A water-based zinc ion electrolyte, a zinc ion battery and a preparation method thereof

Abstract

The application provides a water-based zinc ion electrolyte, a zinc ion battery and a preparation method thereof. The water-based zinc ion electrolyte comprises a zinc salt, a negative electrode additive and a solvent, the negative electrode additive comprises an azacrown ether, and the azacrown ether is one or more of the following molecular formulae: 12 crown: C8H (16+x) N x O (4‑x) (0<=x<=4), 15 crown: C 10 H (20+y) N y O (5‑y) (0<=y<=5), 18 crown: C 12 H (24+z) N y O (6‑z) (0<=z<=6), 21 crown: C 14 H (28+w) N y O (7‑w) (0<=w<=7). The zinc ion battery with a zinc negative electrode provided by the application has excellent cycle stability, high coulomb efficiency and corrosion resistance, and has lower cycle impedance.

Description

Technical Field

[0001] This invention relates to the field of aqueous electrolyte battery technology, and in particular to an aqueous zinc ion electrolyte, a zinc ion battery, and a method for preparing the same. Background Technology

[0002] In recent years, zinc metal has gained popularity due to its suitable redox potential (-0.76V relative to the standard hydrogen electrode) and high capacity (820mAh g). -1 5851mAh cm -3 Zinc-ion batteries, with their low polarization and aqueous design, offer advantages such as high energy density, high power density, safety, low cost, and environmental friendliness. Aqueous zinc-ion batteries with zinc as the negative electrode are receiving increasing attention and are considered a promising new battery system to replace lithium-ion batteries, while also being seen as a bridge between batteries and capacitors. However, it's worth noting that due to the thermodynamically active nature of zinc, it is prone to self-corrosion, passivation, and dendrite formation. These problems severely impact the battery's energy density, power density, and lifespan, hindering the commercial application of aqueous zinc-ion batteries with zinc as the negative electrode. Furthermore, zinc-ion batteries experience rapid capacity decay during cycling, unstable rate cycling performance, and are prone to bulging. Zinc dendrite growth can also puncture the separator, further limiting and affecting the performance of zinc-ion batteries and hindering their large-scale production and application.

[0003] Specifically, in aqueous solutions, the uneven distribution of surface charge on zinc leads to uneven concentration distribution of zinc ions at the interface. This causes zinc ions to deposit nuclei in localized areas of high zinc concentration, which then grow into coarse dendrites. The dendrite tips, acting as charge centers, easily trigger spike effects, leading to continuous charge accumulation and further promoting the growth of zinc dendrites. This results in capacity decay and ultimately a short circuit.

[0004] Furthermore, during Zn deposition, uneven charge distribution leads to localized Zn deposition. 2+ Enrichment occurs, with enriched Zn 2+ Will reject H + Attract more OH - This causes changes in the local pH distribution. Under acidic conditions, the surface of metallic zinc is more prone to hydrogen evolution reaction (HER), leading to zinc corrosion.

[0005] Similarly, due to the uneven distribution of the electric field at the reaction interface, the local alkaline environment will force Zn(OH)4 to react. 2- Formation, Zn(OH)4 2- Subsequently, it transforms into passivated electrochemical zinc oxide and zinc hydroxide precipitates, thereby significantly increasing the interfacial resistance and degrading battery performance.

[0006] In addition, in the zinc sulfate electrolyte system, sulfate ions (SO4) are present on the surface of the negative electrode. 2- The side reactions involved in these processes lead to the formation of irreversible byproducts, such as zinc hydroxysulfate. The formation of these byproducts comes at the cost of continuous consumption of electrolyte and active zinc ions, which reduces the coulombic efficiency of zinc deposition / stripping to some extent.

[0007] Therefore, it is necessary to employ various methods, such as electrode additives and electrolyte additives, to improve the electrochemical performance of zinc electrodes and enhance the discharge and cycle performance of zinc-ion batteries. This will promote the further development and application of zinc-ion batteries and is also of great significance to the development of energy storage devices. Currently, commonly used electrolyte additives are mainly polymer additives and metal ion additives. During zinc deposition, polymers can selectively adsorb onto favorable nucleation sites of zinc, thereby promoting uniform deposition of zinc ions and preventing dendrite growth. In addition to polymers, metal ions also adsorb onto the Zn negative electrode surface, promoting uniform deposition of zinc ions through electrostatic repulsion. For polymer electrolyte additives, the polarity-induced molecular adsorption binding force is too weak to achieve complete site coverage. For metal ions, their surface adsorption has little effect on inhibiting the hydrogen evolution reaction (HER). Patent CN115295885A discloses a liquid electrolyte for metal batteries, its preparation method, and a metal battery, but its cycle stability needs further improvement. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides an aqueous zinc-ion electrolyte, a zinc-ion battery, and a method for preparing the same, which solves the problems of low cycle stability and low high coulombic efficiency in existing aqueous zinc-ion batteries.

[0009] In one aspect, the present invention provides an aqueous zinc ion electrolyte, comprising a zinc salt, a negative electrode additive, and a solvent, wherein the negative electrode additive comprises a nitrile crown ether, and the nitrile crown ether is one or more of the following molecular formulas:

[0010] 12 titles: C8H (16+x) N x O (4-x) (0≤x≤4), 15 crowns: C 10 H (20+y) N y O (5-y) (0≤y≤5), 18 crowns: C 12 H (24+z) N y O (6-z) (0≤z≤6), 21 crowns: C 14 H (28+w) N y O (7-w) (0≤w≤7).

[0011] Furthermore, the molecular structure of the nitrogen-containing heterocyclic ether is as follows: One or more of them.

[0012] Furthermore, the mass percentages of each component in the aqueous zinc ion electrolyte are: zinc salt 10-30%, negative electrode additive 0.1-10%, and solvent 60-89.9%.

[0013] Furthermore, the zinc salt is selected from one or more of zinc sulfate, zinc acetate, zinc nitrate, zinc chloride, and zinc trifluoromethanesulfonate; the solvent is ultrapure water.

[0014] In another aspect, the present invention provides a method for preparing an aqueous zinc ion electrolyte, comprising mixing a zinc salt, a negative electrode additive and a solvent to obtain the electrolyte.

[0015] In another aspect, the present invention provides an application of an aqueous zinc ion electrolyte in a zinc ion battery.

[0016] In another aspect, the present invention provides a zinc-ion battery comprising the above-mentioned aqueous zinc-ion electrolyte.

[0017] Furthermore, the zinc-ion battery also includes a positive electrode material, a negative electrode material, and a separator.

[0018] Furthermore, the positive electrode material is selected from one or more of manganese-based compounds, Prussian blue derivatives, vanadium-based materials, polyanionic compounds, and organic positive electrode materials; the negative electrode material is selected from zinc metal or zinc alloy.

[0019] Furthermore, the diaphragm is selected from one or more of glass fiber, polypropylene / polyolefin microporous membrane, porous polymer membrane, nonwoven fabric diaphragm, and filter membrane.

[0020] As is known to those skilled in the art, the positive electrode material, negative electrode material, and separator in this invention are all materials known in the prior art. Specifically, the manganese-based compound includes, but is not limited to, γ-MnO2 and ZnMnO3; the Prussian blue derivative includes, but is not limited to, K 0.6 Ni 1.2 Fe(CN)6·3.6H2O(NiHCF), CuHCF(K 0.71 Cu[Fe(CN)6] 0.72 • 3.7H2O); the vanadium-based materials include, but are not limited to, NH4V4O 10 K2V6O 10 ·nH2O; the polyanionic compound is not limited to CuSO4; the organic cathode material includes, but is not limited to, polypyrrole and polyaniline.

[0021] The technical principle of this invention is as follows: In the prior art, negative electrode additives used in aqueous zinc-ion batteries include pyridines, imidazoles, alcohols, crown ethers, etc. During the screening of negative electrode additives, the inventors discovered that the addition of azeotropic crown ethers not only improves the cycle stability of zinc batteries but also reduces the cycle impedance performance and corrosion resistance of the zinc electrode, significantly outperforming all-oxygen ligand materials. This may be because azeotropic crown ethers have a stronger binding ability to Zn. Azeotropic crown ethers and zinc ions form a supramolecular complex (azeotropic crown ether-zinc ion) which is deposited on the surface of the zinc negative electrode. This supramolecular complex induces the formation of a thin and stable solid electrolyte interphase (SEI) film by adjusting the composition of the electrical double layer at the interface between the zinc negative electrode and the electrolyte. This SEI film helps suppress side reactions such as hydrogen evolution and the formation of hydroxide sulfates. On the other hand, the reduction potential of the positively charged supramolecular structure is more negative than that of zinc ions, providing an ideal electrostatic shielding layer. This adjusts the deposition around the zinc negative electrode caused by the repulsion of the positively charged electrostatic layer, ensuring uniform deposition of zinc ions on the negative electrode surface, ultimately inhibiting the formation of zinc dendrites and effectively reducing the interfacial impedance between the electrolyte and the electrode. Furthermore, the inventors unexpectedly discovered that zinc batteries using monoaza crown ether as the negative electrode additive outperformed zinc batteries using diaza crown ether as the negative electrode additive.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) Compared with traditional aqueous zinc-ion batteries, the aqueous zinc-ion battery of the present invention has better cycle stability, with more than 1,000 cycles; high coulombic efficiency; better corrosion resistance, with a cumulative hydrogen evolution of only 0.015 ml in 10 hours; and lower cycle impedance, with a DC impedance of only 50 Ω.

[0024] (2) The electrolyte of the present invention can be directly matched with the positive electrode, negative electrode, and separator to form an effective battery. Its preparation method is simple and easy to implement, highly reproducible, and under mild conditions, making it suitable for industrial production. Attached Figure Description

[0025] Figure 1 The Zn||Zn symmetric cell (CR2O32) of the button cell prepared for Experimental Example 1 was tested at a current density of 1 mA cm⁻¹. -2 The deposition capacity is 1 mAh cm⁻¹ -2 Cyclic performance graph under the given conditions;

[0026] Figure 2 The Zn||Zn symmetric cell (CR2O32) of the button cell prepared for Experimental Example 1 was tested at a current density of 1 mA / cm². -2 The deposition capacity is 1 mAh cm⁻¹ -2 Cyclic performance under certain conditions.

[0027] Figure 3The Zn||Zn symmetric cell (CR2O32) of the button cell prepared for Experimental Example 1 was tested at a current density of 1 mA cm⁻¹. -2 The deposition capacity is 1 mAh cm⁻¹ -2 Cyclic performance under certain conditions. Detailed Implementation

[0028] The technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] Example 1: Preparation of Aqueous Zinc Ion Electrolyte and Zinc Ion Battery

[0030] S1. At room temperature, take 40 mg of monoazacrown ether and add it to 10 mL (10 g) of ultrapure water. Stir thoroughly, then add 1.61 g of zinc sulfate and stir thoroughly to obtain an aqueous zinc-ion battery electrolyte containing monoazacrown ether.

[0031] S2. A button cell is assembled using an aqueous zinc-ion battery electrolyte containing monoazine crown ether as the electrolyte, a zinc sheet as the negative electrode, γ-MnO2 as the positive electrode, and glass fiber as the separator.

[0032] Among them, monoazacrown ethers are

[0033] Example 2: Preparation of Aqueous Zinc Ion Electrolyte and Zinc Ion Battery

[0034] Similar to Example 1, except that the monoazacrown ether is replaced with a diazacrown ether.

[0035] Among them, diazacrown ethers are

[0036] Example 3: Preparation of Aqueous Zinc Ion Electrolyte and Zinc Ion Battery

[0037] S1. At room temperature, take 30 mg of diazacrown ether and add it to 10 mL (10 g) of ultrapure water. Stir thoroughly, then add 1.61 g of zinc sulfate and stir thoroughly to obtain an aqueous zinc-ion battery electrolyte containing diazacrown ether.

[0038] S2. A button cell is assembled using an aqueous zinc-ion battery electrolyte containing diazacorona ether as the electrolyte, a zinc sheet as the negative electrode, K0.6Ni1.2Fe(CN)63.6H2O(NiHCF) as the positive electrode, and polyarylethersulfone as the separator.

[0039] Among them, diazacrown ethers are

[0040] Example 4: Preparation of Aqueous Zinc Ion Electrolyte and Zinc Ion Battery

[0041] S1. At room temperature, take 20 mg of monoazacrown ether and add it to 10 mL (10 g) of ultrapure water. Stir thoroughly and then add 1.61 g of zinc sulfate. Stir thoroughly to obtain an aqueous zinc-ion battery electrolyte containing monoazacrown ether.

[0042] S2, using an aqueous zinc-ion battery electrolyte containing monoazine crown ether as the electrolyte, zinc sheet as the negative electrode, and NH4V4O 10 A button cell is assembled using Celgard 2320 (polyolefin membrane) as the positive electrode and Celgard 2320 (polyolefin membrane) as the separator.

[0043] Among them, monoazacrown ethers are

[0044] Example 5: Preparation of Aqueous Zinc Ion Electrolyte and Zinc Ion Battery

[0045] S1. At room temperature, take 10 mg of diazacrown ether and add it to 10 mL (10 g) of ultrapure water. Stir thoroughly, then add 1.11 g of zinc nitrate and stir thoroughly to obtain an aqueous zinc-ion battery electrolyte containing diazacrown ether.

[0046] S2. A button cell is assembled using an aqueous zinc-ion battery electrolyte containing diazacorona ether as the electrolyte, a zinc sheet as the negative electrode, CuSO4 as the positive electrode, and S-PEEK / PVP as the separator.

[0047] Among them, diazacrown ethers are

[0048] Example 6: Preparation of Aqueous Zinc Ion Electrolyte and Zinc Ion Battery

[0049] S1. At room temperature, take 1.67g of monoazacrown ether and add it to 10mL (10g) of ultrapure water. Stir thoroughly, then add 5g of zinc trifluoromethanesulfonate and stir thoroughly to obtain an aqueous zinc-ion battery electrolyte containing monoazacrown ether.

[0050] S2. A button cell is assembled using an aqueous zinc-ion battery electrolyte containing monoazine crown ether as the electrolyte, a zinc sheet as the negative electrode, polyaniline as the positive electrode, and S-PEEK / PVP as the separator.

[0051] Among them, monoazacrown ethers are

[0052] Comparative Example

[0053] Similar to Example 1, except that the monoazacrown ether is replaced with a peroxycrown ether.

[0054] Among them, peroxycrown ether is

[0055] Test Example 1: Battery Cycle Performance Testing

[0056] After the button batteries prepared in Examples 1-2 and the comparative example were left to stand for 6 hours, the cycle performance of Zn||Zn symmetric batteries was tested (current density 1.0 mA cm⁻¹). -2 Discharge depth is 0.5 mAh cm -2 The discharge voltage and cycle life data of the batteries were collected. For comparative analysis, electrolytes without electrolyte negative electrode additives were prepared in Examples 1-2 and the comparative examples, and other conditions were the same as in Examples 1-2 and the comparative examples. Button batteries were made as control samples for testing the cycle performance of Zn||Zn symmetric batteries (current density of 0.5 mA / cm²). -2 The area capacity is 0.5mAh cm -2 Data on battery discharge voltage and cycle life were collected, and the results are as follows: Figures 1 to 3 As shown.

[0057] Depend on Figure 1-2 It can be seen that the zinc anode exhibits superior cycle stability in both the monoazacrown ether-based electrolyte of Example 1 and the diazacrown ether-based electrolyte of Example 2. After more than 800 hours of cycling, its potential showed no significant change. In contrast, the zinc in the zinc sulfate electrolyte only achieved stable cycling for 385 hours, possibly due to short circuits caused by dendrite growth. This demonstrates that the introduction of monoazacrown ether helps suppress dendrite growth and improve the cycle stability of the zinc anode. Furthermore, the overpotential of the monoazacrown ether-based electrolyte is approximately 0.2V, while that of the diazacrown ether-based electrolyte is approximately 0.16V. This indicates that the monoazacrown ether-based electrolyte has a wider potential window and performs better.

[0058] Figure 3 It can be seen that in the comparative example, the zinc anode has slightly better cycle stability than the single zinc sulfate electrolyte in the all-oxygen crown ether electrolyte. The battery short-circuited after 550 cycles, but its cycle count was significantly lower than that of Examples 1-2, and its performance was worse than that of Examples 1-2.

[0059] Furthermore, at 25±2℃, with 1mAcm -2 Current density and 1mAh cm -2 The deposition rate was tested by charging and discharging Zn||Zn symmetric cells under the given conditions. The overpotential and number of cycles were recorded for Examples 1, 2, and the comparative example. The results are shown in Table 1.

[0060] Table 1 Results of Cyclic Performance Testing

[0061] Group Overpotential (V) Loop count Example 1 0.2 1000 Example 2 0.16 900 Comparative Example 0.12 385

[0062] Table 1 shows that the aqueous zinc battery prepared with an electrolyte containing azeotropic crown ether as the negative electrode additive has a higher cycle life, reaching up to 1000 cycles, while the cycle life of the aqueous zinc battery prepared with an electrolyte containing crown ether as the negative electrode additive is significantly lower than that of the battery containing azeotropic crown ether. Furthermore, the overpotentials of Examples 1-2 are higher than those of the comparative example, indicating that the aqueous zinc battery with added azeotropic crown ether can increase the hydrogen evolution overpotential during the zinc electrode formation and charging processes, reducing hydrogen evolution and thus increasing charging efficiency and depth of charge. Further, it can be seen that monoazeotropic crown ether is more effective as a negative electrode additive than diazeotropic crown ether.

[0063] Test Example 2: Battery Cyclic Impedance Testing

[0064] Under conditions of 25±2℃, the battery was fully charged at 0.5C, then adjusted to 50% SOC, discharged at 2C for 15 seconds, and charged at 2C for 15 seconds. The DC resistance (DCR) was then tested. The test results are shown in Table 2.

[0065] Table 2 DC impedance test results

[0066] Group DC impedance (Ω) Example 1 50 Example 2 60 Comparative Example 200

[0067] As shown in Table 2, the DC impedance of Examples 1 and 2 is significantly lower than that of the comparative example. This indicates that the addition of azacrown ethers, compared to the addition of crown ethers, can significantly reduce the cycle impedance performance of the battery and further improve the performance of the aqueous zinc battery.

[0068] Test Example 3 Corrosion Resistance

[0069] Take 1g of the zinc electrodes prepared in Examples 1, 2, and the comparative example, add them to 100mL of 10mol / L potassium hydroxide solution, place them in a sealed container, and maintain a water bath temperature of 50℃. Collect the obtained hydrogen gas, and use a MOT500-H2 hydrogen gas analyzer to measure the amount of hydrogen gas produced by the hydrogen evolution corrosion reaction of the zinc electrodes. Measure the cumulative hydrogen evolution amount at 1h, 3h, 6h, and 10h. The results are shown in Table 3.

[0070] Table 3 Corrosion Resistance Test Results

[0071] Hydrogen evolution volume (ml) 1h 3h 6h 10h Example 1 0.01 0.012 0.014 0.015 Example 2 0.012 0.014 0.015 0.016 Comparative Example 0.02 0.025 0.03 0.035

[0072] As can be seen from Table 3, the amount of hydrogen evolution in Examples 1 and 2 is significantly lower than that in the comparative example, indicating that the addition of azacrown ether can significantly reduce the amount of hydrogen generated by the hydrogen evolution corrosion reaction of the zinc electrode compared to the addition of crown ether, thereby improving the corrosion resistance of the zinc electrode.

[0073] Finally, 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 it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An aqueous zinc ion electrolyte, comprising a zinc salt, a negative electrode additive, and a solvent, characterized in that: The negative electrode additive includes azacrown ether; The molecular structure of the azacrown ether is as follows: , , , , , , , , , , , , , , , , , , , , , , , , , , , , One or more of them.

2. The aqueous zinc ion electrolyte as described in claim 1, characterized in that: The mass percentages of each component in the aqueous zinc ion electrolyte are: zinc salt 10-30%, negative electrode additive 0.1-10%, and solvent 60-89.9%.

3. The aqueous zinc ion electrolyte as described in claim 1, characterized in that: The zinc salt is selected from one or more of zinc sulfate, zinc acetate, zinc nitrate, zinc chloride, and zinc trifluoromethanesulfonate; the solvent is ultrapure water.

4. A method for preparing an aqueous zinc ion electrolyte according to any one of claims 1-3, characterized in that: This involves mixing zinc salt, negative electrode additive, and solvent to obtain the desired product.

5. The application of an aqueous zinc ion electrolyte according to any one of claims 1-3 in a zinc ion battery.

6. A zinc-ion battery comprising the aqueous zinc-ion electrolyte as described in any one of claims 1-3.

7. A zinc-ion battery as described in claim 6, characterized in that: It also includes positive electrode materials, negative electrode materials, and separators.

8. A zinc-ion battery as described in claim 7, characterized in that: The positive electrode material is selected from one or more of manganese-based compounds, Prussian blue derivatives, vanadium-based materials, and polyanionic compounds; the negative electrode material is selected from zinc metal or zinc alloy.

9. A zinc-ion battery as described in claim 7, characterized in that: The diaphragm is selected from one or more of glass fiber, polypropylene / polyolefin microporous membrane, nonwoven membrane, and filter membrane.

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