Simple introduction of the failure of lithium-ion battery
Lithium-ion batteries often fail in the use or storage process, including capacity decay, increased internal resistance, doubling performance reduction, gas production, leakage, short circuit, deformation, thermal control, lithium analysis, etc., which seriously reduces the use performance, reliability and safety of lithium-ion batteries. These failure phenomena are caused by a complex interaction of chemical and physical mechanisms within the battery.
The lithium-ion battery system is complex, involving thermodynamics, dynamics, microstructure, intergroup interaction and reaction, surface interface reaction and other aspects. The correct analysis and understanding of the failure phenomenon plays an important role in the performance and technical improvement of lithium-ion batteries. This paper introduces the introduction of battery failure mechanism.
Failure performance and failure mechanism of lithium-ion battery
capacity decay
It is mainly divided into two categories: reversible capacity decay and irreversible capacity attenuation. Reverversible capacity attenuation can restore the lost capacity by adjusting the battery charging and discharge system and improving the battery use environment; the irreversible capacity decay is an irreversible capacity loss caused by irreversible changes inside the battery.
The root cause of battery capacity attenuation failure is in 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 the failure mainly include the structural failure of the cathode material, the overgrowth of the negative electrode surface SEI, electrolyte decomposition and deterioration, collector fluid corrosion, system trace impurities, etc.
Internal resistance
The internal resistance of the lithium-ion battery is related to the internal electronic transmission and ion transmission process of the battery system, mainly divided into ohmic resistance and polarization internal resistance. The polarization internal resistance is mainly caused by electrochemical polarization, including electrochemical polarization and thick differential polarization. The main factors causing the increase of internal resistance of lithium-ion battery are divided into key battery materials and battery use environment.
Short-circuit
The performance of the short circuit can be divided into four categories:
Short circuit between the copper / aluminum collecting fluid;
The diaphragm failure loses electronic insulation or gap change ambassador positive and negative micro contact, local fever is serious, and then in the process of further charge and discharge, may spread around, to form a loss of thermal control;
The transition metal impurities in the cathode slurry are not removed clean, piercing the diaphragm, or promote the generation of negative lithium crystal leading to the internal short circuit;
Lithium crystal leads an internal short circuit.
In addition, in the battery design and manufacturing or battery pack assembly process, unreasonable design and excessive local pressure will also lead to internal short circuit; under the guidance of overcharging and overrelease of the battery, internal short circuit, mainly due to the corrosion of the collector fluid, deposition phenomenon on the electrode surface, serious cases will connect positive and negative poles through the diaphragm
Gas Production
Gas production of lithium-ion battery is mainly divided into normal gas production and abnormal gas production. The gas production phenomenon in the process of battery battery is normal. H C2H22, CO2 was produced by ester single / double electron reaction. Abnormal gas production is mainly only in the process of battery cycle, the transition consumption of electrolyte release gas or cathode material oxygen release and other phenomena, often appear in the soft pack battery, resulting in excessive internal pressure of the battery, breaking the packaging aluminum film, internal core contact problems, etc.
thermal runaway
Thermal runaway control refers to the rapid rise of local or overall temperature inside the lithium ion battery, heat cannot be dispersed in time, a large amount accumulates in the interior, and induce further secondary reactions.
In order to prevent serious safety problems caused by lithium-ion battery in thermal control, PTC, safety valve and heat conduction film and other measures are often adopted, and at the same time, battery design, battery manufacturing process, battery management system, battery use environment and other aspects need systematic consideration.
lithium precipitation
Lithium precipitation is a relatively common phenomenon of lithium-ion battery aging and failure. The expression is mainly a layer of gray, gray-white, or gray-blue substances appearing on the surface of the negative electrode sheet, which are metal lithium precipitated from the negative electrode surface.
