KR20200071258A - Redox flow battery(rfb) using electrolyte concentration gradient and operation method thereof - Google Patents

Abstract

The present invention relates to a redox flow battery using an electrolyte concentration gradient and a method for operating the same, and more particularly, to a redox flow battery using an electrolyte concentration gradient, of which the efficiency can be increased, and a method for operating the same. To this end, the redox flow battery includes: an anolyte tank provided with an electrolyte inlet at an upper end thereof and an electrolyte outlet at a lower end thereof, and including a vertically installed partition wall to form a concentration gradient of the anolyte accommodated therein; a catholye tank provided with an electrolyte inlet at an upper end thereof and an electrolyte outlet at a lower end thereof, and including a vertically installed partition wall to form a concentration gradient of the catholyte accommodated therein; and a stack part configured to receive electrolytes from the anolyte tank and the catholyte tank to charge and discharge electric power.

Description

REDOX FLOW BATTERY(RFB) USING ELECTROLYTE CONCENTRATION GRADIENT AND OPERATION METHOD THEREOF}

The present invention relates to a redox flow battery using an electrolyte concentration gradient and a method for operating the same, and more specifically, to a redox flow battery using an electrolyte concentration gradient capable of increasing the efficiency of the redox flow battery and its operating method. It is about.

Electric power storage technology is an important technology for efficient use of energy, such as efficiency of power use, improvement of power supply system's ability or reliability, expansion of the introduction of new and renewable energy that fluctuates over time, and energy regeneration of moving objects. The demand for potential and social contribution is increasing.

Adjusting supply and demand balance of semi-autonomous regional power supply systems such as micro grids, and properly distributing uneven output of renewable energy generation such as wind power or solar power, and voltage and frequency fluctuations that arise from differences from existing power systems. In order to control the influence of the secondary battery is actively researched, and in this field, expectations for the utilization of the secondary battery are increasing.

In particular, when looking at the characteristics required for a secondary battery to be used for large-capacity power storage, the energy storage density should be high, and a redox flow battery (RFB) has recently been spotlighted as a high capacity and high efficiency secondary battery suitable for these characteristics. That is true.

The redox flow battery converts and stores the electrical energy input through the charging process into chemical energy, and stores the chemical energy previously stored into electrical energy through the discharging process, and outputs the same. However, the redox flow battery is different from the general secondary battery in that a tank for storing the electrode active material is required because the electrode active material having energy exists in a liquid state rather than a solid state.

In the case of a general redox flow battery, one tank is connected to the positive electrode and the negative electrode and stores electrolyte. The electrolyte stored in the tank is discharged from the tank to the stack to react (charge or discharge) in the stack, and after the reaction is circulated back to the tank, a concentration gradient of the electrolyte is formed in the tank. The concentration gradient thus formed is quickly resolved by natural diffusion, convection or artificial agitation.

However, when the concentration gradient of the naturally-occurring electrolytic solution is used without resolving it, it is judged that an effect capable of improving the efficiency of the entire battery can be obtained, leading to the present invention.

Republic of Korea Patent Publication No. 10-2017-0077720

The present invention is to solve the above problems, and an object of the present invention is to provide a redox flow battery that can improve the efficiency of the entire battery by using a concentration gradient of a naturally formed electrolyte solution and a method of operating the same.

The above and other objects and advantages of the present invention will become apparent from the following description of preferred embodiments.

The above object is an anode electrolyte tank having an electrolyte inlet at the top, an electrolyte outlet at the bottom, and a partition wall installed in a vertical direction to form a concentration gradient of the anode electrolyte accommodated therein; A cathode electrolyte tank having an electrolyte inlet at the top, an electrolyte outlet at the bottom, and a partition wall installed in a vertical direction to form a concentration gradient of the cathode electrolyte accommodated therein; And a stack portion for receiving and receiving electric power from the positive electrode electrolyte tank and the negative electrode electrolyte tank to store and discharge electric power.

At this time, the positive electrode electrolyte tank may be provided with a plurality of partition walls, adjacent partition walls are preferably coupled to the opposite surface of the positive electrode electrolyte tank.

Further, a plurality of partition walls provided in the negative electrode electrolyte tank may be provided, and adjacent partition walls are preferably coupled to opposite surfaces of the negative electrode electrolyte tank.

In addition, the stack portion includes at least one battery cell, and the battery cell includes: an ion exchange membrane; An anode positioned between the ion exchange membranes; And a negative electrode.

In addition, a pump for transferring the positive electrode electrolyte contained in the positive electrode electrolyte tank to the stack portion; And/or a pump for transferring the negative electrode electrolyte contained in the negative electrode electrolyte tank to the stack portion.

In addition, the above object, a first anode electrolyte tank having an electrolyte inlet at the top, an electrolyte outlet at the bottom, and a partition wall installed in a vertical direction to form a concentration gradient of the anode electrolyte accommodated therein; A second anode electrolyte tank having an electrolyte inlet at the top, an electrolyte outlet at the bottom, and a partition wall installed in a vertical direction to form a concentration gradient of the anode electrolyte accommodated therein; A first cathode electrolyte tank having an electrolyte inlet at the top, an electrolyte outlet at the bottom, and a partition wall installed in a vertical direction to form a concentration gradient of the cathode electrolyte accommodated therein; A second cathode electrolyte tank having an electrolyte inlet at the top, an electrolyte outlet at the bottom, and a partition wall installed in a vertical direction to form a concentration gradient of the cathode electrolyte accommodated therein; And a stack portion receiving and receiving electric power from the first and second anode electrolyte tanks and the first and second cathode electrolyte tanks to store and discharge power. have.

In this case, the partition walls provided in the first and second anode electrolyte tanks may be plural, and adjacent partition walls are preferably coupled to opposite surfaces in the first and second anode electrolyte tanks, respectively.

In addition, the first positive electrode electrolyte tank and the second positive electrode electrolyte tank may be connected to a connection tube through which the positive electrode electrolyte contained therein can be moved, and connected to the electrolyte inlet so that the positive electrode electrolyte introduced therein flows into the lower end of each tank. Extension tube; may be provided.

In addition, a plurality of partition walls provided in the first and second negative electrode electrolyte tanks may be provided, and adjacent partition walls are preferably coupled to opposite surfaces in the first and second negative electrode electrolyte tanks, respectively.

In addition, the first cathode electrolyte tank and the second cathode electrolyte tank may be connected to a connecting tube through which the cathode electrolyte accommodated therein can be moved, and connected to the electrolyte inlet so that the cathode electrolyte introduced therein flows into the lower end of each tank. Extension tube; may be provided.

In addition, the stack portion includes at least one battery cell, and the battery cell includes: an ion exchange membrane; An anode positioned between the ion exchange membranes; And a negative electrode.

In addition, a pump for transferring the positive electrode electrolyte contained in the first and second positive electrode electrolyte tanks to the stack portion; And/or a pump for transferring the negative electrode electrolyte contained in the first and second negative electrode electrolyte tanks to the stack.

In addition, the first and second anode electrolyte tanks and the first and second cathode electrolyte tanks are respectively installed in the electrolyte flow paths connected to the control unit for controlling the valve to control the opening and closing of the flow path; may also include.

According to the present invention, by extending the movement path of the electrolyte through the partition wall provided in the tank to form a concentration gradient of the electrolyte in the tank, by transferring the electrolyte with a higher concentration of the reactant to the stack portion overpotential in the stack portion (overpotential ).

In particular, through the partition wall installed in the vertical direction, it is possible to block the circulation of the electrolyte even when the redox flow battery is idle, so that the electrolyte concentration gradient can be maintained. The pressure drop caused by the increase in the flow velocity in the flow path can be blocked.

Furthermore, through this, charging or discharging may be caused by a larger current, voltage efficiency may be increased, and as a result, efficiency of the entire battery may be increased.

However, the effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the following description.

1 is a view schematically showing a redox flow battery according to an embodiment of the present invention.
2 is a view schematically showing a redox flow battery according to an embodiment of the present invention.
3 is a view schematically showing a redox flow battery according to an embodiment of the present invention.
4 is a view schematically showing a charging process of the redox flow battery of FIG. 3.
5 is a view schematically showing a discharge process of the redox flow battery of FIG. 3.
6 is a graph showing an increase in energy efficiency according to a stack overvoltage reduction in Examples 1 to 4 and Comparative Examples.
7 is a graph showing the effect of increasing the system efficiency of Examples 1 to 4.

Hereinafter, the present invention will be described in detail with reference to examples and drawings of the present invention. These examples are only provided by way of example to illustrate the present invention in more detail, it will be apparent to those skilled in the art that the scope of the present invention is not limited by these examples. .

In addition, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs, and in case of conflict, the present specification including definitions. The description will take precedence.

In order to clearly describe the proposed invention in the drawings, parts irrelevant to the description are omitted, and like reference numerals are assigned to similar parts throughout the specification. And, when it is said that a part "includes" a certain component, this means that other components may be further included instead of excluding other components, unless otherwise stated. In addition, "part" described in the specification means a unit or block that performs a specific function.

In each step, the identification numbers (first, second, etc.) are used for convenience of explanation. The identification numbers do not describe the order of each step, and each step does not explicitly describe a specific order in the context. It may be carried out differently from the order specified above. That is, each step may be performed in the same order as specified, or may be performed substantially simultaneously, or in the reverse order.

In the present specification, the flow battery may be a flow battery including various known active materials. Here, for convenience of explanation, the vanadium flow battery is described as an example, but is not limited thereto.

1 is a view schematically showing a redox flow battery according to an embodiment of the present invention. Referring to FIG. 1, the redox flow battery according to an embodiment of the present invention includes electrolyte inlets 111a and 111b at the top, and electrolyte outlets 112a and 112b at the bottom, and is accommodated therein. An anode electrolyte tank 110 having a partition wall 113 installed in a vertical direction to form a concentration gradient of the anode electrolyte; An electrolyte inlet (121a, 121b) is provided at the top, an electrolyte outlet (122a, 122b) is provided at the bottom, and a partition wall (123) installed in a vertical direction is provided to form a concentration gradient of the cathode electrolyte contained therein. Cathode electrolyte tank 120; And a stack unit 130 receiving the electrolyte from the anode electrolyte tank 110 and the cathode electrolyte tank 120 to store and discharge power. The present invention, by extending the movement path of the electrolyte through the partition wall 113 provided in the tank to form a concentration gradient of the electrolyte in the tank, the stack portion 130 of the electrolyte having a higher concentration of the reactant during the charging or discharging process By transferring to the can have an effect that can reduce the overpotential (overpotential) in the stack 130. In particular, through the partition wall installed in the vertical direction, it is possible to block the circulation of the electrolyte even when the redox flow battery is idle, so that the electrolyte concentration gradient can be maintained. The pressure drop caused by the increase in the flow velocity in the flow path can be blocked. Through this, charging or discharging may be caused by a larger current, voltage efficiency may be increased, and as a result, efficiency of the entire battery may be increased.

The anode electrolyte tank 110 accommodates the anode electrolyte inside, and may be formed in various forms. At the top, the electrolyte inlets 111a and 111b are provided, and the anode electrolyte is introduced, and at the bottom, the electrolyte outlets 112a and 112b are provided to accommodate the received anode electrolyte. Valves 114a, 114b, 115a, and 115b capable of controlling opening and closing of the flow path may be installed at the front end of the electrolyte inlets 111a and 111b and the rear end of the electrolyte outlets 112a and 112b, respectively. A partition wall 113 may be provided inside the anode electrolyte tank 110 to form a concentration gradient of the anode electrolyte. That is, the partition wall 113 can control the flow path of the anode electrolyte so that the anode electrolyte flowing into the inlet 111 inside the anode electrolyte tank 110 can be discharged to the outlet 112 to form a gradient of the electrolyte concentration. have. The partition wall 113 may be manufactured in any form as long as it can control the flow path of the positive electrode electrolyte, and may be, for example, a plate shape. In addition, the partition wall 113 is preferably formed in a vertical direction (the vertical direction in FIG. 1) to facilitate the flow of the positive electrode electrolyte, and may be formed in plural. At this time, while the flow of the anode electrolyte is smooth and the flow path is the longest (zigzag flow), the partition wall 113 is formed in a vertical direction so that the concentration gradient of the anode electrolyte is large, but the adjacent partition wall 113 is the anode It is preferable that they are coupled to opposite surfaces of the anode electrolyte tank 110 with respect to each other based on the horizontal cross section of the electrolyte tank 110 (see FIG. 1 ).

The cathode electrolyte tank 120 is configured to accommodate the cathode electrolyte inside, and may be formed in various forms. At the top, the electrolyte inlets 121a and 121b are provided, and the cathode electrolyte is introduced, and at the bottom, the electrolyte outlets 122a and 122b are provided to accommodate the received cathode electrolyte. Valves 124a, 124b, 125a, and 125b that can control opening and closing of the flow path may be installed at the front end of the electrolyte inlets 121a and 121b and the rear end of the electrolyte outlets 122a and 122b, respectively. A partition wall 123 may be provided inside the cathode electrolyte tank 120 to form a concentration gradient of the anode electrolyte. That is, the partition wall 123 is a flow path of the cathode electrolyte to form a gradient of the electrolyte concentration until the cathode electrolyte flowing into the inlets 121a and 121b from the cathode electrolyte tank 120 is discharged to the outlets 122a and 122b. Can be controlled. The partition wall 123 may be manufactured in any form as long as it can control the flow path of the cathode electrolyte, and may be, for example, a plate shape. In addition, the partition wall 123 is preferably formed in a vertical direction (reference vertical direction in FIG. 1) so as to facilitate the flow of the negative electrode electrolyte, and may be formed in plural. In this case, the partition wall 123 is formed in a vertical direction so that the flow path is longest (zigzag flow) while smoothly flowing the cathode electrolyte to form a concentration gradient of the cathode electrolyte, and the adjacent partition walls 123 are the cathode It is preferable that they are coupled to opposite surfaces of the cathode electrolyte tank 120 to each other based on the horizontal cross-section of the electrolyte tank 120 (see FIG. 1).

The stack unit 130 may include one or a plurality of battery cells. The battery cell may include an anode 132 and a cathode 133 positioned between the ion exchange membrane 131 and the ion exchange membrane 131. The positive electrode 132 and the negative electrode 133 may be made of various known materials, and for example, may be made of graphite. It is preferable to use the ion exchange membrane 131 having high selective permeability of ions, small electrical resistance, small diffusion coefficient of solutes and solvents, chemically stable, excellent mechanical strength, and economical. In general, Nafion (Dupnot), CMV, AMV, DMV (Asahi Glass), or the like can be used. However, in the case of a vanadium-based redox flow battery, since an active material in which a transition metal element and a strong acid are mixed as an electrolyte is used, a membrane having high acid resistance, oxidation resistance and selective permeability is required. When a Nafion membrane is applied to a vanadium-based battery, There is a disadvantage in that energy efficiency is lowered due to permeation and life characteristics are lowered in the case of CMV membranes. Therefore, in order to compensate for this disadvantage, an ion exchange membrane using an engineering plastic polymer having excellent mechanical properties in a strong acid atmosphere and a high temperature region may be applied, for example, polyether ether ketone (PEK), polysulfone (PSF), and polybenzimidazole PBI ) And the like.

In addition, the positive electrode electrolyte solution accommodated in the positive electrode electrolyte tank 110 and the negative electrode electrolyte solution accommodated in the negative electrode electrolyte tank 120 may further include pumps 140a and 140b for transferring to the stack 130, respectively.

2 is a view schematically showing a redox flow battery according to an embodiment of the present invention. Referring to FIG. 2, the redox flow battery according to an embodiment of the present invention includes electrolyte inlets 111a and 111b at the top, and electrolyte outlets 112a and 112b at the bottom, and is accommodated therein. A first anode electrolyte tank (110a) having a partition wall (113a) installed in a vertical direction to form a concentration gradient of the anode electrolyte; Second anode electrolyte solution having electrolyte inlets 111c and 111d at the top, electrolyte outlets 112c and 112d at the bottom, and partition walls 113b for forming a concentration gradient of anode electrolytes accommodated therein Tank 110b; An electrolyte inlet (121a, 121b) is provided at the top, and an electrolyte outlet (122a, 122b) is provided at the bottom, and a partition wall (123a) installed in a vertical direction is provided to form a concentration gradient of the negative electrode electrolyte accommodated therein. A first cathode electrolyte tank 120a; An electrolyte inlet (121c, 121d) is provided at the top, an electrolyte outlet (122c, 122d) is provided at the bottom, and a partition wall (123b) installed in a vertical direction is provided to form a concentration gradient of the cathode electrolyte accommodated therein. A second cathode electrolyte tank 120b; And stack units 130 receiving and supplying electrolyte from the first and second anode electrolyte tanks 110a and 110b and the first and second cathode electrolyte tanks 120a and 120b. ;. The present invention is provided with a plurality of anode electrolyte tanks (110a, 110b) and cathode electrolyte tanks (120a, 120b), and extending the path of the electrolyte through the partition walls (113a, 113b, 123a, 123b) provided in the tank A concentration gradient of the electrolyte is formed in the tank, and an electrolyte having a higher concentration of reactants is transferred to the stack 130 during charging or discharging, thereby reducing the overpotential in the stack. have. Through this, charging or discharging may be caused by a larger current, voltage efficiency may be increased, and as a result, efficiency of the entire battery may be increased.

The first anode electrolyte tank 110a accommodates the anode electrolyte inside, and may be formed in various forms. At the top, electrolyte inlets 111a and 111b are provided to allow the anode electrolyte to flow in, and at the bottom, electrolyte outlets 112a and 112b are provided to accommodate the received anode electrolyte. Valves 114a, 114b, 115a, and 115b capable of controlling opening and closing of the flow path may be installed at the front end of the electrolyte inlets 111a and 111b and the rear end of the electrolyte outlets 112a and 112b, respectively. A partition wall 113a may be provided inside the first anode electrolyte tank 110a to form a concentration gradient of the anode electrolyte. That is, the partition wall 113a may control the flow path of the positive electrode electrolyte so that a positive electrode electrolyte solution gradient can be formed until the positive electrode electrolyte is discharged from the first positive electrode electrolyte tank 110a to the outlets 112a and 112b. The partition wall 113a may be manufactured in any form as long as it can control the flow path of the anode electrolyte, and may be, for example, a plate shape. In addition, the partition wall 113a is preferably formed in a vertical direction (reference vertical direction in FIG. 2) to facilitate the flow of the positive electrode electrolyte, and may be formed in plural. At this time, while smoothly flowing the positive electrode electrolyte, the longest flow path (zigzag flow), the partition wall 113a is formed in a vertical direction so as to form a large concentration gradient of the positive electrode electrolyte, but adjacent partition walls 113a are made It is preferable that they are coupled to opposite surfaces of the first positive electrode electrolyte tank 110a to each other based on the horizontal cross-section of the 1 positive electrode electrolyte tank 110a (see FIG. 2).

The second anode electrolyte tank 110b is structurally the same as the first anode electrolyte tank 110a. Therefore, in the overlapped portion described above, the description thereof will be omitted, and a portion not described above, such as a connection relationship between the first anode electrolyte tank 110a and the second anode electrolyte tank 110b will be described.

The first positive electrode electrolyte tank 110a and the second positive electrode electrolyte tank 110b may be connected to a connector 116 so that the positive electrode electrolyte contained therein can be moved in both directions. In addition, the first positive electrode electrolyte tank (110a) and the second positive electrode electrolyte tank (110b) is an electrolyte inlet () so that the positive electrode electrolyte flowing into the lower end of the tank through the electrolyte inlet (111a, 111b, 111c, 111d), respectively 111a, 111b, 111c, 111d) may be provided with extension pipes 117a, 117b. At this time, the positive electrode electrolyte flowing into the lower portion moves to an adjacent tank through the connection pipe 116 and then flows out (for example, after flowing into the first positive electrode electrolyte tank 110a and then flowing into the second positive electrode electrolyte tank 110b) When possible, it is preferable that the positive electrode electrolyte has the longest movement path so that a large concentration gradient can be formed.

The first cathode electrolyte tank 120a accommodates the cathode electrolyte inside, and may be formed in various forms. At the top, electrolyte inlets 121a and 121b are provided to allow the cathode electrolyte to flow, and at the bottom, electrolyte outlets 122a and 122b are provided to accommodate the received cathode electrolyte. Valves 124a, 124b, 125a, and 125b that can control opening and closing of the flow path may be installed at the front end of the electrolyte inlets 121a and 121b and the rear end of the electrolyte outlets 122a and 122b, respectively. A partition wall 123a may be provided inside the first cathode electrolyte tank 120a to form a concentration gradient of the incoming cathode electrolyte. That is, the partition wall 123a may control the flow path of the cathode electrolyte to form a gradient of the electrolyte concentration until the cathode electrolyte flows out of the outlets 122a and 122b inside the first cathode electrolyte tank 120a. The partition wall 123a may be manufactured in any form as long as it can control the flow path of the cathode electrolyte, and may be, for example, a plate shape. In addition, the partition wall 123a is preferably formed in a vertical direction (the vertical direction in FIG. 2) to facilitate the flow of the cathode electrolyte, and may be formed in plural. In this case, the partition wall 123a is formed in a vertical direction so that the flow path is longest (zigzag flow) while smoothly flowing the negative electrode electrolyte to form a concentration gradient of the negative electrode electrolyte, but adjacent partition walls 123a are made. It is preferable that they are coupled to opposite surfaces of the first cathode electrolyte tank 120a to each other based on the horizontal cross-section of the 1 cathode electrolyte tank 120a (see FIG. 2).

The second cathode electrolyte tank 120b is structurally the same as the first cathode electrolyte tank 120a. Therefore, in the overlapped portion described above, the description thereof will be omitted, and a portion not described above, such as a connection relationship between the first cathode electrolyte tank 120a and the second cathode electrolyte tank 120b will be described.

The first cathode electrolyte tank 120a and the second cathode electrolyte tank 120b may be connected to a connector 126 so that the cathode electrolyte contained therein can be moved in both directions. In addition, the first cathode electrolyte tank (120a) and the second cathode electrolyte tank (120b) is an electrolyte inlet () so that the anode electrolyte flowing into the lower end of the tank through the electrolyte inlet (121a, 121b, 121c, 121d) respectively 121a, 121b, 121c, 121d) may be provided with an extension tube (127a, 127b) connected. At this time, the cathode electrolyte flowing into the lower portion moves to an adjacent tank through the connection pipe 126 and then flows out (for example, after flowing into the first cathode electrolyte tank 120a and then flowing into the second cathode electrolyte tank 120b) When possible, it is preferable that the negative electrode electrolyte has the longest movement path so that a large concentration gradient can be formed.

The stack unit 130 may include one or a plurality of battery cells. The battery cell may include an anode 132 and a cathode 133 positioned between the ion exchange membrane 131 and the ion exchange membrane 131. The positive electrode 132 and the negative electrode 133 may be made of various known materials, and may be made of graphite, for example. It is preferable to use the ion exchange membrane 131 having high selective permeability of ions, small electrical resistance, small diffusion coefficient of solutes and solvents, chemically stable, excellent mechanical strength, and economical. In general, Nafion (Dupnot), CMV, AMV, DMV (Asahi Glass), or the like can be used. However, in the case of a vanadium-based redox flow battery, since an active material in which a transition metal element and a strong acid are mixed as an electrolyte is used, a membrane having high acid resistance, oxidation resistance and selective permeability is required. When a Nafion membrane is applied to a vanadium-based battery, There is a disadvantage in that energy efficiency is lowered due to permeation and life characteristics are lowered in the case of CMV membranes. Therefore, in order to compensate for this disadvantage, an ion exchange membrane using an engineering plastic polymer having excellent mechanical properties in a strong acid atmosphere and a high temperature region may be applied, for example, polyether ether ketone (PEK), polysulfone (PSF), and polybenzimidazole PBI ) And the like.

In addition, a pump for transferring the positive electrode electrolyte contained in the first and second positive electrode electrolyte tanks 110a and 110b and the negative electrode electrolyte contained in the first and second negative electrode electrolyte tanks 120a and 120b to the stack 130, respectively. 140a, 140b).

3 is a view schematically showing a redox flow battery according to an embodiment of the present invention. Referring to FIG. 3, the redox flow battery according to an embodiment of the present invention may further include a control unit 150 in the redox flow battery shown in FIG. 2. The control unit 150 is installed in the electrolyte passages connected to the first and second anode electrolyte tanks 110a and 110b and the first and second cathode electrolyte tanks 120a and 120b, respectively, to control opening and closing of the passage ( 114a, 114b, 114c, 114d, 115a, 115b, 115c, 115d, 124a, 124b, 124c, 124d, 125a, 125b, 125c, 125d) can be controlled. 4 and 5 are views schematically showing charging and discharging processes of the redox flow battery of FIG. 3, and the controller 150 will be described in detail with reference to FIGS. 4 and 5. Configurations other than the control unit 150 have been described above, and description thereof will be omitted.

The process of charging the vanadium-based redox flow battery will be described first with reference to FIG. 4. When charging occurs, V ⁴⁺ ions are oxidized to V ⁵⁺ ions at the positive electrode, and V ³⁺ ions are reduced to V ²⁺ ions at the negative electrode. The first anode electrolyte tank 110a accommodates a positive electrode electrolyte rich in V ⁴⁺ ions, the second anode electrolyte tank 110b holds a positive electrode electrolyte rich in V ⁵⁺ ions, and the first cathode electrolyte tank 120a In a state where V ²⁺ ions are enriched in the negative electrolyte, and the second negative electrolyte tank 120b is set to receive V ³⁺ ions rich in the negative electrolyte, the controller 150 is configured to receive the second positive electrolyte tank 110b. ) Of the outlet valve 115d and the outlet valve 125a of the first cathode electrolyte tank 120a are closed, and the outlet valve 115a of the first anode electrolyte tank 110a and the outlet of the second cathode electrolyte tank 120b The valve 125d is opened so that the positive electrode electrolyte rich in V ⁴⁺ ions and the negative electrode electrolyte rich in V ³⁺ ions can move to the stack 130. When the filling process occurs in the stack unit 130, the positive electrode electrolyte and the negative electrode electrolyte are changed to a state rich in V ⁵⁺ ions and V ²⁺ ions, respectively, and the controller 150 inlet valves of the first positive electrode electrolyte tank 110a (114a, 114b) and the inlet valves (124c, 124d) of the second cathode electrolyte tank (120b) are closed, the inlet valve (114d) of the second anode electrolyte tank (110b) and the inlet of the first cathode electrolyte tank (120a) are closed. The valves 124a are opened (114c and 124b are closed) so that electrolytes rich in V ⁵⁺ ions and V ²⁺ ions flow into the second anode electrolyte tank 110b and the first cathode electrolyte tank 120a, respectively. When it is limited to the positive electrode electrolyte tanks 110a and 110b, the positive electrode electrolyte rich in V ⁵⁺ ions flows into the second positive electrode electrolyte tank 110b, and the first positive electrode electrolyte tank 110a is still rich in V ⁴⁺ ions. The positive electrode electrolyte is accommodated, and in the charging process, a positive electrode electrolyte rich in V ⁴⁺ ions may flow into the stack 130. For the same reason, the negative electrode electrolyte rich in V ²⁺ ions flows into the first negative electrode electrolyte tank 120a, and the negative electrode electrolyte rich in V ³⁺ ions is still accommodated in the second negative electrode electrolyte tank 120b, and the charging process continues. As the V ³⁺ ion-rich cathode electrolyte may be introduced into the stack 130, it can be charged at a lower OCV (Open Circuit Voltage) than when using a single tank or a tank without a partition.

Next, a process of discharging through FIG. 5 will be described. When discharge occurs, V ⁵⁺ ions are reduced to V ⁴⁺ ions at the positive electrode, and V ²⁺ ions are oxidized to V ³⁺ ions at the negative electrode. The first anode electrolyte tank 110a accommodates a positive electrode electrolyte rich in V ⁴⁺ ions, the second anode electrolyte tank 110b holds a positive electrode electrolyte rich in V ⁵⁺ ions, and the first cathode electrolyte tank 120a In a state where V ²⁺ ions are enriched in the negative electrode electrolyte, and the second negative electrolyte tank 120b is set to receive V ³⁺ ions rich in the negative electrode electrolyte, the controller 150 controls the first positive electrode electrolyte tank 110a. ) Of the outlet valve 115a and the outlet valve 125d of the second cathode electrolyte tank 120b, and the outlet valve 115d of the second anode electrolyte tank 110b and the outlet of the first cathode electrolyte tank 120a The valve 125a is opened to allow the V ⁵⁺ ion-rich positive electrolyte and the V ²⁺ ion-rich negative electrolyte to move to the stack 130. When the discharge process occurs in the stack 130, the positive electrode electrolyte and the negative electrode electrolyte are changed to a state rich in V ⁴⁺ ions and V ³⁺ ions, respectively, and the controller 150 inlet valves of the second positive electrode electrolyte tank 110b (114c, 114d) and the inlet valves (124a, 124b) of the first cathode electrolyte tank (120a) are closed, the inlet valve (114a) of the first anode electrolyte tank (110a) and the inlet of the second cathode electrolyte tank (120b) The valves 124d are opened (114b and 124c are closed) to allow the electrolytes rich in V ⁴⁺ ions and V ³⁺ ions to flow into the first positive electrolyte tank 110a and the second negative electrolyte tank 120b, respectively. When it is limited to the positive electrode electrolyte tanks 110a and 110b, V ⁴⁺ ion-rich positive electrode electrolyte flows into the first positive electrode electrolyte tank 110a, and the second positive electrolyte tank 110b is still rich in V ⁵⁺ ions. The positive electrode electrolyte is accommodated, and during discharge, the positive electrode electrolyte rich in V ⁵⁺ ions may flow into the stack 130. For the same reason, the negative electrode electrolyte rich in V ³⁺ ions flows into the second negative electrode electrolyte tank 120b, so that the negative electrode electrolyte rich in V ²⁺ ions is still accommodated in the first negative electrode electrolyte tank 120a, and the discharge process continues. As a result, the cathode electrolyte solution rich in V ²⁺ ions may be introduced into the stack 130, and thus, may be discharged at a higher OCV (Open Circuit Voltage) than when using a single tank or a tank without a partition.

As a result, it is possible to form a concentration gradient of the electrolytic solution to use a lower voltage when charging than the OCV of a conventional redox flow battery, and use it higher when discharging, which may delay reaching the upper or lower voltage limit and, thus, greater It can have the effect of driving longer with electric power (improving battery efficiency).

Hereinafter, the configuration of the present invention and its effects will be described in more detail through specific examples and comparative examples. However, the present examples are intended to illustrate the present invention in more detail, and the scope of the present invention is not limited to these examples.

[Example]

A vanadium-based redox flow battery having a positive electrode electrolyte tank and a negative electrode electrolyte tank having vertical barrier ribs as shown in FIG. 1 was prepared. Example 1 (2nd stage) for 1 vertical partition, Example 2 (4th) for 3 vertical partitions, Example 3 (8th) for 7 vertical partitions, 15 vertical partitions The case was set to Example 4 (16 steps). (The higher the number of stages, the larger the gradient of electrolyte concentration.)

[Comparative example]

The same as in Example, but a vanadium-based redox flow battery (1 stage) without a partition was prepared.

[Experimental Example]

The system efficiencies of Examples 1 to 4 and Comparative Examples were simulated and measured. System efficiency is defined as the ratio of charged and discharged energy. At this time, the energy can be defined as [average voltage x average current x time] during charging and discharging. In particular, when calculating the discharge energy, the power consumption (Parasite Loss) of the BOP, such as a pump, is reflected. Can be calculated through In addition, the results according to the experimental examples are shown in FIGS. 6 and 7.

[Equation 1]

Through the simulation results, it was confirmed that ⅰ) stack overvoltage reduction, ii) pump consumption power reduction effect can be obtained. When the stack overvoltage decreases, the current required for discharge decreases, the voltage efficiency inversely proportional to the overvoltage increases, and the DC-DC efficiency increases (see FIG. 6 and Table 1 below).

[Table 1]

In addition, when the VRFB is operated, the concentration of the reactant is lowered immediately before charging/discharging is completed and requires a large flow rate or has to be switched to the CV mode (refer to Table 2 below), and this design can be applied to delay the moment. Accordingly, the required flow rate of the electrolyte solution is lowered, and the power consumption of the pump is reduced. As a result, the parasitic loss of the system can be reduced, and as a result, the system efficiency is increased.

[Table 2] Comparison of the highest required flow rate at the end of charging/discharging

On the other hand, as can be seen in FIG. 7, when the degree of cascading is increased too much, the flow path of the electrolyte becomes complicated, and the pump burden is increased.

As a result, through simulation, ⅰ) OCV increase and overvoltage decrease due to high concentration feed inflow, ii) reduction of applied current based on the same output, ⅲ) battery heat generation decrease due to overvoltage reduction, ⅳ) reduction of pump consumption power due to decrease in electrolyte supply standards The effect was confirmed, and as a result, it was confirmed that the system efficiency can be improved up to 4% compared to the general VRFB structure as in the comparative example.

In this specification, only a few examples of the various embodiments performed by the present inventors are described, but the technical spirit of the present invention is not limited to or limited thereto, and can be variously implemented by a person skilled in the art.

110: anode electrolyte tank
110a: first anode electrolyte tank
110b: second anode electrolyte tank
111, 111a, 111b, 111c, 111d: electrolyte inlet
112, 112a, 112b, 112c, 112d: electrolyte outlet
113, 113a, 113b: bulkhead
114, 114a, 114b, 114c, 114d: electrolyte inlet valve
115, 115a, 115b, 115c, 115d: electrolyte outlet valve
116: connector
117a, 117b: extension tube
120: cathode electrolyte tank
120a: first cathode electrolyte tank
120b: second cathode electrolyte tank
121, 121a, 121b, 121c, 121d: electrolyte inlet
122, 122a, 122b, 122c, 122d: electrolyte outlet
123, 123a, 123b: bulkhead
124, 124a, 124b, 124c, 124d: electrolyte inlet valve
125, 125a, 125b, 125c, 125d: electrolyte outlet valve
126: connector
127a, 127b: extension tube
130: stack
131: ion exchange membrane
132: anode
133: cathode
140a, 140b: pump
150: control unit

Claims (21)

An anode electrolyte tank having an electrolyte inlet at the top, an electrolyte outlet at the bottom, and a partition wall installed in a vertical direction to form a concentration gradient of the anode electrolyte accommodated therein;
A cathode electrolyte tank having an electrolyte inlet at the top, an electrolyte outlet at the bottom, and a partition wall installed in a vertical direction to form a concentration gradient of the cathode electrolyte accommodated therein; And
It characterized in that it comprises a; a stack portion for storing (charge) and discharge (discharge) power receiving the electrolyte from the anode electrolyte tank and the cathode electrolyte tank, characterized in that it comprises, redox flow battery. According to claim 1, The partition wall provided in the anode electrolyte tank,
A redox flow battery, characterized in that it is plural. According to claim 2,
Adjacent partition walls, characterized in that coupled to the opposite side of the anode electrolyte tank, redox flow cell. According to claim 1, The partition wall provided in the cathode electrolyte tank,
A redox flow battery, characterized in that it is plural. The method of claim 4,
Adjacent partition walls, characterized in that coupled to the opposite side of the cathode electrolyte tank, redox flow battery. According to claim 1, The stack portion,
At least one battery cell,
The battery cell,
Ion exchange membranes;
An anode positioned between the ion exchange membranes; And a cathode; a redox flow battery. According to claim 1,
A pump for transferring the positive electrode electrolyte solution accommodated in the positive electrode electrolyte tank to the stack portion, characterized in that it comprises, redox flow battery. According to claim 1,
It characterized in that it comprises a; pump for transferring the cathode electrolyte contained in the cathode electrolyte tank to the stack portion, redox flow battery. A first anode electrolyte tank having an electrolyte inlet at the top, an electrolyte outlet at the bottom, and a partition wall installed in a vertical direction to form a concentration gradient of the anode electrolyte accommodated therein;
A second anode electrolyte tank having an electrolyte inlet at the top, an electrolyte outlet at the bottom, and a partition wall installed in a vertical direction to form a concentration gradient of the anode electrolyte accommodated therein;
A first cathode electrolyte tank having an electrolyte inlet at the top, an electrolyte outlet at the bottom, and a partition wall installed in a vertical direction to form a concentration gradient of the cathode electrolyte accommodated therein;
A second cathode electrolyte tank having an electrolyte inlet at the top, an electrolyte outlet at the bottom, and a partition wall installed in a vertical direction to form a concentration gradient of the cathode electrolyte accommodated therein; And
And a stack unit configured to store and discharge electric power by receiving the electrolyte from the first and second anode electrolyte tanks and the first and second cathode electrolyte tanks. 10. The method of claim 9, The first and second partition walls provided in the anode electrolyte tank,
A redox flow battery, characterized in that it is plural. The method of claim 10,
The adjacent barrier ribs are respectively coupled to opposite surfaces in the first and second anode electrolyte tanks, redox flow cells. The method of claim 9,
The first positive electrode electrolyte tank and the second positive electrode electrolyte tank is characterized in that the positive electrode electrolyte accommodated therein is connected by a connection tube through which the redox flow battery. The method of claim 9, wherein the first anode electrolyte tank and the second anode electrolyte tank,
And an extension tube connected to the electrolyte inlet so that the anode electrolyte introduced into the inside flows into the lower end of the tank, respectively. 10. The method of claim 9, The first and second partition walls provided in the anode electrolyte tank,
A redox flow battery, characterized in that it is plural. The method of claim 14,
Adjacent barrier ribs are characterized in that they are coupled to opposite surfaces in the first and second cathode electrolyte tanks, respectively. The method of claim 9,
The first cathode electrolyte tank and the second cathode electrolyte tank are characterized in that the cathode electrolyte contained therein is connected by a connection tube through which the redox flow cell is characterized in that. The method of claim 9, wherein the first cathode electrolyte tank and the second cathode electrolyte tank,
And an extension tube connected to the electrolyte inlet so that the cathode electrolyte flowing into the inside flows into the lower end of the tank, respectively. The method of claim 9, The stack portion,
At least one battery cell,
The battery cell,
Ion exchange membranes;
An anode positioned between the ion exchange membranes; And a cathode; a redox flow battery. The method of claim 9,
And pumps for transferring the positive electrode electrolyte contained in the first and second positive electrode electrolyte tanks to the stack. The method of claim 9,
And pumps for transferring the negative electrode electrolyte contained in the first and second negative electrode electrolyte tanks to the stack portion. The method of claim 9,
It characterized in that it comprises; a control unit for controlling a valve that can be installed in the electrolyte passage connected to each of the first and second anode electrolyte tanks and the first and second cathode electrolyte tanks to control the opening and closing of the passage; .

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