Lithium metal negative electrode, lithium metal battery, preparation method and application

Abstract

The invention discloses a lithium metal negative electrode, a lithium metal battery, a preparation method and application. The lithium metal negative electrode comprises a metal current collector, a first hexagonal boron nitride layer, a lithium metal layer and a second hexagonal boron nitride layer which are stacked in sequence, wherein the first hexagonal boron nitride layer contains hexagonal boron nitride and a lithium-loving substance, and the lithium-loving substance is embedded into the hexagonal boron nitride and / or the surface of the hexagonal boron nitride; the second hexagonal boron nitride layer comprises hexagonal boron nitride and a lithium penetrating substance which are mixed with each other, and the lithium penetrating substance comprises one or more of lithium fluoride and lithium nitride. The lithium metal negative electrode provided by the invention can improve the first coulombic efficiency of the lithium metal battery and reduce the capacity fading rate.

Description

Technical Field

[0001] This application belongs to the field of battery technology and relates to a lithium metal anode, a lithium metal battery, a preparation method, and an application. Background Technology

[0002] Lithium metal batteries are a type of secondary battery that uses metallic lithium (Li) as the negative electrode, combined with a positive electrode material (such as ternary oxides, lithium iron phosphate, sulfur, oxygen, etc.) and a liquid or solid electrolyte. Their working principle is based on lithium ions (Li... + The migration and electrochemical reactions of lithium metal. During discharge, the lithium metal anode loses electrons (oxidized to Li). + ), Li + Li migrates to the positive electrode via the electrolyte and embeds itself in the positive electrode material; during charging, Li + It is extracted from the positive electrode, reduced to metallic lithium on the surface of the negative electrode, and deposited.

[0003] Compared to lithium-ion batteries (LIBs), the core difference of lithium metal batteries lies in the anode material: lithium-ion batteries use graphite as the anode and have a theoretical capacity of only 372 mAh / g, while lithium metal batteries use metallic lithium as the anode and have a theoretical capacity as high as 3860 mAh / g. In addition, lithium has an extremely low electrochemical potential, so lithium metal batteries are regarded as the core direction of the next generation of high energy density batteries.

[0004] Lithium metal anode refers to an electrode structure that uses pure metallic lithium as the negative electrode of a battery. However, lithium metal anode has inherent defects: for example, lithium dendrites are easily formed during lithium deposition, which affects the performance of lithium metal batteries. Summary of the Invention

[0005] Therefore, it is necessary to provide a lithium metal anode, a lithium metal battery, a preparation method, and an application to improve the performance of lithium metal batteries.

[0006] In some embodiments, a lithium metal anode is provided, comprising a metal current collector, a first hexagonal boron nitride layer, a lithium metal layer, and a second hexagonal boron nitride layer stacked sequentially; wherein,

[0007] The first hexagonal boron nitride layer contains hexagonal boron nitride and a lithiophilic substance, wherein the lithiophilic substance is embedded in and / or on the surface of the hexagonal boron nitride;

[0008] The second hexagonal boron nitride layer includes a mixture of hexagonal boron nitride and lithium-penetrating material, wherein the lithium-penetrating material includes one or more of lithium fluoride and lithium nitride.

[0009] In some embodiments, the provided lithium metal anode satisfies one or more of the following conditions:

[0010] (1) The material of the metal current collector includes copper, nickel, gold, silver or copper-nickel alloy;

[0011] (2) The lithiophilic material includes one or more of zinc oxide, zinc, tin, and tin oxide; and

[0012] (3) The material of the lithium metal layer is lithium.

[0013] In some embodiments, the provided lithium metal anode satisfies one or more of the following conditions:

[0014] (1) The thickness of the metal current collector is 6µm~20µm;

[0015] (2) The thickness of the first hexagonal boron nitride layer is 50 nm to 150 nm;

[0016] (3) The thickness of the lithium metal layer is 5µm~20µm;

[0017] (4) The thickness of the second hexagonal boron nitride layer is 50 nm to 150 nm; and

[0018] (5) The first hexagonal boron nitride and the second hexagonal boron nitride have the same thickness.

[0019] In some embodiments, a method for preparing a lithium metal anode is provided, comprising the following steps:

[0020] Hexagonal boron nitride is deposited on the surface of a pretreated metal current collector, and then electroplated in an aqueous solution containing a lithiophilic material source. After electroplating, oxidation treatment is performed or not performed to embed the lithiophilic material in the hexagonal boron nitride and / or on the surface, forming a first hexagonal boron nitride layer.

[0021] A lithium metal layer is deposited on the surface of the first hexagonal boron nitride layer away from the metal current collector by means of lithium evaporation plating.

[0022] Hexagonal boron nitride is deposited on the side of the lithium metal layer away from the first hexagonal boron nitride layer, and lithium-penetrating material is generated in situ by bombardment with CF4 and / or nitrogen plasma to form a second hexagonal boron nitride layer, thus preparing the lithium metal anode.

[0023] In some embodiments, the provided method for preparing a lithium metal anode satisfies one or both of the following conditions:

[0024] (1) The method for preparing the pretreated metal current collector includes the following steps: pretreating the surface of the metal current collector with argon ions; optionally, in the step of pretreating the surface of the metal current collector, Ar... + The ion energy is 500 eV~1000 eV, and the ion beam current density is 0.1 mA cm⁻¹. -2 ~0.3mA cm-2 The bombardment time is 60s~180s; and

[0025] (2) The surface roughness RA of the pretreated metal current collector is 150nm~250nm.

[0026] In some embodiments, the method for preparing the lithium metal anode involves using radio frequency magnetron sputtering to deposit the hexagonal boron nitride onto the surface of a pretreated metal current collector.

[0027] Optionally, one or both of the following conditions must be met:

[0028] (1) The target material for radio frequency magnetron sputtering is hexagonal boron nitride; and

[0029] (2) The power of radio frequency magnetron sputtering is 80W~120W.

[0030] In some embodiments, the provided method for preparing a lithium metal anode satisfies one or more of the following conditions:

[0031] (1) The lithiophilic material source includes one or more of zinc sulfate, stannous methanesulfonate and stannous sulfate;

[0032] (2) The concentration of the lithiophilic source in the aqueous solution is 0.1 mol / L to 0.5 mol / L;

[0033] (3) With 0.5mA cm -2 ~2 mA cm -2 Electroplating is performed at a current density of 1 min to 3 min;

[0034] (4) After electroplating, the process also includes washing with distilled water and drying at 60℃~80℃ for 15min~20min;

[0035] (5) During the oxidation process, the oxidation is carried out in an environment of 200℃~300℃ for 30min~60min;

[0036] (6) The pressure of lithium evaporation plating is less than or equal to 1×10 -3 Pa, the evaporation rate of lithium evaporation plating is 0.1 nm / s~1.0 nm / s;

[0037] (7) After the lithium metal layer is deposited, the process also includes maintaining pressure in a vacuum environment for 20-30 minutes; and

[0038] (8) In the step of generating lithium-penetrating material in situ by bombardment treatment with CF4 and / or nitrogen plasma, the power is 50W~200W and the bombardment treatment time is 1min~5min.

[0039] In some embodiments, the method for preparing a lithium metal anode includes a step of depositing hexagonal boron nitride on the side of the lithium metal layer away from the first hexagonal boron nitride layer, in which radio frequency magnetron sputtering is used to deposit the hexagonal boron nitride on the surface of the lithium metal layer.

[0040] Optionally, one or more of the following conditions must be met:

[0041] (1) The target material for radio frequency magnetron sputtering is hexagonal boron nitride;

[0042] (2) The power of radio frequency magnetron sputtering is 80W~120W;

[0043] (3) The temperature of the metal current collector during radio frequency magnetron sputtering is less than or equal to 80℃; and

[0044] (4) The linear velocity of the metal current collector during the radio frequency magnetron sputtering process is 0.5 m / min to 1.0 m / min.

[0045] In some embodiments, the lithium metal anode or the lithium metal anode prepared by the preparation method is provided for use in the preparation of lithium metal batteries.

[0046] In some embodiments, a lithium metal battery is provided, comprising the lithium metal anode or the lithium metal anode prepared by the preparation method described above.

[0047] The provided lithium metal anode comprises a metal current collector, a first hexagonal boron nitride layer, a lithium metal layer, and a second hexagonal boron nitride layer, stacked sequentially. The metal current collector serves as the main conductive framework and mechanical support layer of the anode. The first hexagonal boron nitride layer is firmly bonded to the surface of the metal current collector by van der Waals forces and chemical anchoring, providing a stable mechanical substrate for subsequent deposition of lithiophilic materials and the lithium metal layer, eliminating interfacial voids and the risk of delamination. The lithiophilic material uniformly distributed in the first hexagonal boron nitride layer serves as a nucleation site for lithium ions, significantly improving the uniformity of lithium deposition and the first-cycle coulombic efficiency. The lithium metal layer acts as an ion source. The lithium-penetrating material and hexagonal boron nitride in the second hexagonal boron nitride layer form an artificial SEI film, providing high mechanical strength and high ion conductivity. The provided lithium metal anode can improve the first-cycle coulombic efficiency of lithium metal batteries and reduce the capacity decay rate. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments and examples of this application, and to more completely understand this application and its beneficial effects, the accompanying drawings used in the description of the embodiments or examples will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of this application. Those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0049] Figure 1 The diagram shows the lithium metal anode structure in some embodiments, where ① is a metal current collector, ② is hexagonal boron nitride, ③ is a lithiophilic material, ④ is Li metal, and ⑤ is LiF.

[0050] Figure 2 for Figure 1 A schematic diagram of a lithium-philic material intercalated into hexagonal boron nitride. Detailed Implementation

[0051] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0052] It should be noted that when a component is said to be "fixed to" another component, it can be directly attached to the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0054] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings:

[0055] The terms "and / or," "or / and," and "and / or" as used in this application encompass any one of two or more related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected using at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that in this application, the technical solution undoubtedly includes solutions connected by "logical AND," and also undoubtedly includes solutions connected by "logical OR." For example, "A and / or B" includes three parallel solutions: A, B, and "a combination of A and B."

[0056] In this application, the terms "multiple", "various", "multiple times", "multi-dimensional", etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or more than or equal to two.

[0057] The terms “combinations thereof,” “any combination thereof,” and “any combination thereof” as used in this application include all suitable combinations of any two or more of the listed items.

[0058] In this application, the term "suitable" as used in "suitable combination", "suitable method", "any suitable method", etc., refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0059] In this application, terms such as "preferred," "better," "more suitable," and "ideal" are merely used to describe implementation methods or embodiments that achieve better results, and should be understood not to limit the scope of protection of this application.

[0060] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0061] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0062] In this invention, the terms "first aspect," "second aspect," "third aspect," and "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," and "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0063] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0064] In this application, numerical intervals (i.e., numerical ranges) are involved. Unless otherwise specified, the selected numerical distributions within the aforementioned numerical intervals are considered continuous and include the two endpoints (i.e., the minimum and maximum values) of the numerical range, as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints. In this document, this is equivalent to directly listing every integer. For example, if t is an integer selected from 1 to 10, it means that t is any integer selected from the group of integers consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Furthermore, when multiple ranges are provided to describe features or characteristics, these ranges can be merged. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0065] Unless otherwise specified, the temperature parameters in this application are permitted to be either constant-temperature treatment or variations within a certain temperature range. It should be understood that the constant-temperature treatment allows temperature fluctuations within the precision range of the instrument control, such as ±5℃, ±4℃, ±3℃, ±2℃, or ±1℃.

[0066] In this application, % (w / w) and wt% both represent weight percentage, % (v / v) refers to volume percentage, and % (w / v) refers to mass-volume percentage.

[0067] In this application, "room temperature" generally refers to 5℃~30℃, and more preferably 25±5℃.

[0068] Currently, commercial lithium metal battery anodes mainly rely on mechanically rolling or bonding 20–40 μm thick lithium metal foil with copper foil current collectors to obtain high specific capacity anode materials. However, the bonding strength between lithium metal and the current collector is insufficient, and interlayer voids and delamination are easily generated during cycling, leading to increased electrode internal resistance, decreased conductivity, and potential short circuit hazards. Secondly, it is difficult to uniformly control the thickness and morphology of lithium during deposition. Excessively high local current density can promote the preferential formation of dendrites and puncture the separator, causing safety accidents. Thirdly, traditional SEI films are not uniformly formed and have poor stability, with high interface impedance and easy breakage during charge and discharge, further aggravating cycle decay. In addition, lithium metal expands significantly in volume during charge and discharge cycles, and existing interface structures often cannot effectively buffer stress, leading to electrode structure damage and capacity decay. Finally, the preparation process usually relies on multi-step chemical or physical deposition, high temperature treatment, and dehydration treatment, which is complex, energy-intensive, and difficult to achieve continuous production, thus restricting the large-scale commercialization of lithium metal batteries.

[0069] In some embodiments, a lithium metal anode is provided, comprising a metal current collector, a first hexagonal boron nitride layer, a lithium metal layer, and a second hexagonal boron nitride layer stacked sequentially; wherein,

[0070] The first hexagonal boron nitride layer contains hexagonal boron nitride and a lithiophilic substance, with the lithiophilic substance embedded in and / or on the surface of the hexagonal boron nitride;

[0071] The second hexagonal boron nitride layer includes a mixture of hexagonal boron nitride and lithium-penetrating material, wherein the lithium-penetrating material includes one or more of lithium fluoride and lithium nitride.

[0072] Hexagonal boron nitride (h-BN) materials possess a layered structure similar to graphite. Hexagonal boron nitride exhibits a typical hexagonal layered structure, highly similar to the crystal structure of graphite (space group P63 / mmc). Within each layer, B atoms and N atoms are separated by sp... 2 Hybridization forms a six-membered ring planar structure, which has good anisotropy and excellent chemical stability. It exhibits good corrosion resistance to most chemical reagents, such as acids, bases, and organic solvents, making it an ideal material for electrochemical batteries.

[0073] The first hexagonal boron nitride layer can enhance the bonding between lithium metal and copper foil, store lithium-loving substances, induce lithium ion deposition, and reduce the growth of lithium dendrites.

[0074] The second hexagonal boron nitride layer comprises h-BN and a lithium-penetrating material. Hexagonal boron nitride itself has a certain degree of lithium-ion permeability, while the lithium-penetrating material has good lithium-ion permeability. Therefore, the second hexagonal boron nitride layer constitutes an artificial SEI layer that conducts lithium ions but does not conduct electrons. Furthermore, the second hexagonal boron nitride layer can utilize the high-strength physical suppression of lithium dendrite growth by h-BN, and prevent cracking during lithium metal battery cycling, thereby inhibiting the growth of lithium dendrites at cracks in the SEI layer, reducing the consumption of lithium ions and electrolyte, improving the safety of lithium metal batteries, and enhancing the initial coulombic efficiency and cycle performance of lithium metal batteries.

[0075] Hexagonal boron nitride layers are provided on both sides of the lithium metal layer to ensure that the stress of the first hexagonal boron nitride layer, the lithium metal layer and the second hexagonal boron nitride layer is balanced during the expansion and contraction of the negative electrode during the charge and discharge cycle of the lithium metal battery. This prevents cracks from appearing on the negative electrode due to uneven stress, which would affect the cycle performance of the battery.

[0076] In some embodiments, the material of the metal current collector in the provided lithium metal anode includes copper, nickel, gold, silver, or a copper-nickel alloy.

[0077] In some embodiments, the lithium metal anode provided contains one or more of zinc oxide, zinc, tin, and tin oxide.

[0078] In some embodiments, the lithium metal layer in the provided lithium metal anode is made of lithium.

[0079] In some embodiments, the thickness of the metal current collector in the provided lithium metal anode is 6µm to 20µm. For example, the thickness of the metal current collector can be 6µm, 7µm, 8µm, 9µm, 10µm, 11µm, 12µm, 13µm, 14µm, 15µm, 16µm, 17µm, 18µm, 19µm, 20µm, etc., or it can be a range composed of any two of the aforementioned values.

[0080] The thickness of the metal current collector is controlled between 6µm and 20µm to provide conductivity and mechanical support for the negative electrode. The lower limit of 6µm thickness can still provide a tensile strength of ≥200MPa, while the upper limit of 20µm ensures deformation safety during the winding process without excessively sacrificing the battery energy density.

[0081] In some embodiments, the thickness of the first hexagonal boron nitride layer in the provided lithium metal anode is 50nm to 150nm. For example, the thickness of the first hexagonal boron nitride layer can be 50nm, 60µm, 70µm, 80µm, 90µm, 100µm, 110µm, 120µm, 130µm, 140µm, 150µm, etc., or it can be a range composed of any two of the aforementioned values.

[0082] The lower limit of the thickness of the first hexagonal boron nitride layer is 50nm to ensure continuous film coverage and avoid exposing the copper foil; the upper limit of 150nm can maintain sufficient barrier performance while controlling the sheet resistance below 20Ω / sq to avoid negative impact on high-rate performance.

[0083] In some embodiments, the thickness of the lithium metal layer in the provided lithium metal anode is 5µm to 20µm. For example, the thickness of the lithium metal layer can be 5µm, 6µm, 7µm, 8µm, 9µm, 10µm, 11µm, 12µm, 13µm, 14µm, 15µm, 16µm, 17µm, 18µm, 19µm, 20µm, etc., or it can be a range composed of any two of the aforementioned values.

[0084] In some embodiments, the thickness of the second hexagonal boron nitride layer in the provided lithium metal anode is 50 nm to 150 nm. For example, the thickness of the second hexagonal boron nitride layer can be 50 nm, 60 µm, 70 µm, 80 µm, 90 µm, 100 µm, 110 µm, 120 µm, 130 µm, 140 µm, 150 µm, etc., or it can be a range composed of any two of the aforementioned values.

[0085] In some embodiments, the first hexagonal boron nitride and the second hexagonal boron nitride have the same thickness. The upper and lower double-layer h-BN are interconnected, and by controlling the same thickness, this design allows the Li ion beam to be smoothly conducted in a uniform interlayer environment when it permeates from the surface, reducing transmission resistance and fluctuations and ensuring the consistency of the ion flow.

[0086] In some embodiments, a method for preparing a lithium metal anode is provided, comprising the following steps:

[0087] Hexagonal boron nitride is deposited on the surface of a pretreated metal current collector, and then electroplated in an aqueous solution containing a lithiophilic material source. After electroplating, oxidation treatment is performed or not performed to embed the lithiophilic material into the hexagonal boron nitride and / or on the surface, forming a first hexagonal boron nitride layer.

[0088] A lithium metal layer is deposited on the surface of the first hexagonal boron nitride layer away from the metal current collector by means of lithium evaporation plating.

[0089] Hexagonal boron nitride is deposited on the side of the lithium metal layer away from the first hexagonal boron nitride layer. The lithium-penetrating material is generated in situ by bombardment with CF4 and / or nitrogen plasma to form a second hexagonal boron nitride layer, thus preparing a lithium metal anode.

[0090] In some embodiments, the method for preparing a lithium metal anode includes the following steps: pretreating the surface of the metal current collector with argon ions.

[0091] In some embodiments, in the method for preparing a lithium metal anode, during the surface pretreatment step of the metal current collector, Ar... + The ion energy is 500 eV~1000 eV, and the ion beam current density is 0.1 mA cm⁻¹. -2 ~0.3mA cm -2 The bombardment time is 60s to 180s. For example, Ar + The ion energy can be 500 eV, 600 eV, 700 eV, 800 eV, 900 eV, 1000 eV, or any combination of the aforementioned values; the ion beam current density can be 0.1 mA cm⁻¹. -2 0.2mA cm -2 0.3mA cm -2 The values ​​can be any combination of the two aforementioned values; the bombardment time can be 60s, 70s, 80s, 90s, 100s, 110s, 120s, 130s, 140s, 150s, 160s, 170s, 180s, etc., or any combination of the two aforementioned values. Pre-treatment of the metal current collector can enhance the mechanical locking of subsequent functional layers.

[0092] In some embodiments, in the provided method for preparing lithium metal anode, the surface roughness RA of the pretreated metal current collector is 150nm~250nm. For example, the roughness RA can be 150nm, 200nm, 250nm, etc., or it can be a range composed of any two of the aforementioned values.

[0093] In some embodiments, in the method for preparing a lithium metal anode, in the step of depositing hexagonal boron nitride on the surface of a pretreated metal current collector, radio frequency magnetron sputtering is used to deposit hexagonal boron nitride on the surface of the pretreated metal current collector.

[0094] In some embodiments, in the method for preparing the lithium metal anode, in the step of depositing hexagonal boron nitride on the surface of a pretreated metal current collector using radio frequency magnetron sputtering, the target material for radio frequency magnetron sputtering is hexagonal boron nitride.

[0095] In some embodiments, in the method for preparing the lithium metal anode, in the step of depositing hexagonal boron nitride on the surface of a pretreated metal current collector using radio frequency magnetron sputtering, the power of the radio frequency magnetron sputtering is 80W~120W. For example, the power of the radio frequency magnetron sputtering can be 80W, 100W, 120W, etc., or it can be any combination of the two values ​​mentioned above.

[0096] Hexagonal boron nitride was deposited on the surface of a pretreated metal current collector using radio frequency magnetron sputtering. The hexagonal boron nitride was firmly attached to the surface of the metal current collector by van der Waals forces and chemical bonds, which not only avoided interlayer delamination during subsequent zinc electroplating and lithium evaporation processes, but also provided a stable mechanical substrate for embedding lithiophilic materials and confined lithium deposition.

[0097] In some embodiments, the lithium metal anode preparation method provides a lithium-ion source including one or more of zinc sulfate, stannous methanesulfonate, and stannous sulfate.

[0098] In some embodiments, in the provided method for preparing lithium metal anode, the concentration of the lithiophilic source in the aqueous solution of the lithiophilic source is 0.1 mol / L to 0.5 mol / L. For example, the concentration of the lithiophilic source can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, etc., or it can be a range composed of any two of the aforementioned values.

[0099] In some embodiments, the provided method for preparing a lithium metal anode uses 0.5 mA cm -2 ~2mA cm -2Electroplating is performed at a current density of 0.5 mA cm⁻¹ for 1 to 3 minutes. -2 1mA cm -2 1.5mA cm -2 2mA cm -2 The values ​​can also be any range of the two aforementioned values. For example, the electroplating time can be 1 min, 2 min, 3 min, etc., or it can be any range of the two aforementioned values.

[0100] In some embodiments, oxidation treatment may or may not be performed after electroplating. Understandably, after electroplating, metals from the lithiophilic source, such as zinc and / or tin, are embedded in and / or on the surface of hexagonal boron nitride; when oxidation treatment is performed, the metals embedded in and / or on the surface of hexagonal boron nitride are at least partially oxidized to form metal oxides, such as zinc oxide and / or tin oxide.

[0101] In some embodiments, the method for preparing the lithium metal anode includes an oxidation process in which the anode is oxidized at 200°C to 300°C for 30 to 60 minutes.

[0102] The lithiophilic material achieves in-situ coupling with h-BN, providing high interfacial energy sites for subsequent lithium-ion nucleation and buffering local current density.

[0103] Introducing lithiophilic materials into the hexagonal boron nitride (h-BN) system allows for the creation of guiding sites for lithium-ion deposition, effectively regulating lithium-ion deposition behavior. During electrochemical cycling, as lithium metal is continuously consumed, the thickness of the lithium layer on the negative electrode surface gradually decreases. This process exposes the lithiophilic materials previously covered by the lithium layer; the thinner the lithium layer, the greater the probability of exposure. When lithium ions migrate towards the negative electrode, the exposed lithiophilic materials, due to their strong affinity for lithium ions, become the preferred deposition areas. Lithium ions preferentially accumulate and deposit at these exposed sites, gradually covering them through this "targeted filling" effect, ultimately achieving uniform lithium layer growth and surface smoothing. This lithium-ion deposition mechanism guided by lithiophilic materials effectively suppresses the disordered growth of lithium dendrites, providing crucial support for improving the cycle stability and safety of lithium metal batteries. Hexagonal boron nitride can store lithiophilic materials, preventing their shedding during subsequent negative electrode preparation and battery cycling.

[0104] In some embodiments, the method for preparing the lithium metal anode includes washing with distilled water and drying at 60°C to 80°C for 15 to 20 minutes after electroplating.

[0105] In some embodiments, in the provided method for preparing a lithium metal anode, the pressure for evaporating lithium is less than or equal to 1 × 10⁻⁶. -3 Pa, the evaporation rate of lithium evaporation plating is 0.1 nm / s to 1.0 nm / s. For example, the evaporation rate of lithium evaporation plating can be 0.1 nm / s, 0.2 nm / s, 0.3 nm / s, 0.4 nm / s, 0.5 nm / s, 0.6 nm / s, 0.7 nm / s, 0.8 nm / s, 0.9 nm / s, 0.10 nm / s, etc., or it can be any range of two of the aforementioned values.

[0106] When the pressure is less than or equal to 1×10 -3 Lithium deposition by evaporation at a rate of 0.1 nm / s to 1.0 nm / s can achieve a lithium deposition layer thickness of 5 µm to 20 µm, corresponding to an areal capacity of 1–4 mAh / cm². 2 Under these parameters, sufficient surface diffusion time for lithium atoms can be ensured to form a dense and uniform metal layer, while also taking into account production efficiency. After deposition, pressure is maintained in a vacuum for 20 to 30 minutes to allow the lithium film to fully distill with the substrate and relax internal stress, thereby obtaining a dense, firmly attached, and cycle-stable lithium metal layer.

[0107] In some embodiments, the method for preparing a lithium metal anode includes, after depositing the lithium metal layer, maintaining pressure in a vacuum environment for 20 to 30 minutes.

[0108] In some embodiments, in the method for preparing a lithium metal anode, in the step of depositing hexagonal boron nitride on the side of the lithium metal layer away from the first hexagonal boron nitride layer, the hexagonal boron nitride is deposited on the surface of the lithium metal layer by radio frequency magnetron sputtering.

[0109] In some embodiments, in the step of depositing hexagonal boron nitride on the surface of a lithium metal layer using radio frequency magnetron sputtering, the target material for radio frequency magnetron sputtering is hexagonal boron nitride.

[0110] In some embodiments, in the step of depositing the hexagonal boron nitride on the surface of the lithium metal layer using radio frequency magnetron sputtering, the power of the radio frequency magnetron sputtering is 80W~120W. For example, the power of the radio frequency magnetron sputtering can be 80W, 100W, 120W, etc., or it can be any range of two of the aforementioned values.

[0111] In some embodiments, during the step of depositing the hexagonal boron nitride on the surface of the lithium metal layer using radio frequency magnetron sputtering, the temperature of the metal current collector during the radio frequency magnetron sputtering process is less than or equal to 80°C.

[0112] In some embodiments, the step of depositing the hexagonal boron nitride on the surface of the lithium metal layer using radio frequency magnetron sputtering is carried out in which the linear velocity of the metal current collector is 0.5 m / min to 1.0 m / min.

[0113] In some embodiments, a second h-BN film is prepared on the lithium metal surface of the composite using the same process as the first h-BN film, yielding an h-BN coating with a thickness of 50 nm to 150 nm. Following this, CF4 plasma treatment generates a dense LiF-rich layer in situ. This artificial SEI, combined with the high mechanical strength and chemical inertness of h-BN itself, provides robust physical support and chemical anchoring at the interface, ensuring its continuity and integrity during repeated charge-discharge cycles. The excellent ion conductivity of LiF and the electronic insulation properties of h-BN together form an interface that significantly reduces interfacial impedance and accelerates lithium-ion transport.

[0114] In some embodiments, in the method for preparing a lithium metal anode, in the step of generating lithium-penetrating material in situ by bombardment with CF4 and / or nitrogen plasma, the power is 50W to 200W and the bombardment time is 1min to 5min. For example, the power can be 50W, 100W, 150W, 200W, etc., or any combination of the aforementioned two values; the bombardment time can be 1min, 2min, 3min, 4min, 5min, etc., or any combination of the aforementioned two values.

[0115] Specifically, after hexagonal boron nitride (BN) is deposited on the surface of the lithium metal layer, the BN is at least partially embedded in the surface of the lithium metal layer. Since the BN is not a dense structure, it does not completely cover the lithium metal layer; therefore, some lithium metal is "filled" in the gaps of the BN structure. At this point, CF4 and / or nitrogen plasma bombards the surface of the semi-finished product, causing the lithium metal filling the gaps in the BN to generate lithium-penetrating material in situ. This material fills the gaps in the BN, forming a second hexagonal boron nitride layer that is a mixture of lithium-penetrating material and BN. The second hexagonal boron nitride layer prepared by this process has a uniform and dense structure, ensuring the uniformity of lithium-ion flow and preventing the overall structure from being damaged by the expansion of the negative electrode during battery cycling, thereby improving the capacity retention rate after battery cycling.

[0116] In some embodiments, the aforementioned lithium metal anode or the lithium metal anode prepared by the aforementioned preparation method is used in the preparation of lithium metal batteries.

[0117] In some embodiments, a lithium metal battery is provided, comprising the aforementioned lithium metal anode or a lithium metal anode prepared by the aforementioned preparation method.

[0118] The following are specific embodiments. They are intended to provide a more detailed description of this application to help those skilled in the art and researchers better understand it. The technical conditions described do not constitute any limitation on this application. Any modifications made within the scope of the claims of this application are protected by the claims.

[0119] Unless otherwise stated, all raw materials and reagents used in the following examples are commercially available or can be prepared by known methods. Experimental methods not specifying particular conditions in the examples were performed under conventional conditions, such as those described in literature, books, or methods recommended by the manufacturer.

[0120] Example 1

[0121] This embodiment provides a lithium metal anode, which is prepared by the following method:

[0122] (1) Take a 12µm thick high-purity copper foil and heat it under a vacuum of 1×10⁻⁶. -3 Under Pa conditions, at 500 eV and 0.2 mA / cm², 2 Ar of the 90s + Ion bombardment activation;

[0123] (2) Deposit 100 nm thick h-BN by magnetron sputtering at 100 W in an RF magnetron sputtering chamber; then, in a 0.1 mol / L ZnSO4 solution, at 1 mA / cm 2 Zinc was electroplated at a current density for 2 minutes, washed with distilled water and baked at 70°C for 18 minutes, and then oxidized at 250°C for 45 minutes to convert Zn in situ to ZnO, forming a composite containing a first hexagonal boron nitride layer.

[0124] (3) Place the composite in a vacuum evaporation chamber, and apply it at a vacuum level of 1×10⁻⁶. -3 A 10 μm lithium metal layer was deposited at a rate of 0.5 nm / s under Pa conditions, and then held under vacuum for 25 min.

[0125] (4) A 100 nm thick h-BN was deposited by magnetron sputtering at 100 W in the radio frequency magnetron sputtering chamber; finally, the lithium metal anode was prepared by bombarding it with CF4 plasma at 100 W for 3 min and reacting it with the unmasked lithium metal of h-BN to generate about 50 nm LiF in situ, forming a second hexagonal boron nitride layer.

[0126] Example 2

[0127] This embodiment provides a lithium metal anode, and the preparation method is similar to that of Embodiment 1. The difference is that in this embodiment, step (3) involves vacuum evaporation to deposit a lithium metal layer with a thickness of 3µm, while the remaining steps are the same as in Embodiment 1.

[0128] Example 3

[0129] This embodiment provides a lithium metal anode, and the preparation method is similar to that of Embodiment 1. The difference is that in this embodiment, step (3) involves vacuum evaporation to deposit a lithium metal layer with a thickness of 5µm, while the remaining steps are the same as in Embodiment 1.

[0130] Example 4

[0131] This embodiment provides a lithium metal anode, and the preparation method is similar to that of Embodiment 1. The difference is that in this embodiment, step (3) involves vacuum evaporation to deposit a lithium metal layer with a thickness of 20µm, while the remaining steps are the same as in Embodiment 1.

[0132] Example 5

[0133] This embodiment provides a lithium metal anode, and the preparation method is similar to that of Embodiment 1. The difference is that in this embodiment, step (3) involves vacuum evaporation to deposit a lithium metal layer with a thickness of 30µm, while the remaining steps are the same as in Embodiment 1.

[0134] Example 6

[0135] This embodiment provides a lithium metal anode, and the preparation method is similar to that of Example 1. The difference is that in this embodiment, steps (2) and (4) involve magnetron sputtering to deposit an h-BN layer with a thickness of 30 nm. The remaining steps are the same as in Example 1.

[0136] Example 7

[0137] This embodiment provides a lithium metal anode, and the preparation method is similar to that of Example 1. The difference is that in this embodiment, steps (2) and (4) involve magnetron sputtering to deposit an h-BN layer with a thickness of 50 nm. The remaining steps are the same as in Example 1.

[0138] Example 8

[0139] This embodiment provides a lithium metal anode, and the preparation method is similar to that of Example 1. The difference is that in this embodiment, steps (2) and (4) involve magnetron sputtering to deposit an h-BN layer with a thickness of 150 nm. The remaining steps are the same as in Example 1.

[0140] Example 9

[0141] This embodiment provides a lithium metal anode, and the preparation method is similar to that of Example 1. The difference is that in this embodiment, steps (2) and (4) involve magnetron sputtering to deposit an h-BN layer with a thickness of 200 nm. The remaining steps are the same as in Example 1.

[0142] Example 10

[0143] This embodiment provides a lithium metal anode, and the preparation method is similar to that of Example 1. The difference is that in this embodiment, step (2) involves magnetron sputtering to deposit an h-BN with a thickness of 100 nm, and step (4) involves magnetron sputtering to deposit an h-BN with a thickness of 50 nm. The remaining steps are the same as in Example 1.

[0144] Example 11

[0145] This embodiment provides a lithium metal anode, and the preparation method is similar to that of Example 1. The difference is that in this embodiment, step (2) is carried out in a 0.1 mol / L stannous methanesulfonate solution at a flow rate of 1 mA / cm. 2 Electroplating at current density for 2 minutes, with the remaining steps being the same as in Example 1.

[0146] Comparative Example 1

[0147] This comparative example provides a lithium metal anode, on which Zn (1 mA / cm²) is directly electroplated onto a 12 μm copper foil surface. 2 After being oxidized to ZnO (2 min), lithium is directly deposited at a thickness of 10 μm to obtain a lithium metal anode. No h-BN modification or CF4 treatment is performed.

[0148] Comparative Example 2

[0149] This comparative example provides a lithium metal anode, and the preparation method is similar to that of Example 1. The difference is that in this comparative example, step (4) involves magnetron sputtering to deposit an h-BN layer with a thickness of 100 nm, without CF4 plasma treatment.

[0150] Comparative Example 3

[0151] This comparative example provides a lithium metal anode, and the preparation method is similar to that of Example 1. The difference is that in step (2) of this comparative example, magnetron sputtering of h-BN is not performed, and the remaining steps are the same as those in Example 1.

[0152] Comparative Example 4

[0153] This comparative example provides a lithium metal anode, and the preparation method is similar to that of Example 1. The difference is that zinc electroplating is not performed in step (2) of this comparative example, and the remaining steps are the same as those in Example 1.

[0154] Comparative Example 5

[0155] This comparative example provides a lithium metal anode, and the preparation method is similar to that of Example 1. The difference is that in step (4) of this comparative example, magnetron sputtering of h-BN is not performed, and the remaining steps are the same as those in Example 1.

[0156] Performance testing

[0157] Lithium metal batteries are prepared in the following manner, wherein the negative electrode is the lithium metal negative electrode prepared in the examples and comparative examples.

[0158] The lithium metal anodes obtained in the examples and comparative examples, with lithium iron phosphate as the positive electrode active material, 1M LiPF6 / EC:EMC (3:7, w / w) + 2% VC as the electrolyte, and Celgard 2400 as the separator, were stacked and packaged in the order of positive electrode (lithium iron phosphate) → separator → lithium metal anode, and then injected with an electrolyte including LiPF6, EC, EMC and VC to form a lithium metal battery.

[0159] The testing equipment used was the Blue Battery Testing System (CT-4008T), with a voltage window of 0.01-1.5V (vs. Li). + / Li); formation was performed at 25°C (C / 20×2, C / 10×1). The initial charge and initial discharge capacities were measured, and the initial coulombic efficiency (FCE) was calculated as (initial discharge capacity / initial charge capacity) × 100%. Capacity retention was measured after 500 cycles at 1C. The results are shown in Table 1.

[0160] Table 1

[0161]

[0162] As shown in Table 1, the lithium metal batteries prepared using the lithium metal anodes obtained in the examples achieve an initial coulombic efficiency of 93%–97.8%, exhibiting high initial coulombic efficiency. After 500 cycles at 1C, the capacity retention rate reaches 72%–92%, also demonstrating high capacity retention. The provided lithium metal anodes can improve the performance of lithium metal batteries.

[0163] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0164] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A lithium metal anode, characterized in that, It includes a metal current collector, a first hexagonal boron nitride layer, a lithium metal layer, and a second hexagonal boron nitride layer, stacked sequentially; wherein, The first hexagonal boron nitride layer contains hexagonal boron nitride and a lithiophilic substance, wherein the lithiophilic substance is embedded in and / or on the surface of the hexagonal boron nitride; The second hexagonal boron nitride layer includes a mixture of hexagonal boron nitride and lithium-penetrating material, wherein the lithium-penetrating material includes one or more of lithium fluoride and lithium nitride.

2. The lithium metal anode according to claim 1, characterized in that, One or more of the following conditions must be met: (1) The material of the metal current collector includes copper, nickel, gold, silver or copper-nickel alloy; (2) The lithiophilic material includes one or more of zinc oxide, zinc, tin, and tin oxide; and (3) The material of the lithium metal layer is lithium.

3. The lithium metal anode according to claim 1 or 2, characterized in that, One or more of the following conditions must be met: (1) The thickness of the metal current collector is 6µm~20µm; (2) The thickness of the first hexagonal boron nitride layer is 50 nm to 150 nm; (3) The thickness of the lithium metal layer is 5µm~20µm; (4) The thickness of the second hexagonal boron nitride layer is 50 nm to 150 nm; and (5) The first hexagonal boron nitride and the second hexagonal boron nitride have the same thickness.

4. The method for preparing the lithium metal anode according to any one of claims 1 to 3, characterized in that, Includes the following steps: Hexagonal boron nitride is deposited on the surface of a pretreated metal current collector, and then electroplated in an aqueous solution containing a lithiophilic material source. After electroplating, oxidation treatment is performed or not performed to embed the lithiophilic material in the hexagonal boron nitride and / or on the surface, forming a first hexagonal boron nitride layer. A lithium metal layer is deposited on the surface of the first hexagonal boron nitride layer away from the metal current collector by means of lithium evaporation plating. Hexagonal boron nitride is deposited on the side of the lithium metal layer away from the first hexagonal boron nitride layer, and lithium-penetrating material is generated in situ by bombardment with CF4 and / or nitrogen plasma to form a second hexagonal boron nitride layer, thus preparing the lithium metal anode.

5. The method for preparing a lithium metal anode according to claim 4, characterized in that, One or both of the following conditions must be met: (1) The method for preparing the pretreated metal current collector includes the following steps: pretreating the surface of the metal current collector with argon ions; optionally, in the step of pretreating the surface of the metal current collector, Ar... + The ion energy is 500 eV~1000 eV, and the ion beam current density is 0.1 mA cm⁻¹. -2 ~0.3mA cm -2 The bombardment time is 60s~180s; and (2) The surface roughness RA of the pretreated metal current collector is 150nm~250nm.

6. The method for preparing a lithium metal anode according to claim 4, characterized in that, The hexagonal boron nitride was deposited on the surface of a pretreated metal current collector using radio frequency magnetron sputtering. Optionally, one or both of the following conditions must be met: (1) The target material for radio frequency magnetron sputtering is hexagonal boron nitride; and (2) The power of radio frequency magnetron sputtering is 80W~120W.

7. The method for preparing a lithium metal anode according to claim 4, characterized in that, One or more of the following conditions must be met: (1) The lithiophilic material source includes one or more of zinc sulfate, stannous methanesulfonate and stannous sulfate; (2) The concentration of the lithiophilic source in the aqueous solution is 0.1 mol / L to 0.5 mol / L; (3) With 0.5mA cm -2 ~2 mA cm -2 Electroplating is performed at a current density of 1 min to 3 min; (4) After electroplating, the process also includes washing with distilled water and drying at 60℃~80℃ for 15min~20min; (5) During the oxidation process, the oxidation is carried out in an environment of 200℃~300℃ for 30min~60min; (6) The pressure of lithium evaporation plating is less than or equal to 1×10 -3 Pa, the evaporation rate of lithium evaporation plating is 0.1 nm / s~1.0 nm / s; (7) After the lithium metal layer is deposited, the process also includes maintaining pressure in a vacuum environment for 20-30 minutes; and (8) In the step of generating lithium-penetrating material in situ by bombardment treatment with CF4 and / or nitrogen plasma, the power is 50W~200W and the bombardment treatment time is 1min~5min.

8. The method for preparing a lithium metal anode according to any one of claims 4 to 7, characterized in that, In the step of depositing hexagonal boron nitride on the side of the lithium metal layer away from the first hexagonal boron nitride layer, the hexagonal boron nitride is deposited on the surface of the lithium metal layer by radio frequency magnetron sputtering. Optionally, one or more of the following conditions must be met: (1) The target material for radio frequency magnetron sputtering is hexagonal boron nitride; (2) The power of radio frequency magnetron sputtering is 80W~120W; (3) The temperature of the metal current collector during radio frequency magnetron sputtering is less than or equal to 80℃; as well as (4) The linear velocity of the metal current collector during the radio frequency magnetron sputtering process is 0.5 m / min to 1.0 m / min.

9. The application of the lithium metal anode according to any one of claims 1 to 3 or the lithium metal anode prepared by the preparation method according to any one of claims 4 to 8 in the preparation of lithium metal batteries.

10. A lithium metal battery, characterized in that, The lithium metal anode comprises the lithium metal anode according to any one of claims 1 to 3 or the lithium metal anode prepared by the preparation method according to any one of claims 4 to 8.

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