Method for analyzing positive electrode active material, positive electrode active material, positive electrode containing the same, and lithium secondary battery

Abstract

The present invention relates to a method for analyzing positive electrode active materials, positive electrode active materials, positive electrodes, and lithium secondary batteries, and comprises the steps of (S1) preparing a positive electrode active material comprising a layered structure lithium-rich manganese oxide containing a Li2MnO3 phase and a LiMO2 (where M is an element containing one or more elements selected from Ni and Mn) phase simultaneously, and manufacturing a lithium secondary battery comprising a positive electrode including a positive electrode active material layer in which the positive electrode active material is contained in an amount of 80% by weight or more relative to the total weight of the positive electrode active material layer, (S2) obtaining a specific capacity-voltage graph (X axis: specific capacity (mAh / g), Y axis: voltage (V)) obtained while activating the lithium secondary battery at 45°C at a 0.1C-rate, and (S3) linearly fitting the data in the graph in the interval where the voltage is 4.40~4.65V. The present invention relates to a method for analyzing a positive electrode active material, comprising the step of fitting it to obtain a gradient, a positive electrode active material having a gradient of 0.00110 to 0.00130 obtained by the analysis method, a positive electrode containing the same, and a lithium secondary battery.

Description

[Technical Field]

[0001] This application claims priority based on Korean Patent Application No. 10-2023-0108534 dated August 18, 2023, and all content disclosed in the documents of the said Korean Patent Application is incorporated herein by reference.

[0002] This invention relates to a method for analyzing positive electrode active material, a positive electrode active material, a positive electrode containing the same, and a lithium secondary battery. [Background technology]

[0003] Lithium-ion batteries consist of four main components: a positive electrode, a negative electrode, a separator, and an electrolyte. Of these, the positive electrode active material plays a major role in determining the battery's capacity, output, and lifespan. Improving the performance of the positive electrode active material is essential for lithium-ion batteries to have high energy density, output, and lifespan, and therefore, a lot of research has recently been conducted to develop high-performance positive electrode active materials.

[0004] Li- and Mn-rich layered oxide (LMRO), a type of cathode active material, is a mixed phase in which the Li2MnO3 phase and the LiMO2 (M=Ni,Mn,Co) phase are mixed. It can provide high energy density and high stability, making it suitable as a next-generation cathode active material. Furthermore, LMRO has a high content of relatively inexpensive Mn, and its unit cost is lower than conventional high-Ni NCM-based cathode active materials, making it a promising low-cost cathode active material.

[0005] However, when the LMRO is driven under high voltage, irreversible capacity loss occurs in the first activation process, and there is a problem that the efficiency is lower than that of the NCM-based positive electrode active material. During the charge-discharge cycle, voltage fading occurs while changing from a layered structure to a spinel structure and then to a rock salt structure, and there are problems such as the crystal structure collapsing and O2 gas being generated. In order to solve such problems, research on additives and structure improvement has been carried out, but it is still not in a commercialized situation.

[0006] On the other hand, in order to confirm the capacity characteristics of the LMRO, charge-discharge cycles must be performed after the activation process of the battery, so there is a problem that it takes a lot of time for the analysis of the capacity characteristics.

[0007] Therefore, not only is an analysis method capable of predicting the capacity characteristics of the LMRO required, but there is also a need for the development of LMRO that can further improve the performance of the battery.

Summary of the Invention

Problems to be Solved by the Invention

[0008] The problem to be solved by the present invention is to provide an analysis method for a positive electrode active material capable of predicting the capacity characteristics of LMRO by using the gradient obtained from the data of the graph obtained in the high-temperature activation (45 ° C, 0.1 C-rate) process of a lithium secondary battery.

[0009] The present invention also provides a positive electrode active material in which the gradient obtained from the data of the graph obtained by the above analysis method of the positive electrode active material satisfies a specific range.

[0010] The present invention also provides a positive electrode containing the positive electrode active material and a lithium secondary battery.

Means for Solving the Problems

[0011] To solve the above problems, the present invention provides a method for analyzing positive electrode active material, a positive electrode active material, a positive electrode, and a lithium secondary battery.

[0012] (1) The present invention provides a method for analyzing a positive electrode active material, comprising the steps of: (S1) preparing a positive electrode active material comprising a lithium-rich manganese oxide having a layered structure containing both a Li2MnO3 phase and a LiMO2 phase (where M is an element comprising one or more elements selected from Ni and Mn); and manufacturing a lithium secondary battery comprising a positive electrode including a positive electrode active material layer in which the positive electrode active material is present in an amount of 80% by weight or more relative to the total weight of the positive electrode active material layer; (S2) obtaining a specific capacity-voltage graph (X axis: specific capacity (mAh / g), Y axis: voltage (V)) obtained while activating the lithium secondary battery at 45°C at a 0.1C-rate; and (S3) obtaining a gradient by linear fitting the data in the graph in the interval where the voltage is 4.40 to 4.65V.

[0013] (2) The present invention provides a method for analyzing a positive electrode active material in which, according to (1) above, the lithium-rich manganese oxide has a ratio of the number of moles of lithium (Li) to the total number of moles of metals other than lithium (Me) (Li / Me) that is greater than 1.00 and less than or equal to 2.00.

[0014] (3) The present invention provides a method for analyzing a positive electrode active material in which, according to (1) or (2) above, the lithium-rich manganese oxide has a ratio of the number of moles of lithium (Li) to the total number of moles of metals other than lithium (Me) (Li / Me) of 1.24 to 1.36.

[0015] (4) The present invention provides a method for analyzing a positive electrode active material in any one of (1) to (3) above, wherein the lithium-rich manganese oxide has a Mn content of 50 mol% or more among the total metals other than lithium.

[0016] (5) The present invention provides a method for analyzing a positive electrode active material having a composition represented by the following chemical formula 1, in any one of (1) to (4) above. [Chemical formula 1] Li 1+x Ni a Mn b M c O2 In the aforementioned chemical formula 1, M is one or more elements selected from W, Al, B, Mo, Ti, Co, V, P, Mg, Fe, K, Ca, Na, Y, and Nb. 0.10 ≤ x ≤ 0.20, 0 <a≦0.50、0.50≦b<1.0、0≦c≦0.10である。

[0017] (6) The present invention provides a method for analyzing cathode active material in any one of (1) to (5) above, wherein the linear fitting is performed using a weighted least squares method on the Origin program to perform linear regression analysis.

[0018] (7) The present invention provides a positive electrode active material comprising a lithium-rich manganese oxide having a layered structure containing both a Li2MnO3 phase and a LiMO2 phase (wherein M is an element comprising one or more elements selected from Ni and Mn), wherein the slope of the graph obtained by linear fitting of data in the voltage range of 4.40 to 4.65 V in a specific capacity-voltage graph (X axis: specific capacity (mAh / g), Y axis: voltage (V)) obtained while activating a lithium secondary battery comprising a positive electrode containing a positive electrode active material layer in which the positive electrode active material is present at 45°C at a rate of 0.1 C-rate is 0.00115 to 0.00150.

[0019] (8) The present invention provides a positive electrode active material in which, in the present invention, the lithium-rich manganese oxide has a ratio (Li / Me) of the number of moles of lithium to the total number of moles of metals other than lithium (Me) which is greater than 1.00 and less than or equal to 2.00.

[0020] (9) In the present invention, in the above (7) or (8), the lithium-excess manganese-based oxide provides a positive electrode active material in which the ratio (Li / Me) of the number of moles of lithium (Li) to the number of moles of the total metal other than lithium (Me) is 1.24 to 1.36.

[0021] (10) In the present invention, in any one of the above (7) to (9), the lithium-excess manganese-based oxide provides a positive electrode active material in which the content of Mn in the total metal other than lithium is 50 mol% or more.

[0022] (11) In the present invention, in any one of the above (7) to (10), the lithium-excess manganese-based oxide provides a positive electrode active material having a composition represented by the following Chemical Formula 1. [Chemical Formula 1] Li 1+x Ni a Mn b M c O2 In the above Chemical Formula 1, M is one or more selected from W, Al, B, Mo, Ti, Co, V, P, Mg, Fe, K, Ca, Na, Y, and Nb, 0.10 ≦ x ≦ 0.20, 0 < a ≦ 0.50, 0.50 ≦ b < 1.0, 0 ≦ c ≦ 0.10.

[0023] (12) In the present invention, in any one of the above (7) to (11), the lithium-excess manganese-based oxide provides a positive electrode active material having a tap density of 1.5 g / cm 3 or more and 2.5 g / cm 3 or less.

[0024] (13) In the present invention, in any one of the above (7) to (12), the lithium-excess manganese-based oxide provides a positive electrode active material having an average particle diameter (D 50 ) of 2.0 μm or more and 20.0 μm or less.

[0025] (14) The present invention provides a positive electrode including the positive electrode active material according to any one of the above (7) to (13).

[0026] (15) The present invention provides a lithium secondary battery including a positive electrode according to (14) above. [Effects of the Invention]

[0027] The analytical method for positive electrode active materials according to the present invention can predict the capacity characteristics of a lithium-ion diode (LMRO) using the slope obtained from the graph data obtained during the high-temperature activation process (45°C, 0.1C-rate) of a lithium secondary battery. Therefore, the time required for performance analysis of the positive electrode active material can be reduced.

[0028] The positive electrode active material according to the present invention contains a lithium-rich manganese oxide, and when a lithium secondary battery containing the positive electrode active material is activated at 45°C at a rate of 0.1C, the specific capacity-voltage graph (X axis: specific capacity (mAh / g), Y axis: voltage (V)) obtained by linear fitting the data in the voltage range of 4.40 to 4.65V satisfies a specific range, and the battery performance, in particular, can be made excellent.

[0029] The positive electrode and lithium secondary battery according to the present invention can exhibit excellent discharge capacity characteristics. [Brief explanation of the drawing]

[0030] [Figure 1] This is a specific capacity-voltage graph (X axis: specific capacity (mAh / g), Y axis: voltage (V)) obtained when a battery containing the positive electrode active material of Example 1 was evaluated as in Experimental Example 1. [Figure 2] The graph in Figure 1 above shows the slope of the graph obtained by linear fitting data in the voltage range of 4.40 to 4.65V using the Origin program. [Modes for carrying out the invention]

[0031] The present invention will be described in more detail below to aid in understanding the present invention.

[0032] The terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather should be interpreted in a manner consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may define the concepts of terms as appropriate to best describe their invention.

[0033] In this specification, terms such as “includes,” “equip,” or “have” specify the presence of implemented features, figures, steps, components, or combinations thereof, but should be understood not to preclude the existence or possibility of adding one or more other features, figures, steps, components, or combinations thereof.

[0034] In this specification, tap density refers to the apparent density of powder obtained by filling a container of approximately 20 cc with 10 g of powder and then vibrating the container 3,000 times. This can be measured using a standard tap density meter (for example, the GEOPYC-1360 manufactured by Micromeritics).

[0035] In this specification, the average particle size (D 50 ) can be defined as the particle size corresponding to 50% of the cumulative volume distribution in the particle size distribution curve (graph curve of the particle size distribution diagram). The average particle size is calculated by dispersing the powder to be measured in a dispersion medium, introducing it into a commercially available laser diffraction particle size analyzer (for example, Microtrac's S3500), measuring the difference in diffraction patterns due to particle size as the particles pass through the laser beam to calculate the particle size distribution, and calculating the particle size at the point where the cumulative volume distribution by particle size in the measuring device reaches 50%. 50 You can obtain this.

[0036] In this specification, "primary particle" refers to the smallest particle unit recognized when observing a positive electrode active material using a scanning electron microscope (SEM), and "secondary particle" refers to a secondary structure formed by the aggregation of multiple primary particles.

[0037] Analytical methods for positive electrode active materials The present invention provides a method for analyzing a positive electrode active material, comprising the steps of: (S1) preparing a positive electrode active material comprising a layered lithium-rich manganese oxide having a Li2MnO3 phase and a LiMO2 phase (where M is an element comprising one or more elements selected from Ni and Mn), and manufacturing a positive electrode comprising a positive electrode active material layer in which the positive electrode active material is present in an amount of 80% by weight or more relative to the total weight of the positive electrode active material layer; (S2) obtaining a specific capacity-voltage graph (X axis: specific capacity (mAh / g), Y axis: voltage (V)) obtained while activating the lithium secondary battery at 45°C at a 0.1C-rate; and (S3) obtaining a gradient by linear fitting the data in the graph in the interval where the voltage is 4.40 to 4.65V.

[0038] The inventors of the present invention have discovered that when analyzing lithium-rich manganese oxides, using the gradient value of the graph drawn during the high-temperature activation process (45°C, 0.1C-rate), along with XRD and powder properties, as an evaluation criterion for the positive electrode active material, allows for more accurate and rapid analysis, further increasing reliability, and thus completed the present invention. Specifically, the inventors of the present invention confirmed that when the gradient obtained in step (S3) of the positive electrode active material analysis method of the present invention is 0.00115 to 0.00150, the discharge capacity is high at 190 mAh / g or more under 0.33C-rate conditions. In other words, according to the positive electrode active material analysis method of the present invention, it is possible to predict the discharge performance under 0.33C-rate conditions in advance using only the high-temperature activation process (45°C, 0.1C-rate) of a lithium secondary battery, thereby reducing the evaluation and analysis time of the positive electrode active material.

[0039] The following describes in more detail each step of the analytical method for positive electrode active materials according to the present invention.

[0040] (S1) Step Step (S1) is a step of preparing a positive electrode active material comprising a lithium-rich manganese oxide having a layered structure containing both a Li2MnO3 phase and a LiMO2 (where M is an element containing one or more elements selected from Ni and Mn) phase, and manufacturing a lithium secondary battery comprising a positive electrode including a positive electrode active material layer in which the positive electrode active material is present in an amount of 80% by weight or more relative to the total weight of the positive electrode active material layer.

[0041] According to the present invention, the lithium-rich manganese oxide may have a ratio of the number of moles of lithium (Li) to the total number of moles of metals other than lithium (Me) (Li / Me) that is greater than 1.00 and less than or equal to 2.00. Specifically, the lithium-rich manganese oxide may have a ratio of the number of moles of lithium (Li) to the total number of moles of metals other than lithium (Me) (Li / Me) that is 1.24 or more, 1.26 or more, 1.28 or more, or 1.32 or less, 1.34 or less, or 1.36 or less.

[0042] According to the present invention, the lithium-rich manganese oxide may have a Mn content of 50 mol% or more, specifically 60 mol% or more, and more specifically 65 mol% or more, among the total metals other than lithium.

[0043] According to the present invention, the lithium-rich manganese oxide may have a composition represented by the following chemical formula 1.

[0044] [Chemical formula 1] Li 1+x Ni a Mn b M c O2

[0045] In the aforementioned chemical formula 1, M is one or more elements selected from W, Al, B, Mo, Ti, Co, V, P, Mg, Fe, K, Ca, Na, Y, and Nb. 0.10 ≤ x ≤ 0.20, 0 <a≦0.50、0.50≦b<1.0、0≦c≦0.10である。

[0046] Specifically, x may be 0.10 or greater, 0.11 or greater, 0.12 or greater, or 0.13 or greater, and may also be 0.15 or less, 0.16 or less, 0.17 or less, 0.18 or less, 0.19 or less, or 0.20 or less.

[0047] Specifically, value a may be greater than 0, 0.10 or more, 0.15 or more, 0.20 or more, or 0.25 or more, and may also be 0.35 or less, 0.40 or less, 0.45 or less, or 0.50 or less.

[0048] Specifically, value b may be 0.50 or greater, or 0.55 or greater, and may be 0.65 or less, 0.70 or less, 0.75 or less, 0.80 or less, 0.95 or less, or less than 1.0.

[0049] Specifically, c may be 0 or greater, 0.05 or less, or 0.10 or less.

[0050] The aforementioned lithium-rich manganese oxide does not need to contain expensive cobalt.

[0051] The lithium-rich manganese oxide may be doped with tungsten.

[0052] The positive electrode can be manufactured by a conventional method for manufacturing a positive electrode, except that the positive electrode active material is used. Specifically, the positive electrode can be manufactured by coating a positive electrode active material layer-forming composition, which is prepared by dissolving or dispersing the above-mentioned positive electrode active material and, if necessary, a binder, a conductive material, and a selectively dispersant in a solvent, onto a positive electrode current collector, and then drying and rolling it; or by casting the positive electrode active material layer-forming composition onto another support, peeling it off this support, and then laminating the resulting film onto the positive electrode current collector. Here, the drying can be carried out at a temperature of 100°C to 150°C. The rolling can be carried out so that the porosity of the positive electrode is 20 to 30%. That is, the resulting porosity of the manufactured positive electrode may be 20 to 30%.

[0053] Furthermore, the positive electrode active material may be included in an amount of 80% by weight or more, specifically 80% to 99% by weight, or more specifically 85% to 98.5% by weight, relative to the total weight of the positive electrode active material layer.

[0054] Furthermore, the binder may be present in an amount greater than 0% by weight and less than or equal to 15% by weight of the total weight of the positive electrode active material layer, specifically greater than 0% by weight and less than or equal to 10% by weight, and more specifically, 0.1% to 10% by weight.

[0055] Furthermore, the conductive material may be present in an amount greater than 0% by weight and less than or equal to 15% by weight, specifically greater than 0% by weight and less than or equal to 10% by weight, and more specifically between 0.1% by weight and 10% by weight, relative to the total weight of the positive electrode active material layer.

[0056] The lithium secondary battery can be manufactured by a conventional lithium secondary battery manufacturing method. For example, the lithium secondary battery can be manufactured by first creating an electrode assembly with a separator interposed between the positive electrode and the negative electrode, then positioning the electrode assembly inside a battery case, and finally pouring in an electrolyte, but is not limited to this method.

[0057] (S2) Step Step (S2) is a step of obtaining a specific capacity-voltage graph (X axis: specific capacity (mAh / g), Y axis: voltage (V)) obtained while activating the lithium secondary battery at 45°C with a 0.1 C-rate.

[0058] (S3) Step Step (S3) is a step in which the data in the graph in the section where the voltage is 4.40 to 4.65V is linearly fitted to obtain the slope.

[0059] The aforementioned linear fitting can be performed using the weighted least squares method in the Origin program to perform linear regression analysis. In other words, the slope of the graph obtained by linear fitting may be the value analyzed by performing linear regression analysis using the weighted least squares method in the Origin program.

[0060] positive electrode active material The present invention provides a positive electrode active material comprising a lithium-rich manganese oxide having a layered structure simultaneously containing a Li2MnO3 phase and a LiMO2 phase (where M is an element comprising one or more elements selected from Ni and Mn), wherein the positive electrode comprising a positive electrode containing a positive electrode active material layer in which the positive electrode active material is present at 80% by weight or more relative to the total weight of the positive electrode active material layer is activated at 45°C at a 0.1C-rate, and the slope of the graph obtained by linear fitting of the data in the voltage range of 4.40 to 4.65V in a specific capacity-voltage graph (X axis: specific capacity (mAh / g), Y axis: voltage (V)) is 0.00115 to 0.00150.

[0061] The inventors of the present invention have found that when a positive electrode active material contains a lithium-rich manganese oxide, and a lithium secondary battery containing the positive electrode active material is activated at 45°C at a 0.1C-rate, if the slope of the graph obtained by linear fitting the data in the voltage range of 4.40 to 4.65V satisfies a specific range, then the discharge capacity of the battery containing the positive electrode active material, particularly the discharge capacity under 0.33C-rate conditions, is excellent, leading to the completion of the present invention.

[0062] On the other hand, when a lithium secondary battery containing positive electrode active material was activated at 45°C with a 0.1 C-rate, a specific capacity-voltage graph (X-axis: specific capacity (mAh / g), Y-axis: voltage (V)) was obtained. If the slope of the graph obtained by linear fitting the data in the voltage range of 4.40 to 4.65 V deviated from 0.00115 to 0.00150, there was a problem indicating poor battery performance.

[0063] According to the present invention, the lithium-rich manganese oxide may have a ratio of the number of moles of lithium (Li) to the total number of moles of metals other than lithium (Me) (Li / Me) that is greater than 1.00 and less than or equal to 2.00. Specifically, the lithium-rich manganese oxide may have a ratio of the number of moles of lithium (Li) to the total number of moles of metals other than lithium (Me) (Li / Me) that is 1.24 or more, 1.26 or more, 1.28 or more, or 1.32 or less, 1.34 or less, or 1.36 or less. In this case, the initial high-temperature activation charge capacity of the battery containing the positive electrode active material according to the present invention can be secured to a certain extent, and the charge and discharge efficiency can be improved. Furthermore, the amount of oxygen gas generated by structural collapse can be reduced when evaluating the life characteristics of the battery.

[0064] According to the present invention, the lithium-rich manganese oxide may have a Mn content of 50 mol% or more, specifically 60 mol% or more, or more specifically 65 mol% or more, among the total metals other than lithium. In this case, high capacity can be achieved even when charging at high voltage.

[0065] According to the present invention, the lithium-rich manganese oxide may have a composition represented by the following chemical formula 1. In this case, the lithium-rich manganese oxide has the advantage of high energy density and low cost. Furthermore, it has higher stability compared to NCM-based cathode active materials, which can reduce the risk of explosion in lithium secondary batteries.

[0066] [Chemical formula 1] Li 1+x Ni a Mn b M c O2

[0067] In the aforementioned chemical formula 1, M is one or more elements selected from W, Al, B, Mo, Ti, Co, V, P, Mg, Fe, K, Ca, Na, Y, and Nb. 0.10 ≤ x ≤ 0.20, 0 <a≦0.50、0.50≦b<1.0、0≦c≦0.10である。

[0068] Specifically, x may be 0.10 or greater, 0.11 or greater, 0.12 or greater, or 0.13 or greater, and may also be 0.15 or less, 0.16 or less, 0.17 or less, 0.18 or less, 0.19 or less, or 0.20 or less.

[0069] Specifically, value a may be greater than 0, 0.10 or more, 0.15 or more, 0.20 or more, or 0.25 or more, and may also be 0.35 or less, 0.40 or less, 0.45 or less, or 0.50 or less.

[0070] Specifically, value b may be 0.50 or greater, or 0.55 or greater, and may be 0.65 or less, 0.70 or less, 0.75 or less, 0.80 or less, 0.95 or less, or less than 1.0.

[0071] Specifically, c may be 0 or greater, 0.05 or less, or 0.10 or less.

[0072] The aforementioned lithium-rich manganese oxide does not need to contain expensive cobalt, and even without cobalt, it can improve the performance of lithium secondary batteries.

[0073] The lithium-rich manganese oxide may be doped with tungsten. Tungsten has higher stability and superior electrical conductivity compared to manganese, and when the lithium-rich manganese oxide is doped with tungsten, the performance and stability of the lithium secondary battery can be further improved.

[0074] According to the present invention, the lithium-rich manganese oxide has a tap density of 1.5 g / cm³. 3 More than 1.6g / cm 3 More than 1.7g / cm 3 Above, or 1.8 g / cm³ 3 It may be greater than or equal to 2.2 g / cm³. 3 Below, 2.3g / cm 3 The following, or 2.5 g / cm³ 3 The following is also acceptable. When the tap density is within the above range, the packing density of the electrodes increases, which enables high-capacity characteristics and improves cost-effectiveness.

[0075] According to the present invention, the lithium-rich manganese oxide has an average particle size (D 50 The average particle size (D) of the lithium-excess manganese oxide may be 2.0 μm or more, 2.5 μm or more, or 3.0 μm or more, and may be 15.0 μm or less, or 20.0 μm or less. 50 If the value is within the aforementioned range, the electrode can be rolled without particle cracking of the positive electrode active material, and the capacitance characteristics can be improved.

[0076] The positive electrode active material according to the present invention can be manufactured by dry mixing a composite transition metal hydroxide and a lithium-containing raw material, followed by calcination. When dry mixing the composite transition metal hydroxide and the lithium-containing raw material, a doping element-containing raw material may be further mixed in. That is, the doping element-containing raw material can be added selectively.

[0077] The positive electrode active material according to the present invention can be manufactured by adjusting the composition of the composite transition metal hydroxide, the amount of composite transition metal hydroxide mixed with the lithium-containing raw material, whether or not additional doping element-containing raw material is added, the firing temperature, the firing time, and other conditions to be optimal.

[0078] The aforementioned composite transition metal hydroxide can be produced by conventionally known coprecipitation methods and may have a composition represented by the following chemical formula 2.

[0079] [Chemical formula 2] Ni p Mn q M' r (OH)2

[0080] In the aforementioned chemical formula 2, M' is one or more elements selected from Co, W, Al, B, Mo, Ti, Co, V, P, Mg, Fe, K, Ca, Na, Y, and Nb. 0 <p≦0.50、0.50≦q<1.0、0≦r≦0.10である。

[0081] Specifically, p may be greater than 0, 0.10 or more, 0.15 or more, 0.20 or more, or 0.25 or more, and may also be 0.35 or less, 0.40 or less, 0.45 or less, or 0.50 or less.

[0082] Specifically, q may be 0.50 or more, 0.55 or more, 0.60 or more, or 0.65 or more, and may be 0.70 or less, 0.75 or less, 0.80 or less, 0.95 or less, or less than 1.0.

[0083] Specifically, r may be 0 or greater, 0.05 or less, or 0.10 or less.

[0084] The aforementioned composite transition metal hydroxide does not need to contain expensive cobalt, and even without cobalt, it can improve the performance of lithium secondary batteries.

[0085] The lithium-containing raw material is a lithium-containing raw material that can be used in the production of a positive electrode active material, and may be, for example, lithium hydroxide, lithium carbonate, or lithium oxide.

[0086] The doping element-containing raw material is a compound containing one or more selected from Co, W, Al, B, Mo, Ti, Co, V, P, Mg, Fe, K, Ca, Na, Y, and Nb. When the doping element is W, it may be tungsten oxide, and when the doping element is Mo, it may be molarized oxide, ammonium molybdate, lithium molybdate, etc.

[0087] The composite transition metal hydroxide, lithium-containing raw material, and doping element-containing raw material can be added in amounts such that the resulting lithium-rich manganese oxide has the composition represented by the chemical formula 1.

[0088] The composite transition metal hydroxide and the lithium-containing raw material can be mixed in an amount such that the ratio of the total number of moles of metal contained in the composite transition metal hydroxide to the number of moles of lithium contained in the lithium-containing raw material is greater than 1.00 and less than or equal to 2.00, specifically 1.24 to 1.36, 1.26 to 1.36, or 1.28 to 1.34.

[0089] The mixing of the composite transition metal hydroxide and the lithium-containing raw material is a dry mixing process and can be carried out using a blade mixer or an acoustic mixer.

[0090] The doping element-containing raw material can be mixed in an amount of 5,000 ppm to 20,000 ppm based on the total weight of the combined weight of the composite transition metal hydroxide and the lithium-containing raw material.

[0091] The aforementioned firing can be carried out at a temperature of 600°C to 1,000°C, specifically 880°C to 940°C, for the purpose of producing the positive electrode active material (reaction of the reaction raw materials) and improving its crystallinity, and for a period of 5 to 30 hours, specifically 9 to 21 hours, but is not limited thereto.

[0092] The aforementioned calcination can be carried out in an air atmosphere or an oxygen atmosphere in order to improve the reactivity of the reactant materials.

[0093] positive electrode The present invention provides a positive electrode containing the positive electrode active material according to the present invention.

[0094] 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 layer may include the positive electrode active material.

[0095] The positive electrode current collector is not particularly limited as long as it contains a highly conductive metal, allows for easy adhesion of the positive electrode active material layer, and is unreactive within the battery voltage range. The positive electrode current collector can be made of, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. The positive electrode current collector can also typically have a thickness of 3 μm to 500 μm, more specifically 3 μm to 50 μm, or more specifically 10 μm to 30 μm, and fine irregularities can be formed on the surface of the current collector to enhance the adhesion of the positive electrode active material. For example, it can be used in various forms such as film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0096] The positive electrode active material layer may optionally contain a conductive material and a binder along with the positive electrode active material. Here, the positive electrode active material can be included in an amount of 80% by weight or more, specifically 80% to 99% by weight, or more specifically 85% to 98.5% by weight, relative to the total weight of the positive electrode active material layer, and within this range, excellent capacitance characteristics can be observed.

[0097] The conductive material is used to impart conductivity to the electrodes and can be used without particular limitations in the battery it is configured in, as long as it does not cause chemical changes and has electronic conductivity. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. Of these, one or more can be used. The conductive material can be included in the positive electrode active material layer in an amount greater than 0% by weight and less than or equal to 15% by weight, specifically greater than 0% by weight and less than or equal to 10% by weight, and more specifically, 0.1% to 10% by weight, relative to the total weight of the positive electrode active material layer.

[0098] The binder plays a role in improving the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, and polymers in which the hydrogen atoms of these materials are substituted with Li, Na, or Ca, or various copolymers thereof. One of these materials alone or a mixture of two or more materials can be used. The binder may be present in an amount greater than 0% by weight and less than or equal to 15% by weight, specifically greater than 0% by weight and less than or equal to 10% by weight, and more specifically between 0.1% by weight and 10% by weight, relative to the total weight of the positive electrode active material layer.

[0099] The positive electrode can be manufactured by a conventional method for manufacturing a positive electrode, except that the positive electrode active material is used. Specifically, the positive electrode can be manufactured by coating a positive electrode active material layer-forming composition, which is prepared by dissolving or dispersing the positive electrode active material and, if necessary, selectively, a binder, a conductive material, and a dispersant in a solvent, onto a positive electrode current collector, and then drying and rolling it; or by casting the positive electrode active material layer-forming composition onto another support, peeling it off the support, and laminating the resulting film onto the positive electrode current collector. Here, the drying can be carried out at a temperature of 100°C to 150°C. The rolling can be carried out so that the porosity of the positive electrode is 20 to 30%. That is, the porosity of the resulting positive electrode may be 20 to 30%.

[0100] The solvent may be any solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water, and one or more of these can be used individually or in mixtures of two or more. The amount of solvent used should be sufficient to dissolve or disperse the positive electrode active material, conductive material, binder, and dispersant, taking into consideration the coating thickness of the slurry and the manufacturing yield, and to have a viscosity that allows for excellent thickness uniformity when applied for the manufacture of the positive electrode.

[0101] Lithium-ion rechargeable battery The present invention provides a lithium secondary battery including the positive electrode.

[0102] The lithium secondary battery may include a positive electrode, a negative electrode, a separator interposed between the positive and negative electrodes, and an electrolyte. The lithium secondary battery may also selectively further include a battery container for housing the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member for sealing the battery container.

[0103] The negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0104] The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys can be used. The negative electrode current collector can usually have a thickness of 3 μm to 500 μm, and, similar to the positive electrode current collector, fine irregularities can be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it can be used in various forms such as film, sheet, foil, mesh, porous material, foam, and nonwoven fabric.

[0105] The negative electrode active material layer may selectively include a binder and a conductive material together with the negative electrode active material.

[0106] As the negative electrode active material, compounds capable of reversible intercalation and deintercalation of lithium can be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO2. βExamples include metallic oxides that can be doped and dedoped with lithium, such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the metallic compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more mixtures thereof can be used. A metallic lithium thin film can also be used as the negative electrode active material. Furthermore, both low-crystallinity carbon and high-crystallinity carbon can be used as the carbon material. Typical low-crystalline carbons include soft carbon and hard carbon, while typical high-crystalline carbons include amorphous, plate-like, flaky, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbons such as petroleum or coal tar pitch-derived cokes. The anode active material can be present in an amount of 80% to 99% by weight relative to the total weight of the anode active material layer.

[0107] The binder in the negative electrode active material layer is a component that helps to bond the conductive material, active material, and current collector, and is usually added in an amount of 0.1% to 10% by weight relative to the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0108] The conductive material in the negative electrode active material layer is a component for further improving the conductivity of the negative electrode active material, and can be added in an amount of 10% by weight or less, preferably 5% by weight or less, relative to the total weight of the negative electrode active material layer. Such conductive materials are not particularly limited as long as they do not cause chemical changes in the battery and are conductive, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; carbon fluoride; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives can be used.

[0109] The negative electrode can be manufactured by coating a negative electrode active material layer-forming composition, which is prepared by dissolving or dispersing a negative electrode active material and, selectively, a binder and a conductive material in a solvent, onto a negative electrode current collector and then drying it, or by casting the negative electrode active material layer-forming composition onto another support, peeling it off the support, and then laminating the resulting film onto the negative electrode current collector.

[0110] The separator separates the negative and positive electrodes and provides a passage for lithium ions to move. It can be used without particular limitations as long as it is a separator commonly used in lithium secondary batteries. Particularly preferred is one that exhibits low resistance to ion movement of the electrolyte and has excellent electrolyte moisture absorption capacity. Specifically, porous polymer films, such as those made from polyolefin polymers like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or laminated structures of two or more layers thereof, can be used. Alternatively, ordinary porous nonwoven fabrics, such as those made from high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. Furthermore, coated separators containing ceramic components or polymeric substances may be used to ensure heat resistance or mechanical strength, and may be selectively used in single-layer or multi-layer structures.

[0111] Examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries. Specifically, the electrolyte may contain an organic solvent and a lithium salt.

[0112] The organic solvent can be used without particular limitations, as long as it can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvents include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (propylene Carbonate solvents such as carbonate (PC); alcoholic solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and can include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred.

[0113] The lithium salt can be used without particular limitations as long as it is a compound that can provide lithium ions for use in lithium secondary batteries. Specifically, the anion of the lithium salt is F - Cl - , Br - , I - NO3 - , N(CN)2 - BF4 - CF3CF2SO3 - (CF3SO2)2N - , (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2) 2CH - (SF5)3C - , (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - and (CF3CF2SO2)2N - The lithium salt may be selected from the group consisting of LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2, etc. The concentration of the lithium salt is preferably in the range of 0.1M to 2.0M. When the concentration of the lithium salt falls within this range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0114] In addition to the components of the electrolyte, the electrolyte may also contain one or more additives, such as haloalkylene carbonate compounds like difluoroethylene carbonate, pyridine, triethyl phosphite, triethyl alcoholamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethyl alcohol, or aluminum trichloride, for purposes such as improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity. Here, the additive may be present in an amount of 0.1% to 5% by weight relative to the total weight of the electrolyte.

[0115] The lithium secondary battery containing the positive electrode active material according to the present invention exhibits excellent capacity characteristics, output characteristics, and life characteristics in a stable manner, making it useful in fields such as portable devices like mobile phones, notebook computers, and digital cameras, as well as electric vehicles such as hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0116] The external shape of the lithium secondary battery of the present invention is not particularly limited, but it may be cylindrical, rectangular, pouch-type, or coin-type, using a can.

[0117] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for small devices, but also preferably as a unit battery in medium- and large-sized battery modules containing a large number of battery cells.

[0118] This provides a battery module including the lithium secondary battery as a unit cell and a battery pack including the same.

[0119] The aforementioned battery module or battery pack can be used as a power source for one or more medium-to-large devices, including power tools; electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0120] Hereinafter, embodiments of the present invention will be described in detail so that they can be easily implemented by a person with ordinary skill in the art to which the present invention pertains. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0121] Examples and Comparative Examples Example 1 Secondary particle form cathode active material precursor (composition: Ni 0.35 Mn 0.65 (OH)2) and LiOH were dry-mixed to a molar ratio of (Ni+Mn):Li of 1:1.28 to prepare a mixture. The mixture was calcined at 880°C for 9 hours under an atmospheric environment to produce a lithium-rich manganese oxide (cathode active material).

[0122] Examples 2-10 As shown in Table 1 below, the positive electrode active material was manufactured in the same manner as in Example 1, except that the molar ratio of (Ni+Mn):Li and the firing temperature were adjusted.

[0123] Comparative Examples 1-13 As shown in Table 1 below, the positive electrode active material was manufactured in the same manner as in Example 1, except that the molar ratio of (Ni+Mn):Li and the firing temperature were adjusted.

[0124] [Table 1]

[0125] Experimental example Experimental Example 1: Confirmation of the composition of lithium-rich manganese oxides After taking 0.1 g each of the lithium-rich manganese oxides produced in the above examples and comparative examples, 1 ml of hydrochloric acid was added and heated to dissolve the lithium-rich manganese oxides. Next, a small amount of hydrogen peroxide was added to accelerate the reaction and completely dissolve the lithium-rich manganese oxides to produce a solution. Then, the solution was diluted with deionized water to a total volume of 10 ml to prepare the analytical sample. Using an ICP instrument (Perkin Elmer, OPTIMA 7300DV), the weight ratio of the constituent elements present in the analytical sample was measured, and the composition of the lithium-rich manganese oxide and the ratio of the number of moles of lithium (Li) to the total number of moles of metals other than lithium (Me) in the lithium-rich manganese oxide (Li / Me) are shown in Table 2 below.

[0126] [Table 2]

[0127] Referring to Table 2, it can be confirmed that the lithium-rich manganese oxides of Examples 1 to 10 satisfy the composition represented by Chemical Formula 1 described herein, and that the ratio of moles of lithium to the total number of moles of metals other than lithium is 1.28 to 1.32.

[0128] Experimental Example 2: Confirmation of the average particle size of lithium-rich manganese oxides To confirm the average particle size of each lithium-rich manganese oxide particle produced in Examples 5 to 10, the particle size of the lithium-rich manganese oxide was measured using a PSA (Microtrac S3500), and the results are shown in Table 3 below.

[0129] [Table 3]

[0130] Referring to Table 3, it can be confirmed that the lithium-rich manganese oxides of Examples 5 to 10 have an average particle size of 9.50 μm to 9.60 μm.

[0131] Experiment Example 3: Battery Evaluation (Battery manufacturing) A positive electrode slurry was prepared by mixing 92.5% by weight of the respective positive electrode active materials produced in the above examples and comparative examples, 3% by weight of Super P as a conductive material, and 4.5% by weight of polyvinylidene fluoride (PVDF) as a binder in an N-methylpyrrolidone (NMP) solvent. The prepared positive electrode slurry was applied to one surface of an aluminum current collector (thickness: 20 μm), dried at 130°C, and then rolled to produce a positive electrode.

[0132] An electrode assembly was manufactured using a lithium metal electrode as the negative electrode, with a porous polyethylene separator interposed between the positive and negative electrodes. This assembly was placed inside a battery case, and an electrolyte solution (additives: LiBF 40.5%, FEC 3.0%) was injected, which consisted of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) mixed in a volume ratio of 3:7, with 1M LiPF6 dissolved in it, to manufacture a coin-type half-cell.

[0133] (Analysis of positive electrode active material) Using coin-type half-cells containing the positive electrode active materials of the manufactured examples and comparative examples, the cells were charged to 4.65V at 45°C with a constant current of 0.1C, then discharged to 2.0V with a constant current of 0.1C. A specific capacity-voltage graph (X axis: specific capacity (mAh / g), Y axis: voltage (V)) was obtained while performing an activation process. The slope of the graph obtained by linear fitting the data in the voltage range of 4.40 to 4.65V using the Origin program is shown in Table 4 below. The charge and discharge capacities at this time are also shown in Table 4 below, and the percentage of the discharge capacity to the charge capacity is shown in Table 4 as the efficiency of the activation process.

[0134] For reference, the gradient of the graph obtained by linear fitting is the value analyzed using weighted least squares linear regression analysis in the Origin program.

[0135] Figure 1 is a specific capacity-voltage graph (X axis: specific capacity (mAh / g), Y axis: voltage (V)) obtained when a battery containing the positive electrode active material of Example 1 was evaluated as in Experimental Example 1. Figure 2 shows the slope of the graph obtained by linear fitting the data in the voltage range of 4.40 to 4.65V in the graph of Figure 1 using the Origin program.

[0136] (Battery evaluation) After the activation process, the battery was charged to 4.4V at 25°C with a constant current of 0.1C, and then discharged to 2.5V with a constant current of 0.1C to confirm the initial charge / discharge performance. The charge / discharge process was then repeated, changing the current from 0.1C to 0.33C. This cycle was considered one cycle, and the discharge capacity was measured while repeating the charging and discharging process for a total of 30 cycles. The charge and discharge capacities in the first cycle and the percentage of the discharge capacity to the charge capacity at that time are shown in Table 4 below. The percentage of the discharge capacity in the 30th cycle to the discharge capacity in the first cycle was defined as the capacity retention rate and is also shown in Table 4 below.

[0137] [Table 4]

[0138] Referring to Table 4, in the case of the positive electrode active material of the example, it can be confirmed that the gradient obtained by the positive electrode active material analysis method satisfies 0.00115 to 0.00150, and this confirms that the capacity and efficiency in the activation process of the battery containing it, the capacity and efficiency under 0.33C-rate conditions, and the capacity retention rate are all excellent. In particular, it can be confirmed that the discharge capacity of the battery is high at 190mAh / g or more under 0.33C-rate conditions. In other words, it can be seen that by using the gradient obtained from the graph data obtained in the high-temperature activation process (45℃, 0.1C-rate) of a lithium secondary battery using the positive electrode active material analysis method according to the present invention, the capacity characteristics of the LMRO can be predicted, and the performance analysis time of the positive electrode active material can be reduced. Furthermore, in the case of the positive electrode active material according to the present invention, it contains a lithium-rich manganese oxide, and when a lithium secondary battery containing the positive electrode active material is activated at 45°C at a rate of 0.1C, the specific capacity-voltage graph (X axis: specific capacity (mAh / g), Y axis: voltage (V)) obtained by linear fitting the data in the voltage range of 4.40 to 4.65V satisfies a specific range, indicating that the battery performance, in particular, is excellent in terms of discharge capacity characteristics.

Claims

1. (S1) Li ２ MnO ３ Ai and LiMO ２ The steps of manufacturing a lithium secondary battery include: preparing a positive electrode active material containing a lithium-rich manganese oxide in a layered structure that simultaneously contains phases (where M is an element containing one or more selected from Ni and Mn), and a positive electrode containing a positive electrode active material layer in which the positive electrode active material is present in an amount of 80% by weight or more relative to the total weight of the positive electrode active material layer; (S2) The step of obtaining a specific capacity-voltage graph (X axis: specific capacity (mAh / g), Y axis: voltage (V)) obtained while activating the lithium secondary battery at 45°C at a rate of 0.1 C, (S3) A method for analyzing a positive electrode active material, comprising the step of obtaining a gradient by linear fitting of data in the section where the voltage is 4.40 to 4.65 V in the graph.

2. The method for analyzing a positive electrode active material according to claim 1, wherein the lithium-rich manganese oxide has a ratio (Li / Me) of the number of moles of lithium to the total number of moles of metals other than lithium (Me) that is greater than 1.00 and less than or equal to 2.

00.

3. The method for analyzing a positive electrode active material according to claim 1, wherein the lithium-rich manganese oxide has a ratio (Li / Me) of 1.24 to 1.36 of the number of moles of lithium (Li) to the total number of moles of metals other than lithium (Me).

4. The method for analyzing a positive electrode active material according to claim 1, wherein the lithium-rich manganese oxide has a Mn content of 50 mol% or more of the total metals other than lithium.

5. The method for analyzing a positive electrode active material according to claim 1, wherein the lithium-rich manganese oxide has a composition represented by the following chemical formula 1. [Chemical formula 1] Li １＋ｘ Ni ａ Mn ｂ M ｃ O ２ In the aforementioned chemical formula 1, M is one or more selected from W, Al, B, Mo, Ti, Co, V, P, Mg, Fe, K, Ca, Na, Y, and Nb. 0.10 ≤ x ≤ 0.20, 0 < a ≤ 0.50, 0.50 ≤ b < 1.0, and 0 ≤ c ≤ 0.

10.

6. The method for analyzing a positive electrode active material according to claim 1, wherein the linear fitting is performed using a weighted least squares method in the Origin program to perform linear regression analysis.

7. Li ２ MnO ３ phase and LiMO ２ (where M is an element containing one or more selected from Ni and Mn) a positive electrode active material containing a layered lithium-excess manganese-based oxide simultaneously containing a phase, A positive electrode active material in which a lithium secondary battery containing a positive electrode containing a positive electrode active material layer in which the positive electrode active material is present in an amount of 80% by weight or more relative to the total weight of the positive electrode active material layer is activated at 45°C at a rate of 0.1 C-rate, and the slope of the graph obtained by linear fitting of the data in the voltage range of 4.40 to 4.65 V is 0.00115 to 0.00150.

8. The positive electrode active material according to claim 7, wherein the lithium-rich manganese oxide has a ratio (Li / Me) of the number of moles of lithium to the total number of moles of metals other than lithium (Me) that is greater than 1.00 and less than or equal to 2.

00.

9. The lithium-rich manganese oxide has a ratio (Li / Me) of 1.24 to 1.36 for the number of moles of lithium (Li) to the total number of moles of metals other than lithium (Me), as described in claim 7.

10. The lithium-rich manganese oxide has a Mn content of 50 mol% or more of the total metals other than lithium, as described in claim 7.

11. The lithium-rich manganese oxide has a composition represented by the following chemical formula 1, wherein the positive electrode active material is as described in claim 7. [Chemical formula 1] Li １＋ｘ Ni ａ Mn ｂ M ｃ O ２ In the aforementioned chemical formula 1, M is one or more selected from W, Al, B, Mo, Ti, Co, V, P, Mg, Fe, K, Ca, Na, Y, and Nb. 0.10 ≤ x ≤ 0.20, 0 < a ≤ 0.50, 0.50 ≤ b < 1.0, and 0 ≤ c ≤ 0.

10.

12. The aforementioned lithium-rich manganese oxide has a tap density of 1.5 g / cm³. ３ 2.5g / cm or more ３ The positive electrode active material according to claim 7, which is as follows:

13. The lithium-rich manganese oxide has an average particle size (D ５０ The positive electrode active material according to claim 7, wherein the diameter of the ) is 2.0 μm or more and 20.0 μm or less.

14. A positive electrode comprising the positive electrode active material according to any one of claims 7 to 13.

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

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