Lithium battery failure classification and failure reason analysis

Classification and causes of lithium battery failure 1 Lithium battery failure classification In order to prevent functional degradation and battery safety issues, it is imperative to perform failure analysis on lithium batteries. Lithium battery failure refers to the deterioration of battery function or abnormal operation due to some specific material reasons. Common Lithium Battery Failure Classification 2 Causes of Lithium Battery Failure The causes of lithium battery failure can be divided into internal causes and external causes. The importance of internal factors refers to the nature of the physical and chemical changes in the failure. The research scale can be traced back to the atomic and molecular scales to study the thermodynamic and dynamic changes in the failure process. External factors include impact, acupuncture, corrosion, high temperature fire extinguishing, human damage and other external factors. Lithium battery failure classification and failure reason Lithium battery internal failure situation 3. Lithium battery common failure performance and failure mechanism analysis Capacity attenuation failure In the standard cycle life test, the discharge capacity at 500 cycles should not be less than 90% of the initial capacity. Or when the number of cycles reaches 1000, the discharge capacity should not be less than 80% of the initial capacity. If the content volume drops sharply during the standard period, it is a capacity attenuation failure. The root cause of battery capacity decay failure is data failure, and data failure is closely related to objective factors such as battery manufacturing technology and battery working environment. From the data point of view, the important reasons for the failure are the structural failure of the positive electrode data, the SEI transition growth of the negative electrode appearance, the synthesis and disintegration of the electrolyte, the corrosion of the collection liquid, and the trace impurities of the system. Structural failure of positive electrode data: The structural failure of positive electrode data includes particle fragmentation, irreversible phase change, data disorder, etc. During the charging and discharging process, due to the jahn-teller effect, the structure of LiMn2O4 will be distorted, causing the particles to break and the electrical contact between the particles to fail. The limn1.5ni0.5o4 data will have a phase change of the tetragonal-cubic crystal system during the charging and discharging process, although the LiCoO2 data will cause the company to enter the Li layer due to the transition and release of Li during the charging and discharging process, which will constitute The hierarchical structure hinders and limits its capabilities. Negative data failure: graphite electrode failure mainly occurs on the graphite surface. The graphite surface reacts with the electrolyte and consumes the solid electrolyte interface phase (SEI). It is assumed that overgrowth will lead to a decrease in the lithium ion content of the battery's internal system, leading to capacity degradation. The failure of the silicon anode material is mainly due to the excessive shrinkage of its volume, which leads to the failure of the cycle function. Electrolyte failure: LiPF6 has poor stability and simple synthesis, which reduces the replaceable Li+ content in the electrolyte. It also simply reacts with a small amount of water in the electrolyte to form HF and form corrosion inside the battery. Due to insufficient air-tightness, the electrolyte is dissolved, and the viscosity and concentration of the electrolyte changes, resulting in a sharp decline in the ion transport function. Collector fluid failure: the collector fluid corrodes, and the adhesion of the collector fluid decreases. The HF caused by the failure of the above-mentioned electrolyte will corrode the collector solution and produce compounds with poor conductivity, which will cause new ohmic contacts or failure of active materials. During the charging and discharging process, the copper foil dissolves at a low potential and deposits on the surface of the positive electrode, which is called copper evolution. The common method for the failure of the collected fluid is that the separation force between the fluid and the active material is insufficient to cause the active material to peel off, so that the battery cannot be supplied with capacity. Increase in internal resistance The increase in internal resistance of lithium batteries will be accompanied by problems such as a decrease in energy density, a decrease in voltage power, and battery heat generation. The important factors that cause the new internal resistance of lithium batteries are divided into battery key data and battery use environment. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete.