High fused mass strength compound isolating film and preparation method and application thereof

Abstract

The invention relates to a battery polyolefin isolating membrane. The composite isolating film with high fused mass strength of the invention is a microporous membrane which takes the structure of B / A two-layer or B / A / B three-layer, wherein, A layer is a copolymer membrane of polyethylene or ethylene and 5 to 50 percent other olefins or a mixture membrane of the polyethylene or the ethylene and the 5 to 50 percent other olefins, and B layer is a copolymer membrane of propylene and 0.1 to 10 percent other olefins. The invention has the advantages that: a polymer A which provides low obturator temperature and a polymer B which provides high membrane rupture temperature and high fused mass strength are led in a formulation for preparation of the polyolefin composite microporous isolating membrane, thereby the isolating membrane with low obturator temperature, high membrane rupture temperature, high fused mass strength and high use safety is obtained.

Description

technical field [0001] The invention relates to a polyolefin isolation film for a lithium ion battery, in particular to a multi-layer composite polyolefin microporous isolation film with high melt strength. Background technique [0002] Polyolefin microporous film is a plastic film with numerous interconnected micropores with a pore size of 0.01-10 μm. Used as a separator in lithium batteries. Lithium-ion batteries consist of positive and negative electrodes, a separator, and an electrolyte. Among them, the separator connects and separates the positive electrode and negative electrode materials. It is an insulator of electrons, but it allows ions to pass through. The performance of the separator determines the interface structure and internal resistance of the battery, which in turn affects the capacity, cycle, charge and discharge of the battery. Therefore, the performance of the separator plays an important role in improving the overall performance of the battery. [00...

AI Technical Summary

Problems solved by technology

Using this method, the microporous membranes currently produced industrially are basically HDPE single-layer isolation membranes, which have disadvantages such as insufficient safety and insufficient puncture resistance.

[0006] If the multilayer microporous membrane is produced by thermally induced phase separation, if PE and PP layers are directly compounded, on the one hand, due to the compatibility problem between the two, the composite strength of the multilayer film is likely to be low; After the diluent is mixed, the diluent destroys the crystallization ability of PP itself, the melt strength of the mixed system is significantly reduced, and it is difficult to carry out subsequent processing operations such as stretching. question