CN116093391A - Electrolyte for positive electrode of organic flow battery and preparation method thereof - Google Patents

Electrolyte for positive electrode of organic flow battery and preparation method thereof Download PDF

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CN116093391A
CN116093391A CN202310116979.8A CN202310116979A CN116093391A CN 116093391 A CN116093391 A CN 116093391A CN 202310116979 A CN202310116979 A CN 202310116979A CN 116093391 A CN116093391 A CN 116093391A
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tetrathiafulvalene
flow battery
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陈栋阳
陈男杰
吴静姝
陈东初
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Foshan University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
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    • H01M8/18—Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
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    • H01M8/188—Regeneration by electrochemical means by recharging of redox couples containing fluids; Redox flow type batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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Abstract

The invention relates to the technical field of electrochemical energy storage, and discloses electrolyte for an organic flow battery positive electrode and a preparation method thereof, wherein the organic 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 tetrathiafulvalene dimethyl methyl ether is as follows:
Figure DDA0004078909140000011
by introducing a flexible methyl ether end group into tetrathiafulvalene, not only can the stacking of tetrathiafulvalene units be effectively prevented, but also the affinity of tetrathiafulvalene dimethyl formate and an organic solvent is increased, so that the dissolution of the tetrathiafulvalene dimethyl ether in the corresponding organic solvent is improved, the energy density of a flow battery can be favorably improved, and the stable cycle performance is realized.

Description

Electrolyte for positive electrode of organic flow battery and preparation method thereof
Technical Field
The invention relates to the technical field of electrochemical energy storage, in particular to electrolyte for an anode of an organic flow battery and a preparation method thereof.
Background
With the development of environmental protection technology for reducing carbon emissions, the demand for using widely used and pollution-free energy sources to replace traditional petroleum energy sources is increasing.
The new energy technology represented by wind energy and solar energy has the characteristics of unstable power generation time and power generation capacity, and needs a large-scale energy storage battery to be matched with the new energy technology.
The currently commercialized energy storage technology mainly comprises lithium ion batteries and lead acid batteries. The volumetric specific energy density or the mass specific energy density of the lithium ion battery and the lead-acid battery are higher, and if the lithium ion battery and the lead-acid battery are used as large-scale energy storage, the disadvantages of low safety performance and high cost exist.
The flow battery has the characteristics of independent energy and power adjustment, and is low in capacity expansion cost, so that the flow battery is the most promising energy storage technology at present.
In the flow battery in the prior art, the volumetric specific energy density or the mass specific energy density of the flow battery is low due to a large amount of solvent in the flow battery. Therefore, the popularization and the application of the flow battery are limited.
All-vanadium redox flow batteries are mature aqueous redox flow battery technology, but have the defects of strong electrolyte corrosiveness, low discharge voltage and the like.
Disclosure of Invention
In view of the above problems, a first object of the present invention is to provide an electrolyte for an anode of an organic flow battery, which has high solubility in a corresponding organic solvent, is beneficial to improving the energy density of the flow battery, and can realize stable cycle performance.
The invention further aims to provide a preparation method of the electrolyte of the positive electrode of the organic flow battery, which has the advantages of simple synthesis process and convenience for mass production.
To achieve the purpose, the invention adopts the following technical scheme:
the electrolyte is used for an anode of the organic flow battery, and the anode electrolyte of the organic flow battery 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 tetrathiafulvalene dimethyl methyl ether is as follows:
Figure BDA0004078909100000021
furthermore, the invention provides a preparation method of the electrolyte of the positive electrode of the organic flow battery, which is used for preparing the electrolyte of the positive electrode of the organic flow battery and comprises the following steps:
s1) taking anhydrous tetrahydrofuran as a solvent, adding methyl propiolate and carbon disulfide, reacting for 3-10 hours at minus 60 ℃ to minus 80 ℃ in an argon protection atmosphere under the catalysis of tributylphosphine, naturally heating to room temperature, filtering tetrahydrofuran under vacuum, washing the solid obtained by filtering with a small amount of dichloromethane, and purifying the solid filtrate by using a chromatographic column to obtain solid tetrathiafulvalene dimethyl formate;
s2) adding the methyl tetrathiafulvalene diformate prepared in the step S1) into anhydrous tetrahydrofuran, stirring and dissolving, adding 1mol/L of diisobutyl aluminum hydride n-hexane solution under the protection of argon, reacting for 3-10 hours, then dropwise adding saturated potassium sodium tartrate aqueous solution, continuously stirring for 1-3 hours, filtering out tetrahydrofuran under vacuum, filtering out and collecting solid, and purifying the filtered solid by using a chromatographic column to prepare solid tetrathiafulvalene dimethanol;
s3) adding tetrathiafulvalene dimethyl alcohol and methyl iodide into anhydrous tetrahydrofuran under the protection of argon, adding sodium hydride, reacting for 20-40 hours at 60-80 ℃, then adding tetrahydrofuran containing 5wt% of deionized water, performing quenching reaction, filtering tetrahydrofuran under vacuum, adding dichloromethane and deionized water for extraction, collecting dichloromethane solution containing an extract, filtering dichloromethane under vacuum, purifying the filtered solid by using a chromatographic column, and obtaining solid tetrathiafulvalene dimethyl ether;
and S4) adding the tetrathiafulvalene dimethyl methyl ether into a mixed solvent of ethyl methyl carbonate, ethylene carbonate and propylene carbonate, stirring and mixing uniformly, adding lithium hexafluorophosphate, and stirring and dissolving to obtain the organic flow battery positive electrode electrolyte.
Preferably, in the step S1), the molar ratio of the carbon disulfide to the methyl propiolate to the tributylphosphine is 1:0.5-2:0.25-1, and the anhydrous tetrahydrofuran is used in the following amount: the corresponding addition amount of methyl propiolate per gram is 5-40mL.
Preferably, in step S1), the volume of dichloromethane is 0.1-1 times the volume of anhydrous tetrahydrofuran.
Preferably, in the step S2), the molar ratio of the tetrathiafulvalene dimethyl ester to the diisobutyl aluminum hydride is 1: (4-10), and the anhydrous tetrahydrofuran is used in the following amount: the corresponding addition amount of the tetrathiafulvalene methyl ester per gram is 20-160mL.
Preferably, in step S2), the volume of the saturated aqueous solution of potassium sodium tartrate is 0.1 to 1 times the volume of anhydrous tetrahydrofuran.
Preferably, in the step S3), the molar ratio of tetrathiafulvalene dimethanol to methyl iodide to sodium hydride is 1: (2-10): (2-8), and the dosages of anhydrous tetrahydrofuran and tetrahydrofuran containing 5wt% of deionized water are respectively as follows: the corresponding addition amount of the tetrathiofulvalene dimethyl alcohol per gram is 20-160mL.
Preferably, in step S3), the amount of dichloromethane used in the extraction is: the corresponding addition amount of each gram of tetrathiofulvalene dimethyl alcohol is 20-160mL; the volume ratio of dichloromethane to deionized water used in the extraction is 1:1-5.
Preferably, in the step S4), the volume ratio of the ethyl methyl carbonate to the ethylene carbonate to the propylene carbonate is 5:2-6:1-3.
Preferably, in step S4), the concentration of tetrathiafulvalene dimethyl ether is 1-3mol/L, and the concentration of lithium hexafluorophosphate is 2-8mol/L.
The technical scheme of the invention has the beneficial effects that: according to the electrolyte for the positive electrode of the organic flow battery, the flexible methyl ether end group is introduced into the tetrathiafulvalene, so that the stacking of tetrathiafulvalene units can be effectively prevented, the affinity between the methyl tetrathiafulvalene diformate and an organic solvent is increased, the introduced methyl ether has small molecular weight, the dissolution concentration of the tetrathiafulvalene dimethyl ether in the corresponding organic solvent is improved and can reach up to-3 mol/L, and the mass specific capacity of the tetrathiafulvalene cannot be obviously reduced due to the small molecular weight of the introduced methyl ether. The voltage platform of the tetrathiafulvalene dimethyl methyl ether relative to the charge and discharge of Li/Li+ is 3.0-3.6V, so that the energy density of the flow battery can be improved, and stable cycle performance can be realized.
Furthermore, the preparation method of the electrolyte for the positive electrode of the organic flow battery has the advantages of simple synthesis process and convenience for large-scale production, and has a commercialized prospect capable of being widely popularized.
Drawings
FIG. 1 is a nuclear magnetic resonance hydrogen spectrum of tetrathiafulvalene dimethyl ether prepared in example 3;
fig. 2 is a charge-discharge curve of the organic flow battery of application example 1;
FIG. 3 is a specific discharge volume capacity of the organic flow battery of application example 1 in a cycling test;
fig. 4 is coulombic efficiency of the organic flow battery of application example 1 in a cycling test.
Detailed Description
The technical scheme of the invention is further described by the following specific embodiments.
In the description herein, reference to the term "embodiment," "example," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: many changes, modifications, substitutions and variations may be made to the embodiments without departing from the spirit and principles of the invention, the scope of which is defined by the claims and their equivalents.
An electrolyte for an organic flow battery positive electrode, wherein the organic 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 tetrathiafulvalene dimethyl methyl ether is as follows:
Figure BDA0004078909100000051
although the oxidation-reduction potential of tetrathiafulvalene is high, the solubility of tetrathiafulvalene dicarboxylic acid ethyl ester in the electrolyte of a flow battery anode of tetrathiafulvalene dicarboxylic acid ethyl ester in the prior art is not more than 0.03mol/L, and the specific discharge volume capacity of the prepared electrolyte is not more than 0.36Ah/L although the solubility of tetrathiafulvalene dicarboxylic acid ethyl ester is greatly improved compared with that of tetrathiafulvalene dicarboxylic acid methyl ester.
According to the electrolyte for the positive electrode of the organic flow battery, the flexible methyl ether end group is introduced into the tetrathiafulvalene, so that not only can the accumulation of tetrathiafulvalene units be effectively prevented, but also the affinity of the methyl tetrathiafulvalene diformate to an organic solvent is increased, the introduced methyl ether has small molecular weight, the dissolution concentration of the tetrathiafulvalene dimethyl ether in the corresponding organic solvent is improved and can be as high as 3mol/L, and the mass specific capacity of the tetrathiafulvalene cannot be obviously reduced due to the small molecular weight of the introduced methyl ether. The voltage platform of the tetrathiafulvalene dimethyl ether relative to the charge and discharge of Li/Li+ is 3.0-3.6V, which is favorable for improving the energy density of the flow battery and realizing stable cycle performance.
The electrolyte for the positive electrode of the organic flow battery contains tetrathiafulvalene dimethyl methyl ether, has high solubility in ethyl methyl carbonate, ethylene carbonate and propylene carbonate, has concentration of up to 1-3mol/L, has small molecular weight and has mass specific capacity of up to 183mAh/g; the electrolyte for the positive electrode of the organic flow battery has the advantages of high volume specific capacity, high oxidation-reduction potential and high cycle stability, and therefore has good application prospect.
Furthermore, the invention provides a preparation method of the electrolyte of the positive electrode of the organic flow battery, which is used for preparing the electrolyte of the positive electrode of the organic flow battery and comprises the following steps:
s1) taking anhydrous tetrahydrofuran as a solvent, adding methyl propiolate and carbon disulfide, reacting for 3-10 hours at minus 60 ℃ to minus 80 ℃ in an argon protection atmosphere under the catalysis of tributylphosphine, naturally heating to room temperature, filtering tetrahydrofuran under vacuum, washing the solid obtained by filtering with a small amount of dichloromethane, and purifying the solid filtrate by using a chromatographic column to obtain solid tetrathiafulvalene dimethyl formate;
s2) adding the methyl tetrathiafulvalene diformate prepared in the step S1) into anhydrous tetrahydrofuran, stirring and dissolving, adding 1mol/L of diisobutyl aluminum hydride n-hexane solution under the protection of argon, reacting for 3-10 hours, then dropwise adding saturated potassium sodium tartrate aqueous solution, continuously stirring for 1-3 hours, filtering out tetrahydrofuran under vacuum, filtering out and collecting solid, and purifying the filtered solid by using a chromatographic column to prepare solid tetrathiafulvalene dimethanol;
s3) adding tetrathiafulvalene dimethyl alcohol and methyl iodide into anhydrous tetrahydrofuran under the protection of argon, adding sodium hydride, reacting for 20-40 hours at 60-80 ℃, then adding tetrahydrofuran containing 5wt% of deionized water, performing quenching reaction, filtering tetrahydrofuran under vacuum, adding dichloromethane and deionized water for extraction, collecting dichloromethane solution containing an extract, filtering dichloromethane under vacuum, purifying the filtered solid by using a chromatographic column, and obtaining solid tetrathiafulvalene dimethyl ether;
and S4) adding the tetrathiafulvalene dimethyl methyl ether into a mixed solvent of ethyl methyl carbonate, ethylene carbonate and propylene carbonate, stirring and mixing uniformly, adding lithium hexafluorophosphate, and stirring and dissolving to obtain the organic flow battery positive electrode electrolyte.
The reaction formula of the prepared tetrathiafulvalene methyl ester in the step S1) is as follows:
Figure BDA0004078909100000071
the reaction formula of the tetrathiafulvalene dimethanol prepared in the step S2) is as follows:
Figure BDA0004078909100000072
the reaction formula of the tetrathiafulvalene dimethyl methyl ether prepared in the step S3) is as follows:
Figure BDA0004078909100000073
compared with the prior art, the preparation method of the electrolyte of the organic flow battery anode has the advantages of simple synthesis process and convenience for large-scale production, and has a commercialized prospect of being widely popularized.
Preferably, in the step S1), the molar ratio of the carbon disulfide to the methyl propiolate to the tributylphosphine is 1:0.5-2:0.25-1, and the anhydrous tetrahydrofuran is used in the following amount: the corresponding addition amount of methyl propiolate per gram is 5-40mL.
Preferably, in step S1), the volume of dichloromethane is 0.1-1 times the volume of anhydrous tetrahydrofuran.
Preferably, in the step S2), the molar ratio of the tetrathiafulvalene dimethyl ester to the diisobutyl aluminum hydride is 1: (4-10), and the anhydrous tetrahydrofuran is used in the following amount: the corresponding addition amount of the tetrathiafulvalene methyl ester per gram is 20-160mL.
Preferably, in step S2), the volume of the saturated aqueous solution of potassium sodium tartrate is 0.1 to 1 times the volume of anhydrous tetrahydrofuran.
Preferably, in the step S3), the molar ratio of tetrathiafulvalene dimethanol to methyl iodide to sodium hydride is 1: (2-10): (2-8), and the dosages of anhydrous tetrahydrofuran and tetrahydrofuran containing 5wt% of deionized water are respectively as follows: the corresponding addition amount of the tetrathiofulvalene dimethyl alcohol per gram is 20-160mL.
Preferably, in step S3), the amount of dichloromethane used in the extraction is: the corresponding addition amount of each gram of tetrathiofulvalene dimethyl alcohol is 20-160mL; the volume ratio of dichloromethane to deionized water used in the extraction is 1:1-5.
Preferably, in the step S4), the volume ratio of the ethyl methyl carbonate to the ethylene carbonate to the propylene carbonate is 5:2-6:1-3.
Preferably, in step S4), the concentration of tetrathiafulvalene dimethyl ether is 1-3mol/L, and the concentration of lithium hexafluorophosphate is 2-8mol/L.
Examples
Example 1: synthesis of methyl tetrathiofulvalene dicarboxylate
Under the protection of argon, a 500mL three-neck round bottom flask is cooled to-70 ℃ by a dry ice/absolute ethyl alcohol mixed system, 100mL tetrahydrofuran, 19.0g (0.25 mol) of carbon disulfide and 16.8g (0.2 mol) of methyl propiolate are added, then 40.4g (0.2 mol) of tributylphosphine is slowly added dropwise, stirring reaction is carried out for 6 hours, natural temperature is carried out to room temperature, tetrahydrofuran is removed under vacuum condition, 20mL dichloromethane is added into the obtained residue for washing, and the crude product is further purified by passing through a column by using dichloromethane, thus obtaining 4.0g red solid tetrathiofulvalene methyl diformate.
The nuclear magnetic resonance hydrogen spectrum test result of the tetrathiafulvalene methyl ester in deuterated DMSO is as follows:
1 HNMR(400MHz,DMSO-d 6 ,ppm)δ:7.87(s,2H),3.78(s,6H)。
example 2: synthesis of dimethyl tetrathiofulvalene dicarboxylate
To a 500mL three-necked round bottom flask, 4.0g (0.012 mol) of methyl tetrathiafulvalene diformate and 200mL of anhydrous tetrahydrofuran were added and dissolved under stirring, 50mL (0.05 mmol) of 1mol/L of n-hexane solution of diisobutyl aluminum hydride was slowly added dropwise under argon protection, the reaction was carried out at room temperature for 10 hours, then 100mL of saturated aqueous potassium sodium tartrate solution was added dropwise, stirring was continued for 3 hours, tetrahydrofuran was removed under vacuum, the solid was collected by suction filtration, and further column purification was carried out with a methylene chloride/methanol mixed solution (volume ratio 5:1) to obtain 3.2g of tetrathiafulvalene dimethanol as an orange solid.
The nuclear magnetic resonance hydrogen spectrum test result of the tetrathiafulvalene dimethanol in deuterated DMSO is as follows:
1 HNMR(400MHz,DMSO-d 6 ,ppm)δ:6.53(s,2H),5.50(t,2H),4.21(s,4H)。
example 3: synthesis of tetrathiafulvalene dimethyl methyl ether
3.0g (0.011 mol) of tetrathiafulvalene dimethanol and 4.68g (0.033 mol) of methyl iodide are added into a 500mL three-necked round bottom flask containing 150mL of anhydrous tetrahydrofuran under the protection of argon, 1.2g (0.050 mol) of sodium hydride is added, the reaction is carried out at 60 ℃ for 30 hours, then 60mL of tetrahydrofuran containing 5wt% of deionized water is added, the reaction is quenched, the tetrahydrofuran is removed under vacuum, then 100mL of dichloromethane and 100mL of deionized water are used for extraction, a dichloromethane solution is collected, dichloromethane is removed under vacuum, and the obtained solid is purified by passing through a column using a cyclohexane/dichloromethane mixed solution (volume ratio of 5:1) to obtain 2.0g of tetrathiafulvalene dimethyl ether as a dark yellow solid.
The nuclear magnetic resonance hydrogen spectrum test result of the tetrathiafulvalene dimethyl methyl ether in deuterated chloroform is as follows:
1 HNMR(400MHz,CDCl 3 ppm) delta 6.23 (s, 2H), 4.21 (s, 4H), 3.45 (s, 6H), see in particular FIG. 3.
Examples 4-6: preparation of organic flow battery positive electrode electrolyte based on tetrathiofulvalene dimethyl methyl ether
According to the formula shown in Table 1, tetrathiafulvalene dimethyl methyl ether is added into a mixed organic solvent consisting of ethyl methyl carbonate, ethylene carbonate and propylene carbonate, stirred and mixed, and then lithium hexafluorophosphate is added, stirred and dissolved, so that the electrolyte for the positive electrode of the organic flow battery corresponding to the examples 4-6 is obtained.
Table 1 formulation of electrolyte for Positive electrode of organic flow Battery of examples 4-6
Figure BDA0004078909100000091
Figure BDA0004078909100000101
Application examples 1-3: preparation of electrolyte for positive electrode of organic flow battery corresponding to examples 4 to 6:
1. a lithium sheet was used as a battery anode and a porous Celgard2400 was used as a battery separator, wherein the effective area of the separator was 3cm×3cm (9 cm 2 ) The method comprises the steps of carrying out a first treatment on the surface of the The lithium sheet is wetted by electrolyte of mixed solution of ethyl methyl carbonate, ethylene carbonate and propylene carbonate with the composition of 1.0mol/L lithium hexafluorophosphate and the volume ratio of 5:3:2, so as to ensure the full contact between the lithium sheet and the diaphragm; the positive electrode uses graphite felt as a current collector to form the organic flow battery of application examples 1-3.
2.8 mL of the electrolyte of the positive electrode of the corresponding organic flow battery prepared in the embodiment 4-6 is respectively taken and placed in three liquid storage tanks, and then the corresponding electrolyte is respectively input into one side of the positive electrode of the corresponding organic flow battery through a peristaltic pump at the speed of 16mL/min for cycle test.
3. For the assembled organic flow batteries of application examples 1-3, the current density was 5mA/cm, respectively 2 Constant current charge and discharge are carried out, the voltage interval is set to be 2.8-3.8V, and the cycle number is 100.
4. The performance of each cell was evaluated with a discharge volume specific capacity, a discharge volume specific capacity retention rate, and a coulombic efficiency, wherein the discharge volume specific capacity retention rate=100 th discharge volume specific capacity/first discharge volume specific capacity×100%, and the coulombic efficiency=discharge charge amount/charge amount×100%; the battery performance of each application example is shown in table 2.
Table 2 application examples 1-3 battery performance
Figure BDA0004078909100000102
Figure BDA0004078909100000111
As can be seen from table 2, the discharge volume specific capacity of the organic flow battery positive electrode electrolyte prepared in example 4 can be as high as 53.6Ah/L (application example 1) or more. The specific discharge volume capacities of application example 2 and application example 3 were even higher as 80.4Ah/L and 107Ah/L, respectively, when the concentration of tetrathiafulvalene dimethyl methyl ether was increased to 2mol/L and 3 mol/L. The high solubility of tetrathiafulvalene dimethyl methyl ether can effectively improve the specific capacity of discharge volume of the organic flow battery.
FIG. 1 is a nuclear magnetic resonance hydrogen spectrum of tetrathiafulvalene dimethyl methyl ether prepared in example 3, wherein a peak having a chemical shift of 3.42ppm is ascribed to H on methoxy at the tail end of a side chain; peaks with a chemical shift of 4.20ppm are assigned to H on methylene; the peak with a chemical shift of 6.21ppm is ascribed to H on the tetrathiafulvalene unit; the peak with chemical shift of 7.28ppm was assigned to the residual dichloromethane solvent peak; the above results demonstrate the structure of tetrathiafulvalene dimethyl methyl ether.
FIG. 2 is a graph showing that the organic flow battery prepared in application example 1 was operated at 5mA/cm 2 Is a charge-discharge curve of (a). From the figure, it can be seen that two voltage platforms 3.22 and 3.55V respectively correspond to two oxidation reactions of tetrathiafulvalene dimethyl ether in the charging process of the battery; in the discharging process, voltage platforms of 3.17 and 3.50V respectively correspond to two reduction reactions of tetrathiafulvalene dimethyl ether. In a comprehensive view, the flow battery of the positive electrolyte of the organic flow battery based on the tetrathiafulvalene dimethyl methyl ether has higher battery voltage, and the charge and discharge platform of the battery is stable, so that the battery is stable in the running process; the higher discharge plateau and higher discharge volumetric specific capacity in table 2 illustrate that the electrolyte of the positive electrode of the organic flow battery of the present invention has higher volumetric specific energy density.
Figure 3 is an organic flow battery of application example 1,at 5mA/cm 2 The discharge volume specific capacity curve of the battery is charged and discharged for 100 times in a circulating way, and the discharge capacity retention rate is as high as 79.8% after 100 cycles, so that the battery has higher circulating stability.
FIG. 4 is an organic flow battery of application example 1 at 5mA/cm 2 The coulomb efficiency after the battery is stabilized reaches over 94 percent according to the coulomb efficiency curve of 100 times of continuous charge and discharge under the current of (2).
In summary, according to the electrolyte for the positive electrode of the organic flow battery, the flexible methyl ether end group is introduced into tetrathiafulvalene, so that not only can the accumulation of tetrathiafulvalene units be effectively prevented, but also the affinity of tetrathiafulvalene methyl ester and an organic solvent is increased, the introduced methyl ether has small molecular weight, so that the dissolution concentration of the tetrathiafulvalene dimethyl ether in the corresponding organic solvent is improved, and can reach 3mol/L, and the mass specific capacity of the tetrathiafulvalene cannot be obviously reduced due to the small molecular weight of the introduced methyl ether. The voltage platform of the tetrathiafulvalene dimethyl methyl ether relative to the charge and discharge of Li/Li+ is 3.0-3.6V, so that the energy density of the flow battery can be improved, and stable cycle performance can be realized.
Furthermore, the preparation method of the electrolyte for the positive electrode of the organic flow battery has the advantages of simple synthesis process and convenience for large-scale production, and has a commercialized prospect capable of being widely popularized.
The technical principle of the present invention is described above in connection with the specific embodiments. The description is made for the purpose of illustrating the general principles of the invention and should not be taken in any way as limiting the scope of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of this specification without undue burden.

Claims (10)

1. The electrolyte for the positive electrode of the organic flow battery is characterized by comprising tetrathiafulvalene 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 tetrathiafulvalene dimethyl methyl ether is as follows:
Figure FDA0004078909080000011
2. a method for preparing an electrolyte for an organic flow battery positive electrode, which is characterized by comprising the following steps of:
s1) taking anhydrous tetrahydrofuran as a solvent, adding methyl propiolate and carbon disulfide, reacting for 3-10 hours at minus 60 ℃ to minus 80 ℃ in an argon protection atmosphere under the catalysis of tributylphosphine, naturally heating to room temperature, filtering tetrahydrofuran under vacuum, washing the solid obtained by filtering with a small amount of dichloromethane, and purifying the solid filtrate by using a chromatographic column to obtain solid tetrathiafulvalene dimethyl formate;
s2) adding the methyl tetrathiafulvalene diformate prepared in the step S1) into anhydrous tetrahydrofuran, stirring and dissolving, adding 1mol/L of diisobutyl aluminum hydride n-hexane solution under the protection of argon, reacting for 3-10 hours, then dropwise adding saturated potassium sodium tartrate aqueous solution, continuously stirring for 1-3 hours, filtering out tetrahydrofuran under vacuum, filtering out and collecting solid, and purifying the filtered solid by using a chromatographic column to prepare solid tetrathiafulvalene dimethanol;
s3) adding tetrathiafulvalene dimethyl alcohol and methyl iodide into anhydrous tetrahydrofuran under the protection of argon, adding sodium hydride, reacting for 20-40 hours at 60-80 ℃, then adding tetrahydrofuran containing 5wt% of deionized water, performing quenching reaction, filtering tetrahydrofuran under vacuum, adding dichloromethane and deionized water for extraction, collecting dichloromethane solution containing an extract, filtering dichloromethane under vacuum, purifying the filtered solid by using a chromatographic column, and obtaining solid tetrathiafulvalene dimethyl ether;
and S4) adding the tetrathiafulvalene dimethyl methyl ether into a mixed solvent of ethyl methyl carbonate, ethylene carbonate and propylene carbonate, stirring and mixing uniformly, adding lithium hexafluorophosphate, and stirring and dissolving to obtain the organic flow battery positive electrode electrolyte.
3. The method for preparing the electrolyte of the positive electrode of the organic flow battery according to claim 2, wherein in the step S1), the molar ratio of carbon disulfide to methyl propiolate to tributylphosphine is 1: (0.5-2): (0.25-1), and the dosage of anhydrous tetrahydrofuran is as follows: the corresponding addition amount of methyl propiolate per gram is 5-40mL.
4. The method for preparing an electrolyte for an anode of an organic flow battery according to claim 2, wherein in the step S1), the volume of dichloromethane is 0.1 to 1 times the volume of anhydrous tetrahydrofuran.
5. The method for preparing the electrolyte of the positive electrode of the organic flow battery according to claim 2, wherein in the step S2), the molar ratio of the tetrathiafulvalene methyl ester to the diisobutyl aluminum hydride is 1:4-10, and the anhydrous tetrahydrofuran is used in the following amount: the corresponding addition amount of the tetrathiafulvalene methyl ester per gram is 20-160mL.
6. The method for preparing an electrolyte for an anode of an organic flow battery according to claim 2, wherein in the step S2), the volume of the saturated aqueous solution of potassium sodium tartrate is 0.1 to 1 times the volume of anhydrous tetrahydrofuran.
7. The method for preparing the electrolyte of the positive electrode of the organic flow battery according to claim 2, wherein in the step S3), the molar ratio of tetrathiofulvalene dimethanol to methyl iodide to sodium hydride is 1: (2-10): (2-8), and the dosages of anhydrous tetrahydrofuran and tetrahydrofuran containing 5wt% of deionized water are respectively: the corresponding addition amount of the tetrathiofulvalene dimethyl alcohol per gram is 20-160mL.
8. The method for preparing an electrolyte for an organic flow battery positive electrode according to claim 2, wherein in the step S3), the amount of dichloromethane used in the extraction is: the corresponding addition amount of each gram of tetrathiofulvalene dimethyl alcohol is 20-160mL; the volume ratio of dichloromethane to deionized water used in the extraction is 1:1-5.
9. The method for preparing an electrolyte for an anode of an organic flow battery according to claim 2, wherein in the step S4), the volume ratio of ethyl methyl carbonate, ethylene carbonate and propylene carbonate is 5: (2-6): (1-3).
10. The method for preparing an electrolyte for an anode of an organic flow battery according to claim 2, wherein in the step S4), the concentration of tetrathiafulvalene dimethyl methyl ether is 1-3mol/L, and the concentration of lithium hexafluorophosphate is 2-8mol/L.
CN202310116979.8A 2023-02-15 2023-02-15 Electrolyte for positive electrode of organic flow battery and preparation method thereof Pending CN116093391A (en)

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