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

Abstract

This invention relates to a lithium metal electrode and a method for manufacturing the same. The lithium metal electrode of this invention comprises: a current collector, a metal layer, at least one surface of the current collector and comprising a lithium alloy, and a protective layer, located on the metal layer and comprising a carbon-based material; at least one region between the metal layer and the protective layer and within the protective layer may comprise an alloy layer comprising at least one of a nitrogen-based alloy and a magnesium-based alloy.

Description

Technical Field

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

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

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

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

[0005] Although various methods have been proposed to improve lifetime by suppressing dendrite growth, it remains difficult to simultaneously achieve both the high energy density and sufficient lifetime characteristics resulting from lithium electrode thinning. As methods to suppress dendrite growth, several approaches have been proposed, such as using only amorphous carbon as a protective layer on the lithium metal electrode, or employing composite materials formed with high-valence lithium-affinity metals. However, these still suffer from the problem of not achieving sufficient lithium stacking speed and charge-discharge lifetime characteristics. Summary of the Invention

[0006] (a) Technical problems to be solved According to an embodiment of the present invention, a lithium metal electrode for a lithium secondary battery provides a lithium secondary battery that improves lithium stacking speed and charge / discharge life characteristics by increasing lithium-ion conductivity.

[0007] According to another embodiment of the present invention, a method for manufacturing a lithium metal electrode for a lithium secondary battery is provided, which has the above-mentioned advantages.

[0008] (II) Technical Solution According to one embodiment of the present invention, a lithium metal electrode may include: a current collector, a metal layer, at least one surface of the current collector comprising a lithium alloy, and a protective layer, located on the metal layer and comprising a carbon-based material; at least one region between the metal layer and the protective layer and within the protective layer may include an alloy layer comprising at least one of a nitrogen-based alloy and a magnesium-based alloy. In one embodiment, the XRD peak may have at least one peak selected from 21 to 25°, 26 to 30°, 35 to 39°, 45 to 47°, 48 to 51°, and 54 to 56°.

[0009] In one embodiment, the XRD peak value can satisfy the following equation 1. <Formula 1> 3 ≤ Second peak value / First peak value × 100 (%) ≤ 10 (In 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°).

[0010] In one embodiment, the XRD peak value can satisfy the following equation 2. <Formula 2> 3 ≤ Third peak / First peak × 100 (%) ≤ 10 (In 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°).

[0011] In one embodiment, the XRD peak value can satisfy the following equation 3. <Formula 3> 3 ≤ (Second peak + Third peak) / First peak × 100 (%) ≤ 20 (In 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°).

[0012] In one embodiment, a film layer disposed on the protective layer may be included. In one embodiment, the protective layer may comprise a carbon-based material and a metal fluoride or a metal nitride.

[0013] A method for manufacturing a lithium metal electrode according to another embodiment of the present invention may include: a step of preparing a current collector; a step of forming a coating on at least one surface of the current collector using a coating composition comprising a lithium-philic component; and a step of forming a protective layer by coating the coating surface with a slurry; wherein the slurry comprises a carbonaceous material and at least one of a metal fluoride and a metal nitride.

[0014] In one embodiment, after the step of forming the protective layer, the process may include: placing a current collector for forming the protective layer after a plating bath, and configuring a lithium supply source and the protective layer at a predetermined interval; and forming a metal layer comprising a lithium alloy by applying an electric current between the current collector and the lithium supply source, the lithium alloy being formed by alloying metal particles contained in the protective layer with lithium deposited from the lithium supply source.

[0015] In one embodiment, the metal fluoride or metal nitride may comprise at least one of MgF2, Mg3N2, AgF, and Ag3N. In one embodiment, the XRD peak value of the protective layer may have a peak value between 16 and 18° before current is applied between the current collector and the lithium supply source.

[0016] In one embodiment, after a current is applied between the current collector and the lithium supply source, the metal layer may comprise a nitrogen-based alloy or a magnesium-based alloy. In one embodiment, the slurry may comprise 70 to 95% by weight of the amorphous carbon relative to 100% by weight of the total amount of metal material comprising amorphous carbon and metal fluorides or metal nitrides.

[0017] In one embodiment, the slurry comprises amorphous carbon, metal fluoride, and metal nitride, and may contain 8 to 30% by weight of the total amount of the metal fluoride and metal nitride relative to 100% by weight of the total amount of the amorphous carbon, metal fluoride, and metal nitride. In one embodiment, the step of forming a lithium alloy-containing metal layer by applying a current between the current collector and the lithium supply source, the lithium alloy being formed by alloying the metal particles with lithium deposited from the lithium supply source, includes: at a current of 6 to 12 mA / cm². 2 The electrodeposition step is performed using the maximum current density within the specified range.

[0018] (III) Beneficial Effects According to an embodiment of the present invention, a lithium metal electrode for a lithium secondary battery provides a lithium secondary battery that improves lithium stacking speed and charge / discharge life characteristics by mixing amorphous carbon with metal fluoride or metal nitride in a protective layer and forming an SEI layer that is conducive to lithium intermetallic alloy or charge / discharge during electrodeposition.

[0019] According to another embodiment of the present invention, a method for manufacturing a lithium metal electrode for a lithium secondary battery is provided, which has the above-mentioned advantages. Attached Figure Description

[0020] Figure 1a and Figure 1b A lithium metal electrode manufactured according to one embodiment is shown.

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

[0022] Figure 3 a and Figure 3 b shows the fine structure of the surface and cross-section when the protective layer is configured on the current collector.

[0023] Figure 4a and Figure 4b The fine structure of the surface and cross-section is shown when the protective layer is configured on the current collector.

[0024] Figure 5a and Figure 5b The electrodeposition appearance according to the maximum current density is shown in the electrodeposition process according to the embodiments and comparative examples.

[0025] Figures 6a to 6c The XRD phase analysis results of the protective layer before and after lithium battery deposition are shown in the embodiments and comparative examples according to the present invention.

[0026] Figure 7 Battery life assessments of all-solid-state batteries utilizing embodiments and comparative examples of the present invention are shown. Detailed Implementation

[0027] The terms "first," "second," and "third," etc., can be used to describe various parts, components, regions, layers, and / or segments, but are not limited thereto. These terms are used only to distinguish one part, component, region, layer, or segment from another. Therefore, hereinafter, without departing from the scope of the invention, a first part, component, region, layer, or segment may be referred to as a second part, component, region, layer, or segment.

[0028] The technical terms used herein are for illustrative purposes only and are not intended to limit the invention. Unless otherwise expressly stated, the singular forms used herein also include the plural forms. The term "comprising" as used in the specification means specifically describing a particular feature, region, integer, step, action, element, and / or component, and does not exclude the presence or addition of other features, regions, integers, steps, actions, elements, and / or components.

[0029] When one part is located "above" or "on top of" another part, it can be directly on the other part, or there can be other parts between them. Conversely, when one part is "directly on" another part, there are no other parts between them.

[0030] Unless otherwise defined, all terms used herein, including technical and scientific terms, shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms as defined in commonly used dictionaries shall be further interpreted as having meanings consistent with relevant technical literature and the present disclosure, and shall not be construed as having idealized or overly formal meanings unless otherwise defined.

[0031] Figure 1a and Figure 1b A lithium metal electrode 100 manufactured according to one embodiment is shown.

[0032] Reference Figure 1a According to one embodiment, a lithium metal electrode 100 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.

[0033] The current collector 10 can be a component used for electrical connection within a lithium secondary battery. The current collector 10 can be in the form of a thin film (Foil), but is not limited to this; for example, it can also be in the form of a mesh, foam, rod, wire, or sheet woven from wire (fiber).

[0034] The current collector 10 can be made of a material that is conductive and does not readily react with lithium. Specifically, the material of the current collector 10 can be any one or a combination of copper, nickel, titanium, stainless steel, gold, platinum, silver, tantalum, ruthenium and its alloys, carbon, conductive polymers, and composite fibers coated with a conductive layer on a non-conductive polymer.

[0035] In one embodiment, the thickness of the current collector 10 can be from 1 μm to 50 μm. When the current collector 10 is too thick, the battery weight increases, resulting in a decrease in the battery's energy density. When the current collector 10 is too thin, there is a risk of overheating and damage during high-current operation, and it may be damaged due to tension during the battery manufacturing process.

[0036] A metal layer 20 is located on the current collector 10 and may include a lithium alloy layer 21 containing a lithium alloy and a lithium metal layer 22 located on the lithium alloy layer 21. The lithium alloy layer 21 may be formed by means of a current collector 10 and a lithium supply source (…). Figure 2Applying an electric current between the current collector 10 and the lithium supply source 40, the lithium-loving component in the metal layer 20 and the lithium deposited from the lithium supply source 40 are alloyed on the current collector 10, thereby forming a layer containing a lithium alloy.

[0037] In order to increase the deposition rate when forming the metal layer 20, a large current is applied during the electrodeposition process, which can lead to a decrease in the performance of the lithium secondary battery. However, as described in this embodiment, when the metal layer 12 forms a structure containing a lithium alloy layer 21 with lithium components, even if a large current is applied during the electrodeposition process, it is possible to prevent the formation of excessive fine lithium particles or the destruction of the protective layer 30 on the formed lithium metal layer 22 during the electrodeposition process.

[0038] Specifically, since the metal layer 20 in one embodiment includes a lithium alloy layer 21 containing lithium components, when a large current is applied in the electrodeposition process to form a lithium metal layer 22 on the lithium alloy layer 21, it is possible to induce good growth of the initially generated lithium particles, thereby forming a coarse particle structure, and at the same time, it is possible to make the lithium metal layer 22, and thus make the metal layer 20 have a uniform surface.

[0039] Therefore, the performance of the secondary battery using the lithium metal electrode of this embodiment can be significantly improved, specifically in terms of charge-discharge characteristics. Furthermore, even when applying a large current and performing an electrodeposition process at high speed, it is possible to manufacture a high-performance lithium metal electrode for secondary batteries, thus significantly improving the production efficiency of lithium metal electrodes for secondary batteries.

[0040] In this embodiment, the lithium alloy layer 21 comprises a lithium-loving metal. The lithium-loving metal can be, for example, one or more selected from the group consisting of In, Ag, Sn, Zn, Si, Al, and Bi. As described above, when the lithium alloy layer 21 comprises a lithium-loving metal, due to the presence of a lithium-loving metal with high electronic conductivity, electrons can be smoothly supplied by the current collector, thereby reducing lithium ions. Therefore, it has the advantage of facilitating the electrodeposition of the lithium metal layer. The metal layer 20 serves to facilitate the more efficient deposition of lithium beneath the protective layer 30 during battery charging.

[0041] In one embodiment, the thickness of the metal layer 20 can be from 1 μm to 100 μm, more specifically, from 5 μm to 30 μm. If the thickness of the metal layer 20 is too thick, when the lithium metal electrode of this embodiment is applied to a secondary battery, the weight and volume of the battery will increase, resulting in a decrease in energy density. In addition, when forming the metal layer 20, the time and cost of the electrodeposition process increase with the thickness; therefore, the thickness of the metal layer 20 is preferably 100 μm or less.

[0042] If the thickness of the metal layer 20 is too thin, the battery's charge-discharge life will be reduced when the lithium metal electrode of this embodiment is applied to a secondary battery. Specifically, during the charge-discharge process, lithium in the battery is gradually consumed due to side reactions between the lithium contained in the negative electrode active material layer (i.e., the metal layer of this invention) and the electrolyte, resulting in a decrease in battery capacity. Furthermore, the reduced lithium reserves that can replenish the lithium consumed during charge-discharge further decrease the battery's charge-discharge life. Therefore, the thickness of the metal layer 20 is preferably 1 μm or more.

[0043] The protective layer 30 may be disposed on at least one surface of the current collector 10 and comprises a carbon-based material and a metal fluoride or metal nitride. For example, the carbon-based material may comprise amorphous carbon. The amorphous carbon may be one or more selected from, but is not limited to, acetylene black, super P black, carbon black, superconducting denka black, activated carbon, graphite, hard carbon, and soft carbon. The amorphous carbon may be in powder form.

[0044] The metal fluoride can be M x F y Specifically, the metal fluoride can be, for example, MgF2 or AgF. The metal nitride can be M... x N z Specifically, the metal nitride may be, for example, Mg3N2 or Ag3N.

[0045] In one embodiment, the thickness of the protective layer 30 can be from 0.01 μm to 50 μm. Specifically, the thickness of the protective layer 30 can be in the range of 1 μm to 20 μm. The thickness of the protective layer 30 can refer to the average thickness of the region excluding the alloy layer AL. By ensuring that the thickness of the protective layer 30 meets the above range, an extremely thin lithium metal electrode can be provided.

[0046] When the thickness of the protective layer 30 exceeds the upper limit of the above range, the excessive resistance of the protective layer may cause an increase in overvoltage during the operation of the secondary battery, and there is also a problem of reduced battery energy density due to increased weight and volume. When the thickness of the protective layer 30 exceeds the lower limit of the above range, it may fail to function as a protective layer.

[0047] In one embodiment, the protective layer 30 may include an adhesive. The adhesive may be a water-based adhesive, which may be a rubber-based adhesive selected from the group consisting of acrylonitrile-butadiene rubber, styrene-butadiene rubber (SBR), and acrylic rubber, or one or more polymeric resins such as hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinylidene fluoride, but is not limited thereto.

[0048] Here, relative to 100 parts by weight of the carbon-based material and the AL component of the alloy layer, the binder can be added from 1 to 15 parts by weight, specifically from 3 to 10 parts by weight. When the content of the binder meets the above range, the particles constituting the protective layer can be effectively bonded without reducing the battery energy density due to increased weight and volume, thereby forming a high-performance protective layer and further improving the life characteristics of the secondary battery.

[0049] When the content of the adhesive is too low, the interparticle bonding force will be reduced when the protective layer is formed. When the content of the adhesive is too high, not only will the energy density be reduced, but the resistance of the protective layer will also increase significantly, thus hindering lithium-ion conduction.

[0050] In one embodiment, at least one region between the metal layer 20 and the protective layer 30, and within the protective layer 30, may include an alloy layer AL containing at least one of nitrogen-based alloys and magnesium-based alloys. The alloy layer AL containing at least one of nitrogen-based alloys and magnesium-based alloys may be formed by the reaction of a metal fluoride or metal nitride contained in the protective layer 30 with supplied lithium during lithium electrodeposition. For example, when magnesium nitride (Mg3N2) is used as the metal nitride, the nitrogen element contained in the magnesium nitride can combine with lithium ions during the electrodeposition process through reaction with lithium, thereby forming a nitrogen-based alloy such as Li3N. Alternatively, when magnesium fluoride (MgF2) is used as the metal fluoride, the magnesium element contained in the magnesium fluoride can combine with lithium ions during the electrodeposition process, thereby forming a magnesium-based alloy.

[0051] As described above, the alloy layer AL, comprising at least one of nitrogen-based and magnesium-based alloys, is formed during lithium electrodeposition. This layer facilitates lithium-ion conduction and possesses excellent mechanical properties, thus improving the charge-discharge performance of batteries when applied to them. Furthermore, lithium electrodes are manufactured via lithium electrodeposition, and electrodeposition is performed under high current, enabling high-speed fabrication of lithium anodes.

[0052] In one embodiment, an alloy layer AL comprising at least one of a nitrogen-based alloy and a magnesium-based alloy can 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 the reaction of lithium ions with a metal fluoride or metal nitride added to the protective layer during lithium-ion deposition, the alloy layer AL can be formed between the metal layer 20 and the protective layer 30, or it can be disposed within the protective layer 30, for example, in the lower region of the protective layer 30.

[0053] In one embodiment, the lithium metal electrode 100 may further include a film layer disposed in 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 a reaction between lithium metal from the electrodeposited lithium supply source 40 and the plating bath, and by a reaction with metal fluorides or metal nitrides in the protective layer 30. The thickness, composition, and properties of the film can be controlled by adjusting the composition of the plating bath and the electrodeposition process, and can also be controlled by adjusting the content of metal fluorides or metal nitrides.

[0054] In one embodiment, the film layer may at least partially comprise LiF. Because the film layer at least partially comprises LiF, it can improve battery life and suppress dendrite growth during battery operation due to its higher ionic conductivity.

[0055] The thickness of the film layer can be from 2 nm to 2 μm. Specifically, the thickness of the film layer can be in the range of 10 nm to 500 nm. When the thickness of the film layer is too high, it leads to a decrease in lithium-ion conductivity and an increase in interface resistance, resulting in a decrease in charge-discharge characteristics when applied to a battery. When the thickness of the film layer is too thin, the film layer can easily detach during the application of the lithium metal electrode according to the embodiment to the battery. Therefore, the film layer can have a low thickness while meeting the thickness range, and be uniformly and densely formed throughout the entire protective layer 30.

[0056] In one embodiment, the lithium metal electrode 100 may have at least one XRD peak value selected from 21 to 25°, 26 to 30°, 35 to 39°, 45 to 47°, 48 to 51°, and 54 to 56°. These peak values ​​may indicate that the lithium metal electrode 100 comprises at least one of a nitrogen-based alloy and a magnesium-based alloy. For example, when the lithium metal electrode 100 comprises a nitrogen-based alloy, the XRD peak value 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 comprises a magnesium-based alloy, the XRD peak value may include 35 to 39°. These XRD peak values ​​may also indicate that the lithium metal electrode 100 includes an alloy layer AL, which comprises at least one of a nitrogen-based alloy and a magnesium-based alloy in the region between the metal layer 20 and the protective layer 30 or within the protective layer 30.

[0057] In one embodiment, the XRD peak value of the lithium metal electrode 100 can satisfy Equation 1 below.

[0058] <Formula 1> 3.0 ≤ Second peak value / First peak value × 100 (%) ≤ 10.0 (In 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°.) Formula 1 can be used as an indicator to determine whether a nitrogen-based alloy has formed. Formula 1 can satisfy 3 to 10, more specifically, 5 to 8. When Formula 1 satisfies the above range, an appropriate amount of nitrogen-based alloy is generated, which is beneficial to lithium-ion conduction.

[0059] When Formula 1 exceeds the upper limit of the above range, there is a problem of excessive formation of nitrogen-based alloys, resulting in a decrease in the mechanical strength of the Al alloy layer. When Formula 1 exceeds the lower limit of the above range, there is a problem of insufficient formation of nitrogen-based alloys, resulting in a lower lithium-ion conductivity.

[0060] In one embodiment, the XRD peak value of the lithium metal electrode 100 can satisfy Equation 2 below.

[0061] <Formula 2> 3 ≤ Third peak / First peak × 100 (%) ≤ 10 (In 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°.) Formula 2 can be used as an indicator to determine whether a magnesium-based alloy has been formed. Formula 2 can satisfy 3 to 10, more specifically, 5 to 8. When Formula 2 satisfies the above range, an appropriate amount of magnesium-based alloy is generated, which easily combines with lithium ions during charging and discharging, thus having the advantage of improving lithium ion conductivity.

[0062] When Equation 2 exceeds the upper limit of the above range, the excess magnesium alloy generated cannot replenish the reduced lithium reserves consumed during charging and discharging, thus reducing the battery's charge-discharge life. When Equation 2 exceeds the lower limit of the above range, the amount of magnesium alloy is insufficient, resulting in a reduced effect on improving lithium-ion conductivity.

[0063] In one embodiment, the XRD peak value of the lithium metal electrode 100 can satisfy the following equation 3.

[0064] <Formula 3> 3 ≤ (Second peak + Third peak) / First peak × 100 (%) ≤ 20 (In 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°.) Equation 3 can be used as an indicator to determine whether nitrogen-based alloys and magnesium-based alloys have formed. Equation 3 can satisfy 3 to 20, more specifically, 8 to 12. When Equation 3 satisfies the above range, it has advantages that are beneficial to lithium-ion conduction and mechanical strength.

[0065] When Equation 3 meets the upper limit of the above range, there is a problem of reduced mechanical strength or reduced charge / discharge life. When Equation 3 exceeds the lower limit of the above range, there is a problem of reduced lithium-ion conductivity.

[0066] Reference Figure 1b In one embodiment, the lithium metal electrode 100 includes: a current collector 10; a metal layer 20' located on at least one surface of the current collector 10, the metal layer 20' being 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 can be formed by applying a current between the current collector 10 and a lithium supply source 40, causing the metal layer 20' formed on the current collector 10 to alloy with lithium deposited from the lithium supply source 40, containing a lithiophilic component.

[0067] The metal layer 20' may contain a lithium-loving metal. In one embodiment, the metal layer 20' is in the form of containing a lithium-loving metal. When the metal layer 20' containing a lithium-loving metal is formed as described above, since the nucleation free energy of lithium particles can be reduced in the early stage of nucleation during the electrodeposition process, a lithium metal layer with a coarse particle structure can be formed even under high current and overvoltage conditions.

[0068] In one embodiment, at least one region between the metal layer 20' and the protective layer 30, and within the protective layer 30, may include an alloy layer AL containing at least one of a nitrogen-based alloy and a magnesium-based alloy. For a detailed description of this, please refer to... Figure 1a .

[0069] In one embodiment, the metal layer 20' includes a protective layer 30 located on the surface of the metal layer 20', and may include a film layer inside and / or on the surface of the protective layer 30. Detailed descriptions of the protective layer 30 and the film layer can be found in [reference needed]. Figure 1a The content described.

[0070] Figure 2 This is a schematic diagram of the manufacturing method of the lithium metal electrode 100 of the present invention.

[0071] Reference Figure 2 A method for manufacturing a lithium metal electrode 100 according to an embodiment includes: a step of preparing a current collector 10; a step of forming a coating 20 on at least one surface of the current collector 10 using a coating composition containing a lithium-philic component; and a step of forming a protective layer 30 by coating a slurry onto the surface of the coating.

[0072] In the step of preparing the current collector 10, the current collector 10 can be made of a material that is conductive and has limited reactivity with lithium. Specifically, the material of the current collector 10 can be any one or a combination of, for example, copper, nickel, titanium, stainless steel, gold, platinum, silver, tantalum, ruthenium and its alloys, carbon, conductive polymers, and composite fibers coated with a conductive layer on a non-conductive polymer.

[0073] In one embodiment, the step of forming coating 20 can be performed using at least one of electroplating and electroless plating, sputtering, electron beam deposition, and thermal vapor deposition. For example, the step of forming coating 20 can be performed using an electroless plating method.

[0074] A protective layer 30 can be formed on the surface of coating 20 using a slurry containing amorphous carbon. The protective layer 30 is applied to the slurry formed by mixing the amorphous carbon and a binder in water using at least one of the following methods: doctor blade coating, dip coating, reverse roller coating, direct roller coating, gravure coating, extrusion, and brush coating. The protective layer 30 may also include the binder.

[0075] In one embodiment, the slurry may comprise at least one of amorphous carbon, metal fluorides, and metal nitrides. The metal fluoride may be M... x F y Specifically, the metal fluoride can be, for example, a substance such as MgF2 or AgF. The metal nitride can be M... x N zSpecifically, the metal nitride can be, for example, Mg3N2 or Ag3N. By including not only amorphous carbon but also a metallic substance containing at least one of metal fluorides and metal nitrides in the slurry, lithium-ion conduction and mechanical properties are improved, and a protective layer 30 that inhibits dendrite growth can be formed. Furthermore, because it contains a metallic substance containing at least one of the metal fluorides and metal nitrides, an alloy layer containing at least one of nitrogen-based alloys and magnesium-based alloys can be formed during the subsequent lithium-ion deposition process, thereby improving battery performance.

[0076] In one embodiment, the slurry may contain 70 to 95% by weight of the amorphous carbon relative to 100% by weight of the metal material comprising amorphous carbon and metal fluorides or metal nitrides. Specifically, the content of the amorphous carbon may be 70 to 92% by weight, more specifically, 75 to 85% by weight. When the content of amorphous carbon in the slurry is within the above range, the maximum current density during the lithium-ion battery deposition process can be increased, thereby improving the electrodeposition efficiency and increasing the number of charge-discharge cycles of the battery, thus offering the advantage of improved lifespan characteristics.

[0077] In one embodiment, when the slurry simultaneously contains amorphous carbon, metal fluoride, and metal nitride, the content of the metal fluoride and the nitride may be 8 to 30% by weight relative to 100% by weight of the content of amorphous carbon, metal fluoride, and metal nitride.

[0078] When the amorphous carbon content is too high, the content of metal substances containing metal fluorides or metal nitrides is too low, and the amount of magnesium alloys or nitrogen alloys formed is insufficient, thus hindering the improvement of lithium-ion conductivity. When the amorphous carbon content is too low, the content of metal substances containing metal fluorides or metal nitrides is too high, and the amount of magnesium alloys or nitrogen alloys formed is excessive, which can compensate for the reduced lithium reserves consumed during charging and discharging, thus leading to a decrease in battery charge-discharge life or mechanical strength.

[0079] A protective layer 30 can be formed on the surface of the current collector 10 using a slurry containing a carbon-based substance and a metallic substance, specifically a metal fluoride or a metal nitride. The protective layer 30 is applied to the slurry formed by mixing the amorphous carbon and a binder in water using at least one of the following methods: doctor blade coating, dip coating, reverse roller coating, direct roller coating, gravure coating, extrusion, and brush coating. The protective layer 30 may also include a binder. Detailed descriptions of the carbon-based substance and the metallic substance can be found above. Figure 1a .

[0080] In one embodiment, during the step of forming the protective layer 30, the slurry can be coated to a thickness ranging from 3 to 10 μm. Specifically, the coating thickness can be 4 to 7 μm. When the slurry is coated to this thickness, the protective layer 30 can have an appropriate thickness, thereby not only fulfilling its function as a protective layer, but also preventing lithium dendrites from forming on the surface of the protective layer due to its resistance suitable for lithium ion movement. This allows lithium to penetrate well into the interior of the protective layer 30 and conduct, thus enabling lithium to precipitate on the lower surface of the protective layer.

[0081] When the protective layer is too thin, it fails to function properly. When the protective layer is too thick, its resistance is too high, which can lead to overvoltage during battery operation and reduce battery energy density due to increased weight and volume. However, the thickness of this protective layer can be variably adjusted according to the design of the secondary battery structure.

[0082] In one embodiment, the slurry may further include a binder. Relative to 100 parts by weight of the amorphous carbon and metallic substances, 1 to 15 parts by weight, specifically 3 to 10 parts by weight, of the binder may be added. When the content of the binder meets the above range, the battery energy density will not decrease due to increased weight and volume, and a high-performance protective layer can be formed by effectively bonding the particles constituting the protective layer, thereby further improving the lifespan characteristics of the secondary battery.

[0083] When the content of the adhesive is less than the above range, the interparticle bonding force decreases during the formation of the protective layer. When the content of the adhesive is more than the above range, not only does the energy density decrease, but the resistance of the protective layer also increases significantly, thus hindering lithium-ion conduction.

[0084] In one embodiment, a method for manufacturing a lithium metal electrode includes: after forming a protective layer 30, placing a current collector 10 with the protective layer 30 formed thereon in a plating bath 50, and then separating a lithium supply source 40 from the protective layer 30 at a predetermined interval; and forming a metal layer comprising a lithium alloy by applying an electric current between the current collector and the lithium supply source 40, the lithium alloy being formed by alloying a lithiophilic component contained in the coating with lithium deposited from the lithium supply source 40.

[0085] After the step of forming the protective layer 30, the following steps are performed: placing the current collector 10 on which the protective layer 30 is formed in the plating solution 50, and then setting the lithium supply source 40 at a predetermined distance from the current collector 10; and forming the metal layer 20 by applying an electric current between the current collector 10 and the lithium supply source 40.

[0086] Specifically, the current collector 10 with the protective layer 30 formed thereon is placed in the plating solution, and then the lithium supply source 40 is separated from the protective layer 30 by a predetermined interval. For example, the lithium supply source 40 may be lithium metal, lithium alloy, a foil material with the lithium metal or lithium alloy pressed onto the current collector, or a plating solution containing dissolved lithium salts.

[0087] The plating solution 50 can be manufactured by dissolving a lithium salt in several solvents. Specifically, the lithium salt can be LiCl, LiBr, LiI, LiCO3, LiNO3, LiFSI, LiTFSI, LiBF4, LiPF6, LiAsF6, LiClO4, LiN(SO2CF3)2, LiBOB, or a combination thereof. The concentration of the lithium salt relative to the entire electrolyte can be from 1.0 to 3.0 M.

[0088] Specifically, in this embodiment, the plating solution 50 is characterized in that it contains a nitrogen-based compound as the lithium salt and at least one of a plurality of solvents. For example, the nitrogen-based compound may contain one or more selected from the group consisting of lithium nitrate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethane sulfonimide, e-caprolactam, N-methyl-e-caprolactam, triethylamine, and tributylamine.

[0089] Among the nitrogen-based compounds, at least one of lithium nitrate, lithium bisfluorosulfonyl imide, and lithium bis trifluoromethanesulfonimide can be used as a lithium salt.

[0090] In the nitrogen-based compounds, at least one of e-caprolactam, N-methyl-e-caprolactam, triethylamine, and tributylamin can be used as a non-aqueous solvent.

[0091] The plating solution 50 may also be manufactured using only the nitrogen-based compound; however, considering the viscosity of the plating solution 50, it may contain a general non-aqueous solvent as an auxiliary solvent.

[0092] For example, the auxiliary solvent may comprise one or more of the following: ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, and 1,3,5-trioxane.

[0093] In one embodiment, the auxiliary solvent may comprise 5 to 70% by weight of 100% of the total amount of plating solution 50, preferably 10 to 60% by weight, but is not limited thereto. However, when the auxiliary solvent is contained within the range, the viscosity of plating solution 50 is appropriate, thus enabling a shorter electrodeposition time, but is not limited thereto.

[0094] In one embodiment, the plating solution 50 may also contain a fluorine-based compound. When the plating solution 50 also contains the fluorine-based compound, it has the advantage of improving the properties of the film layer on the metal layer or protective layer.

[0095] For example, the fluorinated compound may comprise one or more of the following groups: lithium difluorophosphate, lithium hexafluorophosphate, lithium difluoro bisoxalato phosphate, lithium tetrafluoro oxalato phosphate, lithium difluoro oxalate borate, lithium difluoro oxalato borate, lithium tetrafluorooxalato borate, fluoroethylene carbonate, difluoroethylene carbonate, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether.

[0096] The plating bath 50 may contain 0.1 to 30% by weight of the fluorine-based compound, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, relative to 100% by weight of the total amount of the plating bath 50. When the fluorine compound is contained within the range described above, the interaction between the nitrogen-based and fluorine-based compounds in the plating bath 50 is smooth, thus resulting in excellent improvement in film properties. Furthermore, it suppresses the excessive formation of LiF due to the direct reaction between the fluorine-based compounds and lithium, thereby exhibiting excellent electrochemical properties.

[0097] Next, after an insulating film is placed between the current collector 10 and the lithium supply source 40, the current collector 10, the lithium supply source 40, and the insulating film are stacked using a constraint device and constrained in both directions. As a non-limiting example, the constraint device can employ methods commonly used in the art, such as manual clamping, hydraulic clamping, pneumatic clamping, or other uniaxial pressurization methods.

[0098] In the step of forming a lithium-containing metal layer on at least one surface of the current collector by applying the current, the current density of the applied current may be 0.1 mA / cm². 2 Up to 100mA / cm 2 The range, more specifically, can be 0.2 mA / cm. 2Up to 50mA / cm 2 The range can be 5mA / cm 2 Up to 30mA / cm 2 Range or 7mA / cm 2 Up to 25mA / cm 2 scope.

[0099] In one embodiment, the duration of the applied current can range from 0.05 hours to 50 hours, and more specifically, from 0.25 hours to 25 hours.

[0100] In one embodiment, the step of forming a lithium metal layer on at least one surface of the current collector by applying the current can be performed more than once at different current densities. The current application step can be performed in a multi-stage manner. Specifically, the multi-stage current application step can be performed by gradually increasing the current density from low to high in stages over a predetermined time period. For example, the current application step can be performed at a rate of 0.1 to 0.3 mA / cm². 2 0.3 to 0.7 mA / cm 2 and 0.8 to 1.5 mA / cm 2 Sequential, phased addition and electrodeposition.

[0101] 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 may include at a current of 6 to 12 mA / cm². 2 The electrodeposition step is performed using the maximum current density within a certain range. Specifically, the maximum current density can be between 8 and 12 mA / cm². 2 The maximum current density refers to the limit of the current density that allows the electrodeposited lithium to deposit between the protective layer 30 and the current collector 10 during the electrodeposition process.

[0102] For example, the electrodeposition step at the maximum current density can be a final step performed after lithium has been deposited between the current collector 10 and the protective layer 30 through a multi-stage deposition step. Since the maximum current density meets the above range, lithium can be appropriately deposited between the current collector 10 and the protective layer 30, thus providing the advantages of battery life characteristics and excellent bonding strength between the current collector 10 and the protective layer 30.

[0103] When the maximum current density exceeds the upper limit of the aforementioned range, lithium deposits on the surface of the protective layer 30, resulting in the inability to obtain the desired stable electrode structure. When the maximum current density exceeds the lower limit of the aforementioned range, the lithium deposition time increases, leading to a decrease in production efficiency.

[0104] In one embodiment, the step of forming a lithium metal layer on at least one surface of the current collector by applying the current may include an electrodeposition step of controlling the thickness of the deposited lithium within the range of 5 to 15 μm. Specifically, the thickness of the deposited lithium may be electrodeposited in the range of 8 to 12 μm. The thickness of the deposited lithium may refer to the vertical height of the lithium disposed between the current collector 10 and the protective layer 30.

[0105] When the thickness of the deposited lithium exceeds the upper limit mentioned above, it not only leads to a decrease in the energy density of the battery, but also increases the processing time and the amount of metal raw materials used in forming the metal layer. When the thickness of the deposited lithium exceeds the lower limit mentioned above, the initial coulombic efficiency decreases due to initial irreversibility and insufficient remaining lithium, thus resulting in a decrease in charge-discharge performance.

[0106] According to another embodiment of the present invention, a lithium secondary battery includes a positive electrode, a negative electrode, and an electrolyte located between the positive and negative electrodes. Here, the negative electrode may be a lithium metal electrode according to the present invention.

[0107] In one embodiment, the lithium secondary battery may include an electrode assembly comprising: a positive electrode containing a positive active material; a negative electrode, serving as the lithium metal electrode of the present invention; and a separator disposed between the positive and negative electrodes. This electrode assembly can be housed within a battery casing by winding or folding.

[0108] Next, electrolyte is injected into the battery casing and sealed, thus completing the secondary battery. At this time, the battery casing can have a cylindrical, prismatic, pouch, or button-shaped shape.

[0109] The positive electrode may include a positive electrode active material layer and a positive electrode current collector. For example, the positive electrode active material layer may contain a Li compound, which contains at least one metal selected from Ni, Co, Mn, Al, Cr, Fe, Mg, Sr, V, La, and Ce, and at least one non-metallic element selected from the group consisting of O, F, S, P, and combinations thereof.

[0110] In one embodiment, the positive electrode active material layer may further contain a conductive material. For example, the conductive material may be carbon black, ultrafine graphite particles, fine carbon such as acetylene black, or nano-metal particle slurry, but is not limited to these.

[0111] The positive electrode current collector serves to support the positive electrode active material layer. For example, aluminum foil, nickel foil, or a combination thereof can be used as the positive electrode current collector, but it is not limited to these.

[0112] The electrolyte used to fill the lithium secondary battery can be a non-aqueous electrolyte or a solid electrolyte. Specifically, the electrolyte can be a solid electrolyte. The non-aqueous electrolyte may contain lithium salts such as lithium hexafluorophosphate and lithium perchlorate, and solvents such as ethylene carbonate, propylene carbonate, and butylene carbonate. Alternatively, the solid electrolyte may be a gel polymer electrolyte in which the electrolyte is impregnated in a polymer electrolyte such as polyethylene oxide or polyacrylonitrile, or an inorganic solid electrolyte such as LiI or Li3N.

[0113] The separator is used to separate the positive and negative electrodes and provide a channel for lithium ion movement. Any separator commonly used in lithium secondary batteries can be used. Specifically, the separator can have low resistance and excellent electrolyte retention capabilities for electrolyte ion movement. The separator can be, for example, selected from glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene, or combinations thereof, and can be in the form of non-woven or woven fabric. Alternatively, when a solid electrolyte is used, the solid electrolyte can also serve as the separator.

[0114] Hereinafter, implementation examples of the present invention will be described in detail. However, these are merely examples and are not intended to limit the present invention, which is defined only by the scope of the following claims.

[0115] <Experimental Example> Manufacturing negative electrodes for lithium secondary batteries <Example 1> <Manufacturing Current Collectors> Preparations are made to apply the nickel (Ni) current collector to the negative electrode of the lithium secondary battery of the present invention.

[0116] <Forming a coating> An alloy material is coated onto both sides of the nickel (Ni) current collector using an electroplating method. The alloy material used is silver (Ag), and the plating thickness is approximately 100 nm.

[0117] Figure 3 A photograph of a tissue with a coating applied to a current collector is shown, according to an embodiment of the present invention.

[0118] Reference Figure 3 It can be confirmed that a silver coating is applied to the current collector. It can also be confirmed that the thickness of the coating is approximately 100 nm.

[0119] <Forming a protective layer> The upper surface of the coating is coated with a slurry using a comma coater to form a protective layer of approximately 5 μm. Specifically, a slurry for forming the protective layer is prepared by mixing amorphous carbon and a metal nitride, and further mixing in a binder and solvent. Here, the amorphous carbon is acetylene black, and the metal nitride is magnesium nitride (Mg3N2). The amorphous carbon:metal nitride is added at a weight ratio of 90:10.

[0120] Furthermore, the mixed binder is manufactured by adding 3 parts by weight of carboxymethyl cellulose (CMC) and 6 parts by weight of styrene-butadiene rubber (SBR) relative to the total amount of amorphous carbon and metal nitrides. Additionally, the solvent used is water and ethylene glycol (EG) in an 80:20 weight ratio. The total amount of solvent is approximately 25% by weight of the total amount of amorphous carbon, metal particles, and binder to maintain a suitable viscosity for coating.

[0121] Figure 4a and Figure 4b The fine structure of the surface and cross-section is shown when the protective layer is configured on the current collector.

[0122] Reference Figure 4a and Figure 4b After the solvent evaporates, the porous protective layer has a surface structure and cross-sectional shape. This porous structure allows the plating solution to smoothly penetrate during the subsequent lithium electrode deposition process, which is beneficial to the movement and electrodeposition of lithium ions.

[0123] <Lithium Electrodeposition Process> Subsequently, in order to form a lithium alloy or pure lithium metal between the protective layer and the current collector, an electrodeposition process is used to remove lithium from the lithium supply source and deposit lithium between the protective layer and the current collector. The plating solution used for the electrodeposition as described above is prepared by adding 40% by weight of lithium bis(fluorosulfonyl)imide and 5% by weight of lithium nitrate as nitrogen compounds, respectively, relative to 100% by weight of the plating solution, and adding 5% by weight of fluoroethylene carbonate as a fluorine compound, relative to 100% by weight of the plating solution.

[0124] As a lithium supply source, a lithium metal plate with a purity of 99.9% or higher and a thickness of 500 μm is pressed onto a copper current collector (Cu plate). After the lithium supply source and the current collector are stacked in an electrically insulating state in the plating solution, a current is applied to the lithium supply source and the current collector as (+) electrodes and (-) electrodes, respectively, using a power supply device, thereby causing lithium to precipitate between the current collector and the composite protective layer.

[0125] In the electrodeposition process, the current density is set to 0.2 mA / cm². 2 0.5mA / cm 2 1mA / cm 2 The order was gradually increased, and after each electrodeposition lasted 5 minutes, the maximum current density was set to 10 mA / cm². 2 The electrodeposition time at the maximum current density is calculated as the time required to deposit a final cumulative lithium thickness of 10 μm, and is set variably according to the magnitude of the maximum current density.

[0126] Figure 5a and Figure 5b The electrodeposition appearance according to the maximum current density is shown in the electrodeposition process according to the embodiments and comparative examples.

[0127] Figure 5a This refers to the appearance of electrodeposited material when electrodeposition is performed below the maximum current density. Figure 5b This refers to the appearance of electrodeposition when electrodeposition is performed at current densities exceeding the maximum. (See reference.) Figure 5a and Figure 5b When electrodeposition is performed below the maximum depositable current density, the deposited lithium is confirmed to be stacked under the black protective layer, which is therefore visible. However, when electrodeposition is performed above the maximum depositable current density, the lithium is confirmed to be stacked on the upper surface of the protective layer, resulting in gray lithium deposits on the upper surface of the protective layer. Therefore, the maximum current density at which lithium deposits between the current collector and the protective layer during the electrodeposition process is defined as the maximum depositable current density.

[0128] Manufacturing all-solid-state batteries An all-solid-state battery was fabricated using the negative electrode manufactured according to the above embodiments, and its charge-discharge life was evaluated. To evaluate the all-solid-state battery cell, a pressurized evaluation battery from Teraleader capable of maintaining an inert atmosphere was used. To fabricate the all-solid-state battery cell, a sulfide-based nitrogen-containing heterocyclic magnesium aluminate (Li6PS5Cl) solid electrolyte was used, and the electrolyte was formed into a sheet with a thickness of approximately 0.7 mm. To obtain a dense electrolyte, a pressure of 370 MPa was applied.

[0129] A 0.5 mm thick lithium electrode was attached to one side of the electrolyte as a reference electrode, and a negative electrode manufactured according to the examples and comparative examples was attached to the other side. The reference electrode and the evaluation electrode were attached to the solid electrolyte at a pressure of 50 MPa, and in the charge-discharge evaluation, the battery was pressurized at 16 MPa.

[0130] <Example 2> To prepare the slurry for forming the protective layer, the process was carried out in the same manner as in Example 1, except that amorphous carbon and magnesium fluoride (MgF2) were mixed in a weight ratio of 90:10.

[0131] <Example 3> To prepare the slurry for forming the protective layer, the process was carried out in the same manner as in Example 1, except that amorphous carbon, magnesium nitride (Mg3N2), and magnesium fluoride (MgF2) were mixed in a weight ratio of 80:10:10.

[0132] <Comparative Example 1> To prepare the slurry for forming the protective layer, the process was carried out in the same manner as in Example 1, except that amorphous carbon was mixed in a 100-weight ratio without the use of metal fluorides or metal nitrides.

[0133] <Evaluation Example>: Evaluation examples of the addition of metal fluorides or metal nitrides Table 1 below shows the XRD peak value, maximum current density, and charge-discharge cycle number after electrodeposition, depending on the content of amorphous carbon, magnesium nitride, or magnesium fluoride in the slurry forming the protective layer. The XRD peak value, maximum current density, and charge-discharge cycle number were measured using the following methods.

[0134] XRD Peaks: Following the formation of the protective layer, lithium is further deposited between the protective layer and the current collector via electrodeposition. Phase analysis of the sample is then performed using XRD analysis from Rikaku. XRD analysis is conducted in thin film mode. To prevent the electrodeposited sample from reacting with external air or moisture, the sample is sealed with Kapton tape during measurement. Therefore, the large, slow peaks appearing at low angles may be due to the Kapton tape.

[0135] Maximum current density (mA / cm) 2 The maximum current density refers to the limit of the current density that allows electrodeposited lithium to be deposited between the protective layer and the current collector according to the process described. The maximum current density was measured.

[0136] Charge-discharge cycle count (times): The reference electrode and evaluation electrode were attached to the solid electrolyte at a pressure of 50 MPa. During the charge-discharge evaluation, the electrode was pressurized at 16 MPa in a dedicated evaluation battery. One charge-discharge evaluation was defined as one cycle under the following conditions: at 2 mA / cm². 2 Constant current charging for 0.5 hours, and at 2mA / cm 2 The constant current discharge lasts for 0.5 hours. The charge-discharge life is defined as the end of the life when a short circuit occurs between the reference electrode and the evaluation electrode or the voltage between the two electrodes exceeds 2V during the charge-discharge process.

[0137] Table 1 As can be confirmed from Examples 1, 2, and Comparative Example 1 in Table 1, the maximum current density and charge-discharge cycle number of Examples 1 or 2 containing magnesium nitride or magnesium fluoride are superior compared to Comparative Example 1, which only contains amorphous carbon as a protective layer. As can be confirmed from Examples 1 to 3, the maximum current density and charge-discharge cycle number of Example 3, which contains both magnesium nitride and magnesium fluoride, are superior compared to Examples 1 and 2, which contain only either magnesium nitride or magnesium fluoride.

[0138] Figures 6a to 6c The XRD phase analysis results of the protective layer before and after lithium battery deposition are shown in the embodiments and comparative examples according to the present invention.

[0139] Figure 6a This is Example 1. Figure 6b This is Example 2. Figure 6c This is Example 3. Figure 6d shows the XRD phase analysis results of the protective layer of Comparative Example 1 before and after lithium battery deposition.

[0140] Reference Figure 6a XRD phase analysis performed on the current collector with a protective layer containing magnesium nitride (Mg3N2) confirmed the presence of nickel as the current collector and silver (Ag) plated for alloying with lithium. Furthermore, a Mg(OH)2 peak was observed around 18°, which is the form formed by the decomposition of Mg3N2 nitride during the preparation of the aqueous slurry.

[0141] Subsequently, it was confirmed that after lithium was deposited between the protective layer and the current collector via an electrodeposition process, a Li3N phase was observed in the sample. This phase was confirmed to be formed by the combination of nitrogen elements contained in magnesium nitride and lithium ions generated during the electrodeposition process.

[0142] Reference Figure 6bXRD phase analysis performed on a current collector coated with a protective layer containing magnesium fluoride (MgF2) confirmed the presence of nickel as the current collector and silver (Ag) plating for alloying with lithium. A Li-Mg alloy phase was observed near 36° in samples where lithium was deposited between the protective layer and the current collector via electrodeposition. This phase was confirmed to be formed by the combination of magnesium from the magnesium fluoride with lithium ions generated during the electrodeposition process.

[0143] Reference Figure 6c XRD phase analysis performed on a current collector coated with a protective layer containing both magnesium nitride (Mg3N2) and magnesium fluoride (MgF2) confirmed the presence of nickel as the current collector and silver (Ag) plated to form an alloy with lithium. It was also confirmed that in samples where lithium was deposited via electrodeposition between the protective layer and the current collector, both the Li3N phase and the Li-Mg alloy phase were observed.

[0144] Referring to Figure 6d, XRD phase analysis of the current collector with a protective layer of a slurry composed only of amorphous carbon was confirmed, identifying nickel as the current collector and silver (Ag) plated to form an alloy with lithium. Furthermore, it was confirmed that no other special phases besides the nickel current collector were observed in the electrodeposited sample.

[0145] <Evaluation Example 2>: Evaluation Example of Controlling the Content of Metal Nitrides and Metallic Magnesium <Example 4> To prepare the slurry for forming the protective layer, the process was carried out in the same manner as in Example 1, except that amorphous carbon, magnesium nitride (Mg3N2), and magnesium fluoride (MgF2) were mixed in a weight ratio of 92:4:4.

[0146] <Example 5> To prepare the slurry for forming the protective layer, the process was carried out in the same manner as in Example 1, except that amorphous carbon, magnesium nitride (Mg3N2), and magnesium fluoride (MgF2) were mixed in a weight ratio of 70:15:15.

[0147] <Comparative Example 2> To prepare the slurry for forming the protective layer, the process was carried out in the same manner as in Example 1, except that amorphous carbon, magnesium nitride (Mg3N2), and magnesium fluoride (MgF2) were mixed in a weight ratio of 96:2:2.

[0148] <Comparative Example 3> To prepare the slurry for forming the protective layer, the process was carried out in the same manner as in Example 1, except that amorphous carbon, magnesium nitride (Mg3N2), and magnesium fluoride (MgF2) were mixed in a weight ratio of 60:20:20.

[0149] Table 2 below shows the XRD peak value, maximum current density, and charge-discharge cycle number after electrodeposition, depending on the content of amorphous carbon, magnesium nitride, and magnesium fluoride in the protective layer forming slurry.

[0150] Table 2 As can be confirmed from Table 2, in Examples 3 to 5, Comparative Example 2 and Comparative Example 3, when both magnesium nitride and magnesium fluoride are included, the maximum current density and charge-discharge cycle number of Examples 3 to 5 containing an appropriate range of total magnesium nitride and magnesium fluoride content are superior compared to Comparative Example 2, which has an excessively low total content of magnesium nitride and magnesium fluoride, or Comparative Example 3, which has an excessively high total content of magnesium nitride and magnesium fluoride.

[0151] This invention is not limited to the embodiments described, and can be manufactured in various different forms. Those skilled in the art should understand that it can be implemented in other specific forms without altering the technical concept or basic characteristics of the invention. Therefore, the above embodiments should be understood in all respects as exemplary, not limiting.

Claims

1. A lithium metal electrode, characterized in that, include: current collector, A metal layer, located on at least one surface of the current collector and comprising a lithium alloy, and A protective layer, located on the metal layer, comprises a carbonaceous material; At least one region between the metal layer and the protective layer, and within the protective layer, includes an alloy layer comprising at least one of a nitrogen-based alloy and a magnesium-based alloy.

2. The lithium metal electrode according to claim 1, characterized in that, Among the XRD peaks, at least one peak is found in the range of 21 to 25°, 26 to 30°, 35 to 39°, 45 to 47°, 48 to 51°, and 54 to 56°.

3. The lithium metal electrode according to claim 1, characterized in that, The peak value of XRD satisfies the following equation 1. <Formula 1> 3 ≤ Second peak value / First peak value × 100 (%) ≤ 10 (In 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. The lithium metal electrode according to claim 1, characterized in that, The peak value of XRD satisfies the following equation 2. <Formula 2> 3 ≤ Third peak / First peak × 100 (%) ≤ 10 (In 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. The lithium metal electrode according to claim 1, characterized in that, The peak value of XRD satisfies the following equation 2. <Formula 3> 3 ≤ (Second peak + Third peak) / First peak × 100 (%) ≤ 20 (In 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°).

6. The lithium metal electrode according to claim 1, characterized in that, This includes a film layer disposed on the protective layer.

7. The lithium metal electrode according to claim 6, characterized in that, The protective layer comprises carbonaceous materials and metal fluorides or metal nitrides.

8. A method for manufacturing a lithium metal electrode, characterized in that, include: The steps for preparing a current collector are as follows: The step of forming a coating on at least one surface of a current collector using a coating composition containing a lithium-philic component. The step of applying a slurry to the surface of the coating and forming a protective layer; The slurry contains carbonaceous substances and at least one of metal fluorides and metal nitrides.

9. The method for manufacturing a lithium metal electrode according to claim 8, characterized in that, After the step of forming the protective layer, the following is included: The steps of placing the current collector for forming the protective layer after the plating solution, and configuring the lithium supply source at a predetermined interval from the protective layer; and The step of forming a metal layer comprising a lithium alloy by applying an electric current between the current collector and the lithium supply source, wherein the lithium alloy is formed by alloying metal particles contained in the protective layer with lithium deposited from the lithium supply source.

10. The method for manufacturing a lithium metal electrode according to claim 8, characterized in that, The metal fluoride or metal nitride comprises at least one of MgF2, Mg3N2, AgF, and Ag3N.

11. The method for manufacturing a lithium metal electrode according to claim 9, characterized in that, Before current is applied between the current collector and the lithium supply source, the XRD peak of the protective layer has a peak value between 16 and 18°.

12. The method for manufacturing a lithium metal electrode according to claim 9, characterized in that, After an electric current is applied between the current collector and the lithium supply source, the metal layer comprises a nitrogen-based alloy or a magnesium-based alloy.

13. The method for manufacturing a lithium metal electrode according to claim 9, characterized in that, The slurry contains 70 to 95% by weight of the amorphous carbon relative to 100% by weight of the total amount of metal material comprising amorphous carbon and metal fluorides or metal nitrides.

14. The method for manufacturing a lithium metal electrode according to claim 9, characterized in that, The slurry contains amorphous carbon, metal fluorides, and metal nitrides. The total amount of the amorphous carbon, metal fluoride, and metal nitride is 8 to 30% by weight relative to 100% by weight of the total amount of the metal fluoride and the metal nitride.

15. The method for manufacturing a lithium metal electrode according to claim 9, characterized in that, The step of forming a metal layer comprising a lithium alloy by applying an electric current between the current collector and the lithium supply source, wherein the lithium alloy is formed by alloying the metal particles with lithium deposited from the lithium supply source, includes: With 6 to 12 mA / cm 2 The electrodeposition step is performed using the maximum current density within the specified range.

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