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

Abstract

The present invention provides a positive electrode active material and a positive electrode and a lithium secondary battery including the positive electrode active material. The positive electrode active material includes a lithium composite transition metal oxide containing nickel, cobalt, manganese, and aluminum, wherein the nickel content of the lithium composite transition metal oxide is 90 mol% or more on the basis of metals excluding lithium, and Al / Ni, which is the molar ratio of aluminum to nickel, is 0.015 to 0.034.

Description

Cathode active material, cathode and lithium secondary battery containing same

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0105931, filed August 11, 2023, Korean Patent Application No. 10-2023-0133819, filed October 6, 2023, and Korean Patent Application No. 10-2024-0008351, filed January 18, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a positive electrode active material, a positive electrode including the same, and a lithium secondary battery.

[0003] The recent rapid proliferation of battery-powered electronic devices, such as mobile phones, laptops, and electric vehicles, has led to a rapid increase in demand for compact, lightweight, and relatively high-capacity secondary batteries. In particular, lithium secondary batteries, with their lightweight design and high energy density, are attracting attention as power sources for portable devices. Accordingly, active research and development efforts are underway to improve the performance of lithium secondary batteries.

[0004] Lithium secondary batteries produce electrical energy through oxidation and reduction reactions when lithium ions are inserted / deintercalated between the positive and negative electrodes, which are made of active materials capable of intercalating and deintercalating lithium ions, while charging an organic electrolyte or polymer electrolyte between them.

[0005] Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMn2O4, etc.), lithium iron phosphate compound (LiFePO4), etc. have been used as positive active materials for lithium secondary batteries. In addition, as a method to improve the low thermal stability of LiNiO2 while maintaining the excellent reversible capacity, lithium composite metal oxides (hereinafter simply referred to as 'NCM-based lithium composite transition metal oxides') in which some of the nickel (Ni) is replaced with cobalt (Co) and manganese (Mn) have been developed. However, the conventionally developed NCM-based lithium composite transition metal oxides have insufficient capacity characteristics, which limits their application.

[0006] To address these issues, recent research has focused on increasing the nickel content in NCM lithium composite transition metal oxides. However, high-nickel (High-Ni) cathode active materials with high nickel content suffer from the following problems: Due to the high reactivity of nickel, they generate large amounts of gas during charge / discharge processes, exhibit significant lattice structural instability due to cation mixing and oxygen desorption, and increase the content of lithium impurities remaining on the surface.

[0007] Therefore, there is a need to develop a cathode material that has excellent capacity and structural stability while including a high nickel content.

[0008] The present invention aims to provide a cathode active material with improved dispersibility, a cathode slurry containing the same, a cathode, and a lithium secondary battery.

[0009] The present invention is a cathode active material comprising a lithium composite transition metal oxide containing nickel, cobalt, manganese and aluminum,

[0010] A positive electrode active material is provided, wherein the content of nickel among the metals other than lithium in the lithium composite transition metal oxide is 90 mol% or more, and the molar ratio of aluminum to nickel, Al / Ni, is 0.015 to 0.034.

[0011] In addition, the present invention provides a positive electrode comprising a positive electrode current collector; and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes the positive electrode active material described above.

[0012] In addition, the present invention provides a lithium secondary battery including the above-described positive electrode; a negative electrode including a negative electrode active material; a separator interposed between the positive electrode and the negative electrode; and an electrolyte.

[0013] The cathode active material according to the present invention has a high nickel content, thus providing excellent capacity, and can reduce the amount of cobalt used, thereby being advantageous in terms of material supply and price.

[0014] In addition, it provides an optimal Al / Ni molar ratio that can evenly improve the doping yield, resistance characteristics, and structural stability in NCMA oxide, and accordingly, it is possible to provide a lithium secondary battery with improved charge / discharge capacity and high-temperature lifespan by including the NCMA oxide.

[0015] Figure 1 is a graph showing the change in heat flow according to temperature of a positive electrode active material including a lithium composite transition metal oxide manufactured in an example and a comparative example.

[0016] Figure 2 is a graph showing the capacity retention rate and resistance increase rate at high temperatures of half cells containing lithium composite transition metal oxides manufactured in examples and comparative examples as positive electrode active materials.

[0017] Hereinafter, the present invention will be described in detail.

[0018]

[0019] In the present invention, the content of each element in the positive electrode active material can be measured by inductively coupled plasma optical emission spectroscopy (ICP-OES). Specifically, this means that 0.03 g of the positive electrode active material to be analyzed is dispersed and dissolved in 1 mL of hydrochloric acid, a small amount of hydrogen peroxide and hydrofluoric acid is added, the result is diluted with 50 mL of ultrapure water, and then analyzed using an Avio series (PerkinElmer, Inc) device.

[0020] In the present invention, “primary particle” means a particle unit that has no apparent grain boundary when observed at a magnification of 5,000 to 20,000 times using a scanning electron microscope.

[0021] In the present invention, "a-axis" and "c-axis" refer to the axial directions in the crystal structure of the primary particles. The crystal structure of the primary particles was confirmed through TEM-SAED (Transmission Electron Microscope-Selected Area Electron Diffraction) analysis. The length in the c-axis direction and the length in the a-axis direction can be quantitatively analyzed using X-ray diffraction analysis (XRD) using Cu Kα X-rays.

[0022] In the present invention, "X-ray diffraction analysis (XRD)" can be performed by placing the particles to be measured in a holder, irradiating the particles with X-rays, and analyzing the resulting diffraction grating. Sampling was prepared by placing the powder sample of the particles to be measured into the groove in the center of a general powder holder, smoothing the surface using a slide glass, and ensuring that the sample height was the same as the edge of the holder. Then, X-ray diffraction analysis was performed using a Bruker D8 Endeavor (light source: Cu Kα, λ=1.54Å) equipped with a LynxEye XE-T position sensitive detector, under the conditions of a FDS of 0.5°, a step size of 0.02°, and a total scan time of approximately 20 minutes in the 2θ=15°~90° range. Rietveld refinement was performed on the measured data by considering the charge at each site (metal ions at the transition metal site are +3, Ni ions at the Li site are +2) and cation mixing. Instrumental brodadening was considered using the Fundamental Parameter Approach (FPA) implemented in the Bruker TOPAS program, and the entire peaks of the measurement range were used during fitting. Peak shape was fitted using only the Lorenzian contribution of the First Principle (FP) peak types available in TOPAS, and strain was not considered at this time.

[0023] In the present invention, "particle strength" is a value expressed in pressure units (MPa) by placing the powder to be measured into a micro compression testing machine, Anton Paar, Step 500, and securing the shape of the particle to be measured under a microscope, and then applying force to the particle with a tip to break the particle. Taking into account the variation between particles, the values ​​measured more than 10 times are mapped and the average value is used as the particle strength value.

[0024] In the present invention, "D 50 " refers to the particle size corresponding to 50% of the volume accumulation in the volume accumulation particle size distribution of the corresponding particle powder, and can be measured using a laser diffraction method. For example, after dispersing the positive electrode active material powder in a dispersion medium, it can be measured by introducing it into a commercially available laser diffraction particle size measuring device (e.g., Malvern, Mastersizer 3000) and irradiating it with ultrasonic waves of about 28 kHz at an output of 60 W, obtaining a volume accumulation particle size distribution graph, and finding the particle size at the point where the volume accumulation amount is 50% in the obtained volume accumulation particle size distribution graph.

[0025]

[0026] Hereinafter, each component of the present invention will be described in more detail.

[0027]

[0028] <Cathode active material>

[0029] The present invention relates to a positive electrode active material, and more particularly, to a positive electrode active material for a lithium secondary battery.

[0030] The cathode active material according to the present invention comprises a lithium composite transition metal oxide containing nickel, cobalt, manganese, and aluminum, wherein the content of nickel among the metals excluding lithium in the lithium composite transition metal oxide is 90 mol% or more, and the molar ratio of aluminum to nickel, Al / Ni, is 0.015 to 0.034.

[0031] As mentioned above, increasing the nickel content in lithium composite transition metal oxides can secure higher capacity, but it also reduces structural stability. Specifically, high-nickel cathode active materials exhibit a high amount of lithium compounds remaining on their surfaces, which can cause side reactions during charge / discharge, generating gases and degrading stability.

[0032] Furthermore, high-nickel cathode active materials suffer from significant changes in lattice constants, i.e., changes in volume within the unit cell. These volume changes can cause cracks within the active material particles. These cracks can lead to voids within the active material, potentially degrading battery performance.

[0033] In addition, as the nickel content is high, the phenomenon of cation mixing of lithium ions and nickel ions occurs frequently, which hinders the movement of lithium ions when the battery is operated, causing an increase in battery resistance and a deterioration in lifespan.

[0034] Accordingly, the inventors of the present invention have solved the above problem by controlling the ratio of nickel and doping elements in an ultra-high nickel positive electrode active material having a nickel content of 90 mol% or more, specifically, the molar ratio of Ni and Al in a lithium composite transition metal oxide (hereinafter, NCMA oxide) containing Ni, Co, Mn, and Al, within an optimal range. Al can reduce the volume change within the unit cell in NCMA oxide having a Ni content of 90 mol% or more, thereby suppressing cracks in active material particles and reducing voids to prevent degradation. Therefore, the positive electrode active material according to the present invention can realize high capacity while simultaneously exhibiting excellent thermal stability and lifespan characteristics. However, since Al does not contribute to capacity and excessive Al may rather hinder capacity development, it is important to appropriately control the content of Al relative to Ni.

[0035] Specifically, the molar ratio of aluminum to nickel, Al / Ni, may be 0.015 or more, 0.021 or more, or 0.030 or more, and 0.034 or less or 0.032 or less. When the Al / Ni is less than 0.015, the life characteristics deteriorate due to the rapid volume change within the unit cell caused by the increase in nickel content, and the structural instability increases, so that the main peak temperature, which is the maximum heat flow, drops, making it difficult to implement the aforementioned effect. On the other hand, when it exceeds 0.034, the excess Al is not incorporated into the layered structure but remains as an undoped residue on the surface of the active material, which hinders the movement of lithium ions, so that the surface resistance increases and the expressed capacity decreases, which is not preferable.

[0036]

[0037] In one embodiment of the present invention, the content of nickel among the metals other than lithium in the lithium composite transition metal oxide may be 92 mol% or more, preferably 93 mol% or more, and more preferably 93 mol% to 95 mol%. This is preferable in that it is possible to secure a certain level of Al content while achieving high capacity.

[0038] In addition, the content of cobalt among the metals other than lithium in the lithium composite transition metal oxide may be 0.1 mol% to 1.0 mol%, preferably 0.2 mol% to 0.9 mol%, and more preferably 0.4 mol% to 0.8 mol%. That is, in the present invention, the lifespan, resistance, and output characteristics are improved by controlling the Al / Ni molar ratio while minimizing the content of expensive cobalt.

[0039] In addition, the content of aluminum among the metals other than lithium in the lithium composite transition metal oxide may be 1.0 mol% to 5.0 mol%, preferably 1.5 mol% to 4.0 mol%, and more preferably 2.0 mol% to 3.8 mol%. When the aluminum content is within the above range, it is easy to control the Al / Ni molar ratio in the NCMA oxide having a nickel content of 90 mol% or more within the above-described optimal range.

[0040] Specifically, the lithium composite transition metal oxide may have a composition represented by the following chemical formula 1.

[0041] [Chemical Formula 1]

[0042] Li 1+x (Ni a Co b Mn c Al d M1 e )O2

[0043] In the above chemical formula 1,

[0044] M1 is at least one selected from the group consisting of Ti, Zr, W, Mo, Nb, Cu, Fe, V, Cr, Zn, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Mg and B,

[0045] x, a, b, c, d, and e are -0.2≤x≤0.2, 0.90≤a<1, 0, respectively. <b≤0.01, 0<c≤0.05, 0<d≤0.05, 0≤e≤0.05, a+b+c+d+e=1을 만족한다.

[0046] The above 1+x represents the molar ratio of lithium in the lithium composite transition metal oxide, and may be -0.1≤x≤0.2, or 0≤x≤0.2. When the molar ratio of lithium satisfies the above range, the crystal structure of the lithium composite transition metal oxide can be stably formed.

[0047] The above a represents the molar ratio of nickel among the total metals excluding lithium in the lithium composite transition metal oxide, and may be 0.920≤a<1, 0.930≤a<1, or 0.930≤a≤0.950. When the molar ratio of nickel satisfies the above range, a high energy density is exhibited, enabling high capacity implementation.

[0048] The above b represents the molar ratio of cobalt among all metals excluding lithium in the lithium composite transition metal oxide, and is 0. <b≤0.009, 0<b≤0.008, 또는 0<b≤0.006일 수 있다. 코발트의 몰비가 상기 범위를 만족할 때, 최소한의 양으로 양호한 저항 특성 및 출력 특성을 구현할 수 있다.

[0049] The above c represents the molar ratio of manganese among all metals excluding lithium in the lithium composite transition metal oxide, and is 0. <c≤0.050, 0<c≤0.040, 또는 0<c≤0.030일 수 있다. 망간의 몰비가 상기 범위를 만족할 때, 양극 활물질의 구조 안정성이 우수하게 나타난다.

[0050] The above d represents the molar ratio of Al among the total metals excluding lithium in the lithium composite transition metal oxide, and the above d may be 0.010≤d≤0.050, 0.015≤d≤0.040, or 0.020≤d≤0.038.

[0051] The above e represents the molar ratio of the M1 element among all metals excluding lithium in the lithium composite transition metal oxide, and can be adjusted as needed.

[0052]

[0053] Meanwhile, the positive electrode active material includes primary particles and secondary particles in which the primary particles are aggregated, and the ratio of the length in the a-axis direction to the length in the c-axis direction of the primary particles, c / a, may be 4.9400 to 4.9500, preferably 4.9400 to 4.9450, and more preferably 4.9405 to 4.9422. The c / a ratio being within the above range means that the layered structure of the positive electrode active material is highly complete, and therefore, when the c / a ratio is within the above range, the movement of lithium ions is smooth during charge / discharge, and the volume change is small, which is effective in improving the characteristics of reducing the decline in lifespan according to the progression of the cycle.

[0054] In addition, D of the above positive electrode active material 50 The average particle size of the primary particles may be 8 µm to 15 µm, preferably 10 µm to 13 µm, and more preferably 11 µm to 12 µm, and the average particle size of the primary particles may be 0.3 µm to 2.0 µm, preferably 0.5 µm to 1.5 µm, and more preferably 0.7 µm to 1.0 µm, but is not limited thereto.

[0055] Meanwhile, since the bonding energy between Al and O is greater than the bonding energy between Ni and O, there is an effect of improving particle strength as the molar ratio of Al / Ni is adjusted within the above-described range. For example, the particle strength of the positive electrode active material may be 142 MPa to 160 MPa, preferably 145 MPa to 155 MPa, and more preferably 150 MPa to 155 MPa. When the particle strength is within the above range, the breakage of the positive electrode active material during electrode rolling is minimized, thereby reducing side reactions with the electrolyte, thereby lowering the resistance increase rate of the battery.

[0056] Meanwhile, when the heat flow of the positive electrode active material is measured using differential scanning calorimetry (DSC), the peak with the maximum heat flow may appear at 219°C to 230°C, specifically at 220°C to 230°C, and more specifically at 225°C to 230°C.

[0057] Additionally, the maximum heat flow of the positive electrode active material measured in the range of 25°C to 300°C using differential scanning calorimetry (DSC) may be 85.0 W / g or less, 70.0 W / g or less, or 60.0 W / g or less.

[0058] That is, since the positive electrode active material according to the present invention has a relatively high peak temperature at which the heat flow is maximum and a small maximum heat flow value, it has the advantage of having a relatively low risk of explosion even when the internal temperature of the battery rises.

[0059]

[0060] Meanwhile, the step of forming a composite transition metal precursor having a nickel content of 90 mol% or more by co-precipitation reaction by supplying a transition metal-containing solution containing a transition metal precursor, an ammonium cation complex forming agent, and a basic compound to a reactor, wherein the positive electrode active material is formed;

[0061] It can be manufactured by a manufacturing method including a step of mixing and heat-treating the above composite transition metal precursor, lithium raw material, and aluminum raw material to form an Al-doped lithium composite transition metal oxide.

[0062] At this time, the heat treatment can be performed at 600°C to 900°C, preferably 650°C to 850°C, and more preferably 700°C to 800°C for 15 to 24 hours.

[0063] The step of forming the above-mentioned complex transition metal precursor can be prepared, for example, by dissolving each transition metal precursor in a solvent to prepare a transition metal-containing solution, then mixing the transition metal-containing solution, an ammonium cation complex forming agent, and a basic compound, and then performing a coprecipitation reaction. In addition, an oxidizing agent or oxygen gas may be additionally added during the coprecipitation reaction, if necessary.

[0064] Meanwhile, the transition metal precursor may be an acetate, carbonate, nitrate, sulfate, halide, sulfide, etc. of each transition metal.

[0065] Specifically, the nickel precursor may be at least one selected from the group consisting of NiO, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, NiSO4, NiSO4·6H2O, and nickel sulfide, and the cobalt precursor may be at least one selected from the group consisting of Co(OH)2, Co3O4, CoOOH, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O, and Co(SO4)2·7H2O. In addition, the manganese precursor may be at least one selected from the group consisting of Mn2O3, MnO2, Mn3O4, MnCO3, Mn(NO3)2, MnSO4·H2O, manganese acetate, manganese halides, and manganese sulfide.

[0066] At this time, the input amount of each transition metal precursor can be determined by considering the molar ratio of the transition metal in the positive electrode active material to be ultimately produced.

[0067] 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 the reactor in the form of a solution in which the compound is dissolved in a solvent. At this time, as the solvent, water or a mixture of water and an organic solvent (specifically, alcohol, etc.) that can be uniformly mixed with water may be used.

[0068] The 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. At this time, the solvent may be water, or a mixture of water and an organic solvent (specifically, alcohol, etc.) that can be uniformly mixed with water.

[0069] As described above, when a transition metal-containing solution, an ammonium cation complex forming agent, and a basic compound are introduced into a reactor and stirred, the transition metals in the transition metal-containing solution coprecipitate, generating precursor particles in the form of transition metal hydroxides.

[0070] At this time, the transition metal-containing solution, ammonium cation complex forming agent, and basic compound are added in an amount such that the pH of the reaction solution becomes within the desired range.

[0071] Once precursor particles are formed in the above manner, they are separated from the reaction solution to obtain the precursor. For example, the precursor can be separated from the reaction solution by filtering the reaction solution, and then the separated precursor can be washed and dried to obtain the precursor. Processes such as grinding and / or classification may also be performed as needed.

[0072]

[0073] A lithium composite transition metal oxide is manufactured by mixing and heat-treating a composite transition metal precursor manufactured in this manner with a precursor containing a lithium raw material and a metal element M1.

[0074] As the lithium raw material, lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide or oxyhydroxide may be used, and for example, Li2CO3, LiNO3, LiNO2, LiOH, LiOHㆍH2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7 or a mixture thereof may be used.

[0075] Meanwhile, the lithium raw material and the composite transition metal precursor may be mixed so that the molar ratio of Li: total metal in the precursor is 1:1 to 1.2:1, preferably 1:1 to 1.1:1. When the mixing ratio of the lithium raw material and the metal in the precursor satisfies the above range, the layered crystal structure of the lithium composite transition metal oxide is well developed, so that a positive electrode active material with excellent capacity characteristics and structural stability can be manufactured.

[0076] In addition, the above aluminum raw material is Al It may be an oxide, hydroxide, oxyhydroxide, halide, nitrate, carbonate, acetate, oxalate, citrate or sulfate, etc., and examples thereof include Al2O3, Al(OH)3, Al(NO3)3, Al2(SO4)3, (HO)2AlCH3CO2, HOAl(CH3CO2)2, Al(CH3CO2)3aluminum halide or a combination thereof. Instead of adding the aluminum raw material together with the lithium raw material in the heat treatment step, it may be added to the transition metal-containing solution during the co-precipitation reaction.

[0077] When additionally doping with metal element M1, the type and amount of the metal element M1 can be controlled by considering the type and content of the metal element M1 included in the positive electrode active material described above.

[0078]

[0079] Bipolar

[0080] Next, the anode according to the present invention will be described.

[0081] The positive electrode according to the present invention comprises the positive electrode active material, and specifically, the positive electrode according to the present invention comprises: a positive electrode current collector; and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises the positive electrode active material. Since the positive electrode active material is the same as described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below.

[0082] The positive electrode current collector may include a highly conductive metal, and is not particularly limited as long as it is easily adhered to by the positive electrode active material layer and is non-reactive within the voltage range of the battery. The positive electrode 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. In addition, the positive electrode current collector may typically have a thickness of 3 to 500 μm, and fine unevenness may be formed on the surface of the current collector to increase the adhesion of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0083] The above positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the positive electrode active material is used. Specifically, the positive electrode slurry containing the positive electrode active material can be applied onto a positive electrode current collector, followed by drying and rolling, or the positive electrode slurry can be cast onto a separate support, and then the film obtained by peeling it off from the support can be laminated onto a positive electrode current collector.

[0084] In one embodiment of the present invention, the positive electrode includes a positive electrode active material layer formed by coating positive electrode slurry containing the positive electrode active material on at least one surface of a positive electrode current collector.

[0085] Meanwhile, the positive electrode slurry may include the positive electrode active material, a binder, a conductive material, and a solvent.

[0086] Specifically, the binder may be at least one selected from the group consisting of polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, and various copolymers thereof, and preferably polyvinylidene fluoride.

[0087] The binder may be included in an amount of 0.5 wt% to 3 wt%, preferably 1 wt% to 3 wt%, and more preferably 1.5 wt% to 2.5 wt%, based on the total weight of the solid content in the positive electrode slurry. When the binder content is within the above range, sufficient adhesion to the current collector and bonding between particles can be secured, thereby improving the durability of the positive electrode while maintaining a low initial resistance.

[0088] The conductive material may be at least one selected from the group consisting of graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; carbon-based materials such as carbon fibers and carbon nanotubes; 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; and conductive polymers such as polyphenylene derivatives, and preferably carbon nanotubes or carbon black, and most preferably carbon nanotubes.

[0089] The conductive agent may be included in an amount of 0.1 wt% to 2.5 wt%, preferably 0.5 wt% to 2 wt%, and more preferably 1 wt% to 2 wt%, based on the total weight of the solid content in the positive electrode slurry. When the content of the conductive agent is within the above range, it is preferable in that the dead volume can be reduced while maintaining conductivity between active materials.

[0090] In addition, the above cathode slurry may optionally further include a dispersant, and the dispersant may be hydrogenated nitrile butadiene rubber (HNBR).

[0091] Meanwhile, the solvent of the positive electrode slurry may be a solvent generally used in the art, and examples thereof include N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), isopropyl alcohol, dimethyl formamide (DMF), acetone, water, or a mixture of two or more thereof. The solvent may be used by adjusting the above-described positive electrode slurry to have an appropriate viscosity. For example, the solvent may be included so that the concentration of solid content in the positive electrode slurry is 60 wt% or more, preferably 60 wt% to 90 wt%, and more preferably 60 wt% to 80 wt%.

[0092]

[0093] lithium secondary battery

[0094] Next, a lithium secondary battery according to the present invention will be described.

[0095] The lithium secondary battery specifically includes a positive electrode, a negative electrode including a negative electrode active material, and a separator and electrolyte interposed between the positive electrode and the negative electrode. Since the positive electrode is the same as described above, a detailed description will be omitted, and only the remaining components will be described in detail below.

[0096] In addition, the lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member that seals the battery container.

[0097] In the above lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0098] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 ㎛ to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0099] The above negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material.

[0100] As the 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 alloy, Sn alloy, or Al alloy; SiO β (0 <β< 2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides capable of doping and dedoping lithium; or composites containing the above metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and a mixture of one or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. The negative electrode active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of the negative electrode active material layer.

[0101] The above binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0102] The conductive agent is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10 wt% or less, preferably 5 wt% or less, based on the total weight of the negative electrode active material layer. The conductive agent is not particularly limited as long as it has conductivity and does not cause a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and 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; and conductive materials such as polyphenylene derivatives.

[0103] The above negative electrode active material layer can be manufactured by applying and drying a negative electrode composite prepared by dissolving or dispersing a negative electrode active material and optionally a binder and a conductive material in a solvent on a negative electrode current collector, or by casting the negative electrode composite on a separate support and then laminating the obtained film by peeling it off from the support on a negative electrode current collector.

[0104] Meanwhile, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without special restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, can be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. can also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength can be used, and can optionally be used in a single-layer or multi-layer structure.

[0105] In addition, examples of the electrolyte used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0106] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0107] The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R represents a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, 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 linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.

[0108] The above lithium salt can be used without any special limitation as long as it is a compound that can provide lithium ions used in a lithium secondary battery. 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 - At least one selected from the group consisting of, and the lithium salt is LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO2, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2 can be used. It is recommended that the concentration of the lithium salt be within the range of 0.1 to 4.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0109] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 to 5 wt% based on the total weight of the electrolyte.

[0110] There is no particular limitation on the external shape of the lithium secondary battery of the present invention, but it may be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0111] As described above, since the lithium secondary battery including the positive electrode active material according to the present invention stably exhibits charge / discharge capacity and life characteristics, it can be used not only as a battery cell used as a power source for small devices such as mobile phones, laptop computers, and digital cameras, but can also be preferably used as a unit battery of a battery module for medium- to large-sized devices including a plurality of battery cells.

[0112] Examples of the above medium and large devices include, but are not limited to, power tools, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0113] According to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0114]

[0115] Hereinafter, the present invention will be described in more detail through specific examples.

[0116] [Example: Preparation of positive electrode active material]

[0117] Example 1.

[0118] After adding 4 L of distilled water to a co-precipitation reactor (capacity 20 L), the temperature was maintained at 50°C, and 100 mL of an ammonia aqueous solution with a concentration of 28 wt% was added. Then, a transition metal solution mixed with NiSO4, CoSO4, and MnSO4 such that the molar ratio of Ni:Co:Mn was 97.0:0.5:2.5, an ammonia aqueous solution, and a sodium hydroxide solution were added to the co-precipitation reactor, and a co-precipitation reaction was performed to form a precursor. The precursor particles were separated, washed, and dried in an oven at 130°C to prepare a precursor.

[0119] LiOH as a lithium raw material, the above-mentioned precursor, and Al(OH)3 were mixed so that the molar ratio of Li:(Ni+Co+Mn):Al was 1:0.978:0.022, and heat-treated at 720°C for 20 hours in an oxygen atmosphere to produce a lithium composite transition metal oxide.

[0120]

[0121] Example 2.

[0122] A precursor was prepared using the same process as in Example 1. LiOH, the above-mentioned precursor, and Al(OH)3 were mixed so that the molar ratio of Li:(Ni+Co+Mn):Al was 1:0.968:0.032, and heat-treated at 720°C for 20 hours in an oxygen atmosphere to prepare a lithium composite transition metal oxide.

[0123]

[0124] Comparative Example 1.

[0125] A precursor was prepared using the same process as in Example 1. LiOH was mixed with the prepared precursor so that the molar ratio of Li:(Ni+Co+Mn) was 1:1, and heat-treated at 720°C for 20 hours in an oxygen atmosphere to prepare a lithium composite transition metal oxide.

[0126]

[0127] Comparative Example 2.

[0128] A precursor was prepared using the same process as in Example 1. LiOH, the above-mentioned precursor, and Al(OH)3 were mixed so that the molar ratio of Li:(Ni+Co+Mn):Al was 1:0.989:0.011, and heat-treated at 720°C for 20 hours in an oxygen atmosphere to prepare a lithium composite transition metal oxide.

[0129]

[0130] Comparative Example 3.

[0131] A precursor was prepared using the same process as in Example 1. LiOH, the above-mentioned precursor, and Al(OH)3 were mixed so that the molar ratio of Li:(Ni+Co+Mn):Al was 1:0.964:0.036, and heat-treated at 720°C for 20 hours in an oxygen atmosphere to prepare a lithium composite transition metal oxide.

[0132]

[0133] Comparative Example 4.

[0134] After adding 4 L of distilled water to a co-precipitation reactor (capacity 20 L), the temperature was maintained at 50°C, and 100 mL of an ammonia aqueous solution with a concentration of 28 wt% was added. Then, a transition metal solution mixed with NiSO4, CoSO4, and MnSO4 such that the molar ratio of Ni:Co:Mn was 91.0:6.0:3.0, an ammonia aqueous solution, and a sodium hydroxide solution were added to the co-precipitation reactor, and a co-precipitation reaction was performed to form a precursor. The precursor particles were separated, washed, and dried in an oven at 130°C to prepare a precursor.

[0135] LiOH as a lithium raw material, the above-mentioned precursor, and Al(OH)3 were mixed so that the molar ratio of Li:(Ni+Co+Mn):Al was 1:0.969:0.031, and heat-treated at 720°C for 20 hours in an oxygen atmosphere to produce a lithium composite transition metal oxide.

[0136]

[0137] [Experimental Example]

[0138] Experimental Example 1. Confirmation of doping content

[0139] For each of the lithium composite transition metal oxides manufactured in Examples 1 and 2 and Comparative Examples 1 to 4, the content of Al was measured using an inductively coupled plasma optical emission spectrometer (ICP-OES; Optima 7300DV, PerkinElmer), and the content of Al relative to the total weight and total mole number of the lithium composite transition metal oxide was calculated and shown in Table 1 below.

[0140] Input Composition Ratio (mol%) Doping Yield Al Content in Oxide Al / Ni mol% Ratio NiCoMnAl (ppm) (mol%) Example 194.9 0.5 2.4 2.2 93% 5,580 2.02 0.021 Example 293.9 0.5 2.4 3.2 93% 8,300 2.97 0.032 Comparative Example 197.0 0.5 2.5 0.0-000 Comparative Example 295.9 0.5 2.5 1.1 93% 2,790 1.01 0.011 Comparative Example 393.5 0.5 2.4 3.6 93% 9,300 3.36 0.036 Comparative Example 487.9 6.03.03.1 93% 7,868 2.8 0.032

[0141] As shown in Table 1 above, doping was achieved at a yield of 93% in Examples 1 and 2 and Comparative Examples 2 to 4, and as a result, it can be confirmed that the lithium composite transition metal oxides manufactured in Examples 1 and 2 had a final Al / Ni molar ratio within the range of 0.015 to 0.034. Meanwhile, Comparative Examples 2 and 3 had Al / Ni molar ratios of 0.011 and 0.036, respectively, which were outside the scope of the present invention, and in the case of Comparative Example 4, in which the Ni content was less than 90 mol%, the Al / Ni molar ratio was measured to be the same as in Example 2.

[0142]

[0143] Experimental Example 2. XRD Analysis

[0144] For each of the lithium composite transition metal oxides manufactured in Examples 1 and 2 and Comparative Examples 1 and 2, the c / a ratio was measured using X-ray diffraction analysis (XRD) using Cu Kα X-rays using the above-described method, and the results were as follows.

[0145] Example 1 Example 2 Comparative Example 1 Comparative Example 2 c / a4.94054.94224.93624.9381

[0146] According to Table 2, the lithium composite transition metal oxides of Examples 1 and 2 have a c / a ratio within the range of 4.9400 to 4.9500, which means that lithium composite transition metal oxides having a higher degree of layered structure completion were produced compared to Comparative Examples 1 and 2, which did not have a c / a ratio.

[0147]

[0148] Experimental Example 3. Particle Strength Measurement

[0149] After collecting 3 g of each of the lithium composite transition metal oxides manufactured in Examples 1 and 2 and Comparative Examples 1 and 2, the particle strength was measured by applying increasing pressure using a Micro Compression Testing Machine (Shimadzu, MCT-W500) and measuring the pressure at which the particles were destroyed, and the results are shown in Table 3 below.

[0150] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Particle strength (MPa) 145 15 11 38 140

[0151] Through the results in Table 3 above, it can be confirmed that the lithium composite transition metal oxides manufactured in Examples 1 and 2 have much better particle strength than the lithium composite transition metal oxides manufactured in Comparative Examples 1 and 2.

[0152] This is an effect realized because the bonding energy between Al and O is greater than the bonding energy between Ni and O, and thus, a high particle strength is advantageous in that particle breakage is mitigated during the rolling process.

[0153]

[0154] Experimental Example 4. D 50 measurement

[0155] After dispersing 0.1 g of the lithium composite transition metal oxide powders manufactured in the above Examples 1 and 2 and Comparative Examples 1 to 4 in a dispersion medium, they were introduced into a laser diffraction particle size measuring device (Malvern, Mastersizer 3000) and irradiated with ultrasonic waves of about 28 kHz at an output of 60 W to determine the D of each cathode material powder. 50 was measured. The measurement results are shown in Table 4 below.

[0156] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 D 50 (㎛)11.511.611.611.611.611.4

[0157]

[0158] Experimental Example 5. DSC Evaluation

[0159] In order to evaluate the thermal stability of the lithium composite transition metal oxides manufactured in Examples 1 and 2 and Comparative Examples 1 and 2, heat flow was measured using a differential scanning calorimeter (HP-DSC from Setaram), and the results are shown in Fig. 1 and Table 3 below.

[0160] First, a cathode slurry was prepared by mixing each of the lithium composite transition metal oxides prepared in Examples 1 and 2 and Comparative Examples 1 and 2 as cathode active materials, carbon black (Denka, Li-435) as a conductive material, PVDF (Kureha, KF9709) as a binder, and acrylate (Zeon, BM-730H) as a dispersant in a weight ratio of 95.0:2.0:2.8:0.2 in an NMP solvent. The prepared cathode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and then rolled to prepare a cathode. An electrode assembly was prepared by interposing a porous polyethylene separator between the prepared cathode and the lithium metal anode, and then positioned inside a battery case, and then an electrolyte was injected into the case to prepare a half cell. The above electrolyte was prepared by dissolving 1M LiPF6 in a mixed organic solvent containing ethylene carbonate / dimethyl carbonate / diethyl carbonate in a volume ratio of 3:4:3.

[0161] The manufactured half-cell was charged to 4.25 V at 0.2 C constant current at 25 °C to prepare a 100% SOC cell. The fully charged cell was disassembled to recover the positive electrode, which was washed with DMC for 30 seconds to remove the electrolyte remaining on the positive electrode surface, and then dried. The dried positive electrode was punched out to fit the pan size of a differential scanning calorimeter, and placed in the pan together with 20 μL of the same electrolyte as that injected into the half-cell, and the pan was sealed. Then, the heat flow was measured while the temperature was increased from 25 °C to 300 °C at a rate of 10 °C per minute, and the results are as shown in Fig. 1.

[0162] Meanwhile, the temperature and maximum heat flow value at which the main peak with the maximum heat flow is measured are listed in Table 5 below.

[0163] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Main peak temperature (℃) 219.4 225.4 215.5 219.1 Maximum heat flow (W / g) 83.1 55.8 83.1 80.7

[0164] Through the above Table 5 and Fig. 1, it can be confirmed that when the lithium composite transition metal oxide of Examples 1 and 2 having an Al / Ni molar ratio within the range of 0.015 to 0.034 is used as the positive electrode active material, the main peak with the maximum heat flow is high and the maximum heat flow value is low, so that even when the internal temperature of the battery rises, the risk of explosion is relatively low.

[0165] In particular, in the case of Example 2, the maximum heat flow was 60 W / g or less, while the main peak temperature was 220°C or higher, showing the best thermal safety.

[0166]

[0167] Experimental Example 6. Capacity and Life Evaluation

[0168] (1) Manufacturing of half-cells

[0169] In the same manner as in Experimental Example 5 above, a positive electrode including each of the lithium composite transition metal oxides manufactured in the examples and comparative examples as a positive electrode active material, and a half cell including the same were manufactured.

[0170]

[0171] (2) Initial capacity and efficiency measurement

[0172] For each half cell manufactured in the above (1), an activation (formation) process was performed, and then, using a PNE-0506 charger / discharger (manufacturer: PNE Solution Co., Ltd.), the cells were charged at 0.2C (standard capacity 1C = 200 mAh / g) at 25°C under CC-CV conditions to 4.25 V, and CC discharged at 0.2C to 2.5 V to measure the initial charge / discharge capacity and initial efficiency, which are then recorded in Table 6 below.

[0173]

[0174] (3) High temperature life evaluation

[0175] For each half-cell manufactured in (1) above, an activation (formation) process was performed, and then the PNE-0506 charger / discharger (manufacturer: PNE Solution Co., Ltd.) was used to charge the battery under CC-CV conditions at 0.33C (reference capacity 1C = 200 mAh / g) at 45°C to 4.25 V, and then CC discharged to 2.5 V at 0.33C. This charge / discharge cycle was considered as one cycle, and the initial discharge capacity and initial resistance were measured after one cycle, and then the capacity and resistance values ​​were measured while repeating the same charge / discharge cycle for 30 cycles. Based on this, the capacity retention rate compared to the initial discharge capacity and the resistance increase rate compared to the initial resistance were calculated, and the results are shown in Fig. 2 and Table 6.

[0176] Room temperature initial charge capacity (mAh / g) Room temperature initial discharge capacity (mAh / g) Room temperature initial charge / discharge efficiency (%) High temperature capacity retention rate (%) High temperature resistance increase rate (%) Example 1248.2219.388.493.391.5 Example 2244.8216.488.494.881.5 Comparative example 1254.4228.189.791.4130.2 Comparative example 2250.9224.289.492.5119.3 Comparative example 3240.2211.187.993.494.1 Comparative example 4236.5210.689.194.597.5

[0177] Through the above Table 6, it can be confirmed that the cells of Examples 1 and 2, which used lithium composite transition metal oxides with an Al / Ni molar ratio within the range of 0.015 to 0.034 as positive electrode active materials, both had an initial charge / discharge efficiency of 88% or more, a high-temperature capacity retention rate of 93% or more, and a high-temperature resistance increase rate of 92% or less.

[0178] On the other hand, it can be seen that the cells of Comparative Examples 1 and 2, which did not contain Al as a cathode active material or used a lithium composite transition metal oxide having an Al / Ni molar ratio of 0.011, showed significantly reduced high-temperature capacity retention and high-temperature resistance increase rate. In particular, it can be seen that the high-temperature resistance increase rate was very high, exceeding 110%.

[0179] In addition, it can be confirmed that the cell of Comparative Example 3, which used a lithium composite transition metal oxide having an Al / Ni molar ratio of 0.036 as a cathode active material, had low initial capacity and efficiency and a high rate of increase in high-temperature resistance.

[0180] In addition, the positive electrode active material used in Comparative Example 4 has the same Al / Ni molar ratio as the positive electrode active material used in Example 2, but differs in that the nickel content is less than 90 mol%. As a result, it can be confirmed that the initial charge / discharge capacity itself is low and the resistance increase rate at high temperatures is greatly increased.

Claims

1. A cathode active material comprising a lithium composite transition metal oxide containing nickel, cobalt, manganese and aluminum, A cathode active material, wherein the content of nickel among the metals other than lithium in the lithium composite transition metal oxide is 90 mol% or more, and the molar ratio of aluminum to nickel, Al / Ni, is 0.015 or more and 0.034 or less.

2. In claim 1, A cathode active material, wherein the Al / Ni is 0.021 or more and 0.032 or less.

3. In claim 1, A cathode active material, wherein the content of nickel among the metals other than lithium in the lithium composite transition metal oxide is 93 mol% to 95 mol%.

4. In claim 1, A cathode active material, wherein the content of cobalt among metals other than lithium in the lithium composite transition metal oxide is 0.1 mol% to 1.0 mol%.

5. In claim 1, A cathode active material, wherein the content of aluminum among the metals other than lithium in the lithium composite transition metal oxide is 1.0 mol% to 5.0 mol%.

6. In claim 1, The above lithium composite transition metal oxide is a cathode active material having a composition of the following chemical formula 1: [Chemical Formula 1] Li 1+x (Ni a Co b Mr c Al d M1 e )O 2 In the above chemical formula 1, M1 is at least one selected from the group consisting of Ti, Zr, W, Mo, Nb, Cu, Fe, V, Cr, Zn, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Mg and B, x, a, b, c, d and e are -0.2≤x≤0.2, 0.90≤a<1, 0 respectively. <b≤0.01, 0<c≤0.05, 0<d≤0.05, 0≤e≤0.05, a+b+c+d+e=1을 만족한다.

7. In claim 1, The above positive electrode active material includes primary particles and secondary particles in which the primary particles are aggregated. A cathode active material, wherein c / a, which is a ratio of the length in the a-axis direction to the length in the c-axis direction of the primary particle, is 4.9400 to 4.9500.

8. In claim 1, A cathode active material having a particle strength of 142 MPa to 160 MPa.

9. In claim 1, A cathode active material, wherein, when the heat flow of the cathode active material is measured using differential scanning calorimetry (DSC), a peak with a maximum heat flow appears at 219°C to 230°C.

10. In claim 1, A cathode active material having a maximum heat flow of 85.0 W / g or less as measured in a range of 25°C to 300°C using differential scanning calorimetry (DSC).

11. Anode current collector; and Including a positive electrode active material layer provided on at least one surface of the positive electrode current collector, A positive electrode, wherein the positive electrode active material layer comprises the positive electrode active material according to claim 1.

12. Anode according to claim 11; A cathode comprising a cathode active material; A separator interposed between the positive electrode and the negative electrode; and A lithium secondary battery containing an electrolyte.

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