Preparation method of lithium ion battery diaphragm

A technology for lithium ion batteries and separators, which is applied in the field of preparation of lithium ion battery separators, can solve the problem of uneven pore size and distribution of micropores of separators, widened molecular weight distribution, poor performance of separators such as air permeability, thermal shrinkage and membrane breaking temperature. And other issues

Active Publication Date: 2020-05-08
FOSHAN JINHUI HIGH TECH OPTOELECTRONICS MATERIAL
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The above method can stably prepare the casting base film, and the performance of the separator basically meets the requirements of the lithium-ion battery for the separator, but there are still the following defects: the existence of high-density polyethylene broadens the overall molecular weight distribution of the separator, and the prepared The micropore size and distribution of the lithium-ion battery separator are not uniform, and the performance of the separator such as air permeability, thermal shrinkage and membrane rupture temperature is poor, which affects the performance of the separator in the lithium-ion battery.

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  • Preparation method of lithium ion battery diaphragm

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preparation example Construction

[0021] A preparation method of a lithium-ion battery diaphragm, comprising the following steps:

[0022] (a) mixing ultra-high molecular weight polyethylene and a solvent, heating and stirring for the first time to obtain a pre-swelling mixed solution;

[0023] (b) Grinding the pre-swelling mixture, then adding a fluoropolymer, heating and stirring for the second time to obtain a dispersion;

[0024] (c) melting and extruding the dispersion to obtain a plasticized melt film;

[0025] (d) post-processing the plasticized melt film.

[0026] Preferably, the weight average molecular weight of the ultra-high molecular weight polyethylene is 1.0×10 6 ~8.0×10 6 g / mol; further preferably, the weight average molecular weight of the ultra-high molecular weight polyethylene is 1.5×10 6 ~3.0×10 6 g / mol.

[0027] It can be understood that in the pre-swelling mixed solution of the present invention, the solid content of ultra-high molecular weight polyethylene can be relatively high. ...

Embodiment 1

[0060] (a) 120kg weight average molecular weight is 1.5×10 6 g / mol ultra-high molecular weight polyethylene and 280kg 40 ℃ kinematic viscosity is 40mm 2 / s Add liquid paraffin into the stirring tank, start heating to 110°C at a stirring rate of 150r / min, and keep it warm for 5 hours to obtain a pre-swelling mixture.

[0061] (b) Adding pure zirconium beads with a particle size of 1.2 mm into the sand mill, transporting the pre-swelled mixed solution into the sand mill, and circulating it 6 times at a grinding rate of 800 r / min to obtain a uniformly dispersed mixed solution;

[0062] In the homogeneously dispersed mixed solution, add fluoropolymer (FX5922 of 3M Company), the concentration of the fluoropolymer in the uniformly dispersed mixed solution is 1000ppm, at 80°C with a stirring rate of 200r / min Stir for 3 hours, and stir evenly to obtain a dispersion.

[0063] (c) The dispersion liquid is heated and continuously extruded by a twin-screw extruder, the heating temperatu...

Embodiment 2

[0066] This example is the same as Example 1 except that the amounts of ultra-high molecular weight polyethylene and liquid paraffin are changed to 80kg and 320kg respectively in step (a). The specific technical solutions are:

[0067] (a) 80kg weight average molecular weight is 1.5×10 6 g / mol ultra-high molecular weight polyethylene and 320kg 40 ℃ kinematic viscosity is 40mm 2 / s Add liquid paraffin into the stirring tank, start heating to 110°C at a stirring rate of 150r / min, and keep it warm for 5 hours to obtain a pre-swelling mixture.

[0068] (b) Adding pure zirconium beads with a particle size of 1.2 mm into the sand mill, transporting the pre-swelled mixed solution into the sand mill, and circulating it 6 times at a grinding rate of 800 r / min to obtain a uniformly dispersed mixed solution;

[0069] In the homogeneously dispersed mixed solution, add fluoropolymer (FX5922 of 3M Company), the concentration of the fluoropolymer in the uniformly dispersed mixed solution i...

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Abstract

The invention relates to a preparation method of a lithium ion battery diaphragm. The preparation method comprises the following steps: mixing ultrahigh molecular weight polyethylene and a solvent, and heating and stirring for the first time to obtain a pre-swelling mixed solution; grinding the pre-swelling mixed solution, then adding a fluorine-containing polymer, and heating and stirring for thesecond time to obtain a dispersion solution; carrying out melt extrusion on the dispersion liquid to obtain a plasticized melt film; and carrying out post-treatment on the plasticized melt film. According to the preparation method disclosed by the invention, the ultra-high molecular weight polyethylene can be uniformly plasticized, the formed diaphragm is uniform in thickness distribution, and the method has the advantage of being uniform in micropore size and distribution, small in high-temperature thermal shrinkage, high in puncture strength and high in diaphragm breaking temperature.

Description

technical field [0001] The invention relates to the field of lithium ion batteries, in particular to a preparation method of lithium ion battery separators. Background technique [0002] The lithium-ion battery separator is an important part of the lithium-ion battery. It has the function of preventing the contact between the positive and negative electrodes, preventing the free passage of electrons, and allowing the ions in the electrolyte to pass freely between the positive and negative electrodes. The structure and performance parameters of the separator have a significant impact on key characteristics such as the capacity, cycle performance, charge-discharge rate, and safety performance of the battery. High-performance separators are crucial to the performance and practical application of batteries. [0003] Ultra-high molecular weight polyethylene has extremely high molecular weight, which makes its performance better than ordinary polyethylene. The comprehensive perfor...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M2/14H01M2/16H01M10/0525
CPCH01M10/0525H01M50/403H01M50/411Y02E60/10
Inventor 梁朝伟陈伟健王松钊王辉宋广智
Owner FOSHAN JINHUI HIGH TECH OPTOELECTRONICS MATERIAL
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