Know the cause of lithium battery failure in one article

What is a lithium battery failure? Lithium battery failure refers to some specific substantive reasons or functional dysfunction caused by the degradation of the battery function. This may attack any link in processing, transportation, and use, which will not only affect the function of the battery, but even cause a fire. , Explosion and other safety issues. The failure of lithium battery can be divided into functional failure and safety failure according to its impact type. The important reasons for its appearance are also divided into internal and external causes. Internal causes include physical failures, chemical changes, etc., and external causes include high temperature, impact, acupuncture, and man-made injuries. Next, we will analyze several common lithium battery failures in detail, including capacity decay failure, internal short circuit, internal resistance increase, thermal runaway, etc. Capacity attenuation failure. Under normal circumstances, in the standard cycle life test, the battery capacity should not be less than 90% of the initial value after 500 cycles, and should not be less than 80% of the initial value after 1000 cycles. Lithium battery capacity decay failure is divided into reversible capacity decay and irreversible capacity decay. The reversible attenuation can adjust the battery charging and discharging conditions, improve the battery's use environment and other methods to restore the lost ability, irreversible attenuation, so irreversible changes The internal attack of the battery cannot restore the lost ability, so it cannot be saved . An important cause of battery capacity degradation is data failure, which is also closely related to objective factors such as the battery manufacturing process and operating environment. From the data point of view, the reasons for the capacity attenuation failure include the failure of positive data, the transitional appearance of SEI on the negative surface, the failure of the electrolyte, the failure of the collection fluid, and so on. In the event of a short circuit, an internal short circuit will often cause the lithium battery to self-discharge, attenuate the capacity, and cause safety accidents due to partial heat loss. During the short circuit of the battery, the data of the two electrodes are internally interconnected electronically, resulting in a high local current density. The internal short circuit of a lithium battery may be caused by the composition of lithium dendrites or shrinkage shock. Long-term internal short circuit will cause self-discharge and local temperature rise, and the influence of local temperature rise is very obvious. Due to the assumption that the temperature exceeds a certain threshold, the electrolyte may undergo initial decomposition through an exothermic reaction, resulting in thermal runaway and potential health and safety risks. Click on the picture to have a dialogue. Internal resistance. The internal resistance of the lithium battery and the electron transfer and ion transfer process of the battery are mainly divided into ohmic resistance and polarized internal resistance. This is mainly due to electrochemical polarization, electrochemical polarization and concentration. Poor polarization. When the internal resistance of the battery increases, the energy density decreases, the voltage and power decrease, and the battery heats up and other faults occur. Important factors affecting its attacks are battery key data and battery usage environment, and key data attacks are the root cause of the new influencing factors of internal resistance. Thermal runaway Thermal runaway is a cyclical process of positive energy feedback: a rise in temperature causes the system to heat up, which in turn heats up the system. Lithium battery overheating out of control means that part or all of the internal temperature of the battery rises rapidly, and the heat cannot be dissipated in time, and a large amount of it accumulates inside and induces further side reactions. The thermal runaway reaction involves the cobalt oxide chemistry in lithium batteries. When this chemical substance is heated to a certain temperature, it initially heats itself, and then fires and explosions occur. In some cases, the release pressure of the organic electrolyte can cause the battery to rupture. If exposed to high temperature or sparks, it may burn. In order to prevent out-of-control heat outbreaks, methods such as PTC, safety valves, and thermal conductive films are generally selected, but more importantly, the battery is improved in terms of planning, manufacturing processes, and methods of use. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: Can a ternary lithium battery be used for 8 years?