Surface-modified aluminum foil current collector, method of making the same, and sodium-ion battery

Abstract

The application belongs to the field of batteries, and particularly relates to a surface-modified aluminum foil current collector, a preparation method thereof and a sodium ion battery. The surface-modified aluminum foil current collector comprises an aluminum foil, bismuth nanotubes arranged on the surface of the aluminum foil, and a sodium supplementing agent dispersed between the bismuth nanotubes. The technical scheme of the application is to deposit and form inside the nanochannel of the aluminum oxide template, so as to obtain bismuth nanotubes with a predetermined wall thickness or a wall thickness changing along the axial direction. The bismuth nanotubes can form a bismuth-sodium alloy with sodium, utilize the self-smoothing effect to slow down the dendrite, and promote the uniform deposition of sodium. The volume change in the sodium deposition stripping process of the sodium metal battery is inhibited, the cycle stability is improved, the dendrite growth in the charging and discharging process of the sodium metal battery is inhibited, and the safety and stability of the battery are improved. The pre-sodium agent can provide a large amount of sodium ions in the subsequent pre-sodium process, and the initial efficiency of the sodium metal battery is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of batteries, and particularly relates to a surface-modified aluminum foil current collector, a preparation method thereof and a sodium ion battery. BACKGROUND

[0002] With the increasing demand for clean energy worldwide, sodium ion batteries, as a new type of energy storage device, have attracted widespread attention due to their abundant resources, low cost, high safety and other advantages. However, the overall energy density of sodium ion batteries is relatively low due to the low capacity of hard carbon on the negative electrode side, which is difficult to compare with traditional lithium ion batteries. Using metallic sodium instead of hard carbon as the negative electrode can effectively improve the energy density, but metallic sodium is extremely unstable in air, greatly increasing the processing cost and production difficulty. The no-negative electrode sodium metal battery can well solve the above problems. However, the application and development of the negative electrode current collector also face many challenges, such as low initial efficiency and poor cycle stability due to uneven sodium deposition, sodium dendrite and dead sodium formation.

[0003] In order to solve these problems, researchers have proposed various strategies for modifying the no-negative electrode current collector, such as preparing various coatings on the surface of the no-negative electrode current collector. In patent CN114032532B, a copper-tin alloy plating layer is deposited on the surface of a copper foil by chemical plating. The plating layer can effectively reduce the nucleation overpotential of sodium, promote the uniform deposition of metallic sodium on the copper foil, inhibit the formation of sodium dendrites, achieve stable sodium dissolution and deposition behavior, and exhibit good cycle stability. Patent CN117747847B provides a composite current collector with a sodium-friendly interface based on the double-target co-sputtering preparation idea of metals M and N. It realizes in-situ construction of SEI based on the regulation of interface structure, metal M and metal N composition and proportion, which can effectively improve the stability of the interface and improve the long cycle stability of the no-negative electrode sodium metal battery. Although the existing technical solutions can effectively reduce the sodium nucleation overpotential and improve the cycle stability of the battery, they cannot effectively solve the problems of unstable negative electrode interface and low initial efficiency caused by repeated deposition / peeling of sodium. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art and provide a surface-modified aluminum foil current collector, a preparation method thereof and a sodium ion battery.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0006] A surface-modified aluminum foil current collector, comprising an aluminum foil, bismuth nanotubes arranged on the surface of the aluminum foil, and a sodium supplementing agent dispersed between the bismuth nanotubes.

[0007] The sodium supplement agent is one or more of Na3PS4, Na3PS3O, sodium acetate, sodium iodate, sodium nitrate, sodium phosphate, sodium chlorate, or sodium pyrophosphate, etc.

[0008] The present application also includes a preparation method of the surface-modified aluminum foil current collector, comprising the following steps: 1) preparing an aluminum oxide template with an aluminum oxide surface on the surface of the aluminum foil; 2) depositing bismuth on the aluminum oxide template to form bismuth nanotubes, and removing the aluminum oxide template to obtain an aluminum foil with bismuth nanotubes grown on the surface; and 3) depositing a sodium supplement agent in the gap between the bismuth nanotubes.

[0009] Step 1) is prepared by an anodic oxidation method;

[0010] Preferably, it specifically comprises the following steps: S101: the pretreated aluminum material is used as an anode, a platinum mesh or stainless steel is used as a cathode, and is placed in an electrolytic cell to perform first anodic oxidation in an electrolyte within a specific voltage and time range, so as to form a porous Al2O3 film on the surface of the aluminum, and the pores in the film are disordered;

[0011] S102: the disordered film formed after the first anodic oxidation is selectively dissolved by chemical dissolution to dissolve away the oxide film and reserve the aluminum substrate;

[0012] S103: second anodic oxidation is performed within a specific voltage and time range, and the pores formed this time can grow more orderly and uniformly.

[0013] The aluminum foil pretreatment process comprises one or more of chemical cleaning or mechanical polishing; the electrolyte comprises one of sulfuric acid, oxalic acid or phosphoric acid; the electrolyte solubility range is 0.1M-10M; the specific voltage range of step S101 and step S103 independently comprises 1V-300V; and the time range independently comprises 1min-600min.

[0014] In step 2), the bismuth is deposited on the aluminum oxide template to form bismuth nanotubes by using an electrodeposition method;

[0015] Preferably, it specifically comprises the following steps: S201: sputtering a metal catalyst layer on one side surface of the aluminum oxide template to form a metal layer to obtain a working electrode;

[0016] S202: using a platinum mesh as a counter electrode, using a bismuth salt, a supporting electrolyte and an alkaline solution as an electrolyte, and depositing bismuth by electrodeposition at a current density of 0.1mA / cm 2 -5mA / cm 2 for 10-600min; by adjusting the thickness of the sputtered metal catalyst layer and the current density during electrodeposition, the bismuth nanotubes can be deposited and shaped inside the nanochannel of the aluminum oxide template, so as to obtain bismuth nanotubes with a predetermined wall thickness or a wall thickness varying along the axial direction.

[0017] S203: Then put the aluminum oxide template with electrodeposited bismuth nanotubes into the prepared NaOH solution, check every 5 min to confirm whether the aluminum oxide template starts to dissolve; after the aluminum oxide template is completely dissolved, rinse with deionized water to remove the residual NaOH solution, and dry at 80 DEG C for about 1 hour to obtain an aluminum foil with bismuth nanotubes grown on the surface.

[0018] The metal catalyst in step S201 includes one of nickel (Ni), iron (Fe), cobalt (Co), gold (Au) or copper (Cu);

[0019] The bismuth salt in step S202 includes one of bismuth nitrate or bismuth acetate; the supporting electrolyte includes one or more of sodium sulfate, sodium chloride, sodium nitrate, potassium sulfide, potassium chloride, potassium nitrate, etc.; the alkaline solution includes one of sodium hydroxide and potassium hydroxide; the pH value of the electrolyte ranges from 0.1 to 6;

[0020] The current density in step S202 is 0.5mA / cm 2 -2.5mA / cm 2 .

[0021] The specific steps of step 3) are: S301: mixing a sodium supplement containing a sodium source with a solvent to prepare a chemical pre-sodium solution; S302: then immersing the current collector with bismuth nanotubes grown thereon into the chemical pre-sodium solution for pre-sodium treatment, and obtaining a negative electrode current collector with a 3D sodium supplement and sodium coating after washing and drying after the reaction.

[0022] The solvent includes one or more of N-methyl pyrrolidone, ethanol, isopropanol, dimethylformamide, acetone, butanone, etc.; the molar ratio of the sodium supplement to the solvent ranges from 0.1:1 to 3:1; preferably (0.8-1.2):1.

[0023] The application also includes a sodium metal battery comprising the surface modified aluminum foil current collector; preferably, the sodium metal battery is a negative electrode-free sodium metal battery.

[0024] Compared with the prior art, the application has the following beneficial effects:

[0025] The technical scheme of the present application obtains bismuth nanotubes with a predetermined wall thickness or a wall thickness varying along the axial direction by depositing and forming inside the nanochannel of the alumina template. The bismuth nanotubes can form a bismuth-sodium alloy with sodium, slow down dendrites by using the self-smoothing effect, and promote uniform deposition of sodium. The volume change during the sodium deposition stripping process of the sodium metal battery is inhibited, the cycle stability is improved; at the same time, the dendrite growth of the sodium metal battery during the charging and discharging process is inhibited, the safety and stability of the battery are improved; the pre-sodium agent can provide a large amount of sodium ions in the subsequent pre-sodium process, improve the initial efficiency of the sodium metal battery; the technical scheme of the present application can realize efficient and low-cost production of the battery, and promote large-scale application of the sodium metal battery. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The half-electrode charge-discharge curve of the comparative example 1 is shown in the following figure:

[0027] Figure 2 The half-electrode charge-discharge curve of the comparative example 1 is shown in the following figure:

[0028] Figure 3 The full-electrode charge-discharge curve of the comparative example 1 is shown in the following figure:

[0029] Figure 4 The full-electrode charge-discharge curve of the comparative example 1 is shown in the following figure:

[0030] Figure 5 The half-electrode cycle curve of the comparative example 1 is shown in the following figure:

[0031] Figure 6 The half-electrode cycle curve of the comparative example 1 is shown in the following figure: DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the technical scheme of the present application, the present application will be further described in detail below in combination with the drawings and the best embodiment.

[0033] Embodiment 1

[0034] The preparation method of the surface-modified aluminum foil current collector comprises the following steps:

[0035] 1): The alumina template is prepared by an anodic oxidation method. First, the aluminum foil is ultrasonically cleaned with acetone and ethanol in sequence, and the surface of the aluminum foil is lightly polished with fine sandpaper for pretreatment; the pretreated aluminum material is used as an anode, and a platinum mesh is used as a cathode, and the aluminum material is oxidized in a 0.3M sulfuric acid solution under the condition of 20V for 15min; then the aluminum material is immersed in a 3% phosphoric acid solution for 10min, and after cleaning and drying, the aluminum material is oxidized under the condition of 40V for 30min for the second time of anodic oxidation, thereby obtaining the alumina template.

[0036] 2): Bismuth nanotubes were deposited on the alumina template using electrodeposition method. First, a layer of gold (Au) was sputtered on one side surface of the alumina template; then, with the above-mentioned aluminum foil as the working electrode, platinum mesh as the counter electrode, a salt solution of bismuth nitrate:sodium sulfate in a ratio of 6:4 was configured, and sodium hydroxide solution was added dropwise until the pH was 1, and then deposited for 30 min at a current density of 1.5 mA / cm 2

[0037] Step three: presodium treatment. Na3PS4 and N-methyl pyrrolidone were mixed in a molar ratio of 1:1 and stirred at room temperature for 24 hours to obtain a chemical presodium agent solution. Then the aluminum foil with bismuth nanotubes grown on it was immersed in the chemical presodium agent solution for 24 hours. After soaking, the copper foil was taken out and the surface was rinsed with deionized water to remove the residual chemical reagents; the copper foil loaded with the presodium agent was dried in a vacuum drying oven at 60°C for 12 hours to obtain a negative electrode current collector with a 3D presodium sodium-philic coating, including an aluminum foil, bismuth nanotubes arranged on the surface of the aluminum foil, and a presodium agent dispersed between the bismuth nanotubes.

[0038] Using the negative electrode current collector obtained in step 3), a negative electrode-free sodium metal battery with high initial efficiency and long service life was prepared according to the conventional button cell or monolithic cell preparation method.

[0039] Example 2

[0040] The preparation method of the surface-modified aluminum foil current collector comprises the following steps:

[0041] 1): Alumina template was prepared by anodic oxidation method. First, the aluminum foil was cleaned with acetone and ethanol in sequence and the surface of the aluminum foil was gently polished with fine sandpaper for pretreatment; the pretreated aluminum material was used as an anode and platinum mesh as a cathode, and the aluminum foil was oxidized in 0.3M sulfuric acid solution at 20V for 15 min; then it was immersed in 3% phosphoric acid solution for 10 min, and after cleaning and drying, it was oxidized at 40V for 30 min for the second anodic oxidation to obtain the alumina template.

[0042] 2): Bismuth nanotubes were deposited on the alumina template using electrodeposition method. First, a layer of gold (Au) was sputtered on one side surface of the alumina template; then, with the above-mentioned aluminum foil as the working electrode, platinum mesh as the counter electrode, a salt solution of bismuth nitrate:sodium sulfate in a ratio of 6:4 was configured, and sodium hydroxide solution was added dropwise until the pH was 1, and then deposited for 30 min at a current density of 1.5 mA / cm 2 ​The aluminum foil with bismuth nanotubes grown on the surface was then immersed in the prepared 3% NaOH solution, and the dissolution of the aluminum oxide template was checked every 5 minutes. After the aluminum oxide template was completely dissolved, the aluminum foil was immediately rinsed with a large amount of deionized water to remove the residual NaOH solution, and dried at 80°C for about 1 hour to obtain the aluminum foil with bismuth nanotubes grown on the surface.

[0043] 3) : Pre-sodium treatment. Na3PS4 and N-methyl pyrrolidone were mixed in a molar ratio of 1:1 and stirred at room temperature for 24 hours to obtain a chemical pre-sodium agent solution. Then the aluminum foil with bismuth nanotubes grown on the surface was immersed in the chemical pre-sodium agent solution for 24 hours. After the soaking was completed, the copper foil was taken out and rinsed with deionized water to clean the surface of the residual chemical reagents; the copper foil loaded with the sodium supplement agent was dried in a vacuum drying oven at 60°C for 12 hours to obtain a negative electrode current collector with a 3D sodium supplement sodium coating, including an aluminum foil, bismuth nanotubes arranged on the surface of the aluminum foil, and a sodium supplement agent dispersed between the bismuth nanotubes.

[0044] Using the negative electrode current collector obtained in step 3), a negative electrode-free sodium metal battery with high initial efficiency and long service life was prepared according to the conventional button cell or monolithic cell preparation method.

[0045] Example 3:

[0046] The preparation method of the surface-modified aluminum foil current collector comprises the following steps:

[0047] 1) : Preparation of aluminum oxide template by anodic oxidation. First, the aluminum foil was cleaned with acetone and ethanol in sequence and the surface of the aluminum foil was lightly polished with fine sandpaper for pretreatment; the pretreated aluminum material was used as an anode and a platinum mesh was used as a cathode, and the aluminum oxide template was obtained by anodizing in a 0.3M sulfuric acid solution at 20V for 15min, then immersed in a 3% phosphoric acid solution for 10min, and dried after cleaning, and then anodized at 40V for 30min for the second time to obtain the aluminum oxide template.

[0048] 2) : Bismuth nanotubes were deposited on the aluminum oxide template using an electrodeposition method. First, a layer of gold (Au) was sputtered on one side of the aluminum oxide template; then the above-mentioned aluminum foil was used as a working electrode, a platinum mesh was used as a counter electrode, a salt solution of bismuth nitrate:sodium sulfate was prepared in a molar ratio of 6:4, and sodium hydroxide solution was added dropwise until the pH was 1, and bismuth nanotubes were deposited on the aluminum oxide template at a current density of 2.5mA / cm 2 The aluminum foil with bismuth nanotubes grown on the surface was then immersed in the prepared 3% NaOH solution, and the dissolution of the aluminum oxide template was checked every 5 minutes. After the aluminum oxide template was completely dissolved, the aluminum foil was immediately rinsed with a large amount of deionized water to remove the residual NaOH solution, and dried at 80°C for about 1 hour to obtain the aluminum foil with bismuth nanotubes grown on the surface.

[0049] 3) : Pre-sodium treatment. Mix Na3PS4 and N-methyl pyrrolidone in a molar ratio of 1 : 1, stir at room temperature for 24 hours to obtain a chemical pre-sodium agent solution. Then immerse the aluminum foil with bismuth nanotubes grown on it into the chemical pre-sodium agent solution, and the soaking time is 24 hours. After soaking, take out the copper foil, rinse the surface with deionized water to remove the residual chemical reagents; dry the copper foil loaded with sodium supplement agent in a vacuum drying oven at 60°C for 12 hours to obtain a negative electrode current collector with a 3D sodium supplement sodium coating, including an aluminum foil, bismuth nanotubes arranged on the surface of the aluminum foil, and sodium supplement agents dispersed between the bismuth nanotubes.

[0050] Using the negative electrode current collector obtained in step 3), a negative electrode-free sodium metal battery with high initial efficiency and long service life is prepared according to the conventional button cell or monolithic cell preparation method.

[0051] Example 4

[0052] The preparation method of the surface modified aluminum foil current collector comprises the following steps:

[0053] 1) : Preparation of aluminum oxide template by anodic oxidation method. First, clean the aluminum foil with acetone and ethanol in sequence, and polish the surface of the aluminum foil with fine sandpaper for pretreatment; use the pretreated aluminum material as an anode and platinum mesh as a cathode, oxidize in 0.3M sulfuric acid solution at 20V for 15min; then soak in 3% phosphoric acid solution for 10min, dry and clean, and then oxidize at 40V for 30min for the second time. Anodic oxidation to obtain an aluminum oxide template.

[0054] 2) : Bismuth nanotubes are deposited on the aluminum oxide template using electrodeposition method. First, sputter a layer of gold (Au) on one side of the aluminum oxide template; then use the above aluminum foil as the working electrode, platinum mesh as the counter electrode, configure a salt solution of bismuth nitrate: sodium sulfate in a molar ratio of 6:4, and add sodium hydroxide solution dropwise until the pH is 1. Deposit for 30min at a current density of 1.5mA / cm 2 Then put the aluminum foil with electrodeposited bismuth nanotubes into the prepared 3% NaOH solution, check every 5min to confirm whether the aluminum oxide template starts to dissolve. When the aluminum oxide template is completely dissolved, immediately rinse with a large amount of deionized water to remove the residual NaOH solution, and dry at 80°C for about 1 hour to obtain an aluminum foil with bismuth nanotubes grown on the surface.

[0055] 3): Pre-sodium treatment. Mix Na3PS4 and N-methyl pyrrolidone at a molar ratio of 0.8:1, stir at room temperature for 24 hours to obtain a chemical pre-sodium agent solution. Then immerse the aluminum foil with bismuth nanotubes into the chemical pre-sodium agent solution, and the soaking time is 24 hours. After soaking, take out the copper foil, rinse the surface with deionized water to remove the residual chemical reagents; dry the copper foil loaded with sodium supplement agent in a vacuum drying box at 60°C for 12 hours to obtain a negative electrode current collector with a 3D sodium supplement sodium coating, including an aluminum foil, bismuth nanotubes arranged on the surface of the aluminum foil, and a sodium supplement agent dispersed between the bismuth nanotubes.

[0056] Using the negative electrode current collector obtained in step 3), a negative electrode-free sodium metal battery with high initial efficiency and long service life is prepared according to the conventional button cell or monolithic cell preparation method.

[0057] Example 5

[0058] The preparation method of the surface modified aluminum foil current collector comprises the following steps:

[0059] 1): Alumina template prepared by anodic oxidation method. First, clean the aluminum foil with acetone and ethanol in sequence, and polish the surface of the aluminum foil with fine sandpaper for pretreatment; use the pretreated aluminum material as an anode and platinum mesh as a cathode, oxidize in 0.3M sulfuric acid solution at 20V for 15min; then soak in 3% phosphoric acid solution for 10min, dry and clean, and then oxidize at 40V for 30min for the second anodic oxidation to obtain an alumina template.

[0060] 2): Bismuth nanotubes are deposited on the alumina template using electrodeposition method. First, sputter a layer of gold (Au) on one side of the alumina template; then use the above aluminum foil as the working electrode, platinum mesh as the counter electrode, configure a salt solution of bismuth nitrate:sodium sulfate at a ratio of 6:4, and add sodium hydroxide solution dropwise until the pH is 1, and deposit at a current density of 1.5mA / cm 2 Then put the aluminum foil with electrodeposited bismuth nanotubes into the prepared 3% NaOH solution, check every 5min to confirm whether the alumina template starts to dissolve. When the alumina template is completely dissolved, immediately rinse with a large amount of deionized water to remove the residual NaOH solution, and dry at 80°C for about 1 hour to obtain an aluminum foil with bismuth nanotubes grown on the surface.

[0061] 3) : Pre-sodium treatment. Mix Na3PS4 and N-methyl pyrrolidone at a molar ratio of 1.2:1, stir at room temperature for 24 hours to obtain a chemical pre-sodium agent solution. Then immerse the aluminum foil with bismuth nanotubes into the chemical pre-sodium agent solution, and the soaking time is 24 hours. After soaking, take out the copper foil, rinse the surface with deionized water to remove the residual chemical reagents; dry the copper foil loaded with sodium supplement agent in a vacuum drying oven at 60°C for 12 hours to obtain a negative electrode current collector with a 3D sodium supplement sodium coating, including an aluminum foil, bismuth nanotubes arranged on the surface of the aluminum foil, and sodium supplement agents dispersed between the bismuth nanotubes.

[0062] Using the negative electrode current collector obtained in step 3), a negative electrode-free sodium metal battery with high initial efficiency and long service life is prepared according to the conventional button cell or monolithic cell preparation method.

[0063] Comparative Example 1:

[0064] Cut the conventional aluminum foil into a negative electrode current collector of appropriate size. Using the above negative electrode current collector, a negative electrode-free sodium metal battery is prepared according to the conventional sodium metal battery preparation method.

[0065] Comparative Example 2:

[0066] The preparation method of the surface modified aluminum foil current collector comprises the following steps:

[0067] 1) : Alumina template prepared by anodic oxidation method. First, clean the aluminum foil with acetone and ethanol successively, and polish the surface of the aluminum foil with fine sandpaper for pretreatment; use the pretreated aluminum material as an anode and platinum mesh as a cathode, oxidize in 0.3M sulfuric acid solution at 20V for 15min; then soak in 3% phosphoric acid solution for 10min, dry and clean, and then oxidize at 40V for 30min for the second anodic oxidation to obtain an alumina template.

[0068] 2) : Bismuth nanotubes are deposited on the alumina template using electrodeposition method. First, sputter a layer of gold (Au) on one side of the alumina template; then use the above aluminum foil as the working electrode, platinum mesh as the counter electrode, configure a salt solution of bismuth nitrate:sodium sulfate at a ratio of 6:4, and add sodium hydroxide solution dropwise to pH 1, deposit at a current density of 1.5mA / cm 2 Then, place the aluminum foil with electrodeposited bismuth nanotubes into the prepared 3% NaOH solution, check every 5min to confirm whether the alumina template starts to dissolve. When the alumina template is completely dissolved, immediately rinse with a large amount of deionized water to remove the residual NaOH solution, and dry at 80°C for about 1 hour to obtain an aluminum foil with bismuth nanotubes grown on the surface.

[0069] Utilizing the negative current collector described above, a sodium metal battery without negative electrode is prepared according to the conventional sodium metal battery preparation method.

[0070] Comparative Example 3:

[0071] The preparation method of the surface-modified aluminum foil current collector comprises the following steps:

[0072] 1) Bismuth powder is coated on the surface of the substrate by a conventional coating method. The coating material bismuth powder, conductive agent Super P, and binder PVDF are mixed in a mass ratio of 8:1:1, N-methyl pyrrolidone is added as a solvent, and the mixture is coated on a copper foil after being stirred uniformly, and then subjected to drying, rolling, and slicing processes to obtain a copper foil coated with bismuth nanoparticles.

[0073] 2) Pre-sodium treatment. Na3PS4 and N-methyl pyrrolidone are mixed in a molar ratio of 1:1, stirred at room temperature for 24 hours to obtain a chemical pre-sodium agent solution. Then the aluminum foil with bismuth nanotubes grown thereon is immersed in the chemical pre-sodium agent solution for 24 hours. After the immersion is completed, the copper foil is taken out and rinsed with deionized water to remove the residual chemical reagents on the surface; the copper foil loaded with the sodium supplement agent is dried in a vacuum drying oven at 60°C for 12 hours to obtain a negative current collector with a 3D sodium-supplementing sodiumophilic coating.

[0074] Utilizing the negative current collector obtained in step 2), a sodium metal battery without negative electrode with high initial efficiency and long service life is prepared according to the conventional button cell or monolithic cell preparation method.

[0075] The button cells and monolithic cells are assembled using the negative current collector materials prepared according to the methods of the above examples and comparative examples, and electrochemical performance tests are conducted.

[0076] wherein:

[0077] (1) Button cell preparation process: sodium sheet as negative electrode, the negative current collector in each example and comparative example as positive electrode, matched with ordinary PE separator and ether-based electrolyte (DME+1M NaPF6) to obtain a sodium metal half-cell without negative electrode.

[0078] (2) Monolithic full cell preparation process: the positive electrode active material Na3V2(PO4)3, conductive agent Super P, and binder PVDF are mixed in a mass ratio of 8:1:1, N-methyl pyrrolidone is added as a solvent, and the mixture is coated on an aluminum foil after being stirred uniformly, and then subjected to drying, slicing, and rolling processes to obtain a positive electrode sheet. Then the positive electrode sheet and the negative current collector in each example and comparative example are matched with an ordinary PE separator and an ether-based electrolyte (DME+1M NaPF6) to obtain a sodium metal full cell without negative electrode.

[0079] (3) The test conditions of the button half-cell are as follows: the deposition capacity is 2 mAh / cm 2 ; the deposition current density is 1 mA / cm 2 ; and the cut-off voltage is 2 V.

[0080] (4) The test conditions of the single full-cell are as follows: the charging current is 0.02 C x 60 min, 0.05 C x 90 min, 0.1 C→3.8 V, 3.8 V→0.02 C; the discharging current is 0.1 C; and the voltage interval is 2-3.8 V. The data are shown in Table 1.

[0081] Table 1. Battery performance test data

[0082]

[0083] Figure 1 The button half-cell charge-discharge curve of Comparative Example 1 is shown in FIG. 1. Figure 2 The button half-cell charge-discharge curve of Example 1 is shown in FIG. 2. Figure 3 The single full-cell charge-discharge curve of Comparative Example 1 is shown in FIG. 3. Figure 4 The single full-cell charge-discharge curve of Example 1 is shown in FIG. 4. Figure 5 The button half-cell cycle curve of Comparative Example 1 is shown in FIG. 5. Figure 6 The button half-cell cycle curve of Example 1 is shown in FIG. 6.

[0084] By analyzing the above data, it can be seen from the comparison between Example 1 and Comparative Example 1 that the anode-free current collector prepared by the design scheme has great improvement and improvement in improving the initial efficiency and cycle stability. It can be seen from the comparison between Example 1 and Comparative Example 2 that the pre-sodium treatment can significantly improve the initial efficiency of the battery. Further, the sodium-bismuth alloy formed by the first charge-discharge promotes the uniform deposition of sodium and enhances the cycle stability. It can be seen from the comparison between Example 1 and Comparative Example 3 that the bismuth nanotube can accommodate more volume expansion, thereby enhancing the cycle stability, and the bismuth coating generated by coating cannot effectively absorb the pre-sodium agent. After the pre-sodium treatment, the initial efficiency is not obviously improved.

[0085] It can be seen from the comparison between Example 1 and Examples 2 and 3 that the microstructure of the bismuth nanotube formed under different current densities is crucial. Under the same deposition time, the current density is low, the deposited bismuth is less, and after the removal of the aluminum oxide template, the bismuth nanotube is not formed, which affects the pre-sodium effect and further affects the initial efficiency of the battery. Under the same deposition time, the current density is high, the bismuth deposition is too much and uneven, and after the removal of the aluminum oxide template, the bismuth nanotube has low strength and is easily affected by the volume expansion caused by the bismuth reversible alloying reaction, resulting in poor cycle life. Generally, the current density is 0.1 mA / cm 2 -5 mA / cm 2The current density is preferably deposited for 10-600 min. As can be seen from the comparison of Example 1 and Example 4, Example 5, different concentrations of sodium supplementing agents also affect the subsequent electrical performance test. A lower concentration reduces the effect of pre-sodium; a higher concentration does not further improve the initial efficiency, but also affects the electrical performance due to the introduction of impurities. Therefore, the molar ratio of the sodium supplementing agent to the solvent can be in the range of 0.1:1-3:1, and the molar ratio of the sodium supplementing agent to the solvent in the examples (0.8-1.2):1 is preferred.

[0086] In summary, the technical scheme of the present application is formed by depositing in the nanochannel of the alumina template, thereby obtaining bismuth nanotubes with a predetermined wall thickness or a wall thickness varying along the axial direction. The bismuth nanotubes can form bismuth-sodium alloys with sodium, and the self-smoothing effect can slow down the dendrites and promote the uniform deposition of sodium. The volume change during the sodium deposition and stripping process of the sodium metal battery is inhibited, and the cycle stability is improved; at the same time, the dendrite growth of the sodium metal battery during the charging and discharging process is inhibited, and the safety and stability of the battery are improved; the pre-sodium agent can provide a large amount of sodium ions in the subsequent pre-sodium process, and improve the initial efficiency of the sodium metal battery; the technical scheme of the present application can realize the efficient and low-cost production of the battery, and promote the large-scale application of the sodium metal battery.

[0087] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make some improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for producing a surface-modified aluminum foil current collector, characterized by, The method comprises the following steps: 1) preparing an alumina template with alumina on the surface of the aluminum foil; the alumina template is prepared by an anodic oxidation method; The method comprises the following steps: S101: the pretreated aluminum material is used as an anode, and a platinum net or stainless steel is used as a cathode, which are placed in an electrolytic tank to perform first anodic oxidation in an electrolyte within a specific voltage range and time range, so that a porous Al2O3 film is formed on the surface of the aluminum, and the pores in the film are disordered; S102: the disordered film formed after the first anodic oxidation is selectively dissolved by chemical dissolution to remove the oxide film and reserve the aluminum substrate; S103: second anodic oxidation is performed within a specific voltage range and time range, and the pores formed this time can grow more orderly and uniformly; 2) depositing bismuth on the alumina template to form bismuth nanotubes, and removing the alumina template to obtain an aluminum foil with bismuth nanotubes grown on the surface; the bismuth nanotubes are formed by electrodeposition of bismuth on the alumina template; The method comprises the following steps: S201: sputtering a layer of metal catalyst on one side surface of the alumina template to form a metal layer and obtain a working electrode; S202: using platinum mesh as the counter electrode, using a salt solution containing bismuth salt and a supporting electrolyte as the electrolyte, depositing bismuth by electrodeposition at a current density of 0.1 mA / cm 2 -5 mA / cm 2 for 10-600 min to deposit bismuth by electrodeposition. S203: then, the alumina template with the bismuth nanotubes electrodeposited thereon is placed in a prepared NaOH solution, and after the alumina template is completely dissolved, the obtained aluminum foil with bismuth nanotubes grown on the surface is washed with deionized water and dried; 3) depositing a sodium supplement agent in the gaps between the bismuth nanotubes; the specific steps are as follows: S301: mixing the sodium supplement agent containing a sodium source with a solvent to prepare a chemical pre-sodium agent solution; S302: then, the current collector with the bismuth nanotubes grown thereon is immersed in the chemical pre-sodium agent solution for pre-sodium treatment, and after the reaction is completed, the obtained negative electrode current collector with a 3D sodium supplement and sodium coating is washed and dried.

2. The production method according to claim 1, characterized by, The pretreatment process comprises one or more of chemical cleaning or mechanical polishing; the electrolyte comprises one of sulfuric acid, oxalic acid or phosphoric acid; the electrolyte concentration ranges from 0.1M to 10M; the specific voltage range in steps S101 and S103 independently comprises 1V-300V; and the time range independently comprises 1min-600min.

3. The preparation method according to claim 1, characterized in that, The metal catalyst in step S201 comprises one of nickel (Ni), iron (Fe), cobalt (Co), gold (Au) or copper (Cu); The bismuth salt in step S202 comprises one of bismuth nitrate or bismuth acetate; the supporting electrolyte comprises one or more of sodium sulfate, sodium chloride, sodium nitrate, potassium sulfide, potassium chloride, potassium nitrate; the alkaline solution comprises one of sodium hydroxide or potassium hydroxide; and the pH value of the electrolyte ranges from 0.1 to 6; The current density in step S202 is 0.5 mA / cm 2 - 2.5 mA / cm 2 .

4. The production method according to claim 1, characterized by, The solvent comprises one or more of N-methyl pyrrolidone, ethanol, isopropyl alcohol, dimethylformamide, acetone or butanone; and the molar ratio of the sodium supplement agent to the solvent ranges from 0.1:1 to 3:

1.

5. The preparation method according to claim 1, characterized in that, The molar ratio of the sodium supplement agent to the solvent ranges from 0.8 to 1.2:

1.

6. A surface-modified aluminum foil current collector characterized by, The method is obtained by any one of claims 1-5, comprising an aluminum foil, bismuth nanotubes arranged on the surface of the aluminum foil, and a sodium supplement agent dispersed between the bismuth nanotubes.

7. The surface-modified aluminum foil current collector of claim 6, wherein The sodium supplement is one or more of Na3PS4, Na3PS3O, sodium acetate, sodium iodate, sodium nitrate, sodium phosphate, sodium chlorate or sodium pyrophosphate.

8. A sodium metal battery, characterized by, The sodium metal battery is a negative electrode-free sodium metal battery.

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