LR44 battery

　　Principle of thermal runaway chain reaction of LR44 battery

　　At the level of safety specifications for power lithium batteries, there is a lack of testing standards for the current control modules and systems to prevent thermal runaway thermal triggers, as well as life safety testing standards for cells, modules and system software, and there is an urgent need for scientific research and development. The key to my country's current standards is the hidden dangers of external components of rechargeable batteries, and there is no project to detect thermal runaway inside the battery.

　　Thermal runaway refers to the exothermic chain reaction of a single battery that causes the battery's self-temperature rise rate to change sharply and irreversibly, causing overheating, fire, and explosion.

　　Thermal runaway propagation refers to the thermal runaway phenomenon of the battery pack, or the single battery or battery module unit in the battery system, and triggers the thermal runaway of power lithium batteries in adjacent or other parts of the battery system.

　　Principle of thermal runaway chain reaction of LR44 battery:

　　(1) Causes of thermal runaway

　　The main causes of thermal runaway include: mechanical inducements, electrical inducements and thermal inducements.

　　Classic cases of fire accidents caused by mechanical equipment accidents include the scientific research results of the American General Motors Volt hybrid electric vehicle (volt), which has the highest sales volume in the world. And the world's most popular pure electric vehicle, the Motor Vehicle S, suffered fires throughout the process because the car's chassis was punctured by the road surface.

　　Take a typical example of a fire in a pure electric vehicle in my country, which illustrates the electric vehicle charging station caused by overcharging of the battery caused by the fire incident, and its Tesla model caused by the ultra-low temperature battery charging in winter. Fire safety incident.

　　A typical example is that a pure electric vehicle cannot be thermally controlled during operation. This is due to the release of a connecting component that causes high temperatures in the system software, resulting in thermal control and expansion of the battery pack.

　　The high-voltage system of pure electric vehicles can open up the heat in the bubbles and cause fires in pure electric vehicles. A classic case is that a pure electric vehicle in Nanjing was flooded after a period of time after a heavy rain.

　　In addition, pure electric vehicles in applications have life cycle safety issues. For example, if a pure electric vehicle is used for a period of time without any malicious events, the rechargeable battery components cannot The controlled heat caused a fire when the bus stopped at the station and ignited nearby buses, causing a lot of damage.

　　(2) Thermal runaway mechanism

　　After the entire evolution process, the safety accident of rechargeable batteries may enter the open stage. Generally speaking, after entering the open phase, the kinetic energy inside the lithium-ion battery may be released instantly, which is irreversible and uncontrollable, that is, heat cannot be controlled. Heat cannot control the intense temperatures generated by rechargeable batteries, and dangerous situations such as smoke, fire, and explosions can be observed at high temperatures.

　　Of course, according to the meaning of the theoretical safety factor, the rechargeable battery will not generate heat that cannot be controlled in a production safety accident. For example, rechargeable batteries do not necessarily generate uncontrollable heat after impact safety accidents; the insulation layer of lithium battery packs is ineffective, causing high-voltage accidents to workers; battery leakage current and odor cause physical discomfort to car workers, etc. Rechargeable batteries will not generate uncontrollable heat. heat. In the safety design of power lithium battery system software, the above conditions must be considered.

　　Thermal control is the most common safety factor incident and is a unique characteristic of lithium-ion battery safety factor incidents. Many tests have shown that rechargeable batteries that cannot be thermally controlled will not produce smoke, fire and explosions, nor will they explode.

　　In the case of smoke, in the case of ring v, if the temperature of the rechargeable battery is less than 660°C, the melting temperature of aluminum and platinum, the rechargeable battery is not easily ejected by reflected steam, and smoke is observed; if the temperature of the rechargeable battery is greater than 660°C, liquid aluminum The melt, rechargeable battery is accompanied by a large amount of reflected gas, which is the result of smoke emission.

　　In the event of a fire, generally due to the ignition of the lithium-ion battery electrolyte and dissolved substances, the heat cannot control the ignition in a safe accident. Therefore, starting from linkⅡ, the lithium battery electrolyte leaking out of the valve will be ignited and ignited.

　　According to the three elements of the combustion reaction (combustible, carbon dioxide, igniter), the flammable substance is the lithium battery electrolyte; the carbon dioxide problem in the rechargeable battery, so the lithium battery electrolyte will be exposed to fire; the igniter will come from the short circuit of the rechargeable battery Failures will also come from uncontrollable heat, high-speed injection of steam and valve body friction sparks.

　　In the case of an explosion, the general characteristic of an explosion is the effect of transient out-diffusion of high-pressure steam. The rechargeable battery has high accumulation standards inside, and the valve is an important means to immediately release the high-pressure steam accumulation. If the valve body can be opened before the battery shell cracks and releases enough high-pressure steam before the heat cannot control the entire process, the rechargeable battery will not easily explode; if the valve body cannot be opened immediately, an explosion event will occur.

　　Standard requirements for safety factor of power lithium batteries

　　Safety test specifications are the key to improving the safety factor of power lithium batteries. According to the arrangement of safety factors of power lithium batteries, the requirements for relative safety factors are clarified. At present, the safety test standards for power lithium batteries used in China include and.

　　The safety index values of single-pack and contact-pack power lithium batteries were evaluated, and a series of safety specifications and test standards were derived. gb/t31467 focuses on battery pack or charging system software level testing standards. Established gb/critical safety requirements and testing standards. Combined with gb/t31485-2015, the detailed mechanical energy safety protection standard consists of single battery, touch pack, power lithium battery pack and power lithium battery system software. At this stage, the overall testing standards for power lithium batteries are more stringent than abroad.

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