OCV battery and application

Abstract

The invention relates to an OCV battery, an application and a method, in particular to the field of flow batteries, and the OCV battery comprises three electrode chambers. By using the OCV battery provided by the invention, the open-circuit voltages of the two half batteries of the 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. By implementing the method, the accuracy of the measured OCV value of the flow battery can be ensured, and the battery maintenance can be reduced. And meanwhile, the process is simple, the operation is simple and convenient, the cost is low, and the long-term efficient and stable operation of the flow battery can be ensured.

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] With the continuous depletion of fossil fuels worldwide and the increasing awareness of environmental protection, renewable energy power generation technologies are gaining popularity. Renewable energy sources mainly include wind, solar, biomass, and ocean energy, which are typically converted into electricity. However, these renewable energy power generation methods are significantly discontinuous and unstable due to geographical location, weather conditions, and other factors. To smooth and stabilize renewable energy power generation output, resolve the time difference between power generation and consumption, and improve power quality and grid reliability, it is essential to develop efficient energy storage technologies. Flow batteries, due to their outstanding advantages such as independently adjustable system capacity and power, rapid response, safety and reliability, environmental friendliness, long cycle life, and ease of maintenance and regeneration, have become one of the most promising technologies for large-scale energy storage in renewable energy power generation, grid peak shaving and valley filling, and emergency and backup power stations.

[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 method for monitoring OCV in flow batteries.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] An OCV battery for flow batteries includes a first end plate, a first current collector, an electrode located in a through hole in the middle of an annular electrode frame, a separator, a third current collector, an electrode located in a through hole in the middle of the first annular electrode frame, a separator, an electrode located in a through hole in the middle of the annular electrode frame, a second current collector, and a second end plate, which are stacked sequentially.

[0007] The annular electrode frame is a flat plate structure with a through hole in the middle that penetrates the surface 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 first end plate and the first current collector, as well as on the second end plate and the second 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 first current collector or the second current collector, respectively serving as the electrolyte inlet channel and the electrolyte outlet channel.

[0008] The first annular electrode frame is a flat plate structure with a through hole in the middle that penetrates the surfaces of the two side plates;

[0009] The third current collector has a sheet-like or ring-like structure, is placed on the electrode surface inside the through hole in the middle of the first ring-shaped electrode frame, and is respectively attached to the surface of the electrode.

[0010] An electrode support frame is provided inside the through hole in the middle of the first annular electrode frame;

[0011] The electrode support frame is a perforated plate with through holes having an area of ​​0.05-3 cm². 2 Preferred size: 0.2-1cm 2 The porosity is 20-90% of the surface area, preferably 40-80%.

[0012] At the side edge of the third current collector, a collector ear extends in a direction parallel to and away from the surface of the current collector, and the collector ear extends through the side of the first annular electrode frame to the outside of the electrode frame.

[0013] The two sides of the first annular electrode frame are respectively provided with grooves that penetrate the central through hole and the side walls of its surrounding edges;

[0014] After the collector ear is sealed in the groove, part of the collector ear protrudes outside the side of the electrode frame.

[0015] The shape of the through holes on the electrode support skeleton plate can be selected from one or more of the following: triangle, rectangle, and hexagon.

[0016] The shape and size of the electrode support frame surface are the same as or equivalent to the cross-sectional shape and size of the through hole in the middle of the electrode frame parallel to the plate surface;

[0017] The thickness of the electrode support frame is the same as the thickness of the first annular electrode frame, or the thickness of the electrode support frame plus the thickness of the third current collector equals the thickness of the first annular electrode frame. They are stacked in the middle through hole of the first annular electrode frame.

[0018] The electrode is placed in each through hole of the electrode support skeleton plate, and all or part of the through holes are in contact with the diaphragm and the third current collector at the same time.

[0019] 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;

[0020] The OCV battery contains three electrode chambers. The two electrode chambers on the sides are formed by a first current collector or a second current collector, an annular electrode frame and a separator, respectively, forming two electrolytes flowing through the chambers. The middle electrode chamber is formed by two separators and a first annular electrode frame between them, forming an independent sealed structure.

[0021] The first to third current collectors are made of metal or conductive non-metallic materials, and the electrodes are one or more of carbon felt, carbon cloth, and carbon paper.

[0022] Using the aforementioned OCV battery structure, the positive and negative electrolytes of the flow battery are introduced into the two outer electrode chambers of the OCV battery near the first and second end plates through the electrolyte inlet and electrolyte outlet channels on the first and second end plates, respectively, so that the positive and negative electrolytes of the flow battery flow through the two electrodes near the end plates.

[0023] A constant potential state can be formed by filling the middle electrode chamber with solution or by spraying a solid substance onto the electrode surface in the first annular electrode frame.

[0024] The OCV of the flow battery is obtained by monitoring the voltage between the first current collector or the second current collector and the third current collector respectively.

[0025] The filling solution is an aqueous solution in which different substances form a constant potential state, and is sealed within a first annular electrode frame; the substance is Fe. 3+ / Fe 2+ V 3+ / V 4+ TEMP, Br2 / Br - I2 / I - One or more of the following, wherein the solid substance is anthraquinone or anthraquinone-2,6-disulfonate.

[0026] 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, or vanadium-bromine flow batteries.

[0027] The voltage difference between the first current collector and the third current collector, and the voltage difference between the third current collector and the second current collector, are the OCV values ​​of the flow battery under test.

[0028] Beneficial results of the present invention:

[0029] 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.

[0030] 2) Through this invention, while monitoring the open-circuit voltage of half-cells, the installation of pipelines, pumps and storage tanks can be reduced, costs can be lowered and the system compactness can be increased.

[0031] 3) By setting a support layer in the through hole of the first annular electrode frame, the pressure of the liquid pressure generated when the electrolyte flows through the two end chambers during the operation of the OCV battery can be solved, so that the separator can be kept in good condition and the life of the OCV battery can be increased.

[0032] 3) By sealing the chamber within the first annular electrode frame, a non-flowing medium can be used as the constant potential material, and the necessary accessories due to the flowing phase, such as pumps, pipelines and storage tanks, can be reduced, thereby reducing the cost of the battery and system.

[0033] 4) Since a closed structure is formed between the two diaphragms, using a suitable substance or material as a constant potential substance or material can eliminate the need for daily maintenance, thus ensuring the accuracy of the measured OCV value of the flow battery during long-term operation.

[0034] 5) 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. Attached Figure Description

[0035] Figure 1 The OCV battery structure of the present invention comprises: 1-end plate (first end plate, second end plate), 2-current collector (first current collector, second current collector, third current collector), 3-annular electrode frame, 4-separator, and 5-first annular electrode frame.

[0036] Figure 2 The first annular electrode frame assembly structure is defined as follows: 5-first annular electrode frame, 6-third current collector, and 7-electrode support frame. Detailed Implementation

[0037] The following embodiments are further illustrations of the present invention, but are not intended to limit the scope of the invention.

[0038] Example 1

[0039] Prepare the first and second end plates, annular electrode frames, first annular electrode frames, electrodes, diaphragms, first to third current collectors, sealing gaskets, fastening screws, and other components. The electrodes are made of carbon felt and are 6cm*8cm in size. The electrode frames are all PVC boards with through holes in the middle, and the electrode frame size is 10cm*12cm. The electrode frame thickness is 8mm. The through holes are 6cm*8cm rectangular, and the edge of the through hole is 2cm away from the outer edge of the electrode frame. Meanwhile, the surface of the first annular electrode frame is provided with grooves that penetrate the central through hole and the side walls of its surrounding edges. The third current collector is a sheet structure with a size of 3cm*12cm, and a collecting ear extends from the side edge in a direction parallel to and away from the surface of the current collector. The collecting ear extends through the side of the first annular electrode frame to the outside of the electrode frame. The third current collector and the diaphragm clamp the carbon felt electrode 5' in the first annular electrode frame. The support layer inside the first annular electrode frame is a rectangular perforated plate with a thickness of 8mm and a size of 6cm*8cm made of PVC material. The cross-section of the parallel plate surface of each through hole is a square with a side length of 0.6cm. There are 70 holes with a spacing of 0.2cm, and the opening rate is 52.5%. The electrode 5' inside the first annular electrode frame is also a square with a side length of 0.6cm and a thickness of 8mm. The electrode is placed in each through hole of the perforated plate. The number of through holes in the electrode is the same as that in the perforated plate. The electrode in the through hole is in contact with the diaphragm and the third current collector at the same time.

[0040] The above components are stacked and sealed in sequence to form an OCV battery. The stacking order is as follows: end plate 1, current collector 2, annular electrode frame 3, electrode 3' (placed in the through hole in the middle of the annular electrode frame 3), separator 4, third current collector 6, first annular electrode frame 5 (the middle part houses the electrode support frame and electrode 5'), separator 4, electrode 3' (placed in the through hole in the middle of the annular electrode frame 3), annular electrode frame 3, current collector 2, end plate 1.

[0041] The OCV battery consists of three chambers. When the OCV battery is operating, the two outer electrode chambers near the endplate are respectively supplied with the positive and negative electrolytes of the flow battery under test. When this OCV battery is connected to a vanadium redox flow battery system, the piping assembly includes a negative electrode inlet pipe and a positive electrode inlet pipe. The outlet of the negative electrode electrolyte tank is connected to the negative electrode inlet connector of the OCV battery via the negative electrode inlet pipe. The outlet of the positive electrode electrolyte tank is connected to the positive electrode inlet connector of the OCV battery via the positive electrode inlet pipe. The negative electrode return connector of the OCV battery is connected to the return port of the negative electrode electrolyte tank via the negative electrode return pipe. The positive electrode return connector of the OCV battery is connected to the return port of the positive electrode electrolyte tank via the positive electrode return pipe. The middle chamber is filled with 0.75 mol / L V electrolyte. 3+ / 0.75mol / LV 4+In this aqueous solution, the voltages between the first and second current collectors and the third current collector are monitored and found to be 0.751V and -0.759V respectively, yielding the two open-circuit voltages for the positive and negative electrodes. Therefore, the OCV value of the vanadium redox flow battery is calculated to be 0.751V - (-0.759V) = 1.510V. Based on the standard correspondence between the half-cell voltage and the state of charge, the state of charge (SOC) of the positive electrode electrolyte can be calculated. pos The state of charge (SOC) of the negative electrode electrolyte is 90%. neg It is 73%.

[0042] Comparative Example 1

[0043] A conventional OCV battery structure contains only two electrode chambers, specifically an end plate 1, a current collector 2, an annular electrode frame 3, an electrode 3' (placed within a through hole in the center of the annular electrode frame 3), a separator 4, an electrode 3' (placed within a through hole in the center of the annular electrode frame 3), an annular electrode frame 3, a current collector 2, and an end plate 1, but does not include the first annular electrode frame assembly of this invention. 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 measured.

[0044] Using a conventional OCV battery structure, connected to the vanadium redox flow battery system of Example 1, the piping assembly includes a negative electrode inlet pipe and a positive electrode inlet pipe. The outlet of the negative electrode electrolyte tank is connected to the negative electrode inlet connector of the OCV battery via the negative electrode inlet pipe, and the outlet of the positive electrode electrolyte tank is connected to the positive electrode inlet connector of the OCV battery via the positive electrode inlet pipe. The negative electrode return connector of the OCV battery is connected to the return port of the negative electrode electrolyte tank via the negative electrode return pipe, and the positive electrode return connector of the OCV battery is connected to the return port of the positive electrode electrolyte tank via the positive electrode return pipe. Only the OCV value can be measured, and the measured OCV value is 1.510V. Since there is no half-cell voltage value, the state of charge (SOC) of the positive and negative electrode electrolytes cannot be calculated separately.

[0045] Comparative Example 1'

[0046] A set of OCV battery components was prepared, as shown in Example 1, except that the support layer inside the first annular electrode frame was different. The square in the OCV battery had a side length of 1.9 cm, 12 openings with a spacing of 0.1 cm, and an opening rate of 90.3%. The rest of the components were the same as in Example 1. As described in Example 1, after the OCV battery was connected to the vanadium redox flow battery system, it was found that after only 14 days of operation, the separator broke due to stress on the support layer's framework, causing it to be unable to continue working normally.

[0047] Example 2

[0048] Prepare the first and second end plates, annular electrode frames, first annular electrode frames, electrodes, diaphragms, first to third current collectors, sealing gaskets, fastening screws, and other components. The electrodes are made of carbon felt and are 6cm*8cm in size. The electrode frames are all PVC boards with through holes in the middle, and the electrode frame size is 10cm*12cm. The electrode frame thickness is 8mm, and the through hole size is 6cm*8cm. The edge of the through hole is 2cm away from the outer edge of the electrode frame. Meanwhile, the surface of the first annular electrode frame is provided with grooves that penetrate the central through hole and the side walls of its surrounding edges. The third current collector is a sheet structure with a size of 3cm*12cm, and a collecting ear extends from the side edge in a direction parallel to and away from the surface of the current collector. The collecting ear extends through the side of the first annular electrode frame to the outside of the electrode frame. The third current collector and the diaphragm clamp the carbon felt electrode in the first annular electrode frame. The support layer inside the first annular electrode frame is a rectangular perforated plate with a thickness of 8mm and a size of 6cm*8cm made of PTFE material. The cross-section of the parallel plate surface of each through hole is triangular, with the side length of the equilateral triangle being 1cm. There are 55 openings with a spacing of 0.2cm, and the opening rate is 49.6%. The electrode size inside the first annular electrode frame is also an equilateral triangle with a side length of 1cm and a thickness of 8mm. The electrode is placed in each through hole of the perforated plate, and the number of through holes in the electrode is the same as that in the perforated plate. The electrode in the through hole is in contact with the diaphragm and the third current collector at the same time.

[0049] The above components are stacked and sealed in sequence to form an OCV battery. The stacking order is as follows: end plate 1, current collector 2, annular electrode frame 3, electrode 3' (placed in the through hole in the middle of the annular electrode frame 3), separator 4, third current collector 6, first annular electrode frame 5 (the middle part houses the electrode support frame and electrode 5'), separator 4, electrode 3' (placed in the through hole in the middle of the annular electrode frame 3), annular electrode frame 3, current collector 2, end plate 1.

[0050] The OCV battery consists of three chambers. When the OCV battery is operating, the two outer electrode chambers near the endplate are respectively supplied with the positive and negative electrolytes of the flow battery under test. When this OCV battery is connected to a vanadium redox flow battery system, the piping assembly includes a negative electrode inlet pipe and a positive electrode inlet pipe. The outlet of the negative electrode electrolyte tank is connected to the negative electrode inlet connector of the OCV battery via the negative electrode inlet pipe, and the outlet of the positive electrode electrolyte tank is connected to the positive electrode inlet connector of the OCV battery via the positive electrode inlet pipe. The negative electrode return connector of the OCV battery is connected to the return port of the negative electrode electrolyte tank via the negative electrode return pipe, and the positive electrode return connector of the OCV battery is connected to the return port of the positive electrode electrolyte tank via the positive electrode return pipe. The middle chamber is filled with 0.5 mol / L Fe. 3+ / 0.5mol / L Fe 2+In this solution, the voltages between the first and second current collectors and the third current collector are monitored and found to be 0.312V and -1.105V respectively, yielding the two open-circuit voltages for the positive and negative electrodes. Therefore, the OCV value of the vanadium redox flow battery is 0.312V - (-1.105V) = 1.417V. Based on the standard correspondence between the half-cell voltage and the state of charge, the state of charge (SOC) of the positive electrode electrolyte can be calculated. pos The state of charge (SOC) of the negative electrode electrolyte is 51%. neg It is 48%.

[0051] Comparative Example 2

[0052] Conventional OCV battery structures contain only two electrode chambers and do not include the first annular electrode frame assembly of the present invention. As described in Comparative Example 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.

[0053] Using a conventional OCV battery structure, connected to the all-vanadium redox flow battery system of Example 2, as described in Comparative Example 1, only the OCV value could be measured, which was 1.417V. Since no half-cell voltage value was available, the state of charge (SOC) of the positive and negative electrolytes could not be calculated separately.

[0054] Example 3

[0055] Prepare the first and second end plates, annular electrode frames, first annular electrode frames, electrodes, diaphragms, first to third current collectors, sealing gaskets, fastening screws, and other components. The electrodes are made of carbon felt and are 6cm*8cm in size. The electrode frames are all PVC boards with through holes in the middle, and the electrode frame size is 10cm*12cm. The electrode frame thickness is 8mm, and the through hole size is 6cm*8cm. The edge of the through hole is 2cm away from the outer edge of the electrode frame. Meanwhile, the surface of the first annular electrode frame is provided with grooves that penetrate the central through hole and the side walls of its surrounding edges. The third current collector is a sheet structure with a size of 3cm*12cm, and a collecting ear extends from the side edge in a direction parallel to and away from the surface of the current collector. The collecting ear extends through the side of the first annular electrode frame to the outside of the electrode frame. The third current collector and the diaphragm clamp the carbon felt electrode in the first annular electrode frame. The support layer inside the first annular electrode frame is a rectangular perforated plate with a thickness of 8mm and a size of 6cm*8cm made of PVC material. The cross-section of the parallel plate surface of each through hole is hexagonal with a side length of 0.5cm. There are 30 holes with a spacing of 0.2cm, and the opening rate is 40.6%. The electrode inside the first annular electrode frame is also a regular hexagon with a side length of 0.5cm and a thickness of 8mm. The electrode is placed in each through hole of the perforated plate. The number of through holes in the electrode is the same as the number of through holes in the perforated plate. The electrode in the through hole is in contact with the diaphragm and the third current collector at the same time.

[0056] The above components are stacked and sealed in sequence to form an OCV battery. The stacking order is as follows: end plate 1, current collector 2, annular electrode frame 3, electrode 3' (placed in the through hole in the middle of the annular electrode frame 3), separator 4, third current collector 6, first annular electrode frame 5 (the middle part houses the electrode support frame and electrode 5'), separator 4, electrode 3' (placed in the through hole in the middle of the annular electrode frame 3), annular electrode frame 3, current collector 2, end plate 1.

[0057] The OCV battery consists of three chambers. When the OCV battery is running, the two outer electrode chambers near the endplate are respectively supplied with the positive and negative electrolytes of the flow battery under test. When this OCV battery is connected to a vanadium redox flow battery system, the piping assembly includes a negative electrode inlet pipe and a positive electrode inlet pipe. The outlet of the negative electrode electrolyte tank is connected to the negative electrode inlet connector of the OCV battery via the negative electrode inlet pipe. The outlet of the positive electrode electrolyte tank is connected to the positive electrode inlet connector of the OCV battery via the positive electrode inlet pipe. The negative electrode return connector of the OCV battery is connected to the return port of the negative electrode electrolyte tank via the negative electrode return pipe. The positive electrode return connector of the OCV battery is connected to the return port of the positive electrode electrolyte tank via the positive electrode return pipe. The middle chamber is filled with 0.5 mol / L Br2 / 0.5 mol / L Br2. - In this solution, the voltages between the first and second current collectors and the third current collector can be monitored, yielding -0.084V and -1.478V respectively, thus obtaining the two open-circuit voltages for the positive and negative electrodes. Therefore, the OCV value of the vanadium redox flow battery is -0.084V - (-1.478V) = 1.394V. Based on the standard correspondence between the half-cell voltage and the state of charge, the state of charge (SOC) of the positive electrode electrolyte can be calculated. pos The state of charge (SOC) of the negative electrode electrolyte is 53%. neg It is 50%.

[0058] Comparative Example 3

[0059] Conventional OCV battery structures contain only two electrode chambers and do not include the first annular electrode frame assembly of the present invention. As described in Comparative Example 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.

[0060] Using a conventional OCV battery structure, connected to the all-vanadium redox flow battery system of Example 3, as described in Comparative Example 1, only the OCV value could be measured, which was 1.394V. Since no half-cell voltage value was available, the state of charge (SOC) of the positive and negative electrolytes could not be calculated separately.

[0061] Example 4

[0062] Prepare the first and second end plates, annular electrode frames, first annular electrode frames, electrodes, diaphragms, first to third current collectors, sealing gaskets, fastening screws, and other components. The electrodes are made of carbon felt and are 6cm*8cm in size. The electrode frames are all PVC boards with through holes in the middle, and the electrode frame size is 10cm*12cm. The electrode frame thickness is 8mm, and the through hole size is 6cm*8cm. The edge of the through hole is 2cm away from the outer edge of the electrode frame. Meanwhile, the surface of the first annular electrode frame is provided with grooves that penetrate the central through hole and the side walls of its surrounding edges. The third current collector is annular in structure, and each side edge has a collecting ear extending in a direction parallel to and away from the surface of the current collector. The collecting ear extends through the side of the first annular electrode frame to the outside of the electrode frame. The third current collector and the diaphragm clamp the carbon felt electrode in the first annular electrode frame. The support layer inside the first annular electrode frame is a rectangular perforated plate with a thickness of 8mm and a size of 6cm*8cm made of PTFE material. The cross-section of the parallel plate surface of each through hole is an equilateral triangle with a side length of 1cm. There are 55 openings with a spacing of 0.2cm, and the opening rate is 49.6%. The electrode inside the first annular electrode frame is also an equilateral triangle with a side length of 1cm and a thickness of 8mm. The electrode is placed in each through hole of the perforated plate. The number of through holes in the electrode is the same as the number of through holes in the perforated plate. The electrode in the through hole is in contact with the diaphragm and the third current collector at the same time.

[0063] The above components are stacked and sealed in sequence to form an OCV battery. The stacking order is as follows: end plate 1, current collector 2, annular electrode frame 3, electrode 3' (placed in the through hole in the middle of the annular electrode frame 3), separator 4, third current collector 6, first annular electrode frame 5 (the middle part houses the electrode support frame and electrode 5'), separator 4, electrode 3' (placed in the through hole in the middle of the annular electrode frame 3), annular electrode frame 3, current collector 2, end plate 1.

[0064] The OCV battery consists of three chambers. When the OCV battery is running, the two outer electrode chambers closest to the end plate are respectively filled with the positive and negative electrolytes of the flow battery under test. The OCV battery is connected to the iron-chromium redox flow battery system. The piping assembly includes a negative electrode inlet pipe and a positive electrode inlet pipe. The outlet of the negative electrode electrolyte storage tank is connected to the negative electrode inlet connector of the OCV battery through the negative electrode inlet pipe. The outlet of the positive electrode electrolyte storage tank is connected to the positive electrode inlet connector of the OCV battery through the positive electrode inlet pipe. The negative electrode return connector of the OCV battery is connected to the return port of the negative electrode electrolyte storage tank through the negative electrode return pipe. The positive electrode return connector of the OCV battery is connected to the return port of the positive electrode electrolyte storage tank through the positive electrode return pipe. The intermediate chamber is filled with a 2mol / L sulfuric acid aqueous solution containing 1.5mol / L CCr(III) ions. At this time, the voltages between the first current collector, the second current collector, and the third current collector can be monitored to be 0.831V and -0.314V, respectively, to obtain the two open-circuit voltage values ​​of the positive and negative electrodes. Therefore, the OCV value of the iron-chromium redox flow battery is obtained as 0.831V - (-0.314V) = 1.145V. Based on the standard correspondence between the half-cell voltage and the state of charge, the SOC of the positive electrode electrolyte at this point can be calculated. pos The state of charge (SOC) of the negative electrode electrolyte is 60%. neg It is 55%.

[0065] Comparative Example 4

[0066] Conventional OCV battery structures contain only two electrode chambers and do not include the first annular electrode frame assembly of the present invention. As described in Comparative Example 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.

[0067] Using a conventional OCV battery structure, connected to the iron-chromium redox flow battery system of Example 4, as described in Comparative Example 1, only the OCV value could be measured, which was 1.145V. Since no half-cell voltage value was available, the state of charge (SOC) of the positive and negative electrolytes could not be calculated separately.

[0068] Example 5

[0069] Prepare the first and second end plates, annular electrode frames, first annular electrode frames, electrodes, diaphragms, first to third current collectors, sealing gaskets, fastening screws, and other components. The electrodes are made of carbon felt and are 6cm*8cm in size. The electrode frames are all PVC boards with through holes in the middle, and the electrode frame size is 10cm*12cm. The electrode frame thickness is 8mm, and the through hole size is 6cm*8cm. The edge of the through hole is 2cm away from the outer edge of the electrode frame. Meanwhile, the surface of the first annular electrode frame is provided with grooves that penetrate the central through hole and the side walls of its surrounding edges. The third current collector is a sheet structure with a size of 3cm*12cm, and a collecting ear extends from the side edge in a direction parallel to and away from the surface of the current collector. The collecting ear extends through the side of the first annular electrode frame to the outside of the electrode frame. The third current collector and the diaphragm clamp the carbon felt electrode in the first annular electrode frame. The support layer inside the first annular electrode frame is a rectangular perforated plate with a thickness of 8mm and a size of 6cm*8cm made of PVC material. The cross-section of the parallel plate surface of each through hole is hexagonal with a side length of 0.5cm. There are 30 holes with a spacing of 0.2cm, and the opening rate is 40.6%. The electrode inside the first annular electrode frame is also a regular hexagon with a side length of 0.5cm and a thickness of 8mm. The electrode is placed in each through hole of the perforated plate. The number of through holes in the electrode is the same as the number of through holes in the perforated plate. The electrode in the through hole is in contact with the diaphragm and the third current collector at the same time.

[0070] The above components are stacked and sealed in sequence to form an OCV battery. The stacking order is as follows: end plate 1, current collector 2, annular electrode frame 3, electrode 3' (placed in the through hole in the middle of the annular electrode frame 3), separator 4, third current collector 6, first annular electrode frame 5 (the middle part houses the electrode support frame and electrode 5'), separator 4, electrode 3' (placed in the through hole in the middle of the annular electrode frame 3), annular electrode frame 3, current collector 2, end plate 1.

[0071] The OCV battery consists of three chambers. When the OCV battery is running, the two outer electrode chambers closest to the end plate are respectively filled with the positive and negative electrolytes of the flow battery under test. The OCV battery is connected to a sodium polysulfide bromine flow battery system. The piping assembly includes a negative electrode inlet pipe and a positive electrode inlet pipe. The outlet of the negative electrode electrolyte tank is connected to the negative electrode inlet connector of the OCV battery through the negative electrode inlet pipe. The outlet of the positive electrode electrolyte tank is connected to the positive electrode inlet connector of the OCV battery through the positive electrode inlet pipe. The negative electrode return connector of the OCV battery is connected to the return port of the negative electrode electrolyte tank through the negative electrode return pipe. The positive electrode return connector of the OCV battery is connected to the return port of the positive electrode electrolyte tank through the positive electrode return pipe. The intermediate chamber is filled with 1.3 mol / L sodium polysulfide solution. At this time, the voltages between the first current collector, the second current collector, and the third current collector can be monitored to be 1.269V and -0.433V, respectively, to obtain the two open-circuit voltage values ​​of the positive and negative electrodes. Therefore, the OCV value of the sodium polysulfide bromine flow battery is obtained as 1.269V - (-0.433V) = 1.702V. Based on the standard correspondence between the half-cell voltage and the state of charge, the SOC of the positive electrode electrolyte at this point can be calculated. pos The state of charge (SOC) of the negative electrode electrolyte is 40%. neg It is 46%.

[0072] Comparative Example 5

[0073] Conventional OCV battery structures contain only two electrode chambers and do not include the first annular electrode frame assembly of the present invention. As described in Comparative Example 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.

[0074] Using a conventional OCV battery structure, connected to the sodium polysulfide bromine flow battery system of Example 5, as described in Comparative Example 1, only the OCV value could be measured, which was 1.702V. 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, characterized in that: It includes a first end plate, a first current collector, an electrode located in a through hole in the middle of an annular electrode frame, a diaphragm, a third current collector, an electrode located in a through hole in the middle of the first annular electrode frame, a diaphragm, an electrode located in a through hole in the middle of an annular electrode frame, a second current collector, and a second end plate, which are stacked sequentially. The annular electrode frame is a flat plate structure with a through hole in the middle that penetrates the surface 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 first end plate and the first current collector, as well as on the second end plate and the second 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 first current collector or the second current collector, respectively serving as the electrolyte inlet channel and the electrolyte outlet channel. The first annular electrode frame is a flat plate structure with a through hole in the middle that penetrates the surfaces of the two side plates; The third current collector has a sheet-like or ring-like structure, is placed on the electrode surface inside the through hole in the middle of the first ring-shaped electrode frame, and is in contact with the surface of the electrode. An electrode support frame is provided inside the through hole in the middle of the first annular electrode frame; The electrode support frame is a perforated plate with through holes having an area of ​​0.05-3 cm². 2 Preferred size: 0.2-1cm 2 The porosity is 20-90% of the surface area, preferably 40-80%.

2. The OCV battery according to claim 1, characterized in that: At the side edge of the third current collector, a collector ear extends in a direction parallel to and away from the surface of the current collector, and the collector ear extends through the side of the first annular electrode frame to the outside of the electrode frame.

3. The OCV battery according to claim 1, characterized in that: The two sides of the first annular electrode frame are respectively provided with grooves that penetrate the central through hole and the side walls of its surrounding edges; After the collector ear is sealed in the groove, part of the collector ear protrudes outside the side of the electrode frame.

4. The OCV battery according to claim 1, characterized in that: The shape of the through holes on the electrode support skeleton plate can be selected from one or more of the following: triangle, rectangle, and hexagon. The shape and size of the electrode support frame surface are the same as or equivalent to the cross-sectional shape and size of the through hole in the middle of the electrode frame parallel to the plate surface; The thickness of the electrode support frame is the same as the thickness of the first annular electrode frame, or the thickness of the electrode support frame plus the thickness of the third current collector is equal to the thickness of the first annular electrode frame. They are stacked in the middle through hole of the first annular electrode frame. The electrode is placed in each through hole of the electrode support skeleton plate, and all or part of the through holes are in contact with the diaphragm and the third current collector at the same time.

5. The OCV battery according to claim 1, characterized in that: 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 contains three electrode chambers. The two electrode chambers on the sides are formed by a first current collector or a second current collector, an annular electrode frame and a separator, respectively, forming two electrolytes flowing through the chambers. The middle electrode chamber is formed by two separators and a first annular electrode frame between them, forming an independent sealed structure.

6. The OCV battery according to claim 1, characterized in that: The first to third current collectors are made of metal or conductive non-metallic materials, and the electrodes are one or more of carbon felt, carbon cloth, and carbon paper.

7. An application of an OCV battery, characterized in that: Using any one of the OCV battery structures described in claims 1-6, the positive and negative electrolytes of the flow battery are respectively introduced into the two outer electrode chambers of the OCV battery near the first and second end plates through the electrolyte inlet and electrolyte outlet channels on the first and second end plates, respectively, so that the positive and negative electrolytes of the flow battery flow through the two electrodes near the end plates. The electrode chamber in the middle is filled with solution, and / or the electrode surface in the first annular electrode frame is treated with solid material spraying to form a constant potential state. The OCV of the flow battery is obtained by monitoring the voltage between the first current collector or the second current collector and the third current collector respectively.

8. The application according to claim 7, characterized in that: The filling solution is an aqueous solution in which different substances form a constant potential state, and is sealed within a first annular electrode frame; the substance is Fe. 3+ / Fe 2+ V 3+ / V 4+ TEMP, Br2 / Br - I2 / I - One or more of the following, wherein the solid substance is anthraquinone or anthraquinone-2,6-disulfonate.

9. The application according to claim 7, characterized in that: 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, or vanadium-bromine flow batteries.

10. The application according to claim 7, 8 or 9, characterized in that: The voltage difference between the first current collector and the third current collector, and the voltage difference between the third current collector and the second current collector, are the OCV values ​​of the flow battery under test.

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