Preparation method and application of a metallic zinc negative electrode with a metal soap coating

Abstract

The present invention discloses a preparation method and application of a metal zinc negative electrode with a metal soap coating, belonging to the field of aqueous zinc-ion batteries. It solves the technical problems of the existing zinc metal negative electrode, such as volume expansion at the negative electrode interface, low Coulombic efficiency, and attenuation of cycle life caused by dendrite growth. The preparation method is as follows: adding a metal salt into water and stirring evenly to obtain a metal salt solution; adding a normal fatty acid into an alkaline solution and stirring evenly to obtain a mixture; adding the mixture into the metal salt solution, carrying out a saponification reaction under stirring, washing and drying the reaction product to obtain a metal soap; spraying an ethanol solution of the metal soap obtained by adding the metal soap into ethanol on the surface of a pretreated zinc foil, and then performing a calcination treatment to obtain a metal zinc negative electrode with a metal soap coating. The metal zinc negative electrode with a metal soap coating is used in an aqueous zinc-ion battery, which can greatly improve the cycle life and stability of the aqueous zinc-ion battery.

Description

Technical Field

[0001] The present invention belongs to the field of aqueous zinc-ion batteries, and particularly relates to a preparation method and application of a metallic zinc negative electrode with a metal soap coating. Background Art

[0002] With the development of society, it is urgent to explore diverse energy sources and energy storage modes. The overexploitation and use of fossil fuels have caused serious environmental problems. Climate change has become a global non-traditional security issue, and global air pollution has endangered the basic living conditions of humanity. Therefore, the transformation of the global energy structure is imminent. With the continuous development of new energy technologies, batteries, as important devices for energy storage and conversion, have been widely used. Among them, lithium-ion batteries have been widely used in fields such as electric vehicles, mobile phones, and laptops due to their high energy density and good cycle life. However, lithium-ion batteries have a high cost and potential safety hazards. Therefore, it is of great significance to develop a battery with low cost and high safety performance.

[0003] Zinc-ion batteries have a lower battery redox potential, a higher theoretical capacity, abundant zinc resources, and a safer aqueous electrolyte, and are expected to replace lithium-ion batteries. However, the large-scale application of aqueous zinc-ion batteries has also encountered many bottlenecks, such as corrosion, passivation, dendrite formation, and severe hydrogen evolution reaction of the zinc negative electrode, etc., which limit their practical applications. To solve the problems of dendrite growth, corrosion, and passivation faced by the zinc negative electrode. In this regard, researchers and engineers have found that the negative electrode interface coating technology of aqueous zinc-ion batteries is an effective solution, which can significantly improve the cycle life and safety of the battery. The main functions of the negative electrode coating include preventing dendrite growth of zinc ions during charge and discharge, inhibiting the occurrence of side reactions, and storing zinc ions. Although certain progress has been made in the research of negative electrode coatings, there are still some deficiencies. Some coatings have strong conductivity and cannot inhibit hydrogen evolution problems (Energy Environ. Sci. 2023, 16, 275); they are difficult to prepare, have a high cost, and limit their application prospects (Angew. Chem. Int. Ed. 2023: e202304444); they have poor stability and are prone to falling off during charge and discharge, affecting the cycle life of the battery (Nano Lett. 2022, 22, 3298). Therefore, it is necessary to further optimize the composition and structure of the coating material, explore new coating preparation methods, and establish a more perfect coating performance evaluation system to better improve the performance and sustainability of aqueous zinc-ion batteries. Summary of the Invention

[0004] Aiming at the technical problems of poor battery performance caused by corrosion and dendrites in the aqueous zinc-ion battery with metallic zinc as the negative electrode, the purpose of the present invention is to provide a preparation method of a metallic zinc negative electrode with a metal soap coating, which has a simple process flow and low cost. Another purpose of the present invention is the application of the metallic zinc negative electrode with a metal soap coating in the aqueous zinc-ion battery. The metallic zinc negative electrode with a metal soap coating is used in the aqueous zinc-ion battery, which can greatly improve the cycle life and stability of the aqueous zinc-ion battery.

[0005] To achieve the above purposes, the present invention adopts the following technical solutions: A preparation method of a metallic zinc negative electrode with a metal soap coating, comprising the following steps:

[0006] (1) Add a metal salt into water and stir evenly to obtain a metal salt solution;

[0007] (2) Add a normal fatty acid into an alkaline solution and stir evenly to obtain a mixed solution;

[0008] (3) Add the mixed solution obtained in step (2) into the metal salt solution obtained in step (1), carry out a saponification reaction under stirring, and wash and dry the reaction product to obtain a metal soap;

[0009] (4) Add the metal soap prepared in step (3) into ethanol to obtain an ethanol solution of the metal soap; Spray the ethanol solution of the metal soap on the surface of the pretreated zinc foil, and then carry out a calcination treatment to obtain a metallic zinc negative electrode with a metal soap coating.

[0010] Further, the thickness of the metal soap coating is 10 - 30 microns.

[0011] Further, in step (1), the cation of the metal salt is one or more of copper ions, calcium ions and zinc ions; the anion of the metal salt is one or more of nitrate, sulfate, chloride and bromide.

[0012] Further, in step (2), the number of carbon atoms of the normal fatty acid is 10 - 16.

[0013] Further, in step (3), the stirring time is 0.5 - 1 h.

[0014] Further, in step (4), the pretreatment is to polish the surface of the zinc foil with sandpaper, and then wash it with deionized water and ethanol.

[0015] Further, in step (4), the concentration of the ethanol solution of the metal soap is 0.2 - 1 g / mL.

[0016] Further, in step (4), the temperature of the calcination treatment is 100 - 150 °C, and the time is 0.5 - 1 h.

[0017] The metallic zinc negative electrode with a metal soap coating prepared by the above method.

[0018] Application of the above metallic zinc negative electrode with a metal soap coating in an aqueous zinc ion battery.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] (1) By adding a basic solution of a straight-chain fatty acid with 10 to 16 carbon atoms to a metal salt solution, a metal soap coating is modified on the surface of the metallic zinc negative electrode. The surface contact angle of the metal soap coating is large, which can inhibit the contact between the metallic zinc negative electrode and water in the electrolyte, making it more difficult for water molecules in the electrolyte to reach the zinc metal surface, thus realizing the shielding of water molecules; the metal soap coating has a zinc ion transport channel, and metal cations in the metal soap coating induce zinc ions in the electrolyte, further promoting the efficient transport of zinc ions, enabling zinc ions to be uniformly deposited on the surface of the negative electrode, effectively hindering the generation and growth of zinc dendrites, and avoiding the production of zinc dendrites caused by uneven deposition, which may lead to battery short circuit and affect the service life and stability of the battery;

[0021] (2) The method of spraying and calcination is used to modify the metal soap coating on the surface of the metallic zinc negative electrode. The preparation method is simple and the cost is low, which is conducive to promoting the large-scale production and application of zinc ion batteries. Description of the Drawings

[0022] Figure 1 Comparison diagram of the electrochemical stability performance of the Zn / Zn symmetric batteries of Example 1 and Comparative Example 1 at a current density of 20 mA cm -2 ;

[0023] Figure 2 Surface morphology diagram of the metallic zinc negative electrode with a metal soap coating of Example 1;

[0024] Figure 3 Contact angle measurement diagram of the metallic zinc negative electrode with a metal soap coating of Example 1;

[0025] Figure 4 Comparison diagram of the electrochemical stability performance of the Zn / Zn symmetric batteries of Example 1 and Comparative Example 1 at different current densities;

[0026] Figure 5 For the Zn / Na5V of Example 2 and Comparative Example 2 12 O 32 batteries at a current density of 20 mA cm -2 ;

[0027] Figure 6 For the Zn / Na5V of Example 2 and Comparative Example 212 O 32 Comparison diagram of the electrochemical stability performance of the battery at different current densities. Specific implementation mode

[0028] The present invention will be further described in detail below in conjunction with the embodiments and the accompanying drawings.

[0029] Example 1

[0030] The metal zinc negative electrode with a metal soap coating in this example was prepared by the following method:

[0031] (1) Add 2.41 g of copper nitrate to 10 mL of water and stir evenly at high speed to obtain a copper nitrate solution;

[0032] (2) Add 0.8 g of sodium hydroxide to water and disperse evenly to obtain 10 mL of a sodium hydroxide solution with a molar concentration of 2 mol / L; add 3.44 g of n-decanoic acid to the sodium hydroxide solution and stir evenly at high speed to obtain a mixed solution; among them, the molar ratio of n-decanoic acid to sodium hydroxide is 1:1;

[0033] (3) Add the copper nitrate solution obtained in step (1) to the mixed solution obtained in step (2), carry out a saponification reaction for 0.5 h under stirring at a speed of 1000 rpm, and wash and dry the reaction product to obtain metal soap CuC 10 ; among them, wash three times with water using a high-speed centrifuge;

[0034] (4) Polish the surface of a zinc foil with an area of 1 cm 2 , and then wash it with deionized water and ethanol to obtain a pretreated zinc foil; add 2 g of CuC 10 obtained in step (3) to ethanol to obtain a 4.0 mL ethanol solution with a concentration of 0.5 g / mL of CuC 10 , and spray the ethanol solution of CuC 10 on the surface of the pretreated zinc foil; place the zinc foil coated with the ethanol solution of CuC 10 in a muffle furnace and calcine it at 130 °C for 1 h to obtain a metal zinc negative electrode with a metal soap coating, and the thickness of the metal soap coating is 13 microns.

[0035] The Zn / Zn symmetric battery in this example was assembled by the following method: using a CR2032 button battery case, use the above two metal zincs with a metal soap coating and an area of 1 cm 2 as the positive and negative electrode plates of the symmetric battery respectively, use glass fiber GF / A as the separator, add 100 μL of 2 mol / L ZnSO4 solution to the battery, and assemble it into a Zn / Zn symmetric battery.

[0036] Example 2

[0037] The preparation method of the metallic zinc anode with a metal soap coating in this example is the same as that in Example 1.

[0038] The Zn / Na5V in this example 12 O 32 battery is assembled by the following method:

[0039] Using a CR2032 coin cell case, Na5V 12 O 32 : acetylene black: PVDF is dispersed evenly in N-methylpyrrolidone in a ratio of 7:2:1 to make a slurry, which is drop-coated on a stainless steel mesh disc with an area of 1 cm 2 and dried to be used as the positive electrode plate of the Na5V 12 O 32 battery (the average content of Na5V in a single electrode plate is about 0.5 mg / cm 12 O 32 ), using the above zinc sheet with a metal soap coating as the negative electrode plate of the zinc ion battery, and using 100 μL of 2 mol / L ZnSO4 solution as the electrolyte to assemble the Zn / Na5V 2 ) battery. 12 O 32 Example 3

[0040] The metallic zinc anode with a metal soap coating in this example is prepared by the following method:

[0041] (1) Add 2.41 g of copper nitrate to 10 mL of water and stir evenly at high speed to obtain a copper nitrate solution;

[0042] (2) Add 0.8 g of sodium hydroxide to water and disperse evenly to obtain 10 mL of sodium hydroxide solution with a molar concentration of 2 mol / L; add 5.13 g of palmitic acid to the sodium hydroxide solution and stir evenly at high speed to obtain a mixed solution; among them, the molar ratio of palmitic acid to sodium hydroxide is 1:1;

[0043] (3) Add the copper nitrate solution obtained in step (1) to the mixed solution obtained in step (2), carry out a saponification reaction for 0.5 h under stirring at a rotation speed of 1000 rpm, and wash and dry the reaction product to obtain metal soap CuC

[0044] ; among them, wash three times with water using a high-speed centrifuge; 16 ;

[0045] (4) Polish the surface of a zinc foil with an area of 1 cm 2 with sandpaper, and then wash it with deionized water and ethanol to obtain a pretreated zinc foil; add 2 g of CuC obtained in step (3) to the zinc foil 16Add ethanol to obtain 4.0 mL of a CuC ethanol solution with a concentration of 0.5 g / mL. 16 The ethanol solution of CuC 16 is sprayed onto the surface of the pretreated zinc foil; the zinc foil coated with the ethanol solution of CuC 16 is placed in a muffle furnace and calcined at 130 °C for 1 h to obtain a metal zinc negative electrode with a metal soap coating, and the thickness of the metal soap coating is 13 micrometers.

[0046] The preparation method of the Zn / Zn symmetric battery in this example is the same as that of the Zn / Zn symmetric battery in Example 1.

[0047] Comparative Example 1

[0048] The preparation method of the Zn / Zn symmetric battery in this comparative example is the same as that of the Zn / Zn symmetric battery in Example 1, except that the negative electrode sheet uses a zinc foil without a metal soap coating.

[0049] Comparative Example 2

[0050] The preparation method of the Zn / Na5V 12 O 32 battery in this comparative example is the same as that of the Zn / Na5V 12 O 32 battery in Example 2, except that the negative electrode sheet uses a zinc foil without a metal soap coating.

[0051] Comparative Example 3

[0052] The metal zinc negative electrode with a metal soap coating in this comparative example is prepared by the following method:

[0053] (1) Add 2.41 g of copper nitrate to 10 mL of water and stir evenly at high speed to obtain a copper nitrate solution;

[0054] (2) Add 0.8 g of sodium hydroxide to water and disperse evenly to obtain 10 mL of a sodium hydroxide solution with a molar concentration of 2 mol / L; add 2.04 g of n-valeric acid to the sodium hydroxide solution and stir evenly at high speed to obtain a mixture; among them, the molar ratio of n-valeric acid to sodium hydroxide is 1:1;

[0055] (3) Add the copper nitrate solution obtained in step (1) to the mixture obtained in step (2), carry out a saponification reaction for 0.5 h under stirring at a rotation speed of 1000 rpm, and wash and dry the reaction product to obtain metal soap CuC5; among them, the washing is carried out three times with water using a high-speed centrifuge;

[0056] (4) The area is 1 cm 2The surface of the zinc foil was polished with sandpaper and then washed with deionized water and ethanol to obtain the pretreated zinc foil; 2 g of CuC5 obtained in step (3) was added to ethanol to obtain a 4 mL ethanol solution of CuC5 with a concentration of 0.5 g / mL, and the ethanol solution of CuC5 was sprayed on the surface of the pretreated zinc foil; the zinc foil coated with the ethanol solution of CuC5 was placed in a muffle furnace and calcined at 130 °C for 1 h to obtain a metal zinc negative electrode with a metal soap coating, and the thickness of the metal soap coating was 13 microns.

[0057] The assembly method of the Zn / Zn symmetric battery in this comparative example was the same as that of the Zn / Zn symmetric battery in Example 1.

[0058] Comparative Example 4

[0059] The metal zinc negative electrode with a metal soap coating in this comparative example was prepared by the following method:

[0060] (1) 2.41 g of copper nitrate was added to 10 mL of water and stirred evenly at high speed to obtain a copper nitrate solution;

[0061] (2) 0.8 g of sodium hydroxide was added to water and evenly dispersed to obtain a 10 mL sodium hydroxide solution with a molar concentration of 2 mol / L; 2.88 g of n-octanoic acid was added to the sodium hydroxide solution and stirred evenly at high speed to obtain a mixed solution; among them, the molar ratio of n-octanoic acid to sodium hydroxide was 1:1;

[0062] (3) The copper nitrate solution obtained in step (1) was added to the mixed solution obtained in step (2), and saponification reaction was carried out under stirring at a rotation speed of 1000 rpm for 0.5 h, and the reaction product was washed and dried to obtain metal soap CuC8; among them, washing was carried out three times with water using a high-speed centrifuge;

[0063] (4) The zinc foil with an area of 1 cm 2 The surface of the zinc foil was polished with sandpaper and then washed with deionized water and ethanol to obtain the pretreated zinc foil; 2 g of CuC8 obtained in step (3) was added to ethanol to obtain a 4 mL ethanol solution of CuC8 with a concentration of 0.5 g / mL, and the ethanol solution of CuC8 was sprayed on the surface of the pretreated zinc foil; the zinc foil coated with the ethanol solution of CuC8 was placed in a muffle furnace and calcined at 130 °C for 1 h to obtain a metal zinc negative electrode with a metal soap coating, and the thickness of the metal soap coating was 10 - 30 microns.

[0064] The assembly method of the Zn / Zn symmetric battery in this comparative example was the same as that of the Zn / Zn symmetric battery in Example 1.

[0065] Comparative Example 5

[0066] The metal zinc negative electrode with a metal soap coating in this comparative example was prepared by the following method:

[0067] (1) 2.41 g of copper nitrate was added to 10 mL of water and stirred evenly at high speed to obtain a copper nitrate solution;

[0068] (2) 0.8 g of sodium hydroxide was added to water and evenly dispersed to obtain 10 mL of a sodium hydroxide solution with a molar concentration of 2 mol / L; 6.8 g of docosanoic acid was added to the sodium hydroxide solution and stirred evenly at high speed to obtain a mixed solution; among them, the molar ratio of docosanoic acid to sodium hydroxide was 1:1;

[0069] (3) The copper nitrate solution obtained in step (1) was added to the mixed solution obtained in step (2), and a saponification reaction was carried out under stirring at a rotation speed of 1000 rpm for 0.5 h. The reaction product was washed and dried to obtain metal soap CuC 22 ; among them, the washing was carried out three times with water using a high-speed centrifuge;

[0070] (4) The surface of a zinc foil with an area of 1 cm 2 was polished with sandpaper, and then washed with deionized water and ethanol to obtain a pretreated zinc foil; 2 g of CuC 22 obtained in step (3) was added to ethanol to obtain a 4 mL ethanol solution with a concentration of 0.5 g / mL of CuC 22 . The ethanol solution of CuC 22 was sprayed on the surface of the pretreated zinc foil; the zinc foil coated with the ethanol solution of CuC 22 was placed in a muffle furnace and calcined at 130 °C for 1 h to prepare a metal zinc negative electrode with a metal soap coating, and the thickness of the metal soap coating was 13 microns.

[0071] The assembly method of the Zn / Zn symmetric battery in this comparative example was the same as that of the Zn / Zn symmetric battery in Example 1.

[0072] The electrochemical performance of the batteries in Examples 1 to 3 and Comparative Examples 1 to 5 was tested. The specific test method was as follows: Using a Neware battery test system, the assembled button battery was tested. The symmetric battery was tested under a current density of 20 mA cm -2 , and the full battery was tested under the condition of 2 A g -1 .

[0073] As Figure 1 shown, the comparison results of the electrochemical stability performance of the Zn / Zn symmetric batteries in Example 1 and Comparative Example 1 at a current density of 20 mA cm -2 showed that the cycle life of the Zn / Zn symmetric battery in Comparative Example 1 was only 250 cycles, and the cycle performance of the Zn / Zn symmetric battery in Example 1 was improved by more than 8 times, indicating that in Example 1, due to the use of metal soap CuC 10The metallic zinc anode of the membrane shields the entry of water molecules to the anode surface, inhibits the hydrogen evolution reaction, and at the same time induces the uniform deposition of zinc ions, successfully slowing down the growth of zinc dendrites and increasing the service life of the battery.

[0074] As Figure 2 shown, the surface morphology diagram of the metallic zinc anode with a metal soap coating in Example 1, and the prepared metal soap coating has a uniform morphology.

[0075] As Figure 3 shown, the contact angle of the metallic zinc anode with a metal soap coating in Example 1 is 135.5°, which can greatly inhibit the contact between the anode sheet and water in the aqueous electrolyte, making it more difficult for water molecules in the electrolyte to reach the zinc metal surface, inhibiting the hydrogen evolution reaction, and ensuring the uniform deposition of zinc ions.

[0076] Table 1 shows the battery performance results of the Zn / Zn symmetric batteries in Example 1, Example 3, and Comparative Example 1, Comparative Example 3 - 5 at a current density of 20 mA cm -2 . The number of carbon atoms in the n - fatty acid is different, the overpotential is different, and the number of cycling laps is also different. It can be seen that the present invention realizes the shielding and induction of water molecules and zinc ions by precisely controlling the structure of the metal soap coating. When the number of carbon atoms is less than 10, the metal soap coating channels are too large to shield water molecules; when the number of carbon atoms is greater than 16, the metal soap coating channels are too small, shielding not only water molecules but also zinc ions. It can be found that only when the number of carbon atoms is between 10 and 16, the metal soap coating can shield water molecules and induce zinc ions.

[0077] Table 1 Battery performance results of Zn / Zn symmetric batteries at a current density of 20 mA cm -2

[0078]

[0079]

[0080] As Figure 4 shown, from the change of the current density from 0.5 to 20 mA cm -2 , and then from 20 to 0.5 mA cm -2 , it is found that Example 1 has a smaller overpotential and remains stable during the entire rate change process; while Comparative Example 1 has a larger overpotential and cannot remain stable when the current density is 10 mA cm -2 for the second time. It can be seen that Example 1 has a smaller overpotential and good cycle stability, demonstrating the excellent performance of the metal soap coating.

[0081] As Figure 5 shown, in the full cell of 2Ag -1 ​At the current density, compared with Comparative Example 2, Example 2 has a higher capacity retention rate and a longer service life, maintaining a capacity of up to 93.3% and a stable Coulombic efficiency close to 100% during 2000 cycles. Comparative Example 2 showed rapid capacity degradation after about 500 cycles, with a capacity retention rate of less than 20%. It can be seen that the high capacity retention rate of Example 2 can indicate the excellent performance of the metal soap coating.

[0082] As Figure 6 shown, when the current density is reduced to 0.1 A g -1 ⁻¹, Example 2 maintains a high specific capacity of 187.7 mA h g -1 ⁻¹, with a retention rate of 98%, while the electrochemical capacity of Comparative Example 2 rapidly decays to 147 mA h g -1 ⁻¹ at 0.1 A g -1 ⁻¹, and the capacity retention rate is only 80%. The batteries of Example 2 exhibit higher discharge capacities at different current densities, further demonstrating the practicability of the metal soap-coated CuC 10 .

[0083] By introducing a metal soap coating into the negative electrode of a zinc-ion battery, the present invention can, to a certain extent, shield water molecules, induce uniform deposition of zinc ions, and improve the battery cycling ability. At the same time, this method can also effectively hinder the formation and growth of zinc dendrites. Non-uniform deposition will lead to the formation of zinc dendrites and short circuits. Using it in zinc-ion batteries can significantly improve their cycle life and stability.

[0084] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and it should not be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a metallic zinc negative electrode with a metal soap coating, characterized in that, It includes the following steps: (1) Add metal salt into water and stir evenly to obtain a metal salt solution; (2) Add n-fatty acid into an alkaline solution and stir evenly to obtain a mixture; (3) Add the mixture obtained in step (2) into the metal salt solution obtained in step (1), carry out a saponification reaction under stirring, and wash and dry the reaction product to obtain metal soap; (4) Add the metal soap prepared in step (3) into ethanol to obtain an ethanol solution of the metal soap; spray the ethanol solution of the metal soap on the surface of the pretreated zinc foil, and then carry out a calcination treatment to obtain a metal zinc negative electrode with a metal soap coating; The thickness of the metal soap coating is 10 to 30 microns; In step (2), the n-fatty acid has 10 to 16 carbon atoms.

2. The preparation method according to claim 1, characterized in that, In step (1), the cation of the metal salt is one or more of copper ions, calcium ions and zinc ions; the anion of the metal salt is one or more of nitrate, sulfate, chloride and bromide.

3. The preparation method according to claim 1, characterized in that, In step (3), the stirring time is 0.5 to 1 h.

4. The preparation method according to claim 1, wherein, In step (4), the pretreatment is to polish the surface of the zinc foil with sandpaper, and then wash it with deionized water and ethanol.

5. The preparation method according to claim 1, characterized in that, In step (4), the concentration of the ethanol solution of the metal soap is 0.2 to 1 g / mL.

6. The preparation method according to claim 1, characterized in that In step (4), the temperature of the calcination treatment is 100 to 150 °C, and the time is 0.5 to 1 h.

7. A metal zinc negative electrode with a metal soap coating prepared by the method according to any one of claims 1 to 6.

8. Application of the metal zinc negative electrode with a metal soap coating according to claim 7 in an aqueous zinc ion battery.

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