Methods for Preparing Ferromanganese Oxide, Lithium Manganese Iron Phosphate Material, and Cathode Plate

A method for preparing a ferromanganese oxide, comprising:

• providing a ferromanganese solution, a complexant solution, and a base solution with a pH value of 11 to 12;
• mixing the ferromanganese solution, the complexant solution, and the base solution and then performing a first reaction treatment to obtain a first precursor;
• and
• subjecting the first precursor to a second reaction treatment to obtain the ferromanganese oxide;
• wherein the ferromanganese solution comprises Fe2+ and Mn2+;
• wherein the complexant solution comprises a first complexant, and a ratio of a stability constant of a complex formed by the first complexant with Fe2+ to a stability constant of a complex formed by the first complexant with Mn2+ is in a range of 103 to 105;
• wherein the first complexant is selected from a group consisting of ethylenediamine, 2-methyl-8-hydroxyguinaldine, and a combination thereof.