Graphene oxide slurry, gas diffusion layer, and methods of making and using the same and zinc-air flow battery electrodes

Abstract

The present application relates to the field of gas diffusion layer and flow battery, and particularly relates to a kind of graphene oxide slurry, gas diffusion layer and its preparation method and application and flow battery electrode.The present application provides a kind of graphene oxide slurry, by weight parts, the graphene oxide slurry includes: graphene oxide 0.01-0.20 parts;Fluorine-containing polyolefin 0.50-1.50 parts;Carbon-based conductive agent 0.20-1.00 parts;Solvent 30.00-60.00 parts.The graphene oxide slurry described in the present application includes graphene oxide and fluorine-containing polyolefin, by the electrostatic combination of fluorine atom in graphene oxide and fluorine-containing polyolefin, good conductivity, hydrophobic stable gas diffusion layer is prepared, is applied to flow battery electrode, especially gas-liquid-solid three-phase reaction flow battery electrode, can effectively improve the performance and cycle life of flow battery.

Description

Technical Field

[0001] This invention relates to the fields of gas diffusion layers and flow batteries, specifically to a graphene oxide slurry, a gas diffusion layer, its preparation method and application, and a flow battery electrode. Background Technology

[0002] Flow batteries are a type of high-efficiency, renewable battery system with broad application prospects in energy storage and green chemistry. In flow batteries, the gas diffusion layer is one of the core components, used to balance electrolyte supply and diffusion, ensuring efficient battery operation.

[0003] Currently, various gas diffusion layer materials for fuel cells on the market suffer from varying degrees of defects, such as poor conductivity, poor permeability, and insufficient wettability. This is particularly true when traditional carbon paper is used in flow batteries, leading to negative impacts on battery performance and lifespan. Furthermore, traditional flow battery reactions typically involve solid-liquid or liquid-liquid two-phase reactions, rarely involving gas-liquid-solid three-phase reactions. However, current flow battery systems that typically require gas-liquid-solid three-phase reactions include zinc-air and zinc-nickel-air batteries. If long-term cycling at the gas-liquid-solid three-phase interface is required, a gas diffusion layer specifically designed for flow batteries needs to be developed, possessing high hydrophobicity to prevent "flooding" within the flow battery. Traditional carbon paper, primarily used in fuel cells, suffers a significant decrease in cycle life and other performance characteristics when applied to flow batteries due to the different system requirements. Therefore, improving the performance of gas diffusion layers has become a research hotspot in the field of flow batteries. Summary of the Invention

[0004] This invention addresses the problem of low cycle life and battery performance in existing flow batteries due to the lack of a dedicated gas diffusion layer. It provides a graphene oxide slurry, a gas diffusion layer, its preparation method and application, and a flow battery electrode. The graphene oxide slurry of this invention comprises graphene oxide and a fluorinated polyolefin. A gas diffusion layer with good conductivity and stable hydrophobicity is prepared through the electrostatic bonding of fluorine atoms in the graphene oxide and the fluorinated polyolefin. When applied to flow battery electrodes, particularly those involving a gas-liquid-solid three-phase reaction, it can effectively improve the performance and cycle life of flow batteries.

[0005] To achieve the above objectives, a first aspect of the present invention provides a graphene oxide slurry, which, by weight, comprises:

[0006] 0.01-0.20 parts of graphene oxide;

[0007] Fluorinated polyolefins: 0.50-2.00 parts;

[0008] 0.20-1.00 parts of carbon-based conductive agent;

[0009] Solvent 30.00-60.00 parts.

[0010] A second aspect of the present invention provides a method for preparing a gas diffusion layer, the method comprising:

[0011] A slurry is coated on the surface of the substrate layer, dried, and sintered to obtain a gas diffusion layer; the slurry is the graphene oxide slurry described in this invention.

[0012] A third aspect of the present invention provides a gas diffusion layer prepared by the preparation method described in the present invention.

[0013] The fourth aspect of the present invention provides the application of the gas diffusion layer of the present invention in the electrode of a flow battery with a gas-liquid-solid three-phase reaction.

[0014] The fifth aspect of the present invention provides a zinc-air flow battery electrode, comprising a gas diffusion layer and a catalyst layer, wherein the gas diffusion layer is the gas diffusion layer described in the present invention.

[0015] Through the above technical solution, a gas diffusion layer is prepared using the graphene oxide slurry described in this invention. The graphene oxide electrostatically combines with the fluorine atoms in the fluorinated polyolefin, improving the conductivity and stability of the gas diffusion layer, resulting in a gas diffusion layer with good conductivity and strong hydrophobicity, exhibiting excellent performance.

[0016] The gas diffusion layer of this invention has a microporous structure, which facilitates the transport and diffusion of electrolytes. When applied to flow battery electrodes, especially those with a gas-liquid-solid three-phase reaction, it can significantly improve the output power and energy efficiency of the battery, further optimizing the performance and lifespan of the flow battery. Regarding the improved cycle life of the flow battery, the corrosion resistance mechanism of the gas diffusion layer is speculated to be as follows: After adding graphene oxide to the gas diffusion layer of this invention, the surface has a large number of C=O and CO bonds. These groups can combine with fluorine atoms through induction, enhancing the interfacial properties between the base layer and PTFE in the gas diffusion layer. This maintains the hydrophobic network of PTFE, preventing the entry of corrosive agents such as O2 and H2O, thus improving corrosion resistance compared to commercial carbon paper.

[0017] The method for preparing the gas diffusion layer described in this invention is simple and easy to implement, with relatively low preparation cost, and is suitable for large-scale production. Attached Figure Description

[0018] Figure 1 This is a SEM image of the gas diffusion layer prepared in Example 1 of this invention;

[0019] Figure 2This is the XPS energy spectrum of the gas diffusion layer prepared in Example 1 of this invention;

[0020] Figure 3a This is a schematic diagram of the charging and discharging of Embodiment 1 of the present invention in a zinc-air flow battery;

[0021] Figure 3b This is a schematic diagram of the charging and discharging of Comparative Example 1 of the present invention in a zinc-air flow battery;

[0022] Figure 4 This is a stability test diagram of the application of Embodiment 1 of the present invention in a zinc-air flow battery;

[0023] Figure 5 These are single-cycle charge-discharge curves of Embodiment 1, Comparative Example 1, and Comparative Example 2 of the present invention applied to zinc-air flow batteries;

[0024] Figure 6 These are resistivity bar charts of Embodiment 1, Comparative Example 1, and Comparative Example 2 of the present invention applied to zinc-air flow batteries before and after cycling. Detailed Implementation

[0025] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0026] The first aspect of the present invention provides a graphene oxide slurry, which, by weight, comprises:

[0027] 0.01-0.20 parts of graphene oxide;

[0028] Fluorinated polyolefins: 0.50-2.00 parts;

[0029] 0.20-1.00 parts of carbon-based conductive agent;

[0030] Solvent 30.00-60.00 parts. Compared with the prior art, the graphene oxide slurry of the present invention significantly increases the proportion of fluorinated polyolefins. When the gas diffusion layer is prepared using the graphene oxide slurry of the present invention, the graphene oxide and the fluorine atoms in the fluorinated polyolefins are electrostatically bonded, improving the conductivity and stability of the gas diffusion layer, resulting in a gas diffusion layer with good conductivity and strong hydrophobicity, exhibiting excellent performance.

[0031] In this invention, the high fluorine content of the graphene oxide slurry is beneficial for the electrostatic bonding of fluorine atoms in graphene oxide and fluorinated polyolefins, thereby improving the performance of the gas diffusion layer. According to a preferred embodiment of the invention, the fluorine content in the graphene oxide slurry is 30-70 wt% of the total mass of graphene oxide, fluorinated polyolefins, and carbon-based conductive agent, for example, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, or 60 wt%, preferably 35-55 wt%. Within the aforementioned range, it is beneficial for improving the conductivity and hydrophobicity of the gas diffusion layer.

[0032] In this invention, the oxygen content in the graphene oxide slurry, by mass content, can be selected within a wide range. This is an illustrative example, but does not limit the scope of the invention. According to a preferred embodiment of the invention, the oxygen content in the graphene oxide is 20%-30%, for example, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or any combination of two of the above values. Within the aforementioned range, it is beneficial to improve the conductivity and hydrophobicity of the gas diffusion layer. In this embodiment of the invention, graphene oxide with an oxygen content of 23.1% is used as an example to illustrate the advantages of the invention, but does not limit the scope of the invention.

[0033] In a preferred embodiment of the present invention, the graphene oxide in the graphene oxide slurry is 0.03-0.10 parts by weight, for example, 0.04 parts, 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts, or any combination of two of the above values.

[0034] In a preferred embodiment of the present invention, the fluorinated polyolefin in the graphene oxide slurry is 0.60-1.20 parts by weight, for example 0.70 parts, 0.08 parts, 0.90 parts, 1.00 parts, 1.10 parts, or any combination of two of the above values.

[0035] In a preferred embodiment of the present invention, the carbon-based conductive agent in the graphene oxide slurry is 0.30-0.80 parts by weight, for example, 0.40 parts, 0.45 parts, 0.50 parts, 0.60 parts, 0.65 parts, 0.70 parts, 0.75 parts, or any combination of two of the above values.

[0036] In this invention, the range of types of fluorinated polyolefins is relatively wide. This is an illustrative example, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the fluorine content in the fluorinated polyolefin is not less than 50 wt%, preferably 60 wt%-80 wt%, for example 62 wt%, 65 wt%, 68 wt%, 72 wt%, 75 wt%, and 78 wt%. Within the aforementioned range, graphene oxide can better electrostatically bond with the fluorine in the fluorinated polyolefin.

[0037] According to a preferred embodiment of the present invention, the fluorinated polyolefin is selected from one or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride, and trifluoropropylene, and more preferably polytetrafluoroethylene.

[0038] In this invention, the carbon-based conductive agent is a carbon-based conductive agent material that does not contain graphene oxide. The range of types of carbon-based conductive agents that can be selected is relatively wide. This is an illustrative example, but it does not limit the scope of this invention. The carbon-based conductive agent is selected from one or more of acetylene black, graphite powder, XC-72R, and carbon nanotubes. According to a preferred embodiment of this invention, the carbon-based conductive agent is selected from a mixture of acetylene black, graphite powder, and XC-72R.

[0039] According to a preferred embodiment of the present invention, the mass ratio of acetylene black, graphite powder, and XC-72R is 1:1-2:2-8.

[0040] In this invention, a wide range of solvents can be selected. This is an illustrative example, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the solvent is selected from one or more of water, ethanol, N,N-dimethylformamide and N,N-dimethylacetamide. In the embodiments of the invention, a mixed solvent of ethanol and water is used to illustrate the advantages of the invention, but it does not limit the scope of the invention.

[0041] In this invention, according to a preferred embodiment, the mass ratio of polytetrafluoroethylene to graphene oxide is 10-25:1, for example, 12:1, 15:1, 18:1, 20:1, 22:1, or 24:1.

[0042] In this invention, according to a preferred embodiment, the mass ratio of carbon-based conductive agent to graphene oxide is 5-20:1, for example, 6:1, 8:1, 10:1, 13:1, 15:1, or 18:1.

[0043] In this invention, the graphene oxide slurry described herein can be obtained simply by mixing and dispersing graphene oxide, carbon-based conductive agent, fluorinated polyolefin, and solvent evenly. There are no special requirements for the preparation method of the graphene oxide slurry.

[0044] In this invention, the form of the fluorinated polyolefin is not particularly limited. It can be in powder form or in the form of a dispersion of fluorinated polyolefin, such as an emulsion of fluorinated polyolefin. In the embodiments of this invention, an aqueous emulsion of 10 wt% PTFE is mainly used as an example to illustrate the advantages of this invention, but this does not limit the scope of this invention.

[0045] In this invention, the mixing is not particularly limited, as long as it can be fully mixed so that the slurry is free of obvious particles. According to one embodiment of this invention, graphene oxide and carbon-based conductive agent are mixed and ultrasonically dispersed to achieve uniform dispersion.

[0046] A second aspect of the present invention provides a method for preparing a gas diffusion layer, the method comprising:

[0047] A slurry is coated on the surface of the substrate layer, dried, and sintered to obtain a gas diffusion layer; the slurry is the graphene oxide slurry described in this invention. Through the above preparation method, a gas diffusion layer is prepared using the graphene oxide slurry described in this invention. The graphene oxide electrostatically bonds with the fluorine atoms in the fluorinated polyolefin, improving the conductivity and stability of the gas diffusion layer, resulting in a gas diffusion layer with good conductivity and strong hydrophobicity, exhibiting excellent performance.

[0048] In this invention, the range of materials that can be selected for the base layer is relatively wide. According to a preferred embodiment of this invention, the material of the base layer is selected from one or more of carbon fiber felt or carbon fiber paper. The aforementioned materials have good electrical conductivity and chemical stability, and can be used to prepare a gas diffusion layer with good electrical conductivity and strong stability.

[0049] According to a preferred embodiment of the present invention, the substrate layer is made of carbon fiber paper. The carbon fiber paper is thinner and has greater mechanical strength, making it less prone to breakage, and thus a gas diffusion layer with better electrical conductivity can be prepared.

[0050] In this invention, the coating amount of the slurry can be selected from a wide range. According to a preferred embodiment of this invention, the coating amount of the slurry is 15-1000 mg / cm³. 2 For example, 20 mg / cm 2 50mg / cm 2 80mg / cm 2 100mg / cm 2 200mg / cm 2 300mg / cm 2 400mg / cm 2 500mg / cm 2 600mg / cm 2 700mg / cm 2 800mg / cm 2900mg / cm 2 Or, a range consisting of any two of the above values, more preferably, 50-600 mg / cm³. 2 Within the aforementioned range, the prepared gas diffusion layer exhibits good electrical conductivity and strong hydrophobicity.

[0051] In this invention, the drying conditions are not particularly required, and conventional drying conditions in the art are all acceptable. This is an illustrative example, but it does not limit the scope of the invention. According to one embodiment of the invention, the drying conditions include: a temperature of 60-100℃, for example, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, or 95℃; and a drying time that can be determined according to actual needs. Preferably, the drying time is 12-24 hours. In this embodiment of the invention, drying at 80℃ for 12 hours is used as an example to illustrate the advantages of the invention, but this does not limit the scope of the invention.

[0052] In this invention, the sintering conditions are not particularly required; conventional sintering conditions in the art are acceptable. This is an illustrative example and does not limit the scope of the invention. According to one embodiment of the invention, the sintering conditions include: a temperature of 300-350℃, for example, 300℃, 310℃, 320℃, 330℃, 340℃, or 350℃; and a sintering time that can be determined according to actual needs. Preferably, the time is 0.5-1 hour. In this embodiment, sintering at 300℃ for 0.5 hours is used as an example to illustrate the advantages of the invention, but this does not limit the scope of the invention. Sintering can remove excess surfactants from the slurry, resulting in better conductivity of the gas diffusion layer.

[0053] The sintering is carried out under oxygen-containing conditions, but according to a preferred embodiment of the present invention, sintering is carried out in air.

[0054] In this invention, when the base layer material is carbon fiber paper, the coating process also includes hot pressing. The hot pressing method makes the carbon fiber paper more compact, reduces the volume resistivity, improves conductivity, and gives it strong mechanical properties.

[0055] In this invention, the hot-pressing conditions are not particularly required; conventional hot-pressing conditions in the art are all acceptable. This is an illustrative example, but it does not limit the scope of the invention. According to one embodiment of the invention, the hot-pressing conditions include: a temperature of 150-300℃, for example, 150℃, 180℃, 200℃, 240℃, or 280℃; a hot-pressing pressure of 1-50MPa, for example, 5MPa, 10MPa, 20MPa, 30MPa, or 40MPa; and a hot-pressing time that can be determined according to actual needs. Generally, the time is 2-6 hours. In this embodiment of the invention, hot-pressing at 200℃ and 10MPa for 3 hours is used as an example to illustrate the advantages of the invention, but this does not limit the scope of the invention.

[0056] In this invention, the coating method is not particularly limited, as long as the slurry can be evenly coated on the surface of the substrate. For example, it can be coated using equipment such as a coating machine, or it can be coated manually.

[0057] A third aspect of the present invention provides a gas diffusion layer prepared by the preparation method described in the present invention.

[0058] In this invention, the thickness of the prepared gas diffusion layer can be selected within a wide range. According to a preferred embodiment of this invention, the thickness of the gas diffusion layer is 0.010-0.025 mm, for example, 0.010 mm, 0.014 mm, 0.018 mm, or 0.024 mm. Within the aforementioned range, the prepared gas diffusion layer has good electrical conductivity and gas permeability.

[0059] A fourth aspect of this invention provides the application of the gas diffusion layer described herein in a flow battery electrode for a gas-liquid-solid three-phase reaction. The gas diffusion layer of this invention has a microporous structure. When applied to a flow battery electrode, particularly a flow battery electrode for a gas-liquid-solid three-phase reaction, it facilitates electrolyte transport and diffusion, thereby improving the battery's output power and energy efficiency, and further optimizing the performance and lifespan of the flow battery.

[0060] The gas diffusion layer described in this invention is applicable to various gas-liquid-solid three-phase reaction flow batteries, the construction and preparation methods of which are well known. In this invention, the gas diffusion layer is used to load the positive electrode active material to prepare a positive electrode or oxygen electrode.

[0061] In this invention, the range of liquid flow batteries that can be selected from the gas-liquid-solid three-phase reaction is relatively wide. According to a preferred embodiment of this invention, they are selected from zinc-air liquid flow batteries, sodium-air liquid flow batteries, zinc-nickel-air liquid flow batteries, or lithium-air liquid flow batteries.

[0062] A fifth aspect of this invention provides a zinc-air flow battery electrode, comprising a gas diffusion layer and a catalyst layer, wherein the gas diffusion layer is the gas diffusion layer described in this invention. The flow battery electrode of this invention provides a sufficient three-phase interface for the oxygen reduction and oxygen evolution reactions in a zinc-air flow battery, improving the battery's output power and energy efficiency, and further optimizing the performance and lifespan of the flow battery.

[0063] In this invention, the active material in the catalyst layer is a redox material used in the field for air electrodes. There is no particular limitation on the type of active material. According to a preferred embodiment of this invention, the active material is selected from one or more of Pt / C, noble metal alloys, metal oxides, and doped carbon materials. For example, the active material can be IrO2 / RuO2, Pt / C, etc. The use of Pt / C as the active material in this embodiment exemplifies the advantages of the invention, but does not limit the scope of the invention.

[0064] In this invention, there is no particular limitation on the loading method of the catalyst layer. Conventional loading methods in the art are acceptable. For example, the catalyst layer can be loaded onto the gas diffusion layer by coating or by hot pressing.

[0065] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0066] In the following embodiments, the hydrophobicity of the gas diffusion layer was detected by means of a contact angle measuring instrument. The contact angle parameters were measured using the EASY DROP contact angle tester from KRUSS GmbH, Germany, with a measurement range of 1-180° and a resolution of ±0.1°, in static contact angle measurement mode.

[0067] In the following examples, the graphene oxide was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., and the oxygen content in the graphene oxide was found to be 23.1% by elemental analysis using XPS.

[0068] In the following examples, the positive electrode of a zinc-air flow battery was prepared using the gas diffusion layer obtained in the previous examples, and the zinc-air flow battery was assembled and tested as follows:

[0069] Preparation of integrated oxygen electrode: An integrated oxygen electrode was prepared by hot pressing a catalyst layer with Pt / C (Sigma-Oggrich, Inc., USA, (GR99.5)) as the active material with a gas diffusion layer prepared in the example at 120°C for 2 min.

[0070] Flow battery assembly: The positive electrode uses the integrated oxygen electrode prepared above, with an active material reaction area of ​​1*1cm. 2 The test was conducted; the negative electrode used a polished zinc sheet, the middle flow channel was made of acrylic sheet, and the assembled battery used a peristaltic pump to deliver 7 mol L... -1 KOH, 0.5 mol L -1 The ZnO electrolyte was applied at 30 rpm. -1 The pump is pumped into the zinc-air battery channel at a certain speed.

[0071] Test method for the cycle performance of flow batteries: The geometric area of ​​the positive electrode exposed to air is 1 cm². 2 At 10mA cm -2 Its cycle stability was tested at fixed time intervals (10 minutes of discharge).

[0072] Test method for charge and discharge performance of flow batteries: After discharging, charge for 10 minutes and then use Blue Electric testing equipment to test the charge and discharge performance.

[0073] Power density testing method for flow batteries: Set the power program, with current density ranging from 1-300 mA cm⁻¹. -2 Power density tests were conducted, and the maximum power density was observed based on the maximum value of the curve after the test was completed.

[0074] The resistivity test method for flow batteries involves arranging metal probes linearly and applying pressure to the surface of the material being measured. When a current I is input through the two outer probes 1 and 4, a potential difference V is formed between the inner probes 2 and 3. 2,3 The surface resistivity ρ of the sample is calculated using the formula. xy .

[0075] ρ xy =KV 2,3 / I

[0076] Where, ρ xy : Resistivity at the detection location, in Ωcm; K: Probe coefficient of the four probes;

[0077] V 2,3 2: Potential difference between probes 2 and 3, in V; I: Current passing between probes 1 and 4, in A.

[0078] Example 1

[0079] (1) Mix 0.1g of acetylene black, 0.1g of graphite powder, 0.3g of XC-72R and 0.05g of graphene oxide with 6.5g of 10wt% PTFE in an aqueous emulsion, add 50ml of ethanol solvent, and use mechanical stirring and ultrasonic dispersion to obtain graphene oxide slurry.

[0080] (2) Apply the graphene oxide slurry obtained in step (1) at a coating amount of 500 mg / cm³. 2 The slurry was uniformly coated on the surface of carbon fiber paper, and then hot-pressed at 200℃ and 10MPa for 3 hours to fix the slurry on the surface of carbon fiber paper. After drying at 80℃ for 12 hours, the sintering was carried out at 300℃ for 0.5 hours to prepare a gas diffusion layer with a thickness of 0.02 mm.

[0081] The contact angle of the gas diffusion layer was measured to be 158° using a contact angle measuring instrument.

[0082] Figure 1 The image shown is a SEM image of the gas diffusion layer prepared in Example 1. It illustrates that in this invention, the graphene oxide-gas diffusion layer forms an interwoven structure and porosity through the fusion of multiple materials to ensure the good mechanical strength of the carbon paper. Compared with commercial carbon paper fibers with a smoother and more delicate surface and a simpler surface structure, the graphene oxide-gas diffusion layer carbon paper fiber prepared in this invention has good strength and air permeability, making it suitable as a substrate support material for oxygen electrodes in flow batteries.

[0083] Figure 2 The image shows the XPS spectrum of the gas diffusion layer. After the addition of graphene oxide, the surface of the gas diffusion layer has a large number of C=O and CO bonds. These groups can combine with fluorine atoms through induction. The electronegativity of fluorine atoms in the CF bonds causes the electron clouds of oxygen atoms to shift, thereby electrostatically binding and enhancing the conductive network of the material, thus improving conductivity.

[0084] The gas diffusion layer was fabricated into an electrode using the aforementioned method and applied to a zinc-air flow battery. The charge-discharge performance results of the zinc-air flow battery are as follows: Figure 3a As shown, the cycle life is as high as 300 hours, and the curve is smoother and more stable than that of Comparative Example 1; the cycle stability of the zinc-air flow battery is as follows: Figure 4 As shown, after nearly 300 hours of cycling, the voltage difference of the battery increased by only 0.2V, indicating that the gas diffusion layer has good cycling stability in a strong alkaline liquid flow system.

[0085] According to the energy efficiency cycle test of the zinc-air flow battery, the battery energy efficiency can reach 67% after 1200 cycles.

[0086] The resistivity of the zinc-air flow battery before and after cycling was tested, and the test results are as follows: Figure 6 As shown, the resistivity was 0.01 Ω·cm before cycling, and decreased to 0.02 Ω·cm after 30 cycles.

[0087] Figure 5 The single-cycle charge-discharge curves of the gas diffusion layers of Examples 1, 1, and 2 applied to zinc-air flow batteries are shown. The results show that the zinc-air flow battery prepared with the gas diffusion layer of Example 1 has the highest voltage efficiency of 56.8% and the least battery polarization, indicating that its charge-discharge cycle performance is better than that of Comparative Examples 1 and 2.

[0088] Example 2

[0089] The difference from Example 1 is that the base layer is made of carbon fiber felt; specifically:

[0090] (1) Mix 0.1g of acetylene black, 0.1g of graphite powder, 0.3g of XC-72R and 0.05g of graphene oxide with 6.5g of 10wt% PTFE in an aqueous emulsion, add 50ml of ethanol solvent, and use mechanical stirring and ultrasonic dispersion to obtain graphene oxide slurry.

[0091] (2) Apply the graphene oxide slurry obtained in step (1) at a coating amount of 500 mg / cm³. 2 A gas diffusion layer with a thickness of 0.02 mm was prepared by uniformly coating the surface of carbon fiber felt, drying at 80℃ for 12 h, and sintering at 300℃ for 0.5 h.

[0092] The contact angle of the gas diffusion layer was measured to be 147° using a contact angle meter.

[0093] The gas diffusion layer was fabricated into an electrode using the aforementioned method and applied to a zinc-air flow battery. After 1200 cycles, the battery energy efficiency was 65%.

[0094] Example 3

[0095] The difference from Example 1 is that the amount of 10wt% PTFE emulsion added is 13g; specifically:

[0096] (1) Mix 0.1g of acetylene black, 0.1g of graphite powder, 0.3g of XC-72R and 0.05g of graphene oxide with 13g of 10wt% PTFE in an aqueous emulsion, add 50ml of ethanol solvent, and use mechanical stirring and ultrasonic dispersion to obtain graphene oxide slurry.

[0097] (2) Apply the graphene oxide slurry obtained in step (1) at a coating amount of 500 mg / cm³. 2 The slurry was uniformly coated on the surface of carbon fiber paper, and then hot-pressed at 200℃ and 10MPa for 3 hours to fix the slurry on the surface of carbon fiber paper. After drying at 80℃ for 12 hours, the sintering was carried out at 300℃ for 0.5 hours to prepare a gas diffusion layer with a thickness of 0.02 mm.

[0098] The contact angle of the gas diffusion layer was measured to be 143° using a contact angle meter.

[0099] The gas diffusion layer was fabricated into an electrode using the aforementioned method and applied to a zinc-air flow battery. After 1200 cycles, the battery energy efficiency was 63%.

[0100] Example 4

[0101] The difference from Example 1 is that the coating amount of graphene oxide slurry is 700 mg / cm³. 2 Specifically:

[0102] (1) Mix 0.1g of acetylene black, 0.1g of graphite powder, 0.3g of XC-72R and 0.05g of graphene oxide with 6.5g of 10wt% PTFE in an aqueous emulsion, add 50ml of ethanol solvent, and use mechanical stirring and ultrasonic dispersion to obtain graphene oxide slurry.

[0103] (2) Apply the graphene oxide slurry obtained in step (1) at a coating amount of 700 mg / cm³. 2 The slurry was uniformly coated on the surface of carbon fiber paper, and after hot pressing at 200℃ and 10MPa for 3 hours, the slurry was fixed on the surface of the carbon fiber paper. It was then dried at 80℃ for 12 hours and sintered at 300℃ for 0.5 hours to obtain a gas diffusion layer with a thickness of 0.022 mm.

[0104] The contact angle of the gas diffusion layer was measured to be 154° using a contact angle meter.

[0105] The gas diffusion layer was fabricated into an electrode using the aforementioned method and applied to a zinc-air flow battery. After 1200 cycles, the battery energy efficiency was 62%.

[0106] Example 5

[0107] (1) Mix 0.1g of acetylene black, 0.2g of graphite powder, 0.2g of XC-72R and 0.08g of graphene oxide with 12g of 10wt% polyvinylidene fluoride aqueous emulsion, add 50ml of ethanol solvent, and use mechanical stirring and ultrasonic dispersion to obtain graphene oxide slurry.

[0108] (2) Apply the graphene oxide slurry obtained in step (1) at a coating amount of 200 mg / cm³. 2 The slurry was uniformly coated on the surface of carbon fiber paper, and then hot-pressed at 200℃ and 10MPa for 3 hours to fix the slurry on the surface of carbon fiber paper. After drying at 80℃ for 12 hours, the sintering was carried out at 300℃ for 0.5 hours to prepare a gas diffusion layer with a thickness of 0.015 mm.

[0109] The contact angle of the gas diffusion layer was measured to be 148° using a contact angle meter.

[0110] The gas diffusion layer was fabricated into an electrode using the aforementioned method and applied to a zinc-air flow battery. After 1200 cycles, the battery energy efficiency was 66%.

[0111] Example 6

[0112] (1) Mix 0.1g of acetylene black, 0.1g of graphite powder, 0.3g of XC-72R and 0.05g of graphene oxide with 10g of 10wt% polyhexafluoropropylene water emulsion, add 50ml of ethanol solvent, and use mechanical stirring and ultrasonic dispersion to obtain graphene oxide slurry.

[0113] (2) Apply the graphene oxide slurry obtained in step (1) at a coating amount of 500 mg / cm³. 2 The slurry was uniformly coated on the surface of carbon fiber paper, and then hot-pressed at 200℃ and 10MPa for 3 hours to fix the slurry on the surface of carbon fiber paper. After drying at 80℃ for 12 hours, the sintering was carried out at 300℃ for 0.5 hours to prepare a gas diffusion layer with a thickness of 0.020 mm.

[0114] The contact angle of the gas diffusion layer was measured to be 152° using a contact angle meter.

[0115] The gas diffusion layer was fabricated into an electrode using the aforementioned method and applied to a zinc-air flow battery. After 1200 cycles, the battery energy efficiency was 66%.

[0116] Example 7

[0117] The difference from Example 1 is that the amount of 10wt% PTFE emulsion added is 20g, specifically:

[0118] (1) Mix 0.1g of acetylene black, 0.1g of graphite powder, 0.3g of XC-72R and 0.05g of graphene oxide with 20g of 10wt% PTFE in an aqueous emulsion, add 50ml of ethanol solvent, and disperse evenly by mechanical stirring and ultrasonication to obtain graphene oxide slurry.

[0119] (2) Apply the graphene oxide slurry obtained in step (1) at a coating amount of 500 mg / cm³. 2 The slurry was uniformly coated on the surface of carbon fiber paper, and then hot-pressed at 200℃ and 10MPa for 3 hours to fix the slurry on the surface of carbon fiber paper. After drying at 80℃ for 12 hours, the sintering was carried out at 300℃ for 0.5 hours to prepare a gas diffusion layer with a thickness of 0.02 mm.

[0120] The contact angle of the gas diffusion layer was measured to be 145° using a contact angle meter.

[0121] The gas diffusion layer was fabricated into an electrode using the aforementioned method and applied to a zinc-air flow battery. After 1200 cycles, the battery energy efficiency was 62%.

[0122] Comparative Example 1

[0123] Instead of using the gas diffusion layer described in this invention, commercial carbon paper (Frederick carbon paper, model H14CX653) is directly selected as the gas diffusion layer for use in flow batteries: the contact angle of commercial carbon paper is 132°.

[0124] Electrodes were fabricated from commercial carbon paper using the aforementioned method and applied to a zinc-air flow battery. The charge-discharge performance results of the zinc-air flow battery are as follows: Figure 3b As shown, leakage occurred after 200 hours of cycling; the battery energy efficiency was 60% after 745 cycles.

[0125] The single-cycle charge-discharge curve of the zinc-air flow battery is as follows: Figure 5 As shown, the voltage efficiency is 50.5%, and the battery polarization is relatively large. The resistivity of the zinc-air flow battery before and after cycling was tested, and the test results are as follows. Figure 6 As shown, the resistivity was 0.02 Ω·cm before cycling, and decreased to 0.03 Ω·cm after 30 cycles.

[0126] Comparative Example 2

[0127] The difference from Example 1 is that graphene oxide is replaced with graphene; specifically:

[0128] (1) Mix 0.1g of acetylene black, 0.1g of graphite powder, 0.3g of XC-72R and 0.05g of graphene with 6.5g of 10wt% PTFE in an aqueous emulsion, add 50ml of ethanol solvent, and use mechanical stirring and ultrasonic dispersion to obtain graphene slurry.

[0129] (2) Apply the graphene slurry obtained in step (1) at a coating amount of 500 mg / cm³. 2 The slurry was uniformly coated on the surface of carbon fiber paper, and then hot-pressed at 200℃ and 10MPa for 3 hours to fix the slurry on the surface of carbon fiber paper. After drying at 80℃ for 12 hours, the sintering was carried out at 300℃ for 0.5 hours to prepare a gas diffusion layer with a thickness of 0.2 mm.

[0130] The contact angle of the gas diffusion layer was measured to be 137° using a contact angle meter.

[0131] The gas diffusion layer was fabricated into an electrode using the aforementioned method and applied to a zinc-air flow battery. After 771 cycles, the battery energy efficiency was 60%.

[0132] The single-cycle charge-discharge curve of the zinc-air flow battery is as follows: Figure 5 As shown, the voltage efficiency is 51.5%, and the battery polarization is between Comparative Example 1 and Example 1. The resistivity of the zinc-air flow battery before and after cycling was tested, and the test results are as follows. Figure 6 As shown, the resistivity was 0.02 Ω·cm before the cycle, and decreased to 0.03 Ω·cm after 30 cycles.

[0133] Comparative Example 3

[0134] The difference from Example 1 is that the amount of 10wt% PTFE emulsion added is 4.5g; specifically:

[0135] (1) Mix 0.1g of acetylene black, 0.1g of graphite powder, 0.3g of XC-72R and 0.05g of graphene with 4.5g of 10wt% PTFE in an aqueous emulsion, add 50ml of ethanol solvent, and disperse evenly by mechanical stirring and ultrasonication to obtain graphene oxide slurry.

[0136] (2) Apply the graphene oxide slurry obtained in step (1) at a coating amount of 500 mg / cm³. 2 The slurry was uniformly coated on the surface of carbon fiber paper, and then hot-pressed at 200℃ and 10MPa for 3 hours to fix the slurry on the surface of carbon fiber paper. After drying at 80℃ for 12 hours, the sintering was carried out at 300℃ for 0.5 hours to prepare a gas diffusion layer with a thickness of 0.2 mm.

[0137] The contact angle of the gas diffusion layer was measured to be 141° using a contact angle meter.

[0138] The gas diffusion layer was fabricated into an electrode using the aforementioned method and applied to a zinc-air flow battery. After 753 cycles, the battery energy efficiency was 60%.

[0139] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a gas diffusion layer, characterized in that, The method includes: A slurry is coated on the surface of the substrate layer, dried, and sintered to obtain a gas diffusion layer; the slurry is a graphene oxide slurry. The graphene oxide slurry comprises, by weight: 0.01-0.20 parts of graphene oxide; Fluorinated polyolefins: 0.50-2.00 parts; 0.30-0.80 parts of carbon-based conductive agent; Solvent: 30.00-60.00 parts; The fluorine content is 30-70 wt% of the total mass of graphene oxide, fluorinated polyolefin, and carbon-based conductive agent. The mass ratio of fluorinated polyolefin to graphene oxide is 10-25:1; The oxygen content in graphene oxide is 20%-30% by mass.

2. The preparation method according to claim 1, wherein, The fluorine content in the graphene oxide slurry is 35-55 wt% of the total mass of graphene oxide, fluorinated polyolefin, and carbon-based conductive agent; and / or 0.03-0.10 parts of graphene oxide; and / or Fluorinated polyolefins: 0.60-1.20 parts.

3. The preparation method according to claim 1 or 2, wherein, The fluorine content in fluorinated polyolefins is not less than 50 wt%; The carbon-based conductive agent is selected from one or more of acetylene black, graphite powder, XC-72R, and carbon nanotubes; and / or The solvent is selected from one or more of water, ethanol, N,N-dimethylformamide and N,N-dimethylacetamide.

4. The preparation method according to claim 3, wherein, The fluorinated polyolefin is selected from one or more of polytetrafluoroethylene, polyvinylidene fluoride, and trifluoropropylene; and / or The mass ratio of carbon-based conductive agent to graphene oxide is 5-20:

1.

5. The preparation method according to claim 1, wherein, The substrate material is selected from one or more of carbon fiber felt and carbon fiber paper; and / or The coating amount of the slurry is 15-1000 mg / cm². 2 .

6. The preparation method according to claim 5, wherein, The base layer is made of carbon fiber paper.

7. The preparation method according to claim 1 or 5, wherein, Drying conditions include: temperature of 60-100℃; time of 12-24h; and / or Sintering conditions include: a temperature of 300-350℃; a time of 0.5-1 h; and / or When the base layer material is carbon fiber paper, the coating process also includes hot pressing. The hot pressing conditions include: temperature of 150-300℃; pressure of 1-50 MPa; and time of 2-6 h.

8. The gas diffusion layer prepared by the method of claim 1 or 5.

9. The gas diffusion layer according to claim 8, wherein, The thickness of the gas diffusion layer is 0.010-0.025 mm.

10. The application of the gas diffusion layer according to claim 8 or 9 in the electrode of a flow battery with a gas-liquid-solid three-phase reaction.

11. The application according to claim 10, wherein, The gas-liquid-solid three-phase reaction flow battery is selected from zinc-air flow batteries, sodium-air flow batteries, zinc-nickel-air flow batteries, or lithium-air flow batteries.

12. A zinc-air flow battery electrode, characterized in that, include: A gas diffusion layer and a catalyst layer, wherein the gas diffusion layer is the gas diffusion layer as described in claim 8 or 9.

13. The electrode according to claim 12, wherein, In the catalyst layer, the active material is selected from one or more of Pt / C, noble metal alloys, metal oxides and doped carbon materials.

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