Anode-free electrode for lithium secondary battery, manufacturing method therefor, and lithium secondary battery including same

Abstract

The present invention relates to an anode-free electrode and a manufacturing method therefor. The anode-free electrode of the present invention comprises: a current collector; a coating layer disposed on at least one surface of the current collector and including a lithiophilic material; and a protective layer disposed on the coating layer, wherein the coating layer is disposed in 25.0 to 90.0% of the total area of the current collector.

Description

A negative electrode for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same

[0001] The present invention relates to a lithium secondary battery, and more specifically, to a non-negative electrode for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same.

[0002] This application claims priority to Korean Patent Application No. 10-2024-0190696, filed on December 19, 2024, the entire contents of which are incorporated herein by reference.

[0003] To reduce the cost and increase the energy density of secondary batteries, it is essential to use anode-free electrodes as the negative electrodes in lithium-ion batteries. Specifically, all-solid-state batteries are recently attracting attention as next-generation batteries for high energy density applications, such as electric vehicles (EVs).

[0004] All-solid-state batteries offer various advantages, such as excellent stability due to the absence of liquid electrolytes, the ability to operate at high voltages, improved energy density of the battery pack through the reduction of cooling and safety-related components, and the capacity to operate over a wide temperature range. To achieve high energy density in such all-solid-state batteries, it is advantageous to transition from thick, low-capacity graphite-based anode materials to a cathode-free system. Considering economic efficiency and energy density, a cathode-free electrode with a thickness of 20 μm or less, even including a protective layer, is required.

[0005] Generally, in the case of non-cathode electrodes, there are difficulties in the technology of manufacturing thin lithium metal through commercial processes, and dendrite growth caused by non-uniform current density and electrochemical reactions during the charging and discharging process of secondary batteries is a problem. This can lead to continuous side reactions with the electrolyte and even internal short circuits where the anode and cathode come into contact.

[0006] The growth of the above dendrites can cause significant problems with low lifespan characteristics and stability, and consequently, there are difficulties in practically utilizing ultra-thin lithium metal anodes.

[0007] This relates to a method for increasing lifespan by suppressing the above-mentioned dendrites. Although various methods have been proposed, there is a problem in that it is difficult to simultaneously achieve high energy density through lithium ultra-thinness and sufficient lifespan characteristics. To solve the above problem, a nano-scale metal layer made of a lithium-friendly layer material is coated on a current collector to maximize the surface area of ​​the lithium-friendly material that can react with lithium to form an alloy, and to prevent a decrease in current density caused by the expansion of the surface area of ​​the current collector.

[0008] However, forming a metal layer made of lithium-friendly material on the entire current collector presents a problem where commercialization is difficult due to increased raw material costs.

[0009] According to one embodiment of the present invention, a negative electrode for a lithium secondary battery reduces raw material costs and simultaneously provides a lithium secondary battery with improved charge / discharge life characteristics when applied to a battery.

[0010] A method for manufacturing a non-cathode electrode according to another embodiment of the present invention provides a method for manufacturing a non-cathode electrode for a lithium secondary battery having the aforementioned advantages.

[0011] According to one embodiment of the present invention, a lithium-free negative electrode comprises a current collector, a coating layer located on at least one surface of the current collector and comprising a lithium-friendly material, and a protective layer located on the coating layer, wherein the coating layer may be disposed in an area of ​​25.0 to 90.0% of the total area of ​​the current collector.

[0012] In one embodiment, the coating layer may include a metal material having a plurality of island shapes. In one embodiment, the area of ​​the island shapes may be 0.0001 to 0.50 μm.

[0013] In one embodiment, the current collector may include at least one of copper, nickel, titanium, stainless steel, iron, gold, platinum, silver, tantalum, ruthenium, and alloys thereof. In one embodiment, the lithium-friendly material of the coating layer may include at least one metal selected from the group consisting of In, Ag, Sn, Zn, Si, Al, and Bi.

[0014] In one embodiment, the protective layer may include amorphous carbon. In one embodiment, a metal layer containing lithium may be formed on the current collector during the first charge at the battery terminal.

[0015] According to another embodiment of the present invention, a method for manufacturing a non-cathode electrode, a method for manufacturing a non-cathode electrode that does not contain lithium, comprises the steps of preparing a current collector, forming a coating layer on at least one surface of the current collector using a coating composition containing a lithium-friendly material, and forming a protective layer on the surface of the coating layer containing the lithium-friendly material, wherein the step of forming the coating layer containing the lithium-friendly material may include controlling the coverage of the coating layer to 25.0 to 90.0% by at least one of plating and deposition.

[0016] In one embodiment, the deposition may be performed by any one of physical vapor deposition (PVD), chemical vapor deposition (CVD), electrochemical deposition, spray coating, spin coating, and dipping coating. In one embodiment, the plating may be performed by at least one of electroplating, electroless plating, hot-dip galvanizing, and mechanical plating.

[0017] According to another embodiment of the present invention, a lithium secondary battery may include a positive current collector, a positive electrode containing a positive active material layer, the aforementioned negative electrode, and an electrolyte disposed between the positive active material layer and a protective layer. In one embodiment, a metal layer containing lithium may be formed within the negative electrode during the first charging process.

[0018] According to one embodiment of the present invention, a non-negative electrode for a lithium secondary battery comprises a metal layer having a coverage of a predetermined range on a current collector, thereby enabling economical and improved charge / discharge life characteristics.

[0019] A method for manufacturing a non-cathode electrode for a lithium secondary battery according to another embodiment of the present invention provides a method for manufacturing a non-cathode electrode for a lithium secondary battery having the aforementioned advantages.

[0020] According to another embodiment of the present invention, a lithium secondary battery may have improved electrochemical performance by including a negative electrode having the aforementioned advantages.

[0021] FIG. 1 illustrates a cathode-free electrode according to one embodiment.

[0022] FIGS. 2a and 2b are scanning electron microscope (SEM) images showing the structure and thickness of an alloy material coating layer deposited on a current collector according to one embodiment of the present invention. FIG. 2c is a scanning electron microscope (SEM) image showing the surface microstructure of an alloy material coating layer plated on a current collector according to one embodiment of the present invention.

[0023] Figures 3a and 3b show the microstructure of the surface and cross-section when a protective layer is placed on a current collector coated with an alloy material.

[0024] FIGS. 4a and 4b are drawings showing the surface microstructure and plating layer image mapping results of an embodiment of the present invention, and FIGS. 4c and 4d are drawings showing the surface microstructure and plating layer image mapping results of a comparative example of the present invention.

[0025] Figure 5 shows the charge / discharge life evaluation results of the embodiments and comparative examples of the present invention.

[0026] Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the present invention.

[0027] The technical terms used herein are for the reference of specific embodiments only and are not intended to limit the invention. The singular forms used herein include plural forms unless phrases clearly indicate otherwise. As used in the specification, the meaning of "comprising" specifies certain characteristics, areas, integers, steps, actions, elements, and / or components, and does not exclude the presence or addition of other characteristics, areas, integers, steps, actions, elements, and / or components.

[0028] When it is stated that one part is "on" or "on" another part, it may be directly on or on the other part, or another part may be involved in between. In contrast, when it is stated that one part is "directly on" another part, no other part is interposed in between.

[0029] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with relevant technical literature and the present disclosure, and are not interpreted in an ideal or highly formal sense unless otherwise defined.

[0030] FIG. 1 shows a non-cathode electrode (100) manufactured according to one embodiment.

[0031] Referring to FIG. 1, a non-cathode electrode (100) according to one embodiment comprises a current collector (10) and a coating layer (20) containing a lithium-friendly material located on at least one surface of the current collector (10), and a protective layer (30) on the coating layer (20). The inventors have discovered that when the non-cathode electrode (100) is used in a battery by depositing or coating a coating layer (20) with a predetermined area on a portion of the current collector (10) and using only the non-cathode electrode (100) that does not contain separate lithium, lithium introduced from the positive electrode by charging the battery is uniformly coated on the coating layer, thereby improving the electrochemical performance of the battery.

[0032] The current collector (10) may be a component for electrical connection within a lithium secondary battery. The current collector (10) may have the form of a foil, but is not limited thereto, and may have the form of, for example, a mesh, foam, rod, wire, or a sheet woven from wire or fiber.

[0033] 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, copper, nickel, titanium, stainless steel, gold, platinum, silver, tantalum, ruthenium, and any one or a combination thereof of alloys.

[0034] 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 battery weight increases and the energy density of the battery decreases. If the thickness of the current collector (10) is excessively thin, there is a risk of overheating damage during high-current operation and damage due to tension during the battery manufacturing process.

[0035] A coating layer (20) containing a lithium-friendly material is positioned on a current collector (10) and may be placed in an area of ​​25.0 to 90.0% of the total area of ​​the current collector. Specifically, the coating layer (20) containing a lithium-friendly material may include a lithium-friendly material. Specifically, the coating layer (20) containing a lithium-friendly material may be 30 to 70%, more specifically 35 to 65%, and even more specifically 35.2 to 62.5% of the total area of ​​the current collector. The area of ​​the coating layer (20) containing a lithium-friendly material may refer to the area occupied by the lithium-friendly material in the total area when a metal, for example, a coating layer (20) containing a lithium-friendly material, is coated on the current collector (10) by deposition or plating.

[0036] The coating layer (20) of the present invention is not placed on the front surface of the current collector (10), but is placed on the current collector (10) within the aforementioned range, which has the advantage of allowing lithium to be easily deposited between the protective layer (30) and the current collector (10) by charging.

[0037] If the ratio of the area of ​​the coating layer (20) to the total area of ​​the current collector (10) exceeds the upper limit of the aforementioned range, there is a problem in that lithium is not deposited between the current collector (10) and the protective layer (30) but is deposited on the opposite surface of the protective layer (30) during the process of additionally growing lithium by the method of precipitation or charging the battery. If the ratio of the area of ​​the coating layer (20) to the total area of ​​the current collector (10) exceeds the lower limit of the aforementioned range, there is a problem in that the amount of lithium-friendly material is insufficient, so the alloy cannot be smoothly formed with lithium, and thus the movement of lithium is inhibited, and lithium is likewise deposited on the opposite surface of the protective layer (30).

[0038] In one embodiment, the coating layer (20) may include a metal material having a plurality of island shapes. Specifically, the coating layer (20) may, for example, have an irregular island shape formed by the aggregation of at least one particle. The island shape may be such that the particles of the metal material constituting the coating layer (20) are irregular, and the particles of the metal material are connected and observed in a lump form.

[0039] In one embodiment, the area of ​​the island shape is 0.001 to 0.50 μm 2 It may be. The area of ​​the above island shape is 5 μm in width, 5 μm in height, and 25 μm in area as observed using a scanning electron microscope. 2 It may be a value measured as the range of the minimum to maximum area when an image within the range is divided into individual islands using the ImageJ program and the area of ​​each individual island is calculated. Specifically, the area of ​​the island shape is 0.01 to 0.30㎛ 2 , more specifically 0.01 to 0.25 μm 2 It could be.

[0040] If the area of ​​the island shape exceeds the upper limit of the aforementioned range, the particle size of the coating layer (200) containing individual lithium-friendly alloys is too large and the coverage is excessive, so there is a problem of lithium being deposited on the outer surface of the protective layer. If the area of ​​the island shape exceeds the lower limit of the aforementioned range, the amount of lithium-friendly alloy material is too insufficient to form an alloy smoothly with lithium, so the movement of lithium is hindered during the charging process, etc., and lithium is not deposited between the current collector and the protective layer, but rather there is a problem of lithium being deposited on the opposite surface of the protective layer.

[0041] In one embodiment, the coating layer (20) may include a lithium-friendly metal. Specifically, the lithium-friendly metal may include at least one metal selected from the group consisting of, for example, In, Ag, Sn, Zn, Si, Al, and Bi.

[0042] The protective layer (30) is located on the coating layer (20) containing a lithium-friendly material and may contain amorphous carbon. When the negative electrode (100) of the present invention is used without using a negative electrode containing lithium separately in an all-solid-state battery, high resistance is generated by the reaction between the all-solid-state electrolyte and lithium during the charging and discharging process, and lithium dendrites are continuously generated or high-resistance lithium by-products are generated due to local non-uniformity of current density during the charging and discharging process, resulting in failure due to short circuit or overvoltage during charging and discharging or a decrease in battery capacity.

[0043] According to one embodiment, the non-cathode electrode (100) includes a protective layer (30) containing amorphous carbon, thereby improving not only the output characteristics and lifespan characteristics of the non-cathode electrode (100) but also additional structural safety.

[0044] Specifically, the non-cathode electrode of the present embodiment includes a protective layer (30) containing amorphous carbon, thereby not only improving ion conductivity but also improving the strength of the protective layer (30) and physically blocking dendrites during dendrite growth in the non-cathode electrode, thereby preventing short circuits between electrodes and improving charge / discharge life.

[0045] The above amorphous carbon may be one or more 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.

[0046] In one embodiment, the protective layer (30) may include a binder. The binder may be a water-based binder, and the water-based binder may be 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 polymer resins such as hydroxyethyl cellulose, carboxymethyl cellulose and polyvinyleden fluoride, but is not limited thereto.

[0047] Here, the binder may be added in an amount of 1 to 15 parts by weight, specifically 3 to 10 parts by weight, based on the weight of the slurry formed by mixing the amorphous carbon and water. When the content of the binder satisfies the aforementioned 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 lifespan characteristics of the secondary battery.

[0048] In addition, in one embodiment, the binder may be a non-aqueous binder, and the non-aqueous binder may include at least one selected from PVDF (polyvinylidene fluoride), PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene copolymer), PTFE (polytetrafluoroethylene), PAI (polyamideimide), PEO (polyethylene oxide), PANI (polyaniline), PDO (polypyrrole), and polythiophene.

[0049] Here, the binder may be added in an amount of 1 to 30 parts by weight, specifically 3 to 10 parts by weight, based on 100% of the total weight of the amorphous carbon, additive, and binder. When the content of the binder satisfies the aforementioned 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 lifespan characteristics of the secondary battery.

[0050] If the content of the binder is excessively low compared to the aforementioned range, there is a problem of reduced inter-particle bonding strength when forming the protective layer; and if the content of the binder is excessively high compared to the aforementioned range, not only does it cause a decrease in energy density, but the resistance of the protective layer also increases significantly, which hinders lithium ion conduction.

[0051] In one embodiment, the thickness of the protective layer (30) may be from 0.01 μm to 50 μm. Specifically, the thickness of the protective layer (30) may be in the range of 1 μm to 20 μm. When the thickness of the protective layer satisfies the aforementioned range, having an appropriate thickness of the protective layer not only serves as a protective layer but also prevents the formation of lithium dendrites on the surface of the protective layer due to the effect of having appropriate resistance for the movement of lithium ions, and allows lithium ions to penetrate well into the protective layer and conduct, thereby allowing lithium to be deposited on the lower surface of the protective layer.

[0052] If the thickness of the protective layer is excessively thin, there is a problem in that it cannot perform its function as a protective layer. If the thickness of the protective layer is excessively thick, the resistance of the protective layer becomes excessively high, which can cause an increase in overvoltage during the operation of the secondary battery and cause a decrease in battery energy density due to an increase in weight and volume. However, the thickness of such a protective layer can be variably adjusted according to the design of the secondary battery structure.

[0053] The non-cathode electrode (100) of the present invention may be a non-cathode electrode that does not contain lithium. Specifically, the non-cathode electrode (100) may have a metal layer containing lithium formed on a current collector during the first charging of the battery terminal. More specifically, during charging of the battery, lithium moves from the positive electrode toward the non-cathode electrode (100), and the lithium reacts with the coating layer (20) within the non-cathode electrode (100) to form a metal layer containing lithium. Specifically, the metal layer may contain lithium or a lithium alloy. More specifically, the metal layer may be formed by the reaction of lithium with a lithium-friendly material contained in the coating layer (20).

[0054] According to another embodiment of the present invention, a method for manufacturing a non-cathode electrode comprises the steps of preparing a current collector (10), forming a coating layer (20) containing a lithium-friendly material on at least one surface of the current collector (10) using a coating composition containing a lithium-friendly material, and forming a protective layer (30) on the surface of the coating layer (20) containing the lithium-friendly material using a slurry containing amorphous carbon. The method for manufacturing a non-cathode electrode of the present invention manufactures a non-cathode electrode in which a coating layer and a protective layer are sequentially formed on a current collector without forming a separate metal layer containing lithium. At this time, the step of forming the coating layer controls the coverage of the coating layer to a predetermined range by at least one of plating and deposition, so that when lithium moves from the positive electrode to the non-cathode electrode (100) of the present invention by charging at the battery terminal and forms a lithium layer, the lithium layer is uniformly coated, thereby improving battery performance.

[0055] In the step of preparing the current collector (10), the current collector (10) may be made of a material that has electrical conductivity and has limited reaction with lithium. Specifically, the material of the current collector (10) may be, for example, copper, nickel, titanium, stainless steel, gold, platinum, silver, tantalum, ruthenium, and alloys thereof, carbon, a conductive polymer, a composite fiber with a conductive layer coated on a non-conductive polymer, or a combination thereof.

[0056] The step of forming a coating layer (20) on at least one surface of a current collector (10) using a coating composition containing a lithium-friendly material may involve coating the lithium-friendly material on at least one surface of the current collector. The lithium-friendly material may include, for example, at least one metal selected from the group consisting of In, Ag, Sn, Zn, Si, Al, and Bi.

[0057] In one embodiment, the step of forming a coating layer (20) containing a lithium-friendly material can be performed by a plating and deposition method. Specifically, the plating can be performed by at least one of, for example, electroplating, electroless plating, hot-dip galvanizing, and mechanical plating.

[0058] The above deposition can be performed by any one of physical vapor deposition (PVD), chemical vapor deposition (CVD), electrochemical deposition, spray coating, spin coating, and dipping coating.

[0059] In one embodiment, the step of forming the coating layer may be a step of controlling the coating layer coverage to 25.0 to 90.0%. Specifically, the coating layer coverage refers to the area on which the coating layer is disposed on the current collector based on 100% of the current collector area, and may satisfy 30.0 to 70.0%, more specifically 35.0 to 65.0%, and even more specifically 35.2 to 62.5%.

[0060] By controlling the coverage of the coating layer to the aforementioned range, lithium flowing in from the positive electrode during battery charging is uniformly formed in the coating layer, thereby providing the advantage of excellent charge / discharge performance when applied to the battery. If the coverage of the coating layer deviates from the upper limit of the aforementioned range, there is a problem in that lithium is deposited on the opposite surface of the protective layer because the particle size of the individual lithium-friendly material is too large and the coverage is excessive.

[0061] In one embodiment, when the step of forming the coating layer is performed by plating, the accumulated current is 0.05 to 1.30 mAh / dm 2It can be performed at. The above cumulative current refers to the product of the current density and the plating time. Specifically, the cumulative current is 0.10 to 1.25 mAh / dm 2 , more specifically, 0.10 to 1.00 mAh / dm 2 It can be performed in. Since the above-mentioned cumulative current satisfies the aforementioned range, lithium electrodeposition is advantageous, and there is an advantage of excellent charge-discharge performance cycles when applied to a battery.

[0062] Specifically, the accumulated current can be controlled differently depending on the components of the current collector and the coating layer. In one embodiment, when the component of the current collector is Ni, the accumulated current is 0.10 to 1.25 mAh / dm 2 , more specifically, 0.15 to 1.25 mAh / dm 2 , more specifically, 0.18 to 1.25 mAh / dm 2 It can be performed in.

[0063] In one embodiment, when the component of the current collector is Fe-Ni, the cumulative current is 0.05 to 1.25 mAh / dm 2 , more specifically, 0.07 to 1.00 mAh / dm 2 , more specifically, 0.08 to 0.80 mAh / dm 2 It can be performed in.

[0064] In one embodiment, when the component of the current collector is STS, the cumulative current is 0.05 to 1.20 mAh / dm 2 , more specifically, 0.06 to 0.90 mAh / dm 2 , more specifically, 0.07 to 0.60 mAh / dm 2 It can be performed in.

[0065] If the above accumulated current exceeds the upper limit of the aforementioned range, the plating amount of the lithium-friendly material is excessively large, resulting in excessive coverage and causing lithium to precipitate on the opposite surface of the protective layer. If the above accumulated current exceeds the lower limit of the aforementioned range, the plating amount is excessively small, resulting in an insufficient amount of lithium-friendly material and a problem in that it cannot smoothly form an alloy with lithium.

[0066] In one embodiment, when the step of forming the coating layer is performed by plating, the plating time may be 60 seconds or less. Specifically, the plating time may be 50 seconds or less, specifically 0.1 to 40 seconds, and more specifically 0.5 to 30 seconds.

[0067] In one embodiment, when the step of forming the coating layer is performed by plating, the plating current is 0.1 to 5.0 mA / cm 2 It can be performed within the range. Specifically, the plating current is 0.5 to 4.0 mA / cm² 2 Range, more specifically, 0.5 to 3.5 mA / cm 2 It can be performed within the range.

[0068] By satisfying the aforementioned ranges for the plating current and plating time, there is an advantage in that lithium electrodeposition is easy and a battery with excellent lifespan characteristics can be realized when applied to a battery. If the plating current and plating time deviate from the upper limit of the aforementioned range, the amount of lithium-friendly material plated is too large, resulting in excessive coverage and a problem in which lithium is deposited on the opposite surface of the protective layer. If the plating current and plating time deviate from the lower limit of the aforementioned range, the amount of plating is too small, resulting in an insufficient amount of lithium-friendly material and a problem in that an alloy cannot be smoothly formed with lithium.

[0069] In one embodiment, when the step of forming the coating layer is performed by deposition, the deposition temperature may be performed at 20 to 200 ℃. Specifically, the deposition temperature may be performed at 25 to 150 ℃.

[0070] In one embodiment, when the step of forming the coating layer is performed by deposition, the overspeed voltage during deposition may be performed at 0.5 to 5 kW. Specifically, the pressure may be performed at 1 to 3 kW.

[0071] In one embodiment, when the step of forming the coating layer is performed by deposition, the deposition rate may be performed at 0.1 to 6 MPM. Specifically, the deposition rate may be performed at 0.5 to 3 MPM.

[0072] By forming a coating layer under the above deposition conditions, it was confirmed that the coating layer having the island shape of the present invention is properly formed, and that the non-cathode electrode is highly effective when applied to a battery.

[0073] A protective layer (30) can be formed on the surface of a coating layer (20) containing a lithium-friendly material using a slurry containing amorphous carbon. The protective layer (30) can be formed by applying a slurry formed by mixing the amorphous carbon and a binder in water using at least one of the doctor blade method, dip method, reverse roll method, direct roll method, gravure method, extrusion method, and brush application method. The protective layer (30) may further include a binder.

[0074] Meanwhile, in the step of forming the protective layer (30), the thickness of the lithium ion conduction promoting protective layer formed on the surface of the alloy material coating layer may be in the range of 0.01 μm to 50 μm, more specifically 1 μm to 20 μm.

[0075] According to another embodiment of the present invention, a lithium secondary battery comprises a positive electrode, a negative electrode of the present invention, and an electrolyte located between the positive electrode and the negative electrode. Herein, the negative electrode may be the negative electrode (10) of the present invention that does not contain lithium.

[0076] In one embodiment, a lithium secondary battery may include an electrode assembly comprising a positive electrode including a positive active material, a negative electrode of the present invention, and a separator disposed between the positive electrode and the negative electrode. Such an electrode assembly may be wound or folded and accommodated in a battery case.

[0077] Subsequently, an electrolyte is injected into the battery case and sealed to complete the secondary battery. At this time, the battery case may have a shape such as a cylindrical, prismatic, pouch, or coin type.

[0078] The above-mentioned anode may include an anode active material layer and an anode current collector. The above-mentioned anode active material layer may include, for example, a Li compound comprising 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-metal element selected from O, F, S, P, and combinations thereof.

[0079] In one embodiment, a conductive material may be further added to the positive active material layer. The conductive material may be, for example, carbon black and ultrafine graphite particles, fine carbon such as acetylene black, nano metal particle paste, etc., but is not limited thereto.

[0080] The above positive current collector serves to support the above positive active material layer. As the positive current collector, for example, an aluminum foil, a nickel foil, or a combination thereof may be used, but is not limited thereto.

[0081] The electrolyte filled in the above lithium secondary battery may be a non-aqueous electrolyte or a solid electrolyte. Specifically, the electrolyte may be a solid electrolyte. The above 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 above solid electrolyte may be, for example, a gel-type polymer electrolyte in which an electrolyte is impregnated into a polymer electrolyte such as polyethylene oxide or polyacrylonitrile, or an inorganic solid electrolyte such as LiI or Li3N.

[0082] The above-mentioned separator separates the positive and negative electrodes and provides a pathway for the movement of lithium ions; any separator commonly used in lithium secondary batteries may be used. Specifically, the separator may be one that has low resistance to the movement of electrolyte ions 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 nonwoven or woven fabric. Meanwhile, if a solid electrolyte is used as the electrolyte, the solid electrolyte may also serve as the separator.

[0083] Embodiments of the present invention will be described in detail below. However, these are presented as examples and are not intended to limit the present invention, and the present invention is defined only by the scope of the claims set forth below.

[0084]

[0085] <Experimental Example>

[0086] Manufacturing of non-cathode electrodes for lithium secondary batteries

[0087] <Example 1>

[0088] <Whole House Manufacturing>

[0089] A nickel (Ni) current collector was prepared to be used as the negative electrode for the lithium secondary battery of the present invention.

[0090]

[0091] <Formation of lithium-friendly material coating layer>

[0092] Subsequently, an alloy material was coated on both sides of the nickel current collector using a plasma deposition method. The deposition was performed under conditions of 1.0 MPM, room temperature, and 2 kW.

[0093] FIGS. 2a and 2b are scanning electron microscope (SEM) images showing the microstructure of the surface and cross-section of an alloy material coating layer plated on a current collector according to one embodiment of the present invention.

[0094] Referring to FIGS. 2a and 2b, it can be seen that the lithium-friendly layer on the current collector has an island shape over the entire area and has an appropriate level of coverage on the surface of the current collector.

[0095]

[0096] Formation of a protective layer

[0097] Subsequently, 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, the protective layer was formed by mixing amorphous carbon, a binder, and a solvent. At this time, the binder was prepared by adding a total of 9.0 parts by weight of carboxymethylcellulose (CMC) and styrene-butadiene rubber (SBR) in amounts of 3.0 parts by weight and 6.0 parts by weight, respectively, relative to 100 parts by weight of amorphous carbon. In addition, a solvent was used in which water and ethylene glycol (EG) were mixed in a weight ratio of 80:20. The total amount of solvent was approximately 25% by weight of the total amount of amorphous carbon and binder to maintain a viscosity suitable for coating. Acetylene black was used as the amorphous carbon.

[0098] Figures 3a and 3b show the microstructure of the surface and cross-section when a protective layer is placed on a current collector coated with an alloy material.

[0099] Referring to FIGS. 3a and 3b, it was confirmed that an alloy material coating layer, which is a lithium-friendly metal plating layer, is plated on the current collector, and a protective layer is formed on the coating layer.

[0100]

[0101] Solid-state battery manufacturing

[0102] An all-solid-state battery was fabricated using the anode-free electrode prepared according to Example 1 described above, and its charge-discharge life was evaluated. To evaluate the all-solid-state battery cell, a pressurized evaluation cell from TerraReader, capable of maintaining an inert atmosphere, was used. For the fabrication of the all-solid-state battery cell, a sulfide-based azirodite (Li6P5Cl) solid electrolyte was used, and the electrolyte was formed into pellets with a thickness of approximately 0.7 mm. To ensure a dense electrolyte, it was pressurized to a pressure of 370 MPa.

[0103]

[0104] A lithium electrode with a thickness of 0.5 mm was attached to one side of the *98 electrolyte as a reference electrode, and a non-cathode electrode prepared according to Example 1 was attached to 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-discharge evaluation, the pressure was applied at 16 MPa in a dedicated evaluation cell.

[0105]

[0106] <Example 2>

[0107] In the step of coating the above coating layer, the procedure was performed in the same manner as Example 1, except that the deposition rate was changed to 0.5 MPM.

[0108]

[0109] <Example 3>

[0110] In the step of coating the above coating layer, the procedure was performed in the same manner as Example 1, except that the deposition rate was changed to 1.5 MPM.

[0111]

[0112] <Example 4>

[0113] In the step of coating the above coating layer, the procedure was performed in the same manner as Example 1, except that the lithium-friendly layer material was changed to Ag.

[0114]

[0115] <Comparative Example 1>

[0116] In the step of coating the above coating layer, the procedure was performed in the same manner as Example 1, except that the deposition rate was changed to 0.01 MPM.

[0117]

[0118] <Comparative Example 2>

[0119] In the step of coating the above coating layer, the procedure was performed in the same manner as Example 1, except that the deposition rate was changed to 10 MPM.

[0120]

[0121] <Comparative Example 3>

[0122] In the step of coating the above coating layer, the procedure was performed in the same manner as Example 1, except that the lithium-friendly layer material was changed to Ag and the deposition rate was changed to 0.01 MPM.

[0123]

[0124] <Evaluation Example 1>

[0125] Table 1 below shows the lithium-friendly layer coverage, island area range, and charge / discharge cycles when Sn or Ag is used as the lithium-friendly metal in the Ni current collector and the deposition conditions are controlled.

[0126] The lithium-friendly layer coverage, island area range, and charge / discharge performance cycles were measured by the following method.

[0127] Lithium-Friendly Layer Coverage and Island Area Range: To measure the surface coverage and island area of ​​the lithium-friendly layer, the microstructure was observed using a ZEISS GEMINI-500 scanning electron microscope. The coverage of the lithium-friendly layer was measured as the area of ​​the lithium-friendly layer on a two-dimensional plane relative to the total area, using the ImageJ image software developed by the NIH (National Institute of Health) based on images observed by the scanning electron microscope. The islands were defined as particle shapes each having an independent perimeter, with dimensions of 5 µm in width, 5 µm in length, and an area of ​​25 µm. 2 It was measured as the range of minimum to maximum area for each island included within the image of the range.

[0128] Charge / Discharge Performance Cycles (cycles): The reference electrode and evaluation electrode were attached to the solid electrolyte at a pressure of 50 MPa, and during the charge / discharge evaluation, pressurization was applied to 16 MPa in a dedicated evaluation cell. The charge / discharge evaluation was conducted at 2 mA / cm². 2 Charging for 0.5 hours at a constant current, 2 mA / cm² 2 The test was conducted by defining 0.5 hours of discharge with a constant current as one cycle. The charge / discharge life was defined as ending 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.

[0129] Classification Lithium-friendly layer deposition conditions Product Effect Current collector Lithium-friendly metal deposition temperature Overspeed Voltage Deposition speed Lithium-friendly layer coverage Island area range Charge / discharge performance Cycles Unit -- [kW][MPM][%][㎛ 2][Times] Example 1 NiSn Room Temperature 2167.10.0001~0.10875 Example 2 NiSn Room Temperature 20.572.640.0001~0.10815 Example 3 NiSn Room Temperature 21.554.300.0001~0.10728 Example 4 NiAg Room Temperature 2154.300.0001~0.10951 Comparative Example 1 NiSn Room Temperature 20.01100> 1186 Comparative Example 2 NiSn Room Temperature 21013.910.01~0.20164 Comparative Example 3 NiAg Room Temperature 20.01100> 192

[0130] Referring to Table 1 above, it was confirmed that when the current collector material is Ni, the lithium-friendly metal is Sn, and the deposition temperature and overspeed voltage are the same at room temperature and 2 kW, respectively, controlling the deposition rate to control the lithium-friendly layer coverage within the scope of the present invention results in excellent performance with over 700 cycles. In contrast, Comparative Example 1 shows an excessively high deposition rate, resulting in a lithium-friendly layer coverage of 100%, which covers an excessively large area of ​​the current collector with the lithium-friendly layer; consequently, islands are not realized, and 1 μm 2 It was confirmed that the charge-discharge cycle performance was inferior due to the formation of the above lithium-friendly layer material. In addition, Comparative Examples 2 and 3 had excessively low deposition rates, resulting in lithium-friendly layer materials of 0.01–0.20 μm 2 It appears as an island shape with an area of ​​the range, but it was confirmed that the charge / discharge performance cycles are inferior due to the excessively low coverage of the lithium-friendly layer. FIGS. 4a and 4b are drawings showing the surface microstructure and deposition layer image mapping results of an embodiment of the present invention, and FIGS. 4c and 4d are drawings showing the surface microstructure and deposition layer image mapping results of a comparative example of the present invention.

[0131] FIGS. 4a and 4b are drawings showing the surface microstructure and deposition layer image mapping results of Example 1 of the present invention, and FIGS. 4c and 4d are drawings showing the surface microstructure and deposition layer image mapping results of Comparative Example 1 of the present invention. Referring to FIGS. 4a and 4b, it can be confirmed that the coverage fraction of the lithium-friendly layer material on the surface of the current collector is 67.1%, and the island area is 0.001 to 0.10 μm. 2 It was confirmed that the range of was satisfied.

[0132] Referring to FIGS. 4c and 4d, it can be confirmed that the coverage fraction of the lithium-friendly layer material on the surface of the current collector is 100%, and the island area is 1 μm. 2 It can be confirmed that it is larger. Specifically, it can be seen that the island shape is not manifested and the entire area is evenly covered.

[0133] Figure 5 shows the charge / discharge life evaluation results of the embodiments and comparative examples of the present invention.

[0134] Figure 5 shows the results of the charge-discharge life evaluation of the all-solid-state batteries prepared according to Example 1 and Comparative Example 1. Referring to Figure 5, it can be seen that the charge-discharge life evaluation of Example 1 is superior to that of Comparative Example 1.

[0135]

[0136] The present invention is not limited to the above embodiments and can be manufactured in various different forms, and those skilled in the art will understand that the invention can be implemented in other specific forms without changing the technical concept or essential features of the invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. The present invention relates to a non-cathode electrode that does not contain lithium, wherein The whole house; A coating layer located on at least one surface of the above-mentioned current collector and comprising a lithium-friendly material; and It includes a protective layer located on the above coating layer, and The above coating layer is a non-cathode electrode disposed in an area of ​​25.0 to 90.0% relative to the total area of ​​the current collector.

2. In Paragraph 1, The above coating layer comprises a metal material having a plurality of island shapes, forming a non-cathode electrode.

3. In Paragraph 2, A non-cathode electrode having an area of ​​0.0001 to 0.50 μm in the shape of the island.

4. In Paragraph 1, The above current collector is a non-cathode electrode comprising at least one of copper, nickel, titanium, stainless steel, iron, gold, platinum, silver, tantalum, ruthenium, and alloys thereof.

5. In Paragraph 1, The lithium-friendly material of the coating layer comprises at least one metal selected from the group consisting of In, Ag, Sn, Zn, Si, Al, and Bi, forming a non-cathode electrode.

6. In Paragraph 1, The above protective layer is a non-cathode electrode containing amorphous carbon.

7. In Paragraph 1, A non-cathode electrode in which a metal layer containing lithium is formed on a current collector during the first charge at the battery terminal.

8. In Paragraph 7, The above metal layer is disposed on a lithium alloy layer and comprises a lithium metal layer containing lithium, forming a non-cathode electrode.

9. In Paragraph 1, A non-negative electrode in which a lithium metal layer is formed on the current collector during the first charge at the battery terminal.

10. A method for manufacturing a lithium-free cathode electrode, wherein The stage of preparing the entire house; A step of forming a coating layer on at least one surface of a current collector using a coating composition comprising a lithium-friendly material; and The method includes the step of forming a protective layer on the surface of a coating layer containing the above-mentioned lithium-friendly material, A method for manufacturing a non-cathode electrode comprising the step of forming a coating layer including the above-mentioned lithium-friendly material, wherein the coating layer coverage is controlled to 25.0 to 90.0% by at least one of plating and deposition.

11. In Paragraph 10, A method for manufacturing a cathode-free electrode in which the above deposition is performed by any one of physical vapor deposition (PVD), chemical vapor deposition (CVD), electrochemical deposition, spray coating, spin coating, and dipping coating.

12. In Paragraph 10, A method for manufacturing a cathode-free electrode in which the plating is performed by at least one of electroplating, electroless plating, hot-dip galvanizing, and mechanical plating.

13. In Paragraph 10, The above deposition is a method for manufacturing a cathode-free electrode in which the overspeed voltage is performed in the range of 0.5 to 5 kW.

14. Positive current collector; Anode containing an anode active material layer; A non-cathode electrode according to any one of claims 1 to 9; and Electrolyte placed between the positive active material layer and the protective layer; A lithium secondary battery including 15. In Paragraph 14, A lithium secondary battery in which a metal layer containing lithium is formed within the non-negative electrode during the first charging process.

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