A modified copper foil, a method for manufacturing the same, and an application thereof

Abstract

The application discloses a modified copper foil and a preparation method and application thereof. The preparation method of the modified copper foil comprises the following steps: (1) mixing lithium metal powder, a magnesium source and ammonium hydrogen fluoride powder, heating to a molten state to obtain a molten mixture; (2) uniformly coating the molten mixture prepared in the step (1) on the surface of a pretreated copper foil, then performing an alloying reaction at 200-300 DEG C, and cooling to room temperature after the reaction, so that the modified copper foil is prepared. Through the construction of a double-layer modified structure of an alloy-composite functional layer on the surface of the copper foil, the application realizes the accurate regulation of lithium deposition behavior, and significantly improves the electrochemical performance and safety performance of a lithium metal battery. The application has simple process steps, controllable cost and easy industrialized mass production, and is suitable for the surface modification of copper foil current collectors of various high-energy-density lithium batteries.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage technology, and particularly relates to a modified copper foil, its preparation method and application. Background Technology

[0002] Lithium metal solid-state batteries, using lithium metal (Li) as the negative electrode, are considered an ideal choice for next-generation power batteries. However, their commercialization is severely hampered by the core bottleneck of uncontrollable lithium deposition behavior: the disordered growth of lithium dendrites and the fragile lithium / electrolyte interface result in a loose and porous lithium deposition layer. This non-dense deposition morphology not only causes a large amount of active lithium to be unable to participate in electrochemical reactions due to the formation of "dead lithium," significantly reducing the battery's specific capacity and volumetric energy density, but also poses serious safety hazards.

[0003] Copper, with its excellent conductivity and mechanical stability, is widely used as a current collector and lithium deposition carrier. However, the bare copper surface lacks sufficient lithium affinity, making it difficult to induce uniform lithium ion nucleation. Simultaneously, its surface cannot spontaneously form a uniform and stable solid electrolyte interphase (SEI) layer, leading to uneven local ion flow distribution and exacerbating non-uniform lithium growth. The stability of lithium metal anodes depends primarily on two key factors: the lithium affinity of the current collector (i.e., its ability to attract lithium ions) and the mechanical / chemical durability of the SEI layer (which determines interfacial integrity during cycling). Although researchers have explored various improvement strategies, including enhancing the current collector's lithium affinity, constructing artificial SEI layers, optimizing interfacial contacts, and developing novel electrolyte additives, existing solutions often address one aspect while neglecting another, mostly only improving lithium affinity or strengthening the SEI layer individually, failing to synergistically solve both key problems within the same system. Therefore, existing modification strategies are insufficient to completely suppress dendrite growth and achieve long-term stability.

[0004] In summary, developing an integrated strategy that can simultaneously improve the lithium affinity of copper current collectors and construct a highly stable artificial SEI layer is of vital importance for fundamentally solving the problems of lithium dendrite growth and interface failure, and for promoting the practical application of lithium metal solid-state batteries. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a modified copper foil, its preparation method and application.

[0006] The objective of this invention is achieved through the following technical solution: A method for preparing modified copper foil includes the following steps: (1) Take lithium metal powder, magnesium source and ammonium bifluoride powder, mix them, heat to the molten state to obtain a molten mixture; (2) The molten mixture prepared in step (1) is uniformly coated on the surface of the pretreated copper foil, and then an alloying reaction is carried out at 200~300℃. After the reaction is completed, the mixture is cooled to room temperature to obtain the modified copper foil.

[0007] Preferably, the molar ratio of lithium metal powder, magnesium source and ammonium bifluoride powder in step (1) is 1~2:1:2~4.

[0008] Preferably, in step (1), lithium metal powder, magnesium source and ammonium fluoride powder are mixed, heated to 150~350℃ and held for 10~20min until molten state is obtained to obtain a molten mixture.

[0009] Preferably, the process of mixing lithium metal powder, magnesium source and ammonium bifluoride powder in step (1) and heating to a molten state is carried out in a glove box with a dew point below -45°C.

[0010] Preferably, the magnesium source is at least one of magnesium carbonate and magnesium stearate.

[0011] Preferably, the coating amount of the molten mixture in step (2) on the pretreated copper foil surface is 0.5~2.5 mg / cm². 2 .

[0012] Preferably, in step (2), the molten mixture is uniformly coated on the surface of the pretreated copper foil, and then the alloying reaction is carried out at 200~300°C in a glove box with a dew point below -45°C.

[0013] Preferably, the temperature and time of the alloying reaction in step (2) are 10~30 min.

[0014] Preferably, the pretreated copper foil in step (2) is prepared as follows: commercial electrolytic copper foil is sequentially subjected to degreasing, derusting, water washing and drying to obtain a clean copper foil substrate.

[0015] Preferably, the degreasing method is ultrasonic degreasing; the rust removal method is acid pickling; and the drying method is vacuum drying.

[0016] Preferably, the ultrasonic degreasing time is 10-20 min; the acid pickling and rust removal uses a dilute sulfuric acid solution with a concentration of 0.5-2 mol / L; and the vacuum drying temperature is 60-80℃ and the time is 2-4 h.

[0017] A modified copper foil is prepared by the above-described method for preparing modified copper foil.

[0018] The above-mentioned modified copper foil is used as a negative electrode current collector in lithium metal solid-state batteries.

[0019] Compared with the prior art, the beneficial effects of the present invention include: (1) The preparation process is simple and efficient, and has excellent potential for industrial mass production. The modified copper foil preparation method proposed in this invention has significant advantages such as a short process, convenient operation, and mild reaction conditions; (2) The modified copper foil prepared in this invention has an alloying layer on its surface and is further composited with functional layers (magnesium fluoride and lithium fluoride). Thanks to this unique structure, the copper foil has extremely high lithium affinity, which can effectively induce uniform deposition of lithium metal and significantly improve the structural stability of the electrode. Attached Figure Description

[0020] Figure 1 Microscopic images of the surface morphology of commercial double-sided copper foil and the modified copper foil described in Example 1.

[0021] Figure 2 The graph shows a comparison of the cycle performance of lithium foil / modified copper foil half-cells and lithium foil / commercial copper foil half-cells prepared using the modified copper foil and pure copper foil as shown in Example 1, respectively, at a current density of 1 mA / cm² and an areal capacity of 1 mAh / cm². Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] Although solid-state batteries using lithium metal (Li) as the negative electrode are considered ideal for next-generation power batteries, their progress from laboratory to industrial application is severely hampered by the core challenge of uncontrollable lithium deposition behavior. Specifically, existing technologies suffer from the following key defects and limitations in addressing this problem: (1) The poor surface properties of traditional copper current collectors lead to uncontrolled lithium nucleation and growth. Although copper (Cu) is widely used as a current collector due to its excellent electrical conductivity and mechanical stability, its exposed surface has inherent physicochemical defects: Low lithium affinity: Copper surfaces have a weak adsorption capacity for lithium ions, resulting in a high lithium nucleation overpotential. This causes lithium to tend to nucleate randomly at a few active sites rather than spread uniformly.

[0024] Induced dendrite growth: Initial non-uniform nucleation triggers subsequent non-uniform lithium growth, forming sharp lithium dendrites. This not only consumes active lithium and reduces the battery's specific capacity and volumetric energy density, but more seriously, the growing dendrites can easily pierce the solid electrolyte or separator, causing internal short circuits and posing a significant safety hazard.

[0025] Unable to control ion flow distribution: The exposed copper surface lacks the ability to guide a uniform flux of lithium ions, resulting in excessively high local current density, which further exacerbates the non-compactness of the deposition.

[0026] (2) The solid electrolyte interface (SEI) is fragile and difficult to self-repair. The stability of lithium metal anodes is highly dependent on the quality of the SEI layer; however, existing technologies struggle to construct durable and stable interfaces on copper substrates. The interface is fragile and easily broken: Due to the huge volume change during the lithium deposition / stripping process, the native SEI layer is extremely prone to mechanical fracture.

[0027] Side reactions continue to occur: the ruptured SEI layer exposes fresh lithium surfaces, triggering continuous electrolyte side reactions that consume limited active lithium and electrolyte, leading to low coulombic efficiency and rapid battery failure.

[0028] Lack of homogenization mechanism: Traditional copper surfaces cannot promote the in-situ formation of a uniform and dense SEI layer, resulting in uneven interfacial impedance and exacerbating the local accumulation of lithium ions.

[0029] (3) Existing modification strategies have the limitation of "paying attention to one thing but losing attention to another" (core pain point) To address these issues, researchers have explored various improvement strategies, including enhancing the lithiophilicity of current collectors, constructing artificial SEI layers, optimizing interface structures, and developing novel electrolyte additives. However, existing technologies generally suffer from a fatal flaw: "single-point breakthrough, overall imbalance." The strategies are too simplistic and fail to address all aspects: Most methods focus only on solving a single problem. For example, while some modified layers significantly improve the lithophileness of copper and promote uniform nucleation, they fail to provide sufficient mechanical strength to maintain the long-term stability of the SEI. Conversely, while other artificial SEI layers enhance interface durability, they fail to fundamentally improve the nucleation energy barrier of the copper matrix, resulting in uneven lithium deposition at interface defects.

[0030] Lack of synergistic effect: Currently, few technologies can simultaneously achieve the dual goals of "high lithium affinity-induced uniform nucleation" and "high-stability SEI suppression of side reactions / dendritic formation." This trade-off prevents a fundamental improvement in the stability of lithium metal anodes, limiting the overall cycle life and safety performance of batteries.

[0031] Therefore, the purpose of this invention is to provide a modified copper foil, its preparation method, and its application, to solve the problem of the coexistence of lithium dendrite growth and interface failure.

[0032] The objective of this invention is achieved through the following technical solution: A method for preparing modified copper foil includes the following steps: (1) Take lithium metal powder, magnesium source and ammonium bifluoride powder, mix them, heat to the molten state to obtain a molten mixture; (2) The molten mixture prepared in step (1) is uniformly coated on the surface of the pretreated copper foil, and then an alloying reaction is carried out at 200~300℃. After the reaction is completed, the mixture is cooled to room temperature to obtain the modified copper foil.

[0033] In this invention, lithium, magnesium source, and ammonium bifluoride powder are first mixed and heated to a molten state to obtain a molten mixture. Then, the prepared molten mixture is uniformly coated onto the surface of a pretreated copper foil, and an alloying reaction is carried out at 200-300°C. The main skeletal reaction involved is: Mg 2+ +F - → MgF2, NH4HF2 + Li → LiF + NH3 + H2; finally, cooling to room temperature yields the modified copper foil. We understand that for the modified copper foil of this invention, MgF2 and LiF on the copper foil surface are in-situ transformed into a LiMg alloy during the initial discharge process. The resulting LiMg alloy is thinner than the LiMg alloy produced by rolling a composite of commercially available lithium foil and magnesium foil. The in-situ generated LiMg alloy improves the affinity for lithium. The negative ΔrG value of LiMg in the molten state indicates the newly formed chemical bonds. Furthermore, LiF is generated on the surface of the modified copper foil of this invention, constructing a LiF-rich artificial solid electrolyte interface (SEI) film, which has been proven to be an effective strategy for suppressing the growth of lithium metal anode dendrites.

[0034] Preferably, the mass ratio of lithium metal powder, magnesium source and ammonium bifluoride powder in step (1) is 1~2:1:2~4.

[0035] In some embodiments of the present invention, the mass ratio of lithium metal powder, magnesium source, and ammonium bifluoride powder in step (1) is 1~2:1:2~4; for example, it can be 1:1:2 and 2:1:4 or any two of the above values. In this way, it can be ensured that the amount of each reactant is appropriate, so as to obtain the desired target product after the alloying reaction.

[0036] Preferably, in step (1), lithium metal powder, magnesium source and ammonium fluoride powder are mixed, heated to 150~350℃ and held for 10~20min until molten state is obtained to obtain a molten mixture.

[0037] In some embodiments of the present invention, in step (1), lithium metal powder, magnesium source and ammonium bifluoride powder are mixed and heated to 150~350°C and held for 10~20 minutes until they are in a molten state. For example, the heating temperature can be 150°C, 200°C, 250°C, 300°C and 350°C and any two of the above values. In this way, the method can ensure that each component is in a molten state, thereby promoting their full mixing.

[0038] Preferably, the process of mixing lithium metal powder, magnesium source and ammonium bifluoride powder in step (1) and heating to a molten state is carried out in a glove box with a dew point below -45°C.

[0039] In some embodiments of the present invention, given that lithium is an alkali metal, it readily reacts violently with water to produce lithium hydroxide and hydrogen gas; even in the presence of trace amounts of water vapor, the surface of lithium powder will rapidly oxidize or hydrolyze to form a passivation layer. Furthermore, this operation involves heating to a molten state; increased temperature leads to a sharp increase in the chemical reaction rate, and if water and oxygen are present in the environment, molten lithium is highly susceptible to violent combustion or even explosion. For safety reasons and to ensure product purity, this operation must be carried out in a glove box with a dew point below -45°C. Under these conditions, the ambient moisture content is controlled at a low level, significantly slowing down the corrosion rate of lithium and effectively preventing uncontrollable side reactions during heating. If the dew point is higher than this value (e.g., -20°C), the moisture content may reach hundreds of ppm, posing not only safety hazards but also potential experimental failure.

[0040] Preferably, the magnesium source is at least one of magnesium carbonate and magnesium stearate.

[0041] In some embodiments of the present invention, the magnesium source is at least one of magnesium carbonate and magnesium stearate. Using these magnesium sources can achieve low-temperature melting, thereby significantly reducing energy consumption.

[0042] Preferably, the coating amount of the molten mixture in step (2) on the pretreated copper foil surface is 0.5~2.5 mg / cm². 2 .

[0043] In some embodiments of the present invention, the amount of the molten mixture in step (2) coated on the pretreated copper foil surface is 0.5~2.5 mg / cm². 2 For example, it could be 0.6 mg / cm³ 2 1.1 mg / cm 2 and 2.2 mg / cm 2 And the value between any two of the above. Thus, an excessively thick lithium layer will cause a sharp drop in battery energy density.

[0044] Preferably, in step (2), the molten mixture is uniformly coated on the surface of the pretreated copper foil, and then the alloying reaction is carried out at 200~300°C in a glove box with a dew point below -45°C.

[0045] In some embodiments of the present invention, the molten mixture is uniformly coated onto the surface of the pretreated copper foil, and then the alloying reaction is carried out at 200-300°C in a glove box with a dew point below -45°C. This is because at high temperatures of 200-300°C, the reactivity of water and oxygen is greatly amplified, and even trace amounts of water vapor can cause the copper foil to oxidize and fail instantly, as well as damage the chemical structure of the coating material. Therefore, a glove box with a dew point <-45°C must be used to create an ultra-dry and ultra-inert heat treatment environment to ensure the purity of the interfacial reaction and the high performance of the final battery.

[0046] Preferably, the alloying reaction time in step (2) is 10~30 min.

[0047] In some embodiments of the present invention, the alloying reaction time in step (2) is 10 to 30 minutes; for example, it can be 10 minutes, 20 minutes, and 30 minutes, or any two of these values. This ensures that the alloying reaction proceeds sufficiently and the desired target product is obtained.

[0048] Preferably, the pretreated copper foil in step (2) is prepared as follows: commercial electrolytic copper foil is sequentially subjected to degreasing, derusting, water washing and drying to obtain a clean copper foil substrate.

[0049] In some embodiments of the present invention, performing a series of pretreatments—degreasing, derusting, washing, and drying—on commercial electrolytic copper foil before preparing the modified copper foil is a crucial step in ensuring the final battery performance. By sequentially performing these pretreatments on the commercial electrolytic copper foil, organic oil, inorganic oxide layers, and residual chemical reagents on the surface are effectively removed. This process significantly improves the surface energy and wettability of the copper foil surface, ensuring uniform spreading and defect-free film formation of the subsequent functional coating. Without these treatments, contaminants on the surface of the commercial copper foil would directly lead to the failure of the modified layer.

[0050] Preferably, the degreasing method is ultrasonic degreasing; the rust removal method is acid pickling; and the drying method is vacuum drying.

[0051] In some embodiments of the present invention, ultrasonic degreasing utilizes the cavitation effect to deeply remove organic contaminants within micropores, ensuring uniform surface wettability. Subsequently, acid pickling chemically dissolves the high-resistance oxide layer, exposing the highly active metallic copper lattice to enhance interfacial bonding. Finally, vacuum drying rapidly removes deep-bound water in a low-oxygen, low-temperature environment, effectively preventing secondary oxidation and thermal deformation of the clean copper surface. This combined process maximizes the surface energy and purity of the copper foil substrate, laying a solid foundation for the subsequent construction of a stable modified interface.

[0052] Preferably, the ultrasonic degreasing time is 10-20 min; the acid pickling and rust removal uses a dilute sulfuric acid solution with a concentration of 0.5-2 mol / L; and the vacuum drying temperature is 60-80℃ and the time is 2-4 h.

[0053] In some embodiments of the present invention, the ultrasonic degreasing time is controlled at 10-20 minutes. This time window can thoroughly remove stubborn oil stains in the micropores by utilizing the cavitation effect, while avoiding potential damage to the microstructure of the copper foil caused by prolonged ultrasonication. Acid pickling uses 0.5-2 mol / L dilute sulfuric acid. This concentration range achieves efficient and selective dissolution of copper oxides, rapidly restoring the conductive surface of metallic copper while effectively suppressing excessive corrosion of the copper substrate and hydrogen evolution side reactions. Vacuum drying is set at 60-80°C for 2-4 hours. This condition utilizes the low boiling point of water under low pressure to thoroughly remove free and bound water from the surface and pores at a gentle temperature, while strictly avoiding the risk of secondary oxidation of the copper surface caused by high temperatures. The synergistic optimization of the above parameters ensures that the copper foil substrate reaches an ideal state before entering the modification process.

[0054] A modified copper foil is prepared by the above-described method for preparing modified copper foil.

[0055] The above-mentioned modified copper foil is used as a negative electrode current collector in lithium metal solid-state batteries.

[0056] Example 1 A method for preparing modified copper foil, the specific steps of which are as follows: (1) Copper foil pretreatment: Commercial electrolytic copper foil (commercial double-sided copper foil, thickness of 6μm, purity ≥99.9%) is subjected to ultrasonic degreasing, pickling and rust removal, deionized water rinsing and vacuum drying in sequence to obtain clean copper foil substrate; wherein, the pickling uses a dilute sulfuric acid solution with a concentration of 0.5~2mol / L, the ultrasonic treatment time is 10~20min, the vacuum drying temperature is 60~80℃, and the drying time is 2~4h.

[0057] (2) Weigh 0.7g of micron-sized lithium metal powder, 8.4g of magnesium carbonate and 11.4g of ammonium bifluoride in a glove box with a dew point below -45°C.

[0058] (3) Continue mixing the micron-sized lithium metal powder, magnesium carbonate, and ammonium bifluoride weighed in step (2) thoroughly in a glove box with a dew point below -45°C. Place the mixture in an iron crucible, then heat it in a muffle furnace to 350°C and hold it for 10 minutes until it melts. Remove the crucible containing the molten mixture and coat the molten mixture evenly onto the surface of the copper foil substrate described in step (1) (coating amount is 1.1 mg / cm). 2 The alloying reaction was carried out at 200-300℃ for 30 minutes, and then naturally cooled to room temperature to obtain the modified copper foil.

[0059] Example 2 A method for preparing modified copper foil, the specific steps of which are as follows: (1) Copper foil pretreatment: Commercial electrolytic copper foil (commercial double-sided copper foil, thickness of 6μm, purity ≥99.9%) is subjected to ultrasonic degreasing, pickling and rust removal, deionized water rinsing and vacuum drying in sequence to obtain clean copper foil substrate; wherein, the pickling uses a dilute sulfuric acid solution with a concentration of 0.5~2mol / L, the ultrasonic treatment time is 10~20min, the vacuum drying temperature is 60~80℃, and the drying time is 2~4h.

[0060] (2) Weigh 0.7g of micron-sized lithium metal powder, 59.1g of magnesium stearate and 11.4g of ammonium hydrogen fluoride in a glove box with a dew point below -45°C.

[0061] (3) Continue mixing the micron-sized lithium metal powder, magnesium carbonate, and ammonium bifluoride weighed in step (2) thoroughly in a glove box with a dew point below -45°C. Place the mixture in an iron crucible, then heat it in a muffle furnace to 200°C and hold it for 10 minutes until it melts. Remove the crucible containing the molten mixture and coat it evenly onto the surface of the copper foil substrate described in step (1) (coating amount is 1.1 mg / cm). 2 The alloying reaction was carried out at 200-300℃ for 30 minutes, and then naturally cooled to room temperature to obtain the modified copper foil.

[0062] Example 3 A method for preparing modified copper foil, the specific steps of which are as follows: (1) Copper foil pretreatment: Commercial electrolytic copper foil (commercial double-sided copper foil, thickness of 6μm, purity ≥99.9%) is subjected to ultrasonic degreasing, pickling and rust removal, deionized water rinsing and vacuum drying in sequence to obtain clean copper foil substrate; wherein, the pickling uses a dilute sulfuric acid solution with a concentration of 0.5~2mol / L, the ultrasonic treatment time is 10~20min, the vacuum drying temperature is 60~80℃, and the drying time is 2~4h.

[0063] (2) Weigh 1.4g of micron-sized lithium metal powder, 8.4g of magnesium carbonate and 22.8g of ammonium bifluoride in a glove box with a dew point below -45°C.

[0064] (3) Continue mixing the micron-sized lithium metal powder, magnesium carbonate, and ammonium bifluoride weighed in step (2) thoroughly in a glove box with a dew point below -45°C. Place the mixture in an iron crucible, then heat it in a muffle furnace to 200°C and hold it for 10 minutes until it melts. Remove the crucible containing the molten mixture and coat it evenly onto the surface of the copper foil substrate described in step (1) (coating amount is 1.1 mg / cm). 2 The alloying reaction was carried out at 200-300℃ for 30 minutes, and then naturally cooled to room temperature to obtain the modified copper foil.

[0065] Example 4 A method for preparing modified copper foil, the specific steps of which are as follows: (1) Copper foil pretreatment: Commercial electrolytic copper foil (commercial double-sided copper foil, thickness of 6μm, purity ≥99.9%) is subjected to ultrasonic degreasing, pickling and rust removal, deionized water rinsing and vacuum drying in sequence to obtain clean copper foil substrate; wherein, the pickling uses a dilute sulfuric acid solution with a concentration of 0.5~2mol / L, the ultrasonic treatment time is 10~20min, the vacuum drying temperature is 60~80℃, and the drying time is 2~4h.

[0066] (2) Weigh 1.4g of micron-sized lithium metal powder, 59.1g of magnesium stearate and 22.8g of ammonium bifluoride in a glove box with a dew point below -45°C.

[0067] (3) Continue mixing the micron-sized lithium metal powder, magnesium carbonate, and ammonium bifluoride weighed in step (2) thoroughly in a glove box with a dew point below -45°C. Place the mixture in an iron crucible, then heat it in a muffle furnace to 200°C and hold it for 10 minutes until it melts. Remove the crucible containing the molten mixture and coat it evenly onto the surface of the copper foil substrate described in step (1) (coating amount is 1.1 mg / cm). 2 The alloying reaction was carried out at 200-300℃ for 30 minutes, and then naturally cooled to room temperature to obtain the modified copper foil.

[0068] Figure 1 Microscopic images of the surface morphology of commercial double-sided copper foil and the modified copper foil described in Example 1, from... Figure 1 We can see that the modified copper foil has a slight structural change in surface texture compared to commercial copper foil, but still maintains a relatively flat and uniform surface morphology.

[0069] Figure 2The graphs show a comparison of the cycle performance of lithium foil / modified copper foil half-cells and lithium foil / commercial copper foil half-cells prepared using the modified copper foil and pure copper foil as shown in Example 1, respectively, at a current density of 1 mA / cm² and an areal capacity of 1 mAh / cm². The specific steps for preparing the lithium foil / modified copper foil half-cell using the modified copper foil as shown in Example 1 are as follows: using lithium metal foil as the counter electrode and the modified copper foil sample as the working electrode, a 2032 type button cell is assembled. The electrolyte consists of a mixture of 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME) (volume ratio 1:1), with 1 wt.% LiNO3 added. Celgard 2500 is used as the separator. The specific steps for preparing lithium foil / commercial copper foil half-cells using pure copper foil are as follows: Lithium metal foil is used as the counter electrode, and a modified copper foil sample is used as the working electrode. These are assembled into a 2032 type button cell. The electrolyte consists of a mixture of 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME) (volume ratio 1:1), with 1 wt.% LiNO3 added. Celgard 2500 is used as the separator. Figure 2 We can see that the coulombic efficiency of both half-cells remained high in the early stages, but in subsequent cycles, the coulombic efficiency of the commercial copper foil continuously declined sharply, eventually leading to cell failure. In contrast, the half-cell using modified copper foil current collectors exhibited a significantly improved cycle life, reaching up to 200 cycles while maintaining a high coulombic efficiency throughout.

[0070] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing modified copper foil, characterized in that, Includes the following steps: (1) Take lithium metal powder, magnesium source and ammonium bifluoride powder, mix them, heat to the molten state to obtain a molten mixture; (2) The molten mixture prepared in step (1) is uniformly coated on the surface of the pretreated copper foil, and then an alloying reaction is carried out at 200~300℃. After the reaction is completed, the mixture is cooled to room temperature to obtain the modified copper foil.

2. The method for preparing the modified copper foil according to claim 1, characterized in that, The molar ratio of lithium metal powder, magnesium source and ammonium bifluoride powder in step (1) is 1~2:1:2~4.

3. The method for preparing modified copper foil according to claim 1, characterized in that, Step (1) involves mixing lithium metal powder, magnesium source, and ammonium bifluoride powder, heating to 150-350°C and maintaining the temperature for 10-20 minutes until a molten state is reached, to obtain a molten mixture; and / or The magnesium source is at least one of magnesium carbonate and magnesium stearate.

4. The method for preparing modified copper foil according to claim 1, characterized in that, The process of mixing lithium metal powder, magnesium source, and ammonium bifluoride powder in step (1) and heating it to a molten state is carried out in a glove box with a dew point below -45°C; and / or In step (2), the molten mixture is uniformly coated on the surface of the pretreated copper foil, and then the alloying reaction is carried out at 200~300°C in a glove box with a dew point below -45°C.

5. The method for preparing modified copper foil according to claim 1, characterized in that, In step (2), the amount of the molten mixture coated on the pretreated copper foil surface is 0.5~2.5 mg / cm². 2 .

6. The method for preparing modified copper foil according to claim 1, characterized in that, The alloying reaction in step (2) takes 10 to 30 minutes.

7. The method for preparing the modified copper foil according to claim 1, characterized in that, The pretreated copper foil in step (2) is prepared as follows: commercial electrolytic copper foil is sequentially subjected to degreasing, derusting, water washing and drying to obtain a clean copper foil substrate.

8. The method for preparing modified copper foil according to claim 7, characterized in that, The degreasing method is ultrasonic degreasing; the rust removal method is acid pickling; the drying method is vacuum drying; and / or The ultrasonic degreasing time is 10-20 min; the acid pickling and rust removal uses a dilute sulfuric acid solution with a concentration of 0.5-2 mol / L; the vacuum drying temperature is 60-80℃ and the time is 2-4 h.

9. A modified copper foil, characterized in that, It is prepared by the method for preparing modified copper foil according to any one of claims 1 to 8.

10. The application of the modified copper foil of claim 9 as a negative electrode current collector in a lithium metal solid-state battery.

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