Transfer laminate, method for manufacturing transfer laminate, method for manufacturing electrode for lithium secondary battery, and lithium secondary battery

Abstract

This application relates to a transfer laminate including an electro-lithiation process that adjusts the ratio of lithium element to oxygen element on the surface of the lithium metal layer and in a specific region by adjusting the temperature of the base material layer, and a method for manufacturing the transfer laminate, a method for manufacturing an electrode for a lithium secondary battery, and a lithium secondary battery, in which the lithium metal layer is easily transferred.

Description

[Technical Field]

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2022-0175738, 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 transfer laminate, a method for manufacturing a transfer laminate, a method for manufacturing an electrode for a lithium secondary battery, and a lithium secondary battery. [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 increasing demand for them, 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, it is difficult to control conditions such as moisture content by using inert gas in the chamber where the electrochemical process is performed. 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] In the lithium metal transfer process, which is another method, it is difficult to transfer lithium metal safely and easily, and problems arise such as the lithium not being transferred from the transfer laminate, or even if it is transferred, the highly reactive lithium metal immediately reacting with the negative electrode active material, causing particle cracking on the surface of the negative electrode active material layer.

[0012] In particular, in the pre-lithiation process of the transfer method, it is important to ensure the transferability of the lithium metal layer, and only when transferability is ensured can it be applied to mass production. However, although research has been conducted to easily transfer the lithium metal layer from the transfer laminate, a method for transferring the lithium metal layer more safely and quickly has not yet been clarified.

[0013] Therefore, research is needed into transfer laminates that can more safely and efficiently prelithiate lithium uniformly within the electrode active material layer when prelithiating an electrode. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-080971 Summary of the Invention [Problem to be solved by the invention]

[0015] In the transfer-based pre-lithiation process, a technology that allows for easy transfer of the lithium metal layer onto the electrode active material layer is essential. To address this issue, methods such as including a release layer or adjusting adhesive strength have been investigated, but these methods have not clearly resolved the above problem. In this application, we have found that adjusting the temperature of the substrate layer during the process of forming the lithium metal layer on the substrate layer can control the ratio of lithium and oxygen elements on the surface and in specific regions of the lithium metal layer. Through this research, we have found that adjusting this ratio can facilitate the transfer of the lithium metal layer.

[0016] Therefore, the present application relates to a transfer laminate, a method for manufacturing a transfer laminate, a method for manufacturing an electrode for a lithium secondary battery, and a lithium secondary battery. [Means for solving the problem]

[0017] One embodiment of the present specification provides a transfer laminate comprising a substrate layer and a lithium metal layer laminated on one or both sides of the substrate layer, wherein the lithium metal layer has a thickness of 1 μm or more and 20 μm or less, and a first region having a thickness of 1 nm or more and 500 nm or less, based on the surface of the lithium metal layer opposite the surface facing the substrate layer, satisfies the following formula 1:

[0018] [Formula 1] X / Y×100(%)≦95 In the formula 1, X represents the oxygen element ratio (at%) based on the element content of the first region being 100; Y represents the lithium element ratio (at %) based on the element content of 100 in the first region.

[0019] In yet another embodiment, there is provided a method for manufacturing a transfer laminate, comprising the steps of: preparing a substrate layer; and heating and depositing a lithium source on one surface of the substrate layer to form a lithium metal layer; wherein the surface temperature of the substrate layer in the step of forming the lithium metal layer is 90°C or less.

[0020] In yet another embodiment, there is provided a method for manufacturing an electrode for a lithium secondary battery, 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 a lithium metal layer onto the electrode active material layer, wherein the step of transferring the lithium metal layer comprises the steps of: preparing a transfer laminate according to the present application; laminating the transfer laminate on the electrode active material layer so that the surface of the lithium metal layer opposite to the surface facing the substrate layer is in contact with the surface of the electrode active material layer opposite to the surface that contacts the electrode current collector layer; and removing the substrate layer.

[0021] Finally, 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 an electrode for a lithium secondary battery manufactured by the method described above. [Effects of the Invention]

[0022] The transfer laminate according to one embodiment of the present invention is a transfer laminate used in a transfer-type prelithiation process. In particular, the transfer laminate is formed by heating and depositing a lithium source on a substrate layer to form a lithium metal layer. In this case, the surface temperature of the substrate layer during the lithium metal layer formation step is controlled to 90°C or less.

[0023] Due to the characteristics of the manufacturing method described above, the transfer laminate of the present application is characterized in that a first region having a thickness of 1 nm or more and 500 nm or less, based on the surface opposite to the surface facing the substrate layer of the lithium metal layer, satisfies the range of the above formula 1.

[0024] When the composition near the surface of the lithium metal layer in the transfer laminate satisfies the range of formula 1, the oxygen ratio at the surface of the lithium metal layer can be adjusted to ensure transferability when subsequently transferred to an electrode. That is, the surface of the lithium metal layer is in contact with the surface of the transfer target to which it is ultimately transferred, and adjusting the oxygen ratio at the surface makes it possible to adjust the reactivity with the transfer target and the transfer force during transfer, thereby ensuring productivity and improving transferability in pre-lithiation using a roll-to-roll (R2R) method.

[0025] That is, the transfer laminate according to the present application has an adjusted composition of the lithium metal layer, which improves the lithium transferability during the prelithiation process and thereby suppresses the generation of by-products during prelithiation. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 illustrates a transfer laminate according to one embodiment of the present application. [Figure 2] 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. [Figure 3] 1 is a diagram showing a stack structure of a lithium secondary battery according to an embodiment of the present application. [Figure 4] FIG. 2 is a diagram showing the results of XPS analysis of a transfer laminate according to Example 1 of the present application. [Figure 5] FIG. 10 is a diagram showing the results of XPS analysis of a transfer laminate according to Example 2 of the present application. [Figure 6] FIG. 10 is a diagram showing the results of XPS analysis of a transfer laminate according to Example 3 of the present application. [Figure 7] FIG. 1 is a diagram showing the results of XPS analysis of a transfer laminate according to Comparative Example 1 of the present application. [Figure 8] FIG. 10 is a diagram showing the results of evaluation of the transfer force of a transfer laminate according to Comparative Example 1 of the present application. [Figure 9] FIG. 10 is a diagram showing the results of evaluation of the transfer force of a transfer laminate according to Example 3 of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0027] Before describing the present invention, some terms will first be defined.

[0028] 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.

[0029] In this specification, "p to q" means "at least p and at most q."

[0030] 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.

[0031] In this specification, "Dn" refers to the average particle size, which is the particle size at the n% point in the cumulative particle number distribution by particle size. That is, D50 is the 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, the average particle size 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 depending on the particle size is measured, and the particle size distribution is calculated.

[0032] 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.

[0033] In this specification, the term "polymer" is understood to be used in a broad sense, including copolymers, unless otherwise specified as a "homopolymer."

[0034] 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.

[0035] 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.

[0036] One embodiment of the present specification provides a transfer laminate comprising a substrate layer; and a lithium metal layer laminated on one or both sides of the substrate layer; wherein the lithium metal layer has a thickness of 1 μm or more and 20 μm or less, and a first region having a thickness of 1 nm or more and 500 nm or less, based on the surface of the lithium metal layer opposite the surface facing the substrate layer, satisfies the following formula 1:

[0037] [Formula 1] X / Y×100(%)≦95 In the formula 1, X represents the oxygen element ratio (at%) based on the element content of the first region being 100; Y represents the lithium element ratio (at %) based on the element content of 100 in the first region.

[0038] In the transfer laminate according to the present invention, the composition near the surface of the lithium metal layer satisfies the range of formula 1, thereby controlling the oxygen ratio at the surface of the lithium metal layer and ensuring transferability when subsequently transferred to an electrode. That is, the surface of the lithium metal layer ultimately comes into contact with the surface of the transfer target, and controlling the oxygen ratio at the surface during transfer makes it possible to control the reactivity with the transfer target and the transfer force, thereby ensuring productivity and improving transferability in pre-lithiation in a roll-to-roll (R2R) process.

[0039] 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 the lithium metal layer and can prevent reverse peeling, in which the lithium metal layer is transferred onto the substrate layer during a winding process for transferring the deposited lithium metal.

[0040] Specifically, in one embodiment of the present application, the substrate layer may be one or more selected from the group consisting of polyethylene terephthalate (PET), polyimide (PI), poly(methylmethacrylate) (PMMA), polypropylene, polyethylene, and polycarbonate.

[0041] In one embodiment of the present application, the thickness of the substrate layer 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.

[0042] In one embodiment of the present application, the thickness of the lithium metal layer may be 1 μm or more and 50 μm or less, and preferably may be 3 μm or more and 25 μm or less.

[0043] When the thickness of the substrate layer satisfies the above range, the transfer of the lithium metal layer to the electrode active material layer can be efficiently performed. In particular, when the substrate layer has the above range, heat release can be effectively performed, and problems such as reverse transfer and generation of by-products during pre-lithiation can be prevented.

[0044] In one embodiment of the present application, the transfer laminate may further include a release layer on the surface where the substrate layer and the lithium metal layer 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.

[0045] 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 the lithium metal layer from being transferred onto the substrate layer during a winding process for transferring the deposited lithium metal layer to the electrode, and can also facilitate the separation of the substrate layer after the lithium metal is transferred onto the electrode active material layer.

[0046] In one embodiment of the present application, the thickness of the release layer may be 1 nm or more and 1 μm or less.

[0047] In another embodiment, the thickness of the release layer may be in the range of 1 nm or more and 1 μm or less, preferably 100 nm or more and 1 μm or less, and more preferably 500 nm or more and 1 μm or less.

[0048] The release layer satisfies the above-described thickness range and a specific adhesive strength range. The release layer has the above-described thickness range, and after prelithiation, the range of adhesive strength with the upper part of the prelithiated electrode can be adjusted to the lower limit of a predetermined range, and side reactions between the release layer and the electrode active material layer do not occur.

[0049] The release 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.

[0050] In one embodiment of the present application, the release layer may be formed by a coating method, for example, 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.

[0051] In one embodiment of the present application, the release layer may comprise poly(methyl methacrylate) (PMMA).

[0052] The type of the release layer may be any release layer known in the art, as long as it fulfills its role.

[0053] In one embodiment of the present application, the lithium metal layer may have a thickness of 1 μm or more and 20 μm or less.

[0054] In another embodiment, the thickness of the lithium metal layer may be 1 μm or more and 20 μm or less, preferably 2 μm or more and 15 μm or less, and more preferably 3 μm or more and 10 μm or less.

[0055] In one embodiment of the present application, the first region having a thickness of 1 nm or more and 10 nm or less based on the surface of the lithium metal layer opposite to the surface facing the substrate layer may satisfy formula 1 above.

[0056] The transfer laminate used in the transfer-based prelithiation is formed by heating and depositing a lithium source on a substrate layer using thermal evaporation to form a lithium metal layer having the thickness range described above. Then, a partial deposition film is formed on the top using an inert gas for surface stabilization. During this deposition process, oxygen may be incorporated into the deposition film. In this regard, the present application has found that the ratio of oxygen to lithium on the surface of the lithium metal layer can be controlled by adjusting the temperature range of the substrate layer during lithium metal deposition. It has been found that efficient transfer of the lithium metal layer can be achieved by adjusting the temperature range of the substrate layer during lithium metal deposition within the range of Equation 1.

[0057] In one embodiment of the present application, the formula 1 may satisfy X / Y×100(%)≦95, specifically, X / Y×100(%)≦90, and more specifically, X / Y×100(%)≦89.

[0058] In one embodiment of the present application, the formula 1 may satisfy 50≦X / Y×100(%), specifically 60≦X / Y×100(%), and more specifically 70≦X / Y×100(%).

[0059] 1 is a diagram illustrating a transfer laminate according to one embodiment of the present application. Specifically, it can be seen that a lithium metal layer 20 is laminated on a substrate layer 10, and the transfer laminate further includes a release layer 35 between the substrate layer 10 and the lithium metal layer 20. In particular, the first region A1 may refer to a region having a thickness of 1 nm to 500 nm from the surface of the lithium metal layer opposite the surface facing the substrate layer, and a region having a thickness of 1 nm to 500 nm from the surface of the lithium metal layer.

[0060] In one embodiment of the present application, the first region of the lithium metal layer may be represented by a region determined by XPS elemental analysis (Depthi profile). Specifically, the first region of the lithium metal layer may refer to a region at a thickness of 10 seconds (from the top of the film).

[0061] XPS elemental analysis involves obtaining an as-received survey scan spectrum of a sample, followed by a depth profile to obtain a narrow scan spectrum. Specifically, the analysis is performed for up to 4000 seconds using monatomic Ar ions, and the elemental ratios can be calculated from the narrow scan spectrum.

[0062] In this case, the first region may refer to any region between 1 nm and 500 nm, or may refer to a surface region within 500 nm of the lithium metal layer. In this case, the at% of each element is expressed based on 100 at% of the elements in the first region.

[0063] In one embodiment of the present application, X may mean an oxygen element ratio (at%) based on the element content in the first region being 100. Specifically, X may be 30 at% or more and 41.5 at% or less, preferably 32 at% or more and 41 at% or less, and more preferably 34 at% or more and 41 at% or less.

[0064] In one embodiment of the present application, Y may mean a lithium element ratio (at%) based on the element content in the first region being 100. Specifically, Y may be 43 at% or more and 60 at% or less, preferably 43 at% or more and 55 at% or less, and more preferably 43 at% or more and 50 at% or less.

[0065] The transfer laminate according to the present invention has the characteristic that the composition near the surface of the lithium metal layer satisfies the range of formula 1, and by adjusting the oxygen ratio at the surface of the lithium metal layer, transferability can be ensured when subsequently transferred to an electrode. That is, by adjusting the range of formula 1, it is possible to adjust the reactivity with the transfer target and the transfer force during transfer, thereby ensuring productivity in pre-lithiation in a roll-to-roll (R2R) method and improving transferability.

[0066] In one embodiment of the present application, there is provided a transfer laminate, in which a second region having a thickness of 1500 nm or more and 1800 nm or less, based on the surface of the lithium metal layer opposite the surface facing the substrate layer, satisfies the following formula 2:

[0067] [Formula 2] X1 / Y1×100(%)≦10 In the formula 2, X1 means the oxygen element ratio (at%) based on the element content of 100 in the second region; Y1 means the lithium element ratio (at %) based on the element content of 100 in the second region.

[0068] 1 is a diagram showing a transfer laminate according to one embodiment of the present application, in which the second region A2 can be seen. Specifically, the second region A2 may refer to a region having a thickness of 1500 nm to 1800 nm from the surface of the lithium metal layer opposite the surface facing the substrate layer, and may refer to a region having a thickness of 1500 nm to 1800 nm from the surface of the lithium metal layer.

[0069] In one embodiment of the present application, the second region of the lithium metal layer may be a region determined by XPS elemental analysis as described above. Specifically, the second region of the lithium metal layer may refer to a region at a thickness of 3000 s (from the top of the film).

[0070] That is, the first region and the second region according to the present application may refer to the regions at a depth of 10 seconds and a depth of 3000 seconds according to the XPS elemental analysis, and are applied to the thickness of the lithium metal layer and expressed as the thickness based on the surface of the lithium metal layer.

[0071] In one embodiment of the present application, the formula 2 may satisfy X1 / Y1×100(%)≦10, specifically, X1 / Y1×100(%)≦7, and more specifically, X1 / Y1×100(%)≦6.9.

[0072] In one embodiment of the present application, the formula 2 may satisfy 1≦X1 / Y1×100(%), specifically 2≦X1 / Y1×100(%), and more specifically 4≦X1 / Y1×100(%).

[0073] In one embodiment of the present application, X1 may mean an oxygen element ratio (at%) based on the element content in the second region being 100. Specifically, X1 may be 1 at% or more and 10 at% or less, preferably 2 at% or more and 7 at% or less, and more preferably 3 at% or more and 6.5 at% or less.

[0074] In one embodiment of the present application, Y1 may mean a lithium element ratio (at%) based on the element content in the second region being 100. Specifically, Y1 may be 90 at% or more and 99 at% or less, preferably 92 at% or more and 98 at% or less, and more preferably 92 at% or more and 97 at% or less.

[0075] The second region is a region located deeper from the surface of the lithium metal layer than the first region. Since the ratio in the second region satisfies the above range and contains an appropriate oxygen ratio, problems of ignition and by-product generation during subsequent prelithiation do not occur. Furthermore, the amount of prelithiation is controlled within an appropriate range by containing the lithium element in the above ratio, allowing for sufficient prelithiation.

[0076] In one embodiment of the present application, there is provided a transfer laminate containing 90 wt % or more of lithium element based on 100 wt % of the metal element content in the lithium metal layer.

[0077] In another embodiment, the lithium metal layer may contain 90 wt% or more, preferably 91 wt% or more, of lithium element, based on the metal element content of 100, and 99 wt% or less, more preferably 95 wt% or less.

[0078] That is, the lithium metal layer according to the present application is characterized by containing the maximum amount of lithium element for prelithiation and adjusting the oxygen ratio within the ranges of Formula 1 and Formula 2. By adjusting the oxygen ratio as described above, it is possible to improve transferability during prelithiation, thereby solving the problem of reverse transfer, and also to suppress the generation of by-products due to side reactions during prelithiation, thereby ensuring an electrode with superior performance.

[0079] In one embodiment of the present application, the lithium metal layer may further contain other metal impurities in addition to the lithium and oxygen elements described above.

[0080] In this case, the metal impurities may be contained in an amount of 10 parts by weight or less based on 100 parts by weight of the metal elements in the lithium metal layer.

[0081] The metal impurities may include carbon (C) element, nitrogen (N) element, and the like.

[0082] The method for producing a transfer laminate of the present invention will be described in detail below.

[0083] In one embodiment of the present application, there is provided a method for manufacturing a transfer laminate, comprising the steps of: preparing a substrate layer; and heating and depositing a lithium source on one surface of the substrate layer to form a lithium metal layer; wherein the surface temperature of the substrate layer in the step of forming the lithium metal layer is 90°C or less.

[0084] In one embodiment of the present application, the deposition method for depositing the lithium metal layer on the substrate layer may be selected from among vacuum evaporation deposition, chemical vapor deposition (CVD), and physical vapor deposition, but is not limited thereto, and various deposition methods used in the art may be used.

[0085] The present application provides a method for manufacturing a transfer laminate, which further includes, after the step of forming the lithium metal layer, a step of forming a surface protective layer on the lithium metal layer using CO gas alone or a mixture of an inert gas and CO gas.

[0086] As described above, the method for producing a transfer laminate according to the present application is characterized in that, by adjusting the surface temperature of the substrate layer in the step of depositing the lithium metal layer within the aforementioned range, a lithium metal layer that satisfies the ranges of the aforementioned formulas 1 and 2 can be produced. That is, it has been discovered that, in producing a transfer laminate, the composition of the lithium metal layer can be changed by changing the temperature conditions during deposition of the lithium metal layer, and that when the temperature conditions within the aforementioned ranges are satisfied, a transfer laminate with ensured transferability can be produced.

[0087] In one embodiment of the present application, the surface temperature of the substrate layer in the step of forming the lithium metal layer may be 90°C or less, and may be 50°C or more, preferably 55°C or more.

[0088] In one embodiment of the present application, the lithium metal layer produced by the above-mentioned production method can satisfy the above-mentioned formula 1 and formula 2.

[0089] The contents of Equation 1 and Equation 2 are as described above.

[0090] One embodiment of the present application provides 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 a lithium metal layer onto the electrode active material layer, wherein the step of transferring the lithium metal layer comprises the steps of: preparing the above-mentioned transfer laminate; laminating the transfer laminate onto the electrode active material layer so that a surface of the lithium metal layer opposite to a surface facing the substrate layer is in contact with a surface of the electrode active material layer opposite to a surface of the electrode active material layer that is in contact with the electrode current collector layer; and removing the substrate layer.

[0091] 2 is a diagram showing a process for transferring lithium metal to a lithium secondary battery electrode according to one embodiment of the present application. Specifically, the process shows a transfer laminate 100, in which a substrate layer 10, a release layer 35, and lithium metal 20 are sequentially 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 removing the substrate layer 10 from the transfer laminate 100. This confirms that the lithium metal layer and the release layer are transferred onto the electrode active material layer.

[0092] Hereinafter, a method for manufacturing an electrode for a lithium secondary battery will be described in detail.

[0093] A method for manufacturing an electrode for a lithium secondary battery according to an embodiment of the present application may include forming an electrode current collector layer and an electrode active material layer on one or both surfaces of the electrode current collector layer.

[0094] In one embodiment of the present application, the electrode may be a negative electrode or a positive electrode.

[0095] In one embodiment of the present application, 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 containing an electrode active material layer composition, 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.

[0096] 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 pre-lithiation method for an electrode for a lithium secondary battery.

[0097] In one embodiment of the present application, the electrode may be a negative electrode, and the following describes the method for manufacturing a negative electrode for a lithium secondary battery.

[0098] The method for manufacturing a negative electrode for a lithium secondary battery according to one embodiment of the present application may include 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.

[0099] In one embodiment of the present application, the negative electrode current collector layer usually 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, fired carbon, those surface-treated with carbon, nickel, titanium, silver, etc. on the surface of copper or stainless steel, aluminum-cadmium alloy, etc. may be used. Also, fine irregularities may be formed on the surface to strengthen the binding force of the negative electrode active material, and it may be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric body, etc.

[0100] 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.

[0101] However, the thickness may vary depending on the type and application of the negative electrode used, and is not limited thereto.

[0102] 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 silicon-based active material, a negative electrode conductive material, and a negative electrode binder.

[0103] In one embodiment of the present application, the negative electrode slurry may include a negative electrode active material layer composition and a slurry solvent.

[0104] In one embodiment of the present application, the solid content of the negative electrode slurry may be 5% or more and 40% or less.

[0105] In another embodiment, the solid content of the negative electrode slurry may be in the range of 5% to 40%, preferably 7% to 35%, and more preferably 10% to 30%.

[0106] 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 layer composition based on 100 parts by weight of the negative electrode slurry.

[0107] 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.

[0108] 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. Specifically, distillates may be used.

[0109] The negative electrode according to one embodiment of the present application may be formed by coating and drying the negative electrode slurry on the negative electrode current collector layer.

[0110] The slurry solvent in the negative electrode slurry can be dried by the drying step.

[0111] 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.

[0112] 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.

[0113] In one embodiment of the present application, the silicon-based active material may include one or more selected from the group consisting of SiOx (x = 0), SiOx (0 <x <2), SiC, and Si alloys.

[0114] 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 include 70 parts by weight or more.

[0115] In another embodiment, based on 100 parts by weight of the silicon-based active material, the SiOx (x = 0) may include 70 parts by weight or more, preferably 80 parts by weight or more, more preferably 90 parts by weight or more, and may include 100 parts by weight or less, preferably 99 parts by weight or less, more preferably 95 parts by weight or less.

[0116] In one embodiment of the present application, the silicon-based active material may be, in particular, pure silicon (Si). Using pure silicon (Si) as the silicon-based active material may mean that the silicon-based active material contains pure Si particles (SiOx (x=0)) that are not bonded to other particles or elements in the above range, based on 100 parts by weight of the total silicon-based active material.

[0117] 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.

[0118] In the present invention, to solve the above-mentioned problems, the negative electrode of a lithium secondary battery is prelithiated to solve the initial irreversible capacity problem. Specifically, in the prelithiation process, lithium metal is easily transferred from the transfer laminate during the lithium transfer process, and the generation of by-products is suppressed so that lithium can be uniformly prelithiated within the negative electrode active material layer.

[0119] 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.

[0120] 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).

[0121] 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 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.

[0122] 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.

[0123] 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.

[0124] The negative electrode active material layer composition according to the present application contains a conductive material and a 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 deteriorated and the composition has excellent output characteristics during charge and discharge.

[0125] 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.

[0126] In this application, the circularity is determined by the following formula 1, where A is the area and P is the perimeter.

[0127] [Formula 1] 4πA / P 2

[0128] While graphite-based compounds have traditionally been used exclusively as anode active materials, recent attempts to incorporate silicon-based compounds to increase capacity have 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.

[0129] 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.

[0130] In one embodiment of the present application, the dot-like conductive material can be used to improve the conductivity of the 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.

[0131] 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.

[0132] 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.

[0133] In one embodiment of the present application, the negative electrode conductive material may include a sheet conductive material.

[0134] 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.

[0135] 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.

[0136] 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 is within this range, the viscosity of the negative electrode slurry does not increase excessively, making dispersion easy. Therefore, when dispersion is performed using the same equipment and time, the dispersion effect is excellent.

[0137] 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.

[0138] 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.

[0139] 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, the sheet conductive material of the present application may be affected to some extent by dispersion effects on electrode performance, and it is particularly preferable to use a low-specific surface area sheet conductive material that does not cause dispersion problems.

[0140] In one embodiment of the present application, the sheet conductive material has a BET specific surface area of ​​5 m 2 / g or more.

[0141] 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 300m 2 / g or less.

[0142] 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.

[0143] 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.

[0144] 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.

[0145] 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.

[0146] In yet another embodiment, the negative electrode conductive material may comprise 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.

[0147] 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 serves to control 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.

[0148] 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.

[0149] 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.

[0150] 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 within the negative electrode active material 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.

[0151] 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 secure a conductive path without storing or releasing lithium. In this case, 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.

[0152] 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.

[0153] 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 ​​5 m 2 / g or more.

[0154] 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.

[0155] The negative electrode binder according to one embodiment of the present application controls the negative electrode active material and 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 negative electrode binder fulfills this function, any conventional negative electrode binder can be used, specifically, a water-based binder, or more specifically, a PAM-based binder. In one embodiment of the present application, the negative electrode binder may be included in an amount of 30 parts by weight or less, preferably 25 parts by weight or less, or more preferably 20 parts by weight or less, or may be included in an amount of 5 parts by weight or more, or 10 parts by weight or more, based on 100 parts by weight of the negative electrode active material layer composition.

[0156] 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 pre-lithiation method for a negative electrode for a lithium secondary battery described above may be applied, except that the electrode is a positive electrode.

[0157] 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.

[0158] 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. In addition, 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. For example, the positive electrode current collector may be used in various forms such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] 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 comprises one or more selected from the group consisting of Ni, Co, Mn, LTO, LFP, RuO2, Nb2O5, Mn3O4, Fe2O3, and Co3O4.

[0164] 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 satisfies 0.01≦c2≦0.6); 2-c3 M c3 Examples 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≦0.6) 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.

[0165] 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.

[0166] 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.

[0167] 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 described above.

[0168] In one embodiment of the present application, the method may include a method for manufacturing an electrode for a lithium secondary battery, the method including a step of transferring a lithium metal layer onto the electrode active material layer.

[0169] 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.

[0170] 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 lithium metal from the transfer laminate onto the electrode active material layer.

[0171] In one embodiment of the present application, there is provided a method for producing an electrode for a lithium secondary battery, wherein the step of transferring the lithium metal layer includes the steps of: preparing the aforementioned transfer laminate; laminating the transfer laminate onto the electrode active material layer so that the surface of the lithium metal layer opposite to the surface facing the substrate layer is in contact with the surface of the electrode active material layer opposite to the surface in contact with the electrode current collector layer; and removing the substrate layer.

[0172] In this case, the lamination step is carried out under a temperature condition of 30°C or less and a pressure of 200 kgf / cm 2 The present invention provides a method for manufacturing an electrode for a lithium secondary battery, in which lamination is performed at the following pressure.

[0173] After the laminating step, prelithiation of the electrode active material layer with highly reactive lithium metal may be performed.

[0174] 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 base layer, wherein the step of prelithiating the electrode active material layer is carried out within 30 minutes to 24 hours after transferring lithium metal.

[0175] In the conventional lithium metal layer transfer process, there is a problem in that the substrate layer is difficult to peel off during the prelithiation process after lamination of the transfer laminate. 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. The prelithiation method for a lithium secondary battery electrode according to the present application is characterized in that the substrate layer can be easily peeled off immediately after lamination of the transfer laminate by adjusting the lithium metal layer within the ranges of Formulas 1 and 2 above, and the formation of by-products during prelithiation can be suppressed.

[0176] The step of prelithiating the electrode active material layer is performed at 25° C. and 1 atm for 30 minutes to 24 hours.

[0177] 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.

[0178] In one embodiment of the present application, there is provided a lithium secondary battery including: 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 according to the present application.

[0179] In this case, the release 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 release layer may be used to improve transfer force and protect the lithium metal before pre-lithiation, and may be removed before injecting the electrolyte.

[0180] 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.

[0181] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0182] 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.

[0183] In particular, among the carbonate-based organic solvents, cyclic carbonates such as ethylene carbonate and propylene carbonate are preferably used because they are high-viscosity organic solvents with high dielectric constants and good dissociation of lithium salts. 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 these cyclic carbonates are more preferably used.

[0184] 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:

[0185] 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 the capacity of the battery, and improving the discharge capacity of the battery.

[0186] 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]

[0187] 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. (Manufacturing example)

[0188] <Production of Transfer Laminate> For Li deposition, lithium metal is placed in a crucible in a thermal evaporator, and the PET substrate on which Li is to be deposited is loaded. After that, the vacuum is increased for 10 minutes. -6 The pressure was increased to Torr. Then, lithium metal was evaporated while heating the crucible, and a lithium metal layer was deposited on the PET substrate to a thickness of 3 μm to 10 μm (approximately 6 μm).

[0189] After depositing the lithium metal layer, CO2 gas was injected to form a lithium carbonate layer on the surface. After a predetermined time, the vacuum was vented and the sample was removed. Surface and depth component analysis and transfer evaluation were performed using XPS.

[0190] Each transfer laminate was produced under the temperature conditions shown in Table 1 below.

[0191] [Table 1]

[0192] XPS component analysis (depth profile) For XPS analysis of the resulting transfer laminate, a sample of approximately 1 cm x 1 cm was prepared and measured using an X-ray spot size of 200 μm and argon ion energy of 2 kV. The etching rate was 0.55 nm / sec based on Ta2O5, which was estimated to be the thickness of the Li metal layer used in the present invention.

[0193] For elemental analysis, the as-received survey scan spectrum was obtained, followed by a narrow scan spectrum while performing a depth profile. The depth profile was performed up to 4000 seconds using monatomic Ar ions, and the elemental ratios were calculated from the narrow scan spectrum. - X-ray source: monochromatic Al Kα (1486.6eV) - X-ray spot size: 400μm for as-received analysis, 200μm for depth profile - Sputtering: Ar monatomic (ion energy: 2 kV, current: low, raster width: 1 mm) - Etching rate: 0.55nm / sec based on Ta2O5 - Operation mode: CAE (Constant Analyzer Energy) mode - Survey scan: pass energy 200eV, energy step 1eV - Narrow scan: scanned mode, pass energy 50eV, energy step 0.1eV - Flood gun:off - SF:Al THERMO1, ECF:TPP-2M, BG subtraction:Shirley 12

[0194] Here, although there may be differences in the Li thickness based on Ta2O4, the depth profile was determined to be 3000sec => 1650nm, 10sec => 5.5nm.

[0195] The results of XPS component analysis of the transfer laminate in Table 1 are shown in Table 2 below, and the transfer characteristics were evaluated and shown in Table 2 below. Figures 4 to 6 are diagrams showing the analysis results of Examples 1 to 3 by actual XPS analysis, and Figure 7 is a diagram showing the XPS result of the transfer laminate in Comparative Example 1.

[0196] [Table 2]

[0197] In Table 2, the transfer characteristics were measured by placing a transfer laminate on both sides of the electrode to transfer the transfer electrode assembly, applying a load of approximately 300 kgf, and then removing the lithium metal layer from the PET substrate layer to check whether the sample was transferred. In Examples 1 to 3 of the present application, the surface temperature of the substrate layer during the lithium metal layer formation step was controlled to 90°C or less. Due to these manufacturing method features, Table 2 confirms that the transfer laminate of the present application satisfies the range of Equation 1 in a first region including a thickness of 1 nm to 500 nm, measured from the surface opposite the surface facing the substrate layer. For reference, in Examples 1 and 2, Equations 1 and 2 are similar, and the surface temperature of the PET film on which lithium is deposited corresponds to a range of 50 to 60°C, but the specific temperatures are different, resulting in the results shown in Table 2.

[0198] As a result, it was confirmed that the transfer laminates of Examples 1 to 3 have the characteristic that the oxygen ratio on the surface of the lithium metal layer can be adjusted to ensure transferability when subsequently transferred to an electrode. That is, the surface of the lithium metal layer comes into contact with the surface of the transfer target to which it is ultimately transferred, and by adjusting the oxygen ratio on the surface at this time, it is possible to adjust the reactivity with the transfer target and the transfer force during transfer, and it has been confirmed that the transfer laminates have the characteristic that productivity can be ensured and transferability can be improved in pre-lithiation using a roll-to-roll (R2R) method.

[0199] In other words, the transfer laminate according to the present application has the composition of the lithium metal layer adjusted by adjusting the conditions in the manufacturing process, which has been confirmed to have the characteristic of improving the lithium transferability during the pre-lithiation process and suppressing the generation of by-products during pre-lithiation.

[0200] Comparative Example 1 is a case in which the surface temperature of the substrate layer was too high during the production of the transfer laminate. Specifically, as can be seen in Figure 8, it was confirmed that the transfer of the lithium metal layer was not performed well.

[0201] On the other hand, as can be seen from FIG. 9 (Example 3), when the range of formula 1 of the present invention is satisfied and the range of formula 2 is also satisfied, the transfer characteristics of the lithium metal layer are very excellent.

[0202] Specifically, in the cases of Figures 8 and 9, Nitto-31B tape was applied to the surface, and then the ease of transfer was assessed by checking whether the lithium separated from the PET substrate when the tape was peeled off. In the case of Figure 8, it was shown that the lithium did not separate from the substrate when the tape was applied and then peeled off, while in Figure 9, it was confirmed that the lithium easily separated from the substrate when the tape was applied and then peeled off. In other words, it was confirmed that the Examples according to the present application had superior transfer properties compared to the Comparative Examples, while Comparative Example 1 had poor transfer strength and failed in the transfer evaluation. [Explanation of symbols]

[0203] 10...Base material layer 20 Lithium metal layer 30...electrode active material layer 35...Release layer 40 Electrode current collector layer 50...Separation membrane 60 Electrode current collector layer 70...electrode active material layer 100 Transfer laminate 200 Electrodes for lithium secondary batteries 300 Electrodes for lithium secondary batteries A1...1st area A2...Second area

Claims

1. A transfer laminate comprising: a substrate layer; and a lithium metal layer laminated on one or both sides of the substrate layer; The thickness of the lithium metal layer is 1 μm or more and 20 μm or less, A transfer laminate, wherein a first region having a thickness of 1 nm or more and 500 nm or less based on the surface of the lithium metal layer opposite to the surface facing the substrate layer satisfies the following formula 1: [Formula 1] 50≦(X / Y)×100(%)≦95 In the formula 1, X represents the oxygen element ratio (at %) based on the element content of 100 in the first region; Y represents the ratio (at %) of lithium element based on the element content of 100 in the first region.

2. 2. The transfer laminate according to claim 1, wherein the second region has a thickness of 1500 nm or more and 1800 nm or less based on the surface of the lithium metal layer opposite to the surface facing the substrate layer, and satisfies the following formula 2: [Formula 2] (X1 / Y1)×100(%)≦10 In the formula 2, X1 represents the oxygen element ratio (at%) based on the element content of 100 in the second region; Y1 represents the lithium element ratio (at %) based on the element content of 100 in the second region.

3. The transfer laminate according to claim 1 , wherein the lithium metal layer contains 90 wt % or more of lithium element based on 100 wt % of the metal element content.

4. 2. The transfer laminate according to claim 1, wherein the substrate layer comprises at least one selected from the group consisting of polyethylene terephthalate (PET), polyimide (PI), poly(methyl methacrylate) (PMMA), polypropylene, polyethylene, and polycarbonate.

5. The transfer laminate according to claim 1 , wherein the thickness of the base layer is 1 μm or more and 300 μm or less.

6. The transfer laminate according to claim 1 , further comprising a release layer on a surface of the transfer laminate where the base layer and the lithium metal layer are in contact.

7. providing a substrate layer; and heating and depositing a lithium source on one surface of the substrate layer to form a lithium metal layer; A method for producing a transfer laminate, comprising: the surface temperature of the substrate layer in the step of forming the lithium metal layer is 90° C. or less; the substrate layer contains polyethylene terephthalate, The lithium metal layer satisfies the following formula 1: [Formula 1] 50≦(X / Y)×100(%)≦95 In the formula 1, X represents an oxygen element ratio (at %) in a first region of the lithium metal layer having a thickness of 1 nm to 500 nm on the surface opposite to the surface facing the substrate layer, where the element content is 100; Y represents the ratio (at %) of lithium element in a first region having a thickness of 1 nm to 500 nm on the surface of the lithium metal layer opposite to the surface facing the substrate layer, with the element content being 100.

8. After the step of forming the lithium metal layer, ２ Gas alone or inert gas and CO ２ The method of claim 7 , further comprising forming a surface protection layer on the lithium metal layer using a gas mixture.

9. The method for producing a transfer laminate according to claim 7 , wherein the deposition process for depositing the lithium metal layer on the substrate layer comprises physical vapor deposition.

10. The method for producing a transfer laminate according to claim 7, wherein the lithium metal layer satisfies the following formula 2: [Formula 2] (X1 / Y1)×100(%)≦10 In the formula 2, X1 represents an oxygen element ratio (at %) in a second region of the lithium metal layer having a thickness of 1500 nm to 1800 nm on the surface opposite to the surface facing the substrate layer, where the element content is 100; Y1 means the lithium element ratio (at %) based on the element content of 100 in a second region having a thickness of 1500 nm to 1800 nm on the surface opposite to the surface facing the substrate layer of the lithium metal layer.

11. 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 a lithium metal layer onto the electrode active material layer; A method for producing an electrode for a lithium secondary battery, comprising:

7. A method for manufacturing an electrode for a lithium secondary battery, wherein the step of transferring the lithium metal layer includes the steps of: preparing the transfer laminate according to any one of claims 1 to 6; laminating the transfer laminate onto the electrode active material layer so that a surface of the lithium metal layer opposite to a surface facing the substrate layer is in contact with a surface of the electrode active material layer opposite to a surface in contact with the electrode current collector layer; and removing the substrate layer.

12. The laminating step is carried out under a temperature condition of 30° C. or less and a pressure of 200 kgf / cm ２ The method for producing an electrode for a lithium secondary battery according to claim 11, wherein lamination is performed at a pressure of:

13. 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; The method for producing an electrode for a lithium secondary battery according to claim 11, wherein the electrode active material layer composition comprises at least one selected from the group consisting of an electrode active material, an electrode conductive material, and an electrode binder.

14. the electrode active material includes a silicon-based active material, 14. The method for producing an electrode for a lithium secondary battery according to claim 13, 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.

15. The electrode active material is Ni, Co, Mn, LTO, LFP, or RuO ２ , Nb ２ O ５ , Mn ３ O ４ , and Fe ２ The method for producing an electrode for a lithium secondary battery according to claim 13 , wherein the electrode contains one or more selected from the group consisting of O3.

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