Lithium transition metal mixed oxide containing zirconium-containing oxide prepared by pyrolysis - Patent Application 20070122933

Abstract

1. A method for producing a lithium transition metal mixed oxide useful as a positive electrode active material in a lithium battery, the method comprising: i) dry-mixing a transition metal oxide and / or a transition metal hydroxide and / or a transition metal oxyhydroxide with pyrogenically produced zirconium dioxide and / or a pyrogenically produced zirconium-containing mixed oxide using an electrically driven mixing unit to obtain a coated precursor compound, the mixing unit having a specific power of 0.05-1.5 kW per kg of the coated precursor compound; ii) mixing the coated precursor compound with a lithium-containing compound; and iii) heating the mixture of the coated precursor compound and the lithium-containing compound at a temperature of 500-1400°C to obtain a lithium transition metal mixed oxide.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a lithium transition metal mixed oxide containing a pyrogenically produced zirconium-containing oxide, which is useful as a positive electrode active material in lithium batteries, the lithium transition metal mixed oxide obtained by this method, and the use of such a lithium transition metal mixed oxide. [Background technology]

[0002] Various energy storage technologies have attracted considerable attention in recent years and have been the subject of intensive research and development in both industry and academia. As energy storage technologies have spread to devices such as mobile phones, camcorders, and laptops, and even electric vehicles, there has been an increasing demand for high-energy-density batteries to power such devices. Lithium secondary batteries are one of the most important types of batteries currently in use.

[0003] Lithium secondary batteries typically consist of an anode made of a carbon material or a lithium metal alloy, a cathode made of lithium metal oxide, and an electrolyte, which is a lithium salt dissolved in an organic solvent. The separator in a lithium battery provides a pathway for lithium ions between the positive and negative electrodes during the charge and discharge process.

[0004] One common problem with cathode materials is their rapid aging and therefore loss of performance during cycling. This phenomenon is particularly true for nickel-manganese-cobalt mixed oxides (NMCs) with a high nickel content. The deactivation of cathode materials occurs through several electrochemical degradation mechanisms: surface alteration, e.g., Ni in a highly delithiated state and oxygen loss. 4+The reduction of NMC and the formation of a NiO-like phase due to the rearrangement of transition metals destabilize the crystalline structure. This phase transition is associated with the initial cracks observed on the cathode particle surface and subsequent particle collapse. Furthermore, the electrolyte decomposes at the reactive surface of the NMC, and the electrolyte decomposition products accumulate at the cathode material interface, leading to increased resistance. Furthermore, the conductive salt LiPF6 commonly used in liquid electrolytes reacts with traces of HO present in all commercial formulations to form HF. This highly reactive compound causes lattice distortion in the cathode material by dissolving transition metal ions from the cathode material surface into the electrolyte. All of these degradation mechanisms result in reduced capacity, performance, and cycle life.

[0005] It is known that coating lithium transition metal mixed oxide particles with some metal oxides can suppress undesired reactions between the electrolyte and electrode materials, thus improving the long-life stability of lithium batteries.

[0006] WO 2000 / 70694 (WO 00 / 70694) discloses transition metal mixed oxides coated with oxides or mixed oxides of Zr, Al, Zn, Y, Ce, Sn, Ca, Si, Sr, Mg, and Ti, which are obtained by suspending uncoated particles in an organic solvent, mixing the suspension with a solution of a hydrolyzable metal compound and a hydrolysis solution, filtering off the coated particles, and drying and calcining them.

[0007] US Patent Application Publication No. 2015 / 0340689 (US2015 / 0340689 A1) discloses a cathode active material (CAM) for lithium batteries, which comprises a transition metal oxide core and a coating layer comprising zirconium dioxide. Such coated CAMs are typically made of lithium transition metal oxides, such as LiNi 0.84 Co 0.15 Al 0.01The ZrO2-coated CAM is prepared by mixing ZrO2 with zirconium(IV) oxynitrate having an average particle size of less than 1 μm and calcining the mixture so obtained at 700° C. An alternative embodiment (Comparative Example 5) illustrates mixing a transition metal precursor with lithium(IV) dioxide having an average particle size of less than 1 μm, supplied by Aldrich, and calcining the resulting coated CAM at 700° C. Analysis of these materials by SEM microscopy indicates that the particle size of the ZrO2 particles present in the coating is approximately 400 nm (FIG. 2, Analysis Example 1).

[0008] US Patent Application Publication No. 2016 / 0204414 A1 describes a CAM for use in a battery containing a non-aqueous electrolyte, the non-aqueous electrolyte including a transition metal oxide core and a zirconium compound on the surface of the core. The examples show the use of zirconium dioxide with an average particle size of 1 μm for coating the CAM.

[0009] Chinese Patent Application Publication No. 105161710 (CN105161710 A) discloses a CAM comprising a transition metal mixed oxide core and a coating layer containing alumina or zirconia with a particle size of 5-100 nm. Thus, in Example 4, a CAM of formula LiNi with a particle size of 3 μm is used. 0.5 Co 0.2 Mn 0.3 Mg 0.02 The O2 precursor was mixed with ZrO2 with a particle size of 20 nm by ball milling, and the resulting coated CAM was calcined at 580 °C.

[0010] JP2013235666 A describes a CAM comprising a transition metal oxide core and a layer containing ZrO2 particles, most of which have a monoclinic structure. Thus, in Example 1, the average particle size D 50 LiNi with =10 μm 1 / 3 Co 1 / 3 Mn 1 / 3 O2 particles are divided into 2 groups with an average particle size D 50The mixture was mixed with ZrO2 particles having a diameter of 27 nm at a rotation speed of 4000 rpm and then calcined at 800°C.

[0011] The latter two documents refer to nanostructured ZrO2 particles with an average particle size of 20-30 nm, but do not provide further details, such as the manufacturing method or source of such particles. Presumably, the given average particle size refers to primary ZrO2 particles. Such small primary particles usually undergo strong and weak agglomeration to form much larger particles in the μm range.

[0012] The Journal of the Chinese Institute of Engineers, Vol. 28, No. 7, pp. 1139-1151 (2005) discloses that LiCoO powder can be coated with ZrO having an average particle size of 500-600 nm and produced by spray pyrolysis using the sol-gel or mechanothermal method. In the latter method, LiCoO powder is sonicated with a ZrO dispersion in ethanol for 30 minutes, followed by slow evaporation of the solvent at 50°C and calcination at 450°C for 10 hours.

[0013] The use of some mixed metal oxides containing zirconium in lithium batteries has also been reported.

[0014] US Patent Application Publication No. 2017 / 179544 (US2017179544 A) discloses the preparation of a lithium cathode material doped with a zirconium-based mixed metal oxide. Thus, in Example 1, metal salts are mixed and the mixture is sintered at 1200°C for 10 hours, followed by the formation of a lithium transition metal mixed oxide (Li). 10 / 75 Ni 18 / 75 Co 9 / 75 Mn 38 / 75 )O2 and subsequently heated at 900 °C for 20 hours to form the lithium cathode material. 0.07 O 12.0105 From this manufacturing procedure, large-sized sintered particles of Li7La3Zr2Al were obtained.0.07 O 12.0105 Clearly, only .gtoreq. ...

[0015] Instead of coating the lithium transition metal mixed oxide of the final electrode active material with a metal oxide layer, it is also possible to add a metal oxide coating or dopant to the corresponding precursor of the electrode active material, which is then heat-treated to obtain a doped lithium transition metal mixed oxide.

[0016] International Publication No. 2012 / 022618 (WO2012022618) discloses the preparation of particulate precursor compounds for producing aluminum-doped transition metal oxide powders useful as positive electrode active materials in lithium batteries, wherein each particle of the precursor compound comprises (a) a transition metal hydroxide or transition metal oxyhydroxide core and (b) a non-amorphous aluminum oxide coating layer covering the core.

[0017] U.S. Patent Application Publication No. 2013 / 0136985 (US20130136985 A1) describes the preparation of lithium composite oxides for use in lithium batteries, where the composite oxides are doped with lithium zirconate (LiZrO). Thus, in Examples 1, 15, and 16, lithium carbonate, cobalt oxide (CoO), lithium zirconate, and lithium phosphate are mixed together, and the resulting mixture is calcined in air at 900°C to produce a Zr-doped lithium composite oxide. SEM / EDX analysis of such doped composite oxides shows that Zr particles are present not only on the surface of the composite particles, but also within the particles.

[0018] This type of doping / coating may have the additional advantage of improved cycling performance when compared to surface coatings of the corresponding electrodes.

[0019] It is known to coat lithium battery cathode materials with metal oxides, such as Al2O3, TiO2, and ZrO2, to improve cycling performance. However, practical methods for improving the long-term life of batteries are often limited. Thus, in the case of zirconium dioxide, the use of commercially available nanosized ZrO2 particles often results in a non-uniform distribution and large, weakly agglomerated ZrO2 particles on the surface of the core cathode material, resulting in minimal or no improvement in cycling performance compared to uncoated cathode materials. [Prior art documents] [Patent documents]

[0020] [Patent Document 1] International Publication No. 2000 / 70694 [Patent Document 2] US Patent Application Publication No. 2015 / 0340689 [Patent Document 3] US Patent Application Publication No. 2016 / 0204414 [Patent Document 4] Chinese Patent Application Publication No. 105161710 [Patent Document 5] Japanese Patent Application Laid-Open No. 2013-235666 [Patent Document 6] US Patent Application Publication No. 2017 / 179544 [Patent Document 7] International Publication No. 2012 / 022618 [Patent Document 8] US Patent Application Publication No. 20130136985 [Non-patent literature]

[0021] [Non-Patent Document 1] Journal of the Chinese Institute of Engineers, Vol.28, No.7, pages 1139~1151 (2005) Summary of the Invention [Problem to be solved by the invention]

[0022] The problem addressed by the present invention is the development of cathode active materials, particularly of the high nickel NMC type, for use in lithium batteries. 、 The present invention provides an improved method for producing modified lithium transition metal mixed oxide cathode materials, which should provide greater cycling stability than unmodified materials. [Means for solving the problem]

[0023] During extensive experimentation, it was surprisingly found that pyrogenically produced zirconium dioxide or pyrogenically produced zirconium-containing mixed oxides can be suitably used for coating synthetic precursors of lithium transition metal mixed oxides, such as transition metal oxides, transition metal hydroxides or transition metal oxyhydroxides. The lithium transition metal mixed oxides produced from such precursors are characterized by a very homogeneous zirconium oxide particle distribution and a very small particle size of the zirconium oxide particles, which makes them very useful as cathode active materials in lithium batteries.

[0024] The present invention provides a method for preparing a lithium transition metal mixed oxide useful as a positive electrode active material in a lithium battery, the method comprising the steps of: i) dry-mixing a transition metal oxide and / or a transition metal hydroxide and / or a transition metal oxyhydroxide with pyrogenically produced zirconium dioxide and / or a pyrogenically produced zirconium-containing mixed oxide in a mixing unit to obtain a coated precursor compound, wherein the mixing unit has a specific power of 0.05-1.5 kW / kg of coated precursor compound; ii) mixing the coated precursor compound with a lithium-containing compound; iii) heating the mixture of the coated precursor compound and the lithium-containing compound at a temperature of 500 to 1400°C to obtain a lithium transition metal mixed oxide. The method includes:

[0025] The term "electric mixing unit" in relation to the present invention relates to any mixing device that operates by the supply of electrical energy.

[0026] Power is the rate at which electrical energy is transferred by an electrical circuit per unit time. In the context of the present invention, the term "specific power" relates to the power per kg of lithium transition metal mixed oxide supplied by the electrically driven mixing unit during the mixing process.

[0027] Dry mixing is understood to mean that no liquid is added or used during the mixing process, i.e., for example, substantially dry powders are mixed together. However, it is possible that traces of moisture or liquids other than water are present in the mixed ingredients, or that they contain water of crystallization. Preferably, the mixture of transition metal oxide and / or transition metal hydroxide and / or transition metal oxyhydroxide with pyrogenically produced zirconium dioxide and / or pyrogenically produced zirconium-containing mixed oxide contains less than 5% by weight, more preferably less than 3% by weight, more preferably less than 1% by weight of water and / or other liquids.

[0028] The dry mixing process of the present invention has several advantages over mixing processes requiring wet coating, such as coating using a dispersion containing metal oxides. Such wet coating processes necessarily require the use of a solvent, which must be evaporated after the coating process is completed. Therefore, the dry coating process of the present invention is simpler and more economical than the wet coating processes known from the prior art. On the other hand, it has surprisingly been found that the dry mixing process of the present invention also provides a better distribution of the zirconium-containing metal oxide particles on the surface of the lithium transition metal mixed oxide.

[0029] If the specific power used is less than 0.05 kW per kg of coated precursor compound, this will result in a non-homogeneous distribution of zirconium dioxide or zirconium-containing mixed oxides, which cannot be firmly bonded to the core material of the coated precursor compound.

[0030] Specific powers above 1.5 kW per kg of coated precursor compound result in poorer electrochemical properties and also run the risk of the coating becoming brittle and prone to cracking.

[0031] The nominal power of the mixing unit can vary over a wide range, for example, from 0.1 kW to 1000 kW. Thus, it is possible to use a laboratory-scale mixing unit with a nominal power of 0.1 to 5 kW, or a production-scale mixing unit with a nominal power of 10 to 1000 kW. The nominal power is the maximum absolute power listed on the mixing unit's nameplate.

[0032] The volume of the mixing unit can be adjusted in a wide range, e.g., from 0.1L to 2.5m 3 Thus, laboratory-scale mixing units with volumes between 0.1 and 10 L, or volumes between 0.1 and 2.5 m 3 It is possible to use a production scale mixing unit having

[0033] Preferably, in the process according to the invention, a compulsory mixer is used in the form of an intensive mixer with high-speed mixing equipment. It has been found that a mixing equipment speed of 5 to 30 m / s, more preferably 10 to 25 m / s, gives the best results. Commercially available mixing units well suited for the process according to the invention are, for example, Henschel mixers or Eirich mixers.

[0034] The mixing time is preferably 0.1 to 120 minutes, more preferably 0.2 to 60 minutes, and most preferably 0.5 to 10 minutes.

[0035] Following the mixing, the mixture can be subjected to a heat treatment. Such a treatment can improve the bonding of the coating to the lithium transition metal mixed oxide particles. However, this treatment is not necessary in the process according to the invention, because in this process the pyrogenically produced zirconium dioxide or zirconium-containing mixed oxide adheres sufficiently tightly to the lithium transition metal mixed oxide. Therefore, a preferred embodiment of the process according to the invention does not include any heat treatment after mixing.

[0036] The best results for the deposition of zirconium oxide on the coated precursor compounds were obtained with zirconium dioxide and mixed oxides containing zirconium, with a BET surface area of ​​5 m 2 / g~200m 2 / g, more preferably 10m 2 / g~150m 2 / g, and most preferably 15 to 100 m 2 / g. The BET surface area can be determined by nitrogen adsorption according to the Brunauer-Emmett-Teller procedure in accordance with DIN 9277:2014.

[0037] The zirconium dioxide and zirconium-containing mixed oxides used in the process according to the invention are prepared by the pyrogenic process, which means the pyrolytic process also known as the "fumed" process.

[0038] Such "pyrolytic" or "fumed" methods require the reaction of the corresponding metal precursors in flame hydrolysis or flame oxidation in an oxyhydrogen flame to form metal oxides. This reaction first forms highly dispersed, approximately spherical metal oxide primary particles, which coalesce to form agglomerates during the further course of the reaction. The agglomerates can then aggregate into weaker agglomerates. In contrast to weaker agglomerates, which can generally be relatively easily separated into said agglomerates by the introduction of energy, the agglomerates are only further broken down, if at all, by the strong introduction of energy. The metal oxide powders can be partially broken down by suitable grinding and converted into particles in the nanometer (nm) range, which are advantageous for the present invention.

[0039] The production of pyrogenic zirconium dioxide is further described in EP 717008 A and WO 2009 / 053232 A1.

[0040] The production of some pyrogenic mixed oxides containing zirconium is further described in International Application No. 2015 / 173114 (WO2015173114 A1).

[0041] Pyrolytically produced zirconium dioxide powder and other mixed metal oxides containing zirconium, particularly those produced by flame hydrolysis, can be produced starting from zirconium halides, preferably zirconium chloride, as the Zr precursor. ZrCl4 and, if appropriate, other metal precursors can be evaporated, and the resulting vapors, alone or together with a carrier gas, such as nitrogen, are mixed in a mixing unit with other gases, i.e., air, oxygen, nitrogen, and hydrogen, in a burner. The gases react with each other in a flame in a closed combustion chamber to produce zirconium dioxide (or mixed zirconium oxides) and waste gases. The hot waste gas and metal oxides are then cooled in a heat exchange unit, the waste gas is separated from the metal oxides, and halide residues adhering to the resulting metal oxides are removed by heat treatment with humidified air.

[0042] A suitable flame spray pyrolysis (FSP) process for producing zirconium dioxide or mixed metal oxides containing zirconium comprises the following steps: 1) atomizing a solution containing a zirconium precursor, for example with air or an inert gas, preferably using a multi-substance nozzle; and 2) mixing a combustion gas, preferably hydrogen and / or methane, with air; and 3) burning the mixture in a flame into a reaction chamber surrounded by a casing; 4) cooling the hot gas and solid product and then removing the solid product from the gas. may include:

[0043] The preferred Zr metal precursors used to produce zirconium dioxide and zirconium-containing mixed oxides by flame spray pyrolysis are zirconium carboxylates, particularly zirconium carboxylates of aliphatic carboxylic acids having 6 to 9 carbon atoms, such as zirconium 2-ethylhexanoate.

[0044] The other metal precursors required to prepare the zirconium mixed metal oxide may be either inorganic, such as nitrates, chlorides, or organic compounds, such as carboxylates.

[0045] The metal oxide precursors used can be dissolved in water or an organic solvent and then atomized. Suitable organic solvents include methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, 2-propanone, 2-butanone, diethyl ether, tert-butyl methyl ether, tetrahydrofuran, C1-C8 carboxylic acids, ethyl acetate, toluene, petroleum, and mixtures thereof.

[0046] The pyrogenically produced zirconium dioxide and pyrogenically produced zirconium-containing mixed oxides used in the process according to the invention are therefore in the form of strongly agglomerated primary particles, preferably having a number-average primary particle diameter, as determined by transmission electron microscopy (TEM), of 5 to 100 nm, more preferably 10 to 90 nm, even more preferably 20 to 80 nm, which can be determined by calculating the average size of at least 500 particles analysed by TEM.

[0047] The average diameter of the strong aggregates of pyrogenically produced zirconium dioxide and pyrogenically produced zirconium-containing mixed oxides is typically about 10-1000 nm, and the average diameter of the weak aggregates is typically 1-2 μm. These average values ​​can be determined in a suitable dispersion, e.g., an aqueous dispersion, by static light scattering (SLS). The weak aggregates and partially strong aggregates can be broken down, e.g., by grinding or sonicating the particles, to yield particles with smaller particle sizes.

[0048] Preferably, the average particle size d of zirconium dioxide and / or mixed oxides containing zirconium 50 is 10 to 150 nm, more preferably 20 to 130 nm, and even more preferably 30 to 120 nm, as determined by static light scattering (SLS) after ultrasonic treatment of a mixture consisting of 5 mass % of the particles and 95 mass % of a 0.5 g / L aqueous sodium pyrophosphate solution at 25°C for 60 seconds.

[0049] Therefore, the pyrogenically produced zirconium dioxide and pyrogenically produced zirconium-containing mixed oxides used in the method of the present invention are preferably characterized by high dispersibility, i.e., the ability to form relatively small particles under mild ultrasonic treatment. Dispersion under such mild conditions is believed to correlate with the conditions during the dry coating process. This means that weak aggregates of zirconium oxide are broken down in the mixing step of the present invention in the same way as under ultrasonic treatment, allowing the formation of a homogeneous coating of transition metal oxide.

[0050] The span (d 90 -d 10 ) / d 50 is preferably 0.4 to 1.2, more preferably 0.5 to 1.1, and even more preferably 0.6 to 1.0, as determined by static light scattering (SLS) after subjecting a mixture of 5 mass % of the particles and 95 mass % of a 0.5 g / L aqueous sodium pyrophosphate solution to ultrasonic treatment at 25°C for 60 seconds.

[0051] Thus, the pyrogenically produced zirconium dioxide and pyrogenically produced zirconium-containing mixed oxides used in the process of the present invention are preferably characterized by a relatively narrow particle size distribution, which helps to achieve a high quality zirconium oxide coating on the surface of the transition metal oxide.

[0052] d of d value 10 , d 50 and d 90 is commonly used to evaluate the cumulative particle size distribution of a given sample. For example, d 10 The diameter is d 10 is the diameter of the smaller particles, and d 50 is 50% of the sample volume 50 is the diameter of the smaller particles. 50 is also known as the "volume median diameter" because it divides the sample equally by volume, and d 90 is the volume of the sample that is 90% of the 90 diameter consisting of particles smaller than

[0053] Zirconium dioxide and zirconium-containing mixed oxides are preferably hydrophilic in nature, i.e., they are not further treated with hydrophobic agents, such as silanes, after their synthesis by a pyrolysis process. The particles thus produced typically have a purity of at least 96% by weight, preferably at least 98% by weight, and more preferably at least 99% by weight. The zirconium-containing metal oxide may contain a hafnium compound in the form of hafnium dioxide. The proportion of hafnium dioxide may be 1 to 4% by weight relative to ZrO2. The zirconium dioxide and zirconium-containing mixed oxides used in the method of the present invention preferably contain the elements Cd, Ce, Fe, Na, Nb, P, Ti, and Zn in proportions of <10 ppm, and the elements Ba, Bi, Cr, K, Mn, and Sb in proportions of <5 ppm, with the sum of all the proportions of these elements being <100 ppm. The chloride proportion is preferably less than 0.5% by weight, more preferably 0.01 to 0.3% by weight, relative to the mass of the metal oxide powder. The proportion of carbon is preferably less than 0.2% by mass, more preferably 0.005% to 0.2% by mass, and even more preferably 0.01% to 0.1% by mass, relative to the mass of the metal oxide powder.

[0054] The zirconium-containing mixed oxides may further comprise lithium, and optionally at least one of lanthanum and / or aluminum. The following mixed metal oxides containing zirconium are particularly preferred: LiZrO3, and those of the general formula Li x La3Zr2M y O 8.5+0.5x+z [Wherein 6.5≦x≦8, preferably 7.0≦x≦7.5, 0≦y≦0.5, preferably 0≦y≦0.2, z=2y for M=Hf, Ga, Ge, Nb, Si, Sn, Sr, Ta and Ti; z=1.5y for M=Al, Sc, V and Y; z=y for M=Ba, Ca, Mg and Zn] mixed oxides of, most preferably Li7La3Zr2O 12 .

[0055] The term "transition metal" in relation to the present invention includes the following elements: Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Ta, W, Re, Os, Ir, Pt, Au. Preferably, the transition metal is selected from the group consisting of nickel, manganese, cobalt and mixtures thereof.

[0056] The transition metal oxides used in the process of the present invention are preferably compounds of the general formula MO, MO, MO or MO, where M is at least one transition metal, preferably one selected from the group consisting of nickel, manganese and cobalt, said transition metal oxides being optionally doped with at least one compound selected from aluminum oxide, aluminum hydroxide, aluminum oxyhydroxide, zirconium oxide, zirconium hydroxide, zirconium oxyhydroxide and mixtures thereof.

[0057] The transition metal hydroxide used in the process of the present invention is preferably a compound of the general formula M(OH)2, where M is at least one transition metal, preferably one selected from the group consisting of nickel, manganese, cobalt, and said transition metal hydroxide is optionally doped with at least one compound selected from aluminum oxide, aluminum hydroxide, aluminum oxyhydroxide, zirconium oxide, zirconium hydroxide, zirconium oxyhydroxide and mixtures thereof.

[0058] The transition metal oxyhydroxide is a compound of the general formula MOOH, where M is at least one transition metal, preferably one selected from the group consisting of nickel, manganese, and cobalt, and the transition metal oxyhydroxide is optionally doped with at least one compound selected from aluminum oxide, aluminum hydroxide, aluminum oxyhydroxide, zirconium oxide, zirconium hydroxide, zirconium oxyhydroxide, and mixtures thereof.

[0059] The lithium transition metal mixed oxides preferably produced in the process according to the invention are selected from the group consisting of lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel manganese oxide or mixtures thereof.

[0060] The lithium transition metal mixed oxide preferably has the general formula LiMO2, where M is at least one transition metal selected from nickel, cobalt, manganese, more preferably M=Co or Ni. x Mn y Co z where 0.3≦x≦0.9, 0≦y≦0.45, and 0≦z≦0.4.

[0061] The lithium transition metal mixed oxides of the general formula LiMO2 can be further doped with other metal oxides, in particular with aluminum oxide and / or zirconium oxide.

[0062] The lithium transition metal mixed oxide preferably has a number average particle size of 2 to 20 μm, which can be determined by laser diffraction particle size analysis in accordance with ISO 13320:2009.

[0063] The proportion of zirconium dioxide and / or mixed oxides containing zirconium relative to the total mass of the mixture used of transition metal oxides and / or transition metal hydroxides and / or transition metal oxyhydroxides with zirconium dioxide and / or mixed oxides containing zirconium is 0.05% by mass to 5% by mass.

[0064] If the proportion of zirconium dioxide and / or mixed oxides containing zirconium is less than 0.05% by weight, the beneficial effect of the coating is usually still not observed. If it is more than 5% by weight, the beneficial effect of the additional quality of the zirconium coating above 5% by weight is usually not observed.

[0065] The coated precursor compound preferably has a coating layer thickness of 10 to 200 nm, as determined by TEM analysis.

[0066] The lithium-containing compound used in step ii) of the process according to the invention is preferably selected from the group consisting of lithium oxide, lithium hydroxide, lithium alkoxide, lithium carbonate or mixtures thereof.

[0067] In step iii) of the method of the present invention, the mixture of the coated precursor compound and the lithium-containing compound is preferably heated at a temperature of from 500°C to 1350°C, more preferably from 550°C to 1300°C, even more preferably from 600°C to 1250°C, and even more preferably from 650°C to 1200°C to obtain a lithium transition metal mixed oxide.

[0068] The present invention is further useful as a cathode active material in a lithium battery, 50 The present invention provides a lithium transition metal mixed oxide containing pyrogenically produced zirconium dioxide and / or a pyrogenically produced zirconium-containing mixed oxide, the number average particle size d of which is 10 nm to 150 nm, preferably 20 nm to 130 nm, and more preferably 30 nm to 120 nm. 50 is the average particle size d for the pyrogenically produced zirconium dioxide and / or pyrogenically produced zirconium-containing mixed oxides used in the process of the present invention, as determined by transmission electron microscopy (TEM) analysis and by static light scattering (SLS) after ultrasonic treatment of a mixture of 5% by weight of said particles with 95% by weight of 0.5 g / L aqueous sodium pyrophosphate at 25° C. for 60 seconds. 50 corresponds to.

[0069] The lithium transition metal mixed oxides of the invention are preferably obtainable by the process according to the invention.

[0070] The present invention further provides a coated precursor compound for a lithium transition metal mixed oxide, comprising a number average particle size d 50 The precursor compound contains pyrogenically produced zirconium dioxide and / or pyrogenically produced zirconium-containing mixed oxides having a particle size of 10 nm to 150 nm.

[0071] The further preferred features of the lithium transition metal mixed oxides, the further preferred features of the coated precursor compounds, the further preferred features of pyrogenically produced zirconium dioxide and / or pyrogenically produced zirconium-containing mixed oxides, and the further preferred features of the transition metal oxides, hydroxides and oxyhydroxides described above for the preferred embodiments of the method according to the invention are also preferred features of the corresponding materials for the lithium transition metal mixed oxides, coated precursor compounds, active cathode materials and lithium batteries according to the invention, independently of their production method.

[0072] The present invention further provides a positive electrode active material for a lithium battery comprising a lithium transition metal mixed oxide according to the present invention.

[0073] The active positive electrode, cathode, of a lithium battery typically comprises a current collector and a layer of cathode active material formed on the current collector.

[0074] The current collector may be aluminum foil, copper foil, nickel foil, stainless steel foil, titanium foil, a polymer substrate coated with a conductive metal, or a mixture thereof.

[0075] The positive electrode active material can include materials capable of reversibly inserting and extracting lithium ions, as is well known in the art. Such cathode active materials can include transition metal oxides, such as mixed oxides containing Ni, Co, Mn, V, or other transition metals and, optionally, lithium. Lithium transition metal mixed oxides containing nickel, manganese, and cobalt (NMC) are particularly preferred.

[0076] The present invention further provides a lithium battery comprising the lithium transition metal mixed oxide of the present invention.

[0077] In addition to the cathode, the lithium battery of the present invention may contain an anode, optionally a separator, and an electrolyte containing a lithium salt or lithium compound.

[0078] The anode of a lithium battery can include any suitable material commonly used in lithium secondary batteries that can reversibly insert and extract lithium ions. Typical examples include carbonaceous materials, including crystalline carbon, such as natural or artificial graphite in the form of platelet, flake, spherical, or fibrous graphite, amorphous carbon, such as soft carbon, hard carbon, mesophase pitch carbide, burned coke, etc., or mixtures thereof. Additionally, lithium metal or conversion materials (e.g., Si or Sn) can be used as the anode active material.

[0079] The electrolyte in a lithium battery can be in liquid, gel or solid form.

[0080] The liquid electrolyte of the lithium battery can include any organic solvent commonly used in lithium batteries, such as anhydrous ethylene carbonate (EC), dimethyl carbonate (DMC), propylene carbonate, ethyl methyl carbonate, diethyl carbonate, γ-butyrolactone, dimethoxyethane, fluoroethylene carbonate, vinylethylene carbonate, or mixtures thereof.

[0081] The gel electrolyte comprises a gelling polymer.

[0082] The solid electrolyte of a lithium battery may include an oxide, such as a lithium metal oxide, a sulfide, a phosphate, or a solid polymer.

[0083] The electrolyte of a lithium battery typically contains a lithium salt, examples of which include lithium hexafluorophosphate (LiPF), lithium bis(2-(trifluoromethylsulfonyl)imide (LiTFSI), lithium perchlorate (LiClO), lithium tetrafluoroborate (LiBF), LiSiF, lithium triflate, LiN(SOCFCF) and mixtures thereof.

[0084] The present invention further relates to the use of the lithium transition metal mixed oxide according to the invention as a positive active material in a lithium battery. [Brief explanation of the drawings]

[0085] [Figure 1] FIG. 1 shows particle size distribution of fumed ZrO2. [Figure 2] FIG. 1 shows the particle size distribution of "nano ZrO2." [Figure 3] FIG. 1 shows SEM-EDX mapping of Zr on ZrO2-coated NiO.8MnO.1CoO.1(OH)2 (Example 1) produced using fumed ZrO2. [Figure 4] FIG. 4 shows the analysis results of Ni0.8Mn0.1Co0.1(OH)2 coated with "nano ZrO2" (Comparative Example 1). [Figure 5] FIG. 1 shows the cycling performance of NMC 811 doped with fumed ZrO2, NMC 811 doped with commercial "nano-ZrO2", and undoped NMC 811 as a reference. [Example]

[0086] Starting materials Specific surface area (BET) 40~60m 2 Fumed ZrO2 having a ZnO content of 1000 0.1% by mass was prepared by flame spray pyrolysis according to Example 1 of WO2009 / 053232 A1).

[0087] BET surface area ≧35m 2Commercially available “nanoZrO2” powder (particle size 20–30 nm) with ZnO / g was supplied by ChemPUR Feinchemikalien und Forschungsbedarf GmbH.

[0088] BET surface area 0.35~0.65m 2 / g, median particle size d 50 Commercially available lithium nickel manganese cobalt mixed hydroxide powder with a diameter of 11.0±2 μm (determined by static laser scattering method) 0.8 Mn 0.1 Co 0.1 (OH)2 was supplied by Linyi Gelon LIB Co.

[0089] Particle size distribution of different ZrO2 types Samples of fumed ZrO2 or commercial "nano-ZrO2" powder (5 wt%) were dispersed in a solution of sodium pyrophosphate (0.5 g / L) in distilled water and treated in an external ultrasonic bath (160 W) at 25 °C for 1 min.

[0090] Figure 1 shows the particle size distribution of fumed ZrO2, and Figure 2 shows the particle size distribution of "nano-ZrO2" (analyzed by static laser diffraction (SLS) using a laser diffraction particle size analyzer (HORIBA LA-950)). For fumed ZrO2, a unimodal and very narrow particle size distribution (d 10 =0.06014μm, d 50 =0.07751 μm, d 90 = 0.11406 μm, span = (d 90 -d 10 ) / d 50 = 0.7) was detected, whereas a broad bimodal distribution was detected for ChemPUR's "nanoZrO2", indicating large undispersed particles (d 10 =0.10769μm, d 50 = 3.16297 μm, d 90 = 5.80804 μm, span = (d 90 -d 10 ) / d 50 =1.8).

[0091] Example 1 Ni 0.8 Mn 0.1 Co 0.1 (OH)2 powder (217.8 g) was first mixed with 2.2 g (1.0 wt%) of fumed ZrO2 powder in a laboratory intensive mixer (Somakon mixer MP-GL equipped with a 0.5 L mixing unit) at 500 rpm for 1 min (specific power: 350 W / 1 kg Ni 0.8 Mn 0.1 Co 0.1 (OH)2) and the two powders were mixed homogeneously. Then, the mixing intensity was increased to 2000 rpm (specific power: 800 W / 1 kg of Ni 0.8 Mn 0.1 Co 0.1 (OH)2, tip speed of the mixing tool in the mixing unit: 10 m / s), and the mixing was continued for 5 minutes to obtain Ni by ZrO2. 0.8 Mn 0.1 Co 0.1 A dry coating of the (OH)2 particles is achieved.

[0092] Comparative Example 1 The procedure of Example 1 was exactly repeated except that "nano-ZrO2" powder was used instead of fumed ZrO2.

[0093] SEM-EDX analysis of ZrO2-coated transition metal mixed hydroxides Figure 3 shows a ZrO2-coated Ni substrate fabricated using fumed ZrO2. 0.8 Mn 0.1 Co 0.1 Figure 4 shows the SEM-EDX mapping (white) of Zr on (OH)2 (example 1), and Figure 5 shows the SEM-EDX mapping (white) of Ni coated with "nano-ZrO2". 0.8 Mn 0.1 Co 0.1 The analysis results of (OH)2 (Comparative Example 1) are shown. The axes in Figures 3 and 4 are: x-axis = particle diameter, left y-axis = volume [%], right y-axis = cumulative volume [%]. Ni dry-coated with fumed ZrO2 0.8 Mn 0.1 Co 0.1 (OH)2 is all Ni 0.8 Mn 0.1Co 0.1 The (OH)2 particles are completely and homogeneously coated with ZrO2. No larger ZrO2 weak aggregates are detected, indicating good dispersion of the nanostructured fumed ZrO2. Furthermore, Ni 0.8 Mn 0.1 Co 0.1 No free, unattached ZrO2 particles were found near the (OH)2 particles, and the coating and the substrate (Ni 0.8 Mn 0.1 Co 0.1 In contrast, Figure 5 shows that only the fine ZrO2 particles of "nano-ZrO2" are strongly attached to Ni 0.8 Mn 0.1 Co 0.1 The larger ZrO2 particles are not dispersed and therefore not attached, whereas the Ni 0.8 Mn 0.1 Co 0.1 (OH)2 particles. As a result, Ni 0.8 Mn 0.1 Co 0.1 The (OH)2 particles are not completely covered by zirconium oxide.

[0094] Preparation of lithium transition metal mixed oxides To produce lithium transition metal mixed oxides (NMCs), undoped LiNi 0.8 Mn 0.1 Co 0.1 (OH)2 was mixed with Li2CO3 in a molar ratio of 1:0.54. The mixture was preheated at 600 °C for 7 h and further annealed at 870 °C for 15 h to obtain lithium transition metal mixed oxides.

[0095] Undoped LiNi 0.8 Mn 0.1 Co 0.1 "Nano-ZrO2" doped and "fumed ZrO2" doped LiNi instead of (OH)2 0.8 Mn 0.1 Co 0.1 The above procedure was repeated exactly except that (OH)2 powder was used.

[0096] Electrode manufacturing Electrodes for electrochemical measurements were prepared by blending 90% by weight of NMC with 5% by weight of polyvinylidene fluoride binder (PVDF 5130, manufactured by Solef) and 5% by weight of conductive carbon black (Super PLi, manufactured by Timcal) in an inert gas atmosphere. N-methyl-2-pyrrolidone (NMP) was used as the solvent. The slurry was cast onto aluminum foil and dried at 120°C for 20 minutes on a heated plate under air. The electrode sheet was then dried in a vacuum oven at 120°C for 2 hours. Circular electrodes with a diameter of 12 mm were punched out from the larger pieces, flattened between two rollers at a pressure of 90 psi, and dried again in a vacuum oven at 120°C for 12 hours to remove residual water and NMP.

[0097] Lithium Battery Assembly Lithium battery cells for cycling tests were assembled as CR2032-type coin cells (MTI Corporation) in an argon-filled glovebox (Glovebox Systemtechnik GmbH). Lithium metal (Rockwood Lithium GmbH) was used as the anode material. Celgard 2500 was used as the separator. 25 μL of a 1 M solution of LiPF6 in ethylene carbonate and ethyl methyl carbonate (50:50 wt / wt; Sigma-Aldrich) was used as the electrolyte. The cells were clamped with a crimper (MTI).

[0098] Galvanostatic Cycling Test The galvanostatic cycling performance of the assembled lithium-ion battery was measured at 25 °C using a MACCOR battery cycler with a cutoff voltage of 3.0 to 4.3 V. The cells were cycled at 0.5 C / 0.5 C (0.5 C rate is a current density of 0.7 mAh / cm) to test the long-term stability. 2 (corresponding to).

[0099] For the calculation of capacity and specific current, only the mass of the active material was considered.

[0100] The cycling performance of NMC 811 doped with fumed ZrO2 (Evonik) was compared with NMC 811 doped with commercial "nano-ZrO2" and with undoped (pristine) NMC 811 as a reference. The results (Figure 5) clearly show that fumed ZrO2 doping significantly improves the stability and cycle life of the NMC. Cells using "nano-ZrO2" doped NMC show significantly worse cycling performance.

Claims

1. 1. A method for preparing a lithium transition metal mixed oxide useful as a positive electrode active material in a lithium battery, comprising the steps of: i) dry-mixing a transition metal oxide and / or transition metal hydroxide and / or transition metal oxyhydroxide with pyrogenically produced zirconium dioxide and / or pyrogenically produced zirconium-containing mixed oxides using an electrically driven mixing unit to obtain a coated precursor compound, wherein the mixing unit has a specific power of 0.05-1.5 kW / kg of the coated precursor compound; ii) mixing the coated precursor compound with a lithium-containing compound; iii) heating the mixture of the coated precursor compound and the lithium-containing compound at a temperature of 500-1400° C. to obtain a lithium transition metal mixed oxide. The method comprising:

2. 2. The method of claim 1, wherein the transition metal is selected from the group consisting of nickel, manganese, cobalt, and mixtures thereof.

3. The zirconium dioxide and / or zirconium-containing mixed oxide used to prepare said lithium transition metal mixed oxide has a BET surface area of ​​5 to 200 m 2 3. The method according to claim 1 or 2, characterized in that:

4. 4. The method according to claim 1, wherein the zirconium dioxide and zirconium-containing mixed oxide used to prepare the lithium transition metal mixed oxide are in the form of strongly agglomerated primary particles having a number average diameter of the primary particles of 5 to 100 nm, as determined by transmission electron microscopy (TEM).

5. The average particle size d of the particles of zirconium dioxide and / or zirconium-containing mixed oxides used to prepare the lithium transition metal mixed oxide 50 5. The method according to claim 1, wherein the particle diameter is 10 to 150 nm as determined by static light scattering (SLS) after ultrasonic treatment of a mixture of 5% by weight of the particles and 95% by weight of a 0.5 g / L aqueous solution of sodium pyrophosphate for 60 seconds at 25°C.

6. The span (d 90 -d 10 ) / d 50 6. The method according to claim 1, wherein the σ is 0.4 to 1.2 as determined by static light scattering (SLS) after ultrasonic treatment of a mixture of 5% by weight of the particles and 95% by weight of a 0.5 g / L aqueous solution of sodium pyrophosphate for 60 seconds at 25°C.

7. 7. The method according to claim 1, wherein the zirconium-containing mixed oxide further comprises lithium.

8. The method of claim 7, wherein the zirconium-containing mixed oxide further comprises lithium, and at least one of lanthanum and / or aluminum.

9. The transition metal hydroxide has the general formula M(OH) 2 9. The method according to claim 1, wherein M is at least one transition metal selected from the group consisting of nickel, manganese, and cobalt.

10. The method of claim 9, wherein the transition metal hydroxide is doped with at least one compound selected from aluminum oxide, aluminum hydroxide, aluminum oxyhydroxide, zirconium oxide, zirconium hydroxide, zirconium oxyhydroxide and mixtures thereof.

11. 11. The method of any one of claims 1 to 10, characterized in that the transition metal oxyhydroxide is a compound of the general formula MOOH, where M is at least one transition metal selected from the group consisting of nickel, manganese, and cobalt.

12. The method of claim 11, wherein the transition metal oxyhydroxide is doped with at least one compound selected from aluminum oxide, aluminum hydroxide, aluminum oxyhydroxide, zirconium oxide, zirconium hydroxide, zirconium oxyhydroxide and mixtures thereof.

13. 13. The method according to claim 1, wherein the proportion of zirconium dioxide and / or zirconium-containing mixed oxides is 0.05% by weight to 5% by weight based on the total weight of the mixture used of transition metal oxides and / or transition metal hydroxides and / or transition metal oxyhydroxides with zirconium dioxide and / or zirconium-containing mixed oxides.

14. 14. The method according to any one of claims 1 to 13, characterized in that the lithium transition metal mixed oxide is selected from the group consisting of lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel manganese oxide or mixtures thereof.

15. 15. The method of any one of claims 1 to 14, characterized in that the lithium-containing compound is selected from the group consisting of lithium oxide, lithium hydroxide, lithium alkoxide, lithium carbonate, or mixtures thereof.

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