Silicon negative electrode active material, negative electrode, and secondary battery comprising same

Abstract

Disclosed is a silicon negative electrode active material which improves the lifespan and efficiency of a secondary battery. According to one aspect, provided is a silicon negative electrode active material comprising: silicon particles; a carbon material on the silicon particles; a conductive material; and an inorganic binder.

Description

Silicon negative electrode active material, negative electrode, and secondary battery containing the same

[0001] The present invention relates to a silicon negative electrode active material, and more specifically, to a silicon negative electrode active material, a negative electrode, and a secondary battery including the same.

[0002] The growth of information technology (IT) and the electric vehicle market is driving rapid technological advancements in the secondary battery industry, a key component. Lithium secondary batteries consist of four major materials: a cathode, anode, separator, and electrolyte. Graphite is currently the most widely used anode active material. However, graphite's low theoretical capacity (372 mAh / g, LiC6) hinders the high energy density of secondary batteries. Therefore, active research is underway to address this issue.

[0003] Metals that form alloys with lithium at low potentials, such as aluminum, germanium, silicon, tin, zinc, and lead, are mainly being studied as materials that can replace graphite. Among these, silicon has the highest theoretical capacity (3,579 mAh / g, Li 15 It has Si4) and has the advantage of reacting with lithium at a low potential of 0.4 V, being environmentally friendly and having abundant reserves. However, silicon has a problem in that volume changes occur during the insertion / de-insertion of lithium ions in a lithium secondary battery, which causes destruction of silicon particles and de-insertion from the current collector, resulting in a decrease in the capacity of the secondary battery.

[0004] The purpose of the present invention is to provide a silicon negative electrode active material capable of minimizing volume change of the silicon negative electrode active material.

[0005] Another object of the present invention is to provide a silicon negative electrode active material capable of minimizing capacity reduction of a battery according to charge / discharge cycles.

[0006] Another object of the present invention is to provide a silicon negative electrode active material that improves the capacity and lifespan of a secondary battery.

[0007] Another object of the present invention is to provide a silicon negative electrode active material that can effectively prevent destruction of particles during an electrode rolling process.

[0008] Another object of the present invention is to provide an economical method for producing a silicon negative electrode active material.

[0009] Another object of the present invention is to provide a negative electrode comprising a silicon negative electrode active material.

[0010] Another object of the present invention is to provide a secondary battery with improved lifespan and efficiency.

[0011] The purposes of the present invention are not limited to those mentioned above, and other unmentioned purposes and advantages of the present invention can be understood through the following description and will be more clearly understood through the embodiments of the present invention. Furthermore, it will be readily apparent that the purposes and advantages of the present invention can be realized by the means and combinations thereof described in the specification.

[0012] According to a first aspect of the present invention for achieving the above object, a silicon negative electrode active material is provided, comprising: silicon particles; a carbon material on the silicon particles; a conductive material; and an inorganic binder.

[0013] According to the second aspect of the present invention, the average particle diameter of the silicon particles in the first aspect may be 800 nm or less.

[0014] According to a third aspect of the present invention, the average particle diameter of the inorganic binder in the first or second aspect may be 20 to 100 nm.

[0015] According to a fourth aspect of the present invention, in any one of the first to third aspects, the carbon material on the silicon particle may be partially or completely coated on the surface of the silicon particle.

[0016] According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the conductive material may include at least one of graphene and carbon nanotubes.

[0017] According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the inorganic binder may include a ceramic composition. Here, the ceramic composition may be a vitrified composition of two or more types of metal oxide particles.

[0018] According to the seventh aspect of the present invention, in the sixth aspect, the crystallization temperature (T) of the ceramic composition c ) can be between 300 and 800°C.

[0019] According to the eighth aspect of the present invention, in any one of the first to seventh aspects, the weight ratio of the silicon particles and the inorganic binder may be 1:0.05 to 1:0.2.

[0020] According to the ninth aspect of the present invention, in any one of the first to eighth aspects, the particle size ratio of the silicon particles and the inorganic binder may be 1:0.1 to 1:1.10.

[0021] According to a tenth aspect of the present invention, in any one of the first to ninth aspects, the silicon negative electrode active material may be hollow.

[0022] According to an eleventh aspect of the present invention, any one of the first to tenth aspects may include a hollow region defined by at least one of the silicon particles and the carbon material.

[0023] According to the twelfth aspect of the present invention, the diameter of the hollow region in the eleventh aspect may be 1 to 30 μm.

[0024] According to a thirteenth aspect of the present invention, a negative electrode is provided comprising a silicon negative electrode active material according to any one of the first to twelfth aspects.

[0025] According to a fourteenth aspect of the present invention, a secondary battery is provided, comprising: a negative electrode according to the thirteenth aspect; a positive electrode; a separator interposed between the negative electrode and the positive electrode; and an electrolyte.

[0026] The solutions to the above problems do not enumerate all features of the present invention. The various features of the present invention, along with their corresponding advantages and effects, can be understood in more detail by referring to the detailed description below.

[0027] According to one aspect of the present invention, by inducing bidirectional expansion, the volume change of the entire silicon anode active material can be minimized. Accordingly, when the silicon anode active material is applied to a secondary battery, capacity loss due to charge / discharge cycles can be minimized, while also ensuring long-term cycle stability.

[0028] In addition to the aforementioned effects, specific effects of the present invention are described below along with specific details for implementing the invention. Furthermore, the effects of the present invention are not limited to the effects described above and can be readily achieved using the means and combinations thereof described in the specification.

[0029] Figure 1 is a schematic diagram of a silicon negative electrode active material according to one embodiment of the present invention.

[0030] In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0031] When multiple embodiments are described in this specification, the effects of the present invention may be defined to include not only the operational effects derived from each embodiment itself, but also the effects resulting from the organic combination of each embodiment. For example, even if Embodiments 1 and 2 are described independently in this specification, unless the context clearly indicates otherwise, the effects resulting from the organic combination of Embodiments 1 and 2 may also be included in the effects of the present invention.

[0032] The numerical range indicated by the term "to" in this specification refers to a numerical range that includes the values ​​described before and after the term as the lower limit and the upper limit, respectively. When multiple numerical values ​​are disclosed as the upper and lower limits of an arbitrary numerical range, the numerical range disclosed in this specification can be understood as any numerical range that has any one of the multiple lower limit values ​​and any one of the multiple upper limit values ​​as the lower limit and the upper limit, respectively. For example, when a to b, or c to d is described in the specification, it can be understood that a or more and b or less, a or more and d or less, c or more and d or less, or c or more and b or less is described.

[0033] As used herein, terms such as "about" or "substantially" mean a reasonable amount of variation from the term that does not significantly alter the final result. These terms may be interpreted to include a variation of at least ±5% or at least ±10%, provided that such variation does not alter the meaning of the term and render it invalid.

[0034] In this specification, "average particle size" means the particle size (D) when the cumulative percentage in the volume-based particle size distribution curve is 50% when measured by a laser diffraction particle size distribution measuring device. 50 ) can be defined as.

[0035] According to one aspect of the present invention, a silicon anode active material is provided, comprising: silicon particles; a carbon material on the silicon particles; a conductive material; and an inorganic binder. Conventional silicon has a problem in that volume changes occur during the insertion / de-insertion of lithium ions in a lithium secondary battery, resulting in destruction of the silicon particles and de-insertion from a current collector, thereby causing a decrease in capacity. According to one aspect of the present invention, by organically combining the silicon particles, the carbon material, the conductive material, and the inorganic binder, bidirectional expansion can be induced, thereby minimizing the volume change of the entire silicon anode active material. Accordingly, when the silicon anode active material is applied to a secondary battery, capacity decrease according to the progress of charge / discharge cycles can be minimized, while at the same time realizing long-term cycle stability.

[0036] Figure 1 is a schematic diagram of a silicon negative electrode active material according to one embodiment of the present invention.

[0037] Referring to FIG. 1, the silicon negative electrode active material (100) according to the present invention includes silicon particles (10), carbon material (20), conductive material (30), and inorganic binder (40).

[0038] Below, the configuration of the present invention is described in more detail.

[0039] 1. Silicon negative electrode material

[0040] silicon particles

[0041] The silicon particles according to the present invention can improve the capacity performance of a secondary battery and, at the same time, prevent the particles from being destroyed even when the volume of the particles expands as lithium ions are inserted.

[0042] The silicon particles according to the present invention are silicon particles crushed into nano-sizes, and are composed of Si, SiOx(0 <x≤2), Si-C 복합체 및 Si-Y 합금(Y는 알칼리금속, 알칼리토금속, 전이금속, 13족 원소, 14족 원소 및 희토류 원소로 이루어진 군에서 선택된 어느 하나의 원소이다)으로 이루어진 군에서 선택되는 1종 이상을 포함할 수 있고, 구체적으로 실리콘(Si)을 포함할 수 있다. 본 발명의 일 실시형태에 따르면, 상기 실리콘 입자가 분쇄된 실리콘일 경우 이차전지의 용량 특성이 더욱 개선될 수 있다.

[0043] In some embodiments of the present invention, the silicon particles may be in the form of a slurry and have an average particle diameter of 800 nm or less, 700 nm or less, 600 nm or less, 500 nm or less, specifically 50 to 500 nm, 60 to 400 nm, 70 to 300 nm, 80 to 300 nm, or 80 to 200 nm. According to some embodiments of the present invention, when the average particle diameter of the silicon particles satisfies the numerical range, the lifespan of the secondary battery can be further improved.

[0044] In some embodiments of the present invention, the silicon particles (primary particles) may be pulverized preliminary silicon particles (raw material powder). Specifically, the average particle diameter of the preliminary silicon particles (raw material powder) may be 10 to 100 μm, and more specifically, 30 to 50 μm. According to some embodiments of the present invention, since the average particle diameter of the preliminary silicon particles satisfies the numerical range, the particle diameter of the silicon particles is controlled, so that the lifespan of the secondary battery can be further improved.

[0045] For example, the silicon particles may be obtained by crushing metal silicon (Metallurgical Grade Silicon; MG-Si), which is a preliminary silicon particle. Specifically, the purity of the metal silicon may be 97 wt% or more.

[0046] In some embodiments of the present invention, the content of silicon particles may be 50 to 80 wt%, 60 to 70 wt%, or 62 to 67 wt% based on the total weight of the silicon negative electrode active material. According to some embodiments of the present invention, since the content of the silicon particles satisfies the numerical range, expansion of the volume when lithium ions are inserted can be minimized, thereby effectively preventing destruction of the particles.

[0047] carbon materials

[0048] The silicon anode active material according to the present invention comprises a carbon material on the silicon particles. Specifically, the carbon material is a carbon precursor converted through a sintering process, which suppresses side reactions between the silicon particles and the electrolyte and effectively prevents volume expansion of the silicon particles. In another aspect, the carbon material according to the present invention can further enhance the bonding strength between the silicon particles and the conductive material.

[0049] In this specification, the term “layer” may include cases where the layer is formed not only over the entire region when observing the region where the layer exists, but also cases where the layer is formed over only a portion of the region. For example, the layer may be defined as including a flat surface, a non-flat surface, and a combination thereof; or a continuous surface, a discontinuous surface, and a combination thereof. For example, when another material is formed as a layer directly on top of one material, the coverage of the other material on the surface of the first material may be defined as 1% or more, 5% or more, 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 85% or more, 90% or more, 95% or more, or 99% or more. For example, even when a plurality of particles form a clustered structure, it may be defined as a “layer.”

[0050] In some embodiments of the present invention, the carbon material may be partially or completely coated on the surface of the silicon particle. Specifically, the shape of the carbon material may not be particularly limited, and for example, the carbon material may be in the form of a layer partially or completely coated on the surface of the silicon particle. According to some embodiments of the present invention, since the carbon material is partially or completely coated on the surface of the silicon particle, volume expansion of the silicon particle can be more effectively suppressed, and the bonding strength between the silicon particle and the conductive material can be further enhanced.

[0051] In some embodiments of the present invention, when the carbon material is configured in the form of a carbon layer, the thickness of the carbon layer may be 1 to 30 nm, 5 to 20 nm, or 10 to 15 nm. Specifically, when the thickness of the carbon layer satisfies the above numerical range, volume expansion of silicon particles during a charge / discharge process can be effectively prevented.

[0052] In some embodiments of the present invention, the carbon material may be derived from a carbon precursor, and specifically, may be derived from an amorphous carbon precursor. For example, the amorphous carbon precursor may include at least one of a monosaccharide, a disaccharide, a polysaccharide, a petroleum resin, a polyimide resin, a furan resin, a phenol resin, a polyvinyl alcohol resin, a cellulose resin, an epoxy resin, and a polystyrene resin, and specifically, may include at least one of glucose, sucrose, galactose, fructose, lactose, starch, mannose, ribose, aldohexose, kedohexose, petroleum pitch, and coal pitch. According to some embodiments of the present invention, when a polysaccharide is used as the amorphous carbon precursor, the capacity of the secondary battery can be increased while improving the cycle life.

[0053] In some embodiments of the present invention, the content of the carbon material may be 10 to 40 wt%, 20 to 30 wt%, or 23 to 28 wt% based on the total weight of the silicon negative electrode active material. According to some embodiments of the present invention, by satisfying the content of the carbon material within the above numerical range, side reactions between silicon particles and the electrolyte can be suppressed, while volume expansion of the silicon particles can be more effectively prevented.

[0054] Challenge

[0055] The conductive material according to the present invention can complement the conductivity of silicon particles and effectively suppress volume expansion of silicon particles during the charging / discharging process of a secondary battery.

[0056] The conductive material according to the present invention may include at least one of graphene and carbon nanotubes. For example, the carbon nanotubes may include at least one of single-walled carbon nanotubes, thin-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0057] For example, the graphene is not particularly limited and may be unmodified graphene, graphene oxide, or reduced graphene. In another aspect, the graphene may be single-layer graphene or multi-layer graphene.

[0058] For example, the single-walled carbon nanotube may have a diameter of 0.4 to 3 nm and a length of 5 to 20 μm. For example, the multi-walled carbon nanotube may have an outer diameter of 3 to 40 nm and a length of 5 to 20 μm. For example, the thin-walled carbon nanotube may have a diameter of 5 to 9 nm.

[0059] In some embodiments of the present invention, the carbon nanotubes may have a modified surface. For example, a physical modification method or a chemical modification method may be used to modify the surface.

[0060] In some embodiments of the present invention, the content of the conductive material may be 0.1 to 10 wt%, 0.3 to 7 wt%, 0.5 to 3 wt%, or 1 to 2 wt% based on the total weight of the silicon negative electrode active material. According to some embodiments of the present invention, by satisfying the content of the conductive material within the above numerical range, the conductivity of the silicon particles can be further increased, while at the same time, volume expansion of the silicon particles can be effectively suppressed during the charge / discharge process of the secondary battery.

[0061] Weapon Binder

[0062] In this specification, “inorganic binder” refers to an inorganic substance that does not contain carbon, and may be a term contrasting with organic binder. For example, the organic binder may be a polymer binder, etc.

[0063] The inorganic binder according to the present invention can enhance the bonding between silicon particles and simultaneously increase the strength of the silicon anode active material. In another aspect, the inorganic binder according to the present invention can effectively prevent capacity degradation even with increasing cycle counts by suppressing particle destruction during the electrode rolling process.

[0064] The inorganic binder according to the present invention, unlike the organic binder, can better maintain the properties of the binder during a high-temperature firing process, thereby further strengthening the bonding force between silicon particles.

[0065] In some embodiments of the present invention, the inorganic binder may include a ceramic composition. Here, the ceramic composition may be defined as a vitrified mixture of two or more metal oxide particles. According to some embodiments of the present invention, by using a ceramic composition as the inorganic binder, the strength of the silicon anode active material can be increased while effectively preventing particle breakage during the electrode rolling process, thereby further improving cycle stability. If metal oxide particles composed of only one type are used, vitrification may be difficult, which may prevent them from functioning sufficiently as an inorganic binder, and thus, a problem may arise in which the strength of the silicon anode active material cannot be sufficiently increased.

[0066] In some embodiments of the present invention, the crystallization temperature (T) of the ceramic composition c ) may be 300 to 800°C, 400 to 800°C, 500 to 800°C, 600 to 800°C, or 600 to 700°C. According to some embodiments of the present invention, the crystallization temperature of the ceramic composition satisfies the above numerical range, thereby strengthening the bonding force between silicon particles and further increasing the strength of the silicon negative electrode active material. For example, the crystallization temperature of the ceramic composition can be analyzed using a differential thermal analysis method commonly used in the relevant technical field.

[0067] In some embodiments of the present invention, the content of the inorganic binder may be 3 to 20 wt%, 4 to 15 wt%, or 6 to 12 wt% based on the total weight of the silicon negative electrode active material. According to some embodiments of the present invention, by satisfying the content of the inorganic binder within the above numerical range, the bonding force between silicon particles can be strengthened, and at the same time, the strength of the silicon negative electrode active material having a hollow structure can be further increased.

[0068] For example, the metal oxide is not particularly limited and includes Al2O3, As2O3, As2O5, Ag2O, B2O3, BaO, BeO, Bi2O3, CaCO3, CaO, CeO2, Co3O4, Cr2O3, Cs2O, CuO, Fe2CO3, FeO, Ga2O3, GeO2, H3PO4, In2O, In2O3, K2CO3, K2O, La2O3, Li2CO3, Li2O, MgO, MnO2, MoO2, Na2CO3, Na2O, Nb2O5, NbO2, Nd2O3, NiO, P2O3, P2O5, PbO, PbO2, Rb2O, RuO2, Sb2O3, Sb2O5, SeO2, SeO3, SiO2, SnO2, SrO, Ta2O5, TeO2, It may include two or more types of metal oxides selected from the group consisting of TiO2, V2O5, WO3, Y2O3, ZnO, and ZrO2. Here, when two or more types of metal oxides are included, vitrification of the metal oxides may occur.

[0069] In some embodiments of the present invention, the average particle diameter of the inorganic binder may be 20 to 150 nm, 20 to 140 nm, 20 to 100 nm, or 20 to 50 nm. According to some embodiments of the present invention, when the average particle diameter of the inorganic binder satisfies the numerical range, the capacity and cycle life performance of the secondary battery can be further improved.

[0070] For example, the shape of the inorganic binder is not particularly limited, and may be spherical, rod-shaped, or have a randomly irregular surface. If the shape of the inorganic binder is not spherical, the average particle diameter of the inorganic binder may be defined as the particle diameter along the longitudinal direction.

[0071] Relationships between each component and characteristics of silicon anode materials

[0072] In some embodiments of the present invention, the weight ratio of the silicon particles and the inorganic binder (silicon particles:inorganic binder) may be 1:0.05 to 1:0.2, or 1:0.09 to 1:0.19. According to some embodiments of the present invention, by satisfying the weight ratio of the silicon particles and the inorganic binder within the above numerical range, the capacity of the secondary battery can be increased while further improving the cycle stability.

[0073] In some embodiments of the present invention, the particle size ratio of the silicon particles and the inorganic binder (silicon particles:inorganic binder) may be 1:0.1 to 1:1.10, 1:0.17 to 1:0.45, or 1:0.18 to 1:0.45. According to some embodiments of the present invention, when the particle size ratio of the silicon particles and the inorganic binder satisfies the numerical range, the capacity of the secondary battery can be increased and the cycle stability can be further improved. Here, the particle size can be defined as, for example, an average particle diameter.

[0074] As illustrated in FIG. 1, in some embodiments of the present invention, the silicon anode active material may be hollow. Specifically, when the silicon anode active material is hollow, it can induce bidirectional expansion during the charge / discharge process of a secondary battery, thereby minimizing the volume change of the entire particle. For example, the hollow silicon anode active material can be formed using a spray drying method commonly used in the relevant technical field.

[0075] Specifically, it may include a hollow region defined by at least one of the silicon particles and the carbon material. Specifically, the hollow region may be defined as a region defined by the profile of one or more silicon particles and / or carbon materials. Here, the diameter of the hollow region may be 1 to 30 μm, 4 to 14 μm, and when it satisfies the above numerical range, the capacity of the secondary battery can be increased while further improving the cycle stability.

[0076] In some embodiments of the present invention, the ratio of the diameter of the silicon particles to the diameter of the hollow region (diameter of the silicon particles: diameter of the hollow region) may be 1:10 to 1:300. Specifically, by satisfying the ratio of the diameter of the silicon particles to the diameter of the hollow region within the above numerical range, the capacity of the secondary battery can be increased while further improving the cycle stability. For example, the diameter of the silicon particles may be an average diameter.

[0077] Manufacturing method

[0078] According to another aspect of the present invention, a method for manufacturing a silicon negative electrode active material can be provided.

[0079] According to one embodiment of the present invention, the method may include the steps of: pulverizing a mixture containing preliminary silicon particles and an antioxidant to obtain silicon particles in a slurry form; preparing a mixture containing the silicon particles and a conductive material; dispersing the mixture and then drying it through a spray dryer to obtain particles having a hollow structure; and sintering the particles having a hollow structure to finally produce a silicon negative electrode active material. According to some embodiments of the present invention, compared to a general hollow formation method of coating silicon on a template surface and then removing the mold through heat treatment and acid treatment, a hollow structure is formed through a process of nano-dispersing and spray-drying a slurry, thereby providing a more economical advantage.

[0080] 2. Cathode

[0081] According to another aspect of the present invention, a negative electrode comprising the silicon negative electrode active material is provided.

[0082] A method for manufacturing a negative electrode according to the present invention may include the steps of preparing a negative electrode slurry including a silicon negative electrode active material, an electrode conductive material, and a negative electrode binder according to some embodiments; coating and drying the negative electrode slurry on at least one surface of a negative electrode current collector to form a negative electrode active material layer; and rolling the current collector on which the negative electrode active material layer is formed.

[0083] The above-described negative electrode current collector can serve as a passage to transfer electrons from the outside to cause an electrochemical reaction in the negative electrode active material or to receive electrons from the negative electrode active material and send them to the outside. For example, the negative electrode current collector may be made of copper, stainless steel, nickel, titanium, calcined carbon, or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. Specifically, a transition metal that adsorbs carbon well, such as copper or nickel, may be used as the current collector. For example, the thickness of the negative electrode current collector may be 6 μm to 55 μm, but the thickness of the negative electrode current collector is not limited thereto.

[0084] In some embodiments of the present invention, the step of rolling the current collector having the negative electrode active material layer formed thereon may be performed under conditions of a composite density of 1.0 g / cc or more. When using a silicon negative electrode active material according to some embodiments of the present invention, even if the rolling process is performed under the above conditions, the particles are not destroyed, thereby further improving the compression resistance. Here, the composite density refers to the degree to which the composite material is pressed well, and may vary depending on the pressure and thickness of the roll press.

[0085] In some embodiments of the present invention, the negative electrode slurry may further include a graphite-based active material in addition to the silicon negative electrode active material. For example, the graphite-based active material may include at least one selected from the group consisting of artificial graphite, natural graphite, graphitized carbon fibers, and graphitized mesocarbon microbeads.

[0086] The above-mentioned negative electrode binder can suppress separation between negative electrode active material (silicon negative electrode active material) particles, or between the negative electrode active material layer and the current collector. A polymer commonly used in electrodes in the relevant technical field can be used as the above-mentioned negative electrode binder. These negative electrode binders include, but are not limited to, poly(vinylidene fluoride co-hexafluoropropylene), poly(vinylidene fluoride-co-trichloroethylene), poly(methylmethacrylate), poly(ethylhexylacrylate), poly(butylacrylate), poly(acrylonitrile), poly(vinylpyrrolidone), poly(vinyl acetate), poly(ethylene-co-vinyl acetate), poly(ethylene oxide), polyacrylate, cellulose acetate, cellulose acetate butyrate. Examples of such polymers include, but are not limited to, cellulose acetate propionate, cyano ethyl pullulan, cyano ethyl poly(vinylalcohol), cyanoethylcellulose, cyano ethylsucrose, pullulan, and carboxyl methyl cellulose.

[0087] The conductive material for an electrode according to the present invention is not particularly limited and may be one selected from the group consisting of graphite, carbon black, carbon fibers or metal fibers, metal powders, conductive whiskers, conductive metal oxides, activated carbon, and polyphenylene derivatives, or a mixture of two or more conductive materials thereof, and more specifically, may be one selected from the group consisting of natural graphite, artificial graphite, super-p, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, Denka black, aluminum powder, nickel powder, zinc oxide, potassium titanate, and titanium oxide, or a mixture of two or more conductive materials thereof.

[0088] 3. Secondary batteries

[0089] According to another aspect of the present invention, a secondary battery is provided, comprising: a cathode according to some embodiments; a cathode; a separator interposed between the cathode and the anode; and an electrolyte. The above-described parts and repeated descriptions are briefly described or omitted.

[0090] anode

[0091] The positive electrode according to the present invention may include a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The positive electrode active material layer may include a positive electrode active material, a conductive material, and a positive electrode binder.

[0092] For example, the positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Specifically, the positive electrode current collector may be made of copper, stainless steel, aluminum, titanium, calcined carbon, stainless steel surface-treated with carbon, nickel, titanium, silver, etc., an aluminum-cadmium alloy, etc. The positive electrode current collector may typically have a thickness of 6 to 20 μm.

[0093] For example, the cathode active material may include a lithium transition metal oxide. The lithium transition metal oxide may be, for example, Li x1 CoO2(0.5 <x1<1.3), Li x2 NiO2(0.5 <x2<1.3), Li x3 MnO2(0.5 <x3<1.3), Li x4 Mn2O4(0.5 <x4<1.3), Li x5 (Ni a1 Co b1 Mn c1 )O2(0.5 <x5<1.3, 0<a1<1, 0<b1<1, 0<c1<1, a1+b1+c1=1), Li x6 Ni 1-y1 Co y1 O2(0.5 <x6<1.3, 0<y1<1), Li x7 Co 1-y2 Mn y2 O2(0.5 <x7<1.3, 0≤y2<1), Li x8 Ni 1-y3 Mn y3 O2(0.5 <x8<1.3, O≤y3<1), Li x9 (Ni a2 Co b2 Mn c2 )O4(0.5 <x9<1.3, 0<a2<2, 0<b2<2, 0<c2<2, a2+b2+c2=2), Li x10 Mn 2-z1 Ni z1 O4(0.5 <x10<1.3, 0<z1<2), Li x11 Mn 2-z2 Co z2 O4(0.5 <x11<1.3, 0<z2<2), Li x12 CoPO4(0.5 <x12<1.3) 및 Li x13 FePO4(0.5 <x13<1.3)로 이루어진 군에서 선택되는 하나 이상일 수 있다.

[0094] The conductive material used in the above anode may be the same as or different from the conductive material used in the above cathode.

[0095] The above positive electrode binder may be the same as or different from the above negative electrode binder.

[0096] membrane

[0097] The separation membrane according to the present invention may be composed of a porous substrate or may include a porous substrate and a coating layer.

[0098] The porous substrate according to the present invention can be a porous structure having high resistance to electrolyte and fine pore diameters, capable of providing a path for lithium ions to move while electrically insulating the negative electrode and the positive electrode to prevent short circuits.

[0099] Any organic or inorganic material having electrical insulation properties may be used as a constituent material of the porous substrate without particular limitation. The porous substrate may include, for example, at least one selected from the group consisting of polyolefin, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulphone, polyphenyleneoxide, polyphenylenesulfide, and polyethylenenaphthalate, and may specifically include polyolefin. Polyolefin not only has excellent coating properties, but also allows for thinning the separator, increasing the ratio of the electrode active material layer in the battery, and thus increasing the capacity per volume.

[0100] Specifically, the weight average molecular weight (Mw) of the polyolefin may be 100,000 to 500,000 g / mol. If the weight average molecular weight of the polyolefin is less than the above numerical range, it may be difficult to secure sufficient mechanical properties, and if it exceeds the above numerical range, the shutdown function may not be implemented or molding may become difficult. The shutdown function refers to the function of blocking the movement of ions and preventing thermal runaway of the battery by melting the thermoplastic resin and closing the pores of the porous substrate when the temperature of the secondary battery increases.

[0101] The thickness of the porous substrate may be, for example, 3 to 50 μm or 4 to 30 μm. If the thickness of the porous substrate is less than the numerical range, the function of the conductive barrier may not be sufficient, and if it exceeds the numerical range, the resistance of the separator may excessively increase.

[0102] The average diameter of the pores included in the porous substrate may be, for example, 10 to 100 nm. The pores included in the porous substrate have a structure that is interconnected with each other, so that gas or liquid can pass from one side of the porous substrate to the other side.

[0103] A separator according to another embodiment of the present invention may include a coating layer disposed on at least one surface of the porous substrate, which can improve the mechanical strength and heat resistance of a separator for a secondary battery and increase ion conductivity within the secondary battery.

[0104] The coating layer according to the present invention may include a binder polymer and inorganic particles.

[0105] The binder polymer according to the present invention can connect inorganic particles and stably fix them. The binder polymer may be, for example, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, poly(ethylene-co-vinyl acetate), polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, One or more selected from the group consisting of cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene butadiene copolymer, polyimide, and styrene-butadiene rubber may be used in combination.

[0106] According to another embodiment of the present invention, the weight ratio of the inorganic particles and the binder polymer (inorganic particles: binder polymer) may be 50:50 to 99:1, specifically 70:30 to 95:5. If the content ratio of the inorganic particles to the binder polymer is less than the above numerical range, the content of the binder polymer may increase, thereby deteriorating the thermal stability improvement performance of the separator, and the pore size and porosity may decrease due to a decrease in the empty space formed between the inorganic particles, thereby causing a deterioration in the performance of the final battery, and if the content of the binder polymer is exceeded, the content of the binder polymer may be too small, thereby weakening the peeling resistance of the coating layer.

[0107] The inorganic particles according to the present invention can contribute to improving the mechanical strength and heat resistance of a separator for a secondary battery. Specifically, the inorganic particles are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles that can be used in the present invention can be used within the operating voltage range of the secondary battery to which they are applied (e.g., Li / Li). + There are no particular restrictions as long as no oxidation and / or reduction reaction occurs at a reference voltage of 0 to 5 V. For example, when using inorganic particles with a high dielectric constant, the ionic conductivity of the electrolyte can be improved by contributing to an increase in the degree of dissociation of the electrolyte salt, such as a lithium salt, in the liquid electrolyte.

[0108] For the reasons described above, the inorganic particles may be inorganic particles having a dielectric constant of 5 or more, inorganic particles having lithium ion transport capability, or a mixture thereof.

[0109] The inorganic particles having the dielectric constant of 5 or more are Al2O3, SiO2, ZrO2, AlO(OH), Al(OH)3, Mg(OH)2, BaSO4, TiO2, BaTiO3, Pb(Zr x Ti 1-x )O3(PZT, where 0 <x<1), Pb 1-x La x Zr 1-y Tiy O3(PLZT, where 0 < x < 1, 0 < y < 1), (1-x)Pb(Mg 1 / 3 Nb 2 / 3 )O 3-x It may be a mixture of one or more selected from the group consisting of PbTiO3 (PMN-PT, where 0 < x < 1), HfO2, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, and SiC.

[0110] The inorganic particles having the above lithium ion transfer capability include lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0< x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3), (LiAlTiP) x O y Series glass (0 < x < 4, 0 < y < 13), lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), lithium germanium thiophosphate (Li x Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), lithium nitride (Li x N y , 0 < x <4, 0 < y < 2), SiS2 series glass(Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4) and P2S5 series glass(Li x P y S z, 0 < x < 3, 0 < y < 3, 0 < z < 7) may be a mixture of one or more selected from the group consisting of:

[0111] For example, the average particle diameter (D) of the above inorganic particles 50 ) may be 1 nm to 10 μm, specifically 10 nm to 2 μm, and more specifically 50 nm to 1 μm, for forming a coating layer of uniform thickness and an appropriate porosity. The "average particle diameter (D50)" refers to the particle diameter at the 50% point of the cumulative distribution of the number of particles according to particle diameter. The average particle diameter can be measured using a laser diffraction method. Specifically, after dispersing the target powder in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500) and measuring the difference in diffraction pattern according to particle size when the particles pass through a laser beam, thereby calculating the particle size distribution.

[0112] Specifically, the thickness of the coating layer may be 0.1 to 10 μm, specifically 1 to 3 μm, and more specifically 1.4 to 1.6 μm. When the thickness of the coating layer satisfies the above numerical range, the insulation and thermal stability of the separator can be increased, and the energy density of the battery can be improved at the same time.

[0113] electrolyte

[0114] The electrolyte according to the present invention may include a solvent and a lithium salt.

[0115] The solvent according to the present invention is, for example, propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide (DMSO), acetonitrile (ACN), 1,2-dimethoxyethane (DME), 1,2-diethoxyethane, tetrahydrofuran (THF), N-methylpyrrolidone (NMP), ethyl methyl carbonate (EMC), gamma-butyrolactone (GBL), fluoroethylene carbonate. It may be one or a mixture of two or more selected from the group consisting of methyl carbonate (FEC), methyl formate, ethyl formate, propyl formate, methyl acetate (MA), ethyl acetate (EA), N-propyl acetate, pentyl acetate, methyl propionate, ethyl propionate, and butyl propionate.

[0116] Lithium salt according to the present invention is, for example, NO3 - , F - , Cl - , Br - , I - , PF6 - It may contain anions such as:

[0117] For example, the secondary battery may be a cylindrical, square, or pouch-shaped secondary battery, but is not particularly limited as long as it corresponds to a charging / discharging device.

[0118] Another embodiment of the present invention can provide a battery module including the secondary battery as a unit cell and a battery pack including the same. The battery pack can be used as a power source for one or more medium- to large-sized devices selected from the group consisting of, for example, power tools; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0119] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, this is merely an example, and the scope of the present invention is not limited by the following contents.

[0120] [Manufacturing Example 1: Manufacturing of Negative Electrode Material]

[0121] Steps for obtaining silicon particles:

[0122] To 87 parts by weight of anhydrous ethanol, 12 parts by weight of metallic silicon (MG-Si) having an average particle size of 40 μm and 1 part by weight of an antioxidant (stearic acid) were added and mixed. The mixture was placed in a bead mill and ground to obtain silicon particles (180 g) in the form of a slurry having an average particle size of 100 nm.

[0123] Step of preparing a mixture containing the above silicon particles and a conductive material:

[0124] A mixture was prepared by adding and mixing 180 g of the silicon particles, 40.3 g of an amorphous carbon precursor (except 0 g in Comparative Example 3), 0.64 g of a single-walled carbon nanotube (SWCNT), two types of metal oxides (BaO and ZnO mixed in a weight ratio of 1:0.3) having the contents described in Table 1 below, and 3.45 g of a dispersant (polyvinylpyrrolidone; PVP) having a weight average molecular weight of 40,000 g / mol to a solvent (H2O) having the contents described in Table 1 below.

[0125] With respect to the amorphous carbon precursor, in Examples 1 to 9, a disaccharide (sucrose) was used as the amorphous carbon precursor, in Example 10, a resin (cresolic resin) was used, in Example 11, a monosaccharide (glucose) was used, in Examples 12 to 20, a disaccharide (sucrose) was used, in Comparative Examples 1 and 2, sucrose was used, and in Comparative Example 3, no amorphous carbon precursor was used.

[0126] With regard to metal oxides, in Comparative Example 1, one type of metal oxide (B2O3) was used, in Comparative Example 2, no metal oxide was used, and in Examples 1 to 20, the two types of metal oxides were used.

[0127] Step of dispersing the above mixture:

[0128] A step of dispersing the above mixture using a high pressure homogenizer under conditions of a pressure of 1,800 bar and a flow rate of 250 ml / min was performed to obtain a dispersed slurry.

[0129] Step of drying the above dispersed slurry:

[0130] The above dispersed slurry was dried at 105°C using a spray dryer to obtain hollow sphere-structured particles. At this time, the spray dryer was spray-dried at an inlet temperature of 180°C, an outlet temperature of 105°C, and a flow rate of 4 ml per minute.

[0131] Step of manufacturing a silicon negative electrode active material by sintering the above dried hollow structure particles:

[0132] The above hollow particles were sintered at 900°C for 3 hours in a tube furnace to finally produce a silicon anode active material. Here, the diameter of the hollow region within the silicon anode active material was controlled to approximately 10 μm.

[0133] Composition for manufacturing cathode active material Silicon particle (g) Amorphous carbon precursor (g) Conductive material (g) Metal oxide (g) Solvent (g) Dispersant (g) Remarks Example 1 180 40.30.64 1.93 77 3.68 3.45 Example 2 180 40.30.64 4.13 77 1.48 3.45 Example 3 180 40.30.64 1.93 77 3.68 3.45 Example 4 180 40.30.64 1.93 77 3.68 3.45 Example 5 180 40.30.64 1.93 77 3 .683.45 Example 6 18040.30.64 1.93773.683.45 Example 7 18040.30.64 1.93773.683.45 Example 8 18040.30.64 1.93773.683.45 Example 9 18040.30.64 1.93773.683.45 Carbon precursor: polysaccharide Example 10 18040.30.64 1.93773.683.45 Carbon precursor: resin Example 1118040.30.641.93773.683.45Carbon precursor: Monosaccharide Example 1218040.30.641.93762.953.45 Example 1318040.30.641.93762.953.45 Example 1418040.30.641.93762.953.45 Example 1518040.30.641.93762.953. 45 Example 16 18040.30.64 1.93762.953.45 Example 17 18040.30.64 1.93762.953.45 Example 18 18040.30.64 1.93762.953.45 Example 19 18040.30.64 0.65 775.153.45 Example 2018040.30.64 4.75 770.46 3.45 Comparative Example 118040.30.641.93773.683.45 Metal oxide 1 type Comparative example 218040.30.640764.883.45 Metal oxide excluding Comparative example 318000.641.93762.953.45 Carbon precursor X

[0134] The silicon negative electrode active materials according to Examples 1 to 20 and Comparative Examples 1 to 3 according to Table 1 above may have the characteristics of Table 2 below. In this case, the content unit of the silicon particles, conductive material, carbon material, and inorganic binder (ceramic composition) described in Table 2 below is weight%.

[0135] Classification Negative active material Silicon particle (A) Conductive material Carbon material Ceramic composition (B) Tg of ceramic composition (℃) Tc of ceramic composition (℃) Silicon particle size Ceramic composition Particle size A:B Particle size ratio A:B Weight ratio Example 1 67.00% 2.00% 25.00% 6.00% 5086 15 110 nm 50 nm 1 : 0.451 : 0.09 Example 2 62.70% 1.90% 23.40% 12.00% 5086 15 110 nm 50 nm 1 : 0.451 : 0.19 Example 3 67.00% 2.00% 25.00% 6.00% 4365 20 110 nm 50 nm 1 : 0.451 : 0.09 Example 467.00%2.00%25.00%6.00%527680110nm50nm1 : 0.451 : 0.09 Example 567.00%2.00%25.00%6.00%508615300nm50nm1 : 0.171 : 0.09 Example 667.00%2.00%25.00%6.00%50861560nm50nm1 : 0.831 : 0.09 Example 767.00%2.00%25.00%6.00%508615110nm100nm1 : 0.911 : 0.09 Example 8 67.00% 2.00% 25.00% 6.00% 508615110nm20nm1 : 0.181 : 0.09 Example 9 67.00% 2.00% 25.00% 6.00% 508615110nm50nm1 : 0.451 : 0.19 Example 10 67.00% 2.00% 25.00% 6.00% 508615110nm50nm1 : 0.451 : 0.19 Example 11 67.00% 2.00% 25.00% 6.00% 508615110nm50nm1 : 0.451 : 0.19Example 1267.00%2.00%25.00%6.00%500724110nm50nm1 : 0.451 : 0.09Example 1367.00%2.00%25.00%6.00%386749110nm50nm1 : 0.451 : 0.09Example 1467.00%2.00%25.00%6.00%392480110nm50nm1 : 0.451 : 0.09Example 1567.00%2.00%25.00%6.00%508615600nm50nm1 : 1.081 : 0.09Example 1667.00%2.00%25.00%6.00%50861540nm50nm1 : 1.251 : 0.09Example 1767.00%2.00%25.00%6.00%508615110nm140nm1 : 1.271 : 0.09Example 1867.00%2.00%25.00%6.00%508615110nm10nm1 : 0.091 : 0.09Example 1969.79%2.08%26.04%2.09%508615110nm50nm1 : 0.451 : 0.03Example 2061.61%1.84%22.99%13.56%508615110nm50nm1 : 0.451 : 0.22Comparative Example 167.00%2.00%25.00%6.00%508615110nm50nm1 : 0.451 : 0.19Comparative Example 271.30%2.10%26.60%_ _110nm50nm Comparative Example 3 X 508615110nm50nm1 : 0.451 : 0.091) Tg and Tc of ceramic composition: were analyzed at a heating rate of 10℃ / min using DTA (Differential Thermal Analysis) of TA instruments.

[0136] [Experimental Example: Evaluation of Capacity and Lifespan Characteristics of Secondary Batteries]

[0137] Fabrication of half-cell samples

[0138] Each of the silicon anode active material, conductive agent (Super P), and binder (CMC:SBR = 1:1 weight ratio) according to the above Manufacturing Example 1 was mixed in a weight ratio of 6:2:2, and a solvent (H2O) was added to adjust the viscosity to prepare an anode slurry having a total solid content of 12.4 wt%. The prepared anode slurry was coated on a current collector (copper foil) having a thickness of 10 μm, dried at 90°C for 30 minutes, and then the mixture density was adjusted to 1.0 g / cc using a roll press, and then dried in a vacuum oven at 20°C for 24 hours to prepare an anode (thickness: 19 μm). Li metal was used as a counter electrode, a polyethylene separator (thickness: 80 μm) was used as a separator, and an electrolyte (1.3 mol LiPF6, EC:EMC=3:7(v / v)+FEC 5%) was injected to manufacture a half-cell.

[0139] Evaluation method

[0140] The fabricated half-cells were charged at a charge rate of 0.2C using a constant current (CC) / constant voltage (CV) method until the voltage reached 0.01 V (vs. Li), and discharged at a discharge rate of 0.2C with a cut-off of 1.5 V to conduct a formation process. Subsequently, charging at 1.0C using a CC / CV method until the voltage reached 0.01 V and discharging at 1.0C to 1.0 V were repeated, and the capacity, initial coulombic efficiency, and lifespan were measured for up to 100 cycles.

[0141] Classification Capacity (mAh / g) Initial Coulombic Efficiency (ICE) [%] 100 Cycle Life (%) Example 11, 31 175.29 2.3 Example 21, 22 474.89 4.5 Example 31, 22 875.18 3.6 Example 41, 38 374.9 80.3 Example 51, 33 875.48 8.1 Example 61, 27 074.39 1.9 Example 71, 26 874.38 2.6 Example 81, 30 675.69 2.9 Example 91, 32 074.69 3.6 Example 101, 22 674.39 4.1 Example 111, 39 775.57 7.1 Example 121, 57 474.971.4 Example 131, 86874.569.8 Example 141, 17474.370.5 Example 151, 38976.772.6 Example 161, 22373.673.3 Example 171, 16872.669.4 Example 181, 26974.983.4 Example 191, 33275.171.1 Example 201, 04972.594.5 Comparative Example 11, 14869.864.2 Comparative Example 21, 38474.868.1 Comparative Example 32, 35358.130.5

[0142] When comparing Comparative Example 2 and Examples 1 to 10 in terms of long-term cycle stability according to the inorganic binder in Table 3 above, Examples 1 to 10 including the inorganic binder showed superior performance even as the number of cycles increased compared to Comparative Example 2 not including the inorganic binder.

[0143] Comparing Comparative Example 1 and Examples 1 to 10 with respect to the type of metal oxide forming the inorganic binder, Examples 1 to 10, in which the inorganic binder is composed of two or more types of metal oxides, exhibited superior effects in terms of the initial coulombic efficiency of the secondary battery and lifespan performance under long-term cycling, compared to Comparative Example 1, which was composed of only one type of metal oxide. This suggests that when the secondary battery is composed of only one type of metal oxide, the vitrification of the metal oxide is not sufficiently achieved.

[0144] Comparing Comparative Example 3 and Examples 1 to 10 from the perspective of long-term cycle stability according to the amorphous carbon precursor, it can be confirmed that the amorphous carbon precursor suppresses side reactions between the silicon anode active material and the electrolyte as it is converted into a carbon material within the silicon anode active material, and suppresses volume expansion of the silicon anode active material during the charge / discharge process, thereby demonstrating excellent performance even as the number of cycles increases.

[0145] Comparing Examples 15, 16 and Example 1 with respect to cycle stability according to the average particle size of silicon particles, it can be confirmed that when the average size of silicon particles is 50 to 500 nm, the volume expansion of silicon particles is effectively suppressed during the insertion / de-insertion process of lithium ions, thereby exhibiting cycle stability.

[0146] From the viewpoint of simultaneously achieving the capacity and long-term cycle stability performance of a secondary battery according to the weight ratio of silicon particles and inorganic binder, when Examples 19 and 20 and Example 1 are compared with each other, it can be confirmed that when the weight ratio of silicon particles and inorganic binder satisfies 1:0.05 to 1:0.2, the capacity of the secondary battery is increased and the cycle stability is improved at the same time.

[0147] Comparing Examples 17 and 18 with Example 1 in terms of capacity and long-term cycle stability of the secondary battery according to the particle size ratio of silicon particles and inorganic binder, it can be confirmed that the capacity and long-term cycle stability of the secondary battery are further improved when the size ratio of silicon particles and inorganic binder satisfies 1:0.1 to 1:1.10.

[0148] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

[0149] [Explanation of symbols]

[0150] 10: Silicon particles 20: Carbon material

[0151] 30: Challenger 40: Weapon Binder

[0152] 100: Silicon negative electrode material

Claims

1. Silicon particles; Carbon material on the above silicon particles; Challenge; and including a weapon binder; Silicon negative electrode material.

2. In paragraph 1, The average particle diameter of the above silicon particles is 800 nm or less. Silicon negative electrode material.

3. In paragraph 1, The average particle diameter of the above-mentioned inorganic binder is 20 to 100 nm. Silicon negative electrode material.

4. In paragraph 1, The above carbon material is partially or completely coated on the surface of the silicon particles. Silicon negative electrode material.

5. In paragraph 1, The above challenger is, Containing at least one of graphene and carbon nanotubes, Silicon negative electrode material.

6. In paragraph 1, The above-mentioned inorganic binder comprises a ceramic composition. Silicon negative electrode material.

7. In paragraph 6, The above ceramic composition, Vitrified particles of two or more metal oxides, Silicon negative electrode material.

8. In paragraph 6, Crystallization temperature (T) of the above ceramic composition c ) is 300 to 800℃, Silicon negative electrode material.

9. In paragraph 1, The weight ratio of the silicon particles and the inorganic binder is 1:0.05 to 1:0.2, Silicon negative electrode material.

10. In paragraph 1, The particle size ratio of the silicon particles and the inorganic binder is 1:0.1 to 1:1.

10. Silicon negative electrode material.

11. In paragraph 1, The above silicon negative electrode active material is hollow. Silicon negative electrode material.

12. In paragraph 1, A hollow region defined by at least one of the silicon particles and the carbon material, Silicon negative electrode material.

13. In paragraph 12, The diameter of the above hollow region is 1 to 30㎛, Silicon negative electrode material.

14. A negative electrode comprising a silicon negative electrode active material according to Article 1.

15. Cathode according to Article 14; anode; a separator interposed between the cathode and the anode; and Containing electrolyte Secondary battery.

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