Lithium ion battery diaphragm with three kinds of microporous structures, and polyethylene composition adopted by same

Abstract

The invention discloses a lithium ion battery diaphragm with three kinds of microporous structures, and a polyethylene composition adopted by the same. The composition comprises high-molecular polyethylene, ultra-high-molecular polyethylene and an optional additive. The lithium ion battery diaphragm prepared from the composition has integrally-formed three kinds of microporous structures; and in addition, the lithium ion battery diaphragm has relatively low closed-hole temperature, high heat resistance shrinkage, high tensile strength, high puncture strength and relatively high membrane-rupture temperature, thereby ensuring safety in preparation and usage of the lithium ion battery.

Description

technical field [0001] The invention relates to the field of lithium-ion battery separators, in particular to a lithium-ion battery separator with three microporous structures and a polyolefin (especially polyethylene) composition used. Background technique [0002] Lithium-ion batteries are widely used in the fields of electronic communication, energy storage, and power supply. They are mainly composed of positive electrodes, negative electrodes, electrolytes, and battery separators. Among them, the battery separator is non-conductive and is located between the positive and negative electrodes to prevent positive and negative electrodes. The latter is short-circuited due to contact, and at the same time allows the electrolyte ions to pass through, thereby generating current. The current battery separator is mostly a polyolefin film with a microporous structure, and its performance determines the interface structure and internal resistance of the battery, which directly affec...

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Problems solved by technology

[0005] There are some defects in the traditional battery separator wet preparation process, including: in the casting process, a casting roll with cooling function is usually used for single-sided cooling, and the pore-forming agent is not completely sealed and easy to flow out, resulting in uneven distribution of micropores ;The extrusion equipment in different production steps is different, resulting in different product quality and appearance, and it is difficult to control the consistency; usually the surface of the extrusion equipment and stretching tension equipment is smooth, and the surface of the manufactured diaphragm is smooth, and the adhesion with other substances The ability is poor, which is not conducive to the development of new battery separators; the drying equipment after extraction usually uses two methods of water gun and air gun at the same time, resulting in water marks on the surface of the separator, and the flatness is not good enough

[0006] At present, in the prior art, there is a method of laminating multilayer polyolefin films to make multilayer composite lithium ion battery separators. Not only is the operation complicated, the product quality is unstable, and the equipment used often requires special design.

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