Anode-free electrode for lithium secondary battery, manufacturing method therefor, and lithium secondary battery comprising 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, which is positioned on at least one surface of the current collector and includes a lithiophilic material; and a protective layer positioned on the coating layer, wherein the protective layer can include amorphous carbon and silicate clay mineral that has a 2:1-type crystal structure.

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

[0002] The present invention claims priority based on Korean Patent Application No. 10-2024-0190289 filed on December 18, 2024, the entire contents of said application incorporated herein by reference.

[0003] To reduce the cost and increase the energy density of rechargeable batteries, it is essential to use lithium metal electrodes as the negative electrodes. 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 have advantages in various aspects, such as excellent stability because they do not use liquid electrolytes, the ability to operate at high voltages, improved energy density of the battery pack due to the reduction of cooling and safety-related components, and the ability to operate over a wide temperature range. In order to practically achieve high energy density in such all-solid-state batteries, thick, low-capacity graphite-based anode materials must be replaced with thin, high-capacity lithium; considering economic feasibility and energy density, thin-film lithium metal electrodes with a thickness of 10 to 20 μm are practically required.

[0005] Generally, to form lithium metal electrodes, methods such as rolling copper foil and lithium foil as current collectors or depositing a lithium thin film on copper foil have been used; however, rolling has the disadvantage of difficulty in achieving wide widths and thin films, while deposition has the disadvantage of low economic feasibility. To overcome these drawbacks, a method has been proposed to form a cathode by electrodepositing lithium onto copper foil using an electrochemical method.

[0006] However, when a lithium metal electrode is used as the negative electrode in an all-solid-state battery, a high-resistance phase is formed due to the reaction between lithium and the all-solid-state electrolyte, and lithium dendrites are continuously formed or high-resistance lithium byproducts are formed due to local non-uniformity of current density during the charging and discharging process, resulting in problems such as the battery failing to perform its function due to short circuits or overvoltage during charging and discharging, or a decrease in capacity.

[0007] To date, various methods have been proposed to prevent reaction with all-solid-state batteries and to prevent the precipitation growth of lithium dendrites, such as using amorphous carbon alone as a protective coating layer on lithium metal electrodes or using composite materials with expensive lithium-friendly metals, but sufficient lithium stacking speed and charge / discharge life characteristics have not been achieved.

[0008] The technical problem that the present invention aims to solve is to realize a lithium secondary battery with improved charge / discharge life characteristics and an anode-free electrode that does not include a separate lithium layer, by increasing the concentration of lithium ions during battery charging to improve the lithium stacking speed.

[0009] Another technical problem that the present invention aims to solve is to provide a method for manufacturing a negative electrode for a lithium secondary battery having the aforementioned advantages.

[0010] Another technical problem that the present invention aims to solve is to provide a lithium secondary battery comprising a cathode-free electrode having the aforementioned advantages.

[0011] According to one embodiment of the present invention, a non-cathode electrode relates to a non-cathode electrode that does not contain lithium, and 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 protective layer may comprise amorphous carbon and a silicate clay mineral having a 2:1 layered crystal structure. In one embodiment, the weight ratio of the amorphous carbon to the silicate clay mineral in the protective layer may be 97:3 to 65:35.

[0012] In one embodiment, the silicate clay mineral may include monoclinic crystals. In one embodiment, the silicate clay mineral may have a layer charge of 0.2 to 0.6 per unit cell.

[0013] In one embodiment, the silicate clay mineral may have a cation exchange capacity (me / 100g) of 80 to 150. In one embodiment, the bonding strength between the current collector and the protective layer may be 0.030 to 0.30 N / cm.

[0014] In one embodiment, the coating layer may include one or more of In, Ag, Sn, Zn, Si, Al, and Bi. In one embodiment, the average thickness of the coating layer may be 1 μm to 100 μm. In one embodiment, the average thickness of the protective layer may be 1 μm to 20 μm. In one embodiment, a metal layer containing lithium may be formed on the current collector during the first charging at the electrode end.

[0015] According to another embodiment of the present invention, a method for manufacturing a non-cathode electrode may include the steps of forming a coating layer on at least one surface of a current collector using a coating composition containing a lithium-friendly component, and forming a protective layer on the surface of the coating layer using a slurry containing amorphous carbon and a silicate clay mineral having a 2:1 layered crystal structure. In one embodiment, in the step of forming the protective layer, the weight ratio of the amorphous carbon to the silicate clay mineral may be mixed to be 97:3 to 65:35.

[0016] In one embodiment, the step of forming a protective layer on the surface of the coating layer using a slurry comprising amorphous carbon and a silicate clay mineral having a 2:1 crystal structure may include a step of slurry coating such that the thickness of the protective layer is 1 to 20 μm.

[0017] According to another embodiment of the present invention, a lithium secondary battery may comprise a positive current collector, a positive electrode containing a positive active material layer, a negative electrode according to any one of claims 1 to 10, and an electrolyte disposed between the positive active material layer and the protective layer. In one embodiment, a metal layer containing lithium may be formed in 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 silicate clay mineral having a 2:1 layered crystal structure within a protective layer, thereby improving the stacking rate of lithium flowing in from the positive electrode during lithium charging at the battery terminal and providing a lithium secondary battery with 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 that can improve the stacking rate of lithium flowing in from the positive electrode during battery charging and improve charge / discharge life characteristics by coating a slurry mixed with a silicate clay mineral having a 2:1 layered crystal structure in a protective layer.

[0020] According to another embodiment of the present invention, a lithium secondary battery provides a negative electrode having the aforementioned advantages, thereby improving the stacking rate of lithium flowing in from the positive electrode during battery charging and providing a battery with improved charge / discharge life characteristics.

[0021] Figure 1 shows a cathode-free electrode manufactured according to one embodiment.

[0022] FIG. 2 is a scanning electron microscope (SEM) image of a cross-section when an alloy material coating layer is formed on a current collector according to one embodiment of the present invention.

[0023] FIG. 3a is a scanning electron microscope (SEM) image of the surface when an ion concentration protective layer is formed on a current collector coated with a coating layer according to one embodiment of the present invention, and FIG. 3b is a scanning electron microscope (SEM) image of the cross-section.

[0024] Figure 4 is a graph of the bonding strength between the current collector and the ion concentration protective layer according to the embodiments and comparative examples of the present invention.

[0025] FIG. 5 is a graph evaluating the cell life of an all-solid-state battery using electrodes for a lithium secondary battery of an example and a comparative example according to one embodiment 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 "above" or "on" another part, it may be directly above or on the other part, or other parts may be involved in between. In contrast, when it is stated that one part is "directly above" another part, no other parts are 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) located on at least one surface of the current collector (10), and a protective layer (30) disposed on the current collector (10). The inventors have discovered that when a non-cathode electrode (100) that does not contain separate lithium is utilized in a battery by including amorphous carbon and silicate clay minerals in the protective layer (30) of the non-cathode electrode (100), 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 alloys thereof, carbon, a conductive polymer, a composite fiber with a conductive layer coated on a non-conductive polymer, or a combination thereof.

[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] The coating layer (20) is located on the current collector and may include a lithium-friendly material. The coating layer (20) can assist in uniformly coating a metal layer containing lithium when the non-cathode electrode (100) is used in the battery and the battery is charged.

[0036] Specifically, since the coating layer (20) contains a lithium-friendly metal with high electron conductivity, electrons are smoothly supplied from the current collector (10) and lithium ions are reduced, so when the battery is charged, there is an advantage that some of the lithium introduced from the positive electrode is uniformly distributed into the metal layer. More specifically, the coating layer (20) plays a role in helping lithium to be deposited more effectively on the underside of the protective layer (30) during the charging process of the battery.

[0037] In one embodiment, the thickness of the coating layer (20) may be in the range of 1 μm to 100 μm, more specifically, 5 μm to 30 μm. If the thickness of the coating layer (20) is excessively thick, when the non-cathode electrode of this embodiment is applied to a secondary battery, there is a problem in that the weight and volume of the battery increase and the energy density decreases.

[0038] When the thickness of the coating layer (20) is excessively thin, there is a problem that the charge / discharge life of the battery is reduced when the non-cathode electrode of the present embodiment is applied to a secondary battery. Specifically, during the charge / discharge of the battery, a metal layer containing lithium is formed in the coating layer (20), and the lithium in the battery is gradually consumed due to side reactions between the lithium contained in the metal layer and the electrolyte, etc., thereby reducing the battery capacity. Since the amount of lithium available to replenish the lithium consumed during charge / discharge becomes small, the charge / discharge life of the battery is reduced. Therefore, it is preferable that the thickness of the coating layer (20) be 1 μm or more.

[0039] The protective layer (30) is located on the coating layer (20) and may include amorphous carbon and silicate clay minerals. When the non-cathode electrode (100) of the present invention is used without using a separate lithium-containing negative electrode 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 circuits or overvoltage during charging and discharging or a decrease in battery capacity.

[0040] To solve these problems, the non-cathode electrode (100) may include a protective layer (30) containing amorphous carbon and silicate clay minerals. By having the protective layer (30) simultaneously contain amorphous carbon and silicate minerals, the output characteristics and lifespan characteristics of the non-cathode electrode, as well as additional structural safety, can be improved.

[0041] Specifically, the non-cathode electrode of the present embodiment includes a protective layer (30) comprising amorphous carbon and silicate clay minerals, thereby not only improving ion conductivity but also improving the strength of the protective layer and preventing short circuits between electrodes by physically blocking dendrites when dendrites grow on the non-cathode electrode, which can improve charge / discharge life.

[0042] 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.

[0043] In one embodiment, the amorphous carbon may have an average particle size of 10 nm to 100 nm. If the average particle size of the amorphous carbon deviates from the upper limit of the aforementioned range, there is a problem in that the contact area between the protective layer and the electrodeposited lithium is reduced, thereby lowering the bonding strength. If the average particle size of the amorphous carbon deviates from the lower limit of the aforementioned range, there is a problem in that it is difficult to ensure uniform dispersion of the protective layer slurry.

[0044] The above silicate clay mineral may be a self-concentrating lithium ion material. Specifically, the above silicate clay mineral may have a large specific surface area, high ion exchange capacity, and excellent adsorption performance. By including the aforementioned features, it can not only increase the concentration of lithium ions within the protective layer (30) but also perform the role of homogenizing the distribution of lithium ions.

[0045] Accordingly, as lithium ions move uniformly within the protective layer (30) and at the interface during the charging process of the battery, the growth of lithium dendrites can be suppressed when lithium is deposited at the bottom of the protective layer (30). If lithium ions do not move uniformly within the protective layer (30) and at the interface, lithium dendrites may grow in the area where lithium ions are concentrated, causing a short circuit during the operation of the battery.

[0046] The above silicate clay mineral has high strength, so it can serve as a filler in the protective layer (30). By including the silicate clay mineral, the protective layer (30) improves mechanical strength, thereby maintaining lithium properly under the protective layer during the battery charging and discharging process, and also prevents dendrite growth of the non-negative electrode during the charging and discharging process, thereby preventing short circuits between electrodes and improving lifespan.

[0047] The above silicate clay mineral may have a 2:1 layered crystal structure. A 2:1 layered crystal structure may refer to a structure in which one octahedral layer is sandwiched between two tetrahedral layers. Specifically, a 2:1 layered crystal structure may be a form in which the other anionic face of the octahedral layer, which is not bonded to the tetrahedral layer in the 1:1 layered structure, is bonded by the apical oxygen of another tetrahedral layer, and the apical oxygen substitutes 2 / 3 of the hydroxide ions of the octahedral layer.

[0048] In one embodiment, the silicate clay mineral may have a charge per unit cell of 0.2 to 1.0. Specifically, the silicate clay mineral may have a charge per unit cell of 0.2 to 0.9. The charge per unit cell refers to the charge per unit formula of the clay mineral, which is generated by isomorphic substitution; when a negative charge is generated by isomorphic substitution, it can be balanced by cations present on the surface between lattice layers. Specifically, a 2:1 layered crystal structure can satisfy a charge per unit cell of 0.2 to 1.0.

[0049] In one embodiment, the silicate clay mineral may satisfy a cation exchange capacity (me / 100g) of 80 to 150. Specifically, the cation exchange capacity may be 90 to 100. Cation exchange capacity refers to the total amount of cations adsorbed in a certain amount of soil in a form that can be exchanged with other cations by electrical attraction. Specifically, it refers to a milliequivalent per 100g of soil.

[0050] By satisfying the aforementioned range, the bonding strength between the protective layer and the current collector is strengthened, and excellent lifespan characteristics can be achieved when applied to a battery. If the range is exceeded, there is a problem where the bonding strength between the protective layer and the current collector and the battery lifespan characteristics are inferior.

[0051] In one embodiment, the silicate clay mineral may include a monoclinic crystal structure. The monoclinic crystal is one of seven crystal systems that describe the crystal structure using three vectors, wherein the three vectors have different lengths, and the structure is shaped like a rectangular prism with four rectangular faces and two parallelograms, and among the three angles formed by the three vectors, two are right angles and one (the angle forming the parallelogram) is not a right angle. By including a monoclinic crystal structure in the silicate clay mineral, there is an advantage of improving the stacking speed of lithium.

[0052] In one embodiment, the silicate clay mineral may have an average particle size of 100 nm to 1,000 nm. If the average particle size of the silicate clay mineral deviates from the upper limit of the aforementioned range, large particles act as a resistance layer, causing a problem of reduced lithium-ion conductivity. If the average particle size of the silicate clay mineral deviates from the lower limit of the aforementioned range, there is a problem of non-uniform particle distribution of the clay mineral within the coating layer due to aggregation between primary particles.

[0053] In one embodiment, the silicate clay mineral may include at least one of montmorillonite, nontronite, beidelite, vermiculite, volkonscoite, hectorite, saponite, soconite, sobockite, stevensite, clauconite, biotite, and svinfordite. The aforementioned silicate clay mineral may satisfy the crystal structure, cation exchange capacity, and layer charge per unit cell described above.

[0054] In this way, the silicate clay mineral satisfies the aforementioned characteristics, and by adsorbing a large amount of lithium ions onto the surface of the silicate clay mineral and increasing the concentration of lithium ions, the conduction of lithium ions can be promoted, thereby improving the lifespan characteristics of the battery.

[0055] In addition, when a small amount of silicate clay mineral is added to the liquid electrolyte, the concentration of lithium ions can be increased through high ion exchange capacity and ion adsorption capacity, thereby improving ion conductivity within the liquid electrolyte. However, as in the present invention, by including the silicate clay mineral in the protective layer (30), not only does it improve ion conductivity, but it also improves the strength of the protective layer (30) and physically blocks dendrites during dendrite growth on the non-cathode electrode (100), thereby preventing short circuits between electrodes and improving charge / discharge life.

[0056] The material of the aforementioned protective layer does not react well with the sulfide-based electrolyte material of the all-solid-state battery and has excellent chemical stability, which is advantageous for improving interfacial stability and extending charge / discharge life of the all-solid-state battery. The ion conduction-promoting protective layer can be applied by preparing the above composite in the form of a slurry, and a binder may be additionally included to prepare such a slurry.

[0057] In one embodiment, the protective layer (30) may have a weight ratio of amorphous carbon to silicate clay mineral (weight% of amorphous carbon:weight% of silicate clay mineral) of 97:3 to 65:35. Specifically, the weight ratio of amorphous carbon to silicate clay mineral may be 97:3 to 70:30.

[0058] When the content of the amorphous carbon in the protective layer (30) is excessively high, there is a problem that the effect of the content of the silicate clay mineral is insufficient. When the content of the silicate clay mineral in the protective layer (30) is excessively high, the silicate mineral acts as a barrier to lithium ion conduction rather than lithium ion concentration, causing an increase in resistance and thereby lowering the lithium ion conductivity.

[0059] 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.

[0060] Here, the binder may be added in an amount of 1 to 15 parts by weight, specifically 3 to 10 parts by weight, based on the weight of the slurry formed by mixing the amorphous carbon, the silicate clay mineral, and water.

[0061] 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. 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; conversely, if the content of the binder is excessively high compared to the aforementioned range, not only is there a problem of causing a decrease in energy density, but the resistance of the protective layer also increases significantly, hindering lithium ion conduction.

[0062] 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, the effect obtained by including the amorphous carbon and the silicate clay mineral prevents the formation of lithium dendrites on the surface of the protective layer and allows lithium ions to penetrate well into the protective layer and be conducted, thereby allowing lithium to precipitate on the lower surface of the protective layer.

[0063] 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.

[0064] 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).

[0065] A method for manufacturing a non-cathode electrode according to another embodiment of the present invention comprises the steps of: forming a coating layer on at least one surface of a current collector using a coating composition containing a lithium-friendly component; forming a protective layer on the surface of the coating layer using a slurry containing amorphous carbon and silicate clay minerals; positioning the current collector having the coating layer and the protective layer formed thereon in a plating solution and then positioning a lithium source at a predetermined distance from the protective layer; and applying an electric current between the current collector and the lithium source to form a coating layer comprising a lithium alloy in which the lithium-friendly component contained in the coating layer and the lithium precipitated from the lithium source are alloyed.

[0066] The step of forming a coating layer on at least one surface of a current collector using a coating composition containing a lithium-friendly component may involve coating a lithium-friendly material on at least one surface of the current collector. The lithium-friendly material may be, for example, one or more selected from the group consisting of In, Ag, Sn, Zn, Si, Al, and Bi, but is not limited thereto.

[0067] In one embodiment, the step of forming the coating layer (20) 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.

[0068] 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. For example, the step of forming the coating layer (20) can be performed by an electroless plating method.

[0069] Meanwhile, in the step of forming the coating layer (20), the thickness of the alloy material coating layer (20) formed on at least one surface of the current collector may be 0.001 μm to 10 μm, specifically 0.01 μm to 1 μm, more specifically 150 to 400 nm, more specifically 200 to 400 nm, and more specifically 250 to 350 nm.

[0070] If the thickness of the coating layer (20) is excessively thin, there is a problem that it is difficult to react with the lithium supplied during the charging and discharging process of the battery, and if the thickness is excessively thick, the cost and time required to form the coating layer (20) are excessive, so production efficiency and economic feasibility are reduced, and the weight of the battery increases, resulting in a problem of lower energy density.

[0071] In the step of forming a protective layer (30) on the surface of a coating layer (20) using a slurry containing amorphous carbon and silicate clay minerals, the weight ratio of amorphous carbon to silicate clay minerals may be 97:3 to 65:35. Specifically, the weight ratio of amorphous carbon to silicate clay minerals may be 97:3 to 70:30. For a detailed description of the amorphous carbon and silicate clay minerals and the description of their content, refer to the content described above in FIG. 1.

[0072] The protective layer (30) can be formed by applying a slurry formed by mixing the amorphous carbon, silicate clay mineral, and binder in water using at least one of the doctor blade method, 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, and a detailed description thereof may be provided by referring to the above description in FIG. 1. Meanwhile, in the step of forming the protective layer (30), the thickness of the protective layer (30) may be in the range of 0.01 μm to 50 μm, more specifically 1 μm to 20 μm.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082]

[0083] <Experimental Example>

[0084] Manufacturing of non-cathode electrodes for lithium secondary batteries

[0085] <Example 1>

[0086] According to one embodiment of the present invention, a non-cathode electrode for a lithium secondary battery is manufactured by forming an alloy material coating layer (20) on a current collector and forming a protective layer thereon, thereby producing a non-cathode electrode that does not contain lithium.

[0087]

[0088] <Formation of coating layer>

[0089] Silver (Ag), a lithium-friendly material, was formed on a copper (Cu) current collector with a thickness of 10 μm by an electroless plating method to a thickness of about 300 nm.

[0090] FIG. 2 is a scanning electron microscope (SEM) image of a cross-section when a coating layer is formed on a current collector according to one embodiment of the present invention.

[0091] Referring to FIG. 2, in order to manufacture a non-negative electrode for a lithium secondary battery according to one embodiment of the present invention, a coating layer of an alloy material containing silver (Ag) was formed on a copper current collector by electroless plating to a thickness of about 300 nm.

[0092]

[0093] Formation of a protective layer

[0094] FIG. 3a is a scanning electron microscope (SEM) image of the surface when a protective layer is formed on a current collector coated with a lithium-friendly material according to one embodiment of the present invention, and FIG. 3b is a scanning electron microscope (SEM) image of the cross-section.

[0095] Referring to FIGS. 3a and 3b, a lithium ion concentration protective layer of approximately 5 μm was formed on a copper current collector having a silver-containing coating layer by slurry coating using a comma coater. Specifically, the lithium ion concentration protective layer was prepared by mixing acetylene black, an amorphous carbon, and montmorillonite (MMT), a clay-type mineral, with a weight ratio of 90:10. The slurry was prepared using water as a solvent, and additionally, 3.0 wt% each of carboxymethylcellulose (CMC) and styrene-butadiene rubber (SBR) binders were added.

[0096]

[0097] Solid-state battery manufacturing

[0098] 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 dedicated 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.

[0099] A lithium electrode with a thickness of 0.5 mm was attached to one side of the 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 pressurized to a pressure of 50 MPa.

[0100]

[0101] <Example 2>

[0102] A non-cathode electrode was prepared in the same manner as in Example 1, except that in the step of forming the ion-concentrated protective layer, the weight ratio of amorphous carbon to the additive montmorillonite was 30:70.

[0103]

[0104] <Example 3>

[0105] A non-cathode electrode was prepared in the same manner as in Example 1, except that in the step of forming an ion-concentrated protective layer, nontronite was added as an additive in addition to montmorillonite.

[0106]

[0107] <Example 4>

[0108] A non-cathode electrode was prepared in the same manner as in Example 1, except that vermiculite was added as an additive in addition to montmorillonite in the step of forming an ion-concentrated protective layer.

[0109]

[0110] <Example 5>

[0111] A non-cathode electrode was prepared in the same manner as in Example 1, except that in the step of forming the ion-concentrated protective layer, the weight ratio of amorphous carbon to the additive montmorillonite was 3:97.

[0112]

[0113] <Comparative Example 1>

[0114] A non-cathode electrode was prepared in the same manner as in Example 1, except that in the step of forming the ion-concentrated protective layer, montmorillonite was not added as an additive and only amorphous carbon was used at 100 wt%.

[0115]

[0116] <Comparative Example 2>

[0117] A non-cathode electrode was prepared in the same manner as in Example 1, except that in the step of forming the ion-concentrated protective layer, the weight ratio of amorphous carbon to the additive montmorillonite was 1:99.

[0118]

[0119] <Comparative Example 3>

[0120] A non-cathode electrode was prepared in the same manner as in Example 1, except that in the step of forming the ion-concentrated protective layer, the weight ratio of amorphous carbon to the additive montmorillonite was 40:60.

[0121]

[0122] <Evaluation Example 1>

[0123] Table 1 below shows the bonding strength between the current collector and the protective layer according to the presence and content of montmorillonite as an additive in the ion-enriched protective layer. The bonding strength between the current collector and the protective layer, maximum current density, and charge / discharge cycles were measured.

[0124] Bond strength between the current collector and the protective layer: After the step of forming the protective layer described above, the bond strength between the coating layer and the current collector was measured using a peel strength tester. Specifically, a 10 mm wide polyimide tape (No. 360A, thickness: 0.08 mm, tack: 4.4 N / 19 mm) from Nitto was adhered to the protective layer, and the bond strength was measured through a tensile test using a peel strength tester (AND, MCT-2150 W). At this time, the tensile speed was set to 50 mm / min, and the tensile test distance was set to within a total of 200 mm. The bond strength was calculated as the average strength over a 100 mm section starting from the 50 mm point of the tensile test.

[0125] Maximum current density (mA / cm²) 2 The maximum current density refers to the limit of the current density at which lithium can be deposited between the ion-enriched protective layer and the current collector according to the above process, and the maximum current density was measured.

[0126] 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. 2Charging 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.

[0127] Classification Additive [wt%] Amorphous Carbon [wt%] Additive Type Sheet Bonding Strength [N / cm] Charge / Discharge Performance Cycles [cycles] Example 1 10 90 MMT 0.05 9847 Example 2 30 70 MMT 0.27 2717 Comparative Example 1 0 100 -0.00 9333

[0128] Referring to Table 1 above, it was confirmed that Examples 1 and 2, which had montmorillonite added, had superior bonding strength between the current collector and the ion-concentrated protective layer when compared to Comparative Example 1, in which the protective layer was formed only with amorphous carbon without the addition of montmorillonite. In addition, when comparing Examples 1 and 2, it was confirmed that the bonding strength between the current collector and the ion-concentrated protective layer was superior as the content of the additive increased.

[0129] In addition, when examining the number of charge-discharge cycles of the lithium anode compared to Examples 1 and 2, it can be confirmed that Examples 1 and 2 are superior to Comparative Example 1. Figure 4 is a graph of the bonding strength between the current collector and the ion concentration protective layer according to the examples and comparative examples of the present invention.

[0130] Referring to FIG. 4, it can be seen that Examples 1 and 2, which are embodiments of the present invention with 10 wt% and 30 wt% of montmorillonite added, have higher bonding strength compared to Comparative Example 1, in which a protective layer is formed only with amorphous carbon without the addition of montmorillonite. Specifically, looking at Examples 1 and 2, it can be seen that the bonding strength increases as the content of montmorillonite increases.

[0131]

[0132] <Evaluation Example 2> - Control of Additive Type and Weight Ratio

[0133] Table 1 below measures the bonding strength, maximum current density, and charge / discharge cycles between the current collector and the protective layer according to the type and characteristics of the additive in the ion-concentrated protective layer.

[0134] Classification Additive [wt%] Amorphous Carbon [wt%] Additive Sheet Bonding Strength [N / cm] Charge / Discharge Performance Cycles [Times] Type Layered Composition Crystal Structure Unit Cell Per Layer Charge (X) Cation Exchange Capacity (meq / 100g) Example 1 1090 MMT 2:1 Si substituted with Al monoclinic 0.2~0.6 80~1500 0.0 59847 Example 3 1090 Nontronite 2:1 Al substituted with Fe Substituted monoclinic 0.2~0.680~1500 0.055826 Example 4 1090 Vermiculite 2:1-monoclinic 0.6~0.980~1500 0.063730 Comparative Example 2 1090 Kaolinite 1:1-triclinic 0.3~150 0.052328 Comparative Example 3 1090 Chlorite mixed layer type Mg containing trigonal -10~400 0.061394

[0135] Looking at Table 2 above, it was confirmed that Comparative Examples 2 and 3, which used kaolinite and chlorite, had inferior charge-discharge performance compared to Examples 1, 3, and 4, which used montmorillonite, nontronite, and vermiculite as types of additives.

[0136]

[0137] <Evaluation Example 3> - Evaluation Example According to Additive Content

[0138] Table 3 below shows the bonding strength between the current collector and the protective layer, the maximum current density, and the number of charge / discharge cycles of the battery according to the content of amorphous carbon and additives in the ion-enriched protective layer.

[0139] Classification Additive [wt%] Amorphous Carbon [wt%] Additive Type Sheet Bonding Strength [N / cm] Charge / Discharge Performance Number of Cycles [Cycles] Example 1 1090MMT 0.059847 Example 5 397MMT 0.035914 Example 2 3070MMT 0.272717 Comparative Example 4 199MMT 0.015536 ​​Comparative Example 5 4060MMT 0.302560 Comparative Example 6 1090MMT 0.059325

[0140] Referring to Table 3 above, it was confirmed that Comparative Example 4, which has an excessively low additive content compared to Examples 1, 5, and 6, in which the additive content falls within the scope of the present invention, has problems with inferior bonding strength and charge / discharge cycles. It was also confirmed that Comparative Example 5, which has an excessively high additive content compared to Examples 1, 5, and 6, has inferior charge / discharge cycles. Figure 5 is a graph evaluating the cell life of an all-solid-state battery using electrodes for lithium secondary batteries of the examples and comparative examples according to an embodiment of the present invention.

[0141] Referring to Fig. 5, when examining the cell life evaluation of the all-solid-state battery of Example 1 and Comparative Example 1, it was confirmed that the cell life characteristics of Example 1 were superior to those of Comparative Example 1.

[0142]

[0143] 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 protective layer is a non-cathode electrode comprising amorphous carbon and a silicate clay mineral having a 2:1 layered crystal structure.

2. In Paragraph 1, The above protective layer is a non-cathode electrode in which the weight ratio of the amorphous carbon to the silicate clay mineral is 97:3 to 65:

35.

3. In Paragraph 1, The above silicate clay mineral is a non-cathode electrode containing monoclinic crystals.

4. In Paragraph 1, The above silicate clay mineral is a non-cathode electrode having a layer charge of 0.2 to 0.6 per unit cell.

5. In Paragraph 1, The above silicate clay mineral is a non-cathode electrode having a cation exchange capacity (me / 100g) of 80 to 150.

6. In Paragraph 1, A non-cathode electrode having a bonding strength between the current collector and the protective layer of 0.030 to 0.30 N / cm.

7. In Paragraph 1, The above coating layer is a non-cathode electrode comprising one or more of In, Ag, Sn, Zn, Si, Al, and Bi.

8. In Paragraph 1, A non-cathode electrode having an average thickness of the coating layer of 1 μm to 100 μm.

9. In Paragraph 1, A non-cathode electrode having an average thickness of the protective layer of 1 μm to 20 μm.

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

11. A step of forming a coating layer on at least one surface of a current collector using a coating composition containing a lithium-friendly component; and A method for manufacturing a non-cathode electrode comprising the step of forming a protective layer on the surface of a coating layer using a slurry comprising amorphous carbon and a silicate clay mineral having a 2:1 layered crystal structure.

12. In Paragraph 11, A method for manufacturing a non-cathode electrode in which, in the step of forming the protective layer, the weight ratio of the amorphous carbon to the silicate clay mineral is mixed to be 97:3 to 65:

35.

13. In Paragraph 11, In the step of forming a protective layer on the surface of the coating layer using a slurry comprising amorphous carbon and a silicate clay mineral having a 2:1 crystal structure, A method for manufacturing a non-cathode electrode comprising the step of slurry coating such that the thickness of the protective layer is 1 to 20 μm.

14. Positive current collector; Anode containing an anode active material layer; A non-cathode electrode according to any one of claims 1 to 10; and An electrolyte disposed 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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