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

Abstract

The present application relates to a method for producing an electrode for a lithium secondary battery, a transfer laminate, 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. 10-2022-0175729, filed with the Korean Intellectual Property Office on December 15, 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, a transfer laminate, and a lithium secondary battery including the electrode. [Background technology]

[0003] The rapid increase in the use of fossil fuels has led to an increasing demand for alternative and clean energy, and one of the most actively researched fields in this area is 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 are 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 high 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 / cm3 ) 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 the 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 amount of lithium inserted into the negative electrode during initial charging, which cannot be returned to the positive electrode. This results in a large initial irreversible capacity. This large initial irreversible capacity leads to a rapid decrease in battery capacity and cycle characteristics.

[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 preparing an electrode after lithiating the negative electrode by a physical / chemical method such as electroplating, lithium metal transfer, or lithium metal vapor deposition, and a method of electrochemically prelithiating the negative electrode.

[0010] Conventional electrochemical processes require wet processes in an electrolyte, which can pose risks such as fire and explosion, making it necessary to create an inert environment. To achieve this environment, the electrochemical process requires the use of inert gas, which makes it difficult to control conditions such as moisture content. Furthermore, uniform control of the initial irreversible capacity can only be achieved by slowing down the prelithiation rate as much as possible using the electrochemical process, which increases production costs.

[0011] Furthermore, in the lithium metal transfer step in the pre-lithiation process, it is difficult to safely and easily transfer lithium metal, and either 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 electrode active material, causing problems such as particle cracking on the surface of the electrode active material layer.

[0012] Therefore, research is needed into process conditions and materials that can easily transfer lithium metal to the top of the electrode active material layer during the lithium metal transfer process, are safer and more efficient when prelithiating the electrode, and enable lithium to be prelithiated uniformly within the electrode active material layer. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-080971 Summary of the Invention [Problem to be solved by the invention]

[0014] The lithium metal transfer process in the pre-lithiation process includes a process of transferring a lithium metal layer from a transfer laminate to the top of an electrode active material layer. Research has shown that forming a transfer initiation portion in the lithium metal layer facilitates the transfer of the lithium metal layer from the transfer laminate to the top of the electrode active material layer. Therefore, the present application relates to a method for manufacturing an electrode for a lithium secondary battery, a transfer laminate, and a lithium secondary battery including the electrode. [Means for solving the problem]

[0015] One embodiment of the present specification provides a method for manufacturing an electrode for a lithium secondary battery, including 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; preparing a transfer laminate in which a substrate film, a transfer force improving layer, and a lithium metal layer are sequentially laminated; removing the lithium metal layer in a transverse direction (TD) to form a transfer initiation portion; transferring the lithium metal layer with the transfer initiation portion formed thereon onto an electrode active material layer; and removing the substrate film.

[0016] In yet another embodiment, a transfer laminate is provided, comprising: a substrate film; a transfer force improving layer formed on one side of the substrate film; and a lithium metal layer formed on the side of the transfer force improving layer opposite to the side that contacts the substrate film; wherein the lithium metal layer includes a lithium metal undeposited portion.

[0017] Finally, in one embodiment of the present application, 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 manufactured by the method according to the present application. [Effects of the Invention]

[0018] A method for manufacturing an electrode for a lithium secondary battery according to one embodiment of the present invention utilizes a lithium metal transfer process, and specifically, the method includes the above-mentioned transfer initiation portion for allowing the lithium metal layer to be transferred more easily onto the upper part of the electrode active material layer, and is characterized by excellent surface uniformity and suppression of by-product generation.

[0019] That is, one embodiment of the present application includes a step of preparing a transfer laminate in which a substrate film, a transfer force improving layer, and a lithium metal layer are sequentially stacked, followed by a step of removing the lithium metal layer in the transverse direction (TD) to form a transfer initiation portion, where the lithium metal layer is removed. This step can improve transferability of the electrode active material layer to the upper portion even at high transfer rates, and allows the substrate film to be directly peeled from the transfer laminate. This allows for smooth release of heat generated during pre-lithiation, and reduces the generation of by-products compared to when a substrate film is stacked during pre-lithiation. [Brief explanation of the drawings]

[0020] [Figure 1] 1A to 1C are diagrams illustrating a process for transferring lithium metal to an electrode for a lithium secondary battery according to an embodiment of the present application. [Figure 2] FIG. 1 is a diagram showing experimental results according to Example 1 of the present application. [Figure 3] FIG. 10 is a diagram showing experimental results according to Comparative Example 1 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 "at least p and at most 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 (average 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 also 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] In this specification, 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. In this specification, when a polymer contains a monomer, this is interpreted as the same as when a polymer contains a monomer as a monomer unit.

[0027] In this specification, the term "polymer" is understood to be used in a broad sense, including copolymers, unless otherwise specified 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 provides a method for manufacturing an electrode for a lithium secondary battery, including 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; preparing a transfer laminate in which a substrate film, a transfer force improving layer, and a lithium metal layer are sequentially laminated; removing the lithium metal layer in a transverse direction (TD) to form a transfer initiation portion; transferring the lithium metal layer with the transfer initiation portion formed thereon onto an electrode active material layer; and removing the substrate film.

[0031] FIG. 1 is a diagram showing the structure of a transfer laminate and a transfer step in the method for producing an electrode for a lithium secondary battery according to the present application.

[0032] In one embodiment of the present application, removing the lithium metal layer in the TD (Transverse direction) direction may mean forming a transfer initiation portion in a direction perpendicular to the MD (Machine direction) direction in a roll-to-roll process.

[0033] That is, the base film 10, the transfer force improving layer 35, and the lithium metal layer 20 can be continuously laminated by a roll-to-roll (R2R) process to form a transfer laminate, and the direction in which the roll-to-roll (R2R) process proceeds can be defined as the MD direction, and the direction perpendicular to the process proceeding direction can be defined as the TD direction. In this case, the lithium metal layer can be removed in the TD (transverse direction) to form the transfer initiation part 300.

[0034] Ultimately, in a transfer laminate, the MD direction may refer to the width of the transfer laminate, and the TD direction may refer to the length of the transfer laminate.

[0035] In one embodiment of the present application, the electrode may be a negative electrode or a positive electrode.

[0036] A method for manufacturing an electrode for a lithium secondary battery according to one embodiment of the present invention utilizes a lithium metal transfer process. Specifically, the present invention relates to a pre-lithiation method for an electrode for a lithium secondary battery, which satisfies the conditions for a lithium metal layer to be transferred more easily onto an electrode active material layer, has excellent surface uniformity, and suppresses the generation of by-products.

[0037] 2 is a diagram showing a process of transferring a lithium metal layer to a lithium secondary battery electrode according to one embodiment of the present application. Specifically, a transfer laminate 100, in which a substrate film 10, a transfer force improving layer 35, and a lithium metal layer 20 are sequentially laminated, is laminated on a lithium secondary battery electrode 200 formed of an electrode current collector layer 40 and an electrode active material layer 30, and then the substrate film 10 of the transfer laminate 100 is removed. At this time, it can be seen that a transfer start portion (a portion where lithium is not deposited) 300 is included.

[0038] That is, the problem of transfer force, such as reverse transfer, that occurs in the conventional lithium metal layer transfer process is solved by forming the transfer initiation portion as described above.

[0039] Hereinafter, specific details of the method for manufacturing an electrode for a lithium secondary battery according to the invention of the present application will be described.

[0040] 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.

[0041] 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, and provides a method for manufacturing an electrode for a lithium secondary battery.

[0042] 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 SiOx (x = 0), SiOx (0 < x < 2), SiC, and Si alloys, and provides a method for manufacturing an electrode for a lithium secondary battery.

[0043] In one embodiment of the present application, the electrode may be a negative electrode, and hereinafter, an explanation of the method for manufacturing a negative electrode for a lithium secondary battery will be described.

[0044] 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.

[0045] 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 has high conductivity without inducing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined 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 strength 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.

[0046] 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.

[0047] However, the thickness may vary depending on the type and application of the negative electrode used, and is not limited thereto.

[0048] 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.

[0049] In one embodiment of the present application, the negative electrode slurry may include a negative electrode active material layer composition and a slurry solvent.

[0050] In one embodiment of the present application, the solid content of the negative electrode slurry may be 5% or more and 40% or less.

[0051] 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%.

[0052] In another embodiment, the solid content of the negative electrode slurry may satisfy the range of 5% to 55%, preferably 7% to 35%, more preferably 10% to 30%.

[0053] The solid content of the negative electrode slurry refers to the content of the negative electrode active material layer composition contained in the negative electrode slurry, and may refer to the content of the negative electrode active material layer composition based on 100 parts by weight of the negative electrode slurry.

[0054] 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.

[0055] In one embodiment of the present application, the slurry solvent is not limited as long as it can dissolve the negative electrode active material layer composition, and specifically, distilled water may be used.

[0056] 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.

[0057] The drying step may evaporate the slurry solvent from the negative electrode slurry.

[0058] 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.

[0059] 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 a silicon-based active material and a carbon-based active material together may be used. In this case, a lithium secondary battery with improved various performances such as cycle life characteristics can be manufactured.

[0060] In one embodiment of the present application, the silicon-based active material may include one or more selected from the group consisting of Si particles, SiOx (0 < x < 2), SiC, and Si alloys.

[0061] In one embodiment of the present application, the silicon-based active material includes one or more selected from the group consisting of SiOx (x = 0) and SiOx (0 < x < 2), and based on 100 parts by weight of the silicon-based active material, the SiOx (x = 0) may be included in an amount of 70 parts by weight or more.

[0062] In another embodiment, based on 100 parts by weight of the silicon-based active material, the SiOx (x = 0) may be included in an amount of 70 parts by weight or more, preferably 80 parts by weight or more, more preferably 90 parts by weight or more, and may be included in an amount of 100 parts by weight or less, preferably 99 parts by weight or less, more preferably 95 parts by weight or less.

[0063] In one embodiment of the present application, particularly pure silicon (Si) may be used as the silicon-based active material. Using pure silicon (Si) as the silicon-based active material may mean, as described above, that when the entire silicon-based active material is based on 100 parts by weight, pure Si particles (SiOx (x = 0)) not bonded to other particles or elements are included within the above range.

[0064] In 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 is released from the negative electrode and returned to the positive electrode during discharge. However, in the case of silicon-based negative electrode active materials, significant volume changes and surface side reactions occur, and only a small amount of lithium inserted into the negative electrode during initial charging returns to the positive electrode, resulting in a problem of large initial irreversible capacity. This large initial irreversible capacity causes problems such as a rapid decrease in battery capacity and cycle life.

[0065] 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 involves a process of suppressing the generation of by-products so that the lithium metal layer can be easily transferred from the transfer laminate during the lithium transfer process and lithium can be uniformly prelithiated within the negative electrode active material layer.

[0066] Meanwhile, the average particle size (D50) of the silicon-based active material of the present invention may be 5 μm to 10 μm, specifically 5.5 μm to 8 μm, and more specifically 6 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 the 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. Furthermore, 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.

[0067] 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 determined according to DIN 66131 (using nitrogen).

[0068] In one embodiment of the present application, the silicon-based active material may be, for example, in a crystalline or amorphous form, and is preferably not porous. The silicon particles are preferably spherical or multi-platelet particles. Alternatively, the silicon particles may have a fibrous structure or may be in the form of a silicon-containing film or coating, but this is less preferred.

[0069] 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.

[0070] 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.

[0071] The negative electrode active material layer composition according to the present application contains a negative electrode conductor and a negative electrode binder that can control the volume expansion rate during charge and discharge, even when a silicon-based active material having a significantly high capacity is used within the above range. Therefore, even when the silicon-based active material is contained within the above range, the negative electrode performance is not reduced and the composition has excellent output characteristics during charge and discharge.

[0072] In one embodiment of the present application, the silicon-based active material may have a non-spherical morphology, and the sphericity thereof 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.

[0073] In this application, the circularity is determined by the following formula A, where A is the area and P is the perimeter. [Formula A] 4πA / P 2

[0074] While graphite-based compounds have traditionally been used exclusively as anode active materials, attempts to incorporate silicon-based compounds into batteries to increase capacity have recently been increasing in response to growing demand for high-capacity batteries. However, silicon-based compounds 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 with the silicon-based active material is important.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] In one embodiment of the present application, the negative electrode conductive material may include a sheet conductive material.

[0080] 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-type conductive materials and plate-type conductive materials.

[0081] In one embodiment of the present application, the sheet conductive material may include at least one selected from the group consisting of plate-like graphite, graphene, graphene oxide, and graphite flakes, and may preferably be plate-like graphite.

[0082] 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 this range, the particle size is sufficient, so the viscosity of the negative electrode slurry does not increase excessively, and dispersion is easy. Therefore, when dispersing using the same device and time, the dispersion effect is excellent.

[0083] In one embodiment of the present application, there is provided a negative electrode active material layer composition, wherein 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.

[0084] In one embodiment of the present application, the sheet conductive material may be a high-specific surface area sheet conductive material having a high BET specific surface area; or a low-specific surface area sheet conductive material.

[0085] In one embodiment of the present application, the sheet conductive material may be a high-specific surface area sheet conductive material or a low-specific surface area sheet conductive material without any restrictions. However, since the sheet conductive material of the present application may have electrode performance that is affected to some extent by dispersion, it is particularly preferable to use a low-specific surface area sheet conductive material that does not cause dispersion problems.

[0086] In one embodiment of the present application, the sheet conductive material has a BET specific surface area of ​​5 m 2 / g or more.

[0087] 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 or less.

[0088] In another embodiment, the sheet conductive material is a high specific surface area sheet conductive material having 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.

[0089] In another embodiment, the sheet conductive material is a sheet conductive material with a low specific surface area, and has 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.

[0090] Alternatively, the negative electrode conductive material may be a linear conductive material such as a carbon nanotube. The carbon nanotube may be a bundle-type carbon nanotube. The bundle-type carbon nanotube may include a plurality of carbon nanotube units. Specifically, unless otherwise specified, the term "bundle-type" refers to a secondary shape in which a plurality of carbon nanotube units are arranged parallel to each other or entangled with their longitudinal axes aligned in substantially the same direction, forming a bundle or rope-like shape. The carbon nanotube units have graphite sheets in the form of cylinders with nanosized diameters and an sp2 bonding structure. Depending on the winding angle and structure of the graphite sheets, the carbon nanotubes may exhibit conductive or semiconductive properties. Compared to entangled-type carbon nanotubes, the bundle-type 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.

[0091] 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.

[0092] 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.

[0093] The negative electrode conductive material according to the present application has a completely different structure from the conductive material used in the positive electrode. That is, the negative electrode 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 positive electrode conductive material acts as a buffer during rolling and also provides some conductivity, and is completely different in structure and role from the negative electrode conductive material of the present invention.

[0094] 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.

[0095] In one embodiment of the present application, the planar conductive material used as the negative electrode conductive material has a structure and function different from that of a carbon-based active material generally 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.

[0096] Meanwhile, the planar conductive material used as the negative electrode conductive material is a material having a planar or plate-like shape, which may be expressed as plate-shaped graphite. That is, it is a material contained in the negative electrode active material layer to maintain a conductive path, and does not play a role in storing and releasing lithium, but rather a material for securing a planar conductive path within the negative electrode active material layer.

[0097] That is, in this application, the use of plate-shaped 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 rather than to store or release lithium. In this case, the negative electrode active material included together 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.

[0098] 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.

[0099] 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. In addition, the plate-shaped graphite, which is a planar conductive material, may have a planar shape and a BET specific surface area of ​​5m 2 / g or more.

[0100] 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.

[0101] The binder according to one embodiment of the present application plays a role in controlling the negative electrode active material and the negative electrode conductive material 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 role, any conventional negative electrode binder may be used. Specifically, a water-based binder may be used, and more specifically, a PAM-based binder may be used.

[0102] 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 may be contained in an amount of 1 part by weight or more, or 3 parts by weight or more, based on 100 parts by weight of the negative electrode active material layer composition.

[0103] 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 in the method for manufacturing a negative electrode for a lithium secondary battery described above may be applied, except that the electrode is a positive electrode.

[0104] 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.

[0105] In one embodiment of the present application, the positive electrode current collector is not particularly limited as long as it is conductive and does not induce chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. The positive electrode current collector 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 the adhesive strength of the positive electrode active material. The positive electrode current collector may be used in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0106] The thickness of the positive electrode current collector layer may vary depending on the type and application of the negative electrode used, but is not limited thereto.

[0107] 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 sides of the positive electrode current collector layer includes coating one or both sides 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.

[0108] In one embodiment of the present application, the content of the positive electrode slurry may be the same as that of the negative electrode slurry, except that it is a positive electrode.

[0109] 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.

[0110] 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 (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and 0.01≦c2≦0.3 is satisfied); 2-c3 M c3Examples of suitable lithium manganese composite oxides 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 substituted with an alkaline earth metal ion. The positive electrode may be Li metal.

[0111] In one embodiment of the present application, there is provided a method for producing an electrode for a lithium secondary battery, wherein the electrode active material includes a positive electrode active material, and the positive electrode active material includes one or more selected from the group consisting of Ni, Co, Mn, LTO, LFP, RuO2, Nb2O5, Mn3O4, Fe2O3, and Co3O4.

[0112] The positive electrode may include a sacrificial positive electrode material, and the type of the material may be any material commonly used in the art without limitation.

[0113] In this case, the positive electrode conductive material is used to impart conductivity to the electrode and can be any material that has electronic conductivity without causing chemical changes in the battery that is constructed. 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 materials may be used alone or in combination.

[0114] 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.

[0115] 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.

[0116] Generally, the prelithiation process is performed by chemically or physically prelithiating a lithium metal layer 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 vapor deposition process, and the prelithiation process according to the present application may include a lithium metal transfer process.

[0117] The lithium metal layer 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 allows the lithium metal layer to be easily transferred onto the electrode active material layer from the transfer laminate.

[0118] In one embodiment of the present application, the method includes the steps of: preparing a transfer laminate in which a substrate film, a transfer force improving layer, and a lithium metal layer are sequentially laminated; transferring the lithium metal layer having the transfer initiation portion formed thereon onto an electrode active material layer; and removing the substrate film.

[0119] In this case, the step of removing the lithium metal layer in the TD (Transverse direction) to form a transfer initiation part includes the step of preparing a transfer laminate in which a base film, a transfer force improving layer, and a lithium metal layer are sequentially laminated, and then removing the lithium metal layer using a tape or a knife.

[0120] Specifically, the transfer initiation portion may be formed as a line by removing the lithium metal layer in the TD (Transverse direction) using a knife, and the width of the transfer initiation portion may be 30 μm or more.

[0121] In another embodiment, the width of the transcription start region may be 30 μm or more, preferably 35 μm or more, more preferably 40 μm or more, or may be 100 μm or less, preferably 90 μm or less, more preferably 80 μm or less.

[0122] When the transfer initiation portion is formed to the above width, transferability to the upper portion of the electrode active material layer can be improved even at high transfer rates, and the substrate film can be quickly peeled off from the transfer laminate. This facilitates the release of heat generated during pre-lithiation, and reduces the generation of by-products compared to when a substrate film is laminated during pre-lithiation.

[0123] In one embodiment of the present application, the transcription initiation site may comprise one or more line shapes.

[0124] In one embodiment of the present application, after forming the lithium metal layer, the lithium metal layer is first removed from the portion where transfer is to be initiated to form the transfer initiation portion, but the form thereof is not limited thereto.

[0125] In one embodiment of the present application, the deposition method for depositing the lithium metal layer on the substrate film on which the transfer force improving layer is formed may be selected from among vacuum deposition, chemical vapor deposition (CVD), and physical vapor deposition (PVD), but is not limited thereto, and various deposition methods used in the art may be used.

[0126] At this time, a pressure of 5 kgf / cm was applied to the lithium secondary battery electrode on which the transfer laminate was laminated. 2 ~500kgf / cm 2 The lamination process may be carried out through roll pressing by applying a load of 1000 kJ / cm.sup.2 or more, and then a process of removing the base film is included.

[0127] In one embodiment of the present application, the substrate film can be used without any limitation as long as it can withstand process conditions such as high temperatures in the step of depositing lithium metal and can prevent a reverse peeling problem in which lithium metal is transferred onto the substrate film in a winding process for transferring the deposited lithium metal.

[0128] Specifically, in one embodiment of the present application, the base film may be one or more selected from the group consisting of polyethylene terephthalate (PET), polyimide (PI), poly(methylmethacrylate) (PMMA), polypropylene, polyethylene, and polycarbonate.

[0129] In one embodiment of the present application, the thickness of the substrate film may be in the range of 1 μm or more and 300 μm or less, 5 μm or more and 200 μm or less, or 10 μm or more and 100 μm or less.

[0130] In one embodiment of the present application, the thickness of the lithium metal layer may be 1 μm or more and 10 μm or less, and preferably may be 3 μm or more and 10 μm or less.

[0131] When the thicknesses of the substrate film and the lithium metal layer satisfy the above ranges, the lithium metal layer can be efficiently transferred to the electrode active material layer, and reverse transfer can be prevented.

[0132] In one embodiment of the present application, there is provided a method for manufacturing an electrode for a lithium secondary battery, which includes a transfer force improving layer on the surface of the transfer laminate where the base film and the lithium metal layer come into contact, in order to improve the peelability of the lithium metal layer, ensure transferability to the electrode active material layer, and serve as a protective layer after transfer of the lithium metal layer.

[0133] That is, the substrate film may have a transfer strength improving layer formed on at least one surface thereof, or may have a transfer strength improving layer formed on both surfaces thereof. The transfer strength improving layer can prevent the lithium metal layer from being transferred onto the substrate film during a winding process for transferring the deposited lithium metal layer onto the electrode, and can also easily separate the substrate film after the lithium metal is transferred onto the electrode active material layer.

[0134] The transfer force improving layer may contain at least one selected from the group consisting of silicon-modified polyester in which silicon chains are graft-bonded to a polyester main chain, acrylic resin, Si, melamine, and fluorine.

[0135] In one embodiment of the present application, the transfer force enhancing layer may include poly(methyl methacrylate) (PMMA).

[0136] In one embodiment of the present application, the transfer force improving 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, and various coating methods known in the art for forming a coating layer may be used.

[0137] In one embodiment of the present application, a step is provided in which the transfer laminate is laminated onto the electrode active material layer so that the surface of the lithium metal layer opposite to the surface that contacts the transfer force improving layer is in contact with the surface of the electrode active material layer opposite to the surface that contacts the electrode current collector layer.

[0138] At this time, the lamination step is carried out under the temperature conditions of 20°C to 90°C and 5 kgf / cm 2 ~500kgf / cm 2 The lamination may be performed under the pressure condition.

[0139] In one embodiment of the present application, the laminating step may satisfy a pressure condition of 5 kgf / cm to 500 kgf / cm, preferably a pressure condition of 10 kgf / cm to 150 kgf / cm.

[0140] However, the temperature condition may be omitted in the lamination step. In particular, when the lamination step satisfies the pressure condition described above, the pre-lithiation rate of the lithium metal layer can be smoothly controlled, thereby suppressing the formation of large amounts of oxides and nitrides during the transfer process. Furthermore, by satisfying the pressure range described above, the lithium metal can be smoothly transferred to the top of the electrode active material layer, preventing the problem of reverse transfer.

[0141] After the lamination step, prelithiation of the electrode active material layer with highly reactive lithium metal may be performed, or prelithiation may be performed during battery assembly without allowing the reaction to proceed.

[0142] In one embodiment of the present application, there is provided a method for manufacturing an electrode for a lithium secondary battery, comprising the step of prelithiating the electrode active material layer after the step of removing the substrate film, wherein the step of prelithiating the electrode active material layer is carried out within 30 minutes to 7 days after transferring lithium metal.

[0143] In a conventional lithium metal layer transfer process, there is a problem in that the substrate film is difficult to peel off during the prelithiation process after laminating the transfer laminate. As a result, if the prelithiation is performed without removing the substrate film, the heat generated during the prelithiation is blocked by the substrate film and cannot be released, resulting in the formation of by-products on the surface during the prelithiation of the lithium metal. The prelithiation method for a lithium secondary battery electrode according to the present application has the advantage that, by forming the above-mentioned transfer initiation portion, the substrate film can be easily peeled off immediately after laminating the transfer laminate, and the formation of by-products during the prelithiation can be suppressed.

[0144] In one embodiment of the present application, instead of transferring the lithium metal layer alone, the transfer force improving layer and lithium metal are transferred together onto the electrode active material layer, and in this case, the transfer force improving layer can also serve as a protective layer that can prevent the highly reactive lithium metal layer from reacting in air.

[0145] In one embodiment of the present application, a step of prelithiating the electrode active material layer may be included.

[0146] The step of prelithiating the electrode active material layer is performed at 25° C. and 1 atm for 30 minutes to 24 hours.

[0147] The pre-lithiation step is a step of setting conditions for diffusing lithium metal 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.

[0148] In one embodiment of the present application, the activation reaction time may be 30 minutes to 7 days, preferably 1 hour to 6 hours.

[0149] In one embodiment of the present application, there is provided a transfer laminate comprising a substrate film; a transfer force improving layer formed on one side of the substrate film; and a lithium metal layer formed on the side of the transfer force improving layer opposite to the side that contacts the substrate film, wherein the lithium metal layer includes a lithium metal undeposited portion.

[0150] In one embodiment of the present application, there is provided a transfer laminate, wherein the width of the lithium metal non-deposited portion is 30 μm or more. In this case, the non-deposited portion may have the same meaning as the transfer initiation portion described above.

[0151] In the transfer laminate, the above-described contents can be applied to each configuration.

[0152] In one embodiment of the present application, 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 manufactured by the method of the present application.

[0153] In this case, the transfer force improving layer 35 used during pre-lithiation may 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 transfer force improving layer may be used to improve the transfer force and to protect the lithium metal layer before pre-lithiation, and may be removed before injecting the electrolyte.

[0154] In one embodiment of the present application, examples of the electrolytic solution include, but are not limited to, organic liquid electrolytic solutions, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytic solutions, solid inorganic electrolytic solutions, and molten inorganic electrolytic solutions that can be used in manufacturing lithium secondary batteries.

[0155] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0156] 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.

[0157] In particular, among the carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are highly viscous organic solvents with high dielectric constants and good dissociation of lithium salts, and therefore can be preferably used. Furthermore, when such cyclic carbonates are mixed with linear carbonates having low viscosity and low dielectric constants, such as dimethyl carbonate and diethyl carbonate, in an appropriate ratio, an electrolyte having high electrical conductivity can be produced, and therefore can be more preferably used.

[0158] 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:

[0159] In addition to the components of the electrolyte, the electrolyte may further contain one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing a decrease in battery capacity, and improving the discharge capacity of the battery.

[0160] According to one embodiment of the present invention, there is provided a battery module including the 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 therefore 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]

[0161] Below, preferred examples are presented to help understand the present invention, but these examples are merely illustrative of the present description, and it will be obvious to those skilled in the art that various changes and modifications are possible within the scope and technical idea of ​​the present description, and it is natural that such changes and modifications fall within the scope of the claims.

[0162] (Manufacturing example) <Production of Transfer Laminate> Example 1 A release layer was coated on the PET layer to improve transferability, and then lithium metal was deposited on the PET substrate to a thickness of 6 μm using the PVD method to form a lithium metal layer, thereby producing a transfer laminate.

[0163] At this time, a transfer start line of approximately 40 μm was formed on the upper end of the transfer laminate using a knife, where only the Li portion of the PET film on which lithium was deposited was removed.

[0164] <Example 2> A transfer laminate was manufactured in the same manner as in Example 1, except that a transfer initiation line having a size of about 60 μm was formed on the upper end of the transfer laminate using a knife.

[0165] Example 3 A transfer laminate was manufactured in the same manner as in Example 1, except that a transfer initiation line having a size of about 120 μm was formed on the upper end of the transfer laminate using a knife.

[0166] <Comparative Example 1> A release layer was coated on the PET layer to improve transferability, and then lithium metal was deposited on the PET substrate to a thickness of 6 μm using PVD to form a lithium metal layer, thereby producing a transfer laminate.

[0167] That is, the formation was carried out in the same manner as in Example 1, except that the transcription initiation site was not formed.

[0168] <Production of negative electrodes> Anode slurry was prepared by adding silicon (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 anode slurry (solid concentration: 25 wt%).

[0169] 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.

[0170] The negative electrode current collector was a copper current collector (thickness: 15 μm) and the negative electrode slurry was applied to both sides at 85 mg / 25 cm. 2 The coated layer 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%).

[0171] Then, to transfer the transfer laminate to the negative electrode active material layer, the lithium metal of the transfer laminate was placed on top of the negative electrode active material layer, and then external pressure was applied and roll pressing was performed to bond the lithium metal and the negative electrode active material layer. Immediately after lamination, the PET layer of the transfer laminate was removed, and the negative electrode was prelithiated.

[0172] In the present application, in the experiments of Examples 1 to 3 and Comparative Example 1, Nitto 31b tape was used on top of the lithium metal layer, and then removed to confirm its effectiveness. That is, the transferability of Nitto 31b tape was confirmed during the pre-lithiation process of the electrode.

[0173] 2 shows the case where the transfer laminate according to Example 1 of the present application was transferred using Nitto 31b tape. Specifically, in the case of Example 1 where a transfer initiation portion was formed, it was confirmed that the entire Li metal layer was transferred onto the Nitto 31b tape, and more specifically, it was confirmed that the lithium metal was also completely transferred to the transfer initiation portion.

[0174] 3 shows a case where the transfer laminate according to Comparative Example 1 of the present application was transferred using Nitto 31b tape. Specifically, in the case of Comparative Example 1 where the transfer initiation portion was not formed, it was confirmed that the Li metal layer was not completely transferred onto the Nitto 31b tape, and the Li metal fell off from the middle portion.

[0175] From the above results, it was confirmed that in the case of the transfer laminates of Examples 1 to 3 according to the present application, by forming a transfer initiation part when transferring onto the top of the electrode active material layer, the lithium metal layer can be easily transferred onto the top of the electrode active material layer, thereby resolving the problem of by-products on the top of the electrode active material layer. In Comparative Example 1, a transfer initiation part was not formed, which corresponds to a case where the lithium metal is transferred onto the top of the electrode active material layer unevenly, and it was confirmed that the reaction did not occur uniformly, and by-products were formed on the top of the electrode active material layer, resulting in an increase in battery resistance.

[0176] For reference, in Example 3, the transfer initiation region is 120 μm, which is larger than in Examples 1 and 2. If the transfer initiation region is too small, some of the effectiveness may be reduced, and if the transfer initiation region is large, as in Example 3, lithium consumption is greater than in Examples 1 and 2, which may cause disposal issues. However, even in such cases, it was confirmed that the lithium metal layer was completely transferred compared to Comparative Example 1. [Explanation of symbols]

[0177] 10. Base film 20 Lithium metal layer 30...electrode active material layer 35... Transfer force improvement layer 40 Electrode current collector layer 100 Transfer laminate 200 Electrodes for lithium secondary batteries 300 Transcription start site

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 step of preparing a transfer laminate in which a base film, a transfer force improving layer, and a lithium metal layer are laminated in this order; removing the lithium metal layer in a transverse direction to form a transcription initiation site; transferring the lithium metal layer having the transfer initiation portion formed thereon onto an electrode active material layer; and removing the base film; A method for producing an electrode for a lithium secondary battery, comprising:

2. The method for producing an electrode for a lithium secondary battery according to claim 1 , wherein the width of the transfer initiation portion is 30 μm or more.

3. 2. The method for producing an electrode for a lithium secondary battery according to claim 1, wherein the lithium metal layer has a thickness of 1 μm or more and 10 μm or less.

4. 2. The method for producing an electrode for a lithium secondary battery according to claim 1, wherein the transfer force improving layer comprises at least one selected from the group consisting of a silicon-modified polyester in which a silicon chain is graft-bonded to a polyester main chain, an acrylic resin, Si, melamine, and fluorine.

5. After removing the substrate film, prelithiating the electrode active material layer, 10. The method of claim 1, wherein the prelithiation of the electrode active material layer is performed within 30 minutes to 7 days after transferring the lithium metal layer.

6. The step of forming the electrode current collector layer and the electrode active material layer on one or both surfaces of the electrode current collector layer includes coating one or both surfaces of the electrode current collector layer with an electrode slurry including an electrode active material layer composition, 2. The method for producing an electrode for a lithium secondary battery according to claim 1, wherein the composition of the electrode active material layer comprises at least one selected from the group consisting of an electrode active material, an electrode conductive material, and an electrode binder.

7. the electrode active material includes a silicon-based active material, 7. The method for producing an electrode for a lithium secondary battery according to claim 6, wherein the silicon-based active material comprises one or more selected from the group consisting of SiOx (x=0), SiOx (0<x<2), SiC, and a Si alloy.

8. the electrode active material includes a positive electrode active material, The positive electrode active material is Ni, Co, Mn, LTO, LFP, or RuO ２ , Nb ２ O ５ , Mn ３ O ４ , Fe ２ O ３ , and Co ３ O ４ The method for producing an electrode for a lithium secondary battery according to claim 6, comprising one or more selected from the group consisting of:

9. The step of removing the lithium metal layer in a transverse direction to form a transcription initiation portion includes:

2. The method for manufacturing an electrode for a lithium secondary battery according to claim 1, further comprising the step of removing the lithium metal layer using a tape or a knife after the step of preparing a transfer laminate in which a base film, a transfer force improving layer, and a lithium metal layer are sequentially laminated.

10. The method for manufacturing an electrode for a lithium secondary battery according to claim 1 , wherein the transfer initiation portion includes one or more line shapes.

11. Base film; a transfer force improving layer formed on one surface of the base film; and a lithium metal layer formed on the surface of the transfer force improving layer opposite to the surface that comes into contact with the base film; A transfer laminate comprising: The lithium metal layer includes a lithium metal non-deposited portion.

12. The transfer laminate according to claim 11 , wherein the lithium metal non-deposited portion has a width of 30 μm or more.

13. 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, A lithium secondary battery, wherein at least one of the positive electrode for the lithium secondary battery and the negative electrode for the lithium secondary battery is an electrode for a lithium secondary battery produced by the method according to any one of claims 1 to 10.

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