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Battery separator film and preparation method thereof

A technology of battery diaphragm and diaphragm material, applied in battery pack parts, circuits, electrical components, etc., can solve the problem of low closed cell temperature, poor puncture tensile strength, air permeability of battery diaphragm, and unsatisfactory film breaking temperature at high temperature, etc. question

Active Publication Date: 2013-03-06
BYD CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] In order to solve the technical problems of the existing battery separators, such as unsatisfactory air permeability at high temperature, unsatisfactory rupture temperature at high temperature, and poor piercing tensile strength, the present invention provides a battery with high tensile piercing strength, low closed cell temperature, and thermal stability. Excellent novel battery separator and preparation method thereof

Method used

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  • Battery separator film and preparation method thereof

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preparation example Construction

[0021] The present invention also provides a method for preparing a battery diaphragm, comprising the following steps:

[0022] (a) dissolving and plasticizing the polyethylene mixture and the first solvent to obtain a polyethylene melt; dissolving and plasticizing the polymethylpentene and the second solvent to obtain a polymethylpentene melt;

[0023] (b) mixing polyethylene melt and polymethylpentene melt, casting, cooling, stretching, extracting, drying, and heat setting to obtain a separator;

[0024] Wherein, the first solvent is a good solvent for polyethylene, preferably, one or more selected from decahydronaphthalene, kerosene, liquid paraffin or paraffin; the second solvent is a good solvent for polymethylpentene, preferably , selected from one or more of liquid paraffin, paraffin, benzene, toluene, methanol, cyclohexane, trichloroethylene, tetrahydrofuran, pyridine or butanone.

[0025] In the preparation method of the battery separator provided by the present inve...

Embodiment 1

[0050] The diaphragm in this example is made through the following steps:

[0051] (s1) 5kg, weight average molecular weight of 1.5×10 6 , ultra-high molecular weight polyethylene with a molecular weight distribution of 6, 17.5kg, and a weight-average molecular weight of 2.5×10 5 , high-density polyethylene with a molecular weight distribution of 10.8, 2.5kg, and a weight-average molecular weight of 1×10 4 , low-density polyethylene with a molecular weight distribution of 12, 0.1 kg of 3-(3,5-di-tert-butyl-4-hydroxy)propenyl octadecyl ester and 0.025 kg of tris[2,4-di-tert-butylphenyl] Phosphite and 50kg of liquid paraffin are continuously fed into a twin-screw extruder with a length-to-diameter ratio of 40, and melted and plasticized at a temperature of 160°C-240°C and a shear rate of 120r / min to obtain a molten polyethylene mixture. body;

[0052] 10kg, the weight average molecular weight is 5×10 5 , melt index is 23dg / min, poly-4-methyl-1-pentene and 15kg liquid paraffi...

Embodiment 2

[0060] The difference from Example 1 is that: in step (s1), 1.25kg, weight average molecular weight of 1.5×10 6 , ultra-high molecular weight polyethylene with a molecular weight distribution of 6; 18.75kg, a weight-average molecular weight of 2.5×10 5 , high-density polyethylene with a molecular weight distribution of 10.8; 5kg, a weight-average molecular weight of 1×10 4 , low-density polyethylene with a molecular weight distribution of 12, 0.1 kg of 3-(3,5-di-tert-butyl-4-hydroxy)propenyl octadecyl ester and 0.025 kg of tris[2,4-di-tert-butylphenyl] Phosphite and 50kg of liquid paraffin are continuously fed into a twin-screw extruder with an aspect ratio of 40. The obtained separator is designated as S2.

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Abstract

The invention provides a battery separator film, wherein film materials comprise a polyethylene mixture and polymethylpentene. The polyethylene mixture comprises ultrahigh-molecular-weight polyethylene and high-density polyethylene. The invention also provides a preparation method of the battery separator film. According to the invention, air permeability of the separator film provided by the invention is substantially improved, pore-closing temperature is substantially reduced, piercing strength is substantially increased, and film rupture temperature is substantially increased. Therefore, a safer protection performance is provided for batteries. The film and the method are more suitable to be applied in power batteries.

Description

technical field [0001] The invention relates to a battery separator, in particular to a separator for a power battery and a preparation method thereof. Background technique [0002] Lithium ion secondary battery is a kind of battery with extremely high energy density, but there is a danger of explosion due to short circuit. In lithium-ion secondary batteries, the separator is mainly used for the conduction of lithium ions, and separates the positive and negative electrodes inside the battery from each other, so as to prevent battery self-discharge and short-circuit of the two poles, and play a certain role in safety protection. The thermal stability, permeability, porosity, and film thickness of the separator all have an important impact on the performance of the battery. [0003] In recent years, the application of lithium-ion secondary batteries has been extended to fields such as hybrid electric vehicles, and the thermal stability requirements for separators are becoming...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M2/16
CPCY02E60/12Y02E60/10
Inventor 林妙云尤臻于伟成罗明俊刘会权
Owner BYD CO LTD
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