Benzimidazolyl polymer as well as preparation method and application thereof

Abstract

The invention discloses a benzimidazole-based polymer which is one of ideal materials as an ion solvation membrane filler, and a prepared benzimidazole-based polymer ion solvation membrane shows excellent electrochemical performance and stability, has good universality and has great significance in application in flow batteries.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of liquid flow battery separators, and particularly relates to a benzimidazole-based polymer, a preparation method of the benzimidazole-based polymer, and application of the benzimidazole-based polymer in preparation of a battery separator. BACKGROUND

[0002] With people's attention to energy shortage and environmental problems, water power, wind energy, solar energy and other renewable energy are increasingly attracting people's attention. According to forecasts, by 2050, renewable energy will become the main energy source, with an average annual growth rate of 3.6%, of which solar and wind energy account for 70% of the total renewable energy output. However, the volatility and intermittency of the electricity generated by these renewable energy sources make them challenging in practical applications. Battery energy storage is a powerful tool for improving the flexibility of renewable energy grid connection, improving power grid reliability, improving renewable resource utilization, extending the service life of infrastructure, and improving power quality. Batteries can store the electrical energy generated by renewable energy sources in the form of chemical energy and convert the chemical energy into the required electrical energy. Therefore, battery technology can accelerate the use of renewable energy. The capacity or energy of the redox flow battery can be designed independently, and the power range of the flow battery is 100kW-100MW; the energy range is 100kW·h-100MW·h. Therefore, the flow battery has inherent safety, easy scalability, moderate cost, and flexible operation, and is considered to be a promising large-scale storage technology.

[0003] The separator material is the most critical component of the liquid flow battery, which not only requires high ion conductivity but also has high ion selectivity and excellent mechanical stability. However, the traditional separator faces the trade-off between ion conductivity and ion selectivity. However, the hydrophilic ion conductive region is prone to swelling after hydration, which reduces the ion selectivity and even causes water migration in severe cases, which seriously affects the stability of the long-time energy storage of the flow battery. It has been reported that the ion solvation membrane has high ion conductivity, and the internal functional groups are not too hydrophilic to swell. Therefore, the ion solvation membrane with sub-nanometer size channels is the future development direction of the flow battery. SUMMARY

[0004] The first object of the present application is to provide a benzimidazole-based polymer, which solves the problem of low stability of the separator material in the prior art, which is prone to water migration.

[0005] The second object of the present application is to provide a preparation method of a benzimidazole-based polymer.

[0006] The third object of the present application is to provide a benzimidazole-based polymer for preparing a battery separator.

[0007] To achieve the above object, the following technical solutions are adopted:

[0008] A benzimidazolyl polymer has a general structure as follows:

[0009]

[0010] Ar is a covalent organic framework bridging moiety, and has any one of the following structures:

[0011]

[0012] In the present application, the benzimidazolyl polymer has a structure as follows:

[0013]

[0014] A preparation method of the above benzimidazolyl polymer comprises the following steps:

[0015] Under the protection of inert gas, a carbonyl compound, an organic salt and a ketone compound are dissolved in an organic solvent in a certain molar ratio, and are stirred to react, and the product is subjected to precipitation, washing and drying to obtain the benzimidazolyl polymer.

[0016] In the present application, the ketone compound is triphenylene-2,3,6,7,10,11-hexaketone.

[0017] In the present application, the carbonyl compound is one or more of p-xylylene glycol, 2,5-dimethyl-p-xylylene glycol, trimesylformaldehyde and 2,4,6-trimethylbenzaldehyde.

[0018] In the present application, the organic salt is ammonium acetate.

[0019] In the present application, the molar ratio of the ketone compound to the carbonyl compound is 0.5-3.

[0020] In the present application, the molar ratio of the ketone compound to the organic salt is 1-10.

[0021] In the present application, the organic solvent is one or more of dimethyl sulfoxide, N-methyl pyrrolidone, N',N-dimethylformamide, N',N-dimethylacetamide, ethanol, m-cresol, acetic acid, methane sulfonic acid, trifluoroacetic acid, polyphosphoric acid and Eaton's reagent.

[0022] In the present application, the reaction temperature is 50-200 DEG C, and the reaction time is 12-72 hours.

[0023] The application further discloses an application of the above benzimidazolyl polymer in preparation of a battery diaphragm.

[0024] In the present application, the battery separator is a benzimidazole-based polymer ionic solvation membrane, which is prepared by the following method:

[0025] The benzimidazole-based polymer and the polymer matrix are dissolved in an organic solvent in a certain mass ratio, stirred and uniformly mixed to obtain a casting solution, and the casting solution is filtered, degassed and poured to obtain a benzimidazole-based polymer ionic solvation membrane.

[0026] In the present application, the polymer matrix is one of polysulfone, polyether ether ketone, polybenzimidazole derivative and sulfonated derivative thereof.

[0027] In the present application, the organic solvent is one or more of N-methylpyrrolidone, N,N'-dimethylformamide, N,N'-dimethylacetamide and dimethyl sulfoxide.

[0028] In the present application, the mass ratio of the benzimidazole-based polymer and the polymer matrix is 0-50%.

[0029] In the present application, the mass ratio of the total mass of the benzimidazole-based polymer and the polymer matrix to the solvent is 10-40%.

[0030] In the present application, the thickness of the benzimidazole-based polymer ionic solvation membrane is 30-100 μm.

[0031] The present application has the following beneficial effects:

[0032] (1) The benzimidazole-based polymer ionic solvation membrane constructed by the present application shows excellent electrochemical performance and stability, and has good universality compared with industrial liquid flow batteries.

[0033] (2) The preparation method of the benzimidazole-based polymer of the present application has strong universality. Under the condition of reasonable control of the types and proportions of ketone derivatives and aldehyde derivatives and solvents, the preparation of benzimidazole-based polymers can be realized, and a series of benzimidazole-based ionic solvation membranes are obtained. Such membranes have excellent ion conductivity and ion selectivity and good mechanical stability, and such ionic solvation membranes show great application prospect in liquid flow battery applications. BRIEF DESCRIPTION OF DRAWINGS

[0034] The technical solutions of the present application will be further described below in combination with the drawings and specific embodiments of the present application.

[0035] Figure 1 is the infrared spectrum of the compound of the present application;

[0036] Figure 2 is the rate test situation of the liquid flow battery prepared based on the benzimidazole-based polymer ionic solvation membrane prepared in Example 2 and Example 3 of the present application;

[0037] Figure 3 Figure 3 is a plot of battery performance testing of a benzimidazolium-based polymeric ionic solvated membrane prepared according to Example 3 of the present application;

[0038] Figure 4 Figure 2 is a plot of battery performance testing of a benzimidazolium-based polymeric ionic solvated membrane prepared according to Example 2 of the present application;

[0039] Figure 5 Figure 4 is a plot of water transport of benzimidazolium-based polymeric ionic solvated membranes prepared according to Example 2 and Example 3 of the present application at 80 mAh / cm 2 DETAILED DESCRIPTION

[0040] Example 1

[0041] A benzimidazolium-based polymer having the general structure:

[0042]

[0043] wherein Ar is a covalent organic framework bridging moiety having the structure of any one of the following:

[0044]

[0045] The benzimidazolium-based polymer has the structure:

[0046]

[0047]

[0048] Example 2

[0049] A method of preparing a benzimidazolium-based polymeric ionic solvated membrane, comprising the steps of:

[0050] (1) preparing a benzimidazolium-based polymer

[0051] Dissolve 5.6 g of triphenylen-2,3,6,7,10,11-hexaketone, 7.7 g of ammonium acetate, and 2.01 g of p-xylylene glycol in 300 mL of DMF at room temperature. After 48 h of reaction at 80 °C, perform Soxhlet extraction with methanol and water until the solid particles become dark red, filter the solid polymer and dry to obtain benzimidazolium-based polymer nanoparticles;

[0052] (2) preparing an ionic solvated membrane

[0053] ​The dried polymer nanoparticles and sulfonated polysulfone were dissolved in DMAc solution (solid content: 30%) to prepare a film-forming solution, which was filtered and degassed, and then cast on a glass plate and leveled with a doctor blade. After drying at 60°C for 6h, the film was taken off after vacuum drying at 80°C for 6h to obtain a benzimidazolyl polymer ionic solvated film with a thickness of about 74μm, which was named COP@SPSF.

[0054] Example 3

[0055] A method for preparing a benzimidazolyl polymer ionic solvated film, comprising the following steps:

[0056] (1) Preparation of benzimidazolyl polymer

[0057] 3.18g of triphenylene-2,3,6,7,10,11-hexaketone, 7.7g of ammonium acetate and 2.01g of p-xylylene glycol were dissolved in 600mL of DMF at room temperature. After reaction at 80°C for 48h, Soxhlet extraction with methanol and water was performed until the solid particles turned dark red, the solid polymer was filtered and dried to obtain benzimidazolyl polymer nanoparticles;

[0058] (2) Preparation of ionic solvated film

[0059] The dried polymer nanoparticles and polysulfone were dissolved in DMAc solution (solid content: 30%) to prepare a film-forming solution, which was filtered and degassed, and then cast on a glass plate and leveled with a doctor blade. After drying at 60°C for 6h, the film was taken off after vacuum drying at 80°C for 6h to obtain a benzimidazolyl polymer ionic solvated film with a thickness of about 79μm, which was named COP@PSF.

[0060] Example 4

[0061] A method for preparing a benzimidazolyl polymer ionic solvated film, comprising the following steps:

[0062] (1) Preparation of benzimidazolyl polymer

[0063] 3.18g of triphenylene-2,3,6,7,10,11-hexaketone, 7.7g of ammonium acetate and 2.01g of p-xylylene glycol were dissolved in 600mL of DMF at room temperature. After reaction at 80°C for 48h, Soxhlet extraction with methanol and water was performed until the solid particles turned dark red, the solid polymer was filtered and dried to obtain benzimidazolyl polymer nanoparticles;

[0064] (2) Preparation of ionic solvated film

[0065] The dried polymer nanoparticles and sulfonated polysulfone were dissolved in a DMAc solution (solid content: 30%) to form a film-forming solution, which was filtered and degassed, and then cast on a glass plate and leveled with a doctor blade. After drying at 60°C for 6h and vacuum drying at 80°C for 6h, the film was removed to obtain a benzimidazolyl polymer ionic solvated film with a thickness of about 86μm, which was named COP-1@sPSF.

[0066] Performance test

[0067] The benzimidazolyl polymer ionic solvated film prepared in Example 2-3 was installed as a battery separator in a flow battery device, and the electrochemical performance of the flow battery was detected.

[0068] Specifically comprising the following steps:

[0069] (1) The benzimidazolyl polymer ionic solvated film was soaked in an alkaline solution (alkali concentration: 50wt%) at 80°C for 12-72h; the alkaline solution was one or more of potassium hydroxide, potassium carbonate, sodium hydroxide, sodium carbonate, lithium hydroxide, and lithium carbonate.

[0070] (2) The alkali-doped ionic solvated film obtained in step (1) was installed as a battery separator in a flow battery device, and its electrochemical performance was tested.

[0071] Based on the benzimidazolyl polymer ionic solvated film prepared in the example, the blue test data on the flow battery device was compared with the commercial Nafion 212 separator of DuPont Company. Specifically, under the conditions of positive electrolyte (electrolyte: 0.2M zinc oxide and 3.8M potassium hydroxide), negative electrolyte (electrolyte: 0.4M sodium ferrocyanide and 3M potassium hydroxide), and room temperature, the electrochemical curves were tested under the condition of 80mA / cm 2 current density.

[0072] From Figures 1-5 It can be seen that the benzimidazolyl polymer is introduced into the sulfonated polysulfone matrix to construct a benzimidazolyl mixed matrix film, which is used as a flow battery separator to evaluate its performance in a flow battery (CE, VE and EE in the figure correspond to coulombic efficiency, voltage efficiency and energy efficiency, respectively). The rate efficiency of the COP@SPSF film is the highest. Under the conditions of 80mA / cm -2 current density, 20mAh / cm -2 surface capacity, the energy efficiency is still >80% after 800 cycles. When the surface capacity is increased to 100mAh / cm -2In comparison, the commercial Nafion 212 only lasted for 30 cycles, and the COP@PSF hybrid membrane lasted for about 200 cycles. The ability of COP@SPSF membrane to suppress water transport is attributed to the dense hydrogen-bond network and rigid backbone formed by the benzimidazole groups and sulfonate groups, which inhibit the swelling of the matrix and maintain the stability of the pore size distribution. In summary, the COP@SPSF hybrid matrix membrane has high power efficiency, long cycle life and excellent water transport suppression ability, providing a reliable new type of separator solution for high energy density flow batteries.

[0073] The above disclosure is only the preferred embodiment of the present application, and of course cannot be used to limit the scope of the rights of the present application, so the equivalent changes made according to the claims of the present application still fall within the scope of the present application.

Claims

1. A benzimidazole-based polymer, having the following general structural formula: wherein Ar represents a partial structure connected by a covalent organic framework, and the structure can be any one of the following: Ar:

2. The benzimidazolyl polymer of claim 1, wherein The structure of the benzimidazole-based polymer is as follows:

3. A process for the preparation of a benzimidazolyl polymer according to claim 1 or 2, characterized in that, Includes the following steps: Under inert gas protection, a certain molar ratio of carbonyl compounds, organic salts, and ketone compounds are dissolved in an organic solvent, stirred, and reacted. The product undergoes precipitation, washing, and drying to obtain a benzimidazole polymer.

4. The method of claim 3, wherein the benzimidazolyl polymer is prepared by the reaction of a benzimidazolyl compound and a polymerizable compound. The ketone compound is triphenylene-2,3,6,7,10,11-hexadecanone; the carbonyl compound is one or more of terephthalaldehyde, 2,5-dimethylterephthalaldehyde, pyromellitic terephthalaldehyde, and 2,4,6-trimethylbenzaldehyde.

5. The method of claim 3, wherein the benzimidazolyl polymer is prepared by the reaction of a benzimidazolyl compound and a polymerizable compound in the presence of a base. The molar ratio of the ketone compound to the carbonyl compound is 0.5 to 3; the molar ratio of the ketone compound to the organic salt is 1 to 10.

6. The method of claim 5, wherein the benzimidazolyl polymer is prepared by the reaction of a benzimidazolyl compound of formula (I) with a compound of formula (II) in the presence of a base. The organic solvent is one or more of the following: dimethyl sulfoxide, N-methylpyrrolidone, N',N-dimethylformamide, N',N-dimethylacetamide, ethanol, m-cresol, acetic acid, methanesulfonic acid, trifluoroacetic acid, polyphosphoric acid, and Eaton reagent.

7. The method for preparing the benzimidazole-based polymer according to claim 6, characterized in that, The reaction temperature is 50 to 200°C, and the reaction time is 12 to 72 hours.

8. The use of the benzimidazole-based polymer of claim 1 or 2 in the preparation of battery separators.

9. Use of the benzimidazolyl polymer according to claim 8 for the preparation of a battery separator, characterized in that, The battery separator is a benzimidazole-based polymer ion-solvated membrane, which is prepared by the following method: A benzimidazole-based polymer and a polymer substrate are dissolved in an organic solvent at a certain mass ratio and stirred until homogeneous to obtain a casting solution. The casting solution is then filtered, degassed, and cast to obtain a benzimidazole-based polymer ion-solventized membrane.

10. Use of the benzimidazolyl polymer according to claim 9 for the preparation of a battery separator, characterized in that, The polymer substrate is one of polysulfone, polyetheretherketone, polybenzimidazole derivatives and their sulfonated derivatives; the organic solvent is one or more of N-methylpyrrolidone, N,N'-dimethylformamide, N,N'-dimethylacetamide, and dimethyl sulfoxide.

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