Lithium battery, lithium battery separator and preparation method thereof

Abstract

The embodiment of the present invention discloses a preparation method of a lithium battery diaphragm, comprising the following steps: adding 10-15 parts of poly(vinylidene fluoride-chlorotrifluoroethylene) and 2-7 parts of lactic acid to 50 ‑80 parts of organic solvent, stir to dissolve; add 0.5‑5 parts of initiator and 2‑10 parts of hydrogenation reducing agent, and then stir for reaction; add the reaction mixture into alkaline aqueous solution and stir to precipitate, and the precipitate is filtered and washed , dry to obtain poly(vinylidene fluoride-trifluoroethylene-lactic acid) copolymer resin; poly(vinylidene fluoride-trifluoroethylene-lactic acid) copolymer resin is prepared into lithium battery diaphragm, by using poly(vinylidene fluoride -chlorotrifluoroethylene-lactic acid) copolymer resin to prepare the lithium battery separator, which makes the lithium battery separator have the characteristics of degradability, electrolyte corrosion resistance and high tensile strength.

Description

technical field [0001] The embodiments of the present invention relate to the field of lithium battery separators, and in particular to a lithium battery, a lithium battery separator and a preparation method thereof. Background technique [0002] With the rapid development of the lithium battery industry, the shipment of lithium battery separators reached 2 billion square meters in 2018. Moreover, in the next 5-10 years, the lithium battery separator will maintain a high growth rate of 30%. At this stage, the materials used to prepare lithium battery separators are basically polyethylene and polypropylene. Such materials have very poor biodegradability and cannot be recycled and reused. If they are discarded or buried at will, they will cause serious environmental pollution. Therefore, in order to solve this problem, it is necessary to modify the preparation materials of lithium battery separators to prepare new lithium battery separators with degradable properties. [00...

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Problems solved by technology

But this method has following deficiency: (1) this method adopts polylactic acid to prepare porous membrane completely, because the carbon-oxygen bond in polylactic acid is not resistant to electrolyte corrosion, this product can't really be applied to lithium battery diaphragm industry; (2) in addition , Polylactic acid has a low degree of polymerization and low crystallinity. The product prepared by the casting film-forming method in this patent has low tensile strength and poor mechanical properties, and cannot be applied to mechanical winding of lithium batteries.

But this method has the following disadvantages: (1) the porous membrane prepared by this method is an ion exchange membrane, the process is complicated, and the cost is high, and the product is only applicable to the fuel cell in the lithium battery field, and is not suitable as a lithium battery separator; (2) the method Methods The ion exchange membrane is prepared by blending polylactic acid with other materials. The amount of polylactic acid needs to be controlled at a very low ratio, otherwise due to the difference in molecular weight, crystallinity and compatibility of different polymers, it will obviously affect the various properties of the main material. basic performance

But this method has the following disadvantages: (1) the patent adopts the method of multi-layer co-extrusion and then stretching to prepare a multi-layer film, which has high equipment requirements, complicated process, and high production cost of the product; (2) the product prepared by the patent It is a multi-layer structure, and there is no cross-linking between the layers. Even if degradable biomaterials are used, the layers can only be separated during degradation, but the entire product cannot be broken and decomposed, and the degradability is poor.

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