A magnetic iron-based hybrid flow battery

Abstract

The application relates to a magnetic iron-based hybrid liquid flow battery, which comprises a battery shell (1), a positive electrode (2), a negative electrode (3), an ion exchange membrane (5), a positive electrode electrolyte storage tank (6) and a negative electrode electrolyte storage tank (7), wherein the positive electrode (2) and the negative electrode (3) are installed in the battery shell (1), the positive electrode (2) and the negative electrode (3) and the positive and negative electrode electrolytes thereof are separated by the ion exchange membrane (5), the negative electrode (3) comprises a magnet (4), iron powder, a negative electrode current collector and a negative electrode electrolyte, the iron powder is adsorbed on the magnet, the magnet is arranged in the negative electrode current collector, and the magnetic induction lines of the magnet pass through the negative electrode current collector. Compared with the prior art, the liquid flow battery has the characteristics of long cycle charging and discharging service life, low production cost and high raw material yield, and has wide application value in the field of large-scale and efficient electrochemical energy storage technology.

Description

Technical Field

[0001] This invention belongs to the field of flow battery technology, and in particular relates to a magnetic iron-based hybrid flow battery. Background Technology

[0002] As the installed capacity of new energy sources such as wind and solar power increases, the demand for energy storage devices to overcome the intermittency and volatility of wind and solar power generation is growing significantly. Compared with traditional pumped hydro storage, new energy storage technologies generally have advantages such as shorter construction cycles, more flexible site selection, and stronger regulation capabilities.

[0003] Electrochemical energy storage is a major force in new energy storage technologies, among which flow battery technology has received widespread attention due to its use of aqueous electrolytes, high cycle life, and long lifespan. Flow batteries are a large-scale, high-efficiency electrochemical energy storage technology. Generally, flow batteries have advantages such as long lifespan, high depth of discharge, and high safety due to aqueous electrolytes, but their energy density is not high. Because stationary energy storage systems do not have high energy density requirements, power and capacity designs are independent, and module combination and battery structure placement are easy; therefore, flow batteries are suitable for large-scale energy storage.

[0004] Conventional flow batteries consist of positive and negative electrodes, electrolytes, and other battery components. The positive and negative electrolytes inside the battery are separated by a proton exchange membrane. A large amount of electrolyte is stored in an external container. When the battery is in use, the electrolyte is pumped into the battery to participate in the redox reaction. Flow battery technology has made significant progress in the past half-century, resulting in a series of technical routes and demonstrative products. Representative systems include all-vanadium, iron-chromium, zinc-bromine, zinc-nickel, zinc-iron, zinc-air, and all-iron flow battery technologies. Currently, the all-vanadium flow battery is the most commercially viable and technologically mature flow battery technology. However, all-vanadium flow battery technology is still limited by vanadium production capacity and cost. Therefore, iron-chromium flow batteries have also received extensive research and attention. However, problems such as hydrogen evolution at the negative electrode reduce the battery's energy efficiency; cross-contamination between the positive and negative electrolytes reduces battery capacity and efficiency, limiting further development. Zinc-bromine, zinc-nickel, zinc-iron, and zinc-air flow battery technologies using metallic zinc mainly face insurmountable problems such as the formation of zinc dendrites, which limit the development of this technology.

[0005] Currently, the company that commercializes all-iron flow batteries is ESS in North America. After a period of exploration, ESS has expanded the application scale of all-iron flow batteries from the 100 kW·h level to the MW·h level, and the technology is becoming more and more mature and accepted by the market.

[0006] ESS's invention patent CN110301060B discloses an electrolyte for iron flow batteries that can electroplate ductile Fe onto the negative electrode while maintaining the performance, reliability, and efficiency of iron redox flow batteries. Furthermore, iron can be generated and electroplated onto the electrode more quickly, achieving a higher charging rate for all-iron flow batteries. However, some drawbacks remain. Under certain extreme charging conditions, such as low temperature or high charging current (due to the rapid charging rate, iron is generated quickly at the negative electrode), the iron plating may be stressed and may crack and peel off from the negative electrode. Therefore, high plating stress can degrade the negative electrode, reducing the capacity and efficiency of the redox flow battery cell.

[0007] Chinese patent CN109728314B discloses a flow battery structure and method for attaching magnetic particles to electrodes under an external magnetic field. The flow battery is externally equipped with a magnetic field loading device, which generates a magnetic field that penetrates the positive and negative electrodes. Magnetic nanoparticles, used to increase the specific surface area of ​​the electrodes, are attached to both electrodes, with the attachment surfaces of the nanoparticles facing the same direction, allowing them to adhere tightly to the electrode surface under the influence of the magnetic field. This invention primarily utilizes the attachment of nano-magnetic particles to the electrodes. Under the influence of an external magnetic field, the magnetic particles adhere to the electrode surface by magnetic force rather than van der Waals force, ensuring the uniformity and stability of the nanoparticle attachment. This maintains high electrochemical activity and a high specific surface area during long-term charge-discharge cycles, offering advantages in steadily improving the voltage efficiency of the flow battery. However, this technology uses magnetite (Fe3O4) magnetic particles, resulting in low energy conversion efficiency, and the magnetic field lines passing through the ion exchange membrane of the flow battery can easily cause short circuits.

[0008] Patent application CN113178607A discloses a method for improving the transmission performance of a flow battery through the synergistic effect of magnetic field and temperature, and the flow battery itself. In the flow battery, a magnetic field generator is positioned on both sides of the negative and positive electrodes to provide a magnetic field; a heater provides a suitable temperature environment for the flow battery. By placing the eutectic solvent electrolyte flow battery in a magnetic field and simultaneously maintaining it at a temperature of 15–65°C, the electrochemical and physical properties of the eutectic solvent electrolyte are adjusted, increasing the diffusion coefficient of ions in the electrolyte. This effectively solves the problem of low battery power density caused by the high viscosity and large mass transfer resistance of existing eutectic solvent electrolytes; thereby improving the energy efficiency and power density of the battery. However, the organic eutectic agents used in this technology (ethylene glycol, propylene glycol, urea, and choline chloride, etc.) have problems such as high viscosity, easy oxidation and decomposition, and poor cycle stability, which limit its practical application. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of the prior art and provide a magnetic iron-based hybrid flow battery with cyclic charging and discharging, long service life, low production cost and high raw material yield.

[0010] The objective of this invention can be achieved through the following technical solution: A magnetic iron-based hybrid flow battery, comprising a battery casing, a positive electrode, a negative electrode, an ion exchange membrane, a positive electrode electrolyte storage tank, and a negative electrode electrolyte storage tank, wherein the positive and negative electrodes are installed inside the battery casing, and the positive and negative electrodes and their positive and negative electrolytes are separated by the ion exchange membrane. The negative electrode comprises a magnet, iron powder, a negative electrode current collector, and a negative electrode electrolyte, wherein the iron powder is the negative electrode active material, the iron powder is adsorbed on the magnet, and the magnet is placed inside the negative electrode current collector, so that the magnetic field lines of the magnet pass through the negative electrode current collector.

[0011] Furthermore, the magnet is a U-shaped magnet, and multiple U-shaped magnets are placed in the negative electrode current collector to adsorb the negative electrode iron powder material. This ensures that the magnetic field lines of the magnet pass through the negative electrode current collector but not through the proton exchange membrane or the positive electrode structure of the battery. This prevents the iron powder from falling off the negative electrode of the battery with the flow of the electrolyte during charging and discharging, and avoids the iron powder connecting the positive and negative electrode structures, which would cause a short circuit.

[0012] More preferably, the magnet is a row of U-shaped magnets arranged side by side, and the distance between the top of each U-shaped magnet and the ion exchange membrane is greater than the distance between the magnetic poles of the U-shaped magnets, so that the magnetic field lines of the magnet pass through the negative current collector, but the magnetic field strength is significantly reduced at the location of the proton exchange membrane or the positive electrode structure of the battery.

[0013] Furthermore, the negative electrode current collector is made of stainless steel and covers the U-shaped magnet. Specifically, the negative electrode current collector structure is an open-top groove, with its length matching the length of multiple U-shaped magnets arranged side by side, and its height being the same as the height of a single U-shaped magnet.

[0014] Furthermore, the positive and negative electrodes are placed horizontally, with the negative electrode located below the positive electrode. This utilizes the combined effect of gravity and magnetism to prevent the active material of the negative electrode from detaching from the negative electrode structure.

[0015] Furthermore, the flow battery can adopt a general flow battery structure with independent circulation of positive and negative electrolytes, that is, the positive electrolyte storage tank is connected to the positive electrolyte inlet and outlet through an independent circulation pipeline;

[0016] The negative electrode electrolyte storage tank is connected to the negative electrode electrolyte inlet and outlet via an independent circulation pipeline;

[0017] A circulation pump is installed on the circulation pipeline.

[0018] Furthermore, flow batteries can also achieve the recycling of positive and negative electrolytes through an insulated circulating pump structure connected to the positive and negative electrolytes. Compared with the independent circulation structure of positive and negative electrolytes in general flow batteries, this improves the utilization efficiency of the electrolyte. A preferred specific structure is as follows:

[0019] The positive electrolyte storage tank is connected to the positive electrode via a positive electrolyte conduction pipe;

[0020] The negative electrode electrolyte storage tank is connected to the negative electrode through a negative electrode electrolyte conduction pipe;

[0021] The positive and negative electrodes are connected by a pipe, and an insulated circulation pump is installed on the pipe;

[0022] The positive electrolyte storage tank and the negative electrolyte storage tank are connected by a pressure balancing conduit.

[0023] Furthermore, the insulated circulation pump is a positive displacement pump made of insulating material, meaning that the electrolyte is transported as a discontinuous fluid, preventing the formation of a conductive circuit between the positive and negative electrodes of the battery and thus avoiding energy loss.

[0024] Furthermore, the electrolyte is a mixture containing ferrous and ferric ions, with ferric ion concentrations of 0–5 mol / L and ferrous ion concentrations of 0–5 mol / L, and the combined concentration of ferrous and ferric ions is not less than 0.1 mol / L. The electrolyte is controlled by monitoring the electrode potential during charging and discharging, or by using a separate selective ion concentration sensor, and by adjusting the flow rate of the circulating pump and the load power.

[0025] Pumps used for electrolyte delivery (including circulating pumps and insulated circulating pumps) can regulate the direction of electrolyte flow to achieve forward and reverse flow of electrolyte between the positive and negative electrodes of the battery during charging and discharging.

[0026] One or more pumps are used to transport the electrolyte, connecting multiple flow battery positive and negative electrode structures to achieve the cascade utilization of different voltages formed by different electrolyte concentrations during charging and discharging, thereby improving energy conversion efficiency.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. This invention employs a magnetic battery negative electrode structure, consisting of a magnet, iron powder, a negative electrode current collector, and a negative electrode electrolyte. The magnetic field lines of the magnet pass through the negative electrode current collector but not through the proton exchange membrane or the battery positive electrode structure. It is placed horizontally, and the iron powder, the negative electrode active material, is adsorbed onto the negative electrode current collector through gravity and magnetic induction, thereby preventing the negative electrode active material from falling off.

[0029] 2. In this invention, the magnetic field lines pass through the negative electrode current collector and maintain a distance from the proton exchange membrane of the battery greater than the distance between the magnetic poles of the U-shaped magnet; the active material used in this invention is iron powder, which has good conductivity and can be adsorbed onto the surface of the negative electrode under magnetic induction, reducing the risk of active material shedding.

[0030] 3. This invention proposes a novel flow battery structure that changes the limitation of independent circulation of electrolyte between the positive and negative electrodes in traditional flow batteries, and realizes the recycling of electrolyte between the positive and negative electrodes, thereby improving electrolyte utilization efficiency and reducing the cost of flow batteries.

[0031] 3. The magnetic iron-based hybrid flow battery of the present invention has the characteristics of cyclic charging and discharging, long service life, low production cost and high raw material yield, and has wide application value in the field of large-scale high-efficiency electrochemical energy storage technology. It also has the advantages of low cost of active materials and electrolytes and high energy storage conversion efficiency. This large-scale high-efficiency electrochemical energy storage can be widely used in power grid and related energy storage fields. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the magnetic iron-based flow battery structure with interconnected positive and negative electrode electrolytes in Example 1.

[0033] Figure 2 This is a schematic diagram of the magnetic electrode structure;

[0034] Figure 3 This is a schematic diagram of the magnetic iron-based flow battery structure with an independent positive and negative electrode electrolyte circulation structure, as shown in Example 2.

[0035] Figure 4 This is a schematic diagram of a comparative battery structure;

[0036] The diagram shows a schematic of a novel magnetic electrode flow battery.

[0037] 1: Battery casing 2: Positive electrode 3: Negative electrode

[0038] 4: U-shaped magnet; 5: Ion exchange membrane; 6: Positive electrode electrolyte storage tank

[0039] 7: Negative electrolyte storage tank; 8: Positive electrolyte conduit; 9: Negative electrolyte conduit.

[0040] 10: Insulated circulating pump; 11: Conduit a; 12: Conduit b

[0041] 13: Pressure balancing conduit 14: Circulation pump 15: Filling port b 16: Filling port a. Detailed Implementation

[0042] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0043] Flow batteries can be classified into aqueous electrolytes and non-aqueous electrolytes according to their electrolytes. The cost of non-aqueous flow battery electrolytes consists of the cost of active materials and organic solvents. The high cost of non-aqueous organic electrolytes and the fact that most active materials are toxic and flammable will become bottlenecks in the process of large-scale commercialization.

[0044] The cost of electrolytes in aqueous flow batteries is primarily determined by the cost of active materials. Iron, as the most abundant metal element mined by humans, is low-cost, non-toxic, and environmentally friendly. Therefore, it possesses significant cost and resource advantages, making it an ideal source of active materials for flow batteries and capable of meeting the future demands of large-scale grid-scale energy storage. However, all-iron flow batteries still have certain technical limitations, restricting their further development.

[0045] All-iron flow batteries are divided into acidic and alkaline systems. Acidic all-iron flow batteries are more mature in commercial development. Their positive electrode is the ferric ion / ferrous ion redox couple, and the negative electrode is the ferrous ion / Fe(O) redox couple. The electrode reactions are as follows:

[0046] Positive electrode: Fe 3+ +e - Fe 2+ E 0 =0.77V(1)

[0047] Negative electrode: Fe 2+ +2e - <=>Fe E 0 = -0.44V(2)

[0048] The standard voltage of this flow battery is 1.21V.

[0049] During the charging process, elemental iron is electrodeposited from the ferrous ion solution onto the negative electrode, while at the positive electrode, ferrous ions are oxidized into ferric ions. The discharge process involves the corresponding reverse reaction.

[0050] During the charging process, according to the chemical reaction (2), iron will be generated at the negative electrode of the battery. In order to prevent the iron from falling off the negative electrode current collector and entering the electrolyte, the present invention sets a set of magnetic materials composed of U-shaped magnets in the negative electrode structure of the battery, and the stack structure of the flow battery is placed in a horizontal direction. Iron powder is adsorbed by gravity and magnetic induction to prevent iron powder from falling off the negative electrode current collector structure, so as to enhance the cycle repeatability of the electrode and thus improve the energy storage conversion efficiency.

[0051] Furthermore, since the solid elemental iron is deposited in the iron-based flow battery, it provides the possibility for the recycling of the electrolyte between the positive and negative electrodes. The present invention also develops a novel flow battery structure for recycling the electrolyte between the positive and negative electrodes: (1) During the charging process, a solution containing ferrous ions enters the negative electrode structure of the flow battery from the negative electrode electrolyte storage tank and electrolyzes out elemental iron. The molar ratio of the electrolyzed part is about 1 / 3 or less of the ferrous ion content. The deposited elemental iron is adsorbed on the negative electrode current collector with a magnetic structure. Then, it is transported into the positive electrode area through an insulated circulation pump, and the remaining ferrous ions are oxidized into iron ions in the positive electrode structure and enter the positive electrode electrolyte storage tank; (2) During the discharge process, the electrolyte containing iron ions is transported from the positive electrode electrolyte storage tank, the iron ions are reduced to ferrous ions, and the acidity increases. Then, it is transported into the negative electrode structure through an insulated circulation pump to react with elemental iron, realizing the recycling of the electrolyte and improving the utilization efficiency of the electrolyte.

[0052] This magnetic iron-based hybrid flow battery technology, in addition to possessing the general advantages of flow batteries such as ultra-long cycle life, high safety and stability, scalability, low cost, and environmental friendliness, also has advantages such as lower active material and electrolyte costs and higher energy storage conversion efficiency. This large-scale, high-efficiency electrochemical energy storage technology can be widely used in power grids and related energy storage fields.

[0053] The magnetic iron-based hybrid flow battery structure of this invention includes:

[0054] (I) A magnetic iron-based flow battery with an independent positive and negative electrode electrolyte circulation structure; (Appendix) Figure 3 (As shown)

[0055] (II) A magnetic iron-based flow battery with a circulating structure connecting positive and negative electrode electrolytes; (Appendix) Figure 1 (As shown)

[0056] in

[0057] 1. Magnetic iron-based flow battery with independent circulation of positive and negative electrode electrolytes: including the flow battery shell, the battery negative electrode structure and negative electrode electrolyte storage tank, the battery positive electrode structure and positive electrode electrolyte storage tank, as well as proton exchange membrane, positive electrode transfer pump, negative electrode transfer pump, etc.

[0058] (1) The negative electrode structure of the battery consists of a magnet, iron powder, negative electrode current collector and negative electrode electrolyte. The magnetic field lines of the magnet pass through the negative electrode current collector but do not pass through the proton exchange membrane or the positive electrode structure of the battery.

[0059] (2) The positive electrode structure of the battery consists of a positive electrode current collector and a positive electrode electrolyte containing iron ions;

[0060] (3) When the battery is in use, the positive electrode delivery pump and the negative electrode delivery pump pump the positive and negative electrolyte into the positive and negative electrode structures inside the battery, respectively, to participate in the redox reaction of the battery.

[0061] II. Magnetic iron-based flow battery with interconnected positive and negative electrode electrolyte circulation structure: including flow battery shell, battery negative electrode structure and negative electrode electrolyte storage tank, battery positive electrode structure and positive electrode electrolyte storage tank, as well as proton exchange membrane, bidirectional insulating transfer pump, etc.

[0062] (1) The negative electrode structure of the battery consists of a magnet, iron powder, negative electrode current collector and negative electrode electrolyte. The magnetic field lines of the magnet pass through the negative electrode current collector, but the magnetic field strength is significantly reduced at the proton exchange membrane or the positive electrode structure of the battery.

[0063] (2) The positive electrode structure of the battery consists of a positive electrode current collector and a positive electrode electrolyte containing iron ions;

[0064] (3) By using an insulated circulating pump structure that connects the positive and negative electrolytes, the positive and negative electrolytes are recycled, which is different from the independent circulation structure of the positive and negative electrolytes in general flow batteries. The pump used for electrolyte delivery is a volumetric insulated circulating pump, that is, the delivery of electrolyte is intermittent, to prevent the formation of a conductive circuit between the positive and negative electrodes of the battery, which would cause battery discharge.

[0065] (4) During the charging process, the solution containing ferrous ions enters the negative electrode structure of the flow battery from the negative electrode electrolyte storage tank and electrolyzes out elemental iron. The molar ratio of the electrolyzed part is about 1 / 3 or less of the ferrous ion content. The precipitated elemental iron is adsorbed on the negative electrode current collector with a magnetic structure. Then it is transported into the positive electrode area through an insulated circulation pump, where the remaining ferrous ions are oxidized into iron ions in the positive electrode structure and enter the positive electrode electrolyte storage tank.

[0066] (5) During the discharge process, the electrolyte containing iron ions is transported from the positive electrode electrolyte storage tank. The iron ions are reduced to ferrous ions, and the acidity increases. Then, it is transported to the negative electrode structure through the insulated circulation pump to react with elemental iron, thereby realizing the recycling of the electrolyte and improving the utilization efficiency of the electrolyte.

[0067] This novel flow battery features a long cycle life, low production cost, and high raw material yield, making it widely applicable in the field of large-scale, high-efficiency electrochemical energy storage technology.

[0068] The following detailed description uses specific embodiments.

[0069] Example 1

[0070] Figure 1This is a schematic diagram of a magnetic iron-based hybrid flow battery, including a battery casing 1, a positive electrode 2, a negative electrode 3, an ion exchange membrane 5, a positive electrolyte storage tank 6, and a negative electrolyte storage tank 7. The positive electrode 2 and the negative electrode 3 are installed inside the battery casing 1. Both the positive electrode 2 and the negative electrode 3 include electrolyte and electrodes placed horizontally in the electrolyte and led out of the battery casing 1. The negative electrode 3 is located below the positive electrode 2. The ion exchange membrane 5 is placed between the positive electrode 2 and the negative electrode 3, separating the positive and negative electrolytes. This separation prevents the active materials from mixing and causing "fluid leakage" and self-discharge, while allowing selective permeation of specific ions to ensure the conduction of the internal circuitry of the battery.

[0071] The negative electrode 3 includes a magnet 31, iron powder, a negative electrode current collector 32, and a negative electrode electrolyte. The iron powder is adsorbed onto the magnet, which is placed within the negative electrode current collector, allowing its magnetic field lines to pass through it. The magnet is a U-shaped magnet 4, with multiple U-shaped magnets placed within the negative electrode current collector 32. The negative electrode current collector 32 is made of stainless steel and has an open-top groove shape. Its length matches the length of the multiple U-shaped magnets arranged side-by-side, and its height is the same as the height of a single U-shaped magnet. The magnetic field lines 33 of the magnet pass through the negative electrode current collector, and the distance between the magnet and the ion exchange membrane 5 of the battery is greater than the distance between the poles of the U-shaped magnets. Therefore, the magnetic field strength is significantly reduced at the proton exchange membrane or the positive electrode structure of the battery. Figure 2 As shown.

[0072] In this embodiment, the recycling of the positive and negative electrolytes is achieved through an insulated circulating pump structure connecting the positive and negative electrolytes. Specifically:

[0073] The positive and negative electrolytes are stored in positive electrolyte tank 6 and negative electrolyte tank 7, respectively, and are connected to the positive electrode 2 and negative electrode 3 of the battery via positive electrolyte conduit 8 and negative electrolyte conduit 9, respectively. Positive electrolyte tank 6 and negative electrolyte tank 7 are connected via pressure balancing conduit 13. A volumetric insulated circulation pump 10 is installed between positive electrode 2 and negative electrode 3; positive electrode 2 is connected to the insulated circulation pump 10 via conduit a11, and negative electrode 3 is connected to the insulated circulation pump 10 via conduit b12. Electrochemical charging and discharging reactions occur at the positive electrode 2 and negative electrode 3 of the battery, and the active substances participating in the chemical reaction exist in the corresponding positive electrolyte tank 6 and negative electrolyte tank 7 in the form of aqueous solutions. The electrolyte is transported back and forth between the positive and negative electrodes inside the battery by a volumetric insulated circulating pump 10 and pipeline switching.

[0074] The electrolyte in the positive electrode electrolyte storage tank 6 is an aqueous solution containing iron ions, and in this embodiment, the initial storage capacity before charging is 0. A filling port a16 is provided in the positive electrode electrolyte storage tank 6 for replenishing the electrolyte.

[0075] The electrolyte in the negative electrode electrolyte storage tank 7 is an aqueous solution containing ferrous ions. In this embodiment, it is specifically a 100L solution containing 1.0mol / L FeCl2, 3.0mol / L KCl, and 0.4mol / L H3BO3. A filling port b15 is provided in the negative electrode electrolyte storage tank 7 for replenishing the electrolyte.

[0076] During charging, a solution containing ferrous ions enters the negative electrode 2 structure of the flow battery from the negative electrolyte storage tank 7, electrolytically releasing elemental iron. By controlling the liquid flow rate and electrolysis power, the molar ratio of the electrolytically released portion is approximately 1 / 3 of the ferrous ion content. After charging is completed, approximately 33 mol of elemental iron is deposited and adsorbed onto the magnetic negative electrode current collector. Then, it is transported to the positive electrode region by the insulated circulation pump 10, where the remaining ferrous ions are oxidized into iron ions in the positive electrode structure and enter the positive electrolyte storage tank 6. At this time, the positive electrolyte storage tank 6 contains 100 L of a solution containing 0.667 mol / L iron ions.

[0077] During the discharge process, the electrolyte containing iron ions is transported from the positive electrode electrolyte storage tank 6. The iron ions are reduced to ferrous ions, and the acidity increases. Then, it is transported to the negative electrode structure through the insulated circulation pump 10 to react with elemental iron, realizing the recycling of the electrolyte, improving the utilization efficiency of the electrolyte, and saving the amount of active material.

[0078] In this embodiment, the magnetic iron-based flow battery with a connected positive and negative electrolyte circulation structure achieves electrolyte recycling through an insulated circulation pump connecting the positive and negative electrolytes, unlike the independent circulation structure of typical flow batteries. The electrolyte delivery pump is a volumetric insulated circulation pump, meaning the electrolyte delivery is intermittent to prevent the formation of a conductive circuit between the positive and negative electrodes, which could cause battery discharge.

[0079] Example 2

[0080] Magnetic iron-based hybrid flow batteries employ a typical flow battery structure with independent circulation of positive and negative electrolytes, such as... Figure 3 As shown, the positive electrode electrolyte storage tank 6 is connected to the electrolyte inlet and outlet of the positive electrode 2 through an independent circulation pipeline; the negative electrode electrolyte storage tank 7 is connected to the electrolyte inlet and outlet of the negative electrode 3 through an independent circulation pipeline; and a circulation pump 14 is installed on each circulation pipeline. The rest of the structure is the same as in Embodiment 1.

[0081] In this embodiment, in the magnetic iron-based hybrid flow battery, to prevent elemental iron from suspending in the electrolyte and detaching from the negative electrode with the flow of the electrolyte, a set of magnetic materials composed of U-shaped magnets is installed at the negative electrode to adsorb iron powder. Its structure is as follows: Figure 2The diagram shows the structure of the magnetic negative electrode. The electrode contains a magnet composed of a set of U-shaped magnets. The surface of the magnet is covered with a stainless steel cover. There is a magnetic field outside the magnet as shown in the figure. The magnet attracts iron powder through magnetic induction, preventing the iron powder from falling off the negative electrode current collector structure, thereby enhancing the cycle repeatability of the electrode and improving the energy storage and conversion efficiency.

[0082] The electrolyte in the positive electrode electrolyte storage tank 6 is an aqueous solution containing iron ions. In this embodiment, it is specifically a 100L solution containing 1.0mol / L FeCl3, 3.0mol / L KCl, and 0.4mol / L H3BO3.

[0083] The electrolyte in the negative electrode electrolyte storage tank 7 is an aqueous solution containing ferrous ions. In this embodiment, it is specifically a 100L solution containing 1.0mol / L FeCl2, 3.0mol / L KCl, and 0.4mol / L H3BO3.

[0084] Comparative Example 1

[0085] Figure 4 This is a schematic diagram of a typical flow battery, such as the all-iron flow battery disclosed in ESS's invention patent CN110301060B; it includes a battery casing 1, a positive electrode 2, a negative electrode 3, an ion exchange membrane 5, a positive electrolyte storage tank 6, and a negative electrolyte storage tank 7. The positive electrode 2 and the negative electrode 3 are installed side by side inside the battery casing 1. The positive electrode 2 and the negative electrode 3 and their positive and negative electrolytes are separated by the ion exchange membrane 5. The positive electrolyte storage tank 6 is connected to the positive electrode 2 through an independent circulation pipeline, and the negative electrolyte storage tank 7 is connected to the negative electrode 3 through an independent circulation pipeline.

[0086] The electrolyte in the positive electrode electrolyte storage tank 6 is an aqueous solution containing iron ions. In this embodiment, it is specifically a 100L solution containing 1.0mol / L FeCl3, 3.0mol / L KCl, and 0.4mol / L H3BO3.

[0087] The electrolyte in the negative electrode electrolyte storage tank 7 is an aqueous solution containing ferrous ions. In this embodiment, it is specifically a 100L solution containing 1.0mol / L FeCl2, 3.0mol / L KCl, and 0.4mol / L H3BO3.

[0088] The performance of the flow batteries constructed in Examples 1-2 and Comparative Example 1 was tested as follows:

[0089] Example 1 81％ >20,000 times 51L / kWh Example 2 81％ >20,000 times 68L / kWh Comparative Example 1 75％ >20,000 times 68L / kWh

[0090] *Note: Calculated based on an active iron / ferrous ion concentration of 1.0 mol / L.

[0091] This invention overcomes the risk of the iron coating peeling off from the negative electrode. Under the same conditions, Figure 1-3 The energy conversion efficiency of the magnetic iron-based hybrid flow battery shown is improved by more than 5%; Figure 4 The magnetic iron-based hybrid flow battery shown saves more than 25% of the amount of active material used in the electrolyte. Considering that a relatively high concentration of KCl (about 3 mol / L) needs to be added to the electrolyte, the economic benefits are quite considerable.

[0092] The magnetic iron-based hybrid flow battery of this invention uses iron as the active material of the electrolyte, which is undoubtedly the optimal choice from both the economics of resource acquisition and environmental safety.

[0093] The magnetic iron-based hybrid flow battery proposed in this technology features high capacity, wide applicability, long cycle life, and low production cost. It has significant application value in the field of large-scale, high-efficiency electrochemical energy storage.

Claims

1. A magnetic iron-based hybrid flow battery, comprising a battery casing (1), a positive electrode (2), a negative electrode (3), an ion exchange membrane (5), a positive electrode electrolyte storage tank (6), and a negative electrode electrolyte storage tank (7), wherein the positive electrode (2) and the negative electrode (3) are installed inside the battery casing (1), and the positive electrode (2) and the negative electrode (3) and their positive and negative electrolytes are separated by the ion exchange membrane (5), characterized in that, The negative electrode (3) includes a magnet, iron powder, a negative electrode current collector and a negative electrode electrolyte, wherein the iron powder is adsorbed on the magnet and the magnet is placed in the negative electrode current collector so that the magnetic field lines of the magnet pass through the negative electrode current collector; The magnet is a U-shaped magnet (4), and multiple U-shaped magnets are placed inside the negative electrode current collector; The magnets are arranged in a row of U-shaped magnets, and the distance between the top of each U-shaped magnet and the ion exchange membrane (5) is greater than the distance between the magnetic poles of the U-shaped magnets; The positive electrode electrolyte storage tank (6) is connected to the positive electrode (2) through the positive electrode electrolyte conduction pipe (8); The negative electrode electrolyte storage tank (7) is connected to the negative electrode (3) through the negative electrode electrolyte conduction pipe (9); The positive electrode (2) and the negative electrode (3) are connected by a pipe, and an insulated circulation pump (10) is installed on the pipe. The top of the positive electrode electrolyte storage tank (6) and the top of the negative electrode electrolyte storage tank (7) are connected by a pressure balancing conduit (13).

2. The magnetic iron-based hybrid flow battery according to claim 1, characterized in that, The negative electrode current collector is made of stainless steel and covers the U-shaped magnet.

3. A magnetic iron-based hybrid flow battery according to claim 1, characterized in that, The positive electrode (2) and negative electrode (3) are placed horizontally, with the negative electrode (3) located below the positive electrode (2).

4. A magnetic iron-based hybrid flow battery according to claim 1, characterized in that, The positive electrode electrolyte storage tank (6) is connected to the electrolyte inlet and outlet of the positive electrode (2) through an independent circulation pipeline; The negative electrode electrolyte storage tank (7) is connected to the electrolyte inlet and outlet of the negative electrode (3) through an independent circulation pipeline; A circulation pump (14) is installed on each circulation pipeline.

5. A magnetic iron-based hybrid flow battery according to claim 1, characterized in that, The insulated circulating pump (10) is a positive displacement pump made of insulating material.

6. A magnetic iron-based hybrid flow battery according to claim 1, characterized in that, The electrolyte used is an electrolyte containing ferrous and ferric ions.

7. A magnetic iron-based hybrid flow battery according to claim 1, characterized in that, One or more pumps are used to transport the electrolyte, connecting multiple flow battery positive and negative electrode structures to achieve the cascade utilization of different voltages formed by different electrolyte concentrations during charging and discharging, thereby improving energy conversion efficiency.

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