Positive electrode active material and lithium secondary battery including the same

Abstract

To provide a positive electrode active material including an overlithiated lithium manganese-based oxide, in which, through surface modification of the lithium manganese-based oxide, the surface resistance of the lithium manganese-based oxide is reduced, thereby improving the lifetime characteristics of a lithium secondary battery using the lithium manganese-based oxide as a positive electrode active material, and a lithium secondary battery including the same.SOLUTION: A positive electrode active material includes a lithium manganese-based oxide in which a phase belonging to a C2 / m space group and a phase belonging to a R3-m space group are dissolved in a solid solution. The lithium manganese-based oxide further includes a spinel phase belonging to a Fd-3 m space group. In X-ray diffraction analysis using Cu-Kα rays for the positive electrode active material, the intensity ratio between the diffraction peaks attributed to the (003) and (104) planes satisfies a specific equation, and the intensity ratio between the diffraction peaks attributed to the (018) and (110) planes satisfies a specific equation.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a positive electrode active material and a lithium secondary battery including the same. More specifically, the present invention relates to a positive electrode active material including a lithium-excess lithium-manganese-based oxide, and to a positive electrode active material capable of improving the life characteristics of a lithium secondary battery using the lithium manganese-based oxide as a positive electrode active material by reducing the surface resistance of the lithium manganese-based oxide through surface modification of the lithium manganese-based oxide, and a lithium secondary battery including the same. [Background technology]

[0002] Batteries store electricity by using materials capable of electrochemical reaction at the positive and negative electrodes. A representative example of such batteries is a lithium secondary battery, which stores electrical energy by the difference in chemical potential when lithium ions are intercalated / deintercalated at the positive and negative electrodes.

[0003] The lithium secondary battery is manufactured by using a material capable of reversible intercalation / deintercalation of lithium ions as a positive electrode and a negative electrode active material, and filling an organic electrolyte or a polymer electrolyte between the positive electrode and the negative electrode.

[0004] A typical material used as a positive electrode active material for lithium secondary batteries is a lithium composite oxide. The lithium composite oxide is LiCoO 2 , LiMn 2 O 4 , LiNiO 2 , LiMnO 2 Alternatively, there may be oxides of Ni, Co, Mn, Al, etc. in combination.

[0005] Among the positive electrode active materials, LiCoO 2is the most widely used due to its excellent life characteristics and charge / discharge efficiency, but has a drawback in that it is expensive due to the limited availability of cobalt as a raw material, limiting its price competitiveness.

[0006] LiMnO 2 , LiMn 2 O 4 Lithium manganese oxides such as LiNiO have the advantages of being thermally safe and inexpensive, but they have problems such as small capacity and poor high-temperature properties. 2 Although the positive electrode active material based on this system shows battery characteristics such as high discharge capacity, it is difficult to synthesize it due to the problem of cation mixing between Li and transition metals, and therefore there are serious problems with the rate characteristics.

[0007] In addition, a large amount of Li by-products are generated depending on the extent of the cation mixing. The Li by-products are mostly LiOH and Li 2 CO 3 This may cause gelation during the preparation of the positive electrode paste, or may cause gas generation during repeated charging and discharging after the electrode is manufactured. 2 CO 3 This increases the swelling phenomenon of the cell and reduces the life characteristics.

[0008] To overcome these shortcomings of conventional positive electrode active materials, various candidate materials have been proposed.

[0009] For example, research is being conducted to use lithium-rich lithium manganese oxides, which contain an excess amount of Mn among transition metals and have a lithium content greater than the total content of the transition metals, as a positive electrode active material for lithium secondary batteries. Such lithium-rich lithium manganese oxides are also called overlithiated layered oxides (OLO).

[0010] Although OLO has an advantage of theoretically being able to exhibit high capacity under a high voltage operating environment, in practice, it has a disadvantage in that the rate characteristics of a lithium secondary battery using OLO are low because of its relatively low electrical conductivity due to the excessive amount of Mn contained in the oxide. If the rate characteristics are low, there is a problem in that the charge / discharge capacity and life efficiency (capacity retention) decrease during cycling of the lithium secondary battery.

[0011] In order to solve the above problems, research has been conducted into modifying the composition of OLO, but so far these efforts have not reached a commercial level. Summary of the Invention [Problem to be solved by the invention]

[0012] In the lithium secondary battery market, the growth of lithium secondary batteries for electric vehicles is playing a leading role in the market, and as a result, the demand for positive electrode active materials used in lithium secondary batteries is also continuously increasing.

[0013] For example, lithium secondary batteries using lithium iron phosphate (LFP) have been mainly used in the past due to safety concerns, but recently there has been a trend towards the use of nickel-based lithium composite oxides, which have a higher energy capacity per weight than LFP. Of course, relatively cheap LFP is still sometimes used to save costs.

[0014] In addition, nickel-based lithium composite oxides, which are currently mainly used as positive electrode active materials for high-capacity lithium secondary batteries, essentially contain ternary metal elements such as nickel, cobalt, and manganese or nickel, cobalt, and aluminum. However, since the supply and demand of cobalt is unstable and it is excessively expensive compared to other raw materials, a new positive electrode active material with a reduced cobalt content or an absence of cobalt is required.

[0015] Considering these various circumstances, lithium-rich lithium manganese-based oxides can meet the above-mentioned market expectations, but the lithium manganese-based oxides still have limitations in that they lack electrochemical properties and stability to replace positive electrode active materials such as commercially available ternary lithium composite oxides having nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) compositions.

[0016] For example, the inventors have confirmed that lithium manganese oxides are more likely to have transition metals eluted from the particle surface by repeated charge and discharge than ternary lithium composite oxides. In particular, there is a high possibility that Mn contained in excess in lithium manganese oxides will elute from the particle surface.

[0017] When a transition metal is dissolved from the lithium manganese-based oxide, the dissolved transition metal may react with an electrolyte on the surface of the lithium manganese-based oxide to form impurities, which not only increase the surface resistance of the lithium manganese-based oxide but also act as a cause of reducing the intercalation / deintercalation efficiency of lithium ions through the lithium manganese-based oxide.

[0018] As described above, compared to other types of commercially available positive electrode active materials, conventional lithium-rich lithium manganese-based oxides have disadvantages in terms of electrochemical properties and / or stability. However, the Mn of the lithium manganese-based oxide can be removed by surface modification of the lithium manganese-based oxide. 4+ Mn 2+ The inventors have confirmed that the lithium manganese-based oxide can suppress anionic redox reaction in the positive electrode of a lithium secondary battery by stabilizing an unstable surface of the lithium manganese-based oxide, thereby improving the life characteristics of the lithium secondary battery using the lithium manganese-based oxide as a positive electrode active material.

[0019] The present inventors have confirmed that the surface modification of the lithium manganese-based oxide forms a physical barrier between the lithium manganese-based oxide and an electrolyte to reduce side reactions between the lithium manganese-based oxide and an electrolyte, and that when a spinel phase is formed on at least a portion of the surface of the lithium manganese-based oxide through the surface modification, the spinel phase stabilizes the unstable surface of the lithium manganese-based oxide, thereby improving the life characteristics of a lithium secondary battery using the lithium manganese-based oxide as a positive electrode active material.

[0020] In addition, the present inventors have confirmed that when the surface resistance of the lithium manganese-based oxide is reduced through surface modification of the lithium manganese-based oxide, early deterioration of the lithium manganese-based oxide can be prevented, and thus the life characteristics of a lithium secondary battery using the lithium manganese-based oxide as a positive electrode active material can be improved.

[0021] Accordingly, the present invention aims to provide a positive electrode active material that includes a lithium-excess lithium-manganese-based oxide, and that can reduce the surface resistance of the lithium-manganese-based oxide through surface modification of the lithium-manganese-based oxide using molybdenum, thereby improving the life characteristics of a lithium secondary battery using the lithium-manganese-based oxide as a positive electrode active material.

[0022] Another object of the present invention is to provide a positive electrode including a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, wherein the positive electrode active material layer includes the positive electrode active material defined in the present application.

[0023] Another object of the present invention is to provide a lithium secondary battery that uses a positive electrode defined in the present application, thereby preventing the shortening of life caused by the excess lithium and manganese that are conventionally present in OLO. [Means for solving the problem]

[0024] According to one aspect of the present invention for solving the above technical problems, there is provided a positive electrode active material including a lithium manganese-based oxide in which a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group are dissolved.

[0025] Generally, commercially available ternary lithium composite oxides having a nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) composition have a single phase of a phase belonging to the R3-m space group, whereas the lithium-rich lithium manganese oxide defined in this application is characterized by a solid solution of a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group.

[0026] In one embodiment, the lithium manganese-based oxide may be represented by the following Formula 1:

[0027] [Chemical formula 1] rLi 2 MnO 3-c X′ c (1-r)Li a M1 x M2 y O 2-b X b (wherein M1 is at least one selected from Ni and Mn, M2 is at least one selected from Ni, Mn, Co, Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, Y, Ru, Ge, and Nd, M2 does not overlap with M1, X and X′ are each independently a halogen capable of substituting at least a part of oxygen present in the lithium manganese-based oxide, and 0 <r≦0.7、0<a≦1、0≦b≦0.1、0≦c≦0.1、0<x≦1、0≦y<1、0<x+y≦1である) The lithium manganese-based oxide may further include a spinel phase belonging to the Fd-3m space group, whereby the lithium manganese-based oxide may be a solid solution of a phase belonging to the C2 / m space group, a phase belonging to the R3-m space group, and a spinel phase belonging to the Fd-3m space group.

[0028] In one embodiment, the lithium manganese-based oxide may be represented by the following Formula 2:

[0029] [Chemical formula 2] (1-z){rLi 2 MnO 3-c X′ c (1-r)Li a M1 x M2 y O 2-b X b}·zLi(Li d Mn 2-d-e M3 e )O 4-g X″ g (wherein M1 is at least one selected from Ni and Mn, M2 is at least one selected from Ni, Mn, Co, Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, Y, Ru, Ge, and Nd, M2 does not overlap with M1, M3 is at least one selected from Ni, Co, Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, Y, Ru, Ge, and Nd, X, X′, and X″ are each independently a halogen capable of substituting at least a portion of oxygen present in the lithium manganese-based oxide, and 0 <r≦0.7、0<a≦1、0≦b≦0.1、0≦c≦0.1、0<x≦1、0≦y<1、0<x+y≦1、0<z≦0.5、0≦d≦1、0<e≦1、0≦g≦0.1である) The lithium manganese oxide may be a core-shell particle including a core portion in which a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group are dissolved, and a shell portion, which exists on at least a part of the surface of the core portion and contains a spinel phase belonging to the Fd-3m space group, In this case, the core portion and the shell portion are dissolved in each other, so that there is no interparticle boundary between the core portion and the shell portion.

[0030] A molybdenum-containing coating layer may be present on at least a portion of the surface of the shell portion.

[0031] According to another aspect of the present invention, there is provided a positive electrode comprising the positive electrode active material defined herein. Specifically, the positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and the positive electrode active material is present in the positive electrode active material layer.

[0032] According to yet another aspect of the present invention, there is provided a lithium secondary battery including the positive electrode defined herein. Specifically, the lithium secondary battery may include the positive electrode defined herein, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. Effect of the Invention

[0033] According to the present invention, it is possible to improve upon the limitations of conventional lithium-rich lithium manganese-based oxides, which have various disadvantages in terms of electrochemical properties and / or stability, as compared with commercially available ternary lithium composite oxides having a nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) composition.

[0034] Specifically, according to the present invention, Mn in the lithium manganese-based oxide is removed by surface modification of the lithium manganese-based oxide. 4+ Mn 2+ In this way, the anionic redox reaction of the lithium manganese oxide can be suppressed, and thus the unstable surface of the lithium manganese oxide can be stabilized.

[0035] The OLO such as the lithium manganese-based oxide has an advantage of exhibiting high capacity under a high voltage operating environment. However, since the possibility of side reactions occurring between the lithium manganese-based oxide and the electrolyte may increase as the operating voltage increases, it is important to reduce the side reactions between the lithium manganese-based oxide and the electrolyte.

[0036] Therefore, as the side reaction between the lithium manganese-based oxide and the electrolyte is reduced, the stability and life of the lithium secondary battery using the lithium manganese-based oxide as the positive electrode active material can be improved. In particular, the positive electrode active material in which the side reaction with the electrolyte is suppressed can operate the lithium secondary battery at a higher voltage. In this case, a spinel phase can be formed on at least a part of the surface of the lithium manganese-based oxide during the surface modification of the lithium manganese-based oxide.

[0037] In addition, according to the present invention, the surface resistance of the lithium manganese-based oxide is reduced through surface modification of the lithium manganese-based oxide, and early deterioration of the lithium manganese-based oxide is prevented, thereby improving the life characteristics of a lithium secondary battery using the lithium manganese-based oxide as a positive electrode active material.

[0038] In addition to the above-mentioned advantages, specific advantages of the present invention will be described together with the following description of the preferred embodiments of the present invention. [Brief description of the drawings]

[0039] [Figure 1] FIG. 1 is a diagram showing a surface SEM image and a surface EDS analysis result (target element: Mo) of the lithium manganese-based oxide (secondary particles) according to Example 3. [Diagram 2] FIG. 2 is a diagram showing a line scan direction of a cross-sectional SEM image of the lithium manganese oxide according to Example 3. [Diagram 3]FIG. 3 is a diagram showing a surface SEM image and a surface EDS analysis result (target element: Mo) of the lithium manganese-based oxide (secondary particles) according to Example 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] In order to make the present invention easier to understand, certain terms are defined herein for convenience. Unless otherwise defined herein, scientific and technical terms used in the present invention shall have the meanings commonly understood by those of ordinary skill in the art. Furthermore, unless otherwise specified by the context, singular terms shall be understood to include their plural forms, and plural terms shall be understood to include their singular forms.

[0041] Hereinafter, a positive electrode active material including a lithium-excess lithium manganese-based oxide according to some embodiments of the present invention and a lithium secondary battery including the positive electrode active material will be described in more detail.

[0042] positive electrode active material According to one aspect of the present invention, there is provided a positive electrode active material comprising a lithium manganese-based oxide in which a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group are dissolved.

[0043] The phase belonging to the C2 / m space group and the phase belonging to the R3-m space group can be distinguished not only by the composition of each phase but also by the specific peaks for each phase during XRD analysis. For example, the specific peak for the phase belonging to the C2 / m space group can appear in the 2θ=20.8±1° region, and the specific peak for the phase belonging to the R3-m space group can appear in the 2θ=18.6±1° region.

[0044] The lithium manganese-based oxide is a composite oxide in which a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group are dissolved, and the phase belonging to the C2 / m space group and the phase belonging to the R3-m space group coexist in the lithium manganese-based oxide. The lithium manganese-based oxide is also a composite oxide having a spinel crystal structure belonging to the Fd-3m space group (e.g., LiMn 2 O 4 or oxides having a similar composition).

[0045] The lithium manganese-based oxide contains at least lithium, manganese, and a transition metal. The transition metal may contain at least one selected from nickel, cobalt, and aluminum. The lithium manganese-based oxide may contain lithium, nickel, and manganese, and may further contain a transition metal other than nickel.

[0046] The lithium manganese-based oxide is also called an overlithiated layered oxide (OLO) because the lithium content in the lithium manganese-based oxide is greater than the total content of other transition metals (generally, the molar ratio of lithium to all metal elements other than lithium in the lithium manganese-based oxide (Li / Metal molar ratio) is greater than 1).

[0047] In addition, the lithium manganese-based oxide is also called a lithium and manganese-excess layered oxide because the manganese content in the lithium manganese-based oxide is greater than the content of other transition metals.

[0048] In general, in a commercially available ternary lithium composite oxide having a nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) composition, the manganese content in all metal elements excluding lithium is 20 mol% or less. In consideration of this, the lithium manganese-based oxide has a relatively high ratio of manganese in all metal elements (e.g., 50 mol% or more, 52 mol% or more, 53 mol% or more, or 55 mol% or more) compared to a commercially available ternary lithium composite oxide.

[0049] In addition, considering that commercially available ternary lithium composite oxides having a nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) composition have a nickel content of 60 mol% or more (80 mol% or more in the case of high-Ni type) in all metal elements excluding lithium, the lithium manganese-based oxide has a relatively low ratio of nickel to all metal elements (e.g., less than 50 mol%, 48 mol% or less, 46 mol% or less, 45 mol% or less, 44 mol% or less, 42 mol% or less, or 40 mol% or less) compared to commercially available ternary lithium composite oxides.

[0050] There is also a difference in that the Li / Metal molar ratio measured from the lithium manganese-based oxide defined in the present application is larger than that of ternary lithium composite oxides such as nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA). For example, the Li / Metal molar ratio of ternary lithium composite oxides such as nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) has a value close to 1. On the other hand, the Li / Metal molar ratio of the lithium manganese-based oxide defined in the present application is larger than 1, and preferably has a value of 1.1 to 1.6, 1.1 to 1.5, 1.2 to 1.6, or 1.2 to 1.5.

[0051] Therefore, in the present application, a lithium manganese-based oxide can be defined as a composite oxide in which the manganese content in all metal elements excluding lithium is 50 mol % or more, or a composite oxide in which the manganese content in all metal elements excluding lithium is 50 mol % or more and the nickel content is less than 50 mol %.

[0052] In addition, in the present application, the lithium manganese-based oxide may be defined as a composite oxide in which the molar ratio of lithium to all metal elements excluding lithium is greater than 1, or is a value of 1.1 to 1.6, 1.1 to 1.5, 1.2 to 1.6, or 1.2 to 1.5, and the manganese content in all metal elements excluding lithium is 50 mol% or more; or the lithium manganese content in all metal elements excluding lithium is greater than 1, or is a value of 1.1 to 1.6, 1.1 to 1.5, 1.2 to 1.6, or 1.2 to 1.5, and the manganese content in all metal elements excluding lithium is 50 mol% or more, and the nickel content is less than 50 mol%.

[0053] Despite the above-mentioned differences in composition, the lithium manganese-based oxide can also function as a composite metal oxide capable of intercalating / deintercalating lithium ions.

[0054] The lithium manganese-based oxide contained in the positive electrode active material defined herein may be present as particles including at least one primary particle.

[0055] When the lithium manganese-based oxide exists as a single primary particle, the lithium manganese-based oxide may be referred to as a single particle, whereas when the lithium manganese-based oxide exists as an aggregate of a plurality of primary particles, the lithium manganese-based oxide may be referred to as a secondary particle.

[0056] The positive electrode active material may include at least one selected from a lithium manganese-based oxide that exists as a single particle and a lithium manganese-based oxide that exists as secondary particles formed by aggregation of a plurality of primary particles.

[0057] The primary particles constituting the lithium manganese oxide may have a rod shape, an elliptical shape, and / or an irregular shape. In addition, unless otherwise intended in the manufacturing process, primary particles of various shapes are present in the same positive electrode active material. In addition, the primary particles refer to particle units that do not have grain boundaries in appearance when observed at a magnification of 5,000 to 20,000 times using a scanning electron microscope.

[0058] The primary particles constituting the lithium manganese oxide defined in the present application may have an average particle size of 0.05 μm to 5 μm, 0.05 μm to 1.0 μm, 0.1 μm to 1.0 μm, or 0.25 μm to 0.75 μm. In this case, the average particle size of the primary particles can be calculated by the average value of the length in the major axis direction and the length in the minor axis direction of the primary particles ([major axis length + minor axis length] / 2).

[0059] When the average particle size of the primary particles is less than 0.05 μm, the specific surface area of ​​the lithium manganese oxide (secondary particles) composed of the primary particles is relatively large, and in this case, the lithium manganese oxide and the electrolyte are more likely to cause a side reaction during storage or operation of the lithium secondary battery.

[0060] On the other hand, when the average particle size of the primary particles is larger than 5 μm, the growth of the primary particles is excessively induced, and the diffusion path of the lithium ions in the primary particles is also lengthened. When the diffusion path of the lithium ions in the primary particles is excessively long, the mobility of the lithium ions in the primary particles and the diffusibility of the lithium ions through the primary particles are reduced, which causes the resistance of the lithium manganese-based oxide (secondary particles) composed of the primary particles to increase.

[0061] In order to reduce the specific surface area of ​​the lithium manganese oxide and prevent a decrease in the mobility of lithium ions within the primary particles and the diffusibility of lithium ions through the primary particles, the average particle size of the primary particles may be 0.05 μm to 5 μm, 0.05 μm to 1.0 μm, 0.1 μm to 1.0 μm, or 0.25 μm to 0.75 μm.

[0062] When the lithium manganese oxide exists as secondary particles formed by agglomeration of a plurality of primary particles, the average particle size of the secondary particles may be 0.5 μm to 15 μm, 1.0 μm to 15 μm, 2.0 μm to 15 μm, 3.0 μm to 15 μm, 4.0 μm to 15 μm, or 5.0 μm to 15 μm. The average particle size of the secondary particles may vary depending on the number of the primary particles constituting the secondary particles. The average particle size (D50) of the secondary particles may be measured using a laser diffraction method. For example, the secondary particles are dispersed in a dispersion medium, introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), and irradiated with ultrasonic waves of about 28 kHz at an output of 60 W. Then, a volume cumulative particle size distribution graph is obtained, and the particle size corresponding to 50% of the volume cumulative amount is obtained.

[0063] Unless otherwise defined, the term "surface of the primary particle" used in this application means the outer surface of the primary particle exposed to the outside. Similarly, the term "surface of the secondary particle" used in this application means the outer surface of the secondary particle exposed to the outside. In this case, the "surface of the secondary particle" formed by agglomeration of a plurality of primary particles corresponds to the exposed surface of the primary particle present in the surface portion of the secondary particle.

[0064] In addition, unless otherwise defined, the term "surface portion of a particle" used in this application means a region relatively closer to the "outermost surface" of a particle, and the term "center portion of a particle" means a region relatively closer to the "middle" of a particle than the "surface portion". Thus, the term "surface portion of a primary particle" means a region relatively closer to the "outermost surface" of the primary particle, and the term "center portion of a primary particle" means a region relatively closer to the "middle" of the primary particle than the "surface portion". Similarly, the term "surface portion of a secondary particle" means a region relatively closer to the "outermost surface" of the secondary particle, and the term "center portion of a secondary particle" means a region relatively closer to the "middle" of the secondary particle than the "surface portion".

[0065] In this case, the region within any particle excluding the "surface portion of the particle" can be defined as the "center portion of the particle."

[0066] For example, when the semidiameter of the primary particle is r, the area at a distance of 0 to 0.5r from the surface of the primary particle can be defined as the surface portion of the primary particle, and the area at a distance of 0 to 0.5r from the center of the primary particle can be defined as the center portion of the primary particle. When the semidiameter of the primary particle is 0.5 μm, the surface portion of the primary particle can be defined as the area at a distance of 0 to 0.25 μm from the surface of the primary particle, and the center portion of the primary particle can be defined as the area at a distance of 0 to 0.25 μm from the center of the primary particle.

[0067] Furthermore, if necessary, when the semidiameter of the primary particle is referred to as r, a region that is 0 to 0.1r or 0 to 0.2r away from the surface of the primary particle can be defined as the surface portion of the primary particle, and a region that is 0 to 0.2r or 0 to 0.5r away from the center of the primary particle can be defined as the center portion of the primary particle.

[0068] Similarly, when the semidiameter of the secondary particle is r, the region at a distance of 0 to 0.5r from the surface of the secondary particle can be defined as the surface portion of the secondary particle, and the region at a distance of 0 to 0.5r from the center of the secondary particle can be defined as the center portion of the secondary particle. When the semidiameter of the secondary particle is 2.0 μm, the surface portion of the secondary particle can be defined as the region at a distance of 0 to 1.0 μm from the surface of the secondary particle, and the center portion of the secondary particle can be defined as the region at a distance of 0 to 1.0 μm from the center of the secondary particle.

[0069] Furthermore, if necessary, when the semidiameter of the secondary particle is referred to as r, a region that is 0 to 0.1r or 0 to 0.2r away from the surface of the secondary particle can be defined as the surface portion of the secondary particle, and a region that is 0 to 0.2r or 0 to 0.5r away from the center of the secondary particle can be defined as the center portion of the secondary particle.

[0070] The lithium manganese-based oxide defined herein may be a lithium-excess lithium manganese-based oxide represented by the following Chemical Formula 1:

[0071] [Chemical formula 1] rLi 2 MnO 3-c X′ c (1-r)Li a M1 x M2 y O 2-b X b (0 <r≦0.7、0≦c≦0.1、0<a≦1、0≦b≦0.1、0<x≦1、0≦y<1、0<x+y≦1) Here, M1 is at least one selected from Ni and Mn, M2 is at least one selected from Ni, Mn, Co, Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, Y, Ru, Ge, and Nd, and M2 does not overlap with M1.

[0072] X and X' are each independently a halogen capable of substituting at least a part of the oxygen present in the lithium manganese oxide. The type of halogen usable as X and X' can be F, Cl, Br and / or I, etc., referring to the periodic table, and preferably F.

[0073] In the above Chemical Formula 1, when M1 is Ni, M2 may include Mn, and when M1 is Mn, M2 may include Ni. Also, when M1 is Ni and Mn, M2 may be absent, or if present, may be other elements except Ni and Mn.

[0074] That is, when M1 is Ni, M2 may include at least one selected from Co, Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, Y, Ru, Ge, and Nd (preferably, at least one selected from Co, Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, and W, more preferably, at least one selected from Co, P, B, Si, Ti, Zr, and W, and even more preferably, at least one selected from P, B, and Si) and Mn.

[0075] When M1 is Mn, M2 may include at least one selected from Co, Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, Y, Ru, Ge, and Nd (preferably, at least one selected from Co, Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, and W, more preferably, at least one selected from Co, P, B, Si, Ti, Zr, and W, and even more preferably, at least one selected from P, B, and Si) and Ni.

[0076] When M1 is Ni and Mn, M2 may include at least one selected from Co, Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, Y, Ru, Ge and Nd, preferably at least one selected from Co, Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo and W, more preferably at least one selected from Co, P, B, Si, Ti, Zr and W, and even more preferably at least one selected from P, B and Si.

[0077] The lithium manganese-based oxide represented by Chemical Formula 1 may selectively contain cobalt. When the lithium manganese-based oxide contains cobalt, the mole fraction of the cobalt relative to the moles of all metal elements in the lithium manganese-based oxide may be 20% or less, preferably 15% or less, and more preferably 10% or less. In other cases, the lithium manganese-based oxide represented by Chemical Formula 1 may have a cobalt-free composition that does not contain cobalt.

[0078] The Li / Metal molar ratio measured from the lithium manganese-based oxide represented by Chemical Formula 1 may be more than 1, 1.1 to 1.6, 1.1 to 1.5, 1.2 to 1.6, or 1.2 to 1.5. When the Li / Metal molar ratio measured from the lithium manganese-based oxide has a value greater than 1, it is possible to form a lithium-excess lithium manganese-based oxide. In addition, in order for the lithium manganese-based oxide to properly form a solid solution in which a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group are solid-dissolved and to exhibit high capacity under a high voltage operating environment, it is preferable that the Li / Metal molar ratio of the lithium manganese-based oxide is 1.1 to 1.6, 1.1 to 1.5, 1.2 to 1.6, or 1.2 to 1.5.

[0079] In addition, in order to properly form a solid solution in which a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group are dissolved, the content of manganese in all metal elements excluding lithium present in the lithium manganese-based oxide represented by Chemical Formula 1 is preferably 50 mol% or more. In order for the lithium manganese-based oxide to have the OLO characteristic of exhibiting high capacity in a high voltage operating environment, the content of manganese in all metal elements excluding lithium present in the lithium manganese-based oxide may be 50 mol% or more and less than 80 mol%, 51 mol% or more and less than 80 mol%, 52 mol% or more and less than 80 mol%, 53 mol% or more and less than 80 mol%, 54 mol% or more and less than 80 mol%, 55 mol% or more and less than 80 mol%, 50 mol% or more and less than 75 mol%, 51 mol% or more and less than 75 mol%, 52 mol% or more and less than 75 mol%, 53 mol% or more and less than 75 mol%, 54 mol% or more and less than 75 mol%, or 55 mol% to 75 mol%. If the manganese content in the lithium manganese-based oxide exceeds 80 mol%, a phase transition may occur due to the movement of transition metals (especially manganese) in the lithium manganese-based oxide during formation and / or operation of the lithium secondary battery. Such phase transition may occur at random positions in the lithium manganese-based oxide, which may induce a decrease in charge / discharge capacity or voltage decay during cycling of a lithium secondary battery using the lithium manganese-based oxide as a positive electrode active material. In addition, if the manganese content in the lithium manganese-based oxide exceeds 80 mol%, a phase belonging to the R3-m space group may not be sufficiently generated.

[0080] In order to properly form a solid solution in which a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group are dissolved, the content of nickel in all metal elements excluding lithium present in the lithium manganese-based oxide represented by Chemical Formula 1 may be less than 50 mol%, 48 mol% or less, 46 mol% or less, 45 mol% or less, 44 mol% or less, 42 mol% or less, or 40 mol% or less.

[0081] When the nickel content in the lithium manganese-based oxide is 50 mol % or more, the C2 / m phase may not be sufficiently formed, and the phase belonging to the C2 / m space group and the phase belonging to the R3-m space group may not form a sufficient solid solution, which may cause phase separation during formation and / or operation of the lithium secondary battery.

[0082] Generally, commercially available ternary lithium composite oxides having a nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) composition exist as a single phase belonging to the R3-m space group.

[0083] Meanwhile, the lithium-rich lithium manganese oxide represented by the formula 1 is 2 MnO 3-c X′ c The oxides belonging to the C2 / m space group (hereafter referred to as the "C2 / m phase") and (1-r)Li a M1 x M2 y O 2-b X b In the present application, the term "a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group being solid-solved" means that oxides of the C2 / m phase and oxides of the R3-m phase are present in a state of forming a solid solution.

[0084] In this case, a complex oxide in which a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group are simply physically and / or chemically bonded or attached does not fall under the category of a solid solution as defined in this application.

[0085] For example, a composite oxide having a phase belonging to the C2 / m space group, which is formed by mixing a metal oxide having a phase belonging to the C2 / m space group with a metal oxide having a phase belonging to the R3-m space group and having a surface coated with a metal oxide having a phase belonging to the R3-m space group, does not fall under the category of a solid solution as defined in the present application.

[0086] In the lithium manganese-based oxide represented by the above formula 1, when r is greater than 0.7, the lithium manganese-based oxide is a C2 / m phase oxide, Li 2 MnO 3-c X′ c The proportion of R3-m phase oxide is preferably present at a certain ratio or more in order to sufficiently activate the C2 / m phase oxide, which has a relatively high resistance among the lithium manganese-based oxides, and improve the surface kinetics.

[0087] The lithium manganese-based oxide may further include a spinel phase belonging to the Fd-3m space group, in which case the lithium manganese-based oxide exists as a solid solution of a phase belonging to the C2 / m space group, a phase belonging to the R3-m space group, and a spinel phase belonging to the Fd-3m space group.

[0088] The spinel phase can be formed by surface modification of the lithium manganese-based oxide. The spinel phase is formed on at least a portion of the surface of the lithium manganese-based oxide (i.e., a portion or the entire surface of the lithium manganese-based oxide) by surface modification of the lithium manganese-based oxide, thereby allowing Mn in the lithium manganese-based oxide to be easily removed. 4+ Mn 2+ In this way, the anionic redox reaction of the lithium manganese oxide can be suppressed, and thus the unstable surface of the lithium manganese oxide can be stabilized.

[0089] In addition, since the spinel phase is formed on the surface of the lithium manganese-based oxide, it is different from a phase formed by a phase transition that occurs at random positions within the lithium manganese-based oxide due to the movement of transition metals (especially manganese) within the lithium manganese-based oxide.

[0090] The lithium manganese-based oxide having a solid solution of a phase belonging to the C2 / m space group, a phase belonging to the R3-m space group, and a spinel phase belonging to the Fd-3m space group can be represented by the following Chemical Formula 2.

[0091] [Chemical formula 2] (1-z){rLi 2 MnO 3-c X′ c (1-r)Li a M1 x M2 y O 2-b X b}·zLi(Li d Mn 2-d-e M3 e )O 4-g X″ g (0 <r≦0.7、0≦c≦0.1、0<a≦1、0≦b≦0.1、0<x≦1、0≦y<1、0<x+y≦1、0<z≦0.5、0≦d≦1、0<e≦1、0≦g≦0.1) Here, M1 is at least one selected from Ni and Mn, M2 is at least one selected from Ni, Mn, Co, Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, Y, Ru, Ge, and Nd, and M2 does not overlap with M1.

[0092] X, X', and X" are each independently a halogen capable of substituting at least a portion of the oxygen present in the lithium manganese oxide. The type of halogen usable as X and X' can be F, Cl, Br, and / or I, etc., referring to the periodic table, and preferably F.

[0093] The explanation regarding the phase belonging to the C2 / m space group and the phase belonging to the R3-m space group of the lithium manganese-based oxide represented by Chemical Formula 2 is the same as that of the lithium manganese-based oxide represented by Chemical Formula 1.

[0094] M3 is at least one selected from Ni, Co, Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, Y, Ru, Ge, and Nd. Preferably, M3 is Ni, and may selectively include at least one element selected from Ni, Co, Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, Y, Ru, Ge, and Nd.

[0095] In the above formula 2, the composition of the spinel phase belonging to the Fd-3m space group is zLi(Li d Mn 2-d-e M3 e )O 4-g X″ g For example, the spinel phase is represented by LiMn 1.5 Ni 0.5 O 4 It can be displayed as:

[0096] In the lithium manganese-based oxide represented by Formula 2, when z is greater than 0.5, the ratio of the spinel phase in the lithium manganese-based oxide becomes excessively high, which may ultimately increase the irreversible capacity and resistance of the positive electrode active material, resulting in a decrease in discharge capacity.

[0097] In one embodiment, the lithium manganese-based oxide may be a core-shell particle including a core portion in which a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group are dissolved, and a shell portion that exists on at least a part of the surface of the core portion and in which a spinel phase belonging to the Fd-3m space group is present. In this case, the core portion and the shell portion are dissolved in each other, so that there is no grain boundary between the core portion and the shell portion.

[0098] When the lithium manganese oxide is a core-shell particle, the ratio of the core portion to the total volume of the lithium manganese oxide may be 1% to 99%, preferably 30% to 99%, and more preferably 50% to 99%.

[0099] When the core portion is a secondary particle formed by agglomeration of a plurality of primary particles, the shell portion in which the spinel phase is present may be present on at least a part of the surface of the primary particle, i.e., the primary particle may be present as an independent particle in which a phase belonging to the C2 / m space group, a phase belonging to the R3-m space group, and a spinel phase belonging to the Fd-3m space group are solid-dissolved.

[0100] In addition, when the core portion is a secondary particle formed by agglomeration of a plurality of primary particles, the shell portion in which the spinel phase exists may be present on at least a part of the surface of the secondary particle. That is, the primary particles present inside the secondary particle and / or at the center of the secondary particle may exist as particles in which a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group are solid-dissolved, whereas the primary particles present on the outermost surface of the secondary particle and / or in a region close to the outermost surface of the secondary particle (surface portion of the secondary particle) may exist as particles in which a phase belonging to the C2 / m space group, a phase belonging to the R3-m space group and a spinel phase belonging to the Fd-3m space group are solid-dissolved.

[0101] The shell portion in which the spinel phase exists may be present in a form of being diffused from the surface of the secondary particle toward the center of the secondary particle along the boundary between the primary particles. Thus, the ratio of the spinel phase in the lithium manganese-based oxide may be higher in the surface portion of the secondary particle than in the center of the secondary particle. Similarly, the ratio of the primary particles in which the phase belonging to the C2 / m space group, the phase belonging to the R3-m space group, and the spinel phase belonging to the Fd-3m space group are solid-dissolved may be higher in the surface portion of the secondary particle than in the center of the secondary particle.

[0102] In the present application, the spinel phase may be formed by surface modification of the lithium manganese-based oxide using molybdenum, and the surface modification may form a molybdenum-containing coating layer on at least a portion of the surface of the lithium manganese-based oxide.

[0103] The molybdenum-containing coating layer can reduce the surface resistance of the lithium manganese-based oxide, thereby preventing early deterioration of the lithium manganese-based oxide and thus improving the life characteristics of a lithium secondary battery using the lithium manganese-based oxide as a positive electrode active material. In addition, the molybdenum-containing coating layer can induce the formation of a spinel phase on the surface of the lithium manganese-based oxide.

[0104] The molybdenum-containing coating layer is MoO 3 and Li 2 MoO 4 may include at least one selected from:

[0105] When the lithium manganese-based oxide exists as secondary particles formed by agglomeration of a plurality of primary particles, the molybdenum may be present at a higher concentration on the surface of the secondary particles than in the interior of the secondary particles.

[0106] When the lithium manganese-based oxide is a core-shell particle including a core portion in which a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group are dissolved, and a shell portion which exists on at least a part of the surface of the core portion and in which a spinel phase belonging to the Fd-3m space group is present, a molybdenum-containing coating layer may be present on at least a part of the surface of the shell portion.

[0107] In addition, when the core portion is a secondary particle formed by agglomeration of a plurality of primary particles, molybdenum may be present at a higher concentration on the surface of the secondary particle than in the interior of the secondary particle, and in this case, the molybdenum may form a concentration gradient that decreases from the surface of the secondary particle toward the interior of the secondary particle along the interface between the primary particles.

[0108] A positive electrode active material that has been surface-modified as defined herein may exhibit the following characteristics when subjected to X-ray diffraction analysis using Cu-Kα radiation.

[0109] In one embodiment, in an X-ray diffraction analysis using Cu-Kα radiation for the positive electrode active material, the ratio of the intensities of the diffraction peaks attributable to the (003) plane and the (104) plane satisfies the following formula 1.

[0110] [Formula 1] 1.59≦I(003) / I(104)≦2.6 The I(003) / I(104) according to the formula 1 may be 1.59 or more and 2.6 or less, 1.59 or more and 2.5 or less, 1.59 or more and 2.3 or less, 1.591 or more and 2.1 or less, or 1.591 or more and 2.012 or less.

[0111] As defined in the present application, by forming a spinel phase belonging to the Fd-3m space group in the surface-modified positive electrode active material, the intensity of the diffraction peak belonging to the (104) plane appearing in the 2θ=43.5° to 45.0° region may be weakened.

[0112] When I(003) / I(104) according to formula 1 is greater than 2.6, it means that a spinel phase is excessively formed in the lithium manganese-based oxide. In this case, the irreversible capacity and resistance of the positive electrode active material increase, and the charge / discharge capacity and discharge capacity retention of a lithium secondary battery using the lithium manganese-based oxide as a positive electrode active material may decrease.

[0113] On the other hand, when I(003) / I(104) according to the formula 1 is smaller than 1.59, it means that the spinel phase is hardly formed in the lithium manganese-based oxide. In this case, the anionic redox suppression effect of the spinel phase is insufficient, making it difficult to stabilize the unstable surface of the lithium manganese-based oxide, and making it difficult to improve the life characteristics of a lithium secondary battery using the lithium manganese-based oxide as a positive electrode active material.

[0114] In addition, in an X-ray diffraction analysis using Cu-Kα radiation on the positive electrode active material, the full width at half maximum (FWHM) of a diffraction peak belonging to a (104) plane may be 0.27 to 0.50, 0.27 to 0.40, or 0.27 to 0.382.

[0115] By forming a spinel phase belonging to the Fd-3m space group in the surface-modified positive electrode active material as defined in the present application, the half-width of the diffraction peak belonging to the (104) plane appearing in the 2θ=43.5° to 45.0° region may become large.

[0116] The half-width of the diffraction peak attributable to the (104) plane being greater than 0.50 means that a spinel phase is excessively formed in the lithium manganese-based oxide, and as a result, the irreversible capacity and resistance of the positive electrode active material increase, and the charge / discharge capacity and discharge capacity retention of a lithium secondary battery using the lithium manganese-based oxide as a positive electrode active material may decrease.

[0117] On the other hand, the half-width of the diffraction peak attributable to the (104) plane being 0.27 smaller means that almost no spinel phase is formed in the lithium manganese oxide, and in this case, the anionic redox suppression effect of the spinel phase is insufficient, making it difficult to stabilize the unstable surface of the lithium manganese oxide.

[0118] In addition, in an X-ray diffraction analysis using Cu-Kα radiation for the positive electrode active material, the ratio of the intensities of the diffraction peaks attributable to the (018) plane and the (110) plane satisfies the following formula 2.

[0119] [Formula 2] 1.15≦I(018) / I(110)≦1.55 The I(018) / I(110) according to the formula 2 may be 1.15 or more and 1.55 or less, 1.15 or more and 1.50 or less, or 1.157 or more and 1.545 or less.

[0120] By forming a spinel phase belonging to the Fd-3m space group in the surface-modified positive electrode active material as defined in the present application, the intensity of the diffraction peak belonging to the (110) plane appearing in the 2θ=64.7° to 65.5° region may be weakened.

[0121] When I(018) / I(110) according to the formula 2 is greater than 1.55, it means that a spinel phase is excessively formed in the lithium manganese-based oxide. In this case, the irreversible capacity and resistance of the positive electrode active material increase, and thus the charge / discharge capacity and discharge capacity retention of a lithium secondary battery using the lithium manganese-based oxide as a positive electrode active material may decrease.

[0122] On the other hand, when I(018) / I(110) according to the formula 2 is less than 1.15, it means that the spinel phase is hardly formed in the lithium manganese-based oxide. In this case, the anionic redox suppression effect of the spinel phase is insufficient, making it difficult to stabilize the unstable surface of the lithium manganese-based oxide, and making it difficult to improve the life characteristics of a lithium secondary battery using the lithium manganese-based oxide as a positive electrode active material.

[0123] That is, the lithium manganese-based oxide surface-modified as defined in the present application is a lithium manganese-based oxide having Mn 4+ Mn 2+ In this way, the anionic redox reaction of the lithium manganese oxide can be suppressed, and thus the unstable surface of the lithium manganese oxide can be stabilized.

[0124] In addition, the molybdenum-containing coating layer and spinel phase formed on the surface of the lithium manganese-based oxide by the surface modification act as a barrier to prevent side reactions between the lithium manganese-based oxide and the electrolyte, thereby contributing to improving the stability and lifespan of a lithium secondary battery using the lithium manganese-based oxide as a positive electrode active material. In addition, according to the present invention, the surface modification of the lithium manganese-based oxide reduces the surface resistance of the lithium manganese-based oxide, preventing early deterioration of the lithium manganese-based oxide, and thus improving the lifespan of a lithium secondary battery using the lithium manganese-based oxide as a positive electrode active material.

[0125] Lithium secondary battery According to another aspect of the present invention, there is provided a positive electrode including a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, wherein the positive electrode active material layer may include the lithium manganese-based oxide according to the various embodiments of the present invention as a positive electrode active material.

[0126] Therefore, a specific description of the lithium manganese oxide will be omitted, and only the remaining components not described above will be described below. For convenience, the lithium manganese oxide described above will be referred to as the positive electrode active material.

[0127] The positive electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and has conductivity, and may be, for example, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. The positive electrode current collector may usually have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the current collector to increase the adhesive strength of the positive electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0128] The positive electrode active material layer may be prepared by coating a positive electrode slurry composition containing the positive electrode active material, a conductive material, and optionally a binder, on the positive electrode current collector.

[0129] At this time, the positive electrode active material may be included in a content of 80 wt% to 99 wt%, more specifically, 85 wt% to 98.5 wt%, based on the total weight of the positive electrode active material layer, and excellent capacity characteristics can be exhibited when the content is within this range, but is not necessarily limited thereto.

[0130] The conductive material is used to impart conductivity to the electrode, and can be used without any particular limitation as long as it has electronic conductivity without causing chemical changes in the battery that is constructed. Specific examples include graphite such as natural graphite and artificial graphite, carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon-based materials such as carbon fibers, metal powders or metal fibers such as copper, nickel, aluminum, and silver, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, and conductive polymers such as polyphenylene derivatives, and the like, and one or more of these may be used alone or in combination. The conductive material may be contained in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0131] The binder plays a role of improving the adhesion between the positive electrode active material particles and the adhesive strength between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and among these, one type alone or a mixture of two or more types may be used. The binder may be contained in an amount of 0.1 to 15 wt% based on the total weight of the positive electrode active material layer.

[0132] The positive electrode may be manufactured by a typical method for manufacturing a positive electrode, except for using the positive electrode active material. Specifically, the positive electrode may be manufactured by dissolving or dispersing the positive electrode active material and, optionally, a binder and a conductive material in a solvent to prepare a positive electrode slurry composition, which is then coated on a positive electrode current collector, followed by drying and rolling.

[0133] 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 one or more of these may be used alone or in combination. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, and to provide a viscosity that allows excellent thickness uniformity when applied to manufacture a positive electrode, taking into consideration the coating thickness of the slurry and the production yield.

[0134] In another embodiment, the positive electrode may be manufactured by casting the positive electrode slurry composition on a separate support, peeling the positive electrode slurry composition from the support, and laminating the resulting film on a positive electrode current collector.

[0135] According to yet another aspect of the present invention, there may be provided an electrochemical device including the above-mentioned positive electrode. The electrochemical device may be, for example, a battery or a capacitor, and more specifically, a lithium secondary battery.

[0136] Specifically, the lithium secondary battery may include a positive electrode, a negative electrode facing the positive electrode, and a separator and an electrolyte interposed between the positive electrode and the negative electrode. Here, since the positive electrode is as described above, a detailed description thereof will be omitted for convenience, and only the remaining components not described above will be described in detail below.

[0137] The lithium secondary battery may optionally further include a battery container that houses an electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0138] The negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0139] The negative electrode current collector is not particularly limited as long as it has high conductivity without inducing chemical changes in the battery, and may be, for example, copper, stainless steel, aluminum, nickel, titanium, baked carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, or aluminum-cadmium alloy. The negative electrode current collector may generally have a thickness of 3 μm to 500 μm, and like the positive electrode current collector, the surface of the current collector may be formed with fine irregularities to strengthen the binding force of the negative electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or nonwoven fabric.

[0140] The negative electrode active material layer may be prepared by coating a negative electrode slurry composition containing the negative electrode active material, a conductive material, and optionally a binder, on the negative electrode current collector.

[0141] The negative electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium. Specific examples of the negative electrode active material 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, and Al alloys, and SiO β (0<β<2), SnO 2 , a metal oxide capable of doping and dedoping lithium, such as vanadium oxide or lithium vanadium oxide, or a composite containing the metallic compound and a carbonaceous material, such as a Si-C composite or a Sn-C composite, may be used. Any one or a mixture of two or more of these may be used. A thin film of metallic lithium may be used as the negative electrode active material. As the carbon material, low-crystalline carbon and high-crystalline carbon may be used. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include amorphous, plate-like, scaly, spherical or fibrous natural graphite or artificial graphite, kish graphite, pyrolytic carbon, mesophase pitch based carbon fiber, carbon microbeads, mesophase pitches, and high-temperature fired carbon such as petroleum or coal tar pitch derived cokes.

[0142] The negative electrode active material may be included in an amount of 80 wt % to 99 wt % based on the total weight of the negative electrode active material layer.

[0143] The binder is a component that aids in bonding between the conductive material, the active material, and the current collector, and may be added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0144] The conductive material may be added as a component for further improving the conductivity of the negative electrode active material in an amount of 10 wt% or less, preferably 5 wt% or less, based on the total weight of the negative electrode active material layer. Such a conductive material is not particularly limited as long as it has conductivity without inducing a chemical change in the battery, and may be, for example, graphite such as natural graphite or artificial graphite, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black, conductive fibers such as carbon fibers or metal fibers, metal powders such as carbon fluoride, aluminum, or nickel powder, conductive whiskers such as zinc oxide or potassium titanate, conductive metal oxides such as titanium oxide, or conductive materials such as polyphenylene derivatives.

[0145] In one embodiment, the negative electrode active material layer may be prepared by coating a negative electrode slurry composition 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 and drying the coating. Alternatively, the negative electrode slurry composition may be cast on a separate support, and then peeled off from the support to obtain a film, which may be laminated on the negative electrode current collector.

[0146] In another embodiment, the negative electrode active material layer may be manufactured by coating a negative electrode slurry composition 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 and drying the coating, or by casting the negative electrode slurry composition on a separate support and peeling the composition from the support to obtain a film, which may be laminated on the negative electrode current collector.

[0147] Meanwhile, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode to provide a passage for lithium ions to move. Any separator generally used in lithium secondary batteries may be used without any particular limitation. In particular, it is preferable that the separator has low resistance to ion movement of the electrolyte and has excellent electrolyte humidification ability. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of a high-melting point glass fiber, a polyethylene terephthalate fiber, or the like, may be used. In addition, in order to ensure heat resistance or mechanical strength, a separator coated with a ceramic component or a polymer material may be used, and may be selectively used as a single-layer or multi-layer structure.

[0148] In addition, examples of the electrolyte used in the present invention include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel 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.

[0149] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0150] The organic solvent may be used without any particular limitation as long as it serves as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may be an ester solvent such as methyl acetate, ethyl acetate, γ-butyrolactone, or ε-caprolactone, an ether solvent such as dibutyl ether or tetrahydrofuran, a ketone solvent such as cyclohexanone, an aromatic hydrocarbon solvent such as benzene or fluorobenzene, dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), or propylene carbonate (propylene carbonate). Carbonate-based solvents such as ethylene carbonate (PC), alcohol-based solvents such as ethyl alcohol and isopropyl alcohol, nitriles such as R-CN (R is a straight-chain, branched or cyclic hydrocarbon group having 2 to 20 carbon atoms, which may contain a double bond aromatic ring or an ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, or sulfolanes may be used. Among these, carbonate-based solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ion conductivity and high dielectric constant that can improve the charge / discharge performance of a battery and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate) is more preferred. In this case, the performance of the electrolyte may be excellent if the cyclic carbonate and the chain carbonate are mixed at a volume ratio of about 1:1 to about 1:9.

[0151] The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. 6 , LiClO 4 , LiAsF 6 , LiBF 4 , LiSbF 6 , LiAlO 4 , LiAlCl 4 , LiCF 3 SO 3 , LiC 4 F 9 SO 3 , LiN(C 2 F 5 SO 3 ), LiN(C 2 F 5 SO 2 ) 2 , LiN(CF 3 SO 2 ) 2 , LiCl, LiI, or LiB(C 2 O 4 ) 2 The lithium salt may be used at a concentration within the range of 0.1 to 2.0 M. When the lithium salt concentration is within this range, the electrolyte has appropriate conductivity and viscosity, and therefore can exhibit excellent electrolyte performance and can effectively migrate lithium ions.

[0152] When the electrolyte used in the present application is a solid electrolyte, for example, a solid inorganic electrolyte such as a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a nitride-based solid electrolyte, or a halide-based solid electrolyte may be used, and preferably, a sulfide-based solid electrolyte may be used.

[0153] As the material of the sulfide-based solid electrolyte, a solid electrolyte containing Li, an X element (wherein X is at least one selected from P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In) and S may be used. Examples of the sulfide-based solid electrolyte material include Li 2 SP2 S 5 , Li 2 SP 2 S-LiX (where X is a halogen element such as I or Cl), Li 2 SP 2 S 5 -Li 2 O, Li 2 SP 2 S 5 -Li 2 O-LiI, Li 2 S-SiS 2 , Li 2 S-SiS 2 - LiI, Li 2 S-SiS 2 -LiBr, Li 2 S-SiS 2 -LiCl, Li 2 S-SiS 2 -B 2 S 3 - LiI, Li 2 S-SiS 2 -P 2 S5-LiI, Li 2 S.B. 2 S 3 , Li 2 SP 2 S 5 -ZmSn (where m and n are integers and Z is Ge, Zn or Ga), Li 2 S-GeS 2 , Li 2 S-SiS 2 -Li 3 PO 4 , Li 2 S-SiS 2 -Li p MO q (where p, q are integers and M is P, Si, Ge, B, Al, Ga or In).

[0154] The solid electrolyte, preferably the sulfide-based solid electrolyte, may be amorphous or crystalline, or may be in a mixed amorphous and crystalline state.

[0155] As an oxide-based solid electrolyte material, Li7 La 3 Zr 2 O 12 , Li 7-x La 3 Zr 1-x Nb x O 12 , Li 7-3x La 3 Zr 2 Al x O 12 , Li 3x La 2 / 3-x TiO 3 , Li 1+x Al x Ti 2-x (PO 4 ) 3 , Li 1+x Al x Ge 2-x (PO 4 ) 3 , Li 3 PO 4 , Li 3+x PO 4-x N x (LiPON), Li 2+2x Zinc 1-x GeO 4 (LISICON), etc.

[0156] The solid electrolyte may be disposed as a separate layer (solid electrolyte layer) between the positive electrode and the negative electrode. The solid electrolyte may be included in a portion of the positive electrode active material layer of the positive electrode, independent of the solid electrolyte layer, or the solid electrolyte may be included in a portion of the negative electrode active material layer of the negative electrode, independent of the solid electrolyte layer.

[0157] In addition to the electrolyte components, the electrolyte may further contain one or more additives such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing the decrease in battery capacity, improving the discharge capacity of the battery, etc. In this case, the additives may be contained in an amount of 0.1 to 5 wt% based on the total weight of the electrolyte.

[0158] As described above, the lithium secondary battery including the positive electrode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics and life characteristics, and is therefore useful in the fields of portable devices such as mobile phones, notebook computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0159] The external shape of the lithium secondary battery according to 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, etc. Furthermore, the lithium secondary battery can be used not only as a battery cell used as a power source for a small device, but also preferably as a unit battery for a medium- to large-sized battery module including a plurality of battery cells.

[0160] According to yet another aspect of the present invention, there may be provided a battery module including the lithium secondary battery as a unit cell and / or a battery pack including the same.

[0161] The battery module or the battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool, an electric vehicle (Electric Vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV), or a power storage system.

[0162] The present invention will be described in more detail below with reference to examples. However, these examples are for the purpose of illustrating the present invention, and the scope of the present invention is not to be construed as being limited by these examples.

[0163] Production Example 1. Production of positive electrode active material Comparative Example 1 (a) Preparation of precursor NiSO in the reactor 4 6H 2 O and MnSO 4 H 2 O in a 40:60 molar ratio, NaOH and NH 4 The temperature in the reactor was maintained at 45° C., and N 2 The precursor synthesis reaction was carried out while feeding the gas. After the reaction was completed, the material was washed and dehydrated to obtain Ni with an average particle size of about 12 μm. 0.4 Mn 0.6 (OH) 2 The precursor was obtained.

[0164] (b) First heat treatment The precursor obtained in step (a) was heat-treated at 550° C. in an air atmosphere for 5 hours, and then cooled in a furnace to obtain a precursor in an oxide state.

[0165] (c) Second heat treatment The oxide precursor obtained in step (b) was mixed with a lithium source material LiOH (Li / (Li-excluded metal) molar ratio=1.28) to prepare a mixture.

[0166] Next, O 2 The mixture was heat-treated at 900° C. for 8 hours in an atmosphere, and then cooled in a furnace and classified to obtain a lithium manganese oxide that was not surface-modified.

[0167] Comparative Example 2 2.0 mol% (NH 4 ) 6 Mo 7 O 24 Add NH 3 H 2 A coating solution was prepared whose pH was adjusted to 9-10 using O.

[0168] The lithium manganese oxide obtained in Comparative Example 1 was added to the coating solution, and then stirred at 300 rpm for 30 minutes, and further stirred at 300 rpm at 80° C. for about 12 hours until the water evaporated. Then, it was further dried at 150° C. for 12 hours to prepare a mixture.

[0169] Next, O 2 The mixture was heat-treated at 750° C. for 8 hours in a nitrogen atmosphere, and then cooled in a furnace and classified to obtain Li on the surface. 2 MoO 4 As a result, a lithium manganese-based oxide having a coating layer containing the above-mentioned was obtained.

[0170] Comparative Example 3 The lithium manganese oxide obtained in Comparative Example 1 and 1.0 mol% (NH 4 ) 6 Mo 7 O 24 were dry mixed to prepare a mixture.

[0171] Next, O 2 The mixture was heat-treated at 600° C. for 8 hours in an atmosphere, and then cooled in a furnace and classified to obtain a lithium manganese oxide.

[0172] The lithium manganese oxide was dry mixed with (NH 4 ) 6 Mo 7 O 24 Since most of the Mo still exists in the form of large powder even after heat treatment, it was removed during the classification process, and it was confirmed that no coating layer containing Mo was formed on the surface of the lithium manganese oxide.

[0173] Example 1 100 ml of deionized water with 0.5 mol% (NH 4 ) 6 Mo 7 O 24 Add NH 3 H 2 A coating solution was prepared whose pH was adjusted to 9-10 using O.

[0174] The lithium manganese oxide obtained in Comparative Example 1 was added to the coating solution, and then stirred at 300 rpm for 30 minutes, and further stirred at 80° C. at 300 rpm for about 12 hours until the water evaporated. Then, it was further dried at 150° C. for 12 hours to prepare a mixture.

[0175] Next, O 2 The mixture was heat-treated at 600°C in a nitrogen atmosphere for 8 hours, then cooled in a furnace and classified to form MoO 3 As a result, a lithium manganese-based oxide having a coating layer containing the above-mentioned was obtained.

[0176] Example 2 1.0 mol% (NH 4 ) 6 Mo 7 O 24 Add NH 3 H 2 A coating solution was prepared whose pH was adjusted to 9-10 using O.

[0177] The lithium manganese oxide obtained in Comparative Example 1 was added to the coating solution, and then stirred at 300 rpm for 30 minutes, and further stirred at 300 rpm at 80° C. for about 12 hours until the water evaporated. Then, it was further dried at 150° C. for 12 hours to prepare a mixture.

[0178] Next, O 2 The mixture was heat-treated at 600°C in a nitrogen atmosphere for 8 hours, then cooled in a furnace and classified to form MoO 3 As a result, a lithium manganese-based oxide having a coating layer containing the above-mentioned was obtained.

[0179] Example 3 1.5 mol% (NH 4 ) 6 Mo 7 O 24 Add NH 3 H 2 A coating solution was prepared whose pH was adjusted to 9-10 using O.

[0180] The lithium manganese oxide obtained in Comparative Example 1 was added to the coating solution, and then stirred at 300 rpm for 30 minutes, and further stirred at 300 rpm at 80° C. for about 12 hours until the water evaporated. Then, it was further dried at 150° C. for 12 hours to prepare a mixture.

[0181] Next, O 2 The mixture was heat-treated at 600°C in a nitrogen atmosphere for 8 hours, then cooled in a furnace and classified to form MoO 3 As a result, a lithium manganese-based oxide having a coating layer containing the above-mentioned was obtained.

[0182] Example 4 100 ml of deionized water with 0.5 mol% (NH 4 ) 6 Mo 7 O 24 Add NH3 H 2 A coating solution was prepared whose pH was adjusted to 9-10 using O.

[0183] The lithium manganese oxide obtained in Comparative Example 1 was added to the coating solution, and then stirred at 300 rpm for 30 minutes, and further stirred at 300 rpm at 80° C. for about 12 hours until the water evaporated. Then, it was further dried at 150° C. for 12 hours to prepare a mixture.

[0184] Next, O 2 The mixture was heat-treated at 750° C. for 8 hours in a nitrogen atmosphere, and then cooled in a furnace and classified to obtain Li on the surface. 2 MoO 4 As a result, a lithium manganese-based oxide having a coating layer containing the above-mentioned was obtained.

[0185] Example 5 1.0 mol% (NH 4 ) 6 Mo 7 O 24 Add NH 3 H 2 A coating solution was prepared whose pH was adjusted to 9-10 using O.

[0186] The lithium manganese oxide obtained in Comparative Example 1 was added to the coating solution, and then stirred at 300 rpm for 30 minutes, and further stirred at 300 rpm at 80° C. for about 12 hours until the water evaporated. Then, it was further dried at 150° C. for 12 hours to prepare a mixture.

[0187] Next, O 2 The mixture was heat-treated at 750° C. for 8 hours in a nitrogen atmosphere, and then cooled in a furnace and classified to obtain Li on the surface. 2 MoO 4 As a result, a lithium manganese-based oxide having a coating layer containing the above-mentioned was obtained.

[0188] Comparative Example 4 The surface obtained in Example 5 was coated with Li 2 MoO 4 The lithium manganese-based oxide having a coating layer containing Mo was added to 100 ml of deionized water and stirred at 300 rpm for 10 minutes. After filtering, the lithium manganese-based oxide remaining on the filter was dried at 150°C for 12 hours to obtain a final product. By washing the lithium manganese-based oxide with deionized water, it was confirmed that no coating layer containing Mo was formed on the surface of the lithium manganese-based oxide in the final product.

[0189] Manufacturing example 2. Manufacturing of lithium secondary battery (half cell) A positive electrode slurry was prepared by dispersing 90 wt% of the positive electrode active material prepared in Preparation Example 1, 5.5 wt% of carbon black, and 4.5 wt% of PVDF binder in 30 g of N-methyl-2-pyrrolidone (NMP). The positive electrode slurry was uniformly applied to a thin aluminum film having a thickness of 15 μm and dried in a vacuum at 135° C. to prepare a positive electrode for a lithium secondary battery.

[0190] Lithium foil was used as the counter electrode for the positive electrode, a porous polyethylene film (Celgard 2300, thickness: 25 μm) was used as the separator, and LiPF was dissolved in a solvent containing ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a volume ratio of 2:4:4. 6 A half-cell was fabricated using an electrolyte in which Zn was present at a concentration of 1.15M.

[0191] Manufacturing example 3. Manufacturing of lithium secondary batteries (full cells) 90 wt % of the positive electrode active material prepared in Preparation Example 1, 4.5 wt % of carbon black, and 5.5 wt % of PVDF binder were dispersed in N-methyl-2-pyrrolidone (NMP) to prepare a positive electrode slurry.

[0192] The positive electrode slurry was uniformly applied to a thin aluminum film having a thickness of 15 μm and dried in a vacuum at 135° C. to prepare a positive electrode for a lithium secondary battery having a positive electrode active material layer formed thereon.

[0193] A graphite electrode was used as a counter electrode for the positive electrode, a porous polyethylene film (Celgard 2300, thickness: 25 μm) was used as a separator, and LiPF was dissolved in a solvent containing ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a volume ratio of 2:4:4. 6 A full cell was fabricated using an electrolyte in which Zn was present at a concentration of 1.15M.

[0194] Experimental Example 1. SEM / EDS analysis of positive electrode active material The lithium manganese-based oxides selected from the positive electrode active materials according to Examples 3 and 4 were subjected to SEM / EDS analysis to confirm the surface modification of the lithium manganese-based oxides.

[0195] Referring to Fig. 1 showing a surface SEM image and a surface EDS analysis result (target element: Mo) of the lithium manganese oxide (secondary particles) according to Example 3 and Fig. 3 showing a surface SEM image and a surface EDS analysis result (target element: Mo) of the lithium manganese oxide (secondary particles) according to Example 4, it was confirmed that the lithium manganese oxide exists as secondary particles formed by agglomeration of a plurality of primary particles, and that the target element Mo exists on the surface of the lithium manganese oxide. In addition, it was confirmed from the EDS mapping result that Mo exists in a higher concentration on the surface of the secondary particles than inside the secondary particles.

[0196] In addition, as shown in Figure 2, a cross-sectional SEM image of the lithium manganese-based oxide selected from the positive active material of Example 3 was obtained, and then EDS mapping was performed on the target elements Ni, Mn, and Mo, and the concentrations (at%) of Ni, Mn, and Mo were confirmed at designated points (circles 1, 2, and 3) in the lithium manganese-based oxide through line scanning. The measurement results are shown in Table 1 below.

[0197] [Table 1]

[0198] Referring to the results in Table 1, it can be seen that molybdenum is present at a higher concentration on the surface of the secondary particles than inside the secondary particles.

[0199] Experimental Example 2: XRD analysis of positive electrode active material X-ray diffraction (XRD) analysis was performed on each of the positive electrode active materials prepared in Preparation Example 1 to confirm the space group and coating material of the phase present in the lithium manganese-based oxide contained in the positive electrode active material, and peaks belonging to the (003), (018), (104), and (110) crystal planes of the lithium manganese-based oxide were detected. The XRD analysis was performed using a Bruker D8 Advance diffractometer using Cu-Kα radiation (1.540598 Å).

[0200] Specifically, in the diffraction pattern obtained from the XRD analysis, a peak specific to the phase belonging to the C2 / m space group can appear in the 2θ=20.8±1° region, and a peak specific to the phase belonging to the R3-m space group can appear in the 2θ=18.6±1° region. The presence or absence of the formation of a spinel phase belonging to the Fd-3m space group can be confirmed from a change in the peak specific to the (104) plane that appears in the 2θ=43.5°-45.0° region and a change in the peak specific to the (110) plane that appears in the 2θ=64.7°-65.5° region.

[0201] In addition, in the diffraction pattern obtained from the XRD analysis, a peak specific to the Mo-containing coating layer can be observed at around 2θ=30°. For example, 2 MoO 4 A peak specific to MoO can be seen in the 2θ = 29.8 ± 0.3° region. 3 A peak specific to the above can appear in the 2θ=30.7±0.3° region.

[0202] The XRD analysis results are shown in Tables 2 and 3 below.

[0203] [Table 2]

[0204] [Table 3]

[0205] When a spinel phase belonging to the Fd-3m space group is formed in the lithium manganese-based oxide, the peak specific to the (104) plane and the peak specific to the (110) plane collapse. Therefore, the results for the peak specific to the (104) plane were calculated based on the highest intensity of the pattern appearing in the 2θ=43.5° to 45.0° region, and the results for the peak specific to the (110) plane were calculated based on the highest intensity of the pattern appearing in the 2θ=64.7° to 65.5° region.

[0206] Experimental Example 3: Evaluation of the electrochemical characteristics of a lithium secondary battery (half cell) The lithium secondary battery (half cell) manufactured in Manufacturing Example 2 was subjected to a charge-discharge experiment at 25° C., voltage range of 2.0 V to 4.6 V, and discharge rates of 0.1 C and 2.0 C using an electrochemical analyzer (Toyo, Toscat-3100) to measure the initial charge capacity, initial discharge capacity, initial reversible efficiency, and rate capability (rate capability (C-rate)). For reference, in the case of Comparative Example 3, the lithium manganese oxide and the dry-mixed Li 2 MoO4 Since most of the lithium manganese oxides remain in the form of large particles even after heat treatment, they are removed by the classification process, and the surface of the lithium manganese oxides is left with Li 2 Since the coating layer containing MoO4 was not formed, it was expected to be substantially the same as Comparative Example 1, and therefore the half cell was excluded from the evaluation of the electrochemical properties.

[0207] The measurement results are shown in Table 4 below.

[0208] [Table 4]

[0209] Referring to the evaluation results of the half cells in Table 4, it was confirmed that in the case of the lithium secondary battery using the positive electrode active material according to Comparative Example 2, the spinel phase in the positive electrode active material was excessively formed, and thus the electrochemical characteristics were deteriorated compared to Comparative Example 1. In addition, in the case of the lithium secondary battery using the positive electrode active material according to Comparative Example 4, although the spinel phase was present in the positive electrode active material, not only was the Mo-containing coating layer removed through the subsequent washing process, but defects were also generated on the surface of the positive electrode active material through the washing process, and thus the electrochemical characteristics were rapidly deteriorated.

[0210] Experimental Example 4. Evaluation of the electrochemical characteristics of a lithium secondary battery (full cell) The lithium secondary battery (full cell) manufactured in Manufacturing Example 3 was subjected to a 6-cycle formation process at 25°C, voltage range 2.0V to 4.6V, and 0.2C / 0.2C using an electrochemical analyzer (Toyo, Toscat-3100), and then charged and discharged 500 times at 25°C, voltage range 2.0V to 4.6V, and 1C / 1C. st Cycle) Discharge capacity, 500% of initial discharge capacity th The ratio of discharge capacity per cycle (cycle capacity retention) was measured.

[0211] The measurement results are shown in Table 5 below.

[0212] [Table 5]

[0213] Referring to the results of Table 5, it was confirmed that Comparative Example 1, which showed similar electrochemical characteristics to those of the Examples in the half cell evaluation results, had excessively poor long-term life characteristics compared to the Examples. As a result, it was confirmed that the cathode active material defined in the present application is more suitable for ensuring long-term stable life characteristics of a lithium secondary battery than the cathode active material according to Comparative Example 1.

[0214] Although the embodiments of the present invention have been described above, a person having ordinary knowledge in the art may modify and change the present invention in various ways by adding, changing, deleting or adding elements without departing from the concept of the present invention described in the claims, and this may also be considered to be within the scope of the claims of the present invention.

Claims

1. A positive electrode active material comprising a lithium manganese-based oxide in which a phase belonging to a C2 / m space group and a phase belonging to an R3-m space group are dissolved, The lithium manganese-based oxide further includes a spinel phase belonging to the Fd-3m space group, In an X-ray diffraction analysis of the positive electrode active material using Cu-Kα radiation, the ratio of the intensities of the diffraction peaks attributable to the (003) plane and the (104) plane satisfies the following formula 1: A positive electrode active material, in which a ratio of the intensities of the diffraction peaks belonging to the (018) plane and the (110) plane satisfies the following formula 2: [Formula 1] 1.59≦I(003) / I(104)≦2.6 [Formula 2] 1.15≦I(018) / I(110)≦1.55

2. 2. The positive electrode active material according to claim 1, wherein the full width at half maximum (FWHM) of a diffraction peak belonging to a (104) plane in an X-ray diffraction analysis using Cu-Kα radiation for the positive electrode active material is 0.27 to 0.

50.

3. The positive electrode active material of claim 1 , wherein the lithium manganese-based oxide is represented by the following Chemical Formula 1: [Chemical formula 1] rLi ２ MnO ３－ｃ X′ ｃ ・(1-r)Li ａ M1 ｘ M2 ｙ O ２－ｂ X ｂ (where: M1 is at least one selected from Ni and Mn; M2 is at least one selected from Ni, Mn, Co, Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, Y, Ru, Ge, and Nd, and M2 does not overlap with M1; X and X' are each independently a halogen capable of substituting at least a portion of the oxygen present in the lithium manganese oxide; 0<r≦0.7, 0<a≦1, 0≦b≦0.1, 0≦c≦0.1, 0<x≦1, 0≦y<1, 0<x+y≦1).

4. 2. The positive electrode active material according to claim 1, wherein the lithium manganese-based oxide is a solid solution of a phase belonging to a C2 / m space group, a phase belonging to an R3-m space group, and a spinel phase belonging to an Fd-3m space group.

5. The positive electrode active material of claim 4 , wherein the lithium manganese-based oxide is represented by the following Chemical Formula 2: [Chemical formula 2] <h2 style=";text-align:left;direction:ltr">(1)<h2 style=";text-align:left;direction:ltr"> ２ <h2 style=";text-align:left;direction:ltr"> MnO<h2 style=";text-align:left;direction:ltr"> ３－ｃ <h2 style=";text-align:left;direction:ltr"> 8′<h2 style=";text-align:left;direction:ltr"> ｃ <h2 style=";text-align:left;direction:ltr"> (1)<h2 style=";text-align:left;direction:ltr"> ａ <h2 style=";text-align:left;direction:ltr"> 11<h2 style=";text-align:left;direction:ltr"> ｘ <h2 style=";text-align:left;direction:ltr"> 12<h2 style=";text-align:left;direction:ltr"> ｙ <h2 style=";text-align:left;direction:ltr"> O<h2 style=";text-align:left;direction:ltr"> ２－ｂ <h2 style=";text-align:left;direction:ltr"> 5<h2 style=";text-align:left;direction:ltr"> ｂ <h2 style=";text-align:left;direction:ltr"> I'm sorry<h2 style=";text-align:left;direction:ltr"> ｄ <h2 style=";text-align:left;direction:ltr"> 4Mn<h2 style=";text-align:left;direction:ltr"> ２－ｄ <h2 style=";text-align:left;direction:ltr"> -eM3<h2 style=";text-align:left;direction:ltr"> ｅ <h2 style=";text-align:left;direction:ltr"> )O<h2 style=";text-align:left;direction:ltr"> ４－ｇ <h2 style=";text-align:left;direction:ltr"> 8″<h2 style=";text-align:left;direction:ltr"> ｇ (where: M1 is at least one selected from Ni and Mn; M2 is at least one selected from Ni, Mn, Co, Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, Y, Ru, Ge, and Nd, and M2 does not overlap with M1; M3 is at least one selected from Ni, Co, Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, Y, Ru, Ge, and Nd; X, X', and X" are each independently a halogen capable of substituting at least a portion of the oxygen present in the lithium manganese oxide; 0<r≦0.7, 0<a≦1, 0≦b≦0.1, 0≦c≦0.1, 0<x≦1, 0≦y<1, 0<x+y≦1, 0<z≦0.5, 0≦d≦1, 0<e≦1, 0≦g≦0.1).

6. The spinel phase is LiMn １．５ Ni ０．５ O ４ The positive electrode active material according to claim 5 , wherein

7. The lithium manganese oxide is A core portion in which a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group are solid-dissolved; a shell portion present on at least a part of the surface of the core portion and including a spinel phase belonging to the Fd-3m space group; 2. The positive electrode active material according to claim 1, wherein the core portion and the shell portion are core-shell particles in which the core portion and the shell portion are solid-dissolved.

8. the core portion is a secondary particle formed by agglomeration of a plurality of primary particles, The positive electrode active material according to claim 7 , wherein the shell portion is present on at least a portion of a surface of the primary particle.

9. the core portion is a secondary particle formed by agglomeration of a plurality of primary particles, The positive electrode active material according to claim 7 , wherein the shell portion is present on at least a part of a surface of the secondary particle.

10. The positive electrode active material according to claim 7 , wherein a molybdenum-containing coating layer is present on at least a portion of a surface of the shell portion.

11. The molybdenum-containing coating layer is MoO ３ and Li ２ MoO ４ The positive electrode active material according to claim 10 , comprising at least one selected from the group consisting of:

12. The lithium manganese oxide exists as secondary particles formed by agglomeration of a plurality of primary particles, 2. The positive electrode active material according to claim 1, wherein molybdenum is present at a higher concentration on the surface of the secondary particles than in the interior of the secondary particles.

13. The lithium manganese oxide exists as secondary particles formed by agglomeration of a plurality of primary particles, 2. The cathode active material of claim 1, wherein a gradient of decreasing molybdenum concentration exists along the interface between the primary particles from the surface of the secondary particle to the interior of the secondary particle.

14. A positive electrode comprising the positive electrode active material according to claim 1 .

15. A lithium secondary battery comprising the positive electrode according to claim 14.

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