Cathode active material for lithium-ion batteries, and method for manufacturing the same.

Abstract

The present invention (A) General formula Li 1+x TM 1-x A core material made of O2, wherein TM is a combination of Ni, Al, at least one of Mn and Co, and at least one metal optionally selected from Mg, Zr, Ti, Nb, Ta and W, x is in the range of 0 to 0.2, and at least 80 mol% of TM is nickel. (B) A coating containing at least one boron compound in the oxidized state of (B)+III, Regarding cathode active materials containing, Here, the core material (A) is a polycrystalline material composed of primary particles as secondary particles, and the lattice constant ratio c / a determined by X-ray diffraction and Rietveld refinement is 4.9420 or less. 0.0009 ≤ λ ≤ 0.0024, where λ is the molar ratio of sulfate to TM determined by inductively coupled plasma spectroscopy (ICP), and the sulfate concentration is essentially constant across the secondary particle size.

Description

[Technical Field]

[0001] The present invention (A) General formula Li 1+x TM 1-x A core material made of O2, wherein TM is a combination of Ni, Al, at least one of Mn and Co, and at least one metal optionally selected from Mg, Zr, Ti, Nb, Ta and W, x is in the range of 0 to 0.2, and at least 80 mol% of TM is nickel. (B) A coating containing at least one boron compound in the oxidized state of (B)+III, Regarding cathode active materials containing, Here, the core material (A) is a polycrystalline material composed of primary particles as secondary particles, and the lattice constant ratio c / a determined by X-ray diffraction and Rietveld refinement is 4.9420 or less. 0.0009 ≤ λ ≤ 0.0024, where λ is the molar ratio of sulfate to TM determined by inductively coupled plasma spectroscopy (ICP), and the sulfate concentration is essentially constant across the secondary particle size. [Background technology]

[0002] Lithium-ion rechargeable batteries are state-of-the-art devices for energy storage. Many applications have been considered, from small devices such as mobile phones and laptop computers to car batteries and other e-mobility batteries. Various battery components, such as electrolytes, electrode materials, and separators, play crucial roles in battery performance. Cathode materials, in particular, have received attention. Several materials have been proposed, such as lithium iron phosphate, lithium cobalt oxide, and lithium nickel cobalt manganese oxide. While extensive research has been conducted, the solutions found so far still have room for improvement.

[0003] Currently, a particular interest is observed in so-called Ni-rich (high Ni content) electrode active materials, for example, cathode active materials containing 60 mol% or more of Ni relative to the total content of metals other than lithium. Summary of the Invention Problems to be Solved by the Invention

[0004] Electrochemical properties such as the initial discharge capacity still have room for improvement. The object of the present invention was to provide a cathode active material having high electrochemical performance. Furthermore, it was also an object to provide a cathode active material having a high specific capacity and little resistance growth during cycling. Means for Solving the Problems

[0005] Therefore, the cathode active material defined at the beginning, also referred to hereinafter as the cathode active material of the present invention or the cathode active material according to the present invention, has been found. The cathode active material of the present invention includes a core (A) and a coating (B), also referred to hereinafter as (A) and (B) respectively. The core (A) and the coating (B) will be described in more detail below. Modes for Carrying Out the Invention

[0006] The cathode active material of the present invention is (A) A core material represented by the general formula Li 1+x TM 1-x O2, where TM is a combination of Ni, Al, at least one of Mn and Co, and optionally at least one metal selected from Mg, Zr, Ti, Nb, Ta, and W, x ranges from 0 to 0.2, preferably from 0.01 to 0.05, and at least 80 mol%, preferably at least 90 mol% of TM is nickel, (B) A coating containing at least one boron compound in the +III oxidation state, such as LiBO2, Li2B4O7, B2O3, or a combination of at least two of the foregoing, and includes Here, the core material (A) is a polycrystalline material composed of primary particles as secondary particles, and the lattice constant ratio c / a determined by X-ray diffraction ("XRD") and Rietveld refinement is 4.9420 or less. Preferably, the lattice constant ratio c / a is less than 4.9416. The minimum value is 4.9390. Preferably, the XRD analysis is performed using Cu-Kα radiation.

[0007] In one embodiment of the present invention, the lattice constant is at least 2.8740 Å. Preferably, the lattice constant is in the range of 2.8740 to 2.8765 Å.

[0008] In one embodiment of the present invention, the unit cell value of the cathode active material of the present invention is at least 101.60 Å. 3 The preferred upper limit is 101.80 Å. 3 That is the case.

[0009] In one embodiment of the present invention, the core material (A) has an average particle size (D50) in the range of 3 to 20 μm, preferably 5 to 16 μm. The average particle size can be determined, for example, by light scattering, laser diffraction, or electroacoustic spectroscopy. The secondary particles of the core material (A) are polycrystalline, i.e., composed of a plurality of primary particles, and the above particle size refers to the particle size of the secondary particles.

[0010] In one embodiment of the present invention, core (A) has a unimodal particle size distribution. In another embodiment of the present invention, core (A) has a bimodal particle size distribution having one maximum value in the range of 3 to 7 μm and one maximum value in the range of 9 to 15 μm.

[0011] In one embodiment of the present invention, the core (A) has a narrow-span particle size distribution. The span can be expressed as (D90-D10) / (D50), where D90 and D10 are the respective percentile values.

[0012] The polycrystalline core (A) preferably consists of more than 100 primary particles per secondary particle, more preferably more than 200 primary particles. The upper limit can be 5000 primary particles per secondary particle.

[0013] The coating (B) may be continuous, may have gaps comparable to those of Swiss cheese, or may have an island structure, but a Swiss cheese structure is preferred. "Swiss cheese" means that most of the surface is coated, but there are specific uncoated portions such as holes. The average thickness of the coating can be determined by depth-profile XPS and is in the range of 2 to 50 nm.

[0014] In one embodiment of the present invention, the coating (B) is glassy or amorphous, and no crystalline phase is detected by X-ray diffraction. In the cathode active material of the present invention, 0.0009 ≦ λ ≦  0.0024, preferably 0.0009 ≦ λ ≦ 0.0020, where λ is the molar ratio of sulfate to TM determined by inductively coupled plasma spectroscopy (ICP). The sulfuric acid concentration is essentially constant over the particle size of the secondary particles. "Essentially constant" means that in the analysis by depth-profile XPS, the deviation of the local sulfate concentration is 10 mol% or less, preferably no distinct gradient is detected.

[0015] In one embodiment of the present invention, TM is a combination of metals according to general formula (I). (Ni a Co b Mn c Al d ) 1-e M e (I) (where a is in the range of 0.90 to 0.98, preferably 0.91 to 0.95, b is in the range of 0.005 to 0.09, preferably 0.01 to 0.05, c is in the range of 0.005 to 0.09, preferably 0.01 to 0.05, d is in the range of 0.001 to 0.05. e is in the range of 0 to 0.05. M is selected from Mg, Ti, Zr, Nb, Ta, and W. (a+b+c+d=1)

[0016] In one embodiment of the present invention, M is selected from Ti, Zr, Mg, and combinations thereof, for example, Zr and Ti, Zr and Mg, and in particular combinations of Zr, Ti, and Mg.

[0017] Some elements are ubiquitous. In the context of this invention, trace amounts of ubiquitous metals such as sodium, calcium, iron, or zinc as impurities are not considered in the specification of this invention. In this context, "trace amount" means an amount of 0.05 mol% or less relative to the total metal content of TM or particle (B).

[0018] In one embodiment of the present invention, cobalt is distributed essentially uniformly across the radius of the secondary particles in core (A). Preferably, cobalt is distributed essentially uniformly across the radius of the primary particles in core (A). In this context, "essentially uniform" means that, in depth-profile XPS analysis, the local deviation of cobalt concentration is 10 mol% or less relative to the mean cobalt concentration, and preferably no clear gradient is detected.

[0019] In one embodiment of the present invention, the cathode active material of the present invention has an average diameter of primary particles in the range of 300 to 500 nm, as determined by SEM. In the case of rod-shaped primary particles, the average diameter refers to the length of the primary particle.

[0020] In one embodiment of the present invention, the cathode active material of the present invention has a porosity in the range of 1.5 to 5.0 volume percent, which is determined by analysis of cross-sectional images prepared by TEM and SEM. Porosity refers to the gaps between primary particles within secondary particles.

[0021] In one embodiment of the present invention, the central part of the secondary particles of core (A) contains spherical primary particles, and the outer part of core (A) contains rod-shaped primary particles. This means that the majority of the center of core (A) is occupied by spherical primary particles, and the majority of the outer part of core (A) is occupied by rod-shaped primary particles. Preferably, the rod-shaped primary particles in the outer portion of the core (A) are essentially radially oriented. The term “essentially radially oriented” includes, but is not limited to, particles having perfect radial orientation. It includes, in SEM analysis, that at least 80% of the rod-shaped primary particles in at least 50 randomly selected secondary particles have a deviation from perfect radial orientation of up to 8 degrees. Furthermore, at least 60% of the volume of the secondary particles is filled with radially oriented primary particles. Preferably, only a small inner portion of the volume of those particles, for example, at most 40%, preferably at most 20%, is filled with non-radially oriented primary particles, for example, randomly oriented ones.

[0022] The above characteristics are essentially maintained even after the addition of coating (B). "Essential" means that any changes, if any, are less than 10% or within the margin of experimental error.

[0023] In one embodiment of the present invention, the cathode active material of the present invention has a residual lithium amount on its surface in the range of 0.05 to 0.5% by mass, which is determined by titration.

[0024] In one embodiment of the present invention, the cathode active material of the present invention is determined according to DIN-ISO 9277:2003-05, and is 0.4 to 0.9 m 2 / g, preferably 0.5~0.7m 2 It has a specific surface area (BET) in the range of / g.

[0025] The cathode active material of the present invention exhibits excellent electrochemical behavior. In particular, it shows high initial discharge capacity, good cycleability, and low resistance growth. The present invention further relates to a method for producing the cathode active material of the present invention, and is hereinafter also referred to as "the method of the present invention" or "the method according to the present invention." The method of the present invention comprises at least five steps, (a), (b), (c), (d), and (e), which in the context of the present invention are also referred to as steps (a), (b), (c), (d), and (e), respectively. Steps (a), (b), (d), and (e) are performed sequentially. Steps (b) and (c) may be performed sequentially or simultaneously. The method of the present invention involves the following steps: (a) A step of providing an oxide of TM', wherein TM' is similar to TM but does not contain the aluminum added in step (b), (b) A step of mixing the oxide of TM' with Al2(SO4)3, Al(OH)3, a lithium source, and optionally at least one oxide or (oxy)hydroxide of Mg, Zr, Ti, Nb, Ta, and W. (c) A step of calcining the mixture obtained in step (b) at a temperature in the range of 650 to 800°C to obtain a powder. (d) A step of washing the powder from step (c) in an aqueous medium, then separating the washed powder from the washing water by a solid-liquid separation method to obtain a residue, and (e) Adding a boron compound having boron in the oxidation state of +III to the residue obtained in step (d), then drying and heat-treating at a temperature in the range of 250 to 400°C. Includes.

[0026] Processes (a) through (e) will be explained in detail below.

[0027] The method of the present invention begins with a cathode active material precursor. The precursor is an oxide of TM'. TM' is similar to TM but does not contain the aluminum added in step (b). Thus, TM' is a combination of Ni and at least one of Mn and Co and optionally at least one further metal selected from Mg, Zr, Ti, Nb, Ta and W, and the nickel content is in the range of 80-99 mol% of TM', where Al from step (b) can be ignored. The precursor may hereafter also be referred to as the “starting material”.

[0028] In one embodiment of the present invention, the precursor has an average particle size (D50) in the range of 3 to 20 μm, preferably 5 to 16 μm. The average particle size can be determined, for example, by light scattering, laser diffraction, or electroacoustic spectroscopy. The particles are usually composed of aggregates of primary particles, and the above particle size refers to the particle size of the secondary particles.

[0029] In one embodiment of the present invention, the precursor has a unimodal particle size distribution. In another embodiment of the present invention, the precursor has a bimodal particle size distribution.

[0030] In one embodiment of the present invention, the precursor has a narrow-span particle size distribution. The span can be expressed as (D90-D10) / (D50), where D90 and D10 are the respective percentile values.

[0031] In one embodiment of the present invention, the precursor is 50-250 m 2 It has a specific surface area (hereinafter also referred to as "BET surface area") in the range of / g. The BET surface area can be determined by nitrogen adsorption after gas release of the sample at 120°C for 30 minutes and beyond, according to DIN ISO 9277:2010.

[0032] In one embodiment of the present invention, step (a) provides an oxide of TM' having a water content in the range of 0 to 100 ppm, preferably 1 to 50 ppm, as determined by Karl Fischer titration. In this context, zero means "below the detection level". In the above formula, TM' includes at least one of Mn and Co, preferably both Mn and Co.

[0033] In one embodiment of the present invention, TM' is a combination of metals according to general formula (I), (Ni a Co b Mn c ) 1-e M* e (I a) (In the formula, a is in the range of 0.90 to 0.98, preferably 0.91 to 0.95) b is in the range of 0.005 to 0.09, preferably 0.01 to 0.05. c is in the range of 0.005 to 0.09, preferably 0.01 to 0.05. e is in the range of 0 to 0.05. a+b+c=1-d, where 0.001≦d≦0.05. M * (This is preferably selected from at least one of Mg, Al, Ti, Zr, Nb, Ta, and W).

[0034] The precursor provided in step (a) typically does not contain conductive carbon. That is, the conductive carbon content of the precursor is less than 1% by mass relative to the starting material, and is preferably 0.001 to 1.0% by mass.

[0035] The precursor provided in step (a) is typically lithium-free. That is, the lithium content in the precursor provided in step (a) is less than 0.1% by mass relative to the precursor, preferably in the range of 0 to 100 ppm. Lithium compounds in the starting material are typically impurities.

[0036] Here too, some elements are ubiquitous. In the context of this invention, trace amounts of ubiquitous metals such as sodium, calcium, iron, or zinc as impurities are not considered in the specification of this invention. In this context, "trace amount" means an amount of 0.05 mol% or less of the total metal content of TM. Sulfates derived from the production of the precursor are also ignored.

[0037] In step (b), the oxide of TM' is mixed with a lithium source, Al2(SO4)3, and optionally Al(OH)3, and optionally at least one oxide or (oxy)hydroxide of Mg, Zr, Ti, Nb, Ta, and W.

[0038] Examples of optionally added oxides, hydroxides, or oxyhydroxides of Ti, Zr, W, Ta, Mg, or Nb include TiO2, Ti2O3, TiO(OH)2, TiO2·aq, ZrO2, Zr(OH)4, and ZrO2·aq, and WO3, Li2WO4, Ta2O5, Nb2O5, and Nb2O5·aq ("niobic acid").

[0039] Suitable lithium sources include LiOH or LiOH hydrate, Li2CO3, Li2O2, and mixtures of at least two of the aforementioned, such as a mixture of LiOH and Li2O2. The amount of lithium source is preferably selected such that the overall molar ratio of lithium to non-lithium metal corresponds to (1+x+y) / (1-x), where x is in the range of 0 to 0.05 and y is in the range of 0 to 0.1. The variable y takes into account the amount of lithium lost by sublimation during process (c).

[0040] In one embodiment of the present invention, the molar ratio of Al to TM' in step (b) is in the range of 0.001 to 0.05.

[0041] In one embodiment of the present invention, in step (b), Al(OH)3 and Al2(SO4)3 are applied in a molar ratio in the range of 2:1 to 1:5.

[0042] Al2SO4 can be applied as water-free aluminum sulfate or as a hydrate.

[0043] In one embodiment of the present invention, step (b) is carried out by filling a container with the starting material provided in step (a) and adding a lithium source, Al2(SO4)3, and Al(OH)3. The order in which the lithium source, Al2(SO4)3, and Al(OH)3 are added is not important.

[0044] Step (c) includes firing the mixture obtained from step (b) at a temperature in the range of, for example, 550 to 800°C, preferably 575 to 775°C.

[0045] Step (c) can be carried out in any type of oven, such as a roller hearth kiln, pusher kiln, rotary kiln, pendulum kiln, or, in the case of laboratory-scale testing, a muffle oven. A temperature of 650-800°C corresponds to the maximum temperature in process (c). The mixture obtained in step (b) can also be directly applied to step (c). However, it is preferable to increase the temperature in stages or to increase the temperature gradually. The staged heating or heating can be carried out under normal pressure or reduced pressure, for example, at 1 to 500 millibars.

[0046] Process (c) at the highest temperature can be carried out under atmospheric pressure.

[0047] Step (c) is carried out in an oxygen-containing atmosphere, in oxygen-enriched air containing at least 80 volume percent oxygen, or in pure oxygen.

[0048] In one embodiment of the present invention, step (c) is carried out in an atmosphere having a reduced CO2 content, for example, a carbon dioxide content in the range of 0.01 to 500 ppm by mass, preferably 0.1 to 50 ppm by mass. The CO2 content can be determined, for example, by an optical method using infrared light. It is even more preferable to carry out step (d) in an atmosphere having a carbon dioxide content below the detection limit by an optical method based on infrared light, for example.

[0049] In one embodiment of the present invention, step (c) is carried out in a roller hearth kiln, a pusher kiln, a rotary kiln, or a combination of at least two of the above. The rotary kiln has the advantage of providing very good homogenization of the material produced therein. In roller hearth kilns and pusher kilns, different reaction conditions for different steps can be set very easily. Box furnaces, tubular furnaces, and segmented-tube furnaces can also be used in laboratory-scale tests.

[0050] In one embodiment of the present invention, step (c) is carried out under a forced flow of a gas, such as air, oxygen, or oxygen-enriched air. Such a gas flow can be called a forced gas flow. Such a gas flow is 0.5 to 15 m³ per 1 kg of the mixture from step (b). 3 It can have a specific flow rate in the range of / h. The volume is determined under normal conditions (298 Kelvin and 1 atmosphere). The forced gas flow is useful for removing gaseous cleavage products such as water.

[0051] In one embodiment of the present invention, step (c) has a duration ranging from 2 to 30 hours, preferably from 6 to 24 hours. Cooling time is negligible in this context. In step (c), a powder is obtained which may be deaggregated after cooling.

[0052] In step (d), the powder obtained from step (c) is treated with an aqueous medium, preferably water or an aqueous solution of LiOH. The aqueous medium may have a pH value in the range of 7 to 14, preferably at least 3.5, more preferably 5 to 7 or 10 to 13. The pH value is measured at the beginning of step (d). During step (d), it is observed that the pH value rises to at least 10, for example, 11 to 13. In embodiments where the pH value is in the range of 10 to 11 at the beginning of step (d), it rises to greater than 11 to 13. In embodiments where the pH value is in the range of 3 to less than 10 at the beginning of step (d), it rises to 11 to 13 during the process of step (d).

[0053] It is preferable that the hardness of the water in the aqueous medium used in step (d) is at least partially removed, and it is particularly preferable that calcium is removed. The use of desalinated water is preferred.

[0054] The pH value of the aqueous medium is influenced by substances dissolved or slurryed in the aqueous medium, such as acidic compounds like sulfuric acid or aluminum sulfate, or bases like LiOH or NaOH. In a preferred embodiment, such an aqueous medium is water. In one embodiment of the present invention, step (d) is carried out at a temperature in the range of 5 to 85°C, preferably 5 to 30°C.

[0055] In one embodiment of the present invention, step (d) is performed at atmospheric pressure. However, it is preferable to perform step (d) under high pressure, for example, at a pressure 10 to 10 bar higher than atmospheric pressure, or under suction, for example, at a pressure 50 to 250 millibars lower than atmospheric pressure, preferably at a pressure 100 to 200 millibars lower than atmospheric pressure.

[0056] Step (d) can be carried out in a container that is easily discharged, for example, located above the filter device. Such a container may be filled with material from step (d), and then an aqueous medium may be introduced. In another embodiment, such a container is filled with an aqueous medium following the introduction of material from step (d). In yet another embodiment, material from step (d) and the aqueous medium are introduced simultaneously.

[0057] In one embodiment of the present invention, in step (d), the amounts of water and electrode active material have a mass ratio in the range of 1:5 to 1:5, preferably 2:1 to 1:2.

[0058] Step (d) can be supported by a mixing operation, such as shaking, particularly stirring or shearing. See below.

[0059] In one embodiment of the present invention, step (d) has a duration in the range of 1 minute to 90 minutes, preferably 1 minute to less than 60 minutes. In embodiments where water treatment and water removal are performed overlapping or simultaneously in step (d), a duration of 5 minutes or more is possible.

[0060] In one embodiment of the present invention, the treatment in step (d) and the removal of the aqueous medium are performed consecutively. After or during treatment with the aqueous medium in step (d), water may be removed by any type of filtration, for example, in a band filter or filter press.

[0061] In one embodiment of the present invention, the removal of the aqueous medium is initiated at least 5 minutes after the start of step (d). Such removal involves partially removing water from the treated particulate electrode active material, for example by solid-liquid separation, for example by decantation, or preferably by filtration. The “partial removal” is also called partial separation and removal.

[0062] In one embodiment of the present invention, the slurry obtained in step (d) is discharged directly into a centrifuge, such as a decanter centrifuge or a filter centrifuge, or into a filtration device, such as a suction filter or a filter press, or into a belt filter preferably located directly below the container in which step (b) is carried out. Filtration is then initiated.

[0063] In a particularly preferred embodiment of the present invention, step (d) and the removal of the aqueous medium are carried out using a filter press or a filter device with a stirrer, such as a pressure filter with a stirrer or a suction filter with a stirrer (e.g., German: "Ruehrfilternutsche"). After combining the starting materials and the aqueous medium according to step (d), the removal of the aqueous medium is initiated by starting filtration at a maximum of 5 minutes, preferably at a maximum of 3 minutes, or immediately thereafter. On a laboratory scale, the processing and removal of the aqueous medium may be carried out using a Büchner funnel and may be supported by manual stirring.

[0064] In a preferred embodiment, step (d) is carried out using a filtering device, such as a stirring filter device that allows stirring of the slurry or filter cake in the filter.

[0065] In one embodiment of the present invention, the removal of the aqueous medium or water by step (d) has a duration ranging from 1 minute to 1 hour.

[0066] In one embodiment of the present invention, the stirring in step (d) is performed at a speed in the range of 1 to 50 revolutions per minute ("rpm"), preferably 5 to 20 rpm. In another embodiment, it is 200 to 400 rpm.

[0067] In one embodiment of the present invention, the filter material can be selected from ceramics, sintered glass, sintered metal, organic polymer film, nonwoven fabric, and woven fabric.

[0068] In one embodiment of the present invention, step (d) is carried out in an atmosphere having a reduced CO2 content, for example, a carbon dioxide content in the range of 0.01 to 500 ppm by mass, preferably 0.1 to 50 ppm by mass. The CO2 content can be determined, for example, by an optical method using infrared light. It is even more preferable to carry out step (d) in an atmosphere having a carbon dioxide content below the detection limit by an optical method based on infrared light, for example.

[0069] From step (d), a solid residue is obtained, preferably in the form of a wet filter cake. The moisture content of this solid residue, particularly the filter cake, may be in the range of 3 to 20% by mass, preferably 4 to 9% by mass.

[0070] After step (d), drying can be performed at 50-150°C, for example, under nitrogen or reduced pressure ("in a vacuum"), to obtain a fluid powder.

[0071] Step (e) includes adding compound B in an oxidized state (+III) to the residue obtained in step (d) and performing heat treatment at a temperature in the range of 250 to 400°C.

[0072] Examples of boron compounds with an oxidation state of (+III) include B2O3, boric acid (B(OH)3), and lithium borate, such as LiBO2. Boric acid is preferred. The boron compounds can be added in bulk or as a solution, such as an aqueous solution. In a preferred embodiment, step (d) is carried out as described above, but without drying, and the boron compound is added to a hydrated or even wetter filtration cake.

[0073] In one embodiment of the present invention, the residue obtained from step (d) is subjected to interaction at a temperature of 5 to 85°C for, for example, a period of 10 minutes to 5 hours.

[0074] In one embodiment of the present invention, the amount of boron added in step (e) is in the range of 0.05 to 1.5 mol%, preferably 0.15 to 0.9 mol%, relative to TM.

[0075] After adding the boron compound, heat treatment is performed. The heat treatment can be carried out in any type of oven, such as a roller hearth kiln, pusher kiln, rotary kiln, pendulum kiln, or, in the case of laboratory-scale testing, a muffle oven. The temperature of the heat treatment in step (e) may be in the range of 250 to 400°C. The temperature refers to the highest temperature in step (e). In one embodiment of the present invention, the temperature is raised before reaching a desired temperature of 250 to 400°C. For example, the mixture of step (e) is first heated from 250°C to 300°C, then kept constant for 10 minutes to 4 hours, and then the temperature is raised from 325°C to 400°C. In one embodiment of the present invention, the heating rate in step (e) is in the range of 0.1 to 10°C / min.

[0076] In one embodiment of the present invention, the heat treatment step (e) is carried out in a roller hearth kiln, a pusher kiln, or a rotary kiln, or a combination of at least two of the above. The rotary kiln has the advantage of providing very good homogenization of the material produced therein. In roller hearth kilns and pusher kilns, different reaction conditions for different steps can be set very easily. In laboratory-scale experiments, box furnaces, tubular furnaces, and segmented tubular furnaces can also be used.

[0077] In one embodiment of the present invention, step (e) is carried out in an oxygen-containing atmosphere, such as a nitrogen-air mixture, a noble gas-oxygen mixture, air, oxygen, or oxygen-enriched air or pure oxygen. In a preferred embodiment, the atmosphere in step (e) is selected from air, oxygen, and oxygen-enriched air. Oxygen-enriched air may be, for example, a mixture of air and oxygen in a volume ratio of 50:50. Other options include a mixture of air and oxygen in a volume ratio of 1:2, a mixture of air and oxygen in a volume ratio of 1:3, a mixture of air and oxygen in a volume ratio of 2:1, and a mixture of air and oxygen in a volume ratio of 3:1. Pure oxygen is even more preferred.

[0078] In one embodiment of the present invention, the heat treatment in step (e) has a duration in the range of 30 minutes to 5 hours, preferably 60 minutes to 4 hours. In this context, the cooling time is negligible.

[0079] By performing the method of the present invention, the cathode active material of the present invention can be obtained.

[0080] Further aspects of the present invention relate to electrodes comprising at least one electrode active material according to the present invention. These are particularly useful for lithium-ion batteries. A lithium-ion battery comprising at least one electrode according to the present invention exhibits good discharge behavior. The electrode comprising at least one cathode active material according to the present invention is hereinafter also referred to as the cathode of the present invention or the cathode according to the present invention.

[0081] In one embodiment of the present invention, the electrode of the present invention is (A) at least one cathode active material of the present invention, (B) Conductive carbon, and (C) Binder Includes.

[0082] In a preferred embodiment of the present invention, the cathode of the present invention is based on the sum of (A), (B), and (C), (A) 80-99% by mass of the cathode active material of the present invention, (B) 0.5 to 19.5 mass% of carbon, (C) 0.5-9.5% by mass of binder polymer, Includes.

[0083] Further aspects of the present invention include: (1) At least one electrode according to claim 13, (2) at least one anode, and (3) Electrolyte Regarding secondary batteries, including those mentioned above.

[0084] The cathode according to the present invention may include further components. These may include, but are not limited to, current collectors such as aluminum foil. They may further include conductive carbon and a binder.

[0085] The cathode according to the present invention contains conductively modified carbon, also abbreviated as carbon(B). 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 cathode active material according to the present invention.

[0086] A suitable binder (C) is preferably selected from organic (co)polymers. Suitable (co)polymers, i.e., homopolymers or copolymers, can be selected from (co)polymers that can be obtained by anionic (co)polymerization, catalytic (co)polymerization or free radical (co)polymerization, particularly from copolymers of polyethylene, polyacrylonitrile, polybutadiene, polystyrene, and at least two comonomers selected from ethylene, propylene, styrene, (meth)acrylonitrile, and 1,3-butadiene. Polypropylene is also suitable. Polyisoprene and polyacrylate are even more suitable. Polyacrylonitrile is particularly preferred.

[0087] 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 styrene. Polyacrylonitrile homopolymers are preferred.

[0088] In the context of the present invention, polyethylene means not only homopolyethylene but also at least 50 mol% copolymerized ethylene and 50 mol% or less 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, and C1-C of (meth)acrylic acid. 10 -Alkyl esters, particularly methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, 2-ethylhexyl acrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, and copolymers of ethylene containing maleic acid, maleic anhydride, and itaconic anhydride. Polyethylene may be HDPE or LDPE.

[0089] In the context of the present invention, polypropylene is understood to mean not only homopolypropylene but also copolymers of propylene comprising at least 50 mol% copolymerized propylene and at least one further comonomer of 50 mol% or less, such as ethylene, and α-olefins, such as butylene, 1-hexene, 1-octene, 1-decene, 1-dodecene, and 1-pentene. Polypropylene is preferably isotactic polypropylene or essentially isotactic polypropylene.

[0090] In the context of the present invention, polystyrene refers not only to styrene homopolymers, but also to acrylonitrile, 1,3-butadiene, (meth)acrylic acid, and C1-C of (meth)acrylic acid. 10 -It is understood to also mean copolymers with alkyl esters, divinylbenzene, particularly 1,3-divinylbenzene, 1,2-diphenylethylene, and α-methylstyrene.

[0091] Another preferred binder (C) is polybutadiene.

[0092] Other suitable binders (C) are selected from polyethylene oxide (PEO), cellulose, carboxymethylcellulose, polyimide, and polyvinyl alcohol.

[0093] In one embodiment 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 up to 500,000 g / mol. W Selected from (co)polymers having the following properties.

[0094] The binder (C) may be a crosslinked or uncrosslinked (co)polymer.

[0095] In particularly preferred embodiments of the present invention, the binder (C) is selected from halogenated (co)polymers, particularly fluorinated (co)polymers. Halogenated or fluorinated (co)polymers are understood to mean (co)polymers comprising at least one (co)polymerized (co)monomer having 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.

[0096] Suitable binders (C) include, in particular, polyvinyl alcohol and halogenated (co)polymers, such as polyvinyl chloride or polyvinylidene chloride, and especially fluorinated (co)polymers, such as polyvinyl fluoride and especially polyvinylidene fluoride and polytetrafluoroethylene.

[0097] The cathode of the present invention may contain 1 to 15% by mass of a binder (one or more) relative to the electrode active material. In other embodiments, the cathode of the present invention may contain 0.1 to less than 1% by mass of a binder (one or more).

[0098] A further aspect of the present invention is a battery comprising the electrode active material of the present invention, at least one cathode comprising carbon and a binder, at least one anode, and at least one electrolyte.

[0099] Embodiments of the cathode of the present invention have already been described in detail above.

[0100] The anode may contain at least one anode active material, such as carbon (graphite), TiO2, lithium titanium oxide, silicon, or tin. The anode may further contain a current collector, such as a metal foil like copper foil.

[0101] The electrolyte may include at least one non-aqueous solvent, at least one electrolyte salt, and optionally an additive.

[0102] 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.

[0103] Examples of suitable polymers include, in particular, polyalkylene glycols, preferably poly-C1-C4 alkylene glycols, and especially polyethylene glycols. Here, polyethylene glycol may contain 20 mol% or less of one or more C1-C4 alkylene glycols. The polyalkylene glycol is preferably a polyalkylene glycol having two methyl or ethyl terminal caps.

[0104] A suitable polyalkylene glycol, particularly a polyethylene glycol, with a molecular weight of M W It can be at least 400 g / mol.

[0105] A suitable polyalkylene glycol, particularly a polyethylene glycol, with a molecular weight of M W This can be up to 5,000,000 g / mol, preferably up to 2,000,000 g / mol.

[0106] Examples of suitable acyclic ethers include, for example, diisopropyl ether, di-n-butyl ether, 1,2-dimethoxyethane, and 1,2-diethoxyethane, with 1,2-dimethoxyethane being preferred.

[0107] Suitable examples of cyclic ethers are tetrahydrofuran and 1,4-dioxane.

[0108] Suitable examples of acyclic acetals include, for example, dimethoxymethane, diethoxymethane, 1,1-dimethoxyethane, and 1,1-diethoxyethane.

[0109] Suitable examples of cyclic acetals are 1,3-dioxane and, in particular, 1,3-dioxolane.

[0110] Suitable examples of acyclic organic carbonates include dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.

[0111] Suitable examples of cyclic organic carbonates are compounds of general formulas (II) and (III). [ka] (In the formula, R 1 , R 2 and R 3 These can be the same or different, and are selected from hydrogen and C1-C4 alkyl groups, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl, preferably R 2 and R3 (Neither of them can be tert-butyl.)

[0112] In a particularly preferred embodiment, R 1 is methyl, and R 2 and R 3 Each is either hydrogen or R 1 , R 2 and R 3 Each of these is hydrogen. In another embodiment, R 1 is fluorine, and R 2 and R 3 Each of these is hydrogen.

[0113] Another preferred cyclic organic carbonate is the vinylene carbonate of formula (IV).

[0114] [ka]

[0115] Preferably, the solvent or a plurality of solvents are used in a water-free state, i.e., with a water content in the range of 1 ppm to 0.1% by mass, which can be determined, for example, by Karl Fischer titration.

[0116] The electrolyte further comprises at least one electrolyte salt. Preferred electrolyte salts are lithium salts in particular. Examples of preferred lithium salts are LiPF6, LiBF4, LiClO4, LiAsF6, LiCF3SO3, and 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 in the range of 1 to 20), LiN(SO2F)2, Li2SiF6, LiSbF6, LiAlCl4, and the general formula (C n F 2n+1 SO2) t YLi salt (In the formula, when Y is selected from oxygen and sulfur, t=1, When Y is selected from nitrogen and phosphorus, t=2, (If Y is selected from carbon and silicon, then t=3)

[0117] Preferred electrolyte salts are selected from LiC(CF3SO2)3, LiN(CF3SO2)2, LiPF6, LiBF4, and LiClO4, with LiPF6 and LiN(CF3SO2)2 being particularly preferred.

[0118] In one embodiment of the present invention, the battery according to the present invention includes one or more separators by which electrodes are mechanically separated. Preferred separators are polymer films that do not react with metallic lithium, particularly porous polymer films. Particularly preferred materials for the separators are polyolefins, particularly film-forming porous polyethylene and film-forming porous polypropylene.

[0119] Separators made of polyolefins, particularly polyethylene or polypropylene, can have a porosity in the range of 35-45%. Suitable pore sizes are, for example, in the range of 30-500 nm.

[0120] In another embodiment of the present invention, the separator can be selected from a PET nonwoven fabric filled with inorganic particles. Such a separator may have a porosity in the range of 40 to 55%. A suitable pore size is, for example, in the range of 80 to 750 nm.

[0121] The battery according to the present invention further includes a housing which can have any shape, for example, a cube, or the shape of a cylindrical disk or cylindrical can. In one modified embodiment, a metal foil configured as a pouch is used as the housing.

[0122] The battery according to the present invention exhibits excellent discharge behavior, for example, at low temperatures (below 0°C, e.g., -10°C or lower), and very good discharge and cycle behavior.

[0123] The battery according to the present invention may include two or more electrochemical cells that are combined with each other, for example, connected in series or in parallel. 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 cell contains cathode according to the present invention. Even more preferably, in the battery according to the present invention, all electrochemical cells contain cathode according to the present invention.

[0124] The present invention further provides a method for using the battery according to the present invention in equipment, in particular mobile equipment. Examples of mobile equipment include vehicles, such as automobiles, bicycles, aircraft, or watercraft, such as boats or ships. Other examples of mobile equipment include manually operated devices, such as computers, in particular laptops, telephones, or power tools in the construction sector, such as drills, battery-powered screwdrivers, or battery-powered staplers.

[0125] A suitable binder is preferably selected from organic (co)polymers. Suitable (co)polymers, i.e., homopolymers or copolymers, can be selected from (co)polymers that can be obtained by anionic (co)polymerization, catalytic (co)polymerization or free radical (co)polymerization, particularly from copolymers of polyethylene, polyacrylonitrile, polybutadiene, polystyrene, and at least two comonomers selected from ethylene, propylene, styrene, (meth)acrylonitrile, and 1,3-butadiene. Polypropylene is also suitable. Polyisoprene and polyacrylate are also suitable. Polyacrylonitrile is particularly preferred.

[0126] 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 styrene. Polyacrylonitrile homopolymers are preferred.

[0127] In the context of the present invention, polyethylene means not only homopolyethylene but also at least 50 mol% copolymerized ethylene and 50 mol% or less 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, and C1-C of (meth)acrylic acid. 10 -Alkyl esters, particularly methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, 2-ethylhexyl acrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, and copolymers of ethylene containing maleic acid, maleic anhydride, and itaconic anhydride. Polyethylene may be HDPE or LDPE.

[0128] In the context of the present invention, polypropylene is understood to mean not only homopolypropylene but also copolymers of propylene comprising at least 50 mol% copolymerized propylene and at least one further comonomer of 50 mol% or less, such as ethylene, and α-olefins, such as butylene, 1-hexene, 1-octene, 1-decene, 1-dodecene, and 1-pentene. Polypropylene is preferably isotactic polypropylene or essentially isotactic polypropylene.

[0129] In the context of the present invention, polystyrene refers not only to styrene homopolymers, but also to acrylonitrile, 1,3-butadiene, (meth)acrylic acid, and C1-C of (meth)acrylic acid. 10 -It is understood to also mean copolymers with alkyl esters, divinylbenzene, particularly 1,3-divinylbenzene, 1,2-diphenylethylene, and α-methylstyrene.

[0130] Another preferred binder is polybutadiene.

[0131] Other suitable binders are selected from polyethylene oxide (PEO), cellulose, carboxymethylcellulose, polyimide, and polyvinyl alcohol.

[0132] In one embodiment of the present invention, the binder has an average molecular weight M in the range of 50,000 g / mol to 1,000,000 g / mol, preferably up to 500,000 g / mol. W Selected from (co)polymers having the following properties.

[0133] The binder may be a crosslinked or uncrosslinked (co)polymer.

[0134] In particularly preferred embodiments of the present invention, the binder is selected from halogenated(co)polymers, especially fluorinated(co)polymers. Halogenated or fluorinated(co)polymer is understood to mean a(co)polymer comprising at least one (co)polymerized(co)monomer having 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.

[0135] Suitable binders include, in particular, polyvinyl alcohol and halogenated (co)polymers, such as polyvinyl chloride or polyvinylidene chloride, and especially fluorinated (co)polymers, such as polyvinyl fluoride and especially polyvinylidene fluoride and polytetrafluoroethylene.

[0136] The cathode of the present invention may contain 1 to 15% by mass of a binder (one or more) relative to the cathode active material. In other embodiments, the cathode of the present invention may contain 0.1 to less than 1% by mass of a binder (one or more).

[0137] A further aspect of the present invention is a battery comprising the cathode active material of the present invention, at least one cathode comprising carbon and a binder, at least one anode, and at least one electrolyte.

[0138] Embodiments of the cathode of the present invention have already been described in detail above.

[0139] The anode may contain at least one anode active material, such as carbon (graphite), TiO2, lithium titanium oxide, silicon, or tin. The anode may further contain a current collector, such as a metal foil, such as copper foil.

[0140] The electrolyte may include at least one non-aqueous solvent, at least one electrolyte salt, and optionally an additive.

[0141] The non-aqueous solvent for the electrolyte may 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.

[0142] Examples of suitable polymers include, in particular, polyalkylene glycols, preferably poly-C1-C4 alkylene glycols, and especially polyethylene glycols. Here, polyethylene glycol may contain 20 mol% or less of one or more C1-C4 alkylene glycols. The polyalkylene glycol is preferably a polyalkylene glycol having two methyl or ethyl terminal caps.

[0143] A suitable polyalkylene glycol, particularly a polyethylene glycol, with a molecular weight of M WIt can be at least 400 g / mol.

[0144] A suitable polyalkylene glycol, particularly a polyethylene glycol, with a molecular weight of M W This can be up to 5,000,000 g / mol, preferably up to 2,000,000 g / mol.

[0145] Examples of suitable acyclic ethers include, for example, diisopropyl ether, di-n-butyl ether, 1,2-dimethoxyethane, and 1,2-diethoxyethane, with 1,2-dimethoxyethane being preferred.

[0146] Suitable examples of cyclic ethers are tetrahydrofuran and 1,4-dioxane.

[0147] Suitable examples of acyclic acetals include, for example, dimethoxymethane, diethoxymethane, 1,1-dimethoxyethane, and 1,1-diethoxyethane.

[0148] Suitable examples of cyclic acetals are 1,3-dioxane and, in particular, 1,3-dioxolane.

[0149] Suitable examples of acyclic organic carbonates include dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.

[0150] Suitable examples of cyclic organic carbonates are compounds of general formulas (II) and (III).

[0151] [ka]

[0152] (In the formula, R 1 , R 2 and R 3These can be the same or different, and are selected from hydrogen and C1-C4 alkyl groups, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl, preferably R 2 and R 3 (Neither of them can be tert-butyl.)

[0153] In a particularly preferred embodiment, R 1 is methyl, and R 2 and R 3 Each is either hydrogen or R 1 , R 2 and R 3 Each of these is hydrogen.

[0154] Another preferred cyclic organic carbonate is the vinylene carbonate of formula (IV).

[0155] [ka]

[0156] Preferably, the solvent or a plurality of solvents are used in a water-free state, i.e., with a water content in the range of 1 ppm to 0.1% by mass, which can be determined, for example, by Karl Fischer titration.

[0157] The electrolyte (C) further comprises at least one electrolyte salt. Preferred electrolyte salts are lithium salts in particular. Examples of preferred lithium salts are LiPF6, LiBF4, LiClO4, LiAsF6, LiCF3SO3, and 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 in the range of 1 to 20), LiN(SO2F)2, Li2SiF6, LiSbF6, LiAlCl4, and the general formula (C n F 2n+1 SO2) t YLi salt (In the formula, when Y is selected from oxygen and sulfur, t=1, When Y is selected from nitrogen and phosphorus, t=2, (If Y is selected from carbon and silicon, then t=3)

[0158] Preferred electrolyte salts are selected from LiC(CF3SO2)3, LiN(CF3SO2)2, LiPF6, LiBF4, and LiClO4, with LiPF6 and LiN(CF3SO2)2 being particularly preferred.

[0159] In one embodiment of the present invention, the battery according to the present invention includes one or more separators by which electrodes are mechanically separated. Preferred separators are polymer films that do not react with metallic lithium, particularly porous polymer films. Particularly preferred materials for the separators are polyolefins, particularly film-forming porous polyethylene and film-forming porous polypropylene.

[0160] Separators made of polyolefins, particularly polyethylene or polypropylene, can have a porosity in the range of 35-45%. Suitable pore sizes are, for example, in the range of 30-500 nm.

[0161] In another embodiment of the present invention, the separator can be selected from a PET nonwoven fabric filled with inorganic particles. Such a separator may have a porosity in the range of 40 to 55%. A suitable pore size is, for example, in the range of 80 to 750 nm.

[0162] The battery according to the present invention may further include a housing that can have any shape, for example, a cube, or the shape of a cylindrical disk or cylindrical can. In one modified embodiment, a metal foil configured as a pouch is used as the housing.

[0163] The battery according to the present invention exhibits good discharge behavior, very good discharge and cycle behavior, for example, at low temperatures (below 0°C, for example below -10°C).

[0164] The battery according to the present invention may include two or more electrochemical cells that are combined with each other, for example, connected in series or in parallel. 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 cell contains cathode according to the present invention. Even more preferably, in the battery according to the present invention, all electrochemical cells contain cathode according to the present invention.

[0165] The present invention further relates to a method of using a battery according to the present invention in equipment, in particular in mobile devices. Examples of mobile devices include vehicles, such as automobiles, bicycles, aircraft, or watercraft, such as boats or ships. Other examples of mobile devices include manually operated devices, such as computers, in particular laptops, telephones, or power tools in the construction sector, such as drills, battery-powered screwdrivers, or battery-powered staplers.

[0166] The present invention will be further explained by examples. [Examples]

[0167] Unless otherwise specified, percentages are in mass percent. RPM: Rounds per minute Unless otherwise specified, percentages are in mass percent. RPM: Rounds per minute.

[0168] I. Cathode Active Material I.1 Preparation of Precursors Deionized water was placed in a stirred tank reactor, and ammonium sulfate (49 g per 1 kg of water) was added. The solution temperature was controlled to 55°C, and the pH value was controlled to 12 by adding an aqueous sodium hydroxide solution.

[0169] A transition metal sulfate aqueous solution and a sodium hydroxide aqueous solution were simultaneously supplied to a tank reactor at a flow rate ratio of 1.8, with a total flow rate and residence time of 8 hours. The transition metal sulfate solution contained Ni, Co, and Mn in a molar ratio of 94:3:3 and a total transition metal concentration of 1.65 mol / kg. The sodium hydroxide aqueous solution was a mixture of sodium hydroxide aqueous solution (25% by mass) and ammonia aqueous solution (25% by mass) in a mass ratio of 6. The pH value was maintained at 12 by supplying sodium hydroxide aqueous solution separately. Starting from the initiation of all feeds, the mother liquor was continuously collected. After 27 hours, all feed flows were stopped. The resulting suspension was filtered, washed with distilled water, dried in air at 120°C, and sieved to obtain the mixed transition metal (TM) oxyhydroxide precursor TM-OH.1.

[0170] Next, the obtained oxyhydroxide precursor TM-OH.1 was calcined at 475°C to produce the oxide precursor TM-O.1.

[0171] I.2 Preparation of Cathode Active Material (Initial, Pristine) The oxide precursor TM-O.1 was mixed with 0.5 mol% anhydrous Al2(SO4)3, 0.7 mol% Al(OH)3, and 0.3 mol% ZrO2 (all mol%s are relative to the total Ni, Co, and Mn in TM-O.1) and anhydrous LiOH with a Li / TM molar ratio of 1.03. This mixture was heated at 765°C for 8 hours under an oxygen forced stream to obtain the cathode active material B-CAM.1.I.

[0172] In the comparative example, the same mixture was prepared except that 1.2 mol% of Al(OH)3 was added instead of Al2(SO4)3. After calcining the mixture, the cathode active material C-CAM.2 was obtained.

[0173] The D50, measured using laser diffraction with a Malvern Instruments Mastersizer 3000, was 13.0 μm. The residual moisture content, measured at 230°C, was 140 ppm.

[0174] I.3 Post-processing steps I.3.1. Washing Process The cathode active material according to I.2 was brought into contact with deionized water for 5 minutes while stirring. The mass ratio of cathode active material to water was 2000 g / L. The resulting slurry was filtered and then dried in air at 120°C to obtain the washed cathode active material CAM.W.1(2).

[0175] I.3.2. Coating Process The washed cathode active material CAM.W.1(2) obtained according to I.3.1 was mixed with 0.9 mol% H3BO3 in a roller mill. The mol% is relative to the total amount of Ni, Co, and Mn in CAM.W.1(2). The resulting mixture was then heated at 300°C for 5.5 hours in an oxygen-forced stream to obtain cathode active materials CAM.1 or C-CAM.2, respectively.

[0176] Rietveld refinement based on the XRD pattern of CAM.1 (Cu-Kα line, λ=1.540596 Å) revealed lattice constants a=2.8750 Å, c=14.207 Å, and c / a=4.9416.

[0177] In the case of C-CAM.2, the lattice constants a = 2.8738 Å and c = 14.205 Å, and the ratio of the lattice constants c / a is 4.9429.

[0178] ICP analysis revealed that λ = 0.0016 for CAM.1 and λ = 0.0007 for C-CAM.2.

[0179] Depth-direction profile XPS analysis revealed that in B-CAM.1, there is a sulfur concentration gradient from the outermost surface (1.4 mol% of all detected elements) toward the bulk center, and that it stabilizes at depths greater than 500 nm (0.4 mol%). Furthermore, depth-direction profile XPS analysis showed that in CAM.1, 0.4 mol% sulfur was detected without a clear gradient from the outermost surface to a depth of 300 nm, and was no longer detected beyond 300 nm.

[0180] Surface XPS measurements revealed that LiBO2 / Li2B4O7 was formed on the particle surfaces of CAM.1 and C-CAM.2.

[0181] Cross-sectional TEM-EDX analysis revealed that in B-CAM.1, sulfur was concentrated at the grain boundaries between primary particles, where the primary particles were located on the surface of secondary particles and in the bulk center. In CAM.1, sulfur concentration at the grain boundaries was no longer detected on the surface of secondary particles and in the bulk center. SEM images of the cross-section revealed that the porosity of the secondary particles in CAM.1 was 4.0%. In contrast, the porosity of C-CAM.2 was only 1.5%. Higher porosity leads to greater efficiency in injecting electrolytes into the pores, resulting in faster transport of Li+ ions and thus higher capacity.

[0182] II. Testing of Cathode Active Materials II.1. Electrode Preparation and General Procedure II.1.1. Preparation of Cathode A PVDF binder (Solef® 5130) was dissolved in NMP (Merck) to prepare a 7.5% by mass solution. For electrode preparation, the binder solution (3% by mass), graphite (SFG6L, 2% by mass), and carbon black (Super C65, 1% by mass) were suspended in NMP. After mixing using a planetary centrifugal mixer (ARE-250, Thinky Corp.; Japan), either CAM.1 of the present invention or the comparative cathode active material C-CAM.2 (94% by mass) was added, and the suspension was mixed again to obtain a lump-free slurry. The solid content of the slurry was adjusted to 65%. This slurry was coated onto Al foil using a roll-to-roll coater. Before use, all electrodes were calendered. The thickness of the cathode material was 70 μm, and the concentration was 15 mg / cm². 2 This was equivalent to [a certain value]. Before assembling the battery, all electrodes were dried at 105°C for 7 hours.

[0183] II.2 Preparation of Electrolytes A base electrolyte was prepared by mixing 12.7% by mass of LiPF6, 26.2% by mass of ethylene carbonate (EC), and 61.1% by mass of ethyl methyl carbonate (EMC) (EL Base 1). The mass percentages were based on the total mass of EL Base 1.

[0184] II.3. Manufacturing of Test Cells II.3.1. Coin-type half-cell The cathode prepared as described in II.1.1 and coin-shaped half-cells (20 mm in diameter, 3.2 mm thick) containing lithium metal as the working electrode and counter electrode were assembled in glove boxes filled with Ar. The cathode, anode, and separator were stacked in the order of cathode / separator / Li foil to create a half-coin cell. Then, 0.15 mL of EL base 1, as described in II.2, was added to this coin cell.

[0185] III. Evaluation of Cell Performance Cell performance was evaluated using coin-type half-cells. The coin-type half-cells described in II.3.1 were tested in a voltage range of 4.3 to 2.7 V at ambient temperature. Specifically, a constant current (CC) of 0.05 C was applied, and then a constant voltage (CV) of 4.3 V was maintained until the C reached 0.02 C. After a 5-minute rest period, relithiation was performed with a constant current of 0.05 C to 2.7 V. The cycling current density was C / 3. The results are summarized in Table 1.

[0186] [Table 1]

Claims

1. (A) General formula Li １＋ｘ TM １－ｘ O ２ A core material wherein TM is a combination of Ni, Al, at least one of Mn and Co, and at least one metal optionally selected from Mg, Zr, Ti, Nb, Ta and W, x is in the range of 0 to 0.2, and at least 80 mol% of TM is nickel. (B) A coating containing at least one boron compound in the +III oxidation state, A cathode active material containing, The core material (A) is a polycrystalline material composed of primary particles as secondary particles, and has a lattice constant ratio c / a of 4.9420 or less, determined by X-ray diffraction and Rietveld refinement. A cathode active material in which 0.0009 ≤ λ ≤ 0.0024, where λ is the molar ratio of sulfate to TM determined by inductively coupled plasma spectroscopy (ICP), and the sulfate concentration is essentially constant across the particle size of the secondary particles.

2. TM is a combination of transition metals according to general formula (I). (Ni a Co b Mr c Al d ) 1-e M e (I) (In the formula, a is in the range of 0.90 to 0.98, b is in the range of 0.005 to 0.

09. c is in the range of 0.005 to 0.

09. d is in the range of 0.001 to 0.

05. e is in the range of 0 to 0.

05. M is selected from Mg, Ti, Zr, Nb, Ta, and W. The cathode active material according to claim 1, where a + b + c + d = 1.

3. The coating is LiBO ２ Li ２ B ４ O ７ or B ２ O ３ A cathode active material according to claim 1 or 2, comprising:

4. The cathode active material according to claim 1 or 2, wherein cobalt is distributed essentially uniformly over the radius of the secondary particles.

5. The cathode active material according to claim 1 or 2, wherein the cathode active material has an average diameter of primary particles in the range of 300 to 500 nm, as determined by SEM.

6. The cathode active material according to claim 1 or 2, having a porosity in the range of 1.5 to 5.0 volume percent, as determined by analysis of cross-sectional images by TEM and SEM.

7. The cathode active material according to claim 1 or 2, wherein the central part of the secondary particles of the core (A) contains spherical primary particles, and the outer part of the core (A) contains rod-shaped primary particles.

8. The following steps, (a) A step of providing an oxide of TM', wherein TM' is the same as TM but does not contain the aluminum added in step (b), (b) The oxide of TM' is provided by a lithium source, Al ２ (SO ４ ) ３ , optionally Al(OH) ３ , and optionally a step of mixing with at least one oxide or (oxy)hydroxide of Mg, Zr, Ti, Nb, Ta, and W, (c) A step of calcining the mixture obtained in step (b) at a temperature in the range of 650 to 800°C to obtain a powder. (d) A step of washing the powder from step (c) with an aqueous medium, and then separating the washed powder from the washing water by a solid-liquid separation method, (e) Adding a boron compound having boron in oxidation state +III to the solid obtained in step (d), then drying and heat-treating at a temperature in the range of 250 to 400°C. A method for producing the cathode active material according to claim 1 or 2, comprising the above.

9. The method according to claim 8, wherein in step (b), the molar ratio of Al to TM' is in the range of 0.001 to 0.

05.

10. The method according to claim 8, wherein step (d) is performed at a temperature in the range of 0 to 30°C.

11. The method according to claim 8, wherein step (d) includes filtration as a solid-liquid separation method, and in step (e), boric acid is added to the filtration cake.

12. In process (b), Al(OH) ３ and Al ２ (SO ４ ) ３ The method according to claim 8, wherein the substance is applied in a molar ratio in the range of 2:1 to 1:

5.

13. (A) At least one electrode active material according to claim 1 or 2, (B) Conductive carbon, and (C) Binder Electrodes, including

14. (1) at least one electrode according to claim 13, (2) at least one anode, and (3) Electrolyte A secondary battery containing [a specific component].

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