Preparation method of aqueous composite electrolyte and application thereof

Abstract

The application provides a preparation method and application of an aqueous composite electrolyte, which comprises uniformly mixing an aqueous zinc salt and a water-soluble heterocyclic amine organic additive; adding deionized water and continuously stirring until dissolution, and then standing until the pH value is stable to obtain the aqueous composite electrolyte. The additive can improve the stability of the aqueous electrolyte, and the zincophilic group in the organic additive molecule can form a coordination bond with zinc ions, so that the additive molecules can be adsorbed on the surface of a zinc electrode, balance the electric field distribution on the electrode surface, prevent the non-uniform deposition of zinc ions on the electrode surface, reduce the dendrite growth caused by the excessive local electric field, improve the utilization rate of zinc, and effectively improve the performance of the battery. After the additive molecules are adsorbed on the surface of the zinc electrode, a part of the active sites for the hydrogen evolution reaction on the electrode surface can be covered, the hydrogen evolution reaction can be inhibited, the generation of by-products can be reduced, the coulombic efficiency can be improved, and the corrosion resistance and cycle stability of the zinc negative electrode can be effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a preparation method of a water-based composite electrolyte and application thereof. BACKGROUND

[0002] Water-based zinc ion batteries have attracted extensive attention due to their significant advantages in energy storage applications, and the zinc metal anode has the advantages of high theoretical specific capacity (820 mAh / g), abundant resources, and low cost. The water-based electrolyte provides excellent safety and high ionic conductivity, avoiding the flammable risk of organic electrolytes. Therefore, the water-based zinc ion battery is considered as a potential solution to replace traditional lithium ion batteries in the field of energy storage. However, the water-based zinc ion battery still faces many technical challenges in practical application.

[0003] Firstly, the cycle performance of the battery is greatly reduced due to the dendrite growth of the zinc anode; the uneven deposition and stripping of zinc on the electrode lead to the generation of dendrites, and the zinc dendrites may pierce the battery separator, causing internal short circuit, and further causing the battery to fail, and the continuously growing zinc dendrites will lead to the formation of "dead zinc", reducing the utilization rate of zinc. In addition, the formation of dendrites also increases the surface area of the electrode, further accelerating the consumption of the electrode material.

[0004] Secondly, the water molecules in the electrolyte inevitably produce side reactions in the electrochemical reaction, especially the hydrogen evolution reaction. These reactions not only reduce the coulombic efficiency of the battery, but also lead to the accumulation and passivation of insulating products on the surface of the zinc anode, limiting the effective utilization of zinc. This passivation phenomenon will continue to intensify during charging and discharging, seriously affecting the stability of the battery, and the formation of dendrites, corrosion reaction and hydrogen evolution reaction in the zinc anode interact and affect each other.

[0005] In order to solve the above technical problems, the prior art mainly adopts the method of modifying the zinc anode, using solid electrolyte, designing the separator and optimizing the electrolyte to solve the above technical problems. However, the above methods are difficult to solve the problems of dendrite growth, hydrogen evolution reaction and corrosion reaction at the same time.

[0006] Therefore, a preparation method of a water-based composite electrolyte is provided to improve the stability and cycle life of the water-based zinc ion battery. SUMMARY

[0007] In view of the shortcomings of the prior art, the present application provides a preparation method of a water-based composite electrolyte and application thereof. The present application adjusts the deposition of zinc ions on the surface of the zinc metal electrode to inhibit the growth of zinc dendrites, avoid the formation of "dead zinc", and inhibit the generation of by-products, thereby improving the utilization rate of zinc.

[0008] The technical scheme of the present application is as follows: a preparation method of a water-based composite electrolyte, comprising the following steps:

[0009] S1), a certain amount of water-based zinc salt and water-soluble heterocyclic amine organic additive are mixed uniformly;

[0010] S2), a certain amount of deionized water is added and continuously stirred until dissolved, and the pH value of the composite water-based electrolyte is stable after standing, to obtain a stable water-based composite electrolyte containing water-soluble heterocyclic amine organic additive.

[0011] As preferred, in step S1), the water-soluble heterocyclic amine organic additive is a combination of one or more of 2-aminoimidazole, 3-amino-1, 2, 4-triazole, 2-aminothiazole, 2-aminopyridine, 4-aminopyridine, and 5-amino tetrazole.

[0012] As preferred, in step S1), the water-based zinc salt is selected from one or more of zinc sulfate, zinc chloride, zinc acetate, zinc acetate, zinc nitrate, etc.

[0013] As preferred, in step S1), the concentration of the water-soluble heterocyclic amine organic additive is 1-30 mmol / L.

[0014] As preferred, in step S1), the concentration of the water-soluble heterocyclic amine organic additive is 5-20 mmol / L.

[0015] As preferred, in step S1), the concentration of the water-soluble heterocyclic amine organic additive is 10-20 mmol / L.

[0016] As preferred, in step S1), the concentration of the water-soluble heterocyclic amine organic additive is 20 mmol / L.

[0017] As preferred, in step S1), the concentration of the water-based zinc salt is 1-4 mol / L.

[0018] As preferred, in step S2), the pH value of the stable composite water-based electrolyte is 4.05-5.10.

[0019] As preferred, the present application also provides a battery comprising a positive electrode and a negative electrode, and a water-based composite electrolyte containing a water-soluble heterocyclic amine organic additive.

[0020] As preferred, the battery is a symmetric button cell, a half cell or a water-based zinc ion full cell.

[0021] As preferred, the symmetric button cell uses zinc sheet as the positive and negative electrodes.

[0022] As preferred, the half cell uses zinc sheet as the negative electrode and copper foil as the positive electrode.

[0023] Preferably, the aqueous zinc ion full battery uses zinc sheet as the negative electrode material and I / C as the positive electrode material.

[0024] The present application has the following advantages:

[0025] 1. The water-soluble heterocyclic amine organic additive of the present application can improve the stability of the aqueous electrolyte. The zincophilic group in the water-soluble heterocyclic amine organic additive molecule can form a coordination bond with zinc ions, so that the additive molecules can be adsorbed on the surface of the zinc electrode, balance the electric field distribution on the electrode surface, prevent the uneven deposition of zinc ions on the electrode surface, reduce the dendrite growth caused by the excessive local electric field, and improve the utilization rate of zinc, thereby effectively improving the performance of the aqueous zinc ion battery.

[0026] 2. After the water-soluble heterocyclic amine organic additive molecules are adsorbed on the surface of the zinc electrode, they can cover part of the active sites for hydrogen evolution reaction on the electrode surface, thereby inhibiting the occurrence of hydrogen evolution reaction, reducing the generation of by-products, improving the coulombic efficiency, and effectively improving the corrosion resistance and cycle stability of the zinc negative electrode. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The electrolyte C2H4N4@ZnSO4 prepared in Example 1 of the present application and the electrolyte ZnSO4(aq) of Comparative Example 1 were respectively assembled into symmetric batteries with zinc sheets, and the high-magnification scanning electron microscope (SEM) images of the zinc sheets after 50 cycles under the conditions of 5 mA / cm 2 , 2 mAh / cm 2 ; wherein, Figure 1 (a) is the high-magnification scanning electron microscope (SEM) image of the zinc sheet surface of the symmetric battery with ZnSO4(aq) as the electrolyte, Figure 1 (b) is the high-magnification scanning electron microscope (SEM) image of the zinc sheet surface of the symmetric battery with C2H4N4@ZnSO4 as the electrolyte;

[0028] Figure 2 The electrolyte C2H4N4@ZnSO4 prepared in Example 1 of the present application and the electrolyte ZnSO4(aq) prepared in Comparative Example 1 were respectively assembled into symmetric batteries with zinc sheets, and the X-ray diffraction (XRD) spectra of the zinc sheets after 50 cycles under the conditions of 5 mA / cm 2 , 2 mAh / cm 2 ;

[0029] Figure 3 The electrode kinetics polarization curve of the zinc sheet in the electrolyte C2H4N4@ZnSO4 prepared in Example 1 of the present application and the electrolyte ZnSO4(aq) prepared in Comparative Example 1;

[0030] Figure 4Coulomb efficiency comparison chart of the electrolyte C2H4N4@ZnSO4 of the electrolyte of the present application embodiment 1 and the electrolyte ZnSO4(aq) of the comparative example 1 assembled into half-cell for testing;

[0031] Figure 5 Time-voltage comparison chart of the symmetric cell assembled by the electrolyte C2H4N4@ZnSO4 of the present application embodiment 1 and the electrolyte ZnSO4(aq) of the comparative example 1 under the condition of 5mA / cm 2 , 2mAh / cm 2 for cycle stability test;

[0032] Figure 6 Time-voltage comparison chart of the symmetric cell assembled by the electrolyte C2H4N4@ZnSO4 of the present application embodiment 1 and the electrolyte ZnSO4(aq) of the comparative example 1 under the condition of 1mA / cm 2 , 1mAh / cm 2 for cycle stability test;

[0033] Figure 7 Specific capacity and coulomb efficiency chart of the aqueous zinc ion full cell cycle of the electrolyte C2H4N4@ZnSO4 of the present application embodiment 1 and the electrolyte ZnSO4(aq) of the comparative example 1 assembled. DETAILED DESCRIPTION

[0034] The specific embodiments of the present application will be further described below in conjunction with the accompanying drawings:

[0035] Embodiment 1

[0036] The present embodiment provides a preparation method of a water-based composite electrolyte, comprising the following steps:

[0037] S1), weigh 5.81g of zinc sulfate heptahydrate (purity 99%) and 17.52mg of 3-amino-1,2,4-triazole (purity 96%) powder, and mix them evenly;

[0038] S2), dissolve the above mixture in deionized water, make up to 10ml, and continue to stir until completely dissolved. Then stand for 2 hours, and when the pH value of the solution is stable at 4.43, a stable water-based composite electrolyte containing water-soluble heterocyclic amine organic additive is obtained, which is recorded as C2H4N4@ZnSO4.

[0039] Comparative example 1

[0040] The present embodiment provides a preparation method of a zinc sulfate electrolyte, and the specific steps are as follows:

[0041] S1) Weigh 5.81g of zinc sulfate heptahydrate (99% purity), dissolve it in deionized water, and bring the volume to 10ml. Stir continuously until completely dissolved. Then let it stand for 2 hours until the pH of the solution stabilizes at about 4.4, thus obtaining a stable aqueous zinc sulfate electrolyte, denoted as ZnSO4(aq).

[0042] Example 2

[0043] In this embodiment, a symmetrical battery is assembled using the aqueous composite electrolyte C2H4N4@ZnSO4 prepared in Example 1 and zinc sheets.

[0044] A half-cell was assembled using the aqueous composite electrolyte C2H4N4@ZnSO4 prepared in Example 1, zinc sheet as negative electrode and copper foil as positive electrode.

[0045] An aqueous zinc-ion full cell was assembled using the aqueous composite electrolyte C2H4N4@ZnSO4 prepared in Example 1, zinc sheet as the negative electrode material, and I / C as the positive electrode material.

[0046] Meanwhile, under the same conditions, symmetrical cells, half-cells, and aqueous zinc-ion full cells were assembled using the zinc sulfate aqueous electrolyte ZnSO4(aq) from Comparative Example 1.

[0047] Example 3

[0048] Performance Analysis

[0049] At 5mA / cm 2 Current density and 2mAh / cm 2 At the specified capacity, the composite electrolyte C2H4N4@ZnSO4 of Example 1 and the electrolyte ZnSO4(aq) prepared in Comparative Example 1 were cycled 50 times with symmetrical batteries assembled with zinc sheets, and the surface of the zinc sheets was then tested using scanning electron microscopy. The test results are as follows: Figure 1 (a) and Figure 1 As shown in (b), the symmetrical cell using ZnSO4(aq) as the electrolyte exhibits a plate-like, irregular zinc dendrite morphology after cycling; while the symmetrical cell using C2H4N4@ZnSO4 as the electrolyte exhibits a dense and uniform zinc deposition morphology after cycling. This demonstrates that the introduction of 3-amino-1,2,4-triazole organic additives into the zinc sulfate electrolyte effectively guides uniform zinc ion deposition, significantly inhibits zinc dendrite formation, and improves zinc utilization.

[0050] Figure 2 The display showed that at a current density of 5 mA / cm² 2 The capacity is 2mAh / cm 2Under certain conditions, symmetrical cells assembled with zinc sheets using C2H4N4@ZnSO4 electrolyte and ZnSO4(aq) electrolyte, respectively, were subjected to 50 cycles. The X-ray diffraction (XRD) spectra of the zinc electrode were then obtained. The figures show that the symmetrical cell with ZnSO4(aq) electrolyte exhibited peaks of byproducts such as basic zinc sulfate after cycling, confirming the severe corrosion of the zinc sheet by the ZnSO4(aq) electrolyte. In contrast, the C2H4N4@ZnSO4 electrolyte showed a significantly weakened diffraction peak intensity for the byproduct basic zinc sulfate, in addition to the characteristic peaks of metallic zinc. This indicates that the introduction of the 3-amino-1,2,4-triazole additive limited interfacial parasitic reactions and improved the thermodynamic stability of the zinc anode.

[0051] Figure 3 The results of electrode kinetic polarization curve measurements of zinc sheets in the C2H4N4@ZnSO4 electrolyte of Example 1 and the ZnSO4(aq) electrolyte of Comparative Example 1 are presented. The results show that the zinc sheet in the ZnSO4(aq) electrolyte (2.818 mA / cm²) exhibits the highest polarization. 2 Compared to the previous method, zinc sheets in C2H4N4@ZnSO4 electrolyte exhibited a lower corrosion current density (0.0946 mA / cm²). 2 This reflects that the zinc sheet has a lower tendency to corrode.

[0052] Figure 4 The study demonstrated half-cells assembled using zinc sheet as the negative electrode and copper foil as the positive electrode, with the C2H4N4@ZnSO4 electrolyte of Example 1 and the ZnSO4(aq) electrolyte of Comparative Example 1, respectively, at 1 mA / cm². 2 1mAh / cm 2 Coulomb efficiency plot under the condition of C2H4N4@ZnSO4 half-cell at 1 mA / cm 2 It can stably cycle ≥400 times at a current density and has a coulombic efficiency of up to 99.44%; while the ZnSO4(aq) half-cell can achieve a coulombic efficiency of 1 mA / cm². 2 It exhibited poor cycling performance at current densities, with a stable cycle count of less than 115 and a coulombic efficiency of 99.50%.

[0053] Symmetrical cells were assembled with zinc sheets using the electrolyte C2H4N4@ZnSO4 from Example 1 and the electrolyte ZnSO4(aq) from Comparative Example 1, respectively, at 5 mA / cm. 2 2mAh / cm 2 and 1mA / cm 2 1mAh / cm 2 Deposition / exfoliation stability tests were conducted under the following conditions, such as Figure 5 , Figure 6The symmetric cell with C2H4N4@ZnSO4as electrolyte can be stably cycled for more than 242 h under the condition of 5 mA / cm 2 , 2 mAh / cm 2 , for more than 2330 h under the condition of 1 mA / cm 2 , 1 mAh / cm 2 , and the symmetric cell with ZnSO4(aq) as electrolyte can be stably cycled for no more than 135 h under the condition of 5 mA / cm 2 , 2 mAh / cm 2 , and for no more than 140 h under the condition of 1 mA / cm 2 , 1 mAh / cm 2 . This shows that the cycle stability and cycle life of zinc negative electrode in C2H4N4@ZnSO4electrolyte are greatly improved.

[0054] Figure 7 To take zinc sheet as negative electrode material and I / C as positive electrode material, a full cell was assembled with C2H4N4@ZnSO4electrolyte of Example 1 and ZnSO4(aq) electrolyte of Comparative Example 1 respectively for electrochemical performance test. In the case of similar coulombic efficiency, the specific capacity of C2H4N4@ZnSO4full cell is obviously higher than that of ZnSO4(aq) full cell.

[0055] It can be seen that the aqueous composite electrolyte of Example 1 containing water-soluble heterocyclic amine organic additive can inhibit the growth of zinc dendrites, promote the cycle of zinc ion battery, and has great application prospect in energy storage.

[0056] Examples 4-10

[0057] Based on the scheme of Example 1, by regulating the type and concentration of water-soluble heterocyclic amine organic additive, the corresponding aqueous composite electrolyte was prepared, and Comparative Example 1 was compared to analyze the performance of the assembled symmetric cell, see Table 1.

[0058] Table 1 Regulation of additive type and concentration

[0059]

[0060]

[0061] Among them, Examples 1, 4, 5, 6, 7 and 8 show that the concentration of water-soluble heterocyclic amine organic additive in the aqueous composite electrolyte has a great influence on the performance of the aqueous zinc ion battery, and Examples 1, 9 and 10 show that the type of additive will also affect the performance of the aqueous zinc ion battery to some extent.

[0062] As can be seen from the above examples, the appropriate electrolyte additive type and concentration can strengthen the coordination of the water-soluble heterocyclic amine organic additive molecules and zinc ions, so that the additive molecules can better adsorb on the zinc electrode surface, and through the coordination and charge distribution characteristics, the electric field on the electrode surface can be uniformized, the zinc ions can be uniformly deposited on the electrode surface, the dendrite growth caused by the local electric field being too strong can be reduced, the electrochemical stability of the electrode can be improved, and the risk of internal short circuit of the battery can be reduced.

[0063] The above examples and descriptions in the specification are only to illustrate the principles and the best mode of the present application, and various changes and improvements can be made to the present application without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the present application.

Claims

1. A battery comprising a positive electrode and a negative electrode, characterized in that: The battery further includes an aqueous composite electrolyte containing water-soluble heterocyclic amine organic additives; the preparation of the aqueous composite electrolyte includes the following steps: S1) Mix a certain amount of aqueous zinc salt and water-soluble heterocyclic amine organic additives evenly; The water-soluble heterocyclic amine organic additive is one or a combination of two of 2-aminothiazole and 5-aminotetrazole. S2) Add a certain amount of deionized water and stir continuously until dissolved. Let stand until the pH value of the composite aqueous electrolyte stabilizes to obtain a stable aqueous composite electrolyte containing water-soluble heterocyclic amine organic additives. The battery is a symmetrical button cell, a half-cell, or an aqueous zinc-ion full cell; wherein: The symmetrical button cell described above uses zinc sheets as the positive and negative electrodes; The half-cell described uses a zinc sheet as the negative electrode and a copper foil as the positive electrode. The aforementioned aqueous zinc-ion full battery uses zinc sheet as the negative electrode material and I / C as the positive electrode material.

2. The battery according to claim 1, characterized in that: In step S1), the concentration of the water-soluble heterocyclic amine organic additive is 1-30 mmol / L.

3. A battery according to claim 2, characterized in that: In step S1), the concentration of the water-soluble heterocyclic amine organic additive is 5-20 mmol / L.

4. A battery according to claim 2, characterized in that: In step S1), the concentration of the water-soluble heterocyclic amine organic additive is 10-20 mmol / L.

5. A battery according to claim 1, characterized in that: In step S1), the concentration of the aqueous zinc salt is 1-4 mol / L.

6. A battery according to claim 5, characterized in that: In step S1), the aqueous zinc salt is selected from one or more of zinc sulfate, zinc chloride, zinc acetate, zinc nitrate, and zinc nitrate.

7. A battery according to claim 1, characterized in that: In step S1), the stable pH value of the composite aqueous electrolyte is 4.05-5.10.

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