Positive electrode active material, and positive electrode and lithium secondary battery comprising same

Abstract

The present invention relates to: a bimodal positive electrode active material in which large particles and small particles are mixed, wherein the large particles are overlithiated manganese-rich oxides having a molar ratio of lithium to all transition metals excluding lithium of greater than 1 and a molar content of manganese in the transition metals of 50 mol% or more, and the large particles have a sphericity of 0.8 or more; and a positive electrode and a lithium secondary battery comprising same.

Description

Cathode active material, a cathode including the same, and a lithium secondary battery

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0126153 filed September 13, 2024 and Korean Patent Application No. 10-2025-0130705 filed September 12, 2025, and all contents disclosed in the documents of said Korean patent applications are incorporated herein as part of this specification.

[0003] The present invention relates to a positive electrode active material, a positive electrode containing the same, and a lithium secondary battery.

[0004] Due to the rapid increase in the use of fossil fuels, there is a growing demand for alternative or clean energy, and as part of this, the fields of power generation and energy storage utilizing electrochemistry are the most actively researched.

[0005] Currently, a representative example of an electrochemical device utilizing such electrochemical energy is the secondary battery, and its scope of application is steadily expanding.

[0006] Recently, as technology development and demand for portable devices such as portable computers, mobile phones, and cameras have increased, the demand for secondary batteries as an energy source has been rapidly increasing. Among these secondary batteries, a lot of research has been done on environmentally friendly lithium secondary batteries that exhibit high charge / discharge characteristics and lifespan characteristics, and they have also been commercialized and are widely used.

[0007] Such lithium secondary batteries generally consist of a positive electrode, a negative electrode, a separator, and an electrolyte, and the positive and negative electrodes include active materials capable of lithium ion intercalation and deintercalation.

[0008] Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMnO4, etc.), and lithium iron phosphate compounds (LiFePO4) have been used as cathode active materials for lithium secondary batteries. Among these, lithium cobalt oxide has the advantage of high operating voltage and excellent capacity characteristics, but it is difficult to apply it commercially to high-capacity batteries due to the high cost and unstable supply of cobalt, which is the raw material. Lithium nickel oxide has poor structural stability, making it difficult to achieve sufficient lifespan characteristics. Meanwhile, lithium manganese oxide with a spinel structure has excellent stability but has the problem of poor capacity characteristics. Accordingly, lithium composite transition metal oxides containing two or more transition metals have been developed and are being used to compensate for the problems of lithium transition metal oxides containing Ni, Co, or Mn alone. Among these, as it has become known that oxides containing an excess of lithium while having a higher Mn content than other metals excluding lithium (hereinafter referred to as “lithium-rich manganese oxide”) can secure high energy density as high-capacity active materials, research and interest in this area are increasing significantly.

[0009] However, due to the low density of conventional lithium-rich manganese oxides, the rolling process was performed under high rolling loads to achieve the target electrode density. During this process, breakage of active material particles occurred, leading to a decrease in battery life. Therefore, there is a need to develop a positive electrode active material that can prevent breakage of active material particles and improve battery life by lowering the rolling load.

[0010] The present invention aims to provide a positive electrode active material capable of securing excellent rolling density while suppressing particle breakage during the battery manufacturing process.

[0011] In addition, the present invention aims to provide a positive electrode and a lithium secondary battery with improved lifespan characteristics by including the above-mentioned positive electrode active material.

[0012] According to one embodiment of the present invention, a bimodal positive electrode active material comprising a mixture of large particles and small particles is provided, wherein the large particles are an over-lithium manganese-rich oxide in which the molar ratio of lithium to the total transition metals excluding lithium is greater than 1 and the molar content of manganese among the transition metals is 50 mol% or more, and the degree of sphericity of the large particles is 0.8 or more.

[0013] According to another embodiment of the present invention, a positive electrode comprising the positive electrode active material is provided.

[0014] In addition, according to one embodiment of the present invention, a lithium secondary battery is provided comprising: the positive electrode; a negative electrode facing the positive electrode; and a separator or electrolyte layer interposed between the positive electrode and the negative electrode.

[0015] The present invention relates to a positive electrode active material for a lithium secondary battery, wherein the positive electrode active material is of a bimodal form in which large particles and small particles are mixed, and by mixing the large particles with a lithium manganese-rich oxide having a sphericity of 0.8 or higher, the rolling load required to achieve a target electrode density can be lowered, and accordingly, the breaking of active material particles can be suppressed, thereby improving the lifespan characteristics of the lithium secondary battery.

[0016] Figure 1 is a figure showing scanning electron microscope images of samples 1 to 6, which are large particle powder groups.

[0017] Figure 2 is a figure showing scanning electron microscope images of samples a to e, which are a group of small particle powders.

[0018] Figure 3 shows the volume cumulative particle size distribution curves for the positive electrode active materials of Examples 2 to 4.

[0019] Figure 4 shows the results of evaluating the lifespan characteristics of lithium secondary batteries prepared with the positive active materials of Examples 1 to 5 and Comparative Example 1.

[0020] Hereinafter, the present invention will be described in more detail to aid in understanding the invention.

[0021] Terms and words used in this specification and claims shall not be interpreted as being limited to their ordinary or dictionary meanings, but shall be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0022] In this specification, “lithium manganese-rich oxide” may refer to a lithium metal oxide having a layered crystal structure, wherein the molar ratio of lithium to the total number of moles of transition metals excluding lithium exceeds 1, and the molar content of manganese among the total transition metals excluding lithium is 50 mol% or more, specifically 50 mol% or more and less than 100 mol%.

[0023] The terms used in this specification are used merely to describe exemplary embodiments and are not intended to make the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0024] In this specification, terms such as “comprising,” “comprising,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should not be understood as precluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0025] In the following specifications, “primary particle” refers to a particle unit in which no grain boundaries appear when observed using a scanning electron microscope at a field of view of 5,000 to 20,000 times, and “secondary particle” refers to a particle formed by the aggregation of tens to hundreds of multiple primary particles. More specifically, the secondary particle is an aggregate of 40 or more primary particles.

[0026] The term “particle” as used below may include any one or all of single particles, pseudo-single particles, primary particles, nodules, and secondary particles.

[0027] In the following, the “average particle size of primary particles” can be calculated by measuring the particle size of primary particles by magnifying the sample surface 50,000 times using a scanning electron microscope (e.g., JEOL JSM-7200F) and then calculating the arithmetic mean of the measured particle size data.

[0028] Also, below, “the particle size of the secondary particle (D n )" refers to the particle size corresponding to the volume cumulative n% in the volume cumulative particle size distribution of the powder under measurement. That is, D 50 is the particle size at the 50% volume accumulation point in the volume accumulation particle size distribution, and D 90 is the particle size at the 90% volume accumulation point in the volume accumulation particle size distribution, D 10 is the particle size at the 10% volume cumulative point in the volume cumulative particle size distribution. The above D n D can be measured using the laser diffraction method. Specifically, 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., Malvern Mastersizer 3000) and irradiated with ultrasound at approximately 28 kHz at an output of 60 W. A volume-cumulative particle size distribution graph is obtained, and D is determined by calculating the particle size at points representing 10%, 50%, or 90% of the volume-cumulative amount from the obtained graph. 10 , D 50 and D 90 It can measure.

[0029] In the following, the "porosity (%)" of the cathode active material refers to the percentage of the pore volume within the powder group relative to the total volume of the active material powder group, and can be obtained by calculating the value of {(True Density - Actual Density) / True Density} × 100 of the active material powder group. For example, after placing oxide powder with a true density of 4.4 g / cc into a cylindrical mold, the volume (0.974 cm³) is calculated using the base area of ​​the cylindrical mold and the height filled with powder. 3 The volume was calculated, and the density (actual density, approximately 3.08 g / cc) was calculated using the volume and the mass of the powder (3g). By substituting the actual density and true density obtained through the above calculation into the equation below, it can be confirmed that the porosity is 30%.

[0030] Porosity (%) = {(True Density - Actual Density) / True Density} × 100

[0031] In this case, the term "true density" refers to the density when the space is completely filled with particles, excluding the gaps between particles, and the term "actual density" refers to the density of the active material powder group to be measured. The term "target density" used in the rolling load measurement process described below has the same meaning as the "actual density" defined above.

[0032] In addition, the “porosity” of the electrode in this specification can be measured by analyzing a photograph of a cross-section of the electrode specimen taken with a scanning electron microscope (e.g., JEOL JSM-7200F) at a magnification of 1,000 to 2,000 times.

[0033] Specific embodiments of the present invention will be described in detail below.

[0034]

[0035] Lithium-rich manganese oxide has a lower density compared to other types of cathode active materials, so a high rolling load is required to achieve the target electrode density. However, when rolling under a high rolling load, the active material particles break and generate fine particles, which causes a problem of reduced battery life when applied to a battery.

[0036] Accordingly, the inventors of the present invention continuously studied the relationship with rolling load under various conditions, such as mixing large and small particles, in order to find a method to achieve the target electrode density while lowering the rolling load in the electrode manufacturing process, and as a result, completed the present invention.

[0037] The positive electrode active material of the present invention is a bimodal positive electrode active material in which large particles and small particles are mixed, wherein the large particles are lithium-rich manganese oxides in which the molar ratio of lithium to the total transition metals excluding lithium is greater than 1 and the molar content of manganese among the transition metals is 50 mol% or more, and the degree of sphericity of the large particles is 0.8 or higher.

[0038] A bimodal positive electrode active material refers to a mixture that exhibits a normal distribution with two peaks in the particle distribution, and the positive electrode active material of the present invention has a bimodal form in which large particles and small particles are mixed. In the bimodal positive electrode active material, large particles support the structure of the active material layer, and small particles fill the gaps between large particles to reduce voids. As a result, the target electrode density can be achieved even at low rolling loads.

[0039] In another embodiment, the small particles may be lithium-rich manganese oxide. When lithium-rich manganese oxide is mixed as small particles in the positive electrode active material of the present invention, it may have the effect of compensating for the lower true density compared to when positive electrode active materials such as lithium nickel-cobalt-manganese oxide (NCM) or lithium nickel-cobalt-aluminum oxide (NCA) are mixed. According to one embodiment, when the small particles are lithium-rich manganese oxide, the positive electrode active material of the present invention may have a true density range as described below.

[0040] In this specification, roundness (r) refers to a value obtained according to the following Equation 1, and may be a value calculated by setting the particle parameter to 300 to 400 in Image Analysis Management (IAM) analysis.

[0041] [Equation 1]

[0042] Sphericity = (4×Area) / (π×D max 2 )

[0043] In the above Equation 1,

[0044] Area refers to the surface area of ​​the particle,

[0045] D max represents the major axis length of the particle.

[0046] The area and major axis length of the particles can be obtained using images taken with a scanning electron microscope. Specifically, after uniformly coating a group of positive active material powders onto a substrate such as carbon tape, the positive active material particles are photographed using a scanning electron microscope (e.g., JSM-7200F (JEOL)), and the area and major axis length of the particles are calculated through IAM analysis. In this case, the area of ​​the particles refers to the planar area of ​​the particles shown in the photograph, and the major axis length of the particles refers to the length of the longest axis of the particles shown in the photograph.

[0047] In one embodiment of the present invention, the degree of sphericity of the large particles may be 0.8 or higher, specifically 0.8 or higher and 1.0 or lower, and more specifically 0.8 or higher and 0.9 or higher. When the degree of sphericity of the large particles satisfies the above range, the rolling load in the electrode rolling process can be lowered to minimize breakage of the active material particles. Accordingly, a secondary battery with excellent lifespan performance can be manufactured. Over-lithium manganese-rich oxides containing an excess of lithium and manganese had a problem in that it was difficult to control the degree of sphericity because fine pores and surface irregularities increased due to the layered crystal structure. However, it has become possible to control the degree of sphericity of the over-lithium manganese-rich oxide by appropriately adjusting the concentration of ammonia, stirring speed, pH concentration, temperature, and additives during the manufacturing process. Specifically, increasing the concentration of ammonia (NH3) during the co-precipitation process promotes aggregation between primary particles and forms a uniform aggregate, thereby increasing the degree of sphericity of the secondary particles. In addition, if the stirring speed is appropriately increased, collisions and aggregation occur uniformly during the secondary particle formation process, thereby increasing the degree of sphericity. Furthermore, if the pH is lowered or appropriate additives are added, grain boundary growth of secondary particles can be inhibited and the degree of sphericity can be increased. Additionally, by appropriately controlling temperature conditions during the co-precipitation and calcination processes, particle growth and the internal density and uniformity of the aggregates can be enhanced, thereby increasing the degree of sphericity as well.

[0048] In one embodiment, the large particles may be included in an amount exceeding 50% by weight based on the total weight of the positive electrode active material, specifically 60% to 90% by weight, and more specifically 60% to 70% by weight. As the content of large particles in the positive electrode active material exceeds 50% by weight, the amount of fine particles generated due to particle breakage during the rolling process can be reduced, and the structure of the active material layer can be stably supported. In addition, the density can be effectively increased by rolling.

[0049] In another embodiment, the small particles may be included in an amount of less than 50% by weight, specifically 10% to 40% by weight, and more specifically 30% to 40% by weight, based on the total weight of the positive electrode active material. When the small particles in the positive electrode active material are included within the above range, the small particles fill the gaps between the large particles, thereby reducing the voids and consequently increasing the electrode density.

[0050] In one embodiment of the present invention, the small particles and large particles may each be secondary particles formed by the aggregation of a plurality of primary particles.

[0051] In one embodiment of the present invention, the average particle size of the primary particles of the large particles may be 100 nm to 500 nm, and the average particle size of the secondary particles (D 50 ) has an average particle size (D) of 8㎛ to 12㎛, more specifically 8㎛ to 11㎛, and even more specifically 9㎛ to 11㎛. 50 Can have ).

[0052] In one embodiment of the present invention, the primary particle average diameter of the small particles may be 100 nm to 500 nm, and the secondary particle average diameter (D 50 ) may be 1㎛ to 5㎛, more specifically 2㎛ to 5㎛, and more specifically 3㎛ to 5㎛.

[0053] In addition, the positive active material of the above large and small particles has the above average particle size (D 50 By having a range, the electrode density after rolling can be appropriately realized, and the capacity characteristics of the battery can be improved.

[0054] In one embodiment, the degree of sphericity of the small particles may be 0.7 or higher, specifically 0.7 to 0.8, and more specifically 0.7 to 0.75. When the degree of sphericity of the small particles satisfies the above range, the small particles can effectively fill the gaps between the large particles, thereby reducing the porosity and increasing the electrode density.

[0055] In the present invention, the sphericity of large particles was measured by magnifying the surface of the sample 1,000 times using a scanning electron microscope (e.g., JSM-7200F (JEOL)), and the sphericity of small particles was measured by magnifying the surface of the sample 2,000 times using the same equipment as for large particles.

[0056] In one embodiment, the true density of the positive electrode active material of the present invention may be 3.5 g / cc to 5.5 g / cc, more specifically 3.5 g / cc to 5.3 g / cc, and even more specifically 4 g / cc to 5 g / cc. If the true density of the positive electrode active material is 3.5 g / cc or higher, it may exhibit high energy density, and accordingly, the capacity and lifespan of the battery may be improved. In addition, if the true density of the positive electrode active material is 5.5 g / cc or lower, it may exhibit an appropriate porosity within the electrode, and accordingly, appropriate ion conductivity may be secured.

[0057] The above true density can be measured at room temperature and atmospheric pressure using a gas pycnometer.

[0058] In one embodiment, the porosity of the positive electrode active material may be 15% to 35%, specifically 18% to 35%, and more specifically 20% to 35%. When manufacturing an electrode comprising a positive electrode active material having a porosity within the above range, the porosity within the electrode is optimized, thereby obtaining a positive electrode with improved ion conductivity and energy density. As a result, the capacity and lifespan of the battery are improved.

[0059] According to one embodiment of the present invention, the lithium-rich manganese oxide can be represented by the following formula A.

[0060] [Equation A]

[0061] Li a [Ni b Co c Mn d M e ]O2

[0062] In the above Equation A, 1.0 <a, 0≤b≤0.5, 0≤c≤0.1, 0.5≤d≤1.0, 0≤e≤0.2이고, M은 Al, B, W, Mg, V, Ti, Zn, Ga, In, Ru, Nb, Sn, Sr 및 Zr로 이루어진 군에서 선택된 적어도 하나 이상이다.

[0063] Meanwhile, a is 1.0 as the molar ratio of Li in the lithium-over-manganese-rich oxide. <a, 1.1≤a≤1.5, 또는 1.12<a<1.18일 수 있다. a가 상기 범위를 만족할 때, 고용량 특성 및 단위부피당 높은 에너지 밀도를 구현할 수 있다.

[0064] The above b is the molar ratio of Ni in the lithium-over-manganese-rich oxide, where 0≤b≤0.5, 0.1≤b≤0.4, or 0.24 <b<0.36일 수 있다.

[0065] The above c is the molar ratio of Co in the lithium-over-manganese-rich oxide, where 0≤c≤0.1, 0≤c≤0.05, or 0 <c<0.01일 수 있다. c가 0.1을 초과할 경우, 고용량 확보가 어렵고, 가스 발생 및 양극 활물질의 퇴화가 심화되어 수명 특성이 저하될 수 있다.

[0066] The above d is the molar ratio of Mn in the lithium-rich manganese oxide, and may be 0.5≤d≤1.0, 0.5≤d≤0.8, or 0.5≤d<0.7. If d is less than 0.5, the proportion of rock salt phase becomes too small, so the effect of improving capacity is negligible.

[0067] The above e is the molar ratio of additional element M in the lithium-over-manganese-rich oxide, where 0≤e≤0.2, 0≤e≤0.1, or 0 <e<0.05일 수 있다. 추가 원소의 함량이 너무 많으면 활물질 용량에 악영향을 미칠 수 있다.

[0068] In another embodiment, the lithium-rich manganese oxide may comprise a layered crystal structure. Specifically, the lithium-rich manganese oxide may comprise a mixture of a compound having a layered crystal structure and a compound having a rock salt-like crystal structure. An example of a compound having a layered crystal structure is Li[Ni 1-y-z-w Mn y Co z M w ]O2, Li2MnO3 can be cited as an example of a compound having the above rock salt-like crystal structure. Accordingly, the above lithium manganese-rich oxide may also be represented by the following formula B.

[0069] [Equation B]

[0070] X*Li2MnO3· (1-X)*Li[Ni 1-y-z-w Mn y Co z M w ]O2

[0071] In the above formula B, M is at least one selected from the group consisting of Al, B, W, Mg, V, Ti, Zn, Ga, In, Ru, Nb, Sn, Sr, and Zr.

[0072] The above X represents the ratio of the rock salt phase (Li2MnO3) in the lithium-over-manganese-rich oxide, and may be 0.2≤X≤0.5, 0.25≤X≤0.5, or 0.25≤X≤0.4. When the ratio of the rock salt phase (Li2MnO3) in the lithium-over-manganese-rich oxide satisfies the above range, high capacity characteristics can be achieved.

[0073] The above y is the molar ratio of Mn in the layer (LiM'O2), and may be 0.4≤y<1, 0.4≤y≤0.8, or 0.4≤y≤0.7.

[0074] The above z is the molar ratio of Co in the layered structure (LiM'O2), and may be 0≤z≤0.1, 0≤z≤0.08, or 0≤z≤0.05. If z exceeds 0.1, gas generation and degradation of the cathode active material may be exacerbated, which may lead to a decrease in lifespan characteristics.

[0075] The above w is the molar ratio of additional element M in the layer (LiM'O2), and may be 0≤w≤0.2, 0≤w≤0.1, or 0≤w≤0.05.

[0076] The cathode active material of the above-described embodiment can be manufactured according to a general method for manufacturing lithium-rich manganese oxide. For example, each of the large particle and small particle cathode active materials can be manufactured by mixing a transition metal precursor containing manganese with a lithium raw material and then calcining it. Since the types of each of these precursors and raw materials and the manufacturing conditions can follow the general manufacturing conditions of manganese-rich cathode active materials, further explanation regarding this is omitted.

[0077] However, as described above, a large-particle cathode active material satisfying the degree of sphericity described above can be manufactured by controlling the concentration of ammonia (NH3), stirring speed, pH concentration, additives, and temperature during the manufacturing process, and the cathode active material of one embodiment can be obtained by mixing the manufactured large-particle cathode active material and the small-particle cathode active material in a certain ratio. Since the process conditions for manufacturing the cathode active material to obtain a certain degree of sphericity are obvious to those skilled in the art, further explanation regarding this is omitted.

[0078] Meanwhile, in one embodiment of the present invention, a positive electrode is provided that includes a bimodal positive electrode active material mixed with the large and small particles described above. Such a positive electrode may include a positive electrode active material layer formed on one or both sides of a positive electrode current collector, and the positive electrode active material layer may be manufactured by coating and drying a positive electrode slurry, in which a positive electrode active material and optionally a binder, a conductive material, etc. are mixed in a solvent, onto a positive electrode current collector and then rolling.

[0079] First, according to one embodiment, the positive active material may be included in an amount of 90% to 99% by weight, or 95% to 99% by weight, or 97% to 98% by weight, based on the total weight of the solids (e.g., positive active material, conductive material, and binder) in the positive slurry. If the content of the positive active material in the solids is 90% by weight or less, the energy density may be lowered, and the capacity may be reduced.

[0080] Additionally, the binder may be one or more selected from the group consisting of polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, and various copolymers thereof, and preferably may be polyvinylidene fluoride (PVDF).

[0081] The binder may be included in an amount of 0.5% to 2.5% by weight, or 1% to 2% by weight, or 1.5% to 2% by weight, based on the total weight of the solid content in the anode slurry. When the content of the binder is within the above range, sufficient adhesion to the current collector and inter-particle bonding are secured, thereby improving the durability of the anode while maintaining a low initial resistance.

[0082] The conductive material may be one or more selected from the group consisting of graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black; carbon-based materials such as carbon fibers or carbon nanotubes; metal powders or metal fibers such as copper, nickel, aluminum, or silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives, and preferably carbon nanotubes or carbon black, most preferably carbon black.

[0083] According to one embodiment of the present invention, a dot-shaped conductive material, such as carbon black, may be included in the anode slurry. The dot-shaped conductive material can effectively fill the fine gaps between active material particles to achieve a target electrode density even under low rolling loads, and can exhibit excellent electrical conductivity by being uniformly distributed within the electrode.

[0084] The conductive material may be included in an amount of 0.1% to 2.5% by weight, or 0.3% to 2% by weight, or 0.5% to 1% by weight, based on the total weight of the solid content in the anode slurry. It is preferable that the content of the conductive material be within the above range in that it can reduce the dead volume while maintaining conductivity between active materials.

[0085] In addition, the anode slurry may optionally further include a dispersant, and the dispersant may be hydrogenated nitrile butadiene rubber (HNBR).

[0086] Meanwhile, the solvent of the anode slurry may be a solvent commonly used in the relevant technical field, for example, N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), isopropyl alcohol, dimethyl formamide (DMF), acetone, water, or a mixture of two or more of these may be used. The solvent may be used in an amount adjusted to achieve the viscosity of the anode slurry described above.

[0087] Meanwhile, according to another embodiment of the present invention, a positive electrode comprising the positive electrode active material described above is provided. Such a positive electrode may be manufactured from the positive electrode slurry and may include, for example, a positive electrode current collector; and a positive electrode active material layer formed on the positive electrode current collector and comprising the positive electrode active material of one embodiment. In this case, the positive electrode active material layer may further include a binder and a conductive material by being formed by coating, drying, and rolling, etc., of the slurry described above.

[0088] The above positive current collector may include a highly conductive metal, and is not particularly limited as long as it facilitates the adhesion of the positive active material layer and is non-reactive within the voltage range of the battery. The above positive current collector may be, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. Additionally, the above positive current collector may typically have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the above positive current collector to increase the adhesion of the positive active material. It may be used in various forms, such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

[0089] The above-described anode may be manufactured according to a conventional anode manufacturing method, except for using the anode active material of the above-described embodiment. Specifically, it may be manufactured by applying the anode slurry onto an anode current collector and then drying and rolling, or by casting the anode slurry onto a separate support and then laminating the film obtained by peeling it off from the support onto an anode current collector.

[0090] In one embodiment, the degree of sphericity of the large particles may be 0.8 or higher, specifically 0.8 or higher and 1.0 or lower, and more specifically 0.8 or higher and 0.9 or higher. When the positive electrode active material of the present invention is included, the rolling load in the electrode manufacturing process can be lowered, thereby minimizing breakage of the active material particles. Accordingly, the degree of sphericity of the large particles in the powder state of the positive electrode active material and the degree of sphericity of the large particles in the positive electrode after the rolling process can exhibit substantially the same range.

[0091] In addition, according to one embodiment, the amount of fine particles of the positive electrode active material may be 15 volume% or less of the total positive electrode active material, specifically 0.1 volume% or more and 10 volume% or less, and more specifically 0.1 volume% to 8 volume%. At this time, particles with a particle size of 1 μm or less are defined as fine particles. Specifically, when pressed with a rolling load of 4 to 7 ton, 4.5 to 7 ton, or 4.5 to 6.5 ton in the electrode manufacturing process, the amount of fine particles with a particle size of 1 μm or less after pressing may be 5 volume% or less of the total positive electrode active material, specifically 0.1 volume% or more and 5 volume% or less. The amount of fine particles of the above-mentioned positive electrode active material can be obtained by measuring the volumetric cumulative particle size distribution using a laser diffraction particle size measuring device (e.g., Malvern Mastersizer 3000) for the powder obtained by grinding the high-temperature treated positive electrode, and by calculating the volumetric ratio of particles with a particle size of 1 μm or less in the volumetric cumulative particle size distribution.

[0092] In another embodiment, the porosity of the anode may be 15% to 35%, more specifically 18% to 35%, and even more specifically 20% to 35%. When the porosity of the anode satisfies the above range, it has excellent ionic conductivity and energy density, and accordingly, the capacity and lifespan characteristics of the battery are improved.

[0093] According to one embodiment, the particle size D of the anode active material in the manufactured anode 10 It may be 1.5㎛ to 4㎛, more specifically 1.5㎛ to 3.5㎛, and even more specifically 1.9㎛ to 3㎛, and D 50 It may be 5㎛ to 8㎛, more specifically 6㎛ to 8㎛, and even more specifically 6.5㎛ to 8㎛, and D 90 The thickness may be 11㎛ to 15㎛, more specifically 12㎛ to 15㎛, and even more specifically 12.5㎛ to 15㎛.

[0094] In one embodiment, the particle size D of the large particles within the manufactured anode 10 The size may be 5㎛ to 11㎛, more specifically 6㎛ to 10㎛, and even more specifically 6.5㎛ to 9.5㎛, and D 50 The size may be 6㎛ to 13㎛, more specifically 7㎛ to 12㎛, and even more specifically 7.5㎛ to 11.5㎛, and D 90 The thickness may be 7㎛ to 14㎛, more specifically 8㎛ to 13㎛, and even more specifically 8.5㎛ to 12.5㎛.

[0095] In another embodiment, the particle size D of the small particles in the manufactured anode 10 It may be 1㎛ to 5㎛, more specifically 1.5㎛ to 4.5㎛, and even more specifically 1.9㎛ to 4㎛, and D 50 The size may be 3㎛ to 8㎛, more specifically 3.5㎛ to 7.5㎛, and even more specifically 3.5㎛ to 7㎛, and D 90 The thickness may be 4㎛ to 9㎛, more specifically 4.5㎛ to 8.5㎛, and even more specifically 5㎛ to 8㎛.

[0096] When the particle sizes of large and small particles within the anode each satisfy the above ranges, high ionic conductivity and energy density can be achieved simultaneously, thereby improving the capacity and lifespan characteristics of the battery.

[0097] Meanwhile, according to another embodiment of the present invention, a lithium secondary battery comprising the anode described above is provided. Such a lithium secondary battery may include, for example, the anode described above, a negative electrode facing the anode, a separator or an electrolyte layer interposed between the anode and the negative electrode, and optionally an electrolyte. In this case, since the anode is the same as previously described, a detailed description is omitted, and only the remaining components are described in detail below.

[0098] In the above lithium secondary battery, the negative electrode comprises a negative electrode current collector and a negative electrode active material layer located on one or both sides of the negative electrode current collector.

[0099] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. In addition, the above-mentioned negative current collector may typically have a thickness of 3 μm to 500 μm, and, similar to the positive current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0100] The above-mentioned cathode active material layer optionally includes a binder and a conductive material together with the cathode active material.

[0101] As the above-mentioned negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific 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 β Examples include metal oxides capable of doping and dedoping lithium, such as (0<β<2), SnO2, vanadium 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. The negative electrode active material may be included in an amount of 80% to 99% by weight based on the total weight of the negative electrode active material layer.

[0102] The above binder is a component that assists in the bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 0.1% to 10% by weight based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0103] The above conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode active material layer. Such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon; metal powder such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

[0104] The above-mentioned negative electrode active material layer may be manufactured by applying a negative electrode slurry, prepared by dissolving or dispersing a negative electrode active material and optionally a binder and a conductive material in a solvent, onto a negative electrode current collector and drying it, or by casting the negative electrode slurry onto a separate support and then laminating the film obtained by peeling it off from the support onto a negative electrode current collector.

[0105] Meanwhile, in the above-mentioned lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. Any separator typically used in lithium secondary batteries may be used without special limitations, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity. Specifically, a porous polymer film, such as a porous polymer film made from a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, 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.

[0106] In addition, the above-mentioned separator may be an SRS separator having a structure in which an organic-inorganic mixed layer containing inorganic particles and a binder is formed on one or both sides of a polymer substrate.

[0107] Meanwhile, the lithium secondary battery may include the separator, but may also include an electrolyte layer separately from the separator, or include a laminate in which an electrolyte layer is laminated on the separator. In addition, in a specific example, the electrolyte layer may be a gel electrolyte layer containing a gel electrolyte or a solid electrolyte layer.

[0108] In a more specific example, the electrolyte layer including the gel electrolyte comprises, for example, a matrix including a polyurethane-based or polyacrylic-based crosslinked polymer, a lithium salt, and a non-aqueous organic solvent, and may have a form in which the lithium salt and the non-aqueous organic solvent are dispersed or encapsulated within the matrix. However, since the types of crosslinked polymers, lithium salts, and organic solvents that may be included in the gel electrolyte are obvious to those skilled in the art, further explanation regarding this is omitted.

[0109] In addition, in another specific example, the solid electrolyte layer may include one or more selected from the group consisting of any solid electrolyte, for example, polymer-based solid electrolytes, oxide-based solid electrolytes, sulfide-based solid electrolytes, and halogenated solid electrolytes. However, since the composition of such solid electrolyte layer may follow that of a general solid electrolyte layer known previously, further explanation is omitted.

[0110] Meanwhile, the above-described lithium secondary battery may further include an electrolyte comprising a lithium salt and a non-aqueous organic solvent.

[0111] The above-mentioned non-aqueous organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above-mentioned organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; and aromatic hydrocarbon-based solvents such as benzene and fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.

[0112] The above lithium salt may be used without special restrictions as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, as the anion of the above lithium salt, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - It may be at least one selected from the group consisting of, and the lithium salt is, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2) 2, LiCl, LiI, or LiB(C2O4)2, etc., may be used. It is preferable to use the lithium salt within the range of 0.1 to 4.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0113] 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. In this case, the additive may be included in an amount of 0.1 to 5 weight% based on the total weight of the electrolyte.

[0114] Since the aforementioned lithium secondary battery stably exhibits excellent discharge capacity, output characteristics, and lifespan characteristics, it is useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0115] In addition, there are no special restrictions on the external shape of the above lithium secondary battery, but it may be a cylindrical shape using a can, a prismatic shape, a pouch shape, or a coin shape.

[0116] In addition, the above-described lithium secondary battery can be used not only as a battery cell used as a power source for small devices, but can also preferably be used as a unit cell in a medium-to-large battery module containing a plurality of battery cells.

[0117] Examples of the above-mentioned medium-to-large devices include electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems, but are not limited to these.

[0118] In the present invention, the positive electrode, lithium secondary battery, etc., can be manufactured using materials or manufacturing methods known in this technical field.

[0119]

[0120] The present invention will be explained in more detail below through specific embodiments.

[0121]

[0122] <Manufacturing of Cathode Active Material>

[0123] (1) Preparation of large and small particle positive electrode active materials

[0124] The large particle cathode active materials 1 to 6 and small particle cathode active materials a to f used in the manufacturing example, example, and comparative example each have characteristics as shown in Table 1 and Table 2 below.

[0125] Sample composition (ICP) average particle size (D 50 )Particle Sphericity (r)1Li 1.14 Mn 0.55 Ni 0.31 O29.340.8772Li 1.16 Mn 0.54 Ni 0.30 O29.30.803Li 1.16 Mn 0.54 Ni 0.30 O29.330.8464Li 1.16 Mn 0.54 Ni 0.30 O29.310.8195Li 1.15 Mn 0.55 Ni 0.30 O210.20.806Li 1.15 Mn 0.55 Ni 0.30 O210.40.717

[0126] Sample composition (ICP) average particle size (D 50 ) Degree of small particle sphericity aLi 1.14 Mn 0.55 Ni 0.31 O23.680.734bLi 1.16 Mn 0.54 Ni 0.30 O23.610.730cLi 1.16 Mn 0.54 Ni 0.30 O23.620.736dLi 1.15 Mn 0.54 Ni 0.31O23.580.744eLi 1.15 Mn 0.55 Ni 0.30 O22.80.730fLi 1.15 Mn 0.55 Ni 0.30 O22.9 unmeasurable

[0127] In Tables 1 and 2 above, the average particle size (D 50 The sphericity and sphericity were measured by uniformly coating each powder group of samples 1 to 6 and samples a to f onto a carbon tape, taking photographs of the powder particles using a scanning electron microscope (JEOL, JSM-7200F), and performing IAM analysis. However, since the powder group of sample f had a very irregular particle shape, it was difficult to identify the shape of the small particles from the photographs, so the sphericity could not be measured and was listed as unmeasurable in Table 2. Photographs of each sample are shown in Figures 1 and 2.

[0128]

[0129] (2) Preparation of positive electrode active material of the example and comparative example

[0130] As described in Table 3 below, the anode active materials of Examples 1 to 5 and Comparative Example 1 were prepared by mixing large particle and small particle samples in a weight ratio of 65:35.

[0131] In addition, each of the powder groups of the manufactured examples and comparative examples was placed in a cylindrical mold, and the target density (actual density) to achieve a porosity of approximately 30% was calculated using the true density (g / cc) of each sample. Then, using the target density, the mass of the sample, and the bottom surface area of ​​the cylindrical mold, the rolling thickness to achieve a porosity of approximately 30% (target porosity) was set. The rolling load measured by applying pressure up to the set rolling thickness is listed in Table 3 below.

[0132] Porosity = {(True Density - Actual Density) / True Density} × 100

[0133] Target Density (Actual Density) = True Density × {(100 - Target Porosity) / 100}

[0134] Rolling thickness = Powder group sample mass / (Target density × Mold base area)

[0135] Experimental Example Mixture P (ton) Example 1 Sample 1 + Sample a 4.7 Example 2 Sample 2 + Sample b 5.4 Example 3 Sample 3 + Sample c 6 Example 4 Sample 4 + Sample d 6.4 Example 5 Sample 5 + Sample e 5.9 Comparative Example 1 Sample 6 + Sample f 7.4

[0136] From Table 3 above, it can be seen that the embodiments of the present invention require a lower rolling load to achieve the same porosity compared to Comparative Example 1.

[0137]

[0138] <Manufacturing of Cathodes and Lithium Secondary Batteries>

[0139] A positive electrode slurry was prepared by adding the positive electrode active material of Example 1 prepared above, KF9700 (Kureha) as a binder, Li435 (Denka) as a conductive material, and BM-740H (Zeon) as a dispersant to N-methylpyrrolidone in a weight ratio of 96.25:2.1:1.5:0.15. The positive electrode slurry was applied onto an aluminum current collector sheet and dried, and then the positive electrode was manufactured by rolling it under a rolling load of 4.7 tons.

[0140] A cathode slurry was prepared by mixing a positive active material, a conductive material, and a binder, in which natural graphite and artificial graphite were mixed in a weight ratio of 5:5. The cathode slurry was applied onto a copper current collector sheet, dried, and then rolled to produce a cathode.

[0141] An electrode assembly was manufactured by interposing an SRS separator between the anode and cathode manufactured as described above, and after inserting the electrode assembly into a battery case, an electrolyte was injected, and an activation process was performed by charging at 45°C with a constant current of 0.1C until the voltage reached 4.6V, and then discharging at a constant current of 0.1C until the voltage reached 2.0V to manufacture a lithium secondary battery.

[0142]

[0143] In addition, a lithium secondary battery was manufactured in the same manner as above, except that each of the positive active materials of Examples 2 to 5 and Comparative Example 1 was used and rolled with the rolling load described in Table 3.

[0144]

[0145] Experimental Example 1. Measurement of Anode Porosity

[0146] As a result of analyzing cross-sectional images of the anodes containing the anode active materials of Examples 1 to 5 and Comparative Example 1 prepared above, each magnified 1,000 times using a scanning electron microscope (JEOL JSM-7200F), the porosity of the anodes was all approximately 30%, showing similar electrode densities. From this, it can be confirmed that the embodiments of the present invention require a lower rolling load to achieve the same range of electrode densities compared to Comparative Example 1.

[0147]

[0148] Experimental Example 2. Evaluation of Volume Cumulative Particle Size Distribution and Particle Breakage Rate of Anode

[0149] The cathode containing the cathode active material of Example 2, Example 3, or Example 4 was heat-treated in a furnace at a temperature of 700°C for 10 hours to collect the cathode active material, and then finely ground using a mortar and pestle, and classified using a 250 mesh sieve to obtain the cathode active material powder contained in each cathode. For the obtained powder, the Particle Size Distribution (PSD) was obtained using a Mastersizer 3000 (Malvern). The Particle Size Distribution of the cathode active material is shown in Figure 3.

[0150] From this, the Dn value of each powder, limit rolling, and the volume ratio of particles having a particle size of 1 μm or less among the anode active material contained in the anode were evaluated and are shown in Table 4 below.

[0151] Experimental Example Example 2 Example 3 Example 4 Dn(㎛) D10 2.07 2.05 1.94 D50 7.22 7.47 6.93 D90 13.61 4.11 2.6 Micro amount (%) 4.44 54.8 Limit rolling (%) 28.62 8.82 9.3

[0152] From Figure 3 and Table 4, it can be seen that as the rolling load decreases, the amount of fine particles generated and the limit rolling decrease. From this, it is expected that Comparative Example 1 will generate more fine particles and exhibit a higher limit rolling than Example 4. In addition, it is predicted that a battery with high energy density and excellent performance can be manufactured by applying the cathode active material of the present invention.

[0153]

[0154] Experimental Example 3. Evaluation of Life Characteristics

[0155] For a total of six lithium secondary batteries using the positive active materials of Examples 1 to 5 and Comparative Example 1, a charge and discharge test of 100 cycles was conducted at 45°C and a voltage range of 2.0V to 4.35V under conditions of 0.3C / 0C. The capacity retention rate during these charge and discharge cycles was evaluated and is shown in Fig. 4.

[0156] Referring to FIG. 4, it was confirmed that the lithium secondary batteries of Examples 1 to 5 exhibited superior lifespan characteristics, with a higher capacity retention rate after 100 charge and discharge cycles compared to Comparative Example 1. This is attributed to the effect of reducing the amount of fine particles generated during the rolling process.

[0157]

[0158] Although 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 by those skilled in the art using the basic concept of the present invention as defined in the following claims also fall within the scope of the present invention.

Claims

1. As a bimodal positive electrode active material comprising a mixture of large and small particles, The above-mentioned large particle is an over-lithium manganese-rich oxide in which the molar ratio of lithium to all transition metals excluding lithium is greater than 1, and the molar content of manganese among the transition metals is 50 mol% or more. A positive active material having a sphericity of 0.8 or higher of the above-mentioned particles.

2. In Claim 1, The above-mentioned small particles are a positive electrode active material that is a lithium-rich manganese oxide.

3. In Claim 1, The above-mentioned large particles are included in an amount exceeding 50% by weight based on the total weight of the above-mentioned positive active material.

4. In Claim 1, The average particle size (D) of the above particles 50 ) is a positive electrode active material having a thickness of 8㎛ to 12㎛.

5. In Claim 1, Average particle size (D) of the above small particles 50 ) is a positive electrode active material having a size of 1㎛ to 5㎛.

6. In Claim 1, A positive active material having a degree of sphericity of 0.7 or higher of the above-mentioned small particles.

7. In Claim 1, A positive active material having a true density of 3.5 g / cc to 5.5 g / cc.

8. In Claim 1, A positive active material having a porosity of 15% to 35%.

9. In Claim 1, The above-mentioned lithium-rich manganese oxide is a positive active material represented by the following formula A: [Essence A] Li a [Ni b Co c Mr d M e ]O2 In the above Equation A, 1.0 <a, 0≤b≤0.5, 0≤c≤0.1, 0.5≤d≤1.0, 0≤e≤0.2이고, M은 Al, B, W, Mg, V, Ti, Zn, Ga, In, Ru, Nb, Sn, Sr 및 Zr로 이루어진 군에서 선택된 적어도 하나 이상이다.

10. In Claim 1, The above-mentioned lithium manganese-rich oxide is a positive active material comprising a layered crystal structure.

11. An anode comprising a bimodal anode active material comprising a mixture of large particles and small particles according to any one of claims 1 to 10.

12. In Claim 11, An anode in which the degree of sphericity of the above-mentioned particles is 0.8 or higher.

13. In Claim 11, A cathode in which the fine amount of the above-mentioned positive active material is 15 volume% or less of the total positive active material.

14. In Claim 11, An anode having a porosity of 15% to 35%.

15. In Claim 11, Particle size D of the above positive active material 10 is 1.5㎛ to 4㎛, and D 50 It is 5㎛ to 8㎛, and D 90 An anode having a thickness of 11㎛ to 15㎛.

16. In Claim 11, The above anode is an anode comprising a point-shaped conductive material.

17. Anode according to claim 11; A cathode facing the anode; and A lithium secondary battery comprising a separator or electrolyte layer interposed between the anode and the cathode.

18. In Claim 17, A lithium secondary battery further comprising an electrolyte including a lithium salt and a non-aqueous organic solvent.

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