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

Abstract

The positive active material for a lithium secondary battery according to the present invention is a positive active material for a lithium secondary battery in a bimodal form, and the positive active material may satisfy Formula 1 in this specification.

Description

Technology Field

[0001] The present embodiments relate to a positive electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same. Background Technology

[0002] Recently, the demand for IT mobile devices, small power drive systems (e-bikes, small EVs, etc.), and Energy Storage Systems (ESS) has been increasing explosively. Consequently, the development of high-capacity and high-energy-density secondary batteries to power these devices is actively underway worldwide. To manufacture such high-capacity batteries, high-capacity cathode materials must be used.

[0003] Among existing layered cathode active materials, LiNiO2 has the highest capacity, but commercialization is difficult due to structural collapse occurring easily during charging and discharging and low thermal stability caused by oxidation state issues.

[0004] To solve this problem, other stable transition metals (Co, Mn, etc.) must be substituted at the unstable Ni sites, and for this purpose, ternary NCM systems with Co and Mn substituted have been developed.

[0005] In addition, development is underway for so-called bimodal cathode active materials capable of improving rolling density by mixing small and large particle sizes of cathode active materials to achieve high energy density.

[0006] Accordingly, there is a need to develop cathode active materials that can increase battery life stability while simultaneously exhibiting excellent electrochemical characteristics, such as charge and discharge capacity, in the case of bimodal cathode active materials. The problem to be solved

[0007] In this embodiment, we aim to provide a positive electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same, in which electrochemical characteristics and stability can be improved by satisfying an appropriate range of a specific FWHM (Full Width at Half Maximum) ratio in a bimodal positive electrode active material. means of solving the problem

[0008] A positive electrode active material for a lithium secondary battery according to one embodiment may be a bimodal form comprising a first lithium metal oxide containing 80 mol% or more of nickel based on the total molar amount of metals excluding lithium in the positive electrode active material, and a second lithium metal oxide having a higher nickel content than the first lithium metal oxide, satisfying Formula 1 below.

[0009] [Equation 1]

[0010] 0.8300 ≤ FWHM(101) / FWHM(104) ≤ 0.9600

[0011] In the above Equation 1,

[0012] FWHM (101) represents the full width at half maximum of the (101) peak in X-ray diffraction spectrum analysis, and

[0013] FWHM (104) refers to the full width at half maximum of the (104) peak in X-ray diffraction spectrum analysis.

[0014] At this time, the above FWHM (101) may be in the range of 0.1410 to 0.1630°.

[0015] At this time, the above FWHM (104) may be in the range of 0.1690 to 0.1900°.

[0016] At this time, the crystal grain size of the first lithium metal oxide may be 110 to 135 nm.

[0017] At this time, the weight ratio of the first lithium metal oxide to the second lithium metal oxide (weight of the first lithium metal oxide:weight of the second lithium metal oxide) may be 85:15 to 55:45.

[0018] At this time, the average particle size (Dn50) based on the number of positive electrode active materials may be in the range of 2.71 to 2.93 μm.

[0019] At this time, the volume-based average particle size (Dv50) of the first lithium metal oxide may be in the range of 5 to 20 μm, and the volume-based average particle size (Dv50) of the second lithium metal oxide may be in the range of 1.0 to 5.0 μm.

[0020] At this time, the first lithium metal oxide may be in the form of secondary particles, and the second lithium metal oxide may be in the form of a single crystal in which one or 2 to 20 single particles are aggregated.

[0021] At this time, the first lithium metal oxide and the second lithium metal oxide may each independently be positive active materials for a lithium secondary battery represented by the following chemical formula 1.

[0022] [Chemical Formula 1]

[0023] Li a [Ni x Co y Mn z M w ]O2

[0024] 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 may be Zr, Y, B, Al, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, or a combination thereof.

[0025] 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.

[0026] At this time, the nickel content of the first lithium metal oxide may be 80 to 92 mol% based on the total molar amount of metal excluding lithium, and the nickel content of the second lithium metal oxide may be 92 to 96 mol% based on the total molar amount of metal excluding lithium.

[0027] A lithium secondary battery according to another embodiment may be a lithium secondary battery comprising a positive electrode for a lithium secondary battery comprising a positive electrode active material manufactured according to one embodiment. Effects of the invention

[0028] According to the present embodiment, the stability and electrochemical properties of the positive electrode active material for a lithium secondary battery can be improved by appropriately controlling the manufacturing process to satisfy a specific range of the relationship consisting of a specific FWHM.

[0029] Accordingly, the electrochemical performance of the lithium secondary battery manufactured as in the present embodiment, such as stability and capacity, can be improved. Brief explanation of the drawing

[0030] Figure 1 is an XRD (X-ray diffraction) graph measured for the positive electrode active material according to the example and comparative example. Figure 2 is a graph of the energy density at room temperature at 25°C of a battery containing a positive electrode active material according to an example and a comparative example. Figure 3 is a graph of the room temperature life at 25°C of a battery containing a positive electrode active material according to an example and a comparative example. Figure 4 is a graph of the high-temperature energy density at 45°C of a battery containing a positive electrode active material according to an example and a comparative example. Figure 5 is a graph of the high-temperature life at 45°C of a battery containing a positive electrode active material according to an example and a comparative example. Specific details for implementing the invention

[0031] Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the present invention.

[0032] The technical terms used herein are for the reference of specific embodiments only and are not intended to limit the invention. The singular forms used herein include plural forms unless phrases clearly indicate otherwise. As used in the specification, the meaning of "comprising" specifies certain characteristics, areas, integers, steps, actions, elements, and / or components, and does not exclude the presence or addition of other characteristics, areas, integers, steps, actions, elements, and / or components.

[0033] When it is stated that one part is "above" or "on" another part, it may be directly above or on the other part, or other parts may be involved in between. In contrast, when it is stated that one part is "directly above" another part, no other parts are interposed in between.

[0034] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with relevant technical literature and the present disclosure, and are not interpreted in an ideal or highly formal sense unless otherwise defined.

[0035] Also, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

[0036] In this specification, the term “combination(s) of these” described in the Markush-type expression means one or more mixtures or combinations selected from the group consisting of the components described in the Markush-type expression, and means including any one or more selected from the group consisting of said components.

[0037] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0039] Cathode active material for lithium secondary batteries

[0040] A positive electrode active material for a lithium secondary battery according to one embodiment of the present invention comprises a first lithium metal oxide containing 80 mol% or more of nickel based on the total molar amount of metals excluding lithium, and a second lithium metal oxide having a higher nickel content than the first lithium metal oxide. As such, since the positive electrode active material according to the present invention contains a high amount of nickel in the lithium metal oxide, high capacity characteristics can be realized.

[0041] At this time, the average particle size (D50) of the first lithium metal oxide is larger than the average particle size (D50) of the second lithium metal oxide. That is, the positive electrode active material according to the present invention is a bimodal positive electrode active material in which positive electrode active materials of large particle size and small particle size are mixed. When implementing an electrode with a bimodal positive electrode active material, small particle size particles can occupy the empty spaces between large particle size particles, thereby improving the electrode rolling density.

[0042] However, there is a need to further improve the electrochemical properties of high-nickel cathode active materials in a bimodal form. Accordingly, the present invention can provide a cathode active material for a lithium secondary battery satisfying Formula 1 below.

[0043] [Equation 1]

[0044] 0.8300 ≤ FWHM(101) / FWHM(104) ≤ 0.9600

[0045] In the above Equation 1,

[0046] FWHM (101) represents the full width at half maximum of the (101) peak in X-ray diffraction spectrum analysis, and

[0047] FWHM (104) refers to the full width at half maximum of the (104) peak in X-ray diffraction spectrum analysis.

[0048] In the above Equation 1, FWHM (101) / FWHM (104) may more specifically be in the range of 0.8320 to 0.9400 or 0.8332 to 0.9217.

[0049] At this time, the (101) peak can be identified at 2θ=36.7±1° in the X-ray diffraction spectrum analysis.

[0050] At this time, the (104) peak can be identified at 2θ = 44.5±1° in the X-ray diffraction spectrum analysis.

[0051] Full width at half maximum can refer to the half width of the diffraction peaks that are indexed on each plane.

[0052] By satisfying the above Equation 1, the life characteristics and energy density at room temperature and high temperature can be improved, and the amount of fine particles generated during rolling can be reduced, thereby suppressing the problem of capacity characteristic degradation due to rolling.

[0053] The above FWHM (101) may be in the range of 0.1410 to 0.1630°, more specifically 0.1420 to 0.1620°, or 0.1424 to 0.1612°.

[0054] By satisfying the above range, lifespan characteristics and energy density at room temperature and high temperature are improved, and the amount of fine particles generated during rolling is reduced, thereby suppressing the problem of capacity characteristic degradation due to rolling.

[0055] The above FWHM (104) may be in the range of 0.1690 to 0.1900°, more specifically 0.1700 to 0.1800° or 0.1709 to 0.1762°.

[0056] By satisfying the above range, lifespan characteristics and energy density at room temperature and high temperature are improved, and the amount of fine particles generated during rolling is reduced, thereby suppressing the problem of capacity characteristic degradation due to rolling.

[0057] Meanwhile, the crystal grain size of the first lithium metal oxide may be 110 to 135 nm, more specifically 110 to 130 nm. This can be determined by the temperature at which the first metal precursor is calcined. Specifically, the first lithium metal oxide with the crystal grain size range can be obtained when the calcination temperature after mixing the first metal precursor and the first lithium raw material described below is in the range of 731 to 759°C.

[0058] If it falls below the above lower limit range, a decrease in room temperature charge / discharge capacity and a decrease in high-temperature life characteristics may be observed, and if it exceeds the above upper limit range, a decrease in high-temperature life characteristics may be observed.

[0059] Meanwhile, the weight ratio of the first lithium metal oxide to the second lithium metal oxide (weight of the first lithium metal oxide:weight of the second lithium metal oxide) may be 85:15 to 55:45, more specifically 80:20 to 60:40. If the content of the first lithium metal oxide is too high, the filling density may decrease, and the charge / discharge capacity may decrease. Even if the content of the second lithium metal oxide is too high, the filling density may increase, causing it to deviate from the appropriate rolling density range when pressure is applied, or the fine powder generation rate may increase.

[0060] Meanwhile, the average particle size (Dn50) based on the number of positive electrode active materials may be in the range of 2.71 to 2.93 μm, more specifically 2.76 to 2.92 μm.

[0061] By satisfying the above range, lifespan characteristics and energy density at room temperature and high temperature are improved, and the amount of fine particles generated during rolling is reduced, thereby suppressing the problem of capacity characteristic degradation due to rolling.

[0062] Meanwhile, the volume-based average particle size (Dv50) of the first lithium metal oxide may be in the range of 5.0 to 20 μm, and the volume-based average particle size (Dv50) of the second lithium metal oxide may be in the range of 1.0 to 5.0 μm. In this specification, the average particle size (D50) may mean the volume-based average particle size (Dv50) unless otherwise indicated, and the volume-based average particle size (Dv50) may be defined as the particle size corresponding to 50% of the volume accumulation in the particle size distribution curve. The average particle size may be measured, for example, using a laser diffraction method.

[0063] Meanwhile, the first lithium metal oxide may be in the form of a secondary particle, and the second lithium metal oxide may be in the form of a single crystal in which one or 2 to 20 single particles are aggregated. In this specification, a single particle may refer to a single particle composed of one particle, and the single crystal cathode active material may be a single particle composed of one particle or in the form in which 2 to 20 single particles are aggregated, and more preferably may include both the single particle and the form in which the single particles are aggregated. The “secondary particle” refers to an aggregate, i.e., a secondary structure, in which tens to hundreds of primary particles are aggregated by physical or chemical bonding between primary particles without an intentional aggregation or assembly process of the primary particles. In addition, the “primary particle” refers to the smallest particle unit that is distinguished as a single mass when observing the cross-section of the cathode active material through a scanning electron microscope (SEM), and may consist of a single crystal grain or multiple crystal grains. In addition, “grain” refers to a distinct region in which atoms within a primary particle form a lattice structure in a specific direction.

[0064] Meanwhile, the first lithium metal oxide and the second lithium metal oxide can each be independently represented by the following chemical formula 1.

[0065] [Chemical Formula 1]

[0066] Li a [Ni x Co y Mn z M w ]O2

[0067] 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.

[0068] 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 lifespan characteristics and energy density at room temperature and high temperature can be improved by satisfying Formula 1 of the present invention.

[0069] More specifically, the nickel content of the first lithium metal oxide may be 80 to 92 mol% based on the total molar amount of metal excluding lithium, and the nickel content of the second lithium metal oxide may be 92 to 96 mol% based on the total molar amount of metal excluding lithium.

[0070] In the positive electrode active material of Chemical Formula 1 above, lithium may be included in an amount corresponding to a, i.e., 0.8 ≤ a ≤ 1.2. If a is too small, the capacity may decrease, and if a is too large, the strength of the calcined positive electrode active material may increase, making it difficult to grind, and the amount of gas generated may increase due to an increase in lithium by-products. Considering the effect of improving the capacity characteristics of the positive electrode active material by controlling the lithium content and the balance of sinterability during the manufacture of the active material, the lithium may more preferably be included in an amount of 0.9 ≤ a ≤ 1.1.

[0071] In the positive electrode active material of Chemical Formula 1 above, nickel may be included in an amount corresponding to x, i.e., 0.8≤x<1. As previously mentioned, if the nickel content is too low, it may be difficult to achieve a high capacity of the battery. If the nickel content is too high, the battery life and thermal safety may decrease due to a decrease in the structural stability of the active material, but the present invention has improved this.

[0072] In the positive active material of Chemical Formula 1 above, the content of cobalt corresponding to y may be 0 ≤ y ≤ 0.2. If the cobalt content is too high, the cost of the raw material increases overall and the reversible capacity may decrease.

[0073] In the positive active material of Chemical Formula 1 above, manganese may be included in an amount 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 decrease.

[0074] In the positive active material of the above chemical formula 1, the positive active material may specifically include Zr or Al.

[0075] More specifically, the first lithium metal oxide may include Zr and Al. The content of Zr in the first lithium metal oxide is 1,500 to 5,000 ppm based on the weight of the positive electrode active material, and more specifically, may be 2,000 to 4,500 ppm or 2,200 to 4,000 ppm. Additionally, independently of this, the content of Al in the first lithium metal oxide is 1,500 to 5,000 ppm based on the weight of the positive electrode active material, and more specifically, may be 2,000 to 4,500 ppm or 2,000 to 3,000 ppm.

[0076] More specifically, the second lithium metal oxide may contain Zr. The content of Zr in the first lithium metal oxide is 300 to 3000 ppm based on the weight of the positive electrode active material, and more specifically, it may be 500 to 2000 ppm or 600 to 1500 ppm.

[0077] If the above range is lower, the particle size growth may be minimal, and if the above range is higher, an excess amount of elements may be distributed at the precursor interface during the calcination process, which may actually inhibit the particle size growth. Therefore, when the content of Zr or Al satisfies the above range, the size of the single particles in the cathode active material can be formed within an appropriate range.

[0078] In addition, a 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.

[0079] Specifically, the coating layer on the surface of the first lithium metal oxide may contain B. In this case, 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, 400 to 800 ppm. When the content of B in the coating layer of the first lithium metal oxide satisfies the above range, structural stability is preferably improved, so that the amount of fine particles generated when pressure is applied can be suppressed, and room temperature and high temperature life characteristics can be excellent.

[0080] Additionally, specifically, the coating layer on the surface of the second lithium metal oxide may comprise 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 1500 ppm based on the total weight of the second lithium metal oxide, and more specifically, 300 to 1,000 ppm. When the content of Al in the coating layer of the second lithium metal oxide satisfies the above range, structural stability is preferably improved, so that the amount of fine particles generated when pressure is applied can be suppressed, and room temperature and high temperature life characteristics can be excellent.

[0081] 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, 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, structural stability is preferably improved, so that the amount of fine particles generated when pressure is applied can be suppressed, and room temperature and high temperature life characteristics can be excellent.

[0083] Method for manufacturing a positive electrode active material for a lithium secondary battery

[0084] Meanwhile, the physical properties of the positive electrode active material according to the present invention can vary significantly depending not only 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, and the weight ratio of the first lithium metal oxide and the second lithium metal oxide, but also on the manufacturing process conditions described below. Therefore, a method for manufacturing the positive electrode active material according to the present invention will be described below.

[0085] The positive electrode active material according to the present invention can be manufactured by the steps of: manufacturing a first lithium metal oxide; manufacturing a second lithium metal oxide; and mixing the first lithium metal oxide and the second lithium metal oxide.

[0086] More specifically, the method may include: a step of preparing a first metal precursor; a step of mixing the first metal precursor and a first lithium raw material and then calcining to form a first lithium metal oxide; a step of preparing a second metal precursor; a step of mixing the second metal precursor and a second lithium raw material and then calcining to form a first lithium metal oxide; and a step of mixing the first lithium metal oxide and the second lithium metal oxide.

[0087] Hereinafter, a method for manufacturing a first lithium metal oxide and a method for manufacturing a second lithium metal oxide will be described.

[0088] First, the first lithium metal oxide can be manufactured by the step of preparing a metal precursor; mixing the metal precursor and a lithium raw material, and then calcining to form the first lithium metal oxide, and subsequently, it can be manufactured by further undergoing the step of forming a B-containing coating layer.

[0089] First, prepare a metal precursor.

[0090] The above metal precursor may be, more specifically, a metal hydroxide.

[0091] The above metal precursor may be prepared by co-precipitating a metal-containing solution containing, for example, nickel raw material, manganese raw material, or cobalt raw material by adding a complexing agent-containing solution and a pH adjuster-containing solution.

[0092] The above nickel raw material is not particularly limited as long as it is used in the industry for manufacturing a cathode active material precursor. For example, the above nickel raw material may be a nickel-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, it may be NiSO4, NiSO4·6H2O, Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, nickel fatty acid salt, nickel halide, or a combination thereof, but is not limited thereto.

[0093] The above-mentioned cobalt raw material is not particularly limited as long as it is used in the industry for the manufacture of cathode active material precursors. For example, the above-mentioned cobalt raw material may be a cobalt-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, CoSO₄ 4,It may be CoSO4·7H2O, Co(OH)2, CoOOH, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O, or a combination thereof, but is not limited thereto.

[0094] The above manganese raw material is not particularly limited as long as it is used in the industry for the manufacture of cathode active material precursors. For example, the above manganese raw material may be a manganese-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, oxyhydroxide, or a combination thereof. Specifically, it may be a manganese salt such as MnSO4, MnCO3, Mn(NO3)2, manganese acetate, manganese dicarboxylate, manganese citrate, and manganese fatty acid, manganese oxide such as Mn2O3, MnO2, and Mn3O4, oxyhydroxide, manganese chloride, or a combination thereof, but is not limited thereto.

[0095] 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 that can be uniformly mixed with water (e.g., alcohol).

[0096] The above-mentioned complexing agent-containing solution performs the role of forming a complex, and may include, for example, NH3, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3, or a combination thereof as the complexing agent, but is not limited thereto. Meanwhile, the above-mentioned complexing agent-containing solution may be used in the form of an aqueous solution, and in this case, water or a mixture of water and an organic solvent that is uniformly miscible with water (e.g., alcohol, etc.) may be used as the solvent.

[0097] The above pH-adjusting solution serves as a precipitating agent or a pH regulator and may include alkali compounds such as hydroxides of alkali metals or alkaline earth metals like NaOH, KOH, or Ca(OH)2, their hydrates, or combinations thereof. Meanwhile, the above pH-adjusting solution may also be used in the form of an aqueous solution, in which case water or a mixture of water and an organic solvent that is uniformly miscible with water (e.g., alcohol) may be used as the solvent. In this case, the above pH-adjusting solution may be added in an amount such that the pH of the reaction solution becomes 10 to 13.

[0098] The above co-precipitation reaction can be carried out under an inert atmosphere such as nitrogen or argon, at a temperature of 30 to 70°C, and at a pH of 10 to 13.

[0099] By the above process, particles of nickel (or manganese-cobalt) hydroxide are generated and precipitated in the reaction solution. The precipitated precursor particles can be separated by conventional methods, washed, and dried to obtain a precursor. The precursor may be a secondary particle formed by the aggregation of primary particles.

[0100] 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, the cobalt raw material, or the manganese raw material. That is, the concentrations of the nickel raw material, the cobalt raw material, and the manganese raw material can be controlled so that the molar ratio of nickel, cobalt, or manganese in the final product, the lithium metal oxide, falls within the range according to the present invention.

[0101] Next, the above metal precursor and lithium raw material are mixed and then calcined to form a first lithium metal oxide.

[0102] At this time, the lithium raw material may be a lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, and is not particularly limited as long as it is soluble in water. Specifically, the lithium raw material may be Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, or a combination thereof, but is not limited thereto.

[0103] In the step of mixing the metal precursor and lithium raw material, a doping raw material may be further mixed to prepare the mixture.

[0104] The above doping raw material may include one or more selected from Zr, Al, Y, B, Mg, Ti, Nb, W, Sc, Si, P, V, Fe, Mo, Ce, Hf, Ta, La, and Sr.

[0105] Specifically, the above-mentioned doping raw material may include a Zr raw material or an Al raw material, specifically a Zr raw material and an Al raw material.

[0106] 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.

[0107] 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.

[0108] At this point, the content of the element doped into the metal oxide and the resulting effects are omitted as they are as previously described.

[0109] In addition, the above calcination may be performed at a temperature of 720 to 780°C, more specifically at 731 to 759°C or 734 to 745°C. If the calcination temperature is too low, a layered lithium metal oxide may not form well. If the calcination temperature is too high, over-calcination may occur, and electrochemical properties may deteriorate.

[0110] In addition, the above calcination may be performed for 7 to 15 hours. If the calcination time is too short, a layered lithium metal oxide may not be formed well. If the calcination time is too long, under-calcination may occur, and electrochemical properties may deteriorate.

[0111] In addition, the above 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 better compared to when 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.

[0112] Meanwhile, the step of dissolving the first lithium metal oxide may be further included.

[0113] The above disintegration can be performed after cooling the calcined lithium transition metal oxide to 50 to 200°C. Cooling to the above cooling temperature can suppress the reaction between external moisture and the calcined product and suppress the increase in residual lithium.

[0114] The above crushing can be performed by methods commonly practiced in the industry, for example, using rotor mills, jet mills, ball mills, fin mills, bead mills, or roll mill equipment, but in particular, it can be performed using jet mills and rotor mills.

[0115] Next, a B-containing coating layer can be further formed by mixing the first lithium metal oxide and the B raw material and then performing a coating heat treatment.

[0116] 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 cathode active material, B(OH)3 may be more suitable as the above B raw material.

[0117] At this time, the amount of raw material B added 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 explained above and is therefore omitted.

[0118] 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 Formula 1 can satisfy the range according to the present invention.

[0119] In addition, 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 Formula 1 can satisfy the range according to the present invention.

[0120] In addition, the above coating heat treatment can be performed in an air atmosphere.

[0122] Next, the second lithium metal oxide can be manufactured by the step of preparing a second metal precursor; mixing the second metal precursor and the second lithium raw material, and then calcining to form the second lithium metal oxide, and may further be manufactured by the step of forming an Al, Co-containing coating layer.

[0123] First, prepare the second metal precursor. The step of preparing the metal precursor is the same as the step of preparing the first lithium metal oxide, so it is omitted.

[0124] Meanwhile, the above first metal precursor and second metal precursor may satisfy the following Equation 2.

[0125] [Equation 2]

[0126] 0.80 < A / B < 1.3

[0127] The above A may represent the nickel content based on the total molar amount of the metal of the first metal precursor, and the above B may represent the nickel content based on the total molar amount of the metal of the second metal precursor.

[0128] By satisfying the range of Equation 2 above and satisfying Equation 1 of the present invention, the lifespan characteristics and energy density at room temperature and high temperature can be improved.

[0129] Meanwhile, the BET (Brunauer-Emmett-Teller) specific surface area of ​​the second metal precursor is 5.8 to 6.5 m² 2 / g or 5.9 to 6.4 m 2 It may be in the range of / g. If the BET specific surface area of ​​the second metal precursor is too small, the lithium transport path area is reduced, which may degrade characteristics such as capacity and output. If the BET specific surface area is too large, the surface pores of the cathode active material manufactured with the said precursor become too numerous, and significant collapse of the surface pore structure may occur when pressure is applied (during the rolling process). In this specification, the specific surface area of ​​the precursor or active material can be measured using the BET method (Surface area and Porosity analyzer) (Micromeritics, Tristar2 3020) for the precursor or active material powder.

[0130] Next, the metal precursor and the lithium raw material are mixed and then calcined to form a second lithium metal oxide.

[0131] At this time, the lithium raw material may be a lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, and is not particularly limited as long as it is soluble in water. Specifically, the lithium raw material may be Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, or a combination thereof, but is not limited thereto.

[0132] In the step of mixing the metal precursor and lithium raw material, a mixture may also be prepared by further mixing a doping raw material.

[0133] The above doping raw material may include one or more selected from Zr, Al, Y, B, Mg, Ti, Nb, W, Sc, Si, P, V, Fe, Mo, Ce, Hf, Ta, La, and Sr.

[0134] Specifically, the above-mentioned doping raw material may include a Zr raw material.

[0135] 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.

[0136] At this point, the content of the element doped into the metal oxide and the resulting effects are omitted as they are as previously described.

[0138] In addition, the above firing can be performed by dividing it into first firing and second firing.

[0139] At this time, the first firing temperature may be higher than the second firing temperature, and the first firing time may be shorter than the second firing time. When the first firing temperature is higher than the second firing temperature and the first firing time is shorter than the second firing time, it is advantageous for forming a layered crystal structure, thereby improving the structural stability of the second lithium metal oxide so that Equation 1 can satisfy the range according to the present invention.

[0140] More specifically, the first calcination temperature may be 800 to 850°C, and the second calcination temperature may be 700 to 780°C. Additionally, the first calcination time may be 1 to 5 hours, and the second calcination time may be 6 to 12 hours. When the first and second calcination temperatures, the first calcination time, and the second calcination time satisfy the above ranges, the effect of improving the structural stability of the second lithium metal oxide is more preferably realized, so that Formula 1 can better satisfy the range according to the present invention.

[0141] Meanwhile, it may further include a step of dissolving the second lithium metal oxide.

[0142] The above disintegration can be performed after cooling the calcined lithium transition metal oxide to 50 to 200°C or lower. Cooling to the above cooling temperature can suppress the reaction between external moisture and the calcined product and suppress the increase in residual lithium.

[0143] The above crushing can be performed by methods commonly practiced in the industry, for example, using rotor mills, jet mills, ball mills, fin mills, bead mills, or roll mill equipment, but in particular, it can be performed using jet mills and rotor mills.

[0144] Next, the above second lithium metal oxide and the Al raw material or Co raw material, more specifically both raw materials, are mixed and then subjected to coating heat treatment to form an Al or Co-containing coating layer, specifically an Al and Co-containing coating layer.

[0145] At this time, the above Al raw material is, for example, Al(OH)3, It may be Al2(SO4)3, Al(NO)3, Al2O3, AlCl3, or a combination thereof, but is not necessarily limited thereto.

[0146] In addition, the amount of the above-mentioned Al raw material 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, so that it is 300 to 1,000 ppm. The technical significance of adjusting the Al content has been explained above, so it is omitted.

[0147] At this time, the above 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 H2O, CO3(PO4)2, or a combination thereof, but is not necessarily limited thereto.

[0148] In addition, the amount of the above-mentioned Co raw material 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, so that it is 12,000 to 18,000 ppm. The technical significance of adjusting the Co content has been explained above, so it is omitted.

[0149] In addition, the above coating heat treatment can be performed in an oxygen atmosphere. Since the coating heat treatment is performed in an oxygen atmosphere, there may be an advantage in that the life characteristics are improved compared to when performed in an air atmosphere.

[0151] anode

[0152] In another embodiment of the present invention, a positive electrode is provided comprising a current collector and a positive electrode active material layer located on one surface of the current collector and comprising a positive electrode active material manufactured according to the above embodiment.

[0153] The characteristics of the positive active material constituting the above positive active material layer are the same as those previously described. Therefore, a detailed description of the positive active material will be omitted.

[0154] The above current collector may be, for example, made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treated with carbon, nickel, titanium, silver, etc.

[0155] Meanwhile, the above positive active material layer may include a binder and a conductive material.

[0156] At this time, the binder serves to improve adhesion between positive active material particles and adhesion between the positive active material and the positive current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof. One of these alone or a mixture of two or more may be used, but is not limited thereto. The binder may be included in an amount of 1 to 30 weight% based on the total weight of the positive active material layer.

[0157] In addition, the conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it possesses electronic conductivity without causing chemical changes. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fibers; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used, but is not limited thereto. The conductive material may typically be included in an amount of 1 to 30 weight% relative to the total weight of the positive electrode active material layer.

[0158] Except for being manufactured to fall within the above range, the above anode may be manufactured according to a conventional anode manufacturing method.

[0159] Specifically, the anode may be manufactured by applying a composition for forming an anode active material layer, which optionally includes a binder, a conductive material, or a solvent as needed, onto an anode current collector, followed by drying and rolling. At this time, the types and contents of the anode active material, binder, and conductive material are as described above.

[0160] The above solvent may be a solvent commonly used in the relevant technical field, such as dimethylsulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of these alone or a mixture of two or more may be used. The amount of the above solvent used is sufficient if it has a viscosity that allows for the dissolution or dispersion of the anode active material, conductive material, and binder, taking into account the coating thickness of the slurry and the manufacturing yield, and subsequently provides excellent thickness uniformity when coated for anode manufacturing.

[0161] Alternatively, the anode may be manufactured by casting a composition for forming an anode active material layer onto a separate support, and then laminating the film obtained by peeling off from the support onto an anode current collector.

[0163] lithium secondary battery

[0164] In another embodiment, a lithium secondary battery including the anode is provided.

[0165] Specifically, the lithium secondary battery may include a positive electrode, a negative electrode positioned opposite to 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. Additionally, the lithium secondary battery may optionally further include a battery container housing an electrode assembly comprising the positive electrode, the negative electrode, and the separator, and a sealing member for sealing the battery container.

[0166] In the above lithium secondary battery, the negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0167] The above-mentioned negative 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., and aluminum-cadmium alloy may be used. In addition, the above-mentioned negative current collector may typically have a thickness of 3 to 500 μm, and, similar to the positive current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0168] The above-mentioned cathode active material layer may optionally include a binder and a conductive material together with the cathode active material. The above-mentioned cathode active material layer may be manufactured, as an example, by applying a composition for forming a cathode active material layer, comprising a cathode active material and optionally a binder and a conductive material, onto a cathode current collector and drying it, or by casting the composition for forming a cathode onto a separate support and then laminating the film obtained by peeling it off from the support onto a cathode current collector.

[0169] As the above-mentioned 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 alloys, Sn alloys, or Al alloys; metal oxides capable of doping and dedoping lithium, such as SiOβ (0 ≤ β ≤ 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the above-mentioned metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or more of these may be used. Additionally, a metallic lithium thin film may be used as the above-mentioned negative electrode active material. Furthermore, the carbon material may include both low-crystallinity carbon and high-crystallinity carbon. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0170] The binder and conductive material mentioned above may be the same as those previously described in the anode.

[0171] Next, depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. As such a separator, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof may be used, and a mixed multilayer film 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.

[0172] In addition, regarding the above lithium secondary battery, the electrolyte may include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which are usable when manufacturing a lithium secondary battery, but is not limited to these.

[0173] Specifically, the organic liquid electrolyte may include an organic solvent and a lithium salt.

[0174] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; and aromatic hydrocarbon-based solvents such as benzene and fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having C2 to C20 structures and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, 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 low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.In this case, using a mixture of cyclic carbonate and chain carbonate in a volume ratio of about 1:1 to about 1:9 can result in excellent performance of the electrolyte.

[0175] The above lithium salt can be used without special restrictions as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, 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 2.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and allow lithium ions to move effectively.

[0176] As described above, since the lithium secondary battery including the positive electrode according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, it is useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0178] Preferred embodiments and comparative examples of the present invention are described below. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0180] Preparation of positive electrode active material

[0181] Example 1

[0182] (1) Preparation of a precursor

[0183] (Preparation of the first metal precursor)

[0184] While stirring with water in a batch reactor, the internal temperature was set to 50°C, and nitrogen gas was introduced into the reactor to adjust the atmosphere to an inert atmosphere. Subsequently, an aqueous sulfate solution mixed with nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 90.0 mol% : 7.0 mol% : 3.0 mol%, along with sodium hydroxide and ammonia water, were prepared. After introducing the sodium hydroxide solution and ammonia water 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 to the flow rate of the metal sulfate solution. Subsequently, the dosage of the sodium hydroxide (NaOH) solution was adjusted so that the hydrogen ion concentration (pH) inside the reactor was approximately pH 10.5 to 11.2. Then, while stirring, the reactants were introduced, nitrogen gas was introduced, and the inert atmosphere was maintained. After the reaction was completed, the formed solution was washed and solid-liquid separated using a pressure filter (Filter Press), and a drying process was carried out.

[0185] (Preparation of the second metal precursor)

[0186] Water was placed in a batch reactor and stirred, the internal temperature was set to 50°C, and nitrogen gas was introduced into the reactor to adjust the atmosphere to an inert atmosphere. Subsequently, an aqueous sulfate solution mixed with 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% was prepared, along with sodium hydroxide and ammonia water. The sodium hydroxide solution and ammonia water were introduced into the reactor to form an initial reaction atmosphere, after which the flow rate of the ammonia water was adjusted to a ratio of 1.2 to the flow rate of the metal sulfate solution. Subsequently, the dosage of the sodium hydroxide (NaOH) solution was adjusted so that the hydrogen ion concentration (pH) inside the reactor was approximately 11.8. Then, the reactants were introduced while stirring, and the inert atmosphere was maintained after introducing nitrogen gas. After the reaction was completed, the formed solution was washed and solid-liquid separated using a filter press, followed by a drying process. The BET (Brunauer-Emmett-Teller) specific surface area of ​​the prepared second metal precursor was 6.2 m². 2 5.8 to 6.4 m / g 2 It fell within the / g range.

[0187] (Preparation of first lithium metal oxide)

[0188] To 20.87 kg of the first metal precursor prepared above, 10.00 kg of LiOH·H2O, 175.4 g of Al(OH)3, and 97.6 g of ZrO2 were each weighed and uniformly mixed using a mixer to form a mixture. Subsequently, the mixture was calcined at a temperature of 735°C for 10 hours in an RHK (Roller Hearth Kiln) kiln where an O2 atmosphere was maintained to form a lithium metal oxide. The lithium metal oxide was crushed and classified using a Rotor Mill. Afterward, the crushed and classified lithium metal oxide was placed in distilled water at 9°C and stirred for 10 minutes to wash it. Subsequently, the washed lithium metal oxide was vacuum dried at a temperature of 120°C for at least 6 hours.

[0189] Approximately 0.34 g of B(OH)3 was mixed per 100 g of the dried cathode active material and heat treatment was performed in a box-shaped kiln where an O2 atmosphere was maintained. In a box-shaped kiln where air gas was introduced at a flow rate of 25 L / min, the temperature was raised at 6.0 ℃ / min and maintained at 280℃ for 6 hours, after which it was naturally cooled to produce a polycrystalline first cathode active material with a volume-based average particle size of 13.5 µm and a crystallite size of 113 nm, in which a B coating layer was formed.

[0190] (Preparation of secondary lithium metal oxide)

[0191] 21.81 kg of the second metal precursor prepared above was mixed with 10.19 kg of LiOH·H2O and 31.06 g of ZrO2, respectively, and then uniformly mixed using a mixer. The mixture was then calcined in an RHK kiln where an O2 atmosphere was maintained. The mixture was recovered and placed in a mullite crucible. In an RHK kiln supplied with oxygen at a flow rate of approximately 2800 L / min, the temperature was raised at 4.5 ℃ / min and maintained at 820°C for 4 hours, then lowered to 740°C at a cooling rate of 1.3°C / min and maintained for 8 hours. Subsequently, the temperature was lowered at 4.0 ℃ / min. The obtained sample was crushed using a Rotor-Mill and Jet-Mill equipment to produce a single-crystal cathode active material with an average particle size (Dv50) of 3.6 μm by volume.

[0192] Approximately 0.14g of Al(OH)3 and 1.95g of Co(OH)2 were mixed per 100g of single-crystal cathode active material that had undergone a disintegration process, and heat treatment was carried out in a box-shaped kiln where an O2 atmosphere was maintained. In a box-shaped kiln where O2 gas was introduced at a flow rate of 25 L / min, the temperature was raised at 3.5 ℃ / min and maintained at 680℃ for 6 hours, after which it was naturally cooled to produce a second single-crystal cathode active material with an average particle size (Dv50) of 3.8㎛ based on volume, in which Al and Co coating layers were formed.

[0193] (Manufacturing of bimodal cathode active material)

[0194] A bimodal cathode active material was prepared by mixing the first lithium metal oxide and the second lithium metal oxide in a weight ratio of 8:2 for 1 minute using a C-mixer that mixes materials by rotating at high speed under room temperature conditions (25℃).

[0196] Example 2

[0197] A positive electrode 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.

[0199] Example 3

[0200] A positive electrode 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.

[0202] Comparative Example 1

[0203] A positive electrode 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.

[0205] Comparative Example 2

[0206] A positive electrode 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.

[0208] Comparative Example 3

[0209] In the (preparation of the second metal precursor), the ammonia water input ratio to the flow rate of the metal sulfate aqueous solution was set to 1.0, and the hydrogen ion concentration in the reactor, i.e., the reaction pH, was changed to 11.6. The BET specific surface area of ​​the prepared second metal precursor was 7.1 m² 2 7.0 m / g 2 It fell within the range of / g or higher.

[0210] Except for this, the positive active material was prepared in the same way as in Example 1.

[0212] Comparative Example 4

[0213] In the (preparation of the second metal precursor), the ammonia water input ratio to the flow rate of the metal sulfate aqueous solution was set to 2.0, and the hydrogen ion concentration in the reactor, i.e., the reaction pH, was changed to 12.4. The BET specific surface area of ​​the prepared second metal precursor was 4.7 m² 2 5.0 m / g 2It fell within the range of / g or less.

[0214] Except for this, the positive active material was prepared in the same way as in Example 1.

[0216] Experimental Example 2: Evaluation of Physical Properties of Bimodal Type Anode Active Material

[0217] To evaluate the physical properties of the cathode active materials according to the examples and comparative examples, experiments were performed as follows, and the results are shown in Table 1 below.

[0218] (1) Particle size measurement

[0219] The particle size distribution of the cathode active material according to the examples and comparative examples was measured using a Microtrac (S3000) instrument utilizing the laser diffraction method. The average particle size based on volume (Dv50) can be defined as the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve. The average particle size based on number (Dn50) can be defined as the particle size corresponding to 50% of the cumulative number in the particle size distribution curve.

[0220] (2) Rolling density measurement

[0221] The rolling density of the positive electrode active materials according to the examples and comparative examples was measured using a GEOPYC 1365 (Micromeritics) instrument. Specifically, 10 g of the positive electrode active material was placed into a cylindrical vessel, and then the mold containing the positive electrode active material was pressurized at a pressure of 108 N. Afterward, the rolling density was calculated through the height of the pressurized sample.

[0222] (3) FWHM (Full Width at Half Maximum) measurement

[0223] For the cathode active materials according to the examples and comparative examples, FWHM extracted and analyzed X-ray diffraction patterns using a D8 ENDEAVOR (BRUKER) instrument utilizing X-ray diffraction (XRD). Specifically, the cathode active material was uniformly loaded into a sample holder in powder form, and the 2θ region between 10 and 90 degrees was 10.7 o XRD analysis was performed at a speed of / min, and the X-ray tube was set to 45kV and 200mA. The extracted X-ray diffraction pattern was used to calculate the FWHM values ​​for each (101) and (104) peak using the Smart lab studio program.

[0224] At this time, the (104) peak can be identified at 2θ = 44.5±1° in the X-ray diffraction spectrum analysis, and the (101) peak can be identified at 2θ = 36.7±1° in the X-ray diffraction spectrum analysis.

[0225] Figure 1 is an XRD (X-ray diffraction) graph measured for the cathode active materials according to the examples and comparative examples. The FWHM values ​​of each peak were calculated using the graph, and their ratios are shown in Table 1 below.

[0226] (4) Analysis of physical properties after 9 ton pressurization

[0227] After introducing 3.00g of cathode active material sample into a mold with a diameter of 1.3cm, 67.8 kN / cm 2Pressurization was applied using force. Subsequently, the pressurized pellet-shaped cathode active material was placed in a mortar and pestle and ground to break up the clumped particles. Then, 0.01 g of the cathode active material was added to 61 mL of 10 wt% (NaPO3) as a dispersant, and ultrasonic treatment was performed for 1 minute. Afterward, a particle size distribution curve was obtained by analyzing the particle size using a Malvern (MS3000) instrument. Based on the results, the Dv50 value was verified, and the fraction of particles smaller than 1 µm was summed to calculate the amount of fine particles generated.

[0229] Experimental Example 2: Evaluation of Electrochemical Properties Using a Coin Cell

[0230] To evaluate the physical properties and electrochemistry of the positive electrode active materials according to the examples and comparative examples, coin cells were manufactured as follows.

[0231] Specifically, a positive active material, a polyvinylidene fluoride binder (product name: KF1120), and a carbon black conductive material were mixed in a weight ratio of 96.5:1.5:2.0, and this mixture was added to an N-methyl-2-pyrrolidone solvent to prepare a positive active material slurry.

[0232] The above slurry was coated onto an anode current collector aluminum foil (Al foil, thickness: 20 μm) using a doctor blade, dried, and then rolled to manufacture an anode. The loading amount of the anode was approximately 17.0 mg / cm², and the rolling density was approximately 3.7 g / cm³. 3 It was.

[0233] A 2032 coin-type half-cell was manufactured by a conventional method using the above-mentioned positive electrode, a lithium metal negative electrode (thickness 200 μm, Welcos), an electrolyte, and a polyethylene separator. The electrolyte used was a mixed solution in which 1M LiPF6 was dissolved in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethylmethyl carbonate (EMC) (mixing ratio EC:DMC:EMC = 3:4:3 volume%) together with a mixed solvent of VC (vinylene carbonate), PS (propane sulfone), and ESA (ethylene sulfate) (3.0:0.5:1 wt%).

[0235] (1) Evaluation of initial capacity and initial efficiency

[0236] After fabricating the coin cell, it was aged at 25°C for 10 hours, and then a charge-discharge test was conducted at 25°C. To evaluate the initial capacity, the reference capacity was set to 200 mAh / g, and the cell was charged to 4.3V with a constant current of 0.1C; then, the voltage was switched to a constant voltage, and charging continued until the termination current reached 0.05C. After charging, the cell was discharged with a constant current of 0.1C with a reference capacity of 200 mAh / g until it reached 3.0V.

[0238] (2) Room temperature life evaluation (25℃, 50 cycles)

[0239] After fabricating the lithium secondary battery half cell, it was charged to 4.3V at room temperature (25℃) with a constant current of 0.1C, then switched to a constant voltage and charged until the termination current reached 0.05C. After charging, it was discharged with a constant current of 0.1C until it reached 3.0V.

[0240] After the initial charge / discharge described above, the voltage was charged to 4.3V with a constant current of 0.33C, then switched to a constant voltage and charged until the termination current reached 0.05C, and discharged until it reached 3.0V with a constant current of 0.33C. Subsequently, the voltage was charged to 4.3V with a constant current of 0.5C, then switched to a constant voltage and charged until the termination current reached 0.05C, and discharged 50 times under the condition of reaching 3.0V with a constant current of 1C. After performing 50 charge / discharge cycles under the corresponding charge / discharge cycle conditions, the capacity retention rate of the 50th cycle was calculated relative to the first cycle.

[0242] (3) High temperature life evaluation (45℃, 50 cycles)

[0243] After fabricating a lithium secondary battery half cell, it was charged to 4.3V at 45℃ with a constant current of 0.1C, then switched to a constant voltage and charged until the termination current reached 0.05C. After charging, it was discharged with a constant current of 0.1C until it reached 3.0V.

[0244] After the initial charge / discharge described above, the device was charged to 4.3V with a constant current of 0.5C, then switched to a constant voltage and charged until the termination current reached 0.05C. After charging, the device was discharged with a constant current of 1.0C until it reached 3.0V, and 50 charge / discharge cycles were performed under these conditions, at which time the capacity retention rate of the 50th cycle was calculated compared to the first cycle.

[0246] (4) Energy density calculation

[0247] The energy density (Wh / kg) of each was calculated by multiplying the discharge capacity (mAh) of 50 cycles and the average voltage value (V) obtained from the charge / discharge test equipment (Toscat-3100) at room temperature (25℃) and high temperature (45℃).

[0249] The electrochemical properties derived from this are listed in Table 1 below.

[0250] division Comparative Example 1 Example 1 Example 2 Example 3 Comparative Example 2 Comparative Example 3 Comparative Example 4 Dv50[um] 12.8 12.07 11.15 9.97 7.88 11.99 12.05 Dn50[um] 11.22 2.92 2.76 2.78 2.7 2.94 2.901 C / S [nm] 148 142 136 132 137 138 146 FWHM(101) [°] 0.1325 0.1424 0.1545 0.1612 0.1636 0.14 0.1386 FWHM(104) [°] 0.1622 0.1709 0.1762 0.1749 0.1689 0.1688 0.1685 FWHM(101) / FWHM(104) 0.8169 0.8332 0.8768 0.9217 0.9686 0.8294 0.8226 Rolled density [g / cc] 2.57 2.62 2.64 2.62 2.57 2.6 2.61 D50 [um] after 9-ton Press 11.3 10.76 10.27 8.78 5.88 10.77 9.8 Fine powder generation amount after 9-ton Press [%] 3.39 2.16 1.68 1.65 1.81 2.52 2.55 0.1C Charging Capacity [mAh / g] 240 240.1 241 241.5 242 241.6 240.2 0.1C discharge capacity [mAh / g] 220 219.5 219.1 218.8 217.5 216.4 215.1 Efficiency[%] 91.7 91.4 90.9 90.6 90 89.5 89.6 2C Efficiency[%] 86.5 87.2 87.4 87.4 87.7 87.6 87.5 25℃ Room Temperature Lifespan[%] 94.5 95.9 96 96 96.3 96.4 96.2 Energy density at 25℃ [Wh / kg] 710 715.4 714.2 717 709.5 709.1 707.2 45℃ High Temperature Life[%] 91.4 93.8 94.1 94.2 94 92.7 92.4 45℃ Energy density [Wh / kg] 738 757.5 762 760.9 752.2 743 749.3

[0251] It was confirmed that the positive active material according to the example satisfying the appropriate range of Equation 1 described above has a rolled density of 2.62 g / cc or higher, and that the energy density at room temperature and high temperature is superior to that of the comparative example.

[0252] Figure 2 is a graph of the energy density at room temperature at 25°C of a battery containing a positive electrode active material according to the example and comparative example. Comparative Examples 2 to 4 have lower energy densities than the example throughout the 50 cycles from 0 cycles (before performing charge / discharge), and in the case of Comparative Example 1, it can be seen that the energy density becomes lower than the example after 25 charge / discharge cycles have been performed.

[0253] Figure 3 is a graph of the room temperature life at 25°C of a battery containing a positive electrode active material according to the example and comparative example. It can be seen that the room temperature life of Comparative Example 1, in particular, decreases rapidly as charge-discharge cycles are performed.

[0254] Figure 4 is a graph of the high-temperature energy density at 45°C of a battery containing a positive electrode active material according to an example and a comparative example. It can be seen that after 25 cycles of charge and discharge at high temperature are performed, the energy density of the battery containing the positive electrode active material according to the comparative example is lower than that of the example.

[0255] Figure 5 is a graph of the high-temperature life at 45°C of a battery containing a positive electrode active material according to the example and comparative example. It can be seen that the high-temperature life of Comparative Example 1, in particular, decreases rapidly as charge-discharge cycles are performed.

[0256] More specifically, it was confirmed that in a battery containing the positive electrode active material according to the example, the room temperature energy density is 714.0 Wh / kg or higher and the high temperature energy density is 755.0 Wh / kg or higher. It was confirmed that this is an effect that cannot be achieved with a battery containing the positive electrode active material according to the comparative example.

[0257] In addition, the example satisfies a 0.1C efficiency of 90.1% or higher and a 2C efficiency of 87.0% or higher. When the 2C efficiency is 87.0% or higher, it is expected that the performance when charging and discharging at high speed will be virtually equivalent to that of the case where the efficiency is higher. Therefore, it can be confirmed that the example is electrochemically superior, as it maintains efficiency not only at 0.1C, where charge / discharge capacity and efficiency are generally measured, but also at a higher rate of 2C.

[0258] Specifically, Comparative Examples 2 to 4 have too low an efficiency at 0.1C and are inferior to the Examples, and Comparative Example 1 has low rate characteristics at a high rate of 2C, so it is expected that performance will be inhibited when charging and discharging at high speed.

[0259] In summary, Comparative Example 1 has inferior 2C efficiency and room temperature / high temperature lifetime compared to the Example, and inferior room temperature / high temperature energy density. Meanwhile, Comparative Example 2 has inferior initial capacity and room temperature / high temperature energy density compared to the Example. Meanwhile, Comparative Examples 3 and 4 have inferior initial capacity, room temperature / high temperature lifetime, and room temperature / high temperature energy density compared to the Example.

[0260] Therefore, through a comparison of the examples and comparative examples, it can be confirmed that the positive electrode active material according to Examples 1 to 3 and the battery containing it are electrochemically excellent and at the same time have excellent stability.

[0262] Synthesizing the results of the experimental examples, the positive active material with excellent electrochemical properties is the positive active material according to Examples 1 to 3 that satisfies the appropriate range of Formula 1.

[0263] In addition, it is expected that a lithium secondary battery containing the said cathode active material can be provided as a lithium secondary battery capable of long-term use and offering high energy density at room and high temperatures, while simultaneously preventing gas generation caused by fine particles to maximize battery safety.

[0265] The present invention is not limited to the above embodiments and can be manufactured in various different forms, and those skilled in the art will understand that the invention can be implemented in other specific forms without changing the technical concept or essential features of the invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

Claim 1 A positive electrode active material for a lithium secondary battery, comprising a first lithium metal oxide containing 80 mol% or more of nickel based on the total molar amount of metals excluding lithium, and a second lithium metal oxide having a higher nickel content than the first lithium metal oxide, having a FWHM (101) in the range of 0.1410 to 0.1630° and a FWHM (104) in the range of 0.1690 to 0.1900°, satisfying the following Equation 1: [Equation 1] 0.8300 ≤ FWHM (101) / FWHM (104) ≤ 0.9600. The above FWHM (101) refers to the full width at half maximum of the (101) peak in the X-ray diffraction spectrum analysis, and the above FWHM (104) refers to the full width at half maximum of the (104) peak in the X-ray diffraction spectrum analysis. Claim 2 A positive electrode active material for a lithium secondary battery according to claim 1, wherein the FWHM (101) is in the range of 0.1420 to 0.1620°. Claim 3 A positive electrode active material for a lithium secondary battery according to claim 1, wherein the FWHM (104) is in the range of 0.1700 to 0.1800°. Claim 4 A positive electrode active material for a lithium secondary battery according to claim 1, wherein the crystal grain size of the first lithium metal oxide is 110 to 135 nm. Claim 5 A positive electrode active material for a lithium secondary battery according to claim 1, wherein the mixed weight ratio (weight of first lithium metal oxide: weight of second lithium metal oxide) of the first lithium metal oxide to the second lithium metal oxide is 85:15 to 55:

45. Claim 6 A positive electrode active material for a lithium secondary battery according to claim 1, wherein the number-based average particle size (Dn50) of the positive electrode active material is in the range of 2.71 to 2.93 μm. Claim 7 A positive electrode active material for a lithium secondary battery according to claim 1, wherein the volume-based average particle size (Dv50) of the first lithium metal oxide is in the range of 5 to 20 μm, and the volume-based average particle size (Dv50) of the second lithium metal oxide is in the range of 1.0 to 5.0 μm. Claim 8 A positive electrode active material for a lithium secondary battery according to claim 1, wherein the first lithium metal oxide is in the form of a secondary particle, and the second lithium metal oxide is in the form of a single crystal in which one or 2 to 20 single particles are aggregated. Claim 9 In claim 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 Mn 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. Claim 10 A positive electrode active material for a lithium secondary battery according to claim 1, wherein 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. Claim 11 A positive electrode active material for a lithium secondary battery according to claim 1, wherein the nickel content of the first lithium metal oxide is 80 to 92 mol% based on the total molar amount of metal excluding lithium, and the nickel content of the second lithium metal oxide is 92 to 96 mol% based on the total molar amount of metal excluding lithium. Claim 12 A lithium secondary battery comprising a positive electrode for a lithium secondary battery comprising a positive electrode active material of any one of claims 1 to 11.

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