Ni3S2 / V2O5 / WSC composite material, printing flexible supercapacitor and preparation method thereof

Abstract

The invention discloses a Ni3S2 / V2O5 / WSC composite material, a printing flexible supercapacitor and a preparation method thereof, and belongs to the technical field of supercapacitors. The method comprises the following steps: S1, performing first high-temperature carbonization on a walnut diaphragm in an inert atmosphere to obtain walnut diaphragm carbon, then adding an activating agent, and performing second high-temperature carbonization in the inert atmosphere after activation to obtain walnut diaphragm derived carbon (WSC); s2, dispersing the walnut diaphragm derived carbon obtained in the step S1 into deionized water, adding nickel salt and vanadium salt, uniformly stirring, performing first hydrothermal reaction, and washing and drying to obtain a precursor; and S3, dispersing the precursor obtained in the step S2 in deionized water, adding a sulfur source, uniformly stirring, carrying out a second hydrothermal reaction, and cleaning and drying to obtain the Ni3S2 / V2O5 / WSC composite material. The composite material prepared by the invention has high specific capacitance characteristic and excellent cycling stability, and is suitable for flexible supercapacitors.

Description

Technical Field

[0001] The present invention relates to the technical field of supercapacitors, and particularly to a Ni3S2 / V2O5 / WSC composite material, a printed flexible supercapacitor and a preparation method thereof. Background Art

[0002] Supercapacitors are efficient energy storage devices and have broad application prospects in fields such as flexible electronic devices and wearable devices due to their high power density, long cycle life and fast charge-discharge characteristics. However, the electrode materials of traditional supercapacitors have problems such as low specific capacitance and poor mechanical flexibility, which limit their application in flexible devices. Therefore, how to improve the mechanical properties and electrochemical properties of supercapacitor electrode materials has attracted extensive attention of researchers.

[0003] In recent years, transition metal sulfides (such as Ni3S2) and transition metal oxides (such as V2O5) have received extensive attention due to their high theoretical specific capacitance and excellent electrochemical properties. However, Ni3S2 has low conductivity, resulting in poor rate performance and cycling performance. The conductivity and stability of single materials are poor and it is difficult to meet the actual application requirements. At present, some researchers have proposed using transition metal sulfide / transition metal oxide composite materials as electrode materials for supercapacitors. For example, Chinese Patent CN107086132A discloses a flower-like vanadium pentoxide / nickel trisulfide nanosheet and a preparation method and application thereof. The preparation method includes: 1) pretreating nickel foam; 2) under closed conditions, performing a solvothermal reaction on thiourea, V2O5 and the pretreated nickel foam in a solvent to obtain a flower-like vanadium pentoxide / nickel trisulfide nanosheet. The flower-like vanadium pentoxide / nickel trisulfide nanosheet has excellent capacitance and cycle stability, and thus can be used as an electrode material for supercapacitors or lithium-ion batteries. At the same time, the preparation method has the advantages of controllable product size and morphology. However, the cycle performance of this material is poor, only undergoing 2500 cycles.

[0004] Walnut septum-derived carbon (WSC) has a high specific surface area, excellent conductivity and stable cycle performance, and is suitable as an electrode material for supercapacitors. However, for a supercapacitor using only walnut septum biomass activated carbon as an electrode material, its specific capacitance is low and its power density is also low.

[0005] Therefore, developing a composite material based on Ni3S2 / V2O5 / WSC and applying it to a printed flexible supercapacitor has important scientific significance and application value. Summary of the Invention

[0006] Aiming at the problems of low specific capacitance and poor cycle stability existing in the electrode materials of supercapacitors in the prior art, one of the purposes of the present invention is to provide a preparation method of Ni3S2 / V2O5 / WSC composite materials. The composite materials prepared by the present invention have high specific capacitance characteristics and excellent cycle stability.

[0007] The above object of the present invention is achieved by the following technical solutions:

[0008] A preparation method of Ni3S2 / V2O5 / WSC composite materials includes the following steps:

[0009] S1. Place the walnut diaphragm under an inert atmosphere for the first high-temperature carbonization to obtain walnut diaphragm carbon, then add an activator, and after activation, perform the second high-temperature carbonization under an inert atmosphere to obtain walnut diaphragm-derived carbon (WSC);

[0010] S2. Disperse the walnut diaphragm-derived carbon obtained in step S1 in deionized water, add nickel salt and vanadium salt, stir evenly and then perform the first hydrothermal reaction. After washing and drying, obtain a precursor;

[0011] S3. Disperse the precursor obtained in step S2 in deionized water, add a sulfur source, stir evenly and then perform the second hydrothermal reaction. After cleaning and drying, obtain the Ni3S2 / V2O5 / WSC composite materials.

[0012] The present invention combines the activation carbonization method and the two-step hydrothermal method. First, the activation carbonization method is used to prepare walnut diaphragm-derived carbon (WSC) with a three-dimensional porous structure. The walnut diaphragm itself has a rich natural pore structure, and through activation carbonization, a hierarchical porous carbon material can be formed, which is an ideal composite material substrate. Then, the two-step hydrothermal method is used to grow V2O5 nanosheets and Ni3S2 nanoparticles on the surface of WSC in sequence, and finally, the Ni3S2 / V2O5 / WSC ternary composite material is prepared. Among them, the introduced Ni3S2 and V2O5 can produce a synergistic effect, significantly enhancing the electrochemical performance of the material and endowing the material with high specific capacitance characteristics; while WSC not only serves as a conductive substrate to improve the conductivity of the material, but its unique three-dimensional porous structure also provides sufficient growth space and ion transport channels for the active substances, effectively improving the morphology structure of the material. Its porous structure and surface properties also help to improve the specific capacitance of the material, making the composite material have high specific capacitance, excellent rate performance and long cycle stability.

[0013] Preferably, the walnut diaphragm is first cleaned before use, dried and then ground into powder. Through cleaning, the adhered pollutants and dirt can be removed. Through drying, the decay of the walnut diaphragm can be prevented, and the service time of the walnut diaphragm can be extended; by grinding the dried walnut diaphragm into powder, the walnut diaphragm can be heated evenly during carbonization.

[0014] Preferably, the temperature of the first high-temperature carbonization is 400-600 °C, and the time is 1-4 h.

[0015] Preferably, the temperature of the second high-temperature carbonization is 500-700 °C, and the time is 1-3 h.

[0016] Preferably, the activator includes at least one of KOH, ZnCl2, H3PO4, and H2SO4, and the mass ratio of the activator to the walnut septum carbon is (0.5-3):1.

[0017] Preferably, the nickel salt includes at least one of Ni(NO3)2•6H2O, NiCl2•6H2O, and NiSO4•6H2O, and / or the vanadium salt includes VCl3 and / or NH4VO3.

[0018] Preferably, the molar ratio of the nickel salt to the vanadium salt is (1-2):(1-3).

[0019] Preferably, the mass ratio of the walnut septum-derived carbon to the total mass of the nickel salt and the vanadium salt is 1:(20-100).

[0020] Preferably, the temperature of the first hydrothermal reaction is 100-180 °C, and the time is 6-10 h.

[0021] Preferably, the temperature of the second hydrothermal reaction is 100-140 °C, and the time is 6-10 h.

[0022] Preferably, the mass ratio of the precursor to the sulfur source is 1:(0.5-2).

[0023] Preferably, the sulfur source is Na2S•9H2O or K2S.

[0024] Another object of the present invention is to provide a printed flexible supercapacitor, using the Ni3S2 / V2O5 / WSC composite material prepared by the above method as the positive electrode material, and / or using the walnut septum-derived carbon (WSC) prepared by the above method as the negative electrode material.

[0025] Still another object of the present invention is to provide a method for preparing the printed flexible supercapacitor, including the following steps:

[0026] R1. Mix the Ni3S2 / V2O5 / WSC composite material and the walnut septum-derived carbon (WSC) with a conductive agent and a binder respectively to obtain Ni3S2 / V2O5 / WSC positive electrode ink and WSC negative electrode ink;

[0027] R2. The positive electrode ink and the negative electrode ink are respectively coated on the flexible substrate coated with silver paste by screen printing, and after drying, a flexible positive electrode and a flexible negative electrode are obtained;

[0028] R3. The flexible positive electrode, the flexible negative electrode and the gel electrolyte are assembled into a printed flexible supercapacitor.

[0029] Aiming at the problems of excessive rigidity and difficulty in bending and carrying of existing energy storage devices, the present invention proposes a flexible supercapacitor with high energy density and excellent anti-bending ability. The core innovation of this supercapacitor lies in the adoption of screen printing technology to prepare the positive electrode material Ni3S2 / V2O5 / WSC and the negative electrode material WSC into printable inks respectively, and accurately print them on the flexible substrate through the screen printing process. After printing, the flexible positive and negative electrodes are combined with the gel electrolyte to form a complete supercapacitor structure. Through this design, while maintaining high energy density, this supercapacitor can withstand multiple bends, twists and even stretches, and is suitable for fields with high requirements for portability and flexibility such as wearable devices and flexible electronic devices.

[0030] Preferably, the binder includes at least one of ethyl cellulose, LA133, and resin, and the conductive agent includes acetylene black and / or carbon black.

[0031] Preferably, the gel electrolyte is prepared by the following method: dissolving the gel material in deionized water, pouring it into a mold and curing to obtain a dry gel, and then soaking the dry gel in the electrolyte and swelling to obtain the gel electrolyte.

[0032] More preferably, the gel material includes at least one of PVA, PAM, and PNIPAM, and the electrolyte includes KOH solution and / or Na2SO4 solution.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] (1) The present invention prepares walnut diaphragm-derived carbon (WSC) by the activation carbonization method and prepares the Ni3S2 / V2O5 / WSC ternary composite material by the two-step hydrothermal method. Among them, Ni3S2 and V2O5 can produce a synergistic effect, significantly enhancing the electrochemical performance of the material and endowing the material with high specific capacitance characteristics; WSC improves the conductivity of the material and improves the cycle stability of the composite material. The Ni3S2 / V2O5 / WSC composite material prepared by the present invention has high specific capacitance characteristics and excellent cycle stability.

[0035] (2) The Ni3S2 / V2O5 / WSC composite material prepared by the present invention has a specific capacitance of up to 3786 F g -1 at a current density of 1 A g -1After 10,000 cycles, the capacity retention rate is 92.1%.

[0036] (3)The walnut septum-derived carbon (WSC) material prepared by the present invention has a specific capacitance of 261 F g -1 at a current density of 1 A g -1 . After 20,000 cycles, the Coulomb efficiency is 99.8% and the capacity retention rate is 99.7%. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 SEM image of the Ni3S2 / V2O5 / WSC composite material prepared by the present invention;

[0038] Figure 2 GCD curves of the Ni3S2 / V2O5 / WSC composite materials prepared in Examples 1 to 3, the Ni3S2 / V2O5 composite material prepared in Comparative Example 1, and the Ni3S2 / V2O5 / walnut shell carbon composite material in Comparative Example 2;

[0039] Figure 3 Specific capacitance diagrams of the Ni3S2 / V2O5 / WSC composite materials prepared in Examples 1 to 3, the Ni3S2 / V2O5 composite material prepared in Comparative Example 1, and the Ni3S2 / V2O5 / walnut shell carbon composite material in Comparative Example 2 at different current densities;

[0040] Figure 4 Cycling performance diagrams of the Ni3S2 / V2O5 / WSC composite material prepared in Example 1, the Ni3S2 / V2O5 composite material prepared in Comparative Example 1, and the Ni3S2 / V2O5 / walnut shell carbon composite material in Comparative Example 2;

[0041] Figure 5 GCD curves of the walnut septum-derived carbon (WSC) prepared in Example 1 and the walnut shell biomass charcoal prepared in Comparative Example 2;

[0042] Figure 6 Cycling performance diagram of the walnut septum-derived carbon (WSC) prepared in Example 1;

[0043] Figure 7 Schematic structural diagram of the printed flexible supercapacitor of the present invention;

[0044] Figure 8 Cycling performance diagram of the Ni3S2 / V2O5 / WSC / / WSC printed flexible supercapacitor prepared in Example 5;

[0045] Figure 9 Practical application diagram of the Ni3S2 / V2O5 / WSC / / WSC printed flexible supercapacitor prepared in Example 5. Detailed implementation mode

[0046] The technical solutions of the present invention will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0047] The embodiment of the present invention provides a preparation method of Ni3S2 / V2O5 / WSC composite material, which includes the following steps:

[0048] S1. Place the walnut septum under an inert atmosphere for the first high-temperature carbonization to obtain walnut septum carbon, then add an activator, and after activation, perform the second high-temperature carbonization under an inert atmosphere to obtain walnut septum-derived carbon (WSC);

[0049] S2. Disperse the walnut septum-derived carbon obtained in step S1 in deionized water, add nickel salt and vanadium salt, stir evenly and then perform the first hydrothermal reaction, wash and dry to obtain a precursor;

[0050] S3. Disperse the precursor obtained in step S2 in deionized water, add a sulfur source, stir evenly and then perform the second hydrothermal reaction, wash and dry to obtain the Ni3S2 / V2O5 / WSC composite material.

[0051] In step S1, the temperature of the first high-temperature carbonization can be 400-600°C, and the time is 1-4h; the temperature of the second high-temperature carbonization can be 500-700°C, and the time is 1-3h.

[0052] The activator is selected from at least one of KOH, ZnCl2, H3PO4, and H2SO4, and the mass ratio of the activator to the walnut septum carbon can be (0.5-3):1.

[0053] In step S2, there are various materials available for nickel salt and vanadium salt, and which one to use specifically can be determined according to actual preparation needs. For example, as an example, the nickel salt can be at least one of Ni(NO3)2•6H2O, NiCl2•6H2O, and NiSO4•6H2O, and the vanadium salt can be VCl3 and / or NH4VO3. The dosages of the nickel salt and the vanadium salt can be determined according to actual preparation needs. For example, as an example, the molar ratio of the nickel salt to the vanadium salt is (1-2):(1-3).

[0054] The mass ratio of the walnut septum-derived carbon to the total mass of the nickel salt and the vanadium salt can be 1:(20-100).

[0055] The temperature of the first hydrothermal reaction can be 100-180°C, and the time is 6-10h.

[0056] In step S3, there are various materials available for the sulfur source, and which one to use specifically can be determined according to the actual preparation requirements. For example, as an example, the sulfur source is Na2S•9H2O or K2S. The amounts of the precursor and the sulfur source can be determined according to the actual preparation requirements. For example, as an example, the mass ratio of the precursor to the sulfur source can be 1:(0.5 - 2).

[0057] Example 1

[0058] This example provides a method for preparing a Ni3S2 / V2O5 / WSC composite material, including the following steps:

[0059] S1. Rinse a certain amount of walnut septum material with distilled water multiple times to remove the adhered contaminants and dirt, and dry it in a hot air oven at 65°C for 12 h. Grind the dried walnut septum to make a powder. Take an appropriate amount of the dried walnut septum powder and place it in a quartz boat, then put it into a tubular furnace. Under an argon (Ar) atmosphere, heat it at a heating rate of 5°C / min to 600°C for 2 h to obtain the original walnut septum carbon, denoted as SC;

[0060] After grinding the original walnut septum carbon, add it to 50 mL of water with KOH at a mass ratio of 1:2.5, slowly stir for 1 h, then place the mixture in a vacuum oven and dry it at 60°C for 12 h. Then heat it at 600°C for 1 h in an Ar atmosphere. Collect the obtained sample, wash it with 1M HCl solution until the pH of the filtrate is neutral, then rinse it with deionized water several times to remove the residual KOH and impurities. Finally, dry it at 80°C for 5 h and grind it into a fine powder to obtain the walnut septum-derived carbon, denoted as WSC, for standby;

[0061] S2. Dissolve 0.36 g of Ni(NO3)2•6H2O, 0.62 g of VCl3, and 1.70 mL of DMF in 12 mL of ethanol solution, and stir at room temperature for 1 h to obtain a precursor solution. Then put 0.02 g of WSC into the precursor solution and soak it for 30 min. After sufficient soaking, transfer the whole to a stainless steel autoclave with a polytetrafluoroethylene lining. Seal the autoclave and heat it at 150°C for 9 h. After cooling to room temperature, wash the powder with deionized water and ethanol, and dry it under vacuum at 65°C for 24 h. Obtain the precursor;

[0062] S3. Take 0.34 g of the precursor obtained in step S2 and mix it with 0.61 g of Na2S•9H2O in 30 mL of deionized water, and transfer it to the autoclave. Seal the autoclave and heat it at 100°C for 6 h. After cooling to room temperature, thoroughly wash the final product with deionized water and ethanol, and dry it under vacuum at 60°C for 12 h to obtain Ni3S2 / V2O5 / WSC.

[0063] Example 2

[0064] The preparation method of the Ni3S2 / V2O5 / WSC composite material in this example is basically the same as that in Example 1, except that in step S2, the mass of walnut diaphragm-derived carbon (WSC) is 0.01 g.

[0065] Example 3

[0066] The preparation method of the Ni3S2 / V2O5 / WSC composite material in this example is basically the same as that in Example 1, except that in step S2, the mass of walnut diaphragm-derived carbon (WSC) is 0.04 g.

[0067] Example 4

[0068] This example provides a preparation method of a Ni3S2 / V2O5 / WSC composite material, including the following steps:

[0069] S1. Rinse a certain amount of walnut diaphragm material with distilled water multiple times to remove the adhered contaminants and dirt, and dry it in a hot air oven at 65 °C for 12 h. Grind the dried walnut diaphragm to make powder. Take an appropriate amount of the dried walnut diaphragm powder and place it in a quartz boat, then put it into a tube furnace. Under an argon (Ar) atmosphere, heat it at a heating rate of 5 °C / min at 400 °C for 4 h to obtain the original walnut diaphragm carbon, denoted as SC;

[0070] After grinding the original walnut diaphragm carbon, add it to 50 mL of water with KOH in a mass ratio of 1:1, slowly stir for 1 h, then place the mixture in a vacuum oven and dry it at 60 °C for 12 h. Then heat it at 500 °C for 3 h in an Ar atmosphere. Collect the obtained sample, wash it with 1 M HCl solution until the pH of the filtrate is neutral, then rinse it with deionized water several times to remove the residual KOH and impurities, and finally dry it at 80 °C for 5 h and grind it into fine powder to obtain the walnut diaphragm-derived carbon, denoted as WSC, for standby;

[0071] S2. Dissolve 0.71 g of NiCl2•6H2O, 0.23 g of NH4VO3, and 1.70 mL of DMF in 12 mL of ethanol solution, and stir at room temperature for 1 h to obtain a precursor solution. Then put 0.02 g of WSC into the precursor solution and soak it for 30 min. After sufficient soaking, transfer the whole to a stainless steel autoclave lined with polytetrafluoroethylene. Seal the autoclave and heat it at 110 °C for 10 h. After cooling to room temperature, wash the powder with deionized water and ethanol, and dry it in vacuum at 65 °C for 24 h. Obtain the precursor;

[0072] S3. Take 0.34 g of the precursor obtained in step S2 and mix it with 0.28 g of K2S in 30 mL of deionized water, and transfer it into a reaction kettle. Seal the autoclave and heat it at 140 °C for 6 h. After cooling to room temperature, wash the final product thoroughly with deionized water and ethanol, and dry it in vacuum at 60 °C for 12 h to obtain Ni3S2 / V2O5 / WSC.

[0073] Comparative Example 1

[0074] A preparation method of a Ni3S2 / V2O5 composite material includes the following steps:

[0075] S1. Dissolve 0.36 g of Ni(NO3)2•6H2O, 0.62 g of VCl3, and 1.70 mL of DMF in 12 mL of ethanol solution, stir at room temperature for 1 h, and then transfer it to a stainless-steel autoclave with a polytetrafluoroethylene lining. Seal the autoclave and heat it at 150 °C for 9 h. After cooling to room temperature, wash the powder with deionized water and ethanol, and dry it in vacuum at 65 °C for 24 h. Obtain the precursor;

[0076] S2. Take 0.34 g of the precursor obtained in step S2 and mix it with 0.61 g of Na2S•9H2O in 30 mL of deionized water, and transfer it into a reaction kettle. Seal the autoclave and heat it at 100 °C for 6 h. After cooling to room temperature, wash the final product thoroughly with deionized water and ethanol, and dry it in vacuum at 60 °C for 12 h to obtain the Ni3S2 / V2O5 composite material.

[0077] That is, compared with Example 1, the composite material of this comparative example does not contain walnut diaphragm-derived carbon (WSC).

[0078] Comparative Example 2

[0079] This comparative example is basically the same as Example 1, except that in step S1, walnut shell is used to replace the walnut diaphragm.

[0080] Figure 1 SEM image of the Ni3S2 / V2O5 / WSC composite material prepared for Example 1. It can be seen from the figure that the material presents a nanosheet structure and grows uniformly.

[0081] The Ni3S2 / V2O5 / WSC composite materials prepared in Examples 1-3, the Ni3S2 / V2O5 composite material prepared in Comparative Example 1, and the Ni3S2 / V2O5 / walnut shell carbon composite material of Comparative Example 2 are used as active materials to make electrode materials. The platinum sheet electrode and the mercury / mercuric oxide electrode are used as the counter electrode and the reference electrode respectively, and 3M KOH solution is used as the electrolyte to perform cyclic voltammetry curve (CV) and galvanostatic charge-discharge curve (GCD) electrochemical performance tests on the electrode materials; as Figure 2 andFigure 3 As shown, at a current density of 1 A g -1 , the specific capacitances of the Ni3S2 / V2O5 / WSC composites of Examples 1, 2, and 3 are 3786 F g -1 , 3380 F g -1 , and 2216 F g -1 , respectively, while the specific capacitance of the Ni3S2 / V2O5 composite of Comparative Example 1 is only 1672 F g -1 , and the specific capacitance of the Ni3S2 / V2O5 / walnut shell carbon composite of Comparative Example 2 is 2015 F g -1 . Figure 3 shows the specific capacitances of the Ni3S2 / V2O5 / WSC composites prepared in Examples 1 to 3, the Ni3S2 / V2O5 composite prepared in Comparative Example 1, and the Ni3S2 / V2O5 / walnut shell carbon composite of Comparative Example 2 at different current densities. It can be seen from the figure that compared with the Ni3S2 / V2O5 composite of Comparative Example 1 and the Ni3S2 / V2O5 / walnut shell carbon composite of Comparative Example 2, the Ni3S2 / V2O5 / WSC composites of Examples 1 to 3 of the present invention have higher specific capacitances at different current densities.

[0082] Figure 4 is the cyclic performance diagram of the Ni3S2 / V2O5 / WSC composite prepared in Example 1, the Ni3S2 / V2O5 composite prepared in Comparative Example 1, and the Ni3S2 / V2O5 / walnut shell carbon composite of Comparative Example 2; it can be seen from the figure that at a current density of 1 A g -1 , the capacity retention rate of the Ni3S2 / V2O5 composite prepared in Example 1 after 10,000 cycles is 92.1%, the capacity retention rate of the Ni3S2 / V2O5 composite prepared in Comparative Example 1 after 10,000 cycles is 82.2%, and the capacity retention rate of the Ni3S2 / V2O5 / walnut shell carbon composite prepared in Comparative Example 2 after 10,000 cycles is 87.6%.

[0083] Using the walnut diaphragm-derived carbon (WSC) prepared in Example 1 and the walnut shell biomass charcoal prepared in Comparative Example 2 as active materials to make electrode materials, using a platinum sheet electrode and a mercury / mercuric oxide electrode as the counter electrode and reference electrode respectively, and using a 3M KOH solution as the electrolyte, cyclic voltammetry curve (CV) and galvanostatic charge-discharge curve (GCD) electrochemical performance tests were carried out on the electrode materials; as Figure 5 shown, the specific capacitance of the walnut shell biomass charcoal is 167 F g -1 , and the specific capacitance of the walnut diaphragm-derived carbon is 261 F g -1 . It can be seen that the specific capacitance of the walnut shell biomass charcoal is much lower than that of the walnut diaphragm-derived carbon.Figure 6 Cycling performance graph of the walnut septum-derived carbon (WSC) prepared in Example 1. It can be seen from the graph that at a current density of 1 A g -1 , the Coulombic efficiency of the WSC material after 20,000 cycles is 99.8%, and the capacity retention rate is 99.7%.

[0084] Example 5

[0085] A preparation method of a Ni3S2 / V2O5 / WSC / / WSC printed flexible supercapacitor, comprising the following steps:

[0086] R1. Weigh 1.5 g of ethyl cellulose and dissolve it in 19.928 g of n-propanol solution to prepare an ethyl cellulose-n-propanol solution with a mass percentage of 7% as the binder; the active material ink is formed by the electrode material, acetylene black and the binder in a mass ratio of 7.5:1.5:1, that is, weigh 0.2 g of the WSC negative electrode material and 0.2 g of the Ni3S2 / V2O5 / WSC positive electrode material, and mix them with 0.04 g of acetylene black and 0.3814 g of the ethyl cellulose-n-propanol solution with a mass percentage of 7% respectively, and stir for 15 min to obtain the WSC negative electrode ink and the Ni3S2 / V2O5 / WSC positive electrode ink respectively;

[0087] R2. Use a 200-mesh screen printing plate, and through the screen printing technology, print a layer of silver paste on the PET substrate as the conductive layer; put the printed silver paste substrate into an oven and dry it at 75 °C for 1 h to volatilize the organic materials in the silver paste; then use a 150-mesh screen printing plate to print the WSC negative electrode ink and the Ni3S2 / V2O5 / WSC positive electrode ink on the two silver paste substrates respectively. After printing, put them into an oven and dry them at 65 °C for 3 h to volatilize the organic reagents in the ink, and obtain the WSC flexible negative electrode and the Ni3S2 / V2O5 / WSC flexible positive electrode respectively;

[0088] R3. Weigh 1 g of PVA powder, dissolve it in 9 g of deionized water, heat it in an oil bath at 95 °C, and continuously stir until it is completely dissolved to form a transparent viscous PVA solution. Pour the solution into a mold of 1×2 cm 2 , and cure it with ultraviolet light for 1 h to obtain a dry PVA gel electrolyte; soak the PVA gel electrolyte in 3M KOH solution until it swells to obtain a KOH / PVA gel electrolyte;

[0089] R4. As Figure 7As shown in the figure, the WSC flexible negative electrode, KOH / PVA gel electrolyte, and Ni3S2 / V2O5 / WSC flexible positive electrode are combined in a sandwich structure and encapsulated with tape to prevent the KOH / PVA gel electrolyte from drying, resulting in the Ni3S2 / V2O5 / WSC / / WSC printed flexible supercapacitor.

[0090] For the supercapacitor of this example, at a current density of 1 mA cm -2 , the areal capacitance of the device is 424.4 mF cm -2 , which is significantly higher than most of the reported flexible supercapacitors currently. To evaluate the mechanical stability and cycling durability of the device, 1000 repeated bending tests were carried out; after 1000 bends, the charge-discharge curve of the device still remained in the initial state, still maintaining a similar charge-discharge time, and the capacitance retention rate was as high as 91.83%, fully demonstrating that the flexible supercapacitor has good mechanical flexibility and structural stability.

[0091] Figure 8 Figure 5 shows the cycling performance of the Ni3S2 / V2O5 / WSC / / WSC printed flexible supercapacitor prepared in Example 5. It can be seen from the figure that for the Ni3S2 / V2O5 / WSC / / WSC printed flexible supercapacitor prepared in the present invention, at a current density of 1 mA cm -2 , the Coulombic efficiency after 10000 cycles is 96.3% and the capacity retention rate is 79.2%.

[0092] Figure 9 Figure 6 shows the practical application diagram of the Ni3S2 / V2O5 / WSC / / WSC printed flexible supercapacitor prepared in Example 5. Figure 9 As shown in Figure 6a, two series-connected flexible supercapacitors can light up 5 LED lights and keep the 5 LED lights working continuously for 57 s. Figure 6b shows that the Ni3S2 / V2O5 / WSC / / WSC printed flexible supercapacitor prepared in this example can charge a sports bracelet and extend the usage time of the bracelet.

[0093] The supercapacitor prepared in the present invention has a high energy density and excellent mechanical properties, and can be widely used in fields such as wearable devices and flexible electronics. The process of the present invention is simple and the cost is low, which is suitable for large-scale production.

[0094] Example 6

[0095] A preparation method of a Ni3S2 / V2O5 / WSC / / WSC printed flexible supercapacitor, comprising the following steps:

[0096] R1. Dissolve 0.04 g of LA133 in 0.76 g of deionized water solution, dilute the LA133 solution with a mass fraction of 15% to a mass fraction of 5%, and use it as a binder; the active material ink is formed by the electrode material, acetylene black and the binder in a mass ratio of 7.5:1.5:1, that is, weigh 0.3 g of WSC negative electrode material and 0.3 g of Ni3S2 / V2O5 / WSC positive electrode material, and mix them with 0.06 g of acetylene black and 0.8 g of LA133 solution with a mass fraction of 5% respectively, and stir for 10 min to obtain WSC negative electrode ink and Ni3S2 / V2O5 / WSC positive electrode ink respectively;

[0097] R2. Use a 200-mesh screen printing plate, and print a layer of silver paste on the PET substrate through screen printing technology as the conductive layer; put the printed flexible silver paste substrate into an oven and dry it at 70 °C for 1 h to volatilize the organic materials in the silver paste; then use a 150-mesh screen printing plate to print WSC negative electrode ink and Ni3S2 / V2O5 / WSC positive electrode ink on two silver paste substrates respectively. After printing, put them into the oven and dry them at 70 °C for 3 h to volatilize the organic reagents in the ink, and obtain WSC flexible negative electrode and Ni3S2 / V2O5 / WSC flexible positive electrode respectively;

[0098] R3. Weigh 1.875 g of CMC powder, dissolve it in 25 mL of deionized water, and continuously stir until it is completely dissolved to form a transparent viscous solution. Weigh 0.81 mL of AA, 5.325 g of AM, 0.04 g of MBA and 0.135 g of HE-HMPP reagent, pour them into the uniformly stirred CMC colloidal solution, and continuously stir and wait for complete mixing. Pour the mixed solution into a mold of 1×2 cm 2 and cure it with ultraviolet light for 1 h to obtain a dry gel electrolyte; soak the gel electrolyte in 3M KOH solution until it swells to obtain a KOH gel electrolyte;

[0099] R4. As shown in Figure 7 the figure, combine the WSC flexible negative electrode, the KOH gel electrolyte, and the Ni3S2 / V2O5 / WSC flexible positive electrode in a sandwich structure and encapsulate them with tape to prevent the KOH gel electrolyte from drying, and obtain a Ni3S2 / V2O5 / WSC / / WSC printed flexible supercapacitor.

[0100] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a Ni3S2 / V2O5 / WSC composite material, characterized in that: The following steps are involved: S1. placing the walnut diaphragm in an inert atmosphere for a first high-temperature carbonization to obtain walnut diaphragm carbon, then adding an activator, and after activation, performing a second high-temperature carbonization in an inert atmosphere to obtain walnut diaphragm derived carbon (WSC); S2. The walnut diaphragm-derived carbon obtained in step S1 is dispersed in deionized water, nickel salt and vanadium salt are added, stirred evenly, and then a first hydrothermal reaction is performed, and the precursor is obtained after washing and drying; S3. The precursor obtained in step S2 is dispersed in deionized water, a sulfur source is added, and the mixture is stirred evenly to perform a second hydrothermal reaction. The Ni3S2 / V2O5 / WSC composite material is obtained after washing and drying.

2. The method for preparing a Ni3S2 / V2O5 / WSC composite material according to claim 1, characterized in that: The temperature of the first high-temperature carbonization is 400-600° C., and the time is 1-4 hours, and / or the temperature of the second high-temperature carbonization is 500-700° C., and the time is 1-3 hours.

3. The method for preparing a Ni3S2 / V2O5 / WSC composite material according to claim 1, characterized in that: The activator includes at least one of KOH, ZnCl2, H3PO4, and H2SO4, and the mass ratio of the activator to the walnut membrane carbon is (0.5~3):

1.

4. The method for preparing a Ni3S2 / V2O5 / WSC composite material according to claim 1, characterized in that: The nickel salt includes at least one of Ni(NO3)2•6H2O, NiCl2•6H2O and NiSO4•6H2O, and / or the vanadium salt includes VCl3 and / or NH4VO3.

5. The method for preparing a Ni3S2 / V2O5 / WSC composite material according to claim 1, characterized in that: The molar ratio of the nickel salt to the vanadium salt is (1-2):(1-3).

6. The method for preparing a Ni3S2 / V2O5 / WSC composite material according to claim 1, characterized in that: The ratio of the mass of the walnut diaphragm derived carbon to the total mass of the nickel salt and the vanadium salt is 1:(20-100).

7. The method for preparing a Ni3S2 / V2O5 / WSC composite material according to claim 1, characterized in that: The temperature of the first hydrothermal reaction is 100-180° C., and the time is 6-10 h, and / or the temperature of the second hydrothermal reaction is 100-140° C., and the time is 6-10 h.

8. The method for preparing a Ni3S2 / V2O5 / WSC composite material according to claim 1, characterized in that: The mass ratio of the precursor to the sulfur source is 1:(0.5-2), and / or the sulfur source is Na2S•9H2O or K2S.

9. A printed flexible supercapacitor, characterized in that: The Ni3S2 / V2O5 / WSC composite material prepared by the method described in any one of claims 1 to 8 is used as a positive electrode material, and / or the walnut diaphragm-derived carbon (WSC) prepared by the method described in any one of claims 1 to 3 is used as a negative electrode material.

10. The method for preparing a printed flexible supercapacitor according to claim 9, characterized in that: The following steps are involved: R1. The Ni3S2 / V2O5 / WSC composite material and the walnut separator derived carbon (WSC) are mixed with a conductive agent and a binder to obtain a Ni3S2 / V2O5 / WSC positive electrode ink and a WSC negative electrode ink; R2. The positive electrode ink and the negative electrode ink are respectively coated on the flexible substrate coated with silver paste by screen printing, and a flexible positive electrode and a flexible negative electrode are obtained after drying; R3. Assemble the flexible positive electrode, flexible negative electrode and gel electrolyte into a printed flexible supercapacitor.

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