Positive pole piece and preparation method thereof and lithium ion secondary battery

Abstract

The invention discloses a positive pole piece which comprises a positive pole current collector and a positive pole diaphragm arranged on at least one surface of the positive pole current collector, and the positive pole diaphragm comprises a positive pole active substance; the positive electrode active substance comprises at least two lithium nickel cobalt manganese oxides LiNixCoyMn1-x-yO2 withdifferent morphologies and average particle sizes D50, wherein one type is primary particle single crystal LiNixCoyMn1-x-yO2, and the other type is secondary particle polycrystalline LiNixCoyMn1-x-yO2; the weight ratio [omega] of the single crystal to the polycrystalline LiNixCoyMn1-x-yO2 satisfies the relational expression: 0.1<=[omega]<=9. By adjusting the ratio of the primary particle single crystal to the secondary particle polycrystalline material and the nickel content, the positive pole piece can have better thermal stability and excellent dynamic performance, so that the lithium ion secondary battery based on the positive pole piece has the characteristics of long cycle life at normal temperature and high temperature.

Description

technical field [0001] The invention relates to the technical field of electrochemistry, in particular to a positive pole piece, a preparation method thereof and a lithium ion secondary battery. Background technique [0002] New energy vehicles that use electric drives to replace traditional fuel-powered vehicles have the advantages of energy saving, environmental protection, and comfort. However, service life, safety, charging speed, mileage and battery costs still restrict the wide application of electric vehicles. [0003] In order to increase the rate of lithium-ion batteries and reduce the internal resistance of batteries, researchers usually use secondary particle polycrystalline LiNi x co y mn 1-x-y o 2 The material is used as the positive electrode material of lithium ion battery. However, the structural stability of the secondary particle polycrystalline material is poor, and it is easy to produce gas by side reaction with the electrolyte during the battery cycl...

AI Technical Summary

Problems solved by technology

However, the structural stability of the secondary particle polycrystalline material is poor. During the battery cycle, especially in the high temperature cycle, it is easy to produce gas by side reaction with the electrolyte, thereby reducing the service life of the lithium-ion secondary battery.

[0004] In addition, the secondary particle polycrystalline LiNi with the same nickel content x co y mn 1-x-y o 2 The oxygen evolution peak temperature of the material is lower than that of the primary particle single crystal material, so the thermal stability of the secondary particle polycrystal is poor

[0005] Although the primary particle single crystal LiNi x co y mn 1-x-y o 2 Less side reactions between materials and electrolytes, good thermal stability, but low energy density, poor kinetic performance, and high production costs

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