Lithium-ion rechargeable batteries have become one of the main power sources for portable electronic products such as mobile communications and notebook computers due to their high specific energy, high operating voltage, small size, and lightweight.
However, lithium-ion batteries may explode due to improper use during charging and discharging; especially in the case of abuse (such as heating, overcharging, short circuit, vibration, extrusion, etc.), the battery may burn, explode and even personnel. Injury, etc. Therefore, studying the explosion mechanism of lithium-ion batteries is of great significance for improving the safety of lithium-ion batteries.
According to professional analysis, there are three possibilities for burning or exploding lithium-ion batteries.
1. When the lithium ion battery is heated, the reaction inside the battery is like a reaction chain, and the respective reactions are mutually promoted and sequentially performed. First, the SEI film liberates heat to heat the battery, causing the reaction between the negative electrode and the solvent to release more heat, resulting in the reaction of the negative electrode with the binder, solvent decomposition, and then the positive electrode begins to undergo thermal decomposition reaction, releasing a large amount of heat and gas. Finally, the battery burns or explodes.
2. In the initial stage of charging lithium-ion batteries, a part of the electric energy is converted into heat energy when the current passes through the battery, and ohmic polarization also generates a part of heat, but the surface temperature of the battery rises slowly; when the battery reaches full state, the lithium ion continues to be embedded. The reaction becomes a deposition of lithium metal on the surface of the negative electrode, and the solvent is oxidized (the heat released by the oxidation reaction of the solvent caused by the overcharge is much higher than the heat released by the reaction of the lithium ion and the solvent in the reversible state), and the heat is released to heat the battery; As the temperature of the battery increases, the reaction of lithium metal with the solvent, lithium intercalation with the solvent and the solvent occur one after another, and the heat is out of control, accompanied by the decomposition of the solvent and the reaction of the binder with the lithium metal.
3. Short circuit, acupuncture, and impact on lithium-ion batteries cause the same damage. When a short circuit occurs, a large amount of heat is generated by the current passing through the battery, and the battery is heated to raise the temperature of the battery to the temperature at which the positive electrode is decomposed. The thermal decomposition of the positive electrode causes the heat of the battery to be out of control; when the needling speed is fast, the local portion is acupuncture. Short circuit and generate a large amount of heat, so that the internal temperature of the battery rises to the temperature at which the positive electrode is thermally decomposed; when the lithium-ion battery is hit, the overvoltage loss on the electrode generates heat, which promotes the reaction between the solvent and the negative electrode, and the heat released further heats the battery, causing the positive thermal decomposition reaction to occur, resulting in loss of heat.