A paper sheet supercapacitor and a method of manufacturing the same

Abstract

The application discloses a paper sheet super capacitor and a preparation method thereof, and belongs to the technical field of electrochemical energy sources. The paper sheet is used as a support of the super capacitor, a hydrophobic layer is constructed on a microstructure inside the paper sheet, gel electrolyte, positive active material, negative active material, positive current collector and negative current collector are vertically distributed in designated areas of the paper sheet, and thus the paper sheet super capacitor is obtained. The preparation method of the paper sheet super capacitor comprises the following technical steps: (1) constructing the hydrophobic layer; (2) introducing the gel electrolyte; and (3) spraying active material slurry. The paper sheet super capacitor fully utilizes the porous structure of the paper sheet, reduces device elements, is convenient for pattern design and different structure manufacturing, can improve energy density, and solves the problems of thick size, many elements, poor flexibility and low energy density of traditional flexible super capacitor devices.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electrochemical energy, and particularly relates to a paper sheet supercapacitor and a preparation method thereof. BACKGROUND

[0002] Supercapacitors are a class of high-power electrochemical energy storage devices with energy densities between secondary batteries and conventional capacitors. Supercapacitors can be divided into double-layer capacitors and pseudo-capacitors according to their energy storage mechanisms. Double-layer capacitors store and release electrical energy through the rapid adsorption / desorption of ions at the interface between the electrode material and the electrolyte, while pseudo-capacitors store energy through reversible redox reactions on the surface of the electrode material. However, traditional supercapacitors have many limitations in use due to their rigid electrodes based on powder materials, such as limited mechanical strength and low energy density. Flexible supercapacitors are devices that store energy based on double-layer and pseudo-capacitance effects. Their working principle is based on ion migration and charge distribution between electrode materials, and energy storage is achieved through the process of double-layer charge storage and release. At the same time, the pseudo-capacitance effect also enhances the capacitance and energy density of the capacitor. When charging, a double layer is formed between the positive and negative electrodes, storing electrical charge; when discharging, the electrical charge is released from the electrodes, outputting energy. Due to the advantages of good flexibility, light weight, and strong pressure resistance, flexible supercapacitors have been considered for powering the next generation of electronic devices.

[0003] Currently, the challenge for flexible supercapacitors is how to introduce a flexible substrate with pseudo-capacitance. The flexible substrates that have been studied can be divided into metal-based, plastic-based, and paper-based. Metal-based and plastic-based substrates can give flexible supercapacitors excellent mechanical properties, but they have problems such as poor bending performance, poor cycle stability, and weak bonding with active materials. Paper-based flexible substrates not only guarantee excellent mechanical properties and self-supporting properties, but their porous structure also allows electroactive materials to participate in the energy storage process to the greatest extent. However, using traditional paper-based substrates usually involves pasting active materials onto the surface of the paper substrate, and the structural advantages of the paper's porosity are rarely utilized. In addition, in energy storage devices, electrodes often need to be arranged in the form of a multi-layer sandwich, and a layer of film needs to be added between the electrodes to prevent short circuits. This multi-layer device design requires additional processes and components, increasing the size of the device and continuously increasing its volume and mass.

[0004] To solve the above problems, the present application provides a paper sheet supercapacitor, which fully utilizes the highly porous three-dimensional (3D) layered structure of paper to vertically distribute all components of the electrode material and electrolyte in designated areas of a piece of paper, and fully utilizes the void structure of the paper sheet to absorb active materials into the voids between the fibers of the paper sheet, thereby solving the problems of existing flexible supercapacitor devices, such as large size, multiple components, poor flexibility, and low energy density. SUMMARY

[0005] In order to solve the above problems, the paper sheet super capacitor and the preparation method thereof are provided, the hydrophobic layer is constructed on the microstructure inside the paper sheet, all components of the electrode material and the electrolyte are vertically distributed in the designated area of the paper sheet, and the obtained paper sheet super capacitor is thin in size, high in flexibility and high in energy density.

[0006] The paper sheet super capacitor is realized by the following technical scheme:

[0007] A paper sheet super capacitor, taking a paper sheet as a support of the super capacitor, constructing a hydrophobic layer on the microstructure inside the paper sheet, vertically distributing all components of the gel electrolyte, the positive active material, the negative active material, the positive current collector and the negative current collector in the designated area of the paper sheet, and obtaining the paper sheet super capacitor.

[0008] Further, the effective area of the positive active material and the negative active material is less than the area of the paper sheet, and the thickness on the paper sheet is 5-10 mu m and 5-10 mu m respectively; the positive current collector and the negative current collector are respectively distributed on the surface of the positive active material and the negative active material, and the effective area is less than the area of the paper sheet.

[0009] A preparation method of the paper sheet super capacitor, comprising the following steps:

[0010] (1) Constructing a hydrophobic layer: soaking the paper sheet in a hydrophobic solution with a concentration of 0.1-1.0 g / mL for 40-60 min, taking out the paper sheet and performing the first solidification to obtain a modified paper sheet; the raw material of the hydrophobic solution is one or more of polyvinylidene fluoride, polyvinylidene fluoride hexafluoropropylene and polytetrafluoroethylene;

[0011] (2) Introducing gel electrolyte: soaking the modified paper sheet in the gel electrolyte, taking out the paper sheet after the soaking is completed, and performing the second solidification to obtain a paper sheet gel electrolyte;

[0012] (3) Spraying active material slurry: spraying the positive active material slurry on one side of the paper sheet gel electrolyte by subsonic spraying, completing the third solidification; then spraying the negative active material slurry on the other side of the paper sheet gel electrolyte by subsonic spraying, and spraying the positive current collector and the negative current collector on the surface of the positive active material and the negative active material respectively, the active particle speed in the slurry is 180-300 m / s, the spraying thickness is 5-10 mu m, the fourth solidification is performed after the spraying is completed, and the paper sheet super capacitor is obtained after being plasticized in the hydrophobic solution.

[0013] Further, in step (1), the paper sheet is one or more of A4 paper, draft paper, toilet paper, and rice paper; the first solidification is drying at 60-100°C for 40-60 min.

[0014] Further, in step (2), the gel electrolyte is composed of a polymer, a salt solution, and an additive in a mass ratio of 2-4:1-2:1; the polymer is one or more of polyvinyl alcohol, polymethyl methacrylate, and polyacrylonitrile; the salt solution uses one or more of lithium hexafluorophosphate, N,N-dimethylpyrrolidinium tetrafluoroborate, bispyrrolidine spiro quaternary ammonium salt, sulfate, potassium hydroxide, sodium carbonate, and tetraethylammonium tetrafluoroborate as raw materials; the additive is one or more of p-phenylenediamine, allyl sulfite, 2-methyltetrahydrofuran, methyl formate, and ethyl isobutyl sulfone.

[0015] Further, in step (2), the modified paper sheet is soaked in the gel electrolyte for 100-120 min; the second solidification is drying at 50-80°C for 40-60 min.

[0016] Further, in step (3), the positive electrode active material is composed of active material A, a conductive agent, and a binder in a mass ratio of 1-4:0.5-2:1; the active material A is one or more of nickel-cobalt-manganese material, nickel-cobalt-aluminum material, hard carbon material, nickel-manganese material, and nickel-rich manganese-based material; the conductive agent is one or more of activated carbon, graphite, graphene, black scale, carbon nanotube, conductive graphite, acetylene black, ketjen black, and biologically based derivative carbon.

[0017] The negative electrode active material is composed of active material B and a binder mixed in a mass ratio of 8-10:1; the active material B is one or more of activated carbon, graphite, graphene, silicon, silicon-carbon, soft carbon, hard carbon, black scale, carbon nanotube, conductive graphite, acetylene black, ketjen black, and biologically based derivative carbon.

[0018] Further, in step (3), the positive electrode current collector and the negative electrode current collector are each composed of a conductive agent and a binder in a mass ratio of 3-6:1; the conductive agent is one or more of copper paste, silver paste, tin paste, copper-silver paste, hard carbon, soft carbon, mesocarbon microbeads, silicon, silicon-carbon, and silicon-oxygen.

[0019] Further, the binder is one or more of polyethylene oxide, polyvinylidene fluoride, and methyl cellulose.

[0020] Further, in step (3), the third solidification is drying at 50-80°C for 40-60 min; the fourth solidification is drying at 80-120°C for 100-120 min; the plastic packaging time is 15-20 min.

[0021] The preparation principle of the paper sheet supercapacitor of the present application is as follows:

[0022] Free water molecules can decompose the microstructure inside the paper sheet, and the present application introduces a hydrophobic layer into the pores of the paper sheet to make full use of the pores in the paper sheet. The paper sheet is mostly composed of cellulose, and the cellulose molecular chain has many hydroxyl groups. The molecular chain of the polymer in the hydrophobic solution, such as polyvinylidene fluoride hexafluoropropylene, contains a large number of C-F bonds. The hydroxyl groups and the C-F bonds form hydrogen bonds or van der Waals forces to be closely combined, which plays a role in isolating free water and preventing the destruction of the internal microstructure of the paper sheet. And with the help of the C-F bonds on the surface of the polymer, the gel electrolyte is attracted into the gap by electrostatic attraction. Due to the solvent evaporation during the solidification process, the electrolyte shrinks, leaving some space on the surface of the paper sheet. The prepared positive and negative active slurries are sprayed on both sides of the paper sheet in subsonic speed, and the speed and thickness of the active particles in the spraying process are controlled. Then, the positive and negative current collector materials are sprayed on the surface of the positive and negative active materials. Finally, the paper sheet supercapacitor is plastic sealed.

[0023] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0024] 1. The present application integrates all components of the supercapacitor into a designated area of a paper sheet, reducing the thickness of the device and improving the energy density of the supercapacitor under the same size. The present application makes full use of the porous structure of the paper sheet, constructs a hydrophobic barrier on the internal microstructure surface of the paper sheet through the hydrophobic gel soaking process, prevents water molecules or other solvent molecules from decomposing and destroying the internal microstructure of the paper sheet, facilitates the patterning design and heterogeneous structure manufacturing, reduces the device elements, and reduces the thickness of the device.

[0025] 2. The working voltage window of the paper sheet supercapacitor of the present application is 2.5-4.2V, while the working voltage window of the traditional supercapacitor is 0-2.5V. Compared with the traditional supercapacitor, the paper sheet supercapacitor of the present application has a higher voltage window and can effectively improve the energy density. At the same time, the capacity retention rate of the paper sheet supercapacitor of the present application is improved to 93.47% after 10C current intensity 5000 cycle, which shows that the paper sheet supercapacitor has good cycle stability.

[0026] 3. The traditional supercapacitor has a typical sandwich structure, which is composed of positive electrode, negative electrode, electrolyte and separator. The device is relatively thick. In the present application, the electrolyte is first introduced to the middle position of the paper sheet. Due to the solvent evaporation, the electrolyte shrinks, leaving some space on the surface of the paper sheet. Then, the positive and negative active materials and the positive and negative current collectors are sprayed on the surface of the paper sheet to form an integrated supercapacitor. Compared with the traditional supercapacitor, the present application makes full use of the pores of the paper sheet and can effectively reduce the thickness of the device.

[0027] 4. The paper used in this invention is extremely flexible, enabling the design of energy storage devices with diverse components and strong shape adaptability. The present invention uses a slurry to create the positive and negative current collectors, which not only serve as electron pathways but also as encapsulation, demonstrating dual functionality. This also saves device space and improves energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the preparation process of paper supercapacitors.

[0029] Figure 2 CV curves of the paper supercapacitor of Example 1 in the voltage ranges of 2.5-4.0 V and 2.5-4.2 V at a scan rate of 5 mV / s.

[0030] Figure 3 This is a CV curve diagram of the paper supercapacitor of Example 1 in the voltage range of 2.5 to 4.0 V at a scan rate of 5 to 40 mV / s.

[0031] Figure 4 Graph showing the cycling performance of the paper supercapacitor of Example 1 in the voltage ranges of 2.5-4.0V and 2.5-4.2V.

[0032] Figure 5 This is a rate performance diagram of the paper supercapacitor of Example 1 in the voltage ranges of 2.5-4.0V and 2.5-4.2V. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below through examples. These examples are only used to illustrate the present invention and do not limit the scope of protection of the present invention.

[0034] Example 1

[0035] Preparation of paper supercapacitors:

[0036] (1) Construction of a hydrophobic layer: Dissolve 1 g of polyvinylidene fluoride hexafluoropropylene in 10 mL of N,N-dimethylformamide and stir at 60°C for 60 min to obtain a hydrophobic solution. Soak clean A4 paper in the hydrophobic solution for 60 min, then perform the first curing and dry it in a forced air drying oven at 80°C for 60 min to obtain the modified paper.

[0037] (2) Introducing gel electrolyte: 1.0 g of polyvinyl alcohol powder and 20 mL of ethanol were mixed and magnetically stirred until the polyvinyl alcohol was completely dissolved to obtain a polyvinyl alcohol solution. 0.5 g of tetraethylammonium tetrafluoroborate was dissolved in 5 mL of acetonitrile and stirred until uniform to obtain a salt solution. The polyvinyl alcohol solution and the salt solution were mixed, and 0.5 g of 2-methyltetrahydrofuran was added and magnetically stirred until the solution was fully mixed to obtain a gel electrolyte. The modified paper sheet was soaked in the gel electrolyte for 120 min, then subjected to a second solidification and dried at 60°C for 60 min to obtain a paper sheet gel electrolyte.

[0038] (3) Spraying active material slurry: 0.5 mg of nickel-cobalt-manganese material, 0.2 mg of activated carbon, and 0.3 mg of polyvinylidene fluoride were stirred and mixed to obtain a positive electrode active material slurry. 2.5 mg of activated carbon and 0.3 mg of polyvinylidene fluoride were stirred and mixed to obtain a negative electrode active material slurry. 2.0 g of hard carbon and 0.5 g of polyvinylidene fluoride were dissolved in 10 mL of anhydrous ethanol and stirred until uniform to obtain a positive electrode current collector and a negative electrode current collector. The positive electrode active material slurry was coated on one side of the paper sheet gel electrolyte by subsonic spraying, and after completion, a third solidification was performed and dried at 60°C for 50 min. Then the negative electrode active material slurry was coated on the other side of the paper sheet gel electrolyte by subsonic spraying, and at the same time, the positive electrode current collector and the negative electrode current collector were sprayed on the surface of the positive electrode active material and the negative electrode active material, respectively. The active particle speed in the slurry was 200 m / s, and the spraying thickness was 5 μm. After the spraying was completed, a fourth solidification was performed and baked at 100°C for 120 min. After being placed in a hydrophobic solution for 20 min, a paper sheet supercapacitor was obtained. The preparation process is shown in Figure 1

[0039] Example 2

[0040] Preparation of a paper sheet supercapacitor:

[0041] (1) Constructing a hydrophobic layer: 2 g of polyvinylidene fluoride and 3 g of polyvinylidene fluoride-hexafluoropropylene were dissolved in 10 mL of N,N-dimethylformamide and stirred at 60°C for 60 min to obtain a hydrophobic solution. A clean draft paper was soaked in the hydrophobic solution for 40 min, then subjected to a first solidification and baked at 100°C in a forced air drying oven for 40 min to obtain a modified paper sheet;

[0042] ​(2) Introducing gel electrolyte: 1.5 g of polyvinyl alcohol powder, 0.5 g of polymethyl methacrylate and 20 mL of ethanol were mixed, and magnetic stirring was carried out until the polymer was completely dissolved to obtain a polymer solution. 0.5 g of lithium hexafluorophosphate and 0.5 g of sulfate were dissolved in 10 mL of acetonitrile and stirred until uniform to obtain a salt solution. The polymer solution and the salt solution were mixed, and 0.5 g of p-phenylenediamine was added, and magnetic stirring was carried out until the solution was fully mixed to obtain a gel electrolyte. The modified paper sheet was soaked in the gel electrolyte for 100 min, and then second curing was carried out, and drying was carried out at 80°C for 40 min to obtain a paper sheet gel electrolyte.

[0043] (3) Spraying active material slurry: 0.5 mg of nickel-rich manganese-based material, 0.5 mg of nickel-cobalt-aluminum material, 0.4 mg of graphene and 0.5 mg of polyethylene oxide were stirred to obtain a positive electrode active material slurry. 3 mg of silicon-carbon and 0.3 mg of polyethylene oxide were stirred to obtain a negative electrode active material slurry. 1.0 g of tin slurry, 0.5 g of copper-silver slurry and 0.3 g of polyvinylidene fluoride were dissolved in 10 mL of anhydrous ethanol and stirred until uniform to obtain a positive electrode current collector and a negative electrode current collector. The positive electrode active material slurry was coated on one side of the paper sheet gel electrolyte by subsonic spraying, and after completion, third curing was carried out, and drying was carried out at 80°C for 40 min; then the negative electrode active material slurry was coated on the other side of the paper sheet gel electrolyte by subsonic spraying, and at the same time, the positive electrode current collector and the negative electrode current collector were respectively sprayed on the surface of the positive electrode active material and the negative electrode active material, the active particle speed in the slurry was 250 m / s, the spraying thickness was 5 μm, and after the spraying was completed, fourth curing was carried out, and drying was carried out at 120°C for 100 min, and then placed in a hydrophobic solution for 15 min to obtain a paper sheet supercapacitor.

[0044] Example 3

[0045] Preparation of a paper sheet supercapacitor:

[0046] (1) Constructing a hydrophobic layer: 3 g of polytetrafluoroethylene was dissolved in 10 mL of N,N-dimethylformamide and stirred at 60°C for 60 min to obtain a hydrophobic solution. Clean draft paper and rice paper were soaked in the hydrophobic solution for 60 min, and then first curing was carried out, and drying was carried out in a forced air drying oven at 100°C for 40 min to obtain a modified paper sheet;

[0047] (2) Introducing gel electrolyte: 1.5 g of polyacrylonitrile and 20 mL of ethanol were mixed and magnetically stirred until the polyacrylonitrile was completely dissolved to obtain a polyacrylonitrile solution. 0.5 g of tetraethylammonium tetrafluoroborate was dissolved in 5 mL of acetonitrile and stirred until uniform to obtain a salt solution. The polyacrylonitrile solution and the salt solution were mixed, and 0.2 g of methyl formate and 0.3 g of ethyl isobutyl sulfone were added, and magnetically stirred until the solution was fully mixed to obtain a gel electrolyte. The modified paper sheet was soaked in the gel electrolyte for 120 min, and then subjected to a second solidification and dried at 50°C for 60 min to obtain a paper sheet gel electrolyte.

[0048] (3) Spraying active material slurry: 1.0 mg of nickel-cobalt-aluminum material, 0.2 mg of carbon nanotubes, 0.3 mg of conductive graphite, and 0.3 mg of methyl cellulose were stirred and mixed to obtain a positive electrode active material slurry. 2.0 mg of graphite, 1.0 mg of graphene, and 0.3 mg of polyethylene oxide were stirred and mixed to obtain a negative electrode active material slurry. 1.0 g of silicon-carbon, 1.0 g of silicon-oxygen, and 0.5 g of polyvinylidene fluoride were dissolved in 10 mL of anhydrous ethanol and stirred until uniform to obtain a positive electrode current collector and a negative electrode current collector. The positive electrode active material slurry was coated on one side of the paper sheet gel electrolyte by subsonic spraying, and after completion, a third solidification was performed and dried at 50°C for 60 min. Then, the negative electrode active material slurry was coated on the other side of the paper sheet gel electrolyte by subsonic spraying, and at the same time, the positive electrode current collector and the negative electrode current collector were correspondingly sprayed on the surface of the positive electrode active material and the negative electrode active material, respectively. The active particle speed in the slurry was 300 m / s, and the spraying thickness was 5 μm. After the spraying was completed, a fourth solidification was performed and baked at 120°C for 100 min. After being placed in a hydrophobic solution for 20 min, a paper sheet supercapacitor was obtained.

[0049] Example 4

[0050] Preparation of a paper sheet supercapacitor:

[0051] (1) Constructing a hydrophobic layer: 7 g of polyvinylidene fluoride hexafluoropropylene was dissolved in 10 mL of N,N-dimethylformamide and stirred at 60°C for 60 min to obtain a hydrophobic solution. A clean A4 paper was soaked in the hydrophobic solution for 60 min, and then subjected to a first solidification and baked at 100°C for 40 min in a forced air drying oven to obtain a modified paper sheet.

[0052] (2) Introduction of gel electrolyte: 2.0 g of polymethyl methacrylate and 20 mL of ethanol were mixed and magnetically stirred until the polymethyl methacrylate was completely dissolved to obtain a polymethyl methacrylate solution. 1.0 g of N, N-dimethylpyrrolidinium tetrafluoroborate was dissolved in 5 mL of acetonitrile and stirred until uniform to obtain a salt solution. The polymethyl methacrylate solution and the salt solution were mixed, and 0.5 g of methyl formate was added and magnetically stirred until the solution was fully mixed to obtain a gel electrolyte. The modified paper was placed in the gel electrolyte and soaked for 100 minutes, then cured for the second time and dried at 80°C for 40 minutes to obtain a paper gel electrolyte.

[0053] (3) Spraying active material slurry: Stir and mix 1.0 mg of hard carbon, 0.2 mg of black scale, 0.2 mg of conductive graphite, 0.4 mg of acetylene black, and 0.5 mg of polyethylene oxide to obtain a positive electrode active material slurry. Stir and mix 2.5 mg of soft carbon, 0.5 mg of Ketjen black, and 0.3 mg of methyl cellulose to obtain a negative electrode active material slurry. Dissolve 2.0 g of mesophase carbon microspheres, 1.0 g of silica, 0.2 g of polyethylene oxide, and 0.3 g of polyvinylidene fluoride in 10 mL of anhydrous ethanol and stir until uniform to obtain a positive electrode current collector and a negative electrode current collector. The positive electrode active material slurry is coated on one side of the paper gel electrolyte by subsonic spraying, and then cured for the third time and dried at 80°C for 45 minutes; then the negative electrode active material slurry is coated on the other side of the paper gel electrolyte by subsonic spraying, and the positive electrode collector and the negative electrode collector are sprayed on the surface of the positive electrode active material and the negative electrode active material respectively. The active particle speed in the slurry is 230m / s, and the spraying thickness is 10μm. After spraying, it is cured for the fourth time, dried at 80°C for 120 minutes, and sealed in a hydrophobic solution for 15 minutes to obtain a paper supercapacitor.

[0054] Example 5

[0055] Preparation of paper supercapacitors:

[0056] (1) Construction of a hydrophobic layer: Dissolve 5 g of polyvinylidene fluoride / hexafluoropropylene and 5 g of polytetrafluoroethylene in 10 mL of N,N-dimethylformamide and stir at 60°C for 60 min to obtain a hydrophobic solution. Soak clean rice paper in the hydrophobic solution for 40 min, then perform the first curing and dry it in a forced air drying oven at 80°C for 50 min to obtain the modified paper sheet.

[0057] (2) Introducing gel electrolyte: 1.0 g of polyvinyl alcohol, 1.0 g of polyacrylonitrile and 25 mL of ethanol were mixed, and magnetic stirring was performed until the polymer was completely dissolved to obtain a polymer solution. 0.5 g of bispidine spirocyclic quaternary ammonium salt, 0.3 g of potassium hydroxide were dissolved in 8 mL of acetonitrile and stirred until uniform to obtain a salt solution. The polymer solution and the salt solution were mixed, and 0.2 g of propylene sulfite and 0.3 g of methyl formate were added, and magnetic stirring was performed until the solution was fully mixed to obtain a gel electrolyte. The modified paper sheet was soaked in the gel electrolyte for 110 min, and then second curing was performed, and drying was performed at 80°C for 45 min to obtain a paper sheet gel electrolyte.

[0058] (3) Spraying active material slurry: 1.0 mg of nickel-cobalt-aluminum material, 0.5 mg of carbon nanotube, 0.3 mg of biogenic carbon derived carbon and 0.5 mg of methyl cellulose were stirred and mixed to obtain a positive electrode active material slurry. 1.0 mg of silicon carbon, 0.5 mg of soft carbon, 1.0 mg of hard carbon and 0.3 mg of methyl cellulose were stirred and mixed to obtain a negative electrode active material slurry. 1.0 g of silver paste, 1.0 g of tin paste, 0.5 g of silicon oxide and 0.5 g of polyvinylidene fluoride were dissolved in 10 mL of anhydrous ethanol and stirred until uniform to obtain a positive electrode current collector and a negative electrode current collector. The positive electrode active material slurry was coated on one side of the paper sheet gel electrolyte by subsonic spraying, and after completion, third curing was performed, and drying was performed at 70°C for 60 min; then the negative electrode active material slurry was coated on the other side of the paper sheet gel electrolyte by subsonic spraying, and at the same time, the positive electrode current collector and the negative electrode current collector were respectively sprayed on the surface of the positive electrode active material and the negative electrode active material, and the active particle speed in the slurry was 300 m / s, and the spraying thickness was 5 μm. After the spraying was completed, the fourth curing was performed, and drying was performed at 90°C for 120 min, and then placed in a hydrophobic solution for 20 min to obtain a paper sheet supercapacitor.

[0059] Example 6

[0060] Preparation of a paper sheet supercapacitor:

[0061] (1) Constructing a hydrophobic layer: 2 g of polyvinylidene fluoride was dissolved in 10 mL of N,N-dimethylformamide, and stirring was performed at 60°C for 60 min to obtain a hydrophobic solution. A clean paper towel was soaked in the hydrophobic solution for 60 min, and then first curing was performed, and drying was performed in a forced air drying oven at 100°C for 40 min to obtain a modified paper sheet;

[0062] (2) Introducing gel electrolyte: 1.5 g of polyvinyl alcohol powder and 20 mL of ethanol were mixed and magnetically stirred until the polyvinyl alcohol was completely dissolved to obtain a polyvinyl alcohol solution. 0.5 g of lithium hexafluorophosphate and 0.5 g of sodium carbonate were dissolved in 10 mL of acetonitrile and stirred until uniform to obtain a salt solution. The polyvinyl alcohol solution and the salt solution were mixed, and 0.5 g of 2-methyltetrahydrofuran was added, and magnetically stirred until the solution was fully mixed to obtain a gel electrolyte. The modified paper sheet was soaked in the gel electrolyte for 120 min, and then subjected to a second solidification and dried at 60°C for 60 min to obtain a paper sheet gel electrolyte.

[0063] (3) Spraying active material slurry: 1.0 mg of nickel-rich manganese-based material, 1.0 mg of graphene, 0.2 mg of polyethylene oxide, and 0.2 mg of polyvinylidene fluoride were stirred and mixed to obtain a positive electrode active material slurry. 2.5 mg of black scale and 0.3 mg of methyl cellulose were stirred and mixed to obtain a negative electrode active material slurry. 1.5 g of copper paste, 1.0 g of mesocarbon microbeads, and 0.5 g of polyvinylidene fluoride were dissolved in 10 mL of anhydrous ethanol and stirred until uniform to obtain a positive electrode current collector and a negative electrode current collector. The positive electrode active material slurry was coated on one side of the paper sheet gel electrolyte by subsonic spraying, and after completion, a third solidification was performed and dried at 60°C for 50 min; then the negative electrode active material slurry was coated on the other side of the paper sheet gel electrolyte by subsonic spraying, and at the same time, the positive electrode current collector and the negative electrode current collector were sprayed on the surface of the positive electrode active material and the negative electrode active material, respectively, with an active particle speed of 200 m / s and a spraying thickness of 10 μm. After the spraying was completed, a fourth solidification was performed and dried at 100°C for 120 min, and then placed in a hydrophobic solution for 15 min to obtain a paper sheet supercapacitor.

[0064] Comparative Example 1

[0065] As a comparative example, the article "All-printed paper based surface mountable supercapacitors" discloses an all-printed paper-based surface mountable supercapacitor, which is manufactured by screen printing and stencil printing on the surface of a paper substrate. The supercapacitor was subjected to cyclic voltammetry (CV curve) test, and the test results showed that the working voltage window of the supercapacitor was 0-2.5 V at 20 mV / s.

[0066] Material performance analysis

[0067] The energy density of a supercapacitor is closely related to its working voltage window, and the energy density E = 1 / 2 x C (capacitance) x V (voltage) 2Therefore, the energy density can be directly improved by increasing the voltage window. The paper sheet supercapacitor in Example 1 was tested. Figure 2 The CV curves of the paper sheet supercapacitor in the voltage range of 2.5-4.0 V and 2.5-4.2 V at a scan rate of 5 mV / s were plotted. Figure 2 It can be seen that the increase of the upper cut-off voltage makes the area of the quasi-rectangular CV curve also increase, and the CV curve shape of the cathode composite material does not change significantly, and there is no obvious redox peak in the CV curve, indicating that the paper sheet supercapacitor has both capacitive and battery behaviors, and has good reversibility.

[0068] Figure 3 The CV curves of the paper sheet supercapacitor in the voltage range of 2.5-4.0 V at a scan rate of 5-40 mV / s were plotted. Figure 3 It can be seen that as the scan rate increases, the CV shape is basically unchanged, and the curve moves to the high and low potentials, respectively, indicating that the paper sheet supercapacitor has a good ion transfer rate, and the battery and capacitive characteristics of the cathode material and anode material are exerted in the work.

[0069] Figure 4 and Figure 5 The cycle performance and rate performance of the paper sheet supercapacitor in the voltage range of 2.5-4.0 V and 2.5-4.2 V, respectively. It can be seen that when the voltage range is 2.5-4.0 V, after 5000 cycles at a current intensity of 10C, the capacity retention rate is 91.92%. When the upper cut-off voltage is increased to 4.2 V, it can be seen that after 5000 cycles, the capacity retention rate is increased to 93.47%, indicating that the increase of the upper cut-off voltage does not reduce the cycle stability. On the contrary, compared with the cycle stability in the voltage range of 2.5-4.2 V, there is a slight increase, indicating that the paper sheet supercapacitor in the low rate can still maintain good cycle stability in the voltage range of 2.5-4.2 V. With the gradual increase of the current intensity, the capacity of the prepared lithium ion capacitor shows a slow downward trend. In the voltage range of 2.5-4.2 V, the capacity retention rate at a current density of 7C and 10C is slightly lower than that at an upper cut-off voltage of 4 V. The capacity at 10C is basically close to that in the voltage range of 2.5-4.0 V, but when the current intensity returns to 1C, the capacities of both are restored to the initial level, indicating that the upper cut-off stable voltage of the system can be increased to 4.2 V, which makes the paper sheet supercapacitor have higher voltage advantage in the field of high power and long cycle.

[0070] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A paper sheet supercapacitor, characterized by, The paper sheet is used as a support of the super capacitor, a hydrophobic layer is constructed on the microstructure of the paper sheet, and all components of gel electrolyte, positive active material, negative active material, positive current collector and negative current collector are vertically distributed in the designated area of the paper sheet to obtain the paper sheet super capacitor. The preparation method of the paper sheet super capacitor comprises the following steps: (1) Constructing a hydrophobic layer: the paper sheet is soaked in a hydrophobic solution with a concentration of 0.1-1.0 g / mL for 40-60 min, and then the paper sheet is taken out and subjected to first solidification to obtain a modified paper sheet; the raw material of the hydrophobic solution is one or more of polyvinylidene fluoride, polyvinylidene fluoride hexafluoropropylene and polytetrafluoroethylene; (2) Introducing gel electrolyte: the modified paper sheet is soaked in gel electrolyte, and after the soaking is completed, the paper sheet is taken out and subjected to second solidification to obtain a paper sheet gel electrolyte; the gel electrolyte is composed of a polymer, a salt solution and an additive in a mass ratio of 2-4:1-2:1; the polymer is one or more of polyvinyl alcohol, polymethyl methacrylate and polyacrylonitrile; (3) Spraying active material slurry: the positive active material slurry is sprayed on one side of the paper sheet gel electrolyte by subsonic spraying, and then the third solidification is performed; then the negative active material slurry is sprayed on the other side of the paper sheet gel electrolyte by subsonic spraying, and at the same time, the positive current collector and the negative current collector are respectively sprayed on the surfaces of the positive active material and the negative active material; the active particle speed in the slurry is 180-300 m / s, the spraying thickness is 5-10 μm, and after the spraying is completed, the fourth solidification is performed, and then the paper sheet super capacitor is obtained after being plasticized in the hydrophobic solution.

2. The paper sheet supercapacitor of claim 1, wherein, The effective area of the positive active material and the negative active material is less than the area of the paper sheet, and the thicknesses of the positive active material and the negative active material on the paper sheet are 5-10 μm and 5-10 μm respectively; the positive current collector and the negative current collector are respectively distributed on the surfaces of the positive active material and the negative active material, and the effective areas of the positive current collector and the negative current collector are less than the area of the paper sheet.

3. A method of making a paper sheet supercapacitor as claimed in claim 1 or 2, characterized in that, The preparation method comprises the following steps: (1) Constructing a hydrophobic layer: the paper sheet is soaked in a hydrophobic solution with a concentration of 0.1-1.0 g / mL for 40-60 min, and then the paper sheet is taken out and subjected to first solidification to obtain a modified paper sheet; the raw material of the hydrophobic solution is one or more of polyvinylidene fluoride, polyvinylidene fluoride hexafluoropropylene and polytetrafluoroethylene; (2) Introducing gel electrolyte: the modified paper sheet is soaked in gel electrolyte, and after the soaking is completed, the paper sheet is taken out and subjected to second solidification to obtain a paper sheet gel electrolyte; the gel electrolyte is composed of a polymer, a salt solution and an additive in a mass ratio of 2-4:1-2:1; the polymer is one or more of polyvinyl alcohol, polymethyl methacrylate and polyacrylonitrile; (3) Spraying active material slurry: the positive active material slurry is coated on one side of the paper sheet gel electrolyte by subsonic spraying, and after completion, the third solidification is carried out; then the negative active material slurry is coated on the other side of the paper sheet gel electrolyte by subsonic spraying, and at the same time, the positive current collector and the negative current collector are respectively sprayed on the surface of the positive active material and the negative active material, the active particle speed in the slurry is 180-300 m / s, the spraying thickness is 5-10 μm, and after the spraying is completed, the fourth solidification is carried out, and after being sealed in a hydrophobic solution, the paper sheet supercapacitor is obtained.

4. The method of claim 3, wherein the paper sheet supercapacitor is prepared by the steps of: In step (1), the paper sheet is one or more of A4 paper, draft paper, toilet paper and rice paper; the first solidification is drying at 60-100°C for 40-60 min.

5. The method for preparing a paper supercapacitor according to claim 3, wherein: In step (2), the gel electrolyte is composed of a polymer, a salt solution and an additive in a mass ratio of 2-4:1-2:1; the polymer is one or more of polyvinyl alcohol, polymethyl methacrylate and polyacrylonitrile; the raw material used in the salt solution is one or more of lithium hexafluorophosphate, N,N-dimethylpyrrolidinium tetrafluoroborate, bispyrrolidine spiro quaternary ammonium salt, sulfate, potassium hydroxide, sodium carbonate and tetraethylammonium tetrafluoroborate; the additive is one or more of p-phenylenediamine, allyl sulfite, 2-methyltetrahydrofuran, methyl formate and ethyl isobutyl sulfone.

6. The method of claim 3, wherein the paper sheet supercapacitor is prepared by the steps of: In step (2), the modified paper sheet is soaked in the gel electrolyte for 100-120 min; the second solidification is drying at 50-80°C for 40-60 min.

7. The method of claim 3, wherein the paper sheet supercapacitor is prepared by the steps of: In step (3), the positive active material is composed of active material A, a conductive agent and a binder in a mass ratio of 1-4:0.5-2:1; the active material A is one or more of nickel-cobalt-manganese material, nickel-cobalt-aluminum material, hard carbon material, nickel-manganese material and nickel-rich manganese-based material; the conductive agent is one or more of activated carbon, graphite, graphene, black scale, carbon nanotube, conductive graphite, acetylene black, ketjen black and biologically based derived carbon; The negative active material is composed of active material B and a binder mixed in a mass ratio of 8-10:1; the active material B is one or more of activated carbon, graphite, graphene, silicon, silicon-carbon, soft carbon, hard carbon, black scale, carbon nanotube, conductive graphite, acetylene black, ketjen black and biologically based derived carbon.

8. The method of claim 3, wherein the paper sheet supercapacitor is prepared by the steps of: In step (3), the positive current collector and the negative current collector are each composed of a conductive agent and a binder in a mass ratio of 3-6:1; the conductive agent is one or more of copper paste, silver paste, tin paste, copper-silver paste, hard carbon, soft carbon, mesocarbon microbeads, silicon, silicon-carbon and silicon-oxygen.

9. The method of claim 7 or 8, wherein the paper sheet supercapacitor is prepared by the steps of: The binder is one or more of polyethylene oxide, polyvinylidene fluoride and methyl cellulose.

10. The method for preparing a paper supercapacitor according to claim 3, wherein: In step (3), the third solidification is drying at 50-80°C for 40-60 min; the fourth solidification is drying at 80-120°C for 100-120 min; and the sealing time is 15-20 min.

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