Long-cycle and high-safety power lithium ion battery positive electrode material and preparation method thereof

Abstract

The invention discloses a long- cycle and high-safety power lithium ion battery positive electrode material and a preparation method thereof. The positive electrode material can be shown as a general formula LiNi<(1-a-b-c)>CoMnM<c>O2.xLiM<1>O<y>, wherein a is greater than 0 and less than 1, b is greater than 0 and less than 1, a+b+c is greater than 0 and less tan 1, x is greater than 0 and less than 0.1, and y is greater than 1 and less than 5; LiNi<(1-a-b-c)>CoMnM<c>O2 is a primary active crystalline particle of the positive electrode material, and is a lithiated composite oxide composed of nickel cobalt manganese and doping element M; and the LiM<1>O<y> is a coating layer coating crystal boundary of the primary active crystalline particle and surface of a polycrystalline secondary particle. The positive electrode material provided by the invention has high stability of crystalline main body, surface and crystal boundary, has good compatibility with electrolyte and is not liable to generate side reaction. The material provided by the invention is used for batteries, has long cycle life, high over-charging resisting capability, good high temperature and high voltage performance and high integral safety, and is particularly suitable for power batteries.

Description

technical field [0001] The invention belongs to the field of lithium-ion battery cathode materials, and more specifically relates to a long-cycle high-safety power type lithium-ion battery positive electrode material and a preparation method thereof. Background technique [0002] New energy vehicles, as an emerging strategic industry that is the country's key development, have entered the incubation period of rapid development. It is urgent to solve the mileage, safety and cycle life of batteries. The existing positive electrode materials for power batteries include lithium iron phosphate, spinel lithium manganese oxide, and nickel-cobalt lithium manganese oxide ternary materials. Due to the theoretical The low gram capacity cannot meet the increasing battery life requirements, and will gradually be replaced by the high gram capacity nickel-cobalt-lithium manganese oxide ternary material (276.8mAh / g), and the ternary material must be overcome in order to fully gain the recog...

AI Technical Summary

Problems solved by technology

[0004] In order to stabilize the structure and improve performance, domestic and foreign researchers have found that the application of bulk phase doping substitution and surface coating can improve the performance of materials, such as patent ZL201110222403.7 using solid The positive electrode material prepared by phase method doping aluminum can improve the high temperature safety performance and cycle characteristics of lithium-ion batteries, but the solid phase method is doped, the mixing is difficult to uniform, the solid phase diffusion speed is slow, and the product has large differences in structure and composition. difference, resulting in poor electrochemical performance

[0005] There are two existing coating methods, one is to coat the surface of the secondary particles of the precursor, and the other is to sinter the secondary particles of the lithium transition metal composite oxide The surface coating of the secondary particles is all coated on the surface of the secondary particles, and the coating is uneven, but what is more worthy of attention is that in the electrochemical reaction, with the increase of the delithiation amount, especially at high temperature and high voltage, the solvent and The solvated lithium salt is easy to diffuse into the vacancy unit cell after delithiation, solvating the lattice of the positive electrode material, especially in the crystal interface with more dangling bonds, more defects, and low crystallinity, which is more likely to be penetrated by the electrolyte , at the same time, in the rolling process of sheet making, the fragile grain boundaries are easily crushed and cracked, exposing the surface of the highly active primary particles; during circulation, the reciprocating expansion and contraction deformation of the crystal lattice generates stress, causing the secondary particles to crack at the grain boundaries Obvious pulverization will intensify the side reaction between the electrolyte and the active material. Therefore, in addition to the surface of the polycrystalline secondary particles, the grain boundary between the primary grains is also a very weak place, which seriously affects the cycle and safety performance of the material.

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