① species: mainly related to the internal short circuit of lithium ion batteries. The internal short circuit of lithium -ion batteries is the most important cause of safety issues. Most of the security problems are caused by internal short circuits. The internal short circuit is the positive and negative extremely short circuit in the battery. Generally, it is caused by the metal impurities mixed in the production process, the burrs caused by the cutting during cutting, the formation of lithium -branch crystals during use, and accidental mechanical stress such as being squeezed. A large amount of heat occurs in the short circuit inside, which causes safety problems. In most cases, the safety problems caused by the short circuit inside the lithium -ion battery are manifested as the danger of fire and explosion. Essence
② species: It is mainly related to the circuit failure. In order to charge and discharge management and safety protection of lithium ions, the host equipment or adapter used in the battery needs to be designed and discharged. There is also a load circuit with discharge in some devices.
In order to protect the lithium ion battery, the protection circuit board needs to be added to the battery pack during the packaging process. The internal or external circuits of these battery packs may fail, which in turn causes electrical stress conditions such as overvoltage, excessive charging, excessive discharge, external short circuit, and overload of the battery. These conditions may also lead to overheating, fire, explosion, etc. Danger.
In the electrical stress conditions, over -voltage charging and excessive charging will generate severe side reactions, produce a large amount of heat, which will cause heat out of control. Excessive discharge will cause the battery voltage to be lower than the discharge interception voltage stipulated by the manufacturer. At this time It is mainly the decomposition of the electrolyte, which generates a large amount of gases and causes the shell to bloating and rupture. The external short -circuit and overload will increase the discharge current, which will increase the temperature of the internal temperature of the battery or the temperature of the external conductor, which will cause heating out of control.
③ species: mainly related to misuse and abuse. 误用和滥用包括在高温下使用或存储(如在车内)、用户使用了错误的充电器(过压充电)、极性反接充电、在携带过程中电池端子被外部的导体(金属、 Soluble, etc.) Short circuit. These misuse and abuse may cause a large amount of heat from the battery, and even cause heat loss.
④ species: It is mainly related to the rupture of the battery shell. Internal and external stress that causes the rupture of the shell. Internal stress refers to the internal and external pressure difference caused by sub -reaction such as excessive discharge; external stress refers to the rupture of normal or unexpected mechanical stress during transportation and use, such as vibration, acceleration impact, and falling. The rupture of the shell will leak the internal electrolyte, which will cause danger.
⑤ species: mainly related to consistency. In the battery pack composed of multiple battery (battery) through series, parallel, and skewers, the consistency of the internal resistance, opening voltage, and capacity of the battery will cause The over -voltage charging, under pressure discharge, etc. of the parallel block causes safety problems.
Analysis of the cause of lithium battery damage
There are many causes of damage to lithium -ion batteries. Different reasons may cause the same result and phenomenon, and some are direct causes, and some are indirect reasons. Factors that can be excluded, and then derive the root cause.
The lithium -ion battery fails to get drums, which can be analyzed. The direct reason for the battery drum is due to the decomposition of the electrolyte, which produces gas inside the sealed battery, causing the battery to swell. There are many reasons for the decomposition of electrolytes. All possible factors are shown in Figure 4. Obviously, the electrolyte is the most important cause.
The high temperature that makes the electrolyte suffers from heat -degrading may come from battery overload, external short circuit, high temperature, and internal short circuit of the battery. If the scene application before failure can exclude the previous three projects, the most likely reason is that the internal circuit of the battery is short -circuited.
Battery swelling cause
As a result, there are several possibilities such as lithium branches, burrs and metal impurities in short circuits in the battery. It is necessary to further analyze its possibilities and causes. Taking lithium branches crystal as an example, the direct cause of lithium branch crystals may be caused by poor battery materials, or it may be after the lithium analysis of lithium. The lithium metal grows along the gap between the diaphragm and forms a lithium branch crystal. The cause of the lithium of negative electrode analysis may include the high charging rate, or charging at too low temperature. That is, the battery charging temperature and current are not properly managed. This inappropriate is caused by the comprehensive caused by the protection circuit problem (no design or design), the system charging circuit problem (failure or design), and the user's environmental problems.