Analysis of lithium battery failure and common failure performance of lithium battery

Lithium batteries often have certain failure phenomena during use or storage, including capacity degradation, increase in internal resistance, reduction in rate performance, gas production, leakage, short circuit, deformation, thermal runaway, lithium evolution, etc., which seriously reduce the lithium battery’s Use performance, reliability and safety. These failure phenomena are caused by the mutual use of a series of complex chemical and physical mechanisms inside the battery. Let's analyze the common failure performance of lithium batteries. Lithium battery failure and cause one is performance failure, and the other is safety failure. Performance failure means that the performance of the lithium battery does not meet the use requirements and related indicators. The important ones include capacity degradation or diving, short cycle life, poor rate performance, poor consistency, easy self-discharge, high and low temperature performance degradation, etc.; safety failure refers to What is the failure of lithium batteries with certain safety risks due to improper use or abuse, such as thermal runaway, flatulence, leakage, lithium evolution, short circuit, swelling deformation, etc. The reasons for the failure of lithium batteries can be divided into internal and external causes. The internal cause mainly refers to the nature of the physical and chemical changes of the failure. The research scale can be traced back to the atomic and molecular scales to study the thermodynamic and kinetic changes of the failure process. External factors include impact, acupuncture, corrosion, high-temperature combustion, man-made damage and other external factors. Common failures of lithium batteries ●Capacity decay failure: 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. ●Structural failure of cathode material: The structural failure of cathode material includes crushing of cathode material particles, irreversible phase transition, material disorder, etc. During the charging and discharging process of LiMn2O4, the structure of LiMn2O4 will be distorted due to the Jahn-Teller effect, and the particles may even be broken, causing the electrical contact between the particles to fail. The LiMn1.5Ni0.5O4 material will undergo a tetragonal-cubic phase transition during the charge and discharge process. The LiCoO2 material will enter the Li layer due to the transition of Li during the charge and discharge process, causing the layered structure to become chaotic and restrict Its capacity to play. ●Negative material failure: The failure of graphite electrode mainly occurs on the graphite surface. The graphite surface reacts with the electrolyte to process the solid electrolyte interface phase (SEI). If excessive growth will lead to a decrease in the content of lithium ions in the internal system of the battery, the result is a decrease in capacity . The failure of silicon anode materials is mainly due to the cycle performance problems caused by their huge volume expansion. ●Electrolyte failure: LiPF6 has poor stability and is easy to decompose to reduce the migrating Li+ content in the electrolyte. It also easily reacts with trace amounts of water in the electrolyte to generate HF, causing corrosion inside the battery. Poor air-tightness causes the electrolyte to deteriorate, and the viscosity and chromaticity of the electrolyte change, which ultimately leads to a sharp drop in ion transmission performance. ●The failure of the current collector: the current collector corrodes and the adhesion of the current collector decreases. The HF generated by the failure of the electrolyte will corrode the current collector and generate compounds with poor conductivity, resulting in increased ohmic contact or failure of the active material. After the Cu foil is dissolved at a low potential during the charge and discharge process, it is deposited on the surface of the positive electrode, which is the so-called copper precipitation. The common form of current collector failure is that the binding force between the current collector and the active material is not enough, which causes the active material to peel off and cannot supply capacity for the battery. Lithium battery failure phenomenon Lithium battery failure phenomenon is divided into two parts: dominant and recessive. Dominance refers to directly observable performance and characteristics, such as surface structure fracture and deformation that can be observed at the failure site and can be observed through macroscopic analysis, including fire, heat, swelling (gas production), deformation, liquid leakage, and encapsulation Material damage and distortion, packaging material burrs, virtual or missing welding, plastic material melting and deformation, etc. Implicit refers to the performance and characteristics that cannot be directly observed but must be obtained through disassembly and analysis, or shown in simulation experiments, such as microscopic failures detected through laboratory disassembly. The common hidden failure phenomena in the process of lithium battery failure include internal short circuit of positive and negative electrodes, lithium precipitation, electrode powder loss, diaphragm aging, diaphragm blockage, diaphragm puncture, electrolyte drying up, electrolyte denaturation failure, negative electrode dissolution, and transition metal Precipitation (including copper precipitation), pole piece burrs, abnormal winding (or lamination), capacity diving, abnormal voltage, excessive resistance, abnormal cycle life, abnormal high/low temperature performance, etc. The scope of the failure phenomenon often overlaps with the scope of the failure mode. The failure phenomenon is more inclined to the direct description of the phenomenon, which belongs to the information collection and description of the failure process; the failure mode is generally understood as the nature and type of the failure, which is the classification of the failure. Classes and divisions. Lithium battery failure phenomenon is a large cluster of battery failure performance, and its meaning and classification are very necessary. 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: What is the difference between polymer lithium battery and lithium battery