A composite current collector with a crystal face-induced LiF-Ag mixed SEI film, a preparation method thereof, a negative electrode sheet, and a battery

Abstract

The application discloses a kind of composite current collector with crystal face induced LiF-Ag mixed SEI film and its preparation method, negative plate and battery, comprising the following steps: pre-plating Li precursor layer on the both sides surface of composite copper current collector;The composite copper current collector pre-plated with Li precursor layer is immersed in AgF / EC-DEC solution, and nano-scale LiF crystal and dispersed Ag metal core are generated at the interface, to realize atomic-level self-assembly of SEI film;The composite copper current collector with SEI film self-assembly is dried, so that residual solvent is removed and Ag + The surface initial orientation structure induced to form is formed.The application realizes the plane deposition and self-protection of composite copper current collector negative electrode in high rate cycle by constructing highly oriented LiF-Ag mixed SEI film, and solves the problems of easy growth of dendrite tip on high-energy crystal face, SEI unevenness, high interface impedance, short cycle life and the like in high current density cycle.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a composite current collector with a crystal-inducible LiF-Ag mixed SEI film, its preparation method, a negative electrode, and a battery. Background Technology

[0002] With the increasing demands on lithium-ion battery performance from new energy vehicles and energy storage devices, composite current collectors have been widely used in battery manufacturing due to their lightweight and high conductivity. However, in practical applications, composite current collectors still face many challenges. Especially when the negative electrode material is under high load or high-rate charge / discharge, problems such as interface instability, metal layer peeling, and poor adaptability to volume expansion become particularly prominent. These problems accelerate the degradation of the solid electrolyte interphase (SEI) film, leading to a significant decrease in battery cycle performance. Therefore, developing a novel surface functional film that can improve interface stability, adapt to stress changes, and is compatible with the composite current collector structure has become a key issue that urgently needs to be addressed in the current lithium-ion battery technology field. Summary of the Invention

[0003] The purpose of this invention is to provide a composite current collector with a crystal plane-induced LiF-Ag mixed SEI film, its preparation method, negative electrode sheet, and battery, to solve the problems of dendrite tip growth on high-energy crystal planes, uneven SEI, high interface impedance, and short cycle life of the composite current collector negative electrode during high current density cycling.

[0004] To achieve the above objectives, the technical solution provided by the present invention is as follows: The first aspect of this application provides a method for preparing a composite current collector with a crystal plane-induced LiF-Ag mixed SEI film, comprising the following steps: S1: Pre-plating Li precursor layers on both sides of the composite copper current collector; S2: The composite copper current collector pre-plated with Li precursor layer is immersed in AgF / EC-DEC solution to generate nanoscale LiF crystals and dispersed Ag metal cores at the interface, thereby realizing the atomic-level self-assembly of the SEI film. S3: The composite copper current collector with SEI film self-assembly is dried to remove residual solvent and fix Ag. + Induced initial orientation structure of the surface.

[0005] To optimize the above technical solution, the specific measures also include: Step S1 involves roughening the surface of the composite copper current collector before pre-plating the Li precursor layer; the surface roughening process involves immersing the composite copper current collector in a 1M hydrochloric acid solution for 40-60 seconds.

[0006] In step S1, the pre-plating method of the Li precursor layer is as follows: using a composite copper current collector as the working electrode and a Li foil as the counter electrode, lithium ion pre-plating is performed in a 1M LiPF6 / EC-DEC solution with a current density of 0.02C and a time of 1~10min.

[0007] In the 1M LiPF6 / EC-DEC solution, the volume ratio of ethylene carbonate to diethyl carbonate is 0.5~1:1~2.

[0008] In step S2, the preparation method of the AgF / EC-DEC solution is as follows: ethylene carbonate and diethyl carbonate are mixed in a volume ratio of 0.5~1:1~2 to form a mixed solvent system. High-purity AgF powder is slowly added to the mixed solvent system under anhydrous argon or dry air environment and stirred until dissolved.

[0009] In the mixed solvent system, the concentration of AgF is 0.002~0.2 M, the stirring rate is 200~600 rpm, the stirring temperature is controlled in the range of 20~50°C, and the stirring time is 1~3 hours.

[0010] In step S2, the composite copper current collector pre-plated with the Li precursor layer is immersed in the AgF / EC-DEC solution for a reaction time of 5 to 60 seconds and the immersion temperature is controlled between 20 and 60°C.

[0011] The drying process in step S3 is as follows: the composite copper current collector with SEI film self-assembly is dried in an anhydrous argon atmosphere, the drying temperature is controlled between 40 and 120°C, and the drying time is 5 to 30 minutes.

[0012] The composite copper current collector includes a middle polymer film and two copper metal layers on both sides, with the thickness of the copper metal layer on each side ranging from 400 to 2000 nm.

[0013] The second aspect of this application provides a composite current collector having a crystal plane-induced LiF-Ag mixed SEI film, which is prepared by the method described above.

[0014] A third aspect of this application provides a negative electrode comprising the aforementioned composite current collector having a crystal plane-induced LiF-Ag mixed SEI film.

[0015] A fourth aspect of this application provides a battery comprising the aforementioned negative electrode.

[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention achieves planar deposition and self-protection of the composite copper current collector anode during high-rate cycling by constructing a highly oriented LiF-Ag hybrid SEI film. First, a uniform Li precursor layer is formed on the surface of the composite copper current collector by low-rate Li pre-plating, providing active sites for subsequent AgF replacement. This precursor layer ensures sufficient contact in the replacement reaction and can closely cooperate with the LiF-Ag SEI in subsequent cycles, enhancing interfacial adhesion. Furthermore, the Li-pre-plated current collector is immersed in an AgF / EC-DEC solution, instantly generating nanoscale LiF crystals and dispersed Ag metal nuclei at the interface, achieving atomic-level self-assembly of the SEI film. LiF provides the SEI with high chemical stability and ion-selective channels, while Ag nanoparticles form a continuous electron conduction network. The tiny Ag nuclei formed in the LiF matrix significantly reduce the nucleation potential of metallic Li on the (110) crystal plane, relatively suppressing the deposition of high-energy planes such as (100) and (111). This allows subsequent lithium atoms to preferentially grow on the (110) plane, achieving planar, uniform, dendrite-free deposition. Therefore, LiF provides lithium-ion transport channels and chemical stability, while Ag nanoparticles construct an electron conduction network and optimize crystal orientation, synergistically improving the conductivity, mechanical toughness, and structural uniformity of SEI.

[0017] Furthermore, by pre-treating the surface of the copper current collector with roughening treatment, in conjunction with the Li pre-plating-AgF replacement process, the distribution of active sites can be optimized, the interfacial adhesion can be strengthened, the crystal orientation induction effect can be improved, the interfacial impedance can be reduced, and the long-term protection capability of the SEI film can be enhanced, thereby achieving a comprehensive improvement in the overall performance of the composite current collector and the battery. Detailed Implementation

[0018] The present invention will be further described in detail below through specific embodiments, but it should not be construed as limiting the scope of the subject matter of the present invention to the following embodiments. All technologies implemented based on the above content of the present invention fall within the scope of the present invention.

[0019] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the reagents, methods and equipment used are conventional reagents, methods and equipment in this technical field.

[0020] This invention provides a method for preparing a composite current collector with a crystal plane-induced LiF-Ag mixed SEI film, comprising the following steps: S1: Pre-plating Li precursor layers on both sides of the composite copper current collector; S2: The composite copper current collector pre-plated with Li precursor layer is immersed in AgF / EC-DEC solution to generate nanoscale LiF crystals and dispersed Ag metal cores at the interface, thereby realizing the atomic-level self-assembly of the SEI film. S3: The composite copper current collector with SEI film self-assembly is dried to remove residual solvent and fix Ag. +Induced initial orientation structure of the surface.

[0021] In some embodiments, before pre-plating the Li precursor layer, step S1 involves roughening the surface of the composite copper current collector; the surface roughening process involves immersing the composite copper current collector in a 1M hydrochloric acid solution for 40-60 seconds.

[0022] In step S1, the pre-plating method of the Li precursor layer is as follows: using a composite copper current collector as the working electrode and a Li foil as the counter electrode, lithium ion pre-plating is performed in a 1M LiPF6 / EC-DEC solution with a current density of 0.02C and a time of 1~10min.

[0023] In some embodiments, the volume ratio of ethylene carbonate to diethyl carbonate in the 1M LiPF6 / EC-DEC solution is 0.5~1:1~2.

[0024] In step S2, the AgF / EC-DEC solution is prepared by mixing ethylene carbonate and diethyl carbonate in a volume ratio of 0.5~1:1~2 to form a mixed solvent system. Under an anhydrous argon atmosphere or dry air environment, high-purity AgF powder is slowly added to the mixed solvent system and stirred until dissolved.

[0025] In some embodiments, the concentration of AgF in the mixed solvent system is 0.002~0.2 M, the stirring rate is 200~600 rpm, the stirring temperature is controlled in the range of 20~50°C, and the stirring time is 1~3 hours.

[0026] In step S2, the composite copper current collector pre-plated with the Li precursor layer is immersed in the AgF / EC-DEC solution for a reaction time of 5 to 60 seconds and the immersion temperature is controlled between 20 and 60°C.

[0027] The pre-plated Li precursor layer undergoes a displacement reaction with AgF: Li + AgF → LiF + Ag↓, and the resulting LiF crystals are deposited in AgF. + Under the induction of the crystal orientation along the (110) crystal plane, the Ag metal core is dispersed in the LiF matrix to form a uniform mixed SEI film, realizing atomic-level self-assembly.

[0028] The drying process in step S3 is as follows: the composite copper current collector with SEI film self-assembly is dried in an anhydrous argon atmosphere, the drying temperature is controlled between 40 and 120°C, and the drying time is 5 to 30 minutes.

[0029] Residual solvents can cause instability in the SEI film structure and affect battery performance. During the drying process, the crystallization of LiF crystals is perfected, and the distribution of Ag metal nuclei is fixed.

[0030] The composite copper current collector consists of a central polymer film and two copper metal layers on either side, with the thickness of the copper metal layer on each side ranging from 400 to 2000 nm. The thickness of the central polymer film is 2 to 10 μm, preferably made of PET, PP, or similar materials. The selection criteria include good flexibility and insulation, compatibility with the copper metal layer deposition process, and prevention of deformation during high-temperature deposition.

[0031] The polymer film can be made of PET film, PP film or other polymer substrates, and the copper layer can be prepared by one or more of the following methods: vapor deposition, magnetron sputtering, electroless plating, electroplating, CVD.

[0032] The present invention also provides a composite current collector having a crystal plane-induced LiF-Ag mixed SEI film, which is prepared by the above method.

[0033] The present invention also provides a negative electrode comprising the above-mentioned composite current collector having a crystal plane-induced LiF-Ag mixed SEI film.

[0034] The present invention also provides a battery comprising the above-described negative electrode.

[0035] The technical solution of the present invention will be further described in detail below with reference to specific embodiments: Example 1 (1) A PET film with a thickness of 4.5 μm was selected, and a copper layer of 1000 nm was deposited on both sides of the film by magnetron sputtering to obtain a PET composite copper current collector with a total thickness of about 6.5 μm, wherein the surface roughness of the copper layer is about 250 nm.

[0036] (2) Using the above-mentioned composite copper current collector as the working electrode and Li foil as the counter electrode, lithium was deposited at a constant current of 0.02C for 5 min in a 1 M LiPF6 / EC-DEC solution (EC:DEC=1:1).

[0037] (3) The pre-plated Li current collector is immersed in 0.1M AgF / EC-DEC solution (EC:DEC=1:1), kept at a constant temperature of 30°C, and reacted for 15s to generate LiF-Ag composite SEI.

[0038] (4) The current collector sample of the generated LiF-Ag composite SEI was dried in an anhydrous argon atmosphere. The drying temperature was controlled at about 60°C and the drying time was 5 minutes to obtain the final composite current collector.

[0039] (5) Battery manufacturing Positive electrode: The positive electrode current collector uses 12-micron conventional aluminum foil, and the positive electrode material uses LiNi. 0.6 Mn 0.2 Co 0.2O2 (NCM622); Negative electrode: The negative electrode current collector adopts the above-mentioned composite current collector, and the negative electrode material adopts artificial graphite; The diaphragm is made of alumina ceramic coated polyethylene diaphragm (25μm thick). Electrolyte: 1 mol·L -1 The carbonate solution of LiPF6 is a mixture of propylene carbonate, ethylene carbonate and ethyl methyl carbonate in a mass ratio of 1:1:1. Stacking assembly: The negative electrode, separator, and positive electrode are stacked in sequence, injected with electrolyte (standard electrolyte), and packaged into a soft-pack battery.

[0040] Example 2 Step (1) of this embodiment is as follows: (1) A PET film with a thickness of 4.5 μm was selected, and a 1000 nm copper layer was deposited on both sides of the film by magnetron sputtering to obtain a PET composite copper current collector with a total thickness of about 6.5 μm. The PET composite copper current collector was immersed in a 1 M hydrochloric acid solution for 50 s to give its surface a certain roughness. In this embodiment, the surface roughness of the copper layer was about 510 nm. The other steps are the same as those in Example 1 (2) to (5).

[0041] Example 3 The scheme in this embodiment is basically the same as that in embodiment 1, except that the 1 M LiPF6 / EC-DEC solution (EC:DEC=1:1) in step (2) is replaced with 0.1 M LiPF6 / EC-DEC solution (EC:DEC=1:1).

[0042] Example 4 The scheme in this embodiment is basically the same as that in embodiment 1, except that the 0.1M AgF / EC-DEC solution (EC:DEC=1:1) in step (3) is replaced with 0.002 M AgF / EC-DEC solution (EC:DEC=1:1).

[0043] Example 5 The scheme in this embodiment is basically the same as that in embodiment 1, except that the 0.1M AgF / EC-DEC solution (EC:DEC=1:1) in step (3) is replaced with 0.2M AgF / EC-DEC solution (EC:DEC=1:1).

[0044] Example 6 The scheme of this embodiment is basically the same as that of embodiment 1, except that: in step (3), the current collector after pre-plating Li is immersed in 0.1M AgF / EC-DEC solution (EC:DEC=1:1), and the temperature is kept constant at 30°C for 5s.

[0045] Example 7 The scheme of this embodiment is basically the same as that of embodiment 1, except that: in step (3), the current collector after pre-plating Li is immersed in 0.1M AgF / EC-DEC solution (EC:DEC=1:1), and the temperature is kept constant at 30°C for 60s.

[0046] Comparative Example 1 (without pre-plated Li) (1) A PET film with a thickness of 4.5 μm was selected, and a copper layer of 1000 nm was deposited on both sides of the film by magnetron sputtering to obtain a PET composite copper current collector with a total thickness of about 6.5 μm, wherein the surface roughness of the copper layer is about 250 nm.

[0047] (2) Immerse the PET composite copper current collector in 0.1M AgF / EC-DEC solution (EC:DEC=1:1), keep the temperature at 30°C, and react for 15s to generate LiF-Ag composite SEI.

[0048] The other steps are the same as in Example 1 (4) and (5).

[0049] Comparative Example 2 The steps for this comparative example are as follows: (1) A PET film with a thickness of 4.5 μm was selected, and a copper layer of 1000 nm was deposited on both sides of the film by magnetron sputtering to obtain a PET composite copper current collector with a total thickness of about 6.5 μm, wherein the surface roughness of the copper layer is about 250 nm.

[0050] (2) Prepare a mixed solution with a LiF to Ag molar ratio of 10:1 and a total concentration of 1M, and add 5% by mass of PVDF binder. Stir well, let stand to remove air bubbles, and then set aside. (3) Immerse the composite copper current collector from step (1) into the homogeneous mixture obtained in step (2) for 30 seconds; (4) After the composite copper current collector is taken out, it is dried in an anhydrous argon atmosphere. The drying temperature is controlled at about 60°C and the drying time is 5 minutes to obtain the final composite current collector.

[0051] The other steps are the same as in Example 1 (5).

[0052] Comparative Example 3 The scheme of this comparative example is basically the same as that of Example 1, except that the drying time in step (4) is adjusted to 40 minutes.

[0053] Test Evaluation: The Li(110) crystal orientation of the prepared electrode, the cycle performance and electrochemical performance of the battery were tested. The specific test methods are as follows: Lithium deposition crystal orientation test: The orientation of the lithium deposition crystal planes was determined by X-ray diffraction (XRD). A Li|Cu half-cell system was used for testing, with the composite current collector of this invention as the working electrode, lithium metal foil as the counter electrode, and a 1 mol·L⁻¹ electrolyte. -1 LiPF6 EC / DEC (volume ratio 1:1) solution. At 0.5 mA·cm⁻¹ -2 Deposition of 1 mAh·cm at current density -2 After disassembling the battery with metallic lithium, electrode samples were removed in an argon-protected environment and XRD tests were performed using Cu Kα rays. The orientation degree of the Li(110) crystal plane was obtained by calculating the ratio of the Li(110) diffraction peak intensity to the peak intensity of all lithium crystal planes.

[0054] Lithium nucleation overpotential test: The lithium nucleation overpotential was tested using a Li|Cu half-cell system. The composite current collector of this invention was used as the working electrode, lithium metal foil as the counter electrode, and the electrolyte was 1 mol·L⁻¹. -1 LiPF6 EC / DEC (volume ratio 1:1) solution. At 0.5 mA·cm⁻¹ -2 Constant current deposition tests were conducted at a given current density, and the voltage change curves during the initial deposition stage were recorded. The difference between the lowest voltage point during the initial deposition stage and the voltage at the stable deposition plateau was defined as the lithium nucleation overpotential.

[0055] EIS test: Using GB / T39482.3-2020 as the reference standard, an electrochemical workstation was used to conduct tests under the conditions of frequency 100kHz~10mHz and amplitude 5mV, and the Rct value was extracted.

[0056] Cyclic performance test: The test steps include: 1) Discharge the battery cell I1 (1-hour discharge current) to the discharge termination voltage at 25℃ and let it stand for 30 minutes; 2) Charge the battery cell with constant current I1 to the charging termination voltage, then switch to constant voltage charging. Stop charging when the charging termination current drops to 0.05 times I1, and let it stand for 30 minutes after charging; 3) Discharge the battery cell with I1 to the discharge termination voltage; 4) Cycle 500 times continuously according to steps 1)-3), record the battery capacity at the first cycle and the 500th cycle, and calculate the battery capacity retention rate, which is the battery capacity at the 500th cycle / the battery capacity at the first cycle × 100%.

[0057] The results of the experiments conducted on each embodiment and comparative example are shown in Table 1: Table 1 Comparison of test results between each embodiment and the comparative example

[0058] Based on the above conclusions, we can conclude that: The crystal plane-induced LiF-Ag hybrid SEI film composite current collector constructed in this invention significantly optimizes the crystal plane orientation of lithium deposition, reduces interfacial electrochemical kinetic resistance, and greatly improves the long-term cycle stability of the battery.

[0059] From the perspective of the crystal orientation characteristics of lithium deposition, this invention successfully achieved highly preferred orientation growth of the Li(110) crystal plane through an atomic-level self-assembly process of Li pre-plating and AgF substitution. All embodiments achieved extremely high (110) crystal plane orientation, while the comparative system showed significantly lower orientation. Among them, Example 2, after surface roughening treatment, exhibited the best orientation, further optimizing the distribution of active sites and enhancing the crystal plane induction effect. Comparative Example 1 lacked a pre-plating process, failing to form a uniform Li precursor layer and active sites, making the substitution reaction difficult to fully proceed. The resulting SEI film structure was chaotic, leading to extremely low (110) crystal plane orientation, disordered lithium deposition, and a very high risk of dendrite formation. Comparative Example 2 used an external mixed liquid coating method, which failed to achieve atomic-level self-assembly of the SEI film. The film structure lacked density and uniformity, resulting in a significantly weaker crystal plane orientation induction ability compared to the in-situ self-assembly process. Comparative Example 3, due to excessive drying time, damaged the initial microstructure and orientation of the SEI film, leading to a significant decrease in crystal plane orientation. Experiments show that the pre-plated Li precursor layer provides uniform active sites for the substitution reaction, which is key to inducing LiF crystal growth along specific crystal planes, reducing nucleation potential energy, and suppressing high-energy crystal plane deposition. Without this pre-plating process, or if an external SEI method with artificial coating is used, or if excessive drying damages the structure, this efficient crystal plane orientation induction cannot be achieved, leading to chaotic lithium deposition orientation and the potential risk of dendrite growth.

[0060] Nucleation overpotential and interfacial charge transfer impedance (Rct) are core indicators for evaluating interfacial kinetic performance. Examples 1-7 all exhibited extremely low nucleation overpotential and Rct values, demonstrating the synergistic effect of the hybrid SEI films. Example 2 showed the lowest overpotential and impedance, thanks to surface roughening that strengthened the interfacial adhesion between the current collector and the SEI film, optimizing the transport channels. Examples 3-7 showed a slight decrease in performance due to parameter deviations. Comparative Examples 1-3 exhibited significantly deteriorated interfacial kinetic performance. Comparative Example 1 showed the highest nucleation overpotential and Rct values, indicating that the lack of pre-plated Li resulted in an unstable SEI film, hindering ion transport and making nucleation extremely difficult. Comparative Examples 2 and 3 also showed increased transport impedance due to unstable film structures or poor contact, increasing battery operating energy consumption and heat generation risk.

[0061] In terms of long-term cycle stability, Examples 1-7 all exhibited high capacity retention, with Example 2 showing the best performance. The constructed LiF-Ag hybrid SEI film combined high stability and high conductivity, continuously suppressing lithium dendrite growth and interfacial side reactions. Comparative Examples 1-3 showed significantly lower capacity retention than the Examples. Comparative Example 1 had the lowest capacity retention, lacking effective SEI film protection; continuous lithium dendrite growth and interfacial failure led to a rapid capacity decay. Comparative Examples 2 and 3 also suffered from SEI film structural defects or instability, failing to provide long-term protection and resulting in rapid capacity loss during cycling. The Example systems maintained extremely high capacity retention after numerous cycles, demonstrating the excellent chemical stability and mechanical toughness of their SEI films; the stable interfacial protective layer effectively suppressed dendrite growth and side reactions, ensuring long-term safe operation of the battery. The comparative examples, lacking an effective interfacial protection mechanism, suffered severe interfacial damage during cycling, increasing the risk of dendrite penetration and leading to rapid capacity decay and a significantly shortened cycle life.

[0062] In summary, this invention successfully constructs a composite SEI film with high ionic conductivity, electronic conductivity, and structural toughness through the functional complementarity of LiF and Ag components. This achieves planar, homogeneous, and dendrite-free lithium deposition, fundamentally improving the interface quality of the composite current collector and the overall electrochemical performance of the battery. The copper surface roughening treatment and the Li pre-plating-AgF replacement process synergistically optimize the distribution of active sites, strengthen interfacial adhesion, enhance crystal orientation induction, reduce interfacial impedance, and strengthen the long-term protective capability of the SEI film, thus achieving a comprehensive improvement in the overall performance of the composite current collector and the battery.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent substitutions, and improvements made by those skilled in the art to the above embodiments without departing from the scope of the technical solution of the present invention, based on the technical essence of the present invention, shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a composite current collector having a crystal plane-induced LiF-Ag mixed SEI film, characterized by, Includes the following steps: S1: Pre-plating Li precursor layers on both sides of the composite copper current collector; S2: The composite copper current collector pre-plated with Li precursor layer is immersed in AgF / EC-DEC solution to generate nanoscale LiF crystals and dispersed Ag metal cores at the interface, thereby realizing the atomic-level self-assembly of the SEI film. S3: drying treatment of the composite copper current collector with SEI film self-assembly to remove residual solvent and fix Ag + The surface initial orientation structure is induced to form.

2. The method of claim 1, wherein the method is characterized by: Step S1 involves roughening the surface of the composite copper current collector before pre-plating the Li precursor layer; the surface roughening process involves immersing the composite copper current collector in a 1M hydrochloric acid solution for 40-60 seconds.

3. The method of claim 1, wherein the method comprises: In step S1, the pre-plating method of the Li precursor layer is as follows: using a composite copper current collector as the working electrode and a Li foil as the counter electrode, lithium ion pre-plating is performed in a 1M LiPF6 / EC-DEC solution with a current density of 0.02C and a time of 1~10min. ​ 4. The method of claim 1, wherein the method is characterized by: In step S2, the preparation method of the AgF / EC-DEC solution is as follows: ethylene carbonate and diethyl carbonate are mixed in a volume ratio of 0.5~1:1~2 to form a mixed solvent system. High-purity AgF powder is slowly added to the mixed solvent system under anhydrous argon or dry air environment and stirred until dissolved.

5. The method for preparing the composite current collector with a crystal facet-induced LiF-Ag mixed SEI film according to claim 4, characterized in that: In the mixed solvent system, the concentration of AgF is 0.002~0.2 M, the stirring rate is 200~600 rpm, the stirring temperature is controlled in the range of 20~50°C, and the stirring time is 1~3 hours.

6. The method for preparing the composite current collector with a crystal facet-induced LiF-Ag mixed SEI film according to claim 1, characterized in that: In step S2, the composite copper current collector pre-plated with the Li precursor layer is immersed in the AgF / EC-DEC solution for a reaction time of 5 to 60 seconds and the immersion temperature is controlled between 20 and 60°C.

7. The method for preparing the composite current collector with a crystal facet-induced LiF-Ag mixed SEI film according to claim 1, characterized in that: The drying process in step S3 is as follows: the composite copper current collector with SEI film self-assembly is dried in an anhydrous argon atmosphere, the drying temperature is controlled between 40 and 120°C, and the drying time is 5 to 30 minutes.

8. A composite current collector having a crystal facet-induced LiF-Ag mixed SEI film, characterized in that: Prepared using the method described in any one of claims 1 to 6.

9. A negative electrode sheet, characterized in that: The composite current collector comprising the crystal-faceted LiF-Ag mixed SEI film as described in claim 8.

10. A battery, characterized in that: It includes the negative electrode sheet as described in claim 9.

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