Aqueous electrolyte, preparation and application thereof in aqueous zinc ion battery

Abstract

The application belongs to the field of zinc batteries, and particularly relates to a water-based electrolyte, which is an aqueous solution containing a conductive zinc salt and an additive of formula 1; R1, R2 and R3 are independently C1-C6 alkyl, C1-C6 alkoxy, phenyl, halogen or mercapto; and R4 is H, hydroxyl, amino or C1-C3 alkyl. The application adds the additive of formula 1 to the water-based electrolyte. Based on the combination of the carboxyl group and the highly branched fragment at the beta position of the additive of formula 1, the additive can coordinate with Zn 2+ in the zinc salt, reduce the coordination number of the hydrated zinc ion, improve the stability of the overall electrolyte, inhibit the generation of zinc dendrites, promote the uniform deposition of zinc, and thus realize a high-performance water-based zinc ion battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of zinc ion batteries, and particularly relates to the field of electrolyte. BACKGROUND

[0002] Zinc has a high theoretical capacity (820 mAh·g -1 ), a low redox potential (-0.76 V vs SHE) and green and non-toxic characteristics, making zinc ion batteries (ZIBs) one of the most promising electrochemical energy storage devices. However, the zinc anode in ZIBs faces challenges such as zinc dendrite growth, corrosion and hydrogen evolution reaction (HER), which further hinder the practical application of ZIBs. Among them, the HER occurring in the zinc metal electrode in the aqueous electrolyte is particularly critical. The HER not only leads to a local increase in pH, thereby triggering the continuous growth of by-products, but also accelerates the dissolution of the zinc electrode, thereby causing the reduction of the battery coulombic efficiency. In addition, the uneven surface of the zinc electrode promotes the growth of zinc dendrites, increasing the risk of short circuit of the battery, which is not conducive to its commercial application.

[0003] At present, a large number of studies focus on electrolyte design, zinc anode material modification and the introduction of artificial protective layers and other strategies to solve the challenges encountered by the zinc anode. Among them, the electrolyte, as one of the basic components of the battery, shows significant advantages in manufacturing and design. Therefore, electrolyte design has become one of the important strategies to stabilize the zinc anode. The main methods of electrolyte design include adding additives, modifying zinc salts, adjusting the solvation structure and improving the electrolyte / electrode interface. Generally, the combination of additives and zinc salts of different compositions can effectively adjust the solvation structure of hydrated zinc ions, inhibit the generation of zinc dendrites, and thus prolong the cycle life of the battery. However, the existing problems include the need to improve the compatibility of additives and zinc salts, the difficulty in accurately controlling the amount of additives, the unclear mechanism of electrolyte regulating the performance of zinc anode and the high cost of high-concentration electrolyte. Therefore, it is particularly necessary to explore suitable, efficient and stable electrolyte.

[0004] In view of the problems faced by the electrolyte, the existing technology also reports some improvement methods, for example, the Chinese patent document with publication number CN118073672A discloses the application of a two-phase electrolyte in zinc ion batteries, that is, the negative electrode side uses an organic-rich electrolyte, and the positive electrode side uses an aqueous electrolyte. This combination suppresses the HER of the zinc anode without compromising the performance of the positive electrode, achieving a zinc ion battery with high coulombic efficiency and long cycle life. The Chinese patent document with publication number CN11713001A discloses the use of L-sodium ascorbate as an electrolyte additive for ZIBs. L-sodium ascorbate is rich in carbonyl and hydroxyl functional groups, which can reduce the coordination water of zinc ions and lower the nucleation potential of zinc deposition, thereby achieving uniform deposition of the zinc anode.

[0005] Although the prior art has disclosed some different additives to stabilize the zinc negative electrode, the electrochemical stability of the combined battery at high discharge depth and large current density still needs to be further improved. SUMMARY

[0006] In view of the problems of low conductivity, zinc dendrite growth, excessive hydrogen evolution reaction and unsatisfactory life at high discharge depth existing in the prior art zinc ion battery, the first object of the present application is to provide a water-based electrolyte with a zinc ion battery, aiming to improve the conductivity of the zinc ion battery, inhibit the growth of zinc dendrites and reduce the hydrogen evolution reaction.

[0007] The second object of the present application is to provide preparation and application of the water-based electrolyte in a water-based zinc ion battery.

[0008] The third object of the present application is to provide a familiar zinc ion battery comprising the water-based electrolyte.

[0009] A water-based electrolyte is a water solution dissolving a conductive zinc salt and an additive of formula 1;

[0010]

[0011] R1, R2, R3 are independently C1-C6 alkyl, C1-C6 alkoxy, phenyl, halogen or mercapto; R4 is H, hydroxyl, amino or C1-C3 alkyl.

[0012] The present application innovatively adds the additive of formula 1 in the water-based electrolyte, based on the combination of the carboxyl group of the additive of formula 1 and the high-branched fragment at the beta position, which can coordinate with Zn 2+ in the zinc salt, reduce the coordination number of hydrated zinc ions, improve the stability of the overall electrolyte, inhibit the generation of zinc dendrites, promote the uniform deposition of zinc, and thus realize a high-performance water-based zinc ion battery. For example, the scheme of the present application can improve the long cycle performance under large current.

[0013] In the present application, the conductive zinc salt can be any conductive zinc salt known in the industry, for example, the conductive zinc salt includes at least one of zinc sulfate, zinc chloride, zinc acetate, zinc carbonate, zinc benzoate and zinc acetate.

[0014] In the present application, among R1, R2 and R3, two substituents are C1-C3 alkyl, and the remaining substituents are C1-C3 alkyl, C1-C3 alkoxy, phenyl, mercapto or halogen.

[0015] In the present application, formula 1 includes at least one of formula 1A, formula 1B, formula 1C and formula 1D.

[0016]

[0017] Research shows that, as an additive, formula 1D can obtain a more optimal synergistic effect based on the special branched structure, which helps to further improve the long cycle performance of the prepared electrolyte under high current.

[0018] The formula 1 includes formula 1C and formula 1D, preferably includes formula 1C and formula 1D in a weight ratio of 0.5-2:1. Research shows that the use of the preferred formula 1 can further adapt to the characteristics of the zinc battery system, and can further improve the long cycle performance of the prepared electrolyte under high current.

[0019] In the present application, the concentration of the conductive lithium salt in the aqueous electrolyte is 0.5-5M; preferably 1-3M; the concentration of the formula 1 additive is 0.5-10mg / mL, and considering the cost and effect, it can be further 1-5mg / mL.

[0020] The present application also provides a preparation method of the aqueous electrolyte, which dissolves the conductive zinc salt and the formula 1 additive in water to obtain the aqueous electrolyte.

[0021] The present application also provides an application of the aqueous electrolyte, which is used as an electrolyte to prepare an aqueous zinc ion battery.

[0022] Research shows that the aqueous electrolyte can adapt to the physicochemical characteristics of the aqueous zinc ion battery, and can further improve the performance of the aqueous zinc ion battery.

[0023] The present application also provides an aqueous zinc ion battery, which comprises a positive electrode, a negative electrode, a separator and an electrolyte, and the electrolyte comprises the aqueous electrolyte.

[0024] The aqueous zinc ion battery of the present application can be conventional in other components and structural relationships except that it comprises the aqueous electrolyte of the present application.

[0025] For example, the negative electrode of the present application can be zinc foil.

[0026] In the present application, the positive electrode active material in the positive electrode can be one or more of manganese dioxide, vanadium pentoxide, cobalt trioxide, iron dioxide, and molybdenum disulfide.

[0027] In the present application, the separator can be glass fiber.

[0028] Advantages

[0029] 1. The present application provides an improved electrolyte formulation for use in zinc-ion batteries. The electrolyte exhibits excellent ionic conductivity and good chemical stability. Research has shown that the improved electrolyte can effectively improve the rate performance and cycle stability of zinc-ion batteries, especially at high current densities, the battery exhibits excellent charge and discharge efficiency and long cycle life.

[0030] 2. The present application innovatively introduces specific additives into the electrolyte, which can effectively adjust the ion concentration and pH value of the electrolyte, thereby optimizing the conduction behavior of zinc ions and preventing the formation of zinc dendrites. The electrolyte not only enhances the cycle performance of the battery, but also significantly improves its stability under high-current charge and discharge conditions. By precisely controlling the concentration and ratio of additives, the method of the present application can make the electrolyte exhibit higher electrochemical stability in aqueous zinc-ion batteries, prolonging the service life of the battery.

[0031] 3. On the basis of the innovation, combined with the selection of additives, the optimization of electrolyte components and specific operation conditions, etc., the comprehensive performance of zinc-ion batteries in high-rate and high-capacity operation is further improved. Through these synergistic optimization measures, the present application effectively inhibits the corrosion and uneven deposition of zinc electrodes, ensuring the efficient and safe operation of the battery, especially under high load and long-term cycling conditions. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 Cycle scan graph of the zinc electrode finally prepared in Example 1;

[0033] Figure 2 Cycle graph of Example 2D at a current density of 1 mA / cm 2 , and a surface capacity of 1 mAh / cm 2 . DETAILED DESCRIPTION

[0034] The present application will be further described in detail below in conjunction with specific embodiments, but the present application is not limited to the following embodiments.

[0035] In the present application, the aqueous zinc-ion battery, in addition to containing the aqueous electrolyte containing Formula 1 described in the present application, other components and structures can be known.

[0036] For example, the negative electrode is a zinc foil, which can be obtained based on a conventional acid surface treatment. For example, in the following case, the zinc foil described in the following case can be obtained in the following manner: take 50 ml of dilute hydrochloric acid solution with a concentration of 0.1 mol / L, immerse 3 g of zinc foil (thickness 50 μm) in the dilute hydrochloric acid solution, control the environmental temperature to be 25°C, and immerse for 2 hours. Subsequently, the zinc foil is washed with pure water and anhydrous ethanol in sequence, and is dried in an oven until completely anhydrous to obtain the zinc negative electrode.

[0037] The positive electrode can be a conventional coated positive electrode, which comprises a current collector and a positive electrode material compounded on the surface thereof. For example, the positive electrode is prepared as follows: the positive electrode active material, conductive carbon black, and polyvinylidene fluoride are weighed according to the mass ratio of 7:2:1. After dry grinding for 1 h under room temperature drying conditions, a certain amount of N-methylpyrrolidone is added for wet grinding for 15 min. Subsequently, the slurry is coated on a stainless steel mesh. Finally, the obtained material is sliced after vacuum drying for one night.

[0038] In the present application, the separator is a glass fiber.

[0039] The electrolyte can be obtained by mixing through a conventional mixing means.

[0040] Example 1

[0041] Electrolyte: an aqueous solution dissolving formula 1 and zinc salt, wherein the concentration of formula 1 is 1 mg / mL, and the concentration of the zinc salt is 2 M. In the present case, formula 1 is Formula 1A

[0042] The zinc salt is zinc sulfate.

[0043] Half-cell assembly and performance determination:

[0044] In an atmospheric environment, the components are assembled into a CR2025 button cell in the order of positive electrode shell, zinc electrode, glass fiber separator, zinc electrode, foamed nickel, and negative electrode shell. Subsequently, the electrolyte to be tested is injected into the battery, and finally the battery is sealed by a battery sealing machine.

[0045] Symmetric battery test:

[0046] At an environmental temperature of 25°C, a 1 mA / cm 2 current density, 1 mAh / cm 2 surface capacity, and 10 mA / cm 2 current density, 10 mAh / cm 2The assembled symmetrical batteries were subjected to charge-discharge test to evaluate their electrochemical performance. The instrument used for the test was blue electric electrochemical measurement system. The results are shown in Table 1 and Table 2, respectively. It should be noted that in Table 1 and Table 2, the cycle life refers to the cycle life of short circuit.

[0047] Full battery assembly and performance test:

[0048] In an atmospheric environment, the components were assembled into CR2025 button batteries in the order of positive electrode shell, Mn02positive electrode, glass fiber diaphragm, zinc electrode, foamed nickel and negative electrode shell. Subsequently, the electrolyte to be tested was injected into the battery, and finally the sealing process was performed by a battery sealing machine. During the test, the assembled full battery was subjected to cycle test at a current density of 2A / g in an environment at 25°C to evaluate its electrochemical performance. The instrument used for the test was blue electric electrochemical measurement system. The results are shown in Table 3. The cycle number in Table 3 refers to the cycle number when the capacity decays to 80%.

[0049] Example 2

[0050] Compared with Example 1, the only difference is that the formula 1 in the electrolyte is changed, and the experimental groups are as follows:

[0051] Group A: formula 1 is formula 1B;

[0052] Group B: formula 1 is formula 1C;

[0053] Group C: formula 1 is formula 1D.

[0054] Group D: formula 1 is formula 1C and formula 1D with a weight ratio of 1:1.

[0055] The total amount of formula 1 and other operations and parameters are the same as those in Example 1.

[0056] Example 3

[0057] Compared with Example 1, the only difference is that the formula 1, zinc salt and ratio in the electrolyte are changed, and the experimental groups are as follows:

[0058] Group A: formula 1 is 3mg / mL, and the concentration of the zinc salt (zinc acetate) is 1.5M.

[0059] Group B: formula 1 is 5mg / mL, and the concentration of the zinc salt (zinc triflate) is 2.5M.

[0060] Comparative Example 1

[0061] Compared with Example 1, the only difference is that formula 1 is not added in the electrolyte, and other processes and test conditions are the same as those in Example 1.

[0062] Comparative Example 2

[0063] The difference compared with Example 1 is only that, in the electrolyte, Formula 1 is replaced by the following structure, and the experimental groups are respectively:

[0064] Group A: Comparative Formula A is used to replace Formula 1;

[0065] Group B: Comparative Formula B is used to replace Formula 1;

[0066] Group C: Comparative Formula C is used to replace Formula 1;

[0067] Table 1: Test results of Example and Comparative Example at a current density of 1 mA / cm 2 , and a surface capacity of 1 mAh / cm 2

[0068] Material Cycle life (h) Polarization current (mA) Example 1 6000 132 Example 2A 5565 100 Example 2B 6100 121 Example 2C 8003 81 Example 2D 8125 76 Example 3A 6200 126 Example 3B 6723 129 Comparative Example 1 4980 135 Comparative Example 2A 5000 128 Comparative Example 2B 4996 116 Comparative Example 2C 4983 123

[0069] Table 2: Test results of Example and Comparative Example at a current density of 10 mA / cm 2 , and a surface capacity of 10 mAh / cm 2

[0070] Material Cycle life (h) Polarization current (mA) Example 1 1300 146 Example 2A 1100 96 Example 2B 1154 112 Example 2C 1500 76 Example 2D 1621 73 Example 3A 1200 130 Example 3B 1260 133 Comparative Example 1 850 154 Comparative Example 2A 888 152 Comparative Example 2B 885 147 Comparative Example 2C 921 149

[0071] From Tables 1 and 2, it can be seen that the additive, especially the preferred additive and the combined additive, can effectively improve the cycle life of the battery, especially the cycle life at high current.

[0072] Table 3: Test results of Example and Comparative Example at a current density of 2 A / g

[0073] Material Cycle number Specific capacity (mAh / g) Example 1 3750 90 Example 2A 3596 95 Example 2B 3699 98 Example 2C 4000 120 Example 2D 4125 125 Example 3A 3700 97 Example 3B 3650 95 Comparative Example 1 3450 83 Comparative Example 2A 3311 84 Comparative Example 2B 3124 78 Comparative Example 2C 3234 86

[0074] In summary, the present application innovatively adds the additive of Formula 1 in the aqueous electrolyte, and based on the combination of the carboxyl group and the high-branched fragment at the β position of Formula 1 additive, the coordination with Zn 2+ in the zinc salt can occur, the coordination number in the hydrated zinc ion is reduced, the stability of the overall electrolyte is improved, the generation of zinc dendrites is inhibited, the uniform deposition of zinc is promoted, and thus a high-performance aqueous zinc ion battery is realized.

[0075] In addition, from Examples 1 and 2, it can be seen that by using Formula 1D as an additive, based on the special branched structure, a more optimal synergistic effect can be obtained, which is helpful to further improve the long cycle performance of the prepared electrolyte at high current. From Examples 1-2 and Comparative Example 2, it can be seen that even if the number of substituted carbons is the same, the high-branched structure of the present application can obtain a more optimal effect.​​

Claims

1. An aqueous electrolyte, characterized in that, An aqueous solution containing conductive zinc salt and additive of formula 1; Formula 1 Of R1, R2, and R3, two of the substituents are C1-C3 alkyl groups, and the remaining substituents are C1-C3 alkyl groups, C1-C3 alkoxy groups, phenyl groups, or mercapto groups; R4 is H, hydroxyl, amino, or C1-C3 alkyl groups.

2. The aqueous electrolyte as described in claim 1, characterized in that, The conductive zinc salt includes at least one of zinc sulfate, zinc chloride, zinc acetate, zinc carbonate, zinc benzoate, and zinc acetate.

3. The aqueous electrolyte as described in claim 1, characterized in that, Formula 1 includes at least one of Formula 1A, Formula 1B, Formula 1C, and Formula 1D; Formula 1A Formula 1B Formula 1C Formula 1D.

4. The aqueous electrolyte as described in claim 3, characterized in that, The additives include Formula 1C and Formula 1D.

5. The aqueous electrolyte as described in claim 4, characterized in that, The additives include Formula 1C and Formula 1D in a weight ratio of 0.5 to 2:

1.

6. The aqueous electrolyte according to any one of claims 1 to 5, characterized in that, In the aqueous electrolyte, the concentration of the conductive zinc salt is 0.5~5M; the concentration of the additive of Formula 1 is 0.5~10mg / mL.

7. The aqueous electrolyte as described in claim 6, characterized in that, In the aqueous electrolyte, the concentration of the conductive zinc salt is 1~3M.

8. A method for preparing the aqueous electrolyte according to any one of claims 1 to 7, characterized in that, The aqueous electrolyte is obtained by dissolving the conductive zinc salt and the additive of Formula 1 in water.

9. The application of the aqueous electrolyte according to any one of claims 1 to 7, characterized in that, Using it as an electrolyte, an aqueous zinc-ion battery was prepared.

10. An aqueous zinc-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that, The electrolyte comprises the aqueous electrolyte according to any one of claims 1 to 7.

Images