Why the lithium battery capacity is reduced

1. Changes in the structure of the cathode material The cathode material is an important source of lithium batteries. When lithium ions are removed from the positive electrode, in order to maintain the electrical neutrality of the material, the metal element will be unpreparedly oxidized to a high oxidation state, and accompanied by changes in the composition. The transformation of components simply leads to changes in phase handling and bulk structure. The phase transformation of electrode materials will cause changes in lattice parameters and lattice mismatches. Induced stress will lead to crystal cracking and crack propagation of the materials, leading to mechanical changes in the data structure. Damage, and then lead to the decline of the electrochemical function of the lithium battery. -. 2. The structure of negative electrode materials. Carbon materials and lithium titanate are commonly used materials for commercial lithium batteries. In this paper, a typical anode graphite is selected for decomposition. The decay of the lithium battery capacity is the first time that the current composition stage, during which SEI consumes some lithium ions on the surface of the negative electrode. With the use of lithium batteries, changes in the graphite structure will also lead to a decrease in battery capacity. It is found that although the tracing and structure of graphite are maintained by recycled carbon materials, the half-height and width of the crystal plane of the carbon materials increase, resulting in crystals in the c-axis direction. The reduction in particle size and the modification of the crystal structure lead to cracking of the carbon material, destroying the SEI film on the surface of the negative electrode, and prompting the repair of the SEI film. The excessive growth of the SEI film consumes active lithium and causes the irreversible degradation of the lithium battery capacity. 3. Oxidation and differentiation of electrolyte The function of electrolyte has a significant impact on the specific capacity, life span, charge and discharge function, operating temperature range and safety function of lithium batteries. Electrolyte contains three parts: solvent, electrolyte and additives. The differentiation of solvent and electrolyte will lead to the loss of battery capacity. The differentiation and side effects of electrolyte are important factors for the capacity degradation of lithium batteries. With the recycling of lithium batteries, the differentiation of the electrolyte and the interface reaction with the positive and negative electrode materials will cause the capacity to decline, no matter what kind of positive and negative electrode materials or processes are used. 4. Rapid charging and discharging and rapid charging, the current density is too large, the negative electrode is severely polarized, and the deposition of the lithium battery is more significant, which makes the copper foil brittle at the junction of the copper foil and the carbon active material, and cracks simply occur, and the iron core spontaneously The surrounding is restricted by the fixed space, and the copper foil cannot extend freely to generate pressure. Under pressure applications, due to insufficient expansion space, the copper foil cracks, and the original cracks are scattered and grown. 5. Long-term deep charging and discharging should be carried to the internal structure. One is that the electrolyte is too volatile, and the other is that the excessive reaction of the negative electrode of the lithium battery will cause the modification of its dielectric film, resulting in a decrease in delamination ability and permanent loss of capacity. Charging needs to start with stable voltage and increase in night-time grid voltage. The charger has been suspended and the increase in voltage will cause the battery to be overcharged, resulting in changes in the positive electrode material structure, loss of capacity, differentiation and oxygen release, severe oxidation reaction of the electrolyte, and combustion and explosion ; Electrolyte organic solvent/electrolyte lithium salt differentiation; lithium over-discharge in the negative electrode may cause the negative copper collector to dissolve, and the positive electrode constitutes copper dendrites. 6. Temperature coefficient Temperature is undoubtedly one of the key factors affecting the life of lithium batteries. Too high or too low temperature will lead to a decrease in active lithium ion content, and then reduce the life of the lithium battery. 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: Analysis on the use of lead-acid batteries