Widely used in mobile phones, portable computers, cameras, video cameras and other electronic products field (1) have electronic insulation, ensure the mechanical isolation are aligned; (2) have certain aperture and porosity, ensure low resistance and high conductivity of lithium ion, have very good through the *ual; (3) because of the strong polarity solvent for electrolyte of organic compounds, the diaphragm must electrolyte corrosion resistance, have enough chemical and electrochemical stability; (4) to the electrolyte invasive good and have enough to absorb fluid moisturizing ability; (5) have enough of mechanical properties, including puncture strength, tensile strength, thickness and so on, but as small as possible; (6) space stability and level off the gender is good; (7) thermal stability and automatic shutoff protection performance. PP/PE double film and PP/PE/PP three layers of the diaphragm and merges with low melting temperature of PE and high temperature melt the PP broken two properties, become the hot spot of research and development. Multi-layer diaphragm not only provides low temperature, and the closed pore in PE film closed pore PP layer after maintain the strength, from microporous block to the diaphragm rupture melting temperature range wide, safety between than single-layer film is good. In addition, the structure of the hole also influence of automatic shutoff protection performance, high reliability and small aperture and to stop and to cut off the abnormal current is an advantage, but too high reliability and too small and aperture and affect its ionic conductivity
