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

Abstract

The invention provides a negative-electrode-free sodium ion battery current collector, 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 provided by the invention 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 modified with an AlOOH nanowire array; 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 for a negative-electrode-free sodium ion battery, can promote the formation of a NaF-rich SEI film in the battery formation process, improves the conductivity and stability of the SEI film, realizes the uniform and stable deposition of sodium ions on the current collector, and finally improves the coulombic efficiency and the cycle life of the negative-electrode-free sodium ion battery.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a current collector for a sodium ion battery without an anode, a preparation method and application thereof, and a sodium ion battery without an anode. Background Art

[0002] Anode-free sodium-ion batteries maximize the energy density of the battery because they only use the current collector as a carrier for sodium deposition / stripping on the anode side. In addition, the anode-free design not only eliminates the costs associated with anode production, transportation, and integration, greatly improves the safety of battery operation, but also reduces environmental control costs. However, in the anode-free design, the deposition overpotential of metallic sodium on bare aluminum foil is high and unevenly distributed, which exacerbates the side effects between the deposited sodium and the electrolyte and leads to the formation of sodium dendrites.

[0003] During the battery cycle, 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 the key to achieving stable operation of anode-free sodium-ion batteries. Among the components of the SEI film, NaF promotes the uniform deposition of sodium ions during the cycle of anode-free batteries and enhances the battery's cycling stability due to its low sodium ion diffusion barrier, high interfacial energy, excellent chemical stability and mechanical strength. Therefore, constructing a NaF-rich SEI film is crucial for the stable and safe operation of anode-free sodium-ion batteries. Currently, the source of NaF is mainly F-containing solutes, solvents and additives. It is 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 proposed. Summary of the Invention

[0005] The first object of the present invention is to provide a negative electrode-free sodium ion battery current collector for use in a negative electrode-free sodium ion battery, which can promote the formation of a NaF-rich SEI film during the battery formation process, improve the conductivity and stability of the SEI film, and achieve 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 battery to solve the above-mentioned technical problems.

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

[0007] The third object of the present invention is to provide an application of the above-mentioned negative electrode-free sodium ion battery current collector in a negative electrode-free sodium ion battery.

[0008] A fourth object of the present invention is to provide a negative electrode-free sodium ion battery.

[0009] In order to achieve the above objectives, the following technical solutions are adopted:

[0010] In a first aspect, the present invention provides a negative electrode-free sodium ion battery current collector, comprising 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;

[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, a method for preparing an aluminum foil with a surface modified with an AlOOH nanowire array comprises the following steps:

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

[0015] As a further technical solution, in the solution of urea and aluminum nitrate, 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° C., and the reaction time is 5-7 hours.

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

[0018] In a second aspect, 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. The surface of the aluminum foil modified with AlOOH was placed in a mixed solution of HF and NaOH to react, so that NaF was generated on the surface of the aluminum foil, and then dried, cured and adjusted the porosity of the NaF layer to obtain an aluminum foil having a porous NaF layer on the surface;

[0020] b. placing the aluminum foil with a porous NaF layer on the 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 to obtain the negative electrode-free sodium ion battery current collector.

[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 is to anneal the reacted aluminum foil at 160-200° C. under an inert atmosphere;

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

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

[0025] In a fourth aspect, the present invention provides a negative electrode-free sodium ion battery, using the negative electrode-free sodium ion battery current collector as the negative electrode of the negative electrode-free sodium ion battery.

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

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

[0028] 2. Uniform and stable deposition of sodium ions: The NaF layer, through the coordinated design of micro-nano multi-level pores, not only provides a fast sodium ion transport channel but also increases active sites, promoting the migration and uniform deposition of sodium ions and reducing the formation of dendrites.

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

[0030] Below in conjunction with embodiment and example, embodiment of the present invention is described in detail, but those skilled in the art will appreciate that the following embodiment and example are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiment in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise all fall within the scope of protection of the present invention. Unspecified conditions are carried out according to the conditions of normal conditions or manufacturer's recommendations. Reagents used or instruments not specified by the manufacturer are conventional products that can be purchased commercially.

[0031] In a first aspect, the present invention provides a negative electrode-free sodium ion battery current collector, comprising 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;

[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 cathode-free sodium ion battery current collector provided by the present invention is used in the cathode-free sodium ion battery, can promote the formation of a NaF-rich SEI film during the battery formation process, and improve the conductivity and stability of the SEI film, thereby achieving uniform and stable deposition of sodium ions on the current collector, and ultimately improving the coulombic efficiency and cycle life of the cathode-free sodium battery.

[0035] In some optional embodiments, the method for preparing an aluminum foil with a surface modified with an AlOOH nanowire array comprises the following steps:

[0036] After removing the oxide layer from the aluminum foil, the 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 8 to generate a stable AlOOH nanoarray) for a hydrothermal reaction. After the reaction is completed, an aluminum foil with a surface modified with an AlOOH nanowire array is prepared.

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

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

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

[0040] In some optional embodiments, the thickness of the negative electrode-free sodium ion battery current collector may be, for example, but not limited to, 10-20 um.

[0041] In a second aspect, 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. The aluminum foil having the surface modified with the AlOOH nanowire array was placed in a mixed solution of HF and NaOH to react, so that NaF was generated on the surface of the aluminum foil, and then dried, cured, and the porosity of the NaF layer was adjusted to obtain an aluminum foil having a porous NaF layer on the surface;

[0043] b. placing the aluminum foil with a porous NaF layer on the 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 to obtain the negative electrode-free sodium ion battery current collector.

[0044] The preparation method is simple and convenient, and the prepared negative electrode-free sodium ion battery current collector has good stability. When used in a negative electrode-free sodium ion battery, it can achieve 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 battery.

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

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

[0047] In some optional embodiments, the mixed solution of HF and NaOH further includes aqueous ammonia, and the pH of the solution is maintained stable by the aqueous ammonia.

[0048] In some optional embodiments, the curing is to anneal the reacted aluminum foil at 160-200° C., preferably 180° C., under an inert atmosphere;

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

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

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

[0052] The cathode-free sodium ion battery current collector provided by the present invention is used in the cathode-free sodium ion battery and can effectively improve the coulombic efficiency, cycle life and safety of the sodium ion battery.

[0053] In a fourth aspect, the present invention provides a negative electrode-free sodium ion battery, using the negative electrode-free sodium ion battery current collector as the negative electrode of the negative electrode-free sodium ion battery.

[0054] The negative electrode-free sodium ion battery has high coulombic efficiency, long cycle life and good safety.

[0055] The present invention is further described below by means of specific examples and comparative examples. However, it should be understood that these examples are merely provided for more detailed description and are not to be construed as limiting the present invention in any form.

[0056] Example 1

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

[0058] The preparation method is as follows:

[0059] 1. Aluminum foil pretreatment

[0060] Ultrasonic cleaning of aluminum foil was performed in acetone, anhydrous ethanol, and deionized water for 10 minutes each. After cleaning, the foil was dried with nitrogen to prevent oxidation. The cleaned foil was placed in 5% dilute hydrochloric acid for 10-15 seconds to remove the surface oxide layer. The foil was then placed in a solution of 0.3 mol / L urea and 0.05 mol / L aluminum nitrate, the pH adjusted to 8 with aqueous ammonia, and hydrothermally reacted at 120°C for 6 hours. After cooling, the foil was removed, rinsed with deionized water, and vacuum dried at 60°C.

[0061] 2. Preparation of porous NaF layer

[0062] 0.3 mol / L HF and NaOH were neutralized in equal moles, and ammonia buffer was added to maintain pH 8. The aluminum foil was vertically immersed in the reaction solution and stirred at 200-300 rpm at 25-30°C for 3-5 hours. After the reaction, the aluminum foil was removed and washed three times with deionized water and anhydrous ethanol. After drying for 2 hours at 40°C and relative humidity <30%, it was annealed at 180°C in an inert atmosphere for more than 30 minutes to obtain a NaF layer. It was then placed in an etching solution (0.1 mol / L citric acid), ultrasonically treated for 30 minutes, and vacuum dried at 60°C. The resulting porous NaF layer of 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 ethanol solution) for in situ polymerization to finally obtain a negative electrode-free sodium ion battery current collector.

[0065] Example 2

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

[0067] The preparation method is as follows:

[0068] 1. Aluminum foil pretreatment

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

[0070] 2. Preparation of porous NaF layer

[0071] 0.5 mol / L HF and NaOH were neutralized in equal moles, and ammonia buffer was added to maintain pH 9. The aluminum foil was vertically immersed in the reaction solution and stirred at 200-300 rpm at 25-30°C for 3-5 hours. After the reaction, the aluminum foil was removed and washed three times with deionized water and anhydrous ethanol. After drying for 2 hours at 40°C and relative humidity <30%, it was annealed at 180°C in an inert atmosphere for more than 30 minutes to obtain a NaF layer. It was then placed in an etching solution (0.1 mol / L citric acid), ultrasonically treated for 20 minutes, and vacuum dried at 60°C. The resulting porous NaF layer of the current collector had a porosity of 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 ethanol solution) for in situ polymerization to finally obtain a negative electrode-free sodium ion battery current collector.

[0074] Example 3

[0075] A current collector for a sodium ion battery without an anode comprises a 12 μm aluminum foil, a 2 μm porous NaF layer with a porosity of 20%, and a 4 μm 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 modified with AlOOH; and the polymer layer is polypyrrole.

[0076] The preparation method is as follows:

[0077] 1. Aluminum foil pretreatment

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

[0079] 2. Preparation of porous NaF layer

[0080] 0.6 mol / L HF and NaOH were neutralized in equal moles, and ammonia buffer was added to maintain pH 7. The aluminum foil was vertically immersed in the reaction solution and stirred at 200-300 rpm at 25-30°C for 3-5 hours. After the reaction, the aluminum foil was removed and washed three times with deionized water and anhydrous ethanol. After drying for 2 hours at 40°C and relative humidity <30%, it was annealed at 180°C in an inert atmosphere for more than 30 minutes to obtain a NaF layer. It was then placed in an etching solution (0.1 mol / L citric acid), ultrasonically treated for 10 minutes, and vacuum dried at 60°C. The resulting porous NaF layer of the current collector had a porosity of 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 ethanol solution) for in situ polymerization to finally obtain a negative electrode-free sodium ion battery current collector.

[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 citric acid etching is not performed.

[0087] Comparative Example 3

[0088] A current collector, which differs from that of Example 1 in that it does not have a polymer layer.

[0089] Test Example 1

[0090] The current collectors provided in the above examples and comparative examples were used as negative electrodes to prepare negative electrode-free sodium ion batteries, wherein the positive electrode sheet was composed of sodium iron pyrophosphate, PVDF, and conductive carbon black in a ratio of 95.4:1.8:2.8;

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

[0092] Diaphragm: PP diaphragm.

[0093] The negative electrode-free sodium ion battery was assembled in an inert atmosphere glove box according to 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 testing methods are as follows:

[0095] First coulombic efficiency test of the battery: After the assembled battery is set aside for 10 hours, it is charged to 3.5V at a constant current and constant voltage of 0.2C. After another 0.5 hour, it is discharged to 2.0V at a constant current of 0.5C. The ratio of the battery discharge capacity to the charge capacity is calculated as CE.

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

[0097] Table 1

[0098] Group First coulombic efficiency (%) 100-cycle capacity retention rate (%) 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, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements 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 current collector for a sodium ion battery without a negative electrode, characterized in that: The method 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 modified with an AlOOH nanowire array; The polymer layer includes at least one of polyethylene glycol, polyvinyl alcohol, and polypyrrole.

2. The negative electrode-free sodium ion battery current collector according to claim 1, characterized in that The preparation method of aluminum foil with surface modified AlOOH nanowire array comprises the following steps: After removing the oxide layer of the aluminum foil, the aluminum foil is placed in a solution of urea and aluminum nitrate, and then ammonia water is added to adjust the pH to 7-9 for a hydrothermal reaction. After the reaction is completed, an aluminum foil with an AlOOH nanoarray modified on the surface is prepared.

3. The negative electrode-free sodium ion battery current collector according to claim 2, characterized in that: In the solution of urea and aluminum nitrate, 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 negative electrode-free sodium ion battery current collector according to claim 2, characterized in that: The temperature of the hydrothermal reaction is 110-130° C., and the reaction time is 5-7 hours.

5. The negative electrode-free sodium ion battery current collector 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 a negative electrode-free sodium ion battery current collector according to any one of claims 1 to 5, characterized in that: The steps include: a. The aluminum foil having the surface modified with the AlOOH nanowire array was placed in a mixed solution of HF and NaOH to react, so that NaF was generated on the surface of the aluminum foil, and then dried, cured, and the porosity of the NaF layer was adjusted to obtain an aluminum foil having a porous NaF layer on the surface; b. placing the aluminum foil with a porous NaF layer on the 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 to obtain the negative electrode-free sodium ion battery current collector.

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 is to anneal the aluminum foil after the reaction at 160-200° C. under an inert atmosphere; and / or, adjusting the porosity of the NaF layer by etching; The etching solution of the etching includes citric acid.

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

10. A negative electrode-free sodium ion battery, characterized in that: The negative electrode-free sodium ion battery current collector according to any one of claims 1 to 5 is used as the negative electrode of the negative electrode-free sodium ion battery.