Method for preparing flow battery electrode fabric by adopting CVD (Chemical Vapor Deposition) process

Abstract

The invention discloses a method for preparing a redox flow battery electrode fabric by adopting a CVD (Chemical Vapor Deposition) process, which comprises the following steps of: introducing a graphitized carbon fiber fabric into a continuous activation furnace at the speed of 100-800mm / min, introducing a hydrocarbon atmosphere into a 300-1500 DEG C section of the continuous activation furnace starting from a feeding furnace opening, the atmosphere introduction amount being 5-30L / min, the pressure in the furnace being micro-positive pressure, and the pressure value being less than or equal to 0.5 Mpa; air is introduced into a 600-300 DEG C section of a discharging furnace opening of the continuous activation furnace, the atmosphere introduction amount is 2-30 L / min, the pressure in the furnace is micro-positive pressure, the pressure value is smaller than or equal to 0.5 Mpa, and the flow battery electrode fabric is obtained after the reaction is completed. The prepared electrode fabric has permanent hydrophilicity and catalytic activity, reaction active sites are increased through the high specific surface area of the electrode fabric, and improvement of electrochemical reaction activity is facilitated.

Description

Technical Field

[0001] The invention relates to the field of liquid flow batteries, and in particular to a method for preparing liquid flow battery electrode fabrics by adopting a CVD vapor deposition process. Background Art

[0002] The electrode fabrics currently used in liquid flow batteries on the market are mainly hydrophilic graphite felt and hydrophilic electrodes. The main preparation process is: select pre-oxidized silk fibers with good uniformity and consistency, cut them into short fibers, and then needle-punch them into pre-oxidized silk needle-punched felt or spin-twist them into cloth. The pre-oxidized silk needle-punched felt or pre-oxidized silk cloth is first carbonized and then graphitized to make graphitized carbon fiber cloth or felt. After that, it is activated by one or more mixed gases such as air, carbon dioxide or water vapor in a high temperature environment, and oxygen-containing hydrophilic functional groups are grafted on the surface of the graphitized carbon fiber to make a hydrophilic carbon fiber fabric.

[0003] The existing technology has the following problems: (1) The current activation process of the grafted active functional groups makes it easy for the hydrophilic functional groups grafted on the surface of the carbon fiber to fall off and have relatively poor bonding strength; (2) The hydrophilic functional groups easily react with other substances in the air or substances on the packaging materials, lose their hydrophilicity and cause deactivation; (3) High temperatures, sunlight and salt spray environments can cause the hydrophilic functional groups to fall off or react, lose their hydrophilicity and cause deactivation. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for preparing liquid flow battery electrode fabric by using CVD vapor deposition process.

[0005] The present invention is achieved through the following technical solutions.

[0006] A method for preparing a flow battery electrode fabric using a CVD vapor deposition process comprises the following steps:

[0007] S1. Preparation of graphitized carbon fiber fabric

[0008] S2. CVD vapor deposition active material loading activation

[0009] The graphitized carbon fiber fabric is introduced into a continuous activation furnace at a speed of 100-800mm / min, and a hydrocarbon atmosphere is introduced into the 300-1500°C section starting from the feed furnace port in the continuous activation furnace, the atmosphere introduction amount is 5-30L / min, the pressure in the furnace is a slightly positive pressure, and the pressure value is ≤0.5Mpa; air is introduced into the 600-300°C section of the discharge furnace port of the continuous activation furnace, the atmosphere introduction amount is 2-30L / min, the pressure in the furnace is a slightly positive pressure, and the pressure value is ≤0.5Mpa, and a liquid flow battery electrode fabric is obtained after the reaction is completed.

[0010] By adopting the above technical scheme, the present application combines hydrocarbon atmospheres such as methane, ethylene or acetylene with carbon fibers through a CVD vapor deposition (chemical vapor deposition) process. This process allows the substance attached to the surface of the carbon fiber to form a chemical bond with the carbon fiber itself, which is firmly attached to the surface of the carbon fiber after graphitization through a C-C bond or other chemical bonds, achieving the purpose of high fastness load. This type of structure attached to the surface of the carbon fiber makes the carbon fiber fabric have a strong hydrophilicity through a high specific surface area and capillary phenomenon. At the same time, after sintering with air, partial hydroxyl and carboxyl structures can also be formed to increase hydrophilicity, and oxygen-containing functional groups also contribute to electrochemical activity. In addition, this type of structure attached to the surface of the carbon fiber greatly increases the specific surface area of ​​the electrode fabric and increases the active sites of the active substances in the electrolyte of the flow battery. The nanostructured loaded carbon material (mainly similar to the carbon nanotube structure in appearance) formed by vapor deposition has a certain catalytic activity. At the same time, the nitrogen in the incoming air at high temperature will form pyrrole and pyridine structures with the electrode fabric fibers or the carbon structure loaded on the fiber surface, which can effectively inhibit hydrogen evolution in the liquid flow battery electrolyte and increase battery efficiency.

[0011] Furthermore, in step S1, the preparation method of graphitized carbon fiber fabric is: select pre-oxidized silk fiber with a limiting oxygen index of 38-45%, curl and cut into 30-120mm short fibers with a curl of 2-12 pieces / cm, and then needle-punch to make pre-oxidized silk needle-punched felt or spin-twist to weave into cloth; carbonize and graphitize the pre-oxidized silk needle-punched felt or pre-oxidized silk cloth in argon or nitrogen protection, and the pre-oxidized silk fabric stays in the high temperature section of the carbonization and graphitization furnace for 0.5-3h to make a graphitized carbon fiber fabric.

[0012] Furthermore, the carbonization temperature is 800-1500°C; the graphitization temperature is 1600-2500°C.

[0013] Furthermore, in step S2, the hydrocarbon atmosphere is selected from one or more of methane, ethane, ethylene, and acetylene.

[0014] This application has the following beneficial effects.

[0015] 1. The electrode fabric prepared by the method of the present invention has two ways to maintain hydrophilicity, namely, physical structure and hydrophilic functional groups, and the physical structure is the main one, so it has permanent hydrophilicity and basically does not lose hydrophilicity;

[0016] 2. The partial structure loaded on the surface of the carbon fiber of the present invention has catalytic activity, and through its high specific surface area, the number of reactive active sites is increased, which helps to improve the electrochemical reaction activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1The carbon fiber fabric after carbonization and graphitization of the present application;

[0018] Figure 2 The present application is a flow battery electrode fabric after deposition. DETAILED DESCRIPTION

[0019] The invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] A method for preparing a flow battery electrode fabric using a CVD vapor deposition process comprises the following steps:

[0021] 1. Fabric preparation:

[0022] Select preoxidized silk fibers with a limiting oxygen index of 38-45%, cut them into 30-120mm short fibers, and then needle-punch them into preoxidized silk needle felt or spin-twist them into cloth, with a fabric width of 1-2 meters. The preoxidized silk needle felt or preoxidized silk cloth is carbonized and graphitized in a carbonization graphitization furnace, and argon or nitrogen is introduced into the furnace to maintain a slight positive pressure to provide atmosphere protection for the entire carbonization and graphitization process. The carbonization temperature is 800-1500℃, the graphitization temperature is 1600-2500℃, and the heating curve is determined according to the fabric conditions. The preoxidized silk fabric stays in the high temperature section of the carbonization and graphitization furnace for 0.5-3h to make a graphitized carbon fiber fabric.

[0023] 2. Activation:

[0024] The graphitized carbon fiber fabric passes through a continuous activation furnace at 100-800mm / min, and one or more hydrocarbon atmospheres such as methane, ethane, ethylene, acetylene, etc. are introduced into the activation furnace, and the atmosphere introduction amount is 5-30L / min. The pressure in the furnace is slightly positive, and the pressure value is ≤0.5Mpa. At a temperature of 300-1500°C, the hydrocarbon gas is cracked, and then the cracked carbon is deposited on the fiber surface of the graphitized carbon fiber fabric. Through the control of atmosphere, pressure and temperature, the cracked carbon forms conductive carbon black, CNTs or other amorphous nano-carbon material structures attached to the carbon fiber surface, forming a relatively strong carbon-carbon bond with the carbon fiber. The carbon structure deposited on the carbon fiber surface has a high specific surface area and high porosity, which makes the carbon fiber fabric have good hydrophilicity. At the same time, a certain amount of air is introduced into the 2-5 temperature section at the rear end of the continuous activation furnace, the atmosphere introduction amount is 2-30L / min, the temperature is 300-600℃, and the oxygen and nitrogen in the air form certain oxygen-containing functional groups and certain pyrrole and pyridine structures with the carbon fiber and the carbon structure deposited on the surface of the carbon fiber, so that the carbon fiber fabric not only has good hydrophilicity, but also has good electrochemical activity, which can promote the electrochemical reaction of the liquid flow battery.

[0025] Embodiment 1:

[0026] A method for preparing a flow battery electrode fabric using a CVD vapor deposition process comprises the following steps:

[0027] 1. Fabric preparation:

[0028] Select 2.2Dtex pre-oxidized silk fiber 48K large tow of Jinshan Petrochemical with a limiting oxygen index of 45%, crimp it into 53mm short fibers with a crimp degree of 3-6 / cm, and then needle punch it into 3mm thickness and density of 0.14g / cm 3 Pre-oxidized wire needle felt, the width of the felt is 1.8m. The pre-oxidized wire needle felt is first carbonized in a continuous carbonization furnace, and nitrogen is introduced into the furnace to maintain a slightly positive pressure, and the atmosphere is protected during the entire carbonization process. The carbonization temperature is 1200°C, and the speed of the pre-oxidized wire felt in the continuous carbonization furnace is 250mm / min. The furnace chamber length is 25m to make a carbon fiber fabric. The carbonized carbon fiber fabric is rolled into a roll of 50m long and then placed in an intermittent graphitization furnace for graphitization. The graphitization temperature is 1800°C, and the temperature is increased from room temperature to 1800°C at a rate of 5°C / min. When it reaches 1800°C, it is maintained at 1800°C for 120min, and then the power is cut off and the temperature is naturally cooled to make a graphite felt with a thickness of 2.5mm.

[0029] 2. Activation:

[0030] A graphite felt with a thickness of 2.5 mm is introduced into a continuous activation furnace at a speed of 250 mm / min. A continuous activation furnace with 11 heating temperature zones is used. The single temperature zone of the continuous furnace is 3 m long. The first temperature zone is a transition temperature zone, and the temperature is set at 400°C. An acetylene atmosphere is introduced into the 2-7 temperature zones, the amount of atmosphere introduced is 10 L / min, the pressure in the furnace is a slightly positive pressure, the pressure value is 0.2 Mpa, the temperature is 700°C, acetylene is cracked and deposited, and the deposits are attached to the surface of the carbon fiber. Then air is introduced into the 8-10 temperature zones, the amount of air introduced is 5 L / min, the pressure in the furnace is a slightly positive pressure, the pressure value is 0.2 Mpa, and the temperature is 450°C. In this temperature zone, oxygen-containing energy conversion groups and some pyrrole and pyridine structures are grafted. The 11th temperature zone is a transition temperature zone, the temperature is set at 400°C, and the temperature zone is not passed through the atmosphere.

[0031] 3. Detection:

[0032] (1) Hydrophilicity test: 3 ml of deionized water was sucked in with a straw, and water drops were dropped at five locations on the felt body. The water drops quickly penetrated into the fabric, and there was no water drop contact angle; 50 mm*70 mm electrode fabrics were cut and fixed in a PP pipe, divided into three groups, and 98% concentrated sulfuric acid, 37% concentrated hydrochloric acid and 50% concentrated sodium hydroxide were used in a PP pipe with a diameter of 100 mm at a flow rate of 15 L / min and a temperature of 40°C for continuous flushing for 1500 hours, and then the electrode cloth was dried at 80°C, and 3 ml of deionized water was sucked in with a straw, and water drops were dropped at five locations on the fabric, and the water drops quickly penetrated into the fabric, and there was no water drop contact angle;

[0033] (2) Square resistance test: Use a four-probe square resistance tester to test the square resistance value, where the electrode felt square resistance is ≤0.4Ω;

[0034] (3) Battery installation test: electrode size 60mm*85mm; using graphite bipolar plates with flow channels; using Nafion212 ion membrane; charging and discharging voltage range: 1.00-1.55V; compression ratio: electrode felt 25%; single-layer electrode fabric assembled battery; constant current charge and discharge after 1500 cycles of battery charge and discharge, current density 160mA / cm 2 , Coulombic efficiency (CE) ≥ 99%, voltage efficiency (VE) ≥ 87%, energy efficiency (EE) ≥ 86%; after 1500 battery charge and discharge cycles, Coulombic efficiency (CE) ≥ 97%, voltage efficiency (VE) ≥ 85.5%, energy efficiency (EE) ≥ 83%;

[0035] (4) Strength test: The breaking strength of the electrode felt is ≥10N according to the national standard GB / T 3923.2-2013.

[0036] Embodiment 2:

[0037] A method for preparing a flow battery electrode fabric using a CVD vapor deposition process comprises the following steps:

[0038] 3. Fabric preparation:

[0039] Select 2.2Dtex pre-oxidized silk fiber of ZOLTEK with a limiting oxygen index of 43%, crimp it into 63mm short fibers with a crimp degree of 6-10 / cm, and then use the ring spinning process to make 10s / 2 yarn, and the yarn twist S and Z twist ≥ 400. Then use a rapier loom to make a pre-oxidized silk cloth with a warp and weft density of 38 strands / inch and 30 strands / inch in 2 / 1 twill texture, and the width of the cloth is 1.8m. The pre-oxidized wire cloth is passed through a continuous carbonization graphitization furnace at a speed of 350 mm / min for carbonization graphitization. Argon gas is introduced into the furnace to maintain a slightly positive pressure to provide atmosphere protection for the entire carbonization process. The continuous carbonization graphitization furnace has a total of 20 temperature zones, each of which is 3 meters long. The temperatures of temperature zones 1-4 are 400°C, 700°C, 1000°C, and 1300°C, respectively; the carbonization temperature of temperature zones 5-10 is 1500°C; the carbonization temperature of temperature zones 11-12 is 1600°C and 1800°C; the temperature of temperature zones 14-18 is 2000°C, and the temperature of temperature zones 19-20 is 1700°C and 1400°C, and finally graphite cloth is made.

[0040] 4. Activation:

[0041] The graphite cloth is passed into a continuous activation furnace at a speed of 300mm / min. A continuous activation furnace with 11 heating temperature zones is used. The single temperature zone of the continuous furnace is 3m long. The first temperature zone is a transition temperature zone, and the temperature is set to 450°C. A methane atmosphere is introduced into the 2-7 temperature zones, the atmosphere introduction amount is 15L / min, the pressure in the furnace is a slightly positive pressure, the pressure value is 0.5Mpa, the temperature is 650°C, the methane is cracked and deposited, and the deposits are attached to the surface of the carbon fiber. Then air is introduced into the 8-10 temperature zones, the air introduction amount is 10L / min, the pressure in the furnace is a slightly positive pressure, the pressure value is 0.3Mpa, and the temperature is 450°C. In this temperature zone, oxygen-containing energy conversion groups and some pyrrole and pyridine structures are grafted. The 11th temperature zone is a transition temperature zone, the temperature is set to 400°C, and the temperature zone is not passed through the atmosphere.

[0042] 3. Detection:

[0043] (1) Hydrophilicity test: Use a pipette to suck 3 ml of deionized water, select five positions on each of the front and back surfaces of the fabric, and drop water. The water drop quickly penetrates into the fabric, and there is no water drop contact angle; cut two groups of 30 mm*30 mm electrode fabrics, three pieces in each group, put them into 98% concentrated sulfuric acid and 50% concentrated sodium hydroxide, and keep them at a temperature of 80°C for 100 hours, then dry the electrode fabric at a temperature of 120°C, and then use a pipette to suck 3 ml of deionized water, select five positions on each of the front and back surfaces of the fabric, and drop water. The water drop quickly penetrates into the fabric, and there is no water drop contact angle;

[0044] (2) Square resistance test: Use a four-probe square resistance tester to test the square resistance value, where the electrode cloth square resistance is ≤0.4Ω;

[0045] (3) Battery installation test: electrode cloth size 60mm*85mm; use graphite bipolar plates with flow channels; use Nafion212 ion membrane; charge and discharge voltage range: 1.00-1.55V; compression ratio: electrode cloth 30%; single-layer electrode cloth assembled battery; constant current charge and discharge after 1500 cycles of battery charge and discharge, current density 160mA / cm 2 , Coulombic efficiency (CE) ≥ 99%, voltage efficiency (VE) ≥ 86%, energy efficiency (EE) ≥ 85%; after 1500 battery charge and discharge cycles, Coulombic efficiency (CE) ≥ 97%, voltage efficiency (VE) ≥ 85%, energy efficiency (EE) ≥ 82.5%;

[0046] (4) Strength test: The breaking strength of the electrode felt is ≥10N according to the national standard GB / T 3923.2-2013.

[0047] The embodiments of this specific implementation method are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a flow battery electrode fabric using a CVD vapor deposition process, characterized in that: The following steps are involved: S1. Preparation of graphitized carbon fiber fabric S2. CVD vapor deposition active material loading activation The graphitized carbon fiber fabric is introduced into a continuous activation furnace at a speed of 100-800mm / min, and a hydrocarbon atmosphere is introduced into the 300-1500°C section starting from the feed furnace port in the continuous activation furnace, the atmosphere introduction amount is 5-30L / min, the pressure in the furnace is a slightly positive pressure, and the pressure value is ≤0.5Mpa; air is introduced into the 600-300°C section of the discharge furnace port of the continuous activation furnace, the atmosphere introduction amount is 2-30L / min, the pressure in the furnace is a slightly positive pressure, and the pressure value is ≤0.5Mpa, and a liquid flow battery electrode fabric is obtained after the reaction is completed.

2. The method for preparing a flow battery electrode fabric using a CVD vapor deposition process according to claim 1, characterized in that: In step S1, the preparation method of graphitized carbon fiber fabric is as follows: selecting preoxidized silk fibers with a limiting oxygen index of 38-45%, curling and chopping them into 30-120 mm short fibers with a curling degree of 2-12 pieces / cm, and then needle-punching them into preoxidized silk needle felt or spinning and twisting them into cloth; carbonizing and graphitizing the preoxidized silk needle felt or preoxidized silk cloth in argon or nitrogen protection, and the preoxidized silk fabric stays in the high temperature section of the carbonization and graphitization furnace for 0.5-3 hours to prepare the graphitized carbon fiber fabric.

3. The method for preparing a flow battery electrode fabric using a CVD vapor deposition process according to claim 2, characterized in that: The carbonization temperature is 800-1500℃; the graphitization temperature is 1600-2500℃.

4. The method for preparing a flow battery electrode fabric using a CVD vapor deposition process according to claim 1, characterized in that: In step S2, the hydrocarbon atmosphere is selected from one or more of methane, ethane, ethylene, and acetylene.

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