Functional thin film assembly and method of making and metal lithium battery containing the same

Abstract

The application discloses a functional film assembly and a preparation method and a metal lithium battery containing the film assembly, and belongs to the technical field of lithium ion batteries. The film base is improved by a carbon structure combined with a bonding agent, so that the structural integrity of the film base can be effectively improved. The film base is subjected to surface treatment by using an acid solution with low concentration, so that the surface defects of the carbon-based material can be reduced, the flexibility of the base material can be ensured, the stability of the structure can be maintained, and the film base can be used as an assembly. Compared with a lithium metal electrode, the film surface of the application suspends rich nitrate. Since the nitrate has strong adsorption energy on lithium, the nucleation overpotential of the metal lithium is reduced, more metal lithium deposition sites and growth space are provided, the metal lithium grows more uniformly, the internal porosity of the film is large, space is provided for the storage of the metal lithium, and lithium dendrites are avoided, so that the problems in the prior art are solved.

Description

Technical Field

[0001] This invention relates to functional thin-film components and their preparation methods, as well as lithium metal batteries containing such thin-film components, belonging to the field of lithium-ion battery technology. Background Technology

[0002] Lithium metal has the lowest redox potential ( With a 3.04 V vs. standard hydrogen electrode and extremely high specific capacity (3860 mAh / g), it is an ideal anode material for next-generation high-energy-density batteries. Currently, in practical applications, the porous nature of the lithium metal deposition layer increases the electrode's specific surface area and leads to more side reactions between lithium metal and the electrolyte, resulting in low coulombic efficiency and rapid capacity decay, severely hindering its practical application.

[0003] The existing technologies for solving the above problems are mainly as follows: (1) Electrolyte regulation: Patent CN108630992B proposes that dendrite-free deposition of lithium metal can be achieved by combining two different lipid solvents; (2) Artificial construction of protective film: For example, Professor Zhang Qiang of Tsinghua University proposed to construct a LiF / Cu interface film on the surface of lithium metal, and Professor Linda Nazar proposed to construct a Li-In / LiCl interface film on the surface of lithium metal. Patent CN111293299B also discloses a technical solution to improve the deposition morphology of lithium metal by using acetic acid vapor to form a passivation layer on the surface of lithium metal; (3) Improvement of three-dimensional framework structure: Patent CN114335540A provides a lithium-loving three-dimensional porous carbon framework. The framework is injected into lithium metal by melting method, avoiding the volume change of lithium metal and the growth of dendrites.

[0004] However, the above technologies have the following shortcomings: (1) The plate electrode undergoes volume changes during cycling, which makes it impossible for the solid electrolyte interphase (SEI) film or artificial protective film on the electrode surface to remain intact during long-term service. The rupture of the protective film will cause fresh lithium to react with the electrolyte, resulting in uneven lithium metal deposition; (2) Due to the presence of an intrinsic passivation layer on the surface of the lithium metal foil, the passivation layer is unevenly distributed. Therefore, the large-area protective film artificially constructed on its surface cannot guarantee uniformity. In addition, the artificial construction of the protective film requires the lithium metal foil as a carrier, making it difficult to achieve componentization; (3) The capacity of the three-dimensional framework to accommodate lithium metal is limited. Whether constructing an artificial protective film on the lithium foil surface or using a three-dimensional framework to prepare a composite lithium metal anode, an inert atmosphere is required, which is inconvenient for production. Therefore, a functional thin-film component that can solve the above problems and a lithium metal battery containing such a thin-film component have become an urgent need. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a functional thin-film component, a method for its preparation, and a lithium metal battery containing the thin-film component, thereby solving the problems existing in the prior art.

[0006] The method for preparing the functional thin-film component of the present invention includes a thin-film substrate preparation stage and a thin-film lithiophilic modification stage. The thin-film substrate preparation stage includes the following steps:

[0007] Step 1: Take an appropriate amount of carbon nanotubes or carbon microtubes or porous carbon fibers and adhesive materials, disperse them evenly in a solvent to form a mixed solution;

[0008] Step 2: Place the mixed solution obtained in Step 1 into a container with a filter membrane, filter the solvent and then dry it to form a thin film substrate;

[0009] The thin film lithiophilic modification stage includes the following steps:

[0010] Step 11: Prepare the pretreatment solution, which is a mixed solution containing inorganic acid and nitrate;

[0011] Step 12: Place the thin film substrate obtained in Step 2 into the pretreatment solution for heat treatment;

[0012] Step 13: After heat treatment, remove the film, rinse it with pure water, and then dry it to obtain the functional film assembly.

[0013] Furthermore, in step 1, the mass ratio of carbon nanotubes or carbon microtubes or porous carbon fibers to adhesive materials ranges from 10:1 to 5:1.

[0014] Furthermore, the adhesive material in step 1 is one or more of polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, methylcellulose, sodium carboxymethyl cellulose, bacterial cellulose, and nanocellulose;

[0015] The solvent is one or more of water, N-methylpyrrolidone, and N,N-dimethylformamide.

[0016] Furthermore, the thickness of the thin film substrate obtained in step 2 ranges from 10 μm to 500 μm, and the porosity ranges from 10% to 50%.

[0017] Furthermore, in step 11, the inorganic acid is one or more of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, and perchloric acid;

[0018] The nitrate is one or more of lithium nitrate, nickel nitrate, zinc nitrate, sodium nitrate, and magnesium nitrate.

[0019] Furthermore, the concentration range of inorganic acids is 0.1 mol / L to 3 mol / L, and the concentration range of nitrates is 1 mol / L to 8 mol / L.

[0020] Furthermore, in step 12, the heat treatment has a heating rate of 1-10℃ / min, a final temperature of 50-100℃, and a holding time of 0.5-6h.

[0021] The present invention provides a functional thin film component, comprising a thin film substrate, wherein the interior of the thin film substrate is provided with pores, including the pores inherent within carbon nanotubes, carbon microtubes, or porous carbon fibers, and also including pores formed by the interweaving of carbon nanotubes, carbon microtubes, or porous carbon fibers.

[0022] Furthermore, nitrate ions are suspended on the surface of carbon nanotubes, carbon microtubes, or porous carbon fibers by chemical bonds. These nitrate ions enhance the lithiophilicity of the carbon nanotubes, carbon microtubes, or porous carbon fibers, providing nucleation sites for metallic lithium, thus enabling uniform and dendrite-free deposition of metallic lithium in the pores and on the surface of the functional thin film assembly.

[0023] The lithium metal battery with a functional thin-film component of the present invention includes a lithium iron phosphate positive electrode, a separator, a functional thin-film component and a lithium metal negative electrode stacked in sequence.

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

[0025] The functional thin-film component, its preparation method, and the lithium metal battery containing the thin-film component described in this invention improve the structural integrity of the thin-film substrate by combining a carbon structure with an adhesive. Furthermore, heat treatment of the thin-film substrate with a low-concentration acid solution modifies the carbon structure surface with nitrate ions, enhancing the affinity between the carbon material and lithium. The use of a low-concentration acid solution reduces surface defects in the carbon-based material, which helps maintain the flexibility of the substrate material. The above treatment helps maintain the stability of the structure, making it suitable for use as a component. The preparation process of the functional thin film is simple and has a high safety factor.

[0026] The use of functional thin films in lithium batteries has the following advantages: ① Compared with existing lithium metal electrodes, the surface of the film of this invention is rich in nitrate ions. Since nitrate ions have a strong adsorption energy for lithium (-3.14 eV), this helps to reduce the nucleation overpotential of lithium metal, providing more lithium metal deposition sites and resulting in more uniform lithium metal growth; ② The functional thin film has a large internal porosity, providing space for lithium metal storage; using the functional thin film of this invention, the macroscopic volume of lithium metal hardly changes during cycling, and the SEI film formed on the surface will not be torn, better isolating the electrolyte, avoiding side reactions between lithium metal and the electrolyte, and preventing the formation of lithium dendrites, thus improving the coulombic efficiency of the lithium metal anode; ③ When the lithium metal deposition capacity exceeds the lithium storage capacity of the functional thin film, the nitrate ions provide… More nucleation sites are created, allowing lithium metal to grow outwards when the deposition amount is too large, enabling lithium metal to continue depositing on the functional film with a uniform deposition morphology free of dendrites; ④ Due to the uniform deposition of lithium metal, the contact area with the electrolyte is small, resulting in low loss; simultaneously, during the subsequent stripping process, stripping can be carried out relatively uniformly, without forming dead lithium. Therefore, the lithium metal on the resulting functional film module has high utilization rate and cycle stability; ⑤ During long-term service, the lower lithium foil (sheet) can continuously provide a lithium source, compensating for the loss of active lithium on the functional film. This solves the problems existing in the prior art. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating the overall steps in Embodiment 1 of the present invention;

[0028] Figure 2 This is a cycle life diagram of the lithium metal battery in specific embodiment 1 of the present invention;

[0029] Figure 3 This is a cycle life diagram of the lithium metal battery in Comparative Example 1 of the present invention;

[0030] Figure 4 This is a coulombic efficiency diagram of the lithium metal battery after 400 cycles in specific embodiment 1 of the present invention;

[0031] Figure 5 These are lithium storage diagrams and deposition morphology diagrams of the functional thin-film components in embodiments of the present invention;

[0032] Figure 6 This is the Raman spectrum of the functional thin-film component in an embodiment of the present invention. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0034] Example 1:

[0035] like Figure 1As shown, the method for preparing the functional thin-film component of the present invention includes a thin-film substrate preparation stage and a thin-film lithiophilic modification stage. The thin-film substrate preparation stage includes the following steps:

[0036] Step 1: Take an appropriate amount of carbon nanotubes or carbon microtubes or porous carbon fibers and adhesive materials, disperse them evenly in a solvent to form a mixed solution;

[0037] Step 2: Take an appropriate amount of the mixed solution obtained in Step 1 and place it in a container with a filter membrane. After the solvent is removed by vacuum filtration, place it in an oven to dry and form a thin film substrate.

[0038] The thin film lithiophilic modification stage includes the following steps:

[0039] Step 11: Prepare the pretreatment solution, which is a mixed solution containing inorganic acid and nitrate;

[0040] Step 12: Place the thin film substrate obtained in Step 2 into the pretreatment solution for heat treatment;

[0041] Step 13: After heat treatment, remove the film, rinse it with pure water, and then dry it to obtain a functional thin film module.

[0042] A lithium iron phosphate cathode, a separator, the aforementioned functional thin-film components, and a lithium metal anode are stacked sequentially to assemble a lithium metal battery.

[0043] The functional thin-film module of this invention is a three-dimensional electrode capable of storing lithium metal, and also serves to guide lithium metal deposition and protect the lithium metal. The functional thin-film module is prepared through two stages: a thin-film substrate preparation stage and a lithiophilic modification stage. This allows lithium metal from lithium batteries to be deposited inside, between, or on carbon nanotubes and porous fibers. Simultaneously, the lithiophilic modification stage results in abundant nitrate ions suspended on the surface of the functional thin-film module. Because nitrate ions have a strong adsorption energy for lithium, they provide more lithium metal deposition sites, resulting in more uniform lithium metal growth. Nitrate ions also provide nucleation sites for lithium metal; when the deposition amount is excessive, lithium metal grows outwards, allowing lithium metal to continue depositing on the functional thin-film module, resulting in a uniform, dendrite-free deposition morphology. Specific Implementation Example 1:

[0045] A method for preparing a functional thin-film component specifically includes the following steps:

[0046] a) Take 0.5 g of carbon nanotubes and 0.1 g of nanocellulose and disperse them evenly in water. Transfer the mixed solution to a container with a filter membrane, use vacuum filtration to remove the water, and transfer it to an oven to dry at 60-150℃ for 12 h to form a thin film substrate with a thickness of 50 μm and a porosity of 10%.

[0047] b) Prepare a pretreatment solution by mixing excess 0.5 mol / L sulfuric acid and 3 mol / L lithium nitrate and stirring until the lithium nitrate is completely dissolved.

[0048] c) Immerse the film substrate obtained in step a) in the pretreatment solution, then heat it at a rate of 5°C / min to 100°C and hold for 2 hours; then remove it, rinse it with deionized water, and dry it in a vacuum oven at 60-80°C to form a functional film with a porosity of about 20%.

[0049] In a dry chamber, a lithium iron phosphate cathode, separator, functional film obtained in step c), and lithium metal anode were sequentially stacked to assemble a lithium metal battery. The electrolyte was 1 mol / L LiPF6 EC:DEC:FEC (volume ratio 1:1:1). The battery was initially activated for 5 weeks at an activation rate of 0.1C; subsequently, the charge / discharge rate was maintained at 0.5C. The initial battery capacity was 163 mAh g⁻¹; its cycle life was as follows: Figure 2 As shown, the capacity was 132 mAh g⁻¹ after 500 cycles, with a capacity retention of 81%.

[0050] By bonding a multifunctional thin film to a lithium sheet to form a composite lithium metal anode, the battery cycle life is significantly improved, and the battery capacity is still greater than 80% after 500 cycles.

[0051] Comparative Example 1:

[0052] In a dry chamber, lithium iron phosphate cathode, separator, and lithium metal anode were stacked sequentially to assemble a lithium metal battery. The electrolyte was 1 mol / L LiPF6EC:DEC:FEC (volume ratio 1:1:1). The battery charge / discharge rate was set to 0.5C, and the initial battery capacity was 150 mAh g⁻¹. -1 After 120 cycles, the capacity is 95 mAh g. -1 The capacity retention rate was 63%.

[0053] Comparative Example 2:

[0054] Take 0.5 g of carbon nanotubes and 0.1 g of nanocellulose and disperse them evenly in water. Transfer the mixed solution to a container with a filter membrane, and use vacuum filtration to remove the water. Transfer the solution to an oven and dry it at 60-150℃ for 12 h to form a thin film substrate with a thickness of 50 μm and a porosity of 10%.

[0055] In a dry chamber, lithium iron phosphate cathode, separator, thin film substrate, and lithium metal anode were stacked sequentially to assemble a lithium metal battery. The electrolyte was 1 mol / L LiPF6 EC:DEC:FEC (volume ratio 1:1:1). The battery charge / discharge rate was set to 0.5C, the initial battery capacity was 150 mAh g⁻¹, and the capacity after 120 cycles was 90 mAh g⁻¹, with a capacity retention of 60%.

[0056] In Comparative Example 1, the lithium battery without a functional thin film retained 63% of its capacity after 120 cycles. In Comparative Example 2, a thin film substrate was added, but it was not modified to be lithium-affinity; the capacity retention after 120 cycles was 60%. The reason for this discrepancy is likely that a non-lithiophilic thin film substrate exacerbates uneven lithium deposition, i.e., lithium dendrite growth, thus accelerating capacity decay. Furthermore, in Specific Example 1, the battery capacity was still greater than 80% after 500 cycles. The battery capacity and cycle performance test results for Specific Example 1 and Comparative Example 1 are as follows: Figure 2 and Figure 3 As shown, modifying the thin film substrate with lithium affinity can effectively improve its cycle performance. The reason for this may be that the underlying lithium sheet provides active lithium to compensate for lithium loss.

[0057] Meanwhile, the addition of functional thin-film components allows for effective control of the lithium metal deposition morphology, resulting in a uniform lithium metal deposition. Specifically, Figure 4 The diagram shows the coulombic efficiency of the lithium metal battery after 400 cycles in Specific Example 1. After 400 cycles, the battery coulombic efficiency is still greater than 80%. The reason for this is that the addition of the functional thin film allows the lithium metal anode to maintain stable cycling. The functional thin film component ensures that the macroscopic volume of the lithium metal remains almost unchanged during cycling, and the SEI film generated on the surface will not be torn. This better isolates the electrolyte, avoids side reactions between lithium metal and the electrolyte, and effectively improves the coulombic efficiency of the lithium metal anode.

[0058] Figure 5 Examples of lithium storage and deposition morphology diagrams for functional thin films, such as... Figure 5 As shown, when the lithium metal deposition capacity is less than the thin film substrate's capacity, lithium metal fills the pores of the thin film substrate, exhibiting lithium storage in the thin film substrate; when the lithium metal deposition capacity is greater than the thin film substrate's capacity, lithium metal exhibits a uniform and dense deposition morphology.

[0059] In summary, based on the battery capacity and cycle performance test results of Specific Example 1 and Comparative Example 2, it can be seen that the thin film substrate, after undergoing lithiumophilic modification treatment, can effectively improve its lithiumophilicity, increase the number and uniformity of lithium metal nuclei, thereby improving the deposition behavior of lithium metal and ultimately improving cycle stability, thus significantly enhancing its cycle stability.

[0060] The reason for this is that the surface treatment process modifies the surface of the thin film substrate with a layer of nitrate. Since nitrate has a strong adsorption effect on lithium (adsorption energy of -3.14 eV), it improves lithium affinity, helps reduce the nucleation overpotential of lithium metal, and provides more lithium metal deposition sites, resulting in more uniform lithium metal growth. Figure 6 As shown, the D and G peaks in the Raman spectrum of the functional thin film component are characteristic peaks of carbon materials, and the presence of nitrate signal peaks indicates that the nitrate is indeed modified on the surface of the thin film substrate. Specific Implementation Example 2:

[0062] A method for preparing a functional thin film component involves uniformly dispersing 0.8g of carbon nanotubes and 0.1g of nanocellulose in water, with all other steps being the same as in Specific Example 1, to form the functional thin film, at which point the porosity of the thin film is approximately 15%.

[0063] The obtained functional thin film was assembled into a lithium metal battery. The assembly and activation methods were the same as in Specific Example 1. The battery had an initial capacity of 148 mAh g-1 and a capacity of 114 mAh g-1 after 500 cycles, with a capacity retention of 77%. Specific Implementation Example 3:

[0065] A method for preparing a functional thin film component involves uniformly dispersing 1.0g of carbon nanotubes and 0.1g of nanocellulose in water, with all other steps being the same as in Specific Example 1, to form the functional thin film, at which point the porosity of the thin film is approximately 20%.

[0066] The obtained functional thin film was assembled into a lithium metal battery. The assembly and activation methods were the same as in Specific Example 1. The battery had an initial capacity of 146 mAh g-1 and a capacity of 110 mAh g-1 after 500 cycles, with a capacity retention rate of 75%.

[0067] As can be seen from specific examples 1-3, when the ratio of carbon nanotubes to nanocellulose is different, the capacity retention rate increases as the carbon nanotubes decrease. The reason for this is mainly because the reduction of carbon nanotubes leads to larger pores in the film matrix and higher lithium storage capacity.

[0068] The above embodiments only use carbon nanotubes as an example, but do not affect the use of carbon microtubes and porous carbon fibers in the preparation method of the functional thin film components; the adhesive materials in the above embodiments only use nanocellulose as an example, but do not affect the use of polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, methylcellulose, sodium carboxymethyl cellulose, and bacterial cellulose in the preparation method of the functional thin film components. Specific Implementation Example 4:

[0070] A method for preparing a functional thin film component is identical to that in Specific Example 1, except that the thickness of the thin film substrate is 10 μm and the porosity is 10%, in order to form the functional thin film.

[0071] The obtained functional thin film was assembled into a lithium metal battery. The assembly and activation methods were the same as in Specific Example 1. The battery had an initial capacity of 150 mAh g-1 and a capacity of 100 mAh g-1 after 500 cycles, with a capacity retention of 66.7%. Specific Implementation Example 5:

[0073] A method for preparing a functional thin film component is identical to that in Specific Example 1, except that the thickness of the thin film substrate is 500 μm and the porosity is 50%, in order to form the functional thin film.

[0074] The obtained functional thin film was assembled into a lithium metal battery. The assembly and activation methods were the same as in Specific Example 1. The battery had an initial capacity of 148 mAh g-1 and a capacity of 126 mAh g-1 after 500 cycles, with a capacity retention of 85%.

[0075] As can be seen from specific embodiments 1, 4, and 5, when the thickness and porosity of the thin film substrate are different, its capacity retention rate increases with the increase of the actual number of pores in the thin film substrate. The reason for this is mainly that the increase in the actual number of pores leads to an increase in lithium storage. During long-term service, the lower lithium foil can continuously provide lithium source to compensate for the loss of active lithium on the functional film. Specific Implementation Example 6:

[0077] A method for preparing a functional thin-film component is identical to that in Specific Example 1, except that the pretreatment solution is composed of an excess of 2 mol / L sulfuric acid and 2 mol / L lithium nitrate, in order to form the functional thin film described above.

[0078] The obtained functional thin film was assembled into a lithium metal battery. The assembly and activation methods were the same as in Specific Example 1. The battery had an initial capacity of 150 mAh g-1 and a capacity of 105 mAh g-1 after 500 cycles, with a capacity retention of 70%. Specific Implementation Example 7:

[0080] A method for preparing a functional thin-film component is identical to that in Specific Example 1, except that the pretreatment solution is composed of an excess of 1 mol / L sulfuric acid and 6 mol / L lithium nitrate, in order to form the functional thin film.

[0081] The obtained functional thin film was assembled into a lithium metal battery. The assembly and activation methods were the same as in Specific Example 1. The battery had an initial capacity of 146 mAh g-1 and a capacity of 110 mAh g-1 after 500 cycles, with a capacity retention rate of 75%. Specific Implementation Example 8:

[0083] A method for preparing a functional thin-film component is identical to that in Specific Example 1, except that the pretreatment solution is composed of an excess of 0.1 mol / L hydrofluoric acid and 1 mol / L magnesium nitrate, in order to form the functional thin film described above.

[0084] The obtained functional thin film was assembled into a lithium metal battery. The assembly and activation methods were the same as in Specific Example 1. The battery had an initial capacity of 150 mAh g-1 and a capacity of 78.8 mAh g-1 after 500 cycles, with a capacity retention rate of 75%. Specific Implementation Example 9:

[0086] A method for preparing a functional thin-film component is identical to that in Specific Example 1, except that the pretreatment solution is composed of an excess of 3 mol / L perchloric acid and 8 mol / L zinc nitrate, in order to form the functional thin film.

[0087] The obtained functional thin film was assembled into a lithium metal battery. The assembly and activation methods were the same as in Specific Example 1. The battery had an initial capacity of 158 mAh g-1 and a capacity of 110.6 mAh g-1 after 500 cycles, with a capacity retention of 70%.

[0088] As can be seen from Examples 1 and 6-9, the type of inorganic acid or nitrate is an important factor affecting the lithium affinity modification stage of thin film modules when the current treatment solution is different. Mixing inorganic acids and nitrates of different components helps to improve the lithium affinity performance of functional thin film modules. Lithophilic modification is the key to affecting the nucleation and growth of lithium metal, which in turn affects battery performance.

[0089] The inorganic acids in the above embodiments are only sulfuric acid, hydrofluoric acid, and perchloric acid, but this does not affect the use of hydrochloric acid and nitric acid in the preparation method of the functional thin film components; the nitrates in the above embodiments are only lithium nitrate, zinc nitrate, and magnesium nitrate, but this does not affect the use of nickel nitrate and sodium nitrate in the preparation method of the functional thin film components. Specific Implementation Example 10:

[0091] A method for preparing a functional thin film component is identical to that in Specific Example 1, except that the heat treatment temperature of the thin film substrate is 80°C and held for 2 hours, in order to form the functional thin film.

[0092] The obtained functional thin film was assembled into a lithium metal battery. The assembly and activation methods were the same as in Specific Example 1. The battery had an initial capacity of 149 mAh g-1 and a capacity of 116.2 mAh g-1 after 500 cycles, with a capacity retention of 78%. Specific Implementation Example 11:

[0094] A method for preparing a functional thin film component is identical to that in Specific Example 1, except that the heat treatment temperature of the thin film substrate is 50°C and held for 2 hours, in order to form the functional thin film.

[0095] The obtained functional thin film was assembled into a lithium metal battery. The assembly and activation methods were the same as in Specific Example 1. The battery had an initial capacity of 150 mAh g-1 and a capacity of 105 mAh g-1 after 500 cycles, with a capacity retention of 70%.

[0096] As can be seen from specific embodiments 1, 10, and 11, when the heat treatment temperature is different, the capacity retention rate increases with the increase of the treatment temperature. The reason for this is mainly because the increase of temperature can ensure the loading of nitrate ions, reduce the nucleation overpotential of lithium metal, provide more lithium metal deposition sites and growth space, and make lithium metal growth more uniform and internal porosity larger, providing space for lithium metal storage and avoiding the formation of lithium dendrites. Specific Implementation Example 12:

[0098] A method for preparing a functional thin film component is identical to that in Specific Example 1, except that the heat treatment temperature of the thin film substrate is 80°C and held for 6 hours, in order to form the functional thin film.

[0099] The obtained functional thin film was assembled into a lithium metal battery. The assembly and activation methods were the same as in Specific Example 1. The battery had an initial capacity of 158 mAh g-1 and a capacity of 127 mAh g-1 after 500 cycles, with a capacity retention rate of 81%.

[0100] As can be seen from specific embodiments 1 and 12, when the heat treatment time is different, the capacity retention rate increases with the increase of heat treatment time. The final temperature holding time of heat treatment is 0.5~6h, and the minimum holding time of the final temperature of heat treatment is 0.5h. If it is less than 0.5h, the formation of the lithium-affinity property of the thin film substrate in the pretreatment solution cannot be completed, and the technical effect of the present invention cannot be achieved. The reason for this is that the heat treatment time increases the lithium-affinity property of the thin film substrate, provides space for lithium metal storage, avoids the formation of lithium dendrites, and makes the lithium metal cycle have a high utilization rate and cycle stability.

[0101] In practical applications, battery cathode materials are not limited to lithium iron phosphate cathodes, but can also include lithium cobalt oxide, lithium manganese oxide, nickel-cobalt-manganese ternary cathode materials, sulfur cathode materials, and other cathode materials.

[0102] The functional thin-film module and its preparation method, along with the lithium metal battery containing the thin-film module, described above in conjunction with the accompanying drawings, utilize a low-concentration acid solution for treatment. This minimizes the increase in surface defects on the carbon-based material, ensuring the flexibility of the substrate material and facilitating structural stability. It can be used as a module; the process is simple and has a high safety factor. It solves the problems existing in the prior art. However, this invention is not limited to the described embodiments. Variations, modifications, substitutions, and modifications made to the embodiments without departing from the principles and spirit of this invention still fall within the protection scope of this invention.

Claims

1. A method for preparing a functional thin-film component, characterized in that: The functional thin film component includes a thin film substrate, the interior of which is porous. The porous structure includes pores inherent within carbon nanotubes, carbon microtubes, or porous carbon fibers, as well as pores formed by the interweaving of carbon nanotubes, carbon microtubes, or porous carbon fibers. The method includes a thin film substrate preparation stage and a thin film lithiophilic modification stage. The thin film substrate preparation stage includes the following steps: Step 1: Take an appropriate amount of carbon nanotubes or carbon microtubes or porous carbon fibers and adhesive materials and disperse them evenly in a solvent to form a mixed solution; the adhesive materials are one or more of polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, methylcellulose, sodium carboxymethyl cellulose, bacterial cellulose and nanocellulose; The solvent is one or more of water, N-methylpyrrolidone and N,N-dimethylformamide; the mass ratio of carbon nanotubes or carbon microtubes or porous carbon fibers to adhesive materials ranges from 10:1 to 5:

1. Step 2: Place the mixed solution obtained in Step 1 into a container with a filter membrane, filter the solvent, and then dry it to form a thin film substrate; the thickness of the thin film substrate ranges from 10 μm to 500 μm, and the porosity ranges from 10% to 50%; The thin film lithiophilic modification stage includes the following steps: Step 11: Prepare the pretreatment solution, which is a mixed solution containing inorganic acid and nitrate; Step 12: Place the thin film substrate obtained in Step 2 into the pretreatment solution for heat treatment; Step 13: After heat treatment, remove the film, wash it, and dry it to obtain the functional film assembly; The surface of the carbon nanotubes, carbon microtubes, or porous carbon fibers is suspended with nitrate ions by chemical bonds. The nitrate ions enhance the lithiophilicity of the carbon nanotubes, carbon microtubes, or porous carbon fibers, providing nucleation sites for metallic lithium, thereby enabling metallic lithium to be deposited uniformly and dendrite-free in the pores and surface of the functional thin film module.

2. The method for preparing the functional thin-film component according to claim 1, characterized in that: In step 11, the inorganic acid is one or more of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, and perchloric acid. The nitrate is one or more of lithium nitrate, nickel nitrate, zinc nitrate, sodium nitrate, and magnesium nitrate.

3. The method for preparing the functional thin-film component according to claim 2, characterized in that: The concentration range of the inorganic acid is 0.1 mol / L to 3 mol / L, and the concentration range of the nitrate is 1 mol / L to 8 mol / L.

4. The method for preparing the functional thin-film component according to claim 1, characterized in that: The heating rate of the heat treatment in step 12 is 1-10℃ / min, the final temperature of the heat treatment is 50~100℃, and the holding time of the final temperature is 0.5~6h.

5. A lithium metal battery containing a functional thin-film component, characterized in that: The lithium battery comprises a lithium iron phosphate positive electrode, a separator, a functional thin film component prepared by the method of preparing a functional thin film component as described in any one of claims 1-4, and a lithium metal negative electrode stacked sequentially.

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