Positive active material particles encapsulated in thermolytic

Abstract

Process for producing a coated mixed lithium transition metal oxide, wherein the mixed lithium transition metal oxide and nanostructured, preferably surface-modified magnesium oxide produced by pyrolysis are subjected to dry mixing by means of a mixing unit having a specific electrical power per kg of mixed lithium transition metal oxide of 0.05-1.5 kW. A coated mixed lithium transition metal oxide obtainable by this method, a positive electrode for a lithium ion battery, and a lithium ion battery comprising the mixed coated mixed lithium transition metal oxide.

Description

Technical Field

[0001] The present invention relates to a method for producing encapsulated positive electrode active material particles, wherein lithium mixed oxide particles and fumed nanostructured magnesium oxide are dry mixed under shear conditions. The present invention further relates to fumed magnesium oxide-coated positive electrode materials, as well as battery cells containing these encapsulated lithium mixed oxide particles and their use. Background Art

[0002] Recently, various energy storage technologies have attracted much public attention and have been the subject of intensive research and development in industry and academia. As energy storage technology expands to devices such as cellular phones, camcorders, and laptop computers, and further to electric vehicles, there is an increasing demand for high energy density batteries used as power sources for such devices. Secondary lithium-ion batteries are one of the most important types of batteries in use today.

[0003] The secondary lithium-ion battery is generally composed of a negative electrode (anode) made of a carbon material or a lithium metal alloy, a positive electrode (cathode) made of a lithium metal oxide, and an electrolyte (in which a lithium salt is dissolved in an organic solvent). The separator of the lithium-ion battery provides a lithium ion channel between the positive and negative electrodes during the charging and discharging process.

[0004] One of the common problems of cathode materials is their rapid aging and thus performance loss during cycling. This phenomenon is particularly relevant to nickel-manganese-cobalt mixed oxides (NMC) with high nickel content. During cycling, cathode materials are subject to several electrochemical degradation mechanisms. Deactivation of cathode materials occurs through several electrochemical degradation mechanisms. Surface changes, such as the degradation of Ni in a highly delithiated state, are a result of the degradation of the surface of the cathode material. 4+ The reduction and oxygen loss of NMC and the rearrangement of transition metals form a NiO-like phase, which makes the crystal structure unstable. These phase changes are associated with the initial cracks that appear at the surface of the positive electrode particles and the subsequent particle disintegration. In addition, the electrolyte decomposes at the reactive surface of NMC, and the electrolyte decomposition products are deposited at the interface of the positive electrode material, which leads to increased resistance. In addition, LiPF6, a commonly used conductive salt in liquid electrolytes, reacts with trace amounts of H2O present in all commercial formulations to form HF. This highly reactive compound causes lattice distortion in the positive electrode material by dissolving transition metal ions from the surface of the positive electrode material into the electrolyte. All of these degradation mechanisms lead to reduced capacity, reduced performance, and shortened cycle life.

[0005] It is known that coating mixed lithium transition metal oxide particles with some metal oxides can inhibit unwanted reactions of electrolyte with electrode materials and thus improve the long-term stability of lithium-ion batteries.

[0006] International patent application number WO 00 / 70694 describes mixed transition metal oxide particles coated with oxides or mixed oxides of Zr, Al, Zn, Y, Ce, Sn, Ca, Si, Sr, Mg and Ti. They are obtained by suspending the uncoated particles in an organic solvent, mixing the suspension with a solution of a hydrolyzable metal compound and a hydrolysis solution, and then filtering, drying and calcining the coated particles.

[0007] It is known that coating the positive electrode material of lithium-ion batteries with metal oxides, such as Al2O3, TiO2, ZrO2 and MgO, can improve the cycle performance of the battery.

[0008] Chinese patent document CN 112194196 describes a composite coating agent prepared from at least one of a metal and / or non-metal oxide and an ammonium salt. The metal oxide is said to be at least one of MgO, Al2O3, La2O3, ZrO2 and Nb2O5. The non-metal oxide is SiO2. The ammonium salt is at least one of NH4F, (NH4)3AlF6, NH4H2PO4 and (NH4)2WO4. The composite coating agent is prepared by at least one method of ball milling, air flow crushing, calcination, wet mixing and spray drying. The composite coating agent is said to form a uniform coating layer on the surface of the single crystal material and can improve the cycle performance and safety of the material.

[0009] Chinese patent document CN110165205A describes a positive electrode material comprising a lithium metal oxide matrix, a first coating layer (metal N oxide, N is Al, Zr, Mg, Ti, Co, Y, Ba, Cd) and a second coating layer (N' oxide, N' is B, Sn, S, P). The method described includes adding metal N oxide nanoparticles to deionized water, stirring, ultrasonic dispersion, adding the positive electrode material matrix, stirring, filtering, drying at 80-150°C, mixing with N' element (or N' compound), calcining at 150-500°C, and cooling to obtain the final product.

[0010] Chinese patent document CN108172810A describes a method for preparing a lithium nickel manganese oxide positive electrode material coated with nanoparticles. The patent describes the preparation of composite MgO nanoparticles, adding ethyl silicate to oxalic acid, adding composite MgO nanoparticles and Dy-doped Li Ni Mn oxide active material, performing ultrasonic dispersion, injecting into a stainless steel mold, standing and drying to obtain the product.

[0011] The following article provides an example of using MgO in a cathode material. Zhang et al., “Mesoporous carbon material as cathode for high performance lithium-ion capacitor” Chinese Chemical Letters (2018), 29 (4) 620-623 CODEN CCLEE7; ISSN: 1001-8417. Magnesium citrate is used as a precursor for C mesopores and nano-sized MgO particles are used as a template provided by magnesium citrate.

[0012] Xiang et al., “Flexible 3D multifunctional MgO-decorated carbonfoam@CNTs hybrid as self-supported cathode for high performance lithium-sulfur batteries” in Advanced Functional Materials (2017), 27(37), n / a CODEN:AFMDC6; ISSN:1616-301X, describes the use of ultrafine MgO nanoparticles in lithium-sulfur batteries.

[0013] “Improvement of cycling performance of lithium-sulfurbatteries by using magnesium oxide as a functional additive for trapping lithium polysulfide” in ACS Applied materials & interfaces (2016), 8 (6), 4000-4006 CODEN: AAMICK; ISSN: 1994-8244 describes the use of MgO nanoparticles for trapping lithium polysulfide in lithium-sulfur batteries.

[0014] CM et al., “Surface modification of positive electrode materials for lithium-ion batteries” in Thin Solid Films (2014), 572, 200-207 CODEN: THSFAP; ISSN: 0040-6090, describes various types of surface treatments of positive electrode material particles for lithium-ion batteries.

[0015] “Effects of MgO coating on the structural and electrochemical characteristics of LiCoO2 as cathode materials for lithium-Ion battery” in Chemistry of materials 2014, 26(8), 2537-2543 CODEN: CMATEX; ISSN: 0897-4756 describes the annealing of MgO-coated LiCoO2 at various temperatures of 750-810°C to find the optimal annealing temperature.

[0016] CN 111 354 936 discloses a positive electrode material based on lithium oxide coated with nano-sized magnesium oxide.

[0017] In the article “Performance improvement of surface-modified LiCoO2 Cathode Materials: An infrared absorption and X-Ray Photoelectron Spectroscopic Investigation” by Wang Zhaoxiang et al., published in Journal of the Electrochemical Society, vol. 150, no. 2, (2003), pages A199-A208, ISSN: 0013-4651, a comparative study was conducted to understand the improvement in the electrochemical performance of commercially available LiCoO2 cathode materials modified with nanosized magnesium oxide.

[0018] Although nano-sized MgO particles have been used as additives in lithium-ion batteries, their effectiveness in improving battery cycling stability is limited by poor dispersibility. Practical ways to extend battery life are generally limited. Therefore, in the case of magnesium oxide, the use of commercially available nano-sized MgO particles generally results in an uneven distribution and large agglomerated MgO particles on the surface of the core cathode material, and therefore, little or no improvement in cycling performance is observed when compared to uncoated cathode materials.

[0019] The problem solved by the present invention is to provide a modified mixed lithium transition metal oxide for use as a cathode material in lithium-ion batteries, especially for high-nickel NMC (nickel, magnesium, cobalt) type. Such modified cathode materials provide a cycle stability that is higher than the cycle stability of unmodified materials.

[0020] In the course of comprehensive experiments, it was unexpectedly found that pyrolytically produced nanostructured MgO can be successfully used to coat cathode materials using a dry mixing method to coat metal oxides on cathode materials. It was also unexpectedly found that further surface modification of the pyrolytically produced nanostructured metal oxides prior to dry mixing can further significantly improve the coverage and uniformity of the coating layer. Summary of the invention

[0021] The present invention provides a method for producing a coated active positive electrode material, a coated active positive electrode material, and the use of the coated active positive electrode material in a lithium ion battery. The lithium ion battery of the present invention can be used in electronic and electrical devices, including, for example, mobile phones, computers (laptops, desktop computers, tablet computers), electronic watches, remote control keys (key fabs), electrical appliances, power tools, vacuum cleaners, electric lawn mowers, and electric vehicles.

[0022] According to a first aspect of the present invention, there is provided a method for producing a coated active positive electrode material, preferably a coated mixed lithium transition metal oxide. The method is characterized in that the coated active positive electrode material is obtained by subjecting the active positive electrode material, preferably a mixed lithium transition metal oxide, and pyrolytically produced magnesium oxide to dry mixing in a mixing unit under shear conditions, wherein the coated active positive electrode material, preferably a mixed lithium transition metal oxide, is in the form of particles and the magnesium oxide has a particle size of 5 to 300 m 2 / g BET surface area (DIN 9277:2014), average aggregate diameter d 50 The particle size distribution is mono-modally and narrowly 5-150 nm, as determined by static light scattering (SLS) after ultrasonication of a mixture consisting of 5 wt % of the particles and 95 wt % of a 0.5 g / L aqueous sodium pyrophosphate solution at 25° C. for 60 seconds.

[0023] The pyrolytically produced MgO is hydrophilic. Preferably, in one embodiment, the pyrolytically produced MgO is subjected to surface modification to become hydrophobic.

[0024] In one embodiment, the hybrid unit has a specific electrical power of 0.05-1.5 kW / kg of mixed positive electrode material.

[0025] The coated active positive electrode material, preferably the coated mixed lithium transition metal oxide, is in the form of particles, and the magnesium oxide has a particle size of 5-300 m 2 / g BET surface area, average aggregate diameter d 50A unimodal and narrow particle size distribution of 5-150 nm, more preferably 10-120 nm, even more preferably 20-100 nm, as measured by static light scattering (SLS) after ultrasonication of a mixture consisting of 5 wt % of the particles and 95 wt % of a 0.5 g / L sodium pyrophosphate aqueous solution at 25° C. for 60 seconds.

[0026] SEM-EDX mapping of the coated active cathode material provides complete and uniform coverage of MgO around all cathode particles, with no or only few larger magnesium oxide agglomerates.

[0027] In one embodiment, the method is characterized in that the specific electrical power of the mixing unit is 0.1-1000 kW and the volume of the mixing unit is 0.1 L to 2.5 m 3 , and the speed of the mixing tool in the mixing unit is 5-30m / s.

[0028] The span (d 90 -d 10 ) / d 50 0.4-1.2, as measured by static light scattering (SLS) after ultrasonication of a mixture consisting of 5 wt % of the particles and 95 wt % of a 0.5 g / L aqueous sodium pyrophosphate solution at 25°C for 60 seconds.

[0029] The active positive electrode material may include mixed lithium transition metal oxide particles 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, and mixtures thereof.

[0030] Nanostructured magnesium oxide prepared by flame fusion has a unimodal and narrow particle size distribution and excellent dispersibility during the dry coating process of positive electrode materials. These particles lead to excellent interaction and proper adhesion to positive electrode active materials.

[0031] Furthermore, the additional surface modification of these particles leads to further improvements in interaction and adhesion with the cathode active material. This results in complete disaggregation of the magnesium oxide agglomerates and ultimately provides complete and uniform coverage of the cathode active material particles by the gas phase nanostructured and surface modified magnesium oxide.

[0032] It has been found that the method of the present invention results in significantly improved dispersibility and uniform coating of MgO particles by using a high-intensity dry coating method in combination with pyrolytic nanostructured MgO particles. During dry mixing, the applied shear force (mixing) breaks down any MgO agglomerates into tiny aggregates, which have a very high tendency to settle on the surface of the positive active material powder, thereby producing very good interaction and adhesion, which in turn produces a uniform coating layer. In contrast, conventional MgO particles that are not pyrolytically produced and nanostructured are composed of isolated spherical particles (which are the result of grinding coarser MgO particles) and do not show such behavior.

[0033] These and other features and advantages of the present invention will become better understood from the following detailed description taken in conjunction with the following drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1( a ) shows the particle size distribution of nanostructured hydrophilic magnesium oxide produced by pyrolysis according to one embodiment of the present invention.

[0035] Figure 1(b) shows the particle size distribution of conventional non-fumed magnesium oxide.

[0036] Figures 2(a) and 2(b) show SEM-EDX mapping of a fumed magnesium oxide ("magnesium oxide") coating additive on a NMC positive active material. In Figure 2(b), the magnesium oxide of Figure 1(a) is used. In Figure 2(b), the magnesium oxide of Figure 1(a) is surface modified to become hydrophobic before being applied to the NMC positive active material.

[0037] FIG. 2( c ) shows the SEM-EDX mapping of the non-fumed magnesium oxide of FIG. 1( b ) on the NMC positive electrode active material as a comparative example.

[0038] Figure 3 A lithium-ion battery is shown inside a device according to one embodiment of the present invention. DETAILED DESCRIPTION

[0039] According to a first aspect of the present invention, a method for producing encapsulated positive electrode active material particles is provided, wherein lithium mixed oxide particles, preferably mixed lithium transition metal oxides and fumed nanostructured and surface-modified magnesium oxide are dry mixed under shear conditions. A second aspect of the present invention relates to a positive electrode material coated with fumed magnesium oxide, and a third aspect of the present invention relates to a battery cell containing these encapsulated lithium mixed oxide particles.

[0040] Method for producing coated lithium transition metal oxides

[0041] According to a first aspect of the present invention, there is provided a method for producing a coated mixed lithium transition metal oxide, wherein the mixed lithium transition metal oxide and pyrolytically produced nanostructured magnesium oxide are subjected to dry mixing under shear conditions.

[0042] The fumed nanostructured magnesium oxide is also preferably surface modified to become hydrophobic prior to dry mixing.

[0043] Dry mixing can be carried out, for example, in a mixing unit with a specific electrical power of 0.05-1.5 kW / kg of mixed lithium transition metal oxide. 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 some liquid other than water are present in the mixed raw materials, or that these include water of crystallization.

[0044] If the specific electrical power used is less than 0.05 kW / kg mixed lithium transition metal oxide, this results in an uneven distribution of magnesium oxide on top of the lithium transition metal oxide, which may not be firmly bonded to the core material of the lithium transition metal oxide. A specific electrical power greater than 1.5 kW / kg mixed lithium transition metal oxide leads to poor electrochemical properties. In addition, there is a risk that the coating becomes brittle and easily breaks. The nominal electrical power of the mixing unit can vary over a wide range, for example from 0.1 kW to 1000 kW. Therefore, a laboratory-scale mixing unit with a nominal power of 0.1-5 kW or a production-scale mixing unit with a nominal electrical power of 10 to 1000 kW can be used. The nominal electrical power is the nameplate maximum absolute electrical power of the mixing unit.

[0045] The volume of the mixing unit can vary within a wide range. For example, the volume of the mixing unit can be between 0.1 L and 2.5 m 3 For example, a laboratory scale mixing unit may have a volume of 0.1-10 L, or a production scale mixing unit may have a volume of 0.1-2.5 m 3 volume.

[0046] Preferably, in the method according to the invention, the forced mixer is used in the form of an intensive mixer with high-speed mixing tools. It has been found that a mixing tool speed of 5-30 m / s, more preferably 10-25 m / s, gives the best results. Examples of commercially available mixing units suitable for the method according to the invention include Henschel mixers and Eirich mixers. The Eirich mixer can be, for example, a high-intensity Eirich mixer.

[0047] The mixing time may vary and may preferably be from 0.1 to 120 minutes, more preferably from 0.2 to 60 minutes, and most preferably from 0.5 to 10 minutes.

[0048] The mixing may be followed by a heat treatment of the mixture to improve the bonding of the coating to the mixed lithium transition metal oxide particles. However, this treatment is optional in the method according to the invention, since in this method the nanostructured and surface-modified magnesium oxide produced by pyrolysis adheres to the mixed lithium transition metal oxide with sufficient firmness. A preferred embodiment of the method according to the invention may not include a heat treatment after mixing.

[0049] It has been found that when magnesium oxide has 5m 2 / g-300m 2 / g, more preferably 10m 2 / g-200m 2 / g and most preferably 15-150m 2 The best results with regard to the adhesion of magnesium oxide to the mixed lithium transition metal oxide were obtained when the BET surface area was 1.3 Å / g. The BET surface area can be determined in accordance with DIN 9277:2014 by nitrogen adsorption according to the Brunauer-Emmett-Teller method.

[0050] MgO produced by pyrolysis

[0051] The magnesium oxide used in the process according to the invention is produced pyrolytically, i.e. by a pyrolysis process. Pyrolysis processes are also called "gas phase" processes. Such "pyrolysis" or "gas phase" processes involve the reaction of the corresponding metal precursors in a hydrogen-oxygen flame in a flame hydrolysis or flame oxidation to form metal oxides.

[0052] The hydrophilic magnesium oxide prepared by pyrolysis is characterized by:

[0053] Surface area [m 2 / g] 50 to 350

[0054] Tamped density [g / L] 20 to 100

[0055] Drying loss [%] less than 5

[0056] Loss on ignition [%] 0.1 to 20

[0057] The terms "pyrolytic production or preparation", "pyrolysis" and "gas phase process" are used equivalently in the context of the present invention. Fumed magnesium oxide can be prepared by means of flame hydrolysis or flame oxidation. This involves oxidation or hydrolysis of a hydrolyzable or oxidizable starting material, usually in a hydrogen / oxygen flame. Starting materials typically used in pyrolytic processes include organic or inorganic substances, such as metal chlorides.

[0058] Thus, the hydrophilic magnesium oxide according to the invention can be prepared by means of flame spray pyrolysis, wherein at least one metal precursor solution comprising a magnesium salt, a solvent (eg ethanol, methanol or water) is subjected to flame spray pyrolysis.

[0059] During the flame spray pyrolysis process, a solution of metal compounds (metal precursors) in the form of fine droplets is generally introduced into a flame formed by ignition of a fuel gas and an oxygen-containing gas, wherein the metal precursors used are oxidized and / or hydrolyzed to give the corresponding magnesium oxide.

[0060] The reaction initially forms highly dispersed approximately spherical primary particles, which coalesce to form aggregates in the further reaction process. The aggregates can then accumulate into aggregates. In contrast to the aggregates that can be relatively easily separated into aggregates by introducing energy, if the aggregates are to be further decomposed, only the intensive introduction of energy is required. The metal oxide powder can be partially destroyed and converted into particles in the nanometer (nm) range that are favorable to the present invention by appropriate grinding. The aggregated compound produced can be called "gas phase method (fumed)" or "pyrolysis-produced" magnesium oxide.

[0061] The flame spray pyrolysis process is generally described in WO 2015173114 A1 and other documents.

[0062] The flame spray pyrolysis method of the present invention preferably comprises the following steps:

[0063] a) atomizing a metal precursor solution by means of an atomizer gas to provide an aerosol,

[0064] b) reacting the aerosol in the reaction space of the reactor with a flame obtained by igniting a mixture of a fuel gas and an oxygen-containing gas to obtain a reaction stream,

[0065] c) cooling the reaction stream, and

[0066] d) The solid magnesium oxide is subsequently removed from the reaction stream.

[0067] The metal precursor used in the method of the present invention includes a magnesium salt, such as magnesium chloride, magnesium nitrate or magnesium acetate.

[0068] The solvent for the solution may be all typical solvents such as water, ethanol, methanol and others.

[0069] The amount of the metal precursor in the solution may range from 5 to 80 wt %, preferably from 20 to 70 wt %, based on the total weight of the solution.

[0070] Examples of fuel gases are hydrogen, methane, ethane, natural gas and / or carbon monoxide. Particular preference is given to using hydrogen.

[0071] The oxygen-containing gas is typically air or oxygen-enriched air. The oxygen-containing gas is particularly useful in embodiments where, for example, a high BET surface area of ​​the magnesium oxide to be produced is desired. The total amount of oxygen is typically selected so as to be at least sufficient to completely convert the fuel gas and the metal precursor.

[0072] To obtain an aerosol, the vaporized solution containing the metal precursor can be mixed with an atomizer gas such as nitrogen, air and / or other gases. The fine droplets of the resulting aerosol preferably have an average droplet size of 1-120 μm, particularly preferably 30-100 μm. The droplets are usually produced using a single material or multi-material nozzle. In order to increase the solubility of the metal precursor and obtain a suitable viscosity for solution atomization, the solution can be heated.

[0073] The particle size of the magnesium oxide can be varied by means of the reaction conditions, such as the flame temperature, the hydrogen or oxygen ratio, the amount of magnesium salt, the residence time in the flame or the length of the condensation zone.

[0074] The metal oxide precursor used can be dissolved in water or an organic solvent for atomization. Suitable organic solvents include methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, 2-acetone, 2-butanone, diethyl ether, tert-butyl methyl ether, tetrahydrofuran, C1-C8-carboxylic acid, ethyl acetate, toluene, petroleum and mixtures thereof.

[0075] Thus, the pyrolytically produced, nanostructured and preferably surface-modified magnesium oxide used in the process according to the invention is in the form of aggregated primary particles, preferably having a numerical average aggregate diameter of 5-150 nm, more preferably 10-120 nm, even more preferably 20-100 nm, as determined by transmission electron microscopy (TEM). The numerical average diameter can be determined by calculating the average size of at least 500 particles analyzed by TEM.

[0076] The average diameter of the agglomerates is generally 1-2 μm. These average values ​​can be determined in a suitable dispersion, for example in an aqueous dispersion, by a static light scattering (SLS) method. Agglomerates and partial aggregates can be destroyed, for example by grinding or ultrasonic treatment of the particles to produce particles with a smaller particle size.

[0077] The average aggregate diameter of metal oxides 50 5-150 nm, more preferably 10-120 nm, even more preferably 20-100 nm, as measured by static light scattering (SLS) after ultrasonication of a mixture consisting of 5 wt % of the particles and 95 wt % of a 0.5 g / L sodium pyrophosphate aqueous solution at 25°C for 60 seconds.

[0078] Therefore, the pyrolytically produced, nanostructured and preferably surface-modified magnesium oxide used in the method of the present invention is preferably characterized by high dispersibility, that is, the ability to form relatively small particles under mild ultrasonic treatment. It is believed that the dispersion under such mild conditions is related to the conditions during the dry coating process. This means that the agglomerates of magnesium oxide are destroyed in a similar manner to under ultrasonic treatment during the mixing process of the present invention, and a uniform coating layer of the positive active material particles can be formed. The span (d 90 -d 10 ) / d 50 Preferably it is 0.4-1.2, more preferably 0.5-1.1, and even more preferably 0.6-1.0, as measured by static light scattering (SLS) after ultrasonication of a mixture consisting of 5 wt% of the particles and 95 wt% of a 0.5 g / L sodium pyrophosphate aqueous solution at 25°C for 60 seconds.

[0079] Therefore, the pyrolytically produced, nanostructured and surface-modified magnesium oxide used in the process of the present invention is preferably characterized by a relatively narrow particle size distribution. This helps to obtain a high-quality magnesium oxide coating on the transition metal oxide surface.

[0080] d value 10 ,d 50 and d 90 It is usually used to characterize the cumulative particle size distribution of a given sample. For example, d 10 The diameter is 10% of the sample volume is smaller than d 10 The diameter of the particles, d 50 50% of the sample volume consists of less than d 50 The diameter of the particles. 50 Also called the “volume median diameter” because it divides the sample equally by volume; d 90 90% of the sample volume consists of less than d 90 The diameter of the particles when they are composed.

[0081] Surface treatment of MgO produced by pyrolysis

[0082] Pyrolytically produced MgO is hydrophilic without any further surface treatment, since it is naturally covered with hydroxyl (-OH) groups. By surface modification of pyrolytically produced MgO, hydrophobic MgO is also produced. For example, hydrophobization of MgO can be performed by reacting hydroxyl groups with silanes to form -O-Si-R groups. Thus, preferably, MgO is surface modified, meaning that the surface of MgO is at least partially covered with silanes.

[0083] The pyrolytically produced MgO can be used in its hydrophilic and hydrophobic forms. The use of hydrophilic MgO does not require any further treatment after synthesis by the pyrolytic method. However, after synthesis by the pyrolytic method, the MgO particles can be rendered hydrophobic by further treatment with a hydrophobic agent such as silane. For example, in one embodiment, octylsilane is covalently bonded to the surface of the MgO particles. Using the method of the present invention, hydrophilic and hydrophobic forms of gas-phase nanostructured MgO can be effectively used as a coating via dry mixing with a matrix active positive electrode material. Gas-phase nanostructured and surface-modified MgO is preferred because it shows a more uniform coverage of the matrix active positive electrode material.

[0084] In one embodiment, a pyrolytically prepared, surface-modified magnesium oxide is produced that is characterized by:

[0085] Surface area [m 2 / g] 50 to 350

[0086] Tamped density [g / L] 20 to 100

[0087] Drying loss [%] less than 5

[0088] Loss on ignition [%] 0.1 to 20

[0089] Thus, pyrolytically prepared magnesium oxide is sprayed with a surface modifier at room temperature and the mixture is subsequently heat treated at a temperature of 50 to 300° C., preferably 80-180° C., for a period of 0.5 to 3 hours (“h”).

[0090] In an alternative embodiment, surface modification of pyrolytically prepared magnesium oxide may be performed by treating the pyrolytic magnesium oxide with a surface modifier in vapor form and subsequently heat treating the mixture at a temperature of 50 to 800° C. for a period of 0.5 to 6 hours.

[0091] An alternative method of surface modification of pyrolytically prepared magnesium oxide may be carried out by treating the pyrolytic magnesium oxide with a surface modifier in vapor form and subsequently heat treating the mixture at a temperature of 50 to 800° C. for a period of 0.5 to 6 hours.

[0092] The heat treatment can be carried out under a protective gas such as nitrogen. The surface treatment can be carried out continuously or batchwise in a heatable mixer and dryer with a spray device. Suitable devices can be, for example, plowshare mixers or plates, cyclone or fluidized bed dryers.

[0093] An advantage of the present invention is that commercially available silanes can be used to modify the magnesium oxide and thus individually adjust the properties of the magnesium oxide, depending on the desired properties and the intended purpose.

[0094] As surface modifiers it is possible to use the following compounds and mixtures of the following compounds:

[0095] a) Type (RO) 3Si(C n H 2n+1 ) and (RO)3Si(C n H 2n-1 ) wherein R = alkyl, such as methyl, ethyl, n-propyl, isopropyl, butyl, and n = 1-20

[0096] b) Type R' x (RO) y Si(C n H 2n+1 ) and R' x (RO) y Si(C n H 2n-1 ) of an organosilane, wherein

[0097] R = alkyl, such as methyl-, ethyl-, n-propyl-, isopropyl-, butyl-

[0098] R' = alkyl, such as methyl, ethyl, n-propyl, isopropyl, butyl

[0099] R'=cycloalkyl

[0100] n = 1–20

[0101] x+y=3

[0102] x = 1, 2, and

[0103] y=1,2.

[0104] c) Type X3Si(C n H 2n+1 ) and X3Si(C n H 2n-1 ) of a halogenated organosilane, wherein

[0105] X=Cl、Br

[0106] n = 1–20

[0107] d) Type X2(R')Si(C n H 2n+1 ) and X2(R')Si(C n H 2n-1 ) of a halogenated organosilane, wherein

[0108] X=Cl、Br

[0109] R' = alkyl, such as methyl, ethyl, n-propyl, isopropyl, butyl

[0110] R'=cycloalkyl

[0111] n = 1–20

[0112] e) Type X(R')2Si(C n H 2n+1 ) and X(R')2Si(C n H 2n-1 ) of a halogenated organosilane, wherein

[0113] X=Cl、Br

[0114] R' = alkyl, such as methyl, ethyl, n-propyl, isopropyl, butyl

[0115] R'=cycloalkyl

[0116] n = 1–20

[0117] f) Type (RO) 3Si(CH2) m -R'Organosilane

[0118] R = alkyl, such as methyl, ethyl, propyl,

[0119] m=0.1-20

[0120] R' = methyl-, aryl (eg, -C6H5, substituted phenyl residue), C4F9, OCF2-CHF-CF3, -C6F 13 , -O-CF2-CHF2, -NH2, -N3, -SCN, -CH=CH2, -NH-CH2-CH2-NH2, -N-(CH2-CH2-NH2)2, -OOC(CH3)C=CH2 , -OCH2-CH(O)CH2, -NH-CO-N-CO-(CH2)5, -NH-COO-CH3, -NH-COO-CH2-CH3, -NH-(CH2)3Si(OR)3, -S x -(CH2)3Si(OR)3, -SH, -NR'R"R"', where

[0121] R'=alkyl, aryl;

[0122] R"=H, alkyl, aryl;

[0123] R"'=H, alkyl, aryl, benzyl, C2H4NR""R""', where R""=H, alkyl, and

[0124] R""'=H, alkyl

[0125] g) Type (R") x (RO) ySi(CH2)m-R'organosilane

[0126] R"=alkyl

[0127] x+y=2

[0128] = Cycloalkyl x = 1.2

[0129] y=1.2

[0130] m=0.1-20

[0131] R' = methyl-, aryl (eg, -C6H5, substituted phenyl residue), C4F9, OCF2-CHF-CF3, -C6F 13 , -O-CF2-CHF2, -NH2, -N3, -SCN, -CH=CH2, -NH-CH2-CH2-NH2, -N-(CH2-CH2-NH2)2, -OOC(CH3)C=CH2 , -OCH2-CH(O)CH2, -NH-CO-N-CO-(CH2)5, -NH-COO-CH3, -NH-COO-CH2-CH3, -NH-(CH2)3Si(OR)3, -S x -(CH2)3Si(OR)3, -SH, -NR'R"R"', where

[0132] R'=alkyl, aryl;

[0133] R"=H, alkyl, aryl;

[0134] R"'=H, alkyl, aryl, benzyl, C2H4NR""R""', where R""=H, alkyl, and

[0135] R""'=H, alkyl

[0136] h) Halogenated organosilanes of type X3Si(CH2)m-R'

[0137] X=Cl、Br

[0138] m=0.1-20

[0139] R' = methyl-, aryl (eg, -C6H5, substituted phenyl residue), C4F9, OCF2-CHF-CF3, -C6F 13, -O-CF2-CHF2, -NH2, -N3, -SCN, -CH=CH2, -NH-CH2-CH2-NH2, -N-(CH2-CH2-NH2)2, -OOC(CH3)C=CH2 , -OCH2-CH(O)CH2, -NH-CO-N-CO-(CH2)5, -NH-COO-CH3, -NH-COO-CH2-CH3, -NH-(CH2)3Si(OR)3, -S x -(CH2)3Si(OR)3, -SH

[0140] i) Halogenated organosilanes of type (R)X2Si(CH2)m-R'

[0141] X=Cl、Br

[0142] R = alkyl, such as methyl, ethyl, propyl,

[0143] m=0.1-20

[0144] R' = methyl-, aryl (eg, -C6H5, substituted phenyl residue), C4F9, OCF2-CHF-CF3, -C6F 13 , -O-CF2-CHF2, -NH2, -N3, -SCN, -CH=CH2, -NH-CH2-CH2-NH2, -N-(CH2-CH2-NH2)2, -OOC(CH3)C=CH2 , -OCH2-CH(O)CH2, -NH-CO-N-CO-(CH2)5, -NH-COO-CH3, -NH-COO-CH2-CH3, -NH-(CH2)3Si(OR)3, -S x -(CH2)3Si(OR)3, -SH,

[0145] j) Halogenated organosilanes of the type (R)2XSi(CH2)m-R'

[0146] X=Cl、Br

[0147] R=alkyl

[0148] m=0.1-20

[0149] R' = methyl-, aryl (eg, -C6H5, substituted phenyl residue), C4F9, OCF2-CHF-CF3, -C6F 13, -O-CF2-CHF2, -NH2, -N3, -SCN, -CH=CH2, -NH-CH2-CH2-NH2, -N-(CH2-CH2-NH2)2, -OOC(CH3)C=CH2 , -OCH2-CH(O)CH2, -NH-CO-N-CO-(CH2)5, -NH-COO-CH3, -NH-COO-CH2-CH3, -NH-(CH2)3Si(OR)3, -S x -(CH2)3Si(OR)3, -SH

[0150] Preferably, the following silanes are used as surface modifiers alone or in a mixture: dimethyldichlorosilane, octyltrimethoxysilane, octyltriethoxysilane, hexamethyldisilazane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, dimethylpolysiloxane, glycidyloxypropyltrimethoxysilane, glycidyloxypropyltriethoxysilane, nonafluorohexyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane, aminopropyltriethoxysilane. Particularly preferably, octyltrimethoxysilane and octyltriethoxysilane can be used.

[0151] Hydrophobic MgO is also produced by surface modification of pyrolytically produced MgO. Pyrolytically produced MgO can be used in its hydrophilic and hydrophobic forms. The use of hydrophilic MgO does not require any further treatment by any hydrophobic reagent such as silane after they are synthesized by a pyrolytic method. However, after they are synthesized by a pyrolytic method, the MgO particles can be rendered hydrophobic by further treatment with a hydrophobic reagent such as silane. Using the method of the present invention, hydrophilic and hydrophobic forms of gas-phase nanostructured MgO can be effectively used as a coating via dry mixing with a matrix active positive electrode material. Gas-phase nanostructured and surface-modified MgO is preferred because it shows a more uniform coverage of the matrix active positive electrode material.

[0152] The MgO particles produced via the pyrolysis process generally have a purity of at least 96% by weight, preferably at least 98% by weight, more preferably at least 99% by weight. The magnesium oxide used in the process according to the invention preferably contains the elements Cd, Ce, Fe, Na, Nb, P in a proportion of <10 ppm and the elements Ba, Bi, Cr, K, Mn, Sb in a proportion of <5 ppm, wherein the sum of the proportions of all these elements is <100 ppm. The proportion of carbon in the hydrophilic, non-surface-modified metal oxide is preferably less than 0.2% by weight, more preferably from 0.005% by weight to 0.2% by weight, even more preferably from 0.01% by weight to 0.1% by weight, based on the mass of the metal oxide powder.

[0153] Active cathode material

[0154] In the context of the present invention, the term "transition metal" comprises 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.

[0155] The mixed lithium transition metal oxide preferably used in the process according to the invention 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 and mixtures thereof.

[0156] The mixed lithium transition metal oxide preferably has the general formula LiMO2, wherein M is at least one transition metal selected from nickel, cobalt, manganese; more preferably M=Co or Ni x Mn y Co z , wherein 0.3≤x≤0.9, 0≤y≤0.45, 0≤z≤0.4; most preferably, M is Ni x Mn y Co z , where 0.3≤x≤0.9, 0≤y≤0.45, 0≤z≤0.4.

[0157] The mixed lithium transition metal oxide of the general formula LiMO 2 may further be doped with at least one other metal oxide, in particular with aluminum oxide and / or magnesium oxide.

[0158] The coated mixed lithium transition metal oxide preferably has a numerical average particle size of 2-20 μm. The numerical average particle size can be determined by laser diffraction particle size analysis according to ISO 13320:2009.

[0159] The proportion of magnesium oxide in the coated mixed lithium transition metal oxide is preferably 0.05 wt % to 5 wt %, more preferably 0.1 wt % to 2 wt %, based on the total weight of the coated mixed lithium transition metal oxide. If the proportion of magnesium oxide is less than 0.05 wt %, the beneficial effect of the coating layer is generally not observed. In the case where it is greater than 5 wt %, the beneficial effect of an additional amount of magnesium coating greater than 5 wt % is generally not observed.

[0160] The coated mixed lithium transition metal oxide preferably has a coating layer thickness of 10-200 nm, as determined by TEM analysis.

[0161] The present invention further provides a coated mixed lithium transition metal oxide obtainable by the process according to the present invention. The present invention further provides a coated mixed lithium transition metal oxide comprising a pyrolytically produced nanostructured and surface-modified magnesium oxide coating layer on the surface of the mixed lithium transition metal oxide.

[0162] With regard to the coated mixed lithium transition metal oxide according to the invention, the other preferred features of the coated mixed lithium transition metal oxide, pyrolytically produced nanostructured and surface-modified magnesium oxide described above in the preferred embodiments of the method according to the invention are also preferred features of the coated mixed lithium transition metal oxide, pyrolytically produced nanostructured and surface-modified magnesium oxide, regardless of whether it is produced by the method according to the invention.

[0163] The present invention further provides an active cathode material for a lithium ion battery, which comprises a coated mixed lithium transition metal oxide according to the invention or a coated mixed lithium transition metal oxide obtainable by a process according to the invention.

[0164] The positive electrode (positive electrode) of a lithium-ion battery generally includes a current collector and an active positive electrode material layer formed above or on the current collector. The current collector may be aluminum foil, copper foil, nickel foil, stainless steel foil, titanium foil, a polymer matrix coated with a conductive metal, or a combination thereof.

[0165] The active positive electrode material coated with the pyrolytically produced, nanostructured and preferably surface-modified MgO may include any suitable material capable of reversibly inserting / deinserting lithium ions. Such materials are well known in the art. Such active positive electrode materials may include, for example, transition metal oxides, such as mixed oxides containing Ni, Co, Mn, V or other transition metals and optionally lithium. Particularly preferred are mixed lithium transition metal oxides (NMC) containing nickel, manganese and cobalt.

[0166] The invention further provides a lithium ion battery comprising a coated mixed lithium transition metal oxide or a coated mixed lithium transition metal oxide obtainable by the process according to the invention.

[0167] In addition to the positive electrode, the lithium ion battery of the present invention may also comprise a negative electrode, an optional separator and an electrolyte comprising a lithium salt or a lithium compound.

[0168] The negative electrode of the lithium ion battery may include any suitable material commonly used in the secondary lithium ion battery and capable of reversibly inserting / deinserting lithium ions. Typical examples thereof are carbonaceous materials, including crystalline carbon such as natural or artificial graphite in the form of flake, thin sheet, spherical or fibrous graphite; amorphous carbon such as soft carbon, hard carbon, mesophase pitch carbide, fired coke and the like, or a mixture thereof. In addition, lithium metal or conversion material (e.g., Si or Sn), silicon oxide, and a mixture or composite of silicon, silicon oxide and carbon may be used as the negative electrode active material.

[0169] The electrolyte of the lithium ion battery can be in the form of liquid, gel or solid. The liquid electrolyte of the lithium ion battery can contain any suitable organic solvent commonly used in the lithium ion battery such as anhydrous ethylene carbonate (EC), dimethyl carbonate (DMC), propylene carbonate, ethyl methyl carbonate, diethyl carbonate, γ-butyrolactone, dimethoxyethane, fluoroethylene carbonate, vinylethylene carbonate and mixtures thereof.

[0170] The gel electrolyte includes a gelled polymer. Any suitable gelled polymer may be used.

[0171] The solid electrolyte of the lithium-ion battery may include an oxide (eg, lithium metal oxide), a sulfide, a phosphate, or a solid polymer.

[0172] The electrolyte of the lithium-ion battery may contain a lithium salt. Examples of such lithium salts include lithium hexafluorophosphate (LiPF6), lithium bis (trifluoromethylsulfonyl) imide (LiTFSI), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), Li2SiF6, lithium trifluoromethanesulfonate, LiN(SO2CF2CF3)2, and mixtures thereof.

[0173] The present invention further provides the use of the coated mixed lithium transition metal oxide in an active positive electrode material of a lithium ion battery.

[0174] Even without other explanations, it is assumed that one skilled in the art can fully utilize the above description.The preferred embodiments and examples are therefore to be construed as merely descriptive and not limiting in any way.

[0175] Hereinafter, the present invention is explained in more detail using examples.Alternative embodiments of the present invention can be obtained in a similar manner.

[0176] Example:

[0177] Determination of physicochemical characteristic data

[0178] In the context of the present invention, the following measurement methods for evaluating the characteristics of different materials are used:

[0179] A) BET surface area:

[0180] The BET surface area is determined according to DIN 9277:2014 using nitrogen.

[0181] B) Compacted density:

[0182] The tamped density is determined according to an adaptation of DIN ISO 787 / XI,

[0183] Principle of compacted density determination:

[0184] The tamped density (formerly tamped volume) is equal to the quotient of the mass and volume of the powder after tamping in a tamped volume meter under the predetermined conditions. According to DIN ISO 787 / XI, the tamped density is expressed in g / cm 3 However, due to the very low tamped density of the oxides, we give the value in g / L. Furthermore, the drying and sieving and the repetition of the tamping operation are omitted.

[0185] Equipment for tamped density determination:

[0186] Compaction volume meter

[0187] Graduated Cylinder

[0188] Laboratory scale (read to 0.01g)

[0189] To perform a tamped density determination:

[0190] 200 ± 10 mL of oxide is filled into the graduated cylinder of the compacting volume meter in such a way that there are no pores and the surface is level. The mass of the filled sample is accurately measured to 0.01 g. The graduated cylinder with the sample is placed in the graduated cylinder holder of the compacting volume meter and compacted 1250 times. The volume of the compacted oxide is accurately read once.

[0191] Evaluation of tamped density determination

[0192]

[0193] C) pH value:

[0194] The pH values ​​were determined in a 4% aqueous dispersion of the hydrophobic oxide in water:methanol (1:1).

[0195] Reagents for pH determination:

[0196] Distilled water or completely deionized water, pH>5.5

[0197] Methanol, pa

[0198] Buffer solution pH 7.00 pH 4.66

[0199] Equipment for pH determination:

[0200] Laboratory scale, (read to 0.1g)

[0201] Glass beaker, 250mL

[0202] Magnetic stirrer

[0203] Magnetic bar, 4 cm long

[0204] Combined pH Electrode

[0205] pH Measurement Equipment

[0206] Dispenser, 100mL

[0207] Working procedure for determining pH:

[0208] Determination according to the adaptation of DIN / ISO 787 / IX:

[0209] Calibration: Before pH determination, the measuring device is calibrated with a buffer solution. If several measurements are carried out in succession, a single calibration is sufficient.

[0210] 4 g of the hydrophilic oxide was mixed into a paste in a 250 mL glass beaker containing 96 g (96 mL) of water using a dispenser and stirred with a magnetic stirrer for five minutes while the pH electrode was immersed (rpm about 1000 min -1 ).

[0211] 4 g of the hydrophobic oxide was stirred into a paste in a 250 mL glass beaker containing 48 g (61 mL) of methanol and the suspension was diluted with 48 g (48 mL) of water and stirred with a magnetic stirrer for five minutes while the pH electrode was immersed (rpm about 1000 min -1 ). After turning off the stirrer, read the pH after a one-minute standing time. The result is accurate to one decimal place.

[0212] D) Loss on drying

[0213] In contrast to the 10 g weighed amounts mentioned in DIN ISO 787 II, a weighed amount of 1 g was used for the loss on drying determination.

[0214] The lid is put in place before cooling. No secondary drying is performed.

[0215] About 1 g of sample (accurate to 0.1 mg) was weighed into a weighing pan with a ground cover that had been dried at 105° C., avoiding the formation of dust and dried for two hours in a drying oven at 105° C. After cooling in the desiccator with its cover still on, the sample was reweighed under the blue gel.

[0216]

[0217] The result is accurate to one decimal place.

[0218] E) Loss on ignition

[0219] Equipment for determining loss on ignition:

[0220] Porcelain crucible with crucible cover

[0221] Muffle furnace

[0222] Analytical scale (read to 0.1 mg)

[0223] Dryer

[0224] Loss on ignition:

[0225] In contrast to DIN 55 921, 0.3-1 g of undried substance (accurate to 0.1 mg) are weighed into a porcelain crucible with a crucible cover (the crucible has been previously heated to red heat) and heated red hot in a muffle furnace at 1000° C. for 2 hours. Care is taken to avoid the formation of dust. It has proven to be advantageous to place the weighed sample into the muffle furnace while the muffle furnace is still cold. The slow heating of the furnace prevents the generation of strong air turbulence in the porcelain crucible. After 1000° C. has been reached, the red hot heating is continued for a further 2 hours. Subsequently, the crucible cover is put in place and the weight loss of the crucible is determined on a blue gel in a desiccator.

[0226] Evaluation of loss on ignition

[0227] Since the loss on ignition is measured relative to a sample dried at 105°C for 2 hours, the following calculation formula is obtained:

[0228]

[0229] m0 = weighed amount (g)

[0230] TV = Loss on drying (%)

[0231] m1 = weight of sample after red heat heating (g)

[0232] The result is accurate to one decimal place.

[0233] F) Carbon content

[0234] The carbon content was determined by elemental analysis using a LECO C744 instrument. The measuring principle is based on the oxidation of carbon in the sample to CO2 and subsequent quantification of the CO2 by an infrared detector.

[0235] G) SEM measurement

[0236] Energy dispersive X-ray spectroscopy (EDX) was performed by SEM. For EDX mapping, a representative area of ​​the sample was used at a magnification of 1000x, with an image width of 2048 x 1536 pixels (120 μm x 90.1 μm), resulting in a pixel resolution of 0.059 μm. The mapping was recorded with an accelerating voltage of 20 kV. After the measurement, the elements present in the sample were determined using the sum-spectrum of the mapping. The threshold of the image analysis was adjusted according to the semi-quantitative mass % value of the respective element.

[0237] Preparation of magnesium oxide:

[0238] Example 1: Preparation of magnesium oxide prepared by pyrolysis

[0239] 1.89 kg of an aqueous solution containing 1000 g of Mg(CH3COO)2*4H2O was prepared. 2.5 kg / h of this dispersion and 15 Nm 3 / h of air aerosol and sprayed into a tubular reaction with a combustion flame. The combustion gas of the flame is 8Nm 3 / h of hydrogen and 30Nm 3 / h of air composition. In addition, using 25Nm 3 / h of secondary air. After the reactor, the reaction gas is cooled and filtered.

[0240] The particle characteristics are shown in Table 1, a TEM image of the particles is shown in Figure 1 and XRD analysis (Figure 2) showed that the major phase of the product was cubic magnesium oxide.

[0241] The resulting high surface area, pyrolytically prepared hydrophilic magnesium oxide has the physicochemical characterization data shown in Table I.

[0242] Example 2: Preparation of surface-modified magnesium oxide

[0243] 300 g of pyrolytically prepared magnesium oxide (Example 1) were placed in a mixer and sprayed with 72 g of octyltrimethoxysilane. After the spraying of the silane on the powder was complete, mixing was continued for another 5 minutes. The wetted powder was then tempered in an oven at 130° C. for 3 hours. The surface-modified magnesium oxide formed had the physicochemical characterization data shown in Table 1.

[0244] The hydrophilic and surface-modified magnesium oxide has the physicochemical characteristic data shown in Table 1.

[0245] Table 1: Characteristics

[0246] characteristic Example 1 Example 2 <![CDATA[BET[m 2 / g]]]> 240 225 Compacted density [g / L] 56 78 pH 10.5 10.2 Loss on drying [%] 0.5 0.6 Loss on ignition [%] 12.2 17.6 Carbon content [%] 0.0 9.7

[0247] Starting Materials:

[0248] Dry coating additives:

[0249] The materials described above in Examples 1 and 2 were used, i.e., a BET surface area of ​​250 m 2 / g of the fumed magnesium oxide of Example 1 and a BET surface area of ​​230 m 2 / g of the fumed hydrophobic magnesium oxide of Example 2 (Evonik Operations GmbH). The fumed hydrophobic magnesium oxide of Example 2 was made hydrophobic by subjecting it to a hydrophobizing treatment after the pyrolysis formation process as described above. A 65 m 2 / g of non-fumed magnesium oxide was used as a comparative example. Non-fumed magnesium oxide is not nanostructured, and is a ground material having isolated, non-aggregated particles.

[0250] Positive electrode active material: Commercially available mixed lithium nickel manganese cobalt oxide powder NMC 7 1.5 1.5 powder (PLB-H7 type) with a BET surface area of ​​0.5 m 2 / g, median particle size d 50 =10.6±2 μm (measured by static laser scattering method), provided by LinyiGelon LIB Co.

[0251] Example 3

[0252] First, 217.8 g of NMC powder (PLB-H7) was mixed with 2.2 g (1.0 wt%) of the gas phase nanostructured MgO powder of Example 1 in a high intensity laboratory mixer (Somakon mixer MP-GL with 0.5 L mixing unit) at 100 rpm (specific electrical power: 800 W / kg NMC) for 1 minute. For homogenization of the two powders, the speed was gradually increased from 100 rpm for 1 minute to 200 rpm for another 1 minute, and then at 500 rpm for another 1 minute. After homogenization, the mixing speed was further increased to 2000 rpm (specific electrical power: 800 W / kg NMC, tip speed of the mixing tool in the mixing unit: 10 m / s) and mixing was continued for 5 minutes to obtain a dry coating of the NMC particles with MgO. The coated NMC particles showed a MgO coating thickness of 10-200 nm, as determined by TEM analysis.

[0253] Example 4

[0254] The procedure of Example 1 was repeated exactly, with the only difference being that the surface modified MgO of Example 2 was used instead of the MgO of Example 1. The coated NMC particles showed a MgO coating thickness of 10-200 nm, as determined by TEM analysis.

[0255] Comparative Example 5

[0256] The procedure of Example 1 was repeated with the exception that a powder purchased from Sigma-Aldrich with a BET surface area of ​​65 m 2 / g of non-gas-phase process magnesium oxide replaces the gas-phase process MgO in Example 1.

[0257] When fumed magnesium oxide is used as the coating additive, uniformly coated positive electrode active material particles are obtained, wherein the coating layer thickness on the top of the positive electrode active material particles is 20-200 nm.

[0258] The particle size distribution of the hydrophilic magnesium oxide was measured to visualize the dispersibility behavior during the application of shear forces to the magnesium oxide agglomerates.

[0259] FIG1(a) shows the particle size distribution of the fumed MgO of Example 1, and FIG1(b) shows the particle size distribution of the non-fumed magnesium oxide used in Example 5, analyzed by a laser diffraction particle size analyzer. The x-axis in FIG1 shows the diameter of the particles, the left y-axis shows the volume in % ("q%"), and the right y-axis shows the cumulative volume in ("Q%").

[0260] The samples were dispersed in distilled water and treated in an external ultrasonic bath (160 W) for 15 minutes. For the MgO of Example 1, a nearly monomodal and very narrow particle size distribution with small aggregate sizes of D10 = 58 nm, D50 = 78 nm, D90 = 147 nm was detected. In the case of non-fumed magnesium oxide, a slightly broader particle size distribution with much larger agglomerate sizes of D10 = 2680 nm, D50 = 4080 nm, D90 = 5950 nm was detected, clearly showing the presence of non-dispersed particles.

[0261] Analysis of MgO-coated mixed lithium transition metal oxides by SEM-EDX

[0262] Figure 2a , 2band 2c show SEM-EDX (scanning electron microscopy with energy dispersive X-ray) mapping of different magnesium oxide coating additives on NMC positive active material PLB-H7 (a: fumed hydrophobic MgO of Example 2, b: fumed MgO of Example 1, c: non-fumed magnesium oxide). The mapping of NMC coated with fumed magnesium oxide (a) and (b) shows complete and uniform coverage of MgO around all positive electrode particles. No or only very few larger magnesium oxide agglomerates were detected, indicating that the dispersion of nanostructured fumed magnesium oxide was successful. In addition, almost no unattached MgO particles were found in close proximity to the positive electrode particles, indicating a strong interaction of the high surface area fumed magnesium oxide particles with the surface of the positive active material particles, and therefore indicating excellent adhesion between the coating layer and the substrate.

[0263] In contrast, by using coarser magnesium oxide particles (non-fumed magnesium oxide) as the coating layer of the positive electrode material (c), it can be found that there is almost no coating layer on the surface of the positive electrode active material particles. Instead, larger non-dispersed and thus unattached MgO particles are adjacent to the positive electrode particles, indicating the very poor dispersibility behavior of non-fumed magnesium oxide during the dry coating process, ultimately resulting in the presence of uncoated positive electrode active material particles.

[0264] Thus, the NMC mixed oxide dry-coated with fumed MgO shows that all NMC particles are completely and uniformly covered with MgO. No larger MgO agglomerates were detected, showing good dispersibility of the nanostructured fumed MgO. In addition, no free unattached MgO particles were found next to the NMC particles, indicating strong adhesion between the coating and the matrix (NMC). In contrast, FIG2(c) shows that for non-fumed MgO, only fine particles of "nano-MgO" are attached to the surface of the NMC particles. Larger MgO particles are non-dispersed and therefore not attached, next to the NMC particles. Therefore, the NMC particles are not completely covered by magnesium oxide.

[0265] Figure 3A lithium ion battery, generally indicated by the numeral 10, is shown inside a device 100 powered by a lithium ion battery 10 according to one embodiment of the present invention. The device may be any electronic device, such as a mobile phone, an electronic watch, a key fab, a laptop, a desktop computer, a tablet computer, etc. The device may also be an electrical device, such as a power tool, a vacuum cleaner, an electric lawn mower, an appliance, etc. The lithium ion battery 10 may be packaged in a module, each module having a plurality of lithium batteries 10, and used to power an electric vehicle or a hybrid vehicle. The lithium ion battery 10 includes a negative electrode collector 14 and a positive electrode collector 12, a positive electrode 18 adjacent to the positive electrode collector 12 and a negative electrode 16 adjacent to the negative electrode collector 14, an electrolyte 20, and a separator 22 disposed between the negative electrode 16 and the positive electrode 18. The positive electrode 18 includes a coated mixed lithium transition metal oxide as an active positive electrode material, and is characterized in that the coated mixed lithium transition metal oxide is obtained by subjecting the mixed lithium transition metal oxide and the nanostructured magnesium oxide produced by pyrolysis to dry mixing by means of a mixing unit as described above.

[0266] Although the invention has been described with reference to specific embodiments, it should be understood that the invention is not limited to these embodiments only and that many variations will fall within the scope of the invention as defined by the appended claims.

[0267] Reference Numbers List

[0268] ------------------------------------

[0269] 10 Battery Cells

[0270] 100 Devices powered by battery cells

[0271] 12. Positive electrode current collector

[0272] 14 Negative electrode current collector

[0273] 16 Negative electrode

[0274] 18 Positive electrode

[0275] 20 electrolytes

[0276] 22 Diaphragm

Claims

1. A method for producing a coated mixed lithium transition metal oxide, characterized in that The coated mixed lithium transition metal oxide is obtained by subjecting the mixed lithium transition metal oxide and the pyrolytically produced nanostructured magnesium oxide to dry mixing under shear conditions by means of a mixing unit, characterized in that the coated mixed lithium transition metal oxide is in the form of particles and the magnesium oxide has a particle size of 5-300 m 2 / g BET surface area (DIN 9277:2014), average aggregate diameter d 50 The particle size distribution is unimodal and narrow, ranging from 5 to 150 nm, as determined by static light scattering (SLS) after ultrasonication of a mixture consisting of 5 wt % of the particles and 95 wt % of a 0.5 g / L aqueous sodium pyrophosphate solution at 25° C. for 60 seconds.

2. The method according to claim 1, characterized in that (i) the pyrolytically produced nanostructured magnesium oxide is surface treated to become hydrophobic by reacting hydroxyl groups of MgO with silane to form -O-Si-R groups prior to the dry mixing, and (ii) the mixing unit has a specific electrical power of 0.05-1.5 kW / kg of the mixed lithium transition metal oxide.

3. The method according to claim 1 or 2, characterized in that: The average aggregate diameter d 50 10-120 nm, preferably 20-100 nm, as measured by static light scattering (SLS) after ultrasonication of a mixture consisting of 5 wt % of the particles and 95 wt % of a 0.5 g / L sodium pyrophosphate aqueous solution at 25°C for 60 seconds.

4. The method according to claims 1-3, characterized in that: Scanning electron microscopy with energy dispersive X-ray (SEM-EDX) mapping of the coated mixed lithium transition metal oxide as disclosed in the specification provides complete and uniform coverage of MgO around substantially all of the mixed lithium transition metal oxide particles.

5. The method according to claims 1-4, characterized in that: The specific electrical power of the mixing unit is 0.1-1000 kW, and the volume of the mixing unit is 0.1 L to 2.5 m 3 , and the speed of the mixing tool in the mixing unit is 5-30m / s.

6. The method according to claims 1-5, characterized in that: The span (d 90 -d 10 ) / d 50 0.4-1.2, as measured by static light scattering (SLS) after ultrasonication of a mixture consisting of 5 wt % of the particles and 95 wt % of a 0.5 g / L aqueous sodium pyrophosphate solution at 25°C for 60 seconds.

7. The method according to claims 1-6, characterized in that: The mixed lithium transition metal 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 and mixtures thereof.

8. The method according to claims 1-7, characterized in that The coated mixed lithium transition metal oxide is further subjected to a heat treatment after the dry mixing.

9. The method according to claims 1-8, characterized in that The ratio of the magnesium oxide in the coated mixed lithium transition metal oxide is 0.05 wt % to 5 wt % based on the total weight of the coated mixed lithium transition metal oxide.

10. A coated mixed lithium transition metal oxide comprising a mixed lithium transition metal oxide particle 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 and mixtures thereof, and a coating layer of pyrolytically produced nanostructured magnesium oxide on the surface of the mixed lithium transition metal oxide particle, wherein the coated mixed lithium transition metal oxide is in the form of particles and the magnesium oxide has a nanostructure of 5-300 m 2 / g BET surface area (DIN 9277:2014), average aggregate diameter d 50 The invention relates to a nanostructured magnesium oxide having a unimodal and narrow particle size distribution of 5-150 nm, as measured by static light scattering (SLS) after ultrasonication of a mixture consisting of 5 wt % of the particles and 95 wt % of a 0.5 g / L aqueous solution of sodium pyrophosphate at 25° C. for 60 seconds, and wherein the pyrolytically produced nanostructured magnesium oxide is preferably surface treated to become hydrophobic by reacting the hydroxyl groups of MgO with silane to form —O—Si—R groups.

11. The coated mixed lithium transition metal oxide according to claim 10, characterized in that SEM-EDX mapping of the coated mixed lithium transition metal oxide particles as disclosed in the specification provides complete and uniform coverage of MgO substantially around all mixed lithium transition metal oxide particles.

12. A coated mixed lithium transition metal oxide obtainable by the process according to claims 1 to 9.

13. An active cathode material for a lithium ion battery comprising the coated mixed lithium transition metal oxide according to claims 10 to 12.

14. A lithium ion battery comprising the coated mixed lithium transition metal oxide according to claims 10 to 12.

15. Use of the coated mixed lithium transition metal oxide according to claims 10 to 12 as an active positive electrode material for lithium ion batteries.

16. A device comprising the lithium ion battery according to claim 14, the device comprising an electrical or electronic device, the device comprising a mobile phone, an electronic watch, a remote control key, a laptop computer, a desktop computer, a tablet computer, a power tool, a vacuum cleaner, an electric lawn mower, an electrical appliance and an electric vehicle.

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