Porous aluminum current collector, method for preparing the same, negative electrode sheet, and sodium battery

Abstract

The application discloses a porous aluminum current collector and a preparation method thereof, a negative plate and a sodium battery, and relates to the technical field of sodium ion batteries. The application is characterized in that the aluminum base material is subjected to surface modification, a porous material is prepared through electrochemical etching, sodium-active ions are introduced, a three-dimensional porous structure with high surface energy is prepared, and finally, a thin active material coating (carbon layer) with ion and electron conductivity is coated, so that the negative electrode dosage is reduced, the cost is reduced, the energy density is improved, the fatal defects such as dendrites and unstable interface of the negative electrode-free system are avoided, and the balance between performance and safety is achieved.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, and more specifically, to porous aluminum current collectors and their preparation methods, negative electrode sheets, and sodium batteries. Background Technology

[0002] Sodium-ion batteries are considered a potential alternative to lithium-ion batteries due to abundant sodium resources, considerable cost-effectiveness, and a similar working principle. However, the peak energy density of sodium-ion batteries remains below 160 Wh / kg, significantly limiting their applicability in applications requiring higher energy densities. Electrodeless batteries utilize current collectors as the negative electrode to replace excess metallic sodium, eliminating the need for negative electrode active materials and significantly reducing the overall thickness and weight of the battery, thereby increasing its volumetric and gravimetric energy density. Furthermore, the electrodeless design reduces the presence of metallic sodium on the negative electrode, greatly lowering the battery's safety risks.

[0003] In electrodeless sodium-ion batteries, the rate at which sodium ions diffuse from the electrolyte to the current collector and the nucleation sites determine the uniformity of sodium deposition during cyclic storage. Simultaneously, the deposition of sodium ions and the generation of gas lead to significant volume expansion, which severely hinders the application of the battery. The current collector, as a key component of the battery, determines the uniformity of the initial sodium deposition process and the stability of the cycling process through its structure and properties. Currently, the most common modification is simply coating a thin carbon layer onto the metal foil surface, which cannot promote uniform and stable sodium deposition, nor can it alleviate the volume expansion during cycling in electrodeless sodium-ion batteries.

[0004] In summary, although electrodeless batteries have advantages such as good low-temperature performance, low cost, and high energy density, they still face a series of problems, including the high reactivity of metallic sodium deposited on the current collector, and volume expansion and dendrite formation during cyclic storage.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a porous aluminum current collector and its preparation method, a negative electrode sheet and sodium battery, which can reduce the amount of negative electrode used to reduce costs and increase energy density, while avoiding fatal defects such as dendrites and interface instability in the non-negative electrode system, and achieving a balance between performance and safety.

[0007] This invention is implemented as follows: In a first aspect, the present invention provides a method for preparing a porous aluminum current collector, comprising: Provide aluminum substrate; Electrochemical etching: An aluminum substrate is used as the anode for oxidation etching, followed by a reverse current for reduction etching to obtain a porous material. Introducing sodium-loving active ions: Sodium-loving active ions are implanted into the surface of porous materials by ion implantation to obtain sodium-loving materials; Carbon layer preparation: A carbon layer is formed on the surface of a sodium-loving material.

[0008] In an optional implementation, during the oxidation etching process, a constant current of 0.5 A / cm is controlled. 2 -1.0A / cm 2 Etch at 15℃-30℃ for 20-30 minutes; And / or, the electrolyte used for oxidative etching contains 0.10-0.20 mol / L sodium sulfate and 0.03-0.08 mol / L boric acid; And / or, during the oxidation etching process, the cathode used is selected from at least one of graphite, Pt / C and titanium.

[0009] In an optional implementation, during the reduction etching process, a constant current is applied in reverse while keeping the electrodes unchanged, and the constant current is controlled to be 0.3 A / cm. 2 -0.5A / cm 2 Etch for 10-15 minutes at 15℃-30℃.

[0010] In an optional embodiment, the introduced sodium-loving active ion is selected from at least one of Sn, Zn, and Bi.

[0011] In an optional embodiment, the porous material is placed in an ion implantation device, and the implantation voltage is controlled at 30kV-50kV, with an implantation dose of 1×10⁻⁶. 15 ions / cm 2 –1×10 16 ions / cm 2 .

[0012] In an optional embodiment, the carbon layer preparation process includes: placing a sodium-loving material in a CVD reaction chamber, introducing an inert gas to purge the air, heating to 550°C-600°C, and introducing a carbon source gas and a control gas for deposition. The carbon source gas is selected from at least one of acetylene, methane, ethylene, and propane; The control gas is selected from at least one of hydrogen and ammonia; The volume ratio of carbon source gas to control gas is 1:(2-4); And / or, the preparation process of the aluminum substrate includes: cleaning and degreasing the aluminum foil, removing the surface oxide film, and then oxidizing it in an oxygen-containing atmosphere to form an oxide film.

[0013] In an optional implementation, a segmented deposition method is used to form the carbon layer: In the first stage, the flow rate of the carbon source gas was controlled at 45 sccm-55 sccm, the flow rate of the regulating gas was controlled at 130 sccm-180 sccm, and the deposition time was 10 min-20 min. In the second stage, the flow rate of the carbon source gas was controlled at 25 sccm-35 sccm, the flow rate of the regulating gas was controlled at 180 sccm-220 sccm, and the deposition time was 25 min-35 min. And / or, after the carbon layer has been deposited, it is cleaned and dried.

[0014] Secondly, the present invention provides a porous aluminum current collector, which is prepared by any of the porous aluminum current collector preparation methods described in the foregoing embodiments; Preferably, the dyne value of the porous aluminum current collector is 70-80 mN / m.

[0015] Thirdly, the present invention provides a negative electrode sheet comprising the porous aluminum current collector of the aforementioned embodiments; Preferably, a negative electrode coating is attached to the porous aluminum current collector, and by mass fraction, the negative electrode coating contains 89.5%-94.5% negative electrode active material, 3%-5% porous filler, 1.0%-2.0% conductive agent and 1.5%-3.5% binder; The negative electrode active material is selected from at least one of hard carbon and graphite; The porous filler is selected from at least one of ceramics and molecular sieves; The conductive agent is selected from at least one of conductive carbon black, conductive graphite, and carbon nanotubes; The adhesive is selected from at least one of sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyacrylic acid.

[0016] Fourthly, the present invention provides a sodium battery, including the negative electrode sheet of the aforementioned embodiments.

[0017] The present invention has the following beneficial effects: By modifying the surface of the aluminum substrate, preparing porous materials through electrochemical etching, and then introducing sodium-loving active ions, a three-dimensional porous structure with high surface energy is obtained. Finally, a thin layer of active material coating (carbon layer) with both ion-conducting and electronic properties is coated. This can reduce the amount of negative electrode used, reduce costs, and increase energy density, while avoiding fatal defects such as dendrites and interface instability in the non-negative electrode system, thus achieving a balance between performance and safety. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0019] To address the critical defects of anode-free sodium-ion batteries, such as dendrite formation and interfacial instability, this invention optimizes the preparation process of aluminum current collectors. By modifying the surface to form a three-dimensional porous structure with high surface energy, and finally coating it with a thin layer of active material that has both ion-conducting and electronic properties, this invention can reduce the amount of anode material used, thereby lowering costs and increasing energy density, while avoiding the critical defects of anode-free systems, such as dendrite formation and interfacial instability, thus achieving a balance between performance and safety.

[0020] This invention provides a method for preparing a porous aluminum current collector, comprising the following steps: S1, providing aluminum substrate Aluminum foil with an oxide layer is used as the aluminum substrate, which can be commercially available or prepared in-house.

[0021] In some embodiments, the aluminum foil is cleaned and degreased, and the natural oxide film is removed using dilute acid or dilute alkali. Then, oxidation is performed in an oxygen-containing atmosphere to form a dense oxide film. The oxide film naturally present on the aluminum foil surface is loose and porous with poor surface uniformity. After removing the natural oxide film, a dense oxide film is prepared using conventional oxidation processes.

[0022] Specifically, cleaning can be done with water, and degreasing can be done with anhydrous ethanol.

[0023] S2, Electrochemical Etching An aluminum substrate is used as the anode for oxidation etching, followed by reduction etching with reverse current to obtain a porous material. Oxidation etching forms a preliminary micro-nano porous structure on the aluminum foil surface and introduces -OH active functional groups. Reduction etching removes the residual oxide layer on the surface, making the porous structure more uniform and activating sodium-loving active sites on the aluminum foil surface.

[0024] In some embodiments, the electrolyte used for oxidation etching contains 0.10-0.20 mol / L sodium sulfate and 0.03-0.08 mol / L boric acid. The cathode used is selected from at least one of graphite, Pt / C, and titanium; the cathode can be any one or more of these. During the oxidation etching process, a constant current of 0.5 A / cm is maintained. 2 -1.0A / cm 2Etching was performed at 15℃-30℃ for 20-30 minutes. During the oxidative etching process, Al on the anode surface was oxidized, and oxygen-containing functional groups were introduced.

[0025] Specifically, the constant current applied during oxidation etching can be 0.5 A / cm. 2 0.6A / cm 2 0.7A / cm 2 0.8A / cm 2 0.9A / cm 2 1.0A / cm 2 The etching temperature can be room temperature, specifically 15℃, 20℃, 25℃, 30℃, etc.; the etching time can be 20min, 23min, 25min, 28min, 30min, etc.

[0026] In some embodiments, during the reduction etching process, a constant current is applied in reverse while keeping the electrodes unchanged, and the constant current is controlled to be 0.3 A / cm. 2 -0.5A / cm 2 Etching is performed at 15℃-30℃ for 10-15 minutes. During the reduction etching process, unstable oxide layer fragments, residual loose alumina, and localized over-oxidation products on the aluminum substrate surface are removed, while the surface sodium-loving active sites are activated.

[0027] Specifically, during the reduction etching process, the constant current can be controlled at 0.3 A / cm. 2 0.4A / cm 2 0.5A / cm 2 The etching temperature can be room temperature, specifically 15℃, 20℃, 25℃, 30℃, etc.; the etching time can be 10min, 11min, 12min, 13min, 14min, 15min, etc.

[0028] S3, Introduction of sodium-loving active ions Sodium-loving active ions are implanted into the surface of porous materials via ion implantation, allowing sodium-loving elements to be uniformly doped into the micro-nano structure of aluminum foil surface, forming sodium-loving active sites, and thus preparing sodium-loving materials.

[0029] In some embodiments, the introduced sodium-loving active ion is selected from at least one of Sn, Zn, and Bi, and the sodium-loving active ion can be any one or more of the above. By introducing the above-mentioned sodium-loving active ions, sodium-loving active sites can be formed on the surface of porous materials, which is beneficial to improving battery performance.

[0030] In practice, the porous material is placed in an ion implantation device, and the implantation voltage is controlled between 30kV and 50kV, such as 30kV, 33kV, 35kV, 38kV, 40kV, 43kV, 45kV, 48kV, and 50kV. The implantation dose is 1×10⁻⁶. 15 ions / cm 2 –1×10 16 ions / cm 2 For example, it can be 1×10 15 ions / cm 2 2×10 15 ions / cm 2 3×10 15 ions / cm 2 4×10 15 ions / cm 2 5×10 15 ions / cm 2 6×10 15 ions / cm 2 7×10 15 ions / cm 2 8×10 15 ions / cm 2 9×10 15 ions / cm 2 1×10 16 ions / cm 2 wait.

[0031] S4, Carbon Layer Preparation A carbon layer is formed on the surface of a sodium-loving material, and the method for preparing the carbon layer is not limited.

[0032] In some embodiments, a gradient chemical vapor deposition (CVD) method is used to prepare the carbon layer. The sodium-loving material is placed in a CVD reaction chamber, an inert gas is introduced to purge the air, and the temperature is raised to 550°C-600°C. A carbon source gas and a control gas are then introduced for deposition. Specifically, the type of inert gas is not limited, and argon can be used. The deposition temperature can be 550°C, 555°C, 560°C, 565°C, 570°C, 575°C, 580°C, 585°C, 590°C, 600°C, etc.

[0033] In some embodiments, the carbon source gas is selected from at least one of acetylene, methane, ethylene, and propane, and the carbon source gas can be any one or more of the above. The control gas is selected from at least one of hydrogen and ammonia, and the control gas can be any one or more of the above. The volume ratio of the carbon source gas to the control gas is 1:(2-4), such as 1:2, 1:3, 1:4, etc.

[0034] Furthermore, a segmented deposition method was used to form the carbon layer: In the first stage, the flow rate of the carbon source gas was controlled at 45 sccm-55 sccm, the flow rate of the control gas was controlled at 130 sccm-180 sccm, and the deposition time was 10 min-20 min, resulting in the growth of a dense underlayer; in the second stage, the flow rate of the carbon source gas was controlled at 25 sccm-35 sccm, the flow rate of the control gas was controlled at 180 sccm-220 sccm, and the deposition time was 25 min-35 min, resulting in the growth of a porous surface layer. After the reaction was completed, the temperature was lowered under argon protection, followed by cleaning and drying to obtain a high-dyne coated aluminum foil (dyne value ≥70 mN / m).

[0035] Specifically, in the first stage, the flow rate of the carbon source gas can be 45 sccm, 48 sccm, 50 sccm, 53 sccm, 55 sccm, etc.; the flow rate of the control gas can be 130 sccm, 140 sccm, 150 sccm, 160 sccm, 170 sccm, 180 sccm, etc.; and the deposition time can be 10 min, 13 min, 15 min, 18 min, 20 min, etc.

[0036] Specifically, in the second stage, the flow rate of the carbon source gas can be 25 sccm, 28 sccm, 30 sccm, 33 sccm, 35 sccm, etc.; the flow rate of the control gas can be 180 sccm, 190 sccm, 200 sccm, 210 sccm, 220 sccm, etc.; and the deposition time can be 25 min, 28 min, 30 min, 33 min, 35 min, etc.

[0037] The method for preparing porous aluminum current collectors provided in this invention attempts to modify the surface of the current collector to form a three-dimensional porous structure with high surface energy. This improves the current collector's sodium affinity and adhesion, optimizes the coating process, and addresses anomalies. Subsequently, an active layer with both electron and ion conduction properties promotes uniform sodium deposition on the current collector and absorbs gases generated during circulation, mitigating volume expansion. Finally, a thinner active material coating reduces the amount of negative electrode used, lowering costs and increasing energy density, while avoiding fatal defects such as dendrites and interfacial instability in negative electrode-free systems, achieving a balance between performance and safety.

[0038] This invention also provides a porous aluminum current collector, which is prepared by the method provided in this invention. The prepared porous aluminum current collector has a dyne value ≥70mN / m, such as 70-80.

[0039] This invention provides a negative electrode sheet, including a porous aluminum current collector provided in this invention. A negative electrode coating may be attached to the porous aluminum current collector, and the composition of the negative electrode coating is not limited.

[0040] In some embodiments, the negative electrode coating contains, by mass fraction, 89.5%-94.5% negative electrode active material, 3%-5% porous filler, 1.0%-2.0% conductive agent, and 1.5%-3.5% binder. The negative electrode active material is selected from at least one of hard carbon and graphite, and can be any one or more of the above. The porous filler is selected from at least one of ceramics and molecular sieves, and can be any one or more of the above. The conductive agent is selected from at least one of conductive carbon black, conductive graphite, and carbon nanotubes, and can be any one or more of the above. The binder is selected from at least one of sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and polyacrylic acid (PAA), and can be any one or more of the above.

[0041] The preparation process of the negative electrode sheet is as follows: After the negative electrode active material, porous filler, conductive agent and binder are mixed evenly, they are coated on the surface of the porous aluminum current collector and baked to obtain the negative electrode sheet.

[0042] This invention also provides a sodium battery, including the negative electrode sheet provided in this embodiment, and may further include a positive electrode sheet, a separator, an electrolyte, etc. Improvements to the negative electrode sheet are beneficial for enhancing battery performance and safety.

[0043] Specifically, the positive electrode sheet includes a positive current collector and a positive active coating. The positive active coating includes positive electrode material, conductive agent, binder, etc. The type of positive electrode material in the positive active coating is not limited, and can be sodium iron phosphate, Prussian blue, layered oxides, etc. The positive electrode material, conductive agent, binder, etc. are mixed evenly in NMP and then coated onto the surface of conventional aluminum foil / copper foil / carbon-coated aluminum foil / carbon-coated copper foil, and then baked to obtain the positive electrode sheet.

[0044] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0045] Example 1 1. Surface modification of aluminum foil (1) The surface of the aluminum foil with a thickness of 12 micrometers was cleaned and degreased with deionized water / anhydrous ethanol. Then, the natural oxide film was removed by treatment with a 5% dilute acetic acid solution. Subsequently, it was oxidized in an oxygen atmosphere (temperature 350℃, oxidation time 0.5h) to form a dense oxide film.

[0046] (2) Electrochemical etching: The aluminum foil obtained in step (1) was used as the anode and graphite as the cathode, and placed in an electrolyte with the following composition: 0.15 mol / L sodium sulfate + 0.05 mol / L boric acid. A constant current (0.8 A / cm²) was applied, and oxidation etching was performed at room temperature (25℃) for 25 min; keeping the electrodes unchanged, a constant current (0.4 A / cm²) was applied in reverse. 2 ), reduce etching for 13 minutes.

[0047] (3) Introduction of sodium-loving active ions: The electrochemically etched aluminum foil is placed in an ion implantation device, and a gas source (high-purity Ar) is introduced. The high-purity Sn metal target is ionized into plasma in the device. The sodium-loving ion implantation voltage is controlled at 40kV and the implantation dose is 5×10 15 ions / cm 2 .

[0048] (4) Gradient chemical vapor deposition: The aluminum foil treated in step (3) is placed in the CVD reaction chamber, and argon gas is introduced to purge the air. The temperature is raised to 580°C at 8°C / min. At this time, a mixture of acetylene and hydrogen gas (volume ratio 1:3) is introduced. A segmented deposition process is adopted. Phase 1 (0-15 minutes): Acetylene flow rate 50 sccm, hydrogen flow rate 150 sccm, grow dense sublayer; Second stage (15-45 minutes): Acetylene flow rate 30 sccm, hydrogen flow rate 200 sccm, to grow a porous surface layer. After the reaction is complete, the temperature is lowered under argon protection.

[0049] (5) Clean and dry at low temperature (50℃, 2h) to obtain dyne-coated aluminum foil (dyne value ≥70mN / m).

[0050] 2. Preparation of negative electrode sheet The active material (hard carbon), molecular sieve, conductive agent (conductive graphite), and binder (CMC) were mixed evenly in a mass ratio of 92.0:4.0:1.5:2.5, and then coated onto both sides of the current collector prepared in this embodiment (double-sided density of 7.8 mg / cm³). 2 After baking, a negative electrode sheet is obtained.

[0051] 3. Preparation of positive electrode sheet The positive electrode material (sodium iron phosphate), conductive agent (conductive carbon black), and binder (PVDF) were mixed in a mass ratio of 95.0:2.5:2.5. After being thoroughly mixed in NMP, the mixture was coated onto both sides of a conventional aluminum foil (double-sided density of 36 mg / cm³). 2 After baking, a positive electrode sheet is obtained.

[0052] 4. Sodium battery preparation The positive and negative electrode sheets prepared above are stacked in a Z-shape with the electrolyte (14% sodium hexafluorosulfate + 86% G2 (diethylene glycol dimethyl ether)) and the separator (PP / PE) to form a battery.

[0053] 5. Electrical performance testing The battery underwent its first coulombic efficiency, cycle, and storage gas production tests in a temperature-controlled chamber to evaluate its performance.

[0054] Example 2 The difference from Example 1 lies in the different conditions for surface modification of the aluminum foil, as detailed below: (1) Same as step (1) in Example 1.

[0055] (2) Electrochemical etching: The aluminum foil obtained in step (1) was used as the anode and graphite as the cathode, and placed in an electrolyte with the following composition: 0.15 mol / L sodium sulfate + 0.05 mol / L boric acid. A constant current (0.5 A / cm²) was applied, and oxidative etching was performed at room temperature for 30 min; keeping the electrodes unchanged, a constant current (0.3 A / cm²) was applied in reverse, and reduction etching was performed for 15 min.

[0056] (3) Introduction of sodium-loving active ions: The electrochemically etched aluminum foil is placed in an ion implantation device, and a gas source (as above) is introduced. The high-purity Sn metal target is ionized into plasma in the device. The sodium-loving ion implantation voltage is controlled at 30kV and the implantation dose is 1×10. 15 ions / cm 2 .

[0057] (4) Gradient chemical vapor deposition: The aluminum foil treated in step (3) is placed in the CVD reaction chamber, and argon gas is introduced to purge the air. The temperature is raised to 550°C at 8°C / min. At this time, a mixture of acetylene and hydrogen gas (volume ratio 1:2) is introduced. A segmented deposition process is adopted: Phase 1 (0-10 minutes): Acetylene flow rate 55 sccm, hydrogen flow rate 180 sccm, grow dense sublayer; Second stage (10-35 minutes): Acetylene flow rate 35 sccm, hydrogen flow rate 220 sccm, growing a porous surface layer. After the reaction is complete, the temperature is lowered under argon protection.

[0058] (5) Same as step (5) in Example 1.

[0059] Example 3 The difference from Example 1 lies in the different conditions for surface modification of the aluminum foil, as detailed below: (1) Same as step (1) in Example 1.

[0060] (2) Electrochemical etching: The aluminum foil obtained in step (1) was used as the anode and graphite as the cathode, and placed in an electrolyte with the following composition: 0.15 mol / L sodium sulfate + 0.05 mol / L boric acid. A constant current (1.0 A / cm²) was applied, and oxidative etching was performed at room temperature for 20 min; keeping the electrodes unchanged, a constant current (0.5 A / cm²) was applied in reverse, and reduction etching was performed for 10 min.

[0061] (3) Introduction of sodium-loving active ions: The electrochemically etched aluminum foil is placed in an ion implantation device, and a gas source (as above) is introduced. The high-purity Sn metal target is ionized into plasma in the device. The sodium-loving ion implantation voltage is controlled at 50kV and the implantation dose is 1×10⁻⁶. 16 ions / cm 2 .

[0062] (4) Gradient chemical vapor deposition: The aluminum foil treated in step (3) is placed in the CVD reaction chamber, and argon gas is introduced to purge the air. The temperature is raised to 600°C at 8°C / min. At this time, a mixture of acetylene and hydrogen gas (volume ratio 1:4) is introduced. A segmented deposition process is adopted: Phase 1 (0-20 minutes): Acetylene flow rate 45 sccm, hydrogen flow rate 130 sccm, growing a dense sublayer; Second stage (20-55 minutes): Acetylene flow rate 25 sccm, hydrogen flow rate 180 sccm, growing a porous surface layer. After the reaction is complete, the temperature is lowered under argon protection.

[0063] (5) Same as step (5) in Example 1.

[0064] Example 4 The only difference from Example 1 is that the constant current for oxidation etching is 0.3 A / cm², and the constant current for reduction etching is 0.1 A / cm².

[0065] Example 5 The only difference from Example 1 is that the constant current for oxidation etching is 1.5 A / cm², and the constant current for reduction etching is 1.0 A / cm².

[0066] Example 6 The only difference from Example 1 is that in step (3), the sodium-philic ion implantation voltage is controlled at 20 kV and the implantation dose is 0.3 × 10⁻⁶. 15 ions / cm 2 .

[0067] Example 7 The only difference from Example 1 is that in step (3), the sodium-philic ion implantation voltage is controlled at 70 kV and the implantation dose is 3 × 10⁻⁶ kV. 16 ions / cm 2 .

[0068] Comparative Example 1 The only difference from Example 1 is that steps (2) and (3) are omitted, and step (4) is performed directly.

[0069] Comparative Example 2 The only difference from Example 1 is that step (2) is not performed.

[0070] Comparative Example 3 The only difference from Example 1 is that step (3) is not performed.

[0071] Comparative Example 4 The only difference from Example 1 is that step (4) is omitted. Experimental Example 1 The performance of the batteries prepared in the test examples and comparative examples is shown in Table 1.

[0072] 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. Cycle life test: After the assembled battery is left to rest for 10 hours, it is charged to 3.5V at 0.5C constant current and constant voltage at room temperature of 25℃. After resting for 0.5 hours, it is discharged to 2.0V at 1C constant current. The cycle is repeated 100 times and the capacity retention rate is recorded. Volume change test: After the battery was formed and capacity tested, it was placed at room temperature (25°C) for 10 hours. The initial volume of the battery was measured by the water displacement method and recorded as V1. Then it was placed in a high-temperature room at 45°C for 7 days. After that, it was taken out and cooled to room temperature (25°C). The volume after storage was measured by the water displacement method and recorded as V2. The volume change rate after 7 days of storage at 45°C is ΔV=(V2-V1) / V1×100%.

[0073] Table 1. Performance of batteries prepared in the examples and comparative examples.

[0074] As can be seen from Table 1, by optimizing the surface treatment process of aluminum foil, the present invention can significantly improve the electrochemical performance of the battery and ensure the long-term cycle stability of the battery.

[0075] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a porous aluminum current collector, characterized in that, include: Provide aluminum substrate; Electrochemical etching: Oxidation etching is performed by applying current to the aluminum substrate as the anode, followed by reduction etching by applying current in reverse to obtain a porous material; Introducing sodium-loving active ions: Sodium-loving active ions are implanted into the surface of the porous material by ion implantation to obtain a sodium-loving material; Carbon layer preparation: A carbon layer is formed on the surface of the sodium-loving material.

2. The method for preparing porous aluminum current collector according to claim 1, characterized in that, During the oxidation etching process, the constant current is controlled at 0.5 A / cm. 2 -1.0A / cm 2 Etch at 15℃-30℃ for 20-30 minutes; And / or, the electrolyte used in the oxidation etching contains 0.10-0.20 mol / L sodium sulfate and 0.03-0.08 mol / L boric acid; And / or, in the oxidation etching process, the cathode used is selected from at least one of graphite, Pt / C and titanium.

3. The method for preparing porous aluminum current collector according to claim 1 or 2, characterized in that, During the reduction etching process, a constant current is applied in reverse while keeping the electrodes unchanged, and the constant current is controlled to be 0.3 A / cm. 2 -0.5A / cm 2 Etch for 10-15 minutes at 15℃-30℃.

4. The method for preparing porous aluminum current collector according to claim 1, characterized in that, The introduced sodium-loving active ion is selected from at least one of Sn, Zn and Bi.

5. The method for preparing a porous aluminum current collector according to claim 1 or 4, characterized in that, The porous material was placed in an ion implantation device, and the implantation voltage was controlled at 30kV-50kV, with an implantation dose of 1×10⁻⁶. 15 ions / cm 2 –1×10 16 ions / cm 2 .

6. The method for preparing porous aluminum current collector according to claim 1, characterized in that, The carbon layer preparation process includes: placing the sodium-loving material in a CVD reaction chamber, introducing an inert gas to purge the air, heating to 550℃-600℃, and introducing a carbon source gas and a control gas for deposition; The carbon source gas is selected from at least one of acetylene, methane, ethylene, and propane; The control gas is selected from at least one of hydrogen and ammonia; The volume ratio of the carbon source gas to the control gas is 1:(2-4). And / or, the preparation process of the aluminum substrate includes: cleaning and degreasing the aluminum foil, removing the surface oxide film, and then oxidizing it in an oxygen-containing atmosphere to form an oxide film.

7. The method for preparing porous aluminum current collector according to claim 6, characterized in that, Carbon layers are formed using a segmented deposition method: In the first stage, the flow rate of the carbon source gas is controlled at 45 sccm-55 sccm, the flow rate of the control gas is controlled at 130 sccm-180 sccm, and the deposition time is 10 min-20 min. In the second stage, the flow rate of the carbon source gas is controlled at 25 sccm-35 sccm, the flow rate of the control gas is controlled at 180 sccm-220 sccm, and the deposition time is 25 min-35 min. And / or, after the carbon layer has been deposited, it is cleaned and dried.

8. A porous aluminum current collector, characterized in that, The porous aluminum current collector is prepared by the method described in any one of claims 1-7; Preferably, the dyne value of the porous aluminum current collector is 70-80 mN / m.

9. A negative electrode sheet, characterized in that, Includes the porous aluminum current collector as described in claim 8; Preferably, the porous aluminum current collector is coated with a negative electrode coating, which, by mass fraction, contains 89.5%-94.5% negative electrode active material, 3%-5% porous filler, 1.0%-2.0% conductive agent, and 1.5%-3.5% binder; The negative electrode active material is selected from at least one of hard carbon and graphite; The porous filler is selected from at least one of ceramics and molecular sieves; The conductive agent is selected from at least one of conductive carbon black, conductive graphite, and carbon nanotubes; The adhesive is selected from at least one of sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyacrylic acid.

10. A sodium battery, characterized in that, Includes the negative electrode sheet as described in claim 9.

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