Lithium metal electrode for lithium secondary battery and method for manufacturing the same

Abstract

The present invention relates to a lithium metal electrode and a method of manufacturing the same. The lithium metal electrode of the present invention includes: a current collector; a metal layer on at least one side of the current collector and including a lithium alloy; and a protective layer on the metal layer and including a first amorphous carbon having a specific surface area of 450 m 2 / g or more.

Description

Technical Field

[0001] This invention relates to a lithium secondary battery, and more specifically, to a lithium metal electrode for a lithium secondary battery and a method for preparing the same. Background Technology

[0002] To achieve low cost and high energy density in rechargeable batteries, the use of lithium metal anodes as the negative electrode in lithium rechargeable batteries has become an inevitable trend. Specifically, all-solid-state batteries have recently attracted much attention as a high-energy-density next-generation battery for applications such as electric vehicles (EVs).

[0003] All-solid-state batteries offer various advantages: they do not use liquid electrolytes, thus exhibiting excellent stability and the ability to operate at high voltages; they also reduce the energy density of the battery pack by minimizing cooling and safety-related auxiliary materials; and they can operate over a wide temperature range. To substantially achieve high energy density in such all-solid-state batteries, the thicker, lower-capacity graphite-based anode material needs to be replaced with thinner, higher-capacity lithium. Furthermore, considering both economics and energy density, a thin-film lithium metal anode with a thickness of 10–20 μm is practically required.

[0004] Typically, there are difficulties in the technology of preparing thin layers of lithium metal anodes using commercial processes, and during the charge and discharge of secondary batteries, uneven current density and electrochemical reactions lead to dendrite growth. This can trigger continuous side reactions with the electrolyte and may cause internal short circuits at the contact between the anode and cathode.

[0005] Dendrite growth can lead to low lifetime characteristics and cause significant stability problems, making it difficult to achieve practical applications of ultrathin lithium metal anodes.

[0006] Various methods have been proposed to suppress dendrite growth and improve lifetime; however, it remains difficult to simultaneously achieve high energy density and sufficient lifetime characteristics through lithium ultrathinning. To address this issue, methods using protective layers on lithium metal batteries have been proposed; however, these methods still suffer from limitations in achieving sufficient lithium deposition rates and charge-discharge lifetime characteristics. Summary of the Invention

[0007] (a) Technical problems to be solved An embodiment of the present invention provides a lithium secondary battery using a lithium metal electrode, which improves the lithium deposition rate and charge / discharge life characteristics by increasing the lithium-ion conductivity.

[0008] Another embodiment of the present invention provides a method for preparing a lithium metal electrode for a lithium secondary battery that has the aforementioned advantages.

[0009] (II) Technical Solution An embodiment of the lithium metal electrode of the present invention may include: a current collector; a metal layer located on at least one side of the current collector and comprising a lithium alloy; and a protective layer located on the metal layer and comprising a specific surface area of ​​450 m². 2 The first amorphous carbon has an average particle size D50 of 0.1~1.5 μm. In one embodiment, the first amorphous carbon has an average particle size D50 of 0.1~1.5 μm.

[0010] In one embodiment, the protective layer may further include a second amorphous carbon with a specific surface area smaller than that of the first amorphous carbon, wherein, based on 100% by weight of amorphous carbon in the protective layer, it may include at least 50% by weight of the first amorphous carbon and the balance of the second amorphous carbon. In one embodiment, the specific surface area of ​​the second amorphous carbon may be 40-80 m². 2 / g or less.

[0011] In one embodiment, the average particle size D50 of the second amorphous carbon can be 20-50 nm. In one embodiment, the difference between the specific surface area of ​​the first amorphous carbon and the specific surface area of ​​the second amorphous carbon can be 400-700 nm. 2 / g.

[0012] In one embodiment, the first amorphous carbon in the protective layer may include micropores. In one embodiment, the micropores may account for 10-40% of the total pore volume. In one embodiment, the second amorphous carbon in the protective layer may include mesopores or macropores.

[0013] Another embodiment of the present invention provides a method for preparing a lithium metal electrode, comprising the following steps: preparing a current collector; forming a coating on at least one side of the current collector using a coating composition comprising a lithium-philic component; and forming a protective layer on the surface of the coating, the protective layer comprising a specific surface area of ​​450 m². 2 / g or more of the first amorphous carbon. In one embodiment, after the step of forming the protective layer, the process may include: placing a current collector having the coating and the protective layer formed in an electroplating solution, and then placing a lithium source at a predetermined interval from the protective layer; and applying an electric current between the current collector and the lithium source to form a metal layer comprising a lithium alloy, the lithium alloy being formed by alloying lithium deposited from the lithium source with a lithiophilic component included in the coating.

[0014] In one embodiment, during the step of forming the protective layer, the average particle size D50 of the first amorphous carbon can be 0.1~1.5 μm. In another embodiment, during the step of forming the protective layer, a second amorphous carbon with a specific surface area smaller than that of the first amorphous carbon can be further mixed in, wherein, based on 100% by weight of amorphous carbon in the protective layer, at least 50% by weight (wt%) of the first amorphous carbon and the remainder of the second amorphous carbon are mixed.

[0015] In one embodiment, the specific surface area of ​​the second amorphous carbon can be 40~80m². 2 / g or less. In one embodiment, the average particle size D50 of the second amorphous carbon may be 20~50nm.

[0016] (III) Beneficial Effects An embodiment of the present invention provides a lithium secondary battery with a lithium metal electrode, the lithium secondary battery including a protective layer containing amorphous carbon with high specific surface area, thereby improving lithium-ion conductivity to increase lithium deposition rate and improve charge-discharge life characteristics.

[0017] Another embodiment of the present invention provides a method for preparing a lithium metal electrode for a lithium secondary battery that has the aforementioned advantages. Attached Figure Description

[0018] Figure 1a and Figure 1b This indicates a lithium metal electrode prepared according to one embodiment.

[0019] Figure 2 This is a schematic diagram of the method for preparing the lithium metal electrode of the present invention.

[0020] Figure 3 This is a scanning electron microscope (SEM) image showing the structure and thickness of an alloy material coating deposited on a current collector according to an embodiment of the present invention.

[0021] Figure 4 shows the surface and cross-sectional microstructure of a current collector coated with alloy material in one embodiment when a protective layer is provided.

[0022] Figure 5a and Figure 5b This indicates the appearance of lithium plating according to embodiments and comparative examples of the present invention.

[0023] Figure 6a and Figure 6b The pore volume and cumulative porosity of the first and second amorphous carbons used in the embodiments and comparative examples of the present invention are expressed in terms of pore size.

[0024] Figure 7This describes the cell life evaluation of all-solid-state batteries using embodiments and comparative examples of the present invention. Detailed Implementation

[0025] The terms "first," "second," and "third," etc., are used to describe various parts, components, regions, layers, and / or segments, but are not limited thereto. These terms are used only to distinguish one part, component, region, layer, or segment from another. Therefore, the first part, component, region, layer, or segment described below may be referred to as the second part, component, region, layer, or segment without departing from the scope of the invention.

[0026] The technical terms used herein are for reference only to specific embodiments and are not intended to limit the invention. The singular forms used herein include the plural forms unless the context clearly indicates otherwise. The word "comprising" as used in this specification means that a particular feature, region, integer, step, action, element, and / or component is specified, but does not exclude the presence or addition of other features, regions, integers, steps, actions, elements, and / or components.

[0027] When one part is mentioned as being "above" or "on top of" another part, it can be directly above or on top of the other part, or there may be other parts in between. Conversely, when one part is mentioned as being "directly above" another part, there are no other parts in between.

[0028] Unless otherwise defined, all terms used herein, including technical and scientific terms, shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms as defined in commonly used dictionaries are further interpreted as having meanings consistent with relevant technical literature and current disclosure, and are not to be construed as having ideal or overly formal meanings unless otherwise defined.

[0029] Figure 1a and Figure 1b This refers to a lithium metal electrode 100 prepared according to one embodiment.

[0030] Reference Figure 1a One embodiment of the lithium metal electrode 100 includes a current collector 11, a metal layer 12 located on at least one side of the current collector 11, and a protective layer 30 located on the other side of the metal layer 12 facing the current collector 11.

[0031] The current collector 11 can be a component used for electrical connection within a lithium secondary battery. The current collector 11 can be in the form of a film (Foil), but is not limited thereto; for example, it can also be in the form of a mesh, foam, rod, wire, or sheet made of braided wire (fiber).

[0032] The current collector 11 can be made of a material that is conductive and has limited reactivity with lithium. Specifically, the material of the current collector 11 can be any one or a combination of copper, nickel, titanium, stainless steel, iron, gold, platinum, silver, tantalum, ruthenium and their alloys, carbon, conductive polymers, and composite fibers coated with a conductive layer on a non-conductive polymer.

[0033] In one embodiment, the thickness of the current collector 11 can be 1 μm to 50 μm. If the current collector 11 is too thick, the battery weight increases, resulting in a decrease in battery energy density. If the current collector 11 is too thin, there is a risk of overheating and damage during operation at high current, and it may also be damaged due to tension during battery fabrication.

[0034] Metal layer 12 is located on current collector 11 and may include a lithium alloy layer 21 comprising a lithium alloy and a lithium metal layer 41 located on the lithium alloy layer 21. The lithium alloy layer 21 may be a layer comprising a lithium alloy, which is distributed between the current collector 11 and the lithium source (…). Figure 2 An electric current is applied between reference numerals 40 in the figure, and the current collector 11 is formed by alloying the lithium-loving component included in the metal layer 12 with the lithium deposited from the lithium source 40.

[0035] When forming the metal layer 12, applying a high current to increase the electroplating speed can lead to a decrease in the performance of the lithium secondary battery. However, when the metal layer 12 is formed from a structure including a lithium alloy layer 21 containing lithium, as in this embodiment, even with a high current applied during the electroplating process, it is possible to prevent the formation of excessive microlithium particles or damage to the protective layer 30 on the surface of the formed lithium metal layer 41 during the electroplating process.

[0036] Specifically, in one embodiment, the metal layer 12 includes a lithium alloy layer 21 containing lithium components. Therefore, when a lithium metal layer 41 is formed on the lithium alloy layer 21 by applying a high current in the electroplating process, the early-generated lithium particles can be guided to grow well, thereby forming coarse-structured particles while giving the lithium metal layer 41 (ultimately making the metal layer 12) a uniform surface.

[0037] Therefore, the performance (specifically, charge-discharge characteristics) of the secondary battery using the lithium metal electrode of this embodiment can be significantly improved. Furthermore, even with a high-current, rapid electroplating process, a high-performance lithium metal electrode for secondary batteries can be fabricated, thus significantly improving the productivity of lithium metal electrodes for secondary batteries.

[0038] In this embodiment, the lithium alloy layer 21 comprises a lithium-loving metal. When the lithium alloy layer 21 comprises a lithium-loving metal, it has the advantage of smoothly supplying electrons from the current collector to reduce lithium ions, thus facilitating the electroplating of a lithium metal layer, due to the inclusion of a lithium-loving metal with high electronic conductivity. The metal layer 12 serves to help lithium be deposited more effectively beneath the protective layer 30 during battery charging.

[0039] In one embodiment, the thickness of the metal layer 12 can be in the range of 1 μm to 100 μm, more specifically, in the range of 5 μm to 30 μm. If the thickness of the metal layer 12 is too thick, when the lithium metal electrode of this embodiment is applied to a secondary battery, there is a problem of decreased energy density due to the increase in battery weight and volume. In addition, the time and cost of the electroplating process increase proportionally with the thickness when forming the metal layer 12, therefore the thickness of the metal layer 12 is preferably less than 100 μm.

[0040] If the thickness of the metal layer 12 is too thin, the lithium metal electrode of this embodiment will result in a decrease in the charge-discharge life of the battery when applied to a secondary battery. Specifically, during the charge-discharge process, the lithium contained in the negative electrode active material layer (i.e., the metal layer of this invention) and the electrolyte undergo side reactions, leading to a gradual consumption of lithium within the battery and a reduction in battery capacity. Furthermore, the amount of lithium available to replenish the lithium consumed during charge-discharge decreases, thus reducing the battery's charge-discharge life. Therefore, the thickness of the metal layer 12 is preferably 1 μm or more.

[0041] The protective layer 30 is located on the metal layer 12 and may include a first amorphous carbon. The first amorphous carbon may be amorphous carbon with a high specific surface area. Specifically, the specific surface area of ​​the first amorphous carbon may be 450 m². 2 / g or more. Specifically, the specific surface area of ​​the first amorphous carbon can be 500m². 2 / g or more, more specifically 500~800m 2 / g, more specifically 550~750m 2 / g, more specifically 550~650m 2 / g.

[0042] By satisfying the aforementioned range of specific surface area, the first amorphous carbon exhibits an effect of increasing specific surface area. Furthermore, due to its numerous micropores, it offers the advantage of easy lithium-ion conduction through grain boundaries and pores. If the first amorphous carbon deviates from the upper limit of the aforementioned range, excessive binder or dispersant is required during slurry formation, leading to uneven dispersion. If the first amorphous carbon falls below the lower limit of the aforementioned range, the surface area decreases, resulting in a decrease in the conductivity of lithium ions that primarily migrate through the amorphous carbon surface.

[0043] In one embodiment, the average particle size D50 of the first amorphous carbon can be 0.1~1.5 μm. The average particle size D50 of the first amorphous carbon can be the particle size corresponding to 50% of the volumetric cumulative size distribution of the first amorphous carbon. Specifically, the average particle size D50 of the first amorphous carbon can be 0.3~1.2 μm. More specifically, the average particle size D50 of the first amorphous carbon can be 0.5~1.0 μm. More specifically, it can be 0.6~1.0 μm.

[0044] Meeting the aforementioned range in terms of the average particle size D50 of the first amorphous carbon has the advantage of facilitating stable dispersion of the slurry. If the average particle size D50 of the first amorphous carbon deviates from the upper limit of the aforementioned range, the particle size becomes too large compared to the thickness of the protective layer, resulting in a reduction in the number of particles constituting the entire protective layer and a problem of failing to effectively prevent lithium dendrite growth. If the average particle size D50 of the first amorphous carbon deviates from the lower limit of the aforementioned range, there is a problem that a large number of micropores cannot be formed within the amorphous carbon particles.

[0045] Specifically, the specific surface area of ​​the second amorphous carbon can be 40~80m². 2 / g. Specifically, the specific surface area of ​​the second amorphous carbon can be 50~70m². 2 / g.

[0046] By ensuring the specific surface area of ​​the second amorphous carbon meets the aforementioned range, it has the advantage of being able to form pores of appropriate size. If the second amorphous carbon deviates from the upper limit of the aforementioned range, there is a problem that excessive binder or dispersant is required when forming the slurry. If the second amorphous carbon deviates from the lower limit of the aforementioned range, the specific surface area decreases excessively, resulting in a decrease in the conductivity of lithium ions moving through the surface.

[0047] In one embodiment, based on 100% by weight of amorphous carbon within the protective layer 30, it may include at least 50% by weight (wt%) of first amorphous carbon and the remainder of second amorphous carbon. Specifically, based on 100% by weight of amorphous carbon, the content of first amorphous carbon may be at least 60% by weight (wt%), more specifically at least 80% by weight. Thus, based on the total amount of amorphous carbon (specifically, first and second amorphous carbon), the content of first amorphous carbon is greater than the content of second amorphous carbon, thereby increasing the volume occupied by micropores in all pores and resulting in a larger specific surface area, thus improving lithium-ion conductivity. If the content of first amorphous carbon is less than the content of second amorphous carbon, the proportion of micropores in all pores is lower, thus leading to a decrease in the conductivity of lithium-ions moving through the micropore surface, resulting in a decrease in battery life characteristics.

[0048] In one embodiment, the average particle size D50 of the second amorphous carbon can be 20-50 nm. The average particle size D50 of the second amorphous carbon can be the particle size corresponding to 50% of the volumetric cumulative size distribution of the second amorphous carbon. Specifically, the average particle size D50 of the second amorphous carbon can be 30-40 nm.

[0049] By ensuring that the average particle size D50 of the second amorphous carbon meets the aforementioned range, it has the advantage of increasing the density of the protective layer when mixed with the first amorphous carbon. If the average particle size D50 of the second amorphous carbon deviates from the upper limit of the aforementioned range, there is a problem of increased particle size and decreased specific surface area. If the average particle size D50 of the second amorphous carbon deviates from the lower limit of the aforementioned range, there is a problem of agglomeration or decreased dispersibility when forming a slurry due to excessively small particle size.

[0050] In one embodiment, the difference between the specific surface area of ​​the first amorphous carbon and the specific surface area of ​​the second amorphous carbon can be 400~700m². 2 / g. Specifically, the difference can be 500~600m. 2 / g.

[0051] By ensuring the difference falls within the aforementioned range, the protective layer achieves a proper mixture of micropores and mesopores, and allows small particles to effectively fill the spaces between larger particles, thereby increasing the density of the protective layer. If the difference deviates from the upper limit of the aforementioned range, it results in the inclusion of particles with excessively large specific surface areas, leading to problems such as excessive use of binders or dispersants and dispersibility issues. If the difference deviates from the lower limit of the aforementioned range, the effect of increasing specific surface area is reduced, resulting in a decrease in the effect of improving lithium-ion conductivity.

[0052] In one embodiment, the first amorphous carbon may include micropores as tiny pores. The micropores are pores formed on the particle itself, meaning nanoscale pores.

[0053] Specifically, based on the total volume of all pores, the first amorphous carbon may include 10-40% micropores. More specifically, the included micropores may account for 13-35%, and more specifically, 14.7-30%. In one embodiment, the micropores may have a size of less than 2 nm. Specifically, the diameter of the micropores may be less than 2 nm. By including micropores within the aforementioned range in the first amorphous carbon, a larger specific surface area is achieved, thereby providing the advantage of improved lithium-ion conductivity conducted along the tiny micropores.

[0054] In one embodiment, the second amorphous carbon may include mesopores or macropores. Specifically, the mesopores are pores formed between particles and may have a size of 2-50 nm. The macropores are pores formed between particles and may have a size greater than 50 nm. The particle size of the second amorphous carbon is less than 50 nm, specifically 10-40 nm, more specifically 20-40 nm, and it has fewer pores formed on the particles themselves, and may include the mesopores or macropores formed between particles.

[0055] In one embodiment, when the protective layer simultaneously comprises a first amorphous carbon and a second amorphous carbon, the micropore fraction, based on 100% of the total pore volume, can satisfy 10-40%. The micropore fraction is a factor determined by the content of the first amorphous carbon; the higher the content of the first amorphous carbon, the larger the micropore fraction. By including micropores within the aforementioned range in the protective layer, it has the advantage of improving lithium-ion conductivity conducted along the surface of the tiny micropores.

[0056] When lithium metal is used as the negative electrode in all-solid-state batteries, high resistance is generated through the reaction between the all-solid-state electrolyte and lithium. Furthermore, due to local unevenness in current density during charging and discharging, lithium dendrites or high-resistivity lithium byproducts are continuously generated, which can lead to malfunctions or reduced battery capacity due to short circuits or overvoltages during charging and discharging.

[0057] According to one embodiment, a lithium metal electrode, by including a protective layer containing a first amorphous carbon, can improve the output characteristics and lifetime characteristics of the lithium metal electrode, and also improve structural safety.

[0058] Specifically, the lithium metal electrode in this embodiment includes a protective layer 30 containing a first amorphous carbon, which not only improves the ionic conductivity but also increases the strength of the protective layer 30. Furthermore, it physically prevents dendrites from growing on the lithium electrode, thereby preventing short circuits between electrodes and improving charge-discharge life.

[0059] The first amorphous carbon and the second amorphous carbon may be selected from one or more of acetylene black, super P carbon black, carbon black, Denka carbon black, activated carbon, graphite, hard carbon and soft carbon, but are not limited thereto.

[0060] In one embodiment, the protective layer 30 may include an adhesive. The adhesive may be an aqueous adhesive, and may be a rubber-based adhesive selected from acrylonitrile-butadiene rubber, styrene-butadiene rubber (SBR) and acrylic rubber, as well as one or more polymeric resins selected from hydroxyethyl cellulose, carboxymethyl cellulose and polyvinylidene fluoride, but is not limited thereto.

[0061] Here, based on the weight of the slurry formed by mixing the first amorphous carbon and / or the second amorphous carbon and water, 1 to 15 parts by weight, specifically 3 to 10 parts by weight, of the binder may be added. If the content of the binder meets the aforementioned range, the battery energy density will not decrease due to the increase in weight and volume, and at the same time, it can effectively bind the particles constituting the protective layer to form a high-performance protective layer, further improving the life characteristics of the secondary battery.

[0062] If the content of the included adhesive is less than the aforementioned range, there will be a problem of reduced interparticle bonding force when forming the protective layer. If the content of the included adhesive is more than the aforementioned range, it will not only cause a decrease in energy density, but also a significant increase in the resistance of the protective layer, which will hinder lithium-ion conduction.

[0063] In one embodiment, the thickness of the protective layer 30 can be from 0.01 μm to 50 μm. Specifically, the thickness of the protective layer 30 can be in the range of 1 μm to 20 μm. If the thickness of the protective layer meets the aforementioned range, it can prevent lithium dendrites from forming on the surface of the protective layer due to the amorphous carbon, and enable lithium ions to efficiently penetrate the interior of the protective layer for conduction, thereby allowing lithium to be deposited on the lower surface of the protective layer.

[0064] If the protective layer is too thin, it will fail to function properly. If it is too thick, its resistance will be too high, potentially causing overvoltage during battery operation and reducing energy density due to increased weight and volume. However, the thickness of this protective layer can be adjusted variably according to the design of the secondary battery structure.

[0065] In one embodiment, the lithium metal electrode may include a film layer disposed in at least a portion of the area inside the protective layer 30, between the metal layer 12 and the protective layer 30, and above the protective layer 30. Specifically, the film layer may be disposed in at least a portion of the area inside the protective layer 30, between the metal layer 12 and the protective layer 30, simultaneously inside the protective layer 30, between the metal layer 12 and the protective layer 30, or above the protective layer 30.

[0066] The film layer is formed during the preparation of the metal layer 12 by the reaction between the electroplated lithium metal source 40 and the plating solution. The thickness, composition, and characteristics of the film can be controlled by controlling the composition of the plating solution and the electroplating process conditions.

[0067] In one embodiment, the film layer may include at least some LiF. The LiF may be formed from at least one solvent among a plurality of solvents used in the electroplating process, including a solvent with a high dielectric constant. Specifically, salt decomposition reactions can be suppressed and solvent decomposition reactions promoted during electroplating by increasing the salt dissociation degree of the plating solution solvent, thereby forming a sufficient LiF film inside and / or on the surface of the protective layer. By including a film layer comprising at least some LiF, the battery life can be improved and dendrite growth prevented during battery operation through higher ionic conductivity.

[0068] The thickness of the film layer can be 2 nm to 2 μm. Specifically, the thickness of the film layer can be in the range of 10 nm to 500 nm. If the thickness of the film layer is too thick, the lithium-ion conductivity will decrease and the interface resistance will increase, resulting in a decrease in charge-discharge characteristics when applied to a battery. If the thickness of the film layer is too thin, the film layer may be easily lost during the application of the lithium metal electrode of the embodiment to the battery. Therefore, the film layer can have a relatively thin thickness within the aforementioned thickness range and be uniformly and densely formed on the entire surface of the metal layer 12 and the protective layer 30.

[0069] Reference Figure 1b In one embodiment, the lithium metal electrode 100 includes a current collector 11 and a metal layer 12 located on at least one side of the current collector 11 and composed of a mixture of lithium and a lithium alloy. Here, the lithium alloy may be a coating formed on the current collector 11 by applying a current between the current collector 11 and the lithium source 40. Figure 2 The lithium-loving component included in the figure (reference numeral 20) is formed by alloying lithium deposited from the lithium source 40.

[0070] The metal layer 12 may include a lithium-philic metal. For a detailed explanation, please refer to [link to relevant documentation]. Figure 1aIn one embodiment, the metal layer 12 is in the form of a lithium-loving metal. If the metal layer 12 comprising a lithium-loving metal is formed in this way, the nucleation free energy can be reduced in the early stage of lithium particle nucleation during the electroplating process, so that a lithium metal layer with a coarse particle structure can be formed even under high current and overvoltage conditions.

[0071] In one embodiment, the metal layer 12 may include a protective layer 30 located on the surface of the metal layer 12, and may also include a film layer located inside and / or on the surface of the protective layer 30. For a detailed description of the protective layer 30 and the film layer, please refer to the relevant documentation. Figure 1a The aforementioned content.

[0072] Figure 2 This is a schematic diagram of the method for preparing the lithium metal electrode of the present invention.

[0073] Reference Figure 2 An embodiment of a method for preparing a lithium metal electrode includes the following steps: preparing a current collector 11; forming a coating 20 on at least one side of the current collector 11 using a coating composition including a lithiophilic components; forming a protective layer 30 on the surface of the coating 20 using a slurry including amorphous carbon; placing the current collector 11 with the coating 20 and the protective layer 30 formed in a plating bath 50, and then placing a lithium source 40 at a predetermined interval from the protective layer 30; and applying a current between the current collector and the lithium source 40 to form a metal layer including a lithium alloy, which is formed by alloying the lithiophilic components included in the coating with lithium deposited from the lithium source 40.

[0074] In the step of preparing the current collector 11, the current collector 11 can be made of a material that is conductive and has limited reactivity with lithium. Specifically, the material of the current collector 11 can be any one or a combination of copper, nickel, titanium, stainless steel, iron, gold, platinum, silver, tantalum, ruthenium and its alloys, carbon, conductive polymers, and composite fibers coated with a conductive layer on a non-conductive polymer.

[0075] In the step of forming a coating 20 on at least one side of the current collector 11 using a coating composition including a lithiophilic component, an alloy material may be coated on at least one side of the current collector. The alloy material may be, for example, one or more selected from In, Ag, Sn, Zn, Si, Al and Bi, but is not limited thereto.

[0076] In one embodiment, the step of forming coating 20 may be performed using at least one of electroplating, electroless plating, sputtering, electron beam deposition, and thermal evaporation deposition. For example, the step of forming coating may be performed by an electroless plating method.

[0077] A protective layer 30 can be formed on the surface of coating 20 using a slurry comprising amorphous carbon. The protective layer 30 can be coated using at least one of the following methods: doctor blade coating, dip coating, reverse roll coating, direct roll coating, gravure printing, extrusion, and brush coating, by coating the slurry formed by mixing the amorphous carbon and a binder in water. The protective layer 30 may further include a binder.

[0078] In one embodiment, the step of forming the protective layer 30 may include forming a protective layer comprising a first amorphous carbon with a high specific surface area. Specifically, the amorphous carbon may have a surface area of ​​450 μm. 2 A specific surface area of ​​ / g or higher. For specific characteristics of the first amorphous carbon, please refer to the relevant information. Figure 1a and Figure 1b The aforementioned content.

[0079] In one embodiment, the step of forming the protective layer 30 may further include the step of mixing a second amorphous carbon with a specific surface area smaller than that of the first amorphous carbon. The step of forming the protective layer 30, by mixing the first and second amorphous carbons with different specific surface areas, allows small particles to effectively fill the spaces between large particles, thereby improving the density of the protective layer and achieving a proper mixing of micropores and mesopores. For a detailed description of the second amorphous carbon, please refer to the section on... Figure 1a and Figure 1b The aforementioned content.

[0080] In one embodiment, in the step of forming the protective layer 30, based on 100% by weight of amorphous carbon in the protective layer, specifically based on 100% by weight of the total amount of the first amorphous carbon and the second amorphous carbon, at least 50% by weight (wt%) of the first amorphous carbon and the balance of the second amorphous carbon may be mixed. For a detailed explanation of this, please refer to the section on... Figure 1a and Figure 1b The aforementioned content.

[0081] In addition, in the step of forming the protective layer 30, the thickness of the protective layer formed on the surface of the alloy material coating can be in the range of 0.01 μm to 50 μm, and more specifically in the range of 1 μm to 20 μm.

[0082] After the step of forming the protective layer 30, the following steps are performed: after placing the current collector on which the coating 20 and the protective layer 30 are sequentially formed in the plating solution 50, a lithium source 40 is placed at a predetermined interval from the current collector 11; and an electric current is applied between the current collector 11 and the lithium source 40 to form a metal layer 12.

[0083] Specifically, after placing the current collector 11, which has a coating 20 and a protective layer 30 formed thereon, in the plating solution 50, a lithium source 40 is placed at a predetermined interval from the protective layer 30. The lithium source 40 may be, for example, lithium metal, lithium alloy, a foil in which the lithium metal or lithium alloy is pressed onto the current collector, or a plating solution containing dissolved lithium salt.

[0084] The plating solution 50 can be prepared by dissolving lithium salts in various solvents. Specifically, the lithium salts can be LiCl, LiBr, LiI, LiCO3, LiNO3, LiFSI, LiTFSI, BF4, LiPF6, LiAsF6, LiClO4, LiN(SO2CF3)2, LiBOB, or combinations thereof. The concentration of the lithium salts can be based on the total electrolyte concentration and is 1.0~3.0M.

[0085] Specifically, in this embodiment, the plating solution 50 is characterized by including a nitrogen-based compound as at least one of the lithium salt and various solvents. The nitrogen-based compound may include, for example, one or more selected from lithium nitrate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethane sulfonimide, e-caprolactam, N-methyl-e-caprolactam, triethylamine, and tributylamin.

[0086] Among the nitrogen-based compounds, at least one of lithium nitrate, lithium bisfluorosulfonyl imide, and lithium bis trifluoromethanesulfonimide can be used as a lithium salt.

[0087] In the nitrogen-based compounds, at least one of e-caprolactam, N-methyl-e-caprolactam, triethylamine, and tributylamin can be used as a non-aqueous solvent.

[0088] The plating solution 50 can be prepared using only the nitrogen-based compound, but considering the viscosity of the plating solution 50, it may include common non-aqueous solvents as auxiliary solvents.

[0089] The auxiliary solvent may include, for example, one or more selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, and 1,3,5-trioxane.

[0090] In one embodiment, the auxiliary solvent may comprise 5 to 70% by weight, preferably 10 to 60% by weight, relative to 100% by weight of the total weight of the plating solution 50, but is not limited thereto. However, when the auxiliary solvent is included within the range described above, the time required for forming the metal layer 12 can be shortened due to the appropriate viscosity of the plating solution 50, but is not limited thereto.

[0091] In one embodiment, the plating solution 50 may further include a fluorine-based compound. When the plating solution 50 further includes the fluorine-based compound, it has the advantage of improving the properties of the film layer formed on the lithium metal layer 12.

[0092] The fluorine compounds may include, for example, one or more selected from lithium difluorophosphate, lithium hexafluorophosphate, lithium difluorobisoxalato phosphate, lithium tetrafluorooxalato phosphate, lithium difluorooxalate borate, lithium difluorooxalato borate, lithium tetrafluorooxalato borate, fluoroethylene carbonate, difluoroethylenecarbonate, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0093] The fluorine compound may comprise 0.1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, relative to 100% by weight of the total weight of the plating bath 50. When the fluorine compound is included in the range described above, the interaction between the nitrogen-based compound and the fluorine compound in the plating bath 50 is smoother, thus providing an advantage in improving the properties of the film layer formed on the lithium metal layer 12. Furthermore, it suppresses excessive LiF formation and other behaviors caused by the direct reaction between the fluorine compound and lithium, thus providing an advantage in excellent electrochemical properties.

[0094] Next, after placing a diaphragm between the current collector 11 and the lithium source 20, the current collector 11, the lithium source 20, and the diaphragm are stacked and constrained from two directions using a constraint device. As a non-limiting example, the constraint device can use methods commonly used in the art, such as manual clamping, hydraulic pressure, or uniaxial pressurization using pneumatic pressure.

[0095] In the step of applying current to form a lithium metal layer on at least one side of the current collector, the applied current density may be 0.1 mA / cm². 2 ~100mA / cm 2 The range, more specifically, can be 0.2 mA / cm. 2 ~50mA / cm 2 Range, 5mA / cm 2~30mA / cm 2 Range or 7mA / cm 2 ~25mA / cm 2 scope.

[0096] In one embodiment, the duration of the applied current can be in the range of 0.05 hours to 50 hours, more specifically in the range of 0.25 hours to 25 hours.

[0097] In one embodiment, the step of applying current to form a lithium metal layer on at least one side of the current collector can be performed at least once at different current densities. The current application step can be performed in multiple steps. Specifically, the multi-step current application step can be performed simultaneously by gradually increasing the current density from low to high over a predetermined time. For example, the current application step can be performed at 0.1~0.3 mA / cm. 2 0.3~0.7mA / cm 2 and 0.8~1.5mA / cm 2 Electroplating is performed by gradually increasing the current density in sequence.

[0098] In one embodiment, the step of applying current to form a lithium metal layer 12 on at least one side of the current collector 11 may include applying current at a rate of 6~12 mA / cm². 2 The electroplating process involves applying a current density within the specified range. Specifically, this can be 8~12 mA / cm². 2 The process is performed at the maximum current density within the specified range. The maximum current density refers to the limit of the current density at which lithium to be electroplated in the electroplating process can deposit lithium between the protective layer 30 and the current collector 11.

[0099] The electroplating step at the maximum current density can be, for example, a final step performed after a multi-step deposition process to deposit lithium between the current collector 11 and the protective layer 30. By satisfying the aforementioned range with the maximum current density, lithium is appropriately deposited between the current collector 11 and the protective layer 30, resulting in advantages such as excellent battery life characteristics and superior bonding strength between the current collector 11 and the protective layer 30.

[0100] If the maximum current density deviates from the upper limit of the aforementioned range, lithium will deposit on the surface of the protective layer 30, thus failing to ensure the desired stable electrode structure. If the maximum current density deviates from the lower limit of the aforementioned range, it will lead to an increase in lithium plating time, thus resulting in a decrease in productivity.

[0101] In one embodiment, the step of applying current to form a lithium metal layer on at least one side of the current collector may include electroplating the deposited lithium with a thickness ranging from 5 to 15 μm. Specifically, the deposited lithium may be electroplated with a thickness ranging from 8 to 12 μm. The thickness of the deposited lithium may refer to the vertical height of the lithium disposed between the current collector 11 and the protective layer 30.

[0102] If the thickness of the deposited lithium deviates from the aforementioned upper limit, the battery's energy density will decrease, and the processing time and the amount of metal raw materials used in forming the metal layer will increase. If the thickness of the deposited lithium deviates from the aforementioned lower limit, the initial coulombic efficiency will decrease due to initial irreversibility, and the charge-discharge performance will decrease due to insufficient residual lithium.

[0103] In one embodiment, during the step of applying current to form a lithium metal layer 12 on at least one side of the current collector 11, the thickness of the metal layer 12, comprising a lithium alloy, can be controlled to be 1 to 100 μm. A detailed description of the thickness of the metal layer 12 can be found in the foregoing description with reference to FIG1.

[0104] Thus, in this embodiment, even under high current conditions, the generation of excessive microlithium particles can be prevented, and the early-generated lithium particles can be guided to grow well, thereby preparing a lithium metal electrode 100 with a metal layer, wherein the metal layer includes a lithium metal layer 12 with a coarse particle structure. Furthermore, the metal layer thus prepared also exhibits excellent surface uniformity.

[0105] Another embodiment of the lithium secondary battery of the present invention includes a positive electrode, a negative electrode, and an electrolyte located between the positive electrode and the negative electrode. Here, the negative electrode may be the lithium metal electrode of the present invention.

[0106] In one embodiment, the lithium secondary battery may include an electrode assembly comprising: a positive electrode including a positive electrode active material, a negative electrode serving as a lithium metal electrode of the present invention, and a separator disposed between the positive electrode and the negative electrode. This electrode assembly can be wound or folded and housed in a battery casing.

[0107] Next, electrolyte can be injected into the battery casing and sealed to complete the secondary battery. At this time, the battery casing can have shapes such as cylindrical, square, pouch-shaped, and coin-shaped.

[0108] The positive electrode may include a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer may include a Li compound, which may include, for example, at least one metal selected from Ni, Co, Mn, Al, Cr, Fe, Mg, Sr, V, La, Ce and at least one non-metallic element selected from O, F, S, P and combinations thereof.

[0109] In one embodiment, a conductive material may be further added to the positive electrode active material layer. The conductive material may be, for example, carbon black, ultrafine graphite particles, fine carbon of acetylene black, metal nanoparticle paste, etc., but is not limited to these.

[0110] The positive electrode current collector serves to support the positive electrode active material layer. The positive electrode current collector may be, for example, aluminum foil, nickel foil, or a combination thereof, but is not limited to these.

[0111] The electrolyte filled in the lithium secondary battery can be a non-aqueous electrolyte or a solid electrolyte. Specifically, the electrolyte can be a solid electrolyte. The non-aqueous electrolyte may include, for example, lithium salts such as lithium hexafluorophosphate and lithium perchlorate, and solvents such as ethylene carbonate, propylene carbonate, and butene carbonate. In addition, the solid electrolyte may be, for example, a gel polymer electrolyte in which the electrolyte is impregnated in a polymer electrolyte such as polyethylene oxide or polyacrylonitrile, or an inorganic solid electrolyte such as LiI or Li3N.

[0112] The separator is used to isolate the positive and negative electrodes and provide a channel for lithium ion movement; any material commonly used in lithium secondary batteries can be used. Specifically, the separator can be one that has low resistance to ion movement of the electrolyte and excellent electrolyte impregnation capacity. The separator can be, for example, selected from glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene, or combinations thereof, and can be in non-woven or woven fabric form. Alternatively, when a solid electrolyte is used as the electrolyte, the solid electrolyte can also serve as the separator.

[0113] The following is a detailed description of implementation examples of the present invention. However, this is merely an example, and the present invention is not limited thereto; it is defined only by the scope of the claims.

[0114] <Experimental Example> Preparation of negative electrode for lithium secondary batteries <Example 1> <Preparation of Current Collectors> Prepare Cu foil (Foil) current collectors for use as the negative electrode for lithium secondary batteries in this invention.

[0115] <Formation of Alloy Material Coatings> Subsequently, an alloy material is coated on both sides of the current collector by electroplating. Specifically, the alloy material is coated on both sides of the copper foil current collector by electroless plating. Silver (Ag) is used as the alloy material, and the plating thickness is controlled to be approximately 300 nm.

[0116] Figure 3This is a scanning electron microscope (SEM) image showing the structure and thickness of an alloy material coating deposited on a current collector according to an embodiment of the present invention.

[0117] Reference Figure 3 It can be confirmed that the alloy material coating deposited on the current collector of the present invention has a thickness in the range of about 250~350nm.

[0118] <Formation of the protective layer> Subsequently, a protective layer of approximately 5 μm is formed on the upper surface of the coating by applying slurry using a comma coater. Specifically, the protective layer is formed by mixing amorphous carbon, a binder, and a solvent. Here, as the binder, 3.0 parts by weight of carboxymethyl cellulose (CMC) and 6.0 parts by weight of styrene-butadiene rubber (SBR) are added relative to 100 parts by weight of amorphous carbon, thereby preparing the protective layer. Furthermore, a solvent using water and ethylene glycol (EG) in a weight ratio of 80:20 is used. The total amount of solvent is approximately 25% by weight of the total amount of amorphous carbon and binder, maintaining a viscosity suitable for coating.

[0119] The amorphous carbon used is a powder with high specific surface area, specifically Heraeus L1102, with a median particle size D50 of 0.8 μm and a specific surface area of ​​600 m². 2 / g.

[0120] Figure 4a and Figure 4b This refers to the microstructure of the surface and cross-section when a protective layer is applied to a current collector coated with alloy material.

[0121] Reference Figure 4a and Figure 4b After the solvent evaporates, it has a porous surface and cross-sectional structure. This porous structure allows the plating solution to be easily impregnated during the subsequent lithium plating process, thus facilitating the movement and plating of lithium ions.

[0122] <Lithium-ion plating process> Subsequently, in order to form a lithium alloy or pure lithium metal between the protective layer and the current collector, lithium is stripped from the lithium source using an electroplating process, and lithium is deposited between the protective layer and the current collector. The plating solution used in this electroplating is prepared by the following method: In a 1,2-dimethoxyethane (DME) solvent, 40 wt% and 5 wt% of lithium bis(fluorosulfonyl)imide (a nitrogen-based compound) and lithium nitrate (a fluorine-based compound) are added, respectively, based on 100 wt% of the plating solution. Also, 5 wt% of fluoroethylene carbonate (a fluorine-based compound) is added, based on 100 wt% of the plating solution. A lithium metal plate with a purity of 99.9% or higher and a thickness of 500 μm is pressed onto a copper current collector (Cu plate) as the lithium source 40.

[0123] After a lithium source and a current collector are stacked in an electrically insulating state in a plating solution, a power supply device is used to apply current between the current collector and the ion concentration protective layer by using the lithium source and the current collector as positive (+) and negative (-) electrodes, respectively.

[0124] The current density for the electroplating process is set at 0.2 mA / cm². 2 0.5mA / cm 2 1mA / cm 2 While increasing the electroplating process in stages, each electroplating session lasted 5 minutes, followed by an A / cm charge. 2 Electroplating is performed at the maximum current density. The electroplating time at the maximum current density is calculated to achieve a final lithium deposition thickness of 10 μm, and is variably set according to the magnitude of the maximum current density.

[0125] Figure 5a and Figure 5b The electroplating appearance is shown according to the maximum current density in the electroplating process of the embodiments and comparative examples.

[0126] Figure 5a This indicates the appearance of the electroplated surface when electroplating is performed at current densities below the maximum current density. Figure 5b This indicates the appearance of the plating when electroplating is performed at a current density exceeding the maximum current density. (Refer to...) Figure 5a and Figure 5bWhen electroplating is performed at a current density below the maximum plating current density, it can be confirmed that the deposited lithium is deposited below the black protective layer, thus the black protective layer is visible. When electroplating is performed at a current density exceeding the maximum plating current density, it can be confirmed that lithium is deposited on the upper surface of the protective layer, thus gray lithium is plated on the upper surface of the protective layer. Therefore, the maximum plating current density is defined as the maximum current density at which lithium can be deposited between the current collector and the protective layer in the electroplating process.

[0127] <Comparative Example 1> Except that in the step of forming the protective layer, the high specific surface area particulate amorphous carbon used in Example 1 is completely excluded, and low specific surface area nanoparticle amorphous carbon (second amorphous carbon) is used instead of 100% by weight, the same method as in Example 2 is adopted.

[0128] Fabrication of all-solid-state batteries All-solid-state batteries were fabricated using the negative electrodes prepared according to the foregoing examples and comparative examples, and their charge-discharge life was evaluated. To evaluate the all-solid-state battery cell, a pressurized evaluation cell from TERA LEADER, capable of maintaining an inert atmosphere, was used. For fabricating the all-solid-state battery cell, a sulfide-based silver-germanium ore (Li6PS5Cl) solid electrolyte was used, in particulate form with a thickness of approximately 0.7 mm. To ensure a dense electrolyte, a pressure of 370 MPa was applied.

[0129] A 0.5 mm thick lithium electrode was attached to one side of the electrolyte as a reference electrode, and a negative electrode prepared according to the examples and comparative examples was attached to the opposite side. The reference electrode and the evaluation electrode were attached to the solid electrolyte at a pressure of 50 MPa, and a pressure of 16 MPa was applied for a dedicated evaluation cell during charge-discharge evaluation.

[0130] <Evaluation Example 1>: Performance evaluation based on the difference in specific surface area of ​​amorphous carbon Table 1 below shows the maximum electroplating current and charge / discharge cycles for amorphous carbon with different specific surface areas during the formation of the protective layer. The maximum electroplating current, charge / discharge cycles, specific surface area of ​​amorphous carbon, and average particle size (D50) were determined by the following methods.

[0131] Maximum current density (mA / cm) 2 The maximum current density refers to the limit of the current density that allows lithium deposited according to the process to be deposited between the ion-rich protective layer and the current collector.

[0132] Charge-discharge performance cycles: The reference and evaluation electrodes are attached to the solid electrolyte at a pressure of 50 MPa. During the charge-discharge evaluation, a pressure of 16 MPa is applied to the dedicated evaluation cell. For the charge-discharge evaluation, a pressure of 2 mA / cm² will be used. 2 Charged with a constant current for 0.5 hours at 2mA / cm 2 A constant current discharge of 0.5 hours is defined as one cycle. For charge / discharge lifetime, the lifespan is defined as the occurrence of a short circuit between the reference electrode and the evaluation electrode, or a voltage exceeding 2V between the two electrodes, during the charge / discharge process.

[0133] Specific surface area (m²) 2 / g) and pore fraction (%): The distribution of pores in the protective layer was determined by BET detection of amorphous carbon in the protective layer using a 3Flex device from Micromeritics via nitrogen adsorption.

[0134] [Table 1] As confirmed in Table 1 above, Example 1, which uses a first amorphous carbon with a larger specific surface area and average particle size D50 as a protective layer, has a worse maximum electroplating current and fewer charge-discharge cycles compared to Comparative Example 1, which uses a second amorphous carbon with a smaller specific surface area and average particle size D50 as a protective layer.

[0135] Figure 6a and Figure 6b The specific surface area, pore size, and cumulative distribution of amorphous carbon in the embodiments and comparative examples of the present invention are shown.

[0136] Figure 6a and Figure 6b The specific surface area, pore size, and cumulative distribution of the first amorphous carbon and the second amorphous carbon used in Example 1 and Comparative Example 1 of the present invention are respectively shown. (Refer to...) Figure 6a and Figure 6b The first type of amorphous carbon contains a large number of micropores smaller than 2 nm (commonly referred to as micropores). Based on the total volume of all pores, micropores smaller than 2 nm occupy 30% of the volume. Due to this large number of micropores, the resulting specific surface area is as high as 600 m². 2 / g.

[0137] Without considering particle morphology, generally, larger particle size results in a smaller specific surface area, and vice versa. However, the first type of amorphous carbon has a relatively large particle size in the μm range, and its specific surface area is as high as approximately 600 m². 2 / g. This is because a particle itself is composed of very small micropores.

[0138] Conversely, the second type of amorphous carbon has a very small particle size of about 30 nm, but a low specific surface area of ​​about 60 m². 2 / g. This is because there are almost no micropores formed on the particles themselves; the main pores formed are mesopores (2~50nm) or macropores (over 50nm) between particles. For the second amorphous carbon, the micropore fraction below 2nm was confirmed to be around 0%, which is very low.

[0139] Figure 7 The results of charge-discharge lifetime evaluation of the lithium metal electrodes in the embodiments and comparative examples of the present invention are shown.

[0140] Reference Figure 7 It was confirmed that Example 1, which included the first amorphous carbon with a high specific surface area, had a cycle count of 1044, which was superior to the 481 cycles count of Comparative Example 1, which included the second amorphous carbon with a low specific surface area.

[0141] <Evaluation Example 2> - Content Control of First Amorphous Carbon and Second Amorphous Carbon <Example 2> Except that in the step of forming the protective layer, 80% by weight of the high specific surface area particulate amorphous carbon (first amorphous carbon) and 20% by weight of the low specific surface area nanoparticle amorphous carbon (second amorphous carbon) used in Example 1 are mixed based on 100% by weight of the amorphous carbon, the same method as in Example 1 is used.

[0142] At this point, the average particle size D50 of the low specific surface area nanoparticle-type amorphous carbon can be 30 nm, and the specific surface area can be 60 nm. 2 / g.

[0143] <Example 3> Except that in the step of forming the protective layer, 60% by weight of the high specific surface area particulate amorphous carbon (first amorphous carbon) and 40% by weight of the low specific surface area nanoparticle amorphous carbon (second amorphous carbon) used in Example 1 are mixed with 100% by weight of amorphous carbon, the same method as in Example 2 is used.

[0144] <Comparative Example 2> Except that in the step of forming the protective layer, 40% by weight of the high specific surface area particulate amorphous carbon (first amorphous carbon) and 60% by weight of the low specific surface area nanoparticle amorphous carbon (second amorphous carbon) used in Example 1 are mixed with 100% by weight of amorphous carbon, the same method as in Example 2 is used.

[0145] Table 2 below shows the maximum electroplating current and the number of charge-discharge cycles when the contents of the first amorphous carbon and the second amorphous carbon are changed.

[0146] [Table 2] As confirmed by Table 2 above, when both first amorphous carbon and second amorphous carbon are included, Examples 2 and 3, in which the content of first amorphous carbon is greater than that of second amorphous carbon, have superior maximum electroplating current and charge-discharge performance compared to Comparative Example 2.

[0147] This invention is not limited to the embodiments described, but can be implemented in many different forms. Those skilled in the art will understand that this invention can be implemented in other specific forms without altering the technical concept or essential technical features. Therefore, the embodiments described above are illustrative in all respects and should not be construed as limiting.

Claims

1. A lithium metal electrode, comprising: current collector; A metal layer, located on at least one side of the current collector and comprising a lithium alloy; and A protective layer, located on the metal layer, comprising a specific surface area of ​​450 m². 2 / g or more of the first amorphous carbon.

2. The lithium metal electrode according to claim 1, wherein, The average particle size D50 of the first amorphous carbon is 0.1~1.5μm.

3. The lithium metal electrode according to claim 1, wherein, The protective layer also includes a second amorphous carbon with a specific surface area smaller than that of the first amorphous carbon. The protective layer contains 100% by weight of amorphous carbon, including more than 50% by weight of first amorphous carbon and the remainder of second amorphous carbon.

4. The lithium metal electrode according to claim 3, wherein, The specific surface area of ​​the second amorphous carbon is 40~80m². 2 / g or less.

5. The lithium metal electrode according to claim 3, wherein, The average particle size D50 of the second amorphous carbon is 20~50 nm.

6. The lithium metal electrode according to claim 3, wherein, The difference between the specific surface area of ​​the first amorphous carbon and the specific surface area of ​​the second amorphous carbon is 400~700m². 2 / g.

7. The lithium metal electrode according to claim 1, wherein, The first amorphous carbon within the protective layer includes micropores.

8. The lithium metal electrode according to claim 7, wherein, Based on the total volume of all pores being 100%, the micropores account for 10-40%.

9. The lithium metal electrode according to claim 1, wherein, The second amorphous carbon within the protective layer includes mesopores or macropores.

10. A method for preparing a lithium metal electrode, comprising the following steps: Prepare the current collector; A coating is formed on at least one side of a current collector using a coating composition comprising a lithium-philic component; and A protective layer is formed on the surface of the coating, the protective layer comprising a specific surface area of ​​450 m². 2 / g or more of the first amorphous carbon.

11. The method for preparing a lithium metal electrode according to claim 10, After the step of forming the protective layer, the following is included: After placing a current collector with the coating and the protective layer formed in the plating solution, a lithium source is placed at a predetermined interval from the protective layer; and An electric current is applied between the current collector and the lithium source to form a metal layer comprising a lithium alloy, which is formed by alloying lithium deposited from the lithium source with a lithiophilic component included in the coating.

12. The method for preparing a lithium metal electrode according to claim 10, wherein, In the step of forming the protective layer, the average particle size D50 of the first amorphous carbon is 0.1~1.5μm.

13. The method for preparing a lithium metal electrode according to claim 11, wherein, In the step of forming the protective layer, a second amorphous carbon with a specific surface area smaller than that of the first amorphous carbon is further mixed in. The protective layer contains 100% by weight of amorphous carbon, mixed with more than 50% by weight of first amorphous carbon and the remainder of second amorphous carbon.

14. The method for preparing a lithium metal electrode according to claim 13, wherein, The specific surface area of ​​the second amorphous carbon is 40~80m². 2 / g or less.

15. The method for preparing a lithium metal electrode according to claim 13, wherein, The average particle size D50 of the second amorphous carbon is 20~50 nm.

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