CATTERAL COMPONENT, CATTERY AND SECONDARY BATTERY

Abstract

The cathode component according to a design of the invention consists of silicon-based active material and carbon-based active material, and simultaneously satisfies the optimal spheroid ratio expressed by Formula (1) and the optimal particle diameter ratio expressed by Formula (2). Formula (1): 0.7 ≤ X1 / Y1 ≤ 1.5 Formula (2): 0.08 ≤ X2 / Y2 ≤ 0.5. In Formula (1), X1 represents the spheroid of the silicon-based active material, and Y1 represents the spheroid of the carbon-based active material, and in Formula (2), X2 represents the average particle diameter (D50) of the silicon-based active material, and Y2 represents the average particle diameter (D50) of the carbon-based active material.

Description

Cathode composition, cathode and secondary battery

[0001] The present application claims the benefit of the filing dates of Korean Patent Application No. 10-2024-0124737 filed with the Korean Intellectual Property Office on September 12, 2024, and Korean Patent Application No. 10-2025-0128957 filed with the Korean Intellectual Property Office on September 10, 2025, the entire contents of which are incorporated herein by reference.

[0002] The present application relates to a cathode composition, a cathode, a secondary battery, and a battery module and battery pack comprising the same.

[0003] The rapid increase in the use of fossil fuels has led to a growing demand for alternative and clean energy. In response to this demand, one of the most actively researched fields is power generation and energy storage utilizing electrochemical reactions. Currently, secondary batteries are a representative example of electrochemical devices that utilize such electrochemical energy, and their scope of application is steadily expanding.

[0004] As technological development and demand for mobile devices increase, the demand for secondary batteries is also rising rapidly. Among secondary batteries, lithium-ion batteries, which possess high energy density and voltage, long cycle life, and low self-discharge rates, have been commercialized and are widely used. Furthermore, active research is underway to develop high-density electrodes with higher energy density per unit volume to manufacture electrodes for high-capacity lithium-ion batteries.

[0005] Generally, a secondary battery consists 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, and silicon-based particles with a high discharge capacity can be used as this negative electrode active material.

[0006] The present specification aims to provide a negative electrode composition using a silicon-based active material, a negative electrode including the same, a secondary battery including the negative electrode, a battery module, and a battery pack.

[0007] One embodiment of the present specification provides a cathode composition comprising a silicon-based active material and a carbon-based active material, satisfying the following formulas (1) and (2).

[0008] Equation (1): 0.7 ≤ X1 / Y1 ≤ 1.5

[0009] Equation (2): 0.08 ≤ X2 / Y2 ≤ 0.5

[0010] In the above equation (1), X1 represents the degree of sphericity of the silicon-based active material, and Y1 represents the degree of sphericity of the carbon-based active material.

[0011] In the above equation (2), X2 represents the average particle size (D50) of the silicon-based active material, and Y2 represents the average particle size (D50) of the carbon-based active material.

[0012] In another embodiment, a cathode is provided comprising a cathode current collector layer and a cathode active material layer provided on one or both sides of the cathode current collector layer, wherein the cathode active material layer comprises a cathode composition according to the present application.

[0013] In another embodiment, a secondary battery is provided comprising a positive electrode, a negative electrode according to the present application, and a separator provided between the positive electrode and the negative electrode.

[0014] In another embodiment, a battery module including a secondary battery according to the present application is provided.

[0015] In another embodiment, a battery pack including a secondary battery according to the present application is provided.

[0016] In another embodiment, a battery pack comprising a battery module according to the present application is provided.

[0017] In another embodiment, a vehicle comprising a battery pack according to the present application is provided.

[0018] In another embodiment, the silicon-based active material is 0.01 m 2 / g to 150.0 m 2 It can have a BET (Brunauer, Emmett, Teller) specific surface area of ​​ / g.

[0019] In another embodiment, the carbon-based active material may use natural graphite, artificial graphite, and a mixture of natural graphite and artificial graphite.

[0020] A cathode composition according to one embodiment of the present invention comprises a silicon-based active material and a carbon-based active material, and is characterized by optimizing the ratio of their particle sizes and simultaneously optimizing the ratio of their sphericity.

[0021] A cathode composition according to one embodiment of the present invention controls the particle size ratio of a silicon-based active material and a carbon-based active material, and additionally optimally controls the sphericity ratio, thereby improving dispersibility and providing an electrode of improved quality.

[0022] In addition, in the case of a cathode composition according to one embodiment of the present invention, lifespan performance can be improved by reducing contact loss between active materials and securing a void structure.

[0023] The following drawings attached to this specification illustrate embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings.

[0024] Figure 1 is a diagram illustrating a cathode according to the prior art.

[0025] FIG. 2 is a diagram illustrating a cathode according to one embodiment of the present invention.

[0026] FIG. 3 is a diagram showing a stacked structure of a cathode according to one embodiment of the present invention.

[0027] FIG. 4 is a diagram showing a stacked structure of a secondary battery according to one embodiment of the present application.

[0028] FIG. 5 is a drawing showing a vehicle including a battery pack according to one embodiment of the present application.

[0029] In parts of the attached drawings, corresponding components are given the same reference numerals. Those skilled in the art understand that the drawings are intended to illustrate elements simply and clearly and are not necessarily drawn to scale. For example, to aid in understanding various embodiments, the dimensions of some elements depicted in the drawings may be exaggerated compared to others. Additionally, elements of known technology that are useful or essential in commercially viable embodiments may often be omitted so as not to hinder the spirit of the various embodiments of the present invention.

[0030] [Explanation of the symbol]

[0031] 1: Carbon-based active material

[0032] 2: Silicon-based active material

[0033] 10: Cathode current collector layer

[0034] 20: Cathode active material layer

[0035] 30: Separator

[0036] 40: Positive active material layer

[0037] 50: Positive current collector layer

[0038] 100: Cathode

[0039] 200: Anode

[0040] 500: Battery pack

[0041] V: Car

[0042] Before describing the present invention, we will first define some terms.

[0043] In this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0044] In this specification, "p to q" means a range of p or more and q or less.

[0045] In this specification, "specific surface area" is measured by the BET (Brunauer, Emmett, Teller) method and is calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using BELSORP-mini II of BEL Japan. That is, in this application, the BET specific surface area may refer to the specific surface area measured by the above measurement method. The BET specific surface area may be measured according to DIN 66131 using N2.

[0046] In this specification, "Dn" refers to the particle size distribution and represents the particle size at the n% point of the cumulative distribution of the number of particles according to particle size. That is, D50 is the particle size at the 50% point of the cumulative distribution of the number of particles according to particle size (central particle size), D90 is the particle size at the 90% point of the cumulative distribution of the number of particles according to particle size, and D10 is the particle size at the 10% point of the cumulative distribution of the number of particles according to particle size. Meanwhile, the central particle size can be measured using the laser diffraction method. For example, after dispersing the powder to be measured 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 patterns according to particle size is measured as the particles pass through the laser beam to calculate the particle size distribution.

[0047] In this specification, "particle size (or particle diameter)" may refer to the average diameter or representative diameter of a particle. The particle may be in the form of a primary particle or may be in the form of a secondary particle formed by the aggregation of multiple primary particles. Additionally, the central particle diameter of a particle may be used interchangeably with the average particle diameter, D50, or particle diameter, and the central particle diameter may refer to the size of a particle.

[0048] In this specification, "primary particle" refers to the original particle when a different type of particle is formed from a certain particle, and a plurality of primary particles may be aggregated, combined, or assembled to form a secondary particle.

[0049] The term "secondary particle" used in the present invention refers to a physically distinguishable large particle formed by the aggregation, combination, or assembly of individual primary particles.

[0050] In this specification, the meaning that a polymer contains a monomer in monomer units means that the monomer participates in a polymerization reaction and is included as a repeating unit within the polymer. In this specification, when it is stated that a polymer contains a monomer, this is interpreted as the same as the polymer containing the monomer in monomer units.

[0051] In this specification, the term "polymer" is understood to be used in a broad sense including copolymers unless specified as "homopolymer."

[0052] In this specification, the weight-average molecular weight (Mw) and the number-average molecular weight (Mn) are polystyrene equivalent molecular weights measured by gel permeation chromatography (GPC), using commercially available monodisperse polystyrene polymers of various degrees of polymerization (standard samples) for molecular weight measurement as standard materials. In this specification, the term "molecular weight" means weight-average molecular weight unless otherwise specified.

[0053] With the recent increase in demand for high-density energy batteries, active research is being conducted on methods to increase capacity by using silicon-based compounds, such as Si / C or SiOx, as negative electrode active materials, which offer higher capacity compared to graphite-based materials. While silicon-based compounds, as high-capacity materials, have the advantage of higher capacity than conventionally used graphite, they present a problem in that their volume expands rapidly during the charging process, severing conductive pathways and degrading battery performance.

[0054] Considering these issues, various methods to suppress volume expansion itself—such as controlling the driving potential, additionally coating a thin film on the surface of the active material layer, or controlling the content of silicon-based active material within the anode—or to prevent or suppress the interruption of conductive paths are being discussed. However, since these methods can actually degrade battery performance, their application is limited, and consequently, there are still limitations to the commercialization of anode batteries with high silicon-based compound content.

[0055] In consideration of this, the present invention provides a negative electrode composition using a mixture of a silicon-based active material and a carbon-based active material, a negative electrode including the same, a secondary battery including the negative electrode, a battery module, and a battery pack.

[0056]

[0057] The present invention is described below so that those skilled in the art can easily practice it. However, the present invention may be embodied in various different forms and is not limited to the description below.

[0058]

[0059] cathode composition

[0060] In the present invention, it was found that when a negative electrode active material comprising a mixture of a silicon-based active material and a carbon-based active material, particularly graphite, is applied to the negative electrode composition, high stability can be exhibited while maintaining high capacity and energy density. However, when silicon-based active materials and carbon-based active materials are mixed to improve capacity and energy density, it was observed that the behavior of the silicon-based active material within the mixed electrode exhibits a different trend compared to a negative electrode in which the silicon-based active material is applied alone. In the mixed electrode, the level of swelling between each active material varies depending on the type of active material, and as a result, a problem arises in which resistance increases in the battery operating environment and lifespan characteristics are inferior.

[0061] Accordingly, as a result of research on methods to improve capacity retention and stability in mixed electrodes of silicon-based and carbon-based active materials, it was found that the aforementioned problems can be improved by achieving an optimal size ratio (particle diameter ratio) between the silicon-based and carbon-based active materials and simultaneously controlling the relationship of sphericity between them. Furthermore, while controlling only the optimal size ratio or only the sphericity ratio between the silicon-based and carbon-based active materials did not show a significant improvement in lifespan and resistance characteristics, it was revealed that a secondary battery exhibiting significantly improved lifespan and resistance characteristics can be provided by simultaneously controlling both the optimal size ratio and the sphericity ratio.

[0062] By controlling the average particle size ratio of silicon-based active materials and carbon-based active materials, and additionally optimally controlling the sphericity ratio, it is possible to achieve improvements in electrode quality through enhanced dispersibility and improved lifespan performance through securing a pore structure.

[0063] One embodiment of the present specification provides a cathode composition comprising a silicon-based active material and a carbon-based active material, satisfying the following formulas (1) and (2).

[0064] Equation (1): 0.7 ≤ X1 / Y1 ≤ 1.5

[0065] Equation (2): 0.08 ≤ X2 / Y2 ≤ 0.5

[0066] In the above equation (1), X1 represents the degree of sphericity of the silicon-based active material, and Y1 represents the degree of sphericity of the carbon-based active material.

[0067] In the above equation (2), X2 represents the average particle size (D50) of the silicon-based active material, and Y2 represents the average particle size (D50) of the carbon-based active material.

[0068] According to one embodiment of the present invention, the sphericity ratio represented by Equation (1) and the average particle size ratio represented by Equation (2) can be simultaneously optimized to improve dispersibility within the composition / electrode and reduce contact loss.

[0069] FIG. 1 is a diagram illustrating a cathode according to the prior art, and FIG. 2 is a diagram illustrating a cathode according to an embodiment of the present invention.

[0070] FIG. 1(a) shows the silicon-based active material (2) and carbon-based active material (1) in the cathode before charging and discharging in a cathode manufactured by a conventional cathode composition, and FIG. 1(b) shows the swollen silicon-based active material (2') and carbon-based active material (1) in the cathode that appear during the charging process in a cathode manufactured by a conventional cathode composition.

[0071] In the course of research to increase the capacity of the negative electrode, it was found that even if a negative electrode composition mixed with a silicon-based active material and a carbon-based active material is used to increase capacity, if the size and sphericity of the silicon-based active material and the carbon-based active material are not optimized, the level of swelling between the silicon-based active material and the carbon-based active material differs as the cycle progresses in the battery operating environment, and as shown in Fig. 1(b), the pores within the electrode decrease due to the influence of by-products caused by volume expansion and particle fracture of the expanded silicon-based active material (2'), and consequently, contact loss within the electrode structure occurs, which may result in inferior lifespan and resistance.

[0072] Referring to FIG. 2, a cathode composition according to one embodiment of the present invention optimizes the sphericity ratio represented by Equation (1) in a silicon-based active material and a carbon-based active material, and at the same time optimizes the average particle size ratio represented by Equation (2). FIG. 2(a) shows the silicon-based active material (2) and the carbon-based active material (1) in the cathode prior to charging and discharging, and FIG. 2(b) shows that the expanded silicon-based active material (2') and the carbon-based active material (1) in the cathode are mixed at an optimized sphericity ratio during the charging process, thereby reducing contact loss occurring in the battery operating environment and further improving dispersibility to improve electrode quality.

[0073] Below, Equation (1) and Equation (2) will be explained respectively.

[0074] In one embodiment of the present invention, the silicon-based active material and the carbon-based active material satisfy the sphericity ratio represented by Equation (1).

[0075] Equation (1): 0.7 ≤ X1 / Y1 ≤ 1.5

[0076] In the above equation (1), X1 represents the degree of sphericity of the silicon-based active material, and Y1 represents the degree of sphericity of the carbon-based active material.

[0077] In one embodiment of the present invention, the degree of sphericity refers to the ratio (Dmin / Dmax) of the major axis length (Dmax) and the minor axis length (Dmin) of each active material. In this case, the minor axis length and the major axis length can be measured through cross-sectional analysis of the cathode containing the cathode composition.

[0078] For example, the degree of sphericity can be measured through cross-sectional analysis of an electrode containing the cathode composition, and the cross-sectional analysis of the cathode can be performed using an ion milling device. A cathode sample prepared by coating the cathode composition onto a copper foil (Cu Foil) is milled using a Hitachi IM4000 device. For example, an ion beam can be fired at a voltage of 1.5 kV and processed for about 3 to 4 hours per sample, after which a cross-sectional image can be measured using a Hitachi S-4800 SEM. The degree of sphericity can be measured by calculating the ratio of the major axis to the minor axis for each particle observed in each SEM image obtained from the cross-sectional image, and the average value of the degree of sphericity measured in each cross-sectional image obtained by randomly selecting five regions of the cross-section and photographing the cross-section at 1K magnification can be used.

[0079] The cross-sectional analysis of the above-mentioned cathode may be measured on the electrode before or after electrolyte impregnation in a secondary battery including the above-mentioned cathode, and may be measured before or after the charging and discharging of the secondary battery. Considering that particle deformation may occur after the charging and discharging of the secondary battery, the degree of sphericity may be measured before the charging and discharging of the secondary battery.

[0080] In one embodiment of the present invention, the sphericity ratio (X1 / Y1) of the above formula (1) is 0.7 to 1.5. For example, the sphericity ratio of the above formula (1) may be 0.7 or higher, 0.71 or higher, 0.8 or higher, or 0.81 or higher, and may be 1.5 or lower, 1.2 or lower, 1.1 or lower, or 1.05 or lower. Alternatively, the sphericity ratio of the above formula (1) may be 0.71 to 1.5, 0.71 to 1.2, or 0.71 to 1.05. When the above range is satisfied for the above formula (1), the sphericity ratio of the silicon-based active material and the carbon-based active material is optimized, the dispersibility within the composition is improved, and the battery containing the above negative electrode composition may exhibit a high lifespan and a low resistance increase rate.

[0081] In one embodiment of the present invention, the degree of sphericity X1 of the silicon-based active material is 0.6 to 1. For example, X1 may be 0.6 or more, 0.65 or more, 0.7 or more, or 0.73 or more, and may be 1 or less, 0.99 or less, 0.97 or less, 0.96 or less, or 0.8 or less. Alternatively, X1 may be 0.6 or more and 0.99 or less, 0.65 or more and 0.99 or less, or 0.65 or more and 0.96 or less.

[0082] In one embodiment of the present invention, the degree of sphericity Y1 of the carbon-based active material is 0.7 to 1. For example, Y1 may be 0.7 or more, 0.8 or more, or 0.85 or more, and may be 1 or less, 0.96 or less, 0.93 or less, or 0.91 or less. Alternatively, Y1 may be 0.7 or more and 0.96 or less, 0.8 or more and 0.93 or less, 0.8 or more and 0.91 or less, or 0.85 or more and 0.97 or less.

[0083] In one embodiment of the present invention, the silicon-based active material and the carbon-based active material satisfy the average particle size ratio represented by Equation (2).

[0084] Equation (2): 0.08 ≤ X2 / Y2 ≤ 0.5

[0085] In the above equation (2), X2 represents the average particle size (D50) of the silicon-based active material, and Y2 represents the average particle size (D50) of the carbon-based active material.

[0086] In the above equation (2), the average particle size (D50) may represent the particle size at the 50% point of the cumulative distribution of the number of particles according to particle size (central particle size). The average particle size (D50) is calculated by dispersing the powder to be measured in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500), and measuring the difference in diffraction patterns according to particle size as the particles pass through a laser beam to calculate the particle size distribution.

[0087] In one embodiment of the present invention, the average particle size ratio (X2 / Y2) of the above formula (2) is 0.08 to 0.5. For example, the average particle size ratio of the above formula (2) may be 0.08 or more, 0.1 or more, or 0.2 or more, and may be 0.5 or less, 0.4 or less, or 0.37 or less. Alternatively, the average particle size ratio of the above formula (2) may be 0.08 to 0.4, 0.1 to 0.4, 0.2 to 0.4, or 0.2 to 0.37. When the above range is satisfied for the above formula (2), the average particle size ratio of the silicon-based active material and the carbon-based active material is optimized, so that the dispersibility within the composition is improved and the swelling characteristics are improved, so that a battery including the above negative electrode composition can exhibit a high lifespan and a low resistance increase rate.

[0088] In one embodiment of the present invention, the average particle size X2 of the silicon-based active material is 1 μm to 15 μm. For example, the average particle size X2 of the silicon-based active material may be 1 μm or more, greater than 1 μm, greater than 1.2 μm, 1.3 μm or more, 1.5 μm or more, or 1.7 μm or more, and may be 15 μm or less, 13 μm or less, 10 μm or less, 8 μm or less, or 5 μm or less. Alternatively, X2 may be greater than 1.2 μm and less than 15 μm, 1.3 μm to 15 μm, 1.7 μm to 15 μm, greater than 1.2 μm and less than 10 μm, 1.3 μm to 8 μm, or 1.7 μm to 5 μm.

[0089] In one embodiment of the present invention, the average particle size Y2 of the carbon-based active material is 5 μm to 30 μm. For example, the average particle size Y2 of the carbon-based active material may be 5 μm or more, 6 μm or more, or 7 μm or more, and may be 30 μm or less, 20 μm or less, 18 μm or less, or 17 μm or less. Alternatively, Y2 may be 5 μm to 20 μm or 7 μm to 20 μm.

[0090] In one embodiment of the present invention, the silicon-based active material is Si, SiOx (0 <x<2), Si / C 또는 Si-alloy로부터 선택되는 적어도 1 이상을 포함한다.

[0091] In one embodiment of the present invention, the silicon-based active material is Si and SiOx (0 <x<2)에서 선택되는 1 이상을 포함한다.

[0092] In one embodiment of the present invention, the silicon-based active material is Si. For example, the silicon-based active material is pulverized Si.

[0093] According to one embodiment of the present invention, the silicon-based active material comprises Si, and the Si comprises 70 parts by weight or more with respect to 100 parts by weight of the silicon-based active material. For example, the Si may comprise 70 parts by weight or more, 80 parts by weight or more, 90 parts by weight or more, or 95 parts by weight or more based on 100 parts by weight of the silicon-based active material, and may comprise 100 parts by weight or less, less than 100 parts by weight, 99 parts by weight or less, 97 parts by weight or less, or 95 parts by weight or less.

[0094] In one embodiment of the present invention, the silicon-based active material may be composed of silicon-based particles having 100 parts by weight of Si based on 100 parts by weight of the silicon-based active material.

[0095] In this specification, Si refers to pure silicon (Si) particles, i.e., pure Si. For example, using pure silicon (Si) particles as a silicon-based active material may mean that, when the silicon-based active material is based on 100 parts by weight of the total as described above, pure Si particles (SiOx (x=0)) that are not combined with other particles or elements are included in the above range.

[0096] In one embodiment of the present invention, the silicon-based active material may include metal impurities, wherein the impurities may include 0.1 parts by weight or less based on 100 parts by weight of the negative electrode active material, and the metals that can generally be included in the silicon-based active material.

[0097] In one embodiment of the present invention, 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 0.01 m² 2 / g to 150.0 m 2 / g, 0.1 m 2 / g to 100.0 m 2 / g, 0.2 m 2 / g to 80.0 m 2 / g, or 0.2 m2 / g to 18.0 m 2 / g. BET specific surface area is measured according to DIN 66131 (e.g., using nitrogen).

[0098] In one embodiment of the present invention, the silicon-based active material may exist in, for example, a crystalline or amorphous form, and the silicon particles may be spherical or fragmentary particles. Alternatively, the silicon particles may also have a fibrous structure or exist in the form of a silicon-containing film or coating.

[0099] In one embodiment of the present invention, the carbon-based active material may include at least one selected from artificial graphite and natural graphite.

[0100] For example, the carbon-based active material may be natural graphite, artificial graphite, or a mixture of natural graphite and artificial graphite.

[0101] In another embodiment of the present invention, the carbon-based active material is natural graphite.

[0102] The above artificial graphite is generally manufactured by carbonizing raw materials such as coal tar, coal tar pitch, and petroleum-based heavy oils at temperatures above 2,500°C, and is used as a negative electrode active material after undergoing particle size adjustments such as grinding and secondary particle formation following this graphitization. In the case of artificial graphite, crystals are randomly distributed within the particles, and compared to natural graphite, it has a lower degree of sphericity and a somewhat pointed shape.

[0103] In addition, the artificial graphite may have an average particle size (D50) of 5㎛ to 30㎛ or 10㎛ to 25㎛.

[0104] The above-mentioned natural graphite generally exists as plate-like aggregates prior to processing, and the plate-like particles are manufactured into a spherical shape with a smooth surface through post-processing, such as particle grinding and reassembly, in order to be used as an active material for electrode manufacturing.

[0105] In addition, the natural graphite may have an average particle size (D50) of 5 μm to 30 μm, or 7 μm to 25 μm.

[0106] When the above carbon-based active material is a mixture of artificial graphite and natural graphite, the weight ratio of the artificial graphite and natural graphite may be 9.99:0.01 to 0.01:9.99, or 9.7:0.3 to 7:3. When satisfying this weight ratio range, superior output may be exhibited.

[0107] In one embodiment of the present invention, the silicon-based active material may be in an amount of 1 to 20 parts by weight based on 100 parts by weight of the negative electrode active material. For example, the silicon-based active material may be included in an amount of 1 part by weight or more or 3 parts by weight or more based on 100 parts by weight of the negative electrode active material, and may be included in an amount of 20 parts by weight or less, 15 parts by weight or less, or 10 parts by weight or less.

[0108] In one embodiment of the present invention, the carbon-based active material may be in an amount of 80 to 99 parts by weight based on 100 parts by weight of the negative electrode active material. For example, the carbon-based active material may be included in an amount of 80 parts by weight or more, 85 parts by weight or more, or 90 parts by weight or more based on 100 parts by weight of the negative electrode active material, and may be included in an amount of 99 parts by weight or less, 95 parts by weight or less, 91 parts by weight or less, or 90 parts by weight or less.

[0109] In one embodiment of the present invention, the silicon-based active material may be in an amount of 1 to 20 parts by weight based on 100 parts by weight of the negative electrode composition. For example, the silicon-based active material may be included in an amount of 1 part by weight or more or 3 parts by weight or more based on 100 parts by weight of the negative electrode composition, and may be included in an amount of 20 parts by weight or less, 15 parts by weight or less, or 10 parts by weight or less.

[0110] In one embodiment of the present invention, the carbon-based active material may be in an amount of 70 to 97 parts by weight based on 100 parts by weight of the cathode composition. For example, the carbon-based active material may be included in an amount of 70 parts by weight or more, 75 parts by weight or more, 80 parts by weight or more, or 90 parts by weight or more based on 100 parts by weight of the cathode composition, and may be included in an amount of 97 parts by weight or less, 95 parts by weight or less, 91 parts by weight or less, or 90 parts by weight or less.

[0111] A cathode composition according to one embodiment of the present invention has excellent characteristics of lifespan and resistance growth rate without degrading the performance of the cathode, even when including a silicon-based active material with significantly high capacity within the above range, because the silicon-based active material and the carbon-based active material satisfy the optimal sphericity ratio and the optimal particle size ratio.

[0112] One embodiment of the present invention provides a cathode composition further comprising a cathode binder; and a cathode conductive material.

[0113] In one embodiment of the present invention, the cathode binder comprises at least one of an aqueous binder and a non-aqueous binder.

[0114] In one embodiment of the present invention, the cathode binder may comprise at least one selected from polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, polyacrylamide (PAM), and materials in which hydrogens thereof are substituted with Li, Na, or Ca, etc., and may also comprise various copolymers thereof.

[0115] The above-mentioned cathode binder serves to hold the active material and conductive material in order to prevent or suppress distortion or structural deformation of the cathode structure. Any general binder that satisfies this role can be applied, for example, a water-based binder can be used.

[0116] In one embodiment of the present invention, a cathode composition is provided in which the cathode binder is included in an amount of 1 part by weight or more and 12 parts by weight or less based on 100 parts by weight of the cathode composition. For example, the cathode binder may be included in an amount of 1 part by weight or more or 2 parts by weight or more based on 100 parts by weight of the cathode composition, and may be included in an amount of 12 parts by weight or less, 10 parts by weight or less, 8 parts by weight or less, 6 parts by weight or less, or 5 parts by weight or less.

[0117] In the case of a cathode comprising the cathode composition according to the present invention, the silicon-based active material is used in the above weight portion to maximize capacity characteristics, and the volume expansion during charging and discharging is significantly greater compared to the case where a conventional carbon-based active material is used as the main active material. Accordingly, the cathode has the characteristic of efficiently controlling the volume expansion of the silicon-based active material with high rigidity during charging and discharging by including the cathode binder in the above content.

[0118] In one embodiment of the present invention, the cathode conductive material may include one or more selected from point conductive materials, planar conductive materials, and linear conductive materials.

[0119] In one embodiment of the present invention, the point-shaped conductive material can be used to improve conductivity of the cathode and refers to a spherical or point-shaped conductive material having conductivity without causing chemical changes. For example, the point-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, Farnes black, lamp black, thermal black, conductive fiber, fluorocarbon, aluminum powder, nickel powder, zinc oxide, potassium titanate, titanium oxide, and polyphenylene derivatives, and may include carbon black in terms of achieving high conductivity and excellent dispersibility.

[0120] In one embodiment of the present invention, the point-shaped conductive material has a BET specific surface area of ​​40 m² 2 / g or more 70m 2 It may be less than / g, and 45m 2 / g or more 65m 2 / g or less, or 50m 2 / g or more 60m 2 It may be less than / g.

[0121] In one embodiment of the present invention, the point-shaped conductive material may satisfy a volatile matter content of 0.01% or more and 1% or less, 0.01% or more and 0.3% or less, or 0.01% or more and 0.1% or less.

[0122] When the functional group content of the point-shaped conductive material satisfies the above range, the functional group present on the surface of the point-shaped conductive material is present, so that the point-shaped conductive material can be smoothly dispersed within the solvent when water is used as the solvent.

[0123] In one embodiment of the present invention, the conductive material may include a planar conductive material.

[0124] The above-mentioned planar conductive material can be described as a plate-shaped conductive material or a bulk-shaped conductive material, as it can improve conductivity by increasing surface contact between silicon particles within the cathode and simultaneously suppress the interruption of conductive pathways due to volume expansion.

[0125] In one embodiment of the present invention, the planar conductive material may comprise at least one selected from the group consisting of plate-shaped graphite, graphene, graphene oxide, and graphite flakes, or may be plate-shaped graphite.

[0126] In one embodiment of the present invention, the average particle size (D50) of the planar conductive material may be 2 μm to 7 μm, or 3 μm to 6 μm, or 4 μm to 5 μm. When the above range is satisfied, dispersion is easy without causing an excessive increase in the viscosity of the cathode slurry due to the sufficient particle size. Therefore, when dispersion is performed using the same equipment and time, the dispersion effect is excellent.

[0127] In one embodiment of the present invention, the planar conductive material may be a planar conductive material with a high specific surface area having a high BET specific surface area; or a planar conductive material with a low specific surface area.

[0128] In one embodiment of the present invention, a planar conductive material with a high specific surface area or a planar conductive material with a low specific surface area may be used without limitation as the planar conductive material; however, since the planar conductive material according to the present application may be affected to some extent by dispersion in electrode performance, a planar conductive material with a low specific surface area that does not cause a problem with dispersion may be used.

[0129] In one embodiment of the present invention, the planar conductive material has a BET specific surface area of ​​5 m² 2 It can be more than / g.

[0130] In another embodiment, the planar conductive material has a BET specific surface area of ​​5m² 2 / g or more than 500m 2 It may be less than / g, and 5m 2 / g or more than 300m 2 / g or less, or 5m 2 / g or more 250m 2 It may be less than / g.

[0131] In another embodiment, the planar conductive material is a high specific surface area planar conductive material, and has a BET specific surface area of ​​50 m² 2 / g or more than 500m 2 / g or less, 80m 2 / g or more than 300m 2 / g or less, or 100m 2 / g or more than 300m 2 It can satisfy a range of / g or less.

[0132] In another embodiment, the planar conductive material is a low specific surface area planar conductive material, and the BET specific surface area is 5m² 2 / g or more 40m 2 / g or less, 5m 2 / g or more 30m 2 / g or less, or 5m 2 / g or more 25m 2 It can satisfy a range of / g or less.

[0133] Other conductive materials may include linear conductive materials such as carbon nanotubes. The carbon nanotubes may be bundled carbon nanotubes. The bundled carbon nanotubes may comprise a plurality of carbon nanotube units. For example, "bundle type" here refers to a secondary shape in the form of a bundle or rope in which a plurality of carbon nanotube units are arranged parallel or intertwined with the axes along the longitudinal direction of the carbon nanotube units having substantially the same orientation, unless otherwise noted. The carbon nanotube units have a graphite sheet having a cylindrical shape with a nano-sized diameter, and sp 2 It has a bonded structure. At this time, depending on the angle and structure in which the graphite plane is rolled, it may exhibit conductive or semiconductor characteristics. Compared to entangled type carbon nanotubes, the bundled carbon nanotubes can be uniformly dispersed during cathode manufacturing and smoothly form a conductive network within the cathode, thereby improving the conductivity of the cathode.

[0134] In one embodiment of the present invention, the linear conductive material may include carbon nanotubes (CNT). For example, the carbon nanotubes (CNT) may include single-walled carbon nanotubes (SWCNT); or multi-walled carbon nanotubes (MWCNT).

[0135] In one embodiment of the present invention, the cathode composition is provided such that the cathode conductive material is present in an amount of 0.01 parts by weight or more and 20 parts by weight or less based on 100 parts by weight of the cathode composition. For example, the cathode conductive material may be included in an amount of 0.01 parts by weight or more, 0.1 parts by weight or more, or 0.5 parts by weight or more based on 100 parts by weight of the cathode composition, and may be included in an amount of 20 parts by weight or less, 15 parts by weight or less, 10 parts by weight or less, or 5 parts by weight or less.

[0136] The cathode conductive material according to the present invention has a completely separate composition from the anode conductive material applied to the anode. For example, the cathode conductive material according to the present application serves to hold the contact points between silicon-based active materials, which undergo significant volume expansion of the electrodes due to charging and discharging. The anode conductive material, on the other hand, acts as a buffer during rolling and provides some conductivity; thus, its composition and role are completely different from those of the cathode conductive material of the present invention.

[0137] Furthermore, the cathode conductive material according to the present invention is applied to a cathode composition containing a silicon-based active material and has a completely different composition from a conductive material applied to a cathode composition containing only a carbon-based active material. That is, a conductive material used in an electrode having only a carbon-based active material simply has smaller particles compared to the carbon-based active material (e.g., graphite), and thus possesses characteristics that improve output characteristics and impart some conductivity; thus, its composition and role differ from that of a cathode conductive material applied together with a silicon-based active material as in the invention.

[0138]

[0139] cathode

[0140] According to one embodiment of the present invention, a cathode is provided comprising: a cathode current collector layer; and a cathode active material layer provided on one or both sides of the cathode current collector layer, wherein the cathode active material layer comprises a cathode composition according to one embodiment of the present invention.

[0141] FIG. 3 is a diagram showing a stacked structure of a cathode according to one embodiment of the present invention. For example, a cathode (100) including a cathode active material layer (20) on one side of a cathode current collector layer (10) can be seen, and FIG. 3 shows that the cathode active material layer is formed on one side, but it can be formed on both sides of the cathode current collector layer.

[0142] In one embodiment of the present invention, the cathode may be formed by applying and drying a cathode slurry containing the cathode composition on one or both sides of a cathode current collector layer.

[0143] At this time, the cathode slurry may include the aforementioned cathode composition; and a slurry solvent.

[0144] In one embodiment of the present invention, the cathode may be formed by applying and drying the cathode slurry on one or both sides of the cathode current collector layer.

[0145] In one embodiment of the present invention, the solid content of the cathode slurry may satisfy 5% or more and 50% or less.

[0146] In another embodiment, the solid content of the cathode slurry may satisfy a range of 5% or more and 50% or less, 7% or more and 50% or less, or 10% or more and 46% or less.

[0147] The solid content of the above cathode slurry may refer to the content of the cathode composition included in the above cathode slurry, and may refer to the content of the cathode composition based on 100 parts by weight of the cathode slurry.

[0148] When the solid content of the above cathode slurry satisfies the above range, the viscosity is suitable when forming the cathode active material layer, thereby minimizing particle aggregation of the cathode composition and enabling the cathode active material layer to be formed efficiently.

[0149] In one embodiment of the present application, the slurry solvent may be used without limitation as long as it can dissolve the cathode composition, and for example, water (distilled water) or N-methyl-2-pyrrolidone (NMP) may be used.

[0150] In one embodiment of the present application, the negative current collector layer has a thickness of 1 μm to 100 μm. Such a negative 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., or aluminum-cadmium alloy may be used. In addition, fine irregularities may be formed on the surface to strengthen the bonding strength of the negative active material, and it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0151] In one embodiment of the present invention, a cathode is provided in which the thickness of the cathode current collector layer is 1 μm to 100 μm or less, and the thickness of the cathode active material layer is 5 μm to 500 μm.

[0152] However, the thickness of the above-mentioned cathode current collector layer and cathode active material layer may vary depending on the type and application of the cathode used, and is not limited thereto.

[0153] In one embodiment of the present invention, the porosity of the negative electrode active material layer may satisfy a range of 10% or more and 60% or less.

[0154] In another embodiment, the porosity of the cathode active material layer may satisfy a range of 10% or more and 60% or less, 20% or more and 50% or less, or 30% or more and 45% or less.

[0155] The above porosity varies according to the composition and content of the silicon-based active material, carbon-based active material, cathode conductive material, and cathode binder included in the cathode active material layer, and satisfies the above range by including the silicon-based active material, carbon-based active material, cathode conductive material, and cathode binder according to the present application in a specific composition and content, thereby characterized in that the electrical conductivity and resistance of the electrode have an appropriate range.

[0156]

[0157] secondary battery

[0158] In one embodiment of the present application, a lithium secondary battery is provided comprising: a positive electrode; a negative electrode according to one embodiment of the present invention; a separator provided between the positive electrode and the negative electrode; and an electrolyte.

[0159] FIG. 4 is a diagram showing a stacked structure of a secondary battery according to one embodiment of the present application. For example, a negative electrode (100) including a negative active material layer (20) on one side of a negative current collector layer (10) can be seen, and a positive electrode (200) for a lithium secondary battery including a positive active material layer (40) on one side of a positive current collector layer (50) can be seen, and the structure is formed such that the negative electrode (100) for a lithium secondary battery and the positive electrode (200) for a lithium secondary battery are stacked with a separator (30) in between.

[0160] A secondary battery according to one embodiment of the present specification may include the negative electrode described above. For example, 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, further explanation is omitted.

[0161] 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 comprising the positive electrode active material.

[0162] In the above-mentioned positive electrode, the positive current collector is not particularly limited as long as it is conductive without causing chemical changes 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 above-mentioned positive current collector may typically have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to increase the adhesion of the positive active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0163] The above-mentioned positive electrode active material may be a commonly used positive electrode active material. For example, the above-mentioned positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; or a compound with the chemical formula Li 1+c1 Mn 2-c1 Lithium manganese oxides such as O4 (0≤c1≤0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7, etc.; chemical formula LiNi 1-c2 M c2 Ni-site type lithium nickel oxide represented by O2 (wherein M is at least one selected from Co, Mn, Al, Cu, Fe, Mg, B, and Ga, satisfying 0.01≤c2≤0.3); chemical formula LiMn 2-c3 M c3Examples include lithium manganese composite oxides represented by O2 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn and Ta, satisfying 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 a portion of the Li in the chemical formula is substituted with alkaline earth metal ions, but are not limited thereto. The anode may also be Li-metal.

[0164] The above-described positive active material layer may include a positive conductive material and a positive binder together with the positive active material described above.

[0165] At this time, the positive electrode conductive material is used to impart conductivity to the electrode, and in the battery being constructed, any material that has electronic conductivity without causing chemical changes can be used without special limitations. 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, thermal black, and carbon fibers; metal powder or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used.

[0166] In addition, the anode binder serves to improve adhesion between anode active material particles and adhesion between the anode active material and the anode current collector. Examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used.

[0167] The above separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. Any separator typically used as a separator in a secondary battery may be used without special restrictions, and one that has low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity may be used. For example, a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0168] Examples of the above electrolytes that can be used in the manufacture of lithium secondary batteries include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., but are not limited to these.

[0169] For example, the above electrolyte may include a non-aqueous organic solvent and a metal salt.

[0170] As the above-mentioned non-aqueous organic solvent, for example, aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyl lactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolone, formamide, dimethylformamide, dioxolone, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolone derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, methyl propionate, ethyl propionate, etc. may be used.

[0171] Among the above carbonate-based organic solvents, cyclic carbonates such as ethylene carbonate and propylene carbonate are high-viscosity organic solvents with high dielectric constants that can effectively dissociate lithium salts, and by mixing these cyclic carbonates with low-viscosity, low-dielectric-constant linear carbonates such as dimethyl carbonate and diethyl carbonate in appropriate proportions, an electrolyte with high electrical conductivity can be produced.

[0172] The metal salt mentioned above may be a lithium salt, and the lithium salt is a substance that dissolves well in the non-aqueous electrolyte; for example, as the anion of the lithium salt, 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 types selected from can be used.

[0173] In addition to the above electrolyte components, the above electrolyte may further include one or more additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as, for example, a haloalkylene carbonate-based compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride.

[0174]

[0175] Battery modules and battery packs

[0176] One embodiment of the present invention provides a battery module including a secondary battery according to one embodiment of the present invention.

[0177] One embodiment of the present invention provides a battery pack including a secondary battery according to one embodiment of the present invention.

[0178] One embodiment of the present invention provides a battery pack including a battery module according to one embodiment of the present invention.

[0179] One embodiment of the present invention provides a battery module comprising the secondary battery as a unit cell and a battery pack comprising the secondary battery or the battery module. Since the battery module and the battery pack include the secondary battery having high capacity, high rate capability and cycle capability, they can be used as a power source for a medium-to-large device selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles and power storage systems.

[0180] FIG. 5 is a drawing showing a vehicle according to one embodiment of the present invention.

[0181] Referring to FIG. 5 below, the battery pack (500) according to the present invention can be applied to a vehicle (V), such as an electric vehicle or a hybrid vehicle. That is, the vehicle (V) according to the present invention may include the battery pack (500) according to the present invention. The battery pack (500) may be installed in the vehicle body frame or trunk space under the vehicle seat. Furthermore, the vehicle (V) according to one embodiment of the present invention may include various other components included in the vehicle in addition to the battery pack (500). For example, the vehicle (V) according to one embodiment of the present invention may include, in addition to the battery pack (500) according to one embodiment of the present invention, a vehicle body, a motor, a control device such as an ECU (electronic control unit), etc.

[0182]

[0183] Hereinafter, various embodiments are presented to aid in understanding the present invention; however, the above embodiments are merely illustrative of the description, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and spirit of the description, and that such variations and modifications fall within the scope of the appended claims.

[0184] <Preparation Example>

[0185] Example 1

[0186] 1) Preparation of cathode composition

[0187] A cathode composition was prepared based on 100 parts by weight of a cathode composition, comprising natural graphite (95 parts by weight based on 100 parts by weight of the cathode active material) as a carbon-based active material and 95 parts by weight of ground Si (5 parts by weight based on 100 parts by weight of the cathode active material) as a silicon-based active material, and 2.5 parts by weight of SBR (styrene-butadiene rubber) and 1.1 parts by weight of CMC (carboxymethyl cellulose) as binders, and additionally comprising carbon black as a point-type conductive material and carbon nanotubes (CNT) as a linear conductive material, in amounts of 1.0 parts by weight and 0.4 parts by weight, respectively.

[0188] The degree of sphericity of the carbon-based active material is 0.87 and the average particle size (D50) is 7.6 μm, and the degree of sphericity of the silicon-based active material is 0.74 and the average particle size (D50) is 1.78 μm.

[0189] 2) Preparation of the cathode

[0190] A cathode slurry was prepared by adding distilled water as a solvent to the cathode composition prepared in Preparation Example 1) above (solid content 46 wt%).

[0191] For example, CNT, carbon black, CMC, and SBR were dispersed in distilled water at 2,500 rpm for 30 minutes using a homo mixer, and then the cathode active material was added and dispersed at 2,500 rpm for 30 minutes to prepare a cathode slurry.

[0192] The above CNT has a BET specific surface area of ​​1,000 to 1,500 m² 2 A solution satisfying / g and having an aspect ratio of 10,000 or higher was used, and a solution dispersed in CMC (Carboxymethyl Cellulose) was used.

[0193] As a cathode current collector layer, the above cathode slurry is applied to both sides of a copper current collector (thickness 15㎛) at a ratio of 271 mg / 25 cm 2 A cathode was manufactured by coating with a loading amount, rolling, and drying in a vacuum oven at 130°C for 10 hours to form a cathode active material layer.

[0194] 3) Manufacturing of secondary batteries

[0195] LiNi as a positive electrode active material 0.6 Co 0.2 Mn 0.2 O2 (average particle size (D50): 15㎛), carbon black as a conductive material (product name: Super C65, manufacturer: Timcal), and polyvinylidene fluoride (PVdF) as a binder were prepared in a weight ratio of 97:1.5:1.5, and an anode slurry was prepared by adding them to N-methyl-2-pyrrolidone (NMP) as a solvent for forming the anode slurry (solid content concentration 78 wt%).

[0196] 537 mg / 25 cm of the anode slurry is applied to both sides of an aluminum current collector (thickness: 12 μm) as an anode current collector. 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.

[0197] A lithium secondary battery was manufactured by interposing a polyethylene separator between the anode and the cathode and injecting an electrolyte.

[0198] The above electrolyte was used by adding vinylene carbonate (VC) at 3% by weight 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 adding LiPF6 as a lithium salt at a concentration of 1M.

[0199] Examples 2 to 7 and Comparative Examples 1 to 3

[0200] A secondary battery was manufactured in the same manner as in Example 1, except that silicon-based active material and carbon-based active material having the sphericity and average particle size (D50) of the silicon-based active material and carbon-based active material as shown in Table 1 were used.

[0201] Silicon-based active material Carbon-based active material Formula (1): X1 / Y1 Formula (2): X2 / Y2 Sphericity (X1) D50 (㎛, X2) Sphericity (Y1) D50 (㎛, Y2) Example 1 0.74 1.78 0.877 60.85 0.23 Example 2 0.96 4.96 0.91 171.05 0.29 Example 3 0.65 4.94 0.91 170.71 0.29 Example 4 0.73 2.82 0.877 60.84 0.37 Example 5 0.74 1.78 0.91 170.81 0.10 Example 60.96 2.67 0.769 21.26 0.29 Example 70.732.820.769.20.960.31 Comparative Example 10.611.20.91170.670.07 Comparative Example 20.731.20.91170.800.07 Comparative Example 30.591.20.877.60.680.16

[0202] The following items were evaluated for the above examples and comparative examples, and the results are listed in Table 2.

[0203] Experimental Example 1: Evaluation of Dose Retention Rate

[0204] Life evaluation was performed on secondary batteries containing the negative electrodes prepared in the above examples and comparative examples using an electrochemical charge / discharger. In-situ cycle tests were conducted on the secondary batteries at 4.2-2.5V, charging at 1 / 4C and discharging at 1 / 3C. The test was terminated after 200 cycles of discharge, and the capacity retention rate was measured by charging / discharging at 0.33C / 0.33C (4.2-2.5V) every 50 cycles.

[0205] Capacity Retention Rate (%) = {(Discharge Capacity at the Nth Cycle) / (Discharge Capacity at the 1st Cycle)} × 100 %

[0206]

[0207] Experimental Example 2: Evaluation of Resistance Increase Rate

[0208] In Experimental Example 1 above, the capacity retention rate was measured by charging / discharging at 0.33C / 0.33C (4.2-2.5V) every 50 cycles during the test, and then the resistance was measured by discharging at a 2.5C pulse at SOC 50, and the resistance increase rate was compared and analyzed.

[0209] Equation (1): X1 / Y1 Equation (2): X2 / Y2 Capacitance retention rate (%) after 200 cycles Resistance increase rate (%) after 200 cycles Example 1 0.85 0.236830 Example 2 1.05 0.296732 Example 3 0.71 0.296533 Example 4 0.84 0.376731 Example 5 0.81 0.106435 Example 6 1.26 0.296237 Example 7 0.96 0.316337 Comparative Example 10.67 0.075850 Comparative Example 20.80 0.075945 Comparative Example 30.68 0.166138

[0210] Referring to Table 2, it was confirmed that Examples 1 to 7, which simultaneously satisfy Equation (1) and Equation (2), exhibit a higher capacity retention rate and a lower resistance increase rate compared to Comparative Examples 1 to 3. This is understood to be a phenomenon that occurs because, in the case of Examples 1 to 7, the sphericity and average particle size ratio between active materials are optimized to improve dispersibility, and consequently, the contact loss between active materials within the electrode is reduced. On the other hand, in the case of Comparative Examples 1 to 3, where Equation (1) and Equation (2) are not included within the scope of the present invention, it can be confirmed that they exhibit a lower capacity retention rate and a higher resistance increase rate compared to the Examples. This is understood as a phenomenon that occurs because Comparative Examples 1 to 3 do not simultaneously satisfy Equation (1) and Equation (2), resulting in different levels of swelling between the carbon-based active material and the silicon-based active material in the electrode, and as the cycle progresses, the pores in the electrode decrease due to the volume expansion of the silicon-based active material and the influence of by-products caused by particle fracture, and consequently, the contact loss increases.

[0211] Referring to Comparative Examples 2 and 3, it was confirmed that even if either Equation (1) or Equation (2) satisfies the scope of the present invention, if the cathode composition does not simultaneously satisfy the scopes of Equation (1) and Equation (2), the swelling levels between the active materials still differ, resulting in a low lifespan and a high resistance increase rate.

[0212] The above detailed description is intended to illustrate and explain the present invention. Furthermore, the foregoing merely indicates and describes embodiments of the present invention, and as described above, the present invention may be used in various other combinations, modifications, and environments, and modifications or alterations may be made within the scope of the invention disclosed herein, the scope equivalent to the foregoing disclosure, and / or the scope of the art or knowledge. Accordingly, the above detailed description of the invention is not intended to limit the present invention to the disclosed embodiments. Additionally, the appended claims should be interpreted as including other embodiments.

Claims

1. A negative electrode composition comprising a silicon-based active material; and a carbon-based active material, A cathode composition satisfying the following formulas (1) and (2): Equation (1): 0.7 ≤ X1 / Y1 ≤ 1.5 Equation (2): 0.08 ≤ X2 / Y2 ≤ 0.5 In the above equation (1), X1 represents the degree of sphericity of the silicon-based active material, and Y1 represents the degree of sphericity of the carbon-based active material, In the above equation (2), X2 represents the average particle size (D50) of the silicon-based active material, and Y2 represents the average particle size (D50) of the carbon-based active material.

2. In Claim 1, A cathode composition in which X1 is 0.6 to 1.

3. In Claim 1, A cathode composition in which the above Y1 is 0.7 to 1.

4. In Claim 1, A cathode composition in which the above X2 is 1 μm to 15 μm.

5. In Claim 1, A cathode composition in which the above Y2 is 5 μm to 30 μm.

6. In Claim 1, The above silicon-based active material is Si, SiOx (0 <x<2), Si / C 또는 Si-alloy로부터 선택되는 적어도 1 이상을 포함하는 것인, 음극 조성물.

7. In Claim 1, The above silicon-based active material includes Si, and A cathode composition comprising at least 70 parts by weight of the above Si based on 100 parts by weight of the above silicon-based active material.

8. In Claim 1, A cathode composition comprising at least one carbon-based active material selected from artificial graphite and natural graphite.

9. In Claim 1, The above silicon-based active material is in an amount of 1 to 20 parts by weight based on 100 parts by weight of the above cathode composition.

10. In Claim 1, The cathode composition wherein the carbon-based active material is present in an amount of 70 to 97 parts by weight based on 100 parts by weight of the cathode composition.

11. A negative current collector layer; and a negative active material layer provided on one or both sides of the negative current collector layer, comprising The above-mentioned cathode active material layer comprises a cathode composition according to any one of claims 1 to 10.

12. Anode; The cathode according to claim 11; and A secondary battery comprising a separator provided between the anode and the cathode; and an electrolyte.

13. A battery module comprising the secondary battery according to claim 12.

14. A battery pack comprising the secondary battery according to claim 12.

15. A battery pack comprising the battery module according to claim 13.

16. An automobile comprising the battery pack according to claim 14.

17. In Claim 1, The above silicon-based active material is 0.01 m 2 / g to 150.0 m 2 A cathode composition having a BET (Brunauer, Emmett, Teller) specific surface area of ​​ / g.

18. In Claim 1, The above carbon-based active material is a cathode composition that uses natural graphite, artificial graphite, and a mixture of natural graphite and artificial graphite.

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