A low-temperature-resistant high-voltage aqueous electrolyte, a preparation method thereof, and its application in micro-supercapacitors

Abstract

The present application discloses a low-temperature-resistant, high-voltage aqueous electrolyte, a preparation method thereof, and its application in planar micro-supercapacitors. The low-temperature-resistant, high-voltage aqueous electrolyte comprises a solvent, water, and a solute, lithium bromide; the molar mass ratio of the lithium bromide to water is not less than 5 mol / Kg. In addition, a certain amount of coagulant can be added to form a low-temperature-resistant, high-voltage hydrogel electrolyte. The low-temperature-resistant, high-voltage aqueous electrolyte prepared by this method has the advantages of a wide voltage window, high ionic conductivity, low-temperature resistance, high safety, and has broad application prospects. The low-temperature-resistant, high-voltage aqueous electrolyte can improve the operating voltage, energy density, low-temperature resistance, and safety of aqueous planar micro-supercapacitors.

Description

Technical Field

[0001] The present invention belongs to the field of electrolyte preparation technology and electrochemical energy storage technology, and relates to a low-temperature resistant high-voltage aqueous electrolyte, a preparation method thereof, and an application in a planar micro supercapacitor. Background Art

[0002] Flexible planar micro-supercapacitors have attracted widespread attention from researchers due to their advantages such as light weight, high power density, and strong flexibility. They show great potential in the field of wearable electronic devices. In some cases, flexible planar energy storage devices need to operate in harsh environments, especially in extremely cold regions. Therefore, there is an urgent need to develop flexible planar micro-supercapacitors that can operate under low-temperature conditions. However, because traditional aqueous electrolytes easily freeze at sub-zero temperatures, resulting in insufficient electrolyte ion conductivity, flexible planar micro-supercapacitors with good low-temperature performance have not yet been realized.

[0003] The performance of aqueous electrolytes is one of the key factors affecting the electrochemical performance of flexible planar supercapacitors. Aqueous electrolytes have high conductivity and low cost, but their low decomposition voltage leads to a low electrochemical window for flexible planar supercapacitors, which greatly limits their application range. Furthermore, aqueous electrolytes tend to freeze and freeze at low temperatures, which also greatly restricts their application. Therefore, the development of new low-temperature and high-pressure aqueous electrolytes, and the development of new aqueous electrolytes with high conductivity, wide electrochemical window, and low-temperature resistance, is of great significance to promoting the industrial development of flexible planar supercapacitors that are resistant to low temperatures and high pressures. Summary of the Invention

[0004] The present invention provides a low-temperature-resistant and high-voltage aqueous electrolyte for preparing flexible planar micro supercapacitors.

[0005] The purpose of the present invention is to provide a low-temperature-resistant, high-voltage aqueous electrolyte, a preparation method thereof, and an application thereof. This low-temperature-resistant, high-voltage aqueous electrolyte has a wide voltage window, good low-temperature resistance and high safety, and is suitable for low-temperature-resistant, high-voltage, and high-safety aqueous supercapacitors.

[0006] Another object of the present invention is to provide an application of the low-temperature-resistant and high-voltage aqueous electrolyte provided in the first object above in a flexible planar micro-supercapacitor.

[0007] In one aspect of the present invention, a low-temperature-resistant, high-voltage aqueous electrolyte is provided, wherein the aqueous electrolyte comprises water and lithium bromide;

[0008] The molar mass ratio of the lithium bromide to water is not less than 5 mol / Kg.

[0009] Optionally, the low-temperature-resistant high-voltage aqueous electrolyte further comprises a coagulant, and a certain amount of the coagulant is added to form a low-temperature-resistant high-voltage hydrogel electrolyte.

[0010] Optionally, the coagulant is selected from at least one of polyvinyl alcohol, polyacrylonitrile, polyethylene glycol, polyethylene oxide, and silicon dioxide nanopowder.

[0011] Preferably, the coagulant is polyvinyl alcohol or silicon dioxide nanopowder.

[0012] Optionally, the molar mass ratio of lithium bromide to water is 10 to 20 mol / Kg;

[0013] Optionally, the upper limit of the molar mass ratio of lithium bromide to water can be independently selected from 12mol / Kg, 14mol / Kg, 16mol / Kg, 18mol / Kg, and 20mol / Kg; the lower limit can be independently selected from 10mol / Kg, 12mol / Kg, 14mol / Kg, 16mol / Kg, and 18mol / Kg.

[0014] Optionally, the mass ratio of the coagulant to water is 1:20 to 3:20;

[0015] Optionally, the upper limit of the molar mass ratio of the coagulant to water can be independently selected from 2:20 and 3:20; the lower limit can be independently selected from 1:20 and 2:20.

[0016] Optionally, the ionic conductivity of the low-temperature-resistant and high-voltage aqueous electrolyte is 1 mS / cm to 200 mS / cm.

[0017] In another aspect of the present application, a method for preparing the above-mentioned low-temperature-resistant and high-voltage aqueous electrolyte is provided, wherein the low-temperature-resistant and high-voltage aqueous electrolyte is obtained by mixing raw materials containing water and lithium bromide.

[0018] Optionally, the raw materials further include a coagulant;

[0019] Optionally, the method specifically includes the following steps: mixing lithium bromide with water, and then adding a coagulant and mixing.

[0020] The mixing temperature is 80-100°C; or the mixing is carried out at room temperature;

[0021] The lithium bromide and water were mixed at room temperature by magnetic stirring.

[0022] Another aspect of the present application provides a planar micro supercapacitor, which includes the above-mentioned low-temperature-resistant and high-voltage aqueous electrolyte or the low-temperature-resistant and high-voltage aqueous electrolyte obtained by the above-mentioned preparation method.

[0023] Another aspect of the present application provides a method for preparing the above-mentioned planar micro supercapacitor, the method comprising: coating the low-temperature-resistant high-voltage aqueous electrolyte on the surface of a flexible electrode to obtain the planar micro supercapacitor;

[0024] Optionally, the flexible electrode is an interdigitated electrode;

[0025] Optionally, the material of the interdigitated electrodes is selected from Ti3C2T x At least one of MXene and activated carbon.

[0026] Optionally, the method for preparing the interdigitated electrode includes:

[0027] Ti3C2T was synthesized by 3D printing x MXene ink is printed on polyethylene terephthalate (PET) to obtain flexible Ti3C2T x MXene interdigitated electrodes.

[0028] Optionally, the method for preparing the interdigitated electrode includes:

[0029] Activated carbon or porous carbon is filtered onto a filter membrane through a mask vacuum filtration method to obtain a flexible activated carbon cross-finger electrode.

[0030] As a specific embodiment, the preparation method of the hydrogel electrolyte includes:

[0031] Step A: using water as solvent, lithium bromide as solute, polyvinyl alcohol, polyacrylonitrile, polyethylene glycol, polyethylene oxide or silicon dioxide nanopowder as coagulant, and the molar mass ratio of solute to solvent is 10-20 mol / kg;

[0032] Step B: Weigh a certain amount of the solute, lithium bromide, into a certain amount of solvent water and dissolve thoroughly under magnetic stirring at room temperature to obtain a low-temperature, high-voltage aqueous electrolyte. Then, add a certain amount of a coagulant and thoroughly mix at room temperature using magnetic stirring and / or heating to obtain a low-temperature, high-voltage hydrogel electrolyte.

[0033] As a specific embodiment, the method for preparing the flexible planar micro supercapacitor includes:

[0034] Ti3C2T was synthesized by 3D printing x MXene ink is printed on PET to obtain flexible Ti3C2T x MXene microelectrodes. Activated carbon or porous carbon is filtered onto a filter membrane through a masked vacuum filtration method, creating flexible activated carbon microelectrodes. These are then coated with a low-temperature, high-voltage hydrogel electrolyte to form flexible planar microsupercapacitors.

[0035] The beneficial effects of this application include:

[0036] The low-temperature, high-voltage aqueous electrolyte provided in this application has high ionic conductivity, low melting point, wide voltage window, and high safety, and is suitable for low-temperature, high-voltage, and high-safety aqueous supercapacitors. In the application of the flexible planar micro-supercapacitor provided in this application, the low-temperature performance of the aqueous electrolyte can be improved by adopting the low-temperature, high-voltage aqueous electrolyte of this application, which can broaden the operating voltage window of the flexible planar micro-supercapacitor, thereby improving the electrochemical performance and application range of the aqueous flexible planar micro-supercapacitor, laying the foundation for the promotion and application of aqueous flexible planar micro-supercapacitors. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments.

[0038] Figure 1 Ti3C2T in Example 2 of the present invention x Electrochemical cyclic voltammetry curve of MXene planar micro-supercapacitor;

[0039] Figure 2 Ti3C2T in Example 2 of the present invention x Constant current charge and discharge curves of MXene planar micro supercapacitors at -40°C and 20°C;

[0040] Figure 3 Ti3C2T in Example 4 of the present invention x Electrochemical cyclic voltammetry curve of MXene planar micro-supercapacitor;

[0041] Figure 4 This is an electrochemical cyclic voltammetry curve of the activated carbon planar micro supercapacitor in Example 6 of the present invention;

[0042] Figure 5 Ti3C2T in Comparative Example 2 of the present invention x Electrochemical cyclic voltammetry curves of MXene planar micro-supercapacitors. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described below. In the embodiments, if specific conditions are not specified, the conditions according to normal conditions or manufacturer's recommendations are carried out. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased commercially. It should be understood by those skilled in the art that the content specifically described below is illustrative and non-restrictive, and should not be used to limit the scope of protection of the present invention. Below in conjunction with the examples, the features and performance of the present invention are further described in detail.

[0044] Example 1

[0045] The low-temperature, high-voltage aqueous electrolyte in this example is specifically composed of water as the solvent, lithium bromide as the solute, and silica powder as the coagulant. Its preparation method is as follows: 1.5633 grams of lithium bromide per gram of water (i.e., 18 mol / kg) is added. The lithium bromide is weighed and dissolved in water under magnetic stirring at room temperature to obtain the low-temperature, high-voltage aqueous electrolyte in this example. 0.1 g of silica nanopowder is then added and mixed uniformly at room temperature to obtain the low-temperature, high-voltage hydrogel electrolyte in this example. Its ionic conductivity, measured by a conductivity meter, is approximately 97 mS / cm.

[0046] Example 2

[0047] The low-temperature-resistant and high-voltage hydrogel electrolyte obtained in Example 1 was used in a flexible planar micro-supercapacitor. Ti3C2T x MXene ink was printed on PET with a printing gas flow rate of 25 psi and a printing speed of 4.5 mm / s. A 320 μm thick needle was used to print. The obtained Ti3C2T x MXene microelectrodes. A low-temperature, high-voltage hydrogel electrolyte was coated on the microelectrode finger area to assemble a planar micro-supercapacitor. The electrolyte was the low-temperature, high-voltage hydrogel electrolyte obtained in Example 1. Cyclic voltammetry was performed using an electrochemical workstation at room temperature with a scan rate of 5mV / s. The results are shown in the attached figure. Figure 1 As shown. It can be seen that the 3D printed Ti3C2T x The MXene planar micro-supercapacitor can achieve an operating voltage of 1.8 V at room temperature and an area capacitance of 473 mF cm -2 The constant current charge and discharge tests were performed using an electrochemical workstation at low temperatures of 20°C and -40°C, with a current density of 2 mA / cm 2 The results are as follows Figure 2 The results show that Ti3C2T x MXene planar micro-supercapacitors exhibit an operating voltage of up to 1.8 V and an area capacitance of up to 456 mF cm at 20°C. -2, with an energy density of up to 186 μW h cm -2 It still retains a high capacity at a low temperature of -40°C and maintains 75% of the capacity at 20°C, demonstrating excellent low-temperature performance.

[0048] Example 3

[0049] The low-temperature, high-voltage aqueous electrolyte in this example is composed of water as the solvent, lithium bromide as the solute, and silica powder as the coagulant. The preparation method is as follows: 0.8685 grams of lithium bromide per gram of water (10 mol / kg) is added, and the lithium bromide is weighed and fully dissolved in water to obtain the low-temperature, high-voltage aqueous electrolyte in this example. Then, 0.1 grams of silica nanopowder is added to obtain the low-temperature, high-voltage hydrogel electrolyte in this example. The ionic conductivity of the electrolyte, as measured by a conductivity meter, is approximately 187 mS / cm.

[0050] Example 4

[0051] The low-temperature-resistant and high-voltage hydrogel electrolyte obtained in Example 3 was used in a flexible planar micro-supercapacitor. Ti3C2T x MXene ink is printed on PET to obtain Ti3C2T x MXene microelectrodes. A low-temperature, high-voltage hydrogel electrolyte was coated on the microelectrode finger area to assemble a planar micro-supercapacitor. The electrolyte was the low-temperature, high-voltage aqueous electrolyte obtained in Example 3. Cyclic voltammetry was performed using an electrochemical workstation at 0-1.8V with a scan rate of 5mV / s. The results are shown in the attached figure. Figure 3 3D printed Ti3C2T x The operating voltage of MXene planar micro-supercapacitors can reach 1.6V.

[0052] Example 5

[0053] The low-temperature-resistant, high-voltage hydrogel electrolyte in this example is specifically composed of water as the solvent, lithium bromide as the solute, and polyvinyl alcohol as the coagulant. Its preparation method is as follows: 1.737 grams of lithium bromide is added to each gram of water (20 mol / kg). The lithium bromide is weighed and dissolved in water. Then, 0.1 g of polyvinyl alcohol is added. The solution is heated to 90°C and stirred until completely dissolved. The solution is then cooled naturally to obtain the low-temperature-resistant, high-voltage hydrogel electrolyte.

[0054] Example 6

[0055] The low-temperature-resistant and high-voltage hydrogel electrolyte obtained in Example 5 is used in a flexible planar micro-supercapacitor. The electrochemically stripped graphene ethanol solution is first filtered onto a nylon filter membrane by vacuum filtration through a mask plate, and then a layer of activated carbon (containing 10wt% electrochemically stripped graphene) ethanol solution is extracted. Finally, another layer of electrochemically stripped graphene ethanol solution is extracted. After being completely drained, a tablet press is used to apply a pressure of 20MPa to obtain a flexible activated carbon microelectrode. The low-temperature-resistant and high-voltage hydrogel electrolyte is coated on the microelectrode finger area to assemble a flexible planar micro-supercapacitor. The electrolyte is the low-temperature-resistant and high-voltage hydrogel electrolyte obtained in Example 5. Cyclic voltammetry tests were performed using an electrochemical workstation at room temperature with a scan rate of 50mV / s. The results are shown in the attached figure. Figure 4 As shown in Figure 2, it can be seen that the operating voltage of the activated carbon planar micro supercapacitor can reach 1.8V.

[0056] Comparative Example 1

[0057] The commonly used aqueous electrolyte in this example is specifically composed of water as the solvent, H₂SO₄ as the solute, and polyvinyl alcohol as the coagulant. Its preparation method is as follows: Add 5.4 mL of analytical grade concentrated sulfuric acid to a 100 mL constant volume flask, then add deionized water to 100 mL to obtain a 1 mol / L sulfuric acid solution. Then, add 10 g of polyvinyl alcohol, heat to 90°C, stir until completely dissolved, and allow to cool naturally to obtain the hydrogel electrolyte in this example.

[0058] Comparative Example 2

[0059] The hydrogel electrolyte obtained in Comparative Example 1 was used in a flexible planar micro supercapacitor, and Ti3C2T x MXene was filtered onto a filter membrane and then transferred to polyethylene terephthalate (PET) using a tablet press with a pressure of 20 MPa to obtain a flexible Ti3C2T x MXene microelectrodes were coated with aqueous electrolyte on the microelectrode finger area to assemble into flexible planar microsupercapacitors. Cyclic voltammetry was performed using an electrochemical workstation at room temperature with a scan rate of 50mV / s. The results are shown in the attached figure. Figure 5 As shown. It can be seen that Ti3C2T x The operating voltage of MXene planar micro-supercapacitors is only 0.6V.

[0060] The above descriptions are merely a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application discloses the preferred embodiments as above, they are not intended to limit the present application. Any technical personnel familiar with the present profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A low-temperature resistant high-voltage aqueous electrolyte, characterized in that: The aqueous electrolyte consists of water, lithium bromide and a coagulant; The molar mass ratio of the lithium bromide to water is not less than 5 mol / Kg; The coagulant is selected from at least one of polyvinyl alcohol, polyacrylonitrile, polyethylene glycol, polyethylene oxide, and silicon dioxide nanopowder; The ion conductivity of the low-temperature-resistant and high-voltage aqueous electrolyte is 1 mS / cm to 200 mS / cm.

2. The low-temperature resistant high-voltage aqueous electrolyte according to claim 1, characterized in that: The molar mass ratio of lithium bromide to water is 10 to 20 mol / kg; The mass ratio of the coagulant to water is 1:20 to 3:

20.

3. A method for preparing the low-temperature resistant high-voltage aqueous electrolyte according to claim 1 or 2, characterized in that: The low-temperature-resistant and high-voltage aqueous electrolyte is obtained by mixing water, lithium bromide and a coagulant.

4. The preparation method according to claim 3, characterized in that The specific steps include: The coagulant is mixed under heating conditions of 80-100°C.

5. The preparation method according to claim 3, characterized in that The lithium bromide and water are mixed by magnetic stirring.

6. A planar micro supercapacitor, characterized in that: The planar micro supercapacitor comprises the low-temperature-resistant and high-voltage aqueous electrolyte according to claim 1 or 2 or the low-temperature-resistant and high-voltage aqueous electrolyte obtained by the preparation method according to any one of claims 3 to 5.

7. A method for preparing a planar micro supercapacitor according to claim 6, characterized in that: The low-temperature-resistant and high-voltage aqueous electrolyte is coated on the surface of the flexible electrode to obtain the planar micro supercapacitor.

8. The method according to claim 7, characterized in that The flexible electrodes are interdigitated electrodes.

9. The method according to claim 8, characterized in that The material of the interdigitated electrodes is selected from Ti3C2T x At least one of MXene nanosheets, activated carbon, and porous carbon.

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