Dopamine-polyethylene glycol polymers, methods of making and using the same

Abstract

The application discloses a dopamine-polyethylene glycol polymer and a preparation method and application thereof. The dopamine-polyethylene glycol copolymer with a crosslinked network containing hydrogen bonds and pi-pi stacking is obtained by carrying out a RAFT copolymerization reaction on dopamine-functionalized vinyl monomers, polyethylene glycol monomers and a solvent under an inert gas atmosphere, and then carrying out freeze drying and purification. The dopamine-functionalized vinyl copolymer obtained and dopamine-modified silicon dioxide fillers are added into a solvent and stirred and mixed to obtain a mixed solution; the mixed solution is uniformly coated on a mold, and the solvent is evaporated to obtain a composite polymer electrolyte membrane. The electrolyte membrane has higher ionic conductivity, more superior sodium ion transference number, more excellent self-repairing performance, better electrochemical stability and better application prospect.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion batteries, and relates to electrolyte materials for sodium-ion batteries, specifically to a dopamine-polyethylene glycol polymer and its preparation method and application. Background Technology

[0002] The rapid rise in global lithium resource prices has severely limited the development of lithium-ion rechargeable batteries. Sodium-ion rechargeable batteries, on the other hand, have received extensive research due to their abundant sodium resources and inexpensive raw materials. Currently, the electrolyte in sodium-ion rechargeable batteries is mainly composed of a mixture of liquid electrolytes with organic solvent systems. Compared to traditional liquid electrolytes, the non-flammability of solid-state electrolytes can solve the safety issues associated with the use of sodium-ion batteries.

[0003] Inorganic solid electrolytes possess excellent ionic conductivity and thermal stability, but their processability and compatibility with electrode materials are poor. Polymer electrolytes exhibit low flammability, good processability, and good flexibility. The good processability of polymer electrolytes allows them to be used as power sources for flexible electronic devices, but prolonged bending and folding can lead to mechanical damage. Self-healing electrolytes, as an emerging material technology, are attracting widespread attention and research. They possess the characteristic of automatically repairing and restoring their function during battery use, effectively solving problems such as electrolyte aging, damage, and leakage in batteries. Polymer electrolytes with self-healing capabilities are a promising type of polymer electrolyte. Self-healing electrolytes are bendable and flexible, capable of inhibiting the growth of sodium dendrites and improving battery life.

[0004] The low ionic conductivity of polymer electrolytes at room temperature has consistently hindered the rapid development of self-healing polymerization. To improve the ionic conductivity of polymer electrolytes, numerous modification strategies have been investigated, such as designing and preparing copolymer-grafted electrolytes, cross-linked electrolytes, adding plasticizers, and introducing inorganic nanoparticles as fillers into the system. Furthermore, the high surface energy difference between inorganic filler nanoparticles and polymer electrolytes leads to poor contact between the inorganic filler and the polymer. An effective method to improve the interfacial wettability between inorganic filler nanoparticles and the polymer is to introduce an interfacial layer with good compatibility. Summary of the Invention

[0005] Objective of the invention: The technical problem to be solved by the present invention is to provide a cross-linked network dopamine-polyethylene glycol polymer containing hydrogen bonds and π-π stacking interactions.

[0006] Another technical problem to be solved by the present invention is to provide a method for preparing dopamine-polyethylene glycol polymer.

[0007] The technical problem that this invention also aims to solve is to provide a self-healing composite polymer electrolyte with superior self-healing properties and better electrochemical stability.

[0008] Another technical problem that this invention aims to solve is to provide a method for preparing a self-healing composite polymer electrolyte.

[0009] The final technical problem to be solved by this invention is to provide the application of dopamine-polyethylene glycol polymer and self-healing composite polymer electrolyte in secondary sodium batteries.

[0010] Technical solution: To solve the above technical problems, the present invention provides a dopamine-polyethylene glycol polymer having a chain structure of formula (I):

[0011]

[0012] Where x∶y=4.76~44.75.

[0013] The present invention also includes a dopamine-modified nano-silica composite self-healing polymer electrolyte, wherein the polymer electrolyte is a comb-shaped polymer prepared from the dopamine-polyethylene glycol polymer.

[0014] This invention also includes a method for preparing the dopamine-polyethylene glycol polymer, comprising the following steps:

[0015] (1) Add dopamine hydrochloride to an aqueous solution of sodium bicarbonate and sodium tetraborate, then add methacrylic anhydride and stir at room temperature under a nitrogen atmosphere. The reaction product is extracted, recrystallized and dried to obtain dopamine methacrylamide monomer.

[0016] (2) The dopamine methacrylamide obtained in step (1) is added to toluene and a ketal protecting group reagent is added under the action of an acid catalyst. The mixture is refluxed, stirred and heated. The reaction product is extracted and separated by column chromatography to obtain the ketal-protected dopamine methacrylamide monomer.

[0017] (3) The ketal-protected dopamine methacrylamide monomer, polyethylene glycol methyl ether methacrylate monomer, chain transfer agent, and initiator obtained in step (2) are added to a solvent, heated under a nitrogen atmosphere, purified by dialysis, and then deprotected by adding a deprotecting agent. Further dialysis yields dopamine-polyethylene glycol copolymer.

[0018] The acidic catalyst in step (2) includes one or more of p-toluenesulfonic acid, pyridine p-toluenesulfonate, hydrochloric acid, and sulfuric acid, and the ketal protecting group reagent includes 2,2-dimethoxypropane or (dimethoxymethyl)benzene.

[0019] The chain transfer agent in step (3) includes one or more of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid, 2-mercapto-S-thiobenzoylacetic acid, 4-cyano-4-[(dodecylthiocarbonylthiocarbonyl)thioalkyl]valeric acid, and tetraethylthiuram disulfide; the initiator is one or more of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, and benzoyl tert-butyl peroxide; the solvent includes one or more of acetonitrile, acetone, N-methylpyrrolidone, N,N-dimethyldiamide, and ethyl acetate; and the deprotecting agent includes acetic acid or trifluoroacetic acid.

[0020] This invention also includes a method for preparing the dopamine-modified nano-silica composite self-healing polymer electrolyte, comprising the following steps:

[0021] 1) Aminated hollow mesoporous silica was obtained by using nano-hollow mesoporous silica under the action of silane coupling agent. Then, dibutyltin dilaurate and dopamine methacrylamide were added, heated and stirred, centrifuged and dried to obtain dopamine-modified hollow mesoporous silica.

[0022] 2) Add dopamine-polyethylene glycol copolymer, dopamine-modified hollow mesoporous silica and sodium salt to an organic solvent and stir to mix, so as to obtain a uniformly mixed solution. Coat the mixture evenly on a polytetrafluoroethylene mold, and after vacuum drying the solvent, obtain a self-healing composite polymer electrolyte membrane.

[0023] In step 1), the silane coupling agent is aminopropyltrimethoxysilane or aminopropyltriethoxysilane.

[0024] The preparation method of nano-hollow mesoporous silica in step 1) includes the following steps: dispersing nano-solid silica spheres in deionized water, ultrasonically vibrating them, then sequentially adding hexadecyltrimethylammonium bromide, concentrated ammonia, deionized water, ethanol and tetraethyl orthosilicate, centrifuging, washing with water and drying, redispersing in deionized water, adding sodium carbonate, heating and stirring, centrifuging, washing, drying and high-temperature calcination to obtain nano-hollow mesoporous silica.

[0025] The heating temperature is 60–100°C.

[0026] The particle size of the nano-hollow mesoporous silica is 100–300 nm.

[0027] The organic solvent includes one or more of acetonitrile, tetrahydrofuran, and N,N-dimethyldiamide; the molar ratio of the sodium salt to the ethoxy group in the polymer is 1:15 to 30.

[0028] The mass ratio of the dopamine-polyethylene glycol copolymer to the dopamine-modified hollow mesoporous silica is 0 to 50:1.

[0029] The sodium salt is one or more of sodium perchlorate, sodium hexafluorophosphate, and sodium bis(trifluoromethanesulfonyl)imide.

[0030] The present invention also includes the application of the dopamine-polyethylene glycol polymer and the dopamine-modified silica composite self-healing polymer electrolyte in the preparation of sodium-ion batteries.

[0031] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: the electrolyte membrane of the present invention has higher ionic conductivity, superior sodium ion transport number, better self-healing performance, better electrochemical stability and better application prospects. Attached Figure Description

[0032] Figure 1 It is the polymer in Example 1 1 H NMR spectrum (using deuterated dimethyl sulfoxide as the deuteration reagent);

[0033] Figure 2 It is the polymer in Example 2 1 H NMR spectrum (using deuterated dimethyl sulfoxide as the deuteration reagent);

[0034] Figure 3 It is the polymer in Example 4 1 H NMR spectrum (using deuterated dimethyl sulfoxide as the deuteration reagent);

[0035] Figure 4 These are the current-time curves of the self-healing polymer electrolytes in Examples 1, 2, 3, and 4 at a polarization voltage of 10 mV;

[0036] Figure 5 These are Arrhenius curves of the ionic conductivity of the self-healing polymer electrolytes in Examples 1, 2, 3, and 4.

[0037] Figure 6 These are images of the self-healing polymer composite electrolyte in Example 5 before and after self-healing;

[0038] Figure 7 This is the electrochemical stability window of the self-healing polymer composite electrolyte in Example 5;

[0039] Figure 8 The cycling charge-discharge curves of the NaV2(PO4)3 / Na battery assembled with the self-healing polymer composite electrolyte in Example 5 at 60°C and a current rate of 0.1C are shown.

[0040] Figure 9 The rate performance of the NaV2(PO4)3 / Na battery assembled with the self-healing polymer composite electrolyte in Example 5 at different rates at 60°C is shown. Detailed Implementation

[0041] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0042] Example 1

[0043] 1. Preparation of hollow mesoporous silica spheres: 0.50 g of solid silica spheres with a particle size of approximately 100 nm were dispersed in 100 mL of deionized water and agitated in an ultrasonic apparatus for 30 minutes. Then, 0.75 g of cetyltrimethylammonium bromide (CTAB), 150 mL of deionized water, 150 mL of ethanol, and 2.75 mL of concentrated ammonia were added to the solution. After stirring at room temperature for 30 minutes, 1.25 mL of TEOS was quickly added. After stirring for 6 hours, the precipitate was collected by washing with deionized water and ethanol and centrifuging. The precipitate was dispersed in 100 mL of deionized water. Then, 2.12 g of anhydrous sodium carbonate was added, and the mixture was stirred at 50 °C for 10 hours. After centrifugation, the precipitate was collected and calcined in a muffle furnace at 550 °C for 4 hours to obtain hollow mesoporous silica spheres. 1.00 g of hollow mesoporous silica spheres were dispersed in 50 mL of ethanol under ultrasonic vibration. A mixed solution of 1 mL of 3-aminopropyltrimethoxysilane dissolved in 20 mL of ethanol was added dropwise to the dispersion. The mixture was heated at 80 °C for 12 hours under nitrogen protection. After the reaction was completed, the precipitate was collected by centrifugation and dried to obtain aminated hollow mesoporous silica.

[0044] 2. Add 0.5 g of aminated hollow mesoporous silica and 0.25 g of dopamine methacrylamide to 100 mL of N,N-dimethylformamide, and add 3 drops of dibutyltin dilaurate as a catalyst. Under nitrogen protection, heat at 80 °C for 24 hours. After the reaction is complete, centrifuge the product, collect the precipitate, and dry it to obtain dopamine-modified hollow mesoporous silica.

[0045] 3. Add 4g of dopamine hydrochloride to 100mL of an aqueous solution containing 3.2g of sodium bicarbonate and 8g of sodium tetraborate. Bubble the solution under nitrogen for 30 minutes. Then, add dropwise a mixed solution of 3.76mL of methacrylic anhydride and 20mL of tetrahydrofuran, maintaining the pH of the solution above 8 by adding anhydrous sodium carbonate. Stir at room temperature under a nitrogen atmosphere for 24 hours. After the reaction is complete, extract, recrystallize, and dry the reaction product to obtain a white solid, dopamine methacrylamide.

[0046] 4. Add 9.20 g of the prepared dopamine methacrylamide and 0.38 g of p-toluenesulfonic acid to 100 mL of toluene. Reflux and stir under nitrogen for 1 hour. After the solution cools to room temperature, add 54.6 mL of 2,2-dimethoxypropane. Reflux and stir under nitrogen for 4 hours until the precipitate dissolves and the solution turns dark brown. After the reaction is complete, purify the product by extraction and rapid column chromatography to obtain a white solid powder, ketal-protected dopamine methacrylamide monomer.

[0047] 5. Polyethylene glycol methyl ether methacrylate monomer and ketal-protected dopamine methacrylamide monomer were copolymerized at a molar ratio of 5:1, and the resulting sample was labeled PEG-5-DPM. The initial molar ratio of the two monomers, the chain transfer agent 2-(dodecyltrithiocarbonate)-2-methylpropionic acid, and the initiator azobisisobutyronitrile was kept constant at 300:3:1. The specific preparation method is as follows: 0.524 g of ketal-protected dopamine methacrylamide and 0.044 g of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid were dissolved in 15 mL of N,N-dimethyldiamide. The solution was stirred for 30 minutes under a nitrogen atmosphere, followed by the addition of 5.000 g of polyethylene glycol methyl ether methacrylate and 0.007 g of azobisisobutyronitrile. The reaction was heated at 70 °C for 24 hours under nitrogen protection. After the reaction was completed, the polymer was dialyzed against deionized water for 5 days and then freeze-dried to obtain the acetal-protected polymer. 2,000 g of acetone-protected polymer was dissolved in 74 mL of dichloromethane and 1 mL of deionized water, and the mixture was bubbled under nitrogen for 20 minutes. The mixture was then cooled in an ice bath, and 25 mL of trifluoroacetic acid was added with vigorous stirring. After the reaction proceeded for 30 minutes, the ice bath was removed, and the solution was stirred at room temperature for 60 minutes. After the reaction was complete, the reaction solution was dialyzed against deionized water for 5 days to purify the polymer, which was then freeze-dried to obtain the dopamine-polyethylene glycol copolymer PEG-5-DPM.

[0048] 4. The obtained dopamine-polyethylene glycol copolymer PEG-5-DPM was dissolved in tetrahydrofuran. Sodium bis(trifluoromethanesulfonyl)imide was added at a molar ratio of ethoxy groups to Na of 20:1. Dopamine-modified silica was added at a mass ratio of copolymer to inorganic nanofiller of 1:0. After stirring at room temperature for 8 hours, the solution was poured into a polytetrafluoroethylene mold. After evaporating a large amount of solvent at room temperature, it was dried at 70°C for 24 hours. After removing the solvent, a composite self-healing polymer electrolyte was obtained. The PEG-5-DPM copolymer... 1 H nuclear magnetic resonance spectrum, such as Figure 1 As shown, the chemical formula x∶y=18.70 was obtained by calculating the corresponding peak intensities of the NMR spectrum. The ionic conductivity of the electrolyte at room temperature was measured to be 1.03 × 10⁻⁶ using AC impedance spectroscopy. -5 S cm-1 The sodium ion transport number at 60℃ is 0.16. Its Arrhenius curve for ionic conductivity is shown below. Figure 4 As shown, the polarization curve of the Na / Na symmetric cell assembled based on this polymer electrolyte at a voltage of 10 mV is as follows. Figure 5 As shown.

[0049] Example 2

[0050] The difference from Example 1 is that the ratio of dopamine methacrylamide monomer to polyethylene glycol methyl ether methacrylate monomer is 10:1, while other conditions are the same as in Example 1. The prepared sample is labeled PEG-10-DPM. This copolymer PEG-10-DPM... 1 H nuclear magnetic resonance spectrum, such as Figure 2 As shown, the chemical formula x∶y=4.76 was obtained by calculating the corresponding peak intensity of the NMR spectrum. The prepared composite self-healing polymer electrolyte was tested according to the method in Example 1, and the ionic conductivity of the electrolyte membrane was measured to be 1.67×10⁻⁶ at room temperature. -6 S cm -1 The sodium ion transport number at 60℃ is 0.11. Its Arrhenius curve for ionic conductivity is shown below. Figure 4 As shown, the polarization curve of the Na / Na symmetric cell assembled based on this polymer electrolyte at a voltage of 10 mV is as follows. Figure 5 As shown.

[0051] Example 3

[0052] The difference from Example 1 is that the ratio of dopamine methacrylamide monomer to polyethylene glycol methyl ether methacrylate monomer is 3:1, while other conditions are the same as in Example 1. The prepared sample is labeled PEG-3-DPM. The prepared composite self-healing polymer electrolyte was tested according to the method of Example 1, and the ionic conductivity of the electrolyte membrane was measured to be 7.30 × 10⁻⁶ at room temperature. -6 The sodium ion transference number at 60 °C is 0.17 (S cm⁻¹). Its Arrhenius curve for ionic conductivity is shown below. Figure 4 As shown, the polarization curve of the Na / Na symmetric cell assembled based on this polymer electrolyte at a voltage of 10 mV is as follows. Figure 5 As shown.

[0053] Example 4

[0054] The difference from Example 1 is that the ratio of dopamine methacrylamide monomer to polyethylene glycol methyl ether methacrylate monomer is 1:1, while other conditions are the same as in Example 1. The prepared sample is labeled PEG-1-DPM. This copolymer PEG-1-DPM... 1 H nuclear magnetic resonance spectrum, such as Figure 3 As shown, the chemical formula x∶y=44.75 was obtained by calculating the corresponding peak intensity of the NMR spectrum. The prepared composite self-healing polymer electrolyte was tested according to the method in Example 1, and the ionic conductivity of the electrolyte membrane was measured to be 5.07×10⁻⁶ at room temperature. -6 S cm -1 The sodium ion transport number at 60℃ is 0.19. Its Arrhenius curve for ionic conductivity is shown below. Figure 4 As shown, the polarization curve of the Na / Na symmetric cell assembled based on this polymer electrolyte at a voltage of 10 mV is as follows. Figure 5 As shown.

[0055] Example 5

[0056] The difference from Example 1 is that the mass ratio of the dopamine-polyethylene glycol copolymer and the dopamine-modified hollow mesoporous silica prepared in Example 1 is 20:1, and the other conditions are the same as in Example 1. Figure 6 The image shows the self-healing process of the PEG-5-DPM composite self-healing polymer prepared in Example 1, which is a combination of dopamine-modified hollow mesoporous silica, at room temperature. For ease of observation, the polymer was stained orange in tetrahydrofuran solvent containing 5% methyl orange before film formation. The prepared self-healing polymer film was observed under a microscope, and the polymer was cut with a scalpel. No further processing was performed on the cut sample. After 50 minutes of repair at room temperature, the surface scratches almost disappeared. The composite self-healing electrolyte prepared in Example 5 was used in a sodium metal battery test, with sodium vanadium phosphate (Na3V2(PO4)3) as the positive electrode material and sodium metal as the negative electrode material. Its electrochemical stability window is shown below. Figure 7 As shown. Charge-discharge cycle testing was conducted at 60℃, with a long-cycle charge-discharge rate of 0.1C and a voltage range of 2.5-3.8V. The corresponding cycle stability ( Figure 8 ) and rate performance ( Figure 9 As shown in the figure.

[0057] In summary, it can be found that the present invention, based on dopamine-modified nano-silica and modified polyethylene glycol composite material, has excellent charge-discharge cycle performance as a battery electrolyte. After 100 charge-discharge cycles, the battery capacity remains above 80%, and it can be widely used as a sodium-ion battery electrolyte.

Claims

1. A dopamine-modified nano-silica composite self-healing polymer electrolyte, characterized in that, The polymer electrolyte is a comb-like polymer, which is prepared from a dopamine-polyethylene glycol polymer as described in formula (I). The dopamine-polyethylene glycol polymer has the chain structure of formula (I): Equation (I) Where x:y=18.7, The preparation method of the dopamine-modified nano-silica composite self-healing polymer electrolyte includes the following steps: (1) Add dopamine hydrochloride to an aqueous solution of sodium bicarbonate and sodium tetraborate, then add methacrylic anhydride and stir at room temperature under a nitrogen atmosphere. The reaction product is extracted, recrystallized and dried to obtain dopamine methacrylamide monomer. (2) Add the dopamine methacrylamide and p-toluenesulfonic acid obtained in step (1) to toluene, reflux and stir under nitrogen, cool the solution to room temperature, add 2,2-dimethoxypropane, reflux and heat under nitrogen until the precipitate dissolves and the solution turns dark brown. After the reaction is complete, purify the product by extraction and rapid column chromatography to obtain a white solid powder, dopamine methacrylamide monomer protected by ketal; (3) The ketal-protected dopamine methacrylamide and 2-(dodecyl trithiocarbonate)-2-methylpropionic acid obtained in step (2) were dissolved in N,N-dimethyldiamide. The solution was stirred under a nitrogen atmosphere. Then polyethylene glycol methyl ether methacrylate and azobisisobutyronitrile were added. The reaction was heated under nitrogen protection. After the reaction was completed, the mixture was dialyzed in deionized water and then freeze-dried to obtain the acetal-protected polymer. The acetal-protected polymer was dissolved in dichloromethane and deionized water. The mixture was bubbled with nitrogen. The mixture was then cooled in an ice bath and trifluoroacetic acid was added under vigorous stirring. After the reaction was completed, the ice bath was removed and the solution was stirred at room temperature. After the reaction was completed, the reaction solution was dialyzed in deionized water and then freeze-dried to obtain the dopamine-polyethylene glycol copolymer. 4) Dissolve the obtained dopamine-polyethylene glycol copolymer in tetrahydrofuran, add sodium bis(trifluoromethanesulfonyl)imide at a molar ratio of ethoxy to Na of 20:1, stir at room temperature, pour the solution into a polytetrafluoroethylene mold, evaporate a large amount of solvent at room temperature, dry, remove the solvent, and obtain the composite self-healing polymer electrolyte.

2. The preparation method of the dopamine-modified nano-silica composite self-healing polymer electrolyte according to claim 1, characterized in that, Includes the following steps: (1) Add dopamine hydrochloride to an aqueous solution of sodium bicarbonate and sodium tetraborate, then add methacrylic anhydride and stir at room temperature under a nitrogen atmosphere. The reaction product is extracted, recrystallized and dried to obtain dopamine methacrylamide monomer. (2) Add the dopamine methacrylamide and p-toluenesulfonic acid obtained in step (1) to toluene, reflux and stir under nitrogen, cool the solution to room temperature, add 2,2-dimethoxypropane, reflux and heat under nitrogen until the precipitate dissolves and the solution turns dark brown. After the reaction is complete, purify the product by extraction and rapid column chromatography to obtain a white solid powder, dopamine methacrylamide monomer protected by ketal; (3) The ketal-protected dopamine methacrylamide and 2-(dodecyl trithiocarbonate)-2-methylpropionic acid obtained in step (2) were dissolved in N,N-dimethyldiamide. The solution was stirred under a nitrogen atmosphere. Then polyethylene glycol methyl ether methacrylate and azobisisobutyronitrile were added. The reaction was heated under nitrogen protection. After the reaction was completed, the mixture was dialyzed in deionized water and then freeze-dried to obtain the acetal-protected polymer. The acetal-protected polymer was dissolved in dichloromethane and deionized water. The mixture was bubbled with nitrogen. The mixture was then cooled in an ice bath and trifluoroacetic acid was added under vigorous stirring. After the reaction was completed, the ice bath was removed and the solution was stirred at room temperature. After the reaction was completed, the reaction solution was dialyzed in deionized water and then freeze-dried to obtain the dopamine-polyethylene glycol copolymer. 4) Dissolve the obtained dopamine-polyethylene glycol copolymer in tetrahydrofuran, add sodium bis(trifluoromethanesulfonyl)imide at a molar ratio of ethoxy to Na of 20:1, stir at room temperature, pour the solution into a polytetrafluoroethylene mold, evaporate a large amount of solvent at room temperature, dry, remove the solvent, and obtain the composite self-healing polymer electrolyte.

3. The application of the dopamine-modified silica composite self-healing polymer electrolyte of claim 1 in the preparation of sodium-ion batteries.

Images