Polybenzimidazole polymer containing six-membered cycloalkane as well as preparation method and application of polybenzimidazole polymer

Abstract

The invention discloses a polybenzimidazole polymer containing six-membered cycloalkane as well as a preparation method and application of the polybenzimidazole polymer, and belongs to the field of flow batteries. The structure of the polybenzimidazole polymer containing the six-membered cycloalkane is as shown in the following formula I: # imgabs0 # formula I. The invention further discloses a preparation method of the polybenzimidazole polymer containing the six-membered cycloalkane. The preparation conditions of the polybenzimidazole ion exchange membrane are mild, the preparation process is simple, and batch production is facilitated. The prepared polybenzimidazole ion conduction membrane has excellent mechanical strength and good toughness, and has excellent oxidation resistance, high proton conduction performance and excellent positive and negative electrode vanadium ion permeation blocking performance in an acidic electrolyte flow energy storage battery.

Description

Technical Field

[0001] The present application relates to a polybenzimidazole polymer containing hexacyclic hydrocarbons and a preparation method and application thereof, and belongs to the field of liquid flow batteries. Background Art

[0002] Acid electrolyte flow battery energy storage technology is a new electrochemical energy storage technology with the advantages of high energy conversion efficiency, flexible system design, large storage capacity, free site selection, and deep discharge. It is one of the preferred technologies for large-scale and efficient energy storage technology. Among the many acid electrolyte flow battery energy storage technologies, the all-vanadium flow battery (VFB) relies on the change of the valence state of vanadium ions to achieve energy conversion. It has the advantages of renewable electrolyte, low cross-contamination of positive and negative active substances, high safety, and long cycle life. It is considered to be one of the most promising and representative energy storage batteries in acid electrolyte flow battery energy storage technology.

[0003] As one of the key materials of all-vanadium liquid flow batteries, ion-conducting membranes play the role of blocking the cross-mixing of vanadium ions in the positive and negative electrolytes, and transferring carriers to form a battery circuit. Their physical and chemical properties and costs directly affect the performance and cost of the battery system. An ideal ion-conducting membrane for all-vanadium liquid flow batteries should have high selectivity, high conductivity, excellent stability and low cost. The membrane material currently used is mainly the Nafion membrane developed by DuPont in the United States. The Nafion membrane has excellent performance in terms of electrochemical performance and service life, but it is easy to absorb water and swell in acidic electrolytes, has low ion selectivity, and is expensive, which limits the industrial application of the membrane. Therefore, it is crucial to develop ion exchange membranes with high selectivity, high stability and low cost.

[0004] Polybenzimidazole polymers are polymers with benzimidazole as the main repeating unit. Due to the presence of conjugated aromatic heterocycles in the molecular chain, the arrangement structure of the polymer aromatic hexahedron is maintained, so it has excellent thermal stability, chemical stability and mechanical properties. Polybenzimidazole will be protonated in acidic electrolytes, so it can play the role of conducting protons and be used as a diaphragm for all-vanadium liquid flow batteries. At present, in the synthesis process of polybenzimidazole, the diacid monomers used all contain benzene rings. The synthesized polybenzimidazole has poor stability in strong oxidizing (pentavalent vanadium ions) and strong acidic electrolytes and is easily degraded. Summary of the invention

[0005] According to one aspect of the present application, a polybenzimidazole polymer containing a hexacycloalkane is provided. The hexacycloalkane is a strong electron-donating group, which improves the antioxidant capacity of C on the imidazole ring and is applied to an ion exchange membrane, thereby improving the oxidation stability of the ion exchange membrane and the cycle stability of the battery; and the protonation capacity of the -N- group on the imidazole ring can be improved, and the protonation rate of the polybenzimidazole can be improved, thereby improving the proton conductivity of the ion exchange membrane, reducing the internal resistance of the battery, and thus improving the voltage efficiency of the battery; and based on the Donnan exclusion effect of the protonated -N- group on positively charged ions, the selectivity of the ion exchange membrane can be improved, thereby improving the coulombic efficiency of the battery.

[0006] The polybenzimidazole polymer containing six-membered cycloalkane described in the present application has a structure as shown in the following formula I:

[0007]

[0008] Wherein, the structure of R1 is shown in the following formula II or III:

[0009]

[0010] n is any integer from 10 to 500.

[0011] In this application, n is the degree of polymerization.

[0012] Optionally, the polybenzimidazole polymer containing hexacyclic hydrocarbons is a random copolymer.

[0013] Optionally, the average molecular weight of the polybenzimidazole polymer containing hexacyclic hydrocarbons is 4,000-1,000,000.

[0014] Optionally, the polybenzimidazole-based polymer containing the hexacycloalkane comprises cis- and trans-configurations of the hexacycloalkane.

[0015] In another aspect, the present application provides a method for preparing the polybenzimidazole polymer containing six-membered cycloalkane, comprising: reacting, neutralizing, filtering, and drying a mixture of a catalyst, methanesulfonic acid, a diacid, and benzyltetramine to obtain the polybenzimidazole polymer containing six-membered cycloalkane;

[0016] The diacid structure is shown in the following formula IV or formula V:

[0017]

[0018] Optionally, the diacid comprises cis and trans configurations.

[0019] Optionally, the catalyst is phosphorus pentoxide.

[0020] Optionally, the total mass percentage of the diacid and diphenyltetramine in methanesulfonic acid is 2-20%; preferably, the total mass percentage of the diacid and diphenyltetramine in methanesulfonic acid is 4-18%.

[0021] Optionally, the total mass percentage of the diacid and diphenyltetramine in methanesulfonic acid is independently selected from any value of 2%, 4%, 5%, 10%, 15%, 16%, 18%, 20% or a range between any two of the above.

[0022] Optionally, the molar amount of the diacid is the same as the molar amount of biphenyltetramine.

[0023] Optionally, the mass ratio of the catalyst to methanesulfonic acid is 1:2 to 1:40; preferably, the mass ratio of the catalyst to methanesulfonic acid is 1:5 to 1:15.

[0024] Optionally, the reaction temperature is 100-150°C; preferably, the reaction temperature is 120-140°C.

[0025] Optionally, the reaction temperature is independently selected from any value of 100°C, 110°C, 120°C, 125°C, 130°C, 135°C, 140°C, 150°C or a range between any two of the above values.

[0026] Optionally, the reaction time is 10 min-3 h; preferably, the reaction time is 1-2 h.

[0027] Optionally, the reaction time is independently selected from any value of 10 min, 30 min, 1 h, 1.5 h, 2 h, 3 h, or a range between any two of the above values.

[0028] Optionally, neutralize to neutral.

[0029] Optionally, the method for preparing the polybenzimidazole polymer containing hexacyclic hydrocarbons comprises the following steps:

[0030] (1) mixing a catalyst and methanesulfonic acid, heating, and stirring;

[0031] (2) adding diacid and benzyltetramine to the solution obtained in step (1), reacting, neutralizing, filtering, and drying to obtain the polybenzimidazole polymer containing the six-membered cycloalkane.

[0032] Optionally, the heating temperature is 50-80°C.

[0033] In another aspect, the present application provides an ion exchange membrane, the material of which is the above-mentioned polybenzimidazole polymer containing hexacyclic hydrocarbons.

[0034] In another aspect, the present application provides a method for preparing the ion exchange membrane, comprising: dissolving the polybenzimidazole polymer containing hexacyclic hydrocarbons in an organic solvent to obtain a mixture solution, casting the mixture solution on a glass plate or a stainless steel plate, and drying the mixture to obtain the ion exchange membrane.

[0035] Optionally, the organic solvent is selected from any one or more of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), dimethylacetamide (DMAC), and dimethyl sulfoxide (DMSO).

[0036] Optionally, the concentration of the mixture solution is 2-15wt%; preferably, the concentration of the mixture solution is 2-6wt%.

[0037] Specifically, the concentration of the mixture solution is 4 wt %.

[0038] Optionally, the dissolving temperature is 20-100°C.

[0039] Optionally, the temperature for drying and film formation is 40-100°C; preferably, the temperature for drying and film formation is 70-90°C.

[0040] Specifically, the drying temperature for film formation was 80°C.

[0041] Optionally, the drying time for film formation is greater than 1 hour.

[0042] Optionally, after drying to form a membrane, the membrane is placed in a non-solvent to obtain the ion exchange membrane.

[0043] Optionally, the non-solvent is selected from one or more of water, n-heptane, n-hexane, cyclohexane, methanol, ethanol, propanol and butanol.

[0044] Optionally, the thickness of the ion exchange membrane is 2-200 μm; preferably, the thickness of the ion exchange membrane is 10-30 μm.

[0045] Specifically, the thickness of the ion exchange membrane is 20 μm.

[0046] In another aspect, the present application provides an application of the ion exchange membrane in an acidic electrolyte flow energy storage battery.

[0047] Optionally, the acidic electrolyte flow energy storage battery is a redox flow battery containing an acidic electrolyte, including: all-vanadium flow energy storage battery, iron-chromium flow energy storage battery, zinc-bromine flow energy storage battery, vanadium-bromine flow energy storage battery, and vanadium-niobium flow energy storage battery.

[0048] From the perspective of the practical application of liquid flow batteries, the present application selects a diacid monomer containing a hexacycloalkane to synthesize a polybenzimidazole polymer. The hexacycloalkane has a stronger electron donation ability, which increases the electron cloud density of the C atom on the imidazole ring, thereby improving the oxidative stability of the polybenzimidazole ion exchange membrane. The increase in the electron cloud density of the C atom also increases the protonation ability of the N group on the imidazole ring, thereby improving the proton conductivity and vanadium resistance of the ion exchange membrane, showing excellent performance.

[0049] The beneficial effects of this application include:

[0050] (1) The present application is based on the high protonation rate of polybenzimidazole polymers containing hexacycloalkanes and the high Donnan repulsion effect on positively charged vanadium ions, thereby improving the ionic conductivity of polybenzimidazole and the ability to prevent vanadium ion penetration.

[0051] (2) Based on the strong electron-donating ability of hexacycloalkanes, the C on the imidazole ring in the polybenzimidazole-based polymer containing hexacycloalkanes synthesized in the present application has a strong antioxidant ability, which is beneficial to improving the antioxidant stability of the film and improving the oxidation stability of polybenzimidazole.

[0052] (3) The -N- group on the imidazole ring in the polymer prepared by the reaction has strong protonation ability and high protonation rate. The polybenzimidazole ion exchange membrane containing hexacyclic hydrocarbons is applied to all-vanadium liquid flow batteries and has high proton conductivity and vanadium ion selectivity.

[0053] (4) The present application uses diacids of different structures and benzyltetramine to obtain the polymer through nucleophilic polycondensation reaction. The structure of the diacid in the reaction system is a diacid containing a six-membered cycloalkane, and the polymer prepared by the reaction has good solubility and film-forming properties.

[0054] (5) The ion exchange membrane prepared in this application has good mechanical properties.

[0055] (6) The polybenzimidazole polymer of hexacycloalkane in the present application has low reaction temperature, short reaction time, simple process and is suitable for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 This is the infrared spectrum of the polymer film prepared in Example 1.

[0057] Figure 2 This is the stress-strain curve of the polymer film prepared in Example 1.

[0058] Figure 3 The polymer film prepared in Example 1 was heated to 1.5 M VO 2 + +3M H 2 SO 4Solution, photograph after 7 days in a 50°C water bath.

[0059] Figure 4 Vanadium permeability of the polymer membrane prepared in Example 1 and the commercial Nafion 115 membrane.

[0060] Figure 5 The surface resistance of the polymer membrane prepared in Example 1 and the commercial Nafion 115 membrane.

[0061] Figure 6 The all-vanadium redox flow battery performance of the polymer membrane prepared in Example 1 and the commercial Nafion 115 membrane.

[0062] Figure 7 The chemical structure of the polymer prepared in Comparative Example 1.

[0063] Figure 8 The polymer film prepared in Comparative Example 1 was heated to 1.5 M VO 2 + +3M H 2 SO 4 Solution, photograph after 2 days in a 50°C water bath. DETAILED DESCRIPTION

[0064] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0065] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0066] The molar amounts of diacid and benzyltetramine are the same in the examples.

[0067] The infrared spectrum was tested by a Jasco FTIR 4100 infrared spectrometer, which uses a transmission method to obtain the chemical structure information of the membrane surface. The number of scans was 32 and the resolution was 4 cm -1 .

[0068] The mechanical properties were tested using a Shimadzu AG-2004 universal testing machine. The film was cut into samples of 1 cm × 7 cm in size, and the film thickness was measured and recorded using a micrometer. The sample was then fixed on a universal testing machine with a clamp width of 1 cm for tensile testing.

[0069] The vanadium permeability test instrument is a TU-1901 model UV spectrophotometer. The test conditions are as follows: the test pool includes two chambers, and the effective area between the two chambers is 3×3cm 2 84 mL of 1.5 mol / L was added to the left chamber. -1 VOSO 4+3.0mol L -1 H 2 SO 4 solution, add the same volume of 1.5 mol L -1 MgSO 4 +3.0mol L -1 H 2 SO 4 solution. MgSO 4 Used to balance the ionic strength of the left and right chambers to reduce water migration caused by osmotic pressure. During the test, the solutions in the left and right chambers are stirred simultaneously to reduce concentration polarization. During the test, 3 mL of sample solution is taken out from the right chamber at regular intervals, and 3 mL of the original solution is added to keep the bath volume constant. VO in the sample 2+ The concentration was measured by UV-visible spectrophotometer (TU-1901).

[0070] The surface resistance was tested using Solartron SI 1260 and SI 1287 electrochemical impedance spectroscopy test stations. The test conditions were: the test frequency range was 1 kHz to 1 MHz. The sample to be tested (effective area 1 cm × 1 cm) was fixed in the middle of the homemade conductivity cell, and the cavities on both sides were filled with 3 mol L -1 Sulfuric acid solution. Before testing, the sample to be tested was heated to 3 mol L -1 The membrane was immersed in sulfuric acid solution for more than 10 hours to fill the pores with sulfuric acid solution. The surface resistance of the membrane was calculated by the resistance difference of the conductivity cell with and without the membrane.

[0071] The electrical performance test instrument is a BT 2000 ArBin charge and discharge instrument. The test conditions are: the cut-off voltage is set to 1.55V and 1.0V, and the working current density range is 80mAcm 2 .

[0072] Example 1

[0073] Dissolve 5 grams of phosphorus pentoxide in 50 grams of methanesulfonic acid, add to a 500 ml three-necked flask, heat and stir to form a clear solution, then add 4.31 grams of diphenyltetramine and 3.44 grams of 1,4-trans-cyclohexanedicarboxylic acid, the total mass percentage of diphenyltetramine in the methanesulfonic acid solvent is 15.5%, stir and heat to 130 degrees, react for 1.5 hours, cool down, and pour into a 5wt% sodium hydroxide solution. After standing for 24 hours, wash thoroughly with water until the solution is neutral. Filter and dry. Dissolve the prepared polymer (degree of polymerization is 400) in DMAC to prepare a 4wt% solution, cast the solution on a glass plate, and flatten it with a scraper. After drying at 80°C for 2 hours, remove the membrane from the glass plate. Place the dried polymer membrane in water for 10 minutes to obtain a polybenzimidazole ion exchange membrane containing hexacyclic hydrocarbons with a thickness of about 20 μm, defined as P1 membrane.

[0074] Figure 1 is the infrared spectrum of P1 film, which confirms the structure of the prepared polymer.

[0075] The mechanical and chemical stability of the P1 film was tested. The stress-strain curve of the P1 film is shown in Figure 2 As shown, the tensile strength of the film is 45 MPa and the elastic modulus is 1.4 GPa, showing good mechanical properties.

[0076] The P1 membrane was immersed in 1.5 M VO 2 + +3M H 2 SO 4 The solution was placed in a 50°C water bath and the membrane did not break within 7 days, showing excellent antioxidant stability, such as Figure 3 shown.

[0077] Assemble the permeation cell using P1 membrane, with 1.5M VOSO on the left 4 Dissolved in 3M HO 2 SO 4 In the middle, on the right is 1.5M MgSO 4 Dissolved in 3M HO 2 SO 4 The volume on both sides is 120 mL and both sides are magnetically stirred. 3 mL of sample is taken from the right side at regular intervals and the same volume of original solution is added at the same time. The concentration of the sample is measured as a function of time using a UV spectrophotometer. Figure 4 It can be seen that the VO of P1 film 2+ The permeability is lower than that of the commercial Nafion 115 membrane, whose vanadium permeability coefficient is 1.11×10 -7 cm 2 h -1 , showing higher selectivity.

[0078] In addition, if Figure 5 As shown, the surface resistance of P1 film is 0.010Ωcm 2 , which is less than the surface resistance of commercial Nafion 115 membrane (0.04Ωcm 2 ), proving that the P1 membrane has a higher proton conductivity (Table 1).

[0079] The P1 membrane was used to assemble an all-vanadium liquid flow battery, in which the catalyst layer was activated carbon felt, the bipolar plate was a graphite plate, and the membrane effective area was 48 cm 2 , the current density is 80 mA cm -2 The vanadium ion concentration in the electrolyte is 1.50 mol L -1 , H 2 SO 4 The concentration is 3 mol L -1 The coulombic efficiency of the all-vanadium flow battery assembled with P1 membrane is 99.56%, the voltage efficiency is 90.03%, and the energy efficiency is 89.63%, which are higher than the efficiency of the all-vanadium flow battery assembled with Nafion115 membrane (coulombic efficiency is 94.51%, voltage efficiency is 87.88%, and energy efficiency is 83.06%). Figure 6 As shown. Within 100 cycles, the capacity retention rate of the all-vanadium liquid flow battery assembled with the P1 membrane is 88%, which is higher than the capacity retention rate of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (78%) (Table 2). In addition, the all-vanadium liquid flow battery assembled with the P1 membrane can operate continuously and stably for more than 2000 cycles without obvious performance degradation, proving that the membrane has excellent chemical stability.

[0080] Example 2

[0081] A polybenzimidazole ion exchange membrane containing hexacyclic hydrocarbons was prepared according to the method (process and conditions) described in Example 1, except that the total mass percentage of diacid and diphenyltetramine in methanesulfonic acid solvent was 10%. The prepared membrane was recorded as P2 membrane.

[0082] The mechanical and chemical stability of the P2 membrane was tested. As shown in Table 1, the tensile strength of the membrane was 42 MPa and the elastic modulus was 1.5 GPa, showing good mechanical properties. 2 + +3M H 2 SO 4 The solution was placed in a 50°C water bath. Within 7 days, the membrane would not break, showing excellent antioxidant stability.

[0083] The permeation cell device is assembled using the P2 membrane. The left one is 1.5M VOSO 4 Dissolved in 3M HO2 SO 4 In the middle, on the right is 1.5M MgSO 4 Dissolved in 3M HO 2 SO 4 The volume of both sides is 120 mL and both sides are magnetically stirred. 3 mL of sample is taken from the right side at regular intervals and the same volume of original solution is added at the same time. The concentration of the sample is measured by UV spectrophotometer as a function of time. As shown in Table 1, the VO 2+ The permeability is lower than that of the commercial Nafion 115 membrane, whose vanadium permeability coefficient is 1.56×10 7 cm 2 h -1 , which is higher than the vanadium permeability of P1 membrane. This is because the total mass percentage of diacid and benzyltetramine in methanesulfonic acid solvent is reduced, which makes the polymerization degree of the generated polybenzimidazole decrease, the density of the prepared ion exchange membrane decreases, and its vanadium resistance becomes worse, showing a reduced selectivity. The surface resistance of P2 membrane is 0.018Ωcm 2 , which is lower than the surface resistance of P1. This is because the decrease in the density of the ion exchange membrane reduces its proton transfer impedance, promotes the migration of protons in the membrane, and reduces the surface resistance of the membrane (Table 3). In addition, the surface resistance of the P2 membrane is lower than the surface resistance of the commercial Nafion 115 membrane (0.04Ωcm 2 ), proving that the P2 membrane has excellent proton conductivity.

[0084] The all-vanadium liquid flow battery was assembled using a P2 membrane, in which the catalyst layer was activated carbon felt, the bipolar plate was a graphite plate, and the membrane effective area was 48 cm 2 , current density is 80mAcm -2 The vanadium ion concentration in the electrolyte is 1.50 mol L -1 , H 2 SO 4 The concentration is 3 mol L -1 . As shown in Table 2, the Coulombic efficiency of the all-vanadium liquid flow battery assembled with the P2 membrane is 99.35%, the voltage efficiency is 90.14%, and the energy efficiency is 89.55%, which are higher than the efficiency of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (Coulombic efficiency is 94.51%, voltage efficiency is 87.88%, and energy efficiency is 83.06%). Within 100 cycles, the capacity retention rate of the all-vanadium liquid flow battery assembled with the P2 membrane is 86%, which is higher than the capacity retention rate of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (78%). In addition, the all-vanadium liquid flow battery assembled with the P2 membrane can operate continuously and stably for more than 2000 cycles without obvious performance degradation, proving that the membrane has excellent chemical stability.

[0085] Example 3

[0086] A polybenzimidazole ion exchange membrane containing hexacyclic hydrocarbons was prepared according to the method (process and conditions) described in Example 1, except that the total mass percentage of diacid and diphenyltetramine in methanesulfonic acid solvent was 4%. The prepared membrane was recorded as P3 membrane.

[0087] The mechanical and chemical stability of the P3 membrane was tested. As shown in Table 1, the tensile strength of the membrane was 36 MPa and the elastic modulus was 1.8 GPa, showing good mechanical properties. 2 + +3M H 2 SO 4 The solution was placed in a 50°C water bath. Within 7 days, the membrane would not break, showing excellent antioxidant stability.

[0088] The permeation cell device is assembled using P3 membrane, with 1.5M VOSO on the left. 4 Dissolved in 3M HO 2 SO 4 In the middle, on the right is 1.5M MgSO 4 Dissolved in 3M HO 2 SO 4 The volume of both sides is 120 mL and both sides are magnetically stirred. 3 mL of sample is taken from the right side at regular intervals and the same volume of original solution is added at the same time. The concentration of the sample is measured by UV spectrophotometer as a function of time. As shown in Table 1, the VO 2+ The permeability is lower than that of the commercial Nafion 115 membrane, whose vanadium permeability coefficient is 1.99×10 7 cm 2 h -1 , which is higher than the vanadium permeability of P1 and P2 membranes. This is because the total mass percentage of diacid and benzyltetramine in the methanesulfonic acid solvent is further reduced, which makes the polymerization degree of the generated polybenzimidazole decrease, and the density of the prepared ion exchange membrane is further reduced, and its vanadium resistance capacity is reduced, showing a reduced selectivity. The surface resistance of P3 membrane is 0.012Ωcm 2 , which is lower than the surface resistance of P1 and P2 membranes. This is because the decrease in the density of the ion exchange membrane further reduces its proton transfer impedance, promotes the migration of protons in the membrane, and reduces the surface resistance of the membrane (Table 3). In addition, the surface resistance of the P3 membrane is lower than the surface resistance of the commercial Nafion 115 membrane (0.04Ωcm 2 ), proving that the P3 membrane has excellent proton conductivity.

[0089] The all-vanadium liquid flow battery is assembled using a P3 membrane, in which the catalyst layer is activated carbon felt, the bipolar plate is a graphite plate, and the membrane effective area is 48cm 2 , current density is 80mAcm-2 The vanadium ion concentration in the electrolyte is 1.50 mol L -1 , H 2 SO 4 The concentration is 3 mol L -1 . As shown in Table 2, the Coulombic efficiency of the all-vanadium liquid flow battery assembled with the P3 membrane is 99.12%, the voltage efficiency is 90.54%, and the energy efficiency is 89.74%, which are higher than the efficiency of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (Coulombic efficiency is 94.51%, voltage efficiency is 87.88%, and energy efficiency is 83.06%). Within 100 cycles, the capacity retention rate of the all-vanadium liquid flow battery assembled with the P3 membrane is 83%, which is higher than the capacity retention rate of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (78%). In addition, the all-vanadium liquid flow battery assembled with the P3 membrane can operate continuously and stably for more than 2,000 cycles without obvious performance degradation, proving that the membrane has excellent chemical stability.

[0090] Example 4

[0091] A polybenzimidazole ion exchange membrane containing hexacyclic hydrocarbons was prepared according to the method (process and conditions) described in Example 1, except that the total mass percentage of diacid and diphenyltetramine in methanesulfonic acid solvent was 18%. The prepared membrane was recorded as P4 membrane.

[0092] The mechanical and chemical stability of the P4 membrane was tested. As shown in Table 1, the tensile strength of the membrane was 48 MPa and the elastic modulus was 1.0 GPa, showing good mechanical properties. 2 + +3M H 2 SO 4 The solution was placed in a 50°C water bath. Within 7 days, the membrane would not break, showing excellent antioxidant stability.

[0093] The permeation cell device is assembled using P4 membrane, with 1.5M VOSO on the left. 4 Dissolved in 3M HO 2 SO 4 In the middle, on the right is 1.5M MgSO 4 Dissolved in 3M HO 2 SO 4 The volume on both sides is 120 mL and both sides are magnetically stirred. 3 mL of sample is taken from the right side at regular intervals and the same volume of original solution is added at the same time. The concentration of the sample is measured as a function of time using a UV spectrophotometer. 2+ The permeability is lower than that of the commercial Nafion 115 membrane, whose vanadium permeability coefficient is 1.05×10 7 cm 2 h-1 , which is lower than the vanadium permeability of P1-P3 membranes. This is because the total mass percentage of diacid and benzyltetramine in the methanesulfonic acid solvent increases, which increases the polymerization degree of the generated polybenzimidazole, increases the density of the prepared ion exchange membrane, and enhances its vanadium resistance, showing higher selectivity. The surface resistance of P4 membrane is 0.035Ωcm 2 , which is higher than the surface resistance of P1-P3 membranes. This is because the increase in the density of the ion exchange membrane increases the proton transfer impedance, which is not conducive to the migration of protons in the membrane to a certain extent, increasing the surface resistance of the membrane (Table 3). However, the surface resistance of the P4 membrane is still lower than the surface resistance of the commercial Nafion 115 membrane (0.04Ωcm 2 ), proving that the P4 membrane still has excellent proton conductivity.

[0094] The all-vanadium liquid flow battery is assembled using a P4 membrane, in which the catalyst layer is activated carbon felt, the bipolar plate is a graphite plate, and the membrane effective area is 48cm 2 , the current density is 80 mA cm -2 The vanadium ion concentration in the electrolyte is 1.50 mol L -1 , H 2 SO 4 The concentration is 3 mol L -1 . As shown in Table 2, the Coulombic efficiency of the all-vanadium liquid flow battery assembled with the P4 membrane is 99.76%, the voltage efficiency is 89.39%, and the energy efficiency is 89.18%, which are higher than the efficiency of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (Coulombic efficiency is 94.51%, voltage efficiency is 87.88%, and energy efficiency is 83.06%). Within 100 cycles, the capacity retention rate of the all-vanadium liquid flow battery assembled with the P4 membrane is 91%, which is higher than the capacity retention rate of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (78%). In addition, the all-vanadium liquid flow battery assembled with the P4 membrane can operate continuously and stably for more than 2,000 cycles without obvious performance degradation, proving that the membrane has excellent chemical stability.

[0095] Example 5

[0096] A polybenzimidazole ion exchange membrane containing hexacyclic hydrocarbons was prepared according to the method (process and conditions) described in Example 1, except that the reaction temperature was 120° C. The prepared membrane was denoted as P5 membrane.

[0097] The mechanical and chemical stability of the P5 membrane was tested. As shown in Table 1, the tensile strength of the membrane was 41 MPa and the elastic modulus was 1.6 GPa, showing good mechanical properties. 2 + +3M H 2 SO 4The solution was placed in a 50°C water bath. Within 7 days, the membrane would not break, showing excellent antioxidant stability.

[0098] The permeation cell device is assembled using P5 membrane, with 1.5M VOSO on the left. 4 Dissolved in 3M HO 2 SO 4 In the middle, on the right is 1.5M MgSO 4 Dissolved in 3M HO 2 SO 4 The volume of both sides is 120mL and both sides are magnetically stirred. 3mL of sample is taken from the right side at regular intervals and the same volume of original solution is added at the same time. The concentration of the sample is measured by UV spectrophotometer as a function of time. As shown in Table 1, the VO 2+ The permeability is lower than that of the commercial Nafion 115 membrane, whose vanadium permeability coefficient is 1.58×10 7 cm 2 h -1 , which is higher than the vanadium permeability of the P1 membrane. This is because the reaction temperature decreases, causing the degree of polymerization of the generated polybenzimidazole to decrease, the density of the prepared ion exchange membrane to decrease, and its vanadium resistance becomes worse, showing a reduced selectivity. The surface resistance of the P5 membrane is 0.017Ωcm 2 , which is lower than the surface resistance of P1. This is because the decrease in the density of the ion exchange membrane reduces its proton transfer impedance, promotes the migration of protons in the membrane, and reduces the surface resistance of the membrane (Table 3). In addition, the surface resistance of the P5 membrane is lower than the surface resistance of the commercial Nafion 115 membrane (0.04Ωcm 2 ), proving that the P5 membrane has excellent proton conductivity.

[0099] The P5 membrane is used to assemble an all-vanadium liquid flow battery, in which the catalyst layer is activated carbon felt, the bipolar plate is a graphite plate, and the membrane effective area is 48cm 2 , the current density is 80 mA cm -2 The vanadium ion concentration in the electrolyte is 1.50 mol L -1 , H 2 SO 4 The concentration is 3 mol L -1. As shown in Table 2, the Coulombic efficiency of the all-vanadium liquid flow battery assembled with the P5 membrane is 99.28%, the voltage efficiency is 90.19%, and the energy efficiency is 89.54%, which are higher than the efficiency of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (Coulombic efficiency is 94.51%, voltage efficiency is 87.88%, and energy efficiency is 83.06%). Within 100 cycles, the capacity retention rate of the all-vanadium liquid flow battery assembled with the P5 membrane is 85%, which is higher than the capacity retention rate of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (78%). In addition, the all-vanadium liquid flow battery assembled with the P5 membrane can operate continuously and stably for more than 2,000 cycles without obvious performance degradation, proving that the membrane has excellent chemical stability.

[0100] Example 6

[0101] A polybenzimidazole ion exchange membrane containing hexacyclic hydrocarbons was prepared according to the method (process and conditions) described in Example 1, except that the reaction temperature was 150° C. The prepared membrane was denoted as P6 membrane.

[0102] The mechanical and chemical stability of the P6 membrane was tested. As shown in Table 1, the tensile strength of the membrane was 49 MPa and the elastic modulus was 0.9 GPa, showing good mechanical properties. 2 + +3M H 2 SO 4 The solution was placed in a 50°C water bath. Within 7 days, the membrane would not break, showing excellent antioxidant stability.

[0103] The permeation cell device is assembled using P6 membrane, with 1.5M VOSO on the left. 4 Dissolved in 3M HO 2 SO 4 In the middle, on the right is 1.5M MgSO 4 Dissolved in 3M HO 2 SO 4 The volume of both sides is 120 mL and both sides are magnetically stirred. 3 mL of sample is taken from the right side at regular intervals and the same volume of original solution is added at the same time. The concentration of the sample is measured by UV spectrophotometer as a function of time. As shown in Table 1, the VO 2+ The permeability is lower than that of the commercial Nafion 115 membrane, whose vanadium permeability coefficient is 1.03×10 7 cm 2 h -1 , which is lower than the vanadium permeability of P1 and P5 membranes. This is because the increase in reaction temperature increases the degree of polymerization of the generated polybenzimidazole, increases the density of the prepared ion exchange membrane, and increases its vanadium resistance, showing better selectivity. The surface resistance of P6 membrane is 0.036Ωcm2 , which is higher than the surface resistance of P1 and P5 membranes. This is because the increase in the density of the ion exchange membrane increases the proton transfer impedance, which is not conducive to the migration of protons in the membrane to a certain extent, increasing the surface resistance of the membrane (Table 3). However, the surface resistance of the P6 membrane is less than the surface resistance of the commercial Nafion 115 membrane (0.04Ωcm 2 ), proving that the P6 membrane has excellent proton conductivity.

[0104] The all-vanadium liquid flow battery was assembled using a P6 membrane, in which the catalyst layer was activated carbon felt, the bipolar plate was a graphite plate, and the membrane effective area was 48 cm 2 , the current density is 80 mA cm -2 The vanadium ion concentration in the electrolyte is 1.50 mol L -1 , H 2 SO 4 The concentration is 3 mol L -1 . As shown in Table 2, the Coulombic efficiency of the all-vanadium liquid flow battery assembled with the P6 membrane is 99.79%, the voltage efficiency is 89.31%, and the energy efficiency is 89.12%, which are higher than the efficiency of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (Coulombic efficiency is 94.51%, voltage efficiency is 87.88%, and energy efficiency is 83.06%). Within 100 cycles, the capacity retention rate of the all-vanadium liquid flow battery assembled with the P6 membrane is 89%, which is higher than the capacity retention rate of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (78%). In addition, the all-vanadium liquid flow battery assembled with the P6 membrane can operate continuously and stably for more than 2,000 cycles without obvious performance degradation, proving that the membrane has excellent chemical stability.

[0105] Example 7

[0106] A polybenzimidazole ion exchange membrane containing hexacyclic hydrocarbons was prepared according to the method (process and conditions) described in Example 1, except that the reaction temperature was 110° C. The prepared membrane was denoted as P7 membrane.

[0107] The mechanical and chemical stability of the P7 membrane was tested. As shown in Table 1, the tensile strength of the membrane was 40 MPa and the elastic modulus was 1.7 GPa, showing good mechanical properties. 2 + +3M H 2 SO 4 The solution was placed in a 50°C water bath. Within 7 days, the membrane would not break, showing excellent antioxidant stability.

[0108] The permeation cell device is assembled using the P7 membrane. The left side is 1.5M VOSO 4 Dissolved in 3M HO 2 SO 4In the middle, on the right is 1.5M MgSO 4 Dissolved in 3M HO 2 SO 4 The volume of both sides is 120 mL and both sides are magnetically stirred. 3 mL of sample is taken from the right side at regular intervals and the same volume of original solution is added at the same time. The concentration of the sample is measured by UV spectrophotometer as a function of time. As shown in Table 1, the VO 2+ The permeability is lower than that of the commercial Nafion 115 membrane, whose vanadium permeability coefficient is 1.67×10 7 cm 2 h -1 , which is higher than the vanadium permeability of P1 and P5-P6 membranes. This is because the further decrease in reaction temperature causes the polymerization degree of the generated polybenzimidazole to decrease, the density of the prepared ion exchange membrane to further decrease, and its vanadium resistance capacity to decrease, showing a reduced selectivity. The surface resistance of the P7 membrane is 0.015Ωcm 2 , which is lower than the surface resistance of P1 and P5-P6 membranes. This is because the decrease in the density of the ion exchange membrane further reduces the proton transfer impedance, promotes the migration of protons in the membrane, and reduces the surface resistance of the membrane (Table 3). In addition, the surface resistance of the P7 membrane is lower than the surface resistance of the commercial Nafion115 membrane (0.04Ωcm 2 ), proving that the P7 membrane has excellent proton conductivity.

[0109] The P7 membrane was used to assemble an all-vanadium liquid flow battery, in which the catalyst layer was activated carbon felt, the bipolar plate was a graphite plate, and the membrane effective area was 48 cm 2 , current density is 80mAcm -2 The vanadium ion concentration in the electrolyte is 1.50 mol L -1 , H 2 SO 4 The concentration is 3 mol L -1 . As shown in Table 2, the coulombic efficiency of the all-vanadium liquid flow battery assembled with the P7 membrane is 99.21%, the voltage efficiency is 90.28%, and the energy efficiency is 89.57%, which are higher than the efficiency of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (coulombic efficiency is 94.51%, voltage efficiency is 87.88%, and energy efficiency is 83.06%). Within 100 cycles, the capacity retention rate of the all-vanadium liquid flow battery assembled with the P7 membrane is 84%, which is higher than the capacity retention rate of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (78%). In addition, the all-vanadium liquid flow battery assembled with the P7 membrane can operate continuously and stably for more than 2,000 cycles without obvious performance degradation, proving that the membrane has excellent chemical stability.

[0110] Example 8

[0111] The polybenzimidazole ion exchange membrane containing hexacyclic hydrocarbons was prepared according to the method (process and conditions) described in Example 1, except that the reaction time was 1 h. The prepared membrane was denoted as P8 membrane.

[0112] The mechanical and chemical stability of the P8 membrane was tested. As shown in Table 1, the tensile strength of the membrane was 40 MPa and the elastic modulus was 1.7 GPa, showing good mechanical properties. 2 + +3M H 2 SO 4 The solution was placed in a 50°C water bath. Within 7 days, the membrane would not break, showing excellent antioxidant stability.

[0113] The permeation cell device is assembled using the P8 membrane. The left side is 1.5M VOSO 4 Dissolved in 3M HO 2 SO 4 In the middle, on the right is 1.5M MgSO 4 Dissolved in 3M HO 2 SO 4 The volume of both sides is 120 mL and both sides are magnetically stirred. 3 mL of sample is taken from the right side at regular intervals and the same volume of original solution is added at the same time. The concentration of the sample is measured by UV spectrophotometer as a function of time. As shown in Table 1, the VO 2+ The permeability is lower than that of the commercial Nafion 115 membrane, whose vanadium permeability coefficient is 1.68×10 7 cm 2 h -1 , which is higher than the vanadium permeability of the P1 membrane. This is because the reaction time decreases, which makes the polymerization degree of the generated polybenzimidazole decrease, the density of the prepared ion exchange membrane decreases, and its vanadium resistance becomes worse, showing a reduced selectivity. The surface resistance of the P8 membrane is 0.015Ωcm 2 , which is lower than the surface resistance of P1. This is because the decrease in the density of the ion exchange membrane also reduces the proton transfer impedance, promotes the migration of protons in the membrane, and reduces the surface resistance of the membrane (Table 3). In addition, the surface resistance of the P8 membrane is lower than the surface resistance of the commercial Nafion 115 membrane (0.04Ωcm 2 ), proving that the P8 membrane has excellent proton conductivity.

[0114] The all-vanadium liquid flow battery was assembled using the P8 membrane, in which the catalyst layer was activated carbon felt, the bipolar plate was a graphite plate, and the membrane effective area was 48 cm 2 , the current density is 80 mA cm -2 The vanadium ion concentration in the electrolyte is 1.50 mol L -1 , H 2 SO4 The concentration is 3 mol L -1 . As shown in Table 2, the coulombic efficiency of the all-vanadium liquid flow battery assembled with the P8 membrane is 99.22%, the voltage efficiency is 90.27%, and the energy efficiency is 89.57%, which are higher than the efficiency of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (coulombic efficiency is 94.51%, voltage efficiency is 87.88%, and energy efficiency is 83.06%). Within 100 cycles, the capacity retention rate of the all-vanadium liquid flow battery assembled with the P8 membrane is 84%, which is higher than the capacity retention rate of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (78%). In addition, the all-vanadium liquid flow battery assembled with the P8 membrane can operate continuously and stably for more than 2,000 cycles without obvious performance degradation, proving that the membrane has excellent chemical stability.

[0115] Example 9

[0116] The polybenzimidazole ion exchange membrane containing hexacyclic hydrocarbons was prepared according to the method (process and conditions) described in Example 1, except that the reaction time was 3 h. The prepared membrane was denoted as P9 membrane.

[0117] The mechanical and chemical stability of the P9 membrane was tested. As shown in Table 1, the tensile strength of the membrane was 47 MPa and the elastic modulus was 1.1 GPa, showing good mechanical properties. 2 + +3M H 2 SO 4 The solution was placed in a 50°C water bath. Within 7 days, the membrane would not break, showing excellent antioxidant stability.

[0118] The permeation cell device is assembled using the P9 membrane. The left side is 1.5M VOSO 4 Dissolved in 3M HO 2 SO 4 In the middle, on the right is 1.5M MgSO 4 Dissolved in 3M HO 2 SO 4 The volume of both sides is 120 mL and both sides are magnetically stirred. 3 mL of sample is taken from the right side at regular intervals and the same volume of original solution is added at the same time. The concentration of the sample is measured by UV spectrophotometer as a function of time. As shown in Table 2, the VO 2+ The permeability is lower than that of the commercial Nafion 115 membrane, whose vanadium permeability coefficient is 1.08×10 7 cm 2 h -1, which is lower than the vanadium permeability of P1 and P8 membranes. This is because the reaction time is prolonged, which increases the polymerization degree of the generated polybenzimidazole, increases the density of the prepared ion exchange membrane, and increases its vanadium resistance, showing better selectivity. The surface resistance of P9 membrane is 0.026Ωcm 2 , which is higher than the surface resistance of P1 and P5 membranes. This is because the increase in the density of the ion exchange membrane also increases the proton transfer impedance, which is not conducive to the migration of protons in the membrane to a certain extent, increasing the surface resistance of the membrane (Table 3). However, the surface resistance of the P9 membrane is less than the surface resistance of the commercial Nafion 115 membrane (0.04Ωcm 2 ), proving that the P9 membrane has excellent proton conductivity.

[0119] The P9 membrane was used to assemble an all-vanadium liquid flow battery, in which the catalyst layer was activated carbon felt, the bipolar plate was a graphite plate, and the membrane effective area was 48 cm 2 , the current density is 80 mA cm -2 The vanadium ion concentration in the electrolyte is 1.50 mol L -1 , H 2 SO 4 The concentration is 3 mol L -1 . As shown in Table 2, the coulombic efficiency of the all-vanadium liquid flow battery assembled with the P9 membrane is 99.93%, the voltage efficiency is 89.87%, and the energy efficiency is 89.81%, which are higher than the efficiency of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (coulombic efficiency is 94.51%, voltage efficiency is 87.88%, and energy efficiency is 83.06%). Within 100 cycles, the capacity retention rate of the all-vanadium liquid flow battery assembled with the P9 membrane is 90%, which is higher than the capacity retention rate of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (78%). In addition, the all-vanadium liquid flow battery assembled with the P9 membrane can operate continuously and stably for more than 2000 cycles without obvious performance degradation, proving that the membrane has excellent chemical stability.

[0120] Example 10

[0121] The polybenzimidazole ion exchange membrane containing hexacyclic hydrocarbons was prepared according to the method (process and conditions) described in Example 1, except that the reaction time was 0.5 h. The prepared membrane was denoted as P10 membrane.

[0122] The mechanical and chemical stability of the P10 membrane was tested. As shown in Table 1, the tensile strength of the membrane was 37 MPa and the elastic modulus was 1.8 GPa, showing good mechanical properties. 2 + +3M H 2 SO 4The solution was placed in a 50°C water bath. Within 7 days, the membrane would not break, showing excellent antioxidant stability.

[0123] The permeation cell device is assembled using the P10 membrane. The left side is 1.5M VOSO 4 Dissolved in 3M HO 2 SO 4 In the middle, the right side is 1.5MMgSO 4 Dissolved in 3M HO 2 SO 4 The volume of both sides is 120 mL and both sides are magnetically stirred. 3 mL of sample is taken from the right side at regular intervals and the same volume of original solution is added at the same time. The concentration of the sample is measured as a function of time using a UV spectrophotometer. As shown in Table 1, the VO 2+ The permeability is lower than that of the commercial Nafion 115 membrane, whose vanadium permeability coefficient is 1.84×10 7 cm 2 h -1 , which is higher than the vanadium permeability of P1 and P8-P9 membranes. This is because the further decrease in reaction time makes the polymerization degree of the generated polybenzimidazole decrease, the density of the prepared ion exchange membrane further decreases, and its vanadium resistance decreases, showing a reduced selectivity. The surface resistance of P10 membrane is 0.013Ωcm 2 , which is lower than the surface resistance of P1 and P8-P9 membranes. This is because the decrease in the density of the ion exchange membrane further reduces the proton transfer impedance, promotes the migration of protons in the membrane, and reduces the surface resistance of the membrane (Table 3). In addition, the surface resistance of the P10 membrane is lower than the surface resistance of the commercial Nafion 115 membrane (0.04Ωcm 2 ), proving that the P10 membrane has excellent proton conductivity.

[0124] The P10 membrane was used to assemble an all-vanadium liquid flow battery, in which the catalyst layer was activated carbon felt, the bipolar plate was a graphite plate, and the membrane effective area was 48 cm 2 , current density is 80mAcm -2 The vanadium ion concentration in the electrolyte is 1.50 mol L -1 , H 2 SO 4 The concentration is 3 mol / L -1. As shown in Table 2, the coulombic efficiency of the all-vanadium liquid flow battery assembled with the P10 membrane is 99.17%, the voltage efficiency is 90.36%, and the energy efficiency is 89.61%, which are higher than the efficiency of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (coulombic efficiency is 94.51%, voltage efficiency is 87.88%, and energy efficiency is 83.06%). Within 100 cycles, the capacity retention rate of the all-vanadium liquid flow battery assembled with the P10 membrane is 80%, which is higher than the capacity retention rate of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (78%). In addition, the all-vanadium liquid flow battery assembled with the P10 membrane can operate continuously and stably for more than 2,000 cycles without obvious performance degradation, proving that the membrane has excellent chemical stability.

[0125] Embodiment 11

[0126] A polybenzimidazole ion exchange membrane containing hexacyclic hydrocarbons was prepared according to the method (process and conditions) described in Example 1, except that the diacid used was 1,4-cis-cyclohexanedicarboxylic acid. The prepared membrane was designated as P11 membrane.

[0127] The mechanical and chemical stability of the P11 membrane was tested. As shown in Table 1, the tensile strength of the membrane was 43 MPa and the elastic modulus was 1.5 GPa, showing good mechanical properties. 2 + +3M H 2 SO 4 The solution was placed in a 50°C water bath. Within 7 days, the membrane would not break, showing excellent antioxidant stability.

[0128] The permeation cell device is assembled using the P11 membrane. The left side is 1.5M VOSO 4 Dissolved in 3M HO 2 SO 4 In the middle, the right side is 1.5MMgSO 4 Dissolved in 3M HO 2 SO 4 The volume of both sides is 120 mL and both sides are magnetically stirred. 3 mL of sample is taken from the right side at regular intervals and the same volume of original solution is added at the same time. The concentration of the sample is measured by UV spectrophotometer as a function of time. As shown in Table 1, the VO 2+ The permeability is lower than that of the commercial Nafion 115 membrane, whose vanadium permeability coefficient is 1.13×10 7 cm 2 h -1 , showing higher selectivity (Table 3). In addition, the surface resistance of P11 membrane is 0.012Ωcm 2 , which is less than the surface resistance of commercial Nafion 115 membrane (0.04Ωcm2 ), proving that the P11 membrane has a higher proton conductivity.

[0129] The P11 membrane was used to assemble an all-vanadium liquid flow battery, in which the catalyst layer was activated carbon felt, the bipolar plate was a graphite plate, and the membrane effective area was 48 cm 2 , current density is 80mAcm -2 The vanadium ion concentration in the electrolyte is 1.50 mol L -1 , H 2 SO 4 The concentration is 3 mol / L -1 . As shown in Table 2, the coulombic efficiency of the all-vanadium liquid flow battery assembled with the P11 membrane is 99.81%, the voltage efficiency is 89.66%, and the energy efficiency is 88.45%, which are higher than the efficiency of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (coulombic efficiency is 94.51%, voltage efficiency is 87.88%, and energy efficiency is 83.06%). Within 100 cycles, the capacity retention rate of the all-vanadium liquid flow battery assembled with the P11 membrane is 84%, which is higher than the capacity retention rate of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (78%). In addition, the all-vanadium liquid flow battery assembled with the P11 membrane can operate continuously and stably for more than 2,000 cycles without obvious performance degradation, proving that the membrane has excellent chemical stability.

[0130] Example 12

[0131] A polybenzimidazole ion exchange membrane containing hexacyclic hydrocarbons was prepared according to the method (process and conditions) described in Example 1, except that the diacid used was 1,3-trans-cyclohexanedicarboxylic acid. The prepared membrane was designated as P12 membrane.

[0132] The mechanical and chemical stability of the P12 membrane was tested. As shown in Table 1, the tensile strength of the membrane was 40 MPa and the elastic modulus was 1.6 GPa, showing good mechanical properties. 2 + +3M H 2 SO 4 The solution was placed in a 50°C water bath. Within 7 days, the membrane would not break, showing excellent antioxidant stability.

[0133] The permeation cell device is assembled using the P12 membrane. The left side is 1.5M VOSO 4 Dissolved in 3M HO 2 SO 4 In the middle, the right side is 1.5MMgSO 4 Dissolved in 3M HO 2 SO 4The volume of both sides is 120 mL and both sides are magnetically stirred. 3 mL of sample is taken from the right side at regular intervals and the same volume of original solution is added at the same time. The concentration of the sample is measured using a UV spectrophotometer as a function of time. As shown in Table 1, the VO 2+ The permeability is lower than that of the commercial Nafion 115 membrane, whose vanadium permeability coefficient is 1.05×10 7 cm 2 h -1 , showing higher selectivity (Table 3). In addition, the surface resistance of P12 membrane is 0.011Ωcm 2 , which is less than the surface resistance of commercial Nafion 115 membrane (0.04Ωcm 2 ), proving that the P3 membrane has a higher proton conductivity.

[0134] The P12 membrane was used to assemble an all-vanadium liquid flow battery, in which the catalyst layer was activated carbon felt, the bipolar plate was a graphite plate, and the membrane effective area was 48 cm 2 , the current density is 80 mA cm -2 The vanadium ion concentration in the electrolyte is 1.50 mol L -1 , H 2 SO 4 The concentration is 3 mol / L -1 . As shown in Table 2, the coulombic efficiency of the all-vanadium liquid flow battery assembled with the P12 membrane is 99.22%, the voltage efficiency is 90.01%, and the energy efficiency is 89.31%, which are higher than the efficiency of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (coulombic efficiency is 94.51%, voltage efficiency is 87.88%, and energy efficiency is 83.06%). Within 100 cycles, the capacity retention rate of the all-vanadium liquid flow battery assembled with the P12 membrane is 86%, which is higher than the capacity retention rate of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (78%). In addition, the all-vanadium liquid flow battery assembled with the P12 membrane can operate continuously and stably for more than 2,000 cycles without obvious performance degradation, proving that the membrane has excellent chemical stability.

[0135] Embodiment 13

[0136] A polybenzimidazole ion exchange membrane containing hexacyclic hydrocarbons was prepared according to the method (process and conditions) described in Example 1, except that the diacid used was 1,3-cis-cyclohexanedicarboxylic acid. The prepared membrane was designated as P13 membrane.

[0137] The mechanical and chemical stability of the P13 membrane was tested. As shown in Table 1, the tensile strength of the membrane was 47 MPa and the elastic modulus was 1.5 GPa, showing good mechanical properties. 2 + +3M H2 SO 4 The solution was placed in a 50°C water bath. Within 7 days, the membrane would not break, showing excellent antioxidant stability.

[0138] The permeation cell device is assembled using the P13 membrane. The left side is 1.5M VOSO 4 Dissolved in 3M HO 2 SO 4 In the middle, the right side is 1.5MMgSO 4 Dissolved in 3M HO 2 SO 4 The volume of both sides is 120 mL and both sides are magnetically stirred. 3 mL of sample is taken from the right side at regular intervals and the same volume of original solution is added at the same time. The concentration of the sample is measured by UV spectrophotometer as a function of time. As shown in Table 1, the VO 2+ The permeability is lower than that of the commercial Nafion 115 membrane, whose vanadium permeability coefficient is 1.01×10 7 cm 2 h -1 , showing higher selectivity (Table 3). In addition, the surface resistance of P13 membrane is 0.014Ωcm 2 , which is less than the surface resistance of commercial Nafion 115 membrane (0.04Ωcm 2 ), proving that the P4 membrane has a higher proton conductivity.

[0139] The P13 membrane was used to assemble an all-vanadium liquid flow battery, in which the catalyst layer was activated carbon felt, the bipolar plate was a graphite plate, and the membrane effective area was 48 cm 2 , current density is 80mAcm -2 The vanadium ion concentration in the electrolyte is 1.50 mol L -1 , H 2 SO 4 The concentration is 3 mol / L -1 . As shown in Table 2, the coulombic efficiency of the all-vanadium liquid flow battery assembled with the P13 membrane is 99.14%, the voltage efficiency is 89.72%, and the energy efficiency is 88.94%, which are higher than the efficiency of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (coulombic efficiency is 94.51%, voltage efficiency is 87.88%, and energy efficiency is 83.06%). Within 100 cycles, the capacity retention rate of the all-vanadium liquid flow battery assembled with the P13 membrane is 85%, which is higher than the capacity retention rate of the all-vanadium liquid flow battery assembled with the Nafion 115 membrane (78%). In addition, the all-vanadium liquid flow battery assembled with the P13 membrane can operate continuously and stably for more than 2,000 cycles without obvious performance degradation, proving that the membrane has excellent chemical stability.

[0140] Comparative Example 1

[0141] A polybenzimidazole ion exchange membrane free of hexacyclic alkanes was prepared according to the method (process and conditions) described in Example 1, except that the diacid used was terephthalic acid, the reaction temperature was 200°C, the reaction time was 4 hours, and the prepared membrane was denoted as p1 membrane.

[0142] The structure of the prepared polybenzimidazole is as follows Figure 7 As shown, it does not contain six-membered cycloalkanes.

[0143] The mechanical and chemical stability of the p1 membrane was tested. As shown in Table 1, the tensile strength of the membrane was 30 MPa and the elastic modulus was 0.5 GPa, and the mechanical properties were worse than those of the P1-P13 membranes. The p1 membrane was immersed in 1.5 M VO 2 + +3M H 2 SO 4 The solution was placed in a 50°C water bath. After 2 days, the membrane was broken and its antioxidant stability was worse than that of P1-P13 membranes. Figure 8 shown.

[0144] The permeation cell device is assembled using the p1 membrane. The left side is 1.5M VOSO 4 Dissolved in 3M HO 2 SO 4 In the middle, on the right is 1.5M MgSO 4 Dissolved in 3M HO 2 SO 4 The volume of both sides is 120 mL and both sides are magnetically stirred. 3 mL of sample is taken from the right side at regular intervals and the same volume of original solution is added at the same time. The concentration of the sample is measured using a UV spectrophotometer as a function of time. As shown in Table 1, the vanadium permeability coefficient of the p1 membrane is 2.15×10 -6 cm 2 h -1 , higher than P1-P4 membranes, showing lower selectivity. In addition, the surface resistance of the p1 membrane is 0.40Ωcm 2 , higher than that of P1-P13 membranes, showing lower proton conductivity.

[0145] The all-vanadium liquid flow battery was assembled using the p1 membrane, in which the catalyst layer was activated carbon felt, the bipolar plate was a graphite plate, and the membrane effective area was 48 cm 2 , current density is 80mAcm -2 The vanadium ion concentration in the electrolyte is 1.50 mol L -1 , H 2 SO 4 The concentration is 3 mol L -1. As shown in Table 2, the Coulombic efficiency of the all-vanadium liquid flow battery assembled with the P1 membrane is 94.14%, the voltage efficiency is 87.72%, and the energy efficiency is 82.58%, which are lower than the efficiency of the all-vanadium liquid flow battery assembled with the P1-P13 membrane. Within 100 cycles, the capacity retention rate of the all-vanadium liquid flow battery assembled with the P1 membrane is 77%, which is lower than the capacity retention rate of the all-vanadium liquid flow battery assembled with the P1-P13 membrane. In addition, the all-vanadium liquid flow battery assembled with the P1 membrane can operate continuously and stably for more than 200 cycles without obvious performance degradation, and its chemical stability is lower than that of the P1-P13 membrane.

[0146] Comparative Example 2

[0147] A polybenzimidazole ion exchange membrane free of hexacyclic alkanes was prepared according to the method (process and conditions) described in Example 1, except that the diacid used was isophthalic acid, the reaction temperature was 200°C, the reaction time was 4 hours, and the prepared membrane was denoted as p2 membrane.

[0148] The mechanical and chemical stability of the p2 membrane was tested. As shown in Table 1, the tensile strength of the membrane was 20 MPa and the elastic modulus was 0.91 GPa, and the mechanical properties were worse than those of the PP1-P13 membranes. The p2 membrane was immersed in 1.5 M VO 2 + +3M H 2 SO 4 The solution was placed in a 50°C water bath. After one day, the membrane was broken and its antioxidant stability was worse than that of P1-P13 membranes.

[0149] The permeation cell device is assembled using the p2 membrane. The left one is 1.5M VOSO 4 Dissolved in 3M HO 2 SO 4 In the middle, on the right is 1.5M MgSO 4 Dissolved in 3M HO 2 SO 4 The volume of both sides is 120 mL and both sides are magnetically stirred. 3 mL of sample is taken from the right side at regular intervals and the same volume of original solution is added at the same time. The concentration of the sample is measured using a UV spectrophotometer as a function of time. As shown in Table 1, the vanadium permeability coefficient of the p2 membrane is 2.58×10 -6 cm 2 h -1 , higher than P1-P4 membranes, showing lower selectivity. In addition, the surface resistance of the P2 membrane is 0.39Ωcm 2 , higher than that of P1-P13 membranes, showing lower proton conductivity.

[0150] The all-vanadium liquid flow battery is assembled using a p2 membrane, in which the catalyst layer is activated carbon felt, the bipolar plate is a graphite plate, and the membrane effective area is 48cm 2, current density is 80mAcm -2 The vanadium ion concentration in the electrolyte is 1.50 mol L -1 , H 2 SO 4 The concentration is 3 mol L -1 . As shown in Table 2, the Coulombic efficiency of the all-vanadium liquid flow battery assembled with the P2 membrane is 94.09%, the voltage efficiency is 87.78%, and the energy efficiency is 82.59%, which are lower than the efficiency of the all-vanadium liquid flow battery assembled with the P1-P13 membrane. Within 100 cycles, the capacity retention rate of the all-vanadium liquid flow battery assembled with the p2 membrane is 76%, which is lower than the capacity retention rate of the all-vanadium liquid flow battery assembled with the P1-P13 membrane. In addition, the all-vanadium liquid flow battery assembled with the p2 membrane can operate continuously and stably for more than 100 cycles without obvious performance degradation, and its chemical stability is lower than that of the P1-P13 membrane.

[0151] Comparative Example 3

[0152] The polybenzimidazole ion exchange membrane containing hexacycloalkane was prepared according to the method (process and conditions) described in Example 1, except that the solvent used was polyphosphoric acid, the mass of phosphorus pentoxide was 0, and it was found that polymerization did not occur. This indicates that methanesulfonic acid is one of the key conditions for the successful synthesis of polybenzimidazole containing hexacycloalkane in the present invention (Table 3).

[0153] Comparative Example 4

[0154] The polybenzimidazole ion exchange membrane containing hexacyclic hydrocarbons was prepared according to the method (process and conditions) described in Example 1, except that the total mass percentage of the diacid and diphenyltetramine in the methanesulfonic acid solvent was 22%. It was found that the prepared polymer had a too high degree of polymerization and was insoluble in an organic solvent at room temperature (Table 3).

[0155] Comparative Example 5

[0156] The polybenzimidazole ion exchange membrane containing hexacyclic hydrocarbons was prepared according to the method (process and conditions) described in Example 1, except that the total mass percentage of the diacid and benzyltetramine in the methanesulfonic acid solvent was 3%. It was found that the prepared polymer had too low a degree of polymerization and too low a solution viscosity to form a membrane (Table 3).

[0157] Comparative Example 6

[0158] The polybenzimidazole ion exchange membrane containing hexacyclic hydrocarbons was prepared according to the method (process and conditions) described in Example 1, except that the reaction temperature was 160° C. The results showed that the prepared polymer had a too high degree of polymerization and was insoluble in organic solvents at room temperature (Table 3).

[0159] Comparative Example 7

[0160] The polybenzimidazole ion exchange membrane containing hexacyclic hydrocarbons was prepared according to the method (process and conditions) described in Example 1, except that the reaction temperature was 80° C. It was found that the polymerization reaction did not occur because the reaction temperature was too low (Table 3).

[0161] Comparative Example 8

[0162] The polybenzimidazole ion exchange membrane containing hexacyclic hydrocarbons was prepared according to the method (process and conditions) described in Example 1, except that the reaction time was 5 hours. It was found that the prepared polymer had a too high degree of polymerization and was insoluble in organic solvents at room temperature (Table 3).

[0163] Comparative Example 9

[0164] The polybenzimidazole ion exchange membrane containing hexacyclic hydrocarbons was prepared according to the method (process and conditions) described in Example 1, except that the reaction time was 0.1 h. It was found that due to the short reaction time, the degree of polymerization of the prepared polymer was too low, the solution viscosity was too low, and the membrane could not be formed (Table 3).

[0165] Table 1 Preparation conditions and physicochemical parameters of membranes in different examples

[0166]

[0167]

[0168] Table 2 Performance of membrane-assembled all-vanadium redox flow batteries in different embodiments

[0169]

[0170]

[0171] As described above, by comparing the data of Examples 2-4 with those of Example 1, it is found that the total mass percentage of diacid and diphenyltetramine in the methanesulfonic acid solvent is reduced, so that the degree of polymerization of the generated polybenzimidazole is reduced, the density of the prepared ion exchange membrane is reduced, its vanadium resistance is deteriorated, the proton transfer impedance is reduced, the migration of protons in the membrane is promoted, and the surface resistance of the membrane is reduced.

[0172] On the contrary, the increase in the total mass percentage of diacid and diphenyltetramine in methanesulfonic acid solvent increases the degree of polymerization of the generated polybenzimidazole, increases the density of the prepared ion exchange membrane, and enhances its vanadium resistance, showing higher selectivity. The increase in the density of the ion exchange membrane increases the proton transfer impedance, which is not conducive to the migration of protons in the membrane to a certain extent, and increases the surface resistance of the membrane.

[0173] By comparing the data of Examples 5-7 with that of Example 1, it is found that the decrease in reaction temperature causes the degree of polymerization of the generated polybenzimidazole to decrease, the density of the prepared ion exchange membrane to decrease, and its vanadium resistance capacity to deteriorate, showing a decreased selectivity. The decrease in the density of the ion exchange membrane reduces the proton transfer impedance, promotes the migration of protons in the membrane, and reduces the surface resistance of the membrane.

[0174] On the contrary, the increase in reaction temperature increases the degree of polymerization of the generated polybenzimidazole, increases the density of the prepared ion exchange membrane, increases its vanadium resistance, and shows better selectivity. The increase in the density of the ion exchange membrane increases the proton transfer impedance, which is not conducive to the migration of protons in the membrane to a certain extent, and increases the surface resistance of the membrane.

[0175] By comparing the data of Examples 8-10 with that of Example 1, it is found that the decrease in reaction time causes the degree of polymerization of the generated polybenzimidazole to decrease, the density of the prepared ion exchange membrane to decrease, and its vanadium resistance capacity to deteriorate, showing a decreased selectivity. The decrease in the density of the ion exchange membrane reduces the proton transfer impedance, promotes the migration of protons in the membrane, and reduces the surface resistance of the membrane.

[0176] On the contrary, the longer the reaction time, the higher the degree of polymerization of the generated polybenzimidazole, the higher the density of the prepared ion exchange membrane, the higher its vanadium resistance, and the better selectivity. The higher density of the ion exchange membrane increases the proton transfer impedance, which is not conducive to the migration of protons in the membrane to a certain extent, and increases the surface resistance of the membrane.

[0177] By comparing the data of Comparative Examples 1-2 with Example 1, it is found that the mechanical properties, antioxidant stability, selectivity, conductivity and battery performance of the polybenzimidazole ion exchange membrane without hexacycloalkane are all inferior to those of the polybenzimidazole ion exchange membrane containing hexacycloalkane.

[0178] By comparing the data of Comparative Example 3 with that of Example 1, it is found that methanesulfonic acid is one of the key conditions for the successful synthesis of polybenzimidazole of hexacycloalkane in the present invention.

[0179] By comparing the data of Comparative Example 4 with that of Example 1, it is found that the total mass percentage of the diacid and benzyltetramine in the methanesulfonic acid solvent is too high, so that the prepared polymer has too high a polymerization degree and is insoluble in an organic solvent at room temperature.

[0180] By comparing the data of Comparative Example 5 with that of Example 1, it is found that the total mass percentage of diacid and benzyltetramine in the methanesulfonic acid solvent is too low, so that the prepared polymer has too low polymerization degree and too low solution viscosity to form a film.

[0181] By comparing the data of Comparative Example 6 with that of Example 1, it is found that the reaction temperature is too high, so that the degree of polymerization of the prepared polymer is too high and it is insoluble in an organic solvent at room temperature.

[0182] By comparing the data of Comparative Example 7 with that of Example 1, it is found that when the temperature is too low, the polymerization reaction will not occur.

[0183] By comparing the data of Comparative Example 8 with that of Example 1, it is found that the reaction time is too long, so that the degree of polymerization of the prepared polymer is too high and it is insoluble in organic solvents at room temperature.

[0184] By comparing the data of Comparative Example 9 with that of Example 1, it is found that the reaction time is too short, so that the degree of polymerization of the prepared polymer is too low, the viscosity of the solution is too low, and a film cannot be formed.

[0185] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A polybenzimidazole polymer containing a six-membered cycloalkane, characterized in that: The structure is shown in Formula I below: Wherein, the structure of R1 is shown in the following formula II or III: n is any integer from 10 to 500.

2. The polybenzimidazole polymer containing hexacyclic hydrocarbons according to claim 1, characterized in that: The average molecular weight of the polybenzimidazole polymer containing hexacyclic hydrocarbons is 4000-1000000; Preferably, the polybenzimidazole polymer containing hexacycloalkane comprises cis and trans configurations of hexacycloalkane; Preferably, the polybenzimidazole polymer containing hexacyclic hydrocarbons is a random copolymer.

3. A method for preparing the polybenzimidazole polymer containing hexacyclic hydrocarbons according to claim 1, characterized in that: include: A mixture of a catalyst, methanesulfonic acid, a diacid and benzyltetramine is reacted, neutralized, filtered and dried to obtain the polybenzimidazole polymer containing the six-membered cycloalkane; The diacid structure is shown in the following formula IV or formula V:

4. The method for preparing the polybenzimidazole polymer containing six-membered cycloalkane according to claim 3, characterized in that: The total mass percentage of the diacid and diphenyltetramine in methanesulfonic acid is 2-20%; Preferably, the total mass percentage of the diacid and benzyltetramine in methanesulfonic acid is 4-18%; Preferably, the molar amount of the diacid is the same as the molar amount of biphenyltetramine; Preferably, the mass ratio of the catalyst to methanesulfonic acid is 1:2 to 1:40; Preferably, the mass ratio of the catalyst to methanesulfonic acid is 1:5 to 1:15; Preferably, the catalyst is phosphorus pentoxide; Preferably, the diacid comprises cis and trans configurations.

5. The method for preparing the polybenzimidazole polymer containing six-membered cycloalkane according to claim 3, characterized in that: The reaction temperature is 100-150°C; Preferably, the reaction temperature is 120-140°C; Preferably, the reaction time is 10 min-3 h; Preferably, the reaction time is 1-2 hours.

6. An ion exchange membrane, characterized in that: The material is the polybenzimidazole polymer containing hexacyclic hydrocarbons as described in claim 1 or 2.

7. A method for preparing an ion exchange membrane, characterized in that: include: The polybenzimidazole polymer containing hexacyclic hydrocarbons is dissolved in an organic solvent to obtain a mixture solution, which is cast on a glass plate or a stainless steel plate and dried to form a film to obtain the ion exchange membrane.

8. The method for preparing an ion exchange membrane according to claim 7, characterized in that: The organic solvent is selected from any one or more of N-methylpyrrolidone, N,N-dimethylformamide, dimethylacetamide, and dimethyl sulfoxide; Preferably, the concentration of the mixture solution is 2-15wt%; Preferably, the drying film forming temperature is 40-100°C; Preferably, the drying film-forming time is greater than 1 hour; Preferably, after drying to form a membrane, the membrane is placed in a non-solvent to obtain the ion exchange membrane; Preferably, the non-solvent is selected from one or more of water, n-heptane, n-hexane, cyclohexane, methanol, ethanol, propanol, and butanol; Preferably, the ion exchange membrane has a thickness of 2-200 μm.

9. Use of the ion exchange membrane according to claim 6 in an acidic electrolyte flow energy storage battery.

10. The use according to claim 9, characterized in that: The acid electrolyte flow energy storage battery is a redox flow battery containing an acid electrolyte, including: all-vanadium flow energy storage battery, iron-chromium flow energy storage battery, zinc-bromine flow energy storage battery, vanadium-bromine flow energy storage battery, and vanadium-niobium flow energy storage battery.

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