A cationic mixed electrolyte for zinc capacitors, a method for preparing the same, and an aqueous zinc capacitor

Abstract

The application provides a cation mixed electrolyte of a zinc capacitor, a preparation method of the cation mixed electrolyte and a water-based zinc capacitor, and belongs to the technical field of zinc capacitors. The cation mixed electrolyte of the zinc capacitor comprises an ammonium salt, a zinc salt and a solvent, wherein the solvent is deionized water. The preparation method of the cation mixed electrolyte of the zinc capacitor comprises the following steps: step one, weighing a certain molar ratio of the zinc salt and the ammonium salt; step two, adding the zinc salt and the ammonium salt into water, stirring until uniform, ultrasonicating to obtain a clear solution and standing to obtain the cation mixed electrolyte of the zinc capacitor. The hierarchical solvation structure in the cation mixed electrolyte of the zinc capacitor is beneficial to the reconstruction of a cathode and a Helmholtz layer on the surface of the electrolyte, the redistribution of space charges, the significant reduction of interface electron and ion transmission impedance, the improvement of the reaction activity and reaction kinetics process of the carbon cathode, and the energy storage with high energy density and long cycle life.

Description

Technical Field

[0001] This invention belongs to the field of zinc capacitor technology, specifically relating to a cationic mixed electrolyte for zinc capacitors, its preparation method, and an aqueous zinc capacitor. Background Technology

[0002] Aqueous zinc hybrid capacitors have recently become a highly competitive energy storage system due to their combination of the advantages of battery-type zinc anodes and supercapacitor-type carbon-based cathodes. The reversible deposition / stripping behavior of the zinc anode and the high theoretical specific capacity (820 mAh g⁻¹) are key advantages. -1 The presence of suitable redox potentials (relative to the standard hydrogen electrode -0.76V) provides ample charge and assurance for developing high-energy, long-cycle-life aqueous zinc hybrid capacitors. Therefore, current research focuses primarily on advancing the development of high-performance cathode materials for aqueous zinc hybrid capacitors, mainly concentrating on the development of carbon nanomaterials with high specific surface area. However, developed carbon cathodes still suffer from low energy density due to the inherent insufficient zincophilic activity and unsustainable adsorption at the carbon cathode-electrolyte interface, hindering further performance improvements in aqueous zinc hybrid capacitors. To address these challenges, a key breakthrough lies in designing highly electroactive and stable cathode-electrolyte interfaces to achieve more efficient charge storage.

[0003] Capacitive energy storage in carbon cathodes primarily relies on the double-layer energy storage mechanism, which largely depends on the specific surface area and the distribution of charge carriers in the electrolyte. A large specific surface area can effectively expand the electrode / electrolyte contact, thereby increasing the capacity of the carbon cathode. However, the specific surface area of ​​a carbon cathode cannot be increased indefinitely, and is accompanied by negative effects such as poor pore utilization due to the mismatch between charge carrier and pore structure sizes, resulting in limited capacity enhancement of carbon cathode materials. The size and solvation structure of the charge carriers significantly affect the interfacial electrochemical behavior and the double-layer energy storage mechanism. Charge carriers play a crucial role in regulating the dynamic charge transfer and spatial storage at the carbon cathode interface, with high-density interfacial charge being beneficial for increasing the capacity of the carbon cathode.

[0004] Therefore, the rational design of the solvation structure of charge carriers in the electrolyte and the regulation of the spatial distribution of charge carriers at the cathode-electrolyte interface are crucial for effective charge storage. Summary of the Invention

[0005] The present invention was made to solve the above-mentioned problems, and its purpose is to provide a cationic mixed electrolyte for zinc capacitors, a method for preparing the same, and an aqueous zinc capacitor.

[0006] The present invention provides a cationic mixed electrolyte for zinc capacitors, characterized by comprising: ammonium salt, zinc salt and solvent, wherein the solvent is deionized water.

[0007] The cationic mixed electrolyte of the zinc capacitor provided by the present invention may also have the following characteristics: wherein the ammonium salt is any one of ammonium trifluoromethanesulfonate, sulfuric acid and ammonium acetate, and the zinc salt is any one of zinc trifluoromethanesulfonate, zinc sulfate and zinc acetate.

[0008] The cationic mixed electrolyte of the zinc capacitor provided by the present invention may also have the following characteristic: wherein the concentration of ammonium salt and zinc salt in the cationic mixed electrolyte of the zinc capacitor is 0.1-2 mol / L.

[0009] The cation-mixed electrolyte of the zinc capacitor provided by the present invention may also have the following characteristic: wherein the molar ratio of ammonium salt to zinc salt is 1:5-5:1.

[0010] The present invention also provides a method for preparing a cationic mixed electrolyte for zinc capacitors, characterized by the following steps: Step 1, weighing zinc salt and ammonium salt in a certain molar ratio; Step 2, adding zinc salt and ammonium salt to water, stirring evenly, ultrasonicating to obtain a clear solution, and allowing it to stand to obtain the cationic mixed electrolyte for zinc capacitors.

[0011] The method for preparing the cation-mixed electrolyte for zinc capacitors provided by the present invention may also have the following characteristics: in step two, the mixing method is ultrasonication for 2 hours and the standing time is 24 hours.

[0012] The present invention also provides an aqueous zinc capacitor, characterized by using the cationic mixed electrolyte of the above-mentioned zinc capacitor.

[0013] The aqueous zinc capacitor provided by this invention may also have the following features: the positive electrode material of the aqueous zinc hybrid capacitor is a porous carbon material, the negative electrode material is zinc, and the cationic mixed electrolyte is a cationic mixed electrolyte of the zinc capacitor. When the cationic mixed electrolyte of the zinc capacitor is used in the aqueous zinc capacitor, the hierarchical cationic solvation structure induces the Helmholtz plane reconstruction on the carbon cathode surface, thereby affecting the space charge distribution. The synergistic effect of the cationic mixed electrolyte regulates the interfacial adsorption behavior and electrochemical performance of the zinc capacitor.

[0014] The aqueous zinc capacitor provided by the present invention may also have the following features: the cation adsorption behavior on the carbon cathode surface is controlled by adjusting the ratio of ammonium salt and zinc salt, the hydrated cations of ammonium have a smaller size than the hydrated cations of zinc, and the graded cation mixed electrolyte can control the Helmholtz plane on the cathode surface.

[0015] The role and effect of invention

[0016] According to the present invention, the cationic mixed electrolyte for zinc capacitors, its preparation method, and the aqueous zinc capacitor are described. The cationic mixed electrolyte for zinc capacitors comprises ammonium salt, zinc salt, and a solvent, wherein the solvent is deionized water. In this invention, the concentration range of the electrolyte salt is 0.1–2 mol / L, and the molar ratio of ammonium salt to zinc salt is 1:5–5:1. By adjusting the ratio of ammonium salt to zinc salt, the cation adsorption behavior on the carbon cathode surface is controlled. The hydrated cations of ammonium have a smaller size than those of zinc. The graded cationic mixed electrolyte can control the Helmholtz plane on the cathode surface, achieving a redistribution of space charge, significantly reducing interfacial electron and ion transport impedance, improving the reactivity and reaction kinetics of the carbon cathode, and resulting in high energy density and long cycle life energy storage.

[0017] Furthermore, the raw materials for the cationic mixed electrolyte of the zinc capacitor of the present invention are widely available and low in cost.

[0018] The method for preparing the cationic mixed electrolyte for zinc capacitors of the present invention is as follows: zinc salt and ammonium salt in a certain molar ratio are added to water and mixed evenly to obtain the cationic mixed electrolyte for zinc capacitors. This preparation method is simple to operate and does not involve harmful reagents or vacuum preparation conditions.

[0019] Furthermore, because the electrolyte of the aqueous zinc capacitor of the present invention is the cationic mixed electrolyte of the zinc capacitor of the present invention, the aqueous zinc capacitor has good performance. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the working mechanism of the cationic mixed electrolyte in the zinc capacitor in Embodiment 1 of the present invention;

[0021] Figure 2 These are conductivity performance test graphs of the electrolytes prepared in Example 1, Comparative Examples 1 and 2 of the present invention.

[0022] Figure 3 These are electrochemical impedance spectroscopy performance graphs of the electrolytes prepared in Example 1, Comparative Examples 1 and 2 of the present invention.

[0023] Figure 4 These are differential capacitance curve performance test graphs of the electrolytes prepared in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention.

[0024] Figure 5 This is a micelle size distribution diagram of the electrolyte prepared in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention;

[0025] Figure 6This is a CV curve performance test graph of zinc capacitors prepared in the electrolytes of Example 1, Comparative Examples 1 and 2 of the present invention under a test condition of 2mV / s.

[0026] Figure 7 The figure shows the rate performance test results of a zinc capacitor using the electrolyte prepared in Example 1 of the present invention and the electrolytes prepared in aqueous solutions in Comparative Examples 1 and 2 at 25°C.

[0027] Figure 8 This is a test graph of the cyclic performance of a zinc capacitor using the electrolyte 1M Zn(OTF)2+1M NH4OTF prepared in Example 1 of the present invention at a charge / discharge current density of 30A / g. Detailed Implementation

[0028] To make the technical means, creative features, objectives and effects of the present invention easy to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate the cationic mixed electrolyte of the zinc capacitor of the present invention, its preparation method and aqueous zinc capacitor.

[0029] <Example 1>

[0030] This embodiment provides a cationic mixed electrolyte for a zinc capacitor, which comprises: 1M zinc trifluoromethanesulfonate, 1M ammonium trifluoromethanesulfonate, and water.

[0031] This embodiment also provides a method for preparing the above-mentioned cationic mixed electrolyte for zinc capacitors, which includes the following steps:

[0032] Step 1: Accurately weigh 1 mol of zinc trifluoromethanesulfonate and 1 mol of ammonium trifluoromethanesulfonate.

[0033] Step 2: Add the zinc trifluoromethanesulfonate and ammonium trifluoromethanesulfonate to water, stir until homogeneous, and adjust the volume to the required concentration. Let stand to obtain the cation mixed electrolyte for zinc capacitors.

[0034] This embodiment also provides an aqueous zinc capacitor, wherein the positive electrode of the aqueous zinc capacitor is a graded porous carbon material, the electrolyte is a cationic mixed electrolyte of the zinc capacitor prepared in this embodiment, the negative electrode is a zinc sheet (purity ≥99.99%), and it is assembled using a GE-Whatman glass fiber diaphragm.

[0035] The preparation process of the positive electrode of this aqueous zinc capacitor is as follows:

[0036] ZnCl2 (3.0 g) was dissolved in a solvent mixture consisting of ethanol (30 mL), deionized water (50 mL), ammonium hydroxide (25–28%, 12 mL), and N,dimethylformamide (DMF, 30 mL). Then, 1H-1,2,3-triazole (4 mL) was added dropwise to the mixture and stirred at room temperature for 12 h. The resulting white product was then filtered, washed, and dried at 80 °C for 12 h to obtain a white precursor powder. The synthesized precursor was calcined at 800 °C in a nitrogen atmosphere for 2 h at a heating rate of 2 °C. The carbonized sample was washed with 4 M salt solution for 4 h to remove the zinc component, then rinsed with water and dried at 80 °C for 24 h. The obtained f-graded porous carbon material, 60wt% polytetrafluoroethylene emulsion (purchased from Shanghai Sanai Fu New Material Co., Ltd.), and acetylene black were mixed evenly in the following mass ratio: 8:1:1. The mixture was then dried in an oven. The dried sample was pressed onto a stainless steel mesh (purchased from Jiangsu Ningcong Wire Mesh) under a pressure of 20MPa and vacuum dried at 100℃ for 24h to obtain the positive electrode of the battery.

[0037] The energy storage performance of the aqueous zinc capacitor was tested using a CHI660E electrochemical workstation. After 400,000 charge-discharge cycles, the aqueous zinc capacitor retained over 98.59% of its capacity, demonstrating excellent energy density and outstanding cycle life.

[0038] Figure 1 This is a schematic diagram illustrating the working mechanism of the cationic mixed electrolyte in the zinc capacitor in Embodiment 1 of the present invention.

[0039] like Figure 1 As shown, the cationic mixed electrolyte (1M Zn(OTF)2 + 1MNH4OTF cationic mixed electrolyte) prepared in Example 1 can alter the solvation structure at the cathode-electrolyte interface, leading to the reconstruction of its Helmholtz layer. Ammonium ions have smaller water and ionic radii and lower desolvation energies, thus providing rapid reaction kinetics; while highly reactive zinc ions can form high-energy ionic bonds, providing high specific capacitance for the zinc-ion capacitor. Based on the synergistic effect of the cationic mixed electrolyte, the specific capacitance, rate performance, and cycle stability of the zinc capacitor are simultaneously improved.

[0040] <Comparative Example 1>

[0041] In this comparative example, a 2M aqueous solution of ammonium trifluoromethanesulfonate was prepared as a cationic mixed electrolyte for zinc capacitors as a control sample (to highlight the improvement of electrolyte performance by the dual cations in Example 1, the concentration of ammonium trifluoromethanesulfonate was set to 2M).

[0042] <Comparative Example 2>

[0043] In this comparative example, a 2M aqueous solution of zinc trifluoromethanesulfonate was prepared as the cationic mixed electrolyte for zinc capacitors as the control sample (to highlight the improvement of electrolyte performance by the dual cations in Example 1, the concentration of ammonium trifluoromethanesulfonate was set to 2M).

[0044] <Test Example>

[0045] The electrolytes prepared in Example 1, Comparative Example 1, and Comparative Example 2 were tested for conductivity, electrochemical impedance, differential capacitance curve performance, micelle size distribution, CV curve performance of zinc capacitors, rate performance of zinc capacitors, and cycle performance of zinc capacitors. The zinc capacitors involved were based on the aqueous zinc capacitor of Example 1, with the corresponding electrolytes replaced.

[0046] Figure 2 These are conductivity performance test graphs of the electrolytes prepared in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention.

[0047] like Figure 2 As shown, due to its hierarchical solvation structure, the mixed cationic electrolyte in Example 1 has a higher ionic conductivity than the single cationic electrolytes in Comparative Examples 1 and 2, and exhibits excellent ion and electron conduction during electrochemical testing.

[0048] Figure 3 These are electrochemical impedance spectroscopy performance graphs of the electrolytes prepared in Example 1, Comparative Examples 1 and 2 of the present invention.

[0049] like Figure 3 As shown, the electrochemical impedance spectroscopy (EIS) results include a semi-circular region dominated by charge transport impedance and a diagonal line region dominated by diffusion. The smaller the radius of the semi-circle, the lower the electrochemical impedance of the electrolyte during the test; the steeper the slope of the diagonal line, the faster the diffusion rate. Comparison of the test results of Example 1, Comparative Example 1, and Comparative Example 2 shows that the mixed cation electrolyte prepared in Example 1 has significantly better performance than the electrolytes prepared in Comparative Examples 1 and 2.

[0050] Figure 4 These are differential capacitance curve performance test graphs of the electrolytes prepared in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention.

[0051] A larger value on the vertical axis of the differential capacitance curve indicates a higher capacitive response activity of the carbon cathode material in the electrolyte, which is beneficial for improving the electrochemical performance at the carbon cathode interface. For example... Figure 4As shown in the comparison, the capacitance response of the cationic mixed electrolyte prepared in Example 1 is much higher than that of the 2M NH4OTF electrolyte prepared in Comparative Example 1 and the 2MZn(OTF)2 electrolyte prepared in Comparative Example 2. The capacitance of the cationic mixed electrolyte prepared in Example 1 ensures high capacitance response activity at the interface between the carbon cathode and the electrolyte.

[0052] Figure 5 This is a micelle size distribution diagram of the electrolyte prepared in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention.

[0053] like Figure 5 As shown, the 2M NH4OTF electrolyte prepared in Comparative Example 1 has a smaller average micelle size, while the 2M Zn(OTF)2 electrolyte prepared in Comparative Example 2 has a larger ionic micelle size. The cationic mixed electrolyte prepared in Example 1 combines two different sizes of ionic micelles, and its hierarchical solvation structure is beneficial for the reconstruction of the interfacial Helmholtz layer and for improving the pore size utilization of porous carbon materials.

[0054] Figure 6 This is a CV curve performance test graph of zinc capacitors prepared in the electrolytes of Example 1, Comparative Examples 1 and 2 of the present invention under a test condition of 2mV / s.

[0055] like Figure 6 As shown, the cationic mixed electrolyte prepared in Example 1 has a larger CV peak area compared to Comparative Example 1 and Comparative Example 2, indicating that under the same test conditions, the mixed cationic electrolyte has higher current response activity on the carbon cathode surface.

[0056] Figure 7 This is a rate performance test chart of a zinc capacitor using the electrolyte prepared in Example 1 of the present invention and the electrolytes prepared in aqueous solutions in Comparative Examples 1 and 2, at 25°C.

[0057] like Figure 7 As shown in the figure, the rate performance test graph uses specific capacity as the vertical axis and the number of cycles at different current densities as the horizontal axis. At the same current density, a higher specific capacity value indicates better rate performance of the battery. The comparison shows that the zinc capacitor in the mixed cation electrolyte prepared in Example 1 performs significantly better than the 2M NH4OTF electrolyte prepared in Comparative Example 1 and the 2M Zn(OTF)2 electrolyte prepared in Comparative Example 2, especially showing a significant improvement in rate performance under high current.

[0058] Figure 8 This is a graph showing the cycle performance test of a zinc capacitor using the electrolyte 1M Zn(OTF)2+1MNH4OTF prepared in Example 1 of this invention at a charge-discharge current density of 30A / g.

[0059] like Figure 8 As shown, the cycle performance test graph uses specific capacity as the vertical axis and the number of cycles as the horizontal axis. A higher number of cycles indicates better capacity retention and thus better cycle performance. The zinc capacitor with a hierarchical porous carbon cathode prepared in Example 1 exhibits excellent cycle performance, and the assembled zinc capacitor retains a capacity of 98.59% after 400,000 charge-discharge cycles, demonstrating exceptionally long cycle life and stability.

[0060] The role and effect of the embodiments

[0061] The above experimental results show that the aqueous zinc capacitor prepared in Example 1 has an ultra-high cycle life and excellent rate performance.

[0062] The raw materials used in Example 1 and the comparative example (zinc trifluoromethanesulfonate and ammonium trifluoromethanesulfonate) are widely available, inexpensive and environmentally friendly. The preparation process of the cationic mixed electrolyte of zinc capacitors and aqueous zinc capacitors is simple and easy to operate, and does not involve toxic or harmful reagents or vacuum preparation conditions.

[0063] The hierarchical solvation structure in the cationic mixed electrolyte of the zinc capacitor prepared in Example 1 is beneficial for reconstructing the Helmholtz layer on the cathode and electrolyte surface, realizing the redistribution of space charge, significantly reducing the interfacial electron and ion transport impedance, improving the reactivity and reaction kinetics of the carbon cathode, and achieving high energy density and long cycle life energy storage.

[0064] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A cationic mixed electrolyte for a zinc capacitor, characterized in that, include: Ammonium salt, zinc salt, and solvent, wherein the solvent is deionized water. Wherein, the ammonium salt is ammonium trifluoromethanesulfonate, and the zinc salt is zinc trifluoromethanesulfonate. The concentrations of the ammonium salt and zinc salt in the cation-mixed electrolyte of the zinc capacitor are 2 mol / L.

2. The cationic mixed electrolyte for the zinc capacitor according to claim 1, characterized in that: in, The molar ratio of the ammonium salt to the zinc salt is 1:5-5:

1.

3. A method for preparing a cationic mixed electrolyte for a zinc capacitor, characterized in that, The method for preparing the cationic mixed electrolyte of the zinc capacitor according to claim 1 or 2 includes the following steps: Step 1: Weigh out zinc salt and ammonium salt in a specific molar ratio; Step 2: Add the zinc salt and ammonium salt to deionized water, stir until homogeneous, sonicate to obtain a clear solution, and let stand to obtain the cationic mixed electrolyte of the zinc capacitor.

4. The method for preparing the cationic mixed electrolyte for the zinc capacitor according to claim 3, characterized in that: in, In step two, the ultrasound time is 2 hours, and the settling time is 24 hours.

5. An aqueous zinc capacitor, characterized in that: The cationic mixed electrolyte of the zinc capacitor as described in claim 1 or 2 was used.

6. The aqueous zinc capacitor according to claim 5, characterized in that: in, The positive electrode material of the aqueous zinc capacitor is porous carbon material, the negative electrode material is zinc, and the cationic mixed electrolyte is the same as that used in the zinc capacitor. When the cationic mixed electrolyte of the zinc capacitor is used in the aqueous zinc capacitor, the hierarchical cationic solvation structure induces the Helmholtz plane reconstruction on the carbon cathode surface, thereby affecting the space charge distribution. The synergistic effect of the cationic mixed electrolyte regulates the interfacial adsorption behavior and electrochemical performance of the zinc capacitor.

7. The aqueous zinc capacitor according to claim 5, characterized in that: in, The cation adsorption behavior on the carbon cathode surface can be controlled by adjusting the ratio of the ammonium salt and the zinc salt. The hydrated cations of ammonium have a smaller size than the hydrated cations of zinc. The graded cation mixed electrolyte can control the Helmholtz plane on the cathode surface.

Images