Cathode active material for lithium secondary battery, and lithium secondary batterty comprising same

Abstract

A cathode active material for a lithium secondary battery, according to the present invention, is a bimodal cathode active material for a lithium secondary battery. The cathode active material may satisfy expression 1 in the present specification.

Description

Cathode active material for lithium secondary batteries and lithium secondary batteries containing the same

[0001] These examples relate to a positive electrode active material for a lithium secondary battery and a lithium secondary battery including the same.

[0002] Recently, demand for IT mobile devices, small electric powertrains (e-bikes, small EVs, etc.), and energy storage systems (ESS) has been explosively increasing. Accordingly, the development of high-capacity, high-energy-density secondary batteries to power these devices is actively underway worldwide. Manufacturing these high-capacity batteries requires the use of high-capacity cathode materials.

[0003] Among the existing layered cathode active materials, the material with the highest capacity is LiNiO2, but its structural collapse occurs easily during charge and discharge, and its thermal stability is low due to oxidation number issues, making commercialization difficult.

[0004] To solve these problems, the unstable Ni site must be replaced with another stable transition metal (Co, Mn, etc.), and for this purpose, a ternary NCM system with Co and Mn substituted was developed.

[0005] In addition, development is being carried out on so-called bimodal cathode active materials that can improve the rolling density by mixing cathode active materials of small and large particle sizes to achieve high energy density.

[0006] Accordingly, there is a need for the development of a cathode active material that can increase the life stability of a battery while simultaneously exhibiting excellent electrochemical properties such as charge / discharge capacity in a bimodal form.

[0007] In this embodiment, a cathode active material for a lithium secondary battery and a lithium secondary battery including the same can be provided, in which electrochemical characteristics and stability can be improved by satisfying an appropriate range of a specific formula in a bimodal type cathode active material.

[0008] According to one embodiment, a cathode active material for a lithium secondary battery may be a cathode active material for a lithium secondary battery in a bimodal form, including a first lithium metal oxide; and a second lithium metal oxide having a smaller average particle diameter (D50) than the first lithium metal oxide, and satisfying the following equation 1.

[0009] [Formula 1]

[0010] 12.00 X 10 6 m -1 ≤ (SA*R) / S2 ≤ 14.85 X 10 6 m -1

[0011] In the above equation 1, SA is the BET (Brunauer-Emmett-Teller) specific surface area of ​​the positive electrode active material, R is the weight ratio of the first lithium metal oxide in the positive electrode active material, and S2 is the area between the adsorption isotherm and the desorption isotherm in the range of the relative pressure (p / p0) of 0.1 or more and 0.7 or less in the nitrogen adsorption / desorption isotherm graph measured by the BJH (Barrett-Joyner-Halenda) method for the positive electrode active material.

[0012] A lithium secondary battery according to another embodiment may be a lithium secondary battery including a positive electrode for a lithium secondary battery including the positive electrode active material according to one embodiment.

[0013] According to the present embodiment, the stability and electrochemical properties of a positive electrode active material for a lithium secondary battery can be improved by appropriately controlling the manufacturing process to satisfy a specific range of a relationship consisting of an area for a specific relative pressure section in a BJH graph.

[0014] Accordingly, the lithium secondary battery manufactured as in this example can have improved electrochemical performance, such as stability and capacity.

[0015] Figure 1 is a graph of nitrogen adsorption / desorption isotherms measured by the BJH (Barrett-Joyner-Halenda) method for a positive electrode active material according to Example 1.

[0016] Figure 2 is a graph of nitrogen adsorption and desorption isotherms measured by the BJH (Barrett-Joyner-Halenda) method for a positive electrode active material according to Example 2.

[0017] Figure 3 is a graph of nitrogen adsorption / desorption isotherms measured by the BJH (Barrett-Joyner-Halenda) method for a positive electrode active material according to Example 3.

[0018] Figure 4 is a graph of nitrogen adsorption and desorption isotherms measured by the BJH (Barrett-Joyner-Halenda) method for a positive electrode active material according to Example 4.

[0019] Figure 5 is a graph of nitrogen adsorption and desorption isotherms measured by the BJH (Barrett-Joyner-Halenda) method for the positive electrode active material according to Comparative Example 1.

[0020] Figure 6 is a graph of nitrogen adsorption and desorption isotherms measured by the BJH (Barrett-Joyner-Halenda) method for the positive electrode active material according to Comparative Example 2.

[0021] Figure 7 is a graph of nitrogen adsorption / desorption isotherms measured by the BJH (Barrett-Joyner-Halenda) method for the positive electrode active material according to Comparative Example 3.

[0022] Figure 8 is a graph of nitrogen adsorption / desorption isotherms measured by the BJH (Barrett-Joyner-Halenda) method for the positive electrode active material according to Comparative Example 4.

[0023] Figure 9 is a graph of nitrogen adsorption / desorption isotherms measured by the BJH (Barrett-Joyner-Halenda) method for the positive electrode active material according to Comparative Example 5.

[0024] Figure 10 is a graph of nitrogen adsorption / desorption isotherms measured by the BJH (Barrett-Joyner-Halenda) method for the positive electrode active material according to Comparative Example 6.

[0025] Figure 11 is a graph of nitrogen adsorption / desorption isotherms measured by the BJH (Barrett-Joyner-Halenda) method for the positive electrode active material according to Comparative Example 7.

[0026] Figure 12 is a cross-sectional SEM image measured after Cross Section Polisher (CP) etching of the first lithium metal oxide used in Comparative Example 6.

[0027] Figure 13 is a cross-sectional SEM image measured after Cross Section Polisher (CP) etching of the first lithium metal oxide used in Comparative Example 7.

[0028] Figure 14 is a cross-sectional SEM image measured after Cross Section Polisher (CP) etching of the first lithium metal oxide used in Example 1.

[0029] The terms first, second, and third, etc., are used to describe, but are not limited to, various parts, components, regions, layers, and / or sections. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0030] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "singular" and "comprising" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising" as used herein specifies a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0031] When a part is referred to as being "on" or "over" another part, it can be directly on or over the other part, or there may be other parts intervening. Conversely, when a part is referred to as being "directly on" another part, there are no other parts intervening.

[0032] Although not defined otherwise, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or overly formal unless otherwise defined.

[0033] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0034] In this specification, the term "combination(s) thereof" described in the expression in the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expression in the Makushi format, and means including any one or more selected from the group consisting of said components.

[0035] 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.

[0036]

[0037] Cathode active material for lithium secondary batteries

[0038] A cathode active material for a lithium secondary battery according to one embodiment of the present invention includes a first lithium metal oxide and a second lithium metal oxide.

[0039] At this time, the average particle diameter (D50) of the first lithium metal oxide is larger than the average particle diameter (D50) of the second lithium metal oxide. That is, the cathode active material according to the present invention is a bimodal cathode active material in which large-diameter and small-diameter cathode active materials are mixed. When an electrode is implemented with a bimodal cathode active material, the small-diameter particles can occupy the empty space between the large-diameter particles, thereby improving the electrode rolling density.

[0040] However, there is a need to further improve the electrochemical properties of bimodal high-nickel cathode active materials. Accordingly, the present invention can provide a cathode active material for a lithium secondary battery that satisfies the following equation 1.

[0041] [Formula 1]

[0042] 12.00 X 10 6 m -1 ≤ (SA*R) / S2 ≤ 14.85 X 10 6 m -1

[0043] In the above equation 1,

[0044] The above SA is the BET (Brunauer-Emmett-Teller) specific surface area of ​​the positive electrode active material. Here, the BET specific surface area can be measured using the BET method (Surface area and Porosity analyzer) (Micromeritics, Tristar2 3020) for the active material powder.

[0045] The above R is the weight ratio of the first lithium metal oxide in the positive electrode active material. For example, if the positive electrode active material is manufactured by mixing the first lithium metal oxide and the second lithium metal oxide at a weight ratio of 9:1, R can be calculated as 0.9.

[0046] The above S2 is the area between the adsorption isotherm and desorption isotherm in the nitrogen adsorption / desorption isotherm graph measured by the BJH (Barrett-Joyner-Halenda) method for the positive electrode active material in the range of relative pressure (p / p0) from 0.1 to 0.7. At this time, the nitrogen adsorption / desorption isotherm graph can be obtained using Micromeritics, Tristar2 3020 for the active material powder, but is not limited thereto.

[0047] In the above equation 1, (SA*R) / S2 is more specifically 12.50 X 10 6 m -1 14.80 X 10 6 m -1 , 12.70 X 10 6 m -1 14.70 X 10 6 m -1 , 12.90 X 10 6 m -1 14.65 X 10 6 m -1 , 13.00 X 10 6 m -1 14.60 X 10 6 m -1 , or 13.07 X 10 6 m -1 14.00 X 106 m -1 It could be.

[0048] By satisfying the above equation 1, the charge / discharge efficiency and the life characteristics at high temperatures can be improved. More specifically, the initial charge / discharge efficiency of 89.1% or higher can be satisfied, while at the same time exhibiting excellent life characteristics in more than 30 charge / discharge cycles at a high temperature of 45°C. In this case, the initial charge / discharge efficiency can be calculated as {(initial discharge capacity) / (initial charge capacity)}*100.

[0049] The above SA is 0.5300 to 0.6600 m 2 / g range, more specifically 0.5400 to 0.6500 m 2 / g, 0.5550 to 0.6400 m 2 / g, 0.5700 to 0.6350 m 2 / g, 0.5760 to 0.5870 m 2 / g or 0.5760 to 0.5860 m 2 / g can be in the range.

[0050] By ensuring that the BET surface area satisfies the above range, the cathode active material exhibits specific surface activity, thereby improving the life characteristics and charge / discharge efficiency.

[0051] The above R may be in the range of 0.45 to 0.85, more specifically in the range of 0.47 to 0.83, 0.49 to 0.81, 0.50 to 0.80 or 0.69 to 0.81.

[0052] When the weight ratio R of the first lithium metal oxide in the positive electrode active material satisfies the above range, the charge / discharge capacity can be increased and the fine particle generation rate can be reduced. If the content of the first lithium metal oxide is too high, the packing density may decrease, which may reduce the charge / discharge capacity. Even if the content of the second lithium metal oxide is too high, the packing density may increase, which may cause the pressure to exceed the appropriate rolling density range or increase the fine particle generation rate.

[0053] The above S2 is 0.02250 to 0.03500 cm 3 / g range, more specifically 0.02350 to 0.03400 cm 3 / g, 0.02400 to 0.03350 cm 3 / g, 0.02420 to 0.03340 cm 3 / g or 0.0300 to 0.03340 cm 3 / g can be in the range.

[0054] When S2, which is the area difference between the adsorption and desorption isotherms in the range of relative pressure (p / p0) from 0.10 to 0.70, satisfies the above range, the initial charge / discharge efficiency and cycle characteristics can be improved. More specifically, when it is below the above range, it means that the area difference between the adsorption and desorption isotherms in the section where the relative pressure is not high is not large, in which case the initial charge / discharge efficiency can be reduced, and when it is above the above range, it means that the area difference between the adsorption and desorption isotherms in the section where the relative pressure is not high is large, in which case the high-temperature cycle characteristics can be deteriorated.

[0055]

[0056] In another embodiment of the present invention, the average circumference of the primary particles present in the first lithium metal oxide may be in the range of 2.00 to 3.20 μm, 2.00 to 3.00 μm, or 2.00 to 2.50 μm.

[0057] In the case of a cathode active material including a first lithium metal oxide satisfying the above average circumference range, when applied to a lithium secondary battery, the phenomenon of life deterioration can be suppressed as the contact surface with the electrolyte becomes smaller.

[0058] In the present invention, “primary particle” refers to the smallest particle unit that can be distinguished as a single lump when observing a cross-section of a positive electrode active material through a scanning electron microscope (SEM), and may be composed of a single crystal grain or multiple crystal grains. Here, “crystal grain” refers to a distinct region in which atoms within a primary particle form a lattice structure with a certain direction.

[0059] Additionally, “secondary particle” refers to an aggregate of tens to hundreds of primary particles formed by physical or chemical bonding between the primary particles without any intentional agglomeration or assembly process for the primary particles.

[0060] In the present invention, the “average circumference” can be obtained from an image of a primary particle identified from a cross-sectional image obtained based on the center of the secondary particle. Specifically, the average circumference of the primary particle may be obtained by measuring the primary particle identified from the cross-sectional SEM image of the secondary particle using the Image J Program. More specifically, the average circumference of the primary particle may be obtained by measuring the average of the circumferences of 10 to 50 primary particles in the cross-sectional SEM image of the secondary particle. Specifically, it may be 15 to 50, and more specifically, 20 to 35.

[0061]

[0062] In another embodiment of the present invention, a positive electrode active material for a lithium secondary battery may satisfy the following equation 2.

[0063] [Formula 2]

[0064] 0.6300 ≤ (S3-S2) / S1 ≤ 0.6900

[0065] In the above equation 2,

[0066] S1 is the area between the adsorption and desorption isotherms in the nitrogen adsorption and desorption isotherm graph measured by the BJH (Barrett-Joyner-Halenda) method for the positive electrode active material in the range of relative pressure (p / p0) from 0.10 to 0.99.

[0067] S2 is the area between the adsorption and desorption isotherms in the nitrogen adsorption and desorption isotherm graph measured by the BJH (Barrett-Joyner-Halenda) method for the positive electrode active material, in the range of relative pressure (p / p0) from 0.10 to 0.70.

[0068] S3 is the area between the adsorption and desorption isotherms in the nitrogen adsorption and desorption isotherm graph measured by the BJH (Barrett-Joyner-Halenda) method for the positive electrode active material in the range of relative pressure (p / p0) from 0.70 to 0.99.

[0069] In the above equation 2, (S3-S2) / S1 can be more specifically 0.6350 to 0.6850, 0.6400 to 0.6850, or 0.6500 to 0.6800.

[0070]

[0071] By satisfying the above equation 2, charge-discharge efficiency and high-temperature life characteristics can be improved. Specifically, a lithium secondary battery containing the cathode active material can exhibit superior electrochemical performance by simultaneously improving charge-discharge efficiency and life characteristics at high temperatures above 45°C. In particular, even after 50 repeated charge-discharge cycles at high temperatures above 45°C, it can exhibit excellent life characteristics of 94.7% or more.

[0072] The above S1 is 0.1100 to 0.2300 cm 3 / g, more specifically 0.1200 to 0.2200 cm 3 / g, 0.1300 to 0.2100 cm 3 / g, or 0.1800 to 0.2100 cm3 / g can be in the range.

[0073] When S1, which is the area difference between the adsorption and desorption isotherms in the range of relative pressure (p / p0) from 0.1 to 0.99, satisfies the above range, the initial charge / discharge efficiency and cycle characteristics can be improved. More specifically, when it is below the above range, it means that the area difference between the adsorption and desorption isotherms is not large, in which case the initial charge / discharge efficiency can be reduced, and when it is above the above range, it means that the area difference between the adsorption and desorption isotherms is large, in which case the high-temperature cycle characteristics can be deteriorated.

[0074] The above S3 is 0.0535 to 0.1900 cm 3 / g, more specifically 0.1150 to 0.1900 cm 3 / g, 0.1250 to 0.1850 cm 3 / g, 0.1350 to 0.1800 cm 3 / g, or 0.1500 to 0.1750 cm 3 / g can be in the range.

[0075] When S3, which is the area difference between the adsorption and desorption isotherms in the range of relative pressure (p / p0) from 0.7 to 0.99, satisfies the above range, the initial charge / discharge efficiency and cycle characteristics can be improved. More specifically, when it is below the above range, it means that the area difference between the adsorption and desorption isotherms in the section with high relative pressure is not large, in which case the initial charge / discharge efficiency can be reduced, and when it is above the above range, it means that the area difference between the adsorption and desorption isotherms in the section with high relative pressure is large, in which case the high-temperature cycle characteristics can be deteriorated.

[0076] The above S2 is 0.0300 to 0.0350 cm 3 / g range, more specifically 0.0300 to 0.03340 cm3 / g can be in the range.

[0077] When S2, which is the area difference between the adsorption and desorption isotherms in the range where the relative pressure (p / p0) is 0.10 or more and 0.70 or less, satisfies the above range, the high-temperature life characteristics can be improved. More specifically, when it is below the above range, it means that the area difference between the adsorption and desorption isotherms in the section where the relative pressure is not high is not large, in which case the high-temperature life characteristics can be deteriorated, and when it is above the above range, it means that the area difference between the adsorption and desorption isotherms in the section where the relative pressure is not high is large, in which case the high-temperature life characteristics can also be deteriorated.

[0078]

[0079] In another embodiment of the present invention, the positive electrode active material for a lithium secondary battery may be such that the first lithium metal oxide is in the form of secondary particles including a plurality of primary particles, and the second lithium metal oxide is in the form of a single crystal in which 1 or 2 to 20 single particles are aggregated.

[0080] At this time, the meaning of primary particles and secondary particles, etc. is as described above.

[0081]

[0082] In another embodiment of the present invention, the positive electrode active material for a lithium secondary battery may have a volume-based average particle diameter (Dv50) of the first lithium metal oxide in a range of 5 to 20 μm, and a volume-based average particle diameter (Dv50) of the second lithium metal oxide in a range of 1.0 to 5.0 μm.

[0083] The average particle diameter (Dv50) based on volume of the first lithium metal oxide may preferably be 7 to 18 μm, more preferably 8 to 15 μm.

[0084] The average particle diameter (Dv50) based on volume of the second lithium metal oxide may preferably be 1.5 to 5.0 μm, more preferably 2.0 to 5.0 μm.

[0085] In this specification, the average particle diameter (D50) may mean the average particle diameter by volume (Dv50) unless otherwise indicated, and the average particle diameter by volume (Dv50) may be defined as a particle diameter corresponding to 50% of the volume accumulation amount in a particle diameter distribution curve. The average particle diameter may be measured using, for example, a laser diffraction method.

[0086] When the average particle size satisfies the above range, it is preferable that the capacity of the positive electrode active material be improved.

[0087] In another embodiment of the present invention, the positive electrode active material may include one or more transition metals selected from the group consisting of nickel, cobalt, and manganese.

[0088] In another embodiment of the present invention, the first lithium metal oxide and the second lithium metal oxide are each independently a positive electrode active material for a lithium secondary battery represented by the following chemical formula 1:

[0089] [Chemical Formula 1]

[0090] Li a [Ni x Co y Mn z M w ]O2

[0091] In the above chemical formula 1, 0.8≤a≤1.2, 0.8≤x<1, 0≤y≤0.2, 0≤z≤0.2, 0≤w≤0.1, x+y+z+w=1, and M is Zr, Y, B, Al, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, or a combination thereof.

[0092] At this time, the nickel content of the first lithium metal oxide may be 1.0 to 10.0 mol% less than the nickel content of the second lithium metal oxide. By satisfying the above range, the life characteristics and energy density at room temperature and high temperature may be improved by satisfying Equation 1 of the present invention.

[0093] More specifically, the nickel content of the first lithium metal oxide may be 80 to 92 mol% based on the total mole number of metals excluding lithium, and the nickel content of the second lithium metal oxide may be 92 to 96 mol% based on the total mole number of metals excluding lithium.

[0094] In the positive electrode active material of the above chemical formula 1, lithium may be included in an amount corresponding to a, that is, 0.8≤a≤1.2. If a is too small, the capacity may be reduced, and if a is too large, the strength of the sintered positive electrode active material may be increased, making pulverization difficult, and the amount of gas generated may increase due to an increase in lithium byproducts. Considering the effect of improving the capacity characteristics of the positive electrode active material according to the control of the lithium content and the sinterability balance during the production of the active material, the lithium may be included in an amount of 0.9≤a≤1.1 more preferably.

[0095] In the positive electrode active material of the above chemical formula 1, nickel may be included in an amount corresponding to x, i.e., 0.8≤x<1. As described above, if the nickel content is too low, it may be difficult to achieve high capacity of the battery. If the nickel content is too high, the battery life and thermal safety may be reduced due to the deterioration of the structural stability of the active material, but this has been improved in the present invention.

[0096] In the positive electrode active material of the above chemical formula 1, cobalt may be included in a content corresponding to y such that 0≤y≤0.2. If the cobalt content is too high, the overall cost of the raw material may increase and the reversible capacity may decrease.

[0097] In the positive electrode active material of the above chemical formula 1, manganese may be included in a content corresponding to z, i.e., 0≤z≤0.2. If the manganese content is too high, the capacity and output characteristics of the battery may deteriorate.

[0098] In the positive electrode active material of the above chemical formula 1, the positive electrode active material may specifically include Zr or Al.

[0099] More specifically, the first lithium metal oxide may include Zr and Al. The content of Zr in the first lithium metal oxide may be 1500 to 5000 ppm based on the weight of the positive electrode active material, and more specifically, 2000 to 4500 ppm or 2200 to 4000 ppm. In addition, independently of this, the content of Al in the first lithium metal oxide may be 1500 to 5000 ppm based on the weight of the positive electrode active material, and more specifically, 2000 to 4500 ppm or 2000 to 3000 ppm.

[0100] More specifically, the second lithium metal oxide may include Zr. The content of Zr in the first lithium metal oxide may be 300 to 3000 ppm based on the weight of the positive electrode active material, and more specifically, 500 to 2000 ppm or 600 to 1500 ppm.

[0101] Below the above range, particle size growth may be minimal, and above the above range, excessive elements may be distributed at the precursor interface during the sintering process, which may actually hinder particle size growth. Therefore, when the content of Zr or Al satisfies the above range, the size of single particles within the positive electrode active material can be formed within an appropriate range.

[0102] In addition, the positive electrode active material for a lithium secondary battery according to one embodiment of the present invention may include a coating layer on the surface of the positive electrode active material. Specifically, the coating layer may include Al, W, Co, V, Ti, Nb, Ce, B, P, or a combination thereof.

[0103] Specifically, the coating layer on the surface of the first lithium metal oxide may include B. At this time, the content of B in the coating layer on the surface of the first lithium metal oxide may be 300 to 900 ppm based on the total weight of the first lithium metal oxide, and more specifically, may be 400 to 800 ppm. When the content of B in the coating layer of the first lithium metal oxide satisfies the above range, the structural stability is preferably improved, the amount of fine powder generated when pressure is applied can be suppressed, and the room temperature and high temperature life characteristics can be excellent.

[0104] In addition, specifically, the coating layer on the surface of the second lithium metal oxide may include Al, Co, or a combination thereof. The content of Al in the coating layer on the surface of the second lithium metal oxide may be 300 to 1,500 ppm based on the total weight of the second lithium metal oxide, and more specifically, may be 300 to 1,000 ppm. When the content of Al in the coating layer of the second lithium metal oxide satisfies the above range, the structural stability may be desirably improved, the amount of fine powder generated when pressure is applied may be suppressed, and the room temperature and high temperature life characteristics may be excellent.

[0105] In addition, the content of Co in the coating layer on the surface of the second lithium metal oxide may be 6,000 to 19,000 ppm based on the total weight of the second lithium metal oxide, and more specifically, may be 12,000 to 18,000 ppm. When the content of Co in the coating layer of the second lithium metal oxide satisfies the above range, the structural stability is preferably improved, the amount of fine powder generated when pressure is applied can be suppressed, and the room temperature and high temperature life characteristics can be excellent.

[0106]

[0107] Method for manufacturing positive electrode active material for lithium secondary batteries

[0108] Meanwhile, the properties of the positive electrode active material according to the present invention may sharply vary depending on the composition of the first lithium metal oxide and the second lithium metal oxide, the presence or absence of a coating layer and the content of the coating element, the presence or absence of doping and the content of the doping element, the weight ratio of the first lithium metal oxide and the second lithium metal oxide, as well as the manufacturing process conditions described below. Hereinafter, a method for manufacturing the positive electrode active material according to the present invention will be described.

[0109] The cathode active material according to the present invention can be manufactured by a step of manufacturing a first lithium metal oxide; a step of manufacturing a second lithium metal oxide; and a step of mixing the first lithium metal oxide and the second lithium metal oxide.

[0110] More specifically, it may include a step of preparing a first metal precursor; a step of mixing the first metal precursor and the first lithium raw material and then firing the mixture to form a first lithium metal oxide; a step of preparing a second metal precursor; a step of mixing the second metal precursor and the second lithium raw material and then firing the mixture to form a first lithium metal oxide; and a step of mixing the first lithium metal oxide and the second lithium metal oxide.

[0111] Hereinafter, a method for producing a first lithium metal oxide and a method for producing a second lithium metal oxide will be described.

[0112] First, the first lithium metal oxide can be manufactured by a step of preparing a metal precursor; a step of mixing the metal precursor and a lithium raw material, and then firing the mixture to form the first lithium metal oxide; and then a step of forming a B-containing coating layer can be further performed.

[0113] First, prepare a metal precursor.

[0114] The above metal precursor may more specifically be a metal hydroxide.

[0115] The above metal precursor may be manufactured by, for example, adding a complexing agent-containing solution and a pH adjusting agent-containing solution to a metal-containing solution including a nickel raw material, a manganese raw material, or a cobalt raw material, and performing a co-precipitation reaction.

[0116] The above nickel raw material is not particularly limited as long as it is used in the art for manufacturing a positive electrode active material precursor. For example, the nickel raw material may be a nickel-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, may be NiSO4, NiSO4·6H2O, Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, fatty acid nickel salt, nickel halide, or a combination thereof, but is not limited thereto.

[0117] The above cobalt raw material is not particularly limited as long as it is used in the art for manufacturing a positive electrode active material precursor. For example, the cobalt raw material may be a cobalt-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, CoSO 4,It may be, but is not limited to, CoSO4ㆍ7H2O, Co(OH)2, CoOOH, Co(OCOCH3)2ㆍ4H2O, Co(NO3)2ㆍ6H2O or a combination thereof.

[0118] The manganese raw material is not particularly limited as long as it is used in the art for manufacturing a precursor of a cathode active material. For example, the manganese raw material may be a manganese-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, oxyhydroxide, or a combination thereof, and specifically, may be a manganese salt such as MnSO4, MnCO3, Mn(NO3)2, manganese acetate, manganese dicarboxylic acid salt, manganese citrate, and manganese fatty acid salt, manganese oxide such as Mn2O3, MnO2, and Mn3O4, oxyhydroxide, manganese chloride, or a combination thereof, but is not limited thereto.

[0119] The above metal-containing solution may be prepared by adding a nickel raw material, a manganese raw material, or a cobalt raw material to a solvent, specifically, water, or a mixture of water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water.

[0120] The above complexing agent-containing solution performs the function of forming a complex, and may include, but is not limited to, NH3, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3 or a combination thereof as the complexing agent. Meanwhile, the complexing agent-containing solution may be used in the form of an aqueous solution, and at this time, water or a mixture of water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water may be used as the solvent.

[0121] The above pH adjusting agent-containing solution acts as a precipitant or pH adjusting agent, and may include an alkaline compound such as a hydroxide of an alkali metal or alkaline earth metal, such as NaOH, KOH, or Ca(OH)2, a hydrate thereof, or a combination thereof. Meanwhile, the pH adjusting agent-containing solution may also be used in the form of an aqueous solution, and at this time, water or a mixture of water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water may be used as the solvent. At this time, the pH adjusting agent-containing solution may be added in an amount such that the pH of the reaction solution becomes 10 to 13.

[0122] The above coprecipitation reaction can be performed under an inert atmosphere such as nitrogen or argon, can be performed at a temperature of 30 to 70°C, and can be performed at a pH of 10 to 13.

[0123] Nickel (or manganese-cobalt) hydroxide particles are generated through the above process and precipitated within the reaction solution. The precipitated precursor particles can be separated, washed, and dried using conventional methods to obtain the precursor. The precursor may be a secondary particle formed by the agglomeration of primary particles.

[0124] At this time, the molar ratio of nickel, cobalt, or manganese in the precursor can be controlled by adjusting the concentration of the nickel raw material, cobalt raw material, or manganese raw material. That is, the concentration of the nickel raw material, cobalt raw material, and manganese raw material can be controlled so that the molar ratio of nickel, cobalt, or manganese in the final product, lithium metal oxide, falls within the range according to the present invention.

[0125] Next, the metal precursor and lithium raw material are mixed and then calcined to form a first lithium metal oxide.

[0126] At this time, the lithium raw material may be lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, and is not particularly limited as long as it can be dissolved in water. Specifically, the lithium raw material may be Li2CO3, LiNO3, LiNO2, LiOH, LiOHㆍH2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, or a combination thereof, but is not limited thereto.

[0127] In the mixing step of the above metal precursor and lithium raw material, a doping raw material may be further mixed to produce a mixture.

[0128] The above doping raw material may include at least one selected from among Zr, Al, Y, B, Mg, Ti, Nb, W, Sc, Si, P, V, Fe, Mo, Ce, Hf, Ta, La, and Sr.

[0129] Specifically, the above doping raw material may include a Zr raw material or an Al raw material, specifically a Zr raw material and an Al raw material.

[0130] The above Zr raw material may include, for example, at least one of ZrO2, Zr(SO4)2, ZrS2, and Zr(NO3)4, but is not limited thereto.

[0131] The above Al raw material is, for example, Al(OH)3, It may include at least one of Al2(SO4)3, Al(NO)3, Al2O3, and AlCl3, but is not limited thereto.

[0132] At this time, the content of the element doped into the metal oxide and the effect thereof are omitted as they are as described above.

[0133] Additionally, the sintering may be performed at a temperature of 740 to 780°C, more specifically, 742 to 770°C, 744 to 760°C, or 745 to 755°C. If the sintering temperature is too low, the layered lithium metal oxide may not be formed properly. If the sintering temperature is too high, oversintering may occur, resulting in poor electrochemical properties.

[0134] Additionally, the firing may be performed for 7 to 15 hours. If the firing time is too short, the layered lithium metal oxide may not be formed properly. If the firing time is too long, over-firing may occur, resulting in poor electrochemical properties.

[0135] In addition, the above-described calcination can be performed in an oxygen atmosphere. As the calcination is performed in an oxygen atmosphere, the formation of a layered oxide structure is improved compared to when the calcination is performed in an air atmosphere, thereby improving the structural stability of the active material, and Equation 1 can satisfy the range according to the present invention.

[0136] Meanwhile, a step of decomposing the first lithium metal oxide may be further included.

[0137] The above-mentioned disintegration can be performed after cooling the calcined lithium transition metal oxide to 50 to 200°C. Cooling to the above-mentioned cooling temperature can suppress the reaction between external moisture and the calcined material and suppress the increase of residual lithium.

[0138] The above-mentioned disintegration can be performed by a method commonly performed in the art, for example, using a rotor mill, jet mill, ball mill, pin mill, jet mill, bead mill, or roll mill equipment, but in particular, can be performed using a jet mill and a rotor mill.

[0139] Next, the first lithium metal oxide and the B raw material are mixed, and then a coating heat treatment is performed to further form a B-containing coating layer.

[0140] The above B raw material may be, for example, B(OH)3, B2O3, Li3BO3, WB, WB2, (NH4)3BO3, or a combination thereof, but is not necessarily limited thereto. From the perspective of improving the stability of the pore structure of the positive electrode active material, B(OH)3 may be more appropriate as the B raw material.

[0141] At this time, the input amount of raw material B can be adjusted so that the content of B is 300 to 900 ppm based on the total weight of the first lithium metal oxide. The technical significance of adjusting the content of B has been described above, so it is omitted.

[0142] In addition, the coating heat treatment can be performed at a temperature of 250 to 300°C. When the temperature during the coating heat treatment satisfies the above range, the structural stability of the active material is preferably improved, so that Equation 1 can satisfy the range according to the present invention.

[0143] Additionally, the coating heat treatment can be performed for 3 to 9 hours. When the coating heat treatment time satisfies the above range, the structural stability of the active material is preferably improved, so that Equation 1 can satisfy the range according to the present invention.

[0144] Additionally, the above coating heat treatment can be performed in an air atmosphere.

[0145]

[0146] Next, the second lithium metal oxide can be manufactured by a step of preparing a second metal precursor; a step of mixing the second metal precursor and the second lithium raw material, and then firing the mixture to form the second lithium metal oxide; and a step of forming an Al, Co-containing coating layer can be further manufactured.

[0147] First, a second metal precursor is prepared. The steps for preparing the metal precursor are the same as those for preparing the first lithium metal oxide, and are therefore omitted.

[0148] Meanwhile, the first metal precursor and the second metal precursor may satisfy the following equation 3.

[0149] [Formula 3]

[0150] 0.80 < A / B < 1.3

[0151] The above A may refer to the nickel content based on the total molar number of metals of the first metal precursor, and the above B may refer to the nickel content based on the total molar number of metals of the second metal precursor.

[0152] By satisfying the range of the above formula 3 and satisfying formula 1 of the present invention, the life characteristics and energy density at room temperature and high temperature can be improved.

[0153] Meanwhile, the BET (Brunauer-Emmett-Teller) specific surface area of ​​the second metal precursor is 5.8 to 6.5 m 2 / g or 5.9 to 6.4 m 2 / g range. If the BET specific surface area of ​​the second metal precursor is too small, the lithium migration path area may be reduced, which may result in deterioration of characteristics such as capacity and output. If the BET specific surface area is too large, the surface pores of the positive electrode active material manufactured with the precursor may become too large, and the collapse of the surface pore structure may occur frequently when pressure is applied (during the rolling process). In the present specification, the specific surface area of ​​the precursor or active material may be measured using a BET method (Surface area and Porosity analyzer) (Micromeritics, Tristar2 3020, Macsorb® HM model-1220) for the precursor or active material powder. More specifically, in the case of the precursor, the specific surface area may be measured using Macsorb® HM model-1220, and in the case of the active material, the specific surface area may be measured using Micromeritics, Tristar2 3020 equipment.

[0154] Next, the metal precursor and lithium raw material are mixed and then calcined to form a second lithium metal oxide.

[0155] At this time, the lithium raw material may be lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide or oxyhydroxide, and is not particularly limited as long as it can be dissolved in water. Specifically, the lithium raw material may be Li2CO3, LiNO3, LiNO2, LiOH, LiOHㆍH2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7 or a combination thereof, but is not limited thereto.

[0156] In the above metal precursor and lithium raw material mixing step, a doping raw material may be further mixed to produce a mixture.

[0157] The above doping raw material may include at least one selected from among Zr, Al, Y, B, Mg, Ti, Nb, W, Sc, Si, P, V, Fe, Mo, Ce, Hf, Ta, La, and Sr.

[0158] Specifically, the above doping raw material may include a Zr raw material.

[0159] The above Zr raw material may include, for example, at least one of ZrO2, Zr(SO4)2, ZrS2, and Zr(NO3)4, but is not limited thereto.

[0160] At this time, the content of the element doped into the metal oxide and the effect thereof are omitted as they are as described above.

[0161] Additionally, the above firing can be performed by dividing it into primary firing and secondary firing.

[0162] At this time, the first sintering temperature may be higher than the second sintering temperature, and the first sintering time may be shorter than the second sintering time. When the first sintering temperature is higher than the second sintering temperature, and the first sintering time is shorter than the second sintering time, the formation of a layered crystal structure is advantageous, so that the structural stability of the second lithium metal oxide is improved, and Equation 1 can satisfy the range according to the present invention.

[0163] More specifically, the first firing temperature may be 800 to 850°C, and the second firing temperature may be 700 to 780°C. In addition, the first firing time may be 1 to 5 hours, and the second firing time may be 6 to 12 hours. When the first firing and second firing temperatures, the first firing time, and the second firing time satisfy the above ranges, the effect of improving the structural stability of the second lithium metal oxide is more preferably implemented, so that Equation 1 can better satisfy the range according to the present invention.

[0164] Meanwhile, a step of decomposing the second lithium metal oxide may be further included.

[0165] The above-mentioned disintegration can be performed after cooling the calcined lithium transition metal oxide to 50 to 200°C. Cooling to the above-mentioned cooling temperature can suppress the reaction between external moisture and the calcined material and suppress the increase of residual lithium.

[0166] The above-mentioned disintegration can be performed by a method commonly performed in the art, for example, using a rotor mill, jet mill, ball mill, pin mill, jet mill, bead mill, or roll mill equipment, but in particular, can be performed using a jet mill and a rotor mill.

[0167] Next, the second lithium metal oxide and the Al raw material or Co raw material, more specifically, both raw materials, are mixed and then subjected to a coating heat treatment to form an Al or Co-containing coating layer, specifically, an Al and Co-containing coating layer.

[0168] At this time, the Al raw material is, for example, Al(OH)3, It may be, but is not necessarily limited to, Al2(SO4)3, Al(NO)3, Al2O3, AlCl3 or a combination thereof.

[0169] In addition, the amount of the Al raw material input can be adjusted so that the Al content is 300 to 1,500 ppm based on the total weight of the second lithium metal oxide, and more specifically, can be adjusted so that it is 300 to 1,000 ppm. The technical significance of adjusting the Al content has been described above, and thus is omitted.

[0170] At this time, the Co raw materials are Co(OH)2, CoCl2, CoO, CoF3, CoSO4·xH2O, CoSO4·7H2O, (CH3COO)2Co·4H2O, Co(NO3)2·6H2O, (CH3CO2)2Co, CoCO3· x It may be, but is not necessarily limited to, H2O, Co3(PO4)2 or a combination thereof.

[0171] In addition, the amount of the Co raw material input can be adjusted so that the Co content is 6,000 to 19,000 ppm based on the total weight of the second lithium metal oxide, and more specifically, can be adjusted so that it is 12,000 to 18,000 ppm. The technical significance of adjusting the Co content has been described above, and thus is omitted.

[0172] Additionally, the above coating heat treatment can be performed in an oxygen atmosphere. By performing the coating heat treatment in an oxygen atmosphere, there may be an advantage of improved life characteristics compared to when performing the coating heat treatment in an air atmosphere.

[0173]

[0174] anode

[0175] In another embodiment of the present invention, a positive electrode is provided, which includes a current collector and a positive electrode active material layer positioned on one surface of the current collector and including a positive electrode active material manufactured according to the above-described embodiment.

[0176] The characteristics of the positive electrode active material constituting the positive electrode active material layer are the same as described above. Therefore, a detailed description of the positive electrode active material will be omitted.

[0177] The above-mentioned collector may be, for example, made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc.

[0178] Meanwhile, the positive electrode active material layer may include a binder and a conductive material.

[0179] At this time, the binder plays a role of improving the adhesion between the positive electrode active material particles and the adhesive strength between the positive electrode active material and the positive electrode 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, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one kind alone or a mixture of two or more kinds thereof may be used, but is not limited thereto. The binder may be included in an amount of 1 to 30 wt% based on the total weight of the positive electrode active material layer.

[0180] And, 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 among these may be used, but the present invention is not limited thereto. The conductive material may typically be included in an amount of 1 to 30 wt% based on the total weight of the positive electrode active material layer.

[0181] The above anode can be manufactured according to a conventional anode manufacturing method, except that it is manufactured to fall within the above range.

[0182] Specifically, the positive electrode can be manufactured by applying a composition for forming a positive electrode active material layer, optionally including a binder, a conductive agent, or a solvent, as needed, onto 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 agent are as described above.

[0183] The solvent may be a solvent generally used in the relevant technical field, such as dimethylsulfoxide (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.

[0184] Alternatively, the positive electrode may be manufactured by casting a composition for forming a positive electrode active material layer on a separate support, and then laminating the resulting film on a positive electrode current collector by peeling it off from the support.

[0185]

[0186] lithium secondary battery

[0187]

[0188] In another embodiment, a lithium secondary battery including the positive electrode is provided.

[0189] The lithium secondary battery may specifically include a positive electrode, a negative electrode positioned opposite the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is as described above. In addition, the lithium secondary battery may optionally further include a battery container that houses an electrode assembly including the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0190] In the above lithium secondary battery, the negative electrode may include a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0191] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and 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.

[0192] The negative electrode active material layer may optionally include a binder and a conductive material together with the negative electrode active material. As an example, the negative electrode active material layer may be manufactured by applying a composition for forming a negative electrode active material layer comprising the negative electrode active material and optionally a binder and a conductive material onto a negative electrode current collector and drying the composition, or by casting the negative electrode forming composition onto a separate support and then laminating the resulting film onto a negative electrode current collector by peeling the film off from the support.

[0193] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples thereof 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, and Al alloy; metallic oxides capable of doping and dedoping lithium, such as SiOβ (0 ≤ β ≤ 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the 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.

[0194] The above binder and conductive material may be the same as those described above for the positive electrode.

[0195] Next, depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators may include polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers thereof, and mixed multilayer films such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may also be used.

[0196] In addition, in the lithium secondary battery, examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0197] Specifically, the organic liquid electrolyte may include an organic solvent and a lithium salt.

[0198] The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (wherein R is a C2 to C20 linear, branched, or cyclic hydrocarbon group, and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) 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.

[0199] 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. It is preferable that the concentration of the lithium salt be used within the range of 0.1 to 2.0 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.

[0200] As described above, a lithium secondary battery including a positive electrode according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, 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).

[0201]

[0202] Hereinafter, preferred embodiments and comparative examples of the present invention are described. However, the following examples are only preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0203]

[0204] Manufacturing of positive electrode active materials

[0205] Example 1

[0206] (1) Preparation of precursor

[0207] (Manufacture of the first metal precursor)

[0208] While stirring with water in a batch reactor, the internal temperature was set to 50℃, and nitrogen gas was introduced into the reactor to adjust to an inert atmosphere. Then, a sulfate aqueous solution in which nickel sulfate, cobalt sulfate, and manganese sulfate were mixed in a molar ratio of 90.0 mol%: 7.0 mol%: 3.0 mol%, sodium hydroxide, and ammonia water were prepared. After the sodium hydroxide aqueous solution and ammonia water were introduced into the reactor to form an initial reaction atmosphere, the flow rate of the ammonia water was adjusted to a ratio of 0.3 to 0.5 of the flow rate of the metal sulfate aqueous solution. Thereafter, the amount of sodium hydroxide (NaOH) solution introduced was adjusted so that the hydrogen ion concentration (pH) in the reactor was approximately pH 10.5 to 11.2. Thereafter, the reactants were introduced while stirring, and nitrogen gas was introduced to maintain an inert atmosphere. After the reaction was completed, the formed solution was washed and solid-liquid separated using a pressure filter (filter press), and then dried.

[0209] (Manufacture of second metal precursor)

[0210] A batch reactor was placed with water, stirred, and the internal temperature was set to 50°C, and nitrogen gas was introduced into the reactor to adjust the inert atmosphere. Subsequently, a sulfate aqueous solution containing nickel sulfate, cobalt sulfate, manganese sulfate, and aluminum sulfate in a molar ratio of 95.5 mol%: 2.0 mol%: 2.0 mol%: 0.5 mol%, sodium hydroxide, and ammonia water were prepared. The sodium hydroxide aqueous solution and ammonia water were introduced into the reactor to form an initial reaction atmosphere, and the flow rate of the ammonia water was adjusted to a ratio of 1.0 to the flow rate of the metal sulfate aqueous solution. Thereafter, the amount of sodium hydroxide (NaOH) solution introduced was adjusted so that the hydrogen ion concentration (pH) in the reactor was approximately 11.6. Subsequently, the reactants were introduced while stirring, and nitrogen gas was introduced to maintain the inert atmosphere. After the reaction was completed, the formed solution was washed and solid-liquid separated using a pressure filter (filter press), and then dried.

[0211] (2) Production of lithium metal oxide

[0212] (Preparation of the first lithium metal oxide)

[0213] 12.5 kg of LiOH·H2O, 219.2 g of Al(OH)3, and 122.0 g of ZrO2 were weighed into 26.08 kg of the first metal precursor manufactured above, and then mixed uniformly using a mixer to form a mixture. Thereafter, the mixture was calcined at 750°C for 12.5 hours in a RHK (Roller Hearth Kiln) calciner maintained in an O2 atmosphere to form lithium metal oxide. The lithium metal oxide was crushed and classified using a Rotor-Mill. Thereafter, the crushed and classified lithium metal oxide was washed by pouring it into distilled water and stirring for 15 minutes. Thereafter, the washed lithium metal oxide was vacuum-dried at a temperature of 120°C for more than 6 hours.

[0214] Approximately 0.34 g of B(OH)3 per 100 g of the cathode active material that went through the drying process was heat-treated in a box-shaped kiln maintained in an air atmosphere. In a box-shaped kiln with air gas flowing in at a flow rate of 25 L / min, the temperature was increased at 6.0 ℃ / min, maintained at 280 ℃ for 6 hours, and then naturally cooled to form a B coating layer. The average particle size based on the volume was 13.5 ㎛ and the crystallite size was 133 nm. The BET (Brunauer-Emmett-Teller) specific surface area of ​​the first cathode active material thus manufactured was 0.75 m 2 / g, and the average circumference of the primary particles was 2.26㎛.

[0215] (Manufacture of secondary lithium metal oxide)

[0216] 21.81 kg of the second metal precursor manufactured above, 10.19 kg of LiOH·H2O, and 31.06 g of ZrO2 were weighed, and then uniformly mixed using a mixer, and calcined in an RHK calciner maintained in an O2 atmosphere. The mixture was recovered and placed in a mullite crucible, and in an RHK calciner supplied with oxygen at a flow rate of approximately 2800 L / min, the temperature was increased at 4.5 ℃ / min, maintained in the 820 ℃ range for 4 hours, and then cooled to 740 ℃ at a cooling rate of 1.3 ℃ / min and maintained for 8 hours. Thereafter, the temperature was cooled at 4.0 ℃ / min. The obtained sample was crushed using a rotor mill and a jet mill to manufacture a single-crystal cathode active material having an average particle diameter by volume (Dv50) of 3.6 μm.

[0217] Approximately 0.14 g of Al(OH)3 and 1.95 g of Co(OH)2 per 100 g of the single-crystal form of the cathode active material that had gone through the pulverization process were mixed and heat-treated in a box-type kiln maintaining an O2 atmosphere. In a box-type kiln where O2 gas was introduced at a flow rate of 25 L / min, the temperature was increased at 3.5 ℃ / min and maintained at 680 ℃ for 6 hours, and then naturally cooled to manufacture a single-crystal form of the second cathode active material having an average particle size by volume (Dv50) of 3.8 ㎛ and having an Al and Co coating layer formed thereon.

[0218] (3) Manufacturing of bimodal cathode active material

[0219] A bimodal cathode active material was prepared by mixing a first lithium metal oxide and a second lithium metal oxide in a weight ratio of 8:2 for 1 minute using a C-mixer that rotates at high speed under room temperature conditions (25°C) to mix the materials.

[0220]

[0221] Example 2

[0222] A cathode active material was prepared in the same manner as in Example 1, except that the first lithium metal oxide and the second lithium metal oxide were mixed in a weight ratio of 7:3.

[0223]

[0224] Example 3

[0225] A cathode active material was prepared in the same manner as in Example 1, except that the first lithium metal oxide and the second lithium metal oxide were mixed in a weight ratio of 6:4.

[0226]

[0227] Example 4

[0228] A cathode active material was prepared in the same manner as in Example 1, except that the first lithium metal oxide and the second lithium metal oxide were mixed in a weight ratio of 5:5.

[0229]

[0230]

[0231] Comparative Example 1

[0232] A cathode active material was prepared in the same manner as in Example 1, except that the first lithium metal oxide and the second lithium metal oxide were mixed in a weight ratio of 9:1.

[0233]

[0234] Comparative Example 2

[0235] A cathode active material was prepared in the same manner as in Example 1, except that the first lithium metal oxide and the second lithium metal oxide were mixed in a weight ratio of 4:6.

[0236]

[0237] Comparative Example 3

[0238] A cathode active material was prepared in the same manner as in Example 1, except that the first lithium metal oxide and the second lithium metal oxide were mixed in a weight ratio of 3:7.

[0239]

[0240] Comparative Example 4

[0241] A cathode active material was prepared in the same manner as in Example 1, except that the first lithium metal oxide and the second lithium metal oxide were mixed in a weight ratio of 2:8.

[0242]

[0243] Comparative Example 5

[0244] A cathode active material was prepared in the same manner as in Example 1, except that the first lithium metal oxide and the second lithium metal oxide were mixed in a weight ratio of 1:9.

[0245]

[0246] Comparative Example 6

[0247] When forming the first lithium metal oxide, it was calcined at a temperature of 740℃ for 12 hours, and the BET specific surface area was 0.79 m 2 / g, and the average circumference of the primary particles was 1.73㎛. A positive electrode active material was manufactured in the same manner as in Example 1, except that a first positive electrode active material was used.

[0248]

[0249] Comparative Example 7

[0250] It was calcined at a temperature of 730℃ for 12 hours to form the first lithium metal oxide, and the BET specific surface area was 0.89 m 2 / g, and the average circumference of the primary particles was 1.97㎛. A positive electrode active material was manufactured in the same manner as in Example 1, except that a first positive electrode active material was used.

[0251]

[0252] Experimental Example 1: Evaluation of the properties of bimodal cathode active materials.

[0253] In order to evaluate the physical properties of the positive electrode active materials according to the examples and comparative examples, experiments were conducted as follows, and the results are shown in Table 1 below.

[0254] (1) BET (Brunauer-Emmett-Teller) surface area measurement

[0255] 4 g of the positive electrode active material manufactured according to the examples and comparative examples was vacuum-dried at 250°C, and then nitrogen gas was adsorbed / desorbed on the surface of the positive electrode active material to measure the adsorption amount according to partial pressure, thereby measuring the specific surface area of ​​the positive electrode active material. At this time, the equipment used was Micromeritics, Tristar2 3020.

[0256] The results are shown in Table 1 below.

[0257]

[0258] (2) Analysis of nitrogen adsorption / desorption isotherms measured by the BJH (Barrett-Joyner-Halenda) method

[0259] The hysteresis loops of the adsorption and desorption isotherms obtained from nitrogen adsorption and desorption isotherm measurements were confirmed and quantitatively analyzed.

[0260] Specifically, 4 g of each positive electrode active material according to the examples and comparative examples was subjected to vacuum degassing at 250°C for 2 hours. After the treatment, the nitrogen desorption isotherm and nitrogen adsorption isotherm of the positive electrode active material at the liquid nitrogen temperature (77 K) were measured using a measuring device Micromeritics, Tristar2 3020. The nitrogen adsorption amount per unit weight of the positive electrode active material in the adsorption isotherm was calculated to be expressed as the volume of gaseous nitrogen at the standard state (STP; Standard Temperature and Pressure). The nitrogen desorption amount per unit weight of the positive electrode active material in the desorption isotherm was calculated to be expressed as the volume of gaseous nitrogen at the standard state (STP; Standard Temperature and Pressure).

[0261] The results are shown in Figures 1 to 11 and Table 1.

[0262] Figures 1 to 4 are nitrogen adsorption / desorption isotherm graphs measured by the BJH (Barrett-Joyner-Halenda) method for positive electrode active materials according to Examples 1 to 4.

[0263] Meanwhile, FIGS. 5 to 11 are nitrogen adsorption / desorption isotherm graphs measured by the BJH (Barrett-Joyner-Halenda) method for the positive electrode active materials according to Comparative Examples 1 to 7.

[0264] Comparing FIGS. 1 to 4 and 5 to 11, it can be confirmed that in the case of the embodiment, unlike the comparative example, the area between the adsorption and desorption isotherms in the range of relative pressure (p / p0) from 0.1 to 0.7 satisfies a specific area. A more quantitative area between the adsorption and desorption isotherms for each relative pressure (p / p0) section can be confirmed in Table 1 below.

[0265]

[0266] The ratio of the first lithium metal oxide in the positive electrode active material (R) Surface Area (SA) by relative pressure section in the BETBJH graph [m 2 / g]S1 (0.1~0.99) [cm 3 / g]S2 (0.1~0.7) [cm 3 / g]S3 (0.7~0.99) [cm 3 / g]Comparative Example 10.90.58630.232080.035340.19673Example 10.80.57650.205490.033350.17213Example 20.70.58260.183620.031210.15241Example 30.60.62740.150620.025790.05353Example 40.50.63380.131070.024260.10680Comparative Example 20.40.63370.106710.022160.08455Comparative Example 30.30.63120.096770.020550.07621Comparative example 40.20.61760.070870.017530.05333Comparative example 50.10.61750.046580.015880.03070Comparative example 60.80.26510.023410.007910.01550Comparative example 70.80.28160.025900.006140.01976

[0267] Through the above Table 1, the example has a SA (BET specific surface area of ​​the positive electrode active material) of 0.5300 to 0.6600 m 2 / g range, and 0.1100 to 0.2300 cm in S1. 3 / g range, and 0.02250 to 0.03500 cm in S2. 3 / g range, and 0.0535 to 0.1900 cm in S3. 3 You can see that it falls within the / g range.

[0268] Furthermore, referring to Table 2 below, which organizes the formulas derived through this, the example is 12.00 X 10 in Formula 1. 6 m -1 ≤ (SA*R) / S2 ≤ 14.85 X 106 m -1 It satisfies the range, but the comparative example can be seen to be outside the range.

[0269] In addition, it can be confirmed that Examples 1 and 2 satisfy the range of 0.6300 ≤ (S3-S2) / S1 ≤ 0.6900 in Equation 2.

[0270]

[0271] Equation 1(SA*R / S2)[1 X 10 6 m -1 ]Formula 2 ((S3-S2) / S1) Comparative Example 114.930.6954 Exemplary Example 113.830.6754 Exemplary Example 213.070.6601 Exemplary Example 314.600.1842 Exemplary Example 413.060.6297 Comparative Example 211.440.5847 Comparative Example 39.210.5752 Comparative Example 47.050.5052 Comparative Example 53.890.3182 Comparative Example 626.810.3242 Comparative Example 736.690.5259

[0272] (3) Cross-sectional analysis of the first lithium metal oxide

[0273] The first lithium metal oxide used in the examples and comparative examples was cut into cross sections using an ion beam cross-section polisher under vacuum conditions, and cross-sectional images of the first lithium metal oxide were obtained using a scanning electron microscope (SEM) analysis device, and these are shown in FIGS. 12 to 14.

[0274] The average circumference of the primary particles was derived by measuring the average value of the circumferences of 20 to 35 primary particles in the cross-sectional SEM images. Through this, it was confirmed that the average circumference of the primary particles in the first lithium metal oxide used in the examples was 2.26 μm, the average circumference of the primary particles in the first lithium metal oxide used in Comparative Example 6 was 1.73 μm, and the average circumference of the primary particles in the first lithium metal oxide used in Comparative Example 7 was 1.97 μm.

[0275] That is, when the average circumference of the primary particles is 2.00㎛ or more, excellent electrochemical characteristics can be exhibited as confirmed in the experimental example below.

[0276]

[0277] Experimental Example 2: Evaluation of Electrochemical Characteristics Using Coin Cells

[0278] In order to evaluate the physical properties and electrochemical properties of the positive electrode active materials according to the examples and comparative examples, coin cells were manufactured as follows.

[0279] Specifically, a positive electrode active material, a polyvinylidene fluoride binder (trade name: KF1120), and a carbon black conductive material were mixed at a weight ratio of 96.5:1.5:2.0, and the mixture was added to an N-methyl-2-pyrrolidone solvent to prepare a positive electrode active material slurry.

[0280] The above slurry was coated on an aluminum foil (Al foil, thickness: 20 ㎛) as a positive electrode current collector using a doctor blade, dried, and rolled to manufacture a positive electrode. The loading amount of the positive electrode was about 17.0 mg / cm2, and the rolling density was about 3.7 g / cm 3 It was.

[0281] A 2032 coin-type half-cell was manufactured using the above positive electrode, lithium metal negative electrode (200 μm thick, Welcos), electrolyte and polyethylene separator by a conventional method. The electrolyte was a mixed solution prepared by dissolving 1 M LiPF6 in a mixed solvent of VC (vinylene carbonate), PS (propane sultone) and ESA (ethylene sulfate) (3.0:0.5:1 wt%) and in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (mixing ratio EC:DMC:EMC=3:4:3 vol%).

[0282]

[0283] (1) Initial charge / discharge capacity evaluation and efficiency evaluation

[0284] After manufacturing the coin cell, it was aged at 25°C for 10 hours and then a charge-discharge test was conducted at 25°C. For the initial capacity evaluation, 200 mAh / g was used as the reference capacity, and the cell was charged to 4.3 V at a constant current of 0.1 C. After switching to a constant voltage, the charging was performed until the end current reached 0.05 C. After charging, the cell was discharged to 3.0 V at a constant current of 0.1 C, using 200 mAh / g as the reference capacity. The results are shown in Table 2 below.

[0285]

[0286] (2) High temperature life evaluation (45℃, 30 cycles and 50 cycles)

[0287] After fabricating a lithium secondary battery half-cell, it was charged to 4.3 V at a constant current of 0.1 C at 45°C, then switched to constant voltage and initially charged until the end current reached 0.05 C. After charging, an initial discharge was performed at a constant current of 0.1 C until the voltage reached 3.0 V.

[0288] After the initial charge / discharge described above, the battery was charged to 4.3 V with a constant current of 0.5 C, then switched to a constant voltage and charged until the end current reached 0.05 C. After charging, the battery was discharged to 3.0 V with a constant current of 1.0 C, and 30 and 50 charge / discharge cycles were performed under the corresponding charge / discharge cycle conditions. The capacity retention rate of the 30th cycle compared to the first cycle and the capacity retention rate of the 50th cycle compared to the first cycle were calculated. The results are shown in Table 3 below.

[0289]

[0290] Charge [mAh / g]Discharge [mAh / g]Efficiency [%]45℃, 30th 0.5C / 1C [%]45℃, 50th 0.5C / 1C [%]Comparative Example 1237.1217.391.795.893.9Example 1238.8217.791.296.594.7Example 2239.3215.490.096.995.3Example 3240.6215.989.896.895.0Example 4240.4214.289.197.295.3Comparative Example 2241.0214.689.0--Comparative Example 3242.3214.888.7--Comparative Example 4242.9215.988.996.494.4Comparative example 5244.4216.288.595.793.0Comparative example 6238.1212.989.492.7-Comparative example 7236.9211.789.395.0-

[0291] Referring to Tables 1 to 3, the cathode active material according to the embodiment satisfies Equation 1, and it can be confirmed that the lithium secondary battery using the cathode active material has an excellent initial charge / discharge efficiency of 89.1% or higher, and at the same time, excellent high-temperature lifespan after performing 30 or more charge / discharge cycles. More specifically, the high-temperature lifespan after performing 30 charge / discharge cycles satisfies 96.5% or higher, and the high-temperature lifespan after performing 50 charge / discharge cycles satisfies 94.7% or higher. In other words, it is expected that it will be able to be used for a long time even at high temperatures.

[0292] Therefore, through comparison between the examples and comparative examples, it can be seen that the positive electrode active materials according to examples 1 to 4 and the batteries including the same are electrochemically superior and at the same time have excellent stability.

[0293] In summary of the experimental results, it can be seen that the positive electrode active materials according to Examples 1 to 4 that satisfy the appropriate range of Equation 1 have excellent electrochemical properties.

[0294]

[0295] The present invention is not limited to the above-described embodiments, but can be manufactured in a variety of different forms. Those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. First lithium metal oxide; and A bimodal form comprising a second lithium metal oxide having a smaller average particle diameter (D50) than the first lithium metal oxide; Satisfying the following equation 1, Cathode active material for lithium secondary batteries: [Formula 1] 12.00 X 10 6 m -1 ≤ (SA*R) / S2 ≤ 14.85 X 10 6 m -1 In the above equation 1, SA is the BET (Brunauer-Emmett-Teller) specific surface area of ​​the positive electrode active material, R is the weight ratio of the first lithium metal oxide in the above positive electrode active material, S2 is the area between the adsorption isotherm and desorption isotherm in the nitrogen adsorption / desorption isotherm graph measured by the BJH (Barrett-Joyner-Halenda) method for the positive electrode active material in the range of relative pressure (p / p0) from 0.1 to 0.

7.

2. In paragraph 1, The above SA is 0.5300 to 0.6600 m 2 / g range, Cathode active material for lithium secondary batteries.

3. In paragraph 1, The above R is in the range of 0.45 to 0.85, Cathode active material for lithium secondary batteries.

4. In paragraph 1, The above S2 is 0.02250 to 0.03500 cm 3 / g range, Cathode active material for lithium secondary batteries.

5. In paragraph 1, The average circumference of the primary particles present in the first lithium metal oxide is in the range of 2.00 to 3.20 μm. Cathode active material for lithium secondary batteries.

6. In paragraph 1, It satisfies the following equation 2, Cathode active material for lithium secondary batteries. [Formula 2] 0.6300 ≤ (S3-S2) / S1 ≤ 0.6900 In the above equation 2, S1 is the area between the adsorption and desorption isotherms in the nitrogen adsorption and desorption isotherm graph measured by the BJH (Barrett-Joyner-Halenda) method for the positive electrode active material in the range of relative pressure (p / p0) from 0.10 to 0.

99. S2 is the area between the adsorption and desorption isotherms in the nitrogen adsorption and desorption isotherm graph measured by the BJH (Barrett-Joyner-Halenda) method for the positive electrode active material, in the range of relative pressure (p / p0) from 0.10 to 0.

70. S3 is the area between the adsorption and desorption isotherms in the nitrogen adsorption and desorption isotherm graph measured by the Barrett-Joyner-Halenda (BJH) method for the positive electrode active material in the range of relative pressure (p / p0) from 0.70 to 0.

99.

7. In paragraph 6, The above S1 is 0.1100 to 0.2300 cm 3 / g range, Cathode active material for lithium secondary batteries.

8. In paragraph 6, The above S3 is 0.0535 to 0.1900 cm 3 / g range, Cathode active material for lithium secondary batteries.

9. In paragraph 6, The above S2 is 0.0300 to 0.0350 cm 3 / g range, Cathode active material for lithium secondary batteries.

10. In paragraph 1, The above first lithium metal oxide is in the form of secondary particles including a plurality of primary particles, The second lithium metal oxide is in the form of a single crystal in which 1 or 2 to 20 single particles are aggregated. Cathode active material for lithium secondary batteries.

11. In paragraph 1, The average particle diameter (Dv50) based on volume of the first lithium metal oxide is in the range of 5 to 20 μm, The average particle diameter (Dv50) based on volume of the second lithium metal oxide is in the range of 1.0 to 5.0 μm. Cathode active material for lithium secondary batteries.

12. In paragraph 1, The first lithium metal oxide and the second lithium metal oxide are each independently a positive electrode active material for a lithium secondary battery represented by the following chemical formula 1: [Chemical Formula 1] Li a [Ni x Co y Mr z M w ]O2 In the above chemical formula 1, 0.8≤a≤1.2, 0.8≤x<1, 0≤y≤0.2, 0≤z≤0.2, 0≤w≤0.1, x+y+z+w=1, and M is Zr, Y, B, Al, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, or a combination thereof.

13. In paragraph 1, The nickel content of the first lithium metal oxide is 1.0 to 10.0 mol% less than the nickel content of the second lithium metal oxide. Cathode active material for lithium secondary batteries.

14. In paragraph 1, The nickel content of the first lithium metal oxide is 80 to 92 mol% based on the total mole number of metals excluding lithium, The nickel content of the second lithium metal oxide is 92 to 96 mol% based on the total mole number of metals excluding lithium. Cathode active material for lithium secondary batteries.

15. A positive electrode for a lithium secondary battery comprising the positive electrode active material of any one of claims 1 to 14, Lithium secondary battery.

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