An electrolyte for organic liquid flow battery positive electrode and preparation method thereof

Abstract

The invention relates to the technical field of electrochemical energy storage, and discloses an electrolyte for an organic liquid flow battery positive electrode and a preparation method thereof. The organic liquid flow battery positive electrode electrolyte consists of tetrathiofulvalene dimethyl methyl ether, lithium hexafluorophosphate and an organic solvent; the organic solvent is a mixed solution of ethyl methyl carbonate, ethylene carbonate and propylene carbonate; the chemical structure of the tetrathiofulvalene dimethyl methyl ether is as follows: by introducing a flexible methyl methyl ether end group into tetrathiofulvalene, not only can the accumulation of tetrathiofulvalene units be effectively prevented, but also the affinity of methyl tetrathiofulvalene dicarboxylate with the organic solvent is increased, so that the dissolution of tetrathiofulvalene dimethyl methyl ether in the corresponding organic solvent is improved, and the energy density of the liquid flow battery can be improved to achieve stable cycle performance.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and in particular to an electrolyte for an organic liquid flow battery positive electrode and a preparation method thereof. Background Art

[0002] With the development of environmentally friendly technologies to reduce carbon emissions, there is an increasing demand for using widely available and pollution-free energy to replace traditional petroleum energy.

[0003] New energy technologies represented by wind power and solar energy have the characteristics of unstable power generation time and power generation, and require large-scale energy storage batteries to match them.

[0004] Currently, commercialized energy storage technologies are mainly lithium-ion batteries and lead-acid batteries. The volume-to-energy density or mass-to-energy density of lithium-ion batteries and lead-acid batteries are both high. If used for large-scale energy storage, they have the disadvantages of low safety performance and high cost.

[0005] Liquid flow batteries are currently the most promising energy storage technology because of their independently adjustable energy and power and low expansion costs.

[0006] In the prior art, the liquid flow battery has a large amount of solvent inside, so the volume energy density or mass energy density of the liquid flow battery is low, thus limiting the promotion and application of the liquid flow battery.

[0007] All-vanadium liquid flow battery is a relatively mature aqueous liquid flow battery technology, but it has disadvantages such as strong electrolyte corrosion and low discharge voltage. Summary of the invention

[0008] In view of the above problems, the first object of the present invention is to propose an electrolyte for the positive electrode of an organic liquid flow battery, which has high solubility in the corresponding organic solvent, is beneficial to improving the energy density of the liquid flow battery, and can achieve stable cycle performance.

[0009] Another object of the present invention is to provide a method for preparing an electrolyte for a positive electrode of an organic liquid flow battery, which has the advantages of a simple synthesis process and is convenient for large-scale production.

[0010] To achieve this object, the present invention adopts the following technical solutions:

[0011] An electrolyte for an organic liquid flow battery positive electrode, wherein the organic liquid flow battery positive electrode electrolyte is composed of tetrathiofulvalene dimethyl methyl ether, lithium hexafluorophosphate and an organic solvent;

[0012] The organic solvent is a mixed solution of ethyl methyl carbonate, ethylene carbonate and propylene carbonate; the chemical structure of tetrathiofulvalene dimethyl methyl ether is:

[0013]

[0014] Furthermore, the present invention provides a method for preparing an electrolyte for an organic liquid flow battery positive electrode, which is used to prepare the electrolyte for the organic liquid flow battery positive electrode described above, comprising the following steps:

[0015] S1) using anhydrous tetrahydrofuran as solvent, adding methyl propiolate and carbon disulfide, and reacting at -60°C to -80°C for 3-10 hours in an argon atmosphere under the catalysis of tributylphosphine, then naturally warming to room temperature, filtering out tetrahydrofuran under vacuum, washing the filtered solid with a small amount of dichloromethane, and then using a chromatography column to purify the solid filtrate to obtain solid methyl tetrathiofulvalenedicarboxylate;

[0016] S2) adding the methyl tetrathiofulvalene dicarboxylate obtained in step S1) to anhydrous tetrahydrofuran, stirring to dissolve, adding a 1 mol / L n-hexane solution of diisobutylaluminum hydride under argon protection, reacting for 3-10 hours, then dropping a saturated aqueous solution of potassium sodium tartrate, continuing to stir for 1-3 hours, filtering off the tetrahydrofuran under vacuum, collecting the solid by suction, and purifying the filtered solid by a chromatography column to obtain solid tetrathiofulvalene dimethanol;

[0017] S3) under argon protection, adding the tetrathiofulvalene dimethanol and iodomethane to anhydrous tetrahydrofuran, then adding sodium hydride, reacting at 60° C.-80° C. for 20-40 hours, then adding tetrahydrofuran containing 5 wt % of deionized water to quench the reaction, then filtering out the tetrahydrofuran under vacuum, then adding dichloromethane and deionized water for extraction, collecting the dichloromethane solution containing the extract, filtering out the dichloromethane under vacuum, and then purifying the filtered solid by passing it through a chromatography column to obtain solid tetrathiofulvalene dimethyl methyl ether;

[0018] S4) adding the tetrathiofulvalene dimethyl methyl ether to a mixed solvent of ethyl methyl carbonate, ethylene carbonate and propylene carbonate, stirring and mixing evenly, then adding lithium hexafluorophosphate, stirring and dissolving, to obtain the positive electrode electrolyte of the organic liquid flow battery.

[0019] Preferably, in step S1), the molar ratio of carbon disulfide, methyl propiolate and tributylphosphine is 1:(0.5-2):(0.25-1), and the amount of anhydrous tetrahydrofuran is: the corresponding addition amount per gram of methyl propiolate is 5-40 mL.

[0020] Preferably, in step S1), the volume of dichloromethane is 0.1-1 times the volume of anhydrous tetrahydrofuran.

[0021] Preferably, in step S2), the molar ratio of methyl tetrathiofulvalene dicarboxylate to diisobutylaluminum hydride is 1:(4-10), and the amount of anhydrous tetrahydrofuran is: 20-160 mL per gram of methyl tetrathiofulvalene dicarboxylate.

[0022] Preferably, in step S2), the volume of the saturated sodium potassium tartrate aqueous solution is 0.1-1 times the volume of anhydrous tetrahydrofuran.

[0023] Preferably, in step S3), the molar ratio of tetrathiofulvalene dimethanol, methyl iodide and sodium hydride is 1:(2-10):(2-8), and the amounts of anhydrous tetrahydrofuran and tetrahydrofuran containing 5wt% deionized water are both: the corresponding added amount per gram of the tetrathiofulvalene dimethanol is 20-160 mL.

[0024] Preferably, in step S3), the amount of dichloromethane used in the extraction is: the corresponding amount added per gram of the tetrathiofulvalin dimethanol is 20-160 mL; the volume ratio of dichloromethane to deionized water used in the extraction is 1:(1-5).

[0025] Preferably, in step S4), the volume ratio of ethyl methyl carbonate, ethylene carbonate and propylene carbonate is 5:(2-6):(1-3).

[0026] Preferably, in step S4), the concentration of tetrathiofulvalene dimethyl methyl ether is 1-3 mol / L, and the concentration of lithium hexafluorophosphate is 2-8 mol / L.

[0027] The above technical solution of the present invention has the beneficial effects as follows: the electrolyte for the positive electrode of the organic liquid flow battery can effectively prevent the accumulation of the tetrathiofulvalene unit by introducing a flexible methyl methyl ether end group into the tetrathiofulvalene, and also increase the affinity of the tetrathiofulvalene dicarboxylic acid methyl ester with the organic solvent. The molecular weight of the introduced methyl methyl ether is small, so that the solubility concentration of the tetrathiofulvalene dimethyl methyl ether in the corresponding organic solvent is improved, which can be as high as -3 mol / L. Due to the small molecular weight of the introduced methyl methyl ether, the mass specific capacity of the tetrathiofulvalene will not be significantly reduced. The voltage platform of the tetrathiofulvalene dimethyl methyl ether relative to the charge and discharge of Li / Li+ is 3.0-3.6V, which can be beneficial to improve the energy density of the liquid flow battery and achieve stable cycle performance.

[0028] Furthermore, the present invention proposes a method for preparing the electrolyte for the positive electrode of the organic liquid flow battery, which has the advantages of simple synthesis process and convenience for large-scale production, and has a commercial prospect that can be widely promoted. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1This is the hydrogen nuclear magnetic resonance spectrum of tetrathiofulvalene dimethyl methyl ether prepared in Example 3;

[0030] Figure 2 is the charge and discharge curve of the organic liquid flow battery of Application Example 1;

[0031] Figure 3 The discharge volume specific capacity of the organic liquid flow battery of Application Example 1 in the cycle test;

[0032] Figure 4 This is the coulombic efficiency of the organic liquid flow battery in Application Example 1 during the cycle test. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0034] In the description of this specification, the description with reference to the terms "embodiment", "example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0035] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

[0036] An electrolyte for an organic liquid flow battery positive electrode, the organic liquid flow battery positive electrode electrolyte consisting of tetrathiofulvalene dimethyl methyl ether, lithium hexafluorophosphate and an organic solvent;

[0037] The organic solvent is a mixed solution of ethyl methyl carbonate, ethylene carbonate and propylene carbonate; the chemical structure of tetrathiofulvalene dimethyl methyl ether is:

[0038]

[0039] Although tetrathiofulvalene has a high redox potential, the solubility of ethyl tetrathiofulvalene dicarboxylate in the positive electrolyte of the flow battery of ethyl tetrathiofulvalene dicarboxylate in the prior art does not exceed 0.03 mol / L. Although it is significantly improved compared with methyl tetrathiofulvalene dicarboxylate, the discharge volume specific capacity of the prepared electrolyte does not exceed 0.36 Ah / L.

[0040] The electrolyte for the positive electrode of the organic liquid flow battery of the present invention can effectively prevent the accumulation of the tetrathiofulvalene unit by introducing a flexible methyl methyl ether end group into the tetrathiofulvalene, and also increase the affinity of the tetrathiofulvalene dicarboxylic acid methyl ester with the organic solvent. The molecular weight of the introduced methyl methyl ether is small, so that the solubility concentration of the tetrathiofulvalene dimethyl methyl ether in the corresponding organic solvent is improved, which can be as high as 3 mol / L. Due to the small molecular weight of the introduced methyl methyl ether, the mass specific capacity of the tetrathiofulvalene will not be significantly reduced. The voltage platform of the tetrathiofulvalene dimethyl methyl ether relative to the charge and discharge of Li / Li+ is 3.0-3.6V, which can be beneficial to improve the energy density of the liquid flow battery and achieve stable cycle performance.

[0041] The electrolyte for the positive electrode of the organic liquid flow battery of the present invention contains tetrathiofulvalene dimethyl methyl ether, which has high solubility in ethyl methyl carbonate, ethylene carbonate and propylene carbonate, and the concentration can be as high as 1-3 mol / L. The molecular weight of tetrathiofulvalene dimethyl methyl ether is small, and the mass specific capacity is as high as 183 mAh / g. The electrolyte for the positive electrode of the organic liquid flow battery has the advantages of high volume specific capacity, high redox potential and high cycle stability, and therefore has good application prospects.

[0042] Furthermore, the present invention provides a method for preparing an electrolyte for an organic liquid flow battery positive electrode, which is used to prepare the electrolyte for the organic liquid flow battery positive electrode described above, comprising the following steps:

[0043] S1) using anhydrous tetrahydrofuran as solvent, adding methyl propiolate and carbon disulfide, and reacting at -60°C to -80°C for 3-10 hours in an argon atmosphere under the catalysis of tributylphosphine, then naturally warming to room temperature, filtering out tetrahydrofuran under vacuum, washing the filtered solid with a small amount of dichloromethane, and then using a chromatography column to purify the solid filtrate to obtain solid methyl tetrathiofulvalenedicarboxylate;

[0044] S2) adding the methyl tetrathiofulvalene dicarboxylate obtained in step S1) to anhydrous tetrahydrofuran, stirring to dissolve, adding a 1 mol / L n-hexane solution of diisobutylaluminum hydride under argon protection, reacting for 3-10 hours, then dropping a saturated aqueous solution of potassium sodium tartrate, continuing to stir for 1-3 hours, filtering off the tetrahydrofuran under vacuum, collecting the solid by suction, and purifying the filtered solid by a chromatography column to obtain solid tetrathiofulvalene dimethanol;

[0045] S3) under argon protection, adding the tetrathiofulvalene dimethanol and iodomethane to anhydrous tetrahydrofuran, then adding sodium hydride, reacting at 60° C.-80° C. for 20-40 hours, then adding tetrahydrofuran containing 5 wt % of deionized water to quench the reaction, then filtering out the tetrahydrofuran under vacuum, then adding dichloromethane and deionized water for extraction, collecting the dichloromethane solution containing the extract, filtering out the dichloromethane under vacuum, and then purifying the filtered solid by passing it through a chromatography column to obtain solid tetrathiofulvalene dimethyl methyl ether;

[0046] S4) adding the tetrathiofulvalene dimethyl methyl ether to a mixed solvent of ethyl methyl carbonate, ethylene carbonate and propylene carbonate, stirring and mixing evenly, then adding lithium hexafluorophosphate, stirring and dissolving, to obtain the positive electrode electrolyte of the organic liquid flow battery.

[0047] The reaction formula of methyl tetrathiofulvalenedicarboxylate prepared in step S1) is:

[0048]

[0049] The reaction formula of tetrathiofulvalene dimethanol prepared in step S2) is:

[0050]

[0051] The reaction formula of tetrathiofulvalene dimethyl methyl ether prepared in step S3) is:

[0052]

[0053] Compared with the prior art, the method for preparing the electrolyte of the positive electrode of the organic liquid flow battery of the present invention has the advantages of simple synthesis process and convenience for large-scale production, and has a commercial prospect that can be widely promoted.

[0054] Preferably, in step S1), the molar ratio of carbon disulfide, methyl propiolate and tributylphosphine is 1:(0.5-2):(0.25-1), and the amount of anhydrous tetrahydrofuran is: the corresponding addition amount per gram of methyl propiolate is 5-40 mL.

[0055] Preferably, in step S1), the volume of dichloromethane is 0.1-1 times the volume of anhydrous tetrahydrofuran.

[0056] Preferably, in step S2), the molar ratio of methyl tetrathiofulvalene dicarboxylate to diisobutylaluminum hydride is 1:(4-10), and the amount of anhydrous tetrahydrofuran is: 20-160 mL per gram of methyl tetrathiofulvalene dicarboxylate.

[0057] Preferably, in step S2), the volume of the saturated sodium potassium tartrate aqueous solution is 0.1-1 times the volume of anhydrous tetrahydrofuran.

[0058] Preferably, in step S3), the molar ratio of tetrathiofulvalene dimethanol, methyl iodide and sodium hydride is 1:(2-10):(2-8), and the amounts of anhydrous tetrahydrofuran and tetrahydrofuran containing 5wt% deionized water are both: the corresponding added amount per gram of the tetrathiofulvalene dimethanol is 20-160 mL.

[0059] Preferably, in step S3), the amount of dichloromethane used in the extraction is: the corresponding amount added per gram of the tetrathiofulvalin dimethanol is 20-160 mL; the volume ratio of dichloromethane to deionized water used in the extraction is 1:(1-5).

[0060] Preferably, in step S4), the volume ratio of ethyl methyl carbonate, ethylene carbonate and propylene carbonate is 5:(2-6):(1-3).

[0061] Preferably, in step S4), the concentration of tetrathiofulvalene dimethyl methyl ether is 1-3 mol / L, and the concentration of lithium hexafluorophosphate is 2-8 mol / L.

[0062] Example

[0063] Example 1: Synthesis of Methyl Tetrathiofulvalenedicarboxylate

[0064] Under argon protection, a 500 mL three-necked round-bottom flask was cooled to -70°C with a mixed system of dry ice / anhydrous ethanol, 100 mL of tetrahydrofuran, 19.0 g (0.25 mol) of carbon disulfide, 16.8 g (0.2 mol) of methyl propiolate were added, and then 40.4 g (0.2 mol) of tributylphosphine was slowly added dropwise, stirred for 6 hours, and then naturally warmed to room temperature, tetrahydrofuran was removed under vacuum conditions, 20 mL of dichloromethane was added to the obtained residue for washing, and the crude product was further purified by column chromatography with dichloromethane to obtain 4.0 g of red solid methyl tetrathiofulvalenedicarboxylate.

[0065] The above nuclear magnetic resonance hydrogen spectrum test results of methyl tetrathiofulvalenedicarboxylate in deuterated DMSO are:

[0066] 1 HNMR (400MHz, DMSO-d6, ppm) δ: 7.87 (s, 2H), 3.78 (s, 6H).

[0067] Example 2: Synthesis of Tetrathiofulvalenedicarboxylic Acid Dimethanol

[0068] To a 500mL three-necked round-bottom flask, 4.0g (0.012mol) of methyl tetrathiofulvalene dicarboxylate and 200mL of anhydrous tetrahydrofuran were added and stirred to dissolve. Under argon protection, 50mL (0.05mmol) of 1mol / L diisobutylaluminum hydride in n-hexane solution was slowly added dropwise. The mixture was reacted at room temperature for 10 hours. Then 100mL of saturated sodium potassium tartrate aqueous solution was added dropwise. Stirring was continued for 3 hours. Then, tetrahydrofuran was removed under vacuum. The solid was collected by filtration and further purified by column with a mixed solution of dichloromethane / methanol (volume ratio 5:1) to obtain 3.2g of tetrathiofulvalene dimethanol as an orange solid.

[0069] The above NMR hydrogen spectrum test results of tetrathiofulvalene dimethanol in deuterated DMSO are:

[0070] 1 HNMR (400MHz, DMSO-d6, ppm) δ: 6.53 (s, 2H), 5.50 (t, 2H), 4.21 (s, 4H).

[0071] Example 3: Synthesis of Tetrathiofulvalene Dimethyl Methyl Ether

[0072] Under argon protection, 3.0 g (0.011 mol) of tetrathiofulvalene dimethanol and 4.68 g (0.033 mol) of iodomethane were added to a 500 ml three-necked round-bottom flask containing 150 ml of anhydrous tetrahydrofuran, 1.2 g (0.050 mol) of sodium hydride was added, and the mixture was reacted at 60° C. for 30 hours, and then 60 ml of tetrahydrofuran containing 5 wt % of deionized water was added to quench the reaction, and then tetrahydrofuran was removed under vacuum, and then 100 ml of dichloromethane and 100 ml of deionized water were used for extraction, and the dichloromethane solution was collected, and dichloromethane was removed under vacuum. The obtained solid was then purified by column using a cyclohexane / dichloromethane mixed solution (volume ratio 5:1) to obtain 2.0 g of tetrathiofulvalene dimethyl methyl ether as a dark yellow solid.

[0073] The above nuclear magnetic resonance hydrogen spectrum test results of tetrathiofulvalene dimethyl methyl ether in deuterated chloroform are:

[0074] 1 HNMR (400MHz,CDCl3,ppm)δ:6.23(s,2H),4.21(s,4H),3.45(s,6H), see Figure 3 .

[0075] Example 4-6: Preparation of positive electrolyte for organic flow battery based on tetrathiofulvalene dimethyl methyl ether

[0076] According to the formula shown in Table 1, tetrathiofulvalene dimethyl methyl ether was added to a mixed organic solvent consisting of ethyl methyl carbonate, ethylene carbonate and propylene carbonate, and the mixture was stirred and mixed. Then, lithium hexafluorophosphate was added and stirred and dissolved to obtain the electrolyte for the positive electrode of the organic liquid flow battery corresponding to Examples 4-6.

[0077] Table 1 Formula of electrolyte for positive electrode of organic liquid flow battery of Examples 4-6

[0078]

[0079]

[0080] Application Example 1-3: Preparation of a flow battery containing an electrolyte for the positive electrode of an organic flow battery corresponding to Examples 4-6:

[0081] 1. Use lithium sheet as battery negative electrode and porous Celgard2400 as battery separator, where the effective area of ​​the separator is 3cm×3cm(9cm 2 ); the lithium sheet is moistened with an electrolyte consisting of 1.0 mol / L lithium hexafluorophosphate + a mixed solution of ethyl methyl carbonate, ethylene carbonate and propylene carbonate in a volume ratio of 5:3:2 to ensure sufficient contact between the lithium sheet and the diaphragm; the positive electrode uses graphite felt as a current collector to form an organic liquid flow battery of Application Example 1-3.

[0082] 2. Take 8 mL of the electrolyte of the positive electrode of the corresponding organic liquid flow battery prepared in Examples 4-6 and place them in three liquid storage tanks, and then use a peristaltic pump to input the corresponding electrolyte into the positive electrode side of the corresponding organic liquid flow battery at a rate of 16 mL / min for circulation testing.

[0083] 3. The assembled organic liquid flow batteries of Application Examples 1-3 were respectively subjected to a current density of 5 mA / cm 2 Constant current charging and discharging is performed, the voltage range is set to 2.8~3.8V, and the number of cycles is 100.

[0084] 4. The performance of each battery was evaluated by discharge volume capacity, discharge volume capacity retention rate and coulombic efficiency, where discharge volume capacity retention rate = 100th discharge volume capacity / first discharge volume capacity × 100%, coulombic efficiency = discharge charge / charge charge × 100%; the battery performance of each application example is shown in Table 2.

[0085] Table 2 Battery performance of application examples 1-3

[0086]

[0087]

[0088] As can be seen from Table 2, the discharge volume specific capacity of the positive electrode electrolyte of the organic liquid flow battery prepared in Example 4 can be as high as 53.6Ah / L (Application Example 1) or more. When the concentration of tetrathiofulvalene dimethyl methyl ether is increased to 2mol / L and 3mol / L, the discharge volume specific capacity of Application Example 2 and Application Example 3 is as high as 80.4Ah / L and 107Ah / L, respectively. This shows that the high solubility of tetrathiofulvalene dimethyl methyl ether can effectively improve the discharge volume specific capacity of the organic liquid flow battery.

[0089] Figure 1 This is the H NMR spectrum of tetrathiofulvalene dimethyl methyl ether prepared in Example 3, wherein the peak with a chemical shift of 3.42 ppm is attributed to the H on the methoxy group at the tail end of the side chain; the peak with a chemical shift of 4.20 ppm is attributed to the H on the methylene group; the peak with a chemical shift of 6.21 ppm is attributed to the H on the tetrathiofulvalene unit; and the peak with a chemical shift of 7.28 ppm is attributed to the residual dichloromethane solvent peak; the above results prove the structure of tetrathiofulvalene dimethyl methyl ether.

[0090] Figure 2 The organic liquid flow battery prepared in Application Example 1 is 5 mA / cm 2 The charge and discharge curves. It can be seen from the figure that two voltage platforms of 3.22 and 3.55V appeared in the battery during the charging process, corresponding to the two oxidation reactions of tetrathiofulvalene dimethyl methyl ether respectively; voltage platforms of 3.17 and 3.50V appeared in the discharge process, corresponding to the two reduction reactions of tetrathiofulvalene dimethyl methyl ether respectively. On the whole, the flow battery of the positive electrode electrolyte of the organic liquid flow battery based on tetrathiofulvalene dimethyl methyl ether of the present invention has a higher battery voltage, and the battery's charge and discharge platform is stable, which is conducive to the battery to remain stable during operation; the higher discharge platform and higher discharge volume specific capacity in Table 2 indicate that the electrolyte of the positive electrode of the organic liquid flow battery of the present invention has a higher volume specific energy density.

[0091] Figure 3 This is the organic liquid flow battery of Application Example 1. At 5 mA / cm 2 The discharge volume specific capacity curve after 100 cycles of charge and discharge at a current of , the discharge capacity retention rate after 100 cycles is as high as 79.8%, indicating that the battery has high cycle stability.

[0092] Figure 4 This is the organic liquid flow battery of Application Example 1. At 5 mA / cm 2 The Coulomb efficiency curve of continuous charge and discharge for 100 times at a current of , the Coulomb efficiency of the battery after stabilization reaches more than 94%.

[0093] In summary, the electrolyte for the positive electrode of the organic liquid flow battery, by introducing a flexible methyl methyl ether end group into tetrathiofulvalene, can not only effectively prevent the accumulation of tetrathiofulvalene units, but also increase the affinity of tetrathiofulvalene dicarboxylic acid methyl ester with organic solvents. The molecular weight of the introduced methyl methyl ether is small, so that the solubility concentration of tetrathiofulvalene dimethyl methyl ether in the corresponding organic solvent is improved, which can be as high as 3 mol / L. Due to the small molecular weight of the introduced methyl methyl ether, the mass specific capacity of tetrathiofulvalene will not be significantly reduced. The voltage platform of the tetrathiofulvalene dimethyl methyl ether relative to the charge and discharge of Li / Li+ is 3.0-3.6V, which can be beneficial to improve the energy density of the liquid flow battery and achieve stable cycle performance.

[0094] Furthermore, the present invention proposes a method for preparing the electrolyte for the positive electrode of the organic liquid flow battery, which has the advantages of simple synthesis process and convenience for large-scale production, and has a commercial prospect that can be widely promoted.

[0095] The technical principle of the present invention is described above in conjunction with specific embodiments. These descriptions are only for explaining the principle of the present invention and cannot be interpreted as limiting the scope of protection of the present invention in any way. Based on the explanations herein, those skilled in the art can associate other specific implementations of the present invention without paying creative labor, and these methods will fall within the scope of protection of the present invention.

Claims

1. An electrolyte for an organic liquid flow battery positive electrode, characterized in that: The positive electrode electrolyte of the organic liquid flow battery is composed of tetrathiofulvalene dimethyl methyl ether, lithium hexafluorophosphate and an organic solvent; The organic solvent is a mixed solution of ethyl methyl carbonate, ethylene carbonate and propylene carbonate; the chemical structure of tetrathiofulvalene dimethyl methyl ether is: The method for preparing the electrolyte of the positive electrode of the organic liquid flow battery comprises the following steps: S1) using anhydrous tetrahydrofuran as solvent, adding methyl propiolate and carbon disulfide, and reacting at -60°C to -80°C in an argon atmosphere under the catalysis of tributylphosphine for 3-10 hours, then naturally warming to room temperature, filtering out tetrahydrofuran under vacuum, washing the filtered solid with a small amount of dichloromethane, and then purifying the solid filtrate through a chromatography column to obtain solid methyl tetrathiofulvalenedicarboxylate; S2) adding the methyl tetrathiofulvalene dicarboxylate prepared in step S1) to anhydrous tetrahydrofuran, stirring to dissolve, adding a 1 mol / L n-hexane solution of diisobutylaluminum hydride under argon protection, reacting for 3-10 hours, then dropping a saturated aqueous solution of potassium sodium tartrate, continuing to stir for 1-3 hours, filtering off the tetrahydrofuran under vacuum, collecting the solid by suction, and purifying the filtered solid by passing through a chromatography column to obtain solid tetrathiofulvalene dimethanol; S3) under argon protection, adding the tetrathiofulvalene dimethanol and iodomethane to anhydrous tetrahydrofuran, then adding sodium hydride, reacting at 60° C.-80° C. for 20-40 hours, then adding tetrahydrofuran containing 5 wt % of deionized water to quench the reaction, then filtering out the tetrahydrofuran under vacuum, then adding dichloromethane and deionized water for extraction, collecting the dichloromethane solution containing the extract, filtering out the dichloromethane under vacuum, and then purifying the filtered solid by passing it through a chromatography column to obtain solid tetrathiofulvalene dimethyl methyl ether; S4) adding the tetrathiofulvalene dimethyl methyl ether to a mixed solvent of ethyl methyl carbonate, ethylene carbonate and propylene carbonate, stirring and mixing evenly, and then adding lithium hexafluorophosphate, stirring and dissolving, thereby preparing the positive electrode electrolyte of the organic liquid flow battery; In step S4), the concentration of tetrathiofulvalene dimethyl methyl ether is 1-3 mol / L; When the concentration of tetrathiofulvalene dimethyl methyl ether is 1 mol / L, 2 mol / L and 3 mol / L, the discharge volume specific capacity of the prepared organic liquid flow battery positive electrode electrolyte is as high as 53.6 Ah / L, 80.4 Ah / L and 107 Ah / L, respectively.

2. The electrolyte of the positive electrode of the organic liquid flow battery according to claim 1, characterized in that: In step S1), the molar ratio of carbon disulfide, methyl propiolate and tributylphosphine is 1:(0.5-2):(0.25-1), and the amount of anhydrous tetrahydrofuran is 5-40 mL per gram of methyl propiolate.

3. The electrolyte of the positive electrode of the organic liquid flow battery according to claim 1, characterized in that: In step S1), the volume of dichloromethane is 0.1-1 times the volume of anhydrous tetrahydrofuran.

4. The electrolyte for the positive electrode of the organic liquid flow battery according to claim 1, characterized in that: In step S2), the molar ratio of methyl tetrathiofulvalene dicarboxylate to diisobutylaluminum hydride is 1:(4-10), and the amount of anhydrous tetrahydrofuran is 20-160 mL per gram of methyl tetrathiofulvalene dicarboxylate.

5. The electrolyte for the positive electrode of the organic liquid flow battery according to claim 1, characterized in that: In step S2), the volume of the saturated sodium potassium tartrate aqueous solution is 0.1-1 times the volume of the anhydrous tetrahydrofuran.

6. The electrolyte for the positive electrode of the organic liquid flow battery according to claim 1, characterized in that: In step S3), the molar ratio of tetrathiofulvalene dimethanol, methyl iodide and sodium hydride is 1:(2-10):(2-8), and the amounts of anhydrous tetrahydrofuran and tetrahydrofuran containing 5wt% deionized water are both: the corresponding addition amount per gram of the tetrathiofulvalene dimethanol is 20-160 mL.

7. The method for preparing an electrolyte for an organic liquid flow battery positive electrode according to claim 1, characterized in that: In step S3), the amount of dichloromethane used in the extraction is: the corresponding amount added per gram of the tetrathiofulvar dimethanol is 20-160 mL; the volume ratio of dichloromethane to deionized water used in the extraction is 1: (1-5).

8. The electrolyte for the positive electrode of the organic liquid flow battery according to claim 1, characterized in that: In step S4), the volume ratio of ethyl methyl carbonate, ethylene carbonate and propylene carbonate is 5:(2-6):(1-3).

9. The electrolyte for the positive electrode of the organic liquid flow battery according to claim 1, characterized in that: In step S4), the concentration of lithium hexafluorophosphate is 2-8 mol / L.

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