Time:Feb 08, 2023 Views:660
Spinel LiMn2O4 has rich resources in China, low price, good thermal stability, and is the main material of battery cathode. During the storage of LiMn2O4 positive electrode under high temperature and the battery charging and discharging cycle, the battery capacity will decline, which is mainly caused by the following factors: First, under high voltage conditions, the electrolyte will undergo electrochemical reaction, generally higher than 4.0V; Secondly, Mn contained in LiMn2O4 material is dissolved in electrolyte, resulting in disproportionation reaction, which destroys the crystal phase structure of cathode material.
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For the lithium ion battery with LiMn2O4 as the positive pole and C as the negative pole, it will cause the solvent to decompose under high voltage, and with the oxidation reaction of C negative pole, the generated oxidation products will migrate to the positive pole, and the dissolution reaction will occur with the positive pole. The divalent manganese ions formed after dissolution will be reduced at the negative electrode and deposited together with other impurities. However, Mn oxide will only deposit in the direction of the cathode near the diaphragm, but not in the direction near the collector, that is, Mn oxide will only deposit on the surface of the SEI film, which will cause the battery capacity to decline. Adding inhibitors to the electrolyte can effectively inhibit the dissolution of metal ions and improve the cycle performance of the battery.
In addition, the lithium ion battery with LiMn2O4 as the positive pole and C as the negative pole may cause the lattice constant of LiMn2O4 to change and phase transition between cubic crystal system and tetragonal crystal system with the insertion and removal of lithium ions during the charging and discharging process. The diffusion rate of lithium ions in the cathode material is lower than the embedding rate of lithium ions on the cathode surface. When the potential is about 4V, lithium ions gather on the surface of LiMn2O4, and Jahn Teller effect occurs, leading to the distortion and transformation of the structure, which leads to the attenuation of battery capacity.
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