Preparation process of ultrathin polyimide film and ultrathin polyimide film current collector

Abstract

The application discloses a super-thin polyimide film preparation process and a super-thin polyimide film current collector, relates to the field of polyimide film post-processing, and discloses the super-thin polyimide film preparation process, wherein a polyimide film with a thickness of 8-12 mu m is thinned to a polyimide film with a thickness of 3-6 mu m through alkali immersion; the polyimide film uniformly passes through an alkali tank; the moving speed of the polyimide film is 0.01-1 m / min; the alkali is NaOH solution and KOH solution; the mass concentration of the alkali is 3-10%; and the temperature of the alkali is 25-50 DEG C. The polyimide film with a thickness of 3-6 mu m is formed after acid pickling, water washing and drying; the acid pickling adopts hydrochloric acid with a concentration of 1-4%; and the alkali with a certain concentration can uniformly etch the surface of the polyimide film, so that the thickness of the polyimide film is thinned from 8-12 mu m to 3-6 mu m, the super-thin polyimide film is prepared, the super-thin polyimide film is used as a carrier of the super-thin current collector for preparing new energy batteries, and the super-thin current collector has high strength and stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polyimide film post-processing, and particularly relates to a super-thin polyimide film preparation process and a super-thin polyimide film current collector. BACKGROUND

[0002] Generally, a polyimide (PI for short) film is a high polymer film functional material made by flow casting a polyimide acid solution into a film, stretching, and then high-temperature imidization, and has outstanding high-temperature resistance, radiation resistance, chemical corrosion resistance, and electrical insulation properties. The thinner the polyimide film formed by flow casting and stretching, the more difficult and costly it is to produce, and at present, the stretching limit of this process is about 6 microns, which limits the application of super-thin polyimide films, such as the difficulty in meeting the thickness requirements of the carrier of a thin film current collector.

[0003] In view of this, it is necessary to develop a super-thin polyimide film preparation process and a super-thin polyimide film current collector to prepare a super-thin thin film current collector. SUMMARY

[0004] The present application aims to disclose a super-thin polyimide film preparation process and a super-thin polyimide film current collector, which thins a polyimide film to 3-6 microns by means of an alkali solution or by means of an alternating alkali solution and pure water.

[0005] The first application object of the present application is to provide a super-thin polyimide film preparation process.

[0006] The second application object of the present application is to provide a super-thin polyimide film current collector.

[0007] To achieve the above-mentioned first application object, the present application provides a super-thin polyimide film preparation process, in which a polyimide film with a thickness of 8-12 microns is thinned to a polyimide film with a thickness of 3-6 microns by soaking in an alkali solution.

[0008] Preferably, the polyimide film passes through the alkali solution tank at a uniform speed, and the moving speed of the polyimide film is 0.01-1 m / min.

[0009] To achieve the above-mentioned first application object, the present application also provides a super-thin polyimide film preparation process, in which a polyimide film with a thickness of 8-12 microns is thinned to a polyimide film with a thickness of 3-6 microns by alternating soaking in an alkali solution and pure water.

[0010] Preferably, the polyimide film passes through the alkali solution tank and the pure water tank at a uniform speed, and the moving speed of the polyimide film is 0.01-1 m / min.

[0011] Preferably, the length ratio of the alkali solution tank to the pure water tank is 1:1-4:1.

[0012] Preferably, the alkaline solution is NaOH solution and / or KOH solution, and the mass concentration of the alkaline solution is 3%-10%.

[0013] Preferably, the temperature of the alkaline solution is 25-50℃.

[0014] Preferably, the polyimide film with a thickness of 3-6μm is formed after acid pickling, water washing and drying.

[0015] Preferably, the acid pickling uses hydrochloric acid with a concentration of 1%-4%.

[0016] Based on the same inventive principle, to achieve the above-mentioned second object, the present application provides an ultrathin polyimide film current collector, which is prepared by the process of the first application and is provided with a conductive layer on each surface of the ultrathin polyimide film.

[0017] Compared with the prior art, the present application has the following advantages:

[0018] The alkaline solution with a certain concentration can uniformly etch the surface of the polyimide film, so that the thickness of the polyimide film is reduced from 8-12μm to 3-6μm, and an ultrathin polyimide film is prepared. The ultrathin polyimide film serves as a carrier for preparing an ultrathin current collector for new energy batteries, so that the ultrathin current collector has high strength and stability, and is beneficial to improving the safety performance of new energy batteries. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Figure 1 is a schematic diagram of the preparation of the ultrathin polyimide film according to the first embodiment of the present application.

[0020] Figure 2 Figure 2 is a schematic diagram of the preparation of the ultrathin polyimide film according to the second embodiment of the present application.

[0021] In the figure, 1 is an alkaline solution tank, 2 is an acid pickling tank, 3 is a water washing tank, and 4 is a pure water tank. DETAILED DESCRIPTION

[0022] The present application will be described in detail below with reference to the embodiments shown in the accompanying drawings, but it should be noted that these embodiments are not limiting to the present application, and equivalent transformations or substitutions of functions, methods or structures made by those skilled in the art based on these embodiments are within the scope of protection of the present application.

[0023] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0024] The specific implementation process of the present application is described below through multiple embodiments.

[0025] Example One:

[0026] Referring to Figure 1 The ultra-thin polyimide film preparation process is as follows: the polyimide film with a thickness of 8-12 μm is thinned to a polyimide film with a thickness of 3-6 μm by soaking in an alkali solution.

[0027] Specifically, step S1: an alkali solution with a mass concentration of 3%-10% is configured, the alkali solution is a NaOH solution and / or a KOH solution, the temperature of the alkali solution is 25-50°C, and the alkali solution contains OH which can react with the imide bond in the polyimide to break the imide bond, thereby achieving thinning, in addition, the alkali solution can also soften the surface of the polyimide film.

[0028] Step S2: the polyimide film with a thickness of 8-12 μm in a roll is uniformly passed through the alkali solution tank 1, the moving speed of the polyimide film is 0.01-1 m / min, and the time of the polyimide film in the alkali solution is 30-180 min, thereby obtaining a polyimide film with a thickness of 3-6 μm, and the etching depth of the polyimide film is comprehensively affected by the alkali concentration, soaking time and alkali temperature.

[0029] Step S3: the polyimide film with a thickness of 3-6 μm is formed after acid washing, water washing and drying, the acid washing is performed in the acid washing tank 2, the water washing is performed in the water washing tank 3, the acid washing uses hydrochloric acid with a concentration of 1%-4%, and the purpose of the acid washing is to quickly neutralize the alkali on the surface of the polyimide film and make the ring-opened polyimide quickly close, so as to reduce the loss of mechanical properties of the polyimide.

[0030] The factors affecting the etching depth of the polyimide film are further illustrated in Table 1. Specifically, the etching thickness of the polyimide film is directly related to the concentration of the alkaline solution, the soaking time and the soaking temperature. In the experiments with serial numbers 6 and 9, the polyimide film is directly hydrolyzed into a muddy state, and finally cannot form a film. After repeated experiments, the polyimide film with serial numbers 3, 7, 8, 10-13 can be thinned to 3-6 μm, realizing the preparation of an ultrathin polyimide film.

[0031] Table 1 Factors affecting the etching depth of the polyimide film

[0032]

[0033] Example Two:

[0034] Referring to Figure 2 , the process for preparing an ultrathin polyimide film, the polyimide film with a thickness of 8-12 μm is thinned to a polyimide film with a thickness of 3-6 μm by alternating soaking in an alkaline solution and pure water. Specifically, the polyimide film uniformly passes through a plurality of groups of alternating alkaline solution tank 1 and pure water tank 4, and the moving speed of the polyimide film is 0.01-1 m / min. The alternating setting means that after the polyimide film is soaked in the alkaline tank, it needs to be washed in the pure water tank 4 to break the balance formed by the alkaline solution and the surface of the polyimide film, and to improve the thinning efficiency of the polyimide film surface in the next alkaline tank 1.

[0035] The specific thinning steps of the polyimide film are as follows:

[0036] Step S1: An alkaline solution with a mass concentration of 3-10% is configured, and the alkaline solution is a NaOH solution and / or a KOH solution. The temperature of the alkaline solution is 25-50°C. The alkaline solution contains OH which can react with the imide bond in the polyimide to break the imide bond, thereby achieving thinning. In addition, the alkaline solution can also soften the surface of the polyimide film.

[0037] Step S2: The polyimide film with a thickness of 8-12 μm is uniformly passed through a plurality of groups of alternating alkaline solution tank 1 and pure water tank 4, and the length ratio of the alkaline solution tank 1 to the pure water tank 4 is 1:1-4:1. The moving speed of the polyimide film is 0.01-1 m / min, and the soaking time of the polyimide film in the alkaline solution is 30-180 min. The polyimide film with a thickness of 3-6 μm is obtained. The etching depth of the polyimide film is comprehensively affected by the concentration of the alkaline solution, the soaking time and the temperature of the alkaline solution.

[0038] It should be noted that the soaking time of the polyimide film in the lye refers to the total time of passing through each lye tank 1, and the lye concentrations in different lye tanks 1 can be the same or different, and are actually determined according to the final thickness and mechanical strength of the polyimide film. In step S2, in order to cooperate with the acid pickling in step S3, step S2 ends in the lye tank 1, that is, step S2 does not perform the last pure water cleaning.

[0039] Step S3: The polyimide film with a thickness of 3-6 μm is formed after acid pickling, water washing and drying, the acid pickling is performed in the acid pickling tank 2, and the water washing is performed in the water washing tank 3, the acid pickling uses hydrochloric acid with a concentration of 1-4%, and the purpose of the acid pickling is to quickly neutralize the alkali on the surface of the polyimide film and make the ring-opening polyimide quickly close, so as to reduce the loss of mechanical properties of the polyimide.

[0040] The influencing factors of the etching depth of the polyimide film are further illustrated in Table 2, specifically, the etching thickness of the polyimide film is directly related to the lye concentration, soaking time and soaking temperature, as in the experiments with serial numbers 6 and 9, the polyimide film is directly hydrolyzed into a muddy state, and finally cannot form a film; through repeated experiments, serial numbers 3, 7, 8, 10-13 can all achieve the thinning of the polyimide film to 3-6 μm, realizing the preparation of the ultra-thin polyimide film.

[0041] Table 2: Influencing factors of the etching depth of the polyimide film

[0042]

[0043]

[0044] Example Three:

[0045] The ultra-thin polyimide film current collector is prepared by the ultra-thin polyimide film preparation process described in Example 1 or Example 2, and a conductive layer is arranged on each surface of the ultra-thin polyimide film.

[0046] The 3-6 μm ultra-thin polyimide film has outstanding high-temperature resistance, radiation resistance, chemical corrosion resistance and electrical insulation properties, and after a conductive layer is arranged on each of its front and back surfaces, it has a smaller density compared to copper foil and better high-temperature resistance and insulation properties compared to a PET-based current collector, and it has advantages in improving the safety and energy density of lithium batteries when used as a current collector, especially as a lithium battery current collector.

[0047] It should be further pointed out that when a conductive layer is arranged on one surface of the ultra-thin polyimide film, an ultra-thin polyimide film composite conductive material is formed, which can be used as a shielding film and has outstanding high-temperature resistance, radiation resistance, chemical corrosion resistance and shielding properties compared to a PET-based shielding film.

Claims

1. A process for the production of an ultrathin polyimide film, characterized in that, The method comprises the following steps: Step S1: configure an alkali solution with a mass concentration of 3%-10%, the alkali solution being a NaOH solution and / or a KOH solution, and the temperature of the alkali solution being 25-50°C; Step S2: uniformly pass a polyimide film with a thickness of 8-12μm in a roll through an alkali solution tank, the moving speed of the polyimide film being 0.01-1m / min, and the time of the polyimide film in the alkali solution being 30-180min, to obtain a polyimide film with a thickness of 3-6μm; Step S3: form the polyimide film with a thickness of 3-6μm after acid pickling, water washing and drying, and the acid pickling uses hydrochloric acid with a concentration of 1%-4%.

2. The process for preparing an ultra-thin polyimide film according to claim 1, wherein The polyimide film with a thickness of 8-12μm is thinned to a polyimide film with a thickness of 3-6μm through alternate soaking in an alkali solution and pure water, and the pure water breaks the balance formed by the alkali solution and the surface of the polyimide film.

3. The process for preparing an ultrathin polyimide film according to claim 2, wherein The polyimide film uniformly passes through a plurality of groups of alternately arranged alkali solution tanks and pure water tanks, and the moving speed of the polyimide film is 0.01-1m / min.

4. The process for preparing an ultrathin polyimide film according to claim 3, wherein The length ratio of the alkali solution tank to the pure water tank is 1:1-4:1.

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