High-stability iron-based fuel cell and operation method thereof

Abstract

The invention belongs to the technical field of flow cells, and discloses a high-stability iron-based fuel cell and an operation method thereof.The high-stability iron-based fuel cell comprises a negative electrolyte storage tank, a fuel cell stack and a positive electrolyte storage tank; a liquid outlet of the negative electrolyte storage tank is communicated with a negative electrolyte inlet of the fuel cell stack, and a liquid inlet of the negative electrolyte storage tank is communicated with a negative electrolyte outlet of the fuel cell stack; a liquid outlet of the positive electrolyte storage tank is communicated with a positive electrolyte inlet of the fuel cell stack, and a liquid inlet of the positive electrolyte storage tank is communicated with a positive electrolyte outlet of the fuel cell stack; a supporting layer and an iron source layer are arranged in the negative electrolyte storage tank, the iron source layer is arranged above the supporting layer, a catalyst layer is arranged in the positive electrolyte storage tank, and an oxygen inlet and a pure water injection port are formed in the positive electrolyte storage tank. The cell provided by the invention realizes high discharge power and discharge capacity, high cell performance, long-time high stability, low cost and pollution-free operation of the iron-based fuel cell.

Description

Technical Field

[0001] The present invention belongs to the technical field of liquid flow batteries, and in particular relates to a high-stability iron-based fuel cell and an operation method thereof. Background Art

[0002] Iron-based flow battery is an electrochemical energy storage technology. It consists of a battery stack unit, electrolyte, electrolyte storage and supply unit (liquid storage tank), battery management control unit and other parts. Iron-based flow battery is a high-performance battery that uses positive and negative electrolytes to separate and circulate independently. Iron-based flow battery has the characteristics of high capacity, decoupling of power and capacity, long cycle life and wide temperature range. Iron-based flow battery realizes the mutual conversion of electrical energy and chemical energy through reversible redox reaction (i.e. reversible change of valence state) of active substances in positive and negative electrolyte solutions. During charging, oxidation reaction occurs at the positive electrode to increase the valence state of active substances, and reduction reaction occurs at the negative electrode to reduce the valence state of active substances, and the discharge process is the opposite. Unlike general solid-state batteries, the positive and negative electrolyte solutions of iron-based flow batteries are stored in the positive and negative electrode storage tanks outside the battery respectively, and transported to the inside of the battery through pumps and pipelines for reaction.

[0003] In the iron-based flow battery stack, electrons flow between the positive and negative electrodes in the external circuit, positive and negative ions flow inside the stack, and electrochemical redox reactions occur. The electrochemical reactions and energy storage of the active materials of the positive half-cell or negative half-cell of any battery unit can only occur at the same time. However, electrochemical side reactions will inevitably occur under normal operating conditions of iron-based flow batteries. Side reactions will irreversibly consume electrons, resulting in an imbalance in the charge state of the positive and negative electrolytes (referred to as charge imbalance), and ultimately leading to an imbalance in the capacity of the positive and negative electrodes and a reduction in capacity. Since iron-based flow batteries usually control the charging potential not to exceed the limit value, and due to the extremely slow electrochemical kinetics of the oxygen evolution reaction and the extremely small oxygen evolution side reaction, the main side reaction of aqueous iron-based flow batteries is hydrogen evolution, which is also the main cause of charge imbalance and capacity imbalance in iron-based flow batteries.

[0004] Due to the above side reactions of iron-based liquid flow batteries, there is an urgent need for an iron-based fuel cell that can reduce side reactions, maintain the advantages of high iron-based reaction rate, abundant resources, and low electrolyte cost, prevent electrode passivation, and maintain the stability of long-term battery operation. Summary of the invention

[0005] In view of the above problems, the present invention provides a highly stable iron-based fuel cell and an operation method thereof, which adopts the following technical solutions:

[0006] A highly stable iron-based fuel cell, comprising a cathode electrolyte storage tank, a fuel cell stack and a cathode electrolyte storage tank;

[0007] The liquid outlet of the negative electrolyte storage tank is connected to the negative electrolyte inlet of the fuel cell stack through the negative liquid inlet pipe, and the liquid inlet of the negative electrolyte storage tank is connected to the negative electrolyte outlet of the fuel cell stack through the negative liquid outlet pipe;

[0008] The liquid outlet of the positive electrolyte storage tank is connected to the positive electrolyte inlet of the fuel cell stack through the positive liquid inlet pipe, and the liquid inlet of the positive electrolyte storage tank is connected to the positive electrolyte outlet of the fuel cell stack through the positive liquid outlet pipe;

[0009] A support layer and an iron source layer are arranged in the negative electrode electrolyte storage tank, and the iron source layer is arranged above the support layer. A catalytic layer is arranged in the positive electrode electrolyte storage tank, and an oxygen inlet and a pure water injection port are arranged in the positive electrode electrolyte storage tank above the catalytic layer.

[0010] Furthermore, a first agitator and a first heat exchanger are also provided in the negative electrode electrolyte storage tank;

[0011] The first agitator is arranged at the bottom of the negative electrode electrolyte storage tank, the first heat exchanger is arranged at one side of the first agitator, and the supporting layer is arranged above the first agitator and the first heat exchanger.

[0012] Furthermore, a second agitator and a second heat exchanger are also provided in the positive electrode electrolyte storage tank;

[0013] Among them, the catalytic layer is arranged in the middle of the positive electrode electrolyte storage tank, the second agitator is arranged above the catalytic layer, the second heat exchanger is arranged on the lower side of the catalytic layer, and the positive electrode electrolyte storage tank is also provided with a protective gas inlet on one side of the catalytic layer.

[0014] Furthermore, the discharge port at the bottom of the positive electrode electrolyte storage tank is connected to the sedimentation tank.

[0015] Furthermore, the negative electrode liquid inlet pipe is provided with a first filter and a first electrolyte pump;

[0016] Among them, one end of the first filter is connected to the outlet of the negative electrolyte storage tank, the other end of the first filter is connected to the inlet of the first electrolyte pump, and the outlet of the first electrolyte pump is connected to the negative electrolyte inlet of the fuel cell stack.

[0017] Furthermore, a second filter and a second electrolyte pump are provided on the positive electrode liquid inlet pipe;

[0018] Among them, one end of the second filter is connected to the outlet of the positive electrolyte storage tank, the other end of the second filter is connected to the inlet of the second electrolyte pump, and the outlet of the second electrolyte pump is connected to the positive electrolyte inlet of the fuel cell stack.

[0019] Furthermore, the negative electrode electrolyte storage tank is provided with a feed inlet and a discharge outlet on both sides of the iron source layer.

[0020] Furthermore, it also includes an alkali liquid tank and an alkali liquid pump, and the positive electrode electrolyte storage tank is provided with an exhaust gas discharge port above the catalytic layer;

[0021] Among them, the exhaust gas emission port is connected to one end of the outlet pipe, the other end of the outlet pipe extends to the interior of the alkali liquid tank, the exhaust port at the top of the alkali liquid tank is connected to the emission pipeline, the inlet of the alkali liquid pump is connected to the liquid outlet at the bottom of the alkali liquid tank, and the outlet of the alkali liquid pump is connected to the liquid inlet at the top of the alkali liquid pump.

[0022] Furthermore, a first pressure gauge is disposed on the top of the negative electrode electrolyte storage tank, and a second pressure gauge is disposed on the top of the positive electrode electrolyte storage tank.

[0023] The present invention also provides a method for operating the highly stable iron-based fuel cell, comprising the following steps:

[0024] When the fuel cell stack is electrode-passivated and the battery efficiency is reduced, the operation is stopped, the positive and negative electrodes of the fuel cell stack are reversed and charged. After the charging time is set, part of the Fe in the negative electrode of the fuel cell stack is oxidized and dissolved into Fe 2+ The negative electrode is stored in the negative electrolyte inside the negative electrode; most of the FeOOH in the positive electrode of the fuel cell stack is reduced and dissolved into Fe 2+ Enter the positive electrode electrolyte inside the positive electrode for storage;

[0025] After charging for a set time, the electrolyte in the negative electrode electrolyte storage tank and the positive electrode electrolyte storage tank are driven to enter the negative electrode and positive electrode of the fuel cell stack respectively, taking away the products generated after charging. At the same time, part of the remaining Fe in the negative electrode is oxidized and dissolved into Fe 2+ After entering the negative electrode, the electrolyte circulates and flows back to the negative electrode electrolyte storage tank; some of the remaining FeOOH in the positive electrode is reduced and dissolved into Fe 2+ After entering the positive electrode, it is circulated by the electrolyte and then flows back to the positive electrode electrolyte storage tank.

[0026] Beneficial effects of the present invention:

[0027] 1. The negative electrode electrolyte storage tank of the present invention is provided with a support layer and an iron source layer to provide Fe and an organic active substance OR reaction, and the positive electrode electrolyte storage tank is provided with a catalyst layer, an oxygen inlet and a pure water injection port, so as to realize high discharge power and discharge capacity, high battery performance, long-term high stability, low cost, and pollution-free (closed loop circulation, the product is solid FeOOH that can be recycled) operation of the iron-based fuel cell.

[0028] 2. The active substances of the iron-based fuel cell reaction of the present invention are low-cost iron, oxygen and water, and the medium is a low-cost organic active medium, so that the iron-based fuel cell has low cost.

[0029] 3. The operation method of the iron-based fuel cell of the present invention purifies and regenerates the fuel cell stack electrodes by a two-stage reverse charging method of reversing the polarity of the fuel cell stack and stopping the pump and running the pump.

[0030] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 A schematic structural diagram of a high-stability iron-based fuel cell according to an embodiment of the present invention is shown;

[0033] Figure 2 A schematic flow chart of an operation method of a high-stability iron-based fuel cell according to an embodiment of the present invention is shown.

[0034] In the figure: 1. negative electrolyte storage tank; 101. first pressure gauge; 102. discharge port; 103. feed port; 104. first valve; 105. iron source layer; 106. support layer; 107. second valve; 2. first agitator; 3. first heat exchanger; 4. first filter; 5. first electrolyte pump; 6. negative electrode inlet pipe; 7. fuel cell stack; 8. negative electrode; 9. ion exchange membrane; 10. positive electrode; 11. negative electrode collector plate; 12. positive electrode collector plate; 13. negative electrode outlet pipe; 14. power load; 15. positive electrolyte storage tank; 16. oxygen Import; 161, the third valve; 17, the pure water injection port; 171, the fourth valve; 18, the second pressure gauge; 19, the protective gas inlet; 20, the fifth valve; 21, the catalyst layer; 22, the second agitator; 23, the second heat exchanger; 24, the discharge port; 25, the sixth valve; 26, the sedimentation tank; 27, the exhaust gas discharge port; 28, the seventh valve; 29, the second filter; 30, the second electrolyte pump; 31, the positive electrode liquid inlet pipe; 32, the positive electrode liquid outlet pipe; 33, the alkali liquid tank; 34, the alkali liquid pump; 35, the discharge pipeline; 36, the charging power supply; 37, the battery control system. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] It should be noted that the terms "first", "second", etc. in this application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so as to describe the embodiments of the present application described here.

[0037] like Figure 1 As shown, a high-stability iron-based fuel cell includes a negative electrode electrolyte storage tank 1, a fuel cell stack 7 and a positive electrode electrolyte storage tank 15.

[0038] Among them, the liquid outlet of the negative electrolyte storage tank 1 is connected to the negative electrolyte inlet of the fuel cell stack 7 through the negative liquid inlet pipe 6, and the liquid inlet of the negative electrolyte storage tank 1 is connected to the negative electrolyte outlet of the fuel cell stack 7 through the negative liquid outlet pipe 13.

[0039] A first pressure gauge 101 is arranged on the top of the negative electrode electrolyte storage tank 1, and a first agitator 2, a first heat exchanger 3, a support layer 106 and an iron source layer 105 are arranged in the negative electrode electrolyte storage tank 1, wherein the first agitator 2 is arranged at the bottom of the negative electrode electrolyte storage tank 1, the first heat exchanger 3 is arranged on one side of the first agitator 2, the support layer 106 is arranged above the first agitator 2 and the first heat exchanger 3, and the iron source layer 105 is arranged above the support layer 106.

[0040] The negative electrolyte storage tank 1 is provided with a feed port 103 and a discharge port 102 on both sides of the iron source layer 105 , respectively. The feed port 103 of the negative electrolyte storage tank 1 is provided with a first valve 104 , and the discharge port 102 of the negative electrolyte storage tank 1 is provided with a second valve 107 .

[0041] For example, the support layer 106 can be made of wire mesh or other inert support materials such as SiO2, the iron source layer 105 includes a plurality of stacked iron balls, the negative electrode electrolyte storage tank 1 has the iron source layer 105 and the support layer 106 built in, provides Fe and the organic active substance OR reaction, and has the first stirrer 2 built in to accelerate the reaction of the organic active substance OR - It reacts with Fe in the negative electrode electrolyte tank 1 and provides a uniform active material.

[0042] The first heat exchanger 3 forms the temperature required by the iron-based fuel cell (for example, the operating temperature of the iron-based fuel cell is 30-90°C). When the ambient temperature is low, the first heat exchanger 3 heats the electrolyte; when the battery temperature rises (such as high current density circulation causes the battery to heat up), the first heat exchanger 3 cools the electrolyte.

[0043] The liquid outlet of the positive electrolyte storage tank 15 is connected to the positive electrolyte inlet of the fuel cell stack 7 through the positive liquid inlet pipe 31, and the liquid inlet of the positive electrolyte storage tank 15 is connected to the positive electrolyte outlet of the fuel cell stack 7 through the positive liquid outlet pipe 32.

[0044] For example, the fuel cell stack 7 includes at least one basic battery unit, wherein the basic battery unit includes a negative electrode 8, an ion exchange membrane 9, a positive electrode 10, a negative current collecting plate 11 and a positive current collecting plate 12, the ion exchange membrane 9 is arranged between the negative current collecting plate 11 and the positive current collecting plate 12, the positive electrode 10 is arranged in a cavity formed by the positive current collecting plate 12 and the ion exchange membrane 9, and the negative electrode 8 is arranged in a cavity formed by the negative current collecting plate 11 and the ion exchange membrane 9.

[0045] When the number of basic battery cells is ≥1, a plurality of groups of identical basic battery cells are connected in series through a negative current collecting plate 11 and a positive current collecting plate 12 to form a fuel cell stack 7. At this time, the negative current collecting plate 11 and the positive current collecting plate 12 are respectively a negative bipolar plate and a positive bipolar plate.

[0046] The positive electrode electrolyte of the fuel cell stack 7 includes an electrolyte active substance Fe 3+ and a supporting electrolyte, the supporting electrolyte being acidic HCl or H2SO4 or mixed acid, or neutral or alkaline. The negative electrode electrolyte of the fuel cell stack 7 includes an organic active substance OR - and a supporting electrolyte, which can be acidic, neutral or alkaline.

[0047] The positive electrode of the fuel cell stack 7 is connected to the positive electrode of the power load 14 , and the negative electrode of the fuel cell stack 7 is connected to the negative electrode of the power load 14 .

[0048] For example, the high-stability iron-based fuel cell also includes a charging power supply 36, the positive electrode of the fuel cell stack 7 is connected to the negative electrode of the charging power supply 36, and the negative electrode of the fuel cell stack 7 is connected to the positive electrode of the charging power supply 36; the battery control system 37 is communicatively connected to the charging power supply 36 and the power load 14.

[0049] The battery control system 37 has built-in operation control strategies and codes for controlling and monitoring the charging power supply 36, the charging, discharging and operation of the power load 14, and the start and stop and operation of system-related oxygen flow control, pure water flow control, pumps, valves, heat exchangers and heaters, as well as online monitoring and judgment of the discharge power and discharge capacity of the iron-based fuel cell after purification and regeneration, restarting the discharge of the iron-based fuel cell, and achieving high-stable discharge power and discharge capacity of the iron-based fuel cell and maintaining stable high-performance operation of the system efficiency.

[0050] A second pressure gauge 18 is arranged on the top of the positive electrolyte storage tank 15, and a catalyst layer 21, a second agitator 22 and a second heat exchanger 23 are arranged in the positive electrolyte storage tank 15, wherein the catalyst layer 21 is arranged in the middle of the positive electrolyte storage tank 15, the second agitator 22 is arranged above the catalyst layer 21, and the second heat exchanger 23 is arranged on the lower side of the catalyst layer 21.

[0051] The positive electrode electrolyte storage tank 15 is provided with an oxygen inlet 16 and a pure water injection port 17 above the catalyst layer 21. The positive electrode electrolyte storage tank 15 is also provided with a protective gas inlet 19 on one side of the catalyst layer 21. For example, the oxygen inlet 16 is provided with a third valve 161, the pure water injection port 17 is provided with a fourth valve 171, and the protective gas inlet 19 is provided with a fifth valve 20.

[0052] The discharge port 24 at the bottom of the positive electrode electrolyte storage tank 15 is connected to the sedimentation tank 26 , and a sixth valve 25 is further provided between the discharge port 24 of the positive electrode electrolyte storage tank 15 and the sedimentation tank 26 .

[0053] The catalyst layer 21 is a metal composite catalyst such as Cu x -Ni y Fe zcatalyst, or a magnetic transition metal hydroxide catalyst such as Ni x Fe y OOH, coated on a carbon base (carbon felt or graphite felt, etc.). Oxygen is injected into the positive electrode electrolyte storage tank 15 from the oxygen inlet 16, and pure water is injected into the positive electrode electrolyte storage tank 15 from the pure water injection port 17. The second stirrer 22 accelerates and uniformly dissolves Fe 2+ Reaction with oxygen.

[0054] For example, a first filter 4 and a first electrolyte pump 5 are provided on the negative electrode liquid inlet pipe 6, wherein one end of the first filter 4 is connected to the liquid outlet of the negative electrode electrolyte storage tank 1, and the other end of the first filter 4 is connected to the inlet of the first electrolyte pump 5, and the outlet of the first electrolyte pump 5 is connected to the negative electrolyte inlet of the fuel cell stack 7.

[0055] For example, a second filter 29 and a second electrolyte pump 30 are provided on the positive electrode liquid inlet pipe 31, wherein one end of the second filter 29 is connected to the liquid outlet of the positive electrode electrolyte storage tank 15, and the other end of the second filter 29 is connected to the inlet of the second electrolyte pump 30, and the outlet of the second electrolyte pump 30 is connected to the positive electrolyte inlet of the fuel cell stack 7.

[0056] For example, the high-stability iron-based fuel cell also includes an alkali liquid tank 33 and an alkali liquid pump 34. The positive electrode electrolyte storage tank 15 is provided with an exhaust gas exhaust port 27 above the catalyst layer 21. The exhaust gas exhaust port 27 is connected to one end of the outlet pipe, and the other end of the outlet pipe extends to the interior of the alkali liquid tank 33. For example, a seventh valve 28 is also provided on the outlet pipe.

[0057] The exhaust port at the top of the alkali liquid tank 33 is connected to the discharge pipeline 35 , the inlet of the alkali liquid pump 34 is connected to the liquid outlet at the bottom of the alkali liquid tank 33 , and the outlet of the alkali liquid pump 34 is connected to the liquid inlet at the top of the alkali liquid pump 34 .

[0058] like Figure 2 As shown, an embodiment of the present invention further provides an operation method of the above-mentioned high-stability iron-based fuel cell, comprising the following steps:

[0059] S1, the negative electrode electrolyte in the negative electrode electrolyte storage tank 1 is transported to the fuel cell stack 7 through the negative electrode liquid inlet pipe 6, and the positive electrode electrolyte in the positive electrode electrolyte storage tank 15 is transported to the fuel cell stack 7 through the positive electrode liquid inlet pipe 31, the negative electrode electrolyte and the positive electrode electrolyte undergo electrochemical oxidation-reduction reaction in the fuel cell stack 7, and discharge outward to provide electricity for the power load 14, and the negative electrode electrolyte after the reaction flows back to the negative electrode electrolyte storage tank 1 through the negative electrode liquid outlet pipe 13, and the positive electrode electrolyte after the reaction flows back to the positive electrode electrolyte storage tank 15 through the positive electrode liquid outlet pipe 32, as follows:

[0060] The negative electrode electrolyte and the positive electrode electrolyte undergo an electrochemical redox reaction in the fuel cell stack 7. Electrons flow between the positive and negative electrodes of the fuel cell stack 7 in an external circuit, providing power to the power load 14 during the discharge process. In the external circuit, electrons flow from the negative electrode to the positive electrode. The reactants of the positive and negative electrode electrolytes flow in the positive and negative electrodes of the fuel cell stack 7, respectively, and undergo an electrochemical redox reaction on the positive and negative electrodes. The electrochemical reaction of the active substances and their energy storage in the positive and negative half-cells of the basic battery unit occur simultaneously. During the discharge process of the fuel cell stack 7, the positive electrode Fe 3+ Reduction to Fe 2+ , negative electrode organic active material OR - The electrolyte is oxidized to OR, which flows into the positive electrode electrolyte tank 15 and the negative electrode electrolyte tank 1 for storage.

[0061] The negative electrode reaction of the fuel cell stack 7 is as follows:

[0062] Before the fuel cell stack 7 is operated, a protective gas such as nitrogen is input through the feed port 103 of the negative electrode electrolyte storage tank 1 to purge the negative electrode electrolyte storage tank 1 to prevent impurity contamination, and then the negative electrode electrolyte composed of an organic active medium and a supporting electrolyte is injected.

[0063] The temperature of the negative electrode electrolyte in the negative electrode electrolyte storage tank 1 is maintained within a set range by the first heat exchanger 3. For example, the set range may be 30-90°C, the operating temperature of the iron-based fuel cell. When the ambient temperature is low, the first heat exchanger 3 heats the electrolyte, and when the battery temperature rises (such as high current density circulation causing the battery to heat up), the first heat exchanger 3 cools the electrolyte. The negative electrode electrolyte flows into the fuel cell stack 7 through the first filter 4 and the first electrolyte pump 5 for discharge reaction.

[0064] Fe oxidation reaction occurs in the negative electrode electrolyte storage tank 1 to form a negative electrode electrolyte, OR+Fe=Fe 2+ +OR - The supporting electrolyte is neutral or slightly acidic. The organic active material can oxidize Fe (in a near-neutral electrolyte, Fe is oxidized to Fe 2+ The redox potential of the fluid medium is about -0.4 V vs SHE, and the redox potential can be higher than that of Fe / Fe 2+ Organic active media with high charge and reaction rate. Such organic active media include but are not limited to AQDS (soluble anthraquinone disulfonic acid, redox potential of about 0V vs SHE, high stability, solubility, high reaction activity, low cost, large-scale production cost of about 15 yuan / kg).

[0065] The organic active substance OR generated by the negative electrode discharge reaction of the fuel cell stack 7 flows back to the negative electrode electrolyte storage tank 1 through the negative electrode liquid outlet pipe 13 for storage, and then reacts with Fe in the negative electrode electrolyte storage tank 1 to generate new organic active substance OR. - , providing the fuel cell stack 7 with negative electrode reactant for discharge.

[0066] The positive electrode reaction process of the fuel cell stack 7 is as follows:

[0067] Before the fuel cell stack 7 is operated, a protective gas such as nitrogen is input through the protective gas inlet 19 of the positive electrode electrolyte storage tank 15 to purge the positive electrode electrolyte storage tank 15 to prevent contamination by impurities.

[0068] The temperature required by the iron-based fuel cell (for example, the operating temperature of the iron-based fuel cell is 30-90°C) is formed through the second heat exchanger 23. When the ambient temperature is low, the second heat exchanger 23 heats the electrolyte; when the battery temperature rises (such as high current density circulation causes the battery to heat up), the second heat exchanger 23 cools the electrolyte.

[0069] The positive electrode electrolyte flows out from the positive electrode electrolyte storage tank 15, passes through the second filter 29, is driven by the second electrolyte pump 30, and flows into the positive electrode of the fuel cell stack 7. The positive electrode reaction is to form the electrolyte active substance Fe 3+ Reduction to Fe 2+ .

[0070] The positive electrode electrolyte accelerates the Fe 2+ Oxidation reaction, 6Fe 2+ +3 / 2O2+H2O=2FeOOH+4Fe 3+ During the charging process, the positive electrode electrolyte after the electrochemical reaction flows out of the fuel cell stack 7 and flows into the positive electrode electrolyte storage tank 15 for storage. The generated FeOOH flows from the discharge port 24 of the positive electrode electrolyte storage tank 15 and the sixth valve 25 into the sedimentation tank 26 for recycling.

[0071] The fuel cell stack 7 supplies power to the power load 14. During the discharge process of the fuel cell stack 7, water vapor generated by the positive electrode electrolyte storage tank 15 flows into the alkali liquid tank 33 through the tail gas discharge port 27 and the outlet pipe. The alkali liquid in the alkali liquid tank 33 is driven by the alkali liquid pump 34 and discharged through the discharge pipeline 35.

[0072] Most of the Fe shed from the negative electrolyte storage tank 1 is filtered by the first filter 4, but if a small amount of Fe enters the negative electrode 8 of the fuel cell stack 7, it will cause the negative electrode 8 to be passivated, the battery polarization to increase, the discharge power and capacity to decrease, and the battery system efficiency to decrease. Most of the FeOOH shed from the positive electrolyte storage tank 15 is filtered by the second filter 29, but if a small amount of FeOOH enters the positive electrode 10 of the fuel cell stack 7, it will cause the positive electrode 10 to be passivated, the battery polarization to increase, the discharge power and capacity to decrease, and the battery system efficiency to decrease.

[0073] S2: After the fuel cell stack 7 has been discharged for a period of time, the fuel cell stack 7 stops running when electrode passivation and battery efficiency decreases (the first electrolyte pump 5 and the second electrolyte pump 30 stop running), the positive and negative electrodes of the fuel cell stack 7 are reversed and charged. After the charging set time, most of the Fe in the negative electrode 8 (positive electrode after reversal) of the fuel cell stack 7 is oxidized and dissolved into Fe 2+ The negative electrode electrolyte enters the negative electrode 8 and is stored; most of the FeOOH in the positive electrode 10 (negative electrode after inversion) of the fuel cell stack 7 is reduced and dissolved into Fe 2+ The positive electrode 10 is stored in the positive electrolyte.

[0074] The positive and negative electrodes of the fuel cell stack 7 are reversed and charged, specifically: the fuel cell stack 7 is charged by the charging power supply 36, and the positive and negative electrodes of the fuel cell stack 7 are reversed during the charging process.

[0075] For example, the negative pole of the charging power supply 36 is connected to the positive pole of the fuel cell stack 7, and the positive pole of the charging power supply 36 is connected to the negative pole of the fuel cell stack 7 to achieve the reversal of the positive and negative poles of the fuel cell stack 7, or the positive and negative electrical connections of the stack are swapped to achieve the reversal of the positive and negative poles of the fuel cell stack 7.

[0076] S3. In order to prevent the electrode from being damaged by overcharging, the fuel cell stack 7 stops charging for a set time, then starts the first electrolyte pump 5 and the second electrolyte pump 30, driving the electrolytes in the negative electrolyte storage tank 1 and the positive electrolyte storage tank 15 to enter the negative electrode 8 and the positive electrode 10 of the fuel cell stack 7 respectively, taking away the products generated after charging, and at the same time, a small amount of remaining Fe in the negative electrode 8 (positive electrode after reversal) is oxidized and dissolved into Fe 2+ The electrolyte enters the negative electrode 8 and flows back to the negative electrolyte storage tank 1; the small amount of FeOOH remaining in the positive electrode 10 (negative electrode after reversal) is reduced and dissolved into Fe 2+ After entering the positive electrode 10 , it is circulated by the electrolyte and then flows back to the positive electrode electrolyte storage tank 15 .

[0077] The embodiment of the present invention addresses the problem of electrode passivation and reduced battery efficiency after the fuel cell stack 7 has been discharged for a period of time. The electrodes of the fuel cell stack 7 are purified and regenerated by a two-stage reverse charging method of reversing the polarity of the stack electrodes and stopping the pump and running the pump.

[0078] After the iron-based fuel cell purification and regeneration is performed for a period of time t (according to the battery passivation phenomenon and attenuation, for example, N hours), the iron-based fuel cell is restarted to discharge, the discharge power / discharge capacity / battery system efficiency is measured to recover to the design value, the battery polarization is observed to decrease to the design value through the discharge voltage, and the discharge cycle is re-run. The iron-based fuel cell of the present invention is realized to operate stably for a long time, and its low cost and durability can be applied to large-scale long-term energy storage.

[0079] The present invention proposes a high-stability iron-based fuel cell system and an operation method thereof, which are generally applicable to water-based iron-based fuel cells and air fuel cells, and are particularly applicable to large-scale iron-based fuel cell energy storage systems, and can achieve high discharge power and discharge capacity, high battery performance, long-term high stability, low cost, and pollution-free (closed-loop circulation, the product is solid FeOOH that can be recycled) operation of the iron-based fuel cell.

[0080] The reactive substances are low-cost iron, oxygen and water, the medium is a low-cost organic active medium such as AQDS with a cost as low as 15 yuan / kg, the negative electrode supporting electrolyte is neutral or slightly acidic such as low-concentration hydrochloric acid, and the positive electrode supporting electrolyte is neutral, slightly acidic or slightly alkaline.

[0081] The embodiment of the present invention aims at the problem of electrode passivation and reduced battery efficiency after the fuel cell stack 7 is discharged and operated for a period of time. The fuel cell stack 7 electrodes are purified and regenerated by reversing the polarity of the stack electrodes, stopping the pump and running the pump in two stages of reverse charging. After the iron-based fuel cell system is purified and regenerated for a period of time t (according to the battery passivation phenomenon and attenuation, for example, N hours), the iron-based fuel cell is restarted to discharge, the discharge power / discharge capacity / battery system efficiency is measured to be restored to the design value, and the battery polarization is observed to be reduced to the design value through the discharge voltage, and the discharge cycle is re-run. The iron-based fuel cell of the present invention is realized to operate stably for a long time, and its low cost and durability are suitable for large-scale long-term energy storage.

[0082] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A highly stable iron-based fuel cell, characterized in that: It comprises a negative electrode electrolyte storage tank (1), a fuel cell stack (7) and a positive electrode electrolyte storage tank (15); The liquid outlet of the negative electrode electrolyte storage tank (1) is connected to the negative electrolyte inlet of the fuel cell stack (7) through the negative electrode liquid inlet pipe (6), and the liquid inlet of the negative electrode electrolyte storage tank (1) is connected to the negative electrolyte outlet of the fuel cell stack (7) through the negative electrode liquid outlet pipe (13); The liquid outlet of the positive electrolyte storage tank (15) is connected to the positive electrolyte inlet of the fuel cell stack (7) through the positive electrolyte inlet pipe (31), and the liquid inlet of the positive electrolyte storage tank (15) is connected to the positive electrolyte outlet of the fuel cell stack (7) through the positive electrolyte outlet pipe (32); The negative electrode electrolyte storage tank (1) is provided with a support layer (106) and an iron source layer (105), the iron source layer (105) being provided above the support layer (106), the positive electrode electrolyte storage tank (15) is provided with a catalyst layer (21), and the positive electrode electrolyte storage tank (15) is provided with an oxygen inlet (16) and a pure water injection port (17) above the catalyst layer (21).

2. The highly stable iron-based fuel cell according to claim 1, characterized in that: The negative electrode electrolyte storage tank (1) is also provided with a first stirrer (2) and a first heat exchanger (3); The first agitator (2) is arranged at the bottom of the negative electrode electrolyte storage tank (1), the first heat exchanger (3) is arranged on one side of the first agitator (2), and the support layer (106) is arranged above the first agitator (2) and the first heat exchanger (3).

3. The highly stable iron-based fuel cell according to claim 1, characterized in that: The positive electrode electrolyte storage tank (15) is further provided with a second stirrer (22) and a second heat exchanger (23); The catalytic layer (21) is arranged in the middle of the positive electrode electrolyte storage tank (15), the second agitator (22) is arranged above the catalytic layer (21), the second heat exchanger (23) is arranged on the lower side of the catalytic layer (21), and the positive electrode electrolyte storage tank (15) is also provided with a protective gas inlet (19) on one side of the catalytic layer (21).

4. The highly stable iron-based fuel cell according to claim 1, characterized in that: The discharge port (24) at the bottom of the positive electrode electrolyte storage tank (15) is connected to the sedimentation tank (26).

5. The highly stable iron-based fuel cell according to claim 1, characterized in that: The negative electrode liquid inlet pipe (6) is provided with a first filter (4) and a first electrolyte pump (5); One end of the first filter (4) is connected to the liquid outlet of the negative electrolyte storage tank (1), the other end of the first filter (4) is connected to the inlet of the first electrolyte pump (5), and the outlet of the first electrolyte pump (5) is connected to the negative electrolyte inlet of the fuel cell stack (7).

6. The highly stable iron-based fuel cell according to claim 1, characterized in that: The positive electrode liquid inlet pipe (31) is provided with a second filter (29) and a second electrolyte pump (30); One end of the second filter (29) is connected to the liquid outlet of the positive electrolyte storage tank (15), the other end of the second filter (29) is connected to the inlet of the second electrolyte pump (30), and the outlet of the second electrolyte pump (30) is connected to the positive electrolyte inlet of the fuel cell stack (7).

7. The highly stable iron-based fuel cell according to claim 1, characterized in that: The negative electrode electrolyte storage tank (1) is provided with a feed inlet (103) and a discharge outlet (102) on both sides of the iron source layer (105).

8. The highly stable iron-based fuel cell according to any one of claims 1 to 7, characterized in that: It also includes an alkali liquid tank (33) and an alkali liquid pump (34), and the positive electrode electrolyte storage tank (15) is provided with an exhaust gas discharge port (27) above the catalyst layer (21); The tail gas discharge port (27) is connected to one end of an outlet pipe, the other end of the outlet pipe extends to the interior of the alkali liquid tank (33), the exhaust port at the top of the alkali liquid tank (33) is connected to a discharge pipeline (35), the inlet of the alkali liquid pump (34) is connected to the liquid outlet at the bottom of the alkali liquid tank (33), and the outlet of the alkali liquid pump (34) is connected to the liquid inlet at the top of the alkali liquid pump (34).

9. The highly stable iron-based fuel cell according to claim 1, characterized in that: A first pressure gauge (101) is provided on the top of the negative electrode electrolyte storage tank (1), and a second pressure gauge (18) is provided on the top of the positive electrode electrolyte storage tank (15).

10. A method for operating a high-stability iron-based fuel cell according to any one of claims 1 to 9, characterized in that: The following steps are involved: When the fuel cell stack (7) is electrode-passivated and the battery efficiency is reduced, the operation is stopped, the positive and negative electrodes of the fuel cell stack (7) are reversed and charging is performed. After the charging time is set, part of the Fe in the negative electrode (8) of the fuel cell stack (7) is oxidized and dissolved into Fe 2+ The FeOOH in the positive electrode (10) of the fuel cell stack (7) is reduced and dissolved into Fe 2+ Entering and being stored in the positive electrolyte inside the positive electrode (10); After charging for a set time, the electrolytes in the negative electrode electrolyte storage tank (1) and the positive electrode electrolyte storage tank (15) are driven to enter the negative electrode (8) and the positive electrode (10) of the fuel cell stack (7) respectively, taking away the products generated after charging, and at the same time, part of the remaining Fe in the negative electrode (8) is oxidized and dissolved into Fe 2+ The electrolyte enters the negative electrode (8) and then flows back to the negative electrode electrolyte storage tank (1); the remaining FeOOH in the positive electrode (10) is reduced and dissolved into Fe 2+ After entering the positive electrode (10), it is circulated by the electrolyte and then flows back to the positive electrolyte storage tank (15).

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