Lithium ion battery electrode slice, electric core and its making method

Abstract

This invention discloses pole plates of Li ionic cells, in which, a micro-porous film is set on the pole plate with PVDF as the matrix and chemical gel formed by chimical cross-link is set in the micro-porous film.This invention also discloses a Li-ionic cell core with said pole plates and a preparation method including: the PVDF film forming chemical gel inside by irradiation and cross-link has the heat contraction rate of nearly zero under 100-220deg.C, which can prevent electronic short circuit of positive and negative pole plates caused by over contraction of intensified switchable Polyolefin micro-hole septums under high temperature when being coated on the pole plates.

Description

technical field [0001] The invention relates to the field of lithium-ion batteries, in particular to a high-safety lithium-ion battery pole piece, a battery cell and a preparation method for the battery cell. Background technique [0002] Lithium-ion secondary batteries have the advantages of high working voltage, high energy density, and environmental protection, and are widely used in mobile phones, notebook computers, power tools, electric bicycles and other products. [0003] Polymer lithium-ion secondary batteries usually use porous polyvinylidene fluoride copolymer PVDF-HFP as a physical gel separator. The typical process is the classic Bellcore process. See US Patent 5,540,741. This method uses dibutyl phthalate DBP As a plasticizer, the DBP is removed by methanol multi-stage extraction method to form pores. The physically cross-linked PVDF-HFP has good liquid absorption and liquid retention. It is used as a gel electrolyte after absorbing liquid and swelling. The pro...

AI Technical Summary

Problems solved by technology

However, the strength of the polyvinylidene fluoride microporous film produced by this method is low, and the film thickness usually needs to be about 50 microns, which still cannot meet the high-efficiency winding process requirements. Composite laminate structure; another disadvantage of this method is low extraction efficiency, high requirements for production safety protection, high manufacturing cost, and poor economy

The disadvantage of these methods is that the glue is easy to block the micropores in the PE diaphragm, and it is easy to form an airtight skin layer. It is difficult to control the uniformity and consistency of the micropores during production; At 180-320°C, so it cannot be formed by polycondensation on the surface of the PE separator with a melting point of 135°C

Thermochemical cross-linking technology has been successfully applied in large quantities in the manufacture of cable insulation jackets, but when used in lithium-ion batteries, due to the use of many monomer or polymer precursors, cross-linking agents, peroxide initiators and other compositions, there are reactions Incomplete, residues and impurities can easily affect the electrochemical performance of the battery, and it is difficult to control the quality of mass production

[0010] In order to solve the above-mentioned technical problems, the inventor proposes in document CN200410081129.6 a method for coating and manufacturing a PVDF porous film layer on the pole piece of a lithium-ion cell, which avoids the above-mentioned shortcoming. The pole piece has good adhesion and is not easy to peel off. In addition, the PVDF porous membrane layer has a low thermal shrinkage rate at 100-150°C, which can make up for the lack of high thermal shrinkage rate of high-strength polyolefin diaphragms; There is still a shortage of high production costs. In addition, due to the requirement to prevent thermal runaway inside the battery, it is hoped that the battery will have a high-temperature-resistant and low-heat-shrinkable separator that can prevent the positive and negative electrodes from short-circuiting at a temperature of up to 200°C. Production economy still needs to be improved