KR20200055274A - Bipolar plate and unit cell for redox flow cell battery and redox flow battery comprising the same - Google Patents

Abstract

The present invention relates to a bipolar plate for a redox flow battery, a unit cell including the same, and a redox flow battery. The present invention is a bipolar plate formed with a flow path unit facing an electrode, and a surface bonded with an edge ion exchange membrane of the bipolar plate is formed higher than an upper surface of a flow path forming partition wall of the flow path unit to form an electrode receiving groove.

Description

Bipolar plate, unit cell for redox flow battery including the same, and redox flow battery {Bipolar plate and unit cell for redox flow cell battery and redox flow battery comprising the same}

The present invention relates to a bipolar plate, a unit cell for a redox flow battery comprising the same, and a redox flow battery.

The redox flow battery is a system in which active materials in an electrolyte are oxidized, reduced, and charged and discharged, unlike conventional secondary batteries, and is an electrochemical power storage device that stores chemical energy of the electrolyte directly as electrical energy. Such a battery has the advantage of being easy for large-capacity power storage, having high energy density and efficiency, and long life and safety. In addition, the battery does not require frequent replacement, has low maintenance cost, operates at room temperature, and has the advantage of being capable of designing various capacities and outputs, and has been spotlighted as a next-generation mass storage device.

The basic structure of the redox flow battery includes a stack including a bipolar plate / electrode / ion exchange membrane / electrode / bipolar plate structure, an electrolyte tank in which active materials having different oxidation states are stored, and a pump for circulating it.

The actual electrochemical reaction takes place in a stack, and works by circulating the electrolyte continuously inside the stack using a pump. Redox pairs used as active materials in the electrolyte include V / V, Zn / Br, Fe / Cr, and Zn / air, among which V / V and Zn / Br redox pairs are most widely used.

The electrochemical reaction is determined by the interaction between the electrode and the electrolyte flowing along the bipolar plate in the stack.

Figure 1 is a cross-sectional view showing the contact between the bipolar plate and the electrode according to the prior art, the bipolar plate 11 / electrode 12 / ion exchange membrane 13 / electrode 14 / bipolar plate 15 is stacked from above It has a structure. Such a structure is a method in which an electrolyte is flowed directly into the bipolar plates 11 and 15, and has an advantage of a simple structure. However, when charging / discharging under high power conditions or when increasing the size of the battery, a high differential pressure is generated between the electrolyte inlet and outlet as the electrolyte is accompanied by a high flow rate, resulting in a problem of enormous energy loss.

In an attempt to solve the above problem, a structure in which a flow path through which an electrolyte can flow is formed in a bipolar plate has been proposed.

U.S. Patent Publication No. 2012-0244395 proposes the configuration of a bipolar plate with an interdigitated type (or pod) flow path.

Figure 2 is a cross-sectional view showing the contact between the bipolar plate and the electrode proposed in U.S. Patent Publication No. 2012-0244395, from above, bipolar plate 21 / electrode 22 / ion exchange membrane 23 / electrode 24 / bipolar plate (25) has a stacked structure, and has a structure in which flow paths (27, 29) are formed on each of the bipolar plates (21, 25). When using a bipolar plate of this structure, the differential pressure between the inlet and outlet applied to the battery module was reduced to some extent.

However, referring to FIG. 2, there is a problem in that the contact area between the electrode and the electrolyte is reduced due to the flow path compared to FIG. 1. Due to this, the electrochemical reaction for generating electricity does not sufficiently occur, and accordingly, a problem occurs in that the charge / discharge capacity and speed of the battery are reduced.

Moreover, even if it has a flow path structure for reducing the internal differential pressure, there are certain limitations in stably controlling the flow rate of the electrolyte in all ranges, and the problem that the reaction time is not secured due to the short residence time in the flow path is also Occurred.

In addition, the conventional redox flow battery used an O-ring or a cotton gasket to prevent electrolyte leakage when stacking, but the assembly process was difficult and the surface pressure distribution was uneven and the electrolyte leaked. Showed a limit in preventing it.

Accordingly, there is an increasing demand for a redox flow battery capable of improving airtightness to prevent leakage of the electrolyte solution and improving assembly / discharge capacity and efficiency, while improving assembly convenience.

U.S. Patent Publication No. 2012-0244395

The present inventors designed a bipolar plate of a new structure that can reduce the loss of pressure, increase the gas tightness of the stack to prevent leakage of the electrolyte, facilitate the assembly of the stack, and prevent the deformation of the stack. As a result of applying to the battery, it was confirmed that the energy efficiency increased.

Accordingly, the present invention aims to provide a bipolar plate with a new structure.

In addition, an object of the present invention is to provide a unit cell for a redox flow battery including the bipolar plate.

In addition, an object of the present invention is to provide a redox flow battery comprising a plurality of the unit cells.

In order to achieve the above object,

The present invention is a bipolar plate formed with a flow path portion facing the electrode,

An edge ion exchange membrane bonding surface of the bipolar plate is formed higher than an upper surface of the flow path forming partition wall of the flow path portion to form an electrode receiving groove, thereby providing a bipolar plate for a redox flow battery.

In addition, the present invention is an ion exchange membrane;

Electrode layers disposed on both sides of the ion exchange membrane; And

Includes; bipolar plates respectively disposed on one side of the electrode layer,

The bipolar plate provides a unit cell for a redox flow battery, which is the bipolar plate of the present invention.

In addition, the present invention is a battery module formed by arranging and electrically connecting unit modules including unit stacks for generating electric currents on side surfaces of each other;

An electrolyte tank for supplying an electrolyte to the battery module and storing the electrolyte flowing out of the module; And

Includes; electrolyte pump for circulating the electrolyte between the module and the electrolyte tank;

The unit stack provides a redox flow battery including a plurality of redox flow battery unit cells of the present invention.

The bipolar plate of the present invention can reduce the loss of pressure, increase the flow rate of the electrolyte, increase the airtightness of the stack to prevent leakage of the electrolyte, facilitate assembly of the stack, and prevent deformation of the stack. It has an effect.

In addition, the redox flow battery including the bipolar plate of the present invention has an excellent energy efficiency effect.

1 is a cross-sectional view of a unit cell for a redox flow battery according to the prior art.
2 is a cross-sectional view of a unit cell for a redox flow battery proposed in US Patent Publication No. 2012-0244395.
3 is a schematic diagram of the structure of the redox flow battery of the present invention.
4 is a three-dimensional perspective view of the unit stack of the present invention.
5 is a front view of the bipolar plate of the present invention.
6 is a view showing the electrode receiving groove of the bipolar plate of the present invention.
7 is a cross-sectional view of a unit cell for a redox flow battery of Example 1. FIG.
8 is a cross-sectional view of a redox flow battery unit cell of Comparative Example 1.
9 is a cross-sectional view of a redox flow battery unit cell of Comparative Example 2.
10 is a graph showing the energy efficiency of Experimental Example 1.

Hereinafter, the present invention will be described in more detail.

In the drawings, parts not related to the description are omitted in order to clearly describe the present invention, and similar reference numerals are used for similar parts throughout the specification. In addition, the size and relative size of the components indicated in the drawings are independent of the actual scale, and may be reduced or exaggerated for clarity of explanation.

In the drawings, the thickness of the layers and regions may be exaggerated or omitted for clarity. Throughout the specification, the same reference numbers refer to the same components.

The terms or words used in the present specification and claims should not be interpreted as being limited to ordinary or lexical meanings, and the inventor can appropriately define the concept of terms in order to best describe his or her invention. Based on the principle that it should be interpreted as meanings and concepts consistent with the technical spirit of the present invention.

3 is a schematic view showing a redox flow battery according to an embodiment of the present invention, and FIG. 4 is a three-dimensional perspective view showing a unit stack.

Referring to FIG. 3, the redox flow battery 1000 is a battery module formed by arranging unit modules 101, 102, 103, and 104 including unit stacks generating electric current on each side and electrically connecting them ( 100); An electrolyte tank (202, 204) for supplying an electrolyte to the battery module (100) and for storing the electrolyte flowing out of the battery module (100); And electrolyte pumps 302 and 304 for circulating the electrolyte between the battery module 100 and the electrolyte tanks 202 and 204.

At this time, the unit stack is formed by stacking a plurality of unit cells 130. For convenience, FIG. 4 illustrates a unit stack formed by stacking one unit cell 130.

Referring to FIG. 4, the ion exchange membrane 123 is disposed in the center of the unit cell 130, and the electrodes 120 and 121 and the bipolar plates 118 and 119 are symmetrically disposed on both sides of the ion exchange membrane. .

The unit cell 130 has a stacked structure of one or more plural pieces, and the current collecting plates 115 and 117 and the end plates 111 and 113 are stacked so as to contact the bipolar plates 118 and 119.

Each of the above structures is provided with a unit cell 130 by punching each one side and bonding to each other using a connecting member (for example, a bolt / nut) through a through hole, and a plurality of unit cells 130 are arranged. After that, the unit stack is formed through electrical connection.

Spacers (not shown) for flow or bonding of the electrolyte between the ion exchange membrane 123, the electrodes 120, 121, the bipolar plates 118, 119, the current collecting plates 115, 117, and the end plates 111, 113 ) May be interposed therebetween, and is preferably disposed between the ion exchange membrane 123 and the electrodes 120 and 121 as an example.

The ion exchange membrane 123 has a structure of a plate-shaped cell frame and an ion exchange membrane mounted in the center thereof.

3, the plurality of unit cells 130 are connected in series or in parallel as shown in FIG. 3, and are configured to generate current through circulation of the electrolyte. The unit stack is electrically connected to other neighboring unit stacks through a bus bar (not shown). The unit modules 101, 102, 103, 104 and the battery module 100 discharge current generated inside the unit stacks or are connected to an external power source.

In the present invention, the energy efficiency of the redox flow battery 1000 can be improved by changing the configuration of the bipolar plates 118 and 119 constituting the unit cell 130.

Therefore, the present invention is a bipolar plate formed with a flow path portion facing the electrode,

The edge ion exchange membrane bonding surface of the bipolar plate relates to a bipolar plate for a redox flow battery, which is formed higher than the upper surface of the flow path forming partition wall of the flow path portion to form an electrode receiving groove.

The bipolar plates 118 and 119 in contact with the electrodes 120 and 121 are supplied with an electrolyte from the electrolyte tanks 202 and 204 for electrochemical reaction, and supply them to the electrodes 120 and 121 at a uniform pressure and amount. .

5 is a front view showing the bipolar plate of the present invention.

The flow path portion F of the present invention may include a flow path integrally formed on the bipolar plates 118 and 119, or may be formed by a separate flow path forming separation plate 153 accommodated in the bipolar plates 118 and 119.

The flow path portion F includes a flow path formed to allow the electrolyte to move, and the flow path preferably has an interdigitated flow field (IDFF) pattern.

The interlocking pattern has a structure in which flow paths in a form of interlocking with each other are continuously arranged, and each flow path has a structure in which one surface is closed. In the case of the interlocking flow path structure, not only the electrolyte flows along the flow path, but also flows through the flow path to further increase the chance of electrode reaction, thereby increasing the charge / discharge capacity of the redox flow battery.

The flow path is formed through the flow path forming partition wall 154, wherein the width and thickness of the partition wall 154 can be appropriately adjusted according to the size of the bipolar plate. In general, the spacing between the partition walls 154 is defined as the channel width, and the thickness of the partition walls 154 is defined as the depth of the channel.

The cross-section of the partition wall 154 may be various shapes such as a rectangle, a square, a triangle, a trench structure, a hemispherical shape, and a polygonal shape, and usually has a rectangular shape for the flow of the electrolyte.

For example, when manufacturing a bipolar plate having an area of 5 to 10 cm ² , the width of the partition wall 154 is 3 to 8 mm, the thickness is 1 to 3.5 mm, the channel width is 3 to 8 mm, and the channel channel depth is 1 to 3.5. It can be mm.

In the bipolar plate, which does not include a conventional flow path, a relatively high stack differential pressure is generated, so that even when the electrolyte is supplied at the same flow rate, power loss due to pump driving is relatively large. However, in the present invention, as the flow path of the interlocking pattern is formed, the stack differential pressure can be reduced to supply a high flow rate even under the same pump driving power condition, thereby improving the efficiency of the stack, and the entire system including the pump and the stack. It can improve the efficiency. That is, since the pump-driven electric power is consumed less when supplying the electrolyte at the same flow rate, the efficiency of the system can be increased.

In addition, the bipolar plate (118, 119) may be used a conductive or non-conductive material, in the present invention is not particularly limited. For the conductive material, the surface of the cell frame may be coated with a carbon material such as metal, graphite, or a conductive polymer. For the non-conductive material, ethylene-tetrafluoroethylene (ETFE), polytetrafluoroethylene (PTFE), perfluoroalkoxy (FFA), or fluorinated FEP It can be used by coating fluorine resins such as ethyleneepropylene polymer), ECTFE (Ethylene ChloroTriFluoroEthylene), and PVDF (Polyvinylidene fluoride).

The bipolar plate has an inlet 161 for introducing the electrolyte to supply the electrolyte to the electrode on one side, an outlet 162 for discharging the electrolyte at one side, between the inlet 161 and the flow path portion F Located in the supply passage 171 for the uniform distribution of the electrolyte and the discharge port 162 and the discharge passage 172 for the uniform distribution of the electrolyte is located between the flow path portion (F).

Connection members 181, 182, 183, and 184 are disposed at one end of the bipolar plates 118, 119, and two bipolar plates 118, 119 symmetrically left and right based on the ion exchange membrane when forming a unit cell for a redox flow battery. Can be physically joined.

In addition, the supply flow path 171 and the discharge flow path 172 have various forms to distribute or supply or discharge the electrolyte flow rate evenly, and for example, may have a distribution flow path form having a plurality of branches.

The bipolar plates 118 and 119 include one or more band-shaped gaskets to prevent leakage of the electrolyte, and the gaskets are located on the ion exchange membrane bonding surface 152.

In the past, gaskets or O-rings in the form of cotton have been used, but when uneven clamping pressure is applied to the stack, deformation or distortion occurs, causing deformation of the entire stack, and low adhesion in the stack, resulting in leakage of electrolyte. It can not be effectively prevented, there is a problem that the stack assembly is not easy. More specifically, the gasket in the form of a surface is thin and wide, so it is difficult to handle due to the phenomenon of curling or folding, and thus it is not easy to assemble it according to the shape of the bipolar plates 118 and 119. In addition, when assembling the bipolar plate 119 upside down when assembling the stack, there is a problem that fixing is difficult. Since the O-ring has a narrow contact surface, it is difficult to assemble it to maintain airtightness due to low surface pressure uniformity when assembling a large area stack.

 However, the band-shaped gasket of the present invention can solve the problems caused by the use of the cotton gasket and O-ring. That is, it is easy to handle when compared with a cotton gasket, and can be easily attached to the ion exchange membrane bonding surfaces 152 of the bipolar plates 118 and 119, thereby providing excellent stack assembly convenience. In addition, when compared with the O-ring, the contact area is large and can be flexibly applied to a surface with a low flatness, thereby increasing the adhesion within the stack, thereby improving airtightness, thereby preventing leakage of the electrolyte.

In addition, the edge ion exchange membrane bonding surface 152 of the bipolar plate of the present invention is formed higher than the upper surface of the flow path forming partition wall 154 of the flow path portion F to form an electrode receiving groove (not shown).

The electrode receiving groove is formed to insert the electrodes 120 and 121, and the area of the electrode receiving groove is the same as the area of the flow path portion F. Electrodes 120 and 121 may be inserted into the electrode receiving groove. That is, in the unit cell 130 of the present invention, the upper surface of the flow path portion F may be in contact with the electrodes 120 and 121.

When the electrodes 120 and 121 are inserted into the electrode receiving groove, the ion exchange membrane bonding surfaces 152 at the edges of two bipolar plates that are symmetrical to the left and right based on the ion exchange membrane when forming a unit cell for a redox flow battery are physically in close contact without play. It can increase the airtightness of the stack, prevent leakage of the electrolyte, and prevent the deformation of the stack.

In general, when assembling the stack, the position of the bolt that is the connecting member is located at the edge of the stack. Therefore, when a gap between the bipolar plates 118 and 119 is formed, the edge is compressed according to the stack fastening, and the middle part is convex to deform the stack. This can happen. When the deformation occurs as described above, problems such as uneven surface pressure, increased contact resistance, and leakage of electrolyte may occur. The bipolar plates 118 and 119 of the present invention have a structure in which the ion exchange membrane bonding surfaces 152 at the edge of the bipolar plate are in close contact with each other, so that all of the above problems can be solved.

The difference in height between the upper surface of the channel forming partition wall 154 and the ion exchange membrane bonding surface 152 at the edge of the bipolar plate may be 0.5 to 1.5 mm, and preferably 1 to 1.5 mm. If the height difference is less than 0.5 mm, the height is too low to assemble very difficult, and if it exceeds 1.5 mm, the stack thickness increases to increase the volume and weight of the stack, thereby reducing power, reducing energy density, and increasing resistance. Can cause problems.

In addition, the present invention relates to a redox flow battery unit cell, wherein the unit cell

Ion exchange membranes;

Electrode layers disposed on both sides of the ion exchange membrane; And

Includes; bipolar plates respectively disposed on one side of the electrode layer,

The bipolar plate is the bipolar plate of the present invention described above.

The ion exchange membrane 123 is called an ion permeable membrane or separator, and is configured to pass ions in an electrolyte, and generates electricity through electrochemical reactions of electrodes 120 and 121 located on both sides of the electrolyte. At this time, the material, thickness, and each component of the ion exchange membrane are not particularly limited in the present invention, and known ones can be used. The ion exchange membrane 123 has a structure of a plate-shaped cell frame and an ion exchange membrane mounted in the center thereof.

The electrodes 120 and 121 function as an anode and the other as a cathode, depending on the composition of the electrolyte.

As described above, the edge ion exchange membrane bonding surface 152 of the bipolar plate of the present invention is formed higher than the upper surface of the channel forming partition wall 154 of the channel portion F to form an electrode receiving groove. The electrodes 120 and 121 are inserted into the formed electrode receiving groove.

The thickness of the electrodes 120 and 121 before being inserted into the electrode receiving groove is thicker than the depth of the electrode receiving groove of the bipolar plates 118 and 119, and when assembling the unit cell 130, the bipolar plates 118 and 119 are combined. It can be inserted by compression.

Due to the flow path portion F formed in the bipolar plates 118 and 119, the thickness of the bipolar plate increases, thereby increasing the thickness of the stack, thereby increasing the volume and weight of the stack, thereby reducing power and energy density. The problem of reduction and increased resistance may occur. Therefore, in the present invention, a thinner electrode layer than the electrode layer of a conventional redox flow battery is used, and it is compressed and inserted into an electrode receiving groove, thereby preventing problems due to an increase in thickness.

The thickness of the electrodes 120 and 121 before being inserted into the electrode receiving groove may be 1 to 2 mm. In addition, the height of the electrode receiving groove may be 0.5 to 1.5mm. Therefore, the electrode may be compressed by the height of the electrode receiving groove and inserted into the electrode receiving groove.

In order for the electrodes 120 and 121 to be inserted by being compressed by the height of the electrode receiving groove, the electrodes 120 and 121 must use a conductive material that is easy to adjust the compression ratio, and may preferably be carbon felt.

In addition, the electrodes 120 and 121 of the present invention are in the electrode receiving groove formed by the height difference between the upper surface of the flow path forming partition wall 154 of the flow path portion F and the ion exchange membrane bonding surface 152 at the edge of the bipolar plate. Since it is inserted, the areas of the electrodes 120 and 121 are the same as the areas of the flow path part F, and it is possible to react sufficiently with the electrolyte solution.

As the electrodes 120 and 121 are inserted into the electrode receiving grooves, the edge ion exchange membrane bonding surfaces 152 of each bipolar plate disposed on one side of the electrode may be in close contact without gap. The tightness can increase the airtightness due to the contact structure, thereby preventing leakage of the electrolyte solution and preventing deformation of the stack.

In addition, the present invention relates to a redox flow battery,

A battery module formed by arranging and electrically connecting unit modules including unit stacks for generating currents on side surfaces of each other;

An electrolyte tank for supplying an electrolyte to the battery module and storing the electrolyte flowing out of the module; And

Includes; electrolyte pump for circulating the electrolyte between the module and the electrolyte tank;

The unit stack includes a plurality of unit cells for a redox flow battery of the present invention described above.

Other components constituting the redox flow battery 1000 of the present invention, specifically, various elements for constituting the battery module 100, components such as electrolyte tanks 202 and 204 and electrolyte pumps 302 and 304 Is not particularly limited in the present invention, and follows the contents of the known bar.

The electrolyte solution stored in the electrolyte tanks 202 and 204 is not particularly limited in the present invention, and an electrolyte solution known in the art may be used.

The electrolytic solution includes an active material and a solvent, wherein the active material includes an electrochemically stable redox couple organic material, and the solvent may be an aqueous solvent, an organic solvent, or a mixture thereof.

The electrolyte may be a positive electrode electrolyte for the function of the positive electrode or a negative electrode electrolyte for the function of the negative electrode, and these include an oxidation / reduction pair configuration. That is, in the case of the positive electrode active material, it refers to an oxidation-reduction pair dissolved in a positive electrode electrolyte, and when the oxidation-reduction pair changes to the higher of the two oxidation states, that is, it is charged when oxidation occurs do. In the case of the negative electrode active material, it refers to an oxidation / reduction pair dissolved in a negative electrode electrolyte, and means that it is charged when it is reduced to the lower of two oxidation states of the oxidation / reduction pair, that is, when reduced.

The active material used in the present invention is not particularly limited, and an active material commonly used in the art may be used. For example, V, Fe, Cr, Cu, Ti, Sn, Zn, Br, etc. can be mentioned. Various redox pairs, such as V / V, Zn / Br, and Fe / Cr, can be obtained from the active material by a combination of oxidation and reduction differences. In the present invention, redox pairs made of V / V are used. As described above, there is an advantage in that irreversible contamination by mixing phenomenon between two electrodes can be overcome by using the same type of redox pairs in the positive electrode and the negative electrode, and for example, the positive electrode electrolyte is V ⁴⁺ / V ⁵⁺ . As the anode electrolyte, V ²⁺ / V ³⁺ may be used as a redox pair.

The aqueous solvent is a mixture of one or two or more selected from sulfuric acid, hydrochloric acid, or phosphoric acid, and the organic solvent is acetonitrile, dimethyl carbonate, diethyl carbonate, dimethyl sulfoxide, dimethyl formamide, propylene carbonate, ethylene carbonate, It may be one or a mixture of two or more selected from N-methyl-2-pyrrolidone, fluoroethylene carbonate, ethanol, methanol and gamma-butyrolactone.

Additionally, the electrolyte solution may further include a supporting electrolyte.

The supporting electrolyte can be selected from the group consisting of alkylammonium salts, lithium salts and sodium salts. In the redox flow battery electrolyte according to the present invention, the alkyl ammonium _{^{salt, PF 6 -, BF 4 -}} , AsF 6 -, ClO 4 -, CF 3 SO 3 -, CF 3 SO 3 -, C (SO Combination of one anion selected from ₂ CF ₃ ) ₃ , N (CF ₃ SO ₂ ) ₂ and CH (CF ₃ SO ₂ ) ₂ and an ammonium cation where alkyl is methyl, ethyl, butyl or propyl in the tetraalkylammonium cation It can be made. In the redox flow battery electrolyte according to the present invention, the lithium salt is LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiCF ₃ SO ₃ , LiC (SO ₂ CF ₃ ) ₃ , LiN (CF ₃ SO ₂ ) ₂ and LiCH (CF ₃ SO ₂ ) ₂ . In the electrolyte solution for a redox flow battery according to the present invention, the sodium salt is NaPF ₆ , NaBF ₄ , NaAsF ₆ , NaClO ₄ , NaCF ₃ SO ₃ , NaCF ₃ SO ₃ , NaC (SO ₂ CF ₃ ) ₃ , NaN ( CF ₃ SO ₂ ) ₂ And NaCH (CF ₃ SO ₂ ) _{2 It} may be one or more selected from.

Electrolyte pumps 302 and 304 are not particularly mentioned in the present invention, and known ones can be used.

Redox flow battery 1000 including the above configuration can reduce the loss of pressure as the flow path portion F of the bipolar plates 118 and 119 is formed, thereby increasing the flow rate of the supplied electrolyte. The efficiency of the stack and system can be increased by reducing the pump loss. In addition, as the ion exchange membrane bonding surface 152 of the bipolar plate includes one or more band-shaped gaskets, stack tightness can be improved to prevent leakage of electrolyte, and stack assembly convenience can be increased. In addition, the electrodes 120 and 121 are compressed and inserted into the electrode receiving grooves of the bipolar plates 118 and 119, so that the thickness of the stack is not increased, and the bipolar plates 118 and 119 can be closely adhered without any gap between the electrolyte solution. It can prevent leakage.

Therefore, the redox flow battery 1000 of the present invention can obtain improved energy efficiency.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art to which the present invention pertains can easily practice. However, the present invention may be implemented in various different forms, and is not limited to the embodiments described herein.

Example 1.

An interlocking flow path was formed in the separation plate. The width of the partition wall for forming the flow path was 7 mm, the width of the flow channel channel was 4 mm, and the depth of the flow channel channel was 1.5 mm.

The ion exchange membrane bonding surface of the bipolar plate includes one gasket in the form of a belt.

The difference in height between the ion exchange membrane bonding surface of the bipolar plate and the channel forming partition wall was 1 mm.

A 1.5 mm thick carbon felt was inserted into the electrode receiving groove formed by the height difference.

The above process was repeated in the same manner to prepare two bipolar plates with carbon felt inserted in the electrode receiving grooves.

An ion exchange membrane (Nafion 212, 50 μm) was placed between the bipolar plates into which the carbon felts were inserted, and the redox flow batteries were prepared by fastening them. The ion exchange membrane bonding surfaces of the bipolar plates were in close contact with each other without play, and the carbon felt was compressed in the fastening process, and the thickness of the compressed carbon felt was the same as the height of the electrode receiving groove (FIG. 7).

Electrolytic solution was injected into each of the inlet and outlet of the bipolar plate. At this time, 3L of a 1.6M vanadium sulfuric acid aqueous solution (3M H ₂ SO ₄ ) was used as the electrolyte, and the flow rate was 75 cc / min.

Comparative Example 1.

A bipolar plate was prepared comprising one O-ring gasket on the ion exchange membrane bonding surface of the bipolar plate.

The difference in height between the ion exchange membrane bonding surface of the bipolar plate and the electrode receiving groove was 2.5 mm.

A 3.5 mm thick carbon felt was inserted into the electrode receiving groove.

The above process was repeated in the same manner to prepare two bipolar plates with carbon felt inserted in the electrode receiving grooves.

An ion exchange membrane (Nafion 212, 50 μm) was placed between the bipolar plates into which the carbon felts were inserted, and the redox flow batteries were prepared by fastening them. The ion exchange membrane bonding surfaces of the bipolar plates were in close contact with each other without clearance, and the carbon felt was compressed in the fastening process, and the thickness of the compressed carbon felt was the same as the height of the electrode receiving groove (FIG. 8).

Electrolytic solution was injected into each of the inlet and outlet of the bipolar plate. At this time, 3L of a 1.6M vanadium sulfuric acid aqueous solution (3M H ₂ SO ₄ ) was used as the electrolyte, and the flow rate was 75 cc / min.

Comparative Example 2.

An interlocking flow path was formed in the separation plate. The width of the partition wall for forming the flow path was 7 mm, the flow path channel width was 4 mm, and the flow path channel depth was 2.5 mm.

The ion exchange membrane bonding surface of the bipolar plate includes one gasket in the form of a belt.

The height of the ion exchange membrane bonding surface of the bipolar plate and the height of the channel forming partition wall were the same.

Electrode layers formed by stacking carbon paper on both sides with an ion exchange membrane (Nafion 212, 50 μm) interposed therebetween, were placed bipolar plates on each outside, and then fastened to produce redox flow batteries. The ion exchange membrane bonding surface of the bipolar plate was spaced by the height of the ion exchange membrane and carbon paper (FIG. 9).

The carbon paper had a thickness of 0.6 mm.

Electrolytic solution was injected into each of the inlet and outlet of the bipolar plate. At this time, 3L of a 1.6M vanadium sulfuric acid aqueous solution (3M H ₂ SO ₄ ) was used as the electrolyte, and the flow rate was 75 cc / min.

Experimental Example 1. Energy efficiency measurement of redox flow battery

Energy efficiency was measured using the unit cells prepared in Example 1, Comparative Example 1 and Comparative Example 2. The active area was 325 cm ² , current density 200 mA / cm ² was charged and discharged to measure energy efficiency.

As a result, Example 1 was measured to be 79.5%, Comparative Example 1 to 71%, and Comparative Example 2 to 77.5% (FIG. 10).

The redox flow battery of Example 1 of the present invention in which a flow path portion having an engaging pattern is formed, includes a band-shaped gasket, and an electrode is inserted into the electrode receiving groove, the flow rate of the electrolyte solution supplied due to the flow path is increased, It includes a gasket in the form, and because the electrode is inserted into the electrode receiving groove, it is possible to prevent the leakage of the electrolyte, and thus the energy efficiency is measured best. In addition, the airtightness and the convenience of assembling the stack were also excellent, and the deformation of the stack did not occur.

On the other hand, in the redox flow battery of Comparative Example 1, the thickness of the electrode, the carbon felt, increased, and the thickness of the entire unit cell increased. In addition, since the flow path was not included, pressure loss due to the flow of the electrolyte was large and mass transfer loss was generated under the current density condition. From this, it can be seen that the efficiency is low during output operation, and power loss due to the operation of the pump can be largely generated.

The redox flow battery of Comparative Example 2 used carbon paper as an electrode. Since the carbon paper had difficulty in controlling the compression ratio compared to the carbon felt, it was difficult to increase the active area and make the stack, and it was shown that the energy efficiency decreases when the active area increases.

Therefore, it can be seen that it is very effective to introduce the structure of the present invention into a redox flow battery targeting a high flow rate and a high current density.

11. 15. 21. 25: Bipolar plate
12: 14, 22, 24: electrode
13, 23: ion exchange membrane
27 Euro
1000: redox flow battery
100: battery module
101, 102, 103, 104: Unit module
202, 204: electrolyte tank
302, 304: electrolyte pump
111, 113: end plate
115, 117: current collector plate
118: 119: bipolar plate
120, 121: electrode
123: ion exchange membrane
130: unit cell
152: ion exchange membrane bonding surface
153: separation plate
154: flow path forming bulkhead
155: gasket
161: inlet
162: outlet
171: Supply Euro
172: discharge flow path
181, 182, 183, 184: connecting member
F: Euro part

Claims (10)

Bipolar plate formed with a flow path facing the electrode,
A bipolar plate for a redox flow battery, wherein an edge ion exchange membrane bonding surface of the bipolar plate is formed higher than an upper surface of the flow path forming partition wall of the flow path portion to form an electrode receiving groove. The bipolar plate for a redox flow battery according to claim 1, wherein a height difference between an upper surface of the flow path forming partition wall and an ion exchange membrane bonding surface at the edge of the bipolar plate is 0.5 to 1.5 mm. The bipolar plate for a redox flow battery according to claim 1, wherein the flow path part comprises a flow path integrally formed on the bipolar plate, or is formed by a separate flow path forming separation plate accommodated in the bipolar plate. The bipolar plate according to claim 1, wherein the bipolar plate includes one or more band-shaped gaskets on an ion exchange membrane bonding surface. Ion exchange membranes;
Electrodes disposed on both sides of the ion exchange membrane; And
Includes; bipolar plates respectively disposed on one side of the electrode,
The bipolar plate is a unit cell for a redox flow battery, which is a bipolar plate of any one of claims 1 to 4. The unit cell for a redox flow battery according to claim 5, wherein the electrode is inserted into an electrode receiving groove of a bipolar plate. According to claim 6, The thickness of the electrode is thicker than the depth of the electrode receiving groove of the bipolar plate, the unit cell for a redox flow battery, characterized in that it is compressed and inserted by coupling between the bipolar plates when assembling the unit cell. The redox flow battery unit cell according to claim 7, wherein the thickness of the electrode before being inserted into the electrode receiving groove is 1 to 2 mm. The redox flow battery unit cell according to claim 5, wherein the electrode is a carbon felt. A battery module formed by arranging and electrically connecting unit modules including unit stacks for generating currents on side surfaces of each other;
An electrolyte tank for supplying an electrolyte to the battery module and storing the electrolyte flowing out of the module; And
Includes; electrolyte pump for circulating the electrolyte between the module and the electrolyte tank;
The unit stack is a redox flow battery comprising a plurality of unit cells for a redox flow battery of any one of claims 5 to 9.

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