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, and all of its content is incorporated herein by reference.

[0002] This 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 Art

[0003] Due to the rapid increase in the use of fossil fuels, the demand for alternative and clean energy has been increasing. As part of this, the fields of power generation and energy storage using electrochemical reactions are among the most actively studied.

[0004] Currently, a typical example of an electrochemical device using such electrochemical energy is a secondary battery, and its usage area is showing a trend of increasing more and more.

[0005] With the development of technologies related to mobile devices and the increasing demand, the demand for secondary batteries as an energy source has been rapidly increasing. Among such secondary batteries, lithium secondary batteries having a high energy density, a high voltage, a long cycle life, and a low self-discharge rate have been commercialized and widely used. In addition, research on methods for manufacturing high-density electrodes with a higher energy density per unit volume as electrodes for such high-capacity lithium secondary batteries has been actively conducted.

[0006] Generally, a secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode includes a negative electrode active material that inserts and desorbs lithium ions emitted from the positive electrode, and silicon-based particles having a large discharge capacity may be used as the negative electrode active material.

[0007] Generally, carbon materials such as graphite are used for the negative electrode of a lithium secondary battery, but the theoretical capacity density of carbon is 372 mAh / g (833 mAh / cm3 ) Therefore, in order to improve the energy density of the negative electrode, silicon (Si), tin (Sn), their oxides and alloys, which alloy with lithium, are considered as negative electrode materials. Among them, silicon-based materials have attracted attention due to their low price and high capacity (4200 mAh / g).

[0008] However, when using a silicon-based negative electrode active material, a problem of a large initial irreversible capacity occurs. In the charge-discharge reaction of a lithium secondary battery, lithium released from the positive electrode during charging is inserted into the negative electrode, and during discharging, it desorbs from the negative electrode and returns to the positive electrode again. In the case of a silicon-based negative electrode active material, however, volume change and surface side reactions are significant, and most of the lithium inserted into the negative electrode during the initial charging cannot return to the positive electrode again. Therefore, a problem of a large initial irreversible capacity occurs. When the initial irreversible capacity increases, problems such as a sharp decrease in battery capacity and cycle characteristics occur.

[0009] In order to solve the above problems, a method of pre-lithiating a silicon negative electrode containing a silicon-based negative electrode active material is known. As the pre-lithiation method, there are a method of manufacturing an electrode after lithiating by physical / chemical methods such as electroplating, lithium metal transfer, and lithium metal evaporation, and a method of electrochemically pre-lithiating a negative electrode.

[0010] In order to use the conventional electrochemical method, a wet process must be performed in an electrolyte, which includes risks such as fire and explosion, so it was necessary to adjust an inert environment. That is, in order to form the above environment, it is difficult to adjust conditions such as moisture control using an inert gas in the room where the electrochemical method is performed. Also, in order to uniformly control the initial irreversible capacity, it is possible to implement only by performing the pre-lithiation at the maximum slowest rate using the electrochemical method, so there is a problem that the production cost increases in the application of the electrochemical method.

[0011] In the lithium metal transfer process, which is another method, it is difficult to safely and easily transfer lithium metal. There are problems such as lithium not being transferred from the transfer laminate, or even if it is transferred, the highly reactive lithium metal immediately starts 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. Only when the 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 more safely and rapidly transferring the lithium metal layer has not yet been clarified.

[0013] Therefore, when pre-lithiating the electrode, research on a transfer laminate that can pre-lithiate lithium more safely and efficiently and uniformly into the electrode active material layer is necessary.

Prior Art Documents

Patent Documents

[0014]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0015] In the pre-lithiation process of the transfer method, a technique that can easily transfer the lithium metal layer onto the electrode active material layer is essential. Therefore, methods such as including a release layer or adjusting the adhesive force have been studied, but the above problems have not been clearly solved. In this application, it was found that when adjusting the temperature of the base material layer in the process of forming the lithium metal layer on the base material layer, the ratio of lithium element to oxygen element on the surface and in a specific region of the lithium metal layer can be adjusted. When adjusting this, it was found through research that the lithium metal layer can be easily transferred.

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

Means for Solving the Problems

[0017] One embodiment of the present specification is a transfer laminate including a base material layer; and a lithium metal layer laminated on one or both surfaces of the base material layer, wherein the thickness of the lithium metal layer is 1 μm or more and 20 μm or less, and based on the opposite surface of the surface of the lithium metal layer facing the base material layer, a first region having a thickness of 1 nm or more and 500 nm or less satisfies the following formula 1. A transfer laminate is provided.

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

[0019] In another embodiment, a method for manufacturing a transfer laminate includes preparing a base material layer; and heating and vapor-depositing a lithium source on one surface of the base material layer to form a lithium metal layer, wherein the surface temperature of the base material layer in the step of forming the lithium metal layer is 90° C. or less. A method for manufacturing a transfer laminate is provided.

[0020] In another embodiment, a method for manufacturing an electrode for a lithium secondary battery includes forming an electrode current collector layer and an electrode active material layer on one or both surfaces 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 includes preparing a transfer laminate according to the present application; laminating the transfer laminate on the electrode active material layer such that the opposite surface of the surface of the lithium metal layer facing the base material layer contacts the opposite surface of the surface of the electrode active material layer contacting the electrode current collector layer; and removing the base material layer. A method for manufacturing an electrode for a lithium secondary battery is provided.

[0021] Finally, provided is 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 a lithium secondary battery and the negative electrode for a lithium secondary battery is an electrode for a lithium secondary battery manufactured by the above method.

Advantages of the Invention

[0022] The transfer laminate according to an embodiment of the present invention is a transfer laminate used in a pre-lithiation process of a transfer method. In particular, in the transfer laminate, a lithium source is heated and vapor-deposited on the upper part of a base material layer to form a lithium metal layer. At this time, the surface temperature of the base material layer in the stage of forming the lithium metal layer is adjusted to 90°C or lower.

[0023] Due to the above-described manufacturing method features, the transfer laminate according to the present application is characterized in that, based on the opposite surface of the surface of the base material layer of the lithium metal layer facing the base material layer, it includes a first region having a thickness of 1 nm or more and 500 nm or less and satisfies the range of Formula 1.

[0024] By satisfying the range of Formula 1 for the composition near the surface of the lithium metal layer in the transfer laminate, the oxygen ratio on the surface of the lithium metal layer can be adjusted, and when transferring to an electrode thereafter, the transferability can be ensured. That is, the surface of the lithium metal layer finally comes into contact with the surface of the transfer target to be transferred. At this time, by adjusting the oxygen ratio on the surface, the reactivity problem with the transfer target and the transfer force during transfer can be adjusted, and in the pre-lithiation of the roll-to-roll (R2R) method, productivity can be ensured and the transferability can be improved.

[0025] That is, the transfer laminate according to the present application has an adjusted composition of the lithium metal layer. By this, it is possible to improve the lithium transferability in the prelithiation process, and thus it has the characteristic that the generation of by-products can be suppressed during prelithiation.

Brief Description of the Drawings

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Figure 9

Modes for Carrying Out the Invention

[0027] Before describing the present invention, first, several terms are defined.

[0028] In this specification, when a certain part "includes" a certain component, this means that, unless otherwise stated to the contrary, it does not exclude other components, but may further include other components.

[0029] In this specification, "p to q" means "p or more and q or less".

[0030] In this specification, the "specific surface area" is measured by the BET method. Specifically, it is calculated from the nitrogen gas adsorption amount at the liquid nitrogen temperature (77K) using BELSORP-mini II manufactured by BEL Japan, Inc. That is, in this application, the BET specific surface area can mean the specific surface area measured by the above measurement method.

[0031] In this specification, "Dn" means the average particle diameter and means the particle diameter at the n% point of the cumulative particle number distribution by particle diameter. That is, D50 is the particle diameter at the 50% point of the cumulative particle number distribution by particle diameter, D90 is the particle diameter at the 90% point of the cumulative particle number distribution by particle diameter, and D10 is the particle diameter at the 10% point of the cumulative particle number distribution by particle diameter. On the other hand, the average particle diameter may be measured using the laser diffraction method. Specifically, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (for example, Microtrac S3500). When the particles pass through the laser beam, the difference in the diffraction pattern due to the particle size is measured to calculate the particle size distribution.

[0032] In this specification, the meaning that a polymer contains a certain monomer in monomer units means that the monomer participates in the polymerization reaction and is included as a repeating unit in the polymer. In this specification, when a polymer is said to contain a monomer, this is interpreted to be the same as the polymer containing the monomer in monomer units.

[0033] In this specification, the "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 the number average molecular weight (Mn) are the polystyrene equivalent molecular weights measured by Gel Permeation Chromatography (GPC) using monodisperse polystyrene polymers (standard samples) of various degrees of polymerization commercially available for molecular weight measurement as standard substances. In this specification, unless otherwise specified, the molecular weight means the weight average molecular weight.

[0035] Hereinafter, for those with ordinary knowledge in the technical field to which the present invention pertains to easily implement the present invention, a detailed description will be given with reference to the drawings. However, the present invention can be embodied in various different forms and is not limited to the following description.

[0036] One embodiment of this specification is a transfer laminate including a base material layer; and a lithium metal layer laminated on one or both surfaces of the base material layer, wherein the thickness of the lithium metal layer is 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 opposite surface of the surface of the lithium metal layer facing the base material layer satisfies the following formula 1. A transfer laminate is provided.

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

[0038] In the transfer laminate according to the present invention, by satisfying the composition near the surface of the lithium metal layer within the range of the above formula (1), the oxygen ratio on the surface of the lithium metal layer can be adjusted, and when transferring to an electrode thereafter, the transferability can be ensured. That is, the surface of the lithium metal layer ultimately comes into contact with the surface of the transfer target to be transferred. At this time, by adjusting the oxygen ratio on the surface, the reactivity problem with the transfer target and the transfer force can be adjusted during transfer, ensuring productivity in the roll-to-roll (R2R) pre-lithiation process and having the feature of being able to improve the transferability.

[0039] In one embodiment of the present application, the substrate layer can withstand process conditions such as high temperatures at the stage of depositing the lithium metal layer, and has the feature of being able to prevent the reverse peeling problem where the lithium metal layer is transferred onto the substrate layer in the winding process for transferring the deposited lithium metal, and can be used without limitation as long as it has such a feature.

[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(methyl methacrylate) (PMMA), polypropylene, polyethylene, and polycarbonate.

[0041] In one embodiment of the present application, the thickness of the substrate layer may be 1 μm or more and 300 μm or less, and may also satisfy the range of 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 satisfy 3 μm or more and 25 μm or less.

[0043] By having the thickness of the base material layer satisfy the above range, the transfer of the lithium metal layer to the side of the electrode active material layer can be efficiently performed. In particular, when the base material layer has the above range, heat dissipation can effectively occur, and it will have the characteristic of being able to prevent problems of reverse transfer and generation of by-products during prelithiation.

[0044] In one embodiment of the present application, in order to improve the peelability of the lithium metal layer, ensure the transferability to the electrode active material layer, and play the role of a protective layer after the transfer of the lithium metal layer, the base material layer of the transfer laminate and the surface where the lithium metal layer is in contact may further include a release layer.

[0045] That is, the base material layer may be one with a release layer formed on at least one surface, or may be one with release layers formed on both surfaces. In the winding process for transferring the lithium metal layer deposited by the release layer to the electrode, the problem of reverse peeling where the lithium metal layer is transferred onto the base material layer can be prevented, and after transferring the lithium metal onto the electrode active material layer, the base material layer can be easily separated.

[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 satisfy the range of 1 nm or more and 1 μm or less, preferably 100 nm or more and 1 μm or less, more preferably 500 nm or more and 1 μm or less.

[0048] The release layer satisfies the above thickness range and a specific adhesion force range. The release layer has the above thickness range and, after being prelithiated, can adjust the adhesion force range with the upper part of the prelithiated electrode to the lower limit of the predetermined range, and has the characteristic that no side reaction occurs between the release layer and the electrode active material layer.

[0049] The release layer may contain one or more 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.

[0050] In one embodiment of the present application, the release layer may be formed by a coating method. For example, the coating method may be a method selected from the group consisting of dip coating, spray coating, spin coating, die coating, Gravure coating, Micro-Gravure coating, Comma coating, and roll coating, but is not limited thereto, and various coating methods that can be employed in the art to form a coating layer may be employed.

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

[0052] The type of the release layer may be used without limitation as long as it can fulfill its role, and any release layer used in the art can be used.

[0053] In one embodiment of the present application, the thickness of the lithium metal layer may be 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, a first region having a thickness of 1 nm or more and 10 nm or less, based on the opposite surface of the surface of the lithium metal layer facing the base layer, may satisfy Formula 1.

[0056] The transfer laminate used for pre-lithiation of the transfer method utilizes thermal evaporation to heat and deposit a lithium source on top of the substrate layer to form a lithium metal layer having the thickness range. Then, for surface stabilization, an inert gas is used to form a partial vapor deposition film on top. In such a vapor deposition process, oxygen may be incorporated into the vapor deposition film. At this time, in the present application, the temperature range of the substrate layer during the vapor deposition of the lithium metal can be adjusted to adjust the ratio of oxygen to lithium on the surface of the lithium metal layer. When adjusted to the range of Formula 1, it can be seen that the transfer of the lithium metal layer can be efficiently performed.

[0057] In one embodiment of the present application, 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, Formula 1 may satisfy 50≦X / Y×100(%), specifically, 60≦X / Y×100(%), and more specifically, 70≦X / Y×100(%).

[0059] FIG. 1 is a diagram showing a transfer laminate according to one embodiment of the present application. Specifically, it can be confirmed that a lithium metal layer 20 is laminated on top of the substrate layer 10, corresponding to a transfer laminate further including a release layer 35 between the substrate layer 10 and the lithium metal layer 20. In particular, the first region A1 can mean a region including a thickness of 1 nm or more and 500 nm or less based on the opposite surface of the surface of the lithium metal layer facing the substrate layer of the lithium metal layer, and including a thickness of 1 nm or more and 500 nm or less based on 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 indicated by a region in XPS component analysis (Depthi profile). Specifically, the first region of the lithium metal layer can mean the region at the position of a thickness of 10 seconds (from the top of the film).

[0061] The XPS component analysis means a method of obtaining a narrow scan spectrum while performing a depth profile after obtaining a survey scan spectrum of the sample as-received. Specifically, it is performed up to 4000 seconds using monatomic Ar ions, and the elemental composition ratio can be calculated from the narrow scan spectrum.

[0062] At this time, the first region can mean all regions including 1 nm or more and 500 nm or less, and can mean the region of the surface belonging to 500 nm of the lithium metal layer. At this time, the at% of each element is shown based on 100 at% of the elements in the first region.

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

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

[0065] The transfer laminate according to the present invention is characterized in that the composition near the surface of the lithium metal layer satisfies the range of the above formula 1, and by adjusting the oxygen ratio on the surface of the lithium metal layer, transferability can be ensured when transferring to an electrode thereafter. That is, by adjusting to the range of the above formula 1, problems of reactivity with the transfer target and transfer force can be adjusted during transfer, productivity can be ensured in the pre-lithiation of the roll-to-roll (R2R) method, and transferability can be improved.

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

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

[0068] FIG. 1 is a diagram showing a transfer laminate according to one embodiment of the present application, in which the second region can be confirmed. Specifically, the second region A2 is a region having a thickness of 1500 nm or more and 1800 nm or less based on the opposite surface of the surface of the lithium metal layer facing the base material layer, and can mean a region having a thickness of 1500 nm or more and 1800 nm or less based on the surface of the lithium metal layer.

[0069] In one embodiment of the present application, the second region of the lithium metal layer is a region by XPS component analysis as described above. Specifically, the second region of the lithium metal layer can mean a region at a position having a thickness of 3000 sec (from the top of the film).

[0070] That is, the first region and the second region according to the present application can mean regions at a depth of 10 seconds and a depth of 3000 seconds by XPS component analysis, and when this is applied to the thickness of the lithium metal layer, it is 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 be X1 / Y1×100(%)≦10, specifically, it may satisfy X1 / Y1×100(%)≦7, and more specifically, X1 / Y1×100(%)≦6.9.

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

[0073] In one embodiment of the present application, X1 can mean the oxygen element ratio (at%) based on 100 of the element content in the second region. Specifically, X1 may satisfy 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 can mean the lithium element ratio (at%) based on 100 of the element content in the second region. Specifically, Y1 may satisfy 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 means a region at a deeper position from the surface of the lithium metal layer with respect to the first region. At this time, since the ratio in the second region satisfies the above range and contains an appropriate oxygen ratio, problems such as ignition and by-product generation do not occur during pre-lithiation. In addition, it contains a lithium element in the above ratio, and the pre-lithiation amount is adjusted to an appropriate range, and it has the characteristic that sufficient pre-lithiation can be performed.

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

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

[0078] That is, the lithium metal layer according to the present application is characterized in that, in order to perform prelithiation, it contains the maximum amount of lithium element and the ratio of oxygen is adjusted within the ranges of Formula 1 and Formula 2, respectively. By adjusting the ratio of oxygen as described above, the transferability can be improved during prelithiation, thereby solving the problem of reverse transfer. Also, during prelithiation, the generation of by-products due to side reactions can be suppressed, and electrodes with better performance can be ensured.

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

[0080] At this time, 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 elements such as carbon (C) and nitrogen (N).

[0082] Hereinafter, specific details regarding the method for manufacturing the transfer laminate of the present invention will be described.

[0083] In one embodiment of the present application, a method for manufacturing a transfer laminate includes 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 lower.

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

[0085] In the present application, after the step of forming the lithium metal layer, a method for manufacturing a transfer laminate is provided, which further includes a step of forming a surface protective film on the upper portion of the lithium metal layer by using CO2 gas alone or in a mixture of an inert gas and CO2 gas.

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

[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 lower, and may also satisfy the range of 50 °C or higher, preferably 55 °C or higher.

[0088] In one embodiment of the present application, the lithium metal layer manufactured by the aforementioned manufacturing method can satisfy the aforementioned Formula 1 and Formula 2.

[0089] The content regarding Formula 1 and Formula 2 is as described above.

[0090] One embodiment of the present application includes the steps of forming an electrode current collector layer and an electrode active material layer on one or both surfaces of the electrode current collector layer; and transferring a lithium metal layer onto the electrode active material layer. The step of transferring the lithium metal layer includes the steps of preparing the above-described transfer laminate; laminating the transfer laminate on the electrode active material layer such that the opposite surface of the lithium metal layer facing the base material layer contacts the opposite surface of the electrode active material layer contacting the electrode current collector layer; and removing the base material layer. A method for manufacturing an electrode for a lithium secondary battery is provided.

[0091] Figure 2 is a diagram showing the process of transferring lithium metal onto an electrode for a lithium secondary battery according to an embodiment of the present application. Specifically, after laminating a transfer laminate 100 in which a base material layer 10, a release layer 35, and a 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, the process of removing the base material layer 10 of the transfer laminate 100 can be confirmed. Thereby, it can be confirmed that the lithium metal layer and the release layer are transferred onto the upper part of the electrode active material layer.

[0092] Hereinafter, specific contents regarding the method for manufacturing an electrode for a lithium secondary battery will be described.

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

[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 a pre-lithiation method for an electrode for a lithium secondary battery is provided.

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

[0098] A method for manufacturing a negative electrode for a lithium secondary battery according to one embodiment of the present application may include a negative electrode current collector layer and a step of forming 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 a chemical change in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, a surface-treated product of copper or stainless steel with carbon, nickel, titanium, silver, etc., an aluminum-cadmium alloy, etc. may be used. Further, 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, a sheet, a foil, a net, a porous body, a foam, and a non-woven fabric body.

[0100] In one embodiment of the present application, the thickness of the negative electrode current collector layer is 1 μm or more and 100 μm or less, and the thickness of the negative electrode active material layer may be 20 μm or more and 500 μm or less.

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

[0102] In one embodiment of the present application, the steps 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 include coating one or both surfaces of the negative electrode current collector layer with a negative electrode slurry containing 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. A method for manufacturing an electrode for a lithium secondary battery is provided.

[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 satisfy 5% or more and 40% or less.

[0105] In another embodiment, the solid content of the negative electrode slurry may satisfy a range of 5% or more and 40% or less, preferably 7% or more and 35% or less, and more preferably 10% or more and 30% or less.

[0106] The content of the solid content of the negative electrode slurry may mean the content of the negative electrode active material layer composition contained in the negative electrode slurry, or may mean the content of the negative electrode active material layer composition based on 100 parts by weight of the negative electrode slurry.

[0107] When the content of the solid content of the negative electrode slurry satisfies the above range, at the time of forming the negative electrode active material layer, the viscosity is appropriate, the caking phenomenon of the particles of the negative electrode active material layer composition is minimized, and the negative electrode active material layer can 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 a 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, SiOx (x = 0) may be included in an amount of 70 parts by weight or more.

[0115] In another embodiment, based on 100 parts by weight of the silicon-based active material, 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.

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

[0117] In the charge-discharge reaction of a lithium secondary battery, during charging, lithium released from the positive electrode is inserted into the negative electrode, and during discharging, it desorbs from the negative electrode and returns to the positive electrode again. However, in the case of a silicon-based negative electrode active material, volume change and surface side reactions are significant, and the amount of lithium inserted into the negative electrode during initial charging that returns to the positive electrode is small. Therefore, there is a problem that the initial irreversible capacity increases. When the initial irreversible capacity increases, there is a problem that the battery capacity and cycle rapidly decrease.

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

[0119] On the one hand, the average particle size (D50) of the silicon-based active material of the present invention may be 5 μm to 10 μm, specifically, it may be 5.5 μm to 8 μm, and more specifically, it may be 6 μm to 7 μm. When the average particle size is within the above range, the specific surface area of the particles is included in an appropriate range, and the viscosity of the negative electrode slurry is formed in an appropriate range. Thereby, the dispersion of the particles constituting the negative electrode slurry becomes smooth. Further, since the size of the silicon-based active material has a value equal to or greater than the lower limit value of the above range, the contact area between the silicon particles and the conductive material by the composite composed of the conductive material and the binder in the negative electrode slurry is excellent, and the possibility of maintaining the conductive network is increased, and the capacity retention rate is increased. Further, when the average particle size satisfies the above range, silicon particles that are too large are excluded, and the surface of the negative electrode is smoothly formed, whereby it is possible to prevent the non-uniform phenomenon of the current density during charge and discharge.

[0120] In one embodiment of the present application, the silicon-based active material has a normally specific BET specific surface area. The BET specific surface area of the silicon-based active material is preferably 0.01 m 2 / g to 150.0 m 2 / g, more preferably 0.1 m 2 / g to 100.0 m 2 / g, particularly preferably 0.2 m 2 / g to 80.0 m 2 / g, most preferably 0.2 m 2 / g to 18.0 m 2 / g. The BET specific surface area is measured according to DIN 66131 (using nitrogen).

[0121] In one embodiment of the present application, the silicon-based active material may exist, for example, in a crystalline or amorphous form, and is preferably not porous. The silicon particles are preferably spherical or multi-piece particles. Alternatively, the silicon particles may have a fibrous structure, or may exist in the form of a silicon-containing film or coating, but this is not so preferable.

[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 another embodiment, the silicon-based active material may be contained 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, and may be contained 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, based on 100 parts by weight of the negative electrode active material layer composition.

[0124] The negative electrode active material layer composition according to the present application contains, together with a conductive material and a binder capable of controlling the volume expansion rate during the charge and discharge process, a silicon-based active material having a significantly high capacity within the above range. Therefore, even if the silicon-based active material is contained within the above range, the performance of the negative electrode will not be deteriorated, and it will have the characteristic of excellent output characteristics during charging and discharging.

[0125] In one embodiment of the present application, the silicon-based active material may have a non-spherical form, and its sphericity is, for example, 0.9 or less, for example, 0.7 to 0.9, for example, 0.8 to 0.9, for example, 0.85 to 0.9.

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

[0127] [Formula 1] 4πA / P 2

[0128] Conventionally, it has been common to use only graphite-based compounds as the negative electrode active material. However, recently, as the demand for high-capacity batteries has increased, attempts have been made to mix and use silicon-based compounds to increase the capacity. However, in the case of silicon-based compounds, there is a limit in that the volume rapidly expands during the charge / discharge process, damaging the conductive path formed in the negative electrode active material layer and conversely deteriorating the performance of the battery. Therefore, the type of negative electrode conductive material used together 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 a dot-shaped conductive material, a planar conductive material, and a linear conductive material.

[0130] In one embodiment of the present application, the dot-shaped conductive material can be used to improve the conductivity of the negative electrode, and means a material having conductivity without inducing a chemical change. Specifically, the dot-shaped 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 derivative, and preferably may include carbon black in terms of realizing high conductivity and excellent dispersibility.

[0131] In one embodiment of the present application, the BET specific surface area of the dot-shaped conductive material is 40 m 2 / g or more and 70 m 2 / g or less, preferably 45 m 2 / g or more and 65 m 2 / g or less, more preferably 50 m 2 / g or more and 60 m 2 / g or less.

[0132] In one embodiment of the present application, the particle size of the dot-shaped conductive material may be 10 nm to 100 nm, preferably 20 nm to 90 nm, more preferably 40 nm to 60 nm.

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

[0134] The planar conductive material can play a role in increasing the surface contact between silicon particles in the negative electrode to improve conductivity, and at the same time suppressing the interruption of the conductive path due to volume expansion, and is used in the concept including bulk-type conductive materials or plate-type conductive materials.

[0135] In one embodiment of the present application, the planar conductive material may include at least any one selected from the group consisting of plate-shaped graphite, graphene, graphene oxide, and graphite flakes, and preferably may be plate-shaped graphite.

[0136] In one embodiment of the present application, the average particle size (D50) of the planar conductive material may be 2 μm to 7 μm, specifically, it may be 3 μm to 6 μm, and more specifically, it may be 4 μm to 5 μm. When the above range is satisfied, since the particle size is sufficient, the viscosity of the negative electrode slurry does not increase excessively, and dispersion becomes easy. Therefore, when dispersing using the same equipment and time, the dispersion effect is excellent.

[0137] In one embodiment of the present application, the planar conductive material provides a negative electrode active material layer composition in which D10 is 0.5 μm or more and 1.5 μm or less, D50 is 2.5 μm or more and 3.5 μm or less, and D90 is 7.0 μm or more and 15.0 μm or less.

[0138] In one embodiment of the present application, as the planar conductive material, a high specific surface area planar conductive material with a high BET specific surface area; or a low specific surface area planar conductive material may be used.

[0139] In one embodiment of the present application, as the planar conductive material, a high specific surface area planar conductive material; or a low specific surface area planar conductive material may be used without limitation, but particularly for the planar conductive material according to the present application, the dispersion effect may affect the electrode performance to a certain extent, and it is particularly preferable to use a low specific surface area planar conductive material that does not cause problems in dispersion.

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

[0141] In yet another embodiment, the planar conductive material has a BET specific surface area of 5 m 2 / g or more and 500 m 2 / g or less, preferably 5 m 2 / g or more and 300 m 2 / g or less, more preferably 5 m 2 / g or more and 300 m 2 / g or less.

[0142] In yet another embodiment, the planar conductive material is a high specific surface area planar conductive material, and the BET specific surface area is 50 m 2 / g or more and 500 m 2 / g or less, preferably 80 m 2 / g or more and 300 m 2 / g or less, more preferably 100 m 2 / g or more and 300 m 2 / g or less.

[0143] In yet another embodiment, the planar conductive material is a low specific surface area planar conductive material, and the BET specific surface area is 5 m 2 / g or more and 40 m 2 / g or less, preferably 5 m 2 / g or more and 30 m 2 / g or less, more preferably 5 m 2 / g or more and 25 m 2 / g or less.

[0144] In addition, as the negative electrode conductive material, there may be a linear conductive material such as a carbon nanotube. The carbon nanotube may be a bundled carbon nanotube. The bundled carbon nanotube may include a plurality of carbon nanotube units. Specifically, here, the "bundle type" refers to a bundle or rope-like secondary shape in which a plurality of carbon nanotube units are arranged in parallel with substantially the same orientation along the longitudinal axis of the carbon nanotube unit, or are intertwined, unless otherwise specified. The carbon nanotube unit has a graphite sheet in the form of a cylinder with a nanosize diameter and has an sp2 bonding structure. At this time, depending on the angle and structure of the winding of the graphite sheet, it can exhibit the characteristics of a conductor or a semiconductor. The bundled carbon nanotube can be uniformly dispersed during the production of the negative electrode compared to the entangled type carbon nanotube, and can smoothly form a conductive network in the negative electrode, 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 another embodiment, the negative electrode conductive material may include 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, 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] In the case of the negative electrode conductive material according to the present application, it has a completely different configuration from the conductive material applied to the positive electrode. That is, in the case of the negative electrode conductive material according to the present application, it plays a role of controlling the contact points between silicon-based active materials with a very large volume expansion of the electrode during charging and discharging, and the positive electrode conductive material plays a role of imparting partial conductivity while acting as a buffer with a buffering effect when rolled. The configuration and role of the negative electrode conductive material of the present invention are completely different.

[0148] In addition, the negative electrode conductive material according to the present application is applied to a silicon-based active material and has a completely different configuration from the conductive material applied to a graphite-based active material. That is, the conductive material used for an electrode having a graphite-based active material simply has smaller particles than the active material, and thus has the characteristics of improving output characteristics and imparting some conductivity. Different from the negative electrode conductive material applied together with a silicon-based active material as in the present invention, the configuration and role are completely different.

[0149] In one embodiment of the present application, the planar conductive material used as the aforementioned negative electrode conductive material has a structure and role different from those of the carbon-based active material generally used as the 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 means a material processed into a spherical or dot-like form in order to facilitate the storage and release of lithium ions.

[0150] On the other hand, the planar conductive material used as the negative electrode conductive material is a material having a planar or plate-like form and can be represented by plate-shaped graphite. That is, it is a material included to maintain a conductive path within the negative electrode active material layer, and means a material for ensuring a planar conductive path inside the negative electrode active material layer that does not play a role in the storage and release of lithium.

[0151] That is, in the present application, the fact that plate-shaped graphite is used for the conductive material means that it is processed into a planar or plate-like shape and used as a material for ensuring a conductive path that does not play a role in storing or releasing lithium. At this time, the negative electrode active material included together has high capacity characteristics for the storage and release of lithium and plays a role of being able to store and release all lithium ions transmitted from the positive electrode.

[0152] On the other hand, in the present application, the fact that a carbon-based active material is used as the active material means that it is processed into a dot-like or spherical shape and used as a material that plays a role in storing or releasing lithium.

[0153] That is, in one embodiment of the present application, artificial graphite or natural graphite, which is a carbonaceous active material, may satisfy the range of a BET specific surface area of 0.1 m 2 / g or more and 4.5 m 2 / g or less. Further, plate-shaped graphite, which is a planar conductive material, may have a BET specific surface area of 5 m 2 / g or more in the form of a surface.

[0154] In one embodiment of the present application, the negative electrode binder is polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, poly acrylic acid, and at least any one selected from the group consisting of substances in which hydrogen thereof is substituted with Li, Na, Ca, etc., and various copolymers thereof may also be included.

[0155] The negative electrode 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 in order to prevent the twisting and structural deformation of the negative electrode structure in the volume expansion and relaxation of the silicon-based active material. When the above role is satisfied, all ordinary negative electrode binders can be applied. Specifically, an aqueous binder may be used, and more specifically, a PAM-based binder may be used. In one embodiment of the present application, based on 100 parts by weight of the negative electrode active material layer composition, the negative electrode binder may be included 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, and may also be included in an amount of 5 parts by weight or more and 10 parts by weight or more.

[0156] In one embodiment of the present application, the electrode may be a positive electrode. Hereinafter, a method for manufacturing a positive electrode for a lithium secondary battery will be described. At this time, the same description as the pre-lithiation method of the negative electrode for a lithium secondary battery described above may be applied, except that there is a difference in that it is a positive electrode.

[0157] The method for manufacturing an electrode for a lithium secondary battery according to one embodiment of the present application may include a positive electrode current collector layer and a step of forming 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 has conductivity without inducing a chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or those obtained by surface treatment of the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. may be used. Further, the positive electrode current collector layer may usually 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 increase the adhesive force of the positive electrode active material. For example, it may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric body, etc.

[0159] The thickness of the positive electrode current collector layer may vary variously depending on the type and use of the negative electrode used, and is not limited thereto.

[0160] In one embodiment of the present application, the step of forming a positive electrode active material layer on one or both surfaces of the positive electrode current collector layer and the positive electrode current collector layer includes a step of coating one or both surfaces of the positive electrode current collector layer with a positive electrode slurry containing a positive electrode active material layer composition, and the positive electrode active material layer composition includes one or more selected from the group consisting of a positive electrode active material, a positive electrode conductive material, and a positive electrode binder, and provides a method for manufacturing an electrode for a lithium secondary battery.

[0161] In one embodiment of the present application, the content of the positive electrode slurry described above may be similarly applied to the content of the negative electrode slurry described above, except that there is a difference in 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 manufacturing an electrode for a lithium secondary battery, wherein the electrode active material includes 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 is a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; chemical formula Li 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 O2 (where M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies 0.01 ≦ c2 ≦ 0.6), Ni-site type lithium nickel oxide represented by the formula; chemical formula LiMn 2-c3 M c3 O2 (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 lithium manganese composite oxide represented by Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); LiMn2O4 in which a part of the chemical formula of Li is substituted with an alkaline earth metal ion, etc. can be mentioned, but it is not limited to these. The positive electrode may be Li metal.

[0165] At this time, the positive electrode conductive material is used to impart conductivity to the electrode, and in the battery being configured, it can be used without particular limitation as long as it has electron conductivity without causing a chemical change. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based substances such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, etc. Among these, one kind alone or a mixture of two or more kinds may be used.

[0166] In addition, the positive electrode binder plays a role in improving the adhesion between the positive electrode active material particles and the adhesive force between the positive electrode active material and the positive electrode current collector. Specific examples 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, or various copolymers thereof, etc. Among these, one kind alone or a mixture of two or more kinds may be used.

[0167] In addition, the contents of the positive electrode active material, the positive electrode conductive material, and the positive electrode binder included in the positive electrode active material layer composition may be similarly applied to the content applied to the aforementioned negative electrode active material layer composition.

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

[0169] Generally, the prelithiation process involves chemically or physically prelithiating the electrode with lithium metal. Specifically, it may be performed by a lithium metal transfer process, lithium metal powder deposition, an electro / chemical process, or a lithium metal deposition process. The prelithiation process according to the present application may include a lithium metal transfer process.

[0170] In the case of the lithium metal transfer process, it has the characteristic that highly reactive lithium metal can be transferred more stably onto the electrode active material layer. At this time, a process capable of easily transferring lithium metal from the transfer laminate onto the electrode active material layer is required.

[0171] In one embodiment of the present application, the step of transferring the lithium metal layer includes: preparing the aforementioned transfer laminate; laminating the transfer laminate on the electrode active material layer such that the opposite surface of the lithium metal layer facing the base material layer contacts the opposite surface of the electrode current collector layer of the electrode active material layer; and removing the base material layer. A method for manufacturing an electrode for a lithium secondary battery is provided.

[0172] At this time, the laminating step is performed at a temperature condition of 30 °C or lower and a pressure of 200 kgf / cm 2 or lower. A method for manufacturing an electrode for a lithium secondary battery is provided.

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

[0174] In one embodiment of the present application, after the step of removing the base material layer, it includes a step of prelithiating the electrode active material layer. The step of prelithiating the electrode active material layer is prelithiated within 30 minutes to 24 hours after transferring the lithium metal. A method for manufacturing an electrode for a lithium secondary battery is provided.

[0175] In the conventional transfer process of the lithium metal layer, there was a problem that it was difficult to peel off the substrate layer during the process of pre-lithiation after laminating the transfer laminate. As a result, pre-lithiation was carried out with the substrate layer not removed, and the heat generated during pre-lithiation was blocked by the substrate layer and could not be released, resulting in the problem that by-products were formed on the surface during the pre-lithiation of the lithium metal. The pre-lithiation method of the electrode for a lithium secondary battery according to the present application can easily peel off the substrate layer immediately after laminating the transfer laminate by adjusting the lithium metal layer within the ranges of Formula 1 and Formula 2 as described above, and can suppress the generation of by-products during pre-lithiation.

[0176] The step of pre-lithiating the electrode active material layer provides a method for manufacturing an electrode for a lithium secondary battery, which is pre-lithiated within 30 minutes to 24 hours under the conditions of 25°C and 1 atm.

[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 is completed can be determined by whether the lithium on the upper part 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 a lithium secondary battery and the negative electrode for a lithium secondary battery is an electrode for a lithium secondary battery manufactured according to the present application.

[0179] At this time, the release layer 35 used during pre-lithiation may be removed as described above, thereby preventing an unnecessary increase in resistance remaining on the upper part of the electrode. That is, the release layer may be used to improve the transfer force and also to 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 electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0181] Specifically, the electrolytic solution may contain a non-aqueous organic solvent and a metal salt.

[0182] Examples of the non-aqueous organic solvent may 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, triphosphate ester, trimethoxymethane, dioxolane derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, methyl propionate, and ethyl propionate.

[0183] In particular, among the carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are organic solvents with high viscosity, high dielectric constant, and good dissociation of lithium salts, so they can be preferably used. By mixing linear carbonates with low viscosity and low dielectric constant such as dimethyl carbonate and diethyl carbonate with such cyclic carbonates in an appropriate ratio, an electrolyte with high electrical conductivity can be produced, so it can be more preferably used.

[0184] A lithium salt may be used as the metal salt. The lithium salt is a substance that is easily dissolved in the non-aqueous electrolyte. For example, as the anion of the lithium salt, 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 may be used.

[0185] In addition to the constituent components of the electrolytic solution, for the purpose of improving the life characteristics of the battery, suppressing the reduction of the battery capacity, improving the discharge capacity of the battery, etc., for example, haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, etc., may further contain one or more additives.

[0186] One embodiment of the present invention provides a battery module including the secondary battery as a unit cell, and a battery pack including the same. Since the battery module and the battery pack include the secondary battery having high capacity, high rate characteristics, and cycle characteristics, they 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] Hereinafter, in order to facilitate the understanding of the present invention, preferred examples are presented. However, these examples are merely illustrative of the description, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope of the description and the scope of the technical idea. It is natural that such variations and modifications belong to the scope of the claims. (Production Example)

[0188] <Manufacture of Transfer Laminate> For Li deposition, lithium metal was placed in a crucible in a vacuum evaporation apparatus (Thermal evaporator), and a PET substrate on which Li was to be deposited was loaded. Then, the vacuum was formed to 10 -6 Torr. Thereafter, while heating the crucible, lithium metal was evaporated to deposit a lithium metal layer with a thickness of 3 μm to 10 μm (about 6 μm) on the top of the PET substrate.

[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, the sample was taken out, and surface and depth component analysis and transfer evaluation using XPS were performed.

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

[0191]

Table 1

[0192] XPS Composition Analysis (Depth Profile) For the transfer laminate manufactured as described above, a sample of approximately 1 cm × 1 cm was prepared for XPS composition analysis, the X-ray spot size was set to 200 μm, and measurement was performed using an argon ion energy of 2 kV. The etching rate was 0.55 nm / sec based on Ta2O5, and this was estimated to be the thickness of the Li metal layer and used in the present invention.

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

[0194] Here, although there may be a difference from the thickness of Li based on Ta2O4, it was determined that the depth profile was 3000 sec => 1650 nm and 10 sec => 5.5 nm.

[0195] The XPS component analysis results for the transfer laminate in Table 1 above 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 results of the transfer laminate according to Comparative Example 1.

[0196]

Table 2

[0197] In Table 2 above, for the transfer characteristics, in order to transfer the aforementioned transfer electrode body, after positioning the transfer laminate on both sides of the electrode, a load of about 300 kgf was applied and roll pressing was performed. Then, in order to confirm whether the sample was transferred or not, the lithium metal layer was removed from the PET substrate layer for confirmation. In the case of Examples 1 to 3 of the present application, the surface temperature of the substrate layer in the step of forming the lithium metal layer was adjusted to 90°C or lower. Due to such characteristics of the manufacturing method, it was confirmed from Table 2 that the transfer laminate according to the present application satisfies the range of Formula 1 in the first region having a thickness of 1 nm or more and 500 nm or less, with reference to the opposite surface of the surface of the substrate layer of the lithium metal layer. For reference, in Examples 1 and 2, Formulas 1 and 2 were at a similar level, corresponding to the surface temperature of the PET film on which lithium was vapor-deposited being in the range of 50 to 60°C, and the specific temperatures were different from each other, showing the results as in Table 2.

[0198] As a result, it was confirmed that the transfer laminates of Examples 1 to 3 have the characteristic that the ratio of oxygen on the surface of the lithium metal layer can be adjusted, and then the transferability when transferring to the electrode can be ensured. That is, the surface of the lithium metal layer is in contact with the surface of the transfer target to be finally transferred. At this time, by adjusting the ratio of oxygen on the surface, the problem of reactivity with the transfer target and the transfer force can be adjusted during transfer, and it was confirmed that it has the characteristic of being able to ensure productivity and improve transferability in the pre-lithiation of the roll-to-roll (R2R) method.

[0199] That is, the transfer laminate according to the present application is one in which the composition of the lithium metal layer is adjusted by adjusting the conditions in the manufacturing process. As a result, it was confirmed that the lithium transferability during the pre-lithiation process can be improved, and the generation of by-products during pre-lithiation can be suppressed.

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

[0201] On the other hand, as can be confirmed in 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, it was confirmed that the transfer characteristics of the lithium metal layer are very excellent.

[0202] Specifically, in the cases of FIGS. 8 and 9, after attaching Nitto-31B tape to the surface, when peeling off the tape, it was confirmed whether lithium was peeled off from the PET base material, and this was used as a criterion for judging the ease of transfer. In the case of FIG. 8, it was shown that lithium was not separated from the base material even after attaching and peeling off the tape, and in FIG. 9, it was confirmed that lithium was easily peeled off from the base material when the tape was attached and then peeled off. That is, it was confirmed that the examples according to the present application are superior in transfer characteristics to the comparative examples, and in the case of Comparative Example 1, the transfer force is inferior and it shows a fail in the transfer evaluation.

Explanation of Reference Numerals

[0203] 10 ··· Base material layer 20 ··· Lithium metal layer 30 ··· Electrode active material layer 35 ··· Release layer 40 ··· Electrode current collector layer 50 ··· Separator 60 ··· Electrode current collector layer 70 ··· Electrode active material layer 100 ··· Transfer laminate 200 ··· Electrode for lithium secondary battery 300 ··· Electrode for lithium secondary battery A1 ··· First region A2 ··· Second region

Claims

1. A transfer laminate comprising a base material layer; and a lithium metal layer laminated on one or both surfaces of the base material layer, wherein 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 opposite surface of the lithium metal layer facing the base material layer, satisfies the following formula 1: [Formula 1] X / Y × 100 (%) ≤ 95 In the above formula 1, X means the oxygen element ratio (at%) based on 100 of the element content in the first region, Y means the lithium element ratio (at%) based on 100 of the element content in the first region.

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

4. The transfer laminate according to claim 1, wherein the base material layer contains one or more 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 material 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 the surface of the base material layer of the transfer laminate where the base material layer and the lithium metal layer are in contact.

7. Preparing a base material layer; and Heating and vapor-depositing a lithium source on one surface of the base material layer to form a lithium metal layer; A method for manufacturing a transfer laminate, comprising: The method for manufacturing a transfer laminate, wherein the surface temperature of the base material layer in the step of forming the lithium metal layer is 90°C or less.

8. After the step of forming the lithium metal layer, CO ２ gas alone or a mixture of an inert gas and CO ２ The method for manufacturing a transfer laminate according to claim 7, further comprising a step of forming a surface protective film on the upper portion of the lithium metal layer by using the gas mixture.

9. The method for manufacturing a transfer laminate according to claim 7, wherein the vapor deposition step for depositing the lithium metal layer on the base material layer includes one or more selected from the group consisting of evaporation deposition, chemical vapor deposition, chemical vapor deposition (CVD), and physical vapor deposition.

10. The method for manufacturing a transfer laminate according to claim 7, wherein the lithium metal layer satisfies the following formulas 1 and 2: [Formula 1] X / Y × 100 (%) ≤ 95 In Formula 1, X means the oxygen element ratio (at%) based on 100 of the element content in the first region including a thickness of 1 nm or more and 500 nm or less, with reference to the opposite surface of the lithium metal layer facing the base material layer. Y means the lithium element ratio (at%) based on 100 of the element content in the first region including a thickness of 1 nm or more and 500 nm or less, with reference to the opposite surface of the lithium metal layer facing the base material layer. [Formula 2] X1 / Y1 × 100 (%) ≤ 10 In Formula 2, X1 means the oxygen element ratio (at%) based on 100 of the element content in the second region including a thickness of 1500 nm or more and 1800 nm or less, with reference to the opposite surface of the lithium metal layer facing the base material layer. Y1 means the lithium element ratio (at%) based on 100 of the element content in the second region including a thickness of 1500 nm or more and 1800 nm or less, with reference to the opposite surface of the lithium metal layer facing the base material layer.

11. Forming an electrode current collector layer and an electrode active material layer on one or both surfaces of the electrode current collector layer; and Transferring a lithium metal layer onto the electrode active material layer; A method for manufacturing an electrode for a lithium secondary battery, comprising: The step of transferring the lithium metal layer includes preparing a transfer laminate according to any one of claims 1 to 6; laminating the transfer laminate on the electrode active material layer such that the opposite surface of the lithium metal layer facing the base material layer contacts the opposite surface of the electrode current collector layer of the electrode active material layer; and removing the base material layer. A method for manufacturing an electrode for a lithium secondary battery.

12. The laminating step is carried out at a temperature condition of 30°C or lower and a pressure of 200 kgf / cm ２ or lower, for the method of manufacturing an electrode for a lithium secondary battery according to claim 11.

13. 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 an electrode slurry containing the electrode active material layer composition on one or both surfaces of the electrode current collector layer. The method for manufacturing an electrode for a lithium secondary battery according to claim 11, wherein 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.

14. The electrode active material includes a silicon-based active material. The method for manufacturing an electrode for a lithium secondary battery according to claim 13, wherein the silicon-based active material includes one or more selected from the group consisting of SiO x (x = 0), SiO x (0 < x < 2), SiC, and Si alloys.

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

16. 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. The lithium secondary battery, wherein at least one of the positive electrode for a lithium secondary battery and the negative electrode for a lithium secondary battery is an electrode for a lithium secondary battery manufactured by the method of claim 11.

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