A method for preparing a molybdate conversion film self-supporting aluminum foil negative electrode
By generating a molybdate conversion film in situ on the surface of aluminum foil and combining it with electrochemical pre-lithiation technology, the problem of uneven pre-lithiation of aluminum foil was solved, achieving uniform lithiation and stable contact of the aluminum foil negative electrode, thus improving the cycle performance and safety of lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HARBIN UNIV OF SCI & TECH
- Filing Date
- 2023-05-20
- Publication Date
- 2026-04-28
AI Technical Summary
The aluminum foil was poorly pre-lithiated, with a small lithiation area, and the aluminum foil surface was not fully pre-lithiated, resulting in rapid capacity decay and insufficient contact area of the aluminum foil anode during cycling.
By generating a molybdate conversion film in situ on the surface of aluminum foil and combining it with electrochemical pre-lithiation technology, an artificial SEI film is formed, which stabilizes the interface between the aluminum foil and the electrolyte, limits volume expansion, and uniformly distributes the lithiation layer on the surface of the aluminum foil.
It improves the electrolyte wettability and contact area on the aluminum foil surface, uniformly distributes the lithium layer, avoids stress concentration, and enhances the cycle performance and safety performance of lithium-ion batteries.
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Figure CN116646479B_ABST
Abstract
Description
[0001] A method for preparing a self-supporting aluminum foil anode with molybdate conversion film Technical Field
[0002] This invention belongs to the field of lithium-free anode full batteries, and particularly relates to a method for preparing a molybdate conversion film self-supporting aluminum foil anode. Background Technology
[0003] As an alloyed anode material, metallic aluminum exhibits a high lithium storage specific capacity, with a theoretical specific capacity approximately three times that of LiC6, and a low electrochemical potential (relative to Li). + With its characteristic of Li (approximately 0.2-0.45 V), aluminum foil is an ideal choice for next-generation high-energy-density rechargeable batteries. However, when aluminum foil is used as the negative electrode, its oxide layer undergoes irreversible lithiation during cycling, consuming lithium to form Li. x AlO y This leads to rapid capacity decay of the aluminum foil. Controllable electrochemical pre-lithiation technology can compensate for irreversible lithium consumption and regulate the alloying sites in the full cell. In the full cell, the pre-lithiation region continuously supplies lithium during the dealloying process to compensate for irreversible lithium loss during alloying. The alloying process preferentially alloys the unreacted Al2O3 surface layer along the rolling direction of the aluminum foil until the entire surface is covered with Li. x AlO y Coverage. This lithiation behavior avoids severe stress concentration during alloying, preventing foil perforation and shattering, thus enabling commercial aluminum foil to be successfully used as a single-material anode. The contact area between the electrode and the electrolyte also changes with the amount of electrolyte added and the hydrophilicity of the electrode surface. A higher contact area between the electrode and the electrolyte can effectively improve the battery's cycle performance. By generating a molybdate conversion film in situ on the aluminum foil surface, the hydrophilicity of the aluminum foil surface can be effectively improved, thereby increasing the contact area. Therefore, this patent application utilizes a method for preparing a self-supporting aluminum foil anode with a molybdate conversion film to improve the cycle performance and safety performance of lithium-ion batteries. Summary of the Invention
[0004] The purpose of this invention is to solve the problem of poor pre-lithiation state of aluminum foil and small lithiation area, which fails to achieve comprehensive pre-lithiation of the aluminum foil surface, and to provide a method for preparing a self-supporting aluminum foil anode with molybdate conversion film.
[0005] The method for preparing a self-supporting aluminum foil negative electrode with molybdate conversion film according to the present invention is carried out according to the following steps:
[0006] I. Pretreatment of Aluminum Foil
[0007] After polishing the rough surface of the aluminum foil to a certain thickness, it is placed in an alkaline solution for 3-10 minutes, rinsed several times with distilled water, left to stand at room temperature for 18-24 hours, and then pressed into a circular aluminum foil with a radius of 7-10 mm using a tablet press for later use.
[0008] II. Preparation of molybdate conversion membranes
[0009] The pretreated aluminum foil is placed in a molybdate solution and left to stand at 40-60 ℃ for 3-5 min. It is then rinsed with distilled water 3-5 times and left to stand at 60-80 ℃ for 2-5 h to generate a molybdate conversion film in situ, thus obtaining a self-supporting aluminum foil with a molybdate conversion film.
[0010] III. Pre-lithiated molybdate conversion membrane self-supporting aluminum foil anode
[0011] In an argon-atmospheric glove box, assemble the coin cell in the following order: positive electrode shell, gasket, self-supporting aluminum foil of molybdate conversion film obtained in step two, electrolyte, single-layer PP separator, lithium sheet, and negative electrode shell. Seal the assembly with a sealing machine. After assembly, let the battery stand at 40-80 ℃ for 1-4 h. Then discharge the battery for 24-48 h at 100-150 µA·cm. -2 Discharge is performed at a current density. After the discharge is completed, the molybdate conversion film formed in situ reacts on the surface of the aluminum foil to generate an artificial SEI film, which stabilizes the interface between the aluminum foil and the electrolyte and limits the volume expansion of the aluminum foil. The aluminum foil is then removed to obtain the pre-lithiated molybdate conversion film self-supporting aluminum foil negative electrode.
[0012] This invention includes the following gain effects:
[0013] First, the aluminum foil is pretreated by preparing an alkaline solution to remove residual oil stains and contaminants from the surface of the aluminum foil, thereby increasing the hydrophilicity of the aluminum foil surface. This results in more uniform contact between the electrolyte and the aluminum foil during the electrochemical pre-lithiation process, and a more uniform lithiation nucleation process.
[0014] Secondly, the poor electrolyte wettability of the aluminum foil surface will result in incomplete contact between the aluminum foil and the electrolyte, leading to unreacted areas on the aluminum foil surface during the pre-lithiation stage. The in-situ formation of the molybdate conversion film effectively improves the electrolyte wettability of the aluminum foil surface and increases the contact area between the aluminum foil and the electrolyte, allowing the aluminum foil surface to fully react during the pre-lithiation stage. The in-situ formed molybdate conversion film reacts on the aluminum foil surface to generate substances such as LiF and Li3N, forming an artificial SEI film, as shown in the chemical reaction equations (1)-(3). The formation of molybdate on the aluminum foil surface during the reaction makes the aluminum foil surface rougher, reducing the surface energy of the aluminum foil surface. The metal oxides on the aluminum foil surface, as well as MoO3 and MoO2, are also affected. xIt also helps to increase the electrolyte wettability of the self-supporting aluminum foil of the molybdate conversion film, while the adhesion of this film also limits the volume expansion of the aluminum foil and stabilizes the interface between it and the electrolyte.
[0015]
[0016]
[0017]
[0018] Finally, this invention obtains a lithium-aluminum alloy by pre-lithiating aluminum foil, which serves as the negative electrode material for lithium-ion batteries. The pre-lithiated side of the aluminum foil is the lithium storage active layer, and the reverse side of the pre-lithiated aluminum foil is the current collector. By adopting an in-situ generation method for the negative electrode, the negative electrode and the current collector are integrated into one. Compared with traditional lithium-ion batteries, the structure is simpler, lighter, and the production cost is reduced. Through electrochemical pre-lithiation, the lithiation layer can be generated in situ on the surface of the aluminum foil, making the crystal nuclei more ordered and controllable, and the lithiation is more evenly distributed on the surface of the aluminum foil. This avoids stress concentration that could cause the aluminum foil to shatter, and also preserves part of the aluminum foil substrate as the current collector.
[0019]
[0020] Attached Figure Description
[0021] Figure 1 Optical image of pre-lithiated aluminum foil in Comparative Example 1, which is a method for preparing a self-supporting aluminum foil anode with molybdate conversion film.
[0022] Figure 2 Example 2 of a method for preparing a self-supporting aluminum foil anode with molybdate conversion film: Pre-lithiated aluminum foil
[0023] Optical diagram;
[0024] Figure 3 XRD pattern of pre-lithiated aluminum foil in Comparative Example 1, which is a method for preparing a self-supporting aluminum foil anode with molybdate conversion film.
[0025] Figure 4 XRD pattern of pre-lithiated aluminum foil in Example 1 of a method for preparing a self-supporting aluminum foil anode with molybdate conversion film;
[0026] Figure 5 This is a 2000x SEM image of the aluminum foil without pre-lithiation, representing a method for preparing a self-supporting aluminum foil anode with a molybdate conversion film.
[0027] Figure 6 This is a 2000x SEM image of the pre-lithiated aluminum foil in Comparative Example 1, which is a method for preparing a self-supporting aluminum foil anode with a molybdate conversion film.
[0028] Figure 7 This is a 2000x SEM image of the pre-lithiated aluminum foil from Example 2 of a method for preparing a self-supporting aluminum foil anode with a molybdate conversion film.
[0029] Figure 8 This is a pre-lithiation voltage-current curve of a method for preparing a self-supporting aluminum foil anode with molybdate conversion film.
[0030] Figure 9 Comparative Example 1 and Example 2 show the first charge-discharge capacity-voltage curves of lithium-ion batteries as a method for preparing a self-supporting aluminum foil anode with molybdate conversion film.
[0031] Figure 10 The charge-discharge capacity-voltage curves of lithium-ion batteries after 50 cycles are shown in Comparative Example 1 and Example 2, which are methods for preparing self-supporting aluminum foil anodes with molybdate conversion films.
[0032] Figure 11 Comparative Example 1 and Example 1 show the first charge-discharge capacity-voltage curves of lithium-ion batteries for a method of preparing a self-supporting aluminum foil anode with molybdate conversion film.
[0033] Figure 12 Comparative Example 1 and Example 1: Lithium-ion batteries after 90 cycles of charge-discharge capacity-voltage curves after a method for preparing a molybdate conversion film self-supporting aluminum foil negative electrode.
[0034] Figure 13 This is a charge-discharge cycle curve of a lithium-ion battery at 0.1C, used in a method for preparing a self-supporting aluminum foil anode with a molybdate conversion film, as shown in Comparative Example 1.
[0035] Figure 14 This is a charge-discharge cycle curve of a lithium-ion battery at 0.1C in Example 1 of a method for preparing a self-supporting aluminum foil anode with a molybdate conversion film.
[0036] Figure 15 The specific energy cycling curve of a lithium-ion battery is shown in Comparative Example 1, which is a method for preparing a self-supporting aluminum foil anode with a molybdate conversion film.
[0037] Figure 16 A lithium-ion battery specific energy cycling curve for Example 1 of a method for preparing a molybdate conversion film self-supporting aluminum foil anode;
[0038] Figure 17 EIS images of lithium-ion batteries from Comparative Example 1 and Example 2, representing a method for preparing a self-supporting aluminum foil anode with a molybdate conversion film. Detailed Implementation
[0039] The present invention will be further described below with reference to the preferred embodiments, but the scope of protection of the present invention is not limited to the following embodiments.
[0040] Table 1-1 Reagents used in the experiment
[0041] Reagent Name Chemical formula or abbreviation index Manufacturer polyvinylidene fluoride PVDF Battery level Arkema (Guangzhou) Chemical Co., Ltd. N,N-Dimethylformamide DMF Analytical Pure Tianjin Tianli Chemical Reagent Co., Ltd. Lithium iron phosphate <![CDATA[LiFePO4]]> Battery level Taiyuan City Yingze District Lizhiyuan Battery Sales Department Acetylene black AB Battery level Shenzhen Pengxiang Yunda Machinery Technology Co., Ltd. N-Methylpyrrolidone NMP Analytical Pure Tianjin Guangfu Fine Chemical Research Institute Sodium silicate <![CDATA[Na2SiO3]]> Analytical Pure Tianjin Tianli Chemical Reagent Co., Ltd. Sodium phosphate <![CDATA[Na3PO4]]> Analytical Pure Tianjin Tianli Chemical Reagent Co., Ltd. Sodium carbonate <![CDATA[Na2CO3]]> Analytical Pure Tianjin Tianli Chemical Reagent Co., Ltd. Sodium fluoride NaF Analytical Pure Tianjin Tianli Chemical Reagent Co., Ltd. ethanol <![CDATA[CH3CH2OH]]> Analytical Pure Tianjin Tianli Chemical Reagent Co., Ltd. Lithium ammonium molybdate tetrahydrate tartrate phosphoric acid <![CDATA[Li(NH4)6MoO 24 ·4H2OC4H6O6H3PO4]]> 99.99% analytical purity Suzhou Duoduo Chemical Technology Co., Ltd. BASF Chemical Co., Ltd. BASF Chemical Co., Ltd. BASF Chemical Co., Ltd.
[0042] Table 1-2 List of Instruments Used in the Experiment
[0043] Instrument Name model factory Analytical balance FC-204 Shanghai Jingke Balance Magnetic stirrer CL-200 Gongyi Yuhua Instrument Co., Ltd. Vacuum drying oven ZK-82BB Shanghai Experimental Instrument Factory Co., Ltd. Button battery sealing machine MSK-110 Shenzhen Kejing Zhida Technology Co., Ltd. Electrode punching machine MSK-T10 Shenzhen Kejing Zhida Technology Co., Ltd. LAND Battery Testing System CT2001A Wuhan Jinno Electronics Co., Ltd. X-ray diffraction instrument X'Pert PRO Panaco Netherlands Electrochemical workstation CHI760E Shanghai Chenhua Instrument Co., Ltd. Scanning electron microscope FEI sirion200 FEI Company Vacuum glove box ZKX Nanjing University Instrument Factory
[0044] Comparative Example 1: A method for preparing a molybdate conversion film self-supporting aluminum foil negative electrode according to this embodiment is carried out according to the following steps:
[0045] I. Pretreatment of Aluminum Foil
[0046] A 100 µm thick aluminum foil was roughened and polished to a bright finish, then placed in a solution with a concentration of 0.12 mol·L⁻¹. -1 Na3PO4, 0.12 mol·L -1 Na₂SiO₃, 0.12 mol·L⁻¹ -1 Na2CO3 and 0.24 mol·L -1 The solution was treated in a NaF mixed alkaline solution for 3 min, rinsed 10 times with distilled water, air-dried at room temperature for 24 h, and then pressed into circular aluminum foil with a radius of 7 mm using a tablet press for later use.
[0047] II. Preparation of molybdate conversion membranes
[0048] The pretreated aluminum foil was placed in 0.005 mol·L⁻¹ -1 (NH4)6MoO 24 ·4H₂O, 0.05 mol·L - 1 H3PO4, 0.03 mol·L -1 C4H6O6, 0.2 mol·L -1 In a NaF molybdate solution, the mixture is allowed to stand at 50 °C for 5 min, rinsed three times with distilled water, and allowed to stand at 60 °C for 2 h to form a molybdate conversion film in situ, thus obtaining a self-supporting aluminum foil with a molybdate conversion film.
[0049] III. Pre-lithiated molybdate conversion membrane self-supporting aluminum foil anode
[0050] In an argon-atmospheric glove box, coin cells were assembled in the following order: positive electrode shell, gasket, self-supporting aluminum foil of molybdate conversion film obtained in step two, 200 µL 1.0 M LiPF6, EC:EMC:DMC=1:1:1 Vol% lithium-ion electrolyte, single-layer Celgard 2500PP separator, lithium sheet, and negative electrode shell. The assembly was completed by sealing the cells with a sealing machine. After assembly, the cells were allowed to stand at 40 °C for 1 h, and then discharged for 39 h at 150 µA·cm⁻¹. -2 Discharge at a current density. After discharge, the molybdate conversion film formed in situ reacts on the surface of the aluminum foil to generate an artificial SEI film, which stabilizes the interface between the aluminum foil and the electrolyte, restricts the volume expansion of the aluminum foil, and the aluminum foil is removed to obtain the pre-lithiated aluminum foil.
[0051] IV. Preparation of Lithium-ion Battery Cathode and Battery Assembly
[0052] Lithium iron phosphate, conductive agent acetylene black, and polyvinylidene fluoride were mixed in a mass ratio of 7:2:1 and uniformly dispersed in N-dimethylpyrrolidone. The mixture was stirred at room temperature for 16 h. The resulting slurry was coated onto aluminum foil and vacuum dried at 80 °C for 24 h. After cooling to room temperature, a lithium iron phosphate cathode was obtained. In an argon-atmosphere glove box, a coin cell cathode shell, a lithium iron phosphate cathode, 200 µL of 1.0 M LiPF6, EC:EMC:DMC=1:1:1 Vol% lithium-ion electrolyte, a single-layer Celgard 2500PP separator, a pre-lithiated aluminum foil, and a coin cell anode shell were assembled into a coin cell. The assembly was completed by sealing the coin cell with a sealing machine.
[0053] Example 1: After the aluminum foil pretreatment in step one is completed, step three is directly performed to assemble a pre-lithiated battery for discharge. Other steps are the same as in Comparative Example 1.
[0054] Example 2: The discharge current density in the pre-lithiation stage of step two is 100 µA·cm. -2 The other steps are the same as in Comparative Example 1.
[0055] Performance tests were performed on the above comparative examples and embodiments:
[0056] 1) X-ray diffraction (XRD) test. The composition of the pre-lithiated aluminum foil was analyzed by X-ray diffraction test. The instrument model was X'Pert PRO, the target material was Cu target, the X-ray was CuKα rays, the wavelength was 1.5428 Å, the current was 40 mA, the voltage was 45 kV, and the scanning angle was 20-80°. Before the test, the dry sample was placed on a glass slide and then placed on the sample stage for testing.
[0057] 2) Scanning Electron Microscopy (SEM) Testing. The surface morphology of aluminum foil, pre-lithiated aluminum foil, and lithium sheets was observed using a scanning electron microscope (SEM). The instrument model was FEI sirion200, with an accelerating voltage of 0.2-30 kV and a resolution of 20 kV. The prepared samples were attached to the sample holder for testing.
[0058] 3) Charge and discharge test. Charge and discharge tests are used to obtain many important parameters of the battery during cycling, such as charge / discharge specific capacity, charge / discharge efficiency, and voltage plateau. The instrument used is the LAND Battery Testing System CT2001A. Lithium-aluminum alloy batteries are assembled into lithium iron phosphate full cells for testing.
[0059] 4) Electrochemical impedance spectroscopy (EIS) test. Electrochemical impedance spectroscopy can be used to analyze the internal impedance of the electrode and the diffusion ability of ions, and directly reflect the conductivity of the negative electrode material. The instrument model is CHI760E, with a frequency of 0.01-100000 Hz. Lithium-aluminum alloy is assembled into a lithium iron phosphate full cell for testing.
[0060] Figure 1 The optical image of the pre-lithiated aluminum foil in Comparative Example 1 shows a method for preparing a self-supporting aluminum foil anode with a molybdate conversion film. It can be seen that a dense and uniform alloy layer is generated in situ on the surface of the aluminum foil after electrochemical pre-lithiation.
[0061] Figure 2 The optical image of the pre-lithiated aluminum foil in Example 2 of a method for preparing a self-supporting aluminum foil anode with a molybdate conversion film shows that the low discharge current density during pre-lithiation results in a relatively insufficient distribution of the lithiation layer on the aluminum foil surface, indicating that 100 µA·cm -2 The discharge current density is relatively low.
[0062] Figure 3 The XRD pattern of the pre-lithiated aluminum foil in Comparative Example 1 is shown in the figure. This is part of a method for preparing a self-supporting aluminum foil anode with a molybdate conversion film. Figure 3 Comparison with the LiAl standard diffraction card revealed that the pre-lithiated aluminum foil corresponds to the (1 1 0), (2 2 0), (3 1 1), (3 3 1), (4 2 2), and (5 1 1) crystal planes of LiAl at 24°, 40°, 47°, 64°, 72°, and 77°, indicating that a LiAl alloy is grown on the surface of the aluminum foil.
[0063] Figure 4 The XRD pattern of the pre-lithiated aluminum foil in Example 2 of a method for preparing a self-supporting aluminum foil anode with molybdate conversion film is shown. After comparing the pattern with the standard diffraction cards of Al and LiAl, it was found that the characteristic peaks matched the crystal plane of Al, indicating that the lithiation effect was limited and most areas of the aluminum foil surface were not fully lithiated.
[0064] Effect of current density on pre-lithiation effect
[0065] Figure 5 This is a 2000x SEM image of an unlithiated aluminum foil used in a method for preparing a self-supporting aluminum foil anode with a molybdate conversion film. It can be seen that the surface of the prelithiated aluminum foil is relatively smooth.
[0066] Figure 6 Example 2 shows a 2000x SEM image of pre-lithiated aluminum foil, illustrating a method for preparing a self-supporting aluminum foil anode with a molybdate conversion film. Fine particles can be seen on the surface of the aluminum foil.
[0067] Figure 7 Comparative Example 1: 2000x SEM image of pre-lithiated aluminum foil, showing a method for preparing a self-supporting aluminum foil anode with molybdate conversion film. It can be seen that the particles on the aluminum foil surface are larger and more densely packed.
[0068] Figure 9 The first charge-discharge capacity-voltage curves of lithium-ion batteries in Comparative Example 1 and Example 2 are shown as a method for preparing a self-supporting aluminum foil anode with molybdate conversion film. It can be seen that the polarization voltage of the lithium-ion battery in Comparative Example 1 is lower, only 0.11 V, indicating that its pre-lithiation is more uniform, the degree of lithiation is higher, and the interface contact is better after assembly into a battery.
[0069] Figure 10 This is a charge-discharge capacity-voltage curve of lithium-ion batteries from Comparative Example 1 and Example 2 after 5 cycles, illustrating a method for preparing a self-supporting aluminum foil anode with a molybdate conversion film. The polarization voltage increases compared to the first cycle. The polarization voltage of the lithium-ion battery in Comparative Example 1 is 0.16 V, indicating that battery polarization intensifies after 50 cycles. The discharge current density during pre-lithiation is 100 µA·cm⁻¹. -2 The polarization voltage of the aluminum foil negative electrode cell is 150 µA·cm. -2 The larger aluminum foil indicates that the discharge current density during pre-lithiation was 150 µA·cm. -2 Lithification is more complete, and battery polarization is lower.
[0070] Figure 11 This is a method for preparing a self-supporting aluminum foil anode with a molybdate conversion film. The first charge-discharge capacity-voltage curves of lithium-ion batteries in Comparative Example 1 and Example 1 show that the charge-discharge capacity and polarization voltage of batteries with and without the molybdate conversion film aluminum foil anode are similar during the first charge-discharge.
[0071] Figure 12This is a charge-discharge capacity-voltage curve of lithium-ion batteries after 90 cycles for a method of preparing a self-supporting aluminum foil anode with a molybdate conversion film. After 90 cycles, the charge-discharge capacity of the battery with the aluminum foil anode and the battery without the molybdate conversion film is better maintained than that of the battery without the molybdate conversion film, and the polarization voltage is relatively lower. This indicates that the aluminum foil with the molybdate conversion film is more fully lithiated during the pre-lithiation process.
[0072] Figure 13 The figure shows the charge-discharge cycle curves of a lithium-ion battery at 0.1C for a method of preparing a self-supporting aluminum foil anode with molybdate conversion film. The charge-discharge specific capacity decreases with the increase of cycle number, while the efficiency remains at around 100%. This indicates that the self-supporting aluminum foil anode with molybdate conversion film still inevitably experiences volume expansion and lithium dendrite formation, but the lithiation is relatively sufficient and the cycle stability is relatively stable.
[0073] Figure 14 The image shows the charge-discharge cycle curves of a lithium-ion battery at 0.1C in Example 1 of a method for preparing a self-supporting aluminum foil anode with a molybdate conversion film. The charge-discharge specific capacity decreases with increasing cycle number. Compared to the self-supporting aluminum foil anode with a molybdate conversion film, the charge-discharge specific capacity decreases significantly, indicating that the lithiation of the self-supporting aluminum foil anode without a molybdate conversion film is relatively insufficient, and the cycling is less stable.
[0074] Figure 15 The image shows the specific energy cycling curve of a lithium-ion battery in Comparative Example 1, which is a method for preparing a self-supporting aluminum foil anode with a molybdate conversion film. The specific energy decreases with increasing cycle number, but the specific energy remains relatively stable during the charge and discharge process.
[0075] Figure 16 The image shows the specific energy cycling curve of a lithium-ion battery in Example 1 of a method for preparing a self-supporting aluminum foil anode with a molybdate conversion film. The specific energy decreases with increasing cycle number, and the specific energy decays relatively quickly and is unstable, indicating that the lithiation of the aluminum foil anode without the self-supporting molybdate conversion film is relatively insufficient.
[0076] Figure 17 The image shows the EIS plots of lithium-ion batteries from Comparative Example 1 and Example 2, illustrating a method for preparing a self-supporting aluminum foil anode with a molybdate conversion film. The impedance of the lithium-ion battery in Example 2 is significantly higher than that of the lithium-ion battery in Comparative Example 1, indicating a resistance of 150 µA·cm. -2 Pre-lithiation by discharging at a higher current density results in a more uniform distribution of lithiation regions on the aluminum foil surface, filling the entire foil. (100 µA·cm) -2 Discharging at high current density to pre-lithiate aluminum foil will result in some unlithiated areas on the surface, which reduces the contact area and worsens the conductivity.
Claims
1. A method for preparing a pre-lithiated molybdate conversion film self-supporting aluminum foil anode, characterized in that: The method is performed according to the following steps: I. Pretreatment of Aluminum Foil After polishing the rough surface of the aluminum foil of a certain thickness, it is placed in an alkaline solution for 3-10 minutes, rinsed with distilled water 8-10 times, left to stand at room temperature for 18-24 hours, and then pressed into a circular aluminum foil with a radius of 7-10 mm using a tablet press for later use. II. Preparation of molybdate conversion membranes The pretreated aluminum foil is placed in a molybdate solution and left to stand at 40-60 ℃ for 3-5 min. It is then rinsed with distilled water 3-5 times and left to stand at 60-80 ℃ for 2-5 h to generate a molybdate conversion film in situ, thus obtaining a self-supporting aluminum foil with molybdate conversion film. III. Pre-lithiated molybdate conversion membrane self-supporting aluminum foil anode In an argon-atmospheric glove box, assemble the coin cell in the following order: positive electrode shell, gasket, self-supporting aluminum foil of molybdate conversion film obtained in step two, electrolyte, single-layer PP separator, lithium sheet, and negative electrode shell. Seal the assembly with a sealing machine. After assembly, let the battery stand at 40-80 ℃ for 1-4 h. Then discharge the battery for 24-48 h at 100-150 µA·cm. -2 Discharge is performed at a current density. After the discharge is completed, the molybdate conversion film formed in situ reacts on the surface of the aluminum foil to generate an artificial SEI film, which stabilizes the interface between the aluminum foil and the electrolyte and limits the volume expansion of the aluminum foil. The aluminum foil is then removed to obtain the pre-lithiated molybdate conversion film self-supporting aluminum foil negative electrode.
2. The method according to claim 1, characterized in that... The aluminum foil thickness mentioned in step one is one of 25 µm, 50 µm, 75 µm and 100 µm.
3. The method according to claim 1, characterized in that... The solute in the alkaline solution described in step one is 0.1-0.2 mol·L⁻¹. -1 Na3PO4, 0.1-0.2 mol·L -1 Na₂SiO₃, 0.1-0.2 mol·L⁻¹ -1 Na2CO3 and 0.2-0.4 mol·L -1 NaF.
4. The method according to claim 1, characterized in that... The solute in the molybdate solution described in step two is 0.005-0.01 mol·L⁻¹. -1 (NH4)6MoO 24 ·4H₂O, 0.05-0.1 mol·L⁻¹ -1 H3PO4, 0.03-0.05 mol·L - 1 C4H6O6 and 0.2-0.5 mol·L -1 NaF.
5. The method according to claim 1, characterized in that... The electrolyte mentioned in step three is an electrolyte for lithium-sulfur batteries or an electrolyte for lithium-ion batteries.
6. The method according to claim 1, characterized in that... The volume of electrolyte mentioned in step three is 180-220 μL.
7. The method according to claim 1, characterized in that... The single-layer PP membrane mentioned in step three is one of Celgard 2400 membrane and Celgard 2500 membrane.
8. A battery is assembled using a pre-lithiated molybdate conversion membrane self-supporting aluminum foil negative electrode prepared according to claim 1.
9. The battery according to claim 8, characterized in that... The battery assembly method is as follows: Lithium iron phosphate, conductive agent acetylene black, and polyvinylidene fluoride were mixed in a mass ratio of 7:2:1-9:0.5:0.5 and uniformly dispersed in N-dimethylpyrrolidone. The mixture was stirred at room temperature for 10-16 h. The resulting slurry was coated onto aluminum foil and vacuum dried at 60-100 °C for 18-24 h. After cooling to room temperature, a lithium iron phosphate cathode was obtained. In a glove box under an argon atmosphere, a coin cell was assembled in sequence as follows: coin cell cathode shell, lithium iron phosphate cathode, 180-220 µL lithium-ion electrolyte, single-layer PP separator, pre-lithiated molybdate conversion membrane self-supporting aluminum foil anode, and coin cell anode shell. The assembly was completed by sealing the coin cell with a sealing machine.