Understand the cause of the lithium ion battery failure

Source: 2020 - 03 - 28 16:09 hits: what time is the fault of lithium-ion batteries, lithium ion batteries is refers to the battery function attenuation caused by some specific practical reason or use of dysfunction, which may attack in the production, transportation, the use of any links, not only affects the function of the battery, and even lead to security issues such as fire, explosion. Lithium battery failure by its impact type can be divided into function failure and safety. Its main causes are divided into internal and external causes, the internal cause includes the physical failure, chemical change, etc. , external causes, including high temperature, impact, acupuncture, artificial damage, etc. Next, we will in detail several common lithium battery failure, including fault, internal short circuit capacity attenuation, internal resistance increases, such as thermal runaway. Capacity attenuation failure under normal circumstances, when a standard cycle life test, battery capacity after a 500 - cycle should not be less than 90% of the initial value, after a 1000 - cycle should not be less than 80% of the initial value. Lithium ion battery capacity attenuation failure can be divided into reversible capacity attenuation and irreversible capacity attenuation. Attenuation can adjust in the reversible battery charging and discharging conditions, improve the environment of the battery and other methods to restore the lost ability, irreversible attenuation, so the irreversible change battery internal attack of the attack can not restore lost ability, therefore cannot be saved. Due to battery capacity attenuation is the main reason of the failure data, the and battery manufacturing process, running environment and other objective factors also have inseparable relationship. Look from the data, including data failure, failure reasons of capacity attenuation SEI in negative surface transition, failure, collecting liquid electrolyte, etc. Internal short circuit when short circuit tends to cause the lithium ion battery self-discharge, damping capacity, part of the heat loss caused by accidents. In the process of the battery short circuit, two electrodes of the data in the internal electronically interconnected, lead to local high current density. Lithium ion battery internal short circuit composed of lithium dendrite or contraction caused by impact. Internal short circuit will lead to long-term self-discharge and local temperature rise, and the influence of local temperature rise is very obvious. Due to the assumed temperature above a certain threshold, the electrolyte may through the exothermic reaction initial decomposition, which leads to thermal runaway, there are potential risks to health and safety. Click on the image of internal resistance increase dialogue based on the lithium ion battery internal resistance and the electron transfer and the process of ion transfer cells, mainly divided into the ohmic resistance and the polarization resistance, this is mainly due to the electrochemical polarization, electrochemical polarization and concentration polarization. When the battery internal resistance increases, the energy density is reduced, the voltage and power reduction, such as battery heating failure problems arise. There are many factors that affect their attack cells key data and using the environment, and the key data attack is the root of internal resistance increase influence factors. Thermal energy is a positive feedback loop control thermal runaway process: hot temperature rising system, which in turn allow the system to heat up. Lithium battery overheat control refers to the part or all of the temperature of the battery, a rapid rise, unable to dissipate heat, a large number of accumulation in the internal, and induce further adverse events. 'thermal runaway reaction involving lithium cobalt oxide chemical substances in the battery. When this chemical is heated to a certain temperature, it will initially self heating, and fire and explosion. In some cases, the release of organic electrolyte pressure can lead to cell rupture. If exposed to high temperature or spark, it may burn. In order to prevent the outbreak of the heat out of control, will generally choose methods of PTC, relief valve, thermal conductivity of membrane, but more important is to improve the battery in such aspects as planning, manufacturing process, using method.