Aqueous composite electrolyte containing amide polar organic additive as well as preparation method and application of aqueous composite electrolyte

Abstract

The invention discloses an aqueous composite electrolyte containing an amide polar organic additive and a preparation method and application thereof, and belongs to the technical field of aqueous zinc ion batteries. The aqueous composite electrolyte comprises electrolyte salt, an amide polar additive and deionized water, wherein the concentration of the amide polar additive is 0.005 to 0.04 mol L <-1 >, and the concentration of the electrolyte salt is 1 to 3 mol L <-1 >. N-(2-ethoxyl) succinimide is most preferably selected as the amide polar organic additive. The preparation method comprises the following steps: adding electrolyte salt into deionized water to prepare an aqueous zinc salt electrolyte; and after the pH value of the aqueous zinc salt electrolyte is stable, the carbonyl polar additive is added, and the aqueous composite electrolyte containing the carbonyl polar additive is obtained. The aqueous composite electrolyte can enhance the cycling stability, coulombic efficiency and reversible capacity of the battery in the aqueous zinc battery.

Description

Technical Field

[0001] The present invention relates to the technical field of aqueous zinc ion batteries, and in particular to an aqueous composite electrolyte containing an amide polar organic additive, and a preparation method and application thereof. Background Art

[0002] As a promising candidate for aqueous metal batteries, zinc metal exhibits higher safety, low cost, good stability in aqueous environments, a good redox potential (-0.762 V vs. standard hydrogen electrode (SHE)), and a high theoretical capacity (820 mAh g -1 ), making it a highly competitive anode for aqueous metal-ion batteries.

[0003] However, due to the uneven nucleation of Zn and the 2+ The slow diffusion kinetics may lead to the formation of Zn dendrites of various shapes growing perpendicular to the electrode surface, which can puncture the separator and cause battery short circuits. In addition, during the cycling process, the hydrogen evolution reaction and anode surface corrosion caused by the side reaction of zinc with active water will continuously consume the electrolyte and zinc anode, and cause the accumulation of insulating byproducts on the surface of the zinc negative electrode and the continuous occurrence of surface passivation, which seriously affects the stability and service life of the zinc-ion battery.

[0004] These two intertwined factors significantly reduce the Coulombic efficiency and cycle life of aqueous zinc-ion batteries, making it difficult for their excellent electrochemical performance to meet the stringent requirements of practical applications and significantly limiting their practicality as large-scale energy storage systems.

[0005] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the Invention

[0006] The technical problem to be solved by the present invention is that the uneven zinc deposition in existing aqueous metal batteries leads to dendrite growth, poor corrosion resistance of the negative electrode, poor electrochemical performance and cycle stability, and low electrolyte stability.

[0007] In order to solve the above technical problems, the present invention provides an aqueous composite electrolyte containing additives, which comprises: electrolyte salt, polar organic additive containing carbonyl group and deionized water; wherein the concentration of polar organic additive containing carbonyl group is 0.005-0.04 mol L -1 The concentration of electrolyte salt is 0.5-3.5 mol L -1 The concentration of the above-mentioned amide polar organic additive should not be too high, especially not more than 0.1 mol L -1The higher the concentration of the amide polar organic additive, the more it affects the zinc transfer efficiency in the electrolyte, making the polarization voltage during the cycle larger. Preferably, the concentration of the amide polar organic additive is 0.02 mol L -1 .

[0008] In one or more embodiments of the present invention, the carbonyl-containing polar organic additive is any one of an aldehyde compound, a ketone compound, a carboxylic acid compound, and an amide compound.

[0009] In one or more embodiments of the present invention, the aldehyde compound is a combination of one or more of formaldehyde, acetaldehyde, benzaldehyde, phenylacetaldehyde, and acrolein.

[0010] In one or more embodiments of the present invention, the ketone compound is a combination of one or more of acetone, cyclohexanone, and acetophenone.

[0011] In one or more embodiments of the present invention, the carboxylic acid compound is a combination of one or more of acetic acid, propionic acid, acrylic acid, oleic acid, benzoic acid, phthalic acid, oxalic acid, and citric acid.

[0012] In one or more embodiments of the present invention, the above-mentioned amide polar organic additive is a combination of one or more of butanamide, caprylamide, laurylamide, stearylamide, benzamide, phthalocyanine amide, N-(2-hydroxyethyl)succinamide, N-methylpyrrolidone, pyrrolamide, thiazoleamide, and acetamide.

[0013] In one or more embodiments of the present invention, the aldehyde compound is one or both of formaldehyde and acrolein; the ketone compound is one or both of acetone and cyclohexanone; and the carboxylic acid compound is a combination of one or more of acetic acid, benzoic acid, and citric acid.

[0014] In one or more embodiments of the present invention, the amide compound is a combination of one or more of N-(2-hydroxyethyl)succinamide and N-methylpyrrolidone.

[0015] In one or more embodiments of the present invention, the amide polar organic additive is N-(2-hydroxyethyl)succinamide.

[0016] The present invention adds an amide-type polar organic additive to an aqueous electrolyte containing an electrolyte salt to prepare an aqueous composite electrolyte. The inventor utilizes the characteristics of the carbonyl group of any one of the amide-type polar organic additives, especially N-(2-hydroxyethyl)succinamide, to achieve stronger adsorption energy with the zinc anode, preferentially adsorbing on active sites on the surface of the zinc anode, reducing the binding of water molecules with the zinc metal, forming a water-poor double layer, and then forming a smooth deposition surface through two-dimensional diffusion. At the same time, the carbonyl group in the additive participates in the solvation structure of the zinc ion, replacing the active water molecules therein, effectively controlling the free water content, inhibiting hydrogen evolution corrosion and dendrite growth of the zinc anode, promoting uniform zinc deposition, and achieving the excellent effect of improving the reversibility of zinc deposition / stripping.

[0017] In one or more embodiments of the present invention, the electrolyte salt is a soluble zinc salt; preferably, the soluble zinc salt is selected from one or a combination of two or more of zinc sulfate, zinc trifluoromethanesulfonimide, zinc trifluoromethanesulfonate, zinc acetate, zinc chloride, zinc nitrate, zinc perchlorate, and zinc tetrafluoroborate.

[0018] In one or more embodiments of the present invention, the concentration of the amide polar organic additive is 0.005-0.03 mol L -1 , the concentration of electrolyte salt is 0.5-3.0 mol L -1 .

[0019] In one or more embodiments of the present invention, the concentration of the amide polar organic additive is 0.01-0.03 mol L -1 , the concentration of electrolyte salt is 1.0-3.0 mol L -1 .

[0020] The present invention also provides a method for preparing an aqueous composite electrolyte, comprising the following steps:

[0021] Step 1: Add the above electrolyte salt to deionized water to prepare an aqueous electrolyte;

[0022] Step 2: After the pH value of the aqueous electrolyte obtained in step (1) is stabilized, the above-mentioned amide polar organic additive is added, stirred until dissolved, and allowed to stand to obtain a stable aqueous composite electrolyte containing the amide polar organic additive; preferably, the pH value is 2.5-4.5, and most preferably, the pH value is 3.14; wherein the concentration of the above-mentioned amide polar organic additive is 0.005-0.04 mol L -1 The concentration of electrolyte salt is 0.5-3.5 mol L -1 .

[0023] The present invention also provides a battery comprising positive and negative electrodes, a battery separator and the above aqueous composite electrolyte, and further comprising a battery case, a spring and a gasket.

[0024] In one or more embodiments of the present invention, the battery separator is a glass fiber separator.

[0025] The present invention also provides an application of the aqueous composite electrolyte or the aqueous composite electrolyte prepared by the above preparation method. The aqueous composite electrolyte can be used to prepare a symmetrical battery, a half-cell or an aqueous zinc ion battery.

[0026] In one or more embodiments of the present invention, the symmetrical battery is assembled by the aqueous composite electrolyte and commercial zinc sheets.

[0027] In one or more embodiments of the present invention, the half-cell is assembled by using the aqueous composite electrolyte and a commercial current collector.

[0028] In one or more embodiments of the present invention, the commercial current collector is selected from any one of copper foil, titanium foil, nickel foil, copper mesh, nickel mesh, stainless steel mesh, foam copper, and foam nickel.

[0029] In one or more embodiments of the present invention, the aqueous zinc ion battery is assembled by the aqueous composite electrolyte, commercial zinc sheets, and MnO2 or V2O5 as a positive electrode.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention adds amide-containing polar organic additives to an aqueous composite electrolyte. Since amide-containing polar organic additives have a large number of carbonyl groups, they can enter the solvation structure of metal ions such as zinc ions in aqueous zinc salt electrolytes, replacing the active water molecules therein, effectively controlling the free water content. In addition, amide-containing polar organic additives have stronger adsorption energy with the zinc anode and preferentially adsorb on the active sites on the surface of the zinc anode, reducing the binding of water molecules to the zinc anode, forming a water-poor double layer, and then forming a smooth deposition surface through two-dimensional diffusion. The inhibition of the adsorption and decomposition of active water molecules on the electrode surface inhibits hydrogen evolution corrosion and dendrite growth of the zinc anode, promoting uniform zinc deposition, thereby improving the cycle stability of the zinc negative electrode. DFT calculations have shown that the adsorption energy of N-(2-hydroxyethyl)succinamide on the zinc surface is -7.23eV, significantly higher than the -1.22eV of water molecules (see Supplementary Example 5).

[0032] Amide-based polar organic additives also contain amino groups, which can anchor to the surface of the zinc anode, reducing the contact between water molecules and metallic zinc and protecting the zinc anode from corrosion. Furthermore, amino groups synergize with other polar groups to guide the uniform deposition of zinc ions and inhibit dendrite growth. Furthermore, amino groups can improve the battery's cycle stability and broaden its operating temperature range. These effects collectively enhance the performance and safety of aqueous zinc-ion batteries.

[0033] The present invention adds a concentration of 0.005-0.04 mol L -1 The amide-based polar organic additive (preferably N-(2-hydroxyethyl)succinamide or N-methyl-2-pyrrolidone) significantly improves the stability of the electrolyte. Specific technical effects include:

[0034] Dendrite inhibition: The carbonyl groups in the additive are preferentially adsorbed on the surface of the zinc anode, forming a water-poor double layer (see SEM images and NMR data of Examples 1-3).

[0035] Reduce hydrogen evolution: carbonyl anchors the zinc surface, reducing free water activity (see Figure 9-10 1H spectroscopy analysis).

[0036] Improved cycle life: Symmetrical battery cycle exceeds 7500h, and the capacity retention rate of the full battery after 7000 cycles is ≥80% (see Example 1 and comparative data).

[0037] Different from existing carboxylate additives, the present invention achieves synergistic enhancement through the dual effects of amide groups (carbonyl coordination and amino adsorption), thereby improving battery cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The electrokinetic polarization curves of commercial zinc flakes in the 2M zinc sulfate aqueous solution obtained in Example 1 and the aqueous composite electrolyte containing an amide polar organic additive;

[0039] Figure 2 (a) SEM image of the negative electrode surface of a symmetrical battery assembled with a commercial zinc sheet and the 2M zinc sulfate aqueous solution electrolyte obtained in Example 1 after 10 cycles;

[0040] Figure 2 (b) is a SEM image of the negative electrode surface of a symmetrical battery assembled with a commercial zinc sheet using the 2M zinc sulfate aqueous solution obtained in Example 1 and an aqueous composite electrolyte containing an amide polar organic additive after 10 cycles;

[0041] Figure 3 The Zn in the symmetrical battery assembled with commercial zinc sheets in different electrolytes obtained in Example 1 2+ Schematic diagram of the solvation structure and its deposition behavior, Figure 3(a) The Zn in the symmetrical cell assembled with the commercial zinc sheet and the 2M zinc sulfate aqueous solution electrolyte obtained in Example 1 2+ Schematic diagram of the solvation structure and its deposition behavior, Figure 3 (b) The Zn content in the symmetrical cell assembled by the commercial zinc flakes with the 2M zinc sulfate aqueous solution obtained in Example 1 and the aqueous composite electrolyte containing the amide polar organic additive is 2+ Schematic diagram of the solvation structure and its deposition behavior;

[0042] Figure 4 Comparative curves of coulombic efficiency tests of half-cells assembled with commercial zinc sheet, copper foil, 2M zinc sulfate aqueous solution obtained in Example 1, and aqueous composite electrolyte containing amide polar organic additives;

[0043] Figure 5 The time-voltage comparison graph of the cycling stability test of symmetrical batteries assembled with commercial zinc sheets, the 2M zinc sulfate aqueous solution obtained in Example 1, and the aqueous composite electrolyte containing an amide polar organic additive;

[0044] Figure 6 Specific capacity and efficiency diagrams of full battery cycles assembled with commercial V2O5, 2M aqueous zinc sulfate solution obtained in Example 1, and aqueous composite electrolyte containing amide polar organic additives;

[0045] Figure 7 Time-voltage comparison graph of cycling stability tests of symmetrical cells assembled using a commercial zinc sheet as the negative electrode, using the 2M zinc sulfate aqueous solution (aqueous zinc salt electrolyte) obtained in Example 1 of the present invention and the aqueous composite electrolyte containing an amide polar organic additive, the aqueous composite electrolyte containing an amide polar organic additive obtained in Comparative Example 1, the aqueous composite electrolyte containing an amide polar organic additive obtained in Comparative Example 2, and the aqueous composite electrolyte containing an amide polar organic additive obtained in Comparative Example 3, respectively;

[0046] Figure 8 Specific capacity diagram of full battery cycles assembled with commercial V2O5, the 2M aqueous zinc sulfate solution (aqueous zinc salt electrolyte) obtained in Example 1 and the 2M aqueous composite electrolyte containing an amide-type polar organic additive, the 1M aqueous zinc sulfate solution (aqueous zinc salt electrolyte) obtained in Example 3 and the 1M aqueous composite electrolyte containing an amide-type polar organic additive, and the 3M aqueous zinc sulfate solution (aqueous zinc salt electrolyte) obtained in Example 4 and the 3M aqueous composite electrolyte containing an amide-type polar organic additive;

[0047] Figure 9 Chemical shift spectrum of H NMR spectrum test for pure aqueous solution;

[0048] Figure 10Chemical shift spectra obtained by nuclear magnetic resonance hydrogen spectroscopy testing of the 2M zinc sulfate aqueous solution (aqueous zinc salt electrolyte) and the aqueous composite electrolyte containing a polycarboxyl salt additive obtained in Example 1 of the present invention, the aqueous composite electrolyte containing a polycarboxyl salt additive obtained in Comparative Example 3, and the aqueous solution containing a polycarboxyl salt additive obtained in Example 2. DETAILED DESCRIPTION

[0049] To make the present invention easier to understand, the present invention is further described below with reference to specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0050] Unless otherwise defined, the professional terms used below have the same meanings as those understood by professionals in the field; unless otherwise specified, the raw materials and reagents involved in this article can be purchased from the market or prepared by known methods.

[0051] Among them, "ZnSO4" in the drawings of this application is an aqueous solution of zinc sulfate (also known as: aqueous zinc salt electrolyte); "1M ZnSO4" in the drawings of this application is 1 mol L -1 "2M ZnSO4" in the drawings of this application is 2 mol L -1 "3M ZnSO4" in the drawings of this application is 3 mol L -1 The "ZnSO4+NHS" in the drawings of this application is an aqueous composite electrolyte containing an amide polar organic additive, and the additive is an amide polar organic additive N-(2-hydroxyethyl)succinamide; the "ZnSO4+NHS(0.005molL -1 )" is an aqueous composite electrolyte containing an amide polar organic additive, wherein the amide polar organic additive is N-(2-hydroxyethyl) succinamide, and the concentration of N-(2-hydroxyethyl) succinamide is 0.005 mol L -1 ; "ZnSO4+NHS(0.01mol L -1 )" is an aqueous composite electrolyte containing an amide polar organic additive, wherein the amide polar organic additive is N-(2-hydroxyethyl) succinamide, and the concentration of N-(2-hydroxyethyl) succinamide is 0.001 mol L -1 ;"ZnSO4+NHS(0.02mol L -1)" is an aqueous composite electrolyte containing an amide polar organic additive, wherein the amide polar organic additive is N-(2-hydroxyethyl) succinamide, and the concentration of N-(2-hydroxyethyl) succinamide is 0.02 mol L -1 ;"ZnSO4+NHS(0.03mol L -1 )" is an aqueous composite electrolyte containing an amide polar organic additive, wherein the amide polar organic additive is N-(2-hydroxyethyl) succinamide, and the concentration of N-(2-hydroxyethyl) succinamide is 0.03 mol L -1 ;"ZnSO4+NHS(0.04mol L -1 )" is an aqueous composite electrolyte containing an amide polar organic additive, wherein the amide polar organic additive is N-(2-hydroxyethyl) succinamide, and the concentration of N-(2-hydroxyethyl) succinamide is 0.04 mol L -1 ; "0.04 mol L -1 NHS contains an amide polar organic additive, and the amide polar organic additive is N-(2-hydroxyethyl) succinamide, and the concentration of N-(2-hydroxyethyl) succinamide is 0.04 mol L -1 ;"1M ZnSO4+NHS(0.02mol L -1 )" is an aqueous composite electrolyte containing an amide polar organic additive, wherein the amide polar organic additive is N-(2-hydroxyethyl) succinamide, and the concentration of N-(2-hydroxyethyl) succinamide is 0.02 mol L -1 ;"2M ZnSO4+NHS(0.02mol L -1 )" is an aqueous composite electrolyte containing an amide polar organic additive, wherein the amide polar organic additive is N-(2-hydroxyethyl) succinamide, and the concentration of N-(2-hydroxyethyl) succinamide is 0.02 mol L -1 ;"3M ZnSO4+NHS(0.02mol L -1 )" is an aqueous composite electrolyte containing an amide polar organic additive, wherein the amide polar organic additive is N-(2-hydroxyethyl) succinamide, and the concentration of N-(2-hydroxyethyl) succinamide is 0.02 mol L -1 ;

[0052] The “1mAcm -2 ,1mAh cm -2 " indicates that the current density is 1 mA cm -2 Under the condition that the charge and discharge are cycled for 1 hour, the capacity of charging or discharging for 1 hour is 1mAh; the “1mAcm -2 ,0.5mAh cm -2” is the current density of 1mAcm -2 Under the condition that the charge and discharge are cycled for 0.5h respectively, the capacity of charging or discharging for 0.5h is 0.5mAh; the “10mAcm -2 ,3mAh cm -2 ” is the current density of 10 mA cm -2 Under the condition of charging and discharging, the cycle is carried out for 0.3h respectively, and the capacity of charging or discharging for 0.3h is 3mAh; Figure 1 The vertical coordinate "Log(|i|mAcm -2 )” represents the logarithm of the absolute value of the current; Figure 1 The unit of voltage on the abscissa "V vs. Ag / AgCl" represents the voltage against the Ag / AgCl reference electrode.

[0053] The present invention provides a method for preparing an aqueous composite electrolyte containing an amide-type polar organic additive, comprising the following steps:

[0054] Step 1: Add soluble zinc salt to deionized water to prepare an aqueous zinc salt electrolyte;

[0055] Step 2: When the pH value of the aqueous zinc salt electrolyte is 2.5-4.5, add an amide polar organic additive, continue stirring until it is completely dissolved, and let it stand to obtain a stable aqueous composite electrolyte containing an amide polar organic additive.

[0056] Preferably, the soluble zinc salt is selected from one or a combination of two or more of zinc sulfate, zinc trifluoromethanesulfonimide, zinc trifluoromethanesulfonate, zinc acetate, zinc chloride, zinc nitrate, zinc perchlorate, and zinc tetrafluoroborate.

[0057] Preferably, the concentration of soluble zinc salt in the aqueous zinc salt electrolyte is 0.5-3 mol L -1 .

[0058] Preferably, the amide polar organic additive is N-(2-hydroxyethyl)succinamide.

[0059] Preferably, the concentration of the amide polar organic additive in the aqueous composite electrolyte is 0.001-0.04 mol L -1 .

[0060] The present application also discloses an aqueous composite electrolyte containing an amide polar organic additive, which is prepared by any of the above-mentioned methods for preparing an aqueous composite electrolyte containing an amide polar organic additive.

[0061] The present application also discloses a battery, which includes an aqueous composite electrolyte containing an amide polar organic additive prepared by any of the above-mentioned methods for preparing an aqueous composite electrolyte containing an amide polar organic additive.

[0062] Preferably, the battery is a symmetrical battery assembled by the aqueous composite electrolyte and a commercial zinc sheet; or a half-cell assembled by the aqueous composite electrolyte and a commercial current collector; or an aqueous zinc ion battery assembled by using the aqueous composite electrolyte as the electrolyte, a commercial zinc sheet as the negative electrode, and MnO2 or V2O5 as the positive electrode.

[0063] Preferably, the commercial current collector is selected from any one of copper foil, titanium foil, nickel foil, copper mesh, nickel mesh, stainless steel mesh, foam copper, and foam nickel.

[0064] Test Example 1

[0065] This example is a H-NMR spectrum test, comparing the changes in peaks at different concentrations, specifically:

[0066] Take 0.5726 g of N-(2-hydroxyethyl)succinamide and dissolve it in deionized water. Stir continuously until the solution is clear. Titrate to 100 mL in a volumetric flask. The concentration of the N-(2-hydroxyethyl)succinamide aqueous solution is 0.04 mol L -1 , a stable aqueous solution containing an amide polar organic additive is obtained; the aqueous solution containing an amide polar organic additive obtained in this embodiment is subjected to a nuclear magnetic resonance hydrogen spectrum test to obtain a chemical shift spectrum of a pure aqueous solution subjected to a nuclear magnetic resonance hydrogen spectrum test (see Figure 9 ) and chemical shift spectra of nuclear magnetic resonance hydrogen spectroscopy test on the 2M zinc sulfate aqueous solution (aqueous zinc salt electrolyte) obtained in Example 1 of the present invention and the aqueous composite electrolyte containing polyvalent carboxyl salt additives, the aqueous composite electrolyte containing polyvalent carboxyl salt additives obtained in Comparative Example 3 and the aqueous solution containing polyvalent carboxyl salt additives obtained in Example 2 (see Figure 10 ).

[0067] Example 1: Preparation method of an aqueous composite electrolyte

[0068] The method steps include:

[0069] First, prepare an aqueous zinc salt electrolyte: dissolve 287.56 g of zinc sulfate heptahydrate in deionized water and stir until the solution is clear to prepare an aqueous electrolyte.

[0070] Adjust the pH of the aqueous electrolyte to 3.25 and titrate to 500 mL in a volumetric flask to obtain 2 mol L -1 Aqueous zinc sulfate solution (aqueous zinc salt electrolyte);

[0071] Add 1.4314 g of N-(2-hydroxyethyl)succinamide to the above 500 mL of zinc sulfate aqueous solution, stir rapidly until the powder is dissolved, and let it stand for 5 hours to obtain a stable 0.02 mol L -1 Aqueous composite electrolyte containing amide polar organic additives.

[0072] The cycle life of the symmetrical battery assembled with the obtained electrolyte reaches 7500h (see Figure 5 ).

[0073] Example 2: Preparation method of an aqueous composite electrolyte

[0074] The method steps include:

[0075] First, prepare an aqueous zinc salt electrolyte: dissolve 143.78 g of zinc sulfate heptahydrate in deionized water and stir until the solution becomes clear.

[0076] Adjust the pH of the aqueous electrolyte to 4.1 and titrate to 500 mL in a volumetric flask to obtain 1 mol L -1 Aqueous zinc sulfate solution (aqueous zinc salt electrolyte);

[0077] Add 1.4314 g of N-(2-hydroxyethyl)succinamide to the above 500 mL of zinc sulfate aqueous solution, stir rapidly until the powder is dissolved, and let it stand for 5 hours to obtain a stable 0.02 mol L -1 Aqueous composite electrolyte containing amide polar organic additives.

[0078] Example 3: Preparation method of an aqueous composite electrolyte

[0079] The method steps include:

[0080] First, prepare an aqueous zinc salt electrolyte: dissolve 431.34 g of zinc sulfate heptahydrate in deionized water and stir continuously until the solution becomes clear to prepare an aqueous electrolyte.

[0081] The pH of the aqueous electrolyte was adjusted to 3.02 and titrated to 500 mL in a volumetric flask to obtain 3 mol L -1 Aqueous zinc sulfate solution (aqueous zinc salt electrolyte);

[0082] 1.4314 g of N-(2-hydroxyethyl)succinamide was added to the above 500 mL of zinc sulfate aqueous solution, and the mixture was stirred rapidly until the powder dissolved. The mixture was allowed to stand for 5 hours to obtain a stable 0.02 mol L -1 Aqueous composite electrolyte containing amide-type polar organic additives.

[0083] Example 4

[0084] This example is a DFT calculation test that compares the adsorption energies of N-(2-hydroxyethyl)succinamide and water on the zinc surface. Specifically:

[0085] To investigate the interaction characteristics between Zn, HO, and NHS molecules, we performed quantum chemical calculations. The binding energies of Zn-HO, Zn-NHS, and HO-NHS were compared. The results showed that the binding energy of Zn-NHS (-8.9047 eV) was significantly stronger than that of Zn-HO (-4.3402 eV). This suggests that Zn prefers to bind to NHS compared to HO, forming a new Zn ion solubility structure. Furthermore, it is worth noting that HO and NHS interact with each other, with a binding energy of -1.53 eV. The interaction between HO and NHS is achieved through hydrogen bonding between the OH groups of HO and the C=O groups of NHS. Furthermore, the adsorption of various solvent molecules on the Zn metal surface was investigated. The interaction between Zn and HO at various sites was relatively weak, with the most stable bridge structure having an adsorption energy of -1.22 eV. However, the interaction between Zn and NHS was significantly stronger at the top, bridge, hollow, and parallel positions on the Zn surface. It is worth noting that the adsorption energy of NHS on the Zn hollow site is as high as −7.23 eV.

[0086] Comparative Example 1 (low additive concentration)

[0087] This comparative example was tested in parallel with Example 1, wherein the concentration of N-(2-hydroxyethyl)succinamide added was 0.005 mol L -1 The other preparation methods are exactly the same as those in Example 1 to obtain an aqueous composite electrolyte containing an amide polar organic additive.

[0088] Comparative Example 2 (low additive concentration)

[0089] This comparative example was tested in parallel with Example 1, wherein N-(2-hydroxyethyl)succinamide was added at a concentration of 0.01 mol L -1 The other preparation methods are exactly the same as those in Example 1 to obtain an aqueous composite electrolyte containing an amide polar organic additive.

[0090] Comparative Example 3 (additive concentration is high)

[0091] This comparative example was tested in parallel with Example 1, wherein the concentration of N-(2-hydroxyethyl)succinamide added was 0.03 mol L -1 The other preparation methods are exactly the same as those in Example 1 to obtain an aqueous composite electrolyte containing an amide polar organic additive.

[0092] Comparative Example 4 (high additive concentration)

[0093] This comparative example was tested in parallel with Example 1, wherein the concentration of N-(2-hydroxyethyl)succinamide added was 0.04 mol L -1 The other preparation methods are exactly the same as those in Example 1 to obtain an aqueous composite electrolyte containing an amide polar organic additive.

[0094] Comparative Example 5 (additive replaced by N-(2-hydroxyethyl)succinamide with acetone)

[0095] This comparative example was tested in parallel with Example 1, except that N-(2-hydroxyethyl)succinamide was replaced by acetone, and the acetone concentration was 0.02 mol L -1 The other preparation methods are exactly the same as those in Example 1 to obtain an aqueous composite electrolyte containing an amide polar organic additive. The cycle life of the acetone electrolyte is only 3000h, which proves the irreplaceability of amide additives (see Figure 7 ).

[0096] Comparative Example 6 (additive replaced by N-(2-hydroxyethyl)succinamide with dimethyl carbonate)

[0097] This comparative example was tested in parallel with Example 1, except that N-(2-hydroxyethyl)succinamide was replaced by dimethyl carbonate, and the concentration of dimethyl carbonate was 0.02 mol L -1 The other preparation methods are exactly the same as those in Example 1 to obtain an aqueous composite electrolyte containing an amide polar organic additive.

[0098] Comparative Example 7 (additive replaced by N-(2-hydroxyethyl)succinamide with ethylene glycol phenyl ether)

[0099] This comparative example was tested in parallel with Example 1, except that N-(2-hydroxyethyl)succinamide was replaced with ethylene glycol phenyl ether, and the concentration of ethylene glycol phenyl ether was 0.02 mol L -1 The other preparation methods are exactly the same as those in Example 1 to obtain an aqueous composite electrolyte containing an amide polar organic additive.

[0100] Battery performance testing

[0101] The commercial zinc flakes were placed in the 2M (mol L -1 ) Electrokinetic polarization curves were measured in aqueous zinc sulfate solution (aqueous zinc salt electrolyte) and aqueous composite electrolyte containing amide polar organic additives, such as Figure 1 As shown, the aqueous composite electrolyte containing amide polar organic additives obtained in Example 1 significantly reduces the corrosion current and reduces the corrosion damage of the aqueous electrolyte to the zinc negative electrode.

[0102] like Figure 2 The following are SEM images of the negative electrode surface of a symmetrical battery assembled with the 2M zinc sulfate aqueous solution (aqueous zinc salt electrolyte) obtained in Example 1 and a symmetrical battery assembled with an aqueous composite electrolyte containing an amide-type polar organic additive after 10 cycles; a large amount of byproducts accumulate on the surface of the commercial zinc sheet immersed in the 2M zinc sulfate aqueous solution due to corrosion, indicating that the aqueous composite electrolyte containing an amide-type polar organic additive significantly improves the corrosion resistance of the zinc negative electrode, reduces the content of free water at the interface between the electrolyte and the electrode, and ensures long-term stable circulation of the negative electrode.

[0103] A commercial zinc sheet was used as the negative electrode and a commercial copper foil was used as the positive electrode. A half-cell was assembled using the 2M zinc sulfate aqueous solution (aqueous zinc salt electrolyte) obtained in Example 1 and an aqueous composite electrolyte containing an amide-type polar organic additive for electrochemical testing. The results are shown in FIG. Figure 4 As shown, at 1 mA cm -2 After discharging for 0.5h at a current density of , the battery was charged to 1V to test the cycle stability. Figure 4 It can be seen that the commercial zinc sheet exhibited better cycle performance in the aqueous composite electrolyte containing amide polar organic additives obtained in Example 1 of the present invention. -2 The commercial zinc sheet showed poor cycling performance in the aqueous zinc sulfate solution (aqueous zinc salt electrolyte) obtained in Example 1 of the present invention, and the cycling performance was stable at a current density of 1 mA cm -2 The number of stable cycles at a current density of less than 200 is lower than the coulombic efficiency of the aqueous composite electrolyte containing amide polar organic additives obtained in Example 1.

[0104] The commercial zinc sheet was used as the negative electrode, and the aqueous composite electrolyte containing amide polar organic additives obtained in Example 1 of the present invention and the 2M zinc sulfate aqueous solution electrolyte were used to assemble a symmetrical cell for electrochemical testing. The results are as follows: Figure 5 As shown, at 1mAcm -2 The cycle stability and cycle life of the zinc negative electrode in the electrolyte were tested by continuous charge and discharge at a current density of 1 h each. Figure 5 It can be seen that the commercial zinc flakes exhibited better cycle stability and life in the aqueous composite electrolyte containing amide polar organic additives obtained in Example 1 of the present invention. -2 The commercial zinc sheet showed poor cycle stability and life in the 2M zinc sulfate aqueous solution (aqueous zinc salt electrolyte) obtained in Example 1 of the present invention. -2 The stable cycle time is less than 300 h at a current density of , and its cycle stability and life are much lower than those of the symmetrical battery made of the aqueous composite electrolyte containing amide polar organic additives obtained in Example 1 of the present invention.

[0105] Commercial zinc sheet was used as negative electrode, commercial V2O5 was used as positive electrode material, and a full battery was assembled using the 2M zinc sulfate aqueous solution (aqueous zinc salt electrolyte) obtained in Example 1 of the present invention and an aqueous composite electrolyte containing an amide polar organic additive to test the electrochemical performance. -1 The charge and discharge test was carried out at a current density of Figure 6 As shown, the stable cycle time exceeds 7000 cycles without obvious capacity decay.

[0106] A commercial zinc sheet was used as the negative electrode, and symmetrical cells were assembled using the 2M zinc sulfate aqueous solution (aqueous zinc salt electrolyte) obtained in Example 1 of the present invention and the aqueous composite electrolyte containing an amide polar organic additive, the aqueous composite electrolyte containing an amide polar organic additive obtained in Comparative Example 1, the aqueous composite electrolyte containing an amide polar organic additive obtained in Comparative Example 2, the aqueous composite electrolyte containing an amide polar organic additive obtained in Comparative Example 3, and the aqueous composite electrolyte containing an amide polar organic additive obtained in Comparative Example 4 for electrochemical testing. The results are shown in FIG. Figure 7 As shown, at 10mAcm -2 The battery was continuously charged and discharged for 0.3 h at a current density of 100 nm to test the cycle stability and cycle life of the zinc negative electrode in the electrolyte. The electrochemical performance of the symmetrical battery using the aqueous composite electrolyte containing amide polar organic additives obtained in Comparative Example 3 was significantly reduced and the polarization voltage was significantly increased. This is because the higher additive concentration caused a sharp decrease in the number of coordinated water molecules and a larger charge transfer resistance, which seriously affected the deposition process of zinc ions in the aqueous electrolyte.

[0107] Commercial zinc sheet was used as negative electrode, commercial V2O5 was used as positive electrode material, and a full battery was assembled using the 2M aqueous zinc sulfate solution (aqueous zinc salt electrolyte) obtained in Example 1 of the present invention and a 2M aqueous composite electrolyte containing an amide-type polar organic additive; the 1M aqueous zinc sulfate solution (aqueous zinc salt electrolyte) obtained in Example 3 and a 1M aqueous composite electrolyte containing an amide-type polar organic additive; the 3M aqueous zinc sulfate solution (aqueous zinc salt electrolyte) obtained in Example 4 and a 3M aqueous composite electrolyte containing an amide-type polar organic additive for electrochemical performance testing. -1 The charge and discharge test was carried out at a current density of Figure 8 As shown, within the concentration gradient range of 1M-3M, the full battery has a good capacity retention rate during cyclic charge and discharge in the aqueous composite electrolyte of amide polar organic additives.

[0108] The 2M zinc sulfate aqueous solution (aqueous zinc salt electrolyte) obtained in Example 1 of the present invention and the aqueous composite electrolyte of the amide polar organic additive, the aqueous composite electrolyte of the amide polar organic additive obtained in Comparative Example 4, and the aqueous solution of the amide polar organic additive obtained in Example 2 were subjected to nuclear magnetic resonance hydrogen spectrum testing, and the results are as follows: Figure 9 As shown in Figure 1, the 1H peak of pure H2O without any solute added is located at 3.33 ppm. Figure 10 As shown, the 2M zinc sulfate aqueous solution obtained in Example 1 has a 2+ The strong coordination with H2O reduces the free water in the zinc sulfate system, and the 1H peak moves to 3.70ppm. The 1H peaks of the aqueous composite electrolyte of the amide polar organic additive obtained in Example 1 and the aqueous composite electrolyte of the amide polar organic additive obtained in Comparative Example 4 begin to move forward to 3.68 and 3.664ppm, which means that the anions of the amide polar organic additive participate in the solvation shell, so that more water is in a free state. In addition, the aqueous solution of the amide polar organic additive obtained in Example 2, the 1H peak will move to 3.633ppm. This shows that the anions of the amide polar organic additive can combine with part of the free water, resulting in a weaker shielding effect of the proton. This can suppress the amount of active water to a certain extent and reduce the occurrence of side reactions.

[0109] Therefore, the potent effect of the carbonyl group in the amide polar organic additive of the present application achieves the improvement of the corrosion resistance and cycle stability of the zinc negative electrode, and is suitable for the long-term storage and use of commercial aqueous zinc-ion battery electrolytes. The symmetrical battery cycle exceeds 7500 hours, and the full battery still has an 80% capacity retention rate after 7000 cycles, which effectively improves the performance of the aqueous zinc-ion battery.

[0110] Comparative Table of Electrochemical Performance of Example 1, Example 3, Example 4 and Comparative Examples 1-7

[0111]

[0112] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many modifications and variations are possible in light of the foregoing teachings. The exemplary embodiments have been selected and described to explain the specific principles of the invention and their practical application, thereby enabling those skilled in the art to make and utilize a variety of exemplary embodiments of the invention and various options and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

[0113] Legal Notice

[0114] The protection scope of the present invention shall be based on the claims, and any equivalent replacement based on the core of the present invention shall fall within the protection scope of the present invention.

Claims

1. An aqueous composite electrolyte, characterized in that: The aqueous composite electrolyte comprises: electrolyte salt, amide polar organic additive and deionized water; wherein the concentration of the amide polar organic additive is 0.005-0.04 mol L -1 The electrolyte salt is at least one of zinc sulfate, zinc trifluoromethanesulfonate or zinc chloride, and the concentration of the electrolyte salt is 1-3 molL -1 .

2. The aqueous composite electrolyte according to claim 1, characterized in that The amide polar organic additive is a combination of one or more of butyramide, caprylamide, laurylamide, stearylamide, benzamide, N-(2-hydroxyethyl)succinamide, N-methylpyrrolidone, pyrrolamide, thiazoleamide, and acetamide.

3. The aqueous composite electrolyte according to claim 2, characterized in that The amide polar organic additive is any one of N-(2-hydroxyethyl)succinamide and N-methylpyrrolidone.

4. The aqueous composite electrolyte according to claim 1, characterized in that The concentration of the amide polar organic additive is 0.005-0.03 mol L -1 .

5. A method for preparing the aqueous composite electrolyte according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1: adding the electrolyte salt to deionized water to prepare an aqueous electrolyte; Step 2: After the pH value of the aqueous electrolyte obtained in step (1) stabilizes to 2.5-4.5, the amide polar organic additive is added, dissolved at a stirring speed of 500-1000 rpm, and allowed to stand for ≥12 hours to obtain a stable aqueous composite electrolyte containing an amide polar organic additive.

6. A battery, characterized in that: The battery comprises positive and negative electrode sheets, a battery separator and the aqueous composite electrolyte according to any one of claims 1 to 4, wherein the positive electrode sheet comprises MnO2 or V2O5, and the negative electrode sheet is zinc metal with a purity of ≥99.9%.

7. The battery according to claim 6, characterized in that The battery separator is a glass fiber separator, a polypropylene separator or a polyethylene separator.

8. Use of the aqueous composite electrolyte according to any one of claims 1 to 4 or the aqueous composite electrolyte prepared by the preparation method according to claim 5, characterized in that: The aqueous composite electrolyte is used to prepare a symmetrical battery, a half-cell or an aqueous zinc ion battery.

9. The use according to claim 8, characterized in that The symmetrical battery is obtained by assembling the aqueous composite electrolyte according to any one of claims 1 to 4 and a commercial zinc sheet, wherein the commercial zinc sheet has a purity of ≥99.9% and a thickness of 0.1-1.0 mm; The half-cell is obtained by assembling the aqueous composite electrolyte according to any one of claims 1 to 4 and a commercial current collector, wherein the commercial current collector is selected from any one of copper foil, titanium foil, nickel foil, copper mesh, nickel mesh, stainless steel mesh, foam copper, and foam nickel; The aqueous zinc ion battery is obtained by assembling the aqueous composite electrolyte according to any one of claims 1 to 4, commercial zinc sheets, and MnO2 or V2O5 as a positive electrode.

Images