Anode for lithium secondary battery, method for manufacturing anode for lithium secondary battery, and lithium secondary battery including anode

Abstract

The present application relates to a negative electrode for a lithium secondary battery, a method for manufacturing the negative electrode for a lithium secondary battery, and a lithium secondary battery including the negative electrode.

Description

[Technical Field]

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2022-0184204, filed with the Korean Intellectual Property Office on December 26, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present application relates to a negative electrode for a lithium secondary battery, a method for producing a negative electrode for a lithium secondary battery, and a lithium secondary battery including the negative electrode. [Background technology]

[0003] The rapid increase in fossil fuel use has led to an increasing demand for alternative and clean energy, and one of the most actively researched fields in this area is the field of power generation and storage using electrochemical reactions.

[0004] Currently, a typical example of an electrochemical element that uses electrochemical energy is a secondary battery, and the range of its use is expanding.

[0005] With the development of mobile device technologies and the increase in demand, the demand for secondary batteries as energy sources is rapidly increasing. Among such secondary batteries, lithium secondary batteries, which have high energy density and voltage, long cycle life, and low self-discharge rate, have been commercialized and widely used. In addition, active research is being conducted on methods for manufacturing high-density electrodes with higher energy density per unit volume as electrodes for such high-capacity lithium secondary batteries.

[0006] Generally, a secondary battery comprises a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode contains a negative electrode active material that inserts and extracts lithium ions from the positive electrode. The negative electrode active material may be silicon-based particles with a large discharge capacity.

[0007] In particular, in response to the recent demand for high-density energy batteries, active research has been conducted into methods for increasing capacity by using silicon-based compounds such as Si / C and SiOx as anode active materials, which have capacities more than 10 times greater than graphite-based materials. However, while silicon-based compounds, which are high-capacity materials, have superior capacity characteristics compared to conventional graphite, their rapid volume expansion during charging can disrupt conductive pathways, degrading battery performance and resulting in a decrease in capacity from the start. Furthermore, silicon-based anodes face challenges in that lithium ions cannot be uniformly charged throughout the anode depth during repeated charge and discharge cycles, and reactions occur on the surface, accelerating surface degradation. This calls for improved performance in terms of battery cycles.

[0008] Therefore, various methods are being discussed to solve the problems associated with using silicon-based compounds as negative electrode active materials, such as adjusting the driving potential, coating a thin film on the active material layer, suppressing volume expansion itself by adjusting the particle size of the silicon-based compound, or developing a binder that controls the volume expansion of the silicon-based compound to prevent the conductive path from being broken. Research is also being conducted to improve the lifespan characteristics of silicon-based negative electrodes by limiting the proportion of silicon-based active material used during initial charge and discharge and providing a reservoir role through the use of a method of prelithiating the silicon-based active material layer.

[0009] However, in the case of the above method, there is a risk that the performance of the battery may be deteriorated, and therefore there is a limit to its applicability, and there is still a limit to the commercialization of the production of negative electrode batteries with a high content of silicon-based compounds. As the proportion of silicon-based active material in the silicon-based active material layer increases, pre-lithiation is concentrated on the surface of the negative electrode, which in turn causes damage to the silicon-based active material on the surface side and causes non-uniform pre-lithiation, resulting in problems in improving life characteristics.

[0010] Furthermore, in the case of silicon-based anodes, a single charge and discharge is performed during the activation process, but the highly reactive silicon-based active material prevents high-rate charging, which increases the activation process time and causes problems in the manufacturing process.

[0011] Therefore, research is needed into a negative electrode that can improve capacity characteristics without causing a decrease in capacity characteristics even when a silicon-based compound is used as an active material, can prevent electrode surface degradation during charge and discharge cycles, improve cycle performance, and can shorten the activation process time, and has an optimal silicon phase arrangement through the activation process. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-080971 Summary of the Invention [Problem to be solved by the invention]

[0013] The present application relates to a negative electrode for a lithium secondary battery that uses a silicon-based active material in a negative electrode, while maximizing capacity characteristics, which is the main purpose of using a silicon-based active material, while preventing electrode surface degradation, which has been a conventional problem, during charge and discharge cycles, and achieving optimal arrangement of silicon phases in the negative electrode active material layer through a high-rate activation process; a method for manufacturing a negative electrode for a lithium secondary battery; and a lithium secondary battery including the negative electrode.

[0014] That is, the negative electrode for a lithium secondary battery according to the present application exhibits capacity retention and resistance characteristics equivalent to or better than those of a negative electrode in which a low-rate activation process is applied and the process time is increased, and is mainly characterized by defining the state of the silicon phase of the negative electrode for a lithium secondary battery, which can ensure processability. [Means for solving the problem]

[0015] One embodiment of the present specification is a negative electrode for a lithium secondary battery including a negative electrode current collector layer; and a negative electrode active material layer provided on one or both surfaces of the negative electrode current collector layer, wherein the negative electrode active material layer includes a first negative electrode active material layer provided on the negative electrode current collector layer; and a second negative electrode active material layer provided on the opposite surface of the first negative electrode active material layer facing the negative electrode current collector layer, the first negative electrode active material layer includes a first negative electrode active material layer composition including a first negative electrode active material, the second negative electrode active material layer includes a second negative electrode active material layer composition including a second negative electrode active material, the first negative electrode active material includes one or more selected from the group consisting of SiOx (x = 0) and SiOx (0 < x < 2), based on 100 parts by weight of the first negative electrode active material, the SiOx (x = 0) is included in an amount of 95 parts by weight or more, the second negative electrode active material includes a mixture of one or more selected from the group consisting of a carbon-based active material, a silicon-based active material, a metal-based active material capable of alloying with lithium, and a lithium-containing nitride, the ratio of amorphous silicon contained in the first negative electrode active material layer is lower than the ratio of amorphous silicon contained in the second negative electrode active material layer, and the ratio of the silicon phase contained in the negative electrode active material layer satisfies the following formula 1, and a negative electrode for a lithium secondary battery is provided.

[0016] [Formula 1] 5 ≤ B / (A + B) × 100 (%) ≤ 30 In Formula 1, A is the part by weight of the crystalline phase based on 100 parts by weight of the silicon phase contained in the negative electrode active material layer, and B is the part by weight of the amorphous phase based on 100 parts by weight of the silicon phase contained in the negative electrode active material layer.

[0017] In another embodiment, a lithium secondary battery including a positive electrode; the negative electrode for a lithium secondary battery according to the present application; a separator provided between the positive electrode and the negative electrode; and an electrolyte is provided.

[0018] Finally, a step of preparing a lithium secondary battery including a positive electrode, a negative electrode for a lithium secondary battery, a separator, and an electrolyte; and a step of activating the lithium secondary battery; A method for manufacturing a lithium secondary battery, wherein the activation step includes a high C-rate activation step (high-rate charging), and the step of preparing the negative electrode for the lithium secondary battery includes: preparing a negative electrode current collector layer; applying a first negative electrode active material layer composition to one or both surfaces of the negative electrode current collector layer using a coater to form a first negative electrode active material layer; and applying a second negative electrode active material layer composition to the opposite surface of the first negative electrode active material layer that contacts the negative electrode current collector layer using a coater to form a second negative electrode active material layer; The first negative electrode active material includes one or more selected from the group consisting of SiOx (x = 0) and SiOx (0 < x < 2), and based on 100 parts by weight of the first negative electrode active material, the SiOx (x = 0) is included in an amount of 95 parts by weight or more, and the second negative electrode active material includes one or more selected from the group consisting of a carbon-based active material, a silicon-based active material, a metal-based active material capable of alloying with lithium, and a lithium-containing nitride. Provide a method for manufacturing a lithium secondary battery.

Effect of the Invention

[0019] In the case of the negative electrode for a lithium secondary battery according to an embodiment of the present invention, it has a double-layer active material layer composed of a first negative electrode active material layer and a second negative electrode active material layer. In particular, the first negative electrode active material contained in the first negative electrode active material layer includes one or more selected from the group consisting of SiOx (x = 0) and SiOx (0 < x < 2), and based on 100 parts by weight of the first negative electrode active material, the SiOx (x = 0) is included in an amount of 95 parts by weight or more, and the second negative electrode active material contained in the second negative electrode active material layer includes one or more selected from the group consisting of a carbon-based active material, a silicon-based active material, a metal-based active material capable of alloying with lithium, and a lithium-containing nitride.

[0020] The negative electrode for a lithium secondary battery according to the present application has a dual-layer active material layer having the specific composition and content described above. In particular, since the first negative electrode active material layer contains a high content of SiOx (x=0), it can have the advantages of high capacity, high density, and fast charging. Furthermore, since the second negative electrode active material layer contains a silicon-based and / or carbon-based active material, it can prevent electrode surface degradation during charge and discharge cycles and improve the uniformity of prelithiation.

[0021] In particular, the negative electrode for a lithium secondary battery according to the present application is characterized in that it can enable high-C-rate charging during the activation process, thereby achieving optimal arrangement of the silicon phase in the negative electrode active material layer and satisfying the range of formula 1.

[0022] Therefore, the lithium secondary battery containing this has the main feature of satisfying cycle characteristics as well as optimal capacity characteristics, which are the advantages of the Si anode.

[0023] In conclusion, the negative electrode for a lithium secondary battery according to the present application has the advantages of an electrode using a high content of Si particles as a single-layer active material, while at the same time resolving the disadvantages of such an electrode, such as surface degradation, uniformity during pre-lithiation, and poor life characteristics. To address these issues, the negative electrode for a lithium secondary battery according to the present application is characterized by coating a second negative electrode active material layer on top of a first negative electrode active material layer, and adjusting the conditions of the activation process to achieve optimal arrangement of silicon phases in the negative electrode active material layer (particularly, arrangement of silicon phases in the first negative electrode active material layer), thereby satisfying the range of Formula 1. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a diagram showing a laminated structure of a negative electrode for a lithium secondary battery according to an embodiment of the present application. [Figure 2] 1 is a diagram showing a laminated structure of a negative electrode for a lithium secondary battery according to an embodiment of the present application. [Figure 3]1 is a flow diagram illustrating a wet-on-dry process according to one embodiment of the present application. [Figure 4] 1 is a flow diagram illustrating a wet-on-wet process according to one embodiment of the present application. [Figure 5] FIG. 2 is a diagram showing the distribution of silicon phases by Raman analysis for the negative electrodes (first negative electrode active material layers) for lithium secondary batteries of Examples 1 to 4 according to the present application. [Figure 6] FIG. 1 is a diagram showing the distribution of silicon phases by Raman analysis for the negative electrodes (first negative electrode active material layers) for lithium secondary batteries of Comparative Examples 1 to 4 according to the present application. [Figure 7] FIG. 10 is a view showing an SEM photograph of a cross section of a negative electrode for a lithium secondary battery according to Comparative Example 5 of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0025] Before describing the present invention, some terms will first be defined.

[0026] In this specification, when a part is said to "comprise" a certain component, this does not mean that it excludes other components, but that it may further include other components, unless otherwise specified.

[0027] In this specification, "p to q" means "not less than p and not more than q."

[0028] In this specification, the "specific surface area" is measured by the BET method, and specifically, is calculated from the amount of nitrogen gas adsorption at liquid nitrogen temperature (77 K) using a BELSORP-mini II manufactured by BEL Japan Co., Ltd. That is, in the present application, the BET specific surface area can mean the specific surface area measured by the above-mentioned measurement method.

[0029] In this specification, "Dn" refers to particle size distribution, and refers to the particle size at the n% point in the cumulative particle number distribution by particle size. That is, D50 is the particle size (average particle size, median particle size) at the 50% point in the cumulative particle number distribution by particle size, D90 is the particle size at the 90% point in the cumulative particle number distribution by particle size, and D10 is the particle size at the 10% point in the cumulative particle number distribution by particle size. Meanwhile, particle size distribution may also be measured using the laser diffraction method. Specifically, the powder to be measured is dispersed in a dispersion medium and then introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac S3500). When the particles pass through a laser beam, the difference in diffraction pattern due to particle size is measured to calculate the particle size distribution.

[0030] In this specification, when a polymer contains a certain monomer as a monomer unit, it means that the monomer participates in a polymerization reaction and is included as a repeating unit in the polymer. In this specification, when a polymer contains a monomer, this is interpreted as the same as when a polymer contains a monomer as a monomer unit.

[0031] In this specification, the term "polymer" is understood to be used in a broad sense, including copolymers, unless otherwise specified as a "homopolymer."

[0032] In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) are polystyrene-equivalent molecular weights measured by gel permeation chromatography (GPC) using commercially available monodisperse polystyrene polymers (standard samples) with various degrees of polymerization that are commercially available for molecular weight measurement as standard substances. In this specification, molecular weight means weight average molecular weight unless otherwise specified.

[0033] Hereinafter, in order for those with ordinary knowledge in the technical field to which the present invention pertains to easily implement the present invention, a detailed description will be given with reference to the drawings. However, the present invention can be embodied in various different forms and is not limited to the following description.

[0034] One embodiment of the present specification is a negative electrode for a lithium secondary battery including a negative electrode current collector layer; and a negative electrode active material layer provided on one or both surfaces of the negative electrode current collector layer, wherein the negative electrode active material layer includes a first negative electrode active material layer provided on the negative electrode current collector layer; and a second negative electrode active material layer provided on the opposite surface of the surface of the first negative electrode active material layer facing the negative electrode current collector layer, the first negative electrode active material layer includes a first negative electrode active material layer composition containing a first negative electrode active material, the second negative electrode active material layer includes a second negative electrode active material layer composition containing a second negative electrode active material, the first negative electrode active material includes one or more selected from the group consisting of SiOx (x = 0) and SiOx (0 < x < 2), based on 100 parts by weight of the first negative electrode active material, the SiOx (x = 0) contains 95 parts by weight or more, the second negative electrode active material includes a mixture of one or more selected from the group consisting of a carbon-based active material, a silicon-based active material, a metal-based active material capable of alloying with lithium, and a lithium-containing nitride, the ratio of amorphous silicon contained in the first negative electrode active material layer is lower than the ratio of amorphous silicon contained in the second negative electrode active material layer, and the ratio of the silicon phase in the negative electrode active material layer satisfies the following formula 1, and a negative electrode for a lithium secondary battery is provided.

[0035] [Formula 1] 5 ≦ B / (A + B) × 100 (%) ≦ 30 In Formula 1, A is the part by weight of the crystalline phase based on 100 parts by weight of the silicon phase contained in the negative electrode active material layer, and B is the part by weight of the amorphous phase based on 100 parts by weight of the silicon phase contained in the negative electrode active material layer.

[0036] The negative electrode for a lithium secondary battery according to the present application has the advantages of an electrode using a high content of Si particles as a single-layer active material, but in order to solve the disadvantages of using such an electrode, such as surface degradation, uniformity during pre-lithiation, and poor life characteristics, a second negative electrode active material layer is coated on top of a first negative electrode active material layer, and the activation process conditions are adjusted to optimally arrange the silicon phase in the negative electrode active material layer and satisfy the range of Formula 1.

[0037] FIG. 1 is a diagram illustrating a laminated structure of a negative electrode for a lithium secondary battery according to one embodiment of the present application. Specifically, a negative electrode for a lithium secondary battery 100 including a first negative electrode active material layer 20 and a second negative electrode active material layer 10 on one side of a negative electrode current collector layer 30 can be seen. While FIG. 1 illustrates the first negative electrode active material layer formed on one side, it may also be formed on both sides of the negative electrode current collector layer. As described above, in one embodiment of the present application, the first negative electrode active material layer may be formed on the front surface of the negative electrode current collector layer, and the second negative electrode active material layer may be formed on the front surface of the first negative electrode active material layer.

[0038] FIG. 2 illustrates a stacked structure of a negative electrode for a lithium secondary battery according to an embodiment of the present application. Specifically, as illustrated in FIG. 2, a first negative electrode active material layer 20 and a second negative electrode active material layer 10 may be formed on both sides of a negative electrode current collector layer 30. Alternatively, the stacked structure may be 10>20>30>20>10. Additionally, the stacked structure may be 10>20>30>20, 10>20>30>10, or 10>20>30>10>20, regardless of the stacked structure on the opposite side, as long as the first negative electrode active material layer and the second negative electrode active material layer are stacked sequentially on only one side of the negative electrode current collector layer. Preferably, both sides of the negative electrode current collector layer have the same composition, specifically, a 10>20>30>20>10 structure may be used.

[0039] The negative electrode for a lithium secondary battery of the present invention will be described in more detail below.

[0040] In one embodiment of the present application, a negative electrode for a lithium secondary battery includes a negative electrode current collector layer; and a negative electrode active material layer provided on one or both surfaces of the negative electrode current collector layer. The negative electrode active material layer includes a first negative electrode active material layer provided on the negative electrode current collector layer; and a second negative electrode active material layer provided on the opposite surface of the first negative electrode active material layer facing the negative electrode current collector layer. A negative electrode for a lithium secondary battery is provided.

[0041] In one embodiment of the present application, the negative electrode current collector layer generally has a thickness of 1 μm to 100 μm. Such a negative electrode current collector layer is not particularly limited as long as it has high conductivity without inducing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, those surface-treated with carbon, nickel, titanium, silver, etc. on the surface of copper or stainless steel, aluminum-cadmium alloy, etc. may be used. Also, fine irregularities may be formed on the surface to strengthen the bonding force of the negative electrode active material, and it may be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric body, etc.

[0042] In one embodiment of the present application, the thickness of the negative electrode current collector layer may be 1 μm or more and 100 μm or less.

[0043] However, the thickness may vary variously depending on the type and application of the negative electrode used, and is not limited thereto.

[0044] In one embodiment of the present application, the first negative electrode active material includes one or more selected from the group consisting of SiOx (x = 0) and SiOx (0 < x < 2), and based on 100 parts by weight of the first negative electrode active material, it may contain 95 parts by weight or more of SiOx (x = 0).

[0045] In one embodiment of the present application, the first negative electrode active material contains one or more selected from the group consisting of SiOx (x = 0) and SiOx (0 < x < 2). Based on 100 parts by weight of the first negative electrode active material, the SiOx (x = 0) may contain 95 parts by weight or more, preferably 97 parts by weight or more, more preferably 99 parts by weight or more, and may also contain 100 parts by weight or less.

[0046] In one embodiment of the present application, the first negative electrode active material may particularly use pure silicon (Si) particles. Using pure silicon (Si) as the first negative electrode active material can mean, as described above, that the first negative electrode active material contains pure Si particles (SiOx (x = 0)) that are not combined with other particles or elements within the above range based on a total of 100 parts by weight.

[0047] In one embodiment of the present application, the first negative electrode active material may consist of SiOx (x = 0).

[0048] The first negative electrode active material layer according to the present application contains the first negative electrode active material, and specifically contains pure silicon particles containing 95 parts by weight or more of SiOx (x = 0). When a high content of pure silicon particles is contained, the capacity characteristics are excellent, but the life reduction characteristics due to surface non-uniform reaction occur. Accordingly, the problem has been solved by including the second negative electrode active material layer according to the present invention at a specific weight loading amount.

[0049] Meanwhile, the average particle size (D50) of the first negative electrode active material of the present invention may be 3 μm to 10 μm, specifically 4 μm to 8 μm, and more specifically 5 μm to 7 μm. When the average particle size is within this range, the specific surface area of ​​the particles is within an appropriate range, and the viscosity of the negative electrode slurry is formed within an appropriate range. This facilitates dispersion of the particles constituting the negative electrode slurry. Furthermore, when the size of the first negative electrode active material is equal to or greater than the lower limit of the range, the contact area between the silicon particles and the conductive material is excellent due to the composite of the conductive material and the binder in the negative electrode slurry, increasing the likelihood of maintaining a conductive network and improving the capacity retention rate. Meanwhile, when the average particle size is within this range, excessively large silicon particles are excluded, resulting in a smooth negative electrode surface, thereby preventing non-uniform current density during charge and discharge.

[0050] In one embodiment of the present application, the first negative electrode active material typically has a characteristic BET specific surface area. The BET specific surface area of ​​the first negative electrode active material is preferably 0.01 m 2 / g~150.0m 2 / g, more preferably 0.1m 2 / g~100.0m 2 / g, particularly preferably 0.2m 2 / g~80.0m 2 / g, most preferably 0.2m 2 / g~18.0m 2 / g. The BET specific surface area is determined in accordance with DIN 66131 (using nitrogen).

[0051] In one embodiment of the present application, the first negative electrode active material may be, for example, in a crystalline or amorphous form, and is preferably not porous. The silicon particles are preferably spherical or platelet-shaped particles. Alternatively, the silicon particles may have a fibrous structure or may be in the form of a silicon-containing thin film or coating, but this is less preferred.

[0052] In one embodiment of the present application, the first negative electrode active material may have a non-spherical morphology, and the sphericity thereof is, for example, 0.9 or less, for example, 0.7 to 0.9, for example, 0.8 to 0.9, for example, 0.85 to 0.9.

[0053] In this application, the circularity is determined by the following formula A-1, where A is the area and P is the perimeter.

[0054] [Formula 1-1] 4πA / P 2

[0055] In one embodiment of the present application, there is provided a negative electrode for a lithium secondary battery, wherein the first negative electrode active material is 60 parts by weight or more based on 100 parts by weight of the first negative electrode active material layer composition.

[0056] In yet another embodiment, the first negative electrode active material may comprise 60 parts by weight or more, preferably 65 parts by weight or more, more preferably 70 parts by weight or more, based on 100 parts by weight of the first negative electrode active material layer composition, and may comprise 95 parts by weight or less, preferably 90 parts by weight or less, more preferably 80 parts by weight or less.

[0057] The first anode active material layer composition according to the present application uses a first anode active material having a significantly high capacity within the above range, and by using the second anode active material layer described below together, the capacity performance of the entire anode is not reduced, and the problems of surface degradation during charge and discharge, uniformity during pre-lithiation, and life characteristics are solved.

[0058] While graphite-based compounds have traditionally been used exclusively as anode active materials, attempts to incorporate silicon-based compounds into batteries to increase capacity have recently been increasing in response to growing demand for high-capacity batteries. However, silicon-based compounds have a limitation in that their volume rapidly expands during charge / discharge processes, damaging the conductive pathways formed within the anode active material layer and reducing battery performance.

[0059] Therefore, in one embodiment of the present application, the first negative electrode active material layer composition may further include one or more selected from the group consisting of a first negative electrode conductive material and a first negative electrode binder.

[0060] In this case, the first negative electrode conductive material and the first negative electrode binder contained in the first negative electrode active material layer composition may be any materials commonly used in the art without any limitations.

[0061] In one embodiment of the present application, the first negative electrode conductive material may be any material commonly used in the art without limitation, and may specifically include one or more selected from the group consisting of dot-like conductive materials, planar conductive materials, and linear conductive materials.

[0062] In one embodiment of the present application, the dot-like conductive material refers to a dot-like or spherical conductive material that can be used to improve the conductivity of a negative electrode and has conductivity without inducing chemical changes. Specifically, the dot-like conductive material may be at least one selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, conductive fiber, fluorocarbon, aluminum powder, nickel powder, zinc oxide, potassium titanate, titanium oxide, and polyphenylene derivatives, and preferably includes carbon black in view of achieving high conductivity and excellent dispersibility.

[0063] In one embodiment of the present application, the point-like conductive material has a BET specific surface area of ​​40 m 2 / g or more 70m 2 / g or less, preferably 45m 2 / g or more 65m 2 / g or less, more preferably 50m 2 / g or more 60m 2 / g or less.

[0064] In one embodiment of the present application, the particle size of the dotted conductive material may be 10 nm to 100 nm, preferably 20 nm to 90 nm, and more preferably 20 nm to 60 nm.

[0065] In one embodiment of the present application, the first negative electrode conductive material may include a sheet conductive material.

[0066] The planar conductive material can improve conductivity by increasing surface contact between silicon particles in the negative electrode, while simultaneously suppressing the disconnection of conductive paths due to volume expansion. The planar conductive material may be referred to as a planar conductive material, a plate-type conductive material, or a bulk-type conductive material.

[0067] In one embodiment of the present application, the sheet conductive material may include at least one selected from the group consisting of plate-like graphite, graphene, graphene oxide, and graphite flakes, and may preferably be plate-like graphite.

[0068] In one embodiment of the present application, the average particle size (D50) of the sheet conductive material may be 2 μm to 7 μm, specifically 3 μm to 6 μm, and more specifically 4 μm to 5 μm. When the average particle size is within this range, the particle size is sufficient, which facilitates dispersion without excessively increasing the viscosity of the negative electrode slurry. Therefore, when dispersing using the same equipment and time, the dispersion effect is excellent.

[0069] In one embodiment of the present application, there is provided a negative electrode composition in which the planar conductive material has a D10 of 0.5 μm or more and 1.5 μm or less, a D50 of 2.5 μm or more and 3.5 μm or less, and a D90 of 7.0 μm or more and 15.0 μm or less.

[0070] In one embodiment of the present application, the sheet conductive material may be a sheet conductive material having a high BET specific surface area; or a sheet conductive material having a low specific surface area.

[0071] In one embodiment of the present application, the planar conductive material may be a planar conductive material with a high specific surface area or a planar conductive material with a low specific surface area without any restrictions. However, the planar conductive material according to the present application may be subject to some dispersion influence on electrode performance, and it is particularly preferable to use a planar conductive material with a low specific surface area that does not cause dispersion problems.

[0072] In one embodiment of the present application, the sheet conductive material has a BET specific surface area of ​​5 m 2 / g or more.

[0073] In another embodiment, the sheet conductive material has a BET specific surface area of ​​5 m 2 / g or more 500m 2 / g or less, and preferably 5m 2 / g or more 300m 2 / g or less, more preferably 5m 2 / g or more 250m 2 / g or less.

[0074] In another embodiment, the sheet conductive material is a sheet conductive material having a high specific surface area, and a BET specific surface area of ​​50 m 2 / g or more 500m 2 / g or less, preferably 80m 2 / g or more 300m 2 / g or less, more preferably 100m 2 / g or more 300m 2 / g or less can be satisfied.

[0075] In another embodiment, the sheet conductive material is a sheet conductive material having a low specific surface area, and a BET specific surface area of ​​5 m 2 / g or more 40m 2 / g or less, preferably 5m 2 / g or more 30m 2 / g or less, more preferably 5m 2 / g or more 25m 2 / g or less can be satisfied.

[0076] Other conductive materials include linear conductive materials such as carbon nanotubes. The carbon nanotubes may be bundled carbon nanotubes. The bundled carbon nanotubes may include a plurality of carbon nanotube units. Specifically, unless otherwise specified, the term "bundle type" refers to a secondary shape in which a plurality of carbon nanotube units are arranged parallel to each other or twisted with the longitudinal axes of the carbon nanotube units substantially aligned in the same direction, forming a bundle or rope. The carbon nanotube units have cylindrical graphite sheets with nanosized diameters and an sp2 bonding structure. Depending on the winding angle and structure of the graphite sheets, they can exhibit conductive or semiconductive properties. Compared to entangled carbon nanotubes, the bundled carbon nanotubes can be more uniformly dispersed during negative electrode fabrication and can smoothly form a conductive network within the negative electrode, thereby improving the conductivity of the negative electrode.

[0077] In one embodiment of the present application, the first negative electrode conductive material may be present in an amount of 10 parts by weight to 40 parts by weight based on 100 parts by weight of the first negative electrode active material layer composition.

[0078] In yet another embodiment, the first negative electrode conductive material may comprise, based on 100 parts by weight of the first negative electrode active material layer composition, 1 part by weight or more and 40 parts by weight or less, preferably 3 parts by weight or more and 30 parts by weight or less, and more preferably 5 parts by weight or more and 25 parts by weight or less.

[0079] In one embodiment of the present application, the first negative electrode conductive material includes dot-like conductive material, sheet-like conductive material, and line-like conductive material, and the dot-like conductive material:sheet-like conductive material:line-like conductive material ratio can satisfy 1:1:0.01 to 1:1:1.

[0080] In one embodiment of the present application, the dot-like conductive material may be present in an amount of 1 part by weight or more and 60 parts by weight or less, preferably 5 parts by weight or more and 50 parts by weight or less, and more preferably 10 parts by weight or more and 50 parts by weight or less, based on 100 parts by weight of the first negative electrode conductive material.

[0081] In one embodiment of the present application, the sheet conductive material can satisfy the range of 1 part by weight or more and 60 parts by weight or less, preferably 5 parts by weight or more and 50 parts by weight or less, and more preferably 10 parts by weight or more and 50 parts by weight or less, based on 100 parts by weight of the first negative electrode conductive material.

[0082] In one embodiment of the present application, the linear conductive material may satisfy the range of 0.01 parts by weight or more and 10 parts by weight or less, preferably 0.05 parts by weight or more and 8 parts by weight or less, and more preferably 0.1 parts by weight or more and 5 parts by weight or less, based on 100 parts by weight of the first negative electrode conductive material.

[0083] In one embodiment of the present application, the first negative electrode conductive material may include a linear conductive material and a planar conductive material.

[0084] In one embodiment of the present application, the first negative electrode conductive material includes a linear conductive material and a sheet conductive material, and the weight ratio of the linear conductive material to the sheet conductive material may satisfy 0.01:1 to 0.1:1.

[0085] In one embodiment of the present application, the first negative electrode conductive material satisfies the above composition and ratio, and thus does not significantly affect the life characteristics of conventional lithium secondary batteries, and has the characteristics of having excellent output characteristics at a high C rate by increasing the number of points at which charging and discharging are possible. The first anode conductive material according to the present application has a completely different structure from the conductive material used in the positive electrode. That is, the first anode conductive material according to the present application controls the contact points between the silicon-based active material, which experiences a large volume expansion during charging and discharging, while the positive electrode conductive material acts as a buffer during rolling and also provides some conductivity, and therefore has a completely different structure and role from the anode conductive material of the present invention.

[0086] Furthermore, the first negative electrode conductive material according to the present application is applied to a silicon-based active material and has a completely different structure from conductive materials applied to graphite-based active materials. That is, conductive materials used in electrodes with graphite-based active materials simply have smaller particles than the active material, and therefore have the properties of improving output characteristics and imparting some conductivity, and are completely different in structure and role from the first negative electrode conductive material applied together with a silicon-based active material as in the present invention.

[0087] In one embodiment of the present application, the first negative electrode binder may include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, and substances in which hydrogen is substituted with Li, Na, Ca, or the like, or may include various copolymers thereof.

[0088] The first negative electrode binder according to one embodiment of the present application serves to control the first negative electrode active material and the first negative electrode conductive material to prevent twisting and structural deformation of the negative electrode structure during volume expansion and relaxation of the first negative electrode active material. Any common binder may be used as long as it fulfills this role. Specifically, a water-based binder may be used, and more specifically, a PAM-based binder may be used.

[0089] In one embodiment of the present application, the first negative electrode binder may include 30 parts by weight or less, preferably 25 parts by weight or less, more preferably 20 parts by weight or less, or may include 5 parts by weight or more, or 10 parts by weight or more, based on 100 parts by weight of the first negative electrode active material layer composition.

[0090] Compared to conventional carbon-based negative electrodes, when a silicon-based negative electrode is used, a water-based binder may be applied in the above weight part and a dot-like conductive material may be used. Due to this characteristic, the dot-like conductive material has hydrophobicity, which results in excellent bonding strength between the conductive material and the binder.

[0091] In one embodiment of the present application, the second negative electrode active material may include a mixture of one or more materials selected from the group consisting of a carbon-based active material, a silicon-based active material, a metal-based active material capable of forming an alloy with lithium, and a lithium-containing nitride.

[0092] In yet another embodiment, the second negative electrode active material may include a mixture of one or more and three or less types selected from the group consisting of a carbon-based active material, a silicon-based active material, a metal-based active material capable of forming an alloy with lithium, and a lithium-containing nitride.

[0093] In another embodiment, the second negative electrode active material may include a carbon-based active material and a silicon-based active material.

[0094] In another embodiment, the second negative electrode active material may include a silicon-based active material.

[0095] In one embodiment of the present application, the second negative electrode active material includes one or more mixtures selected from the group consisting of a carbon-based active material, a silicon-based active material, a metal-based active material capable of alloying with lithium, and a lithium-containing nitride, and the silicon-based active material is 50 parts by weight or more and 100 parts by weight or less based on 100 parts by weight of the second negative electrode active material, and a negative electrode for a lithium secondary battery is provided.

[0096] In another embodiment, the second negative electrode active material includes one or more mixtures selected from the group consisting of a carbon-based active material, a silicon-based active material, a metal-based active material capable of alloying with lithium, and a lithium-containing nitride.

[0097] In one embodiment of the present application, the silicon-based active material included in the second negative electrode active material may include one or more selected from the group consisting of SiOx (0 < x < 2), SiC, and Si alloys.

[0098] In one embodiment of the present application, the silicon-based active material included in the second negative electrode active material includes one or more selected from the group consisting of SiOx (0 < x < 2), SiC, and Si alloys, and may include 1 part by weight or more of SiOx (0 < x < 2) based on 100 parts by weight of the second negative electrode active material.

[0099] In another embodiment, the silicon-based active material included in the second negative electrode active material includes one or more selected from the group consisting of SiOx (0 < x < 2), SiC, and Si alloys, and based on 100 parts by weight of the second negative electrode active material, may include 1 part by weight or more and 10 parts by weight or more of SiOx (0 < x < 2), and may include 99 parts by weight or less.

[0100] In another embodiment, the silicon-based active material included in the second negative electrode active material may include SiOx (0 < x < 2).

[0101] In another embodiment, the silicon-based active material included in the second negative electrode active material may include SiC.

[0102] The negative electrode for a lithium secondary battery according to the present application includes the second negative electrode active material in the second negative electrode active material layer, as described above. This allows the negative electrode to maintain high capacity and high density characteristics by including the first negative electrode active material, while the second negative electrode active material acts as a buffer layer, thereby resolving problems such as surface degradation during charge and discharge, uniformity during pre-lithiation, and lifespan characteristics.

[0103] As an example, the second negative electrode active material layer of the present application can function as a buffer layer. Electrodes containing Si active material have superior capacity characteristics compared to electrodes containing SiO or carbon-based active materials. However, electrodes containing Si active material experience concentrated surface degradation of the negative electrode active material layer due to rapid reaction with Li ions during charge and discharge. This also occurs during the pre-lithiation process, in which lithium ions are pre-doped into the negative electrode active material layer. During the pre-lithiation process, the buffer layer prevents direct contact between the Si-based electrode and lithium, thereby preventing surface degradation. Therefore, the second negative electrode active material layer of the present invention has the same role and effect as a buffer layer during the pre-lithiation process.

[0104] In one embodiment of the present application, the carbon-based active material may be any material commonly used in carbon materials for lithium secondary batteries, such as natural graphite, artificial graphite, expanded graphite, carbon fiber, non-graphitizable carbon, carbon black, carbon nanotubes, fullerene, or activated carbon, and may be used without limitation. Specifically, the carbon-based active material may be processed into a spherical or dot-like shape.

[0105] In one embodiment of the present application, the planar conductive material used as the first negative electrode conductive material has a structure and function different from that of a carbon-based active material generally used as a negative electrode active material. Specifically, the carbon-based active material used as a negative electrode active material may be artificial graphite or natural graphite, and refers to a material that is processed into a spherical or dot-like shape to facilitate the storage and release of lithium ions.

[0106] Meanwhile, the planar conductive material used as the first negative electrode conductive material is a material having a planar or plate-like shape, which may be expressed as plate-like graphite. That is, it is a material contained in the negative electrode active material layer to maintain a conductive path within the layer, and does not play a role in storing or releasing lithium, but rather serves to ensure a planar conductive path within the negative electrode active material layer.

[0107] That is, in this application, the use of plate-shaped graphite as a conductive material means that it is processed into a planar or plate-like shape and used as a material to ensure a conductive path, not for the purpose of storing or releasing lithium. In this case, the negative electrode active material included therein has high capacity characteristics for storing and releasing lithium, and plays a role in storing and releasing all lithium ions transferred from the positive electrode.

[0108] Meanwhile, in the present application, the term "carbon-based active material is used as an active material" means that the carbon-based active material is processed into a dotted or spherical shape and used as a material that stores or releases lithium.

[0109] That is, in one embodiment of the present application, the carbon-based active material, artificial graphite or natural graphite, has a BET specific surface area of ​​0.1 m 2 / g or more 4.5m 2 / g or less. In addition, the plate-type graphite, which is a planar conductive material, has a BET specific surface area of ​​5 m 2 / g or more.

[0110] Representative examples of the metal-based active material include compounds containing one or more metal elements selected from the group consisting of Al, Sn, Ag, Bi, Mg, Zn, In, Ge, Pb, Pd, Pt, Ti, Sb, Ga, Mn, Fe, Co, Ni, Cu, Sr, and Ba. These metal compounds can be used in any form, such as simple substances, alloys, oxides (TiO2, SnO2, etc.), nitrides, sulfides, borides, and alloys with lithium, but simple substances, alloys, oxides, and alloys with lithium can achieve high capacity.

[0111] In one embodiment of the present application, there is provided a negative electrode for a lithium secondary battery, wherein the second negative electrode active material is contained in an amount of 60 parts by weight or more based on 100 parts by weight of a second negative electrode active material layer composition.

[0112] In another embodiment, the second negative electrode active material may be 60 parts by weight or more, and may be 100 parts by weight or less, or 99 parts by weight or less, based on 100 parts by weight of the second negative electrode active material layer composition.

[0113] The second negative electrode active material layer composition according to the present application has lower capacity characteristics than the first negative electrode active material, but by using a second negative electrode active material that is less susceptible to particle cracking due to charge and discharge within the above range, it is possible to suppress the surface reaction of the negative electrode without reducing the capacity performance of the negative electrode, thereby achieving the characteristic of improved life characteristics.

[0114] In one embodiment of the present application, there is provided a negative electrode for a lithium secondary battery, wherein the second negative electrode active material layer composition further comprises one or more selected from the group consisting of a second negative electrode conductive material and a second negative electrode binder.

[0115] In this case, the second negative electrode conductive material and the second negative electrode binder may be the same as the first negative electrode conductive material and the first negative electrode binder.

[0116] In one embodiment of the present application, there is provided a negative electrode for a lithium secondary battery, wherein the ratio of amorphous silicon contained in the first negative electrode active material layer is lower than the ratio of amorphous silicon contained in the second negative electrode active material layer, and the ratio of silicon phase contained in the negative electrode active material layer satisfies the following formula 1:

[0117] [Formula 1] 5≦B / (A+B)×100(%)≦30 In the formula 1, A is the weight part of the crystalline phase based on 100 parts by weight of the silicon phase contained in the negative electrode active material layer, B is the weight part of the amorphous phase based on 100 weight parts of the silicon phase contained in the negative electrode active material layer.

[0118] In one embodiment of the present application, the formula 1 can satisfy 5≦B / (A+B)×100(%)≦30, preferably 6≦B / (A+B)×100(%)≦25, and more preferably 7≦B / (A+B)×100(%)≦20.

[0119] The negative electrode for a lithium secondary battery according to the present application can include high-C-rate charging in the activation process, compared to when a conventional single-layer silicon-based active material layer is used, thereby shortening the activation process itself, and the ratio of the silicon phase in the negative electrode active material layer can be adjusted to the range of the above-described formula 1. As a result, the negative electrode for a lithium secondary battery can be manufactured in a shorter time, and has the characteristics of high capacity and life characteristics at room temperature.

[0120] In one embodiment of the present application, there is provided a negative electrode for a lithium secondary battery, wherein the second negative electrode active material layer contains amorphous phase silicon and crystalline phase silicon, and the amorphous phase is contained in an amount of 90 parts by weight or more based on 100 parts by weight of the silicon phase contained in the second negative electrode active material layer.

[0121] In yet another embodiment, the second negative electrode active material layer contains amorphous silicon and crystalline silicon, and based on 100 parts by weight of the silicon phase contained in the second negative electrode active material layer, the amorphous phase may be 90 parts by weight or more, preferably 91 parts by weight or more, and specifically, 99 parts by weight or less, or 95 parts by weight or less.

[0122] That is, the second negative electrode active material layer (upper layer) serves as a buffer layer and is coated to a thickness that allows high activation with a minimum thickness. In addition, the high capacity and high density of the first negative electrode active material layer has an important effect on negative electrode performance.

[0123] In one embodiment of the present application, there is provided a negative electrode for a lithium secondary battery, wherein the first negative electrode active material layer contains amorphous phase silicon and crystalline phase silicon, and the crystalline phase is contained in an amount of 50 parts by weight or more based on 100 parts by weight of the silicon phase contained in the first negative electrode active material layer.

[0124] In yet another embodiment, the first negative electrode active material layer contains amorphous phase silicon and crystalline phase silicon, and based on 100 parts by weight of the silicon phase contained in the first negative electrode active material layer, the crystalline phase may be 60 parts by weight or more, preferably 65 parts by weight or more, and specifically, 99 parts by weight or less, or 95 parts by weight or less.

[0125] In one embodiment of the present application, there is provided a negative electrode for a lithium secondary battery, wherein, when the total thickness of the negative electrode active material layer is defined as T, the negative electrode active material layer includes a first region that is 0.2 T or less and a second region that is more than 0.5 T or less, based on the surface opposite to the surface facing the negative electrode current collector layer, and the amorphous phase in the first region is included in an amount of 90 parts by weight or more, based on 100 parts by weight of a silicon phase in the negative electrode active material layer, and the crystalline phase in the second region is included in an amount of 60 parts by weight or more, based on 100 parts by weight of a silicon phase in the negative electrode active material layer.

[0126] In one embodiment of the present application, the total thickness T of the negative electrode active material layer may refer to the combined thickness of the first negative electrode active material layer and the second negative electrode active material layer, or may be expressed by dividing the total thickness into the above-mentioned regions. In this case, the reference surface for thickness measurement may be the surface of the second negative electrode active material layer opposite to the surface facing the first negative electrode active material layer.

[0127] That is, the negative electrode active material layer according to the present application is characterized by being formed as a double layer in which a first negative electrode active material layer and a second negative electrode active material layer are stacked. The inclusion of the second negative electrode active material layer enables high-rate charging during the activation process, and thus the ratio of the silicon phase in the negative electrode for a lithium secondary battery satisfies the above-mentioned range.

[0128] In this application, the distribution of the silicon phase can be determined by Raman analysis of the negative electrode for a lithium secondary battery to confirm the change in the silicon phase in the depth direction, and this analysis can also be used to determine the weight distribution ratio of the silicon phase within the negative electrode. In this case, the activation process is performed on the surface portion of the negative electrode active material layer, and considering that the surface portion (region far from the negative electrode current collector layer) of the negative electrode active material layer contains an amorphous phase and the interior portion (region close to the negative electrode current collector layer) of the negative electrode active material layer contains a crystalline phase, the thickness T is shown as the weight ratio of the silicon phase.

[0129] Broadly speaking, it may be divided into an amorphous phase region, a crystalline phase region, and a mixed region of amorphous and crystalline phases, and the first region described above may be represented as an amorphous phase region, the second region may be represented as a crystalline phase region, and the intermediate region in the above range (i.e., greater than 0.2 T and equal to or less than 0.5 T) may be represented as a mixed region of amorphous and crystalline phases.

[0130] By adjusting the distribution of the crystalline phase and the amorphous phase as described above, it is possible to achieve high capacity and high energy density, and also to have the characteristics of excellent cycle life at room temperature.

[0131] In one embodiment of the present application, there is provided a negative electrode for a lithium secondary battery, wherein the first negative electrode active material layer composition has a shear viscosity of 2,000 cPs or more and 15,000 cPs or less at a shear rate of 2.5 (1 / s), and the second negative electrode active material layer composition has a lower viscosity than the first negative electrode active material layer composition.

[0132] In yet another embodiment, the viscosity of the first negative electrode active material layer composition can satisfy the shear viscosity of 2,000 cPs or more and 15,000 cPs or less, preferably 2,300 cPs or more and 14,000 cPs or less, more preferably 2,500 cPs or more and 12,000 cPs or less at a shear rate of 2.5 (1 / s).

[0133] In this case, the viscosity of the second negative electrode active material layer composition must be maintained lower than the viscosity of the first negative electrode active material layer composition in order to form a two-layer negative electrode active material layer as in the present application. More specifically, the viscosity of the second negative electrode active material layer composition must be lower than but equal to the viscosity of the first negative electrode active material layer composition.

[0134] In one embodiment of the present application, the negative electrode for a lithium secondary battery may be pre-lithiated.

[0135] The negative electrode for a lithium secondary battery according to the present application is composed of a double layer, and in particular, can include high-rate charging during the activation process. It also serves to adjust the ratio of silicon phase in the negative electrode active material layer, allowing uniform lithiation to occur in the depth direction of the electrode during subsequent cyclic charging and discharging.

[0136] In one embodiment of the present application, there is provided a lithium secondary battery including: a positive electrode; a negative electrode for a lithium secondary battery according to the present application; a separator provided between the positive electrode and the negative electrode; and an electrolyte.

[0137] A secondary battery according to an embodiment of the present specification may include the negative electrode for a lithium secondary battery described above. Specifically, the secondary battery may include a negative electrode, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, and the negative electrode is the same as the negative electrode described above. Since the negative electrode has been described above, detailed description thereof will be omitted.

[0138] In one embodiment of the present application, a step of preparing a lithium secondary battery including a positive electrode, a negative electrode for a lithium secondary battery, a separator, and an electrolyte; and a step of activating the lithium secondary battery; A method for manufacturing a lithium secondary battery, wherein the activation step includes a high C-rate activation step (high-rate charging), and the step of preparing the negative electrode for the lithium secondary battery includes: preparing a negative electrode current collector layer; A step of applying a first negative electrode active material layer composition using a coater on one or both surfaces of the negative electrode current collector layer to form a first negative electrode active material layer; and applying a second negative electrode active material layer composition using a coater on the opposite surface of the first negative electrode active material layer that contacts the negative electrode current collector layer to form a second negative electrode active material layer; wherein the first negative electrode active material includes one or more selected from the group consisting of SiOx (x = 0) and SiOx (0 <x <2), and based on 100 parts by weight of the first negative electrode active material, the SiOx (x = 0) contains 95 parts by weight or more, and the second negative electrode active material is a carbon-based active material, a silicon-based active material, a metal-based active material capable of alloying with lithium, and a lithium-containing nitride. Provided is a method for manufacturing a lithium secondary battery including a mixture of one or more selected from the group consisting of.

[0139] In the manufacturing method, the composition and content included in each step may be applied to the above-described content.

[0140] That is, as described above, by forming a second negative electrode active material layer, which is not the first negative electrode active material layer alone, and including high-rate charging in the activation step, the silicon phase of the above-described formula 1 can be arranged, and thus the life characteristics can be ensured.

[0141] In one embodiment of the present application, provided is a negative electrode for a lithium secondary battery, wherein the thickness of the second negative electrode active material layer is 25% or more and 45% or less of the total thickness of the first negative electrode active material layer and the second negative electrode active material layer.

[0142] In another embodiment, the thickness of the first negative electrode active material layer may be 10 μm or more and 200 μm or less, specifically 15 μm or more and 190 μm or less, more specifically 20 μm or more and 170 μm or less.

[0143] In another embodiment, the thickness of the second negative electrode active material layer may be 5 μm or more and 150 μm or less, specifically 6 μm or more and 145 μm or less, more specifically 7 μm or more and 140 μm or less.

[0144] In one embodiment of the present application, a step of forming a first negative electrode active material layer by applying a first negative electrode active material layer composition to one or both surfaces of the negative electrode current collector layer using a coater is provided.

[0145] That is, the step may refer to a step of forming an active material layer on a negative electrode current collector layer, in which the active material layer is formed on a surface (lower layer) of a double layer structure that contacts the negative electrode current collector layer.

[0146] In one embodiment of the present application, applying the first negative electrode active material layer composition includes applying and drying a first negative electrode slurry containing the first negative electrode active material layer composition and a negative electrode slurry solvent.

[0147] In this case, the solid content of the first negative electrode slurry may be in the range of 10% to 40%.

[0148] In one embodiment of the present application, forming the first negative electrode active material layer may include mixing the first negative electrode slurry; and coating the mixed first negative electrode slurry on one or both surfaces of the negative electrode current collector layer using a coater. The coating may be performed using a coating method commonly used in the art.

[0149] In one embodiment of the present application, a step of forming a second negative electrode active material by applying a second negative electrode active material layer composition to a surface of the first negative electrode active material layer opposite to a surface in contact with the negative electrode current collector layer using a coater is provided.

[0150] That is, the step may refer to a step of forming a second negative electrode active material layer on the first negative electrode active material layer, that is, a step of forming an active material layer on a surface (upper layer) of a double layer structure that is away from the negative electrode current collector layer.

[0151] In one embodiment of the present application, applying the second negative electrode active material layer composition includes applying and drying a second negative electrode slurry containing the second negative electrode active material layer composition and a negative electrode slurry solvent.

[0152] In this case, the solid content of the second negative electrode slurry may be in the range of 10% to 40%.

[0153] In one embodiment of the present application, there is provided a method for manufacturing a lithium secondary battery, wherein the forming of the second negative electrode active material layer includes: mixing the second negative electrode slurry; and coating the mixed second negative electrode slurry on a surface of the first negative electrode active material layer opposite to a surface that contacts the negative electrode current collector layer.

[0154] The coating may be carried out by a coating method generally used in the art.

[0155] The description of the forming of the first negative electrode active material layer may be similarly applied to the forming of the second negative electrode active material layer.

[0156] In one embodiment of the present application, there is provided a method for manufacturing a lithium secondary battery, wherein the step of forming the second negative electrode active material layer on the first negative electrode active material layer includes a wet-on-dry process or a wet-on-wet process.

[0157] In one embodiment of the present application, the wet-on-dry process refers to a process of applying a first negative electrode active material layer composition, partially or completely drying it, and then applying a second negative electrode active material layer composition thereon.

[0158] 3 is a flow chart illustrating a wet-on-dry process according to one embodiment of the present application. Specifically, in the wet-on-dry process, a first negative electrode slurry mixture (first negative electrode active material, first negative electrode conductive material, first negative electrode binder, and first solvent) is prepared and applied to a negative electrode current collector layer. The first negative electrode slurry mixture is then dried to form a first negative electrode active material layer. A second negative electrode slurry mixture is then prepared and applied to the first negative electrode active material layer and dried to form a second negative electrode active material layer. The layers are then rolled and pressed to form a negative electrode for a lithium secondary battery according to the present application.

[0159] In one embodiment of the present application, the wet-on-wet process refers to a process of applying a first negative electrode active material layer composition on top of the first negative electrode active material layer composition without drying it.

[0160] 4 is a flow chart illustrating a wet-on-wet process according to one embodiment of the present application. Specifically, in the wet-on-wet process, a first negative electrode slurry mixture is prepared and applied to a negative electrode current collector layer, and simultaneously a second negative electrode slurry mixture is prepared and applied to the first negative electrode slurry mixture. The first and second negative electrode slurry mixtures are then dried. The layers are then rolled and pressed together to form a negative electrode for a lithium secondary battery according to the present application.

[0161] In particular, the wet-on-dry process involves coating a first negative electrode active material layer composition, completely drying it, and then coating a second negative electrode active material layer composition on top of it. This process allows the first negative electrode active material layer and the second negative electrode active material layer to have a clear boundary. This allows the compositions contained in the first negative electrode active material layer and the second negative electrode active material layer to be formed as a double layer without mixing.

[0162] In one embodiment of the present application, the negative electrode slurry solvent may be any solvent that can dissolve the first negative electrode active material layer composition and the second negative electrode active material layer composition, and specifically, water or NMP may be used.

[0163] As a result of the wet-on-wet process, a junction region where the first and second negative electrode active material layers are mixed can be formed. To perform the wet-on-wet process, the viscosity of the first negative electrode active material layer composition must be lower than the viscosity of the second negative electrode active material layer composition, so that intermixing can occur during the process. Meeting this viscosity range enables stable double-layer coating during the wet-on-wet process.

[0164] In the present application, the second negative electrode active material layer is formed after the first negative electrode active material layer is dried (wet-on-dry process), resulting in a clearly defined interface between the two layers. Furthermore, if the second negative electrode active material layer is applied before the first negative electrode active material layer composition is completely dried (the first and second negative electrode active material layer compositions are applied simultaneously), mixing occurs at the interface between the two layers, forming a bonded region. In this case, the formation of a mixed region is undesirable in a wet-on-dry process. To ensure wet-on-wet processability, the viscosity of the second negative electrode active material layer composition should be lower than that of the first negative electrode active material layer, as described above, to ensure good coating performance up to the coating edge during the coating process.

[0165] In one embodiment of the present application, there is provided a method for manufacturing a lithium secondary battery, the method including: pre-lithiating a negative electrode in which a first negative electrode active material layer and a second negative electrode active material layer are formed on the negative electrode current collector layer, wherein the pre-lithiating the negative electrode includes a lithium electroplating process; a lithium metal transfer process; a lithium metal vapor deposition process; or a stabilized lithium metal powder (SLMP) coating process.

[0166] As described above, the second anode active material layer includes the second anode active material described above and has a mixed composition of a silicon-based active material and a carbon-based active material, thereby maintaining the advantages of fast charging. In particular, the second anode active material has a mixed composition and is highly irreversible, which provides advantageous effects in a pre-lithiation process in which the anode is pre-charged. Compared to a case where only a first anode active material layer is used, the second anode active material layer has the second anode active material having the above composition, which enables a uniform pre-lithiation process at the upper end of the anode, thereby improving the lifespan.

[0167] In one embodiment of the present application, the porosity of the first negative electrode active material layer and the second negative electrode active material layer may satisfy the range of 10% to 60%.

[0168] In another embodiment, the porosity of the first negative electrode active material layer and the second negative electrode active material layer can satisfy the range of 10% or more and 60% or less, preferably 20% or more and 50% or less, and more preferably 30% or more and 45% or less.

[0169] The porosity varies depending on the composition and content of the active material, conductive material, and binder contained in the first and second negative electrode active material layers, thereby allowing the electrodes to have appropriate ranges of electrical conductivity and resistance.

[0170] In one embodiment of the present application, the positive electrode may include a positive electrode current collector layer, and a positive electrode active material layer formed on the positive electrode current collector layer and including a positive electrode active material.

[0171] The positive electrode current collector layer in the positive electrode is not particularly limited as long as it is conductive and does not induce chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. The positive electrode current collector layer may typically have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the current collector to enhance adhesion of the positive electrode active material. The positive electrode current collector layer may be used in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0172] The positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; a lithium iron oxide such as LiFe3O4; 1+c1 Mn 2-c1 O4 (0≦c1≦0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; chemical formula LiNi 1-c2 Ni-site type lithium nickel oxide represented by the chemical formula LiMn 2-c3 M c3Examples of the lithium manganese composite oxide include, but are not limited to, lithium manganese composite oxides represented by Li2Mn3MO8 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01≦c3≦0.1) or Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); and LiMn2O4, in which part of the Li in the chemical formula is replaced with an alkaline earth metal ion. The positive electrode may be Li metal.

[0173] The positive electrode active material layer may contain a positive electrode conductive material and a positive electrode binder in addition to the positive electrode active material described above.

[0174] In this case, the positive electrode conductive material is used to impart conductivity to the electrode and can be any material that has electronic conductivity without causing chemical changes in the battery that is constructed. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives. These materials may be used alone or in combination.

[0175] The positive electrode binder improves adhesion between positive electrode active material particles and between the positive electrode active material and the positive electrode current collector. Specific examples of the positive electrode binder include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof. These may be used alone or in combination.

[0176] The separator separates the negative electrode and the positive electrode and provides a path for lithium ions to move. Any separator typically used in secondary batteries can be used without particular limitations. In particular, a separator with low resistance to ion migration and excellent humidifying ability for the electrolyte is preferred. Specifically, a porous polymer film, such as 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, or an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof, can be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. Furthermore, a coated separator containing a ceramic component or a polymeric material to ensure heat resistance or mechanical strength can be used, and it can be selectively used in a single-layer or multi-layer structure.

[0177] Examples of the electrolyte include 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 manufacturing lithium secondary batteries, but are not limited to these.

[0178] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0179] Examples of the non-aqueous organic solvent that can be used include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0180] In particular, among the carbonate-based organic solvents, cyclic carbonates such as ethylene carbonate and propylene carbonate are preferred because they are high-viscosity organic solvents with high dielectric constants and good dissociation of lithium salts. Furthermore, when such cyclic carbonates are mixed with linear carbonates having low viscosity and low dielectric constants, such as dimethyl carbonate and diethyl carbonate, in an appropriate ratio, an electrolyte having high electrical conductivity can be produced, and thus these cyclic carbonates are more preferred.

[0181] The metal salt may be a lithium salt, which is a substance that is easily dissolved in the non-aqueous electrolyte. For example, the anion of the lithium salt may be F - , Cl - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2- , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - One or more selected from the group consisting of:

[0182] In addition to the constituent components of the electrolyte, the electrolyte may further contain one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing a decrease in battery capacity, and improving the discharge capacity of the battery.

[0183] According to another aspect of the present invention, there is provided a battery module including the secondary battery as a unit cell, and a battery pack including the battery module. The battery module and the battery pack include the secondary battery having high capacity, high rate characteristics, and high cycle characteristics, and therefore 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. [Example]

[0184] In the following, preferred examples are presented to aid in understanding the present invention. However, the following examples are merely illustrative of the present description, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope of the scope and technical ideas of the present description. Naturally, such changes and modifications fall within the scope of the claims.

[0185] <Production example> <Production of negative electrodes> Manufacture of the first negative electrode active material layer A first negative electrode slurry was prepared by adding Si (average particle size (D50): 5 μm) as a silicon-based active material, a first conductive material, a second conductive material, and polyacrylamide as a binder in a weight ratio of 70:10:10:10 to distilled water as a solvent for forming a negative electrode slurry (solid concentration: 25 wt %).

[0186] The first conductive material is carbon black C (specific surface area: 58 m 2 / g, diameter: 37 nm), and the second conductive material is plate-shaped graphite (specific surface area: 17 m 2 / g, average particle size (D50): 3.5 μm).

[0187] As a mixing method, the first conductive material, the second conductive material, the binder, and the water were dispersed using a homomixer at 2500 rpm for 30 minutes, and then the active material was added and dispersed at 2500 rpm for 30 minutes to prepare a slurry.

[0188] The first negative electrode slurry was coated on both sides of a copper current collector (thickness: 8 μm) as a negative electrode current collector, roll pressed, and dried in a vacuum oven at 130° C. for 10 hours to form a first negative electrode active material layer.

[0189] Manufacture of second negative electrode active material layer A second negative electrode slurry was prepared by adding SiO (average particle size (D50): 3.5 μm) as a silicon-based active material, artificial graphite as a carbon-based active material, a first conductive material, a second conductive material, and polyacrylamide as a binder in a weight ratio of 50:30:5.5:10 to distilled water as a solvent for forming a negative electrode slurry (solid concentration: 25 wt %).

[0190] The first conductive material is carbon black C (specific surface area: 58 m 2 / g, diameter: 37 nm), and the second conductive material is plate-shaped graphite (specific surface area: 17 m 2 / g, average particle size (D50): 3.5 μm).

[0191] As a mixing method, the first conductive material, the second conductive material, the binder, and the water were dispersed using a homomixer at 2500 rpm for 30 minutes, and then the active material was added, followed by dispersion at 2500 rpm for 30 minutes to prepare a slurry.

[0192] The second negative electrode slurry was coated on the first negative electrode active material layer, roll pressed, and dried in a vacuum oven at 130° C. for 10 hours to form a second negative electrode active material layer.

[0193] <Secondary battery manufacturing> As the positive electrode active material, LiNi 0.6 Co 0.2 Mn 0.2 O2 (average particle size (D50): 15 μm), carbon black (product name: Super C65, manufacturer: Timcal) as a conductive material, and polyvinylidene fluoride (PVdF) as a binder were added in a weight ratio of 97:1.5:1.5 to N-methyl-2-pyrrolidone (NMP) as a solvent for forming a positive electrode slurry to prepare a positive electrode slurry (solid concentration: 78 wt%).

[0194] The positive electrode current collector was an aluminum current collector (thickness: 12 μm) and the positive electrode slurry was applied to both sides of the aluminum current collector at a rate of 537 mg / 25 cm. 2The coated layer was rolled and dried in a vacuum oven at 130°C for 10 hours to form a positive electrode active material layer (thickness: 65 μm) to prepare a positive electrode (thickness: 77 μm, porosity: 26%).

[0195] A polyethylene separator was interposed between the positive electrode and the negative electrode of each of the Examples and Comparative Examples, and an electrolyte was injected thereinto to prepare a lithium secondary battery.

[0196] The electrolyte was prepared by adding 3 wt % vinylene carbonate (based on the total weight of the electrolyte) to an organic solvent in which fluoroethylene carbonate (FEC) and diethyl carbonate (DMC) were mixed in a volume ratio of 30:70, and LiPF6 was added as a lithium salt at a concentration of 1M.

[0197] The activation step was then carried out under the conditions shown in Table 1 below, and the results are shown in Table 2 below.

[0198] [Table 1]

[0199] [Table 2]

[0200] FIG. 5 is a diagram showing the distribution of silicon phases by Raman analysis for the negative electrodes for lithium secondary batteries of Examples 1 to 4 according to the present application, and FIG. 6 is a diagram showing the distribution of silicon phases by Raman analysis for the negative electrodes for lithium secondary batteries of Comparative Examples 1 to 4 according to the present application.

[0201] Specifically, for the above-described Examples and Comparative Examples, Raman analysis was performed on the first negative electrode active material layer of the cross-section electrode to examine the change in silicon phase in the electrode depth direction. Specifically, red (top) indicates the amorphous phase, blue (bottom) indicates the crystalline phase, and green (middle) indicates a mixture of amorphous and crystalline phases. In the case of the second negative electrode active material layer, the amorphous phase ratio was 95 weight parts or more based on the total silicon phase of the second negative electrode active material layer. However, because the second negative electrode active material layer was formed thinner than the first negative electrode active material layer, Raman analysis of the first negative electrode active material layer showed only a certain increase in the amorphous phase (5 to 7 weight parts increase compared to the total) when viewed as a whole negative electrode for a lithium secondary battery, with no significant difference.

[0202] <Comparative Example 5> A silicon-based active material, Si (average particle size (D50): 5 μm), a first conductive material, a second conductive material, and polyacrylamide as a binder were added in a weight ratio of 70:10:10:10 to distilled water as a solvent for forming a negative electrode slurry to prepare a negative electrode slurry (solid concentration: 25 wt%).

[0203] The first conductive material is carbon black C (specific surface area: 58 m 2 / g, diameter: 37 nm), and the second conductive material is plate-shaped graphite (specific surface area: 17 m 2 / g, average particle size (D50): 3.5 μm).

[0204] As a mixing method, the first conductive material, the second conductive material, the binder, and the water were dispersed using a homomixer at 2500 rpm for 30 minutes, and then the active material was added, followed by dispersion at 2500 rpm for 30 minutes to prepare a slurry.

[0205] The negative electrode slurry was coated on both sides of a copper current collector (thickness: 8 μm) as a negative electrode current collector, rolled, and dried in a vacuum oven at 130° C. for 10 hours to form a negative electrode active material layer. Thereafter, a positive electrode was fabricated as in Example 1, and a lithium secondary battery was fabricated in the same manner.

[0206] Thereafter, an activation step was carried out under the same conditions as in Example 1.

[0207] 7 is a SEM photograph of a cross section of a negative electrode for a lithium secondary battery according to Comparative Example 5. Specifically, as in Example 1, a high-rate charging process of 1C was performed, and it was confirmed that a reaction was concentrated on the surface of the electrode made of pure silicon, causing surface degradation. It was also confirmed that the surface degradation reaction was easily observed in the SEM photograph alone, even before the Raman analysis.

[0208] Experimental example 1: Lifetime characteristic evaluation The secondary batteries including the negative electrodes prepared in the Examples and Comparative Examples were subjected to a lifespan evaluation using an electrochemical charger / discharger to evaluate the capacity retention. The secondary batteries were subjected to an in-situ cycle test at 4.2-3.0 V and 1 C / 0.5 C. During the test, the secondary batteries were charged / discharged (4.2-3.0 V) at 0.33 C / 0.33 C every 50 cycles, and the capacity retention was measured. Table 3 below shows the in-situ capacity retention, not the RPT capacity retention.

[0209] Capacity retention rate (%) = {(discharge capacity at Nth cycle) / (discharge capacity at first cycle)} × 100

[0210] Experimental example 2: Resistance increase rate measurement evaluation In Experimental Example 1, the test was performed by charging / discharging (4.2-3.0V) at 0.33C / 0.33C every 50 cycles to measure the capacity retention rate, and then discharging at 2.5C pulse at SOC50 to measure the resistance and compare the resistance increase rate.

[0211] Furthermore, data at 200 cycles for the life characteristic evaluation and the resistance increase rate measurement evaluation were calculated, and the results are shown in Table 3 below.

[0212] [Table 3]

[0213] As can be seen from Table 3, the lithium secondary battery according to the present application includes a second negative electrode active material layer, and when the activation process is performed under the activation conditions of Table 1, it is possible to manufacture a lithium secondary battery that satisfies the optimum silicon phase.

[0214] Specifically, Examples 1 to 4 according to the present application were cases where high-rate charging of 1 C or more was performed, and included a second negative electrode active material layer, and as can be seen in Table 2, it was found that the ratio of the silicon amorphous phase to the crystalline phase satisfied specific formula 1. In other words, even when activation conditions were performed at high rates (1 C or more), it was confirmed that the capacity retention rate and resistance increase rate during battery operation satisfied specific ranges, and the activation time was minimized, making the battery suitable for mass production.

[0215] That is, the negative electrodes of Examples 1 to 4 according to the present application include a second negative electrode active material layer and a high-rate (1 C or more) activation process, which ensures the processability of mass production. Despite the high-rate (1 C or more) activation process, they satisfy the same capacity characteristics as conventional negative electrodes, have a low resistance increase rate, and are characterized by a defined ratio between the silicon amorphous phase and the crystalline phase.

[0216] Comparative Examples 1 to 4 correspond to measurements taken on the same negative electrode as in the Examples, but with the activation conditions changed as shown in Table 2. That is, the activation process is excellent in terms of capacity characteristics and resistance increase rate when charging is performed for a long time under low charging conditions (low rate), but when the activation process time exceeds 2 hours, as in Comparative Examples 1 to 4, problems arise in mass production, and it was confirmed that this is not suitable for the process.

[0217] Furthermore, the higher the SiO content in the second negative electrode active material layer, the better the retention tends to be. The SiO content in the composition of the second negative electrode active material layer can be adjusted to such an extent that the performance can be improved compared to a negative electrode containing Si as a single active material layer, and may be equal to or greater than the content in Example 1.

[0218] For reference, Comparative Example 5 corresponds to a negative electrode fabricated with only the first negative electrode active material layer according to the present application, i.e., a single-active material layer structure. In this case, the second negative electrode active material layer is not included, and when a high-rate activation process like that of Example 1 is performed, the processability is similar to that of Example 1. However, as shown in Table 3, the capacity retention rate is slightly lower than that of Examples 1 to 4 of the present application, and the resistance increase rate is also higher than that of the Examples. This indicates that the reaction is concentrated on the surface of the negative electrode containing only pure silicon during activation, resulting in surface degradation and a rapid deterioration of life characteristics. In other words, in such cases, a low-rate or other activation method is required by adjusting the activation process conditions.

[0219] That is, as can be seen from Table 3, the batteries of Examples 1 to 4 according to the present application exhibited capacity retention and resistance characteristics equivalent to or better than those of Comparative Examples 1 to 4, which were activated at a low rate and for an extended period of time, and the state of the silicon phase of the negative electrode for a lithium secondary battery was defined, ensuring processability, which corresponds to a feature of the present invention. [Explanation of symbols]

[0220] 10...Second negative electrode active material layer 20...first negative electrode active material layer 30 Negative electrode current collector layer 100 ··Anode for lithium secondary battery

Claims

1. A negative electrode for a lithium secondary battery, comprising: a negative electrode current collector layer; and a negative electrode active material layer provided on one or both surfaces of the negative electrode current collector layer, the negative electrode active material layer includes: a first negative electrode active material layer provided on the negative electrode current collector layer; and a second negative electrode active material layer provided on a surface of the first negative electrode active material layer opposite to a surface facing the negative electrode current collector layer; the first negative electrode active material layer includes a first negative electrode active material layer composition including a first negative electrode active material, and the second negative electrode active material layer includes a second negative electrode active material layer composition including a second negative electrode active material; the first negative electrode active material includes one or more selected from the group consisting of SiOx (x=0) and SiOx (0<x<2), and the SiOx (x=0) is included in an amount of 95 parts by weight or more based on 100 parts by weight of the first negative electrode active material; the second negative electrode active material includes a carbon-based active material and a silicon-based active material; the ratio of amorphous silicon contained in the first negative electrode active material layer is lower than the ratio of amorphous silicon contained in the second negative electrode active material layer; The ratio of the silicon phase contained in the negative electrode active material layer satisfies the following formula 1: [Formula 1] 5≦B / (A+B)×100(%)≦30 In the formula 1, A is the weight part of the crystalline phase based on 100 parts by weight of the silicon phase contained in the negative electrode active material layer, B is the weight part of the amorphous phase based on 100 weight parts of the silicon phase contained in the negative electrode active material layer.

2. the second negative electrode active material layer contains amorphous phase silicon and crystalline phase silicon, 2 . The negative electrode for a lithium secondary battery according to claim 1 , wherein the amorphous phase is contained in an amount of 90 parts by weight or more based on 100 parts by weight of the silicon phase contained in the second negative electrode active material layer.

3. the first negative electrode active material layer contains amorphous phase silicon and crystalline phase silicon, 2 . The negative electrode for a lithium secondary battery according to claim 1 , wherein the crystalline phase is contained in an amount of 50 parts by weight or more based on 100 parts by weight of the silicon phase contained in the first negative electrode active material layer.

4. When the total thickness of the negative electrode active material layer is defined as T, the negative electrode active material layer includes a first region in the range of 0.2 T or less and a second region in the range of more than 0.5 T or less, based on the surface opposite to the surface facing the negative electrode current collector layer, the amorphous phase in the first region is included in an amount of 90 parts by weight or more based on 100 parts by weight of the silicon phase in the negative electrode active material layer; 2 . The negative electrode for a lithium secondary battery according to claim 1 , wherein the crystalline phase in the second region is contained in an amount of 60 parts by weight or more based on 100 parts by weight of the silicon phase in the negative electrode active material layer.

5. A negative electrode for a lithium secondary battery as described in claim 1, wherein the silicon-based active material is 65 parts by weight or more and 100 parts by weight or less, based on 100 parts by weight of the second negative electrode active material.

6. 2. The negative electrode for a lithium secondary battery according to claim 1, wherein the silicon-based active material comprises one or more selected from the group consisting of SiOx (0<x<2), SiC, and a Si alloy.

7. 2. The negative electrode for a lithium secondary battery according to claim 1, wherein the silicon-based active material comprises SiOx (0<x<2).

8. The negative electrode for a lithium secondary battery according to claim 1 , wherein the first negative electrode active material is present in an amount of 60 parts by weight or more based on 100 parts by weight of the first negative electrode active material layer composition.

9. The viscosity of the first negative electrode active material layer composition is 2,000 cPs to 15,000 cPs at a shear rate of 2.5 (1 / s), The negative electrode for a lithium secondary battery according to claim 1 , wherein the viscosity of the second negative electrode active material layer composition is lower than the viscosity of the first negative electrode active material layer composition.

10. the first negative electrode active material layer is formed on a front surface of the negative electrode current collector layer, The negative electrode for a lithium secondary battery according to claim 1 , wherein the second negative electrode active material layer is formed on a front surface of the first negative electrode active material layer.

11. Positive electrode; A negative electrode for a lithium secondary battery according to any one of claims 1 to 10; a separator disposed between the positive electrode and the negative electrode; and Electrolyte; A lithium secondary battery comprising:

12. providing a lithium secondary battery including a positive electrode, a lithium secondary battery negative electrode, a separator, and an electrolyte; and activating the lithium secondary battery; A method for producing a lithium secondary battery, comprising: The activation step includes a high-C-rate activation process (high-rate charging) of 1 C or more, The step of preparing the negative electrode for the lithium secondary battery includes: preparing a negative electrode current collector layer; applying a first negative electrode active material layer composition to one or both surfaces of the negative electrode current collector layer using a coater to form a first negative electrode active material layer; and applying a second negative electrode active material layer composition to a surface of the first negative electrode active material layer opposite to a surface in contact with the negative electrode current collector layer using a coater to form a second negative electrode active material layer; Including, The first negative electrode active material included in the first negative electrode active material layer composition includes one or more selected from the group consisting of SiOx (x=0) and SiOx (0<x<2), and includes 95 parts by weight or more of the SiOx (x=0) based on 100 parts by weight of the first negative electrode active material, the second negative electrode active material contained in the second negative electrode active material layer composition includes a carbon-based active material and a silicon-based active material.

13. pre-lithiating the negative electrode in which the first negative electrode active material layer and the second negative electrode active material layer are formed on the negative electrode current collector layer; 13. The method of claim 12, wherein the prelithiation of the negative electrode comprises a lithium electroplating process; a lithium metal transfer process; a lithium metal vapor deposition process; or a stabilized lithium metal powder (SLMP) coating process.

14. forming the second negative electrode active material layer on the first negative electrode active material layer includes a wet-on-dry process; The wet-on-dry process includes applying a first negative electrode active material layer composition; partially or entirely drying the applied first negative electrode active material layer composition to form a first negative electrode active material layer; and applying the second negative electrode active material layer composition to the first negative electrode active material layer; The method for producing the lithium secondary battery according to claim 12, comprising:

15. forming the second negative electrode active material layer on the first negative electrode active material layer includes a wet-on-wet process; The wet-on-wet process includes applying a first negative electrode active material layer composition; and applying the second negative electrode active material layer composition onto the first negative electrode active material layer composition while the first negative electrode active material layer composition is still wet; The method for producing the lithium secondary battery according to claim 12, comprising:

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