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Here is a professional company talking about the failure reason of lithium-ion battery.
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Lithium Iron Phosphate Battery
Commercial lithium-ion batteries often exhibit some failure phenomena during use or storage, including capacity reduction, internal resistance increase, rate performance reduction, gas production, liquid leakage, short circuit, deformation, thermal runaway, and lithium deposition. The performance, reliability and safety of lithium-ion batteries. These failures are caused by a series of complex chemical and physical mechanisms within the battery.
(1) Capacity attenuation: The capacity attenuation of ion batteries is mainly divided into two categories: reversible capacity attenuation and irreversible capacity attenuation. Reversible capacity attenuation can restore the lost capacity by adjusting the battery charge and discharge system and improving the battery usage environment; irreversible capacity decay is an irreversible change in the internal battery that produces an unrecoverable capacity loss. The root cause of battery capacity attenuation is the failure of materials, and it is closely related to objective factors such as battery manufacturing process and battery use environment. From the material point of view, the main causes of failure are structural failure of the positive electrode material, SEI transition growth of the negative electrode surface, decomposition and deterioration of the electrolyte, corrosion of the current collector, and trace impurities in the system.
(2) Increase of internal resistance: The internal resistance of lithium-ion battery is related to the internal electron transport and ion transport process of the battery system. It is mainly divided into ohmic resistance and polarization internal resistance, wherein the polarization internal resistance is mainly caused by electrochemical polarization. There are two types of electrochemical polarization and concentration polarization. The main factors leading to the increase of the internal resistance of lithium-ion batteries are the key materials of the battery and the environment in which the battery is used. The use of synchrotron radiation technology to propose the transition mechanism of transition elements is the cause of potential hysteresis and voltage decay: It is shown that within the battery system, the abnormality of key materials is the fundamental influencing factor of internal resistance increase and battery polarization.
(3) Internal short circuit: The performance of short circuit can be divided into: 1 short circuit between copper/aluminum current collector; 2 diaphragm failure loses electronic insulation or void becomes large, causing positive contact between positive and negative electrodes, local heat generation is serious, and further charging and discharging During the process, it may diffuse to the surrounding, forming thermal runaway; 3 the transition metal impurities in the positive electrode slurry are not removed, piercing the separator, or causing the lithium dendrites to form an internal short circuit; 4 lithium dendrites cause internal short circuits. In addition, unreasonable design and excessive local pressure can lead to internal short circuits during battery design and battery assembly. For example, the South Korean media SBS reported that Samsung Note7 caused a fire explosion, which pointed out that the positive and negative contacts caused by internal extrusion caused an internal short circuit, which caused thermal runaway of the battery. Under the induction of overcharge and overdischarge of the battery, internal short circuit will also occur, mainly due to the corrosion of the current collector, and deposition on the surface of the electrode. In severe cases, the positive and negative electrodes will be connected through the diaphragm.
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