Method for manufacturing electrodes, electrodes manufactured thereby, and lithium secondary batteries containing the electrodes

Abstract

The present invention relates to a method for manufacturing an electrode, and the manufacturing method comprises a P1 step of arranging a transfer laminate including a lithium metal layer having lithium buffer layers formed on both sides on a preliminary electrode active material layer, and forming an electrode structure such that the lithium buffer layer and the preliminary electrode active material layer are in contact; a P2 step of rolling the electrode structure; and a P3 step of aging the rolled electrode structure in a nitrogen atmosphere, wherein the nitrogen atmosphere contains 80% by volume or more of nitrogen.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0066491 filed on May 23, 2023, and all the contents disclosed in the literature of the Korean patent application are incorporated herein by reference as part of this specification.

[0002] The present invention relates to a method for manufacturing an electrode, an electrode manufactured thereby, and a lithium secondary battery including the electrode.

Background Art

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

[0004] Currently, a typical example of an electrochemical device using such electrochemical energy is a secondary battery, and its usage areas are gradually expanding. Recently, as technology development and demand for portable devices such as portable computers, mobile phones, and cameras have increased, the demand for secondary batteries as an energy source has increased rapidly. Among such secondary batteries, various studies have been conducted on lithium secondary batteries with a high energy density, that is, a high capacity, and they have also been commercialized and widely used.

[0005] Generally, a secondary battery is composed of 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 as the negative electrode active material, silicon-based active material particles having a large discharge capacity can be used. The silicon-based active material particles can correspond to Si or SiO X (0 < X < 2), etc. The silicon-based active material particles have the advantages of a large theoretical capacity and low cost. However, the silicon-based active material particles have a drawback in that the volume change is excessively large during the operation of the battery, so the battery life rapidly decreases as the battery cycles progress.

[0006] Therefore, in order to minimize the change in volume of silicon-based active material particles, there is a method that uses only a portion of the total volume of silicon-based active material particles. For this purpose, a so-called pre-lithification process is used, in which lithium ions are pre-inserted into the negative electrode containing silicon-based active material particles. Specifically, by inserting lithium ions into the negative electrode by methods such as transferring lithium metal to the negative electrode, the lithium ions react with irreversible sites in the negative electrode, and the total volume of the negative electrode can be reduced to a reversible capacity level. Therefore, when the battery is operated, the amount of lithium ions inserted can be suitably reduced to the level required to operate the battery, and the change in volume of silicon-based active material particles can be minimized.

[0007] However, during the pre-lithification process, which involves placing lithium metal on the surface of the negative electrode, excessive heat is generated by the alloy reaction between lithium and silicon, increasing the possibility of ignition due to the reaction between lithium and water. Furthermore, during the notching and punching processes on the negative electrode, the reaction area between lithium and silicon-based active material increases, potentially further increasing the possibility of ignition. There is also a serious safety issue of the possibility of ignition from the pre-lithified silicon-based active material particles.

[0008] Therefore, there is a need for a new technology that can improve battery life and suppress excessive heat generation and the possibility of fire by pre-inserting lithium ions into the negative electrode before the battery is activated. [Overview of the project] [Problems that the invention aims to solve]

[0009] One problem that the present invention aims to solve is to provide a method for manufacturing electrodes in which, when transferring lithium metal to an electrode to perform pre-lithification, lithium buffer layers are formed on both sides of the lithium metal layer, thereby preventing the formation of an inert layer on the surface of the lithium metal layer due to side reactions of highly reactive lithium, and enabling the pre-lithification reaction to be carried out in a stable atmosphere. Furthermore, after pre-lithification, the lithium buffer layer is decomposed during activation and does not affect the thickness of the electrode, thus preventing a decrease in energy density. In addition, the decomposition allows the lithium buffer layer to be utilized as a further lithium source, thereby maximizing the pre-lithification effect.

[0010] Another problem that the present invention aims to solve is to provide a secondary battery that includes an electrode manufactured by the above manufacturing method, in which the lifespan characteristics are improved by controlling the usable region of the negative electrode, and the inherent properties of the negative electrode active material can be realized without any disadvantages. [Means for solving the problem]

[0011] To solve the above problems, in one aspect of the present invention, a method for manufacturing an electrode is provided, comprising the steps of: 1) placing a transfer laminate including a lithium metal layer having lithium buffer layers formed on both sides on a preliminary electrode active material layer, and forming an electrode structure such that the lithium buffer layer and the preliminary electrode active material layer are in contact; 2) rolling the electrode structure; and 3) aging the rolled electrode structure in a nitrogen atmosphere, wherein the nitrogen atmosphere contains 80% by volume or more of nitrogen.

[0012] To solve the above problems, in another aspect of the present invention, an electrode is provided comprising a current collector, an electrode active material layer disposed on the current collector, and a lithium buffer layer disposed on the electrode active material layer, wherein the lithium buffer layer comprises lithium carbonate and one or more of lithium oxide and lithium hydroxide, and does not contain lithium nitride.

[0013] To solve the above problems, in yet another aspect of the present invention, a lithium secondary battery is provided which includes a positive electrode as described above, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, wherein the positive electrode or the negative electrode is the electrode described above. [Effects of the Invention]

[0014] The electrode manufacturing method according to the present invention has the advantage of using a lithium metal layer with lithium buffer layers formed on both sides, thereby preventing the formation of an inert layer on the surface of the lithium metal layer due to side reactions of highly reactive lithium, and eliminating the problem of increased resistance. Furthermore, since the lithium buffer layer is decomposed during activation after pre-lithification and does not affect the electrode thickness, a decrease in energy density can be prevented. In addition, since the lithium buffer layer can be utilized as a further lithium source after decomposition, the pre-lithification effect can be maximized, and process risks that occur when lithium metal is in direct contact with the negative electrode can be reduced.

[0015] Furthermore, the lithium secondary battery according to the present invention, by including electrodes manufactured by the manufacturing method described above, can increase the usable area of ​​the negative electrode, thereby increasing its capacity. In particular, when using a silicon-based negative electrode active material, pre-lithified lithium allows for the use of only a portion of the usable area without lithium loss in the positive electrode, which has the advantage of minimizing volume changes and improving lifespan characteristics. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic diagram showing step P1 in a method for manufacturing electrodes according to one embodiment of the present invention. [Figure 2] This is a schematic diagram showing step P1 in a method for manufacturing an electrode according to one embodiment of the present invention, in which a transfer laminate containing a polymer layer is used. [Figure 3] This is a schematic diagram showing step P2 in a method for manufacturing an electrode according to one embodiment of the present invention. [Figure 4] This is a schematic diagram showing the P2' step in a method for manufacturing electrodes according to one embodiment of the present invention. [Figure 5] This is a photograph of the electrode surface of Example 1-1 taken after pre-lithiumization was performed according to one embodiment of the present invention. [Figure 6] This is a photograph of the electrode surface of Comparative Example 1-1, taken after pre-lithiumization. [Figure 7] These are photographs of the electrode surfaces of Comparative Examples 1-4 taken after pre-lithiumization. [Modes for carrying out the invention]

[0017] The present invention will be described in more detail below to facilitate understanding of it.

[0018] The terms and words used herein and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may define the concepts of terms as appropriate to best describe their invention.

[0019] The terms used herein are for illustrative purposes only and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0020] In this specification, terms such as “includes,” “equip,” or “have” indicate the presence of implemented features, figures, steps, components, or combinations thereof, but should be understood not to preclude the existence or possibility of adding one or more different features, figures, steps, components, or combinations thereof.

[0021] In this specification, D 50This can be defined as the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve. 50 This can be measured, for example, using the laser diffraction method. The laser diffraction method can generally measure particle sizes from the submicron region to several millimeters in size, and can obtain highly reproducible and high-resolution results.

[0022] <Method of manufacturing electrodes> The present invention provides a method for manufacturing an electrode, comprising the steps of: 1) placing a transfer laminate including a lithium metal layer with lithium buffer layers formed on both sides on a preliminary electrode active material layer, and forming an electrode structure such that the lithium buffer layer and the preliminary electrode active material layer are in contact; 2) rolling the electrode structure; and 3) aging the rolled electrode structure in a nitrogen atmosphere.

[0023] According to one embodiment of the present invention, step P1 of the method for manufacturing the electrode is a step of arranging a transfer laminate including a lithium metal layer having lithium buffer layers formed on both sides on a preliminary electrode active material layer formed on a current collector, thereby forming an electrode structure such that the lithium buffer layer and the preliminary electrode active material layer are in contact.

[0024] Referring to Figure 1, the transfer laminate 300 includes a lithium metal layer 320, and lithium buffer layers 321 are formed on both sides of the lithium metal layer. Preferably, the transfer laminate 300 may further include a base film 310, in which case it may include the base film 310 and the lithium metal layer 320 located on the base film 310, and the lithium buffer layers 321 may be formed on both sides of the lithium metal layer. The base film 310 can be used without limitation as long as it is made of a material that can withstand the high temperature conditions that occur during the process of depositing the lithium metal layer 320 onto the base film 310. Specifically, the base film may include one or more materials selected from the group consisting of polyethylene terephthalate (PET), polyimide (PI), poly(methylmethacrylate) (PMMA), polypropylene, polyethylene, and polycarbonate.

[0025] According to one embodiment of the present invention, the lithium metal layer plays a role in supplying lithium ions to the preliminary electrode active material layer. Specifically, the preliminary electrode active material layer can be located between the electrode current collector and the lithium buffer layer on the lithium metal layer.

[0026] The lithium metal layer comprises solid-phase lithium metal, and specifically, the lithium metal layer can consist of solid-phase lithium metal. The lithium metal layer can be inserted into the electrode active material layer by diffusion of the solid phase of lithium metal into the active material layer through a series of processes such as transfer, rolling, and aging. As a result, after activation, the lithium metal layer may not be present, or it may exist in an extremely thin state.

[0027] On the other hand, the lithium metal layer can consist of solid-phase lithium metal, which is a highly reactive metal that can react with oxygen (O2), nitrogen (N2), or water vapor (H2O) even in an air atmosphere. This reaction can result in losses in the lithium metal or the formation of an inert layer on the surface, such as lithium nitride or lithium oxide. The presence of such an inert layer can act as a resistor, potentially causing problems that degrade the output characteristics of the secondary battery. While the impact may not be significant at the cell level, given that the layer does not perform any special function, a decrease in energy density can become a problem at the module or pack level.

[0028] To solve these problems, the lithium metal layer according to one embodiment of the present invention is applied with lithium buffer layers formed on both sides, so that even if the base film is removed from the electrode structure, the lithium metal layer is not exposed to the outside and the lithium buffer layer is present as the uppermost layer. The lithium buffer layer may contain lithium carbonate (Li2CO3), and the main component may be lithium carbonate, and may further contain one or more of lithium oxide (LiO, Li2O) and lithium hydroxide (LiOH) as by-products, but is characterized by not containing lithium nitride (Li3N). Specifically, the lithium buffer layer may contain 80% by weight or more of lithium carbonate, preferably 85% by weight or more, more preferably 90% by weight or more, or 95% by weight or more. If the amount of lithium carbonate is less than the above amount, the amount of other lithium compounds will relatively increase, and in this case, it may be difficult to expect the above-mentioned effects.

[0029] According to one embodiment of the present invention, the lithium buffer layer formed between the lithium metal layer and the substrate film can significantly reduce the possibility of side reactions by preventing the lithium metal layer from being exposed to air before, after, or during the pre-lithiation process, thereby preventing the formation of an inert layer, mainly composed of lithium nitride and / or lithium oxide, on the surface of the lithium metal layer.

[0030] Furthermore, the lithium carbonate, which is the main component of the lithium buffer layer, can be decomposed in the activation process after pre-lithification. The lithium generated during decomposition can be used as an additional lithium source, which has the advantage of improving the battery's capacity and lifespan. Moreover, after the activation process, there is no transfer laminate used for pre-lithification remaining on the electrodes, which does not affect the electrode thickness at all. This allows for an improvement in energy density at the module or pack level.

[0031] On the other hand, the lithium buffer layer may contain lithium oxide and / or lithium hydroxide, which are compounds that inevitably occur when forming the lithium buffer layer on the lithium metal layer.

[0032] Furthermore, while the lithium nitride is characterized by not being included in the lithium buffer layer, lithium nitride has higher stability than other lithium compounds and is less likely to decompose even after tens to hundreds of cycles. It fixes lithium in a large proportion, which can lead to significant lithium loss, and thereafter it may act as a resistor, potentially causing problems that reduce output characteristics. Therefore, the lithium buffer layer according to one embodiment of the present invention may not contain lithium nitride, and this can be appropriately controlled by surface treatment of the lithium metal layer when manufacturing the transfer laminate.

[0033] According to one embodiment of the present invention, the transfer laminate can be manufactured by a method including the step (S1) of surface-treating both sides of a lithium metal layer to form a lithium buffer layer. Furthermore, if the transfer laminate includes a base film, it can be manufactured by a method further including the step (S2) of placing the base film on one of the lithium buffer layers.

[0034] The method for surface-treating both sides of the lithium metal layer can involve creating a mixed gas atmosphere of CO2 and Ar in the initial stages of deposition to induce a reaction with lithium, and then creating the mixed gas atmosphere again after the deposition of lithium to a desired thickness is completed. Alternatively, by placing the lithium metal film into a vacuum chamber to create the mixed gas atmosphere, a lithium buffer layer mainly composed of lithium carbonate can be formed simultaneously on both sides. The mixed gas can be a mixture of CO2 and Ar in a volume ratio of approximately 3:97 to 40:60, preferably a volume ratio of 5:95 to 30:70, and more preferably 5:95 to 20:80.

[0035] According to one embodiment of the present invention, the thickness of the lithium buffer layer can be 50 nm or less, and this can be controlled to an appropriate level by adjusting the conditions of the method. When the thickness of the lithium buffer layer is 50 nm or less, it can act as a lithium source at a level that can be decomposed by activation, and side reactions of the lithium metal layer can be effectively prevented.

[0036] According to one embodiment of the present invention, in the transfer laminate, the thickness of the lithium metal layer can be 1 μm to 10 μm, more specifically 3 μm to 9 μm, and more specifically 4 μm to 6.5 μm. When this range is met, the degree of fracture of positive electrode active material particles on the surface of the positive electrode can be reduced, explosive reactions at the negative electrode can be prevented in advance, and a decrease in the initial capacity of the battery can be suppressed.

[0037] According to one embodiment of the present invention, the loading amount of the lithium metal layer (unit: mAh / cm²) 2 ) is the loading amount of the preliminary electrode active material layer (unit: mAh / cm²). 2 This can be 4% to 40%, specifically 12% to 35%, and more specifically 20% to 30%. When this range is satisfied, the generation of by-products is small, lithium can be easily inserted into the electrode active material, and the target lithium insertion capacity can be easily achieved.

[0038] According to one embodiment of the present invention, in step P1, referring to Figure 1, the preliminary electrode active material layer 120' is located on the electrode current collector 110, the transfer laminate 300 is placed on the preliminary electrode active material layer 120', and the electrode structure 400 can be formed such that the lithium buffer layer 321 and the preliminary electrode active material layer are in contact with each other.

[0039] On the other hand, referring to Figure 2, the transfer laminate 300 according to one embodiment of the present invention may further include a polymer layer 330. The polymer layer 330 may be located on the lithium buffer layer 321. The polymer layer can play a role in ensuring that the lithium metal layer is effectively peeled off from the transfer laminate and that the lithium metal layer is easily transferred to the electrode active material layer during the manufacture of the electrode. That is, the polymer layer may be separated from the transfer laminate together with the lithium metal layer and located on the electrode active material layer. The polymer layer may exist in contact with the electrode active material layer, or, in contrast, if none of the lithium metal layers have been transferred to the electrode active material layer, a lithium metal layer may exist between the polymer layer and the electrode active material layer.

[0040] The polymer layer can be at least one selected from the group consisting of polyethylene terephthalate (PET), polyimide (PI), poly(methylmethacrylate) (PMMA), polypropylene, polyethylene, and polycarbonate. This allows the polymer layer to dissolve in the electrolyte contained in the secondary battery, preventing an increase in the battery's resistance. In particular, the polymer layer can contain PMMA, in which case the above-mentioned effects can be further improved.

[0041] The thickness of the polymer layer can be 0.1 μm to 10 μm, more specifically 0.5 μm to 5 μm, and more specifically 1 μm to 2.5 μm. When this range is met, the lithium metal layer can be easily transferred to the electrode active material layer, and the reverse transfer phenomenon in which the electrode active material layer is transferred to the transfer laminate can be prevented.

[0042] According to one embodiment of the present invention, step P2 of the method for manufacturing the electrode is a step of rolling the electrode structure.

[0043] Referring to Figure 3, in step P2, the manufactured electrode structure 400 can be rolled. The rolling can be performed using a roll press. Specifically, pressure can be applied vertically to the electrode structure 400 passing through a space between two rolls R spaced apart with a predetermined space between them in the vertical direction, and this pressure can be linear pressure. Through this rolling process, the lithium metal layer contained in the transfer laminate can be fixed as a single layer within the positive electrode structure, and at least a portion of the lithium can begin to be inserted into the preliminary electrode active material layer.

[0044] During the rolling process, the pressure applied to the electrode structure can be between 10 kgf / cm and 90 kgf / cm, more specifically between 15 kgf / cm and 80 kgf / cm, and more specifically between 20 kgf / cm and 40 kgf / cm.

[0045] When the rolling pressure is applied within the specified range, the lithium metal layer can be effectively transferred. This makes it possible to simultaneously improve lifespan and capacity characteristics.

[0046] According to one embodiment of the present invention, if the transfer laminate 300 includes a base film 310, the method for manufacturing the electrode may further include a step of removing the base film from the electrode structure after the rolling of step P2.

[0047] Referring to Figure 4, in step P2', after the rolling performed in step P2, the base film 310 can be removed from the electrode structure to manufacture the electrode 100. When the polymer layer 330 is located on the lithium buffer layer 321, the polymer layer 330 is located between the base film 310 and the lithium buffer layer 321, thereby making it easier to remove the base film 310.

[0048] According to one embodiment of the present invention, the method for manufacturing the electrode includes a P3 step of aging the rolled electrode structure in a nitrogen atmosphere.

[0049] The aging process can consist of a step of leaving the product idle (standing) in a nitrogen atmosphere for 1 minute to 600 minutes, specifically 1 minute to 30 minutes. The nitrogen atmosphere can have a nitrogen concentration of 80% by volume or more, or 85% by volume or more, preferably 90% by volume or more. The aging process can be carried out at a temperature of 15°C to 40°C, preferably 17°C or more, or 20°C or more, preferably 35°C or lower, and more preferably 30°C or lower, or 28°C or lower. The aging conditions offer the advantage of significantly reducing the risk of fire and ensuring stable reaction by effectively controlling the explosive pre-lithification reaction through the application of a nitrogen atmosphere. Furthermore, despite the application of a nitrogen atmosphere, the lithium buffer layer prevents the formation of lithium nitride on the surface of the lithium metal, thus preventing problems such as increased resistance caused by the formation of lithium nitride.

[0050] <Electrode> The electrode according to the present invention comprises a current collector, an electrode active material layer disposed on the current collector, and a lithium buffer layer disposed on the electrode active material layer, wherein the lithium buffer layer comprises lithium carbonate and one or more of lithium oxide and lithium hydroxide, and does not contain lithium nitride.

[0051] Specifically, the electrode may be derived from an electrode structure comprising a transfer laminate including a lithium metal layer with lithium buffer layers formed on both sides, a current collector, and a pre-electrode including a pre-electrode active material layer disposed on the current collector, wherein the lithium buffer layer of the transfer laminate and the pre-electrode active material layer of the pre-electrode are arranged in contact with each other.

[0052] According to one embodiment of the present invention, the electrode can be a positive electrode, and the positive electrode includes a positive electrode active material layer. The positive electrode active material layer can itself constitute the positive electrode, but the positive electrode active material layer can be located on the positive electrode current collector, and the positive electrode active material layer can be located on one or both surfaces of the positive electrode current collector.

[0053] According to one embodiment of the present invention, the positive electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or those obtained by surface treatment with carbon, nickel, titanium, silver, etc. on the surface of aluminum or stainless steel can be used. Also, the positive electrode current collector can usually have a thickness of 3 μm to 500 μm, and fine irregularities can be formed on the surface of the current collector to enhance the adhesion of the positive electrode active material. For example, it can be used in various forms such as films, sheets, foils, meshes, porous bodies, foams, non-woven fabrics, etc.

[0054] According to one embodiment of the present invention, the positive electrode active material layer contains a positive electrode active material, and the positive electrode active material is a substance capable of undergoing an electrochemical reaction and can be a lithium transition metal oxide. For example, the positive electrode active material is a layered compound such as lithium cobalt oxide or lithium nickel oxide substituted with one or more transition metals; lithium manganese oxide substituted with one or more transition metals; Li 1-y M 1 y O2 (where M 1 is at least one selected from Co, Mn, Al, Cu, Fe, Mg, B, Cr, Zn, and Ga, and 0.01 ≦ y ≦ 0.7); Li 1+z [Ni b Mn c Co 1-(b+c+d) M 2 d O (2-e) A e (where M 2A is at least one selected from the group consisting of Al, Mg, Cr, Ti, Si, and Y, and A is at least one selected from the group consisting of F, P, and Cl, and is represented as lithium nickel cobalt manganese composite oxide (where -0.5≦z≦0.5, 0.1≦b≦0.8, 0.1≦c≦0.8, 0≦d≦0.2, 0≦e≦0.2, b+c+d<1); Li 1+x [M 3 1-q M 4 q ]PO 4-r X r (Here, M 3 is at least one selected from the group consisting of Fe, Mn, Co, and Ni, and M 4 X is at least one selected from the group consisting of Al, Mg, and Ti, and X is at least one selected from the group consisting of F, S, and n, and can include at least one selected from the group consisting of olivine-based lithium metal phosphates (where -0.5 ≤ x ≤ 0.5, 0 ≤ q ≤ 0.5, and 0 ≤ r ≤ 0.1).

[0055] Specifically, the positive electrode active material can consist of a lithium nickel-based oxide, a lithium nickel-cobalt-manganese composite oxide, an olivine-based lithium metal phosphate, or a combination thereof, and these can be combined to form a positive electrode active material layer in one or another layers.

[0056] According to one embodiment of the present invention, more specifically, the positive electrode active material may include a compound of the following chemical formula 1, and more specifically, may be a compound of the following chemical formula 1.

[0057] [Chemical formula 1] Li 1+x [Ni a Co b Mn c M 1 (1-a-b-c) ]O (2-d) A d

[0058] In the above Chemical Formula 1, M 1 can be at least any one selected from the group consisting of Al, Mg, Cr, Ti, Si, and Y, and specifically can be Al.

[0059] A is at least any one selected from the group consisting of F, P, and Cl, and specifically can be F.

[0060] The above x can satisfy -0.5 ≦ x ≦ 0.5, specifically -0.3 ≦ x ≦ 0.3.

[0061] The above a can satisfy 0.6 ≦ a < 1, specifically 0.7 ≦ a ≦ 0.9.

[0062] The above b can satisfy 0.03 ≦ b ≦ 0.1, specifically 0.05 ≦ b ≦ 0.1.

[0063] The above c can satisfy 0.03 ≦ c ≦ 0.1, specifically 0.05 ≦ c ≦ 0.1.

[0064] The above d can satisfy 0 ≦ d ≦ 0.1, specifically 0 ≦ d ≦ 0.05.

[0065] The above a, b, and c satisfy 0 < a + b + c ≦ 1, specifically a + b + c = 1.

[0066] The compound of Chemical Formula 1 can be in a particulate form.

[0067] The compound of Chemical Formula 1 can be in the form of secondary particles in which a plurality of primary particles are bonded to each other. Specifically, the compound of Chemical Formula 1 can be in the form of secondary particles in which 10 or more primary particles are bonded to each other. Thereby, there is an effect that lithium can be uniformly inserted and extracted inside the positive electrode active material.

[0068] The D of the compound of Chemical Formula 1 50The size can be 5 μm to 15 μm, more specifically 7 μm to 12 μm, and more specifically 9 μm to 10 μm. 50 D is a secondary particle. 50 This can be the case. When the above range is satisfied, the positive electrode slurry dispersion is easy, and a uniform coating of the positive electrode active material layer is possible.

[0069] The positive electrode active material can be contained in the positive electrode active material layer in an amount of 90% to 99% by weight, more specifically 92% to 98% by weight, and more specifically 95% to 98% by weight.

[0070] According to one embodiment of the present invention, the positive electrode active material layer may further include a positive electrode binder. The positive electrode binder plays a role in improving adhesion between positive electrode active material particles and adhesion between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, of which one alone or a mixture of two or more may be used.

[0071] The positive electrode binder can be contained in the positive electrode active material layer in an amount of 0.5% to 5.0% by weight, more specifically, 1.0% to 2.5% by weight, and more specifically, 1.0% to 2.0% by weight.

[0072] According to one embodiment of the present invention, the positive electrode active material layer may further include a positive electrode conductive material. The positive electrode conductive material is used to impart conductivity to the electrode and can be used without particular limitation as long as it has electron conductivity and does not cause chemical changes in the battery being constructed. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal 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. Among these, one kind alone or a mixture of two or more kinds can be used.

[0073] The positive electrode conductive material can be contained in the positive electrode active material layer at 0.5% to 30.0% by weight, specifically 0.5% to 10.0% by weight, and more specifically 1.0% to 4.0% by weight.

[0074] According to one embodiment of the present invention, in the positive electrode, the porosity of the positive electrode active material layer can be 10% to 40%, specifically 15% to 35%, and more specifically 25% to 30%. In this case, no further change in thickness can occur during rolling.

[0075] According to one embodiment of the present invention, the electrode can be a negative electrode. The negative electrode includes a negative electrode active material layer, and the negative electrode active material layer can include a negative electrode active material. The negative electrode active material can be a silicon-based negative electrode active material, a carbon-based negative electrode active material, or a combination thereof.

[0076] According to one embodiment of the present invention, the negative electrode active material can include a silicon-based negative electrode active material. The silicon-based negative electrode active material can include at least one of Si and SiO x (0 < X < 2).

[0077] The Si is silicon particles, which can be silicon particles (particles made of silicon) referred to as so-called pure silicon. The silicon particles can effectively improve the capacity of the negative electrode. The SiO x (0 < X < 2) can be in a form containing Si and SiO2, and the Si can also form a phase. That is, the X corresponds to the ratio of the number of O to Si contained in the SiO x (0 < X < 2). When the silicon-based composite particles contain the SiO x (0 < X < 2), the discharge capacity of the secondary battery can be improved.

[0078] According to one embodiment of the present invention, the silicon-based negative electrode active material has a problem that the volume change during battery driving is intense and the life characteristics are very poor. However, when combined with the positive electrode by the electrode manufacturing method according to the present invention, from the prelithiated positive electrode, during activation, instead of lithium in the positive electrode active material that determines the capacity with the silicon-based negative electrode active material, excess lithium ions move and react with the silicon-based negative electrode active material in advance to form an irreversible phase and reduce the available area. Thereby, the volume change during battery driving becomes less intense, the life can be significantly improved, and the high-capacity characteristics, which are the inherent characteristics of the silicon-based negative electrode active material, can be fully exhibited. Furthermore, when the manufacturing method according to one embodiment of the present invention is applied to the silicon-based negative electrode active material itself, the above-described effects can be obtained, and the prelithiation reaction can be controlled by the lithium buffer layer, and the risk due to the existing alloy reaction of lithium and silicon can be reduced.

[0079] According to one embodiment of the present invention, the negative electrode active material can further include a carbon-based negative electrode active material. The carbon-based negative electrode active material can include at least any one selected from the group consisting of artificial graphite, natural graphite, and graphitized mesocarbon microbeads.

[0080] According to one embodiment of the present invention, the negative electrode active material layer may further comprise a negative electrode binder. The negative electrode binder may comprise at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, and substances in which the hydrogens of these substances are substituted with Li, Na, or Ca, and may also comprise various copolymers thereof.

[0081] According to one embodiment of the present invention, the negative electrode active material layer may further include a negative electrode conductive material. The negative electrode conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; fluorocarbons; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives can be used.

[0082] In one embodiment of the present invention, the electrode is constructed by a transfer method, in which a lithium metal layer is placed on the electrode, and the lithium from the lithium metal layer is inserted into the electrode active material layer by solid-phase diffusion through rolling. This lithium can play a role in reducing the usable area of ​​the negative electrode.

[0083] Therefore, pre-lithiumized lithium can reduce the usable region of the negative electrode capacity without lithium loss in the positive electrode active material, and in particular, it can suppress excessive volume changes of silicon-based active materials, thereby improving the battery's lifespan characteristics. Furthermore, this has the advantage of making the capacity of the positive electrode active material usable over its entire range, increasing battery efficiency and maximizing energy density.

[0084] One embodiment of the present invention is characterized in that, instead of pre-lithifying by bringing a lithium metal layer into contact with the negative electrode as is usually done, a lithium metal layer is transferred and rolled onto the positive electrode, and then the lithium ions inserted into the positive electrode are moved to the negative electrode during the battery activation process.

[0085] An electrode according to one embodiment of the present invention can be a positive electrode or a negative electrode, preferably a negative electrode, and more preferably a negative electrode in which a silicon-based active material is applied as the negative electrode active material, specifically the silicon-based active material can be silicon (Pure Si).

[0086] <Lithium-ion secondary battery> The present invention provides a lithium secondary battery comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, wherein the positive electrode or the negative electrode is manufactured by the method described above.

[0087] Since the explanations regarding the positive electrode and the negative electrode have been given above, they will be omitted here.

[0088] According to one embodiment of the present invention, the secondary battery includes a separator. The separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in secondary batteries can be used without particular limitations, but one that has low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity is particularly preferred. Specifically, porous polymer films, such as porous polymer films made from polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or laminated structures of two or more layers thereof can be used. Alternatively, ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. Furthermore, coated separators containing ceramic components or polymeric substances can be used to ensure heat resistance or mechanical strength, and can be selectively used in single-layer or multi-layer structures.

[0089] According to one embodiment of the present invention, the secondary battery may further include an electrolyte. The electrolyte may include, but is not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0090] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt. Examples of non-aqueous organic solvents that can be used include 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, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyropionate, and ethyl propionate.

[0091] In particular, among the carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, can be preferably used because they are high-viscosity organic solvents with high dielectric constants and readily dissociate lithium salts. Furthermore, when such cyclic carbonates are mixed with low-viscosity, low-dielectric-constant linear carbonates such as dimethyl carbonate and diethyl carbonate in appropriate ratios, electrolytes with high electrical conductivity can be produced, and these can be used even more preferably.

[0092] The metal salt can be a lithium salt, which is a substance that dissolves easily in the non-aqueous electrolyte, for example, the anion of the lithium salt is 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 - You may use one or more selected from the group consisting of the following.

[0093] In addition to the components of the electrolyte, the electrolyte may also contain one or more additives for the purpose of improving the battery's lifespan, suppressing the decrease in battery capacity, and improving the battery's discharge capacity, such as haloalkylene carbonate compounds like difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride.

[0094] As described above, the secondary battery containing the positive electrode according to the present invention exhibits excellent capacity and stable capacity retention, making it useful in portable devices such as mobile phones, notebook computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0095] Accordingly, according to another embodiment of the present invention, a battery module including the secondary battery as a unit cell and a battery pack including the same are provided.

[0096] The aforementioned battery module or battery pack can be used as a power source for one or more medium-to-large devices, including power tools; electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0097] <Examples> Hereinafter, preferred embodiments are presented to facilitate understanding of the present invention. However, these embodiments are merely illustrative examples, and it will be obvious to those skilled in the art that various changes and modifications are possible within the scope of the present description and the technical concept. It goes without saying that such variations and modifications fall within the scope of the appended claims.

[0098] <Electrode Manufacturing> [Example 1-1: Manufacturing of the negative electrode] A lithium metal sample was placed in a vacuum chamber so that both sides were fully exposed. At room temperature (approximately 25°C), a mixed gas atmosphere of 95% Ar and 25% CO was created, and a lithium buffer layer with a thickness of 50 nm was formed on the surface. The lithium buffer layer was analyzed by X-ray photoelectron spectroscopy (XPS) (Nexsa ESCA System, Thermo Fisher Scientific (ESCA-02)) and it was confirmed that lithium carbonate was the main component, as it was found to be present in a composition of 35% Li, 25% C, and 40% O.

[0099] A PET film (base film), a polymer layer made of PMMA (thickness 1 μm) disposed on the PET film, and a lithium metal layer (thickness 6.2 μm, 1.28 mAh / cm²) disposed on the polymer layer, made of solid-phase lithium metal with lithium buffer layers formed on both sides. 2 A transfer layer containing the loading amount was prepared.

[0100] On the other hand, as the negative electrode active material, the average particle size D 50 Silicon particles with a diameter of 5 μm were used. A negative electrode was prepared containing a preliminary negative electrode active material layer containing the aforementioned negative electrode active material, carboxymethylcellulose (CMC) as a negative electrode binder, and carbon nanotubes as a negative electrode conductive material in a weight ratio of 80:10:10. The loading amount of the preliminary negative electrode active material layer was 10 mAh / cm². 2 The thickness was 75 μm.

[0101] The transfer laminate is placed in the pre-negative electrode active material layer, and the lithium buffer layer and the pre-negative electrode active material layer are brought into contact. After rolling using a roll press method, the material is aged for 120 minutes at room temperature in an atmosphere of 90% nitrogen by volume, so that lithium is inserted into the negative electrode active material layer.

[0102] [Example 1-2: Manufacturing of the negative electrode] When preparing the transfer laminate, the thickness of the lithium metal layer should be approximately 4 μm (0.82 mAh / cm²). 2 A pre-lithified negative electrode was manufactured using the same method as in Example 1-1, except for the loading amount.

[0103] [Examples 1-3: Manufacturing of the negative electrode] A pre-lithified negative electrode was manufactured in the same manner as in Example 1-1, except that the exposure time of the lithium metal layer to the mixed gas atmosphere was controlled to set the thickness of the lithium buffer layer formed on both sides of the lithium metal layer to approximately 30 nm.

[0104] [Comparative Example 1-1: Manufacturing of the negative electrode] The negative electrode was manufactured in the same manner as in Example 1-1, except that a lithium metal layer without a lithium buffer layer was used.

[0105] [Comparative Example 1-2: Manufacturing of the negative electrode] The negative electrode was manufactured in the same manner as in Example 1-1, except that a lithium metal layer without a lithium buffer layer was used, and the aging process was carried out in an air atmosphere (containing approximately 78% nitrogen by volume) instead of a nitrogen atmosphere.

[0106] [Examples 1-4: Manufacturing of the positive electrode] A transfer laminate was prepared using the same method as in Example 1-1.

[0107] On the other hand, as the positive electrode active material, Li[Ni 0.86 Co 0.05 Mn 0.08 Al 0.01 O2 was used. The positive electrode active material was Li[Ni 0.86 Co 0.05 Mn 0.08 Al 0.01 Multiple (10 or more) primary O2 particles are bound together to form secondary particles, and the average particle size of the secondary particles is D 50 The thickness was 9 μm. A positive electrode was prepared that included an aluminum foil (thickness: 12 μm) which served as the positive electrode current collector, and a preliminary positive electrode active material layer containing the positive electrode active material, PVdF as a positive electrode binder, and carbon nanotubes as a positive electrode conductive material in a weight ratio of 98:1:1. The loading amount of the preliminary positive electrode active material layer was 4.5 mAh / cm². 2 The thickness was 140 μm.

[0108] The transfer laminate is placed in the pre-negative electrode active material layer, and the lithium buffer layer and the pre-negative electrode active material layer are brought into contact. After rolling using a roll press method, the material is aged for 120 minutes at room temperature in an atmosphere of 90% nitrogen by volume, so that lithium is inserted into the positive electrode active material layer.

[0109] [Examples 1-5: Manufacturing of the positive electrode] When preparing the transfer laminate, the thickness of the lithium metal layer should be approximately 4 μm (0.82 mAh / cm²). 2 A pre-lithified negative electrode was manufactured using the same method as in Examples 1-4, except for the loading amount.

[0110] [Examples 1-6: Manufacturing of the positive electrode] A pre-lithified negative electrode was manufactured in the same manner as in Examples 1-4, except that the exposure time of the lithium metal layer to the mixed gas atmosphere was controlled to set the thickness of the lithium buffer layer formed on both sides of the lithium metal layer to approximately 30 nm.

[0111] [Comparative Example 1-3: Manufacturing of the positive electrode] The positive electrode was manufactured in the same manner as in Examples 1-4, except that a lithium metal layer without a lithium buffer layer was used.

[0112] [Comparative Example 1-4: Manufacturing of the positive electrode] The cathode was manufactured using the same method as in Examples 1-4, except that a lithium metal layer without a lithium buffer layer was used, and the aging process was carried out in an air atmosphere (containing approximately 78% nitrogen by volume) instead of a nitrogen atmosphere.

[0113] [Experimental Example 1: Evaluation of the pre-lithiumization reaction] For the pre-lithiation reactions of Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-4, the peak reaction temperature and the time required for lithium nitride formation were measured and are shown in Table 1 below.

[0114] 1) Peak temperature (°C): The peak temperature is the highest reaction temperature recorded during the pre-lithiation reaction. 2) Formation time of lithium nitride (min): The formation time of lithium nitride was recorded when the electrode surface began to turn green during the pre-lithification reaction, without removing the polymer layer (release layer) from the electrode structure. When lithium nitride is formed on the electrode surface, the polymer layer on the surface causes it to turn green. For electrodes whose surface color did not change to green during the pre-lithification reaction, the change in electrode state was observed for up to 7 days.

[0115] [Table 1]

[0116] Referring to Table 1 above, in the case of the examples, during the reaction, lithium nitride was not formed, and as a result of continuous observation during subsequent storage, even after about 7 days, as shown in Figure 5, no green color was confirmed, and it was confirmed that the surface polymer layer exhibited a purple color. It can be seen that the prelithiation reaction was also carried out very stably within the normal temperature range. However, in the cases of Comparative Examples 1-1 and 1-3, since the surface treatment was not performed on the lithium metal layer, it was confirmed that the peak temperature of the prelithiation reaction was relatively high, and it was observed that lithium nitride was formed 10 minutes after the start of the reaction. From Figure 6, it can be confirmed that green lithium nitride was formed on the entire surface of the electrode of Comparative Example 1-1. In addition, Comparative Examples 1-2 and 1-4 are cases where prelithiation was carried out under general atmospheric conditions without surface treatment. For the negative electrode of Comparative Example 1-2, during the prelithiation reaction, when the reaction temperature exceeded 60°C due to the explosion risk, the reaction was interrupted. For Comparative Example 1-4, the prelithiation reaction was carried out at a somewhat dangerous level, and the formation of lithium nitride was observed on a part of the electrode surface 10 minutes after the start of the reaction. As can be confirmed from Figure 7, it can be seen that lithium nitride with a greenish color was formed on a part of the surface.

[0117] <Manufacture of Lithium Secondary Battery> 〔Examples 2-1 to 2-2 and Comparative Examples 2-1 to 2-2: Manufacture of Lithium Secondary Battery〕 As the positive electrode active material, Li[Ni 0.86 Co 0.05 Mn 0.08 Al 0.01 O2 was used. The positive electrode active material is composed of a plurality (10 or more) of primary particles of Li[Ni 0.86 Co 0.05 Mn 0.08 Al 0.01 O2 bonded to each other, showing a secondary particle form, and the average particle diameter D 50 of the secondary particles was 9 μm. A positive electrode was prepared, which included a positive electrode active material layer containing the positive electrode active material, PVdF as the positive electrode binder, and carbon nanotubes as the positive electrode conductive material in a weight ratio of 98:1:1, and an aluminum foil (thickness: 12 μm) as the positive electrode current collector. The loading amount of the positive electrode active material layer was 4.5 mAh / cm 2The thickness was 140 μm.

[0118] The negative electrode, positive electrode, and porous polyethylene separator of Examples 1-1, 1-2, and Comparative Examples 1-1 and 1-2 were assembled separately for each example and comparative example using a winding method. A spare lithium-ion secondary battery was then manufactured by injecting the electrolyte (ethylene carbonate (EC) / ethyl methyl carbonate (EMC) = 3 / 7 (volume ratio) and lithium hexafluorophosphate (LiPF 61 mol)) into the assembled battery.

[0119] The aforementioned spare lithium-ion secondary battery was charged at 4.2V at a rate of 0.1CC, and then discharged to 2.5V to perform an activation process.

[0120] [Examples 2-4 to 2-5 and Comparative Examples 2-3 to 2-4: Manufacturing of Lithium Secondary Batteries] As the negative electrode active material, the average particle size D 50 Silicon particles with a diameter of 5 μm were used. A negative electrode was prepared containing a preliminary negative electrode active material layer containing the aforementioned negative electrode active material, CMC as a negative electrode binder, and carbon nanotubes as a negative electrode conductive material in a weight ratio of 80:10:10. The loading amount of the preliminary negative electrode active material layer was 10 mAh / cm². 2 The thickness was 75 μm.

[0121] In Examples 1-4, 1-5, and Comparative Examples 1-3 and 1-4, the positive electrode, the negative electrode, and the porous polyethylene separator were assembled separately for each example and comparative example using a winding method. The assembled batteries were then filled with electrolytes (ethylene carbonate (EC) / ethyl methyl carbonate (EMC) = 3 / 7 (volume ratio) and lithium hexafluorophosphate (LiPF 61 mol)) to produce a preliminary lithium-ion secondary battery.

[0122] The aforementioned spare lithium-ion secondary battery was charged at 4.2V at a rate of 0.1CC, and then discharged to 2.5V to perform an activation process.

[0123] [Experimental Example 2: Evaluation of Resistance and Lifetime Characteristics] For each of the lithium secondary batteries in Examples 2-1, 2-2, 2-4, and 2-5 and Comparative Examples 2-1 to 2-4, charging and discharging were performed, and the resistance characteristics and life characteristics were evaluated using the method described below. The results are shown in Table 2 below.

[0124] 1) Resistance characteristics: The lithium secondary battery was subjected to repeated charge-discharge cycles under the following conditions, and a 2.5C pulse current was applied for a specific time at a discharge state of charge (SOC) of 50% per cycle, and the resistance was measured.

[0125] Resistance increase rate: [(Resistance value after 200 cycles) / (Resistance value at 1st cycle)] × 100

[0126] 2) Lifetime characteristics: For the first and second cycles, the batteries were charged and discharged at 0.1C. From the third cycle onward, the cycle was repeated with 1C charging and 0.5C discharging, and the number of cycles required to maintain a State of Charge (SOC) of 80% or higher was measured.

[0127] Charging conditions: CC (constant current) / CV (constant voltage) (5mV / 0.005C current cut-off) 4.2V

[0128] Discharge condition: CC (constant current) condition 2.5V

[0129] [Table 2]

[0130] Referring to Table 2 above, it can be confirmed that the lithium secondary batteries of Examples 2-1 and 2-2, which are equipped with a negative electrode to which the pre-lithiumization method according to the present invention has been applied, exhibit lower initial resistance and a lower resistance increase rate, and thus superior resistance characteristics compared to the lithium secondary batteries of Comparative Examples 2-1 and 2-2, which are equipped with a negative electrode to which the method has not been applied. This is understood to be because lithium nitride is formed on the surface and acts as a resistor, and it can be seen that it continues to act as a resistor without decomposing during the cycle. Similar results can be confirmed in the case of the positive electrode by comparing Examples 2-4 and 2-5 and Comparative Examples 2-3 and 2-4. In particular, in the case of the positive electrode, there was not as drastic a difference in initial resistance values ​​as in the negative electrode, but it can be confirmed that the resistance increased significantly in the case of the comparative examples.

[0131] On the other hand, when comparing Examples 2-1 and 2-2 with Comparative Examples 2-1 and 2-2 regarding lifespan characteristics, it was found that the effect of the present invention is maximized when applied to the negative electrode. Comparing Examples 2-4 and 2-5, which are positive electrodes, with Comparative Examples 2-3 and 2-4, a clear improvement can be confirmed, although the difference is not as large as with the negative electrodes. [Explanation of symbols]

[0132] 110 Electrode current collector 120' Pre-electrode active material layer 300 Transfer Layers 310 Base film 320 Lithium metal layer 321 Lithium buffer layer 330 Polymer layer 400 electrode structure R Roll

Claims

1. Step P1 involves placing a transfer laminate containing a lithium metal layer with lithium buffer layers formed on both sides onto a preliminary electrode active material layer, and forming an electrode structure such that the lithium buffer layer and the preliminary electrode active material layer are in contact. Step P2 involves rolling the electrode structure, The process includes step P3 of aging the rolled electrode structure in a nitrogen atmosphere, A method for manufacturing electrodes, wherein the nitrogen atmosphere is an atmosphere containing 80% or more by volume of nitrogen.

2. The method for manufacturing an electrode according to claim 1, wherein the aging in step P3 is performed at 15°C to 40°C.

3. The method for manufacturing an electrode according to claim 1, wherein the lithium buffer layer contains lithium carbonate.

4. The method for manufacturing an electrode according to claim 3, wherein the lithium buffer layer further comprises one or more of lithium oxide and lithium hydroxide.

5. The method for manufacturing an electrode according to claim 3, characterized in that the lithium buffer layer does not contain lithium nitride.

6. The method for manufacturing an electrode according to claim 1, wherein the thickness of the lithium metal layer is 1 μm to 10 μm.

7. The method for manufacturing an electrode according to claim 1, wherein the thickness of the lithium buffer layer is 50 nm or less.

8. The method for manufacturing an electrode according to claim 1, wherein the transfer laminate is manufactured by a method including the step (S1) of surface treating both sides of a lithium metal layer to form a lithium buffer layer.

9. A method for manufacturing an electrode according to any one of claims 1 to 8, wherein the electrode is a negative electrode, and the electrode active material includes a silicon-based negative electrode active material as the negative electrode active material.

10. The current collector comprises a current collector, an electrode active material layer disposed on the current collector, and a lithium buffer layer disposed on the electrode active material layer. The electrode comprises a lithium buffer layer containing lithium carbonate and one or more of lithium oxide and lithium hydroxide, but does not contain lithium nitride.

11. The electrode is A transfer laminate containing a lithium metal layer with lithium buffer layers formed on both sides, The current collector and the pre-electrode, which includes a pre-electrode active material layer disposed on the current collector, The electrode according to claim 10, which is derived from an electrode structure in which the lithium buffer layer of the transfer laminate and the preliminary electrode active material layer of the preliminary electrode are arranged in contact.

12. The electrode according to claim 10, wherein the electrode is a negative electrode, and the electrode active material includes a silicon-based negative electrode active material as the negative electrode active material.

13. A lithium secondary battery comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, wherein the positive electrode or the negative electrode is an electrode according to any one of claims 10 to 12.

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