Cathode for lithium ion battery and method for making same

Abstract

(1) A lithium-containing cathode active material having a molar content of manganese in the range of 50 to 85 mol % relative to the metals other than lithium contained in the cathode active material; (2) Particulate SiO2, (3) Carbon in a conductive state, and (4) a binder polymer, A cathode containing a mass comprising:

Description

[Technical field]

[0001] The present invention relates to (1) A lithium-containing cathode active material having a molar content of manganese in the range of 50 to 85 mol % relative to the metals other than lithium contained in the cathode active material; (2) Particulate SiO2, (3) Carbon in a conductive state, and (4) a binder polymer, The present invention relates to a cathode comprising a mass comprising:

[0002] The present invention further relates to electrochemical cells containing the particular cathodes. [Background technology]

[0003] Lithiated transition metal oxides are currently used as electrode active materials in lithium-ion batteries. Extensive research and development has been carried out over the past few years to improve properties such as charge density, specific energy, and other properties such as cycle life degradation and capacity loss that adversely affect the life or applicability of lithium-ion batteries. Further efforts are being made to improve the manufacturing methods.

[0004] Many of the electrode active materials currently under discussion are of the lithiated nickel-cobalt-manganese oxide ("NCM material") or lithiated nickel-cobalt-aluminum oxide ("NCA material") type.

[0005] In a typical process for the preparation of cathode materials for lithium-ion batteries, a so-called precursor is first formed by co-precipitation of a transition metal as a carbonate, oxide or preferably as an (oxy)hydroxide. This precursor is then mixed with a lithium compound, such as but not limited to LiOH, Li2O or Li2CO3, and calcined at high temperature. The lithium compound(s) can be used as hydrate(s) or in dehydrated form. The calcination or calcination, also commonly referred to as thermal or heat treatment of the precursor, is usually carried out at temperatures in the range of 600-1000°C. If hydroxides or carbonates are used as precursors, removal of water or carbon dioxide is first carried out, followed by the lithiation reaction. The heat treatment is carried out in a heated zone of an oven or kiln.

[0006] Much research has been done on improving various properties of cathode active materials, such as energy density, charge-discharge performance such as capacity fade, etc. However, many cathode active materials have problems with limited cycle life and voltage fade. This is especially true for many Mn-rich cathode active materials, where manganese dissolution is observed. The manganese can then poison the anode. Furthermore, gassing during cycling is another observation that results from the limited cycle life of manganese-rich cathodes. Summary of the Invention [Problem to be solved by the invention]

[0007] It was therefore an object of the present invention to provide an electrochemical cell having high energy density retention and reduced tendency to capacity loss due to manganese leaching. [Means for solving the problem]

[0008] Thus, a cathode as defined at the outset has been found, which in the following is also called the cathode of the invention. (1) A lithium-containing cathode active material having a molar content of manganese in the range of 50 to 85 mol % relative to the metals other than lithium contained in the cathode active material, hereinafter also referred to as cathode active material (1), (2) Particulate SiO2, hereafter also referred to as silica (2), (3) carbon in a conducting state, hereinafter also referred to as carbon (3), and (4) a binder polymer, hereinafter also referred to as binder (4), The binder (4) may comprise a single polymer or a blend of at least two polymers.

[0009] The mass is typically attached to a current collector, such as a metal foil, preferably aluminum foil. The mass may appear homogeneous to the naked eye. However, under 500-1000x magnification, different components can be distinguished, such as the cathode active material (1), silica (2), and carbon (3). A binder (4) acts as an adhesive to bond the mass to the current collector. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The cathode active material (1), silica (2), carbon (3) and binder (4) are described in further detail below.

[0011] In the context of the present invention, such cathode active materials having a manganese molar content in the range of 50 to 85 mol % relative to the metals other than lithium in said cathode active material include those having the composition LiNi 0.5 Mn 1.5 The so-called high-voltage spinels having O4, for example high-voltage spinels doped with Co, Fe, Ti, Al or Cu, and in particular those of the general formula Li 1+x TM 1-x The lithium-rich material has a layered structure of O2 (wherein x is in the range of 0.1 to 0.35, TM contains two or more transition metals, and 50 to 85 mol %, preferably 60 to 70 mol % of TM is Mn).

[0012] In a preferred embodiment of the present invention, the cathode active material has the composition Li 1+x TM 1-x O2, where x is in the range of 0.1 to 0.35, preferably 0.12 to 0.2, and TM is a combination of elements of general formula (I); (Ni a Co b Mn c ) 1-d M 1 d (I) (In the formula, a is in the range of 0.20 to 0.40, preferably 0.25 to 0.35, b is in the range of zero to 0.20, preferably 0.05 to 0.15; c is in the range of 0.50 to 0.85, preferably 0.60 to 0.70; d ranges from zero to 0.02; M 1 is selected from Al, Ti, Zr, W, Mo, Mg, Nb, and combinations of at least two of the foregoing; a+b+c=1).

[0013] The cathode active material (1) can be coated or uncoated.

[0014] A coated cathode active material as discussed in the context of the present invention refers to a batch of particulate cathode active material in which at least 50% of the particles are coated, with 0.5-2.5%, such as 0.75-1.25%, of the surface of each particle being coated. The coating may include a non-lithiated oxide, a lithiated oxide, or a combination of a non-lithiated oxide and a lithiated oxide. Examples of non-lithiated oxides include Al2O3, B2O3, TiO2, Sb2O3, ZrO2, WO3, Nb2O5, and combinations of at least two of the foregoing. Examples of lithiated oxides include Li2TiO3, Li4TiO4, Li2ZrO3, LiNbO3, LiSbO3, Li2WO4, LiBO2, Li3BO3, Li2B4O7, and combinations of at least two of the foregoing.

[0015] In one embodiment of the present invention, the cathode active material (1) has an average particle size D50 in the range of 2 to 20 μm, preferably 5 to 16 μm. The average particle size can be determined, for example, by light scattering or laser diffraction or electroacoustic spectroscopy. The particles are usually composed of aggregates from primary particles, and the above particle size refers to the particle size of the secondary particles.

[0016] In one embodiment of the present invention, the cathode active material (1) has a solubility in the range of 0.7 to 6.0 m, as determined according to DIN-ISO 9277:2003-05. 2 / g range of surface area (BET) of 1.7 to 3.8 m 2 / g or 3.0~5.5m 2 / g is preferred.

[0017] Some metals are ubiquitous, e.g., sodium, calcium or zinc, and trace amounts of them are present virtually everywhere, but such trace amounts are not considered in the context of the present invention, trace amounts in this context meaning amounts of 0.05 mol % or less based on the total metal content TM.

[0018] M 1 may be uniformly or non-uniformly distributed in the particles of the cathode active material (1). 1 In the particles of the cathode active material (1), the M 1 The concentration of the particles is higher in the center of the particle than in the center of the particle.

[0019] In one embodiment of the present invention, the cathode active material (1) is composed of spherical particles, i.e., particles having a spherical shape, including not only particles that are precisely spherical, but also particles in which the difference between the maximum and minimum diameters of at least 90% (number average) of a representative sample is 10% or less.

[0020] In one embodiment of the present invention, the cathode active material (1) is composed of secondary particles that are aggregates of primary particles. Preferably, the cathode active material of the present invention is composed of spherical secondary particles that are aggregates of primary particles. Even more preferably, the cathode active material of the present invention is composed of spherical secondary particles that are aggregates of platelet-shaped primary particles.

[0021] In one embodiment of the present invention, the primary particles of the cathode active material (1) have an average diameter in the range of 1 to 2000 nm, preferably 10 to 1000 nm, particularly preferably 50 to 500 nm. The average primary particle size can be determined, for example, by SEM or TEM. SEM is an abbreviation for scanning electron microscope, and TEM is an abbreviation for transmission electron microscope.

[0022] In one embodiment of the invention, the cathode active material (1) has a unimodal particle size distribution. In an alternative embodiment, the cathode active material (1) has a bimodal particle size distribution, for example with a maximum in the range of 3 to 6 μm and another maximum in the range of 9 to 12 μm.

[0023] In one embodiment of the present invention, the compressed density of the cathode active material (1) is determined at a pressure of 250 MPa and is 2.75 to 3.1 g / cm 3 The range is 2.85 to 3.10 g / cm 3 is preferred.

[0024] The cathode of the present invention preferably further comprises silica (2) having an average particle size (d50) in the range of 5 to 100 nm, preferably 5 to 20 nm. The average particle size (d50) refers to the average particle size of the primary particles. The primary particles may aggregate to form agglomerates, but deagglomeration may be achieved, for example, by stirring during the manufacture of the cathode. The agglomerates may have an average diameter (D50) in the range of 100 nm to 100 μm, preferably 100 nm to 1 μm. The determination of the particle size may be performed by particle size analysis, for example using a Malvern Panalytical.

[0025] In one embodiment of the present invention, silica (2) is employed as sand. In a preferred embodiment of the present invention, silica (2) is selected from spray-dried silica and fumed silica. Spray-dried silica can be produced by acidifying an aqueous solution of water glass and then spray-drying. Fumed silica can be produced by flame pyrolysis of SiCl4 or from quartz silica vaporized by electric arc.

[0026] The silica (2) is in the form of particles. Preferably, the particles are spherical or globular.

[0027] Silica (2) may have an acidic surface, which is determined by mixing the silica with water and determining the pH value. The pH value of a 10% by weight solution, measured at 23° C., may be in the range of 3.5 to 6.5.

[0028] The cathode of the present invention further comprises carbon (3), which can be selected from soot, activated carbon, carbon nanotubes, graphene, graphite, and a combination of at least two of the foregoing.

[0029] Suitable binders (4) are preferably selected from organic (co)polymers. Suitable (co)polymers, i.e. homopolymers or copolymers, can be selected, for example, from (co)polymers obtainable by anionic, catalytic or free radical (co)polymerization, in particular from polyethylene, polyacrylonitrile, polybutadiene, polystyrene and copolymers of at least two comonomers selected from ethylene, propylene, styrene, (meth)acrylonitrile and 1,3-butadiene. Polypropylene is also suitable. Polyisoprene and polyacrylates are furthermore suitable. Polyacrylonitrile is particularly preferred.

[0030] In the context of the present invention, polyacrylonitrile is understood to mean not only polyacrylonitrile homopolymers but also copolymers of acrylonitrile with 1,3-butadiene or with styrene. Polyacrylonitrile homopolymers are preferred.

[0031] In the context of the present invention, polyethylene refers not only to homopolyethylenes, but also to copolymerized ethylene with at least 50 mol % and up to 50 mol % of at least one further comonomer, such as α-olefins, such as propylene, butylene (1-butene), 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-pentene, and also isobutene, vinyl aromatics, such as styrene, and also (meth)acrylic acid, vinyl acetate, vinyl propionate, C1-C2 copolymers of (meth)acrylic acid. 10 -alkyl esters, in particular methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, 2-ethylhexyl acrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, and also copolymers of ethylene with maleic acid, maleic anhydride and itaconic anhydride. The polyethylene may be HDPE or LDPE.

[0032] In the context of the present invention, polypropylene is understood to mean not only homopolypropylene but also copolymers of propylene with at least 50 mol % copolymerized propylene and up to 50 mol % of at least one further comonomer, such as ethylene, and α-olefins, such as butylene, 1-hexene, 1-octene, 1-decene, 1-dodecene and 1-pentene. The polypropylene is preferably isotactic polypropylene or essentially isotactic polypropylene.

[0033] In the context of the present invention, polystyrene refers not only to homopolymers of styrene, but also to C1-C4 copolymers of acrylonitrile, 1,3-butadiene, (meth)acrylic acid, and (meth)acrylic acid. 10 -alkyl esters, divinylbenzene, in particular 1,3-divinylbenzene, 1,2-diphenylethylene and α-methylstyrene copolymers are also understood to mean.

[0034] Another preferred binder (4) is polybutadiene.

[0035] Other suitable binders (4) are selected from polyethylene oxide (PEO), cellulose, carboxymethyl cellulose, polyimides and polyvinyl alcohol.

[0036] In one embodiment of the invention, the binder (4) has an average molecular weight M ranging from 50,000 g / mol to 1,000,000 g / mol, preferably up to 500,000 g / mol. W The (co)polymers are selected from those having the formula:

[0037] The binder (4) may be a crosslinked or non-crosslinked (co)polymer.

[0038] In a particularly preferred embodiment of the present invention, the binder (4) is selected from halogenated (co)polymers, in particular fluorinated (co)polymers. Halogenated or fluorinated (co)polymers are understood to mean (co)polymers that contain at least one (co)polymerized (co)monomer with at least one halogen atom or at least one fluorine atom per molecule, more preferably at least two halogen atoms or at least two fluorine atoms per molecule. Examples include polyvinyl chloride, polyvinylidene chloride, polytetrafluoroethylene, polyvinylidene fluoride (PVdF), tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), vinylidene fluoride-tetrafluoroethylene copolymer, perfluoroalkyl vinyl ether copolymer, ethylene-tetrafluoroethylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, and ethylene-chlorofluoroethylene copolymer.

[0039] Suitable binders (4) are especially polyvinyl alcohol and halogenated (co)polymers, such as polyvinyl chloride or polyvinylidene chloride, in particular fluorinated (co)polymers, such as polyvinyl fluoride and especially polyvinylidene fluoride and polytetrafluoroethylene.

[0040] In one embodiment of the present invention, the cathode of the present invention comprises (1) in the range of 80 to 95% by weight, preferably 90 to 95% by weight, of a cathode active material; (2) Particulate SiO2 in the range of 1 to 10% by mass, preferably 1 to 5% by mass; (3) 1 to 10% by mass, preferably 1 to 3% by mass, of carbon in a conductive state; (4) a binder polymer in the range of 1 to 5% by weight, preferably 2 to 4% by weight, Including, The percentage is based on the sum of (1), (2), (3) and (4), therefore ignoring the mass of the current collector.

[0041] Electrochemical cells containing the cathodes of the present invention exhibit excellent electrochemical properties, especially with regard to Mn dissolution.

[0042] A further aspect of the present invention is (A) A cathode of the present invention comprising an electrode active material of the present invention, carbon, and a binder. (B) anode, (C) a separator, and (D) Electrolyte An electrochemical cell comprising:

[0043] The embodiments of the cathode (A) of the present invention have already been described in detail above.

[0044] The anode (B) may contain at least one anode active material, such as carbon (graphite), TiO2, lithium titanium oxide, silicon or tin or a silicon alloy. The anode may further contain a current collector, such as a metal foil, such as a copper foil.

[0045] In one embodiment of the invention, the cell according to the invention comprises one or more separators (C) by means of which the electrodes are mechanically separated. Suitable separators (C) are polymer films, in particular porous polymer films, which are unreactive towards metallic lithium. Particularly suitable materials for the separators are polyolefins, in particular film-forming porous polyethylene and film-forming porous polypropylene.

[0046] The separator (C) made of polyolefin, particularly polyethylene or polypropylene, may have a porosity in the range of 35 to 45%. The suitable pore size is, for example, in the range of 30 to 500 nm.

[0047] In another embodiment of the present invention, the separator (C) is selected from PET nonwoven fabrics filled with inorganic particles. Such separators may have a porosity in the range of 40-55%. Suitable pore sizes are, for example, in the range of 80-750 nm.

[0048] Preferred separators (C) are selected from those containing glass fibers.

[0049] The electrolyte (D) may comprise at least one non-aqueous solvent, at least one electrolyte salt, and optionally additives.

[0050] The non-aqueous solvent for the electrolyte can be liquid or solid at room temperature and is preferably selected from polymers, cyclic or acyclic ethers, cyclic and acyclic acetals, and cyclic or acyclic organic carbonates.

[0051] Examples of suitable polymers are in particular polyalkylene glycols, preferably poly-C1-C4-alkylene glycols and in particular polyethylene glycols, where the polyethylene glycols may contain up to 20 mol % of one or more C1-C4-alkylene glycols.The polyalkylene glycols are preferably polyalkylene glycols with two methyl or ethyl end caps.

[0052] The molecular weight M of suitable polyalkylene glycols, particularly suitable polyethylene glycols, W may be at least 400 g / mol.

[0053] The molecular weight M of suitable polyalkylene glycols, particularly suitable polyethylene glycols, W can be up to 5,000,000 g / mol, preferably up to 2,000,000 g / mol.

[0054] Examples of suitable acyclic ethers are, for example, diisopropyl ether, di-n-butyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, with 1,2-dimethoxyethane being preferred.

[0055] Examples of suitable cyclic ethers are tetrahydrofuran and 1,4-dioxane.

[0056] Examples of suitable acyclic acetals are, for example, dimethoxymethane, diethoxymethane, 1,1-dimethoxyethane and 1,1-diethoxyethane.

[0057] An example of a suitable cyclic acetal is 1,3-dioxane, and especially 1,3-dioxolane.

[0058] Examples of suitable acyclic organic carbonates are dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.

[0059] Examples of suitable cyclic organic carbonates are compounds according to the general formulae (II) and (III): [ka]

[0060] (In the formula, R 1 , R 2 and R 3can be the same or different and are selected from hydrogen and C1-C4-alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl, preferably R 2 and R 3 (Both cannot be tert-butyl).

[0061] In a particularly preferred embodiment, R 1 is methyl, R 2 and R 3 are each hydrogen or R 1 , R 2 and R 3 Each is hydrogen. In another embodiment, R 1 is F and R 2 and R 3 are hydrogen.

[0062] Another preferred cyclic organic carbonate is vinylene carbonate of formula (IV).

[0063] [ka]

[0064] Preferably, the solvent or solvents are used in an aqueous state, ie with a water content in the range of 1 ppm to 0.1% by weight, which can be determined, for example, by Karl Fischer titration.

[0065] The electrolyte further comprises at least one electrolyte salt. Suitable electrolyte salts are in particular lithium salts. Examples of suitable lithium salts are LiPF6, LiBF4, LiClO4, LiAsF6, LiCF3SO3, LiC(C n F 2n+1 SO2)3, lithium imide, e.g. LiN(C n F 2n+1 SO2)2 (wherein n is an integer ranging from 1 to 20), LiN(SO2F)2, Li2SiF6, LiSbF6, LiAlCl4, and compounds of the general formula (C n F 2n+1SO2) t Salt of YLi where t=1 when Y is selected from oxygen and sulfur; when Y is selected from nitrogen and phosphorus, t=2; When Y is selected from carbon and silicon, t=3).

[0066] Preferred electrolyte salts are selected from LiC(CF3SO2)3, LiN(CF3SO2)2, LiPF6, LiBF4, LiClO4, with LiPF6 and LiN(CF3SO2)2 being particularly preferred.

[0067] The battery according to the invention further comprises a housing which may have any shape, for example a cube, or the shape of a cylindrical disk or can. In one variant, a metal foil configured as a pouch is used as the housing.

[0068] The cell according to the invention exhibits good discharge behavior, very good discharge and cycling behavior, and a greatly reduced tendency towards manganese leaching.

[0069] The battery according to the present invention may comprise two or more electrochemical cells that are combined with each other, for example, connected in series or connected in parallel. A series connection is preferred. In the battery according to the present invention, at least one electrochemical cell contains at least one cathode according to the present invention. Preferably, in the electrochemical cell according to the present invention, the majority of the electrochemical cells contain the cathode according to the present invention. Even more preferably, in the battery according to the present invention, all the electrochemical cells contain the cathode according to the present invention.

[0070] The present invention further provides a method for using the battery according to the present invention in equipment, especially mobile equipment.Examples of mobile equipment are vehicles, such as automobiles, bicycles, aircraft, or water vehicles, such as boats or ships.Other examples of mobile equipment are manually operated, such as computers, especially laptops, phones, or powered hand tools, for example in the construction sector, especially drills, battery-powered drivers, or battery-powered staplers.

[0071] A further aspect of the present invention relates to a method for producing an inventive cathode, hereinafter also called the inventive method or the inventive method. The inventive method comprises the following steps: (a) in the presence of an organic solvent or water, (1) A lithium-containing cathode active material having a molar content of manganese in the range of 50 to 85 mol % relative to the metals other than lithium contained in the cathode active material; (2) Particulate SiO2, (3) Carbon in a conductive state, and (4) a binder polymer, and combining the (b) applying the mixture from step (a) to a current collector; (c) removing the water or organic solvent from step (a); Includes.

[0072] The cathode active material (1), silica (2), carbon (3) and binder (4) are described in detail above.

[0073] Step (a) may be abbreviated below as (a), step (b) may be abbreviated below as (b), and step (c) may be abbreviated below as (c).

[0074] In step (a), the cathode active material (1), silica (2), carbon (3) and binder (4) are combined in one step or in two or more sub-steps. One step is preferred. Combining the cathode active material (1), silica (2), carbon (3) and binder (4) may be supported by a mixing operation, such as stirring. High speed stirring at 1000 to 15000 revolutions per minute ("rpm") is preferred.

[0075] Step (a) is carried out in the presence of water, an organic solvent, a combination of water and an organic solvent, or a combination of at least two organic solvents. Among the organic solvents, non-chlorinated solvents are preferred. Among the organic solvents, aprotic solvents are preferred. More preferred examples of organic solvents include acetone, tetrahydrofuran (THF), N-ethylpyrrolidone (NEP), N-methylpyrrolidone (NMP), and N,N-dimethylformamide (DMF).

[0076] Step (a) may be carried out at a temperature in the range of from 5 to 60° C., preferably from 15 to 40° C., and even more preferably at ambient temperature.

[0077] The mixture resulting from step (a) has the appearance of a slurry or paste and may have a solids content ranging from 5 to 80% or 80.5% to 95%.

[0078] Preferably, the mixture resulting from step (a) is free of nodules, with no nodules detectable by the naked eye.

[0079] In one embodiment of the invention, the mixture resulting from step (a) has a dynamic viscosity at 23° C. determined at a shear rate of 10 Hz in the range of 200 to 5,000 mPa s, preferably 100 to 800 mPa s. The dynamic viscosity can be determined, for example, using a rotational viscometer, such as a Haake viscometer.

[0080] Then, in step (b), the mixture obtained in step (a) is applied to a current collector. Depending on the viscosity of the mixture, said application can be carried out using a slit nozzle, a spray, a doctor blade. Extrusion is also possible.

[0081] The mixture obtained in step (a) may have a thickness in the range of 30 to 500 μm, preferably 50 to 200 μm, which is determined after step (c) to eliminate the effect of the solvent.

[0082] The mixture obtained in step (a) may be applied to one or preferably both sides of a current collector by repeating steps (b) and (c) one or more times.

[0083] Step (c) comprises removing the water or organic solvent from step (a), which may be accomplished by freeze-drying, vacuum drying, heating, for example to a temperature of 25-150° C., preferably 100-130° C., or a combination of heating and vacuum drying, or a combination of freeze-drying and vacuum drying.

[0084] If vacuum drying is performed, a pressure in the range of 10-100 mbar (abs) is preferred. Furthermore, it is preferred to displace the vapor from the solvent(s) and to supply an inert gas, e.g. N2, at operating conditions, e.g. 100 mbar.

[0085] The duration of step (c) can range from 1 minute to 24 hours, preferably from 10 minutes to 24 hours.

[0086] Step (c) can be carried out, for example, in a drying tunnel. The residence time in the drying tunnel can range from 5 to 30 minutes, preferably from 10 to 20 minutes.

[0087] From step (c) a blank is obtained which can either function directly as a cathode or can be customized ("finished"), for example by cutting to the desired shape. In a preferred embodiment, the blank is first compressed in step (d), heat treated in step (e) and then finished. A preferred method is for step (d) to be carried out in a calendar or press.

[0088] Preferred conditions for carrying out step (d) with a calender are a line pressure of the rollers of said calender in the range of 100-500 N / mm, preferably 110-150 N / mm.The preferred processing speed is 0.1-1 m / min.

[0089] Preferred conditions for carrying out step (d) in a press are pressures in the range of 100-1000 MPa, preferably 100-500 MPa. The preferred residence time is 5-10 minutes.

[0090] Suitable treatment temperatures for step (d) are in the range of 15 to 95°C, preferably 25 to 35°C.

[0091] The heat treatment step (e) involves heating the compressed blank from step (d) to a temperature 35-5° C. below the melting or softening point of the binder (4) (see, for example, US 2015 / 0280206), or even higher, for example a temperature above the melting or softening point of the binder (4), for example 50° C. above. However, decomposition of the binder (4) should be avoided.

[0092] Examples of finishing steps include stamping, cutting, or punching to obtain the desired shape. EXAMPLES

[0093] The present invention is further illustrated by the following examples.

[0094] The average particle size (D50) was determined by dynamic light scattering ("DLS"). Percentages are by weight unless otherwise stated.

[0095] The surface acidity was determined after stirring 500 mg of silica (2.1) in 5 ml of distilled water for 15 min.

[0096] Unless otherwise stated, percentages and ppm refer to percent by weight and ppm by weight, respectively.

[0097] Starting materials: Cathode active material (1.1) ("CAM (1.1)"): Li 1.14 (Ni 0.26 Co 0.14 Mn 0.60 ) 0.86 O2 CAM (1.1) was prepared as follows: The precursor was prepared by precipitating Ni-Co-Mn mixed carbonates from a solution of nickel sulfate / cobalt sulfate / manganese sulfate in a molar ratio of 26:14:60, followed by drying at 200°C under air. The precipitant was an aqueous solution of sodium carbonate in aqueous ammonia. Average particle size (D50): 10.2 μm.

[0098] In the roller hearth kiln, a homogeneous mixture of precursors and Li2CO3 was placed in a sagger in a forced air flow such that the molar ratio of lithium to the sum of the transition metals was 1.42:1. The mixture was heated to 800 °C. Once 800 °C was reached, heating was continued at 800 °C for 4 h. Li(Ni)O3 with the formula 0.33 Li2MnO3 0.67 was obtained. 0.4 Co 0.2 Mn 0.4 )O2, the formation of a metal oxide of the formula Li 1.14 TM 0.86 Compatible with O2.

[0099] Silica (2.1): (Details: fumed silica, particle size 5-15 nm, acidity: pH value 6.5 at 23°C, purchased from Sigma-Aldrich) Carbon (3.1): Carbon black, commercially available as SuperC65, Imerys, Switzerland Binder (4.1): Polyvinylidene fluoride (PVDF, Solef5130, Solvay, Belgium) All operations in step (a) were carried out in a glove box (less than 0.1 ppm O2 and H2O).

[0100] I. Cathode Fabrication I.1 Preparation of the cathode (A.1) of the invention: CAM (1.1), silica (2.1), carbon (3.1), and binder (4.1) were mixed in a mass ratio of 87.5:5.0:4.0:3.5.

[0101] Step (a.1): Carbon (3.1) and binder (4.1) were placed in a dissolver (Dispermat LC30, VMA-Getzmann, Germany) and stirred at 5000 rpm for 5 min. Then, silica (2.1) at 50% solids in NMP was added in three portions and the resulting ink-like slurry was mixed at 10000 rpm for 5 min after each NMP addition. Then, CAM (1.1) was added and the resulting slurry was mixed for another 5 min at 10,000 rpm.

[0102] Step (b.1): The mixture from step (a.1) was then coated onto an aluminum foil (thickness 18 μm, MTI Corporation, USA) using a four-edged blade (RK PrintCoat Instruments, UK). A coated aluminum foil was obtained.

[0103] Step (c.1): The coated aluminum foil was dried at ambient temperature in a glove box for 15 hours to allow the NMP to evaporate.

[0104] Steps (d.1) and (e.1) were performed after customization.

[0105] Finishing: A crude cathode in the shape of a disk having a diameter of 14 mm was punched out.

[0106] Steps (d.1) and (e.1): The disk-shaped crude cathode was compressed in a 2.5 ton (corresponding to ≈160 MPa) hydraulic press and dried in a glass oven (Drying Oven 585, Büchi, Switzerland) at 120 °C under dynamic vacuum for 15 h. The CAM loading was 8.5 mg CAM(1.1) / cm. 2 and 2.1mA / h / cm 2 (based on the nominal specific capacity of CAM (1.1) of 250 mA / h / g). A cathode (A.1) according to the invention was obtained.

[0107] I.2 Preparation of Comparative Cathode (A.2): CAM (1.1), silica (2.1), carbon (3.1), and binder (4.1) were mixed in a mass ratio of 92.5:0:4.0:3.5.

[0108] Step C-(a.2): Carbon (3.1) and binder (4.1) were placed in a dissolver (Dispermat LC30, VMA-Getzmann, Germany) and stirred at 5000 rpm for 5 min. Silica (2.1) at 50% solids in NMP was then added in three portions and the resulting ink-like slurry was mixed at 10000 rpm for 5 min after each NMP addition. CAM (1.1) was then added and the resulting slurry was mixed for an additional 5 min at 10,000 rpm.

[0109] Step (b.2): The mixture from step C-(a.2) was then coated onto an aluminum foil (thickness 18 μm, MTI Corporation, USA) using a four-edged blade (RK PrintCoat Instruments, UK). A coated aluminum foil was obtained.

[0110] Step (c.2): The coated aluminum foil was dried at ambient temperature in a glove box for 15 hours to allow the NMP to evaporate.

[0111] Steps (d.2) and (e.2) were performed after customization.

[0112] Finishing: A crude cathode in the shape of a disk having a diameter of 14 mm was punched out.

[0113] Steps (d.2) and (e.2): The disk-shaped crude cathode was compressed in a 2.5 ton (corresponding to ≈160 MPa) hydraulic press and dried in a glass oven (Drying Oven 585, Büchi, Switzerland) at 120 °C under dynamic vacuum for 15 h. The CAM loading was 8.5 mg CAM(1.1) / cm. 2 and 2.1mA / h / cm 2 (based on the nominal specific capacity of CAM (1.1) of 250 mA / h / g). A comparative cathode C-(A.2) was obtained.

[0114] II. Electrochemical Cell Construction and Testing II.1 Coin Cell Manufacturing Anode (B.1): Graphite on copper foil.

[0115] II.2 Testing Galvanostatic cycling was performed using a battery cycler (Series 4000, Maccor, USA) at 25 °C in a temperature-controlled oven (Binder, Germany) using 2032-type coin cells (Hohsen Corp., Japan). For full-cell experiments, a graphite anode with a diameter of 15 mm and a cathode with a diameter of 14 mm were assembled with two Celgard® polypropylene separators (CG, C2500, Celgard, USA) (C.1) or two glass fiber separators (GF, glass microfiber, GF / A, VWR, Germany) (C.2), in each case containing 80 μl of 1 M LiPF6 in fluoroethylene carbonate / diethyl carbonate (2:8, g:g) electrolyte. After assembly, all cells were rested for 2 h (to fully wet the separator) before charge-discharge cycling, and C-rates were based on a nominal capacity of 250 mAh / g. A full cell with an LRM-NCM cathode was activated in a constant current procedure (CC) at a C-rate of C / 15 to 4.7 V in the first cycle, and then discharged at C / 15 to 2.0 V (CC). In the three subsequent cycles, the upper cutoff cell voltage was lowered to 4.6 V during charging and discharging, and the C-rate was C / 10. This was followed by fast cycling, where the cell was charged and discharged at C / 2 (CCCV) / 3C (CC) for three cycles each, with all constant voltage (CV) steps terminated after 1 h or when the current dropped below C / 100. Then, 33 cycles were performed at a charge rate of C / 2 (CCCV) and a discharge rate of 1C (CC), with the CV steps defined as above. This sequence of three C / 10 discharges, three 3C discharges, and 33 1C discharges was repeated for a total of 120 cycles.

[0116] [Table 1]

Claims

1. (1)A lithium-containing cathode active material having a molar content of manganese in the range of 50 to 85 mol% with respect to a metal other than lithium contained in the cathode active material, (2)Particulate SiO having an average particle size (D50) in the range of 5 to 100 nm ２ , (3)Carbon in a conductive state, and (4)A binder polymer, A cathode containing a mass containing the above, The cathode, wherein the mass is coated on a current collector.

2. (1)A cathode active material in the range of 80 to 95% by mass, (2) particulate SiO in the range of 1 to 10% by mass ２ , (3)Carbon in a conductive state in the range of 1 to 10% by mass, (4)A binder polymer in the range of 1 to 5% by mass, Including, The cathode according to claim 1, wherein the percentages are based on the total of (1), (2), (3) and (4).

3. The SiO ２ is selected from spray-dried silica and fumed silica, the cathode according to claim 1 or 2.

4. The cathode active material has the composition LiNi ０．５ Mn １．５ O ４ The cathode according to claim 1 or 2, having said composition.

5. wherein the cathode active material has a composition Li １＋ｘ TM １－ｘ O ２ where x ranges from 0.1 to 0.35, and TM is a combination of elements of general formula (I). (Ni a Co b Mn c ) 1-d M 1 d (I) (Wherein a is in the range of 0.20 to 0.40, b is in the range of zero to 0.20, c is in the range of 0.60 to 0.70, d is in the range of zero to 0.02, M １ is selected from Al, Ti, Zr, W, Mo, Mg, and Nb, a + b + c = 1), the cathode according to claim 1 or 2.

6. The cathode according to claim 5, wherein a > b.

7. (A)The cathode according to claim 1 or 2, An electrochemical cell containing the same.

8. (B)A separator containing glass fibers, The electrochemical cell according to claim 7, further comprising the same.

9. The following steps: (a)In the presence of an organic solvent or water, (1)A lithium-containing cathode active material having a molar content of manganese in the range of 50 to 85 mol% with respect to a metal other than lithium contained in the cathode active material, (2)Particulate SiO having an average particle diameter (D50) in the range of 5 to 100 nm ２ , (3)Carbon in a conductive state, and (4)A binder polymer, Combining the steps, (b)Applying the mixture from step (a) to a current collector, (c)Removing water or an organic solvent from step (a) A method for producing the cathode according to claim 1 or 2, comprising the steps.