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

Abstract

The present invention relates to a lithium metal electrode, and a method for 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 which includes a lithium alloy; and a protective layer which is disposed on the metal layer and which includes a carbon-based material, wherein at least one of a nitrogen-based alloy and a magnesium-based alloy is included in a region between the metal layer and the protective layer and / or a region inside the protective layer.

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, dendrite growth, caused by uneven current density and electrochemical reactions during the charging and discharging of secondary batteries, poses a challenge. This can lead to persistent side reactions with the electrolyte and even internal short circuits where the cathode and anode contact each other. This dendrite growth can also cause significant problems, including poor cycle life and stability.

[0005] While various methods have been proposed to suppress dendrite growth and extend battery life, it remains challenging to simultaneously achieve high energy density through ultrathin lithium and sufficient battery life characteristics. Various methods have been proposed to suppress dendrite growth, including using amorphous carbon alone as a protective layer on a lithium metal electrode or in combination with expensive lithium-affinity metals. However, these methods fail to achieve sufficient lithium deposition speed and charge / discharge life characteristics.

[0006] 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.

[0007] 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.

[0008] According to one embodiment of the present invention, a lithium metal electrode may include a current collector, a metal layer positioned on at least one surface of the current collector and including a lithium alloy, a protective layer disposed on the metal layer and including a carbon-based material, and an alloy layer including at least one of a nitrogen-based and a magnesium-based alloy in at least one region between the metal layer and the protective layer and within the protective layer. In one embodiment, the lithium metal electrode may have at least one peak value from among 21 to 25°, 26 to 30°, 35 to 39°, 45 to 47°, 48 to 51°, and 54 to 56° in XRD peak values.

[0009] In one embodiment, the XRD peak value may satisfy the following equation 1.

[0010] <Formula 1>

[0011] 3 ≤ 2nd peak value / 1st peak value × 100(%) ≤ 10

[0012] (In the above equation 1, the first peak value is the intensity value at 44 to 46°, and the second peak value is the intensity value at 26 to 30°)

[0013] In one embodiment, the XRD peak value may satisfy Equation 2 below.

[0014] <Formula 2>

[0015] 3 ≤ 3rd peak value / 1st peak value × 100(%) ≤ 10

[0016] (In the above equation 2, the first peak value is the intensity value at 44 to 46 °, and the third peak value is the intensity value at 35 to 39 °)

[0017] In one embodiment, the XRD peak value may satisfy Equation 3 below.

[0018] <Formula 3>

[0019] 3 ≤ (second peak value + third peak value) / first peak value × 100(%) ≤ 20

[0020] (In the above equation 3, the first peak value is the intensity value at 44 to 46 °, the second peak value is the intensity value at 26 to 30 °, and the third peak value is the intensity value at 35 to 39 °)

[0021] In one embodiment, the protective layer may include a film layer disposed over the protective layer. In one embodiment, the protective layer may include a carbon-based material and a metal fluoride or metal nitride.

[0022] According to another embodiment of the present invention, a method for manufacturing a lithium metal electrode includes the steps of preparing a current collector, forming a coating layer on at least one surface of the current collector using a coating composition including a lithium-philic component, and coating a slurry on the surface of the coating layer to form a protective layer, wherein the slurry may include a carbon-based material and at least one of a metal fluoride and a metal nitride. In one embodiment, after the step of forming the protective layer, the method may include the steps of: positioning the current collector on which the protective layer is 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 metal particles included in the protective layer are alloyed with lithium precipitated from the lithium source.

[0023] In one embodiment, the metal fluoride or metal nitride may include at least one of MgF2, Mg3N2, AgF, and Ag3N. In one embodiment, before applying a current between the current collector and the lithium source, the XRD peak value of the protective layer may have a peak value between 16 and 18°.

[0024] In one embodiment, after applying a current between the current collector and the lithium source, the metal layer may include a nitrogen-based or magnesium-based alloy. In one embodiment, the slurry may include a content of amorphous carbon of 70 to 95 wt% based on 100 wt% of the total amount of the metal material including amorphous carbon and metal fluoride or metal nitride.

[0025] In one embodiment, the slurry includes amorphous carbon, metal fluoride, and metal nitride, and the combined amount of the metal fluoride and the metal nitride may include 8 to 30 wt% based on 100 wt% of the combined amount of the amorphous carbon, the metal fluoride, and the metal nitride. In one embodiment, in 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 the metal particles and lithium precipitated from the lithium source are alloyed, a current of 6 to 12 mA / cm 2 It includes a step of electrodeposition at the maximum current density of the range.

[0026] According to one embodiment of the present invention, a lithium metal electrode for a lithium secondary battery mixes amorphous carbon and metal fluoride or metal nitride in a protective layer and forms an alloy between lithium metals or an SEI layer advantageous for charge and discharge during an electrodeposition process, thereby improving lithium ion conductivity, increasing the lithium stacking speed, and providing a lithium secondary battery with improved charge and discharge life characteristics.

[0027] 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 having the above-described advantages.

[0028] Figures 1a and 1b illustrate a lithium metal electrode manufactured according to one embodiment.

[0029] Figure 2 is a schematic diagram of a method for manufacturing a lithium metal electrode of the present invention.

[0030] Figures 3a and 3b show the microstructure of the surface and cross-section when a protective layer is placed on the collector.

[0031] Figures 4a and 4b show the microstructure of the surface and cross-section when a protective layer is placed on the collector.

[0032] 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.

[0033] Figures 6a to 6c show the results of XRD phase analysis before and after lithium deposition on the protective layer according to examples and comparative examples of the present invention.

[0034] Figure 7 shows the cell life evaluation of an all-solid-state battery using an example and a comparative example of the present invention.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] FIG. 1a and FIG. 1b illustrate a lithium metal electrode (100) manufactured according to one embodiment.

[0040] Referring to FIG. 1a, a lithium metal electrode (100) according to one embodiment includes a current collector (10), a metal layer (20) disposed on at least one surface of the current collector (10), and a protective layer (30) disposed on the metal layer (20).

[0041] The current collector (10) may be a member for electrical connection within a lithium secondary battery. The current collector (10) 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).

[0042] The current collector (10) may be made of a material that is electrically conductive and has limited reaction with lithium. Specifically, the material of the current collector (10) 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.

[0043] In one embodiment, the thickness of the current collector (10) may be 1 μm to 50 μm. If the thickness of the current collector (10) is excessively thick, there is a problem that the weight of the battery increases, thereby lowering the energy density of the battery. If the thickness of the current collector (10) is excessively thin, there is a risk of overheating damage during high-current operation, and damage may occur due to tension during the battery manufacturing process.

[0044] The metal layer (20) is positioned on the current collector (10) and may include a lithium alloy layer (21) including a lithium alloy and a lithium metal layer (22) 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 (20) and lithium precipitated from the lithium source (40) are alloyed by applying a current between the current collector (10) and the lithium source (40 in FIG. 2).

[0045] When the electrodeposition process is performed by applying a high current to increase the speed of electrodeposition during the formation of the metal layer (20), 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 lithium metal layer (22) already formed in the electrodeposition process.

[0046] Specifically, since the metal layer (20) 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 (22) 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 (22), and consequently the metal layer (20), can have a uniform surface.

[0047] 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.

[0048] In this embodiment, the lithium alloy layer (21) includes a lithium-philic metal. The lithium-philic metal may be, for example, one or more selected from the group consisting of In, Ag, Sn, Zn, Si, Al, and Bi. In this way, when the lithium alloy layer (21) includes a lithium-philic metal, since it includes a lithium-philic metal with high electronic conductivity, electrons are smoothly supplied from the current collector, and lithium ions are reduced, so that electrodeposition of the lithium metal layer is easily performed, which has the advantage of being advantageous. The metal layer (20) plays a role in helping lithium to be more effectively deposited under the protective layer (30) during the charging process of the battery.

[0049] In one embodiment, the thickness of the metal layer (20) 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 (20) 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 (20), the thickness of the metal layer (20) is preferably 100 μm or less.

[0050] When the thickness of the metal layer (20) 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 lithium contained in the negative active material layer, i.e., the metal layer of the present invention, and the electrolyte, etc., 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 (20) is preferably 1 ㎛ or more.

[0051] The protective layer (30) is disposed on at least one surface of the current collector (10) and may include a carbon-based material and a metal fluoride or a metal nitride. The carbon-based material may include, for example, amorphous carbon. The amorphous carbon may be, for example, 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. The amorphous carbon may be in a powder form.

[0052] The above metal fluoride is M x F y It can be. Specifically, the metal fluoride can be a material such as, for example, MgF2 or AgF. The metal nitride is M x N z It can be. Specifically, the metal nitride can be, for example, Mg3N2 or Ag3N.

[0053] 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. The thickness of the protective layer (30) may refer to the average thickness of the area excluding the alloy layer (AL). By satisfying the above-described range in the thickness of the protective layer (30), an ultra-thin lithium metal electrode can be provided.

[0054] If the thickness of the protective layer (30) exceeds the upper limit of the aforementioned range, the resistance of the protective layer becomes excessively large, which may cause an increase in overvoltage during the operation of the secondary battery, and there is a problem of causing a decrease in the battery energy density due to an increase in weight and volume. If the thickness of the protective layer (30) exceeds the lower limit of the aforementioned range, there is a problem of the protective layer not being able to function.

[0055] 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, one or more selected from the group consisting of a rubber-based binder selected from the group consisting of acrylonitrile-butadiene rubber, styrene-butadiene rubber (SBR), and acrylic rubber, and a group consisting of polymer resins such as hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinylidene fluoride.

[0056] 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 100 parts by weight of the combined amount of the carbon-based material and the alloy layer (AL) component. 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.

[0057] 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.

[0058] In one embodiment, an alloy layer (AL) including at least one of a nitrogen-based and a magnesium-based alloy may be included in at least one region between the metal layer (20) and the protective layer (30) and within the protective layer (30). The alloy layer (AL) including at least one of a nitrogen-based and a magnesium-based alloy may be formed by a reaction between a metal fluoride or a metal nitride included in the protective layer (30) and lithium supplied during a lithium electrodeposition process. For example, when magnesium nitride (Mg3N2) is used as the metal nitride, a nitrogen-based alloy such as Li3N may be formed through a reaction between the nitrogen element included in the magnesium nitride and lithium ions during the electrodeposition process. In addition, when magnesium fluoride (MgF2) is used as the metal fluoride, a magnesium-based alloy such as LiMg may be formed through a combination of the magnesium element included in the magnesium fluoride and lithium ions during the electrodeposition process.

[0059] Thus, the alloy layer (AL) comprising at least one of a nitrogen-based and a magnesium-based alloy is formed during the lithium electrodeposition process, and is advantageous for lithium ion conduction and exhibits excellent mechanical properties. Therefore, when applied to a battery, it can enhance the charge-discharge performance of the battery. Furthermore, since lithium electrodes can be manufactured through lithium electrodeposition and electrodeposition can be performed at high currents, lithium anodes can be manufactured at high speeds.

[0060] In one embodiment, an alloy layer (AL) including at least one of a nitrogen-based and a magnesium-based alloy may be disposed in at least one region between the metal layer (20) and the protective layer (30) and within the protective layer (30). As described above, since the alloy layer (AL) is formed by a reaction between lithium ions and a metal fluoride or metal nitride added to the protective layer during a lithium electrodeposition process, the alloy layer (AL) may be formed between the metal layer (20) and the protective layer (30), and may also be disposed within the protective layer (30), for example, in a lower region of the protective layer (30).

[0061] In one embodiment, the lithium metal electrode (100) may further include a film layer disposed on at least a portion of the protective layer (30). The film layer may be formed during the manufacturing process of the metal layer (20) by reacting not only the lithium metal of the electrodeposited lithium source (40) with the plating solution, but also with the metal fluoride or metal nitride within the protective layer (30). 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, and can also be controlled by adjusting the content of the metal fluoride or metal nitride.

[0062] In one embodiment, the film layer may include at least a portion of LiF. By including at least a portion of LiF, the film layer can improve the lifespan and prevent dendrite growth during battery operation due to high ionic conductivity.

[0063] 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 over the entire protective layer (30).

[0064] In one embodiment, the lithium metal electrode (100) may have at least one of the XRD peak values ​​of 21 to 25°, 26 to 30°, 35 to 39°, 45 to 47°, 48 to 51°, and 54 to 56°. The aforementioned peak values ​​may be exhibited when the lithium metal electrode (100) includes at least one of a nitrogen-based alloy and a magnesium-based alloy. For example, when the lithium metal electrode (100) includes a nitrogen-based alloy, the XRD peak values ​​may include at least one of 21 to 25°, 26 to 30°, 45 to 47°, 48 to 51°, and 54 to 56°. When the lithium metal electrode (100) includes a magnesium-based alloy, the XRD peak values ​​may include 35 to 39°. The aforementioned XRD peak values ​​may be due to the lithium metal electrode (100) including an alloy layer (AL) including at least one of a nitrogen-based and a magnesium-based alloy between the metal layer (20) and the protective layer (30) or in the internal region of the protective layer (30).

[0065] In one embodiment, the lithium metal electrode (100) may have an XRD peak value satisfying the following equation 1.

[0066] <Formula 1>

[0067] 3.0 ≤ second peak value / first peak value × 100(%) ≤ 10.0

[0068] (In the above equation 1, the first peak value is the intensity value at 44 to 46°, and the second peak value is the intensity value at 26 to 30°)

[0069] The above formula 1 may be an indicator of whether a nitrogen-based alloy is formed. The above formula 1 may satisfy 3 to 10, more specifically, 5 to 8. By satisfying the above-described range, the nitrogen-based alloy is formed in an appropriate amount, which is advantageous for lithium ion conduction.

[0070] If the above equation 1 exceeds the upper limit of the aforementioned range, there is a problem that the mechanical strength of the alloy layer (AL) is reduced due to excessive production of nitrogen-based alloy. If the above equation 1 exceeds the lower limit of the aforementioned range, there is a problem that the lithium ion conductivity is low due to insufficient production of nitrogen-based alloy.

[0071] In one embodiment, the lithium metal electrode (100) may have an XRD peak value satisfying the following equation 2.

[0072] <Formula 2>

[0073] 3 ≤ value of the third peak / value of the first peak × 100(%) ≤ 10

[0074] (In the above equation 2, the first peak value is the intensity value at 44 to 46 °, and the third peak value is the intensity value at 35 to 39 °)

[0075] The above formula 2 may be an indicator of whether a magnesium alloy is formed. The above formula 2 may satisfy 3 to 10, more specifically, 5 to 8. By satisfying the above-mentioned range, the magnesium alloy is formed in an appropriate amount and easily combines with lithium ions during charging and discharging, thereby having the advantage of improving the conduction of lithium ions.

[0076] If the above equation 2 exceeds the upper limit of the aforementioned range, an excess of magnesium-based alloy is generated, which reduces the amount of lithium available to replenish the lithium consumed during charge and discharge, thereby reducing the charge and discharge life of the battery. If the above equation 2 exceeds the lower limit of the aforementioned range, there is a problem in that the effect of improving lithium ion conduction is reduced due to an insufficient amount of magnesium-based alloy.

[0077] In one embodiment, the lithium metal electrode (100) may have an XRD peak value satisfying the following equation 3.

[0078] <Formula 3>

[0079] 3 ≤ (second peak value + third peak value) / first peak value × 100(%) ≤ 20

[0080] (In the above equation 3, the first peak value is the intensity value at 44 to 46 °, the second peak value is the intensity value at 26 to 30 °, and the third peak value is the intensity value at 35 to 39 °)

[0081] The above formula 3 may be an indicator of whether a nitrogen-based and magnesium-based alloy is formed. The above formula 3 may satisfy 3 to 20, more specifically 8 to 12. Since the above formula 3 satisfies the above-mentioned range, there is an advantage in lithium ion conductivity and mechanical strength.

[0082] If the above equation 3 exceeds the upper limit of the aforementioned range, there is a problem of reduced mechanical strength or reduced charge / discharge life. If the above equation 3 exceeds the lower limit of the aforementioned range, there is a problem of low lithium ion conductivity.

[0083] Referring to FIG. 1B, in one embodiment, a lithium metal electrode (100) includes a current collector (10), a metal layer (20') positioned on at least one surface of the current collector (10), which is composed of a mixture of lithium and a lithium alloy, and a protective layer (30) disposed on the metal layer (20'). Here, the lithium alloy may be formed by applying a current between the current collector (10) and a lithium source (40), thereby alloying a lithium-philic component included in the metal layer (20') formed on the current collector (10) with lithium precipitated from the lithium source (40).

[0084] The metal layer (20') may include a lithium-philic metal. In one embodiment, the metal layer (20') includes a lithium-philic metal. When the metal layer (20') 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, thereby forming a lithium metal layer having a coarse particle structure even under high current and overvoltage conditions.

[0085] In one embodiment, an alloy layer (AL) including at least one of a nitrogen-based and a magnesium-based alloy may be included in at least one region between the metal layer (20') and the protective layer (30) and within the protective layer (30). A detailed description thereof may be provided with reference to FIG. 1A.

[0086] In one embodiment, the metal layer (20') includes a protective layer (30) positioned on the surface of the metal layer (20') 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.

[0087] Figure 2 is a schematic diagram of a method for manufacturing a lithium metal electrode (100) of the present invention.

[0088] Referring to FIG. 2, a method for manufacturing a lithium metal electrode (100) according to one embodiment includes a step of preparing a current collector (10), a step of forming a coating layer (20) on at least one surface of the current collector (10) using a coating composition including a lithium-philic component, and a step of forming a protective layer (30) by coating slurry on the surface of the coating layer.

[0089] In the step of preparing the current collector (10), the current collector (10) may be made of a material that is electrically conductive and has limited reaction with lithium. Specifically, the material of the current collector (10) may be, for example, one or a combination of 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.

[0090] In one embodiment, the step of forming the coating layer (20) may be performed using at least one of electrolytic and electroless plating, sputtering, electron beam, and thermal vapor deposition. For example, the step of forming the coating layer (20) may be coated using an electroless plating method.

[0091] 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.

[0092] In one embodiment, the slurry may include amorphous carbon and at least one of a metal fluoride and a metal nitride. The metal fluoride may be M x F y It can be. Specifically, the metal fluoride can be a material such as, for example, MgF2 or AgF. The metal nitride is Mx N z It can be. Specifically, the metal nitride can be, for example, Mg3N2 or Ag3N. By including a metal material including at least one of a metal fluoride and a metal nitride as well as amorphous carbon in the slurry, a protective layer (30) that is advantageous for lithium ion conduction and mechanical properties and prevents the growth of dendrites can be formed. In addition, by including a metal material including at least one of the metal fluoride and the metal nitride, an alloy layer including at least one of a nitrogen-based and a magnesium-based alloy can be formed in a subsequent lithium electrodeposition process, thereby improving the performance of the battery.

[0093] In one embodiment, the slurry may include a content of amorphous carbon of 70 to 95 wt% based on 100 wt% of the total amount of the metal material including amorphous carbon and metal fluoride or metal nitride. Specifically, the content of the amorphous carbon may include 70 to 92 wt%, and more specifically, 75 to 85 wt%. By including the content of amorphous carbon in the slurry within the above-described range, the maximum current density during lithium electrodeposition can be improved, thereby increasing electrodeposition efficiency, and there is an advantage in that the number of charge / discharge cycles of the battery increases, thereby improving life characteristics.

[0094] In one embodiment, when the slurry simultaneously includes amorphous carbon, metal fluoride, and metal nitride, the combined amount of the metal fluoride and the nitride may be 8 to 30 wt% based on 100 wt% of the combined amount of the amorphous carbon, metal fluoride, and metal nitride.

[0095] When the content of the above amorphous carbon is excessively high, the content of the metal material including metal fluoride or metal nitride becomes excessively low, so that the amount of magnesium-based alloy or nitrogen-based alloy produced is insufficient, which causes a problem of hindering the improvement of lithium ion conductivity. When the content of the above amorphous carbon is excessively low, the content of the metal material including metal fluoride or metal nitride becomes excessive, so that the amount of magnesium-based alloy or nitrogen-based alloy produced is excessive, so that the amount of lithium retained that can replenish lithium consumed during charge and discharge becomes low, which causes a problem of reduced charge and discharge life of the battery or reduced mechanical strength.

[0096] A protective layer (30) can be formed on the surface of a current collector (10) using a slurry containing a carbon-based material and a metal material including at least one of a metal fluoride and a metal nitride. 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. For a detailed description of the carbon-based material and the metal material, reference can be made to the aforementioned FIG. 1A.

[0097] In one embodiment, the step of forming the protective layer (30) may include coating the slurry in a range of 3 to 10 μm. Specifically, the slurry may be coated in a range of 4 to 7 μm. As the slurry is coated in the aforementioned range, not only does it function as a protective layer by having an appropriate thickness of the protective layer (30), but it also prevents lithium dendrites from forming on the surface of the protective layer due to the effect of having an appropriate resistance for the movement of lithium ions, and enables lithium to penetrate well into the interior of the protective layer (30) and conduct, thereby allowing lithium to be precipitated from the lower surface of the protective layer.

[0098] 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.

[0099] In one embodiment, the slurry may further include a binder. The binder may be added in an amount of 1 to 15 parts by weight, specifically 3 to 10 parts by weight, based on 100 parts by weight of the total amount of the amorphous carbon and the metal material. When the content of the binder satisfies the above-described range, the particles constituting the protective layer are efficiently bound together 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.

[0100] 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.

[0101] In one embodiment, a method for manufacturing a lithium metal electrode includes, after a step of forming a protective layer (30), a step of positioning a current collector (10) on which a protective layer (30) is formed in a plating solution (50), and then positioning a lithium source (40) at a predetermined distance from the protective layer (30), and a step of applying a current between the current collector and the lithium source (40) 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 (40) are alloyed.

[0102] After the step of forming a protective layer (30), a step of positioning a current collector (10) on which the protective layer (30) is formed in a plating solution (50), a step of positioning a lithium supply source (40) at a predetermined distance from the current collector (10), and a step of applying current between the current collector (10) and the lithium supply source (40) to form a metal layer (20) are performed.

[0103] Specifically, after positioning a current collector (10) having 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). For example, the lithium supply source (40) may be 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] The 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.

[0109] 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.

[0110] 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 deposition time, but is not limited thereto.

[0111] 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 on the metal layer or protective layer can be improved.

[0112] 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.

[0113] 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 there is an excellent advantage in that the film layer properties are improved. 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.

[0114] Next, after positioning an insulating film between the current collector (10) and the lithium supply source (40), the current collector (10), the lithium supply source (40), 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 be a method commonly used in the art, such as a manual clamping method, a uniaxial pressurization method such as hydraulic pressure, or pneumatic pressure.

[0115] In the step of forming a metal layer containing lithium on at least one surface of the collector by applying the 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.

[0116] 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.

[0117] 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.

[0118] In one embodiment, the step of forming a metal layer (20) on at least one surface of the current collector (10) 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 (10).

[0119] 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 (10) and the protective layer (30). By satisfying the above-described range, lithium is appropriately deposited between the current collector (10) and the protective layer (30), thereby providing the advantages of excellent battery life characteristics and bonding strength between the current collector (10) and the protective layer (30).

[0120] 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.

[0121] 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 (10) and the protective layer (30).

[0122] 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 the process time and the amount of metal raw materials used in forming the metal layer will also increase. If the thickness of the precipitated lithium exceeds the lower limit of the aforementioned thickness, there will be problems such as a decrease in the initial coulombic efficiency due to the initial irreversibility and a decrease in the charge / discharge performance due to a lack of excess lithium.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132]

[0133] <Experimental Example>

[0134] Manufacturing of cathodes for lithium secondary batteries

[0135] <Example 1>

[0136] <Manufacturing the entire house>

[0137] A nickel (Ni) current collector was prepared for use in the negative electrode of the lithium secondary battery of the present invention.

[0138]

[0139] <Coating layer formation>

[0140] An alloy material was coated on both sides of the above nickel (Ni) current collector using an electrolytic plating method. At this time, the alloy material used was silver (Ag), and the plating thickness was approximately 100 nm.

[0141] FIG. 3 shows a photograph of a tissue in which a coating layer is applied on a collector according to one embodiment of the present invention.

[0142] Referring to Fig. 3, it can be confirmed that a silver coating layer is applied on the entire collector. The thickness of the coating layer can be confirmed to be approximately 100 nm.

[0143]

[0144] <Protective layer formation>

[0145] A protective layer of approximately 5 μm was formed on the upper surface of the coating layer by slurry coating using a comma coater. Specifically, a slurry was prepared to form the protective layer, and the slurry was a mixture of amorphous carbon and metal nitride, and additionally a binder and a solvent were mixed. At this time, acetylene black was used as the amorphous carbon, and magnesium nitride (Mg3N2) was used as the metal nitride. The weight ratio of amorphous carbon to metal nitride was 90:10.

[0146] Additionally, the mixed binder was prepared by adding carboxymethylcellulose (CMC) and styrene butadiene rubber (SBR) in amounts of 3 parts by weight and 6 parts by weight, respectively, based on the total amount of amorphous carbon and metal nitride. 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 approximately 25 wt% of the total amount of amorphous carbon, metal particles, and binder to maintain an appropriate viscosity for coating.

[0147] Figures 4a and 4b show the microstructure of the surface and cross-section when a protective layer is placed on the collector.

[0148] Referring to FIGS. 4a and 4b, the protective layer has a porous surface structure and cross-sectional shape 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.

[0149]

[0150] Lithium electrodeposition process

[0151] 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 40 wt% and 5 wt% of lithium bis(fluorosulfonyl)imide and lithium nitrate, which are nitrogen compounds, based on 100 wt% of the plating solution, to a 1,2-dimethoxyethane solvent, and adding 5 wt% of fluoroethylene carbonate, which is a fluorine compound, based on 100 wt% of the plating solution.

[0152] A lithium metal plate with a purity of 99.9% or higher and a thickness of 500 μm was pressed onto a copper current collector (Cu Plate) as a lithium source. After the lithium source and the current collector were electrically insulated and laminated in a plating solution, a power supply was used to apply current to the lithium source and the current collector as (+) and (-) electrodes, respectively, to deposit lithium between the current collector and the composite protective layer.

[0153] 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.

[0154] 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.

[0155] 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 precipitated 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.

[0156]

[0157] All-solid-state battery manufacturing

[0158] Using the cathode manufactured according to the above-described example, an all-solid-state battery was fabricated, and its charge-discharge life was evaluated. To evaluate the all-solid-state battery cell, a pressurized, dedicated evaluation cell from Terraleader, capable of maintaining an inert atmosphere, was used. For the fabrication of the all-solid-state battery cell, 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 cell was pressurized at a pressure of 370 MPa.

[0159] 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.

[0160]

[0161] <Example 2>

[0162] To prepare a slurry used to form a protective layer, the same procedure as Example 1 was followed, except that amorphous carbon and magnesium fluoride (MgF2) were mixed in a weight ratio of 90:10.

[0163]

[0164] <Example 3>

[0165] To prepare a slurry used for forming a protective layer, the same procedure as in Example 1 was followed, except that amorphous carbon, magnesium nitride (Mg3N2), and magnesium fluoride (MgF2) were mixed in a weight ratio of 80:10:10.

[0166]

[0167] <Comparative Example 1>

[0168] To prepare a slurry used for forming a protective layer, the same procedure as Example 1 was followed, except that only amorphous carbon was mixed at a weight ratio of 100 without using metal fluoride or metal nitride.

[0169]

[0170] <Evaluation Example>: Evaluation Example according to addition of metal fluoride or metal nitride

[0171] Table 1 below shows the XRD peak value, maximum current density, and number of charge / discharge cycles after electrodeposition according to the content of amorphous carbon, magnesium nitride, or magnesium fluoride in the protective layer-forming slurry in forming the protective layer. The XRD peak value, maximum current density, and number of charge / discharge cycles were measured using the following methods.

[0172] XRD Peak Values: After forming a protective layer and further depositing lithium between the protective layer and the current collector through an electrodeposition process, the sample was subjected to phase analysis using XRD analysis by Rikaku. The XRD analysis was performed in thin film mode, and the specimen was sealed with Kapton tape to prevent the electrodeposited sample from reacting with the external air or moisture. Therefore, the broad, gentle peaks appearing at low angles in the sample may be due to the Kapton tape.

[0173] 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 protective layer and the current collector, and the maximum current density was measured.

[0174] 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.

[0175] Evaluation of XRD peak values ​​after electrodeposition of the protective layer composition Amorphous carbon [wt%] Magnesium nitride (Mg3N2) [wt%] Magnesium fluoride (MgF2) [wt%] Formula 1 * Equation 2 ** Equation 3 *** Maximum current density [mA / cm 2] Charge / discharge performance times (times) Example 19010-6.50.16.610826 Example 290-100.15.95.910912 Example 38010106.24.010.212934 Comparative example 1100--0.10.10.24481* Equation 1: Second peak / First peak × 100(%) (In Equation 1, the first peak value is the first peak value of Ni, the second peak value is the second peak value of Li3N, and specifically, the first peak value is an intensity value at 44 to 46°, and the second peak value is an intensity value at 26 to 30°)** Equation 2: Third peak / First peak × 100(%) (In Equation 1, the first peak value is the first peak value of Ni, and the third peak value is a peak value of the Li-Mg alloy phase, Specifically, the first peak value is the intensity value at 44 to 46 °, and the third peak value is the intensity value at 35 to 39 °)*** Equation 3: (Second peak + Third peak) / First peak × 100(%)

[0176] Looking at Table 1 above, looking at Examples 1 and 2 and Comparative Example 1, it was confirmed that Example 1 or Example 2 including magnesium nitride or magnesium fluoride had superior maximum current density and charge / discharge performance number compared to Comparative Example 1 which only included amorphous carbon as the composition of the protective layer. Looking at Examples 1 to 3, it was confirmed that Example 3 including both magnesium nitride and magnesium fluoride had superior maximum current density and charge / discharge performance number compared to Examples 1 and 2 which included only one of magnesium nitride and magnesium fluoride.

[0177] Figures 6a to 6d show the results of XRD phase analysis before and after lithium deposition on the protective layer according to examples and comparative examples of the present invention.

[0178] Fig. 6a shows the XRD phase analysis results before and after lithium deposition of the protective layer according to Example 1, Fig. 6b shows the XRD phase analysis results before and after lithium deposition of the protective layer according to Example 2, Fig. 6c shows the XRD phase analysis results before and after lithium deposition of the protective layer according to Example 3, and Fig. 6d shows the XRD phase analysis results before and after lithium deposition of the protective layer according to Comparative Example 1.

[0179] Referring to Fig. 6a, when a protective layer containing magnesium nitride (Mg3N2) was coated on the current collector, XRD phase analysis was performed, and it was confirmed that a phase of a material such as silver (Ag) plated for an alloy with nickel and lithium, which are current collectors, was observed. In addition, it was confirmed that an Mg(OH)2 peak was observed around 18°, which is a form generated by the decomposition of Mg3N2 nitride during the process of preparing a slurry containing water.

[0180] Afterwards, lithium was deposited and deposited between the protective layer and the current collector through an electrodeposition process, and it was confirmed that a Li3N phase was observed in the sample. This was confirmed to be generated by the combination of nitrogen element contained in magnesium nitride and lithium ions during the electrodeposition process.

[0181] Referring to Fig. 6b, when a protective layer containing magnesium fluoride (MgF2) was coated on the current collector, XRD phase analysis was performed, and it was confirmed that phases such as nickel, which is the current collector, and silver (Ag) plated for alloying with lithium were observed. In the post-electrodeposition sample where lithium was deposited through the electrodeposition process between the protective layer and the current collector, a Li-Mg alloy phase was observed around 36°. This was confirmed to be generated by the combination of magnesium element contained in the magnesium fluoride and lithium ions during the electrodeposition process.

[0182] Referring to Fig. 6c, when XRD phase analysis was performed on a current collector with a protective coating containing both magnesium nitride (Mg3N2) and magnesium fluoride (MgF2), phases such as nickel and silver (Ag) plated for alloying with lithium, which are current collectors, were observed. After electrodeposition, in which lithium was deposited between the protective layer and the current collector through an electrodeposition process, it was confirmed that the sample simultaneously observed Li3N phase and Li-Mg alloy phase.

[0183] Referring to Fig. 6d, XRD phase analysis was performed on a current collector with a protective coating of a slurry composed solely of amorphous carbon. It was confirmed that a phase similar to silver (Ag) plated for an alloy with nickel and lithium, which are current collectors, was observed. Subsequently, it was confirmed that no specific phases other than the nickel current collector were observed in the sample after electrodeposition.

[0184]

[0185] <Evaluation Example 2>: Evaluation Example According to Control of Content of Metal Nitride and Metal Magnesium

[0186] <Example 4>

[0187] To prepare a slurry used for forming a protective layer, the same procedure as in Example 1 was followed, except that amorphous carbon, magnesium nitride (Mg3N2), and magnesium fluoride (MgF2) were mixed in a weight ratio of 92:4:4.

[0188]

[0189] <Example 5>

[0190] To prepare a slurry used for forming a protective layer, the same procedure as in Example 1 was followed, except that amorphous carbon, magnesium nitride (Mg3N2), and magnesium fluoride (MgF2) were mixed in a weight ratio of 70:15:15.

[0191]

[0192] <Comparative Example 2>

[0193] To prepare a slurry used for forming a protective layer, the same procedure as in Example 1 was followed, except that amorphous carbon, magnesium nitride (Mg3N2), and magnesium fluoride (MgF2) were mixed in a weight ratio of 96:2:2.

[0194]

[0195] <Comparative Example 3>

[0196] To prepare a slurry used for forming a protective layer, the same procedure as in Example 1 was followed, except that amorphous carbon, magnesium nitride (Mg3N2), and magnesium fluoride (MgF2) were mixed in a weight ratio of 60:20:20.

[0197] Table 2 below shows the XRD peak value, maximum current density, and charge / discharge performance number after electrodeposition according to the contents of amorphous carbon, magnesium nitride, and magnesium fluoride in the protective layer forming slurry in forming the protective layer.

[0198] Evaluation of XRD peak values ​​after electrodeposition of the protective layer composition Amorphous carbon [wt%] Magnesium nitride (Mg3N2) [wt%] Magnesium fluoride (MgF2) [wt%] Formula 1 * Equation 2 ** Equation 3 *** Maximum current density [mA / cm 2 ] Charge / discharge performance times (times) Example 3 8 0 1 0 1 0 6.2 4.0 1 0.2 1 2 9 3 4 Example 4 9 2 4 4 3.8 3.2 7.0 1 0 8 7 2 Example 5 7 0 1 5 1 5 9.3 8.8 1 8.1 1 0 7 1 7 Comparative Example 2 9 6 2 2 1.5 1.4 2.9 6 5 8 7 Comparative Example 3 6 0 2 0 2 0 1 3.5 1 2.8 2 6.3 6 5 5 8 * Equation 1: Second peak / First peak x 100 (%) (In Equation 1 above, the first peak value is the first peak value of Ni, the second peak value is the second peak value of Li3N, and specifically, the first peak value is the intensity value at 44 to 46 °, and the second peak value is the intensity value at 26 to 30 °) ** Equation 2: Third peak / First peak x 100 (%) (In Equation 1 above, The first peak value is the first peak value of Ni, and the third peak value is the peak value of the Li-Mg alloy phase, specifically, the first peak value is the intensity value at 44 to 46 °, and the third peak value is the intensity value at 35 to 39 °)*** Equation 3: (second peak + third peak) / first peak x 100(%)

[0199] Looking at Table 2 above, when magnesium nitride and magnesium fluoride are simultaneously included in Examples 3 to 5 and Comparative Examples 2 and 3, it was confirmed that the maximum current density and charge / discharge performance number of Examples 3 to 5 including the combined amount of magnesium nitride and magnesium fluoride in an appropriate range were superior to Comparative Example 2 having an excessively small combined amount of magnesium nitride and magnesium fluoride or Comparative Example 3 having an excessively large combined amount of magnesium nitride and magnesium fluoride.

[0200] 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 A protective layer is disposed on the metal layer and includes a carbon-based material, A lithium metal electrode comprising an alloy layer including at least one of a nitrogen-based and a magnesium-based alloy in at least one region between the metal layer and the protective layer and within the protective layer.

2. In paragraph 1, A lithium metal electrode having at least one peak value among 21 to 25°, 26 to 30°, 35 to 39°, 45 to 47°, 48 to 51°, and 54 to 56° in XRD peak values.

3. In paragraph 1, A lithium metal electrode having an XRD peak value satisfying the following equation 1. <Formula 1> 3 ≤ 2nd peak value / 1st peak value × 100(%) ≤ 10 (In the above equation 1, the first peak value is the intensity value at 44 to 46 °, and the second peak value is the intensity value at 26 to 30 °) 4. In paragraph 1, A lithium metal electrode having an XRD peak value satisfying the following equation 2. <Formula 2> 3 ≤ 3rd peak value / 1st peak value × 100(%) ≤ 10 (In the above equation 2, the first peak value is the intensity value at 44 to 46 °, and the third peak value is the intensity value at 35 to 39 °) 5. In paragraph 1, A lithium metal electrode having an XRD peak value satisfying the following equation 3. <Formula 3> 3 ≤ (2nd peak value + 3rd peak value) / 1st peak value × 100(%) ≤ 20 (In the above formula 3, the first peak value is an intensity value at 44 to 46°, the second peak value is an intensity value at 26 to 30°, and the third peak value is an intensity value at 35 to 39°) 6. In paragraph 1, A lithium metal electrode comprising a film layer disposed on the protective layer.

7. In paragraph 6, The above protective layer is a lithium metal electrode including a carbon-based material and a metal fluoride or metal nitride.

8. Step 8: Preparing 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; Comprising a step of forming a protective layer by coating slurry on the surface of the coating layer, A method for producing a lithium metal electrode, wherein the slurry comprises a carbon-based material and at least one of a metal fluoride and a metal nitride.

9. In paragraph 8, After the step of forming the above protective layer, A step of positioning a current collector having 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 metal particles included in the protective layer and lithium precipitated from the lithium source are alloyed.

10. In paragraph 8, A method for producing a lithium metal electrode, wherein the metal fluoride or metal nitride comprises at least one of MgF2, Mg3N2, AgF, and Ag3N.

11. In paragraph 9, A method for producing a lithium metal electrode having a peak value between 16 and 18° in the XRD peak value of the protective layer before applying a current between the current collector and the lithium source.

12. In paragraph 9, After applying a current between the above-mentioned collector and the above-mentioned lithium supply source, A method for manufacturing a lithium metal electrode, wherein the metal layer includes a nitrogen-based or magnesium-based alloy.

13. In paragraph 9, A method for producing a lithium metal electrode, wherein the slurry contains 70 to 95 wt% of the amorphous carbon based on 100 wt% of the total amount of the metal material including amorphous carbon and metal fluoride or metal nitride.

14. In paragraph 9, The above slurry comprises amorphous carbon, metal fluoride, and metal nitride, A method for producing a lithium metal electrode, wherein the combined amount of the metal fluoride and the metal nitride is 8 to 30 wt%, based on 100 wt% of the amorphous carbon, metal fluoride, and metal nitride.

15. In paragraph 9, 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 metal particles and lithium precipitated from the lithium supply source are alloyed, 6 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.

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