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

Abstract

The present invention relates to a method for analyzing a positive electrode active material, a positive electrode active material having a slope of 0.00110 to 0.00130 measured by the analysis method, and a positive electrode and a lithium secondary battery comprising the same, the method comprising: (S1) preparing a positive electrode active material comprising a lithium-rich manganese oxide; the lithium-rich manganese oxide has a layered structure including a Li2MnO3 phase and a LiMO2 phase (where M is an element including at least one element selected from Ni and Mn), and a lithium secondary battery including a positive electrode including a positive electrode active material layer is manufactured, where M is an element including at least one element selected from Ni and Mn relative to the total weight of the positive electrode active material layer, and M is an element including at least one element selected from Ni and Mn relative to the total weight of the positive electrode active material layer. The positive electrode active material layer includes the positive electrode active material in an amount of at least 80 wt%; (S2) obtaining a specific capacity-voltage map (X-axis: specific capacity (mAh / g), Y-axis: voltage (V)) by activating the lithium secondary battery at a rate of 0.1 C at 45 DEG C; and (S3) applying a linear fit to the data in the voltage range of 4.40 to 4.65 V in the map to obtain a slope.

Description

Technical Field

[0001] This application claims priority to Korean Patent Application No. 10-2023-0108534, filed on August 18, 2023, the disclosure of which is incorporated herein by reference.

[0002] This invention relates to analytical methods for positive electrode active materials, positive electrode active materials, and positive electrodes and lithium secondary batteries including the same. Background Technology

[0003] Lithium-ion batteries consist of four key components: the positive electrode, the negative electrode, the separator, and the electrolyte. In particular, the positive electrode active material contained in the positive electrode is a crucial factor determining the battery's capacity, power output, and lifespan. To achieve high energy density, power output, and lifespan in lithium-ion batteries, it is necessary to improve the performance of the positive electrode active material; therefore, extensive research has recently been conducted to develop high-performance positive electrode active materials.

[0004] Layered oxides rich in Li and Mn (LMRO) (a cathode active material) are mixed phases composed of Li₂MnO₃ and LiMO₂ (M = Ni, Mn, Co), offering high energy density and enhanced stability, making them suitable as next-generation cathode active materials. Furthermore, the high Mn content (a relatively inexpensive element) in LMRO makes it a more cost-effective option compared to typical high-Ni NCM cathode materials.

[0005] However, LMRO experiences irreversible capacity loss during the first formation process at high voltages, resulting in reduced efficiency compared to NCM-based cathode materials. Furthermore, it undergoes structural changes from layered to spinel and ultimately to rock salt structures, leading to voltage decay and O2 gas release due to crystal structure degradation. To address these issues, research is underway to achieve enhanced additives or structures, but commercialization has not yet been achieved.

[0006] Meanwhile, in order to evaluate the capacity characteristics of LMRO, a charge-discharge cycle is required after the battery activation process, which makes the capacity characteristic analysis very time-consuming.

[0007] Therefore, it is not only necessary to develop analytical methods for predicting the capacity characteristics of LMRO, but also to develop LMROs that exhibit further improved battery performance. Summary of the Invention

[0008] Technical issues

[0009] The objective of this invention is to provide an analytical method for positive electrode active materials that can predict LMRO capacity characteristics by using the slope obtained from data in a graph obtained from a high-temperature activation (45°C, 0.1 C rate) process of a lithium secondary battery.

[0010] Furthermore, the present invention provides a positive electrode active material wherein the slope obtained from data of a graph obtained by analyzing the positive electrode active material satisfies a specific range.

[0011] Furthermore, the present invention provides a positive electrode comprising a positive electrode active material and a lithium secondary battery.

[0012] Technical solution

[0013] To address the aforementioned issues, this invention provides an analytical method for positive electrode active materials, positive electrode active materials, and a positive electrode and a lithium secondary battery comprising the same.

[0014] (1) The present invention provides a method for analyzing positive electrode active materials, the method comprising: (S1) preparing a positive electrode active material comprising lithium-rich manganese oxide having a layered structure comprising a Li2MnO3 phase and a LiMO2 phase (where M is an element comprising at least one selected from Ni and Mn), and manufacturing a lithium secondary battery comprising a positive electrode containing a positive electrode active material layer, wherein the positive electrode active material layer comprises at least 80% by weight of the positive electrode active material relative to the total weight of the positive electrode active material layer; (S2) activating the lithium secondary battery at 0.1 C rate at 45°C to obtain a specific capacity-voltage graph (X-axis: specific capacity (mAh / g), Y-axis: voltage (V)); and (S3) applying linear fitting to the data in the voltage range of 4.40 to 4.65 V in the graph to obtain a slope.

[0015] (2) The present invention provides the method described in (1) above, wherein the lithium-rich manganese oxide exhibits a Li / Me molar ratio (the molar ratio of lithium (Li) to all metals (Me) other than lithium) greater than 1.00 and less than 2.00.

[0016] (3) The present invention provides the method described in (1) or (2) above, wherein the lithium-rich manganese oxide exhibits a Li / Me molar ratio of 1.24 to 1.36 (the molar ratio of lithium (Li) to all metals (Me) other than lithium).

[0017] (4) The present invention provides the method of any one of (1) to (3) above, wherein the lithium-rich manganese oxide contains Mn accounting for at least 50 moles of all metals other than lithium.

[0018] (5) The present invention provides the method according to any one of (1) to (4) above, wherein the lithium-rich manganese oxide has a composition represented by the following formula 1: [Formula 1] Li 1+x Ni a Mn b M c O2 Wherein, in the above formula 1, M is at least one selected from W, Al, B, Mo, Ti, Co, V, P, Mg, Fe, K, Ca, Na, Y, and Nb, and 0.10 ≤ x ≤ 0.20, 0 < a ≤ 0.50, 0.50 ≤ b < 1.0, and 0 ≤ c ≤ 0.10.

[0019] (6) The present invention provides the method according to any one of (1) to (5) above, wherein the linear fitting includes performing linear regression analysis using the weighted least squares method in the Origin program.

[0020] (7) The present invention provides a positive electrode active material containing a lithium-rich manganese oxide, the lithium-rich manganese oxide having a layered structure containing a Li2MnO3 phase and a LiMO2 phase (where M is an element containing at least one selected from Ni and Mn), wherein in the specific capacity-voltage graph (X-axis: specific capacity (mAh / g), Y-axis: voltage (V)) obtained by activating a lithium secondary battery containing a positive electrode with a positive electrode active material layer at 45 °C at a 0.1 C rate, the slope of the fitting line obtained by applying linear fitting to the data in the voltage range of 4.40 V to 4.65 V is 0.00115 to 0.00150, and in the positive electrode active material layer, the positive electrode active material layer contains at least 80% by weight of the amount of the positive electrode active material relative to the total weight of the positive electrode active material layer.

[0021] (8) The present invention provides the positive electrode active material according to (7) above, wherein the lithium-rich manganese oxide exhibits a Li / Me molar ratio (molar ratio of lithium (Li) to all metals (Me) other than lithium) greater than 1.00 and not more than 2.00.

[0022] (9) The present invention provides the positive electrode active material according to (7) or (8) above, wherein the lithium-rich manganese oxide exhibits a Li / Me molar ratio (molar ratio of lithium (Li) to all metals (Me) other than lithium) of 1.24 to 1.36.

[0023] (10) The present invention provides the positive electrode active material according to any one of (7) to (9) above, wherein the manganese contained in the lithium-rich manganese oxide accounts for at least 50 mol% of all metals other than lithium.

[0024] (11) The present invention provides a positive electrode active material as described in any one of (7) to (10) above, wherein the lithium-rich manganese oxide has a composition represented by the following formula 1: [Formula 1] Li 1+x Ni a Mn b M c O2 Wherein, in the above formula 1, M is at least one selected from W, Al, B, Mo, Ti, Co, V, P, Mg, Fe, K, Ca, Na, Y, and Nb, and 0.10 ≤ x ≤ 0.20, 0 < a ≤ 0.50, 0.50 ≤ b < 1.0, and 0 ≤ c ≤ 0.10.

[0025] (12) The present invention provides a positive electrode active material as described in any one of (7) to (11) above, wherein the lithium-rich manganese oxide has a tap density of 1.5 g / cm 3 to 2.5 g / cm 3 .

[0026] (13) The present invention provides a positive electrode active material as described in any one of (7) to (12) above, wherein the lithium-rich manganese oxide has an average particle size (D 50 ) of 2.0 μm to 20.0 μm.

[0027] (14) The present invention provides a positive electrode comprising the positive electrode active material as described in any one of (7) to (13) above.

[0028] (15) The present invention provides a lithium secondary battery comprising the positive electrode as described in (14) above.

[0029] Beneficial effects

[0030] The method for analyzing the positive electrode active material of the present invention can predict the LMRO capacity characteristics by using the slope obtained from the data of the graph, which is obtained from the high-temperature activation (45 °C, 0.1 C rate) process of the lithium secondary battery. Therefore, the time for analyzing the performance of the positive electrode active material can be reduced.

[0031] The positive electrode active material according to the present invention may include lithium-rich manganese oxide, and in the specific capacity-voltage diagram (X-axis: specific capacity (mAh / g), Y-axis: voltage (V)) obtained by activating a lithium secondary battery at 45°C at a rate of 0.1 C, the slope of the fitted line obtained by applying linear fitting to data in the voltage range of 4.40 to 4.65 V satisfies a specific range. Therefore, the battery can exhibit excellent performance, especially excellent discharge capacity characteristics.

[0032] The positive electrode and lithium secondary battery of the present invention exhibit excellent discharge capacity characteristics. Attached Figure Description

[0033] Figure 1 This is a specific capacity-voltage graph (X-axis: specific capacity (mAh / g), Y-axis: voltage (V)) obtained when evaluating a battery including the positive electrode active material of Example 1, as in Experimental Example 1; and

[0034] Figure 2 It shows the source Figure 1 The graph is a view of the slope of the fitted line obtained by linearly fitting data in the voltage range of 4.40 V to 4.65 V using the Origin program. Detailed Implementation

[0035] The invention will be described in detail below to aid in understanding it.

[0036] It should be understood that the words or terms used in the specification and claims should not be interpreted as having the meaning defined in a common dictionary, and it should also be understood that, based on the inventor's ability to appropriately define the meaning of words or terms to best explain the principles of the invention, the words or terms should be interpreted as having a meaning consistent with their meaning in the relevant field and in the context of the technical idea of ​​the invention.

[0037] It will be further understood that the terms “comprising,” “including,” or “having” as used herein specify the presence of the said feature, number, step, element, or combination thereof, but do not exclude the presence or addition of one or more other features, numbers, steps, elements, or combinations thereof.

[0038] In this paper, tap density can be measured using a typical tap density meter (e.g., the GEOPYC-1360 from Micromeritics), which indicates the apparent density of powder obtained by packing 10 g of powder into a container of about 20 cc and vibrating the container 3,000 times.

[0039] In this paper, the average particle size D 50The particle size distribution can be defined as the particle size at which the cumulative volume distribution reaches 50% of the particle size distribution curve (the curve on the particle size distribution map). After dispersing the target powder in a dispersion medium, the dispersion medium is introduced into a commercially available laser diffraction particle size analyzer (e.g., the S3500 from Microtrac). The particle size distribution is calculated by measuring the difference in the diffraction pattern caused by the particle size as the particles pass through the laser beam. The particle size distribution (D) can be obtained by calculating the particle size at 50% of the cumulative volume distribution using the analyzer. 50 .

[0040] In this paper, "primary particle" refers to the smallest unit of a particle identified when observing a positive electrode active material by scanning electron microscopy (SEM), and "secondary particle" refers to a secondary structure in which multiple primary particles are aggregated.

[0041] Methods for analyzing positive electrode active materials

[0042] This invention provides a method for analyzing positive electrode active materials, the method comprising: (S1) preparing a positive electrode active material comprising lithium-rich manganese oxide having a layered structure comprising a Li2MnO3 phase and a LiMO2 phase (where M is an element comprising at least one selected from Ni and Mn), and manufacturing a lithium secondary battery comprising a positive electrode containing a positive electrode active material layer, wherein the positive electrode active material layer comprises at least 80% by weight of the positive electrode active material 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)) by activating the lithium secondary battery at 45°C and a 0.1 C rate; and (S3) applying linear fitting to the data in the voltage range of 4.40 to 4.65 V in the graph to obtain a slope.

[0043] The inventors of this invention have discovered that in the analysis of lithium-rich manganese oxides, when the slope value of the graph obtained during the high-temperature activation process (45°C, 0.1 C rate) is used together with XRD and powder properties as an evaluation criterion for positive electrode active materials, more accurate and faster analysis can be performed, and reliability can be further increased, thus completing this invention. Specifically, the inventors of this invention have discovered that when the slope obtained in step (S3) of the method for analyzing positive electrode active materials according to this invention is 0.00115 to 0.00150, the discharge capacity at 0.33 C rate is as high as 190 mAh / g or more. In summary, it can be seen that the method for analyzing positive electrode active materials according to this invention allows for easy prediction of discharge performance at 0.33 C rate in advance through the high-temperature activation process (45°C, 0.1 C rate) of lithium secondary batteries, and thus reduces the time required for evaluating and analyzing positive electrode active materials.

[0044] In the following, each step of the analysis method of the positive electrode active material according to the present invention will be described in more detail.

[0045] Step (S1)

[0046] Step (S1) includes preparing a positive electrode active material containing lithium-rich manganese oxide, the lithium-rich manganese oxide having a layered structure containing a Li2MnO3 phase and a LiMO2 phase (where M is an element containing at least one selected from Ni and Mn), and manufacturing a lithium secondary battery including a positive electrode containing a positive electrode active material layer, the positive electrode active material layer containing at least 80% by weight of the positive electrode active material with respect to the total weight of the positive electrode active material layer.

[0047] According to the present invention, the lithium-rich manganese oxide may exhibit a Li / Me molar ratio (molar ratio of lithium (Li) to all metals (Me) other than lithium) greater than 1.00 and 2.00 or less. Specifically, the lithium-rich manganese oxide may exhibit a Li / Me molar ratio (molar ratio of lithium (Li) to all metals (Me) other than lithium) of 1.24 or more, 1.26 or more, 1.28 or more, 1.32 or less, 1.34 or less, or 1.36 or less.

[0048] According to the present invention, the Mn contained in the lithium-rich manganese oxide may account for 50 mol% or more, particularly 60 mol% or more, and more particularly 65 mol% or more of all metals other than lithium.

[0049] According to the present invention, the lithium-rich manganese oxide may have a composition represented by the following Formula 1.

[0050] [Formula 1]

[0051] Li 1+x Ni a Mn b M c O2

[0052] In the above Formula 1, M is at least one selected from W, Al, B, Mo, Ti, Co, V, P, Mg, Fe, K, Ca, Na, Y, and Nb, and 0.10 ≤ x ≤ 0.20, 0 < a ≤ 0.50, 0.50 ≤ b < 1.0, and 0 ≤ c ≤ 0.10.

[0053] Specifically, the above x may be 0.10 or more, 0.11 or more, 0.12 or more, or 0.13 or more, and may 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.

[0054] Specifically, a can be greater than 0, greater than 0.10, greater than 0.15, greater than 0.20, or greater than 0.25, and can be less than 0.35, less than 0.40, less than 0.45, or less than 0.50.

[0055] Specifically, the value of b can be greater than or equal to 0.50 or greater than 0.55, and can be less than or equal to 0.65, 0.70, 0.75, 0.80, 0.95, or less than 1.0.

[0056] Specifically, the value of c can be greater than 0, or less than 0.05, or less than 0.10.

[0057] Lithium-rich manganese oxides may not contain expensive cobalt.

[0058] Lithium-rich manganese oxides can be doped with tungsten.

[0059] The positive electrode can be prepared according to typical methods for preparing a positive electrode, the difference being the use of the aforementioned positive electrode active material. Specifically, the positive electrode can be prepared by applying a composition for forming the positive electrode active material layer (which is prepared by dissolving or dispersing the positive electrode active material and, if necessary, a binder, conductive material, and optional dispersant, in a solvent) onto a positive electrode current collector, followed by drying and rolling; or it can be prepared by casting the composition for forming the positive electrode active material layer onto a separate support, and then pressing the film layer, separated from the support, onto the positive electrode current collector. In this case, drying can be carried out at a temperature of 100°C to 150°C. Furthermore, rolling can be performed so that the positive electrode has a porosity of 20% to 30%. In other words, the porosity of the prepared positive electrode can be 20% to 30%.

[0060] Furthermore, relative to the total weight of the positive electrode active material layer, the content of the positive electrode active material can be more than 80% by weight, especially 80% to 99% by weight, and even more particularly 85% to 98.5% by weight.

[0061] In addition, relative to the total weight of the positive electrode active material layer, the content of the binder can be greater than 0% by weight and less than 15% by weight, especially greater than 0% by weight and less than 10% by weight, and even more particularly from 0.1% by weight to 10% by weight.

[0062] Furthermore, relative to the total weight of the positive electrode active material layer, the content of conductive material can be greater than 0 wt% and less than 15 wt%, particularly greater than 0 wt% and less than 10 wt%, and even more particularly from 0.1 wt% to 10 wt%.

[0063] Lithium-ion batteries can be manufactured according to typical methods used in the manufacture of lithium-ion batteries. For example, an electrode assembly can be prepared by placing a separator between the positive and negative electrodes, positioning the electrode assembly within a battery casing, and injecting an electrolyte to manufacture the aforementioned lithium-ion battery. However, embodiments of the present invention are not limited to these methods.

[0064] Step (S2)

[0065] Step (S2) includes obtaining a specific capacity-voltage graph (X-axis: specific capacity (mAh / g), Y-axis: voltage (V)) by activating the lithium secondary battery at 45°C and a 0.1 C rate. Step (S3) Step (S3) involves obtaining the slope by applying a linear fit to the data in the voltage range of 4.40 to 4.65 V in the above figure.

[0066] Linear fitting can include linear regression analysis using weighted least squares in the Origin program. In other words, the slope of the fitted line obtained through linear fitting can be the value analyzed by performing linear regression analysis using weighted least squares in the Origin program.

[0067] Positive electrode active material

[0068] This invention provides a positive electrode active material comprising lithium-rich manganese oxide having a layered structure comprising a Li2MnO3 phase and a LiMO2 phase (where M is an element comprising at least one selected from Ni and Mn), wherein in a specific capacity-voltage graph (X-axis: specific capacity (mAh / g), Y-axis: voltage (V)) obtained by activating a lithium secondary battery at 45°C at a rate of 0.1 C, the slope of the fitted line obtained by applying linear fitting to data in a voltage range of 4.40 V to 4.65 V is 0.00115 to 0.00150, the positive electrode of the lithium secondary battery comprising a positive electrode active material layer, wherein the positive electrode active material layer comprises at least 80% by weight of the positive electrode active material relative to the total weight of the positive electrode active material layer.

[0069] The inventors of this invention discovered that when the positive electrode active material includes lithium-rich manganese oxide, and when the slope of the fitted line obtained by applying linear fitting to data in the voltage range of 4.40 V to 4.65 V satisfies a specific range in the specific capacity-voltage graph (X-axis: specific capacity (mAh / g), Y-axis: voltage (V)) obtained by activating a lithium secondary battery containing the positive electrode active material at 45°C and a rate of 0.1 C, the battery including the positive electrode active material exhibits excellent discharge capacity, particularly in terms of discharge capacity at a rate of 0.33 C, thus completing this invention.

[0070] Meanwhile, in the specific capacity-voltage graph (X-axis: specific capacity (mAh / g), Y-axis: voltage (V)) obtained by activating a lithium secondary battery including a positive electrode active material at 45 °C at a 0.1 C rate, when the slope of the fitting line obtained by applying linear fitting to the data in the voltage range of 4.40 to 4.65 V is outside the range of 0.00115 to 0.00150, the battery exhibits deteriorated performance.

[0071] According to the present invention, the lithium-rich manganese oxide may exhibit a Li / Me molar ratio (molar ratio of lithium (Li) to all metals (Me) other than lithium) greater than 1.00 and 2.00 or less. Specifically, the lithium-rich manganese oxide may exhibit a Li / Me molar ratio (molar ratio of lithium (Li) to all metals (Me) other than lithium) of 1.24 or more, 1.26 or more, 1.28 or more, 1.32 or less, 1.34 or less, or 1.36 or less. In this case, a battery including the positive electrode active material of the present invention can achieve a certain level of initial charge capacity and improved charge / discharge efficiency at high temperatures. In addition, when evaluating the life characteristics of the battery, the amount of oxygen generated due to structural deterioration can also be reduced.

[0072] According to the present invention, the Mn contained in the lithium-rich manganese oxide may account for 50 mol% or more, specifically 60 mol% or more, and more particularly 65 mol% or more of all metals other than lithium. In this case, high capacity can be achieved even under high-voltage charging conditions.

[0073] According to the present invention, the lithium-rich manganese oxide may have a composition represented by the following formula 1. In this case, the lithium-rich manganese oxide has the advantages of high energy density and low cost. In addition, the lithium-rich manganese oxide is more stable than the NCM-based positive electrode active material, thereby reducing the risk of explosion of the lithium secondary battery.

[0074] [Formula 1]

[0075] Li 1+x Ni a Mn b M c O2

[0076] In the above formula 1, M is at least one selected from W, Al, B, Mo, Ti, Co, V, P, Mg, Fe, K, Ca, Na, Y, and Nb, and 0.10 ≤ x ≤ 0.20, 0 < a ≤ 0.50, 0.50 ≤ b < 1.0, and 0 ≤ c ≤ 0.10.

[0077] Specifically, x can be greater than or equal to 0.10, greater than or equal to 0.11, greater than or equal to 0.12, or greater than or equal to 0.13, and can be less than or equal to 0.15, less than or equal to 0.16, less than or equal to 0.17, less than or equal to 0.18, less than or equal to 0.19, or less than or equal to 0.20.

[0078] Specifically, a can be greater than 0, greater than 0.10, greater than 0.15, greater than 0.20, or greater than 0.25, and can be less than 0.35, less than 0.40, less than 0.45, or less than 0.50.

[0079] Specifically, the value of b can be greater than or equal to 0.50 or greater than 0.55, and can be less than or equal to 0.65, 0.70, 0.75, 0.80, 0.95, or less than 1.0.

[0080] Specifically, the value of c can be greater than 0, or less than 0.05, or less than 0.10.

[0081] Lithium-rich manganese oxides can be produced without expensive cobalt and can improve the performance of lithium secondary batteries in the absence of cobalt.

[0082] Lithium-rich manganese oxides can be doped with tungsten. Tungsten is superior to manganese in terms of stability and conductivity; therefore, when lithium-rich manganese oxides are doped with tungsten, lithium secondary batteries can exhibit further improved performance and stability.

[0083] According to the present invention, lithium-rich manganese oxide can have a content of 1.5 g / cm³. 3 Above, 1.6 g / cm 3 Above, 1.7 g / cm 3 Above, or 1.8 g / cm 3 Above, 2.2 g / cm 3 Below, 2.3 g / cm 3 Below or 2.5 g / cm 3 The following tap densities are specified. When the tap density is within the above range, the electrode has an increased packing density, and therefore high capacity characteristics and improved cost-effectiveness can be achieved.

[0084] According to the present invention, lithium-rich manganese oxides may have an average particle size (D) of 2.0 μm or more, 2.5 μm or more, or 3.0 μm or more. 50 It can have an average particle size of less than 15.0 μm or less than 20.0 μm (D). 50 When the average particle size (D) of lithium-rich manganese oxides 50 Within the above range, electrode rolling is achieved without damaging the particles of the positive electrode active material, thereby achieving enhanced capacity characteristics.

[0085] The positive electrode active material of the present invention can be prepared by dry mixing a composite transition metal hydroxide and a lithium-containing raw material, followed by calcination of the mixture. In the dry mixing of the composite transition metal hydroxide and the lithium-containing raw material, a raw material containing a dopant element can be further mixed in. In other words, a raw material containing a dopant element can be optionally added.

[0086] The positive electrode active material of the present invention can be prepared by optimizing conditions such as the composition of the composite transition metal hydroxide, the mixing amount of the composite transition metal hydroxide and the lithium-containing raw material, the addition of raw materials containing doped elements, and the firing temperature and time.

[0087] Complex transition metal hydroxides can be prepared by commonly known coprecipitation methods and can have a composition represented by Formula 2.

[0088] [Equation 2]

[0089] Ni p Mn q M' r (OH)2

[0090] In equation 2 above, M' is selected from at least one of Co, W, Al, B, Mo, Ti, Co, V, P, Mg, Fe, K, Ca, Na, Y, and Nb, and 0 <p≤0.50,0.50≤q<1.0,0≤r≤0.10。

[0091] Specifically, the above p can be greater than 0, greater than 0.10, greater than 0.15, greater than 0.20, or greater than 0.25, and can be less than 0.35, less than 0.40, less than 0.45, or less than 0.50.

[0092] Specifically, the above q can be greater than 0.50, greater than 0.55, greater than 0.60, or greater than 0.65, and can be less than 0.65, less than 0.70, less than 0.75, less than 0.80, less than 0.95, or less than 1.0.

[0093] Specifically, the value of r can be greater than 0, and can be less than 0.05 or less than 0.10.

[0094] Composite transition metal hydroxides can be made without expensive cobalt and can improve the performance of lithium secondary batteries without cobalt.

[0095] Lithium-containing raw materials are lithium-containing raw materials that can be used to prepare positive electrode active materials, and can be, for example, lithium hydroxide, lithium carbonate or lithium oxide.

[0096] For raw materials containing doped elements, that is, compounds containing at least one of Co, W, Al, B, Mo, Ti, Co, V, P, Mg, Fe, K, Ca, Na, Y and Nb, when the doped element is W, it can be tungsten oxide, and when the doped element is Mo, it can be molybdenum oxide, ammonium molybdate, lithium molybdate, etc.

[0097] The amount of composite transition metal hydroxide, lithium-containing raw material, and raw material containing doped elements added can make the resulting lithium-rich manganese oxide have the composition represented by Formula 1 above.

[0098] The mixing amount of the composite transition metal hydroxide and the lithium-containing raw material can make the molar ratio of all metals in the composite transition metal hydroxide to lithium in the lithium-containing raw material greater than 1.00 and less than 2.00, especially 1.24 to 1.36, 1.26 to 1.36 or 1.28 to 1.34.

[0099] The mixing of complex transition metal hydroxides and lithium-containing raw materials can include dry mixing and can be carried out using a blade mixer or an acoustic mixer.

[0100] The doped material can be mixed in amounts ranging from 5,000 ppm to 20,000 ppm relative to the total weight of the complex transition metal hydroxide and the lithium-containing material.

[0101] Firing can be carried out at temperatures of 600°C to 1,000°C, especially 880°C to 940°C, for 5 to 30 hours, and more particularly for 9 to 21 hours, to enhance the preparation (reaction of raw materials) and crystallinity of the positive electrode active material.

[0102] Firing can be carried out in an air atmosphere or an oxygen atmosphere to improve the reactivity of the reactants.

[0103] positive electrode

[0104] This invention provides a positive electrode comprising the positive electrode active material of this invention.

[0105] 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 aforementioned positive electrode active material.

[0106] The positive electrode current collector can include highly conductive metals, and there are no particular limitations, as long as the positive electrode active material layer can easily adhere to it and the positive electrode current collector is non-reactive within the battery's voltage range. Examples of materials that can be used as the positive electrode current collector include stainless steel, aluminum, nickel, titanium, sintered carbon, or aluminum or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc. Furthermore, the thickness of the positive electrode current collector can typically range from 3 μm to 500 μm, particularly from 3 μm to 50 μm, and even more particularly from 10 μm to 30 μm. Fine irregularities can be formed on the surface of the current collector to improve the adhesion of the positive electrode active material. For example, the positive electrode current collector can be used in various forms, such as films, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics.

[0107] Depending on the requirements, in addition to the positive electrode active material, the positive electrode active material layer may optionally include conductive materials and binders. In this case, the content of the positive electrode active material relative to the total weight of the positive electrode active material layer can be more than 80% by weight, particularly 80% to 99% by weight, and even more particularly 85% to 98.5% by weight, and excellent capacity characteristics can be obtained within this range.

[0108] Conductive materials are used to impart conductivity to the electrodes, and any conductive material can be used without particular limitation, as long as it is conductive without causing a chemical change in the battery. Specific examples may include graphite, such as natural or artificial graphite; carbon-based materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermally cracked carbon black, and carbon fibers; metal powders or metal fibers, such as copper, nickel, aluminum, and silver; conductive tubes, such as carbon nanotubes; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium oxide; or conductive polymers, such as polyphenylene derivatives, and any one or a mixture of two or more of these may be used. The content of the conductive agent relative to the total weight of the positive electrode active material layer may be greater than 0 wt% and less than 15 wt%, particularly greater than 0 wt% and less than 10 wt%, and more particularly 0.1 wt% to 10 wt%.

[0109] Adhesives are used to improve the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples may include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, and polymers obtained by replacing hydrogen in the above materials with Li, Na, or Ca, or various copolymers, and any one or a mixture of two or more of them may be used. The content of the adhesive relative to the total weight of the positive electrode active material layer may be greater than 0% by weight and less than 15% by weight, particularly greater than 0% by weight and less than 10% by weight, and more particularly from 0.1% by weight to 10% by weight.

[0110] The positive electrode can be prepared according to typical methods for preparing a positive electrode, the difference being the use of the aforementioned positive electrode active material. Specifically, a composition for forming the positive electrode active material layer, prepared by dissolving or dispersing the positive electrode active material, along with optional binders and conductive agents, in a solvent, is coated onto a positive electrode current collector. The positive electrode can then be prepared by drying and rolling the coated positive electrode current collector. Alternatively, the positive electrode can be prepared by casting the composition for forming the positive electrode active material layer onto a separate support, and then pressing the film layer, separated from the support, onto the positive electrode current collector. In this case, drying can be carried out at a temperature of 100°C to 150°C. Furthermore, rolling can be performed to give the positive electrode a porosity of 20% to 30%. In other words, the porosity of the prepared positive electrode can be 20% to 30%.

[0111] The solvent can be a commonly used solvent in the art, and can be dimethyl sulfoxide (DMSO), isopropanol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water, etc., and any one or a mixture of two or more of them can be used. Considering the application thickness and preparation yield of the slurry, the amount of solvent used is sufficient if it can dissolve or disperse the positive electrode active material, conductive agent, binder, and dispersant, and exhibits excellent thickness uniformity when applied to prepare the positive electrode.

[0112] Lithium secondary batteries

[0113] The present invention provides a lithium secondary battery including the above-described positive electrode.

[0114] A lithium secondary battery may include a positive electrode, a negative electrode, a separator disposed between the positive and negative electrodes, and an electrolyte. Additionally, a lithium secondary battery may optionally include a battery casing for housing an electrode assembly consisting of the positive electrode, negative electrode, and separator, and a sealing member for sealing the battery casing.

[0115] The negative electrode may include a negative electrode current collector and a layer of negative electrode active material disposed on the negative electrode current collector.

[0116] There are no particular limitations on the negative electrode current collector, as long as it has high conductivity and does not cause chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, sintered carbon, or copper or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys can be used. Furthermore, the negative electrode current collector can typically have a thickness from 3 μm to 500 μm, and as in the case of the positive electrode current collector, fine irregularities can be formed on the surface of the negative electrode current collector to improve the adhesion of the negative electrode active material. For example, the negative electrode current collector can be used in various shapes, such as films, sheets, foils, meshes, porous bodies, foams, non-woven fabrics, etc.

[0117] In addition to the negative electrode active material, the negative electrode active material layer may optionally include a binder and a conductive material.

[0118] Compounds capable of reversibly inserting and de-intercalating lithium can be used as anode active materials. Specific examples include: carbonaceous materials, such as artificial graphite, natural graphite, graphitized carbon fibers, and amorphous carbon; metallic compounds that can alloy with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and metal oxides that can be doped and de-doped with lithium, such as SiO₂. β (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composite materials including metal compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more thereof may be used. Furthermore, lithium metal films may be used as the negative electrode active material. Additionally, both low-crystallinity carbon and high-crystallinity carbon can be used as carbon materials. Typical examples of low-crystallinity carbon can be soft carbon and hard carbon, and typical examples of high-crystallinity carbon can be irregular, planar, sheet-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fibers, mesophase carbon microspheres, mesophase pitch, and high-temperature calcined carbon, such as coke derived from petroleum or coal tar pitch. The content of the negative electrode active material may be from 80% to 99% by weight relative to the total weight of the negative electrode active material layer.

[0119] The binder in the negative electrode active material layer is a component that facilitates adhesion between the conductive agent, the active material, and the current collector, and is typically 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 binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile rubber, fluororubber, and various copolymers thereof.

[0120] The conductive material in the negative electrode active material layer is a component used to further improve 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. There are no particular limitations on such conductive materials, as long as they are conductive without causing chemical changes in the battery. Examples of conductive materials that can be used include: graphite, such as natural and artificial graphite; carbon black, such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermally cracked carbon black; conductive fibers, such as carbon fibers and metal fibers; metal powders, such as fluorinated carbon powder, aluminum powder, and nickel powder; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium oxide; or polyphenylene derivatives, etc.

[0121] A negative electrode can be prepared by applying a composition for forming a negative electrode active material layer, prepared by dissolving or dispersing the negative electrode active material and optionally a binder and conductive material in a solvent, onto a negative electrode current collector and then drying it; or by casting the composition for forming a negative electrode active material layer onto a separate support and then pressing the film layer, separated from the support, onto the negative electrode current collector.

[0122] The separator separates the negative and positive electrodes and provides a path for lithium ions to move. Any separator can be used without particular limitation, as long as it is typically used in secondary batteries. In particular, separators with excellent electrolyte retention and low resistance to ion movement in the electrolyte are preferred. Specifically, porous polymer membranes can be used, for example, porous polymer membranes prepared using polyolefin-based polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminated structures with two or more layers. Furthermore, typical porous nonwoven fabrics can be used, such as nonwoven fabrics formed from high-melting-point glass fibers or polyethylene terephthalate fibers. Additionally, coated separators including ceramic components or polymer materials can be used to ensure heat resistance or mechanical strength, and separators with single-layer or multi-layer structures can optionally be used.

[0123] As the electrolyte, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, inorganic solid electrolytes, molten inorganic electrolytes, etc., which are used in the manufacture of lithium secondary batteries, can be used, but are not limited to these. As a specific example, the electrolyte may include organic solvents and lithium salts.

[0124] Any organic solvent can be used without particular limitation, as long as it can serve as a medium through which the ions involved in the electrochemical reactions of the battery can move. Specifically, as organic solvents, ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone can be used; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic solvents such as benzene and fluorobenzene; or carbonate solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethanol and isopropanol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic C2-C20 hydrocarbon group and may include double-bonded aromatic rings or ether bonds); amides such as dimethylformamide; dioxolane solvents such as 1,3-dioxolane; or sulfolane. Among these solvents, carbonate solvents are preferred, and mixtures of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) with high ionic conductivity and high dielectric constant and low viscosity linear carbonate compounds (e.g., methyl ethyl carbonate, dimethyl carbonate or diethyl carbonate) are more preferred, as they can improve the charge / discharge performance of the battery.

[0125] Any compound can be used as a lithium salt without particular limitation, as long as it is a compound capable of providing lithium ions for lithium secondary batteries. Specifically, the anion of the lithium salt can be selected from 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 -At least one of the group consisting of (CF3CF2SO2)2N, and as a lithium salt, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2 can be used. The lithium salt can preferably be used in a concentration range of 0.1 M to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte has suitable conductivity and viscosity, thus exhibiting excellent performance, and lithium ions can move efficiently.

[0126] In order to improve battery life characteristics, suppress battery capacity reduction, and improve battery discharge capacity, the electrolyte may further include one or more additives, such as alkylene carbonate halogenated compounds (e.g., ethylene difluorocarbonate), pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glycol dimethyl ether, hexamethylphosphotriamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolides, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxyethanol, or aluminum trichloride, etc. In this case, the content of the additives may be from 0.1% by weight to 5% by weight relative to the total weight of the electrolyte.

[0127] Lithium secondary batteries incorporating the positive electrode active material of the present invention stably exhibit excellent capacity, output, and lifespan characteristics, and are therefore suitable for use in portable devices such as mobile phones, laptops, and digital cameras, as well as in electric vehicles such as hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0128] The external shape of the lithium secondary battery of the present invention is not particularly limited, so cylindrical, prismatic, bag-shaped or coin-shaped batteries in the form of cans can be used.

[0129] The lithium secondary battery according to the present invention can be used in battery cells as power sources for small devices, and is also preferably used as a cell in medium and large battery modules comprising multiple battery cells.

[0130] Therefore, a battery module including a lithium secondary battery as a unit cell and a battery pack including the battery module are provided.

[0131] The battery module or battery pack can be used as a power source for at least one of the following medium and large devices: power tools; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0132] Example

[0133] In the following, embodiments of the invention will be described in detail in a manner readily apparent to those skilled in the art. However, the invention can be embodied in many different forms and is not limited to the embodiments set forth herein.

[0134] Examples and Comparative Examples

[0135] Example 1

[0136] Secondary particulate positive electrode active material precursor (composition: Ni) 0.35 Mn 0.65 (OH)2) and LiOH were dry-mixed to prepare a mixture with a (Ni+Mn):Li molar ratio of 1:1.28. The mixture was then calcined in air at 880°C for 9 hours to prepare lithium-rich manganese oxide (positive electrode active material).

[0137] Examples 2 to 10

[0138] The positive electrode active material was prepared in the same manner as in Example 1, except that the molar ratio of (Ni+Mn):Li and the firing temperature were adjusted as shown in Table 1 below.

[0139] Comparative Examples 1 to 13

[0140] The positive electrode active material was prepared in the same manner as in Example 1, except that the molar ratio of (Ni+Mn):Li and the firing temperature were adjusted as shown in Table 1 below.

[0141] [Table 1]

[0142]

[0143]

[0144] Experimental Example

[0145] Experimental Example 1: Determination of the composition of lithium-rich manganese oxides

[0146] Take 0.1 g of each of the lithium-rich manganese oxides prepared in the examples and comparative examples, then add 1 mL of hydrochloric acid and heat to dissolve the lithium-rich manganese oxides. Subsequently, a small amount of hydrogen peroxide is added to promote the reaction and completely dissolve the lithium-rich manganese oxides to prepare a solution. The solution is then diluted with deionized water to a total volume of 10 mL to prepare the analytical sample. Using an ICP apparatus (Perkin Elmer, OPTIMA 7300 DV), the weight ratio of the constituent elements present in the analytical sample was measured, and the composition of the lithium-rich manganese oxides and the Li / Me molar ratio (the molar ratio of lithium (Li) to all metals (Me) except lithium) are shown in Table 2 below.

[0147] [Table 2]

[0148]

[0149] Referring to Table 2, the lithium-rich manganese oxides of Examples 1 to 10 were determined to satisfy the composition represented by Formula 1 as described herein, and the molar ratio of lithium to all metals other than lithium was satisfied to be 1.28 to 1.32.

[0150] Experimental Example 2: Determination of the average particle size of lithium-rich manganese oxides

[0151] To determine the average particle size of each lithium-rich manganese oxide prepared in Examples 5 to 10 above, 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.

[0152] [Table 3]

[0153]

[0154] Referring to Table 3, the lithium-rich manganese oxides of Examples 5 to 10 were determined to have an average particle size of 9.50 μm to 9.60 μm.

[0155] Experiment Example 3: Battery Evaluation

[0156] (Battery manufacturing)

[0157] A positive electrode slurry was prepared by mixing 92.5 wt% of the positive electrode active materials prepared in the examples and comparative examples, 3 wt% of Super P as a conductive material, and 4.5 wt% 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 prepare the positive electrode.

[0158] A lithium metal electrode is used as the negative electrode, and an electrode assembly is prepared by placing a porous polyethylene membrane between the positive and negative electrodes. The electrode assembly is placed inside a battery casing, and an electrolyte (additives: 0.5% LiBF4, 3.0% FEC) is injected to manufacture a coin-shaped half-cell, wherein 1 M LiPF6 in the electrolyte is dissolved in an organic solvent (in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed in a volume ratio of 3:7).

[0159] (Analysis of positive electrode active materials)

[0160] Coin-shaped half-cells containing the positive electrode active materials prepared in the examples and comparative examples were charged to 4.65 V at a constant current of 0.1 C at 45 °C, and then discharged to 2.0 V at a constant current of 0.1 C. The slope of the fitted line obtained by linearly fitting the data in the voltage range of 4.40 to 4.65 V using the Origin program in the specific capacity-voltage graph (X-axis: specific capacity (mAh / g), Y-axis: voltage (V)) obtained during the activation process (formation) is shown in Table 4 below. Furthermore, the charge and discharge capacities obtained under these conditions are shown in Table 4 below, and the efficiency of the activation process (defined as the percentage of discharge capacity relative to charge capacity under these conditions) is also shown in Table 4 below.

[0161] For reference, the slope of the fitted line obtained by linear fitting is the value analyzed by performing linear regression analysis using weighted least squares in the Origin program.

[0162] Figure 1 The specific capacity-voltage graph (X-axis: specific capacity (mAh / g)) and Y-axis: voltage (V)) were obtained when evaluating a battery containing the positive electrode active material of Example 1, as in Experimental Example 1. Figure 2 It is shown in Figure 1 The figure shows a view of the slope of the fitted line obtained by applying linear fitting to data in the voltage range of 4.40 V to 4.65 V using the Origin program.

[0163] (Battery Evaluation)

[0164] The activated battery was charged to 4.4 V at a constant current of 0.1 C at 25°C, and then discharged to 2.5 V at a constant current of 0.1 C to determine the initial charge / discharge performance. This process was repeated by changing the charge / discharge rate from 0.1 C to 0.33 C, and this cycle was considered one cycle. Based on this, a total of 30 charge and discharge cycles were repeated to determine the discharge capacity. The charge and discharge capacities in the first cycle, and the percentage of discharge capacity relative to charge capacity under these conditions, are shown in Table 4 below. The percentage of discharge capacity in the 30th cycle relative to the discharge capacity in the first cycle is shown in Table 4 below as capacity retention.

[0165] [Table 4]

[0166]

[0167] Referring to Table 4, it was determined that in the positive electrode active material of the embodiments, the slope obtained according to the positive electrode active material analysis method satisfies 0.00115 to 0.00150, and therefore, the battery performance including the positive electrode active material is excellent, such as capacity and efficiency during activation, capacity and efficiency at 0.33 C rate, and capacity retention. In particular, the discharge capacity of the battery at 0.33 C rate was determined to be as high as 190 mAh / g or more. In summary, it can be seen that, according to the positive electrode active material analysis method of the present invention, when using the slope obtained through the high-temperature activation process (45°C, 0.1 C rate) of a lithium secondary battery, the LMRO capacity characteristics can be predicted, thus reducing the time required to analyze the performance of the positive electrode active material. Furthermore, in the positive electrode active material according to the present invention, it can be seen that lithium-rich manganese oxide is included, and in the specific capacity-voltage diagram (X-axis: specific capacity (mAh / g), Y-axis: voltage (V)) obtained by activating a lithium secondary battery including the positive electrode active material at 0.1 C rate at 45°C, the slope of the fitted line obtained by applying linear fitting to the data in the voltage range of 4.40 V to 4.65 V meets a specific range. Therefore, the battery exhibits excellent performance, especially excellent discharge capacity characteristics.

Claims

1. A method for analyzing a positive electrode active material, the method comprising: (S1) Preparing a positive electrode active material comprising a lithium-rich manganese oxide having a layered structure comprising a Li2MnO3 phase and a LiMO2 phase, wherein M is an element comprising at least one selected from Ni and Mn; and manufacturing a lithium secondary battery comprising a positive electrode having a positive electrode active material layer, wherein, relative to the total weight of the positive electrode active material layer, the positive electrode active material layer comprises at least 80% by weight of the positive electrode active material; (S2) Activating the lithium secondary battery at 45 °C at a rate of 0.1 C to obtain a specific capacity-voltage graph, wherein the X-axis of the specific capacity-voltage graph is specific capacity (mAh / g) and the Y-axis is voltage (V); and (S3) In the graph, applying linear fitting to data within a voltage range of 4.40 V to 4.65 V to obtain a slope.

2. The method as described in claim 1, wherein, The lithium-rich manganese oxide exhibits a Li / Me molar ratio greater than 1.00 and not exceeding 2.00, that is, the molar ratio of lithium (Li) to all metals (Me) other than lithium.

3. The method as described in claim 1, wherein, The lithium-rich manganese oxide exhibits a Li / Me molar ratio of 1.24 to 1.36, that is, the molar ratio of lithium (Li) to all metals (Me) other than lithium.

4. The method of claim 1, wherein, The lithium-rich manganese oxide contains at least 50 mol% of Mn based on all metals other than lithium.

5. The method of claim 1, wherein, The lithium-rich manganese oxide has a composition represented by the following formula 1: [Formula 1] Li 1+x Ni a Mr b M c O2 Wherein, in the above formula 1, M is at least one selected from W, Al, B, Mo, Ti, Co, V, P, Mg, Fe, K, Ca, Na, Y and Nb, and 0.10 ≤ x ≤ 0.20, 0 < a ≤ 0.50, 0.50 ≤ b < 1.0, and 0 ≤ c ≤ 0.

10.

6. The method of claim 1, wherein, The linear fitting includes performing linear regression analysis using the weighted least squares method in the Origin program.

7. A positive electrode active material comprising a lithium-rich manganese oxide having a layered structure comprising a Li2MnO3 phase and a LiMO2 phase, wherein M is an element comprising at least one selected from Ni and Mn, in, A specific capacity-voltage graph is obtained by activating a lithium secondary battery comprising a positive electrode having a positive electrode active material layer at 45 °C at a rate of 0.1 C, wherein the X-axis of the specific capacity-voltage graph is specific capacity (mAh / g) and the Y-axis is voltage (V), and in the specific capacity-voltage graph, the slope of the fitting line obtained by applying linear fitting to data within a voltage range of 4.40 V to 4.65 V is 0.00115 to 0.00150, and relative to the total weight of the positive electrode active material layer, the positive electrode active material layer comprises at least 80% by weight of the positive electrode active material.

8. The positive electrode active material as described in claim 7, wherein, The lithium-rich manganese oxide exhibits a Li / Me molar ratio greater than 1.00 and not exceeding 2.00, that is, the molar ratio of lithium (Li) to all metals (Me) other than lithium.

9. The positive electrode active material as described in claim 7, wherein, The lithium-rich manganese oxide exhibits a Li / Me molar ratio of 1.24 to 1.36, that is, the molar ratio of lithium (Li) to all metals (Me) other than lithium.

10. The positive electrode active material as described in claim 7, wherein, The Mn contained in the lithium-rich manganese oxide accounts for at least 50 mol% of all metals other than lithium.

11. The positive electrode active material as described in claim 7, wherein, The lithium-rich manganese oxide has a composition represented by the following formula 1: [Formula 1] Li 1+x Ni a Mr b M c O2 Wherein, in the above formula 1, M is at least one selected from W, Al, B, Mo, Ti, Co, V, P, Mg, Fe, K, Ca, Na, Y and Nb, and 0.10 ≤ x ≤ 0.20, 0 < a ≤ 0.50, 0.50 ≤ b < 1.0, and 0 ≤ c ≤ 0.

10.

12. The positive electrode active material as described in claim 7, wherein, The lithium-rich manganese oxide has a concentration of 1.5 g / cm³. 3 Up to 2.5g / cm 3 The tap density.

13. The positive electrode active material as described in claim 7, wherein, The lithium-rich manganese oxide has an average particle size (D) of 2.0 μm to 20.0 μm. 50 ).

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 according to claim 14.

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