Bimodal positive active material, method for producing same, and all-solid-state batteries comprising same

Abstract

An embodiment of the present invention provides bimodal positive active material comprising first and second lithium metal oxide, the average particle diameter (D50) of the first lithium metal oxide being larger than the average particle diameter (D50) of the second lithium metal oxide. The first and second lithium metal oxide comprise first and second coating layers, respectively, coating the entire or a part of the surface, and the first and second coating layers contain a Zr- or Nb-containing compound or a combination thereof, and the Zr- and Nb-containing compounds are represented by chemical formulae 1 and 2, respectively. [Chemical formula 1] LixZryOz [Chemical formula2] LiaNbbOc In chemical formula 1, 0<x≤3, 0<y≤2, and 0<z≤4, and in chemical formula 2, 0<a≤3, 0<b≤2, and 0<c≤4.

Description

Bimodal cathode active material, method for producing the same, and all-solid-state battery comprising the same

[0001] The present invention relates to a bimodal cathode active material, a method for producing the same, and an all-solid-state battery comprising the same, and more particularly, to a bimodal cathode active material having medium and small particle sizes, a method for producing the same, and an all-solid-state battery comprising the same.

[0002] Today, secondary batteries are widely used in everything from large devices like automobiles and power storage systems to smaller devices like mobile phones and laptops. As the applications of secondary batteries expand, demand for improved safety and higher performance is also increasing.

[0003] Among secondary batteries, lithium secondary batteries offer higher energy density and greater capacity per unit area than nickel-manganese or nickel-cadmium batteries. However, the electrolytes used in lithium secondary batteries are mostly liquid, such as organic solvents, raising safety concerns such as electrolyte leakage and the resulting risk of fire.

[0004] Accordingly, active research is being conducted on all-solid-state batteries to improve the safety of existing secondary batteries and increase their energy density. All-solid-state batteries replace the liquid electrolytes used in conventional lithium secondary batteries with solid electrolytes. Because they do not use flammable solvents, they eliminate the risk of ignition or explosion due to reactions such as the decomposition of conventional electrolytes, thereby improving battery safety.

[0005] Accordingly, in the past, LiCoO2 cathode active material was widely used, but recently, development is being carried out on high-nickel lithium nickel cobalt manganese oxide, which is capable of achieving high capacity and has excellent price competitiveness.

[0006] 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.

[0007] However, since high-nickel lithium metal oxides inherently have weak particle strength and low structural stability, there is a problem that capacity characteristics are reduced due to collapse of the surface structure of the positive electrode active material when the electrode is strongly rolled to further improve the rolling density of the bimodal positive electrode active material.

[0008] Accordingly, efforts are needed to improve the problem of deterioration in capacity characteristics when increasing the energy density per volume to increase the energy density of bimodal cathode active materials.

[0009] One object of the present invention is to provide an all-solid-state battery that improves energy density per volume while maintaining capacity by using a bimodal positive electrode active material coated with zirconium or niobium as a bimodal lithium metal oxide containing a high nickel content.

[0010] One embodiment of the present invention comprises a first lithium metal oxide and a second lithium metal oxide, and the average particle diameter (D) of the first lithium metal oxide 50 ) is the average particle diameter (D) of the second lithium metal oxide. 50 ), and the first lithium metal oxide includes a first coating layer coated on the entire or a portion of the surface, the second lithium metal oxide includes a second coating layer coated on the entire or a portion of the surface, and the first coating layer and the second coating layer include a Zr-containing compound, an Nb-containing compound, or a combination thereof, and the Zr-containing compound is represented by the following chemical formula 1, and the Nb-containing compound is represented by the following chemical formula 2.

[0011] [Chemical Formula 1]

[0012] Li x Zr y O z

[0013] [Chemical Formula 2]

[0014] Li a Nb b O c

[0015] The above chemical formula 1 is 0 <x≤3, 0<y≤2, 0<z≤4이고, 상기 화학식 2는 0<a≤3, 0<b≤2, 0<c≤4이다.

[0016] The electronic conductivity of the above bimodal positive electrode active material may be 10 to 50 mS / cm.

[0017] The average particle diameter (D) of the first lithium metal oxide 50 ) is 7.0 to 8.0 μm, and the average particle diameter (D) of the second lithium metal oxide 50 ) can be 4.0 to 5.0 μm.

[0018] The weight ratio of the first lithium metal oxide and the second lithium metal oxide may be 90:10 to 60:40.

[0019] The content of the coating element of the first coating layer may be 0.1 to 3.0 wt% based on the total weight of the first lithium metal oxide.

[0020] The content of the coating element of the second coating layer may be 0.1 to 3.0 wt% based on the total weight of the second lithium metal oxide.

[0021] The thickness of the first coating layer may be 5 to 50 nm.

[0022] The thickness of the second coating layer may be 5 to 50 nm.

[0023] The nickel content of the first lithium metal oxide and the second lithium metal oxide may be 80 to 90 mol% based on the total mole number of metals excluding lithium.

[0024] The density of the pellet of the above bimodal positive electrode active material is 3.0 to 3.7 g / cm 3 It could be.

[0025] Another embodiment of the present invention comprises the steps of: preparing a first metal hydroxide and a second metal hydroxide; forming a mixture including the first metal hydroxide or the second metal hydroxide and a lithium raw material; firing the mixture to form a first lithium metal oxide or the second lithium metal oxide; forming a first coating layer containing a Zr-containing compound, a Nb-containing compound, or a combination thereof on the entirety or a portion of the surface of the first lithium metal oxide; and forming a second coating layer containing a Zr-containing compound, a Nb-containing compound, or a combination thereof on the entirety or a portion of the surface of the second lithium metal oxide; wherein the Zr-containing compound comprises the following chemical formula 1 and the Nb-containing compound comprises the following chemical formula 2.

[0026] The average particle diameter (D) of the first lithium metal oxide 50 ) is the average particle diameter (D) of the second lithium metal oxide. 50 ) is larger than.

[0027] [Chemical Formula 1]

[0028] Li x Zr y O z

[0029] [Chemical Formula 2]

[0030] Li a Nb b O c

[0031] The above chemical formula 1 is 0 <x≤3, 0<y≤2, 0<z≤4이고, 상기 화학식 2는 0<a≤3, 0<b≤2, 0<c≤4이다.

[0032] Another embodiment of the present invention is a positive electrode comprising a bimodal positive electrode active material for an all-solid-state battery.

[0033] Another embodiment of the present invention is an all-solid-state battery comprising: a positive electrode; a negative electrode; and a solid electrolyte layer disposed therebetween, wherein the positive electrode comprises a bimodal positive electrode active material for an all-solid-state battery.

[0034] A bimodal cathode active material according to one embodiment of the present invention comprises a lithium metal oxide having a medium particle size and a small particle size containing a high content of nickel, and improves stability by coating the surface of the cathode active material with Zr or Nb, thereby improving the energy density per volume while maintaining the capacity of an all-solid-state battery.

[0035] 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 solely 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0040] 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.

[0041] 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.

[0042] 1. Bimodal positive electrode active material

[0043] A bimodal cathode active material according to one embodiment of the present invention comprises a first lithium metal oxide and a second lithium metal oxide, and the average particle diameter (D) of the first lithium metal oxide 50 ) is the average particle diameter (D) of the second lithium metal oxide. 50), and the first lithium metal oxide includes a first coating layer coated on the entire or part of the surface, and the second lithium metal oxide includes a second coating layer coated on the entire or part of the surface, and the first coating layer and the second coating layer include a Zr-containing compound, an Nb-containing compound, or a combination thereof, and the Zr-containing compound is represented by the following chemical formula 1, and the Nb-containing compound is represented by the following chemical formula 2.

[0044] [Chemical Formula 1]

[0045] Li x Zr y O z

[0046] [Chemical Formula 2]

[0047] Li a Nb b O c

[0048] The above chemical formula 1 is 0 <x≤3, 0<y≤2, 0<z≤4이고, 상기 화학식 2는 0<a≤3, 0<b≤2, 0<c≤4이다.

[0049] The Zr-containing compound may be of the above chemical formula 1 and the Nb-containing compound may be of the above chemical formula 2, but is not limited thereto, and any element capable of coating the entire or partial surface of the first lithium metal oxide or the second metal oxide may be used.

[0050] In a bimodal positive electrode active material according to an embodiment of the present invention, the electronic conductivity of the bimodal positive electrode active material may be 10 to 50 mS / cm, specifically 20 to 40 mS / cm. When the electronic conductivity of the bimodal positive electrode active material satisfies the above range, the first lithium metal oxide and the second lithium metal oxide are uniformly mixed, so that the electrical conductivity increases compared to when the lithium metal oxide is used alone, thereby improving the electrochemical characteristics of the lithium secondary battery. On the other hand, when the electronic conductivity of the bimodal positive electrode active material is less than 10 mS / cm, there may be non-uniformity in contact between the two positive electrode active materials, the first lithium metal oxide and the second lithium metal oxide, and as a result, a phenomenon in which the discharge capacity of the positive electrode active material in the electrode decreases may occur. This phenomenon may occur more significantly, especially under conditions of high current density, that is, high C-rate. In addition, when the electronic conductivity of the bimodal positive electrode active material exceeds 50 mS / cm, even though the electronic conductivity of the bimodal positive electrode active material has increased, the contact interface between the first lithium metal oxide and the second lithium metal oxide and the solid electrolyte is insufficient, so that ion transfer between the positive electrode active material and the solid electrolyte is uneven, resulting in a tendency for the discharge capacity of the positive electrode active material to decrease and thermal stability to deteriorate. This phenomenon can occur more significantly, especially under conditions of high current density, i.e., high C-rate.

[0051] In a bimodal positive electrode active material according to one embodiment of the present invention, the average particle diameter (D) of the first lithium metal oxide 50 ) may include 7.0 to 8.0 μm and specifically may be 7.3 to 8.0 μm, and the average particle diameter (D) of the second lithium metal oxide 50 ) may include 4.0 to 5.0 μm, and specifically may be 4.3 to 5.0 μm. The average particle diameter (D) of the first lithium metal oxide 50) satisfies the above range, the composite density and surface stability are excellent, so that the energy density per volume can be improved while maintaining the capacity of the all-solid-state battery. On the other hand, the average particle diameter (D of the first lithium metal oxide 50 ) is less than 7.0 μm, the composite density decreases, the specific surface area increases, the surface reactivity increases, and the high-voltage stability decreases, which may reduce the life of the battery. In addition, the average particle diameter (D of the first lithium metal oxide 50 ) exceeds 8.0 μm, the time required for diffusion of Li ions becomes longer, so that the high-capacity and high-output characteristics may deteriorate, and the deterioration of characteristics due to particle size may become more noticeable.

[0052] When the average particle size of the second lithium metal oxide satisfies the above range, the volumetric energy density can be improved while maintaining the capacity of the all-solid-state battery. On the other hand, when the average particle size of the second lithium metal oxide is less than 4.0 μm, the particles are small and difficult to handle, which reduces process efficiency, and the content of conductive carbon may need to be increased when forming an electrode. In this case, the carbon particles may interfere with the contact between the solid electrolyte and the positive electrode active material, and a side reaction may occur between the carbon and the solid electrolyte material, which may lower the electrode energy density. In addition, when the average particle size of the second lithium metal oxide exceeds 5.0 μm, the particles are excessively large, making it difficult for the small particles to be effectively positioned in the space between the neutral diameters, which may lower the composite density. In addition, as the secondary particle size of the small particles increases, the high-output characteristics may be hindered.

[0053] The weight ratio of the first lithium metal oxide and the second lithium metal oxide may be 90:10 to 60:40, and specifically may include a ratio range of 80:20 to 70:30. When the weight ratio of the first lithium metal oxide and the second lithium metal oxide satisfies the above range, the final packing density of the positive electrode active material can be increased, so that the capacity per volume can be increased. On the other hand, when the small particle size of the second lithium metal oxide exceeds about 30% of the total weight of the medium particle size of the first lithium metal oxide and the small particle size of the second lithium metal oxide, the volume of the small particle size becomes larger than the spaces existing between the medium particle sizes, so that the electrode relative packing density decreases, and thus the energy density per volume can decrease. In addition, when the particle size of the second lithium metal oxide is less than about 10% of the total weight of the medium particle size of the first lithium metal oxide and the small particle size of the second lithium metal oxide, the deviation between the occupancy ratios of the medium particle size of the first lithium metal oxide and the small particle size of the second lithium metal oxide becomes severe, and the effect of improving the electrochemical characteristics and stability of the bimodal positive electrode active material may be limited.

[0054] In a bimodal positive electrode active material according to an embodiment of the present invention, the content of the coating element of the first coating layer may be 0.1 to 3.0 wt% based on the total weight of the first lithium metal oxide, and specifically, may be 0.3 to 2.0 wt%. When the content of the coating element of the first coating layer satisfies the above range based on the total weight of the first lithium metal oxide, the structural stability of the first lithium metal oxide may be increased, and when the positive electrode active material is used in a lithium secondary battery, the high-temperature storage stability and lifespan characteristics of the positive electrode active material may be improved. In addition, by reducing residual lithium on the surface of the first lithium metal oxide and simultaneously acting as a migration path of lithium ions, it may affect improving the efficiency characteristics of the lithium secondary battery. On the other hand, when the content of the coating element of the first coating layer is less than 0.1 wt% based on the total weight of the first lithium metal oxide, the entire or a portion of the surface of the first lithium metal oxide may not be coated, and thus the stability and lifespan characteristics of the positive electrode active material may be deteriorated. In addition, when the content of the first coating element exceeds 3.0 wt% based on the total weight of the first lithium metal oxide, the coating on the entire or part of the surface of the first lithium metal oxide becomes thick, so that the resistance of the positive electrode active material is high, making it difficult to implement the charge / discharge capacity of the positive electrode active material.

[0055] In the bimodal positive electrode active material according to one embodiment of the present invention, the content of the coating element of the second coating layer may be 0.2 to 3.0 wt% based on the total weight of the second lithium metal oxide, and specifically, may be 0.3 to 2.0 wt%. When the content of the coating element of the second coating layer satisfies the above range based on the total weight of the second lithium metal oxide, the structural stability of the second lithium metal oxide may be increased, and when the positive electrode active material is used in a lithium secondary battery, the high-temperature storage stability and lifespan characteristics of the positive electrode active material may be improved. On the other hand, when the content of the coating element of the second coating layer is less than 0.2 wt% based on the total weight of the second lithium metal oxide, the entire or a portion of the surface of the second lithium metal oxide may not be coated, and thus the stability and lifespan characteristics of the positive electrode active material may be deteriorated. In addition, when the content of the second coating element exceeds 3.0 wt% based on the total weight of the second lithium metal oxide, the remaining coating element material after coating the entire or partial surface of the second lithium metal oxide may act as an impurity, thereby lowering the efficiency characteristics of the lithium secondary battery.

[0056] In the bimodal positive electrode active material according to one embodiment of the present invention, the thickness of the first coating layer may be 5 to 50 nm, specifically 5 to 20 nm. When the thickness of the first coating layer satisfies the above range, the structural stability of the first lithium metal oxide may be improved, thereby improving the electrochemical characteristics. On the other hand, when the thickness of the first coating layer is less than 5 nm, the electrochemical characteristics and stability of the first lithium metal oxide may be deteriorated. In addition, when the thickness of the first coating layer exceeds 50 nm, the surface occupancy ratio of the first coating layer in the first lithium metal oxide may be excessively large, which may cause a gap in the resistance of the positive electrode active material with the surface characteristics of the first lithium metal oxide, thereby deteriorating the electrochemical characteristics and stability of the positive electrode active material.

[0057] In the bimodal positive electrode active material according to one embodiment of the present invention, the thickness of the second coating layer may be 5 to 50 nm, specifically 10 to 20 nm. When the thickness of the second coating layer satisfies the above range, the structural stability of the second lithium metal oxide may be improved, thereby improving the electrochemical characteristics. On the other hand, when the thickness of the second coating layer is less than 5 nm, the electrochemical characteristics and stability of the first lithium metal oxide may be deteriorated. In addition, when the thickness of the second coating layer exceeds 50 nm, the surface occupancy ratio of the second coating layer in the surface of the second lithium metal oxide may be excessively large, resulting in a gap in the surface characteristics of the second lithium metal oxide, which may deteriorate the electrochemical characteristics and stability of the positive electrode active material.

[0058] In a bimodal cathode active material according to one embodiment of the present invention, the nickel content of the first lithium metal oxide and the second lithium metal oxide may be 80 to 90 mol% based on the total mole number of metals excluding lithium. When the nickel content satisfies the above range, the energy density of the battery increases, thereby increasing the driving range per single charge of the electric vehicle and enabling the production of an electric vehicle with higher output. In addition, nickel has the advantage of providing strong energy instantaneously due to its high energy density, and may be price competitive compared to other metals.

[0059] In a bimodal positive electrode active material according to one embodiment of the present invention, the pellet density of the bimodal positive electrode active material is 3.0 to 3.7 g / cm 3 It can be, specifically, 3.5 to 3.6 g / cm 3 It can be. When the density of the pellet of the bimodal positive electrode active material satisfies the above range, there may be an advantage of increasing the energy density per unit volume. On the other hand, when ... is 3.0 g / cm 3If it is less than 3.7 g / cm, the energy density per unit volume may be low. Also, if the density of the pellet is less than 3.7 g / cm 3 If it is excessive, the absolute amount of the contact interface between the positive electrode active material and the solid electrolyte may decrease, which may cause problems such as increased resistance and decreased discharge capacity.

[0060] 2. Method for manufacturing bimodal cathode active material

[0061] According to another embodiment of the present invention, a method for manufacturing a bimodal cathode active material comprises the steps of: preparing a first metal hydroxide and a second metal hydroxide; forming a mixture including the first metal hydroxide or the second metal hydroxide and a lithium raw material; firing the mixture to form a first lithium metal oxide or the second lithium metal oxide; forming a first coating layer containing a Zr-containing compound, a Nb-containing compound, or a combination thereof on the entirety or a portion of the surface of the first lithium metal oxide; and forming a second coating layer containing a Zr-containing compound, a Nb-containing compound, or a combination thereof on the entirety or a portion of the surface of the second lithium metal oxide; wherein the Zr-containing compound comprises the following chemical formula 1 and the Nb-containing compound comprises the following chemical formula 2, and the average particle diameter (D) of the first lithium metal oxide 50 ) is the average particle diameter (D) of the second lithium metal oxide. 50 ) is larger than.

[0062] [Chemical Formula 1]

[0063] Li x Zr y O z

[0064] [Chemical Formula 2]

[0065] Li a Nb b O c

[0066] The above chemical formula 1 is 0 <x≤3, 0<y≤2, 0<z≤4이고, 상기 화학식 2는 0<a≤3, 0<b≤2, 0<c≤4이다.

[0067] Hereinafter, a method for manufacturing a bimodal positive electrode active material according to another embodiment of the present invention will be described in detail step by step.

[0068] First, in the step of preparing a first metal hydroxide and a second metal hydroxide, the first metal hydroxide and the second metal hydroxide are precursors of a positive electrode active material. The positive electrode active material precursor may be a secondary particle formed by agglomeration of primary particles.

[0069] The above transition metal hydroxide may be manufactured by, for example, adding an ammonia solution and a caustic soda solution to a transition metal-containing solution containing a nickel raw material, a cobalt raw material, a manganese raw material, and a doping raw material including Al, Mg, Ti, Nb, W, Sc, Zr, Si, V, Fe, Y, Mo, or a combination thereof, and performing a co-precipitation reaction.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] The above transition metal-containing solution may be prepared by adding the raw materials to a solvent, specifically, a mixed solvent of water or an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water, or may be prepared by mixing aqueous solutions containing each raw material.

[0074] The ammonia solution may include, but is not limited to, a complex forming agent, for example, NH3, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3, or a combination thereof. Meanwhile, the ammonia solution may also be used in the form of an aqueous solution, and in this case, a solvent may be water, or a mixture of water and an organic solvent (specifically, alcohol, etc.) that can be uniformly mixed with water.

[0075] The above caustic soda solution may contain an alkali 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, as a precipitant or pH adjuster. The above caustic soda solution may also be used in the form of an aqueous solution, and in this case, water or a mixture of water and an organic solvent (specifically, alcohol, etc.) that can be uniformly mixed with water may be used as a solvent.

[0076] The above coprecipitation reaction can be performed under an inert atmosphere such as nitrogen or argon.

[0077] Next, a mixture containing the first metal hydroxide or the second metal hydroxide and a lithium raw material can be formed.

[0078] 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, but is not limited to, Li2CO3, LiNO3, LiNO2, LiOH, LiOHㆍH2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, or a combination thereof.

[0079] The above mixture may further include a doping raw material including Al, Mg, Ti, Nb, W, Sc, Zr, Si, V, Fe, Y, Mo or a combination thereof.

[0080] Next, the mixture can be calcined to form the first lithium metal oxide or the second lithium metal oxide.

[0081] The average particle diameter (D) of the first lithium metal oxide 50) may include 7.0 to 8.0 μm and specifically may be 7.3 to 8.0 μm, and the average particle diameter (D) of the second lithium metal oxide 50 ) may include 4.0 to 5.0 μm, and specifically may be 4.3 to 5.0 μm. Accordingly, the average particle diameter (D) of the positive electrode active material 50 ) can be easily obtained within this target range.

[0082] At this time, the above-mentioned firing can be performed at a maximum temperature of 700 to 800°C. When the firing temperature satisfies the above range, there is an advantage in that an optimal crystal grain size can be secured.

[0083] The above firing can be performed in an oxygen atmosphere.

[0084] The maximum temperature maintenance time of the above firing time can be performed for 3 to 24 hours, and more specifically, can be performed for 5 to 15 hours.

[0085]

[0086] Next, the method may include forming a first coating layer containing a Zr-containing compound, a Nb-containing compound, or a combination thereof on the entire or a portion of the surface of the first lithium metal oxide, and forming a second coating layer containing a Zr-containing compound, a Nb-containing compound, or a combination thereof on the entire or a portion of the surface of the second lithium metal oxide. Since the Zr and Nb compounds are as described above, a detailed description thereof will be omitted.

[0087] Meanwhile, the method for forming the coating layer is not particularly limited. For example, the coating layer may be formed by spraying a coating solution containing a coating raw material onto the surface of a first lithium metal oxide or a second lithium metal oxide, followed by heat treatment and drying. However, this is not limited thereto, and any method available in the art may be used without limitation.

[0088]

[0089] 3. All-solid-state battery

[0090] Another embodiment of the present invention provides a positive electrode comprising the bimodal positive electrode active material for an all-solid-state battery described above.

[0091] More specifically, the positive electrode may include a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, and the positive electrode active material layer may include the positive electrode active material for the all-solid-state battery described above, a sulfide-based solid electrolyte, and a conductive material. In addition, the positive electrode active material layer may further include a binder.

[0092] At this time, the sulfide-based solid electrolyte may be, for example, a sulfide-based solid electrolyte having an argyrodite-based crystal structure.

[0093] The sulfide-based solid electrolyte having the above-mentioned argyrodite-based crystal structure may be, for example, Li6PS5Cl, Li6PS5Br, Li6PS5I, or a combination thereof, but is not limited thereto.

[0094] The sulfide-based solid electrolyte having the above argyrodite-based crystal structure may have at least a portion of the crystal structure doped with a doping element.

[0095] The above-mentioned conductive material may be, for example, graphite, carbon black, acetylene black, Ketjen black, carbon nanofibers, carbon nanotubes, or a combination thereof.

[0096] The binder may be, for example, polyvinylidene fluoride, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, or a combination thereof.

[0097] The above-described positive electrode active material layer may further include additives such as fillers, coating agents, dispersants, and ion conductive aids in addition to the above-described positive electrode active material, solid electrolyte, binder, and conductive agent.

[0098] Another embodiment of the present invention provides an all-solid-state battery comprising a positive electrode, a negative electrode, and a solid electrolyte layer disposed therebetween, wherein the positive electrode comprises the positive electrode active material for an all-solid-state battery as described above.

[0099] Description of the above anodes is omitted as they have been explained previously.

[0100] The above solid electrolyte layer may include a sulfide-based solid electrolyte.

[0101] The above sulfide-based solid electrolyte is, for example, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x , may be an argyrodite-type compound including at least one selected from 0≤x≤2. In particular, the sulfide-based solid electrolyte may be an argyrodite-type compound including at least one selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I. However, the present invention is not limited thereto.

[0102] The above sulfide-based solid electrolyte may have at least a portion of the crystal structure of the above-described argyrodite-type compound doped with a doping element.

[0103] The above solid electrolyte layer may further include a binder. The binder included in the solid electrolyte layer may be, but is not limited to, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., and any binder used in the relevant technical field may be used. The binder of the solid electrolyte layer may be the same as or different from the binder included in the positive electrode active material layer and the negative electrode active material layer.

[0104] The above negative electrode may include a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, and the negative electrode active material layer may include a negative electrode active material.

[0105] The above negative active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0106] The material capable of reversibly intercalating / deintercalating the lithium ions is a carbon material, and any carbon-based negative electrode active material generally used in lithium ion secondary batteries can be used, and representative examples thereof include crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in an amorphous, plate-like, flake-like, spherical, or fibrous form, and examples of the amorphous carbon include soft carbon (low-temperature calcined carbon) or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0107] As the above lithium metal alloy, an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0108] Materials capable of doping and dedoping the lithium include Si, SiOx (0< x < 2), Si-Y alloy (wherein Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn, SnO2, Sn-Y (wherein Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn), and at least one of these may be mixed with SiO2 for use. The above element Y may be selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

[0109] Examples of the above transition metal oxides include vanadium oxide, lithium vanadium oxide, etc.

[0110] The above negative active material layer also includes a binder and may optionally further include a conductive material.

[0111] The above binder serves to adhere the negative electrode active material particles well to each other and also to adhere the negative electrode active material well to the current collector, and representative examples thereof include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0112] The above conductive material is used to provide conductivity to the electrode, and in the battery to be formed, any material that does not cause a chemical change and is electronically conductive can be used. Examples of conductive materials that can be used include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fiber; metal-based materials such as metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive polymer materials such as polyphenylene derivatives; or conductive materials containing mixtures thereof.

[0113] The current collector may be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with a conductive metal, and combinations thereof.

[0114] Hereinafter, embodiments of the present invention will be described in more detail through examples. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0115] Example 1: Method for manufacturing a bimodal positive electrode active material

[0116] (1) Medium-diameter manufacturing method

[0117] Average particle diameter (D 50) Ni of 6 to 7 μm 0.83 Co 0.12 Mn 0.05 (OH)2 metal hydroxide precursor and lithium raw material LiOH·H2O were mixed in a molar ratio of 1:1.05 to form a mixture. 1 kg of the mixture was charged into a tube furnace, and the temperature was increased at a rate of 2.5°C / min. The sintering temperature was maintained at 750°C for 10 hours, and then the temperature was lowered at a rate of 2.5°C / min. Pure O2 was supplied so that the O2 concentration could be maintained at 99% or higher during the sintering process, and the average particle diameter (D 50 ) is a first lithium metal oxide having a thickness of 7 to 8 μm, LiNi 0.83 Co 0.12 Mn 0.05 O2 was formed.

[0118] The first coating layer coated on the entire or part of the surface of the first lithium metal oxide was prepared by dissolving the first lithium metal oxide in dehydrated ethanol, adding zirconium(IV) tetrapropoxide (70 wt% in 1-propanol) in an amount such that the molar ratio of the first lithium metal oxide: zirconium ion = 2:1, and stirring to prepare a coating solution containing lithium ions and zirconium ions. At this time, the concentration of zirconium ions in the coating solution was set to 0.1 mol / L.

[0119] The coating process was performed by spraying 400 mL of the first coating solution onto 1 kg of the first lithium metal oxide formed above using a fluid coating device (MP-01, POWREX). The operating conditions of the fluid coating device were intake gas (nitrogen), intake gas temperature (80°C), intake air volume (0.3 m 3 / h), rotation speed (400 rpm), and coating solution spraying speed (10 mL / min) were used for a total of 40 minutes. After that, the lithium transition metal oxide sprayed with the first coating solution was loaded into Saggar, and then heat-treated at 300°C while supplying oxygen in a box-type electric furnace, thereby manufacturing a cathode active material in which an amorphous coating layer of Li2ZrO3 was formed on the surface of the lithium transition metal oxide.

[0120] (2) Small particle size manufacturing method

[0121] Ni with an average particle size of 4 μm 0.83 Co 0.12 Mn 0.05 (OH)2 transition metal hydroxide precursor and lithium raw material LiOH·H2O were mixed in a molar ratio of 1:1.05 to form a mixture. 1 kg of the mixture was charged into a tube furnace, and the temperature was increased at a rate of 2.5°C / min. The sintering temperature was maintained at 750°C for 10 hours, and then the temperature was lowered at a rate of 2.5°C / min. Pure O2 was supplied so that the O2 concentration could be maintained at 99% or higher during the sintering process, and the average particle diameter (D 50 ) is a second lithium transition metal oxide with a thickness of 5 μm, LiNi 0.83 Co 0.12 Mn 0.05 O2 was formed.

[0122] The first coating layer coated on the entire or part of the surface of the second lithium metal oxide was prepared by dissolving the second lithium metal oxide in dehydrated ethanol, adding zirconium(IV) tetrapropoxide (70 wt. % in 1-propanol) in an amount such that the molar ratio of the second lithium metal oxide:zirconium ion = 2:1, and stirring to prepare a coating solution containing lithium ions and zirconium ions. At this time, the concentration of zirconium ions in the coating solution was set to 0.1 mol / L.

[0123] The coating process was performed by spraying 400 mL of the second coating solution onto 1 kg of the second lithium metal oxide formed above using a fluid coating device (MP-01, POWREX). The operating conditions of the fluid coating device were intake gas (nitrogen), intake gas temperature (80°C), intake air volume (0.3 m 3 / h), rotation speed (400 rpm), and coating solution spraying speed (10 mL / min) were used for a total of 40 minutes. After that, the lithium transition metal oxide sprayed with the second coating solution was loaded into Saggar, and then heat-treated at 300°C while supplying oxygen in a box-type electric furnace, thereby manufacturing a cathode active material in which an amorphous coating layer of Li2ZrO3 was formed on the surface of the lithium transition metal oxide.

[0124] (3) Method for manufacturing bimodal positive electrode active material

[0125] The first lithium transition metal oxide LiNi having the first coating layer coated on the entire surface or part thereof 0.83 Co 0.12 Mn 0.05 LiNi, a second lithium transition metal oxide having O270 wt% and the second coating layer coated on the entire or part of the surface 0.83 Co 0.12 Mn 0.05 A bimodal cathode material was prepared by mixing 30 wt% of O2 in a mixer for 30 minutes.

[0126] (4) All-solid-state battery manufacturing method

[0127] 75 wt% of the above-mentioned manufactured bimodal cathode active material, 22 wt% of Argyrodite solid electrolyte (Li6PS5Cl), and Super C as a conductive material 65A mixture paste was prepared by mixing 3 wt% of the binder with a solvent containing a small amount of the binder. The mixture paste was used to manufacture a plate, which was then dried to produce a composite plate for a cathode. 100 mg of argyrodite solid electrolyte (Li6PS5Cl), which functions as a separator, was first placed in a jig for evaluating all-solid-state batteries, and pressurized at 300 MPa or more to a thickness of approximately 800 μm. Then, a cathode plate was placed on one side, and a second pressurization was performed to produce the cathode portion. Afterwards, a Li-In alloy was placed on the other side, and an appropriate pressure was applied to produce a battery for evaluating all-solid-state batteries.

[0128] Comparative Example 1: Method for manufacturing positive electrode active material

[0129] (1) Medium-diameter manufacturing method

[0130] Ni with an average particle size of 6 to 7 μm 0.83 Co 0.12 Mn 0.05 (OH)2 metal hydroxide precursor and lithium raw material LiOH·H2O were mixed in a molar ratio of 1:1.05 to form a mixture. 1 kg of the mixture was charged into a tube furnace, and the temperature was increased at a rate of 2.5°C / min. The sintering temperature was maintained at 750°C for 10 hours, and then the temperature was lowered at a rate of 2.5°C / min. Pure O2 was supplied so that the O2 concentration could be maintained at 99% or higher during the sintering process, and the average particle diameter (D 50 ) is a first lithium metal oxide having a thickness of 7 to 8 μm, LiNi 0.83 Co 0.12 Mn 0.05 O2 was formed, and the coating of the first lithium metal oxide was performed in the same manner as in Example 1.

[0131] (2) Small particle size manufacturing method

[0132] Ni with an average particle size of 4 μm 0.83 Co 0.12 Mn 0.05A mixture was formed by mixing (OH)2 metal hydroxide precursor and LiOH·H2O as lithium raw material at a molar ratio of 1:1.05.

[0133] 1 kg of the above mixture was charged into the tube, and the temperature was increased at a rate of 2.5°C / min. The firing temperature was maintained at 750°C for 10 hours, and then the temperature was lowered at a rate of 2.5°C / min. Pure O2 was supplied so that the O2 concentration could be maintained at 99% or higher during the firing process, and the average particle diameter (D 50 ) is a second lithium metal oxide of 5 μm, LiNi 0.83 Co 0.12 Mn 0.05 O2 was formed, and the coating of the second lithium metal oxide was performed in the same manner as in Example 1.

[0134] Experimental Example 1: Evaluation of particle size of bimodal cathode active material

[0135] The average particle diameter (D) of the positive electrode active material used in the examples and comparative examples 50 ) was dispersed in distilled water as a positive electrode active material powder, and then analyzed using a Horiba LA-960V2 particle size analyzer while maintaining a well-dispersed state using an ultrasonic vibrator built into the particle size analyzer.

[0136] Experimental Example 2: Evaluation of the Electrochemical Characteristics of All-Solid-State Batteries

[0137] (1) Initial capacity and initial efficiency evaluation

[0138] After fabricating a lithium secondary battery half-cell, it was aged at 30°C for 4 hours and then subjected to a charge-discharge test at 30°C. To evaluate the initial capacity, the battery was charged to 3.63 V at a constant current of 0.1 C with a reference capacity of 200 mAh / g, then switched to a constant voltage and charged until the end current reached 0.05 C. After a 10-minute rest time after charging, the battery was discharged to 1.9 V at a constant current of 0.1 C with a reference capacity of 200 mAh / g.

[0139] (2) Life characteristics evaluation (30℃, 60 cycles)

[0140] After fabricating a lithium secondary battery half-cell, it was charged to 3.63 V at a constant current of 0.5 C at 30°C, then switched to a constant voltage and charged until the end current reached 0.1 C. After a 10-minute rest period after charging, it was discharged at a constant current of 0.5 C until it reached 1.9 V. Under these charge-discharge cycle conditions, 30 charge-discharge cycles were performed, and the capacity retention rate of the 30th cycle was calculated compared to the first cycle.

[0141] Nickel Composition (%)Particle Size (μm)Initial Capacity (mAh / g)High Cycle (0.5C / 0.1C)Retention (%)Comparative Example 1Medium Particle Size 837.5202.290.299.1Comparative Example 2Small Particle Size 834.0 to 5.0214.091.899.1Example 1Bimodal 83214.094.599.1

[0142] Looking at Table 1, the initial capacity of the bimodal positive electrode active material of Example 1 was superior to the initial capacity of the medium particle size of Comparative Example 1, but there was no significant difference from the initial capacity of the small particle size of Comparative Example 2. However, looking at the cycle performance (0.5C / 0.1C) results of Example 1 and Comparative Examples 1 and 2, it was confirmed that the cycle performance of the bimodal positive electrode active material of Example 1 was superior to those of Comparative Examples 1 and 2. Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the claims, the detailed description of the invention, and the attached drawings, and this also falls within the scope of the present invention.

[0143] Therefore, the actual scope of the present invention can be said to be defined by the attached patent claims and their equivalents.

Claims

1. Containing a first lithium metal oxide and a second lithium metal oxide, The average particle diameter (D) of the first lithium metal oxide 50 ) is the average particle diameter (D) of the second lithium metal oxide. 50 ) is greater than The above first lithium metal oxide comprises a first coating layer coated on the entire surface or a portion thereof, The second lithium metal oxide includes a second coating layer coated on the entire or part of the surface, The first coating layer and the second coating layer include a Zr-containing compound, a Nb-containing compound, or a combination thereof, The above Zr-containing compound is of the following chemical formula 1 and the above Nb-containing compound is of the following chemical formula 2, a bimodal positive electrode active material: [Chemical formula 1] Li x Zr y About z [Chemical formula 2] Li a No b O c The above chemical formula 1 is 0 <x≤3, 0<y≤2, 0<z≤4이고, 상기 화학식 2는 0<a≤3, 0<b≤2, 0<c≤4이다.

2. In paragraph 1, A bimodal cathode active material having an electronic conductivity of 10 to 50 mS / cm.

3. In paragraph 1, The average particle diameter (D) of the first lithium metal oxide 50 ) is 7.0 to 8.0 μm, and the average particle diameter (D) of the second lithium metal oxide 50 ) is a bimodal positive electrode active material having a particle size of 4.0 to 5.0 μm.

4. In paragraph 1, A bimodal positive electrode active material, wherein the weight ratio of the first lithium metal oxide and the second lithium metal oxide is 90:10 to 60:

40.

5. In paragraph 1, A bimodal positive electrode active material, wherein the content of the coating element of the first coating layer is 0.1 to 3.0 wt% based on the total weight of the first lithium metal oxide.

6. In paragraph 1, A bimodal cathode active material, wherein the content of the coating element of the second coating layer is 0.1 to 3.0 wt% based on the total weight of the second lithium metal oxide.

7. In paragraph 1, A bimodal positive electrode active material, wherein the thickness of the first coating layer is 5 to 50 nm.

8. In paragraph 1, A bimodal positive electrode active material, wherein the thickness of the second coating layer is 5 to 50 nm.

9. In paragraph 1, A bimodal cathode active material, wherein the nickel content of the first lithium metal oxide and the second lithium metal oxide is 80 to 90 mol% based on the total mole number of metals excluding lithium.

10. In paragraph 1, The density of the pellet of the above bimodal positive electrode active material is 3.0 to 3.7 g / cm 3 In, bimodal positive electrode active material.

11. Step of preparing a first metal hydroxide and a second metal hydroxide; A step of forming a mixture comprising the first metal hydroxide or the second metal hydroxide and a lithium raw material; A step of calcining the mixture to form a first lithium metal oxide or the second lithium metal oxide; A step of forming a first coating layer containing a Zr-containing compound, a Nb-containing compound, or a combination thereof on the entire or part of the surface of the first lithium metal oxide; and A step of forming a second coating layer containing a Zr-containing compound, a Nb-containing compound, or a combination thereof on the entire or a portion of the surface of the second lithium metal oxide; The above Zr-containing compound comprises the following chemical formula 1, and the above Nb-containing compound comprises the following chemical formula 2. A method for manufacturing a bimodal cathode active material, wherein 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: [Chemical formula 1] Li x Zr y About z [Chemical formula 2] Li a No b O c The above chemical formula 1 is 0 <x≤3, 0<y≤2, 0<z≤4이고, 상기 화학식 2는 0<a≤3, 0<b≤2, 0<c≤4이다.

12. A cathode comprising a bimodal cathode active material according to any one of claims 1 to 10.

13. An all-solid-state battery comprising a positive electrode; a negative electrode; and a solid electrolyte layer disposed therebetween, wherein the positive electrode comprises a bimodal positive electrode active material according to any one of claims 1 to 10.