The widely used positive electrode material for lithium-ion batteries is lithium cobalt oxide. The theoretical capacity of lithium cobalt oxide is 270mAh/g, but in reality, it can only exert a capacity of 135-140mAh/g. Excessive use will damage its material structure. If certain accidents occur, such as damage to the management system causing the charging voltage of the battery to be too high, the remaining lithium in the positive electrode will come out and deposit in the form of metallic lithium on the surface of the negative electrode through the electrolyte. The surface of metallic lithium is prone to the formation of "dendrites", which can puncture the insulation film, cause a short circuit between the positive and negative electrodes, and cause the battery to quickly heat up, leading to safety accidents. Overcharging the battery can also cause the positive electrode to accelerate the oxidation of the electrolyte at high voltage, resulting in thermal runaway of the battery due to the heat and gas generated. Overheating inside the battery can accelerate the reaction of lithium cobalt oxide. The internal temperature of the battery can instantly exceed 150 ℃, the separator is melted, the positive and negative poles are directly short circuited, and the battery burns and explodes. If other metal impurities are mixed in during the battery production process, it is also easy to cause local overheating of the battery during charging and discharging, thereby causing safety issues.

　　Although lithium-ion batteries have safety issues, there are currently no other types of batteries that can replace them due to their inherent performance. Major lithium-ion battery companies have also strengthened their control over safety, mainly focusing on the following areas: replacing lithium cobalt oxide with new positive electrode materials in areas with high safety requirements (such as lithium manganese oxide, lithium iron phosphate, ternary systems, etc.)

　　To make our lithium batteries safer, we need to do the following:

　　1. Adopting stricter methods to control the production environment and product quality;

　　2. Develop more detailed and strict industry and enterprise standards;

　　3. Develop new electrolyte additives, separators, negative electrode materials, etc;

　　4. Strengthen the control of the battery protection system to prevent overcharging of the battery.

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