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Irradiation cross-linking lithium-ion battery diaphragm and preparation method thereof

A technology of irradiation and diaphragm, applied in the direction of battery pack components, circuits, electrical components, etc., can solve the problems of insufficient current, low closed cell temperature, high hole temperature, etc., to improve power battery power and high temperature thermal shrinkage rate The effect of reducing and increasing the electrolyte absorption rate

Active Publication Date: 2015-04-29
ZHEJIANG UNIV +2
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

But its disadvantages are: first, to make the middle polyethylene layer close normally, and the polypropylene layers on both sides keep the dimensions stable, its thickness will be much larger than that of the single-layer film, thus occupying the limited space in the lithium-ion battery. If the three-layer film is made to monolayer thickness, the middle polyethylene layer will be very thin, and this thickness will not be enough to fully close the cells to block the current flow
Second, the mechanical strength of the three-layer composite film is low, and the heat shrinkage is relatively large at 120°C. During use, the battery winding short circuit rate is high, which is not conducive to production
Third, the puncture temperature of this diaphragm is still difficult to meet the high-power power lithium-ion battery field, such as power bicycles, power cars, etc.
But on the one hand, it is difficult to control the uniformity of coating thickness in this coating process; on the other hand, the coating liquid will block some channels
[0006] In order to solve the aforementioned shortcoming of insufficient safety performance of the lithium-ion battery separator, it is necessary to study a lithium-ion battery separator, which has a low closed-cell temperature and a higher hole-breaking temperature, and the thickness is not too thick. Separators with superior performance to meet the increasingly demanding market requirements for lithium-ion battery separators

Method used

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  • Irradiation cross-linking lithium-ion battery diaphragm and preparation method thereof
  • Irradiation cross-linking lithium-ion battery diaphragm and preparation method thereof
  • Irradiation cross-linking lithium-ion battery diaphragm and preparation method thereof

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preparation example Construction

[0028] The preparation method of the irradiation crosslinked polyethylene porous diaphragm of the present invention comprises the following steps:

[0029] The first step: Soak the polyethylene porous diaphragm in a volatile organic solvent containing a photoinitiator with a mass concentration of 0.01-10% and a crosslinking agent with a mass concentration of 0.01-10% for more than 5 seconds, take it out and dry it at room temperature .

[0030] Step 2: Place the diaphragm soaked in Step 1 at a place 1-50mm below the surface of the aqueous solution of a hydrophilic monomer with a mass concentration of 0-5% and irradiate it with a radiation source for more than 2 seconds, or directly place the diaphragm after soaking The diaphragm is placed in an inert gas protective atmosphere and irradiated with a radiation source for more than 2 seconds. The radiation temperature is from room temperature to 110 ° C. The distance between the surface of the diaphragm and the radiation source is...

Embodiment 1

[0048] Soak the diaphragm 1 in a dichloromethane solution containing 1% mass concentration of photoinitiator BP and 1% mass concentration of crosslinking agent TAC for 1 min, take it out and dry it at room temperature. Soak the diaphragm in a constant temperature water bath filled with pure water and irradiate on both sides for 3 minutes in the irradiation device. The position of the film is 2mm away from the water surface, the water temperature is 30°C, the irradiation source is a 2KW high-pressure mercury lamp, and the distance between the mercury lamp and the film is 10cm. , irradiated to obtain a cross-linked polyethylene porous membrane.

[0049] figure 1 Shown are the electron microscope pictures of the surface morphology of the diaphragm 1 before and after irradiation on both sides for 3 minutes, (a) before irradiation; (b) after irradiation. It can be seen from the figure that there is no change in the pore size of the diaphragm before and after irradiation. figure ...

Embodiment 2

[0060] Soak the diaphragm 1 in a dichloromethane solution containing 1% mass concentration of photoinitiator BP and 1% mass concentration of crosslinking agent TAC for 1 min, take it out and dry it at room temperature. Soak the diaphragm in a constant temperature water bath filled with pure water and irradiate on both sides for 1min in the irradiation device. The position of the film is 2mm away from the water surface, the water temperature is 30°C, the irradiation source is a 2KW high-pressure mercury lamp, and the distance between the mercury lamp and the film is 10cm. , irradiated to obtain a cross-linked polyethylene porous membrane.

[0061] It can be seen from Table 2 that there is no change in the porosity of the separator after irradiation. Figure 5 Shown are the changes in water contact angle on the membrane surface before and after the double-sided irradiation of membrane 1 for 1 min, (a) before irradiation, (b) after irradiation. It can be seen from the figure tha...

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Abstract

The invention discloses a method for preparing a radiation cross-linked polyethylene porous separator. In this method, the polyethylene porous separator is soaked to absorb a volatile solvent containing an initiator and a cross-linking agent, and the initiator and cross-linking agent are introduced on the surface and inside the porous separator. Linking agent is used, and then the film is irradiated and cross-linked under the water surface or under the protection of inert gas. By controlling the irradiation conditions, a partially cross-linked separator is obtained. The advantages of this irradiation cross-linked polyethylene porous separator are: the tensile strength and hydrophilicity are greatly improved; the high-temperature thermal shrinkage is greatly reduced; it makes up for the low rupture temperature of the separator and ensures the normal closure of the separator. At the same time, the membrane rupture temperature of the film is greatly increased. The closing temperature of the separator of the present invention is between 120 and 140°C, and the membrane rupture temperature is increased to above 160°C.

Description

Technical field [0001] The present invention relates to the field of lithium ion batteries, and in particular to a radiation cross-linked lithium ion battery separator and a preparation method thereof. Background technique [0002] Lithium-ion battery is a new type of rechargeable battery developed on the basis of lithium storage battery. It was successfully developed and commercialized by SONY in 1990. Because of its advantages such as high specific energy, long cycle life, and no memory effect, it has become a research hotspot in new power technology in recent years. It can be widely used in portable electronic products such as mobile phones, laptops, digital cameras, camcorders, and even in fields such as electric bicycles, electric vehicles, and energy storage batteries that are currently strongly advocated in the world. [0003] The main components of a lithium-ion battery include electrodes, isolation membranes and electrolytes. The isolation membrane plays a key role...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C08J9/42C08J7/18H01M2/16C08L23/06H01M50/403H01M50/417H01M50/491
CPCY02E60/10
Inventor 高翔盛伟李伯耿罗英武林叶刚王永常
Owner ZHEJIANG UNIV
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