Two-dimensional double-hydroxide zinc negative electrode and preparation method and application thereof

Abstract

This invention discloses a two-dimensional double hydroxide zinc anode, its preparation method, and its application, comprising the following steps: A. Mixing soluble zinc salt and soluble tin salt and adding them to a sodium carbonate solution, adjusting the pH to alkaline, and allowing it to settle and precipitate; B. Filtering to separate the precipitate, washing the precipitate, and drying it to obtain metal hydroxide powder; C. Mixing the metal hydroxide powder and a binder in a solvent, stirring until uniformly dispersed to obtain a coating solution; D. Spin-coating the coating solution onto the surface of a zinc foil, drying, and cutting to obtain the final product. The two-dimensional double hydroxide coating of this invention has a large surface area, providing more active sites for zinc ion deposition and reducing Zn... 2+ The accumulation of these substances inhibits the continuous growth of zinc ions at the dendrite tips. Simultaneously, the two-dimensional double hydroxide coating, with its large surface area, increases the surface wettability of the electrolyte, reduces the interfacial resistance of the zinc anode, and improves reaction kinetics, ultimately resulting in excellent electrochemical performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of zinc-ion battery technology, and in particular to a two-dimensional double hydroxide zinc anode, its preparation method, and its application. Background Technology

[0002] Aqueous zinc-ion batteries, employing mild aqueous electrolytes, have garnered widespread attention due to their high safety, low cost, and environmental friendliness. Aqueous zinc-ion batteries offer the following advantages: (1) inherent safety due to the use of non-flammable aqueous electrolytes; (2) low cost due to the inexpensive availability of zinc and aqueous electrolytes, and simple manufacturing process; (3) environmental friendliness, containing no harmful organic components or Co / Ni elements; (4) suitable redox potentials for both positive and negative electrodes; and (5) acceptable energy density due to the high theoretical specific capacity of zinc metal (approximately 820 mAh·g⁻¹). -1 and 5851mAh·cm -3 (6) Due to the high ionic conductivity of aqueous electrolytes and the relatively fast Zn content in active materials 2+ Ion transport kinetics lead to high power density. However, during the cycling process of aqueous zinc-ion batteries, the zinc anode also suffers from severe problems such as dendrite formation, irreversible byproducts, hydrogen evolution, and zinc metal corrosion, ultimately resulting in low coulombic efficiency and poor cycle performance. Simultaneously, the zinc foil surface inevitably contains many native protrusions. Due to the uneven electric field distribution, these protrusions promote severe dendrite growth, which can puncture the separator and cause short circuits. Furthermore, dendrite formation is accompanied by side reactions, leading to Zn anode passivation and battery swelling, ultimately causing battery failure.

[0003] To suppress dendrite growth on the surface of zinc anodes, researchers often improve battery performance by protecting the zinc anode. Currently reported methods for zinc anode protection include electrolyte optimization, separator modification, and anode structure design. Among these, surface modification, as a simple, low-cost, and environmentally friendly strategy, is particularly suitable for preventing dendrite growth and side reactions. Chinese patent CN111933912A discloses a zinc anode with a zinc ion conductivity interface modification layer, which forms a zinc ion conductivity interface modification layer (Zn) on the surface of the metallic zinc anode through a spontaneous reaction. x M, Zn x The M-interface modification layer is used to protect the zinc anode to effectively suppress the growth of zinc dendrites. M is a layered structure material with a large interlayer spacing, including one or more of the following materials: vanadium-based materials and their hydrates, manganese-based materials, layered bimetallic hydroxides and their hydrates, Chevrel phase compounds, Prussian blue compounds, and MXene-type materials. The general chemical formula of layered bimetallic hydroxides and their hydrates is [M]. z+ 1-x M3+ x (OH)2] b+ [A n- b / n ]·mH₂O, where M represents a metallic element, M = Ca, Mg, Mn, Fe, Co, Ni, Cu, Zn, Li or / and Al, and A represents an interlayer anion, A = Cl - ,Br - NO 3- CO3 2- SO4 2- and / or SeO4 2- b = x or 2x - 1, z = 2 or 1, 0.2 ≤ x ≤ 1, 0.5 ≤ m ≤ 4. The interface modification layer in this patent possesses zinc ion conductivity, thus improving zinc ion transport at the zinc anode interface, promoting uniform ion deposition, effectively suppressing zinc dendrite growth, and increasing battery cycle life by tens of times. However, aqueous zinc-ion batteries assembled with interface-modified anode materials exhibit low cycle stability at high current densities. Summary of the Invention

[0004] The objective of this invention is to address the aforementioned problems by providing a two-dimensional double hydroxide zinc anode, its preparation method, and its applications. This invention employs a spin-coating method to synthesize a two-dimensional double hydroxide coating on the surface of a zinc anode. The two-dimensional structure of the coating increases the surface area, which not only increases the surface wettability of the electrolyte but also reduces the interfacial resistance of the zinc anode, thus improving reaction kinetics. Furthermore, the double hydroxide containing abundant metal sites can increase the active sites for zinc ion deposition, providing uniform Zn... 2+ Flux, avoid Zn 2+ The accumulation of these elements can inhibit dendrite growth and help zinc ions to be uniformly deposited on the surface of the zinc anode, giving aqueous zinc-ion batteries excellent electrochemical performance.

[0005] The technical solution adopted in this invention is as follows: A method for preparing a two-dimensional zinc double hydroxide anode, characterized by comprising the following steps:

[0006] A. Mix soluble zinc salt and soluble tin salt and add them to sodium carbonate solution, adjust the pH to alkaline, and let it stand to precipitate;

[0007] B. Filter and separate the precipitate, wash the precipitate and dry it to obtain metal hydroxide powder;

[0008] C. Mix the metal hydroxide powder and binder in a solvent and stir until evenly dispersed to obtain a coating solution;

[0009] D. Spin-coat the zinc foil surface with the coating solution, dry and cut it in an oven at 70°C.

[0010] Furthermore, the soluble zinc salt is selected from one or more of zinc chloride, zinc chloride hydrate, zinc acetate, zinc acetate hydrate, zinc nitrate, zinc nitrate hydrate, zinc sulfate, and zinc sulfate hydrate.

[0011] Furthermore, the soluble tin salt is selected from one or more of tin chloride, tin chloride hydrate, tin acetate, tin acetate hydrate, tin nitrate, tin nitrate hydrate, tin sulfate, and tin sulfate hydrate. The introduction of tin raises the hydrogen evolution barrier, suppresses hydrogen evolution side reactions, lowers the zinc nucleation barrier, and facilitates zinc ion deposition.

[0012] Furthermore, the mass ratio of soluble zinc salt to soluble tin salt is 4-6:4-6, for example, it can be 4:6, 5:5, 6:4, etc. The amount of tin salt added should not be too much or too little, as too much or too little will produce unnecessary impurities and reduce the content of pure double hydroxide.

[0013] Furthermore, in step A, the pH value is adjusted to 8-11.

[0014] Furthermore, the binder is selected from polyvinylidene fluoride and polyvinylidene fluoride-hexafluoropropylene, and the mass ratio of metal hydroxide powder to binder is 1-4:6-9, with the specific ratio selected according to the actual situation.

[0015] Further, in step D, a spin coater is used for coating. The working speed of the spin coater is 200-800 r / min (the speed should not be too low or too high. When the speed is lower than 200 r / min, the coating liquid will solidify due to the slow speed, resulting in it not being able to disperse on the zinc foil surface. When the speed is higher than 800 r / min, the coating liquid will be thrown onto the inner surface of the spin coater due to the fast speed, resulting in a very thin coating film). The rotation time is 10-30 seconds.

[0016] Furthermore, in step D, the coating thickness is 30-100 μm. The coating thickness should not be too small or too large. If the coating is too thin, it will not provide good protection and will be easily damaged by dendrites. If the coating is too thick, it will increase the transport distance of zinc ions, which is not conducive to the rapid transport of zinc ions and reduces the electrochemical performance of the battery.

[0017] Furthermore, the negative electrode sheet can be circular, rectangular, or square in shape, and its area can be 1 mm². 2 -0.5m 2 .

[0018] Furthermore, the present invention also includes a two-dimensional zinc double hydroxide anode, which is prepared by the above preparation method.

[0019] Furthermore, the present invention also includes the application of a two-dimensional double hydroxide zinc anode in an aqueous zinc-ion battery, wherein the anode of the aqueous zinc-ion battery is the aforementioned two-dimensional double hydroxide zinc anode.

[0020] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: the two-dimensional double hydroxide coating of the present invention has a large surface area, which can provide more active sites for zinc ion deposition and reduce Zn 2+ The accumulation of these substances inhibits the continuous growth of zinc ions at the dendrite tips. Simultaneously, the two-dimensional double hydroxide coating, with its large surface area, increases the surface wettability of the electrolyte, reduces the interfacial resistance of the zinc anode, and improves reaction kinetics, ultimately resulting in excellent electrochemical performance of the battery. Attached Figure Description

[0021] Figure 1 This is a photograph of the zinc electrode with a two-dimensional double hydroxide coating prepared in Example 1 of the present invention;

[0022] Figure 2 This is a SEM image of the two-dimensional double hydroxide powder prepared in Example 1 of this invention;

[0023] Figure 3 This is a graph showing the cycle performance of the zinc anode with a two-dimensional double hydroxide coating prepared in Example 1 of the present invention. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings.

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0026] A two-dimensional zinc double hydroxide anode is prepared by the following steps:

[0027] S1. Prepare the reaction solution by mixing zinc salt and tin salt in a certain mass ratio and adding them to a sodium carbonate solution of a certain concentration. Adjust the pH to alkaline. ZnCl2 is preferred for zinc salt and SnCl4·5H2O is preferred for tin salt. The mass ratio of zinc salt to tin salt is 4-6:4-6. The concentration of sodium carbonate solution can be 2 mmol / L (or other concentrations). Adjust the pH value to the range of 8-11 with NaOH solution. The concentration of NaOH solution can be 1 mol / L. Then let it stand to precipitate.

[0028] S2. Filter and collect the precipitate, then centrifuge with water or alcohol at a speed of 500-1800 r / min for 2-10 min. The precipitate should be washed more than 5 times.

[0029] S3. Prepare the coating solution by mixing the precipitate and binder in a solvent (e.g., NMP) at a certain mass ratio and stirring at a certain temperature (e.g., 10-100℃) until fully dispersed; wherein the binder is selected from polyvinylidene fluoride or polyvinylidene fluoride-hexafluoropropylene, the mass ratio of precipitate to binder is 1-40:6-9, and the stirring time is between 24-72h;

[0030] S4. Use a spin coater to evenly coat the solution from step S3 onto the surface of zinc foil, and place it in a drying oven to dry. The spin coater speed is 200-800 r / min, the rotation time is 10-30 s, the thickness of the spin-coated film is 50 μm-100 μm, and the drying time needs to be more than 24 hours.

[0031] S5. Prepare the negative electrode for the aqueous zinc-ion battery. Cut the zinc foil with the double hydroxide coating obtained in step S4 into negative electrode sheets to obtain the zinc negative electrode. The shape and size of the negative electrode sheet can be any shape and size according to the needs of the battery. It is preferred that the shape of the electrode sheet is circular, rectangular or square, and the preferred area of ​​the electrode sheet is 1 mm². 2 -0.5m 2 This invention utilizes zinc foil coated with a two-dimensional double hydroxide coating to prepare a zinc anode for an aqueous zinc-ion battery. Other metal foils coated with a two-dimensional double hydroxide coating can also be used to prepare other aqueous ion battery anodes.

[0032] The two-dimensional zinc double hydroxide anode coating prepared by this invention has a large specific surface area (e.g., Figure 2 As shown, the sheet-like microstructure reveals a large specific surface area, providing more active sites for zinc ion deposition and reducing Zn content. 2+ The accumulation of zinc ions inhibits the continuous growth of zinc ions at the dendrite tips.

[0033] To better explain the present invention, the following detailed description is provided through some embodiments.

[0034] Example 1

[0035] A method for preparing an aqueous zinc-ion battery includes the following steps:

[0036] S1. Take 2g of ZnCl2 powder and 3g of SnCl4·5H2O, and dissolve them in 20mL of deionized water to obtain solution 1;

[0037] S2. Prepare 50 mL of 2 mM Na2CO3 solution and add it to solution 1 and stir well. Then add NaOH to the solution until the pH value of the solution reaches 9, stir well, and let it stand for 24 hours.

[0038] S3. Filter the precipitate, add the precipitate to water or alcohol, and then put it into a centrifuge. Set the speed to 1800 r / min and the centrifugation time to 5 min. Repeat the process 6 times. Place the final precipitate in a 70℃ drying oven and dry it for 24 h.

[0039] S4. Place the dried powder into a mortar and grind it evenly. Take 1.5g of powder and 0.5g of PVDF and dissolve them in NMP solvent. Stir at 25℃ for 24h to obtain a uniform spin-coating liquid.

[0040] S5. Set the spin coater speed to 500 r / min, the spin coating time to 20 s, the spin coating substrate to zinc foil, slowly drip the spin coating liquid until the spin coating is finished, and obtain zinc foil covered with a two-dimensional double hydroxide coating. Place it in a 70℃ drying oven to dry for 24 h.

[0041] S6. Cut the two-dimensional double hydroxide coated zinc foil into negative electrode sheets with a diameter of 14mm, such as... Figure 1 As shown, a symmetrical battery (two-dimensional double hydroxide coated zinc foil || zinc sulfate electrolyte || two-dimensional double hydroxide coated zinc foil) was assembled by matching the diameter of the glass fiber diaphragm (19 mm) and the aqueous electrolyte (preferably zinc sulfate with a concentration of 2 M). The control sample consisted of two pure zinc foils without the two-dimensional double hydroxide coating assembled into a symmetrical battery.

[0042] The electrochemical performance of the battery assembled in Example 1 was tested at a charge-discharge rate of 1 mA·cm. -2 The current density and charge / discharge capacity are 1 mAh·cm⁻¹. -2 Under the test conditions, such as Figure 2 As shown, the symmetrical battery assembled with the two-dimensional double hydroxide coated zinc foil negative electrode prepared in Example 1 maintained a polarization voltage of 30 mV after 800 h of cycling, while the symmetrical battery assembled with the zinc foil negative electrode without the two-dimensional double hydroxide coating had a polarization voltage of about 50 mV at the beginning of cycling and poor cycle stability (this symmetrical battery could only cycle for 80 h). This indicates that the two-dimensional double hydroxide coating is beneficial to the uniform deposition of zinc ions and the suppression of dendrite growth, thereby increasing the cycle life of the battery and improving the electrochemical performance of the aqueous zinc-ion battery.

[0043] Example 2

[0044] A method for preparing an aqueous zinc-ion battery includes the following steps:

[0045] S1. Take 1.8g of ZnCl2 powder and 2.3g of SnCl4·5H2O, and dissolve them in 20mL of deionized water to obtain solution 1;

[0046] S2. Prepare 50 mL of 2 mM Na2CO3 solution and add it to solution 1 and stir well. Then add NaOH to the solution until the pH value of the solution reaches 9, stir well, and let it stand for 24 hours.

[0047] S3. Filter the precipitate, add the precipitate to water or alcohol, and then put it into a centrifuge. Set the speed to 1800 r / min and the centrifugation time to 5 min. Repeat the process 6 times. Place the final precipitate in a 70℃ drying oven and dry it for 24 h.

[0048] S4. Place the dried powder into a mortar and grind it evenly. Take 1.5g of powder and 0.5g of PVDF and dissolve them in NMP solvent. Stir at 25℃ for 24h to obtain a uniform spin-coating liquid.

[0049] S5. Set the spin coater speed to 500 r / min, the spin coating time to 20 s, the spin coating substrate to zinc foil, slowly drip the spin coating liquid until the spin coating is finished, and obtain zinc foil covered with a two-dimensional double hydroxide coating. Place it in a 70℃ drying oven to dry for 24 h.

[0050] S6. Cut the two-dimensional double hydroxide coated zinc foil into a negative electrode sheet with a diameter of 14 mm, match it with a glass fiber diaphragm with a diameter of 19 mm and an aqueous electrolyte (preferably zinc sulfate with a concentration of 2 M), and assemble a symmetrical battery (two-dimensional double hydroxide coated zinc foil || zinc sulfate electrolyte || two-dimensional double hydroxide coated zinc foil); the control sample is two pieces of pure zinc foil without two-dimensional double hydroxide coating assembled into a symmetrical battery.

[0051] The electrochemical performance of the battery assembled in Example 2 was tested at a charge-discharge rate of 1 mA·cm. -2 The current density and charge / discharge capacity are 1 mAh·cm⁻¹. -2 Under the test conditions, the symmetrical battery assembled with the two-dimensional double hydroxide coated zinc foil negative electrode prepared in Example 2 maintained a polarization voltage of 25 mV after 1200 h of cycling, while the symmetrical battery assembled with the zinc foil negative electrode without the two-dimensional double hydroxide coating had a polarization voltage of about 50 mV at the beginning of cycling and poor cycle stability. This indicates that the two-dimensional double hydroxide coating is beneficial to the uniform deposition of zinc ions and the suppression of dendrite growth, thereby increasing the cycle life of the battery and improving the electrochemical performance of aqueous zinc-ion batteries.

[0052] Example 3

[0053] A method for preparing an aqueous zinc-ion battery includes the following steps:

[0054] S1. Take 3g of ZnCl2 powder and 2g of SnCl4·5H2O, and dissolve them in 20mL of deionized water to obtain solution 1;

[0055] S2. Prepare 50 mL of 2 mM Na2CO3 solution and add it to solution 1 and stir well. Then add NaOH to the solution until the pH value of the solution reaches 9, stir well, and let it stand for 24 hours.

[0056] S3. Filter the precipitate, add the precipitate to water or alcohol, and then put it into a centrifuge. Set the speed to 1800 r / min and the centrifugation time to 5 min. Repeat the process 6 times. Place the final precipitate in a 70℃ drying oven and dry it for 24 h.

[0057] S4. Place the dried powder into a mortar and grind it evenly. Take 1.5g of powder and 0.5g of PVDF and dissolve them in NMP solvent. Stir at 25℃ for 24h to obtain a uniform spin-coating liquid.

[0058] S5. Set the spin coater speed to 500 r / min, the spin coating time to 20 s, the spin coating substrate to zinc foil, slowly drip the spin coating liquid until the spin coating is finished, and obtain zinc foil covered with a two-dimensional double hydroxide coating. Place it in a 70℃ drying oven to dry for 24 h.

[0059] S6. Cut the two-dimensional double hydroxide coated zinc foil into a negative electrode sheet with a diameter of 14 mm, match it with a glass fiber diaphragm with a diameter of 19 mm and an aqueous electrolyte (preferably zinc sulfate with a concentration of 2 M), and assemble a symmetrical battery (two-dimensional double hydroxide coated zinc foil || zinc sulfate electrolyte || two-dimensional double hydroxide coated zinc foil); the control sample is two pieces of pure zinc foil without two-dimensional double hydroxide coating assembled into a symmetrical battery.

[0060] The electrochemical performance of the battery assembled in Example 3 was tested at a charge-discharge rate of 1 mA·cm. -2 The current density and charge / discharge capacity are 1 mAh·cm⁻¹. -2 Under the test conditions, the symmetric battery assembled with the two-dimensional double hydroxide coated zinc foil anode prepared in Example 3 maintained a polarization voltage of 40 mV after 600 h of cycling, while the symmetric battery assembled with the zinc foil anode without the two-dimensional double hydroxide coating had a polarization voltage of about 50 mV at the beginning of cycling and poor cycle stability. This indicates that the two-dimensional double hydroxide coating is beneficial to the uniform deposition of zinc ions and the suppression of dendrite growth, thereby increasing the cycle life of the battery and improving the electrochemical performance of aqueous zinc-ion batteries.

[0061] Comparative Example 1

[0062] Comparative Example 1 is the same as Example 1, except that the zinc salts are replaced with equimolar amounts of MgCl2, MnCl2, NiCl2, and FeCl3, respectively.

[0063] The test results are as follows: at a charge / discharge rate of 1 mA·cm -2 The current density and charge / discharge capacity are 1 mAh·cm⁻¹. -2 Under the test conditions, the symmetrical battery assembled with its negative electrode was damaged within 500 hours of cycling, and the polarization voltage reached 60mV, indicating poor cycle stability.

[0064] Comparative Example 2

[0065] Comparative Example 2 is the same as Example 1, except that the amount of SnCl4·5H2O added is doubled to 6g.

[0066] The test results are as follows: at a charge / discharge rate of 1 mA·cm -2 The current density and charge / discharge capacity are 1 mAh·cm⁻¹. -2 Under the test conditions, the symmetrical battery assembled with its negative electrode was damaged after 1200 hours of cycling. Although the cycle time was significantly improved, the stability was still not optimal.

[0067] Comparative Example 3

[0068] Comparative Example 3 is the same as Example 1, except that equal molar amounts of Zn(OH)2 powder and Sn(OH)4 powder are taken, the powders are mixed, 1.5g of the mixed powder and 0.5g of PVDF are dissolved in NMP solvent, and stirred at 25°C for 24h to obtain a uniform spin-coating liquid. The subsequent steps are the same as in Example 1.

[0069] The test results are as follows: at a charge / discharge rate of 1 mA·cm -2 The current density and charge / discharge capacity are 1 mAh·cm⁻¹. -2 Under the test conditions, the symmetrical battery assembled with its negative electrode was damaged after 200 hours of cycling, and the polarization voltage reached 80mV, which has a large polarization voltage and poor cycle stability.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a two-dimensional zinc double hydroxide anode, characterized in that, Includes the following steps: A. Mix soluble zinc salt and soluble tin salt and add them to sodium carbonate solution, adjust the pH to alkaline, and let it stand to precipitate; B. Filter and separate the precipitate, wash the precipitate and dry it to obtain metal hydroxide powder; C. Mix the metal hydroxide powder and binder in a solvent and stir until evenly dispersed to obtain a coating solution; D. Spin-coat the zinc foil surface with the coating solution, dry and cut to obtain the final product.

2. The method for preparing the two-dimensional zinc double hydroxide anode as described in claim 1, characterized in that, The soluble zinc salt is selected from one or more of zinc chloride, zinc chloride hydrate, zinc acetate, zinc acetate hydrate, zinc nitrate, zinc nitrate hydrate, zinc sulfate, and zinc sulfate hydrate.

3. The method for preparing the two-dimensional zinc double hydroxide anode as described in claim 1, characterized in that, The soluble tin salt is selected from one or more of tin chloride, tin chloride hydrate, tin acetate, tin acetate hydrate, tin nitrate, tin nitrate hydrate, tin sulfate, and tin sulfate hydrate.

4. The method for preparing the two-dimensional zinc double hydroxide anode as described in any one of claims 1-3, characterized in that, The mass ratio of soluble zinc salt to soluble tin salt is 4-6:4-6.

5. The method for preparing the two-dimensional zinc double hydroxide anode as described in claim 4, characterized in that, In step A, the pH value is adjusted to 8-11.

6. The method for preparing the two-dimensional zinc double hydroxide anode as described in claim 5, characterized in that, The binder is selected from polyvinylidene fluoride and polyvinylidene fluoride-hexafluoropropylene, and the mass ratio of metal hydroxide powder to binder is 1-4:6-9.

7. The method for preparing the two-dimensional double hydroxide zinc anode as described in claim 6, characterized in that, In step D, a spin coater is used for coating. The spin coater operates at a speed of 200-800 r / min and a rotation time of 10-30 s.

8. The method for preparing the two-dimensional zinc double hydroxide anode as described in claim 7, characterized in that, In step D, the coating thickness is 30-100 μm.

9. A two-dimensional zinc double hydroxide negative electrode, characterized in that, It is prepared by any one of the preparation methods described in claims 1-8.

10. The application of a two-dimensional double hydroxide zinc anode in an aqueous zinc-ion battery, characterized in that, The negative electrode of the aqueous zinc-ion battery is the two-dimensional double hydroxide zinc negative electrode as described in claim 9.

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