Electrolyte of titanium-manganese flow battery and titanium-manganese flow battery

Abstract

The invention relates to the technical field of electrochemical energy storage batteries, in particular to an electrolyte of a titanium-manganese flow battery and the titanium-manganese flow battery. The additive boron cage acid salt is introduced, electron clouds on the additive can interact with an empty orbit of Mn < 3 + > so as to be coordinated, a rigid and approximately spherical three-dimensional cage structure is formed, a boron cage structure on the periphery of the Mn < 3 + > boron cage compound generates huge steric hindrance, electron transfer between the two boron cage compounds is hindered, and the electron transfer efficiency of the two boron cage compounds is improved. The electron density of the Mn < 3 + > center is reduced, so that the energy barrier of the disproportionation reaction is improved, the disproportionation reaction is inhibited, particularly, fluorine atoms in the fluoro boron cage acid salt have a very strong electron withdrawing effect, and can be transferred to the metal center through a boron cage skeleton, so that the electron cloud density of the Mn < 3 + > is further reduced, and the electron stabilization effect is remarkably enhanced; meanwhile, the introduction of fluorine atoms also enhances the hydrophobicity of the additive, reduces the coordination of water molecules to Mn < 3 + >, and greatly prolongs the cycle life of the battery.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage battery technology, and in particular to an electrolyte for a titanium-manganese flow battery and the titanium-manganese flow battery itself. Background Technology

[0002] Flow batteries, due to their advantages such as independently designable power and capacity, long cycle life, and high safety, have shown broad application prospects in large-scale energy storage. Titanium-manganese flow batteries (Ti / Mn RFBs), as an emerging flow battery system, have attracted widespread attention due to the abundance, low cost, and environmental friendliness of titanium and manganese, the active materials. However, the commercial application of titanium-manganese flow batteries faces a key technical bottleneck: the instability of manganese ions. During battery charging, the Mn in the positive electrode electrolyte... 2+ Oxidized to Mn 3+ Mn 3+ It is very unstable in acidic aqueous solutions and readily undergoes the following disproportionation reaction: 2Mn 3+ +2H₂O→Mn 2+ +MnO2↓+4H + .

[0003] This disproportionation reaction presents two fatal problems: First, the generated MnO2 is a solid precipitate that can clog flow channels, contaminate electrodes and membranes, leading to increased battery internal resistance and decreased efficiency; second, it consumes electrochemically active Mn. 3+ This leads to a rapid decline in the actual capacity of the battery. These problems severely limit the cycle life and reliability of titanium-manganese redox flow batteries.

[0004] Currently, researchers have tried various methods to address the manganese disproportionation problem, such as adding inorganic complexing agents like phosphoric acid and pyrophosphate, or certain organic ligands. However, these methods suffer from limited complexing ability, instability, or side reactions on the electrode surface, resulting in less than ideal outcomes.

[0005] Therefore, there is an urgent need in this field to develop a novel electrolyte system that can efficiently and stably suppress the disproportionation reaction of manganese ions. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of the prior art by providing an electrolyte for a titanium-manganese flow battery and a titanium-manganese flow battery itself.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The first aspect of the present invention is to provide an electrolyte for a titanium-manganese flow battery, comprising: 0.5 mol / L to 2.0 mol / L of manganese salt; 0.5 mol / L to 6 mol / L of additive; 0.5 mol / L to 5 mol / L of acid; and 0.5 mol / L to 3 mol / L of titanium salt; wherein the additive is closed sodium borate.

[0009] Preferably, the closed sodium borate salt includes at least one of: disodium dodecyl borate, sodium hydroborate, disodium carborane, and halogenated, alkyl, or amino-substituted derivatives thereof.

[0010] More preferably, the halogen-substituted derivative is a fluorinated boron cage compound.

[0011] More preferably, the fluorinated boron cage compound includes: Na2B 12 H 12-x F x NaCB 11 H 12-y F y Na2C2B 10 H 10-z F z At least one of them.

[0012] More preferably, x takes the values ​​1, 2, 4, 5, 6; y takes the values ​​1, 2, 5, 6, 11, 12; and z takes the values ​​1, 2, 5, 10.

[0013] Preferably, the manganese salt includes at least one of manganese sulfate, manganese chloride, and manganese acetate; the titanium salt is titanium oxysulfide; and the acid includes at least one of sulfuric acid, hydrochloric acid, and phosphoric acid.

[0014] A second aspect of the present invention is to provide a method for preparing the above-mentioned electrolyte, comprising the steps of:

[0015] S1. Weigh out titanium salt and dissolve it in acid solution, stir at 60℃-80℃ for 24h to obtain titanium hydrochloride solution;

[0016] S2. Weigh out closed-cell sodium borate and add it to the titanium hydrochloric acid solution. Stir under inert gas protection for 2-2.5 hours to obtain a pre-complexed solution.

[0017] S3. Weigh out the manganese salt and slowly add it to the pre-complexed solution, stir for 1.5h-2h to obtain the electrolyte.

[0018] Preferably, the preparation steps of the closed-cell borate salt include: mixing and reacting a parent borate cage compound with a fluorinating agent, condensing and refluxing the product to obtain a mixture, and filtering, purifying, and drying the mixture to obtain the fluorinated borate cage compound; wherein the parent borate cage compound includes at least one of: disodium dodecylborate, sodium hydroborate, and disodium carborane.

[0019] More preferably, the fluorinating agent is a mixture of fluorine gas and an inert gas; wherein the inert gas includes at least one of nitrogen and argon; and the volume fraction of the fluorine gas is 10%-50%.

[0020] More preferably, the reaction temperature is 80℃-120℃ and the reaction time is 2h-4h.

[0021] A third aspect of the present invention is to provide a titanium-manganese redox flow battery, wherein the positive and negative electrode electrolytes both use the above-mentioned electrolyte.

[0022] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0023] This invention introduces the additive borosilicate, whose electron cloud can interact with Mn. 3+ The empty orbitals interact and coordinate to form a rigid, approximately spherical, three-dimensional cage-like structure, Mn 3+ - The boron cage structure surrounding the boron cage compound creates significant steric hindrance, hindering electron transfer between the two boron cage compounds and reducing Mn. 3+ The electron density at the center increases the energy barrier for the disproportionation reaction, thus suppressing it. In particular, the fluorine atoms in fluoroborate cages have a strong electron-withdrawing effect, which can be transferred to the metal center through the boron cage framework, further lowering the electron density of Mn. 3+ The increased electron cloud density significantly enhances the electron stabilization effect; simultaneously, the introduction of fluorine atoms also enhances the hydrophobicity of the additive, reducing the impact of water molecules on Mn. 3+ The coordination of the components effectively suppresses disproportionation reactions, thereby greatly improving the cycle life of the battery. Attached Figure Description

[0024] Figure 1 The image shows the positive electrode CV curve of Embodiment 1 of the present invention. The curve after 100 cycles highly coincides with the initial state.

[0025] Figure 2 This is the positive electrode CV curve of Comparative Example 1 of the present invention.

[0026] Figure 3 This is the negative electrode CV curve of Embodiment 1 of the present invention.

[0027] Figure 4This is the negative electrode CV curve of Comparative Example 1 of the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0031] Example 1

[0032] This embodiment provides an electrolyte for a titanium-manganese flow battery, comprising: 1.0 mol / L MnSO4, 1.5 mol / L TiOSO4, 2.0 mol / L H2SO4, and 1.1 mol / L NaCB. 11 F 12 .

[0033] Among them, the additive NaCB 11 F 12 The synthesis method is as follows: NaCB 11 H 12 The mixture was reacted with a 95% F2 / N2 gas at 100℃ and 0.5MPa for 48 hours, and then recrystallized from acetonitrile to obtain a high-purity white powder, NaCB. 11 F 12 .

[0034] Example 2

[0035] This embodiment provides another electrolyte for a titanium-manganese flow battery, with NaCB as an additive. 11 H 11 In the synthesis method of F, the fluorinating agent is a 15% F2 / N2 mixture, and the rest are the same as in Example 1.

[0036] Example 3

[0037] This embodiment provides another electrolyte for a titanium-manganese flow battery, with NaCB as an additive. 11 H 10 In the synthesis method of F2, the fluorinating agent is a 25% F2 / N2 mixture, and the rest are the same as in Example 1.

[0038] Example 4

[0039] This embodiment provides another electrolyte for a titanium-manganese flow battery, with NaCB as an additive. 11 In the synthesis method of H7F5, the fluorinating agent is a 50% F2 / N2 mixture, and the rest are the same as in Example 1.

[0040] Example 5

[0041] This embodiment provides another electrolyte for a titanium-manganese flow battery, with NaCB as an additive. 11 In the synthesis method of H6F6, the fluorinating agent is a 70% F2 / N2 mixture, and the rest are the same as in Example 1.

[0042] Example 6

[0043] This embodiment provides another electrolyte for a titanium-manganese flow battery, with NaCB as an additive. 11 HF 11 In the synthesis method, the fluorinating agent is a 90% F2 / N2 mixture, and the rest are the same as in Example 1.

[0044] Example 7

[0045] This embodiment provides another electrolyte for a titanium-manganese flow battery, with the additive Na2C2B. 12 F 10 The synthesis method is as follows: using Na2C2B 12 H 10 Na₂C₂B was prepared by reacting a boron cage compound as the parent compound with a 95% F₂ / N₂ mixture at 120°C and 0.7 MPa for 48 hours, followed by recrystallization from acetonitrile to obtain a high-purity white powder. 12 F 10 The rest are the same as in Example 1.

[0046] Example 8

[0047] This embodiment provides another electrolyte for a titanium-manganese flow battery, with the additive Na2C2B. 12 In the synthesis method of H9F, the fluorinating agent is a 20% F2 / N2 mixture, and the rest are the same as in Example 7.

[0048] Example 9

[0049] This embodiment provides another electrolyte for a titanium-manganese flow battery, with the additive Na2C2B. 12 In the synthesis method of H8F2, the fluorinating agent is a 30% F2 / N2 mixture, and the rest are the same as in Example 7.

[0050] Example 10

[0051] This embodiment provides another electrolyte for a titanium-manganese flow battery, with the additive Na2C2B. 12In the synthesis method of H5F5, the fluorinating agent is a 60% F2 / N2 mixture, and the rest are the same as in Example 7.

[0052] Example 11

[0053] This embodiment provides another electrolyte for a titanium-manganese flow battery, with NaCB as an additive. 11 F 12 The content of [agent] was 0.5 mol / L, and the rest were the same as in Example 1.

[0054] Example 12

[0055] This embodiment provides another electrolyte for a titanium-manganese flow battery, with NaCB as an additive. 11 F 12 The content was 1.5 mol / L, and the rest were the same as in Example 1.

[0056] Example 13

[0057] This embodiment provides another electrolyte for a titanium-manganese flow battery, with NaCB as an additive. 11 F 12 The content of [agent] was 2 mol / L, and the rest were the same as in Example 1.

[0058] Example 14

[0059] This embodiment provides another electrolyte for a titanium-manganese flow battery, with the additive Na2C2B. 12 F 10 The content of [agent] was 0.5 mol / L, and the rest were the same as in Example 7.

[0060] Example 15

[0061] This embodiment provides another electrolyte for a titanium-manganese flow battery, with the additive Na2C2B. 12 F 10 The content was 1.5 mol / L, and the rest were the same as in Example 7.

[0062] Example 16

[0063] This embodiment provides another electrolyte for a titanium-manganese flow battery, with the additive Na2C2B. 12 F 10 The content of [agent] was 2 mol / L, and the rest were the same as in Example 7.

[0064] Comparative Example 1

[0065] This comparative example provides another electrolyte for a titanium-manganese flow battery, comprising: a solution of 1.0 mol / L manganese sulfate and 2.0 mol / L dilute sulfuric acid as the positive electrode electrolyte, and a solution of 1.0 mol / L titanium oxysulfate and 2.0 mol / L dilute sulfuric acid as the negative electrode electrolyte.

[0066] Comparative Example 2

[0067] This comparative example provides another electrolyte for a titanium-manganese flow battery, comprising: 1.0 mol / L manganese sulfate, 2.0 mol / L dilute sulfuric acid, and 1.1 mol / L Na[CB]. 11 H 12 A solution of 1.0 mol / L titanium oxysulfate and 2.0 mol / L dilute sulfuric acid was used as the positive electrode electrolyte, and a solution of 1.0 mol / L titanium oxysulfate and 2.0 mol / L dilute sulfuric acid was used as the negative electrode electrolyte.

[0068] Comparative Example 3

[0069] This comparative example provides another electrolyte for a titanium-manganese flow battery, comprising: 1.0 mol / L manganese sulfate, 2.0 mol / L dilute sulfuric acid, and 1.1 mol / L Na[B] 12 F 12 A solution of 1.0 mol / L titanium oxysulfate and 2.0 mol / L dilute sulfuric acid was used as the positive electrode electrolyte, and a solution of 1.0 mol / L titanium oxysulfate and 2.0 mol / L dilute sulfuric acid was used as the negative electrode electrolyte.

[0070] Detection Examples

[0071] Batteries were fabricated using the electrolytes of Examples 1-16 and Comparative Examples 1-3, respectively. Carbon cloth was used as the working electrode and counter electrode, and a saturated calomel electrode was used as the reference electrode. CV tests were performed, and the test results are as follows: Figure 1-4 And as shown in Table 1.

[0072] Table 1

[0073]

[0074] The test results show that, compared with Comparative Example 1 (without additives), the addition of boron cage additives reduced the potential difference of Comparative Examples 2-3 from 46mV to 39 / 43mV after 100 cycles. This demonstrates that the boron cage additives effectively suppressed Mn. 3+ The disproportionation reaction, but without fluorinated boron cage compounds (NaCB) 11 H 12 NaB 12 H 12 Due to the lack of electronic regulation and hydrophobic optimization effects of fluorine atoms, Mn 3 + The inhibition effect of the disproportionation reaction is weaker than that of the fluorinated boron cage additive, and the corresponding battery potential difference should be significantly higher than that of the fluorinated example. NaB 12 H 12 It is a "pure boron cage structure" whose cage-like framework is a highly symmetrical sphere, and the coordination sites are more evenly distributed in space, enabling it to interact with Mn. 3+ This forms a more compact multi-toothed coordination structure, while NaCB 11 H 12It is a "single-carbon substituted boron cage". Carbon substitution disrupts the perfect symmetry of the pure boron cage, reduces the spatial uniformity of the coordination sites, and affects the interaction with Mn. 3+ The coordination binding is slightly weaker, resulting in a poorer inhibitory effect on disproportionation reactions.

[0075] Compared with Comparative Examples 2-3, the positive and negative electrodes of the battery of the present invention both use the electrolyte of the present invention, and fluorine atoms are introduced into the additives. 3+ :Na2C2B 12 F 10 When the Mn ratio is 1:1.1, the potential difference further decreases to 11 mV after 100 cycles; when Mn 3+ NaCB 11 F 12 When the ratio is 1:1.1, the potential difference further decreases to 1mV after 100 cycles, and the battery potential stability is significantly improved. This shows that the fluorine atoms in the fluoroborate can achieve a good effect in suppressing the disproportionation reaction, which greatly improves the cycle life of the battery.

[0076] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. An electrolyte for a titanium-manganese flow battery, characterized in that, The components include: manganese salt 0.5 mol / L-2.0 mol / L; additive 0.5 mol / L-6 mol / L; acid 0.5 mol / L-5 mol / L; titanium salt 0.5 mol / L-3 mol / L; wherein the additive is closed sodium borate.

2. The electrolyte according to claim 1, characterized in that, The closed-cell sodium borate salts include at least one of the following: disodium dodecyl borate, sodium hydroborate, disodium carborane, and their halogenated, alkylated, or amino-substituted derivatives.

3. The electrolyte according to claim 2, characterized in that, The halogen-substituted derivative is a fluorinated boron cage compound.

4. The electrolyte according to claim 3, characterized in that, The fluorinated boron cage compound includes: Na2B 12 H 12-x F x NaCB 11 H 12-y F y Na2C2B 10 H 10-z F z At least one of them.

5. The electrolyte according to claim 4, characterized in that, x takes the values ​​1, 2, 4, 5, 6; y takes the values ​​1, 2, 5, 6, 11, 12; z takes the values ​​1, 2, 5, 10.

6. The electrolyte according to claim 1, characterized in that, The manganese salt includes at least one of manganese sulfate, manganese chloride, and manganese acetate; the titanium salt is titanium oxysulfide; and the acid includes at least one of sulfuric acid, hydrochloric acid, and phosphoric acid.

7. A method for preparing the electrolyte as described in any one of claims 1-6, characterized in that, step... include: S1. Weigh out titanium salt and dissolve it in acid solution, stir at 60℃-80℃ for 24h to obtain titanium hydrochloride acid solution; S2. Weigh out closed-cell sodium borate and add it to the titanium hydrochloric acid solution. Stir under inert gas protection for 2-2.5 hours to obtain a pre-complexed solution. S3. Weigh out the manganese salt and slowly add it to the pre-complexed solution, stir for 1.5h-2h to obtain the electrolyte.

8. The preparation method according to claim 7, characterized in that, The preparation steps of the closed sodium borate salt include: mixing and reacting a parent boron cage compound with a fluorinating agent, condensing and refluxing the product to obtain a mixture, and filtering, purifying, and drying the mixture to obtain the closed sodium borate salt; wherein the parent boron cage compound includes at least one of: disodium dodecylborohydride, sodium hydroborate, and disodium carborane.

9. The preparation method according to claim 8, characterized in that, The fluorinating agent is a mixture of fluorine gas and an inert gas; wherein the inert gas includes at least one of nitrogen and argon; and the volume fraction of the fluorine gas is 10%-50%.

10. A titanium-manganese redox flow battery, characterized in that, Both the positive and negative electrode electrolytes are the electrolytes described in any one of claims 1-6 or the electrolytes prepared by the preparation method described in any one of claims 7-9.

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