Negative electrode for lithium secondary battery and lithium secondary battery including the negative electrode

Abstract

The negative electrode for a lithium secondary battery of the present invention includes a negative electrode current collector layer; a primer coating layer containing a primer coating layer composition provided on one or both surfaces of the negative electrode current collector layer; and a negative electrode active material layer provided on the surface of the primer coating layer opposite to the surface in contact with the negative electrode current collector layer. The negative electrode active material layer includes a negative electrode active material layer composition containing a silicon-based active material, a negative electrode conductive material, and a negative electrode binder. The silicon-based active material includes at least one selected from the group consisting of SiOx (x = 0) and SiOx (0 < x < 2), and contains 95 parts by weight or more of the SiOx (x = 0) based on 100 parts by weight of the silicon-based active material. The primer coating layer composition includes at least one selected from the group consisting of a binder and a conductive material. The porosity of the negative electrode active material layer is 50% or more, and the D50 particle size of the silicon-based active material contained in the negative electrode active material layer is 5 μm or more.

Description

[Technical Field]

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2022-0076794, filed with the Korean Intellectual Property Office on June 23, 2022, the entire contents of which are incorporated herein by reference.

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

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

[0004] Currently, a typical example of an electrochemical element that utilizes such electrochemical energy is a secondary battery, and the range of its use is tending to expand more and more.

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

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

[0007] In recent years, in response to the demand for high-density energy batteries, active research has been conducted into methods for increasing capacity by using silicon-based compounds such as Si / C and SiOx as anode active materials, which have capacities more than 10 times greater than graphite-based materials. However, while silicon-based compounds, which are high-capacity materials, have superior capacity characteristics compared to conventional graphite, their volume expands rapidly during charging, disrupting the conductive path and reducing battery performance, resulting in a decrease in capacity from the beginning. Furthermore, silicon-based anodes face challenges in that they do not charge lithium ions uniformly throughout the anode depth during repeated charge and discharge cycles, and reactions occur on the surface, accelerating surface degradation. This means that improvements are needed in terms of battery cycle performance.

[0008] Furthermore, when making anodes using silicon-based active materials, it is important that the pore structure of the anode is simple. It is known that the better the tortuosity of the pores in anodes using silicon-based active materials, the better the diffusion resistance. However, if the porosity is increased infinitely to improve the tortuosity of the pores, the fewer contact points with the anode current collector layer will be, which will weaken the adhesion to the anode current collector layer and cause detachment, resulting in a decrease in lifespan characteristics.

[0009] Various studies are underway to solve the above problems, but there are limitations to their application because they may actually reduce battery performance. There are also limitations to the commercialization of anode batteries with a high silicon-based compound content. As the proportion of silicon-based active material in the silicon-based active material layer increases, reactions with lithium ions tend to concentrate on the surface of the anode, causing damage to the silicon-based active material on the surface side and resulting in reduced life characteristics.

[0010] Therefore, even when a silicon-based compound is used as an active material, it is necessary to develop a lithium secondary battery that improves the tortuosity of the negative electrode pores during charge and discharge cycles and also has excellent adhesion to the negative electrode current collector layer. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Patent Publication No. 2009-080971 Summary of the Invention [Problem to be solved by the invention]

[0012] In the case of existing carbon-based negative electrodes, there is no problem associated with volume expansion, and the porosity of the carbon-based negative electrode active material layer can be adjusted or the adhesive strength with the current collector layer can be eliminated.

[0013] However, in order to ensure the capacity characteristics, the negative electrode was changed from a carbon-based active material to a silicon-based active material, and although the volume expansion problem of general silicon-based active materials (such as SiO) is more severe than that of carbon-based active materials, no problems were caused by this.

[0014] However, in recent years, pure silicon (Pure Si) active materials have been used among silicon-based active materials to maximize capacity characteristics and ensure fast charging. However, this has led to problems such as rapid volume expansion and reduced lifespan due to detachment from the negative electrode current collector layer.

[0015] Therefore, the present application relates to a negative electrode for a lithium secondary battery, which uses a silicon-based active material in the negative electrode, but which improves the tortuosity of the voids to prevent degradation of the electrode surface during charge and discharge cycles, and further improves the adhesive strength with the negative electrode current collector layer, thereby improving cycle performance, and a lithium secondary battery including the negative electrode. [Means for solving the problem]

[0016] One embodiment of the present specification is a negative electrode for a lithium secondary battery, comprising: a negative electrode current collector layer; a primer coating layer containing a primer coating layer composition provided on one or both surfaces of the negative electrode current collector layer; and a negative electrode active material layer provided on the opposite surface of the primer coating layer to the surface in contact with the negative electrode current collector layer. The negative electrode active material layer contains a negative electrode active material layer composition including a silicon-based active material, a negative electrode conductive material, and a negative electrode binder. The silicon-based active material includes at least one selected from the group consisting of SiOx (x = 0) and SiOx (0 < x < 2), and contains 95 parts by weight or more of SiOx (x = 0) based on 100 parts by weight of the silicon-based active material. The primer coating layer composition includes at least one selected from the group consisting of a binder and a conductive material. The porosity of the negative electrode active material layer is 50% or more, and the D50 particle size of the silicon-based active material contained in the negative electrode active material layer is 5 μm or more.

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

Advantages of the Invention

[0018] The negative electrode for a lithium secondary battery according to one embodiment of the present invention is characterized in that the active material layer has a single layer structure, the content of the silicon-based active material in the negative electrode active material layer is increased to raise the energy density of the negative electrode, and the range of the particle size and porosity of the silicon-based active material satisfies the range according to the present application, simplifying the pore structure and improving the tortuosity of the pores.

[0019] Therefore, the negative electrode active material layer may experience significant volume expansion during charge and discharge, leading to detachment from the negative electrode current collector as cycles progress. Furthermore, to achieve high energy density, the amounts of negative electrode conductive material and negative electrode binder must be minimized, reducing contact points with the negative electrode current collector. The primary objective of the present invention is to solve these problems by coating a primer coating layer containing a primer coating composition with specific composition and content on top of the negative electrode current collector layer.

[0020] That is, the present invention is characterized in that it can maximize the high energy density and capacity characteristics that are advantages of silicon-based negative electrodes, while also improving the lifespan characteristics by adjusting the porosity range of the negative electrode active material layer and further applying a primer coating layer, which are problems that have existed until now.

[0021] In conclusion, the negative electrode for a lithium secondary battery according to the present invention is characterized by its excellent output and life characteristics, as it uses a silicon-based active material to maximize capacity characteristics, has a negative electrode active material layer that satisfies a specific porosity range to simplify the pore structure, and uses a primer coating layer with a specific composition to improve adhesion to the negative electrode current collector. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a diagram showing a laminated structure of a negative electrode for a lithium secondary battery according to an embodiment of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0023] Before describing the present invention, some terms will first be defined. In this specification, when a part is said to "comprise" a certain component, this does not mean that it may further include other components, unless specifically stated to the contrary, but rather that it does not exclude other components.

[0024] In this specification, "p to q" means a range of "not less than p and not more than q." In this specification, the "specific surface area" is measured by the BET method, and specifically, is calculated from the amount of nitrogen gas adsorption at liquid nitrogen temperature (77 K) using a BELSORP-mini II manufactured by BEL Japan Co., Ltd. That is, in the present application, the BET specific surface area may mean the specific surface area measured by the above-mentioned measurement method.

[0025] In this specification, "Dn" refers to particle size distribution, and refers to the particle size at the n% point in the cumulative particle number distribution by particle size. That is, D50 is the particle size (average particle size) at the 50% point in the cumulative particle number distribution by particle size, D90 is the particle size at the 90% point in the cumulative particle number distribution by particle size, and D10 is the particle size at the 10% point in the cumulative particle number distribution by particle size. Meanwhile, particle size distribution can be measured using the laser diffraction method. Specifically, the powder to be measured is dispersed in a dispersion medium and then introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac S3500). The particle size distribution is calculated by measuring the difference in diffraction patterns due to particle size when the particles pass through a laser beam.

[0026] In this specification, when a polymer contains a certain monomer as a monomer unit, it means that the monomer is involved in a polymerization reaction and is contained as a repeating unit in the polymer. In this specification, when a polymer contains a monomer, this is interpreted as the same as when a polymer contains a monomer as a monomer unit.

[0027] In this specification, the term "polymer" is understood to be used in a broad sense, including copolymers, unless otherwise specified as a "homopolymer."

[0028] In this specification, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) are the polystyrene-equivalent molecular weights measured by gel permeation chromatography (GPC) using monodisperse polystyrene polymers (standard samples) of various degrees of polymerization commercially available for molecular weight measurement as the standard substance. In this specification, the molecular weight means the weight-average molecular weight unless otherwise specified.

[0029] Hereinafter, for those with ordinary knowledge in the technical field to which the present invention pertains to easily implement the present invention, a detailed description will be given with reference to the drawings. However, the present invention can be embodied in various different forms and is not limited to the following description.

[0030] One embodiment of this specification is a negative electrode for a lithium secondary battery including a negative electrode current collector layer; a primer coating layer including a primer coating layer composition provided on one or both surfaces of the negative electrode current collector layer; and a negative electrode active material layer provided on the opposite surface of the primer coating layer to the surface in contact with the negative electrode current collector layer. The negative electrode active material layer includes a negative electrode active material layer composition including a silicon-based active material, a negative electrode conductive material, and a negative electrode binder. The silicon-based active material includes at least one selected from the group consisting of SiOx (x = 0) and SiOx (0 < x < 2). Based on 100 parts by weight of the silicon-based active material, it contains 95 parts by weight or more of SiOx (x = 0). The primer coating layer composition includes at least one selected from the group consisting of a binder and a conductive material. The porosity of the negative electrode active material layer is 50% or more, and the D50 particle size of the silicon-based active material contained in the negative electrode active material layer is 5 μm or more. A negative electrode for a lithium secondary battery is provided.

[0031] The negative electrode for a lithium secondary battery according to this application has the advantages of an electrode that applies silicon particles with a high content using a single-layer active material, and to solve the problems of simplification of the negative electrode pore structure, improvement of the adhesion force with the negative electrode current collector layer, and output characteristics, which are the disadvantages when having this, it is characterized in that a primer coating layer having a specific composition is configured.

[0032] FIG. 1 is a diagram showing the layered structure of a negative electrode for a lithium secondary battery according to one embodiment of the present application. Specifically, a negative electrode for a lithium secondary battery 100 can be seen, including a primer coating layer 20 and a negative electrode active material layer 10 on one side of a negative electrode current collector layer 30. While FIG. 1 shows the negative electrode active material layer and primer coating layer formed on one side, they may be formed on both sides of the negative electrode current collector layer. When they are formed on both sides, the primer coating layer may be formed on both sides or on one side of the negative electrode current collector layer.

[0033] The negative electrode for a lithium secondary battery of the present invention will be described in more detail below. In one embodiment of the present application, there is provided a negative electrode for a lithium secondary battery, comprising: a negative electrode current collector layer; a primer coating layer provided on one or both sides of the negative electrode current collector layer; and a negative electrode active material layer provided on the surface of the primer coating layer opposite to the surface in contact with the negative electrode current collector layer.

[0034] In one embodiment of the present application, the negative electrode current collector layer generally has a thickness of 1 μm to 100 μm. Such a negative electrode current collector layer is not particularly limited as long as it has high conductivity without inducing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like, aluminum-cadmium alloy, etc., can be used. Furthermore, the bonding strength of the negative electrode active material can be strengthened by forming fine irregularities on the surface, and the negative electrode current collector layer can be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0035] In one embodiment of the present application, the negative electrode current collector layer may have a thickness of 1 μm or more and 100 μm or less.

[0036] However, the thickness may vary depending on the type and application of the negative electrode used, and is not limited thereto.

[0037] In one embodiment of the present application, the negative electrode active material layer includes a negative electrode active material layer composition containing a silicon-based active material, a negative electrode conductive material, and a negative electrode binder.

[0038] In one embodiment of the present application, the silicon-based active material includes a silicon-based active material containing silicon particles having a particle size distribution of 0.01 μm or more and 50 μm or less, and a negative electrode for a lithium secondary battery is provided in which the D50 particle size of the silicon-based active material contained in the negative electrode active material layer is 5 μm or more.

[0039] In one embodiment of the present application, the silicon-based active material includes at least one selected from the group consisting of SiOx (x = 0) and SiOx (0 < x < 2), and based on 100 parts by weight of the silicon-based active material, the SiOx (x = 0) may be contained in an amount of 95 parts by weight or more.

[0040] In one embodiment of the present application, the silicon-based active material includes at least one selected from the group consisting of SiOx (x = 0) and SiOx (0 < x < 2), and based on 100 parts by weight of the silicon-based active material, the SiOx (x = 0) is contained in an amount of 95 parts by weight or more, preferably 97 parts by weight or more, more preferably 99 parts by weight or more, and may be contained in an amount of 100 parts by weight or less.

[0041] In one embodiment of the present application, the silicon-based active material may particularly use pure silicon (Si) particles. Using pure silicon (Si) as the silicon-based active material can mean that, as described above, when the total amount of the silicon-based active material is based on 100 parts by weight, pure Si particles (SiOx (x = 0)) that are not combined with other particles or elements are included within the above range.

[0042] In one embodiment of the present application, the silicon-based active material may consist of SiOx (x = 0).

[0043] The negative electrode for a lithium secondary battery according to the present application includes the above-described silicon-based active material in the negative electrode active material layer, specifically, pure silicon particles containing 95 parts by weight or more of SiOx (x = 0). In this case, when the pure silicon particles are included in a high content, excellent capacity characteristics are obtained. In order to solve the problem of reduced lifespan due to the resulting simplified pore structure, the negative electrode includes a primer coating layer according to the present invention, thereby solving the above problem.

[0044] The silicon-based active material of the present invention may have an average particle size (D50) of 3 μm to 10 μm, specifically 4 μm to 8 μm, and more specifically 5 μm to 7 μm. When the average particle size is within this range, the specific surface area of ​​the particles is within an appropriate range, and the viscosity of the negative electrode slurry is formed within an appropriate range. This allows for smooth dispersion of the particles constituting the negative electrode slurry. Furthermore, when the size of the first negative electrode active material is equal to or greater than the lower limit of the range, the composite of the conductive material and the binder in the negative electrode slurry has an excellent contact area between the silicon particles and the conductive material, increasing the likelihood of maintaining a conductive network and improving the capacity retention rate. When the average particle size is within this range, excessively large silicon particles are excluded, resulting in a smooth negative electrode surface, thereby preventing non-uniform current density during charge and discharge.

[0045] In particular, the negative electrode for a lithium secondary battery according to the present application has a porosity of 50% or more in the negative electrode active material layer.

[0046] The porosity control affects the overall composition and content of the negative electrode active material layer composition, and is mainly influenced by the D50 particle size of the silicon-based active material contained in the negative electrode active material layer composition.

[0047] In one embodiment of the present application, there is provided a negative electrode for a lithium secondary battery, wherein the silicon-based active material contained in the negative electrode active material layer has a D50 particle size of 5 μm or more.

[0048] In another embodiment, the D50 particle size of the silicon-based active material contained in the negative electrode active material layer may be in the range of 6 μm or more, preferably 7 μm or more, more preferably 8 μm or more, and 15 μm or less.

[0049] In one embodiment of the present application, there is provided a negative electrode for a lithium secondary battery, wherein the silicon-based active material contained in the negative electrode active material layer has a D50 particle size of 8 μm or more and 15 μm or less.

[0050] In one embodiment of the present application, there is provided a negative electrode for a lithium secondary battery, in which the porosity of the negative electrode active material layer is 60% or more and 90% or less.

[0051] In one embodiment of the present application, the porosity of the negative electrode active material layer may be 50% or more, preferably 60% or more, and may be 90% or less, preferably 80% or less.

[0052] By satisfying the above-mentioned particle size distribution and porosity ranges, the negative electrode for a lithium secondary battery according to the present application satisfies the above-mentioned ranges of porosity and simplifies the pore structure, thereby improving the phenomenon in which the reaction between lithium ions and silicon-based active materials is concentrated only on the surface, thereby improving diffusion resistance. Furthermore, by including a primer coating layer with a specific composition, the adhesion to the negative electrode current collector layer is improved, thereby increasing the adhesion even with continued charge / discharge cycles, resulting in enhanced life characteristics.

[0053] In one embodiment of the present application, the silicon-based active material generally has a characteristic BET specific surface area. The BET specific surface area of ​​the silicon-based active material is preferably 0.01 m 2 / g~150.0m 2 / g, more preferably 0.1m 2 / g~100.0m 2 / g, particularly preferably 0.2m 2 / g~80.0m 2 / g, most preferably 0.2m 2 / g~18.0m 2 / g. The BET surface area is measured according to DIN 66131 (using nitrogen).

[0054] In one embodiment of the present application, the silicon-based active material can be, for example, in a crystalline or amorphous form and is preferably not porous. The silicon particles are preferably spherical or shard-like particles. Alternatively, but less preferably, the silicon particles may also have a fibrous structure or be in the form of a silicon-containing film or coating.

[0055] In one embodiment of the present application, the silicon-based active material may have a non-spherical shape, and the sphericity thereof is, for example, 0.9 or less, for example, 0.7 to 0.9, for example, 0.8 to 0.9, for example, 0.85 to 0.9.

[0056] In this application, the circularity is determined by the following formula 1, where A is the area and P is the perimeter. [Formula 1] 4πA / P 2

[0057] In one embodiment of the present application, the silicon-based active material may be 80 parts by weight or more based on 100 parts by weight of the negative electrode active material layer composition.

[0058] In another embodiment, the amount of the silicon-based active material may be 80 parts by weight or more, preferably 85 parts by weight or more, based on 100 parts by weight of the negative electrode active material layer composition, and may be 99 parts by weight or less, preferably 97 parts by weight or less, and more preferably 95 parts by weight or less.

[0059] The negative electrode active material layer composition according to the present application has the effect of improving capacity characteristics by using a silicon-based active material with extremely high capacity in the above range, and in particular, by adjusting the range of the silicon-based active material contained in the negative electrode active material layer to the above range, the problems of surface degradation during charge and discharge, problems with life characteristics, and problems with ensuring conductive paths are solved without reducing the capacity performance of the entire negative electrode.

[0060] While graphite-based compounds have traditionally been used exclusively as anode active materials, attempts to incorporate silicon-based compounds into batteries to increase capacity have been increasing in recent years as demand for high-capacity batteries has grown. However, silicon-based compounds have limitations, such as their rapid volume expansion during charge / discharge processes, damaging the conductive pathways formed within the anode active material layer and reducing battery performance.

[0061] Furthermore, when a silicon-based active material of a certain particle size is contained within the above range in order to adjust the porosity range as described above, the volume expansion during charging and discharging makes it impossible to secure a conductive path, resulting in a decrease in output characteristics and, therefore, a decrease in life characteristics.

[0062] Therefore, in one embodiment of the present application, the negative electrode conductive material may include at least one selected from the group consisting of dot-like conductive material; linear conductive material; and sheet-like conductive material.

[0063] In one embodiment of the present application, the negative electrode conductive material may be any material commonly used in the art without limitation, and may be selected from the group consisting of dot-shaped conductive materials, planar conductive materials, and linear conductive materials.

[0064] In one embodiment of the present application, the dot-like conductive material refers to a dot-like or spherical conductive material that can be used to improve conductivity to the negative electrode and exhibits conductivity without inducing a chemical change. Specifically, the dot-like conductive material may be at least one selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, conductive fiber, fluorocarbon, aluminum powder, nickel powder, zinc oxide, potassium titanate, titanium oxide, and polyphenylene derivatives, and preferably includes carbon black, which realizes high conductivity and excellent dispersibility.

[0065] In one embodiment of the present application, the point-like conductive material has a BET specific surface area of ​​40 m 2 / g or more 70m 2 / g or less, preferably 45m 2 / g or more 65m 2 / g or less, more preferably 50m 2 / g or more 60m 2 / g or less.

[0066] In one embodiment of the present application, the particle size of the dotted conductive material may be 10 nm to 100 nm, preferably 20 nm to 90 nm, and more preferably 20 nm to 60 nm.

[0067] In one embodiment of the present application, the planar conductive material can improve conductivity by increasing surface contact between silicon particles in the negative electrode, and at the same time, can prevent the conductive path from being disconnected due to volume expansion, and can be expressed as a plate-shaped conductive material or a bulk-type conductive material.

[0068] In one embodiment of the present application, the sheet conductive material may include at least one selected from the group consisting of platelet graphite, graphene, graphene oxide, and graphite flakes, and may be preferably platelet graphite.

[0069] In one embodiment of the present application, the average particle size (D50) of the sheet conductive material may be 2 μm to 7 μm, specifically 3 μm to 6 μm, and more specifically 4 μm to 5 μm. When the average particle size satisfies this range, the sufficient particle size facilitates dispersion without causing an excessive increase in the viscosity of the negative electrode slurry. Therefore, when dispersion is performed using the same equipment and time, the dispersion effect is excellent.

[0070] In one embodiment of the present application, the sheet 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.

[0071] In one embodiment of the present application, the sheet conductive material may be a sheet conductive material having a high BET specific surface area; or a sheet conductive material having a low specific surface area.

[0072] In one embodiment of the present application, the planar conductive material may be a high-specific surface area planar conductive material or a low-specific surface area planar conductive material without any restrictions. However, the planar conductive material of the present application may be affected to some extent by dispersion in terms of electrode performance, and it may be particularly preferable to use a low-specific surface area planar conductive material that does not cause dispersion problems.

[0073] In one embodiment of the present application, the sheet conductive material has a BET specific surface area of ​​5 m 2 / g or more.

[0074] In another embodiment, the sheet conductive material has a BET specific surface area of ​​5 m 2 / g or more 500m 2 / g or less, preferably 5m 2 / g or more 300m 2 / g or less, more preferably 5m 2 / g or more 250m 2 / g or less.

[0075] In another embodiment, the sheet conductive material is a high specific surface area sheet conductive material having a BET specific surface area of ​​50 m 2 / g or more 500m 2 / g or less, preferably 80m 2 / g or more 300m 2 / g or less, more preferably 100m 2 / g or more 300m 2 / g or less.

[0076] In another embodiment, the sheet conductive material is a sheet conductive material with a low specific surface area, and has a BET specific surface area of ​​5 m 2 / g or more 40m 2 / g or less, preferably 5m 2 / g or more 30m 2 / g or less, more preferably 5m 2 / g or more 25m2 / g or less.

[0077] Other conductive materials include linear conductive materials such as carbon nanotubes. The carbon nanotubes may be bundled carbon nanotubes. The bundled carbon nanotubes may include multiple carbon nanotube units. Specifically, unless otherwise specified, the term "bundle type" refers to a secondary shape in which multiple carbon nanotube units are arranged side by side or entangled with their longitudinal axes aligned in substantially the same direction, forming a bundle or rope-like shape. The carbon nanotube units have cylindrical graphite sheets with nanosized diameters and an sp2 bonding structure. Depending on the winding angle and structure of the graphite sheets, the carbon nanotubes may exhibit conductive or semiconductive properties. Compared to entangled carbon nanotubes, the bundled carbon nanotubes can be more uniformly dispersed during negative electrode fabrication, smoothly forming a conductive network within the negative electrode, and improving the conductivity of the negative electrode.

[0078] In one embodiment of the present application, the negative electrode conductive material may be present in an amount of 0.01 parts by weight or more and 40 parts by weight or less based on 100 parts by weight of the negative electrode active material layer composition.

[0079] In yet another embodiment, the negative electrode conductive material may be 0.01 parts by weight or more and 40 parts by weight or less, preferably 0.1 parts by weight or more and 30 parts by weight or less, and more preferably 0.5 parts by weight or more and 25 parts by weight or less, based on 100 parts by weight of the negative electrode active material layer composition.

[0080] In one embodiment of the present application, when the negative electrode conductive material contains only linear conductive material, the content may be 0.01 parts by weight or more and 5 parts by weight or less based on 100 parts by weight of the negative electrode active material layer composition.

[0081] In yet another embodiment, when the negative electrode conductive material contains only a linear conductive material, the amount may be 0.01 parts by weight or more and 5 parts by weight or less, preferably 0.03 parts by weight or more and 3 parts by weight or less, and more preferably 0.1 parts by weight or more and 2 parts by weight or less, based on 100 parts by weight of the negative electrode active material layer composition.

[0082] In one embodiment of the present application, the negative electrode conductive material includes dot-like conductive material; sheet-like conductive material; and linear conductive material, and the dot-like conductive material:sheet-like conductive material:linear conductive material may satisfy a ratio of 1:1:0.01 to 1:1:1.

[0083] In one embodiment of the present application, the content of the dot-like conductive material may be in the range of 1 part by weight or more and 60 parts by weight or less, preferably 5 parts by weight or more and 50 parts by weight or less, and more preferably 10 parts by weight or more and 50 parts by weight or less, based on 100 parts by weight of the negative electrode conductive material.

[0084] In one embodiment of the present application, the sheet conductive material may satisfy the range of 1 part by weight or more and 60 parts by weight or less, preferably 5 parts by weight or more and 50 parts by weight or less, and more preferably 10 parts by weight or more and 50 parts by weight or less, based on 100 parts by weight of the negative electrode conductive material.

[0085] In one embodiment of the present application, the linear conductive material may satisfy the range of 0.01 parts by weight or more and 10 parts by weight or less, preferably 0.05 parts by weight or more and 8 parts by weight or less, and more preferably 0.1 parts by weight or more and 5 parts by weight or less, based on 100 parts by weight of the negative electrode conductive material.

[0086] In one embodiment of the present application, the negative electrode conductive material may include a linear conductive material and a planar conductive material.

[0087] In one embodiment of the present application, the negative electrode conductive material may include linear conductive material and sheet conductive material, and the ratio of the linear conductive material to the sheet conductive material may satisfy 0.01:1 to 0.1:1.

[0088] In one embodiment of the present application, the negative electrode conductive material particularly includes a linear conductive material and a planar conductive material, and by satisfying the above-mentioned composition and ratio, respectively, the battery does not have a significant effect on the life characteristics of existing lithium secondary batteries, and the number of points at which charging and discharging are possible increases, resulting in excellent output characteristics at a high C-rate.

[0089] The negative electrode conductive material according to the present application has a completely different structure from the positive electrode conductive material used in the positive electrode. That is, the negative electrode conductive material according to the present application serves to secure the contact points between the silicon-based active materials, which experience a large volume expansion of the electrode upon charge and discharge, while the positive electrode conductive material serves to provide a buffer during rolling and also to impart some conductivity, and therefore has a completely different structure and role from the negative electrode conductive material of the present invention.

[0090] Furthermore, the negative electrode conductive material according to the present application is applied to a silicon-based active material and has a completely different structure from conductive materials applied to graphite-based active materials. That is, conductive materials used in electrodes having graphite-based active materials simply have smaller particles than the active material, and therefore have the properties of improving output characteristics and imparting some conductivity, and are completely different in structure and role from negative electrode conductive materials applied together with silicon-based active materials as in the present invention.

[0091] In one embodiment of the present application, the negative electrode binder may be included in an amount of 1 part by weight to 20 parts by weight based on 100 parts by weight of the negative electrode active material layer composition.

[0092] In another embodiment, the amount of the negative electrode binder may be in the range of 1 part by weight to 20 parts by weight, preferably 2 parts by weight to 15 parts by weight, and more preferably 3 parts by weight to 15 parts by weight, based on 100 parts by weight of the negative electrode active material layer composition.

[0093] 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, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, and substances in which hydrogen is substituted with Li, Na, Ca, or the like, or may include various copolymers thereof.

[0094] The negative electrode binder according to one embodiment of the present application plays a role in holding down the active material and conductive material to prevent twisting and structural deformation of the negative electrode structure during volume expansion and relaxation of the negative electrode silicon-based active material. Any common binder can be used as long as it fulfills the above role, and specifically, an aqueous binder can be used, and more specifically, a PAM-based binder can be used.

[0095] In one embodiment of the present application, the negative electrode current collector layer includes a primer coating layer including a primer coating layer composition provided on one or both surfaces thereof, and the primer coating layer composition may include at least one selected from the group consisting of a binder and a conductive material.

[0096] In one embodiment of the present application, there is provided a negative electrode for a lithium secondary battery, wherein the thickness of the primer coating layer is 1 nm or more and 1 μm or less.

[0097] In one embodiment of the present application, there is provided a negative electrode for a lithium secondary battery, wherein the binder is contained in an amount of 10 parts by weight or more and 100 parts by weight or less, based on 100 parts by weight of the primer coating layer composition.

[0098] The primer coating layer composition according to the present application may comprise the binder alone.

[0099] The primer coating layer composition according to the present application may include a binder and a conductive material.

[0100] In this case, the present application provides a negative electrode for a lithium secondary battery, wherein the binder is contained in an amount of 10 parts by weight to 100 parts by weight based on 100 parts by weight of the primer coating layer composition.

[0101] In one embodiment of the present application, there is provided a negative electrode for a lithium secondary battery, in which the adhesive strength of the surface of the negative electrode active material layer in contact with the primer coating layer satisfies 100 gf / 5 mm or more and 500 gf / 5 mm or less under conditions of 25°C and normal pressure.

[0102] In yet another embodiment, the adhesive strength of the surface of the negative electrode active material layer in contact with the primer coating layer may satisfy the conditions of 300 gf / 5 mm or more and 500 gf / 5 mm or less, preferably 300 gf / 5 mm or more and 450 gf / 5 mm or less, and more preferably 350 gf / 5 mm or more and 430 gf / 5 mm or less, at 25°C and normal pressure.

[0103] The adhesive strength was measured using a peel strength tester with 3M 9070 tape at a 90° angle and a speed of 5 mm / s. Specifically, one side of the negative electrode active material layer of the negative electrode for the lithium secondary battery was adhered to one side of a slide glass (3M 9070 tape) to which an adhesive film had been attached. Thereafter, a 2 kg rubber roller was used to roll the adhesive film back and forth 5 to 10 times, and the adhesive strength (peel strength) was measured at a 90° angle and a speed of 5 mm / s. The adhesive strength was measured at 25°C and normal pressure.

[0104] Specifically, the adhesive strength was measured on a 5 mm x 15 cm electrode at 25°C and normal pressure.

[0105] In one embodiment of the present application, normal pressure can mean pressure in a state where no specific pressure is applied or reduced, and can be used in the same sense as atmospheric pressure. Generally, it can be expressed as 1 atmosphere.

[0106] In one embodiment of the present application, there is provided a negative electrode for a lithium secondary battery, wherein the thickness of the negative electrode current collector layer is 1 μm or more and 100 μm or less, and the thickness of the negative electrode active material layer is 20 μm or more and 500 μm or less.

[0107] In one embodiment of the present application, there is provided a lithium secondary battery including: a positive electrode; a negative electrode for a lithium secondary battery according to the present application; a separator disposed between the positive electrode and the negative electrode; and an electrolyte.

[0108] A secondary battery according to an embodiment of the present specification may include the negative electrode for a lithium secondary battery described above. Specifically, the secondary battery may include a negative electrode, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, and the negative electrode may be the same as the negative electrode described above. Since the negative electrode has been described above, detailed description thereof will be omitted.

[0109] The positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and including the positive electrode active material.

[0110] In the positive electrode, the positive electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. can be used. In addition, the positive electrode current collector typically has a thickness of 3 μm to 500 μm, and fine irregularities can be formed on the surface of the current collector to enhance the adhesive strength of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0111] The positive electrode active material may be a commonly used positive electrode active material, such as a layered compound or a compound substituted with one or more transition metals, such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2); a lithium iron oxide such as LiFe3O4; 1+c1 Mn 2-c1 O4 (0≦c1≦0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; chemical formula LiNi 1-c2 M c2 O2 (where M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and 0.01≦c2≦0.3 is satisfied); 2-c3 M c3 Examples of suitable lithium manganese composite oxides include, but are not limited to, lithium manganese composite oxides represented by Li2Mn3MO8 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01≦c3≦0.1) or Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); and LiMn2O4, in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion. The positive electrode may be metallic lithium (Li-metal).

[0112] The positive electrode active material layer may contain a positive electrode conductive material and a positive electrode binder in addition to the above-mentioned positive electrode active material.

[0113] In this case, the positive electrode conductive material is used to impart conductivity to the electrode, and can be used without any particular limitation as long as it has electronic conductivity without undergoing chemical changes in the battery that is constructed. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives, and the like, and one or more of these may be used alone or in combination.

[0114] The positive electrode binder improves adhesion between particles of the positive electrode active material and between the positive electrode active material and the positive electrode current collector. Specific examples of the positive electrode binder include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof. These may be used alone or in combination.

[0115] The separator separates the negative electrode and positive electrode and provides a path for lithium ions to move. Any separator typically used in secondary batteries can be used without particular limitations. In particular, a separator that exhibits low resistance to electrolyte ion migration and excellent electrolyte humidification capacity is preferred. Specifically, a porous polymer film, such as a porous polymer film made from a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof, may be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made from high-melting-point glass fibers or polyethylene terephthalate fibers, may also be used. To ensure heat resistance or mechanical strength, a separator coated with a ceramic component or a polymeric material may also be used, and may be used in a single-layer or multi-layer structure.

[0116] 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 manufacturing lithium secondary batteries. Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0117] Examples of the non-aqueous organic solvent that may be used include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0118] In particular, among the carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are preferably used because they are high-viscosity organic solvents with high dielectric constants and can dissociate lithium salts well. When such cyclic carbonates are mixed with chain carbonates with low viscosity and low dielectric constants, such as dimethyl carbonate and diethyl carbonate, in an appropriate ratio, an electrolyte with high electrical conductivity can be produced, and these cyclic carbonates are more preferably used.

[0119] The metal salt may be a lithium salt, which is a substance that is easily dissolved in the non-aqueous electrolyte. For example, the anion of the lithium salt may be F - , Cl - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3- , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - One or more selected from the group consisting of:

[0120] In addition to the electrolyte components, the electrolyte may further contain one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purposes of improving the life characteristics of the battery, suppressing a decrease in battery capacity, and improving the discharge capacity of the battery.

[0121] The lithium secondary battery according to the present invention is useful in portable devices such as mobile phones, laptops, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs), and is particularly suitable as a component battery of medium- to large-sized battery modules. Accordingly, the present invention also provides a medium- to large-sized battery module including the above-described lithium secondary battery as a unit cell.

[0122] 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 the battery pack include the secondary battery having high capacity, excellent rate-limiting characteristics, and excellent cycle characteristics, and 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.

[0123] Below, preferred examples are presented to help understand the present invention, but these examples are for the purpose of illustrating the present description, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope of the scope and technical ideas of the present description, and it is natural that such changes and modifications fall within the scope of the appended claims.

[0124] <Example> Preparation of primer coating layer <Production of the first primer coating layer> A PAM binder and SWCNTs were dissolved in water at a weight ratio of 95:5 to obtain a slurry for forming the primer coating layer. In this case, 1.5 times as much CMC as SWCNTs was used as a dispersant (solid content: 5%).

[0125] Next, the slurry for forming the primer coating layer was applied to both sides of an 8 μm-thick copper foil (Cu foil) current collector to a thickness of 0.5 μm, and then vacuum dried at 120° C. for 24 hours to form a negative electrode current collector layer having a first primer coating layer.

[0126] <Production of the second primer coating layer> A rubber-based (SBR) binder and Super-C (Carbon Black) as a conductive material were dissolved in a water:IPA=9:1 solvent at a weight ratio of 30:70 to obtain a slurry for forming a primer coating layer (solid content: 20%).

[0127] Next, the slurry for forming the primer coating layer was applied to both sides of an 8 μm-thick copper foil (Cu foil) current collector to a thickness of 0.5 μm, and then vacuum dried at 120° C. for 24 hours to form a negative electrode current collector layer having a second primer coating layer.

[0128] <Production of negative electrodes> Example 1: Preparation of negative electrode A negative electrode active material layer composition was prepared using a silicon-based active material, Si (average particle size (D50): 8 μm), SWCNTs, and a binder, polyacrylamide, in a weight ratio of 89:1:10. The negative electrode slurry was prepared by adding the composition to distilled water as a solvent for forming the negative electrode slurry (solid concentration: 25 wt%).

[0129] The mixing method was as follows: SWCNT, binder, and water were dispersed using a homomixer at 2500 rpm for 30 minutes, and then the active material was added, followed by dispersion at 2500 rpm for 30 minutes to prepare a slurry.

[0130] The negative electrode slurry was applied to both sides of an 8 μm-thick copper foil current collector on which the first primer coating layer was formed at a rate of 2.75 mg / cm. 2 The coated film was rolled and dried in a vacuum oven at 130°C for 10 hours to form a negative electrode active material layer (thickness: 33 μm) (porosity: 55%).

[0131] The battery was manufactured in the same manner as in Example 1, except that the negative electrode current collector layer and silicon-based active material shown in Table 1 below were used. [Table 1]

[0132] <Secondary battery manufacturing> LiNi as the positive electrode active material 0.6 Co 0.2 Mn 0.2O2 (average particle size (D50): 15 μm), carbon black (product name: Super C65, manufacturer: Timcal) as a conductive material, and polyvinylidene fluoride (PVdF) as a binder were added in a weight ratio of 97:1.5:1.5 to N-methyl-2-pyrrolidone (NMP) as a solvent for forming the cathode slurry to prepare a cathode slurry (solid concentration: 78 wt%).

[0133] The positive electrode slurry was applied to both sides of an aluminum current collector (thickness: 12 μm) at a rate of 537 mg / 25 cm. 2 The coated layer was rolled and dried in a vacuum oven at 130°C for 10 hours to form a positive electrode active material layer (thickness: 65 μm), and a positive electrode was fabricated (positive electrode thickness: 77 μm, porosity: 26%).

[0134] An electrolyte was injected between the positive electrode and the negative electrode of Example 1 via a polyethylene separator to prepare a secondary battery.

[0135] The electrolyte was prepared by adding 3 wt% vinylene carbonate (based on the total weight of the electrolyte) to an organic solvent in which fluoroethylene carbonate (FEC) and diethyl carbonate (DEC) were mixed in a volume ratio of 10:90, and LiPF6 was added as a lithium salt at a concentration of 1M.

[0136] Mono-cells were fabricated in the same manner as above, except that the negative electrodes of the Examples and Comparative Examples were used, and life characteristics were evaluated in the range of 4.2-3.0V.

[0137] Experimental example 1: Lifetime characteristic evaluation The secondary batteries including the negative electrodes prepared in the Examples and Comparative Examples were subjected to a lifespan evaluation using an electrochemical charger / discharger to evaluate the capacity retention rate. The secondary batteries were subjected to a cycle test at 4.2-3.0 V, 1 C / 0.5 C, and the number of cycles at which the capacity retention rate reached 80% was measured.

[0138] Capacity retention rate (%) = {(discharge capacity at Nth cycle) / (discharge capacity at 1st cycle)} × 100 The results are shown in Table 2 below.

[0139] Experimental example 2: Resistance increase rate measurement evaluation In the test of Experimental Example 1, the capacity retention rate was measured by charging / discharging at 0.33C / 0.33C (4.2-3.0V) every 50 cycles, and then the resistance was measured by discharging at 2.5C pulse at SOC50, and the resistance increase rate was compared and analyzed.

[0140] Regarding the resistance increase rate measurement evaluation, data at 250 cycles was calculated, and the results are shown in Table 2 below. [Table 2]

[0141] As can be seen from Table 2, in the case of the negative electrode for a lithium secondary battery according to the present invention, the capacity characteristics are maximized by using a silicon-based active material, and the negative electrode active material layer satisfies a specific porosity range to simplify the pore structure. At the same time, a primer coating layer having a specific composition is used to improve adhesion to the negative electrode current collector, thereby demonstrating excellent output and life characteristics.

[0142] When the particle size (D50) of existing silicon-based active materials is large, the initial diffusion resistance can be improved, but the adhesion to the negative electrode current collector layer is insufficient, resulting in increased resistance as the cycles progress and reduced life characteristics. In the examples of the present application, the particle size of the silicon-based active material was increased compared to existing products by applying a primer coating layer.

[0143] In other words, compared to Comparative Example 6, which had a large particle size and no primer coating layer applied, it was found that the lifespan characteristics of Examples 1 to 5 were improved. In particular, when Comparative Example 6 was compared with Example 5, it was found that although the particle size was the same, there was a difference in lifespan performance depending on whether or not a primer coating layer was applied.

[0144] In Table 2, a resistance increase rate of >250 means that resistance measurement is not possible. Generally, resistances of 250% or more have a high R value, so when a current of 2.5 C is applied, the device is turned off due to the upper safety voltage limit, making resistance measurement impossible.

[0145] In conclusion, in Comparative Examples 1, 2, 5, and 6, which do not include a primer coating layer like the present invention, when a large particle size active material is used, volume expansion is large, which reduces adhesion to the negative electrode current collector layer, increasing resistance and resulting in a deterioration in life performance. On the other hand, in the examples in which a primer coating layer is applied, adhesion and diffusion characteristics are improved, and it was confirmed that when a 5 μm silicon-based active material is used, better performance characteristics are achieved. [Explanation of symbols]

[0146] 10...Negative electrode active material layer 20 Primer coating layer 30 Negative electrode current collector layer

Claims

1. a negative electrode current collector layer; a primer coating layer including a primer coating layer composition disposed on one or both surfaces of the negative electrode current collector layer; and a negative electrode active material layer provided on the surface of the primer coating layer opposite to the surface that contacts the negative electrode current collector layer; A negative electrode for a lithium secondary battery comprising: the negative electrode active material layer includes a negative electrode active material layer composition including a silicon-based active material, a negative electrode conductive material, and a negative electrode binder; The silicon-based active material includes one or more selected from the group consisting of SiOx (x=0) and SiOx (0<x<2), and the silicon-based active material includes 95 parts by weight or more of the SiOx (x=0) based on 100 parts by weight of the silicon-based active material; The primer coating layer composition may be composed of a binder alone or may contain a binder and a conductive material; the binder comprises a PAM-based binder or an SBR binder; The negative electrode active material layer has a porosity of 50% or more, The negative electrode for a lithium secondary battery, wherein the silicon-based active material contained in the negative electrode active material layer has a D50 particle size of 5 μm or more.

2. The negative electrode for a lithium secondary battery according to claim 1 , wherein the thickness of the primer coating layer is from 1 nm to 1 μm.

3. 2. The negative electrode for a lithium secondary battery according to claim 1, wherein the negative electrode active material layer has a porosity of 60% to 90%.

4. 2. The negative electrode for a lithium secondary battery according to claim 1, wherein the silicon-based active material contained in the negative electrode active material layer has a D50 particle size of 8 μm or more and 15 μm or less.

5. 2. The negative electrode for a lithium secondary battery according to claim 1, wherein the silicon-based active material is present in an amount of 80 parts by weight or more based on 100 parts by weight of the negative electrode active material layer composition.

6. 2. The negative electrode for a lithium secondary battery according to claim 1, wherein the negative electrode conductive material comprises at least one selected from the group consisting of a dot-like conductive material, a linear conductive material, and a sheet-like conductive material.

7. The negative electrode for a lithium secondary battery according to claim 1 , wherein the binder is present in an amount of 10 parts by weight to 100 parts by weight based on 100 parts by weight of the primer coating layer composition.

8. 2. The negative electrode for a lithium secondary battery according to claim 1, wherein an adhesive strength of a surface of the negative electrode active material layer in contact with the primer coating layer satisfies a range of 100 gf / 5 mm to 500 gf / 5 mm under conditions of 25° C. and normal pressure.

9. the thickness of the negative electrode current collector layer is 1 μm or more and 100 μm or less, 2. The negative electrode for a lithium secondary battery according to claim 1, wherein the thickness of the negative electrode active material layer is 20 μm or more and 500 μm or less.

10. positive electrode, The negative electrode for a lithium secondary battery according to any one of claims 1 to 9, a separator provided between the positive electrode and the negative electrode; and electrolyte, A lithium secondary battery comprising:

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