Positive electrode active material, method for preparing same, and positive electrode and lithium secondary battery each comprising same

Abstract

The present invention relates to a positive electrode active material, a method for preparing same, and a positive electrode and a lithium secondary battery each comprising same. The positive electrode active material of the present invention comprises a lithium nickel-based transition metal oxide in the form of a single particle and satisfies that, upon XRD measurement, a peak appears in a section of 2θ = 28-30° and no peak appears in sections of 2θ = 37-37.8° and 2θ = 45-46°, thereby significantly enhancing initial resistance characteristics and improving the capacity retention rate and the resistance increase rate at high temperature. In the method of preparing the positive electrode active material, the above-described positive electrode active material can be prepared by controlling firing conditions.

Description

A positive electrode active material, a method for manufacturing the same, and a positive electrode and a lithium secondary battery including the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2025-0032604 filed on March 13, 2025, and all contents disclosed in the document of said Korean patent application are incorporated herein as part of this specification.

[0003] Technology field

[0004] The present invention relates to a positive electrode active material, a method for manufacturing the same, and a positive electrode and a lithium secondary battery comprising the same.

[0005]

[0006] With the increasing technological development and demand for mobile devices, the demand for rechargeable batteries as an energy source is rapidly rising. Among these rechargeable batteries, lithium-ion batteries, which possess high energy density and voltage, long cycle life, and low self-discharge rates, have been commercialized and are widely used.

[0007] Lithium secondary batteries consist of four major components: a positive electrode, a negative electrode, a separator, and an electrolyte. Among these, the positive electrode active material, which is included in the positive electrode, plays a significant role in determining the battery's capacity, output, and lifespan. Currently used positive electrode active materials include NCM-based positive electrode active materials containing nickel, cobalt, manganese, and / or aluminum, and LFP (lithium iron phosphate)-based positive electrode active materials. Meanwhile, improving the performance of the positive electrode active material is essential for lithium secondary batteries to have high energy density, output, and lifespan; consequently, much research is currently being conducted to develop high-performance positive electrode active materials.

[0008] Recently, single-particle cathode active materials have been developed to address the problems associated with such secondary particle-type cathode active materials. However, single-particle cathode active materials have a long Li path, which leads to a degradation in cell performance, such as efficiency and resistance. Consequently, there is a need for single-particle cathode materials that have undergone surface modification through doping, coating, etc., to enable their use even at high voltages.

[0009]

[0010] The problem to be solved by the present invention is to provide a positive electrode active material that includes a lithium nickel-based transition metal oxide in the form of a single particle, and satisfies the condition that a peak appears in the 2θ=28~30° range and no peaks appear in the 2θ=37~37.8° range and the 2θ=45~46° range when measured by XRD, thereby improving initial resistance performance and improving high-temperature life, capacity retention rate, and resistance increase rate during high-temperature storage.

[0011]

[0012] (1) The present invention provides a positive electrode active material comprising a lithium nickel-based transition metal oxide in the form of a single particle, wherein when XRD measurement is performed, a peak appears in the 2θ=28~30° range and no peak appears in the 2θ=37~37.8° range and the 2θ=45~46° range.

[0013] (2) The present invention provides a positive electrode active material according to (1) above, wherein the lithium nickel-based transition metal oxide comprises yttrium (Y) and one or more selected from the group consisting of cobalt (Co) and manganese (Mn).

[0014] (3) The present invention provides a positive electrode active material according to (1) or (2), wherein the positive electrode active material comprises a coating portion including cobalt (Co) formed on the lithium nickel-based transition metal oxide.

[0015] (4) The present invention provides a positive electrode active material in any one of (1) to (3) above, wherein the lithium nickel-based transition metal oxide has a composition represented by the following chemical formula 1.

[0016] [Chemical Formula 1]

[0017] Li x1 Ni a1 Co b1 Mn c1 M 1 d1 O2

[0018] In the above chemical formula 1,

[0019] M 1 is one or more selected from the group consisting of Y, Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, V, F, P, and S, and

[0020] 0.9≤x1≤1.3, 0.5≤a1<1.0, 0 <b1<0.4, 0<c1<0.4, 0<d1≤0.2, a1+b1+c1+d1=1이다.

[0021] (5) The present invention provides a positive electrode active material in any one of (1) to (4) above, wherein the single particle form is a single particle form or a form in which two or more and 30 or fewer primary particles are aggregated.

[0022] (6) The present invention provides a positive electrode comprising a positive electrode active material according to any one of (1) to (5) above.

[0023] (7) The present invention provides a lithium secondary battery comprising a positive electrode according to (6) above.

[0024]

[0025] The positive electrode active material according to the present invention comprises a lithium nickel-based transition metal oxide in the form of a single particle, and satisfies the condition that when XRD measurement is performed, a peak appears in the 2θ=28~30° range and no peaks appear in the 2θ=37~37.8° range and the 2θ=45~46° range, thereby significantly improving the initial resistance characteristics and the capacity retention rate and resistance increase rate at high temperatures.

[0026]

[0027] Figure 1 is a graph showing the XRD analysis results for the cathode active materials of Examples 1 and 2 and Comparative Examples 1 to 4.

[0028]

[0029] The present invention will be described in more detail below to aid in understanding. In this regard, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0030] The terms used in this specification are used merely to describe exemplary embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0031] 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 be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0032] In this specification, 'primary particle' refers to the smallest unit of particle recognized when observing the positive electrode active material through a scanning electron microscope, and may consist of a single crystal or multiple crystal grains, and 'secondary particle' refers to a secondary structure formed by the aggregation of multiple primary particles. 'Single particle form' is a concept contrasted with the spherical secondary particle form formed by the aggregation of tens to hundreds of primary particles, and refers to a structure formed by the aggregation of a single particle or two or more, and thirty or fewer, primary particles.

[0033]

[0034] positive electrode active material

[0035] The present invention provides a positive electrode active material comprising a lithium nickel-based transition metal oxide in the form of a single particle, wherein, when XRD measured, a peak appears in the 2θ=28~30° range and no peaks appear in the 2θ=37~37.8° range and the 2θ=45~46° range.

[0036] The inventors confirmed that when XRD measurements are performed on a positive electrode active material containing a lithium nickel-based transition metal oxide in the form of a single particle, the coating structure stability is secured when a peak appears in the 2θ=28~30° range, and the surface structure is optimized when no peaks appear in the 2θ=37~37.8° range and the 2θ=45~46° range. They also discovered that when these conditions are satisfied, the initial resistance of the positive electrode active material and the capacity retention rate and resistance increase rate of its long-term performance (high-temperature life, high-temperature storage) are improved, and thus completed the present invention.

[0037] The peak in the 2θ=28~30° range may represent Y2O3, and the cathode active material of the present invention may include Y2O3. The Y2O3 may be present throughout within the lithium nickel-based transition metal oxide particles and may be distributed more on the surface than in the center of the particles. The peaks in the 2θ=37~37.8° and 2θ=45~46° ranges may represent LiCoO2.

[0038] The above single particle form may be a single particle form or a form in which two or more and 30 or fewer primary particles are aggregated.

[0039]

[0040] According to the present invention, the lithium nickel-based transition metal oxide may include yttrium (Y) and one or more selected from the group consisting of cobalt (Co) and manganese (Mn). More specifically, the lithium nickel-based transition metal oxide may include all of yttrium (Y), cobalt (Co), and manganese (Mn).

[0041]

[0042] According to the present invention, the positive electrode active material may comprise a coating portion comprising cobalt (Co) formed on the lithium nickel-based transition metal oxide. The coating portion comprising cobalt may be formed on a crystal interface existing on the surface of the lithium nickel-based transition metal oxide particles and may exist in the form of a very thin film.

[0043]

[0044] According to the present invention, the lithium nickel-based transition metal oxide may have a composition represented by the following chemical formula 1.

[0045] [Chemical Formula 1]

[0046] Li x1 Ni a1 Co b1 Mn c1 M 1 d1 O2

[0047] In the above chemical formula 1,

[0048] M 1 is one or more selected from the group consisting of Y, Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, V, F, P, and S, and

[0049] 0.9≤x1≤1.3, 0.5≤a1<1.0, 0 <b1<0.4, 0<c1<0.4, 0<d1≤0.2, a1+b1+c1+d1=1이다.

[0050] The above a1 represents the atomic fraction of nickel among the metal elements in the lithium composite transition metal oxide, and may be 0.5≤a1<1.0, 0.6≤a1≤0.9, or 0.6≤a1≤0.8.

[0051] The above b1 refers to the atomic fraction of cobalt among the metal elements in the lithium complex transition metal oxide, where 0 <b1<0.4, 0.01≤b1≤0.2, 0.01≤b1≤0.15 또는 0.01≤b1≤0.1일 수 있다.

[0052] The above c1 refers to the atomic fraction of manganese among the metal elements in the lithium complex transition metal oxide, where 0 <c1<0.4, 0.01≤c1<0.4, 0.05≤c1<0.4 또는 0.1≤c1≤0.3일 수 있다.

[0053] The above d1 is M among the metal elements in the lithium complex transition metal oxide. 1 It refers to the atomic fraction of, 0 <d1≤0.2, 0<d1≤0.15, 0<d1≤0.1 또는 0<d1≤0.05일 수 있다.

[0054]

[0055] According to the present invention, the lithium nickel-based transition metal oxide may have a composition represented by the following chemical formula 2.

[0056] [Chemical Formula 2]

[0057] Li x2 Ni a2 Co b2 Mn c2 Y d2 M 2 e2 O2

[0058] In the above chemical formula 2,

[0059] M 2is one or more selected from the group consisting of Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, V, F, P, and S, and

[0060] 0.9≤x2≤1.3, 0.5≤a2<1.0, 0 <b2<0.4, 0<c2<0.4, 0<d2≤0.2, 0≤e2≤0.2, a2+b2+c2+d2+e2=1이다.

[0061] The above a2 represents the atomic fraction of nickel among the metal elements in the lithium composite transition metal oxide, and may be 0.5≤a2<1.0, 0.6≤a2≤0.9, or 0.6≤a2≤0.8.

[0062] The above b2 refers to the atomic fraction of cobalt among the metal elements in the lithium complex transition metal oxide, where 0 <b2<0.4, 0.01≤b2≤0.2, 0.01≤b2≤0.15 또는 0.01≤b2≤0.1일 수 있다.

[0063] The above c2 refers to the atomic fraction of manganese among the metal elements in the lithium complex transition metal oxide, and is 0 <c2<0.4, 0.01≤c2<0.4, 0.05≤c2<0.4 또는 0.1≤c2≤0.3일 수 있다.

[0064] The above d2 refers to the atomic fraction of yttrium among the metal elements in the lithium complex transition metal oxide, where 0 <d2≤0.2, 0.001≤d2≤0.15, 0.001≤d2≤0.1 또는 0.001≤d2≤0.05일 수 있다.

[0065] The above e2 is M among the metal elements in the lithium complex transition metal oxide. 2 It refers to the atomic fraction of , which can be 0≤e2≤0.2, 0≤e2≤0.15, 0≤e2≤0.1 or 0≤e2≤0.05.

[0066]

[0067] Method for manufacturing positive electrode active material

[0068] The present invention provides a method for manufacturing an anode active material comprising the steps of: mixing a nickel-based transition metal hydroxide, a lithium raw material, and an additional metal raw material, and then calcining at a temperature of 900°C or higher and 1000°C or lower to produce a calcined product (S10); mixing the calcined product with a coating raw material and then heat-treating at a temperature of 800°C or higher and 1000°C or lower (S20); wherein the additional metal raw material in step (S10) comprises yttrium (Y) and the coating raw material in step (S20) comprises cobalt (Co).

[0069]

[0070] Below, the method for manufacturing the above-mentioned positive active material is described in detail step by step.

[0071]

[0072] (S10) Step

[0073] The method for manufacturing a positive electrode active material of the present invention includes the step (S10) of mixing a nickel-based transition metal hydroxide, a lithium raw material, and an additional metal raw material, and then manufacturing a sintered product by sintering at a temperature of 900°C or higher and 1000°C or lower.

[0074]

[0075] The above nickel-based transition metal hydroxide may include one or more selected from the group consisting of cobalt (Co) and manganese (Mn).

[0076] The above nickel-based transition metal hydroxide can be prepared, for example, by introducing an aqueous transition metal solution, an ammonium cation complex forming agent, and a basic compound into a reactor and carrying out a co-precipitation reaction while stirring.

[0077] The above transition metal aqueous solution can be prepared by dissolving a transition metal-containing raw material in a solvent such as water, for example, by dissolving a nickel-containing raw material, a cobalt-containing raw material, or a manganese-containing raw material in water.

[0078] Meanwhile, the above transition metal-containing raw material may be an acetate, carbonate, nitrate, halide, sulfide, or oxide of the transition metal.

[0079] Specifically, the nickel-containing raw material may be, for example, NiO, NiCO3ㆍ2Ni(OH)2ㆍ4H2O, NiC2O2ㆍ2H2O, Ni(NO3)2ㆍ6H2O, NiSO4, NiSO4ㆍ6H2O, nickel halides, or a combination thereof.

[0080] The above cobalt-containing raw material may be, for example, CoSO4, Co(OCOCH3)2ㆍ4H2O, Co(NO3)2ㆍ6H2O, CoSO4ㆍ7H2O, or a combination thereof.

[0081] The above manganese-containing raw materials are, for example, Mn2O3, MnO2, Mn3O 4, It may be MnCO3, Mn(NO3)2, MnSO4·H2O, manganese acetate, manganese halides, or a combination thereof.

[0082] The input amount of each of the above transition metal-containing raw materials can be determined by considering the molar ratio of the transition metal in the cathode active material to be finally produced.

[0083] Meanwhile, the ammonium cation complex forming agent may include at least one compound selected from the group consisting of NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, and NH4CO3, and may be introduced into a reactor in the form of a solution in which said compound is dissolved in a solvent. At this time, the solvent may be water, or a mixture of water and an organic solvent that is uniformly miscible with water (specifically, alcohol, etc.).

[0084] The above basic compound may be at least one compound selected from the group consisting of NaOH, KOH, and Ca(OH)2, and may be introduced into the reactor in the form of a solution in which the compound is dissolved in a solvent. In this case, water or a mixture of water and an organic solvent that is uniformly miscible with water (specifically, alcohol, etc.) may be used as the solvent.

[0085] As described above, the transition metal aqueous solution, ammonium cation complex forming agent, and basic compound are added in amounts such that the pH of the reaction solution becomes within the desired range.

[0086] When nickel-based transition metal hydroxide particles are formed by the method described above, the particles are separated from the reaction solution to obtain the nickel-based transition metal hydroxide. For example, the nickel-based transition metal hydroxide can be obtained by filtering the reaction solution to separate it, and then washing and drying the separated nickel-based transition metal hydroxide. At this time, processes such as grinding and / or classification may be performed as necessary.

[0087] The nickel-based transition metal hydroxide obtained as described above may have the composition of Chemical Formula 3 below.

[0088] [Chemical Formula 3]

[0089] Ni a3 Co b3 Mn c3 (OH)2

[0090] In the above chemical formula 3, 0.5 ≤ a3 < 1.0, 0 <b3<0.4, 0<c3<0.4, a3+b3+c3=1일 수 있다.

[0091] The above a3 represents the atomic fraction of nickel among the metal elements in the nickel-based transition metal hydroxide, and may be 0.5≤a3<1.0, 0.6≤a3≤0.9, or 0.6≤a3≤0.8.

[0092] The above b3 refers to the atomic fraction of cobalt among the metal elements in the nickel-based transition metal hydroxide, and is 0 <b3<0.4, 0.01≤b3≤0.2, 0.01≤b3≤0.15 또는 0.01≤b3≤0.1일 수 있다.

[0093] The above c3 refers to the atomic fraction of manganese among the metal elements in the nickel-based transition metal hydroxide, and is 0 <c3<0.4, 0.01≤c3<0.4, 0.05≤c3<0.4 또는 0.1≤c3≤0.3일 수 있다.

[0094]

[0095] Next, the nickel-based transition metal hydroxide, lithium raw material, and additional metal raw material are mixed, and then fired at a temperature of 900°C or higher and 1000°C or lower to produce a fired product.

[0096] The above lithium raw material may be, for example, a lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, and more specific examples may be Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, Li3C6H5O7, or a mixture thereof.

[0097] Meanwhile, the above lithium raw material can be mixed such that the molar ratio of lithium to the total molar amount of transition metal included in the nickel-based transition metal hydroxide is 0.9 or more and 1.3 or less, preferably 0.93 or more and 1.15 or less, and more preferably 0.95 or more and 1.09 or less. When the molar ratio of the nickel-based transition metal hydroxide and the lithium raw material satisfies the above range, the layered crystal structure of the cathode active material is well developed, and a cathode material with excellent electrochemical performance can be manufactured.

[0098] The above additional metal raw material includes yttrium (Y). In addition, the above additional metal raw material may further include one or more selected from the group consisting of Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, V, F, P, and S. The above additional metal raw material may be a hydroxide, oxide, etc. containing the metal element.

[0099] The above additional metal raw materials may be one or more selected from the group consisting of Y2O3, Y(OH)3, Y2(CO3)3, Y(O2C2H3)3, YCl3, YF3, YN, Y(NO3)3, YP, YPO4, and Y2S3.

[0100] The content of the additional metal raw material may be 500 ppm or more and 5,000 ppm or less relative to the total weight of the nickel-based transition metal hydroxide. If there are two or more types of additional metal raw materials, the content of each additional metal raw material may be within the above range. Specifically, the content of the additional metal raw material may be 500 ppm or more, 700 ppm or more, 900 ppm or more, 1,100 ppm or more, 1,300 ppm or more, 1,500 ppm or more, 2,000 ppm or more, and 2,500 ppm or more relative to the total weight of the nickel-based transition metal hydroxide, and may be 3,500 ppm or less, 4,000 ppm or less, 4,500 ppm or less, and 5,000 ppm or less. When the additional metal raw material is included in the above content, the binding force with oxygen can be increased, thereby improving the structural stability of the cathode active material.

[0101] The above calcination temperature is 900°C or higher and 1000°C or lower. Specifically, it may be 900°C or higher, 905°C or higher, 910°C or higher, and 930°C or lower, 940°C or lower, 950°C or lower, 960°C or lower, 970°C or lower, 980°C or lower, 990°C or lower, and 1000°C or lower. When the calcination temperature satisfies the above range, particles in the form of single particles can be formed, thereby enabling the production of a structurally stable positive active material.

[0102] In addition, the above firing time may be 4 hours or more and 15 hours or less, and specifically, it may be 4 hours or more, 5 hours or more, 6 hours or more, 7 hours or more, and 9 hours or less, 10 hours or less, 11 hours or less, 12 hours or less, 13 hours or less, 14 hours or less, and 15 hours or less.

[0103] In addition, the above-mentioned firing may be performed in an atmospheric or oxygen atmosphere, and preferably in an oxygen atmosphere. In the present invention, an oxygen atmosphere refers to an atmosphere containing a sufficient amount of oxygen for firing, including an atmospheric atmosphere. In particular, it refers to an atmosphere in which the partial pressure of oxygen is higher than that of an atmospheric atmosphere.

[0104]

[0105] (S20) Step

[0106] The method for manufacturing a positive electrode active material of the present invention includes a step (S20) of mixing the sintered product of step (S10) with a coating raw material and then heat-treating at a temperature of 800°C or higher and 1000°C or lower.

[0107] The above (S20) step may further include a step of crushing the sintered product before heat treatment.

[0108] The above grinding step is intended to break down aggregated cathode active materials and appropriately control the particle size and shape of particles within the cathode material, and can be performed using a grinding device well known in the art, such as a jet-mill grinder or a ball-mill grinder.

[0109] In the above grinding step, by appropriately adjusting grinding conditions such as grinding pressure and input speed, the particle size distribution and primary particle shape of lithium nickel-based transition metal oxide particles can be controlled.

[0110]

[0111] In the above step (S20), a coating raw material that is highly reactive with lithium in the heat treatment temperature range may be used. When such a coating raw material is used, the coating raw material can sufficiently react with the lithium present in the sintered product of the above step (S10) or with the lithium oxide of the additional metal raw material (e.g., LiYO2, etc.), thereby forming a lithium oxide of the coating raw material. Accordingly, the lithium oxide of the additional metal raw material can be converted into an oxide form that does not contain lithium (e.g., Y2O3).

[0112] The above coating raw material contains cobalt (Co). For example, the above coating raw material may be one or more selected from the group consisting of cobalt-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, oxyhydroxide, Co(OCOH3)2ㆍ4H2O, Co(NO3)2ㆍ6H2O, Co(SO4)2ㆍ7H2O, fatty acid cobalt, and cobalt halides.

[0113] The above heat treatment temperature is 800°C or higher and 1000°C or lower; specifically, it may be 800°C or higher, 850°C or lower, 900°C or lower, 950°C or lower, and 1000°C or lower. When the above heat treatment temperature satisfies the above range, LiCoO2 formed by the reaction between cobalt and lithium on the surface of the active material can be allowed to diffuse well into the interior of the active material. In this way, when LiCoO2 diffuses into the interior, it can diffuse to the vicinity of the surface of the positive active material particles. In this case, a thin film-shaped LiCoO2 coating layer may be formed covering the crystal interface present on the surface of the positive active material particles, or it may diffuse into the crystals on the surface to form a form in which cobalt is doped into the positive active material. Accordingly, when analyzing XRD, the peaks representing LiCoO2 in the 2θ=37~37.8° and 2θ=45~46° ranges may not appear.

[0114] In addition, the heat treatment time may be 1 hour or more and 10 hours or less, and specifically, it may be 1 hour or more, 1.5 hours or more, 2 hours or more, 2.5 hours or more, 3 hours or more, 3.5 hours or more, and 5 hours or less, 6 hours or less, 7 hours or less, 8 hours or less, 9 hours or less, and 10 hours or less.

[0115] In addition, the above heat treatment may be performed in an atmospheric or oxygen atmosphere, and preferably in an oxygen atmosphere. In the present invention, an oxygen atmosphere refers to an atmosphere containing oxygen in an amount sufficient for firing, including an atmospheric atmosphere. In particular, it refers to an atmosphere in which the partial pressure of oxygen is higher than that of an atmospheric atmosphere.

[0116]

[0117] anode

[0118] The present invention provides a positive electrode comprising the above positive electrode active material.

[0119] The above positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and the positive electrode active material layer may include the positive electrode active material.

[0120] 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 μm to 500 μm, and may form fine irregularities on the surface of the 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.

[0121] The positive active material layer may include, together with the positive active material, a conductive material and a binder as needed. In this case, the positive active material may be included in an amount of 80% to 99% by weight, more specifically 85% to 98.5% by weight, based on the total weight of the positive active material layer, and may exhibit excellent capacity characteristics within this range.

[0122] The above conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it possesses electronic conductivity without causing chemical changes. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fibers; metal powder or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used. The above conductive material may be included in an amount of 0.1% to 15% by weight relative to the total weight of the positive electrode active material layer.

[0123] The above binder serves to improve the adhesion between positive active material particles and the adhesion between the positive active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, and polymers in which hydrogens thereof are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these alone or a mixture of two or more may be used. The above binder may be included in an amount of 0.1% to 15% by weight relative to the total weight of the positive active material layer.

[0124] The above-described anode may be manufactured according to a conventional anode manufacturing method, except for using the above-described anode active material. Specifically, the above-described anode may be manufactured by applying a composition for forming an anode active material layer (anode slurry), prepared by dissolving or dispersing the above-described anode active material and, optionally, a binder, a conductive material, and a dispersant in a solvent, onto an anode current collector, followed by drying and rolling, or by casting the composition for forming an anode active material layer onto a separate support and then laminating the film obtained by peeling off from the support onto an anode current collector.

[0125] The above solvent may be a solvent generally used in the relevant technical field, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water, and one of these alone or a mixture of two or more may be used. The amount of the above solvent used is sufficient if it is sufficient to dissolve or disperse the anode active material, conductive material, binder, and dispersant, taking into account the coating thickness of the slurry and the manufacturing yield, and to have a viscosity that can exhibit excellent thickness uniformity when coated for anode manufacturing thereafter.

[0126]

[0127] lithium secondary battery

[0128] The present invention provides a lithium secondary battery comprising the above positive electrode.

[0129] The above lithium secondary battery may comprise the positive electrode; the negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte. Additionally, the lithium secondary battery may optionally further comprise a battery container housing an electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member sealing the battery container.

[0130] The above cathode may include a cathode current collector and a cathode active material layer located on the cathode current collector.

[0131] 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.

[0132] The above-mentioned cathode active material layer may optionally include a binder and a conductive material together with the cathode active material.

[0133] 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 βExamples 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. Furthermore, the carbon material may include low-crystallinity carbon and high-crystallinity carbon. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes. The above-mentioned cathode active material may be included in an amount of 80% to 99% by weight based on the total weight of the cathode active material layer.

[0134] The binder of the above-mentioned negative electrode active material layer 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.

[0135] The conductive material of the above-mentioned negative electrode active material layer 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 fiber or metal fiber; 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.

[0136] The above cathode may be manufactured by applying a composition for forming a cathode active material layer (cathode slurry), prepared by dissolving or dispersing a cathode active material and optionally a binder and a conductive material in a solvent, onto a cathode current collector and drying it, or by casting the composition for forming a cathode active material layer onto a separate support and then laminating the film obtained by peeling off from the support onto a cathode current collector.

[0137] The above separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. It can be used without special limitations as long as it is typically used as a separator in a lithium secondary battery, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte wettability. Specifically, a porous polymer film, such as a porous polymer film made of 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 it may optionally be used in a single-layer or multi-layer structure.

[0138] Examples of the above electrolytes include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which can be used in the manufacture of lithium secondary batteries, but are not limited to these. As a specific example, the above electrolyte may include an organic solvent and a lithium salt.

[0139] The above 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 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.

[0140] 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, the anion of the above lithium salt is 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 - The lithium salt may be at least one selected from the group consisting of 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. It is preferable to use the lithium salt within the range of 0.1 M to 2.0 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.

[0141] 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, haloalkylene carbonate-based compounds 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% by weight based on the total weight of the electrolyte.

[0142]

[0143] A lithium secondary battery comprising a positive electrode active material according to the present invention can be utilized in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in electric vehicle fields such as hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0144] The external shape of the lithium secondary battery of the present invention is not particularly limited, but can be a cylindrical shape using a can, a prismatic shape, a pouch shape, or a coin shape.

[0145] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but can also preferably be used as a unit cell in a medium-to-large battery module comprising a plurality of battery cells.

[0146] Accordingly, a battery module including the above-mentioned lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0147] The above battery module or battery pack can be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle, including an electric vehicle, a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0148]

[0149] Examples

[0150] The present invention will be explained in more detail below through examples. However, the following examples are intended to illustrate the present invention and do not limit the scope of the present invention.

[0151]

[0152] Example 1

[0153] Ni 0.70 Co 0.07 Mn 0.23 A positive electrode active material precursor having a composition represented by (OH)2 and Li2CO3 were mixed such that the molar ratio of lithium (Li) to transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) was 1.05. In addition, ZrO2 at a content of 1500 ppm and Y2O3 at a content of 3000 ppm relative to the total weight of the positive electrode active material precursor were added and mixed to prepare a mixture.

[0154] The above mixture was placed in an alumina crucible and calcined at 910°C for 8 hours under an oxygen atmosphere to obtain a calcined product. The calcined product was ground at room temperature (using a jet mill under 3 bar conditions) to obtain an average particle size of 3.7 μm, and Li 1.05 Ni 0.702 Co 0.068 Mn 0.226 Zr 0.001 Y 0.003 A lithium nickel-based transition metal oxide in a single-particle form was prepared having a composition represented by O2.

[0155] A mixture was prepared by adding Co(OH)2 to the above-prepared single-particle lithium-nickel-based transition metal oxide and Co(OH)2 such that the molar ratio of cobalt (Co) contained in Co(OH)2 to the metal excluding lithium contained in the lithium-nickel-based transition metal oxide was 0.03, and mixing them uniformly. The mixture was placed in an alumina crucible and heat-treated at 820°C for 4 hours under an oxygen atmosphere to produce a coated product. The coated product was ground to 3.7 μm at room temperature (using a jet mill under 2 bar conditions) to produce an anode active material in which a coating portion containing Co was formed on the single-particle lithium-nickel-based transition metal oxide.

[0156]

[0157] Example 2

[0158] Ni 0.70 Co 0.07 Mn 0.23 A positive electrode active material precursor having a composition represented by (OH)2 and Li2CO3 were mixed such that the molar ratio of lithium (Li) to transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) was 1.05. In addition, ZrO2 at a content of 1500 ppm and Y2O3 at a content of 3000 ppm relative to the total weight of the positive electrode active material precursor were added and mixed to prepare a mixture.

[0159] The above mixture was placed in an alumina crucible and calcined at 910°C for 8 hours under an oxygen atmosphere to obtain a calcined product. The calcined product was ground at room temperature (using a jet mill under 3 bar conditions) to obtain an average particle size of 3.7 μm, and Li 1.05 Ni 0.702 Co 0.068 Mn 0.226 Zr 0.001 Y 0.003 A lithium nickel-based transition metal oxide in a single-particle form was prepared having a composition represented by O2.

[0160] A mixture was prepared by adding Co(OH)2 to the above-prepared single-particle lithium-nickel-based transition metal oxide and Co(OH)2 such that the molar ratio of cobalt (Co) contained in Co(OH)2 to the metal excluding lithium contained in the lithium-nickel-based transition metal oxide was 0.03, and mixing them uniformly. The mixture was placed in an alumina crucible and heat-treated at 800°C for 4 hours under an oxygen atmosphere to produce a coating product. The coating product was ground to 3.7 μm at room temperature (using a jet mill under 2 bar conditions) to produce an anode active material in which a coating portion containing Co was formed on the single-particle lithium-nickel-based transition metal oxide.

[0161]

[0162] Comparative Example 1

[0163] Ni 0.70 Co 0.07 Mn 0.23 A positive electrode active material precursor having a composition represented by (OH)2 and Li2CO3 were mixed such that the molar ratio of lithium (Li) to transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) was 1.05. In addition, ZrO2 at a content of 1500 ppm and Y2O3 at a content of 3000 ppm relative to the total weight of the positive electrode active material precursor were added and mixed to prepare a mixture.

[0164] The above mixture was placed in an alumina crucible and calcined at 910°C for 8 hours under an oxygen atmosphere to obtain a calcined product. The calcined product was ground at room temperature (using a jet mill under 3 bar conditions) to obtain an average particle size of 3.7 μm, and Li 1.05 Ni 0.702 Co 0.068 Mn 0.226 Zr 0.001 Y 0.003 A lithium nickel-based transition metal oxide in a single-particle form was prepared having a composition represented by O2.

[0165] A mixture was prepared by adding Co(OH)2 to the above-prepared single-particle lithium-nickel-based transition metal oxide and Co(OH)2 such that the molar ratio of cobalt (Co) contained in Co(OH)2 to the metal excluding lithium contained in the lithium-nickel-based transition metal oxide was 0.03, and mixing them uniformly. The mixture was placed in an alumina crucible and heat-treated at 780°C for 4 hours under an oxygen atmosphere to produce a coating product. The coating product was ground to 3.7 μm at room temperature (using a jet mill under 2 bar conditions) to produce an anode active material in which a coating portion containing Co was formed on the single-particle lithium-nickel-based transition metal oxide.

[0166]

[0167] Comparative Example 2

[0168] Ni 0.70 Co 0.07 Mn 0.23 A positive electrode active material precursor having a composition represented by (OH)2 and Li2CO3 were mixed such that the molar ratio of lithium (Li) to transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) was 1.05. In addition, ZrO2 at a content of 1500 ppm and Y2O3 at a content of 3000 ppm relative to the total weight of the positive electrode active material precursor were added and mixed to prepare a mixture.

[0169] The above mixture was placed in an alumina crucible and calcined at 910°C for 8 hours under an oxygen atmosphere to obtain a calcined product. The calcined product was ground at room temperature (using a jet mill under 3 bar conditions) to obtain an average particle size of 3.7 μm, and Li 1.05 Ni 0.702 Co 0.068 Mn 0.226 Zr 0.001 Y 0.003 A lithium nickel-based transition metal oxide in a single-particle form was prepared having a composition represented by O2.

[0170] A mixture was prepared by adding Co(OH)2 to the above-prepared single-particle lithium-nickel-based transition metal oxide and Co(OH)2 such that the molar ratio of cobalt (Co) contained in Co(OH)2 to the metal excluding lithium contained in the lithium-nickel-based transition metal oxide was 0.03, and mixing them uniformly. The mixture was placed in an alumina crucible and heat-treated at 760°C for 4 hours under an oxygen atmosphere to produce a coating product. The coating product was ground to 3.7 μm at room temperature (using a jet mill under 2 bar conditions) to produce an anode active material in which a coating portion containing Co was formed on the single-particle lithium-nickel-based transition metal oxide.

[0171]

[0172] Comparative Example 3

[0173] Ni 0.70 Co 0.07 Mn 0.23 A positive electrode active material precursor having a composition represented by (OH)2 and Li2CO3 were mixed such that the molar ratio of lithium (Li) to transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) was 1.05. In addition, ZrO2 at a content of 1500 ppm and Y2O3 at a content of 3000 ppm relative to the total weight of the positive electrode active material precursor were added and mixed to prepare a mixture.

[0174] The above mixture was placed in an alumina crucible and calcined at 910°C for 8 hours under an oxygen atmosphere to obtain a calcined product. The calcined product was ground at room temperature (using a jet mill under 3 bar conditions) to obtain an average particle size of 3.7 μm, and Li 1.05 Ni 0.702 Co 0.068 Mn 0.226 Zr 0.001 Y 0.003 A lithium nickel-based transition metal oxide in a single-particle form was prepared having a composition represented by O2.

[0175] A mixture was prepared by adding Co(OH)2 to the above-prepared single-particle lithium-nickel-based transition metal oxide such that the molar ratio of cobalt (Co) contained in Co(OH)2 to the metal excluding lithium contained in the lithium-nickel-based transition metal oxide is 0.03, and uniformly mixing LiOH such that the molar ratio of lithium (Li) contained in LiOH to the metal excluding lithium contained in the lithium-nickel-based transition metal oxide is 0.01. The mixture was placed in an alumina crucible and heat-treated at 760°C for 4 hours under an oxygen atmosphere to produce a coated product. The coated product was ground to 3.7 μm at room temperature (using a jet mill under 2 bar conditions) to produce an anode active material in which a coating portion containing Co is formed on the single-particle lithium-nickel-based transition metal oxide.

[0176]

[0177] Comparative Example 4

[0178] Ni 0.70 Co 0.07 Mn 0.23 A positive electrode active material precursor having a composition represented by (OH)2 and Li2CO3 were mixed such that the molar ratio of lithium (Li) to transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) was 1.05. In addition, ZrO2 at a content of 1500 ppm and Y2O3 at a content of 3000 ppm relative to the total weight of the positive electrode active material precursor were added and mixed to prepare a mixture.

[0179] The above mixture was placed in an alumina crucible and calcined at 910°C for 8 hours under an oxygen atmosphere to obtain a calcined product. The calcined product was ground at room temperature (using a jet mill under 3 bar conditions) to obtain an average particle size of 3.7 μm, and Li 1.05 Ni 0.702 Co 0.068 Mn 0.226 Zr 0.001 Y 0.003 A lithium nickel-based transition metal oxide in a single-particle form was prepared having a composition represented by O2.

[0180] A mixture was prepared by adding the above-prepared single-particle lithium nickel-based transition metal oxide and TiO2 such that the molar ratio of titanium (Ti) contained in TiO2 to the metal excluding lithium contained in the lithium nickel-based transition metal oxide was 0.03, and mixing them uniformly. The mixture was placed in an alumina crucible and heat-treated at 820°C for 4 hours under an oxygen atmosphere to produce a coating product. The coating product was ground to 3.7 μm at room temperature (using a jet mill under 2 bar conditions) to produce an anode active material in which a coating portion containing Ti was formed on the single-particle lithium nickel-based transition metal oxide.

[0181]

[0182] Comparative Example 5

[0183] Ni 0.70 Co 0.07 Mn 0.23 A positive electrode active material precursor having a composition represented by (OH)2 and Li2CO3 were mixed such that the molar ratio of lithium (Li) to transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) was 1.05. In addition, a mixture was prepared by adding and mixing ZrO2 at a content of 1,500 ppm relative to the total weight of the positive electrode active material precursor.

[0184] The above mixture was placed in an alumina crucible and calcined at 910°C for 8 hours under an oxygen atmosphere to obtain a calcined product. The calcined product was ground at room temperature (using a jet mill under 3 bar conditions) to obtain an average particle size of 3.7 μm, and Li 1.05 Ni 0.705 Co 0.068 Mn 0.226 Zr 0.001 A lithium nickel-based transition metal oxide in a single-particle form was prepared having a composition represented by O2.

[0185] A mixture was prepared by adding Co(OH)2 to the above-prepared single-particle lithium-nickel-based transition metal oxide such that the molar ratio of cobalt (Co) contained in Co(OH)2 to the metal excluding lithium contained in the lithium-nickel-based transition metal oxide is 0.03, and uniformly mixing LiOH such that the molar ratio of lithium (Li) contained in LiOH to the metal excluding lithium contained in the lithium-nickel-based transition metal oxide is 0.01. The mixture was placed in an alumina crucible and heat-treated at 820°C for 4 hours under an oxygen atmosphere to produce a coated product. The coated product was ground to 3.7 μm at room temperature (using a jet mill under 2 bar conditions) to produce an anode active material in which a coating portion containing Co is formed on the single-particle lithium-nickel-based transition metal oxide.

[0186]

[0187] Experimental Example

[0188] Experimental Example 1: XRD Analysis

[0189] X-ray diffraction analysis (Cu target, 2theta 18-50˚ scan, 3200 step conditions) was performed on the cathode active materials of Examples 1 and 2 and Comparative Examples 1 to 5 using D8 endeavor (Bruker), and the results are shown in Table 1 and Figure 1 below.

[0190]

[0191] Classification Peak in the θ=28~30° range Peak in the θ=37~37.8° range Peak in the θ=45~46° range Example 1 OXX Example 2 OXX Comparative Example 1 OOO Comparative Example 2 OOO Comparative Example 3 XOO Comparative Example 4 XXX Comparative Example 5 XXX

[0192]

[0193] Referring to Table 1 and Figure 1 above, the positive active materials of Examples 1 and 2 showed a peak in the 2θ=28~30° range and no peak in the 2θ=37~37.8° range and 2θ=45~46° range, whereas the positive active materials of Comparative Examples 1 and 2 showed a peak in all of the above ranges, and the positive active material of Comparative Example 3 showed no peak in the 2θ=28~30° range and no peak in the 2θ=37~37.8° range and 2θ=45~46° range, contrary to the positive active materials of Examples 1 and 2, and the positive active materials of Comparative Examples 4 and 5 did not show a peak in all of the above ranges.

[0194] The peak in the 2θ = 28–30° range may represent Y2O3; if this peak appears, it may indicate that the coating raw material reacted sufficiently with lithium during the coating step, resulting in a well-formed coating layer. If this peak does not appear, it may indicate that yttrium (Y) exists in the form of LiYO2, or that the coating raw material failed to react with an appropriate amount of lithium during the coating step, thereby confirming a decrease in the structural stability of the coating. As in Comparative Example 3, if additional lithium is added during the coating step, sufficient lithium is present; therefore, even if the coating raw material and lithium react sufficiently, the excess lithium may cause yttrium to exist in the form of LiYO2, which may prevent the peak from appearing. As in Comparative Example 4, if a material with low reactivity with lithium within the heat treatment temperature range of the coating step of the present invention is used as the coating raw material, the coating raw material may not react sufficiently with lithium, and thus the peak may not appear. In Comparative Example 5, yttrium doping was not performed, so the peak did not appear.

[0195] Peaks in the 2θ=37~37.8° and 2θ=45~46° ranges may represent LiCoO2. If such peaks appear, it may indicate that cobalt reacts with lithium present on the surface to form LiCoO2 on the surface of the active material, which may result in reduced storage performance. If such peaks do not appear, it may indicate that LiCoO2 formed by the reaction between cobalt and lithium has diffused into the active material, forming a coating containing cobalt (specifically, cobalt oxide) on the surface of the active material, which can be confirmed to have optimized the surface structure.

[0196]

[0197] Experimental Example 2: Measurement of Electrochemical Performance

[0198] For each of Examples 1 and 2 and Comparative Examples 1 to 5, a positive electrode slurry was prepared by mixing Super P as the positive electrode active material and polyvinylidene fluoride (PVDF) as the binder in a weight ratio of 95:2:3 in an N-methylpyrrolidone (NMP) solvent. The positive electrode slurry was applied to one surface of an Al current collector, dried at 130°C, and then rolled to produce a positive electrode with a porosity of 21% in the positive electrode active material layer.

[0199] A negative electrode slurry was prepared by mixing a negative electrode active material, a mixture of natural graphite and artificial graphite in a weight ratio of 5:5, a Super C conductive material, an additive (Daicel, DAICEL2200), and a binder (ZEON, BML302) in water in a weight ratio of 95.6:1.0:2.3:1.1. The negative electrode slurry was coated on one side of a copper current collector, dried at 130°C, and then rolled to produce a negative electrode. This was placed inside a battery case, and a pouch-type monocell was manufactured by injecting an electrolyte solution in which 0.7M LiPF6 and 0.3M LiFSI were dissolved in an organic solvent mixed with ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7.

[0200] Each pouch-type monocell manufactured as described above was charged in CC / CV mode to 4.4V with a constant current of 0.1C at 25℃ (termination current 0.01C), and then discharged twice in CC mode with a constant current of 0.1C until it reached 2.5V, after which the discharge capacity was measured. After setting the SOC state based on the measured discharge capacity, the initial SOC50 resistance at 25℃ was measured and is shown in Table 2 below. The SOC50 resistance is a value calculated by applying a discharge current of 2.5C at SOC50 for 30 seconds at 25℃ to measure the voltage drop, and then dividing the voltage drop during the initial 10 seconds by the applied current.

[0201] In addition, charging was performed in CC / CV mode at 45°C with a constant current of 0.33C to 4.4V (termination current 0.01C), and then discharging in CC mode at a constant current of 0.33C until the voltage reached 2.5V was counted as one cycle, and a total of 200 cycles of charging and discharging were repeated. Immediately after the 200th cycle, charging was performed in CC / CV mode at 25°C with a constant current of 0.1C to 4.4V (termination current 0.01C), and then discharging was performed in CC mode at a constant current of 0.1C until the voltage reached 2.5V. After measuring the discharge capacity and the SOC50 resistance, the percentage of the SOC50 resistance immediately after the 200th cycle relative to the initial SOC50 resistance was used as the high-temperature life resistance increase rate and is shown together in Table 2 below. In addition, the percentage of the discharge capacity measured immediately after the 200th cycle relative to the discharge capacity measured during the initial SOC50 resistance measurement was used as the high-temperature life capacity retention rate and is shown together in Table 2 below.

[0202] In addition, each of the above-manufactured pouch-type monocells was charged in CC / CV mode at 25°C with a constant current of 0.33C to 4.4V (termination current 0.01C), stored at 60°C for 8 weeks, discharged in CC mode with a constant current of 0.33C until it reached 2.5V, charged in CC / CV mode with a constant current of 0.33C to 4.4V, and discharged with a constant current of 0.33C until it reached 2.5V, with this being one cycle. A total of 2 cycles were repeated, and the percentage of the discharge capacity of the second cycle relative to the discharge capacity measured during the initial SOC50 resistance measurement was defined as the high-temperature storage capacity retention rate and is shown together in Table 2 below. Furthermore, the SOC50 resistance was measured based on the discharge capacity of the second cycle, and the value obtained by dividing the resistance value by the initial SOC50 resistance was defined as the high-temperature storage resistance increase rate and is shown together in Table 2 below.

[0203]

[0204] Classification Initial SOC50 Resistance (Ω) High-temperature life capacity retention rate (%) High-temperature life resistance growth rate (%) High-temperature storage capacity retention rate (%) High-temperature storage resistance growth rate (%) Example 1 28.19 0.08 7.39 2.325 3.0 Example 2 28.88 9.09 2.59 0.827 0.4 Comparative Example 1 30.78 5.91 13.58 1.836 3.5 Comparative Example 2 33.18 3.71 19.38 0.54 04.5 Comparative Example 3 32.88 5.21 15.77 7.24 58.3 Comparative Example 4 32.58 0.21 30.78 5.63 34.5 Comparative Example 5 31.18 5.41 22.58 7.33 32.5

[0205]

[0206] Referring to Table 2 above, it can be seen that the battery containing the positive active material of Examples 1 and 2 of the present invention has low initial resistance, improved high-temperature life capacity retention rate, significantly reduced high-temperature life resistance increase rate, improved high-temperature storage capacity retention rate, and improved high-temperature storage resistance increase rate.

[0207] In contrast, it can be confirmed that the batteries containing the positive active materials of Comparative Examples 1 to 5 have high initial resistance, and that the high-temperature life capacity retention rate and resistance increase rate, as well as the high-temperature storage capacity retention rate and resistance increase rate, are all inferior to the batteries containing the positive active materials of Examples 1 and 2 of the present invention.

Claims

1. Includes lithium nickel-based transition metal oxide in the form of a single particle, and A positive active material in which a peak appears in the 2θ=28~30° range and no peaks appear in the 2θ=37~37.8° and 2θ=45~46° ranges during XRD measurement.

2. In Claim 1, The above lithium nickel-based transition metal oxide comprises yttrium (Y) and one or more selected from the group consisting of cobalt (Co) and manganese (Mn), forming a positive electrode active material.

3. In Claim 1, The above positive active material comprises a coating portion containing cobalt (Co) formed on the lithium nickel-based transition metal oxide.

4. In Claim 1, A positive electrode active material having a composition represented by the following chemical formula 1, wherein the above lithium nickel-based transition metal oxide is: [Chemical Formula 1] Li x1 Ni a1 Co b1 Mr c1 M 1 d1 O2 In the above chemical formula 1, M 1 is one or more selected from the group consisting of Y, Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, V, F, P, and S, and 0.9≤x1≤1.3, 0.5≤a1<1.0, 0 <b1<0.4, 0<c1<0.4, 0<d1≤0.2, a1+b1+c1+d1=1이다.

5. In Claim 1, The above single-particle form is a positive active material in the form of a single particle or in the form of two or more and thirty or fewer primary particles aggregated.

6. A positive electrode comprising a positive electrode active material according to any one of claims 1 to 5.

7. A lithium secondary battery comprising a positive electrode according to claim 6.

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