Method for manufacturing lithium secondary battery electrode, lithium secondary battery electrode manufactured using same, and lithium secondary battery comprising same

Abstract

The present invention relates to a method for manufacturing a lithium secondary battery electrode, a lithium secondary battery electrode manufactured using same, and a lithium secondary battery comprising same, the method comprising the steps of: making one surface of an electrode active material layer come in contact with a transfer laminate in which a substrate layer and a lithium metal layer are in direct contact with each other, so that the electrode active material layer and the lithium metal layer face each other; and pressing, at a pressure of 6 kgf / cm2 or less, and aging the electrode active material layer in contact with the transfer laminate, wherein the transfer laminate is formed by making the lithium metal layer come in contact with one surface of the substrate layer and rolling same.

Description

Method for manufacturing an electrode for a lithium secondary battery, an electrode for a lithium secondary battery manufactured thereby, and a lithium secondary battery comprising the same

[0001] The present invention relates to a method for manufacturing an electrode for a lithium secondary battery, an electrode for a lithium secondary battery manufactured thereby, and a lithium secondary battery including the same.

[0002] This invention claims the benefit of Korean Patent Application No. 10-2024-0120032, filed with the Korean Intellectual Property Office on September 4, 2024, and Korean Patent Application No. 10-2025-0124502, filed with the Korean Intellectual Property Office on September 3, 2025, the entire contents of which are incorporated herein by reference.

[0003] Due to the rapid increase in fossil fuel use, the demand for alternative or clean energy is increasing, and as part of this, the most actively researched field is power generation and storage using electrochemical reactions.

[0004] A representative example of an electrochemical device that currently utilizes this electrochemical energy is the secondary battery, and its application area is gradually expanding.

[0005] With the increasing technological development and demand for mobile devices, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which boast high energy density and voltage, long cycle life, and low self-discharge rates, are commercialized and widely used. Furthermore, active research is being conducted on methods for manufacturing high-density electrodes with even higher energy density per unit volume as electrodes for these high-capacity lithium secondary batteries.

[0006] Typically, a secondary battery includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, an electrolyte, and the like. In addition, electrodes such as the positive electrode and the negative electrode may have an electrode active material layer provided on a current collector.

[0007] Meanwhile, lithium secondary batteries begin to lose lithium from the first charge after manufacturing. This continued loss, albeit small, occurs during subsequent charge-discharge cycles and high-temperature storage, leading to battery degradation. To compensate for this lithium loss, a pre-lithiation process is employed, which additionally injects lithium into the battery prior to operation. However, the residual lithium left over during the pre-lithiation process is not fully utilized, negatively impacting battery performance.

[0008] [Prior Art Literature]

[0009] [Patent Document]

[0010] (Patent Document 1) Japanese Patent Publication No. 2009-080971

[0011] The present invention provides a method for manufacturing an electrode for a lithium secondary battery for preventing the generation of residual lithium, an electrode for a lithium secondary battery manufactured thereby, and a lithium secondary battery including the same.

[0012] One embodiment of the present specification is a step of contacting a transfer laminate in which a substrate layer and a lithium metal layer are in direct contact with one surface of an electrode active material layer so that the electrode active material layer and the lithium metal layer face each other; and

[0013] The electrode active material layer in contact with the above transfer layer is 6 kgf / cm 2 It includes a step of pressurizing and aging at the following pressure:

[0014] The above-mentioned transfer laminate provides a method for manufacturing an electrode for a lithium secondary battery, wherein the electrode is formed by contacting and rolling a lithium metal layer on one surface of a substrate layer.

[0015] One embodiment of the present specification comprises an electrode current collector layer; and

[0016] Including an electrode active material layer provided on at least one surface of the electrode current collector layer,

[0017] An electrode for a lithium secondary battery manufactured by the above-described manufacturing method is provided.

[0018] One embodiment of the present specification is an electrode for a lithium secondary battery as described above;

[0019] membrane;

[0020] And a lithium secondary battery including an electrolyte is provided.

[0021] Another embodiment of the present disclosure provides a battery module including the aforementioned lithium secondary battery.

[0022] Another embodiment of the present disclosure provides a battery pack including the aforementioned lithium secondary battery.

[0023] Finally, one embodiment of the present disclosure provides a battery pack comprising the battery module described above.

[0024] The method for manufacturing an electrode for a lithium secondary battery according to the embodiments described herein can provide an electrode for a lithium secondary battery having an excellent lithium secondary battery dosage and charge / discharge efficiency by suppressing the generation of residual lithium that is not used for lithium secondary battery charging and remains on the electrode surface, and an electrode for a lithium secondary battery including the same by suppressing the lithium plating phenomenon, thereby improving the life performance and voltage stability.

[0025] Figure 1 is a flow chart showing a method for manufacturing an electrode for a lithium secondary battery according to one embodiment of the present specification.

[0026] Figure 2 is a diagram showing a laminated structure of a lithium secondary battery according to one embodiment of the present specification.

[0027] Figure 3 is a diagram showing the surface appearance of the electrode immediately after pressurization and after completion of prelithiation in examples and comparative examples of the present invention.

[0028] Figure 4 is a diagram showing the results of evaluating the charge / discharge efficiency of half-cells of examples and comparative examples of the present invention.

[0029] Figure 5 is a diagram showing the results of evaluating the lifespan and voltage drop of half-cells of examples and comparative examples of the present invention.

[0030] Before explaining the present invention, some terms are first defined.

[0031] When a part of this specification is said to "include" a certain component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise stated.

[0032] It should be understood that the terms “include,” “comprising,” or “having” used in this specification are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0033] In this specification, when a part of a layer or the like is said to be "above" or "on" another part, this includes not only cases where it is "directly above" the other part, but also cases where there is another part in between. Conversely, when a part is said to be "directly above" another part, it means that there is no other part in between. Furthermore, when a part is said to be "above" or "on" a reference part, it means that it is located above or below the reference part, and does not necessarily mean that it is located "above" or "on" in the direction opposite to gravity.

[0034] In this specification, when it is said that a certain member is provided on "both sides" of another member, this means that a certain member is provided on one side of the other member, and another member is provided on another side corresponding to said side. Furthermore, this includes not only cases where a certain member is in direct contact with one side of another member and its corresponding side, but also cases where another member exists between the two members.

[0035] In this specification, ‘p to q’ means a range of ‘p or more and q or less.’

[0036] In this specification, terms such as “unit”, “device”, etc. mean a unit that processes at least one function or operation.

[0037] In this specification, "Dn" means particle size distribution, and means particle size (average particle size) at the n% point of the cumulative particle number distribution according to particle size. That is, D 50 is the particle size at the 50% point of the cumulative particle number distribution according to particle size, and D 90 D is the particle size at the 90% point of the cumulative distribution of particle numbers according to particle size. 10 is the particle size at the 10% point of the cumulative particle number distribution according to particle size. Meanwhile, the average particle size can be measured using the laser diffraction method. Specifically, after the powder to be measured is dispersed in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500), and the difference in diffraction pattern according to particle size when the particles pass through the laser beam is measured to calculate the particle size distribution.

[0038] In one embodiment of the present specification, particle size or particle diameter may mean the average diameter or representative diameter of each grain forming the metal powder.

[0039] As used herein, the singular expression of a term includes the plural expression unless the context clearly indicates otherwise.

[0040] The terms and words used in this specification should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0041] Hereinafter, preferred embodiments of the present invention will be described in detail. However, the embodiments of the present invention may be modified in various ways, and the scope of the present invention is not limited to the embodiments described below.

[0042] Manufacturing method

[0043] A method for manufacturing an electrode for a lithium secondary battery according to one embodiment of the present specification comprises the steps of: contacting a transfer laminate in which a substrate layer and a lithium metal layer are in direct contact with one surface of an electrode active material layer so that the electrode active material layer and the lithium metal layer face each other; and applying a pressure of 6 kgf / cm to the electrode active material layer contacted by the transfer laminate. 2 A step of pressurizing and aging at the following pressure is included, and the transfer laminate is formed by contacting and rolling a lithium metal layer on one surface of the substrate layer.

[0044] The present invention is a method of electrolithiating a transfer laminate formed by rolling a lithium metal layer on a substrate layer by a direct contact method on an electrode active material layer. In a transfer laminate formed by a rolling method, the substrate layer and the lithium metal layer are in direct contact, and the substrate layer can be easily removed from the lithium metal layer compared to a transfer laminate formed by a deposition method, so there is no need for a separate release layer between the substrate layer and the lithium metal layer. Since a release layer is not provided between the substrate layer and the lithium metal layer, the interference of heat dissipation by the release layer can be prevented. However, since the surface roughness of the lithium metal layer is large and the lithium metal grains fall off and are transferred when transferred onto the electrode active material layer, areas in which the electrode active material layer and the lithium metal layer do not properly contact each other occur. In areas where the lithium metal layer does not make proper contact, lithium that is not used in the pre-lithiation reaction remains on the surface of the electrode. This residual lithium is not easily decomposed during the operation process, which may reduce the pre-lithiation capacity and charge / discharge efficiency, or the residual lithium may act as a seed to form dendrites on the electrode surface. In this case, the lifespan may be rapidly reduced and a sudden voltage drop may occur due to an internal short.

[0045] Therefore, the present invention is characterized in that it can secure excellent lithium dosage and charge / discharge efficiency by suppressing the generation of residual lithium remaining on the electrode surface by evenly contacting the lithium metal layer and the electrode active material layer through the aging step without peeling off the substrate layer, and can improve life performance and voltage stability by suppressing the lithium plating phenomenon. In addition, if high pressure is applied during transfer, a lot of heat is generated as the lithium plating reaction is promoted during the aging step, and the generated heat is not properly dissipated by the substrate layer, so that a thick byproduct layer can be formed at the center of the electrode surface. Therefore, the present invention is characterized in that it can suppress the generation of residual lithium remaining on the electrode surface by evenly contacting the lithium metal layer and the electrode active material layer through the aging step without peeling off the substrate layer, and can secure excellent lithium dosage and charge / discharge efficiency by evenly contacting the lithium metal layer and the electrode active material layer ...2 It is characterized by being able to suppress the formation of a by-product layer on the electrode surface by pressurizing with an appropriate pressure below.

[0046] A method for manufacturing an electrode for a lithium secondary battery according to one embodiment of the present specification includes a step of contacting the transfer laminate with one surface of the electrode active material layer so that the electrode active material layer and the lithium metal layer face each other, and the transfer laminate is such that the substrate layer and the lithium metal layer are in direct contact with each other.

[0047] According to one embodiment of the present specification, a method for manufacturing an electrode for a lithium secondary battery can compensate for irreversible capacity by preventing lithium loss by applying prelithiation, thereby improving battery capacity or cycle performance. At this time, prelithiation methods include prelithiation by an electrochemical method, prelithiation using SLMP, and prelithiation by a direct contact method, and the present invention performs prelithiation by a direct contact method, particularly a transfer method by direct contact of a lithium metal layer, so that lithium remaining on the electrode surface can be minimized, and since it can be applied to a roll-to-roll process useful for mass production of electrodes compared to other methods, the process speed is fast, so it has the advantage of being effective for mass production.

[0048] In one embodiment of the present specification, the step of contacting the transfer laminate with one surface of the electrode active material layer so that the electrode active material layer and the lithium metal layer face each other is a step of laminating the transfer laminate with the lithium metal layer so that the lithium metal layer faces each surface of the electrode active material layer, which is a step for transferring the electrode active material layer to the lithium metal.

[0049] For a transfer method by direct contact with a lithium metal layer, a transfer laminate including a lithium metal layer for lithiating an electrode active material layer and a substrate layer supporting the same is required. Since the transfer laminate is formed by contacting and rolling the substrate layer and the lithium metal layer, the substrate layer and the lithium metal layer may be in direct contact with each other.

[0050] The transfer laminate according to one embodiment of the present specification is in direct contact with the substrate layer and the lithium metal layer without a separate release layer between them, and thus has the advantage that heat dissipation is not hindered by the release layer, and thus the formation of by-products on the surface of the prelithiated electrode is not accelerated.

[0051] In one embodiment of the present specification, the transfer laminate includes a lithium metal layer. In this case, the lithium metal layer is a layer including lithium metal for lithiating one surface of the electrode active material layer, and a commonly used Li metal foil may be used, but is not limited thereto.

[0052] In one embodiment of the present specification, the thickness of the lithium metal layer may be 0.1 μm or more and 30 μm or less, specifically 1 μm or more and 25 μm or less, and more specifically 1 μm or more and 20 μm or less. In this case, the thickness of the lithium metal layer refers to the thickness before rolling on one side of the base layer to form a transfer laminate.

[0053] When the thickness of the lithium metal layer satisfies the above range, the irreversible capacity during charge and discharge of the lithium secondary battery can be sufficiently compensated.

[0054] In one embodiment of the present specification, the substrate layer can be used without limitation as long as it has the characteristics of being able to withstand process conditions such as high pressure in the step of rolling the lithium metal layer and preventing the problem of reverse peeling in which the lithium metal layer is transferred onto the substrate layer during the winding process for transferring the rolled lithium metal layer.

[0055] In one embodiment of the present specification, the substrate layer may be at least one selected from the group consisting of polyethylene terephthalate (PET), polyimide (PI), poly(methylmethacrylate) (PMMA), polypropylene, polyethylene, and polycarbonate, and specifically, at least one selected from the group consisting of polyethylene terephthalate (PET), polyimide (PI), and poly(methylmethacrylate) (PMMA), and more specifically, polyethylene terephthalate (PET).

[0056] In one embodiment of the present specification, the thickness of the substrate layer may be 1 μm or more and 300 μm or less, specifically 5 μm or more and 200 μm or less, and more specifically 10 μm or more and 100 μm or less.

[0057] As the thickness of the above-mentioned substrate layer satisfies the above range, the transfer of lithium metal toward the electrode active material layer can occur efficiently, and it has the characteristic of being able to prevent reverse transfer.

[0058] A transfer laminate according to one embodiment of the present specification may be formed by contacting and rolling the lithium metal layer on one surface of the substrate layer.

[0059] The transfer laminate of the present invention is formed by rolling a lithium metal layer on a substrate layer, so that the substrate layer is easily peeled off, and since a separate release layer does not need to be provided between the substrate layer and the lithium metal layer, heat dissipation is not hindered by the release layer, so there is an advantage in that the formation of by-products on the surface of the prelithiated electrode is not accelerated.

[0060] In the case of a transfer laminate formed by depositing a lithium metal layer on a substrate layer, the peeling force of the substrate layer increases due to the heat generated during deposition, and the thicker the deposited lithium metal layer, the more the peeling force of the substrate layer increases. This makes it difficult to peel the substrate layer during prelithiation, and rather, detachment of the lithium metal layer or the electrode active material layer may occur when the substrate layer is peeled. Therefore, to prevent this, a separate release layer is provided between the substrate layer and the lithium metal layer. For example, when a 5 μm thick lithium metal layer is deposited on the substrate layer, even if a PMMA (polyacrylamide) release layer of about 500 nm is provided between the substrate layer and the lithium metal layer, the peeling force of the substrate layer is significantly high at 53.76 gf / 20 mm (measured at a peeling angle of 90° and a peeling speed of 30 cm / min), and the peeling force increases as the lithium metal layer becomes thicker. However, when a 5 μm lithium metal layer is rolled on the substrate layer, the peeling force of the substrate layer during prelithiation is only 9.38 gf / 20 mm (measured at a peeling angle of 90° and a peeling speed of 30 cm / min), so the substrate layer can be easily removed without a separate release layer. That is, the transfer laminate of the present invention is characterized by the fact that the substrate layer can be easily removed even without a release layer. In addition, the release layer can accelerate the formation of electrode surface byproducts by impeding the dissipation of heat generated by the prelithiation reaction, but the transfer laminate of the present invention can prevent the above problem because it does not have a release layer.

[0061] The method for manufacturing an electrode for a lithium secondary battery according to one embodiment of the present specification may further include a step of forming a transfer laminate by contacting and rolling a lithium metal layer on one surface of a substrate layer, and the step of contacting the lithium metal layer on one surface of the substrate layer and the step of rolling may be performed sequentially or simultaneously, and there is no limitation thereon.

[0062] Specifically, a transfer laminate according to one embodiment of the present specification can be manufactured by contacting a lithium metal layer with one surface of a substrate layer and then rolling at room temperature using a roll-to-roll method. More specifically, the laminate can be manufactured by rolling the lithium metal layer several times until the lithium metal layer reaches a target thickness. In this case, the target thickness of the lithium metal layer may be 0.1 μm or more and 15 μm or less. In addition, the contact and rolling may be performed simultaneously or sequentially.

[0063] That is, in one embodiment of the present specification, the thickness of the lithium metal layer after contacting and rolling one surface of the substrate layer may be 0.1 μm or more and 15 μm or less, specifically 1 μm or more and 10 μm or less, and more specifically 1 μm or more and 6 μm or less. When the thickness of the lithium metal layer after contacting and rolling satisfies the above range, the irreversible capacity during charging and discharging of the lithium secondary battery can be sufficiently compensated.

[0064] In addition, when forming a transfer laminate according to one embodiment of the present specification, the pressure when rolling by the roll-to-roll method is 80 kgf / cm 2 It could be strange.

[0065] That is, in one embodiment of the present specification, the transfer laminate contacts a lithium metal layer on one side of the substrate layer and applies 80 kgf / cm 2 It may be formed by rolling under a pressure of more than 90 kgf / cm. Specifically, 2Above, more specifically 100kgf / cm 2 It may be formed by rolling under the above pressure.

[0066] In addition, in one embodiment of the present specification, the transfer laminate is formed by contacting a lithium metal layer on one surface of the substrate layer and applying 300 kgf / cm 2 It may be formed by rolling under a pressure below, specifically 280 kgf / cm 2 Below, more specifically 250 kgf / cm 2 It may be formed by rolling under the following pressure.

[0067] However, in the transfer laminate formed by rolling a lithium metal layer on one side of the substrate layer as described above, when transferred to the electrode active material layer, the grains of the lithium metal layer fall off, making it difficult to perform the transfer cleanly, and the surface roughness of the lithium metal layer portion of the transfer laminate increases, and areas that do not make proper contact with the electrode occur. The portion of the lithium metal layer that does not make proper contact with the electrode does not undergo lithiation all the way into the electrode and remains on the electrode surface. In order to prevent this, if high pressure is applied after contact of the transfer laminate with the electrode active material layer, the lithiation reaction may become excessively active, the amount of heat generated may increase, and a by-product layer may be formed, and damage to the active material layer on the electrode surface may also occur.

[0068] Therefore, the present invention aims to suppress the formation of residual lithium remaining on the electrode surface by applying an appropriately low pressure when pressing after contact of a transfer laminate with an electrode active material layer, and to perform a clean lithiation reaction without forming a by-product layer or damaging the active material layer.

[0069] In one embodiment of the present specification, the step of contacting a transfer laminate with one surface of the electrode active material layer and the step of pressing the electrode active material layer with which the transfer laminate has contacted may be performed sequentially or simultaneously, and there is no limitation thereon.

[0070] For example, when the step of contacting a transfer laminate with one surface of the electrode active material layer and the step of pressing the electrode active material layer with which the transfer laminate has contacted are performed sequentially, the prelithiation reaction may start from the moment a point of the transfer laminate contacts one surface of the electrode active material layer, or the prelithiation reaction may start from the moment a point of the electrode active material layer with which the transfer laminate has contacted is pressed, and there may be a time difference of several seconds to several minutes between the contacting step and the pressing step.

[0071] For example, when the step of contacting a transfer laminate with one surface of the electrode active material layer and the step of pressing the electrode active material layer with which the transfer laminate has contacted are performed simultaneously, the point of the electrode active material layer with which the transfer laminate has contacted may be pressed at the same time as the moment when the point of the transfer laminate is contacted with one surface of the electrode active material layer, and in this case, the lithiation reaction may start from the moment when the contact and pressing begin, and may start several seconds to several minutes later.

[0072] A method for manufacturing an electrode for a lithium secondary battery according to one embodiment of the present specification comprises: applying a pressure of 6 kgf / cm to the electrode active material layer in contact with the transfer laminate; 2 It includes a step of pressurizing and aging at the following pressure.

[0073] The method for manufacturing an electrode for a lithium secondary battery according to one embodiment of the present specification has the effect of enabling more active prelithiation due to transfer to an electrode active material layer through the pressurizing step, and forming the electrode thin despite having a high energy density.

[0074] In one embodiment of the present specification, the pressure in the pressurizing step is 6 kgf / cm 2 Below, specifically 4.5 kgf / cm 2Below, more specifically 4.2 kgf / cm 2 It could be as follows:

[0075] In addition, in one embodiment of the present specification, the pressure in the pressurizing step is 1 kgf / cm 2 Above, specifically 1.5 kgf / cm 2 Above, more specifically 2kgf / cm 2 It could be strange.

[0076] In one embodiment of the present specification, when the pressure in the pressurizing step satisfies the above range, the electrode active material layer and the lithium metal layer can be brought into even contact, thereby suppressing the formation of residual lithium remaining on the surface of the electrode after the pre-lithiation is completed, and pre-lithiation can be performed cleanly without damage to the electrode active material layer or by-product layer.

[0077] A method for manufacturing an electrode for a lithium secondary battery according to one embodiment of the present specification includes a step of aging the electrode active material layer in contact with the transfer laminate. The aging step is a step of storing the electrode active material layer while one surface thereof reacts with a lithium metal layer and is prelithiated.

[0078] In one embodiment of the present specification, the aging step may be performed before the step of pressing the electrode active material layer in contact with the transfer laminate, may be performed simultaneously, or may be performed after the step of pressing, and there is no limitation thereon.

[0079] For example, the aging may begin several seconds to several minutes before pressurization begins at a point on the electrode active material layer that the transfer laminate contacts. In this case, the aging step may begin simultaneously with the step of contacting the transfer laminate, or may begin within several seconds to several minutes from the step of contacting. In this case, the prelithiation reaction may proceed before the pressurization step, and the pressurization step may be a step for promoting the prelithiation reaction.

[0080] For example, the aging may begin simultaneously with the moment when pressure is applied at a point on the electrode active material layer that the transfer laminate contacts. In this case, the step of contacting the transfer laminate, the step of pressing, and the step of aging may all begin simultaneously, or the step of pressing and the step of aging may begin within seconds to minutes of the step of contacting.

[0081] For example, the aging may begin from the moment when the pressurization is terminated at the last point of the electrode active material layer that the transfer laminate is in contact with.

[0082] In one embodiment of the present specification, the aging step may be performed at any one temperature of 0°C or more and 40°C or less, specifically at any one temperature of 10°C or more and 30°C or less, and more specifically at any one temperature of 20°C or more and 28°C or less.

[0083] In one embodiment of the present specification, the aging step may be performed at room temperature.

[0084] In a method for manufacturing an electrode for a lithium secondary battery according to one embodiment of the present specification, the temperature range of the aging step can be controlled within the above range to control the rate of the prelithiation reaction within an appropriate range.

[0085] In one embodiment of the present specification, in the aging step, the transfer laminate may be in a state including the substrate layer until the prelithiation of one side of the electrode active material layer is completed. At this time, whether the prelithiation is completed can be confirmed by visually observing the color change of the electrode surface. Specifically, it can be confirmed that the surface of the electrode, which was silver like lithium metal immediately after lithium transfer, completely changes to the original color of the electrode (black) after the prelithiation is completed. At this time, since the substrate layer is transparent, the silver color of the lithium metal or the original color of the electrode can be confirmed regardless of whether the substrate layer is peeled off.

[0086] The present invention promotes a chemical reaction between an electrode active material layer and a lithium metal layer by carrying out the process of contacting a transfer laminate with an electrode active material layer and then pressing and aging without removing the substrate layer, thereby suppressing the formation of residual lithium remaining on the electrode surface. However, if the pressurizing process is performed with a large pressure, the prelithiation reaction may be promoted, which may cause a problem in that a thick by-product layer is formed on the electrode surface after aging. Therefore, the present invention suppresses the formation of residual lithium and the formation of a by-product layer on the electrode surface by pressing with an appropriate pressure that satisfies the range according to one embodiment of the present specification.

[0087] A method for manufacturing an electrode for a lithium secondary battery according to one embodiment of the present specification may further include a step of removing the substrate layer from the transfer laminate after the aging step.

[0088] In one embodiment of the present specification, the step of removing the substrate layer may be performed after the lithiumization is completed.

[0089] In one embodiment of the present specification, the prelithiation may be a prelithiation reaction between the electrode active material layer and the lithium metal layer that starts from the time point at which the lithium metal layer comes into contact with one surface of the electrode active material layer, may start within several seconds to several minutes from the time point at which the lithium metal layer comes into contact, or may start from the time point at which the base layer begins to be removed.

[0090] In one embodiment of the present specification, the lithiation reaction may be completed within several days from the time the lithium metal layer comes into contact with one surface of the electrode active material layer, may be completed within 24 hours, or may be completed within several minutes to several seconds.

[0091] Figure 1 is a flow chart showing a method for manufacturing an electrode for a lithium secondary battery according to one embodiment of the present specification.

[0092] Specifically, FIG. 1(a) is a step (S1) of contacting a transfer laminate in which a substrate layer and a lithium metal layer are in direct contact with one surface of an electrode active material layer so that the electrode active material layer and the lithium metal layer face each other; and the electrode active material layer contacted by the transfer laminate is applied with a pressure of 6 kgf / cm 2 A method for manufacturing an electrode for a lithium secondary battery is shown, including a step (S2) of pressurizing and aging at the following pressure. Although not shown in Fig. 1(a), the transfer laminate may be formed by contacting and rolling a lithium metal layer on one surface of a substrate layer. In one embodiment of the present specification according to Fig. 1(a), the step (not shown) of preparing an electrode active material layer on at least one surface of an electrode current collector layer may be performed in a step before step S1 of Fig. 1(a).

[0093] FIG. 1(b) shows a method for manufacturing an electrode for a lithium secondary battery, including a step (S1-1) of forming a transfer laminate by contacting and rolling a lithium metal layer on one surface of a substrate layer; a step (S1-2) of contacting a transfer laminate on one surface of an electrode active material layer so that the electrode active material layer and the lithium metal layer face each other; a step (S2-1) of pressing the electrode active material layer and the transfer laminate together; a step (S2-2) of aging the electrode active material layer and the transfer laminate together; and a step (S3) of removing a substrate layer from the transfer laminate.

[0094] At this time, steps S2-1 to S2-2 of Fig. 1(b) may be performed simultaneously or each step may be performed sequentially, but there is no limitation on this.

[0095] In one embodiment of the present specification according to FIG. 1(b), the step (not shown) of preparing an electrode active material layer on at least one surface of the electrode current collector layer may be performed before step S1-1, may be performed simultaneously with step S1-1, or may be performed in a step between S1-1 and S1-2, and there is no limitation thereon.

[0096] In addition, in step S1 or S1-2 of FIG. 1(a) and FIG. 1(b), the electrode active material layer may be provided on one side of the electrode current collector layer or may be provided on both sides, and there is no limitation thereon.

[0097] Electrode active material layer

[0098] A method for manufacturing an electrode for a lithium secondary battery according to one embodiment of the present specification may further include a step of providing an electrode active material layer on at least one surface of an electrode current collector layer before the step of contacting the transfer laminate with one surface of the electrode active material layer.

[0099] In this specification, the 'electrode' may be a cathode or an anode, and specifically, may be a cathode.

[0100] That is, in one embodiment of the present specification, the step of providing an electrode active material layer on at least one surface of the electrode current collector layer may be a step of providing a negative electrode active material layer on at least one surface of the negative electrode current collector layer, or may be a step of providing a positive electrode active material layer on at least one surface of the positive electrode current collector layer.

[0101] Below, the step of preparing a negative electrode active material layer is first described, but the same method can also be applied to the step of preparing a positive electrode active material layer.

[0102] The step of providing a negative electrode active material layer on at least one surface of the negative electrode current collector layer according to one embodiment of the present specification includes the step of preparing a negative electrode slurry; and the step of applying and drying the negative electrode slurry on at least one surface of the negative electrode current collector layer.

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

[0104] In one embodiment of the present specification, the solid content of the cathode slurry can satisfy a range of 1% or more and 40% or less, specifically 5% or more and 35% or less, and more specifically 7% or more and 30% or less.

[0105] In the present specification, the solid content of the negative electrode slurry may mean the content of the negative electrode active material layer composition included in the negative electrode slurry, and may mean the content of the negative electrode active material composition based on 100 parts by weight of the negative electrode slurry.

[0106] When the solid content of the above-mentioned negative electrode slurry satisfies the above range, the viscosity is appropriate when forming the negative electrode active material layer, thereby minimizing particle agglomeration of the negative electrode active material layer composition, thereby enabling the formation of the negative electrode active material layer efficiently.

[0107] In one embodiment of the present specification, the slurry solvent is not limited thereto as long as it can dissolve the negative electrode active material layer composition, and for example, the slurry solvent may be water (e.g., distilled water) or NMP.

[0108] According to one embodiment of the present specification, a negative electrode can be formed by applying and drying the negative electrode slurry on a negative electrode current collector layer, and the slurry solvent in the negative electrode slurry can be dried through the drying step.

[0109] In one embodiment of the present specification, the negative electrode active material layer composition may include at least one selected from the group consisting of a negative electrode active material described below; a negative electrode binder; and a conductive dispersion, and specifically, the negative electrode active material may include a carbon-based active material and a silicon-based active material.

[0110] In other words, the negative electrode active material layer according to one embodiment of the present specification may include a carbon-based active material and a silicon-based active material as the negative electrode active material, and the silicon-based active material may include at least one selected from the group consisting of Si, silicon oxide, Si / C, and Si alloy.

[0111] Specifically, in one embodiment of the present specification, the silicon-based active material may include at least one selected from the group consisting of Si and silicon oxide, and more specifically, the silicon-based active material may include Si.

[0112] In one embodiment of the present specification, the carbon-based active material may include at least one selected from the group consisting of graphite such as natural graphite or artificial graphite, carbon fiber, non-graphitizable carbon, carbon black, carbon nanotubes, fullerene, and activated carbon, and specifically, may include at least one selected from the group consisting of natural graphite and artificial graphite.

[0113] When the above carbon-based active material is used as an anode active material according to one embodiment of the present specification, reversible lithium ion intercalation and deintercalation are possible, and structural and electrical properties can be maintained. Among these, the graphite-based active material can guarantee the life characteristics of a lithium secondary battery due to its excellent reversibility. Since the graphite-based active material has a low discharge voltage of -0.2 V compared to lithium, a battery using the graphite-based active material can exhibit a high discharge voltage of 3.6 V, and thus can provide many advantages in terms of energy density of a lithium secondary battery.

[0114] In one embodiment of the present specification, when artificial graphite is used as a carbon-based active material, the orientation degree is relatively low during electrode rolling, so that the lithium ion inflow / outflow characteristics are good, and thus the rapid charging performance of the battery is excellent, and the degree of expansion due to charge and discharge is low, so that the life characteristics can be excellent.

[0115] In one embodiment of the present specification, the average particle diameter (D) of the artificial graphite 50 ) may be 5 μm or more and 20 μm or less, preferably 8 μm or more and 18 μm or less, and more preferably 10 μm or more and 16 μm or less.

[0116] In one embodiment of the present specification, when natural graphite is used as a carbon-based active material, the output and capacity of a lithium secondary battery are improved, and since the adhesive strength is excellent, the amount of binder, etc. used can be reduced, and a high-capacity, high-density negative electrode can be realized. In this case, the natural graphite may generally be in the form of a plate-shaped aggregate before being processed, and the plate-shaped particles may be manufactured into a spherical shape with a smooth surface through post-processing such as particle crushing and reassembly processes in order to be used as an active material for manufacturing an electrode.

[0117] In one embodiment of the present specification, the average particle diameter (D) of the natural graphite 50) may be 5 μm or more and 20 μm or less, preferably 7 μm or more and 18 μm or less, and more preferably 9 μm or more and 15 μm or less.

[0118] In one embodiment of the present specification, the negative electrode active material layer includes a carbon-based active material and a silicon-based active material as the negative electrode active material, and the carbon-based active material includes at least one selected from the group consisting of natural graphite and artificial graphite, and the silicon-based active material may include Si.

[0119] In one embodiment of the present specification, the negative electrode active material may include the carbon-based active material and the silicon-based active material in a weight ratio of 95:5 to 40:60, specifically, in a weight ratio of 90:10 to 50:50, and more specifically, in a weight ratio of 85:15 to 60:40.

[0120] In one embodiment of the present specification, the negative electrode active material may be included in an amount of 60 parts by weight or more and 99 parts by weight or less based on 100 parts by weight of the negative electrode active material layer, specifically, 70 parts by weight or more and 98 parts by weight or less, and more specifically, 80 parts by weight or more and 97 parts by weight or less.

[0121] In one embodiment of the present specification, the conductive dispersion may include a cathode conductive material and a dispersant.

[0122] In one embodiment of the present specification, the negative electrode conductive material is a material used to improve the electron transfer characteristics between active materials or between active materials and a current collector, and is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, paneth black, lamp black, thermal black; conductive fibers such as carbon fiber or metal fiber; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive materials such as polyphenylene derivatives can be used.

[0123] In one embodiment of the present specification, the negative electrode conductive material may include at least one selected from the group consisting of graphite, carbon black, graphene, and carbon nanotubes (CNTs), and specifically may include carbon nanotubes (CNTs).

[0124] In one embodiment of the present specification, the 'carbon nanotube' is a secondary structure formed by assembling carbon nanotube units in a bundle shape in whole or in part, and the carbon nanotube units have a graphite sheet in the shape of a cylinder with a nano-sized diameter, and sp 2It has a bonding structure. At this time, depending on the angle and structure at which the graphite plane is rolled, it can exhibit the characteristics of a conductor or a semiconductor. The carbon nanotube unit can be classified into single-walled carbon nanotube (SWCNT, single-walled carbon nanotube), double-walled carbon nanotube (DWCNT, double-walled carbon nanotube), and multi-walled carbon nanotube (MWCNT, multi-walled carbon nanotube) depending on the number of bonds forming the wall, and the thinner the wall thickness, the lower the resistance.

[0125] In one embodiment of the present specification, the negative electrode conductive material may further include graphite, carbon black, graphene, etc., and any conductive material that does not cause chemical changes in the battery may be used without limitation.

[0126] In one embodiment of the present specification, the dispersant is for improving the dispersibility of the negative electrode conductive material and ensuring stability after dispersion, and may be, for example, a cellulose-based polymer, at least one selected from the group consisting of carboxymethyl cellulose (CMC), methyl cellulose (MC), hydroxypropyl cellulose (HPC), methyl hydroxypropyl cellulose (MHPC), ethyl hydroxyethyl cellulose (EHEC), methyl ethyl hydroxyethyl cellulose (MEHEC), and cellulose gum.

[0127] In one embodiment of the present specification, the content of the conductive dispersion in the negative electrode active material layer may be 0.01 parts by weight to 30 parts by weight, specifically 0.01 parts by weight to 10 parts by weight, based on 100 parts by weight of the negative electrode active material layer composition.

[0128] In one embodiment of the present specification, the negative electrode binder may serve to improve adhesion between negative electrode active material particles and adhesive strength between the negative electrode active material particles and the negative electrode current collector. The above-mentioned negative electrode binder may be one known in the art, and non-limiting examples thereof include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluoroelastomer, polyacrylic acid, and a material in which hydrogens thereof are substituted with Li, Na, Ca, etc., and may also include various copolymers thereof.

[0129] In particular, the negative electrode binder according to one embodiment of the present specification serves to hold the negative electrode active material and the negative electrode conductive material in order to prevent distortion and structural deformation of the negative electrode structure in the expansion and relaxation of the volume of the silicon-based active material, and all general negative electrode binders satisfying the above-mentioned role can be applied, and specifically, styrene butadiene rubber (SBR) binder and carboxymethyl cellulose (CMC) can be used.

[0130] In one embodiment of the present specification, the content of the negative electrode binder may include 30 parts by weight or less, specifically 25 parts by weight or less, and more specifically 20 parts by weight or less, based on 100 parts by weight of the negative electrode active material layer composition, and may include 1 part by weight or more, specifically 3 parts by weight or more.

[0131] In one embodiment of the present specification, the negative electrode current collector layer may generally have a thickness of 1 μm to 100 μm, specifically 3 μm to 50 μm, and more specifically 5 μm to 40 μm. The negative electrode current collector layer is not particularly limited as long as it has high conductivity without causing a chemical change in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. may be used. In addition, the bonding strength of the negative electrode active material may be strengthened by forming fine unevenness on the surface, and may be used in various forms such as a film, sheet, foil, net, porous body, foam, and non-woven fabric.

[0132] In one embodiment of the present specification, the step of providing an electrode active material layer on at least one surface of the electrode current collector layer may be a step of providing a positive electrode active material layer on at least one surface of the positive electrode current collector layer.

[0133] In one embodiment of the present specification, the step of providing a positive electrode active material layer on at least one surface of the positive electrode current collector layer may include the steps of preparing a positive electrode slurry containing a positive electrode active material; and applying and drying the positive electrode slurry on at least one surface of the positive electrode current collector layer.

[0134] In one embodiment of the present specification, the positive electrode active material layer may include a lithium composite transition metal compound as the positive electrode active material, which includes nickel (Ni) and cobalt (Co), and further includes one or more elements selected from the group consisting of Na, K, Mg, Ca, Sr, Ni, Co, Ti, Al, Si, Sn, Mn, Cr, Fe, V, and Zr.

[0135] In one embodiment of the present specification, the positive electrode active material layer may include a lithium composite transition metal compound including nickel (Ni), cobalt (Co), and manganese (Mn) as the positive electrode active material.

[0136] In one embodiment of the present specification, the positive electrode slurry includes a positive electrode conductive material, a positive electrode binder, and may further include a thickener and a slurry solvent.

[0137] In one embodiment of the present specification, additional components such as the positive electrode current collector layer, positive electrode conductive material, positive electrode binder, thickener, and slurry solvent, and the method for manufacturing the positive electrode may be used without limitation as long as they are known in the art within the scope to which the above-described description applies.

[0138] Electrodes for lithium secondary batteries and lithium secondary batteries

[0139] An electrode for a lithium secondary battery according to one embodiment of the present specification includes an electrode current collector layer; and an electrode active material layer provided on at least one surface of the electrode current collector layer, and may be manufactured using the manufacturing method described above.

[0140] An electrode for a lithium secondary battery according to one embodiment of the present specification may have increased lithium storage capacity and charge / discharge efficiency by suppressing the generation of residual lithium that is not easily decomposed during the driving process.

[0141] Specifically, the prelithiation dosage of the electrode for a lithium secondary battery according to one embodiment of the present specification is 0.7 mAh / cm 2And the charging and discharging efficiency can be over 93%.

[0142] At this time, the prelithiation dosage can be obtained from the difference in charge (lithiation) capacity between a half-cell manufactured using an electrode for a lithium secondary battery according to one embodiment of the present specification and a half-cell using an electrode manufactured under all the same conditions except that prelithiation was not applied.

[0143] The above half-cell comprises a lithium secondary battery electrode manufactured above as a working electrode and a counter electrode of 1.7671 cm 2 A 100 μm thick lithium metal thin film cut into a circle can be used, a polyethylene separator is interposed between the working electrode and the counter electrode to manufacture an electrode assembly, and then the electrode assembly is built into a coin-type case and the manufactured electrolyte is injected therein. At this time, the electrolyte used may be a mixed organic solvent of EC (ethylene carbonate) / EMC (ethyl methyl carbonate) / DEC (diethyl carbonate) = 20 / 70 / 10 (Vol%), in which FEC (fluoroethylene carbonate) is added at 10 wt% with respect to the total 100 wt% of the electrolyte, and LiPF6 as a lithium salt is added at a concentration of 1.0 M.

[0144] In addition, the charge / discharge efficiency of the electrode for the lithium secondary battery can be obtained by the following equation E. At this time, when measuring the charge (lithiation) capacity, the rate is 0.1C, the lower limit voltage is 5mV, the CCCV condition is set, and the cut-off current is 0.005C, and when measuring the discharge (de-lithiation) capacity, the rate is 0.1C, the upper limit voltage is 1.5V, and the CC condition is set, and the charge and discharge capacities obtained through this are substituted into the following equation E to calculate the charge / discharge efficiency.

[0145] [Formula E]

[0146] Charge / discharge efficiency (%) = {(discharge capacity (mAh / cm 2 )) / (Charging capacity (mAh / cm) 2 ))} x 100%

[0147] A lithium secondary battery according to one embodiment of the present specification may include the aforementioned lithium secondary battery electrode; a separator; and an electrolyte. By including the aforementioned lithium secondary battery electrode, the lithium secondary battery can prevent lithium plating due to residual lithium generation on the electrode surface, thereby enabling normal operation and ensuring excellent life performance and voltage stability.

[0148] In one embodiment of the present specification, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used as a separator in secondary batteries can be used without special restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0149] In one embodiment of the present specification, the electrolyte may include, but is not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc. that can be used in the manufacture of a lithium secondary battery.

[0150] FIG. 2 is a diagram showing a laminated structure of a lithium secondary battery according to an embodiment of the present specification. Specifically, a lithium secondary battery negative electrode (100) including a negative electrode active material layer (20) on one surface of a negative electrode current collector layer (10) can be confirmed, and a lithium secondary battery positive electrode (200) including a positive electrode active material layer (40) on one surface of a positive electrode current collector layer (50) can be confirmed, and it is shown that the lithium secondary battery negative electrode (100) and the lithium secondary battery positive electrode (200) are formed in a laminated structure with a separator (30) interposed therebetween. At this time, the lithium secondary battery electrode according to an embodiment of the present specification may be the lithium secondary battery negative electrode (100) or the lithium secondary battery positive electrode (200), and specifically, may be the lithium secondary battery negative electrode (100).

[0151] According to another embodiment of the present specification, a battery module including the lithium secondary battery as a unit cell, a battery pack including the same, and a battery pack including the lithium secondary battery can be provided. The battery module and the battery pack include the lithium secondary battery having high capacity, high rate characteristics, and cycle characteristics, and thus can 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.

[0152] Hereinafter, preferred embodiments are presented to help understand the present invention, but the above embodiments are only illustrative of the present disclosure, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and technical idea of ​​the present disclosure, and it is natural that such changes and modifications fall within the scope of the appended patent claims.

[0153] Manufacturing example

[0154] Example 1

[0155] <Electrode Manufacturing>

[0156] A negative electrode slurry was prepared by including 16 kg (96.28 parts by weight) of Si and graphite in a ratio of 15:85 as negative electrode active materials, 0.4 kg (2.4 parts by weight) of SBR (styrene butadiene rubber) and 0.2 kg (1.2 parts by weight) of CMC (carboxymethyl cellulose) as binders, and, in addition, 0.01 kg of a dispersant and 0.12 parts by weight of a CNT predispersion solution containing 0.01 kg of single-wall CNT.

[0157] The above cathode slurry was placed on a copper foil (thickness 15 μm) with a capacity per unit area of ​​4.3 mAh / cm. 2 The negative electrode active material layer was manufactured by coating and drying to achieve this.

[0158] After contacting a lithium metal layer on one side of a polyethylene terephthalate (PET) substrate, a roll-to-roll method is applied at room temperature under 100 kgf / cm until the thickness of the lithium metal layer becomes 5 μm. 2 A transfer laminate was prepared by repeatedly rolling under the above pressure.

[0159] After contacting the transfer laminate so that the lithium metal layer is in contact with the upper part of the negative active material layer in a dry room, 4.2 kgf / cm 2 Pressurized with a pressure of , and aging was performed at a temperature of 25℃ until the full lithiumization was completed without peeling off the substrate layer, resulting in 0.838 mAh / cm 2 A lithium-ion cathode was manufactured with a capacity of .

[0160] At this time, the completion of the lithium conversion was confirmed by the complete change of the silver-colored cathode surface to black due to the transfer of the lithium metal layer.

[0161] <Half-cell manufacturing>

[0162] The cathode manufactured above is used as the working electrode, and 1.7671 cm is used as the counter electrode. 2An electrode assembly was manufactured by using a 100 μm thick lithium metal thin film cut into a circular shape and interposing a polyethylene separator between the working electrode and the counter electrode.

[0163] In addition, an electrolyte was prepared by adding 10 wt% of FEC (fluoroethylene carbonate) to a mixed organic solvent of EC (ethylene carbonate) / EMC (ethyl methyl carbonate) / DEC (diethyl carbonate) = 20 / 70 / 10 (Vol%) based on 100 wt% of the total electrolyte, and adding LiPF6 as a lithium salt at a concentration of 1.0 M.

[0164] The above electrode assembly was built into a coin-type case, and the manufactured electrolyte was injected to manufacture a coin-type half-cell lithium secondary battery.

[0165] Comparative Example 1

[0166] The transfer laminate is contacted so that the lithium metal layer is in contact with the upper part of the negative active material layer and 4.2 kgf / cm 2 An electrode and half-cell for a lithium secondary battery of Comparative Example 1 were manufactured in the same manner as in Example 1, except that the substrate layer was peeled off immediately after pressurization (i.e., aging was performed with the substrate layer peeled off).

[0167] Comparative Example 2

[0168] The transfer laminate is contacted so that the lithium metal layer is in contact with the upper part of the negative active material layer and 6.7 kgf / cm 2 An electrode and half-cell for a lithium secondary battery of Comparative Example 2 were manufactured in the same manner as Comparative Example 1 (i.e., aging was performed with the substrate layer peeled off), except that the electrode was pressurized with a pressure of .

[0169] Comparative Example 3

[0170] The transfer laminate is contacted so that the lithium metal layer is in contact with the upper part of the negative active material layer and 6.7 kgf / cm 2An electrode and half-cell for a lithium secondary battery of Comparative Example 3 were manufactured in the same manner as in Example 1 (i.e., aging was performed without peeling off the substrate layer), except that the electrode was pressurized with a pressure of .

[0171] Comparative Example 4

[0172] An electrode and half-cell for a lithium secondary battery of Comparative Example 4 were manufactured in the same manner as in Example 1, except that the transfer layer was not contacted (i.e., prelithiation was not performed).

[0173] The pressure in the pressing step after contact with the transfer laminate during the manufacture of the lithium secondary battery electrodes of Example 1 and Comparative Examples 1 to 3 and the removal of the substrate layer in the aging step (if aging was performed with the substrate layer peeled off, it was marked as 'O', and if aging was performed without peeling off, it was marked as 'X') are summarized in Table 1 below. Comparative Example 4 was marked as '-' because prelithiation was not performed by contact with the transfer laminate.

[0174] Pressure (kgf / cm) 2 ) Base layer removal example 14.2X Comparative example 14.2O Comparative example 26.7O Comparative example 36.7X Comparative example 4--

[0175] Experimental Example 1: Evaluation of the formation of residual lithium and by-product layers on the electrode surface.

[0176] For the lithium secondary battery electrodes of Example 1 and Comparative Examples 1 to 3, the appearance of the electrode surface immediately after contact and pressurization of the transfer laminate and the appearance of the electrode surface after completion of prelithiation were photographed (photographing equipment: digital camera) and are shown in Fig. 3.

[0177] The electrode of Example 1 is 6 kgf / cm 2Even though the pressure was applied at a low pressure below, the aging process was performed without peeling off the substrate layer, which promoted the chemical reaction between the electrode active material layer and the lithium metal layer. As a result, no residual lithium was generated on the surface of the electrode after the pre-lithiation process was completed, as confirmed in Fig. 3(a). In addition, since the pressure was applied at a low pressure, the amount of heat generated by the pre-lithiation process was not large, so it was confirmed that the pre-lithiation process was completed cleanly without the formation of a by-product layer.

[0178] However, 6kgf / cm 2 In the electrode of Comparative Example 1, which was aged with the substrate layer peeled off immediately after pressurization at the low pressure below, the surface of the lithium metal layer of the transfer laminate formed by rolling was uneven, so there was an area where the electrode active material layer and the lithium metal layer did not properly contact each other, and as a result, a considerable amount of residual lithium was generated on the electrode surface, as confirmed through Fig. 3(b).

[0179] The electrode of Comparative Example 3 was aged until the full-lithiation was completed without peeling off the substrate layer, but at 6 kgf / cm 2 As the lithium ion reaction actively occurred under high pressure exceeding , a lot of heat was generated, and the generated heat was trapped by the substrate layer, forming a thick by-product layer on the surface of the center of the electrode, as shown in Fig. 3(d). This thick by-product layer is mainly composed of Li3N, and since it does not decompose during charge and discharge, it acts as a resistive layer that increases the resistance by causing Li loss.

[0180] The electrode of comparative example 2 is 6 kgf / cm 2As the lithium ion reaction actively occurred by pressurizing at excessively high pressure, almost no lithium remained on the electrode surface, and as the substrate layer was peeled off and aged, it was confirmed through Fig. 3(c) that a thick byproduct layer was not formed on the surface of the center of the electrode. However, as can be confirmed in Experimental Example 2 below, the electrode of Comparative Example 2 had a problem in that the initial temperature increased rapidly.

[0181] Experimental Example 2: Initial Temperature Evaluation of the Electrode Surface

[0182] In order to confirm whether the initial temperature increases due to the heat of reaction and heat generated by the lithium metal layer reacting with the air in the dry room and the prelithiation when aging is performed with the substrate layer peeled off, the initial peak temperatures of the electrodes of Comparative Examples 1 and 2, which were aged with the substrate layer peeled off, were measured and are shown in Table 2 below.

[0183] The initial peak temperature of the electrode was measured by fixing a k-type thermocouple to the electrode surface that was in contact with the lithium metal layer immediately after removing the substrate layer.

[0184] Pressure (kgf / cm) 2 ) Base layer removal Initial peak temperature (℃) Comparative example 14.2024 Comparative example 26.7030

[0185] Referring to Table 2 above, the electrode of Comparative Example 2, which was pressurized at a higher pressure than the pressurization pressure of Comparative Example 1, generated more heat as the prelithiation reaction was further promoted, and the heat generated by the oxidation reaction of the lithium metal layer exposed by peeling off the substrate layer immediately after pressurization and the air in the dry room was added to confirm that the initial peak temperature of the electrode was significantly higher than that of Comparative Example 1. In other words, it can be seen that Comparative Example 2 has a higher possibility of occurring a thermal runaway phenomenon, etc., compared to Example 1, Comparative Example 1, or 3.

[0186] Experimental Example 3: Evaluation of Charge-Discharge Efficiency of Half-Cells

[0187] Residual lithium generated on the electrode surface during the pre-lithiation process may occur due to poor contact between the lithium metal layer and the electrode active material layer, and since this is not easily decomposed during the battery operation process, the degree of pre-lithiation varies, resulting in differences in efficiency when measuring half-cell capacity.

[0188] To verify this, the half-cells of Example 1, which was aged without peeling off the substrate layer, Comparative Example 1, which was aged with all conditions identical to Example 1 except for peeling off the substrate layer, and Comparative Example 4, which was aged with all conditions identical to Example 1 except for not performing prelithiation, were used to measure the prelithiation dosage and efficiency, and the results are shown in Figure 4 and Table 3 below.

[0189] Specifically, the pre-lithiation dosage can be obtained from the difference in charge (lithiation) capacity with respect to the half-cell of Comparative Example 4 to which pre-lithiation was not applied, and the charge / discharge efficiency can be obtained by the following Equation E. At this time, when measuring the charge (lithiation) capacity, the rate was 0.1C, the lower limit voltage was 5mV, the CCCV conditions were set, and the cut-off current was 0.005C, and when measuring the discharge (de-lithiation) capacity, the rate was 0.1C, the upper limit voltage was 1.5V, and the CC conditions were set. The charge and discharge capacities obtained through this were substituted into the following Equation E to calculate the charge / discharge efficiency.

[0190] [Formula E]

[0191] Charge / discharge efficiency (%) = {(discharge capacity (mAh / cm 2 )) / (Charging capacity (mAh / cm) 2 ))} x 100%

[0192] Charging capacity (mAh / cm) 2 )Discharge capacity (mAh / cm 2 ) Lithium dosage (mAh / cm) 2)Charge / discharge efficiency (%)Example 13.9193.8010.83896.99Comparative example 14.1003.8010.65792.71Comparative example 44.7573.802-79.93

[0193] Referring to Table 3 and Figure 4 above, the half-cell of Comparative Example 1, which had a significantly large amount of residual lithium on the surface, did not easily decompose the residual lithium during the operation process, so even if the pre-lithiation was performed with a lithium metal layer of the same thickness (5 μm), the actual applied pre-lithiation dosage was 0.657 mAh / cm 2 As in Example 1 (lithiation dosage of 0.838 mAh / cm 2 ) was confirmed to be significantly less than that of the half-cell of Example 1. That is, it was confirmed that the half-cell of Example 1 secured a pre-lithiation dosage that was about 27% improved compared to the half-cell of Comparative Example 1, and as a result, it was found that the charge / discharge efficiency was also 96.99%, which was significantly higher than the efficiency (92.71%) in Comparative Example 1.

[0194] Experimental Example 4: Evaluation of Half-Cell Lifespan and Voltage Drop

[0195] If a large amount of residual lithium is generated on the electrode surface, rapid degradation of battery life occurs during cycling due to lithium plating. Furthermore, self-discharge is exacerbated by micro-shorts caused by lithium plating.

[0196] To verify this, a life evaluation and voltage drop evaluation were performed using an electrochemical charge / discharge tester on the half-cells of Example 1, which were aged without peeling off the substrate layer, and Comparative Example 1, which had all the same conditions as Example 1 except that the substrate layer was peeled off, and the results are shown in Figure 5 below.

[0197] Specifically, the life evaluation was conducted through an in-situ cycle test at 4.2-3.1V 1C / 0.5C, and the voltage drop evaluation was conducted by charging to 4.2V at 1C, resting for 20 minutes, and then starting 0.5C discharge, and measuring and comparing the cell voltage at the point where the discharge started.

[0198] Referring to Fig. 5, it was confirmed that the half-cell of Example 1, in which no residual lithium was generated on the surface, had improved life performance and voltage stability during cycling.

[0199] In contrast, it was confirmed that the half-cell of Comparative Example 1 had a large amount of residual lithium that had formed on the electrode surface precipitated (lithium plating) during the cycle, and even when fully charged to 4.2 V, the voltage dropped to below 4.1 V during a 20-minute rest period, and the life performance also rapidly deteriorated.

[0200] Therefore, the method for manufacturing an electrode for a lithium secondary battery according to one embodiment of the present specification is to form a transfer laminate by contacting and rolling a lithium metal layer on one surface of a substrate layer, and then directly contacting the transfer laminate on an electrode active material layer to prelithiate the electrode active material layer, thereby not providing a release layer, thereby preventing interference with heat dissipation by the release layer, and by applying an appropriate pressure during transfer and then aging without peeling off the substrate layer, thereby evenly contacting the lithium metal layer and the electrode active material layer, thereby suppressing the generation of residual lithium remaining on the electrode surface, and preventing the formation of a thick byproduct layer at the center of the electrode. As a result, the manufactured electrode for a lithium secondary battery and the lithium secondary battery can secure excellent prelithiation dosage and charge / discharge efficiency, and can secure normal life performance and voltage stability by suppressing the lithium plating phenomenon.

[0201]

[0202] [Explanation of symbols]

[0203] 10: Negative current collector layer

[0204] 20: Negative active material layer

[0205] 30: Membrane

[0206] 40: Positive active material layer

[0207] 50: Positive current collector layer

[0208] 100: Cathode for lithium secondary batteries

[0209] 200: Cathode for lithium secondary batteries

Claims

A step of contacting a transfer laminate in which the substrate layer and the lithium metal layer are in direct contact with one surface of the electrode active material layer so that the electrode active material layer and the lithium metal layer face each other; and The electrode active material layer in contact with the above transfer layer is 6 kgf / cm 2 It includes a step of pressurizing and aging at the following pressure: A method for manufacturing an electrode for a lithium secondary battery, wherein the above-mentioned transfer laminate is formed by contacting and rolling a lithium metal layer on one surface of a substrate layer. In claim 1, A method for manufacturing an electrode for a lithium secondary battery, further comprising a step of removing the substrate layer from the transfer laminate after the aging step. In claim 1, A method for manufacturing an electrode for a lithium secondary battery, wherein, in the aging step, the transfer laminate is in a state including the substrate layer until the prelithiation of one side of the electrode active material layer is completed. In claim 1, The above transfer laminate is made by contacting a lithium metal layer on one side of the substrate layer and applying 80 kgf / cm 2 A method for manufacturing an electrode for a lithium secondary battery formed by rolling under the above pressure. In claim 1, A method for manufacturing an electrode for a lithium secondary battery, wherein the thickness of the lithium metal layer after contacting and rolling one surface of the substrate layer is 0.1 μm or more and 15 μm or less. In claim 1, The above electrode active material layer includes a carbon-based active material and a silicon-based active material as negative electrode active materials, A method for manufacturing an electrode for a lithium secondary battery, wherein the silicon-based active material comprises at least one selected from the group consisting of Si, silicon oxide, Si / C, and Si alloy. electrode current collector layer; and Including an electrode active material layer provided on at least one surface of the electrode current collector layer, An electrode for a lithium secondary battery manufactured by a manufacturing method according to any one of claims 1 to 6. An electrode for a lithium secondary battery according to claim 7; membrane; A lithium secondary battery comprising an electrolyte. A battery module comprising a lithium secondary battery according to claim 8. A battery pack comprising a lithium secondary battery according to claim 8. A battery pack comprising a battery module according to claim 9.

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