Electrolyte precursor of iron-chromium flow battery, electrolyte, preparation method and application

Abstract

The invention relates to an electrolyte precursor of an iron-chromium flow battery, an electrolyte, a preparation method and an application. The electrolyte precursor comprises a basic electrolyte and a stabilizer; the stabilizer comprises an indium-containing compound and amino acid. According to the electrolyte precursor of the iron-chromium flow battery, provided by the invention, the combination of the indium-containing compound and the amino acid is used as a stabilizer of the electrolyte, and under the synergistic matching condition of the indium-containing compound, the amino acid and chromium ions can be subjected to complex reaction, so that the inactivated hydrated chromium ions are converted into active chromium ions, and the chromium ions are converted into active chromium ions. Therefore, the reaction activity of the electrolyte is improved, and the cycling stability of the electrolyte is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid flow batteries, and in particular to an electrolyte precursor, an electrolyte, a preparation method and an application of an iron-chromium liquid flow battery. Background Art

[0002] Liquid flow batteries are one of the most suitable electrochemical energy storage technologies for large-capacity, long-term energy storage, due to their high safety, decoupling of power and capacity, high number of cycles, and recyclable electrolytes. The basic principle of liquid flow batteries is to achieve bidirectional conversion of electrical energy and chemical energy by transporting the positive and negative electrolytes from the circulation system to the stack, where the valence state of the active substances in the electrolyte changes. In terms of inherent safety, liquid flow battery energy is stored in an aqueous electrolyte, and no solid-liquid phase transition occurs during the energy conversion process, eliminating the risk of combustion and explosion. Liquid flow batteries also have significant advantages in terms of cycle life. For example, the commercially available all-vanadium liquid flow battery not only has a charge and discharge cycle that is more than three times that of a lithium battery, reaching 20,000, but also features an environmentally friendly and recyclable vanadium electrolyte.

[0003] The iron-chromium flow battery was first proposed in 1974. After more than 40 years of development, the technology has developed rapidly. Compared with the all-vanadium flow battery, the iron-chromium flow battery has attracted widespread attention in the industry due to its abundant resources, easy availability and low cost. It is expected to solve the problem of high one-time investment costs and break the last barrier to the application of flow batteries in the energy storage industry. However, there are still three problems with the chromium-iron flow battery: First, due to the different osmotic pressures on both sides of the ion conduction membrane, the electrolytes of the chromium-iron flow battery will penetrate and mix with each other; second, Cr 2+ / Cr 3+ The standard potential of the redox couple is very close to the overpotential required for hydrogen evolution from water on the carbon electrode surface, and Cr 2+ / Cr 3+ The reactivity of Fe 2+ / Fe 3+ The difference causes hydrogen evolution at the anode; the third is Cr 3+ It is easy to form hydrated chromium ions in aqueous solution, causing Cr to lose its electrochemical activity.

[0004] CN118099496A discloses an iron-chromium flow battery electrolyte containing a composite additive and its preparation method. The additives, sodium phosphate and ammonium citrate, enhance battery performance and improve the stability of the iron-chromium flow battery during cycling tests. The published results show that compared to an electrolyte without the composite additive, the energy efficiency increased from 75.19% to 77.79%, and the average attenuation rate over 60 cycles decreased from 1.22% to 1.06%. While these results demonstrate some success, they still fall short of meeting the requirements for long-term, high-performance energy storage applications.

[0005] The composite additive containing bismuth and lead is added to the basic electrolyte of the iron-chromium flow battery disclosed in CN110729506A. After the addition, the lead ions in the electrolyte are Pb 2+ , Pb 4+ One or two of the bismuth ion is Bi 3+ After 200 cycles, the capacity retention rate was 70%, and the average attenuation rate per cycle was 0.15%, which improved the long-term operation stability of the electrolyte, but its electrochemical performance still has room for improvement.

[0006] More importantly, the electrochemical activity and cycle stability of the electrolyte of iron-chromium flow batteries have hindered the commercial application of iron-chromium flow batteries. Solving related technical problems is still a challenge facing the iron-chromium flow battery industry.

[0007] Therefore, how to provide a method for improving the electrochemical activity and cycle stability of iron-chromium flow batteries has become an urgent problem to be solved. Summary of the Invention

[0008] To address the above-mentioned technical problems, the present invention aims to provide an electrolyte precursor, electrolyte, preparation method, and application for an iron-chromium flow battery. The electrolyte precursor for an iron-chromium flow battery provided by the present invention utilizes a combination of an indium-containing compound and an amino acid as an electrolyte stabilizer. Under the synergistic conditions of the indium-containing compound, the amino acid and chromium ions undergo a complex reaction, converting inactivated hydrated chromium ions into active chromium ions, thereby enhancing the reactivity of the electrolyte and increasing its cyclic stability.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides an electrolyte precursor for an iron-chromium flow battery, wherein the electrolyte precursor comprises a base electrolyte and a stabilizer; the stabilizer comprises an indium-containing compound and an amino acid.

[0011] The electrolyte precursor of the iron-chromium flow battery provided by the present invention uses a combination of an indium compound and an amino acid as an electrolyte stabilizer, and the two have a synergistic promoting effect. On the one hand, the stabilizer amino acid directly complexes with the free chromium ions in the electrolyte to prevent the hydration and aging of the chromium ions and maintain the stability of the chromium ions; on the other hand, the amino acid can activate the aged and inactivated chromium ions under the catalysis of the indium ions. 3+The electrode potential of In is about -0.338V. Under the action of N atoms in amino acids, its electrode potential is reduced, and the electron transfer rate is faster than that of inactivated chromium ions. When the battery is charged, the indium ions combined with amino acids preferentially obtain electrons to generate elemental indium, and the amino acids release ammonia nitrogen groups with stronger coordination. The active ammonia nitrogen groups attack the inactivated [Cr(H2O)6] 3+ , replacing some water molecules and inactivating [Cr(H2O)6] 3+ Converted into electrochemically active [Cr(H2O)4(AA)Cl] 2+ or [Cr(H2O)3(AA)Cl2] + (AA is amino acid). The composition of the electrolyte precursor provided by the present invention is to improve the Cr content in the electrolyte. 3+ While reducing the reaction activity of the electrolyte, it can also maintain the stability of chromium ions in the electrolyte, thereby optimizing the comprehensive electrochemical performance of the iron-chromium flow battery.

[0012] Preferably, the indium-containing compound includes any one of indium chloride, indium methanesulfonate, indium trifluoromethanesulfonate, indium oxide, indium acetate or indium acetylacetonate, or a combination of at least two thereof.

[0013] Preferably, the amino acids include acidic amino acids and / or neutral amino acids.

[0014] Preferably, the acidic amino acids include glutamic acid and / or aspartic acid.

[0015] Preferably, the neutral amino acids include L-alanine and / or serine.

[0016] Preferably, in the electrolyte precursor, the mass ratio of the amino acid to the indium ions in the indium-containing compound is (1 to 25):1, for example, 1:1, 2:1, 4:1, 6:1, 8:1, 10:1, 12:1, 14:1, 16:1, 18:1, 20:1, 22:1, 24:1 or 25:1, etc.

[0017] Preferably, in the electrolyte precursor, the concentration of indium ions in the indium-containing compound is 1.0 to 300.0 mmol / L, for example, 1.0 mmol / L, 50.0 mmol / L, 100.0 mmol / L, 150.0 mmol / L, 200.0 mmol / L, 250.0 mmol / L or 300.0 mmol / L, etc., preferably 2.0 to 100.0 mmol / L.

[0018] Preferably, in the electrolyte precursor, the concentration of the amino acid is 0.01 to 1.0 mol / L, for example, 0.01 mol / L, 0.05 mol / L, 0.10 mol / L, 0.20 mol / L, 0.30 mol / L, 0.40 mol / L, 0.50 mol / L, 0.60 mol / L, 0.70 mol / L, 0.80 mol / L, 0.90 mol / L or 1.00 mol / L, etc., preferably 0.05 to 0.50 mol / L.

[0019] Preferably, the basic electrolyte comprises chromium salt, ferrous salt, acidic reagent and solvent.

[0020] Preferably, the chromium salt comprises chromium chloride.

[0021] Preferably, the ferrous salt comprises ferrous chloride.

[0022] Preferably, the acidic reagent comprises hydrochloric acid.

[0023] Preferably, the solvent comprises deionized water.

[0024] Preferably, in the basic electrolyte, the concentration of chromium ions in the chromium salt is 0.5 to 3.0 mol / L, such as 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L or 3.0 mol / L, and preferably 1.0 to 1.5 mol / L.

[0025] Preferably, in the basic electrolyte, the concentration of ferrous ions in the ferrous salt is 0.5 to 3.0 mol / L, such as 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L or 3.0 mol / L, and preferably 1.0 to 1.5 mol / L.

[0026] Preferably, in the basic electrolyte, the concentration of the acidic reagent is 1.0 to 5.0 mol / L, for example, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, 3.5 mol / L, 4.0 mol / L, 4.5 mol / L or 5.0 mol / L, etc., preferably 1.5 to 3.0 mol / L.

[0027] In a second aspect, the present invention provides a method for preparing an electrolyte precursor for an iron-chromium flow battery according to the first aspect, the preparation method comprising the following steps:

[0028] The indium-containing compound and the amino acid are dissolved in a basic electrolyte to obtain the electrolyte precursor.

[0029] The preparation method of the electrolyte precursor provided by the present invention directly adopts the method of dissolving an indium-containing compound and an amino acid in a basic electrolyte. The preparation method adopted is simple and easy to operate, and does not require additional equipment and instruments.

[0030] Preferably, the basic electrolyte comprises chromium salt, ferrous salt, acidic reagent and solvent.

[0031] Preferably, the chromium salt comprises chromium chloride.

[0032] Preferably, the ferrous salt comprises ferrous chloride.

[0033] Preferably, the acidic reagent comprises hydrochloric acid.

[0034] Preferably, the solvent comprises deionized water.

[0035] In a third aspect, the present invention provides an electrolyte for an iron-chromium flow battery, wherein the electrolyte for the iron-chromium flow battery is prepared using the electrolyte precursor for the iron-chromium flow battery as described in the first aspect.

[0036] The iron-chromium flow battery electrolyte provided by the present invention is prepared using a specific iron-chromium flow battery electrolyte precursor. A combination of an indium-containing compound and an amino acid is introduced into the electrolyte precursor as an electrolyte stabilizer. The two act synergistically. Under the mutual cooperation of indium ions and amino acids, the amino acids and chromium ions produce a complex reaction, thereby maintaining the stability of the chromium ions and converting inactivated hydrated chromium ions into active chromium ions, thereby enhancing the reaction activity of the electrolyte and improving the electrochemical performance of the electrolyte.

[0037] Preferably, the viscosity of the electrolyte of the iron-chromium flow battery is 1.3 mm 2 / s or less, for example 1.3mm 2 / s、1.2mm 2 / s、1.1mm 2 / s、1.0mm 2 / s、0.9mm 2 / s、0.8mm 2 / s or 0.7mm 2 / s, etc.

[0038] Preferably, the electrolyte of the iron-chromium flow battery is prepared by complexing the electrolyte precursor of the iron-chromium flow battery described in the first aspect.

[0039] In a fourth aspect, the present invention provides a method for preparing an electrolyte for an iron-chromium flow battery according to the third aspect, the preparation method comprising the following steps:

[0040] The electrolyte precursor of the iron-chromium flow battery according to the first aspect is subjected to a complexation reaction to obtain the electrolyte of the iron-chromium flow battery.

[0041] The iron-chromium flow battery electrolyte provided by the present invention undergoes a complexation reaction through an electrolyte precursor, wherein an indium-containing compound and an amino acid are introduced into the precursor to cooperate with each other. Under the action of the indium-containing compound, the amino acid acts as a complexing group and, under the conditions of the complexation reaction, preferentially combines with chromium ions before water to form a highly active complex of chromium and amino acid, thereby increasing the Cr content in the electrolyte. 3+ The electrochemical activity of chromium ions can be improved, and the stability of chromium ions can be maintained to prepare an electrolyte with better electrochemical performance.

[0042] Preferably, the temperature of the complexation reaction is 50-125°C, for example, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C or 125°C.

[0043] Preferably, the complexation reaction time is 1 to 24 hours, for example, 1 hour, 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours.

[0044] Preferably, the complexation reaction is carried out under hydrothermal conditions.

[0045] The complexation reaction provided by the present invention is carried out under hydrothermal conditions and can be combined with a stabilizer in an electrolyte precursor to obtain an iron-chromium liquid electrolyte with more stable performance and better reaction activity.

[0046] In a fifth aspect, the present invention provides an iron-chromium flow battery, which uses the electrolyte of the iron-chromium flow battery described in the third aspect as the negative electrode electrolyte and the positive electrode electrolyte, or uses the electrolyte of the iron-chromium flow battery described in the third aspect as the negative electrode electrolyte.

[0047] The iron-chromium flow battery provided by the present invention uses the electrolyte of the iron-chromium flow battery with a specific composition as the electrolyte, and the combination of amino acid and indium-containing compound works together to improve Cr 3+ Electrochemical reaction activity and stability, improving the overall electrochemical performance of the battery.

[0048] In the present invention, the positive electrode electrolyte may also be a basic electrolyte.

[0049] Preferably, the iron-chromium flow battery further comprises a separator.

[0050] Preferably, the membrane comprises a porous membrane.

[0051] Preferably, the porous membrane includes any one of a polyarylethersulfone membrane, a polyaryletherketone membrane, a polyetheretherketone membrane or a polybenzimidazole membrane.

[0052] Preferably, the iron-chromium flow battery further comprises a negative electrode material.

[0053] Preferably, the negative electrode material includes a negative electrode matrix material.

[0054] Preferably, the negative electrode matrix material includes carbon cloth or carbon felt.

[0055] Preferably, the negative electrode base material further comprises a modifying material disposed on the surface of the negative electrode base material.

[0056] Preferably, in the negative electrode material, the modified material includes any one of graphene, carbon nanotubes, transition metals or metal oxides, or a combination of at least two thereof.

[0057] The negative electrode material in the present invention may be carbon felt or carbon cloth, or may be carbon felt or carbon cloth loaded with a modified material.

[0058] Preferably, the iron-chromium flow battery further comprises a positive electrode material.

[0059] Preferably, the positive electrode material includes a positive electrode matrix material.

[0060] Preferably, the positive electrode matrix material includes carbon cloth or carbon felt.

[0061] Preferably, the positive electrode base material further includes a modifying material disposed on the surface of the positive electrode base material.

[0062] The positive electrode material in the present invention may be carbon felt or carbon cloth, or may be carbon felt or carbon cloth loaded with a modified material.

[0063] Preferably, in the positive electrode material, the modified material includes any one of graphene, carbon nanotubes, transition metals or metal oxides, or a combination of at least two thereof.

[0064] Compared with the prior art, the present invention has at least the following beneficial effects:

[0065] (1) The electrolyte precursor of the iron-chromium flow battery provided by the present invention uses a combination of an indium-containing compound and an amino acid as a stabilizer for the electrolyte. Under the synergistic coordination conditions of the indium-containing compound, the amino acid can undergo a complex reaction with the chromium ions, and the inactivated hydrated chromium ions can be converted into active chromium ions, thereby improving the reaction activity of the electrolyte and increasing the cyclic stability of the electrolyte.

[0066] (2) The preparation method of the electrolyte precursor provided by the present invention directly adopts the indium-containing compound and the amino acid to dissolve in the basic electrolyte. The preparation method adopted is simple and easy to operate, and does not require additional equipment and instruments.

[0067] (3) The iron-chromium flow battery electrolyte provided by the present invention is prepared using a specific iron-chromium flow battery electrolyte precursor. A combination of an indium-containing compound and an amino acid is introduced into the electrolyte precursor as a stabilizer for the electrolyte. The two act synergistically. Under the mutual cooperation of indium ions and amino acids, the amino acids react with chromium ions to produce a complex reaction, thereby maintaining the stability of the chromium ions and converting inactivated hydrated chromium ions into active chromium ions, thereby enhancing the reaction activity of the electrolyte and increasing the electrochemical performance of the electrolyte.

[0068] (4) The iron-chromium flow battery electrolyte provided by the present invention undergoes a complexation reaction through an electrolyte precursor. Indium-containing compounds and amino acids are introduced into the precursor to cooperate with each other. Under the action of metal indium ions, amino acids act as complexing groups and, under the conditions of the complexation reaction, preferentially combine with chromium ions before water to form a complex of chromium and amino acids with high activity, so that the electrolyte Cr 3+ It has electrochemical activity and can maintain the stability of chromium ions, so as to prepare an electrolyte with better electrochemical performance.

[0069] (5) The iron-chromium flow battery provided by the present invention uses an iron-chromium flow battery electrolyte of a specific composition as the electrolyte, and the combination of amino acids and indium-containing compounds synergistically improves the Cr content in the battery. 3+ Electrochemical reaction activity and stability, improving the overall comprehensive performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 Application Example 1 and Comparative Application Example 1 provide cycle performance diagrams of the iron-chromium flow battery. DETAILED DESCRIPTION

[0071] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0072] Example 1

[0073] This embodiment provides an electrolyte precursor for an iron-chromium flow battery, including a basic electrolyte and a stabilizer. The basic electrolyte includes chromium chloride, ferrous chloride, hydrochloric acid, and deionized water. In the basic electrolyte, the concentration of chromium chloride is 1.2 mol / L, the concentration of ferrous chloride is 1.2 mol / L, and the concentration of hydrochloric acid is 2.0 mol / L; the stabilizer includes L-alanine and indium acetate. In the electrolyte precursor, the concentration of indium ions is 100 mmol / L, the concentration of L-alanine is 0.5 mol / L, and the mass ratio of L-alanine to indium ions is 3.9:1.

[0074] This embodiment also provides a method for preparing the electrolyte precursor of the above-mentioned iron-chromium flow battery, comprising the following steps:

[0075] (1) Chromium chloride, ferrous chloride, hydrochloric acid and deionized water are mixed according to the formula to obtain a basic electrolyte.

[0076] (2) Dissolving L-alanine and indium acetate according to the formula amount into the basic electrolyte obtained in step (1) to obtain an electrolyte precursor.

[0077] This embodiment also provides a method for preparing an electrolyte for an iron-chromium flow battery, comprising the following steps:

[0078] The electrolyte precursor was subjected to a complexation reaction under hydrothermal conditions at a temperature of 55°C and a time of 22 hours to obtain an electrolyte for an iron-chromium flow battery having a viscosity of 1.2214 mm 2 / s.

[0079] Example 2

[0080] This embodiment provides an electrolyte precursor for an iron-chromium flow battery, including a basic electrolyte and a stabilizer. The basic electrolyte includes chromium chloride, ferrous chloride, hydrochloric acid and deionized water. In the basic electrolyte, the concentration of chromium chloride is 1.0 mol / L, the concentration of ferrous chloride is 1.0 mol / L, and the concentration of hydrochloric acid is 1.5 mol / L; the stabilizer includes L-alanine and indium chloride (InCl3). In the electrolyte precursor, the concentration of indium ions is 2 mmol / L, the concentration of L-alanine is 0.05 mol / L, and the mass ratio of L-alanine to indium ions is 19.4:1.

[0081] This embodiment also provides a method for preparing the electrolyte precursor of the above-mentioned iron-chromium flow battery, comprising the following steps:

[0082] (1) Chromium chloride, ferrous chloride, hydrochloric acid and deionized water are mixed according to the formula to obtain a basic electrolyte.

[0083] (2) Dissolving L-alanine and indium chloride according to the formula amount into the basic electrolyte obtained in step (1) to obtain an electrolyte precursor.

[0084] This embodiment also provides a method for preparing an electrolyte for an iron-chromium flow battery, comprising the following steps:

[0085] The electrolyte precursor was subjected to a complexation reaction under hydrothermal conditions at a temperature of 120°C and a time of 1 h to obtain an electrolyte for an iron-chromium flow battery having a viscosity of 1.0114 mm 2 / s.

[0086] Example 3

[0087] This embodiment provides an electrolyte precursor for an iron-chromium flow battery, including a basic electrolyte and a stabilizer. The basic electrolyte includes chromium chloride, ferrous chloride, hydrochloric acid, and deionized water. In the basic electrolyte, the concentration of chromium chloride is 1.5 mol / L, the concentration of ferrous chloride is 1.5 mol / L, and the concentration of hydrochloric acid is 3.0 mol / L; the stabilizer includes L-alanine and indium methanesulfonate. In the electrolyte precursor, the concentration of indium ions is 50 mmol / L, the concentration of L-alanine is 0.2 mol / L, and the mass ratio of L-alanine to indium ions is 3.1:1.

[0088] This embodiment also provides a method for preparing the electrolyte precursor of the above-mentioned iron-chromium flow battery, comprising the following steps:

[0089] (1) Chromium chloride, ferrous chloride, hydrochloric acid and deionized water are mixed according to the formula to obtain a basic electrolyte.

[0090] (2) L-alanine and indium methanesulfonate are dissolved in the basic electrolyte obtained in step (1) according to the formula amount to obtain an electrolyte precursor.

[0091] This embodiment also provides a method for preparing an electrolyte for an iron-chromium flow battery, comprising the following steps:

[0092] The electrolyte precursor was subjected to a complexation reaction under hydrothermal conditions at a temperature of 80°C and a time of 15 hours to obtain an electrolyte for an iron-chromium flow battery having a viscosity of 1.1025 mm 2 / s.

[0093] Example 4

[0094] This embodiment differs from Example 1 only in that the stabilizer includes indium methanesulfonate and glutamic acid, the concentration of indium ions in the electrolyte precursor is 10 mmol / L, the concentration of glutamic acid is 0.1 mol / L, and the mass ratio of amino acid to indium ions is 12.8:1. All other details are the same as in Example 1.

[0095] Example 5

[0096] This embodiment differs from Example 1 only in that the stabilizer includes indium trifluoromethanesulfonate and aspartic acid. In the electrolyte precursor, the concentration of indium ions is 50 mmol / L, the concentration of aspartic acid is 0.3 mol / L, and the mass ratio of aspartic acid to indium ions is 7.0:1. All other details are the same as in Example 1.

[0097] Example 6

[0098] The only difference between this embodiment and embodiment 1 is that L-alanine is replaced by serine in the electrolyte precursor, and accordingly, the mass ratio of serine to indium ion is 4.6:1. The rest of the contents are the same as those in embodiment 1.

[0099] Example 7

[0100] The only difference between this embodiment and embodiment 1 is that the concentration of indium ions in the electrolyte precursor is 1 mmol / L, the concentration of L-alanine is 0.01 mol / L, and the mass ratio of L-alanine to indium ions is 7.8:1. The rest of the contents are the same as those in embodiment 1.

[0101] Example 8

[0102] The only difference between this embodiment and embodiment 1 is that the concentration of indium ions in the electrolyte precursor is 300 mmol / L, the concentration of L-alanine is 0.8 mol / L, and the mass ratio of L-alanine to indium ions is 2.1:1. The rest of the contents are the same as those in embodiment 1.

[0103] Example 9

[0104] The only difference between this embodiment and embodiment 1 is that the concentration of indium ions in the electrolyte precursor is 500 mmol / L, the concentration of L-alanine is 1.0 mol / L, and the mass ratio of L-alanine to indium ions is 1.55:1. The rest of the contents are the same as those in embodiment 1.

[0105] Example 10

[0106] The only difference between this embodiment and embodiment 1 is that the concentration of indium ions in the electrolyte precursor is 100 mmol / L, the concentration of L-alanine is 0.05 mol / L, and the mass ratio of L-alanine to indium ions is 0.4:1. The rest of the contents are the same as those in embodiment 1.

[0107] Example 11

[0108] The only difference between this embodiment and embodiment 1 is that the concentration of indium ions in the electrolyte precursor is 12 mmol / L, the concentration of L-alanine is 0.5 mol / L, and the mass ratio of L-alanine to indium ions is 32.3:1. The rest of the contents are the same as those in embodiment 1.

[0109] Example 12

[0110] The only difference between this embodiment and embodiment 1 is that in the method for preparing the electrolyte of the iron-chromium flow battery provided in this embodiment, the temperature of the complexation reaction is 40° C. The rest of the contents are the same as those in embodiment 1.

[0111] Example 13

[0112] The only difference between this embodiment and embodiment 1 is that in the method for preparing the electrolyte for the iron-chromium flow battery provided in this embodiment, the temperature of the complexation reaction is 140° C. The rest of the contents are the same as those in embodiment 1.

[0113] Example 14

[0114] The only difference between this embodiment and embodiment 1 is that the viscosity of the electrolyte obtained by the preparation method of the iron-chromium flow battery provided in this embodiment is 1.5 mm 2 / s, correspondingly, the concentration of L-alanine is 2 mol / L, and the rest of the contents are the same as those in Example 1.

[0115] Example 15

[0116] The only difference between this embodiment and embodiment 1 is that L-alanine is replaced with histidine in the electrolyte precursor. The rest of the contents are the same as those in embodiment 1.

[0117] Comparative Example 1

[0118] The only difference between this comparative example and Example 1 is that indium acetate and L-alanine are omitted from the electrolyte precursor, and only the basic electrolyte is used as the electrolyte precursor. The rest of the contents are the same as Example 1.

[0119] Comparative Example 2

[0120] The only difference between this comparative example and Example 1 is that L-alanine is omitted from the electrolyte precursor. The rest of the contents are the same as Example 1.

[0121] Comparative Example 3

[0122] The only difference between this comparative example and Example 1 is that indium acetate is omitted from the electrolyte precursor. The rest of the contents are the same as Example 1.

[0123] Application Example 1

[0124] This application example provides an iron-chromium liquid flow battery, including a positive electrode, a diaphragm, a negative electrode, a positive electrode liquid storage tank connected to the interlayer space between the positive electrode and the diaphragm, and a negative electrode liquid storage tank connected to the interlayer space between the negative electrode and the diaphragm. The positive electrode liquid storage tank and the negative electrode liquid storage tank respectively contain a positive electrode electrolyte and a negative electrode electrolyte. The positive electrode electrolyte and the negative electrode electrolyte are both 200 mL of the iron-chromium liquid flow battery electrolyte prepared in Example 1. The diaphragm is a porous diaphragm using a polyarylethersulfone membrane. The negative electrode and the positive electrode are both graphite carbon felt with graphene deposited on the surface. The total thickness of each is 4.3 mm, and the amount of graphene deposited on the surface of the graphite carbon felt is 0.1 g / cm 2 .

[0125] Application Example 2-15 and Comparative Application Example 1-3

[0126] The only difference between Application Examples 2-15 and Comparative Application Examples 1-3 and Application Example 1 is that the iron-chromium flow battery electrolytes in Application Examples 2-15 and Comparative Application Examples 1-3 are prepared using the preparation methods provided in Example 2-15 and Comparative Example 1-3, respectively. All other details are the same as in Application Example 1.

[0127] The battery capacity test and battery energy efficiency test of the iron-chromium flow battery provided in Example 1-15 and Comparative Application Example 1-3 were carried out at different charge and discharge cycle times, and the current density was 100 mA / cm at 65 ° C. 2 In the constant current charge and discharge experiment, the charge start voltage and discharge cut-off voltage are 0.7V, and the charge cut-off voltage is 1.2V.

[0128] The test results are shown in Table 1.

[0129] Table 1

[0130]

[0131] The test results show that:

[0132] (1) It can be seen from Application Examples 1 to 6 that the electrolyte precursor of the iron-chromium flow battery provided by the present invention uses a combination of an indium-containing compound and an amino acid as a stabilizer for the electrolyte. Under the synergistic coordination conditions of the indium-containing compound, the amino acid can undergo a complex reaction with the chromium ions, and the inactivated hydrated chromium ions can be converted into active chromium ions, thereby improving the reaction activity of the electrolyte and increasing the cycle stability of the electrolyte.

[0133] In addition, the amino acid used in the present invention further selects L-alanine, which has a small molecular weight, a relatively high isoelectric point, a simple structure, and a small steric hindrance, which is more conducive to replacing the inactive Cr(H2O) 3+ Water molecules make inactive Cr 3+ Converted into electrochemically active chromium ions.

[0134] (2) By comparing Application Example 1 with Application Examples 7-9, it can be seen that the present invention further regulates the amount of stabilizer added, which can significantly improve the cyclic stability of the electrolyte. If the concentrations of indium ions and amino acids are too low, they cannot play a stabilizing role. If the concentrations of the two are too high, the viscosity of the electrolyte increases, affecting the ion transmission rate and the stability deteriorating.

[0135] (3) By comparing Application Example 1 with Application Examples 10-11, it can be seen that if the mass ratio of the two is too low, the energy efficiency will be reduced; if the mass ratio of amino acid to indium ion is too high, the capacity will decay quickly.

[0136] (4) By comparing Application Example 1 with Application Examples 12-13, it can be seen that if the temperature of the complexation reaction is too low, the complexation reaction will not proceed sufficiently, and the inactivated Cr 3+ If not complexed, the cycle stability and energy efficiency are poor; if the temperature of the complexation reaction is too high, some ferrous ions will be oxidized, increasing the resistance of the battery system, reducing energy efficiency, and poor cycle stability.

[0137] (5) By comparing Application Example 1 and Application Example 14, it can be seen that if the viscosity of the electrolyte of the present invention is too high, the mass transfer and charge transfer process during the electrochemical reaction will be slowed down, thereby reducing the performance of the electrolyte.

[0138] (6) By comparing Application Example 1 and Application Example 15, it can be seen that if the present invention uses basic amino acids, the basic amino acids will react with the acid in the electrolyte, consuming part of the H + , which leads to poor conductivity of the electrolyte, reduced energy efficiency and poor cycle stability.

[0139] (7) By comparing Application Example 1 with Comparative Application Examples 1-3, it can be seen that if any one or both of the amino acid or the indium-containing compound are omitted from the electrolyte precursor of the present invention, the activity of the electrolyte will decrease and the stability will deteriorate, thereby affecting the electrochemical performance of the iron-chromium flow battery.

[0140] Figure 1 Application Example 1 and Comparative Application Example 1 provide cycle performance diagrams of the iron-chromium flow battery. As can be seen from the diagram, the amino acid and indium compound-containing additives added in the present invention work synergistically to improve the activity of the electrolyte and maintain the stability of the chromium ion activity, thereby improving the capacity retention rate of the iron-chromium flow battery.

[0141] In summary, the electrolyte precursor of the iron-chromium flow battery provided by the present invention uses a combination of an indium compound and an amino acid as an electrolyte stabilizer, and the two have a synergistic promoting effect. On the one hand, the stabilizer amino acid can bind to chromium ions preferentially over water under the catalytic action of indium ions, preventing the hydration of chromium ions and maintaining the stability of chromium ions; on the other hand, In 3+ The electrode potential of In is about -0.338V. Under the action of N atoms in amino acids, its electrode potential is reduced, and the electron transfer rate is faster than that of inactivated chromium ions. When the battery is charged, the indium ions combined with amino acids preferentially obtain electrons to generate elemental indium, and the amino acids release ammonia nitrogen groups with stronger coordination. The active ammonia nitrogen groups attack the inactivated [Cr(H2O)6] 3+ , replacing some water molecules, making Cr 3+ Has higher electrochemical activity.

[0142] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. An electrolyte precursor for an iron-chromium flow battery, characterized in that: The electrolyte precursor includes a basic electrolyte and a stabilizer; the stabilizer includes an indium-containing compound and an amino acid.

2. The electrolyte precursor for the iron-chromium flow battery according to claim 1, characterized in that: The indium-containing compound includes any one or a combination of at least two of indium chloride, indium methanesulfonate, indium trifluoromethanesulfonate, indium oxide, indium acetate or indium acetylacetonate; Preferably, the amino acids include acidic amino acids and / or neutral amino acids; Preferably, the acidic amino acids include glutamic acid and / or aspartic acid; Preferably, the neutral amino acids include L-alanine and / or serine; Preferably, in the electrolyte precursor, the mass ratio of the amino acid to the indium ions in the indium-containing compound is (1-25):1; Preferably, in the electrolyte precursor, the concentration of indium ions in the indium-containing compound is 1.0 to 300.0 mmol / L, preferably 2.0 to 100.0 mmol / L; Preferably, in the electrolyte precursor, the concentration of the amino acid is 0.01 to 1.0 mol / L, preferably 0.05 to 0.50 mol / L.

3. The electrolyte precursor for the iron-chromium flow battery according to claim 1 or 2, characterized in that: The basic electrolyte includes chromium salt, ferrous salt, acidic reagent and solvent; Preferably, in the basic electrolyte, the concentration of chromium ions in the chromium salt is 0.5 to 3.0 mol / L, preferably 1.0 to 1.5 mol / L; Preferably, in the basic electrolyte, the concentration of ferrous ions in the ferrous salt is 0.5 to 3.0 mol / L, preferably 1.0 to 1.5 mol / L; Preferably, in the basic electrolyte, the concentration of the acidic reagent is 1.0 to 5.0 mol / L, preferably 1.5 to 3.0 mol / L.

4. A method for preparing an electrolyte precursor for an iron-chromium flow battery according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: The indium-containing compound and the amino acid are dissolved in a basic electrolyte to obtain the electrolyte precursor.

5. An electrolyte for an iron-chromium flow battery, characterized in that: The electrolyte of the iron-chromium flow battery is prepared using the electrolyte precursor of the iron-chromium flow battery according to any one of claims 1 to 3.

6. The electrolyte of the iron-chromium flow battery according to claim 5, characterized in that The viscosity of the electrolyte of the iron-chromium flow battery is 1.3 mm 2 / s or less.

7. A method for preparing an electrolyte for an iron-chromium flow battery according to claim 5 or 6, characterized in that: The preparation method comprises the following steps: The electrolyte precursor of the iron-chromium flow battery according to any one of claims 1 to 3 is subjected to a complexation reaction to obtain the electrolyte of the iron-chromium flow battery.

8. The preparation method according to claim 7, characterized in that The temperature of the complexation reaction is 50-125°C; Preferably, the complexation reaction time is 1 to 24 hours; Preferably, the complexation reaction is carried out under hydrothermal conditions.

9. An iron-chromium flow battery, characterized in that: The iron-chromium flow battery uses the electrolyte of the iron-chromium flow battery according to claim 5 or 6 as the negative electrode electrolyte and the positive electrode electrolyte, or uses the electrolyte of the iron-chromium flow battery according to claim 5 or 6 as the negative electrode electrolyte.

10. The iron-chromium flow battery according to claim 9, characterized in that: The iron-chromium flow battery further includes a diaphragm; Preferably, the diaphragm comprises a porous diaphragm; Preferably, the porous membrane comprises any one of a polyarylethersulfone membrane, a polyaryletherketone membrane, a polyetheretherketone membrane or a polybenzimidazole membrane; Preferably, the iron-chromium flow battery further comprises a negative electrode material; Preferably, the negative electrode material includes a negative electrode matrix material; Preferably, the negative electrode matrix material comprises carbon cloth or carbon felt; Preferably, the negative electrode base material further comprises a modifying material disposed on the surface of the negative electrode base material; Preferably, in the negative electrode material, the modified material includes any one of graphene, carbon nanotubes, transition metals or metal oxides, or a combination of at least two thereof.

Images