A positive pole piece and a lithium ion battery using the positive pole piece

Abstract

The invention provides a lithium ion battery, which comprises a positive pole piece, a negative pole piece, a separator and an electrolyte. The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer that is arranged on the surface of the positive electrode current collector and contains a positive electrode active material. An inorganic dielectric layer that does not contain a binder is arranged on the surface of the positive electrode active material layer, and the resistance of the positive electrode sheet is constant. Above 8ohm. Due to the good chemical stability of the inorganic dielectric layer, it can exist stably under high voltage, which can slow down the change of the surface structure of the active material caused by the over-high voltage of the positive electrode active material, improve the stability of the positive electrode material, and effectively isolate the strong oxidation. The positive electrode active material is in direct contact with the poorly stable additives, solvents in the electrolyte, and the outer surface of the separator to reduce the gas production of the lithium-ion battery and prevent the polymer on the surface of the separator from failing under high voltage; the resistance of the positive electrode sheet is not high It is beneficial to ensure that the internal resistance of the battery is low, the polarization is small, and the cycle performance and rate performance are good.

Description

technical field [0001] The invention relates to the technical field of batteries, in particular to a positive pole piece, a preparation method thereof and a lithium ion battery using the positive pole piece. Background technique [0002] Lithium-ion batteries have broad application prospects in the field of electric vehicles due to their high energy density, long cycle life, and no pollution. In order to meet the requirements of consumers for the extended range of electric vehicles, it is one of the effective ways to develop positive electrode active materials with high specific capacity. [0003] At present, lithium-nickel-cobalt-manganese ternary materials have become a research hotspot due to their high theoretical specific capacity and safety characteristics. However, the high nickel content in lithium-nickel-cobalt-manganese ternary materials makes them highly oxidizable, resulting The electrolyte is prone to electrochemical oxidation reaction on the surface of the pos...

AI Technical Summary

Problems solved by technology

[0003] At present, lithium-nickel-cobalt-manganese ternary materials have become a research hotspot due to their high theoretical specific capacity and safety characteristics. However, the high nickel content in lithium-nickel-cobalt-manganese ternary materials makes them highly oxidizable, resulting The electrolyte is prone to electrochemical oxidation reaction on the surface of the positive electrode, and at the same time, it will cause changes in the structure of the lithium-nickel-cobalt-manganese ternary material, and the transition metals such as nickel and cobalt will undergo a reduction reaction and dissolve, causing the deterioration of the electrochemical performance of the lithium-ion battery. It is the high temperature performance that deteriorates significantly

In addition, during the preparation process of lithium-nickel-cobalt-manganese ternary materials, an excessive amount of lithium salt is added to compensate for the loss of lithium caused by the sintering process, so that there will be a small amount of Li residue on the surface of the prepared positive electrode active material, which will be at high temperature. Li 2 Exists in the form of O, when the temperature drops to room temperature, Li 2 O will absorb CO in the air 2 and H 2 O to form LiOH and Li 2 CO 3 and other residual lithium, the existence of these residual lithium will intensify the gas production of lithium-ion batteries and deteriorate the storage performance

Lithium-nickel-cobalt-manganese ternary materials are usually in the form of secondary particles formed by the agglomeration of primary particles, and the compressive strength is poor. After crushing, the specific surface area of ​​the positive electrode active material increases significantly, resulting in an increase in the contact area with the electrolyte. Gas production problem worsens

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