Preparation method and application of zinc ion supercapacitor high specific capacity hydrogel electrolyte

Abstract

The application discloses a preparation method and application of a zinc ion supercapacitor high specific capacity hydrogel electrolyte, solves the problems of low zinc ion migration rate and low electrolyte contribution to device specific capacity, and belongs to the field of electrochemical energy storage. Specifically, polyvinyl alcohol, a titanyl reagent, zinc ions and electrolyte salts are mixed in a certain proportion, a coordination complex is formed by the titanyl reagent and the zinc ions, the crosslinking effect of the zinc ions is reduced, the migration rate of the zinc ions is improved, meanwhile, the coordination complex can effectively participate in electrode reaction, and the specific capacity, coulombic efficiency and cycle stability of the supercapacitor are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage technology, and in particular to a method for preparing and applying a high-specific-capacitance hydrogel electrolyte for zinc-ion supercapacitors. Background Technology

[0002] In recent years, quasi-solid-state supercapacitors based on hydrogel electrolytes have attracted widespread attention. However, the energy density of currently reported supercapacitors is limited and requires further improvement. The electrolyte, as a key component of quasi-solid-state supercapacitors, has significantly improved performance by introducing additional Faraday reactions through the addition of redox active materials, thereby increasing the energy density of the device. Due to the volatility and potential leakage issues of aqueous electrolytes, adding redox additives to aqueous electrolytes is unsuitable as an electrolyte for energy storage devices in wearable electronic devices. Hydrogels, with their excellent flexibility, good mechanical properties, and high ionic conductivity, show great promise as electrolytes for quasi-solid-state supercapacitors. Traditional supercapacitors are typically fabricated using symmetrical electrodes, which limits their energy density. Here, we combine a battery with a supercapacitor to prepare a hybrid supercapacitor. The battery exhibits high energy density, reasonable cycle life, and moderate power density. In contrast, the supercapacitor has higher power density and longer cycle life, but its energy density is far lower than that of the battery. The energy of supercapacitors is primarily stored in the electric double-layer capacitance (EDLC) at the electrode / electrolyte interface or in surface-controllable Faraday redox pseudocapacitance, and exhibits rapid ion diffusion. Zinc-ion supercapacitors combine some advantages of both batteries and supercapacitors, including long cycle life and high rate performance. Therefore, designing a device that combines the advantages of supercapacitors and batteries holds great promise.

[0003] Hydrogels, due to their softness and unique porous structure, show great promise in the fabrication of high-performance supercapacitor electrolytes and separators. Generally, adding variable-valence metal ions and electrochemically active organic compounds to the electrolyte, utilizing the redox reactions of these active substances on the electrode surface, can improve the specific capacitance of supercapacitors. Unfortunately, the addition of redox additives to hydrogels can limit ion or redox additive transport due to potential ionic crosslinking and hydrogen bonding interactions with the matrix. This results in limited contribution of redox active additives to device capacity and poor cycle stability. In zinc-ion supercapacitors, zinc ions act as charge carriers; however, in hydrogel electrolytes, zinc ions can undergo ionic crosslinking with the hydrogel matrix, limiting their efficient migration. Therefore, improving the migration rate of zinc ions in hydrogel electrolytes while simultaneously increasing the energy storage contribution of the hydrogel electrolyte remains a pressing technical challenge. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes introducing phenolic compounds and zinc ions into a hydrogel electrolyte. By utilizing the coordination effect between phenolic compounds and zinc ions, the migration rate of zinc ions in the hydrogel is improved. Simultaneously, by utilizing the electrochemical activity of the complex, the specific capacitance, coulombic efficiency, and cycle stability of the zinc ion supercapacitor are improved through the Faraday reaction of the complex on the electrode surface.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] First, phenolic compounds, zinc ions, electrolyte salts, and polyvinyl alcohol are added to water in a certain proportion, heated and stirred to dissolve, resulting in a viscous and transparent mixed solution. Then, the solution is placed in a glass mold and subjected to repeated freeze-thaw cycles at -20℃ and room temperature three times to obtain a high specific capacity hydrogel electrolyte. This provides an application of zinc-ion batteries assembled with zinc sheets as the anode and laser-written graphene as the cathode, using a sandwich structure.

[0007] A method for preparing and applying a high-specific-capacitance hydrogel electrolyte for zinc-ion supercapacitors is characterized by including the preparation of the high-specific-capacitance hydrogel electrolyte and its application in zinc-ion supercapacitors, as detailed below:

[0008] a. Preparation of high specific volume hydrogel electrolytes

[0009] Phenolic compounds, zinc ions and electrolyte salts in different proportions were dissolved in water and mixed evenly. A certain amount of polyvinyl alcohol was added, and the mixture was heated and stirred to dissolve, resulting in a viscous and transparent mixed solution. The solution was then placed in a glass mold and repeatedly frozen and thawed three times at -20℃ / room temperature to obtain a high specific volume hydrogel electrolyte.

[0010] b. Applications in zinc-ion supercapacitors

[0011] Using zinc sheets as the anode and laser-written graphene as the cathode, a high-capacitance hydrogel electrolyte is sandwiched between the anode and cathode to assemble a zinc-ion supercapacitor, which is then encapsulated with a plastic film. Figure 1 As shown, its electrochemical performance was tested.

[0012] The zinc ions mentioned are either zinc chloride or zinc sulfate.

[0013] The molar ratio of the phenolic compound to zinc ions is 3:1 to 1:3.

[0014] The electrolyte salt is any one of potassium chloride, sodium chloride, sodium perchlorate, and potassium perchlorate, with a concentration of 0.1 to 1 mol / L.

[0015] The mass ratio of polyvinyl alcohol to water is 1:10-15.

[0016] The heating temperature is between 45 and 95°C.

[0017] The freeze-thaw cycle consists of freezing for 12 hours and thawing at room temperature for 1 hour.

[0018] The zinc-ion supercapacitor also includes a current collector.

[0019] The advantages of this invention are:

[0020] (1) The hydrogel electrolyte preparation strategy provided by the present invention has the advantages of being simple, green and environmentally friendly.

[0021] (2) The optimized combination of phenolic compounds and zinc ions reduced the cross-linking effect of zinc ions and improved the migration rate of zinc ions.

[0022] (3) Phenolic compounds and zinc ion complexes participate in the electrode reaction, providing pseudocapacitance contribution and significantly improving the specific capacitance, coulombic efficiency and cycle stability of zinc ion supercapacitors. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly described below.

[0024] Figure 1 This is a schematic diagram of the structure of the supercapacitor provided in Embodiment 1 of the present invention, wherein the upper layer is marked as a zinc sheet (anode), the middle layer is a hydrogel (electrolyte), and the lower layer is a graphene electrode (cathode).

[0025] Figure 2 The cyclic voltammetry curve of the supercapacitor provided in Embodiment 1 of the present invention was measured at a scan rate of 10 mV / s.

[0026] Figure 3 The supercapacitor provided in Embodiment 1 of this invention has a current rating of 1 mA / cm². -2 Constant current charge-discharge curves at current density. Detailed Implementation

[0027] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0028] Example 1.

[0029] a. Preparation of high specific volume hydrogel electrolytes

[0030] Add 0.19g of ferrotitanium reagent, 0.24g of zinc chloride, and 1.22g of sodium perchlorate to 20ml of deionized water and stir to dissolve for 20min. Then, add 2g of polyvinyl alcohol and heat and stir at 90℃ for 1h to obtain a viscous and transparent hydrogel solution. Finally, pour the cooled solution onto a clean glass plate, cover it with a lid, clamp it with clips, and place it vertically. After the air bubbles disappear, freeze it at -20℃ to solidify. Take it out every 12h for thawing and repeat 3 times to obtain a high specific volume hydrogel electrolyte.

[0031] b. Applications in zinc-ion supercapacitors

[0032] The specific preparation method for electrode materials is as follows:

[0033] 1) Wipe the polyimide film with anhydrous ethanol and fix it on a steel substrate, then dry it at room temperature for 5 minutes. Then place it under a laser with a wavelength of 450nm and a power of 3.5W for laser direct writing to prepare a graphene electrode. After cleaning and drying, the graphene electrode is used as a cathode material, and conductive silver paste is coated on its top to obtain the cathode material.

[0034] 2) Cut a 1×1cm zinc sheet, grind its surface to remove surface oxides, and obtain the anode material.

[0035] The fabrication process of a zinc-ion supercapacitor based on hydrogel electrolyte is as follows:

[0036] 1) The prepared hydrogel is coated onto the prepared graphene electrode, and a zinc sheet is used as the other electrode. The hydrogel electrolyte also acts as a membrane, such as... Figure 1 As shown.

[0037] 2) Simply press the supercapacitor and encapsulate it with a plastic film.

[0038] Comparative Example 1

[0039] 0.24 g of zinc chloride and 1.22 g of sodium perchlorate were added to 20 ml of deionized water and stirred for 20 min to dissolve. Then, 2 g of polyvinyl alcohol was added, and the mixture was heated and stirred at 90 °C for 1 h to obtain a viscous and transparent hydrogel solution. Finally, the cooled solution was poured onto a clean glass plate, covered, clamped, and placed vertically. After the air bubbles disappeared, it was frozen at -20 °C to solidify. The solution was thawed every 12 h, and this process was repeated 3 times to obtain a blank hydrogel electrolyte. Zinc ion supercapacitors were assembled using the same method as in Example 1.

[0040] The prepared zinc-ion supercapacitor was subjected to cyclic voltammetry and constant current charge-discharge tests, and the results are as follows: Figure 2 and Figure 3 As shown. Figure 2 The cyclic voltammetry results showed that the zinc ion supercapacitor in Comparative Example 1 exhibited double-layer capacitance characteristics, while the zinc ion supercapacitor in Example 1 showed obvious redox peaks on its cyclic voltammetry curve, corresponding to the redox reaction between phenolic compounds and zinc ion coordination complexes. Figure 2 In the constant current charge-discharge curve, the specific capacitance of the comparative zinc-ion supercapacitor is 1.63 mF / cm². -2 The specific capacitance of the zinc-ion supercapacitor in Example 1 is 41 mF / cm². -2 It is 25 times that of Comparative Example 1.

[0041] Example 2.

[0042] The specific process for preparing the hydrogel electrolyte used is as follows:

[0043] 1) Pour catechol, zinc sulfate and sodium perchlorate into an Erlenmeyer flask in a mass ratio of 0.1g:0.24g:1.22g, add 20ml of deionized water, and stir on a magnetic stirrer for 20min.

[0044] 2) Add a certain amount of polyvinyl alcohol to the above-prepared mixed solution, seal it with plastic wrap (to prevent moisture evaporation), and then stir and heat it at 90°C for 1 hour on a heat-collecting constant temperature magnetic stirrer to obtain a viscous and transparent hydrogel solution.

[0045] 3) Pour the cooled solution onto a glass plate that has been cleaned with deionized water, cover it with a lid, clamp it tightly, and place it vertically. After the air bubbles disappear, put it in the refrigerator to freeze and solidify. Take it out every 12 hours for thawing, and repeat 3 times.

[0046] 4) Cut the soaked hydrogel into 1×1cm pieces, blot the solution off the surface of the hydrogel with filter paper, and it can then be used as an electrolyte.

[0047] The specific preparation method for electrode materials is as follows:

[0048] 1) Wipe the polyimide film with anhydrous ethanol and fix it on a steel substrate, then dry it at room temperature for 5 minutes. Then place it under a laser with a wavelength of 450nm and a power of 3.5W for laser direct writing to prepare a graphene electrode. After cleaning and drying, the graphene electrode is used as a cathode material, and conductive silver paste is coated on its top to obtain the cathode material.

[0049] 2) Cut zinc sheets to a certain size, grind their surface to remove surface oxides, and obtain the anode material;

[0050] The fabrication process of a supercapacitor based on hydrogel electrolyte is as follows:

[0051] 1) The prepared hydrogel is covered onto the previously prepared graphene electrode, and a zinc sheet is used as the other electrode. The hydrogel electrolyte also acts as a membrane.

[0052] 2) Simply press the supercapacitor and encapsulate it with a plastic film.

[0053] Thus, the zinc ion hybrid supercapacitor with zinc ion-phenol coordination complex doped hydrogel as electrolyte is successfully prepared.

[0054] Example 3.

[0055] The specific process for preparing the hydrogel electrolyte used is as follows:

[0056] 1) Pour phloroglucinol, zinc chloride and sodium perchlorate into an Erlenmeyer flask in a mass ratio of 0.16g:0.09g:1.22g, add 20ml of deionized water, and stir on a magnetic stirrer for 20min.

[0057] 2) Add a certain amount of polyvinyl alcohol to the above-prepared mixed solution, seal it with plastic wrap (to prevent moisture evaporation), and then stir and heat it at 90°C for 1 hour on a heat-collecting constant temperature magnetic stirrer to obtain a viscous and transparent hydrogel solution.

[0058] 3) Pour the cooled solution onto a glass plate that has been cleaned with deionized water, cover it with a lid, clamp it with a clip, and place it vertically. After the air bubbles disappear, put it in the refrigerator to freeze and solidify. Take it out every 12 hours for thawing, and repeat 3 times.

[0059] 4) Cut the soaked hydrogel into 1×1cm pieces, blot the solution off the surface of the hydrogel with filter paper, and it can then be used as an electrolyte.

[0060] The specific preparation method for electrode materials is as follows:

[0061] 1) Wipe the polyimide film with anhydrous ethanol and fix it on a steel substrate, then dry it at room temperature for 5 minutes. Then place it under a laser with a wavelength of 450nm and a power of 3.5W for laser direct writing to prepare a graphene electrode. After cleaning and drying, the graphene electrode is used as a cathode material, and conductive silver paste is coated on its top to obtain the cathode material.

[0062] 2) Cut zinc sheets to a certain size, grind their surface to remove surface oxides, and obtain the anode material;

[0063] The fabrication process of a supercapacitor based on hydrogel electrolyte is as follows:

[0064] 1) The prepared hydrogel is covered onto the previously prepared graphene electrode, and a zinc sheet is used as the other electrode. The hydrogel electrolyte also acts as a membrane.

[0065] 2) Simply press the supercapacitor and encapsulate it with a plastic film.

[0066] Thus, the zinc ion hybrid supercapacitor with zinc ion-phenol coordination complex doped hydrogel as electrolyte is successfully prepared.

Claims

1. A method for preparing and applying a high-specific-capacitance hydrogel electrolyte for zinc-ion supercapacitors, characterized in that, This includes the preparation of high-specific-capacity hydrogel electrolytes and their application in zinc-ion supercapacitors, as detailed below: a. Preparation of high specific volume hydrogel electrolytes Different proportions of titanium iron reagent, zinc ions and electrolyte salts were dissolved in water and mixed evenly. A certain amount of polyvinyl alcohol was added, and the mixture was heated and stirred to dissolve, resulting in a viscous and transparent mixed solution. The solution was then placed in a glass mold and repeatedly frozen and thawed three times at -20℃ / room temperature to obtain a high specific volume hydrogel electrolyte. b. Applications in zinc-ion supercapacitors Using zinc sheet as the anode and laser-written graphene as the cathode, a high-specific-capacitance hydrogel electrolyte was sandwiched between the anode and cathode to assemble a zinc-ion supercapacitor, which was then encapsulated with a plastic film to test its electrochemical performance.

2. According to claim 1, the characteristic is that, The zinc ions mentioned are either zinc chloride or zinc sulfate.

3. According to claim 1, the characteristic is that, The phenolic compound is any one of titanium iron reagent, catechol, and phloroglucinol.

4. According to claim 1, the characteristic is that, The molar ratio of the phenolic compound to zinc ions is 3:1 to 1:

3.

5. According to claim 1, the characteristic is that, The electrolyte salt is any one of potassium chloride, sodium chloride, sodium perchlorate, and potassium perchlorate, with a concentration of 0.1 to 1 mol / L.

6. According to claim 1, the characteristic is that, The mass ratio of polyvinyl alcohol to water is 1:10-15.

7. According to claim 1, the characteristic is that, The heating temperature is between 45 and 95°C.

8. According to claim 1, the characteristic is that, The freeze-thaw cycle consists of freezing for 12 hours and thawing at room temperature for 1 hour.

9. According to claim 1, the characteristic is that, The zinc-ion supercapacitor also includes a current collector.

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