Capactive deionization electrode and capactive deionization module including same

Abstract

This capacitive deionization (CDI) electrode comprises a current collector and an active material layer formed on one surface of the current collector, the active material layer comprising: a binder; and an activated carbon composite in which crystalline carbon is formed on the surface of activated carbon, wherein the specific surface area of the activated carbon exceeds 2000 m2 / g and the volume of pores having a diameter of 2-5 nm in the activated carbon is at least 70 percent.

Description

Capacitive deionization electrode and capacitive deionization module including the same

[0001] The present invention relates to a capacitive deionization electrode and a capacitive deionization module including the same.

[0002] The capacitive deionization (CDI) process is based on the electric double layer, which electrically adsorbs ions using carbon electrodes. When a voltage is applied to two porous carbon electrodes and water containing ions flows between them, cations are adsorbed at the cathode and anions at the anode, thereby removing ions.

[0003] Porous carbon electrodes are advantageous for use in capacitive desalination processes. Porous carbon electrodes are used in a variety of applications due to their large surface area and low reactivity. In particular, activated carbon, among porous carbon materials, boasts excellent pore volume, high specific surface area, high desorption performance, and a long service life.

[0004] In the capacitive desalination process, the primary mechanism is adsorption in the electric double layer, which occurs due to the electrostatic attraction between ions and electrodes. The capacitive desalination system utilizes the principle of the electric double layer. When electrodes are manufactured from porous activated carbon, improvements are needed to enhance the removal efficiency of ions generated from solutions containing various ions.

[0005] One aspect of the present disclosure provides a capacitive desalination electrode and a capacitive desalination module including the same, which improves the electrical conductivity of the capacitive desalination electrode by increasing the desorption and adsorption efficiency of divalent ions using activated carbon having a specific surface area exceeding 2000 m2 / g and a volume of pores with a diameter of 2 to 5 nm of 70% or more, thereby providing excellent divalent ion removal efficiency in a solution, and forming crystalline carbon by utilizing defects on the surface of the activated carbon as nucleation sites.

[0006] The technical problems to be achieved in this document are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0007] A capacitive deionization (CDI) electrode according to one embodiment of the present disclosure includes a current collector and an active material layer formed on one surface of the current collector, wherein the active material layer may include a binder and an activated carbon complex in which crystalline carbon is formed on the surface of activated carbon having a specific surface area exceeding 2000 m2 / g and a volume of pores having a diameter of 2 to 5 nm of 70% or more.

[0008] Additionally, the activated carbon may include defect sites on the surface, and may optionally include crystalline carbon at the defect sites of the activated carbon.

[0009] Additionally, the crystalline carbon may include carbon allotropes based on sp2 bonding.

[0010] Additionally, the crystalline carbon may be included in an amount of 1 to 70 wt% relative to the weight of the activated carbon.

[0011] Additionally, the binder may include one or more of SBR (styrene butadiene rubber), CMC (carboxy methyl cellulose), PTFE (polytetrafluoroethylene), PDVF (polyvinylidene fluoride), PDMS (polydimethylsiloxane), PVA (polyvinyl alcohol), PVB (polyvinyl butyral), or PAA (poly(acrylic acid)).

[0012] Additionally, the activated carbon complex may be included in the active material layer at 1 to 20 wt%.

[0013] In addition, the active material layer further includes activated carbon having a specific surface area exceeding 2000 m2 / g and a pore volume of 2 to 5 nm in diameter of 70% or more, and the activated carbon can be included in the active material layer at 60 to 96 wt%.

[0014] Additionally, the active material layer may have a thickness of 100 to 400 μm.

[0015] A method for manufacturing a capacitive desalination electrode according to one embodiment of the present disclosure may include manufacturing an electrode slurry comprising an activated carbon composite having crystalline carbon formed on a surface of activated carbon having a specific surface area exceeding 2000 m2 / g and a pore volume of 2 to 5 nm in diameter of 70% or more, activated carbon having a specific surface area exceeding 2000 m2 / g and a pore volume of 2 to 5 nm in diameter of 70% or more, a binder, and a solvent, coating the electrode slurry on a current collector to form an active material layer, and removing the solvent from the active material layer.

[0016] Additionally, the activated carbon complex may include crystalline carbon formed on the surface of the activated carbon by chemical vapor deposition (CVD) of hydrocarbon gas onto the activated carbon.

[0017] Additionally, the hydrocarbon gas may comprise one of polypropylene, polyethylene, or a mixture thereof.

[0018] Additionally, the hydrocarbon gas may include hydrocarbon gas generated during pyrolysis of a plastic precursor.

[0019] Additionally, the plastic precursor may include commercial plastic or waste plastic.

[0020] Additionally, the hydrocarbon gas generated during the pyrolysis of the plastic precursor may include one of polypropylene, polyethylene, polystyrene, polyethylene terephthalate, polyvinyl chloride, polyurethane, or a mixture thereof.

[0021] Additionally, the polyethylene may include one of high density polyethylene (HDPE), low density polyethylene (LDPE), or linear low density polyethylene (LLDPE).

[0022] In addition, the above chemical vapor deposition can be performed at a temperature of 500 to 1500°C, at a heating rate of 1 to 10°C / min, and maintained for 0.5 to 6 hours.

[0023] A capacitive desalination module according to one embodiment of the present disclosure may include the capacitive desalination electrode.

[0024] According to the idea of ​​the present disclosure, by using activated carbon having a specific surface area exceeding 2000 m2 / g and a pore volume of 2 to 5 nm in diameter of 70% or more, the desorption and adsorption efficiency of divalent ions can be increased, thereby improving the removal efficiency of divalent ions in a solution, and by forming crystalline carbon using defects on the surface of the activated carbon as nucleation sites, a capacitive desalination electrode having improved electrical conductivity of the capacitive desalination electrode and a capacitive desalination modium including the same can be provided.

[0025] The effects that can be obtained from the present disclosure are not limited to the effects mentioned above, and other effects that are not mentioned can be clearly understood by a person having ordinary skill in the art to which the present disclosure belongs from the description below.

[0026] Figure 1 is a schematic diagram of a capacitive desalination electrode according to one embodiment of the present disclosure.

[0027] FIG. 2 is a block diagram showing a method for manufacturing a capacitive desalination electrode according to one embodiment of the present disclosure.

[0028] Figure 3 is a schematic diagram of a capacitive desalination module according to one embodiment of the present disclosure.

[0029] FIG. 4 is a schematic diagram comparing the divalent ion adsorption performance of activated carbon having 80% of the volume of pores with a diameter of 2 to 5 nm according to one embodiment of the present disclosure and conventional activated carbon with a focus on micropores.

[0030] FIG. 5 is a diagram showing the results of measuring the specific surface area (BET) of activated carbon having a pore volume of 80% with a diameter of 2 to 5 nm according to one embodiment of the present disclosure.

[0031] Figure 6 is a schematic diagram showing an activated carbon complex in which crystalline carbon is formed by using defects on the surface of activated carbon, which has a specific surface area exceeding 2000 m2 / g and a pore volume of 2 to 5 nm in diameter accounting for 70% or more, as nucleation sites, and activated carbon before crystalline carbon is formed.

[0032] Preferred embodiments of the present invention are described below. However, the embodiments of the present invention may be modified in various ways, and the technical concept of the present invention is not limited to the embodiments described below. Furthermore, the embodiments of the present invention are provided to more fully explain the present invention to those of ordinary skill in the art.

[0033] The terminology used in this application is solely for the purpose of describing specific examples. Therefore, for example, singular expressions include plural expressions unless the context clearly dictates otherwise. Additionally, it should be noted that terms such as "comprise" or "have" used in this application are used to clearly indicate the presence of features, steps, functions, components, or combinations thereof described in the specification, and are not used to preliminarily exclude the presence of other features, steps, functions, components, or combinations thereof.

[0034] Meanwhile, unless otherwise defined, all terms used herein should be considered to have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Therefore, unless explicitly defined herein, specific terms should not be interpreted in an overly idealistic or formal sense. For example, singular expressions herein include plural expressions unless the context clearly indicates otherwise.

[0035] In addition, the terms "about", "substantially", etc. in this specification are used in the sense of or close to the numerical value when manufacturing and material tolerances inherent to the meanings mentioned are presented, and are used to prevent unscrupulous infringers from unfairly using the disclosure contents in which exact or absolute numerical values ​​are mentioned to aid in the understanding of the present invention.

[0036] A capacitive deionization (CDI) electrode according to one embodiment of the present disclosure includes a current collector and an active material layer formed on one surface of the current collector, wherein the active material layer may include a binder and an activated carbon complex in which crystalline carbon is formed on the surface of an activated carbon having a specific surface area exceeding 2000 m2 / g and a volume of pores having a diameter of 2 to 5 nm of 70% or more.

[0037] The current collector included in the capacitive desalination electrode of the present disclosure is preferably one that can uniformly distribute an electric field on the surface of the ion-selective capacitive desalination electrode when current is supplied to the ion-selective capacitive desalination electrode manufactured as described above using a power supply device, and is also preferably one that has excellent conductivity. Examples thereof include, but are not limited to, sheets, thin films, and mesh forms made of aluminum, nickel, copper, titanium, platinum, iron, stainless steel, and graphite.

[0038] The active material layer included in the capacitive desalination electrode of the present disclosure is formed on one surface of the current collector.

[0039] The above active material layer may include a binder and an activated carbon complex, and the activated carbon complex may include crystalline carbon formed on the surface of the activated carbon having a specific surface area exceeding 2000 m2 / g and a volume of pores having a diameter of 2 to 5 nm of 70% or more.

[0040] Ca 2+ , Mg 2+ Divalent ions such as these have a property of good ion pairing, making it difficult for them to pass through pores smaller than 2 nm. In addition, activated carbon applied to conventional capacitive desalination electrodes contained pores smaller than 2 nm in diameter at a volume level of 70-80%, making it unsuitable for use as an electrode for adsorption of polyvalent ions larger than 2 nm.

[0041] Accordingly, in the present disclosure, it is preferable to use activated carbon having a specific surface area exceeding 2000 m2 / g and a volume of pores having a diameter of 2 to 5 nm of 70% or more in order to improve the adsorption performance of divalent ions while allowing divalent ions to pass through well.

[0042] If the specific surface area of ​​the above activated carbon is less than 2000㎡ / g, the hard water component Ca 2+ , Mg 2+ Since the performance of adsorbing divalent ions such as carbon may be inferior, it is preferable that the specific surface area of ​​the activated carbon exceeds 2000㎡ / g.

[0043] In addition, when the pore diameter of the activated carbon is less than 2 nm, it is difficult for divalent ions to pass through, making it unsuitable for use as an electrode for divalent ion adsorption, and when the diameter exceeds 5 nm, it may only function as a passage for divalent ions and may not function as an active material for a capacitive desalination electrode. In addition, it is preferable that the activated carbon contains pores having a diameter of 2 to 5 nm in an amount of 70% or more by volume, but when the pore volume is less than 70%, it may be difficult to obtain the divalent ion adsorption performance aimed at in the present invention, making it unsuitable for use as an electrode for divalent ion adsorption.

[0044] The above activated carbon may be purchased and used as activated carbon having a commercially available specific surface area exceeding 2000 m2 / g and a pore volume of 2 to 5 nm in diameter of 70% or more, or may be manufactured and used according to the following conventional method.

[0045] To illustrate a typical method for manufacturing activated carbon, an activated carbon precursor is heat-treated to carbonize it, and a mixture of the carbonized activated carbon precursor and an activator is heat-treated to manufacture activated carbon.

[0046] The above activated carbon precursor may be coconut shell, coal, starch, tangerine peel, orange peel, coffee grounds, bamboo stems, wood chips, pitch, polyvinylidene polymer, phenol polymer, urethane polymer, polyacrylonitrile polymer, etc.

[0047] The above activated carbon precursor can be carbonized by heat treatment at 500 to 1500°C at a heating rate of 1 to 20°C / min for 0.5 to 6 hours.

[0048] The above carbonized activated carbon precursor can then be mixed with an activator and heat-treated to produce activated carbon.

[0049] The above activator may be an activator commonly used in the manufacture of activated carbon, and examples thereof include KOH, NaOH, K2CO3, C2H3O2K, etc.

[0050] The above-mentioned carbonized activated carbon precursor and activator can be mixed in a ratio of 1:5 or more. In particular, it is preferable that the activated carbon precursor and activator be mixed in a ratio of 1:6, and in this case, it is more preferable for producing activated carbon having a specific surface area exceeding 2000 m2 / g and a volume of pores having a diameter of 2 to 5 nm of 70% or more.

[0051] The above mixed activated carbon precursor and activator can be heat-treated at 500 to 1500°C at a heating rate of 1 to 20°C / min for 0.5 to 6 hours to produce activated carbon having a specific surface area exceeding 2000 m2 / g and a pore volume of 2 to 5 nm in diameter of 70% or more.

[0052] In general, activated carbon has many defect sites such as vacancies and holes, and has low electrical conductivity due to the coexistence of crystalline and amorphous phases. In addition, transition metals and polymer templates were used as nuclei sites for the formation of crystalline carbon in the past, but post-treatment using strong acids and organic solvents was required to remove them, which caused environmental pollution issues. In addition, in the past, a separate conductive agent was added to improve the electrical conductivity of activated carbon. However, although the addition of the conductive agent is effective in improving the electrical conductivity of the electrode, there is a problem in that the low specific surface area adversely affects the performance of the electrode.

[0053] Accordingly, the active material layer of the present disclosure can improve the removal efficiency of divalent ions in a solution by increasing the desorption and adsorption efficiency of divalent ions using activated carbon having a specific surface area exceeding 2000 m2 / g and a pore volume of 70% or more with a diameter of 2 to 5 nm, and can form crystalline carbon by utilizing defects on the surface of the activated carbon as nucleation sites, thereby pursuing improvement of the electrical conductivity of the electrode and simultaneously solving the issue of environmental pollution.

[0054] Specifically, the activated carbon complex may include crystalline carbon formed on the surface of the activated carbon by chemical vapor deposition (CVD) of hydrocarbon gas on the activated carbon having a specific surface area exceeding 2000 m2 / g as described above and a pore volume of 2 to 5 nm in diameter of 70% or more.

[0055] That is, when hydrocarbon gas is chemically vapor-deposited on activated carbon, unstable and high-energy defects on the surface of the activated carbon act as nucleation sites, and crystalline carbon is selectively formed at the nucleation sites.

[0056] The hydrocarbon gas used may be polypropylene, polyethylene, etc.

[0057] Additionally, the hydrocarbon gas generated during the thermal decomposition of a plastic precursor may be used as the hydrocarbon gas.

[0058] The above plastic precursor is not limited in type as long as it is a common plastic, and may include, for example, commercial plastic or waste plastic.

[0059] In particular, the present invention can be said to be environmentally friendly because waste plastic is used as a plastic precursor, so waste plastic that is released into the natural environment and causes various problems can be chemically recycled.

[0060] The hydrocarbon gas generated during the pyrolysis of the above plastic precursor may include polypropylene, polyethylene, polystyrene, polyethylene terephthalate, polyvinyl chloride, polyurethane, etc. In addition, the polyethylene may include high density polyethylene (HDPE), low density polyethylene (LDPE), or linear low density polyethylene (LLDPE).

[0061] The above chemical vapor deposition can be performed at a temperature of 500 to 1500°C and a heating rate of 1 to 10°C / min for 0.5 to 6 hours, and the heat treatment time can be appropriately adjusted from 0.5 to a maximum of 6 hours depending on the type of hydrocarbon gas, the degree of formation of crystalline carbon, the temperature and heating rate during chemical vapor deposition, etc.

[0062] When the temperature is less than 500°C during the above chemical vapor deposition, the diffusion of hydrocarbon gas may not occur well due to insufficient activation energy for the formation of crystalline carbon, and thus the formation of crystalline carbon may not be smooth. When the temperature exceeds 1500°C, it is difficult to control the growth rate of crystalline carbon due to the high energy, and thus stable crystalline carbon formation may not occur, and it may be difficult to form high-quality crystalline carbon.

[0063] In addition, if the heating rate during the chemical vapor deposition is less than 1°C / min, the time spent at a temperature other than the main growth temperature may be long, making it difficult to form the targeted crystalline carbon, and if it exceeds 10°C / min, only the temperature near the heating wire of the heat treatment device (furnace) may rise more quickly, and the internal temperature may rise unevenly, making it difficult to form the targeted crystalline carbon.

[0064] As described above, the crystalline carbon formed on the surface of activated carbon having a specific surface area exceeding 2000 m2 / g and a pore volume of 2 to 5 nm in diameter of 70% or more may include a carbon isotrope based on sp2 bonding, and thus the crystalline carbon may have an sp2 structure as its crystal structure.

[0065] The crystalline carbon as described above is preferably included in an amount of 1 to 70 wt% based on the weight of the activated carbon, and more preferably in an amount of 5 to 60 wt%. If the content is less than 1 wt%, the improvement in the conductivity of the material is minimal, and thus the performance may deteriorate compared to using a conductive material in the manufacture of the electrode. On the other hand, if the content exceeds 70 wt%, the specific surface area of ​​the activated carbon composite is greatly reduced, and thus the performance may be similar to that of a general conductive material.

[0066] The activated carbon complex including crystalline carbon formed on the surface of the activated carbon, which has a specific surface area exceeding 2000㎡ / g and a pore volume of 2 to 5 nm in diameter of 70% or more, is preferably included in the active material layer at 1 to 20 wt%, and more preferably at 1 to 10 wt%. If the content is less than 1 wt%, the electrical conductivity may be low, making it difficult to efficiently adsorb and desorb ions, and if it exceeds 20 wt%, it may be difficult to secure a sufficient ion adsorption amount due to a decrease in the specific surface area.

[0067] In addition, the active material layer of the capacitive desalination electrode of the present disclosure includes a binder and an activated carbon complex including crystalline carbon formed on the surface of the activated carbon having a specific surface area exceeding 2000 m2 / g and a volume of pores having a diameter of 2 to 5 nm of 70% or more as described above.

[0068] The above binder is not particularly limited in type as long as it is an aqueous binder or an oil-based binder used in the manufacture of a conventional capacitive desalination electrode, and for example, SBR (styrene butadiene rubber), CMC (carboxy methyl cellulose), PTFE (polytetrafluoroethylene), PDVF (polyvinylidene fluoride), PDMS (polydimethylsiloxane), PVA (polyvinyl alcohol), PVB (polyvinyl butyral), PAA (poly(acrylic acid)), etc. can be used.

[0069] The above binder is preferably included in the active material layer at 5 to 20 wt%. If the content is less than 5 wt%, the shape of the electrode may not be maintained, may break, or the activated carbon powder may melt out. If the content exceeds 20 wt%, the pores of the activated carbon may be blocked by the binder, significantly reducing the performance of the electrode.

[0070] In addition, the active material layer of the capacitive desalination electrode of the present disclosure may further include activated carbon having a specific surface area exceeding 2000 m2 / g and a pore volume of 2 to 5 nm in diameter of 70% or more. At this time, the activated carbon is preferably included in the active material layer in an amount of 60 to 96 wt%, and more preferably in an amount of 70 to 90 wt%. When the content is less than 60 wt%, the electrode performance may be deteriorated due to a decrease in the electrode specific surface area, and when it exceeds 96 wt%, the performance and durability may be deteriorated due to a decrease in conductivity and a decrease in the mechanical stability of the electrode.

[0071] Preferably, the activated carbon complex, binder and activated carbon are mixed in a weight ratio of 0.5 to 2:0.1 to 2:5 to 8, and more preferably, they are mixed in a weight ratio of 1:1:8. When the mixing ratio of the activated carbon complex, binder and activated carbon is within the above-mentioned range, Ca 2+ , Mg 2+ It is more desirable to improve the adsorption performance of divalent ions such as the following.

[0072] Hereinafter, a capacitive deionization electrode, a method for manufacturing a capacitive deionization electrode, and a capacitive deionization module according to an embodiment of the present disclosure will be described with reference to the drawings.

[0073] FIG. 1 is a schematic diagram of a capacitive deionization electrode according to one embodiment of the present disclosure, FIG. 2 is a block diagram showing a method for manufacturing a capacitive deionization electrode according to one embodiment of the present disclosure, and FIG. 3 is a schematic diagram of a capacitive deionization module according to one embodiment of the present disclosure.

[0074] Referring to FIG. 1, a capacitive deionization (CDI) electrode according to one embodiment of the present disclosure includes a current collector and an active material layer formed on one surface of the current collector. In addition, the active material layer may include a binder, an activated carbon complex in which crystalline carbon is formed on the surface of the activated carbon having a specific surface area exceeding 2000 m2 / g and a pore volume of 2 to 5 nm in diameter of 70% or more, and, if necessary, activated carbon having a specific surface area exceeding 2000 m2 / g and a pore volume of 2 to 5 nm in diameter of 70% or more.

[0075] The above active material layer is preferably formed on one surface of the current collector to a thickness of 100 to 400 μm. If the thickness of the active material layer is less than 100 μm, the amount of active material per unit area is insufficient, making it difficult to secure sufficient ion adsorption capacity. If the thickness exceeds 400 μm, the active material layer may be unstably attached to the surface of the current collector, causing detachment, which may deteriorate the mechanical stability of the electrode.

[0076] Next, a method for manufacturing a capacitive desalination electrode according to one embodiment of the present disclosure is described.

[0077] Referring to FIG. 2, a method for manufacturing a capacitive desalination electrode according to one embodiment of the present disclosure may include manufacturing an electrode slurry including an activated carbon composite, activated carbon, a binder, and a solvent (S10), coating the electrode slurry on a current collector to form an active material layer (S20), and removing a solvent from the active material layer (S30).

[0078] In manufacturing the above electrode slurry (S10), the activated carbon complex can form crystalline carbon by chemical vapor deposition of hydrocarbon gas on activated carbon having a specific surface area exceeding 2000 m2 / g and a pore volume of 2 to 5 nm in diameter of 70% or more, using defects on the surface of the activated carbon as nucleation sites.

[0079] That is, the activated carbon complex has a high specific surface area and can increase the adsorption capacity of divalent ions by using activated carbon having a specific surface area exceeding 2000 m2 / g and a pore volume of 2 to 5 nm in diameter of 70% or more, and by forming crystalline carbon by using defect sites on the surface of the activated carbon as nucleation sites, it pursues improvement of the electrical conductivity of the electrode, and at the same time, there is no need for a post-treatment chemical for removing transition metals, polymer templates, etc. used for forming crystalline carbon in the past, so that the issue of environmental pollution can also be solved.

[0080] The hydrocarbon gas may include propylene, ethylene, etc., or hydrocarbon gas generated during the thermal decomposition of a plastic precursor.

[0081] At this time, commercial plastic or waste plastic can be used as the plastic precursor, and the hydrocarbon gas generated during the pyrolysis of the plastic precursor can be polyethylene such as high density polyethylene (HDPE), low density polyethylene (LDPE), or linear low density polyethylene (LLDPE), polypropylene, polystyrene, polyethylene terephthalate, polyvinyl chloride, polyurethane, etc.

[0082] By introducing hydrocarbon gas into a reactor containing activated carbon and maintaining the temperature at 500 to 1500°C, at a heating rate of 1 to 10°C / min, for 0.5 to 6 hours, crystalline carbon can be formed on the surface of the activated carbon through chemical vapor deposition.

[0083] The above-mentioned activated carbon may be activated carbon having a specific surface area exceeding 2000㎡ / g and a pore volume of 70% or more with a diameter of 2 to 5㎚, and the binder may be an aqueous or oil-based binder such as SBR (styrene butadiene rubber), CMC (carboxy methyl cellulose), PTFE (polytetrafluoroethylene), PDVF (polyvinylidene fluoride), PDMS (polydimethylsiloxane), PDMS (polydimethylsiloxane), PVA (polyvinyl alcohol), PVB (polyvinyl butyral), PAA (poly(acrylic acid)). In addition, it is preferable to use an aqueous solvent or a polar organic solvent that can be mixed well with water and thus dissolved in water. For example, dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, acetone, chloroform, dichloromethane, trichloroethylene, ethanol, methanol, normal hexane, etc. can be used as the polar organic solvent.

[0084] After evenly mixing the activated carbon complex and activated carbon as described above, a binder and a solvent are added and mixed evenly to prepare an electrode slurry.

[0085] In forming the above active material layer (S20), the current collector can be made of aluminum, nickel, copper, titanium, iron, stainless steel, graphite, etc., which have excellent conductivity, so that when current is supplied to the capacitive deionization electrode, an electric field can be uniformly distributed on the surface of the capacitive deionization electrode.

[0086] The method for coating the electrode slurry on the above-mentioned collector may use knife casting, doctor blade, spin coating, dip coating, spraying, silk screening, etc., and it is most preferable for application to a capacitive desalination electrode to make the coating thickness of the active material layer 100 to 400 ㎛.

[0087] The above active material layer refers to an active material layer before being cured, and the active material layer is cured in the solvent removal step (S30) described below to manufacture the final capacitive desalination electrode.

[0088] In removing the solvent (S30), the solvent can be removed using hot air drying or oven drying at 60°C or higher, thereby allowing the activated carbon complex, activated carbon, and binder to be combined in the active material layer. The capacitive desalination electrode manufactured in this way is simple in process as the electrode is manufactured through only a drying process, and can reduce interfacial resistance that may occur due to a separate bonding process.

[0089] Also described is a capacitor-type desalination module according to one embodiment of the present disclosure.

[0090] Referring to FIG. 3, a capacitive desalination module according to one embodiment of the present disclosure includes a channel (20) through which introduced hard water flows, an anode electrode (10a) disposed on one side of the channel (20), and a cathode electrode (10b) disposed on the other side of the channel, wherein the anode electrode (10a) includes a cathode current collector (11a) and a cathode active material layer (12a) formed on the cathode current collector (11a), and the cathode electrode (10b) may include a cathode current collector (11b) and a cathode active material layer (12b) formed on the cathode current collector (11b).

[0091] The above-mentioned euro (20) is a passage through which hard water requiring softening treatment flows in and circulates.

[0092] The above-mentioned positive electrode collector (11a) and negative electrode collector (11b) can be electrically connected to a power source provided externally in the capacitive deionization module of the present disclosure and serve to apply voltage to the capacitive deionization electrodes (10a, 10b).

[0093] The above-described positive electrode active material layer (12a) and negative electrode active material layer (12b) may include an activated carbon complex in which crystalline carbon is formed on the surface of activated carbon having a specific surface area exceeding 2000 m2 / g and a pore volume of 2 to 5 nm in diameter of 70% or more, an activated carbon having a specific surface area exceeding 2000 m2 / g and a pore volume of 2 to 5 nm in diameter of 70% or more, and a binder.

[0094] In addition, the capacitive desalination electrode of the present disclosure may additionally include, as necessary, an anion exchange membrane or a cation exchange membrane to selectively transmit ions in the introduced hard water, or a spacer installed to form the flow path (20), in addition to the above-mentioned components.

[0095] Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are intended only to illustrate the present invention and the scope of the present invention is not limited to these examples.

[0096] Example 1. Preparation of activated carbon composite for capacitive desalination electrode

[0097] (Activated carbon manufacturing)

[0098] Coconut skin, an activated carbon precursor, was carbonized at 800°C for 2 hours at a heating rate of 5°C. The carbonized activated carbon precursor was mixed with KOH in a ratio of 1:6 and heat-treated at 800°C for 2 hours at a heating rate of 5°C to produce activated carbon having a specific surface area of ​​3212 m2 / g and a pore volume of 2-5 nm in diameter of 80%.

[0099] A schematic diagram of the divalent ion adsorption performance of the activated carbon having 80% of the volume of pores with a diameter of 2 to 5 nm manufactured as described above is shown in Fig. 4 in comparison with the conventional activated carbon with a focus on micropores. In addition, the results of measuring the specific surface area (BET) of the activated carbon having pores with a diameter of 2 to 5 nm manufactured as described above are shown in Fig. 5.

[0100] As shown in Fig. 4, in the case of conventional micro-pore-based activated carbon, the pore diameter is less than 2 nm, so Ca 2+ , Mg 2+ It can be confirmed that divalent ions have difficulty passing through the pores of activated carbon, and that the adsorption of divalent ions is also significantly low. On the other hand, in the case of the activated carbon according to the present disclosure, the volume of pores with a diameter of 2 to 5 nm is 80%, and it can be confirmed that it serves as a passage for divalent ions to pass through, while efficiently adsorbing divalent ions.

[0101] In addition, as shown in Fig. 5, in the case of the activated carbon according to the present disclosure, the volume of pores having a diameter of 2 to 5 nm is high, and after the micropore adsorption is completed in the low relative pressure range, the adsorption amount shows a shape in which it increases linearly according to the relative pressure, and it was confirmed that the hysteresis is very small or does not appear at high pressure.

[0102] (Manufacturing of activated carbon complex)

[0103] An activated carbon composite was manufactured as follows using the activated carbon having a surface area of ​​3212 m2 / g and a pore volume of 80% with a diameter of 2 to 5 nm.

[0104] First, low density polyethylene (LDPE) was introduced as a hydrocarbon gas into a chamber containing the above-mentioned manufactured activated carbon, and crystalline carbon was formed at defect sites on the surface of the activated carbon by chemical vapor deposition at a heating rate of 10°C / min at 800°C for 2 hours. A schematic diagram of the activated carbon composite in which crystalline carbon is formed on the surface of the activated carbon is shown in Fig. 6.

[0105] As shown in Fig. 6, it can be confirmed that there are defect sites such as vacancies and holes on the surface of the activated carbon before forming crystalline carbon. However, as a result of forming crystalline carbon on the surface of the activated carbon according to the present disclosure, it can be confirmed that the crystalline carbon is formed using the defects on the surface of the activated carbon as nuclei sites, and thus the defects on the surface of the activated carbon are significantly reduced. That is, when crystalline carbon is formed on the surface of activated carbon having a specific surface area exceeding 2000 m2 / g and a volume of pores with a diameter of 2 to 5 nm of 70% or more according to the present disclosure, the defects on the surface of the activated carbon can be reduced, thereby improving the electrical conductivity of the electrode and at the same time increasing the adsorption performance of divalent ions.

[0106] Example 2. Preparation of a capacitive desalination electrode

[0107] An activated carbon composite having a surface area of ​​3212 m2 / g and a pore volume of 2-5 nm in diameter, which was manufactured in Example 1, and in which crystalline carbon was formed on the surface of the activated carbon, was uniformly mixed with SBR (styrene butadiene rubber) binder and water using a mixer to prepare an electrode slurry. The prepared electrode slurry was coated at a constant speed on a graphite sheet, which was a current collector, using a knife coating machine to form an active material layer having a thickness of 300 μm. At this time, the current collector was formed in a roll-to-roll form using a roller. Then, the final capacitive desalination electrode was manufactured by drying with hot air at 80°C or higher for more than 2 minutes.

[0108] Example 3. Preparation of a capacitive desalination electrode

[0109] An activated carbon composite having a surface area of ​​3212 m2 / g and a pore volume of 2-5 nm in diameter accounting for 80% of the activated carbon manufactured in Example 1, in which crystalline carbon is formed on the surface, and an activated carbon having a surface area of ​​3212 m2 / g and a pore volume of 2-5 nm in diameter accounting for 80% of the activated carbon were uniformly mixed. An electrode slurry was manufactured by uniformly mixing the mixture with a styrene butadiene rubber (SBR) binder and water using a mixer. The manufactured electrode slurry was coated at a constant speed on a graphite sheet, which is a current collector, using a knife coating machine to form an active material layer having a thickness of 250 μm. At this time, the current collector was formed in a roll-to-roll form using a roller. Subsequently, the final capacitive desalination electrode was manufactured by drying with hot air at 80°C or higher for more than 2 minutes.

[0110] Example 4. Manufacturing of a capacitive desalination module

[0111] Using the capacitive deionization electrode manufactured in Example 3, a capacitive deionization module was manufactured including a cathode electrode and an anode electrode installed spaced apart from one side and the other side of the channel by a spacer for forming the channel.

[0112] Although the embodiments of the invention disclosed above have been illustrated and described, the disclosed invention is not limited to the specific embodiments described above, and various modifications may be implemented by a person having ordinary skill in the art to which the disclosed invention pertains without departing from the gist claimed in the claims.

Claims

1. Comprising a current collector and an active material layer formed on one or both sides of the current collector, A capacitive deionization (CDI) electrode comprising an activated carbon complex in which the active material layer comprises a binder and crystalline carbon formed on the surface of the activated carbon having a specific surface area exceeding 2000 m2 / g and a pore volume of 70% or more having a diameter of 2 to 5 nm.

2. In paragraph 1, A capacitive desalination electrode, wherein the activated carbon includes defect sites on the surface and selectively includes crystalline carbon at the defect sites of the activated carbon.

3. In paragraph 1, The above crystalline carbon is a capacitive desalination electrode comprising a carbon isotrope based on sp2 bonding.

4. In paragraph 1, A capacitive desalination electrode, wherein the above-mentioned crystalline carbon is contained in an amount of 1 to 70 wt% based on the weight of the above-mentioned activated carbon.

5. In paragraph 1, A capacitive desalination electrode in which the activated carbon complex is included in the active material layer at 1 to 20 wt%.

6. In paragraph 1, A capacitive desalination electrode, wherein the active material layer further comprises activated carbon having a surface area exceeding 2000 m2 / g and a pore volume of 70% or more having a diameter of 2 to 5 nm, and wherein the activated carbon is contained in the active material layer at 60 to 96 wt%.

7. In paragraph 1, A capacitive desalination electrode having an active material layer having a thickness of 100 to 400 μm.

8. Manufacturing an electrode slurry comprising an activated carbon complex having crystalline carbon formed on the surface of the activated carbon having a specific surface area exceeding 2000㎡ / g and a pore volume of 2 to 5㎚ in diameter of 70% or more, a binder, and a solvent, and a specific surface area exceeding 2000㎡ / g and a pore volume of 2 to 5㎚ in diameter of 70% or more. Forming an active material layer by coating the above electrode slurry on a current collector, and A method for manufacturing a capacitive desalination electrode, comprising removing a solvent from the active material layer.

9. In paragraph 8, The above activated carbon complex is a method for manufacturing a capacitive desalination electrode including crystalline carbon formed on the surface of activated carbon by chemical vapor deposition (CVD) of hydrocarbon gas onto activated carbon.

10. In paragraph 9, A method for manufacturing a capacitive desalination electrode, wherein the hydrocarbon gas comprises hydrocarbon gas generated during thermal decomposition of a plastic precursor.

11. In paragraph 10, The above plastic precursor is a method for manufacturing a capacitive desalination electrode including commercial plastic or waste plastic.

12. In paragraph 10, A method for manufacturing a capacitive desalination electrode, wherein the hydrocarbon gas generated during the thermal decomposition of the above plastic precursor comprises one of polypropylene, polyethylene, polystyrene, polyethylene terephthalate, polyvinyl chloride, polyurethane or a mixture thereof.

13. In paragraph 12, A method for manufacturing a capacitive desalination electrode, wherein the polyethylene comprises one of high density polyethylene (HDPE), low density polyethylene (LDPE), or linear low density polyethylene (LLDPE).

14. In paragraph 9, A method for manufacturing a capacitive desalination electrode, wherein the above chemical vapor deposition is performed at a temperature of 500 to 1500°C, at a heating rate of 1 to 10°C / min, and maintained for 0.5 to 6 hours.

15. A capacitive deionization module including the capacitive deionization electrode described in paragraph 1.

Images