Flexible composite plastic film, and preparation method and test method thereof

Abstract

The invention discloses a flexible composite plastic film resistant to electrolyte corrosion, and a preparation method and a test method thereof. The plastic film comprises a plastic film layer, middle reinforcing layers, metal layers and a surface tolerance layer. The middle reinforcing layers are arranged on the two sides of the plastic film, the metal layers are arranged on the outer sides of the middle reinforcing layers, and the surface tolerance layers wrap the outer sides of the metal layers. The tensile strength of the composite plastic film is 130-300 Mpa, the elongation at break is 50-150%, and the elastic modulus is 3200-5500. The surface mass is only 6-12 g/m<2>, the thickness is 4-20 microns, and meanwhile, good chemical stability is achieved. The water vapor permeability is less than 0.15 g/(m<2>. 24h), and the oxygen permeability is less than 0.002 cm<3>/(m<2>. 24h). And the composite plastic film can resist normal temperature 25 DEG C, high temperature 60 DEG C and 85 DEG C electrolyte soaking. The surface of the composite plastic film is not prone to eroding, has good tolerance and does not generate volume expansion; and the composite plastic film has good corrosion resistance, the metal layer is protected from being corroded in an acid electrolyte system through the surface tolerance layer, and the chemical stability of the original metal/plastic composite film is effectively improved.

Description

technical field [0001] The invention relates to the technical field related to lithium ion batteries, and more specifically, to a flexible composite plastic film, and a preparation and testing method thereof. Background technique [0002] The future development direction of lithium batteries should be high energy, low cost, and high safety. The current collector not only plays the role of carrying active materials, but also collects the electrons generated by the electrochemical reaction and guides them to the external circuit, so as to realize the process of converting chemical energy into electrical energy. The current collector is one of the indispensable components in the lithium-ion battery. At present, the thickness of the positive electrode aluminum foil current collector used in the production of batteries is 10-20um, and the thickness of the negative electrode copper foil is 6-8um. The aluminum foil is mainly rolled aluminum foil, and the copper foil is mainly elec...

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Problems solved by technology

However, in the case of long-term storage in the charged state, multiple charge-discharge cycles, and overcharge, it was found that the original surface passivation film of Al was damaged and corrosion occurred. After the corrosion phenomenon occurred, it was easy to cause the metal layer and the plastic film The detachment and exposure of the white film not only increase the internal resistance, but the corrosion products passivate or attack the positive active material; the solid products of corrosion will also increase the resistance; the soluble products of corrosion will contaminate the electrolyte solution and increase the self-discharge rate of the battery; Al3+ will migrate to the negative electrode and reduce the deposition

All of the above will cause the attenuation of battery capacity

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