A lithium metal electrode for a lithium secondary battery and a manufacturing method thereof

Abstract

The present application relates to a lithium metal electrode and a manufacturing method thereof, the lithium metal electrode of the present application comprising: a current collector; a coating layer located on at least one surface of the current collector and comprising a lithiumophilic alloy material; and a protective layer located on the coating layer; the coating layer accounting for 25.0 to 80.0% of the total area of the current collector.

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 manufacturing the same. Background Technology

[0002] To achieve both low cost and high energy density in secondary batteries, lithium metal electrodes must be used as the negative electrode. Specifically, in recent years, all-solid-state batteries have attracted much attention as a new generation of batteries that meet the high energy density requirements of electric vehicles (EVs).

[0003] Because all-solid-state batteries do not use liquid electrolytes, they offer excellent safety, can operate at high voltages, and allow for increased energy density by reducing the need for cooling and safety-related auxiliary materials. They also operate over a wide temperature range, providing advantages in several aspects. To practically achieve high energy density in all-solid-state batteries as described above, it is necessary to replace the thick, low-capacity graphite-based anode material with thin, high-capacity lithium. Considering both economics and energy density, a thin-film lithium metal electrode with a thickness of 10 to 20 μm is practically required.

[0004] Typically, for lithium metal electrodes, there are difficulties in manufacturing thinner lithium metal electrodes using commercial processes. Furthermore, dendrite growth due to uneven current density and electrochemical reactions during the charging and discharging of secondary batteries is also a problem. This can lead to continuous side reactions with the electrolyte and may even cause internal short circuits due to contact between the negative and positive electrodes.

[0005] Dendrite growth can also significantly impact low lifespan and safety, making it difficult to apply ultrathin lithium metal anodes in practice.

[0006] Various methods have been proposed to suppress dendrites and improve lifetime, but the challenge remains in simultaneously achieving high energy density and sufficient lifetime characteristics through lithium ultrathinning. To address this issue, a nanoscale metal layer composed of a lithiophilic material is coated onto the current collector. This maximizes the surface area of ​​the lithiophilic material, which can react with lithium to form an alloy, thereby preventing a decrease in current density due to the increased surface area of ​​the current collector.

[0007] However, forming a metal layer made of lithium-philic materials on the current collector presents a challenge to commercialization due to the increased cost of raw materials. Summary of the Invention

[0008] (a) Technical problems to be solved According to an embodiment of the present invention, a lithium metal electrode for a lithium secondary battery is provided, which reduces raw material costs and improves charge-discharge life characteristics when applied to a battery.

[0009] According to another embodiment of the present invention, a method for manufacturing a lithium metal electrode for a lithium secondary battery is provided, which has the above-mentioned advantages.

[0010] (II) Technical Solution According to one embodiment of the present invention, a lithium metal electrode includes: a current collector; a coating located on at least one surface of the current collector and comprising a lithium-philic alloy material; and a protective layer located on the coating. The coating may be configured to cover an area of ​​25.0% to 80.0% relative to the total area of ​​the current collector. In one embodiment, the coating may comprise a metallic material having a plurality of island-like structures.

[0011] In one embodiment, the area of ​​the island may be from 0.01 to 0.50 μm. In one embodiment, the current collector may comprise at least one of copper, nickel, titanium, stainless steel, iron, gold, platinum, silver, tantalum, ruthenium, and alloys thereof.

[0012] In one embodiment, the lithiophilic alloy material of the coating may comprise at least one metal selected from the group consisting of In, Ag, Sn, Zn, Si, Al, and Bi. In one embodiment, the protective layer may comprise amorphous carbon.

[0013] In one embodiment, a metal layer may be included, the metal layer comprising the coating and a lithium alloy layer forming a lithium alloy. In another embodiment, the metal layer may be disposed on the lithium alloy layer and contain lithium.

[0014] A lithium metal electrode according to another embodiment of the present invention may include: a current collector, a metal layer, a coating comprising a lithiophilic alloy material and a lithium alloy layer forming a lithium alloy, located on at least one surface of the current collector, and a protective layer disposed on the metal layer; the coating may be disposed over an area of ​​25.0% to 80.0% relative to the total area of ​​the current collector. In one embodiment, the metal layer may be disposed on the lithium alloy layer and contain lithium.

[0015] A method for manufacturing a lithium metal electrode according to another embodiment of the present invention may include: a step of preparing a current collector; a step of forming a coating comprising a lithium-loving alloy material on at least one surface of the current collector using a coating composition comprising a lithium-loving component; and a step of forming a protective layer on the surface of the coating comprising the lithium-loving alloy material; the step of forming the coating comprising the lithium-loving alloy material satisfies the following formula 1: <Formula 1> 3.40 ≤ Plating time (hours (h)) × Coating coverage (%) × 100 ≤ 75.0 (In Formula 1, the plating time refers to the electroplating time in the step of forming a coating containing a lithium-ion alloy material, and the coating coverage refers to the area of ​​the coating containing the lithium-ion alloy material disposed relative to 100% of the current collector area).

[0016] In one embodiment, the step of forming a coating comprising the lithiophilic alloy material may include controlling the coating coverage to 25.0% to 80.0%. In one embodiment, after forming the protective layer, the process may include: placing a current collector for forming the coating comprising the lithiophilic alloy material and the protective layer in a plating bath, and then positioning a lithium supply source at a predetermined distance from the protective layer; and forming a metal layer comprising a lithium alloy by applying an electric current between the current collector and the lithium supply source, the lithium alloy being formed by alloying the lithiophilic component contained in the coating with lithium deposited from the lithium supply source.

[0017] In one embodiment, the step of forming a coating comprising a lithiophilic alloy material can be performed at a cumulative current of 0.10 to 1.30 mAh / dm³. 2 The process is carried out under specific conditions. In one embodiment, the step of forming a coating comprising a lithium-philic alloy material is performed under conditions where the plating time is less than 45 seconds.

[0018] In one embodiment, the step of forming a coating comprising a lithiophilic alloy material is performed at a plating current of 0.5 to 2.0 mA / cm. 2 The process is carried out under controlled conditions. In one embodiment, the step of forming a lithium alloy-containing metal layer by applying a current between the current collector and the lithium supply source, the lithium alloy being formed by alloying the lithium-loving component contained in the coating containing the lithium-loving alloy material with lithium deposited from the lithium supply source, may include: applying a current at 6 to 12 mA / cm². 2 The electrodeposition step is performed using the maximum current density within the specified range.

[0019] (III) Beneficial Effects According to an embodiment of the present invention, a lithium metal electrode for a lithium secondary battery provides a lithium secondary battery that is economically efficient and has improved charge-discharge life characteristics due to the inclusion of a metal layer with a predetermined coverage on the current collector.

[0020] According to another embodiment of the present invention, a method for manufacturing a lithium metal electrode for a lithium secondary battery is provided, which has the above-mentioned advantages. Attached Figure Description

[0021] Figures 1a to 1cA lithium metal electrode manufactured according to one embodiment is shown.

[0022] Figure 2 This is a schematic diagram of the manufacturing method of the lithium metal electrode of the present invention.

[0023] Figure 3 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.

[0024] Figure 4a and Figure 4b The fine structure of the surface and cross-section is shown when the protective layer is configured on a current collector coated with an alloy material.

[0025] Figure 5a and Figure 5b The electrodeposition appearance according to the maximum current density is shown in the electrodeposition process according to the embodiments and comparative examples.

[0026] Figure 6a and Figure 6b The image shows the result of mapping the surface microstructure and coating of an embodiment of the present invention. Figure 6c and Figure 6d The image shows the surface microstructure and coating image mapping results of a comparative example of the present invention. Figure 6e and Figure 6f The image shows the result of mapping the surface microstructure and coating of a comparative example of the present invention.

[0027] Figure 7 The charge / discharge lifetime evaluation results of embodiments and comparative examples of the present invention are shown. Detailed Implementation

[0028] The terms "first," "second," and "third," etc., can be 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, hereinafter, without departing from the scope of the invention, a first part, component, region, layer, or segment may be referred to as a second part, component, region, layer, or segment.

[0029] The technical terms used herein are for illustrative purposes only and are not intended to limit the invention. Unless otherwise expressly stated, the singular forms used herein also include the plural forms. The term "comprising" as used in the specification means specifically describing a particular feature, region, integer, step, action, element, and / or component, and does not exclude the presence or addition of other features, regions, integers, steps, actions, elements, and / or components.

[0030] When one part is located "above" or "on top of" another part, it can be directly on the other part, or there can be other parts between them. Conversely, when one part is "directly on" another part, there are no other parts between them.

[0031] 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 shall be further interpreted as having meanings consistent with relevant technical literature and the present disclosure, and shall not be construed as having idealized or overly formal meanings unless otherwise defined.

[0032] Figures 1a to 1c A lithium metal electrode 100 manufactured according to one embodiment is shown.

[0033] Reference Figure 1a According to one embodiment, a lithium metal electrode 100 includes a current collector 11 and a coating 20 containing a lithium-philic alloy material located on at least one surface of the current collector 11, and includes a protective layer 30 located on another surface of the coating 20 containing a lithium-philic alloy material opposite to the current collector 11.

[0034] The current collector 11 can be a component used for electrical connection within a lithium secondary battery. The current collector 11 can have a film (Foil) form, but is not limited to this; for example, it can also have a mesh, foam, rod, wire, or sheet form woven from wire (fiber).

[0035] The current collector 11 can be made of a material that is conductive and does not readily react with lithium. Specifically, the material of the current collector 11 can be any one or a combination of, for example, copper, nickel, titanium, stainless steel, gold, platinum, silver, tantalum, ruthenium, and their alloys.

[0036] In one embodiment, the thickness of the current collector 11 can be from 1 μm to 50 μm. When the current collector 11 is too thick, the battery weight increases, resulting in a decrease in the battery's energy density. When the current collector 11 is too thin, there is a risk of overheating and damage during high-current operation, and it may also be damaged due to tension during the battery manufacturing process.

[0037] A coating 20 containing a lithium-ion alloy material is located on the current collector 11 and can be disposed within an area of ​​25.0% to 80.0% relative to the total area of ​​the current collector. Specifically, the coating 20 containing the lithium-ion alloy material can contain a lithium-ion alloy material. Specifically, the coating 20 containing the lithium-ion alloy material can occupy 30% to 70% of the total area of ​​the current collector, more specifically, 35% to 65%, more specifically, 35.2% to 62.5%, and more specifically, 38% to 62.5%. The area of ​​the coating 20 containing the lithium-ion alloy material can refer to the area occupied by the lithium-ion alloy material in the total area when a metal, such as the coating 20 containing the lithium-ion alloy material, is plated onto the current collector 11.

[0038] The coating 20 of the present invention is not disposed on the entire surface of the current collector 11, but on the current collector 11 within the range described above, thus having the advantage of facilitating the easy precipitation of lithium between the protective layer 30 and the current collector 11.

[0039] When the area ratio of coating 20 relative to the total area of ​​current collector 11 exceeds the upper limit of the aforementioned range, the following problem arises: during further lithium growth by precipitation or battery charging, lithium cannot precipitate between current collector 11 and protective layer 30, but instead precipitates on the other side of the protective layer 30. When the area ratio of coating 20 relative to the total area of ​​current collector 11 exceeds the lower limit of the aforementioned range, due to insufficient amount of lithiophilic alloy material, lithium cannot smoothly form an alloy, thus hindering lithium movement, and similarly, lithium precipitates on the other side of the protective layer 30.

[0040] In one embodiment, coating 20 may include a metallic substance having multiple island-like structures. Specifically, coating 20 may, for example, have at least one irregular island-like structure with aggregated particles. The island-like structure may refer to the metallic particles constituting coating 20 having an irregular shape and being observed to be connected and clustered together.

[0041] In one embodiment, the area of ​​the island can be from 0.01 to 0.50 μm. 2 The area of ​​the island-like structure was determined using ImageJ, with dimensions of 5 μm laterally, 5 μm vertically, and 25 μm in area observed using a scanning electron microscope. 2 The image range is classified as a single island, and the area of ​​a single island is calculated using a value ranging from the minimum to the maximum measured area. Specifically, the area of ​​the island can be between 0.01 and 0.20 μm. 2 More specifically, it can be 0.01 to 0.15 μm. 2 .

[0042] When the area of ​​the island exceeds the upper limit of the above range, the following problem exists: due to the excessively large particle size and excessive coverage of the coating 200 containing a single lithiophilic alloy, lithium precipitates on the outer surface of the protective layer. When the area of ​​the island exceeds the lower limit of the above range, the following problem exists: due to the insufficient amount of lithiophilic alloy material, it cannot smoothly form an alloy with lithium, thus hindering the movement of lithium during charging and other conditions. Consequently, lithium cannot precipitate between the current collector and the protective layer, but instead precipitates on the other side of the protective layer.

[0043] In one embodiment, coating 20 may comprise a lithium-loving metal. Specifically, for example, the lithium-loving metal may comprise at least one metal selected from the group consisting of In, Ag, Sn, Zn, Si, Al, and Bi.

[0044] The protective layer 30 is located on the coating 20 containing a lithium-philic alloy material and may contain amorphous carbon. In all-solid-state batteries, when lithium metal is used as the negative electrode, high resistance is generated due to the reaction between the all-solid-state electrolyte and lithium. Furthermore, during charging and discharging, lithium dendrites or high-resistivity lithium byproducts are continuously generated due to localized uneven current density, which can lead to malfunctions or reduced battery capacity due to short circuits or overvoltages during charging and discharging.

[0045] According to one embodiment, the lithium metal electrode includes a protective layer 30 containing amorphous carbon, which not only improves the output characteristics and lifetime characteristics of the lithium metal electrode, but also further enhances structural safety.

[0046] Specifically, the lithium metal electrode of this embodiment includes a protective layer 30 containing amorphous carbon, which not only provides ionic conductivity but also enhances the strength of the protective layer 30. It also prevents short circuits between electrodes by physically blocking the growth of dendrites in the lithium electrode, thereby extending the charge and discharge life.

[0047] The amorphous carbon may be one or more selected from the group consisting of acetylene black, super P black, carbon black, superconducting acetylene carbon (denka black), activated carbon, graphite, hard carbon and soft carbon, but is not limited thereto.

[0048] In one embodiment, the protective layer 30 may comprise an adhesive. The adhesive may be a water-based adhesive, which may be a rubber-based adhesive selected from the group consisting of acrylonitrile-butadiene rubber, styrene-butadiene rubber (SBR), and acrylic rubber, or one or more polymeric resins such as hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinylidene fluoride, but is not limited thereto.

[0049] Here, relative to the weight of the slurry formed by mixing the first amorphous carbon and / or the second amorphous carbon with water, 1 to 15 parts by weight, specifically 3 to 10 parts by weight of the binder, may be added. When the content of the binder meets the above range, the particles constituting the protective layer can be effectively bonded without reducing the energy density of the battery due to the increase in weight and volume, thereby forming a protective layer with excellent performance and further improving the life characteristics of the secondary battery.

[0050] When the content of the adhesive is less than the above range, there is a problem of reduced interparticle bonding force when forming the protective layer. When the content of the adhesive is more than the above range, not only does the energy density decrease, but the resistance of the protective layer also increases significantly, thereby hindering lithium-ion conduction.

[0051] 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. When the thickness of the protective layer meets the above range, the appropriate thickness of the protective layer not only serves as a protective layer, but also, due to its appropriate resistance to the movement of lithium ions, prevents the formation of lithium dendrites on the surface of the protective layer, and allows lithium ions to pass smoothly through the interior of the protective layer and be conducted, thereby enabling lithium to be deposited on the lower surface of the protective layer.

[0052] When the protective layer is too thin, it fails to function properly. When the protective layer is too thick, its high resistance may cause increased overvoltage during battery operation, and the increased weight and volume can lead to a decrease in battery energy density. However, the thickness of this protective layer can be variably adjusted according to the secondary battery structure design.

[0053] In one embodiment, the lithium metal electrode may include a film layer disposed in at least a portion of the following regions: inside the protective layer 30, between the metal layer 12 and the protective layer 30, and on the protective layer 30. Specifically, the film layer may be disposed in at least a portion of the region inside the protective layer 30, between the metal layer 12 and the protective layer 30, simultaneously inside the protective layer 30 and between the metal layer 12 and the protective layer 30, or on the protective layer 30.

[0054] The film is formed during the manufacturing process of the metal layer 12 by a reaction between lithium metal from the electrodeposited lithium supply source 40 and the plating solution. The thickness, composition, and properties of the film can be controlled by adjusting the composition of the plating solution and the conditions of the electrodeposition process.

[0055] In one embodiment, the film layer at least partially comprises LiF. The LiF can be formed because at least one of the plurality of solvents used in the electrodeposition process contains a solvent with a high dielectric constant. Specifically, by increasing the salt dissociation degree of the solvent used for electrodeposition, salt decomposition reactions are suppressed during electrodeposition, and solvent decomposition reactions are promoted, thereby enabling the formation of a sufficiently large LiF film within and / or on the surface of the protective layer. By including a film layer at least partially comprising LiF, the battery lifetime can be improved and dendrite growth can be prevented during battery operation due to the high ionic conductivity.

[0056] The thickness of the film layer can be from 2 nm to 2 μm. Specifically, the thickness of the film layer can be in the range of 10 nm to 500 nm. When the thickness of the film layer is too thick, the lithium-ion conductivity decreases and the interface resistance increases, resulting in a decrease in charge-discharge characteristics when applied to a battery. When the thickness of the film layer is too thin, the film layer may easily detach during the application of the lithium metal electrode according to the embodiment to the battery. Therefore, the film layer can have a relatively thin thickness within the thickness range, and is uniformly and densely formed on the surface of the metal layer 12 and the entire protective layer 30.

[0057] Reference Figure 1b and Figure 1c ,and Figure 1a The difference lies in that, through a lithium-ion deposition process, a coating 20 containing a lithium-ion alloy material forms an alloy with lithium, thereby forming a layer containing a lithium alloy.

[0058] Refer again Figure 1b In one embodiment, the metal layer 12 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 disposed between the current collector 11 and the lithium supply source (…). Figure 2 A current is applied between the current collector 11 and the lithium supply source 40 to alloy the lithium contained in the metal layer 12 formed on the current collector 11 with the lithium deposited from the lithium supply source 40. Specifically, the metal layer 12 may include: a lithium alloy layer 21, formed by alloying the coating 20 containing a lithium-loving alloy material with electrodeposited lithium; and a lithium metal layer 41 disposed on the lithium alloy layer 21.

[0059] In one embodiment, the thickness of the metal layer 12 can be from 1 μm to 100 μm, more specifically, it can be in the range of 5 μm to 30 μm. Specifically, the thickness of the metal layer 12 can refer to the thickness of the lithium alloy layer 21 and the lithium metal layer 41, wherein the lithium alloy layer 21 is formed by alloying with a coating 20 comprising a plurality of island-shaped lithium-loving alloy materials, and the lithium metal layer 41 is located on the lithium alloy layer 21.

[0060] 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, the weight and volume of the battery will increase, resulting in a decrease in energy density. In addition, when forming the metal layer 12, the time and cost of the electrodeposition process increase with the thickness. Therefore, the thickness of the metal layer 12 is preferably 100 μm or less.

[0061] If the thickness of the metal layer 12 is too thin, the battery's charge-discharge life will be reduced when the lithium metal electrode of this embodiment is applied to a secondary battery. Specifically, during the charge-discharge process, lithium in the battery is gradually consumed due to side reactions between the lithium contained in the negative electrode active material layer, i.e., the metal layer of this invention, and the electrolyte, resulting in a decrease in battery capacity. Furthermore, the lithium reserves available to replenish the lithium consumed during charge-discharge are reduced, thus decreasing the battery's charge-discharge life. Therefore, the thickness of the metal layer 12 is preferably 1 μm or more.

[0062] In order to increase the deposition rate when forming the metal layer 12, a large current is applied during the electrodeposition process, which can lead to a decrease in the performance of the lithium secondary battery. However, as described in this embodiment, when the metal layer 12 is formed into a structure containing a lithium alloy layer 21 with lithium components, even if a large current is applied during the electrodeposition process, it is possible to prevent the formation of excessive fine lithium particles or the destruction of the protective layer 30 on the surface of the formed lithium metal layer 41 during the electrodeposition process.

[0063] Specifically, since the metal layer 12 in one embodiment includes a lithium alloy layer 21 containing lithium components, when a large current is applied in the electrodeposition process to form a lithium metal layer 41 on the lithium alloy layer 21, it is possible to induce good growth of the initially generated lithium particles, thereby forming a coarse particle structure, and at the same time, it is possible to make the lithium metal layer 41, and thus the metal layer 12, have a uniform surface.

[0064] Therefore, the performance of the secondary battery using the lithium metal electrode of this embodiment can be significantly improved, specifically in terms of charge-discharge characteristics. Furthermore, even when applying a large current and performing an electrodeposition process at high speed, it is possible to manufacture a high-performance lithium metal electrode for secondary batteries, thus significantly improving the production efficiency of lithium metal electrodes for secondary batteries.

[0065] In one embodiment, the lithium alloy layer 21 comprises a lithium-loving metal. As described above, when the lithium alloy layer 21 comprises a lithium-loving metal, electrons can be smoothly supplied by the current collector due to the presence of a lithium-loving metal with high electronic conductivity, thereby reducing lithium ions. Therefore, it has the advantage of facilitating the electrodeposition of the lithium metal layer. The metal layer 12 serves to facilitate the more efficient deposition of lithium beneath the protective layer 30 during battery charging.

[0066] In one embodiment, the protective layer 30 may be located on the metal layer 12. Specifically, the protective layer 30 may be located on the metal layer 12 during the lithium-ion battery deposition process. During the lithium-ion battery deposition process, lithium is deposited between the current collector 11 and the protective layer 30, and the metal layer 12 may be disposed thereon, the metal layer 12 comprising: a lithium alloy layer 21, formed by alloying lithium with a coating 20 containing a lithium-philic alloy material; and a lithium metal layer 41 disposed on the lithium alloy layer 21 and containing lithium.

[0067] In one embodiment, the protective layer 30 may comprise amorphous carbon. In all-solid-state batteries, when lithium metal is used as the negative electrode, the reaction between the all-solid-state electrolyte and lithium produces high resistance, and due to local non-uniformity of current density during charging and discharging, lithium dendrites or high-resistivity lithium byproducts are continuously generated, leading to malfunctions or battery capacity reduction during charging and discharging due to short circuits or overvoltages.

[0068] Refer again Figure 1c In one embodiment, the lithium metal electrode 100 includes: a current collector 11; and a metal layer 12 located on at least one surface of the current collector 11, the metal layer 12 being composed of a mixture of lithium and a lithium alloy. Here, the lithium alloy may be formed by applying an electric current between the current collector 11 and the lithium supply source 40, causing the lithium-affinity alloy material in a coating 20 containing a lithium-affinity alloy material formed on the current collector 11 to alloy with lithium deposited from the lithium supply source 40.

[0069] The metal layer 12 may contain a lithium-philic metal. For a detailed explanation, please refer to [link to relevant documentation]. Figure 1a .

[0070] In one embodiment, the metal layer 12 is in the form of containing a lithium-loving metal. When the metal layer 12 containing a lithium-loving metal is formed as described above, since the nucleation free energy of lithium particles can be reduced in the early stage of nucleation during the electrodeposition process, 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 includes a protective layer 30 located on the surface of the metal layer 12, and may include a film layer inside and / or on the surface of the protective layer 30. Detailed descriptions of the protective layer 30 and the film layer can be found in [reference needed]. Figure 1a The content described.

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

[0073] Reference Figure 2A method for manufacturing a lithium metal electrode according to an embodiment includes: a step of preparing a current collector 11; a step of forming a coating 20 containing a lithium-ion alloy material on at least one surface of the current collector 11 using a coating composition containing a lithium-ion component; a step of forming a protective layer 30 on the surface of the coating 20 containing the lithium-ion alloy material using a slurry containing amorphous carbon; a step of placing the current collector 11, which has formed the coating 20 and the protective layer 30 containing the lithium-ion alloy material, in a plating bath 50, and then setting a lithium supply source 40 at a predetermined distance from the protective layer 30; and a step of forming a metal layer containing a lithium alloy by applying an electric current between the current collector and the lithium supply source 40, wherein the lithium alloy is formed by alloying the lithium-ion component contained in the coating with lithium deposited from the lithium supply 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, for example, copper, nickel, titanium, stainless steel, 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] The step of forming a coating 20 containing a lithium-loving alloy material on at least one surface of the current collector 11 using a coating composition containing a lithium-loving component allows the lithium-loving alloy material to be coated on at least one surface of the current collector. The lithium-loving alloy material, for example, may contain one or more metals selected from the group consisting of In, Ag, Sn, Zn, Si, Al, and Bi.

[0076] In one embodiment, the step of forming the coating 20 comprising a lithiophilic alloy material can be performed using at least one of electroplating or electroless plating, sputtering, electron beam deposition, and thermal vapor deposition. For example, the coating formation step can be performed using an electroless plating method.

[0077] In one embodiment, the step of forming the coating coverage can satisfy the following formula 1.

[0078] Formula 1 3.40 ≤ Plating time (hours (h)) × Coating coverage (%) × 100 ≤ 75.0 (In Formula 1, the plating time refers to the electroplating time in the step of forming a coating containing a lithium-ion alloy material, and the coating coverage refers to the area of ​​the coating containing the lithium-ion alloy material disposed relative to 100% of the current collector area.) Formula 1 can serve as an indicator of whether lithium can be deposited between the current collector 11 and the protective layer 30 during the growth of the battery by further lithium deposition or during battery charging. Specifically, Formula 1 can satisfy 3.53 to 75.0, more specifically, it can satisfy 3.53 to 73.0, more specifically, it can satisfy 40.0 to 72.5, and more specifically, it can satisfy 45.0 to 60.0. When Formula 1 is satisfied, it has the advantages of excellent lithium deposition characteristics and excellent charge and discharge performance when applied to batteries.

[0079] When Formula 1 exceeds the upper limit of the above range, the following problem arises: during the growth of the battery by further lithium deposition or during battery charging, lithium cannot be deposited between the current collector and the protective layer, but instead deposits on the other side of the protective layer. When Formula 1 exceeds the lower limit of the above range, due to insufficient amount of lithiophilic alloy material, lithium cannot smoothly form an alloy, thus hindering lithium movement, and similarly, lithium deposits on the other side of the protective layer.

[0080] In one embodiment, the step of forming the coating may be a step of controlling the coating coverage to be between 25.0% and 80.0%. Specifically, the coating coverage refers to the area of ​​the current collector over which the coating is disposed relative to 100% of the current collector area, which can be between 30.0% and 70.0%, more specifically, 35.0% and 65.0%, more specifically, 35.2% and 62.5%, and more specifically, 38.0% and 62.5%.

[0081] By controlling the coating coverage within the aforementioned range, it exhibits excellent characteristics during lithium deposition and superior charge / discharge performance when applied to batteries. When the coating coverage exceeds the upper limit of the aforementioned range, the following problem arises: due to the excessively large particle size and high coverage of individual lithiophilic alloy materials, lithium deposits on the outer surface of the protective layer. Similarly, when Formula 1 exceeds the lower limit of the aforementioned range, the lithiophilic alloy material particles are too small to smoothly form an alloy with lithium, thus hindering lithium movement and causing lithium deposits on the other side of the protective layer 30.

[0082] In one embodiment, the step of forming the coating can be performed when the cumulative current is between 0.10 and 1.30 mAh / dm³. 2 The process is carried out under the following conditions. The cumulative current refers to the product of the current density and the plating time. The cumulative current can be from 0.14 to 1.25 mAh / dm³. 2 More specifically, 0.40 to 1.00 mAh / dm 2 More specifically, 0.42 to 0.83 mAh / dm 2 When the accumulated current meets the above range, it has the advantages of being conducive to lithium deposition and having excellent charge-discharge cycle life when applied to batteries.

[0083] Specifically, the accumulated current can be controlled differently depending on the composition of the current collector and the coating. In one embodiment, when the current collector is composed of Ni, the accumulated current can be from 0.20 to 1.25 mAh / dm³. 2 More specifically, 0.80 to 1.25 mAh / dm 2 More specifically, 0.83 to 1.25 mAh / dm 2 .

[0084] In one embodiment, when the current collector is composed of Fe-Ni, the cumulative current can be from 0.14 to 1.25 mAh / dm³. 2 More specifically, 0.15 to 0.50 mAh / dm 2 More specifically, 0.20 to 0.30 mAh / dm 2 .

[0085] In one embodiment, when the current collector is composed of STS, the cumulative current can be from 0.08 to 0.40 mAh / dm³. 2 More specifically, 0.10 to 0.25 mAh / dm 2 More specifically, 0.11 to 0.20 mAh / dm 2 .

[0086] When the accumulated current exceeds the upper limit of the above range, due to excessive plating of the lithiophilic alloy material and excessive coverage, lithium may deposit on the other side of the protective layer. When the accumulated current exceeds the lower limit of the above range, due to insufficient plating and insufficient amount of lithiophilic alloy material, there is a problem that the alloy cannot be smoothly formed with lithium.

[0087] In one embodiment, the coating formation step can be performed with a plating time of 45 seconds or less. Specifically, the plating time can be 30 seconds or less, more specifically, 2.5 to 30 seconds, and more specifically, 30 to 40 seconds.

[0088] In one embodiment, the coating formation step can be performed at a plating current of 0.5 to 2.0 mA / cm. 2 The plating is performed within a specified range. Specifically, the plating current can be from 0.5 to 1.5 mA / cm. 2 The range, more specifically, is 0.5 to 1.0 mA / cm. 2 scope.

[0089] When the plating current and plating time meet the above-mentioned ranges, it has the advantages of easy lithium deposition and the ability to achieve excellent battery life characteristics when applied to batteries. When the plating current and plating time exceed the upper limit of the above-mentioned ranges, due to excessive plating amount and overly high coverage of the lithiophilic alloy material, there is a problem of lithium deposition on the other side of the protective layer. When the plating current and plating time exceed the lower limit of the above-mentioned ranges, due to insufficient plating amount and insufficient amount of lithiophilic alloy material, there is a problem of inability to smoothly form an alloy with lithium.

[0090] A protective layer 30 can be formed on the surface of a coating 20 containing a lithium-philic alloy material using a slurry containing amorphous carbon. The protective layer 30 is applied to the slurry formed by mixing the amorphous carbon and a binder in water using at least one of the following methods: doctor blade coating, dip coating, reverse roll coating, direct roll coating, gravure coating, extrusion, and brush coating. The protective layer 30 may also include the binder.

[0091] On the other hand, in the step of forming the protective layer 30, the thickness of the protective layer that promotes lithium ion conduction formed on the surface of the alloy material coating can be from 0.01 μm to 50 μm, and more specifically, it can be in the range of 1 μm to 20 μm.

[0092] After the step of forming the protective layer 30, the following steps are performed: placing the current collector on which the coating 20 containing the lithium-philic alloy material and the protective layer 30 are sequentially formed in the plating solution 50, and then setting the lithium supply source 40 and the current collector 11 at a predetermined distance; and forming the metal layer 12 by applying an electric current between the current collector 11 and the lithium supply source 40.

[0093] Specifically, the current collector 11, which has a coating 20 containing a lithium-philic alloy material and a protective layer 30, is placed in a plating solution, and then the lithium supply source 40 is separated from the protective layer 30 by a predetermined interval. For example, the lithium supply source 40 can be lithium metal, lithium alloy, a foil material with the lithium metal or lithium alloy pressed onto the current collector, a plating solution containing dissolved lithium salt, etc.

[0094] The plating solution 50 can be manufactured by dissolving a lithium salt in several solvents. Specifically, the lithium salt can be LiCl, LiBr, LiI, LiCO3, LiNO3, LiFSI, LiTFSI, LiBF4, LiPF6, LiAsF6, LiClO4, LiN(SO2CF3)2, LiBOB, or a combination thereof. The concentration of the lithium salt relative to the entire electrolyte can be from 1.0 to 3.0 M.

[0095] Specifically, in this embodiment, the plating solution 50 is characterized in that it contains a nitrogen-based compound as the lithium salt and at least one of a plurality of solvents. For example, the nitrogen-based compound may contain one or more selected from the group consisting of lithium nitrate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethane sulfonimide, e-caprolactam, N-methyl-e-caprolactam, triethylamine, and tributylamine.

[0096] 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.

[0097] 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.

[0098] The plating solution 50 may also be manufactured using only the nitrogen-based compound; however, considering the viscosity of the plating solution 50, it may contain a general non-aqueous solvent as an auxiliary solvent.

[0099] For example, the auxiliary solvent may comprise one or more of the following: 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.

[0100] In one embodiment, the auxiliary solvent may comprise 5 to 70% by weight of 100% of the total amount of the plating solution 50, preferably 10 to 60% by weight, but is not limited thereto. However, when the auxiliary solvent is contained within the range, the viscosity of the plating solution 50 is appropriate, thus shortening the process time required to form the lithium metal layer 41, but is not limited thereto.

[0101] In one embodiment, the plating solution 50 may also contain a fluorine-based compound. When the plating solution 50 also contains the fluorine-based compound, it has the advantage of improving the properties of the film formed on the lithium metal layer 41.

[0102] For example, the fluorinated compound may comprise one or more of the following groups: lithium difluorophosphate, lithium hexafluorophosphate, lithium difluoro bisoxalato phosphate, lithium tetrafluoro oxalato phosphate, lithium difluoro oxalate borate, lithium difluoro oxalato borate, lithium tetrafluorooxalato borate, fluoroethylene carbonate, difluoroethylene carbonate, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether.

[0103] The plating bath 50 may contain 0.1 to 30% by weight of the fluorine-based compound, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, relative to 100% by weight of the total amount of the plating bath 50. When the fluorine compound is contained within the range described above, the interaction between the nitrogen-based compound and the fluorine-based compound in the plating bath 50 is smooth, thus resulting in an excellent improvement in the properties of the film formed on the lithium metal layer 41. Furthermore, it suppresses the excessive formation of LiF due to the direct reaction between the fluorine-based compound and lithium, thereby exhibiting excellent electrochemical properties.

[0104] Next, after an insulating film is placed between the current collector 11 and the lithium supply source 40, the current collector 11, the lithium supply source 40, and the insulating film are stacked using a constraint device and constrained in both directions. As a non-limiting example, the constraint device can employ methods commonly used in the art, such as manual clamping, hydraulic clamping, pneumatic clamping, or other uniaxial pressurization methods.

[0105] In the step of forming a lithium metal layer on at least one surface of the current collector by applying the current, the current density of the applied current may be 0.1 mA / cm². 2 Up to 100mA / cm 2 The range, more specifically, can be 0.2 mA / cm.2 Up to 50mA / cm 2 The range can be 5mA / cm 2 Up to 30mA / cm 2 Range or 7mA / cm 2 Up to 25mA / cm 2 scope.

[0106] In one embodiment, the duration of the applied current can range from 0.05 hours to 50 hours, and more specifically, from 0.25 hours to 25 hours.

[0107] In one embodiment, the step of forming a lithium metal layer on at least one surface of the current collector by applying the current can be performed more than once at different current densities. The current application step can be performed in a multi-stage manner. Specifically, the multi-stage current application step can be performed by gradually increasing the current density from low to high in stages over a predetermined time period. For example, the current application step can be performed at a rate of 0.1 to 0.3 mA / cm². 2 0.3 to 0.7 mA / cm 2 and 0.8 to 1.5 mA / cm 2 Sequential, phased addition and electrodeposition.

[0108] In one embodiment, the step of forming a lithium metal layer 12 on at least one surface of the current collector 11 by applying the current may include an application rate of 6 to 12 mA / cm². 2 The electrodeposition step is performed using the maximum current density within a certain range. Specifically, the maximum current density can be between 8 and 12 mA / cm². 2 The maximum current density refers to the limit of the current density that allows the electrodeposited lithium to deposit between the protective layer 30 and the current collector 11 during the electrodeposition process.

[0109] For example, the electrodeposition step at the maximum current density can be a final step performed after lithium has been deposited between the current collector 11 and the protective layer 30 through a multi-stage deposition step. Since the maximum current density meets the above range, lithium can be appropriately deposited between the current collector 11 and the protective layer 30, thus providing the advantages of battery life characteristics and excellent bonding strength between the current collector 11 and the protective layer 30.

[0110] When the maximum current density exceeds the upper limit of the aforementioned range, lithium deposits on the surface of the protective layer 30, resulting in the inability to obtain the desired stable electrode structure. When the maximum current density exceeds the lower limit of the aforementioned range, the lithium deposition time increases, leading to a decrease in production efficiency.

[0111] In one embodiment, the step of forming a lithium metal layer on at least one surface of the current collector by applying the current may include an electrodeposition step of controlling the thickness of the deposited lithium within the range of 5 to 15 μm. Specifically, the thickness of the deposited lithium may be electrodeposited in the range of 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.

[0112] When the thickness of the deposited lithium exceeds the upper limit mentioned above, it not only leads to a decrease in the energy density of the battery, but also increases the processing time and the amount of metal raw materials used in forming the metal layer. When the thickness of the deposited lithium exceeds the lower limit mentioned above, the initial coulombic efficiency decreases due to initial irreversibility and insufficient remaining lithium, thus resulting in a decrease in charge-discharge performance.

[0113] In one embodiment, during the step of forming a metal layer 12 on at least one surface of the current collector 11 by applying the current, the thickness of the metal layer 12, including the lithium alloy layer 21, can be controlled to be between 1 and 100 μm. A detailed description of the thickness of the metal layer 12, including the lithium alloy layer 21, can be found above. Figure 1b and Figure 1c The content.

[0114] As described above, in this embodiment, even under high current conditions, excessive generation of fine lithium particles is prevented, and good growth of initially generated lithium particles is induced, thereby enabling the fabrication of a lithium metal electrode 100 having a metal layer including a lithium alloy layer 21 with a coarse particle structure. Furthermore, the metal layer fabricated as described above also exhibits excellent surface uniformity.

[0115] According to another embodiment of the present invention, a lithium secondary battery includes a positive electrode, a negative electrode, and an electrolyte located between the positive and negative electrodes. Here, the negative electrode may be a lithium metal electrode according to the present invention.

[0116] In one embodiment, the lithium secondary battery may include an electrode assembly comprising: a positive electrode containing a positive active material; a negative electrode, serving as the lithium metal electrode of the present invention; and a separator disposed between the positive and negative electrodes. This electrode assembly can be housed within a battery casing by winding or folding.

[0117] Next, electrolyte is injected into the battery casing and sealed, thus completing the secondary battery. At this time, the battery casing can have a cylindrical, prismatic, pouch, or button-shaped shape.

[0118] The positive electrode may include a positive electrode active material layer and a positive electrode current collector. For example, the positive electrode active material layer may contain a Li compound, which contains at least one metal selected from Ni, Co, Mn, Al, Cr, Fe, Mg, Sr, V, La, and Ce, and at least one non-metallic element selected from the group consisting of O, F, S, P, and combinations thereof.

[0119] In one embodiment, the positive electrode active material layer may further contain a conductive material. For example, the conductive material may be carbon black, ultrafine graphite particles, fine carbon such as acetylene black, or nano-metal particle slurry, but is not limited to these.

[0120] The positive electrode current collector serves to support the positive electrode active material layer. For example, aluminum foil, nickel foil, or a combination thereof can be used as the positive electrode current collector, but it is not limited to these.

[0121] The electrolyte used to fill 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 contain lithium salts such as lithium hexafluorophosphate and lithium perchlorate, and solvents such as ethylene carbonate, propylene carbonate, and butylene carbonate. Alternatively, the solid electrolyte may be 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.

[0122] The separator is used to separate the positive and negative electrodes and provide a channel for lithium ion movement. Any separator commonly used in lithium secondary batteries can be used. Specifically, the separator can have low resistance and excellent electrolyte retention capabilities for electrolyte ion movement. The separator can be, for example, selected from glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene, or combinations thereof, and can be in the form of non-woven or woven fabric. Alternatively, when a solid electrolyte is used, the solid electrolyte can also serve as the separator.

[0123] Hereinafter, implementation examples of the present invention will be described in detail. However, these are merely examples and are not intended to limit the present invention, which is defined only by the scope of the following claims.

[0124] <Experimental Example> Manufacturing negative electrodes for lithium secondary batteries <Example 1> <Manufacturing Current Collectors> Preparations are made to apply the nickel (Ni) current collector to the negative electrode of the lithium secondary battery of the present invention.

[0125] <Forming an alloy material coating> Subsequently, an alloy material was electroplated onto both sides of the nickel current collector. Silver (Ag) was used as the alloy material, and the current density for the lithium-affinity layer plating was controlled at 1 mA / cm². 2 The plating time was controlled at 30 seconds, resulting in a cumulative current of 0.83 mAh / dm³. 2 .

[0126] Figure 3a and Figure 3b This is a scanning electron microscope (SEM) image showing the fine structure of the surface and cross-section of an alloy material coating deposited on a current collector according to an embodiment of the present invention.

[0127] Reference Figure 3a and Figure 3b It can be confirmed that the total area of ​​the lithiophilic layer on the current collector is island-shaped, and it has an appropriate level of coverage on the surface of the current collector.

[0128] <Forming a protective layer> Subsequently, a slurry is applied to the upper surface of the coating using a comma coater to form a protective layer of approximately 5 μm. Specifically, the protective layer is formed by mixing amorphous carbon, a binder, and a solvent. The binder is prepared by adding 3.0 parts by weight of carboxymethyl cellulose (CMC) and 6.0 parts by weight of styrene-butadiene rubber (SBR) to each 100 parts by weight of amorphous carbon, for a total addition of 9.0 parts by weight. The solvent is a mixture of water and ethylene glycol (EG) at a weight ratio of 80:20. The total amount of solvent is approximately 25% by weight relative to the total amount of amorphous carbon and binder to maintain a suitable viscosity for coating. The amorphous carbon used is acetylene black.

[0129] Figure 4a and Figure 4b The fine structure of the surface and cross-section is shown when the protective layer is configured on a current collector coated with an alloy material.

[0130] Reference Figure 4a and Figure 4b It can be confirmed that an alloy material coating, which serves as a lithium-philic metal plating layer, is deposited on the current collector, and a protective layer is formed on the coating.

[0131] <Lithium Electrodeposition Process> Subsequently, in order to form a lithium alloy or pure lithium metal between the protective layer and the current collector, an electrodeposition process is used to remove lithium from the lithium supply source and deposit lithium between the protective layer and the current collector. The plating solution used for electrodeposition as described above is prepared by adding 40% by weight of lithium bis(fluorosulfonyl)imide and 5% by weight of lithium nitrate (as nitrogen compounds) to a composite solvent containing a first solvent 1,2-dimethoxyethane (DME) and a second solvent sulfolane (SL) in a 90:10 molar ratio, and 5% by weight of fluoroethylene carbonate (as fluorine compounds) to a 100% by weight ratio 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 supply source 40.

[0132] After stacking the lithium supply source and current collector in an electrically insulating state in the plating solution, a power supply device is used to apply current to the lithium supply source and current collector as (+) electrodes and (-) electrodes respectively, so that lithium is deposited between the current collector and the protective layer.

[0133] In the electrodeposition process, the current density is set to 0.2 mA / cm². 2 0.5mA / cm 2 1mA / cm 2 The order was gradually increased, and after each electrodeposition lasted 5 minutes, the maximum current density was set to 10 mA / cm². 2 The electrodeposition time at the maximum current density is calculated as the time required to deposit a final cumulative lithium thickness of 10 μm, and is set variably according to the magnitude of the maximum current density.

[0134] Figure 5a and Figure 5b The electrodeposition appearance according to the maximum current density is shown in the electrodeposition process according to the embodiments and comparative examples.

[0135] Figure 5a This refers to the appearance of electrodeposited material when electrodeposition is performed below the maximum current density. Figure 5b This refers to the appearance of electrodeposition when electrodeposition is performed at current densities exceeding the maximum. (See reference.) Figure 5a and Figure 5bWhen electrodeposition is performed below the maximum depositable current density, the deposited lithium is confirmed to be stacked under the black protective layer, which is therefore visible. However, when electrodeposition is performed above the maximum depositable current density, the lithium is confirmed to be stacked on the upper surface of the protective layer, resulting in gray lithium deposits on the upper surface of the protective layer. Therefore, the maximum current density at which lithium deposits between the current collector and the protective layer during the electrodeposition process is defined as the maximum depositable current density.

[0136] Manufacturing all-solid-state batteries All-solid-state batteries were fabricated using the negative electrodes manufactured according to the above embodiments and comparative examples, and their charge-discharge life was evaluated. For evaluating the all-solid-state battery cell, a pressurized evaluation battery from Teraleader capable of maintaining an inert atmosphere was used. To fabricate the all-solid-state battery cell, a sulfide-based nitrogen-containing heterocyclic magnesium aluminate (Li6P5Cl) solid electrolyte was used, and the electrolyte was formed into a sheet with a thickness of approximately 0.7 mm. To obtain a dense electrolyte, a pressure of 370 MPa was applied.

[0137] A 0.5 mm thick lithium electrode was attached to one side of the electrolyte as a reference electrode, and a negative electrode manufactured according to the examples and comparative examples was attached to the other side. The reference electrode and the evaluation electrode were attached to the solid electrolyte at a pressure of 50 MPa, and in the charge-discharge evaluation, the battery was pressurized at 16 MPa.

[0138] <Example 2> In the alloy material coating process, the coating time is 45 seconds and the cumulative current is 1.25 mAh / dm³. 2 Otherwise, it is carried out in the same manner as in Example 1.

[0139] <Example 3> In the alloy material coating process, the coating time is 10 seconds and the cumulative current is 0.28 mAh / dm³. 2 Otherwise, it is carried out in the same manner as in Example 1.

[0140] <Comparative Example 1> In the alloy material coating process, the coating time is 50 seconds and the cumulative current is 1.39 mAh / dm³. 2 Otherwise, it is carried out in the same manner as in Example 1.

[0141] <Comparative Example 2> In the alloy material coating process, the coating time is 5 seconds and the cumulative current is 0.14 mAh / dm³. 2 Otherwise, it is carried out in the same manner as in Example 1.

[0142] <Evaluation Example 1> - Evaluation based on the same plating current Table 1 below shows the coverage, island area range, maximum current that can be electrodeposited, and charge / discharge cycle count when Ag is used as the lithiophilic metal in the Ni current collector and the plating current, plating time, and cumulative current are controlled.

[0143] The lithiophilic layer coverage, island area range, maximum electrodeposition current, and number of charge-discharge cycles were measured using the following methods.

[0144] Lithophilic coating coverage and island area range: To measure the surface coverage and island area of ​​the lithophilic coating, the microstructure was observed using a ZEISS GEMINI-500 scanning electron microscope. The coverage of the lithophilic coating was measured using the ImageJ image processing software developed by the National Institutes of Health (NIH) on the two-dimensional plane relative to the total area of ​​the lithophilic coating, based on images obtained from scanning electron microscopy. Islands were defined as the morphology of particles with independent boundaries, measured at 5 μm laterally, 5 μm longitudinally, and with an area of ​​25 μm. 2 The image includes the range from the minimum to the maximum area of ​​each island.

[0145] Maximum current density (mA / cm) 2 The maximum current density refers to the limit of the current density that allows electrodeposited lithium to be deposited between the ion concentration protective layer and the current collector according to the process described. The maximum current density was measured.

[0146] Charge-discharge cycle count (times): The reference electrode and evaluation electrode were attached to the solid electrolyte at a pressure of 50 MPa. During the charge-discharge evaluation, the electrode was pressurized at 16 MPa in a dedicated evaluation battery. One charge-discharge evaluation was defined as one cycle under the following conditions: at 2 mA / cm². 2 Constant current charging for 0.5 hours, and at 2mA / cm 2 The constant current discharge lasts for 0.5 hours. The charge-discharge life is defined as the end of the life when a short circuit occurs between the reference electrode and the evaluation electrode or the voltage between the two electrodes exceeds 2V during the charge-discharge process.

[0147] Table 1 Referring to Table 1, it can be confirmed that when the current collector material is Ni, the lithiophilic metal is Ag, and the plating current is 1 mA / cm, the plating results are consistent. 2When the plating time and cumulative current are controlled to keep the coverage of the lithiophilic layer within the range of this invention, the maximum electrodeposition current and charge-discharge cycle number are 8 mA / cm. 2 With over 700 cycles, it performed excellently. Conversely, in Comparative Example 1, it was confirmed that the plating time and cumulative current were too high, resulting in a lithiophilic layer coverage of 83.8%, with an excessively large area of ​​the current collector covered by the lithiophilic layer. This confirmed that no islands were formed, but rather a 1μm thick layer was created. 2 The above-mentioned lithiophilic layer materials therefore exhibit low maximum electrodeposition current and poor charge-discharge cycle life. Furthermore, in Comparative Example 2, it was confirmed that the plating time and cumulative current were too low, resulting in a lithiophilic layer material with a thickness of 0.01~0.20 μm. 2 The area is island-shaped, but the coverage of the lithiophilic layer is too low, so the maximum current that can be electrodeposited is low and the number of charge-discharge cycles is poor.

[0148] Furthermore, it can be confirmed that the embodiments of the present invention satisfy the value of Equation 1, while the comparative examples do not satisfy the value of Equation 1, and therefore the maximum current that can be electrodeposited and the number of charge-discharge cycles are lower.

[0149] Figure 6a and Figure 6b The image shows the result of mapping the surface microstructure and coating of an embodiment of the present invention. Figure 6c and Figure 6d The image shows the surface microstructure and coating image mapping results of a comparative example of the present invention. Figure 6e and Figure 6f The image shows the result of mapping the surface microstructure and coating of a comparative example of the present invention.

[0150] Figure 6a and Figure 6b The image shown is a mapping result of the surface microstructure and coating in Embodiment 1 of the present invention. Figure 6c and Figure 6d The image shows the result of mapping the surface microstructure and coating of Comparative Example 1 of the present invention. Figure 6e and Figure 6f A mapping diagram of the surface microstructure and coating image of Comparative Example 2 of the present invention is shown. (Refer to...) Figure 6a and Figure 6b It can be confirmed that the coverage of the lithiophilic layer on the current collector surface is 51.5%, and the island area meets the requirements of 0.01 to 0.10 μm. 2 The scope. (Refer to...) Figure 6c and Figure 6d It can be confirmed that the coverage of the lithiophilic layer on the current collector surface is 83.3%, and the island area is greater than 1 μm. 2 Specifically, it can be confirmed that no island-like structures were formed, but rather a granular, integrated morphology. (See reference...) Figure 6e and Figure 6f It can be confirmed that the coverage of the lithiophilic layer on the current collector surface is 17.6%, and the island area meets the requirements of 0.01 to 0.20 μm. 2 The range.

[0151] Figure 7 The charge / discharge lifetime evaluation results of embodiments and comparative examples of the present invention are shown.

[0152] Figure 7 The charge-discharge life evaluation results of the all-solid-state batteries manufactured using Example 1 and Comparative Example 1 are shown. (Refer to...) Figure 7 It can be confirmed that the charge-discharge life assessment of Example 1 is better than that of Comparative Example 1.

[0153] <Evaluation Example 2> - Based on the current collector material and the lithium-ion plating conditions of the lithium-ion layer metal <Example 4> In the alloy material coating process, the coating current is 1.5 mA / cm. 2 The plating time was 20 seconds and the cumulative current was 0.83 mAh / dm³. 2 Otherwise, it is carried out in the same manner as in Example 1.

[0154] <Example 5> In the alloy material coating process, Sn is used instead of Ag as the lithium-loving metal, and the coating current is 0.5 mA / cm². 2 The plating time was 30 seconds and the cumulative current was 0.42 mAh / dm³. 2 Otherwise, it is carried out in the same manner as in Example 1.

[0155] <Example 6> In the alloy material coating process, Fe-Ni is used as the current collector, and the coating current is 2 mA / cm². 2 The plating time was 5 seconds and the cumulative current was 0.28 mAh / dm³. 2 Otherwise, it is carried out in the same manner as in Example 1.

[0156] <Example 7> In the alloy material coating process, STS (stainless steel) is used as the current collector, and the coating current is 0.5 mA / cm. 2 The plating time was 10 seconds and the cumulative current was 0.14 mAh / dm³. 2 Otherwise, it is carried out in the same manner as in Example 1.

[0157] <Example 8> In the alloy material coating process, STS (stainless steel) is used as the current collector, and the coating current is 1.0 mA / cm.2 The plating time was 5 seconds and the cumulative current was 0.14 mAh / dm³. 2 Otherwise, it is carried out in the same manner as in Example 1.

[0158] <Example 9> In the alloy material coating process, STS (stainless steel) is used as the current collector, and the coating current is 2.0 mA / cm. 2 The plating time was 2.5 seconds and the cumulative current was 0.14 mAh / dm³. 2 Otherwise, it is carried out in the same manner as in Example 1.

[0159] <Comparative Example 3> In the alloy material coating process, the coating current is 0.5 mA / cm. 2 The plating time was 60 seconds and the cumulative current was 0.83 mAh / dm³. 2 Otherwise, it is carried out in the same manner as in Example 1.

[0160] <Comparative Example 4> In the alloy material coating process, STS (stainless steel) is used as the current collector, and the coating current is 0.5 mA / cm. 2 The plating time was 30 seconds and the cumulative current was 0.42 mAh / dm³. 2 Otherwise, it is carried out in the same manner as in Example 1.

[0161] <Comparative Example 5> In the alloy material coating process, STS (stainless steel) is used as the current collector, and the coating current is 0.5 mA / cm. 2 The plating time was 30 seconds and the cumulative current was 0.07 mAh / dm³. 2 Otherwise, it is carried out in the same manner as in Example 1.

[0162] Table 2 Referring to Table 2, even if the types of current collectors and the lithiophilic metals are different, as long as the coverage of the lithiophilic layer is controlled within the range of the present invention, it can be confirmed that there are significant differences between the embodiments and comparative examples in terms of the maximum electrodepositable current and the number of charge-discharge cycles. Furthermore, it can be confirmed that compared with the comparative examples that do not satisfy Formula 1, the embodiments that satisfy Formula 1 have a higher maximum electrodepositable current and a superior number of charge-discharge cycles.

[0163] This invention is not limited to the embodiments described, and can be manufactured in various different forms. Those skilled in the art should understand that it can be implemented in other specific forms without altering the technical concept or basic characteristics of the invention. Therefore, the above embodiments should be understood in all respects as exemplary, not limiting.

Claims

1. A lithium metal electrode, characterized in that, include: current collector, A coating, located on at least one surface of the current collector and comprising a lithium-philic alloy material, and A protective layer is located on the coating. The coating covers 25.0% to 80.0% of the total area of ​​the current collector.

2. The lithium metal electrode according to claim 1, characterized in that, The coating comprises a metallic substance having multiple island-like structures.

3. The lithium metal electrode according to claim 2, characterized in that, The area of ​​the island is 0.01 to 0.50 μm.

4. The lithium metal electrode according to claim 1, characterized in that, The current collector comprises at least one of copper, nickel, titanium, stainless steel, iron, gold, platinum, silver, tantalum, ruthenium, and alloys thereof.

5. The lithium metal electrode according to claim 1, characterized in that, The lithium-loving alloy material of the coating comprises at least one metal selected from the group consisting of In, Ag, Sn, Zn, Si, Al, and Bi.

6. The lithium metal electrode according to claim 1, characterized in that, The protective layer contains amorphous carbon.

7. The lithium metal electrode according to claim 1, characterized in that, It includes a metal layer, which includes the coating and a lithium alloy layer forming a lithium alloy.

8. The lithium metal electrode according to claim 7, characterized in that, The metal layer includes a lithium metal layer disposed on a lithium alloy layer and containing lithium.

9. A lithium metal electrode, characterized in that, include: current collector, A metal layer, located on at least one surface of the current collector and comprising a coating containing a lithium-philic alloy material and a lithium alloy layer forming a lithium alloy, and A protective layer is disposed on the metal layer; The coating covers 25.0% to 80.0% of the total area of ​​the current collector.

10. The lithium metal electrode according to claim 9, characterized in that, The metal layer includes a lithium metal layer disposed on the lithium alloy layer and containing lithium.

11. A method for manufacturing a lithium metal electrode, characterized in that, include: The steps for preparing a current collector, The step of forming a coating comprising a lithium-philic alloy material on at least one surface of a current collector using a coating composition containing a lithium-philic component, and The step of forming a protective layer on the surface of a coating containing the lithiophilic alloy material; The steps of forming a coating comprising the lithiophilic alloy material satisfy the following formula: <Formula 1> 3.40 ≤ Plating time (hours) × Coating coverage (%) × 100 ≤ 75.0 (In Formula 1, the plating time refers to the electroplating time in the step of forming a coating containing a lithium-ion alloy material, and the coating coverage refers to the area of ​​the coating containing the lithium-ion alloy material disposed relative to 100% of the current collector area).

12. The method for manufacturing a lithium metal electrode according to claim 11, characterized in that, The step of forming a coating comprising the lithiophilic alloy material includes controlling the coating coverage to be between 25.0% and 80.0%.

13. The method for manufacturing a lithium metal electrode according to claim 11, characterized in that, After the step of forming the protective layer, the following is included: The steps of placing a current collector containing the lithium-philic alloy material and the protective layer in a plating bath, and then positioning a lithium supply source at a predetermined distance from the protective layer; and The step of forming a metal layer containing a lithium alloy by applying an electric current between the current collector and the lithium supply source, wherein the lithium alloy is formed by alloying a lithiophilic component contained in the coating with lithium deposited from the lithium supply source.

14. The method for manufacturing a lithium metal electrode according to claim 11, characterized in that, The step of forming a coating comprising a lithiophilic alloy material is performed when the cumulative current is 0.10 to 1.30 mAh / dm³. 2 It is carried out under the following conditions.

15. The method for manufacturing a lithium metal electrode according to claim 14, characterized in that, The step of forming a coating containing a lithiophilic alloy material is performed under conditions where the plating time is less than 45 seconds.

16. The method for manufacturing a lithium metal electrode according to claim 12, characterized in that, The step of forming a coating comprising a lithiophilic alloy material is performed at a plating current of 0.5 to 2.0 mA / cm. 2 It is carried out under the conditions of the range.

17. The method for manufacturing a lithium metal electrode according to claim 11, characterized in that, The step of forming a lithium alloy-containing metal layer by applying an electric current between the current collector and the lithium supply source, wherein the lithium alloy is formed by alloying a lithium-loving component contained in a coating comprising the lithium-loving alloy material with lithium deposited from the lithium supply source, includes: With 6 to 12 mA / cm 2 The electrodeposition step is performed using the maximum current density within the specified range.

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