Lithium ion battery membrane prepared by polypropylene mixture and preparing method thereof
A technology for lithium-ion batteries and polypropylene-based membranes, which can be applied to battery components, circuits, electrical components, etc., and can solve problems such as uneven pore size distribution and pore structure, and low porosity and air permeability of polypropylene microporous membranes. , to achieve excellent mechanical properties, good performance, and improve production efficiency
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Embodiment 1
[0052] The linear polypropylene with a melt flow rate of 2.3g / 10min is made into a hard elastic base film through an extrusion casting film-making device under the condition of a die temperature of 210°C, with a die opening of 1.0 mm, and extruded The rotation speed of the machine screw is 10 rpm, the temperature of the casting roll is 95° C., the draft ratio is 57, and an air knife cooling device is installed at the exit of the die to cool the base film. The obtained cast film had a thickness of 20 μm. Then the base film was annealed at 145° C. for 30 min. The annealed film was first stretched 1.3 times at a stretching rate of 400% / min at 25°C, then stretched 1.8 times at a stretching rate of 50% / min at 145°C, and finally heat-set at 150°C for 30 minutes , to obtain a polypropylene microporous membrane.
Embodiment 2
[0054] The linear polypropylene with a melt flow rate of 2.3g / 10min and the long-chain branched polypropylene with a melt flow rate of 2.4g / 10min and a long-chain branching degree of 0.23 are mixed according to a mass ratio of 98 / 2, and double After melt blending and granulation in the screw extruder, under the condition that the temperature of the die is 210°C, a hard elastic base film is made through an extrusion casting film-making device, the die opening is 1.0 mm, and the screw speed of the extruder is The temperature is 10rpm, the casting roll temperature is 95°C, the draft ratio is 57, and an air knife cooling device is installed at the exit of the die to cool the base film. The obtained cast film had a thickness of 20 μm. Then the base film was annealed at 145° C. for 30 min. The annealed film was first stretched 1.3 times at a stretching rate of 400% / min at 25°C, then stretched 1.8 times at a stretching rate of 50% / min at 145°C, and finally heat-set at 150°C for 30 m...
Embodiment 3
[0056] The linear polypropylene whose melt flow rate is 2.3g / 10min is mixed with the long-chain branched polypropylene whose melt flow rate is 2.4g / 10min and the degree of long-chain branching is 0.23 according to the mass ratio of 94 / 6, and the rest are the same as Example 2. A polypropylene microporous membrane was prepared.
[0057] The performance index of polypropylene hard elastic base film and polypropylene microporous film in the embodiment 1-3 of table 1
[0058]
[0059] Comparing Examples 1, 2, and 3, it can be seen that the elastic recovery rate and mechanical properties of the polypropylene hard elastic base film prepared by adding 2% long-chain branched polypropylene to the linear polypropylene resin are improved, and the polypropylene hard elastic base film After the base film is stretched to form pores, the porosity and air permeability increase significantly, the pore diameter increases, and the pore distribution and pore size distribution are more uniform...
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Abstract
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