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

Abstract

The invention discloses a method for preparing a radiation-crosslinked polyethylene porous membrane. In the method, the polyethylene porous membrane is soaked to absorb a volatile solvent containing an initiator and a crosslinking agent, and the initiator and crosslinking agent are introduced into the surface and inside of the membrane. Linking agent, 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 diaphragm is obtained. The advantages of the irradiation cross-linked polyethylene porous diaphragm are: the tensile strength and hydrophilicity are greatly improved; the high-temperature thermal shrinkage rate is greatly reduced; the deficiency of the diaphragm rupture temperature is made up for, and the normal closure of the diaphragm is ensured. At the same time, the rupture temperature of the membrane is greatly improved. The membrane closure temperature of the membrane of the present invention is 120-140° C., and the membrane rupture temperature is increased to above 160° C.

Description

technical field [0001] The invention relates to the field of lithium ion batteries, in particular to a diaphragm for irradiation crosslinked lithium ion batteries and a preparation method thereof. Background technique [0002] Lithium-ion battery is a new type of rechargeable battery developed on the basis of lithium batteries. 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 supply technology in recent years. It can be widely used in portable electronic products such as mobile phones, notebook computers, digital cameras, video cameras, and even electric bicycles, electric vehicles, and energy storage batteries that are vigorously advocated in the world. [0003] The main components of lithium-ion batteries include electrodes, separators and electrolytes. The separator plays a key role in lithium-ion batteries. It is a...

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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

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