Electrolysis device for preparing vanadium battery electrolyte and method for preparing vanadium battery electrolyte

Abstract

The invention provides an electrolysis device for preparing a vanadium battery electrolyte and a method for preparing the vanadium battery electrolyte. The electrolysis device comprises an anode and a cathode, the anode comprises stainless steel; the cathode comprises a graphite felt and a modification layer, the modification layer is arranged on at least part of the surface of the graphite felt, and the modification layer comprises nickel manganese oxide. By means of the electrolysis device, the side reaction of the cathode and the anode can be reduced, the electrolysis efficiency is improved, and the loss of active substances in the electrolyte is reduced.

Description

Technical Field

[0001] This application relates to the field of materials preparation, and more specifically, to an electrolysis apparatus and a method for preparing vanadium battery electrolyte. Background Technology

[0002] With the increasing depletion of fossil fuel resources and the growing environmental pollution, finding new energy sources and energy storage technologies has become an urgent issue for energy development. Vanadium redox flow batteries are a new type of high-efficiency electrochemical energy storage battery, characterized by ultra-long cycle life, flexible capacity with expandable design, fast response rate, and intrinsic safety, which has made them widely popular in the new energy field.

[0003] The electrolyte is the energy unit of a vanadium redox flow battery, determining its capacity. In the electrolytic reduction process for preparing the electrolyte, the reduction reaction typically occurs at the cathode, while oxygen evolution occurs at the anode, leading to problems such as numerous anode side reactions or low reaction rates. Side reactions are also prone to occur at the cathode, such as hydrogen evolution and the formation of metal carbides, resulting in substandard electrolytes and significant losses of active materials, thus limiting the preparation and application of electrolytes. Summary of the Invention

[0004] This application aims to at least partially address one of the technical problems in related technologies. To this end, this application proposes an electrolysis apparatus and a method for preparing vanadium battery electrolyte. Using the electrolysis apparatus of this application can reduce side reactions at the cathode and anode, improve electrolysis efficiency, and reduce the loss of active materials in the electrolyte.

[0005] In a first aspect, this application proposes an electrolysis apparatus for preparing vanadium battery electrolyte. According to an embodiment of this application, the electrolysis apparatus includes: an anode and a cathode;

[0006] The anode comprises stainless steel;

[0007] The cathode comprises a graphite felt and a modification layer, the modification layer being disposed on at least a portion of the surface of the graphite felt, the modification layer comprising nickel manganese oxide.

[0008] The electrolysis apparatus according to the embodiments of this application uses stainless steel as the anode, which is less likely to increase the cell voltage due to increased anode resistance, effectively preventing side reactions caused by excessive cell voltage. A graphite felt with a nickel-manganese oxide modified layer is used as the cathode. Nickel-manganese oxide has good catalytic activity and stability, easily participates in the reaction, and improves the electrolysis efficiency. Furthermore, nickel-manganese oxide can isolate vanadium ions from carbon, making it less likely to form vanadium carbide precipitation, reducing the loss of active materials in the electrolyte.

[0009] According to embodiments of this application, the electrolysis apparatus for preparing vanadium battery electrolyte may also have the following additional technical features:

[0010] According to an embodiment of this application, the content of the modification layer is 2% to 3% based on the total mass of the cathode.

[0011] According to embodiments of this application, the graphite felt is selected from one of polyacrylonitrile-based graphite felt, viscose-based graphite felt, cellulose-based graphite felt, and pitch-based graphite felt.

[0012] According to embodiments of this application, the stainless steel includes at least one of type 316 stainless steel, type 304 stainless steel, and type 430 stainless steel.

[0013] According to an embodiment of this application, the electrolysis apparatus further includes:

[0014] Diaphragm;

[0015] An anode tank is disposed on one side of the diaphragm, and the anode is disposed in the anode tank;

[0016] A cathode tank is disposed on the side of the diaphragm away from the anode tank, and the cathode is disposed in the cathode tank.

[0017] According to embodiments of this application, the diaphragm comprises a perfluorosulfonic acid membrane and / or polybenzimidazole.

[0018] In a second aspect, this application proposes a method for preparing vanadium battery electrolyte using the aforementioned electrolysis apparatus for preparing vanadium battery electrolyte. According to an embodiment of this application, the method includes:

[0019] A vanadium-containing solution is placed in a cathode tank, and the cathode is provided in the cathode tank;

[0020] The anolyte is placed in an anode tank, and the anode is disposed in the anode tank.

[0021] Connect the cathode and anode to a power supply device, turn on the power supply device, and perform electrolysis to obtain vanadium battery electrolyte in the cathode tank.

[0022] According to an embodiment of this application, the method for preparing the cathode includes:

[0023] Using a graphite felt electrode as the working electrode, an Hg / Hg2SO4 electrode as the reference electrode, a platinum sheet electrode as the counter electrode, and a mixed solution containing manganese and nickel compounds as the electrolyte, cyclic voltammetry was performed to obtain the cathode.

[0024] Wherein, the cyclic voltammetric scan satisfies at least one of the following conditions:

[0025] The scan rate is 80mV / s to 120mV / s;

[0026] The scanning voltage range is 0.4V to 1.2V;

[0027] The number of cycles is 3 to 5.

[0028] According to embodiments of this application, the manganese-containing compound includes at least one of manganese acetate, manganese sulfate, and manganese nitrate;

[0029] And / or, the nickel-containing compound includes at least one of nickel acetate, nickel sulfate, and nickel nitrate;

[0030] And / or, the electrolyte further comprises: a buffer, the buffer comprising at least one of sodium acetate, sodium sulfate and sodium nitrate;

[0031] And / or, based on the total mass of the mixture, the concentration of the manganese-containing compound is 0.01 mol / L to 0.1 mol / L;

[0032] And / or, based on the total mass of the mixture, the concentration of the nickel-containing compound is 0.05 mol / L to 0.2 mol / L.

[0033] According to embodiments of this application, the vanadium-containing solution comprises a vanadium-containing compound, which includes vanadium pentoxide and / or ammonium metavanadate.

[0034] According to embodiments of this application, the concentration of the vanadium-containing compound is 1 mol / L to 2 mol / L.

[0035] According to embodiments of this application, the vanadium-containing solution further comprises sulfuric acid.

[0036] According to embodiments of this application, the anolyte comprises sulfuric acid and / or sodium sulfate.

[0037] According to an embodiment of this application, the electrolysis treatment is performed using a constant current of 400mA to 600mA for 6 to 7 hours.

[0038] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0039] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0040] Figure 1 A schematic diagram of an electrolysis apparatus for preparing vanadium battery electrolyte according to an embodiment of this application is shown.

[0041] Figure label:

[0042] 10: Electrolysis device; 100: Anode; 200: Cathode; 300: Diaphragm; 400: Anode tank; 500: Cathode tank. Detailed Implementation

[0043] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0044] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0045] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is also expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers, and ranges defined in this way can include endpoints a and b. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0046] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0047] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0048] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0049] The electrolyte in a vanadium redox flow battery is its energy unit, determining the battery's capacity. The electrolyte for vanadium redox flow batteries (in this text, it can be used interchangeably with "vanadium electrolyte" or "vanadium battery electrolyte") is generally obtained by reduction with ammonium metavanadate or vanadium pentoxide. Electrolysis and reduction with reducing agents are two commonly used methods for preparing vanadium electrolytes. Electrolysis introduces fewer impurities into its system and is more efficient than the reduction method. The electrolytes prepared by electrolysis and chemical methods exist in different states. Studies have shown that electrolytes obtained by electrolysis are more suitable for the requirements of vanadium batteries; therefore, electrolysis is widely used in the large-scale production of vanadium electrolytes.

[0050] In the process of preparing electrolytes by electrolysis, an electrolytic reduction reaction generally occurs at the cathode to obtain the electrolyte. Taking the cathode electrolytic reduction of pentavalent vanadium ion solution and the anode as an example, the reduction reaction occurs at the cathode during electrolysis: VO2 + +e - →VO 2+ At the anode, oxygen evolution occurs. Typically, the current density for electrolysis is 10-100 mA / cm². 2 At a voltage of 1-5V, the anode and cathode will react differently depending on the electrode.

[0051] For the anode of the electrolytic cell, when using electrodes with low oxygen evolution overpotentials, such as platinum, only the oxygen evolution reaction occurs at the anode, resulting in high electrolysis efficiency. However, due to the high cost of platinum, it is not suitable for large-scale vanadium electrolyte production. When using titanium or lead electrodes, the anode is unlikely to undergo the oxygen evolution reaction due to its high oxygen evolution overpotential, and instead, the titanium or lead will undergo oxidation. Titanium oxide and lead oxide have poor conductivity and high resistance. To continue constant current electrolysis, the cell voltage will increase accordingly. Even so, most of the voltage is consumed by the high-resistivity anode, generating heat. This process slows down the electrolytic cell. Overall reaction rate; when using carbonaceous felt electrodes such as graphite felt, platinum electrode clips are generally used to hold the graphite felt for electrolysis. However, the electrolyte wets the felt material, causing the electrolyte to rise until it contacts the electrode clip, making the clip part of the anode. This corrosion and oxidation of the electrode clip results in excessively high local resistance in the system, and in severe cases, can even cause a circuit break, affecting the normal progress of electrolysis. When using anodes such as graphite blocks, which do not allow the electrolyte to rise easily, their high oxygen evolution overpotential leads to graphite oxidation, increasing the anode voltage, increasing energy consumption during electrolysis, and slowing down the electrolysis efficiency. Therefore, the development of non-precious metal highly conductive electrodes is of great significance in the large-scale industrial production of vanadium electrolytes.

[0052] For the cathode of the electrolytic cell, the main reaction is VO2. + +e - →VO 2+ With VO 2+ +e - →V 3+ However, side reactions still exist at the cathode, such as hydrogen evolution reaction and the formation of metal carbides. The hydrogen evolution reaction affects the hydrogen ion concentration in the cathode electrolyte, consuming water in the solvent and resulting in a lower hydrogen ion concentration and a higher vanadium ion concentration in the electrolyte, thus affecting its performance. Furthermore, continuous electrolysis causes carbon on the electrode to combine with vanadium ions to form vanadium carbide, a precipitate insoluble in acid. This vanadium ion precipitate cannot form part of the electrolyte, leading to the loss of active material and wasting vanadium resources.

[0053] Therefore, in a first aspect of this application, an electrolysis apparatus for preparing vanadium battery electrolyte is provided. According to an embodiment of this application, see [link to embodiment]. Figure 1 The electrolysis device 10 includes: an anode 100 and a cathode 200;

[0054] The anode 100 comprises stainless steel;

[0055] The cathode 200 includes a graphite felt and a modification layer disposed on at least a portion of the surface of the graphite felt, the modification layer comprising nickel manganese oxide.

[0056] Stainless steel has good electrical conductivity and a low oxygen evolution overpotential. Even after oxidation, its products retain good conductivity. For the entire electrolytic cell, the electrolysis process can be maintained within a suitable voltage range, preventing an increase in cell voltage due to increased anode resistance. This effectively prevents side reactions caused by excessive cell voltage, which could affect electrolysis efficiency and saves energy. Furthermore, using a non-precious metal as the anode reduces the cost of the electrolysis equipment.

[0057] Nickel and manganese oxides possess excellent electrical conductivity and electrochemical activity, making them suitable catalysts for accelerating the reduction of high-valence vanadium ions to lower-valence ions. Nickel, a transition metal, contains d orbitals, and electrons in these orbitals participate in reactions more readily than those in s and p orbitals, thus improving the electrolysis reaction rate and efficiency. However, nickel oxide exhibits poor stability in acids and gradually decomposes during long-term electrolysis. Manganese, also a transition metal, has relatively stable d orbitals with a half-filled state. Manganese doping can further modulate the electronic structure within the catalyst, enhancing its stability and catalytic activity against the cathode electrolyte. Simultaneously, the deposition of nickel-manganese oxides results in a highly stable modified layer with excellent catalytic performance. Furthermore, the deposition of nickel-manganese oxides on the graphite felt electrode surface also provides some isolation between vanadium ions and carbon, preventing the formation of vanadium carbide and reducing the loss of active materials in the electrolyte.

[0058] According to embodiments of this application, based on the total mass of the cathode, the content of the modification layer is 2% to 3%, for example, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, or 3%. The modification layer content meeting the above conditions can improve the catalytic activity and stability of the cathode, which is beneficial for the efficient reduction of vanadium ions and improves electrolysis efficiency. It can also improve the conductivity of the cathode, reduce the cell voltage of the electrolytic cell, thereby reducing side reactions caused by excessive cell voltage and saving energy.

[0059] According to embodiments of this application, the graphite felt is selected from one of polyacrylonitrile-based graphite felt, viscose-based graphite felt, cellulose-based graphite felt, and pitch-based graphite felt.

[0060] According to embodiments of this application, the stainless steel includes at least one of type 316 stainless steel, type 304 stainless steel, and type 430 stainless steel. Type 304, type 316, and type 430 are three commonly used stainless steels. Among the three, type 304 has the lowest Ni content and the worst electrical conductivity; type 430 has the highest Ni content and the best electrical conductivity, but its price is also higher; type 316 has moderate electrical conductivity and price, making it a preferred anode material.

[0061] According to an embodiment of this application, the electrolysis device 10 further includes a diaphragm 300. The diaphragm physically isolates the anode and cathode, preventing direct contact between the two electrodes and thus a short circuit, while allowing ions to pass through to maintain charge balance in the electrolyte, ensuring the smooth progress of the electrolysis reaction. It can also suppress side reactions between the anode and cathode, improving electrolysis efficiency and helping to maintain the stability of the electrolyte. Exemplarily, the diaphragm 300 includes a perfluorosulfonic acid membrane and / or a polybenzimidazole membrane.

[0062] According to an embodiment of this application, the electrolysis apparatus 10 further includes: an anode tank 400, which is disposed on one side of the diaphragm 300, and an anode 100 is disposed in the anode tank 400. This allows for the containment of anolyte.

[0063] According to an embodiment of this application, the electrolysis apparatus 10 further includes a cathode tank 500, which is disposed on the side of the diaphragm 300 away from the anode tank 400, and a cathode 200 is disposed in the cathode tank 500. This allows for the containment of cathode electrolyte, and vanadium battery electrolyte can be generated in the cathode tank.

[0064] In a second aspect, this application proposes a method for preparing vanadium battery electrolyte using the aforementioned electrolysis apparatus for preparing vanadium battery electrolyte. According to an embodiment of this application, the method includes:

[0065] A vanadium-containing solution is placed in a cathode tank, and the cathode is provided in the cathode tank;

[0066] The anolyte is placed in an anode tank, and the anode is disposed in the anode tank.

[0067] Connect the cathode and anode to a power supply device, turn on the power supply device, and perform electrolysis to obtain vanadium battery electrolyte in the cathode tank.

[0068] Therefore, the above-described method for preparing vanadium battery electrolyte can reduce side reactions at the cathode and anode, improve electrolysis efficiency, and reduce the loss of active materials in the electrolyte. Furthermore, this method is inexpensive, simple, and requires minimal equipment, making it suitable for industrial production. The features and advantages described above regarding the electrolysis apparatus for preparing vanadium battery electrolyte also apply to this method and will not be repeated here.

[0069] It should be noted that this application does not strictly limit the order of the two steps of "placing the vanadium-containing solution in the cathode tank" and "placing the anolyte in the anode tank". The former can be carried out first and then the latter, or the latter can be carried out first and then the former, or both can be carried out simultaneously.

[0070] For the cathode, it can be placed in the cathode tank before the vanadium-containing solution is placed in the cathode tank; it can be placed in the cathode tank after the vanadium-containing solution is placed in the cathode tank; or it can be placed in the cathode tank simultaneously with the vanadium-containing solution. Similarly, for the anode, the above-described cathode implementation method can be referred to.

[0071] According to an embodiment of this application, the method for preparing the cathode includes:

[0072] The cathode was obtained by performing cyclic voltammetry using a graphite felt electrode as the working electrode, an Hg / Hg₂SO₄ electrode as the reference electrode, a platinum sheet electrode as the counter electrode, and a mixture containing manganese and nickel compounds as the electrolyte. During the cyclic voltammetry scan, the manganese and nickel compounds can undergo a redox reaction on the graphite felt electrode to generate nickel-manganese oxides.

[0073] According to embodiments of this application, the cyclic voltammetric scan satisfies at least one of the following conditions:

[0074] The scan rate is 80mV / s to 120mV / s, for example, it can be 80mV / s, 90mV / s, 100mV / s, 110mV / s, or 120mV / s;

[0075] The scanning voltage range is 0.4V to 1.2V, for example, it can be 0.4V, 0.6V, 0.8V, 1.0V, or 1.2V;

[0076] The number of cycles is 3 to 5, for example, 3, 4, or 5 times.

[0077] Cyclic voltammetry scanning meets the above conditions, and the content of the nickel-manganese oxide-containing modification layer deposited on the graphite felt is appropriate. This can improve the conductivity of the cathode, reduce the cell voltage of the electrolytic cell, thereby reducing side reactions caused by excessive cell voltage and saving energy. In addition, the surface of the formed modification layer is uniformly deposited, with high flatness, and is not prone to modification layer peeling.

[0078] According to embodiments of this application, the manganese-containing compound includes at least one of manganese acetate, manganese sulfate, and manganese nitrate.

[0079] According to embodiments of this application, the nickel-containing compound includes at least one of nickel acetate, nickel sulfate, and nickel nitrate.

[0080] According to embodiments of this application, the electrolyte further comprises a buffer, wherein the buffer comprises at least one selected from sodium acetate, sodium sulfate, and sodium nitrate. The main function of the buffer in the electrolyte is to maintain a stable pH value, preventing pH fluctuations caused by redox reactions during electrolysis. This pH stability is crucial for protecting the electrodes, improving electrode performance, preventing electrolyte decomposition, and extending battery life. Furthermore, the buffer can also improve the conductivity and electrochemical stability of the electrolyte, reduce side reactions, thereby improving electrolysis efficiency and product quality.

[0081] According to embodiments of this application, based on the total mass of the mixture, the concentration of the manganese-containing compound is 0.01 mol / L to 0.1 mol / L, for example, 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, or 0.1 mol / L. The concentration of the manganese-containing compound meeting the above conditions helps to form a uniform, dense, and appropriately thick deposition layer. The mixture viscosity is suitable, the ion migration rate is fast, and the electrolysis efficiency is high.

[0082] According to embodiments of this application, based on the total mass of the mixture, the concentration of the nickel-containing compound is 0.05 mol / L to 0.2 mol / L, for example, 0.05 mol / L, 0.06 mol / L, 0.08 mol / L, 0.1 mol / L, 0.12 mol / L, 0.14 mol / L, 0.15 mol / L, 0.16 mol / L, 0.18 mol / L, or 0.2 mol / L. The concentration of the nickel-containing compound meeting the above conditions helps to form a uniform, dense, and appropriately thick deposition layer. The mixture viscosity is suitable, the ion migration rate is fast, and the electrolysis efficiency is high.

[0083] According to embodiments of this application, the vanadium-containing solution comprises a vanadium-containing compound, which includes vanadium pentoxide and / or ammonium metavanadate.

[0084] According to embodiments of this application, the concentration of the vanadium-containing compound is 1 mol / L to 2 mol / L, for example, it can be 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.8 mol / L, or 2 mol / L. Meeting the above conditions with the concentration of the vanadium-containing compound can improve the energy density of the battery and prevent precipitation during charging and discharging, thus avoiding blockage of the pipeline.

[0085] According to embodiments of this application, the vanadium-containing solution further comprises sulfuric acid.

[0086] According to embodiments of this application, the anolyte comprises sulfuric acid and / or sodium sulfate. This facilitates efficient completion of the electrolysis process.

[0087] It should be noted that this application does not impose special requirements on the power supply device, as long as it can be used as a power source for electrolysis, including but not limited to a potentiometer. The power supply device has a positive terminal and a negative terminal, with the positive terminal connected to the anode of the electrolysis device and the negative terminal connected to the cathode of the electrolysis device.

[0088] According to embodiments of this application, the electrolysis treatment is performed using a constant current of 400mA to 600mA, for example, 400mA, 420mA, 440mA, 450mA, 460mA, 480mA, 500mA, 520mA, 540mA, 550mA, 560mA, 580mA, or 600mA; and for a duration of 6h to 7h, for example, 6h, 6.25h, 6.5h, 6.75h, or 7h. This accelerates the electrochemical reaction rate, reduces energy consumption, suppresses side reactions, extends electrode life, and improves battery charge-discharge performance.

[0089] The following will explain the solution of this application with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0090] Example 1

[0091] In this embodiment, vanadium electrolyte is prepared by electrolysis, and the specific method is as follows:

[0092] 1. Experimental materials and equipment:

[0093] Sodium acetate, nickel acetate, manganese acetate, vanadium pentoxide (99%), sulfuric acid (3 mol / L), perfluorosulfonic acid membrane, plexiglass electrolytic cell, 316 stainless steel electrode, 3 mm graphite felt electrode (unmodified).

[0094] 2. Steps:

[0095] (1) An electrolyte containing 0.05 mol / L manganese acetate, 0.1 mol / L nickel acetate, and 0.2 mol / L sodium acetate was prepared. A graphite felt electrode was used as the working electrode, a platinum electrode as the counter electrode, and Hg / Hg2SO4 as the reference electrode. Cyclic voltammetry was performed using the three-electrode system in the voltage range of 0.4-1.2 V. Electrodeposition was completed in four cycles at 100 mV / s to obtain a graphite felt with a nickel manganese oxide modified layer.

[0096] (2) Vanadium pentoxide was dissolved in sulfuric acid to prepare a suspension solution with a vanadium ion concentration of 1.5 mol / L. This suspension was then transferred to the cathode tank of an acrylic electrolytic cell, while sulfuric acid was placed in the anode tank. The anode and cathode were separated by a perfluorosulfonic acid membrane. The cathode was made of graphite felt deposited with nickel-manganese oxide, and the anode was made of a 3cm × 3cm 316 stainless steel sheet. The electrodes were clamped with platinum battery clips. The electrolytic cell was connected to a potentiostat, and electrolysis was performed with a constant current of 500mA. The electrolyte in the cathode tank was the electrolyte for the vanadium redox flow battery.

[0097] Example 2

[0098] The difference from Example 1 is that in step (1), the number of cycles is 3.

[0099] Example 3

[0100] The difference from Example 1 is that in step (1), the number of cycles is 5.

[0101] Example 4

[0102] The difference from Example 1 is that the anode is 304 stainless steel.

[0103] Example 5

[0104] The difference from Example 1 is that in step (1), an electrolyte containing 0.05 mol / L manganese acetate, 0.2 mol / L nickel acetate and 0.2 mol / L sodium acetate is prepared to modify the graphite felt electrode.

[0105] Example 6

[0106] The difference from Example 1 is that in step (1), an electrolyte containing 0.05 mol / L manganese acetate, 0.05 mol / L nickel acetate and 0.2 mol / L sodium acetate is prepared to modify the graphite felt electrode.

[0107] Example 7

[0108] The difference from Example 1 is that in step (1), an electrolyte containing 0.05 mol / L manganese acetate, 0.15 mol / L nickel acetate and 0.2 mol / L sodium acetate is prepared to modify the graphite felt electrode.

[0109] Comparative Example 1

[0110] The difference from Example 1 is that the cathode is an unmodified graphite felt.

[0111] Comparative Example 2

[0112] The difference from Example 1 is that in step (1), the electrolyte used to prepare the graphite felt contains 0.1 mol / L nickel acetate and 0.2 mol / L sodium acetate, resulting in a graphite felt with a nickel oxide modified layer deposited.

[0113] Comparative Example 3

[0114] The difference from Example 1 is that in step (1), the electrolyte contains 0.05 mol / L manganese acetate and 0.2 mol / L sodium acetate, resulting in a graphite felt with a manganese oxide modified layer deposited.

[0115] Comparative Example 4

[0116] The difference from Example 1 is that step (1) is as follows:

[0117] An electrolyte containing 0.05 mol / L ferric acetate, 0.15 mol / L nickel acetate, and 0.2 mol / L sodium acetate was prepared to obtain a graphite felt with a nickel-iron oxide modified layer deposited on it.

[0118] Comparative Example 5

[0119] The difference from Example 1 is that the anode is an unmodified graphite felt.

[0120] Comparative Example 6

[0121] The difference from Example 1 is that the anode used is a titanium sheet.

[0122] Comparative Example 7

[0123] The difference from Example 1 is that the anode used is a platinum sheet.

[0124] Comparative Example 8

[0125] The difference from Example 1 is that the anode used is a graphite sheet.

[0126] Test methods

[0127] 1. Method for determining the time required to complete the preparation of vanadium battery electrolyte in Examples 1-7 and Comparative Examples 1-8: After a certain period of electrolysis, the cathode electrolyte is taken and the concentration and valence state of the electrolyte are tested by potentiometric titration. If the test results meet the requirements that the concentration of vanadium ions in the electrolyte is ≥1.5mol / L and the ratio of +3 to +4 valence vanadium ions is 1:1, then the reaction progress is determined to be complete. The electrolysis time is recorded, and the results are shown in Table 1.

[0128] 2. The electrolyte temperatures of Examples 1-7 and Comparative Examples 1-8 were obtained by measuring with a thermometer, and the results are shown in Table 1.

[0129] 3. The current, starting voltage, and ending voltage of the electrolytic cell during the preparation process of vanadium battery electrolyte in Examples 1-7 and Comparative Examples 1-8 were read from a potentiostat, and the results are shown in Table 1.

[0130] 4. Test the content of the cathode surface modification layer in Examples 1-7 and Comparative Example 1 respectively, and observe whether there is precipitation in the electrolyte of Examples 1-7 and Comparative Example 1. The content of the cathode surface modification layer is calculated by the following formula: weigh the graphite felt before and after deposition, and divide the difference by the mass of the graphite felt after deposition to get the content of the cathode surface modification layer; the results are shown in Table 2.

[0131] The results are shown in Table 1. The electrolysis performance of Examples 1-7 is generally better than that of Comparative Examples 1-8. The heat generation after electrolysis is not obvious (the heat generation is mainly due to the excessive electrode resistance).

[0132] As can be seen from Comparative Example 1, when graphite felt without a modification layer is used as the cathode, the electrolysis completion time is relatively long, requiring 8 hours. The starting voltage and termination voltage are relatively high in all test cases, indicating that the electrode resistance is high when there is no modification layer, which increases the overall cell voltage of the electrolytic cell, raises the electrolyte temperature, and increases the energy consumption of the electrolysis process.

[0133] As can be seen from Comparative Example 2, when using graphite felt modified only by Ni as the cathode, the starting voltage and ending voltage during the electrolysis process are higher, and the temperature rises in the electrolytic cell, indicating that the energy consumption of electrolysis under this condition is higher than that in the example. Since the stability of graphite felt electrode modified only by Ni is poor, Ni will gradually dissolve in the electrolyte during the electrolysis process, introducing impurity Ni into the vanadium electrolyte and contaminating the vanadium electrolyte.

[0134] As can be seen from Comparative Example 3, the electrolysis time is longer than that of the examples when using graphite felt modified only by Mn as the cathode. This is because Mn oxide has poor conductivity, and the modification of the graphite felt surface by Mn oxide alone will increase the resistance of the cathode and slow down the rate of electrolysis. Due to the high resistance of the cathode, the starting and ending voltages of the electrolysis process are also increased. The high resistance generates heat during the electrolysis process, causing the electrolyte environment to heat up to 38°C when the electrolysis is completed, which is higher than all the electrolysis systems in the examples.

[0135] Comparative Example 4 shows that the stability of FeNi oxide loaded on the cathode graphite felt surface as an electrode catalyst is not ideal. During electrolysis, the surface-loaded FeNi catalyst gradually dissolves in the electrolyte. Not only is the electrolysis rate not enhanced, but the dissolution of the catalyst also introduces impurities into the vanadium electrolyte in the cathode. Therefore, electrolysis can be completed within 7 hours under the condition of nickel-manganese oxide as a catalyst, and the rate is faster than the electrolysis systems without a catalyst, with a single catalyst, and with other catalysts. This indicates that nickel-manganese oxide has the effect of accelerating the electrolysis reaction. Moreover, the temperature of the electrolyte remains basically at room temperature at the end of electrolysis, indicating that the energy consumption of electrolysis is very low when the cathode is loaded with nickel-manganese oxide as a catalyst.

[0136] As can be seen from Comparative Example 5, although the electrolysis can proceed normally when using unmodified graphite felt as the anode, the electrochemical activity of graphite felt as the anode is not ideal. It takes 8 hours of electrolysis to complete the preparation of the electrolyte, and the electrolysis system shows a significant temperature rise, indicating that a large part of the electrical energy is consumed in heat generation.

[0137] As can be seen from Comparative Example 6, when Ti electrode is used as the anode, it will be rapidly oxidized during the electrolysis process. Since titanium oxide has a high resistance, the potential of the electrolytic cell will continue to increase. When the electrolytic cell is kept at a constant current of 500mA, the voltage exceeds the range of the potentiostat. This shows that constant current electrolysis cannot be completed with this system when using titanium electrode.

[0138] As can be seen from Comparative Example 7, when platinum is used as the anode and the cell pressure is within a suitable range, no temperature rise occurs during the electrolysis process, and the electrolysis efficiency is comparable to that of stainless steel. However, platinum is expensive, which increases the cost of electrolyte preparation.

[0139] As can be seen from Comparative Example 8, when graphite sheets are used as the anode and the cell voltage is 3.0V, the cell voltage rises to 7.0V after electrolysis. At this time, the temperature of the electrolyte rises, indicating that the energy consumption of the electrolytic cell is high. In addition, many pores appear on the surface of the graphite sheet electrode, which may be caused by the oxidation of graphite under high voltage, affecting the reuse of the graphite sheet electrode.

[0140] Table 1

[0141] Electrolysis time / h Electrolyte temperature / ℃ Current / mA Starting voltage / V Termination voltage / V reaction progress Example 1 6 25 500 3.0 4.5 Finish Example 2 6.5 25 500 3.0 5.0 Finish Example 3 7 25 500 3.0 5.5 Finish Example 4 6.5 25 500 3.0 5.5 Finish Example 5 6 25 500 3.0 5.0 Finish Example 6 6.5 25 500 3.0 5.5 Finish Example 7 6.25 25 500 3.0 5.0 Finish Comparative Example 1 8 50 500 5.0 8.5 Finish Comparative Example 2 7 35 500 4.0 5.5 Finish Comparative Example 3 7.5 38 500 4.0 6.0 Finish Comparative Example 4 8 40 500 3.0 6.5 Finish Comparative Example 5 8 40 500 4.5 8.0 Finish Comparative Example 6 / / 500 7.0 / Incomplete Comparative Example 7 6 25 500 3.0 4.5 Finish Comparative Example 8 8 40 500 3.0 7.0 Finish

[0142] The results are shown in Table 2. Compared with Comparative Example 1, the graphite felt cathode of Example 1, after being modified with nickel manganese oxide, showed increased conductivity and decreased voltage in the corresponding electrolytic cell. Furthermore, no precipitation was generated in the cathode cell. This indicates that electrodepositing nickel manganese oxide on the cathode surface to isolate vanadium ions from carbon is effective.

[0143] As can be seen from Examples 1-3, different deposition cycles result in different masses of nickel-manganese oxide deposited, and the corresponding electrolysis conditions also vary slightly. The more deposition cycles, the more material is deposited. When using an electrode deposited for 3-5 cycles, the electrode surface is smooth and the modified layer content is high. Nickel has good conductivity, and the cathode receives a lower voltage, resulting in a lower overall electrolytic cell potential, thus allowing electrical energy to be effectively used for the electrolytic reaction. When using an electrode deposited for more than five cycles, although the modified layer content is highest, the electrode surface uniformity is low, and the electrolysis effect is weak. When using an electrode deposited for fewer than three cycles, although the electrode surface smoothness is high, the insufficient deposition cycles result in insufficient material loading on the electrode surface, and the effect on improving the electrolysis rate and saving energy is not significant.

[0144] As can be seen from Examples 1 and 5-7, the content of nickel acetate in the electrolyte used for deposition is within the range of this application, which reduces the electrolysis endpoint voltage and accelerates the electrolysis rate, thus achieving beneficial effects such as increasing the reaction rate, reducing electrolysis energy consumption, and lowering the temperature of the electrolytic cell.

[0145] Table 2

[0146] Number of electrodeposition cycles Current (mA) Electrolyte precipitation Modification layer content (%) Example 1 500 No sediment 2.19 Example 2 500 No sediment 2.05 Example 3 500 No sediment 2.38 Example 4 500 No sediment 2.10 Example 5 500 No sediment 2.28 Example 6 500 No sediment 2.01 Example 7 500 No sediment 2.24 Comparative Example 1 500 There is sediment 0

[0147] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. An electrolysis apparatus for preparing vanadium battery electrolyte, characterized in that, include: Anode and cathode; The anode comprises stainless steel; The cathode comprises a graphite felt and a modification layer, the modification layer being disposed on at least a portion of the surface of the graphite felt, the modification layer comprising nickel manganese oxide.

2. The electrolysis apparatus according to claim 1, characterized in that, Based on the total mass of the cathode, the content of the modification layer is 2% to 3%.

3. The electrolysis apparatus according to claim 1, characterized in that, The graphite felt is selected from polyacrylonitrile-based graphite felt, viscose-based graphite felt, cellulose-based graphite felt, or pitch-based graphite felt.

4. The electrolysis apparatus according to claim 1, characterized in that, The stainless steel includes at least one of type 316 stainless steel, type 304 stainless steel, and type 430 stainless steel.

5. The electrolysis apparatus according to claim 1, characterized in that, Further includes: Diaphragm; An anode tank is disposed on one side of the diaphragm, and the anode is disposed in the anode tank; A cathode tank is disposed on the side of the diaphragm away from the anode tank, and the cathode is disposed in the cathode tank.

6. The electrolysis apparatus according to claim 5, characterized in that, The diaphragm comprises a perfluorosulfonic acid membrane and / or polybenzimidazole.

7. A method for preparing vanadium battery electrolyte using the electrolysis apparatus for preparing vanadium battery electrolyte as described in any one of claims 1 to 6, characterized in that, include: A vanadium-containing solution is placed in a cathode tank, and the cathode is provided in the cathode tank; The anolyte is placed in an anode tank, and the anode is disposed in the anode tank. Connect the cathode and anode to a power supply device, turn on the power supply device, and perform electrolysis to obtain vanadium battery electrolyte in the cathode tank.

8. The method according to claim 7, characterized in that, The method for preparing the cathode includes: Using a graphite felt electrode as the working electrode, an Hg / Hg2SO4 electrode as the reference electrode, a platinum sheet electrode as the counter electrode, and a mixed solution containing manganese and nickel compounds as the electrolyte, cyclic voltammetry was performed to obtain the cathode. Wherein, the cyclic voltammetric scan satisfies at least one of the following conditions: The scan rate is 80mV / s to 120mV / s; The scanning voltage range is 0.4V to 1.2V; The number of cycles is 3 to 5.

9. The method according to claim 8, characterized in that, The manganese-containing compound includes at least one of manganese acetate, manganese sulfate, and manganese nitrate; And / or, the nickel-containing compound includes at least one of nickel acetate, nickel sulfate, and nickel nitrate; And / or, the electrolyte further comprises: a buffer, the buffer comprising at least one of sodium acetate, sodium sulfate and sodium nitrate; And / or, based on the total mass of the mixture, the concentration of the manganese-containing compound is 0.01 mol / L to 0.1 mol / L; And / or, based on the total mass of the mixture, the concentration of the nickel-containing compound is 0.05 mol / L to 0.2 mol / L.

10. The method according to claim 7, characterized in that, The vanadium-containing solution includes vanadium-containing compounds, which include vanadium pentoxide and / or ammonium metavanadate.

11. The method according to claim 10, characterized in that, The concentration of the vanadium-containing compound is 1 mol / L to 2 mol / L.

12. The method according to claim 7, characterized in that, The vanadium-containing solution further includes sulfuric acid.

13. The method according to claim 7, characterized in that, The anolyte comprises sulfuric acid and / or sodium sulfate.

14. The method according to claim 7, characterized in that, The electrolytic treatment is performed using a constant current of 400mA to 600mA for 6 to 7 hours.

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