High-compaction-density lithium iron phosphate, preparation method thereof and lithium ion battery positive electrode material

The invention relates to a preparation method of lithium iron phosphate with high compaction density. The preparation method comprises the following steps: mixing iron phosphate, lithium carbonate and a carbon source to obtain a mixture; placing the mixture in a carbon dioxide atmosphere, and carrying out pressure calcination to obtain a calcined material; dividing the calcined material into a first calcined material, a second calcined material and a third calcined material; a step for obtaining a first powder material having D50 of 1-4 [mu] m by pulverizing the first calcined material; a step for obtaining a second powder material having a D50 of 5-10 [mu] m by pulverizing the second calcined material; a step for obtaining a third powder material having D50 of 11-15 [mu] m by pulverizing the third calcined material; and mixing the first powder material, the second powder material and the third powder material, and performing electromagnetic iron removal to obtain the high-compaction-density lithium iron phos