Lithium ion battery

Abstract

The invention provides a lithium ion battery, which includes a positive pole piece, a negative pole piece, a diaphragm, and an electrolyte. The positive pole piece includes a positive electrode current collector and a positive electrode membrane disposed on the surface of the positive electrode current collector and containing a positive electrode active material, wherein the positive electrode active material includes a substrate, a first coating layer coating the surface of the substrate in a discrete island form, and a second coating layer coating the first coating layer and the surface ofthe substrate in a continuous layered form. The electrolyte includes an additive A and an additive B. The additive A is selected from one or more of cyclic sulfate compounds represented by Formulas 1and 2. The additive B is selected from one or two of lithium difluorobisoxalate phosphate and lithium tetrafluorooxalate phosphate. The gas output of the lithium ion battery can be reduced, the cyclelife and the storage life of the lithium ion battery can be prolonged, and an increase in DC internal resistance of the lithium ion battery can be significantly inhibited during the cycle and storageprocesses.

Description

technical field [0001] The invention relates to the technical field of batteries, in particular to a lithium ion battery. 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 positive electrode, and at the same time, it will cause changes in the structure of the l...

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 will be added to make up for the lithium loss caused by the sintering process, so that there will be a small amount of Li remaining on the surface of the prepared positive electrode active material, which will be converted into Li at high temperature. 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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