Positive electrode active material, method for manufacturing same, and positive electrode and lithium secondary battery comprising same

Abstract

The present invention relates to a positive electrode active material, a method for manufacturing same, and a positive electrode and a lithium secondary battery comprising same, wherein the positive electrode active material comprises a lithium-rich manganese-based oxide which comprises a Li2MnO3 phase and a LiMO2 phase (where M is an element comprising at least one selected from Ni, Co, and Mn), wherein the lithium-rich manganese-based oxide is in the form of a single particle and has a single crystallinity (χ) of between 0.51 and 0.70 according to formula 1 described in the present specification.

Description

Positive electrode active material, method for producing the same, and positive electrode and lithium secondary battery including the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0100308, filed August 1, 2023, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a positive electrode active material, a method for producing the same, and a positive electrode and a lithium secondary battery including the same.

[0005]

[0006] Lithium secondary batteries are composed of four major components: a cathode, an anode, a separator, and an electrolyte. Among these, the cathode active material contained in the cathode plays a significant role in determining the battery's capacity, output, and lifespan. For lithium secondary batteries to achieve high energy density, output, and lifespan, improving the performance of the cathode active material is essential. Consequently, extensive research has been conducted recently to develop high-performance cathode active materials.

[0007] Li-rich layered oxide, a type of cathode active material, is a mixed phase of Li2MnO3 phase and LiMO2 (where M is an element including at least one selected from Ni, Co, and Mn) phase, and has a high operating voltage (>3.5 V vs. Li / Li). + ) has the characteristic of providing a very large capacity of 250 mAh / g. Therefore, the lithium-excess oxide is attracting attention as a low-cost, high-capacity cathode active material.

[0008] However, the lithium-excess oxide has a fine average particle diameter (D 50) is a secondary particle form in which primary particles having agglomeration are formed, and has a large specific surface area and low particle strength. Therefore, when an electrode is manufactured with a positive electrode active material including secondary particles in which the primary particles are agglomerated and then rolled, there is a problem in that the particle breakage is severe, and when the cell is operated, a large amount of gas is generated, resulting in poor stability and lifespan characteristics.

[0009] Therefore, it is necessary to secure technology to improve the stability, life characteristics, and capacity characteristics of the lithium-excess oxide.

[0010]

[0011] [Prior Art Literature]

[0012] [Patent Document]

[0013] (Patent Document 1) Korean Patent Publication No. 10-2016-0080865

[0014]

[0015] The present invention is intended to solve the above problems, and to provide a cathode active material and a method for manufacturing the same that can improve the life characteristics and capacity characteristics of a battery.

[0016] In addition, the present invention seeks to provide a cathode and secondary battery having excellent life characteristics and capacity characteristics, including the cathode active material as described above.

[0017]

[0018] To solve the above problem, the present invention provides a positive electrode active material, a method for producing the same, and a positive electrode and a lithium secondary battery including the same.

[0019] (1) The present invention provides a cathode active material comprising a lithium-excess manganese oxide including a Li2MnO3 phase and a LiMO2 (wherein M is an element including at least one selected from Ni, Co, and Mn) phase, wherein the lithium-excess manganese oxide is in the form of a single particle, and the lithium-excess manganese oxide has a single crystallinity (χ) of 0.51 or more and 0.70 or less according to the following formula 1.

[0020] [Formula 1]

[0021]

[0022] In the above equation 1, a i When a single particle is composed of i crystal grains, the cross-sectional area of ​​the i-th crystal grain (A) is the cross-sectional area of ​​the single particle (A). i ) value (A i / A) means.

[0023] (2) In the present invention, in the above (1), the lithium-excess manganese oxide is a positive electrode active material represented by the following chemical formula 1.

[0024] [Chemical Formula 1]

[0025] Li x Ni a Mn b M 1 c O2

[0026] In the above chemical formula 1, M 1 is at least one selected from the group consisting of Co, Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, Sn, Y and Zn, and 1.00 <x≤1.30, 0.10≤a≤0.50, 0.50≤b≤0.90, 0≤c≤0.10, x+a+b+c=2이다.

[0027] (3) In the present invention, in the above (1) or (2), the lithium-excess manganese oxide has an average particle diameter (D 50 ) provides a positive electrode active material having a diameter of 0.6㎛ to 1.5㎛.

[0028] (4) In any one of the above (1) to (3), the lithium-excess manganese oxide has a BET specific surface area of ​​1.5 m 2 / g to 3.0m 2 / g provides a positive electrode active material.

[0029] (5) The present invention provides a positive electrode active material, which further comprises a coating layer formed on the lithium-excess manganese oxide in any one of the above (1) to (4), and which includes at least one coating element selected from the group consisting of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Sr, Sb, Bi, Si and S.

[0030] (6) The present invention provides a method for producing a positive electrode active material according to claim 1, comprising the steps of: (S10) introducing a lithium (Li)-containing raw material, a nickel (Ni)-containing raw material, and a manganese (Mn)-containing raw material into a grinding device, and dry mixing and grinding to produce a mixture; (S20) firing the mixture at a temperature of more than 900°C and less than or equal to 1,100°C to produce a fired product; and (S30) crushing the fired product to obtain a positive electrode active material including a lithium-excess manganese oxide, wherein the grinding device includes a chamber and a rotor rotatable inside the chamber, and the mixing and grinding in step (S10) is performed by introducing the lithium (Li)-containing raw material, the nickel (Ni)-containing raw material, and the manganese (Mn)-containing raw material and beads into the chamber of the grinding device, and rotating the rotor.

[0031] (7) The present invention provides a method for manufacturing a positive electrode active material, wherein in the above (6), the calcination in the above (S20) step is performed for 6 to 15 hours.

[0032] (8) The present invention provides a method for manufacturing a positive electrode active material, wherein, in step (6) or (7), after crushing the sintered product in step (S30), a step of mixing and heat-treating the lithium-excess manganese oxide and the coating raw material to form a coating layer on the lithium-excess manganese oxide is further included, and the heat treatment is performed at a temperature of 300°C to 600°C.

[0033] (9) The present invention provides a positive electrode comprising a positive electrode active material according to any one of (1) to (5).

[0034] (10) The present invention provides a secondary battery including a positive electrode according to (9).

[0035]

[0036] The cathode active material according to the present invention is in the form of a single particle, has a single crystallinity within a specific range, and includes a lithium-excess manganese oxide including a Li2MnO3 phase and a LiMO2 (wherein M is an element including at least one selected from Ni, Co, and Mn) phase, so that when the cathode active material is rolled for electrode manufacture, the generation of fine particles due to particle breakage can be prevented, and when applied to a battery, the generation of gas can be suppressed. Accordingly, the performance of a cathode and a secondary battery including the cathode active material, particularly, charge / discharge characteristics and cycle life characteristics, can be improved.

[0037] In addition, according to the method for manufacturing a positive electrode active material of the present invention, the positive electrode active material described above can be effectively manufactured.

[0038]

[0039] Figure 1 shows XRD data for each of the positive electrode active materials manufactured in Example 1, Example 2, and Comparative Examples 1 to 4.

[0040] Figure 2 is an SEM image of the positive electrode active materials manufactured in Examples 1 to 3 and Comparative Examples 1, 3, and 4.

[0041] Figure 3 shows an IPF map, a boundary image, and a segmentation image obtained by EBSD analysis of a cathode for EBSD analysis manufactured using the cathode active materials manufactured in Examples 1 to 3 and Comparative Example 1.

[0042] Figure 4 is a schematic diagram of a crushing device for carrying out the method for manufacturing a positive electrode active material of the present invention.

[0043] Figure 5 is a schematic diagram of a crushing device for carrying out the method for manufacturing a positive electrode active material of the present invention.

[0044] FIG. 6 is an image of the surface of a positive electrode including each of the positive electrode active materials manufactured in Examples 1 to 3, Comparative Example 3, and Comparative Example 4.

[0045]

[0046] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0047] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best possible manner.

[0048] In this specification, it should be understood that terms such as “include,” “have,” or “have” are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0049] In the present specification, the single particle form includes both a single particle form of the positive electrode active material and / or the lithium-excess manganese oxide and an aggregate form of 2 or more and 10 or less particles. That is, the single particle form of the positive electrode active material and / or the single particle form of the lithium-excess manganese oxide of the present invention may include at least one selected from the group consisting of a single particle form of the positive electrode active material and / or a particle form of an aggregate form of 2 or more and 10 or less particles.

[0050] In this specification, 'primary particle' means the smallest particle unit recognized when observing a positive electrode active material using a scanning electron microscope (SEM), and 'secondary particle' means a secondary structure formed by the aggregation of multiple primary particles.

[0051] In this specification, 'single crystal' means a crystal that does not contain grain boundaries inside the particles.

[0052] In this specification, "crystal grain" refers to a particle unit having substantially the same crystal orientation, which may be measured by Electron Backscatter Diffraction (EBSD). Specifically, it refers to the smallest particle unit displayed in the same color in an IPF map obtained by EBSD analysis of a cross-section of a positive electrode active material cut through ion milling.

[0053] In this specification, the content of each element in the lithium-excess manganese oxide may be measured through ICP (Inductive Coupled Plasma) analysis using an inductively coupled plasma optical emission spectrometer (ICP-OES; Optima 7300DV, PerkinElmer).

[0054] In this specification, the average particle diameter (D 50 ) can be defined as the particle size corresponding to 50% of the volume cumulative distribution in the particle size distribution curve (graph curve of particle size distribution) of each particle. The above 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 measuring device (e.g., S3500 of Microtrac), and measuring the difference in diffraction pattern according to particle size when the particles pass through the laser beam, and calculating the particle diameter at the point where it becomes 50% of the volume cumulative distribution according to the particle size in the measuring device, thereby obtaining D 50 can be measured.

[0055] In this specification, the term "rotor" means one or more rotating blades attached to a rotating shaft (rotor centerpiece). The number, shape, size, and angle of the rotating blades can be changed, and the rotating force can be adjusted.

[0056]

[0057] positive electrode active material

[0058] Hereinafter, the positive electrode active material according to the present invention will be described.

[0059]

[0060] The cathode active material according to the present invention includes a lithium-excess manganese oxide including a Li2MnO3 phase and a LiMO2 (wherein M is an element including at least one selected from Ni, Co, and Mn) phase, wherein the lithium-excess manganese oxide is in the form of a single particle, and the lithium-excess manganese oxide has a single crystallinity (χ) of 0.51 or more and 0.70 or less according to the following equation 1.

[0061] [Formula 1]

[0062]

[0063] In the above equation 1,

[0064] a i When a single particle is composed of i crystal grains, the cross-sectional area of ​​the i-th crystal grain (A) is the cross-sectional area of ​​the single particle (A). i ) value (A i / A) means.

[0065] Meanwhile, if the positive electrode active material does not include a lithium-excess manganese oxide, or if the lithium-excess manganese oxide does not include a Li2MnO3 phase and a LiMO2 (wherein M is an element including at least one selected from Ni, Co, and Mn) phase, is not a single particle, and has a single crystallinity of less than 0.51, there is a problem that fine particles are generated due to particle breakage when the positive electrode active material is rolled for electrode manufacturing, and when this is applied to a battery, there is a problem that the capacity characteristics are poor, and there is a problem that the life characteristics of the battery are reduced due to the generation of gas.

[0066] The present inventors have conducted repeated studies to solve the above problems and have found that, in the case of a cathode active material including a lithium-excess manganese oxide including a Li2MnO3 phase and a LiMO2 (wherein M is an element including at least one selected from Ni, Co, and Mn) phase, having a single particle form, and having a single crystallinity within a specific range, the area of ​​grain boundaries on the particle surface can be minimized to improve thermal stability, the breakage of the cathode active material when rolling for electrode production can be suppressed, and when applied to a battery, unnecessary side reactions with an electrolyte and the amount of gas generated can be improved, and capacity characteristics can be improved, thereby completing the present invention. As described above, a battery using the cathode active material according to the present invention can have a small volume change due to charge and discharge, and excellent cycle characteristics and capacity characteristics.

[0067] The lithium-excess manganese oxide includes a Li2MnO3 phase and a LiMO2 (wherein M is an element including at least one selected from Ni, Co, and Mn) phase. The lithium-excess manganese oxide according to the present invention does not include a LiMn2O4 phase. That is, the lithium-excess manganese oxide does not include a LiMn2O4 phase, as is known in the art, and is different from a lithium manganese oxide having a spinel structure and a composition similar to LiMn2O4.

[0068] The lithium-excess manganese oxide is in the form of a single particle. That is, the lithium-excess manganese oxide may be in the form of a single particle or a single particle formed by agglomeration of 2 to 10 particles. The single particle form is distinguished from a secondary particle formed by agglomeration of more than 10 primary particles. When the lithium-excess manganese oxide has a single particle form, it has excellent stability, and even when a positive electrode active material including the same is rolled, the positive electrode active material does not break or crack. This can lead to an improvement in the charge / discharge efficiency of the positive electrode active material, and a reduction in side reactions between the positive electrode active material and the electrolyte. This can improve the durability against volume change during charge / discharge of a battery using the same, and can improve high-temperature performance.

[0069] In the present invention, the degree of single crystallinity is evaluated and expressed as a parameter represented by the above formula 1. The degree of single crystallinity as referred to in the present invention is a value that is adjusted according to the cross-sectional area of ​​a single particle, the number of crystal grains forming one single particle, and the cross-sectional area of ​​each crystal grain. The higher the cross-sectional area of ​​a specific crystal grain having the largest cross-sectional area within one single particle, the closer it is to the cross-sectional area of ​​the entire single particle, the higher the degree of single crystallinity.

[0070] That is, the degree of single crystallinity shown in the present invention can be higher as the number of crystal grains forming a single particle is smaller, and if the number of crystal grains is the same, the degree of single crystallinity is higher when a specific crystal grain has a larger cross-sectional area than other crystal grains rather than when the cross-sectional areas of the crystal grains are similar, and the difference between the cross-sectional areas of the entire single particle is small.

[0071] For example, the maximum value of the single crystallinity is 1, which means that one single particle is composed of one crystal grain. In addition, when one single particle is composed of N crystal grains, the single crystallinity varies depending on the cross-sectional area of ​​each crystal grain, but the minimum value of the single crystallinity that can be had when there are N crystal grains is 1 / N, which is when all N crystal grains have the same cross-sectional area. Even if one single particle is composed of N crystal grains, if a specific crystal grain has a larger cross-sectional area than the other crystal grains, the single crystallinity is higher than 1 / N, because the shape is closer to a single crystal when a specific crystal grain has the largest cross-sectional area than when N crystal grains have the same area.

[0072] From this point of view, the smaller the cross-sectional area of ​​the added crystal grains, the smaller the degree of single crystallinity decreases. This is because the cross-sectional area of ​​small-sized crystal grains is smaller than the cross-sectional area of ​​the total particles, so the effect of the small-sized crystal grains on the decrease in the degree of single crystallinity is small.

[0073] The lithium-excess manganese oxide has a single crystallinity (χ) of 0.51 or more and 0.70 or less. Specifically, the single crystallinity of the lithium-excess manganese oxide may be 0.51 or more, 0.52 or more, 0.53 or more, 0.54 or more, 0.55 or more, 0.56 or more, 0.57 or more, 0.58 or more, 0.59 or more, 0.6 or more, 0.61 or more, or 0.62 or more, and may be 0.68 or less, 0.69 or less, or 0.70 or less. Specifically, when the single crystallinity (χ) is 0.62 to 0.68, it can be seen that the lithium-excess manganese oxide of the present invention has a specific crystal grain having the largest cross-sectional area within a single particle having a cross-sectional area close to about half of the cross-sectional area of ​​the entire single particle. Accordingly, when rolling for electrode manufacturing or operating a cell, particle breakage due to grain boundaries can be suppressed, the grain boundary area in contact with the electrolyte is reduced, and gas generation due to side reactions with the electrolyte is reduced, so that the lifespan of the secondary battery can be significantly improved. On the other hand, when the single crystallinity is less than 0.51, particle breakage due to grain boundaries occurs when rolling for electrode manufacturing or operating a cell, and the grain boundary area in contact with the electrolyte is greatly increased, so that the amount of gas generation due to side reactions with the electrolyte increases and the charge / discharge efficiency is reduced. When the single crystallinity is greater than 0.70, there is a problem of poor capacity characteristics. Specifically, when manufacturing a lithium-excess manganese oxide so that the single crystallinity is greater than 0.70, the specific surface area is greatly increased by performing high-temperature heat treatment, so that the reaction area is greatly reduced, so there is a problem of poor capacity characteristics.

[0074]

[0075] According to one embodiment of the present invention, the lithium-excess manganese oxide may be represented by the following chemical formula 1.

[0076] [Chemical Formula 1]

[0077] Li x Ni a Mnb M 1 c O2

[0078] In the above chemical formula 1,

[0079] M 1 is at least one selected from the group consisting of Co, Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, Sn, Y and Zn,

[0080] 1.00 <x≤1.30, 0.10≤a≤0.50, 0.50≤b≤0.90, 0≤c≤0.10, x+a+b+c=2이다.

[0081]

[0082] Above M 1 is a doping element, specifically the above M 1 It may be at least one selected from the group consisting of Co, Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, Sn, Y and Zn. The above M 1 Although it is not essential, when included in an appropriate amount, it can improve the crystal structure stability of the positive electrode active material and / or the charge / discharge characteristics of a secondary battery manufactured therefrom.

[0083] Meanwhile, the above x may be greater than 1.00, greater than 1.05, greater than 1.10, or greater than 1.15, and may be less than or equal to 1.20, less than or equal to 1.25, or less than or equal to 1.30. When x satisfies the above range, high capacity characteristics and high energy density per unit volume can be realized.

[0084] The above a may be 0.10 or more, 0.15 or more, or 0.20 or more, and may be 0.25 or less, 0.30 or less, 0.35 or less, 0.40 or less, 0.45 or less, or 0.50 or less. When a satisfies the above range, the initial charge / discharge capacity of the secondary battery can be improved at a voltage of 4.4 V or less.

[0085] The above b may be 0.50 or more, 0.55 or more, or 0.60 or more, and may be 0.75 or less, 0.80 or less, 0.85 or less, or 0.90 or less. When b satisfies the above range, the initial charge / discharge capacity of the secondary battery can be improved at a voltage of 4.4 V or more.

[0086] The above c may be 0 or more, 0.03 or more, 0.04 or more, or 0.05 or more, and may be 0.08 or less, 0.09 or less, or 0.10 or less. When c satisfies the above range, the crystal structure stability of the positive electrode active material and / or the charge / discharge characteristics of the secondary battery manufactured therefrom may be improved.

[0087] In chemical formula 1, x, a, b, and c may be x+a+b+c=2.

[0088]

[0089] In addition, according to one embodiment of the present invention, the lithium-excess manganese oxide has an average particle diameter (D 50 ) may be 0.6 ㎛ to 1.5 ㎛. The average particle diameter of the lithium-excess manganese oxide may be specifically, 0.6 ㎛ or more, 0.7 ㎛ or more, or 0.8 ㎛ or more, and 1.3 ㎛ or less, 1.4 ㎛ or less, or 1.5 ㎛ or less. The average particle diameter (D 50 ) satisfies the above range, compared to conventional secondary particles in which primary particles are aggregated, particle breakage is suppressed, side reactions with the electrolyte and gas generation are reduced, and thus the life characteristics can be improved. In addition, the reduction in capacity and the decrease in performance due to the lowered rolling density can be prevented, and the increase in resistance can be suppressed, thereby improving the output characteristics.

[0090]

[0091] In addition, according to one embodiment of the present invention, the lithium-excess manganese oxide has a BET specific surface area of ​​1.5 m 2 / g to 3.0m 2 / g. Specifically, the lithium-excess manganese oxide has a BET surface area of ​​1.5 m 2 / g or more, 1.6m 2 / g or more, or 1.7m 2 / g can be more than 2.4m 2 / g or less, 2.7m 2 / g or less, or 3.0m 2 / g can be less.

[0092] The higher the degree of single crystallinity of the particles, the smaller the grain boundary area on the particle surface, which can lead to a lower BET specific surface area. Therefore, a BET specific surface area that satisfies the above range indicates a relatively high degree of single crystallinity. When the BET specific surface area satisfies the above range, side reactions with the electrolyte and gas generation are reduced during the charge / discharge process, which can improve the cycle life characteristics.

[0093]

[0094] In addition, according to one embodiment of the present invention, a coating layer formed on the lithium-excess manganese oxide and including at least one coating element selected from the group consisting of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Sr, Sb, Bi, Si and S may be further included. By suppressing side reactions with the electrolyte by the coating layer, the life characteristics can be further improved. Specifically, the coating element may include at least one element selected from the group consisting of Al, W, V and B.

[0095]

[0096] Method for manufacturing positive electrode active material

[0097] Next, a method for manufacturing the positive electrode active material of the present invention will be described. The method for manufacturing the positive electrode active material of the present invention is a method for manufacturing the positive electrode active material according to the present invention.

[0098]

[0099] The method for manufacturing a positive electrode active material according to the present invention comprises the steps of (S10) introducing a lithium (Li)-containing raw material, a nickel (Ni)-containing raw material, and a manganese (Mn)-containing raw material into a grinding device, and dry mixing and grinding to prepare a mixture; (S20) firing the mixture at a temperature of more than 900°C and less than or equal to 1,100°C to produce a fired product; and (S30) crushing the fired product to obtain a positive electrode active material including a lithium-excess manganese oxide, wherein the grinding device includes a chamber and a rotor rotatable inside the chamber, and the mixing and grinding in step (S10) is performed by introducing the lithium (Li)-containing raw material, the nickel (Ni)-containing raw material, and the manganese (Mn)-containing raw material and beads into the chamber of the grinding device, and rotating the rotor.

[0100]

[0101] The cathode active material according to the present invention described above can be manufactured by appropriately controlling the type of raw material, mixing ratio, firing stage, firing temperature, firing atmosphere, etc.

[0102]

[0103] Hereinafter, each step of the present invention will be described in detail.

[0104]

[0105] (S10) Step

[0106] The lithium-excess manganese oxide of the present invention utilizes a dry mixing process of solid raw materials, and since no medium is used, energy from the beads is directly transferred to the raw material particles, which is energy efficient, and the process of medium filtration and drying is not required, which is simple. On the other hand, if a process of wet mixing a positive electrode active material precursor and a lithium-containing raw material to produce a mixture is used, particle growth may not be smooth, so single particles may not sufficiently progress, and since an over-sintering process is required, a capacity reduction may occur during battery use due to reasons such as the formation of a rock-salt phase. In addition, since a precursor-based secondary particle form coexists, the degree of single crystallinity targeted by the present invention cannot be achieved.

[0107]

[0108] In selecting raw materials for lithium (Li), nickel (Ni), and manganese (Mn)-containing raw materials, any raw material applicable to a solid-state synthesis method may be used without limitation. However, since residual sulfur after synthesis may cause problems in the positive electrode active material and sintering equipment, it is preferable to exclude sulfate-based compounds. Specifically, oxide, carbonate, and hydroxide-based compounds may be used.

[0109] For example, the lithium (Li)-containing raw material may be at least one selected from the group consisting of LiOH, Li2CO3, LiNO3, LiNO2, LiOHㆍH2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li acetate, Li dicarboxylic acid, Li citrate, Li fatty acid, alkyl lithium, and lithium halides, and a mixture of one or two or more of these may be used. Specifically, considering the melting point, LiOH may be used.

[0110] The above nickel (Ni)-containing raw material may be at least one selected from the group consisting of NiO, Ni(OH)2, NiOOH, NiCO3ㆍ2Ni(OH)2ㆍ4H2O, NiC2O4ㆍ2H2O, Ni(NO3)2ㆍ6H2O, fatty acid nickel, and nickel halides, and a mixture of one or two or more of these may be used. Specifically, in order to prevent CO2 from being generated during firing and reacting with residual lithium, and considering the melting point, Ni(OH)2 may be used.

[0111] The above manganese (Mn)-containing raw material may be at least one selected from the group consisting of MnCO3, Mn2O3, MnO2, Mn3O4, Mn(NO3)2, manganese acetate, manganese dicarboxylate, manganese citrate, manganese salts of fatty acid manganese, oxyhydroxides, and halides of manganese chloride, and a mixture of one or two or more of these may be used. Specifically, MnO2 may be used to prevent CO2 from being generated during firing and reacting with residual lithium.

[0112] According to the present invention, the lithium (Li)-containing raw material, the nickel (Ni)-containing raw material, and the manganese (Mn)-containing raw material can be mixed in an amount such that they have a composition represented by the chemical formula 1.

[0113]

[0114] The lithium-excess manganese oxide of the present invention utilizes a process of mixing and crushing using a rotor and beads. By using the rotor and beads, the crushing and mixing efficiency is improved compared to a ball mill, and crushing is possible at a level equivalent to or higher than that of a ball mill in a matter of minutes to hours.

[0115] In addition, since the size of the raw material particles is small and they are mixed uniformly through the mixing and crushing process, the particles grow smoothly during firing, so that excellent single crystallinity can be exhibited.

[0116] A crushing device that can be used in the above method for manufacturing a positive electrode active material is a crushing device such as that illustrated in FIG. 4. FIG. 5 is a front view of the crushing device illustrated in FIG. 4 with the chamber open. The crushing device (100) has a cylindrical chamber (110) whose central axis (C) is horizontally positioned, and a rotor (120) capable of high-speed rotation is provided on the internal central axis. The rotation axis of the rotor (120) is horizontally positioned in line with the central axis of the chamber (110). Since the rotation axis of the rotor (120) is horizontal and the raw material particles rotate along the rotation axis, it can be called a horizontal mill. The rotating blades coupled to the rotor (120) can have various shapes such as a plate shape, a trapezoid shape, and a spiral shape.

[0117] Meanwhile, if the above-mentioned crushing device is not a crushing device as shown in Fig. 4, there is a problem that a LiMn2O4 phase is formed in addition to a Li2MnO3 phase and a LiMO2 (wherein M is an element including at least one selected from Ni, Co, and Mn) phase during the manufacture of the positive electrode active material. If the positive electrode active material includes a LiMn2O4 phase, there is a problem that the capacity characteristics and life characteristics of the battery including it are inferior.

[0118]

[0119] (S20) Step

[0120] Thereafter, a step of firing the mixture to manufacture a fired product is included.

[0121]

[0122] The above mixture may be sintered at a temperature exceeding 900°C, 950°C, or 1,000°C, and 1,050°C or lower, or 1,100°C or lower. In the above temperature range, not only is the formation of a secondary phase suppressed, but a lithium-excess manganese oxide in the form of a single particle and having a high degree of single crystallinity is formed, thereby preventing a decrease in the charge and discharge capacity of the positive electrode active material and improving the life characteristics of a secondary battery manufactured therefrom. When sintering at a temperature below 900°C, a positive electrode active material in the form of a secondary particle is manufactured, and there is a problem with the formation of a single particle shape, and when sintering at a temperature exceeding 1,100°C, there is a problem with the deterioration of the electrochemical characteristics because a layered crystal structure is not properly formed due to over-sintering.

[0123]

[0124] The above firing may be performed for 6 hours or more, 7 hours or more, 8 hours or more, 9 hours or more, 10 hours or more, or 11 hours or more, or 12 hours or less, 13 hours or less, 14 hours or less, or 15 hours or less. Within the above time range, it is advantageous for the formation of a single particle shape, and the particles can grow sufficiently.

[0125]

[0126] (S30) Step

[0127] Thereafter, a step of disintegrating the sintered product to obtain a positive electrode active material including a lithium-excess manganese oxide is included.

[0128] After the above-mentioned sintered product is crushed, a step of mixing and heat-treating the lithium-excess manganese oxide and the coating raw material to form a coating layer on the lithium-excess manganese oxide may be further included.

[0129] The above coating layer can be formed using a method known in the art, for example, a wet coating method, a dry coating method, a plasma coating method, or ALD (Atomic Layer Deposition).

[0130] The above wet coating method can be performed, for example, by adding lithium-excess manganese oxide and coating raw material to an appropriate solvent such as ethanol, water, methanol, acetone, etc., and then mixing until the solvent disappears.

[0131] The above dry coating method is a method of mixing lithium-excess manganese oxide and coating raw material in a solid state without a solvent, and for example, a grinder mixing method or a mechanofusion method can be used.

[0132] The above coating raw material may be an oxide, hydroxide, oxyhydroxide, carbonate, sulfate, halide, sulfide, acetate, carboxylate or a combination thereof containing one or more elements (hereinafter referred to as “coating elements”) selected from the group consisting of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Sr, Sb, Bi, Si and S, for example, ZnO, Al2O3, Al(OH)3, AlSO4, AlCl3, Al-isopropoxide, AlNO3, TiO2, WO 3,　 AlF,H2BO3, HBO2, H3BO3, H2B4O 7,　 B2O3, C6H5B(OH)2, (C6H5O)3B, (CH3(CH2)3O)3B, C3H9B3O6, (C3H7O3)B, Li3WO4, (NH4) 10 W 12 O 41 ·5H2O, NH4H2PO4, etc., but are not limited thereto.

[0133]

[0134] After the coating raw material is attached to the lithium-excess manganese oxide through the above method, a coating layer can be formed through heat treatment. At this time, the heat treatment can be performed at a temperature of 300°C or higher, 350°C or higher, or 400°C or higher, and 450°C or lower, 500°C or lower, 550°C or lower, or 600°C or lower. In the above temperature range, a coating layer in the form of a lithium complex formed by a reaction between the coating raw material and the surface residual lithium can be formed, or a coating layer in the form of a coating raw material coated by melting the coating raw material can be formed, and a coating layer of an appropriate thickness can be formed on the lithium-excess manganese oxide.

[0135]

[0136] anode

[0137] Next, the anode according to the present invention will be described.

[0138] The positive electrode according to the present invention comprises a positive electrode active material layer comprising the positive electrode active material according to the present invention. Specifically, the positive electrode comprises a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and comprising the positive electrode active material. Since the positive electrode active material has been described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below.

[0139]

[0140] The positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of 3 µm to 500 µm, and fine unevenness may be formed on the surface of the positive electrode current collector to increase the adhesive strength of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0141]

[0142] The above-mentioned positive electrode active material layer may include a conductive material and a binder together with the positive electrode active material. At this time, the positive electrode active material may be included in an amount of 80 wt% to 99 wt%, more specifically 85 wt% to 98.5 wt%, based on the total weight of the positive electrode active material layer, and excellent capacity characteristics may be exhibited within this range.

[0143]

[0144] The conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. 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, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One type alone or a mixture of two or more types of these may be used. The conductive material may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0145]

[0146] The above binder serves to improve the adhesion between positive electrode active material particles and the adhesive strength between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The binder may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0147]

[0148] The positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the positive electrode active material described above is used. Specifically, the positive electrode can be manufactured by coating a composition for forming a positive electrode active material layer, which is manufactured by dissolving or dispersing the positive electrode active material and optionally a binder and a conductive material in a solvent, on a positive electrode current collector, followed by drying and rolling. At this time, the types and contents of the positive electrode active material, binder, and conductive material are as described above. Alternatively, the positive electrode can be manufactured by casting the composition for forming a positive electrode active material layer on a separate support, and then laminating the film obtained by peeling it from the support on a positive electrode current collector.

[0149]

[0150] The solvent may be a solvent generally used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these may be used alone or a mixture of two or more thereof may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, taking into account the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0151]

[0152] lithium secondary battery

[0153] Next, a lithium secondary battery according to the present invention will be described.

[0154] The present invention can manufacture an electrochemical device including the above-described positive electrode. The electrochemical device may be, specifically, a battery, a capacitor, or the like, and more specifically, a lithium secondary battery.

[0155]

[0156] The lithium secondary battery specifically includes a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator and electrolyte interposed between the positive electrode and the negative electrode. Since the positive electrode is the same as described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below.

[0157]

[0158] In addition, the lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0159]

[0160] In the above lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0161] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 ㎛ to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0162]

[0163] The above negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material.

[0164]

[0165] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may 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 alloy, Sn alloy, or Al alloy; SiO β(0<β<2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides capable of doping and dedoping lithium; or composites containing the above metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fiber-like forms, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes.

[0166] The above negative electrode active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of the negative electrode active material layer.

[0167]

[0168] The above binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and can typically be added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0169]

[0170] The conductive agent is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10 wt% or less, specifically, 5 wt% or less, based on the total weight of the negative electrode active material layer. The conductive agent is not particularly limited as long as it has conductivity and does not cause a chemical change in the battery, and examples thereof include 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 fiber or metal fiber; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0171]

[0172] The negative electrode active material layer may be manufactured by applying and drying a composition for forming a negative electrode active material layer prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on a negative electrode current collector, or by casting the composition for forming a negative electrode active material layer on a separate support, and then laminating the film obtained by peeling it off from the support on a negative electrode current collector.

[0173]

[0174] Meanwhile, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without special restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, can be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. can also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength can be used, and can optionally be used in a single-layer or multi-layer structure.

[0175]

[0176] In addition, examples of the electrolyte used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0177] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0178] As the organic solvent, any solvent that can serve as a medium through which ions involved in the electrochemical reaction of the battery can move may be used without particular limitation. Specifically, the organic solvent includes 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; carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); Alcohol solvents such as ethyl alcohol, isopropyl alcohol, etc.; nitriles such as R-CN (R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes, etc. can be used. Among these, carbonate solvents are preferable, 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 / discharge performance of a battery and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferable.In this case, the performance of the electrolyte may be improved when the cyclic carbonate and the chain carbonate are mixed and used in a volume ratio of about 1:1 to about 1:9.

[0179]

[0180] The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably used within the range of 0.1 to 5.0 M, specifically, 0.1 to 3.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0181]

[0182] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additive may be included in an amount of 0.1 to 10 wt%, specifically, 0.1 to 5 wt%, based on the total weight of the electrolyte.

[0183]

[0184] As described above, a lithium secondary battery including a cathode active material according to the present invention exhibits excellent life characteristics and capacity characteristics, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0185] Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0186] The above battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0187] There is no particular limitation on the external shape of the lithium secondary battery of the present invention, but it may be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0188] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but can also be preferably used as a unit battery in a medium- to large-sized battery module including a plurality of battery cells.

[0189]

[0190] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0191]

[0192] Example

[0193] Example 1

[0194] 103.99 g of LiOH, 38.29 g of Ni(OH)2, and 107.22 g of MnO2 were placed inside the chamber of a grinding device equipped with a rotor of Fig. 5, and 2.0 kg of zirconia beads with a diameter of 5 mm were placed inside the chamber of the grinding device so that 40% by volume of the volume inside the chamber of the grinding device was made. After that, mixing and grinding were performed by rotating the rotor at 1,600 rpm for 30 minutes. 100 g of the raw material powder obtained through grinding and mixing was taken and placed in a crucible and fired at 1,000 ℃ for 12 hours in an air atmosphere to manufacture a fired product. After the fired product was crushed, it was classified and Li 1.20 Ni 0.20 Mn 0.60 A positive electrode active material (lithium-excess manganese oxide) powder having an average composition of O2 was obtained.

[0195]

[0196] Example 2

[0197] 103.60 g of LiOH, 53.40 g of Ni(OH) and 93.00 g of MnO were placed inside the chamber of a grinding device equipped with a rotor of Fig. 5, and 2.0 kg of zirconia beads with a diameter of 5 mm were placed inside the chamber of the grinding device so that 40% by volume of the volume inside the chamber of the grinding device was made. After that, the rotor was rotated at 1,600 rpm for 30 minutes to perform mixing and grinding. 100 g of the raw material powder obtained through grinding and mixing was taken and placed in a crucible and fired at 1,000 ℃ for 12 hours in an air atmosphere to manufacture a fired product. After the fired product was crushed, it was classified and Li 1.20 Ni 0.28 Mn 0.52 A positive electrode active material (lithium-excess manganese oxide) powder having an average composition of O2 was obtained.

[0198]

[0199] Example 3

[0200] A positive electrode active material (lithium-excess manganese oxide) powder was obtained by performing the same method as in Example 1, except that 100 g of the raw material powder obtained through crushing and mixing was placed in a crucible and fired at 1,050°C for 12 hours in an air atmosphere to produce a fired product.

[0201]

[0202] Comparative Example 1

[0203] Ni0. 25 Mn 0.75 (OH)2 precursor and LiOHㆍH2O were mixed in a stirring mixer (Waring, 7011S) and calcined at 1,000℃ for 12 hours in an air atmosphere to produce a cathode active material. The calcined product was crushed and classified to obtain Li 1.20 Ni 0.20 Mn 0.60 A positive electrode active material (lithium-excess manganese oxide) powder having an average composition of O2 was obtained.

[0204]

[0205] Comparative Example 2

[0206] LiOH 103.99 g, Ni(OH) 238.29 g, and MnO 107.22 g were added to a stirring mixer (Waring, 7011S) and mixed. 100 g of the raw material powder obtained through mixing was placed in a crucible and fired at 1,000 ℃ for 12 hours in an air atmosphere to produce a fired product. The fired product was crushed and classified to obtain Li 1.20 Ni 0.20 Mn 0.60 A positive electrode active material powder having an average composition of O2 was obtained.

[0207]

[0208] Comparative Example 3

[0209] A positive electrode active material (lithium-excess manganese oxide) powder was obtained by performing the same method as in Example 1, except that 100 g of the raw material powder obtained through crushing and mixing was placed in a crucible and fired at 850°C for 12 hours in an air atmosphere to produce a fired product.

[0210]

[0211] Comparative Example 4

[0212] A positive electrode active material (lithium-excess manganese oxide) powder was obtained by performing the same method as in Example 1, except that 100 g of the raw material powder obtained through grinding and mixing was placed in a crucible and fired at 900°C for 12 hours in an air atmosphere to produce a fired product.

[0213]

[0214] Experimental example

[0215] Experimental Example 1: XRD Analysis

[0216] For each positive electrode active material manufactured in the above examples and comparative examples, after XRD measurement, the XRD data is shown in Fig. 1.

[0217] At this time, the XRD (Bruker, D8 Endeavor) collected 2g to 3g of positive electrode active material particles from each positive electrode active material powder, and measured them using an X-ray diffraction analysis method in the 2θ range of 15° to 80° at a scan speed of 0.2° / sec at an acceleration voltage of 40 kV / 40 mA using Cu-Kα rays (wavelength 1.54 Å).

[0218]

[0219] Figure 1 shows XRD data for each of the positive electrode active materials manufactured in Example 1, Example 2, and Comparative Examples 1 to 4.

[0220]

[0221] Through Figure 1, it was confirmed that the positive electrode active materials manufactured in Examples 1, 2, Comparative Examples 1, 3, and 4 simultaneously contained two phases. Specifically, it was confirmed that the positive electrode active materials contained a Li2MnO3 phase with a small peak present at 20° to 25°, that the positive electrode active materials contained a LiMO2 phase (wherein M is an element including Ni, Mn, or a combination thereof) with a large peak present at 18°, and that the positive electrode active materials did not contain a LiMn2O4 phase.

[0222] Meanwhile, in Comparative Example 2, that is, the cathode active material manufactured using a mixing device rather than a grinding device equipped with a rotor of FIG. 5, it was confirmed that it contained Li2MnO3 phase and LiMO2 (wherein M is an element including Ni, Mn or a combination thereof) phase simultaneously, as it had the same peaks as the Example at 20° to 25° and 18°, and it was confirmed that the peak patterns were different from the Example at about 36.5°, about 44.5°, and about 60° to 70° due to non-uniform mixing. In particular, it was confirmed that it contained LiMn2O4 phase with a split peak existing at about 44.5°.

[0223] In conclusion, it was confirmed that the positive electrode active materials manufactured in Examples 1, 2, Comparative Examples 1, 3, and 4 were lithium-excess manganese oxides including a Li2MnO3 phase and a LiMO2 (wherein M is an element including at least one selected from Ni, Co, and Mn) phase, and the positive electrode active material manufactured in Comparative Example 2 was confirmed not to be a lithium-excess manganese oxide according to the present invention because it included a LiMn2O4 phase.

[0224]

[0225] Experimental Example 2: Morphology, particle size, and BET surface area analysis

[0226] -form

[0227] For each of the positive electrode active materials manufactured in the above examples and comparative examples, SEM images were obtained using a scanning electron microscope (SEM) (JEOL, JSM7610F), and are shown in Fig. 2.

[0228]

[0229] Specifically, FIG. 2(A) is an SEM image of a positive electrode active material manufactured in Example 1, FIG. 2(B) is an SEM image of a positive electrode active material manufactured in Example 2, FIG. 2(C) is an SEM image of a positive electrode active material manufactured in Example 3, FIG. 2(D) is an SEM image of a positive electrode active material manufactured in Comparative Example 1, FIG. 2(E) is an SEM image of a positive electrode active material manufactured in Comparative Example 3, and FIG. 2(F) is an SEM image of a positive electrode active material manufactured in Comparative Example 4.

[0230]

[0231] As shown in Fig. 2, it was confirmed that the positive electrode active materials manufactured in Examples 1 to 3 according to the present invention were in the form of single particles.

[0232]

[0233] -Intake

[0234] For the positive electrode active material particles manufactured in the above examples and comparative examples, the minimum particle diameter (D) of the positive electrode active material was measured using PSA (Microtrac, S3500). min )(㎛), average particle diameter(D 50 )(㎛) and maximum particle diameter (D max )(㎛) was measured, and the results are shown in Table 1 below.

[0235]

[0236] -BET specific surface area

[0237] The positive electrode active materials manufactured in the above examples and comparative examples were fired at 120°C for 6 hours in a vacuum atmosphere to remove all moisture, and then the specific surface area was measured by the BET method using BELSORP-mini II from BEL Japan, calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77K). The results are shown in Table 1 below.

[0238]

[0239] Minimum particle diameter (D min ) (㎛)Average particle diameter (D) 50 ) (㎛) Maximum particle diameter (D) max ) (㎛)BET specific surface area (m 2 / g)Example 10.540.873.862.32Example 20.620.943.972.24Example 30.771.244.781.78Comparative Example 10.210.472.323.57Comparative Example 20.520.904.022.30Comparative Example 30.100.545.165.48Comparative Example 40.140.625.324.73

[0240]

[0241] Through the above Table 1, the positive electrode active materials manufactured in Examples 1 to 3 had an average particle diameter (D 50 ) was confirmed to be 0.6㎛ to 1.5㎛. On the other hand, the positive electrode active materials manufactured in Comparative Examples 1 and 3 had an average particle diameter (D 50 ) is less than 0.6㎛, and the average particle diameter (D) compared to the example 50 ) was measured relatively low.

[0242] In addition, the positive electrode active materials manufactured in Examples 1 to 3 have a BET specific surface area of ​​1.5 m 2 / g to 3.0m 2 / g. On the other hand, the positive electrode active materials manufactured in Comparative Examples 1 to 4 had a BET specific surface area of ​​3.0 m 2 / g, the BET specific surface area was measured to be relatively high compared to the example.

[0243] In conclusion, it can be seen that the positive electrode active material according to the present invention has a single particle form and a small specific surface area, thereby improving structural stability.

[0244]

[0245] Experimental Example 3: Single Crystallinity Analysis

[0246] For each of the positive electrode active materials manufactured in the above examples and comparative examples, 92.5 wt% of the positive electrode active material, 3.0 wt% of Super P as a conductive agent, and 4.5 wt% of polyvinylidene fluoride (PVDF) as a binder were mixed in an N-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry. The prepared positive electrode slurry was applied to one surface of an aluminum current collector and then dried at 130°C to prepare a positive electrode for EBSD analysis. Rolling was not performed during the manufacture of the positive electrode.

[0247] Using an ion milling device (HITACHI IM-500, acceleration voltage 6 kV), the anode was cut into cross-sections, and an FE-SEM equipped with a backscatter electron diffraction pattern analyzer (EBSD) (JEOL JSM-7900Fw, Oxford Symmetry EBSD detector) was used to perform EBSD analysis on the cross-section of the anode to obtain an IPF map, which is shown in Fig. 3. The EBSD analysis was performed under the conditions of an acceleration voltage of 20 kV and a WD of 18 mm.

[0248] A two-dimensional segmentation image divided into primary particle units is obtained by image processing the crystal grains identified in the IPF map image using an artificial intelligence model. The segmentation image can be obtained by performing EBSD analysis on an EBSD analysis positive electrode manufactured using a positive electrode active material to be measured, inputting the obtained image into a U-NET structure or the like to generate a boundary image, identifying a plurality of objects included in the boundary image, and then segmenting the IPF map image into primary particle units based on the plurality of objects.

[0249] In this specification, the cross-sectional area (A) of a single particle may be measured by the number of pixels corresponding to each of n single particles present in the segmentation image. Specifically, it may be calculated by the number of pixels of the cross-sectional area corresponding to each single particle when the IPF map image is converted into a segmentation image, which is an image projected onto a two-dimensional plane.

[0250] In this specification, the cross-sectional area of ​​a crystal grain may be measured by the number of pixels corresponding to each of n crystal grains present in the segmentation image. Specifically, it may be calculated by the number of pixels corresponding to the cross-sectional area of ​​each crystal grain when the IPF map image is converted into a segmentation image, which is an image projected onto a two-dimensional plane.

[0251]

[0252] Specifically, FIG. 3(A) is an IPF map, a boundary image, and a segmentation image obtained by EBSD analysis of a positive electrode for EBSD analysis manufactured using the positive electrode active material manufactured in Example 1, FIG. 3(B) is an IPF map, a boundary image, and a segmentation image obtained by EBSD analysis of a positive electrode for EBSD analysis manufactured using the positive electrode active material manufactured in Example 2, FIG. 3(C) is an IPF map, a boundary image, and a segmentation image obtained by EBSD analysis of a positive electrode for EBSD analysis manufactured using the positive electrode active material manufactured in Example 3, and FIG. 3(D) is an IPF map, a boundary image, and a segmentation image obtained by EBSD analysis of a positive electrode for EBSD analysis manufactured using the positive electrode active material manufactured in Comparative Example 1.

[0253]

[0254] The cross-sectional area of ​​a single particle (A) and the cross-sectional area of ​​the i-th crystal grain (A i ) is calculated by substituting the single crystallinity (χ) into Equation 1 described in this specification and is shown in Table 2 below.

[0255]

[0256] Single crystallinity (χ) Example 10.647 Example 20.621 Example 30.676 Comparative example 10.509

[0257] Through the above Table 2, it was confirmed that the positive electrode active materials manufactured in Examples 1 to 3 had a single crystallinity (χ) according to Equation 1 described herein of 0.51 or more and 0.70 or less. On the other hand, it was confirmed that the positive electrode active material manufactured in Comparative Example 1 had a single crystallinity according to Equation 1 described herein of less than 0.51.

[0258] Meanwhile, in the case of the positive electrode active material manufactured in Comparative Example 2, since the LiMn2O4 phase was formed, it was not a lithium-excess manganese oxide according to the present invention, and therefore the single crystallinity was not additionally calculated. In addition, in the case of the positive electrode active materials manufactured in Comparative Examples 3 and 4, it was confirmed that it was difficult to derive the single crystallinity because almost all the particles existed in an agglomerated form.

[0259]

[0260] Experimental Example 4: Battery Characteristics Analysis

[0261] - Manufacturing of coin-type half-cells

[0262] A positive electrode slurry was prepared by mixing 92.5 wt% of each of the positive electrode active materials manufactured in the above examples and comparative examples, 3.0 wt% of Super P as a conductive agent, 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, dried at 130°C, and then rolled to manufacture a positive electrode.

[0263] An electrode assembly was manufactured using a lithium metal electrode as the negative electrode and a porous polyethylene separator interposed between the positive and negative electrodes. This was placed inside a battery case, and a coin-type half-cell was manufactured by injecting an electrolyte solution containing 1 M LiPF6 dissolved in an organic solvent containing ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) in a volume ratio of 3:4:3.

[0264]

[0265] - Evaluation of the occurrence of bipolar defects

[0266] For the positive electrodes including each of the positive electrode active materials manufactured in the above examples and comparative examples, the surface of the positive electrode was photographed using a camera, and the images of the surfaces of the positive electrodes including each of the positive electrode active materials manufactured in Examples 1 to 3 and Comparative Examples 3 and 4 are shown in Fig. 6.

[0267] Specifically, FIG. 6(A) is an image of the surface of a positive electrode including a positive electrode active material manufactured in Example 1, FIG. 6(B) is an image of the surface of a positive electrode including a positive electrode active material manufactured in Example 2, FIG. 6(C) is an image of the surface of a positive electrode including a positive electrode active material manufactured in Example 3, FIG. 6(D) is an image of the surface of a positive electrode including a positive electrode active material manufactured in Comparative Example 3, and FIG. 6(E) is an image of the surface of a positive electrode including a positive electrode active material manufactured in Comparative Example 4.

[0268]

[0269] Through Fig. 6, it was confirmed that the surface of the positive electrode including the positive electrode active material manufactured in Examples 1 to 3 had no lumped portions and was even. On the other hand, it was confirmed that the surface of the positive electrode including the positive electrode active material manufactured in Comparative Examples 3 and 4 had many lumped portions (indicated by circles) corresponding to defects and was uneven.

[0270]

[0271] - Battery characteristic evaluation

[0272] Coin-type half-cells containing each of the positive electrode active materials manufactured in the above examples and comparative examples were charged (0.1C) in a CC-CV manner at 45°C to 4.65 V, and then discharged (0.1C) in a CC manner to 2.0 V to perform an activation process (formation), and the charge and discharge capacities at this time were measured. The measured charge and discharge capacities and the percentage of discharge capacity to charge capacity (efficiency (%)) are shown in Table 3 below.

[0273] Next, the initial charge-discharge process was performed by charging (0.1C) to 4.4 V at 25°C using the CC-CV method, and then discharging (0.1C) to 2.5 V using the CC method, and the charge and discharge capacities at this time were measured. The measured charge and discharge capacities and the percentage of discharge capacity to charge capacity (efficiency (%)) are shown in Table 3 below.

[0274] After charging (0.33C) to 4.4 V at 25°C using the CC-CV method, the initial charge-discharge process was performed by discharging (0.33C) to 2.5 V using the CC method, and the charge and discharge capacities at this time were measured. The measured charge and discharge capacities and the percentage of discharge capacity to charge capacity (efficiency (%)) are shown in Table 3 below.

[0275] After charging (0.33C) to 4.4 V at 25 ℃ in a CC-CV manner, and then discharging (0.33C) to 2.5 V in a CC manner, one cycle was defined as a cycle, and a total of 30 cycles of charging and discharging were repeated, and the discharge capacities in the first and 30th cycles were measured. The measured discharge capacities in the first cycle and the percentage of the discharge capacity in the 30th cycle to the discharge capacity in the first cycle (capacity retention rate (%)) are shown in Table 3 below.

[0276]

[0277] Distinction activation process @ 45℃ / 4.65V / 0.1C Initial charge and discharge @ 4.4V / 0.1C Initial charge and discharge @ 4.4V / 0.33C 30 cycles Charge capacity (mAh / g) Discharge capacity (mAh / g) Efficiency (%) Charge capacity (mAh / g) Discharge capacity (mAh / g) Efficiency (%) Charge capacity (mAh / g) Discharge capacity (mAh / g) Efficiency (%) Capacity retention rate Example 1314.2275.087.5222.5202.290.9199.9185.192.699.3 Example 2310.1270.787.3223.4203.491.0198.9184.492.799.4 Example 3311.1270.586.9219.7200.891.4198.1180.491.199.6Comparative example 1315.3267.684.9213.4193.790.8194.1178.091.798.5Comparative example 2308.2255.482.8202.4179.288.5181.8161.588.896.5

[0278] As shown in Table 3 above, the batteries including the positive electrode active materials manufactured in Examples 1 to 3, which mixed the raw materials using the rotor-equipped grinding device of FIG. 5, were confirmed to have superior discharge capacity and efficiency in the activation process, initial charge / discharge capacity and efficiency at 0.1 C conditions, initial charge / discharge capacity and efficiency at 0.33 C conditions, and capacity retention rate compared to the batteries including the positive electrode active materials manufactured in Comparative Example 1, which mixed the precursors without using the rotor-equipped grinding device of FIG. 5, and the batteries including the positive electrode active materials manufactured in Comparative Example 2, which did not use the rotor-equipped grinding device of FIG. 5. On the other hand, the positive electrode active materials manufactured in Comparative Examples 3 and 4, which were fired at a firing temperature of 900°C or lower, had a high incidence of electrode defects due to small particle size and high specific surface area, making battery production impossible.

[0279] In conclusion, it can be seen that the cathode active material according to the present invention has improved structural stability, so that not only does it cause less irreversible capacity loss during the activation process, but it is also stable with little structural change during charge / discharge cycles.

Claims

1. Contains a lithium-excess manganese oxide including a Li2MnO3 phase and a LiMO2 (wherein M is an element including at least one selected from Ni, Co, and Mn) phase, The above lithium-excess manganese oxide is in the form of single particles, The above lithium-excess manganese oxide is a cathode active material having a single crystallinity (χ) of 0.51 or more and 0.70 or less according to the following formula 1: [Formula 1] In the above equation 1, a i When a single particle is composed of i crystal grains, the cross-sectional area of ​​the i-th crystal grain (A) is the cross-sectional area of ​​the single particle (A). i ) value (A i / A) means.

2. In claim 1, The above lithium-excess manganese oxide is a cathode active material represented by the following chemical formula 1: [Chemical Formula 1] Li x Ni a Mr b M 1 c O2 In the above chemical formula 1, M 1 is at least one selected from the group consisting of Co, Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, Sn, Y and Zn, 1.00 <x≤1.30, 0.10≤a≤0.50, 0.50≤b≤0.90, 0≤c≤0.10, x+a+b+c=2이다.

3. In claim 1, The above lithium-excess manganese oxide has an average particle diameter (D 50 ) A positive electrode active material having a diameter of 0.6㎛ to 1.5㎛.

4. In claim 1, The above lithium-excess manganese oxide has a BET surface area of ​​1.5 m 2 / g to 3.0m 2 / g positive electrode active material.

5. In claim 1, A cathode active material further comprising a coating layer formed on the lithium-excess manganese oxide and including at least one coating element selected from the group consisting of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Sr, Sb, Bi, Si and S. 6.(S10) A step of introducing a lithium (Li)-containing raw material, a nickel (Ni)-containing raw material, and a manganese (Mn)-containing raw material into a crushing device, and dry mixing and crushing to produce a mixture; (S20) A step of manufacturing a sintered product by firing the mixture at a temperature of more than 900°C and less than or equal to 1,100°C; and (S30) A step of crushing the above-mentioned product to obtain a positive electrode active material including a lithium-excess manganese oxide, The above crushing device comprises a chamber and a rotor rotatable inside the chamber, The method for producing a cathode active material according to claim 1, wherein the mixing and crushing in the above step (S10) is performed by placing lithium (Li)-containing raw material, nickel (Ni)-containing raw material, and manganese (Mn)-containing raw material and beads into the chamber of the crushing device and rotating the rotor.

7. In claim 6, A method for manufacturing a positive electrode active material, wherein the calcination in the above step (S20) is performed for 6 to 15 hours.

8. In claim 6, In the above step (S30), after the sintered product is crushed, a step of mixing and heat-treating the lithium-excess manganese oxide and the coating raw material to form a coating layer on the lithium-excess manganese oxide is further included. A method for producing a positive electrode active material, wherein the above heat treatment is performed at a temperature of 300°C to 600°C.

9. A positive electrode comprising the positive electrode active material of any one of claims 1 to 5.

10. A lithium secondary battery comprising the positive electrode of claim 9.

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