Manganese-based cathode materials are expected to be widely used in energy storage batteries

Research status of manganese-based cathode materials Lithium manganate is a typical spinel-type structure of anode materials. According to literature reports, the theoretical energy density is 148mAh/g, which is lower than lithium cobalt oxide and ternary materials. It has the characteristics of low price, high thermal stability, environmental friendliness, and convenient preparation. It is expected to be widely used in energy storage batteries and power lithium batteries. Among power lithium batteries, compared with ternary materials and lithium iron phosphate, lithium manganate is not widely used in my country. The important reason is that its low energy density and poor cycle life result in short battery life and low service life. The cycle performance of lithium manganate, especially the cycle performance at high temperature (55°C) has been widely criticized. The important influencing factors are as follows: the surface Mn3+ dissolves. Because the traditional electrolyte is used for lithium hexafluorophosphate (LiPF6), the electrolyte itself contains a certain amount of hydrofluoric acid (HF) impurities, a small amount of water in the battery system will cause the decomposition of high-frequency LiPF6, and the presence of high-frequency weakens the lithium manganate (LiMn2O4). ) And cause disproportionation and dissolution of Mn3+, Mn3+ (solid) -> Mn4+2 (solid) + Mn2+ (solution). At the end of the discharge, the Mn3+ content on the surface of the material is higher than that of the bulk phase, and the dissolution of the Mn3+ content on the surface of the material is intensified under the condition of large multiple discharges. Ginger Taylor effect. During battery discharge, especially in the case of overdischarge, the formation of Li1+[Mn2]O4 on the material surface is thermodynamically unstable. At the same time, because the material structure changes from the tertiary phase to the secondary phase, the original structure is destroyed, and the cycle performance of the material deteriorates. High oxidation of Mn4+. At the end of charging or overcharging, Mn4+ has strong oxidation in the highly defogging Li1+[Mn2]O4 material, which will oxidize and decompose the organic electrolyte and deteriorate the cycle performance of the battery. At present, the energy density of most lithium-ion manganese batteries is less than 100mAh/g, and the normal temperature cycle can only reach 400 to 500 times, and the high temperature cycle can only reach 100 to 200 times, which cannot meet the needs of mass production. But in fact, the battery system of Nissan Leaf, which accounts for nearly 20% of global electric vehicle sales, is lithium manganese oxide, with a cruising range of about 200 kilometers. Although the performance of lithium manganate batteries is limited by the structure of the material itself, as long as the problems of low energy density and poor cycle performance are solved, there is still a very broad application space in the field of power lithium batteries in the future. In order to improve the energy density and cycle performance of lithium manganate electrode materials, some researchers increase the voltage of the cathode by doping modified materials, such as LiMxMn2-xO4[(Mu003dchromium (Cr), iron (Fe) Co., Ltd. nickel, Copper (copper)] 5 volt high voltage cathode material, among which ni-mnLiNi0.5Mn1.5O4 high voltage material has been widely studied. The discharge specific capacity of nickel manganese high voltage material can reach 130mAh/g, the platform can reach about 4.7v, and the energy under normal working voltage The density is higher than that of lithium cobalt oxide, and there is basically no ginger Taylor effect of Mn3+. When the operating voltage is increased to about 5V, compared with traditional lithium cobalt acid, lithium manganese acid, ternary and lithium iron, nickel manganese high voltage materials It has the advantages of large gram capacity, high discharge platform, good safety performance, and high rate. It has great advantages in the configuration of battery packs, but its performance is poor at high temperatures and cycles and needs to be improved. From the current application point of view, It is still only a small batch production stage of steel shell batteries, and there is still a long way to go about the doping modification and surface coating of nickel-manganese high-voltage materials. Disclaimer: Some pictures and content of articles published on this site are from the Internet. , If there is any infringement, please contact to delete the previous article: How will the lithium-ion battery market change in the future?