Lithium manganese iron phosphate material, preparation method thereof, and lithium battery

A method for preparing a lithium manganese iron phosphate material, comprising the following steps:

• providing a first slurry comprising a lithium source, a manganese source, an iron source, a phosphorus source, a carbon source, and a D source;
• grinding the first slurry to obtain a second slurry;
• subjecting the second slurry to spray drying to obtain a pre-sintered material;
• and
• sintering the pre-sintered material under an atmosphere of a protective gas, and
• obtaining the lithium manganese iron phosphate material;
• wherein the obtained lithium manganese iron phosphate material comprises a core and a coating layer on the core;
• a material of the core comprises Li, M and PO4 in a non-stoichiometric ratio, in which Mis FeyMnxDz, in which D is a metal except Fe or Mn, x, y and z represent a molar amount of Fe, Mn and the metal in the lithium manganese iron phosphate material, respectively, and a sum of molar amounts of Fe, Mn and the metal is A;
• the coating layer comprises a carbon material;
• and in the lithium manganese iron phosphate material, a ratio of a molar amount of Li to A is 1.01 to 1.10, a ratio of the molar amount of Li to a molar amount of PO4 is 0.95 to 1.10, and a ratio of A to the molar amount of PO4 is 0.90 to 1.15.

A lithium battery comprising one or more battery cell units, wherein each of the battery cell units comprises a positive electrode sheet, a separator, and a negative electrode sheet, which are stacked in sequence, the positive electrode sheet comprises a positive current collector and a positive active material layer disposed on one or more surfaces of the positive current collector, and the positive active material layer comprises a lithium manganese iron phosphate material;

• the lithium manganese iron phosphate material comprises a core and a coating layer on the core;
• a material of the core comprises Li, M and PO4 in a non-stoichiometric ratio, in which M is FeyMnxDz, D is a metal except Fe or Mn, in which x, y and z represent a molar amount of Fe, Mn and the metal in the lithium manganese iron phosphate material, respectively, and a sum of molar amounts of Fe, Mn and the metal is A;
• and the coating layer comprises a carbon material;
• in the lithium manganese iron phosphate material, a ratio of a molar amount of Li to A is 1.01 to 1.10, a ratio of the molar amount of Li to a molar amount of PO4 is 0.95 to 1.10, and a ratio of A to the molar amount of PO4 is 0.90 to 1.15.