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

Abstract

The present invention relates to a lithium metal electrode and a method of manufacturing same. The lithium metal electrode of the present invention comprises: a current collector; a metal layer, which is positioned on at least one surface of the current collector and includes a lithium alloy; and a protective layer positioned on the metal layer, wherein the protective layer can include amorphous carbon and silicate clay mineral that has a 2:1-type crystal structure.

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 are formed by rolling copper foil as a current collector and lithium foil, or by depositing a lithium thin film on copper foil. However, rolling is difficult to produce wide and thin films, and deposition is uneconomical. To address these shortcomings, a method has been proposed to form an anode by electrochemically depositing lithium on copper foil.

[0005] However, when a lithium metal electrode is used as a cathode in an all-solid-state battery, a high-resistance phase is created by the reaction between lithium and the all-solid-state electrolyte, and lithium dendrites are continuously created or high-resistance lithium byproducts are created due to local unevenness in the current density during the charge and discharge process, which causes problems such as the battery not being able to perform its function due to a short circuit or overvoltage during charge and discharge, or a problem of reduced capacity.

[0006] Until now, various methods have been proposed to prevent reaction with all-solid-state batteries and to prevent the precipitation and growth of lithium dendrites, such as using amorphous carbon alone as a protective coating layer on a lithium metal electrode or using a composite material with an expensive lithium-friendly metal. However, sufficient lithium deposition speed and charge-discharge life characteristics have not been achieved.

[0007] According to one embodiment of the present invention, a lithium metal electrode for a lithium secondary battery increases the concentration of lithium ions to improve the lithium stacking speed and implement a lithium secondary battery with 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 protective layer positioned on the metal layer, wherein the protective layer comprises amorphous carbon and a silicate clay mineral having a 2:1 layered crystal structure.

[0010] In one embodiment, the protective layer may have a weight ratio of the amorphous carbon to the silicate clay mineral of 97:3 to 65:35. In one embodiment, the silicate clay mineral may comprise a monoclinic crystal.

[0011] In one embodiment, the silicate clay mineral may have a layer charge per unit volume of 0.2 to 0.6. In one embodiment, the silicate clay mineral may have a cation exchange capacity (me / 100g) of 80 to 150.

[0012] In one embodiment, the bonding strength between the current collector and the protective layer may be 0.030 to 0.30 N / cm. In one embodiment, the metal layer including the lithium alloy may include one or more of In, Ag, Sn, Zn, Si, Al, and Bi.

[0013] In one embodiment, the average thickness of the metal layer may be from 1 μm to 100 μm. In one embodiment, the average thickness of the protective layer may be from 1 μm to 20 μm.

[0014] In another embodiment of the present invention, a method for manufacturing a lithium metal electrode includes the steps of forming a coating layer on at least one surface of a current collector using a coating composition including a lithium-philic component, forming a protective layer on the surface of the coating layer using a slurry including amorphous carbon and a silicate clay mineral having a 2:1 layered crystal structure, placing 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 the lithium-philic component included in the coating layer and lithium precipitated from the lithium source are alloyed.

[0015] In one embodiment, in the step of forming the protective layer, the weight ratio of the amorphous carbon to the silicate clay mineral may be mixed in a range of 97:3 to 65:35. In one embodiment, in the step of forming a metal layer including a lithium alloy in which a lithium-philic component included in the coating layer and lithium precipitated from the lithium source are alloyed by applying a current between the current collector and the lithium source, 8 to 12 mA / cm 2 A step of electrodeposition at a maximum current density of the range may be included.

[0016] In one embodiment, 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 may include a step of electrodepositing the precipitated lithium to a thickness in the range of 5 to 15 μm.

[0017] In one embodiment, in the step of forming a protective layer on the surface of the coating layer using a slurry including amorphous carbon and a silicate clay mineral having a 2:1 type crystal structure, a step of slurry coating may be included so that the thickness of the protective layer becomes 1 to 20 ㎛. In one embodiment, the current density of the current applied in the step of forming a lithium metal layer on at least one surface of the current collector is 0.1 mA / cm 2 100 mA / cm 2 It could be.

[0018] According to one embodiment of the present invention, a lithium metal electrode for a lithium secondary battery includes a silicate clay mineral having a 2:1 layered crystal structure in a protective layer, thereby promoting lithium ion conduction, thereby improving a lithium stacking speed and implementing a lithium secondary battery with improved charge / discharge cycle life characteristics.

[0019] According to another embodiment of the present invention, a method for manufacturing a lithium metal electrode for a lithium secondary battery comprises coating a slurry containing a silicate clay mineral having a 2:1 layered crystal structure within a protective layer and inserting lithium through an electrodeposition process, thereby promoting lithium ion conduction, thereby improving the lithium stacking speed and implementing a lithium secondary battery with improved charge / discharge cycle life characteristics.

[0020] Figures 1a and 1b illustrate a lithium metal electrode manufactured according to one embodiment.

[0021] Figure 2 is a schematic diagram of a method for manufacturing a lithium metal electrode of the present invention.

[0022] FIG. 3 is a scanning electron microscope (SEM) photograph of a cross-section when an alloy material coating layer is formed on a current collector according to one embodiment of the present invention.

[0023] FIG. 4a is a scanning electron microscope (SEM) photograph of the surface when an ion concentration protective layer is formed on a current collector coated with an alloy material according to one embodiment of the present invention, and FIG. 4b is a scanning electron microscope (SEM) photograph of a cross-section.

[0024] FIG. 5 is a graph showing the bonding strength between a current collector and an ion concentration protective layer according to examples and comparative examples of the present invention.

[0025] FIGS. 6a and 6b are photographs comparing the appearance of electrodeposition between a current collector and an ion concentration protective layer when electrodeposited at the maximum current density according to one embodiment of the present invention, and FIG. 6c is a scanning electron microscope (SEM) photograph of the cross-sectional structure of a lithium metal layer formed on the lower surface of a protective layer by an electrodeposition process according to one embodiment of the present invention.

[0026] FIG. 7 is a graph evaluating the life of an all-solid-state battery cell using an electrode for a lithium secondary battery of an embodiment and a comparative example according to one embodiment of the present invention.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] FIG. 1a and FIG. 1b illustrate a lithium metal electrode (100) manufactured according to one embodiment.

[0032] 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).

[0033] 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).

[0034] 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, gold, platinum, silver, tantalum, ruthenium, and alloys thereof, carbon, conductive polymers, and composite fibers coated with a conductive layer on a non-conductive polymer.

[0035] 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.

[0036] 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 coating layer of the current collector (11) and lithium precipitated from the lithium source are alloyed by applying a current between the current collector (11) and a lithium source.

[0037] 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 deteriorates. 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 film, which is a surface protective layer of the lithium metal layer already formed in the electrodeposition process.

[0038] Specifically, since the metal layer (12) of one embodiment includes a lithium alloy layer containing a lithium component, when a high current is applied in the electrodeposition process to form a lithium metal layer on the lithium alloy layer, 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, and consequently the metal layer (12), can have a uniform surface.

[0039] 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.

[0040] The lithium alloy layer (21) may be an alloy composed of lithium and a lithium-friendly metal, wherein the lithium-friendly metal may be at least one selected from the group consisting of In, Ag, Sn, Zn, Si, Al, and Bi, but is not limited thereto.

[0041] 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 (11) to reduce lithium ions, thereby facilitating electrodeposition of the lithium metal layer. The metal layer (21) plays a role in helping lithium to be more effectively deposited under the protective layer during the charging process of the battery.

[0042] 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.

[0043] 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 consumed lithium 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.

[0044] The protective layer (30) is positioned on the metal layer (12) and may include amorphous carbon and silicate clay minerals. When lithium metal is used as an anode 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 the current density during the charge / discharge process, resulting in a failure or a decrease in battery capacity due to a short circuit or overvoltage during charge / discharge.

[0045] 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 amorphous carbon and silicate clay minerals together.

[0046] Specifically, the lithium metal electrode of the present embodiment includes a protective layer (30) including amorphous carbon and silicate clay minerals, thereby not only improving ion conductivity, but also improving the strength of the protective layer, and preventing short circuits between electrodes by physically blocking dendrites when they grow on the lithium electrode, thereby improving the charge / discharge life.

[0047] The above 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 is not limited thereto.

[0048] In one embodiment, the amorphous carbon may have an average particle size of 10 nm to 100 nm. If the average particle size of the amorphous carbon exceeds the upper limit of the aforementioned range, there is a problem that the contact area between the protective layer and the deposited lithium is reduced, resulting in a decrease in bonding strength. If the average particle size of the amorphous carbon exceeds the lower limit of the aforementioned range, there is a problem that it is difficult to ensure uniform dispersion of the slurry of the protective layer.

[0049] The above-mentioned silicate clay mineral may be a self-concentrating lithium ion material. Specifically, the silicate clay mineral may have a large specific surface area, high ion exchange capacity, and excellent adsorption performance. By including the aforementioned characteristics, it may not only increase the concentration of lithium ions within the protective layer (30), but also serve to uniformly distribute the lithium ions.

[0050] Accordingly, as lithium ions move uniformly within and at the interface of the protective layer (30) during the charging process of the battery, the growth of lithium dendrites can be suppressed when lithium is deposited under the protective layer (30). If lithium ions do not move uniformly within and at the interface of the protective layer (30), lithium dendrites may grow in areas where lithium ions are concentrated, causing a short circuit during the operation of the battery.

[0051] The above silicate clay mineral has high strength and can thus serve as a filler in the protective layer (30). The protective layer (30) not only improves mechanical strength by including the silicate clay mineral, thereby maintaining the proper formation of the protective layer during the lithium electrodeposition process, but also prevents dendrite growth of the lithium negative electrode during the charge / discharge process, thereby improving the lifespan by preventing short circuits between electrodes.

[0052] The above silicate clay mineral may have a 2:1 layered crystal structure. The 2:1 layered crystal structure may refer to a structure in which one octahedral layer is sandwiched between two tetrahedral layers. Specifically, the 2:1 layered crystal structure may be a structure in which the other anionic face of an octahedral layer that is not bonded to a tetrahedral layer in the 1:1 layered structure is bonded by the apex oxygen of another tetrahedral layer, and the apex oxygen substitutes for 2 / 3 of the hydroxide ions of the octahedral layer.

[0053] In one embodiment, the silicate clay mineral may have a layer charge per unit cell of 0.2 to 1.0. Specifically, the silicate clay mineral may have a layer charge per unit cell of 0.2 to 0.9. The layer charge per unit cell refers to the charge per unit formula of the clay mineral, and is generated by isomorphous substitution. When a negative charge is generated by isomorphous substitution, it can be balanced by cations present on the surface between lattice layers. Specifically, a 2:1 layered crystal structure can satisfy a layer charge per unit cell of 0.2 to 1.0.

[0054] In one embodiment, the silicate clay mineral may have a cation exchange capacity (me / 100g) of 80 to 150. Specifically, the cation exchange capacity may be 90 to 100. The cation exchange capacity refers to the total amount of cations adsorbed in a form exchangeable with other cations by electrical attraction to a certain amount of soil. Specifically, it refers to milliequivalents per 100 g of soil.

[0055] By meeting the aforementioned range, the bonding strength between the protective layer and the current collector is strengthened, and the battery life characteristics can be improved. If the aforementioned range is exceeded, the bonding strength between the protective layer and the current collector and the battery life characteristics can be degraded.

[0056] In one embodiment, the silicate clay mineral may include a monoclinic crystal structure. The monoclinic crystal is one of seven crystal systems that describe a crystal structure with three vectors, the three vectors having different lengths, having the shape of a square prism with four rectangles and two parallelograms, and two of the three angles formed by the three vectors are right angles and one (the angle forming the parallelogram) is not a right angle. Since the silicate clay mineral includes a monoclinic crystal structure, it has the advantage of improving the stacking speed of lithium.

[0057] In one embodiment, the silicate clay mineral may have an average particle size of 100 nm to 1,000 nm. If the average particle size of the silicate clay mineral exceeds the upper limit of the aforementioned range, there is a problem that large particles act as a resistive layer, thereby reducing lithium ion conductivity. If the average particle size of the silicate clay mineral exceeds the lower limit of the aforementioned range, there is a problem that the particle distribution of the clay mineral within the coating layer becomes uneven due to agglomeration between primary particles.

[0058] In one embodiment, the silicate clay mineral may include at least one of montmorillonite, nontronite, beidellite, vermiculite, volconscoite, hectorite, saponite, soconite, sorbokite, stevensite, clauconite, biotite, and svinfordite. The silicate clay mineral may satisfy the crystal structure, cation exchange capacity, and layer charge per unit volume described above.

[0059] In this way, by satisfying the above-described characteristics, the silicate clay mineral can improve the life characteristics of the battery by promoting the conduction of lithium ions by adsorbing a large amount of lithium ions on the surface of the silicate clay mineral and increasing the concentration of lithium ions.

[0060] In addition, when a small amount of silicate clay mineral is added to a liquid electrolyte, the concentration of lithium ions can be increased due to high ion exchange capacity and ion adsorption capacity, thereby improving ion conductivity within the liquid electrolyte. However, as in the present invention, by including the silicate clay mineral in the protective layer (30), not only does it play a role in improving ion conductivity, but it also improves the strength of the protective layer (30), and when dendrites grow on the lithium negative electrode, it physically blocks them, thereby preventing short circuits between electrodes, thereby improving the charge / discharge life.

[0061] The material of the aforementioned protective layer does not react well with the sulfide-based electrolyte material of an all-solid-state battery, exhibiting excellent chemical stability, thereby contributing to improved interfacial stability and enhanced charge-discharge life of the all-solid-state battery. The ion conductivity-promoting protective layer can be applied by preparing the above complex in a slurry form, and an additional binder may be included to prepare such a slurry.

[0062] In one embodiment, the protective layer (30) may have a weight ratio of amorphous carbon to silicate clay mineral of 97:3 to 65:35. Specifically, the weight ratio of amorphous carbon to silicate clay mineral may be 97:3 to 70:30.

[0063] If the content of the amorphous carbon in the protective layer (30) is excessively high, there is a problem that the effect according to the content of the silicate clay mineral is minimal. If the content of the silicate clay mineral in the protective layer (30) is excessively high, there is a problem that the silicate mineral acts as a barrier to lithium ion conduction rather than lithium ion concentration, thereby causing an increase in resistance and lowering the lithium ion conductivity.

[0064] 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.

[0065] 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 amorphous carbon, the silicate clay mineral, and water.

[0066] When the content of the binder satisfies the above-mentioned 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. When 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 the protective layer, and when the content of the binder is excessively more than the above-mentioned range, not only does it cause a decrease in energy density, but also the resistance of the protective layer is greatly increased, which causes a problem of interfering with lithium ion conduction.

[0067] 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 effect obtained by including the amorphous carbon and the silicate clay mineral prevents the formation of lithium dendrites on the surface of the protective layer, and allows lithium ions to penetrate well inside the protective layer and conduct, thereby allowing lithium to be precipitated from the lower surface of the protective layer.

[0068] 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.

[0069] Meanwhile, although not shown, the metal layer (12) of the present embodiment may further include a film layer (SEI, Solid-Electrolyte Interphase) located on the surface of the metal layer (12). The film layer is formed during the manufacturing process of the metal layer (12) by a reaction between lithium metal of an electrodeposited lithium source and a 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.

[0070] 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 located on the surface of the metal layer (12) is excessively thick, there is a problem that the lithium ion conductivity decreases and the interface resistance increases, resulting in a deterioration of the charge / discharge characteristics 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, it is preferable that the film layer has a thin thickness within the range satisfying the above thickness range and is uniformly and densely formed on the entire surface of the metal layer (12).

[0071] In one embodiment, the film layer may include one or more materials selected from the group consisting of Li-NCHO-based ionic compounds, Li-PCHO-based ionic compounds, LiF, and Li3N.

[0072] 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, thereby alloying a lithium-affinity component included in a coating layer formed on the current collector (11) with lithium precipitated from the lithium source.

[0073] The metal layer (12) may include a lithium-friendly metal. Here, the lithium-friendly metal may be, for example, one or more selected from the group consisting of In, Ag, Sn, Zn, Si, Al, and Bi, but is not limited thereto.

[0074] In one embodiment, the metal layer (12) is in a form that includes a lithium-philic metal. When the metal layer (12) including a lithium-philic metal is formed in this way, the free energy for nucleation of lithium particles can be lowered in the early stage of nucleation during the electrodeposition process, so that a lithium metal layer having a coarse particle structure can be formed even under high current and overvoltage conditions.

[0075] 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. In one embodiment, when the metal layer (12) satisfies the above thickness range, it is possible to maximize the energy density of the battery while improving the charge / discharge life of the battery, and also has the advantage of minimizing the time and cost of the electrodeposition process when forming the metal layer (12).

[0076] If the metal layer is too thin, the initial coulombic efficiency decreases due to initial irreversibility, and the charge-discharge performance deteriorates due to insufficient excess lithium. If the metal layer is too thick, not only does the battery's energy density decrease, but the process time and amount of metal raw materials used during the metal layer formation also increase.

[0077] In one embodiment, the metal layer (12) includes a protective layer (30) positioned on the surface of the metal layer (12), and may further include a film layer. For a detailed description of the protective layer (30) and the film layer, reference may be made to the description given above with reference to FIG. 1A. In addition, although FIGS. 1A and 1B illustrate that the metal layer (12) and the protective layer (30) are formed on one surface of the current collector (11), this is a non-limiting example, and may also include a case where they are formed symmetrically on both surfaces of the current collector (11).

[0078] Figure 2 is a schematic diagram of a method for manufacturing a lithium metal electrode of the present invention.

[0079] Referring to FIG. 2, a method for manufacturing a lithium metal electrode according to one embodiment includes the steps of forming a coating layer on at least one surface of a current collector using a coating composition including a lithium-philic component, forming a protective layer on the surface of the coating layer using a slurry including amorphous carbon and silicate clay mineral, placing 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 the lithium-philic component included in the coating layer and lithium precipitated from the lithium source are alloyed.

[0080] The step of forming a coating layer (20) on at least one surface of a current collector using a coating composition including a lithium-friendly component may include coating an alloy material on at least one surface of the current collector. Specifically, the coating layer (20) may be an alloy material coating layer. 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.

[0081] 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 (20) may be performed by coating using an electroless plating method.

[0082] Meanwhile, in the step of forming the coating layer (20), the thickness of the alloy material coating layer formed on at least one surface of the current collector may be 0.001 µm to 10 µm, specifically 0.01 µm to 1 µm, more specifically 150 to 400 nm, more specifically 200 to 400 nm, and more specifically 250 to 350 nm.

[0083] If the thickness of the coating layer (20) is excessively thin, it is insufficient to perform the role of forming lithium and a lithium alloy, and if the thickness is excessively thick, a large amount of cost and time are consumed in forming the alloy material coating layer (20), so that production efficiency and economic feasibility are reduced, and the weight and weight of the battery increase, resulting in a problem of lowering the energy density.

[0084] In the step of forming a protective layer (30) on the surface of the coating layer using a slurry containing amorphous carbon and silicate clay minerals, the weight ratio of amorphous carbon to silicate clay minerals may be 97:3 to 65:35. Specifically, the weight ratio of amorphous carbon to silicate clay minerals may be 97:3 to 70:30. For a detailed description and content of amorphous carbon and silicate clay minerals, reference may be made to the above-described contents of FIG. 1.

[0085] The protective layer (30) can be applied by applying a slurry formed by mixing the amorphous carbon, silicate clay mineral, and binder in water using at least one of the doctor blade method, the dip method, the reverse roll method, the direct roll method, the gravure method, the extrusion method, and the brush application method. The protective layer (30) can further include a binder, and for a detailed description thereof, reference can be made to the contents described above in FIG. 1.

[0086] Meanwhile, in the step of forming the protective layer (30), the thickness of the protective layer (30) formed on the surface of the coating layer (20) including the alloy material may be in the range of 0.01 µm to 50 µm, more specifically, 1 µm to 20 µm.

[0087] After the step of forming a protective layer (30), a current collector on which the alloy material coating layer (20) and the protective layer (30) are sequentially formed is positioned in the plating solution, and then a step of positioning a lithium source at a predetermined distance from the current collector (11), and a step of applying current between the current collector (11) and the lithium source to form a metal layer (12) are performed.

[0088] 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.

[0089] The plating solution (50) can be prepared by dissolving a lithium salt in a non-aqueous solvent. 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.

[0090] Specifically, in the present embodiment, the plating solution is characterized in that it contains a nitrogen-based compound as at least one of the lithium salt and the non-aqueous solvent. 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.

[0091] 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.

[0092] 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.

[0093] Meanwhile, the plating solution may be supplemented with a general non-aqueous solvent, taking into account the viscosity of the plating solution. If the viscosity of the plating solution is excessively high, the mobility of lithium ions decreases, thereby lowering the ionic conductivity of the plating solution, thus increasing the time required for the electrodeposition process and reducing productivity.

[0094] The 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.

[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 (21) on at least one surface of the current collector (11) 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 (21) on at least one surface of the current collector (11) by applying the current is 8 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 10 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, in the step of forming a lithium metal layer (21) on at least one surface of the current collector (11) by applying the current, the step of electrodepositing the deposited lithium to a thickness in the range of 5 to 15 μm may be included. 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 on at least one surface of the current collector by applying the current, the thickness of the metal layer including the lithium alloy can be controlled to 1 to 100 μm. For a detailed description of the thickness of the metal layer, reference may be made to the contents of the aforementioned Fig. 1.

[0104] In this way, in this embodiment, a lithium metal electrode can be manufactured in which a metal layer including a lithium metal layer having a coarse particle structure is formed by preventing the 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] <Formation of alloy material coating layer>

[0119] According to one embodiment of the present invention, a lithium metal electrode for a lithium secondary battery is formed by forming a coating layer (20) including an alloy material on a current collector, forming a lithium ion concentration protective layer thereon, and then forming a lithium or lithium alloy layer between the current collector and the protective layer through an electrodeposition method.

[0120] FIG. 3 is a scanning electron microscope (SEM) photograph of a cross-section when an alloy material coating layer is formed on a current collector according to one embodiment of the present invention.

[0121] Referring to FIG. 3, in order to manufacture a lithium metal electrode for a lithium secondary battery according to one embodiment of the present invention, a silver (Ag)-containing alloy material coating layer was formed by plating to a thickness of about 300 nm on both sides of a copper current collector using an electroless plating method.

[0122] <Formation of ion-concentrated protective layer>

[0123] FIG. 4a is a scanning electron microscope (SEM) photograph of the surface when the protective layer (30) of the present invention, which is an ion concentration protective layer, is formed on a current collector coated with an alloy material according to one embodiment of the present invention, and FIG. 4b is a scanning electron microscope (SEM) photograph of a cross-section.

[0124] Referring to FIGS. 4a and 4b, a lithium ion concentration protective layer of about 5 μm was formed on a copper current collector having a silver-containing alloy material coating layer by slurry coating using a comma coater. Specifically, the lithium ion concentration protective layer was formed by mixing acetylene black, which is an amorphous carbon, and montmorillonite (MMT), which is a clay-type mineral, at a weight ratio of 90:10. The slurry was prepared using water as a solvent, and additionally adding 3.0 wt% each of carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) binders.

[0125] Lithium electrodeposition process

[0126] Afterwards, lithium was removed from the lithium source using an electrodeposition process to form a lithium alloy or pure lithium metal between the ion concentration protective layer and the current collector, and lithium was deposited between the ion concentration 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 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.

[0127] 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.

[0128] 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.

[0129]

[0130] <Example 2>

[0131] In the step of forming the ion concentration protective layer, the weight ratio of amorphous carbon and the additive montmorillonite is 30:70, and the maximum electrodeposition current in the lithium electrodeposition process is 8 mA / cm. 2 A lithium metal electrode was manufactured in the same manner as in Example 1, except for this point.

[0132]

[0133] <Example 3>

[0134]

[0135] In the step of forming the ion concentration protective layer, nontronite is added as an additive in addition to montmorillonite, and the maximum electrodeposition current in the lithium electrodeposition process is 8 mA / cm. 2 A lithium metal electrode was manufactured in the same manner as in Example 1, except for this point.

[0136]

[0137] <Example 4>

[0138] In the step of forming the ion concentration protective layer, vermiculite is added as an additive in addition to montmorillonite, and the maximum electrodeposition current in the lithium electrodeposition process is 8 mA / cm. 2 A lithium metal electrode was manufactured in the same manner as in Example 1, except for this point.

[0139]

[0140] <Example 5>

[0141] In the step of forming the ion-concentrated protective layer, a lithium metal electrode was manufactured in the same manner as in Example 1, except that the weight ratio of amorphous carbon and the additive montmorillonite was 3:97.

[0142]

[0143] <Comparative Example 1>

[0144] In the step of forming the ion concentration protective layer, only 100 wt% of amorphous carbon was used without adding montmorillonite as an additive, and the maximum electrodeposition current in the lithium electrodeposition process was 6 mA / cm. 2 A lithium metal electrode was manufactured in the same manner as in Example 1, except for this point.

[0145]

[0146] <Comparative Example 2>

[0147] In the step of forming the ion concentration protective layer, kaolinite is added as an additive in addition to montmorillonite, and the maximum electrodeposition current in the lithium electrodeposition process is 4 mA / cm. 2 A lithium metal electrode was manufactured in the same manner as in Example 1, except for this point.

[0148]

[0149] <Comparative Example 3>

[0150] In the step of forming the ion concentration protective layer, chlorite is added as an additive in addition to montmorillonite, and the maximum electrodeposition current in the lithium electrodeposition process is 4 mA / cm. 2 A lithium metal electrode was manufactured in the same manner as in Example 1, except for this point.

[0151]

[0152] <Comparative Example 4>

[0153] In the step of forming the ion-concentrated protective layer, the weight ratio of amorphous carbon and the additive montmorillonite is 1:99 and the maximum electrodeposition current is 6 mA / cm. 2 A lithium metal electrode was manufactured in the same manner as in Example 1, except for this point.

[0154]

[0155] Comparative Example 5

[0156] In the step of forming the ion-concentrated protective layer, the weight ratio of amorphous carbon and the additive montmorillonite is 40:60 and the maximum electrodeposition current is 4 mA / cm. 2 A lithium metal electrode was manufactured in the same manner as in Example 1, except for this point.

[0157]

[0158] <Comparative Example 6>

[0159] The maximum electrodeposition current in the lithium electrodeposition process is 15 mA / cm 2 A lithium metal electrode was manufactured in the same manner as in Example 1, except for this point.

[0160]

[0161] All-solid-state battery manufacturing

[0162] 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 (Li6P5Cl) 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.

[0163] Lithium having a thickness of 0.5 mm was attached to one side of the electrolyte as a reference electrode, and the negative electrode manufactured according to the examples and comparative examples was attached to the opposite side. The reference electrode and the evaluation electrode were pressurized at a pressure of 50 MPa.

[0164] Lithium having a thickness of 0.5 mm was attached as a reference electrode to one side of the electrolyte, and the negative electrode manufactured according to the examples and comparative examples was attached to the opposite side.

[0165]

[0166] <Evaluation Example 1>

[0167] Table 1 below shows the bonding strength between the current collector and the protective layer according to the presence and content of montmorillonite as an additive in the ion-concentrating protective layer. The bonding strength, maximum current density, and charge-discharge performance number between the current collector and the protective layer were measured.

[0168] Bonding strength between the current collector and the protective layer: After the step of forming the ion-concentrating protective layer described above, the bonding strength between the coating layer (20) and the current collector (11) was measured using a peel strength meter. Specifically, a 10 mm wide polyimide tape (No. 360A, thickness: 0.08 mm, adhesive strength: 4.4 N / 19 mm) from Nitto was adhered on the protective layer, and then the bonding strength was measured through a tensile test using a peel strength meter (AND, MCT-2150 W). At this time, the tensile speed was 50 mm / min, and the tensile test distance was set to be within 200 mm in total. The bonding strength was obtained as the average strength over a 100 mm section starting from the 50 mm point in the tensile test.

[0169] 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.

[0170] 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 2 Charge 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.

[0171] Classification Additive [wt%] Amorphous carbon [wt%] Additive type Sheet bonding strength [N / cm] Charge / discharge performance Number of cycles [cycles] Example 1 1090 MMT 0.059872 Example 2 3070 MMT 0.272744 Comparative example 10100-0.009418

[0172] Referring to Table 1 above, Examples 1 and 2, in which montmorillonite was added, showed superior bonding strength between the current collector and the ion-concentrating protective layer, compared to Comparative Example 1, in which the protective layer was formed only with amorphous carbon without the addition of montmorillonite. In addition, when Examples 1 and 2 were compared, it was confirmed that the higher the content of the additive, the better the bonding strength between the current collector and the ion-concentrating protective layer.

[0173] In addition, when examining the number of charge / discharge performances of the lithium negative electrode compared to Examples 1 and 2, it can be confirmed that Examples 1 and 2 are superior to Comparative Example 1.

[0174] FIG. 5 is a graph showing the bonding strength between a current collector and an ion concentration protective layer according to examples and comparative examples of the present invention.

[0175] Referring to FIG. 5, it can be confirmed that Examples 1 and 2, which are examples of the present invention, in which the content of montmorillonite was added at 10 wt% and 30 wt%, respectively, have higher bonding strength compared to Comparative Example 1, in which a protective layer was formed only with amorphous carbon without the addition of montmorillonite. Specifically, looking at Examples 1 and 2, it can be confirmed that the bonding strength increases as the content of montmorillonite increases.

[0176]

[0177] <Evaluation Example 2> - Additive Type and Maximum Current Density Control

[0178] Table 1 below shows the bonding strength, maximum current density, and charge / discharge performance number between the current collector and the protective layer measured according to the type and characteristics of the additive in the ion concentration protective layer.

[0179] Additive [wt%] Amorphous carbon [wt%] Additive Sheet bonding strength [N / cm] Maximum current density [mA / cm 2 ]Charge and discharge performance Number of times [times] Type Layered Expansion Whether or not Crystal structure Unit cell per layer Charge (X) Cation exchange capacity (me / 100g) Example 1 1090 MMT 2:1 Expanded lattice Monoclinic 0.2~0.680~1500.05 9 10872 Example 3 1090 Nontronite 2:1 Expanded lattice Monoclinic 0.2~0.680~1500.05 58826 Example 4 1090 Vermiculite 2:1 Expanded lattice Monoclinic 0.6~0.980~1500.06 387 30 Comparative Example 2 1090 Kaolinite 1:1 Non-expanded lattice Triclinic 0.3~150.05 24 328 Comparative Example 3 1090 Chlorite Mixed-layered - Trigonal - 10~400.06 14 394

[0180] Looking at Table 2 above, it was confirmed that Comparative Examples 2 and 3 using kaolinite and chlorite had inferior maximum current density and charge / discharge performance number compared to Examples 1, 3, and 4 using montmorillonite, nontronite, and vermiculite as the type of additive.

[0181]

[0182] <Evaluation Example 3> - Evaluation Example Based on Additive Content and Maximum Current Density

[0183] Table 3 below shows the bonding strength between the current collector and the protective layer, the maximum current density, and the number of charge / discharge cycles of the battery according to the content of amorphous carbon and the content of additives in the ion-concentrating protective layer.

[0184] Classification Additive [wt%] Amorphous carbon [wt%] Additive type Sheet bonding strength [N / cm] Maximum current density [mA / cm 2 ]Charge and discharge performance times [times]Example 11090MMT0.05910872Example 5397MMT0.03510912Example 23070MMT0.2728744Comparative example 4199MMT0.0156583Comparative example 54060MMT0.3024558Comparative example 61090MMT0.05915346

[0185] Referring to Table 3 above, it was confirmed that Comparative Example 4, which had an excessively low additive content compared to Examples 1, 5, and 6, which are within the scope of the present invention, had inferior bonding strength and charge / discharge cycle performance. In contrast to Examples 1, 5, and 6, it was confirmed that Comparative Example 5, which had an excessively high additive content, had inferior maximum electrodeposition current density and charge / discharge cycle performance. FIGS. 6a and 6b are photographs comparing the appearance of electrodeposition between a current collector and an ion concentration protective layer when electrodeposited at the maximum current density according to an embodiment of the present invention, and FIG. 6c is a scanning electron microscope (SEM) photograph of a cross-sectional structure of a lithium metal layer formed on the lower surface of a protective layer by an electrodeposition process according to an embodiment of the present invention.

[0186] Figure 6a is a photograph showing the appearance after electrodeposition of Example 1, in which lithium is deposited between the current collector and the ion concentration protective layer when electrodeposition is performed at the maximum current density. Figure 6b shows a comparison of the appearance when lithium is deposited on the ion concentration protective layer when electrodeposition is performed at a current density exceeding the maximum current density.

[0187] When electrodeposition is performed at a current density lower than the maximum possible for electrodeposition, as shown in Fig. 6c, the precipitated lithium is deposited under the black protective layer, so a black protective layer is visible in appearance. When electrodeposition is performed at a current density exceeding this, as shown in Comparative Example 6, it was confirmed that 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.

[0188] FIG. 7 is a graph evaluating the life of an all-solid-state battery cell using an electrode for a lithium secondary battery of an embodiment and a comparative example according to one embodiment of the present invention.

[0189] Referring to Fig. 7, when examining the evaluation of the all-solid-state battery cell life of Example 1 and Comparative Example 1, it was confirmed that the cell life characteristics of Example 1 were better than those of Comparative Example 1.

[0190]

[0191] 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 comprising lithium or a lithium alloy, positioned on at least one surface of the above-described collector; and A protective layer positioned on the above metal layer is included, The above protective layer is a lithium metal electrode comprising amorphous carbon and a silicate clay mineral having a 2:1 layered crystal structure.

2. In paragraph 1, The above protective layer is a lithium metal electrode having a weight ratio of the amorphous carbon to the silicate clay mineral of 97:3 to 65:

35.

3. In paragraph 1, The above silicate clay mineral is a lithium metal electrode containing a monoclinic crystal.

4. In paragraph 1, The above silicate clay mineral is a lithium metal electrode having a layer charge per unit area of ​​0.2 to 0.

6.

5. In paragraph 1, The above silicate clay mineral is a lithium metal electrode having a cation exchange capacity (me / 100g) of 80 to 150.

6. In paragraph 1, A lithium metal electrode having a bonding strength between the entire collector and the protective layer of 0.030 to 0.30 N / cm.

7. In paragraph 1, A lithium metal electrode, wherein the metal layer including the lithium alloy is a composite layer including at least one of In, Ag, Sn, Zn, Si, Al, and Bi.

8. In paragraph 1, A lithium metal electrode having an average thickness of the metal layer of 1 ㎛ to 100 ㎛.

9. In paragraph 1, A lithium metal electrode having an average thickness of the protective layer of 1 ㎛ to 20 ㎛.

10. 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; A step of forming a protective layer on the surface of the coating layer using a slurry containing amorphous carbon and silicate clay minerals having a 2:1 layered crystal structure; A step of positioning a current collector having the coating layer and protective layer formed in the 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.

11. In Article 10, A method for manufacturing a lithium metal electrode, wherein the weight ratio of the amorphous carbon to the silicate clay mineral is mixed in a range of 97:3 to 65:35 in the step of forming the protective layer.

12. In paragraph 10, In the step of applying a current between the above-described collector and the lithium supply source to form a metal layer including a lithium alloy in which the lithium-friendly component included in the coating layer and lithium precipitated from the lithium supply source are alloyed, 8 to 12 mA / cm 2 A method for manufacturing a lithium metal electrode, comprising the step of electrodepositing at a maximum current density in the range.

13. In paragraph 10, In the step of applying a current between the above-described collector and the lithium supply source to form a metal layer including a lithium alloy in which the lithium-friendly component included in the coating layer and lithium precipitated from the lithium supply source are alloyed, A method for manufacturing a lithium metal electrode, comprising a step of depositing precipitated lithium to a thickness in the range of 5 to 15 ㎛.

14. In paragraph 10, In the step of forming a protective layer on the surface of the coating layer using a slurry containing amorphous carbon and silicate clay minerals having a 2:1 type crystal structure, A method for manufacturing a lithium metal electrode, comprising a step of slurry coating such that the thickness of the protective layer becomes 1 to 20 ㎛.

15. In paragraph 10, The current density of the current applied in the step of forming a lithium metal layer on at least one surface of the above collector is 0.1 mA / cm 2 Within 100 mA / cm 2 A method for producing a lithium metal electrode.

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