Cathode active material particles encapsulated in fired nanostructured magnesium oxide, a method for producing the same, and a method for using the same

Abstract

A method for producing a coated mixed lithium transition metal oxide, wherein the mixed lithium transition metal oxide and magnesium oxide, which is produced by firing, nanostructured, and preferably surface-modified, are subjected to dry mixing by a mixing unit having a specific power of 0.05 to 1.5 kW per 1 kg of the mixed lithium transition metal oxide. A coated mixed lithium transition metal oxide obtainable by this method, a cathode for a lithium-ion battery, and a lithium-ion battery comprising the mixed and coated mixed lithium transition metal oxide.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing encapsulated cathode active material particles in which lithium mixed oxide particles and nanostructured magnesium oxide burned in a flame are dry mixed under shear conditions. The present invention further relates to a cathode material coated with magnesium oxide burned in a flame, and to a battery cell containing these encapsulated lithium mixed oxide particles and their use.

Background Art

[0002] In recent years, various energy storage technologies have received extensive attention and have been the subject of intensive research and development in the industrial and academic fields. As energy storage technologies spread to devices such as mobile phones, camcorders, notebook PCs, and even electric vehicles, the demand for high-energy density batteries used as power sources for such devices is increasing. Secondary lithium-ion batteries are one of the most important battery types currently in use.

[0003] A secondary lithium-ion battery generally consists of an anode made of a carbon material or a lithium metal alloy, a cathode made of a lithium metal oxide, and an electrolyte in which a lithium salt is dissolved in an organic solvent. The separator of a lithium-ion battery provides a passage for lithium ions between the positive electrode and the negative electrode during the charge and discharge processes.

[0004] One of the common problems associated with cathode materials is their rapid aging and thus loss of performance during cycling. This phenomenon is particularly relevant to nickel manganese cobalt mixed oxides (NMC) with a high nickel content. During cycling, the cathode material undergoes several electrochemical degradation mechanisms. The deactivation of the cathode material is caused by several electrochemical degradation mechanisms. Ni in a highly delithiated state 4+Surface transformations such as the reduction of [[ID=]] and oxygen loss, the formation of NiO-like phases, and the rearrangement of transition metals destabilize the crystal structure. These phase transitions have been associated with initial cracks appearing on the surface of cathode particles and subsequent particle disintegration. Furthermore, the electrolyte decomposes at the reactive surface of NMC, and the electrolyte decomposition products deposit at the interface of the cathode material, which leads to an increase in resistance. Additionally, the conductive salt LiPF6 commonly used in liquid electrolytes reacts with trace amounts of H2O present in all commercial formulations to form HF. This highly reactive compound causes lattice strain in the cathode material by dissolving transition metal ions from the surface of the cathode material into the electrolyte. All of these degradation mechanisms result in a decrease in capacity, performance, and cycle life.

[0005] It is known that coating mixed lithium transition metal oxide particles with several metal oxides can suppress the undesirable reaction between the electrolyte and the electrode material, and thus improve the long-term stability of lithium-ion batteries.

[0006] International Patent Application No. 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. These particles 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, then filtering off the coated particles, drying, and firing.

[0007] It is known to coat the cathode material of lithium-ion batteries with metal oxides such as Al2O3, TiO2, ZrO2, and MgO to improve cycle performance.

[0008] Chinese Patent No. 112194196 describes a composite coating agent prepared from at least one of metal and / or non-metal oxides and ammonium salts. It is stated that the metal oxide is 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 process of ball milling, jet milling, calcination, wet mixing and spray drying. The composite coating agent is stated to form a uniform coating on the surface of single crystal materials and can improve the cycle performance and safety of the materials.

[0009] Chinese Patent No. 110165205 describes a cathode material comprising a lithium metal oxide substrate, a first coating layer (metal N oxide, where N is Al, Zr, Mg, Ti, Co, Y, Ba, Cd), and a second coating layer (N' oxide, where N' is B, Sn, S, P). The described method includes adding metal N oxide nanoparticles to deionized water, stirring, ultrasonic dispersing, adding the cathode material substrate, 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 No. 108172810 describes a method for preparing a lithium nickel manganese oxide cathode material coated with nanoparticles. This patent describes preparing composite MgO nanoparticles, adding Et 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] Examples of the use of MgO in cathode materials are provided in the following papers. "Mesoporous carbon material as cathode for high performance lithium-ion capacitor" by Zhang et al., Chinese Chemical Letters (2018), 29(4) 620-623, CODEN CCLEE7; ISSN: 1001-8417. Mg citrate was used as a precursor of mesoporous carbon, and nano-sized MgO particles were used as a template provided by Mg citrate.

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

[0013] "Improvement of cycling performance of lithium-sulfur batteries 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] "Surface modification of positive electrode materials for lithium-ion batteries" in "Thin Solid Films (2014), 572, 200 - 207 CODEN: THSFAP; ISSN: 0040 - 6090" by C.M. et al. describes various types of surface treatments for cathode material particles of 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 MgO-coated LiCoO2 annealed at various temperatures from 750 to 810 °C to find the optimal annealing temperature.

[0016] Chinese Patent No. 111 354 936 discloses a cathode material based on lithium oxide coated with nanosized magnesium oxide.

[0017] In the paper "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 to understand the improvement of the electrochemical performance of commercially available LiCoO2 cathode materials modified with nanometer-sized magnesium oxide.

Prior Art Documents

Patent Documents

[0018]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Non-Patent Documents

[0019]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Problems to be Solved by the Invention

[0020] Although nano-sized MgO particles have been used as an additive in lithium-ion batteries, their effectiveness in improving cycle stability has been limited by poor dispersibility. Practical methods for improving the long life of batteries are often limited. Therefore, in the case of magnesium oxide, the use of commercially available nano-sized MgO particles often results in non-uniform distribution and large agglomerates of MgO particles on the surface of the core cathode material, and as a result, minimal improvement in cycle performance or no improvement in cycle performance is observed compared to the uncoated cathode material.

[0021] The problem addressed by the present invention is to provide a modified mixed lithium transition metal oxide as a cathode material for use in lithium-ion batteries, particularly for high-nickel NMC (nickel, magnesium, cobalt) types. Such a modified cathode material provides higher cycle stability than the unmodified material.

[0022] During the thorough experimental process, surprisingly, it was found that nanostructured MgO produced by firing can be successfully used to coat the cathode material using a dry mixing process for coating the cathode material with a metal oxide. Surprisingly, it was also found that further surface modification of the nanostructured metal oxide produced by firing before dry mixing can significantly further improve the coating coverage and uniformity.

[0023] The present invention provides a method for manufacturing a coated active cathode material, the coated active cathode material, and the use of the coated active cathode material in a lithium-ion battery. The lithium-ion battery of the present invention can be used in electronic devices and electrical devices including, for example, mobile phones, computers (laptop computers, desktop computers, computer pads), electronic watches, key fobs, electric appliances, power tools, vacuum cleaners, electric lawn mowers, and electric vehicles.

Means for Solving the Problems

[0024] According to a first aspect of the present invention, there is provided a method for manufacturing a coated active cathode material, which is preferably a coated mixed lithium transition metal oxide. This method is obtained by subjecting a coated cathode material, which is preferably an active cathode material that is a mixed lithium transition metal oxide, and a nanoscale magnesium oxide produced by calcination to dry mixing in a mixing unit under shear conditions. The coated active cathode material, which is preferably a mixed lithium transition metal oxide, is in the form of particles, and the magnesium oxide has a BET surface area (DIN 9277:2014) of 5 to 300 m 2 / g, 5 wt% of said particles and 95 wt% of a mixture consisting of an aqueous solution of 0.5 g / L of sodium pyrophosphate, having an average aggregate diameter d of 5 to 150 nm as determined by static light scattering (SLS) after 60 seconds of ultrasonic treatment at 25°C. 50 It is characterized by having a unimodal and narrow particle size distribution.

[0025] The MgO produced by calcination is hydrophilic. Preferably, in one embodiment, the MgO produced by calcination is subjected to surface modification so as to be hydrophobic.

[0026] In one embodiment, the mixing unit has a specific power of 0.05 to 1.5 kW per kg of the mixed cathode material.

[0027] The coated active cathode material, which is preferably a coated mixed lithium transition metal oxide, is in the form of particles, and magnesium oxide has a BET surface area of 5 to 300 m 2 / g, 5 wt% of said particles and 95 wt% of a mixture consisting of an aqueous solution of 0.5 g / L of sodium pyrophosphate, when determined by static light scattering (SLS) for 60 seconds at 25°C, has an average aggregate diameter d of 5 to 150 nm, more preferably 10 to 120 nm, even more preferably 20 to 100 nm 50 and has a unimodal and narrow particle size distribution.

[0028] SEM-EDX mapping of the coated active cathode material provides a complete and uniform coating of MgO around all cathode particles, and there are no or very few larger magnesium oxide bulk compositions present.

[0029] In one embodiment, the method is characterized in that the specific power of the mixing unit is 0.1 to 1000 kW, 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 to 30 m / s.

[0030] The span (d 90 -d 10 ) / d 50 of the particles of magnesium oxide and / or mixed oxides containing magnesium is 0.4 to 1.2 when determined by static light scattering (SLS) after ultrasonic treatment for 60 seconds at 25°C of a mixture consisting of 5 wt% of said particles and 95 wt% of an aqueous solution of 0.5 g / L of sodium pyrophosphate.

[0031] The active cathode material may comprise 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.

[0032] Magnesium oxide nanostructures made by the flame process have both a unimodal and narrow particle size distribution and excellent dispersibility during the dry coating process of cathode materials. These particles provide excellent interaction and proper adhesion to the cathode active material.

[0033] Furthermore, additional surface modification of these particles results in further improvement of the interaction with and adhesion to the cathode active material. This leads to complete de-agglomeration of the magnesium oxide bulk composition and ultimately provides cathode active material particles completely and uniformly covered by flame-combusted, nanostructured, surface-modified magnesium oxide.

[0034] By using a high-strength dry coating process in combination with calcined nanostructured MgO particles, the method of the present invention has been found to provide significantly improved dispersibility and uniform coating of the MgO particles. During dry mixing, the applied shear force (mixing) decomposes the MgO bulk composition into extremely small aggregates, which have a very high tendency to settle on the surface of the cathode active material particle powder, resulting in excellent interaction and adhesion, which in turn provides a uniform coating. In contrast, conventional MgO particles that are not produced by calcination and are not nanostructured are composed of isolated spherical particles (which are the result of milling coarser MgO particles) and do not exhibit such behavior.

[0035] These and other features and advantages of the present invention will be better understood from the following detailed description in conjunction with the following drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036]

Fig. 1a

[0037]

Fig. 1b

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Fig. 2a

Fig. 2b

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Fig. 2c

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Fig. 3

[0041] According to a first aspect of the present invention, there is provided a method for manufacturing encapsulated cathode active material particles, in which lithium mixed oxide particles, preferably mixed lithium transition metal oxides, and nanostructured, surface-modified magnesium oxide burned by a flame are dry-mixed under shear conditions. A second aspect of the present invention relates to a cathode material coated with magnesium oxide burned by a flame, and a third aspect of the present invention relates to a battery cell containing these encapsulated lithium mixed oxide particles.

[0042] Method for manufacturing a coated lithium transition metal oxide

[0043] According to a first aspect of the present invention, there is provided a method for manufacturing a coated mixed lithium transition metal oxide, wherein the mixed lithium transition metal oxide and the nanofabricated magnesium oxide produced by calcination are subjected to dry mixing under shear conditions.

[0044] The nanofabricated magnesium oxide burned by flame is preferably surface-modified to be hydrophobic before dry mixing.

[0045] The dry mixing can be carried out, for example, in a mixing unit having a specific power of 0.05 to 1.5 kW per 1 kg of the mixed lithium transition metal oxide. Dry mixing is understood to mean that no liquid is added or used during the mixing process, that is, for example, substantially dry powders are mixed together. However, it is possible that trace amounts of moisture or something other than liquid water are present in the raw materials to be mixed, or that they contain water of crystallization.

[0046] If the specific power used is less than 0.05 kW per 1 kg of the mixed lithium transition metal oxide, this may give a non-uniform distribution of magnesium oxide over the lithium transition metal oxide, and the magnesium oxide may not be firmly bonded to the core material of the lithium transition metal oxide. A specific power exceeding 1.5 kW per 1 kg of the mixed lithium transition metal oxide results in poorer electrochemical properties. Furthermore, there is a risk that the coating becomes brittle and is prone to breakage. The nominal power of the mixing unit can vary over a wide range, for example, from 0.1 kW to 1000 kW. Therefore, it is possible to use a laboratory-scale mixing unit having a nominal power of 0.1 kW to 5 kW, or a production-scale mixing unit having a nominal power of 10 kW to 1000 kW. The nominal power is the maximum absolute power on the nameplate of the mixing unit.

[0047] The volume of the mixing unit can vary over a wide range. For example, the volume of the mixing unit is 0.1 L to 2.5 m 3It can be in the range of. For example, a laboratory-scale mixing unit can have a volume of 0.1 to 10 L, or a production-scale mixing unit can have a volume of 0.1 to 2.5 m 3 It can have a volume of.

[0048] Preferably, in the method according to the present invention, a forced action mixer is used in the form of an intensive mixer equipped with a high-speed mixing tool. It has been found that a mixing tool speed of 5 to 30 m / s, more preferably 10 to 25 m / s, gives the best results. Examples of commercially available mixing units suitable for the method of the present invention include Henschel mixers and Eirich mixers. The Eirich mixer can be, for example, a high-intensity Eirich mixer.

[0049] The mixing time can vary and can preferably be 0.1 to 120 minutes, more preferably 0.2 to 60 minutes, and most preferably 0.5 to 10 minutes.

[0050] After mixing, the mixture can be heat-treated to improve the binding of the coating to the mixed lithium transition metal oxide particles. However, in the method according to the present invention, since the nanostructured, surface-modified magnesium oxide produced by calcination adheres to the mixed lithium transition metal oxide with sufficient firmness, this treatment is optional in the method according to the present invention. A preferred embodiment of the method according to the present invention may not include a heat treatment after mixing.

[0051] The best results regarding the adhesion of magnesium oxide to the mixed lithium transition metal oxide are obtained when the magnesium oxide has a BET surface area of 5 m 2 / g to 300 m 2 / g, more preferably 10 m 2 / g to 200 m 2 / g, and most preferably 15 to 150 m 2 / g. The BET surface area can be determined in accordance with DIN 9277:2014 by nitrogen adsorption according to the Brunauer-Emmett-Teller procedure.

[0052] Pyrogenically produced MgO In the process according to the invention, the magnesium oxide used is produced pyrogenically, i.e. by a pyrogenic process, also called the "flame combustion" process. Such a "pyrogenic" or "flame combustion" process involves the reaction of the corresponding metal precursor in flame hydrolysis or flame oxidation in an oxyhydrogen flame to form the metal oxide.

[0053] The hydrophilic magnesium oxide prepared pyrogenically is characterized as follows: Surface area [m 2 / g] 50 - 350 Tamped density [g / L] 20 - 100 Loss on drying [%] less than 5 Loss on ignition [%] 0.1 - 20

[0054] The terms "pyrogenically produced or prepared", "pyrogenic" and "fumed" are used interchangeably in the context of the present invention. Fumed magnesium oxide can be prepared by flame hydrolysis or flame oxidation, which generally involves oxidizing or hydrolyzing a hydrolyzable or oxidizable starting material in a hydrogen / oxygen flame. Starting materials typically used in the pyrogenic process include organic or inorganic substances such as metal chlorides.

[0055] Thus, the hydrophilic magnesium oxide according to the invention can be prepared by flame spray pyrolysis, in which at least one solution of a metal precursor containing a magnesium salt and a solvent such as ethanol, methanol or water is subjected to flame spray pyrolysis.

[0056] During the flame spray pyrolysis process, a solution of the metal compound (metal precursor) in the form of fine droplets is typically introduced into the flame formed by the ignition of a fuel gas and an oxygen-containing gas, and the metal precursor used is oxidized and / or hydrolyzed to give the corresponding magnesium oxide. This reaction initially forms highly dispersed, nearly spherical primary particles, which combine during further reaction steps to form aggregates. Subsequently, the aggregates can stack to form agglomerates. In contrast to agglomerates, which can be relatively easily separated into aggregates by the introduction of energy in principle, aggregates can only be further decomposed by the intensive introduction of energy, even if they may decompose. The metal oxide powder can be partially broken down by appropriate grinding and converted into particles in the nanometer (nm) range, which is advantageous for the present invention. The resulting aggregated compound can be referred to as "magnesium oxide burned in a flame" or "manufactured by calcination."

[0057] The flame spray pyrolysis process is generally described in WO 2015173114 and elsewhere.

[0058] The flame spray pyrolysis process of the present invention preferably comprises the following steps. a) Atomizing a solution of a metal precursor to obtain an aerosol with an atomizing gas b) Reacting the aerosol with a flame obtained by ignition of a mixture of a fuel gas and an oxygen-containing gas in the reaction space of a reactor to obtain a reaction stream c) Cooling the reaction stream, and d) Subsequently removing solid magnesium oxide from the reaction stream.

[0059] Examples of metal precursors used in the method of the present invention include magnesium salts such as magnesium chloride, magnesium nitrate, or magnesium acetate.

[0060] The solvent for this solution can be any typical solvent such as water, ethanol, methanol, etc.

[0061] The amount of the metal precursor in the solution can range from 5 to 80% by weight, preferably from 20 to 70% by weight, based on the total weight of the solution.

[0062] Examples of the fuel gas are hydrogen, methane, ethane, natural gas and / or carbon monoxide. It is particularly preferred to use hydrogen.

[0063] The oxygen-containing gas is generally air or oxygen-enriched air. The oxygen-containing gas is particularly used, for example, for embodiments where a high BET surface area of the magnesium oxide produced is desired. The total amount of oxygen is generally selected to be sufficient for at least complete conversion of the fuel gas and the metal precursor.

[0064] To obtain an aerosol, the vaporization solution containing the metal precursor can be mixed with an atomizing gas such as nitrogen, air, and / or other gases. The resulting fine droplets of the aerosol preferably have an average droplet size of 1 to 120 μm, particularly preferably 30 to 100 μm. The droplets are typically produced using a nozzle of single or multiple materials. The solution may be heated to increase the solubility of the metal precursor and obtain a viscosity suitable for atomization of the solution.

[0065] The particle size of magnesium oxide can be varied by reaction conditions such as, for example, the flame temperature, the ratio of hydrogen or oxygen, the amount of magnesium salt, the residence time in the flame, or the length of the coagulation zone.

[0066] The metal oxide precursor used can be dissolved in water or an organic solvent and 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.

[0067] Thus, the calcined, nanostructured, preferably surface-modified magnesium oxide used in the process according to the invention is, when determined by transmission electron microscopy (TEM), preferably in the form of aggregated primary particles having a number-average aggregate diameter of 5 to 150 nm, more preferably 10 to 120 nm, even more preferably 20 to 100 nm. This numerical average diameter can be determined by calculating the average size of at least 500 particles analyzed by TEM.

[0068] The average diameter of the agglomerates is usually 1 to 2 μm. These average numerical values can be determined by static light scattering (SLS) method in a suitable dispersion, for example, an aqueous dispersion. The agglomerates and some aggregates can be broken, for example, by crushing or sonication of the particles, resulting in particles with smaller particle sizes.

[0069] The average aggregate diameter d of the metal oxide 50 is 5 to 150 nm, more preferably 10 to 120 nm, even more preferably 20 to 100 nm when determined by static light scattering (SLS) after 60 seconds of sonication at 25 °C of a mixture consisting of 5 wt% particles and 95 wt% of a 0.5 g / L aqueous solution of sodium pyrophosphate.

[0070] Thus, the calcined, nanostructured, preferably surface-modified magnesium oxide used in the method of the invention is preferably characterized by high dispersibility, i.e., the ability to form relatively small particles under gentle sonication. Dispersion under such gentle conditions is thought to correlate with the conditions during the dry coating process. That is, the agglomerates of magnesium oxide are broken in the mixing process of the invention in the same way as under sonication, and a uniform coating of the cathode active material particles can be formed. The span (d 90 -d 10 ) / d 50is preferably 0.4 to 1.2, more preferably 0.5 to 1.1, and even more preferably 0.6 to 1.0 when determined by static light scattering (SLS) after 60 seconds of ultrasonic treatment at 25 °C of a mixture consisting of 5% by weight of said particles and 95% by weight of an aqueous solution of 0.5 g / L of sodium pyrophosphate.

[0071] Therefore, the sintered, nanostructured, surface-modified magnesium oxide used in the method of the present invention is preferably characterized by a relatively narrow particle size distribution. This helps to achieve a high-quality magnesium oxide coating on the surface of the transition metal oxide.

[0072] The d values d 10 , d 50 and d 90 are generally used to characterize the cumulative particle size distribution of a given sample. For example, the d 10 diameter is the diameter at which 10% of the volume of the sample consists of particles smaller than d 10 particles, and d 50 is the diameter at which 50% of the volume of the sample consists of particles smaller than d 50 particles. d 50 is also known as the "volume median diameter" because it divides the sample into equal volumes, and d 90 is the diameter at which 90% of the volume of the sample consists of particles smaller than d 90 particles.

[0073] Surface treatment of sintered MgO.

[0074] MgO produced by sintering is hydrophilic in its natural state because it is covered with hydroxyl (-OH) groups. Through surface modification of sintered MgO, hydrophobic MgO can also be produced. For example, hydrophobization of MgO can be achieved by reacting hydroxyl groups with silane to form -O-Si-R groups. Therefore, preferably, MgO is surface-modified, which means that the surface of MgO is at least partially covered with silane.

[0075] MgO produced by calcination can be used in its hydrophilic form and hydrophobic form. The use of hydrophilic MgO does not require any further treatment after synthesis by the calcination process. However, after synthesis by the calcination process, MgO particles can be made hydrophobic by further treatment with a hydrophobic reagent such as silane. For example, in one embodiment, octylsilane is covalently bonded to the surface of the MgO particles. Both the hydrophilic form and the hydrophobic form of the flame-combusted nanostructured MgO can be effectively used as coatings using the process of the present invention via dry mixing with a substrate active cathode material. Flame-combusted, nanostructured, surface-modified MgO is preferred because it shows a more uniform coating of the substrate active cathode material.

[0076] In one embodiment, a surface-modified magnesium oxide prepared by calcination is produced, which is characterized by: Surface area [m 2 / g] 50 - 350 Tap density [g / L] 20 - 100 Loss on drying [%] less than 5 Loss on ignition [%] 0.1 - 20

[0077] Accordingly, the calcination-prepared magnesium oxide is sprayed with a surface modifier at room temperature, and then the mixture is heat-treated at a temperature of 50 - 300 °C, preferably 80 - 180 °C, for 0.5 - 3 hours ("h").

[0078] In another embodiment, the surface modification of the calcination-prepared magnesium oxide can be carried out by treating the calcined magnesium oxide with a surface modifier in vapor form and then thermally treating the mixture at a temperature of 50 - 800 °C for 0.5 - 6 hours.

[0079] An alternative method for the surface modification of the calcination-prepared magnesium oxide can be carried out by treating the calcined magnesium oxide with a surface modifier in vapor form and then thermally treating the mixture at a temperature of 50 - 800 °C for 0.5 - 6 hours.

[0080] The heat treatment can be carried out under a protective gas such as nitrogen, for example. The surface treatment can be carried out either continuously or batchwise in a dryer equipped with a heatable mixer and a spraying device. Suitable devices can be, for example, a plowshare mixer or plate, a cyclone, or a fluidized bed dryer.

[0081] The present invention has the advantage that magnesium oxide can be modified according to the desired properties and intended purposes, thereby using commercially available silanes to individually adapt the properties of magnesium oxide.

[0082] As the surface modifier, the following compounds and mixtures of the following compounds can be used. a) (RO)3Si(C n H 2n+1 ) and (RO)3Si(C n H 2n-1 ) type organosilanes, where R = alkyl, for example, methyl, ethyl, n-propyl, i-propyl, butyl and n = 1 to 20, etc. b) R’ x (RO) y Si(CnH 2n+1 ) and R’x(RO) y Si(C n H 2n-1 ) type organosilanes, where R = alkyl, for example, methyl-, ethyl-, n-propyl-, i-propyl-, butyl-, etc. R’ = alkyl, for example, methyl, ethyl, n-propyl, i-propyl, butyl, etc. R’ = cycloalkyl n = 1 to 20 x + y = 3 x = 1, 2, and y = 1, 2 c) X3Si(C n H 2n+1 ) and X3Si(C n H 2n-1 ) type halogen organosilanes, where X = Cl, Br n = 1 - 20 d) X2(R’)Si(C n H 2n+1 ) and X2(R’)Si(C n H 2n-1 ) type of halogen organosilane, where X = Cl, Br R’ = alkyl, for example, methyl, ethyl, n - propyl, i - propyl, butyl, etc. R’ = cycloalkyl n = 1 - 20 e) X(R’)2Si(C n H 2n+1 ) and X(R’)2Si(C n H 2n-1 ) type of halogen organosilane, where X = Cl, Br R’ = alkyl, for example, methyl, ethyl, n - propyl, i - propyl, butyl, etc. R’ = cycloalkyl n = 1 - 20 f) (RO)3Si(CH2) m - R’ type of organosilane R = alkyl, for example methyl, ethyl, propyl m = 0.1 - 20 R’ = methyl -, aryl (for example, - 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 R’ = alkyl, aryl; R’’ = H, alkyl, aryl; R’’’ = H, alkyl, aryl, benzyl, C2H4NR’’’’R’’’’’, where R’’’’ = H, alkyl and R’’’’’ = H, alkyl g)(R’’) x (RO) y Organosilane of the Si(CH2)m-R’ type R’’ = alkyl x + y = 2 R = cycloalkyl x = 1.2 y = 1.2 m = 0.1 - 20 R’ = methyl-, aryl (e.g., -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 R’ = alkyl, aryl; R’’ = H, alkyl, aryl; R’’’ = H, alkyl, aryl, benzyl, C2H4NR’’’’R’’’’’, where R’’’’ = H, alkyl and R’’’’’ = H, alkyl h) Halogen organosilane of the X3Si(CH2)m-R’ type X = Cl, Br m = 0.1 - 20 R’ = methyl-, aryl (e.g., -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 i) A halogenated organosilane of the (R)X2Si(CH2)m-R' type X = Cl, Br R = alkyl, such as methyl, ethyl, propyl m = 0.1 - 20 R' = methyl-, aryl (e.g., -C6H5, a 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, j) A halogenated organosilane of the (R)2XSi(CH2)m-R' type X = Cl, Br R = alkyl m = 0.1 - 20 R' = methyl-, aryl (e.g., -C6H5, a 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

[0083] Preferably, as the surface modifier, the following silanes: dimethyldichlorosilane, octyltrimethoxysilane, octyltriethoxysilane (oxtyltriethoxysilane), hexamethyldisilazane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, dimethylpolysiloxane, glycidyloxypropyltrimethoxysilane, glycidyloxypropyltriethoxysilane, nanofluorohexyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane, aminopropyltriethoxysilane are used individually or as a mixture. Particularly preferably, octyltrimethoxysilane and octyltriethoxysilane can be used.

[0084] Hydrophobic MgO is also produced through the surface modification of MgO produced by calcination. MgO produced by calcination can be used in its hydrophilic form and hydrophobic form. The use of hydrophilic MgO does not require any further treatment with a hydrophobic reagent such as silane after the synthesis of hydrophilic MgO by the calcination process. However, after the synthesis of hydrophilic MgO by the calcination process, by further treating with a hydrophobic reagent such as silane, the MgO particles can become hydrophobic. Both the hydrophilic form and the hydrophobic form of the nanostructured MgO burned in a flame can be effectively used as a coating using the process of the present invention through dry mixing with a substrate active cathode material. The nanostructured, surface-modified MgO burned in a flame is preferred because it shows a more uniform coating of the substrate active cathode material.

[0085] MgO particles produced via a firing process usually have a purity of at least 96 wt%, preferably at least 98 wt%, more preferably at least 99 wt%. The magnesium oxide used in the method of the present invention preferably contains elements Cd, Ce, Fe, Na, Nb, P at a ratio of less than 10 ppm and elements Ba, Bi, Cr, K, Mn, Sb at a ratio of less than 5 ppm, and the total of the ratios of all these elements is less than 100 ppm. The ratio of carbon in the hydrophilic, non-surface-modified metal oxide is preferably less than 0.2 wt%, more preferably 0.005 wt% - 0.2 wt%, even more preferably 0.01 wt% - 0.1 wt% based on the mass of the metal oxide powder.

[0086] Active cathode material The term "transition metal" in the context of 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.

[0087] The mixed lithium transition metal oxide preferably used in the method according to the present 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.

[0088] The mixed lithium transition metal oxide preferably has the general formula LiMO2, where M is at least one transition metal selected from nickel, cobalt, manganese, and more preferably, M = Co or Ni x Mn y Co z and where 0.3 ≦ x ≦ 0.9, 0 ≦ y ≦ 0.45, 0 ≦ z ≦ 0.4, and most preferably, M is Ni x Mn y Co zwhere 0.3 ≦ x ≦ 0.9, 0 ≦ y ≦ 0.45, and 0 ≦ z ≦ 0.4.

[0089] The mixed lithium transition metal oxide of the general formula LiMO₂ can be further doped with at least one other metal oxide, particularly aluminum oxide and / or magnesium oxide.

[0090] The coated mixed lithium transition metal oxide preferably has a number average particle size of 2 to 20 μm. The number average particle size can be determined according to ISO 13320:2009 by laser diffraction particle size analysis.

[0091] The proportion of magnesium oxide in the coated mixed lithium transition metal oxide is preferably 0.05% by weight to 5% by weight, more preferably 0.1% by weight to 2% by weight, based on the total weight of the coated mixed lithium transition metal oxide. When the proportion of magnesium oxide is less than 0.05% by weight, the beneficial effect of the coating usually cannot yet be observed. When it exceeds 5% by weight, the beneficial effect of the additional amount of magnesium coating exceeding 5% by weight is usually not observed.

[0092] The coated mixed lithium transition metal oxide preferably has a coating layer thickness of 10 to 200 nm when determined by TEM analysis.

[0093] The present invention further provides a coated mixed lithium transition metal oxide obtainable by the method according to the present invention. The present invention further provides a coated mixed lithium transition metal oxide containing a nanostructured, surface-modified magnesium oxide coating produced by firing on the surface of the mixed lithium transition metal oxide.

[0094] A further preferred feature of the coated mixed lithium transition metal oxide, i.e., the nanostructured, surface-modified magnesium oxide produced by firing as described above in a preferred embodiment of the method according to the invention, is a preferred feature of the coated mixed lithium transition metal oxide according to the invention, whether produced by the method according to the invention or not, and also of the nanostructured, surface-modified magnesium oxide produced by firing.

[0095] The present invention further provides an active cathode material for a lithium-ion battery comprising a coated mixed lithium transition metal oxide according to the invention or a coated mixed lithium transition metal oxide obtainable by the method according to the invention.

[0096] The positive electrode, i.e., the cathode, of a lithium-ion battery includes a current collector and an active cathode material layer formed above or on the current collector. The current collector may be an aluminum foil, a copper foil, a nickel foil, a stainless-steel foil, a titanium foil, a polymer substrate coated with a conductive metal, or a combination thereof.

[0097] The active cathode material coated with MgO produced by firing, which is nanostructured and preferably surface-modified, may include any suitable material capable of reversible intercalation / deintercalation of lithium ions. Such materials are well known in the art. Such active cathode materials may include, for example, transition metal oxides such as mixed oxides containing Ni, Co, Mn, V, or other transition metals and optionally lithium. Mixed lithium transition metal oxides containing nickel, manganese, and cobalt (NMC) are particularly preferred.

[0098] The present invention also provides a lithium-ion battery comprising a coated mixed lithium transition metal oxide or a coated mixed lithium transition metal oxide obtainable by the method according to the invention.

[0099] Apart from the cathode, the lithium-ion battery of the present invention may also include an anode, optionally a separator, and an electrolyte containing a lithium salt or a lithium compound.

[0100] The anode of the lithium-ion battery may include any suitable material commonly used in secondary lithium-ion batteries that can reversibly intercalate / deintercalate lithium ions. Typical examples thereof include crystalline carbon such as natural or artificial graphite in the form of plate-like, flaky, spherical or fibrous types; amorphous carbon such as soft carbon, hard carbon, mesophase pitch carbide, calcined coke, or carbonaceous materials containing mixtures thereof. Furthermore, lithium metal or conversion materials (e.g., Si or Sn), silicon oxide, and mixtures or composites of silicon, silicon oxide, and carbon can be used as anode active materials.

[0101] The electrolyte of the lithium-ion battery can be in the form of a liquid, gel, or solid. The liquid electrolyte of the lithium-ion battery may include any suitable organic solvent commonly used in lithium-ion batteries, such as anhydrous ethylene carbonate (EC), dimethyl carbonate (DMC), propylene carbonate, methyl ethyl carbonate, diethyl carbonate, gamma-butyrolactone, dimethoxyethane, fluoroethylene carbonate, vinylethylene carbonate, and mixtures thereof.

[0102] The gel electrolyte contains a gelling polymer. Any suitable gelling polymer can be used.

[0103] The solid electrolyte of the lithium-ion battery may include oxides, such as lithium metal oxides, sulfides, phosphates, or solid polymers.

[0104] The electrolyte of the lithium-ion battery can contain a lithium salt. Examples of such lithium salts include lithium hexafluorophosphate (LiPF6), lithium bis 2-(trifluoromethylsulfonyl)imide (LiTFSI), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), Li2SiF6, lithium triflate, LiN(SO2CF2CF3)2, and mixtures thereof.

[0105] The present invention further provides for the use of a coated mixed lithium transition metal oxide in the active cathode material of a lithium-ion battery.

[0106] Even without further explanation, it is assumed that those skilled in the art can make full use of the above description. Therefore, the preferred embodiments and examples should be understood only as illustrative and should in no way be construed as limiting.

[0107] Hereinafter, the present invention will be described in more detail using examples. Alternative embodiments of the present invention are available in a similar manner.

Examples

[0108] Determination of Data on Physicochemical Characteristics

[0109] In the context of the present invention, the following measurement methods were used to evaluate the properties of different materials.

[0110] A) BET surface area: The BET surface area is determined using nitrogen in accordance with DIN 9277:2014.

[0111] B) Tap density: Determination of tap density with a modification of DIN ISO 787 / XI, Basis for tap density determination: The bulk density (formerly the bulk volume) is equal to the quotient of the mass and volume of the powder after tamping in a tamping volume meter under predetermined conditions. According to DIN ISO 787 / XI, the bulk density is given in g / cm 3 However, since the bulk density of the oxide is extremely low, the value is given in g / L by the inventors. Furthermore, drying, sieving, and repetition of the tamping operation are not performed.

[0112] Apparatus for determining bulk density: Tamping volume meter Graduated cylinder Laboratory scale (reading up to 0.01 g)

[0113] To determine the bulk density: Fill the graduated cylinder of the tamping volume meter with 200 ± 10 mL of the oxide so that no pores remain and the surface is horizontal. The mass of the filled sample is determined to be exactly 0.01 g. Place the graduated cylinder containing the sample in the graduated cylinder holder of the tamping volume meter and tamp 1250 times. Read the volume of the tamped oxide exactly once. Evaluation of bulk density determination

[0114]

Number

[0115] C) pH value: The pH value is determined in a 4% aqueous dispersion of the hydrophobic oxide in water:methanol (1:1). Reagents for pH value determination: Distilled water or completely deionized water, pH > 5.5 Methanol, p.a. Buffer solution pH 7.00 pH 4.66 Apparatus for pH value determination: Laboratory scale, (reading up to 0.1 g) Glass beaker, 250 mL Magnetic stirrer Magnetic bar, 4 cm in length Combined pH electrode pH measuring device Dispenser, 100 mL

[0116] Procedure for determining the pH value: The determination is carried out in accordance with the modification of DIN / ISO 787 / IX: Calibration: Before determining the pH value, calibrate the measuring device with a buffer solution. If several measurements are carried out continuously, a single calibration is sufficient. Using a dispenser, stir 4 g of hydrophilic oxide into a paste in a 250 mL glass beaker containing 96 g (96 mL) of water, and stir with a magnetic stirrer for 5 minutes (rpm about 1000 min -1 ) while immersing the pH electrode. Stir 4 g of hydrophobic oxide into a paste in a 250 mL glass beaker containing 48 g (61 mL) of methanol, dilute the suspension with 48 g (48 mL) of water, and stir with a magnetic stirrer for 5 minutes (rpm about 1000 min-1) while immersing the pH electrode. After switching off the stirrer, read the pH after a standing time of 1 minute. The result is given to within the first decimal place.

[0117] D) Loss on drying Instead of the weighed amount of 10 g mentioned in DIN ISO 787 II, a weighed amount of 1 g is used for the determination of loss on drying. Before cooling, place the cover in place. A second drying is not carried out. Weigh exactly 0.1 mg of approximately 1 g of sample into a weighing dish equipped with a ground cover dried at 105 °C, avoiding the formation of dust, and dry at 105 °C in a drying cabinet for 2 hours. After cooling in a desiccator with the cover on, reweigh the sample under blue gel.

[0118]

Number

[0119] E) Loss on Ignition Apparatus for determining loss on ignition: Porcelain crucible with crucible cover Muffle furnace Analytical balance (reading up to 0.1 mg) Desiccator Carrying out loss on ignition: Deviating from DIN 55 921, accurately weigh 0.3 - 1 g of non-dried substance to 0.1 mg in a porcelain crucible with a crucible cover that has been pre-heated to red heat, and heat it to red heat in a muffle furnace at 1000 °C for 2 hours. The formation of dust should be carefully avoided. It has been found advantageous to place the weighed sample in the muffle furnace while the muffle furnace is still at a low temperature. The slow heating of the furnace prevents the generation of stronger air turbulence inside the porcelain crucible. After reaching 1000 °C, continue heating at red heat for an additional 2 hours. Subsequently, place the crucible cover in a predetermined position and determine the weight loss of the crucible on blue gel in a desiccator.

[0120] Evaluation of the determination of loss on ignition The loss on ignition is determined for a sample dried at 105 °C for 2 hours, so the following calculation formula is obtained.

[0121]

Equation

[0122] F) Carbon content The carbon content is determined by elemental analysis using a LECO C744 apparatus. The measurement principle is based on oxidizing the carbon in the sample to CO2, which is then quantified by an infrared detector.

[0123] G) SEM measurement

[0124] Using SEM, energy-dispersive X-ray spectroscopy (EDX) was performed. For EDX mapping, a representative area of the sample was used at a magnification of 1000 times, and the image width was 2048×1536 pixels (120μm×90.1μm), resulting in a pixel resolution of 0.059μm. Mapping was recorded at an acceleration voltage of 20 kV. Following the measurement, the elemental composition of the sample was determined using the mapping sum spectrum. The threshold value for image analysis was adjusted according to the semi-quantitative mass% values of each element.

[0125] Preparation of magnesium oxide:

[0126] Example 1: Preparation of calcined magnesium oxide 1.89 kilograms of an aqueous solution containing 1000 g of Mg(CH3COO)2·4H2O was prepared. Through a two-component nozzle, an aerosol of this dispersion at 2.5 kg / h and air at 15 Nm 3 / h was formed and sprayed into a tubular reactor together with a combustion flame. The combustion gas of the flame consisted of 8 Nm 3 / h of hydrogen and 30 Nm 3 / h of air. Additionally, 25 Nm 3 / h of secondary air was used. After the reactor, the reaction gas was cooled and filtered.

[0127] The particle characteristics are shown in Table 1, and the TEM image of the particles is shown in Figure 1. XRD analysis (Figure 2) showed that the main phase of the product is cubic magnesium oxide.

[0128] The hydrophilic magnesium oxide prepared by firing to form a high surface area has the data of the physicochemical characteristics shown in Table 1.

[0129] Example 2: Preparation of surface-modified magnesium oxide Put 300 g of the fired-prepared magnesium oxide (Example 1) into a mixer and spray 72 g of octyltrimethoxysilane. After the spraying of the silane onto the powder is completed, the mixing is continued for another 5 minutes. Then, the wet powder is calcined in an oven at 130 °C for 3 hours. The surface-modified magnesium oxide formed has the data of the physicochemical characteristics shown in Table 1.

[0130] The hydrophilic surface-modified magnesium oxide has the data of the physicochemical characteristics shown in Table 1.

[0131]

Table 1

[0132] Starting materials: Dry coating additives: The materials described above in Examples 1 and 2, namely, the magnesium oxide burned in the flame of Example 1 with a BET surface area of 250 m 2 / g and the hydrophobic magnesium oxide burned in the flame of Example 2 with a BET surface area of 230 m 2 / g were used. By subjecting the hydrophobic magnesium oxide burned in the flame of Example 2 to a hydrophobization treatment after the firing formation process as described above, the hydrophobic magnesium oxide burned in the flame of Example 2 was made hydrophobic. Magnesium oxide that was not burned in the flame and had a BET surface area of 65 m 2 / g, purchased from Sigma-Aldrich in Germany, was also used as a comparative example. The magnesium oxide that was not burned in the flame is not nanostructured and is a pulverized material with isolated non-aggregated particles.

[0133] Cathode active material: commercially available mixed lithium nickel manganese cobalt oxide powder NMC 7 1.5 1.5 powder (PLB-H7 type) supplied by Linyi Gelon LIB Co., having a BET surface area of 0.5 m 2 / g and a median particle size d 50 = 10.6 ± 2 μm (measured by static laser scattering method).

[0134] Example 3

[0135] In a high-intensity laboratory mixer (Somakon mixer MP-GL equipped with a 0.5 L mixing unit), 217.8 g of NMC powder (PLB-H7) was first mixed with 2.2 g (1.0 wt%) of the nanostructured MgO powder burned in the flame of Example 1 at 100 rpm (specific power: 800 W / kg NMC) for 1 minute. For the 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 to 500 rpm for another 1 minute. After homogenization, the mixing speed was further increased to 2000 rpm (specific 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 achieve dry coating of NMC particles with MgO. The coated NMC particles showed a MgO coating layer thickness of 10 - 200 nm as determined by TEM analysis.

[0136] Example 4

[0137] The procedure of Example 1 was exactly repeated, 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 layer thickness of 10 - 200 nm as determined by TEM analysis.

[0138] Comparative Example 5

[0139] The procedure of Example 1 was exactly repeated, with the only difference being that instead of the MgO burned in the flame of Example 1, MgO purchased from Sigma-Aldrich, 65 m2 It is by using magnesium oxide powder that has not been burned by a flame and has a BET specific surface area of / g.

[0140] Uniformly coated cathode active material particles are achieved when magnesium oxide burned by a flame having a coating layer thickness of 20 to 200 nm on the cathode active material particles is used as a coating additive.

[0141] In order to visualize the dispersibility behavior while applying a shearing force to the magnesia agglomerates, the particle size distribution of hydrophilic magnesium oxide was measured.

[0142] Figure 1(a) shows the particle size distribution of MgO burned by the flame of Example 1, and Figure 1(b) shows the particle size distribution of magnesium oxide that has not been burned by the flame used in Example 5 and analyzed by a laser diffraction particle size analyzer. The x-axis in Figure 1 indicates the particle diameter, the left y-axis indicates the volume in % ("q%"), and the right y-axis indicates the cumulative volume in ("Q%").

[0143] The sample was dispersed in distilled water and treated in an external ultrasonic bath (160 W) for 15 minutes. For the MgO of Example 1, a small aggregate size of D10 = 58 nm, D50 = 78 nm, D90 = 147 nm was detected, and a nearly unimodal and extremely narrow particle size distribution was detected. In the case of magnesium oxide that has not been burned by a flame, a slightly wider particle size distribution with a much larger agglomerate size of D10 = 2680 nm, D50 = 4080 nm, D90 = 5950 nm was detected, clearly indicating the presence of undispersed particles.

[0144] Analysis of MgO-Coated Mixed Lithium Transition Metal Oxide by SEM-EDX Figures 2a, 2b, and 2c show SEM-EDX (scanning electron microscope with energy-dispersive X-rays) mappings of different magnesia coating additives on the NMC cathode active material PLB-H7 (a: hydrophobic MgO burned in the flame of Example 2, b: MgO burned in the flame of Example 1, c: magnesium oxide not burned in the flame). The mappings of NMC coated with magnesia burned in the flame (a) and (b) show a complete and uniform coating of MgO around all cathode particles. Larger magnesium oxide bulk compositions are detected hardly or only very slightly, indicating the successful dispersion of nanostructured magnesia burned in the flame. Furthermore, hardly any MgO particles not adhering to the adjacent cathode particles are seen, indicating a strong interaction between the high-surface-area magnesia particles burned in the flame and the surface of the cathode active material particles, and thus excellent adhesion between the coating layer and the substrate.

[0145] In contrast, by using coarser magnesia particles (magnesium oxide not burned in the flame) (c) as the coating of the cathode material, hardly any coating layer can be observed on the surface of the cathode active material particles. Instead, larger, undispersed, and thus non-adhering MgO particles are located adjacent to the cathode particles, indicating that the dispersibility behavior of magnesium oxide not burned in the flame during the dry coating process is extremely poor, ultimately resulting in the presence of uncoated cathode active material particles.

[0146] Therefore, the NMC mixed oxide dry-coated with MgO burned by the flame shows complete and uniform coating of all NMC particles by MgO. No larger MgO agglomerates were detected, indicating excellent dispersion of the nanostructured, flame-burned MgO. Furthermore, no free MgO particles were seen adjacent to the NMC particles, indicating strong adhesion between the coating and the substrate (NMC). In contrast, Fig. 2(c) shows that in the case of non-flame-burned MgO, only fine particles of "nano MgO" adhere to the surface of the NMC particles. Larger MgO particles are not dispersed and thus not adhered, and are located adjacent to the NMC particles. As a result, the NMC particles are not completely covered by magnesium oxide.

[0147] Fig. 3 shows a lithium-ion battery generally denoted by the numeral 10, inside an apparatus 100 supplied with electricity by a lithium-ion battery 10 according to an embodiment of the present invention. The apparatus can be any electronic device such as, for example, a mobile phone, an electronic clock, a key fob, a laptop computer, a desktop computer, a computer pad, etc. The apparatus can also be an electrical device such as a power tool, a vacuum cleaner, an electric lawn mower, an electrical appliance, etc. The lithium-ion battery 10 is grouped into modules each having a plurality of lithium batteries 10 and can be used to supply electricity to an electric vehicle or a hybrid vehicle. The lithium-ion battery 10 includes negative and positive current collectors 14 and 12, a cathode 18 adjacent to the positive current collector 12, an anode 16 adjacent to the negative current collector 14, an electrolyte 20, and a separator 22 disposed between the anode 16 and the cathode 18. The cathode 18 includes a mixed lithium transition metal oxide coated as an active cathode material, and the coated mixed lithium transition metal oxide is obtained by subjecting the mixed lithium transition metal oxide and nanostructured magnesium oxide produced by firing to dry mixing using a mixing unit as described above.

[0148] The present invention has been described with reference to specific embodiments, but it should be understood that the present invention is not limited to these embodiments only, and many modifications thereof fall within the scope of the present invention defined by the appended claims.

Explanation of Reference Numerals

[0149] 10 Battery cell 100 Device supplied with electricity by the battery cell 12 Positive current collector 14 Negative current collector 16 Anode 18 Cathode 20 Electrolyte 22 Separator

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

2. The method according to claim 1, characterized in that (i) prior to the dry mixing, the surface treatment is performed so that the nanostructured magnesium oxide produced by calcination becomes hydrophobic by reacting the hydroxyl group of the MgO with silane to form an -O-Si-R group, and (ii) the mixing unit has a specific power of 0.05 to 1.5 kW per 1 kg of the mixed lithium transition metal oxide.

3. The average aggregate diameter d ５０ The method according to claim 1, characterized in that the wavelength is 10 to 120 nm when determined by static light scattering (SLS) after sonication of a mixture consisting of 5% by weight of the particles and 95% by weight of a 0.5 g / L aqueous solution of sodium pyrophosphate at 25°C for 60 seconds.

4. The method according to claim 1, characterized in that scanning electron microscopy (SEM-EDX) mapping of the coated mixed lithium transition metal oxide, as disclosed herein, provides a complete and uniform coating of MgO around substantially all of the mixed lithium transition metal oxide particles.

5. The specific power of the mixing unit is 0.1 to 1000 kW, and the volume of the mixing unit is 0.1 L to 2.5 m³. ３ The method according to claim 1, characterized in that the speed of the mixing tool in the mixing unit is 5 to 30 m / second.

6. The span (d) of the magnesium oxide particles ９０ -d １０ ) / d ５０ The method according to claim 1, characterized in that the ratio is 0.4 to 1.2 when determined by static light scattering (SLS) after sonication of a mixture consisting of 5% by weight of the particles and 95% by weight of a 0.5 g / L aqueous solution of sodium pyrophosphate at 25°C for 60 seconds.

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

9. The method according to claim 1, characterized in that the proportion of magnesium oxide in the coated mixed lithium transition metal oxide is 0.05% by weight to 5% by weight with respect to the total weight of the coated mixed lithium transition metal oxide.

10. A coated mixed lithium transition metal oxide comprising 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 manganese nickel oxide or mixtures thereof, and a coating of nanostructured magnesium oxide produced by calcination on the surface of the mixed lithium transition metal oxide particles, wherein the coated mixed lithium transition metal oxide is in the form of particles, and the magnesium oxide has a BET surface area (DIN 9277: 2014) of 5 to 300 m ２ / g, 5 wt% of the particles and 95 wt% of a 25°C static light scattering (SLS) of a mixture consisting of a 0.5 g / L aqueous solution of sodium pyrophosphate after 60 seconds of ultrasonic treatment, having an average aggregate diameter d of 5 to 150 nm when determined by ５０ A coated mixed lithium transition metal oxide having a unimodal and narrow particle size distribution and having the nanostructured magnesium oxide produced by calcination surface-treated to be hydrophobic.

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 herein, provides a complete and uniform coating of MgO around substantially all of the mixed lithium transition metal oxide particles.

12. Coated mixed lithium obtainable by the method described in claim 1 Transition metal oxides.

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

14. A lithium-ion battery comprising a coated mixed lithium transition metal oxide according to claim 10.

15. Use of the coated mixed lithium transition metal oxide according to claim 10 in the active cathode material of a lithium-ion battery.

16. An apparatus comprising an electrical or electronic device, comprising a mobile phone, an electronic clock, a key fab, a laptop computer, a desktop computer, a computer pad, a power tool, a vacuum cleaner, an electric lawnmower, an electrical appliance, and an electric vehicle, comprising a lithium-ion battery according to claim 14.

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