有机-无机双层包覆协同优化LiNi0.5Mn1.5O4高压正极材料的界面及电化学性能OA

To address the modification limitations of a single inorganic or polymeric coating for spinel-type LiNi0.5Mn1.5O4(LNMO)cathode materials,mitigate interfacial failure,transition-metal dissolution and structural collapse under high-voltage conditions,and improve cycling stability and rate performance,this work proposes an organic-inorganic dual-layer composite coating modification strategy.Single-crystal LNMO substrates are synthesized via the sol-gel method,and a dual-layer composite coating system consisting of a LiNbO3 inorganic conductive layer and a PMMA-Li flexible polymeric layer is constructed through a stepwise modification process.XRD,FTIR,SEM-EDS,TEM,quantitative ICP-MS metal-dissolution measurements and comprehensive electrochemical tests are employed to investigate the modulating effects of inorganic coating loading and organic polymer dosage on the microstructure,interfacial properties and electrochemical performance of LNMO,and the optimal modification procedure is determined.The experimental results demonstrate that the 1.0％LiNbO3 inorganic coating well preserves the crystal structure of LNMO,builds rapid Li+transport pathways,and isolates the substrate from direct electrolyte contact,achieving over 80％suppression efficiency for Mn and Ni transition-metal ion dissolution.On this basis,the introduction of a 0.5％PMMA-Li flexible polymeric layer effectively buffers cycling-induced stress,fills micro-defects and cycling-generated microcracks in the inorganic coating,and avoids particle surface cracking and structural delamination,thus realizing synergistic advantages of high ionic conductivity from the inorganic layer and superior structural toughness from the organic layer.The optimally modified sample LNMO-LN1.0-P5 exhibits outstanding electrochemical performance:its initial Coulombic efficiency reaches 91.36％;the capacity retention is 98.8％after 200 cycles at 1 C,and 99.5％after 100 cycles at a high rate of 5 C.At an elevated temperature of 55℃,the capacity retention attains 90.38％over 100 cycles.After 200 cycles,the charge-transfer resistance is only 5.1 Ω,and the solid-phase lithium-ion diffusion coefficient is enhanced by two orders of magnitude compared with pristine LNMO,indicating remarkably improved ion-transport kinetics and rate capability.This study clarifies the synergistic modification mechanism between LiNbO3 and PMMA-Li,and effectively alleviates interfacial failure and structural degradation of high-voltage LNMO cathodes.It provides a feasible technical route and experimental reference for interfacial modification and development of high-performance high-voltage spinel lithium nickel-manganese oxide cathode materials.