Why does the capacity of the ternary lithium battery decline?

Reasons for the capacity decay of ternary lithium batteries 1. The structure of the positive electrode material. The positive electrode material is an important source of lithium ions. When lithium ions are extracted from the positive electrode, in order to maintain the neutral state of the material, the metal elements will inevitably be oxidized to a high level. The oxidation state of, here is accompanied by the transformation of the composition. The transformation of components easily leads to phase transition and changes in bulk structure. The phase transition of the electrode material can cause the change of the lattice parameters and the lattice mismatch. The induced stress caused by this causes the breakage of the crystal grains, and initiates the propagation of cracks, causing mechanical damage to the structure of the material, thereby causing degradation of electrochemical performance. 2. Anode material structure Commonly used anode materials for commercial lithium batteries include carbon materials, lithium titanate, etc. This article uses typical anode graphite for analysis. The decay of the lithium battery capacity occurs for the first time in the formation stage, during this stage SEI will be formed on the surface of the negative electrode, consuming some lithium ions. With the use of lithium batteries, changes in the graphite structure will also cause the battery capacity to decrease. Liu et al. studied the capacity decay mechanism of LiFePO4/C batteries, which is also applicable to ternary lithium batteries. They found that although the carbon material after cycling maintains the morphology and structure of graphite, the half-height width of its crystal plane becomes larger, resulting in c The crystal grain size in the axial direction becomes smaller, and the change in the crystal structure causes cracks in the carbon material, which destroys the SEI film on the negative electrode surface and promotes the repair of the SEI film. The excessive growth of the SEI film consumes active lithium, which causes the irreversible capacity degradation of the battery. . 3. Oxidative decomposition and interface reaction of electrolyte. The nature of electrolyte significantly affects the specific capacity, life, rate charge and discharge performance, operating temperature range and safety performance of lithium batteries. The electrolyte mainly includes three parts: solvent, electrolyte and additives. The decomposition of the solvent and the decomposition of the electrolyte will cause the loss of battery capacity. The decomposition and side reactions of the electrolyte are important factors for the capacity degradation of lithium batteries. Regardless of the positive and negative electrode materials and processes used, as the lithium battery is recycled, the decomposition of the electrolyte and the interface between the positive and negative materials will occur. Reactions will cause capacity attenuation. 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: How to test the performance of lithium batteries?