Electrolytes and electrochemical devices

Abstract

This application relates to electrolytes and electrochemical devices. The electrolyte comprises an active material and a solvent; the active material comprises a polytert-amine-substituted biphenylquinone compound with an oxidation state as shown in Formula I; in Formula I, each R1 is independently a C2-C10 branched or straight-chain alkyl group, and each R2 is independently a C1-C5 straight-chain alkylene group. The active material in the above electrolyte, including a polytert-amine-substituted biphenylquinone compound with a specific structure, possesses high potential, structural stability, and two-electron transfer characteristics, making it less prone to cross-membrane crosstalk leading to battery capacity decay. When the electrolyte containing this active material is used in electrochemical devices such as flow batteries, long-term stable operation can be achieved. Furthermore, the preparation process of this type of biphenylquinone compound is green, simple, low-cost, and easily industrialized, facilitating widespread use. Formula I

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and in particular to electrolytes and electrochemical devices. Background Technology

[0002] Flow batteries are a key energy storage technology for the smooth integration of renewable energy into the grid. They possess characteristics such as high safety, independent controllable battery energy and power, and long cycle life, showing promising development prospects in large-scale energy storage. As the core component of redox flow batteries, the electrolyte's cycle stability and manufacturing cost are important evaluation parameters in their large-scale application. In recent years, the strategy of constructing aqueous organic flow batteries for redox charge-discharge by partially or completely replacing metal ions with organic molecules has increasingly attracted researchers' attention.

[0003] Aqueous organic flow batteries use water as a solvent, eliminating the risk of fire and explosion, offering high safety and environmental friendliness. The organic molecules within them possess advantages such as structural diversity, tunable structure, and low raw material costs. Aqueous organic flow batteries are considered a crucial development direction in the field of electrochemical energy storage. Their core performance depends on the electrochemical redox activity, structural stability, and electron transfer number of the organic active molecules in the electrolyte. Among these, biphenylquinone derivatives are used as positive electrode active materials in aqueous organic flow batteries due to their excellent electrochemical activity and reversible multi-electron transfer characteristics.

[0004] Currently, the preparation technology of biphenylquinone molecules as positive electrode electrolytes mainly revolves around biphenyl hydroquinone derivatives. Typical preparation routes include: using biphenyl hydroquinone derivatives as raw materials, introducing hydrophilic functional groups (such as sulfonic acid groups, mercapto groups, amino groups, etc.) at the ortho position of the phenolic hydroxyl group. The introduction of sterically hindered substituents leads to changes in the charge distribution and molecular structure of biphenyl hydroquinone, thereby regulating its redox potential, water solubility and stability. Then, phenol is converted into a benzoquinone structure through an electro-oxidation process to prepare multi-substituent modified biphenylquinone molecules to meet its requirements as an active redox couple for charging and discharging. Finally, biphenylquinone-type aqueous organic flow batteries are used to realize the conversion between electrical energy and chemical energy.

[0005] Currently, the stability of biphenylquinone molecules is one of the limiting factors for their use in aqueous organic flow batteries. Firstly, there is the intrinsic stability issue of biphenylquinone molecules. Potential side reactions in the electrolyte system can lead to irreversible structural changes, resulting in loss of electrochemical reversibility and capacity decay. Secondly, there is the problem of active molecule permeation. In flow batteries, biphenylquinone molecules migrate from the positive electrode side to the negative electrode side through the ion-conducting membrane, reducing the concentration of biphenylquinone molecules at the positive electrode and contaminating the electrolyte at the negative electrode. This leads to a continuous decrease in battery charge / discharge capacity and increased battery polarization, resulting in reduced battery efficiency and lifespan. Summary of the Invention

[0006] Therefore, it is necessary to provide electrolytes and electrochemical devices that combine high electrical activity and structural stability.

[0007] In one aspect, the present invention provides an electrolyte comprising an active substance and a solvent;

[0008] The active substance includes a polytert-amine substituted biphenylquinone compound with the structure shown in Formula I below in an oxidation state:

[0009] Formula I

[0010] In Formula I, each R1 is independently a C2-C10 branched or straight-chain alkyl group, and each R2 is independently a C1-C5 straight-chain alkylene group.

[0011] In some embodiments, the electrolyte satisfies at least one of the following characteristics:

[0012] (1) Each of the R1s is independently a C2-C5 branched or straight-chain alkyl group;

[0013] (2) Each of the R2s is independently a C1-C3 straight-chain alkylene group;

[0014] (3) All R1 values ​​are the same;

[0015] (4) All R2 values ​​are the same.

[0016] In some embodiments, the active substance comprises any one or more compounds with the following structural formulas in an oxidation state:

[0017] (1) (2) (3).

[0018] In some embodiments, the electrolyte further includes an acid; optionally, the acid is selected from any one or more of sulfuric acid, hydrochloric acid, phosphoric acid, acetic acid, citric acid, trifluoroacetic acid, and trifluoromethanesulfonic acid.

[0019] In some embodiments, the proton concentration of the electrolyte is 0.001 mol / L to 10.0 mol / L.

[0020] In some embodiments, the concentration of the active substance is 0.001 mol / L to 2.0 mol / L.

[0021] In some embodiments, the solvent includes any one or more of water, ethanol, N,N-dimethylformamide, and dimethyl sulfoxide.

[0022] Secondly, an electrochemical device is provided, comprising the electrolyte of any of the above.

[0023] In some embodiments, the electrochemical device includes a three-electrode electrochemical cell, a four-electrode H-type electrolytic cell, or a flow cell.

[0024] In some embodiments, the electrochemical device is a flow battery, which includes an independent electrolyte system A and an electrolyte system B, wherein the electrolyte in electrolyte system A is any of the electrolytes described above.

[0025] Optionally, the electrolyte system A is a positive electrode electrolyte system;

[0026] Optionally, the redox couple in the electrolyte system B includes V 3+ / V 2+ TiO 2+ / Ti 3+ One or more of silicotungstic acid, and optionally, the concentration of the redox couple in the electrolyte system B is 0.001~2.0 mol / L.

[0027] The active material in the aforementioned electrolyte includes a polytert-amine-substituted biphenylquinone compound with a specific structure. This compound exhibits high potential, structural stability, and two-electron transfer characteristics, making it less prone to cross-membrane cross-contamination that could lead to battery capacity decay. When this electrolyte containing the active material is used in electrochemical devices such as flow batteries, it enables long-term stable operation. Furthermore, the preparation process for this type of biphenylquinone compound is green, simple, low-cost, and easily industrialized, facilitating its widespread use. Attached Figure Description

[0028] Figure 1 The biphenyl hydroquinone product prepared in Example 1 of this application 1 HNMR spectrum;

[0029] Figure 2 This is a cyclic voltammetry test diagram of the electrolyte prepared in Example 1 of this application;

[0030] Figure 3 The biphenyl hydroquinone product prepared in Example 2 of this application 1 HNMR spectrum;

[0031] Figure 4 This is a cyclic voltammetry test diagram of the electrolyte prepared in Example 2 of this application;

[0032] Figure 5 The biphenyl hydroquinone product prepared in Example 3 of this application 1 HNMR spectrum;

[0033] Figure 6 This is a cyclic voltammetry test diagram of the electrolyte prepared in Example 3 of this application;

[0034] Figure 7 The charge-discharge curves of the biphenylquinone-based flow battery in Example 4 of this application are shown.

[0035] Figure 8 The discharge capacity curve of the biphenylquinone-based flow battery in Example 5 of this application is shown.

[0036] Figure 9 The continuous charge-discharge curve of the biphenylquinone-based flow battery in Example 6 of this application is shown.

[0037] Figure 10 The biphenyl hydroquinone product prepared in Comparative Example 1 of this application 1 HNMR spectrum;

[0038] Figure 11 The cyclic voltammetry test results are for the electrolyte prepared in Comparative Example 1 of this application.

[0039] Figure 12 The discharge capacity curve of the biphenylquinone-based flow battery in Comparative Example 1 of this application is shown. Detailed Implementation

[0040] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0042] the term

[0043] In this application, unless otherwise specified, the term "alkyl" refers to a residue formed by the loss of a hydrogen atom from a saturated hydrocarbon, and alkyl can represent a straight-chain, branched, and / or cyclic alkyl group. The number of carbon atoms contained in an alkyl group can be 1 to 50, 1 to 30, 1 to 20, 1 to 10, 1 to 6, or other suitable ranges. Phrases containing the term "alkyl," such as "C1-C9 alkyl," refer to alkyl groups containing 1 to 9 carbon atoms, and each occurrence can independently be C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, C7 alkyl, C8 alkyl, or C9 alkyl. Suitable examples include, but are not limited to: methyl (Me, -CH3), ethyl (Et, -CH2CH3), 1-propyl (n-Pr, n-propyl, -CH2CH2CH3), 2-propyl (i-Pr, i-propyl, -CH(CH3)2), 1-butyl (n-Bu, n-butyl, -CH2CH2CH2CH3), 2-methyl-1-propyl (i-Bu, i-butyl, -CH2CH(CH3)2), 2-butyl (s-Bu, s-butyl, -CH(CH3)CH2CH3), 2-methyl-2-propyl (t-Bu, t-butyl, -C(CH3)3), etc.

[0044] In this application, unless otherwise specified, the term "tertiary amine" refers to an organic compound in which the nitrogen atom (N) is directly bonded to three hydrocarbon groups (carbon-hydrogen groups) and no hydrogen atoms are bonded to the nitrogen atom.

[0045] In this application, unless otherwise specified, the term "alkylene" refers to a divalent residue that has lost two hydrogen atoms from an alkane. The two hydrogen atoms may be on one carbon atom or on two carbon atoms.

[0046] In this application, unless otherwise specified, the term "linear alkylene" refers to a divalent residue that has lost two hydrogen atoms from a straight-chain alkane, with the two lost hydrogen atoms located on the carbon atoms at both ends of the group.

[0047] Currently disclosed biphenylquinone molecules used in aqueous organic flow batteries suffer from poor intrinsic stability and diffusion problems. To address these issues, this application provides at least one electrolyte and an electrochemical device.

[0048] According to a typical embodiment of this application, an electrolyte is provided, comprising an active substance and a solvent; the active substance comprises a polytert-amine substituted biphenylquinone compound having an oxidation state as shown in Formula I:

[0049] Formula I

[0050] In Formula I, each R1 is independently a C2-C10 branched or straight-chain alkyl group, and each R2 is independently a C1-C5 straight-chain alkylene group.

[0051] The active material in the aforementioned electrolyte includes a polytert-amine-substituted biphenylquinone compound with a specific structure. This compound exhibits high potential, structural stability, and two-electron transfer characteristics, making it less prone to cross-membrane cross-contamination that could lead to battery capacity decay. When this electrolyte containing the active material is used in electrochemical devices such as flow batteries, it enables long-term stable operation. Furthermore, the preparation process for this type of biphenylquinone compound is green, simple, low-cost, and easily industrialized, facilitating its widespread use.

[0052] The active material of the polytert-amine-substituted biphenylquinone compound with the oxidation state shown in Formula I, after being discharged and converted to the reduced state, has a biphenyl diphenol structure as shown in Formula II:

[0053] Formula II

[0054] In some embodiments, in the structure shown in Formula I above, each R1 is independently a C2-C5 branched or straight-chain alkyl group.

[0055] Furthermore, each R2 is independently a C1-C3 straight-chain alkylene group.

[0056] Optionally, each R1 is the same, and each R2 is the same, which facilitates the synthesis and preparation.

[0057] In some embodiments, the active substance includes any one or more compounds with the following structural formulas in an oxidation state:

[0058] (1) (2) (3)

[0059] The redox couple formed with the above formula (1) is a reduced biphenyl phenol having the structure of formula (4):

[0060] (4)

[0061] The redox couple formed with the above formula (2) is a reduced biphenyl phenol having the structure of formula (5):

[0062] (5)

[0063] The redox couple formed with the above formula (3) is a reduced biphenyl phenol having the structure of the following formula (6):

[0064] (6)

[0065] In some embodiments, the concentration of the active substance is 0.001 mol / L to 2.0 mol / L. Non-limitingly, the concentration of the active substance is 0.001 mol / L, 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, etc.

[0066] In some embodiments of this application, the solvent includes any one or more of water, ethanol, N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO); non-limitingly, the solvent can be water, a mixture of water and ethanol, a mixture of water and N,N-dimethylformamide (DMF), or a mixture of water and dimethyl sulfoxide (DMSO). Optionally, the water content in the solvent is 60%-100% by mass.

[0067] In some embodiments, the electrolyte further includes an acid, which acts as an electrolyte in the electrolyte, providing and maintaining high ionic conductivity, which is beneficial for maintaining ion balance and charge compensation. Optionally, the acid is selected from any one or more of sulfuric acid, hydrochloric acid, phosphoric acid, acetic acid, citric acid, trifluoroacetic acid, and trifluoromethanesulfonic acid.

[0068] In some embodiments, the proton concentration of the electrolyte is 0.001 mol / L to 10.0 mol / L. Here, "proton" refers to a positively charged particle formed after a hydrogen atom loses an electron. Non-limitingly, the proton concentration of the electrolyte can be 0.001 mol / L, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 3 mol / L, 5 mol / L, 7 mol / L, 9 mol / L, 10 mol / L, etc.

[0069] Understandably, additives can be added to the electrolyte according to the specific usage environment to achieve the expected function, and this application does not have any particular limitations in this regard. For example, additives include, but are not limited to, any one or more of ammonia, methylamine, dimethylamine, trimethylamine, ammonium chloride, ammonium sulfate, ammonium acetate, tetramethylammonium chloride, and tetramethylammonium sulfate.

[0070] In some embodiments, when R1 is methylene, the electrolyte containing the above-mentioned polytert-amine-substituted biphenylquinone compound is prepared by a method comprising the following steps.

[0071] S1. Using biphenyl hydrochloride as the initial reaction raw material, dissolve it in a solvent (such as ethanol) to prepare a biphenyl hydrochloride solution;

[0072] S2. Under ice-water bath conditions, formaldehyde aqueous solution (for example, a concentration of 30%-40%) and a dialkyl secondary amine are added sequentially to a biphenyl hydroquinone solution, and the mixture is heated under reflux for more than 12 hours to obtain a tetratert-amine-substituted biphenyl hydroquinone compound; wherein, the general structural formula of the dialkyl secondary amine is... Optionally, the reaction temperature is 120~140℃, and the reaction time is 6h~24h.

[0073] S3. Cool the reaction solution obtained in step S2 to room temperature, and remove the solvent, generated water, remaining formaldehyde and dialkyl secondary amine components by vacuum distillation to obtain a tetratert-amine substituted biphenyl diphenol solid product.

[0074] S4. Dissolve the solid biphenyl product in an acidic aqueous solution to prepare a biphenyl-type acidic electrolyte;

[0075] S5. The biphenyl acid electrolyte is electro-oxidized by an electrochemical device to obtain the electrolyte containing the above-mentioned polytert-amine substituted biphenyl quinone compound.

[0076] Alternatively, the dialkyl secondary amine has the following structural formula: or or .

[0077] According to another typical embodiment of the application, an electrochemical device is provided, comprising the electrolyte of any of the above.

[0078] Because the active material in the electrolyte includes a polytert-amine-substituted biphenylquinone compound with a specific structure, this compound exhibits high potential, structural stability, and two-electron transfer characteristics, making it less prone to cross-contamination that could lead to battery capacity decay. When this electrolyte containing the active material is used in electrochemical devices such as flow batteries, it enables long-term stable operation.

[0079] Optionally, the electrochemical device includes a three-electrode electrochemical cell, a four-electrode H-type electrolytic cell, or a flow cell.

[0080] In some embodiments, the electrochemical device is a flow battery, which includes an independent electrolyte system A and an electrolyte system B. The electrolyte in electrolyte system A is any of the active materials described above, including an electrolyte containing a polytert-amine substituted biphenylquinone compound with an oxidation state as shown in Formula I.

[0081] Optionally, the electrolyte system A is a positive electrode electrolyte system.

[0082] Optionally, the redox couple in electrolyte system B includes V 3+ / V 2+ TiO 2+ / Ti 3+One or more of silicotungstic acid, and optionally, the concentration of the redox couple in electrolyte system B is 0.001~2.0 mol / L.

[0083] Further optionally, electrolyte system B includes an acid. For example, the acid is selected from, but not limited to, one or more of sulfuric acid, hydrochloric acid, phosphoric acid, acetic acid, citric acid, trifluoroacetic acid, and trifluoromethanesulfonic acid. Optionally, the solvent of electrolyte system B is an acidic aqueous solution. Optionally, the proton concentration in electrolyte system B is 0.001~10.0 mol / L.

[0084] In some embodiments, the types and concentrations of acids contained in electrolyte system A and electrolyte system B of the flow battery are kept the same or similar to reduce electrolyte imbalance caused by solution migration.

[0085] In some embodiments, the redox couple in electrolyte system A is an active substance with the above-described structure in an oxidized state, and the redox couple in electrolyte system B is in a reduced state.

[0086] In some embodiments, the redox couple in electrolyte system A is the active substance with the above-described structure in a reduced state, and the redox couple in electrolyte system B is in an oxidized state.

[0087] The following detailed embodiments and comparative examples further illustrate the beneficial effects that this application can achieve.

[0088] Example 1

[0089] 5.58 g of biphenyl hydroquinone solid was dissolved in 80 mL of ethanol and stirred at room temperature until a colorless, transparent liquid was obtained. Nitrogen gas was bubbled for 20 min. Then, 13.2 mL of 37% formaldehyde aqueous solution and 13.14 g of diethylamine were added sequentially. The mixture was refluxed at 120 °C for 12 h. The product was then distilled under reduced pressure to obtain a brownish-red solid. The product was dried under vacuum at 80 °C for 10 h to obtain the target product. 1 HNMR spectra as follows Figure 1 As shown. The equation for the reaction is as follows:

[0090]

[0091] 0.263 g of the dried solid was dissolved in 50 mL of 3 M sulfuric acid aqueous solution to prepare a biphenyl hydrochloride electrolyte, which was then transferred to an electrochemical cell. Cyclic voltammetry of the electrolyte was performed using a three-electrode method. The working electrode was a 1 cm × 1 cm graphite electrode, the counter electrode was a 2 cm × 2 cm graphite electrode, and the reference electrode was Ag / AgCl. The scan rate was 50 mV / s, and the voltage range was 0–1 V. The cyclic voltammetry results are shown below. Figure 2As shown in the equation below, in the stage where the potential increases (electrooxidation), polysubstituted biphenylhydrazine is oxidized to polysubstituted biphenylquinone, and in the stage where the potential decreases (electroreduction), polysubstituted biphenylquinone is reduced to polysubstituted biphenylhydrazine.

[0092]

[0093] Example 2

[0094] 5.58 g of biphenyl hydroquinone solid was dissolved in 80 mL of ethanol and stirred at room temperature until a colorless, transparent liquid was obtained. Nitrogen gas was bubbled for 20 min. Then, 13.2 mL of 37% formaldehyde aqueous solution and 18.18 g of di-n-propylamine were added sequentially. The mixture was refluxed at 120 °C for 24 h. Vacuum distillation was performed to obtain a brownish-brown gel-like product. The obtained product was dried under vacuum at 80 °C for 10 h to obtain the target product. 1 HNMR spectra as follows Figure 3 As shown. The equation for the reaction is as follows:

[0095]

[0096] 0.320 g of the dried product was dissolved in 50 mL of 3 M sulfuric acid aqueous solution to prepare a biphenyl hydrochloride electrolyte, which was then transferred to an electrochemical cell. Cyclic voltammetry of the electrolyte was performed using a three-electrode method. The working electrode was a 1 cm × 1 cm graphite electrode, the counter electrode was a 2 cm × 2 cm graphite electrode, and the reference electrode was Ag / AgCl. The scan rate was 50 mV / s, and the voltage range was 0–1 V. The cyclic voltammetry results are shown below. Figure 4 As shown in the equation below, in the stage where the potential increases (electrooxidation), polysubstituted biphenylhydrazine is oxidized to polysubstituted biphenylquinone, and in the stage where the potential decreases (electroreduction), polysubstituted biphenylquinone is reduced to polysubstituted biphenylhydrazine.

[0097]

[0098] Example 3

[0099] 5.58 g of biphenyl hydroquinone solid was dissolved in 80 mL of ethanol and stirred at room temperature until a colorless, transparent liquid was obtained. Nitrogen gas was bubbled for 20 min. Then, 13.2 mL of 37% formaldehyde aqueous solution and 23.22 g of di-n-butylamine were added sequentially. The mixture was refluxed at 140 °C for 12 h. Vacuum distillation under reduced pressure yielded a brownish-red viscous liquid. The product was dried under vacuum at 80 °C for 10 h to obtain the target product. 1 HNMR spectra as follows Figure 5 As shown. The equation for the reaction is as follows:

[0100]

[0101] 0.375 g of the dried product was dissolved in 50 mL of 3 M sulfuric acid aqueous solution to prepare a biphenyl hydrochloride electrolyte, which was then transferred to an electrochemical cell. Cyclic voltammetry of the electrolyte was performed using a three-electrode method. The working electrode was a 1 cm × 1 cm graphite electrode, the counter electrode was a 2 cm × 2 cm graphite electrode, and the reference electrode was Ag / AgCl. The scan rate was 50 mV / s, and the voltage range was 0-1 V. The cyclic voltammetry results are shown below. Figure 4 As shown in the equation below, in the stage where the potential increases (electrooxidation), polysubstituted biphenylhydrazine is oxidized to polysubstituted biphenylquinone, and in the stage where the potential decreases (electroreduction), polysubstituted biphenylquinone is reduced to polysubstituted biphenylhydrazine.

[0102]

[0103] Example 4

[0104] 0.21 g of tetrazolium-diethyl-substituted biphenyl phenol was dissolved in 3 M sulfuric acid aqueous solution to prepare 8 mL of tetrazolium-diethyl-substituted biphenyl phenol electrolyte as the positive electrode of the flow battery. 2.878 g of silicotungstic acid was dissolved in 3 M sulfuric acid aqueous solution to prepare 20 mL of silicotungstic acid electrolyte as the negative electrode of the flow battery. A polybenzimidazole ion-exchange membrane was used as the separator of the flow battery, and 3 cm × 3 cm graphite felt was used as the electrode. Constant current charging was employed, with a charge / discharge current of ±0.18 A. The charge / discharge cutoff voltages were set to 1.2 V and 0.1 V, respectively. The pump speed at both the positive and negative electrodes was 80 rpm. Charge / discharge voltage curves are shown below. Figure 7 As shown, the battery voltage curve is continuous, smooth, and without abnormal fluctuations.

[0105] Example 5

[0106] 0.30 g of tetraazadibutyl-substituted biphenyl phenol was dissolved in 3 M sulfuric acid aqueous solution to prepare 8 mL of tetraazadibutyl-substituted biphenyl phenol electrolyte as the positive electrode of the flow battery. 5.756 g of silicotungstic acid was dissolved in 3 M sulfuric acid aqueous solution to prepare 20 mL of silicotungstic acid electrolyte as the negative electrode of the flow battery. A polybenzimidazole ion-exchange membrane was used as the separator of the flow battery, and 3 cm × 3 cm graphite felt was used as the electrode. Constant current charging was employed, with a charge / discharge current of ±0.18 A. The charge / discharge cutoff voltages were set to 1.2 V and 0.1 V, respectively. The pump speed at both the positive and negative electrodes was 80 rpm. Continuous charge / discharge tests were conducted, and the charge / discharge cycle capacity curves are shown below. Figure 8 As shown, the battery charge and discharge capacity is relatively stable, with a capacity retention rate of 99.85% per cycle.

[0107] Example 6

[0108] 0.42 g of tetraazadipropyl-substituted biphenyl hydrochloride was dissolved in 3 M sulfuric acid aqueous solution to prepare 8 mL of tetraazadipropyl-substituted biphenyl hydrochloride electrolyte as the positive electrode of the flow battery. A 3 M sulfuric acid aqueous solution of titanium sulfate was used as the negative electrode. A polybenzimidazole membrane was used as the separator, and 3 cm × 3 cm graphite felt was used as the electrode. Constant current charging was employed, with a charge / discharge current of ±0.18 A. The charge / discharge cutoff voltages were set to 1.2 V and 0.1 V, respectively. The pump speed at both the positive and negative electrodes was 80 rpm. Continuous charge / discharge tests were conducted, and the continuous charge / discharge voltage curves are shown below. Figure 9 As shown, the battery voltage changes periodically over time, and the voltage curve is continuous, smooth, and without abnormal fluctuations.

[0109] Comparative Example 1

[0110] 5.58 g of biphenyl hydroquinone solid was dissolved in 80 mL of ethanol and stirred at room temperature until a colorless, transparent liquid was obtained. Nitrogen gas was bubbled for 20 min. Then, 13.2 mL of 37% formaldehyde aqueous solution and 26 mL of 40% dimethylamine aqueous solution were added sequentially. The mixture was refluxed at 120 °C for 12 h. Vacuum distillation was performed to obtain a brownish-red solid product. The product was dried under vacuum at 80 °C for 10 h to obtain the target product. 1 HNMR spectra as follows Figure 10 As shown, the reaction equation is as follows:

[0111]

[0112] 0.124 g of the dried solid was dissolved in 50 mL of 3 M sulfuric acid aqueous solution to prepare a biphenyl hydrochloride electrolyte, which was then transferred to an electrochemical cell. Cyclic voltammetry of the electrolyte was performed using a three-electrode method. The working electrode was a 1 cm × 1 cm graphite electrode, the counter electrode was a 2 cm × 2 cm graphite electrode, and the reference electrode was Ag / AgCl. The scan rate was 50 mV / s, and the voltage range was 0–1 V. The cyclic voltammetry results are shown below. Figure 11 As shown, the redox potential, electrochemical reversibility, and electrochemical activity are similar to those of the electrolyte samples in Examples 1-3.

[0113] 0.17 g of the dried solid was dissolved in a 3 M sulfuric acid aqueous solution to prepare 8 mL of tetranitrodimethyl-substituted biphenyl hydrochloride electrolyte as the positive electrode of the flow battery. The negative electrode of the flow battery was the same as in Example 5, using a polybenzimidazole membrane as the separator and 3 cm × 3 cm graphite felt as the electrode. Constant current charging was used, with a charge / discharge current of ±0.18 A. The charge / discharge cutoff voltages were set to 1.2 V and 0.1 V, respectively. The pump speeds at both the positive and negative electrodes were 80 rpm. Continuous charge / discharge tests were conducted, with the discharge capacity decreasing with each cycle. Figure 12As shown, the electrolyte exhibits severe transmembrane permeation due to its small molecular size, resulting in a continuous decrease in battery capacity. After 100 charge-discharge cycles, the capacity decayed to 42.8%.

[0114] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0115] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. An electrolyte, characterized in that, Includes active substances and solvents; The active substance includes a polytert-amine substituted biphenylquinone compound with the structure shown in Formula I below in an oxidation state: Formula I In Formula I, each R1 is independently a C2-C10 branched or straight-chain alkyl group, and each R2 is independently a C1-C5 straight-chain alkylene group.

2. The electrolyte according to claim 1, characterized in that, It satisfies at least one of the following characteristics (1)-(4): (1) Each of the R1s is independently a C2-C5 branched or straight-chain alkyl group; (2) Each of the R2s is independently a C1-C3 straight-chain alkylene group; (3) All R1 values ​​are the same; (4) All R2 values ​​are the same.

3. The electrolyte according to claim 1, characterized in that, The active substance includes any one or more compounds with the following structural formulas in an oxidation state: (1)、 (2)、 (3)。 4. The electrolyte according to claim 1, characterized in that, The electrolyte also includes acid; Optionally, the acid is selected from any one or more of sulfuric acid, hydrochloric acid, phosphoric acid, acetic acid, citric acid, trifluoroacetic acid, and trifluoromethanesulfonic acid.

5. The electrolyte according to claim 4, characterized in that, The proton concentration of the electrolyte is 0.001 mol / L to 10.0 mol / L.

6. The electrolyte according to any one of claims 1 to 5, characterized in that, The concentration of the active substance is 0.001 mol / L to 2.0 mol / L.

7. The electrolyte according to any one of claims 1 to 5, characterized in that, The solvent includes any one or more of water, ethanol, N,N-dimethylformamide, and dimethyl sulfoxide.

8. An electrochemical device, characterized in that, Includes the electrolyte as described in any one of claims 1 to 7.

9. The electrochemical device according to claim 8, characterized in that, The electrochemical device includes a three-electrode electrochemical cell, a four-electrode H-type electrolytic cell, or a flow cell.

10. The electrochemical device according to claim 8, characterized in that, The electrochemical device is a flow battery, which includes an independent electrolyte system A and an electrolyte system B, wherein the electrolyte in electrolyte system A is the electrolyte according to any one of claims 1 to 7; Optionally, the electrolyte system A is a positive electrode electrolyte system; Optionally, the redox couple in the electrolyte system B includes V 3+ / V 2+ TiO 2+ / Ti 3+ One or more of silicotungstic acid, and optionally, the concentration of the redox couple in the electrolyte system B is 0.001~2.0 mol / L.

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