A dual-base mixed electrolyte, a method, a supercapacitor, and its application in asymmetric supercapacitors.

Abstract

This invention belongs to the field of supercapacitor electrolyte preparation technology, and discloses a dual-base mixed electrolyte, a method, a supercapacitor, and its application in asymmetric supercapacitors. The electrolyte comprises an electrolyte and a solvent, wherein the concentration of the electrolyte in the solvent is 0.7~1.3 mol kg. ‑1 The electrolyte consists of a monovalent quaternary ammonium salt and a polyvalent cation quaternary ammonium salt, with a molar ratio of monovalent quaternary ammonium salt to polyvalent cation quaternary ammonium salt of 1:0.1~0.3. The solvent consists of a main solvent and a co-solvent, with the co-solvent accounting for 1%~30% of the total mass. This invention overcomes the problems of low stable operating voltage and small capacity caused by the strong solvent structure of propylene carbonate, thus providing a simple, green, and low-cost preparation method using hydrofluoroether as a weak solvating co-solvent. This dual-base mixed electrolyte can be used in supercapacitors. The dual-salt electrolyte of this invention exhibits increased conductivity due to increased charge density.

Description

Technical Field

[0001] This invention belongs to the field of supercapacitor electrolyte preparation technology, and in particular to a dual-base mixed electrolyte, method, supercapacitor, and its application in asymmetric supercapacitors. Background Technology

[0002] Supercapacitors are known for their excellent power density (up to 10 kW kg⁻¹). -1 With its ultra-long cycle life (100,000 cycles) and rapid charge / discharge capability, supercapacitors show great application potential in electric vehicles (start-stop systems, energy recovery), rail transit, smart grid frequency regulation, and high-power starting power supplies. However, the energy density of its physical adsorption double-layer energy storage method is much lower than that of secondary batteries, severely limiting its response to long-term energy storage demands. According to the energy density formula E = 1 / 2CV... 2 The contribution of increasing operating voltage (V) to energy density (E) increases quadratically, which is considered a more effective strategy to break through the energy density bottleneck besides capacity (C).

[0003] Although current research mostly uses propylene carbonate (PC)-based electrolytes to improve the stable operating voltage of devices, large-size solvated cations such as TEA... + TEMA + SBP + and DMP + There are still some limitations in forming the double-layer structure: (1) A large number of ion coordination numbers leads to an excessive number of solvent molecules at the electrode interface, which are prone to decomposition and gas generation under high voltage, resulting in capacity decay and safety risks. (2) The large size of solvated ions not only prolongs the distance between the charge center in the double-layer structure and the electrode surface, but also reduces the utilization of some small micropores in the electrode material, increasing the internal resistance to capacity decay under high current. (3) The low charge density per unit space affects the specific capacity of the electrode.

[0004] Although existing studies have explored ways to reduce the double-layer thickness by increasing electrolyte concentration or adding other ions to the electrolyte, or by using divalent cations to increase charge density, the balance between increasing charge density and improving conductivity remains unresolved. Therefore, designing a supercapacitor with high capacity, high rate capability, and high voltage stability is of great significance for the development of long-duration, rapid energy storage devices. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a dual-base mixed electrolyte, a method, a supercapacitor, and its application in asymmetric supercapacitors.

[0006] The technical solution adopted by this invention to solve its technical problem is: A dual-base mixed electrolyte, comprising an electrolyte and a solvent, wherein the concentration of the electrolyte in the solvent is 0.7~1.3 mol kg. -1 The electrolyte is composed of a monovalent quaternary ammonium salt and a polyvalent cation quaternary ammonium salt, with a molar ratio of monovalent quaternary ammonium salt to polyvalent cation quaternary ammonium salt of 1:0.1~0.3; the solvent is composed of a main solvent and a co-solvent, with the mass percentage of the co-solvent being 1%~30%.

[0007] Furthermore, the single-charge quaternary ammonium salt includes at least one of tetraethyltetrafluoroborate (TEA-BF4), triethylmethylammonium tetrafluoroborate, and spirocyclic quaternary ammonium tetrafluoroborate. Alternatively, the polyvalent cationic quaternary ammonium salt includes, but is not limited to, at least one of N,N-diethyl-1,4-diazabicyclo[2.2.2]octane-1,4-dionium tetrafluoroborate, i.e., DEDABCO-(BF4)2, and N,N-dimethyl-1,4-diazabicyclo[2.2.2]octane-1,4-dionium tetrafluoroborate, i.e., DMDABCO-(BF4)2; Alternatively, the solvent of the electrolyte may include at least one of esters, nitriles, ethers, and sulfones. Alternatively, the co-solvent of the electrolyte may include 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, i.e., TTE. Alternatively, the solvent can be prepared by mixing the main solvent and the co-solvent and stirring for 30 minutes to obtain the solvent; wherein the mass ratio of the main solvent to the co-solvent is in the range of 1:(0.01~0.5). Alternatively, the solvent is prepared in a nitrogen atmosphere.

[0008] Further, the electrolyte is composed of tetraethylammonium tetrafluoroborate and N,N-1,4-diethyltrivinyldiamine tetrafluoroborate, with a molar ratio of 1:(0.1~0.3), such as 1:0.1, 1:0.2, 1:0.3, etc., including but not limited to the ratios listed above, with 1:0.2 being the most preferred; the concentration of tetraethyltetrafluoroborate in the electrolyte is 0.7-1 mol kg. -1 The concentration of N,N-1,4-diethyltrivinyldiamine tetrafluoroborate in the electrolyte is 0.1~0.3 mol kg. -1 ; Alternatively, the solvent of the electrolyte is composed of propylene carbonate (PC) and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), wherein the mass percentage of the co-solvent is 1% to 30%, such as 5%, 10%, 20%, 30%, etc., including but not limited to the ratios listed above, with 10% being the most preferred.

[0009] The preparation method of the dual-base mixed electrolyte as described above includes the following steps: Add the corresponding electrolyte to the solvent, stir for 30 minutes, add 4Å molecular sieve, let stand for one week, and then use a Karl Fischer moisture analyzer (Mettler~Toledo C20, Switzerland) to measure that the moisture content is less than 20ppm, thus obtaining the electrolyte; Alternatively, the electrolyte is prepared in a nitrogen atmosphere.

[0010] The application of the dual-base mixed electrolyte in asymmetric supercapacitors as described above.

[0011] The supercapacitor prepared using the dual-base mixed electrolyte as described above, the asymmetric supercapacitor includes a positive electrode, a negative electrode, and an electrolyte, the positive electrode includes a positive active material, and the negative electrode includes a negative active material.

[0012] Furthermore, the positive electrode includes a positive electrode active layer with a current collector substrate disposed on at least one side of the current collector along the thickness direction, and the positive electrode active material is a microporous carbon material with an average pore size of <2 nm; Alternatively, the negative electrode may include a current collector substrate disposed on at least one side of the current collector along its thickness direction as a negative electrode active layer, wherein the negative electrode active material is a mesoporous carbon material with an average pore size of 2-10 nm.

[0013] Furthermore, the mesoporous channels and expanded interlayer spacing of mesoporous carbon are utilized as ion buffers; DED is used... 2+ Competitive coordination reduces the cationic solvation shell; the weak solvation of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) weakens ion-solvent interactions and suppresses interfacial side reactions.

[0014] Using the method described above for increasing the operating voltage of supercapacitors with a hydrofluoroether co-solvent in a dual-base mixed electrolyte, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) is added to the dual-base mixed electrolyte. The weak electron-donating properties and low dielectric constant of TTE allow it to competitively enter the cation exchange, namely TEA. + and DED 2+ The first solvated sheath layer replaces PC molecules, reducing the thickness of the solvated shell, promoting ion desolvation, and inhibiting the co-adsorption of PC solvent at the electrode interface.

[0015] An asymmetric supercapacitor prepared using the dual-base mixed electrolyte as described above includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes a positive active material, and the negative electrode includes a negative active material.

[0016] The advantages and positive effects of this invention are as follows: 1. This invention constructs a novel weakly solvated dual-base hybrid organic electrolyte for asymmetric supercapacitors. Hydrofluoroether (TTE) is added to a propylene carbonate (PC)-based dual-salt electrolyte containing the doubly charged cationic electrolytes N,N-1,4-diethyl-trivinyldiamine tetrafluoroborate (DEDABCO-(BF4)2) and tetraethylammonium tetrafluoroborate (TEA-BF4) to regulate the solvation structure of the cations. By precisely controlling the ratio of PC to TTE, desolvation of the cations is achieved, thereby suppressing solvent co-adsorption and increasing the adsorption charge density at the electrode interface. This invention, through precise control of the electrolyte formulation, ensures that the asymmetric high-energy-density supercapacitor achieves higher energy and power densities at a high voltage of 3.4V, while exhibiting excellent cycle stability. The preparation method of this invention meets the requirements of green environmental protection.

[0017] 2. In order to increase the adsorption charge density at the electrode interface, the dual-base mixed electrolyte of the present invention, based on 1 mol kg... -1 A certain amount of weakly solvated hydrofluoroether solvent was added to a dual-salt electrolyte of propylene carbonate tetraethylammonium tetrafluoroborate (1 M TEA-BF4 / PC) + 0.2 MN,N-1,4-diethyl-trivinyldiamine tetrafluoroborate (DEDABCO~(BF4)2). This was achieved by adding the hydrofluoroether solvent to the bivalent cationic electrolyte. + The weak solvation structure of the supercapacitor enhances the binding of PC, utilizes charge-driven ion rearrangement to reduce the amount of solvent at the interface, suppresses interfacial side reactions under high voltage, and increases the charge density in the electric double layer. On the other hand, the introduction of hydrofluoroether further modifies the weak solvation structure of the cation, suppressing solvent co-adsorption during the formation of the electric double layer. This improves the energy density and cycling stability of the supercapacitor at high voltage (3.4V).

[0018] 3. This invention overcomes the problems of low stable operating voltage and small capacity caused by the strong solvent structure of propylene carbonate, thus providing a simple, green, and low-cost preparation method for a dual-base mixed electrolyte using hydrofluoroether as a weak solvation co-solvent. This dual-base electrolyte can be used in supercapacitors. Due to the increased charge density, the conductivity of the dual-base electrolyte of this invention is improved.

[0019] 4. In this invention, the low dielectric constant, high conductivity, and high oxidation stability of TTE provide the basic characteristics such as low viscosity and high chemical stability for its weak solvation regulation effect.

[0020] 5. In this invention, TTE can competitively enter the cation (TEA) + and DED 2+The first solvated sheath layer of the cation partially replaces the coordination sites of PC molecules, thereby weakening the interaction between the cation and PC and reducing the thickness of the solvated shell. Simultaneously, the addition of TTE weakens the aggregation between cations and improves the ion diffusion coefficient.

[0021] 6. The electrolyte of the preferred embodiment of the present invention, when applied to an asymmetric supercapacitor, achieves a maximum energy density of 51.25 Wh / kg at 3.4 V. -1 Thanks to the mesoporous network channels and weak solvation design, the current density was increased to 10 A g. -1 At that time, the capacity retention rate was 83%. Attached Figure Description

[0022] Figure 1 The following are the scaling factors of the asymmetric supercapacitors used in Comparative Examples 1-2 and Examples 1-4 of this invention at different current densities; Figure 2 The diagram shows the cycle life of the asymmetric supercapacitors in Comparative Examples 1, 2, and 4 at different temperatures.

[0023] Figure 3 This is a comparison chart of the energy density / power density of supercapacitors using Comparative Example 1 and Examples 1-4, as well as other electrolytes, in this invention. Detailed Implementation

[0024] The present invention will be further described below with reference to the embodiments. The following embodiments are descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0025] The various experimental operations involved in the specific embodiments are all conventional techniques in the field. For parts not specifically annotated in this document, those skilled in the art can refer to various commonly used reference books, scientific and technological documents or related instructions and manuals prior to the filing date of this invention to carry out the operations.

[0026] A dual-base mixed electrolyte, comprising an electrolyte and a solvent, wherein the concentration of the electrolyte in the solvent is 0.7~1.3 mol kg. -1 The electrolyte is composed of a monovalent quaternary ammonium salt and a polyvalent cation quaternary ammonium salt, with a molar ratio of monovalent quaternary ammonium salt to polyvalent cation quaternary ammonium salt of 1:0.1~0.3; the solvent is composed of a main solvent and a co-solvent, with the mass percentage of the co-solvent being 1%~30%.

[0027] Furthermore, the single-charge quaternary ammonium salt includes at least one of tetraethyltetrafluoroborate (TEA-BF4), triethylmethylammonium tetrafluoroborate, and spirocyclic quaternary ammonium tetrafluoroborate. Alternatively, the polyvalent cationic quaternary ammonium salt includes, but is not limited to, at least one of N,N-diethyl-1,4-diazabicyclo[2.2.2]octane-1,4-dionium tetrafluoroborate, i.e., DEDABCO-(BF4)2, and N,N-dimethyl-1,4-diazabicyclo[2.2.2]octane-1,4-dionium tetrafluoroborate, i.e., DMDABCO-(BF4)2; Alternatively, the solvent of the electrolyte may include at least one of esters, nitriles, ethers, and sulfones. Alternatively, the co-solvent of the electrolyte may include 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, i.e., TTE. Alternatively, the solvent can be prepared by mixing the main solvent and the co-solvent and stirring for 30 minutes to obtain the solvent; wherein the mass ratio of the main solvent to the co-solvent is in the range of 1:(0.01~0.5). Alternatively, the solvent is prepared in a nitrogen atmosphere.

[0028] Further, the electrolyte is composed of tetraethylammonium tetrafluoroborate and N,N-1,4-diethyltrivinyldiamine tetrafluoroborate, with a molar ratio of 1:(0.1~0.3), such as 1:0.1, 1:0.2, 1:0.3, etc., including but not limited to the ratios listed above, with 1:0.2 being the most preferred; the concentration of tetraethyltetrafluoroborate in the electrolyte is 0.7-1 mol kg. -1 The concentration of N,N-1,4-diethyltrivinyldiamine tetrafluoroborate in the electrolyte is 0.1~0.3 mol kg. -1 ; Alternatively, the solvent of the electrolyte is composed of propylene carbonate (PC) and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), wherein the mass percentage of the co-solvent is 1% to 30%, such as 5%, 10%, 20%, 30%, etc., including but not limited to the ratios listed above, with 10% being the most preferred.

[0029] The preparation method of the dual-base mixed electrolyte as described above includes the following steps: Add the corresponding electrolyte to the solvent, stir for 30 minutes, add 4Å molecular sieve, let stand for one week, and then use a Karl Fischer moisture analyzer (Mettler~Toledo C20, Switzerland) to measure that the moisture content is less than 20ppm, thus obtaining the electrolyte; Alternatively, the electrolyte is prepared in a nitrogen atmosphere.

[0030] The application of the dual-base mixed electrolyte in asymmetric supercapacitors as described above.

[0031] The supercapacitor prepared using the dual-base mixed electrolyte as described above, the asymmetric supercapacitor includes a positive electrode, a negative electrode, and an electrolyte, the positive electrode includes a positive active material, and the negative electrode includes a negative active material.

[0032] Furthermore, the positive electrode includes a positive electrode active layer with a current collector substrate disposed on at least one side of the current collector along the thickness direction, and the positive electrode active material is a microporous carbon material with an average pore size of <2 nm; Alternatively, the negative electrode may include a current collector substrate disposed on at least one side of the current collector along its thickness direction as a negative electrode active layer, wherein the negative electrode active material is a mesoporous carbon material with an average pore size of 2-10 nm.

[0033] Furthermore, the mesoporous channels and expanded interlayer spacing of mesoporous carbon are utilized as ion buffers; DED is used... 2+ Competitive coordination reduces the cationic solvation shell; the weak solvation of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) weakens ion-solvent interactions and suppresses interfacial side reactions.

[0034] Using the method described above for increasing the operating voltage of supercapacitors with a hydrofluoroether co-solvent in a dual-base mixed electrolyte, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) is added to the dual-base mixed electrolyte. The weak electron-donating properties and low dielectric constant of TTE allow it to competitively enter the cation exchange, namely TEA. + and DED 2+ The first solvated sheath layer replaces PC molecules, reducing the thickness of the solvated shell, promoting ion desolvation, and inhibiting the co-adsorption of PC solvent at the electrode interface.

[0035] An asymmetric supercapacitor prepared using the dual-base mixed electrolyte as described above includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes a positive active material, and the negative electrode includes a negative active material.

[0036] Specifically, the relevant preparation and testing methods are as follows: Comparative Example 1 A dual-base mixed electrolyte, comprising: The solute is tetraethylammonium tetrafluoroborate (1 M TEA-BF4 / PC) 1 mol kg -1 N,N'-Diethyl-1,4-diazabicyclo[2.2.2]octyl-2-dioxane bis(tetrafluoroborate) (DEDABCO-(BF4)2) 0.2 mol kg -1 .

[0037] The solvent is propylene carbonate (PC), which accounts for 100% by mass.

[0038] At room temperature and in a glove box, the electrolyte was dissolved in propylene carbonate solvent and stirred for 30 minutes. Then, 4 Å molecular sieves were added, which were about 1 / 3 to 1 / 2 of the total electrolyte volume. After standing for one week, the moisture content was measured to be less than 20 ppm using a Karl Fischer moisture analyzer (Mettler~Toledo C20, Switzerland), and the electrolyte was obtained.

[0039] Comparative Example 2 A single-base mixed electrolyte, comprising: The solute is tetraethylammonium tetrafluoroborate (1 M TEA-BF4 / PC) 1 mol kg -1 N,N'-Diethyl-1,4-diazabicyclo[2.2.2]octyl-2-dioxane bis(tetrafluoroborate) (DEDABCO-(BF4)2) 0.2 mol kg -1 .

[0040] The solvent is a mixture of propylene carbonate (PC) at 90% by mass and acetonitrile (ACN) at 10% by mass.

[0041] At room temperature and in a glove box, the electrolyte was dissolved in propylene carbonate and acetonitrile solvents. After stirring for 30 minutes, 4 Å molecular sieves were added, which were about 1 / 3 to 1 / 2 of the total electrolyte volume. After standing for one week, the moisture content was measured to be less than 20 ppm using a Karl Fischer moisture analyzer (Mettler~Toledo C20, Switzerland), and the electrolyte was obtained.

[0042] Example 1 A dual-base mixed electrolyte, comprising: The solute is tetraethylammonium tetrafluoroborate (1 M TEA-BF4 / PC) 1 mol kg -1 N,N'-Diethyl-1,4-diazabicyclo[2.2.2]octyl-2-dioxane bis(tetrafluoroborate) (DEDABCO~(BF4)2) 0.2 mol kg -1 .

[0043] The solvent is a mixture of propylene carbonate (PC) at 95% by mass and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) at 5% by mass.

[0044] Under room temperature and glove box conditions, the electrolyte was dissolved in the solvent of the mixture. After stirring for 30 minutes, 1 / 3 to 1 / 2 of the total electrolyte volume of 4Å molecular sieve was added. After standing for one week, the moisture content was measured to be less than 20ppm using a Karl Fischer moisture analyzer (Mettler~Toledo C20, Switzerland), and the electrolyte was obtained.

[0045] Example 2 A dual-base mixed electrolyte, comprising: The solute is tetraethylammonium tetrafluoroborate (1 M TEA-BF4 / PC) 1 mol kg -1 N,N'-Diethyl-1,4-diazabicyclo[2.2.2]octyl-2-dioxane bis(tetrafluoroborate) (DEDABCO~(BF4)2) 0.2 mol kg -1 .

[0046] The solvent is a mixture of propylene carbonate (PC) at 90% by mass and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) at 10% by mass.

[0047] Under room temperature and glove box conditions, the electrolyte was dissolved in the solvent of the mixture. After stirring for 30 minutes, 1 / 3 to 1 / 2 of the total electrolyte volume of 4Å molecular sieve was added. After standing for one week, the moisture content was measured to be less than 20ppm using a Karl Fischer moisture analyzer (Mettler~Toledo C20, Switzerland), and the electrolyte was obtained.

[0048] Example 3 A dual-base mixed electrolyte, comprising: The solute is tetraethylammonium tetrafluoroborate (1 M TEA-BF4 / PC) 1 mol kg -1 N,N'-Diethyl-1,4-diazabicyclo[2.2.2]octyl-2-dioxane bis(tetrafluoroborate) (DEDABCO~(BF4)2) 0.2 mol kg -1 .

[0049] The solvent is a mixture of propylene carbonate (PC) at 80% by mass and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) at 20% by mass.

[0050] Under room temperature and glove box conditions, the electrolyte was dissolved in the solvent of the mixture. After stirring for 30 minutes, 1 / 3 to 1 / 2 of the total electrolyte volume of 4Å molecular sieve was added. After standing for one week, the moisture content was measured to be less than 20ppm using a Karl Fischer moisture analyzer (Mettler~Toledo C20, Switzerland), and the electrolyte was obtained.

[0051] Example 4 A dual-base mixed electrolyte, comprising: The solute is tetraethylammonium tetrafluoroborate (1 M TEA-BF4 / PC) 1 mol kg -1 N,N'-Diethyl-1,4-diazabicyclo[2.2.2]octyl-2-dioxane bis(tetrafluoroborate) (DEDABCO~(BF4)2) 0.2 mol kg -1 .

[0052] The solvent is a mixture of propylene carbonate (PC) at 70% by mass and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) at 30% by mass.

[0053] Under room temperature and glove box conditions, the electrolyte was dissolved in the solvent of the mixture. After stirring for 30 minutes, 1 / 3 to 1 / 2 of the total electrolyte volume of 4Å molecular sieve was added. After standing for one week, the moisture content was measured to be less than 20 ppm using a Karl Fischer moisture analyzer (Mettler~Toledo C20, Switzerland), thus obtaining the electrolyte.

[0054] The dual-base mixed electrolytes prepared in the comparative examples and Examples 1-4 were respectively applied to AC / / MC asymmetric supercapacitors. The assembly and testing methods included the following steps: Assembly and testing of AC / / MC asymmetric supercapacitors: Preparation of AC electrode sheets: Activated carbon powder (YP~50F), conductive carbon black (Super P), and binder (PTFE) were weighed out in a mass ratio of 82:10:8, and an appropriate amount of anhydrous ethanol was added. The mixture was thoroughly mixed to ensure uniform dispersion and reached a paste-like consistency. The mixed slurry was then rolled onto carbon-coated aluminum foil, with an electrode sheet thickness of 90-110 μm, and dried (in a vacuum drying oven at 100℃ for at least 12 hours). The rolled aluminum foil was cut into electrode sheets with a diameter of 13 mm, vacuum dried at 120℃ for 12 hours, and weighed after cooling. The average loading of active material in the electrode sheet was approximately 4-5 mg / cm³. -2 .

[0055] Preparation of MC electrode sheets: Mesoporous carbon material, conductive carbon black (VXC72), and binder (PTFE) were weighed out in a mass ratio of 85:7:8, and an appropriate amount of anhydrous ethanol was added. The mixture was thoroughly mixed to ensure uniform dispersion, reaching a paste-like consistency. The mixed slurry was then rolled onto carbon-coated aluminum foil, resulting in an electrode sheet thickness of 250–300 μm. The foil was then dried (in a vacuum oven at 100°C for at least 12 hours). The rolled aluminum foil was cut into electrode sheets with a diameter of 13 mm, vacuum dried at 120°C for 12 hours, and weighed after cooling. The average loading of active material in the electrode sheet was approximately 4–5 mg / cm³. -2 Two electrodes of equal mass were selected and grouped together. Assembly was performed in a glove box. Inside the negative electrode shell with a rubber ring, the MC negative electrode, separator, AC positive electrode, flat gasket, and spring sheet were added sequentially. After leveling, the electrolytes from Comparative Examples 1-2 and Examples 1-4 were added. Finally, the positive electrode shell was covered, and the assembly was completed using a sealing machine to form an R2430 type button capacitor. The specific capacitance and rate capability of the capacitor were tested and compared with test data from other examples.

[0056] Table 1. Basic physical properties of the five mixed electrolytes from Comparative Examples 1-2 and Examples 1-4

[0057] Table 1 shows the basic physical properties of the six mixed electrolytes in Comparative Examples 1-2 and Examples 1-4. It can be seen that although the conductivity and viscosity are improved compared to the electrolyte with pure PC solvent when ACN is used as the co-solvent, the electrochemical stability window of the mixed electrolyte is narrow due to the properties of acetonitrile. With the introduction of TTE, the conductivity increases, but the rate of increase decreases after the TTE content exceeds 10%. However, Example 2 exhibits the highest conductivity, lowest viscosity, and largest electrochemical stability window. This is due to the low viscosity, high conductivity, and inert solvent properties of TTE, which not only achieves a weak solvation design with two cations but also improves the electrochemical stability of the electrolyte.

[0058] Meanwhile, comparative examples 2, 1, and 2 also demonstrate that propylene carbonate and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) in the solvent of the electrolyte of the present invention exhibit a synergistic effect, synergistically improving the conductivity of the prepared electrolyte and synergistically reducing the viscosity of the prepared electrolyte. In particular, the propylene carbonate and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) in the solvent of the electrolyte of the present invention, at a mass ratio of 9:1, exhibit a significant synergistic effect, significantly synergistically improving the conductivity of the prepared electrolyte and synergistically reducing the viscosity of the prepared electrolyte.

[0059] Figure 1 To compare the specific capacitance and rate performance of Comparative Examples 1-2 and Examples 1-4 in asymmetric supercapacitors. As can be seen from the figures, the addition of a small amount of TTE to the PC solvent, due to its weak solvation adjustment effect, effectively regulates the solvation layer of ions, reduces solvent coordination of ions, and facilitates rapid ion entry into the pores and charge transfer during the double-layer formation process. Simultaneously, the presence of TTE reduces solvent co-adsorption at the interface, improving the stable operating voltage of the device by suppressing interfacial side reactions under high voltage. Therefore, at a high operating voltage of 3.4 V, the AC / / MC asymmetric supercapacitor of Comparative Example 1 was used at 0.1 A g... -1 The maximum specific capacity at current density is only 120 F g -1 When the current density is increased to 10 A g -1 At that time, the capacity retention rate was 58.3%. Meanwhile, the AC / / MC asymmetric supercapacitor of Example 1 maintained a capacity retention rate of 0.1 A g. -1 The maximum specific capacity at current density reaches 124 F g. -1 When the current density is increased to 10 A g -1 At that time, 78.2% of the capacity can be maintained. After using Example 2, the capacity increase is smaller, but 10A g... -1 The capacitance retention rate was improved to 83.7%, achieving optimal rate performance. The AC / / MC asymmetric supercapacitors used in Examples 3 and 4 were tested at 0.1 A g. -1 The maximum specific capacity at current density is only 117~119 F g -1 When the current density is increased to 10 A g -1 At that time, the capacity retention rate dropped to 66.7%~66.5%. This indicates that excessive TTE can affect the uniformity of the ion-solubilized structure and charge-discharge kinetics, leading to a decrease in the capacity retention rate of the device at high current densities.

[0060] Figure 2 To compare the cycle life curves of the examples and embodiments in asymmetric supercapacitors at room temperature and high temperature, respectively, using 1 A g... -1The asymmetric supercapacitor using the electrolyte system of Example 2 (TTE-10%) exhibited a capacity retention of approximately 96.1% after 10,000 charge-discharge cycles when charged and discharged within a voltage range of 0–3.4 V. This is higher than that of the device using the pure solvent system (Comparative Example 1). Furthermore, after 10,000 cycles at 65 °C, the capacity retention of the supercapacitor increased to 84.7%. Moreover, with increasing charge-discharge cycle count, the initial discharge voltage drop was observed to be small, consistently less than 0.35 V. However, the addition of excessive TTE significantly reduced the cycle stability of the system. These results indicate that adding 10% hydrofluoroether as a co-solvent to a 1+0.2 dual-salt electrolyte can effectively improve the energy density and high-voltage cycle stability of the supercapacitor.

[0061] Figure 3 This is a comparison graph showing the energy density and power density of supercapacitors prepared using the example and those prepared using other types of electrolytes. The introduction of hydrofluoroether (TTE) in Example 2 increases the stable operating voltage and charge adsorption capacity in the electric double layer of the supercapacitor, and achieves a weak solvation structure for cations, thus improving ion transport and adsorption efficiency. Therefore, the supercapacitor prepared using Example 2 has the highest energy density and power density compared to other reported supercapacitors of the same type.

[0062] Although embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the scope of the invention is not limited to the contents disclosed in the embodiments.

Claims

1. A dual-base mixed electrolyte, characterized in that: The electrolyte comprises an electrolyte and a solvent, wherein the concentration of the electrolyte in the solvent is 0.7–1.3 mol / kg. -1 The electrolyte is composed of a monovalent quaternary ammonium salt and a polyvalent cation quaternary ammonium salt, with a molar ratio of monovalent quaternary ammonium salt to polyvalent cation quaternary ammonium salt of 1:0.1~0.3; the solvent is composed of a main solvent and a co-solvent, with the co-solvent accounting for 1%~30% of the total mass of the solvent.

2. The dual-base mixed electrolyte according to claim 1, characterized in that: The single-charge quaternary ammonium salt includes at least one of tetraethyltetrafluoroborate (TEA-BF4), triethylmethylammonium tetrafluoroborate, and spirocyclic quaternary ammonium salt of tetrafluoroborate. Alternatively, the polyvalent cationic quaternary ammonium salt includes at least one of N,N-diethyl-1,4-diazabicyclo[2.2.2]octane-1,4-dionium tetrafluoroborate, namely DEDABCO-(BF4)2, and N,N-dimethyl-1,4-diazabicyclo[2.2.2]octane-1,4-dionium tetrafluoroborate, namely DMDABCO-(BF4)2; Alternatively, the solvent of the electrolyte may include at least one of esters, nitriles, ethers, and sulfones. Alternatively, the co-solvent of the electrolyte may include 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, i.e., TTE. Alternatively, the solvent can be prepared by mixing the main solvent and the co-solvent and stirring for 30 minutes to obtain the solvent; wherein the mass ratio of the main solvent to the co-solvent is 1:(0.01~0.5); Alternatively, the solvent is prepared in a nitrogen atmosphere.

3. The dual-base mixed electrolyte according to claim 1 or 2, characterized in that: The electrolyte is composed of tetraethylammonium tetrafluoroborate and N,N-1,4-diethyltrivinyldiamine tetrafluoroborate in a molar ratio of 1:0.1, 1:0.2, and 1:0.3; the concentration of tetraethylammonium tetrafluoroborate in the electrolyte is 0.7-1 mol / kg. -1 The concentration of N,N-1,4-diethyltrivinyldiamine tetrafluoroborate in the electrolyte is 0.1~0.3 mol kg. -1 ; Alternatively, the solvent of the electrolyte is composed of propylene carbonate (PC) and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), wherein the mass percentage of the co-solvent is 5%, 10%, 20%, or 30%.

4. The method for preparing the dual-base mixed electrolyte according to any one of claims 1 to 3, characterized in that: Includes the following steps: Add the appropriate electrolyte to the solvent, stir for 30 minutes, add 4Å molecular sieve, let stand for a week and measure the moisture content to be less than 20ppm to obtain the electrolyte; Alternatively, the electrolyte is prepared in a nitrogen atmosphere.

5. The application of the dual-base mixed electrolyte as described in any one of claims 1 to 3 in asymmetric supercapacitors.

6. A supercapacitor prepared using the dual-base mixed electrolyte as described in any one of claims 1 to 3, characterized in that: The asymmetric supercapacitor includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes a positive active material, and the negative electrode includes a negative active material.

7. The supercapacitor according to claim 6, characterized in that: The positive electrode includes a positive active layer with a current collector substrate disposed on at least one side of the current collector along the thickness direction, and the positive active material is a microporous carbon material with an average pore size of <2 nm; Alternatively, the negative electrode may include a current collector substrate disposed on at least one side of the current collector along its thickness direction as a negative electrode active layer, wherein the negative electrode active material is a mesoporous carbon material with an average pore size of 2-10 nm.

8. The supercapacitor according to claim 6 or 7, characterized in that: Utilizing the mesoporous channels and expanded interlayer spacing of mesoporous carbon as ion buffers; utilizing DED 2+ Competitive coordination reduces the cationic solvation shell; the weak solvation of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) weakens ion-solvent interactions and suppresses interfacial side reactions.

9. A method for increasing the operating voltage of a supercapacitor using a dibasic mixed electrolyte as described in any one of claims 1 to 3, characterized in that: 1,1,2,2-Tetrafluoroethyl-2,2,3,3-Tetrafluoropropyl ether (TTE) is added to a dibasic mixed electrolyte. Utilizing TTE's weak electron-donating properties and low dielectric constant, it competitively enters the cation exchange, TEA. + and DED 2+ The first solvation sheath layer replaces PC molecules, reducing the thickness of the solvation shell, promoting ion desolvation, and inhibiting the co-adsorption of PC solvent at the electrode interface.

10. An asymmetric supercapacitor prepared using the dual-base mixed electrolyte as described in any one of claims 1 to 3, characterized in that: The asymmetric supercapacitor includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes a positive active material, and the negative electrode includes a negative active material.

Images