Anode active material, anode composition, anode comprising same, and secondary battery

Abstract

Disclosed herein is a negative electrode active material, a negative electrode composition, a negative electrode including the same, a secondary battery including the negative electrode, a battery module, and a battery pack. According to an embodiment of the present disclosure, the negative electrode active material includes a silicon-based active material; and a coating layer provided on the silicon-based active material. The coating layer includes a metal oxide and an aqueous binder.

Description

Cathode active material, cathode composition, cathode including the same, and secondary battery

[0001] This application is based on Korean Patent Application No. 10-2024-0145317, the contents of which are incorporated in whole into this application by reference herein, and claims priority thereof.

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

[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] Meanwhile, 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] The present application provides a technology capable of improving the capacity retention rate and stability of a battery through a surface treatment comprising a coating layer on a silicon-based active material.

[0006] One embodiment of the present specification provides a negative electrode active material comprising a silicon-based active material and a coating layer provided on the silicon-based active material, wherein the coating layer comprises a metal oxide and a water-based binder.

[0007] In another embodiment, a cathode composition comprising the above-described cathode active material according to the present application is provided.

[0008] In another embodiment, the cathode comprises 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 the cathode composition according to the present application.

[0009] In another embodiment, a secondary battery comprising a positive electrode and the negative electrode according to the present application is provided.

[0010] In another embodiment, a battery module or battery pack comprising the above-described secondary battery according to the present application is provided.

[0011] In another embodiment, a battery pack comprising the above-described battery module according to the present application is provided.

[0012] In the case of a negative electrode active material according to one embodiment of the present invention, it comprises silicon-based particles and a coating layer comprising a metal oxide and a water-based binder on the silicon-based particles.

[0013] In the case of a negative electrode active material according to one embodiment of the present invention, by providing a coating layer on a silicon-based active material through surface treatment, the surface exposed due to particle expansion and particle fracture of the silicon-based active material in a battery operating environment can be reduced, thereby improving the capacity retention rate and stability of the battery.

[0014] For example, the above coating layer can act as a resistor for the silicon-based active material to mitigate particle breakage.

[0015] In addition, when a cathode active material according to one embodiment of the present invention is applied, the generation of gas that may occur in an aqueous process can be reduced, making it easy to manufacture the electrode.

[0016] The following drawings attached to this specification illustrate preferred 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.

[0017] FIG. 1 is a diagram illustrating a negative electrode active material according to one embodiment of the present invention.

[0018] FIG. 2 is a diagram showing a stacked structure of a cathode according to one embodiment of the present invention.

[0019] FIG. 3 is a diagram showing a stacked structure of a secondary battery according to one embodiment of the present invention.

[0020] 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.

[0021] Before describing the present invention, we will first define some terms.

[0022] In this specification, when a part is described as "comprising" a certain component, it means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0023] In this specification, "p to q" means a range of p or more and q or less.

[0024] In this specification, "specific surface area" is measured by the BET method and is calculated, for example, from the amount of nitrogen gas adsorbed at a liquid nitrogen temperature (77K) using the BELSORP-mini II of BEL Japan. For example, 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.

[0025] In this specification, "Dn" refers to a 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. For example, 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 a 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.

[0026] In this specification, particle size or particle diameter may refer to the average diameter or representative diameter of each individual grain constituting the particle powder.

[0027] 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 single particle or 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.

[0028] In this specification, "particle" may be in the form of a single particle, a pseudo-single particle, or a secondary particle.

[0029] In this specification, "single particle" may mean one primary particle and may include pseudo-single particles formed by aggregating, combining, or assembling 30 or fewer primary particles.

[0030] The term "secondary particles" as used in this specification refers to particles formed by the aggregation of dozens to hundreds, for example, more than 30 primary particles, by combining, combining, or assembling.

[0031] 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.

[0032] In this specification, the term "polymer" is understood to be used in a broad sense including copolymers unless specified as "homopolymer."

[0033] 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.

[0034] As used herein, “about,” “approximately,” and “substantially” are used to mean a range of figures or degrees or approximations thereof, taking into account inherent manufacturing and material tolerances (e.g., ±5%).

[0035] 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.

[0036] Furthermore, due to the recent increase in demand for high-density energy batteries, research is actively underway on methods to increase capacity by using silicon-based compounds, such as Si / C or SiOx, as negative electrode active materials, which have a higher capacity compared to graphite-based materials. While silicon-based compounds, which are high-capacity materials, have the advantage of having a larger capacity compared to conventionally used graphite, they have a problem in that their volume expands rapidly during the charging process, severing conductive pathways and degrading battery characteristics. For example, Japanese Patent Publication No. 2009-080971 discloses the use of polyacrylate as a binder in a graphite-based negative electrode active material layer.

[0037] Accordingly, various measures are being discussed to address the problems associated with using silicon-based active materials as negative electrode active materials, such as controlling the driving potential, additionally coating a thin film on the surface of the active material layer, controlling the content of silicon-based active material within the negative electrode to suppress volume expansion itself, or preventing the interruption of conductive paths. However, since these measures can actually degrade battery performance, their application is limited, and consequently, there are still limitations to the commercialization of negative electrode batteries with high silicon-based compound content.

[0038] Considering these points, the present invention provides a technology that improves the capacity retention rate and stability of a lithium secondary battery by applying a silicon-based active material used as a negative electrode active material through a surface treatment that provides a coating layer.

[0039] The present invention is described in detail 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.

[0040] Recently, there have been continuous attempts to apply silicon-based active materials to the anode to increase capacity. However, when silicon-based active materials are used as the anode active material, there is a problem in that they exhibit inferior characteristics in terms of capacity retention rate and stability due to issues such as volume expansion and gas generation during the process.

[0041] cathode active material

[0042] One embodiment of the present invention provides a negative electrode active material comprising: a silicon-based active material; and a coating layer provided on the silicon-based active material, wherein the coating layer comprises a metal oxide and a water-based binder.

[0043] By providing a coating layer comprising a metal oxide and a water-based binder on the above silicon-based active material, the surface exposed due to particle expansion and particle fracture of the silicon-based active material can be reduced, thereby improving the capacity retention rate and stability of the battery and reducing the amount of unnecessary gas generated during the process.

[0044] In one embodiment of the present invention, the average particle size (D50) of the silicon-based active material may be about 1 μm to 20 μm. For example, the average particle size (D50) of the silicon-based active material may be about 1 μm or more, greater than 1 μm, 2 μm or more, or 3 μm or more, and may be 20 μm or less, 15 μm or less, 14 μm or less, 13 μm or less, or 10 μm or less.

[0045] In one embodiment of the present invention, the silicon-based active material generally has a characteristic BET specific surface area. The BET surface area of ​​the silicon-based active material is about 0.01 m² 2 / g to 150 m 2 / g, approx. 0.1 m 2 / g to 100 m 2 / g, approx. 0.2 m 2 / g to 80 m 2 / g, or about 0.2 m 2 / g to 18 m 2 / g. The BET surface area is measured according to DIN 66131 (using nitrogen).

[0046] In one embodiment of the present invention, the silicon-based active material is Si, SiOx (0 <x<2), Si / C 및 Si-alloy로부터 선택되는 적어도 1 이상을 포함한다.

[0047] In one embodiment of the present invention, the silicon-based active material comprises Si, and the Si may comprise at least about 70 parts by weight based on 100 parts by weight of the silicon-based active material. For example, the Si may comprise at least about 70 parts by weight, at least 80 parts by weight, at least 90 parts by weight, or at least 95 parts by weight based on 100 parts by weight of the silicon-based active material, and may comprise at least about 100 parts by weight, 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.

[0048] 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.

[0049] 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 negative electrode active material, and the silicon-based particles may be in the form of powder.

[0050] In one embodiment of the present invention, the silicon-based active material may include metal impurities, wherein the impurities may include, for example, a metal that can generally be included in the silicon-based active material, in an amount of about 0.1 parts by weight or less based on 100 parts by weight of the silicon-based active material.

[0051] In one embodiment of the present invention, the silicon-based active material may include Si / C.

[0052] In this specification, Si / C refers to a silicon carbon composite. The silicon carbon composite may consist of Si and C that are not bonded to each other, but may include additional components as needed. For example, the silicon carbon composite may or may not include silicon carbide, denoted as SiC. If the silicon carbon composite includes silicon carbide, its content is about 3 weight percent or less. The silicon carbon composite may exist in a crystalline, amorphous, or mixed state. According to one example, C in the silicon carbon composite may exist in an amorphous state.

[0053] The above silicon-carbon composite may be a composite of silicon and carbon, etc., and may form a structure in which graphite, graphene, or amorphous carbon, etc., surrounds a core composed of silicon and carbon, etc. In the above silicon-carbon composite, the silicon may be nano-silicon.

[0054] The above silicon carbon composite may be a physically or chemically composited carbon and silicon material, and is not limited to any composition in which carbon and silicon material form a composite.

[0055] According to one embodiment of the present invention, the Si / C may comprise porous carbon and silicon deposited on the porous carbon. For example, the silicon-carbon composite comprises porous carbon-based particles and silicon particles located on the surface or within the pores of the porous carbon-based particles.

[0056] The silicon particles formed on the surface and internal pores of the carbon-based particles may be silicon nanoparticles, and these may be crystalline, semicrystalline, amorphous, or a combination thereof.

[0057] A silicon-based active material according to one embodiment of the present invention comprises a carbon layer provided on at least a portion of the porous carbon. For example, the carbon layer can prevent or suppress gas generation caused by contact with water during an aqueous process or the deterioration of the lifespan characteristics of the silicon-carbon composite by blocking the exposure of silicon on the outer surface of the porous carbon or by reducing the reactivity of silicon. In addition, conductivity is imparted to the silicon-based active material by the carbon layer, and the initial efficiency, lifespan characteristics, and battery capacity characteristics of the secondary battery can be improved.

[0058] As a non-limiting example, the carbon layer may be formed prior to the formation of the coating layer comprising the metal oxide and water-based binder described later, or after the formation of the coating layer. Accordingly, the carbon layer may be provided on a silicon-carbon composite core in the aforementioned core where the coating layer is not provided, or on at least a portion of the coating layer that is first provided on the silicon-carbon composite core. Additionally, the carbon layer may completely surround the coating layer, but may also be formed only on a portion of the coating layer; thus, both the coating layer and the carbon layer may be observed on the surface of the negative electrode active material.

[0059] According to one embodiment of the present invention, the carbon layer may be formed after the formation of a coating layer comprising a metal oxide and a water-based binder, which will be described later. That is, the coating layer may be provided on at least a portion of the carbon layer first provided on the silicon-carbon composite core. Additionally, although the coating layer may completely enclose the carbon layer, it may be formed only on a portion of the carbon layer, so both the coating layer and the carbon layer may be observed on the surface of the negative electrode active material.

[0060] In one embodiment of the present invention, the carbon layer may include at least one of amorphous carbon and crystalline carbon.

[0061] According to one embodiment, the carbon layer may be an amorphous carbon layer. The amorphous carbon can appropriately maintain the strength of the carbon layer to suppress the expansion of the silicon carbon composite. Additionally, the carbon layer may additionally include or not include crystalline carbon.

[0062] The crystalline carbon can further improve the conductivity of the cathode active material. The crystalline carbon may include at least one selected from fullene, carbon nanotubes, and graphene.

[0063] The amorphous carbon can adequately maintain the strength of the carbon layer and suppress the expansion of the silicon-carbon composite. The amorphous carbon may be a carbon-based material formed using at least one carbide selected from tar, pitch, and other organic materials, or a hydrocarbon as a source for chemical vapor deposition.

[0064] The above-mentioned other organic carbons may be carbons of organic materials selected from sucrose, glucose, galactose, fructose, lactose, mannose, ribose, aldohexose, or kedohexose and combinations thereof.

[0065] The above hydrocarbon may be a substituted or unsubstituted aliphatic or alicyclic hydrocarbon, or a substituted or unsubstituted aromatic hydrocarbon. The aliphatic or alicyclic hydrocarbon of the substituted or unsubstituted aliphatic or alicyclic hydrocarbon may be methane, ethane, ethylene, acetylene, propane, butane, butene, pentane, isobutane, or hexane, etc. The aromatic hydrocarbon of the substituted or unsubstituted aromatic hydrocarbon may be benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, anthracene, or phenanthrene, etc.

[0066] In one embodiment of the present invention, the carbon layer may be included in an amount of about 0.1 to 50 parts by weight, 0.1 to 30 parts by weight, or 0.1 to 20 parts by weight based on 100 parts by weight of the total silicon-based active material. For example, it may be included in an amount of about 0.5 to 15 parts by weight or 1 to 10 parts by weight. When satisfying the above ranges, conductivity can be improved while preventing a decrease in the capacity and efficiency of the silicon-based active material.

[0067] In one embodiment of the present invention, the thickness of the carbon layer may be about 1 nm to 500 nm, for example, 5 nm to 300 nm, or 5 nm to 100 nm. When the above range is satisfied, the conductivity of the silicon-based active material is improved, the volume change of the silicon-based active material is easily suppressed, and side reactions between the electrolyte and the silicon-based active material are suppressed, thereby improving the initial efficiency and / or lifespan of the battery.

[0068] According to one embodiment, the carbon layer may be formed by chemical vapor deposition (CVD) using at least one hydrocarbon gas selected from methane, ethane, and acetylene.

[0069] According to another embodiment of the present invention, the Si / C (silicon carbon composite) may be configured such that carbon material is coated on the surface of particles by firing carbon in a state where carbon is bonded with silicon or silicon oxide particles, or such that carbon is dispersed in an atomic state inside silicon particles, or such that a structure is formed in which graphite, graphene, or amorphous carbon is wrapped around a core in which silicon and carbon are composited.

[0070] According to one embodiment of the present invention, when a silicon-based active material contains Si / C, the Si:C elemental ratio on the surface of the silicon-based active material is about 1:1 to 1:4, for example, about 1:2 to 1:4, or 1:3 to 1:4. Since the silicon-based active material has a carbon layer on its surface, this means that the carbon ratio appears higher on the surface. Having such an elemental ratio implies that the carbon coating on the surface of the silicon-based active material is well formed, which can be measured via XPS. Adjusting the elemental ratio can be achieved by adjusting the amount of carbonized material or changing the heat treatment time during the process of introducing the carbon layer.

[0071] According to one embodiment of the present invention, when a silicon-based active material contains Si / C, the Si:C elemental ratio in the silicon-based active material is approximately 0.9:1.1 to 1.1:0.9, for example, approximately 1:0.95 to 1:1.1. The above range of Si:C elemental ratios is advantageous for satisfying capacity, lifespan, and processability. The Si / C is mainly composed of two elements, Si and C, and the influence of the remaining elements is excluded. C is measured through a CS analyzer, and the value obtained by subtracting its ratio from the total can be calculated as the Si content.

[0072] The above Si / C can be manufactured by including the steps of forming a core comprising a silicon carbon composite (Si / C) and forming a carbon layer provided on at least a portion of the core.

[0073] According to one embodiment, the step of forming a core including the silicon carbon composite may be manufactured by a method comprising: etching carbon-based particles (e.g., porous carbon) containing internal pores to expand the internal pores of the carbon-based particles; and forming silicon particles on the surface and internal pores of the carbon-based particles with expanded internal pores.

[0074] The step of expanding the internal pores of the carbon-based particles can be performed in a nitrogen (N2) atmosphere, an oxygen (O2) atmosphere, or an air atmosphere. For example, the flow rate of the oxygen (O2) or the air containing oxygen can be controlled to about 0.1 L / min to 10 L / min.

[0075] The step of expanding the internal pores of the carbon-based particles can be performed for 30 minutes to 4 hours at a temperature range of about 400°C to 1200°C.

[0076] Depending on the conditions for expanding the internal pores of the above-mentioned carbon-based particles, the pore characteristics of the obtained porous carbon-based particles may vary.

[0077] An etching agent may be used to expand the internal pores of the carbon-based particles, and a basic material such as KOH may be used. For example, the internal pores of the carbon-based particles may be expanded by mixing the carbon-based particles and KOH in a weight ratio of about 1:1 to 1:5.

[0078] The step of forming the silicon particles can be performed using chemical vapor deposition (CVD). At this time, silicon nanoparticles are deposited on the surface and / or internal pores of the carbon-based particles with expanded internal pores, thereby forming a silicon coating layer in the form of a film, an island, or a mixture thereof.

[0079] The step of forming the silicon particles above can be performed by using a chemical vapor deposition (CVD) apparatus to flow SiH4 / H2 gas through carbon-based particles at approximately 500°C to 900°C to form a silicon-carbon composite.

[0080] The step of forming the carbon layer above can be performed by using a chemical vapor deposition (CVD) method using a carbon-based material, for example, a hydrocarbon gas, or by carbonizing a material that serves as a carbon source.

[0081] For example, a carbon layer can be formed by introducing a core containing the above silicon-carbon composite into a reactor and then chemically vaporizing (CVD) a hydrocarbon gas at about 600°C to 700°C. The hydrocarbon gas may be at least one hydrocarbon gas selected from methane, ethane, propane, and acetylene.

[0082] In one embodiment of the present invention, the coating layer included in the negative electrode active material together with the silicon-based active material comprises a metal oxide and a water-based binder.

[0083] Since the above metal oxide is characterized by having high hardness, the coating layer containing the metal oxide can increase the durability of the silicon-based active material and suppress rapid volume expansion of the silicon-based active material in the operating environment.

[0084] In one embodiment of the present invention, the metal oxide may be represented by the following formula 1.

[0085] [Equation 1]

[0086] M a O b (1≤a≤2, 1≤b≤5)

[0087] In the above Equation 1, M is any one of Al, Ti, and Mg. In the above Equation 1, when M is any one of Al, Ti, and Mg, volume expansion can be mitigated by forming a coating layer on a silicon-based active material without degrading the performance of the secondary battery. For example, in the above Equation 1, if M is a metal oxide including Zn, Fe, Cu, Ni, Sn, Sb, Cr, Zr, and V, a short circuit may occur due to metal leaching, etc., within the metal oxide depending on the operating voltage range, and thus the battery operating voltage may be lowered. Therefore, M can be selected as any one of Al, Ti, and Mg.

[0088] In one embodiment of the present invention, the metal oxide may include at least one selected from Al2O3, TiO2, and MgO. When the metal oxide includes the above types, a coating layer can be formed on a silicon-based active material to mitigate volume expansion without degrading the performance of the secondary battery.

[0089] In one embodiment of the present invention, the metal oxide may comprise at least one selected from Al2O3, TiO2, and MgO, and for example, the metal oxide may be Al2O3.

[0090] According to one embodiment of the present invention, the average particle size (D50) of the metal oxide may be about 1 nm to 100 nm. For example, the average particle size (D50) of the metal oxide may be about 1 nm or more or 2 nm or more, and may be 100 nm or less, 80 nm or less, 50 nm or less, 30 nm or less, or 20 nm or less. When the average particle size (D50) of the metal oxide falls within the above range and is a nano particle, a coating layer can be uniformly formed on the surface of the active material without interfering with the behavior of lithium ions in a cell operating environment.

[0091] The average particle size of the above metal oxide is the volume average of the diameter (sphere-converted particle diameter) when each metal oxide particle is converted into a sphere of the same volume, and this value can be obtained by electron microscope observation. For example, when observing metal oxides with an electron microscope, the value is obtained by measuring the diameters of 200 or more metal oxide particles within a certain field of view, determining the sphere-converted particle diameter of each particle, and calculating the average value.

[0092] The above-mentioned aqueous binder has flexibility and is included in the coating layer to mitigate particle breakage even when the particle volume of the silicon-based active material expands; additionally, by being mixed with a metal oxide within the silicon-based active material coating layer, it serves to improve the adhesion between the silicon-based active material and the coating layer.

[0093] In addition, in the aqueous process of the cathode slurry manufacturing process, in the case of silicon-based active materials, gas such as hydrogen may be generated during the process, causing problems in the process progress; however, the cathode active material according to one embodiment of the present invention can reduce gas generation in the slurry during the aqueous process because the coating layer can block direct contact between the silicon-based active material core and the aqueous solvent (e.g., distilled water).

[0094] In this specification, the aqueous binder included in the coating layer is distinguished from the cathode binder to be described later, and the aqueous binder according to one embodiment of the present invention is included in the coating layer provided on silicon-based active material particles. For example, the aqueous binder is located on the coating layer surrounding the silicon-based active material, whereas the cathode binder to be described later is observed between the cathode active material particles in a form evenly dispersed in the cathode active material layer.

[0095] In one embodiment of the present invention, the aqueous binder may comprise at least one selected from polyacrylamide (PAM), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyethylene glycol (PEG), carboxymethyl cellulose (CMC), polyvinyl acetate (PVAc), polyvinylpyrrolidone (PVP), and materials in which the hydrogens thereof are substituted with Li, Na, or Ca.

[0096] In one embodiment of the present invention, the aqueous binder may comprise at least one selected from polyacrylamide (PAM), polyacrylic acid (PAA), and materials in which the hydrogens thereof are substituted with Li, Na, or Ca.

[0097] For example, the above-mentioned aqueous binder may include at least one selected from polyacrylamide (PAM) and materials in which the hydrogens thereof are substituted with Li, Na, or Ca.

[0098] In one embodiment of the present invention, the weight-average molecular weight (Mw) of the aqueous binder may be about 1,000 g / mol to 1,000,000 g / mol. For example, the weight-average molecular weight (Mw) of the aqueous binder may be about 1,000 g / mol or more, 10,000 g / mol or more, 50,000 g / mol or more, 100,000 g / mol or more, 500,000 g / mol or more, and about 1,000,000 g / mol or less, 800,000 g / mol or less, or 700,000 g / mol or less. When the weight-average molecular weight of the aqueous binder falls within the above range, the aqueous binder may be evenly dispersed on the coating layer.

[0099] FIG. 1 is a diagram illustrating a negative electrode active material according to one embodiment of the present invention. Referring to FIG. 1, a coating layer (2) is provided to surround at least a portion of a silicon-based active material (1), and the coating layer (2) is provided by mixing a metal oxide (21) and a water-based binder (22).

[0100] According to one embodiment of the present invention, the coating layer (2) is provided on at least a portion of the silicon-based active material (1), for example, on at least a portion of the surface of the silicon-based active material.

[0101] The coating layer (2) may exist as an island-type or thin film-type layer on the silicon-based active material (1), and may exist in various forms, not limited thereto.

[0102] In one embodiment of the present invention, since the coating layer (2) contains both a water-based binder (22) and a metal oxide (21), the adhesion between the silicon-based active material (1) and the coating layer (2) is excellent compared to cases where the coating layer is formed with only the metal oxide or only the water-based binder, and a thin and uniform coating layer (2) can be formed. If the coating layer (2) contains only the metal oxide (21), the metal oxide is not evenly dispersed on the coating layer (2), so the coating layer (2) may be formed unevenly, and if the coating layer (2) contains only the water-based binder (22), there is a problem that the coating layer (2) is not formed on the negative electrode active material (1).

[0103] In one embodiment of the present invention, the coating layer (2) may contain the metal oxide (21) and the water-based binder (22) in a weight ratio of about 50:50 to 95:5, for example, in a weight ratio of about 70:30 to 90:10. For example, the coating layer (2) may contain the metal oxide and the water-based binder in a weight ratio of about 70:30 or more, and may contain them in a weight ratio of about 90:10 or less or 85:15 or less.

[0104] When the metal oxide (21) and the aqueous binder (22) are included within the above range, the coating layer (2) can perform a sufficient resistance on the surface of the silicon-based active material (1), the coating layer is formed uniformly, and the battery performance can be improved.

[0105] Another feature of the present invention is that by optimizing the weight ratio of the metal oxide (21) and the water-based binder (22) in the coating layer (2) as described above, it is possible to prevent or suppress performance degradation caused by particle expansion of the silicon-based active material (1) without affecting the operation of the lithium ion.

[0106] According to one embodiment of the present invention, the average thickness of the coating layer (2) may be about 100 nm to 1 μm. For example, the average thickness of the coating layer (2) may be about 200 nm or more, 230 nm or more, 250 nm or more, or 280 nm or more, and may be about 1 μm or less, 500 nm or less, or 400 nm or less. That the average thickness of the coating layer falls within the above range means that the coating layer (2) is provided on at least a portion of the silicon-based active material (1), and that 50% or more of the thickness of the coating layer (2) falls within the above range.

[0107] When the average thickness of the coating layer (2) falls within the above range, external exposure of the surface of the silicon-based active material (1) can be blocked, or the physical resistance of the silicon-based active material itself can be increased to prevent or suppress deterioration caused by volume expansion and particle fracture of the silicon-based active material. In addition, when the thickness of the coating layer (2) falls within the above range, direct contact between the silicon-based active material (1) core and the aqueous solvent can be blocked, thereby reducing the generation of unnecessary gas (e.g., hydrogen (H2) gas) in the slurry during the aqueous process, and thus improving the processability of the aqueous process.

[0108] The thickness of the coating layer (2) can be measured through cross-sectional analysis of the cathode containing the cathode active material (1), and the cross-sectional analysis of the cathode can be performed using an ion milling device. For example, an electrode sample is milled using a Hitachi IM4000 device. After processing the sample for about 3 to 4 hours by firing an ion beam at a voltage of 1.5 kV, a cross-sectional image can be measured using a Hitachi S-4800 SEM. The thickness can be measured for each particle observed in each SEM image obtained from the cross-sectional image, and the average value of the thickness of the coating layer (2) measured in each cross-sectional image obtained by randomly selecting five regions of the cross-section and photographing the cross-section with 10K magnification can be used.

[0109] In one embodiment of the present invention, the average particle size (D50) of the negative electrode active material may be about 1 μm to 20 μm. When the average particle size is within the above range, the specific surface area of ​​the particles does not increase excessively, and the viscosity of the negative electrode slurry does not increase excessively. Accordingly, the dispersion of particles constituting the negative electrode slurry can be smooth. Furthermore, when the average particle size is within the above range, the contact area between silicon particles and conductive materials is appropriately maintained by a composite of a conductive material and a binder within the negative electrode slurry, so the conductive network is not interrupted and the capacity retention rate is improved. In addition, when the average particle size is within the above range, excessively large silicon particles are not present, so the surface of the negative electrode becomes smooth, and accordingly, non-uniformity of current density does not occur during charging and discharging. In addition, since the phase stability of the negative electrode slurry is stabilized, processability is improved. Accordingly, the capacity retention rate of the battery is improved.

[0110] The above “average particle size (D50) of the negative electrode active material” is distinguished from the “average particle size (D50) of the silicon-based active material” and refers to the average particle size (D50) of the final negative electrode active material having a coating layer on the silicon-based active material.

[0111] cathode composition

[0112] One embodiment of the present invention provides a cathode composition comprising a cathode active material according to one embodiment of the present invention.

[0113] The above cathode composition may further include an additional cathode active material. As the additional cathode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO₂ βExamples include metal oxides capable of doping and dedoping lithium, such as (0 < β < 2), SnO2, vanadium oxide, lithium titanium oxide, and lithium vanadium oxide; or composites comprising the metal compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more of these may be used. Additionally, a metallic lithium thin film may be used as the negative electrode active material. Furthermore, the carbon material may include low-crystallinity carbon and high-crystallinity carbon. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0114] One embodiment of the present invention provides a cathode composition further comprising a carbon-based active material as a cathode active material. The carbon-based active material comprises at least one selected from natural graphite and artificial graphite.

[0115] According to one embodiment of the present invention, the additional negative electrode active material may be a carbon-based active material. The carbon-based active material may be graphite, and the graphite may include at least one type selected from natural graphite and artificial graphite.

[0116] The above carbon-based active material may be natural graphite, artificial graphite, or a mixture of natural graphite and artificial graphite.

[0117] 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.

[0118] In addition, the artificial graphite may have an average particle size (D50) of about 5 μm to 30 μm, for example, about 10 μm to 25 μm.

[0119] The above natural graphite generally exists as plate-like aggregates before 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.

[0120] In addition, the natural graphite may have a particle size of about 5 µm to 30 µm, or about 10 µm to 25 µm.

[0121] 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 about 9.99 : 0.01 to 0.01 : 9.99, or about 9.7 : 0.3 to 7:3. When satisfying this weight ratio range, superior output can be exhibited.

[0122] When a silicon-based negative electrode active material according to one embodiment of the present invention is referred to as a first negative electrode active material and the additional carbon-based negative electrode active material is referred to as a second negative electrode active material, the first negative electrode active material may be included in an amount of about 1 to 30 parts by weight based on 100 parts by weight of the total first and second negative electrode active materials. For example, the first negative electrode active material may be included in an amount of about 1 part by weight or more or 2 parts by weight or more based on 100 parts by weight of the total first and second negative electrode active materials, and may be included in an amount of about 30 parts by weight or less, 25 parts by weight or less, 20 parts by weight or less, or 15 parts by weight or less.

[0123] In one embodiment of the present invention, the second negative electrode active material may be included in an amount of about 70 parts by weight or more based on 100 parts by weight of the total first and second negative electrode active materials. For example, the second negative electrode active material may be included in an amount of about 70 parts by weight or more, 75 parts by weight or more, 80 parts by weight or more, 90 parts by weight or more, 98 parts by weight or more, or 99 parts by weight or more based on 100 parts by weight of the total first and second negative electrode active materials, and may be included in an amount of about 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.

[0124] A cathode composition according to one embodiment of the present invention may include a first cathode active material having a significantly high capacity, such that the first cathode active material (1), which is a silicon-based cathode active material (1), includes a coating layer (2) capable of preventing or suppressing volume expansion and particle breakage during the charging and discharging process, within the above range. Accordingly, it has the characteristic of having excellent output characteristics and capacity during charging and discharging without degrading the performance of the cathode.

[0125] One embodiment of the present invention provides a cathode composition in which the cathode composition further comprises a cathode binder.

[0126] In one embodiment of the present invention, the cathode binder comprises a water-based binder.

[0127] In one embodiment of the present invention, the cathode binder may comprise at least one selected from polyvinylidenefluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidenefluoride, 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, and may also comprise various copolymers thereof.

[0128] A cathode binder according to one embodiment of the present invention serves to hold active material and conductive material in order to prevent or suppress distortion or structural deformation of the cathode structure, and any general binder that satisfies the above role may be applied, and according to one embodiment, a water-based binder may be used.

[0129] In one embodiment of the present invention, the cathode binder comprises a water-based binder, and the cathode binder comprises about 1 part by weight or more and 10 parts by weight or less based on 100 parts by weight of the cathode composition.

[0130] In another embodiment, the cathode binder may be included in an amount of about 1 part by weight or more, 2 parts by weight or more, 2.5 parts by weight or more, or about 3 parts by weight or less based on 100 parts by weight of the cathode composition, and may be included in an amount of 10 parts by weight or less, 7 parts by weight or less, 5 parts by weight or less, or 3 parts by weight or less.

[0131] In the case of the negative electrode according to the present invention, a silicon-based active material (1) or a modified version thereof is used in the above weight portion to maximize capacity characteristics, and compared to a secondary battery using only a conventional carbon-based active material, the volume expansion during charging and discharging is significantly increased. Accordingly, the negative electrode binder in the above content portion has the characteristic of efficiently controlling the volume expansion of the silicon-based active material (1) with high rigidity during charging and discharging.

[0132] One embodiment of the present invention provides a cathode composition in which the cathode composition further comprises a cathode binder; and a cathode conductive material.

[0133] In one embodiment of the present invention, the conductive material may include one or more selected from point-type conductive materials, planar-type conductive materials, and linear-type conductive materials.

[0134] 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 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, or may include carbon black in terms of achieving high conductivity and excellent dispersibility.

[0135] In one embodiment of the present invention, the point-shaped conductive material has a BET specific surface area of ​​approximately 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.

[0136] In one embodiment of the present invention, the conductive material may include a planar conductive material.

[0137] 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.

[0138] 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.

[0139] In one embodiment of the present invention, the average particle size (D50) of the planar conductive material may be about 2 μm to 7 μm, for example, about 3 μm to 6 μm, or about 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.

[0140] In one embodiment of the present invention, the planar conductive material may be a high specific surface area planar conductive material having a high BET specific surface area; or a low specific surface area planar conductive material.

[0141] 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.

[0142] In one embodiment of the present invention, the planar conductive material has a BET specific surface area of ​​approximately 5 m² 2 It can be more than / g.

[0143] In another embodiment, the planar conductive material has a BET specific surface area of ​​approximately 5 m² 2 / g or more than 500m 2 It may be less than / g, for example, about 5m 2 / g or more than 300m 2 / g or less, or about 5m 2 / g or more 250m 2 It may be less than / g.

[0144] In another embodiment, the planar conductive material is a high specific surface area planar conductive material, with a BET specific surface area of ​​approximately 50 m² 2 / g or more than 500m 2 / g or less, or about 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.

[0145] In another embodiment, the planar conductive material is a low specific surface area planar conductive material, with a BET specific surface area of ​​approximately 5 m² 2 / g or more 40m 2 / g or less, e.g., about 5m 2 / g or more 30m 2 / g or less, or about 5m 2 / g or more 25m 2 It can satisfy a range of / g or less.

[0146] 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 length 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.

[0147] In one embodiment of the present invention, the linear conductive material may include SWCNT; or MWCNT.

[0148] In one embodiment of the present invention, a cathode composition is provided in which the cathode conductive material is in an amount of about 0.01 parts by weight or more and 10 parts by weight or less based on 100 parts by weight of the cathode slurry.

[0149] In another embodiment, the cathode conductive material may be included in an amount of about 0.01 parts by weight or more or 0.05 parts by weight or more based on 100 parts by weight of the cathode composition, and may be included in an amount of about 10 parts by weight or less, 5 parts by weight or less, or 3 parts by weight or less.

[0150] 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, whereas the anode conductive material serves as a buffer during rolling and provides some conductivity; thus, their composition and roles are completely different from those of the cathode conductive material of the present invention.

[0151] Furthermore, the cathode conductive material according to the present invention is applied to a silicon-based active material and has a completely different composition from a conductive material applied to a cathode composition containing only a graphite-based active material. For example, a conductive material used in an electrode having a graphite-based active material simply has particles smaller than the active material, thereby providing improved output characteristics and some conductivity; thus, its composition and role are completely different from a cathode conductive material applied together with a silicon-based active material as in the present invention.

[0152] cathode

[0153] FIG. 2 is a diagram showing a stacked structure of a cathode according to one embodiment of the present invention.

[0154] Referring to FIG. 2, a cathode (100) according to one embodiment of the present invention comprises a cathode current collector layer (10); and a cathode active material layer (20) provided on one or both sides of the cathode current collector layer (10), wherein the cathode active material layer (20) comprises a cathode composition according to one embodiment of the present invention.

[0155] Meanwhile, FIG. 2 shows that the negative active material layer (20) is formed on one side of the negative current collector layer (10), but is not limited thereto, and for example, the negative active material layer (20) can be formed on both sides of the negative current collector layer (10).

[0156] In one embodiment of the present invention, the cathode (100) 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 (10).

[0157] At this time, the cathode slurry may include the aforementioned cathode composition; and a slurry solvent.

[0158] In one embodiment of the present invention, the solid content of the cathode slurry may satisfy an amount of about 5% or more and 60% or less. In another embodiment, the solid content of the cathode slurry may satisfy an amount of about 5% or more and 60% or less, for example, an amount of about 7% or more and 50% or less, or an amount of about 10% or more and 50% or less.

[0159] 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.

[0160] 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.

[0161] 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 or NMP (N-Methyl-2Pyrrolidone) may be used.

[0162] In one embodiment of the present application, the negative current collector layer (10) has a thickness of about 1 μm to 100 μm. The negative current collector layer (10) 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, a surface treated with carbon, nickel, titanium, silver, etc. on the surface of copper or stainless steel, an aluminum-cadmium alloy, etc. 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 body, etc.

[0163] In one embodiment of the present invention, a cathode (100) is provided in which the thickness of the cathode current collector layer (10) is about 1 μm to 100 μm or less, and the thickness of the cathode active material layer (20) is about 5 μm to 500 μm.

[0164] However, the thickness of the above-mentioned negative current collector layer (10) and negative active material layer (20) can be varied in various ways depending on the type and use of the negative electrode (100) used, and is not limited thereto.

[0165] In one embodiment of the present invention, the porosity of the negative electrode active material layer (20) is not particularly limited but can satisfy a range of about 10% or more and 60% or less.

[0166] In another embodiment, the porosity of the cathode active material layer (20) may satisfy a range of about 10% or more and 60% or less, for example, about 20% or more and 50% or less, or about 30% or more and 45% or less.

[0167] The above porosity varies according to the composition and content of the cathode active material; conductive material; and binder included in the cathode active material layer (20). For example, the above range is satisfied by including the cathode active material; and conductive material according to the present application in a specific composition and content, and accordingly, the electrical conductivity and resistance of the electrode have an appropriate range.

[0168] secondary battery

[0169] FIG. 3 is a diagram showing a stacked structure of a secondary battery according to one embodiment of the present application.

[0170] Referring to FIG. 3, a secondary battery (300) according to one embodiment of the present application further comprises: a positive electrode (200); a negative electrode (100) according to one embodiment of the present invention; a separator (30) provided between the positive electrode (200) and the negative electrode (100); and an electrolyte (not shown).

[0171] A secondary battery (300) according to one embodiment of the present invention comprises a negative electrode (100) including a negative electrode active material layer (20) on one surface of a negative electrode current collector layer (10), and a positive electrode (200) including a positive electrode active material layer (40) on one surface of a positive electrode current collector layer (50), wherein the negative electrode (100) and the positive electrode (200) are formed in a structure in which they are stacked with a separator (30) in between.

[0172] The above positive electrode (200) 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.

[0173] In the above positive electrode (200), the positive electrode 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 positive electrode current collector may typically have a thickness of about 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 electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven body, etc.

[0174] 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 (wherein M is at least one selected from Co, Ni, Fe, Cr, Zn and Ta, satisfying 0.01≤c3≤0.1) or Li2Mn3MO8 (wherein M is at least one selected from 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. According to one embodiment, the anode may be Li-metal.

[0175] 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.

[0176] The above-mentioned positive electrode conductive material is used to impart conductivity to the electrode, and in the battery being constructed, any material that possesses electronic conductivity without causing chemical changes can be used without any 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 powders 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.

[0177] 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.

[0178] The separator (30) above separates the negative electrode (100) and the positive electrode (200) and provides a pathway for the movement of lithium ions. Any separator typically used in secondary batteries can be used without special limitations, 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.

[0179] Examples of the above electrolytes that can be used when manufacturing a lithium secondary battery (300) 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.

[0180] The above electrolyte may include a non-aqueous organic solvent and a metal salt.

[0181] 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.

[0182] Among the above carbonate-based organic solvents, cyclic carbonates such as ethylene carbonate and propylene carbonate can be preferably used as high-viscosity organic solvents with high dielectric constants that effectively dissociate lithium salts. Additionally, if low-viscosity, low-dielectric constant linear carbonates such as dimethyl carbonate and diethyl carbonate are mixed with these cyclic carbonates in appropriate proportions, an electrolyte with high electrical conductivity can be produced.

[0183] 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.

[0184] 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.

[0185] Battery modules and battery packs

[0186] One embodiment of the present invention provides a battery module including a secondary battery (300) according to one embodiment of the present invention.

[0187] One embodiment of the present invention provides a battery pack including a secondary battery (300) according to one embodiment of the present invention.

[0188] One embodiment of the present invention provides a battery pack including a battery module according to one embodiment of the present invention.

[0189] One embodiment of the present invention provides a battery module comprising the secondary battery (300) as a unit cell and a battery pack comprising the secondary battery (300) or the battery module. Since the battery module and the battery pack include the secondary battery (300) 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.

[0190] Hereinafter, examples are presented to aid in understanding the present invention; however, the above examples 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.

[0191] <Preparation Example>

[0192] <Example 1>

[0193] 1) Preparation of cathode active material

[0194] Aluminum oxide (Al2O3, average particle size (D50) = 11 nm) as a metal oxide and polyacrylamide (PAM, weight-average molecular weight (MW) = 650,000 g / mol) as a water-based binder were prepared in a ratio of metal oxide to water-based binder = 80:20 parts by weight. The metal oxide, water-based binder, and silicon-based active material (pure Si powder, average particle size (D50) = 2.95 μm) were prepared in a weight ratio of 95:4:1, and a coating composition was formed by adding them to distilled water as a solvent. The above coating composition was injected into a ball mill device (manufacturer: Laval lab, product name: Planetary ball mill pulverisette 5) and wet milling was performed at 1,000 rpm for 6 hours. After wet milling, the coating composition was filtered to obtain a solid material, which was then vacuum dried at 120°C for 24 hours to remove residual solvent on the surface, thereby producing a powder-type negative electrode active material with a coating layer formed on the surface of the silicon-based active material.

[0195] The average particle size (D50) of the manufactured cathode active material was 3.7 μm, and the average thickness of the coating layer was 350 nm.

[0196] 2) Preparation of cathode slurry

[0197] As the first cathode active material, the cathode active material prepared in 1) of Example 1 above was mixed with graphite (natural graphite (average particle size (D50): 17 μm)) as the second cathode active material in a ratio of 5:95 to prepare a cathode active material mixture. For every 100 parts by weight of the cathode composition, 96 parts by weight of the cathode active material mixture, 0.85 parts by weight of SWCNT (single-walled carbon nanotube) as a conductive material, and 1.7 parts by weight, 1.4 parts by weight, and 0.05 parts by weight of polyacrylamide (PAM), SBR, and CMC as binders (total binder 3.15 parts by weight) were prepared, and a cathode slurry was prepared by adding it to distilled water as a solvent (solid content 46 wt%).

[0198] For example, SWCNT, PAM, SBR, and CMC and distilled water were dispersed using a homo mixer at 2,500 rpm for 30 minutes, and then the cathode active material was added and dispersed at 2,500 rpm for 30 minutes to prepare a cathode slurry.

[0199] The above SWCNT 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.

[0200] The above PAM was used in an aqueous form with a weight-average molecular weight (Mw) of 500,000 g / mol to 800,000 g / mol and a number-average molecular weight (Mn) of 100,000 to 400,000, having a PDI value of 10 to 30. The binder was in an aqueous form, and the weight-average molecular weight and number-average molecular weight were measured using aqueous GPC (Gel permeation chromatography).

[0201] 3) Preparation of the cathode

[0202] As a cathode current collector layer, the above cathode slurry is applied at a rate of 189 mg / 25 cm on both sides of a copper current collector (thickness 15 μm). 2 A cathode was manufactured by forming a cathode active material layer by coating with a loading amount, rolling, and drying in a vacuum oven at 130°C for 10 hours (cathode thickness 65㎛).

[0203] 4) Manufacturing of secondary batteries

[0204] LiNi as a positive electrode active material 0.6 Co 0.2 Mn 0.2O2 (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%).

[0205] 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 An anode was manufactured by forming an anode active material layer by coating with a loading amount, rolling, and drying in a vacuum oven at 130°C for 10 hours (anode thickness: 75㎛).

[0206] A lithium secondary battery was manufactured by interposing a polyethylene separator between the anode and the cathode and injecting an electrolyte.

[0207] 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.

[0208] Example 2

[0209] A secondary battery was manufactured in the same manner as in Example 1, except that in the preparation of the negative electrode active material in 1) of Example 1, the metal oxide and water-based binder were mixed in a ratio of 70:30 by weight. The average particle size (D50) of the negative electrode active material prepared in 1) was 3.7 μm, and the average thickness of the coating layer was 350 nm.

[0210] Example 3

[0211] A secondary battery was manufactured in the same manner as in Example 1, except that in the preparation of the negative electrode active material in 1) of Example 1, the metal oxide and water-based binder were mixed in a ratio of 90:10 by weight. The average particle size (D50) of the negative electrode active material prepared in 1) was 3.6 μm, and the average thickness of the coating layer was 300 nm.

[0212] Example 4

[0213] A secondary battery was manufactured in the same manner as in Example 1, except that in the preparation of the negative electrode active material in 1) of Example 1, the metal oxide and water-based binder were mixed in a ratio of 60:40 by weight. The average particle size (D50) of the negative electrode active material prepared in 1) was 3.7 μm, and the average thickness of the coating layer was 350 nm.

[0214] Example 5

[0215] A secondary battery was manufactured in the same manner as in Example 1, except that in the preparation of the negative electrode active material in 1) of Example 1, the metal oxide and water-based binder were mixed in a ratio of 95:5 by weight. The average particle size (D50) of the negative electrode active material prepared in 1) was 3.5 μm, and the average thickness of the coating layer was 250 nm.

[0216] Comparative Example 1

[0217] A secondary battery was manufactured in the same manner as in Example 1, except that in the preparation of the negative electrode active material in Example 1 1) a silicon-based active material (pure Si powder, average particle size (D50) = 2.95 μm) was prepared as the negative electrode active material. That is, in Comparative Example 1, a silicon-based active material without a coating layer was used as the negative electrode active material.

[0218] Comparative Example 2

[0219] Aluminum oxide (Al2O3, average particle size (D50) = 11 nm) was prepared as a metal oxide. The metal oxide and a silicon-based active material (pure Si powder, average particle size (D50) = 2.95 μm) were prepared in a weight ratio of 95:5 and added to distilled water as a solvent to form a coating composition. The coating composition was injected into a ball mill device (manufacturer: Laval lab, product name: Planetary ball mill pulverisette 5) and wet milling was performed at 1,000 rpm for 6 hours. After wet milling, the coating composition was filtered to obtain a solid material, which was then vacuum dried at 120°C for 24 hours to remove residual solvent from the surface, thereby producing a powder-type negative electrode active material with a coating layer formed on the surface of the silicon-based active material. The average particle size (D50) of the manufactured cathode active material was 3.1 μm, the coating layer was formed unevenly, and the average thickness of the coating layer was 50 nm.

[0220] The subsequent process involved manufacturing a secondary battery in the same manner as in Example 1. That is, Comparative Example 2 was used as a negative electrode active material in which the coating layer did not contain a water-based binder.

[0221] Comparative Example 3

[0222] Polyacrylamide (PAM, weight-average molecular weight (MW) = 650,000 g / mol) was prepared as an aqueous binder. The above aqueous binder and a silicon-based active material (pure Si powder, average particle size (D50) = 2.95 μm) were prepared in a weight ratio of 95:5 and added to distilled water as a solvent to form a coating composition. The coating composition was injected into a ball mill device (manufacturer: Laval lab, product name: Planetary ball mill pulverisette 5) and wet milling was performed at 1,000 rpm for 6 hours. After wet milling, the coating composition was filtered to obtain a solid material, which was then vacuum dried at 120°C for 24 hours to remove residual solvent from the surface, thereby producing a powder-type negative electrode active material with a coating layer formed on the surface of the silicon-based active material. The average particle size (D50) of the manufactured negative electrode active material was 3 μm, and since almost no coating layer was observed on the silicon-based active material, the thickness of the coating layer could not be measured.

[0223] The subsequent process involved manufacturing a secondary battery in the same manner as in Example 1. That is, Comparative Example 3 was used as a negative electrode active material in which the coating layer did not contain metal oxide.

[0224] Example 6

[0225] Spherical particles were synthesized by placing a 0.5 M aqueous sucrose solution into an autoclave and reacting it at 180°C for 24 hours. The carbon-based particles obtained after the reaction were washed with ethanol 2 to 3 times. Porous carbon was prepared by mixing the carbon-based particles, dried at 100°C for more than 12 hours, with KOH in a 1:3 weight ratio and heating at 800°C for 2 hours under a nitrogen atmosphere to expand the pores. Subsequently, the porous carbon was washed with distilled water and dried at 100°C for more than 12 hours. The porous carbon with the formed oxide layer was placed in the hot zone of a CVD apparatus, and SiH4 / H2=5 / 95 gas was flowed at a flow rate of 50 ml / min at 600°C for 2 hours to deposit silicon inside the porous carbon, thereby producing a Si / C (silicon carbon composite). Subsequently, a silicon-carbon composite was placed in the hot zone of a CVD device, and methane was blown into a hot zone at 700°C using Ar as a carrier gas and reacted for 1 hour to form a carbon layer on the surface, thereby producing a silicon-based active material Si / C (average particle size (D50): 8.1 μm) containing a carbon layer on the surface of the silicon-carbon composite.

[0226] Subsequently, a secondary battery was manufactured in the same manner as in Example 1, except that in the preparation of the negative electrode active material of Example 1 1) the silicon-based active material, Si / C prepared in the same manner was used instead of pure Si powder. The average particle size (D50) of the manufactured negative electrode active material was 8.6 μm, and the average thickness of the coating layer was 270 nm.

[0227] Example 7

[0228] A secondary battery was manufactured in the same manner as in Example 6, except that in the preparation of the negative electrode active material in 1) of Example 6, the metal oxide and water-based binder were mixed in a ratio of 70:30 by weight. In the preparation of the negative electrode active material in 1) above, the average particle size (D50) of the manufactured negative electrode active material was 8.7 μm, and the average thickness of the coating layer was 300 nm.

[0229] Example 8

[0230] A secondary battery was manufactured in the same manner as in Example 6, except that in the preparation of the negative electrode active material in 1) of Example 6, the metal oxide and water-based binder were mixed in a ratio of 90:10 by weight. In the preparation of the negative electrode active material in 1) above, the average particle size (D50) of the manufactured negative electrode active material was 8.7 μm, and the average thickness of the coating layer was 280 nm.

[0231] Example 9

[0232] A secondary battery was manufactured in the same manner as in Example 6, except that in the preparation of the negative electrode active material in 1) of Example 6, the metal oxide and water-based binder were mixed in a ratio of 95:5 by weight. In the preparation of the negative electrode active material in 1) above, the average particle size (D50) of the manufactured negative electrode active material was 8.6 μm, and the average thickness of the coating layer was 230 nm.

[0233] Comparative Example 4

[0234] A secondary battery was manufactured in the same manner as in Example 6, except that in the preparation of the negative electrode active material in 1) of Example 6, a silicon-based active material (Si / C, average particle size (D50) = 8.1 μm) was prepared as the negative electrode active material. That is, in Comparative Example 4, a silicon-based active material without a coating layer was used as the negative electrode active material.

[0235] Comparative Example 5

[0236] A secondary battery was manufactured using the same method as Comparative Example 2, except that in the manufacturing method of Comparative Example 2, Si / C of Example 6 was used instead of pure Si powder as the silicon-based active material.

[0237] The average particle size (D50) of the manufactured negative electrode active material was 8.2 μm, the coating layer was formed non-uniformly, and the average thickness of the coating layer was 70 nm. Subsequently, a secondary battery was manufactured in the same manner as in Example 6. That is, Comparative Example 5 was used as a negative electrode active material in which the coating layer did not contain a water-based binder.

[0238] Comparative Example 6

[0239] A secondary battery was manufactured using the same method as Comparative Example 3, except that in the manufacturing method of Comparative Example 3, Si / C of Example 6 was used instead of pure Si powder as the silicon-based active material.

[0240] The average particle size (D50) of the manufactured negative electrode active material was 8.1 μm, and since almost no coating layer was observed on the silicon-based active material, the thickness of the coating layer could not be measured.

[0241] Experimental Example 1: Evaluation of Dose Retention Rate

[0242] For the secondary batteries prepared in the above examples and comparative examples, a lifespan evaluation was conducted using an electrochemical charge / discharger, and the capacity retention rate was evaluated. The secondary batteries were subjected to in-situ cycle tests at 4.2-2.5V, 1C charge, and 1C discharge. The test was terminated after 200 cycles of discharge, and the capacity retention rate was measured by performing 0.33C / 0.33C charge / discharge (4.2-2.5V) every 50 cycles and is shown in Tables 1 and 2.

[0243] Capacity Retention Rate (%) = {(Discharge Capacity at the Nth Cycle) / (Discharge Capacity at the 1st Cycle)} * 100 %

[0244] Experimental Example 2: Evaluation of Slurry Water Processability

[0245] For the cathode slurries prepared in the above examples and comparative examples, the water-based processability of the slurry was evaluated by measuring the change in gas generated after placing the cathode slurry in a battery case and storing it at a high temperature.

[0246] For example, each cathode slurry was placed in a battery case and stored in a 60°C constant temperature chamber for 3 days, and after 3 days, the volume difference before and after storage was measured. In the case of the generated gas volume, the difference in mass measured in the cathode slurry was converted into volume based on Archimedes' principle and expressed, and the amount of gas generated is shown in Tables 1 and 2 below.

[0247] Gas generation amount (%) = (Volume after storage - Volume before storage) / (Volume before storage) * 100 %

[0248] Type of silicon-based active material Coating layer Metal oxide: Water-based binder (weight ratio) Coating layer thickness (nm) Capacity retention rate (%) Gas generation amount (%) Example 1 Pure Si 80: 20 30 0 680 Example 2 Pure Si 70: 30 35 0 650 Example 3 Pure Si 90: 10 30 0 660 Example 4 Pure Si 60: 40 35 0 620 Example 5 Pure Si 95: 52 50 630 Comparative Example 1 Pure Si - 60 8.9 Comparative Example 2 Pure Si 100: 0 50 58 6.7 Comparative Example 3 Pure Si 0: 100 Coating layer cannot be formed 61 8.3

[0249] Referring to Table 1, Examples 1 to 5, which include a silicon-based negative electrode active material according to one embodiment of the present invention, showed a capacity retention rate of 62%-68% and a gas generation rate of 0%, while Comparative Examples 1 to 3 showed a capacity retention rate of 58%-61% and a gas generation rate of 6.7%-8.9%, confirming that Examples 1 to 5 exhibit superior capacity retention rates and gas generation rates compared to Comparative Examples 1 to 3.

[0250] Type of silicon-based active material Coating layer Metal oxide: Water-based binder (weight ratio) Coating layer thickness (nm) Capacity retention rate (%) Gas generation amount (%) Example 6 Deposited type Si / C 80:20 270 99.10 Example 7 Deposited type Si / C 70:30 300 98.30 Example 8 Deposited type Si / C 90:10 280 97.70 Example 9 Deposited type Si / C 95:52 30 96.80 Comparative Example 4 Deposited type Si / C -96.123 Comparative Example 5 Deposited type Si / C 100:07 095.512 Comparative Example 6 Deposited type Si / C 0:100 Coating layer cannot be formed 95.820

[0251] Referring to Table 2, Examples 6 to 9, which include a cathode active material according to one embodiment of the present invention, showed a capacity retention rate of 96.8% to 99.1% and a gas generation rate of 0%, while Comparative Examples 4 to 6 showed a capacity retention rate of 95.5% to 96.1% and a gas generation rate of 12% to 23%, confirming that Examples 6 to 9 exhibit superior capacity retention rates and gas generation rates compared to Comparative Examples 4 to 6.

[0252] Referring to Tables 1 and 2, Comparative Examples 1 and 4 used silicon-based active materials that did not undergo a separate coating layer formation process, and thus showed inferior capacity retention rate and gas generation amount. For example, regarding the gas generation amount, a large amount of gas was generated when comparing Comparative Example 1 with Comparative Examples 2 and 3, and Comparative Example 4 with Comparative Examples 5 and 6. This is understood to be because a large amount of gas (e.g., H2 gas) was generated in the slurry during the aqueous process as the silicon-based active material came into direct contact with the aqueous solvent.

[0253] In the case of Comparative Examples 2 and 5, silicon-based active materials with a coating layer formed solely of metal oxides were used; as the coating layer did not contain a water-based binder, the coating layer was formed unevenly on the silicon-based active material. Furthermore, in the case of Comparative Examples 3 and 6, silicon-based active materials with a coating layer formed solely of a water-based binder were used; as the coating layer did not contain metal oxides, almost no coating layer was formed on the silicon-based active material, and the thickness of the coating layer could not be measured. Consequently, in Comparative Examples 2, 3, 5, and 6, the coating layer failed to perform a sufficient resistance function, resulting in an inferior capacity retention rate; additionally, due to the insufficient coating layer, excessive gas generation occurred during the water-based process.

[0254] It is confirmed that Examples 1 to 3 exhibit a superior level of capacity retention rate compared to Examples 4 and 5. Additionally, it is confirmed that Examples 6 to 8 exhibit a superior level of capacity retention rate compared to Example 9. Through this, it can be confirmed that when the content of metal oxide and water-based binder within the coating layer is controlled to an optimal level, the coating layer is uniformly formed on the silicon-based active material. In the case of Example 4, it is understood that the coating layer did not sufficiently perform the role of a resistor because it contained relatively less metal oxide. Furthermore, in the case of Examples 5 and 9, it is understood that the capacity retention rate is low because the coating layer contained relatively less water-based binder, which reduced the flexibility of the coating layer, causing particle breakage due to changes in particle volume during charging and discharging to occur relatively more frequently, resulting in the generation of byproducts.

[0255] Although the foregoing has been described with reference to the embodiments of the present disclosure, a person skilled in the art or having ordinary knowledge in the art will understand that various modifications and changes can be made to the various embodiments of the present disclosure without departing from the technical scope of the various embodiments of the present disclosure as set forth in the claims below. Accordingly, the technical scope of the various embodiments of the present disclosure should not be limited to the contents described in the detailed description of the specification, but should be determined by the claims.

Claims

1. Silicon-based active material; and It includes a coating layer provided on the above silicon-based active material, and The above coating layer comprises a metal oxide and a water-based binder, and is a cathode active material.

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

3. In Claim 2, The above silicon-based active material includes Si, and A negative electrode active material comprising at least 70 parts by weight based on 100 parts by weight of the silicon-based active material.

4. In Claim 1, The above silicon-based active material is a negative electrode active material comprising Si / C.

5. In Claim 4, The above Si / C comprises porous carbon and silicon deposited on the porous carbon, a negative electrode active material.

6. In Claim 1, A cathode active material wherein the above metal oxide is represented by the following formula 1: [Equation 1] M a O b (1≤a≤2, 1≤b≤5) In the above Equation 1, M is any one of Al, Ti, and Mg.

7. In Claim 1, A negative electrode active material comprising at least one metal oxide selected from Al2O3, TiO2, and MgO.

8. In Claim 1, The above aqueous binder comprises at least one selected from polyacrylamide (PAM), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyethylene glycol (PEG), carboxymethyl cellulose (CMC), polyvinyl acetate (PVAc), polyvinylpyrrolidone (PVP), and materials in which the hydrogens thereof are substituted with Li, Na, or Ca, in a negative electrode active material.

9. In Claim 1, A negative electrode active material in which the coating layer comprises the metal oxide and the aqueous binder in a weight ratio of 70:30 to 90:

10.

10. In Claim 1, A cathode active material having an average particle size (D50) of 1 μm to 20 μm.

11. In Claim 1, A negative electrode active material having an average thickness of the coating layer of 100 nm to 1 μm.

12. A cathode composition comprising a cathode active material according to any one of claims 1 to 11.

13. In Claim 12, A cathode composition further comprising a carbon-based active material as the above-mentioned cathode active material.

14. In Claim 13, The above carbon-based active material comprises at least one selected from natural graphite and artificial graphite, forming a cathode composition.

15. In Claim 13, A cathode composition comprising at least 70 parts by weight of the above carbon-based active material based on 100 parts by weight of the cathode active material.

16. In Claim 12, The above cathode composition further comprises a cathode binder, and A cathode composition wherein the above cathode binder comprises a water-based binder.

17. 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, The cathode, wherein the cathode active material layer comprises the cathode composition according to claim 12.

18. Anode; and A secondary battery comprising a negative electrode according to claim 17.

19. A battery module comprising a secondary battery according to claim 18.

20. A battery pack comprising a secondary battery according to claim 18.