Cathode active material for lithium secondary battery, and lithium secondary batterty comprising same

Abstract

The positive electrode active material for a lithium secondary battery according to the present invention may have a CS x Li / Ni x FWHM (101) of less than or equal to 22.00 nm*%, wherein CS represents the crystal grain size of the positive electrode active material, Li / Ni represents the Li / Ni disorder of the positive electrode active material, and FWHM (101) represents the full width at half maximum of the (101) peak measured using X-ray diffraction.

Description

Technology Field

[0001] The present embodiments relate to a positive electrode active material for a lithium secondary battery and a lithium secondary battery containing the same. Background Technology

[0002] Recently, the demand for IT mobile devices, small power drive systems (e-bikes, small EVs, etc.), and Energy Storage Systems (ESS) has been increasing explosively. Consequently, the development of high-capacity and high-energy-density secondary batteries to power these devices is actively underway worldwide. To manufacture such high-capacity batteries, high-capacity cathode materials must be used.

[0003] Among existing layered cathode active materials, LiNiO2 has the highest capacity, but commercialization is difficult due to structural collapse occurring easily during charging and discharging and low thermal stability caused by oxidation state issues.

[0004] To solve this problem, other stable transition metals (Co, Mn, etc.) must be substituted at the unstable Ni sites, and for this purpose, ternary NCM systems with Co and Mn substituted have been developed.

[0005] For NCM-based cathode active materials, it is necessary to improve Li-ion absorption / emission performance by ensuring a uniform arrangement of the layered structure within the active material. Additionally, capacity and stability during charge and discharge must be satisfied within the required range, and it is important to increase energy density within the same electrode volume by packing the active material at a higher density during electrode manufacturing.

[0006] At this time, when manufacturing conventional NCM-based cathode active materials, it is necessary to make the arrangement of the layered structure uniform according to the firing process, so firing at high temperature and for a long time is usually required, and there is a problem that defective products that are under-fired may be manufactured.

[0007] Therefore, there is a need to develop positive electrode active materials with excellent electrochemical properties such as charge / discharge capacity and efficiency, and to develop a method to manufacture good positive electrode active materials from defective products that are under-calibrated. The problem to be solved

[0008] In this embodiment, we aim to provide a positive electrode active material for a lithium secondary battery and a lithium secondary battery containing the same, wherein the electrochemical characteristics and stability can be improved by additionally adding a lithium raw material together with coating raw materials after calcining the positive electrode active material, thereby satisfying a specific range in Formula 1 for the formed positive electrode active material. means of solving the problem

[0009] A positive electrode active material for a lithium secondary battery according to one embodiment may be a positive electrode active material for a lithium secondary battery that satisfies Formula 1 below.

[0010] [Equation 1]

[0011] CS x Li / Ni x FWHM(101) ≤ 22.00 nm*%

[0012] In the above Equation 1,

[0013] CS refers to the grain size of the positive active material, and

[0014] Li / Ni refers to the Li / Ni disorder of the cathode active material, and

[0015] FWHM (101) refers to the full width at half maximum of the (101) peak measured using X-ray diffraction.

[0016] The above CS may be in the range of 161 to 190 nm.

[0017] The above Li / Ni may be in the range of 1.00 to 1.45%.

[0018] The above FWHM (101) may be in the range of 0.0800 to 0.0900.

[0019] The above positive active material may satisfy the following Equation 2.

[0020] [Equation 2]

[0021] 330 nm*g / cc ≤ CS x PD ≤ 365 nm*g / cc

[0022] PD refers to the rolling density derived through the height of the positive active material pressurized to a pressure of 108 N.

[0023] The above PD may be in the range of 1.90 to 2.09 g / cc.

[0024] The above positive active material may be a positive active material for a lithium secondary battery represented by the following chemical formula 1.

[0025] [Chemical Formula 1]

[0026] Li a [Ni x Co y Mn z M w ]O2

[0027] In the above chemical formula 1, 0.8≤a≤1.2, 0.70≤x≤0.99, 0.01≤y≤0.30, 0≤z≤0.30, 0≤w≤0.20, x+y+z+w=1, and M is Al, Zr, Y, B, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, or a combination thereof.

[0028] The above positive active material includes Al, and

[0029] The total content of the above Al may be in the range of 300 to 5000 ppm based on the weight of the above positive active material.

[0030] The above positive active material includes a coating layer on its surface, and

[0031] The coating layer may comprise Al, Co, W, V, Ti, Nb, Ce, B, P, or a combination thereof.

[0032] The above coating layer comprises Al and Co, and

[0033] The content of Co in the above coating layer may be in the range of 1.5 to 3.0 mol% based on the positive active material.

[0034] A lithium secondary battery according to another embodiment may be a lithium secondary battery comprising a positive electrode for a lithium secondary battery comprising the positive electrode active material according to one embodiment. Effects of the invention

[0035] According to the present embodiment, the electrochemical properties of the positive electrode active material for a lithium secondary battery can be improved by appropriately controlling the manufacturing process to satisfy a specific range of the formula consisting of grain size, Li / Ni Disorder, and a specific full width at half maximum.

[0036] Accordingly, the electrochemical performance of the lithium secondary battery manufactured as in the present embodiment, such as charge / discharge capacity and efficiency, can be improved. Specific details for implementing the invention

[0037] Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the present invention.

[0038] The technical terms used herein are for the reference of specific embodiments only and are not intended to limit the invention. The singular forms used herein include plural forms unless phrases clearly indicate otherwise. As used in the specification, the meaning of "comprising" specifies certain characteristics, areas, integers, steps, actions, elements, and / or components, and does not exclude the presence or addition of other characteristics, areas, integers, steps, actions, elements, and / or components.

[0039] When it is stated that one part is "above" or "on" another part, it may be directly above or on the other part, or other parts may be involved in between. In contrast, when it is stated that one part is "directly above" another part, no other parts are interposed in between.

[0040] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with relevant technical literature and the present disclosure, and are not interpreted in an ideal or highly formal sense unless otherwise defined.

[0041] Also, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

[0042] In this specification, the term “combination(s) of these” described in the Markush-type expression means one or more mixtures or combinations selected from the group consisting of the components described in the Markush-type expression, and means including any one or more selected from the group consisting of said components.

[0043] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0045] Cathode active material for lithium secondary batteries

[0046] As mentioned above, there is a need to improve the electrochemical properties of existing cathode active materials for lithium secondary batteries.

[0047] In this embodiment, the electrochemical characteristics were improved by deriving the grain size, Li / Ni Disorder, and a specific full width at half maximum for the positive electrode active material, and satisfying a specific range of the formula composed thereof.

[0048] Specifically, a positive electrode active material for a lithium secondary battery according to one embodiment may satisfy the following Formula 1.

[0049] [Equation 1]

[0050] CS x Li / Ni x FWHM(101) ≤ 22.00 nm*%

[0051] In the above Equation 1,

[0052] CS refers to the grain size of the positive active material, and

[0053] Li / Ni refers to the Li / Ni disorder of the cathode active material, and

[0054] FWHM (101) represents the full width at half maximum of the (101) peak measured using X-ray diffraction.

[0055] The above CS x Li / Ni x FWHM (101) may more specifically be 14.00 to 22.00 nm*%, 14.50 to 22.00 nm*%, 15.50 to 21.80 nm*%, 16.50 to 21.70 nm*%, or 17.50 to 21.50 nm*%.

[0056] By satisfying the above range, the charge / discharge capacity can be increased and efficiency improved, and excellent electrochemical characteristics can be exhibited by reducing room temperature resistance.

[0058] The above CS may be in the range of 161 to 190 nm, more specifically 165 to 188 nm or 169 to 184 nm.

[0059] By satisfying the above range, it is possible to reduce residual lithium with an appropriate grain size, increase charge / discharge capacity and efficiency, and exhibit excellent electrochemical characteristics by reducing room temperature resistance.

[0060] In this specification, “crystal” refers to at least one crystal growth unit in a crystalline material. Additionally, “grain” refers to a distinct region in which atoms within a single particle form a lattice structure in a specific direction. Here, “grain size” can be estimated using peak broadening of XRD data and can be quantitatively calculated using the Scherrer equation.

[0061] <Scherrer equation>

[0062] Crystalite size =κλ / βcosθ

[0063] κ: Shape factor

[0064] λ: X-ray radiation

[0065] β: Full width at half maximum (FWHM)

[0066] θ: Diffraction angle

[0068] The above Li / Ni may be in the range of 1.00 to 1.45%, 1.05 to 1.43%, or 1.10 to 1.41%.

[0069] By satisfying the above range, the charge / discharge capacity can be increased and efficiency improved, and excellent electrochemical characteristics can be exhibited by reducing room temperature resistance.

[0070] In this specification, “Li / Ni disorder” refers to the ratio of Ni atoms to the total amount of lithium sites in a Li atomic layer, and accurate crystallographic analysis results can be obtained by measuring it using X-ray diffraction (XRD) and Rietveld analysis. The Rietveld analysis can be performed using the High score plus program and the pseudo-Voight function model. However, there are no specific limitations on the program used in the Rietveld analysis.

[0071] The above Li / Ni disorder may refer to the cation mixing ratio. Cation mixing refers to a phenomenon in which the positions of the two ions are partially swapped because the size of Ni2+ ions (0.69 Å) and Li+ ions (0.76 Å) are similar in the structure of a lithium-metal oxide with a layered crystalline structure. For example, it refers to a phenomenon in which some Ni atoms in the transition metal layer enter the Li atomic layer and swap positions with each other to form a crystal during high-temperature calcination of the positive electrode active material.

[0073] The above FWHM (101) may be in the range of 0.0800 to 0.0900, 0.0820 to 0.0895, or 0.0840 to 0.0890.

[0074] By satisfying the above range, the charge / discharge capacity can be increased and efficiency improved, and excellent electrochemical characteristics can be exhibited by reducing room temperature resistance.

[0075] The full width at half maximum can refer to the half width of the diffraction peak that is indexed to the plane. In this case, the (101) peak can be identified at 2θ=36.5±1° in the X-ray diffraction spectrum analysis.

[0077] Meanwhile, a positive electrode active material for a lithium secondary battery according to one embodiment may satisfy the following Equation 2.

[0078] [Equation 2]

[0079] 330 nm*g / cc ≤ CS x PD ≤ 365 nm*g / cc

[0080] PD refers to the rolling density derived through the height of the positive active material pressurized to a pressure of 108 N.

[0081] The above CS x PD may be more specifically 330 to 365 nm*g / cc, 335 to 365 nm*g / cc, 340 to 364 nm*g / cc, or 345 to 363 nm*g / cc.

[0082] By satisfying the above range, the charge / discharge capacity can be increased and efficiency improved, and excellent electrochemical characteristics can be exhibited by reducing room temperature resistance.

[0084] The above PD may be in the range of 1.90 to 2.09 g / cc, 1.90 to 2.09 g / cc, or 1.90 to 2.09 g / cc.

[0085] By satisfying the above range, the charge / discharge capacity can be increased and efficiency improved, and excellent electrochemical characteristics can be exhibited by reducing room temperature resistance, and the problem of capacity degradation due to rolling can be suppressed by reducing the amount of fine particles generated during rolling.

[0087] A positive electrode active material for a lithium secondary battery according to one embodiment is a positive electrode active material for a single-crystal lithium secondary battery, and the positive electrode active material may include a form in which 1 to 20 single particles are aggregated.

[0088] In this specification, a single particle may mean a single particle composed of one particle, and the single crystal cathode active material may be a single particle composed of one particle, or may be in the form of 2 to 20 aggregated single particles, and more preferably may include both the single particle and the aggregated form of the single particles.

[0089] In addition, the positive electrode active material for the lithium secondary battery may contain 70 to 99 mol% of nickel (Ni) based on the total molar amount of transition metals. If the nickel content is lower than this, the capacity may be reduced.

[0090] More specifically, it can be represented by the following chemical formula 1.

[0091] [Chemical Formula 1]

[0092] Li a [Ni x Co y Mn z M w ]O2

[0093] In the above chemical formula 1, 0.8≤a≤1.2, 0.70≤x≤0.99, 0.01≤y≤0.30, 0≤z≤0.30, 0≤w≤0.20, x+y+z+w=1, and M is Al, Zr, Y, B, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, or a combination thereof.

[0094] In the positive electrode active material of Chemical Formula 1 above, lithium may be included in an amount corresponding to a, i.e., 0.8 ≤ a ≤ 1.2. If a is too small, the capacity may decrease, and if a is too large, the strength of the calcined positive electrode active material may increase, making it difficult to grind, and the amount of gas generated may increase due to an increase in lithium by-products. Considering the effect of improving the capacity characteristics of the positive electrode active material by controlling the lithium content and the balance of sinterability during the manufacture of the active material, the lithium may more preferably be included in an amount of 0.9 ≤ a ≤ 1.1.

[0095] In the positive active material of Chemical Formula 1 above, nickel may be included in an amount corresponding to x, i.e., 0.70≤x≤0.99. As previously mentioned, if the nickel content is low, it may be difficult to achieve a high capacity of the battery.

[0096] In the positive electrode active material of Chemical Formula 1 above, cobalt may be included in an amount corresponding to y, i.e., 0.01 ≤ y ≤ 0.30. If the cobalt content is too low, it may be difficult to simultaneously achieve sufficient rate characteristics and high powder density of the active material. If the cobalt content is too high, the cost of raw materials increases overall and the reversible capacity may decrease.

[0097] In the positive electrode active material of Chemical Formula 1 above, manganese may be included in an amount corresponding to z, i.e., 0 ≤ z ≤ 0.30 or 0.1 ≤ z ≤ 0.30. If the manganese content is too low, the production cost may increase and the stability of the positive electrode active material may decrease. If the manganese content is too high, the capacity and output characteristics of the battery may decrease.

[0098] In the positive active material of Chemical Formula 1 above, the positive active material may specifically include Al, and the total content of Al is in the range of 300 to 5000 ppm based on the weight of the positive active material, and more specifically, may be 400 to 4500 ppm or 450 to 4000 ppm. If the content is below the above range, the growth of particle size may be negligible, and if the content is above the above range, an excess amount of element may be distributed at the precursor interface during the calcination process, which may actually inhibit the growth of particle size. Therefore, when the total content of Al satisfies the above range, the size of the single particles within the positive active material can be formed within an appropriate range.

[0100] In addition, a positive electrode active material for a lithium secondary battery according to one embodiment of the present invention may include a coating layer on the surface of the positive electrode active material. Specifically, the coating layer may include Al, Co, W, V, Ti, Nb, Ce, B, P, or a combination thereof.

[0101] More specifically, the coating layer comprises Al and Co, and the content of Co in the coating layer may be in the range of 1.5 to 3.0 mol% based on the positive electrode active material, more specifically 1.8 to 2.8 mol%.

[0102] Satisfying the above range offers the advantage of improved discharge capacity and efficiency. If the above range is exceeded, there is a problem in that the efficiency improvement effect is reduced due to the formation of unstable substances on the surface of the positive active material or at the interface between single-particle positive active materials.

[0104] Method for manufacturing a positive electrode active material for a lithium secondary battery

[0105] In another embodiment of the present invention, a method for manufacturing a positive electrode active material for a lithium secondary battery is provided, comprising the steps of: preparing a transition metal precursor; mixing the transition metal precursor and a lithium raw material and calcining to form a lithium transition metal oxide; dissolving the lithium transition metal oxide to form a positive electrode active material for a single-crystal lithium secondary battery; and mixing the positive electrode active material with an aluminum raw material, a cobalt raw material, and an additional lithium raw material and then heat-treating; wherein the lithium content added through the additional lithium raw material is 0.1 to 2.0 mol% based on the positive electrode active material.

[0106] Hereinafter, a method for manufacturing a positive electrode active material for a lithium secondary battery according to one embodiment of the present invention will be described step by step.

[0107] First, prepare a transition metal precursor.

[0108] The above transition metal precursor is not particularly limited, but may be, for example, a transition metal hydroxide.

[0109] The above transition metal hydroxide may be prepared by co-precipitating a transition metal-containing solution containing a nickel raw material and optionally a cobalt raw material or a manganese raw material by adding a complexing agent-containing solution and a pH adjusting agent-containing solution to the transition metal-containing solution.

[0110] The above nickel raw material is not particularly limited as long as it is used in the industry for manufacturing a cathode active material precursor. For example, the above nickel raw material may be a nickel-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, it may be NiSO4, NiSO4·6H2O, Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, nickel fatty acid salt, nickel halide, or a combination thereof, but is not limited thereto.

[0111] The above-mentioned cobalt raw material is not particularly limited as long as it is used in the industry for the manufacture of cathode active material precursors. For example, the above-mentioned cobalt raw material may be a cobalt-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, CoSO₄ 4, It may be CoSO4·7H2O, Co(OH)2, CoOOH, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O, or a combination thereof, but is not limited thereto.

[0112] The above manganese raw material is not particularly limited as long as it is used in the industry for the manufacture of cathode active material precursors. For example, the above manganese raw material may be a manganese-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, oxyhydroxide, or a combination thereof. Specifically, it may be a manganese salt such as MnSO4, MnCO3, Mn(NO3)2, manganese acetate, manganese dicarboxylate, manganese citrate, and manganese fatty acid, manganese oxide such as Mn2O3, MnO2, and Mn3O4, oxyhydroxide, manganese chloride, or a combination thereof, but is not limited thereto.

[0113] The above transition metal-containing solution may be prepared by adding a nickel raw material and optionally a cobalt raw material or a manganese raw material to a solvent, specifically water, or a mixture of water and an organic solvent that can be uniformly mixed with water (e.g., alcohol).

[0114] The above-mentioned complexing agent-containing solution performs the role of forming a complex, and may include, for example, NH3, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3, or a combination thereof as the complexing agent, but is not limited thereto. Meanwhile, the above-mentioned complexing agent-containing solution may be used in the form of an aqueous solution, and in this case, water or a mixture of water and an organic solvent that is uniformly miscible with water (e.g., alcohol, etc.) may be used as the solvent.

[0115] At this time, the molar ratio of nickel, cobalt, and manganese in the precursor can be controlled by adjusting the concentrations of the nickel raw material, cobalt raw material, and manganese raw material.

[0116] Accordingly, the nickel content in the transition metal precursor may be 70 to 99 mol% based on the total molar amount of the transition metal.

[0117] In addition, the content of cobalt in the transition metal precursor may be 1 to 30 mol% based on the total molar amount of the transition metal.

[0118] In addition, the manganese content in the transition metal precursor may be 0 to 30 mol% based on the total molar amount of the transition metal. In this case, 0 mol% means that manganese is not included.

[0119] The technical significance of controlling the nickel, cobalt, and manganese content in transition metal precursors is as previously described and is therefore omitted.

[0120] In addition, a doping raw material may be further included in the step of mixing the transition metal precursor and the lithium raw material. Specifically, the doping raw material may be a Zr raw material.

[0121] The above Zr raw material may be Zr(SO4)2, ZrS2, ZrO2, Zr(NO3)4, or a combination thereof, but is not necessarily limited thereto.

[0123] Next, the above transition metal precursor and lithium raw material are mixed and then calcined to obtain a lithium transition metal oxide. Specifically, a lithium metal oxide can be obtained through two stages of calcination.

[0124] Conventionally, to form a single-crystal lithium metal oxide, the process was carried out through calcination at high temperatures for a long time; however, in this case, there was a problem in which the electrochemical properties of the active material deteriorated due to nickel cation mixing caused by over-calcination and the formation of rock salt impurities. On the other hand, the manufacturing method according to the present invention can prevent the above problems by controlling the calcination temperature and time when proceeding with first and second calcination, and has the advantage of increasing particle strength and increasing production volume.

[0125] At this time, the atmosphere during the above-mentioned calcination is not particularly limited. For example, it may be performed in an air or oxygen (O2) atmosphere, but more specifically, it may be performed in an oxygen atmosphere. Since the formation of a layered crystal structure is not well achieved when the high-nickel cathode active material is performed in an air atmosphere, leading to a significant degradation of electrochemical properties, it may be preferable to perform the process in an oxygen atmosphere.

[0126] The above first firing is performed for 2 to 14 hours while maintaining a temperature of 800 to 900°C, and the above second firing may be performed for 6 to 18 hours while maintaining a temperature of 700 to 800°C. More specific control ranges for firing temperature and time are explained in more detail below.

[0127] If the primary calcination temperature is lower than 800°C, specifically 810°C, the growth of individual particles within the lithium transition metal oxide is reduced, and a single-crystal lithium transition metal oxide may not be easily formed. If the primary calcination temperature is too high, under-calcination occurs, and particularly as the rock-salt structure crystal phase increases within the surface of the positive electrode active material, electrochemical properties such as the capacity of the active material may deteriorate.

[0128] When the second firing is performed at a lower temperature than the first firing as described above, the structural stability of the first-fired active material can be reduced by decreasing the amount of heat required for firing the active material compared to when only the first firing is performed, thereby reducing process costs.

[0129] In particular, it is desirable that the crystal structure of the positive electrode active material can be stabilized when the above secondary calcination is performed within the above temperature and time range. In addition, lithium byproducts remaining on the surface of the metal oxide are decomposed by heat and diffused into the interior of the metal oxide, thereby reducing the amount of lithium remaining on the surface. Furthermore, as the lithium ions react with the surface of the metal oxide, a stable layered structure is formed, thereby stabilizing the surface structure of the metal oxide surface. Consequently, it is desirable to have the advantage of improving the resistance characteristics and lifespan characteristics of the battery.

[0130] The above first and second calcination steps may be characterized by not including a cooling or grinding step between them, and the first and second calcination steps may be performed continuously at different temperatures. Accordingly, the reaction between external moisture and the calcined material can be suppressed, and while suppressing the increase in residual lithium, the degradation of the active material due to over-calcination can be suppressed and the active material can be structurally stabilized.

[0131] A method for manufacturing a positive electrode active material for a lithium secondary battery according to the present invention includes the step of crushing a lithium metal oxide to obtain a positive electrode active material in the form of a single particle or in which 1 to 20 of the single particles are aggregated.

[0132] The above disintegration can be performed after cooling the calcined lithium transition metal oxide to 50 to 200°C. Cooling to the above cooling temperature can suppress the reaction between external moisture and the calcined product and suppress the increase in residual lithium.

[0133] The above-mentioned disintegration can be performed by methods commonly practiced in the industry, for example, using rotary mills, jet mills, ball mills, fin mills, bead mills, or roll mills, but in particular, it can be performed using a jet mill, more specifically an air jet mill using compressed air, and can be performed at a grinding pressure of 1.5 to 5.5 bar, specifically 2.0 to 5.0 bar. The above-mentioned disintegration can be performed by adjusting the grinding pressure differently depending on the cohesive force between single particles according to the calcination temperature or time during calcination, but when performed within the above range, the generation of fine particles due to unnecessary particle breakage is suppressed, thereby suppressing side reactions with the electrolyte during operation when the electrode containing the above-mentioned positive active material is included in a secondary battery, and can perform separation between sufficiently grown single particles, thereby realizing the stability of the desired single-crystal positive active material.

[0134] Additionally, after the step of obtaining a single-crystal positive active material through the above-mentioned disintegration, the method may further include the step of mixing the single-crystal positive active material, a coating raw material, and an additional lithium raw material, and then heat-treating them to obtain a positive active material having a coating layer formed on its surface.

[0135] The lithium content added through the above additional lithium raw material may be 0.1 to 2.0 mol% based on the above positive active material, more specifically 0.2 to 1.8 mol%, or 0.4 to 1.5 mol%.

[0136] If the value falls below the specified range, electrochemical characteristics such as charge / discharge capacity and efficiency may be inferior, similar to the case where no additional lithium is added; if the value exceeds the specified range, unreacted lithium exists in the form of lithium hydroxide or lithium carbonate, which hinders the smooth insertion / extraction behavior of lithium during electrochemical evaluation and causes additional side reactions with the electrolyte, potentially leading to problems such as reduced battery life characteristics and high resistance.

[0137] At this time, the technical significance and characteristics of the coating layer, the standard input content range of the cobalt raw material for the cathode active material to derive an appropriate Co content within the coating layer, and the significance of said range are as described above.

[0138] The above heat treatment can be performed at 600 to 750°C, more specifically at 650 to 750°C or 660 to 720°C, and for 5 to 15 hours, more specifically at 5.5 to 12 hours.

[0139] If the heat treatment temperature and time range are lower than the above range, a large amount of unreacted coating layer may remain, which may impair the charge / discharge capacity and efficiency of the battery containing the corresponding positive electrode active material. If the heat treatment temperature and time range are higher than the above range, excessive process costs may occur, which may reduce economic effectiveness, and there may be problems such as increased residual lithium and excessive particle sintering, which may result in inferior electrochemical properties.

[0141] anode

[0142] In another embodiment of the present invention, a positive electrode is provided comprising a current collector and a positive electrode active material layer located on one surface of the current collector and comprising a positive electrode active material manufactured according to the above embodiment.

[0143] The characteristics of the positive active material constituting the above positive active material layer are the same as those previously described. Therefore, a detailed description of the positive active material will be omitted.

[0144] The above current collector may be, for example, made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treated with carbon, nickel, titanium, silver, etc.

[0145] Meanwhile, the above positive active material layer may include a binder and a conductive material.

[0146] At this time, the binder serves to improve adhesion between positive active material particles and adhesion between the positive active material and the positive current collector. Specific examples include 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, or various copolymers thereof. One of these alone or a mixture of two or more may be used, but is not limited thereto. The binder may be included in an amount of 1 to 30 weight% based on the total weight of the positive active material layer.

[0147] In addition, the 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 powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used, but is not limited thereto. The conductive material may typically be included in an amount of 1 to 30 weight% relative to the total weight of the positive electrode active material layer.

[0148] Except for being manufactured to fall within the above range, the above anode may be manufactured according to a conventional anode manufacturing method.

[0149] Specifically, the anode may be manufactured by applying a composition for forming an anode active material layer, which optionally includes a binder, a conductive material, or a solvent as needed, onto an anode current collector, followed by drying and rolling. At this time, the types and contents of the anode active material, binder, and conductive material are as described above.

[0150] The above solvent may be a solvent commonly used in the relevant technical field, such as dimethylsulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), 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 has a viscosity that allows for the dissolution or dispersion of the anode active material, conductive material, and binder, taking into account the coating thickness of the slurry and the manufacturing yield, and subsequently provides excellent thickness uniformity when coated for anode manufacturing.

[0151] Alternatively, the anode may be manufactured by casting a 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.

[0153] lithium secondary battery

[0154] In another embodiment, a lithium secondary battery including the anode is provided.

[0155] Specifically, the lithium secondary battery may include a positive electrode, a negative electrode positioned opposite to the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is as described above. Additionally, the lithium secondary battery may optionally further include a battery container housing an electrode assembly comprising the positive electrode, the negative electrode, and the separator, and a sealing member for sealing the battery container.

[0156] In the above lithium secondary battery, the negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0157] 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 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.

[0158] The above-mentioned cathode active material layer may optionally include a binder and a conductive material together with the cathode active material. The above-mentioned cathode active material layer may be manufactured, as an example, by applying a composition for forming a cathode active material layer, comprising a cathode active material and optionally a binder and a conductive material, onto a cathode current collector and drying it, or by casting the composition for forming a cathode onto a separate support and then laminating the film obtained by peeling it off from the support onto a cathode current collector.

[0159] 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; metal oxides capable of doping and dedoping lithium, such as SiOβ (0 ≤ β ≤ 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the above-mentioned metallic compounds and carbonaceous materials, 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 above-mentioned negative electrode active material. Furthermore, the carbon material may include both 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.

[0160] The binder and conductive material mentioned above may be the same as those previously described in the anode.

[0161] Next, depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. As such a separator, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof may be used, and a mixed multilayer film such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may also be used.

[0162] In addition, regarding the above lithium secondary battery, the electrolyte may include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which are usable when manufacturing a lithium secondary battery, but is not limited to these.

[0163] Specifically, the organic liquid electrolyte may include an organic solvent and a lithium salt.

[0164] 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 C2 to C20 structures 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.In this case, using a mixture of cyclic carbonate and chain carbonate in a volume ratio of about 1:1 to about 1:9 can result in excellent performance of the electrolyte.

[0165] The above lithium salt can be used without special restrictions as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably used within the range of 0.1 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 allow lithium ions to move effectively.

[0166] As described above, since the lithium secondary battery including the positive electrode according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, 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).

[0168] Preferred embodiments and comparative examples of the present invention are described below. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0170] Preparation of positive electrode active material

[0171] Example 1

[0172] (1) Preparation of a precursor

[0173] In a batch reactor, the internal temperature was set to 50°C while stirring with water, and nitrogen gas was introduced into the reaction vessel to adjust the atmosphere to an inert atmosphere. Subsequently, an aqueous sulfate solution mixed with nickel sulfate, cobalt sulfate, manganese sulfate, and aluminum sulfate in a molar ratio of 95.5 mol% : 2.0 mol% : 2.0 mol% : 0.5 mol%, sodium hydroxide, and ammonia water were prepared. After introducing the sodium hydroxide aqueous solution and ammonia water into the reactor to form an initial reaction atmosphere, the flow rate of the ammonia water was adjusted to a ratio of 1.2 to the flow rate of the metal sulfate aqueous solution.

[0174] Subsequently, the dosage of sodium hydroxide (NaOH) solution was adjusted so that the hydrogen ion concentration (pH) inside the reactor was approximately 11.8. Then, while stirring, the reactants were introduced, nitrogen gas was introduced, and an inert atmosphere was maintained. After the reaction was completed, the formed solution was washed and solid-liquid separated using a pressure filter (Filter Press), and a drying process was carried out.

[0176] (2) Preparation of positive electrode active material

[0177] 21.81 kg of the precursor prepared above was mixed with 10.19 kg of LiOH·H2O and 31.06 g of ZrO2, respectively, and then uniformly mixed using a mixer. The mixture was then calcined in an RHK kiln where an O2 atmosphere was maintained. The mixture was recovered and placed in a mullite crucible. In an RHK kiln supplied with oxygen at a flow rate of approximately 2800 L / min, the temperature was raised at 4.5 ℃ / min and maintained at 820°C for 4 hours, then lowered to 740°C at a cooling rate of 1.3°C / min and maintained for 8 hours. Subsequently, the temperature was lowered at a cooling rate of 4.0 ℃ / min. The obtained sample was crushed using a Rotor-Mill and Jet-Mill equipment to produce a single-crystal cathode active material with a central particle size of approximately 3.6 μm.

[0178] Lithium was added by adding 0.22g of LiOH·H2O per 100g of single-crystal cathode active material that had undergone a disintegration process, and about 0.14g of Al(OH)3 and 1.95g of Co(OH)2 per 100g of cathode active material were mixed and heat treatment was carried out in a box-shaped kiln where an O2 atmosphere was maintained. In a box-shaped kiln where O2 gas was introduced at a flow rate of 25 L / min, the temperature was increased at a rate of 3.5 ℃ / min and maintained at 680℃ for 6 hours, after which it was naturally cooled to produce a single-crystal cathode active material with a central particle size of 3.8㎛ with Al and Co coating layers formed.

[0180] Examples 2 to 7 and Comparative Examples 1 to 4

[0181] A positive electrode active material was prepared in the same manner as in Example 1, except that the heat treatment conditions, lithium additional input conditions, and Co input conditions were adjusted as shown in Table 1 below. In this case, if lithium was not additionally added, it was indicated as '-'.

[0183] Heat treatment temperature [°C] In the cathode active material, additional lithium input amount [mol%] In the positive electrode active material, Co coating content [mol%] Example 1 680 0.5 2.0 Example 2 680 0.5 2.2 Example 3 680 0.5 2.4 Example 4 680 1.0 2.0 Example 5 680 1.0 2.2 Example 6 680 1.0 2.4 Example 7 700 0.5 2.0 Comparative Example 1 680 - 2.0 Comparative Example 2 700 - 2.0 Comparative Example 3 680 - 2.2 Comparative Example 4 550 - 2.0

[0184] Experimental Example 1: Measurement of particle size of positive electrode active material

[0185] The particle size distribution of the cathode active materials according to the examples and comparative examples was measured using a Microtrac (S3000) instrument utilizing the laser diffraction method. The average particle size based on volume (Dv50) can be defined as the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve. The average particle size based on number (Dn50) can be defined as the particle size corresponding to 50% of the cumulative number in the particle size distribution curve. The results are shown in Table 2 below.

[0187] Experimental Example 2: Measurement of Rolled Density of Anode Active Material

[0188] Press Density (PD) for the cathode active materials according to the examples and comparative examples was measured using a GEOPYC 1365 (Micromeritics) instrument. Specifically, 10 g of the cathode active material was placed into a cylindrical vessel, and then the mold containing the cathode active material was pressurized at a pressure of 108 N. Subsequently, the press density was calculated through the height of the pressurized sample. The results are shown in Table 2 below.

[0190] Experimental Example 3: XRD Analysis of Anode Active Material

[0191] For the cathode active materials according to the examples and comparative examples, Li / Ni disorder (Li / Ni), crystalline size (c / s), and full width at half maximum (FWHM) were measured using X-ray diffraction (XRD). Specifically, the analysis was performed using the following method.

[0193] (1) Li / Ni disorder analysis

[0194] For the cathode active materials prepared in the examples and comparative examples, the Li / Ni disorder corresponding to the ratio of nickel within the lithium sites, i.e., the cation mixing ratio, was analyzed through Rietveld analysis using neutron diffraction analysis. The results are shown in Table 2 below.

[0196] (2) Measurement of grain size and FWHM

[0197] positive active material Grain size and FWHM was analyzed by extracting X-ray diffraction patterns using a D8 ENDEAVOR (BRUKER) instrument that uses X-ray diffraction (XRD).

[0198] Specifically, the positive active material is uniformly loaded into a sample holder in powder form, and the 2θ region between 10 and 90 is 10.7 oXRD analysis was performed at a rate of / min. The X-ray tube was set to 45kV and 200mA. The extracted X-ray diffraction patterns were analyzed using the Smart Lab Studio program to calculate the FWHM values ​​for each crystal size and the (101) and (104) peaks. The results are shown in Table 2 below.

[0200] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 PSD (Volume) [um] D5 2.10 2.13 2.08 2.31 2.13 2.11 2.11 2.19 2.18 2.15 2.14 D50 3.83 3.85 3.84 4.15 3.88 3.88 3.82 3.94 3.95 3.89 3.86 D95 7.15 7.10 7.27 7.38 7.21 7.75 7.01 7.34 7.36 7.24 7.08 PSD (Number) [um] D5 1.32 1.34 1.31 1.31 1.33 1.31 1.33 1.35 1.34 1.33 1.34 D50 2.55 2.60 2.52 2.79 2.59 2.55 2.58 2.66 2.64 2.61 2.61 D95 4.61 4.65 4.61 4.98 4.68 4.65 4.61 4.77 4.76 4.70 4.66 Rolling density (PD) [g / cc] 2.10 2.10 2.14 2.06 2.02 2.06 2.07 2.01 2.04 2.06 1.98 XRD C / S (nm) 175 183 180 160 177 173 173 174 171 170 183 Li / Ni(%) 1.5 1.5 1.5 1.6 1.4 1.2 1.2 1.3 1.3 1.4 1.2 FWHM(101) 0.0862 0.0821 0.0847 0.093 0.0862 0.0867 0.087 0.0888 0.0886 0.0886 0.0847 Equation 1 CS x Li / Ni x FWHM(101) 22.63 22.54 22.87 23.81 21.36 18.00 18.06 20.09 19.70 21.09 18.60 Equation 2 CS x PD 367.5 384.3 385.2 329.6 357.5 356.4 358.1 349.7 348.8 350.2 362.3

[0201] Referring to Table 2 above, it can be seen that the example satisfies the range of 22.00 nm*% or less in Formula 1 (CS x Li / Ni x FWHM (101)), and the comparative example does not satisfy the range.

[0202] In addition, it can be confirmed that the example satisfies the range of 330 to 365 nm*g / cc in Formula 2 (CS x PD), and the comparative example does not satisfy the corresponding range.

[0204] Experimental Example 4: Evaluation of Electrochemical Properties via Coin Cell

[0205] Coin cell manufacturing

[0206] To evaluate the physical properties and electrochemistry of the positive electrode active materials according to the examples and comparative examples, coin cells were manufactured as follows.

[0207] Specifically, a positive active material, a polyvinylidene fluoride binder (product name: KF1120), and a carbon black conductive material were mixed in a weight ratio of 96.5:1.5:2.0, and this mixture was added to an N-methyl-2-pyrrolidone solvent to prepare a positive active material slurry.

[0208] The above slurry was coated onto an aluminum foil (thickness: 20 μm), which serves as an anode current collector, using a doctor blade, and an anode was manufactured by drying and rolling. The loading amount of the anode was approximately 16.0–17.0 mg / cm², and the rolling density was approximately 3.7 g / cm³.3 It was.

[0209] A 2032 coin cell was manufactured by a conventional method using the above-mentioned anode, lithium metal cathode (thickness 200 μm, NEBA), electrolyte, and polyethylene separator. The electrolyte used was a mixed solution in which 1M LiPF6 was dissolved in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethylmethyl carbonate (EMC) (mixing ratio EC:DMC:EMC = 3:4:3 volume%) together with a mixed solvent of VC (vinylene carbonate), PS (propane sulfone), and ESA (ethylene sulfate) (3.0:0.5:1 wt%).

[0211] Charge / Discharge Test

[0212] After fabricating the coin cell, it was aged at 25°C for 10 hours, and then a charge-discharge test was conducted at 25°C. To evaluate the discharge capacity, the reference capacity was set to 200 mAh / g, and the cell was charged to 4.3V with a constant current of 0.1C. Then, the voltage was switched to a constant voltage, and charging continued until the termination current reached 0.05C. After a 10-minute rest time following charging, the cell was discharged until it reached 3.0V with a constant current of 0.1C and a reference capacity of 200 mAh / g.

[0214] The electrochemical properties derived from this are listed in Table 3 below.

[0215] 0.1C Charging Capacity [mAh / g] 0.1C Discharge Capacity [mAh / g] Efficiency [%] 2C Efficiency [%] Room temperature resistance [Ω] Example 1 246.3 219.5 89.1 89.9 34.2 Example 2 247.5 221.9 89.6 89.6 34.1 Example 3 247.2 221.5 89.6 89.8 30.6 Example 4 246.6 220.2 89.3 89.2 34.6 Example 5 247.0 222.5 90.1 89.6 33.0 Example 6 247.2 222.3 89.9 89.7 33.3 Example 7 248.5 221.8 89.3 89.2 35.6 Comparative Example 1 244.3 217.5 89.0 89.5 36.6 Comparative Example 2 245.5 218.6 89.0 89.8 36.0 Comparative Example 3 245.1 218.1 89.1 89.5 34.2 Comparative Example 4 245.7 218.5 88.9 89.4 35.1

[0216] It was confirmed that a coin cell containing a positive active material according to an embodiment satisfying the appropriate range of Equation 1 or Equation 2 described above has an excellent discharge capacity of 219.0 mAh / g or higher. On the other hand, it was confirmed that a coin cell containing a positive active material according to a comparative example has a discharge capacity of 219.0 mAh / g or lower, which is inferior to that of the embodiment.

[0217] In addition, it was confirmed that the coin cell containing the positive electrode active material according to the example had an efficiency of 89.1% or higher and simultaneously had an efficiency of 89.0% or higher in 2C. On the other hand, the efficiency of the coin cell containing the positive electrode active material according to the comparative example was 89.1% or lower, which was inferior to that of the example.

[0218] Meanwhile, in the case of the example, it was confirmed that the room temperature resistance was 35.6Ω or less, indicating an excellent resistance value. For reference, in the case of Comparative Example 3 and Comparative Example 4, the room temperature resistance was 35.6Ω or less, but the charge / discharge capacity and efficiency were found to be inferior.

[0219] Therefore, through a comparison of the examples and comparative examples, it can be seen that the battery containing the positive active material according to Examples 1 to 7 is electrochemically superior.

[0221] The present invention is not limited to the above embodiments and can be manufactured in various different forms, and those skilled in the art will understand that the invention can be implemented in other specific forms without changing the technical concept or essential features of the invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

Claim 1 A positive electrode active material for a lithium secondary battery satisfying the following Equation 1: [Equation 1] CS x Li / Ni x FWHM (101) ≤ 22.00 nm*% In the above Equation 1, CS represents the crystal grain size of the positive electrode active material, Li / Ni represents the Li / Ni disorder of the positive electrode active material, and FWHM (101) represents the full width at half maximum of the (101) peak measured using X-ray diffraction. Claim 2 A positive electrode active material for a lithium secondary battery according to claim 1, wherein the CS is in the range of 161 to 190 nm. Claim 3 A positive electrode active material for a lithium secondary battery according to claim 1, wherein the Li / Ni is in the range of 1.00 to 1.45%. Claim 4 A positive electrode active material for a lithium secondary battery according to claim 1, wherein the FWHM (101) is in the range of 0.0800 to 0.0900. Claim 5 A positive electrode active material for a lithium secondary battery that satisfies the following Equation 2 in claim 1: [Equation 2] 330 nm*g / cc ≤ CS x PD ≤ 365 nm*g / cc PD represents the rolled density derived through the height of the positive electrode active material pressurized to a pressure of 108 N. Claim 6 In claim 5, the positive electrode active material for a lithium secondary battery, wherein the PD is in the range of 1.90 to 2.09 g / cc. Claim 7 In claim 1, a positive electrode active material for a lithium secondary battery represented by the following chemical formula 1: [Chemical Formula 1]Li a [Ni x Co y Mn z M w ]O2 In the above chemical formula 1, 0.8≤a≤1.2, 0.70≤x≤0.99, 0.01≤y≤0.30, 0≤z≤0.30, 0≤w≤0.20, x+y+z+w=1, and M is Al, Zr, Y, B, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr or a combination thereof. Claim 8 A positive active material for a lithium secondary battery according to claim 7, wherein the positive active material comprises Al, and the total content of Al is in the range of 300 to 5000 ppm based on the weight of the positive active material. Claim 9 A positive active material for a lithium secondary battery according to claim 1, wherein the positive active material comprises a coating layer on its surface, and the coating layer comprises Al, Co, W, V, Ti, Nb, Ce, B, P, or a combination thereof. Claim 10 A positive electrode active material for a lithium secondary battery according to claim 9, wherein the coating layer comprises Al and Co, and the content of Co in the coating layer is in the range of 1.5 to 3.0 mol% based on the positive electrode active material. Claim 11 A lithium secondary battery comprising a positive electrode for a lithium secondary battery comprising a positive electrode active material of any one of claims 1 to 10.

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