Anode 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 manufacturing a coated active anode material, comprising subjecting a mixed anode material and a nanostructured, preferably surface-modified magnesium oxide produced by calcination to dry mixing by a mixing unit having a specific power of 0.05 to 1.5 kW per 1 kg of the mixed anode material. A coated mixed anode material obtainable by this method. An anode for a lithium-ion battery and a lithium-ion battery comprising such a coated active anode material.

Description

Technical Field

[0001] The present invention relates to a method for producing encapsulated anode active material particles in which carbon and / or Si-based particles are dry-mixed with nanostructured magnesium oxide combusted by a flame under shear conditions. The present invention further relates to an anode material coated with magnesium oxide combusted by a flame, and a battery cell containing encapsulated carbon and / or Si-based anode particles and use thereof.

Background Art

[0002] In recent years, various energy storage technologies have attracted wide 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] Secondary lithium ion batteries typically consist of an anode made of, for example, a carbon material or a lithium metal alloy, a cathode made of, for example, a lithium metal oxide, and an electrolyte, for example, a lithium salt dissolved in an organic solvent. The separator of a lithium ion battery provides a passage for lithium ions between the cathode and the anode during charging and discharging of the battery.

[0004] U.S. Patent Application Publication No. 2019 / 0393543 describes a lithium metal secondary battery including a cathode, an anode, and a porous separator or electrolyte disposed between the cathode and the anode, wherein the anode includes (a) an anode active layer containing a layer of lithium or a lithium alloy in the form of a foil, a coating, or a plurality of aggregated particles as an anode active material, and (b) an anode protective layer of a conductive sulfone oxide elastomer composite material disposed between the anode active layer and the separator / electrolyte.

[0005] U.S. Patent Application Publication No. 2019 / 363345 describes forming a graphene protective coating on a negative lithium metal electrode for a lithium-ion battery. The graphene protective coating is stated to reduce dendrite growth.

[0006] International Application Publication No. 2019215406 describes an anode for a lithium-ion battery comprising at least one anode material coated with a protective coating that includes a very long list of materials deemed suitable according to its claims, but the application publication does not disclose the materials or methods of the present disclosure.

[0007] Chinese Patent Application Publication No. 106025242 describes a composite anode material for a lithium-ion battery comprising a core layer of carbon nanotubes and porous silicon alloy nanowires and a shell layer made of a conductive polymer film of polypropylene oxide, polyethylene succinate, polyethylene succinate or polyethylene glycol imine mixed with graphene.

[0008] Generally, to improve cycle performance, coatings of cathode materials for lithium-ion batteries with metal oxides such as Al2O3, TiO2, ZrO2, and MgO have been described in the literature.

[0009] Some examples of the use of MgO in anode materials are provided in the following papers. In the paper titled "Homogenizing Silicon Domains in SiOx Anode during Cycling and Enhancing Battery Performance via Magnesium Doping" published in ACS Appl. Mater. Interfaces 2021, 13, 52202-52214 by Han et al., magnesium was used as a dopant for the SiOx anode active material. However, the modification and reaction of the components to finally form a protective Mg-silicate compound require temperatures exceeding 1000 °C.

[0010] In the paper titled "Improvement of cycling performance of lithium-sulfur batteries by using magnesium oxide as a functional additive for trapping lithium polysulfide" by Ponraj et al. published in ACS Appl. Mater. Interfaces 2016, 8, 4000-4006, hydrophilic magnesium oxide was used as an additive on the surface of the active sulfur of the sulfur cathode to trap polysulfides.

[0011] Also, in general, elements such as carbon and their allotropes (graphene) have been used as anode materials in lithium-ion secondary batteries, but there are some problems with their structural stability. In the paper titled "An electrode comprising of graphene nano-powder inserted in an enclosed structure in anodic aluminum oxide coated with polyaniline by using low temperature hydrothermal process" by Sugam et al. published in the 62nd DAE Solid State Physics Symposium on January 1942, 2017, graphene nano powder was inserted and confined on anodic aluminum oxide of the anode coated with polyaniline.

[0012] In the paper titled "An Alumina-Coated Fe3O4-Reduced Graphene Oxide Composite Electrode as a Stable Anode for Lithium-ion Battery" by Qi-Hui et al. published in Electrochimica Acta (2015), 156, 147-153, an Al2O3 coating was used for the graphene oxide composite anode material reduced with Fe3O4.

[0013] Chinese Patent No. 103 441 252 discloses a lithium-rich anode active material coated with nano-sized magnesium oxide.

[0014] In the paper "Nanocrystalline NiO thin film anode with MgO coating for Li-ion batteries" by Wang et al. published in Electrochimica Acta (2003), vol. 48, no. 28, pages 4253-4259, the formation of nanocrystalline NiO thin films by pulsed laser reactive ablation in an oxygen atmosphere and subsequent coating of the NiO thin film surface with MgO.

[0015] Wang Bo et al. published the synthesis of a flexible carbon fiber thin film co-doped with P-S incorporated with SiO2 and MgO nanoparticles in "Rational formation of solid electrolyte interface for high-rate potassium ion batteries" in Nano Energy, vol. 75 (2020), page 104979.

Prior Art Documents

Patent Documents

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Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Non-Patent Documents

[0017]

Non-Patent Document 1

Non - Patent Document 6

Summary of the Invention

Problems to be Solved by the Invention

[0018] A rather significant general problem associated with anode materials, particularly silicon - based anode materials, is the uncontrolled solid electrolyte interface (SEI) formation during the initial charge - discharge process of the battery. Furthermore, the aging process within most of this material results in a loss of performance during cycling. This aging phenomenon is particularly relevant for Si - based anode active materials. During cycling, the negative electrode material undergoes several electrochemical degradation mechanisms. The deactivation of the negative electrode material is caused by several electrochemical degradation mechanisms. Surface transformation induced by the electrolyte and unwanted side reactions with lithium species result in the formation of an SEI layer with an increased thickness, ultimately leading to a decrease in performance and battery life.

[0019] Surface coating has been proven to be a very important method to address this aging problem by suppressing the direct contact between the active material surface and the liquid electrolyte.

[0020] Nanoscale MgO particles have been used as additives in lithium-ion batteries, but their effectiveness is 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 nanoscale MgO particles often results in non-uniform distribution and large agglomerates of MgO particles on the surface of anode materials such as carbon and / or Si-based materials. As a result, the anode material particles are not completely covered by the magnesium oxide particles, and large undispersed magnesium oxide particles are present, located adjacent to the anode particles that can be clearly seen by SEM elemental mapping.

[0021] The problem addressed by the present invention is to provide a uniform coating layer of metal oxide around carbon and / or Si-based particles made by dry coating of powders.

[0022] During the thorough experimental process, surprisingly, the sintered-produced nanostructured magnesium oxide can be successfully used for the uniform coating of anode materials such as carbon and / or Si-based particles using a dry mixing process for coating magnesium oxide on the anode material. Surprisingly, it has also been found that further surface modification of the sintered-produced nanostructured magnesium oxide before dry mixing can significantly further improve the coating coverage and uniformity.

[0023] The present invention provides a method for manufacturing a coated active anode material, a coated active anode material, and the use of the coated active anode 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 Problem

[0024] According to a first aspect of the present invention, a method for manufacturing a coated active anode material is provided. This method is such that the coated active anode material is obtained by subjecting an active anode material and magnesium oxide produced by calcination to dry mixing in a mixing unit under shear conditions. The coated active anode material is in the form of particles, and the magnesium oxide has a BET surface area of 5 to 300 m 2 / g (DIN 9277:2014), and when determined by static light scattering (SLS) after 60 seconds of ultrasonic treatment 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, has a unimodal and narrow particle size distribution with an average aggregate diameter d of 5 to 150 nm 50 characterized by having.

[0025] MgO produced by calcination is hydrophilic. Preferably, in one embodiment, 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 1 kg of the mixed anode material.

[0027] The coated active anode material is in the form of particles, and the magnesium oxide has a BET surface area of 5 to 300 m 2 / g, and when determined by static light scattering (SLS) after 60 seconds of ultrasonic treatment 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, 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 characterized by having a unimodal and narrow particle size distribution.

[0028] In one embodiment, 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 m 3 3

[0029] The span (d 90 -d 10 ) / d 50 of the magnesium oxide and / or mixed oxide particles containing magnesium is 0.4 to 1.2 when determined by static light scattering (SLS) after 60 seconds of ultrasonic treatment 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.

[0030] The active anode material contains carbon and / or Si-based particles. As used herein, the term Si-based particles means any combination of silicon particles (e.g., pure silicon particles), silicon oxide (SiOx) particles, and mixtures and composites of silicon, silicon oxide, and carbon particles, including mixtures and composites thereof. The silicon oxide can be SiO and / or SiO2.

[0031] In one embodiment, the coated active anode material is further subjected to heat treatment after dry mixing.

[0032] In one embodiment, the proportion of magnesium oxide in the coated active anode material is 0.05 wt% to 5 wt% based on the total weight of the coated mixed anode material.

[0033] Another aspect of the present invention relates to a coated active anode material obtainable by the above method.

[0034] According to yet another aspect of the present invention, there is provided a coated active anode material comprising an active anode material and a coating of a nanostructured magnesium oxide produced by calcination on the surface of the mixed anode material, wherein the coated active anode material 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, and when determined by static light scattering (SLS) after 60 seconds of ultrasonic treatment 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, has an average aggregate diameter d 50 ranging from 5 to 150 nm, having a unimodal and narrow particle size distribution, and the nanostructured magnesium oxide produced by calcination is preferably surface-treated to be hydrophobic by reacting the hydroxyl groups of MgO with silane to form -O-Si-R groups. The magnesium oxide is hydrophilic or hydrophobic, preferably hydrophobic. The active anode material is carbon, silicon, silicon oxide (SiOx), or any combination thereof including mixtures and / or composites of carbon, silicon and silicon oxide.

[0035] SEM-EDX mapping of the coated active anode material provides a complete and uniform coating of MgO produced by calcination around substantially all anode particles, with no or only very few larger magnesium oxide bulk compositions present.

[0036] Another aspect of the present invention relates to an active negative electrode material for a lithium-ion battery comprising the coated active anode material, to a lithium-ion battery comprising the coated active anode material, and to the use of the coated active anode material in an active negative electrode material of a lithium-ion battery.

[0037] Yet another aspect of the present invention relates to a device powered by the lithium-ion battery.

[0038] The magnesium oxide nanostructures produced by the flame process have both a unimodal and narrow particle size distribution and excellent dispersibility during the dry coating process of the anode material. These particles provide excellent interaction and proper adhesion to the anode active material.

[0039] Furthermore, additional surface modification of these particles results in further improvement in the interaction with and adhesion to the anode active material. This leads to complete de-agglomeration of the magnesium oxide bulk composition and ultimately provides anode active material particles that are completely and uniformly covered by nanostructured, surface-modified magnesium oxide burned by the flame.

[0040] 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 anode active material particle powder, providing extremely excellent interaction and adhesion, which in turn results in 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.

[0041] 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

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Fig. 1a

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Fig. 1b

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Fig. 2a

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Fig. 2b

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Fig. 2c

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Fig. 3

Mode for Carrying Out the Invention

[0048] According to a first aspect of the present invention, there is provided a method for manufacturing encapsulated active anode material particles, in which an active anode material and nanostructured, preferably surface-modified, magnesium oxide burned by a flame are dry-mixed under shear conditions. A second aspect of the present invention relates to an anode material coated with magnesium oxide burned by a flame, and a third aspect of the present invention relates to a battery cell containing encapsulated carbon and / or Si-based anode particles.

[0049] Method for manufacturing a coated anode active material

[0050] According to a first aspect of the present invention, there is provided a method for manufacturing a coated active anode material, wherein carbon and / or Si-based anode particles and a nano-structured, preferably surface-modified magnesium oxide produced by calcination are subjected to dry mixing under shear conditions. The Si-based anode particles include silicon particles, silicon oxide particles, and any combination of silicon, silicon oxide, and carbon particles.

[0051] The nano-structured magnesium oxide burned by the flame is preferably surface-modified to be hydrophobic before dry mixing.

[0052] The active anode material may also be referred to as a core active anode material or a substrate active anode material or particles. The nano-structured, preferably surface-modified MgO magnesium oxide produced by calcination may also be referred to as a coating. The coated active anode material refers to a mixed active anode material having a coating produced by dry mixing. When the dry mixing is completed, the carbon and / or Si-based particles are covered with the MgO.

[0053] Dry mixing

[0054] Dry mixing can be carried out, for example, in a mixing unit having a specific power of 0.05 to 1.5 kW per kg of the mixed anode material. Dry mixing means 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 there is a trace amount of moisture or something other than liquid water present in the raw materials to be mixed, or that they contain water of crystallization.

[0055] When the specific power used is less than 0.05 kW per 1 kg of the mixed anode material, this may give a non-uniform distribution of magnesium oxide over the anode active material particles, and the magnesium oxide may not be firmly bonded to the core material of the anode active material particles. A specific power exceeding 1.5 kW per 1 kg of the mixed anode material 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.

[0056] The volume of the mixing unit can vary over a wide range. For example, the volume of the mixing unit can be in the range of 0.1 L to 2.5 m 3 ³. 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 ³.

[0057] 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.

[0058] The mixing time can vary and can 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.

[0059] After mixing, the mixture can be heat-treated to improve the binding of the coating to the anode active material particles. However, in the method according to the invention, the heat treatment is optional in the method according to the invention, since the nanostructured, surface-modified magnesium oxide produced by calcination adheres firmly enough to the core anode active material particles, i.e. carbon and / or Si-based particles. Thus, a preferred embodiment of the method according to the invention may not include a heat treatment after mixing.

[0060] The best results regarding the adhesion of magnesium oxide to the core anode active material particles are found 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, most preferably 15 to 150 m 2 / g. The BET surface area can be determined according to DIN 9277:2014 by nitrogen adsorption according to the Brunauer-Emmett-Teller procedure.

[0061] Calcination formation of MgO

[0062] The magnesium oxide used in the method according to the invention is produced by calcination, i.e. by the calcination method. The calcination method is also called the "flame combustion" method. Such a "calcination" or "flame combustion" method involves the reaction of the corresponding metal precursor in flame hydrolysis or flame oxidation in an oxyhydrogen flame to form a metal oxide.

[0063] The hydrophilic magnesium oxide prepared by calcination is characterized by: Surface area [m 2 / g] 50 - 350 Tapped density [g / L] 20 - 100 Loss on drying [%] less than 5 Loss on ignition [%] 0.1 - 20

[0064] The terms "pyrogenically produced", "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. This 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.

[0065] 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 comprising a magnesium salt and a solvent such as ethanol, methanol or water is subjected to flame spray pyrolysis.

[0066] During the flame spray pyrolysis process, a solution of a metal compound (metal precursor) in the form of fine droplets is typically introduced into a flame formed by 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.

[0067] This reaction first forms highly dispersed, substantially spherical primary particles, which coalesce in a further process of the reaction to form aggregates. The aggregates can then stack up to form agglomerates. In contrast to agglomerates, which can be relatively easily separated into aggregates by the introduction of energy in principle, aggregates are only 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.

[0068] The resulting aggregated compound can be referred to as "fumed" or "pyrogenically produced" magnesium oxide.

[0069] The flame spray pyrolysis process is generally described in WO 2015173114 and elsewhere.

[0070] The flame spray pyrolysis process of the present invention preferably includes 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) Then removing solid magnesium oxide from the reaction stream.

[0071] Examples of metal precursors used in the method of the present invention include magnesium salts such as magnesium chloride, magnesium nitrate or magnesium acetate.

[0072] The solvent of this solution can be any typical solvent such as water, ethanol, methanol, etc.

[0073] The amount of the metal precursor in the solution can range from 0.5 to 80% by weight, preferably from 20 to 70% by weight, based on the total weight of the solution.

[0074] Examples of fuel gases are hydrogen, methane, ethane, natural gas and / or carbon monoxide. It is particularly preferred to use hydrogen.

[0075] 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 at least sufficient for the complete conversion of the fuel gas and the metal precursor.

[0076] To obtain an aerosol, a vaporization solution containing a 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 generated using a nozzle of a 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.

[0077] The particle size of magnesium oxide can be varied by reaction conditions such as, for example, flame temperature, the ratio of hydrogen or oxygen, the amount of magnesium salt, residence time in the flame, or the length of the coagulation zone.

[0078] 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.

[0079] Therefore, the calcined, nanostructured, preferably surface-modified magnesium oxide used in the process according to the invention is 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, as determined by transmission electron microscopy (TEM). This number average diameter can be determined by calculating the average size of at least 500 particles analyzed by TEM.

[0080] 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 particle crushing or sonication, resulting in particles having a smaller particle size.

[0081] 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 ultrasonic treatment at 25 °C of a mixture consisting of 5% by weight of the particles and 95% by weight of an aqueous solution of 0.5 g / L of sodium pyrophosphate.

[0082] Therefore, the calcined, nanostructured, preferably surface-modified magnesium oxide used in the method of the present invention is preferably characterized by high dispersibility, i.e., the ability to form relatively small particles under gentle ultrasonic treatment. Dispersion under such gentle conditions is considered to correlate with the conditions during the dry coating process. That is, the bulk of magnesium oxide can be broken down in the mixing process of the present invention in the same way as under ultrasonic treatment and can form a uniform coating of anode active material particles.

[0083] The span (d 90 -d 10 ) / d 50 is preferably 0.4 to 1.2, more preferably 0.5 to 1.1, 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 the said particles and 95% by weight of an aqueous solution of 0.5 g / L of sodium pyrophosphate.

[0084] Therefore, the calcined, nanostructured 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 anode material particles.

[0085] 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, d 10The diameter is such that 10% of the volume of the sample is smaller than d 10 and is composed of particles smaller than the particles, where d 50 is such that 50% of the volume of the sample is smaller than d 50 and is composed of particles smaller than the particles. d 50 Since it equally divides the sample by volume, it is also known as the "volume median diameter", where d 90 is such that 90% of the volume of the sample is smaller than d 90 and is composed of particles smaller than the particles.

[0086] Magnesium oxide produced by calcination is hydrophilic. Through surface modification of magnesium oxide produced by calcination, hydrophobic magnesium oxide is then produced. The surface treatment can include using any of many suitable hydrophobic reagents such as silanes. Both the hydrophilic and hydrophobic forms of the nanostructured magnesium oxide burned in a flame can be used as a coating using the process of the present invention via dry mixing with the substrate active anode material. However, nanostructured, surface-modified hydrophobic magnesium oxide burned in a flame is preferred as it shows a more uniform coating and complete coating of the substrate active anode material.

[0087] Surface treatment of MgO produced by calcination.

[0088] MgO produced by calcination without further surface treatment is hydrophilic as it is naturally covered with hydroxyl (-OH) groups in its natural state. However, through surface modification of MgO produced by calcination, hydrophobic MgO is also produced. For example, hydrophobization of MgO can be done by reacting the hydroxyl groups with silane to form -O-Si-R groups. Thus, preferably, MgO is surface-modified, which means that the surface of MgO is at least partially covered by silane.

[0089] The 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, the MgO particles can become 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 nanostructured MgO burned in a flame can be effectively used as a coating using the process of the present invention via dry mixing with a substrate active anode material. The nanostructured, surface-modified MgO burned in a flame is preferred because it shows a more uniform coating of the substrate active anode material.

[0090] 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

[0091] Therefore, the magnesium oxide prepared by calcination 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").

[0092] In another embodiment, the surface modification of the magnesium oxide prepared by calcination 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.

[0093] An alternative method for the surface modification of the magnesium oxide prepared by calcination 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.

[0094] 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 a plate, cyclone, or fluidized bed dryer.

[0095] The present invention has the advantage that commercially available silanes can be used to modify magnesium oxide and thereby individually adapt the properties of magnesium oxide according to the desired properties and intended purposes.

[0096] As surface modifiers, the following compounds and mixtures of the following compounds can be used. a) Organosilanes of the 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, i-propyl, butyl and n = 1 to 20, etc. b) Organosilanes of the type R’ x (RO) y Si(CnH 2n+1 ) and R’x(RO) y Si(C n H 2n-1 ), wherein R = alkyl, such as methyl-, ethyl-, n-propyl-, i-propyl-, butyl-, etc. R’ = alkyl, such as 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) Haloorganosilanes of the type X3Si(C n H 2n+1 ) and X3Si(C n H 2n-1 ), wherein X = Cl, Br n = 1 to 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’’’’’ and R’’’’ = H, alkyl and R’’’’’ = H, alkyl g)(R’’) x (RO) y An organosilane of the Si(CH2)m-R’ type with (RO) 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’’’’’, and R’’’’ = H, alkyl and R’’’’’ = H, alkyl h) A 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) (R)X2Si(CH2)m-R’ type halogenated organosilane X = Cl, Br R = alkyl, such as methyl, ethyl, propyl 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 j) (R)2XSi(CH2)m-R’ type halogenated organosilane X = Cl, Br R = alkyl 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

[0097] 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.

[0098] 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 less than 10 ppm of the elements Cd, Ce, Fe, Na, Nb, P and less than 5 ppm of the elements Ba, Bi, Cr, K, Mn, Sb, and the total proportion of all these elements is less than 100 ppm. The proportion of carbon in the hydrophilic, unmodified 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.

[0099] Active anode material

[0100] Substrate anode particles encapsulated or coated with MgO burned by flame may include any suitable material used as an anode active material in a secondary lithium-ion battery capable of reversible intercalation / deintercalation of lithium ions and / or reversible reaction with lithium species. Examples thereof include crystalline carbon such as natural or artificial graphite in the form of plate-like, flake, spherical or fibrous type graphite; amorphous carbon such as soft carbon, hard carbon, mesophase pitch carbide, calcined coke, or a carbonaceous material containing a mixture thereof. Further, Si-based particles can be used as the anode active material. Preferred anode active materials are carbon and / or Si-based particles. The Si-based particles include any combination of silicon particles (e.g., pure silicon particles), silicon oxide (SiOx) particles, and mixtures and composites of silicon, silicon oxide, and carbon particles. The silicon oxide can be SiO and / or SiO2. In one embodiment, the active anode material can be a nanostructured porous silicon material. In one embodiment, the anode material is SiOx, and x can vary from 0 to about 2, such as Si, SiO, SiO2, or any combination thereof.

[0101] Preferred anode active materials are carbon and / or Si-based particles, including a composite material of C and Si-based particles. The "composite material" refers to a composition containing both a carbon material and a silicon material. The carbon and silicon materials can be a mixture of carbon powder and nano-sized silicon powder. In one embodiment, the composite material can include individually chemically bonded carbon and silicon particles. In another embodiment, the composite material can include porous nano-sized silicon particles impregnated with carbon within a silicon porous structure.

[0102] The active anode material mixed with and coated with a metal oxide may include carbon and / or Si-based particles. In some embodiments, the active anode material comprises a composite SiOx / C material, where x can vary from 0 to about 2, composed of 60 to 99% carbon and 40 to 1% silicon oxide, preferably 70 to 95% carbon and 30 to 5% silicon oxide, more preferably 80 to 90% carbon and 20 to 10% silicon oxide. The composite SiOx / C material can be in the form of a powder or particles.

[0103] In one embodiment, the active anode material may include a composite SiO / C material composed of 60 to 99% carbon and 40 to 1% SiO, preferably 70 to 95% carbon and 30 to 5% SiO, more preferably 80 to 90% carbon and 20 to 10% SiO. The composite SiO / C material can be in the form of a powder or particles.

[0104] In some embodiments, the active anode material may include a composite Si / C material composed of 60 to 99% carbon and 40 to 1% silicon, preferably 70 to 95% carbon and 30 to 5% silicon, more preferably 80 to 90% carbon and 20 to 10% silicon. The composite Si / C material can be in the form of a powder or particles.

[0105] The coated active anode material has a number average particle size of 1 to 50 μm, preferably 1 to 40, more preferably 2 to 20 μm. The number average particle size can be determined according to ISO 13320:2009 by laser diffraction particle size analysis.

[0106] The active anode material can also be referred to as the core active anode material or the substrate active anode material or particles. MgO can also be referred to as a coating, and the mixed active anode material with a coating can be called a coated active anode material or particles.

[0107] The proportion of magnesium oxide in the coated mixed anode material 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 anode material. When the proportion of magnesium oxide is less than 0.05 wt%, the beneficial effects of the coating are usually not yet observable. When it exceeds 5 wt%, the beneficial effects of the additional amount of magnesium coating exceeding 5 wt% are usually not observed.

[0108] The coated mixed anode material preferably has a coating layer thickness of 10 to 200 nm as determined by TEM analysis.

[0109] The present invention further provides a coated mixed anode material obtainable by the method according to the present invention. The present invention further provides a coated mixed anode material containing a nano-structured, surface-modified magnesium oxide coating produced by firing on the surface of anode active material particles.

[0110] A further preferred feature of the coated mixed anode material, i.e., the nano-structured, surface-modified magnesium oxide produced by firing as described above in a preferred embodiment of the method according to the present invention, is a preferred feature of the coated mixed anode material according to the present invention, regardless of whether it is produced by the method according to the present invention, with respect to the coated mixed anode material, i.e., the nano-structured, surface-modified magnesium oxide produced by firing.

[0111] The present invention further provides an active negative electrode material for a lithium-ion battery comprising the coated anode material according to the present invention or a coated anode material obtainable by the method according to the present invention.

[0112] The negative electrode of a lithium-ion battery, i.e., the anode, includes a current collector and coated active anode material particles formed above or on the current collector. The current collector may be, for example, aluminum foil, copper foil, nickel foil, stainless steel foil, titanium foil, a polymer substrate coated with a conductive metal, or a combination thereof.

[0113] The present invention also provides a lithium-ion battery including a coated anode material or a coated anode material obtainable by the method according to the present invention.

[0114] In addition to the anode, the lithium-ion battery according to the present invention may also include a cathode, optionally a separator, and an electrolyte containing, for example, a lithium salt or a lithium compound.

[0115] The cathode of a lithium-ion battery may include any suitable material commonly used in secondary lithium-ion batteries that can reversibly intercalate / deintercalate lithium ions.

[0116] Cathode materials preferably used in the method according to the present invention are selected from the group consisting of lithium-cobalt oxide, lithium-manganese oxide, lithium nickel cobalt oxide, lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel manganese oxide, and mixtures thereof.

[0117] The electrolyte of a lithium-ion battery can be in liquid, gel, or solid form. The liquid electrolyte of a 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, vinyl ethylene carbonate, and mixtures thereof.

[0118] The gel electrolyte contains a gelling polymer. Any suitable gelling polymer can be used.

[0119] The solid electrolyte of a lithium-ion battery can include an oxide, such as a lithium metal oxide, a sulfide, a phosphate, or a solid polymer.

[0120] The electrolyte of a 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.

[0121] The present invention further provides for the use of a coated anode material in an active anode material of a lithium-ion battery.

[0122] Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. Accordingly, the preferred specific embodiments and examples are to be construed as merely illustrative, and not limitative of the invention in any way.

[0123] Hereinafter, the present invention will be described in more detail with reference to examples. Alternative embodiments of the present invention are available in a similar manner.

Examples

[0124] Determination of Physicochemical Characteristic Data

[0125] In the context of the present invention, the following measurement methods were used to evaluate the properties of different materials.

[0126] A) BET surface area: The BET surface area is determined according to DIN 9277:2014 using nitrogen.

[0127] B) Tamp density: Determination of tamp density in accordance with the modification of DIN ISO 787 / XI, Basis for determination of tamp density: The tamp density (formerly tamp volume) is equal to the quotient of the mass and volume of the powder after tamping in a tamping volumeter under defined conditions. In accordance with DIN ISO 787 / XI, the tamp density is given in g / cm 3 However, since the tamp density of the oxide is extremely low, the value is given by the inventors in g / L. Furthermore, drying, sieving and repetition of the tamping operation are not carried out.

[0128] Apparatus for determination of tamp density: Tamping volumeter Measuring cylinder Laboratory scale (reading up to 0.01 g)

[0129] Procedure for determination of tamp density: Fill the measuring cylinder of the tamping volumeter with 200 ± 10 mL of oxide so that no pores remain and the surface is horizontal. The mass of the filled sample is determined accurately to 0.01 g. Place the measuring cylinder containing the sample in the measuring cylinder holder of the tamping volumeter and tamp 1250 times. Read the volume of the tamped oxide exactly once. Evaluation of determination of tamp density

[0130]

No.

[0131] C) pH value: The pH value is determined in a 4% aqueous dispersion of the hydrophobic oxide in water:methanol (1:1). Reagents for determination of pH value: Distilled water or completely deionized water, pH > 5.5 Methanol, p.a. Buffer solution pH 7.00 pH 4.66 Device for pH value determination: Laboratory scale, (reading up to 0.1 g) Glass beaker, 250 mL Magnetic stirrer Magnetic bar, length 4 cm Combined pH electrode pH measuring device Syringe, 100 mL

[0132] 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 the buffer solution. If several measurements are carried out continuously, a single calibration is sufficient. Using a syringe, stir 4 g of hydrophilic oxide in a 250 mL glass beaker containing 96 g (96 mL) of water to make a paste, and stir with a magnetic stirrer for 5 minutes (rpm about 1000 min -1 -1). Stir 4 g of hydrophobic oxide in a 250 mL glass beaker containing 48 g (61 mL) of methanol to make a paste, 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 turning off the stirrer, read the pH after a standing time of 1 minute. The result is given to within the first decimal place.

[0133] D) Loss on drying Different from 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 the predetermined position. A second drying is not carried out. Weigh exactly 1 g of the sample to 0.1 mg in a weighing dish equipped with a ground cover dried at 105°C, avoiding the formation of dust, and dry it in a drying cabinet at 105°C for 2 hours. After cooling in a desiccator with the cover on, reweigh the sample under blue gel.

[0134]

Number

[0135] 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, weigh exactly 0.3 - 1 g of the 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 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 to 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.

[0136] Evaluation of the determination of loss on ignition Since the loss on ignition is determined for a sample dried at 105°C for 2 hours, the following calculation formula is obtained.

[0137]

Number

[0138] 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.

[0139] G) SEM Measurement 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, 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 sum spectrum of the mapping. The threshold for image analysis was adjusted according to the semi-quantitative mass % values of each element.

[0140] Preparation of Magnesium Oxide:

[0141] Example 1: Preparation of Fired 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 the tubular reactor together with the combustion flame. The combustion gas of the flame consisted of hydrogen at 8 Nm 3 / h and air at 30 Nm 3 / h. Additionally, 25 Nm 3 / h of secondary air was used. After the reactor, the reaction gas was cooled and filtered.

[0142] The particle properties are shown in Table 1, the TEM image of the particles is shown in Figure 1, and the XRD analysis (Figure 2) showed that the main phase of the product is cubic magnesium oxide.

[0143] The high-surface-area calcined hydrophilic magnesium oxide formed has the data of the physicochemical characteristics shown in Table 1.

[0144] Example 2: Preparation of surface-modified magnesium oxide Put 300 g of calcined 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.

[0145] The hydrophilic surface-modified magnesium oxide has the data of the physicochemical characteristics shown in Table 1.

[0146]

Table 1

[0147] Examples of coated anode active materials Starting materials:

[0148] Dry coating additives: The materials described above in Examples 1 and 2, namely, magnesium oxide burned in the flame of Example 1 with a BET surface area of 250 m 2 / g and hydrophobic magnesium oxide burned in the flame of Example 2 with a BET surface area of 230 m 2 / g were used. The hydrophobic magnesium oxide burned in the flame of Example 2 was made hydrophobic by subjecting it to a hydrophobization treatment after the calcination formation process as described above. The 65 m purchased from Sigma-Aldrich, Germany2 Magnesium oxide that has not been burned in a flame and has a BET surface area of / g was also used as a comparative example. Magnesium oxide that has not been burned in a flame is not a nanostructure but a pulverized material with isolated, non-aggregated particles.

[0149] Anode active material: Hereinafter, a composite Si / C material composed of 86 wt% carbon and 14 wt% silicon, which is referred to as powder or particles of Si86 / C14 base anode active material ("Si86 / C14_AAM") and is commercially available under the trademark of DXB8 Shandong Gelon Lib Co., Ltd., China. As shown by SEM analysis, Si86 / C14_AAM is a mixture of SiOx and carbon and has the following characteristics.

[0150]

Table 0

[0151] Example 3 In a high-strength experiment mixer (SOMAKON mixer MP-GL equipped with a 0.5 L mixing unit), Si86 / C14_AAM was mixed with magnesium oxide burned in the flame of Example 1 in their respective amounts (1.0 wt%). To homogenize the two powders, the speed was increased stepwise: 100 rpm for 1 minute, 200 rpm for 1 minute, 500 rpm for 1 minute. After homogenization, the mixing speed was further increased to 2000 rpm for 5 minutes to achieve dry coating of Si86 / C14_AAM particles with each magnesium oxide additive. When determined by TEM analysis, the Si86 / C14_AAM particles were coated with a MgO coating layer having a thickness of 10 - 200 nm. When determined by TEM analysis, the Si86 / C14_AAM particles were coated with a uniform MgO coating layer having a thickness of 20 - 200 nm.

[0152] Example 4 The procedure of Example 3 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. When determined by TEM analysis, the Si86 / C14_AAM particles were coated with a MgO coating layer having a thickness of 20 - 200 nm. When the hydrophobic magnesium oxide burned in the flame of Example 2 having a MgO coating layer with a thickness of 20 - 200 nm on the Si86 / C14_AAM particles was used as a coating additive, a uniform coating of the SI86 / C14_AAM particles was achieved.

[0153] Comparative Example 5 The procedure of Example 3 was exactly repeated, with the only difference being that instead of the MgO burned in the flame of Example 1, magnesium oxide powder that was not burned in the flame and had a BET surface area of 65 m 2 / g purchased from Sigma - Aldrich was used.

[0154] When the magnesium oxides burned in the flames of Examples 1 and 2 having a coating layer with a thickness of 20 - 200 nm on the Si86 / C14_AAM particles were used as coating additives, uniformly coated active anode particles were achieved.

[0155] To visualize the dispersibility behavior of the magnesium oxide bulk composition while applying shear force, the particle size distribution of hydrophilic magnesium oxide was measured.

[0156] Figure 1(a) shows the particle size distribution of the MgO burned in the flame of Example 1, and Figure 1(b) shows the particle size distribution of the magnesium oxide that was not burned in 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 (「Q%」).

[0157] The sample was dispersed in distilled water and treated in an external ultrasonic bath (160 W) for 15 minutes. For the MgO burned in the flame of Example 1, small aggregate sizes of d10 = 58 nm, d50 = 78 nm, and d90 = 147 nm were detected, with a nearly unimodal and extremely narrow particle size distribution. In the case of magnesium oxide not burned in the flame, much larger agglomerate sizes of d10 = 2680 nm, d50 = 4080 nm, and d90 = 5950 nm were detected, with a slightly broader particle size distribution, clearly indicating the presence of undispersed particles.

[0158] Analysis of the Coated Anode Material by SEM-EDX

[0159] Figure 2 (2a, 2b, and 2c) shows SEM-EDX (scanning electron microscope with energy-dispersive X-rays) mappings of different magnesium oxide coating additives (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) on Si86 / C14_AAM particles. On the left side of each of Figures 2a, 2b, and 2c, Si mapping is shown to visualize the silicon distribution within the anode active material (a mixture of carbon and silicon). This information is useful when comparing with the Al / Ti distribution of the coating additive on the right side, clearly showing the interaction between the coating additive and the surface of the anode material. The mapping of Si86 / C14_AAM coated with hydrophobic magnesia (a) burned in the flame shows a complete and uniform coating of MgO around substantially all anode particles (silicon-rich and carbon-rich ones). No large magnesium oxide agglomerates were detected, indicating that the dispersion of the nanostructured hydrophobic magnesia burned in the flame was the most effective. Furthermore, no free non-attached MgO particles were seen next to the anode particles, indicating a strong interaction between the surface-modified, flame-burned magnesium oxide particles and the surface of the Si86 / C14_AAM particles, and thus excellent adhesion between the coating MgO layer and the substrate.

[0160] The hydrophilic, flame-combusted material of Example 1 exhibits excellent dispersibility of the agglomerates and preferably interacts with Si-rich particles instead of the carbon-rich particles (b), compared to the surface-modified and thus hydrophobic, flame-combusted magnesia. Therefore, the magnesia coating is more prominent on the surface of the Si-rich particles. Some undispersed and thus independent hydrophilic MgO particles that are not coated on the Si86 / C14_AAM particles are present next to the coated Si86 / C14_AAM particles.

[0161] In contrast, by using coarser magnesia particles (uncombusted magnesium oxide) (c) as the coating for the Si86 / C14_AAM particles, only a very small amount of finer-sized MgO particles adhere to the surface of the Si86 / C14_AAM particles. Many of the larger, undispersed and thus unadhered MgO particles are located next to the Si86 / C14_AAM particles that are not fully coated. As a result, the Si86 / C14_AAM particles are not completely covered by these coarser, un-surface-modified, uncombusted MgO particles.

[0162] Therefore, the Si86 / C14_AAM particles dry-coated with flame-combusted MgO show complete and uniform coating of all the Si86 / C14_AAM particles with MgO. No larger magnesia agglomerates were detected, indicating excellent dispersibility of the nanostructured, flame-combusted MgO. Furthermore, no free, unadhered MgO particles were observed next to the Si86 / C14_AAM particles. The surface-modified (i.e., hydrophobic), flame-combusted MgO of Example 2 shows a more uniform coating of both the carbon-rich substrate particles and the silicon-rich silicon particles than the un-surface-modified, flame-combusted MgO.

[0163] FIG. 3 shows a lithium ion battery generally designated by the numeral 10, which is inside a device 100 supplied with electricity by the lithium ion battery 10 according to an embodiment of the present invention. The device can be any electronic device such as, for example, a mobile phone, an electronic watch, a key fob, a laptop computer, a desktop computer, a computer pad, etc. The device 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 can be grouped into modules in which each module has 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 a negative and a positive current collector 14 and 12, a cathode 18 adjacent to the positive current collector 12, an anode adjacent to the negative current collector 14, an electrolyte 20, and a separator 22 disposed between the anode 16 and the cathode 18. The anode 16 includes a coated active anode material, and the coated active anode material is obtained by subjecting a mixture unit of the active anode material and a nanostructured magnesium oxide produced by firing to dry mixing. The active anode material is in powder form and includes carbon particles, silicon particles, silicon oxide particles, or any combination thereof.

[0164] Although the present invention has been described with reference to specific embodiments, it should be understood that the present invention is not limited to these embodiments only, and that many variations thereof fall within the scope of the present invention as defined by the appended claims.

Description of Reference Numerals

[0165] 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 active anode material, characterized in that the coated active anode material is obtained by dry mixing an active anode material and a nanostructured magnesium oxide produced by calcination in a mixing unit under shear conditions, wherein the coated active anode material 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 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 anode material.

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 mapping of the coated active anode material using energy-dispersive X-rays, as disclosed herein, provides a complete and uniform coating of MgO around substantially all anode 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 active anode material is in the form of a powder and comprises carbon particles, silicon particles, silicon oxide particles, or any combination thereof.

8. The method according to claim 1, characterized in that the coated active anode material 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 active anode material is 0.05% to 5% by weight relative to the total weight of the coated mixed anode material.

10. A coated active anode material comprising an active anode material of carbon particles, silicon particles, silicon oxide particles or any combination thereof, and a coating of nanostructured magnesium oxide produced by calcination on the surface of the mixed anode material, wherein the coated active anode material 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 when determined by static light scattering (SLS) after 60 seconds of ultrasonic treatment at 25 °C ５０ having a unimodal and narrow particle size distribution, and the nanostructured magnesium oxide produced by calcination is surface-treated to be hydrophobic, the coated active anode material.

11. The coated active anode material according to claim 10, characterized in that SEM-EDX mapping of the coated active anode material, as disclosed herein, provides a complete and uniform coating of MgO around substantially all anode particles.

12. A coated active anode material obtainable by the method described in claim 1.

13. An active anode material for a lithium-ion battery comprising the coated active anode material according to claim 10.

14. A lithium-ion battery comprising the coated active anode material according to claim 10.

15. Use of the coated active anode material according to claim 10 in the active anode material of a lithium-ion battery.

16. An apparatus comprising an electrical or electronic device, comprising 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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