Preparation And Carbon Coating Modification Of Lithium Ion Battery Cathode Material LiMnPO₄

Lithium-ion batteries are the main technology for energy storage,and they play an increasingly important social role due to their high energy density.A key factor in good battery design is the choice of electrode materials.The cathode must be an ion and an electron conductor to ensure high lithium and electronic conductivity during charging and discharging of the battery^[1].Nowadays,lithium iron phosphate has been widely used as a positive electrode material,except that lithium iron phosphate LiMPO₄ orthophosphate?M=Ni,Co,Fe and Mn?exhibits high safety and stability as an olivine-type structural material.Low-cost good properties,so orthophosphate is considered a very promising cathode material^[2].Lithium iron phosphate,currently used in the market,has a low energy density due to its own voltage platform of only3.4 V.Therefore,the researchers have set their sights on phosphoric acid,the voltage platform is 4.1 V,and the production cost is lower.In this paper,a LPAN-coated lithium manganese phosphate cathode material with excellent properties was prepared by spray-high temperature solid phase method.This paper first discusses the effect of different manganese sources on the electrochemical performance of the prepared lithium manganese phosphate cathode material:?1?LiMnPO₄ materials were prepared by high-speed grinding of Li₂CO₃,Mn₃O₄and H₃PO₄ with liquid polyacrylonitrile?LPAN?as carbon source and deionized water as dispersion medium in high speed grinding.The optimum calcination temperature,calcination holding time,final firing temperature,final calcination time and optimum coating amount of LPAN are obtained.Material characterization of the prepared LiMnPO4/C,Raman and TEM test cyclic voltammetry,EIS,CV test by XRD.It is concluded that the best condition for using trimanganese tetraoxide as the manganese source is to coat 15%of LPAN,preheating at 350°C,holding for 6 hours and then finishing at 750°C for 6 h.?2?LiMnPO₄ material was prepared by high-speed grinding in a sand mill with Li2CO3,Mn?CH₃COO?₂ and NH₄H₂PO₄ as raw materials,liquid polyacrylonitrile?LPAN?as carbon source and deionized water as dispersion medium.The analysis explored the optimum calcination temperature,pre-burning holding time,final burning temperature,final burning holding time and the optimal coating amount of LPAN.Material characterization of the prepared LiMnPO₄/C,Raman and TEM test cyclic voltammetry,EIS,CV test by XRD.It is concluded that lithium manganese phosphate is prepared by using manganese acetate as manganese source.The optimum condition is to coat 13%LPAN,pre-burning temperature at 350°C,heat preservation for 6 hours and then final burning at 750°C,and heat-treating for 6 hours for reaction nucleation crystallization..The addition of liquid acrylonitrile during the preparation of the precursor suppresses the growth of crystal grains,refines the size of the crystal grains,and forms a graphene-like coating on the crystal grains at a high temperature to enhance the electrical contact between the particles during the calcination process.The material's impedance is reduced,and the material's high charge and discharge performance and stability are enhanced.The maximum discharge capacity at 0.1 C and 1 C was 92.5 mA?h g^-11 and 52 mA?h g^-1,respectively,when lithium manganese phosphate prepared by using manganese trioxide as the manganese source was added to 15%of LPAN.When lithium manganese phosphate prepared by using manganese acetate as the manganese source was added to 13%of LPAN,the highest discharge capacities at 0.1 C and 1 C were 103 mA·h g^-1and 59.1 mA·h g^-1,respectively.?3?Further optimize the primary particle size of lithium manganese phosphate.When the ultrafine grinding of the sand mill is carried out,as the grinding time increases,the particle size of the primary particles decreases,and the surface energy increases,thereby causing the primary particles to be between The force is increased,which increases the agglomeration of the particles.Grinding?agglomerates occur during the grinding process.In order to promote the balance to the right,the most effective method is to add grinding aids to the raw materials to reduce the surface energy between the particles and reduce agglomeration^[4].In order to make lithium manganese phosphate and LPAN more dispersed,I tried to add polyvinylpyrrolidone?PVP?as a grinding aid during the experiment.In the process of preparing raw materials,PVP was added for grinding.The electrochemical properties of lithium manganese phosphate prepared by different manganese sources and PVP were investigated.The modification results of battery materials after adding different PVP amounts were discussed.It is concluded that manganese oxide is used as the manganese source,and LiMnPO₄ cathode material prepared by adding PVP of 1.5%of the raw material mass is added.The specific capacity of the discharge reaches126.1 mA·h g^-11 at 0.1 C,and the interface resistance is lower at 20.56?,D Li⁺value.It is 2.08×10^-15.The LiMnPO₄-PVP/C cathode material prepared by the research in this paper has excellent electrochemical performance,simple synthesis conditions,very low preparation cost,low energy consumption,environmental friendliness,and meets the requirements of mass production of the factory.A replacement for future lithium iron phosphate cathode materials.