High-voltage-resistant gel polymer electrolyte for supercapacitor and preparation method and application of high-voltage-resistant gel polymer electrolyte

Abstract

The invention discloses a high-voltage-resistant gel polymer electrolyte for a supercapacitor and a preparation method and application thereof, and belongs to the technical field of supercapacitors. In the electrolyte, the high-pressure-resistant additive, the auxiliary additive, the lithium salt and the mixed solvent are reasonably matched. The high-pressure-resistant additive contains two key functional groups, namely trifluorosulfonyloxy and cyano, so that a stable multifunctional protective layer can be constructed on the interface of the positive electrode and the negative electrode, and the problem of interface degradation is solved. According to the preparation method, additives and lithium salt are added step by step, a cross-linked structure is finally formed on the surface of the electrode in situ, the binding force of the electrolyte and the electrode is enhanced, and smooth ion transmission is guaranteed. When the composite material is applied to preparation of a supercapacitor, the performance and stability of the supercapacitor under a high-voltage working condition can be improved, the energy density and the power density are improved, the service life is prolonged, the requirement of the market for the high-performance supercapacitor is met, and technical development and application of the supercapacitor are promoted.

Description

Technical Field

[0001] This invention belongs to the field of supercapacitor technology, specifically relating to a high-voltage resistant gel polymer electrolyte for supercapacitors, its preparation method, and its application. Background Technology

[0002] With the rapid development of new energy storage technologies, supercapacitors have attracted much attention due to their high power density and long cycle life. However, traditional liquid electrolytes are typically composed of organic solvents and electrolyte salts, and these organic solvents are highly volatile. During the use of supercapacitors, especially in high-temperature environments, the organic solvents gradually evaporate, causing changes in electrolyte concentration. This not only affects the performance stability of the supercapacitor, causing fluctuations in parameters such as capacitance and internal resistance, but also, after long-term use, the evaporation problem can lead to electrolyte desiccation, causing the supercapacitor to fail completely and cease normal operation. Secondly, most organic solvents are flammable substances. If the internal temperature of the supercapacitor rises due to overcharging, over-discharging, short circuits, or mechanical damage, it can easily lead to combustion or even explosion. Thirdly, during the production, transportation, and use of supercapacitors, if the packaging is not airtight or if they are subjected to external impact, the liquid electrolyte may leak out. Leaked electrolyte not only pollutes the environment, causing long-term adverse effects on soil and water sources, but may also corrode and damage surrounding electronic equipment and other materials, affecting the normal operation and lifespan of the equipment. In addition, traditional liquid electrolytes are highly corrosive. It corrodes the electrode materials, current collectors, and casing of supercapacitors. Over time, corrosion leads to structural damage to the electrode materials, decreased conductivity of the current collectors, and poorer casing sealing, gradually reducing the performance of these components and shortening the lifespan of the supercapacitor. These problems become even more pronounced under high-voltage conditions.

[0003] To overcome the aforementioned bottlenecks in traditional liquid electrolyte supercapacitors, researchers have turned their attention to novel solid-state electrolyte materials. Among these, gel polymer electrolytes, as a novel solid-state electrolyte material, have become a research hotspot in the high-voltage field. Firstly, gel polymer electrolytes lock in the electrolyte through a polymer network structure, preserving high ionic conductivity while eliminating the safety hazards of liquid electrolytes. Secondly, the high voltage withstand capability of gel electrolytes is achieved through material composites and structural innovation. Through safety performance, voltage withstand capability, and structural innovation, gel polymer electrolytes provide key technological support for high-voltage supercapacitors and have become a core direction for patent development in the energy storage field. Summary of the Invention

[0004] In view of the current technical situation where existing gel polymer electrolytes are prone to interface degradation with the positive and negative electrodes of supercapacitors under high voltage conditions, which disrupts the stable contact between the electrolyte and the electrode, leading to obstructed ion transport and thus affecting the performance and stability of supercapacitors, this invention aims to provide a high-voltage resistant gel polymer electrolyte for supercapacitors, its preparation method, and its application.

[0005] To achieve the above objectives, the present invention employs the following technical solution: This invention provides a high-voltage resistant gel polymer electrolyte for supercapacitors, wherein the gel polymer electrolyte comprises, by mass percentage, 1% to 3% high-voltage resistant additives, 0.5% to 2% auxiliary additives, 12% to 15% lithium salts, and the balance being a mixed solvent; The high-pressure resistant additive is ethyl 3-cyano-4-trifluorosulfonyloxybenzoate; The structural formula of the ethyl 3-cyano-4-trifluorosulfonyloxybenzoate is:

[0006] The auxiliary additive is vinyl sulfate; The lithium salt is one or a combination of lithium hexafluorophosphate or lithium bis(trifluoromethanesulfonylimide); The mixed solvent is prepared by volume percentage from 45% to 65% ether solvent, 15% to 35% cyclic carbonate solvent and 15% to 35% chain carbonate solvent.

[0007] The ether solvent is any one or more of 1,3-dioxolane, tetrahydrofuran, and ethylene glycol dimethyl ether.

[0008] Preferably, the ether solvent is 1,3-dioxolane.

[0009] The cyclic carbonate solvent is any one or more of fluoroethylene carbonate, ethylene carbonate, and propylene carbonate.

[0010] Preferably, the cyclic carbonate solvent is fluoroethylene carbonate or ethylene carbonate.

[0011] The chain carbonate solvent is any one or more of diethyl carbonate, ethyl methyl carbonate, and dimethyl carbonate.

[0012] This invention provides a method for preparing a high-voltage resistant gel polymer electrolyte for supercapacitors, comprising: Step 1: Add high-pressure resistant additives and auxiliary additives to the mixed solvent, stir until completely dissolved, and obtain a mixed solution; Step 2: Add lithium salt to the mixed solution, stir to dissolve, and obtain the precursor solution; Step 3: The precursor solution is dropped onto the electrode surface and assembled into a supercapacitor. The ring-opening polymerization of 1,3-dioxolane is initiated by heating to form a high-voltage resistant gel polymer electrolyte with a cross-linked structure in situ on the electrode surface.

[0013] In step 1, the mixed solvent is obtained by mixing ether solvent, cyclic carbonate solvent and chain carbonate solvent under argon protection, and the volume ratio of the ether solvent, cyclic carbonate solvent and chain carbonate solvent is (4.5~6.5):(1.5~3.5):(2.0~3.5).

[0014] In step 1, the mass ratio of the high-pressure resistant additive to the auxiliary additive is (1-3):(0.5-2).

[0015] In step 2, the amount of lithium salt added is 12-15% of the total mass of the obtained precursor solution; in step 3, the heating temperature is 60-90℃.

[0016] This invention provides the application of the above-mentioned high-voltage resistant gel polymer electrolyte for supercapacitors in the preparation of supercapacitors.

[0017] The present invention provides a supercapacitor, wherein the supercapacitor uses the aforementioned high-voltage resistant gel polymer electrolyte.

[0018] Compared with the prior art, the present invention achieves the following technical effects: This invention designs a high-voltage resistant gel polymer electrolyte for supercapacitors. The synergistic effect of different components helps optimize the performance of the supercapacitor under high-voltage conditions. The rational combination of high-voltage resistant additives, auxiliary additives, lithium salts, and mixed solvents lays the foundation for constructing a stable electrolyte system to address issues such as interface degradation under high voltage, thereby improving the performance and stability of the supercapacitor. Compared with existing technologies, after adding high-voltage resistant additives, the high-voltage resistant molecular structure contains two key functional groups: the highly reactive trifluorosulfonyloxy group (-OSO2CF3) and the strongly electron-withdrawing cyano group (-CN). Through preferential oxidation and reduction, a stable multifunctional protective layer is constructed at the positive and negative electrode interfaces, thus synergistically solving the interface degradation problem in supercapacitors under high voltage. On the positive electrode side, the trifluorosulfonyloxy group (-OSO2CF3) is very active and easily breaks down under oxidative conditions, decomposing to produce sulfonate (-SO2-) and fluoride (F2-) compounds. -The decomposition products, including free radicals or anions containing carbon fragments, react with each other or polymerize on the cathode surface to form a robust cathode electrolyte interphase (CEI) film rich in LiF and sulfonate components. The strongly electron-withdrawing cyano group not only enhances the overall oxidative stability of the molecule, causing it to decompose only at high potentials, thus enabling controllable film formation, but its decomposition products (such as cyanides and polycyanides) can also be integrated into the CEI film, enhancing its stability and ion conductivity.

[0019] The preparation method provided by this invention involves the stepwise addition of additives and lithium salts, ultimately forming a high-voltage resistant gel polymer electrolyte with a cross-linked structure in situ on the electrode surface. This preparation method ensures thorough mixing and uniform distribution of the components on the electrode surface. The in-situ cross-linked structure enhances the bonding force between the electrolyte and the electrode, improves interface stability, effectively solves the problem of easy degradation of the electrolyte-electrode interface under high voltage, ensures smooth ion transport at the interface, and improves the overall performance of the supercapacitor.

[0020] The application provided by this invention, by using high-voltage resistant gel polymer electrolyte in the preparation of supercapacitors, can utilize its high-voltage resistance, stable interface and other properties to improve the performance and stability of supercapacitors under high-voltage conditions, meet the market demand for high-performance supercapacitors, and promote the development of supercapacitor technology.

[0021] The supercapacitor using this high-voltage resistant gel polymer electrolyte provided by this invention can maintain good performance and stability under high voltage, solving the problems of interface degradation and ion transport obstruction faced by existing supercapacitors under high voltage conditions, improving the energy density, power density and service life of the supercapacitor, and providing possibilities for the application of supercapacitors in a wider range of fields. Detailed Implementation

[0022] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0023] Where specific experimental steps or conditions are not specified in the embodiments, they can be performed according to the conventional experimental steps or conditions described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available products. In this invention, unless otherwise specified, all experimental materials used are commercially available commodities well-known to those skilled in the art.

[0024] Example 1 This embodiment provides a high-voltage resistant gel polymer electrolyte for supercapacitors, and the specific preparation steps include: Step 1: Form a homogeneous solution in solvents containing 1,3-dioxolane (DOL), fluoroethylene carbonate (FEC), ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC). The solvents are calculated based on a total volume of 100%, with 1,3-dioxolane (DOL) comprising 50%, fluoroethylene carbonate (FEC) comprising 3%, ethylene carbonate (EC) comprising 15%, diethyl carbonate (DEC) comprising 15%, and methyl ethyl carbonate (EMC) comprising 17%.

[0025] Step 2: Add 1% of ethyl 3-cyano-4-trifluorosulfonyloxybenzoate high-pressure resistant additive and 0.5% of vinyl sulfate auxiliary additive to the solution obtained in Step 1 to form a mixed solution.

[0026] Step 3: Add 12% lithium hexafluorophosphate to the mixed solution obtained in Step 2, and stir on a stirring table for 30 minutes to obtain the precursor solution.

[0027] Step 4: Prepare the supercapacitor in the following order: positive electrode shell, positive electrode plate, separator, precursor solution, graphite sheet, stainless steel sheet, spring sheet, and negative electrode shell. NCM811 is selected for the positive electrode and natural graphite is selected for the negative electrode.

[0028] Step 4: Initiate monomer polymerization at 60°C for 3 hours to form a cross-linked gel polymer electrolyte on the electrode surface in situ.

[0029] Example 2 The only difference between this embodiment and Example 1 is that the amount of ethyl 3-cyano-4-trifluorosulfonyloxybenzoate added to the electrolyte is 2%, otherwise it is the same as Example 1.

[0030] Example 3 The only difference between this embodiment and Example 1 is that the amount of ethyl 3-cyano-4-trifluorosulfonyloxybenzoate added to the electrolyte is 3%, otherwise it is the same as Example 1.

[0031] Example 4 The only difference between this embodiment and Example 1 is that the amount of vinyl sulfate added to the electrolyte is 1%, otherwise it is the same as Example 1.

[0032] Example 5 The only difference between this embodiment and Example 1 is that the amount of vinyl sulfate added to the electrolyte is 2%, otherwise it is the same as Example 1.

[0033] Comparative Example 1 The only difference between this comparative example and Example 1 is that the electrolyte does not contain high-voltage resistant additives; otherwise, they are the same as Example 1.

[0034] Table 1: Performance Comparison of Different Electrolytes

[0035] As shown in Table 1, the electrochemical window of Examples 1-5 was significantly broadened after the addition of the high-voltage additive. The electrochemical window of Example 1 was 5.43 V, Example 2 was 5.65 V, Example 3 reached 5.80 V, while Examples 4 and 5 were 5.47 V and 5.39 V, respectively. In contrast, Comparative Example 1, without the high-voltage additive, had an electrochemical window of only 4.87 V. This indicates that the addition of the high-voltage additive can effectively improve the electrochemical stability of the electrolyte and broaden its operating voltage range. The highly reactive trifluorosulfonyloxy group (-OSO2CF3) and the strongly electron-withdrawing cyano group (-CN) in the high-voltage molecular structure preferentially oxidize and reduce to construct a stable multifunctional protective layer at the positive and negative electrode interfaces, thereby reducing side reactions at the electrolyte-electrode interface under high voltage and improving the high-voltage performance of the electrolyte.

[0036] Regarding cycling performance, the capacity retention rates of Examples 1-5 after 300 cycles were all higher than those of Comparative Example 1. Example 1 achieved a capacity retention rate of 94.4% after 300 cycles, Example 2 94.7%, Example 3 93.3%, Example 4 93.9%, and Example 5 94.0%, while Comparative Example 1 only achieved 89.3%. This indicates that the addition of high-voltage resistant additives helps improve the cycling stability of supercapacitors. During cycling, the stable protective layer constructed by the high-voltage resistant additives can reduce the degradation of the electrode-electrolyte interface, maintain the unobstructed ion transport channels, thereby slowing down capacity decay and improving capacity retention.

[0037] This experiment demonstrates that adding high-voltage resistant additives can significantly broaden the electrochemical window of gel polymer electrolytes used in supercapacitors, thereby improving the cycling performance of the supercapacitors. The amount of different additives added has a certain impact on electrolyte performance, and the amount of additives needs to be optimized to obtain the electrolyte with the best performance. High-voltage resistant additives effectively solve the interface problem in supercapacitors under high voltage by constructing a stable multifunctional protective layer at the positive and negative electrode interfaces, providing an important approach for developing high-performance supercapacitor electrolytes.

[0038] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A high-voltage resistant gel polymer electrolyte for supercapacitors, characterized in that, The gel polymer electrolyte comprises, by weight percentage, 1% to 3% high-pressure resistant additives, 0.5% to 2% auxiliary additives, 12% to 15% lithium salts, and the balance being a mixed solvent. The high-pressure resistant additive is ethyl 3-cyano-4-trifluorosulfonyloxybenzoate; The auxiliary additive is vinyl sulfate; The lithium salt is one or a combination of lithium hexafluorophosphate or lithium bis(trifluoromethanesulfonylimide); The mixed solvent is prepared by volume percentage from 45% to 65% ether solvent, 15% to 35% cyclic carbonate solvent and 15% to 35% chain carbonate solvent.

2. The high-voltage resistant gel polymer electrolyte for supercapacitors according to claim 1, characterized in that, The ether solvent is any one or more of 1,3-dioxolane, tetrahydrofuran, and ethylene glycol dimethyl ether.

3. The high-voltage resistant gel polymer electrolyte for supercapacitors according to claim 1, characterized in that, The cyclic carbonate solvent is any one or more of fluoroethylene carbonate, ethylene carbonate, and propylene carbonate.

4. The high-voltage resistant gel polymer electrolyte for supercapacitors according to claim 1, characterized in that, The chain carbonate solvent is any one or more of diethyl carbonate, ethyl methyl carbonate, and dimethyl carbonate.

5. A method for preparing a high-voltage resistant gel polymer electrolyte for supercapacitors according to any one of claims 1 to 4, characterized in that, include: Step 1: Add high-pressure resistant additives and auxiliary additives to the mixed solvent, stir until completely dissolved, and obtain a mixed solution; Step 2: Add lithium salt to the mixed solution, stir to dissolve, and obtain the precursor solution; Step 3: The precursor solution is dropped onto the electrode surface and assembled into a supercapacitor. The ring-opening polymerization of 1,3-dioxolane is initiated by heating to form a high-voltage resistant gel polymer electrolyte with a cross-linked structure in situ on the electrode surface.

6. The method for preparing a high-voltage resistant gel polymer electrolyte for supercapacitors according to claim 5, characterized in that, In step 1, the mixed solvent is obtained by mixing ether solvent, cyclic carbonate solvent and chain carbonate solvent under argon protection, and the volume ratio of the ether solvent, cyclic carbonate solvent and chain carbonate solvent is (4.5~6.5):(1.5~3.5):(2.0~3.5).

7. The method for preparing a high-voltage resistant gel polymer electrolyte for supercapacitors according to claim 5, characterized in that, In step 1, the mass ratio of the high-pressure resistant additive to the auxiliary additive is (1-3):(0.5-2).

8. The method for preparing a high-voltage resistant gel polymer electrolyte for supercapacitors according to claim 5, characterized in that, In step 2, the amount of lithium salt added is 12-15% of the total mass of the obtained precursor solution; in step 3, the heating temperature is 60-90℃.

9. The use of the high-voltage resistant gel polymer electrolyte for supercapacitors as described in any one of claims 1 to 4 in the preparation of supercapacitors.

10. A supercapacitor, characterized in that, The supercapacitor uses the high-voltage resistant gel polymer electrolyte as described in any one of claims 1 to 4.

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