High-temperature-resistant safe lithium ion battery diaphragm and preparation method thereof

The invention discloses a high-temperature-resistant safety lithium ion battery diaphragm, which is prepared by compounding two different polyolefins, the high-temperature-resistant effect is achieved by utilizing different melting points between the two polyolefins, and the safety effect is achieved by a double-layer structure. Polypropylene and polyethylene are compounded together in a dry stretching mode, the melting point of the polypropylene is about 160 DEG C, the melting point of the polyethylene is about 130 DEG C, when the temperature of the battery rises to 120 DEG C, the polyethylene begins to shrink, gaps are closed, and the polypropylene still keeps the mechanical integrity. The advantage of the polypropylene and polyethylene double-layer structure is that tiny solid particles on the pole piece are not easy to pierce the double-layer diaphragm. The diaphragm can reach the thickness of a common diaphragm through a specific production process, the weight of the battery cannot be increased due to th