Aqueous zinc ion battery electrolyte additive, electrolyte and preparation method thereof

Abstract

The invention discloses an aqueous zinc ion battery electrolyte additive, an electrolyte and a preparation method of the electrolyte, and belongs to the technical field of zinc ion batteries. According to the invention, 1, 3-dimethyl-2-imidazolidinone (DMI) and N, N-dimethyl trifluoroacetamide (FDMAC) are added into a zinc sulfate electrolyte, an inert organic layer is formed on the surface of the zinc foil, and the inert layer can inhibit dendritic crystal growth on the surface of the zinc foil. The addition of DMI and FDMAC also destroys the original hydrogen bond network in the system, and inhibits the generation of hydrogen evolution reaction, surface corrosion and other side reactions.

Description

Technical Field

[0001] The invention belongs to the technical field of zinc ion batteries, and particularly relates to an aqueous zinc ion battery electrolyte additive, an electrolyte and a preparation method thereof. Background Art

[0002] In recent years, aqueous zinc-ion batteries (Zn-ion batteries) have become a research hotspot in the energy storage field due to their unique electrochemical properties. Aqueous Zn-ion batteries use metallic zinc as the anode material, which not only possesses a suitable redox potential but also boasts significantly more abundant zinc resources than lithium. The higher ionic conductivity of AZI batteries compared to conventional lithium batteries enables them to exhibit rapid reaction kinetics and excellent rate capability, eliminating the combustion risk associated with organic systems and significantly reducing production costs. These properties hold great promise for applications in energy storage and wearable devices. However, their large-scale application remains challenging. For example, uneven zinc ion deposition on the Zn metal anode surface, leading to dendrite growth that can pierce the separator and cause battery short circuits, and side reactions such as hydrogen evolution and corrosion at the anode-electrolyte interface, which can cause battery swelling and electrolyte leakage. These issues severely impact the cycle life of Zn-ion batteries and limit their development. Therefore, developing electrolyte additives to mitigate Zn dendrite growth and inhibit side reactions is crucial for the future large-scale application of Zn-ion batteries. Summary of the Invention

[0003] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0004] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0005] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide an aqueous zinc ion battery electrolyte additive.

[0006] As a preferred solution of the aqueous zinc ion battery electrolyte additive of the present invention, the volume concentration of the 1,3-dimethyl-2-imidazolidinone in the electrolyte is 10-25%.

[0007] As a preferred embodiment of the aqueous zinc ion battery electrolyte additive of the present invention, the electrolyte additive further comprises N,N-dimethyltrifluoroacetamide.

[0008] As a preferred embodiment of the aqueous zinc ion battery electrolyte additive of the present invention, the volume ratio of the 1,3-dimethyl-2-imidazolidinone to N,N-dimethyltrifluoroacetamide is 1:2.

[0009] Another object of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing an aqueous zinc ion battery electrolyte.

[0010] In order to solve the above technical problems, the present invention provides the following technical solutions, including:

[0011] Zinc sulfate is dissolved in water to obtain a zinc sulfate solution, and the electrolyte additive according to claims 1 to 4 is added thereto, and the solution is stirred and dissolved to obtain an aqueous zinc ion battery electrolyte.

[0012] As a preferred embodiment of the method for preparing the aqueous zinc ion battery electrolyte of the present invention, the concentration of the zinc sulfate solution is 1 mol / L.

[0013] The third object of the present invention is to overcome the deficiencies in the prior art and provide an aqueous zinc ion battery electrolyte.

[0014] As a preferred embodiment of the aqueous zinc ion battery electrolyte of the present invention, the volume ratio of water, 1,3-dimethyl-2-imidazolidinone and N,N-dimethyltrifluoroacetamide in the electrolyte is 7:0-3:0-3.

[0015] As a preferred embodiment of the aqueous zinc ion battery electrolyte of the present invention, the volume ratio of water, 1,3-dimethyl-2-imidazolidinone and N,N-dimethyltrifluoroacetamide in the electrolyte is 7:1:2.

[0016] As a preferred embodiment of the aqueous zinc ion battery electrolyte of the present invention, the volume concentration of 1,3-dimethyl-2-imidazolidinone in the zinc sulfate solution in the electrolyte is 10%.

[0017] Beneficial effects of the present invention:

[0018] The present invention adds 1,3-dimethyl-2-imidazolidinone (DMI) and N,N-dimethyltrifluoroacetamide (FDMAC) additives to the aqueous zinc ion battery electrolyte to form an inert organic layer on the zinc foil surface. This organic layer isolates the zinc anode from the electrolyte, effectively inhibiting hydrogen evolution and dendrite growth. This significantly extends the short-circuit time of the zinc anode and improves the device life of the aqueous zinc ion battery. The present invention clarifies the structure-activity relationship between DMI and FDMAC concentrations and zinc deposition behavior, providing an important reference for optimizing aqueous zinc battery electrolytes. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be derived from these drawings without inventive efforts. Among them:

[0020] Figure 1 The XRD patterns of the negative electrode surface products of zinc in the zinc ion battery after cycling of the electrolyte system prepared in Examples 1, 2 and Comparative Example 1.

[0021] Figure 2 The electrolyte system zinc ion battery prepared in Examples 1, 2 and Comparative Example 1 is 1 mA / cm 2 Current density and 1mAh / cm 2 Scanning electron micrographs of the capacity density after 50 cycles. (a) 0% DMI / ZnSO4-based electrolyte (b) 10% DMI / ZnSO4-based electrolyte (c) 25% DMI / ZnSO4-based electrolyte.

[0022] Figure 3 In situ optical microscopy is used to directly observe Zn 2+ Deposition process at the electrolyte / electrode interface in the electrolyte systems of Example 1, Example 2, and Comparative Example 1: (a) 0% DMI / ZnSO4-based electrolyte, (b) 10% DMI / ZnSO4-based electrolyte, and (c) 25% DMI / ZnSO4-based electrolyte.

[0023] Figure 4 It is the ionic conductivity of the aqueous zinc ion battery electrolyte of Examples 1, 2 and Comparative Example 1.

[0024] Figure 5 The figures are the hydrogen evolution test results of the aqueous zinc ion battery electrolytes of Examples 1 and 2 and Comparative Example 1.

[0025] Figure 6 The Zn||Cu half-cell of the electrolyte system of Examples 1, 2 and Comparative Example 1 is at 0.5 mA / cm 2 Current density and 0.5 mAh / cm 2 Comparison of Coulomb efficiency cycle curves under capacity density.

[0026] Figure 7 The Zn||Zn symmetrical cells prepared in Examples 3 to 5 were tested at 1 mA / cm 2 Current density and 1mAh / cm 2 Cycling performance diagram at capacity density.

[0027] Figure 8The Zn||Zn symmetrical cells prepared in Examples 3 to 5 were tested at 1 mA / cm 2 Current density and 1mAh / cm 2 Scanning electron micrographs after 50 cycles at the same capacity density. (a) Water: DMI: FDMAC = 7:0:3 (b) Water: DMI: FDMAC = 7:1:2 (c) Water: DMI: FDMAC = 7:3:0.

[0028] Figure 9 The Zn in the electrolyte with the volume ratio of water, DMI and FDMAC being 7:0:3 (a), 7:1:2 (b) and 7:3:0 (c) respectively. 2+ Migration number test chart.

[0029] Figure 10 The electrolyte prepared in Examples 3 to 5 was 2 mA / cm 2 Diagram of zinc nucleation overpotential at different current densities. DETAILED DESCRIPTION

[0030] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0031] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0032] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0033] Unless otherwise specified, the raw materials used in the present invention are all commercially available.

[0034] The electrochemical performance of the symmetrical battery prepared in the embodiment of the present invention was tested as follows:

[0035] The symmetrical cell was charged at 1 mA / cm 2 Current density and 1mAh / cm 2 The charge density was measured by cyclic charge-discharge test. When a potential mutation was observed, the mutation time point was taken as the short-circuit time of the symmetrical battery.

[0036] Example 1

[0037] This embodiment provides an electrolyte catalyst and a method for preparing the electrolyte, specifically:

[0038] 1) Preparation of electrolyte:

[0039] Ultrapure water was used as the solvent, and zinc sulfate was added and dissolved by stirring to prepare a 1 mol / L zinc sulfate aqueous solution. 1,3-Dimethyl-2-imidazolidinone (DMI) was added to the zinc sulfate solution and dissolved by stirring to obtain an aqueous zinc ion battery electrolyte, wherein the volume concentration of DMI in the zinc sulfate aqueous solution was 10%.

[0040] 2) Preparation of Zn / / Zn symmetric battery

[0041] Clean zinc foil with a thickness of 80 μm was selected, polished with sandpaper, and cut into discs with a diameter of 12 mm to be used as electrodes of a symmetrical battery. The double sulfonated membrane was used as the diaphragm, and the above-mentioned electrolyte was used to encapsulate CR2025 button batteries.

[0042] Example 2

[0043] The difference between this embodiment and embodiment 1 is that the volume concentration of DMI in the zinc sulfate aqueous solution is adjusted to 25%. The rest of the preparation process is the same as that of embodiment 1 to prepare an aqueous zinc ion battery electrolyte, and symmetrical batteries are assembled.

[0044] Comparative Example 1

[0045] The difference between this comparative example and Example 1 is that the volume concentration of the additive is adjusted to 0, and the rest of the preparation process is the same as Example 1 to prepare an aqueous zinc ion battery electrolyte, i.e., a 1 mol / L zinc sulfate electrolyte, and symmetrical batteries are assembled.

[0046] Figure 1 XRD patterns of zinc anode surface products after cycling in zinc-ion batteries using the electrolytes prepared in Examples 1 and 2 and Comparative Example 1. In a pure ZnSO₄ electrolyte, the Zn anode of a symmetrical Zn-Zn cell exhibited a significant increase in byproducts after 100 cycles. Adding DMI significantly reduced the byproduct signal on the Zn anode surface. These results demonstrate that the DMI additive effectively inhibits side reactions at the zinc anode-electrolyte interface.

[0047] Figure 2 The electrolyte system zinc ion battery prepared in Examples 1, 2 and Comparative Example 1 is 1 mA / cm 2 Current density and 1mAh / cm 2Scanning electron micrograph after 50 cycles at the same capacity density. After multiple charge-discharge cycles in a 1 mol / L zinc sulfate electrolyte, the surface of the zinc foil negative electrode was severely corroded, with noticeable dendrite growth. The zinc foil surface became rough and uneven, with larger deposited particles. After cycling in an electrolyte containing 10% DMI additive, the surface of the zinc electrode sheet became relatively smooth, and dendrite formation and growth were significantly suppressed, demonstrating that DMI can effectively slow dendrite growth. Adding 25% DMI reduced the smoothness of the zinc foil surface, demonstrating that a 10% DMI additive was more effective than a 25% addition.

[0048] Figure 3 In situ optical microscopy is used to directly observe Zn 2+ The deposition process of the electrolyte / electrode interface in the electrolyte systems of Example 4, Example 5 and Comparative Example 1. 2 Deposition was performed for 1 hour under the conditions of the current density, and the deposition status was photographed every 10 minutes. The electrolyte was a 1 mol / L zinc sulfate mixed solution with DMI added. Among them, a is a 1M ZnSO4 symmetrical cell, b is a 1M ZnSO4+10% symmetrical cell, and c is a 1M ZnSO4+25% symmetrical cell. When 0% DMI was added, the fine dendrites on the zinc surface gradually grew into tree-like dendrites. When 10% DMI was added, the zinc surface remained flat and no tip dendrites were generated. When 25% DMI was added, spotty deposits appeared on the zinc surface. The dendrite inhibition effect of 10% DMI was better than that of 25% DMI.

[0049] Figure 4 The ionic conductivity of the aqueous zinc ion battery electrolytes of Examples 1 and 2 and Comparative Example 1 was measured using a conductivity meter. As can be seen from the figure, the ionic conductivity shows a downward trend as the concentration of the DMI additive increases.

[0050] Different aqueous zinc ion battery electrolytes were tested by linear sweep voltammetry (LSV) using an electrochemical workstation CHI 760E. The reference electrode was an Ag / AgCl electrode, the counter electrode was Pt, and the working electrode was a zinc sheet. The potential window of the LSV test was -1.2V to -0.7V, and the scan rate was 1mV / s. The hydrogen evolution test results are shown in Figure 2. Figure 5 As shown in Figure 3, it shows that the potential shifts negatively after adding DMI additive to ZnSO4, which indicates that DMI has a certain inhibitory effect on the hydrogen evolution reaction.

[0051] Figure 6 The Zn||Cu half-cell of the electrolyte system of Examples 1, 2 and Comparative Example 1 is at 0.5 mA / cm 2 Current density and 0.5 mAh / cm 2Comparison of Coulombic efficiency cycle curves at different capacity densities. The battery assembled with a pure aqueous ZnSO4-based electrolyte began to experience dramatic fluctuations after 137 cycles. The CE of the asymmetric Cu||Zn battery with 10% DMI addition significantly improved, with the Coulombic efficiency approaching 100%, indicating that the DMI additive facilitates uniform zinc plating / stripping in the asymmetric Cu||Zn battery.

[0052] Example 3

[0053] This embodiment differs from Example 1 in that the preparation method for adjusting the electrolyte is to add 1 mol zinc sulfate to 700 ml of water, and then add 100 mL of DMI and 200 mL of FDMAC; that is, the electrolyte additives are 1,3-dimethyl-2-imidazolidinone (DMI) and N,N-dimethyltrifluoroacetamide (FDMAC), and the volume ratio of water, DMI, and FDMAC is 7:1:2. The remaining preparation processes are the same as in Example 1, and an aqueous zinc ion battery electrolyte is prepared and assembled into a symmetrical battery.

[0054] Example 4

[0055] This embodiment differs from Example 1 in that the preparation method for adjusting the electrolyte is to add 1 mol zinc sulfate to 700 ml of water and then add 300 mL of DMI; that is, the electrolyte additive is 1,3-dimethyl-2-imidazolidinone (DMI), and the volume ratio of water, DMI, and FDMAC is 7:3:0. The remaining preparation processes are the same as in Example 1, and an aqueous zinc ion battery electrolyte is obtained and assembled into a symmetrical battery.

[0056] Example 5

[0057] This embodiment differs from Example 1 in that the preparation method for adjusting the electrolyte is to add 1 mol of zinc sulfate to 700 ml of water, and then add 300 mL of FDMAC; that is, the electrolyte additive is N,N-dimethyltrifluoroacetamide (FDMAC), and the volume ratio of water, DMI, and FDMAC is 7:0:3. The rest of the preparation process is the same as in Example 1, and an aqueous zinc ion battery electrolyte is prepared and assembled into a symmetrical battery.

[0058] Figure 7 The Zn||Zn symmetrical cells prepared in Examples 3 to 5 were tested at 1 mA / cm 2 Current density and 1mAh / cm 2 The cycling performance diagram under capacity density shows that the electrolyte with a volume ratio of water, DMI, and FDMAC of 7:1:2 exhibits the best cycling stability with a cycle time of more than 550h.

[0059] Figure 8 The Zn||Zn symmetrical cells prepared in Examples 3 to 5 were tested at 1 mA / cm2 Current density and 1mAh / cm 2 Scanning electron micrographs after 50 cycles at the same capacity density. (a) Water: DMI: FDMAC = 7:0:3 (b) Water: DMI: FDMAC = 7:1:2 (c) Water: DMI: FDMAC = 7:3:0. It can be seen that the zinc surface of the electrolyte of Example 1 remains flat after multiple charge-discharge cycles, indicating that DMI and FDMAC synergistically slow dendrite growth, demonstrating excellent dendrite suppression, superior to electrolyte systems containing only a single component (DMI or FDMAC).

[0060] Figure 9 The Zn in the electrolyte with the volume ratio of water, DMI and FDMAC being 7:0:3 (a), 7:1:2 (b) and 7:3:0 (c) respectively. 2+ From the migration number test chart, we can see that Zn 2+ The migration numbers are 0.56, 0.86 and 0.268 respectively, which indicates that the synergistic effect of DMI and FDMAC additives accelerates the migration of Zn 2+ The migration of Zn 2+ Uniform deposition.

[0061] Figure 10 The electrolyte prepared in Examples 3 to 5 was 2 mA / cm 2 The zinc nucleation overpotential plot at different current densities shows that the zinc nucleation overpotential (106 mV) in the electrolyte of Example 1 is significantly higher than that in the electrolytes containing either DMI or FDMAC alone. Furthermore, the ionic conductivities of the electrolytes prepared in Examples 3-5 were 25.23, 22.3, and 6.59 mS / cm, respectively, with the electrolyte of Example 3 having the highest ionic conductivity.

[0062] In summary, the present invention forms an inert organic layer on the surface of zinc foil by adding 1,3-dimethyl-2-imidazolidinone (DMI) and N,N-dimethyltrifluoroacetamide (FDMAC) additives to the zinc sulfate electrolyte. This inert layer can inhibit the growth of dendrites on the surface of zinc foil. The addition of DMI also inhibits the occurrence of side reactions such as hydrogen evolution reaction. This work systematically studies the effects of different concentrations of 1,3-dimethyl-2-imidazolidinone (DMI) and N,N-dimethyltrifluoroacetamide (FDMAC) additives on zinc deposition behavior, solvation structure and interface stability. Experiments show that when the volume ratio of water, DMI and FDMAC is 7:1:2, uniform Zn 2+ transport, excessive additives can lead to an imbalance in the solvation structure, triggering unwanted side reactions and reducing interfacial stability.

[0063] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. An aqueous zinc ion battery electrolyte additive, characterized in that: The electrolyte additive includes 1,3-dimethyl-2-imidazolidinone.

2. The aqueous zinc ion battery electrolyte additive according to claim 1, wherein: The volume concentration of the 1,3-dimethyl-2-imidazolidinone in the electrolyte is 10-25%.

3. The aqueous zinc ion battery electrolyte additive according to claim 1, wherein: The electrolyte additive further includes N,N-dimethyltrifluoroacetamide.

4. The aqueous zinc ion battery electrolyte additive according to claim 3, wherein: The volume ratio of the 1,3-dimethyl-2-imidazolidinone to N,N-dimethyltrifluoroacetamide is 1:

2.

5. A method for preparing an aqueous zinc ion battery electrolyte, characterized in that: include, Zinc sulfate is dissolved in water to obtain a zinc sulfate solution, and the electrolyte additive according to claims 1 to 4 is added thereto, and the solution is stirred and dissolved to obtain an aqueous zinc ion battery electrolyte.

6. The method for preparing an aqueous zinc ion battery electrolyte according to claim 5, wherein: The concentration of the zinc sulfate solution is 1 mol / L.

7. The aqueous zinc ion battery electrolyte prepared by the preparation method according to claim 5 or 6.

8. The aqueous zinc ion battery electrolyte according to claim 7, wherein: The volume concentration of 1,3-dimethyl-2-imidazolidinone in the zinc sulfate solution in the electrolyte is 10%.

9. The aqueous zinc ion battery electrolyte according to claim 7, wherein: The volume ratio of water, 1,3-dimethyl-2-imidazolidinone and N,N-dimethyltrifluoroacetamide in the electrolyte is 7:0-3:0-3.

10. The aqueous zinc ion battery electrolyte according to claim 7, wherein: The volume ratio of water, 1,3-dimethyl-2-imidazolidinone and N,N-dimethyltrifluoroacetamide in the electrolyte is 7:1:2.

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