Why does the capacity of lithium batteries decay

Lithium-ion batteries have a limited lifespan. As the number of uses increases, the capacity of lithium-ion batteries is also depleted. Until the end it loses its use value. Then why does the capacity of the lithium battery decay? 1) The structure of the positive electrode material The positive electrode material is the main source of power for the lithium ion battery. When the lithium ions are extracted from the positive electrode, in order to maintain the neutral state of the material, the metal element will inevitably be oxidized to reach A high oxidation state is accompanied by a change in 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 the resultant breakage of the crystal grains and the propagation of cracks, causing mechanical damage to the structure of the material, and thus causing electrochemistry in the lithium battery Performance degradation. 2) Anode material structure Commonly used anode materials for 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 part of the lithium ions. With the use of lithium batteries, changes in the graphite structure will also cause the battery capacity to decrease. Although the morphological structure of graphite is maintained, the half-height width of the crystal plane becomes larger, resulting in a smaller crystal grain size in the c-axis direction. The change in the crystal structure leads to cracks in the carbon material, which in turn 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, thus causing the irreversible capacity degradation of the lithium battery. 3) The oxidative decomposition and interface reaction of the electrolyte. The nature of the electrolyte significantly affects the specific capacity, life, rate charge and discharge performance, operating temperature range and safety performance of lithium-ion 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 the capacity of the lithium battery. The decomposition and side reactions of the electrolyte are the main factors for the capacity degradation of lithium batteries. Regardless of the positive and negative 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. 4) Positive electrode overcharge reaction When the ratio of positive electrode active material to negative electrode active material is too low, positive electrode overcharge is likely to occur. The capacity loss caused by overcharging of the positive electrode of a lithium battery is mainly due to the production of electrochemical inert substances (such as Co3O4, Mn2O3, etc.), which destroy the capacity balance between the electrodes, and the capacity loss is irreversible. 5) Electrode instability. When the positive electrode active material is unstable during charging, it will react with the electrolyte and cause the capacity to decrease. Factors affecting the instability of positive electrode materials include structural defects of the positive electrode material, carbon black content, and high charging potential. Among them, the structural defects of the positive electrode material are the most important influencing factors. Lithium battery capacity refers to the size of the battery's stored power. We are now designing electronic products and often use lithium batteries for power supply. Just like mobile phones or tablet computers using lithium batteries, we are familiar with the knowledge of lithium battery capacity. Perhaps it is very important for the use and design of lithium battery power supply, including the design of battery chargers. necessary. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: How to buy lithium battery electric scooters