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

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, which includes Fe and Ni, and a coating layer, which is positioned on at least one surface of the current collector and includes a lithiophilic material.

Description

Negative electrode for lithium secondary battery and method for manufacturing 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 and a method for manufacturing the same. The present application claims priority to Korean Patent Application No. 10-2024-0190695 filed on December 19, 2024, the entire contents of which are incorporated herein by reference.

[0002]

[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, copper is widely used as a current collector for negative electrodes. However, there is a problem with applying copper as a current collector in sulfide-based all-solid-state batteries because copper corrodes. To solve this, there is growing interest in using nickel (Ni) or stainless steel (STS) as current collectors. However, while nickel has superior corrosion resistance compared to copper, it still presents a problem regarding corrosion. Although stainless steel has excellent corrosion resistance, it is not economically viable in terms of process to produce a thickness of 20 μm or less for application as a current collector, and surface treatment is difficult.

[0006] Therefore, research is needed on non-cathode electrodes that can replace existing current collectors and include corrosion-resistant current collectors, as well as those that are stable and have excellent lifespan characteristics.

[0007] According to one embodiment of the present invention, a non-cathode electrode for a lithium secondary battery provides a battery that is resistant to corrosion and has excellent battery life characteristics.

[0008] 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.

[0009] According to one embodiment of the present invention, a non-cathode electrode may include a current collector comprising Fe and Ni; and a coating layer located on at least one surface of the current collector and comprising a lithium-friendly material. In one embodiment, it may include a protective layer located on the coating layer.

[0010] In one embodiment, the current collector comprising Fe and Ni may comprise Fe: 10 to 90 weight% and the remainder Ni, based on 100 weight% of the alloy in the current collector. In one embodiment, the current collector comprising Fe and Ni may comprise Fe: 55 to 70 weight% and the remainder Ni, based on 100 weight% of the alloy in the current collector.

[0011] In one embodiment, the lithium-friendly material in the coating layer may include at least one of gold (Au), silver (Ag), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), and tin (Sn). In one embodiment, the thickness of the coating layer may be 20 to 300 nm. In one embodiment, the standard deviation of the thickness of the coating layer may be 80 nm or less. In one embodiment, a lithium layer may be formed on the current collector of the non-cathode electrode when the electrode is charged.

[0012] According to another embodiment of the present invention, a method for manufacturing a non-cathode electrode may include the steps of preparing a current collector comprising Fe and Ni, and forming a coating layer on at least one surface of the current collector using a coating composition comprising a lithium-friendly material. In one embodiment, after the step of forming the coating layer, the method may include the step of forming a protective layer on the surface of the coating layer.

[0013] In one embodiment, the step of preparing a current collector comprising Fe and Ni may include Fe: 10 to 90 weight% and the remainder Ni, based on 100 weight% of the alloy in the current collector. In one embodiment, the current collector comprising Fe and Ni may include Fe: 55 to 70 weight% and the remainder Ni, based on 100 weight% of the alloy in the current collector.

[0014] In one embodiment, the step of forming a coating layer on at least one surface of a current collector using a coating composition containing the lithium-friendly material can control the thickness of the coating layer to a range of 20 to 300 nm. In one embodiment, the step of forming a coating layer on at least one surface of a current collector using a coating composition containing the lithium-friendly material can control the standard deviation of the thickness of the coating layer to 3 to 80 nm.

[0015] In one embodiment, in the step of forming a coating layer on at least one surface of a current collector using a coating composition containing the lithium-friendly material, the coating layer may include at least one lithium-friendly material among gold (Au), silver (Ag), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), and tin (Sn).

[0016] According to one embodiment of the present invention, a non-negative electrode for a lithium secondary battery comprises an alloy layer containing Fe and Ni within a current collector, thereby providing a battery that is resistant to corrosion and has excellent battery life characteristics.

[0017] 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.

[0018] FIG. 1 shows a non-cathode electrode according to one embodiment of the present invention.

[0019] FIG. 2 is a scanning electron microscope (SEM) image showing the structure and thickness of an alloy material coating layer plated on a current collector according to one embodiment of the present invention.

[0020] Figure 3 is a photograph of the corrosion evaluation of a non-cathode electrode according to an embodiment and a comparative example of the present invention.

[0021] Figure 4 shows the cell life evaluation of an all-solid-state battery using an embodiment and a comparative example of the present invention.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] FIG. 1 shows a non-cathode electrode (100) manufactured according to one embodiment.

[0027] Referring to FIG. 1a, a non-cathode electrode (100) according to one embodiment comprises a current collector (10) and a coating layer (20) located on at least one surface of the current collector (10), and also comprises a protective layer (30) located on the other surface of the coating layer (20) facing the current collector (10).

[0028] 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.

[0029] 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, iron, 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.

[0030] 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.

[0031] In one embodiment, the current collector (10) may include Fe and Ni. Specifically, the current collector (10) may include an alloy containing Fe and Ni. Since the current collector (10) includes Fe and Ni, it has the advantage of having a low coefficient of thermal expansion, which is advantageous for battery application, excellent corrosion resistance, and at the same time, easy surface treatment, which is advantageous for application to all-solid-state batteries.

[0032] In one embodiment, the current collector (10) may comprise Fe: 10 to 90 weight% and the remainder Ni, based on 100 weight% of the alloy in the current collector (10). The Fe and Ni in the current collector (10) satisfy the aforementioned ranges and have the following advantages.

[0033] Fe: 10 to 90 weight%

[0034] Fe is included in an appropriate amount within the current collector (10), thereby increasing corrosion resistance and providing economic advantages. Fe may be included in an amount of 10 to 90 weight% based on 100 weight% of the current collector (10). Specifically, Fe may be included in an amount of 55 to 70 weight%, more specifically, 60 to 70 weight% based on 100 weight% of the current collector (10).

[0035] If the above Fe content deviates from the upper or lower limit of the aforementioned range, there is a problem in that the reactivity with the electrolyte actually increases compared to the value within the appropriate range.

[0036] Ni: 10 to 90 weight%

[0037] Ni is included in the current collector (10), which has the advantage of increasing corrosion resistance. Based on 100 weight% of the current collector (10), Ni may comprise the remainder excluding Fe: 10 to 90 weight%, specifically 90 to 10 weight%. For example, if Fe is 10 weight%, Ni may be 90 weight%.

[0038] If the above Ni content is excessive, cell instability increases, resulting in poor reproducibility. If the above Ni content is insufficient, the corrosion resistance effect of Ni is negligible.

[0039] The coating layer (20) is located on at least one surface of the current collector (10) and may be a layer that forms lithium when lithium is charged into the electrode. Specifically, the non-cathode electrode of the present invention does not contain separate lithium in the initial stage of the product, and lithium that has moved from the positive electrode during the battery operation process forms a lithium layer on the negative electrode, and the coating layer (20) plays a role in assisting in the easy formation of the lithium layer.

[0040] In one embodiment, the coating layer (120) may include a lithium-friendly material. Specifically, the lithium-friendly material may assist lithium in forming a lithium layer when lithium that has moved from the positive electrode moves to the electrode of the present invention during the battery operation process. Specifically, the lithium forms a layer on the surface of the lithium-friendly material as the surface energy of the lithium ions decreases.

[0041] The above-mentioned lithium-friendly material may be, for example, an alloy made of metal. The metal may include at least one of gold (Au), silver (Ag), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), and tin (Sn). Specifically, the above-mentioned lithium-friendly material may include tin (Sn). Specifically, by including tin in the above-mentioned lithium-friendly material, it is advantageous to apply it to a current collector (10) containing Fe and Ni, and prevents lithium dendrite growth, thereby enabling a stable and long-life non-cathode battery.

[0042] In one embodiment, the thickness of the coating layer (20) may be 20 to 300 nm. The thickness of the coating layer (20) may be 25 to 200 nm, specifically 50 to 150 nm.

[0043] If the above thickness exceeds the upper limit of the aforementioned range, there is a problem with reduced thickness uniformity. If the above thickness exceeds the lower limit of the aforementioned range, there is a problem with adverse cell driving characteristics.

[0044] In one embodiment, the thickness standard deviation of the coating layer (20) may be 80 nm or less. Specifically, the thickness standard deviation of the coating layer (20) may be 80 nm or less, specifically 3 to 80 nm, specifically 3 to 70 nm, more specifically 3 to 55 nm, and more specifically 3 to 30 nm.

[0045] The thickness standard deviation of the coating layer (20) refers to a value measured by Cross-section polishing (CP) and Focused ion beam (FIB) methods by extracting several random portions of the sample, and since the thickness standard deviation satisfies the aforementioned range, the uniformity satisfies a certain range condition, which has the advantage of effectively preventing lithium dendrite growth.

[0046] If the thickness standard deviation of the coating layer (20) exceeds the upper limit of the aforementioned range, there is a problem that the uniformity of the coating layer (20) differs significantly, making it disadvantageous for inhibiting lithium dendrite growth.

[0047] Specifically, during the charging and discharging of a battery, lithium ions move between the negative and positive electrodes. Since a sufficient amount of lithium-friendly material must be distributed on the negative electrode to maintain the force of the lithium-friendly material attracting lithium ions even when the battery is repeatedly charged and discharged, thereby enabling stable behavior, if an insufficient amount of lithium-friendly material is present, the battery's charge and discharge lifespan is reduced.

[0048] The protective layer (30) is located on the coating layer (20) and may contain amorphous carbon. When only a non-negative electrode is used as the negative electrode in an all-solid-state battery, high resistance is generated by the reaction between the all-solid-state electrolyte and lithium, and lithium dendrites are continuously generated or high-resistance lithium byproducts are generated due to local non-uniformity of current density during the charging and discharging process, resulting in failure due to short circuits or overvoltage during charging and discharging or a decrease in battery capacity.

[0049] According to one embodiment, the non-cathode electrode includes a protective layer containing amorphous carbon, thereby improving not only the output characteristics and lifespan characteristics of the non-cathode electrode but also additional structural safety.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] In one embodiment, the thickness of the protective layer (30) may be 0.01 μm to 50 μm. Specifically, the thickness of the protective layer (30) may be in the range of 1 μm to 20 μm. When the thickness of the protective layer satisfies the aforementioned range, lithium dendrites are prevented from forming on the surface of the protective layer, and lithium ions can penetrate well into the protective layer and be conducted, thereby allowing lithium to be precipitated on the lower surface of the protective layer.

[0058] 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.

[0059] A method for manufacturing a non-cathode electrode according to another embodiment of the present invention comprises the steps of preparing a current collector (10), forming a coating layer (20) 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) using a slurry containing amorphous carbon.

[0060] The step of preparing a current collector (10) may be a step of preparing a current collector containing Fe and Ni. The step of preparing a current collector containing Fe and Ni may include Fe: 10 to 90 weight% and the remainder Ni, based on 100 weight% of the alloy in the current collector. Specifically, the current collector containing Fe and Ni may include Fe: 55 to 70 weight% and the remainder Ni, based on 100 weight% of the alloy in the current collector. The detailed description of Fe and Ni is the same as that described above in FIG. 1 to the extent that it does not contradict.

[0061] By satisfying the aforementioned range of Fe and Ni content in the current collector (10), there is an advantage that not only is the corrosion resistance of the current collector increased, but most of the reproducibility problems can also be solved. If the Fe content exceeds the upper or lower limit of the aforementioned range, there is a problem that the reactivity between the current collector and the electrolyte increases. If the Ni content is excessively high, there is a problem that cell instability increases and reproducibility is poor. If the Ni content is insufficient, there is a problem that the corrosion resistance effect of Ni is insufficient.

[0062] 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, which is an alloy material, on at least one surface of the current collector. As described above in FIG. 1, the lithium-friendly material may include at least one of gold (Au), silver (Ag), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), and tin (Sn), and specifically, may include tin (Sn).

[0063] After undergoing the process described below, the coating layer (20) may be formed such that a lithium alloy layer (21) is formed by a lithium-friendly material forming an alloy with lithium, as described above in FIG. 1a and FIG. 1b. In one embodiment, the coating layer (20) may specifically be placed between the current collector (10) and the protective layer (30), and subsequently, the lithium alloy layer (21) may be formed through an electroplating or charging process.

[0064] In one embodiment, 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 can control the thickness of the coating layer to a range of 20 to 300 nm. Specifically, the thickness of the coating layer may be 25 to 200 nm, specifically 50 to 150 nm.

[0065] In one embodiment, 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 can control the standard deviation of the thickness of the coating layer to 80 nm or less. Specifically, the standard deviation of the thickness of the coating layer may be 3 to 87.1 nm, more specifically 3 to 70 nm, and even more specifically 3 to 30 nm.

[0066] In one embodiment, the step of forming the coating layer (20) may be performed using at least one method among electrolytic and electroless plating, sputtering, electron beam, and thermal vapor deposition. For example, the step of forming the coating layer may be performed by an electrolytic plating method.

[0067] A protective layer (30) can be formed on the surface of a coating layer (20) 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 a solvent 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.

[0068] Meanwhile, in the step of forming the protective layer (30), the thickness of the protective layer formed on the surface of the alloy material coating layer may be in the range of 0.01 μm to 50 μm, more specifically 1 μm to 20 μm.

[0069] If the above thickness exceeds the upper limit of the aforementioned range, there is a problem where lithium precipitates on the protective layer during the battery charging and discharging process. If the above thickness exceeds the lower limit of the aforementioned range, there is a problem that is disadvantageous to the cell driving characteristics.

[0070] In this way, in this embodiment, it is possible to manufacture a non-cathode electrode (100) having a coating layer (20) with a coarse particle structure by preventing the excessive generation of fine lithium particles even under high current conditions and inducing the initially generated lithium particles to grow well. In addition, the coating layer (20) manufactured in this way has excellent surface uniformity.

[0071] According to another embodiment of the present invention, a lithium secondary battery comprises a positive electrode, a negative electrode, and an electrolyte located between the positive electrode and the negative electrode. Herein, the negative electrode may be a non-negative electrode according to the present invention.

[0072] In one embodiment, a lithium secondary battery may include an electrode assembly comprising a positive electrode including a positive active material, a negative electrode which is a non-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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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 wettability. 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.

[0079] 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.

[0080]

[0081] <Experimental Example>

[0082] Manufacturing of non-cathode electrodes for lithium secondary batteries

[0083] <Example 1>

[0084] <Whole House Manufacturing>

[0085] Fe-Ni current collectors (10) were manufactured by rolling or electrolytic methods. At this time, based on 100 wt% of an alloy of Fe and Ni, Fe-Ni current collectors (10) were manufactured by controlling Fe: 90 wt% and Ni: 10 wt%.

[0086]

[0087] <Formation of coating layer>

[0088] Subsequently, a coating layer (20) was formed on the cross-section of the manufactured current collector by a sputtering method. At this time, tin (Sn) was used as the coating layer, and the plating thickness was controlled to about 80 nm.

[0089] FIG. 2 is a scanning electron microscope (SEM) image showing the structure and thickness of a coating layer (20) plated on a current collector (10) according to one embodiment of the present invention.

[0090] Referring to FIG. 2, it can be seen that the coating layer (20) plated on the current collector (10) of the present invention has a thickness of about 80 nm and a standard deviation of thickness of about 3 nm.

[0091]

[0092] Formation of a protective layer

[0093] Subsequently, a protective layer (30) of approximately 5 μm was formed on the upper surface of the coating layer (20) by slurry coating using a comma coater. Specifically, the protective layer (30) was formed by mixing a binder with acetylene black, which is amorphous carbon. At this time, the binder was prepared by using 3% by weight of a polyvinyl alcohol copolymer or a mixture thereof as a water-based binder, or by adding 2.25% by weight of polyvinylidene fluoride (PVdF) as a non-water-based binder.

[0094]

[0095] <Comparative Example 1>

[0096] A cathode-free electrode was prepared in the same manner as in Example 1, except that it did not contain any Ni and contained only 100 wt% of Fe during the step of forming the current collector.

[0097]

[0098] <Comparative Example 2>

[0099] A cathode-free electrode was prepared in the same manner as in Example 1, except that in the step of forming the current collector, it does not contain any Fe and contains only 100 wt% Ni.

[0100]

[0101] Solid-state battery manufacturing

[0102] All-solid-state batteries were fabricated using the anode-free electrodes prepared according to the aforementioned examples and comparative examples, and their charge-discharge life was evaluated. To evaluate the all-solid-state battery cells, a dedicated pressurized evaluation cell from TerraReader, capable of maintaining an inert atmosphere, was used. For the fabrication of the all-solid-state battery cells, 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] A lithium electrode with a thickness of 0.5 mm was attached as a reference electrode on one side of the electrolyte, and a non-cathode electrode prepared according to the examples and comparative examples was attached on the opposite side. The reference electrode and the evaluation electrode were pressurized at a pressure of 50 MPa.

[0104]

[0105] <Evaluation Example 1>: Control of Fe-Ni content in current collector

[0106] Table 1 below shows the number of charge-discharge cycles when the ratio of Fe and Ni content in the current collector is varied. The standard deviation of the coating layer thickness and the number of charge-discharge cycles were measured by the following method.

[0107] Standard deviation of coating layer thickness (nm): Several random portions of the sample were extracted and measured using the Cross-section polishing (CP) and Focused ion beam (FIB) methods.

[0108] 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.

[0109] Classification Total Alloy Content Coating Layer Charge / Discharge Performance Cycles [Times] Fe [wt%] Ni [wt%] Sn Thickness [nm] Sn Thickness Standard Deviation [nm] Example 1 90 108 037 05 Comparative Example 1 10 008 05 83 Comparative Example 2 0 10 08 033 56

[0110] Referring to Table 1 above, it was confirmed that Example 1, which contains both Fe and Ni as alloy components in the current collector, exhibited a high number of charge-discharge cycles. In contrast, Comparative Examples 1 and 2, which contain only Fe or Ni as alloy components in the current collector, exhibited low number of charge-discharge cycles. <Evaluation Example 2> - Fe:Ni Content Control

[0111]

[0112] <Example 2>

[0113] A non-cathode electrode and an all-solid-state battery were manufactured in the same manner as in Example 1, except that the weight percentage of Fe : Ni was changed to 64 wt% : 36 wt% in the step of forming the current collector.

[0114]

[0115] <Example 3>

[0116] A non-cathode electrode and an all-solid-state battery were manufactured in the same manner as in Example 1, except that the weight percentage of Fe : Ni was changed to 10 wt% : 90 wt% in the step of forming the current collector.

[0117]

[0118] Table 2 below shows the number of charge-discharge cycles when the ratio of Fe and Ni content in the current collector is varied. The standard deviation of the Sn layer thickness and the number of charge-discharge cycles were measured by the following method.

[0119] Classification Total Alloy Content Coating Layer Charge / Discharge Performance Cycles [Times] Fe [wt%] Ni [wt%] Sn Thickness [nm] Sn Thickness Standard Deviation [nm] Example 1 90 108 037 05 Example 2 64 368 048 01 Example 3 109 08 046 18

[0120] Referring to Table 2 above, it was confirmed that the charge-discharge cycle performance is excellent when both Fe and Ni are included in the current collector, as in Examples 1 to 3. At this time, when comparing Examples 1 and 3 with Example 2, it was confirmed that the charge-discharge cycle performance of Example 2 is even superior. <Evaluation Example 3> - Coating layer thickness control

[0121] <Example 4>

[0122] A non-cathode electrode and an all-solid-state battery were manufactured in the same manner as in Example 2, except that the thickness of the coating layer was controlled to 25 nm during the step of forming the coating layer.

[0123]

[0124] <Example 5>

[0125] A non-cathode electrode and an all-solid-state battery were manufactured in the same manner as in Example 2, except that the thickness of the Sn layer was controlled to 200 nm in the step of forming the coating layer.

[0126]

[0127] <Comparative Example 3>

[0128] A non-cathode electrode and an all-solid-state battery were manufactured in the same manner as in Example 2, except that the thickness of the Sn layer was controlled to 500 nm in the step of forming the coating layer.

[0129]

[0130] <Comparative Example 4>

[0131] A non-cathode electrode and an all-solid-state battery were manufactured in the same manner as in Example 2, except that the thickness of the Sn layer was controlled to 10 nm during the step of forming the coating layer.

[0132]

[0133] <Comparative Example 5>

[0134] A non-cathode electrode and an all-solid-state battery were manufactured in the same manner as in Example 2, except that the thickness of the Sn layer was controlled to 0 nm during the step of forming the coating layer.

[0135]

[0136] Table 3 below shows the number of charge / discharge cycles when the thickness of the coating layer on the current collector is varied. The standard deviation of the coating layer thickness and the number of charge / discharge cycles were measured by the following method.

[0137] Classification Total Alloy Content Coating Layer Charge / Discharge Performance Cycles [Times] Fe [wt%] Ni [wt%] Sn Thickness [nm] Sn Layer Thickness Standard Deviation [nm] Example 2 64 36 80 4801 Example 4 64 36 25 36 89 Example 5 64 36 200 15 6 54 Comparative Example 3 64 36 500 57 306 Comparative Example 4 64 36 100 327 Comparative Example 5 64 36 00 -

[0138] Looking at Table 3 above, it was confirmed that when the Sn thickness and the Sn thickness standard deviation satisfy the range of the present invention, as in Examples 2, 4, and 5, the charge-discharge performance cycles are excellent with 600 or more. However, when the Sn thickness is excessively thick, it was confirmed that the charge-discharge performance cycles decrease, as in Comparative Example 3, and when the Sn thickness is excessively thin, it was confirmed that the charge-discharge performance cycles decrease, as in Comparative Example 4. In addition, when a coating layer is not formed on the current collector at all, as in Comparative Example 5, a phenomenon in which lithium precipitates on the upper surface of the protective layer during the battery charging process was observed. Furthermore, when a cell is fabricated without a coating layer, as in Comparative Example 5, it was confirmed that approximately 80% of the cells do not undergo normal cycle progression and internal short circuits occur. Additionally, looking at Table 3 above, while no difference in the coating layer thickness standard deviation was observed according to the current collector composition, it was confirmed that it tended to increase as the Sn plating thickness increased.

[0139] Figure 3 is a photograph of the corrosion evaluation of a non-cathode electrode according to an embodiment and a comparative example of the present invention.

[0140] Referring to FIG. 3, the image shows the surface of the solid electrolyte in contact with the current collector after disassembling the cell and fabricating an all-solid-state cell using a sulfide-based solid electrolyte for the non-cathode electrode according to the embodiments and comparative examples of the present invention. At this time, starting from the left, the current collectors used are Cu 100 wt%, Fe 100 wt%, Ni 100 wt%, Fe 10 wt% and Ni 90 wt%, Fe 64 wt% and Ni 36 wt%, and Fe 90 wt% and Ni 10 wt%.

[0141] Referring to Figure 3, it can be seen that when Cu, Fe, or Ni are used alone in the current collector, severe corrosion occurs. In contrast, it was confirmed that the current collector containing both Fe and Ni simultaneously exhibits excellent corrosion resistance compared to when Cu, Fe, or Ni are used alone. Furthermore, among the current collectors containing both Fe and Ni, it was confirmed that the corrosion resistance is best when Fe is 64% and Ni is 36%.

[0142] Figure 4 shows the cell life evaluation of an all-solid-state battery using an embodiment and a comparative example of the present invention.

[0143] Figure 4 shows the cell life evaluation of an all-solid-state battery using the lithium electrodes of Example 2 and Comparative Example 1 of the present invention. Looking at Figure 4, it was confirmed that when Fe and Ni were controlled within the range of the present invention as components of the alloy in the current collector, the cell life characteristics were excellent at 705 cycles. In contrast, when only Fe was used as an alloy component in the current collector, it was confirmed that the cell life characteristics were inferior at 83 cycles.

[0144]

[0145] 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 Current collectors including Fe and Ni; and A non-cathode electrode comprising a coating layer containing a lithium-friendly material located on at least one surface of the above-mentioned current collector.

2. In Paragraph 1, A non-cathode electrode comprising a protective layer located on the above coating layer.

3. In Paragraph 1, The current collector comprising Fe and Ni is a non-cathode electrode comprising Fe: 10 to 90 weight% and the remainder Ni, based on 100 weight% of the alloy within the current collector.

4. In Paragraph 1, The current collector comprising Fe and Ni is a non-cathode electrode comprising Fe: 55 to 70 weight% and the remainder Ni, based on 100 weight% of the alloy within the current collector.

5. In Paragraph 1, The lithium-friendly material in the coating layer comprises at least one of gold (Au), silver (Ag), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), and tin (Sn), forming a non-cathode electrode.

6. In Paragraph 1, A non-cathode electrode having a coating layer thickness of 20 to 300 nm.

7. In Paragraph 1, A non-cathode electrode having a standard deviation of the thickness of the coating layer of 80 nm or less.

8. In Paragraph 1, A non-negative electrode in which a lithium layer is formed on the current collector during charging.

9. A step of preparing a current collector containing Fe and Ni; and A method for manufacturing a non-cathode electrode comprising the step of forming a coating layer on at least one surface of a current collector using a coating composition containing a lithium-friendly material.

10. In Paragraph 9, After the step of forming the above coating layer, A method for manufacturing a non-cathode electrode comprising the step of forming a protective layer on the surface of the coating layer.

11. In Paragraph 9, The step of preparing a current collector comprising Fe and Ni is a method for manufacturing a non-cathode electrode comprising Fe: 10 to 90 weight% and the remainder Ni, based on 100 weight% of the alloy in the current collector.

12. In Paragraph 11, A method for manufacturing a non-cathode electrode comprising, based on 100 weight% of the alloy in the current collector, Fe: 55 to 70 weight% and the remainder being Ni, wherein the current collector comprising Fe and Ni is used.

13. In Paragraph 9, A method for manufacturing a non-cathode electrode, wherein the step of forming a coating layer on at least one surface of a current collector using a coating composition containing the above-mentioned lithium-friendly material controls the thickness of the coating layer to a range of 20 to 300 nm.

14. In Paragraph 9, A method for manufacturing a non-cathode electrode, wherein the step of forming a coating layer on at least one surface of a current collector using a coating composition containing the above-mentioned lithium-friendly material controls the thickness standard deviation of the coating layer to 3 to 80 nm.

15. In Paragraph 9, A method for manufacturing a non-cathode electrode comprising, in the step of forming a coating layer on at least one surface of a current collector using a coating composition containing the above-mentioned lithium-friendly material, wherein the coating layer comprises at least one lithium-friendly material selected from gold (Au), silver (Ag), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), and tin (Sn).

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