Polyolefin composite microporous membrane with low hot-shrinkage rate and preparation method

The invention discloses a polyolefin composite microporous membrane with low hot-shrinkage rate and a preparation method. The polyolefin composite microporous membrane is prepared by compounding a high-density polyethylene (HDPE) microporous membrane and an ultra-high molecular weight polyethylene (UHMWPE) microporous membrane, and has relatively low hot-shrinkage rate, so that the safety performance and the operation performance of a lithium-ion battery are improved. The polyolefin composite microporous membrane with low hot-shrinkage rate prepared by the method has low hot-shrinkage rate; the shrinkage rate in a machine direction is less than or equal to 2.5%; and the shrinkage rate in a vertical machine direction is less than or equal to 1%. Therefore, the safety performance and the operation performance of subsequently produced lithium-ion battery are greatly improved.