Negative electrode for lithium secondary battery, method for manufacturing negative electrode for lithium secondary battery, and lithium secondary battery comprising negative electrode

Abstract

The present invention provides a negative electrode for a lithium secondary battery, comprising: a negative electrode current collector layer; a first negative electrode active material layer provided on one surface of the negative electrode current collector layer; and a second negative electrode active material layer provided on the other surface of the negative electrode current collector layer, wherein the first and second negative electrode active material layers each include upper-layer and lower-layer negative electrode active material layers, the first lower-layer negative electrode active material layer and the second upper-layer negative electrode active material layer have the same composition, and the first upper-layer negative electrode active material layer and the second lower-layer negative electrode active material layer have the same composition.

Description

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

[0001] This application claims the benefit of Korean Patent Application No. 10-2023-0158202, filed with the Korean Intellectual Property Office on November 15, 2023, 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 manufacturing a negative electrode for a lithium secondary battery, and a lithium secondary battery including the negative electrode.

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

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

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

[0006] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode includes a negative electrode active material that inserts and deintercalates lithium ions from the positive electrode. Silicon particles with a high discharge capacity can be used as the negative electrode active material.

[0007] Lithium secondary batteries are being applied in various industrial fields such as automobiles, small modules, and mobile phones, and the performance of lithium secondary batteries targeted for each field includes various factors, but in general, the development of technology aimed at increasing energy density, ensuring stability, ensuring rapid charging, and securing life performance is fundamentally required.

[0008] In particular, carbon-based materials such as graphite, while excellent in stability and reversibility as anode materials, have limitations in terms of capacity. Therefore, in fields where the goal is to maximize high capacity, or energy density, attempts are increasing to use Si-based materials with high theoretical capacity as anode materials. However, when the purpose of high capacity is simply to include a high content of the Si-based material, the life performance deteriorates rapidly due to issues related to volume expansion compared to carbon-based materials, making it difficult to apply in real life.

[0009] In order to solve the above problems when using Si-based materials in the anode, various methods are being discussed, such as a method of controlling the driving potential, a method of additionally coating a thin film on the active material layer, a method of suppressing the volume expansion itself such as a method of controlling the particle size of the silicon-based compound, or the development of a binder that can control the volume expansion of the silicon-based compound to prevent the conductive path from being cut off. In addition, research is also being conducted to supplement the life characteristics of silicon-based anodes by limiting the proportion of silicon-based active materials used during initial charge and discharge and providing a reservoir role through a method of prelithiating the silicon-based active material layer.

[0010] However, the above methods may actually lower the performance of the battery, so their application is limited, and there are still limitations in the commercialization of negative electrode batteries with a high content of silicon compounds.

[0011] Additionally, in order to solve the above problems, research has been conducted to prevent volume expansion and surface-concentrated degradation by using a double layer of negative electrode active materials, such as carbon-based active materials that can act as a buffer layer on top of silicon-based active materials. However, recently, such negative electrodes have also been experiencing a problem in that heat is rapidly transferred to other cells as heat is applied in the cell, causing safety issues.

[0012] Therefore, in the development of lithium secondary batteries aimed at increasing energy density, securing rapid charging, and securing life performance, research on securing thermal safety is necessary.

[0013] <Prior Art Literature>

[0014] Japanese Patent Publication No. 2009-080971

[0015] The present application relates to an anode for a lithium secondary battery, and relates to an anode for a lithium secondary battery that can prevent electrode surface degradation during charge and discharge cycles, which is a problem with existing silicon-based active materials, and can improve cycle performance along with capacity characteristics of a lithium secondary battery, and can ensure thermal safety (thermal propagation), a method for manufacturing an anode for a lithium secondary battery, and a lithium secondary battery including the anode.

[0016] One embodiment of the present specification provides a negative electrode for a lithium secondary battery, comprising: a negative electrode current collector layer; a first negative electrode active material layer provided on one surface of the negative electrode current collector layer; and a second negative electrode active material layer provided on the other surface of the negative electrode current collector layer, wherein the first negative electrode active material layer includes a first lower layer negative electrode active material layer in contact with the negative electrode current collector layer; and a first upper layer negative electrode active material layer provided on an opposite surface of the first lower layer negative electrode active material layer in contact with the negative electrode current collector layer; and the second negative electrode active material layer includes a second lower layer negative electrode active material layer in contact with the negative electrode current collector layer; And a second upper layer negative electrode active material layer provided on the opposite side of the surface of the second lower layer negative electrode active material layer that contacts the negative electrode current collector layer; wherein one of the first lower layer negative electrode active material layer and the first upper layer negative electrode active material layer includes a silicon-based active material, and the first lower layer negative electrode active material layer and the second upper layer negative electrode active material layer have the same composition, and the first upper layer negative electrode active material layer and the second lower layer negative electrode active material layer have the same composition.

[0017] One embodiment of the present application provides a method for manufacturing an anode for a lithium secondary battery, comprising the steps of: preparing a first anode slurry and a second anode slurry; applying the first anode slurry on one surface of a anode current collector layer, and applying the second anode slurry on the first anode slurry applied on one surface of the anode current collector layer; and applying the second anode slurry on the opposite surface of the anode current collector layer, and applying the first anode slurry on the second anode slurry applied on the opposite surface of the anode current collector layer; wherein one of the first anode slurry and the second anode slurry includes a silicon-based active material.

[0018] Finally, a lithium secondary battery is provided, including: a cathode; an anode for a lithium secondary battery according to the present application; a separator provided between the cathode and the anode; and an electrolyte.

[0019] In the development of automotive batteries, thermal propagation is the biggest safety issue. When heat is generated in one cell, it is confirmed how quickly and explosively it is transferred to other cells, and ensuring thermal safety is a major part.

[0020] In particular, as silicon-based materials are used to achieve high capacity recently, the problem of thermal stability is becoming more prominent, and accordingly, the negative electrode for a lithium secondary battery according to one embodiment of the present invention has a negative electrode active material layer having a double-layer structure on the upper and lower surfaces (first negative electrode active material layer and second negative electrode active material layer) based on the negative electrode current collector layer, and specifically, the first lower layer negative electrode active material layer and the second upper layer negative electrode active material layer have the same composition, and the first upper layer negative electrode active material layer and the second lower layer negative electrode active material layer have the same composition, which is the main feature.

[0021] As described above, by improving the structure of a negative electrode for a lithium secondary battery, the explosive power of the negative electrode can be reduced when heat is applied. Specifically, the double-layer active materials included in the first negative electrode active material layer and the second negative electrode active material layer are arranged to have an asymmetrical structure, so that even if thermal runaway occurs in the negative electrode active material layer including the silicon-based active material, another negative electrode active material layer that can act as a barrier is arranged, thereby providing a feature that can control it.

[0022] Figure 1 is a diagram showing a laminated structure of a negative electrode for a lithium secondary battery according to one embodiment of the present application.

[0023] <Explanation of symbols>

[0024] 10-1: First lower negative electrode active material layer

[0025] 10-2: First upper layer negative electrode active material layer

[0026] 20: Negative current collector layer

[0027] 30-1: Second lower negative electrode active material layer

[0028] 30-2: Second upper layer negative electrode active material layer

[0029] Before explaining the present invention, some terms are first defined.

[0030] When a part of this specification is said to "include" a certain component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise stated.

[0031] In this specification, ‘p to q’ means a range of ‘p or more and q or less.’

[0032] In this specification, "specific surface area" is measured by the BET method, and specifically, is calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77K) using BELSORP-mino II of BEL Japan. That is, in this application, the BET specific surface area may mean the specific surface area measured by the above measurement method.

[0033] In this specification, "Dn" means particle size distribution, and means the particle size at the n% point of the cumulative distribution of particle numbers according to particle size. That is, D50 is the particle size (average particle size) at the 50% point of the cumulative distribution of particle numbers according to particle size, D90 is the particle size at the 90% point of the cumulative distribution of particle numbers according to particle size, and D10 is the particle size at the 10% point of the cumulative distribution of particle numbers according to particle size. Meanwhile, the particle size distribution can be measured using the laser diffraction method. Specifically, after the target powder is dispersed in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500) and the difference in diffraction pattern according to particle size is measured when the particles pass through a laser beam, thereby calculating the particle size distribution.

[0034] As used herein, the term "a polymer comprises a monomer as a monomer unit" means that the monomer participates in a polymerization reaction and is included as a repeating unit within the polymer. As used herein, "a polymer comprises a monomer" is interpreted to mean that the polymer comprises the monomer as a monomer unit.

[0035] In this specification, the term 'polymer' is understood to be used in a broad sense including copolymers unless 'homopolymer' is specified.

[0036] In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) are polystyrene-converted molecular weights measured by gel permeation chromatography (GPC) using monodisperse polystyrene polymers (standard samples) of various degrees of polymerization commercially available for molecular weight measurement as standard materials. In this specification, molecular weight means weight average molecular weight unless otherwise specified.

[0037] Hereinafter, the present invention will be described in detail with reference to the drawings so that those skilled in the art can easily practice it. However, the present invention can be implemented in various different forms and is not limited to the following description.

[0038] One embodiment of the present specification provides a negative electrode for a lithium secondary battery, comprising: a negative electrode current collector layer; a first negative electrode active material layer provided on one surface of the negative electrode current collector layer; and a second negative electrode active material layer provided on the other surface of the negative electrode current collector layer, wherein the first negative electrode active material layer includes a first lower layer negative electrode active material layer in contact with the negative electrode current collector layer; and a first upper layer negative electrode active material layer provided on an opposite surface of the first lower layer negative electrode active material layer in contact with the negative electrode current collector layer; and the second negative electrode active material layer includes a second lower layer negative electrode active material layer in contact with the negative electrode current collector layer; And a second upper layer negative electrode active material layer provided on the opposite side of the surface of the second lower layer negative electrode active material layer that contacts the negative electrode current collector layer; wherein one of the first lower layer negative electrode active material layer and the first upper layer negative electrode active material layer includes a silicon-based active material, and the first lower layer negative electrode active material layer and the second upper layer negative electrode active material layer have the same composition, and the first upper layer negative electrode active material layer and the second lower layer negative electrode active material layer have the same composition.

[0039] As described above, by improving the structure of a negative electrode for a lithium secondary battery, the explosive power of the negative electrode can be reduced when heat is applied. Specifically, the double-layer active materials included in the first negative electrode active material layer and the second negative electrode active material layer are arranged to have an asymmetrical structure, so that even if thermal runaway occurs in the negative electrode active material layer including the silicon-based active material, another negative electrode active material layer that can act as a barrier is arranged, thereby reducing the explosive pressure of one part and controlling the acceleration of thermal runaway of the positive electrode.

[0040] FIG. 1 is a diagram showing a laminated structure of an anode for a lithium secondary battery according to one embodiment of the present application. Specifically, a lithium secondary battery anode (100) can be confirmed, which includes a first anode active material layer including a first lower anode active material layer (10-1) and a first upper anode active material layer (10-2) on one surface of a cathode current collector layer (20), and a second anode active material layer including a second lower anode active material layer (30-1) and a second upper anode active material layer (30-2). At this time, one of the first lower anode active material layer and the first upper anode active material layer includes a silicon-based active material, the first lower anode active material layer and the second upper anode active material layer have the same composition, and the first upper anode active material layer and the second lower anode active material layer have the same composition.

[0041] The existing negative electrode structure has a structure in which the first lower negative electrode active material layer (10-1) and the second lower negative electrode active material layer (30-1) have the same composition, and the first upper negative electrode active material layer (10-2) and the second upper negative electrode active material layer (30-2) have the same composition, and has a structure in which at least one of the first lower negative electrode active material layer (10-1) and the second lower negative electrode active material layer (30-1) includes a silicon-based active material. That is, in the existing double layer structure, a symmetrical structure has been developed in which the silicon-based active material is concentrated toward the negative electrode current collector layer or toward the outside. However, when the silicon-based active material is concentrated toward the negative electrode current collector, there is a problem in which the negative electrode current collector layer easily melts, thereby increasing the explosive power. In addition, in the case of the thermal runaway mechanism toward the outer periphery, it is known that the cathode is the starting point and accelerates the thermal runaway at the anode. However, in the case where the silicon-based active material gathers toward the outer periphery of the cathode as described above, there was a problem that the thermal runaway at the anode was accelerated due to the thermal trigger, resulting in a decrease in safety. However, the present application was able to solve the above problem.

[0042] In the present application, the first negative electrode active material layer includes a first lower negative electrode active material layer in contact with the negative electrode current collector layer; and a first upper negative electrode active material layer provided on the opposite side of the side of the first lower negative electrode active material layer in contact with the negative electrode current collector layer; this may mean that the first lower negative electrode active material layer and the first upper negative electrode active material layer of the negative electrode current collector layer are sequentially laminated.

[0043] In the present application, the second negative electrode active material layer includes a second lower negative electrode active material layer in contact with the negative electrode current collector layer; and a second upper negative electrode active material layer provided on the opposite side of the surface of the second lower negative electrode active material layer in contact with the negative electrode current collector layer; which may mean that the negative electrode current collector layer, the second lower negative electrode active material layer, and the second upper negative electrode active material layer are sequentially laminated.

[0044] In one embodiment of the present application, the first negative electrode active material layer and the second negative electrode active material layer can be formed on the entire surface of the negative electrode current collector layer.

[0045] Below, the negative electrode for a lithium secondary battery of the present invention is described in more detail.

[0046] A negative electrode for a lithium secondary battery, comprising: a negative electrode current collector layer; a first negative electrode active material layer provided on one surface of the negative electrode current collector layer; and a second negative electrode active material layer provided on the other surface of the negative electrode current collector layer, wherein the first negative electrode active material layer includes a first lower layer negative electrode active material layer in contact with the negative electrode current collector layer; and a first upper layer negative electrode active material layer provided on an opposite surface of the first lower layer negative electrode active material layer in contact with the negative electrode current collector layer; and the second negative electrode active material layer includes a second lower layer negative electrode active material layer in contact with the negative electrode current collector layer; and a second upper layer negative electrode active material layer provided on an opposite surface of the second lower layer negative electrode active material layer in contact with the negative electrode current collector layer.

[0047] In one embodiment of the present application, the negative electrode current collector layer generally has a thickness of 1 μm to 100 μm. The negative electrode current collector layer is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the bonding strength of the negative electrode active material can be strengthened by forming fine unevenness on the surface, and can be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc.

[0048] 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.

[0049] However, the thickness can be varied depending on the type and purpose of the cathode used and is not limited thereto.

[0050] One embodiment of the present application is that one of the first lower negative electrode active material layer and the first upper negative electrode active material layer includes a silicon-based active material, the first lower negative electrode active material layer and the second upper negative electrode active material layer have the same composition, and the first upper negative electrode active material layer and the second lower negative electrode active material layer have the same composition.

[0051] In this application, having the same composition may mean that the composition and content contained in each active material layer are identical. In this case, the same may include some errors that may be included in the art. However, in this application, having the same composition only means the composition, and physical properties (thickness, loading amount, etc.) may be different.

[0052] One embodiment of the present application is that the first lower negative electrode active material layer includes a silicon-based active material, the first lower negative electrode active material layer and the second upper negative electrode active material layer have the same composition, and the first upper negative electrode active material layer and the second lower negative electrode active material layer have the same composition.

[0053] One embodiment of the present application is that the first upper negative electrode active material layer includes a silicon-based active material, the first lower negative electrode active material layer and the second upper negative electrode active material layer have the same composition, and the first upper negative electrode active material layer and the second lower negative electrode active material layer have the same composition.

[0054] That is, as described above, in the case of the negative electrode for a lithium secondary battery of the present application, it is characterized by including a silicon-based active material, but rather than including it continuously within the negative electrode, it is provided discontinuously with another negative electrode active material layer or negative electrode current collector layer acting as a barrier. Accordingly, even when thermal runaway occurs, heat transfer is prevented due to the barrier function, so thermal stability is secured.

[0055] That is, the present application provides a negative electrode for a lithium secondary battery in which the first negative electrode active material layer and the second negative electrode active material layer are asymmetrical with respect to the negative electrode current collector layer.

[0056] In addition, the present application provides an anode for a lithium secondary battery, wherein the first lower layer anode active material layer and the second lower layer anode active material layer have different compositions, and the second upper layer anode active material layer and the second upper layer anode active material layer have different compositions.

[0057] At this time, having different compositions can be defined as having different compositions when the type or content of the active material included in each active material layer is different.

[0058] In the present application, a lithium secondary battery negative electrode is provided, wherein the first lower layer negative electrode active material layer includes a first lower layer negative electrode active material layer composition, the first upper layer negative electrode active material layer includes a first upper layer negative electrode active material layer composition, the first lower layer negative electrode active material layer composition includes a first lower layer negative electrode active material; a first lower layer negative electrode conductive material; and a first lower layer negative electrode binder, and the first upper layer negative electrode active material layer composition includes a first upper layer negative electrode active material; a first upper layer negative electrode conductive material; and a first upper layer negative electrode binder.

[0059] In the present application, a negative electrode for a lithium secondary battery is provided, wherein one of the first lower layer negative electrode active material and the first upper layer negative electrode active material includes at least one selected from the group consisting of a carbon-based active material, a silicon-based active material, a metal-based active material capable of being alloyed with lithium, and a lithium-containing nitride, and the other of the first lower layer negative electrode active material and the first upper layer negative electrode active material includes a carbon-based active material.

[0060] In the present application, a negative electrode for a lithium secondary battery is provided, wherein the first lower layer negative electrode active material includes at least one selected from the group consisting of a carbon-based active material, a silicon-based active material, a metal-based active material capable of being alloyed with lithium, and a lithium-containing nitride, and the first upper layer negative electrode active material includes a carbon-based active material.

[0061] In addition, the first upper layer negative electrode active material includes at least one selected from the group consisting of a carbon-based active material, a silicon-based active material, a metal-based active material capable of being alloyed with lithium, and a lithium-containing nitride, and the first lower layer negative electrode active material includes a carbon-based active material.

[0062] In the present application, a negative electrode for a lithium secondary battery is provided, wherein one of the first lower layer negative electrode active material and the first upper layer negative electrode active material includes a carbon-based active material and a silicon-based active material, and the other of the first lower layer negative electrode active material and the first upper layer negative electrode active material includes a carbon-based active material.

[0063] In the present application, the first lower layer negative electrode active material includes a carbon-based active material and a silicon-based active material, the first upper layer negative electrode active material includes a carbon-based active material, and the silicon-based active material may be included in an amount of 1 part by weight or more and 50 parts by weight or less based on 100 parts by weight of the first lower layer negative electrode active material.

[0064] In another embodiment, the first lower layer negative electrode active material includes a carbon-based active material and a silicon-based active material, the first upper layer negative electrode active material includes a carbon-based active material, and the silicon-based active material may include 1 part by weight or more and 50 parts by weight or less, preferably 3 parts by weight or more and 40 parts by weight or less, and more preferably 5 parts by weight or more and 20 parts by weight or less, based on 100 parts by weight of the first lower layer negative electrode active material.

[0065] In the present application, the first upper layer negative electrode active material includes a carbon-based active material and a silicon-based active material, the first lower layer negative electrode active material includes a carbon-based active material, and the silicon-based active material may include 1 part by weight or more and 50 parts by weight or less based on 100 parts by weight of the first upper layer negative electrode active material.

[0066] In another embodiment, the first upper layer negative electrode active material includes a carbon-based active material and a silicon-based active material, the first lower layer negative electrode active material includes a carbon-based active material, and the silicon-based active material may include 1 part by weight or more and 50 parts by weight or less, preferably 3 parts by weight or more and 40 parts by weight or less, and more preferably 5 parts by weight or more and 20 parts by weight or less, based on 100 parts by weight of the first upper layer negative electrode active material.

[0067] As described above, the first lower layer negative electrode active material or the first upper layer negative electrode active material can secure high energy density by including the silicon-based active material in the above weight portion, and further, by including the above weight portion, the life performance issue due to volume expansion can be minimized, thereby providing a high-capacity negative electrode along with life performance. That is, the negative electrode active material layer composition according to the present application uses a silicon-based active material having a significantly high capacity in the above range, and does not lower the capacity performance of the entire negative electrode by using another negative electrode active material layer that is laminated together, and solves the problem of surface degradation during charge and discharge, the problem of uniformity during lithiation, and the problem of life characteristics.

[0068] In the present application, the silicon-based active material is SiOx (x=0); SiOx (0 <x<2); 또는 SiC를 포함하는 것인 리튬 이차 전지용 음극을 제공한다.

[0069] In one embodiment of the present application, the silicon-based active material may particularly use pure silicon (SiOx (x=0)) particles.

[0070] Meanwhile, the average particle diameter (D50) of the silicon-based 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 diameter is within the above range, the specific surface area of ​​the particles is within an appropriate range, so that the viscosity of the negative electrode slurry is formed within an appropriate range. Accordingly, the particles constituting the negative electrode slurry are smoothly dispersed. In addition, since the size of the first negative electrode active material is greater than or equal to the lower limit, the contact area between the silicon particles and the conductive material is excellent due to the composite composed of the conductive material and the binder in the negative electrode slurry, so that the possibility of the conductive network continuing increases, thereby increasing the capacity retention rate. Meanwhile, when the average particle diameter satisfies the above range, excessively large silicon particles are excluded, so that the surface of the negative electrode is formed smoothly, and thus the phenomenon of uneven current density during charge and discharge can be prevented.

[0071] In one embodiment of the present application, the silicon-based active material generally has a characteristic BET surface area. The BET surface area of ​​the silicon-based active material is preferably 0.01 m 2 / g to 150.0 m 2 / g, more preferably 0.1m 2 / g to 100.0 m 2 / g, especially preferably 0.2m 2 / g to 80.0 m 2 / g, most preferably 0.2m 2 / g to 18.0 m 2 / g. BET surface area is measured according to DIN 66131 (using nitrogen).

[0072] In one embodiment of the present application, the silicon-based active material may exist in a crystalline or amorphous form, and is preferably non-porous. The silicon particles are preferably spherical or fragmented. Alternatively, but less preferably, the silicon particles may also have a fibrous structure or exist in the form of a silicon-containing film or coating.

[0073] In one embodiment of the present application, the silicon-based active material may have a non-spherical shape and its sphericity is, for example, 0.9 or less, for example, 0.7 to 0.9, for example, 0.8 to 0.9, for example, 0.85 to 0.9.

[0074] In the present application, the circularity is determined by the following equation 1, where A is the area and P is the boundary line.

[0075] [Formula 1]

[0076] 4ðA / P 2

[0077] In one embodiment of the present application, the carbon-based active material is, as a representative example, natural graphite, artificial graphite, expanded graphite, carbon fiber, non-graphitizable carbon, carbon black, carbon nanotubes, fullerene, or activated carbon, and can be used without limitation as long as it is commonly used in carbon materials for lithium secondary batteries, and specifically, can be used by processing it into a spherical or dot-shaped shape.

[0078] In one embodiment of the present application, a negative electrode for a lithium secondary battery is provided, wherein the carbon-based active material includes graphite, the graphite includes artificial graphite and natural graphite, and the weight ratio of the artificial graphite and natural graphite is 5:5 to 9.5:0.5.

[0079] The artificial graphite according to one embodiment of the present invention may be in the form of primary particles, or may be in the form of secondary particles in which a plurality of the primary particles are aggregated.

[0080] The term "initial particle" used in the present invention means an original particle from which another type of particle is formed, and a plurality of primary particles can be assembled, combined, or assembled to form a secondary particle.

[0081] The term "secondary particles" as used in the present invention means physically distinguishable large particles formed by aggregation, combination or assembly of individual primary particles.

[0082] The artificial graphite of the above primary particles may be manufactured by heat treating at least one selected from the group consisting of needle cokes, mosaic cokes, and coaltar pitch.

[0083] The above artificial graphite is generally manufactured by carbonizing raw materials such as coal tar, coal tar pitch, and petroleum heavy oils at temperatures above 2,500°C. After graphitization, the particle size can be adjusted through grinding and secondary particle formation to enable use as a negative electrode active material. In the case of artificial graphite, crystals are randomly distributed within the particles, and compared to natural graphite, the sphericity is lower and the shape is somewhat pointed.

[0084] The artificial graphite used in one embodiment of the present invention may include MCMB (mesophase carbon microbeads), MPCF (mesophase pitch-based carbon fiber), artificial graphite graphitized in block form, artificial graphite graphitized in powder form, etc., which are widely used commercially. The sphericity of the artificial graphite may be 0.91 or less, or 0.6 to 0.91, or 0.7 to 0.9.

[0085] Additionally, the artificial graphite may have a particle size of 5 to 30 μm, preferably 10 to 25 μm.

[0086] Specifically, the D50 of the artificial graphite primary particles may be 6 µm to 15 µm, or 6 µm to 10 µm, or 6 µm to 9 µm. When the D50 of the primary particles satisfies this range, the primary particles can be formed to have high graphitization, and the orientation index of the negative electrode active material particles can be appropriately secured, thereby improving the rapid charging performance.

[0087] The above artificial graphite secondary particles may be formed by assembling primary particles. That is, the secondary particles may be a structure formed by agglomerating the primary particles through an assembling process. The secondary particles may include a carbonaceous matrix that allows the primary particles to agglomerate. The carbonaceous matrix may include at least one of soft carbon and graphite. The soft carbon may be formed by heat-treating pitch.

[0088] The above carbonaceous matrix may be included in the secondary particles in an amount of 8 wt% to 16 wt%, specifically 9 wt% to 12 wt%. The above range is lower than the content of the carbonaceous matrix used in conventional artificial graphite secondary particles. This means that the particle size of the primary particles in the secondary particles is controlled, so that even if the content of the carbonaceous matrix required for assembly is small, structurally stable secondary particles can be manufactured, and the amount of primary particles constituting the secondary particles can also be uniform.

[0089] The artificial graphite secondary particle includes a carbon coating layer on the surface, and the carbon coating layer may include at least one of amorphous carbon and crystalline carbon.

[0090] The above crystalline carbon can further improve the conductivity of the negative electrode active material. The above crystalline carbon can include at least one selected from the group consisting of fluorene and graphene.

[0091] The amorphous carbon can appropriately maintain the strength of the covering layer and suppress the expansion of the natural graphite. The amorphous carbon can be a carbonaceous material formed using at least one carbide or hydrocarbon selected from the group consisting of tar, pitch, and other organic substances as a source of a chemical vapor deposition method.

[0092] The above-mentioned other organic carbide may be a carbide of an organic carbide selected from sucrose, glucose, galactose, fructose, lactose, mannose, ribose, aldohexose or kedohexose and combinations thereof.

[0093] The D50 of the above artificial graphite secondary particles may be 10 ㎛ to 25 ㎛, specifically 12 ㎛ to 22 ㎛, and more specifically 13 ㎛ to 20 ㎛. When the above range is satisfied, the artificial graphite secondary particles can be evenly dispersed within the slurry, and the charging performance of the battery can also be improved.

[0094] The tap density of the above artificial graphite secondary particles may be 0.85 g / cc to 1.30 g / cc, specifically 0.90 g / cc to 1.10 g / cc, and more specifically 0.90 g / cc to 1.07 g / cc. When the above range is satisfied, the packing of the artificial graphite secondary particles within the negative electrode can be smoothly performed, which means that the negative electrode adhesive strength can be improved.

[0095] The above natural graphite may generally be in the form of plate-shaped aggregates before being processed, and the plate-shaped particles may be manufactured into a spherical shape with a smooth surface through post-processing such as particle crushing and reassembly processes in order to be used as an active material for manufacturing electrodes.

[0096] The natural graphite used in one embodiment of the present invention may have a sphericity of greater than 0.91 and less than or equal to 0.97, or from 0.93 to 0.97, or from 0.94 to 0.96.

[0097] The above natural graphite may have a particle size of 5 to 30 μm, or 10 to 25 μm.

[0098] According to one embodiment of the present invention, the weight ratio of the artificial graphite and natural graphite may be 5:5 to 9.5:0.5, or 5:5 to 9.3:0.7, or 5:5 to 9:1, or 6:4 to 9:1. When the weight ratio of the artificial graphite and natural graphite satisfies this range, a better output may be exhibited, and lifespan and rapid charging performance may be advantageous.

[0099] In one embodiment of the present application, the planar conductive material used as the negative electrode conductive material described below has a structure and function different from the carbon-based active material generally used as the negative electrode active material. Specifically, the carbon-based active material used as the negative electrode active material may be artificial graphite or natural graphite, and refers to a material processed into a spherical or dot-shaped form to facilitate the storage and release of lithium ions.

[0100] On the other hand, the planar conductive material used as the negative electrode conductive material described below is a material having a planar or plate-like shape, and can be expressed as plate-like graphite. In other words, it refers to a material included to maintain a conductive path within the negative electrode active material layer, and is not a material that plays a role in storing and releasing lithium, but rather a material that secures a conductive path in a planar shape within the negative electrode active material layer.

[0101] That is, in the present application, the use of plate-shaped graphite as a conductive material means that it is processed into a planar or plate-shaped form and used as a material that secures a conductive path rather than a role for storing or releasing lithium. In this case, the included negative electrode active material has high capacity characteristics for lithium storage and release, and serves to store and release all lithium ions delivered from the positive electrode.

[0102] On the other hand, in the present application, the use of a carbon-based active material as an active material means that it is processed into a dot or spherical shape and used as a material that plays a role in storing or releasing lithium.

[0103] 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 than 4.5 m 2 / g or less can be satisfied. In addition, the plate-shaped graphite, which is a planar conductive material, has a BET surface area of ​​5 m in the form of a planar surface. 2 / g can be more than that.

[0104] The above metal-based active material may be a compound 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, as representative examples. These metal compounds may be used in any form, such as a simple substance, alloy, oxide (TiO2, SnO2, etc.), nitride, sulfide, boride, or alloy with lithium, but the simple substance, alloy, oxide, or alloy with lithium can be made into a high-capacity material.

[0105] In one embodiment of the present application, a negative electrode for a lithium secondary battery is provided, wherein the first lower layer negative electrode active material is at least 60 parts by weight based on 100 parts by weight of the first lower layer negative electrode active material layer composition.

[0106] In another embodiment, the first lower layer negative electrode active material may be at least 60 parts by weight, preferably at least 65 parts by weight, more preferably at least 70 parts by weight, and may be at most 95 parts by weight, preferably at most 90 parts by weight, more preferably at most 80 parts by weight, based on 100 parts by weight of the first lower layer negative electrode active material layer composition.

[0107] In one embodiment of the present application, a negative electrode for a lithium secondary battery is provided, wherein the first upper layer negative electrode active material is 60 parts by weight or more based on 100 parts by weight of the first upper layer negative electrode active material layer composition.

[0108] In another embodiment, the first upper layer negative electrode active material may be at least 60 parts by weight, preferably at least 65 parts by weight, more preferably at least 70 parts by weight, and may be at most 95 parts by weight, preferably at most 90 parts by weight, more preferably at most 80 parts by weight, based on 100 parts by weight of the first upper layer negative electrode active material layer composition.

[0109] Traditionally, graphite compounds were used exclusively as anode active materials. However, with the increasing demand for high-capacity batteries, attempts to blend silicon-based compounds to increase capacity are increasing. However, silicon-based compounds have limitations: their rapid volume expansion during charge / discharge processes damages the conductive paths formed within the anode active material layer, thereby degrading battery performance.

[0110] Therefore, in one embodiment of the present application, the first lower layer negative electrode active material layer composition may include a first lower layer negative electrode active material; a first lower layer negative electrode conductive material; and a first lower layer negative electrode binder, and the first upper layer negative electrode active material layer composition may include a first upper layer negative electrode active material; a first upper layer negative electrode conductive material; and a first upper layer negative electrode binder.

[0111] At this time, the description of the first lower layer cathode conductive material and the first upper layer cathode conductive material can be applied in the same way as the description of the cathode conductive material described later, and the description of the first lower layer cathode binder and the first upper layer cathode binder can be applied in the same way as the description of the cathode binder described later.

[0112] In one embodiment of the present application, the cathode conductive material may be any material generally used in the art without limitation, and specifically may include at least one selected from the group consisting of point-shaped conductive materials, planar conductive materials, and linear conductive materials.

[0113] In one embodiment of the present application, the dot-shaped conductive material can be used to improve conductivity of the negative electrode, and refers to a conductive material having a dot-shaped or spherical shape that has conductivity without causing chemical change. Specifically, the dot-shaped conductive material may be at least one selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, channel black, paneth black, lamp black, thermal black, conductive fiber, fluorocarbon, aluminum powder, nickel powder, zinc oxide, potassium titanate, titanium oxide, and polyphenylene derivatives, and preferably may include carbon black in terms of implementing high conductivity and excellent dispersibility.

[0114] In one embodiment of the present application, the dot-shaped conductive material has a BET specific surface area of ​​40 m 2 / g or more than 70m 2 / g or less, preferably 45m 2 / g or more than 65m 2 / g or less, more preferably 50m 2 / g or more than 60m 2 / g can be less.

[0115] In one embodiment of the present application, the particle size of the dot-shaped conductive material may be 10 nm to 100 nm, preferably 20 nm to 90 nm, and more preferably 20 nm to 60 nm.

[0116] In one embodiment of the present application, the second cathode conductive material may include a planar conductive material.

[0117] The above-mentioned planar conductive material can improve conductivity by increasing planar contact between silicon particles within the cathode, and at the same time, can suppress disconnection of the conductive path due to volume expansion, and can be expressed as a plate-shaped conductive material or a bulk conductive material.

[0118] In one embodiment of the present application, the planar conductive material may include at least one selected from the group consisting of plate-shaped graphite, graphene, graphene oxide, and graphite flakes, and may preferably be plate-shaped graphite.

[0119] In one embodiment of the present application, the average particle diameter (D50) of the surface-shaped 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 above range is satisfied, the sufficient particle size facilitates dispersion without causing excessive viscosity increase in the negative electrode slurry. Therefore, the dispersion effect is excellent when dispersion is performed using the same equipment and time.

[0120] In one embodiment of the present application, the surface-shaped conductive material provides a negative electrode composition having 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.

[0121] In one embodiment of the present application, the planar conductive material may be a high-specific surface area planar conductive material having a high BET surface area; or a low-specific surface area planar conductive material.

[0122] In one embodiment of the present application, a high surface area surface conductive material or a low surface area surface conductive material may be used without limitation as the surface conductive material, but in particular, since the surface conductive material according to the present application may be affected to some extent by dispersion in electrode performance, it may be particularly preferable to use a low surface area surface conductive material that does not cause dispersion problems.

[0123] In one embodiment of the present application, the surface-shaped conductive material has a BET specific surface area of ​​5 m 2 / g can be more than that.

[0124] In another embodiment, the surface-shaped conductive material has a BET surface area of ​​5 m 2 / g or more than 500m 2 / g or less, preferably 5m 2 / g or more than 300m 2 / g or less, more preferably 5m 2 / g or more than 250m 2 / g can be less.

[0125] In another embodiment, the surface-shaped conductive material is a high surface area surface-shaped conductive material, and has a BET surface area of ​​50 m 2 / g or more than 500m 2 / g or less, preferably 80m 2 / g or more than 300m 2 / g or less, more preferably 100m 2 / g or more than 300m 2 / g can satisfy the range below.

[0126] In another embodiment, the surface-shaped conductive material is a low surface area surface-shaped conductive material, and has a BET surface area of ​​5 m 2 / g or more than 40m 2 / g or less, preferably 5m 2 / g or more than 30m 2 / g or less, more preferably 5m 2 / g or more than 25m 2 / g can satisfy the range below.

[0127] Other conductive materials may include linear conductive materials such as carbon nanotubes. The carbon nanotubes may be bundle-type carbon nanotubes. The bundle-type carbon nanotubes may include a plurality of carbon nanotube units. Specifically, the term "bundle type" herein refers to a secondary shape in the form of a bundle or rope, in which a plurality of carbon nanotube units are arranged in a substantially identical orientation in parallel or entangled with their longitudinal axes in the carbon nanotube unit direction, unless otherwise specified. The carbon nanotube units have a cylindrical shape of a graphite sheet with a nano-sized diameter and an sp2 bonding structure. At this time, the graphite sheets may exhibit conductor or semiconductor properties depending on the curling angle and structure. The above bundled carbon nanotubes can be uniformly dispersed during the manufacture of a cathode compared to entangled type carbon nanotubes, and can smoothly form a conductive network within the cathode, thereby improving the conductivity of the cathode.

[0128] In particular, the linear conductive material according to one embodiment of the present application may be a single-walled carbon nanotube (SWCNT).

[0129] In the present application, a negative electrode for a lithium secondary battery is provided, wherein the first lower layer negative electrode conductive material and the first upper layer negative electrode conductive material include at least a linear conductive material.

[0130] The single-walled carbon nanotube is a material in which carbon atoms are arranged in a hexagonal shape to form a tube, and exhibits properties of insulator, conductor, or semiconductor depending on its unique chirality. Since the carbon atoms are connected by strong covalent bonds, its tensile strength is approximately 100 times greater than that of steel, and it has excellent flexibility and elasticity, and is also chemically stable.

[0131] The average diameter of the single-walled carbon nanotubes is 0.5 nm to 15 nm. According to one embodiment of the present invention, the average diameter of the single-walled carbon nanotubes may be 1 to 10 nm, or 1 nm to 5 nm, or 1 nm to 2 nm. When the average diameter of the single-walled carbon nanotubes satisfies this range, the electrical conductivity of the negative electrode can be maintained even if the single-walled carbon nanotubes are included in a very small amount, and desirable viscosity and solid content can be derived when preparing a conductive dispersion. In the conductive dispersion, the single-walled carbon nanotubes may clump together and exist in an entangled state (aggregate). Accordingly, the average diameter can be derived by confirming the diameter of any entangled single-walled carbon nanotube aggregate extracted from the conductive dispersion using SEM or TEM, and then dividing the diameter of the aggregate by the number of single-walled carbon nanotubes constituting the aggregate.

[0132] The BET specific surface area of ​​the single-walled carbon nanotube may be 500 m2 / g to 1,500 m2 / g, or 900 m2 / g to 1,200 m2 / g, and specifically 250 m2 / g to 330 m2 / g. When the above range is satisfied, a conductive dispersion having a desirable solid content is produced, and the viscosity of the cathode slurry is prevented from increasing excessively. The BET specific surface area can be measured through the nitrogen adsorption BET method.

[0133] The aspect ratio of the single-walled carbon nanotube may be 50 to 20,000, or the length of the single-walled carbon nanotube may be 5 to 100 μm, or 5 to 50 μm. When the aspect ratio or length satisfies these ranges, since the specific surface area is high, the single-walled carbon nanotube can be strongly attracted to the active material particles within the negative electrode. Accordingly, the conductive network can be smoothly maintained even when the volume of the negative electrode active material expands. The aspect ratio can be confirmed by obtaining the average aspect ratio of 15 single-walled carbon nanotubes with a large aspect ratio and 15 single-walled carbon nanotubes with a small aspect ratio when observing the single-walled carbon nanotube powder through an SEM.

[0134] Compared to multi-walled carbon nanotubes or double-walled carbon nanotubes, commercial single-walled carbon nanotubes have an advantage in that they are long and have a large volume due to their large aspect ratio, allowing them to be used in small quantities to build electrical networks.

[0135] In one embodiment of the present application, the first lower layer negative electrode conductive material can satisfy 1 part by weight or more and 40 parts by weight or less based on 100 parts by weight of the first lower layer negative electrode active material layer composition.

[0136] In another embodiment, the first lower layer negative electrode conductive material may be in an amount of 1 part by weight or more and 40 parts by weight or less, preferably 10 parts by weight or more and 30 parts by weight or less, and more preferably 15 parts by weight or more and 25 parts by weight or less, based on 100 parts by weight of the first lower layer negative electrode active material layer composition.

[0137] In one embodiment of the present application, the first upper layer negative electrode conductive material can satisfy 1 part by weight or more and 40 parts by weight or less based on 100 parts by weight of the first upper layer negative electrode active material layer composition.

[0138] In another embodiment, the first upper layer negative electrode conductive material may be in an amount of 1 part by weight or more and 40 parts by weight or less, preferably 10 parts by weight or more and 30 parts by weight or less, and more preferably 15 parts by weight or more and 25 parts by weight or less, based on 100 parts by weight of the first upper layer negative electrode active material layer composition.

[0139] In one embodiment of the present application, the negative electrode conductive material includes a dot-shaped conductive material; a planar conductive material; and a linear conductive material, and the dot-shaped conductive material: planar conductive material: linear conductive material can satisfy a ratio of 1:1:0.01 to 1:1:1.

[0140] In one embodiment of the present application, the dot-shaped conductive material can satisfy a 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 cathode conductive material.

[0141] In one embodiment of the present application, the surface-shaped conductive material can satisfy a 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 negative conductive material.

[0142] In one embodiment of the present application, the linear conductive material can satisfy a range of 0.01 to 10 parts by weight, preferably 0.05 to 8 parts by weight, and more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the cathode conductive material.

[0143] In one embodiment of the present application, the cathode conductive material may include a linear conductive material and a planar conductive material.

[0144] In one embodiment of the present application, the negative electrode conductive material includes a linear conductive material and a planar conductive material, and the ratio of the linear conductive material to the planar conductive material can satisfy 0.01:1 to 0.1:1.

[0145] In one embodiment of the present application, since the negative electrode conductive material particularly includes a linear conductive material and a planar conductive material and satisfies the above composition and ratio, respectively, it does not have a significant effect on the life characteristics of an existing lithium secondary battery, and the number of points at which charging and discharging are possible increases, so that it has the characteristic of excellent output characteristics at a high C-rate.

[0146] In one embodiment of the present application, the cathode conductive material may be formed of a linear conductive material.

[0147] At this time, the linear conductive agent may be 0.1 to 2 parts by weight, or 0.1 to 0.7 parts by weight, or 0.1 to 0.3 parts by weight based on 100 parts by weight of the negative active material. When the content of the linear conductive agent satisfies this range, an electrical network can be sufficiently established within the negative active material layer, and it is advantageous in terms of mixing and coating processability during electrode manufacturing. In addition, in the negative electrode according to one embodiment of the present invention, since the linear conductive agent is included in both the first negative active material layer and the second negative active material layer, the conductive network between the active materials can be maintained according to the volume expansion and contraction of the Si electrode, which is advantageous in terms of lifespan, and rapid charge performance can be maintained. Basically, rapid charge performance is advantageous because the Si-based negative electrode can be coated with a thin film compared to graphite, but the linear conductive agent maintains a strong conductive network, which is helpful for rapid charging, and further, can be more helpful in improving the initial drop in the lifespan of the Si-based negative electrode and maintaining the lifespan.

[0148] The negative electrode conductive material according to the present application has a completely separate composition from the positive electrode conductive material applied to the positive electrode. That is, the second negative electrode conductive material according to the present application serves to secure the contact between silicon-based active materials, which undergo a large volume expansion of the electrode due to charging and discharging, and the positive electrode conductive material serves to provide some conductivity while acting as a buffer when rolled, and is completely different in composition and role from the negative electrode conductive material of the present invention.

[0149] In addition, the negative electrode conductive material according to the present application is applied to a silicon-based active material and has a completely different composition from the conductive material applied to a graphite-based active material. That is, the conductive material used in an electrode having a graphite-based active material simply has smaller particles than the active material, and thus has the characteristics of improving output characteristics and imparting some conductivity, and is completely different in composition and role from the negative electrode conductive material applied together with a silicon-based active material as in the present invention.

[0150] In one embodiment of the present application, the negative electrode binder may include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluoroelastomer, polyacrylic acid, and a material in which hydrogens thereof are substituted with Li, Na, Ca, or the like, and may also include various copolymers thereof.

[0151] The negative electrode binder according to one embodiment of the present application serves to hold the active material and the conductive material in order to prevent distortion and structural deformation of the negative electrode structure when the volume of the negative electrode active material expands and relaxes. If the above-mentioned role is satisfied, all general binders can be applied, and specifically, an aqueous binder can be used, and more specifically, a PAM binder can be used.

[0152] In one embodiment of the present application, the first lower layer negative electrode binder is 30 parts by weight or less, preferably 25 parts by weight or less, more preferably 20 parts by weight or less, and may be 5 parts by weight or more, or 10 parts by weight or more, based on 100 parts by weight of the first lower layer negative electrode active material layer composition.

[0153] In one embodiment of the present application, the first upper layer negative electrode binder is 30 parts by weight or less, preferably 25 parts by weight or less, more preferably 20 parts by weight or less, and may be 5 parts by weight or more, or 10 parts by weight or more, based on 100 parts by weight of the first upper layer negative electrode active material layer composition.

[0154] In the present application, a lithium secondary battery negative electrode is provided, wherein the second lower layer negative electrode active material layer includes a second lower layer negative electrode active material layer composition, the second upper layer negative electrode active material layer includes a second upper layer negative electrode active material layer composition, the second lower layer negative electrode active material layer composition includes a second lower layer negative electrode active material; a first lower layer negative electrode conductive material; and a second lower layer negative electrode binder, and the second upper layer negative electrode active material layer composition includes a second upper layer negative electrode active material; a second upper layer negative electrode conductive material; and a second upper layer negative electrode binder.

[0155] At this time, the first lower layer negative electrode active material layer and the second upper layer negative electrode active material layer differ only in the layers (second, first) used, and the same description may be applied to them. In addition, the first upper layer negative electrode active material layer and the second lower layer negative electrode active material layer differ only in the layers (second, first) used, and the same description may be applied to them.

[0156] In one embodiment of the present application, a method for manufacturing an anode for a lithium secondary battery is provided, comprising the steps of: preparing a first anode slurry and a second anode slurry; applying the first anode slurry on one surface of a anode current collector layer, and applying the second anode slurry on the first anode slurry applied on one surface of the anode current collector layer; and applying the second anode slurry on the opposite surface of the anode current collector layer, and applying the first anode slurry on the second anode slurry applied on the opposite surface of the anode current collector layer, wherein one of the first anode slurry and the second anode slurry includes a silicon-based active material.

[0157] In one embodiment of the present application, the first cathode slurry may include a first composition and a cathode slurry solvent.

[0158] At this time, the description of the first lower layer negative electrode active material layer composition or the second upper layer negative electrode active material layer composition can be applied to the first composition.

[0159] In one embodiment of the present application, the second cathode slurry may include a second composition and a cathode slurry solvent.

[0160] At this time, the description of the first upper layer negative electrode active material layer composition or the second lower layer negative electrode active material layer composition can be applied to the second composition.

[0161] In the present application, the solid content of the first cathode slurry and the second cathode slurry can satisfy a range of 10% to 40%.

[0162] The above slurry solvent may be used without limitation as one used in the art, and specifically, NMP or water may be used.

[0163] In one embodiment of the present application, a method for manufacturing a negative electrode for a lithium secondary battery is provided, wherein the step of applying a first negative electrode slurry on one surface of the negative electrode current collector layer and applying a second negative electrode slurry on the first negative electrode slurry applied on one surface of the negative electrode current collector layer includes the step of partially drying or completely drying the first negative electrode slurry after applying it; and the step of applying a second negative electrode slurry on the first negative electrode slurry.

[0164] The above coating method is a wet-on-dry process. Specifically, in the wet-on-dry process, a first negative electrode slurry is prepared and applied to a negative electrode current collector layer. Thereafter, the first negative electrode slurry mixture is dried to form a first lower negative electrode active material layer. Thereafter, a second negative electrode slurry mixture is prepared, applied to the first lower negative electrode active material layer, and dried to form a first upper negative electrode active material layer. Thereafter, each layer is rolled and pressed to form a negative electrode for a lithium secondary battery according to the present application.

[0165] In one embodiment of the present application, a method for manufacturing a negative electrode for a lithium secondary battery is provided, wherein the step of applying a second negative electrode slurry on the opposite surface of the negative electrode current collector layer, and applying a first negative electrode slurry on the second negative electrode slurry applied on the opposite surface of the negative electrode current collector layer comprises the steps of: applying the second negative electrode slurry and then partially drying or completely drying it; and applying the first negative electrode slurry on the second negative electrode slurry.

[0166] In one embodiment of the present application, a method for manufacturing a negative electrode for a lithium secondary battery is provided, wherein the step of applying a first negative electrode slurry on one surface of the negative electrode current collector layer and applying a second negative electrode slurry on the first negative electrode slurry applied on one surface of the negative electrode current collector layer includes the step of applying a second negative electrode slurry on the first negative electrode slurry in an undried state after applying the first negative electrode slurry.

[0167] The above coating method is a wet-on-wet process, and specifically, in the wet-on-wet process, a first negative electrode slurry is prepared and applied to a negative electrode current collector layer. Thereafter, a second negative electrode slurry mixture is prepared while the first negative electrode slurry mixture is not dried, and the second negative electrode slurry mixture is applied on the first negative electrode slurry and dried to form a first negative electrode active material layer. Thereafter, each layer is rolled and pressed to form a negative electrode for a lithium secondary battery according to the present application.

[0168] In one embodiment of the present application, a method for manufacturing a negative electrode for a lithium secondary battery is provided, wherein the step of applying a second negative electrode slurry on the opposite surface of the negative electrode current collector layer and applying a first negative electrode slurry on the second negative electrode slurry applied on the opposite surface of the negative electrode current collector layer includes the step of applying the first negative electrode slurry on the second negative electrode slurry in an undried state after applying the second negative electrode slurry.

[0169] In particular, the wet on dry process is a process in which the first negative electrode slurry composition is applied, partially or completely dried, and then the second negative electrode slurry composition is applied thereon. Through the above process, the first lower negative electrode active material layer and the first upper negative electrode active material layer can have a clear boundary. Accordingly, the compositions included in the first lower negative electrode active material layer and the first upper negative electrode active material layer do not mix, and they have the characteristic of being configured as a double layer.

[0170] As a result of the aforementioned wet-on-wet process, a bonding region can be formed where the first lower negative electrode active material layer and the first upper negative electrode active material layer are mixed. At this time, in order for the wet-on-wet process to occur, the viscosity of the first lower negative electrode active material layer composition must be lower than the viscosity of the first upper negative electrode active material layer composition, so that mutual mixing can occur in the bonding region and during the process.

[0171] In one embodiment of the present application, a lithium secondary battery is provided, comprising: a positive electrode; an anode for a lithium secondary battery according to the present application; a separator provided between the positive electrode and the negative electrode; and an electrolyte.

[0172] A secondary battery according to one embodiment of the present specification may particularly include the negative electrode for a lithium secondary battery as 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, wherein the negative electrode is identical to the negative electrode described above. Since the negative electrode has been described above, a detailed description thereof will be omitted.

[0173] The above positive electrode is formed on the positive electrode current collector and the positive electrode current collector, and may include a positive electrode active material layer including the positive electrode active material.

[0174] In the above positive electrode, the positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of 3 to 500 ㎛, and fine unevenness may be formed on the surface of the current collector to increase the adhesive strength of the positive electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0175] The above 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), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; or a compound having the chemical formula Li 1+c1 Mn 2-c1 Lithium manganese oxides such as O4(0≤c1≤0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-c2 M c2 Ni-site type lithium nickel oxide represented by O2 (wherein, M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies 0.01≤c2≤0.3); chemical formula LiMn 2-c3 M c3 Lithium manganese composite oxide represented by O2 (wherein, 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 (wherein, M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); LiMn2O4, etc., in which a part of Li in the chemical formula is replaced with an alkaline earth metal ion, but is not limited thereto. The positive electrode may be Li-metal.

[0176] The above-described positive electrode active material layer may include a positive electrode conductive material and a positive electrode binder together with the positive electrode active material described above.

[0177] At this time, the positive electrode conductive material is used to provide conductivity to the electrode, and in the battery to be constructed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like, and one of these may be used alone or a mixture of two or more may be used.

[0178] In addition, the positive electrode binder plays a role of improving the adhesion between positive electrode active material particles and the adhesiveness between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof.

[0179] The separator separates the negative and positive electrodes and provides a passage for lithium ions to move. Any separator commonly used in secondary batteries can be used without any particular restrictions, and in particular, one that has low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, can be used. In addition, a conventional porous non-woven fabric, for example, a non-woven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. can also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength can be used, and can optionally be used in a single-layer or multi-layer structure.

[0180] Examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

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

[0182] As the above non-aqueous organic solvent, for example, an aprotic organic solvent such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolan, formamide, dimethylformamide, dioxolan, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxy methane, dioxolan derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyrropionate, ethyl propionate, etc. can be used.

[0183] In particular, among the above carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are high-viscosity organic solvents with high dielectric constants and thus can be preferably used because they easily dissociate lithium salts. In addition, when low-viscosity, low-dielectric constant linear carbonates such as dimethyl carbonate and diethyl carbonate are mixed and used in an appropriate ratio with these cyclic carbonates, an electrolyte with high electrical conductivity can be produced, so that they can be used even more preferably.

[0184] The metal salt may be a lithium salt, and the lithium salt is a substance that is easily dissolved in the non-aqueous electrolyte, for example, the anion of the lithium salt is F - , Cl - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 -, CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - One or more selected from the group consisting of may be used.

[0185] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as, for example, a haloalkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, a cyclic ether, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine 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 battery capacity decrease, and improving the discharge capacity of the battery.

[0186] One embodiment of the present invention provides a battery module including the secondary battery as a unit cell and a battery pack including the same. The battery module and battery pack include the secondary battery having high capacity, high rate characteristics, and cycle characteristics, and thus can be used as a power source for medium- to large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0187] Hereinafter, preferred embodiments are presented to help understand the present invention, but the above embodiments are only illustrative of the present disclosure, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and technical idea of ​​the present disclosure, and it is natural that such changes and modifications fall within the scope of the appended patent claims.

[0188] <Manufacturing Example>

[0189] <Manufacturing of the cathode>

[0190] <Example 1>

[0191] <Manufacture of the first cathode slurry>

[0192] As the active material of the first negative electrode slurry, artificial graphite (average particle diameter (D50) = 19 ㎛) and spherical natural graphite (average particle diameter (D50) = 11 ㎛) were uniformly mixed at a weight ratio of 8:2, and then carbon black as the first conductive material, SBR as the binder, and carboxymethyl cellulose (CMC) as the thickener were mixed at a weight ratio of 95:1.5:2.3:1.2, respectively, and then these were mixed with water (H2O) as the first solvent to prepare the first negative electrode slurry.

[0193] <Manufacture of the second cathode slurry>

[0194] As the active material of the second negative electrode slurry, artificial graphite (average particle diameter (D50) = 19 ㎛), spherical natural graphite (average particle diameter (D50) = 11 ㎛), and SiO were uniformly mixed at a weight ratio of 56:14:30, and then CNT as the first conductive material, SBR as the binder, and carboxymethyl cellulose (CMC) as the thickener were mixed at a weight ratio of 96.293:0.043:3.6:0.065, respectively, and then these were mixed with water (H2O) as the first solvent to prepare the second negative electrode slurry.

[0195] The second negative electrode slurry manufactured above was applied to the top surface of Cu as a negative electrode current collector layer, and the first negative electrode slurry was applied on top to form a first negative electrode active material layer. At this time, each loading (mAh / cm 2) was coated so that it was 1:1.

[0196] As described above, the first negative electrode slurry prepared above was applied to the back surface of Cu as a negative electrode current collector layer after coating, and the second negative electrode slurry was applied thereon and dried to form a second negative electrode active material layer.

[0197] In the above Example 1, the information on the slurry applied to the first negative electrode active material layer and the second negative electrode active material layer was as shown in Table 1 below.

[0198] First negative electrode active material layerSecond negative electrode active material layerElectrode structureFirst lower layer negative electrode active material layerFirst upper layer negative electrode active material layerSecond lower layer negative electrode active material layerSecond upper layer negative electrode active material layerExample 1Second negative electrode slurryFirst negative electrode slurrySecond negative electrode slurryDLExample 2First negative electrode slurrySecond negative electrode slurrySecond negative electrode slurryFirst negative electrode slurryDLComparative example 1Second negative electrode slurryFirst negative electrode slurrySecond negative electrode slurryFirst negative electrode slurryDLComparative example 2First negative electrode slurrySecond negative electrode slurryFirst negative electrode slurrySecond negative electrode slurryDLComparative example 3First negative electrode slurrySecond negative electrode slurrySLComparative example 4Third negative electrode slurryThird negative electrode slurrySL

[0199] In Table 1 above, DL means Double layer, meaning that the negative electrode active material layer has a double layer, and SL means Single layer, meaning that the negative electrode active material layer has a single layer.

[0200] For reference, the manufacturing method of Comparative Example 4 in Table 1 above was as follows.

[0201] <Manufacture of the third cathode slurry>

[0202] As the active material of the third negative electrode slurry, artificial graphite (average particle diameter (D50) = 19 ㎛), spherical natural graphite (average particle diameter (D50) = 11 ㎛), and SiO were uniformly mixed at a weight ratio of 68:17:15, and then CNT as the first conductive material, SBR as the binder, and carboxymethyl cellulose (CMC) as the thickener were mixed at a weight ratio of 96.293:0.043:3.6:0.065, respectively, and then these were mixed with water (H2O) as the first solvent to prepare the third negative electrode slurry.

[0203] Cu was prepared as a negative electrode current collector layer, and the third negative electrode slurry was coated on both sides of the Cu to produce a single layer.

[0204] <Manufacturing of secondary batteries>

[0205] LiNi as a cathode active material 0.6 Co 0.2 Mn 0.2 O2 (average particle size (D50): 15㎛), carbon black (product name: Super C65, manufacturer: Timcal) as a conductive agent, and polyvinylidene fluoride (PVdF) as a binder were added to N-methyl-2-pyrrolidone (NMP) as a solvent for forming a cathode slurry at a weight ratio of 97:1.5:1.5 to prepare a cathode slurry (solid content concentration: 78 wt%).

[0206] The positive electrode slurry was applied to both sides of an aluminum current collector (thickness: 12㎛) as a positive electrode collector at a density of 537mg / 25cm. 2 A positive electrode was manufactured by coating with a loading amount, rolling, and drying in a vacuum oven at 130°C for 10 hours to form a positive electrode active material layer (thickness: 65 μm) (positive electrode thickness: 77 μm, porosity 26%).

[0207] A polyethylene separator was interposed between the positive electrode and the negative electrode of Example 1, and an electrolyte was injected to manufacture a secondary battery of Example 1.

[0208] The above electrolyte was an organic solvent containing fluoroethylene carbonate (FEC) and diethyl carbonate (DMC) mixed in a volume ratio of 30:70, vinylene carbonate added at 3 wt% based on the total weight of the electrolyte, and LiPF6 added as a lithium salt at a concentration of 1 M.

[0209] Secondary batteries were manufactured in the same manner as above, except that the negative electrodes of the above examples and comparative examples were used.

[0210] Experimental Example 1: Life Characteristics Evaluation

[0211] The secondary batteries containing the negative electrodes manufactured in the above examples and comparative examples were subjected to a life evaluation using an electrochemical charger / discharger, and the capacity retention rate was evaluated. The secondary batteries were subjected to a cycle test at 4.2-3.0 V 1C / 0.5C, and the capacity retention rate was measured by charging / discharging at 0.33C / 0.33C (4.2-3.0 V) every 50 cycles during the test.

[0212] Capacity retention rate (%) = {(discharge capacity at Nth cycle) / (discharge capacity at first cycle)} Υ 100

[0213] Experimental Example 2: Measurement and Evaluation of Resistance Increase Rate

[0214] In the above experimental example 1, the capacity retention rate was measured by performing 0.33C / 0.33C charge / discharge (4.2-3.0V) every 50 cycles during the test, and then the resistance increase rate was compared and analyzed by measuring the total resistance by discharging at 2.5C pulse at SOC50.

[0215] In addition, for the above life characteristic evaluation and the above resistance increase rate measurement evaluation, data at 200 cycles were calculated, and the results were as shown in Table 2 below.

[0216] Experimental Example 3: TP Evaluation

[0217] For the lithium secondary batteries manufactured in the above examples and comparative examples, a structure as shown in Fig. 2 was formed for evaluation, and a heat pad in contact with the cell was heated to induce thermal runaway of the cell.

[0218] The experiment was conducted in an autoclave (isolated from the external environment / atmosphere) under an N2 atmosphere. The pressure of the gas emitted when thermal runaway occurred was measured using a pressure gauge in the autoclave, and the resulting TR rate is shown in Table 2 below.

[0219] TR Rate = (Max pressure - Pre-ignition pressure) / (Cell capacity) / (Time before ignition - Time to Max pressure)

[0220] Capacity retention rate evaluation (%, @200 cycle) Resistance increase rate (%, @200 cycle) TR rate evaluation Example 189205.3 Example 289205.4 Comparative example 1873512.3 Comparative example 2881910.9 Comparative example 3824011.5 Comparative example 4862510.7

[0221] As can be seen from Tables 1 and 2 above, the explosive power of the negative electrode can be reduced when heat is applied by improving the structure of the negative electrode for a lithium secondary battery according to the present application. Specifically, it was confirmed that the double-layer active materials included in the first negative electrode active material layer and the second negative electrode active material layer are arranged to have an asymmetrical structure, so that even if thermal runaway occurs in the negative electrode active material layer including the silicon-based active material, another negative electrode active material layer that can act as a barrier is arranged, thereby having the characteristic of being able to control it.

[0222] In Comparative Examples 1 and 2, the negative electrodes of the DL structure are the same, but it can be confirmed that the TOP surface and the BOTTOM surface (i.e., the first negative electrode active material layer and the second negative electrode active material layer) are symmetrical based on the negative electrode current collector layer. In this case, in Comparative Example 1, the negative electrode active material layer including a silicon-based active material is provided on the negative electrode current collector layer side, and in Comparative Example 2, the negative electrode active material layer including a silicon-based active material is concentrated on the side facing the positive electrode, so that the evaluation results in the life and resistance evaluations are somewhat lower than those of the examples, but the thermal stability evaluation results are particularly poor. This corresponds to the result that another negative electrode active material layer that can act as a barrier as described above is not arranged.

[0223] In Comparative Examples 3 and 4, the SL-structured negative electrodes were shown. In Comparative Example 3, the negative electrode had a carbon-based active material on the top surface (first negative electrode active material layer) and a silicon-based active material on the back surface (second negative electrode active material layer), and in Comparative Example 4, the negative electrode was a mixture of silicon and carbon-based active materials. In this case as well, it was confirmed that the thermal stability was inferior to that of Examples 1 and 2 of the present invention. In addition, it was found that the performance was inferior to that of the present example in terms of lifespan and resistance increase rate.

Claims

1. A negative electrode for a lithium secondary battery comprising: a negative electrode current collector layer; a first negative electrode active material layer provided on one surface of the negative electrode current collector layer; and a second negative electrode active material layer provided on the other surface of the negative electrode current collector layer, The first negative electrode active material layer includes a first lower layer negative electrode active material layer in contact with the negative electrode current collector layer; and a first upper layer negative electrode active material layer provided on the opposite side of the surface of the first lower layer negative electrode active material layer in contact with the negative electrode current collector layer; The second negative electrode active material layer includes a second lower negative electrode active material layer in contact with the negative electrode current collector layer; and a second upper negative electrode active material layer provided on the opposite side of the surface of the second lower negative electrode active material layer in contact with the negative electrode current collector layer; One of the first lower layer negative electrode active material layer and the first upper layer negative electrode active material layer includes a silicon-based active material, The first lower layer negative electrode active material layer and the second upper layer negative electrode active material layer have the same composition, A negative electrode for a lithium secondary battery, wherein the first upper negative electrode active material layer and the second lower negative electrode active material layer have the same composition.

2. In claim 1, A negative electrode for a lithium secondary battery, wherein the first negative electrode active material layer and the second negative electrode active material layer are asymmetrical with respect to the negative electrode current collector layer.

3. In claim 1, The first lower negative electrode active material layer and the second lower negative electrode active material layer have different compositions, A negative electrode for a lithium secondary battery, wherein the second upper layer negative electrode active material layer and the second upper layer negative electrode active material layer have different compositions.

4. In claim 1, The first lower layer negative electrode active material layer comprises a first lower layer negative electrode active material layer composition, The first upper layer negative electrode active material layer comprises a first upper layer negative electrode active material layer composition, The first lower layer negative electrode active material layer composition comprises a first lower layer negative electrode active material; a first lower layer negative electrode conductive material; and a first lower layer negative electrode binder. A negative electrode for a lithium secondary battery, wherein the first upper layer negative electrode active material layer composition comprises a first upper layer negative electrode active material; a first upper layer negative electrode conductive material; and a first upper layer negative electrode binder.

5. In claim 4, One of the first lower layer negative electrode active material and the first upper layer negative electrode active material includes at least one 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, A negative electrode for a lithium secondary battery, wherein the other one of the first lower layer negative electrode active material and the first upper layer negative electrode active material includes a carbon-based active material.

6. In claim 5, The above silicon-based active material is SiOx (x=0); SiOx (0 <x<2); 또는 SiC를 포함하는 것인 리튬 이차 전지용 음극.

7. In claim 5, A negative electrode for a lithium secondary battery, wherein the silicon-based active material is contained in an amount of 1 part by weight or more and 50 parts by weight or less, based on 100 parts by weight of the first lower layer negative electrode active material.

8. In claim 1, The thickness of the first negative electrode active material layer is 10 μm or more and 200 μm or less, A negative electrode for a lithium secondary battery, wherein the thickness of the second negative electrode active material layer is 10 μm or more and 200 μm or less.

9. In claim 4, A negative electrode for a lithium secondary battery, wherein the first lower layer negative electrode conductive material and the first upper layer negative electrode conductive material include at least a linear conductive material.

10. Bipolar; A negative electrode for a lithium secondary battery according to any one of claims 1 to 9; A separator provided between the anode and the cathode; and A lithium secondary battery comprising an electrolyte.

11. A step of preparing a first cathode slurry and a second cathode slurry; A step of applying a first negative electrode slurry on one surface of a negative electrode current collector layer, and applying a second negative electrode slurry on the first negative electrode slurry applied on one surface of the negative electrode current collector layer; and A step of applying a second negative electrode slurry on the opposite surface of the negative electrode current collector layer, and applying the first negative electrode slurry on the second negative electrode slurry applied on the opposite surface of the negative electrode current collector layer; A method for manufacturing a negative electrode for a lithium secondary battery, comprising: A method for manufacturing an anode for a lithium secondary battery, wherein one of the first anode slurry and the second anode slurry contains a silicon-based active material.

12. In claim 11, A method for manufacturing an anode for a lithium secondary battery, wherein the step of applying a first anode slurry onto one surface of the anode current collector layer and applying a second anode slurry onto the first anode slurry applied onto one surface of the anode current collector layer includes the step of simultaneously applying a second anode slurry onto the first anode slurry in an undried state after applying the first anode slurry.

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