\u3000\u30001. Introduction of lithium manganese iron phosphate material. Lithium manganese iron phosphate (limnxfe1-xpo4) is a new type of phosphate lithium battery cathode material formed by doping a certain proportion of manganese on lithium iron phosphate (LiFePO4). On the one hand, doping can effectively combine the advantages and characteristics of iron and manganese, on the other hand, manganese and iron are adjacent in the periodic table and have similar ion radius, so doping will not significantly affect the original structure. X in limnxfe1-xpo4 represents the ratio of manganese to iron, that is, the doping ratio of manganese. The doping ratio of manganese has an important influence on the properties of lithium ferromanganese phosphate. On the one hand, the voltage platform of lithium iron phosphate is about 3.4V, while after doping manganese, the voltage platform can be increased to 3.8-4.1v, which can significantly improve the voltage platform; On the other hand, if the manganese doping ratio is too high, the specific capacity of the material will be reduced and attenuated rapidly due to the John teller effect, so it is not suitable to be used as the cathode material of lithium-ion battery. For the solid-state preparation method, it has an ideal energy density when the manganese iron ratio is about 4:6.
\u3000\u30002. Preparation method of lithium manganese iron phosphate. The preparation methods of lithium manganese iron phosphate can be divided into solid-phase method and liquid-phase method. Specifically, the solid-phase method includes high-temperature solid-phase method, carbothermal reduction method and so on. The advantages are that the process is simple and mature, the preparation cost is low, and it is easy to realize large-scale industrialization; The disadvantage is that the product has poor mixing uniformity and poor quality. At present, China mainly produces lithium manganese iron phosphate by solid-state method. The manufacturer is Jiangsu Litai lithium energy company. Liquid phase method includes solvothermal method, sol gel method, coprecipitation method, etc. The advantages are good inclusiveness of raw materials and high product quality; The disadvantage is that the process control is difficult and the process is difficult. The possibility of manganese ion dissolution is higher than that of solid-phase method. If manganese ion is doped to lithium position, it will affect the rate performance and cycle life. At present, the manufacturer of lithium manganese iron phosphate produced by liquid method in China is Shenzhen Dynanonic Co.Ltd(300769) .
\u3000\u30003. Comparison of performance characteristics of lithium manganese iron phosphate. Compared with lithium iron phosphate, the high voltage characteristic of manganese makes lithium manganese iron phosphate have a higher voltage platform, which also leads to its higher energy density when the specific capacity is the same. Under the same conditions, the energy density is 10% - 20% higher than that of lithium iron phosphate, but the disadvantage is that the introduction of manganese significantly reduces the conductivity of the material. At the same time, higher voltage platform also means higher requirements for electrolyte, and there are relatively few types of electrolyte to meet the discharge characteristics; Compared with the layered structure of ternary NCM material, lithium manganese iron phosphate has the same olivine structure as lithium iron phosphate, and the structure is more stable during charge and discharge. Even if all lithium ions are embedded during charging, the structure will not collapse, so the safety is better. The disadvantage is that compared with efficient ternary materials, the specific capacity and energy density of lithium manganese iron phosphate are still very low, and there is a greater gap in conductivity. However, lithium manganese iron phosphate has obvious advantages in cost.
\u3000\u30004. Application prospect of lithium manganese iron phosphate. In the development of this material, on the one hand, on the basis of pure LMFP, its conductivity is improved by coating, doping and nanocrystallization; On the other hand, compounding lithium manganese iron phosphate with ternary 523, LCO and other materials can further integrate the advantages of materials, realize short board complementarity through compounding, improve energy density, and have more comprehensive and comprehensive battery performance, but at the same time, the corresponding production cost will also increase.
\u3000\u30005. Risk statement The further technological development of lithium manganese iron phosphate and the construction of production capacity of related products were not as expected.
