u003cpu003e Lithium-ion secondary 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 working voltage, small size, and light weight. However, lithium-ion batteries may explode due to improper use during charging and discharging; especially under abusive conditions (such as heat, overcharge, short circuit, vibration, extrusion, etc.), the battery may burn, explode, and even personnel Injuries, etc. Therefore, studying the explosion mechanism of lithium-ion batteries is of great significance to improve the safety of lithium-ion batteries. u003c/pu003eu003cpu003e u003c/pu003eu003cpu003e Seeing the image of the battery explosion in the picture above, I went to the battery network industry to analyze the three possibilities of burning or exploding lithium-ion batteries, mainly as follows. u003c/pu003eu003cpu003e 1. When a lithium battery pack
is heated, the internal reactions of the battery are like a reaction chain, and each reaction promotes each other and proceeds in sequence. First, the SEI film releases heat to heat the battery, which promotes the reaction between the negative electrode and the solvent to release more heat, leading to the reaction between the negative electrode and the binder and solvent decomposition, and then the positive electrode begins to undergo thermal decomposition reaction, releasing a lot of heat and gas. , And finally cause the battery to burn or explode. u003c/pu003eu003cpu003e 2. In the initial stage of lithium battery pack
charging, part of the electrical energy is converted into heat when the current passes through the battery, and ohmic polarization also generates part of the heat, but the surface temperature of the battery rises slowly; when the battery reaches a fully charged state , The continued intercalation reaction of lithium ions becomes the 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 overcharge 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; as the battery temperature rises, the reaction of metallic lithium with the solvent and the reaction of the lithium-intercalated carbon with the solvent occur successively, and the heat is out of control, accompanied by the decomposition of the solvent and the reaction between the binder and the lithium metal. u003c/pu003eu003cpu003e Third, the harm caused by short circuit, needle stick and impact to lithium ion batteries is roughly the same. In a short circuit, a large amount of heat is generated when the current passes through the battery, heating the battery, and the temperature of the battery rises to the temperature at which the positive electrode decomposes. The thermal decomposition of the positive electrode causes the battery heat to run out of control; Short circuit and generate a lot of heat, which raises the internal temperature of the battery to the temperature of thermal decomposition of the positive electrode; when the lithium ion battery is impacted, 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 , Which promotes the thermal decomposition reaction of the positive electrode to occur, causing the heat to run out of control. u003c/pu003eu003c/pu003e
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