Lithium metal electrode for lithium secondary battery and method for making same

Abstract

The present invention relates to a lithium metal electrode and a method for making same, the lithium metal electrode of the present invention comprising: a current collector; a metal layer positioned on at least one surface of the current collector and comprising a lithium alloy; and a protection layer positioned on the metal layer and comprising a first amorphous carbon having a specific surface area of 450 m2 / g or greater.

Description

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

[0001] The present invention relates to a lithium secondary battery, and more particularly, to a lithium metal electrode for a lithium secondary battery and a method for manufacturing the same.

[0002] To reduce the cost and increase the energy density of secondary batteries, the use of lithium metal electrodes as cathodes in lithium secondary batteries is essential. Specifically, all-solid-state batteries are attracting attention as next-generation batteries for high-energy densities, such as those required for electric vehicles (EVs).

[0003] All-solid-state batteries offer numerous advantages, including superior stability and high-voltage operation due to the elimination of liquid electrolytes. Furthermore, they reduce the need for cooling and safety-related components, resulting in higher energy density within the battery pack. Furthermore, they operate over a wide temperature range. To achieve truly high energy densities in these all-solid-state batteries, the thick, low-capacity graphite-based anode materials must be replaced with thin, high-capacity lithium. Considering cost-effectiveness and energy density, a thin-film lithium metal electrode with a thickness of 10 to 20 μm is practically required.

[0004] Typically, lithium metal electrodes face challenges in manufacturing thin layers of lithium metal through commercial processes. Furthermore, uneven current density and dendrite growth caused by electrochemical reactions during the charging and discharging of secondary batteries pose challenges. This can lead to persistent side reactions with the electrolyte and even internal short circuits where the cathode and anode come into contact.

[0005] The growth of the above dendrites can cause significant problems in terms of low life characteristics and stability, and thus, it is difficult to practically utilize ultra-thin lithium metal anodes.

[0006] Various methods have been proposed to suppress dendrites and increase battery life. However, they face the challenge of simultaneously achieving high energy density through ultra-thin lithium and sufficient battery life characteristics. To address this issue, a method using a protective layer on a lithium metal electrode has been proposed. However, this method fails to achieve sufficient lithium deposition speed and charge / discharge life characteristics.

[0007] According to one embodiment of the present invention, a lithium metal electrode for a lithium secondary battery improves lithium ion conductivity to increase a lithium stacking speed and provides a lithium secondary battery having improved charge / discharge life characteristics.

[0008] According to another embodiment of the present invention, a method for manufacturing a lithium metal electrode for a lithium secondary battery provides a method for manufacturing a lithium metal electrode for a lithium secondary battery having the advantages described above.

[0009] According to one embodiment of the present invention, a lithium metal electrode comprises a current collector, a metal layer positioned on at least one surface of the current collector and comprising a lithium alloy, and a lithium metal electrode positioned on the metal layer and having a thickness of 450 m 2 / g or more of a protective layer including a first amorphous carbon having a specific surface area. In one embodiment, the first amorphous carbon may have an average particle diameter D50 of 0.1 to 1.5 μm.

[0010] In one embodiment, the protective layer further comprises a second amorphous carbon having a lower specific surface area than the first amorphous carbon, and based on 100 wt% of the amorphous carbon in the protective layer, the first amorphous carbon may comprise 50 wt% or more, and the remainder may comprise the second amorphous carbon. In one embodiment, the specific surface area of ​​the second amorphous carbon may be 40 to 80 m 2 / g can be less.

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

[0012] In one embodiment, the protective layer may include micropores of the first amorphous carbon. In one embodiment, the micropores may be 10 to 40% of the total pore volume based on 100%. In one embodiment, the second amorphous carbon within the protective layer may include mesopores or macropores.

[0013] According to another embodiment of the present invention, a method for manufacturing a lithium metal electrode comprises the steps of preparing a current collector, forming a coating layer on at least one surface of the current collector using a coating composition containing a lithium-philic component, and applying a coating layer having a thickness of 450 m to the surface of the coating layer. 2 / g or more of a first amorphous carbon having a specific surface area. In one embodiment, after the step of forming the protective layer, the method may include the step of positioning the current collector on which the coating layer and the protective layer are formed in a plating solution, and then positioning a lithium source at a predetermined distance from the protective layer, and applying a current between the current collector and the lithium source to form a metal layer including a lithium alloy in which a lithium-loving component included in the coating layer and lithium precipitated from the lithium source are alloyed.

[0014] In one embodiment, in the step of forming the protective layer, the first amorphous carbon may have an average particle diameter D50 of 0.1 to 1.5 μm. In one embodiment, in the step of forming the protective layer, second amorphous carbon having a lower specific surface area than the first amorphous carbon may be further mixed, and based on 100 wt% of amorphous carbon in the protective layer, the first amorphous carbon may be 50 wt% or more, and the remainder may be the second amorphous carbon.

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

[0016] According to one embodiment of the present invention, a lithium metal electrode for a lithium secondary battery includes a protective layer including amorphous carbon having a large specific surface area, thereby improving lithium ion conductivity, thereby increasing a lithium stacking speed, and providing a lithium secondary battery having improved charge / discharge life characteristics.

[0017] According to another embodiment of the present invention, a method for manufacturing a lithium metal electrode for a lithium secondary battery provides a method for manufacturing a lithium metal electrode for a lithium secondary battery having the advantages described above.

[0018] Figures 1a and 1b illustrate a lithium metal electrode manufactured according to one embodiment.

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

[0020] FIG. 3 is a scanning electron microscope (SEM) photograph showing the structure and thickness of an alloy material coating layer plated on a current collector according to one embodiment of the present invention.

[0021] FIG. 4 shows the microstructure of the surface and cross-section when a protective layer is placed on a current collector coated with an alloy material according to one embodiment.

[0022] Figures 5a and 5b show the appearance when lithium is deposited according to an embodiment and a comparative example of the present invention.

[0023] Figures 6a and 6b show the pore volume and cumulative porosity according to the pore size of the first amorphous carbon and the second amorphous carbon used in the examples and comparative examples of the present invention.

[0024] Figure 7 shows the cell life evaluation of an all-solid-state battery using an embodiment and a comparative example of the present invention.

[0025] The terms first, second, and third, etc., are used to describe, but are not limited to, various parts, components, regions, layers, and / or sections. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0026] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "singular" and "comprising" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising" as used herein specifies a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0027] When a part is referred to as being "on" or "over" another part, it can be directly on or over the other part, or there may be other parts intervening. Conversely, when a part is referred to as being "directly on" another part, there are no other parts intervening.

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

[0029] FIG. 1a and FIG. 1b illustrate a lithium metal electrode (100) manufactured according to one embodiment.

[0030] Referring to FIG. 1a, a lithium metal electrode (100) according to one embodiment includes a current collector (11) and a metal layer (12) positioned on at least one surface of the current collector (11), and also includes a protective layer (30) positioned on the other surface of the metal layer (12) facing the current collector (11).

[0031] The current collector (11) may be a member for electrical connection within a lithium secondary battery. The current collector (11) may have a foil form, but is not limited thereto, and may have, for example, a mesh, foam, rod, wire, or sheet made by weaving wire (fiber).

[0032] The current collector (11) may be made of a material that is electrically conductive and has limited reaction with lithium. Specifically, the material of the current collector (11) may be any one or a combination of, for example, copper, nickel, titanium, stainless steel, iron, gold, platinum, silver, tantalum, ruthenium, and alloys thereof, 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) may be 1 μm to 50 μm. If the thickness of the current collector (11) is excessively thick, there is a problem that the battery weight increases and the energy density of the battery decreases. If the thickness of the current collector (11) is excessively thin, there is a risk of overheating damage during high current operation and damage due to tension during the battery manufacturing process.

[0034] The metal layer (12) is positioned on the current collector (11), and may include a lithium alloy layer (21) including a lithium alloy, and a lithium metal layer (41) positioned on the lithium alloy layer (21). The lithium alloy layer (21) may be a layer including a lithium alloy in which a lithium-friendly component included in the metal layer (12) and lithium precipitated from the lithium source (40) are alloyed by applying a current between the current collector (11) and the lithium source (40 in FIG. 2).

[0035] When the electrodeposition process is performed by applying a high current to increase the speed of electrodeposition during the formation of the metal layer (12), there is a problem that the performance of the lithium secondary battery is reduced. However, when the metal layer (12) is formed with a structure including a lithium alloy layer (21) containing a lithium component as in the present embodiment, even if the electrodeposition process is performed by applying a high current, it is possible to prevent excessive generation of fine lithium particles or destruction of the protective layer (30) located on the surface of the lithium metal layer (41) already formed in the electrodeposition process.

[0036] Specifically, since the metal layer (12) of one embodiment includes a lithium alloy layer (21) containing a lithium component, when a high current is applied in the electrodeposition process to form a lithium metal layer (41) on the lithium alloy layer (21), the initially generated lithium particles are induced to grow well, thereby forming particles with a coarse structure, and at the same time, the lithium metal layer (41), and consequently the metal layer (12), can have a uniform surface.

[0037] Therefore, the performance, specifically the charge / discharge characteristics, of a secondary battery using the lithium metal electrode according to the present embodiment can be significantly improved. Furthermore, since a high-performance lithium metal electrode for a secondary battery can be manufactured even when a high current is applied and the electrodeposition process is performed at a high speed, the productivity of the lithium metal electrode for a secondary battery can also be significantly improved.

[0038] In this embodiment, the lithium alloy layer (21) includes a lithium-friendly metal. In this way, when the lithium alloy layer (21) includes a lithium-friendly metal, since it includes a lithium-friendly metal with high electronic conductivity, there is an advantage in that electrons are smoothly supplied from the current collector, lithium ions are reduced, and thus electrodeposition of the lithium metal layer is easily performed. The metal layer (12) plays a role in helping lithium to be more effectively deposited under the protective layer (30) during the charging process of the battery.

[0039] In one embodiment, the thickness of the metal layer (12) may be in the range of 1 μm to 100 μm, more specifically, 5 μm to 30 μm. If the thickness of the metal layer (12) is excessively thick, when the lithium metal electrode of the present embodiment is applied to a secondary battery, there is a problem in that the weight and volume of the battery increase, resulting in a decrease in energy density. In addition, since the time and cost of the electrodeposition process increase in proportion to the thickness when forming the metal layer (12), the thickness of the metal layer (12) is preferably 100 μm or less.

[0040] When the thickness of the metal layer (12) is excessively thin, when the lithium metal electrode of the present embodiment is applied to a secondary battery, there is a problem that the charge / discharge life of the battery is reduced. Specifically, during charge / discharge of the battery, lithium in the battery is gradually consumed due to side reactions between the lithium contained in the negative active material layer, i.e., the metal layer of the present invention, and the electrolyte, so that the battery capacity is reduced, and the amount of lithium that can replenish the lithium consumed during charge / discharge is reduced, so that the charge / discharge life of the battery is reduced. Therefore, the thickness of the metal layer (12) is preferably 1 ㎛ or more.

[0041] The protective layer (30) may be positioned on the metal layer (12) and may include first amorphous carbon. The first amorphous carbon may be amorphous carbon having a high specific surface area. Specifically, the first amorphous carbon may have a specific surface area of ​​450 m 2 / g or more. Specifically, the first amorphous carbon is 500 m 2 / g or more, more specifically, 500 to 800 m 2 / g, more specifically, 550 to 750 m 2 / g, more specifically, 550 to 650 m 2 / g could be.

[0042] Since the first amorphous carbon satisfies the specific surface area of ​​the aforementioned range, there is an advantage of easy lithium ion conduction through grain boundaries and pores by having an effect of expanding the specific surface area and including a large number of fine micro pores. If the first amorphous carbon exceeds the upper limit of the aforementioned range, an excessive amount of binder or dispersant is required when forming a slurry, and a problem of uneven dispersion occurs. If the first amorphous carbon exceeds the lower limit of the aforementioned range, there is a problem of low conductivity of lithium ions moving mainly through the surface of the amorphous carbon because the surface area is reduced.

[0043] In one embodiment, the first amorphous carbon may have an average particle diameter D50 of 0.1 to 1.5 μm. The average particle diameter D50 of the first amorphous carbon may be a particle diameter corresponding to 50% of the volume accumulation of the particle size distribution of the first amorphous carbon. Specifically, the average particle diameter D50 of the first amorphous carbon may be 0.3 to 1.2 μm. Specifically, the average particle diameter D50 of the first amorphous carbon may be 0.5 to 1.0 μm. More specifically, it may be 0.6 to 1.0 μm.

[0044] Since the average particle diameter D50 of the first amorphous carbon satisfies the above-mentioned range, there is an advantage in stable dispersion of the slurry. If the average particle diameter D50 of the first amorphous carbon exceeds the upper limit of the above-mentioned range, the size of the particles becomes excessively large compared to the thickness of the protective coating layer, so that the number of particles constituting the entire protective layer decreases, which causes a problem in that the growth of lithium dendrites cannot be effectively prevented. If the average particle diameter D50 of the first amorphous carbon exceeds the lower limit of the above-mentioned range, there is a problem in 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 is 40 to 80 m 2 / g may be. Specifically, the specific surface area of ​​the second amorphous carbon is 50 to 70 m 2 / g could be.

[0046] Since the second amorphous carbon satisfies the specific surface area within the aforementioned range, there is an advantage in that pores of an appropriate size can be formed. If the second amorphous carbon exceeds the upper limit of the aforementioned range, there is a problem in that an excessive amount of binder or dispersant is required when forming a slurry. If the second amorphous carbon exceeds the lower limit of the aforementioned range, there is a problem in that the specific surface area is excessively reduced, thereby lowering the conductivity of lithium ions moving through the surface.

[0047] In one embodiment, based on 100 wt% of amorphous carbon in the protective layer (30), the protective layer may include first amorphous carbon: 50 wt% or more, and the remainder second amorphous carbon. Specifically, the content of the first amorphous carbon may be 60 wt% or more, more specifically, 80 wt% or more, based on 100 wt% of amorphous carbon. In this way, since the content of the first amorphous carbon is greater than that of the second amorphous carbon based on 100 wt% of the total amount of amorphous carbon, specifically the first amorphous carbon and the second amorphous carbon, the volume occupied by the micropores in the entire pores increases, so that the specific surface area is large, and accordingly, the conductivity of lithium ions is improved, which is advantageous. When the content of the first amorphous carbon is less than that of the second amorphous carbon, since the proportion of the micropores in the entire pores is low, there is a problem that the life characteristics of the battery are deteriorated due to the decrease in the conductivity of lithium ions moving through the surface of the micropores.

[0048] In one embodiment, the second amorphous carbon may have an average particle diameter D50 of 20 to 50 nm. The average particle diameter D50 of the second amorphous carbon may be a particle diameter corresponding to 50% of the volume cumulative particle size distribution of the second amorphous carbon. Specifically, the average particle diameter D50 of the second amorphous carbon may be 30 to 40 nm.

[0049] Since the average particle diameter D50 of the second amorphous carbon satisfies the above-mentioned range, there is an advantage in that the density of the protective layer is improved when mixed with the first amorphous carbon. If the average particle diameter D50 of the second amorphous carbon exceeds the upper limit of the above-mentioned range, there is a problem in that the specific surface area decreases due to an increase in the particle size. If the average particle diameter D50 of the second amorphous carbon exceeds the lower limit of the above-mentioned range, there is a problem in that the particle size is too small, causing agglomeration or deterioration in dispersibility when a slurry is made.

[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 is 400 to 700 m 2 / g may be. Specifically, the value is 500 to 600 m 2 / g could be.

[0051] When the difference value satisfies the above-mentioned range, there is an advantage in that the density of the protective layer is improved by appropriately mixing micropores and mesopores and effectively filling the space between large particles with small particles. When the difference value exceeds the upper limit of the above-mentioned range, particles with excessively large specific surface areas are included, which causes problems with excessive use of binder or dispersant and dispersibility. When the difference value exceeds the lower limit of the above-mentioned range, the effect of increasing the specific surface area is reduced, which causes problems in reducing the effect of improving lithium ion conductivity.

[0052] In one embodiment, the first amorphous carbon may include micropores, which are microscopic pores formed within the particle itself and are nanometer-sized pores.

[0053] Specifically, the first amorphous carbon may include micropores in an amount of 10 to 40% based on 100% of the total pore volume. Specifically, the micropores may include 13 to 35%, more specifically, 14.7 to 30%. In one embodiment, the micropores may have a size of 2 nm or less. Specifically, the micropores may have a diameter of 2 nm or less. By including micropores in the aforementioned range, the first amorphous carbon has an advantage of having a high specific surface area and thus improving the conductivity of lithium ions conducted along the micro 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 to 50 nm. The macropores are pores formed between particles and may have a size greater than 50 nm. The second amorphous carbon has a particle size of 50 nm or less, specifically, 10 to 40 nm, and more specifically, 20 to 40 nm, and has few micropores formed in the particles themselves, and may include the mesopores or macropores formed between particles.

[0055] In one embodiment, when the protective layer simultaneously includes the first amorphous carbon and the second amorphous carbon, the fraction of micropores can satisfy 10 to 40% based on 100% of the total pore volume. The fraction of micropores is a factor determined by the content of the first amorphous carbon, and the higher the content of the first amorphous carbon, the larger the fraction of micropores. Since the protective layer includes micropores in the aforementioned range, there is an advantage in that the conductivity of lithium ions conducted along the surface of the fine micropores can be improved.

[0056] When lithium metal is used as a cathode in an all-solid-state battery, high resistance is generated by the reaction between the all-solid-state electrolyte and lithium, and lithium dendrites are continuously generated or high-resistance lithium byproducts are generated due to local unevenness in current density during the charge / discharge process, which causes failure or a decrease in battery capacity due to a short circuit or overvoltage during charge / discharge.

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

[0058] Specifically, the lithium metal electrode of the present embodiment includes a protective layer (30) including the first amorphous carbon, thereby not only improving ion conductivity, but also improving the strength of the protective layer (30), and preventing short circuits between electrodes by physically blocking dendrites when they grow on the lithium electrode, thereby improving the charge / discharge life.

[0059] The first amorphous carbon and the second amorphous carbon may be at least one selected from the group consisting of acetylene black, super P black, carbon black, denka black, activated carbon, graphite, hard carbon, and soft carbon, but are not limited thereto.

[0060] In one embodiment, the protective layer (30) may include a binder. The binder may be an aqueous binder, and the aqueous binder may be, but is not limited to, a rubber-based binder selected from the group consisting of acrylonitrile-butadiene rubber, styrene-butadiene rubber (SBR), and acrylic rubber, and at least one selected from the group consisting of polymer resins such as hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinylidene fluoride.

[0061] Here, the binder may be added in an amount of 1 to 15 parts by weight, specifically 3 to 10 parts by weight, based on the weight of the slurry formed by mixing the first amorphous carbon and / or the second amorphous carbon and water. When the content of the binder satisfies the above-described range, the particles constituting the protective layer are efficiently bound to form a protective layer with excellent performance without causing a decrease in battery energy density due to an increase in weight and volume, thereby further improving the life characteristics of the secondary battery.

[0062] If the content of the binder is excessively less than the above-mentioned range, there is a problem that the bonding force between particles is reduced when forming a protective layer, and if the content of the binder is excessively more than the above-mentioned range, there is a problem that not only does it cause a decrease in energy density, but also the resistance of the protective layer is greatly increased, hindering lithium ion conduction.

[0063] In one embodiment, the thickness of the protective layer (30) may be 0.01 μm to 50 μm. Specifically, the thickness of the protective layer (30) may be in the range of 1 μm to 20 μm. When the thickness of the protective layer satisfies the above-described range, the amorphous carbon prevents lithium dendrites from forming on the surface of the protective layer, and allows lithium ions to penetrate well into the protective layer and conduct, thereby allowing lithium to be precipitated from the lower surface of the protective layer.

[0064] If the thickness of the protective layer is excessively thin, there is a problem in that it cannot function as a protective layer. If the thickness of the protective layer is excessively thick, the resistance of the protective layer may be excessively high, which may cause an increase in overvoltage during secondary battery operation, and there is a problem in that it causes a decrease in battery energy density due to an increase in weight and volume. However, the thickness of the protective layer can be variably adjusted depending on the design of the secondary battery structure.

[0065] In one embodiment, the lithium metal electrode may include a film layer disposed within the protective layer (30), between the metal layer (12) and the protective layer (30), and at least a portion of the protective layer (30). Specifically, the film layer may be disposed within at least a portion of the protective layer (30), between the metal layer (12) and the protective layer (30), may be disposed simultaneously within the protective layer (30) and between the metal layer (12) and the protective layer (30), and may be disposed on the protective layer (30).

[0066] The above film layer is formed during the manufacturing process of the metal layer (12) by a reaction between the lithium metal of the electrodeposited lithium source (40) and the plating solution, and the thickness, composition, and characteristics of the film can be controlled by adjusting the composition of the plating solution used and the conditions of the electrodeposition process.

[0067] In one embodiment, the film layer may include at least a portion of LiF. The LiF may be formed by including at least one solvent having a high dielectric constant among a plurality of solvents used in the electrodeposition process. Specifically, by increasing the salt decomposition dissociation degree of the solvent of the electrodeposition plating solution, the salt decomposition reaction may be suppressed and the solvent decomposition reaction may be promoted during electrodeposition, thereby allowing a sufficient LiF film to be formed within and / or on the surface of the protective layer. By including the film layer including at least a portion of LiF, the battery can have a high ionic conductivity, thereby improving the lifespan and preventing dendrite growth during battery operation.

[0068] The thickness of the film layer may be 2 nm to 2 ㎛. Specifically, the thickness of the film layer may be specifically in the range of 10 nm to 500 nm. If the thickness of the film layer is excessively thick, the lithium ion conductivity decreases and the interfacial resistance increases, which causes a problem in that the charge / discharge characteristics deteriorate when applied to a battery. If the thickness of the film layer is excessively thin, the film layer may be easily lost during the process of applying the lithium metal electrode according to the embodiment to a battery. Therefore, the film layer may have a thin thickness within the range satisfying the above thickness range and may be uniformly and densely formed on the entire surface of the metal layer (12) and the protective layer (30).

[0069] Referring to FIG. 1b, in one embodiment, a lithium metal electrode (100) includes a current collector (11) and a metal layer (12) positioned on at least one surface of the current collector (11) and composed of a mixture of lithium and a lithium alloy. Here, the lithium alloy may be formed by applying a current between the current collector (11) and a lithium source (40), thereby alloying a lithium-affinity component included in a coating layer (20 in FIG. 2) formed on the current collector (11) with lithium precipitated from the lithium source (40).

[0070] The above metal layer (12) may include a lithium-philic metal. For a detailed description thereof, refer to FIG. 1A. In one embodiment, the metal layer (12) includes a lithium-philic metal. When a metal layer (12) including a lithium-philic metal is formed in this manner, the free energy for nucleation of lithium particles can be lowered in the early stage of nucleation during the electrodeposition process, thereby forming a lithium metal layer having a coarse particle structure even under high current and overvoltage conditions.

[0071] In one embodiment, the metal layer (12) includes a protective layer (30) positioned on the surface of the metal layer (12), and may include a film layer on the interior and / or surface of the protective layer (30). For a detailed description of the protective layer (30) and the film layer, reference may be made to the description given above in FIG. 1A.

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

[0073] Referring to FIG. 2, a method for manufacturing a lithium metal electrode according to one embodiment includes the steps of preparing a current collector (11), forming a coating layer (20) on at least one surface of the current collector (11) using a coating composition including a lithium-philic component, forming a protective layer (30) on the surface of the coating layer (20) using a slurry including amorphous carbon, positioning the current collector (11) on which the coating layer (20) and the protective layer (30) are formed in a plating solution (50), and then positioning a lithium source (40) at a predetermined distance 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 in which the lithium-philic component included in the coating layer and lithium precipitated from the lithium source (40) are alloyed.

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

[0075] The step of forming a coating layer (20) on at least one surface of a current collector (11) using a coating composition containing a lithium-friendly component may include coating an alloy material on at least one surface of the current collector. The alloy material may be, for example, at least one selected from the group consisting of the lithium-friendly metal, for example, In, Ag, Sn, Zn, Si, Al, and Bi, but is not limited thereto.

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

[0077] A protective layer (30) can be formed on the surface of the coating layer (20) using a slurry containing amorphous carbon. The protective layer (30) can be applied by mixing the amorphous carbon and a binder in water using at least one of a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush application method. The protective layer (30) can further include a binder.

[0078] In one embodiment, the step of forming the protective layer (30) may include the step of forming the protective layer by including a first amorphous carbon having a high specific surface area. Specifically, the amorphous carbon has a specific surface area of ​​450 m 2 / g or more of a specific surface area. Specific characteristics of the first amorphous carbon may be referred to the contents of the above-described FIGS. 1a and 1b.

[0079] In one embodiment, the step of forming the protective layer (30) may further include a step of mixing a second amorphous carbon having a lower specific surface area than the first amorphous carbon. The step of forming the protective layer (30) has the advantage of improving the density of the protective layer by mixing the first amorphous carbon and the second amorphous carbon having different specific surface areas, thereby effectively filling the spaces between large particles with small particles, and appropriately mixing micropores and mesopores. For a specific description of the second amorphous carbon, reference may be made to the contents of the aforementioned FIGS. 1A and 1B.

[0080] In one embodiment, in the step of forming the protective layer (30), 100 wt% of amorphous carbon in the protective layer, specifically, based on the combined amount of the first amorphous carbon and the second amorphous carbon of 100 wt%, the first amorphous carbon may be mixed in an amount of 50 wt% or more, and the remainder may be the second amorphous carbon. For a detailed description thereof, reference may be made to the aforementioned FIGS. 1A and 1B.

[0081] Meanwhile, in the step of forming the protective layer (30), the thickness of the protective layer formed on the surface of the alloy material coating layer may be in the range of 0.01 µm to 50 µm, more specifically, 1 µm to 20 µm.

[0082] After the step of forming a protective layer (30), a step of positioning a current collector in which the coating layer (20) and the protective layer (30) are sequentially formed in a plating solution (50), a step of positioning a lithium supply source (40) at a predetermined distance from the current collector (11), and a step of applying current between the current collector (11) and the lithium supply source (40) to form a metal layer (12) are performed.

[0083] Specifically, after positioning a current collector (11) having a coating layer (20) and a protective layer (30) formed within a plating solution, a lithium supply source (40) is positioned at a predetermined distance from the protective layer (30). The lithium supply source (40) may be, for example, lithium metal, a lithium alloy, a foil obtained by pressing the lithium metal or lithium alloy onto a current collector, a plating solution in which a lithium salt is dissolved, etc.

[0084] The plating solution (50) can be prepared by dissolving a lithium salt in a plurality of 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 can be 1.0 to 3.0 M based on the total electrolyte.

[0085] Specifically, in the present embodiment, the plating solution (50) is characterized in that it includes a nitrogen-based compound as at least one of the lithium salt and a plurality of solvents. The nitrogen-based compound may include, for example, one or more selected from the group consisting of lithium nitrate, lithium bis fluorosulfonyl imide, lithium bis trifluoromethane sulfonimide, e-caprolactam, N-methyl-e-caprolactam, triethylamine, and tributylamin.

[0086] Among the above nitrogen compounds, at least one of lithium nitrate, lithium bis fluorosulfonyl imide, and lithium bis trifluoromethane sulfonimide can be used as a lithium salt.

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

[0088] The above plating solution (50) may be manufactured using only the nitrogen-based compound, but may include a general non-aqueous solvent as an auxiliary solvent in consideration of the viscosity of the plating solution (50), etc.

[0089] The auxiliary solvent may include, for example, at least one selected from the group consisting of 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 be included in an amount of 5 to 70 wt%, preferably 10 to 60 wt%, based on 100 wt% of the total plating solution (50), but is not limited thereto. However, when the auxiliary solvent is included within the above range, the viscosity of the plating solution (50) may be appropriate, thereby shortening the time required for the formation process of the metal layer (12), 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, there is an advantage in that the properties of the film layer formed on the lithium metal layer (12) can be improved.

[0092] The fluorine-based compounds include, for example, lithium difluoro phosphate, lithium hexafluorophosphate, lithium difluoro bisoxalato phosphate, lithium tetrafluoro oxalato phosphate, lithium difluoro oxalate borate, lithium difluoro oxalato borate, lithium tetrafluoro oxalato borate, fluoroethylene carbonate, difluoroethylene carbonate, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether. It may include at least one selected from the group consisting of 2,2,3,3-Tetrafluoropropyl ether.

[0093] The above fluorine-based compound may be included in an amount of 0.1 to 30 wt%, preferably 1 to 20 wt%, and more preferably 1 to 10 wt%, based on 100 wt% of the total plating solution (50). When the fluorine-based compound is included within the above range, the interaction between the nitrogen-based compound and the fluorine-based compound in the plating solution (50) is favorable, so that there is an excellent advantage in improving the properties of the film layer formed on the lithium metal layer (12). In addition, there is an advantage in that the electrochemical properties are excellent because excessive generation of LiF, etc. due to the direct reaction between the fluorine-based compound and lithium is suppressed.

[0094] Next, after positioning an insulating film between the current collector (11) and the lithium supply source (20), the current collector (11), the lithium supply source (20), and the insulating film can be laminated and restrained in both directions using a restraining device. The restraining device can be a non-limiting example, and can use a method commonly used in the art, such as a manual clamping method, a uniaxial pressurization method such as hydraulic pressure, or pneumatic pressure.

[0095] In the step of forming a lithium metal layer on at least one surface of the current collector by applying the above current, the current density of the current applied is 0.1 mA / cm 2 100 mA / cm 2 range, more specifically 0.2 mA / cm 2 50 mA / cm 2 Range, 5 mA / cm 2 30 mA / cm 2 range or 7 mA / cm 2 25 mA / cm 2 It could be a range.

[0096] In one embodiment, the time for applying the current may 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 the current to form a lithium metal layer on at least one surface of the current collector may be performed at least once at different current densities. The step of applying the current may be performed in multiple stages. Specifically, the step of applying the current in multiple stages may be performed by increasing the current density from a low current density to a high current density in predetermined time steps. For example, the step of applying the current may be performed at a current density of 0.1 to 0.3 mA / cm. 2 , 0.3 to 0.7 mA / cm 2 , and 0.8 to 1.5 mA / cm 2 It can be applied step by step and increased sequentially.

[0098] 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 is 6 to 12 mA / cm 2 A step of electrodeposition at a maximum current density of the range may be included. Specifically, the maximum current density is 8 to 12 mA / cm 2 It can be performed in the range. The above maximum current density means the limit of the current density at which lithium deposited in the electrodeposition process can precipitate lithium between the protective layer (30) and the current collector (11).

[0099] The step of electrodeposition at the above maximum current density may be a final step performed after the step of depositing in multiple stages, for example, for lithium deposition between the current collector (11) and the protective layer (30). By satisfying the above-described range, lithium is appropriately deposited between the current collector (11) and the protective layer (30), thereby providing advantages such as excellent battery life characteristics and bonding strength between the current collector (11) and the protective layer (30).

[0100] If the maximum current density exceeds the upper limit of the aforementioned range, lithium is deposited on the surface of the protective layer (30), which causes a problem in that the targeted stabilized electrode structure cannot be secured. If the maximum current density exceeds the lower limit of the aforementioned range, the time for lithium to be deposited increases, which causes a problem in that productivity decreases.

[0101] 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 a step of electrodepositing the deposited lithium to a thickness in the range of 5 to 15 μm. Specifically, the thickness of the deposited lithium may be electrodeposited to a thickness 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).

[0102] If the thickness of the precipitated lithium exceeds the upper limit of the aforementioned thickness, not only will the energy density of the battery decrease, but there will also be problems such as increased process time and metal raw material usage during metal layer formation. If the thickness of the precipitated lithium exceeds the lower limit of the aforementioned thickness, there will be problems such as decreased initial coulombic efficiency due to initial irreversibility and decreased charge / discharge performance due to insufficient excess lithium.

[0103] In one embodiment, in the step of forming a lithium 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 a lithium alloy can be controlled to 1 to 100 μm. For a detailed description of the thickness of the metal layer (12), reference may be made to the contents of the aforementioned FIG. 1.

[0104] In this way, in this embodiment, a lithium metal electrode (100) can be manufactured in which a metal layer including a lithium metal layer (12) having a coarse particle structure is formed by preventing excessive generation of fine lithium particles even under high current conditions and inducing the initially generated lithium particles to grow well. In addition, the metal layer manufactured in this way also has excellent surface uniformity.

[0105] According to another embodiment of the present invention, a lithium secondary battery includes a positive electrode, a negative electrode, and an electrolyte positioned between the positive electrode and the negative electrode. Here, the negative electrode may be a lithium metal electrode according to the present invention.

[0106] In one embodiment, a lithium secondary battery may include an electrode assembly including a positive electrode including a positive active material, a negative electrode which is a lithium metal electrode of the present invention, and a separator disposed between the positive electrode and the negative electrode. This electrode assembly may be wound or folded and accommodated in a battery case.

[0107] Thereafter, an electrolyte may be injected into the battery case and sealed to complete the secondary battery. At this time, the battery case may have a cylindrical, square, pouch-shaped, coin-shaped, etc. shape.

[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, for example, a Li compound including at least one metal selected from the group consisting of 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.

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

[0110] The above-described positive electrode current collector serves to support the positive electrode active material layer. Examples of positive electrode current collectors that can be used include, but are not limited to, aluminum foil, nickel foil, or a combination thereof.

[0111] The electrolyte to be filled in the lithium secondary battery may be a non-aqueous electrolyte or a solid electrolyte. Specifically, the electrolyte may be a solid electrolyte. The non-aqueous electrolyte may include, for example, a lithium salt such as lithium hexafluorophosphate or lithium perchlorate, and a solvent such as ethylene carbonate, propylene carbonate, or butylene carbonate. In addition, the solid electrolyte may be, for example, a gel polymer electrolyte obtained by impregnating a polymer electrolyte such as polyethylene oxide or polyacrylonitrile with an electrolyte, or an inorganic solid electrolyte such as LiI or Li3N.

[0112] The separator may be any membrane commonly used in lithium secondary batteries, as it separates the positive and negative electrodes and provides a passage for lithium ions to move. Specifically, the separator may be one that has low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity. The separator may be selected from, for example, glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene, or a combination thereof, and may be in the form of a non-woven fabric or a woven fabric. Meanwhile, when a solid electrolyte is used as the electrolyte, the solid electrolyte may also function as the separator.

[0113] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples, and the present invention is not limited thereby, and the present invention is defined only by the scope of the claims set forth below.

[0114]

[0115] <Experimental Example>

[0116] Manufacturing of cathodes for lithium secondary batteries

[0117] <Example 1>

[0118] <Manufacturing the entire house>

[0119] A current collector made of Cu foil was prepared for use in the negative electrode of the lithium secondary battery of the present invention.

[0120]

[0121] <Formation of alloy material coating layer>

[0122] Thereafter, an alloy material was coated on both sides of the current collector using an electrolytic plating method. Specifically, the alloy material was coated on both sides of the current collector made of copper foil using an electroless plating method. Silver (Ag) was used as the alloy material, and the plating thickness was controlled to approximately 300 nm.

[0123] FIG. 3 is a scanning electron microscope (SEM) photograph showing the structure and thickness of an alloy material coating layer plated on a current collector according to one embodiment of the present invention.

[0124] Referring to FIG. 3, it can be confirmed that the alloy material coating layer plated on the current collector of the present invention has a thickness in the range of about 250 to 350 nm.

[0125]

[0126] <Protective layer formation>

[0127] Afterwards, a protective layer of about 5 ㎛ was formed on the upper surface of the coating layer by slurry coating using a comma coater. Specifically, the protective layer was formed by mixing amorphous carbon, a binder, and a solvent. At this time, the binder was prepared by adding 3.0 parts by weight and 6.0 parts by weight of carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR), respectively, based on 100 parts by weight of amorphous carbon. In addition, the solvent was used so that water and ethylene glycol (EG) were in a weight ratio of 80:20. The total amount of the solvent was about 25 wt% of the total of the amorphous carbon and the binder to maintain an appropriate viscosity for the coating.

[0128] The above amorphous carbon is a high surface area microparticle, the L1102 model of Heraeus, with a median particle size D50 of 0.8 ㎛ and a specific surface area of ​​600 m 2 / g powder was used.

[0129] Figures 4a and 4b show the microstructure of the surface and cross-section when a protective layer is placed on a current collector coated with an alloy material.

[0130] Referring to FIGS. 4a and 4b, the surface structure and cross-sectional shape are porous after the solvent has evaporated, and this porous structure facilitates the movement and deposition of lithium ions by allowing the plating solution to be smoothly impregnated during the subsequent lithium deposition process.

[0131]

[0132] Lithium electrodeposition process

[0133] Afterwards, lithium was removed from the lithium source using an electrodeposition process to form a lithium alloy or pure lithium metal between the protective layer and the current collector, and lithium was deposited between the protective layer and the current collector. The plating solution used for this electrodeposition was prepared by adding lithium bis(fluorosulfonyl)imide, a nitrogen-based compound, and lithium nitrate in amounts of 40 wt% and 5 wt%, respectively, based on 100 wt% of the plating solution, to a 1,2-dimethoxyethane (DME) solvent, and adding fluoroethylene carbonate, a fluorine-based compound, in an amount of 5 wt% based on 100 wt% of the plating solution. A lithium metal plate having a purity of 99.9% or higher and a thickness of 500 ㎛ was pressed onto a copper current collector (Cu Plate) and used as a lithium source (40).

[0134] After electrically insulating the lithium source and the current collector in the plating solution, a current was applied using a power supply device with the lithium source and the current collector as (+) and (-) electrodes, respectively, to deposit lithium between the current collector and the ion concentration protective layer.

[0135] The current density of the electrodeposition process was 0.2 mA / cm 2 , 0.5 mA / cm 2 , 1 mA / cm 2 Increasing step by step in order, after 5 minutes of deposition, 10 mA / cm 2 The maximum current density was set. The deposition time at the maximum current density was calculated as the time required for a final accumulated lithium thickness of 10 ㎛ to be deposited, and was set variably depending on the size of the maximum current density.

[0136] Figures 5a and 5b show the appearance of electrodeposition according to the maximum current density in the electrodeposition process according to the examples and comparative examples.

[0137] Fig. 5a shows the appearance of the electrodeposition when electrodeposition is performed below the maximum current density, and Fig. 5b shows the appearance of the electrodeposition when electrodeposition is performed above the maximum current density. Referring to Figs. 5a and 5b, when electrodeposition is performed below the maximum possible current density, the deposited lithium is deposited under the black protective layer, so that a black protective layer is visible in appearance. When electrodeposition is performed above the maximum possible current density, lithium is deposited on the upper surface of the protective layer, so that gray-colored lithium is deposited on the upper surface of the protective layer. Through this, the maximum current density is defined as the maximum possible current density for electrodeposition, which is the maximum current density at which lithium is deposited between the current collector and the protective layer in the electrodeposition process.

[0138]

[0139] <Comparative Example 1>

[0140] In the step of forming the protective layer, the same method as Example 2 was used, except that 100 wt% of the low-surface-area nano-particle amorphous carbon (second amorphous carbon) was used instead of the high-surface-area micro-particle amorphous carbon used in Example 1 based on 100 wt% of the amorphous carbon.

[0141]

[0142] All-solid-state battery manufacturing

[0143] All-solid-state batteries were fabricated using the cathodes manufactured according to the aforementioned examples and comparative examples, and their charge-discharge cycle life was evaluated. To evaluate the all-solid-state battery cells, a pressurized, dedicated evaluation cell from Terraleader, capable of maintaining an inert atmosphere, was used. For the fabrication of the all-solid-state battery cells, a sulfide-based argyrodite (Li6PS5Cl) solid electrolyte was used, and the electrolyte was in pellet form with a thickness of approximately 0.7 mm. To ensure a dense electrolyte, the electrolyte was pressurized at a pressure of 370 MPa.

[0144] Lithium having a thickness of 0.5 mm was attached as a reference electrode on one side of the electrolyte, and the negative electrode manufactured according to the examples and comparative examples was attached on the opposite side. The reference electrode and the evaluation electrode were attached to the solid electrolyte at a pressure of 50 MPa, and during the charge and discharge evaluation, the pressure was applied to 16 MPa in a dedicated evaluation cell.

[0145]

[0146] <Evaluation Example 1>: Performance Evaluation According to the Difference in Specific Surface Area of ​​Amorphous Carbon

[0147] Table 1 below shows the maximum electrodeposition current and charge / discharge performance cycles when amorphous carbons with different specific surface areas are included in forming a protective layer. The maximum electrodeposition current, charge / discharge performance cycles, specific surface area of ​​the amorphous carbon, and average particle diameter (D50) were measured using the following methods.

[0148] Maximum current density (mA / cm 2 ): The maximum current density refers to the limit of the current density at which lithium deposited according to the above process can precipitate lithium between the ion concentration protective layer and the current collector, and the maximum current density was measured.

[0149] Charge / discharge performance number (cycles): The reference electrode and evaluation electrode were attached to the solid electrolyte at a pressure of 50 MPa, and the dedicated evaluation cell was pressurized at 16 MPa during the charge / discharge evaluation. The charge / discharge evaluation was performed at 2 mA / cm 2Charge for 0.5 hours at constant current of 2 mA / cm 2 A 0.5-hour discharge at constant current was defined as one cycle. The charge-discharge life was defined as the end of the life when a short circuit occurred between the reference electrode and the evaluation electrode during the charge-discharge process or when the voltage between the two electrodes exceeded 2 V.

[0150] Specific surface area (m 2 / g) and micropore fraction (%): The BET measurement of amorphous carbon in the protective layer and the distribution of pores were measured by nitrogen adsorption using a 3Flex device on Micrometics.

[0151] Classification 1 Amorphous carbon Classification 2 Amorphous carbon Specific surface area [m 2 / g]Micropore fraction [%]Average particle size [um]Maximum deposition current [mA / cm 2 ]Charge / discharge performance number of times [times]Content [wt%]Content [wt%]Example 1100-600300.8121044Comparative example 1-1006000.034481

[0152] Looking at Table 1 above, it was confirmed that Example 1, which includes a first amorphous carbon having a large specific surface area and an average particle size D50 as a protective layer, has inferior maximum electrodeposition current and charge / discharge performance number compared to Comparative Example 1, which includes a second amorphous carbon having a small specific surface area and an average particle size D50 as a protective layer. FIGS. 6a and 6b show the specific surface area, pore size, and cumulative distribution of amorphous carbon according to Examples and Comparative Examples of the present invention.

[0153] Figures 6a and 6b show 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, respectively. Referring to Figures 6a and 6b, the first amorphous carbon contains a large amount of micropores of 2 nm or less (generally referred to as micropores). Micropores of 2 nm or less occupy 30% of the total pore volume. Since the micropores are contained in such a large amount, the specific surface area is 600 m 2 It comes out high like / g.

[0154] When the shape of the particle is not taken into account, it is common for the specific surface area to be small when the particle size is large, and for the specific surface area to be large when the particle size is small. However, the first amorphous carbon has a relatively large particle size of the order of ㎛, and the specific surface area is also 600 m 2 / g is very high. This is because each particle itself is made up of very small micropores.

[0155] In contrast, the second amorphous carbon has a very small particle size of 30 nm, but a specific surface area of ​​60 m 2 / g. This is because there are almost no micropores formed in the particles themselves, and mainly mesopores (2 to 50 nm) or macropores (over 50 nm) formed between particles are formed. In the case of the second amorphous carbon, the fraction of micropores less than 2 nm was confirmed to be very low at 0%.

[0156] Figure 7 shows the results of evaluating the charge / discharge life of a lithium metal electrode according to an embodiment and a comparative example of the present invention.

[0157] Referring to FIG. 7, it was confirmed that Example 1 including the first amorphous carbon having a high specific surface area had an excellent lifespan characteristic with 1044 cycles compared to 481 cycles of Comparative Example 1 including the second amorphous carbon having a low specific surface area.

[0158]

[0159] <Evaluation Example 2> - Control of the content of first amorphous carbon and second amorphous carbon

[0160] <Example 2>

[0161] In the step of forming the protective layer, 80 wt% of the high surface area micro particle-type amorphous carbon (first amorphous carbon) used in Example 1 and 20 wt% of the low surface area nano particle-type amorphous carbon (second amorphous carbon) were mixed based on 100 wt% of the amorphous carbon, and the same method as Example 1 was used.

[0162] At this time, the low surface area nano particle type amorphous carbon has an average particle size D50 of 30 nm and a specific surface area of ​​60 m 2 / g could be.

[0163]

[0164] <Example 3>

[0165] In the step of forming the protective layer, 60 wt% of the high surface area micro particle-type amorphous carbon (first amorphous carbon) used in Example 1 and 40 wt% of the low surface area nano particle-type amorphous carbon (second amorphous carbon) were mixed based on 100 wt% of the amorphous carbon, and the same method as Example 2 was used.

[0166]

[0167] Comparative Example 2

[0168] In the step of forming the protective layer, the same method as Example 2 was used, except that 40 wt% of the high-surface-area micro-particle-type amorphous carbon (first amorphous carbon) used in Example 1 and 60 wt% of the low-surface-area nano-particle-type amorphous carbon (second amorphous carbon) were mixed based on 100 wt% of the amorphous carbon.

[0169]

[0170] Table 2 below shows the maximum electrodeposition current and charge / discharge performance number when the content of the first amorphous carbon and the second amorphous carbon is changed.

[0171] Classification 1 Amorphous carbon Classification 2 Amorphous carbon Specific surface area [m 2 / g]Micropore fraction [%]Average particle size [um]Maximum deposition current [mA / cm 2 ]Charge / discharge performance Number of times [times]Content [wt%]Content [wt%]Example 2802049021.50.6510948Example 3604038014.70.4910902Comparative example 240602709.00.346613

[0172] Looking at Table 2 above, when the first amorphous carbon and the second amorphous carbon are included simultaneously in the protective layer, it was confirmed that Examples 2 and 3, in which the content of the first amorphous carbon is greater than the content of the second amorphous carbon, have superior maximum deposition current and charge / discharge performance numbers compared to Comparative Example 2.

[0173] The present invention is not limited to the above-described embodiments, but can be manufactured in a variety of different forms. Those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. Whole house; A metal layer positioned on at least one surface of the above collector and comprising a lithium alloy; and Located on the above metal layer and 450 m 2 A lithium metal electrode comprising a protective layer comprising a first amorphous carbon having a specific surface area of ​​ / g or more.

2. In paragraph 1, The above first amorphous carbon is a lithium metal electrode having an average particle diameter D50 of 0.1 to 1.5 ㎛.

3. In paragraph 1, The above protective layer further includes a second amorphous carbon having a lower specific surface area than the first amorphous carbon, A lithium metal electrode comprising first amorphous carbon in an amount of 50 wt% or more and second amorphous carbon in the remainder, based on 100 wt% of amorphous carbon in the protective layer.

4. In paragraph 3, The specific surface area of ​​the above second amorphous carbon is 40 to 80 m 2 Lithium metal electrode having a density of / g or less.

5. In paragraph 3, A lithium metal electrode wherein the average particle diameter D50 of the second amorphous carbon is 20 to 50 nm.

6. In paragraph 3, The difference value between the specific surface area of ​​the first amorphous carbon and the specific surface area of ​​the second amorphous carbon is 400 to 700 m 2 / g lithium metal electrode.

7. In paragraph 1, The first amorphous carbon in the above protective layer is a lithium metal electrode including micropores.

8. In paragraph 7, A lithium metal electrode having micropores in an amount of 10 to 40% based on 100% of the total pore volume.

9. In paragraph 1, A lithium metal electrode wherein the second amorphous carbon in the protective layer includes mesopores or macropores.

10. Step to prepare the entire house; A step of forming a coating layer on at least one surface of a current collector using a coating composition containing a lithium-friendly component; and 450 m on the surface of the above coating layer 2 A method for manufacturing a lithium metal electrode, comprising the step of forming a protective layer comprising first amorphous carbon having a specific surface area of ​​ / g or more.

11. In clause 10, After the step of forming the above protective layer, A step of positioning a current collector having the coating layer and the protective layer formed thereon within a plating solution and then positioning a lithium supply source at a predetermined distance from the protective layer; and A method for manufacturing a lithium metal electrode, comprising the step of applying a current between the current collector and the lithium source to form a metal layer including a lithium alloy in which a lithium-friendly component included in the coating layer and lithium precipitated from the lithium source are alloyed.

12. In paragraph 10, A method for manufacturing a lithium metal electrode, wherein in the step of forming the protective layer, the first amorphous carbon has an average particle diameter D50 of 0.1 to 1.5 ㎛.

13. In paragraph 11, In the step of forming the above protective layer, second amorphous carbon having a lower specific surface area than the first amorphous carbon is further mixed, A method for manufacturing a lithium metal electrode, wherein the first amorphous carbon is 50 wt% or more and the second amorphous carbon is mixed as the remainder, based on 100 wt% of the amorphous carbon in the protective layer.

14. In paragraph 13, The specific surface area of ​​the above second amorphous carbon is 40 to 80 m 2 / g or less. A method for manufacturing a lithium metal electrode.

15. In paragraph 13, A method for manufacturing a lithium metal electrode, wherein the average particle diameter D50 of the second amorphous carbon is 20 to 50 nm.

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