Ocv cell for flow battery and flow battery ocv monitoring method

Abstract

The application relates to an OCV battery for a liquid flow battery and a liquid flow battery OCV monitoring method, wherein the OCV battery comprises four electrode chambers, and the battery used in the monitoring method is the OCV battery. According to the OCV battery and the monitoring method, the open circuit voltages of two half batteries of the liquid flow battery can be measured at the same time, and the open circuit voltage of the whole battery can be calculated according to the open circuit voltages of the two half batteries. Moreover, the accuracy of the measured OCV value of the liquid flow battery can be ensured during long-term operation of the battery by regularly replacing the constant potential solution. Meanwhile, the application has the advantages of simple process, simple operation, low cost and long-term efficient and stable operation of the battery.

Description

Technical Field

[0001] This invention relates to the field of flow batteries, and in particular to an OCV battery for flow batteries and a monitoring method thereof. Background Technology

[0002] Flow batteries have become one of the most promising technologies for large-scale energy storage in renewable energy generation, grid peak shaving and valley filling, emergency and backup power stations due to their outstanding advantages such as independent and adjustable system capacity and power, rapid response, safety and reliability, environmental friendliness, long cycle life, and easy maintenance and regeneration.

[0003] When designing flow batteries and systems, an OCV (Optical Calibration Value) battery is required to monitor the electrolyte state and ensure it remains under control. During flow battery operation, active materials in the electrolyte migrate through the separator. Due to factors such as varying migration rates, the valence states of the positive and negative electrolytes shift over long-term operation. However, the voltage values ​​obtained by measuring electrolytes with imbalanced valence states using existing OCV batteries do not accurately reflect the electrolyte's state. Therefore, designing and inventing a new OCV battery and monitoring method plays a crucial role in ensuring the long-term reliability of the system. Summary of the Invention

[0004] The purpose of this invention is to solve the above-mentioned problems and to provide an OCV battery for flow batteries and a monitoring method thereon.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: An OCV battery for flow batteries includes an end plate, a current collector, an electrode located in a through hole in the middle of an annular electrode frame, a separator, an electrode located in a through hole in the middle of a first annular electrode frame, a current collector with a through hole in the middle, an electrode located in a through hole in the middle of a second annular electrode frame, a separator, an electrode located in a through hole in the middle of an annular electrode frame, a current collector, and an end plate, all stacked sequentially. The annular electrode frame is a flat plate structure with a through hole in the middle that runs through the surfaces of the two side plates. The flat plate electrode is placed in the through hole in the middle of the annular electrode frame. Two corresponding through holes are opened on the end plate and the current collector, forming two sets of channels that are connected to the through holes in the middle of the annular electrode frame adjacent to the current collector, respectively serving as the electrolyte inlet channel and the electrolyte outlet channel. The first and second annular electrode frames are flat plate structures with through holes in the middle that penetrate the surfaces of the two side plates. A through hole A and a through hole B, which are connected to the through hole in the middle of the annular electrode frame, are respectively opened on the outer side wall of the first and second annular electrode frames, serving as the inlet and outlet channels of the liquid. The current collector with a through hole in the middle is a flat plate structure with one or more through holes in the middle that penetrate the surfaces of the two side plates; the through holes in the middle of the first annular electrode frame and the second annular electrode frame are connected through the through holes in the middle of the current collector with a through hole in the middle.

[0006] The battery components are stacked and sealed in sequence to form an OCV battery; the electrodes on both sides of the separator are respectively arranged opposite to each other on both sides of the separator; The OCV battery includes four electrode chambers. The two electrode chambers on both sides are formed by a current collector, an annular electrode frame, and a separator, respectively. The two electrode chambers in the middle are formed by a separator, a first annular electrode frame or a second annular electrode frame, and a current collector with a through hole in the middle, respectively.

[0007] The two open ends of the through holes on the current collector with through holes in the middle part are in contact with the electrodes located in the through holes in the first annular electrode frame and the electrodes located in the through holes in the second annular electrode frame, respectively. The number of through holes on the current collector is an integer not less than 1, and the total area of ​​all through holes is not greater than the area of ​​any single electrode in the through holes in the first annular electrode frame and the through holes in the second annular electrode frame.

[0008] Liquid inlets or liquid outlets are respectively provided on the sidewalls of the first and second annular electrode frames; the liquid inlets or outlets are located on the side of the electrode frames.

[0009] The current collector is made of conductive metal or conductive non-metal.

[0010] A flow battery OCV monitoring method, using any of the OCV battery structures, introduces the positive and negative electrolytes of the flow battery into the two outer electrode chambers near the end plates of the OCV battery through the electrolyte inlet and electrolyte outlet channels on the two end plates, respectively, so that the positive and negative electrolytes of the flow battery flow through the two electrodes near the end plates. The solution outside the battery is introduced into the through hole in the middle of the first or second annular electrode frame through the liquid inlet channel on the first or second annular electrode frame, and then enters the through hole in the middle of the second or first annular electrode frame through the through hole of the current collector, and then flows out through the liquid outlet channel on the second or first annular electrode frame, so that the solution flows sequentially through the two electrodes near the through hole current collector in the middle. The OCV of the flow battery is obtained by monitoring the voltage between the current collector with the through hole in the middle and the two current collectors near the end plate.

[0011] The solution is a solution with a constant potential value, which is filled in a solution storage tank and circulated back and forth in the through hole in the first annular electrode frame, the through hole in the second annular electrode frame, and the solution storage tank by a liquid pump. The constant potential solution is one or more of the following: a solution containing macromolecules, the electrolyte of the flow battery, cadmium and cadmium sulfate, copper and copper oxide, and lead.

[0012] The flow batteries include, but are not limited to, all-vanadium flow batteries, sodium polysulfide bromine flow batteries, iron-chromium flow batteries, all-chromium flow batteries, and vanadium-bromine flow batteries.

[0013] The voltage difference between the current collector with the through hole in the middle and the two current collectors near the end plate, which are monitored separately, is the OCV value of the flow battery under test. Attached Figure Description

[0014] Figure 1 The diagram shows the structure of the OCV battery according to the present invention, wherein: 1 and 1' - first and second end plates, 2 and 2' - first and second current collectors, 3 and 3' - annular electrode frames, 4 and 4' - first and second separators, 5 - first annular electrode frame, 5' - second annular electrode frame, and 6 - current collector with through holes; Figure 2 The diagram shows a current collector structure with a through hole, wherein: 6 - current collector with a through hole, 7 - through hole; Figure 3 The diagram shows a current collector structure with a through hole, wherein: 6 - current collector with a through hole, 7 - through hole; Figure 4 The diagram shows a current collector structure with a through hole, wherein: 6 - current collector with a through hole, 7 - through hole; Figure 5 The diagram shows the structure of the first and second annular electrode frames, where A or B is a through hole.

[0015] 1) This invention proposes an OCV battery structure and detection method, which can simultaneously measure the open-circuit voltage of two half-cells of a flow battery, and calculate the state of charge of the electrolyte based on the open-circuit voltage values ​​of the half-cells. Furthermore, the open-circuit voltage of the full cell can be calculated based on the open-circuit voltages of the two half-cells.

[0016] 2) Regularly replacing the constant potential solution described in this invention can ensure the accuracy of the measured OCV value of the flow battery during long-term operation of the battery, and at the same time ensure the accuracy of the calculated state of charge of the electrolyte.

[0017] 3) The process of this invention is simple, easy to operate, and low in cost, while ensuring that the battery can operate efficiently and stably for a long time. Detailed Implementation

[0018] The following embodiments are further illustrations of the present invention, but are not intended to limit the scope of the invention.

[0019] Example 1 Prepare first and second end plates 1 and 1', first and second current collectors 2 and 2', annular electrode frames 3 and 3', electrodes, first and second diaphragms 4 and 4', sealing gaskets, first annular electrode frame 5 and second annular electrode frame 5', current collector 6 with through holes, fastening screws, etc. The electrodes are made of carbon felt, with dimensions of 6cm*8cm. Both the first and second annular electrode frames 5 and 5' are PVC boards with through holes in the middle, with dimensions of 10cm*12cm and a thickness of 8mm. The through holes are 6cm*8cm in size, and the edge of the through hole is 2cm from the outer edge of the electrode frame. Through holes A and B, connected to the through holes in the middle of the annular electrode frames, are opened on the outer side walls of the first and second annular electrode frames 5 and 5'. The diameter of through holes A and B is 3mm. Figure 5 As shown, the carbon felt within the first annular electrode frame 5 and the second annular electrode frame 5' is represented by carbon felt 1 and carbon felt 2. The current collector with through holes in the middle is a carbon composite plate with a thickness of 2mm and a size of 10cm*12cm. This current collector has through holes 7 penetrating the surfaces of both sides of the plate, and the through holes have a size of 4cm*6cm. Figure 4 As shown, the edge of the through hole is 3cm away from the outer edge of the electrode frame.

[0020] The above components are stacked and sealed in sequence to form an OCV battery. The stacking order is as follows: first end plate 1, first current collector 2, annular electrode frame 3, carbon felt, first separator 4, first carbon felt, first annular electrode frame 5, current collector with through holes 6, second annular electrode frame 5', second carbon felt, second separator 4', carbon felt, annular electrode frame 3', second current collector 2', second end plate 1'. Figure 1 As shown.

[0021] The OCV battery consists of four chambers, but the two middle chambers contain the same liquid due to their perforated current collector structure. When the OCV battery is running, liquid from outside the battery is introduced into the first annular electrode frame 5 through liquid port A. After flowing through the first carbon felt, the liquid enters the second carbon felt through the perforated current collector 7, flows through the second carbon felt, and then exits the battery through liquid port B on the second annular electrode frame 5'.

[0022] The OCV battery was connected to a vanadium redox flow battery system. The two outer electrode chambers near the endplate were circulated with the positive and negative electrolytes from a long-term operating vanadium redox flow battery, respectively. The two middle chambers were circulated with a sulfuric acid aqueous solution containing 1.5 mol / L V(III) ions. The voltages between current collectors 2 and 6, and between 2' and 6, were monitored to be 1.123V and -0.218V, respectively, yielding the two open-circuit voltages for the positive and negative electrodes. The OCV value of the vanadium redox flow battery was then calculated as 1.123V - (-0.218V) = 1.341V. Based on the half-cell voltage, the state of charge (SOC) of the positive electrolyte could be calculated. pos and the state of charge (SOC) of the negative electrode electrolyte neg .

[0023] Comparative Example 1 A conventional OCV battery structure contains only two electrode chambers (corresponding to the two electrode chambers on both sides of the embodiment of the present invention, which are respectively surrounded by a current collector, an annular electrode frame and a separator, and contain only one separator, which is composed of a first end plate 1, a first current collector 2, an annular electrode frame 3, carbon felt, a first separator 4, carbon felt, an annular electrode frame 3', a second current collector 2', and a second end plate 1'). The positive and negative electrolytes of the battery under test are respectively introduced into the two chambers, and the voltage between the two current collectors of the OCV battery is detected.

[0024] Using a conventional OCV battery structure, connected to the all-vanadium redox flow battery system of Example 1, only the OCV value could be measured, which was 1.341V. Since no half-cell voltage value was available, the state of charge (SOC) of the positive and negative electrolytes could not be calculated separately.

[0025] Example 2 Prepare first and second end plates 1 and 1', first and second current collectors 2 and 2', annular electrode frames 3 and 3', electrodes, first and second diaphragms 4 and 4', sealing gaskets, first annular electrode frame 5 and second annular electrode frame 5', current collector 6 with through holes, fastening screws, and other components. The electrodes are carbon felt with dimensions of 6cm*8cm. The first annular electrode frame 5 and the second annular electrode frame 5' are both PVC boards with through holes in the middle. The electrode frame dimensions are 10cm*12cm, and the electrode frame thickness is 8mm. The through holes are 6cm*8cm in size, and the edge of the through hole is 2cm away from the outer edge of the electrode frame. Through holes A and B are opened on the outer side wall of the first annular electrode frame 5 and the second annular electrode frame 5', which are connected to the through holes in the middle of the annular electrode frame. The diameter of through holes A and B is 3mm. The carbon felt inside the first annular electrode frame 5 and the second annular electrode frame 5' is represented by carbon felt 1 and carbon felt 2. The current collector with through holes in the middle is a carbon composite plate with a thickness of 2mm and a size of 10cm*12cm. The current collector has through holes 7 that penetrate the surface of the plates on both sides. The through holes are circles with a diameter of 5cm. The distance from the edge of the through circle to the outer edge of the electrode frame is 2.5cm, 3.5cm, 2.5cm, and 3.5cm.

[0026] The above components are stacked and sealed in sequence to form an OCV battery. The stacking order is as follows: first end plate 1, first current collector 2, annular electrode frame 3, carbon felt, first separator 4, first carbon felt, first annular electrode frame 5, current collector with through hole 6, second annular electrode frame 5', second carbon felt, second separator 4', carbon felt, annular electrode frame 3', second current collector 2', and second end plate 1'.

[0027] The OCV battery consists of four chambers, but the two middle chambers contain the same liquid due to their perforated current collector structure. When the OCV battery is running, liquid from outside the battery is introduced into the first annular electrode frame 5 through liquid port A. After flowing through the first carbon felt, the liquid enters the second carbon felt through the perforated current collector 7, flows through the second carbon felt, and then exits the battery through liquid port B on the second annular electrode frame 5'.

[0028] The OCV battery was connected to an iron-chromium redox flow battery system. The two outer electrode chambers near the end plates were irrigated with the positive and negative electrolytes of the iron-chromium redox flow battery, respectively. The two middle chambers were irrigated with a sulfuric acid aqueous solution containing 1.5 mol / L LCr(III) ions. The voltages between current collectors 2 and 6, and between 2' and 6, were monitored and found to be 0.843 V and -0.328 V, respectively, yielding the two open-circuit voltages for the positive and negative electrodes. The OCV value of the iron-chromium redox flow battery was then calculated as 0.843 V - (-0.328 V) = 1.171 V. Based on the half-cell voltage, the state of charge (SOC) of the positive electrolyte could be calculated. pos and the state of charge (SOC) of the negative electrode electrolyte neg .

[0029] Comparative Example 2 A conventional OCV battery structure contains only two electrode chambers (corresponding to the two electrode chambers on both sides of the embodiment of the present invention, which are respectively surrounded by a current collector, an annular electrode frame and a separator, and contain only one separator, which is composed of a first end plate 1, a first current collector 2, an annular electrode frame 3, carbon felt, a first separator 4, carbon felt, an annular electrode frame 3', a second current collector 2', and a second end plate 1'). The positive and negative electrolytes of the battery under test are respectively introduced into the two chambers, and the voltage between the two current collectors of the OCV battery is detected.

[0030] Using a conventional OCV battery structure, connected to the iron-chromium redox flow battery system of Example 2, only the OCV value could be measured, which was 1.171V. Since no half-cell voltage value was available, the state of charge (SOC) of the positive and negative electrolytes could not be calculated separately.

[0031] Example 3 Prepare first and second end plates 1 and 1', first and second current collectors 2 and 2', annular electrode frames 3 and 3', electrodes, first and second diaphragms 4 and 4', sealing gaskets, first annular electrode frame 5 and second annular electrode frame 5', current collector 6 with through holes, fastening screws, and other components. The electrodes are carbon felt with dimensions of 6cm*8cm. The first annular electrode frame 5 and the second annular electrode frame 5' are both PVC boards with through holes in the middle. The electrode frame dimensions are 10cm*12cm, and the electrode frame thickness is 8mm. The through holes are 6cm*8cm in size, and the edge of the through hole is 2cm away from the outer edge of the electrode frame. Through holes A and B are opened on the outer side wall of the first annular electrode frame 5 and the second annular electrode frame 5', which are connected to the through holes in the middle of the annular electrode frame. The diameter of through holes A and B is 3mm. The carbon felt inside the first annular electrode frame 5 and the second annular electrode frame 5' is represented by carbon felt 1 and carbon felt 2. The central current collector with through holes is a 2mm thick carbon composite plate, measuring 10cm x 12cm. This current collector has through-hole areas 7 penetrating the surfaces of both sides of the plate, each 4cm x 6cm in size. The edge of each through-hole area 7 is 3cm from the outer edge of the electrode frame. Fifteen circles with a diameter of 1cm are located within the through-hole area. The above components are stacked and sealed in sequence to form an OCV battery. The stacking order is as follows: first end plate 1, first current collector 2, annular electrode frame 3, carbon felt, first separator 4, first carbon felt, first annular electrode frame 5, current collector with through hole 6, second annular electrode frame 5', second carbon felt, second separator 4', carbon felt, annular electrode frame 3', second current collector 2', and second end plate 1'.

[0032] The OCV battery consists of four chambers, but the two middle chambers contain the same liquid due to their perforated current collector structure. When the OCV battery is running, liquid from outside the battery is introduced into the first annular electrode frame 5 through liquid port A. After flowing through the first carbon felt, the liquid enters the second carbon felt through the perforated current collector 7, flows through the second carbon felt, and then exits the battery through liquid port B on the second annular electrode frame 5'.

[0033] The OCV battery was connected to a sodium polysulfide bromine flow battery system. The two outer electrode chambers near the endplate were supplied with the positive and negative electrolytes of a vanadium redox flow battery, respectively. The two middle chambers were supplied with a solution containing 1.3 mol / L sodium polysulfide. The voltages between current collectors 2 and 6, and between 2' and 6, were monitored to be 1.254V and -0.426V, respectively, yielding the open-circuit voltages of the positive and negative electrodes. Therefore, the OCV value of the sodium polysulfide bromine flow battery was calculated to be 1.254V - (-0.426V) = 1.68V. Based on the half-cell voltage, the state of charge (SOC) of the positive electrolyte could be calculated.pos and the state of charge (SOC) of the negative electrode electrolyte neg .

[0034] Comparative Example 3 A conventional OCV battery structure contains only two electrode chambers (corresponding to the two electrode chambers on both sides of the embodiment of the present invention, which are respectively surrounded by a current collector, an annular electrode frame and a separator, and contain only one separator, which is composed of a first end plate 1, a first current collector 2, an annular electrode frame 3, carbon felt, a first separator 4, carbon felt, an annular electrode frame 3', a second current collector 2', and a second end plate 1'). The positive and negative electrolytes of the battery under test are respectively introduced into the two chambers, and the voltage between the two current collectors of the OCV battery is detected.

[0035] Using a conventional OCV battery structure, connected to the sodium polysulfide bromine flow battery system of Example 3, only the OCV value could be measured, which was 1.68V. Since no half-cell voltage value was available, the state of charge (SOC) of the positive and negative electrolytes could not be calculated separately.

Claims

1. An OCV battery for flow batteries, characterized in that: The device includes, in sequence, an end plate, a current collector, an electrode located in a through hole in the middle of an annular electrode frame, a diaphragm, an electrode located in a through hole in the middle of a first annular electrode frame, a current collector with a through hole in the middle, an electrode located in a through hole in the middle of a second annular electrode frame, a diaphragm, an electrode located in a through hole in the middle of an annular electrode frame, a current collector, and an end plate; The annular electrode frame is a flat plate structure with a through hole in the middle that runs through the surfaces of the two side plates. The flat plate electrode is placed in the through hole in the middle of the annular electrode frame. Two corresponding through holes are opened on the end plate and the current collector, forming two sets of channels that are connected to the through holes in the middle of the annular electrode frame adjacent to the current collector, respectively serving as the electrolyte inlet channel and the electrolyte outlet channel. The first and second annular electrode frames are flat plate structures with through holes in the middle that penetrate the surfaces of the two side plates. A through hole A and a through hole B, which are connected to the through hole in the middle of the annular electrode frame, are respectively opened on the outer side wall of the first and second annular electrode frames, serving as the inlet and outlet channels of the liquid. The current collector with a through hole in the middle is a flat plate structure with one or two or more through holes in the middle that penetrate the surfaces of both sides of the plate; the through holes in the middle of the first annular electrode frame and the through holes in the middle of the second annular electrode frame are connected through the through holes in the middle of the current collector with a through hole in the middle. The battery components are stacked and sealed in sequence to form an OCV battery; the electrodes on both sides of the separator are respectively arranged opposite to each other on both sides of the separator; The OCV battery includes four electrode chambers. The two electrode chambers on both sides are formed by a current collector, an annular electrode frame, and a separator, respectively. The two electrode chambers in the middle are formed by a separator, a first annular electrode frame or a second annular electrode frame, and a current collector with a through hole in the middle, respectively.

2. The OCV battery according to claim 1, characterized in that: The two open ends of the through holes on the current collector with through holes in the middle part are in contact with the electrodes located in the through holes in the first annular electrode frame and the electrodes located in the through holes in the second annular electrode frame, respectively. The number of through holes on the current collector is an integer not less than 1, and the total area of ​​all through holes is not greater than the area of ​​any single electrode in the through holes in the first annular electrode frame and the through holes in the second annular electrode frame.

3. The OCV battery according to claim 1, characterized in that: Liquid inlets or liquid outlets are respectively provided on the sidewalls of the first and second annular electrode frames; the liquid inlets or outlets are located on the side of the electrode frames.

4. The OCV battery according to claim 1 or 2, characterized in that: The current collector is made of conductive metal or conductive non-metal.

5. A method for monitoring the OCV of a flow battery, characterized in that: Using any one of the OCV battery structures described in claims 1-4, the positive and negative electrolytes of the flow battery are respectively introduced into the two outer electrode chambers of the OCV battery near the end plates through the electrolyte inlet channel and the electrolyte outlet channel on the two end plates, so that the positive and negative electrolytes of the flow battery flow through the two electrodes near the end plates respectively. The solution outside the battery is introduced into the through hole in the middle of the first or second annular electrode frame through the liquid inlet channel on the first or second annular electrode frame, and then enters the through hole in the middle of the second or first annular electrode frame through the through hole of the current collector, and then flows out through the liquid outlet channel on the second or first annular electrode frame, so that the solution flows through the two electrodes near the through hole current collector in the middle in sequence; The OCV of the flow battery is obtained by monitoring the voltage between the current collector with the through hole in the middle and the two current collectors near the end plate.

6. The OCV monitoring method for a flow battery according to claim 5, characterized in that: The solution is a solution with a constant potential value, which is filled in a solution storage tank and is circulated back and forth in the middle through hole of the first annular electrode frame, the middle through hole of the second annular electrode frame, and the solution storage tank by a liquid pump; The solution with a constant potential value is one of the following: a solution containing organic macromolecules, a flow battery electrolyte, cadmium and cadmium sulfate solution, copper and copper oxide solution, and lead solution.

7. The flow battery OCV monitoring method according to claim 5, characterized in that: The flow battery is one of the following: vanadium redox flow battery, sodium polysulfide bromine flow battery, iron-chromium flow battery, chromium redox flow battery, or vanadium-bromine flow battery.

8. The method for monitoring the OCV of a flow battery according to claim 5, 6, or 7, characterized in that: The voltage difference between the current collector with the through hole in the middle and the two current collectors near the end plate, which are monitored separately, is the OCV value of the flow battery under test.

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