Method for synthesizing lithium iron manganese phosphate positive electrode material by recycling waste lithium manganate positive electrode material

The invention provides a method for synthesizing a lithium iron manganese phosphate positive electrode material by recycling a waste lithium manganate positive electrode material, which comprises the following steps: uniformly mixing the waste lithium manganate positive electrode material with a concentrated sulfuric acid solution, roasting at low temperature, and carrying out water immersion treatment on the roasted product; removing impurities from the leachate, concentrating and drying to obtain a solid product containing lithium and manganese, supplementing a phosphorus source and an iron source into the solid product according to a corresponding molar ratio, and uniformly ball-milling to obtain a lithium iron manganese phosphate precursor; and carrying out high-temperature calcination reaction on the precursor to obtain the lithium iron manganese phosphate positive electrode material. According to the method, the waste lithium manganate material is used for recycling and secondary synthesis, valuable met