A kind of polyolefin microporous film for lithium battery and preparation method thereof

A technology of microporous membrane and polyolefin, which is used in applications, household appliances, flat products, etc., can solve the problems of poor membrane rupture resistance, difficult to form porosity, and reduced crystallization degree, and achieves low porosity, puncture Improved wear strength and uniform strength

Active Publication Date: 2011-12-07
XINXIANG ZHONGKE SCI&TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Using this method reduces the melting temperature to a certain extent. Due to the poor compatibility between ultra-high molecular weight polyethylene and these two density polyethylenes, it is easy to break the film from the interface of the two polyethylenes. Difference
In addition, the degree of crystallization of the membrane is reduced, it is difficult to form porosity, and the permeability is affected.

Method used

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  • A kind of polyolefin microporous film for lithium battery and preparation method thereof
  • A kind of polyolefin microporous film for lithium battery and preparation method thereof

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preparation example Construction

[0022] The preparation method of the polyolefin microporous membrane used in lithium batteries according to the present invention comprises the following steps: 1) melting polyolefin resin, pore shape modifying agent and plasticizer at a temperature of 150°C to 280°C to form a uniform 2) Extrude the molten liquid from the die head, and cool it on the cooling roll to form a thick sheet, the cooling temperature is 5-30° C; Forming into a film, the stretching temperature is below the melting point of the resin + 10°C, and the total stretching ratio is 10 to 80 times; 4) Extracting the plasticizer from the film, and heat-setting at 80 to 150°C to obtain the polymer Olefin microporous membrane.

[0023] The extraction solvent used in step 4 is one of the following: n-hexane, heptane, methylene chloride, methanol or ethanol.

[0024] According to the polyolefin microporous membrane obtained by the preparation method of the present invention, the polyolefin microporous membrane incl...

Embodiment 1

[0031] 15% (accounting for the percentage of total feeding weight) of high-density polyethylene (HDPE, viscosity-average molecular weight 2.5 * 10 5 , melting point is 130 ℃), 2% (accounting for the percentage of total feeding weight) of low-density polyethylene (LDPE, viscosity-average molecular weight 2.0 * 10 5, melting point is 128 ℃), 6% (accounting for the percentage of total feeding weight) of ultra-high molecular weight polyethylene (UHMWPE, viscosity-average molecular weight 1 × 10 6 , melting point 134 ° C), 2% (accounting for the percentage of total feed weight) of diphenyl ether and 2% (accounting for the percentage of total feed weight) of dioctyl phthalate are dry mixed in a mixer, added to the twin-screw In the extruder (diameter 58mm, L / D=52, strong mixing type), use metering pump then, add 73% (accounting for the percentage of total feeding weight) liquid paraffin (dynamic viscosity 90cst / 40°C), under the conditions of 170°C and 156 rpm, melt and mix the res...

Embodiment 2

[0034] 15% (accounting for the percentage of total feeding weight) of high-density polyethylene, 6% (accounting for the percentage of total feeding weight) of low-density polyethylene, 5% (accounting for the percentage of total feeding weight) poly-1-butene, 5% (accounting for the percentage of total feed weight) of diphenyl ether and 2% (accounting for the percentage of total feed weight) of dibutyl phthalate. Mix dryly in the mixer, join in the twin-screw extruder (diameter 58mm, L / D=52, strong mixing type), then use metering pump, add 67% (accounting for total feeding weight) percentage) of liquid paraffin (dynamic viscosity 90cst / 40°C), melting and mixing the resin at 150°C and 156 rpm. The mixed resin solution was extruded through a T-die, and the cast sheet was cooled on a cooling roll with a surface temperature of 5° C. to obtain a thick sheet with a thickness of 0.30 mm.

[0035] The thick sheet is sequentially stretched longitudinally and transversely at a certain te...

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Abstract

The invention discloses a polyolefin microporous film for a lithium battery and a preparation method thereof. The preparation method comprises the following steps that 1, one or more polyolefin resins, one or more porous modification agents and a plasticizer are melted into a uniform solution at a temperature of 150 to 280 DEG C; 2, the melted solution obtained by the step 1 is extruded from a mold head and is cooled on a cooling roll at a temperature of 5 to 30 DEG C to be cast into a thick sheet; 3, the thick sheet is stretched in double directions to be made into a film, wherein the thick sheet is stretched in the vertical direction first and then is stretched in the transverse direction; a stretching temperature value is less than a value equal to the sum of a resin melting point temperature value and 10; and a total stretching rate is in a range of 10 to 80 times; and 4, the plasticizer is extracted from the film obtained by the step 3 and the polyolefin microporous film is obtained through heat shaping at a temperature of 80 to 150 DEG C. Through the added one or more porous modification agents with a high boiling point or a high flash point, aperture shapes and aperture sizes of the polyolefin microporous film are adjusted to realize that an average aperture size of the polyolefin microporous film is appropriate; the aperture shapes are nearly circular; and strength in either direction is uniform and consistent.

Description

technical field [0001] The invention relates to a polyolefin microporous membrane for lithium batteries and a preparation method thereof, in particular to a polyolefin microporous membrane for lithium batteries with good air permeability and better pore size distribution and a preparation method thereof. Background technique [0002] Due to the characteristics of high energy density, long cycle life, light weight, small size, etc., and the advantages of safety, reliability, and fast charging and discharging, lithium batteries have become a hot spot in the research of new power supply technologies in recent years. popular. In the structure of lithium batteries, the separator is one of the key inner components. The diaphragm is made of plastic film, which can isolate the positive and negative poles of the battery to prevent short circuit; it can also block the current conduction in the battery by closing the pores when the battery is overheated. It directly affects the capac...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B29C55/14B29C47/92C08L23/00C08L33/12C08K5/01B29L7/00B29C48/92
Inventor 袁新豪古继峰
Owner XINXIANG ZHONGKE SCI&TECH
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