Preparation method of integrated current collector for vanadium battery

Abstract

The application discloses a preparation method of an integrated current collector for a vanadium battery, and comprises the following steps: preparing carbon nanotube deposited nickel foam; pressing conductive particles into a sheet, and sequentially placing the conductive sheet, modified nickel foam and conductive sheet into a mold to be integrally formed into a composite bipolar plate by using a hot press; preparing silver-copper composite powder by adopting chemical plating to plate silver on the surface of copper powder, preparing conductive adhesive containing the silver-copper metal powder, and bonding the copper plate and the composite bipolar plate by using the conductive adhesive to prepare the integrated current collector. The application takes the nickel foam as a skeleton material, improves the interface between the nickel foam and the carbon composite layer by depositing carbon nanotubes on the surface of the nickel foam, improves the mechanical strength and conductivity of the composite bipolar plate, melts the nanoscale silver particles on the surface of the copper powder by heat treatment of the silver-copper composite powder, forms a continuous silver film, improves the conductivity and oxidation resistance of the conductive adhesive, reduces the contact resistance between the bipolar plate and the copper plate, and thus improves the performance of the flow battery.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid flow batteries, and in particular to a method for preparing an integrated current collecting plate for a vanadium battery. Background Art

[0002] In recent years, all-vanadium redox flow batteries have become the focus of new energy storage batteries. They have the advantages of independent capacity, high power, long life, deep discharge and no emission pollution. They can be used as supporting energy storage devices in the power generation process of renewable energy such as wind and solar energy, and can also achieve frequency and peak regulation in the power grid system. They are suitable for electrochemical energy storage devices for large-scale energy storage.

[0003] Copper plates are commonly used as current collectors in existing technologies. While these current collectors offer excellent conductivity and are easy to manufacture, they cannot come into direct contact with strongly acidic electrolytes, as they would corrode and dissolve in the electrolyte. Covering the current collectors with bipolar plates addresses this issue. Bipolar plates are key components in all-vanadium redox flow batteries, connecting the positive and negative electrodes of each battery cell in the stack, collecting electrons, and isolating the positive and negative electrodes from the electrolyte. Therefore, they must possess high conductivity and stability in strongly acidic media, as well as low resistivity and contact resistance with the electrode material. Vanadium liquid flow batteries use bipolar plates and current collecting plates together, but there are several problems with their use: 1) The bipolar plates seal the electrolyte inside the battery stack through pressure. If the seal is not good or the bipolar plates have micropores, electrolyte leakage will corrode the current collecting plates, thereby causing degradation of battery stack performance; 2) The mechanical strength of the bipolar plates is insufficient, and they are prone to physical damage during pressure and use. Once damaged, the battery will become unusable; 3) The bipolar plates and current collecting plates are in physical contact through pressure, and this method has a large contact resistance, which affects the performance of the battery stack. Summary of the Invention

[0004] In order to solve the above technical problems, the present application provides a method for preparing an integrated current collecting plate for a vanadium battery.

[0005] The technical solution is as follows: A method for preparing an integrated current collecting plate for a vanadium battery comprises the following steps:

[0006] S1: adding carbon nanotubes and a dispersant to a mixed electrolyte, and ultrasonically dispersing the mixture to obtain a composite dispersion; using nickel foam as a cathode and the composite dispersion as an electrodeposition solution to perform electrodeposition, and heat-treating the electrodeposited nickel foam to obtain a nickel foam with carbon nanotubes deposited thereon;

[0007] S2: Melting and mixing the resin and the conductive carbon material in an internal mixer, cooling and crushing the mixture, and then pressing the mixture into a mold to obtain a conductive sheet;

[0008] S3: placing the conductive sheet and the carbon nanotube-deposited nickel foam into a mold for integral compression molding to obtain a composite bipolar plate;

[0009] S4: preparing a reducing solution and a silver-ammine complex solution; adding copper powder to the reducing solution, slowly adding the silver-ammine complex solution under stirring, reacting at room temperature, filtering to obtain a filter residue, vacuum drying, and calcining to obtain spherical silver-copper metal powder;

[0010] S5: adding the spherical silver-copper metal powder into a thermosetting resin and dispersing it evenly to obtain a conductive adhesive; coating the conductive adhesive on the surface of a copper plate, placing the composite bipolar plate on the coated surface of the copper plate, and compression molding the composite bipolar plate on a hot press to obtain an integrated current collecting plate.

[0011] Furthermore, in said S1:

[0012] The components of the mixed electrolyte include 150g / L nickel sulfate, 20g / L nickel chloride, and 10g / L boric acid;

[0013] The concentration of the carbon nanotubes in the composite dispersion is 1-10 g / L;

[0014] The dispersant is selected from at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and dodecyltrimethylammonium bromide, and the concentration of the dispersant in the composite dispersion is 0.05-0.1 g / L, mainly used to improve the uniformity of carbon nanotube deposition;

[0015] The frequency of the ultrasonic dispersion is 50-100 Hz, and the time is 10-30 min.

[0016] Furthermore, in said S1:

[0017] The electrodeposition current is 20-50A and the time is 20-60min. A layer of carbon nanotubes is deposited on the surface of the nickel foam, which can effectively improve the interface contact between the nickel foam and the functional carbon material composite layer, reduce the contact resistance between the two, improve the voltage efficiency of the battery, and simultaneously improve the mechanical strength and conductivity of the composite bipolar plate.

[0018] The heat treatment temperature is 400-600° C., the time is 3-8 hours, and the atmosphere is a mixed gas consisting of hydrogen and nitrogen in a volume ratio of 3:1.

[0019] Furthermore, in said S2:

[0020] The resin is selected from at least one of polyethylene and polypropylene;

[0021] The conductive carbon material is selected from at least one of carbon black, graphite, carbon fiber, and carbon nanotubes;

[0022] The mass ratio of the conductive carbon material to the resin is 1:(0.4-2.3).

[0023] Furthermore, in said S2:

[0024] The melting and mixing is performed at a temperature of 150-200°C and a time of 30-60 minutes;

[0025] The compression molding process is performed at a temperature of 150-200° C., a pressure of 50-100 MPa, and a time of 5-10 minutes.

[0026] Furthermore, in said S3:

[0027] The integral compression molding process is performed at a temperature of 150-200° C., a pressure of 50-100 MPa, and a time of 5-10 minutes.

[0028] Furthermore, in said S4:

[0029] The reducing solution is prepared by adding 40 to 100 parts by mass of glucose and 2 to 10 parts by mass of tartaric acid to 1000 parts by mass of distilled water, boiling for 10 minutes, cooling, adding 50 to 200 parts by mass of ethanol, and mixing to obtain the reducing solution.

[0030] Furthermore, in said S4:

[0031] The preparation method of the silver-ammine complex solution is as follows: 50 to 100 parts by volume of a 4% NaOH solution is added to 50 to 100 parts by volume of a 5% AgNO3 solution to form an AgOH precipitate, and then 5 to 50 parts by volume of ammonia water is slowly added under stirring to dissolve the AgOH precipitate into a transparent liquid, thereby obtaining the silver-ammine complex solution.

[0032] Furthermore, in said S4:

[0033] The amount of copper powder is 10-30 g / L;

[0034] The volume ratio of the reducing solution to the silver ammonia complex solution is 1:(0.5~1);

[0035] The reaction time of the reaction at room temperature is 30 min;

[0036] The vacuum drying temperature is 40-60°C and the time is 2-5 hours;

[0037] The calcination temperature is 200-500° C., the calcination time is 0.5-3 hours, and the atmosphere is air.

[0038] Furthermore, in said 5:

[0039] The thermosetting resin is selected from at least one of epoxy resin, unsaturated resin and vinyl resin;

[0040] The mass fraction of the spherical silver-copper metal powder in the conductive adhesive is 4% to 10%;

[0041] The coating thickness is 50-100 μm;

[0042] The temperature of the molding process on the hot press is 80-120° C., and the molding time is 5-20 minutes.

[0043] The beneficial effects of the present invention are:

[0044] 1. The present invention uses modified nickel foam as the skeleton material and improves the interface between the nickel foam and the carbon composite layer by depositing carbon nanotubes on the surface of the nickel foam, thereby providing mechanical strength and conductivity for the composite bipolar plate.

[0045] 2. The present invention prepares silver-copper composite powder by chemically plating silver on the surface of copper powder. Then, heat treatment can melt the nano-scale silver particles on the surface of the copper powder to form a continuous silver film, thereby improving the conductivity and oxidation resistance of the conductive adhesive.

[0046] 3. The present invention uses a homemade conductive adhesive to bond the copper plate and the composite bipolar plate. The process is environmentally friendly and simple. Thermosetting resin is used as the conductive adhesive to improve the bonding strength between the copper plate and the composite bipolar plate, reduce the contact resistance between the bipolar plate and the graphite felt, and thus improve the performance of the liquid flow battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The figure is a schematic flow chart of a method for preparing an integrated current collecting plate for a vanadium battery according to the present invention.

[0048] Figure 2 This is the SEM image of the spherical silver-copper metal powder prepared in Example 1. DETAILED DESCRIPTION

[0049] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention, its application, or use. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0050] See also Figure 1 A method for preparing an integrated current collecting plate for a vanadium battery comprises the following steps:

[0051] S1: adding carbon nanotubes and a dispersant to a mixed electrolyte, and ultrasonically dispersing the mixture to obtain a composite dispersion; using nickel foam as a cathode and the composite dispersion as an electrodeposition solution to perform electrodeposition, and heat-treating the nickel foam after electrodeposition to obtain nickel foam with carbon nanotube deposition; the components of the mixed electrolyte include 150 g / L nickel sulfate, 20 g / L nickel chloride, and 10 g / L boric acid; the concentration of the carbon nanotubes in the composite dispersion is 1-10 g / L; the dispersant is selected from at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and dodecyltrimethylammonium bromide, and the concentration of the dispersant in the composite dispersion is 0.05-0.1 g / L; the frequency of the ultrasonic dispersion is 50-100 Hz, and the time is 10-30 min. The current of the electrodeposition is 20-50A, and the time is 20-60min; the temperature of the heat treatment is 400-600°C, and the time is 3-8h, and the atmosphere is a mixed gas composed of hydrogen and nitrogen in a volume ratio of 3:1.

[0052] S2: Melt-mixing a resin and a conductive carbon material in an internal mixer, cooling and crushing the mixture, and then compression molding the mixture in a mold to obtain a conductive sheet. The resin is selected from at least one of polyethylene and polypropylene; the conductive carbon material is selected from at least one of carbon black, graphite, carbon fiber, and carbon nanotubes; and the mass ratio of the conductive carbon material to the resin is 1:(0.4-2.3). The melt-mixing process is performed at a temperature of 150-200°C for 30-60 minutes. The compression molding process is performed at a temperature of 150-200°C, a pressure of 50-100 MPa, and a time of 5-10 minutes.

[0053] S3: placing the conductive sheet and the carbon nanotube-deposited nickel foam into a mold for integral compression molding to obtain a composite bipolar plate; the integral compression molding temperature is 150-200° C., the pressure is 50-100 MPa, and the time is 5-10 min.

[0054] S4: preparing a reducing solution and a silver-ammine complex solution; adding copper powder to the reducing solution, slowly adding the silver-ammine complex solution under stirring, reacting at room temperature, filtering to obtain a filter residue, vacuum drying, and calcining to obtain spherical silver-copper metal powder; the reducing solution is prepared by adding 40 to 100 parts by mass of glucose and 2 to 10 parts by mass of tartaric acid to 1000 parts by mass of distilled water, boiling for 10 minutes, cooling, adding 50 to 200 parts by mass of ethanol, and mixing to obtain the reducing solution. The silver-ammine complex solution is prepared by adding 50 to 100 parts by volume of a 4% NaOH solution to 50 to 100 parts by volume of a 5% AgNO3 solution to form an AgOH precipitate, and then slowly adding 5 to 50 parts by volume of ammonia water under stirring to dissolve the AgOH precipitate into a transparent liquid to obtain the silver-ammine complex solution. The amount of the copper powder is 10-30 g / L; the volume ratio of the reducing solution to the silver ammonia complex solution is 1:(0.5-1); the reaction time at room temperature is 30 minutes; the vacuum drying temperature is 40-60° C., the time is 2-5 hours; the calcination temperature is 200-500° C., the time is 0.5-3 hours, and the atmosphere is air.

[0055] S5: Add the spherical silver-copper metal powder to a thermosetting resin and disperse it evenly to obtain a conductive adhesive; apply the conductive adhesive to the surface of a copper plate, place the composite bipolar plate on the coated copper plate, and perform compression molding on a hot press to obtain an integrated current collector. The thermosetting resin is selected from at least one of epoxy resin, unsaturated resin, and vinyl resin; the mass fraction of the spherical silver-copper metal powder in the conductive adhesive is 4% to 10%; the coating thickness is 50 to 100 μm; and the compression molding temperature on the hot press is 80 to 120°C and the time is 5 to 20 minutes.

[0056] Example 1: A method for preparing an integrated current collecting plate for a vanadium battery, comprising the following steps:

[0057] Step S1: adding 150g of nickel sulfate, 20g of nickel chloride, and 10g of boric acid to 1L of sulfuric acid electrolyte to prepare a mixed electrolyte, then adding 1g of carbon nanotubes and 0.05g of sodium dodecylbenzenesulfonate, and performing ultrasonic dispersion at a frequency of 50Hz and a dispersion time of 20min to obtain a composite dispersion; using nickel foam as a cathode, the composite dispersion as an electrodeposition liquid, and an electrolytic nickel plate as an anode, performing electrodeposition at a current of 20A for 60min, placing the electrodeposited material in a 400°C muffle furnace, and filling the furnace with hydrogen and nitrogen with volume fractions of 75% and 25%, respectively, for protection, and heat treating for 8h to obtain carbon nanotube-deposited nickel foam;

[0058] Step S2: 30 parts by mass of polyethylene, 35 parts by mass of graphite, and 35 parts by mass of carbon black were melted and mixed in an internal mixer at a melting temperature of 180°C for 45 minutes, crushed to obtain modified conductive particles, placed in a mold, and pressed using a hot press at a molding temperature of 200°C, a pressure of 50 MPa, and a time of 5 minutes to obtain a conductive sheet;

[0059] Step S3: placing the conductive sheet, modified nickel foam, and conductive sheet into a mold and using a hot press to integrally mold the composite bipolar plate at a molding temperature of 200° C., a pressure of 100 MPa, and a molding time of 5 minutes; the bending strength thereof was tested to be 28.9 MPa;

[0060] Step S4: adding 40g of glucose and 2g of tartaric acid to 1000g of distilled water, boiling for 10min, and adding 50g of ethanol after cooling to obtain a reducing solution; adding 5g of silver nitrate to 100g of distilled water to obtain a silver nitrate solution, adding 4g of sodium hydroxide to 100g of distilled water to obtain a sodium hydroxide solution, adding 50ml of NaOH solution to 50ml of AgNO3 solution to form an AgOH precipitate; slowly adding 5ml of ammonia water under stirring to dissolve the AgOH precipitate into a transparent liquid to obtain a silver ammonia complex solution, adding 1g of copper powder to 100ml of the reducing solution, slowly adding 100ml of the silver ammonia complex solution under magnetic stirring, reacting at room temperature for 30min, filtering, and drying in a 40°C vacuum oven for 5h to obtain silver-copper metal powder, and then calcining in a 200°C muffle furnace for 3h to obtain spherical silver-copper metal powder;

[0061] Step S5: Add 2 g of spherical silver-copper metal powder to 50 g of epoxy resin, disperse evenly to obtain a conductive adhesive, and apply it to the surface of the copper plate with a coating thickness of 50 μm. Then place the composite bipolar plate and press it on a hot press at 80°C for 20 minutes to obtain an integrated current collecting plate.

[0062] like Figure 2 This is the SEM image of the spherical silver-copper metal powder prepared in step S4. It can be seen that fine silver is distributed on the surface of the copper particles, indicating that a layer of silver has grown on the surface of the copper powder through chemical reduction.

[0063] Example 2: A method for preparing an integrated current collecting plate for a vanadium battery, comprising the following steps:

[0064] Step S1: adding 150g of nickel sulfate, 20g of nickel chloride, and 10g of boric acid to 1L of sulfuric acid electrolyte to prepare a mixed electrolyte, then adding 2g of carbon nanotubes and 0.06g of sodium dodecylbenzenesulfonate, and performing ultrasonic dispersion at a frequency of 60Hz for a dispersion time of 30min to obtain a composite dispersion; using nickel foam as a cathode, the composite dispersion as an electrodeposition liquid, and an electrolytic nickel plate as an anode, performing electrodeposition at a current of 30A for 50min, placing the electrodeposited material in a muffle furnace at 450°C, and filling the furnace with hydrogen and nitrogen with volume fractions of 75% and 25% respectively for protection, and heat treating for 7h to obtain carbon nanotube-deposited nickel foam;

[0065] Step S2: 45 parts by mass of polyethylene, 25 parts by mass of graphite, 20 parts by mass of carbon black, and 10 parts by mass of carbon fiber were melted and mixed in an internal mixer at a melting temperature of 150° C. for 60 minutes, and the modified conductive particles were crushed to obtain modified conductive particles. The particles were placed in a mold and pressed using a hot press at a molding temperature of 150° C., a pressure of 100 MPa, and a time of 10 minutes to obtain a conductive sheet.

[0066] Step S3: placing the conductive sheet, modified nickel foam, and conductive sheet into a mold and using a hot press to integrally mold them into a composite bipolar plate at a molding temperature of 150° C., a pressure of 100 MPa, and a molding time of 10 min.

[0067] Step S4: adding 50g of glucose and 3g of tartaric acid to 1000g of distilled water, boiling for 10min, and adding 100g of ethanol after cooling to obtain a reducing solution; adding 5g of silver nitrate to 100g of distilled water to obtain a silver nitrate solution, adding 4g of sodium hydroxide to 100ml of distilled water to obtain a sodium hydroxide solution, and adding 50ml of NaOH solution to 100ml of AgNO3 solution to form an AgOH precipitate; slowly adding 10ml of ammonia water under stirring to dissolve the AgOH precipitate into a transparent liquid to obtain a silver ammonia complex solution, adding 2g of copper powder to 100ml of the reducing solution, slowly adding 50ml of the silver ammonia complex solution under magnetic stirring, reacting at room temperature for 30min, filtering, and drying in a 50°C vacuum oven for 4h to obtain silver-copper metal powder, and then calcining in a 300°C muffle furnace for 2.5h to obtain spherical silver-copper metal powder;

[0068] Step S5: Add 3 g of spherical silver-copper metal powder to 50 ml of epoxy resin, disperse evenly to obtain a conductive adhesive, and apply it to the surface of the copper plate with a coating thickness of 75 μm. Then place the composite bipolar plate and press it on a hot press at 90°C for 15 minutes to obtain an integrated current collecting plate.

[0069] Example 3: A method for preparing an integrated current collecting plate for a vanadium battery, comprising the following steps:

[0070] Step S1: adding 150g of nickel sulfate, 20g of nickel chloride, and 10g of boric acid to 1L of sulfuric acid electrolyte to prepare a mixed electrolyte, then adding 3g of carbon nanotubes and 0.07g of sodium dodecylbenzenesulfonate, and performing ultrasonic dispersion at a frequency of 70Hz and a dispersion time of 20min to obtain a composite dispersion; using nickel foam as a cathode, the composite dispersion as an electrodeposition liquid, and an electrolytic nickel plate as an anode, performing electrodeposition at a current of 40A for 40min, placing the electrodeposited material in a 500°C muffle furnace, and filling the furnace with hydrogen and nitrogen with volume fractions of 75% and 25%, respectively, for protection, and heat treating for 6h to obtain carbon nanotube-deposited nickel foam;

[0071] Step S2: 35 parts by mass of polyethylene, 20 parts by mass of graphite, 30 parts by mass of carbon black, and 15 parts by mass of carbon nanotubes were melted and mixed in an internal mixer at a melting temperature of 200°C for 30 minutes. The modified conductive particles were crushed to obtain modified conductive particles, which were placed in a mold and molded using a hot press at a molding temperature of 200°C, a pressure of 50 MPa, and a time of 5 minutes to obtain a conductive sheet.

[0072] Step S3: placing the conductive sheet, modified nickel foam, and conductive sheet into a mold and using a hot press to integrally mold them to obtain a composite bipolar plate. The molding temperature is 160° C., the pressure is 50 MPa, and the time is 5 minutes.

[0073] Step S4: adding 60g of glucose and 4g of tartaric acid to 1000g of distilled water, boiling for 10min, and adding 150g of ethanol after cooling to obtain a reducing solution; adding 5g of silver nitrate to 100g of distilled water to obtain a silver nitrate solution, adding 4g of sodium hydroxide to 100g of distilled water to obtain a sodium hydroxide solution, and adding 100ml of NaOH solution to 100ml of AgNO3 solution to form an AgOH precipitate; slowly adding 15ml of ammonia water under stirring to dissolve the AgOH precipitate into a transparent liquid to obtain a silver ammonia complex solution, adding 3g of copper powder to 100ml of the reducing solution, slowly adding 75ml of the silver ammonia complex solution under magnetic stirring, reacting at room temperature for 30min, filtering, and drying in a 60°C vacuum oven for 3h to obtain silver-copper metal powder, and then calcining in a 400°C muffle furnace for 2h to obtain spherical silver-copper metal powder;

[0074] Step S5: Add 4 g of spherical silver-copper metal powder to 50 ml of epoxy resin, disperse evenly to obtain a conductive adhesive, and apply it to the surface of the copper plate with a coating thickness of 100 μm. Then place the composite bipolar plate and press it on a hot press at 100°C for 10 minutes to obtain an integrated current collecting plate.

[0075] Example 4: A method for preparing an integrated current collecting plate for a vanadium battery, comprising the following steps:

[0076] Step S1: adding 150g of nickel sulfate, 20g of nickel chloride, and 10g of boric acid to 1L of sulfuric acid electrolyte to prepare a mixed electrolyte, then adding 4g of carbon nanotubes and 0.08g of sodium dodecylbenzenesulfonate, and performing ultrasonic dispersion at a frequency of 80Hz and a dispersion time of 20min to obtain a composite dispersion; using nickel foam as a cathode, the composite dispersion as an electrodeposition liquid, and an electrolytic nickel plate as an anode, performing electrodeposition at a current of 50A for 20min, placing the electrodeposited material in a muffle furnace at 550°C, and filling the furnace with hydrogen and nitrogen with volume fractions of 75% and 25% respectively for protection, and heat treating for 5h to obtain carbon nanotube-deposited nickel foam;

[0077] Step S2: 65 parts by mass of polypropylene, 15 parts by mass of graphite, 10 parts by mass of carbon black, and 10 parts by mass of carbon fiber were melted and mixed in an internal mixer at a melting temperature of 180°C for 40 minutes, crushed to obtain modified conductive particles, placed in a mold, and pressed using a hot press at a molding temperature of 160°C, a pressure of 60 MPa, and a time of 6 minutes to obtain a conductive sheet;

[0078] Step S3: placing the conductive sheet, modified nickel foam, and conductive sheet into a mold and using a hot press to integrally mold them to obtain a composite bipolar plate. The molding temperature is 170° C., the pressure is 60 MPa, and the time is 6 minutes.

[0079] Step S4: adding 70g of glucose and 5g of tartaric acid to 1000g of distilled water, boiling for 10min, and adding 200g of ethanol after cooling to obtain a reducing solution; adding 5g of silver nitrate to 100g of distilled water to obtain a silver nitrate solution, adding 4g of sodium hydroxide to 100g of distilled water to obtain a sodium hydroxide solution, adding 50ml of NaOH solution to 80ml of AgNO3 solution to form an AgOH precipitate; slowly adding 30ml of ammonia water under stirring to dissolve the AgOH precipitate into a transparent liquid to obtain a silver ammonia complex solution, adding 1.5g of copper powder to 100ml of the reducing solution, slowly adding 50ml of the silver ammonia complex solution under magnetic stirring, reacting at room temperature for 30min, filtering, and drying in a 40°C vacuum oven for 5h to obtain silver-copper metal powder, and then calcining in a 500°C muffle furnace for 1.5h to obtain spherical silver-copper metal powder;

[0080] Step S5: Add 5 g of spherical silver-copper metal powder to 50 ml of epoxy resin, disperse evenly to obtain a conductive adhesive, and apply it to the surface of the copper plate with a coating thickness of 50 μm. Then place the composite bipolar plate and press it on a hot press at 110°C for 10 minutes to obtain an integrated current collecting plate.

[0081] Example 5: A method for preparing an integrated current collecting plate for a vanadium battery, comprising the following steps:

[0082] Step S1: adding 150g of nickel sulfate, 20g of nickel chloride, and 10g of boric acid to 1L of sulfuric acid electrolyte to prepare a mixed electrolyte, then adding 5g of carbon nanotubes and 0.09g of sodium lauryl sulfate, and performing ultrasonic dispersion at a frequency of 90Hz for a dispersion time of 15min to obtain a composite dispersion; using nickel foam as a cathode, the composite dispersion as an electrodeposition liquid, and an electrolytic nickel plate as an anode, performing electrodeposition at a current of 30A for 30min, placing the electrodeposited material in a muffle furnace at 600°C, and filling the furnace with hydrogen and nitrogen with volume fractions of 75% and 25%, respectively, for protection, and heat treating for 3h to obtain carbon nanotube-deposited nickel foam;

[0083] Step S2: 60 parts by mass of polypropylene, 20 parts by mass of graphite, 10 parts by mass of carbon black, and 10 parts by mass of carbon nanotube sheets were melted and mixed in an internal mixer at a melting temperature of 175°C for 50 minutes, crushed to obtain modified conductive particles, placed in a mold, and pressed using a hot press at a molding temperature of 170°C, a pressure of 70 MPa, and a time of 7 minutes to obtain a conductive sheet;

[0084] Step S3: placing the conductive sheet, modified nickel foam, and conductive sheet into a mold and using a hot press to integrally mold them to obtain a composite bipolar plate. The molding temperature is 180° C., the pressure is 70 MPa, and the time is 7 minutes.

[0085] Step S4: adding 80g of glucose and 6g of tartaric acid to 1000g of distilled water, boiling for 10min, and adding 80g of ethanol after cooling to obtain a reducing solution; adding 5g of silver nitrate to 100g of distilled water to obtain a silver nitrate solution, adding 4g of sodium hydroxide to 100g of distilled water to obtain a sodium hydroxide solution, and adding 100ml of NaOH solution to 100ml of AgNO3 solution to form an AgOH precipitate; slowly adding 40ml of ammonia water under stirring to dissolve the AgOH precipitate into a transparent liquid to obtain a silver ammonia complex solution, adding 2.5g of copper powder to 100ml of the reducing solution, slowly adding 50ml of the silver ammonia complex solution under magnetic stirring, reacting at room temperature for 30min, filtering, and drying in a 40°C vacuum oven for 5h to obtain silver-copper metal powder, and then calcining in a 250°C muffle furnace for 1h to obtain spherical silver-copper metal powder;

[0086] Step S5: Add 2.5 g of spherical silver-copper metal powder to 50 ml of unsaturated resin, disperse evenly to obtain a conductive adhesive, and apply it to the surface of the copper plate with a coating thickness of 75 μm. Then place the composite bipolar plate and press it on a hot press at 120°C for 5 minutes to obtain an integrated current collecting plate.

[0087] Example 6: A method for preparing an integrated current collecting plate for a vanadium battery, comprising the following steps:

[0088] Step S1: adding 150g of nickel sulfate, 20g of nickel chloride, and 10g of boric acid to 1L of sulfuric acid electrolyte to prepare a mixed electrolyte, then adding 6g of carbon nanotubes and 0.1g of sodium lauryl sulfate, and performing ultrasonic dispersion at a frequency of 100Hz and a dispersion time of 10min to obtain a composite dispersion; using nickel foam as a cathode, the composite dispersion as an electrodeposition liquid, and an electrolytic nickel plate as an anode, performing electrodeposition at a current of 40A for 60min, placing the electrodeposited material in a 400°C muffle furnace, and filling the furnace with hydrogen and nitrogen with volume fractions of 75% and 25%, respectively, for protection, and heat treating for 4h to obtain carbon nanotube-deposited nickel foam;

[0089] Step S2: 50 parts by mass of polypropylene, 20 parts by mass of graphite, 20 parts by mass of carbon black, and 10 parts by mass of carbon fiber were melted and mixed in an internal mixer at a melting temperature of 170°C for 45 minutes, crushed to obtain modified conductive particles, placed in a mold, and pressed using a hot press at a molding temperature of 180°C, a pressure of 80 MPa, and a time of 8 minutes to obtain a conductive sheet;

[0090] Step S3: placing the conductive sheet, modified nickel foam, and conductive sheet into a mold and using a hot press to integrally mold them to obtain a composite bipolar plate. The molding temperature is 190° C., the pressure is 80 MPa, and the time is 8 minutes.

[0091] Step S4: adding 90g of glucose and 7g of tartaric acid to 1000g of distilled water, boiling for 10min, and adding 120g of ethanol after cooling to obtain a reducing solution; adding 5g of silver nitrate to 100g of distilled water to obtain a silver nitrate solution, adding 4g of sodium hydroxide to 100g of distilled water to obtain a sodium hydroxide solution, adding 50ml of NaOH solution to 100ml of AgNO3 solution to form an AgOH precipitate; slowly adding 50ml of ammonia water under stirring to dissolve the AgOH precipitate into a transparent liquid to obtain a silver ammonia complex solution, adding 1g of copper powder to 100ml of the reducing solution, slowly adding 50ml of the silver ammonia complex solution under magnetic stirring, reacting at room temperature for 30min, filtering, and drying in a 40°C vacuum oven for 5h to obtain silver-copper metal powder, and then calcining in a 500°C muffle furnace for 0.5h to obtain spherical silver-copper metal powder;

[0092] Step S5: Add 2 g of spherical silver-copper metal powder to 50 ml of unsaturated resin, disperse evenly to obtain a conductive adhesive, and apply it to the surface of the copper plate with a coating thickness of 100 μm. Then place the composite bipolar plate and press it on a hot press at 100°C for 10 minutes to obtain an integrated current collecting plate.

[0093] Example 7: A method for preparing an integrated current collecting plate for a vanadium battery, comprising the following steps:

[0094] Step S1: adding 150g of nickel sulfate, 20g of nickel chloride, and 10g of boric acid to 1L of sulfuric acid electrolyte to prepare a mixed electrolyte, then adding 7g of carbon nanotubes and 0.05g of sodium dodecylbenzenesulfonate, and performing ultrasonic dispersion at a frequency of 80Hz and a dispersion time of 15min to obtain a composite dispersion; using nickel foam as a cathode, the composite dispersion as an electrodeposition liquid, and an electrolytic nickel plate as an anode, performing electrodeposition at a current of 50A for 60min, placing the electrodeposited material in a muffle furnace at 450°C, and filling the furnace with hydrogen and nitrogen with volume fractions of 75% and 25% respectively for protection, and heat treating for 7h to obtain a nickel foam with carbon nanotube deposition;

[0095] Step S2: 40 parts by mass of polyethylene, 25 parts by mass of graphite, 25 parts by mass of carbon black, and 10 parts by mass of carbon nanotubes were melted and mixed in an internal mixer at a melting temperature of 180°C for 40 minutes, crushed to obtain modified conductive particles, placed in a mold, and pressed using a hot press at a molding temperature of 190°C, a pressure of 60 MPa, and a time of 9 minutes to obtain a conductive sheet;

[0096] Step S3: placing the conductive sheet, modified nickel foam, and conductive sheet into a mold and using a hot press to integrally mold them to obtain a composite bipolar plate. The molding temperature is 200° C., the pressure is 60 MPa, and the time is 9 minutes.

[0097] Step S4: adding 100g of glucose and 8g of tartaric acid to 1000g of distilled water, boiling for 10min, and adding 50g of ethanol after cooling to obtain a reducing solution; adding 5g of silver nitrate to 100g of distilled water to obtain a silver nitrate solution, adding 4g of sodium hydroxide to 100g of distilled water to obtain a sodium hydroxide solution, adding 50ml of NaOH solution to 50ml of AgNO3 solution to form an AgOH precipitate; slowly adding 5ml of ammonia water under stirring to dissolve the AgOH precipitate into a transparent liquid to obtain a silver ammonia complex solution, adding 1.5g of copper powder to 100ml of the reducing solution, slowly adding 60ml of the silver ammonia complex solution under magnetic stirring, reacting at room temperature for 30min, filtering, and drying in a 40°C vacuum oven for 5h to obtain silver-copper metal powder, and then calcining in a 300°C muffle furnace for 3h to obtain spherical silver-copper metal powder;

[0098] Step S5: Add 2.5 g of spherical silver-copper metal powder to 50 ml of epoxy resin, disperse evenly to obtain a conductive adhesive, and apply it to the surface of the copper plate with a coating thickness of 60 μm. Then place the composite bipolar plate and press it on a hot press at 100°C for 20 minutes to obtain an integrated current collecting plate.

[0099] Example 8: A method for preparing an integrated current collecting plate for a vanadium battery, comprising the following steps:

[0100] Step S1: adding 150g of nickel sulfate, 20g of nickel chloride, and 10g of boric acid to 1L of sulfuric acid electrolyte to prepare a mixed electrolyte, then adding 8g of carbon nanotubes and 0.07g of dodecyltrimethylammonium bromide, and performing ultrasonic dispersion at a frequency of 60Hz and a dispersion time of 20min to obtain a composite dispersion; using nickel foam as a cathode, the composite dispersion as an electrodeposition liquid, and an electrolytic nickel plate as an anode, performing electrodeposition at a current of 20A for 40min, placing the electrodeposited material in a 500°C muffle furnace, and filling the furnace with hydrogen and nitrogen with volume fractions of 75% and 25%, respectively, for protection, and heat treating for 6h to obtain carbon nanotube-deposited nickel foam;

[0101] Step S2: 70 parts by mass of polypropylene, 10 parts by mass of graphite, 10 parts by mass of carbon black, and 10 parts by mass of carbon nanotubes were melted and mixed in an internal mixer at a melting temperature of 160°C for 35 minutes, and the modified conductive particles were crushed to obtain modified conductive particles. The particles were placed in a mold and pressed using a hot press at a molding temperature of 175°C, a pressure of 90 MPa, and a time of 6 minutes to obtain a conductive sheet.

[0102] Step S3: placing the conductive sheet, modified nickel foam, and conductive sheet into a mold and using a hot press to integrally mold them to obtain a composite bipolar plate. The molding temperature is 175° C., the pressure is 90 MPa, and the time is 7 minutes.

[0103] Step S4: adding 50g of glucose and 9g of tartaric acid to 1000g of distilled water, boiling for 10min, and adding 120g of ethanol after cooling to obtain a reducing solution; adding 5g of silver nitrate to 100g of distilled water to obtain a silver nitrate solution, adding 4g of sodium hydroxide to 100g of distilled water to obtain a sodium hydroxide solution, adding 50ml of NaOH solution to 60ml of AgNO3 solution to form an AgOH precipitate; slowly adding 5ml of ammonia water under stirring to dissolve the AgOH precipitate into a transparent liquid to obtain a silver ammonia complex solution, adding 2g of copper powder to 100ml of the reducing solution, slowly adding 100ml of the silver ammonia complex solution under magnetic stirring, reacting at room temperature for 30min, filtering, and drying in a 40°C vacuum oven for 5h to obtain silver-copper metal powder, and then calcining in a 500°C muffle furnace for 3h to obtain spherical silver-copper metal powder;

[0104] Step S5: Add 2.5 g of spherical silver-copper metal powder to 50 ml of vinyl resin, disperse evenly to obtain a conductive adhesive, and apply it to the surface of the copper plate with a coating thickness of 70 μm. Then place the composite bipolar plate and press it on a hot press at 110°C for 20 minutes to obtain an integrated current collecting plate.

[0105] Example 9: A method for preparing an integrated current collecting plate for a vanadium battery, comprising the following steps:

[0106] Step S1: adding 150g of nickel sulfate, 20g of nickel chloride, and 10g of boric acid to 1L of sulfuric acid electrolyte to prepare a mixed electrolyte, then adding 9g of carbon nanotubes and 0.05g of dodecyltrimethylammonium bromide, and performing ultrasonic dispersion at a frequency of 70Hz and a dispersion time of 20min to obtain a composite dispersion; using nickel foam as a cathode, the composite dispersion as an electrodeposition liquid, and an electrolytic nickel plate as an anode, performing electrodeposition at a current of 30A for 20min, placing the electrodeposited material in a 400°C muffle furnace, and filling the furnace with hydrogen and nitrogen with volume fractions of 75% and 25%, respectively, for protection, and heat treating for 8h to obtain carbon nanotube-deposited nickel foam;

[0107] Step S2: 45 parts by mass of polypropylene, 30 parts by mass of graphite, 20 parts by mass of carbon black, and 10 parts by mass of carbon fiber were melted and mixed in an internal mixer at a melting temperature of 190°C for 60 minutes, and the modified conductive particles were crushed to obtain modified conductive particles. The particles were placed in a mold and pressed using a hot press at a molding temperature of 180°C, a pressure of 60 MPa, and a time of 7 minutes to obtain a conductive sheet.

[0108] Step S3: placing the conductive sheet, modified nickel foam, and conductive sheet into a mold and using a hot press to integrally mold them to obtain a composite bipolar plate. The molding temperature is 185° C., the pressure is 75 MPa, and the time is 6 minutes.

[0109] Step S4: adding 100g of glucose and 10g of tartaric acid to 1000g of distilled water, boiling for 10min, and adding 150g of ethanol after cooling to obtain a reducing solution; adding 5g of silver nitrate to 100g of distilled water to obtain a silver nitrate solution, adding 4g of sodium hydroxide to 100g of distilled water to obtain a sodium hydroxide solution, adding 50ml of NaOH solution to 70ml of AgNO3 solution to form an AgOH precipitate; slowly adding 10ml of ammonia water under stirring to dissolve the AgOH precipitate into a transparent liquid to obtain a silver ammonia complex solution, adding 2g of copper powder to 100ml of the reducing solution, slowly adding 70ml of the silver ammonia complex solution under magnetic stirring, reacting at room temperature for 30min, filtering, and drying in a 50°C vacuum oven for 5h to obtain silver-copper metal powder, and then calcining in a 400°C muffle furnace for 3h to obtain spherical silver-copper metal powder;

[0110] Step S5: Add 5 g of spherical silver-copper metal powder to 50 ml of vinyl resin, disperse evenly to obtain a conductive adhesive, and apply it to the surface of the copper plate with a coating thickness of 50 μm. Then place the composite bipolar plate and press it on a hot press at 90°C for 10 minutes to obtain an integrated current collecting plate.

[0111] Example 10: A method for preparing an integrated current collecting plate for a vanadium battery, comprising the following steps:

[0112] Step S1: adding 150g of nickel sulfate, 20g of nickel chloride, and 10g of boric acid to 1L of sulfuric acid electrolyte to prepare a mixed electrolyte, then adding 10g of carbon nanotubes and 0.05g of dodecyltrimethylammonium bromide, and performing ultrasonic dispersion at a frequency of 100Hz and a dispersion time of 10min to obtain a composite dispersion; using nickel foam as a cathode, the composite dispersion as an electrodeposition liquid, and an electrolytic nickel plate as an anode, performing electrodeposition at a current of 60A for 20min, placing the electrodeposited material in a muffle furnace at 600°C, and filling the furnace with hydrogen and nitrogen with volume fractions of 75% and 25% respectively for protection, and heat treating for 3h to obtain a nickel foam with carbon nanotube deposition;

[0113] Step S2: 45 parts by mass of polypropylene, 25 parts by mass of graphite, 25 parts by mass of carbon black, and 5 parts by mass of carbon fiber were melted and mixed in an internal mixer at a melting temperature of 175°C for 30 minutes, and the modified conductive particles were crushed to obtain modified conductive particles. The particles were placed in a mold and pressed using a hot press at a molding temperature of 170°C, a pressure of 80 MPa, and a time of 8 minutes to obtain a conductive sheet.

[0114] Step S3: placing the conductive sheet, modified nickel foam, and conductive sheet into a mold and using a hot press to integrally mold the composite bipolar plate at a molding temperature of 165° C., a pressure of 85 MPa, and a molding time of 8 minutes.

[0115] Step S4: adding 50g of glucose and 10g of tartaric acid to 1000g of distilled water, boiling for 10min, and adding 50g of ethanol after cooling to obtain a reducing solution; adding 5g of silver nitrate to 100g of distilled water to obtain a silver nitrate solution, adding 4g of sodium hydroxide to 100g of distilled water to obtain a sodium hydroxide solution, adding 50ml of NaOH solution to 50ml of AgNO3 solution to form an AgOH precipitate; slowly adding 10ml of ammonia water under stirring to dissolve the AgOH precipitate into a transparent liquid to obtain a silver ammonia complex solution, adding 2g of copper powder to 100ml of the reducing solution, slowly adding 100ml of the silver ammonia complex solution under magnetic stirring, reacting at room temperature for 30min, filtering, and drying in a 40°C vacuum oven for 5h to obtain silver-copper metal powder, and then calcining in a 500°C muffle furnace for 3h to obtain spherical silver-copper metal powder;

[0116] Step S5: Add 2.5 g of spherical silver-copper metal powder to 50 ml of epoxy resin, disperse evenly to obtain a conductive adhesive, and apply it to the surface of the copper plate with a coating thickness of 100 μm. Then place the composite bipolar plate and press it on a hot press at 110°C for 10 minutes to obtain an integrated current collecting plate.

[0117] Comparative Example 1: The preparation process of this comparative example differs from that of Example 1 only in that: unmodified nickel foam is used to prepare the composite bipolar plate; and the bending strength of the composite bipolar plate is tested to be 24.1 MPa.

[0118] Comparative Example 2: The preparation process of this comparative example differs from that of Example 1 only in that copper powder and silver powder are directly added to the thermosetting resin instead of spherical silver-copper metal powder.

[0119] Comparative Example 3: This comparative example is a blank control group, that is, the copper plate and the bipolar plate are directly assembled into a fuel cell stack without integrated preparation.

[0120] The integrated current collecting plates prepared in Examples 1-10 and Comparative Examples 1-3 were tested for contact resistance using a Burster 2316 precision resistance meter.

[0121] The embodiment and the comparative example were assembled into a stack for testing, and the current density was 80 mA / cm 2 , record the coulombic efficiency, voltage efficiency and energy efficiency. The test results are shown in Table 1:

[0122] Table 1: Battery performance test table of battery stacks assembled using the embodiment and comparative example

[0123]

[0124] It can be seen that by comparing Example 1 with Comparative Example 1, when the nickel foam is not modified with carbon nanotubes, the compatibility between the nickel foam and the carbon composite layer is poor, which affects the conductivity and the electrical properties of the integrated current collecting plate; by comparing Example 1 with Comparative Example 2, it can be seen that the test voltage efficiency of the comparative small battery stack is low. This is because silver-copper composite powder is prepared by silver plating on the surface of copper powder, and then heat treatment can melt the nano-scale silver particles on the surface of copper powder to form a continuous silver film, which improves the conductivity of the conductive adhesive. The direct use of copper powder and silver powder has poor compatibility; by comparing Example 1 with Comparative Example 3, it can be seen that the failure to use an integrated current collecting plate results in a large contact resistance between the electrode plate and the copper plate, thereby reducing the battery performance. Therefore, the present invention uses nickel foam as the skeleton material and improves the interface between the nickel foam and the carbon composite layer by depositing carbon nanotubes on the surface of the nickel foam, thereby improving the mechanical strength and conductivity of the composite bipolar plate. Heat treatment of the silver-copper composite powder can melt the nano-scale silver particles on the surface of the copper powder to form a continuous silver film, thereby improving the conductivity and oxidation resistance of the conductive adhesive and reducing the contact resistance between the bipolar plate and the copper plate, thereby improving the performance of the liquid flow battery.

[0125] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing an integrated current collecting plate for a vanadium battery, characterized in that: The following steps are involved: S1: adding carbon nanotubes and a dispersant to a mixed electrolyte to obtain a composite dispersion; using the composite dispersion to electrodeposit nickel foam to obtain a carbon nanotube-deposited nickel foam; the mixed electrolyte comprises 150 g / L nickel sulfate, 20 g / L nickel chloride, and 10 g / L boric acid; S2: Compression molding the resin and the conductive carbon material to obtain a conductive sheet; S3: integrally molding the conductive sheet and the carbon nanotube-deposited nickel foam to obtain a composite bipolar plate; S4: adding copper powder to the reducing solution, and then slowly adding the silver ammonia complex solution to obtain spherical silver-copper metal powder after the reaction; S5: adding the spherical silver-copper metal powder to a thermosetting resin to obtain a conductive adhesive; coating the conductive adhesive on the surface of a copper plate, placing the composite bipolar plate on the coated surface of the copper plate, and compression molding to obtain an integrated current collecting plate.

2. The preparation method according to claim 1, wherein In said S1: The concentration of the carbon nanotubes in the composite dispersion is 1-10 g / L; The dispersant is selected from at least one of sodium dodecylbenzenesulfonate, sodium lauryl sulfate, and dodecyltrimethylammonium bromide, and the concentration of the dispersant in the composite dispersion is 0.05-0.1 g / L; The composite dispersion liquid needs to be ultrasonically dispersed, and the frequency of the ultrasonic dispersion is 50-100 Hz and the time is 10-30 minutes.

3. The preparation method according to claim 1, wherein In said S1: The electrodeposition current is 20-50A and the time is 20-60min; After the electrodeposition, the nickel foam is heat treated at a temperature of 400-600° C. for 3-8 hours in an atmosphere of a mixed gas of hydrogen and nitrogen in a volume ratio of 3:

1.

4. The preparation method according to claim 1, wherein In said S2: The resin is selected from at least one of polyethylene and polypropylene; The conductive carbon material is selected from at least one of carbon black, graphite, carbon fiber, and carbon nanotubes; The mass ratio of the conductive carbon material to the resin is 1:(0.4-2.3).

5. The preparation method according to claim 1, wherein In said S2: The resin and the conductive carbon material are melt-mixed before being molded, wherein the temperature of the melt-mixing is 150-200° C. and the time is 30-60 minutes; The compression molding process is performed at a temperature of 150-200° C., a pressure of 50-100 MPa, and a time of 5-10 minutes.

6. The preparation method according to claim 1, wherein In said S3: The integral compression molding process is performed at a temperature of 150-200° C., a pressure of 50-100 MPa, and a time of 5-10 minutes.

7. The preparation method according to claim 1, wherein In said S4: The reducing solution is prepared by adding 40 to 100 parts by mass of glucose and 2 to 10 parts by mass of tartaric acid to 1000 parts by mass of distilled water, boiling for 10 minutes, cooling, adding 50 to 200 parts by mass of ethanol, and mixing to obtain the reducing solution.

8. The preparation method according to claim 1, wherein In said S4: The preparation method of the silver-ammine complex solution is as follows: 50 to 100 parts by volume of a 4% NaOH solution is added to 50 to 100 parts by volume of a 5% AgNO3 solution to form an AgOH precipitate, and then 5 to 50 parts by volume of ammonia water is slowly added under stirring to dissolve the AgOH precipitate into a transparent liquid, thereby obtaining the silver-ammine complex solution.

9. The preparation method according to claim 1, wherein In said S4: The amount of copper powder is 10-30 g / L; The volume ratio of the reducing solution to the silver ammonia complex solution is 1:(0.5~1); The reaction conditions are as follows: reacting at room temperature, filtering to obtain filter residue, vacuum drying, and calcining to obtain the spherical silver-copper metal powder; wherein, The reaction time of the reaction at room temperature is 30 min; The vacuum drying temperature is 40-60°C and the time is 2-5 hours; The calcination temperature is 200-500° C., the calcination time is 0.5-3 hours, and the atmosphere is air.

10. The preparation method according to claim 1, wherein In said S5: The thermosetting resin is selected from at least one of epoxy resin, unsaturated resin and vinyl resin; The mass fraction of the spherical silver-copper metal powder in the conductive adhesive is 4% to 10%; The coating thickness is 50-100 μm; The integrated current collecting plate obtained by compression molding is performed on a hot press, and the temperature of the compression molding on the hot press is 80-120° C. and the time is 5-20 minutes.

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