An aqueous all-chromium flow battery electrolyte, a method of preparation and a battery comprising the same

Abstract

The application discloses a water-based full-chromium liquid flow battery electrolyte, a preparation method and a battery comprising the same, and belongs to the technical field of electrochemical energy storage. The positive and negative active materials of the water-based full-chromium liquid flow battery provided by the application both adopt chromium elements, and a soluble compound containing cations or anions in the form of oxygen-containing acid radicals is used as an additive, so that the capacity attenuation problem caused by cross contamination of different metal ions is fundamentally eliminated, and the water-based full-chromium liquid flow battery has the advantages of low theoretical cost, long life cycle and high energy density. The application introduces the additive, solves the problems of slow chromium ion reaction kinetics, serious hydrogen evolution side reaction and poor chemical stability, so that the water-based full-chromium liquid flow battery system can be stably operated, and a new solution is provided for large-scale energy storage.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage technology, and particularly relates to an aqueous all-chromium redox flow battery electrolyte, its preparation method, and a battery containing the electrolyte. Background Technology

[0002] With the acceleration of the global energy transition, the scale of grid connection for renewable energy sources such as wind and solar power is expanding rapidly. However, their intermittent and fluctuating characteristics pose a significant challenge to the stable operation of the power grid. Therefore, developing efficient and reliable large-scale long-term energy storage technologies has become crucial for ensuring energy security. Among various energy storage technologies, flow batteries are considered one of the most promising large-scale energy storage technologies due to their unique advantages such as power-capacity decoupling, long cycle life, and high safety. Vanadium redox flow battery technology is the most mature, using vanadium as the active material, effectively avoiding the problem of cross-contamination between different metal ions. However, the development of vanadium redox flow battery systems is heavily constrained by the high price and fluctuating supply of vanadium resources. To reduce costs, bimetallic systems such as iron-chromium flow batteries have been proposed, using abundant iron and chromium as active materials. However, these systems face a new technical challenge of cross-contamination due to the different electrolytes at the positive and negative electrodes, leading to continuous capacity decay and increasing the complexity of system control.

[0003] Chromium is abundant and inexpensive, and has been studied for many years as a negative electrode active material in iron-chromium flow batteries. However, to date, no research or technical solution has successfully proposed or constructed an all-chromium flow battery system in which both the positive and negative electrode active materials are chromium. This is mainly due to the slow reaction kinetics of the Cr(VI) / Cr(III) redox couple and the poor chemical stability of hexavalent chromium in acidic aqueous solutions, which easily leads to side reactions or decomposition. Therefore, developing a novel all-chromium flow battery system based on a single element, chromium, has significant scientific value and application prospects. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes an aqueous all-chromium flow battery electrolyte, its preparation method, and a battery containing the same electrolyte. The all-chromium system of this invention fundamentally eliminates the capacity decay problem caused by cross-contamination of different metal ions, offering advantages such as low cost, long lifespan, and high energy density. Furthermore, by introducing additives, this invention solves problems such as slow chromium ion reaction kinetics, severe hydrogen evolution side reactions, and poor chemical stability. The introduction of additives also significantly improves the long-term chemical stability of the electrolyte and the cycle life of the battery.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides an aqueous full-chromium flow battery electrolyte, which is composed of a positive electrode electrolyte and a negative electrode electrolyte. The positive electrode electrolyte and the negative electrode electrolyte are independently composed of the following raw materials: active material, additives, supporting electrolyte and solvent.

[0007] The active material is a soluble trivalent chromium salt, and the active materials of both the positive and negative electrode electrolytes are soluble trivalent chromium salts.

[0008] The supporting electrolyte is selected from one of the following soluble compounds containing the following anions and hydrogen ions: sulfate, chloride, nitrate, bromide, iodide, perchlorate, or methanesulfonate.

[0009] The additive is selected from at least one of soluble compounds containing the following cations or anions in the form of oxyacid radicals: Bi 3+ Cu 2+ Pb 2+ In 3+ Al 3+ Fe 3+ Co 2+ Ni 2+ Sn 2+ Sb 3+ Ru 3+ Mg 2+ Mn 2+ Ag + Ce 3+ Cd 2+ Ga 3+ Ti 3+ Pd 2+ 、Ge 4+ 、Tl + Pt 4+ 、Nd 3+ Ba 2+ Ca 2+ Au 3+ SeO3 2- TeO3 2- MoO3 2- WO3 2- [PMo] 12 O 40 ] 3- [PW] 12 O 40 ] 3- and [SiW 12 O 40 ] 3- ;

[0010] The solvent is water.

[0011] The positive electrode reaction of the existing iron-chromium flow battery is: Fe3+ +e - ↔Fe 2+ Unlike related technologies of iron-chromium flow batteries, the positive electrode reaction of the aqueous all-chromium flow battery of this invention is: Cr2O7 2- +6e - +14H + ↔2Cr 3+ +7H2O. The all-chromium system of this invention is not a simple improvement on the existing iron-chromium system, but a completely new system built from a fundamentally different technical problem. The all-chromium system faces the following technical barriers: 1. The stability and reaction kinetics challenges of high-valence chromium at the cathode: the higher valence state Cr generated in the cathode reaction... 6+ It possesses strong oxidizing properties, placing extremely stringent requirements on the corrosion resistance of key battery materials such as separators and electrodes. Meanwhile, Cr... 3+ / Cr 6+ 1. The reaction kinetics of the chromium-containing electrode couple are generally slower, reducing battery performance. 2. Increased risk of chromium ion hydrolysis and precipitation: In a full chromium system, the concentration of chromium ions doubles, and the chemical environment of the entire system must simultaneously meet the requirements of the positive and negative electrode reactions. This greatly increases the risk of trivalent chromium ions hydrolyzing to form chromium hydroxide precipitate. Precipitation can clog flow channels and cover electrode active sites, leading to rapid degradation of battery performance. 3. Risk of hydrogen evolution side reaction: The negative electrode chromium-containing electrode couple (Cr... 2+ / Cr 3+ The standard potential of chromium redox flow batteries is relatively negative, very close to the hydrogen evolution potential in aqueous electrolytes. During charging, hydrogen evolution side reactions easily occur at the negative electrode, leading to a decrease in coulombic efficiency and continuous capacity decay. This invention successfully solves the above problems by adding specific additives. The core of this invention is to construct a multifunctional composite catalytic interface through in-situ electrochemical deposition at the electrode interface. This interface specifically addresses three major technical challenges faced by all-chromium redox flow batteries. The specific principles are as follows: 1. Solving the stability and reaction kinetics problems of high-valent chromium at the positive electrode: When the metal ions in the additive are charged at the positive electrode, they preferentially undergo reduction deposition on the surface of the carbon felt electrode, forming a dense nanoscale metal or metal oxide protective layer. This protective layer acts as a physical barrier, effectively isolating the highly oxidizing chromium. 6+ Direct contact with the electrode substrate material significantly improves the corrosion resistance of the cathode material and extends battery life. More importantly, this deposited layer is not an inert layer, but a highly efficient electrocatalyst, capable of providing a suitable environment for Cr... 3+ / Cr 6+1. The redox reaction of the redox couple provides a large number of highly active sites, significantly reducing the activation energy barrier of the reaction, thereby accelerating the positive electrode reaction kinetics and improving battery efficiency. 2. Mitigating the risk of chromium ion hydrolysis and precipitation: The most important role of the additive is to fundamentally avoid a sharp increase in the local pH value of the electrolyte caused by hydrogen evolution side reactions by inhibiting negative electrode precipitation. Maintaining a stable and suitable acidic environment is the most critical factor in preventing the hydrolysis and precipitation of trivalent chromium. At the same time, the deposition layer formed by the additive changes the properties of the electrode-electrolyte interface, which may make the charge distribution at the interface more uniform and reduce local pH fluctuations caused by uneven current density. 3. Mitigating the risk of negative electrode hydrogen evolution side reactions: The metal ions in the additive deposit during negative electrode charging, and the metal layer itself is a weak catalyst for the hydrogen evolution reaction, that is, it has a high hydrogen evolution overpotential, covering the original active sites on the electrode that are prone to initiating hydrogen evolution. This makes the energy required for hydrogen evolution reaction to occur at the negative electrode higher, thus preferentially allowing chromium to undergo hydrogen evolution. 2+ / Cr 3+ The reaction occurs. Simultaneously, this deposition interface is also Cr... 2 + / Cr 3+ The redox couple provides a superior reaction pathway, reducing the over-electrolysis of chromium ion reduction and thus further suppressing hydrogen evolution both thermodynamically and kinetically, resulting in a substantial improvement in coulombic efficiency. This invention fundamentally eliminates cross-contamination, achieving an ultra-long cycle life for the battery. Since the active materials of the positive and negative electrodes are essentially the same, even if ions cross the separator, it will not lead to permanent capacity decay. This invention's aqueous all-chromium flow battery system successfully utilizes the higher valence state of chromium, resulting in a theoretical voltage higher than that of iron-chromium flow batteries (1.74V vs 1.18V), thereby achieving higher energy density.

[0012] Furthermore, in the positive electrode electrolyte, the concentration of the soluble trivalent chromium salt is 0.2 mol / L to 2 mol / L, the concentration of the additive is 0.05 mol / L to 0.5 mol / L, and the concentration of hydrogen ions in the supporting electrolyte is 1 mol / L to 3 mol / L.

[0013] And / or, in the negative electrode electrolyte, the concentration of the soluble trivalent chromium salt is 0.2 mol / L to 2 mol / L, the concentration of the additive is 0.05 mol / L to 0.5 mol / L, and the concentration of hydrogen ions in the supporting electrolyte is 1 mol / L to 3 mol / L.

[0014] Furthermore, in the positive electrode electrolyte, the concentration of the soluble trivalent chromium salt is 0.5 mol / L to 1.5 mol / L, the concentration of the additive is 0.1 mol / L to 0.2 mol / L, and the concentration of hydrogen ions in the supporting electrolyte is 1 mol / L to 2 mol / L;

[0015] And / or, in the negative electrode electrolyte, the concentration of the soluble trivalent chromium salt is 0.5 mol / L to 1.5 mol / L, the concentration of the additive is 0.1 mol / L to 0.2 mol / L, and the concentration of hydrogen ions in the supporting electrolyte is 1 mol / L to 2 mol / L.

[0016] The present invention also provides a method for preparing the electrolyte of the above-mentioned aqueous full chromium redox flow battery, wherein the method for preparing the positive electrode electrolyte includes the following steps: dissolving the active material and additives in a solvent, adding a supporting electrolyte, stirring evenly, and obtaining the positive electrode electrolyte;

[0017] The preparation method of the negative electrode electrolyte is as follows: dissolve the active material and additives in a solvent, add the supporting electrolyte, stir evenly, and obtain the negative electrode electrolyte.

[0018] The present invention also provides an aqueous full-chromium flow battery containing the above-mentioned aqueous full-chromium flow battery electrolyte.

[0019] Furthermore, the aqueous full-chromium redox flow battery includes a negative electrode, a positive electrode, a negative electrolyte storage tank, a positive electrolyte storage tank, a diaphragm, a negative peristaltic pump, and a positive peristaltic pump.

[0020] The negative electrode electrolyte storage tank is used to store the negative electrode electrolyte, and the positive electrode electrolyte storage tank is used to store the positive electrode electrolyte;

[0021] The negative electrode peristaltic pump is used to pump the negative electrode electrolyte to the negative electrode; the positive electrode peristaltic pump is used to pump the positive electrode electrolyte to the positive electrode.

[0022] The diaphragm is used to separate the negative electrode electrolyte and the positive electrode electrolyte.

[0023] Furthermore, both the negative electrode and the positive electrode are made of porous carbon materials;

[0024] And / or, the membrane is a polymer membrane with ion-selective permeability.

[0025] Furthermore, the porous carbon material is selected from graphite felt, carbon felt, carbon cloth, or carbon paper;

[0026] Furthermore, the polymer membrane with ion-selective permeability is selected from perfluorosulfonic acid proton exchange membranes, sulfonated polyether ether ketone membranes, polyethylene porous membranes, or anion exchange membranes.

[0027] Compared with the prior art, the present invention has the following advantages and technical effects:

[0028] This invention is the first to explicitly propose a novel flow battery system, the "aqueous all-chromium flow battery," and provides a feasible technical solution for realizing this system, filling a gap in the existing flow battery technology field. Compared with traditional multi-metal systems, the all-chromium system fundamentally eliminates the capacity decay problem caused by cross-contamination of different metal ions, and has the advantages of low theoretical cost, long life cycle, and high energy density. By introducing additives, this invention solves problems such as slow chromium ion reaction kinetics, severe hydrogen evolution side reactions, and poor chemical stability, thereby enabling the aqueous all-chromium flow battery system to operate stably and providing a new solution for large-scale energy storage. Attached Figure Description

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0030] Figure 1 This is a schematic diagram of the structure of the aqueous full-chromium redox flow battery of the present invention, wherein the negative electrode-1, the positive electrode-2, the negative electrode electrolyte storage tank-3, the positive electrode electrolyte storage tank-4, the separator-5, the negative electrode peristaltic pump-6, and the positive electrode peristaltic pump-7 are shown.

[0031] Figure 2 Rate performance of the aqueous all-chromium redox flow battery prepared in Example 1;

[0032] Figure 3 The results of operational stability tests of the aqueous all-chromium redox flow battery prepared in Example 2 at different depths of charge;

[0033] Figure 4 The results of long-term cycling performance tests for the aqueous all-chromium redox flow battery prepared in Example 3;

[0034] Figure 5 The cycling performance test results are for the aqueous all-chromium flow battery prepared in Example 4. Detailed Implementation

[0035] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0036] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0037] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0038] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0039] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0040] An embodiment of the present invention provides an aqueous full-chromium flow battery electrolyte, which is composed of a positive electrode electrolyte and a negative electrode electrolyte. The positive electrode electrolyte and the negative electrode electrolyte are independently composed of the following raw materials: active material, additives, supporting electrolyte and solvent.

[0041] The active material is a soluble trivalent chromium salt, and the active materials of both the positive and negative electrode electrolytes are soluble trivalent chromium salts.

[0042] The supporting electrolyte is selected from one of the following soluble compounds containing the following anions and hydrogen ions: sulfate, chloride, nitrate, bromide, iodide, perchlorate, or methanesulfonate.

[0043] The additive is selected from at least one of the following soluble compounds containing cations or anions in the form of oxyanions: Bi 3+ Cu 2+ Pb 2+ In 3+ Al 3+ Fe 3+ Co 2+ Ni2+ Sn 2+ Sb 3+ Ru 3+ Mg 2+ Mn 2+ Ag + Ce 3+ Cd 2+ Ga 3+ Ti 3+ Pd 2+ 、Ge 4+ 、Tl + Pt 4+ 、Nd 3+ Ba 2+ Ca 2+ Au 3+ SeO3 2- TeO3 2- MoO3 2- WO3 2- [PMo] 12 O 40 ] 3- [PW] 12 O 40 ] 3- and [SiW 12 O 40 ] 3- ;

[0044] The solvent is water.

[0045] In embodiments of the present invention, the soluble trivalent chromium salt is selected from chromium trichloride hexahydrate, chromium sulfate, chromium acetate, or chromium nitrate.

[0046] In embodiments of the present invention, the supporting electrolyte is selected from sulfuric acid, hydrochloric acid, nitric acid, hydrobromic acid, hydroiodic acid, perchloric acid, or methanesulfonic acid. The supporting electrolyte is used not only to adjust the pH value of the electrolyte but also to improve the electrolyte conductivity and maintain the osmotic pressure balance between the positive and negative electrodes.

[0047] In embodiments of the present invention, the additives are selected from bismuth nitrate, copper sulfate, lead sulfate, indium chloride, aluminum chloride, ferric chloride, cobalt sulfate, nickel sulfate, stannous chloride, antimony trichloride, ruthenium trichloride, magnesium chloride, manganese chloride, silver nitrate, cerium chloride, cadmium sulfate, gallium trichloride, titanium trichloride, palladium chloride, germanium dioxide, thallium nitrate, chloroplatinic acid, neodymium chloride, barium chloride, calcium chloride, chloroauric acid, sodium selenite, sodium tellurite, ammonium molybdate, sodium tungstate, phosphomolybdic acid, phosphotungstic acid, and phosphotungstic acid. Through controllable in-situ electrochemical deposition, a functionalized composite interface layer is constructed on the surface of the carbon felt electrode, thereby systematically regulating and optimizing the reaction kinetics and selectivity of the chromium couple.

[0048] In embodiments of the present invention, in the positive electrode electrolyte, the concentration of the soluble trivalent chromium salt is 0.2 mol / L to 2 mol / L, the concentration of the additive is 0.05 mol / L to 0.5 mol / L, and the concentration of hydrogen ions in the supporting electrolyte is 1 mol / L to 3 mol / L; in the negative electrode electrolyte, the concentration of the soluble trivalent chromium salt is 0.2 mol / L to 2 mol / L, the concentration of the additive is 0.05 mol / L to 0.5 mol / L, and the concentration of hydrogen ions in the supporting electrolyte is 1 mol / L to 3 mol / L. Preferably, in the positive electrode electrolyte, the concentration of the soluble trivalent chromium salt is 0.5 mol / L to 1.5 mol / L, the concentration of the additive is 0.1 mol / L to 0.2 mol / L, and the concentration of hydrogen ions in the supporting electrolyte is 1 mol / L to 2 mol / L; in the negative electrode electrolyte, the concentration of the soluble trivalent chromium salt is 0.5 mol / L to 1.5 mol / L, the concentration of the additive is 0.1 mol / L to 0.2 mol / L, and the concentration of hydrogen ions in the supporting electrolyte is 1 mol / L to 2 mol / L.

[0049] The embodiments of the present invention also provide a method for preparing the above-mentioned aqueous full chromium redox flow battery electrolyte, wherein the method for preparing the positive electrode electrolyte includes the following steps: dissolving the active material and additives in a solvent, adding a supporting electrolyte, stirring evenly, and obtaining the positive electrode electrolyte;

[0050] The preparation method of negative electrode electrolyte is as follows: dissolve the active material and additives in a solvent, add the supporting electrolyte, stir evenly, and obtain the negative electrode electrolyte.

[0051] An embodiment of the present invention also provides an aqueous full-chromium flow battery containing the above-mentioned aqueous full-chromium flow battery electrolyte.

[0052] The positive and negative electrolytes of the aqueous full-chromium redox flow battery of this invention both contain active materials, additives, and supporting electrolytes. The reactions at the positive and negative electrodes of the aqueous full-chromium redox flow battery of this invention are as follows:

[0053] Negative electrode: Cr 3+ +e - ↔Cr 2+ ;

[0054] Positive electrode: Cr2O7 2- +6e - +14H + ↔2Cr 3+ +7H2O.

[0055] In an embodiment of the present invention, the aqueous full-chromium redox flow battery includes a negative electrode 1, a positive electrode 2, a negative electrolyte storage tank 3, a positive electrolyte storage tank 4, a separator 5, a negative peristaltic pump 6, and a positive peristaltic pump 7 (structural schematic diagram shown). Figure 1 (as shown)

[0056] The negative electrode electrolyte storage tank 3 is used to store the negative electrode electrolyte, and the positive electrode electrolyte storage tank 4 is used to store the positive electrode electrolyte;

[0057] The negative electrode peristaltic pump 6 is used to pump the negative electrode electrolyte to the negative electrode 1; the positive electrode peristaltic pump 7 is used to pump the positive electrode electrolyte to the positive electrode 2;

[0058] The diaphragm 5 is used to separate the negative electrode electrolyte and the positive electrode electrolyte.

[0059] The aqueous full-chromium flow battery provided by this invention uses chromium as the active material for both the positive and negative electrodes. It is an all-chromium flow battery that utilizes the different valence states of chromium for energy storage and conversion. The specific working principle of this aqueous full-chromium flow battery is as follows: The negative electrolyte in the negative electrode electrolyte storage tank 3 enters the negative electrode 1 through the negative electrode peristaltic pump 6. The active material in the negative electrolyte will undergo an electrochemical reaction on the surface of the negative electrode 1. Afterwards, the negative electrolyte flows out of the negative electrode 1 and re-enters the negative electrolyte storage tank 3. The positive electrolyte in the positive electrode electrolyte storage tank 4 enters the positive electrode 2 through the positive electrode peristaltic pump 7. The active material in the positive electrolyte will undergo an electrochemical reaction on the surface of the positive electrode 2. Afterwards, the positive electrolyte flows out of the positive electrode 2 and re-enters the positive electrolyte storage tank 4. Because of the presence of the separator 5, the negative electrolyte on the surface of the negative electrode 1 and the positive electrolyte on the surface of the positive electrode are independent of each other; only protons can pass through the separator 5.

[0060] In embodiments of the present invention, both the negative electrode and the positive electrode are porous carbon materials; the membrane is a polymer membrane with ion-selective permeability.

[0061] For example, the porous carbon material is selected from graphite felt, carbon felt, carbon cloth or carbon paper; the polymer membrane with ion-selective permeability is selected from perfluorosulfonic acid proton exchange membrane, sulfonated polyether ether ketone membrane, polyethylene porous membrane or anion exchange membrane.

[0062] All raw materials used in the embodiments of the present invention were obtained through commercial purchase.

[0063] The technical solution of the present invention will be further illustrated by the following embodiments.

[0064] Example 1

[0065] An aqueous full-chromium flow battery electrolyte is composed of the following substances: active material chromium trichloride hexahydrate, additive indium chloride, supporting electrolyte hydrochloric acid, and solvent deionized water;

[0066] The preparation method of the electrolyte for the above-mentioned aqueous all-chromium flow battery includes the following steps:

[0067] Preparation of the positive electrode electrolyte: Weigh 10.8751 g of chromium trichloride hexahydrate and 2.2117 g of indium chloride, place them in a beaker, and dissolve them in deionized water; then use a pipette to transfer 2.007 mL of 37% hydrochloric acid dropwise into the beaker, pour it into a 20 mL volumetric flask, and mix thoroughly to obtain the positive electrode electrolyte; wherein, in the positive electrode electrolyte: the concentration of chromium trichloride hexahydrate is 2 mol / L, the concentration of indium chloride is 0.5 mol / L, and the concentration of hydrochloric acid is 3 mol / L;

[0068] The preparation method of the negative electrode electrolyte is the same as that of the positive electrode electrolyte.

[0069] A method for preparing an aqueous all-chromium redox flow battery includes the following steps: using the prepared positive and negative electrolytes as the battery electrolytes; both positive and negative electrodes are graphite felt electrodes with an electrode area of ​​2*2 cm². 2 The diaphragm used is Nafion 212 membrane, with a diaphragm area of ​​4*4cm. 2 The bakelite board, aluminum end plate, gold-plated copper current collector, graphite plate, electrode 1, PTFE gasket, separator 5, PTFE gasket, electrode 2, graphite plate, gold-plated copper current collector, aluminum end plate, and bakelite board are stacked sequentially and then fastened with bolts and nuts to assemble an aqueous full-chromium redox flow battery. The negative electrolyte in the negative electrode storage tank 3 enters the negative electrode 1 through the negative electrode peristaltic pump 6. The active substances in the negative electrolyte will undergo an electrochemical reaction on the surface of the negative electrode 1. Afterwards, the negative electrolyte flows out of the negative electrode 1 and re-enters the negative electrolyte storage tank 3. The positive electrolyte in the positive electrode storage tank 4 enters the positive electrode 2 through the positive electrode peristaltic pump 7. The active substances in the positive electrolyte will undergo an electrochemical reaction on the surface of the positive electrode 2. Afterwards, the positive electrolyte flows out of the positive electrode 2 and re-enters the positive electrolyte storage tank 4.

[0070] To evaluate the rate performance of the aqueous all-chromium flow battery prepared in this embodiment, under a fixed capacity of 40 mAh, a test was conducted at 20 mA·cm⁻¹. -2 Up to 70mA·cm -2 The test was conducted within the current density range, and the test results are as follows: Figure 2 As shown, the coulombic efficiency remains above 80%, and at high current density, it remains at 95%. Voltage efficiency and energy efficiency decrease with increasing current density, but remain at relatively high levels, and return to normal at current density around 20 mA·cm⁻¹. -2 The battery recovered to its initial good state within a short time, indicating that the aqueous all-chromium flow battery prepared in this embodiment can withstand 20 mA·cm⁻¹. -2 Up to 70mA·cm -2The battery maintains high coulombic efficiency, voltage efficiency, and energy efficiency across a wide current density range. This indicates that the aqueous all-chromium flow battery possesses excellent high power output / input capabilities, making it suitable for fast charging and discharging scenarios such as grid frequency regulation.

[0071] Example 2

[0072] An aqueous full-chromium flow battery electrolyte, the raw materials of which are composed of the following substances: active material chromium sulfate, additive lead sulfate, supporting electrolyte sulfuric acid, and solvent deionized water;

[0073] The preparation method of the electrolyte for the above-mentioned aqueous all-chromium flow battery includes the following steps:

[0074] Preparation of the positive electrode electrolyte: Weigh 1.5686 g of chromium sulfate and 0.3032 g of lead sulfate, place them in a beaker, and dissolve them in deionized water. Then, use a pipette to transfer 0.5326 mL of 98% (mass fraction) concentrated sulfuric acid dropwise into the beaker, pour it into a 20 mL volumetric flask, and mix thoroughly to obtain the positive electrode electrolyte. In the positive electrode electrolyte, the concentration of chromium sulfate is 0.2 mol / L, the concentration of lead sulfate is 0.05 mol / L, and the concentration of sulfuric acid is 0.5 mol / L.

[0075] The preparation method of the negative electrode electrolyte is the same as that of the positive electrode electrolyte.

[0076] A method for preparing an aqueous all-chromium redox flow battery includes the following steps: using the prepared positive and negative electrolytes as the battery electrolytes; both positive and negative electrodes are graphite felt electrodes with an electrode area of ​​2*2 cm². 2 The diaphragm used is Nafion 211 membrane, with a diaphragm area of ​​4*4cm. 2 They were assembled into an aqueous full-chromium flow battery (assembly method is the same as in Example 1).

[0077] To verify the operational stability of the aqueous all-chromium redox flow battery prepared in this embodiment at different depths of charge, the following tests were conducted: at a constant current density of 30 mA·cm⁻¹ -2 Under these conditions, cyclic tests were conducted with charging capacities set to 40 mAh, 80 mAh, 120 mAh, and 160 mAh, respectively. The test results are as follows: Figure 3 As shown, the aqueous full-chromium flow battery prepared in this embodiment exhibits a coulombic efficiency of over 90% at all charging capacities, demonstrating excellent reversibility and proving that the battery has good deep-charge adaptability and cycle stability.

[0078] Example 3

[0079] An aqueous full-chromium flow battery electrolyte, the raw materials of which are composed of the following substances: active material chromium acetate, additive copper sulfate, supporting electrolyte sulfuric acid, and solvent deionized water;

[0080] The preparation method of the electrolyte for the above-mentioned aqueous all-chromium flow battery includes the following steps:

[0081] Preparation of the positive electrode electrolyte: Weigh 3.666 g of chromium acetate and 0.3192 g of copper sulfate, place them in a beaker, and dissolve them in deionized water; then, use a pipette to transfer 1.0652 mL of 98% concentrated sulfuric acid dropwise into the beaker, pour it into a 20 mL volumetric flask, and mix thoroughly to obtain the positive electrode electrolyte; wherein, in the positive electrode electrolyte: the concentration of chromium acetate is 0.8 mol / L, the concentration of copper sulfate is 0.1 mol / L, and the concentration of sulfuric acid is 1 mol / L;

[0082] The preparation method of the negative electrode electrolyte is the same as that of the positive electrode electrolyte.

[0083] A method for preparing an aqueous all-chromium redox flow battery includes the following steps: using the prepared positive and negative electrolytes as the battery electrolytes; both the positive and negative electrodes are carbon felt electrodes with an electrode area of ​​3*3 cm². 2 The diaphragm is a sulfonated polyetheretherketone membrane with a diaphragm area of ​​5*5cm. 2 They were assembled into an aqueous full-chromium flow battery (assembly method is the same as in Example 1).

[0084] To evaluate the long-term cycling performance of the aqueous all-chromium flow battery prepared in this embodiment, a long-cycle test was conducted under the following conditions: a constant current density of 20 mA·cm⁻¹. -2 The charging and discharging process was performed, with each charge lasting a fixed 0.5 hours, and all other conditions remaining the same as in Example 1. The test results are as follows: Figure 4 As shown, the aqueous all-chromium flow battery prepared in this embodiment can operate continuously for 200 cycles, and the coulombic efficiency remains stable at over 98%. These results fully demonstrate that the aqueous all-chromium flow battery of this invention possesses excellent electrochemical stability and cycle life, providing crucial data support for its application in large-scale, long-term energy storage.

[0085] Example 4

[0086] An aqueous full-chromium flow battery electrolyte is composed of the following substances: active material chromium nitrate nonahydrate, additive bismuth nitrate pentahydrate, supporting electrolyte nitric acid, and solvent deionized water;

[0087] The preparation method of the electrolyte for the above-mentioned aqueous all-chromium flow battery includes the following steps:

[0088] Preparation of the positive electrode electrolyte: Weigh 8.003 g of chromium nitrate nonahydrate and 1.4552 g of bismuth nitrate pentahydrate, place them in a beaker, and dissolve them in deionized water; then use a pipette to transfer 1.6691 mL of 68% (mass fraction) nitric acid dropwise into the beaker, pour it into a 20 mL volumetric flask, and mix thoroughly to obtain the positive electrode electrolyte; wherein, in the positive electrode electrolyte: the concentration of chromium nitrate nonahydrate is 1 mol / L, the concentration of bismuth nitrate pentahydrate is 0.15 mol / L, and the concentration of nitric acid is 2 mol / L;

[0089] The preparation method of the negative electrode electrolyte is the same as that of the positive electrode electrolyte.

[0090] A method for preparing an aqueous all-chromium redox flow battery includes the following steps: using the prepared positive and negative electrolytes as the battery electrolytes; both positive and negative electrodes are carbon felt electrodes with an electrode area of ​​2*2.5cm². 2 The diaphragm is made of porous polyethylene membrane with a diaphragm area of ​​4*5cm. 2 They were assembled into an aqueous full-chromium flow battery (assembly method is the same as in Example 1).

[0091] To evaluate the long-term cycling performance of the aqueous all-chromium redox flow battery prepared in this embodiment, long-cycle testing was conducted. This was done at a constant current density of 20 mA·cm⁻¹. -2 The charging and discharging process was performed, with each charge lasting a fixed 0.5 hours. The test results are as follows: Figure 5 As shown, the aqueous full-chromium flow battery prepared in this embodiment can run continuously for 120 cycles, and the coulombic efficiency remains stable at over 95%.

[0092] Example 5

[0093] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is ferric chloride.

[0094] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0095] Charge-discharge tests were performed according to the method in Example 1, at 40 mA cm⁻¹. -2 At current density, the coulombic efficiency is 95%; at a constant current density of 20 mA·cm⁻¹, the efficiency is 95%. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 200 cycles, and the coulombic efficiency remains stable at over 95%.

[0096] Example 6

[0097] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is aluminum chloride.

[0098] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0099] Charge-discharge tests were performed according to the method in Example 1, at 40 mA cm⁻¹. -2 At the current density, the coulombic efficiency is 94.6%; at a constant current density of 20 mA·cm⁻¹, the efficiency is 94.6%. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 150 cycles, and the coulombic efficiency remains stable at over 93%.

[0100] Example 7

[0101] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is cobalt sulfate.

[0102] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0103] Charge-discharge tests were performed according to the method in Example 1, at 30 mA cm⁻¹. -2 At current density, the coulombic efficiency is 95%; at a constant current density of 20 mA·cm⁻¹, the efficiency is 95%. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 180 cycles, and the coulombic efficiency remains stable at over 94%.

[0104] Example 8

[0105] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is nickel sulfate.

[0106] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0107] Charge-discharge tests were performed according to the method in Example 1, at 40 mA cm⁻¹. -2 At the current density, the coulombic efficiency is 97%; at a constant current density of 40 mA·cm⁻¹, the efficiency is 97%. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 80mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 200 cycles, and the coulombic efficiency remains stable at over 97%.

[0108] Example 9

[0109] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is stannous chloride.

[0110] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0111] Charge-discharge tests were performed according to the method in Example 1, at a temperature of 20 mA cm⁻¹. -2 At the current density, the coulombic efficiency is 92%; at a constant current density of 20 mA·cm⁻¹, the efficiency is 92%. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium redox flow battery prepared in this embodiment can run continuously for 220 cycles, and the coulombic efficiency remains stable at over 92%.

[0112] Example 10

[0113] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except for the addition of antimony trichloride.

[0114] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0115] Charge-discharge tests were performed according to the method in Example 1, at 40 mA cm⁻¹. -2 At current density, the coulombic efficiency is 95%; at a constant current density of 20 mA·cm⁻¹, the efficiency is 95%. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 180 cycles, and the coulombic efficiency remains stable at over 93%.

[0116] Example 11

[0117] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is ruthenium trichloride.

[0118] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0119] Charge-discharge tests were performed according to the method in Example 1, at 40 mA cm⁻¹. -2 At the current density, the coulombic efficiency is 96%; at a constant current density of 40 mA·cm⁻¹, the efficiency is 96%. -2 The battery is charged and discharged at a fixed time of 0.25 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 190 cycles, and the coulombic efficiency remains stable at over 96%.

[0120] Example 12

[0121] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is magnesium chloride and the supporting electrolyte is hydrobromic acid.

[0122] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0123] Charge-discharge tests were performed according to the method in Example 1, at a temperature of 20 mA cm⁻¹. -2 At the current density, the coulombic efficiency is 93.2%; at a constant current density of 20 mA·cm⁻¹, the efficiency is 93.2%. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 120 cycles, and the coulombic efficiency remains stable at over 93%.

[0124] Example 13

[0125] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is manganese chloride.

[0126] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0127] Charge-discharge tests were performed according to the method in Example 1, at 40 mA cm⁻¹. -2 At the current density, the coulombic efficiency is 91.1%; at a constant current density of 20 mA·cm⁻¹, the efficiency is 91.1%. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 120 cycles, and the coulombic efficiency remains stable at over 91%.

[0128] Example 14

[0129] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is silver nitrate.

[0130] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0131] Charge-discharge tests were performed according to the method in Example 1, at 30 mA cm⁻¹. -2 At the given current density, the coulombic efficiency is 95.5%; at a constant current density of 20 mA·cm⁻¹, the efficiency is [missing value]. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 150 cycles, and the coulombic efficiency remains stable at over 94%.

[0132] Example 15

[0133] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is cerium chloride.

[0134] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0135] Charge-discharge tests were performed according to the method in Example 1, at 40 mA cm⁻¹. -2 At the current density, the coulombic efficiency is 95.6%; at a constant current density of 20 mA·cm⁻¹, the efficiency is 95.6%. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 200 cycles, and the coulombic efficiency remains stable at over 94%.

[0136] Example 16

[0137] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is cadmium sulfate.

[0138] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0139] Charge-discharge tests were performed according to the method in Example 1, at 40 mA cm⁻¹. -2 At the given current density, the coulombic efficiency is 95.2%; at a constant current density of 40 mA·cm⁻¹, the efficiency is [missing value]. -2 The battery is charged and discharged at a fixed time of 0.25 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 250 cycles, and the coulombic efficiency remains stable at over 94%.

[0140] Example 17

[0141] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is gallium trichloride.

[0142] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0143] Charge-discharge tests were performed according to the method in Example 1, at 40 mA cm⁻¹. -2 At the current density, the coulombic efficiency is 92.6%; at a constant current density of 20 mA·cm⁻¹, the efficiency is 92.6%. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 110 cycles, and the coulombic efficiency remains stable at over 91%.

[0144] Example 18

[0145] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is titanium trichloride and the supporting electrolyte is hydroiodic acid.

[0146] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0147] Charge-discharge tests were performed according to the method in Example 1, at 40 mA cm⁻¹. -2 At the current density, the coulombic efficiency is 91.5%; at a constant current density of 20 mA·cm⁻¹, the efficiency is 91.5%. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium redox flow battery prepared in this embodiment can run continuously for 150 cycles, and the coulombic efficiency remains stable at over 90%.

[0148] Example 19

[0149] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is palladium chloride and the supporting electrolyte is perchloric acid.

[0150] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0151] Charge-discharge tests were performed according to the method in Example 1, at 40 mA cm⁻¹. -2 At the current density, the coulombic efficiency is 92%; at a constant current density of 40 mA·cm⁻¹, the efficiency is 92%. -2 The battery is charged and discharged at a fixed time of 0.25 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 130 cycles, and the coulombic efficiency remains stable at over 91%.

[0152] Example 20

[0153] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is germanium dioxide.

[0154] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0155] Charge-discharge tests were performed according to the method in Example 1, at 40 mA cm⁻¹. -2 At the current density, the coulombic efficiency is 90.5%; at a constant current density of 20 mA·cm⁻¹, the efficiency is 90.5%. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium redox flow battery prepared in this embodiment can run continuously for 150 cycles, and the coulombic efficiency remains stable at over 90%.

[0156] Example 21

[0157] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is thallium nitrate.

[0158] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0159] Charge-discharge tests were performed according to the method in Example 1, at a temperature of 20 mA cm⁻¹. -2 At the current density, the coulombic efficiency is 92.5%; at a constant current density of 20 mA·cm⁻¹, the efficiency is 92.5%. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 110 cycles, and the coulombic efficiency remains stable at over 90%.

[0160] Example 22

[0161] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is chloroplatinic acid and the supporting electrolyte is hydroiodic acid.

[0162] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0163] Charge-discharge tests were performed according to the method in Example 1, at 40 mA cm⁻¹. -2 At the current density, the coulombic efficiency is 92%; at a constant current density of 40 mA·cm⁻¹, the efficiency is 92%. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 80mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 80 cycles, and the coulombic efficiency remains stable at over 92%.

[0164] Example 23

[0165] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is neodymium chloride.

[0166] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0167] Charge-discharge tests were performed according to the method in Example 1, at 40 mA cm⁻¹. -2 At the given current density, the coulombic efficiency is 96.6%; at a constant current density of 20 mA·cm⁻¹, the efficiency is [missing value]. -2 The battery is charged and discharged at a fixed time of 1 hour each time. Under the condition of a fixed capacity of 80mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 130 cycles, and the coulombic efficiency remains stable at over 95%.

[0168] Example 24

[0169] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is barium chloride and the supporting electrolyte is methanesulfonic acid.

[0170] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0171] Charge-discharge tests were performed according to the method in Example 1, at a temperature of 20 mA cm⁻¹. -2 At current density, the coulombic efficiency is 94%; at a constant current density of 20 mA·cm⁻¹, the efficiency is 94%. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 150 cycles, and the coulombic efficiency remains stable at over 93%.

[0172] Example 25

[0173] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is calcium chloride.

[0174] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0175] Charge-discharge tests were performed according to the method in Example 1, at 40 mA cm⁻¹. -2 At the current density, the coulombic efficiency is 92.1%; at a constant current density of 20 mA·cm⁻¹, the efficiency is 92.1%. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 180 cycles, and the coulombic efficiency remains stable at over 91%.

[0176] Example 26

[0177] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is chloroauric acid.

[0178] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0179] Charge-discharge tests were performed according to the method in Example 1, at 60 mA cm⁻¹. -2 At current density, the coulombic efficiency is 95%; at a constant current density of 40 mA·cm⁻¹, the efficiency is 95%. -2 The battery is charged and discharged at a fixed time of 0.25 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 110 cycles, and the coulombic efficiency remains stable at over 93%.

[0180] Example 27

[0181] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is sodium selenite.

[0182] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0183] Charge-discharge tests were performed according to the method in Example 1, at 50 mA cm⁻¹. -2 At current density, the coulombic efficiency is 93%; at a constant current density of 40 mA·cm⁻¹, the efficiency is 93%. -2 The battery is charged and discharged at a fixed time of 0.25 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 120 cycles, and the coulombic efficiency remains stable at over 93%.

[0184] Example 28

[0185] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is sodium tellurite.

[0186] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0187] Charge-discharge tests were performed according to the method in Example 1, at a temperature of 20 mA cm⁻¹. -2 At current density, the coulombic efficiency is 95%; at a constant current density of 20 mA·cm⁻¹, the efficiency is 95%. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 200 cycles, and the coulombic efficiency remains stable at over 93%.

[0188] Example 29

[0189] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is ammonium molybdate.

[0190] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0191] Charge-discharge tests were performed according to the method in Example 1, at a temperature of 20 mA cm⁻¹. -2 At the current density, the coulombic efficiency is 92%; at a constant current density of 20 mA·cm⁻¹, the efficiency is 92%. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 170 cycles, and the coulombic efficiency remains stable at over 91%.

[0192] Example 30

[0193] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is sodium tungstate.

[0194] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0195] Charge-discharge tests were performed according to the method in Example 1, at 60 mA cm⁻¹. -2 At current density, the coulombic efficiency is 95%; at a constant current density of 40 mA·cm⁻¹, the efficiency is 95%. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 80mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 220 cycles, and the coulombic efficiency remains stable at over 93%.

[0196] Example 31

[0197] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is phosphomolybdic acid.

[0198] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0199] Charge-discharge tests were performed according to the method in Example 1, at 40 mA cm⁻¹. -2 At current density, the coulombic efficiency is 93%; at a constant current density of 20 mA·cm⁻¹, the efficiency is 93%. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 180 cycles, and the coulombic efficiency remains stable at over 91%.

[0200] Example 32

[0201] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is phosphotungstic acid.

[0202] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0203] Charge-discharge tests were performed according to the method in Example 1, at 40 mA cm⁻¹. -2 At current density, the coulombic efficiency is 94%; at a constant current density of 20 mA·cm⁻¹, the efficiency is 94%. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 40mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 210 cycles, and the coulombic efficiency remains stable at over 93%.

[0204] Example 33

[0205] The raw material composition of the electrolyte for the aqueous full-chromium flow battery is the same as in Example 1, except that the additive is silicotungstic acid.

[0206] The preparation method of the aqueous full-chromium redox flow battery is the same as in Example 1.

[0207] Charge-discharge tests were performed according to the method in Example 1, at 30 mA cm⁻¹. -2 At current density, the coulombic efficiency is 94%; at a constant current density of 40 mA·cm⁻¹, the efficiency is 94%. -2 The battery is charged and discharged at a fixed time of 0.5 hours each time. Under the condition of a fixed capacity of 80mAh, the aqueous full chromium flow battery prepared in this embodiment can run continuously for 180 cycles, and the coulombic efficiency remains stable at over 92%.

[0208] The above results indicate that this invention prepares an all-chromium flow battery electrolyte and an all-chromium flow battery, using soluble trivalent chromium salts (such as chromium trichloride hexahydrate, chromium sulfate, chromium acetate, or chromium nitrate nonahydrate) as the positive and negative electrode active materials, and Bi... 3+ Cu 2+ Pb 2+ In 3+ Al 3+ Fe 3+ Co 2+ Ni 2+ Sn 2+ Sb 3+ Ru 3+ Mg 2+ Mn 2+ Ag + Ce 3+ Cd 2+ Ga 3 + Ti 3+ Pd 2+ 、Ge 4+ 、Tl + Pt 4+ 、Nd 3+ Ba 2+ Ca 2+ Au 3 SeO3 2- TeO3 2- MoO3 2- WO3 2- [PMo] 12 O 40 ] 3- [PW] 12 O 40 ] 3- and [SiW 12 O 40 ] 3- At least one of the components is used as an additive, which solves key problems such as slow chromium ion reaction kinetics, severe hydrogen evolution side reaction and poor chemical stability, thereby constructing a high-efficiency and stable aqueous all-chromium flow battery system.

[0209] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. An aqueous all-chromium flow battery electrolyte, characterized in that, It is composed of a positive electrolyte and a negative electrolyte, wherein the positive electrolyte and the negative electrolyte are independently composed of the following raw materials: active material, additives, supporting electrolyte and solvent; The active material is a soluble trivalent chromium salt, and the active materials of both the positive and negative electrode electrolytes are soluble trivalent chromium salts. The supporting electrolyte is selected from one of the following soluble compounds containing the following anions and hydrogen ions: sulfate, chloride, nitrate, bromide, iodide, perchlorate, or methanesulfonate. The additive is selected from at least one of soluble compounds containing the following cations or anions in the form of oxyacid radicals: Bi 3+ Cu 2+ Pb 2+ In 3+ Al 3+ Fe 3+ Co 2+ Ni 2+ Sn 2+ Sb 3+ Ru 3+ Mg 2+ Mn 2+ Ag + Ce 3+ Cd 2+ Ga 3+ Ti 3+ Pd 2+ 、Tl + Pt 4+ 、Nd 3+ Ba 2+ Ca 2+ Au 3+ SeO3 2- TeO3 2- MoO3 2- WO3 2- [PMo] 12 O 40 ] 3- [PW] 12 O 40 ] 3- and [SiW 12 O 40 ] 3- ; The solvent is water; In the positive electrode electrolyte, the concentration of the soluble trivalent chromium salt is 0.2 mol / L to 2 mol / L, the concentration of the additive is 0.05 mol / L to 0.5 mol / L, and the concentration of hydrogen ions in the supporting electrolyte is 1 mol / L to 3 mol / L. In the negative electrode electrolyte, the concentration of the soluble trivalent chromium salt is 0.2 mol / L to 2 mol / L, the concentration of the additive is 0.05 mol / L to 0.5 mol / L, and the concentration of hydrogen ions in the supporting electrolyte is 1 mol / L to 3 mol / L.

2. The aqueous all-chromium flow battery electrolyte according to claim 1, characterized in that, In the positive electrode electrolyte, the concentration of the soluble trivalent chromium salt is 0.5 mol / L to 1.5 mol / L, the concentration of the additive is 0.1 mol / L to 0.2 mol / L, and the concentration of hydrogen ions in the supporting electrolyte is 1 mol / L to 2 mol / L. And / or, in the negative electrode electrolyte, the concentration of the soluble trivalent chromium salt is 0.5 mol / L to 1.5 mol / L, the concentration of the additive is 0.1 mol / L to 0.2 mol / L, and the concentration of hydrogen ions in the supporting electrolyte is 1 mol / L to 2 mol / L.

3. A method for preparing the electrolyte for an aqueous all-chromium flow battery according to any one of claims 1 to 2, characterized in that, The preparation method of the positive electrode electrolyte includes the following steps: dissolving the active material and additives in a solvent, adding the supporting electrolyte, stirring evenly, and obtaining the positive electrode electrolyte; The preparation method of the negative electrode electrolyte is as follows: dissolve the active material and additives in a solvent, add the supporting electrolyte, stir evenly, and obtain the negative electrode electrolyte.

4. An aqueous all-chromium flow battery, characterized in that, The electrolyte is the aqueous full-chromium redox flow battery electrolyte as described in any one of claims 1 to 2.

5. The aqueous all-chromium redox flow battery according to claim 4, characterized in that, It includes a negative electrode, a positive electrode, a negative electrolyte storage tank, a positive electrolyte storage tank, a diaphragm, a negative peristaltic pump, and a positive peristaltic pump; The negative electrode electrolyte storage tank is used to store the negative electrode electrolyte, and the positive electrode electrolyte storage tank is used to store the positive electrode electrolyte; The negative electrode peristaltic pump is used to pump the negative electrode electrolyte to the negative electrode; the positive electrode peristaltic pump is used to pump the positive electrode electrolyte to the positive electrode. The diaphragm is used to separate the negative electrode electrolyte and the positive electrode electrolyte.

6. The aqueous all-chromium redox flow battery according to claim 5, characterized in that, Both the negative electrode and the positive electrode are made of porous carbon materials; And / or, the membrane is a polymer membrane with ion-selective permeability.

7. The aqueous all-chromium redox flow battery according to claim 6, characterized in that, The porous carbon material is selected from graphite felt, carbon felt, carbon cloth or carbon paper.

8. The aqueous all-chromium redox flow battery according to claim 6, characterized in that, The polymer membrane with ion-selective permeability is selected from perfluorosulfonic acid proton exchange membranes, sulfonated polyether ether ketone membranes, polyethylene porous membranes, or anion exchange membranes.

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