Safety analysis of lithium-ion batteries

The safety of lithium-ion batteries Ion batteries have the advantages of high energy density, high output voltage, long cycle life, and low environmental pollution, and have been widely used in the field of microelectronics. At the same time, they also have broad application prospects in electric vehicles, military, space technology and other fields [1-2]. However, lithium-ion batteries bring some safety hazards while benefiting mankind. In recent years, lithium-ion battery safety accidents have occurred from time to time. For example, in 2006, Apple and Lenovo laptops were recalled due to battery safety issues; in 2008, Honda hybrid vehicles caught fire; and 825 all-electric buses caught fire due to battery overheating. Due to these incidents, the safety of lithium-ion batteries has attracted more and more attention. Safety analysis of lithium-ion batteries The safety of lithium-ion batteries can be attributed to two factors: one is the characteristics of the lithium-ion battery itself; the other is caused by emergency or improper use of the battery. Lithium-ion batteries have a series of potential exothermic reactions, which are the source of safety problems for lithium-ion batteries. 1. The reason for the lithium ion battery itself The characteristics of the lithium ion battery itself are the fundamental factor determining its safety [3-4]: (1) Due to the high energy density, the lithium ion battery is prone to unsafe behavior due to thermal runaway; ( 2) When the lithium ion battery is overcharged, the structure of the positive electrode material lithium ion changes, which makes it have a strong oxidizing ability; or the positive electrode material directly releases oxygen, causing the solvent in the electrolyte to be strongly oxidized; the solid state of the negative electrode surface The decomposition of the electrolyte interface (seI) film and the reaction between the metallic lithium precipitated from the negative electrode and the electrolyte, if the heat released by these processes accumulates, may cause thermal runaway. (3) Lithium-ion battery electrolyte is mostly organic solvent, the important component is carbonate, it flashes, the boiling point is very low, it is easy to be oxidized at about 4.6V, if there is leakage, it is easy to cause the battery to catch fire, or even burn and explode; (4) ) When the lithium ion battery binder crystallizes, it is easy to form copper dendrites and peel off the active material, resulting in a short circuit inside the battery and posing safety hazards. 2. Emergencies or reasons for abuse In some emergency situations, such as battery overcharging, acupuncture penetration, squeezing, and high-temperature environments, the electrodes and organic electrolytes are prone to chemical reactions, such as the decomposition of the SE membrane and the organic electrolyte. Oxidation and reduction, the decomposition of the positive electrode, the oxygen generated in the positive electrode decomposes, and further reacts with the organic electrolyte. If the large amount of heat generated by these reactions cannot be dissipated to the surrounding environment in time, it will cause thermal runaway, and eventually cause the battery to burn and explode. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete.