Negative electrode active material, method for preparing negative electrode active material, negative electrode composition, negative electrode comprising same for lithium secondary battery, and lithium secondary battery comprising negative electrode

Abstract

The present application relates to a negative electrode active material, a method for preparing a negative electrode active material, a negative electrode composition, a negative electrode comprising same for a lithium secondary battery, and a lithium secondary battery comprising the negative electrode, the negative electrode active material comprising a silicon-based active material, which is a mixture of silicon-based particles and a binder, wherein the silicon-based particles have a grain size of 100 nm or less, the particle size (D50) of the silicon-based active material is 1 to 20 μm, and the binder is contained in a content of 1 to 15 parts by weight relative to 100 parts by weight of the silicon-based active material.

Description

Negative active material, method for producing negative active material, negative electrode composition, negative electrode for lithium secondary battery including the same, and lithium secondary battery including the negative electrode

[0001] This application claims the benefit of Korean Patent Application No. 10-2023-0091763, filed with the Korean Intellectual Property Office on July 14, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present application relates to a negative electrode active material, a method for producing a negative electrode active material, a negative electrode composition, a negative electrode for a lithium secondary battery including the same, 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] In particular, with the recent demand for high-density energy batteries, research is actively being conducted on methods to increase capacity by using silicon compounds such as Si / C or SiOx, which have a capacity more than 10 times greater than graphite materials, as anode active materials. However, in the case of silicon compounds, which are high-capacity materials, although the capacity is large compared to the graphite used in the past, there is a problem that the volume expands rapidly during the charging process, which cuts off the conductive path and deteriorates the battery characteristics.

[0008] Accordingly, in order to solve the problems when using a silicon-based compound as an anode active material, various methods are being discussed, such as a method for controlling the driving potential, a method for additionally coating a thin film on the active material layer, a method for controlling the particle size of the silicon-based compound, a method for suppressing the volume expansion itself, or a method for preventing the conductive path from being cut off. However, the above methods may actually lower the performance of the battery, so there are limitations in their application, and there are still limitations in the commercialization of anode batteries with a high silicon-based compound content.

[0009] Furthermore, research results regarding the aforementioned issues have revealed that, in silicon-based active materials, smaller grain sizes lead to improved life performance. However, as silicon-based active materials become smaller to improve life performance, coating on the electrodes becomes less effective. Furthermore, low electrode adhesion can lead to problems with cell life performance, such as detachment from the negative current collector.

[0010] Therefore, when using a silicon-based active material as a negative electrode active material to improve capacity performance, research is needed on a method to solve the above-mentioned problems.

[0011] [Prior Art Literature]

[0012] [Patent Document]

[0013] Japanese Patent Publication No. 2009-080971

[0014] As a result of research on a method to improve the life performance of a negative electrode containing a silicon-based active material, it was found that when nano-sized silicon-based particles are mixed with a binder to form secondary particles, the binder acts as a buffer and improves the particle pulverization phenomenon.

[0015] Accordingly, the present application relates to a negative electrode active material capable of solving the above-mentioned problems, a method for producing the negative electrode active material, a negative electrode composition, a negative electrode for a lithium secondary battery including the same, and a lithium secondary battery including the negative electrode.

[0016] One embodiment of the present specification provides an anode active material comprising a silicon-based active material, wherein the silicon-based active material is a mixture of silicon-based particles and a binder, the silicon-based particles have a crystal grain size of 100 nm or less, the particle size (D50) of the silicon-based active material is 1 µm or more and 20 µm or less, and the binder is contained in an amount of 1 part by weight or more and 15 parts by weight or less based on 100 parts by weight of the silicon-based active material.

[0017] In another embodiment, a method for producing an anode active material is provided, comprising the steps of: preparing a silicon raw material; pulverizing the silicon raw material to form silicon particles; and mixing a solvent and a binder with the silicon particles to form a silicon active material, wherein the silicon particles have a crystal grain size of 100 nm or less, a particle size (D50) of the silicon active material is 1 µm or more and 20 µm or less, and the binder is contained in an amount of 1 part by weight or more and 15 parts by weight or less based on 100 parts by weight of the silicon active material.

[0018] In another embodiment, an object of the present invention is to provide a negative electrode composition comprising a negative electrode active material according to the present application; a negative electrode conductive material; and a negative electrode binder.

[0019] In another embodiment, there is provided an anode for a lithium secondary battery, comprising: a negative electrode current collector layer; and a negative electrode active material layer provided on one or both sides of the negative electrode current collector layer, wherein the negative electrode active material layer comprises a negative electrode composition according to the present application or a cured product thereof.

[0020] 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.

[0021] In the case of a negative electrode active material according to one embodiment of the present invention, it is characterized by including a spherical silicon-based active material having a micro-sized particle size by mixing silicon-based particles having a nano-sized size with a binder.

[0022] That is, the silicon-based active material is a mixture of silicon-based particles and a binder, and the silicon-based particles have a crystal grain size of 100 nm or less, and the particle size (D50) of the silicon-based active material satisfies a range of 1 ㎛ or more and 20 ㎛ or less, so that problems with life performance can be solved and it has the feature of being easy to manufacture an electrode.

[0023] In addition, since the binder constituting the secondary particles (a mixture of silicon-based particles and a binder) is included in an amount of 1 to 15 parts by weight based on 100 parts by weight of silicon-based active material, it can also play a role in improving particle pulverization phenomenon compared to micron-sized polycrystalline particles while acting as a buffer within the silicon-based active material.

[0024] 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.

[0025] Figure 2 is a diagram showing a laminated structure of a lithium secondary battery according to one embodiment of the present application.

[0026] [Explanation of symbols]

[0027] 10: Negative current collector layer

[0028] 20: Negative active material layer

[0029] 30: Membrane

[0030] 40: Positive active material layer

[0031] 50: Positive current collector layer

[0032] 100: Cathode for lithium secondary batteries

[0033] 200: Cathode for lithium secondary batteries

[0034] Before explaining the present invention, some terms are first defined.

[0035] 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.

[0036] In this specification, ‘p to q’ means a range of ‘p or more and q or less.’

[0037] 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.

[0038] 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 average particle size can be measured using the laser diffraction method. Specifically, after the powder to be measured is dispersed in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500) and the difference in diffraction pattern according to particle size is measured when the particles pass through a laser beam, thereby calculating the particle size distribution.

[0039] In one embodiment of the present application, particle size or particle diameter may mean the average diameter or representative diameter of each grain forming the metal powder.

[0040] 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.

[0041] In this specification, the term 'polymer' is understood to be used in a broad sense including copolymers unless 'homopolymer' is specified.

[0042] 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.

[0043] 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.

[0044] One embodiment of the present specification provides an anode active material comprising a silicon-based active material, wherein the silicon-based active material is a mixture of silicon-based particles and a binder, the silicon-based particles have a crystal grain size of 100 nm or less, the particle size (D50) of the silicon-based active material is 1 µm or more and 20 µm or less, and the binder is contained in an amount of 1 part by weight or more and 15 parts by weight or less based on 100 parts by weight of the silicon-based active material.

[0045] In one embodiment of the present application, since the silicon-based active material includes a binder, for example, when nano-sized silicon-based particles are mixed with the binder and composited in the form of secondary particles, compared to when the silicon-based active material does not include the binder and is not composited, the volume expansion can be efficiently controlled, so that a high content of negative active material can be included, and the binder acts as a buffer to improve the particle pulverization phenomenon, which is also effective in increasing the content of Si active material in the electrode.

[0046] In the case of a negative electrode active material according to one embodiment of the present invention, a silicon-based active material having a spherical shape with a micro-sized particle size is included by mixing silicon-based particles having a nano-size with a binder, that is, the silicon-based active material is a mixture of silicon-based particles and a binder, and the silicon-based particles have a crystal grain size of 100 nm or less, and the particle size (D50) of the silicon-based active material satisfies a range of 1 ㎛ or more and 20 ㎛ or less, thereby solving a problem with regard to life performance and providing a feature of easy electrode manufacturing.

[0047] In one embodiment of the present application, the silicon-based active material is SiOx (x=0), SiOx (0 <x<2) 및 SiC로 이루어진 군에서 선택되는 1 이상을 포함할 수 있다.

[0048] In one embodiment of the present application, the silicon-based active material is SiOx (x=0) and SiOx (0 <x<2)로 이루어진 군에서 선택되는 1 이상을 포함하며, 상기 실리콘계 활물질 100 중량부 기준 상기 SiOx (x=0)를 70 중량부 이상 포함할 수 있다.

[0049] In one embodiment of the present application, the silicon-based active material includes SiOx (x=0), and may include 70 parts by weight or more of the SiOx (x=0) based on 100 parts by weight of the silicon-based active material.

[0050] In one embodiment of the present application, the silicon-based active material is SiOx (0 <x<2)를 더 포함할 수 있다.

[0051] In another embodiment, the silicon-based active material may contain 70 parts by weight or more, preferably 80 parts by weight or more, more preferably 90 parts by weight or more, of the SiOx (x=0) based on 100 parts by weight of the silicon-based active material, and may contain 100 parts by weight or less, preferably 99 parts by weight or less, more preferably 95 parts by weight or less.

[0052] In one embodiment of the present application, in particular, pure silicon (Si) particles may be used as the silicon-based active material. Using pure silicon (Si) particles as the silicon-based active material may mean that, based on 100 parts by weight of the total silicon-based active material, pure Si particles (SiOx (x=0)) not combined with other particles or elements are included within the above range.

[0053] In one embodiment of the present application, the silicon-based active material may be formed of silicon-based particles having 100 parts by weight of SiOx (x=0) based on 100 parts by weight of the silicon-based active material.

[0054] In one embodiment of the present application, the silicon-based active material may contain a metal impurity, and at this time, the impurity may be a metal that may be generally contained in the silicon-based active material, and specifically, may contain 0.1 part by weight or less based on 100 parts by weight of the silicon-based active material.

[0055] Meanwhile, in one embodiment of the present application, the particle size of the silicon-based active material, i.e., the average particle diameter (D50), may be 1 μm or more and 20 μm or less, may be 5 μm to 10 μm, specifically 5 μm to 8 μm, and more specifically 5 μm to 7 μm. When the average particle diameter is less than 5 μm, the specific surface area of ​​the particles increases excessively, and the viscosity of the negative electrode slurry increases excessively. Accordingly, the dispersion of the particles constituting the negative electrode slurry is not smooth. In addition, when the size of the silicon-based active material is excessively small, the contact area between the silicon particles and the conductive material is reduced by the complex composed of the conductive material and the binder in the negative electrode slurry, so that the possibility of the conductive network being disconnected increases, and the capacity retention rate is lowered. On the other hand, when the average particle diameter exceeds 10 μm, excessively large silicon particles are present, making the surface of the negative electrode unsmooth, and thus causing current density unevenness during charge and discharge. Additionally, if the silicon particles are excessively large, the phase stability of the cathode slurry becomes unstable, reducing processability. Consequently, the battery's capacity retention rate decreases.

[0056] 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 0.1 m 2 / g to 100.0 m 2 / g, especially preferably 0.2 m 2 / g to 80.0 m 2 / g, most preferably 0.2 m 2 / g to 18.0 m 2 / g. BET surface area is measured according to DIN 66131 (using nitrogen).

[0057] In one embodiment of the present application, the silicon-based active material may exist in a crystalline or amorphous form, for example, and is preferably non-porous. The silicon particles are preferably spherical or fragment-shaped. Alternatively, but less preferably, the silicon particles may also have a fibrous structure or be present in the form of a silicon-containing film or coating.

[0058] 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.

[0059] In the present application, the circularity is determined by the following equation 1, where A is the area and P is the boundary line.

[0060] [Formula 1]

[0061] 4πA / P 2

[0062] In the case of silicon-based active materials, compared to the existing graphite-based active materials, the capacity is significantly higher, so attempts to apply it are increasing. However, because the volume expansion rate is high during the charge / discharge process, it is limited to cases where a small amount is mixed with the graphite-based active material and used.

[0063] Therefore, in the case of the present invention, in order to improve capacity performance, only a silicon-based active material is used as an anode active material, and in order to solve the above-mentioned problem, rather than adjusting the composition of the conductive material and the binder, the silicon-based active material is manufactured in the form of secondary particles as described below, thereby solving the existing problem.

[0064] In one embodiment of the present application, the silicon-based active material is in the form of secondary particles which are a mixture of silicon-based particles and a binder.

[0065] That is, the silicon-based active material has silicon-based particles as primary particles and can be composed of secondary particles that are a mixture of primary particles and a binder.

[0066] In one embodiment of the present application, the crystal grain size of the silicon-based particles may be 100 nm or less.

[0067] In one embodiment of the present application, the crystal grain size of the silicon-based particles may be 10 nm or more and 80 nm or less.

[0068] In another embodiment, the crystal grain size of the silicon-based particles may be 100 nm or less, 95 nm or less, 90 nm or less, or 80 nm or less, and may be 1 nm or more, 5 nm or more, 7 nm or more, or 10 nm or more.

[0069] In another embodiment, the silicon-based particles may have a crystal grain size of 10 nm or more and 80 nm or less.

[0070] The above silicon particles have the above crystal grain size, and satisfy the above range so that the grain boundaries are widely distributed, so that when lithium ions are inserted, they are uniformly inserted, thereby reducing the stress applied when lithium ions are inserted into the silicon particles, and thus alleviating particle breakage. As a result, it has a characteristic that can improve the life stability of the negative electrode. When the crystal grain size exceeds the above range, the grain boundaries within the particles become narrowly distributed, and in this case, lithium ions within the particles are inserted unevenly, so that the stress due to ion insertion is large, resulting in particle breakage.

[0071] In the present application, a crystal grain means a crystal particle that is a collection of irregularly shaped microscopic particles in a metal or material, and the crystal grain size may refer to the diameter of an observed crystal grain. That is, in the present application, the crystal grain size refers to the size of a domain that shares the same crystal direction within a particle, and is a different concept from the particle size or particle diameter that expresses the size of a material.

[0072] In one embodiment of the present application, the crystal grain size can be calculated as the FWHM (Full Width at Half Maximum) value through XRD analysis. The remaining values, excluding L, are measured through XRD analysis of a silicon-based active material, and the crystal grain size can be measured through the Debey-Scherrer equation, which states that the FWHM and the crystal grain size are inversely proportional. In this case, the Debey-Scherrer equation is as shown in Equation 1-1 below.

[0073] [Formula 1-1]

[0074] FWHM=Kλ / LCosθ

[0075] In the above formula 1-1,

[0076] L represents the grain size, K is a constant, θ is the bragg angle, and λ is the wavelength of the X-ray.

[0077] In addition, the shape of the crystal grains is diverse and can be measured three-dimensionally, and the size of the crystal grains can generally be measured using the commonly used circle method and diameter measurement method, but is not limited thereto.

[0078] The above diameter measurement method can be measured by drawing 5-10 equilibrium lines, each of which is L mm long, on a microscopic photograph of the target particle, counting the number of grains z on the lines, and averaging them. At this time, only those that are completely included are counted, and those that cross are excluded. If the number of lines is P and the magnification is V, the average grain diameter can be calculated using the following equations 1-2.

[0079] [Formula 1-2]

[0080] Dm = (L*P*10 3 ) / (zV) (um)

[0081] In addition, the above circle method is a method of calculating the average area of ​​crystal grains by drawing a circle of a set diameter on a microscopic photograph of the target particle and calculating the number of crystal grains within the circle and the number of crystal grains that fall on the boundary line using the following equation 1-3.

[0082] [Formula 1-3]

[0083] Fm = (Fk * 10 6 ) / ((0.67n + z) V 2 ) (um 2 )

[0084] In the above equation 1-3, Fm represents the average particle area, Fk represents the measured area on the photograph, z represents the number of particles inside the circle, n represents the number of particles in the circular arc, and V represents the magnification of the microscope.

[0085] In one embodiment of the present application, a negative electrode active material is provided in which the silicon-based particles are single-crystal silicon-based particles or polycrystalline silicon-based particles.

[0086] In one embodiment of the present application, the silicon-based particles may be single-crystal silicon-based particles.

[0087] In one embodiment of the present application, the silicon-based particles may be polycrystalline silicon-based particles.

[0088] In one embodiment of the present application, the silicon-based active material is formed in the form of secondary particles, which are a mixture of silicon-based particles and a binder. In this case, the binder serves to mix the silicon-based particles, which are primary particles, with each other to form secondary particles.

[0089] In one embodiment of the present application, a negative electrode active material is provided in which the binder is a binder having a linear chain structure.

[0090] In one embodiment of the present application, a negative electrode active material is provided, wherein the binder includes an aqueous binder, and the aqueous binder includes at least one selected from the group consisting of polyvinylpyrrolidone (PVP); polyacrylic acid (PAA); and polyacrylamide (PAM).

[0091] In one embodiment of the present application, the binder may be included in an amount of 1 part by weight or more and 15 parts by weight or less based on 100 parts by weight of the silicon-based active material.

[0092] In another embodiment, the binder may be included in an amount of 1 part by weight or more and 15 parts by weight or less, preferably 3 parts by weight or more and 15 parts by weight or less, and more preferably 5 parts by weight or more and 15 parts by weight or less, based on 100 parts by weight of the silicon-based active material.

[0093] As described above, if the content of the binder is satisfied, if it exceeds the above range, it may cause a decrease in the capacity and life performance of the battery, and if it is below the above range, the binder may not properly function as a buffer, and may cause a decrease in life performance due to particle pulverization.

[0094] In particular, when the content of the binder exceeds 15 parts by weight based on 100 parts by weight of the silicon-based active material, for example, when the binder included in the silicon-based active material exceeds the above range, the binder itself becomes a type of resistor, and the efficiency characteristics are lowered, and the energy density may be inferior, and the capacity characteristics may be lowered.

[0095] The binder according to the present application has a different composition from the negative electrode binder described below.

[0096] In one embodiment of the present application, a method for producing an anode active material is provided, comprising the steps of: preparing a silicon raw material; pulverizing the silicon raw material to form silicon particles; and mixing a solvent and a binder with the silicon particles to form a silicon active material, wherein the silicon particles have a crystal grain size of 100 nm or less, a particle size (D50) of the silicon active material of 1 µm or more and 20 µm or less, and the binder is contained in an amount of 1 part by weight or more and 15 parts by weight or less based on 100 parts by weight of the silicon active material.

[0097] In the manufacturing method, each composition and content is the same as described above.

[0098] In the present application, a method for producing a negative electrode active material is provided, which further includes a step of mixing a solvent and a binder with the silicon particles and then drying the mixture.

[0099] In the present application, the mixing rpm of the step of forming a silicon-based active material by mixing a solvent and a binder with the silicon-based particles may be 2000 rpm or more and 3000 rpm or less.

[0100] In the present application, the silicon raw material may be a raw material used in the manufacture of silicon active materials used in the art, and may include silicon lumps or MG-Si, etc.

[0101] In one embodiment of the present application, a negative electrode composition is provided, including the negative electrode active material; a negative electrode conductive material; and a negative electrode binder.

[0102] In one embodiment of the present application, a negative electrode composition is provided in which the negative electrode active material is at least 40 parts by weight based on 100 parts by weight of the negative electrode composition.

[0103] In another embodiment, the negative electrode active material may be included in an amount of 40 parts by weight or more, preferably 60 parts by weight or more, more preferably 65 parts by weight or more, and even more preferably 70 parts by weight or more, based on 100 parts by weight of the negative electrode composition, and may be included in an amount of 95 parts by weight or less, preferably 90 parts by weight or less, and even more preferably 85 parts by weight or less.

[0104] The negative electrode composition according to the present application uses a negative electrode active material having a significantly high capacity within the above range, and satisfies a specific surface area size that can control the volume expansion rate during the charge and discharge process, so that the performance of the negative electrode is not deteriorated even within the above range, and has excellent output characteristics during charge and discharge.

[0105] Previously, graphite compounds were typically used solely as negative electrode active materials. However, with the increasing demand for high-capacity batteries, attempts to mix silicon-based active materials to increase capacity have been increasing. However, even if the properties of silicon-based active materials themselves are adjusted as described above, the rapid expansion of volume during the charge / discharge process can cause some problems, damaging the conductive path formed within the negative electrode active material layer.

[0106] Therefore, in one embodiment of the present application, the negative electrode conductive material may include at least one selected from the group consisting of a dot-shaped conductive material, a planar conductive material, and a linear conductive material.

[0107] In one embodiment of the present application, the dot-shaped conductive material may be used to improve conductivity of the negative electrode, and refers to a dot-shaped or spherical conductive material having 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.

[0108] 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.

[0109] In one embodiment of the present application, the dot-shaped conductive material can satisfy a volatile matter content of 0.01% or more and 1% or less, preferably 0.01% or more and 0.3% or less, and more preferably 0.01% or more and 0.1% or less.

[0110] In particular, when the functional group content of the dot-shaped conductive material satisfies the above range, the functional groups present on the surface of the dot-shaped conductive material exist, so that when water is used as a solvent, the dot-shaped conductive material can be smoothly dispersed within the solvent. In particular, in the present invention, the functional group content of the dot-shaped conductive material can be reduced by using a specific silicon-based active material, thereby having an excellent effect in improving dispersibility.

[0111] In one embodiment of the present application, it is characterized by including a dot-shaped conductive material having a functional group content within the above range together with a silicon-based active material, and the functional group content can be controlled by adjusting the degree of heat treatment of the dot-shaped conductive material.

[0112] 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.

[0113] In one embodiment of the present application, the conductive material may include a planar conductive material.

[0114] The above-mentioned planar conductive material can improve conductivity by increasing planar contact between silicon particles within the cathode, and at the same time, suppress the disconnection of conductive paths due to volume expansion. The above-mentioned planar conductive material can be expressed as a plate-shaped conductive material or a bulk conductive material.

[0115] 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.

[0116] 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 3.5 μm to 5 μm. When the above range is satisfied, dispersion is easy without causing excessive viscosity increase of the negative electrode slurry due to sufficient particle size. Therefore, the dispersion effect is excellent when dispersion is performed using the same equipment and time.

[0117] 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 2.0 µm or less, a D50 of 2.5 µm or more and 3.5 µm or less, and a D90 of 6.5 µm or more and 15.0 µm or less.

[0118] 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.

[0119] 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.

[0120] In one embodiment of the present application, the surface-shaped conductive material has a BET specific surface area of ​​0.25 m 2 / g can be more than that.

[0121] In another embodiment, the surface-shaped conductive material has a BET surface area of ​​1 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.

[0122] The planar conductive material according to the present application may be a planar conductive material with a high specific surface area; or a planar conductive material with a low specific surface area.

[0123] 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.

[0124] In another embodiment, the surface-shaped conductive material is a low surface area surface-shaped conductive material, and has a BET surface area of ​​1 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.

[0125] 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.

[0126] In one embodiment of the present application, a negative electrode composition is provided in which the negative electrode conductive material is present in an amount of 10 parts by weight or more and 40 parts by weight or less based on 100 parts by weight of the negative electrode composition.

[0127] In another embodiment, the negative electrode conductive material may be included in an amount of 0.1 to 40 parts by weight, preferably 0.2 to 30 parts by weight, more preferably 0.4 to 25 parts by weight, and most preferably 0.4 to 10 parts by weight, based on 100 parts by weight of the negative electrode composition.

[0128] In one embodiment of the present application, a negative electrode composition is provided, wherein the negative electrode conductive material includes a planar conductive material and a linear conductive material.

[0129] In one embodiment of the present application, the negative electrode conductive material provides a negative electrode composition comprising 80 parts by weight or more and 99.9 parts by weight or less of the planar conductive material and 0.1 parts by weight or more and 20 parts by weight or less of the linear conductive material based on 100 parts by weight of the negative electrode conductive material.

[0130] In another embodiment, the negative electrode conductive material may include 80 parts by weight or more and 99.9 parts by weight or less of the planar conductive material, preferably 85 parts by weight or more and 99.9 parts by weight or less, and more preferably 95 parts by weight or more and 98 parts by weight or less, based on 100 parts by weight of the negative electrode conductive material.

[0131] In another embodiment, the negative electrode conductive material may include 0.1 to 20 parts by weight of the linear conductive material, preferably 0.1 to 15 parts by weight, and more preferably 0.2 to 5 parts by weight, based on 100 parts by weight of the negative electrode conductive material.

[0132] In one embodiment of the present application, since the negative electrode conductive material includes a planar conductive material and a linear conductive material and satisfies the above composition and ratio, it does not have a significant effect on the life characteristics of an existing lithium secondary battery, and in particular, when the planar conductive material and the linear conductive material are included, the number of points at which charging and discharging are possible increases, resulting in excellent output characteristics at a high C-rate and a reduced amount of high-temperature gas generation.

[0133] In one embodiment of the present application, the cathode conductive material may be formed of a linear conductive material.

[0134] In particular, when a linear conductive material is used alone, the electrode tortuosity, which is a problem of silicon-based negative electrodes, can be simplified, thereby improving the electrode structure and thus reducing the resistance to movement of lithium ions within the electrode.

[0135] In one embodiment of the present application, when the negative electrode conductive material comprises a linear conductive material alone, the negative electrode conductive material may comprise 0.1 parts by weight or more and 5 parts by weight or less, preferably 0.2 parts by weight or more and 3 parts by weight or less, and more preferably 0.4 parts by weight or more and 1 part by weight or less, based on 100 parts by weight of the negative electrode composition.

[0136] 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 negative electrode conductive material according to the present application serves to secure the contact between silicon-based active materials, which undergo a significant 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 during rolling, and is completely different in composition and role from the negative electrode conductive material of the present invention.

[0137] 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.

[0138] In one embodiment of the present application, the planar conductive material used as the aforementioned negative electrode conductive material has a structure and function different from those of carbon-based active materials generally used as negative electrode active materials. 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.

[0139] On the other hand, the planar conductive material used as the negative electrode conductive material 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.

[0140] 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.

[0141] 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.

[0142] That is, in one embodiment of the present application, the carbon-based active material, artificial graphite or natural graphite, is in a dot-like shape and 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.

[0143] 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.

[0144] The negative electrode binder according to one embodiment of the present application serves to hold the active material and conductive material in order to prevent distortion and structural deformation of the negative electrode structure when the volume of the silicon-based 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-based binder can be used.

[0145] In one embodiment of the present application, the negative electrode binder may be 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 negative electrode composition.

[0146] In one embodiment of the present application, a negative electrode for a lithium secondary battery is provided, including: a negative electrode current collector layer; and a negative electrode active material layer including a negative electrode composition according to the present application or a cured product thereof formed on one or both sides of the negative electrode current collector layer.

[0147] 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) including an anode active material layer (20) on one surface of an anode current collector layer (10) can be confirmed, and although Fig. 1 shows that the anode active material layer is formed on one surface, it can be included on both surfaces of the anode current collector layer.

[0148] In one embodiment of the present application, the negative electrode for the lithium secondary battery can be formed by applying and drying a negative electrode slurry containing the negative electrode composition to one or both sides of a negative electrode current collector layer.

[0149] At this time, the cathode slurry may include the cathode composition described above; and a slurry solvent.

[0150] In one embodiment of the present application, the solid content of the cathode slurry can satisfy 5% or more and 40% or less.

[0151] In another embodiment, the solid content of the cathode slurry can satisfy a range of 5% or more and 40% or less, preferably 7% or more and 35% or less, and more preferably 10% or more and 30% or less.

[0152] The solid content of the above cathode slurry may mean the content of the cathode composition included in the cathode slurry, and may mean the content of the cathode composition based on 100 parts by weight of the cathode slurry.

[0153] When the solid content of the above negative electrode slurry satisfies the above range, the viscosity is appropriate when forming the negative electrode active material layer, thereby minimizing particle agglomeration of the negative electrode composition, and thus has the characteristic of efficiently forming the negative electrode active material layer.

[0154] In one embodiment of the present application, the slurry solvent can be used without limitation as long as it can dissolve the negative electrode composition, and specifically, water or NMP can be used.

[0155] 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.

[0156] In one embodiment of the present application, a negative electrode for a lithium secondary battery is provided, 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 5 µm or more and 500 µm or less.

[0157] However, the thickness can be varied depending on the type and purpose of the cathode used and is not limited thereto.

[0158] In one embodiment of the present application, the porosity of the negative electrode active material layer can satisfy a range of 10% or more and 60% or less.

[0159] In another embodiment, the porosity of the negative electrode active material layer can satisfy a range of 10% or more and 60% or less, preferably 20% or more and 50% or less, and more preferably 30% or more and 45% or less.

[0160] The above porosity varies depending on the composition and content of the silicon-based active material; conductive material; and binder included in the negative electrode active material layer, and in particular, the silicon-based active material and conductive material according to the present application are included in a specific composition and content portion to satisfy the above range, and accordingly, the electrode is characterized by having an appropriate range of electrical conductivity and resistance.

[0161] In one embodiment of the present application, a lithium secondary battery is provided, including: 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.

[0162] FIG. 2 is a diagram showing a laminated structure of a lithium secondary battery according to one embodiment of the present application. Specifically, a lithium secondary battery negative electrode (100) including a negative electrode active material layer (20) on one surface of a negative electrode current collector layer (10) can be confirmed, and a lithium secondary battery positive electrode (200) including a positive electrode active material layer (40) on one surface of a positive electrode current collector layer (50) can be confirmed, and it is shown that the lithium secondary battery negative electrode (100) and the lithium secondary battery positive electrode (200) are formed in a laminated structure with a separator (30) interposed therebetween.

[0163] 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.

[0164] The above 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.

[0165] 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.

[0166] 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 c2Ni-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.

[0167] 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.

[0168] At this time, the positive electrode conductive material is used to provide conductivity to the electrode, and in the battery to be formed, 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 whiskers 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.

[0169] 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.

[0170] The separator is used to separate the negative electrode and the positive electrode and to provide a passage for lithium ions. Any separator commonly used in secondary batteries can be used without any particular restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, may 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. may be used. In addition, a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0171] 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.

[0172] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0173] 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.

[0174] 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.

[0175] 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.

[0176] 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.

[0177] 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.

[0178] 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.

[0179] <Manufacturing Example>

[0180] <Manufacturing of silicon-based active materials>

[0181] <Example 1>

[0182] MG-Si was pulverized to form primary silicon particles with a particle size (crystalline size) of approximately 100 nm and in the form of a single crystal or polycrystalline silicon. The primary silicon particles were then mixed with water as a solvent, with PAA as a binder at a weight ratio of 9:1. The resulting slurry was then spray-dried to form granules, thereby producing silicon-based active materials in the form of secondary particles with a D50 of 5 μm.

[0183] <Example 2>

[0184] MG-Si was pulverized to form primary silicon particles with a particle size (crystal grain size) of approximately 100 nm and in the form of a single crystal or polycrystalline silicon. Subsequently, the primary silicon particles were mixed with PAM as a binder in a weight ratio of 9:1 using water as a solvent. The resulting slurry was then spray-dried to form granules, thereby producing a silicon-based active material in the form of secondary particles with a D50 of 5 μm.

[0185] <Example 3>

[0186] MG-Si was pulverized to form primary silicon particles with a particle size (crystal grain size) of approximately 100 nm and in the form of a single crystal or polycrystalline silicon. The primary silicon particles were then mixed with water as a solvent, with PVP as a binder at a weight ratio of 9:1. The resulting slurry was then spray-dried to form granules, thereby producing silicon-based active materials in the form of secondary particles with a D50 of 5 μm.

[0187] <Example 4>

[0188] MG-Si was pulverized to form primary silicon particles with a particle size (crystal grain size) of approximately 100 nm and in the form of a single crystal or polycrystalline silicon. Subsequently, the primary silicon particles were mixed with PAA as a binder in a weight ratio of 10:1.5 using water as a solvent. The resulting slurry was then spray-dried to form granules, thereby producing a silicon-based active material in the form of secondary particles with a D50 of 5 μm.

[0189] <Example 5>

[0190] MG-Si was pulverized to form primary silicon particles with a particle size (crystal grain size) of approximately 100 nm and in the form of a single crystal or polycrystalline silicon. Subsequently, the primary silicon particles were mixed with PAA as a binder in a weight ratio of 10:0.5 using water as a solvent. The resulting slurry was then spray-dried to form granules, thereby producing a silicon-based active material in the form of secondary particles with a D50 of 5 μm.

[0191] <Comparative Example 1>

[0192] After mechanically crushing MG-Si using a jaw crusher or roll crusher, the particles were crushed using a jet mill utilizing centrifugal force and particle-to-particle impact, and the particle size was controlled using a classifier. The particle size was 5㎛, and primary silicon particles in the form of single crystals or polycrystalline particles were formed.

[0193] <Comparative Example 2>

[0194] It was manufactured by chemically reacting silane gas to deposit a silicon-based active material on a substrate, and then controlling the particle size using a classifier, thereby forming silicon-based particles with a particle size of about 5 μm.

[0195] <Comparative Example 3>

[0196] In the above Example 1, the primary silicon-based particles and PAA as a binder were mixed in a weight ratio of 10:2.5 using water as a solvent, and the mixture was manufactured in the same manner as in Example 1.

[0197] Comparative Example 4

[0198] In the above Example 1, the primary silicon-based particles and PAA as a binder were mixed in a weight ratio of 10:0.2 using water as a solvent, and the mixture was manufactured in the same manner as in Example 1.

[0199] <Manufacturing of the cathode>

[0200] A negative electrode slurry was prepared by adding a negative electrode active material including the silicon-based active material of the above examples and comparative examples, a first conductive material, a second conductive material, and polyacrylamide as a binder in a weight ratio of 80:9.6:0.4:10 to distilled water as a solvent for forming a negative electrode slurry (solid content concentration 25 wt%).

[0201] Specifically, the first challenge material is a plate-shaped graphite (specific surface area: 17 m 2 / g, average particle diameter (D50): 3.5㎛), and the second conductive material was SWCNT.

[0202] As a specific mixing method, the first conductive agent, the second conductive agent, the binder, and water were dispersed using a homogenous mixer at 2500 rpm for 30 minutes, and then the silicon-based active material was added and dispersed at 2500 rpm for 30 minutes to produce a negative electrode slurry.

[0203] The negative electrode slurry is applied at 85 mg / 25 cm on both sides of a copper current collector (thickness: 8 μm) as a negative electrode current collector layer. 2 The coating was carried out with a loading amount of , rolled (roll pressed), and dried in a vacuum oven at 130°C for 10 hours to form a negative electrode active material layer (thickness: 33 μm), which was used as a negative electrode (thickness of negative electrode: 41 μm, porosity of negative electrode: 40.0%).

[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 lithium secondary battery was manufactured by interposing a polyethylene separator between the positive electrode and the negative electrode of the above examples and comparative examples and injecting an electrolyte.

[0208] The above electrolyte was an organic solvent containing fluoroethylene carbonate (FEC) and diethyl carbonate (DMC) mixed in a volume ratio of 10:90, 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] <Experimental Example>

[0210] Experimental Example 1: Monocell Life Performance Results

[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 an in-situ 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, and is listed in Table 1.

[0212] Life retention rate (%) = {(discharge capacity at Nth cycle) / (discharge capacity at 1st cycle)} Х 100

[0213]

[0214] Lifespan after 200 cycles (%) Example 190 Example 289 Example 391 Example 488 Example 586 Comparative Example 182 Comparative Example 284 Comparative Example 384 Comparative Example 483

[0215]

[0216] As can be confirmed in Table 1 above, it was confirmed that the negative electrodes of Examples 1 to 5 according to the present application had superior life maintenance rates compared to the negative electrodes of Comparative Examples 1 to 4. In Examples 1 to 3, the type of binder was changed, and in Examples 4 and 5, the content thereof was changed. In Comparative Examples 3 and 4, the upper or lower limit of the optimal binder content was exceeded. When the upper limit was exceeded, the capacity maintenance rate decreased compared to the Examples due to a decrease in the ratio of the active material. When the binder content was less than the lower limit, the ratio of the active material increased, but the capacity maintenance rate decreased due to an increase in fine particles. In addition, in Comparative Examples 1 and 2, since a single-particle silicon-based active material was used alone, it was confirmed that the pulverization phenomenon was not improved and the life performance was deteriorated because it did not have the role of a buffer in the silicon-based active material.

[0217]

[0218] Experimental Example 2: Changes in Monocell Resistance

[0219] 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.

[0220] For the above resistance increase rate measurement evaluation, data at 200 cycles were calculated, and the results were as shown in Table 2 below.

[0221]

[0222] Resistance increase rate (%) after 200 cycles Example 17 Example 27 Example 35 Example 410 Example 58 Comparative Example 120 Comparative Example 216 Comparative Example 315 Comparative Example 417

[0223]

[0224] Table 2 above shows the change in resistance, and as in Table 1, there was no difference in resistance in Examples 1 to 3, and it was confirmed that the resistance increased due to the binder when the binder content exceeded the upper limit, and it was confirmed that the resistance increase rate in Examples 1 to 5 was lower than when it was below the lower limit or when the binder was not included. That is, it was confirmed through the experiment that the binder constituting the secondary particles (a mixture of silicon-based particles and binder) was included in an amount of 1 to 15 parts by weight based on 100 parts by weight of silicon-based active material, thereby acting as a buffer within the silicon-based active material and improving the particle pulverization phenomenon compared to micron-sized polycrystalline particles, thereby improving the life performance and resistance characteristics.

Claims

1. A negative electrode active material containing a silicon-based active material, The above silicon-based active material is a mixture of silicon-based particles and a binder. The above silicon particles have a crystal grain size of 100 nm or less, The particle size (D50) of the above silicon-based active material is 1㎛ or more and 20㎛ or less, A negative electrode active material, wherein the binder is contained in an amount of 1 part by weight or more and 15 parts by weight or less based on 100 parts by weight of the above silicon-based active material.

2. In claim 1, the silicon-based active material is SiOx (x=0) and SiOx (0 <x<2)로 이루어진 군에서 선택되는 1 이상을 포함하며, 상기 실리콘계 활물질 100 중량부 기준 상기 SiOx (x=0)를 70 중량부 이상 포함하는 것인 음극 활물질.

3. A negative electrode active material according to claim 1, wherein the silicon-based particles are single-crystal silicon-based particles or polycrystalline silicon-based particles.

4. In claim 1, The above silicon-based particles are a negative electrode active material having a crystal grain size of 10 nm or more and 80 nm or less.

5. In claim 1, The above binder is a negative active material having a linear chain structure.

6. In claim 1, The above binder includes an aqueous binder, The above-mentioned aqueous binder is a negative electrode active material comprising at least one selected from the group consisting of polyvinylpyrrolidone (PVP); polyacrylic acid (PAA); and polyacrylamide (PAM).

7. Step for preparing silicone raw materials; A step of forming silicon particles by crushing the silicon raw material; and A step of forming a silicon-based active material by mixing a solvent and a binder into the silicon-based particles; A method for manufacturing a negative electrode active material including: The above silicon particles have a crystal grain size of 100 nm or less, The particle size (D50) of the above silicon-based active material is 1㎛ or more and 20㎛ or less, A method for manufacturing a negative electrode active material, wherein the binder is included in an amount of 1 part by weight or more and 15 parts by weight or less based on 100 parts by weight of the above silicon-based active material.

8. In claim 7, A method for producing a negative electrode active material, further comprising a step of mixing a solvent and a binder into the above-mentioned silicon particles and then drying them.

9. In claim 7, A method for producing a negative electrode active material, wherein the mixing rpm of the step of forming a silicon-based active material by mixing a solvent and a binder with the above silicon-based particles is 2000 rpm or more and 3000 rpm or less.

10. A negative electrode composition comprising a negative electrode active material according to any one of claims 1 to 6; a negative electrode conductive material; and a negative electrode binder.

11. In claim 10, A negative electrode composition in which the negative electrode active material is at least 40 parts by weight based on 100 parts by weight of the negative electrode composition.

12. In claim 10, A cathode composition comprising the above cathode conductive material, a planar conductive material, and a linear conductive material.

13. A negative electrode current collector layer; and a negative electrode active material layer provided on one or both sides of the negative electrode current collector layer, A negative electrode for a lithium secondary battery, wherein the negative electrode active material layer comprises the negative electrode composition according to claim 10 or a cured product thereof.

14. In claim 13, The thickness of the above negative electrode current collector layer is 1㎛ or more and 100㎛ or less, A negative electrode for a lithium secondary battery, wherein the thickness of the negative active material layer is 5 ㎛ or more and 500 ㎛ or less.

15. Bipolar; A negative electrode for a lithium secondary battery according to claim 13; A separator provided between the anode and the cathode; and A lithium secondary battery comprising an electrolyte.

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