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Polyethylene microporous membrane and preparation method of polyethylene microporous membrane

A microporous diaphragm, polyethylene technology, applied in the direction of separators/films/diaphragms/spacers, electrical components, circuits, etc. Stability and safety, improved thickness uniformity, improved poor ventilation

Inactive Publication Date: 2017-05-31
UNIV OF SCI & TECH OF CHINA
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The separator obtained by this stretching method has poor uniformity, mainly manifested in large fluctuations in thickness, large air permeability difference, and uneven distribution of microstructure, which seriously hinders its application in the field of high-end batteries.

Method used

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  • Polyethylene microporous membrane and preparation method of polyethylene microporous membrane
  • Polyethylene microporous membrane and preparation method of polyethylene microporous membrane
  • Polyethylene microporous membrane and preparation method of polyethylene microporous membrane

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preparation example Construction

[0022] The invention provides a preparation method of a polyethylene microporous diaphragm, comprising the following steps:

[0023] A) mixing ultra-high molecular weight polyethylene with white oil to obtain oil flakes through melt extrusion and casting;

[0024] B) Stretching the oil sheet in the first step in the direction of casting, stretching in the second step perpendicular to the direction of casting, and stretching in the third step in accordance with the direction of casting to obtain a film;

[0025] The stretching strain of the first step is 1-4, the stretching strain of the second step is 5-7, and the stretching strain of the third step is 1-4;

[0026] The stretching temperatures of the first step stretching, the second step stretching and the third step stretching are independently 95-105°C, and the first step stretching, the second step stretching and the third step stretching The stretching speed is independently 1-3mm / s.

[0027] see figure 1 , figure 1 T...

Embodiment 1

[0043] Put ultra-high molecular weight polyethylene and white oil into the mixing container at a ratio of 2:8, stir well and use for melt extrusion. The molecular weight of ultra-high molecular weight polyethylene is 340,000 g / mol. After the mixture of polyethylene and white oil is extruded by a twin-screw extruder, an oil sheet is formed on a casting roll. During casting, the roll temperature was set at 60° C., and the thickness of the obtained oil sheet was 0.9 mm.

[0044] Two-way three-step stretching is carried out on the oil sheet by using a film bidirectional stretching device. The stretching temperature was 100° C., and the stretching speed was 3 mm / s. The first step of the three-step stretching process is stretching along the longitudinal direction to a strain of 4, the second step is stretching along the transverse direction to a strain of 7, and the third step is stretching along the longitudinal direction to a strain of 1. The parameters of the three-step stretch...

Embodiment 2

[0052] Add ultra-high molecular weight polyethylene and white oil into the mixing container at a ratio of 5:5, stir well and use for melt extrusion. The molecular weight of ultra-high molecular weight polyethylene is 470,000 g / mol. After the mixture of polyethylene and white oil is extruded by a twin-screw extruder, an oil sheet is formed on a casting roll. During casting, the roll temperature was set at 30° C., and the thickness of the obtained oil sheet was 1.5 mm.

[0053] Two-way three-step stretching is carried out on the oil sheet by using a film bidirectional stretching device. The stretching temperature was 98° C., and the stretching speed was 1.5 mm / s. The first step of the three-step stretching process is stretching along the longitudinal direction to a strain of 3, the second step is stretching along the transverse direction to a strain of 5.5, and the third step is stretching along the longitudinal direction to a strain of 2. The parameters of the three-step stre...

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Abstract

The invention provides a preparation method of a polyethylene microporous membrane. When an oil sheet is stretched, a three-step stretching manner is adopted, and the defect that the membrane obtained by existing bidirectional two-step stretching is not uniform can be overcome and the membrane with a uniformly-distributed microstructure is prepared, so that the thickness uniformity of the membrane is improved and a condition that the air permeability of the membrane is extremely poor is improved; the stability and safety of the battery can be improved and the polyethylene microporous membrane is used for the field of high-end lithium batteries.

Description

technical field [0001] The invention belongs to the technical field of microporous diaphragms for lithium ion batteries, and in particular relates to a polyethylene microporous diaphragm and a preparation method thereof. Background technique [0002] The microporous diaphragm for lithium-ion batteries is a functional film placed between the positive and negative electrodes of the battery to conduct lithium ions and hinder electron migration. It is mostly made of polyolefin materials through stretching. The wet process microporous diaphragm is prepared by mixing ultra-high molecular weight polyethylene and white oil in a certain proportion, and then melt extrusion-casting, stretching, extraction and other processes. At present, when stretching the oil sheet obtained by extrusion-casting during wet-process diaphragm processing, a two-way two-step stretching method is often used, that is, stretching in the longitudinal direction first, and then stretching in the transverse dire...

Claims

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Application Information

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IPC IPC(8): H01M2/14H01M2/16H01M2/18
CPCH01M50/403H01M50/409H01M50/463Y02E60/10
Inventor 李良彬孟令蒲万彩霞
Owner UNIV OF SCI & TECH OF CHINA
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