Negative plate and lithium ion battery

Abstract

The invention provides a negative plate and a lithium ion battery. The negative plate comprises a negative electrode current collector and a negative electrode diaphragm; the negative electrode diaphragm comprises a negative electrode active substance and a conductive adhesive; the negative electrode current collector is prepared from rolled copper foil or stainless steel foil; the conductive adhesive is polyimidesiloxane containing conductive polymer chains; the conductive adhesive is prepared via amidation of tetra formic acid or tetra formic anhydride with diamine siloxane containing conductive polymer chains; and the molar ratio of the tetra formic acid or the tetra formic anhydride to the diamine siloxane containing conductive polymer chains is controlled to be (1.1-1.3):1. The negative plate possesses excellent conductivity and adhesive performance, and relatively low expansion ratio; and the lithium ion battery possesses excellent electrical properties and cycle performance.

Description

technical field [0001] The invention relates to the technical field of lithium ion batteries, in particular to a negative electrode sheet and a lithium ion battery. Background technique [0002] In recent years, the wide application of lithium-ion batteries has put forward higher requirements on the energy density of batteries. In the lithium-ion battery system, the energy density of graphite is far from meeting the market demand, so it is necessary to apply alloy materials with high energy density. However, the volume of such alloy materials, especially silicon alloys, changes greatly during the charge and discharge process. The negative electrode sheet prepared by using commonly used binders such as SBR often has a large rebound due to its low adhesion, thereby reducing the The energy density, what's more, the de-filming of the negative electrode sheet leads to a sharp decline in battery cycle performance, which is far from meeting the needs of silicon alloys. [0003] A...

AI Technical Summary

Problems solved by technology

However, the volume of such alloy materials, especially silicon alloys, changes greatly during the charge and discharge process. The negative electrode sheet prepared by using commonly used binders such as SBR often has a large rebound due to its low adhesion, thereby reducing the The energy density, what's more, the de-filming of the negative electrode leads to a sharp decline in the battery cycle performance, which is far from meeting the needs of silicon alloys.

[0003] Adhesives with high adhesion, such as polyacrylonitrile, polyacrylic acid and its salts, polyimides and polyamideimides, etc., have relatively poor conductivity, and a small amount of addition cannot effectively bond If the addition amount is too large, the electrical contact of the negative electrode active material may deteriorate. Therefore, a binder with both high adhesion and certain conductivity is required to truly meet the needs of high energy density negative electrodes.

On the other hand, if such a highly cohesive binder is applied to the general electrolytic copper foil, although the tensile strength of the electrolytic copper foil is small, although it can effectively reduce the rebound of the negative electrode sheet in thickness, it causes negative electrode damage. The extension of the sheet in the length and width direction may even cause the negative electrode sheet to break and shatter, making the battery unable to perform normal cycle

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