| 摘要 |
PROBLEM TO BE SOLVED: To achieve a high porosity and a high mechanical strength and excellent heat resistance by reducing a pressure of a polytetrafluoroethylene(PTFE) film having a specific pore diameter, a specific porosity and a specific thickness, introducing a predetermined mixture gas, aging the film in a plasma, and coating the film with a carbon oxide compound layer. SOLUTION: A drawn porous PTFE film having a maximum pore diameter of 0.01-1μm, a porosity of 75-95% and a thickness of 10-50μm is contained inside a vacuum container, and is reduced in pressure of 0.02mTorr. Subsequently, mixture gas of oxygen with argon is introduced and a pressure is increased up to 20mTorr. Furthermore, the PTFE film is aged for 45 minutes by a plasma treatment, and then, is coated with a carbon oxide compound layer. Herein, since the pore diameter is 0.2-0.5μm, it is possible to prevent a short phenomenon due to a growth of a needle-like dendrite crystal in a pore, which may occur during lithium deposition. Moreover, since the porosity is 90% or less, tensile breakage strength can be maintained. Consequently, it is possible to provide a separator film having a high porosity and a high mechanical strength and being excellent in heat resistance and stability.
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