Method for preparing cathode active material and cathode active material obtained thereby

Abstract

The present invention relates to a compound represented by the formula (I) LiNi x Co y Mn z The present invention provides a method for preparing an O2 cathode active material, the method comprising the steps of: i) preparing a precursor of hydroxides or carbonates of Ni, Co and Mn; ii) mixing the precursor obtained from step i) with a Li source; and iii) calcining the mixture obtained from step ii), wherein step iii) comprises a multi-step calcination, wherein x is in the range of 0.80-0.95, preferably 0.80-0.92; y is in the range of 0.01-0.15, preferably 0.01-0.12; z is in the range of 0.01-0.15, preferably 0.01-0.12; and the sum of x, y and z is 1.

Description

[Technical field]

[0001] The present invention relates to a method for preparing a cathode active material, and more particularly to a method for preparing a cathode active material having a single crystal of an octahedral structure. [Background technology]

[0002] Lithium-ion batteries are widely used in various fields, from small devices such as mobile phones and laptops to automotive batteries and other batteries for e-mobility. Electrodes, electrolytes and separators are the main components of a battery and together determine the performance of the battery. Among them, cathode active materials (CAMs) account for about 30% of the total battery manufacturing cost and play a key role in lithium-ion battery technology. Commonly used cathode active materials include lithium iron phosphate, lithium cobalt oxide, and lithiated nickel-cobalt-manganese oxide ("NCM").

[0003] NCMs are the preferred choice since they have a higher diffusion rate of Li-ions and electron mobility, thus reaching higher energy density. Also, high-Ni NCMs, i.e., NCMs with a Ni content of at least 80 mol % relative to the total moles of Ni, Co, and Mn, have been developed to meet the requirements of electric vehicles (EVs). Examples of high-Ni NCMs include LiNi 0.80 Co 0.10 Mn 0.10 O2(Ni80), LiNi 0.83 Co 0.12 Mn 0.05 O2(Ni83), LiNi 0.88 Co 0.06 Mn 0.06 O2(Ni88), LiNi 0.90 Co 0.05 Mn 0.05 O2(Ni90) and LiNi 0.92 Co 0.04 Mn 0.04 Contains O2(Ni92).

[0004] On the other hand, single crystal CAMs (SCMs) are becoming increasingly attractive because they have fewer phase boundaries and exposed surfaces compared to polycrystalline materials, which can effectively reduce structural degradation of the cathode active material, electrolyte side reactions and gas generation, and further improve cycle stability and safety. However, SCMs on the market exhibit irregular and shapeless bulk morphology, which is clearly different from the definition of SCMs, i.e., regular polyhedral shapes with well-defined edges.

[0005] It has been reported that the addition of Na2SO4 and NaCl as fluxing agents during the calcination step of SCM production can produce well-formed SCM, but a washing step is required to remove the residual Na2SO4 and NaCl, which adds additional cost and process complexity, especially when the preparation is scaled up from the laboratory to mass production. Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, there remains a need to provide a method for producing well-formed SCM that can be applied on an industrial scale. [Means for solving the problem]

[0007] In one embodiment, the present invention provides a compound of formula (I): LiNi x Co y Mn z O2(I) 1. A method for preparing a cathode active material of claim 1, comprising the steps of: i). Preparing precursors of hydroxides or carbonates of Ni, Co and Mn; ii). mixing the precursor obtained from step i) with a Li source; and iii). A step of firing the mixture obtained from step ii). The present invention provides a method for producing a semiconductor device, comprising: The step iii) comprises a multi-stage calcination, In the above formula, x is in the range of 0.80 to 0.95, and preferably 0.80 to 0.92, y is in the range of 0.01 to 0.15, and preferably 0.01 to 0.12, z is in the range of 0.01 to 0.15, and preferably 0.01 to 0.12, and the sum of x, y and z is 1.

[0008] In another aspect, the present invention relates to a single crystalline form of the compound of formula (I) having an octahedral structure. LiNi x Co y Mn z O2(I) and providing a cathode active material of In the above formula, x is in the range of 0.80 to 0.95 and preferably 0.80 to 0.02, y is in the range of 0.01 to 0.15 and preferably 0.01 to 0.12, z is in the range of 0.01 to 0.15 and preferably 0.01 to 0.12, and the sum of a, b and c is 1; The lattice parameters a, b, and c are 2.88047 Å, 2.88047 Å, and 14.20877 Å, respectively. The cathode active material has an average particle size of 3.5um-4.5um by PSD (particle size distribution) measurement, a press density of 3.0g / ml-4.0g / ml as tested by Mitsubishi Chemical Analytech's Powder Resistivity Measurement Unit MCP-PD51, and a conductivity of 0.004S / m-0.08S / m according to JIS K7194 / JIS R1637.

[0009] In a further aspect, the present invention provides a method for producing a method for treating a cancer cell comprising the steps of: (A) 50% by weight to 98.99% by weight of the cathode active material obtainable from the method of the present invention; (B) 1% to 5% by weight of carbon in an electrically conductive state; (C) 0.01% to 5% by weight of a binder, and (D) 0 to 50% by mass, based on the total mass of components (A), (B), (C) and (D), of a solid electrolyte. A cathode comprising: [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 shows the calcination profile of the TTT procedure in the synthesis of single crystal NCM Ni90. [Diagram 2] FIG. 2 shows the calcination profile of the general procedure for the synthesis of NCM Ni90. [Diagram 3] FIG. 3(a) shows an SEM image at 10 kx magnification of a sample synthesized by the normal procedure. [Figure 4] FIG. 3(b) shows an SEM image at a magnification of 20 kx of the sample synthesized by the normal procedure. [Diagram 5] FIG. 3(c) shows an SEM image at 10 kx magnification of the sample synthesized by the TTT procedure. [Figure 6] FIG. 3(d) shows a SEM image at 20 kx magnification of the sample synthesized by the TTT procedure. [Figure 7] FIG. 4 shows the XRD of single crystal NCM Ni90 synthesized by the TTT procedure. [Figure 8] FIG. 5 shows the firing profiles at different TTT temperatures. [Figure 9] FIG. 6(a) shows an SEM image of the sample synthesized without TTT. [Figure 10] FIG. 6(b) shows an SEM image of the sample synthesized at a TTT temperature of 900° C. [Figure 11] FIG. 6(c) shows an SEM image of the sample synthesized at a TTT temperature of 970° C. [Figure 12] FIG. 6(d) shows an SEM image of the sample synthesized at a TTT temperature of 1040° C. [Figure 13] FIG. 7 shows a comparison of the pressed densities of samples synthesized at different TTT temperatures. [Figure 14] FIG. 8 shows a comparison of the electrical conductivities of samples synthesized at different TTT temperatures. [Figure 15] FIG. 9 is a diagram showing the firing profile at each time point during the transient heat treatment. [Figure 16]FIG. 10(a) shows an SEM image of the sample synthesized in step B, which involves sequential 15 min TTT and 10 h baseline heating. [Figure 17] FIG. 10(b) shows an SEM image of the sample synthesized in step B, which involves sequentially performing 2 hours of baseline heating, 15 minutes of TTT, and 8 hours of baseline heating. [Figure 18] FIG. 10(c) shows an SEM image of the sample synthesized in step B, which involves sequentially performing 4 hours of baseline heating, 15 minutes of TTT, and 6 hours of baseline heating. [Figure 19] FIG. 10(d) shows an SEM image of the sample synthesized in step B, which involves sequentially performing 6 hours of baseline heating, 15 minutes of TTT, and 4 hours of baseline heating. [Figure 20] FIG. 10(e) shows an SEM image of the sample synthesized in step B, which involves sequentially performing 8 hours of baseline heating, 15 minutes of TTT, and 2 hours of baseline heating. [Figure 21] FIG. 10(f) shows an SEM image of the sample synthesized in step B, which involves 10 hours of baseline heating followed by 15 minutes of TTT. [Figure 22] FIG. 11 shows the pressed density comparison of samples subjected to TTT at different time points. [Diagram 23] FIG. 12 shows a comparison of the electrical conductivity of samples subjected to TTT at different time points. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention relates to a compound represented by formula (I) LiNi x Co y Mn z O2(I) 1. A method for preparing a cathode active material of claim 1, comprising the steps of: i). Preparing precursors of hydroxides or carbonates of Ni, Co and Mn; ii). mixing the precursor obtained from step i) with a Li source; and iii). A step of firing the mixture obtained from step ii). The present invention provides a method for producing a semiconductor device, comprising: The step iii) comprises a multi-stage calcination, In the above formula, x is in the range of 0.80 to 0.95, and preferably 0.80 to 0.92, y is in the range of 0.01 to 0.15, and preferably 0.01 to 0.12, z is in the range of 0.01 to 0.15, and preferably 0.01 to 0.12, and the sum of x, y and z is 1.

[0012] The cathode active material of formula (I) is a Ni-rich NCM product containing at least 80 mole % of element Ni relative to the total moles of elements Ni, Co and Mn. For example, LiNi 0.80 Co 0.10 Mn 0.10 O2(Ni80), LiNi 0.83 Co 0.12 Mn 0.05 O2(Ni83), LiNi 0.88 Co 0.06 Mn 0.06 O2(Ni88), LiNi 0.90 Co 0.05 Mn 0.05 O2(Ni90) and LiNi 0.92 Co 0.04 Mn 0.04 O2(Ni92), preferably LiNi 0.83 Co 0.12 Mn 0.05 O2(Ni83), LiNi 0.88 Co 0.06 Mn 0.06 O2(Ni88), LiNi 0.90 Co 0.05 Mn 0.05 O2(Ni90) and LiNi 0.92 Co 0.04 Mn 0.04 O2(Ni92), more preferably LiNi 0.88 Co 0.06 Mn 0.06 O2(Ni88), LiNi 0.90 Co 0.05 Mn 0.05 O2(Ni90) and LiNi 0.92 Co 0.04 Mn 0.04O2(Ni92), and even more preferably LiNi 0.90 Co 0.05 Mn 0.05 O2(Ni90)andLiNi 0.92 Co 0.04 Mn 0.04 Examples include O2(Ni92).

[0013] Steps (i) to (iii) of the method of the present invention are performed in sequence, and may or may not include one or more intermediate steps. In some embodiments, the precursor of step (i) may be prepared by co-precipitating Ni, Co, and Mn as hydroxides. In this case, a solution containing water-soluble salts of nickel, cobalt, and manganese is contacted with a base, such as a solution of an alkali metal hydroxide or an alkali metal carbonate, preferably a solution of an alkali metal hydroxide. Examples of alkali metal hydroxides are potassium hydroxide and sodium hydroxide. Examples of alkali metal carbonates are sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate. The contact with the base may be performed by simultaneously charging the base and a solution of one or more water-soluble salts of nickel, cobalt, and manganese into a vessel, preferably with stirring. Such contact is preferably performed by providing a solution of an alkali metal hydroxide and a solution containing water-soluble salts of cobalt, nickel, and manganese according to the molar ratio of formula (I). Water-soluble in the context of the present invention means that such salts have a solubility of at least 20 g / l in distilled water at 20° C., the amount of salt being determined omitting water of crystallization and water resulting from aquo complexes. The water-soluble salts of nickel, cobalt and manganese are preferably Ni 2+ , Co 2+ and Mn 2+ and the like.

[0014] The co-precipitation of step (i) is preferably carried out at a temperature in the range of 10° C. to 85° C., more preferably 20° C. to 60° C. The co-precipitation of step (i) is preferably carried out at a pH value in the range of 8 to 13, more preferably 11 to 12.5, and even more preferably 11.5 to 12.2, measured in the mother liquor at 23° C. The co-precipitation is carried out under a pressure in the range of 0.5 bar to 20 bar, preferably 1 atm.

[0015] A stoichiometric or excess amount of base, for example an alkali metal hydroxide, is used relative to the total moles of the elements Ni, Co and Mn. The molar excess may be, for example, in the range of 1.01:1 or more, and it is preferred to use the stoichiometric ratio. The aqueous solution of the alkali metal hydroxide has a concentration in the range of 1% to 50% by weight, preferably 10% to 25% by weight. The concentration of the aqueous solution of nickel, cobalt and manganese salts can be chosen within wide limits, preferably in the range of 1 mol / L to 1.8 mol / L, more preferably 1.5 mol / L to 1.7 mol / L of the total moles of nickel, cobalt and manganese relative to the volume of the solution.

[0016] The coprecipitation in step (i) is carried out in the presence of at least one compound L capable of functioning as at least one ligand of the transition metal, such as an organic amine, preferably ammonia. The concentration of compound L, such as ammonia, is preferably in the range of 0.05 mol / L to 1 mol / L, more preferably 0.1 mol / L to 0.7 mol / L. Preferably, the amount of ammonia is in a range of 0.05 mol / L to 1 mol / L, more preferably 0.1 mol / L to 0.7 mol / L. 2+ The amount of ions should be less than 1000 ppm, more preferably less than 500 ppm.

[0017] During the coprecipitation in step (i), the mixing using a stirrer is preferably carried out at a stirring speed of at least 1 W / l, more preferably at least 3 W / l, and even more preferably at least 5 W / l, and not more than 25 W / l. During the coprecipitation in step (i), it is preferred not to use any reducing agent, such as hydrazine, ascorbic acid, glucose, or alkali metal sulfite.

[0018] The coprecipitation in step (i) can be carried out in air, in an inert gas atmosphere, such as a rare gas or nitrogen atmosphere, or in a reducing atmosphere, such as SO2, and is preferably carried out in air or an inert gas atmosphere.

[0019] By the coprecipitation of step (i), mixed hydroxides or carbonates, preferably hydroxides of nickel, cobalt and manganese, are obtained in the form of a particle slurry in a mother liquor. The particles preferably have a spherical shape. The spherical particles are not limited to those having a strictly spherical shape, but also include particles whose maximum and minimum diameters differ by no more than 10%, preferably no more than 5%. In some embodiments of the present invention, the coprecipitation in step (i) is carried out for a period of 1 hour to 40 hours, preferably 2 hours to 30 hours, and in some other embodiments, step (i) is carried out with an intermediate step, and the period excluding the intermediate step ranges from 1 hour to 40 hours, preferably 2 hours to 30 hours.

[0020] The resulting precursor is removed from the mother liquor and dried in the presence of an oxygen-containing atmosphere. The removal can be achieved by filtration, centrifugation, decantation, spray drying, settling or a combination thereof. Suitable devices are for example filter presses, belt filters, spray dryers, hydrocyclones, tilted clarifiers or a combination thereof.

[0021] After removal, the precursor may be washed. Washing can be accomplished, for example, with pure water or an aqueous solution of an alkali metal carbonate or alkali metal hydroxide, preferably an aqueous solution of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide or ammonia, more preferably an aqueous solution of water and sodium hydroxide. Washing can be accomplished, for example, at elevated pressure or temperature, for example, 30°C to 50°C. In some embodiments, washing is performed at room temperature. The efficiency of washing can be confirmed by analytical measurements. For example, the content of transition metal(s) in the washing water can be analyzed. When washing is performed with water rather than an aqueous solution of an alkali metal hydroxide, the conductivity of the water after washing can be used to confirm whether water-soluble substances, for example water-soluble salts, can still be washed away.

[0022] After removal, drying may be performed in the presence of oxygen. The presence of oxygen here refers to the presence of a gas containing oxygen, such as air, pure oxygen, a mixture of oxygen and air, and an atmosphere of air diluted with an inert gas such as nitrogen. Drying may be performed, for example, at a temperature in the range of 30°C to 150°C.

[0023] To carry out step (ii) of the method of the invention, the precursor can be mixed with at least one lithium source, such as at least one compound selected from Li2O, LiOH and Li2CO3, the preferred lithium source being Li2CO3. The amounts of precursor and lithium compound are selected so as to obtain the stoichiometry of formula (I).

[0024] The mixing in step (ii) may be carried out at ambient temperature and at 1 atmosphere pressure. In some embodiments, the mixing is carried out in a mixer, such as a paddle mixer, a ploughshare mixer, a free-fall mixer, a roller mill, or a high-shear mixer. And a ploughshare mixer is preferred. The mixing can be carried out at a speed ranging from 5 rpm to 500 rpm, preferably from 5 rpm to 60 rpm. When applying a free-fall mixer, a speed ranging from 5 rpm to 25 rpm is preferred, and a range from 5 rpm to 10 rpm is more preferred. When applying a ploughshare mixer, a speed ranging from 50 rpm to 400 rpm is preferred, and a range from 100 rpm to 250 rpm is more preferred. When applying a high-shear mixer, the agitator has a speed ranging from 100 rpm to 950 rpm, and the chopper has a speed ranging from 100 rpm to 3750 rpm.

[0025] To carry out step (iii) of the method of the present invention, the mixture of precursor and lithium compound is calcined in multiple steps. The multiple steps include step A, which is heated at a temperature in the range of 300°C to 600°C, and preferably 400°C to 600°C, and step B, which is followed by step A, which is heated at a temperature in the range of 750°C to 900°C, and preferably 750°C to 850°C. The step A has a duration of 1 hour to 7 hours, and preferably 3 hours to 5 hours. And the step B has a duration of 6 hours to 16 hours, and preferably 8 hours to 14 hours. From step A to step B, a heating rate of 1 K / min to 10 K / min, preferably 2 K / min to 5 K / min, can be applied. During step A, the heating temperature is kept stable within a fluctuation of ±5°C.

[0026] Step (iii) of the method of the present invention can be carried out in a furnace, such as a rotary tube furnace, a muffle furnace, a pendulum furnace, a roller hearth furnace, a push-through furnace, and combinations thereof. In some embodiments, step (iii) is carried out in an oxygen-containing atmosphere. Examples of oxygen-containing atmospheres include air, pure oxygen, a mixture of oxygen and air, and air diluted with an inert gas such as nitrogen. It is preferred to use an atmosphere of oxygen, or oxygen diluted with air or nitrogen, and the minimum content of oxygen is 21% by volume. In some other embodiments, step (iii) is carried out in an atmosphere with a reduced CO2 content, for example, a carbon dioxide content in the range of 0.01 ppm to 500 ppm by weight, preferably 0.1 ppm to 50 ppm by weight. The CO2 content may be measured, for example, by optical methods using infrared light. More preferably, step (iii) is carried out in an atmosphere having a carbon dioxide content lower than the limit detectable by optical methods using infrared light.

[0027] Step B includes a transient thermal treatment (TTT). As used herein, "transient thermal treatment (TTT)" means that during step B of step (iii), the temperature is increased by 100°C to 450°C above the baseline temperature of step B and maintained for a short period of time. The temperature of the TTT can be in the range of 1000°C to 1400°C, preferably 1000°C to 1200°C, for example, 1000°C to 1100°C. The duration of the TTT can be 1 minute to 1 hour, preferably 1 minute to 30 minutes, more preferably 5 minutes to 20 minutes. During step B, except for the period of the TTT, the heating temperature is kept stable within a fluctuation of ±5°C.

[0028] TTT is carried out in an oxygen-containing atmosphere. Examples of oxygen-containing atmospheres include air, pure oxygen, a mixture of oxygen and air, and air diluted with an inert gas such as nitrogen. It is preferred to use an atmosphere of oxygen, or oxygen diluted with air or nitrogen, in TTT, and the minimum content of oxygen is 21% by volume.

[0029] During the temperature change from the baseline temperature of step B to the baseline temperature of TTT a heating rate of 1 K / min to 10 K / min, and preferably 2 K / min to 5 K / min can be applied. During the temperature change from the baseline temperature of TTT back to the baseline temperature of step B the same cooling rate can be applied.

[0030] TTT can be carried out at any stage of step B from the start to the end of step B. Preferably, TTT can be started at 1 / 10 to 9 / 10, more preferably 1 / 5 to 4 / 5, and even more preferably 2 / 5 to 4 / 5 of the duration of step B.

[0031] Surprisingly, it was found that the addition of TTT during step B results in a single-crystalline NCM with a homogeneous octahedral shape. Moreover, the press density and electronic conductivity of the single-crystalline NCM were shown to be at least 3.257 g / mL and at least 0.022 S / m, respectively, which are about 7.0% and 1.5 times higher than the market average level (3.046 g / mL, 0.00873 S / m). As known in the art, the press density is related to the energy density of the battery, and the higher the press density, the higher the energy density of the battery. Meanwhile, the conductivity of the material is related to the charge and discharge rate of the battery. Such a comparison shows that the potential of standard SCM as a cathode active material is considerable. Moreover, the high simplicity of the TTT procedure largely overcomes the technical barriers for the scale-up of the product and is applicable in industrial production compared to the prior art.

[0032] A further aspect of the present invention relates to electrodes comprising monocrystalline NCM obtained by the method of the present invention. These are particularly useful for lithium-ion batteries. Lithium-ion batteries comprising at least one electrode of the present invention exhibit very good charge-discharge and high capacity. An electrode comprising monocrystalline NCM obtained by the method of the present invention is hereinafter also referred to as an electrode of the present invention or an electrode according to the invention or a cathode of the present invention.

[0033] In some embodiments of the present invention, the electrode of the present invention is in the form of a thin film electrode. The thin film electrode comprises the electrode active material of the present invention. Physical vapor deposition or chemical vapor deposition techniques may be used to fabricate the thin film. The electrode film has a thickness in the range of 10 nm to 10,000 nm, preferably 100 nm to 5,000 nm.

[0034] In some embodiments of the present invention, an electrode of the present invention comprises a current collector, and (A) Single crystal NCM obtained by the method of the present invention; (B) an electrically conductive form of carbon; (C) a binder, and (D) optionally a solid electrolyte Contains:

[0035] In some embodiments of the present invention, an electrode of the present invention comprises a current collector, and (A) 50% by mass to 98.99% by mass of single crystal NCM obtained by the method of the present invention; (B) 1% to 5% by weight of carbon in an electrically conductive form; (C) 0.01% by weight to 5% by weight of a binder, and (D) 0 to 50% by mass of a solid electrolyte based on the total mass of the components (A), (B), (C) and (D). Contains:

[0036] The current collector used in the electrode of the present invention may be, but is not limited to, aluminum foil.

[0037] The electrode according to the invention further contains an electrically conductive form of carbon, also called carbon (B) for short. Carbon (B) can be selected from soot, activated carbon, carbon nanotubes, graphene and graphite. Carbon (B) can be added directly during the preparation of the electrode material according to the invention.

[0038] In some embodiments, the amount of carbon (B) in the electrode material of the present invention is in the range of 1% to 15% by weight, preferably at least 2% by weight, based on the total of components (A), (B), (C) and (D).

[0039] The electrode of the invention further comprises a binder (C). Suitable binders (C) 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 from 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. 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, with polyacrylonitrile homopolymers being preferred. In the present invention, polyethylene refers not only to homopolyethylenes, but also to copolymerized ethylenes having 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 isobutene, vinyl aromatics, such as styrene, and (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 copolymers of ethylene with maleic acid, maleic anhydride, itaconic anhydride. The polyethylene may be HDPE or LDPE.

[0040] In the present invention, polypropylene is understood to mean not only homopolypropylene but also copolymers of propylene with at least 50 mol % and up to 50 mol % of at least one further comonomer, such as copolymers of propylene with ethylene and an α-olefin, such as butylene, 1-hexene, 1-octene, 1-decene, 1-dodecene and 1-pentene. The polypropylene is preferably isotactic or essentially isotactic polypropylene.

[0041] In the present invention, polystyrene includes not only homopolymers of styrene, but also 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.

[0042] Another preferred binder (C) is polybutadiene. Other suitable binders (C) are selected from polyethylene oxide (PEO), cellulose, carboxymethyl cellulose, polyimide and polyvinyl alcohol.

[0043] In some embodiments of the present invention, the binder (C) has an average molecular weight M in the range of 50,000 g / mol to 1,000,000 g / mol, preferably 50,000 g / mol to 500,000 g / mol. w The (co)polymers are selected from those having the formula:

[0044] The binder (C) may be a crosslinked or non-crosslinked (co)polymer. In a particularly preferred embodiment of the present invention, the binder (C) 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 are 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.

[0045] Suitable binders (C) are especially polyvinyl alcohols and halogenated (co)polymers, such as polyvinyl chloride or polyvinylidene chloride, especially fluorinated (co)polymers, such as polyvinyl fluoride and especially polyvinylidene fluoride and polytetrafluoroethylene.

[0046] The electrode of the present invention may contain 0.01% to 5% by mass of binder(s) (C) based on the total of components (A), (B), (C) and (D). The solid electrolyte (D) is a lithium ion conductive material that is solid at a temperature of at least 30°C, preferably at least 50°C. Examples of solid electrolytes (D) include preferably lithium ion conductive materials, such as lithium ion conductive ceramics, sintered ceramics, glass ceramics, glasses, and polymer compounds. A preferred solid electrolyte (D) is a lithium ion conductive material that is solid at a temperature of at least 10°C at 25°C. -7 Higher than 1·10 S / cm at 25°C -6 S / cm~5·10 -2They exhibit lithium ion conductivities in the range of 10 ...

[0047] A further aspect of the present invention is at least one electrode of the invention as a cathode, At least one anode, and At least one electrolyte An electrochemical cell comprising:

[0048] The cathode embodiment has been described in detail above. The anode and electrolyte are those commonly used in the art. The anode may contain at least one anode active material commonly used in the art, such as carbon (graphite), lithium metal, TiO2, lithium titanium oxide, silicon or tin. The anode may further contain a current collector, for example, a metal foil such as a copper foil. The electrolyte may include at least one non-aqueous solvent, at least one electrolyte salt, and optionally an additive.

[0049] The non-aqueous solvent for the electrolyte may be liquid or solid at room temperature and is preferably selected from among polymers, cyclic or acyclic ethers, cyclic and acyclic acetals, and cyclic or acyclic organic carbonates.

[0050] 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.

[0051] The molecular weight M of suitable polyalkylene glycols, particularly suitable polyethylene glycols, w The molecular weight M of suitable polyalkylene glycols, especially suitable polyethylene glycols, can be at least 400 g / mol. w can be less than or equal to 5,000,000 g / mol, preferably less than or equal to 2,000,000 g / mol. 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. Examples of suitable cyclic ethers are, for example, tetrahydrofuran and 1,4-dioxane. Examples of suitable acyclic acetals are, for example, dimethoxymethane, diethoxymethane, 1,1-dimethoxyethane and 1,1-diethoxyethane. Examples of suitable cyclic acetals are, for example, 1,3-dioxane, and in particular 1,3-dioxolane. Examples of suitable acyclic organic carbonates are, for example, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.

[0052] Examples of suitable cyclic organic carbonates are those of the general formula (III.1) and formula (III.2) [ka] (In the formula, R 1 , R 2 and R 3 may 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; R 2 and R 3and R are preferably not both tert-butyl. 1 is methyl, R 2 and R 3 are each hydrogen or R 1 , R 2 and R 3 are hydrogen.

[0053] Another preferred cyclic organic carbonate has the formula (IV): [ka] Vinylene carbonate.

[0054] The solvent or solvents are preferably used in an aqueous state, ie with a water content in the range of 1 ppm to 0.1% by weight, which can be measured, for example, by Karl Fischer titration.

[0055] 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 the general formula (C n F 2n+1 SO2) t YLi, where n, t and Y are defined as follows: When Y is selected from oxygen and sulfur, t=1, When Y is selected from nitrogen and phosphorus, t=2; When Y is selected from carbon and silicon, t=3; and and n is an integer ranging from 1 to 20.

[0056] Preferred electrolyte salts are selected from LiC(CF3SO2)3, LiN(CF3SO2)2, LiPF6, LiBF4, LiClO4, with LiPF6 and LiN(CF3SO2)2 being particularly preferred.

[0057] In some embodiments of the invention, the cell according to the invention includes one or more separators, which mechanically separate the electrodes. Suitable separators are polymer films, especially porous polymer films that are non-reactive with metallic lithium. Particularly suitable materials for the separator are polyolefins, especially film-forming porous polyethylene and film-forming porous polypropylene.

[0058] A separator containing polyolefin, particularly polyethylene or polypropylene, may have a porosity in the range of 35% to 45%. Suitable pore sizes are, for example, in the range of 30 nm to 500 nm.

[0059] In some embodiments of the present invention, the separator can be selected from PET nonwovens filled with inorganic particles. Such separators can have a porosity in the range of 40% to 55%. Suitable pore sizes are, for example, in the range of 80 nm to 750 nm.

[0060] The electrochemical cell according to the invention may further comprise a housing, which may have any shape, for example a cubic or cylindrical disk shape. In one variant, a metal foil configured as a pouch is used as the housing. The electrochemical cell according to the invention provides very good charge / discharge and high capacity.

[0061] The battery according to the invention may comprise two or more electrochemical cells combined with each other, for example connected in series or in parallel. A series connection is preferred. In the battery according to the invention, at least one of the electrochemical cells contains at least one electrode according to the invention. Preferably, in the electrochemical cell according to the invention, the majority of the electrochemical cells contain an electrode according to the invention. Even more preferably, in the battery according to the invention, every electrochemical cell contains an electrode according to the invention.

[0062] The present invention further provides a method for using the battery according to the present invention in equipment, in particular in 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, in particular laptops, telephones, or powered hand tools, such as in the construction field, in particular drills, battery-powered screwdrivers, or battery-powered staplers.

[0063] The present invention will be further described with reference to examples, but the present invention is not limited thereto.

[0064] drawing Figure 1: Calcination profile of the TTT procedure in the synthesis of single-crystalline NCM Ni90.

[0065] Figure 2: Calcination profile of the normal procedure for the synthesis of NCM Ni90.

[0066] Figure 3(a): SEM image at 10kx magnification of the sample synthesized by the standard procedure.

[0067] Figure 3(b): SEM image at 20kx magnification of the sample synthesized by the standard procedure.

[0068] Figure 3(c): SEM image of the sample synthesized by the TTT procedure at 10 kx magnification.

[0069] Figure 3(d): SEM image at 20 kx magnification of the sample synthesized by the TTT procedure.

[0070] Figure 4: XRD of single crystal NCM Ni90 synthesized by the TTT procedure.

[0071] Figure 5: Firing profiles at different TTT temperatures: 830°C (no TTT), 900°C, 970°C and 1040°C.

[0072] Figure 6(a): SEM image of the sample synthesized without TTT.

[0073] Figure 6(b): SEM image of the sample synthesized at a TTT temperature of 900 °C.

[0074] Figure 6(c): SEM image of the sample synthesized at a TTT temperature of 970 °C.

[0075] Figure 6(d): SEM image of the sample synthesized at a TTT temperature of 1040 °C.

[0076] Figure 7: Press density comparison of samples synthesized at different TTT temperatures: 830 °C (no TTT), 900 °C, 970 °C, and 1040 °C.

[0077] Figure 8: Comparison of electrical conductivity of samples synthesized at different TTT temperatures: 830 °C (no TTT), 900 °C, 970 °C and 1040 °C.

[0078] Figure 9: Firing profile at each time point during the transient heat treatment.

[0079] Figure 10(a): SEM image of the sample synthesized in step B, which sequentially involves 15 min of TTT and 10 h of baseline heating (0 h / 15 min-TTT / 10 h).

[0080] Figure 10(b): SEM image of the sample synthesized in step B, which involves sequential baseline heating for 2 h, TTT for 15 min, and baseline heating for 8 h (2 h / 15 min-TTT / 8 h).

[0081] Figure 10(c): SEM image of the sample synthesized in step B, which sequentially involves 4 h baseline heating, 15 min TTT, and 6 h baseline heating (4 h / 15 min-TTT / 6 h).

[0082] Figure 10(d): SEM image of the sample synthesized in step B, which sequentially involves 6 h baseline heating, 15 min TTT, and 4 h baseline heating (6 h / 15 min-TTT / 4 h).

[0083] Figure 10(e): SEM image of the sample synthesized in step B, which sequentially involves 8 h of baseline heating, 15 min of TTT, and 2 h of baseline heating (8 h / 15 min-TTT / 2 h).

[0084] Figure 10(f): SEM image of the sample synthesized in step B, which sequentially involves 10 h of baseline heating and 15 min of TTT (10 h / 15 min-TTT / 0 h).

[0085] Figure 11: Press density comparison of samples with TTT applied at different time points (0 hr / 15 min and 0 hr-TTT / 10 hr, 2 hr / 15 min-TTT / 8 hr, 4 hr / 15 min-TTT / 6 hr, 6 hr / 15 min-TTT / 4 hr, 8 hr / 15 min-TTT / 2 hr and 10 hr / 15 min-TTT).

[0086] FIG. 12: Comparison of electrical conductivity of samples with TTT applied at different time points (0 h / 15 min-TTT / 10 h, 2 h / 15 min-TTT / 8 h, 4 h / 15 min-TTT / 6 h, 6 h / 15 min-TTT / 4 h, 8 h / 15 min-TTT / 2 h and 10 h / 15 min-TTT).

[0087] EMBODIMENT 1 Formula (I) LiNi x Co y Mn z O2(I) 1. A method for preparing a cathode active material of claim 1, comprising the steps of: i). Preparing precursors of hydroxides or carbonates of Ni, Co and Mn; ii). mixing the precursor obtained from step i) with a Li source; and iii). A step of firing the mixture obtained from step ii). Including, The step iii) comprises a multi-stage calcination, wherein, in the above formula, x is in the range of 0.80 to 0.95, and preferably 0.80 to 0.92, y is in the range of 0.01 to 0.15, and preferably 0.01 to 0.12, and z is in the range of 0.01 to 0.15, and preferably 0.01 to 0.12, and the sum of x, y and z is 1.

[0088] EMBODIMENT 2 2. The method according to embodiment 1, wherein the multi-stage calcination comprises a step of transient heat treatment (TTT) to a temperature in the range of 1000°C to 1400°C, preferably 1000°C to 1200°C.

[0089] EMBODIMENT 3 3. The method according to embodiment 2, wherein the TTT temperature is maintained for a period of from 1 minute to 1 hour, preferably from 1 minute to 30 minutes, and more preferably from 5 minutes to 20 minutes.

[0090] EMBODIMENT 4 4. The method according to any one of the preceding embodiments, wherein the multi-stage calcination comprises step A of heating at a temperature in the range of 300°C to 600°C, and preferably 400°C to 600°C.

[0091] EMBODIMENT 5 5. The method according to embodiment 4, wherein step A has a duration of from 1 hour to 7 hours, and preferably from 3 hours to 5 hours.

[0092] EMBODIMENT 6 6. The method according to any one of the preceding embodiments, wherein the multi-step calcination comprises step A followed by step B of heating at a temperature in the range of 750°C to 900°C, and preferably 750°C to 850°C.

[0093] EMBODIMENT 7 7. The method according to embodiment 6, wherein step B has a duration of from 6 hours to 16 hours, and preferably from 8 hours to 14 hours.

[0094] EMBODIMENT 8 The method according to any one of embodiments 2 to 7, wherein the TTT is carried out at any time between the start and end of step B, and preferably, the TTT starts at 1 / 10 to 9 / 10, more preferably 1 / 5 to 4 / 5, and even more preferably 2 / 5 to 4 / 5 of the total period of step B.

[0095] EMBODIMENT 9 9. The method of any one of the preceding claims, wherein the Li source is at least one compound selected from Li2O, LiOH, and Li2CO3.

[0096] EMBODIMENT 10 10. A cathode active material produced by the method of any one of embodiments 1 to 9.

[0097] EMBODIMENT 11 11. The cathode active material of embodiment 10, comprising a single crystal of an octahedral structure with lattice parameters a, b, and c of 2.88047 Å, 2.88047 Å, and 14.20877 Å, respectively.

[0098] EMBODIMENT 12 12. The cathode active material of embodiment 11, wherein the single crystals have an average grain size of 3.5 um to 4.5 um by PSD (particle size distribution) measurement. (Ni92). EMBODIMENT 13 13. The cathode active material of any one of embodiments 11 to 12, wherein the single crystal has a pressed density of 3.0 g / ml to 4.0 g / ml as tested by a Mitsubishi Chemical Analytech powder resistivity measurement unit MCP-PD51.

[0099] EMBODIMENT 14 14. The cathode active material of any one of embodiments 11 to 13, wherein the single crystal has a conductivity according to JIS K7194 / JIS R1637 of 0.004 S / m to 0.08 S / m.

[0100] EMBODIMENT 15 LiNi 0.80 Co 0.10 Mn 0.10 O2(Ni80), LiNi 0.83 Co 0.12 Mn 0.05 O2(Ni83), LiNi 0.88 Co 0.06 Mn 0.06 O2(Ni88), LiNi 0.90 Co 0.05 Mn 0.05 O2(Ni90) and LiNi 0.92 Co 0.04 Mn 0.04 15. The cathode active material of any one of embodiments 11 to 14, comprising at least one selected from the group consisting of: O2(Ni92).

[0101] EMBODIMENT 16 Octahedral structure of single crystal formula (I) LiNi x Co y Mn z O2(I) a cathode active material comprising: In the above formula, x is in the range of 0.80 to 0.95 and preferably 0.80 to 0.02, y is in the range of 0.01 to 0.15 and preferably 0.01 to 0.12, z is in the range of 0.01 to 0.15 and preferably 0.01 to 0.12, and the sum of a, b and c is 1; The lattice parameters a, b, and c are 2.88047 Å, 2.88047 Å, and 14.20877 Å, respectively. The cathode active material has an average particle size of 3.5um to 4.5um as measured by PSD (particle size distribution), a press density of 3.0g / ml to 4.0g / ml as tested by a powder resistivity measuring unit MCP-PD51 from Mitsubishi Chemical Analytech Co., Ltd., and a conductivity of 0.004S / m to 0.08S / m as measured by JIS K7194 / JIS R1637.

[0102] EMBODIMENT 17 LiNi 0.80 Co 0.10 Mn 0.10 O2(Ni80), LiNi 0.83 Co 0.12 Mn 0.05 O2(Ni83), LiNi 0.88 Co 0.06 Mn 0.06 O2(Ni88), LiNi 0.90 Co 0.05 Mn 0.05 O2(Ni90) and LiNi 0.92 Co 0.04 Mn 0.04 17. The cathode active material of embodiment 16, comprising at least one selected from the group consisting of: O2(Ni92).

[0103] EMBODIMENT 18 (A) 50% to 98.99% by weight of the cathode active material of any one of embodiments 10 to 17; (B) 1% to 5% by weight of carbon in an electrically conductive state; (C) 0.01% to 5% by weight of a binder, and (D) 0 to 50% by mass, based on the total mass of components (A), (B), (C) and (D), of a solid electrolyte. a cathode comprising:

[0104] EMBODIMENT 19 20. An electrochemical cell comprising the cathode of embodiment 18, an anode, and an electrolyte. EXAMPLES

[0105] In the following examples, Ni90 precursor prepared by the method described in Comparative Example 1 of CN113373517A was used as the raw material, and this precursor was mixed with Li2CO3 in a plowshare mixer at a speed of 100 rpm for 5 minutes. The resulting product was LiNi 0.90 Co 0.05 Mn 0.05 The Ni90 precursor had a composition of 02 and was synthesized by coprecipitation and then dried without calcination. The Ni90 precursor contained certain water or hydroxide anions.

[0106] I. Effect of the presence of TTT Example 1 Firing was performed applying the same firing profile as in Comparative Example 1, except that TTT was applied in step B, as shown in Figure 1. In detail, after step B at 830°C for 4 hours, a 5°C / min ramp was performed to reach 1040°C and hold at 1040°C for 15 minutes. The temperature was then reduced to 830°C with the same ramp and held at 830°C for another 6 hours. Finally, a 4.3°C / min cooling ramp was applied to reach 400°C, followed by natural cooling to room temperature.

[0107] Comparative Example 2 Regular firing was performed in a conventional manner, i.e. without TTT. The firing profile included two sectors, pre-firing and step B, as shown in Figure 2. First, the sample was heated from room temperature to 500 °C with a ramp of 5 °C / min and held at 500 °C for 180 min (3 h) to complete the pre-firing. Then, a ramp of 3.3 °C / min was applied to reach the step B temperature of 830 °C and held at 830 °C for 600 min (10 h). The temperature was then reduced to 400 °C with a ramp of 4.3 °C / min, followed by natural cooling to room temperature.

[0108] The morphology of the samples synthesized by the conventional and TTT procedures was investigated by scanning electron microscope (SEM) with JSM-7800, 5keV, working distance (WD) = 15-15.33mm. The morphology comparison of the samples synthesized by the conventional and TTT procedures is shown in Figure 3, which shows that the spherical particles can be transformed into octahedral particles by TTT. In addition, the crystal size also changed from about 1.5um to 2.2um. Therefore, it can be concluded that the direct effect of TTT is to form octahedrons and increase the grain size.

[0109] Figure 4 shows the XRD pattern of the TTT sample (measured with a Rigaku-600 X-ray diffractometer, using Cu-Kα radiation in the range of 10° to 110°), which shows a closed peak characteristic with the conventionally synthesized sample. This indicates that TTT results in an ordered morphology, but the corresponding chemical composition of the bulk is not affected. Press density is an important index that affects the energy density of CAM. Therefore, a comparison was made between samples from the TTT procedure and the normal procedure using a powder resistivity measurement unit MCP-PD51 from Mitsubishi Chemical Analytech Co., Ltd., and it was found that the TTT procedure yielded a press density of 3.725 g / ml, 18% higher than the normal one (3.151 g / ml). Such an improvement is favorable for improving the energy density for further performance improvement. Also, electrical conductivity is essential to reflect the electron transport of CAM.

[0110] The electrical conductivity was measured by a Mitsubishi Chemical Analytech powder resistivity measuring unit MCP-PD51 in accordance with the JIS K7194 / JIS R1637 4-pin probe. TTT caused a sudden increase in conductivity of 0.149 S / m, which was surprisingly 489% higher than the normal (0.025 S / m). This means that the electron transport in the CAM generated by TTT became faster and stronger.

[0111] Advantages beyond the octahedral morphology are the enhanced press density and electrical conductivity, suggesting the possibility of achieving higher energy density and faster electron transport for CAMs.

[0112] II. Effect of temperature on TTT Three TTT temperatures were applied to investigate the effects of TTT temperature on morphology, pressed density, and conductivity.

[0113] Comparative Example 3 For comparison, a firing experiment was also performed that included step B below 830 °C and without TTT, which is shown as “830 °C” in Figures 5 to 8 .

[0114] Comparative Example 4 A TTT temperature ladder experiment was performed as shown in Figure 5. First, the sample was heated from room temperature to 500°C with a 5°C / min ramp and held at 500°C for 180 minutes (3 hours) to complete the pre-bake. Following this, a 3.3°C / min ramp was applied to reach the Step B temperature of 830°C and held at 830°C for 600 minutes (10 hours). A 5°C / min ramp was then performed to reach 900°C and held at 900°C for 15 minutes. Finally, a 4.3°C / min cooling ramp was applied to reach 400°C and then allowed to cool naturally to room temperature.

[0115] Comparative Example 5 The ladder experiment for TTT temperature was carried out in the same manner as in Comparative Example 4, except that the transient treatment temperature was 970°C.

[0116] Example 6 The ladder experiment for TTT temperature was carried out in the same manner as in Comparative Example 4, except that the transient treatment temperature was 1040°C.

[0117] Comparing the morphologies in Figure 6, it can be seen that when the transient treatment temperature reaches 1040°C, octahedrons can be observed from the SEM images. The average particle size is about 2.6um. In contrast, when the temperature is reduced to 970°C, the octahedrons disappear. Instead, regular spherical particles are formed. This suggests that 1040°C is responsible for the formation of octahedrons, and temperatures lower than 1000°C have little effect on the morphology. Figure 7 shows the pressed density of the four samples, with the sample treated at 1040°C showing an 8% increase with an absolute value of 3.415 g / ml compared to the sample treated with the normal procedure. Furthermore, an upward trend is observed in terms of pressed density, suggesting a positive correlation between the transient treatment temperature and pressed density.

[0118] A comparison of the electrical conductivity of the samples is shown in Figure 8. When applying the TTT treatment at 900°C, an increase of 0.025 S / m is observed, reaching 0.050 S / m. It then decreases to 0.022 S / m at 970°C. Finally, when the temperature reaches 1040°C, the conductivity reaches 0.061, resulting in an increase of 143% compared to the normal procedure.

[0119] It was concluded that 1040°C is an effective temperature for achieving octahedral morphology while significantly increasing press density and conductivity. Furthermore, the trend from 830°C to 1040°C shows a positive correlation between temperature, morphology change, and press density. Furthermore, the conductivity does not show a similar correlation, but reaches a maximum at 1040°C.

[0120] III. Effect of TTT time Further ladder studies were carried out for the flexibility of 1040°C as the TTT temperature in the process B stage, as shown in Figure 9. Six time points with 15 min TTT were performed at 2-h intervals from the start to the end of process B. Morphology, press density, and conductivity were also evaluated.

[0121] Example 7 First, the sample was ramped from room temperature to 500°C at a rate of 5°C / min and held at 500°C for 180 minutes (3 hours) to complete the pre-bake. This was followed by a ramp of 3.3°C / min to reach a step B temperature of 830°C. After reaching 830°C, a ramp of 5°C / min was applied to reach a TTT temperature of 1040°C and held at 1040°C for 15 minutes. This was followed by a ramp of 5°C / min to 830°C and held at 830°C for 600 minutes (10 hours). The sample was then ramped down to 400°C at a rate of 4.3°C / min and then allowed to cool naturally to room temperature.

[0122] Example 8 The same procedure as in Example 7 was carried out, with the only difference being that the 15 min-TTT was applied 2 hours after the start of step B.

[0123] First, the sample was heated from room temperature to 500°C with a 5°C / min ramp and held at 500°C for 180 minutes (3 hours) to complete the pre-bake. This was followed by a 3.3°C / min ramp to reach a Step B temperature of 830°C and held at 830°C for 120 minutes (2 hours). This was followed by a 5°C / min ramp to reach a TTT temperature of 1040°C and held at 1040°C for 15 minutes. This was followed by a 5°C / min ramp to 830°C and held at 830°C for an additional 480 minutes (8 hours). The temperature was then ramped down to 400°C with a 4.3°C / min ramp and then allowed to cool naturally to room temperature.

[0124] Example 9 The same procedure as in Example 7 was carried out, with the only difference being that the 15 min-TTT was applied 4 hours after the start of step B.

[0125] First, the sample was heated from room temperature to 500°C with a 5°C / min ramp and held at 500°C for 180 minutes (3 hours) to complete the pre-bake. This was followed by a 3.3°C / min ramp to reach a Step B temperature of 830°C and held at 830°C for 240 minutes (4 hours). This was followed by a 5°C / min ramp to reach a TTT temperature of 1040°C and held at 1040°C for 15 minutes. This was followed by a 5°C / min ramp to 830°C and held at 830°C for an additional 360 minutes (6 hours). The temperature was then ramped down to 400°C with a 4.3°C / min ramp and then allowed to cool naturally to room temperature.

[0126] Example 10 The same procedure as in Example 7 was carried out, with the only difference being that the 15 min-TTT was applied 6 hours after the start of step B.

[0127] First, the sample was ramped from room temperature to 500°C at a rate of 5°C / min and held at 500°C for 180 minutes (3 hours) to complete the pre-bake. This was followed by a ramp of 3.3°C / min to reach a step B temperature of 830°C and held at 830°C for 360 minutes (6 hours). This was followed by a ramp of 5°C / min to reach a TTT temperature of 1040°C and held at 1040°C for 15 minutes. This was followed by a ramp of 5°C / min to 830°C and held at 830°C for an additional 240 minutes (4 hours). The temperature was then ramped down to 400°C at a rate of 4.3°C / min and then allowed to cool naturally to room temperature.

[0128] Example 11 The same procedure as in Example 7 was carried out, with the only difference being that the 15 min-TTT was applied 8 hours after the start of step B.

[0129] First, the sample was heated from room temperature to 500°C with a 5°C / min ramp and held at 500°C for 180 minutes (3 hours) to complete the pre-bake. This was followed by a 3.3°C / min ramp to reach a step B temperature of 830°C and held at 830°C for 480 minutes (8 hours). This was followed by a 5°C / min ramp to reach a TTT temperature of 1040°C and held at 1040°C for 15 minutes. This was followed by a 5°C / min ramp to 830°C and held at 830°C for an additional 120 minutes (2 hours). The temperature was then ramped down to 400°C with a 4.3°C / min ramp and then allowed to cool naturally to room temperature.

[0130] Example 12 The same procedure as in Example 7 was carried out, with the only difference being that the 15 min-TTT was applied 10 hours after the start of step B, i.e. at the end of step B.

[0131] First, the sample was heated from room temperature to 500°C with a 5°C / min ramp and held at 500°C for 180 minutes (3 hours) to complete the pre-bake. This was followed by a 3.3°C / min ramp to reach a step B temperature of 830°C and held at 830°C for 600 minutes (10 hours). This was followed by a 5°C / min ramp to reach a TTT temperature of 1040°C and held at 1040°C for 15 minutes. This was followed by a 5°C / min ramp to 830°C. The temperature was then ramped down to 400°C with a 4.3°C / min ramp and then allowed to cool naturally to room temperature.

[0132] Figure 10 shows a collection of morphologies at various TTT time points, showing closed octahedra but with different particle sizes. Samples treated with 15min-TTT / 10h, 2h / 15min-TTT / 8h, 8h / 15min-TTT / 2h and 10h / 15min-TTT show sizes around 3.5um, whereas samples treated with 4h / 15min-TTT / 6h and 6h / 15min-TTT / 4h show smaller sizes, especially 4h / 15min-TTT / 6h, showing sizes around 2.0um.

[0133] A comparison of pressed densities is shown in Figure 11, where all samples had higher pressed densities than normal (>3.4g / ml), again confirming the effect of TTT, with the 4h / 15min-TTT / 6h and 8h / 15min-TTT / 2h samples yielding the first two values ​​of 3.725g / ml and 3.818g / ml.

[0134] As for the electrical conductivity, from the beginning to the end of the TTT, the value first increased to 0.081, 0.096, and 0.148 S / m, then decreased to 0.124, 0.031 S / m, and finally reached 0.066 S / m, as shown in Figure 12. The highest value (0.148 S / m) was obtained for the sample treated with 4 h / 15 min-TTT / 6 h.

Claims

1. Formula (I) L)) ｘ Co ｙ Mn ｚ O ２ (I) 1. A method for preparing a cathode active material of claim 1, comprising the steps of: i). Preparing hydroxide or carbonate precursors of Ni, Co and Mn; ii). mixing the precursor obtained from step i) with a Li source; and iii). Calcining the mixture obtained from step ii). Including, Step iii) comprises a multi-stage calcination; wherein x ranges from 0.80 to 0.95, and preferably from 0.80 to 0.92; y ranges from 0.01 to 0.15, and preferably from 0.01 to 0.12; and z ranges from 0.01 to 0.15, and preferably from 0.01 to 0.12; and the sum of x, y and z is 1.

2. The method according to claim 1, wherein the multi-stage firing comprises a step of transient thermal treatment (TTT) to a temperature in the range of 1000°C to 1400°C, preferably 1000°C to 1200°C.

3. 3. The method of claim 2, wherein the TTT temperature is held for a period of from 1 minute to 1 hour, preferably from 1 minute to 30 minutes, and more preferably from 5 minutes to 20 minutes.

4. The method according to claim 1 or 2, wherein the multi-stage calcination comprises step A of heating at a temperature in the range of 300°C to 600°C, and preferably 400°C to 600°C.

5. 5. The method according to claim 4, wherein step A has a duration of from 1 hour to 7 hours, and preferably from 3 hours to 5 hours.

6. 3. The method according to claim 1 or 2, wherein the multi-step calcination comprises step A followed by step B of heating at a temperature in the range of from 750°C to 900°C, and preferably from 750°C to 850°C.

7. 7. The method according to claim 6, wherein step B has a duration of from 6 hours to 16 hours, and preferably from 8 hours to 14 hours.

8. 3. The method of claim 2, wherein the TTT is carried out at any time from the start to the end of step B, and preferably the TTT starts at a time between 1 / 10 and 9 / 10, more preferably between 1 / 5 and 4 / 5, and even more preferably between 2 / 5 and 4 / 5 of the total period of step B.

9. The Li source is Li ２ O, LiOH and Li ２ CO ３ The method according to claim 1 or 2, wherein the compound is at least one compound selected from the group consisting of:

10. 3. A cathode active material produced by the method of claim 1 or 2.

11. 11. The cathode active material of claim 10, comprising a single crystal of an octahedral structure having lattice parameters a, b, and c of 2.88047 Å, 2.88047 Å, and 14.20877 Å, respectively.

12. 12. The cathode active material of claim 11, wherein the single crystals have an average grain size of 3.5 um to 4.5 um by PSD (particle size distribution) measurement.

13. 12. The cathode active material of claim 11, wherein the single crystal has a pressed density of 3.0 g / ml to 4.0 g / ml as tested by a Mitsubishi Chemical Analytech powder resistivity measurement unit MCP-PD51.

14. 12. The cathode active material of claim 11, wherein the single crystal has a conductivity of 0.004 S / m to 0.08 S / m according to JIS K7194 / JIS R1637.

15. LiNi ０．８０ Co ０．１０ Mn ０．１０ O ２ (Ni80), LiNi ０．８３ Co ０．１２ Mn ０．０５ O ２ (Ni83), LiNi ０．８８ Co ０．０６ Mn ０．０６ O ２ (Ni88), LiNi ０．９０ Co ０．０５ Mn ０．０５ O ２ (Ni90) and LiNi ０．９２ Co ０．０４ Mn ０．０４ O ２ 12. The cathode active material of claim 11 comprising at least one selected from the group consisting of: (Ni92).

16. Octahedral structure of the single crystal of formula (I) L)) ｘ Co ｙ Mn ｚ O ２ (I) a cathode active material comprising: wherein x ranges from 0.80 to 0.95 and preferably from 0.80 to 0.02, y ranges from 0.01 to 0.15 and preferably from 0.01 to 0.12, z ranges from 0.01 to 0.15 and preferably from 0.01 to 0.12, and the sum of a, b, and c is 1; The lattice parameters a, b, and c are 2.88047 Å, 2.88047 Å, and 14.20877 Å, respectively; Average particle size of 3.5um to 4.5um as measured by PSD (particle size distribution), press density of 3.0g / ml to 4.0g / ml as tested by Mitsubishi Chemical Analytech's Powder Resistivity Measurement Unit MCP-PD51, and conductivity of 0.004S / m to 0.08S / m as per JIS K7194 / JIS R1637 a cathode active material having a

17. LiNi ０．８０ Co ０．１０ Mn ０．１０ O ２ (Ni80), LiNi ０．８３ Co ０．１２ Mn ０．０５ O ２ (Ni83), LiNi ０．８８ Co ０．０６ Mn ０．０６ O ２ (Ni88), LiNi ０．９０ Co ０．０５ Mn ０．０５ O ２ (Ni90) and LiNi ０．９２ Co ０．０４ Mn ０．０４ O ２ 17. The cathode active material of claim 16, comprising at least one selected from the group consisting of: (Ni92).

18. (A) 90% to 98.99% by weight of the cathode active material of claim 10; (B) 1% to 5% by weight of carbon in an electrically conductive state; (C) 0.01% to 5% by weight of a binder, and (D) 0 to 50% by weight, based on the total weight of components (A), (B), (C) and (D), of a solid electrolyte. a cathode comprising:

19. 20. An electrochemical cell comprising the cathode of claim 18, an anode, and an electrolyte.

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