Lithium metal electrode materials with hydrophobic artificial SEI films, their preparation and application

Abstract

This invention discloses a lithium metal electrode material with a hydrophobic artificial SEI film, its preparation, and its application, comprising the following steps: preparation of a fluorinated polyurethane dispersion: dispersing fluorinated polyurethane in an organic solvent to obtain a fluorinated polyurethane dispersion; coating the surface of a lithium metal substrate: coating the fluorinated polyurethane dispersion onto a lithium metal substrate and drying it to obtain the lithium metal electrode material with a hydrophobic artificial SEI film. Compared with other lithium metal modification methods, this lithium metal electrode material with a hydrophobic artificial SEI film exhibits a certain degree of hydrophobicity, enabling stable storage of the lithium metal electrode material under extreme conditions of humid air. Furthermore, this lithium metal electrode material with a hydrophobic artificial SEI film possesses excellent mechanical strength and also has fluorine-rich genes, enabling uniform deposition of lithium ions, inhibiting the growth of lithium dendrites, and achieving a long cycle life for the battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium metal battery technology, and particularly relates to a lithium metal electrode material with a hydrophobic artificial SEI film, its preparation and application. Background Technology

[0002] Lithium-ion batteries have profoundly impacted daily life, and the energy density of current lithium-ion batteries using graphite as the negative electrode is approaching their theoretical capacity, making it difficult to meet the increasingly demanding application requirements of portable electronic devices, electric vehicles, and large-scale energy storage. Among materials that can be used as negative electrodes for lithium batteries, metallic lithium stands out due to its extremely high theoretical energy density (3860 mAh g⁻¹). -1 With its extremely low electrochemical potential (3.04V relative to the standard hydrogen electrode), it is considered the best choice for the anode material of the next generation of high-energy lithium batteries (such as lithium-sulfur and lithium-air batteries).

[0003] Studies have shown that uneven ion flux distribution, volume variations, and SEI instability on the lithium metal surface can lead to uncontrolled lithium dendrite growth, low coulombic efficiency and lithium utilization, and even serious safety issues. More importantly, the industrial-scale application of lithium metal anodes is limited by the high cost of anhydrous manufacturing environments, requiring complete avoidance of any humid air exposure; otherwise, cycle performance and lifespan will significantly decrease, or even fail. This stringent anhydrous and oxygen-free assembly environment poses a challenge to its widespread practical application. Therefore, solving the safety and interface stability issues of lithium metal anodes is crucial for their industrialization.

[0004] Currently, methods for improving lithium metal anodes mainly include: electrolyte modification, application of 3D current collectors, application of solid electrolytes, and protection with artificial SEI films. Among these, the method of constructing an effective SEI film to protect lithium metal is the most widely used. For example, patent document CN107068971A introduces a stable SEI film by electrochemical pretreatment of the lithium anode; another example is patent document CN110289448A, which discloses a lithium metal anode with an artificially constructed SEI film. However, these methods do not fundamentally solve the problems of uneven lithium distribution during deposition, lithium dendrite growth, and the instability of lithium metal under extreme conditions of humid air, thus hindering the long-term development of lithium metal. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a lithium metal electrode material with a hydrophobic artificial SEI film, its preparation, and its application. This invention coats a lithium metal substrate with fluorine-modified polyurethane, fully utilizing the hydrophobic properties of the fluorine-modified polyurethane. A simple method is used to prepare a lithium metal electrode material with a hydrophobic artificial SEI film, achieving stable lithium metal under extreme conditions of humid air. Simultaneously, the fluorine-modified polyurethane, with its excellent mechanical properties, enables uniform lithium ion deposition due to the presence of fluorine-rich groups, thereby fundamentally inhibiting the growth of lithium dendrites.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for preparing a lithium metal electrode material with a hydrophobic artificial SEI film includes the following steps:

[0008] S1: Preparation of fluorinated polyurethane dispersion: Disperse fluorinated polyurethane in an organic solvent to obtain the fluorinated polyurethane dispersion;

[0009] S2: Coating of the surface of the lithium metal substrate: The fluorine-modified polyurethane dispersion is coated on the lithium metal substrate and dried to obtain the lithium metal electrode material with the hydrophobic artificial SEI film.

[0010] Preferably, the organic solvent in step S1 is anhydrous dichloromethane.

[0011] Preferably, in the fluorinated polyurethane dispersion of step S1, each 1g of fluorinated polyurethane is added to 25-50mL of anhydrous dichloromethane.

[0012] Preferably, in step S1, the dispersion is carried out by stirring dispersion and / or ultrasonic dispersion, wherein the stirring dispersion temperature is 30-60℃ and the stirring time is 10-24h.

[0013] Preferably, in step S2, the fluorinated polyurethane dispersion is spin-coated onto a lithium metal substrate, wherein the spin-coating speed is 800-2000 r / min, the acceleration is 200-500 r / min, and the spin-coating time is 5-30 min.

[0014] Preferably, in step S2, the drying temperature is 50-100℃ and the drying time is 6-24h.

[0015] Preferably, in step S1, the preparation steps of fluorinated polyurethane are as follows: 3-5g of polypropylene glycol and 1.6-2.8g of isophorone diisocyanate are added to a three-necked flask and reacted at 80-100℃ for 2-4h; then 1.02-3.05g of dimethylolpropionic acid and 2.1-2.7g of 1,4-butanediol are added sequentially, stannous octoate and dibutyltin dilaurate are added as catalysts, and a predetermined amount of acetone is added to adjust the viscosity of the reaction system; then 0.1-0.3ml of perfluorooctylpropanol is added for end-capping, and after end-capping is completed, 1.05-1.35ml of triethylamine is added for neutralization, followed by emulsification and distillation to remove acetone.

[0016] Preferably, in step S2, the lithium metal substrate is a lithium sheet or a lithium strip.

[0017] Based on the same inventive concept, the present invention also provides a lithium metal electrode material with a hydrophobic artificial SEI film, wherein the lithium metal electrode material with a hydrophobic artificial SEI film is prepared by the method for preparing a lithium metal electrode material with a hydrophobic artificial SEI film as described in any one of the above embodiments.

[0018] Based on the same inventive concept, the present invention also provides an application of a lithium metal electrode material with a hydrophobic artificial SEI film in the preparation of a lithium metal battery anode. The lithium metal electrode material with a hydrophobic artificial SEI film is the lithium metal electrode material with a hydrophobic artificial SEI film prepared by the method described in any one of the above embodiments or the lithium metal electrode material with a hydrophobic artificial SEI film described in the above embodiments.

[0019] Because of the above technical solutions, this invention has the following advantages and positive effects compared with the prior art:

[0020] This invention provides a method for preparing a lithium metal electrode material with a hydrophobic artificial SEI film. The method involves using a hydrophobic fluorinated polyurethane as a raw material to prepare a fluorinated polyurethane dispersion, which is then coated onto the surface of a lithium metal substrate. After drying and solvent evaporation, a polymeric artificial SEI film is formed. Compared with other lithium metal modification methods, this application offers advantages such as low raw material cost and simple preparation process, making it suitable for large-scale production of artificial SEI films. This lithium metal electrode material with a hydrophobic artificial SEI film exhibits a certain degree of hydrophobicity, enabling stable storage under extreme conditions of humid air. Furthermore, it possesses excellent mechanical strength and a fluorine-rich gene, allowing for uniform lithium ion deposition, inhibiting lithium dendrite growth, and achieving a long battery cycle life. Attached Figure Description

[0021] Figure 1 The infrared spectrum of the lithium metal electrode material with a hydrophobic artificial SEI film prepared in Example 1 of this invention;

[0022] Figure 2 The contact angle between the lithium metal electrode material with a hydrophobic artificial SEI film prepared in Example 1 of this invention and water;

[0023] Figure 3 An optical photograph of the lithium metal electrode material with a hydrophobic artificial SEI film prepared in Example 1 of the present invention stored in humid air;

[0024] Figure 4 The Young's modulus of the surface of the lithium metal electrode material with a hydrophobic artificial SEI film prepared in Example 1 of this invention;

[0025] Figure 5 This is a cycle performance diagram of a coin cell assembled from a lithium metal electrode material with a hydrophobic artificial SEI film prepared in Example 1 of the present invention.

[0026] Figure 6 The diagram shows the cycle performance of the coin cell assembled with the lithium metal electrode material having a hydrophobic artificial SEI film prepared in Example 1 of this invention.

[0027] Figure 7 This is an in-situ polarized light microscope image of the lithium metal electrode material with a hydrophobic artificial SEI film prepared in Example 1 of the present invention during battery cycling. Detailed Implementation

[0028] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a further detailed account of the lithium metal electrode material with a hydrophobic artificial SEI film proposed in this invention, as well as its preparation and application. The advantages and features of this invention will become clearer from the following description.

[0029] The first aspect of this application provides a method for preparing a lithium metal material with a hydrophobic artificial SEI film. The method uses hydrophobic fluorinated modified polyurethane as a raw material to prepare a fluorinated modified polyurethane dispersion and spin-coats it onto the surface of lithium metal. After the solvent evaporates, a polymer artificial SEI film is formed, resulting in a lithium metal material with a hydrophobic artificial SEI film.

[0030] According to the method for preparing lithium metal material with a hydrophobic artificial SEI film according to the embodiments of this application, by selecting the solvent for preparing the fluorinated polyurethane dispersion, controlling the concentration of the fluorinated polyurethane dispersion and the content of the fluorinated polyurethane dispersion spin-coated on the surface of the lithium metal material, the fluorinated polyurethane can be uniformly distributed on the surface of the lithium metal material, thereby endowing the lithium metal material with both superhydrophobicity and excellent mechanical properties.

[0031] The specific preparation method includes the following steps:

[0032] S1: Preparation of fluorinated polyurethane dispersion: Disperse fluorinated polyurethane in an organic solvent to obtain fluorinated polyurethane dispersion;

[0033] Further, the preparation steps of fluorinated polyurethane are as follows: 3-5g of polypropylene glycol and 1.6-2.8g of isophorone diisocyanate are added to a three-necked flask and reacted at 80-100℃ for 2-4h; then 1.02-3.05g of dimethylolpropionic acid and 2.1-2.7g of 1,4-butanediol are added sequentially, stannous octoate and dibutyltin dilaurate are added as catalysts, and a predetermined amount of acetone is added to adjust the viscosity of the reaction system; then 0.1-0.3ml of perfluorooctylpropanol is added for end-capping, and after end-capping is completed, 1.05-1.35ml of triethylamine is added for neutralization, emulsification, and distillation to remove acetone.

[0034] In this preferred embodiment, the organic solvent is anhydrous dichloromethane. Because lithium metal has high reactivity and readily undergoes severe side reactions with most organic solvents, and because the objective of this application is to ensure that the fluorinated polyurethane is uniformly distributed on the lithium metal surface, dichloromethane, which is volatile and has low reactivity, is chosen as the organic solvent for the fluorinated polyurethane dispersion.

[0035] In this preferred embodiment, in step S1, 1g of fluorinated polyurethane is added to 25-50mL of anhydrous dichloromethane. Because the film-forming properties of the fluorinated polyurethane dispersion are poor on the lithium metal surface when the concentration is too low or too high, the artificial SEI film on the lithium metal surface may be non-dense, leading to cracking. Therefore, by controlling the concentration of the fluorinated polyurethane dispersion, a uniform and dense artificial SEI film is formed on the surface of the lithium metal material, thereby enabling the lithium metal material to exist stably in a humid air environment.

[0036] In the preferred embodiment of this example, in step S1, the dispersion is carried out by stirring dispersion and / or ultrasonic dispersion, and the stirring dispersion temperature is 30-60℃, and the stirring time is 10-24h.

[0037] S2: Coating of the surface of the lithium metal substrate: Spin-coating the fluorine-modified polyurethane dispersion onto the lithium metal substrate and drying it to obtain the lithium metal electrode material with a hydrophobic artificial SEI film.

[0038] In this embodiment, the lithium metal substrate in step S2 can be a lithium sheet or a lithium strip, and there is no limitation here.

[0039] In this embodiment, the spin coating speed is 800-2000 r / min, the acceleration is 200-500 r / min, and the spin coating time is 5-30 min. The speed, acceleration, and spin coating time of the spin coating equipment all affect the adhesion amount and uniformity of the fluorinated polyurethane dispersion on the lithium metal material surface. Therefore, by adjusting the spin coating equipment parameters, a uniform and dense artificial SEI film with both superhydrophobicity and excellent mechanical properties is formed on the lithium metal material surface, thereby enabling the lithium metal material to exist stably in a humid air environment.

[0040] In this preferred embodiment, in step S2, the drying temperature is 50-100℃ and the drying time is 6-24h.

[0041] Based on the same inventive concept, the present invention also provides a lithium metal material with a hydrophobic artificial SEI film, which is prepared by any of the above-described methods for preparing lithium metal electrode materials with a hydrophobic artificial SEI film.

[0042] Based on the same inventive concept, the present invention also provides an application of a lithium metal electrode material with a hydrophobic artificial SEI film in the preparation of a lithium metal battery anode. The lithium metal battery electrode material with a hydrophobic artificial SEI film is a lithium metal electrode material with a hydrophobic artificial SEI film prepared by any one of the above embodiments or a lithium metal electrode material with a hydrophobic artificial SEI film in the above embodiments.

[0043] Example 1

[0044] This embodiment describes in detail a method for preparing a lithium metal electrode material with a hydrophobic artificial SEI film according to the present invention, including the following steps:

[0045] S1: 3.5g of polypropylene glycol and 1.3g of isophorone diisocyanate were added to a three-necked flask and reacted at 80℃ for 3 hours. Then, 1.08g of dimethylolpropionic acid and 2.3g of 1,4-butanediol were added sequentially, followed by stannous octoate and dibutyltin dilaurate as catalysts, and 20-50ml of acetone to adjust the viscosity of the system. Finally, 0.25ml of perfluorooctylpropanol was added for end-capping. After end-capping, 1.15ml of triethylamine was added for neutralization, and water was added for emulsification under high-speed stirring. Acetone was then removed by vacuum distillation to obtain fluorinated polyurethane.

[0046] (2) Take 1g of the fluorinated polyurethane obtained in step (1) and add it to 40mL of anhydrous dichloromethane. Stir at 40℃ for 12h to obtain a fluorinated polyurethane dispersion.

[0047] (3) Take 40 μL of the fluorine-modified polyurethane dispersion obtained in step (2) and add it to the lithium metal sheet by spin coating. Increase the spin coating speed to 8000 r / min with an acceleration of 200 r / min and maintain this speed for 20 min. Then place the lithium metal material with the fluorine-modified polyurethane dispersion on a heating table and heat it to 60°C and keep it for 12 h to dry the dichloromethane solvent. Finally, a lithium metal electrode material with a hydrophobic artificial SEI film is obtained.

[0048] The prepared lithium metal electrode material was subjected to infrared spectroscopy testing, and the results are as follows: Figure 1 As shown, by Figure 1 It can be found that the prepared lithium metal electrode material with hydrophobic artificial SEI film has fluorine-rich groups, which make the fluorine-modified polyurethane hydrophobic.

[0049] The water contact angle of the prepared lithium metal electrode material sample with an artificial SEI film was tested, and the results are as follows: Figure 2 As shown, from Figure 2 It can be observed that the lithium metal electrode material prepared in this embodiment exhibits significant hydrophobicity. Furthermore, when the prepared lithium metal electrode material with a hydrophobic artificial SEI film is placed in humid air, such as... Figure 3 As shown, after being placed in humid air for 12 hours, the material showed no significant changes and can remain stable in humid air environments.

[0050] See Figure 4 It can be concluded that the lithium metal electrode material with hydrophobic artificial SEI film has a large Young's modulus, indicating that the prepared lithium metal electrode material with hydrophobic artificial SEI film has excellent mechanical properties.

[0051] The electrochemical performance of the lithium metal electrode material was assessed using an electrochemical workstation and blue-light testing. Electrochemical performance testing was conducted using 2032 coin cells assembled in an argon-filled glove box, where the water and oxygen content were maintained below 1.0 ppm. Full-cell testing was performed using commercial lithium iron phosphate as the positive electrode and the prepared lithium metal electrode material with a hydrophobic artificial SEI film as the negative electrode. The testing rate was 1C, and the results are as follows: Figure 5 As shown, according to Figure 5 It can be clearly seen that the reversible capacity is 154 mAh / g, and the capacity retention rate is 99.5% after 300 cycles.

[0052] (4) The lithium metal electrode material with hydrophobic artificial SEI film prepared by the above steps is used as the negative electrode, and lithium iron phosphate and nickel cobalt manganese 811 are used as the positive electrode to assemble a 2032 coin cell and test it.

[0053] The results are as follows Figure 6As shown, the test results indicate that using lithium metal electrode materials with a hydrophobic artificial SEI film as electrodes to assemble a 2032 coin cell achieved 1800 hours of cycling at a charge / discharge current density of 1 mA / cm² and a charge / discharge area capacity of 1 mAh / cm², with a polarization voltage of only 20 mV. According to... Figure 7 As can be seen, no dendrite growth was observed compared to bare lithium, indicating that the lithium metal electrode material with a hydrophobic artificial SEI film has excellent lithium dendrite suppression capability.

[0054] Example 2

[0055] This embodiment describes in detail a method for preparing a lithium metal electrode material with a hydrophobic artificial SEI film according to the present invention, including the following steps:

[0056] (1) 3.75 g of polypropylene glycol and 1.4 g of isophorone diisocyanate were added to a three-necked flask and reacted at 90 °C for 3 h. Then, 1.1 g of dimethylolpropionic acid and 2.4 g of 1,4-butanediol were added sequentially, and stannous octoate and dibutyltin dilaurate were added as catalysts, along with 20-50 ml of acetone to adjust the viscosity of the system. Finally, 0.25 ml of perfluorooctylpropanol was added for end-capping. After end-capping, 1.35 ml of triethylamine was added for neutralization, and water was added for emulsification under high-speed stirring. Acetone was then removed by vacuum distillation to obtain fluorinated polyurethane.

[0057] (2) Take 1g of the fluorinated polyurethane obtained in step (1) and add it to 25mL of anhydrous dichloromethane. Stir at 40℃ for 12h to obtain a fluorinated polyurethane dispersion.

[0058] (3) Take 20 μL of the fluorine-modified polyurethane dispersion obtained in step (2) and add it to the lithium metal sheet by spin coating. Increase the spin coating speed to 10000 r / min with an acceleration of 200 r / min and maintain this speed for 30 min. Then place the lithium metal material with the fluorine-modified polyurethane dispersion on a heating table and heat it to 60°C and keep it for 12 h to dry the dichloromethane solvent. Finally, a lithium metal electrode material with a hydrophobic artificial SEI film is obtained.

[0059] (4) Using the lithium metal electrode material with hydrophobic artificial SEI film prepared by the above steps as the negative electrode, and lithium iron phosphate and nickel cobalt manganese 811 as the positive electrode, a 2023 coin cell was assembled and tested.

[0060] Test results show that using lithium metal electrode materials with hydrophobic artificial SEI film as electrodes to assemble 2032 coin cells, 1000 cycles were achieved at a charge / discharge current density of 1 mA / cm2 and a charge / discharge area capacity of 1 mAh / cm2, with a polarization voltage of only 25 mV.

[0061] Example 3

[0062] This embodiment provides a method for preparing a lithium metal electrode material with a hydrophobic artificial SEI film, including the following steps:

[0063] (1) 3.8 g of polypropylene glycol and 1.5 g of isophorone diisocyanate were added to a three-necked flask and reacted at 90 °C for 4 h. Then, 1.1 g of dimethylolpropionic acid and 2.5 g of 1,4-butanediol were added sequentially, followed by stannous octoate and dibutyltin dilaurate as catalysts, and 20-50 ml of acetone to adjust the viscosity of the system. Finally, 0.35 ml of perfluorooctylpropanol was added for end-capping. After end-capping, 1.35 ml of triethylamine was added for neutralization, and water was added for emulsification under high-speed stirring. Acetone was then removed by vacuum distillation to obtain fluorinated polyurethane.

[0064] (2) Take 1g of the fluorinated polyurethane obtained in step (1) and add it to 35mL of anhydrous dichloromethane. Stir at 40℃ for 12h to obtain a fluorinated polyurethane dispersion.

[0065] (3) Take 30 μL of the fluorine-modified polyurethane dispersion obtained in step (2) and add it to the lithium metal sheet by spin coating. Increase the spin coating speed to 10000 r / min at an acceleration of 200 r / min and maintain this speed for 30 min. Then place the lithium metal material with the fluorine-modified polyurethane dispersion on a heating stage and heat it to 60°C and keep it for 12 h to dry the dichloromethane solvent. Finally, a lithium metal electrode material with a hydrophobic artificial SEI film is obtained.

[0066] (4) Using the lithium metal electrode material with hydrophobic artificial SEI film prepared by the above steps as the negative electrode, and lithium iron phosphate and nickel cobalt manganese 811 as the positive electrode, a 2023 coin cell was assembled and tested.

[0067] Test results show that using lithium metal electrode material with a hydrophobic artificial SEI film as the electrode to assemble a 2032 coin cell, a charge-discharge current density of 1 mA / cm2 and a charge-discharge area capacity of 1 mAh / cm2 were achieved, with a polarization voltage of only 22 mV.

[0068] Example 4

[0069] This embodiment provides a method for preparing a lithium metal electrode material with a hydrophobic artificial SEI film, including the following steps:

[0070] (1) 3.85 g of polypropylene glycol and 1.5 g of isophorone diisocyanate were added to a three-necked flask and reacted at 90 °C for 4 h. Then, 1.15 g of dimethylolpropionic acid and 2.5 g of 1,4-butanediol were added sequentially, and stannous octoate and dibutyltin dilaurate were added as catalysts, along with 20-50 ml of acetone to adjust the viscosity of the system. Finally, 0.35 ml of perfluorooctylpropanol was added for end-capping. After end-capping, 1.35 ml of triethylamine was added for neutralization, and water was added for emulsification under high-speed stirring. Acetone was then removed by vacuum distillation to obtain fluorinated polyurethane.

[0071] (2) Take 1g of the fluorinated polyurethane obtained in step (1) and add it to 50mL of anhydrous dichloromethane. Stir at 40℃ for 12h to obtain a fluorinated polyurethane dispersion.

[0072] (3) Take 45 μL of the fluorinated polyurethane dispersion obtained in step (2), increase the spin coating speed to 8000 r / min with an acceleration of 200 r / min, maintain this speed for 20 min, and drop it onto the lithium metal sheet by spin coating. Then place the lithium metal material with the fluorinated polyurethane dispersion on a heating stage and heat it to 60°C and keep it for 12 h to dry the dichloromethane solvent. Finally, a lithium metal electrode material with a hydrophobic artificial SEI film is obtained.

[0073] (4) The lithium metal electrode material with hydrophobic artificial SEI film prepared by the above steps is used as the negative electrode, and lithium iron phosphate and nickel cobalt manganese 811 are used as the positive electrode to assemble a 2032 coin cell and test it.

[0074] Test results show that using lithium metal electrode material with a hydrophobic artificial SEI film as the electrode to assemble a 2032 coin cell, a charge-discharge current density of 1 mA / cm2 and a charge-discharge area capacity of 1 mAh / cm2 were achieved, with a polarization voltage of only 25 mV.

[0075] Example 5

[0076] This embodiment provides a method for preparing a lithium metal electrode material with a hydrophobic artificial SEI film, including the following steps:

[0077] (1) 3.8 g of polypropylene glycol and 1.5 g of isophorone diisocyanate were added to a three-necked flask and reacted at 90 °C for 3 h. Then, 1.15 g of dimethylolpropionic acid and 2.45 g of 1,4-butanediol were added sequentially, and stannous octoate and dibutyltin dilaurate were added as catalysts, along with 20-50 ml of acetone to adjust the viscosity of the system. Finally, 0.3 ml of perfluorooctylpropanol was added for end-capping. After end-capping, 1.35 ml of triethylamine was added for neutralization, and water was added for emulsification under high-speed stirring. Acetone was then removed by vacuum distillation to obtain fluorinated polyurethane.

[0078] (2) Take 1g of the fluorinated polyurethane obtained in step (1) and add it to 60mL of anhydrous dichloromethane. Stir at 40℃ for 12h to obtain a fluorinated polyurethane dispersion.

[0079] (3) Take 60 μL of the fluorinated polyurethane dispersion obtained in step (2) and add it to the lithium metal sheet by spin coating. Increase the spin coating speed to 8000 r / min with an acceleration of 200 r / min and maintain this speed for 20 min. Then place the lithium metal material with the fluorinated polyurethane dispersion on a heating stage and heat it to 60°C and keep it for 12 h to dry the dichloromethane solvent. Finally, a lithium metal electrode material with a hydrophobic artificial SEI film is obtained.

[0080] (4) Using the lithium metal electrode material with hydrophobic artificial SEI film prepared by the above steps as the negative electrode, and lithium iron phosphate and nickel cobalt manganese 811 as the positive electrode, a 2023 coin cell was assembled and tested.

[0081] Test results show that using lithium metal electrode materials with hydrophobic artificial SEI film as electrodes to assemble 2032 coin cells, 1400 cycles were achieved at a charge / discharge current density of 1 mA / cm2 and a charge / discharge area capacity of 1 mAh / cm2, with a polarization voltage of only 23 mV.

[0082] Example 6

[0083] This embodiment provides a method for preparing a lithium metal electrode material with a hydrophobic artificial SEI film, including the following steps:

[0084] (1) 3.85 g of polypropylene glycol and 1.5 g of isophorone diisocyanate were added to a three-necked flask and reacted at 90 °C for 4 h. Then, 1.15 g of dimethylolpropionic acid and 2.5 g of 1,4-butanediol were added sequentially, and stannous octoate and dibutyltin dilaurate were added as catalysts, along with 20-50 ml of acetone to adjust the viscosity of the system. Finally, 0.35 ml of perfluorooctylpropanol was added for end-capping. After end-capping, 1.35 ml of triethylamine was added for neutralization, and water was added for emulsification under high-speed stirring. Acetone was then removed by vacuum distillation to obtain fluorinated polyurethane.

[0085] (2) Take 1g of the fluorinated polyurethane obtained in step (1) and add it to 60mL of anhydrous dichloromethane. Stir at 40℃ for 12h to obtain a fluorinated polyurethane dispersion.

[0086] (3) Take 60 μL of the fluorinated polyurethane dispersion obtained in step (2) and add it to the lithium metal sheet by spin coating. Increase the spin coating speed to 8000 r / min with an acceleration of 200 r / min and maintain this speed for 20 min. Then place the lithium metal material with the fluorinated polyurethane dispersion on a heating stage and heat it to 60°C and keep it for 12 h to dry the dichloromethane solvent. Finally, a lithium metal electrode material with a hydrophobic artificial SEI film is obtained.

[0087] (4) The lithium metal electrode material with hydrophobic artificial SEI film prepared by the above steps is used as the negative electrode, and lithium iron phosphate and nickel cobalt manganese 811 are used as the positive electrode to assemble a 2032 coin cell and test it.

[0088] Test results show that using lithium metal electrode materials with hydrophobic artificial SEI film as electrodes to assemble 2032 coin cells, 1200 cycles were achieved at a charge / discharge current density of 1 mA / cm2 and a charge / discharge area capacity of 1 mAh / cm2, with a polarization voltage of only 25 mV.

[0089] This application discloses a lithium metal material with a hydrophobic artificial SEI film. By controlling the selection of the solvent for preparing the fluorinated polyurethane dispersion, the concentration of the fluorinated polyurethane dispersion, and the content of the fluorinated polyurethane dispersion spin-coated onto the surface of the lithium metal material, these factors work together to form a uniform and dense polymer film on the surface of the lithium metal material, thereby endowing the lithium metal material with both superhydrophobicity and excellent mechanical properties. Furthermore, the preparation method of the lithium metal material with the hydrophobic artificial SEI film is simple, well-compatible with existing processes, and batteries containing the lithium metal material with the hydrophobic artificial SEI film exhibit good cycle stability, showing great potential for large-scale application.

[0090] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a lithium metal electrode material with a hydrophobic artificial SEI film, characterized in that, Includes the following steps: S1: Preparation of fluorinated polyurethane dispersion: The fluorinated polyurethane is a polyurethane with a main chain of polyurethane and end-capped with perfluorooctylpropanol; the fluorinated polyurethane is dispersed in an organic solvent to obtain the fluorinated polyurethane dispersion. S2: Coating of the surface of the lithium metal substrate: The fluorine-modified polyurethane dispersion is coated on the lithium metal substrate, dried, and after the organic solvent evaporates, a pre-formed hydrophobic artificial SEI film is directly formed, thus obtaining the lithium metal electrode material with the hydrophobic artificial SEI film.

2. The method for preparing a lithium metal electrode material with a hydrophobic artificial SEI film according to claim 1, characterized in that, The organic solvent in step S1 is anhydrous dichloromethane.

3. The method for preparing a lithium metal electrode material with a hydrophobic artificial SEI film according to claim 2, characterized in that, In the fluorinated polyurethane dispersion of step S1, 1g of fluorinated polyurethane is added to 25-50mL of anhydrous dichloromethane.

4. The method for preparing a lithium metal electrode material with a hydrophobic artificial SEI film according to claim 1, characterized in that, In step S1, the dispersion is achieved by stirring and / or ultrasonic dispersion, with a stirring temperature of 30-60℃ and a stirring time of 10-24h.

5. The method for preparing a lithium metal electrode material with a hydrophobic artificial SEI film according to claim 1, characterized in that, In step S2, the fluorinated polyurethane dispersion is spin-coated onto a lithium metal substrate, wherein the spin-coating speed is 800-2000 r / min, the acceleration is 200-500 r / min, and the spin-coating time is 5-30 min.

6. The method for preparing a lithium metal electrode material with a hydrophobic artificial SEI film according to claim 1, characterized in that, In step S2, the drying temperature is 50-100℃ and the drying time is 6-24h.

7. The method for preparing a lithium metal electrode material with a hydrophobic artificial SEI film according to claim 1, characterized in that, In step S1, the preparation steps of fluorinated polyurethane are as follows: 3-5g of polypropylene glycol and 1.6-2.8g of isophorone diisocyanate are added to a three-necked flask and reacted at 80-100℃ for 2-4h; then 1.02-3.05g of dimethylolpropionic acid and 2.1-2.7g of 1,4-butanediol are added sequentially, stannous octoate and dibutyltin dilaurate are added as catalysts, and a predetermined amount of acetone is added to adjust the viscosity of the reaction system; then 0.1-0.3ml of perfluorooctylpropanol is added for end-capping, and after end-capping is completed, 1.05-1.35ml of triethylamine is added for neutralization, emulsification, and distillation to remove acetone.

8. The method for preparing a lithium metal electrode material with a hydrophobic artificial SEI film according to any one of claims 1-7, characterized in that, In step S2, the lithium metal substrate is a lithium sheet or a lithium strip.

9. A lithium metal electrode material with a hydrophobic artificial SEI film, characterized in that, The lithium metal electrode material with a hydrophobic artificial SEI film is prepared by the method for preparing the lithium metal electrode material with a hydrophobic artificial SEI film according to any one of claims 1-8.

10. An application of a lithium metal electrode material with a hydrophobic artificial SEI film in the preparation of a lithium metal battery anode, characterized in that, The lithium metal electrode material with a hydrophobic artificial SEI film is the lithium metal electrode material with a hydrophobic artificial SEI film prepared by the method described in any one of claims 1-8 or the lithium metal electrode material with a hydrophobic artificial SEI film as described in claim 9.

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