Positive electrode and lithium secondary battery including the same

Abstract

The present invention relates to a positive electrode containing a perlithiated manganese-based oxide as a positive electrode active material, in which the molar ratio of lithium to all metals other than lithium (Li / Me) exceeds 1.1, the manganese content of all metals other than lithium is 50 mol % or more, and the positive electrode satisfies the following formula (1), and a lithium secondary battery containing the same. Formula (1): 0.05 TM / I Li <0.13 In the formula (1), I TM and I Li are the sum of the areas of the peaks in the 1000 to 2500 ppm region and the 300 to 900 ppm region, respectively, when the 1D NMR center band spectrum extracted from the 2D 7Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR spectrum of the perlithiated manganese oxide is subjected to waveform analysis (peak deconvolution).​

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0134434, filed on October 18, 2022, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a positive electrode and a lithium secondary battery, and more specifically to a positive electrode containing a perlithiated manganese oxide as a positive electrode active material and having excellent life characteristics, and a lithium secondary battery containing the same. [Background technology]

[0003] Recently, interest in energy storage technology has been gradually increasing, and as its application fields have expanded to include mobile phones, camcorders, laptop computers, and even electric vehicles, efforts in the research and development of electrochemical devices have gradually become more concrete. Among electrochemical devices, interest in the development of rechargeable secondary batteries has been growing, and in particular, lithium secondary batteries, developed in the early 1990s, have been attracting attention due to their advantages of high operating voltage and remarkably high energy density.

[0004] Meanwhile, the recent rise in demand for high-energy-density secondary batteries, such as those used in electric vehicles, has led to a growing need for high-capacity cathode active materials. To increase the capacity of cathode active materials, development has focused primarily on high-nickel cathode active materials, which increase the nickel content in ternary lithium composite transition metal oxides (NCMs) containing nickel, cobalt, and manganese. However, high-nickel cathode active materials face limitations in cost reduction due to the high cost of raw materials such as nickel and cobalt. Furthermore, their fragile structural stability can lead to structural collapse at high temperatures and voltages, leaching of transition metals, and gas generation.

[0005] Therefore, active development has been underway recently for lithium secondary battery cathodes that utilize perlithiated manganese oxides, which have a lower content of precious metals compared to NCMs and can achieve high capacity. Perlithiated manganese oxides have a lithium to transition metal molar ratio greater than 1 and a manganese content of 50 mol% or more. They have a mixed structure consisting of a rock-salt Li2MnO3 phase and a layered LiMO2 phase (where M is Ni, Co, or Mn). Perlithiated manganese oxides achieve capacity in the low voltage range through transition metal oxidation, as with existing NCMs, and in the high voltage range through oxygen redox, thereby achieving higher capacity than existing high-nickel NCMs. However, they suffer from the drawback of reduced cell life due to the generation of excessive reactive oxygen during the oxygen redox reaction.

[0006] Therefore, there is a need for the development of a lithium secondary battery that contains a perlithiated manganese oxide and has excellent life characteristics. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made to solve the above problems, and aims to provide a positive electrode for a lithium secondary battery that can achieve excellent life characteristics by applying a perlithiated manganese-based oxide in which the Li ratio in the lithium layer and the transition metal layer satisfies specific conditions, and a lithium secondary battery including the same. [Means for solving the problem]

[0008] In one aspect, the present invention provides a positive electrode comprising a perlithiated manganese-based oxide as a positive electrode active material, in which the molar ratio of lithium to all metals other than lithium (Li / Me) exceeds 1.1, the manganese content of all metals other than lithium is 50 mol % or more, and the following formula (1) is satisfied: Formula (1): 0.05 <ITM / I Li <0.13 In the formula (1), I TM and I Li are the sum of the areas of the peaks in the 1000 to 2500 ppm region and the 300 to 900 ppm region, respectively, when the 1D NMR center band spectrum extracted from the 2D 7Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR spectrum of the perlithiated manganese oxide is subjected to waveform analysis (peak deconvolution).

[0009] Preferably, the perlithiated manganese oxide satisfies the following formula (1-1): Formula (1-1): 0.06≦I TM / I Li ≦0.12 In the formula (1-1), I TM and I Li is as defined in equation (1).

[0010] In another aspect, the present invention provides a lithium secondary battery including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is the positive electrode according to the present invention described above. [Effects of the Invention]

[0011] The positive electrode according to the present invention includes a perlithiated manganese-based oxide as a positive electrode active material, in which the molar ratio of lithium to all metals other than lithium (Li / Me) is greater than 1.1, and the manganese content of all metals other than lithium is 50 mol% or more, and the perlithiated manganese-based oxide is 2D 7 The I peak deconvolution was performed on the 1D NMR centerband spectrum extracted by Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR analysis. TM / I Li The present invention is characterized in that a substance having a specific range of I (i.e., greater than 0.05 and less than 0.13) is used. TM is a value obtained by adding up the areas of the peaks in the 1000 to 2500 ppm region during the waveform analysis, and represents the ratio of lithium located in the transition metal layer. Li is a value obtained by adding up the areas of peaks in the 300 to 900 ppm region during the waveform analysis, and represents the ratio of lithium located in the lithium layer. When the ratio of Li present in the transition metal layer increases, the capacity increases, but the oxygen oxidation-reduction reaction increases, resulting in a decrease in life characteristics. Conversely, when the ratio of Li present in the transition metal layer decreases, the effect of increasing the capacity is not so great. Therefore, in the present invention, a positive electrode active material is used in which the ratio of the amount of Li present in the lithium layer, the amount of Li present in the transition metal layer, and the ratio of Li present in the lithium layer are within a specific condition (i.e., I TM / I Li By using a perlithiated manganese oxide that satisfies the above condition (greater than 0.05 but less than 0.13), it has become possible to achieve high capacity characteristics and obtain the effect of significantly improving life characteristics. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a comparison of the NMR spectrum obtained by analyzing a perlithiated manganese oxide by 1D Hahn-echo MAS NMR analysis and the NMR spectrum obtained by analyzing the same by 2D 7Li MATPASS NMR analysis. [Figure 2] FIG. 1 shows 1D NMR center band spectra extracted from 2D 7Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR spectra of perlithiated manganese oxides A to F. [Figure 3] 1 is a graph showing the results of evaluation of the room-temperature life characteristics of the lithium secondary batteries of Examples 1 to 4 and Comparative Examples 1 and 2. [Figure 4]1 is a graph showing the results of measuring the discharge capacity of the lithium secondary batteries of Examples 1 to 4 and Comparative Examples 1 and 2. [Figure 5] 1 is a graph showing the evaluation results of the high-temperature life characteristics of the lithium secondary batteries of Examples 1 to 4 and Comparative Examples 1 and 2. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be specifically described below.

[0014] The present inventors have conducted extensive research to improve the life characteristics of lithium secondary batteries that use perlithiated manganese oxide as a positive electrode active material, and as a result have found that when a perlithiated manganese oxide in which the Li ratio present in the lithium layer and transition metal layer satisfies specific conditions is used as a positive electrode active material, the life characteristics of lithium secondary batteries that use perlithiated manganese oxide are significantly improved, leading to the completion of the present invention.

[0015] positive electrode The positive electrode according to the present invention includes a perlithiated manganese-based oxide as a positive electrode active material, in which the molar ratio of lithium to all metals other than lithium (Li / Me) exceeds 1.1 and the manganese content of all metals other than lithium is 50 mol% or more, and the perlithiated manganese-based oxide is characterized by satisfying the following formula (1):

[0016] Formula (1): 0.05 TM / I Li <0.13

[0017] In the formula (1), I TM and I Li are the 2D structures of perlithiated manganese oxides, respectively. 7 ​This is the sum of the areas of the peaks in the 1000-2500 ppm region and the 300-900 ppm region when peak deconvolution is performed on the 1D NMR centerband spectrum extracted from the Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR spectrum.

[0018] 2D in this invention 7 The Li MATPASS NMR measurement conditions are as follows:

[0019] <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 -1 ppm Pulse program: 2D MATPASS Spectral width (sw): 1250kHz Acquisition time: 5ms Carrier frequency (o1p) at 800 ppm Pulse length (p1): 1 μs Recycle delay(d1): 1s TD of F1 dimension (L1): 16 Number of scans: 30000

[0020] After the measurement, the 2D data was processed by xfb, and then a centerband slice ((L1 / 2+1)=(16 / 2+1)=9th slice) was taken to obtain the 1D NMR centerband spectrum.

[0021] On the other hand, 2D 7 Peak deconvolution of the 1D NMR centerband spectrum extracted from the Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR spectrum can be performed using DMFIT (64-bit, release #20190125) NMR software. Specifically, the peak deconvolution can be performed using the following: 7 After importing the 1D NMR centerband spectrum extracted from the Li MATPASS NMR spectrum into the DMFIT program, the Gaussian / Lorentzian fitting model for waveform analysis was selected, and appropriate initial values ​​were set for the peak amplitude, peak position, peak width, and Gaussian / Lorentzian ratio (xG / (1-x)L). Fitting was then repeated until an appropriate convergence value was reached. In this study, the Gaussian / Lorentzian ratio (xG / (1-x)L) was fixed at 0.5 during waveform analysis, and fitting was performed under the conditions of nParVar = 15, step = 1, and Thresh = 0.001.

[0022] Conventionally, one-dimensional (1D) echo MAS NMR analysis has been mainly used for structural analysis of positive electrode active materials. However, perlithiated manganese oxides were analyzed by 1D solid-state NMR. 7 When measuring using Li NMR analysis, it is difficult to distinguish the main peak due to the overlap of the spinning sideband (indicated by * in Figure 1) and the main peak. In particular, the peak near 1500 ppm, which is a characteristic peak of Li2MnO3 contained in perlithiated manganese oxide, overlaps with the spinning sideband, making it difficult to analyze the structural characteristics of the positive electrode active material (see Figure 1).

[0023] But 2D 7 By applying the Li MATPASS NMR analysis method, high-resolution NMR spectra can be obtained, and structural features of perlithiated manganese oxides can be distinguished by waveform analysis of the extracted spectra. We have investigated various perlithiated manganese oxides in 2D. 7 The results of the Li MATPASS NMR analysis showed that I TM / I Li The present inventors have found that when a perlithiated manganese oxide satisfying a specific condition (greater than 0.05 and less than 0.13) is used in the positive electrode, the life characteristics of a lithium secondary battery are significantly improved, and have completed the present invention.

[0024] I TM / I Li is a value that represents the ratio of lithium located in the transition metal layer and lithium layer of the perlithiated manganese oxide crystal structure, and I TM / I Li When the ratio is more than 0.05 and less than 0.13, the degree of oxygen redox occurring during charge / discharge is appropriately controlled, thereby achieving high capacity and excellent life characteristics.

[0025] Preferably, the perlithiated manganese oxide is TM / I Lican be 0.06 to 0.12, and more preferably I TM / I Li may be 0.08 to 0.12, more preferably 0.09 to 0.12, even more preferably 0.097 to 0.11, and most preferably 0.10 to 0.11. TM / I Li When the above range is satisfied, the material exhibits better high-temperature life characteristics.

[0026] Meanwhile, in the perlithiated manganese oxide, the molar ratio of Li to the total number of moles of metal elements other than Li (Li / Me) can be 1.1 to 1.5, 1.2 to 1.5, 1.25 to 1.5, or 1.25 to 1.4. When the Li / Me ratio satisfies the above range, excellent rate characteristics and capacity characteristics are exhibited. If the Li / Me ratio is too high, electrical conductivity decreases and the rock salt phase (Li2MnO3) increases, which can lead to an accelerated degradation rate. If the Li / Me ratio is too low, the effect of improving energy density is not significant.

[0027] The perlithiated manganese oxide may contain nickel:manganese in a molar ratio of 30:70 to 45:55, preferably 31:69 to 45:55. When the molar ratio of nickel to manganese in the perlithiated manganese oxide satisfies the above range, both the capacity and life characteristics are excellent. If the nickel content is less than 30 mol%, the rock salt phase (Li2MnO3) increases, which can accelerate cell degradation.

[0028] Preferably, the perlithiated manganese-based oxide may be represented by Chemical Formula 1.

[0029] [Chemical formula 1] Li a Ni b Co c Mn d M e O2

[0030] In the chemical formula 1, M can be at least one selected from the group consisting of Al, B, Co, W, Mg, V, Ti, Zn, Ga, In, Ru, Nb, Sn, Sr, and Zr.

[0031] On the other hand, a is the molar ratio of Li in the over-lithiated manganese-based oxide, and can be 1 < a, 1.1 ≤ a ≤ 1.5, or 1.1 ≤ a ≤ 1.3. When a satisfies the above range, the irreversible capacity of the Si-based negative electrode active material can be sufficiently compensated, and high-capacity characteristics can be realized.

[0032] The b is the molar ratio of Ni in the over-lithiated manganese-based oxide, and can be 0.1 ≤ b < 0.5, 0.2 ≤ b < 0.5, or 0.3 ≤ b < 0.5.

[0033] The c is the molar ratio of Co in the over-lithiated manganese-based oxide, and can be 0 ≤ c < 0.1, 0 ≤ c ≤ 0.08, or 0 ≤ c ≤ 0.05. When c is 0.1 or more, it is difficult to ensure high capacity, and gas generation and deterioration of the positive electrode active material may become severe, resulting in a decrease in life characteristics.

[0034] The d is the molar ratio of Mn in the over-lithiated manganese-based oxide, and can be 0.5 ≤ d ≤ 0.9, 0.50 ≤ d ≤ 0.8, or 0.50 ≤ d ≤ 0.70. When d is less than 0.5, the ratio of the rock salt phase becomes too small, and the effects of negative electrode irreversible compensation and capacity improvement are not significant.

[0035] The e is the molar ratio of the doping element M in the over-lithiated manganese-based oxide, and can be 0 ≤ e ≤ 0.1 or 0 ≤ e ≤ 0.05. If the content of the doping element is too much, it may have an adverse effect on the capacity of the active material.

[0036] On the other hand, the over-lithiated manganese-based oxide has a structure in which a rock salt phase (Li2MnO3) and a layered phase (LiM’O2, where M' contains Ni and Mn) are mixed, and its composition can also be represented by the following [Chemical formula 2].

[0037] [Chemical formula 2] X Li2MnO3·(1-X)Li[Ni 1-y-z-w Mn y Co z M w ]O2

[0038] In the formula 2, M may be at least one selected from the group consisting of metal ions Al, B, Co, W, Mg, V, Ti, Zn, Ga, In, Ru, Nb, Sn, Sr, and Zr.

[0039] The X represents the ratio of the Li2MnO3 phase in the perlithiated manganese-based oxide, and may be 0.2≦X≦0.5, 0.25≦X≦0.5, or 0.25≦X≦0.4. When the ratio of the Li2MnO3 phase in the perlithiated manganese-based oxide satisfies this range, the irreversible capacity of the SiOx negative electrode active material can be sufficiently compensated for, and high capacity characteristics can be achieved.

[0040] The y is the molar ratio of Mn in the LiM'O2 layer, and can be 0.4≦y<1, 0.4≦y≦0.8, or 0.4≦y≦0.7.

[0041] The z is the molar ratio of Co in the LiM'O2 layer structure, and may be 0≦z≦0.1, 0≦z≦0.08, or 0≦z≦0.05. If z exceeds 0.1, gas generation and deterioration of the positive electrode active material may become severe, resulting in reduced life characteristics.

[0042] The w is the molar ratio of the doping element M in the LiM'O2 layer, and can be 0≦w≦0.1, or 0≦w≦0.05.

[0043] Meanwhile, the cathode active material according to the present invention may further include a coating layer on the surface of the perlithiated manganese-based oxide, if necessary. When the cathode active material includes the coating layer, the coating layer prevents contact between the perlithiated manganese-based oxide and the electrolyte, thereby reducing electrolyte side reactions and improving the lifespan.

[0044] The coating layer is made of a coating element M 1 The coating element M 1 For example, the coating element M can be at least one selected from the group consisting of Al, B, Co, W, Mg, V, Ti, Zn, Ga, In, Ru, Nb, Sn, Sr, and Zr, and is preferably Al, Co, Nb, W, and combinations thereof, and more preferably Al, Co, and combinations thereof. 1 may contain two or more kinds, for example, Al and Co.

[0045] The coating elements are in the form of oxides in the coating layer, i.e., M 1 It can exist as Oz (1≦z≦4).

[0046] The coating layer can be formed by dry coating, wet coating, chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), etc. Among them, atomic layer deposition is preferred because it allows the coating layer to be formed over a large area.

[0047] The area on which the coating layer is formed may be 10 to 100%, preferably 30 to 100%, and more preferably 50 to 100% of the total surface area of ​​the perlithiated manganese oxide particles. When the area on which the coating layer is formed satisfies this range, the effect of improving the life characteristics is excellent.

[0048] Meanwhile, the cathode active material according to the present invention may be in the form of secondary particles formed by agglomeration of a plurality of primary particles, and the average particle diameter D 50 The D of the positive electrode active material can be 2 μm to 10 μm, preferably 2 μm to 8 μm, and more preferably 4 μm to 8 μm. 50When satisfies the above range, excellent electrode density can be achieved and the deterioration of capacity and rate characteristics can be minimized.

[0049] The positive electrode active material has a BET specific surface area of ​​1 m 2 / g~10m 2 / g, 3-8m 2 / g or 4~6m 2 If the BET specific surface area of ​​the positive electrode active material is too low, the reaction area with the electrolyte is insufficient, making it difficult to achieve sufficient capacity, whereas if the specific surface area is too high, moisture absorption is rapid, accelerating side reactions with the electrolyte and making it difficult to ensure long life characteristics.

[0050] Meanwhile, the perlithiated manganese-based oxide may be prepared by mixing a transition metal precursor and a lithium source material and then calcining the mixture.

[0051] Examples of the lithium source material include lithium-containing carbonates (e.g., lithium carbonate, etc.), hydrates (e.g., lithium hydroxide hydrate (LiOH·H2O)), hydroxides (e.g., lithium hydroxide, etc.), nitrates (e.g., lithium nitrate (LiNO3), etc.), and chlorides (e.g., lithium chloride (LiCl)), and any of these may be used alone or in combination.

[0052] Meanwhile, the transition metal precursor may be in the form of a hydroxide, oxide, or carbonate. When a carbonate precursor is used, it is more preferable in that a positive electrode active material having a relatively high specific surface area can be prepared.

[0053] The transition metal precursor can be prepared by a co-precipitation process. For example, the transition metal precursor can be prepared by dissolving each transition metal-containing raw material in a solvent to prepare a metal solution, and then mixing the metal solution, an ammonium cation complexing agent, and a basic compound, followed by co-precipitation. If necessary, an oxidizing agent or oxygen gas can be further added during the co-precipitation reaction.

[0054] Here, the transition metal-containing raw material may be acetate, carbonate, nitrate, sulfate, halide, sulfide, etc. of each transition metal. Specifically, the transition metal-containing raw material may be NiO, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, NiSO4, NiSO4·6H2O, Mn2O3, MnO2, Mn3O4, MnCO3, Mn(NO3)2, MnSO4·H2O, manganese acetate, manganese halide, Co2O3, cobalt sulfate, cobalt nitrate, cobalt carbonate, cobalt acetate, cobalt halide, etc.

[0055] The ammonium cation complexing agent may be at least one selected from the group consisting of NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, and (NH4)2CO3.

[0056] The basic compound may be at least one selected from the group consisting of NaOH, Na2CO3, KOH, and Ca(OH)2. The form of the precursor may vary depending on the type of basic compound used. For example, when NaOH is used as the basic compound, a hydroxide-form precursor can be obtained, and when Na2CO3 is used as the basic compound, a carbonate-form precursor can be obtained. Furthermore, when a basic compound and an oxidizing agent are used together, an oxide-form precursor can be obtained.

[0057] Meanwhile, the transition metal precursor and the lithium source material may be mixed in amounts such that the molar ratio of the total transition metals (Ni+Co+Mn):Li is 1:1.05 to 1:2, preferably 1:1.1 to 1:1.8, and more preferably 1:1.25 to 1:1.8.

[0058] The firing may be performed at a temperature of 600 to 1000°C or 700 to 950°C for a period of 5 to 30 hours or 5 to 20 hours. The firing atmosphere may be air or oxygen, for example, an atmosphere containing 20 to 100% by volume of oxygen.

[0059] Meanwhile, the positive electrode according to the present invention may further include a conductive material and a binder in addition to the positive electrode active material, if necessary.

[0060] Examples of the conductive material include spherical or flake graphite; carbonaceous materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, single-walled carbon nanotubes, and multi-walled carbon nanotubes; metal powder or metal fiber 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 any of these may be used alone or in combination. The conductive material may be included in an amount of 0.1 to 20 wt %, 1 to 20 wt %, or 1 to 10 wt % based on the total weight of the positive electrode active material layer.

[0061] Examples of the binder include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (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 these may be used alone or in combination. The binder may be included in an amount of 1 to 20 wt %, 2 to 20 wt %, or 2 to 10 wt % of the total weight of the positive electrode active material layer.

[0062] The positive electrode may be manufactured by a method known in the art, for example, by coating a positive electrode slurry, which is prepared by dissolving or dispersing a positive electrode active material and, optionally, a binder and a conductive material in a solvent, on a positive electrode current collector, followed by rolling and drying, or by casting the positive electrode slurry on a separate support, peeling off the support, and laminating the resulting film on the positive electrode current collector.

[0063] 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 surface-treated with carbon, nickel, titanium, silver, etc. can be used. The positive electrode current collector typically has a thickness of 3 to 500 μm, and fine irregularities can be formed on the surface of the positive electrode current collector to enhance the adhesive strength of the positive electrode active material. It can be used in various forms, such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0064] The solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and may be used alone or in combination. The amount of the solvent used is not particularly limited, as long as it is adjusted to an appropriate viscosity of the positive electrode slurry, taking into consideration the coating thickness of the positive electrode slurry, production yield, workability, etc.

[0065] As described above, a positive electrode containing a perlithiated manganese oxide satisfying formula (1) as a positive electrode active material can be stably driven even when the end-of-charge voltage is set as high as 4.3 V to 4.5 V, can achieve high capacity characteristics, and exhibits excellent life characteristics at room temperature and high temperature.

[0066] Lithium secondary battery Next, the lithium secondary battery according to the present invention will be described.

[0067] The lithium secondary battery according to the present invention includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. Here, the positive electrode is the positive electrode according to the present invention. Since the positive electrode has been described above, detailed description thereof will be omitted.

[0068] negative electrode The negative electrode according to the present invention includes a negative electrode active material layer containing a negative electrode active material, and the negative electrode active material layer may further include a conductive material and / or a binder, if necessary.

[0069] The negative electrode active material may be any of various negative electrode active materials used in the art, such as silicon-based negative electrode active materials, carbon-based negative electrode active materials, metal alloys, or combinations thereof, and is not particularly limited.

[0070] Preferably, the negative electrode active material may include a silicon-based negative electrode active material.

[0071] The silicon-based negative electrode active material is, for example, Si, SiO m (where 0 < m < 2), Si-C composite, Si-M a alloy (M a is selected from the group consisting of one or more selected from the group consisting of Al, Sn, Mg, Cu, Fe, Pb, Zn, Mn, Cr, Ti, Ni) and combinations thereof.

[0072] Also, the silicon-based negative electrode active material may be doped with M b metal, where the M b metal can be a Group 1 alkali metal element and / or a Group 2 alkaline earth metal element, and can be, for example, Li, Mg, etc. Specifically, the silicon negative electrode active material is M b Si doped with metal, SiO m (where 0 < m < 2), Si-C composite, etc. In the case of a metal-doped silicon-based negative electrode active material, the active material capacity decreases due to the doping element, but it has high efficiency, so a high energy density can be realized.

[0073] Also, the silicon-based negative electrode active material can further include a carbon coating layer on the surface of the particles. Here, the amount of the carbon coating can be 20% by weight or less, preferably 0.1 to 20% by weight based on the total weight of the silicon-based negative electrode active material. The carbon coating layer can be formed by methods such as dry coating, wet coating, chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD).

[0074] Also, the particle diameter D 50 of the silicon-based negative electrode active material is 3 to 8 μm, preferably 4 to 7 μm, and D min ~D max is 0.5 to 30 μm, preferably 0.5 to 20 μm, more preferably 1 to 15 μm.

[0075] The silicon-based negative electrode active material may be included in an amount of 1 to 100 wt %, 1 to 50 wt %, 1 to 30 wt %, 1 to 15 wt %, 10 to 70 wt %, or 10 to 50 wt % based on the total weight of the negative electrode active material included in the negative electrode.

[0076] The negative electrode may include a carbon-based negative electrode active material, which may be, but is not limited to, artificial graphite, natural graphite, graphitized carbon fiber, amorphous carbon, soft carbon, or hard carbon.

[0077] The carbon-based negative electrode active material may be included in an amount of 1 to 100 wt %, 50 to 99 wt %, 70 to 99 wt %, 85 to 99 wt %, 30 to 90 wt %, or 50 to 90 wt % based on the total weight of the negative electrode active material included in the negative electrode.

[0078] According to one embodiment, the negative electrode active material may be a mixture of a silicon-based negative electrode active material and a carbon-based negative electrode active material, and the mixing ratio of the silicon-based negative electrode active material to the carbon-based negative electrode active material may be 1:99 to 50:50 by weight, preferably 3:97 to 30:70. When the mixing ratio of the silicon-based negative electrode active material to the carbon-based negative electrode active material satisfies this range, capacity characteristics are improved and volume expansion of the silicon-based negative electrode active material is suppressed, thereby ensuring excellent cycle performance.

[0079] The negative electrode active material may be contained in an amount of 80 to 99 wt % based on the total weight of the negative electrode active material layer. When the content of the negative electrode active material satisfies this range, excellent capacity characteristics and electrochemical characteristics can be obtained.

[0080] Examples of the conductive material include spherical or flake graphite; carbonaceous materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, single-walled carbon nanotubes, and multi-walled carbon nanotubes; metal powder or metal fiber 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 any of these may be used alone or in combination. The conductive material may be included in an amount of 0.1 to 30 wt %, 1 to 20 wt %, or 1 to 10 wt % based on the total weight of the negative electrode active material layer.

[0081] Preferably, single-walled carbon nanotubes can be used as the conductive material. When single-walled carbon nanotubes are used as the conductive material, conductive paths are uniformly formed on the surface of the negative electrode active material, thereby improving cycle characteristics.

[0082] Examples of the binder include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylic acid, polyacrylamide, polyacrylonitrile, carboxymethyl cellulose (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 these may be used alone or in combination. The binder may be included in an amount of 1 to 20 wt %, 2 to 20 wt %, or 2 to 10 wt % of the total weight of the negative electrode active material layer.

[0083] The negative electrode may have a single-layer or multi-layer structure in which the negative electrode active material layer is composed of two or more layers. When the negative electrode active material layer is composed of two or more layers, the layers may differ in the type and / or content of the negative electrode active material, binder, and / or conductive material. For example, in the negative electrode according to the present invention, the lower layer may have a higher content of carbon-based negative electrode active material than the upper layer, and the upper layer may have a higher content of silicon-based negative electrode active material. In this case, the effect of improving fast charging performance can be obtained compared to when the negative electrode active material layer is composed of a single layer.

[0084] On the other hand, the lithium secondary battery of the present invention is preferably configured so that the N / P ratio, which is the ratio of the negative electrode capacity to the positive electrode capacity, varies depending on the type of negative electrode active material used. For example, when 100% Si is used as the negative electrode active material, the N / P ratio is preferably about 150% to 300%, and when a mixture of SiOm and a carbon-based negative electrode active material is used as the negative electrode active material, the N / P ratio is preferably about 100% to 150%.

[0085] The negative electrode may be manufactured by a method known in the art, for example, by coating a negative electrode slurry, which is 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, followed by rolling and drying, or by casting the negative electrode slurry on a separate support, peeling off the support, and laminating the resulting film on the negative electrode current collector.

[0086] The negative electrode current collector may be any material that does not cause chemical changes in the battery and has high conductivity, and examples of such materials include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surfaces treated with carbon, nickel, titanium, silver, or the like, and aluminum-cadmium alloys. The negative electrode current collector typically has a thickness of 3 μm to 500 μm. As with the positive electrode current collector, the surface of the current collector may be provided with fine irregularities to enhance the binding strength of the negative electrode active material. The negative electrode current collector may be used in various forms, such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0087] The solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and may be used alone or in combination. The amount of the solvent used is not particularly limited as long as it is sufficient to adjust the viscosity of the negative electrode slurry to an appropriate level, taking into consideration the coating thickness of the negative electrode composite, production yield, workability, etc.

[0088] Separator In the lithium secondary battery of the present invention, the separator separates the negative electrode and the positive electrode and provides a path for lithium ion migration. Any separator typically used in lithium secondary batteries can be used without particular limitation. In particular, a separator that exhibits low resistance to ion migration and excellent humidification ability for the electrolyte solution is preferred. Specifically, a porous polymer film, such as 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, or an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof, can be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. To ensure heat resistance or mechanical strength, a separator coated with a ceramic component or a polymer material can also be used, and can be selectively used in a single-layer or multi-layer structure.

[0089] electrolyte Furthermore, examples of the electrolyte used in the present invention include 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 production of lithium secondary batteries, but are not limited to these.

[0090] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0091] The organic solvent may be any solvent that can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether and tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate. Examples of solvents that can be used include carbonate solvents such as propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (R is a hydrocarbon group having 2 to 20 carbon atoms and having a linear, branched, or cyclic structure, which may contain a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; and sulfolanes.

[0092] The lithium salt can be any compound that can provide lithium ions used in lithium secondary batteries without any particular limitations. Specifically, the anion of the lithium salt can be F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 -, CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - The lithium salt may be at least one selected from the group consisting of LiPF6, LiN(FSO2)2, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, LiB(C2O4)2, etc. The lithium salt is preferably used at a concentration within a range of 0.1 to 5.0M.

[0093] The electrolyte may contain additives for the purpose of improving the life characteristics of the battery, suppressing capacity reduction, suppressing gas generation, etc. Examples of the additives include various additives used in the art, such as fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinylethylene carbonate (VEC), ethylene sulfate (ESa), lithium difluorophosphate (LiPO2F2), lithium bis(oxalato)borate (LiBOB), lithium tetrafluoroborate (LiBF4), lithium difluorooxalatoborate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFBP), lithium tetrafluorooxalatophosphate (LiTFOP), lithium methyl sulfate (LiMS), lithium ethyl sulfate (LiES), propane sultone (PS), propene sultone (PRS), succinonitrile (SN), and adiponite. Examples of compounds that can be used include aryl (AND), 1,3,6-hexenetricarbonitrile (HTCN), 1,4-dicyano-2-butene (DCB), fluorobenzene (FB), ethyl di(prop-2-yn-1-yl)phosphate (EDP), 5-methyl-5 propargyloxylcarbonyl-1,3-dioxan-2-one (MPOD), a compound represented by the following chemical formula A (e.g., cyanoethyl polyvinyl alcohol, PVA-CN), a compound represented by the following chemical formula B (e.g., heptafluorobutyl cyanoethyl polyvinyl alcohol, PF-PVA-CN), a compound represented by the following chemical formula C (e.g., propargyl 1H-imidazole-1-carboxylate, PAC), and / or a compound represented by the following chemical formula D (e.g., allylimidazole such as CHN).

[0094] [Chemical formula A] [ka]

[0095] In the above chemical formula A, m and n are each independently an integer of 1-100.

[0096] [Chemical formula B] [ka]

[0097] [Chemical formula C] [ka]

[0098] In the above chemical formula C, R 16 is a linear or non-linear alkylene group having 1 to 3 carbon atoms, and R 17 ~R 19 are each independently at least one selected from the group consisting of hydrogen, an alkyl group having 1 to 3 carbon atoms, and -CN, and D is CH or N.

[0099] [Chemical formula D] [ka]

[0100] In the above chemical formula D, R1, R2, R3, and R4 can each independently represent hydrogen; or an alkyl group having 1 to 5 carbon atoms, a cyano group (CN), an allyl group, a propargyl group, an amine group, a phosphate group, an ether group, a benzene group, a cyclohexyl group, a silyl group, an isocyanate group (-NCO), or a fluoro group (-F).

[0101] Preferably, the additive may be a compound that acts as an oxygen scavenger, such as a phosphite-based substance (see Chemical Formula E) such as tris(methylsilyl)phosphite (TMSPi), trimethylphosphite (TMPi), or tris(2,2,2-trifluoroethyl)phosphite (TTFP); tris(methylsilyl)phosphate (TMSPa); polyphosphonic acid trimethylsilyl ester (PPSE); tris(pentafluorophenyl)borane (TPFPB); coumarin-3-carbonitrile (CMCN), 7-ethynylcoumarin (ECM), or 3-acetyl Compounds that can be used as oxygen scavengers include compounds containing a coumarin structure such as coumarin (AcCM) and 3-(trimethylsilyl)coumarin (TMSCM) (see chemical formula F); 3-[(trimethylsilyl)oxyl]-2H-1-benzopyran-2-one (TMSOCM), 3-(2-propyn-1-yloxyl)-2H-1-benzopyran-2-one (POCM), and 2-propyn-1-yl-2-oxo-2H-1-benzopyran-3-carboxylate (OBCM).

[0102] [Chemical formula E] [ka]

[0103] [Chemical formula F] [ka]

[0104] In the chemical formulas E and F, R1 to R6 can each independently include a substituted or unsubstituted alkenyl group having 2 to 20 carbon atoms and a substituted or unsubstituted alkynyl group having 2 to 20 carbon atoms, a cyano group, a fluoro group (F), an ether group (COC), a carboxyl group (OC=O), a trimethylsilyl group (-TMS), an isocyanate group (-NCO), and / or an isothiocyanate group (-NCS).

[0105] The lithium secondary battery according to the present invention can be usefully used in portable devices such as mobile phones, notebook computers, and digital cameras, and in electric vehicles such as hybrid electric vehicles (HEVs).

[0106] Therefore, according to another embodiment of the present invention, there is provided a battery module including the lithium secondary battery as a unit cell, and a battery pack including the same.

[0107] The battery module or battery pack may be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and an electric vehicle (PHEV), including a plug-in hybrid electric vehicle; or a power storage system.

[0108] The external shape of the lithium secondary battery of the present invention is not particularly limited, and may be a cylindrical shape using a can, a square shape, a pouch shape, a coin shape, or the like.

[0109] The lithium secondary battery according to the present invention can be used as a battery cell used as a power source for a small device, and can also be preferably used as a unit battery in a medium- to large-sized battery module including a large number of battery cells.

[0110] The present invention will be described in more detail below with reference to specific examples.

[0111] Experimental Example 1: Metal Composition Ratio, I TM / I Li Measurement of Six commercially available perlithiated manganese oxides A to F were prepared, and the metal component ratios of each perlithiated manganese oxide were measured by ICP analysis, with the measurement results shown in Table 1 below. Here, the mol% of Ni, Co, and Mn represents the percentage of the number of moles of each metal element relative to the total number of moles of the remaining metals other than lithium.

[0112] Next, the perlithiated manganese oxides A to F are subjected to 2D 7 After measuring the Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR spectrum, the 1D NMR centerband spectrum was extracted. Figure 2 shows the 2D NMR spectra of the perlithiated manganese oxides A to F. 7 The 1D NMR centerband spectrum extracted from the Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR spectrum is shown.

[0113] Then, by waveform analysis of the 1D NMR center band spectrum, I TM / I Li The values ​​were measured, and the measurement results are shown in Table 1 below.

[0114] where I TM is the sum of the areas of the peaks in the 1000 to 2500 ppm region during the waveform analysis, and I Li is the sum of the areas of the peaks in the 300 to 900 ppm region during the waveform analysis, and 7 Measurement of Li MATPASS NMR spectrum, extraction of 1D NMR center band spectrum, and waveform analysis were carried out under the same conditions as described above.

[0115] [Table 1]

[0116] Example 1 The perlithiated manganese oxide A, conductive material (Super C 65), and PVDF binder were mixed in N-methylpyrrolidone in a weight ratio of 96.5:1.5:2 to prepare a positive electrode slurry. The positive electrode slurry was applied to one side of an aluminum current collector, dried, and rolled to prepare a positive electrode.

[0117] An electrode assembly was fabricated by interposing a separator between the positive electrode and the lithium metal electrode, and then the electrode assembly was placed inside a battery case and an electrolyte solution was injected to fabricate a lithium secondary battery. The electrolyte solution 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 wt% vinylene carbonate (VC).

[0118] The lithium secondary battery prepared as described above was charged at 45° C. at 0.1 C up to 4.65 V, and then discharged at 0.1 C down to 2.0 V to perform an activation process.

[0119] Example 2 A positive electrode and a lithium secondary battery were produced in the same manner as in Example 1, except that perlithiated manganese oxide B was used instead of perlithiated manganese oxide A.

[0120] Example 3 A positive electrode and a lithium secondary battery were produced in the same manner as in Example 1, except that perlithiated manganese oxide C was used instead of perlithiated manganese oxide A.

[0121] Example 4 A positive electrode and a lithium secondary battery were produced in the same manner as in Example 1, except that perlithiated manganese oxide D was used instead of perlithiated manganese oxide A.

[0122] Comparative Example 1 A positive electrode and a lithium secondary battery were produced in the same manner as in Example 1, except that perlithiated manganese oxide E was used instead of perlithiated manganese oxide A.

[0123] Comparative Example 2 A positive electrode and a lithium secondary battery were produced in the same manner as in Example 1, except that perlithiated manganese oxide F was used instead of perlithiated manganese oxide A.

[0124] Experimental example 2: Room temperature life characteristics Each of the lithium secondary batteries manufactured in the Examples and Comparative Examples was charged to 4.4 V at 25° C. with a constant current of 0.33 C and then discharged to 2.5 V with a constant current of 0.33 C for 50 cycles, and the capacity retention rate was measured to evaluate room temperature life characteristics. The measurement results are shown in FIG. 3. As shown in FIG. 3, the I TM / I Li The lithium secondary batteries of Examples 1 to 4, which used the perlithiated manganese oxides A to D satisfying the range of 0.06 to 0.12 as the positive electrode active material, were TM / I Li The lithium secondary battery of Comparative Example 1, in which the perlithiated manganese oxide E having a value exceeding 0.12 was used as the positive electrode active material, and the TM / I Li It can be seen that the battery has excellent room temperature life characteristics compared to the lithium secondary battery of Comparative Example 2, which used perlithiated manganese oxide F with a value of less than 0.06 as the positive electrode active material. TM / I Li In the case of the lithium secondary battery of Comparative Example 1 in which the perlithiated manganese oxide E having a value of more than 0.12 was used as the positive electrode active material, it can be confirmed that the room temperature life characteristics were significantly reduced.

[0125] Experimental Example 3: Initial Capacity Evaluation The lithium secondary batteries prepared in the examples and comparative examples were charged at 25° C. with a constant current of 0.1 C up to 4.4 V, and then discharged at a constant current of 0.1 C down to 2.5 V to measure the discharge capacity. The measurement results are shown in FIG. 4 and Table 2 below.

[0126] [Table 2]

[0127] According to Figure 4 and Table 2, I TM / I Li It can be seen that the initial capacity characteristics of the lithium secondary batteries of Comparative Examples 1 and 2, which employ perlithiated manganese-based oxides whose ranges are outside the scope of the present invention, are lower than those of the lithium secondary batteries of Examples 1, 2, and 4. Meanwhile, it can be seen that the initial capacity of the lithium secondary battery employing the perlithiated manganese-based oxide of Example 3 is somewhat low due to its small Li / Me ratio, but achieves a higher initial capacity than the lithium secondary battery employing the perlithiated manganese-based oxide of Comparative Example 1, which has a higher Li / Me ratio.

[0128] Experimental example 4: High temperature life characteristics Each of the lithium secondary batteries manufactured in the Examples and Comparative Examples was charged at 45° C. at a constant current of 0.33 C up to 4.4 V and then discharged at a constant current of 0.33 C down to 2.5 V, and the capacity retention and voltage drop were measured during 50 charge-discharge cycles. Here, the average voltages after 25 cycles and 50 cycles were measured, and the voltage drop was calculated as the difference between the average voltages measured after 25 cycles / 50 cycles and the average voltage at 1 cycle.

[0129] The measurement results of the capacity retention rate are shown in FIG. 5, and the voltage drop (ΔV) is shown in Table 3 below.

[0130] [Table 3]

[0131] It can be seen from Table 3 above that the lithium secondary battery of Comparative Example 2 exhibits a greater degree of voltage drop after the high-temperature cycle than the lithium secondary batteries of Examples 1 to 4. Also, from Fig. 5 it can be seen that the lithium secondary battery of Comparative Example 1 exhibits a significantly lower capacity retention rate after the high-temperature cycle than the lithium secondary batteries of Examples 1 to 4. As such, the lithium secondary batteries of Comparative Examples 1 and 2 exhibit a decrease in capacity or voltage after the high-temperature cycle, and therefore exhibit inferior energy density (capacity x voltage) after the high-temperature cycle.

Claims

1. A positive electrode comprising a perlithiated manganese-based oxide as a positive electrode active material, in which the molar ratio of lithium to all metals other than lithium (Li / Me) exceeds 1.1, the content of manganese among all metals other than lithium is 50 mol% or more, and the positive electrode satisfies the following formula (1): Formula (1): 0.05<I ＴＭ / I Ｌｉ <0.13 In the formula (1), I ＴＭ and I Ｌｉ are the sum of the areas of the peaks in the 1000 to 2500 ppm region and the 300 to 900 ppm region, respectively, when the 1D NMR center band spectrum extracted from the 2D 7Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) NMR spectrum of the perlithiated manganese oxide is subjected to waveform analysis (peak deconvolution).

2. The positive electrode according to claim 1, wherein the perlithiated manganese oxide satisfies the following formula (1-1): Formula (1-1): 0.06≦I ＴＭ / I Ｌｉ ≦0.12 In the formula (1-1), I ＴＭ and I Ｌｉ are the 2D values ​​of the perlithiated manganese oxide, respectively. ７ Li MATPASS (Magic Angle Turning Phase Adjusted Spinning Sideband) is a 1D NMR centerband spectrum extracted from the NMR spectrum, and the peak area is calculated by peak deconvolution. The peak area is the sum of the areas of the peaks in the 1000 to 2500 ppm region and the 300 to 900 ppm region.

3. 2. The positive electrode according to claim 1, wherein the perlithiated manganese oxide has a molar ratio of lithium to the remaining metals other than lithium, Li / Me, of 1.2 to 1.

5.

4. 2. The positive electrode of claim 1, wherein the molar ratio of nickel to manganese in the perlithiated manganese-based oxide is from 30:70 to 45:

55.

5. The positive electrode of claim 1 , wherein the perlithiated manganese-based oxide is represented by the following chemical formula 1: [Chemical formula 1] Li ａ Ni ｂ Co ｃ Mn ｄ M １ ｅ O ２ In the formula 1, 1.05≦a≦1.5, 0.1≦b<0.5, 0≦c<0.1, 0.5≦d≦0.9, and 0≦e≦0.1; M １ is at least one selected from the group consisting of Al, B, Co, W, Mg, V, Ti, Zn, Ga, In, Ru, Nb, Sn, Sr and Zr.

6. 6. The positive electrode according to claim 5, wherein, in Chemical Formula 1, 1.1≦a≦1.3, 0.3≦b<0.5, 0≦c≦0.05, 0.5≦d<0.7, and 0≦e≦0.

1.

7. 2. The positive electrode according to claim 1, wherein the perlithiated manganese oxide has a structure in which a rock salt phase and a layered phase are mixed.

8. The positive electrode according to claim 1 , wherein the perlithiated manganese-based oxide is represented by the following chemical formula 2: [Chemical formula 2] X Li ２ MnO ３ ・(1-^)L[Ni １－ｙ－ｚ－ｗ Mn ｙ Co ｚ M ２ ｗ ]O ２ In the above [Chemical Formula 2], M ２ is at least one selected from the group consisting of Al, B, Co, W, Mg, V, Ti, Zn, Ga, In, Ru, Nb, Sn, Sr, and Zr, and 0.2≦x≦0.5, 0.4≦y<1, 0≦z≦0.1, and 0≦w≦0.

1.

9. A lithium secondary battery comprising: a positive electrode; a negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte, wherein the positive electrode is the positive electrode according to any one of claims 1 to 8.

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