Preparation method of lithium manganese iron phosphate

The invention provides a preparation method of lithium manganese iron phosphate, which comprises the following steps: S1, taking deionized water as a solvent, and mixing with a mixture containing a phosphorus source, a manganese source and an iron source to obtain a mixture I; s2, adding a lithium source and a carbon source into the mixture I to obtain a mixture II; s3, the mixture II is subjected to granulation, and granulated particles are obtained; s4, mixing and drying the granulated particles to obtain a preparation precursor; and S5, performing high-temperature sintering on the prepared precursor to complete the preparation of the lithium manganese iron phosphate. According to the preparation method provided by the invention, aiming at the problem that a manganese-rich phase is not easy to exert the electrochemical capacity, the nano-sized lithium manganese iron phosphate is prepared from phosphoric acid, manganese monoxide and iron monoxide, so that the problem that the capacity is too low is well solv