Lithium manganese iron phosphate composite material, preparation method thereof and secondary battery

The invention belongs to the technical field of batteries, and particularly relates to a lithium manganese iron phosphate composite material, a preparation method and a secondary battery. The preparation method of the carbon-coated lithium manganese iron phosphate composite material comprises the following steps: respectively obtaining a lithium manganese iron phosphate recycled material, a conductive agent recycled material and a fluorine-containing recycled material; preparing a precursor from the lithium manganese iron phosphate reclaimed material, lithium iron phosphate and a lithium source; carrying out sintering treatment on the precursor, then mixing the precursor with a conductive agent reclaimed material and a fluorine-containing reclaimed material, and carrying out secondary sintering to obtain the carbon-coated lithium manganese iron phosphate composite material with a core-shell structure; comprising a lithium iron manganese phosphate inner core, a lithium iron phosphate middle layer and a carbon