SINGLE-CORE MULTI-SHELL LITHIUM MANGANESE IRON PHOSPHATE COMPOSITE MATERIAL AND PREPARATION METHOD THEREFOR, AND SECONDARY BATTERY

The application discloses a single-core multi-shell lithium manganese iron phosphate cathode material and a preparation method thereof, and a secondary battery. The composite material includes: a carbon-coated lithium iron phosphate core, and a plurality of lithium manganese iron phosphate cladding layers cladded on an outer surface of the carbon-coated lithium iron phosphate core. Each of the plurality of lithium manganese iron phosphate cladding layers includes lithium manganese iron phosphate particles and a carbon material coated on the lithium manganese iron phosphate particles. The lithium manganese iron phosphate particles in the plurality of the lithium manganese iron phosphate cladding layers have particle sizes increase in a radial direction from inside to outside. The composite material prepared by the method of the present application is in a single-core multi-shell structure, in which, the core is carbon-coated lithium iron phosphate, and the shell includes a plurality of lithium manganese iron phosphate cladding layers. Based on the lithium iron phosphate core and multiple shell layers of lithium manganese iron phosphate, as well as the regular arrangement of the particle sizes, the composite material has high energy density, electrical conductivity, compaction density, safety, stability, and other electrochemical properties.