Paper super capacitor and preparation method thereof

Abstract

The invention discloses a paper super capacitor and a preparation method thereof, and belongs to the technical field of electrochemical energy. The paper serves as a support of the supercapacitor, after a hydrophobic layer is constructed on a microstructure in the paper, all assemblies of a gel electrolyte, a positive active material, a negative active material, a positive current collector and a negative current collector are vertically distributed in a designated area of the paper, and the paper supercapacitor is obtained. The preparation method of the paper super capacitor comprises the following technical steps: (1) constructing the hydrophobic layer; (2) introducing a gel electrolyte; and (3) spraying active material slurry. According to the paper sheet supercapacitor, the porous structure of the paper sheet is fully utilized, device elements are reduced, patterning design and different structure manufacturing are facilitated, the energy density can be improved, and the problems that a traditional flexible supercapacitor is thick in device size, large in number of elements, poor in flexibility, low in energy density and the like are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical energy, and in particular relates to a paper supercapacitor and a preparation method thereof. Background Art

[0002] Supercapacitors are a type of high-power electrochemical energy storage device with an energy density between that of secondary batteries and conventional capacitors. Supercapacitors can be divided into double-layer capacitors and pseudocapacitors according to their energy storage mechanism. Double-layer capacitors store and release electrical energy through the rapid adsorption / desorption of ions on the interface between electrode materials and electrolytes, while pseudocapacitors store energy through reversible redox reactions on the surface of electrode materials. 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 capacitance and pseudocapacitor effects. Their working principle is based on the ion migration and charge distribution between electrode materials, and energy storage is achieved through the process of charge storage and release formed by the double layer. At the same time, the pseudocapacitor effect also enhances the capacitance and energy density of the capacitor. During charging, a double layer is formed between the positive and negative electrodes to store charge; during discharging, the charge is released from the electrodes to output energy. Flexible supercapacitors have been considered for powering the next generation of electronic devices due to their advantages such as good flexibility, light weight and strong pressure resistance.

[0003] At present, the challenge facing flexible supercapacitors is how to introduce flexible substrates with pseudocapacitance. The flexible substrates that have been studied can be divided into metal-based, plastic-based, paper-based, etc. Metal substrates and plastic substrates can give flexible supercapacitors excellent mechanical properties, but there are problems such as poor bending performance, poor cycle stability and weak binding force with active substances. While ensuring excellent mechanical properties and self-supporting properties, the porous structure of paper-based flexible substrates can also enable electroactive substances to participate in the energy storage process to the greatest extent. However, the use of traditional paper-based substrates usually involves pasting active materials to the surface of the paper base, and rarely utilizes the structural advantages of the porosity of paper. In addition, in energy storage devices, electrodes usually need to be arranged in the form of multi-layer sandwich sheets, and a layer of membrane needs to be added between the electrodes to prevent short circuits. The design of such multi-layer devices requires additional processes and components, increases the size of the device, and increases its volume and mass.

[0004] To solve the above problems, the present invention provides a paper supercapacitor, which makes full use of the highly porous three-dimensional (3D) layered structure of paper, vertically distributes all components of electrode materials and electrolytes in a designated area of ​​a piece of paper, and makes full use of the void structure of paper to absorb active materials into the voids between paper fibers, so as to solve the problems of existing flexible supercapacitor devices such as thick size, many components, poor flexibility and low energy density. Summary of the invention

[0005] In view of the above problems, the present invention provides a paper supercapacitor and a preparation method thereof. After constructing a hydrophobic layer on the internal microstructure of the paper, all components of the electrode material and the electrolyte are vertically distributed in a designated area of ​​the paper. The obtained paper supercapacitor has a thin size, high flexibility and high energy density.

[0006] The present invention is achieved through the following technical solutions:

[0007] A paper supercapacitor uses paper as a support for the supercapacitor. After a hydrophobic layer is constructed on the internal microstructure of the paper, all components including a gel electrolyte, a positive electrode active material, a negative electrode active material, a positive electrode current collector and a negative electrode current collector are vertically distributed in a designated area of ​​the paper to obtain a paper supercapacitor.

[0008] Furthermore, the effective distribution area of ​​the positive electrode active material and the negative electrode active material is smaller than the area of ​​the paper sheet, and the thickness on the paper sheet is 5-10 μm and 5-10 μm respectively; the positive electrode collector and the negative electrode collector are respectively distributed on the surface of the positive electrode active material and the negative electrode active material, and the effective area is smaller than the area of ​​the paper sheet.

[0009] A method for preparing the paper supercapacitor as described above comprises the following steps:

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

[0011] (2) Introducing gel electrolyte: soaking the modified paper in gel electrolyte. After soaking, take out the paper and perform a second curing to obtain paper gel electrolyte.

[0012] (3) Spraying active material slurry: The positive electrode active material slurry is applied to one side of the paper gel electrolyte by subsonic spraying, and then a third curing is performed; then the negative electrode active material slurry is applied to the other side of the paper gel electrolyte by subsonic spraying, and at the same time, 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 180 to 300 m / s, and the spraying thickness is 5 to 10 μm. After the spraying is completed, a fourth curing is performed, and the paper supercapacitor is obtained after being placed in a hydrophobic solution and plastic-sealed.

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

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

[0015] Furthermore, in step (2), the modified paper sheet is immersed in the gel electrolyte for 100 to 120 minutes; and the second curing is drying at 50 to 80° C. for 40 to 60 minutes.

[0016] Furthermore, in step (3), the positive electrode active material is composed of active material A, conductive agent and binder in a mass ratio of 1 to 4:0.5 to 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-manganese-rich material; the conductive agent is one or more of activated carbon, graphite, graphene, black scale, carbon nanotubes, conductive graphite, acetylene black, Ketjen black and bio-derived carbon;

[0017] The negative electrode active material is composed of an active material B and a binder mixed in a mass ratio of 8 to 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 nanotubes, conductive graphite, acetylene black, Ketjen black and bio-derived carbon.

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

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

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

[0021] Preparation principle of the paper supercapacitor of the present invention:

[0022] Free water molecules can decompose the microstructure inside the paper. The present invention makes full use of the pores in the paper and introduces a hydrophobic layer into the pores of the paper. Most of the paper is composed of cellulose, and the cellulose molecular chain has many hydroxyl groups, and the polymers in the hydrophobic solution, such as polyvinylidene fluoride hexafluoropropylene, contain a large number of CF bonds in the molecular chain. Hydrogen bonds or van der Waals forces are generated between the hydroxyl groups and the CF bonds to form a tight bond, which plays a role in isolating free water and preventing the destruction of the internal microstructure of the paper. And with the help of the CF bonds on the surface of the polymer, the gel electrolyte is attracted into the gap through the action of electrostatic attraction. Due to the volatilization of the solvent during the curing process, the electrolyte shrinks, and the electrolyte leaves some space on the surface of the paper. The configured positive and negative active slurries are applied to both sides of the paper by subsonic spraying, and the active particle speed and spraying thickness during 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 supercapacitor is plastic-sealed.

[0023] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0024] 1. The present invention integrates all components of the supercapacitor into a designated area of ​​a piece of paper, reduces the thickness of the device, and improves the energy density of the supercapacitor at the same size. The present invention makes full use of the porous structure of the paper, and through the process of soaking in hydrophobic gel, constructs a hydrophobic barrier on the microscopic surface inside the paper to prevent water molecules or other solvent molecules from decomposing and destroying the microscopic structure inside the paper, which is convenient for pattern design and heterogeneous structure production, reduces device components, and reduces the thickness of the device.

[0025] 2. The working voltage window of the paper supercapacitor of the present invention 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 supercapacitor of the present invention has a higher voltage window and can effectively improve the energy density. At the same time, at a voltage of 2.5-4.2V, the capacity retention rate of the paper supercapacitor of the present invention is increased to 93.47% after 5000 cycles of 10C current intensity, indicating that the paper supercapacitor has good cycle stability.

[0026] 3. Traditional supercapacitors are typical sandwich structures, which are assembled from positive electrodes, negative electrodes, electrolytes, and diaphragms, and the devices are relatively thick. However, the present invention first guides the electrolyte to the middle of the paper sheet, and the electrolyte shrinks due to the evaporation of the solvent, leaving some space between the electrolyte and the paper sheet surface, and then the positive and negative electrode active materials and the positive and negative electrode current collectors are sprayed on the paper sheet surface to form an integrated supercapacitor. Compared with traditional supercapacitors, the present invention makes full use of the gaps in the paper sheet and can effectively reduce the thickness of the device.

[0027] 4. The paper sheet used in the present invention has extremely strong flexibility, which provides the possibility for energy storage devices with different components and has strong shape adaptability. The present invention uses slurry to make positive and negative current collectors, which not only play the role of electronic pathways but also play a packaging role, showing dual functions. At the same time, it saves device structure 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 This is a cycle performance diagram of the paper supercapacitor of Example 1 in the voltage range 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 range of 2.5-4.0V and 2.5-4.2V. DETAILED DESCRIPTION

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

[0034] Example 1

[0035] Preparation of paper supercapacitors:

[0036] (1) Construction of hydrophobic layer: Dissolve 1 g of polyvinylidene fluoride hexafluoropropylene in 10 mL of N,N-dimethylamide 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 a modified paper sheet;

[0037] (2) Introducing gel electrolyte: Mix 1.0 g of polyvinyl alcohol powder and 20 mL of ethanol, and stir magnetically until the polyvinyl alcohol is completely dissolved to obtain a polyvinyl alcohol solution. Dissolve 0.5 g of tetraethylammonium tetrafluoroborate in 5 mL of acetonitrile and stir until uniform to obtain a salt solution. Mix the polyvinyl alcohol solution and the salt solution, and add 0.5 g of 2-methyltetrahydrofuran, and stir magnetically until the solution is fully mixed to obtain a gel electrolyte. Soak the modified paper in the gel electrolyte for 120 minutes, then perform a second curing, and dry at 60°C for 60 minutes to obtain a paper gel electrolyte.

[0038] (3) Spraying active material slurry: Stir and mix 0.5 mg of nickel-cobalt-manganese material, 0.2 mg of activated carbon and 0.3 mg of polyvinylidene fluoride to obtain a positive electrode active material slurry. Stir and mix 2.5 mg of activated carbon and 0.3 mg of polyvinylidene fluoride to obtain a negative electrode active material slurry. Dissolve 2.0 g of hard carbon and 0.5 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 applied to one side of the paper gel electrolyte by subsonic spraying, and then cured for the third time and dried at 60°C for 50 minutes; then the negative electrode active material slurry is applied to 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 200m / s, and the spraying thickness is 5μm. After spraying, it is cured for the fourth time, dried at 100°C for 120min, and sealed in a hydrophobic solution for 20min to obtain a paper supercapacitor. The preparation process diagram is shown in the figure. Figure 1 shown.

[0039] Example 2

[0040] Preparation of paper supercapacitors:

[0041] (1) Construction of hydrophobic layer: Dissolve 2 g of polyvinylidene fluoride and 3 g of vinylidene fluoride hexafluoropropylene in 10 mL of N,N-dimethylamide and stir at 60°C for 60 min to obtain a hydrophobic solution. Soak clean draft paper in the hydrophobic solution for 40 min, then perform the first curing, and dry it in a forced air drying oven at 100°C for 40 min to obtain a modified paper sheet;

[0042] (2) Introducing gel electrolyte: Mix 1.5g of polyvinyl alcohol powder, 0.5g of polymethyl methacrylate and 20mL of ethanol, and stir magnetically until the polymer is completely dissolved to obtain a polymer solution. Dissolve 0.5g of lithium hexafluorophosphate and 0.5g of sulfate in 10mL of acetonitrile and stir until uniform to obtain a salt solution. Mix the polymer solution and the salt solution, add 0.5g of p-phenylenediamine, and stir magnetically until the solution is fully mixed to obtain a gel electrolyte. Soak the modified paper in the gel electrolyte for 100 minutes, then perform a second curing, and dry at 80°C for 40 minutes to obtain a paper gel electrolyte.

[0043] (3) Spraying active material slurry: 0.5 mg of nickel-manganese-rich material, 0.5 mg of nickel-cobalt-aluminum material, 0.4 mg of graphene and 0.5 mg of polyethylene oxide were stirred and mixed to obtain a positive electrode active material slurry. 3 mg of silicon carbon and 0.3 mg of polyethylene oxide were stirred and mixed to obtain a negative electrode active material slurry. 1.0 g of tin paste, 0.5 g of copper-silver paste 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 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 40 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 250m / s, and the spraying thickness is 5μm. After spraying, it is cured for the fourth time, dried at 120°C for 100min, and sealed in a hydrophobic solution for 15min to obtain a paper supercapacitor.

[0044] Example 3

[0045] Preparation of paper supercapacitors:

[0046] (1) Construction of hydrophobic layer: 3 g of polytetrafluoroethylene was dissolved in 10 mL of N, N-dimethylamide 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, then cured for the first time and dried in a forced air drying oven at 100°C for 40 min to obtain a modified paper sheet;

[0047] (2) Introducing gel electrolyte: Mix 1.5 g of polyacrylonitrile and 20 mL of ethanol, and stir magnetically until the polyacrylonitrile is completely dissolved to obtain a polyacrylonitrile solution. Dissolve 0.5 g of tetraethylammonium tetrafluoroborate in 5 mL of acetonitrile and stir until uniform to obtain a salt solution. Mix the polyacrylonitrile solution and the salt solution, and add 0.2 g of methyl formate and 0.3 g of ethyl isobutyl sulfone, and stir magnetically until the solution is fully mixed to obtain a gel electrolyte. Soak the modified paper in the gel electrolyte for 120 minutes, then perform a second curing, and dry at 50°C for 60 minutes to obtain a paper 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 is coated on one side of the paper gel electrolyte by subsonic spraying, and then cured for the third time and dried at 50°C for 60 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 300m / s, and the spraying thickness is 5μm. After spraying, it is cured for the fourth time, dried at 120°C for 100min, and sealed in a hydrophobic solution for 20min to obtain a paper supercapacitor.

[0049] Example 4

[0050] Preparation of paper supercapacitors:

[0051] (1) Construction of hydrophobic layer: Dissolve 7 g of polyvinylidene fluoride hexafluoropropylene in 10 mL of N,N-dimethylamide 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 100°C for 40 min to obtain a modified paper sheet;

[0052] (2) Introduction of gel electrolyte: Mix 2.0 g of polymethyl methacrylate and 20 mL of ethanol, and stir magnetically until the polymethyl methacrylate is completely dissolved to obtain a polymethyl methacrylate solution. Dissolve 1.0 g of N, N-dimethylpyrrolidinium tetrafluoroborate in 5 mL of acetonitrile and stir until uniform to obtain a salt solution. Mix the polymethyl methacrylate solution and the salt solution, and add 0.5 g of methyl formate, and stir magnetically until the solution is fully mixed to obtain a gel electrolyte. Soak the modified paper in the gel electrolyte for 100 minutes, then perform a second curing, and dry at 80°C for 40 minutes to obtain a paper gel electrolyte.

[0053] (3) Spraying active material slurry: 1.0 mg hard carbon, 0.2 mg black scale, 0.2 mg conductive graphite, 0.4 mg acetylene black and 0.5 mg polyethylene oxide were stirred and mixed to obtain positive electrode active material slurry. 2.5 mg soft carbon, 0.5 mg Ketjen black and 0.3 mg methyl cellulose were stirred and mixed to obtain negative electrode active material slurry. 2.0 g mesophase carbon microspheres, 1.0 g silica, 0.2 g polyethylene oxide and 0.3 g polyvinylidene fluoride were dissolved in 10 mL of anhydrous ethanol and stirred until uniform to obtain positive electrode collector and negative electrode 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 120min, and sealed in a hydrophobic solution for 15min to obtain a paper supercapacitor.

[0054] Example 5

[0055] Preparation of paper supercapacitors:

[0056] (1) Construction of hydrophobic layer: 5 g of polyvinylidene fluoride hexafluoropropylene and 5 g of polytetrafluoroethylene were dissolved in 10 mL of N, N-dimethylamide and stirred at 60°C for 60 min to obtain a hydrophobic solution. Clean rice paper was soaked in the hydrophobic solution for 40 min, then cured for the first time, and dried in a forced air drying oven at 80°C for 50 min to obtain a modified paper sheet;

[0057] (2) Introducing gel electrolyte: Mix 1.0g polyvinyl alcohol, 1.0g polyacrylonitrile and 25mL ethanol, and stir magnetically until the polymer is completely dissolved to obtain a polymer solution. Dissolve 0.5g of bipyrrolidine spirocyclic ammonium salt and 0.3g potassium hydroxide in 8mL acetonitrile and stir until uniform to obtain a salt solution. Mix the polymer solution and the salt solution, and add 0.2g of propylene sulfite and 0.3g of methyl formate, and stir magnetically until the solution is fully mixed to obtain a gel electrolyte. Soak the modified paper in the gel electrolyte for 110min, then perform a second curing, and dry at 80°C for 45min to obtain a paper gel electrolyte.

[0058] (3) Spraying active material slurry: Stir and mix 1.0 mg of nickel-cobalt-aluminum material, 0.5 mg of carbon nanotubes, 0.3 mg of bio-derived carbon and 0.5 mg of methyl cellulose to obtain a positive electrode active material slurry. Stir and mix 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 to obtain a negative electrode active material slurry. Dissolve 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 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 70°C for 60 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 300m / s, and the spraying thickness is 5μm. After spraying, it is cured for the fourth time, dried at 90°C for 120 minutes, and sealed in a hydrophobic solution for 20 minutes to obtain a paper supercapacitor.

[0059] Example 6

[0060] Preparation of paper supercapacitors:

[0061] (1) Constructing a hydrophobic layer: dissolve 2 g of polyvinylidene fluoride in 10 mL of N,N-dimethylamide and stir at 60°C for 60 min to obtain a hydrophobic solution. Soak clean toilet paper in the hydrophobic solution for 60 min, then perform the first curing, and dry it in a forced air drying oven at 100°C for 40 min to obtain a modified paper sheet;

[0062] (2) Introducing gel electrolyte: Mix 1.5g of polyvinyl alcohol powder and 20mL of ethanol, and stir magnetically until the polyvinyl alcohol is completely dissolved to obtain a polyvinyl alcohol solution. Dissolve 0.5g of lithium hexafluorophosphate and 0.5g of sodium carbonate in 10mL of acetonitrile and stir until uniform to obtain a salt solution. Mix the polyvinyl alcohol solution and the salt solution, add 0.5g of 2-methyltetrahydrofuran, and stir magnetically until the solution is fully mixed to obtain a gel electrolyte. Soak the modified paper in the gel electrolyte for 120 minutes, then perform a second curing, and dry at 60°C for 60 minutes to obtain a paper 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 slurry, 1.0 g of mesophase carbon microspheres 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 is coated on one side of the paper gel electrolyte by subsonic spraying, and then cured for the third time and dried at 60°C for 50 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 200m / s, and the spraying thickness is 10μm. After spraying, it is cured for the fourth time, dried at 100°C for 120min, and sealed in a hydrophobic solution for 15min to obtain a paper supercapacitor.

[0064] Comparative Example 1

[0065] Taking the article "All-printed paper based surface mountable supercapacitors" as a comparative example, the article discloses a fully printed paper-based surface mount supercapacitor, which is manufactured by patching on the surface of a paper base through screen printing and template printing processes. The supercapacitor was tested for cyclic voltammetry (CV curve), and the test results showed that at 20mV / s, the supercapacitor had an operating voltage window of 0 to 2.5V.

[0066] Material performance analysis

[0067] The energy density of a supercapacitor is closely related to its operating voltage window. Energy density E = 1 / 2 × C (capacitance) × V (voltage) 2Therefore, the energy density can be directly increased by increasing the voltage window. The paper supercapacitor in Example 1 was tested. Figure 2 The CV curves of paper supercapacitors in the voltage range of 2.5-4.0V and 2.5-4.2V at a scan rate of 5mV / s. Figure 2 It can be seen that the increase in the cut-off upper limit voltage causes the area of ​​the rectangular CV curve to increase accordingly. There is no obvious change in the shape of the CV curve of the cathode composite material, and there is no obvious redox peak in the CV curve, indicating that the paper supercapacitor has both capacitor and battery behavior and good reversibility.

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

[0069] Figure 4 and Figure 5 These are the cycle performance and rate performance diagrams of paper supercapacitors in the voltage range of 2.5-4.0V and 2.5-4.2V, respectively. It can be seen that when the voltage range is 2.5-4.0V, after 5000 cycles at a current intensity of 10C, the capacity retention rate is 91.92%. When the voltage cutoff upper limit is increased to 4.2V, it can be seen that the capacity retention rate is increased to 93.47% after 5000 cycles, indicating that the increase in the voltage cutoff upper limit does not reduce its cycle stability. On the contrary, there is a slight improvement compared to the cycle stability in the voltage range of 2.5-4.2V, indicating that the paper supercapacitor can still maintain good cycle stability performance in the voltage range of 2.5-4.2V at low rates. As the current intensity gradually increases, the capacity of the prepared lithium ion capacitor shows a slow downward trend. When the capacity is 2.5-4.2V, at current densities of 7C and 10C, the capacity retention rate is slightly lower than the upper limit cutoff voltage of 4V. The corresponding capacity at 10C is basically close to the capacity of 2.5-4.0V, but when the current intensity is restored to 1C, the capacity of both can be restored to near the initial level, indicating that the upper limit cutoff stable voltage of the system can be increased to 4.2V, which enables paper supercapacitors to play a higher voltage advantage in the field of high-power long cycles.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A paper supercapacitor, characterized in that: Using paper as the support of the supercapacitor, after constructing a hydrophobic layer on the internal microstructure of the paper, all components of the gel electrolyte, positive electrode active material, negative electrode active material, positive electrode current collector and negative electrode current collector are vertically distributed in the designated area of ​​the paper to obtain a paper supercapacitor.

2. The paper supercapacitor according to claim 1, characterized in that: The effective distribution area of ​​the positive electrode active material and the negative electrode active material is smaller than the area of ​​the paper sheet, and the thickness on the paper sheet is 5-10 μm and 5-10 μm respectively; the positive electrode collector and the negative electrode collector are respectively distributed on the surface of the positive electrode active material and the negative electrode active material, and the effective area is smaller than the area of ​​the paper sheet.

3. A method for preparing a paper supercapacitor as claimed in claim 1 or 2, characterized in that: The following steps are involved: (1) constructing a hydrophobic layer: soaking a paper sheet in a hydrophobic solution with a concentration of 0.1 to 1.0 g / mL for 40 to 60 minutes, taking out the paper sheet and performing a first curing to obtain a modified paper sheet; the raw material used in the hydrophobic solution is one or more of polyvinylidene fluoride, polyvinylidene fluoride hexafluoropropylene and polytetrafluoroethylene; (2) Introducing gel electrolyte: soaking the modified paper in gel electrolyte. After soaking, take out the paper and perform a second curing to obtain paper gel electrolyte. (3) Spraying active material slurry: The positive electrode active material slurry is applied to one side of the paper gel electrolyte by subsonic spraying, and then a third curing is performed; then the negative electrode active material slurry is applied to the other side of the paper gel electrolyte by subsonic spraying, and at the same time, 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 180 to 300 m / s, and the spraying thickness is 5 to 10 μm. After the spraying is completed, a fourth curing is performed, and the paper supercapacitor is obtained after being placed in a hydrophobic solution and plastic-sealed.

4. The method for preparing a paper supercapacitor according to claim 3, characterized in that: In step (1), the paper sheet is one or more of A4 paper, draft paper, toilet paper and rice paper; and the first curing is drying at 60-100° C. for 40-60 minutes.

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

6. The method for preparing a paper supercapacitor according to claim 3, characterized in that: In step (2), the modified paper sheet is immersed in the gel electrolyte for 100 to 120 minutes; and the second curing is drying at 50 to 80° C. for 40 to 60 minutes.

7. The method for preparing a paper supercapacitor according to claim 3, characterized in that: In step (3), the positive electrode active material is composed of active material A, conductive agent and binder in a mass ratio of 1 to 4:0.5 to 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-manganese-rich material; the conductive agent is one or more of activated carbon, graphite, graphene, black scale, carbon nanotubes, conductive graphite, acetylene black, Ketjen black and bio-derived carbon; The negative electrode active material is composed of an active material B and a binder mixed in a mass ratio of 8 to 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 nanotubes, conductive graphite, acetylene black, Ketjen black and bio-derived carbon.

8. The method for preparing a paper supercapacitor according to claim 3, characterized in that: In step (3), the positive electrode current collector and the negative electrode current collector are both composed of a conductive agent and a binder in a mass ratio of 3 to 6:1; the conductive agent is one or more of copper paste, silver paste, tin paste, copper-silver paste, hard carbon, soft carbon, mesophase carbon microspheres, silicon, silicon carbon and silicon oxygen.

9. The method for preparing a paper supercapacitor according to claim 7 or 8, characterized in that: 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, characterized in that: In step (3), the third curing is drying at 50-80° C. for 40-60 min; the fourth curing is drying at 80-120° C. for 100-120 min; and the plastic sealing time is 15-20 min.

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