Method for manufacturing an electrode for a lithium secondary battery, and a lithium secondary battery including the electrode

Abstract

The present application relates to a method for producing an electrode for a lithium secondary battery, the method comprising the steps of: forming an electrode current collector layer, and an electrode active material layer on one or both sides of the electrode current collector layer; and transferring lithium metal onto the electrode active material layer, the step of transferring the lithium metal comprising the steps of: preparing a transfer laminate in which a base layer, a release layer, and lithium metal are sequentially laminated; laminating the transfer laminate on the electrode active material layer so that a surface of the lithium metal opposite to a surface that contacts the release layer contacts a surface of the electrode active material layer opposite to a surface that contacts the electrode current collector layer; removing the base layer; and removing the release layer, the laminating step being carried out at a temperature condition of 30° C. or less and a pressure of 10 kgf / cm 2 More than 150kgf / cm 2 The present invention relates to a method for producing an electrode for a lithium secondary battery, in which lamination is performed at a pressure below 1000° C., and a lithium secondary battery including the electrode.

Description

[Technical Field]

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2022-0061177, filed with the Korean Intellectual Property Office on May 19, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present application relates to a method for producing an electrode for a lithium secondary battery, and to a lithium secondary battery including the electrode. [Background technology]

[0003] The rapid increase in fossil fuel use has led to an increasing demand for alternative and clean energy, and one of the most actively researched fields in this area is the field of power generation and storage using electrochemical reactions.

[0004] Currently, a typical example of an electrochemical element that uses electrochemical energy is a secondary battery, and the range of its use is expanding.

[0005] With the development of mobile device technologies and the increase in demand, the demand for secondary batteries as energy sources is rapidly increasing. Among such secondary batteries, lithium secondary batteries, which have high energy density and voltage, long cycle life, and low self-discharge rate, have been commercialized and widely used. In addition, active research is being conducted on methods for manufacturing high-density electrodes with higher energy density per unit volume as electrodes for such high-capacity lithium secondary batteries.

[0006] Generally, a secondary battery comprises a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode contains a negative electrode active material that inserts and extracts lithium ions from the positive electrode. The negative electrode active material may be silicon-based particles with a large discharge capacity.

[0007] Generally, carbon materials such as graphite are used for the negative electrode of lithium secondary batteries, and the theoretical capacity density of carbon is 372 mAh / g (833 mAh / cm 3) Therefore, in order to improve the energy density of the anode, silicon (Si), tin (Sn), and their oxides and alloys, which are alloyed with lithium, are being considered as anode materials. Among these, silicon-based materials have attracted attention due to their low cost and high capacity (4200mAh / g).

[0008] However, the use of silicon-based negative electrode active materials poses a problem of high initial irreversible capacity. During the charge-discharge reaction of a lithium secondary battery, lithium is released from the positive electrode and inserted into the negative electrode during charging, and then released from the negative electrode and returned to the positive electrode during discharge. However, with silicon-based negative electrode active materials, significant volume changes and surface side reactions occur, resulting in a large initial irreversible capacity, which in turn leads to a rapid decrease in battery capacity and cycle life.

[0009] To solve the above problems, a method of prelithiating a silicon negative electrode containing a silicon-based negative electrode active material is known. Known prelithiation methods include a method of lithiating a silicon negative electrode by a physical / chemical method such as electrolytic plating, lithium metal transfer, or lithium metal deposition, followed by fabrication of an electrode, and a method of electrochemically prelithiating a negative electrode.

[0010] In particular, in the lithium metal transfer process, it is difficult to transfer lithium metal safely and easily, and lithium is not transferred from the transfer laminate, or even if it is transferred, the highly reactive lithium metal immediately begins to react with the negative electrode active material, causing problems such as particle cracking on the surface of the negative electrode active material layer.

[0011] In addition, to control the reactivity and transferability of lithium metal, a release layer is used during the transfer of lithium metal, but after the pre-lithiation process, the adhesive strength of the release layer increases due to temperature increases and changes in pressure conditions, making it difficult to remove. In this case, the release layer acts as a resistor in the battery, causing an increase in resistance.

[0012] Therefore, research is needed into a method for prelithiating an electrode more safely and efficiently, without increasing the resistance of the battery, and for uniformly prelithiating lithium within the electrode active material layer. Summary of the Invention [Problem to be solved by the invention]

[0013] The lithium metal transfer process includes a process of transferring lithium metal from a transfer laminate to the top of an electrode active material layer during a pre-lithiation process, and it has been confirmed through research that adjusting the amount of heat generated per unit time of the electrode active material layer during pre-lithiation can increase the transferability of lithium metal and facilitate removal of the release layer after completion of pre-lithiation. Therefore, an object of the present application is to provide a method for manufacturing an electrode for a lithium secondary battery, and a lithium secondary battery including the electrode. [Means for solving the problem]

[0014] One embodiment of the present specification is a method for manufacturing an electrode for a lithium secondary battery, the method comprising: forming an electrode current collector layer and an electrode active material layer on one or both sides of the electrode current collector layer; and transferring lithium metal onto the electrode active material layer, wherein the step of transferring the lithium metal comprises: preparing a transfer laminate in which a substrate layer, a release layer, and lithium metal are sequentially laminated; laminating the transfer laminate on the electrode active material layer so that a surface of the lithium metal opposite to a surface that contacts the release layer is in contact with a surface of the electrode active material layer opposite to a surface that contacts the electrode current collector layer; removing the substrate layer; and removing the release layer, The lamination step is carried out under a temperature condition of 30°C or less and a pressure of 10 kgf / cm 2 More than 150kgf / cm 2 The present invention provides a method for manufacturing an electrode for a lithium secondary battery, in which the electrodes are laminated at the following pressure:

[0015] In yet another embodiment, there is provided a lithium secondary battery comprising: a positive electrode for a lithium secondary battery; a negative electrode for a lithium secondary battery; a separator provided between the positive electrode and the negative electrode; and an electrolyte, wherein at least one of the positive electrode for the lithium secondary battery and the negative electrode for the lithium secondary battery is a lithium secondary battery electrode produced by the method described above. [Effects of the Invention]

[0016] Generally, a release layer must be used to facilitate the transfer of lithium metal from a transfer laminate to the top of an electrode active material layer. However, if a battery is manufactured with the release layer itself included in the electrode after pre-lithiation, a problem occurs in that the resistance of the battery increases.

[0017] Therefore, a method for manufacturing an electrode for a lithium secondary battery according to one embodiment of the present invention is characterized by including a step of removing the release layer in the pre-lithiation step of the transfer process.

[0018] In particular, the present invention relates to a process in which the release layer can be easily separated from the top of the electrode active material layer by adjusting the process conditions during the prelithiation process of the electrode active material layer, and to a process in which the release layer on the top of the prelithiated electrode can be easily removed by adjusting the pressure, temperature, and heat generation per unit time during the transfer of lithium metal.

[0019] The electrode manufactured by the above process does not have a separate layer, such as a release layer, on the electrode active material layer, and therefore has the characteristic that the resistance does not increase when the battery is operated after assembling the cell. [Brief explanation of the drawings]

[0020] [Figure 1] 1A to 1C are diagrams illustrating a process of transferring lithium metal to an electrode for a lithium secondary battery according to an embodiment of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0021] Before describing the present invention, some terms will first be defined.

[0022] In this specification, when a part is said to "comprise" a certain component, this does not mean that it may further include other components, unless specifically stated to the contrary, but rather that it does not exclude other components.

[0023] In this specification, "p to q" means a range of "not less than p and not more than q."

[0024] In this specification, the "specific surface area" is measured by the BET method, and specifically, is calculated from the amount of nitrogen gas adsorption at liquid nitrogen temperature (77 K) using a BELSORP-mini II manufactured by BEL Japan Co., Ltd. That is, in the present application, the BET specific surface area can mean the specific surface area measured by the above-mentioned measurement method.

[0025] In this specification, "Dn" refers to particle size distribution, and refers to the particle size at the n% point in the cumulative particle number distribution by particle size. That is, D50 is the particle size (median particle size) at the 50% point in the cumulative particle number distribution by particle size, D90 is the particle size at the 90% point in the cumulative particle number distribution by particle size, and D10 is the particle size at the 10% point in the cumulative particle number distribution by particle size. Meanwhile, particle size distribution may be measured using the laser diffraction method. Specifically, the powder to be measured is dispersed in a dispersion medium and then introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac S3500). When the particles pass through a laser beam, the difference in diffraction pattern due to particle size is measured to calculate the particle size distribution.

[0026] As used herein, when a polymer contains a certain monomer as a monomer unit, it means that the monomer participates in a polymerization reaction and is included as a repeating unit in the polymer. As used herein, when a polymer contains a monomer, this is interpreted as the same as when a polymer contains a monomer as a monomer unit.

[0027] It is understood that the term "polymer" is used in the broad sense herein to include copolymers unless specifically referred to as a "homopolymer."

[0028] In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) are polystyrene-equivalent molecular weights measured by gel permeation chromatography (GPC) using commercially available monodisperse polystyrene polymers (standard samples) with various degrees of polymerization that are commercially available for molecular weight measurement as standard substances. In this specification, molecular weight means weight average molecular weight unless otherwise specified.

[0029] DETAILED DESCRIPTION OF THE INVENTION The present invention will now be described in detail with reference to the accompanying drawings so that those skilled in the art can easily practice the present invention. However, the present invention may be embodied in many different forms and should not be construed as limited to the following description.

[0030] One embodiment of the present specification is a method for manufacturing an electrode for a lithium secondary battery, the method comprising the steps of: forming an electrode current collector layer and an electrode active material layer on one or both sides of the electrode current collector layer; and transferring lithium metal onto the electrode active material layer, wherein the step of transferring lithium metal comprises the steps of: preparing a transfer laminate in which a base layer, a release layer, and lithium metal are sequentially laminated; laminating the transfer laminate on the electrode active material layer so that the surface of the lithium metal opposite to the surface that contacts the release layer is in contact with the surface of the electrode active material layer opposite to the surface that contacts the electrode current collector layer; removing the base layer; and removing the release layer, wherein the laminating step is performed at a temperature of 30° C. or less and a pressure of 10 kgf / cm 2 More than 150kgf / cm 2 The present invention provides a method for manufacturing an electrode for a lithium secondary battery, in which the electrodes are laminated at the following pressure:

[0031] In one embodiment of the present application, the electrode may be a negative electrode or a positive electrode.

[0032] FIG. 1 is a diagram showing a process of transferring lithium metal onto an electrode for a lithium secondary battery according to an embodiment of the present application. Specifically, after laminating a transfer laminate 100 in which a base material layer 10, a release layer 35, and lithium metal 20 are sequentially laminated on an electrode 200 for a lithium secondary battery formed of an electrode current collector layer 40 and an electrode active material layer 30, a process of removing the base material layer 10 of the transfer laminate 100 can be confirmed.

[0033] Hereinafter, specific contents of the method for manufacturing an electrode for a lithium secondary battery according to the invention of the present application will be described.

[0034] The method for manufacturing an electrode for a lithium secondary battery according to an embodiment of the present application may include a step of forming an electrode current collector layer and an electrode active material layer on one or both surfaces of the electrode current collector layer.

[0035] In one embodiment of the present application, the step of forming an electrode current collector layer and an electrode active material layer on one or both surfaces of the electrode current collector layer includes a step of coating an electrode slurry containing an electrode active material layer composition on one or both surfaces of the electrode current collector layer, and the electrode active material layer composition includes one or more selected from the group consisting of an electrode active material, an electrode conductive material, and an electrode binder. A method for manufacturing an electrode for a lithium secondary battery is provided.

[0036] At this time, the electrode active material includes a silicon-based active material, and the silicon-based active material includes one or more selected from the group consisting of SiO x (x = 0), SiO x (0 < x < 2), SiC, and Si alloy. A method for pre-lithiation of an electrode for a lithium secondary battery is provided.

[0037] In one embodiment of the present application, the electrode may be a negative electrode, and hereinafter, an explanation of a method for manufacturing a negative electrode for a lithium secondary battery will be described.

[0038] The method for manufacturing an electrode for a lithium secondary battery according to an embodiment of the present application may include a step of forming a negative electrode current collector layer and a negative electrode active material layer on one or both surfaces of the negative electrode current collector layer.

[0039] In one embodiment of the present application, the negative electrode current collector layer typically has a thickness of 1 μm to 100 μm. Such a negative electrode current collector layer is not particularly limited as long as it does not induce chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, plastic carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like, or an aluminum-cadmium alloy may be used. Furthermore, the surface may be provided with fine irregularities to strengthen the binding force of the negative electrode active material, and the negative electrode current collector layer may be used in various forms such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0040] In one embodiment of the present application, the negative electrode current collector layer may have a thickness of 1 μm or more and 100 μm or less, and the negative electrode active material layer may have a thickness of 20 μm or more and 500 μm or less.

[0041] However, the thickness may vary depending on the type and application of the negative electrode used, and is not limited thereto.

[0042] In one embodiment of the present application, there is provided a method for manufacturing an electrode for a lithium secondary battery, wherein the step of forming a negative electrode current collector layer and a negative electrode active material layer on one or both sides of the negative electrode current collector layer includes coating one or both sides of the negative electrode current collector layer with a negative electrode slurry including a negative electrode active material layer composition, and the negative electrode active material layer composition includes one or more selected from the group consisting of a negative electrode active material, a negative electrode conductive material, and a negative electrode binder.

[0043] In one embodiment of the present application, the negative electrode slurry may include a negative electrode active material layer composition and a slurry solvent.

[0044] In one embodiment of the present application, the solid content of the negative electrode slurry may be 5% or more and 40% or less.

[0045] In another embodiment, the solid content of the negative electrode slurry may be in the range of 5% to 40%, preferably 7% to 35%, more preferably 10% to 30%.

[0046] The solid content of the negative electrode slurry may refer to the content of the negative electrode active material layer composition contained in the negative electrode slurry, or may refer to the content of the negative electrode active material composition based on 100 parts by weight of the negative electrode slurry.

[0047] When the solid content of the negative electrode slurry satisfies the above range, the viscosity is appropriate during the formation of the negative electrode active material layer, and the caking phenomenon of particles of the negative electrode active material layer composition is minimized, thereby enabling the negative electrode active material layer to be efficiently formed.

[0048] In one embodiment of the present application, the slurry solvent is not limited to a solvent as long as it can dissolve the negative electrode active material layer composition, and specifically, distilled water may be used.

[0049] The negative electrode according to one embodiment of the present application may be formed by coating the negative electrode slurry on a negative electrode current collector layer and drying it.

[0050] The drying step may evaporate the slurry solvent from the negative electrode slurry.

[0051] In one embodiment of the present application, the negative electrode active material layer composition may include one or more selected from the group consisting of a negative electrode active material, a negative electrode conductive material, and a negative electrode binder.

[0052] In one embodiment of the present application, a silicon-based active material may be used as the negative electrode active material, or a negative electrode containing both a silicon-based active material and a carbon-based active material may be used, in which case a lithium secondary battery with improved performance characteristics such as cycle life characteristics may be manufactured.

[0053] In one embodiment of the present application, the silicon-based active material is SiOx (x = 0), SiO x It may contain one or more selected from the group consisting of (0 < x < 2), SiC, and Si alloy.

[0054] In one embodiment of the present application, the silicon-based active material is SiO x (x = 0) and SiO x It may contain one or more selected from the group consisting of (0 < x < 2), and based on 100 parts by weight of the silicon-based active material, the SiO x (x = 0) may contain 70 parts by weight or more.

[0055] In another embodiment, based on 100 parts by weight of the silicon-based active material, the SiO x (x = 0) may contain 70 parts by weight or more, preferably 80 parts by weight or more, more preferably 90 parts by weight or more, and may contain 100 parts by weight or less, preferably 99 parts by weight or less, more preferably 95 parts by weight or less.

[0056] In one embodiment of the present application, the silicon-based active material may particularly use pure silicon (Si) as the silicon-based active material. Using pure silicon (Si) as the silicon-based active material means that, as described above, when based on 100 parts by weight of the entire silicon-based active material, it may mean containing pure Si particles (SiO x (x = 0)) within the above range and not combined with other particles or elements.

[0057] In the charge-discharge reaction of a lithium secondary battery, during charging, lithium released from the positive electrode is inserted into the negative electrode, and during discharging, it desorbs from the negative electrode and returns to the positive electrode again. However, in the case of a silicon-based negative electrode active material, volume change and surface side reactions are serious, and during the initial charging, most of the amount of lithium inserted into the negative electrode cannot return to the positive electrode again. Therefore, a problem occurs in that the initial irreversible capacity increases. When the initial irreversible capacity increases, problems occur in that the battery capacity and cycle rapidly decrease.

[0058] In order to solve the above-mentioned problems, the present invention prelithiates the negative electrode of a lithium secondary battery to solve the initial irreversible capacity problem. Specifically, the prelithiation process is characterized by suppressing the generation of by-products so that lithium metal can be easily transferred from the transfer laminate during the lithium transfer process and lithium in the negative electrode active material layer can be uniformly prelithiated, thereby preventing an increase in the resistance of the manufactured cell.

[0059] The average particle size (D50) of the silicon-based active material of the present invention may be 1 μm to 10 μm, specifically 3 μm to 8 μm, and more specifically 3.5 μm to 7 μm. When the average particle size is within this range, the specific surface area of ​​the particles is within an appropriate range, and the viscosity of the negative electrode slurry is formed within an appropriate range. This facilitates dispersion of the particles constituting the negative electrode slurry. Furthermore, when the size of the silicon-based active material is equal to or greater than the lower limit of this range, the contact area between the silicon particles and the conductive material is excellent due to the composite of the conductive material and the binder in the negative electrode slurry, increasing the likelihood of maintaining a conductive network and improving capacity retention. When the average particle size is within this range, excessively large silicon particles are excluded, resulting in a smooth negative electrode surface, thereby preventing non-uniform current density during charge and discharge.

[0060] In one embodiment of the present application, the silicon-based active material usually has a characteristic BET specific surface area. The BET specific surface area of ​​the silicon-based active material is preferably 0.01 m 2 / g~150.0m 2 / g, more preferably 0.1m 2 / g~100.0m 2 / g, particularly preferably 0.2m 2 / g~80.0m 2 / g, most preferably 0.2m 2 / g~18.0m 2 / g. The BET specific surface area is measured (using nitrogen) according to DIN 66131.

[0061] In one embodiment of the present application, the silicon-based active material may be, for example, in crystalline or amorphous form, and is preferably not porous. The silicon particles are preferably spherical or shard-like particles. Alternatively, the silicon particles may have a fibrous structure or may be in the form of a silicon-containing thin film or coating, but this is less preferred.

[0062] In one embodiment of the present application, the silicon-based active material may be 60 parts by weight or more based on 100 parts by weight of the negative electrode active material layer composition.

[0063] In yet another embodiment, the silicon-based active material may be included in an amount of 60 parts by weight or more, preferably 65 parts by weight or more, more preferably 70 parts by weight or more, based on 100 parts by weight of the negative electrode active material layer composition, and may be included in an amount of 95 parts by weight or less, preferably 90 parts by weight or less, more preferably 80 parts by weight or less.

[0064] The negative electrode active material layer composition according to the present application includes a silicon-based active material having a significantly high capacity within the above range, and also includes a negative electrode conductive material and a negative electrode binder that can control the volume expansion rate during charge and discharge. Even when the silicon-based active material and a negative electrode binder are included within the above range, the negative electrode performance is not reduced and the negative electrode has excellent output characteristics during charge and discharge.

[0065] In one embodiment of the present application, the silicon-based active material may have a non-spherical morphology, and the sphericity is, for example, 0.9 or less, for example, 0.7 to 0.9, for example, 0.8 to 0.9, for example, 0.85 to 0.9.

[0066] In this application, the circularity is determined by the following formula A, where A is the area and P is the perimeter.

[0067] [Formula A] 4πA / P 2

[0068] While graphite-based compounds have traditionally been used exclusively as anode active materials, attempts to incorporate silicon-based active materials into batteries to increase capacity have recently been increasing in response to growing demand for high-capacity batteries. However, silicon-based active materials have limitations, such as their rapid volume expansion during charge / discharge processes, damaging the conductive pathways formed within the anode active material layer and reducing battery performance. Therefore, the type of anode conductive material used together with the silicon-based active material is important.

[0069] In one embodiment of the present application, the negative electrode conductive material may include one or more selected from the group consisting of dot-like conductive materials, planar conductive materials, and linear conductive materials.

[0070] In one embodiment of the present application, the dot-like conductive material refers to a conductive material that can be used to improve the conductivity of a negative electrode and has conductivity without inducing chemical changes. Specifically, the dot-like conductive material may be at least one selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, conductive fiber, fluorocarbon, aluminum powder, nickel powder, zinc oxide, potassium titanate, titanium oxide, and polyphenylene derivatives, and preferably includes carbon black in view of realizing high conductivity and excellent dispersibility.

[0071] In one embodiment of the present application, the point-like conductive material has a BET specific surface area of ​​40 m 2 / g or more 70m 2 / g or less, preferably 45m 2 / g or more 65m 2 / g or less, more preferably 50m 2 / g or more 60m 2 / g or less.

[0072] In one embodiment of the present application, the particle size of the dotted conductive material may be 10 nm to 100 nm, preferably 20 nm to 90 nm, and more preferably 40 nm to 60 nm.

[0073] In one embodiment of the present application, the negative electrode conductive material may include a sheet conductive material.

[0074] The planar conductive material can improve conductivity by increasing surface contact between silicon particles in the negative electrode, and at the same time, can prevent the conductive path from being broken due to volume expansion. The planar conductive material is used in a concept including bulk conductive materials and plate-shaped conductive materials.

[0075] In one embodiment of the present application, the planar conductive material may include at least one selected from the group consisting of platelet graphite, graphene, graphene oxide, and graphite flakes, and may preferably be platelet graphite.

[0076] In one embodiment of the present application, the average particle size (D50) of the sheet conductive material may be 2 μm to 7 μm, specifically 3 μm to 6 μm, and more specifically 4 μm to 5 μm. When the average particle size satisfies the above range, the particle size is sufficient, which facilitates dispersion while preventing excessive increase in the viscosity of the negative electrode slurry. Therefore, when dispersing using the same equipment and time, the dispersion effect is excellent.

[0077] In one embodiment of the present application, there is provided a negative electrode composition in which the planar conductive material has a D10 of 0.5 μm or more and 1.5 μm or less, a D50 of 2.5 μm or more and 3.5 μm or less, and a D90 of 7.0 μm or more and 15.0 μm or less.

[0078] In one embodiment of the present application, the sheet conductive material may be a sheet conductive material having a high BET specific surface area; or a sheet conductive material having a low specific surface area.

[0079] In one embodiment of the present application, the planar conductive material may be a planar conductive material with a high specific surface area or a planar conductive material with a low specific surface area without any restrictions. However, the planar conductive material of the present application may be particularly susceptible to the influence of dispersion to some extent in terms of electrode performance, and it is particularly preferable to use a planar conductive material with a low specific surface area that does not cause dispersion problems.

[0080] In one embodiment of the present application, the sheet conductive material has a BET specific surface area of ​​5 m 2 / g or more.

[0081] In another embodiment, the sheet conductive material has a BET specific surface area of ​​5 m 2 / g or more 500m 2 / g or less, and preferably 5m 2 / g or more 300m 2 / g or less, more preferably 5m 2 / g or more 250m 2 / g.

[0082] In another embodiment, the sheet conductive material is a sheet conductive material having a high specific surface area, and a BET specific surface area of ​​50 m 2 / g or more 500m 2 / g or less, preferably 80m 2 / g or more 300m 2 / g or less, more preferably 100m 2 / g or more 300m 2 / g or less.

[0083] In another embodiment, the sheet conductive material is a sheet conductive material having a low specific surface area, and a BET specific surface area of ​​5 m 2 / g or more 40m 2 / g or less, preferably 5m 2 / g or more 30m 2 / g or less, more preferably 5m 2 / g or more 25m 2 / g or less.

[0084] Other conductive materials include linear conductive materials such as carbon nanotubes. The carbon nanotubes may be bundled carbon nanotubes. The bundled carbon nanotubes may include multiple carbon nanotube units. Specifically, unless otherwise specified, the term "bundle type" refers to a secondary shape in which multiple carbon nanotube units are arranged parallel or twisted with the longitudinal axes of the carbon nanotube units in substantially the same orientation, forming a bundle or rope. The carbon nanotube units each have a cylindrical graphite sheet with a nanosized diameter and an sp2 bonding structure. Depending on the angle and structure of the graphite sheet, the carbon nanotube unit may exhibit conductive or semiconductive properties. Compared to entangled carbon nanotubes, the bundled carbon nanotubes can be more uniformly dispersed during negative electrode fabrication and can smoothly form a conductive network within the negative electrode, thereby improving the conductivity of the negative electrode.

[0085] In one embodiment of the present application, the negative electrode conductive material may be 10 parts by weight or more and 40 parts by weight or less based on 100 parts by weight of the negative electrode active material layer composition.

[0086] In yet another embodiment, the negative electrode conductive material may be included in an amount of 10 parts by weight or more and 40 parts by weight or less, preferably 10 parts by weight or more and 30 parts by weight or less, and more preferably 15 parts by weight or more and 25 parts by weight or less, based on 100 parts by weight of the negative electrode active material layer composition.

[0087] The anode conductive material according to the present application has a completely different structure from the cathode conductive material used in the cathode. That is, the anode conductive material according to the present application controls the contact points between the silicon-based active material, which experiences a large volume expansion of the electrode during charging and discharging, while the cathode conductive material acts as a buffer when rolled and also provides some conductivity, and therefore has a completely different structure and role from the anode conductive material of the present invention.

[0088] Furthermore, the negative electrode conductive material according to the present application is applied to a silicon-based active material and has a completely different structure from conductive materials applied to graphite-based active materials. That is, conductive materials used in electrodes having graphite-based active materials simply have smaller particles than the active material, and therefore have the properties of improving output characteristics and imparting some conductivity, and are completely different in structure and role from negative electrode conductive materials applied together with silicon-based active materials as in the present invention.

[0089] In one embodiment of the present application, the dot-like conductive material used as the negative electrode conductive material has a structure and function different from that of a carbon-based active material typically used as a negative electrode active material. Specifically, the carbon-based active material used as the negative electrode active material may be artificial graphite or natural graphite, and refers to a material that is processed into a spherical or dot-like shape to facilitate the storage and release of lithium ions.

[0090] Meanwhile, the planar conductive material used as the negative electrode conductive material is typically a material having a planar or plate-like shape, such as plate-shaped graphite. That is, it is a material contained in the negative electrode active material layer to maintain a conductive path within the layer, and does not play a role in storing or releasing lithium, but rather serves to ensure a planar conductive path within the negative electrode active material layer.

[0091] In other words, in this application, the use of plate-like graphite as a conductive material means that it is processed into a planar or plate-like shape and used as a material to ensure a conductive path, not to store or release lithium. At this time, the negative electrode active material included therein has high capacity characteristics for storing and releasing lithium, and plays a role in storing and releasing all lithium ions transferred from the positive electrode.

[0092] Meanwhile, in the present application, the term "carbon-based active material is used as an active material" means that the carbon-based active material is processed into a dotted or spherical shape and used as a material that stores or releases lithium.

[0093] That is, in one embodiment of the present application, the carbon-based active material, artificial graphite or natural graphite, has a BET specific surface area of ​​0.1 m 2 / g or more 4.5m 2 / g or less. The plate-shaped graphite, which is a planar conductive material, has a planar shape and a BET specific surface area of ​​5m 2 / g or more.

[0094] In one embodiment of the present application, the negative electrode binder may include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, and substances in which hydrogen is substituted with Li, Na, Ca, or the like, or may include various copolymers thereof.

[0095] The negative electrode binder according to one embodiment of the present application serves to control the negative electrode active material and the negative electrode conductive material in order to prevent twisting and deformation of the negative electrode structure during volume expansion and relaxation of the silicon-based active material. When the binder fulfills the above-mentioned role, any conventional negative electrode binder may be used. Specifically, a water-based binder may be used, and more specifically, a PAM-based binder or an SBR binder may be used.

[0096] In one embodiment of the present application, the negative electrode binder may be contained in an amount of 30 parts by weight or less, preferably 25 parts by weight or less, more preferably 20 parts by weight or less, or 1 part by weight or more, preferably 3 parts by weight or more, based on 100 parts by weight of the negative electrode active material layer composition.

[0097] In one embodiment of the present application, the electrode may be a positive electrode, and a method for manufacturing a positive electrode for a lithium secondary battery will be described below. In this case, the same description as for the method for manufacturing a negative electrode for a lithium secondary battery may be applied, except for the positive electrode.

[0098] A method for manufacturing an electrode for a lithium secondary battery according to an embodiment of the present application may include forming a positive electrode current collector layer and a positive electrode active material layer on one or both surfaces of the positive electrode current collector layer.

[0099] In one embodiment of the present application, the positive electrode current collector layer is not particularly limited as long as it does not induce chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, plastic carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. The positive electrode current collector layer may typically have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the positive electrode current collector layer to enhance adhesion of the positive electrode active material. The positive electrode current collector layer may be used in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0100] The thickness of the positive electrode current collector layer may vary depending on the type and application of the positive electrode, but is not limited thereto.

[0101] In one embodiment of the present application, there is provided a method for manufacturing an electrode for a lithium secondary battery, wherein the step of forming a positive electrode current collector layer and a positive electrode active material layer on one or both surfaces of the positive electrode current collector layer includes coating one or both surfaces of the positive electrode current collector layer with a positive electrode slurry containing a positive electrode active material layer composition, and the positive electrode active material layer composition includes one or more selected from the group consisting of a positive electrode active material, a positive electrode conductive material, and a positive electrode binder.

[0102] In one embodiment of the present application, the contents of the positive electrode slurry may be the same as those of the negative electrode slurry, except for the positive electrode.

[0103] In one embodiment of the present application, the positive electrode active material layer composition may include one or more selected from the group consisting of a positive electrode active material, a positive electrode conductive material, and a positive electrode binder.

[0104] The positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; a lithium iron oxide such as LiFe3O4; 1+c1 Mn 2-c1 O4 (0≦c1≦0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; chemical formula LiNi 1-c2 M c2 Ni-site type lithium nickel oxide represented by the chemical formula LiMnO2 (where M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies 0.01≦c2≦0.3); 2-c3 M c3Examples of the lithium manganese composite oxide include, but are not limited to, lithium manganese composite oxides represented by Li2Mn3MO8 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01≦c3≦0.1) or Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); and LiMn2O4, in which part of the Li in the chemical formula is replaced with an alkaline earth metal ion. The positive electrode may be Li metal.

[0105] The positive electrode conductive material is used to impart conductivity to the electrode and may be any material that has electronic conductivity without causing chemical changes in the battery. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives. These may be used alone or in combination.

[0106] The positive electrode binder improves adhesion between positive electrode active material particles and between the positive electrode active material and the positive electrode current collector. Specific examples of the positive electrode binder include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof. These may be used alone or in combination.

[0107] In addition, the contents of the positive electrode active material, the positive electrode conductive material, and the positive electrode binder contained in the positive electrode active material layer composition may be the same as those applied to the negative electrode active material layer composition.

[0108] In one embodiment of the present application, the present invention may include a method for pre-lithiation of an electrode for a lithium secondary battery, the method including a step of transferring lithium metal onto the electrode active material layer.

[0109] Generally, the prelithiation process is performed by chemically or physically prelithiating lithium metal onto an electrode, and specifically, may be performed by a lithium metal transfer process, a lithium metal powder deposition process, an electrochemical process, or a lithium metal deposition process, and the prelithiation process according to the present application may include a lithium metal transfer process.

[0110] The lithium metal transfer process is characterized by the fact that highly reactive lithium metal can be transferred more stably onto the electrode active material layer. In this case, a process is required that can easily transfer the lithium metal from the transfer laminate onto the electrode active material layer.

[0111] In one embodiment of the present application, the method may include the steps of: preparing the transfer laminate; laminating the transfer laminate onto the electrode active material layer so that the surface of the lithium metal opposite to the surface that contacts the release layer contacts the surface of the electrode active material layer opposite to the surface that contacts the electrode current collector layer; removing the base layer; and removing the release layer.

[0112] In one embodiment of the present application, the step of preparing the transfer laminate includes a step of coating and laminating a release layer on the substrate layer; a drying step; and a step of laminating the lithium metal on the release layer; and the drying step may include a step of drying for 5 minutes to 1 hour at a drying temperature of 30°C to 90°C.

[0113] That is, by adjusting the conditions of the drying step, the adhesive strength of the release layer can be controlled within a specific range, which can facilitate the transfer of lithium metal during pre-lithiation in the transfer process.

[0114] In one embodiment of the present application, the substrate layer may be any layer that can withstand process conditions such as high temperatures during the deposition of lithium metal and can prevent reverse peeling, in which lithium metal is transferred onto the substrate layer during a winding process for transferring the deposited lithium metal.

[0115] Specifically, in one embodiment of the present application, the base layer may be one or more selected from the group consisting of polyethylene terephthalate (PET), polyimide (PI), poly(methylmethacrylate) (PMMA), polypropylene, polyethylene, and polycarbonate.

[0116] In one embodiment of the present application, the thickness of the substrate layer may be 1 μm or more and 300 μm or less, or may satisfy the range of 5 μm or more and 200 μm or less, or 10 μm or more and 30 μm or less.

[0117] In one embodiment of the present application, the thickness of the lithium metal may be 1 μm or more and 10 μm or less, and preferably may be 3 μm or more and 10 μm or less.

[0118] When the thicknesses of the substrate layer and the lithium metal satisfy the above ranges, the lithium metal can be efficiently transferred to the electrode active material layer side, and reverse transfer can be prevented.

[0119] In one embodiment of the present application, the transfer laminate includes a release layer on the surface where the base material layer and the lithium metal come into contact in order to improve the peelability of the lithium metal, ensure transferability to the electrode active material layer, and serve as a protective layer after transfer of the lithium metal.

[0120] That is, the substrate layer may have a release layer formed on at least one surface thereof, or may have release layers formed on both surfaces thereof. The release layer can prevent reverse peeling, in which lithium metal is transferred onto the substrate layer during a winding process for transferring the deposited lithium metal to the electrode, and can also facilitate separation of the substrate layer after the lithium metal is transferred onto the electrode active material layer.

[0121] In one embodiment of the present application, there is provided a method for producing an electrode for a lithium secondary battery, wherein the release layer comprises one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polyethylene (PE), polypropylene (PP), polyacrylic acid (PAA), and polyester.

[0122] In one embodiment of the present application, there is provided a method for producing an electrode for a lithium secondary battery, wherein the thickness of the release layer is 0.1 μm or more and 2 μm or less.

[0123] When the thickness of the release layer satisfies the above range, lithium metal can be easily transferred from the transfer laminate to the electrode active material layer, and when the release layer is removed from the top of the electrode active material layer after pre-lithiation, it can be easily removed without being torn or peeled off.

[0124] In one embodiment of the present application, a deposition method for depositing the lithium metal on the substrate layer on which the release layer is formed may be selected from the group consisting of vacuum deposition (evaporation deposition), chemical vapor deposition (CVD), and physical vapor deposition (physical vapor deposition), but is not limited thereto, and various deposition methods used in the art may be used.

[0125] In one embodiment of the present application, a physical vapor deposition method may be used as a deposition method for depositing the lithium metal on the substrate layer on which the release layer is formed.

[0126] At this time, the lithium secondary battery electrode on which the transfer laminate was laminated was subjected to a pressure of 5 kgf / cm 2 ~500kgf / cm 2 The lamination process can be performed by roll pressing while applying a load of 1000. A subsequent process of removing the substrate layer is included, and the inclusion of the release layer according to the present application prevents problems such as reverse transfer of lithium metal during removal.

[0127] In one embodiment of the present application, the release layer may be formed by a coating method. For example, the coating method may be a method selected from the group consisting of dip coating, spray coating, spin coating, die coating, gravure coating, micro-gravure coating, comma coating, and roll coating, but is not limited thereto. Various coating methods available in the art for forming a coating layer may be used.

[0128] In one embodiment of the present application, the transfer laminate is laminated on the electrode active material layer so that a surface of the lithium metal opposite to a surface that contacts the release layer is in contact with a surface of the electrode active material layer opposite to a surface that contacts the current collector layer, and the lamination is performed at a temperature of 30° C. or less and under a pressure of 10 kgf / cm 2 More than 150kgf / cm 2 The following pressures may be used for lamination:

[0129] After the lamination step, prelithiation of the electrode active material layer with highly reactive lithium metal may be performed.

[0130] In another embodiment, the lamination step may be performed at a temperature of 30°C or less, preferably 25°C or less, or at a temperature of 10°C or more, preferably 15°C or more.

[0131] That is, as described above, when lamination is performed under conditions that allow heat generated within the electrode to be easily released, and the temperature range is met, the pre-lithiation reaction rate during lamination is appropriate, thereby preventing heat accumulation and creating a state in which the release layer can be easily removed later.

[0132] In one embodiment of the present application, the laminating step is performed at a pressure of 10 kgf / cm 2 More than 150kgf / cm 2 The following pressures may be used for lamination:

[0133] In yet another embodiment, the laminating step is performed at a pressure of 150 kgf / cm 2 Preferably, 100 kgf / cm or less 2 It may be less than 50 kgf / cm 2 It may be less than 10 kgf / cm 2 The above range may be satisfied.

[0134] As described above, the pressure range during lamination is satisfied, which corresponds to the appropriate pressure condition for transferring lithium metal, and the release layer can be prevented from detaching from the surface of the electrode.Furthermore, by satisfying the pressure and temperature conditions, the release layer can be easily removed later, which prevents an increase in resistance during cell assembly.

[0135] Specifically, the lamination step is performed at 150 kgf / cm 2 If lamination is performed with a pressure exceeding 10 kgf / cm, the adhesive strength of the release layer to the lithium metal increases, making it difficult to remove the release layer. If the release layer is forcibly removed, the electrode may detach. 2 If lamination is performed with a pressure less than 1000 MPa, the transfer of lithium metal to the electrode active material layer may not be successful.

[0136] In one embodiment of the present application, there is provided a method for manufacturing an electrode for a lithium secondary battery, wherein the step of transferring the lithium metal includes a step of laminating the transfer laminate onto the electrode active material layer to prelithiate the electrode active material layer, and the step of prelithiating the electrode active material layer is performed within 30 minutes to 24 hours after transferring the lithium metal.

[0137] When the electrode active material layer is prelithiated, the electrode active material layer generates heat at a rate of 5°C / min for 30 seconds to 3 minutes and then cools down.

[0138] The step of prelithiating the electrode active material layer is performed at 25° C. and 1 atm within 30 minutes to 24 hours.

[0139] The pre-lithiation step is a step of setting conditions for lithium metal to diffuse into the electrode active material layer, and whether the pre-lithiation step is complete can be determined by whether lithium at the top of the electrode active material layer has completely disappeared.

[0140] In one embodiment of the present application, the activation reaction time may be 30 minutes to 48 hours, preferably 1 hour to 2 hours.

[0141] In one embodiment of the present application, the step of transferring the lithium metal includes the step of removing the substrate layer.

[0142] In a conventional lithium metal transfer process, there is a problem in that the substrate layer is difficult to peel off during the prelithiation process after the transfer laminate is laminated. As a result, prelithiation is performed without removing the substrate layer, and the heat generated during prelithiation is blocked by the substrate layer and cannot be released, resulting in the formation of by-products on the surface during prelithiation of the lithium metal, which causes polymer crosslinking in the release layer, making it difficult to remove the release layer.

[0143] However, by adjusting the lamination pressure, temperature, and heat generation per hour during the pre-lithiation process within appropriate ranges, the substrate layer was easily peeled off after laminating the transfer laminate, and as a result, the release layer could be easily removed without polymer crosslinking occurring in the release layer.

[0144] In one embodiment of the present application, the step of removing the substrate layer may be performed within 1 hour after the step of laminating the transfer laminate onto the electrode active material layer, preferably within 30 minutes after the lamination step, and most preferably, the substrate layer is removed immediately after the lamination step.

[0145] The step of removing the substrate layer is preferably performed within the above-mentioned time range. In particular, if the substrate layer is removed after 1 hour from the lamination step, a large amount of lithium by-products are rapidly generated, which increases the adhesive strength between the release layer and the electrode active material layer, making it difficult to remove the release layer.

[0146] In one embodiment of the present application, the step of transferring the lithium metal includes a step of removing the release layer, specifically, a step of removing the release layer from above the pre-lithiated electrode active material layer after pre-lithiation as described above.

[0147] If the above process conditions are met, polymer cross-linking of the release layer does not occur, thereby facilitating removal of the release layer. If the above conditions are not met, cross-linking of the release layer occurs, preventing removal of the release layer and increasing the force required for removal, which may result in problems such as electrode detachment.

[0148] That is, by adjusting the process conditions as described above, the prelithiation method for a lithium secondary battery electrode according to the present application has the following characteristics: the substrate layer can be easily peeled off immediately after lamination of the transfer laminate, the generation of by-products during prelithiation can be suppressed, and the release layer can be easily removed by preventing an increase in the adhesive strength between the release layer and the prelithiated electrode active material layer.

[0149] At this time, the release layer 35 used during pre-lithiation can be removed as described above, so that it does not remain on the electrode and can prevent an unnecessary increase in resistance. That is, the release layer can improve transfer force and also serve to protect the lithium metal before pre-lithiation, and can be removed before injecting the electrolyte.

[0150] In one embodiment of the present application, examples of the electrolyte include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in manufacturing lithium secondary batteries, but are not limited to these.

[0151] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0152] Examples of the non-aqueous organic solvent that can be used include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0153] In particular, among the carbonate-based organic solvents, cyclic carbonates such as ethylene carbonate and propylene carbonate are preferred because they are high-viscosity organic solvents with high dielectric constants and good dissociation of lithium salts. Mixing such cyclic carbonates with linear carbonates having low viscosity and low dielectric constants, such as dimethyl carbonate and diethyl carbonate, in an appropriate ratio can produce an electrolyte having high electrical conductivity, making them more preferred.

[0154] The metal salt may be a lithium salt, which is a substance that is easily dissolved in the non-aqueous electrolyte solution. For example, the anion of the lithium salt may be F - , Cl - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - One or more selected from the group consisting of:

[0155] In addition to the components of the electrolyte, the electrolyte may further include one or more additives, such as a haloalkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity.

[0156] In one embodiment of the present invention, there is provided a lithium secondary battery comprising: a positive electrode for a lithium secondary battery; a negative electrode for a lithium secondary battery; a separator provided between the positive electrode and the negative electrode; and an electrolyte, wherein at least one of the positive electrode for the lithium secondary battery and the negative electrode for the lithium secondary battery is a lithium secondary battery electrode that has been prelithiated according to the present application.

[0157] According to another aspect of the present invention, there is provided a battery module including the lithium secondary battery as a unit cell, and a battery pack including the same. The battery module and the battery pack include the secondary battery having high capacity, high rate characteristics, and high cycle characteristics, and may be used as a power source for medium- to large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems. [Example]

[0158] Below, preferred examples are presented to help understand the present invention. However, these examples are merely illustrative of the present description, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope of the scope and technical ideas of the present description. Naturally, such changes and modifications fall within the scope of the claims.

[0159] <Example> <Production of Transfer Laminate> An acrylate polymer release layer was coated on top of a PET (25 μm) substrate layer to improve transferability, and then lithium metal was deposited on the PET substrate to a thickness of 6 μm using PVD to produce a transfer laminate.

[0160] <Production of negative electrodes> A negative electrode slurry was prepared by adding Si (average particle size (D50): 3.5 μm) as a silicon-based active material, Denka Black as a conductive material, SBR as a binder, and CMC as a thickener in a weight ratio of 80:15.8:3:1.2 to distilled water as a solvent for forming a negative electrode slurry (solid concentration: 25 wt%).

[0161] The mixing method was as follows: the conductive material, binder, thickener and water were dispersed using a homomixer at 2500 rpm for 30 minutes, and then the active material was added, followed by dispersion at 2500 rpm for 30 minutes to prepare a slurry.

[0162] The negative electrode current collector was a copper current collector (thickness: 8 μm) and the negative electrode slurry was applied to both sides of the copper current collector at a rate of 85 mg / 25 cm. 2 The coated film was rolled and dried in a vacuum oven at 130°C for 10 hours to form a negative electrode active material layer (thickness: 33 μm), which was used as a negative electrode (negative electrode thickness: 41 μm, negative electrode porosity: 40.0%).

[0163] Example 1 Thereafter, to transfer the transfer laminate to the negative electrode active material layer, the lithium metal of the transfer laminate was positioned on top of the negative electrode active material layer, and then the lithium metal and the negative electrode active material layer were bonded by roll pressing under external pressure conditions of the load and temperature conditions shown in Table 1. Immediately after lamination, the PET layer of the transfer laminate was removed, and the negative electrode was prelithiated.

[0164] The conditions for pre-lithiation are as shown in Table 1. After pre-lithiation of the negative electrode, the release layer remaining on the surface of the negative electrode active material layer was removed using scotch tape (3M tape).

[0165] Examples 2 and 3 In Example 2, the negative electrode was prelithiated in the same manner as in Example 1, except that the external pressure conditions were slightly higher than in Example 1. In Example 3, the negative electrode was prelithiated in the same manner as in Example 1, except that the lithium metal in Example 1 was deposited on the PET substrate to a thickness of 8 μm.

[0166] Comparative Examples 1 to 4 In Comparative Example 1, the negative electrode was prelithiated in the same manner as in Example 1, except that the PET substrate was removed 1 hour after lamination. In Comparative Example 2, the external pressure was 180 kgf / c m 2 The PET substrate was removed immediately after lamination, but the release layer was not removed. In Comparative Example 3, the external pressure was set to 180 kgf / c m 2 The negative electrode was prelithiated in the same manner as in Example 1, except that the external pressure was set high at 5 kgf / c m 2 The negative electrode was prelithiated in the same manner as in Example 1, except that the temperature was set low.

[0167] At this time, the adhesive strength between the release layer and the electrode active material layer in Examples 1 to 3 and Comparative Examples 1 to 4 is as shown in Table 1 below, and the evaluation results after pre-lithiation are as shown in Table 2 below.

[0168] [Table 1]

[0169] The adhesive strength in Table 1 was measured by attaching 3M double-sided tape to glass (22 mm wide) and then cutting the electrode to a 20 mm width. The sample was then placed at a 90° angle in the adhesive strength measurement equipment and peeled at a predetermined speed, measuring the force. The measurement unit was gf, and since the sample width was 20 mm, the unit was gf / 20 mm. The physical properties listed in Table 2 below were measured by fabricating a bi-cell battery using the prepared anode and cathode NCM as counter electrodes. The electrolyte used in this battery was ethylene carbonate (EC) / ethyl methyl carbonate (EMC) = 3 / 7 (volume ratio) dissolved in 1M LiPF6.

[0170] The capacity of the bi-cell battery fabricated above was confirmed using an electrochemical charge / discharger. It was charged to 4.2 V (vs. Li / Li+) at 0.05 C with a current density of 1 C, and discharged to 2.5 V at 0.5 C (vs. Li / Li+). It was then charged again to 4.2 V and discharged to SOC50. A 2.5 C current pulse was applied for 30 seconds, and the voltage change was observed. Resistance was calculated for 0.1 seconds, 0.1 to 30 seconds, and 0 to 30 seconds, as shown in Table 2 below. The results are shown in Table 2 below.

[0171] [Table 2]

[0172] As can be seen from Examples 1 to 3 in Tables 1 and 2, it was confirmed that the release layer can be easily separated from the top of the electrode active material layer by adjusting the process conditions in the pre-lithiation process of the electrode active material layer according to the present application. In particular, it was confirmed in detail from Table 2 that the release layer can be easily removed, and since the electrode manufactured by the above process does not have a separate layer such as a release layer on the top of the electrode active material layer, there is no increase in resistance during battery operation after cell assembly.

[0173] In Example 3, when the thickness of the lithium was increased compared to Examples 1 and 2, the thicker the lithium, the more lithium entered the electrode, creating more space, resulting in a thicker electrode, which can lead to an increase in resistance due to by-products of lithium that were not inserted into the active material. However, as can be seen in Table 2, the release layer was easily removed, and therefore the increase in resistance was not as high as in Comparative Examples 1 and 2.

[0174] In Comparative Example 1, the PET film was not immediately removed after pre-lithiation, resulting in no heat generation and the rapid generation of a large amount of lithium by-products. This increased the adhesive strength between the release layer and the electrode active material layer, preventing the release layer from being removed. In particular, when the release layer was forcibly removed, the electrode detached, causing problems and increasing resistance.

[0175] In the case of Comparative Example 2, since the release layer was not removed, it was confirmed that the resistance increased when the electrode was driven as shown in Table 2 compared to Examples 1 to 3.

[0176] In Comparative Example 3, the pressure during the lamination step was too high, which increased the adhesive strength between the release layer and the electrode active material layer, and therefore the release layer was not removed. In Comparative Example 4, the pressure during the lamination step was too low, which prevented successful pre-lithiation, and therefore increased the electrode resistance in Comparative Examples 3 and 4.

[0177] As a result, compared to Comparative Examples 1 to 4, in Examples 1 to 3, the predetermined pressure conditions in the lamination step of the pre-lithiation process were satisfied, making it easier to remove the release layer, and it was confirmed that the resistance decreased as shown in Table 2 when the electrode from which the release layer was removed was operated. [Explanation of symbols]

[0178] 10...Base material layer 20 Lithium metal 30...electrode active material layer 35...Release layer 40 Electrode current collector layer 100 Transfer laminate 200 Electrodes for lithium secondary batteries

Claims

1. forming an electrode current collector layer and an electrode active material layer on one or both sides of the electrode current collector layer; a prelithiation step; A method for producing an electrode for a lithium secondary battery, comprising: the pre-lithiation process includes transferring lithium metal onto the electrode active material layer; the step of transferring the lithium metal includes the steps of: preparing a transfer laminate in which a substrate layer, a release layer, and lithium metal are sequentially laminated; laminating the transfer laminate on the electrode active material layer so that a surface of the lithium metal opposite to a surface that contacts the release layer contacts a surface of the electrode active material layer opposite to a surface that contacts the electrode current collector layer; removing the substrate layer; prelithiating the electrode active material layer; and removing the release layer, The lamination step is carried out under a temperature condition of 30° C. or less and a pressure of 10 kgf / cm ２ More than 150kgf / cm ２ The lamination is performed at the following pressure: The step of removing the substrate layer is performed within 30 minutes after the step of laminating the transfer laminate onto the electrode active material layer, the electrode active material layer contains an electrode active material, the electrode active material includes a silicon-based active material, the silicon-based active material includes one or more selected from the group consisting of SiO x (x=0), SiO x (0<x<2), SiC, and a Si alloy; the substrate layer is at least one selected from the group consisting of polyethylene terephthalate (PET), polyimide (PI), poly(methylmethacrylate) (PMMA), polypropylene, polyethylene, and polycarbonate; A method for manufacturing an electrode for a lithium secondary battery, wherein the release layer comprises one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polyethylene (PE), polypropylene (PP), polyacrylic acid (PAA), and polyester.

2. The lamination step is carried out under a temperature condition of 30° C. or less and a pressure of 10 kgf / cm ２ More than 100kgf / cm ２ 2. The method for producing an electrode for a lithium secondary battery according to claim 1, wherein lamination is performed at a pressure of:

3. A method for manufacturing an electrode for a lithium secondary battery as described in claim 1, comprising a step of removing the release layer after the step of pre-lithiating the electrode active material layer.

4. 2. The method for manufacturing an electrode for a lithium secondary battery according to claim 1, wherein, when the electrode active material layer is prelithiated, the electrode active material layer generates heat at a rate of 5° C. / min for 30 seconds to 3 minutes and then cools down.

5. The method for producing an electrode for a lithium secondary battery according to claim 1 , wherein the thickness of the release layer is 0.1 μm or more and 2 μm or less.

6. The method for producing an electrode for a lithium secondary battery according to claim 1 , wherein the thickness of the substrate layer is 10 μm or more and 30 μm or less.

7. forming the electrode current collector layer and the electrode active material layer on one or both sides of the electrode current collector layer includes coating one or both sides of the electrode current collector layer with an electrode slurry including an electrode active material layer composition; 2. The method for manufacturing an electrode for a lithium secondary battery according to claim 1, wherein the electrode active material layer composition comprises one or more selected from the group consisting of an electrode active material; an electrode conductive material; and an electrode binder.

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