Negative electrode-free sodium-ion battery current collector, preparation method and application thereof, and negative electrode-free sodium-ion battery

Abstract

The application provides a negative-electrode-free sodium-ion battery current collector and a preparation method and application thereof, and a negative-electrode-free sodium-ion battery, and relates to the technical field of batteries.The negative-electrode-free sodium-ion battery current collector comprises an aluminum foil, a porous NaF layer and a polymer layer; the porous NaF layer is arranged on the surface of the aluminum foil, and the polymer layer is arranged on the surface of the porous NaF layer; the surface of the aluminum foil is decorated with an AlOOH nanowire array; and the polymer layer comprises at least one of polyethylene glycol, polyvinyl alcohol and polypyrrole.The negative-electrode-free sodium-ion battery current collector is used in a negative-electrode-free sodium-ion battery, can promote the formation of a NaF-rich SEI film in the formation process of the battery, improve the conductivity and stability of the SEI film, realize the uniform and stable deposition of sodium ions on the current collector, and finally improve the coulomb efficiency and cycle life of the negative-electrode-free sodium battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a current collector for a negative electrode-free sodium-ion battery, its preparation method and application, and a negative electrode-free sodium-ion battery. Background Technology

[0002] Electrodeless sodium-ion batteries maximize energy density by using only a current collector as a carrier for sodium deposition / stripping on the negative electrode side. Furthermore, the electrodeless design eliminates costs associated with negative electrode production, transportation, and integration, significantly improving battery safety and reducing environmental control expenses. However, in electrodeless designs, the deposition overpotential of metallic sodium on the aluminum foil is high and unevenly distributed, exacerbating side effects between the deposited sodium and the electrolyte, leading to sodium dendrite formation.

[0003] During battery cycling, the stability of the SEI film formed on the negative electrode side significantly affects the deposition / stripping behavior of sodium. Therefore, constructing an inorganic-rich SEI film with high ionic conductivity and good chemical / structural stability is crucial for achieving stable operation of anode-free sodium-ion batteries. Among the components of the SEI film, NaF, due to its low sodium-ion diffusion barrier, high interfacial energy, excellent chemical stability, and mechanical strength, promotes uniform sodium-ion deposition during anode-free battery cycling and enhances the battery's cycle stability. Therefore, constructing a NaF-rich SEI film is essential for the stable and safe operation of anode-free sodium-ion batteries. Currently, NaF is mainly derived from F-containing solutes, solvents, and additives, generated through a series of chemical reactions during battery formation. Its content in the SEI film is reduced, and its distribution is uneven, making it impossible to construct a truly NaF-rich SEI film.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The primary objective of this invention is to provide a current collector for a negative electrode-free sodium-ion battery. This current collector promotes the formation of a NaF-rich SEI film during battery formation and improves the conductivity and stability of the SEI film. It also enables uniform and stable deposition of sodium ions on the current collector, ultimately improving the coulombic efficiency and cycle life of the negative electrode-free sodium-ion battery, thereby solving the aforementioned technical problems.

[0006] The second objective of this invention is to provide a method for preparing the above-mentioned negative electrode-free sodium-ion battery current collector.

[0007] A third objective of this invention is to provide the application of the above-mentioned negative electrode-free sodium-ion battery current collector in a negative electrode-free sodium-ion battery.

[0008] The fourth objective of this invention is to provide a sodium-ion battery without a negative electrode.

[0009] To achieve the above objectives, the following technical solution is adopted:

[0010] In a first aspect, the present invention provides a current collector for a negative electrode-free sodium-ion battery, comprising an aluminum foil, a porous NaF layer, and a polymer layer; wherein the porous NaF layer is disposed on the surface of the aluminum foil, and the polymer layer is disposed on the surface of the porous NaF layer;

[0011] The surface of the aluminum foil is modified with an AlOOH nanowire array;

[0012] The polymer layer includes at least one of polyethylene glycol, polyvinyl alcohol, and polypyrrole.

[0013] As a further technical solution, the preparation method of aluminum foil with AlOOH nanowire arrays on the surface includes the following steps:

[0014] After removing the oxide layer, the aluminum foil was placed in a solution of urea and aluminum nitrate, and then ammonia was added to adjust the pH to 7-9 for hydrothermal reaction. After the reaction was completed, aluminum foil with AlOOH nanowire arrays on the surface was prepared.

[0015] As a further technical solution, in the urea and aluminum nitrate solution, the concentration of urea is 0.3-0.6 mol / L and the concentration of aluminum nitrate is 0.05-0.2 mol / L.

[0016] As a further technical solution, the temperature of the hydrothermal reaction is 110-130℃, and the reaction time is 5-7h.

[0017] As a further technical solution, the thickness of the porous NaF layer is 100nm-2um, and the porosity is 20%-70%.

[0018] Secondly, the present invention provides a method for preparing the above-mentioned negative electrode-free sodium-ion battery current collector, comprising the following steps:

[0019] a. An aluminum foil with AlOOH surface-modified is placed in a mixed solution of HF and NaOH to react, so that NaF is generated on the surface of the aluminum foil. After drying, curing and adjusting the porosity of the NaF layer, an aluminum foil with a porous NaF layer on the surface is obtained.

[0020] b. Place the aluminum foil with a porous NaF layer on its surface obtained in step a into a polymerization solution for in-situ polymerization, so that a polymer layer is formed on the surface of the porous NaF layer, thereby obtaining the current collector of the negative electrode-free sodium-ion battery.

[0021] As a further technical solution, in the mixed solution of HF and NaOH, the concentration of HF is 0.3-0.6 mol / L and the concentration of NaOH is 0.3-0.6 mol / L.

[0022] As a further technical solution, the curing process involves annealing the reacted aluminum foil at 160-200°C under an inert atmosphere.

[0023] And / or, adjust the porosity of the NaF layer by etching; the etching solution includes citric acid.

[0024] Thirdly, the present invention provides the application of the above-mentioned negative electrode-free sodium-ion battery current collector in a negative electrode-free sodium-ion battery.

[0025] Fourthly, the present invention provides a negative electrode-free sodium-ion battery, wherein the negative electrode-free sodium-ion battery current collector is used as the negative electrode of the negative electrode-free sodium-ion battery.

[0026] Compared with existing technologies, the negative electrode-free sodium-ion battery current collector provided by this invention has the following beneficial effects:

[0027] 1. Highly stable and non-shedding NaF layer: The interfacial bonding between the surface NaF layer and the aluminum foil is enhanced by the physical anchoring and chemical bonding (Al-OF) of the nanowire array on the aluminum foil surface, ensuring that the NaF layer does not shed during long-term cycling.

[0028] 2. Uniform and stable deposition of sodium ions: The NaF layer, through the synergistic design of micro-nano hierarchical channels, not only provides a fast sodium ion transport channel, but also increases active sites, promotes the migration and uniform deposition of sodium ions, and reduces dendrite formation.

[0029] 3. Flexible interface ensures long-term cycling: The polymer flexible interface can adapt to the volume changes of sodium deposition / stripping during cycling, reduce cracking of the coating interface, and thus improve battery cycle life and safety performance. Detailed Implementation

[0030] The embodiments and examples of the present invention will be described in detail below. However, those skilled in the art will understand that the following embodiments and examples are for illustrative purposes only and should not be considered as limiting the scope of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise specified, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0031] In a first aspect, the present invention provides a current collector for a negative electrode-free sodium-ion battery, comprising an aluminum foil, a porous NaF layer, and a polymer layer; wherein the porous NaF layer is disposed on the surface of the aluminum foil, and the polymer layer is disposed on the surface of the porous NaF layer;

[0032] The surface of the aluminum foil is modified with an AlOOH nanowire array;

[0033] The polymer layer includes, but is not limited to, at least one of polyethylene glycol, polyvinyl alcohol, and polypyrrole.

[0034] The electrodeless sodium-ion battery current collector provided by this invention can promote the formation of a NaF-rich SEI film during the battery formation process, improve the conductivity and stability of the SEI film, achieve uniform and stable deposition of sodium ions on the current collector, and ultimately improve the coulombic efficiency and cycle life of the electrodeless sodium battery.

[0035] In some optional embodiments, the preparation method of aluminum foil with AlOOH nanowire arrays on its surface includes the following steps:

[0036] After removing the oxide layer, the aluminum foil is placed in a solution of urea and aluminum nitrate, and then ammonia is added to adjust the pH to 7-9 (preferably to pH 8 to generate a stable AlOOH nanoarray) for hydrothermal reaction. After the reaction is completed, aluminum foil with AlOOH nanowire array modified on the surface is obtained.

[0037] In some alternative embodiments, the concentration of urea in the urea and aluminum nitrate solution may be, for example, but not limited to, 0.3-0.6 mol / L, and the concentration of aluminum nitrate may be, for example, but not limited to, 0.05-0.2 mol / L.

[0038] In some alternative embodiments, the temperature of the hydrothermal reaction may be, for example, but not limited to, 110°C, 120°C or 130°C, and the reaction time may be, for example, but not limited to, 5h, 6h or 7h.

[0039] In some alternative embodiments, the thickness of the porous NaF layer may be, for example, but not limited to, 100 nm-2 μm, and the porosity may be, for example, but not limited to, 20%-70%.

[0040] In some alternative embodiments, the thickness of the current collector in the negative electrode-free sodium-ion battery can be, for example, but is not limited to, 10-20 μm.

[0041] Secondly, the present invention provides a method for preparing the above-mentioned negative electrode-free sodium-ion battery current collector, comprising the following steps:

[0042] a. An aluminum foil with an AlOOH nanowire array on its surface is placed in a mixed solution of HF and NaOH to react, so that NaF is generated on the surface of the aluminum foil. After drying, curing and adjusting the porosity of the NaF layer, an aluminum foil with a porous NaF layer on its surface is obtained.

[0043] b. Place the aluminum foil with a porous NaF layer on its surface obtained in step a into a polymerization solution for in-situ polymerization, so that a polymer layer is formed on the surface of the porous NaF layer, thereby obtaining the current collector of the negative electrode-free sodium-ion battery.

[0044] The preparation method is simple and convenient, and the current collector of the prepared electrodeless sodium-ion battery has good stability. When used in electrodeless sodium-ion batteries, it can achieve uniform and stable deposition of sodium ions on the current collector, ultimately improving the coulombic efficiency and cycle life of the electrodeless sodium-ion battery.

[0045] In some optional embodiments, the concentration of HF in the mixed solution of HF and NaOH can be, for example, but not limited to, 0.3-0.6 mol / L, and the concentration of NaOH can be, for example, but not limited to, 0.3-0.6 mol / L.

[0046] In some alternative embodiments, the pH of the mixed solution of HF and NaOH is 7-9, preferably 8.

[0047] In some alternative embodiments, the mixed solution of HF and NaOH further includes ammonia water to maintain the pH stability of the solution.

[0048] In some alternative embodiments, the curing process involves annealing the reacted aluminum foil at 160-200°C, preferably 180°C, under an inert atmosphere.

[0049] In some alternative embodiments, the porosity of the NaF layer is adjusted by etching; the etching solution used for etching includes citric acid.

[0050] By controlling the degree of etching, NaF layers with different porosities were obtained.

[0051] Thirdly, the present invention provides the application of the above-mentioned negative electrode-free sodium-ion battery current collector in a negative electrode-free sodium-ion battery.

[0052] The present invention provides a current collector for a negative electrode-free sodium-ion battery, which can effectively improve the coulombic efficiency, cycle life and safety of sodium-ion batteries.

[0053] Fourthly, the present invention provides a negative electrode-free sodium-ion battery, wherein the negative electrode-free sodium-ion battery current collector is used as the negative electrode of the negative electrode-free sodium-ion battery.

[0054] This electrodeless sodium-ion battery has high coulombic efficiency, long cycle life, and good safety.

[0055] The present invention will be further illustrated below with specific embodiments and comparative examples. However, it should be understood that these embodiments are merely for the purpose of more detailed illustration and should not be construed as limiting the present invention in any way.

[0056] Example 1

[0057] A current collector for a negative electrode-free sodium-ion battery includes a 12µm aluminum foil, a 100nm porous NaF layer with a porosity of 70%, and a 1µm polymer layer; the porous NaF layer is disposed on the surface of the aluminum foil, and the polymer layer is disposed on the surface of the porous NaF layer; the surface of the aluminum foil is modified with an AlOOH nanowire array; the polymer layer is polypyrrole.

[0058] The preparation method is as follows:

[0059] 1. Aluminum foil pretreatment

[0060] The aluminum foil was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 10 minutes each, and then dried with nitrogen to prevent oxidation. The cleaned aluminum foil was then placed in 5% dilute hydrochloric acid for 10-15 seconds to remove the surface oxide layer. Subsequently, it was placed in a solution of 0.3 mol / L urea and 0.05 mol / L aluminum nitrate, and the pH was adjusted to 8 with ammonia. A hydrothermal reaction was carried out at 120°C for 6 hours. After cooling, the aluminum foil was removed, washed with deionized water, and then vacuum dried at 60°C.

[0061] 2. Preparation of porous NaF layer

[0062] 0.3 mol / L HF was neutralized with an equimolar amount of NaOH, and ammonia was added as a buffer to maintain pH 8. Aluminum foil was vertically immersed in the reaction solution and stirred at 25-30℃ and 200-300 rpm for 3-5 hours. After stirring, the aluminum foil was removed and washed three times with deionized water and anhydrous ethanol. It was then dried at 40℃ and relative humidity <30% for 2 hours, followed by annealing at 180℃ under an inert atmosphere for at least 30 minutes to obtain a NaF layer. Subsequently, it was placed in an etching solution (0.1 mol / L citric acid), sonicated for 30 minutes, and then vacuum dried at 60℃. The resulting porous NaF layer for the current collector had a porosity of 70%.

[0063] 3. Polymer coating

[0064] The current collector obtained above was placed in a polymerization solution (0.1 mol / L pyrrole monomer + 0.05 mol / L FeCl3 in ethanol solution) for in-situ polymerization, and finally a current collector for a negative electrode-free sodium-ion battery was obtained.

[0065] Example 2

[0066] A current collector for a negative electrode-free sodium-ion battery includes an aluminum foil of 12 μm, a porous NaF layer of 1 μm with a porosity of 40%, and a polymer layer of 2 μm. The porous NaF layer is disposed on the surface of the aluminum foil, and the polymer layer is disposed on the surface of the porous NaF layer. The surface of the aluminum foil is modified with an AlOOH nanowire array. The polymer layer is polypyrrole.

[0067] The preparation method is as follows:

[0068] 1. Aluminum foil pretreatment

[0069] The aluminum foil was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 10 minutes each, and then dried with nitrogen to prevent oxidation. The cleaned aluminum foil was then placed in 5% dilute hydrochloric acid for 10-15 seconds to remove the surface oxide layer. Subsequently, it was placed in a solution of 0.5 mol / L urea and 0.2 mol / L aluminum nitrate, and the pH was adjusted to 8 with ammonia. A hydrothermal reaction was carried out at 120°C for 6 hours. After cooling, the aluminum foil was removed, cleaned with deionized water, and then vacuum dried at 60°C.

[0070] 2. Preparation of porous NaF layer

[0071] 0.5 mol / L HF was neutralized with an equimolar amount of NaOH, and ammonia was added as a buffer to maintain pH 9. Aluminum foil was vertically immersed in the reaction solution and stirred at 25-30℃ and 200-300 rpm for 3-5 hours. After stirring, the aluminum foil was removed and washed three times with deionized water and anhydrous ethanol. It was then dried at 40℃ and relative humidity <30% for 2 hours, followed by annealing at 180℃ under an inert atmosphere for at least 30 minutes to obtain a NaF layer. Subsequently, it was placed in an etching solution (0.1 mol / L citric acid), sonicated for 20 minutes, and then vacuum dried at 60℃. The porosity of the resulting porous NaF layer for the current collector was 40%.

[0072] 3. Polymer coating

[0073] The current collector obtained above was placed in a polymerization solution (0.1 mol / L pyrrole monomer + 0.05 mol / L FeCl3 in ethanol solution) for in-situ polymerization, and finally a current collector for a negative electrode-free sodium-ion battery was obtained.

[0074] Example 3

[0075] A current collector for a sodium-ion battery without a negative electrode includes an aluminum foil of 12 μm, a porous NaF layer of 2 μm with a porosity of 20%, and a polymer layer of 4 μm. The porous NaF layer is disposed on the surface of the aluminum foil, and the polymer layer is disposed on the surface of the porous NaF layer. The surface of the aluminum foil is modified with AlOOH. The polymer layer is polypyrrole.

[0076] The preparation method is as follows:

[0077] 1. Aluminum foil pretreatment

[0078] The aluminum foil was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 10 minutes each, and then dried with nitrogen to prevent oxidation. The cleaned aluminum foil was then placed in 5% dilute hydrochloric acid for 10-15 seconds to remove the surface oxide layer. Subsequently, it was placed in a solution of 0.4 mol / L urea and 0.1 mol / L aluminum nitrate, and the pH was adjusted to 8 with ammonia. A hydrothermal reaction was carried out at 120°C for 6 hours. After cooling, the aluminum foil was removed, cleaned with deionized water, and then vacuum dried at 60°C.

[0079] 2. Preparation of porous NaF layer

[0080] 0.6 mol / L HF was neutralized with an equimolar amount of NaOH, and ammonia was added as a buffer to maintain pH 7. Aluminum foil was vertically immersed in the reaction solution and stirred at 25-30℃ and 200-300 rpm for 3-5 hours. After stirring, the aluminum foil was removed and washed three times with deionized water and anhydrous ethanol. It was then dried at 40℃ and relative humidity <30% for 2 hours, followed by annealing at 180℃ under an inert atmosphere for at least 30 minutes to obtain a NaF layer. Subsequently, it was placed in an etching solution (0.1 mol / L citric acid), sonicated for 10 minutes, and then vacuum dried at 60℃. The porosity of the resulting porous NaF layer for the current collector was 20%.

[0081] 3. Polymer coating

[0082] The current collector obtained above was placed in a polymerization solution (0.1 mol / L pyrrole monomer + 0.05 mol / L FeCl3 in ethanol solution) for in-situ polymerization, and finally a current collector for a negative electrode-free sodium-ion battery was obtained.

[0083] Comparative Example 1

[0084] A current collector, which differs from Example 1 in that it does not have an AlOOH layer.

[0085] Comparative Example 2

[0086] A current collector, which differs from Example 1 in that it has not undergone citric acid etching.

[0087] Comparative Example 3

[0088] A current collector, which differs from Embodiment 1 in that it has no polymer layer.

[0089] Experimental Example 1

[0090] A negative electrode-free sodium-ion battery was prepared by using the current collectors provided in the above embodiments and comparative examples as negative electrodes, wherein the positive electrode sheet is composed of sodium iron pyrophosphate, PVDF, and conductive carbon black in a ratio of 95.4:1.8:2.8.

[0091] The electrolyte is: diethylene glycol dimethyl ether containing 1M NaPF6;

[0092] The diaphragm is a PP diaphragm.

[0093] A negative electrode-free sodium-ion battery was assembled in a glove box under an inert atmosphere using the same preparation method.

[0094] The first coulombic efficiency and cycle performance of the negative electrode-free sodium metal batteries prepared in each embodiment and comparative example were tested. The specific test methods are as follows:

[0095] First Coulomb efficiency test of the battery: After the assembled battery was left to stand for 10 hours, it was charged to 3.5V at a constant current and constant voltage of 0.2C, then left to stand for another 0.5 hours, and then discharged to 2.0V at a constant current of 0.5C. The ratio of the battery's discharge capacity to its charge capacity was calculated as CE.

[0096] Cycle life test: After the assembled battery was left to rest for 10 hours, it was charged to 3.5V at a constant current and constant voltage of 0.5C at room temperature (25℃), left to rest for 0.5 hours, and then discharged to 2.0V at a constant current of 1C. The cycle was repeated 100 times, and the capacity retention rate was recorded. The test results are shown in Table 1.

[0097] Table 1

[0098] Example 1 97.6 98.8 Example 2 96.3 98.5 Example 3 94.8 96.2 Comparative Example 1 90.3 78.2 Comparative Example 2 88.3 82.3 Comparative Example 3 91.4 81.5

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A negative electrode-free sodium-ion battery current collector, characterized in that, It includes an aluminum foil, a porous NaF layer, and a polymer layer; the porous NaF layer is disposed on the surface of the aluminum foil, and the polymer layer is disposed on the surface of the porous NaF layer. The surface of the aluminum foil is modified with an AlOOH nanowire array; The polymer layer includes at least one of polyethylene glycol, polyvinyl alcohol, and polypyrrole.

2. The anode-free sodium-ion battery current collector of claim 1, wherein, The preparation method of aluminum foil with AlOOH nanowire array on surface includes the following steps: After removing the oxide layer from the aluminum foil, it was placed in a solution of urea and aluminum nitrate, and then ammonia was added to adjust the pH to 7-9 for hydrothermal reaction. After the reaction was completed, aluminum foil with AlOOH nanoarrays on the surface was prepared.

3. The current collector for a negative electrodeless sodium-ion battery according to claim 2, characterized in that, In the urea and aluminum nitrate solution, the concentration of urea is 0.3-0.6 mol / L and the concentration of aluminum nitrate is 0.05-0.2 mol / L.

4. The current collector for a negative electrodeless sodium-ion battery according to claim 2, characterized in that, The hydrothermal reaction is carried out at a temperature of 110-130℃ for 5-7 hours.

5. The current collector for a negative electrodeless sodium-ion battery according to claim 1, characterized in that, The thickness of the porous NaF layer is 100 nm-2 μm, and the porosity is 20%-70%.

6. The method for preparing the current collector of a negative electrodeless sodium-ion battery according to any one of claims 1-5, characterized in that, Includes the following steps: a. An aluminum foil with an AlOOH nanowire array on its surface is placed in a mixed solution of HF and NaOH to react, so that NaF is generated on the surface of the aluminum foil. After drying, curing and adjusting the porosity of the NaF layer, an aluminum foil with a porous NaF layer on its surface is obtained. b. Place the aluminum foil with a porous NaF layer on its surface obtained in step a into a polymerization solution for in-situ polymerization, so that a polymer layer is formed on the surface of the porous NaF layer, thereby obtaining the current collector of the negative electrode-free sodium-ion battery.

7. The preparation method according to claim 6, characterized in that, In the mixed solution of HF and NaOH, the concentration of HF is 0.3-0.6 mol / L and the concentration of NaOH is 0.3-0.6 mol / L.

8. The preparation method according to claim 6, characterized in that, The curing process involves annealing the reacted aluminum foil at 160-200°C under an inert atmosphere. And / or, adjust the porosity of the NaF layer by etching; The etching solution used for etching includes citric acid.

9. The application of the negative electrode-free sodium-ion battery current collector according to any one of claims 1-5 in a negative electrode-free sodium-ion battery.

10. A sodium-ion battery without a negative electrode, characterized in that, The current collector of the non-negative electrode sodium-ion battery according to any one of claims 1-5 is used as the negative electrode of the non-negative electrode sodium-ion battery.