Positive electrode active material, positive electrode containing the same, and lithium secondary battery

Abstract

The present invention relates to a positive electrode active material containing a lithium composite transition metal oxide that contains nickel, cobalt, manganese, and aluminum, the positive electrode active material containing 85 mol % to 97 mol of nickel and 2 mol % to 5 mol % of cobalt relative to the total number of moles of remaining metals other than lithium, and satisfying the following formula (1), and a positive electrode and a lithium secondary battery containing the same. Formula (1): 0.25≦I 550 / I 700 ≦0.4 In the formula (1), I 700 and I 550 respectively represent the 2D 7 When the 1D NMR centerband spectrum extracted from the Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR spectrum is subjected to spectral analysis (peak deconvolution), it is the maximum peak intensity shown in the 600 to 800 ppm region and the maximum peak intensity shown in the 450 to 650 ppm region.

Description

[Technical Field]

[0001] This application claims priority under Korean Patent Application No. 10-2022-0043660 dated April 7, 2022, and all content disclosed in the said Korean Patent Application is incorporated herein by reference.

[0002] The present invention relates to a positive electrode active material, a positive electrode containing the same, and a lithium secondary battery, and more particularly to a positive electrode active material with improved lifespan characteristics, a positive electrode containing the same, and a lithium secondary battery. [Background technology]

[0003] A lithium secondary battery generally consists of a positive electrode, a negative electrode, a separator, and an electrolyte, and the positive electrode and negative electrode contain an active material that allows for the insertion and deintercalation of lithium ions.

[0004] Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMnO4, etc.), and lithium iron phosphate compounds (LiFePO4) have been used as positive electrode active materials for lithium secondary batteries. Of these, lithium cobalt oxide has the advantage of a high operating voltage and excellent capacity characteristics, but the high price of cobalt, the raw material, and the unstable supply make commercial application to high-capacity batteries difficult. Lithium nickel oxide has poor structural stability, making it difficult to achieve sufficient lifespan characteristics. On the other hand, lithium manganese oxide has excellent stability but suffers from poor capacity characteristics. Therefore, in order to complement the problems of lithium transition metal oxides containing Ni, Co, or Mn alone, lithium composite transition metal oxides containing two or more transition metals have been developed, and among them, lithium nickel cobalt manganese oxide containing Ni, Co, and Mn is widely used in the field of electric vehicle batteries.

[0005] Recently, there has been an increasing demand for high-power, high-capacity batteries, such as those for electric vehicles, and consequently, the nickel content in the positive electrode active material is gradually increasing. While an increase in nickel content in the positive electrode active material improves capacity characteristics, repeated charging and discharging can lead to a decrease in the highly reactive nickel content. 4+ A large amount of ions are generated, causing structural breakdown of the positive electrode active material. This increases the degradation rate of the positive electrode active material, leading to a decrease in its lifespan characteristics.

[0006] Therefore, in order to achieve high capacity, there is a need to develop a cathode active material that contains an excess amount of nickel and can also achieve excellent lifespan characteristics. [Overview of the project] [Problems that the invention aims to solve]

[0007] The present invention aims to solve the above-mentioned problems and to provide a positive electrode active material, a positive electrode containing the positive electrode active material, and a lithium secondary battery that have a high capacity with a molar ratio of Ni of 85 mol% or more among the total metals other than lithium, and that have excellent structural stability and can achieve long life characteristics. [Means for solving the problem]

[0008] According to one embodiment, the present invention provides a positive electrode active material comprising a lithium composite transition metal oxide containing nickel, cobalt, manganese, and aluminum, wherein the positive electrode active material contains 85 mol% to 97 mol%, preferably 85 mol% to 95 mol%, more preferably 90 mol% to 95 mol%, of nickel and 2 mol% to 5 mol% of cobalt, relative to the total number of moles of the remaining metals other than lithium, and satisfies the following formula (1). Formula (1): 0.25≦I 550 / I 700 ≤0.4 In the above formula (1), I 700 and I 550 These are the 2D of the positive electrode active material, respectively. 7When the 1D NMR center band spectrum extracted from the Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR spectrum is subjected to spectral analysis (peak deconvolution), they are the maximum peak intensities shown in the region of 600 to 800 ppm and the maximum peak intensities shown in the region of 450 to 650 ppm.

[0009] On the other hand, the 2D 7 The 1D NMR center band spectrum extracted from the Li MATPASS NMR spectrum has a first peak shown in the region of 550 ppm to 850 ppm and a second peak shown in the region of -10 ppm to 10 ppm.

[0010] Preferably, the positive electrode active material according to the present invention can satisfy the following formula (1-1). Formula (1-1): 0.30 ≤ I 550 / I 700 ≤ 0.4 In the formula (1-1), I 700 and I 550 are as defined in formula (1).

[0011] On the other hand, the 2D 7 When the 1D NMR center band spectrum extracted from the Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR spectrum is subjected to spectral analysis (peak deconvolution), the maximum full width at half maximum (FWHM 700 ) of the peak shown in the region of 600 to 800 ppm is 250 ppm or less, the maximum full width at half maximum (FWHM 550 ) of the peak shown in the region of 450 to 650 ppm is 250 ppm or less, and the maximum full width at half maximum (FWHM0) of the peak shown in the region of -10 to 10 ppm is preferably 50 ppm or less.

[0012] Furthermore, the positive electrode active material may contain 0.5 mol% or more and less than 5 mol% of manganese and 0.5 mol% or more and less than 5 mol% of aluminum, relative to the total number of moles of the remaining metals other than lithium. Specifically, it may have a composition represented by the following [Chemical Formula 1]. [Chemical formula 1] Li a Ni b Co c Mn d Al e M 1 f O2 In the above [Chemical Formula 1], M 1 is one or more elements selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb, with the following inequalities: 0.8 ≤ a ≤ 1.2, 0.85 ≤ b ≤ 0.97, 0.02 ≤ c ≤ 0.05, 0.005 ≤ d < 0.05, 0.005 ≤ e < 0.05, and 0 ≤ f ≤ 0.02.

[0013] According to another embodiment, the present invention provides a method for producing a positive electrode active material, comprising: a first step of forming a precursor by coprecipitation of an aqueous transition metal solution containing nickel ions, cobalt ions, and manganese ions; a second step of forming a lithium composite transition metal oxide by mixing the precursor, a lithium raw material, and an aluminum raw material, and then calcining the mixture; and a third step of producing a positive electrode active material by mixing the lithium composite transition metal oxide and a cobalt raw material, and then heat-treating the mixture.

[0014] The ratio of the number of moles of cobalt contained in the cobalt raw material of the third step to the number of moles of cobalt contained in the precursor of the first step can be 1 to 1.5.

[0015] In the third step described above, the heat treatment temperature can be 600°C to 750°C.

[0016] In further embodiments, the present invention provides a positive electrode containing the positive electrode active material according to the present invention and a lithium secondary battery containing the positive electrode. [Effects of the Invention]

[0017] The positive electrode active material according to the present invention always contains Ni, Co, Mn, and Al, with a Ni content of 85 mol% to 97 mol%, a Co content of 2 mol% to 5 mol%, and 2D 7 When the 1D NMR center band spectrum extracted from the NMR spectrum obtained by analysis using the Li MATPASS NMR method is spectrally analyzed, the maximum peak intensity I shown in the 600-800 ppm region is... 700 Maximum peak intensity I shown in the 450-650 ppm range for [the specified value] 550 The ratio of 0.25 to 0.4 is a characteristic feature.

[0018] While a high content of Ni (85 mol% or more) has the advantage of achieving high energy density, the surface of the positive electrode active material is highly reactive Ni. 4+ As the amount of Co increases, side reactions with the electrolyte increase, leading to a decrease in structural stability and a rapid deterioration of lifespan characteristics. However, as in the present invention, when Co is included in a specific amount and the peak characteristics of the NMR spectrum satisfy the conditions of formula (1), excellent lifespan characteristics can be achieved even when Ni is included at a high concentration. Therefore, by applying the positive electrode active material according to the present invention, a lithium secondary battery with high capacity and excellent lifespan characteristics can be realized. [Brief explanation of the drawing]

[0019] [Figure 1] This figure shows the 1D NMR center band spectra extracted from the NMR spectra obtained by analyzing the cathode active materials produced in Examples 1-2 and Comparative Examples 1-2 using 2D 7Li MATPASS NMR analysis. [Figure 2] This figure shows the NMR spectra obtained by analyzing the cathode active materials produced in Example 1 and Comparative Example 1 using 1D Hahn-echo MAS NMR analysis. [Figure 3]This figure illustrates the results of spectral analysis of the 1D NMR center band spectrum extracted from the 2D 7Li MATPASS NMR spectrum of the positive electrode active material of Example 1. [Figure 4] This graph shows the life characteristics of lithium secondary batteries using the positive electrode active materials of Examples 1-2 and Comparative Examples 1-2. [Modes for carrying out the invention]

[0020] The present invention will be described in detail below.

[0021] positive electrode active material The inventors of this invention have diligently conducted research to improve the lifetime characteristics of high-nickel cathode active materials containing 85 mol% or more of Ni. As a result, they have discovered that when the cobalt content in the cathode active material is between 2 and 5 mol%, and the ratio of coordination metals surrounding the lithium element is appropriately adjusted, the lifetime characteristics of the high-nickel cathode active material are significantly improved, leading to the completion of this invention.

[0022] Specifically, the positive electrode active material according to the present invention comprises a lithium composite transition metal oxide containing nickel, cobalt, manganese, and aluminum, wherein the nickel content of the positive electrode active material is 85 mol% to 97 mol%, the cobalt content is 2 mol% to 5 mol%, and the following formula (1) is satisfied.

[0023] Formula (1): 0.25≦I 550 / I 700 ≤0.4

[0024] In the above formula (1), I 700 and I 550 These are the 2D of the positive electrode active material, respectively. 7These are the maximum peak intensities shown in the 600-800 ppm region and the 450-650 ppm region when the 1D NMR center band spectrum extracted from the Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR spectrum is subjected to spectral analysis (peak deconvolution).

[0025] 2D in the present invention 7 The Li MATPASS NMR measurement conditions are as follows:

[0026] <Measurement conditions> Solid 400MHz WB (wide bore) NMR system MAS(magic angle spinning)rate:55kHz Spectral frequency(sfo1):155.62MHz( 7 Li) Temperature: ambient temperature 7 Li Chemical shift reference:secondary LiF(S)reference at -1ppm Pulse program: 2D MATPASS Spectral width (sw): 1250kHz Acquisition time: 5ms Carrier frequency (o1p) at 500ppm Pulse length (p1): 1 μs Recycle delay (d1): 35ms TD of F1 dimension (L1): 8 Number of scans: 30000

[0027] After measurement, the 2D data was processed with xfb, and then the 5th slice ((L1 / 2+1)=(8 / 2+1)=5th slice) was extracted to obtain the 1D NMR centerband spectrum.

[0028] On the other hand, 2D 7 Spectral analysis (peak deconvolution) of the 1D NMR center band spectrum extracted from the Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR spectrum can be performed using the DMFIT (64-bit, release #20190125) NMR software. Specifically, the spectral analysis is performed as follows: 7 The 1D NMR center band spectrum extracted from the Li MATPASS NMR spectrum can be imported into the DMFIT program. Then, the Gaussian / Lorentzian model is selected as the fitting model for spectral analysis. Appropriate initial values ​​are set for the peak size (Amplitude), peak position, peak width at half maximum (FWHM), and Gaussian / Lorentzian fraction (xG / (1-x)L). The fitting process is then repeated until an appropriate convergence value is reached. In this invention, during spectral analysis, the Gaussian / Lorentzian fraction (xG / (1-x)L) was fixed at 0.5, and fitting was performed under the conditions nParVar=15, step=1, and Thresh=0.001.

[0029] Conventionally, for structural analysis of positive electrode active materials, one-dimensional (1D) solid-state analysis was used. 7Li NMR analysis was primarily used. However, high-nickel cathode active materials containing an excess amount of the paramagnetic metal Ni were found in 1D solid-state materials. 7 When measuring using Li NMR analysis, the paramagnetic effect reduces the NMR resolution, and the overlap between the spinning sideband and the main peak causes a phase error, making it difficult to analyze the structural characteristics of the positive electrode active material (see Figure 2).

[0030] However, 2D 7 By applying the Li MATPASS NMR analysis method, high-resolution NMR spectra can be obtained, and the structural characteristics of the cathode active material can be distinguished by spectral analysis of the extracted spectra. The inventors have developed a method for analyzing various cathode active materials using 2D 7 Analysis using Li MATPASS NMR analysis revealed that cathode active materials formed to satisfy the conditions of equation (1) below exhibited a significant improvement in lifetime characteristics.

[0031] 2D 7 The peak shown around 700 ppm in the Li MATPASS NMR spectrum is the peak shown when the metal surrounding Li in the crystal structure consists solely of Ni, while the peak shown around 550 ppm is the peak shown when some of the metals surrounding Li in the crystal structure are Co and Al. On the other hand, when some of the metals surrounding Li is Mn, a peak is shown above 700 ppm. Therefore, the peak intensity I shown around 550 ppm is... 550 A high I value indicates a high proportion of Co or Al surrounding lithium within the crystal structure, resulting in a peak intensity I value around 700 ppm. 700 A high ratio means that the proportion of nickel surrounding lithium in the crystal structure is high. Therefore, I 550 / I 700This can be analyzed as a value corresponding to the ratio of Co arranged around lithium within the crystal structure.

[0032] According to the inventors' research, it has been shown that when a high-nickel cathode active material with a nickel content of 85 mol% to 97 mol% satisfies the conditions of formula (1), the high-temperature life characteristics of lithium secondary batteries are significantly improved. Specifically, I of formula (1) 550 / I 700 In the case of a lithium secondary battery using a positive electrode active material that satisfies the range of 0.25 to 0.4, 550 / I 700 Compared to lithium secondary batteries using positive electrode active materials with a ratio of less than 0.25 or greater than 0.4, the capacity retention rate after 200 cycles at 45°C increased by 2-10%, and the resistance increase rate decreased by 25-50%.

[0033] The reason why the improvement in lifespan characteristics is observed when the conditions of equation (1) are met is not clear, but it is presumed that this is because a predetermined ratio of cobalt out of the total cobalt contained in the positive electrode active material is arranged on the surface of the positive electrode active material, thereby suppressing changes in the crystal structure of the positive electrode active material during charge-discharge cycles, and increasing the stability of the crystal structure because the ratio of cobalt among the metals arranged around lithium in the crystal structure meets a specific range.

[0034] Preferably, the positive electrode active material can satisfy the following formula (1-1). When the positive electrode active material satisfies formula (1-1), the effect of improving the lifespan characteristics becomes even better.

[0035] Formula (1-1): 0.30≦I 550 / I 700 ≤0.4

[0036] In the above equation (1-1), I 700 and I 550 This is as defined in equation (1).

[0037] More preferably, the positive electrode active material can satisfy the following formula (1-2). When the positive electrode active material satisfies formula (1-2), the effect of improving the lifetime characteristics becomes even better.

[0038] Formula (1-2): 0.35≦I 550 / I 700 ≤0.4

[0039] In the above equation (1-2), I 700 and I 550 This is as defined in equation (1).

[0040] On the other hand, the positive electrode active material according to the present invention is 2D 7 The 1D NMR center band spectrum extracted from the NMR spectrum obtained by Li MATPASS NMR analysis shows two peaks: a first peak in the 550 ppm–850 ppm region and a second peak in the -10 ppm–10 ppm region. This indicates a one-dimensional (1D) solid-state NMR spectrum. 7 This is in contrast to the NMR spectrum obtained by Li NMR analysis, which shows three or more peaks.

[0041] Furthermore, the 2D of the positive electrode active material according to the present invention 7 When the 1D NMR center band spectrum extracted from the Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR spectrum is subjected to spectral analysis (peak deconvolution), the maximum full width at half maximum (FWHM) of the peak shown in the 600-800 ppm region can be 250 ppm or less, preferably 70-230 ppm, and more preferably 100-200 ppm. 700When the above range is satisfied, the NMR peak information of Li surrounded only by Ni can be accurately extracted during spectral analysis, and the local structural information of the positive electrode active material can be grasped more accurately.

[0042] Furthermore, the 2D of the positive electrode active material according to the present invention 7 When the 1D NMR center band spectrum extracted from the Li MATPASS (Magic Angle Turning-Phase Adjusted Spinning Sideband) NMR spectrum is subjected to spectral analysis (peak deconvolution), the maximum full width at half maximum (FWHM) of the peak shown in the 450-650 ppm region can be 250 ppm or less, preferably 70-230 ppm, and more preferably 100-200 ppm. 550 When the above range is satisfied, NMR peak information of Li to which Co or Al is partially coordinated can be accurately extracted during spectral analysis, and the local structure of the positive electrode active material can be more accurately understood.

[0043] Furthermore, the 2D of the positive electrode active material according to the present invention 7 When the 1D NMR center band spectrum extracted from the Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR spectrum is subjected to spectral analysis (peak deconvolution), the maximum full width at half maximum (FWHM0) of the peak shown in the -10 ppm to 10 ppm region can be 50 ppm or less, preferably 5 to 45 ppm, and more preferably 10 to 30 ppm. When the maximum full width at half maximum (FWHM) of the peak shown in the -10 ppm to 10 ppm region satisfies this range, diamagnetic Li peak information can be extracted accurately during spectral analysis, allowing for a more precise understanding of the local structure of the positive electrode active material.

[0044] Next, the composition of the positive electrode active material according to the present invention will be described.

[0045] The positive electrode active material according to the present invention comprises a lithium composite transition metal oxide containing nickel, cobalt, manganese, and aluminum.

[0046] The positive electrode active material may contain 85 mol% or more, preferably 85 mol% to 97 mol%, more preferably 85 mol% to 95 mol%, and even more preferably 90 mol% to 95 mol%, of nickel relative to the total number of moles of the remaining metals other than lithium. When the nickel content in the positive electrode active material satisfies the above range, excellent capacity characteristics can be achieved.

[0047] The positive electrode active material may contain 2 mol% to 5 mol%, preferably 3 mol% to 4 mol%, of cobalt relative to the total number of moles of the remaining metals other than lithium. In a high-nickel positive electrode active material with a nickel content of 85 mol% or more, if the cobalt content is less than 2 mol%, structural stability decreases, long-term life characteristics deteriorate, and resistance increases. If the cobalt content exceeds 5 mol%, the capacity may decrease.

[0048] The positive electrode active material may contain 0.5 mol% to less than 5 mol% of manganese, preferably 1 mol% to less than 5 mol%, and more preferably 1 mol% to 3 mol%, relative to the total number of moles of the remaining metals other than lithium. When the manganese content satisfies the above range, it has the advantage of excellent structural stability and suppression of catalytic reactions on the surface, thereby suppressing gas generation.

[0049] The positive electrode active material may contain 0.5 mol% to less than 5 mol%, preferably 1 mol% to less than 5 mol%, and more preferably 1 mol% to 3 mol%, of aluminum relative to the total number of moles of the remaining metals other than lithium. If the aluminum content exceeds the above range, it may cause a decrease in capacity, and if it is below the above range, structural stability and surface stability may decrease, leading to a decrease in lifetime characteristics and an increase in resistance.

[0050] On the other hand, the positive electrode active material may, if necessary, contain doping elements other than nickel, cobalt, manganese, and aluminum. 1 The doping element M may further be included. 1 For example, it can be one or more elements selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb.

[0051] Specifically, the positive electrode active material may have a composition represented by the following [Chemical Formula 1].

[0052] [Chemical formula 1] Li a Ni b Co c Mn d Al e M 1 f O2

[0053] In the above [Chemical Formula 1], M 1 is one or more elements selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb, and the following inequalities apply: 0.8 ≤ a ≤ 1.2, 0.85 ≤ b ≤ 0.97, 0.02 ≤ c ≤ 0.05, 0.005 ≤ d < 0.05, 0.005 ≤ e < 0.05, and 0 ≤ f ≤ 0.05.

[0054] Preferably, b can be 0.85 ≤ b ≤ 0.95 or 0.90 ≤ b ≤ 0.95, c can be 0.03 ≤ c ≤ 0.05 or 0.03 ≤ c ≤ 0.04, d can be 0.01 ≤ d < 0.05 or 0.01 ≤ d ≤ 0.03, and e can be 0.01 ≤ e < 0.05 or 0.01 ≤ e ≤ 0.03.

[0055] Method for manufacturing positive electrode active material Next, a method for producing a positive electrode active material according to the present invention will be described.

[0056] The positive electrode active material according to the present invention, having the above-described composition and NMR peak characteristics, can be manufactured by adding the cobalt contained in the positive electrode active material in two stages at a specific molar ratio, rather than adding it all at once.

[0057] Specifically, the method for producing a positive electrode active material according to the present invention includes: a first step of forming a precursor by coprecipitation reaction of an aqueous transition metal solution containing nickel ions, cobalt ions, and manganese ions; a second step of forming a lithium composite transition metal oxide by mixing the precursor, a lithium raw material, and an aluminum raw material, and then calcining the mixture; and a third step of producing a positive electrode active material by mixing the lithium composite transition metal oxide and a cobalt raw material, and then heat-treating the mixture.

[0058] Step 1 First, a precursor is formed by coprecipitation of an aqueous solution of a transition metal containing nickel ions, cobalt ions, and manganese ions.

[0059] The transition metal aqueous solution can be produced by dissolving a transition metal-containing raw material in a solvent such as water. For example, it can be produced by dissolving nickel-containing raw material, cobalt-containing raw material, or manganese-containing raw material in water. Furthermore, if necessary, the transition metal aqueous solution can be M 1 It can further contain metallic raw materials.

[0060] On the other hand, the transition metal-containing raw material can be an acetate, carbonate, nitrate, sulfate, halide, sulfide, hydroxide, or oxide of the transition metal.

[0061] Specifically, the nickel-containing raw material can be, for example, NiO, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, NiSO4, NiSO4·6H2O, nickel halides, or combinations thereof.

[0062] The cobalt-containing raw material can be, for example, CoSO4, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O, CoSO4·7H2O, or a combination thereof.

[0063] The manganese-containing raw material can be, for example, Mn2O3, MnO2, Mn3O4, MnCO3, Mn(NO3)2, MnSO4·H2O, manganese acetate, manganese halides, or combinations thereof.

[0064] Said M 1 Metal raw materials include, for example, M 1 This can be a metal acetate, carbonate, nitrate, sulfate, halide, sulfide, or oxide, M 1 This can be one or more elements selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb.

[0065] Here, the amount of each transition metal-containing raw material to be added can be determined by considering the molar ratio of the transition metal in the positive electrode active material to be ultimately produced. For example, in the present invention, the nickel-containing raw material can be added in an amount such that the nickel content in the final positive electrode active material is 85 mol% or more, preferably 85 mol% to 97 mol%, more preferably 85 mol% to 95 mol%, and even more preferably 90 mol% to 95 mol% of the total transition metal.

[0066] On the other hand, the cobalt-containing raw material can be added in an amount such that it is 0.4 to 0.5 times the cobalt content contained in the final positive electrode active material. In this invention, by adding only a portion of the cobalt contained in the positive electrode active material during the coprecipitation reaction and adding the remaining cobalt in the third step described later, it is possible to adjust the ratio of lithium coordinated with cobalt in the crystal structure compared to the case where all of the cobalt is added during the coprecipitation reaction.

[0067] On the other hand, the ammonium cation complex-forming agent may contain at least one compound selected from the group consisting of NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, and (NH4CO3)2, and the compound may be introduced into the reactor in the form of a solution in which it is dissolved in a solvent. Here, the solvent may be water, or a mixture of water and an organic solvent that can be homogeneously mixed with water (specifically, an alcohol, etc.).

[0068] The basic compound can be at least one compound selected from the group consisting of NaOH, KOH, and Ca(OH)2, and the compound can be introduced into the reactor in the form of a solution in which it is dissolved in a solvent. Here, the solvent can be water, or a mixture of water and an organic solvent that is homogeneously miscible with water (specifically, an alcohol, etc.).

[0069] As described above, when an aqueous transition metal solution, an ammonium cation complex-forming agent, and a basic compound are added to the reactor and stirred, the transition metal in the aqueous transition metal solution coprecipitates, generating precursor particles in the form of transition metal hydroxides.

[0070] Here, the transition metal aqueous solution, ammonium cation complex-forming agent, and basic compound are added in amounts such that the pH of the reaction solution falls within the desired range.

[0071] Once the precursor particles are formed by the method described above, the positive electrode active material precursor is separated from the reaction solution to obtain the positive electrode active material precursor. For example, the positive electrode active material precursor can be obtained by filtering the reaction solution to separate it, and then washing and drying the separated positive electrode active material precursor. Here, if necessary, steps such as grinding and / or classification can also be performed.

[0072] Step 2 Next, the positive electrode active material precursor, lithium raw material, and aluminum raw material are mixed and then calcined to produce a lithium composite transition metal oxide. Here, if necessary, M1 Metal-containing raw materials can be mixed together and fired.

[0073] As the lithium raw material, lithium-containing sulfates, nitrates, acetates, carbonates, oxalates, citrates, halides, hydroxides, or oxyhydroxides can be used, for example, Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, or mixtures thereof can be used.

[0074] The aluminum-containing raw material can be, for example, Al2O3, Al(OH)3, Al(NO3)3, Al2(SO4)3, (HO)2AlCH3CO2, HOAl(CH3CO2)2, Al(CH3CO2)3 aluminum halides, or combinations thereof.

[0075] Said M 1 Metal raw materials include, for example, M 1 This can be a metal acetate, carbonate, nitrate, sulfate, halide, sulfide, or oxide, M 1 This can be one or more elements selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb.

[0076] On the other hand, the lithium raw material can be mixed in such an amount that the molar ratio of Li:Ni+Co+Mn+Al in the mixture is 1:1 to 1.2:1, preferably 1:1 to 1.1:1, and more preferably 1:1 to 1.06:1. When the mixing ratio of the lithium raw material satisfies the above range, the layered crystal structure of the positive electrode active material develops well, and a positive electrode active material with excellent capacity characteristics and structural stability can be produced.

[0077] On the other hand, the firing can be carried out at a temperature of, for example, 650°C to 800°C, preferably 690°C to 770°C, in an oxygen atmosphere for 5 to 35 hours, preferably 8 to 20 hours. In this specification, an oxygen atmosphere means an atmosphere containing an amount of oxygen sufficient for firing, including an atmospheric atmosphere. In particular, it is preferable to carry out the firing in an atmosphere in which the partial pressure of oxygen is higher than that of the atmospheric atmosphere.

[0078] Step 3 Next, the lithium composite transition metal oxide produced as described above and the cobalt raw material are mixed and then heat-treated to produce the positive electrode active material.

[0079] Here, the cobalt raw material can be, for example, Co(OH)2, CoO, CoSO4, Co(NO3)2, CoCO3, Co3(PO4)2, etc.

[0080] On the other hand, the cobalt raw material can be mixed in an amount such that the ratio of the number of moles of cobalt contained in the cobalt raw material of the third step to the number of moles of cobalt contained in the precursor of the first step is 1 to 1.5, preferably 1 to 1.3, and more preferably 1 to 1.2. When the ratio of the number of moles of cobalt added in the first step to the number of moles of cobalt added in the third step satisfies the above range, the ratio in which lithium and cobalt are coordinated in the crystal structure is adjusted, and a positive electrode active material satisfying formula (1) can be obtained.

[0081] Furthermore, the heat treatment temperature can be 600°C to 750°C, preferably 600°C to 700°C. When the heat treatment temperature satisfies the above range, the ratio of lithium and cobalt coordinated within the crystal structure is adjusted, and a positive electrode active material satisfying equation (1) can be obtained. Depending on the heat treatment temperature, the degree of diffusion of the Co element changes, which in turn changes the ratio of lithium and cobalt coordinated within the crystal structure. Therefore, in order to appropriately adjust the ratio of Co-coordinated lithium, the heat treatment temperature must be appropriately adjusted. If the heat treatment temperature is less than 600°C, the ratio of Co penetrating into the secondary particles of the positive electrode active material is excessively low, and if it exceeds 750°C, the Co content diffusing into the crystal lattice becomes excessively high, making it difficult to obtain a positive electrode active material satisfying equation (1).

[0082] As described above, a portion of the total cobalt content contained in the positive electrode active material is added during the coprecipitation reaction for precursor formation, and the remaining amount is added after the formation of the lithium composite transition metal oxide. By performing heat treatment at an appropriate temperature, a positive electrode active material satisfying equation (1) can be produced.

[0083] Furthermore, although not mandatory, a coating layer formation step may be carried out after the third step if necessary. The coating layer formation step can be performed by mixing the positive electrode active material and the coating raw material and then heat-treating them.

[0084] The coating raw material can be an acetate, carbonate, nitrate, sulfate, halide, sulfide, or oxide containing a coating element, and the coating element can be one or more selected from the group consisting of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si, and S.

[0085] Here, the mixing can be carried out as a solid-phase or liquid-phase mixing, and the heat treatment can be carried out at an appropriate temperature depending on the coating raw material. For example, the heat treatment in the coating process can be carried out at a temperature of 200°C to 700°C, or 300°C to 600°C, but is not limited thereto.

[0086] positive electrode Next, the positive electrode according to the present invention will be described.

[0087] The positive electrode according to the present invention includes a positive electrode active material layer containing the positive electrode active material according to the present invention. Specifically, the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and containing the positive electrode active material.

[0088] In the positive electrode, the positive electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., can be used. The positive electrode current collector can usually have a thickness of 3 to 500 μm, and fine irregularities can be formed on the surface of the positive electrode current collector to increase the adhesion strength of the positive electrode active material. For example, it can be used in various forms such as film, sheet, foil, mesh, porous material, foam, nonwoven fabric.

[0089] Furthermore, the positive electrode active material layer may include a conductive material and a binder in addition to the positive electrode active material described above.

[0090] The conductive material is used to impart conductivity to the electrodes and can be used without particular limitations in the battery it is configured in, as long as it does not cause chemical changes and has electronic conductivity. 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, carbon fiber, 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; or conductive polymers such as polyphenylene derivatives. One of these alone or a mixture of two or more can be used. The conductive material can usually be contained in an amount of 1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, relative to the total weight of the positive electrode active material layer.

[0091] The binder plays a role in improving the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the positive electrode 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, of which one or more can be used. The binder may be present in an amount of 1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, relative to the total weight of the positive electrode active material layer.

[0092] The positive electrode can be manufactured by a conventional method for manufacturing a positive electrode. For example, the positive electrode can be manufactured by mixing a positive electrode active material, a binder, and / or a conductive material in a solvent to produce a positive electrode slurry, applying the positive electrode slurry onto a positive electrode current collector, and then drying and rolling it. Here, the types and contents of the positive electrode active material, binder, and conductive material are as described above.

[0093] The solvent can be any solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of these alone or a mixture of two or more can be used. The amount of solvent used should be such that it dissolves or disperses the positive electrode active material, conductive material, and binder, and has a viscosity that allows for excellent thickness uniformity when applied for the manufacture of the positive electrode, taking into consideration the coating thickness of the slurry and the manufacturing yield.

[0094] Alternatively, the positive electrode can be manufactured by casting the positive electrode slurry onto another support, peeling it off the support, and then laminating the resulting film onto the positive electrode current collector.

[0095] Lithium-ion battery Next, the lithium secondary battery according to the present invention will be described.

[0096] The lithium secondary battery of the present invention includes the positive electrode according to the present invention. Specifically, the lithium secondary battery includes a positive electrode, a negative electrode positioned opposite 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. The lithium secondary battery may further optionally include a battery container for housing the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member for sealing the battery container.

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

[0098] The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys can be used. The negative electrode current collector can usually have a thickness of 3 to 500 μm, and, similar to the positive electrode current collector, fine irregularities can be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it can be used in various forms such as film, sheet, foil, mesh, porous material, foam, and nonwoven fabric.

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

[0100] As the negative electrode active material, compounds capable of reversible intercalation and deintercalation of lithium can be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO2. β Examples include (0<β<2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides that can be doped and dedoped with lithium; or composites containing the metallic compound and carbonaceous material, such as Si-C composites or Sn-C composites, and one or more mixtures of these can be used.

[0101] Furthermore, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystallinity carbon and high-crystallinity carbon can be used as carbon materials. Typical low-crystallinity carbons include soft carbon and hard carbon, while typical high-crystallinity carbons include amorphous, plate-like, flaky, 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.

[0102] The conductive material is used to impart conductivity to the electrodes and can be used without particular limitations in the battery it is configured in, as long as it does not cause chemical changes and has electronic conductivity. 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, carbon fiber, 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; or conductive polymers such as polyphenylene derivatives. One of these alone or a mixture of two or more can be used. The conductive material can usually be contained in an amount of 1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, relative to the total weight of the negative electrode active material layer.

[0103] The binder plays a role in improving adhesion between negative electrode active material particles and adhesion between the negative electrode active material and the negative electrode 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, of which one or more can be used. The binder may be present in an amount of 1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, relative to the total weight of the negative electrode active material layer.

[0104] The negative electrode active material layer can also be manufactured, for example, by applying a negative electrode slurry containing a negative electrode active material and selectively a binder and conductive material onto a negative electrode current collector and drying it, or by casting the negative electrode slurry onto another support, peeling it off this support, and then laminating the resulting film onto the negative electrode current collector.

[0105] On the other hand, 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 particular limitations, but those with low resistance to ion movement of the electrolyte and excellent moisture-absorbing capacity for the electrolyte are particularly preferred. Specifically, porous polymer films, such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminated structures of two or more layers thereof, can be used. Alternatively, ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, coated separators containing ceramic components or polymeric substances may be used to ensure heat resistance or mechanical strength, and can be selectively used as single-layer or multi-layer structures.

[0106] Furthermore, the electrolytes 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.

[0107] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0108] The organic solvent can be used without particular limitations as long as it serves as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvents 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; dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (propylene Carbonate solvents such as carbonate (PC); alcoholic solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a C2-C20 linear, branched, or cyclic hydrocarbon group, which can include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred.

[0109] The lithium salt can be used without particular limitations as long as it is a compound that can provide lithium ions for use in lithium secondary batteries. Specifically, the lithium salt can 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, etc. The concentration of the lithium salt is preferably used within the range of 0.1 to 5.0 M, more preferably 0.1 to 3.0 M. When the concentration of the lithium salt falls within this range, the electrolyte can exhibit excellent electrolyte performance due to having appropriate conductivity and viscosity, and lithium ions can move effectively.

[0110] In addition to the electrolyte components, the electrolyte may further contain additives for purposes such as improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity. For example, the additives may be, but are not limited to, haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethyl alcoholamine, cyclic ether, ethylenediamine, n-glyme, hexamethyl phosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethyl alcohol, or aluminum trichloride, either alone or in combination. The additives may be present in an amount of 0.1 to 10% by weight, preferably 0.1 to 5% by weight, relative to the total weight of the electrolyte.

[0111] As described above, lithium secondary batteries containing the positive electrode active material according to the present invention exhibit excellent discharge capacity, output characteristics, and capacity retention rate stably, making them useful in portable devices such as mobile phones, notebook computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0112] Accordingly, 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.

[0113] The aforementioned battery module or battery pack can be used as a power source for one or more medium-to-large devices, including power tools; electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0114] Hereinafter, embodiments of the present invention will be described in detail so that they can be easily implemented by a person with ordinary skill in the art to which the present invention pertains. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0115] Example 1 A transition metal solution, consisting of NiSO4, CoSO4, and MnSO4 mixed in a Ni:Co:Mn molar ratio of 92:2:2, an aqueous ammonia solution, and a sodium hydroxide solution were added to a coprecipitation reactor and a coprecipitation reaction was carried out to form a precursor. The precursor particles were separated, washed, and then dried to produce the precursor.

[0116] A lithium composite transition metal oxide was produced by mixing a precursor synthesized by coprecipitation with LiOH and aluminum hydroxide in a molar ratio of Ni+Co+Mn:Al:Li of 96:2:98, and then calcining the mixture in an oxygen atmosphere at 750°C for 12 hours.

[0117] The lithium composite transition metal oxide and Co(OH)2 were mixed in amounts such that the molar ratio of Ni:Co:Mn:Al was 92:4:2:2, and then heat-treated at 650°C for 8 hours to produce a positive electrode active material.

[0118] Example 2 A transition metal solution, consisting of NiSO4, CoSO4, and MnSO4 mixed in a Ni:Co:Mn molar ratio of 92:2:2, an aqueous ammonia solution, and a sodium hydroxide solution were added to a coprecipitation reactor and a coprecipitation reaction was carried out to form a precursor. The precursor particles were separated, washed, and then dried to produce the precursor.

[0119] A lithium composite transition metal oxide was produced by mixing a precursor synthesized by coprecipitation with LiOH and aluminum hydroxide in a molar ratio of Ni+Co+Mn:Al:Li of 96:2:98, and then calcining the mixture in an oxygen atmosphere at 750°C for 12 hours.

[0120] The lithium composite transition metal oxide and Co(OH)2 were mixed in amounts such that the molar ratio of Ni:Co:Mn:Al was 92:4:2:2, and then heat-treated at 600°C for 8 hours to produce a positive electrode active material.

[0121] Comparative Example 1 A transition metal solution, prepared by mixing NiSO4, CoSO4, and MnSO4 in a Ni:Co:Mn molar ratio of 92:4:2, along with an aqueous ammonia solution and a sodium hydroxide solution, was added to a coprecipitation reactor to form a precursor. The precursor particles were separated, washed, and then dried to produce the precursor.

[0122] The precursor synthesized by coprecipitation was mixed with LiOH and aluminum hydroxide in a molar ratio of Ni+Co+Mn:Al:Li of 98:2:100, and the mixture was calcined in an oxygen atmosphere at 750°C for 12 hours to produce the cathode active material.

[0123] Comparative Example 2 A transition metal solution (NiSO4 and MnSO4 mixed in a Ni:Mn molar ratio of 92:2), an aqueous ammonia solution, and a sodium hydroxide solution were added to a coprecipitation reactor, and a coprecipitation reaction was carried out to form a precursor. The precursor particles were separated, washed, and then dried to produce the precursor.

[0124] A lithium composite transition metal oxide was produced by mixing a precursor synthesized by a coprecipitation reaction with LiOH and aluminum hydroxide in a molar ratio of Ni+Mn:Al:Li of 94:2:96, and then calcining the mixture in an oxygen atmosphere at 750°C for 12 hours.

[0125] The lithium composite transition metal oxide and Co(OH)2 were mixed in amounts such that the molar ratio of Ni:Co:Mn:Al was 92:4:2:2, and then heat-treated at 650°C for 8 hours to produce a positive electrode active material.

[0126] Experimental Example 1: NMR Spectral Analysis 2D of the positive electrode active material produced by Examples 1-2 and Comparative Examples 1-2 7 Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR spectra were obtained, and the 1D NMR center band spectrum was extracted.

[0127] Figure 1 shows the 2D positive electrode active materials of Examples 1-2 and Comparative Examples 1-2. 7 The 1D NMR center band spectra extracted from the Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR spectra are shown. For comparison, the 1D Hahn-echo MAS NMR spectra of the cathode active materials of Example 1 and Comparative Example 1 were measured and are shown in Figure 2.

[0128] Refer to Figures 1 and 2, 2D 7The 1D NMR center band spectrum extracted from the NMR spectrum obtained by the Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) analysis has only two peaks shown in the regions of 550 ppm to 850 ppm and -10 ppm to 10 ppm. In contrast, the 1D Hahn-echo MAS NMR spectrum shows many more peaks as a result of magic angle spinning, and it can be confirmed that overlap occurred between the spinning sidebands (indicated by *) thus generated and the main peak.

[0129] Next, the 2D obtained above 7 By spectral analysis of the 1D NMR center band spectrum extracted from the Li MATPASS (Magic Angle Turning-Phase Adjusted Spinning Sideband) NMR spectrum, the I of the cathode active materials of Examples 1 to 2 and Comparative Examples 1 to 2 550 / I 700 value, the maximum full width at half maximum (FWHM 700 ) of the peak shown in the region of 600 to 800 ppm, the maximum full width at half maximum (FWHM 550 ) of the peak shown in the region of 450 to 650 ppm, and the maximum full width at half maximum (FWHM0) of the peak shown in the region of -10 to 10 ppm were measured. The measurement results are shown in [Table 1]. Also, in FIG. 3, the results of spectral analysis of the 1D NMR center band spectrum extracted from the 2D 7 Li MATPASS NMR spectrum of the cathode active material of Example 1 are illustrated.

[0130] On the other hand, the measurement conditions and spectral analysis conditions of the 2D 7 Li MATPASS NMR spectrum are as described above.

[0131]

Table 1

[0132] Experimental Example 2: Evaluation of High-Temperature Life Characteristics The positive electrode active material, conductive material (Super C65), and PVDF binder prepared in Examples 1-2 and Comparative Examples 1-2 were mixed in N-methylpyrrolidone in a weight ratio of 96.5:1.5:2 to produce a positive electrode slurry. The positive electrode slurry was applied to one surface of an aluminum current collector, dried, and then rolled to produce a positive electrode.

[0133] A negative electrode slurry was prepared by mixing a mixture of natural graphite (GT, manufactured by Zichen) and artificial graphite (AGP8, manufactured by BTR) (weight ratio 5:5) as the negative electrode active material, Super-C65 (manufactured by Timcal), SBR binder (BM-L302, manufactured by Zeon), and additive (Daicel 2200, Daicel Chemical Industry) with water in a weight ratio of 95.6:1:2.3:1.1. After applying the negative electrode slurry to one surface of a copper current collector, it was dried and then rolled to produce the negative electrode.

[0134] After manufacturing an electrode assembly by interposing a separator between the positive and negative electrodes, the assembly was placed inside a battery case, and then an electrolyte was injected into the case to manufacture a lithium secondary battery. The electrolyte was prepared by dissolving 1M LiPF6 in a mixed organic solvent of ethylene carbonate / dimethyl carbonate / diethyl carbonate in a volume ratio of 1:2:1, and adding 2% by weight of vinylene carbonate (VC).

[0135] For each lithium secondary battery manufactured as described above, the battery was charged at 45°C in CC-CV mode at 0.3C until it reached 4.25V, and then discharged at a constant current of 0.3C until it reached 2.5V. This cycle was performed for 200 cycles, after which the capacity retention rate and resistance increase rate were measured to evaluate its lifespan characteristics. The measurement results are shown in Figure 4.

[0136] Refer to Figure 4, I 550 / I 700The lithium secondary battery applying the cathode active materials of Example 1 and Example 2 satisfying 0.3 to 0.4 has I 550 / I 700 The cathode active material of Comparative Example 1 in which I exceeds 0.4 and I 550 / I 700 It can be confirmed that the lithium secondary battery applying the cathode active material of Comparative Example 2 in which I is less than 0.25 exhibits excellent life characteristics as compared with the lithium secondary battery applying the cathode active material of Comparative Example 2 in which I is less than 0.25.

Claims

1. A positive electrode active material comprising a lithium composite transition metal oxide containing nickel, cobalt, manganese, and aluminum, The positive electrode active material contains 85 mol% to 97 mol% nickel and 2 mol% to 5 mol% cobalt, relative to the total number of moles of the remaining metals other than lithium. Positive electrode active material that satisfies the following equation (1): Formula (1): 0.25≦I ５５０ / I ７００ ≤0.4 In the above formula (1), I ７００ and I ５５０ These are the 2D of the positive electrode active material, respectively. ７ This refers to the maximum peak intensity values ​​in the 600–800 ppm region and the 450–650 ppm region when the 1D NMR center band spectrum extracted from the Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR spectrum is subjected to spectral analysis (peak deconvolution).

2. The 2D of the positive electrode active material ７ The positive electrode active material according to claim 1, wherein the 1D NMR center band spectrum extracted from the Li MATPASS NMR spectrum has a first peak in the region of 550 ppm to 850 ppm and a second peak in the region of -10 ppm to 10 ppm.

3. The positive electrode active material according to claim 1, satisfying the following formula (1-1): Formula (1-1): 0.30≦I ５５０ / I ７００ ≤0.4 In the formula (1-1), I ７００ and I ５５０ are respectively the maximum peak intensity shown in the region of 600 to 800 ppm and the maximum peak intensity shown in the region of 450 to 650 ppm when the 1D NMR center band spectrum extracted from the 2D Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR spectrum of the positive electrode active material is subjected to spectral analysis (peak deconvolution).​​

4. The 2D of the positive electrode active material ７ When the 1D NMR center band spectrum extracted from the Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR spectrum is subjected to spectral analysis (peak deconvolution), the maximum half-width (FWHM) of the peak shown in the 600–800 ppm region is obtained. ７００ The positive electrode active material according to claim 1, wherein the concentration of ) is 250 ppm or less.

5. The 2D of the positive electrode active material ７ When the 1D NMR center band spectrum extracted from the Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR spectrum is subjected to spectral analysis (peak deconvolution), the maximum half-width (FWHM) of the peak shown in the 450–650 ppm region is obtained. ５５０ The positive electrode active material according to claim 1, wherein the concentration of ) is 250 ppm or less.

6. The 2D of the positive electrode active material ７ When the 1D NMR center band spectrum extracted from the Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR spectrum is subjected to spectral analysis (peak deconvolution), the maximum half-width (FWHM) of the peak shown in the -10 to 10 ppm region is obtained. ０ The positive electrode active material according to claim 1, wherein the concentration of ) is 50 ppm or less.

7. The positive electrode active material according to claim 1, wherein the positive electrode active material contains 85 mol% to 95 mol% nickel with respect to the total number of moles of the remaining metals other than lithium.

8. The positive electrode active material according to claim 1, wherein the positive electrode active material contains 90 mol% to 95 mol% nickel with respect to the total number of moles of the remaining metals other than lithium.

9. The positive electrode active material according to claim 1, wherein the positive electrode active material contains 0.5 mol% to 5 mol% of manganese and 0.5 mol% to 5 mol% of aluminum, relative to the total number of moles of the remaining metals other than lithium.

10. The positive electrode active material has a composition represented by the following [Chemical Formula 1], as described in claim 1: [Chemical formula 1] Li ａ Ni ｂ Co ｃ Mn ｄ Al ｅ M １ ｆ O ２ In the above [Chemical Formula 1], M １ is one or more elements selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb, and the following conditions apply: 0.8 ≤ a ≤ 1.2, 0.85 ≤ b ≤ 0.97, 0.02 ≤ c ≤ 0.05, 0.005 ≤ d < 0.05, 0.005 ≤ e < 0.05, and 0 ≤ f ≤ 0.

02.

11. A method for producing a positive electrode active material according to Claim 1, The first step involves a coprecipitation reaction of an aqueous transition metal solution containing nickel ions, cobalt ions, and manganese ions to form a precursor, The second step involves mixing the aforementioned precursor, lithium raw material, and aluminum raw material, and then calcining them to form a lithium composite transition metal oxide. A method for producing a positive electrode active material, comprising a third step of mixing the lithium composite transition metal oxide with a cobalt raw material and then heat-treating it to produce a positive electrode active material.

12. A method for producing a positive electrode active material according to claim 11, wherein the ratio of the number of moles of cobalt contained in the cobalt raw material of the third step to the number of moles of cobalt contained in the precursor of the first step is 1 to 1.

5.

13. The method for producing a positive electrode active material according to claim 11, wherein in the third step, the heat treatment temperature is 600°C to 750°C.

14. A positive electrode comprising the positive electrode active material according to any one of claims 1 to 10.

15. A lithium secondary battery comprising the positive electrode described in claim 14.

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