KR101637008B1 - Carbon felt with the differened in the active site and redox flow secondary battery comprises a the same - Google Patents

Abstract

The present invention relates to a carbon felt having a difference in active points and a redox flow secondary cell comprising the carbon felt, wherein the carbon felt having a plurality of layers has different surface areas, porosity, surface treatment processes, And it is possible to solve the current density nonuniformity and the local resistance phenomenon according to the concentration nonuniformity in the electrode and to reduce the acceleration of the partial deterioration of the electrode as well as increase the voltage efficiency, the energy efficiency and the coulombic efficiency.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a carbon felt having different active points and a redox flow secondary battery comprising the carbon felt.

The present invention relates to a redox flow secondary cell, particularly to a carbon felt having a difference in active points from one layer to another and a redox flow secondary battery comprising the same.

Existing power generation systems, such as thermal power generation using nuclear fossil fuels and large-scale greenhouse gas and environmental pollution problems, and nuclear power generation, which have the problems of stability of the facility itself or waste disposal problems, have various limitations and are more environmentally friendly and highly efficient Research on the development of energy and the development of power supply system using it has been greatly increased.

Particularly, the power storage technology can utilize the renewable energy which is greatly influenced by the external conditions and can be utilized more widely, and the efficiency of the power utilization can be further improved. The interest and R & D of the research has been increasing.

The redox flow secondary cell is an oxidation / reduction cell that can convert the chemical energy of the active material directly into electric energy. It stores renewable energy with high output fluctuation depending on the external environment such as sunlight and wind power, It is an energy storage system that can be converted. Specifically, in the redox flow secondary battery, the electrolytic solution containing the active material causing the oxidation / reduction reaction is circulated between the opposite electrode and the storage tank, and charging / discharging proceeds.

The redox flow secondary battery generally includes a tank in which an active material is stored, a pump for circulating the active material during charging and discharging, a cell frame, a current collector, and a unit cell, and the unit cell includes carbon felt as an electrode.

Redox flow secondary batteries have the advantage of stacking multiple electrodes, but as the reaction area increases, a concentration gradient necessarily occurs between the inlet and outlet of the electrolyte on a single electrode surface, thereby increasing the concentration overvoltage , Local resistance in the electrode due to non-uniformity of the current density occurs.

This is a phenomenon in which the electrode area becomes larger as the surface area becomes larger, and it causes difficulties in long-term operation due to electrode deterioration due to overvoltage at a specific site.

In addition, voltage and current non-uniformity due to unevenness of concentration of reactants in the laminate can accelerate the partial deterioration of the electrode upon application of a high current and cause decrease in efficiency.

Korean Patent Publication No. 10-2011-0072284 (June 29, 2011)

It is therefore an object of the present invention to provide a carbon felt having a difference in active points for improving the efficiency of the redox flow secondary battery by solving the current density nonuniformity and the local resistance phenomenon according to the concentration non-uniformity in the electrode, And a secondary battery comprising the secondary battery.

In order to achieve the above-mentioned object, the carbon felt of the present invention is porous carbon felt having a plurality of layers, and the active points of the carbon felt are different from each other.

The carbon felt having a difference in active points according to the present invention may be characterized in that the active points of the layer located at the outlet of the electrolyte at the inlet of the electrolyte are increased.

The carbon felt having different active points according to the present invention may be characterized in that the surface area, the porosity, the surface treatment process, or the amount of introduced catalyst are different for each layer.

The carbon felt having a difference in active points according to the present invention may be characterized in that the surface area increases and the porosity decreases as the layer located at the outlet of the electrolyte solution inlet portion.

The carbon felt having a difference in active sites according to the present invention may be characterized in that the catalyst is platinum, iridium, lead, gold, bisuptite, manganese, cobalt, nickel, aluminum or zinc.

The carbon felt having a difference in active sites according to the present invention may be characterized in that the amount of catalyst introduced increases with the layer located at the outlet of the electrolyte inlet.

A redox flow secondary battery according to the present invention comprises: a pair of cell frames arranged to face each other; A pair of current collectors respectively disposed on the inner side surfaces of the pair of cell frames; A unit cell disposed between a pair of collectors; The unit cell is composed of a plurality of layers and includes a carbon felt having a difference in active points from one layer to another.

The redox flow secondary battery according to the present invention may be characterized in that the carbon felt has different porosity, surface treatment process or catalyst introduction amount per layer.

According to the present invention, there is a difference in active points between the electrodes in the electrode layer, so that current density nonuniformity and local resistance phenomenon due to concentration nonuniformity in the electrode can be solved, acceleration of partial deterioration of the electrode can be reduced, The efficiency is improved.

FIGS. 1 and 2 are views for explaining a redox flow secondary battery including a carbon felt having a difference in active points according to the present invention. FIG.
3 is a view for explaining a carbon felt having a difference in active points according to the present invention.
4 to 6 are views for explaining a method of manufacturing carbon felt having different active points according to the present invention.
7 is a graph illustrating the coulomb efficiency according to an embodiment of the present invention.

In the following description, only parts necessary for understanding the embodiments of the present invention will be described, and the description of other parts will be omitted so as not to obscure the gist of the present invention.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary meanings and the inventor is not limited to the meaning of the terms in order to describe his invention in the best way. It should be interpreted as meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely preferred embodiments of the present invention, and are not intended to represent all of the technical ideas of the present invention, so that various equivalents And variations are possible.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

A redox flow secondary battery (hereinafter, referred to as a 'secondary battery') according to the present invention will be described. The secondary battery is a battery in which the active material of the electrode is composed of a positive electrode electrolyte and a negative electrode electrolyte different in oxidation state and in a solution state in which the active material is not a solid. When the system is divided into different types, a vanadium redox battery, a polysulfide bromide Polysulfide bromide redox battery, Zinc bromine redox battery, and the like.

 1 and 2 are a perspective view and a cross-sectional view of a redox flow secondary cell comprising a carbon felt having different active points according to the present invention.

Referring to FIGS. 1 and 2, the secondary battery includes a unit cell 100 having a plate-like multi-layer structure, a pair of current collectors 40 joined to both outer surfaces of the unit cell 100 and made of a plate, And a cell frame 50 joined to the outer surface of the current collector 40 and formed in a plate shape.

The unit cell 100 includes a plate-like ion exchange membrane 10, an electrode 20, and a bipolar plate 30 (hereinafter, referred to as a plate). The unit cell 100 includes a pair of electrodes 20 on both sides of the ion exchange membrane 10 facing each other with a pair of cathodes and anodes facing each other with the ion exchange membrane 10 as a center, And the plate 30 is joined to the outer surface. That is, the electrodes 20 of the positive and negative electrodes are attached to the inner surface of each plate 30.

The secondary battery according to the present invention further comprises the positive electrode tank 60 and the negative electrode tank 70, the pumps 61 and 71, the inlets 63 and 73 and the outlets 65 and 75.

The positive electrode tank (60) and the negative electrode tank (70) store the electrolyte so that it can be drawn out if necessary. The positive electrode tank 60 stores a positive electrode electrolyte for providing the positive electrode 20 and the negative electrode tank 70 stores a negative electrode electrolyte for providing the negative electrode 20.

The positive electrode tank 60 and the negative electrode tank 70 are disposed on the left and right of the unit cell 100 corresponding to the positive electrode and the negative electrode in the electrode 20 of the unit cell 100. The positive electrode tank 60 and the negative electrode tank 70 are connected to the cell frame 60 through the inflow ports 63 and 73 and the outflow ports 65 and 75. The inlet ports 63 and 73 are the passages through which the electrolytes of the anode tank 60 and the cathode tank 70 enter the unit cell 100 and the outlets 65 and 75 are the passages through which the electrolyte returns.

Pumps 61 and 71 are for supplying the electrolyte from the anode tank 60 and the cathode tank 70 to the unit cell 100. The anode tank 60 and the cathode tank 70 70 and the inlets 63, 73, respectively. That is, the electrolyte drawn out from the positive electrode tank 60 and the negative electrode tank 70 is supplied to the pumps 61 and 71, the inflow ports 63 and 73, the respective cell frames 50 and the respective current collectors 40 And then stored in the anode tank 60 and the cathode tank 70 in the reverse order.

The electrode 20 according to the present invention is a carbon felt having a mesh-like porous structure and having a difference in active points from layer to layer.

According to the present invention, such a carbon felt may have a higher active point at the inlet of the electrolyte than at the outlet of the electrolyte.

According to the present invention, there is a difference in the active points of the carbon felt due to differences in surface area, porosity, surface treatment method, or amount of introduced catalyst.

In the case where there is a difference in the active points in the carbon felt in the electrode as in the present invention, non-uniformity of reaction, non-uniformity in current density and increase in local resistance are inevitably caused by the concentration gradient between the inlet and outlet of the electrolyte solution on the electrode surface The energy efficiency of the secondary battery can be increased.

3 is a view showing a carbon felt 200 having a difference in active points according to the present invention.

Referring to FIG. 3, the carbon felt 200 includes a first layer 110, a second layer 120, and a third layer 130. It is to be understood that the present invention is not limited thereto but may include two or more layers.

The active layer may be raised from the second layer 120 to the third layer 130, where the active layer is relatively low and the first layer 110 located close to the inlet of the electrolyte is located relatively close to the outlet of the electrolyte.

The carbon felt 200 having a difference in active points according to the present invention can differentiate the active points by making the surface treatment process different for each layer.

The surface treatment process refers to a process in which a carbon felt having no surface treatment is used as an electrode of a secondary battery, and the energy efficiency is very low due to a very high affinity with an electrolyte solution to increase the energy efficiency of the battery.

The surface treatment process according to the present invention is characterized in that a surface treatment by heat treatment, a surface treatment using a metal or oxide-based catalyst, a surface treatment using a corona discharge, a surface treatment using an ultrasonic wave after carrying an oxidizing agent, And a process of treating the surface using ultrasonic waves.

The carbon felt 200 having a difference in active sites according to the present invention can differentiate the active points by making the amount of introduced catalyst different for each layer.

The introduction of the catalyst according to the present invention means introduction of the catalyst to suppress the side reaction in the cathode to increase the energy efficiency of the secondary battery.

The catalyst according to the present invention may be, but is not limited to, platinum, iridium, lead, gold, bisulfite, manganese, cobalt, nickel, aluminum or zinc.

The amount of catalyst introduced according to the present invention may increase as the layer located at the outlet of the electrolyte at the inlet of the electrolyte.

Therefore, the layer located at the outlet of the electrolyte having a relatively high catalyst loading amount has a higher active point than the layer located at the inlet of the electrolyte having a relatively small catalyst loading amount.

In the carbon felt 200 having a difference in active points according to the present invention, the surface area increases and the porosity of the carbon felt 200 increases as the layer located at the outlet of the electrolyte in the electrolyte inlet portion.

4 is a flow chart for explaining an example of a method of manufacturing carbon felt according to the present invention.

Referring to FIG. 4, a method of manufacturing a carbon felt having different active points according to the present invention includes preparing a first base material, which is porous carbon felt (S10), preparing a second base material (S20) , And attaching the first and second base metals (S30).

Here, the first and second base materials are carbon felt materials as the base material of each layer forming the carbon felt.

The step of preparing the first base material may or may not include the step of compressing the first base material by applying a first pressure.

Preparing the second base material may include compressing the second base material by applying a second pressure higher than the first pressure to the second base material.

The prepared first and second base metals are attached to produce a carbon felt 200 having a difference in active points.

5 is a flow chart for explaining another example of a method of manufacturing a carbon felt according to the present invention.

Referring to FIG. 5, a method of manufacturing a carbon felt 200 having a difference in active points according to the present invention includes a step (S40) of attaching first and second base materials, a step of compressing the attached first and second base materials (S50).

6 is a view for explaining a method of manufacturing a carbon felt according to the present invention.

Referring to FIG. 6, a method of manufacturing the carbon felt 240 having a difference in active points according to the present invention will be described in detail.

Before the compression, the carbon felt 230 is prepared by attaching a first base material 111 and a second base material 121 having a relatively higher height than the first base material 111. As the first and second base metals 111 and 121, a carbon felt base metal having the same or similar porosity may be used.

The attached first base material 111 and the second base material 121 are used as the base material of the carbon felt forming the positive electrode and the negative electrode. After the first and second base materials 111 and 121 attached to both sides of the ion exchange membrane are positioned and pressed, the unit cell is manufactured.

At this time, the first and second base materials 111 and 121 are pressed to form the carbon felt 240 which forms the anode and the cathode by the pressure applied during the process of manufacturing the unit cell.

The carbon felt 240 after the compression is composed of the first layer 110 and the second layer 120. Since the compression ratio of the second layer 120 is higher than that of the first layer 110, Is low.

Example 1 and Comparative Example 1 were conducted to determine the coulomb efficiency of the redox flow secondary battery including the carbon felt having different active points according to the present invention.

[Example 1]

A first base material of carbon felt having a size of 3 mm * 50 mm * 50 mm and a second base material of 6 mm * 50 mm * 50 mm were prepared. One side of the prepared first base material and the second base material were attached. This was repeated to prepare two carbon felt before being compressed. A pair was prepared so as to face each other before compression, and an ion exchange membrane was disposed therebetween. A pair of plates was arranged on the opposite surface on which the ion exchange membrane was disposed. The unit cell was constituted by squeezing it. The first base material is compressed to a compression ratio of 33% to form a first layer, the second base material is compressed to a compression ratio of 66% to form a second layer, and the carbonaceous material including the first and second layers .

[Comparative Example 1]

A pair of carbon felt having a size of 3 mm * 50 mm * 100 mm was prepared. A pair of base materials were disposed so as to face each other, and an ion exchange membrane was disposed therebetween. A pair of plates was arranged on the opposite surface on which the ion exchange membrane was disposed. The unit cell was constituted by squeezing it. A pair of base materials were compressed to a compression ratio of 33% and made into a positive electrode and a negative electrode.

7 is a graph showing the coulombic efficiency of the redox flow secondary battery including the unit cells according to Example 1 and Comparative Example 1. FIG.

Referring to FIG. 7, when the charge / discharge cycle was performed once to five times in the region of 72.73 mA cm ^-2 , the secondary cell including the unit cell of Example 1 had a 1 ≪ / RTI > to 2% Coulomb efficiency. This is because the secondary battery including the unit cell of Example 1 contains carbon felt having different active points.

The secondary battery including the unit cell of Example 1 had a Coulomb efficiency of 3 to 4% higher than that of the secondary battery including the unit cell of Comparative Example 1 when the charging and discharging cycles of 6 to 10 were performed in the region of 145.8 mA cm ^-2 As shown in FIG. This is because the secondary battery including the unit cell of Example 1 contains carbon felt having different active points.

In addition, since the secondary battery according to the present invention includes carbon felt having a difference in active points, it is possible to solve the current density non-uniformity and the local resistance phenomenon according to the concentration non-uniformity in the electrode through the increase of active points in the low concentration region, Acceleration can be reduced.

In addition, the secondary battery according to the present invention can improve the voltage efficiency and the energy efficiency by including the carbon felt having a difference in active points from layer to layer.

10.. . Ion exchange membranes 60,70. . .Pump
20.. Electrodes 63, 73. . . Inlet
30. . Bipolar plate 65, 75. . Outlet
40.. 100 whole house. Unit cell
50.. Cell frame 110.. . The first layer
111.. First Base Material 121.. Secondary base material
120.. . The second layer 130.. Third Floor
200. Carbon felt 230 with difference in active points. Carbon felt before compression
240. Carbon felt after compression

Claims (8)

The active point of the layer located at the outlet of the electrolyte at the electrolyte inlet is higher than that of the layer located at the outlet of the electrolyte,
Wherein the plurality of layers has an active point higher by increasing the amount of the catalyst introduced into the layer located at the electrolyte outlet in the electrolyte inlet. delete delete The method according to claim 1,
Characterized in that the plurality of layers have increased surface area and lower porosity as the layer located at the outlet of the electrolyte in the electrolyte inlet portion has a different active point. The method according to claim 1,
Characterized in that the catalyst is platinum, iridium, lead, gold, bispite, manganese, cobalt, nickel, aluminum or zinc. delete A pair of cell frames arranged to face each other;
A pair of current collectors respectively disposed on inner surfaces of the pair of cell frames; And
A unit cell including a carbon felt disposed between the pair of current collectors, the carbon felt having a plurality of layers and having active points higher at a layer positioned at an electrolyte outlet at an electrolyte inlet; / RTI >
Wherein the plurality of layers of the carbon felt have a higher active point due to an increase in the amount of the introduced catalyst in the layer located at the outlet of the electrolyte in the electrolyte inlet. 8. The method of claim 7,
Wherein the active point has a higher active point at a layer located at an electrolyte outlet at an electrolyte inlet, the carbon point being different from the active point.

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