battery, which heats the battery and raises the battery temperature to the temperature at which the positive electrode decomposes. The thermal decomposition of the positive electrode causes the battery to lose control of heat; Short circuit and generate a lot of heat, so that the internal temperature of the battery rises to the temperature where the positive electrode thermally decomposes; when the lithium-ion battery is hit, the overvoltage on the electrode generates heat, which promotes the reaction between the solvent and the negative electrode, and the released heat further heats the battery. , prompting the thermal decomposition reaction of the positive electrode to occur, resulting in the runaway of heat.

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