Mixed positive material of lithium-ion power battery

Abstract

The invention belongs to the technical field of lithium-ion power batteries, and in particular relates to a mixed positive material of a high-capacity lithium-ion power battery. The mixed positive material comprises lithium iron phosphate A and a lithium nickel cobalt manganese ternary active substance B, wherein the surface of the A is coated with a polypyrrole layer; the median particle size of the A is smaller than or equal to 15 microns; the sizes of single-crystal particles of the B are greater than or equal to 1.0 microns; the surface of the B is coated with a metal fluoride layer. Compared with the prior art, the disadvantage of low compaction density caused by a ternary material is effectively overcome by reasonably optimizing the sizes of the single-crystal particles of the ternary material and the median particle size of the lithium iron phosphate, so that the mixed positive material has high compaction density; the surface of the lithium iron phosphate is coated with the polypyrrole layer and the surface of the ternary material is coated with the metal fluoride layer, so that the safety performance, the rate performance, the high-temperature cycling performance, the low-temperature performance and the safety performance of the lithium-ion power battery with the mixed positive material can be improved.

Description

technical field [0001] The invention belongs to the technical field of lithium-ion power batteries, and in particular relates to a high-capacity, high-safety lithium-ion power battery mixed cathode material. Background technique [0002] With the development of lithium-ion power batteries, people have higher and higher requirements for the endurance, service life, safety performance and price of lithium-ion batteries. The cathode material is one of the key materials that restrict the cost performance of lithium-ion power batteries. Improving the capacity and safety of cathode materials is the two main aspects to improve the battery life of lithium-ion power batteries. [0003] Lithium iron phosphate has been widely used in the field of power batteries, which has the advantages of high safety and high cycle life. However, lithium iron phosphate also has obvious disadvantages, such as poor conductivity, slow diffusion rate of lithium ions, and low actual specific capacity dur...

AI Technical Summary

Problems solved by technology

Therefore, ternary materials have attracted much attention in recent years, but the material also has certain defects: its actual compacted density is only 3.6g / cm 3 , low discharge voltage platform and strong water absorption; it is particularly noteworthy that: Li in the structure + and Ni 2+ It is easy to mix and discharge, which leads to the release of active oxygen and makes the high-priced nickel ions easy to catalyze the decomposition of the electrolyte, so that the lithium-ion battery made of ternary materials will generate a large amount of gas when stored at high temperature, which will deteriorate the performance of the battery, especially for the use of aluminum Plastic composite film is used as the outer packaging of lithium-ion batteries, and the outer shell is relatively soft. The generation of gas will cause the rapid expansion and deformation of the battery, which will bring serious safety hazards and limit its use.

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