Lithium manganese ferric phosphate-ternary material composite positive electrode material and preparation method therefor

Abstract

The invention discloses a lithium manganese ferric phosphate-ternary material composite positive electrode material and a preparation method therefor. Lithium manganese ferric phosphate nanoparticlesare fixed on the surfaces of the ternary material granules through a mechanical fusion method to form a tight porous coating layer; therefore, the problem of easy segregation caused by different densities of the ternary material and the lithium manganese ferric phosphate positive electrode material when the mixed paste of the ternary material and the lithium manganese ferric phosphate positive electrode material is needed in the paste mixing stage in the use process of the ternary material and the lithium manganese phosphate positive electrode material can be solved; and by virtue of tight coating of the lithium manganese ferric phosphate on the surface of the ternary material, a stable core-shell structure can be obtained, so that the surface of the ternary material (particularly a high-nickel ternary material) can be protected by the lithium manganese ferric phosphate material, degradation of the ternary material caused by absorption of water contents in the environments can be prevented, direct contact between the ternary material and an electrolyte in the battery can be lowered, and the stability and cyclicity of the ternary material are improved.

Description

technical field [0001] The invention relates to the technical field of positive electrode materials for lithium ion batteries, in particular to a positive electrode material composed of lithium manganese iron phosphate-ternary materials and a preparation method thereof. Background technique [0002] Ternary materials are widely used in positive electrode materials of electric vehicle batteries due to their high energy density. 1 / 3 co 1 / 3 mn 1 / 3 o 2 to LiNi 0.5 co 0.2 mn 0.3 o 2 Transformation, and even many ternary material companies have begun to develop LiNi 0.6 co 0.2 mn 0.2 o 2 、LiNi 0.8 co 0.1 mn 0.1 o 2 , LiNiO 2 , NCA and other high nickel materials. [0003] With the continuous increase of nickel content in ternary materials, the specific capacity of ternary materials has also increased significantly, but it also caused two direct effects: 1) The thermal stability temperature of ternary materials after the content of nickel is increased Constantly de...

AI Technical Summary

Problems solved by technology

However, in this patent, lithium iron phosphate manganese phosphate and ternary materials are simply physically mixed during homogenization, and lithium iron phosphate is only in point contact with the surface of some ternary material particles, so the improvement effect is limited; Delamination will occur during the electrode distribution process, resulting in segregation of the two components

In addition, ternary materials generally have larger particles, with a particle size D50 of about 10 microns, while lithium manganese phosphate particles are generally smaller, with a particle size D50 of about 1-2 microns. Through traditional mixing, coating, and drying methods, due to Both particles are difficult to distribute evenly, and it is difficult to obtain high compaction density

[0005] Chinese patents CN103682318A and CN104201366A use the high safety performance of ternary materials to compound lithium iron phosphate and ternary materials in the homogenization process. In addition to the same problem of material uniformity in the above two patents, due to the energy The density is lower than that of the ternary material, which leads to a decrease in the energy density of the hybrid electrode after compounding, that is, the performance improvement is at the expense of the energy density

But this method is only suitable for experiments in the laboratory, not suitable for mass production

Because when lithium manganese iron phosphate and ternary materials are sintered, the argon protective atmosphere required by lithium manganese iron phosphate is used, but it is well known that air or oxygen-enriched atmosphere is required when ternary materials are sintered, and they are fired in an inert atmosphere Will severely damage the performance of ternary materials, so the two cannot be well coordinated and cannot be used by the general public

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