Continuous flow-electrode system, and high-capacity power storage and water treatment method using the same

Abstract

The present invention uses the principles of electrochemical ion absorption (charging) and ion desorption (discharge), and relates to a continuous flow-electrode system, a high-capacity energy storage system, and a water treatment method using the same, in which high-capacity electric energy is stored as electrode materials of a slurry phase and electrolytes simultaneously flow in a successive manner within a fine flow channel structure formed on an electrode. More specifically, the present invention relates to a continuous flow-electrode system, an energy storage system, and a water treatment method, wherein electrode active materials consecutively flow in a slurry state whereby a high capacity is easily obtained without enlarging or stacking electrodes.

Claims

1. A continuous flow-electrode system comprising: (i) a flow-cathode comprising a current collector; a cathode separation layer; a cathode flow channel formed between the current collector and the cathode separation layer; and a solid ion-chargeable cathode active material flowing continuously in the cathode flow channel, (ii) a flow-anode comprising a current collector; an anode separation layer; an anode flow channel formed between the current collector and the anode separation layer; and a solid ion-chargeable anode active material flowing continuously in the anode flow channel, (iii) a channel type insulating spacer formed between the cathode and the anode, wherein liquid electrolyte flows continuously into and out of the channel type insulating spacer in a direction parallel to a flow direction of the anode flow channel, wherein when potential is applied between the cathode and the anode, the solid, ion-chargeable cathode active material is charged with cations of the electrolyte, which is passing through the cathode separation layer into the cathode flow channel and then the solid, ion-chargeable cathode active material flows continuously out of the cathode flow channel; and the solid, ion-chargeable anode active material is charged with anions of the electrolyte, which is passing through the anode separation layer into the anode flow channel and then the solid, ion-chargeable anode active material flows continuously out of the anode flow channel.

2. The continuous flow-electrode system of claim 1, wherein the anode separation layer is a microporous insulation separation membrane or an anion-exchange conductive membrane (AEM), and the cathode separation layer is a microporous insulation separation membrane or a cation-exchange conductive membrane (CEM).

3. The continuous flow-electrode system of claim 1, wherein the solid, ion-chargeable cathode active material or the solid, ion-chargeable anode active material is mixed with the electrolyte to form an active material in a slurry phase.

4. The continuous flow-electrode system of claim 1, wherein the solid, ion-chargeable cathode active material and the solid, ion-chargeable anode active material include the same materials.

5. The continuous flow-electrode system of claim 1, wherein the anode separation layer and/or the cathode separation layer is a microporous insulation separation membrane.

6. The continuous flow-electrode system of claim 1, wherein a flow direction of the electrolyte is opposed to a flow direction of both the solid, ion-chargeable cathode active material of the flow-cathode and the solid, ion-chargeable anode active material of the flow-anode wherein these two active materials flow in the same direction.

7. The continuous flow-electrode system of claim 1, wherein the solid, ion-chargeable cathode active material of the flow cathode has a flow rate different from that of the solid, ion-chargeable anode active material of the flow anode.

8. The continuous flow-electrode system of claim 1, wherein the continuous flow-electrode system is a secondary battery or an electric double layer capacitor (EDLC).

9. A high-capacity energy storage system comprising: the continuous flow-electrode system of claim 1; a feeding device to supply the solid, ion-chargeable cathode active material, solid, ion-chargeable anode active material and electrolyte, respectively; a power supply to apply power to the continuous flow-electrode system; a change-over switch to control a potential difference occurring in the power supply; and storage tanks for storing each of the solid, ion-chargeable cathode active material, solid, ion-chargeable anode active material and electrolyte.

10. The high-capacity energy storage system of claim 9, further comprising a resistor connected to the change-over switch.

11. The high-capacity energy storage system of claim 9, wherein the feeding device comprises a feeding tank and a feeding pump to supply the solid, ion-chargeable cathode active material, solid, ion-chargeable anode active material and electrolyte, respectively.

12. The high-capacity energy storage system of claim 11, wherein a single feeding tank functions as a solid, ion-chargeable cathode active material feeding tank to supply the solid, ion-chargeable cathode active material and simultaneously with a solid, ion-chargeable anode active material feeding tank to supply the solid, ion-chargeable anode active material.

13. The high-capacity energy storage system of claim 11, wherein two continuous flow-electrode systems are provided, wherein a part of the continuous flow-electrode systems is used as a charge device while the remainder is used as a discharge device, and the solid, ion-chargeable cathode active material and the solid, ion-chargeable anode active material flowing out of the energy storage device for discharge are again recycled to the solid, ion-chargeable cathode active material feeding tank and the solid, ion-chargeable anode active material feeding tank, respectively.

14. The high-capacity energy storage system of claim 9, wherein the storage tank is an electrically insulated storage container.

15. The high-capacity energy storage system of claim 9, wherein the electrolyte comprises sea water or industrial wastewater.

16. A water treatment method through capacitive deionization (CDI) using the high-capacity energy storage system of claim 9, wherein sea water or industrial wastewater flows into an electrolyte feeding tank and passes through the continuous flow electrode system, wherein a potential difference occurs in the continuous flow-electrode system, and wherein the sea water or industrial wastewater is deionized and stored in an electrolyte storage tank.

17. A method for desalination of sea water through capacitive deionization (CDI) using the high-capacity energy storage system according to claim 9, wherein the electrolyte includes sea water, wherein the sea water flows into an electrolyte feeding tank and passes through the continuous flow electrode system, wherein a potential difference occurs in the continuous flow-electrode system, and wherein the sea water is deionized and stored in an electrolyte storage tank.

18. A method for purification of wastewater through capacitive deionization (CDI)-using the high-capacity energy storage system according to claim 9, wherein the electrolyte includes industrial wastewater, wherein the industrial wastewater flows into an electrolyte feeding tank and passes through the continuous flow electrode system, wherein a potential difference occurs in the continuous flow-electrode system, and wherein the industrial wastewater is deionized and stored in an electrolyte storage tank.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1 is a schematic view illustrating a continuous flow-electrode system according to one embodiment of the present invention.

(2) FIG. 2 is a cross-sectional view illustrating a microcapsule containing an electrode material according to one embodiment of the present invention.

(3) FIG. 3 is a schematic view illustrating a high-capacity electrode system according to one embodiment of the present invention.

(4) FIG. 4 is a schematic view illustrating a continuous flow-electrode system according to another embodiment of the present invention.

(5) FIG. 5 is a schematic view illustrating a continuous flow-electrode system according to yet another embodiment of the present invention.

DETAILED DESCRIPTION

(6) Hereinafter, the present invention will be described in detail. However, the following description is given for more specifically explaining the present invention, of which design may be appropriately altered or modified by those skilled in the art.

(7) According to one embodiment of the present invention, the continuous flow-electrode system includes a flow anode containing a flowing anode active material; a flow cathode containing a flowing cathode active material; and a flowing electrolyte.

(8) The anode active material, cathode active material and electrolyte may include any one used in a typical continuous flow-electrode system, that is, a battery or storage battery, which may be appropriately selected by those skilled in the art in consideration of purposes and/or circumstances of using the same.

(9) According to one embodiment of the present invention, the anode active material and the cathode active material may include different materials, or otherwise, the same material.

(10) According to one embodiment of the present invention, an electrode material such as anode active material and/or the cathode active material may include porous carbon (activated carbon, carbon aerosol, carbon nanotube, etc.), graphite powder, metal oxide powder, and the like, which may be mixed with the electrolyte to be used in a fluidized state.

(11) According to one embodiment of the present invention, the electrolyte includes a water-soluble electrolyte such as NaCl, H.sub.2SO.sub.4, HCl, NaOH, KOH, Na.sub.2NO.sub.3, etc. and an organic electrolyte such as propylene carbonate (PC), diethyl carbonate (DEC), tetrahydrofuran (THF), etc.

(12) According to one embodiment of the present invention, the electrode active material flows alone while the electrolyte may be a solid or fixed phase electrolyte.

(13) According to one embodiment of the present invention, the anode includes an anode collector; an anode separation layer; an anode flow channel formed between the anode collector and the anode separation layer; and an anode active material flowing through the anode flow channel, and the cathode includes a cathode collector; a cathode separation layer; a cathode flow channel formed between the cathode collector and the cathode separation layer; and a cathode active material flowing through the cathode flow channel, wherein the electrolyte flows through a flow channel formed between the anode separation layer and the cathode separation layer.

(14) The electrode collector and the electrode separation layer may include any one used in conventional continuous flow-electrode systems (battery, storage battery, etc.), which may be appropriately selected or adopted by those skilled in the art in consideration of purposes and conditions of using the same.

(15) A width of the anode flow channel or the cathode flow channel may be formed in a size equal to or less than a space between an electrode collector and a separation layer in a conventional continuous flow-electrode system. Since the electrode active material is conventionally fixed, it causes a problem that a size of the continuous flow-electrode system is increased when attempting to obtain a desired capacity of the active material required for charge/discharge, to thus limit the space between the electrode collector and the separation layer. On the other hand, according to the present invention, since the electrode active material may be continuously supplied, design alteration and/or modification may be freely performed depending upon purposes, active materials of electrolyte to be used, etc., without limitation thereto. According to one embodiment of the present invention, a width and height of the flow channel used herein may range from several tens of m to several mm.

(16) Likewise, a width of an insulating spacer may be appropriately altered without limitation caused by a dimension of the continuous flow-electrode system since the electrolyte can be continuously supplied.

(17) However, in order to increase charge/discharge efficiency, velocities of the electrolyte and active material may be different from each other, or otherwise, a ratio of widths between the active material and an insulating spacer may be restricted.

(18) According to one embodiment of the present invention, the anode separation layer may be a microporous insulation separation membrane or anion-exchange (conductive) membrane, while the cathode separation layer may be a microporous insulation separation membrane or cation-exchange (conductive) membrane.

(19) The separation layer is used for electrical and physical separation, and the microporous insulation separation membrane allows ion transfer only while an ion-exchange (conductive) membrane may selectively transfer either cations or anions.

(20) Additionally, according to one embodiment of the present invention, the anode active material or the cathode active material may include a slurry phase active material including the anode active material or the cathode active material mixed with the electrolyte.

(21) Meanwhile, according to another embodiment of the present invention, the electrolyte may flow in the opposite direction to the anode active material and the cathode active material. Therefore, it is possible to construct a continuous flow-electrode system in various forms.

(22) Further, adopting different flow rates of the anode active material in the anode and the cathode active material in the cathode may possibly induce different reaction times of the anode active material and the cathode active material, respectively, with the electrolyte. Thereby, a variety of design modifications may be possible.

(23) Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

(24) FIG. 1 is a schematic view illustrating a continuous flow-electrode system according to one embodiment of the present invention. Referring to FIG. 1, the system includes an anode 10 including an anode collector 11, an anode separation layer 13, and an anode active material 12 flowing through an anode flow channel 14 formed between the anode collector 11 and the anode separation layer 13; a cathode 20 including a cathode collector 21, a cathode separation layer 23, and a cathode active material 22 flowing through a cathode flow channel 24 formed between the cathode collector 21 and the cathode separation layer 23; and an electrolyte 30 flowing through an insulating spacer 34 formed between the anode separation layer 13 and the cathode separation layer 23.

(25) The continuous flow-electrode system may be a unit cell wherein two or more unit cells may be consecutively arranged, and may simultaneously and continuously flow an electrode material as well as the electrolyte.

(26) Further, as shown in FIG. 4, it is possible to make a direction of movement of the electrolyte 30 to be opposed to the anode active material 12 and cathode active material 22.

(27) Referring to FIG. 2, the electrode material may be micro-capsulated to increase a contact area between the electrolyte and the electrode material. More particularly, an anion separation layer (a dense layer selectively passing anions while blocking flow-through of a liquid electrolyte) and a cation separation layer (a dense layer selectively passing only cations) are used.

(28) However, if using an electrode active material encapsulated by each selective ion layer (see FIG. 2), it is not necessary to provide ion conductive dense layers between two electrodes. Alternatively, when a microporous insulation separation membrane allowing flow-through of the electrolyte as well as ions is used, a contact area between the electrolyte and encapsulated electrode active material particles is increased.

(29) The micro-capsulated electrode includes a core at the center and a shell surrounding the periphery of the core, wherein a shell material has the property of exchanging ions present in the electrolyte. According to one embodiment of the present invention, the shell material may include a polymer membrane containing a sulfonic acid group (SO.sub.3.sup.), carboxyl group (COO.sup.) or phosphoric acid group (PO.sub.4.sup.), etc., which is capable of exchanging cations; or a polymer membrane containing a primary, secondary, tertiary or quaternary ammonium group bonded thereto, which is capable of exchanging anions. The micro-capsule may be prepared by a solid or liquid phase method. In particular, in the liquid phase method, a core/shell structure may be formed by, for example, an emulsion method using a surfactant, a polymerization method polymerizing monomers to prepare a shell material, or a method of injecting or extruding the core and shell, simultaneously or separately, in order to form a micro-capsulated electrode. Since the micro-capsulated electrode includes a single granule or individual granules agglomerated together and a shell surrounding the same, it has an advantage in that an electrode area per unit weight or volume is larger than that of a bulk electrode formed of all agglomerated granules.

(30) In particular, as shown in FIG. 5, when a continuous flow-electrode system 60 free from a separation layer is fabricated, it is possible to avoid direct mixing of an anode active material and cathode active material with an electrolyte.

(31) Next, referring to FIG. 3, an energy storage system 100 according to one embodiment of the present invention includes a continuous flow-electrode system 1 in a unit cell form; a cathode active material feeding tank 2a and a feeding pump 41 to supply a cathode active material which was prepared in a slurry phase by mixing the cathode active material 22 with an electrolyte 30; an anode active material feeding tank 2b and a feeding pump 42 to supply an anode active material which was prepared in a slurry phase by mixing the anode active material 12 with the electrolyte 30; an electrolyte feeding tank 5 and a feeding pump 43 to supply the electrolyte 30; a power supply 7 to apply direct current to the continuous flow-electrode system 1; a change-over switch 9 to control a potential difference occurring in the power supply 7; an anion storage tank 3 in which the anode active material containing ions adsorbed (charged) therein while passing through the potential-applied continuous flow-electrode system 1 is stored; a cation storage tank 4 in which the cathode active material containing ions adsorbed (charged) therein is stored; and a deionized electrolyte storage tank 6.

(32) The energy storage system 100 has technical functions as follows.

(33) While applying a potential difference occurring in the direct current power supply 7, for example, ranging from 0.5 to 2.0 v to the continuous flow-electrode system 1 through a change-over switch 9, the anode active material 12, cathode active material 22 and electrolyte 30 in a slurry phases simultaneously and continuously pass through the continuous flow-electrode system 1.

(34) The anode active material 12 and cathode active material 22 may be mixed with the electrolyte 30 beforehand, then, flow out of the cathode active material feeding tank 2a, the anode active material feeding tank 2b and the electrolyte feeding tank 5, respectively, and feed into the continuous flow-electrode system 1 through the feeding pumps 41, 42 and 43, respectively. In this case, if the used anode active material 12 and cathode active material 22 are the same as each other, it is not necessary to provide both the feeding pumps 2b and 2a, respectively, instead, only a feeding tank 2 is preferably used. The electrolyte in the electrolyte feeding tank 5 is supplied from sea water or sewage through a feeding pump 44 and control valve 45.

(35) As mentioned above, when the anode active material 12, cathode active material 22 and electrolyte 30 flow to pass through the potential-applied continuous flow-electrode system 1 (in the direction of the solid line), the electrode active materials 12 and 22 ion-adsorbed (charged) while passing through the system and the electrolyte 30 free from the ions are stored in the storage tanks 3, 4 and 6, respectively. According to one embodiment, the storage tank is preferably an electrically insulated storage tank.

(36) For a conventional fixed phase active material electrode, further charging is impossible after ions are charged in the electrode active material. Therefore, in order to achieve high-capacity, the electrode must have a large area or several electrodes must be stacked, thus causing a problem of significant increase in device manufacturing or operating costs. However, according to the present invention, it is possible to continuously supply the active material, and store the ion-adsorbed active material in an additionally provided storage tank, therefore, high-capacity may be easily accomplished without enlarging the continuous flow-electrode system 1 or stacking the same. Further, since the continuous flow-electrode system 1 may be further provided if required, scaling-up suitable to various capacities, may be further easily conducted.

(37) Meanwhile, a method of outputting (applying) ion-adsorbed (charged) power to the electrode active material stored in each storage tank may be the reverse of an ion adsorption (charge) process and include: turning off a direct current power supply 7; converting the change-over switch 9 to connect the power supply to a resistor 8 and, simultaneously, to flow the anode active material, cathode active material and electrolyte stored in storage tanks 3, 4 or 6 in reverse order through the continuous flow-electrode system 1 (in the direction of the dotted line, to thus proceed ion desorption (discharge) while passing through the continuous flow-electrode system 1.

(38) In this regard, if it is required to simultaneously and continuously conduct charge and discharge for a long time, two or more continuous flow-electrode systems 1 may be provided to construct a final system. Among these, a part of the systems may function as a charge device while the remainder may function as a discharge device. Herein, with no requirement of additionally providing storage tanks 3 and 4 for the anode active material 12 and cathode active material 22, electrode active materials ion-adsorbed (charged) in the continuous flow-electrode system 1 for discharge may be directly recycled toward the feeding tanks 2b and 2a without passing through the storage tanks described above.

(39) More particularly, the additionally installed continuous flow-electrode system 1 for discharge may include a separation layer having an ion conductive property or use a micro-capsulated electrode material, so as to accomplish prevention of contamination of the electrode material, and quick desorption of stored ions and concentration of the electrolyte by polarity reversal.

(40) The energy storage system 100 according to the present invention may be applied to capacitive deionization type water treatment techniques. For instance, when sea water or industrial wastewater flows into the electrolyte feeding tank 5 and passes through a continuous flow-electrode system 1 in which a potential difference occurs, the water is desalted (deionized) and stored in the electrolyte storage tank 6, thereby enabling desalination of sea water and purification of industrial wastewater.

(41) Accordingly, compared to existing evaporation or RO methods, water treatment may be possible with very low energy costs. High-capacity of water treatment may be achieved.

EXAMPLES

(42) Hereinafter, the present invention will be described in detail by means of examples. However, the following examples are given for more concretely describing the present invention and may not be construed as a limitation of the scope of the present invention.

Example 1

Fluidized Deionization Properties of Activated Carbon Powder Slurry from NaCl Electrolyte

(43) A unit cell (a continuous flow-electrode system) having a microfine flow channel structure, wherein a cation-exchange membrane (SO.sub.3.sup.), an anion-exchange membrane (R.sub.3N.sup.+) and a spacer are isolated between rectangular cathode and anode collectors (SUS316, 9552 mm, a contact area of 22.4 cm.sup.2), has been fabricated. As shown in Table 2, an aqueous NaCl electrolyte with an electrical conductivity (concentration) ranging from 1,030 s to 11,000 s passed through the unit cell at a flow rate of 3 to 5 cc/min using a micro-metering pump (Japan Fine Chemicals Co. Ltd., Minichemi Pump).

(44) At the same time, a micro-pulverized electrode active material having a mean particle size of about 95 nm with fine pore properties shown in Table 1, that is, activated carbon powder was mixed with the same electrolyte at concentrations in Table 2, respectively. Then, while passing the mixture through an electrode material part of each of a cathode flow channel and an anode flow channel in the unit cell at a slurry phase flow rate of about 20 to 25 cc/min, a DC potential difference of about 1.2 to 1.5 v was applied to terminals of both of a cathode and an anode. In the present example, the slurry phase electrode active material which was ion-adsorbed (charged) while passing through two collectors, was not further stored but recycled toward a feeding and storage container and, at the same time, subjected to measurement of current variation of a collector and concentration (electrical conductivity) of the electrolyte at an interval of about 30 minutes. Results of the measurement are shown in Table 2.

(45) TABLE-US-00001 TABLE 1 BET Volume of specific Mean diameter Overall volume microfine Mean surface area of fine pores of fine pores pores particle size (m.sup.2/g) () (cc/g) (cc/g) (nm) 3.263 21 1.71 1.1 95

(46) TABLE-US-00002 TABLE 2 Concentration of electrolyte Concentration of Applied Measured Feed active material voltage current solution permeate Completion (V) (mA) (s) (s) Initial (s) (s) 1.5 30 1,030 643 135 324 1.5 50 3,290 2,230 324 887 1.2 90 11,000 7,700 887 2,762

(47) According to measured results shown in Table 2, the existing fixed phase electrode exhibited that a current flow was sharply decreased while the electrode active material was saturated by adsorbed ion (charged) over time (for example, Korean Patent Laid-Open No. 2002-0076629). On the other hand, the continuous flow-electrode of the present invention showed a constant current flow if the concentration of the electrolyte is constantly maintained. From the fact that a concentration of the recycled slurry phase electrode active material was increased when the concentration (electrical conductivity) of the electrolyte penetrated through the collector was decreased by about 30 to 40% depending upon a concentration of a given feed solution (electrolyte), it was identified that electrolyte ions are possibly adsorbed and stored by the continuous flow-electrode material of the present invention. Accordingly, the present invention easily solved problems of existing fixed phase electrode systems which involved limitations in the coating extent of an electrode material in power storage and CDI desalination technologies, whereby high equipment costs and operation costs due to high-capacity may be remarkably improved.

DESCRIPTION OF REFERENCE NUMERALS IN DRAWINGS

(48) 1, 60: continuous flow-electrode system, 2: active material feeding tank 3: anion storage tank, 4: cation storage tank 5: electrolyte feeding tank, 6: electrolyte storage tank 7: power supply, 8: resistor 9: change-over switch, 41, 42, 43, 44: feeding pump 10: anode, 11: anode collector 12: anode active material, 13: anode separation layer 14: anode flow channel, 20: cathode 21: cathode collector, 22: cathode active material 23: cathode separation layer, 24: cathode flow channel 30: electrolyte, 34: insulating spacer 50: capsule membrane (ionic membrane)

CONCLUSION

(49) All of the various embodiments or options described herein can be combined in any and all variations. While the invention has been particularly shown and described with reference to some embodiments thereof, it will be understood by those skilled in the art that they have been presented by way of example only, and not limitation, and various changes in form and details can be made therein without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

(50) All documents cited herein, including journal articles or abstracts, published or corresponding U.S. or foreign patent applications, issued or foreign patents, or any other documents, are each entirely incorporated by reference herein, including all data, tables, figures, and text presented in the cited documents.