A type of electrolyte containing metal ion indicator and its preparation method and application

Abstract

The present invention discloses a class of electrolytes containing metal ion indicators and their preparation methods and applications; the metal ion indicator is an organic compound or its salt; the organic compound has a parent core structure and a substituent, and the parent core structure is 4-dibenzylidene-2,5-cyclohexadiene-1-one, phenylazonaphthalene, triazinylphenylazonaphthalene, naphthylazonaphthalene, diphenyldiazonaphthalene, phenylazobenzene or triphenylmethane. The present invention uses a metal ion indicator as an electrolyte additive, not only its color change characteristics can be more convenient for characterization of boundaries and composition and structure, and after the metal indicator is combined with the metal ion, the metal ion solvation structure is improved, the occurrence of electrode side reactions can be reduced, the electrode stability is improved, and additional capacity is provided for the energy storage device by its reversible redox reaction. Therefore, the application of the metal ion indicator as an additive in the electrolyte provides new possibilities for the design of energy storage devices.

Description

Technical Field

[0001] The present invention belongs to the field of electrochemical technology, and in particular relates to an electrolyte containing a metal ion indicator and a preparation method and application thereof. Background Art

[0002] In today's society, with the continuous development of renewable energy technologies, the demand for energy storage devices is increasing. The rapid adoption of electric vehicles, smart grids, and large-scale energy storage systems has made efficient and safe energy storage technologies a research hotspot. While traditional lithium-ion batteries offer excellent energy density and cycle life, their limitations are gradually becoming apparent due to the poor safety and environmental pollution issues associated with the organic electrolytes they use. In contrast, aqueous energy storage devices, with their advantages of low cost, environmental friendliness, and high safety, are becoming a key area of future energy storage technology. Aqueous electrolytes not only offer excellent conductivity and thermal stability but also offer the potential for achieving higher energy densities in battery design and applications. However, aqueous energy storage devices still face numerous challenges. For example, zinc anodes are prone to zinc dendrite formation during charge and discharge, which not only affects battery performance but can also pose safety risks. Copper anodes are also susceptible to corrosion and uneven deposition in the electrolyte. These issues limit the application of aqueous electrolytes in high-performance energy storage devices, necessitating the urgent need for new materials and technologies to improve overall battery performance.

[0003] In the regulation of aqueous electrolytes, the introduction of organic molecules is considered an effective strategy. Organic additives can improve battery performance by changing the chemical and physical properties of the electrolyte. For example, additives can optimize the solvation environment of zinc ions by adjusting the solvation structure, thereby inhibiting the formation of zinc dendrites. In addition, adjusting the pH value of the electrolyte can also effectively improve the stability of the electrode and reduce corrosion and uneven deposition problems. However, there are also some problems in the current research on additives, mainly manifested in single function and unstable structure. Many additives may degrade or lose their effectiveness under certain conditions, which limits their practical application. Therefore, the development of electrolytes with multifunctionality and high stability is crucial to improving the overall performance of aqueous electrochemical energy storage. Researchers urgently need to explore new additives and improve their application effect in electrolytes by optimizing their molecular structure and function. Summary of the Invention

[0004] To overcome the problems of the prior art, one objective of the present invention is to provide an electrolyte solution containing a metal ion indicator. A second objective of the present invention is to provide an aqueous electrochemical energy storage device. A third objective of the present invention is to provide applications of the aqueous electrochemical energy storage device.

[0005] Metal ion indicators are primarily used in titration, and their color change mechanism and complexing ability with metal ions have attracted considerable attention. These indicators typically contain ring structures with delocalized electrons, such as benzene, naphthalene, pyridine, or triphenylmethane. These ring structures not only impart excellent optical properties to the indicators but also enhance their chemical stability and selectivity. To enhance their complexing ability with metal ions, these indicators often contain functional groups with lone pairs of electrons, such as hydroxyl, sulfonic acid, carboxyl, azo, and halogen groups. These functional groups can form strong coordination interactions with metal ions. In the presence of metal ions, the indicator complexes with the metal ion. When the metal ion binds to the indicator, the resulting new compound has different electronic structure and optical properties. This structural change results in a shift in the absorption spectrum, resulting in a significant color change. This property enables real-time monitoring of metal ion concentrations. By adjusting the type and position of these functional groups, researchers can design metal ion indicators with specific functions to meet diverse application requirements.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] The first aspect of the present invention provides an electrolyte containing a metal ion indicator, wherein the metal ion indicator is an organic compound or a salt thereof; the organic compound has a parent core structure and a substituent, and the parent core structure is selected from 4-diphenylmethylene-2,5-cyclohexadiene-1-one, phenylazonaphthalene, triazine-phenylazonaphthalene, naphthylazonaphthalene, diphenyldiazonaphthalene, phenylazobenzene, benzene or triphenylmethane; the substituent of the organic compound is selected from at least one of a hydroxyl group, a sulfonic acid group, a carboxyl group, a halogen group, an arsonyl group, and a dicarboxymethyl nitrogen group.

[0008] The present invention uses a metal ion indicator as an electrolyte additive. After the metal ion indicator is complexed with the metal ions in the electrolyte, it can effectively adjust the solvation structure of the metal ions, thereby reducing the occurrence of side reactions and improving device performance, showing great application potential in the field of aqueous energy storage devices. Compared with traditional additives, the molecular structure of metal ion indicators is generally more stable and can maintain its function during multiple charge and discharge processes. In addition, when these indicators complex metal ions, they can often adjust the pH value of the electrolyte to avoid corrosion problems caused by acid-base imbalance. More importantly, due to the participation of functional groups such as hydroxyl and azo groups, these indicators can undergo reversible redox reactions, thereby increasing the energy density of the battery. This feature not only enhances the performance of the battery, but also helps improve its cycle life.

[0009] At the same time, metal ion indicators have the characteristic of changing color after complexing with metal ions. By observing the color change and using color-sensitive test methods, such as ultraviolet-visible absorption spectroscopy, it is possible to further detect changes in the electrolyte structure and analyze its change mechanism, providing a systematic strategy for electrolyte analysis and design. Therefore, metal ion indicators have broad application prospects in aqueous electrolytes.

[0010] The term "salt" refers to a salt of the compound of the present invention, which is prepared by reacting the compound having the specified substituents discovered by the present invention with a relatively non-toxic acid or base. Preferably, it is an electrochemically acceptable salt.

[0011] Preferably, when the core structure is 4-benzylidene-2,5-cyclohexadien-1-one, the metal ion indicator is pyrogallol purple, m-cresol purple, m-cresol purple sodium, xylenol orange sodium, methylthymol blue, bromocresol purple, bromocresol purple sodium, bromocresol green, or bromocresol green sodium. The information of the above organic compounds is shown in Table 1:

[0012] Table 1 Metal ion indicators whose core structure is selected from 4-benzylidene-2,5-cyclohexadiene-1-one

[0013]

[0014]

[0015] Preferably, when the parent core structure is phenylazonaphthalene, the metal ion indicator is acidic mordant blue K, 1-(2-pyridyl azo)-2-naphthol, or chrome blue SE. The information of the above organic compounds is shown in Table 2:

[0016] Table 2 Metal ion indicators whose parent core structure is selected from phenylazonaphthalene

[0017]

[0018] Preferably, when the parent core structure is triazine phenyl azonaphthalene, the metal ion indicator is Reactive Red 2. The information of the above organic compounds is shown in Table 3:

[0019] Table 3 The metal ion indicator whose parent core structure is selected from triazinylphenylazonaphthalene

[0020]

[0021] Preferably, when the parent core structure is naphthyl azonaphthalene, the metal ion indicator is chrome black T or chrome blue black R. The information of the above organic compounds is shown in Table 4:

[0022] Table 4 Metal ion indicators whose parent core structure is selected from naphthyl azo naphthalene

[0023]

[0024] Preferably, when the parent core structure is diphenylbis(azo)naphthalene, the metal ion indicator is arsenazo III. The information of the above organic compounds is shown in Table 5:

[0025] Table 5 The metal ion indicator whose parent core structure is selected from diphenylbis(azo)naphthalene

[0026]

[0027] Preferably, when the core structure is phenylazobenzene, the metal ion indicator is 4-(2-pyridyl azo) resorcinol. The information of the above organic compounds is shown in Table 6:

[0028] Table 6 Metal ion indicators whose core structure is selected from phenylazobenzene

[0029]

[0030] Preferably, when the parent core structure is triphenylmethane, the metal ion indicator is bromophenol blue, bromophenol blue sodium, bromophenol red, or bromophenol red sodium. The information of the above organic compounds is shown in Table 7:

[0031] Table 7 Metal ion indicators whose core structure is selected from triphenylmethane

[0032]

[0033] Preferably, the components of the electrolyte include: one or more metal ion indicators, a soluble electrolyte, and water.

[0034] More preferably, the soluble electrolyte includes at least one of zinc sulfate, zinc trifluoromethanesulfonate, zinc perchlorate, zinc sulfate, zinc chloride, zinc nitrate, zinc acetate, copper sulfate, copper chloride, magnesium chloride, calcium chloride, lithium chloride, sodium chloride, potassium chloride, and potassium hydroxide.

[0035] More preferably, the total concentration of the metal ion indicator in the electrolyte is 0.01 to 3000 mmol·L -1 More preferably, it is 0.1 to 50 mmol·L -1 More preferably, it is 1 to 10 mmol·L -1 .

[0036] More preferably, the concentration of the soluble electrolyte is 0.1 to 10 mol·L -1 More preferably, it is 1 to 3 mol·L -1 .

[0037] Preferably, the method for preparing the electrolyte containing the metal ion indicator comprises the following steps: mixing one or more of the metal ion indicators, a soluble electrolyte, and water to prepare the electrolyte containing the metal ion indicator.

[0038] A second aspect of the present invention provides an aqueous electrochemical energy storage device comprising a positive electrode, a negative electrode, and the electrolyte containing the metal ion indicator according to the first aspect.

[0039] Preferably, the positive electrode is a positive electrode current collector loaded or unloaded with a positive electrode active material; the positive electrode active material is selected from at least one of activated carbon, carbon nanotubes, MXene, manganese-based oxides, vanadium-based oxides, Prussian blue derivatives, polyanion compounds, and organic positive electrode materials.

[0040] Preferably, the negative electrode is at least one of metal zinc or metal zinc modified metal, metal copper or metal copper modified metal, metal tin or metal tin modified metal, metal magnesium or metal magnesium modified metal, metal calcium or metal calcium modified metal, metal lithium or metal lithium modified metal, metal potassium or metal potassium modified metal.

[0041] Preferably, the aqueous electrochemical energy storage device further includes a diaphragm.

[0042] More preferably, the separator is selected from separator glass fiber, polyethylene, polypropylene polyolefin microporous membrane, porous polymer membrane, non-woven separator, filter paper or filter membrane.

[0043] The third aspect of the present invention provides any of the following applications of the aqueous electrochemical energy storage device described in the second aspect:

[0044] 1) Supercapacitors; 2) Hybrid capacitors; 3) Metal ion batteries; 4) Flow batteries.

[0045] Preferably, the aqueous electrochemical energy storage device is used in a Zn / / Zn symmetrical battery.

[0046] Preferably, the aqueous electrochemical energy storage device is used in a Cu / / Cu symmetric battery.

[0047] Preferably, the aqueous electrochemical energy storage device is used in a Zn / / Cu asymmetric battery.

[0048] Preferably, the aqueous electrochemical energy storage device is used in a Zn / / AC zinc ion hybrid capacitor.

[0049] The beneficial effects of the present invention are:

[0050] (1) The present invention discloses an electrolyte containing a metal ion indicator. The metal ion indicator is used as an electrolyte additive. Not only can its color change characteristics be more convenient for characterizing the boundary, composition, and structure, but also after the metal indicator is combined with the metal ion, the solvation structure of the metal ion is improved, the occurrence of electrode side reactions can be reduced, and the electrode stability is improved. The Zn / / Zn symmetrical battery using the BCPS color-changing electrolyte is at 25°C and 2 mA cm -2 , 1mAh·cm -2 Under these conditions, the cycle life can be increased from 33h without additives to 2000h. At the same time, its reversible redox reaction provides additional capacity for the energy storage device. Therefore, the application of metal ion indicators as additives in electrolytes provides new possibilities for the design of energy storage devices.

[0051] (2) The electrolyte containing the metal ion indicator of the present invention can be used as a new type of color-changing electrolyte. The present invention uses a metal ion indicator that can change color after combining with metal ions. When the metal ions combine with the indicator, it will cause the redistribution of electrons. This change in energy level will cause the molecules to change their absorption characteristics of light, affecting the color of the solution, thereby causing a color change in the visible light region. The occurrence of the transformation can be directly observed with the naked eye, and the absorption spectrum changes due to the structural transformation. In related tests, the test results are more obvious, such as the ultraviolet-visible absorption spectrum. Therefore, the present invention takes color change as the design subject, provides a more direct electrolyte modification and characterization idea, and successfully applies the color-changing electrolyte to energy storage devices, promotes subsequent electrolyte research and development, and provides a new direction for the optimization of energy storage device design strategies and research paths in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 The following is a color comparison chart of the color-changing electrolytes prepared with different ion indicators in Example 1 (c in the figure), Example 2 (a in the figure), and Example 3 (b in the figure);

[0053] Figure 2 Figure 1 shows the UV-visible spectra and color comparison of the color-changing electrolytes containing BCPS prepared in Example 1 at different molar ratios of zinc sulfate and copper sulfate. Figure a shows the UV-visible spectrophotometry (UV-Vis) when zinc sulfate is added; figure b shows the color change when zinc sulfate is added; figure c shows the UV-visible spectrophotometry (UV-Vis) when copper sulfate is added; and figure d shows the color change when copper sulfate is added.

[0054] Figure 3 Scanning electron micrographs of the metallic zinc negative electrodes prepared in Example 1 (d in the figure), Example 2 (b in the figure), Example 3 (c in the figure), and Comparative Example 1 (a in the figure) after charge and discharge cycles;

[0055] Figure 4The Zn / / Zn symmetrical cells prepared in Example 1 (d in the figure), Example 2 (b in the figure), Example 3 (c in the figure) and Comparative Example 1 (a in the figure) were heated to 25°C and the current density was 2 mA·cm -2 and 1mAh·cm -2 Time voltage curve under the conditions;

[0056] Figure 5 The Cu / / Cu symmetrical battery prepared in Example 1 (b) and Comparative Example 1 (a) was heated to 25°C and the current density was 2 mA·cm -2 and 1mAh·cm -2 Time voltage curve under the conditions;

[0057] Figure 6 Graph showing the charge and discharge coulombic efficiency (CE) of the Zn / / Cu asymmetric battery prepared in Example 1 and Comparative Example 1;

[0058] Figure 7 CV test results and redox reaction mechanism diagrams of the Zn / / AC zinc ion hybrid capacitors prepared in Examples 1-2 and Comparative Example 1; wherein a is the CV test result diagram of Example 1; b is the CV test result diagram of Example 2; c is the redox reaction mechanism diagram;

[0059] Figure 8 Graph showing the charge and discharge results of the Zn / / AC zinc ion hybrid capacitors prepared in Example 1 and Comparative Example 1;

[0060] Figure 9 Schematic diagram of optimizing the control of the color-changing electrolyte by the metal ion indicator prepared in Examples 1-3. DETAILED DESCRIPTION

[0061] The present invention is further described in detail below through specific examples. Unless otherwise specified, the raw materials used in the following examples can be obtained from conventional commercial sources or prepared and isolated by simple synthesis; unless otherwise specified, the processes used are conventional processes in the art.

[0062] Example 1

[0063] This embodiment provides an electrolyte containing a metal ion indicator, and the preparation method thereof is as follows:

[0064] At room temperature, 28753.00 mg of zinc sulfate heptahydrate was completely dissolved in 50 mL of deionized water, and then 281.10 mg of bromocresol purple sodium (BCPS, 10 mmol·L -1 ) and used as a color-changing electrolyte for zinc negative electrode energy storage devices.

[0065] Example 2

[0066] This embodiment provides an electrolyte containing a metal ion indicator, and the preparation method thereof is as follows:

[0067] At room temperature, 28753.00 mg of zinc sulfate heptahydrate was completely dissolved in 50 mL of deionized water, and then 38.64 mg of pyrogallol purple (PV, 10 mmol·L) was added. -1 ) and used as a color-changing electrolyte for zinc negative electrode energy storage devices.

[0068] Example 3

[0069] This embodiment provides an electrolyte containing a metal ion indicator, and the preparation method thereof is as follows:

[0070] At room temperature, 28753.00 mg of zinc sulfate heptahydrate was completely dissolved in 50 mL of deionized water, and then 61.53 mg of Reactive Red 2 (RR, 10 mmol·L) was added. -1 ) and used as a color-changing electrolyte for zinc negative electrode energy storage devices.

[0071] Comparative Example 1

[0072] The comparative example provides an electrolyte that does not contain a metal ion indicator, and the preparation method thereof is as follows: 28753.00 mg of zinc sulfate heptahydrate is completely dissolved in 50 mL of deionized water at room temperature, and the electrolyte is used as the zinc negative electrode energy storage device.

[0073] Color change test

[0074] 1. Dissolve 0.19 mg of pyrogallol purple (PV) in 10 ml of deionized water at room temperature to prepare 0.05 mmol·L -1 Dissolve 0.31 mg of Reactive Red 2 (RR) in 10 ml of deionized water to prepare 0.05 mmol·L -1 Reactive Red 2 aqueous solution, set aside. Mix two 0.06mg portions of zinc sulfate heptahydrate (ZnSO4·7H2O, 0.05mmol·L -1 ) were added with 4 ml of the above-prepared 0.05 mmol·L -1 In aqueous solution of pyrogallol violet and aqueous solution of reactive red 2.

[0075] Color changes such as Figure 1 For a and b in the figure, the solution color changed significantly after adding ZnSO4, indicating that PV and RR can undergo chelation and coordination with zinc ions.

[0076] At room temperature, dissolve 1.40 mg of bromocresol purple sodium in 50 ml of deionized water to prepare 0.05 mmol·L -1Bromocresol purple sodium aqueous solution, set aside. 0.06 mg zinc sulfate heptahydrate (ZnSO4·7H2O, 0.05 mmol·L -1 ), 0.03 mg copper sulfate (CuSO4, 0.05 mmol·L -1 ), 0.02mg lithium chloride (LiCl, 0.05mmol·L -1 ), 0.01mg magnesium chloride (MgCl2, 0.05mmol·L -1 ) were added with 4 ml of the above-prepared 0.05 mmol·L -1 Bromocresol purple sodium aqueous solution.

[0077] Color changes such as Figure 1 As shown in Figure c, after adding ZnSO4, CuSO4, LiCl, and MgCl2 respectively, the BCPS solution underwent different degrees of color changes, indicating that BCPS coordinated with metal ions.

[0078] 2. Add 0.01mg, 0.02mg, 0.03mg, 0.04mg, 0.06mg, 0.09mg and 0.11mg of zinc sulfate heptahydrate to 4ml of the above-prepared 0.05mmol / L -1 Bromocresol purple sodium aqueous solution.

[0079] Color change and UV-Vis spectrophotometry (UV-Vis) test Figure 2 As shown in a and b, after adding different molar ratios of ZnSO4 to the BCPS solution, the color changed to varying degrees, and the hydroxyl peak near 427.5nm in the UV-Vis test underwent an obvious red shift as the molar ratio of BCPS to ZnSO4 continued to increase, indicating that BCPS has a strong coordination effect with zinc ions and forms a relatively stable complex.

[0080] Add 0.006 mg, 0.01 mg, 0.02 mg, 0.025 mg, 0.03 mg, 0.05 mg, and 0.6 mg of copper sulfate to 4 ml of the 0.05 mmol·L -1 Bromocresol purple sodium aqueous solution.

[0081] Color change and UV-Vis test Figure 2 As shown in c and d, after adding different molar ratios of CuSO4 to the BCPS solution, the color changed to varying degrees. In the UV-Vis test, the hydroxyl peak near 427.5nm underwent an obvious red shift as the molar ratio of BCPS to CuSO4 continued to increase, and the conjugated structure peak at 588nm decreased significantly, indicating that BCPS also has a strong coordination effect with copper ions, forming a relatively stable complex.

[0082] Electrochemical performance test

[0083] 1. Preparation of batteries and capacitors

[0084] A Zn / / Zn symmetric cell was assembled using zinc foil as the positive and negative electrodes and filter paper as the separator. A Zn / / Cu asymmetric cell was assembled using copper foil as the positive electrode, zinc foil as the negative electrode, and glass fiber as the separator. A Zn / / AC zinc ion hybrid capacitor was assembled using activated carbon as the positive electrode, zinc foil as the negative electrode, and filter paper as the separator. A Cu / / Cu symmetric cell was assembled using copper foil as the positive and negative electrodes and filter paper as the separator.

[0085] Preparation process of activated carbon (AC) positive electrode sheet: 800 mg of AC, 100 mg of conductive carbon black, and 100 mg of PVDF were weighed into an agate mortar according to the mass ratio of 8:1:1 and stirred evenly. Then 3 mL of NMP was dropped into the slurry and ground for 10 minutes until it became a uniform slurry. The slurry was evenly coated on the surface of the stainless steel sheet with an applicator, and then dried in a vacuum drying oven at 60°C for 12 hours. The positive electrode sheet was then taken out and cut into a diameter of 11.3 mm.

[0086] Preparation process of zinc electrode sheet: Use sandpaper to polish the surface of zinc foil, then cut it into negative electrode sheets with a diameter of 11.3 mm, add ethanol for ultrasonic cleaning, put it in an oven for drying, and take it out for use.

[0087] Preparation process of copper electrode sheet: polish the surface of copper-zinc foil with sandpaper, then cut it into negative electrode sheets with a diameter of 11.3 mm, add ethanol for ultrasonic cleaning, put it in an oven for drying, and take it out for use.

[0088] Glass fiber diaphragm preparation process: Cut the uncontaminated glass fiber diaphragm into a diameter of 16 mm.

[0089] Preparation process of cellulose filter paper membrane: Cut uncontaminated cellulose filter paper membrane into 16mm diameter.

[0090] The assembly process for the button-type LIR2032 Zn / / Zn symmetrical battery, Zn / / Cu asymmetric battery, and Zn / / AC hybrid capacitor is as follows: First, place the spring element on the negative electrode shell side, followed by the gasket, zinc sheet, and separator. The electrolyte prepared in the above examples and comparative examples is added dropwise to wet the separator. The zinc sheet (symmetrical battery), activated carbon positive electrode sheet (hybrid capacitor), copper positive electrode sheet (half-cell), and positive electrode shell are then added. The battery is then sealed in a static press. The assembled battery is placed in a vacuum drying oven (25°C) for 4 hours to obtain the Zn / / Zn symmetrical battery, Zn / / AC zinc ion hybrid capacitor, and Zn / / Cu asymmetric battery, ready for use. Cycling performance testing is then performed.

[0091] The assembly process for the button-type LIR2032 Cu / / Cu symmetrical battery is as follows: First, place the spring element into the negative electrode casing, followed by the gasket, copper sheet, and separator. The electrolyte prepared in the above examples and comparative examples is dripped onto the separator to wet it. The copper sheet and positive electrode casing are then placed. The battery is then sealed with a static press. The assembled battery is placed in a vacuum drying oven (25°C) for 4 hours before use. The assembled Cu / / Cu symmetrical battery is then used for cycling performance testing.

[0092] 2. Test methods and results

[0093] (1) Scanning electron microscope (SEM) sample preparation: at 25°C, 2 mA·cm -2 , 1mAh·cm -2 , conditions, the zinc sulfate solutions prepared in the above examples and comparative examples were used as electrolytes to assemble Zn / / Zn symmetrical batteries. After cycling for 100 h, the zinc negative electrode samples were taken for SEM observation.

[0094] SEM test results are as follows Figure 3 As shown, Figure 3 a in the figure is the test result of Comparative Example 1 (hereinafter, Examples 1-3 and Comparative Example 1 refer to the corresponding batteries), and it can be observed that the dendrites grow in disorder and the interface is uneven; Figure 3 b and c are the test results of Examples 2 and 3, respectively. It can be observed that the zinc crystals grow flat and dense, which is conducive to the long cycle process of the battery; Figure 3 d in the figure is the test result of Example 1. It can be observed that the zinc crystals grow flat and dense, which is beneficial to the long cycle process of the battery.

[0095] (2) The test results of Zn / / Zn symmetrical battery are as follows Figure 4 As shown, the Zn / / Zn symmetrical battery of Comparative Example 1 is at 25°C and 2 mA·cm -2 , 1mAh·cm -2 Under these conditions, the cycle life is only 33h ( Figure 4 a); Zn / / Zn symmetric battery using PV and RR color-changing electrolytes at 25°C, 2 mA cm -2 , 1mAh·cm -2 Under these conditions, the cycle life reaches 400h and 831h respectively ( Figure 4 b, c); Zn / / Zn symmetric battery using BCPS color-changing electrolyte at 25℃, 2mA·cm -2 , 1mAh·cm -2 Under these conditions, the cycle life reaches 2000h( Figure 4 d) in the above.

[0096] (3) The test results of Cu / / Cu symmetrical battery are as follows Figure 5 As shown, the Cu / / Cu symmetrical battery of Comparative Example 1 is at 25°C and 2 mA·cm -2 , 1mAh·cm -2 Under these conditions, the cycle life is only 56h ( Figure 5 a); Cu / / Cu symmetric cell using BCPS color-changing electrolyte at 25°C, 2 mA·cm -2 , 1mAh·cm -2 Under these conditions, the cycle life reaches 590h( Figure 5 b) in the above example.

[0097] (4) Zn / / Cu asymmetric battery at 25°C, 2 mA·cm -2 , 1mAh·cm -2 Charge and discharge test under the conditions Figure 6 As shown, the coulombic efficiency of the Zn / / Cu asymmetric battery in comparative example 1 fluctuated violently at 227 cycles, and the coulombic efficiency dropped to 0%; the coulombic efficiency of the Zn / / Cu asymmetric battery using BCPS color-changing electrolyte remained 100% at 429 cycles.

[0098] (5) CV test results of Zn / / AC zinc ion hybrid capacitor are as follows Figure 7 As shown, the CV curve of comparative example 1 is quasi-rectangular, which is a typical feature of hybrid ion capacitors, but has no additional capacity; the CV test results of the Zn / / AC zinc ion hybrid capacitor using BCPS color-changing electrolyte are shown in Figure 7 As shown in a, the CV curve has a clear prominent peak, indicating that there is an additional capacity; the CV test results of the Zn / / AC zinc ion hybrid capacitor using PV color-changing electrolyte are shown in Figure 7 As shown in Figure b, the CV curve has a prominent peak, indicating that there is an additional capacity. The additional redox reaction mechanism of BCPS and PV is as follows Figure 7 As shown in c.

[0099] (6) Zn / / AC zinc ion hybrid capacitor at 1A·g -1 The test results under current density charge and discharge are as follows Figure 8 As shown in Figure 2, the coulombic efficiency of comparative example 1 is close to 100%, but the capacity before cycling is 62.0 mAh g -1 The capacity after 1000 cycles is 54.6 mAh g -1 , the capacity retention rate is only 88.1%; the coulombic efficiency of the Zn / / AC zinc ion hybrid capacitor using BCPS color-changing electrolyte is 100%, and the capacity before cycling is 69.8 mAh g -1 The capacity after 1000 cycles is 62.4 mAh g -1, the capacity retention rate is 89.4%.

[0100] In summary, the present invention uses a metal ion indicator to prepare a color-changing electrolyte, and its color-changing characteristics can more conveniently characterize the boundary, composition, and structure. Moreover, after the metal indicator combines with the metal ion, the solvation structure of the metal ion is improved. Figure 9 This diagram shows the optimized control of the color-changing electrolyte using the metal ion indicator prepared in Examples 1-3. This method can reduce electrode side reactions, improve electrode stability, and provide additional capacity for energy storage devices through its reversible redox reaction. Further research has shown that the metal ion indicator is applicable to different metal ions, providing a universal optimization strategy for metal electrodes. This invention has the advantages of simple process and low cost, which is of great significance for promoting the commercialization of aqueous electrolytes.

[0101] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. An electrolyte containing a metal ion indicator, characterized in that: The metal ion indicator is an organic compound or a salt thereof; the organic compound has a parent core structure and a substituent, and the parent core structure is selected from 4-dibenzylidene-2,5-cyclohexadiene-1-one, phenylazonaphthalene, triazine-phenylazonaphthalene, naphthylazonaphthalene, diphenylbisazonaphthalene, phenylazobenzene, or triphenylmethane; the substituent of the organic compound is selected from at least one of a hydroxyl group, a sulfonic acid group, a carboxyl group, a halogen group, an arsonyl group, and a dicarboxymethyl nitrogen group.

2. The electrolyte containing a metal ion indicator according to claim 1, characterized in that When the core structure is 4-benzylidene-2,5-cyclohexadien-1-one, the metal ion indicator is pyrogallol purple, meta-cresol purple, meta-cresol purple sodium, xylenol orange sodium, methylthymol blue, bromocresol purple, bromocresol purple sodium, bromocresol green or bromocresol green sodium.

3. The electrolyte containing a metal ion indicator according to claim 1, wherein When the parent core structure is phenylazonaphthalene, the metal ion indicator is acidic mordant blue K, 1-(2-pyridylazo)-2-naphthol or chrome blue SE; and / or, when the parent core structure is triazine-phenylazonaphthalene, the metal ion indicator is reactive red 2; and / or, when the parent core structure is naphthylazonaphthalene, the metal ion indicator is chrome black T or chrome blue black R; and / or, when the parent core structure is diphenyldisazonaphthalene, the metal ion indicator is azoarsine III; and / or, when the parent core structure is phenylazobenzene, the metal ion indicator is 4-(2-pyridylazo)resorcinol.

4. The electrolyte containing a metal ion indicator according to claim 1, wherein When the parent core structure is triphenylmethane, the metal ion indicator is bromophenol blue, bromophenol blue sodium, bromophenol red, or bromophenol red sodium.

5. The electrolyte containing a metal ion indicator according to any one of claims 1 to 4, characterized in that The components of the electrolyte include: one or more metal ion indicators, a soluble electrolyte, and water.

6. The electrolyte containing a metal ion indicator according to claim 5, characterized in that The soluble electrolyte includes at least one of zinc sulfate, zinc trifluoromethanesulfonate, zinc perchlorate, zinc sulfate, zinc chloride, zinc nitrate, zinc acetate, copper sulfate, copper chloride, magnesium chloride, calcium chloride, lithium chloride, sodium chloride, potassium chloride, and potassium hydroxide.

7. The electrolyte containing a metal ion indicator according to claim 1, wherein The total concentration of the metal ion indicator in the electrolyte is 0.01-3000 mmol·L -1 .

8. An aqueous electrochemical energy storage device, characterized in that: The invention comprises a positive electrode, a negative electrode and an electrolyte containing a metal ion indicator according to any one of claims 1 to 7.

9. The aqueous electrochemical energy storage device according to claim 8, characterized in that: The positive electrode is a positive electrode current collector loaded with a positive electrode active material; the positive electrode active material is selected from at least one of activated carbon, carbon nanotubes, MXene, manganese-based oxides, vanadium-based oxides, Prussian blue derivatives, polyanion compounds, and organic positive electrode materials; And / or, the negative electrode is at least one of metal zinc or metal zinc modified metal, metal copper or metal copper modified metal, metal tin or metal tin modified metal, metal magnesium or metal magnesium modified metal, metal calcium or metal calcium modified metal, metal lithium or metal lithium modified metal, metal potassium or metal potassium modified metal.

10. Any of the following uses of the aqueous electrochemical energy storage device according to claim 8 or 9: 1) Supercapacitors; 2) Hybrid capacitors; 3) Flow batteries; 4) Metal ion batteries.

Images