A gel polymer electrolyte, a method for preparing the same, and an electrochromic device

Abstract

The present invention provides a gel polymer electrolyte, a preparation method thereof, and an electrochromic device. The preparation method includes: adding polymethyl methacrylate and cellulose into polyethylene glycol for mixing to make the polymethyl methacrylate and cellulose disperse evenly, thereby obtaining a matrix solution; wherein the mass ratio of polymethyl methacrylate to cellulose is 1:9 to 9:1; Step S2, adding lithium bis(trifluoromethanesulfonyl)imide into a mixed solvent of carboxylic acid ester and polyethylene glycol, and mixing evenly to obtain an electrolyte solution; Step S3, mixing the matrix solution and the electrolyte solution evenly to obtain a gel electrolyte; wherein, the mass ratio of the total mass of polymethyl methacrylate and cellulose to the mass of lithium bis(trifluoromethanesulfonyl)imide is 1-5:1. By adopting the technical solution of the present invention, the obtained gel polymer electrolyte has both high ionic conductivity and mechanical strength, providing guarantee for the response speed and cycle stability of the electrochromic device.

Description

Technical Field

[0001] The present invention belongs to the technical field of materials, and particularly relates to a gel polymer electrolyte, a preparation method thereof, and an electrochromic device. Background Art

[0002] An electrochromic device (ECD) realizes reversible color change by applying a voltage to an electrochromic material, and has broad application prospects.

[0003] In an electrochromic device, the electrolyte is located between the electrochromic layer and the ion storage layer. As an ion transport channel, it provides the necessary compensating ions for the redox reaction of the electrochromic material and is an important part of the ECD. In the ECD, the performance of the electrolyte, such as ionic conductivity, light transmittance, cycling stability, and mechanical strength, is crucial for the entire device. Currently, commonly used electrolytes include liquid electrolytes, solid polymer electrolytes, and gel electrolytes. Solid polymer electrolytes have the property of ionic conduction by dissolving salts in a polymer matrix, which are easy to process and encapsulate. However, they have low ionic conductivity at room temperature. Liquid electrolytes are usually composed of lithium salts dissolved in organic solvents, with high ionic conductivity and stable contact with electrodes, enabling the electrochromic device to respond quickly. However, the defects of being difficult to encapsulate and prone to leakage, leading to safety problems, limit their practical applications.

[0004] Gel polymer electrolytes are prepared by adding a plasticizer to solid electrolytes, combining the advantages of easy encapsulation of solid electrolytes and high ionic conductivity of liquid electrolytes. The performance of gel polymer electrolytes depends to a certain extent on the selection of the matrix. The matrix has an important influence on the conductivity, mechanical properties, and stability of the electrolyte. Polymethyl methacrylate (PMMA) is a transparent amorphous polymer composed of an amorphous phase and a flexible main chain, and it has good compatibility with liquid electrolytes, showing a high electrolyte absorption capacity. Therefore, it has a high ionic conductivity. However, PMMA-based electrolytes have poor mechanical properties and thus need to be modified. Summary of the Invention

[0005] Aiming at the above technical problems, the present invention discloses a gel polymer electrolyte, a preparation method thereof, and an electrochromic device, which improve the ionic conductivity, mechanical strength, and stability, and make up for the deficiencies of the PMMA matrix.

[0006] For this, the technical solution adopted by the present invention is as follows:

[0007] A preparation method of a gel polymer electrolyte, comprising:

[0008] Step S1, add polymethyl methacrylate and cellulose into polyethylene glycol for mixing to make the polymethyl methacrylate (PMMA) and cellulose disperse evenly, obtaining a matrix solution; the mass ratio of polymethyl methacrylate to cellulose is 1:9 to 9:1;

[0009] Step S2, add lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) into a mixed solvent of carboxylic acid ester (EA) and polyethylene glycol (PEG), mix evenly to obtain an electrolyte solution;

[0010] Step S3, mix the matrix solution and the electrolyte solution evenly to obtain a gel electrolyte; the mass ratio of the total mass of polymethyl methacrylate and cellulose to the mass of lithium bis(trifluoromethanesulfonyl)imide is 1 - 5:1. Further preferably, the mass ratio of the total mass of polymethyl methacrylate and cellulose to the mass of lithium bis(trifluoromethanesulfonyl)imide is 1.25 - 5:1.

[0011] The PMMA gel electrolyte has advantages such as high ionic conductivity, high transparency, and good compatibility, but its mechanical properties are poor. With this technical solution, using the cellulose polymer matrix with advantages such as many polar hydroxyl groups, biodegradability, and low cost, HPC is selected as the blend matrix of PMMA. Because the molecular groups and intermolecular hydrogen bond network of cellulose endow it with ionic conductivity, high mechanical strength, and stability, making up for the deficiencies of the PMMA matrix, so that the prepared gel polymer electrolyte has both high ionic conductivity and mechanical strength, providing guarantee for the response speed and cycle stability of electrochromic devices.

[0012] In addition, the polyethylene glycol therein serves both as a solvent and as a plasticizer. PEG is a good plasticizer for cellulose, and the good compatibility it provides is conducive to reducing the interaction between polymers and increasing the service life. As a further improvement of the present invention, in step S1, ultrasonic mixing and dispersion are carried out for 30 - 90 min.

[0013] As a further improvement of the present invention, in step S1, the cellulose is carboxymethyl cellulose, hydroxyethyl cellulose, or hydroxypropyl cellulose.

[0014] As a further improvement of the present invention, in step S1, the mass ratio of polymethyl methacrylate to cellulose is 1:9 to 9:1.

[0015] As a further improvement of the present invention, in the matrix solution, the concentration of polymethyl methacrylate is 0.01 - 0.5 g / mL. Further, in the matrix solution, the concentration of polymethyl methacrylate is 0.05 - 0.4 g / mL.

[0016] As a further improvement of the present invention, in step S2, in the electrolyte solution, the concentration of lithium bis(trifluoromethanesulfonyl)imide is 0.05 - 0.8 g / mL. As a further improvement of the present invention, in step S2, when preparing the mixed solvent of carboxylic ester and polyethylene glycol, the volume ratio of carboxylic ester to polyethylene glycol is 1:5 to 5:1.

[0017] As a further improvement of the present invention, in step S2, it is mixed evenly by magnetic stirring, the stirring temperature is 60°C to 75°C, the stirring time is 60 - 180 min, and the rotation speed is 2000 - 3500 r / min.

[0018] As a further improvement of the present invention, in step S3, the volume ratio of the matrix solution to the electrolyte solution added drop by drop is 2 - 10:1.

[0019] As a further improvement of the present invention, in step S3, magnetic stirring is used for mixing, and the magnetic stirring time is 1 h to 5 h.

[0020] The present invention also discloses a gel polymer electrolyte, which is prepared by using the preparation method of the gel polymer electrolyte described in any one of the above.

[0021] The present invention also discloses an electrochromic device, which includes an electrochromic layer, an ion storage layer and an electrolyte. The electrolyte is located between the electrochromic layer and the ion storage layer, and the electrolyte uses the gel polymer electrolyte described above. Further, each layer is printed on a substrate by screen printing to assemble an electrochromic device.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] By adopting the technical scheme of the present invention, the problem of poor mechanical properties of PMMA-based electrolytes in the prior art is overcome. HPC is used as a blend matrix of PMMA. Due to the strong intramolecular and intermolecular hydrogen bond networks of HPC, it has high mechanical strength and stability, making up for the shortcomings of PMMA, and enabling the prepared gel polymer electrolyte to have both high ionic conductivity and mechanical strength, providing guarantee for the response speed and cycle stability of electrochromic devices. Moreover, cellulose is composed of a large amount of polysaccharides, is an environmentally friendly material, and has a low cost. Specific Embodiments

[0024] The specific embodiments and effects of the present invention will be further described in detail below.

[0025] A gel polymer electrolyte is prepared by the following steps:

[0026] Add polymethyl methacrylate (PMMA) and cellulose in a mass ratio of 1:9 to 9:1 to 20 - 60 mL of polyethylene glycol (PEG), and disperse them under ultrasonic mixing for 30 - 90 min until PMMA and HPC are evenly dispersed to obtain a matrix solution.

[0027] Add 2 - 8 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to a beaker containing a mixed solvent of 10 - 40 mL of carboxylic ester (EA) and PEG, where EA and PEG are mixed in a volume ratio of 1:5 to 5:1. Mix evenly under magnetic stirring to form a colorless transparent solution, and then cool it to room temperature to obtain an electrolyte solution. Among them, set the temperature of magnetic stirring to 60°C - 75°C, the stirring time to 60 - 180 min, and the rotation speed to 2000 - 3500 r / min.

[0028] Under stirring conditions, gradually add the prepared matrix solution dropwise to the electrolyte solution, with a volume ratio of the two being 2:1 to 10:1, and the total mass of polymethyl methacrylate and cellulose to the mass of lithium bis(trifluoromethanesulfonyl)imide being 1 - 5:1. After the dropwise addition is completed, continue stirring to obtain a uniformly mixed gel - state electrolyte. Set the stirring time to 1 h - 5 h.

[0029] The following is illustrated with specific examples.

[0030] Example 1

[0031] Add 1 g of polymethyl methacrylate (PMMA) and 9 g of hydroxypropyl cellulose (HPC) to 20 mL of polyethylene glycol (PEG), and disperse them under ultrasonic mixing for 30 min until PMMA and HPC are evenly dispersed to obtain a matrix solution.

[0032] Add 2 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to a beaker containing a mixed solvent of 10 mL of carboxylic ester (EA) and PEG, where EA and PEG are mixed in a volume ratio of 1:5. Mix evenly under magnetic stirring to form a colorless transparent solution, and then cool it to room temperature to obtain an electrolyte solution. Among them, set the temperature of magnetic stirring to 60°C, the stirring time to 60 min, and the rotation speed to 2000 r / min.

[0033] Under stirring conditions, gradually add the prepared matrix solution dropwise to the electrolyte solution, with a volume ratio of the two being 2:1. After the dropwise addition is completed, continue stirring to obtain a uniformly mixed gel - state electrolyte. Set the stirring time to 1 h.

[0034] Example 2

[0035] Add 9 g of polymethyl methacrylate (PMMA) and 1 g of hydroxymethyl cellulose to 60 mL of polyethylene glycol (PEG), and disperse them under ultrasonic mixing for 90 min until the PMMA and HPC are evenly dispersed.

[0036] Add 8 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to a beaker containing 40 mL of a mixed solvent of carboxylic acid ester (EA) and PEG (EA and PEG are mixed in a volume ratio of 5:1), and mix evenly under magnetic stirring to form a colorless transparent solution. Then cool it to room temperature to obtain an electrolyte solution. Among them, set the temperature of magnetic stirring to 75 °C, the stirring time to 180 min, and the rotation speed to 3500 r / min.

[0037] Under stirring conditions, gradually add the prepared matrix solution dropwise to the electrolyte solution, and the ratio of the two is 10:1. After the dropping is completed, continue stirring to obtain a uniformly mixed gel electrolyte. Set the stirring time to 5 h.

[0038] Comparative Example 1

[0039] Add 1 g of polymethyl methacrylate (PMMA) and 15 g of hydroxypropyl cellulose (HPC) to 80 mL of polyethylene glycol (PEG), and disperse them under ultrasonic mixing for 20 min until the PMMA and HPC are evenly dispersed to obtain a matrix solution.

[0040] Add 1 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to a beaker containing 60 mL of a mixed solvent of carboxylic acid ester (EA) and PEG, where EA and PEG are mixed in a volume ratio of 1:8, and mix evenly under magnetic stirring to form a colorless transparent solution. Then cool it to room temperature to obtain an electrolyte solution. Set the temperature of magnetic stirring to 50 °C, the stirring time to 30 min, and the rotation speed to 500 r / min.

[0041] Under stirring conditions, gradually add the prepared matrix solution dropwise to the electrolyte solution, and the ratio of the two is 12:1. After the dropping is completed, continue stirring to obtain a uniformly mixed gel electrolyte. Set the stirring time to 0.5 h.

[0042] Comparative Example 2

[0043] Add 6 g of polyacrylonitrile (PAN) to 20 mL of polyethylene glycol (PEG), and disperse it under ultrasonic mixing for 30 min until evenly dispersed to obtain a matrix solution.

[0044] Add 2 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to 10 mL of N,N-dimethylformamide (DMF), and mix well under magnetic stirring to form a colorless transparent solution. Then cool it to room temperature to obtain an electrolyte solution. Set the temperature of magnetic stirring to 60 °C, the stirring time to 60 min, and the rotation speed to 2000 r / min.

[0045] Under stirring conditions, gradually add the prepared matrix solution dropwise to the electrolyte solution, and the ratio of the two is 2:1. After the addition is complete, continue stirring to obtain a uniformly mixed gel electrolyte. Set the stirring time to 1 h.

[0046] Comparative Example 3

[0047] Add 1 g of polymethyl methacrylate (PMMA) and 8 g of hydroxypropyl cellulose (HPC) to 40 mL of ethyl acetate (EA), and disperse for 30 min under ultrasonic mixing until PMMA and HPC are uniformly dispersed to obtain a matrix solution.

[0048] Add 2 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to a beaker containing 30 mL of ethyl acetate (EA) solvent, and mix well under magnetic stirring to form a colorless transparent solution. Then cool it to room temperature to obtain an electrolyte solution. Set the temperature of magnetic stirring to 60 °C, the stirring time to 60 min, and the rotation speed to 3500 r / min.

[0049] Under stirring conditions, gradually add the prepared matrix solution dropwise to the electrolyte solution, and the ratio of the two is 2:1. After the addition is complete, continue stirring to obtain a uniformly mixed gel electrolyte. Set the stirring time to 2 h.

[0050] The gel electrolytes obtained from the examples and comparative examples are used to fabricate electrochromic devices between the electrochromic layer and the ion storage layer for performance testing. The results are shown in Table 1. It can be seen that the gel electrolyte using the technical solution of the examples of the present invention has a high electrochemical window value, reaching more than 4 V, the color change time is within 5 s, the fading time is within 6 s, and the reaction is rapid. For Comparative Example 1, the ion conductivity of the mass ratio of polymethyl methacrylate (PMMA) to hydroxypropyl cellulose (HPC) being 1:15 is weaker than that of Example 1 and Example 2. For Comparative Example 2, because polyacrylonitrile (PAN) is used, although the ion conductivity is high, the color change time and the fading time are both very long and do not meet the requirements. For Comparative Example 3, because EA is used as the solvent, the cycle stability is poor, only 6400 times, lower than 10000 times of the examples. It can be seen that compared with the comparative examples, the examples have a higher electrochemical window value, shorter color change time and fading time, and a rapid reaction.

[0051] Table 1 Comparison of test results between examples and comparative examples

[0052]

[0053] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, and all should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for preparing a gel polymer electrolyte, characterized in that, Including: Step S1: Mix polymethyl methacrylate and cellulose in polyethylene glycol to make the polymethyl methacrylate and cellulose evenly dispersed, obtaining a matrix solution; wherein the mass ratio of polymethyl methacrylate to cellulose is 1:9 - 9:

1. Step S2: Add lithium bis(trifluoromethanesulfonyl)imide to a mixed solvent of carboxylic acid ester and polyethylene glycol, and mix evenly to obtain an electrolyte solution. Step S3: Mix the matrix solution and the electrolyte solution evenly to obtain a gel-state electrolyte; wherein, the total mass ratio of polymethyl methacrylate and cellulose to the mass of lithium bis(trifluoromethanesulfonyl)imide is 1 - 5:

1.

2. The preparation method of the gel polymer electrolyte according to claim 1, wherein, In step S1, ultrasonic mixing and dispersion are carried out for 30 - 90 min.

3. The preparation method of the gel polymer electrolyte according to claim 1, characterized in that, In step S1, the cellulose is carboxymethyl cellulose, hydroxyethyl cellulose or hydroxypropyl cellulose; the mass ratio of polymethyl methacrylate to cellulose is 1:9 - 9:

1.

4. The preparation method of the gel polymer electrolyte according to claim 1, characterized in that, In step S2, in the electrolyte solution, the concentration of lithium bis(trifluoromethanesulfonyl)imide is 0.05 - 0.8 g / mL.

5. The preparation method of the gel polymer electrolyte according to claim 1, characterized in that, In step S2, in the mixed solvent of carboxylic acid ester and polyethylene glycol, the volume ratio of carboxylic acid ester to polyethylene glycol is 1:5 - 5:

1.

6. The preparation method of the gel polymer electrolyte according to claim 5, characterized in that, In step S2, mix evenly by magnetic stirring, the stirring temperature is 60°C - 75°C, the stirring time is 60 - 180 min, and the rotation speed is 2000 - 3500 r / min.

7. The preparation method of the gel polymer electrolyte according to any one of claims 1 to 6, characterized in that, In step S3, the volume ratio of the matrix solution to the electrolyte solution is 2 - 10:

1.

8. The preparation method of the gel polymer electrolyte according to claim 7, characterized in that, In step S3, magnetic stirring is used for mixing, and the magnetic stirring time is 1 h - 5 h.

9. A gel polymer electrolyte, characterized in that, It is prepared by using the preparation method of the gel polymer electrolyte as described in any one of claims 1 - 8.

10. An electrochromic device, characterized in that, It includes an electrochromic layer, an ion storage layer and an electrolyte, the electrolyte is located between the electrochromic layer and the ion storage layer, and the electrolyte uses the gel polymer electrolyte as described in claim 9.

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