Low-pore closing high-diaphragm splitting polyolefin diaphragm and preparation method thereof

Abstract

The invention discloses a low-pore closing high-diaphragm splitting polyolefin diaphragm and a preparation method thereof. The polyolefin diaphragm is mainly formed by blending polyethylene, polypropylene and polypropylene grafted branched polyethylene; and the polyethylene comprises low-melting-point polyethylene and high-melting-point polyethylene. Thus, the problem of compatibility of polyethylene and polypropylene is solved, the homogeneous phase capability of polyethylene and polypropylene in a molten state is improved, so that polypropylene molecular chains are interspersed among polyethylene molecular chains, a rigid skeleton supporting effect is achieved, and the diaphragm is prevented from being split, thereby acquiring relatively high diaphragm splitting temperature and excellentthermal shrinkage performance. In addition, through blending of high / low melting point polyethylene, the melting starting temperature of the blended polyethylene is reduced, the melting range is prolonged, the duration of the pore closing process is prolonged, and the continuous pore closing characteristic is formed.

Description

technical field [0001] The invention belongs to the field of diaphragm materials for lithium batteries, and in particular relates to a polyolefin diaphragm with low closed cells and high membrane rupture and a preparation method thereof. Background technique [0002] Polyolefin microporous membranes are used for precision filtration membranes, separators for batteries, separators for capacitors, materials for fuel cells, etc. Among these uses, when used as a separator for batteries, especially when used as a separator for lithium ion batteries, the polyolefin microporous membrane is required to have excellent ion permeability, excellent mechanical strength, and the like. [0003] In order to ensure the safety of batteries, "low closed cell temperature characteristics", "high membrane rupture temperature characteristics" and "low heat shrinkage" are required for separators for high-capacity batteries in recent years. In addition, in order to reduce variations in battery char...

AI Technical Summary

Problems solved by technology

However, polyethylene and polypropylene have poor compatibility, which affects the uniformity of the mixture in the melting process, resulting in large deviations in film thickness, which in turn affects the stable acquisition of low closed cell temperature characteristics, high film rupture temperature characteristics, and thermal shrinkage properties.

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