What is the important performance of lithium-ion battery failure

What is the important reason for the failure of lithium-ion batteries? 1) Capacity attenuation: The capacity attenuation of ion batteries is mainly divided into two types: reversible capacity attenuation and irreversible capacity attenuation. Reversible capacity decay can restore the lost capacity by adjusting the battery charging and discharging system and improving the battery usage environment. Irreversible capacity decay is an irreversible change in the battery's internal capacity and an irreversible capacity loss. The root cause of battery capacity decay failure is the failure of materials, and it is closely related to objective factors such as battery manufacturing process and battery use environment. From a material point of view, the main reasons for the failure are the structural failure of the positive electrode material, the transitional growth of SEI on the negative electrode surface, the decomposition and deterioration of the electrolyte, the corrosion of the current collector, and the trace impurities of the system [2]. (2) Increase in internal resistance: The internal resistance of lithium-ion batteries is related to the electron transmission and ion transmission processes within the battery system. It is mainly divided into ohmic resistance and polarized internal resistance. The polarized internal resistance is mainly caused by electrochemical polarization. There are two kinds of electrochemical polarization and concentration polarization. The important factors that lead to the increase of the internal resistance of lithium-ion batteries are divided into key battery materials and battery use environment. my country University of Science and Technology Que Yongchun et al. [3] used synchrotron radiation technology to propose that the jumping mechanism of transition elements is the cause of potential hysteresis and voltage attenuation: it explains that in the battery system, the abnormality of key materials is the root of the increase in internal resistance and the polarization of the battery. Influencing factors. (3) Internal short circuit: The performance of short circuit can be divided into: ①Short circuit between copper/aluminum current collector; ②Diaphragm fails to lose electrical insulation or the gap becomes micro-contact between positive and negative electrodes, local heating is serious, and then further charge and discharge During the process, it may diffuse to the surroundings and cause thermal runaway [4]; ③The transition metal impurities in the positive electrode slurry are not removed cleanly, piercing the separator, or promoting the formation of negative electrode lithium dendrites, causing internal short circuits; ④Lithium dendrites cause internal short circuits Happened [5-7]. In addition, in the process of battery design and manufacturing or battery pack assembly, unreasonable design and excessive local pressure can also cause internal short circuits. For example, the South Korean media SBS reported that the cause of the fire and explosion of SamsungNote7 pointed out that the positive and negative electrodes contact caused by internal extrusion caused an internal short circuit, which in turn caused the thermal runaway of the battery. Under the induction of battery overcharge and overdischarge, internal short circuit will also occur. The important reason is that the current collector corrodes and deposits on the electrode surface. In severe cases, the positive and negative electrodes will be connected through the diaphragm. (4) Gas production: lithium ion battery Gas production is mainly divided into normal gas production and abnormal gas production [9]. During the battery formation process, the gas production phenomenon that occurs when the electrolyte is consumed to form a stable SEI film is normal gas production. The gas production in the formation stage is mainly due to the emergence of H2, CO2, C2H2, etc. from the one/two-electron reaction of esters [10-11]. Abnormal gas production is important only in the battery cycle process, excessive consumption of electrolyte release gas or cathode material oxygen release, etc., which often occur in soft pack batteries, resulting in excessive internal pressure and deformation of the battery, breaking the packaging aluminum film and internal Battery contact problems, etc. (5) Thermal runaway: Thermal runaway refers to the rapid increase in temperature inside the lithium-ion battery. The heat cannot be dissipated in time, and a large amount of heat accumulates inside and induces further side reactions [12-14]. Table 1 lists the common thermal behavior inside lithium-ion batteries. In order to prevent lithium-ion batteries from causing serious safety problems in thermal runaway, measures such as PTC, safety valves, and thermally conductive films are often used. At the same time, the battery design, battery manufacturing process, battery management system, battery use environment, etc. must be systematic (6) Lithium analysis: Lithium analysis is a relatively common phenomenon of aging and failure of lithium-ion batteries. The most important manifestation is the appearance of a layer of gray, off-white or gray-blue material on the surface of the negative electrode. These substances are metallic lithium precipitated on the surface of the negative electrode. Figure 3 is a common lithium evolution phenomenon. Figure 4 analyzes the reasons for the phenomenon of lithium evolution in batteries from two aspects, and combines the emergence of lithium with battery cell manufacturing process and battery use environment (including charging and discharging system and charging and discharging environment) and other factors. Tsinghua University Zhang Qiang et al. [18] pointed out that the important factors affecting dendrite growth are current density, temperature, and electricity. They are achieved by adding electrolyte additives, artificial SEI, high salt concentration electrolyte, structured negative electrodes, and optimizing battery configuration design. Inhibit the growth of dendrites. 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 post: Is the leakage of dry battery toxic?