POSITIVE ELECTRODE ADDITIVE AND PREPARATION METHOD THEREFOR, POSITIVE ELECTRODE AND PREPARATION METHOD THEREFOR, AND LITHIUM ION BATTERY

A positive electrode additive, comprising, in percentage by mass, 10% to 40% of carbon-coated lithium manganese iron phosphate and an organic solvent. The carbon-coated lithium manganese iron phosphate is dispersed in the organic solvent, and the median particle diameter of the carbon-coated lithium manganese iron phosphate is 30 nm to 100 nm.