Preparation method and application of chitosan-based composite organic ionic liquid gel electrolyte

Abstract

The application provides a preparation method and application of a chitosan-based composite organic ionic liquid gel electrolyte; the method is prepared by using a mixed solution of an ionic liquid and an organic solvent as an electrolyte solvent, using chitosan as a high polymer, and adding inorganic nanoparticles. The gel electrolyte can be widely applied in supercapacitors. The application has the characteristics of low preparation cost, wide applicable temperature range of the electrolyte, high ionic conductivity and good mechanical properties; in addition, the preparation process is simple and easy to popularize in industry.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method and application of an electrolyte, in particular to a preparation method and application of a chitosan-based composite organic ionic liquid gel electrolyte and application. BACKGROUND

[0002] With the rapid development of electronic technology, the design and preparation of flexible energy storage devices have attracted extensive attention in academic and industrial fields. Among them, supercapacitors have fast charging and discharging capacity and long cycle life, and can be widely used in consumer electronics, emergency power supply, electric vehicles and other fields.

[0003] The electrolyte is one of the important components of the supercapacitor. At present, liquid electrolyte has been widely used due to its high conductivity, but it also has problems such as liquid leakage, electrode corrosion, packaging difficulty, self-discharge and difficulty in designing different shapes. Gel electrolyte not only overcomes the above shortcomings of liquid electrolyte, but also is easy to process, has certain mechanical strength and conductivity, and shows broad application prospects. Therefore, based on the comprehensive consideration of safety, flexibility and other aspects, using gel electrolyte instead of liquid electrolyte is one of the key research directions for the development of flexible supercapacitors. Among the many types of gel electrolytes, ionic liquid gel electrolyte has outstanding energy storage performance and is the best choice for flexible supercapacitor electrolyte.

[0004] Traditionally, polyolefin polymers based on petroleum chemicals (such as polyacrylamide) are widely designed for the skeleton material of gel electrolyte, but have disadvantages such as non-renewable. Using natural polymers with abundant reserves, wide sources and renewable in nature as polymer materials for constructing gel electrolyte has attracted more and more interest. Among them, chitosan is a linear polysaccharide mainly derived from marine biomass resources such as shrimp shells and crab shells, and a large number of amino and hydroxyl groups in its molecular chain provide great opportunities for its derivatization or construction of multiple hydrogen bonds with other components, so it is expected to be used in flexible gel electrolyte. However, due to the highly ordered structure of chitosan and the strong intermolecular and intramolecular hydrogen bonds, its practical application in the field of energy storage is limited. Ionic liquid has excellent solubility for chitosan, which provides an effective way for preparing chitosan ionic liquid gel electrolyte based on ionic liquid platform.

[0005] However, ionic liquids are usually expensive and have low ionic conductivity at low temperature, which limits their application at low temperature. SUMMARY

[0006] The purpose of the present application is to provide a preparation method and application of a chitosan-based composite organic ionic liquid gel electrolyte. The present application has the characteristics of low preparation cost, wide temperature range of electrolyte, high ionic conductivity and good mechanical properties. In addition, the preparation process of the present application is simple and easy to industrialize.

[0007] The technical scheme of the present application is a preparation method of a chitosan-based composite organic ionic liquid gel electrolyte, which uses a mixed solution of an ionic liquid and an organic solvent as an electrolyte solvent, uses chitosan as a high polymer, and is prepared by adding inorganic nanoparticles.

[0008] The aforementioned preparation method of the chitosan-based nanocomposite organic ionic liquid gel electrolyte comprises the following steps:

[0009] 1) adding inorganic nanoparticles into an electrolyte solvent composed of an ionic liquid and an organic solvent, and uniformly dispersing;

[0010] 2) adding chitosan into the solution obtained in step 1), and stirring to dissolve the chitosan;

[0011] 3) transferring the solution obtained in step 2) to a mold for gelation treatment, thereby obtaining the chitosan-based nanocomposite organic ionic liquid gel electrolyte.

[0012] The aforementioned preparation method of the chitosan-based nanocomposite organic ionic liquid gel electrolyte, wherein the degree of deacetylation of the chitosan is 50%-100%, and the chemical structural formula is shown as formula (I):

[0013]

[0014] wherein 50 < n < 1000.

[0015] The aforementioned preparation method of the chitosan-based nanocomposite organic ionic liquid gel electrolyte, wherein the inorganic nanoparticles are one or more of silica, montmorillonite, attapulgite, halloysite, titanium dioxide, aluminum oxide, calcium carbonate, or aluminum nitride in any ratio.

[0016] The aforementioned preparation method of the chitosan-based nanocomposite organic ionic liquid gel electrolyte, wherein the ionic liquid is one of the following structures:

[0017]

[0018] The aforementioned preparation method of the chitosan-based nanocomposite organic ionic liquid gel electrolyte, wherein the organic solvent is one or two or more of dimethyl sulfoxide, N-methyl pyrrolidone, γ-butyrolactone, γ-valerolactone, γ-hexalactone, N,N-dimethyl imidazolidinone, N,N-dimethyl formamide, N,N-dimethyl acetamide, N,N-diethyl acetamide, 2-pyrrolidone, 2-azepanone, propylene carbonate, or sulfolane in any mixture.

[0019] The preparation method of the aforementioned chitosan-based nanocomposite organic ionic liquid gel electrolyte, in step 1), the molar ratio of the ionic liquid and the organic solvent is any ratio, and the mass concentration of the inorganic nanoparticles in the solution system is 0.1-20 wt%; after the chitosan is added in step 2), the mass concentration of the chitosan in the solution is 1-16 wt%, the dissolving temperature is 60-150 DEG C, and the dissolving time is 0.5-24 h.

[0020] The preparation method of the aforementioned chitosan-based nanocomposite organic ionic liquid gel electrolyte, in step 3), the gelation treatment is carried out at a temperature of 0-60 DEG C and a humidity of 10-100% for 1-96 h.

[0021] A gel electrolyte prepared by the aforementioned method.

[0022] The application of a gel electrolyte prepared by the aforementioned method in a supercapacitor.

[0023] Advantages

[0024] The present application uses chitosan as a high polymer raw material, which has the advantages of wide source and renewability. The gel electrolyte prepared by the method of the present application has the following advantages:

[0025] (1) The present application adds an organic solvent to the ionic liquid to form a mixed solvent, and compared with a pure ionic liquid solvent, the solvent system of the present application has a lower cost.

[0026] (2) The present application adds a low-melting-point organic solvent to the ionic liquid, which can reduce the melting point and viscosity of the entire electrolyte system, improve the ionic conductivity of the chitosan ionic liquid gel electrolyte at high and normal temperatures, and also improve the ionic conductivity of the chitosan ionic liquid gel electrolyte at low temperatures, so that the chitosan ionic liquid gel electrolyte has a wider applicable temperature range.

[0027] (3) The organic solvent of the present application serves as a solvent for chitosan and also as an electrolyte for the gel electrolyte, and does not need to be removed during preparation, which further reduces the cost of the chitosan ionic liquid gel electrolyte.

[0028] (4) The present application adds inorganic nanoparticles to the chitosan ionic liquid gel electrolyte, and through the hydrogen bonding between the inorganic nanoparticles and the chitosan, the mechanical properties of the gel electrolyte are improved, and the ionic conductivity of the gel electrolyte is further improved.

[0029] (5) The inorganic nanoparticles of the present application only need to be simply physically blended with the solvent system and the chitosan to achieve the purpose of improving the mechanical properties and the ionic conductivity, and the preparation method is simple and conducive to industrialized popularization and implementation. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 SEM spectrum of the chitosan-based nanocomposite organic ionic liquid gel electrolyte prepared in Example 1, from which it can be seen that the gel electrolyte has a porous structure, providing a transmission path for ions;

[0031] Figure 2 VTF curve of the ionic conductivity of the chitosan-based nanocomposite organic ionic liquid gel electrolyte prepared in Example 1 with respect to temperature, the ionic conductivity gradually increases with increasing temperature. The calculated activation energy is 9.98 kJ / mol;

[0032] Figure 3 Cyclic voltammograms of the supercapacitor assembled from the chitosan-based nanocomposite organic ionic liquid gel electrolyte prepared in Example 1 and an activated carbon electrode at different scanning frequencies, at different scanning frequencies, the curves all exhibit ideal quasi-rectangular double-layer behavior;

[0033] Figure 4 Constant current charge-discharge curves of the supercapacitor assembled from the chitosan-based nanocomposite organic ionic liquid gel electrolyte prepared in Example 1 and an activated carbon electrode at different current densities, all maintain an isosceles triangle at different current densities, indicating that no redox reaction occurs during the charge-discharge process, and the supercapacitor has good double-layer behavior;

[0034] Figure 5 Cycling stability results of the supercapacitor assembled from the chitosan-based nanocomposite organic ionic liquid gel electrolyte prepared in Example 1 and an activated carbon electrode in a wide temperature range (-25-80℃), after continuous reversible temperature changes, the specific capacitance at 25℃ is almost the same as the initial value, proving that the prepared supercapacitor has good cycling stability in a wide temperature range;

[0035] Figure 6 Working state curves of the supercapacitor assembled from the chitosan-based nanocomposite organic ionic liquid gel electrolyte prepared in Example 1 and an activated carbon electrode at different bending angles, the curves are basically coincident, indicating that the supercapacitor has flexibility. DETAILED DESCRIPTION

[0036] The following further describes the described method of the present application through specific examples, but is not limited to the content of the present application.

[0037] Example 1:

[0038] (1) 0.2 g of silica nanoparticles was added to an organic electrolyte solvent composed of 1-ethyl-3-methylimidazole acetate (6.3 g) and γ-valerolactone (3.7 g), and a uniform dispersion system was obtained by ultrasonic treatment for 2 hours;

[0039] (2) 0.8 g of chitosan with a deacetylation degree of 100% was added, and chitosan was dissolved by mechanical stirring at 90°C for 3 hours;

[0040] (3) The above solution was transferred to a mold, and gelling was performed at a humidity of 65% and a temperature of 30°C for 48 hours to obtain a gel.

[0041] Example 2:

[0042] According to the procedure of Example 1, 0.1 g of silica nanoparticles was added to an organic electrolyte solvent composed of 1-ethyl-3-methylimidazole acetate (6.3 g) and γ-valerolactone (3.7 g), and a uniform dispersion system was obtained by ultrasonic treatment for 0.5 hours; then 1.6 g of chitosan with a deacetylation degree of 90% extracted from crab shells was added, and chitosan was dissolved by mechanical stirring at 150°C for 0.5 hours; the above solution was transferred to a mold, and gelling was performed at a humidity of 10% and a temperature of 20°C for 96 hours to obtain a gel.

[0043] Example 3:

[0044] According to the procedure of Example 1, 2 g of silica nanoparticles was added to an organic electrolyte solvent composed of 1-butyl-3-methylimidazole acetate (6.3 g) and γ-valerolactone (3.7 g), and a uniform dispersion system was obtained by ultrasonic treatment for 5 hours; then 0.1 g of chitosan with a deacetylation degree of 80% extracted from the mycelium of Pleurotus ostreatus was added, and chitosan was dissolved by mechanical stirring at 60°C for 24 hours; the above solution was transferred to a mold, and gelling was performed at a humidity of 100% and a temperature of 60°C for 1 hour to obtain a gel.

[0045] Example 4:

[0046] According to the procedure of Example 1, 0.5 g of attapulgite was added to an organic electrolyte solvent composed of 1-allyl-3-methylimidazole chloride (5.0 g) and dimethyl sulfoxide (5.0 g), and a uniform dispersion system was obtained by ultrasonic treatment for 2 hours; then 1 g of chitosan with a deacetylation degree of 70% extracted from silkworm chrysalis was added, and chitosan was dissolved by mechanical stirring at 100°C for 4 hours; the above solution was transferred to a mold, and gelling was performed at a humidity of 80% and a temperature of 0°C for 96 hours to obtain a gel.

[0047] Example 5:

[0048] By the procedure of Example 1, 0.9 g of aluminum oxide nanoparticles was weighed into an organic electrolyte solvent consisting of 1-butyl-3-methylimidazolium chloride (3.0 g) and propylene carbonate (7.0 g) and sonicated for 5 hours to obtain a homogeneous dispersion; 1 g of chitosan extracted from silkworm pupa with a deacetylation degree of 60% was then added and mechanically stirred at 120 °C for 5 hours to dissolve the chitosan; the above solution was transferred into a mold and gelled at a humidity of 100% and a temperature of 10 °C for 60 hours to obtain a gel.

[0049] Example 6

[0050] 0.01 g of silicon dioxide nanoparticles was weighed into an organic electrolyte solvent consisting of 1-ethyl-3-methylimidazolium chloride (2 g) and γ-butyrolactone (8 g) and sonicated for 2 hours to obtain a homogeneous dispersion; 0.8 g of chitosan extracted from shrimp shells with a deacetylation degree of 50% was then added and mechanically stirred at 90 °C for 3 hours to dissolve the chitosan; the above solution was transferred into a mold and gelled at a humidity of 80% and a temperature of 50 °C for 12 hours to obtain a gel.

Claims

1. A method for preparing a chitosan-based composite organic ionic liquid gel electrolyte, characterized by, The method comprises the following steps: 1) adding inorganic nanoparticles into an electrolyte solvent composed of ionic liquid and organic solvent, and uniformly dispersing; 2) adding chitosan into the solution obtained in step 1), and stirring to dissolve the chitosan; 3) transferring the solution obtained in step 2) to a mold for gelation treatment, thereby obtaining a chitosan-based nanocomposite ionic liquid gel electrolyte; The degree of deacetylation of the chitosan is 50%-100%, and the chemical structural formula is shown as formula (I): （I）； wherein 50 < n < 1000; The ionic liquid is one of the following structures: ； The gelation treatment in step 3) is gelation for 1-96 h under the environment of temperature 0-60 ℃ and humidity 10-100%; The inorganic nanoparticles are one or more of silica, montmorillonite, attapulgite, halloysite, titanium dioxide, aluminum oxide, calcium carbonate or aluminum nitride in any ratio; dimethylsulfoxide, N - methylpyrrolidone, γ - butyrolactone, γ - valerolactone, γ - caprolactone, N, N - dimethylimidazolidinone, N,N - dimethylformamide, N,N - dimethylacetamide, N,N - diethylacetamide, 2-pyrrolidone, 2-azahexanone, propylene carbonate or sulfolane.

2. The method for preparing a chitosan-based nanocomposite organic ionic liquid gel electrolyte according to claim 1, characterized by: The molar ratio of the ionic liquid and the organic solvent in step 1) is any ratio, and the mass concentration of the inorganic nanoparticles in the solution system is 0.1-20 wt%; after adding the chitosan in step 2), the mass concentration of the chitosan in the solution is 1-16 wt%, the dissolving temperature is 60-150 ℃, and the dissolving time is 0.5-24 h.

3. A gel electrolyte prepared by the method according to any one of claims 1-2.

4. Application of the gel electrolyte prepared by the method according to any one of claims 1-2 in supercapacitors.

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