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

Abstract

The invention belongs to the field of zinc batteries, and particularly relates to an aqueous electrolyte which is an aqueous solution in which conductive zinc salt and a formula 1 additive # imgabs0 # are dissolved, r1, R2 and R3 are independently a C1-C6 alkyl group, a C1-C6 alkoxy group, a phenyl group, a halogen group or a sulfydryl group; and R4 is H, a hydroxyl group, an amino group or a C1-C3 alkyl group. According to the invention, the additive shown in the formula 1 is creatively added into the aqueous electrolyte, and based on the combination of carboxyl of the additive shown in the formula 1 and highly branched fragments of the beta site of the additive, the additive can be coordinated with Zn < 2 + > in zinc salt, so that the coordination number in hydrated zinc ions is reduced, the stability of the whole electrolyte is improved, the generation of zinc dendrites is inhibited, and the uniform deposition of zinc is promoted; and thus, a high-performance aqueous zinc ion battery is realized.

Description

Technical Field

[0001] The invention belongs to the field of zinc ion batteries, and in particular to the field of electrolytes. Background Art

[0002] Zinc has a high theoretical capacity (820 mAh g -1 ), low redox potential (-0.76VVs SHE) and green and non-toxic characteristics make 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 problems 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. 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, resulting in a decrease in the coulombic efficiency of the battery. In addition, the uneven surface of the zinc electrode promotes the growth of zinc dendrites, increases the risk of battery short circuit, and is not conducive to its commercial application.

[0003] At present, a large number of studies focus on strategies such as electrolyte design, zinc anode material modification and introduction of artificial protective layers to solve the challenges encountered by zinc anodes. Among them, 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 for stabilizing zinc anodes. The main methods of electrolyte design include adding additives, zinc salt modification, adjusting the solvation structure and improving the electrolyte / electrode interface. Generally, combining additives with zinc salts of different compositions can effectively adjust the solvation structure of hydrated zinc ions and inhibit the formation of zinc dendrites, thereby extending the cycle life of the battery. However, the current problems include the need to improve the compatibility of additives and zinc salts, the difficulty in accurately controlling the dosage of additives, the unclear mechanism of electrolyte regulation of zinc anode performance, and the high cost of high-concentration electrolytes. Therefore, it is particularly necessary to explore suitable, efficient and stable electrolytes.

[0004] In view of the problems faced by the electrolyte, some improvement methods have also been reported in the prior art. For example, the Chinese patent document with publication number CN118073672A discloses the application of a two-phase electrolyte in a zinc ion battery, that is, an electrolyte rich in organic phase is used on the negative electrode side, and an aqueous electrolyte is used on the positive electrode side. This combination suppresses the HER of the zinc negative electrode without damaging the positive electrode performance, thereby achieving a zinc ion battery with high coulomb efficiency and long cycle life. The Chinese patent document with publication number CN11713001A discloses the use of sodium L-ascorbate as an electrolyte additive for ZIBs. Sodium L-ascorbate is rich in carbonyl and hydroxyl functional groups, which can reduce the coordinated water of zinc ions and reduce the nucleation potential of zinc deposition, thereby achieving uniform deposition of the zinc negative electrode.

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

[0006] In view of the problems of low conductivity, zinc dendrite growth, overly intense hydrogen evolution reaction, and unsatisfactory life span of existing zinc ion batteries, especially at high discharge depth, the first object of the present invention is to provide an aqueous electrolyte for 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 invention is to provide a method for preparing the aqueous electrolyte and its application in an aqueous zinc ion battery.

[0008] The third object of the present invention is to provide a conventional zinc ion battery comprising the aqueous electrolyte.

[0009] An aqueous electrolyte is an aqueous solution in which a conductive zinc salt and an additive of formula 1 are dissolved;

[0010]

[0011] The R 1 , R 2 , R 3 Alone for C 1 ~C 6 Alkyl, C 1 ~C 6 alkoxy, phenyl, halogen or mercapto; said R 4 is H, hydroxyl, amino or C 1 ~C 3 of alkyl.

[0012] The present invention innovatively adds the additive of formula 1 to the aqueous electrolyte, based on the combination of the carboxyl group of the additive of formula 1 and the highly branched fragment at the β position thereof, so that the additive can react with the Zn in the zinc salt. 2+ A coordination effect occurs, which reduces the coordination number in the hydrated zinc ions, improves the stability of the overall electrolyte, inhibits the formation of zinc dendrites, promotes the uniform deposition of zinc, and thus realizes a high-performance aqueous zinc ion battery. For example, the scheme described in the present invention can improve the long cycle performance under high current.

[0013] In the present invention, 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 invention, the R 1 , R2 , R 3 In which two of the substituents are C 1 ~C 3 The remaining substituents are C 1 ~C 3 Alkyl, C 1 ~C 3 alkoxy, phenyl, mercapto or halogen.

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

[0016]

[0017] Studies have shown that formula 1D as an additive can achieve better synergistic effects 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 including formula 1C and formula 1D in a weight ratio of 0.5 to 2: 1. The present invention 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 invention, in the aqueous electrolyte, the concentration of the conductive lithium salt is 0.5 to 5 M, preferably 1 to 3 M; the concentration of the additive of formula 1 is 0.5 to 10 mg / mL, and can be further 1 to 5 mg / mL in consideration of cost and effect.

[0020] The present invention also provides a method for preparing the aqueous electrolyte, wherein the conductive zinc salt and the additive of formula 1 are dissolved in water to obtain the aqueous electrolyte.

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

[0022] The research of the present invention shows that the aqueous electrolyte can adapt to the physical and chemical characteristics of the aqueous zinc ion battery and can further improve the performance of the aqueous zinc ion battery.

[0023] The present invention also provides an aqueous zinc ion battery, comprising a positive electrode, a negative electrode, a diaphragm and an electrolyte, wherein the electrolyte comprises the aqueous electrolyte.

[0024] The aqueous zinc ion battery of the present invention, in addition to comprising the aqueous electrolyte of the present invention, may have conventional components and structural relationships in addition.

[0025] For example, the negative electrode of the present invention may be zinc foil.

[0026] In the present invention, the positive electrode active material in the positive electrode can be one or more of manganese dioxide, vanadium pentoxide, cobalt tetroxide, ferric oxide, and molybdenum disulfide.

[0027] In the present invention, the diaphragm may be glass fiber.

[0028] Beneficial Effects

[0029] 1. The present invention provides an improved electrolyte formula for use in zinc ion batteries, wherein the electrolyte has excellent ionic conductivity and good chemical stability. The present invention's research shows that the improved electrolyte can effectively improve the rate performance and cycle stability of zinc ion batteries, especially at high current density, the battery exhibits excellent charge and discharge efficiency and long cycle life.

[0030] 2. The present invention 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 can not only enhance the cycle performance of the battery, but also significantly improve its stability under high current charge and discharge conditions. By precisely controlling the concentration and ratio of the additives, the method of the present invention can make the electrolyte show higher electrochemical stability in aqueous zinc ion batteries and extend the service life of the battery.

[0031] 3. Based on the above innovation, the comprehensive performance of zinc ion batteries at high rate and high capacity is further improved by combining the selection of additives, optimized electrolyte composition and specific operating conditions. Through these synergistic optimization measures, the present invention 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 cycle conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a scanning diagram of the zinc electrode finally prepared in Example 1 after cycling;

[0033] Figure 2 For Example 2D, at a current density of 1 mA / cm 2 , with a surface capacity of 1 mAh / cm 2 The following cycle diagram. DETAILED DESCRIPTION

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

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

[0036] For example, the negative electrode is a zinc foil, which can be obtained based on conventional acid surface treatment. For example, in the following case, as an illustrative scheme, the zinc foil described in the following case can be obtained by the following method: take 50 ml of a 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 ambient temperature to 25°C, and immerse for 2 hours. Subsequently, the zinc foil is washed with pure water and anhydrous ethanol in turn, and placed in an oven to dry until completely anhydrous to obtain a zinc negative electrode.

[0037] The positive electrode can be a conventional coated positive electrode, which includes a current collector and a positive electrode material composited on its surface. For example, the positive electrode is prepared as follows: the positive electrode active material, conductive carbon black, and polyvinylidene fluoride are weighed in a mass ratio of 7:2:1. After dry grinding for 1 hour at room temperature, a certain amount of N-methylpyrrolidone is added for wet grinding for 15 minutes. The slurry is then coated on a stainless steel mesh. Finally, the obtained material is sliced ​​after vacuum drying overnight.

[0038] In the present invention, the diaphragm is glass fiber.

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

[0040] Example 1

[0041] Electrolyte: An aqueous solution containing 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 this case, Formula 1 is Formula 1A

[0042] The zinc salt is zinc sulfate.

[0043] Half-cell assembly and performance determination:

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

[0045] Symmetrical battery test:

[0046] At 25°C, 1mA / cm 2 Current density, 1mAh / cm 2 Surface capacity and 10mA / cm 2 Current density, 10mAh / cm 2The assembled symmetrical battery was charged and discharged to evaluate its electrochemical performance. The instrument used for the test was a Blue Electric electrochemical measurement system. The results are shown in Tables 1 and 2. It should be noted that in Tables 1 and 2, the cycle life refers to the short-circuit cycle life.

[0047] Full battery assembly and performance testing:

[0048] In the atmospheric environment, according to the positive electrode shell, MnO 2 The components are assembled into a CR2025 button cell in the order of positive electrode, glass fiber separator, zinc electrode, nickel foam and negative electrode shell. Subsequently, the electrolyte to be tested is injected into the battery, and finally the battery is sealed by a battery packaging machine. During the test, the assembled full battery was cycled at a current density of 2A / g at 25°C to evaluate its electrochemical performance. The instrument used in the test is the Blue Electric Electrochemical Measurement System. The results are shown in Table 3. The number of cycles in Table 3 refers to the number of cycles 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:

[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 in a weight ratio of 1:1;

[0055] The total dosage 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. The experimental groups are:

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

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

[0060] Comparative Example 1

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

[0062] Comparative Example 2

[0063] Compared with Example 1, the only difference is that the following structure is used to replace Formula 1 in the electrolyte, and the experimental groups are:

[0064] Group A: Comparative A Replacement formula 1;

[0065] Group B: Comparative B Replacement formula 1;

[0066] Group C: Comparative C Replacement formula 1;

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

[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: Examples and Comparative Examples at a current density of 10 mA / cm 2 , surface capacity is 10 mAh / cm 2 Test results

[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] It can be seen from Tables 1 and 2 that the additives described in the present invention, especially the preferred additives and combined additives, can effectively improve the cycle life of the battery, especially can improve its cycle life under high current.

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

[0073] Material Number of cycles 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 invention innovatively adds the additive of formula 1 to the aqueous electrolyte, based on the combination of the carboxyl group of the additive of formula 1 and the highly branched fragment at the β position thereof, so that the Zn in the zinc salt can be 2+ The coordination effect occurs, reducing the coordination number in the hydrated zinc ions, improving the stability of the overall electrolyte, inhibiting the formation of zinc dendrites, and promoting the uniform deposition of zinc, thereby realizing a high-performance aqueous zinc-ion battery.

[0075] In addition, it can be seen from Examples 1 and 2 that by using Formula 1D as an additive, based on the special branched structure, a better synergistic effect can be obtained, which helps to further improve the long cycle performance of the prepared electrolyte under high current. It can be seen from Examples 1 to 2 and Comparative Example 2 that even if the number of substituted carbons is the same, a better effect can be obtained by using the highly branched structure described in the present invention.

Claims

1. An aqueous electrolyte, characterized in that: An aqueous solution containing a conductive zinc salt and an additive of formula 1; The R1, R2, and R3 are independently C1-C6 alkyl, C1-C6 alkoxy, phenyl, halogen, or mercapto; and the R4 is H, hydroxyl, amino, or C1-C3 alkyl.

2. The aqueous electrolyte according to 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 according to claim 1 or 2, characterized in that Among the 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, mercapto groups or halogen groups.

4. The aqueous electrolyte according to claim 3, characterized in that The formula 1 includes at least one of formula 1A, formula 1B, formula 1C, and formula 1D; 5. The aqueous electrolyte according to claim 4, characterized in that The formula 1 includes formula 1C and formula 1D.

6. The aqueous electrolyte according to claim 5, characterized in that The formula 1 includes formula 1C and formula 1D in a weight ratio of 0.5 to 2:

1.

7. The aqueous electrolyte according to any one of claims 1 to 6, characterized in that In the aqueous electrolyte, the concentration of the conductive lithium salt is 0.5 to 5 M, preferably 1 to 3 M; the concentration of the additive of formula 1 is 0.5 to 10 mg / mL.

8. A method for preparing an aqueous electrolyte according to any one of claims 1 to 7, characterized in that: The conductive zinc salt and the additive of formula 1 are dissolved in water to obtain the aqueous electrolyte.

9. Use of the aqueous electrolyte according to any one of claims 1 to 7, characterized in that: It is used as an electrolyte to prepare an aqueous zinc ion battery.

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