Capacitive deionization electrodes and capacitive deionization devices

Abstract

The application provides a capacitive deionization electrode and a capacitive deionization device. The capacitive deionization electrode comprises a current collector and an active material layer laminated to at least one side of the current collector, wherein the active material layer comprises an active carbon material and a binder, the binder comprises an active group grafted cellulose binder, the cellulose binder is sodium carboxymethyl cellulose and / or carboxymethyl cellulose, and the active group comprises at least one of a sulfonic acid group, a carboxyl group and an amino group. The capacitive deionization electrode has excellent ion adsorption, low common ion effect, large ion adsorption capacity and high ion removal rate.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a capacitive deionization electrode and a capacitive deionization device. Background Technology

[0002] Most residential water purification equipment uses RO membranes, which are non-selective and have a desalination rate of over 90%. With increasing demand for healthy living, water purifiers that retain minerals are becoming a new trend. Electrochemical deionization technology can effectively achieve adjustable desalination rates.

[0003] However, most electrochemical solutions require ion exchange membranes, such as electrodialysis and membrane capacitive deionization. Ion exchange membranes are costly and prone to bacterial growth after prolonged operation, making them unsuitable for ordinary household use. Meanwhile, capacitive deionization technology without ion exchange membranes has a lower desalination rate and cannot simultaneously meet the needs of households for both mineral water and purified water. Therefore, developing a capacitive deionization module electrode with high adsorption capacity to improve the device's desalination rate can effectively promote the application and widespread adoption of capacitive deionization technology in ordinary households. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the prior art. Therefore, one object of the present invention is to provide a capacitive deionization electrode and a capacitive deionization device.

[0005] In a first aspect, the present invention provides a capacitive deionization electrode. According to an embodiment of the invention, it includes a current collector and an active material layer, the active material layer being laminated on at least one side of the current collector. The active material layer includes an activated carbon material and a binder, the binder comprising a cellulose binder grafted with active groups, the cellulose binder being sodium carboxymethyl cellulose and / or carboxymethyl cellulose, and the active groups comprising at least one selected from sulfonic acid groups, carboxyl groups, and amino groups.

[0006] According to the capacitive deionization electrode of the above embodiments of the present invention, the binder includes a cellulose-based binder grafted with active groups. The cellulose-based binder is sodium carboxymethyl cellulose and / or carboxymethyl cellulose, and the active groups include at least one of sulfonic acid groups, carboxyl groups, and amino groups. Cellulose-based binders have a large number of hydroxyl groups. On the one hand, during cyclic electrolysis, -CH2-OH is easily oxidized to form carboxyl groups. The presence of carboxyl groups in the negative electrode material is beneficial for enhancing the adsorption capacity for cations, inhibiting the adsorption of anions, reducing common ion repulsion, and increasing the adsorption capacity. On the other hand, cellulose-based binders are easily grafted with sulfonic acid groups, amino groups, etc. The grafted binder has cation and anion selectivity, reducing the decrease in adsorption capacity caused by common ion repulsion and significantly increasing the ion adsorption capacity. Therefore, this capacitive deionization electrode has excellent ion adsorption performance and a high ion removal rate.

[0007] In addition, the capacitive deionization electrode according to the above embodiments of the present invention also has the following technical features:

[0008] In some embodiments of the present invention, the cellulose-based binder accounts for no less than 1% of the total mass of the active material layer. This improves the ion adsorption and ion removal rate of the electrode.

[0009] In some embodiments of the present invention, the adhesive further includes at least one of styrene-butadiene rubber, polytetrafluoroethylene, and polyvinylidene fluoride.

[0010] In some embodiments of the present invention, the mass percentage of the adhesive is 2% to 15% based on the total mass of the active material layer.

[0011] In some embodiments of the present invention, the mass percentage of the adhesive is 5% to 7% based on the total mass of the active material layer.

[0012] In some embodiments of the present invention, the activated carbon material is grafted with the active groups, which include at least one of sulfonic acid groups, carboxyl groups, and amino groups. This improves the ion adsorption capacity and ion removal rate of the electrode.

[0013] In some embodiments of the present invention, the activated carbon material includes at least one of activated carbon and carbon aerogel.

[0014] In some embodiments of the present invention, the active material layer further includes a conductive agent. This improves the conductivity of the electrode.

[0015] In some embodiments of the present invention, the conductive agent accounts for 5% to 15% of the total mass of the active material layer. This improves the conductivity of the electrode.

[0016] In some embodiments of the present invention, the conductive agent includes at least one of carbon black, graphene, carbon nanotubes, and polyaniline.

[0017] In a second aspect, the present invention provides a capacitive deionization device. According to an embodiment of the present invention, the capacitive deionization device includes the aforementioned capacitive deionization electrode. Therefore, the capacitive deionization device exhibits excellent ion removal capability and a high ion removal rate. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a capacitor deionization electrode structure according to an embodiment of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0021] To improve the desalination rate of capacitive deionization devices, ion exchange membranes are typically added to the device, or activated carbon is modified as reported in existing technologies, thereby improving the desalination rate of capacitive deionization devices. However, whether adding ion exchange membranes or modifying activated carbon, the production cost is high, and the activated carbon modification process is complex. Furthermore, the activated carbon used in the electrodes accounts for a high percentage of the total mass, which will inevitably indirectly increase the production cost and operational difficulty.

[0022] In view of this, in a first aspect, the present invention provides a capacitive deionization electrode. According to an embodiment of the present invention, reference is made to... Figure 1 The device includes a current collector 100 and an active material layer 200, wherein the active material layer 200 is stacked on at least one side of the current collector 100, and the active material layer 200 includes activated carbon material and a binder, wherein the binder includes a cellulose binder grafted with active groups, wherein the cellulose binder is sodium carboxymethyl cellulose and / or carboxymethyl cellulose, and the active groups include at least one of sulfonic acid group, carboxyl group, and amino group.

[0023] According to the capacitive deionization electrode of the above embodiments of the present invention, the binder includes a cellulose-based binder grafted with active groups. The cellulose-based binder is sodium carboxymethyl cellulose and / or carboxymethyl cellulose, and the active groups include at least one of sulfonic acid groups, carboxyl groups, and amino groups. Cellulose-based binders have a large number of hydroxyl groups. On the one hand, during cyclic electrolysis, -CH2-OH is easily oxidized to form carboxyl groups. The presence of carboxyl groups in the negative electrode material is beneficial for improving the adsorption capacity for cations, inhibiting the adsorption of anions, reducing common ion repulsion, and increasing the adsorption capacity. On the other hand, cellulose-based binders are easily grafted with sulfonic acid groups, amino groups, etc. The grafted binder has cation and anion selectivity, reducing the decrease in adsorption capacity caused by common ion repulsion and significantly increasing the ion adsorption capacity. Therefore, this capacitive deionization electrode has excellent ion adsorption performance and a high ion removal rate. It should be noted that the current collector is a conventional component in the art, such as copper foil, titanium foil, titanium sheet, graphite sheet, graphite paper, etc.

[0024] According to an embodiment of the present invention, the capacitor deionization electrode is the negative electrode, and the active group includes at least one of sulfonic acid group and carboxyl group.

[0025] According to an embodiment of the present invention, the capacitor deionization electrode is a positive electrode, and the active group includes amino groups.

[0026] According to embodiments of the present invention, the mass percentage of the cellulose-based binder is not less than 1% based on the total mass of the active material layer. For example, the mass percentage of the cellulose-based binder is not less than 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, etc. By controlling the mass percentage of the cellulose-based binder to be not less than 1%, it can be ensured that the binder has a large number of active groups, thereby ensuring a large ion adsorption capacity and improving the ion adsorption and ion removal rate of the electrode.

[0027] According to embodiments of the present invention, the binder further includes at least one of styrene-butadiene rubber, polytetrafluoroethylene, and polyvinylidene fluoride. By adding binders of the above type, the stability of the activated material layer in water is improved, and phenomena such as dissolution, detachment, peeling, and cracking of the activated carbon material layer during operation are reduced.

[0028] According to embodiments of the present invention, the mass percentage of the binder is 2% to 15% based on the total mass of the active material layer. Preferably, it is 3% to 7%. For example, the mass percentages are 2%, 5%, 7%, 10%, 12%, 15%, etc., and even greater than or equal to 2%, 5%, 7%, 10%, etc., and less than or equal to 10%, 12%, 15%, etc. The inventors have found that controlling the mass percentage of the binder to 2% to 15% based on the total mass of the active material layer can maintain the bonding performance, provide usable selective groups, and ensure the ratio of active ingredients and conductive agents, thus maintaining the total adsorption capacity. In the active material layer of the electrode, the mass percentage of the binder is very small compared to the activated carbon material. Therefore, compared to existing modifications of activated carbon materials, the binder modification used in this application can significantly reduce production costs. Furthermore, from the perspective of electrode adsorption performance, the electrode prepared by binder modification in this application does not perform worse than the electrode prepared by activated carbon material modification. Therefore, the present invention provides a new approach to improving the adsorption performance of capacitive deionization electrodes.

[0029] According to embodiments of the present invention, the activated carbon material is grafted with the active groups, which include at least one selected from sulfonic acid groups, carboxyl groups, and amino groups. By grafting active groups onto the activated carbon material, the ion adsorption capacity and ion removal rate of the electrode can be further improved.

[0030] According to an embodiment of the present invention, the activated carbon material includes at least one of activated carbon and carbon aerogel.

[0031] According to an embodiment of the present invention, the active material layer further includes a conductive agent. By adding a certain amount of conductive agent to the active material, the conductivity of the electrode can be improved.

[0032] According to embodiments of the present invention, the mass percentage of the conductive agent is 5% to 15% based on the total mass of the active material layer. For example, the mass percentage of the conductive agent can be 5%, 7%, 9%, 11%, 13%, 15%, etc., or greater than or equal to 5%, 7%, 9%, etc., and less than or equal to 11%, 13%, 15%, etc. Controlling the mass percentage of the conductive agent to 5% to 15% can improve the conductivity of the electrode.

[0033] According to embodiments of the present invention, the conductive agent includes, but is not limited to, at least one of carbon black, graphene, carbon nanotubes, and polyaniline.

[0034] In a second aspect, the present invention provides a capacitive deionization device. According to an embodiment of the present invention, the capacitive deionization device includes the aforementioned capacitive deionization electrode. Therefore, the capacitive deionization device exhibits excellent ion removal capability and a high ion removal rate. It should be noted that the features and advantages described above for the capacitive deionization electrode also apply to the capacitive deionization device, and will not be repeated here.

[0035] According to an embodiment of the present invention, the capacitor deionization device is assembled as follows:

[0036] The capacitor deionization negative electrode-spacer-capacitor deionization positive electrode-spacer are arranged alternately to prepare a plate-shaped or spiral-wound capacitor deionization module, which is then assembled into a water purifier.

[0037] Water purification process: The negative electrode of the capacitor deionization is connected to a negative charge, and the positive electrode of the capacitor deionization is connected to a positive charge, so as to adsorb ions in the water; Regeneration process: The negative electrode of the capacitor deionization is connected to a positive charge, and the positive electrode of the capacitor deionization is connected to a negative charge, so as to desorb ions from the electrode and regenerate the electro-deionization module.

[0038] According to an embodiment of the present invention, another assembly method for the capacitor deionization device is as follows:

[0039] The capacitor deionization negative electrode, the separator, the conventional activated carbon electrode, and the separator are arranged alternately to prepare a plate-shaped or spiral-wound capacitor deionization module, which is then assembled into a water purifier.

[0040] Water purification process: The capacitor deionization negative electrode is connected to a negative charge, and the conventional activated carbon electrode is connected to a positive charge, which performs ion adsorption in the water; Regeneration process: The capacitor deionization negative electrode is connected to a positive charge, and the conventional activated carbon electrode is connected to a negative charge, which performs electrode ion desorption, and the electro-deionization module is regenerated.

[0041] According to an embodiment of the present invention, another assembly method of the capacitor deionization device is as follows:

[0042] Conventional activated carbon electrodes, separators, capacitor deionization positive electrodes, and separators are arranged alternately to prepare plate-shaped or spiral-wound capacitor deionization modules, which are then assembled into water purifiers.

[0043] Water purification process: The conventional activated carbon electrode is connected to a negative charge, and the capacitor deionization positive electrode is connected to a positive charge, which performs ion adsorption in the water; Regeneration process: The conventional activated carbon electrode is connected to a positive charge, and the capacitor deionization positive electrode is connected to a negative charge, which performs electrode ion desorption and regeneration of the electro-deionization module.

[0044] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0045] Example 1

[0046] (1) Preparation of capacitor deionization positive electrode

[0047] Weigh out the appropriate mass of pure activated carbon, conductive carbon black, and binder (50wt% sodium carboxymethyl cellulose and 50wt% styrene-butadiene rubber) in a mass ratio of 88:5:7 and mix them into powder. After mixing, add the solid powder to the solvent to form a solution with a solid content of 30%. Stir the mixture for 4 hours to form a uniform slurry. Then, use a scraping device to scrape the slurry onto the current collector. Dry it at 80℃ for 4 hours. After rolling it with a 90T roller press, a positive electrode with a single-sided coating thickness of 85µm is formed.

[0048] (2) Preparation of capacitor deionization negative electrode

[0049] Weigh out the appropriate mass of pure activated carbon, conductive carbon black, and binder (50wt% active group modified sodium carboxymethyl cellulose and 50wt% styrene-butadiene rubber, with active groups being sulfonic acid groups) in a mass ratio of 88:5:7 and mix them into powder. After mixing, add the solid powder to the solvent to form a solution with a solid content of 30%. Stir the mixture for 4 hours to form a uniform slurry. Then, use a scraping device to scrape the slurry onto the current collector, dry it at 80℃ for 4 hours, and roll it with a 90T roller press to form a negative electrode with a single-sided coating thickness of 85µm.

[0050] Active group modified sodium carboxymethyl cellulose: Sodium carboxymethyl cellulose and 10% sulfuric acid are mixed evenly at a mass ratio of 1:10 and dried at 80°C to obtain sulfonic acid group-grafted sodium carboxymethyl cellulose. When using, the pH is adjusted to neutral with sodium bicarbonate.

[0051] (3) Fabrication of capacitor deionization devices

[0052] The positive electrode, separator, negative electrode, and separator are arranged alternately to form a plate-shaped or spiral-wound capacitor deionization module.

[0053] Example 2

[0054] The difference between Example 2 and Example 1:

[0055] (2) Preparation of capacitor deionization negative electrode

[0056] Weigh out the appropriate mass of pure activated carbon, conductive carbon black, and binder (50wt% active group modified sodium carboxymethyl cellulose and 50wt% styrene-butadiene rubber, with carboxyl groups as the active group) in a mass ratio of 88:5:7 and mix them into powder. After mixing, add the solid powder to the solvent to form a solution with a solid content of 30%. Stir the mixture for 4 hours to form a uniform slurry. Then, use a scraping device to scrape the slurry onto the current collector, dry it at 80℃ for 4 hours, and roll it with a 90T roller press to form a negative electrode with a single-sided coating thickness of 85µm.

[0057] Sodium carboxymethyl cellulose modified with active groups: Sodium carboxymethyl cellulose and 10% nitric acid are mixed evenly at a mass ratio of 1:10 and dried at 80°C to obtain sodium carboxymethyl cellulose containing carboxyl groups. When using, the pH is adjusted to neutral with sodium bicarbonate.

[0058] Example 3

[0059] (1) Preparation of capacitor deionization positive electrode

[0060] Weigh out the appropriate mass of pure activated carbon, conductive carbon black, and binder (50wt% active group modified sodium carboxymethyl cellulose and 50wt% styrene-butadiene rubber, with amino active groups) in a mass ratio of 88:5:7 and mix them into powder. After mixing, add the solid powder to the solvent to form a solution with a solid content of 30%. Stir the mixture for 4 hours to form a uniform slurry. Then, use a scraping device to scrape the slurry onto the current collector, dry it at 80℃ for 4 hours, and roll it with a 90T roller press to form a positive electrode with a single-sided coating thickness of 85µm.

[0061] Sodium carboxymethyl cellulose modified with active groups: Purchase channel - Tyson Biotechnology Co., Ltd., S800.

[0062] (2) Preparation of capacitor deionization negative electrode

[0063] Weigh out the appropriate amounts of pure activated carbon, conductive carbon black, and binder (50wt% sodium carboxymethyl cellulose and 50wt% styrene-butadiene rubber) in a mass ratio of 88:5:7 and mix them into powder. After mixing, add the solid powder to the solvent to form a solution with a 30% solid content. Stir the mixture for 4 hours to form a uniform slurry. Then, use a scraping device to coat the slurry onto the current collector. Dry it at 80℃ for 4 hours. After rolling it with a 90T roller press, a negative electrode with a single-sided coating thickness of 85µm is formed.

[0064] (3) Fabrication of capacitor deionization devices

[0065] Same as Example 1.

[0066] Example 4

[0067] (1) Preparation of capacitor deionization positive electrode

[0068] Same as Example 3.

[0069] (2) Preparation of capacitor deionization negative electrode

[0070] Same as Example 1.

[0071] (3) Fabrication of capacitor deionization devices

[0072] Same as Example 1.

[0073] Example 5

[0074] (1) Preparation of capacitor deionization positive electrode

[0075] Same as Example 3.

[0076] (2) Preparation of capacitor deionization negative electrode

[0077] Same as Example 2.

[0078] (3) Fabrication of capacitor deionization devices

[0079] Same as Example 1.

[0080] Example 6

[0081] (1) Preparation of capacitor deionization positive electrode

[0082] Same as Example 1.

[0083] (2) Preparation of capacitor deionization negative electrode

[0084] Difference from Example 1: Example 6 does not use pure activated carbon, but uses sulfonic acid-modified activated carbon.

[0085] Sulfonic acid-modified activated carbon: Prepare a saturated solution of 20% sulfuric acid and potassium persulfate, add activated carbon, reflux at 70°C for 5 hours, filter and wash until neutral.

[0086] (3) Fabrication of capacitor deionization devices

[0087] Same as Example 1.

[0088] Comparative Example 1

[0089] (1) Preparation of capacitor deionization positive electrode

[0090] Weigh out the appropriate mass of pure activated carbon, conductive carbon black, and binder (50wt% sodium carboxymethyl cellulose and 50wt% styrene-butadiene rubber) in a mass ratio of 88:5:7 and mix them into powder. After mixing, add the solid powder to the solvent to form a solution with a solid content of 30%. Stir the mixture for 4 hours to form a uniform slurry. Then, use a scraping device to scrape the slurry onto the current collector. Dry it at 80℃ for 4 hours. After rolling it with a 90T roller press, a positive electrode with a single-sided coating thickness of 85µm is formed.

[0091] (2) Preparation of capacitor deionization negative electrode

[0092] Weigh out the appropriate amounts of pure activated carbon, conductive carbon black, and binder (50wt% sodium carboxymethyl cellulose and 50wt% styrene-butadiene rubber) in a mass ratio of 88:5:7 and mix them into powder. After mixing, add the solid powder to the solvent to form a solution with a 30% solid content. Stir the mixture for 4 hours to form a uniform slurry. Then, use a scraping device to coat the slurry onto the current collector. Dry it at 80℃ for 4 hours. After rolling it with a 90T roller press, a negative electrode with a single-sided coating thickness of 85µm is formed.

[0093] (3) Fabrication of capacitor deionization devices

[0094] Same as Example 1.

[0095] Comparative Example 2

[0096] (1) Preparation of capacitor deionization positive electrode

[0097] Same as Example 1.

[0098] (2) Preparation of capacitor deionization negative electrode

[0099] The appropriate mass of sulfonic acid-modified activated carbon, conductive carbon black, and binder (50wt% sodium carboxymethyl cellulose and 50wt% styrene-butadiene rubber) in a mass ratio of 88:5:7 was weighed and mixed into powder. After mixing, the solid powder was added to the solvent to form a solution with a solid content of 30%. The mixture was stirred for 4 hours to form a uniform slurry. The slurry was then coated onto the current collector using a scraping device and dried at 80℃ for 4 hours. After being rolled by a 90T roller press, a negative electrode with a single-sided coating thickness of 85µm was formed.

[0100] The sulfonic acid-modified activated carbon is the same as in Example 6.

[0101] (3) Fabrication of capacitor deionization devices

[0102] Same as Example 1.

[0103] The performance of the capacitor deionization devices prepared in Examples 1-6 and Comparative Examples 1-2 was tested using the following methods:

[0104] Adsorption process: The influent flow rate is kept at 0.5 L / min·m2 with respect to the total electrode area. The positive electrode is connected to positive charge and the negative electrode is connected to negative charge to perform ion adsorption in the water. The influent concentration is 200 ppm aqueous solution, the positive and negative electrode voltage is 1.5V, the TDS of the effluent is measured, and the adsorption capacity per unit area per unit time is calculated from this. Regeneration process: The negative electrode is connected to positive charge and the positive electrode is connected to negative charge to perform electrode ion desorption and regeneration of the electro-deionization module.

[0105] The performance test results of the capacitor deionization devices prepared in Examples 1-6 and Comparative Examples 1-2 are shown in Table 1.

[0106] Table 1

[0107]

[0108] As shown in Table 1, the adsorption performance of the devices in Examples 1-6 is significantly better than that of the device in Comparative Example 1, indicating that the modified binder used in this application to prepare the electrode can significantly improve the adsorption performance of the device. Comparing Example 1 and Comparative Example 2, it is shown that the electrode prepared using the modified binder in this application has better performance than the electrode prepared using modified activated carbon. Comparing Example 1 and Example 2, it is shown that the electrode prepared using the sulfonated modified binder has better performance than the carboxylated modified electrode. Comparing Examples 1, 2, and Example 3, it is shown that the positive electrode modified by ammoniation has better performance than the negative electrode modified.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A capacitive deionization electrode, characterized in that, The device includes a current collector and an active material layer, wherein the active material layer is stacked on at least one side of the current collector, the active material layer includes activated carbon material and a binder, the binder includes a cellulose binder grafted with active groups, the cellulose binder being sodium carboxymethyl cellulose and / or carboxymethyl cellulose, and the active groups including amino groups; The adhesive also includes at least one of styrene-butadiene rubber, polytetrafluoroethylene, and polyvinylidene fluoride; The activated carbon material includes at least one of activated carbon and carbon aerogel; the activated carbon material is grafted with at least one of sulfonic acid group, carboxyl group, and amino group. The active material layer further includes a conductive agent; the conductive agent includes at least one of carbon black, graphene, carbon nanotubes, and polyaniline.

2. The electrode according to claim 1, characterized in that, based on the total mass of the active material layer, the mass percentage of the cellulose binder is not less than 1%.

3. The electrode according to claim 1 or 2, characterized in that, Based on the total mass of the active material layer, the mass percentage of the conductive agent is 5% to 15%.

4. A capacitor deionization device, characterized in that, Includes the capacitive deionization electrode as described in any one of claims 1-3.

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