Polyolefin microporous film preparation method for lithium ion battery and microporous film

A technology of polyolefin microporous membrane and lithium ion battery, applied in battery pack parts, applications, circuits, etc., can solve the problems of low membrane porosity, unstable tensile temperature field, uneven product performance, etc. Through performance and mechanical properties, the effect of reducing the use of the site and equipment, tension and temperature ease of control

Inactive Publication Date: 2014-01-22
乐凯胶片股份有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] 1. Stretching to form a film with a single high-magnification after casting is prone to clipping, edge tearing, uneven film thickness, thin middle and thick sides, etc. If the width is too large; if the film width is too large, it will easily lead to unstable stretching temperature field and uneven temperature control, which will directly affect the consistency of film thickness and microstructure;
[0006] 2. If the width of the film is too large, it is easy to cause uneven tension during extraction, resulting in poor consistency in film thickness;
[0007] 3. If the width of the film

Method used

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  • Polyolefin microporous film preparation method for lithium ion battery and microporous film
  • Polyolefin microporous film preparation method for lithium ion battery and microporous film
  • Polyolefin microporous film preparation method for lithium ion battery and microporous film

Examples

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Effect test

Embodiment 1

[0032] (1) Extrusion casting: inject polyethylene resin and liquid paraffin into a twin-screw extruder, and melt and knead them into a uniform melt in the twin-screw. Then the melt is continuously extruded from the die, and rapidly cooled and shaped by cooling rollers to obtain thick sheets. Wherein, the weight average molecular weight of the polyethylene resin is 500,000, and the viscosity grade of the liquid paraffin is 40. The mass ratio of polyolefin resin to liquid paraffin is 1:2, the melting temperature is 200°C, and the temperature of the cooling roll is 30°C.

[0033] (2) The first biaxial stretching: Preheat the thick sheet to 115°C, and carry out the first synchronous biaxial stretching with a stretching ratio of 4 times (2.0 times in the longitudinal direction and 2.0 times in the transverse direction) on the stretching machine to obtain oily film;

[0034] (3) Extraction: Extract the liquid paraffin in the oil-containing film with dichloromethane to obtain the m...

Embodiment 2

[0039] (1) Extrusion casting: inject polyethylene resin and liquid paraffin into a twin-screw extruder, and melt and knead them into a uniform melt in the twin-screw. Then the melt is continuously extruded from the die, and rapidly cooled and shaped by cooling rollers to obtain thick sheets. Among them, the weight average molecular weight of the polyethylene resin is 800,000, and the viscosity grade of the liquid paraffin is 45. The mass ratio of polyolefin resin to liquid paraffin is 1:3, the melting temperature is 210°C, and the temperature of the cooling roll is 30°C.

[0040] (2) The first biaxial stretching: Preheat the thick sheet to 115°C, and carry out the first synchronous biaxial stretching with a stretching ratio of 7 times (including 3.0 times in the longitudinal direction and 2.3 times in the transverse direction) on the stretching machine to obtain oily film;

[0041] (3) Extraction: Extract the liquid paraffin in the oil-containing film with dichloromethane to...

Embodiment 3

[0046] (1) Extrusion casting: inject polyethylene resin and liquid paraffin into a twin-screw extruder, and melt and knead them into a uniform melt in the twin-screw. Then the melt is continuously extruded from the die, and rapidly cooled and shaped by cooling rollers to obtain thick sheets. Wherein, the polyethylene resin is a composition of polyethylene resin with a weight average molecular weight of 1.3 million and a weight average molecular weight of 500,000, and its ratio in the composition is 3:7; the viscosity grade of liquid paraffin is 45. The mass ratio of the polyolefin resin composition to the liquid paraffin is 1:3, the melting temperature is 215°C, and the temperature of the cooling roll is 30°C.

[0047] (2) The first biaxial stretching: Preheat the thick sheet to 120°C, and carry out the first synchronous biaxial stretching with a stretching ratio of 10 times (including 3.3 times in the longitudinal direction and 3.0 times in the transverse direction) on the st...

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Abstract

The invention discloses a polyolefin microporous film preparation method for a lithium ion battery and a microporous film. A mode of twice bidirectional drawing is adopted, and the overall rate of the twice drawing is 16 to 100 times. The preparation method comprises the following steps of (a) extruding a casting piece; (b) performing primary bidirectional drawing at a bidirectional drawing rate which is controlled to be 4 to 10 times to obtain an oily thin film; (c) performing extraction to obtain a microporous film A; (d) performing secondary bidirectional drawing at a bidirectional drawing rate which is controlled to be 4 to 10 times to obtain a thinner microporous film B; (e) performing heat setting to obtain a polyolefin microporous film. The polyolefin microporous film microcosmically has a completely drawn fiber structure, is uniform in aperture and high in performance consistency, and has higher mechanical performance, higher air permeability and enhanced ionic conductivity; the yield can be greatly improved; the lithium ion battery adopting the microporous film has high assembling performance, and the performance and the stability of the battery are enhanced.

Description

technical field [0001] The invention relates to the technical field of polymer microporous membrane materials, in particular to a preparation method of polyolefin microporous membranes for lithium ion batteries. Background technique [0002] With the gradual promotion of lithium-ion batteries in electric vehicles and new energy industries, the global demand for lithium-ion batteries continues to grow. Due to its high porosity, tear strength, low electrical resistance, good acid and alkali resistance and elasticity, polyolefin microporous membranes are the first choice for lithium-ion battery separators. The performance of the separator determines the interface structure and internal resistance of the battery, which directly affects the capacity, cycle and safety performance of the battery. A separator with excellent performance plays an important role in improving the overall performance of the battery. [0003] At present, the polyolefin microporous membrane prepared by t...

Claims

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Application Information

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IPC IPC(8): B29C69/00B29C47/00B29C55/12H01M2/16B29L7/00B23K23/00H01M50/403H01M50/417
CPCY02E60/12Y02E60/10
Inventor 宋红芹韩继庆张永生千昌富
Owner 乐凯胶片股份有限公司
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