Analyze what is a lithium battery failure

Lithium battery failure refers to the degradation of battery function or abnormal application function due to some specific material reasons. It may occur in any link of processing, transportation and application, not only affecting the function of the battery, but even causing safety issues such as fire and explosion. Lithium battery failures can be divided into functional failures and safety failures according to different types of impact. The important reasons for its occurrence are also divided into internal and external causes. Internal causes include physical failures, chemical changes, etc., and external causes include high temperature, collisions, needle sticks, and man-made injuries. Next, we will analyze in detail several common failures of lithium batteries, including capacity decay failure, internal short circuit, internal resistance increase, thermal runaway, and so on. Capacity attenuation failure is generally 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 1,000 cycles. If the capacity does not meet the specification requirements and excessive attenuation occurs, then the capacity attenuation has failed. Lithium battery capacity decay failure is divided into reversible capacity decay and irreversible capacity decay. At the same time, the reversible attenuation can restore the lost ability by adjusting the charging and discharging conditions of the battery, improving the operating environment of the battery, etc., and the irreversible attenuation cannot be saved because of the irreversible change of the battery, and the lost ability cannot be restored. An important reason for battery capacity degradation is data failure, which is also inseparable from objective factors such as battery manufacturing technology and application environment. From the data point of view, the reasons for the capacity attenuation failure include positive data failure, negative surface SEI transition, electrolyte failure, fluid collection failure and so on. In the case of a short circuit, an internal short circuit often causes self-discharge, capacity degradation, partial thermal runaway and safety accidents of lithium batteries. During a short circuit inside the battery, the two electrodes are electronically interconnected, resulting in a high local current density. The internal short circuit of a lithium battery may be caused by the formation of lithium dendrites or compression shock. Long-term internal short circuit will cause self-discharge and local temperature rise, and the influence of local temperature rise is very significant. When the temperature exceeds a certain threshold, the electrolyte may differentiate through an exothermic reaction, leading to thermal runaway and potential health and safety hazards. Internal resistance: The internal resistance of lithium batteries and the battery in the process of electron transmission and ion transmission are mainly divided into ohmic resistance and polarized internal resistance. This is mainly due to electrochemical polarization, and then divided into electrochemical polarization and concentration difference. polarization. When the internal resistance of the battery increases, the energy density decreases, the voltage power decreases, and the battery generates heat and other malfunctions. Important factors affecting its occurrence are battery critical data and battery usage environment, but the abnormality of critical data is the fundamental factor influencing the increase of internal resistance. Thermal runaway Thermal runaway is a process of positive energy feedback: an increase in temperature causes the system to heat up, which in turn causes the system to heat up. Thermal runaway of lithium battery refers to the rapid increase in the temperature of part or the whole of the battery, and the heat cannot be dispersed in time, and a large amount of it accumulates inside, which induces further secondary uses. Participating in the heat escape reaction is the cobalt oxide chemical substance in lithium batteries. When this chemical substance is heated to a certain temperature, it starts to heat up spontaneously, and then explodes into fire and explosion. In some cases, the release pressure of the organic electrolyte can cause the battery to rupture. It may also burn if exposed to high temperatures or sparks. In order to prevent the occurrence of thermal runaway, PTC, safety valve, thermal film and other methods are generally used, but more importantly, it is necessary to improve the planning, production skills and use methods of the battery. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: How to prevent automobile lithium battery from catching fire?