Preparation And Modification Of Lithium-Rich Manganese-Based Cathode Materials With Semi-Hollow Porous Microsphere Structure

Lithium-and manganese-rich cathode material（LMR）has been widely studied as one of the lithium-ion battery materials with high energy density and excellent electrochemical properties.However,the easy collapse of the multi-component alternating stack structure due to factors such as volume expansion during charging and discharging,as well as severe surface side reactions,surface phase transitions,and erosion of the side reaction products HF,have caused great obstacles to the practical application of LMR materials in daily production and life.Therefore,a synergistic scheme combining morphology control and surface modification is proposed in this paper to solve the above problems together.We first synthesized the semi-hollow porous microsphere structure Li_1.2Mn_0.54Ni_0.13Co_0.13O₂（H-LMR）by a template-free rapid co-precipitation method and high-temperature solid-phase sintering.Its unique design alleviates the structural expansion due to charging and discharging while providing bidirectional ion channels and a suitable spatial basis for in-situ coated modification.Through the investigation of the precursor synthesis process and the factors in the solid phase sintering process,the final material has an initial discharge-specific capacity of 286.8 m Ah·g^-1 and an initial coulomb efficiency of 77.56%.At the same time,considering that its unique space structure can be used in solid-state batteries,the final assembled solid-state battery possesses 121.2 m Ah·g^-1and 98.56%capacity retention after 100 cycles at 0.1C.To alleviate the erosion of HF as well as to improve the conductivity of the electrode,conductive C materials,and Li F can be added to the electrode material.The traditional method is to prepare electrodes by adding two materials to LMR materials.In our work,we innovatively propose in-situ coated LMR materials,i.e.,adding CF_x to the electrode preparation process so that CF_x generates Li F and C in the battery.This process greatly mitigates the occurrence of surface-side reactions,alleviates the erosion of HF,and further enhances ionic conductivity.The unique structural characteristics and the bi-directional synergistic effect of Li F in-situ coated modification further improve the actual discharge capacity,multiplicity performance,and,cycling stability of the material.The actual discharge capacity of the material is 313.1 m Ah·g^-1 at a current density of 0.1C,with a multiplier performance of 182.7 m Ah·g^-1 at 2C and a capacity retention rate of 90.96%after 100 cycles at 0.5C.