Preparation And Electrochemical Performance Of High Voltage LiNi_0.5Mn_1.5O₄ Electrode Materials

The vigorous development of new energy electric vehicles has driven the research boom of developing high energy density and high power density lithium ion power batteries.In lithium-ion batteries,the price of cathode materials is approximately 44%of the total cost of batteries.It can be seen that the development of high-performance cathode materials is the key to promoting the development of lithium-ion power batteries.The spinel LiNi_0.5Mn_1.5O₄?LNMO?cathode material is one of the research hotspots of high power and high energy density cathode materials because of its high voltage platform of 4.7 V,high theoretical energy density(⁶50 Wh kg^-1),three-dimensional Li⁺ions diffusion channel and environmental friendliness.Therefore,we hope to prepare the spinel LNMO cathode materials with high energy density and cycle stability through morphology control and coating modification.The main research contents and results are listed as follows:?1?Two kinds of nano-microspherical LNMO cathode materials?LNMO1 and LNMO2?were prepared by the combination of coprecipitation method and high temperature solid phase reaction using different lithium sources?Li₂CO₃ and LiOH?.We explored the effect of lithium source on the electrochemical performance of the product LNMO materials.The results indicated that the lithium source had some influence on the microstructure and crystal structure of LNMO,which affected its discharge capacity and cycle stability.The LNMO2cathode material exhibited better electrochemical performance.At 1 C,the initial discharge capacity of LNMO2 was 116.9 mAh g^-1.After 400 cycles,the discharge capacity remained at110.2 mAh g^-1.?2?The Li_1.2Ni_0.2Mn_0.6O₂?LIR?layered materials were prepared by co-precipitation method as a coating material of LNMO.We explored the effects of different calcination atmospheres?oxygen and air?on the electrochemical performance of the product LIR materials.The results showed that the LIR-O materials exhibited better electrochemical performance due to their nano-microsphere structure and lower lithium nickel mixed degree,which were prepared under oxygen atmosphere.The initial discharge capacity of the LIR-O was 246.5 mAh g^-1 at the current density of 0.1 C,and the coulombic efficiency was 86.45%.After 110 cycles,the discharge capacity remained at 240.3 mAh g^-1,and the capacity retention rate reached 97.4%.?3?The LNMO were modified by LIR-O materials to prepare LNMO@LIR materials.The electrochemical performance of LNMO@LIR materials were studied.The results showed that the LIR coating increased the deintercalation of lithium ions in the LNMO materials,which reduced the Mn³⁺on the surface of the LNMO materials.It was beneficial to reduce the dissolution of the electrode materials.At lower current densities?0.5 C?,LNMO@LIR materials exhibited higher discharge specific capacity and better cycle stability than LNMO.The initial discharge capacity of the LNMO@LIR materials was 125.99 mAh g^-1 at the current density of 1 C.After 300 cycles,the discharge capacity maintained at116.34 mAh g^-1,and the capacity retention rate was 92.3%.