Lithium-ion batteries have many advantages such as high energy density, good cycle performance, no memory effectand so on. They are widely used in many fields such as electronic products, electric traffic, and energy storage system, which have greatly improved the modern human's life. Lithium iron phosphate (LiFePO4), as a cathode electrode material, possesses high safety, excellent cycle performance and thermal stability, and it is widely used in lithium-ion power battery. However, its energy density is low, which restricts its further development and application. Lithium manganese phosphate (LiMnPO4) has high safety and stability similar to LiFePO4, and its theoretical energy density is 21% higher than that of the latter, so it is considered to be the most promising cathode material for next-generation power lithium-ion power battery. However, the olivine-structured LiMnPO4 still has some inherent defects that restrict its development and application: (1) the ionic conductivity and electronic conductivity of the material are very low, which make it's difficult to make full use of the material capacity; (2) LiMnPO4 reacts with the electrolyte to produce the product Li4P2O7, etc. which will result in the activity will gradually lose as charge and discharge process; (3) the manganese phosphate (MnPO4) formed after delithiation will be affected by the Jahn-Teller effect, the crystal structure will change from octahedron to cubic phase, and the channel of lithium-ion decompression is compressed, causing structural irreversible changes; (4) part of manganese ions are dissolved in the disproportionation reaction that occurs in the electrolyte causes the material to cycle poorly. A lot of work has been done to overcome these problems. In order to improve the electrochemical performance of LiMnPO4, the researchers have made continuous attempts in the preparation and modification of materials: (1) nanocrystallization, shortening the solid-state diffusion path of lithium-ion, and increasing the reaction area of the electrode, thereby increasing the ionic conductivity of the material in macro; (2) selection control of planes, increasing the area of the crystal plane for rapid migration of lithium ions, thereby increasing the ionic conductivity of the material in micro; (3) body doping, in-situ substitution of heteroatoms or formation of solid solution to stabilize the crystal structure and improve ionic/electronic conductivity, thereby improving the cyclic and rate performance of the material; (4) surface coating, by coating conductive carbon, metal oxide layer, etc. on the surface of the material to improve the ionic/electronic conductivity of the material and prevent LiMnPO4 from directly contacting the electrolyte. Since now, LiMnPO4 has been developed from the original almost playno specific capacity, and developed to a theoretical value at a low rate. In this paper, the research progress on the preparation and modification of high performance LiMnPO4 is summarized. The approaches to improve the material properties are analyzed from the aspects of material structure, surface interface properties and electrode reaction kinetics. Finally, we believe that the crystal surface control and surface coating modification on the basis of element doping and nanocrystallization is the most effective way to maximize the material properties, thus promoting its commercialization process. © 2019, Materials Review Magazine. All right reserved.
