All-inorganic flexible capacitor and preparation method thereof

Abstract

The invention relates to an all-inorganic flexible capacitor and a preparation method thereof, the all-inorganic flexible capacitor comprises at least one all-inorganic flexible capacitor unit, and the all-inorganic flexible capacitor unit comprises a metal electrode, a flexible electrode and a dielectric layer between the two electrodes; the dielectric layer is a metal oxide, the dielectric layer is generated by electrolysis on the surface of the metal foil through an electrochemical oxidation method, the metal foil is not completely electrolyzed, the remaining part of the metal foil after electrolysis serves as a flexible electrode, the dielectric layer is tightly attached to the flexible electrode, and a metal film is deposited on the surface of the dielectric layer to serve as a metal electrode. Compared with the prior art, the full-inorganic flexible capacitor can bear high voltage and is high in energy density, simple in structure and excellent in breakdown resistance, and the preparation method is simple, high in operability, low in cost, suitable for large-scale preparation and high in industrial production feasibility.

Description

Technical Field

[0001] The present invention belongs to the technical field of capacitors and relates to an all-inorganic flexible capacitor and a preparation method thereof. Background Art

[0002] Dielectric capacitors are one of the essential components of modern electronic circuits, with high power density and fast charge and discharge capabilities. In recent years, flexible electronic devices have become more and more popular. As one of the essential components of electronic circuits, small and bendable flexible dielectric capacitors are an inevitable trend of development.

[0003] Dielectric capacitors are generally composed of an upper electrode, a dielectric layer, and a lower electrode in a sandwich structure. The necessary condition for realizing flexible dielectric capacitors is to select suitable flexible electrodes and dielectric layers. Organic polymer materials have natural advantages in flexibility. Therefore, all-organic flexible dielectric capacitors are currently more mature flexible capacitors. However, all-organic flexible dielectric capacitors have the following problems: the organic dielectric layer has a lower dielectric constant than the inorganic dielectric layer, which seriously affects the energy density of the all-organic flexible dielectric capacitor. In addition, organic materials have poor temperature resistance, poor environmental adaptability, and poor stability under extreme working conditions, which limits their further application.

[0004] All-inorganic flexible capacitors can effectively solve the above problems. Inorganic materials have good environmental stability and can withstand temperatures of up to 500°C or even more than 1000°C, which effectively avoids the problem of device temperature resistance. The dielectric constant and withstand voltage performance of the inorganic dielectric layer are also better, so flexible inorganic dielectric capacitors with high energy density can be obtained. However, most traditional inorganic substrates are hard and brittle, and it is difficult to find a suitable flexible inorganic substrate. The first to attract the attention of researchers are metal foils such as Cu, Al, and Ni. These films are low in cost, flexible, and highly operable, but these metal foils are easily oxidized in the air to form a dense insulating oxide layer, which greatly hinders its use as a conductive substrate. Mica is a new type of flexible inorganic substrate material developed in recent years, with a temperature resistance of at least 750°C. However, most flexible dielectric capacitors based on mica are prepared by excimer pulse laser deposition. This type of preparation method is expensive and difficult to mass-produce and apply. In addition, due to the different structures of electrode materials and dielectric materials, it is easy to cause stratification of electrode materials and dielectric materials during use, affecting the service life.

[0005] Patent CN 112466665 B discloses an all-inorganic flexible dielectric capacitor assembled with metal foil as flexible electrode and oxide prepared by sol-gel method as dielectric layer. The capacitor in the above patent is assembled into a device by preparing flexible electrodes and oxide dielectric layers separately, which is relatively complicated in process. In addition, the assembled all-inorganic flexible dielectric capacitor may have potential problems of separation of electrodes and dielectric layers due to bending during actual use, thus affecting its service life. Summary of the invention

[0006] The purpose of the present invention is to provide a new, simple-to-prepare all-inorganic flexible dielectric capacitor and its preparation method in view of the problems existing in the above-mentioned prior art. In the capacitor, the dielectric layer is directly generated on the flexible metal foil, and the dielectric layer and the flexible metal foil are effectively combined at the atomic energy level, which can avoid the problem of separation of the electrode and the dielectric layer after bending and use. The all-inorganic flexible dielectric capacitor of the present invention can withstand higher voltages, has high energy density, simple structure, and excellent breakdown resistance. Even after being bent 1,000 times, it still exhibits good electrical properties.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A first aspect of the present invention provides an all-inorganic flexible capacitor, comprising at least one all-inorganic flexible capacitor unit, wherein the all-inorganic flexible capacitor unit comprises a metal electrode film, a flexible electrode, and a dielectric layer between the two electrodes; the dielectric layer is a metal oxide, and the dielectric layer is generated by electrolysis on the surface of a metal foil by an electrochemical oxidation method. The metal foil is not completely electrolyzed, and the remaining part of the metal foil after electrolysis serves as a flexible electrode. The dielectric layer is tightly attached to the flexible electrode, and a metal film is deposited on the surface of the dielectric layer as a metal electrode.

[0009] Furthermore, the metal foil is an oxidizable metal foil.

[0010] Furthermore, the metal foil is selected from any one of aluminum foil, nickel foil or copper foil.

[0011] Furthermore, the thickness of the metal foil is 0.008-0.012 mm, and this thickness makes the metal foil flexible.

[0012] Furthermore, the metal film is a conductive metal film.

[0013] Furthermore, the metal film is a common conductive metal film, such as any one of an aluminum film, a silver film, a copper film, a gold film or a nickel film.

[0014] Furthermore, the thickness of the metal film is 100-1000 nm.

[0015] The second aspect of the present invention provides a method for preparing an all-inorganic flexible capacitor, wherein ammonium pentaborate is used as an electrolyte, a metal foil is used as an anode, and an inert platinum sheet is used as a cathode. A voltage is applied to the metal foil to electrolyze and generate a dielectric layer. The metal foil is not completely electrolyzed, and the unelectrolyzed metal foil is used as an electrode on one side. A metal film is prepared on the other side of the dielectric layer to obtain an all-inorganic flexible capacitor with a simple sandwich structure. The preparation method specifically comprises the following steps:

[0016] 1) Connecting the metal foil to the positive electrode of a power source and the inert platinum sheet to the negative electrode of the power source, placing the metal foil in an ammonium pentaborate electrolyte, applying voltage to the metal foil to electrolyze and prepare a dielectric layer, obtaining a metal foil with a dielectric layer on one side and using the metal foil as a flexible electrode;

[0017] 2) washing and drying the metal foil with a dielectric layer on one side obtained in step 1), and then preparing a metal electrode on the surface of the dielectric layer to obtain an all-inorganic flexible capacitor unit;

[0018] 3) The all-inorganic flexible capacitor unit obtained in step 2) is encapsulated and cured by an insulating medium, or the all-inorganic flexible capacitor units are combined and then encapsulated and cured by an insulating medium, and then the leads are connected at both ends to obtain an all-inorganic flexible capacitor.

[0019] Among them, ammonium pentaborate electrolyte is used to generate the corresponding metal oxide (dielectric layer) on the surface of the metal foil, and the dielectric layer is directly and tightly combined with the metal foil (one side electrode), eliminating the cumbersome process of peeling the traditional inorganic film from the substrate and then attaching it to the electrode surface. The preparation process is simple. Commercially available metal foil is used as one side electrode, which is low in cost. In addition, the dielectric layer and the electrode structure are tightly combined, and a high breakdown voltage can be maintained under multiple bending.

[0020] Furthermore, in step 1), the metal foil is aluminum foil, and the area of ​​the metal foil is 5*5 cm.

[0021] Furthermore, in step 1), the concentration of the ammonium pentaborate electrolyte is 0.1-0.5 mol / L, and is prepared by dissolving and diluting the ammonium pentaborate solid.

[0022] Furthermore, in step 1), the voltage applied is 80-200 V for 5-20 min, and the time can be adjusted according to the required thickness of the dielectric layer.

[0023] Furthermore, in step 1), the dielectric layer is an aluminum oxide film, and the thickness of the aluminum oxide film is 50-1000nm.

[0024] Furthermore, in step 2), the drying temperature is 80-90°C and the time is 1-3 hours; the metal electrode is prepared by vacuum coating, magnetron sputtering, blade coating or drop coating. Preferably, the metal electrode is prepared by vacuum coating.

[0025] Furthermore, in step 3), the insulating medium is a packaging insulating medium commonly used in circuits, such as plastic.

[0026] Compared with the prior art, the present invention has the following characteristics:

[0027] 1) The all-inorganic flexible dielectric capacitor provided by the present invention is a dielectric layer obtained by directly oxidizing the surface of a commercially available flexible metal foil, and the metal foil that is not completely electrolytically oxidized is used as one side electrode, which is low in cost and highly economical;

[0028] 2) The oxide dielectric layer / electrode structure prepared by the present invention is tightly fitted together, and can still maintain a high breakdown voltage after multiple bending, thus getting rid of the problem of easy separation from the electrode;

[0029] 3) The present invention provides a method for preparing a fully inorganic flexible dielectric capacitor, which utilizes an electrolyte to generate a corresponding metal oxide (dielectric layer) on the surface of a metal foil, and the dielectric layer is directly and tightly combined with the metal foil (one side electrode), so that the preliminary structure of the dielectric layer / electrode is prepared in one step, bypassing the process of transferring / re-bonding the dielectric layer, that is, eliminating the cumbersome process of peeling off the traditional inorganic film from the substrate and then attaching it to the electrode surface. Compared with the production of traditional flexible dielectric capacitors, the present invention has a simple production process, high operability, low cost, is suitable for large-scale preparation, and has high feasibility for industrial production;

[0030] 4) The all-inorganic flexible capacitor prepared by the present invention can withstand higher voltage, has high energy density, and excellent flexibility, which is conducive to its application in small and flexible products;

[0031] 5) The present invention has low preparation cost and high economy. The prepared capacitor has a simple structure, excellent breakdown resistance, safety and reliability, and provides a new method for preparing all-inorganic flexible capacitors, which is of great significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the basic structure of the flexible all-inorganic capacitor in Example 1;

[0033] Description of the markings in the figure:

[0034] 1-metal electrode, 2-oxide dielectric layer, 3-metal foil;

[0035] Figure 2 This is a surface scanning electron microscope image of the flexible aluminum foil in Example 1;

[0036] Figure 3 is a surface scanning electron microscope image of the aluminum oxide dielectric layer in Example 1;

[0037] Figure 4 This is a scanning electron microscope image of the cross section of the aluminum foil after electrolysis in Example 1;

[0038] Figure 5 is the spectrum of the aluminum oxide dielectric layer in Example 1;

[0039] Figure 6 are the current-voltage characteristic curves of Example 4, Example 5, Example 6 and Example 10;

[0040] Figure 7 This is the current-voltage characteristic curve obtained after the all-inorganic flexible dielectric capacitor in Example 1 was bent 1000 times. DETAILED DESCRIPTION

[0041] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0042] The following are more detailed implementation cases, which further illustrate the technical solutions of the present invention and the technical effects that can be obtained.

[0043] In the following examples, unless otherwise specified, raw materials, reagents or processing techniques are all conventional commercial products or conventional processing techniques in the art.

[0044] Embodiment 1:

[0045] A flexible all-inorganic capacitor is assembled from a single all-inorganic flexible capacitor unit, and the basic structure is as follows Figure 1 As shown, it can be seen that it has a sandwich structure, including a metal electrode 1, a flexible electrode 3 and a dielectric layer 2 between the two electrodes. In this embodiment, the flexible electrode 3 uses a flexible aluminum foil. The main preparation process of the flexible all-inorganic capacitor is: using ammonium pentaborate as the electrolyte, the flexible aluminum foil as the anode, and the inert electrode platinum sheet as the cathode, electrolyzing a certain thickness of an aluminum oxide dielectric layer on the surface of the flexible aluminum foil under different electrolysis time and voltage conditions, and the flexible aluminum foil is not completely electrolyzed, and the unelectrolyzed flexible aluminum foil can be directly used as one side electrode, that is, the above-mentioned flexible electrode 3; then prepare a metal film on the other side of the aluminum oxide dielectric layer, and then encapsulate and solidify it through an insulating medium, and perform leads at both ends to obtain an all-inorganic flexible capacitor with a simple sandwich structure. The specific preparation method is as follows:

[0046] (1) Cut the flexible aluminum foil into a size of 5*5 cm, and ultrasonically clean the surface with deionized water, acetone solution, and ethanol solution for 3 to 5 minutes;

[0047] (2) placing the cleaned flexible aluminum foil in step (1) into an oven and drying at 80° C.;

[0048] (3) Weigh 2.7 g of ammonium pentaborate tetrahydrate and dissolve it in 100 mL of deionized water to obtain a 0.1 mol / L ammonium pentaborate electrolyte;

[0049] (4) connecting the flexible aluminum foil to the positive electrode of the power supply, connecting the inert platinum sheet to the negative electrode of the power supply, placing the foil in the ammonium pentaborate electrolyte in step (3), setting the constant voltage to 100 V, and the time to 10 min, to obtain a flexible aluminum foil with an aluminum oxide dielectric layer deposited on one side;

[0050] (5) Rinse the flexible aluminum foil having an aluminum oxide dielectric layer on one side in step (4) with deionized water and bake in an oven at 80° C. for 5-6 hours;

[0051] (6) A silver electrode is prepared on the surface of the alumina dielectric layer in step (5) by a vacuum coating method to obtain an all-inorganic flexible capacitor unit, that is, a silver film is deposited on the surface of the alumina dielectric layer at a deposition rate of about The thickness of the silver film is

[0052] (7) The all-inorganic flexible capacitor unit prepared in step (6) is encapsulated and solidified through an insulating medium, and then wired at both ends to obtain an all-inorganic flexible capacitor.

[0053] In the process of preparing the above-mentioned all-inorganic flexible capacitor, the morphology of the flexible aluminum foil in the above-mentioned step (2) is analyzed, and the surface scanning electron microscope image of the flexible aluminum foil is as follows: Figure 2 As shown, it can be seen that the striped structure is present; in the above step (4), the aluminum foil is electrolyzed to obtain a flexible aluminum foil with an aluminum oxide dielectric layer deposited on one side, wherein the surface scanning electron microscope image of the aluminum oxide dielectric layer is as shown Figure 3 As shown in the scanning electron microscope image of the cross section of the aluminum foil after electrolysis Figure 4 As shown in Figure 1, the aluminum oxide dielectric layer presents a dense structure, which helps to improve its breakdown resistance. Figure 5 As shown, it can be seen that its dielectric constant in the range of 4-8000000 Hz is distributed between 7.5-9, which is consistent with the distribution law of the dielectric constant of aluminum oxide. The all-inorganic flexible capacitor obtained in the above step (7) was subjected to a current-voltage test, and its breakdown voltage was 60V (as shown in Table 1). The all-inorganic flexible dielectric capacitor was bent 1000 times and its current-voltage characteristic curve (breakdown voltage curve) was tested ( Figure 7), its breakdown voltage is still 50V, and the breakdown voltage retention rate is 83.3%, that is, the all-inorganic flexible dielectric capacitor still exhibits good electrical properties even after being bent 1000 times.

[0054] Embodiment 2:

[0055] A flexible all-inorganic capacitor, the preparation method thereof is different from that of Example 1 in that the constant voltage of the electrochemical workstation is set to 150V and the time is 10 minutes. The other conditions are the same as those of Example 1.

[0056] Embodiment 3:

[0057] A flexible all-inorganic capacitor, the preparation method thereof is different from that of Example 1 in that the constant voltage of the electrochemical workstation is set to 180V and the time is 10 minutes. The other conditions are the same as those of Example 1.

[0058] Embodiment 4:

[0059] A flexible all-inorganic capacitor, the preparation method thereof is different from that of Example 1 in that: the constant voltage of the electrochemical workstation is set to 100V, the time is 10min; the upper electrode material is an aluminum electrode with a thickness of The remaining conditions are the same as in Example 1.

[0060] Embodiment 5:

[0061] A flexible all-inorganic capacitor, the preparation method thereof is different from that of Example 4 in that the constant voltage of the electrochemical workstation is set to 150V and the time is 10 minutes. The other conditions are the same as those of Example 4.

[0062] Embodiment 6:

[0063] A flexible all-inorganic capacitor, the preparation method thereof is different from that of Example 4 in that the constant voltage of the electrochemical workstation is set to 180V and the time is 10 minutes. The other conditions are the same as those of Example 4.

[0064] Embodiment 7:

[0065] A flexible all-inorganic capacitor, the preparation method thereof is different from that of Example 1 in that the constant voltage of the electrochemical workstation is set to 50V and the time is 10 minutes. The other conditions are the same as those of Example 1.

[0066] Embodiment 8:

[0067] A flexible all-inorganic capacitor, the preparation method thereof is different from that of Example 4 in that the constant voltage of the electrochemical workstation is set to 50V and the time is 10 minutes. The other conditions are the same as those of Example 4.

[0068] Embodiment 9:

[0069] A flexible all-inorganic capacitor, the preparation method thereof is different from that of Example 1 in that the constant voltage of the electrochemical workstation is set to 200V and the time is 10 minutes. The other conditions are the same as those of Example 1.

[0070] Embodiment 10:

[0071] A flexible all-inorganic capacitor, the preparation method thereof is different from that of Example 4 in that the constant voltage of the electrochemical workstation is set to 200V and the time is 10 minutes. The other conditions are the same as those of Example 4.

[0072] Figure 6 Graphs showing the current-voltage characteristic curves (breakdown voltage curves) of Example 4, Example 5, Example 6 and Example 10, and their breakdown voltage correspondences are shown in Table 1.

[0073] The breakdown voltages of the flexible all-inorganic capacitors of Examples 1-10 are shown in Table 1:

[0074] Table 1

[0075]

[0076] Embodiment 11:

[0077] A flexible all-inorganic capacitor, the preparation method thereof is different from that of Example 1 in that the constant voltage of the electrochemical workstation is set to 100V and the time is 20 minutes. The other conditions are the same as those of Example 1.

[0078] Embodiment 12:

[0079] A flexible all-inorganic capacitor, the preparation method thereof is different from that of Example 4 in that the constant voltage of the electrochemical workstation is set to 100V and the time is 20 minutes. The other conditions are the same as those of Example 4.

[0080] Embodiment 13:

[0081] A flexible all-inorganic capacitor, the preparation method thereof is different from that of Example 1 in that the constant voltage of the electrochemical workstation is set to 150V and the time is 20 minutes. The other conditions are the same as those of Example 1.

[0082] Embodiment 14:

[0083] A flexible all-inorganic capacitor, the preparation method of which is different from that of Example 4 in that the constant voltage of the electrochemical workstation is set to 150V and the time is 20 minutes. The other conditions are the same as those of Example 4.

[0084] Embodiment 15:

[0085] A flexible all-inorganic capacitor, the preparation method thereof is different from that of Example 1 in that the constant voltage of the electrochemical workstation is set to 180V and the time is 20 minutes. The other conditions are the same as those of Example 1.

[0086] Embodiment 16:

[0087] A flexible all-inorganic capacitor, the preparation method thereof is different from that of Example 4 in that the constant voltage of the electrochemical workstation is set to 180V and the time is 20 minutes. The other conditions are the same as those of Example 4.

[0088] The breakdown voltages of the flexible all-inorganic capacitors of Examples 11-16 are shown in Table 2:

[0089] Table 2

[0090]

[0091] Embodiment 17:

[0092] A flexible all-inorganic capacitor, the preparation method thereof is different from that of Example 1 in that the constant voltage of the electrochemical workstation is set to 100V and the time is 5 minutes. The other conditions are the same as those of Example 1.

[0093] Embodiment 18:

[0094] A flexible all-inorganic capacitor, the preparation method thereof is different from that of Example 4 in that the constant voltage of the electrochemical workstation is set to 100V and the time is 5 minutes. The other conditions are the same as those of Example 4.

[0095] Embodiment 19:

[0096] A flexible all-inorganic capacitor, the preparation method thereof is different from that of Example 1 in that the constant voltage of the electrochemical workstation is set to 150V and the time is 5 minutes. The other conditions are the same as those of Example 1.

[0097] Embodiment 20:

[0098] A flexible all-inorganic capacitor, the preparation method thereof is different from that of Example 4 in that the constant voltage of the electrochemical workstation is set to 150V and the time is 5 minutes. The other conditions are the same as those of Example 4.

[0099] Embodiment 21:

[0100] A flexible all-inorganic capacitor, the preparation method thereof is different from that of Example 1 in that the constant voltage of the electrochemical workstation is set to 180V and the time is 5 minutes. The other conditions are the same as those of Example 1.

[0101] Embodiment 22:

[0102] A flexible all-inorganic capacitor, the preparation method thereof is different from that of Example 4 in that the constant voltage of the electrochemical workstation is set to 180V and the time is 5 minutes. The other conditions are the same as those of Example 4.

[0103] The breakdown voltages of the flexible all-inorganic capacitors of Examples 17-22 are shown in Table 3:

[0104] Table 3

[0105]

[0106] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. An all-inorganic flexible capacitor, characterized in that: The invention comprises at least one all-inorganic flexible capacitor unit, wherein the all-inorganic flexible capacitor unit comprises a metal electrode (1), a flexible electrode (3) and a dielectric layer (2) between the two electrodes; the dielectric layer (2) is a metal oxide, the dielectric layer (2) is generated by electrolysis on the surface of a metal foil by an electrochemical oxidation method, the remaining part of the metal foil after electrolysis serves as the flexible electrode (3), the dielectric layer (2) is tightly attached to the flexible electrode (3), and a metal film is deposited on the surface of the dielectric layer (2) as the metal electrode (1).

2. The all-inorganic flexible capacitor according to claim 1, characterized in that: The metal foil is selected from any one of aluminum foil, nickel foil or copper foil, and the thickness of the metal foil is 0.008-0.012 mm.

3. The all-inorganic flexible capacitor according to claim 1, characterized in that: The metal film is any one of an aluminum film, a silver film, a copper film, a gold film or a nickel film.

4. The all-inorganic flexible capacitor according to claim 1, characterized in that: The thickness of the metal film is 100-1000 nm.

5. A method for preparing an all-inorganic flexible capacitor according to any one of claims 1 to 4, characterized in that: The following steps are involved: 1) Connecting the metal foil to the positive electrode of a power source and the inert platinum sheet to the negative electrode of the power source, placing the metal foil in an ammonium pentaborate electrolyte, applying voltage to the metal foil to electrolyze and prepare a dielectric layer, obtaining a metal foil with a dielectric layer on one side and using the metal foil as a flexible electrode; 2) washing and drying the metal foil with a dielectric layer on one side obtained in step 1), and then preparing a metal electrode on the surface of the dielectric layer to obtain an all-inorganic flexible capacitor unit; 3) The all-inorganic flexible capacitor unit obtained in step 2) is encapsulated and cured by an insulating medium, or the all-inorganic flexible capacitor units are combined and then encapsulated and cured by an insulating medium, and then the leads are connected at both ends to obtain an all-inorganic flexible capacitor.

6. The method for preparing the all-inorganic flexible capacitor according to claim 5, characterized in that: In step 1), the metal foil is aluminum foil.

7. The method for preparing the all-inorganic flexible capacitor according to claim 5, characterized in that: In step 1), the concentration of the ammonium pentaborate electrolyte is 0.1-0.5 mol / L.

8. The method for preparing an all-inorganic flexible capacitor according to claim 5, characterized in that: In step 1), the voltage applied is 80-200V and the time is 5-20min.

9. The method for preparing an all-inorganic flexible capacitor according to claim 5, characterized in that: In step 1), the dielectric layer is an aluminum oxide film, and the thickness of the aluminum oxide film is 50-1000 nm.

10. The method for preparing an all-inorganic flexible capacitor according to claim 5, characterized in that: In step 2), the drying temperature is 80-90° C. and the drying time is 1-3 hours; the metal electrode is prepared by vacuum coating, magnetron sputtering, blade coating or drop coating.

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