Process for making a cathode active material, cathode active material and its use

Abstract

The present invention is directed towards a process for making a cathode active material, wherein the process comprises the following steps: (a) providing an (oxy)hydroxide or oxide of TM, (b) Providing a LiOH with an average particle diameter (D50) in the range of from 200 µm to 1 mm, (c) Processing LiOH in a mass colloider mill, thus generating LiOH with a bimodal or multi- modal particle size distribution, (d) Mixing (oxy)hydroxide or oxide of TM from step (a) and LiOH from step (c) in a molar ratio of Li to TM in the range of from 1.0 : 1.0 to 1.08 to 1.0, with or without addition of at least one (oxy)hydroxide or oxide of Al, Mg, Ce, Ti, Zr, Nb, Ta, W, or Y, (e) Treating the mixture resulting from step (d) at a temperature in the range of from 650 to 950°C, thereby generating a cathode active material.

Description

[0001] Process for making a cathode active material, cathode active material and its use

[0002] The present invention is directed towards a process for making a cathode active material, wherein the process comprises the following steps:

[0003] (a) providing an (oxy)hydroxide or oxide of TM wherein TM is a combination of metals according to general formula (I)

[0004] (NiaCObMnc)i-dM1d (I) with a being in the range of from 0.8 to 0.99, b being in the range of from 0.005 to 0.195, c being in the range of from 0.005 to 0.195, and d being in the range of from zero to 0.1 , or a being in the range of from 0.3 to 0.4 b being zero or in the range of from 0.01 to 0.05, c being in the range of from 0.55 to 0.7, and d being in the range of from zero to 0.1 ,

[0005] M1is selected from Al, Mg, Ti, Zr, Nb, Ta, Y, Ce, and W, and a + b + c = 1 ,

[0006] (b) Providing a LiOH with an average particle diameter (D50) in the range of from 200 pm to 1 mm,

[0007] (c) Processing LiOH from step (b) in a mass colloider mill, thus generating LiOH with a bi- modal or multimodal particle size distribution,

[0008] (d) Mixing (oxy)hydroxide or oxide of TM from step (a) and LiOH from step (c) in a molar ratio of Li to TM in the range of from 1.0 : 1.0 to 1.08 to 1.0, with or without addition of at least one (oxy)hydroxide or oxide of Al, Mg, Ce, Ti, Zr, Nb, Ta, W, or Y,

[0009] (e) Treating the mixture resulting from step (d) at a temperature in the range of from 650 to 950°C, thereby obtaining a cathode active material.

[0010] Lithiated transition metal oxides are currently being used as electrode active materials for lithium-ion batteries. Extensive research and developmental work have been performed in the past years to improve properties like charge density, specific energy, but also other properties like the reduced cycle life and capacity loss that may adversely affect the lifetime or applicability of a lithium-ion battery. Additional effort has been made to improve manufacturing methods.

[0011] In a typical process for making cathode materials for lithium-ion batteries, first a so-called precursor is formed by co-precipitating the transition metals preferably as hydroxides that may or may not be basic, for example oxyhydroxides. Hydroxides may be pre-calcined and turned into oxides or oxyhydroxides, or they are directly mixed with a source of lithium such as, but not limited to LiOH, LizO, U2O2 or U2CO3 and calcined (fired) at high temperatures. The source of lithium can be employed as hydrate(s) or in dehydrated form. The calcination - or firing - often also referred to as thermal treatment or heat treatment of the precursor - is usually carried out at temperatures in the range of from 600 to 1 ,000 °C. During the thermal treatment a solid-state reaction takes place, and the electrode active material is formed. The thermal treatment is performed in the heating zone of an oven or kiln.

[0012] A typical class of cathode active materials delivering high energy density contains a high amount of Ni (so-called Ni-rich cathode active materials), for example at least 80 mol-%, referring to the content of non-lithium metals. However, the cycling performance still needs improvement.

[0013] In a typical process for making cathode active materials in a roller hearth kiln, it is observed that significant amounts of lithium source are lost. This may be caused by evaporation of Li source and / or melting of Li source and accumulation at the bottom of the ceramic crucible used in calcination, where the material becomes very hard and is lost for the further process. Moreover, it is known that the molar ratio between Li and the sum of transition metals Ni, Co and Mn plays a critical role in determining the product quality of cathode active materials and local inhomogeneities due to Li loss will lead to reduced cathode active material properties. In addition, a certain crucible loading should not be exceeded when performing the calcination in a roller hearth kiln, otherwise an inhomogeneous cathode active material is obtained. Said inhomogeneity may expressed, e.g., by determination of the lithium / nickel molar ratio of a sample of particles. It was therefore an objective to avoid lithium loss during calcination and to provide a process that allows improved crucible loading and thus higher capacity of the respective furnace.

[0014] It was an objective of the present invention to provide cathode active materials with reduced loss of lithium source and a more homogeneous cathode active material homogeneity.

[0015] Accordingly, the process as defined at the outset has been found, hereinafter also referred to as “inventive process” or “process according the (present) invention”. The inventive process comprises the following steps (a) and (b) and (c) and (d) and (e), hereinafter also referred to as step (a) and step (b) and step (c) and step (d) and step (e), or briefly as (a) or (b) or (c) or (d) or (e), respectively. The inventive process will be described in more detail below.

[0016] It was found that the particle size distribution of the source of lithium does not only influence the crucible loading in a roller hearth kiln or a related furnace, e.g., a muffle oven but also the quality of the cathode active material obtained.

[0017] Step (a) includes an (oxy)hydroxide or oxide of TM wherein TM is a combination of metals according to general formula (I)

[0018] (NiaCobl\ / lnc)i-dM1d (I) with a being in the range of from 0.80 to 0.97, preferably from 0.83 to 0.95, b being zero or in the range of from 0.025 to 0.2, preferably from 0.025 to 0.15, c being in the range of from zero to 0.2, preferably from zero to 0.15, or from 0.01 to 0.15, and d being in the range of from zero to 0.1 , preferably from zero to 0.05, or a being in the range of from 0.3 to 0.4, b being zero or in the range of from 0.01 to 0.05, c being in the range of from 0.55 to 0.7, and d being in the range of from zero to 0.1 ,

[0019] M1is selected from Al, Mg, Ti, Zr, Nb, Ta, Y, Ce, and W, and a + b + c = 1 .

[0020] In a preferred embodiment, b + c > zero.

[0021] In a preferred embodiment, d is zero.

[0022] TM may contain traces of further metal ions, for example traces of ubiquitous metals such as sodium, calcium or zinc, as impurities but such traces will not be taken into account in the description of the present invention. Traces in this context will mean amounts of 0.05 mol-% or less, referring to the total metal content of TM. (Oxy)hydroxide or oxide of TM as provided in step (a) is in particulate form. The particles size distribution may be determined by light scattering or LASER diffraction or electroacoustic spectroscopy, LASER diffraction being preferred. The particle size distribution may be characterized by the span, (D90 - D10) divided by D50, D50 being the median value. Preferably, the span of the resultant (oxy)hydroxide is below 0.95, more preferably from 0.2 to 0.35 or from 0.36 to 0.50 or from 0.50 to 0.80, even more preferably 0.20 to 0.30. D10 and D90 are the respective percentiles.

[0023] In one embodiment of the present invention, the particle shape of secondary particles of (oxy)hydroxide or oxide as provided in step (a) is spheroidal, that are particles that have a spherical shape. The term “spheroidal” shall include not just those particles which are exactly spherical but also those particles in which the maximum and minimum diameter of at least 90% (number average) of a representative sample differ by not more than 10%.

[0024] In one embodiment of the present invention, (oxy) hydroxi de or oxide as provided in step (a) are comprised of secondary particles that are agglomerates of primary particles.

[0025] In one embodiment of the present invention the specific surface (BET) of (oxy)hydroxide or oxide as provided in step (a) is in the range of from 2 to 120 m2 / g, determined by nitrogen adsorption, for example in accordance with to DIN-ISO 9277:2003-05.

[0026] In one embodiment of the present invention, (oxy)hydroxide or oxide of TM as provided in step (a) have a span of the particle diameter distribution (D90-D10) / D50 below 0.95, preferably from 0.50 to 0.80 or 0.15 to 0.49, more preferably 0.15 to 0.35, even more preferably 0.15 to 0.33. D10, D90 and D50 are the respective percentiles. They refer to the volume and may be determined by LASER diffraction. The value D50 is strictly speaking the median value but is - in the context of the present invention - also referred to as average or mean particle diameter. The span in each case refers to the secondary particles.

[0027] Step (b) includes providing a LiOH with an average particle diameter (D50) in the range of from 200 pm to 1 mm. LiOH without water of hydration is commercially available. LiOH may also be made by converting a hydrate, e.g., UOH H2O, to LiOH by a thermal treatment in the range of from 150 to 400°C.

[0028] Step (c) includes processing LiOH in a mass colloider mill, thus generating LiOH with a bimodal or multimodal particle size distribution. Mass colloider mills comprise plates with a gap in between. The gap size between the plates of a mass colloider mill may be set in the range of from 50 pm to 500 pm, preferably from 100 pm to 300 pm. Examples of mass colloider mills are the “supermasscolloider a series” from Masuko Sangyo Co., LTD and the XRS series “micro-stone disc mill” from Company Suzhou Xiran Industrial Equipment Co., LTD.

[0029] The duration of step (c) may be in the range of from 0.5 to 10 seconds, preferably 0.1 to 5 seconds. The duration is defined as the time during which a particle of LiOH flies in the mill.

[0030] The particles of LiOH that are obtained from step (c) preferably have irregular shape. Irregular in this context means that the average form factor is below 0.8.

[0031] The form factor of individual particles is calculated from the perimeter and area determined from top view SEM images:

[0032] Form factor = (4iT area) / (perimeter)2

[0033] While a perfect sphere would possess a form factor of 1.0, any deviation from perfect sphericity leads to form factors < 1 .0.

[0034] To determine the average form factor, the form factor is first determined for at least 50 individual particles of a representative sample and then averaged. This is why it may be referred to as average form factor as well.

[0035] A LiOH with a bimodal or multimodal, preferably bimodal particle size distribution is obtained from step (c). In a preferred embodiment, LiOH generated in step (c) has an average particle diameter (D50) in the range of from 200 to 300 pm and a local maximum in the particle size distribution in the range of from 30 to 90 pm and another local maximum in the range of from 300 to 700 pm, determined by LASER scattering and referring to the average volume value.

[0036] Without wishing to be bound by any theory, we assume that the bimodal or multimodal particle diameter distribution is caused by the short residence time and a comparably large gap size in the mass colloider mill.

[0037] Step (d) includes mixing (oxy) hydroxide or oxide of TM from step (a) and LiOH from step (c) in a molar ratio of Li to TM in the range of from 1 .0 : 1 .0 to 1.40 to 1 .0, with or without addition of at least one (oxy)hydroxide or oxide of M1that is selected from Al, Mg, Ce, Ti, Zr, Nb, Ta, W, or Y, In embodiments wherein the variable a in formula (I) is 0.8 or higher, a molar ratio Li to TM in the range of from 1.0 : 1.0 to 1. 08 to 1.0 is preferred, more preferred is from 1.01 : 1.0 to 1.05 : 1.0.

[0038] In embodiments wherein the variable a in formula (I) is from 0.3 to 0.4, a molar ratio Li to TM in the range of from 1.1 : 1.0 to 1. 30 to 1.0 is preferred.

[0039] Examples of suitable compounds of W are WO3, WO3 ■ H2O, Na2WO4, ammonium tungstate and tungstic acid. An example of a suitable compound of cerium is CeC>2. Examples of suitable compounds of magnesium are MgO, Mg(OH)2, MgSC>4, preference being given to MgO and to Mg(OH)2. Examples of suitable compounds of niobium are LiNbO3, Nb2C>5 and niobic acid, Nb2Os ■ H2O. Examples of suitable compounds of tantalum are Ta2Os and LiTaO3. Examples of suitable compounds of titanium are TiO2, TiO(OH)2, Ti(OH)4, Li2TiC>3, and TiO2aq, preference is given to TiO2. Examples of suitable compounds of zirconium are ZrO2, ZrO(OH)2, Li2ZrOs,, Zr(OH)4, and ZrO2aq, preference is given to Zr(OH)4and ZrO2.

[0040] Examples of suitable compounds of aluminum are, e.g., AI2C>3, AI(OH)3, LiAIO2, AIOOH, AI2O3aq, preference being given to AIOOH and AI2O3, especially y-AI2O3. An example of a suitable compound of yttrium is Y2O3.

[0041] If desired, least one (oxy)hydroxide or oxide of M1is added in an amount that the molar share of M1is in the range of from above zero up to 10 mol-%, referring to the sum of Ni, Co and Mn, preferred are 0.5 to 3 mol-%.

[0042] Step (d) may be performed in various types of vessels that allow mixing, e.g., in blenders, ball mills, planetary ball mills, plough share mixers, and high speed mixers. For laboratory scale experiments, mortars with pestles are suitable as well.

[0043] The duration of step (d) may be in the range of from 1 minute to 120 minutes. Preferred are 5 to 60 minutes.

[0044] In order to avoid dusting, small amounts of water may be added at the beginning of step (d), for example up to 10 vol-%, referring to (oxy)hydroxide or oxide of TM. However, it is preferred to not add any water.

[0045] Step (d) is preferably performed without external heating or cooling. Step (d) may be performed in one step or in the form of sub-steps, for example by first mixing LiOH and (oxy)hydroxide(s) or oxide(s) of M1and then (oxy)hydroxide or oxide of TM. However, it is preferred to perform step (d) in one step.

[0046] A mixture is obtained from step (d).

[0047] Step (e) includes treating the mixture resulting from step (d) at a temperature in the range of from 650 to 950°C, thereby obtaining a cathode active material.

[0048] Especially in embodiments wherein the variable a in formula (I) is 0.8 or higher, step (e) is preferably performed in an atmosphere of oxygen or oxygen-enriched air, for example with at least 60 vol-% of oxygen, preferably 80 vol-% of oxygen and more preferably at least 90 vol-% oxygen. In embodiments wherein TM of inventive (oxy)hydroxides corresponds to formula (I), said calcination may be performed in air atmosphere.

[0049] Examples of suitable set-ups for step (e) are rotary kilns, roller hearth kilns, and pusher kilns.

[0050] In one embodiment of the present invention, the mixture obtained from step (d) is heated to 700 to 900 °C with a heating rate of 0.1 to 10 °C / min.

[0051] In one embodiment of the present invention, the temperature is ramped up before reaching the desired temperature of from 700 to 900°C, preferably 750 to 850°C. For example, first the mixture obtained from step (d) is heated to a temperature to 350 to 550°C and then held constant for a time of 10 min to 4 hours, and then the temperature is raised to 700°C up to 900°C, preferably 750 to 850°C.

[0052] In one embodiment of the present invention, the thermal treatment is performed in a roller hearth kiln, a pusher kiln or a rotary kiln or a combination of at least two of the foregoing. Rotary kilns have the advantage of a very good homogenization of the material made therein. In roller hearth kilns and in pusher kilns, different reaction conditions with respect to different steps may be set quite easily. In lab scale trials, box-type and tubular furnaces, muffle ovens and split tube furnaces are feasible as well.

[0053] In one embodiment of the present invention, step (e) is performed in an oxygen-containing atmosphere, for example in a nitrogen-air mixture, in a rare gas-oxygen mixture, in air, in oxygen or in oxygen-enriched air. 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 50:50 by volume mix of air and oxygen. Other options are 1 :2 by volume mixtures of air and oxygen, 1 :3 by volume mixtures of air and oxygen, 2:1 by volume mixtures of air and oxygen, and 3:1 by volume mixtures of air and oxygen.

[0054] In one embodiment of the present invention, step (e) is performed under a forced flow of gas, for example air, oxygen and oxygen-enriched air. Such stream of gas may be termed a forced gas flow. Such stream of gas may have a specific flow rate in the range of from 0.5 to 15 m3 / h kg material according to general formula Lii+xTMi-xO2. The volume is determined under normal conditions: 298 Kelvin and 1 atmosphere. Said forced flow of gas is useful for removal of gaseous cleavage products such as water and carbon dioxide.

[0055] In one embodiment of the present invention, step (e) has a duration in the range of from one hour to 30 hours. Preferred are 10 to 24 hours. The cooling time is neglected in this context.

[0056] After step (e), the cathode active material so obtained is cooled down before further processing. Additional - optional - steps before further processing the resultant electrode active materials are sieving and de-agglomeration steps.

[0057] In one embodiment of the present invention, the inventive process comprises at least one additional step selected from water washing steps and coating steps.

[0058] In a water washing step - hereinafter also referred to as step (f) - cathode active material obtained from step (e) is treated with an aqueous medium, preferably with water. Said aqueous medium may have a pH value in the range of from 2 up to 14, preferably at least 3.5, more preferably from 5 to 7. The pH value is measured at the beginning of step (f). It is observed that in the course of a step (f), the pH value raises to at least 10, for example 11 to 13. In embodiments wherein the pH value is in the range of from 10 to 11 at the beginning of step (f) it raises to more than 11 to up to 13. In embodiments wherein the pH value is in the range of 3 to below 10 at the beginning of step (b) it raises to 11 to up to 13 in the course of step (f).

[0059] Aqueous medium used in step (f) may contain ingredients to be deposited on cathode active material from step (e), e.g., Ah SC h, or for pH value adjustment, e.g., LiOH.

[0060] It is preferred that the water hardness of said aqueous medium used in step (f) is at least partially removed, especially calcium. The use of de-ionized or distilled water is preferred.

[0061] Unless a step (g) is desired, vide infra, the solid residue from step (f) is dried, for example at temperatures in the range of from 50 to 150°C, under air or nitrogen or in vacuo. Additionally, a thermal post-treatment may be performed, for example by calcining under air or oxygen or ni- trogen at 350 to 600°C. Such thermal post-treatment may be performed in a roller hearth kiln or in a rotary kiln. On laboratory scale, muffle ovens are suitable as well.

[0062] Drying and thermal post-treatment are preferably performed under an atmosphere with reduced CO2 content, e.g., a carbon dioxide content in the range of from 0.01 to 500 ppm by weight, preferred are 0.1 to 50 ppm by weight. The CO2 content may be determined by, e.g., optical methods using infrared light. It is even more preferred to perform step (f) under an atmosphere with a carbon dioxide content below detection limit for example with infrared-light based optical methods, so-called decarbonized air or carbon-free air.

[0063] In order to perform an - optional - coating step - hereinafter step (g), it is possible to contact cathode active material from step (e) or (f) with a coating material. Such coating material may be in particulate form and applied as a slurry in alcohol such as isopropanol or water, or it may be in the form of a powder. Examples are alumina, titania, zirconia, boric acid, niobium oxide, tungsten oxide and zirconia. In other embodiments, such coating material may be formed in situ, for example by contacting cathode active material from step (e) or (f) with a solution of a precursor of the coating material, e.g., aluminum sulfate or titanium sulfate or the like.

[0064] In coating processes that involve water it is preferred to perform a thermal post-treatment of the freshly coated cathode active material, as described above.

[0065] A further aspect of the present invention is related to cathode active materials, hereinafter also referred to as inventive cathode active materials or cathode active materials according to the (present) invention. Inventive cathode active materials may advantageously be manufactured according to the inventive process. Inventive cathode active materials are characterized by the general formula Lii+xTMi.xO2 wherein x is in the range of from - 0.01 to 0.08 and TM is a combination of metals according to general formula (I)

[0066] (NiaCObMnc)i-dM1d(I) with a being in the range of from 0.80 to 0.97, preferably from 0.83 to 0.95, b being zero or in the range of from 0.025 to 0.2, preferably from 0.025 to 0.15, c being in the range of from zero to 0.2, preferably from zero to 0.15, or from 0.01 to 0.15, and d being in the range of from zero to 0.1 , preferably from zero to 0.05, or a being in the range of from 0.3 to 0.4, b being zero or in the range of from 0.01 to 0.05, c being in the range of from 0.55 to 0.7, and d being in the range of from zero to 0.1 ,

[0067] M1is selected from Al, Mg, Ti, Zr, Nb, Ta, Y, Ce, and W, and a + b + c = 1.

[0068] In one embodiment of the present invention, inventive cathode active material is composed of secondary particles that are agglomerates of primary particles and wherein said cathode active material has a crystallite size of from 50nm to 300 nm as determined by X-ray diffraction, and said cathode active material has a bulk Li / TM molar ratio A measured with ICP-OES, with TM as the sum of Ni, Co and Mn, and each secondary particle has a particle Li / TM molar ratio B measured with LA-ICP-MS, and at least 70% of the secondary particles have a particle Li / TM ratio B70in the range of from (A - 0.1) to (A + 0.1) and at least 50% of the secondary particles have a particle Li / TM ratio B50in the range of from (A - 0.05) to (A + 0.05).

[0069] In an alternative embodiment, inventive cathode active materials have a general formula Lii+xTMi-xO2 wherein x is in the range of from - 0.01 to 1.40 and TM is a combination of metals according to general formula (I)

[0070] (NiaCObMnc)i-dM1d(I) with a being in the range of from 0.8 to 0.99, b being in the range of from 0.005 to 0.195, c being in the range of from 0.005 to 0.195, and d being in the range of from zero to 0.1 , wherein said cathode active material is composed of monoliths, and wherein said cathode active material has a bulk Li / TM molar ratio A measured with ICP- OES, with TM as the sum of Ni, Co and Mn, and each secondary particle has a particle Li / TM molar ratio B measured with LA-ICP-MS, and at least 70% of the secondary particles have a particle Li / TM ratio B70in the range of from (A - 0.1) to (A + 0.1) and at least 50% of the secondary particles have a particle Li / TM ratio B50in the range of from (A - 0.05) to (A + 0.05), Inventive cathode active materials may bear a coating with an oxide of aluminum, boron, cobalt, titanium or tungsten. Said coating may have a thickness in the range of from 2 to 100 nm, preferably 5 to 50 nm, and it may be homogeneous or non-homogeneous with respect to composition and thickness.

[0071] In a preferred embodiment, said cathode active material that is composed of monoliths is coated with an oxide of aluminum, boron, cobalt or tungsten or a combination of an oxide of cobalt and at least one of boron and aluminum. Said oxide may contain lithium, e.g., LiCoO2.

[0072] Examples of non-homogeneous thickness coatings may result in an island structure or Swiss cheese structure of the coating.

[0073] Said coating may contain compounds other than the oxide of aluminum, boron or tungsten, for example lithiated species like UAIO2, UBO2 or U2WO4.

[0074] In one embodiment of the present invention, inventive cathode active materials have an average particle diameter (D50) in the range of from 3 to 15 pm. The average particle may be determined by light scattering or LASER diffraction or electroacoustic spectroscopy. The particles are usually composed of agglomerates from primary particles, and the above particle diameter refers to the secondary particle diameter.

[0075] In one embodiment of the present invention, inventive cathode active materials have a span of the particle diameter distribution of the secondary particles in the range of from 0.2 to 1.0, preferably 0.2 to 0.33, wherein said span is defined as (D90 - D10) / D50, wherein D10, D50 and D90 are the respective percentiles and refer to the volume. The value D50 is strictly speaking the median but is often simply referred to as average (or mean) particle diameter.

[0076] In one embodiment of the present invention, inventive cathode active materials are composed of primary particles that are platelet shaped. Preferably, no indications for insufficiently lithiated particles are visible as determined by SEM image analysis.

[0077] In one embodiment of the present invention, inventive cathode active materials show a low amount of so-called residual lithium. The term residual (or extractable) lithium includes compounds like LiOH, U2CO3 and U2O that are in the cathode active material but not incorporated in the crystal lattice. They may be extracted by a treatment with acid, for example 0.1 M aqueous HCI, and determined by titration. In one embodiment of the present invention, the amount of residual U2CO3 is in the range of from 0.05% to 0.20 wt%, the amount of residual LiOH is in the range of from 0.30 to 0.40 wt% and the total extractable lithium as a combination is in the range of from 1000 to 2000 ppm, ppm being in both cases ppm by weight and determined by titration methods.

[0078] A further aspect of the present invention relates to cathodes, hereinafter also referred to as inventive cathodes. Inventive cathodes contain at least one inventive electrode active material.

[0079] Specifically, inventive cathodes contain

[0080] (A) at least one inventive electrode active material,

[0081] (B) carbon in electrically conductive form,

[0082] (C) a binder material, also referred to as binders or binders (C), and, preferably,

[0083] (D) a current collector.

[0084] In a preferred embodiment, inventive cathodes contain

[0085] (A) 80 to 98 % by weight inventive electrode active material,

[0086] (B) 1 to 17 % by weight of carbon,

[0087] (C) 1 to 15 % by weight of binder material, percentages referring to the sum of (A), (B) and (C).

[0088] Cathodes according to the present invention can comprise further components. They can comprise a current collector, such as, but not limited to, an aluminum foil. They can further comprise conductive carbon and a binder.

[0089] Cathodes according to the present invention contain carbon in electrically conductive modification, in brief also referred to as carbon (B). Carbon (B) can be selected from soot, active carbon, carbon nanotubes, graphene, and graphite, and from combinations of at least two of the foregoing.

[0090] 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, especially from polyethylene, polyacrylonitrile, polybutadiene, polystyrene, and copolymers of at least two comonomers selected from ethylene, propylene, styrene, (meth)acrylonitrile and 1 ,3-butadiene. Polypropylene is also suitable. Polyisoprene and polyacrylates are additionally suitable. Particular preference is given to polyacrylonitrile.

[0091] 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. Preference is given to polyacrylonitrile homopolymers. In the context of the present invention, polyethylene is not only understood to mean homopolyethylene, but also copolymers of ethylene which comprise at least 50 mol-% of copolymerized ethylene and up to 50 mol-% of at least one further comonomer, for example a-olefins such as propylene, butylene (1 -butene), 1 -hexene, 1 -octene, 1 -decene, 1 -dodecene, 1 -pentene, and also isobutene, vinylaromatics, for example styrene, and also (meth)acrylic acid, vinyl acetate, vinyl propionate, Ci-C -alkyl esters of (meth)acrylic acid, especially methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, 2-ethylhexyl acrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, and also maleic acid, maleic anhydride and itaconic anhydride. Polyethylene may be HDPE or LDPE.

[0092] In the context of the present invention, polypropylene is not only understood to mean homopolypropylene, but also copolymers of propylene which comprise at least 50 mol-% of copolymerized propylene and up to 50 mol-% of at least one further comonomer, for example ethylene and a-olefins such as butylene, 1 -hexene, 1 -octene, 1 -decene, 1 -dodecene and 1 -pentene. Polypropylene is preferably isotactic or essentially isotactic polypropylene.

[0093] In the context of the present invention, polystyrene is not only understood to mean homopolymers of styrene, but also copolymers with acrylonitrile, 1 ,3-butadiene, (meth)acrylic acid, Ci- Cio-alkyl esters of (meth)acrylic acid, divinylbenzene, especially 1,3-divinylbenzene, 1 ,2- diphenylethylene and a-methylstyrene.

[0094] Another preferred binder (C) is polybutadiene.

[0095] Other suitable binders (C) are selected from polyethylene oxide (PEO), cellulose, carboxymethylcellulose, polyimides and polyvinyl alcohol.

[0096] In one embodiment of the present invention, binder (C) is selected from those (co)polymers which have an average molecular weight Mwin the range from 50,000 to 1 ,000,000 g / mol, preferably to 500,000 g / mol.

[0097] Binder (C) may be cross-linked or non-cross-linked (co)polymers.

[0098] In a particularly preferred embodiment of the present invention, binder (C) is selected from halogenated (co)polymers, especially from fluorinated (co)polymers. Halogenated or fluorinated (co)polymers are understood to mean those (co)polymers which comprise at least one (co)polymerized (co)monomer which has 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 copolymers, vinylidene fluoride-hexafluoropropylene copolymers (PVdF-HFP), vinylidene fluoride-tetrafluoroethylene copolymers, perfluoroalkyl vinyl ether copolymers, ethylene-tetrafluoroethylene copolymers, vinylidene fluoride-chlorotrifluoroethylene copolymers and ethylene-chlorofluoroethylene copolymers.

[0099] Suitable binders (C) are especially polyvinyl alcohol and halogenated (co)polymers, for example polyvinyl chloride or polyvinylidene chloride, especially fluorinated (co)polymers such as polyvinyl fluoride and especially polyvinylidene fluoride and polytetrafluoroethylene.

[0100] Inventive cathodes may comprise 1 to 15% by weight of binder(s), referring to electrode active material. In other embodiments, inventive cathodes may comprise 0.1 up to less than 1 % by weight of binder(s).

[0101] A further aspect of the present invention is a battery, containing at least one cathode comprising inventive electrode active material, carbon, and binder, at least one anode, and at least one electrolyte.

[0102] Embodiments of inventive cathodes have been described above in detail.

[0103] Said anode may contain at least one anode active material, such as carbon (graphite), TiC>2, lithium titanium oxide, silicon or tin. Said anode may additionally contain a current collector, for example a metal foil such as a copper foil.

[0104] Said electrolyte may comprise at least one non-aqueous solvent, at least one electrolyte salt and, optionally, additives.

[0105] Non-aqueous solvents for electrolytes can 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.

[0106] Examples of suitable polymers are, in particular, polyalkylene glycols, preferably poly-Ci-C4- alkylene glycols and in particular polyethylene glycols. Polyethylene glycols can here comprise up to 20 mol-% of one or more Ci-C4-alkylene glycols. Polyalkylene glycols are preferably polyalkylene glycols having two methyl or ethyl end caps. The molecular weight Mwof suitable polyalkylene glycols and in particular suitable polyethylene glycols can be at least 400 g / mol.

[0107] The molecular weight Mwof suitable polyalkylene glycols and in particular suitable polyethylene glycols can be up to 5 000 000 g / mol, preferably up to 2 000 000 g / mol.

[0108] Examples of suitable acyclic ethers are, for example, diisopropyl ether, di-n-butyl ether, 1 ,2-dimethoxyethane, 1 ,2-diethoxyethane, with preference being given to 1 ,2-dimethoxyethane.

[0109] Examples of suitable cyclic ethers are tetra hydrofuran and 1 ,4-dioxane.

[0110] Examples of suitable acyclic acetals are, for example, dimethoxymethane, diethoxymethane, 1 ,1 -di meth oxy ethane and 1 ,1 -diethoxyethane.

[0111] Examples of suitable cyclic acetals are 1,3-dioxane and in particular 1 ,3-dioxolane.

[0112] Examples of suitable acyclic organic carbonates are dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate.

[0113] Examples of suitable cyclic organic carbonates are compounds according to the general formulae (III a) and (III b) where R1, R2and R3can be identical or different and are selected from among hydrogen and Ci-C4-alkyl, for example methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tertbutyl, with R2and R3preferably not both being tert-butyl.

[0114] In particularly preferred embodiments, R1is methyl and R2and R3are each hydrogen, or R1, R2and R3are each hydrogen.

[0115] In yet another embodiment, in formula (III a) R1is fluorine and both R2and R3are hydrogen. Another preferred cyclic organic carbonate is vinylene carbonate, formula (IV).

[0116] The solvent or solvents is / are preferably used in the water-free state, i.e. with a water content in the range from 1 ppm to 0.1% by weight, which can be determined, for example, by Karl-Fischer titration.

[0117] Electrolyte (C) further comprises at least one electrolyte salt. Suitable electrolyte salts are, in particular, lithium salts. Examples of suitable lithium salts are LiPFs, LiBF4, LiCIO4, LiAsF6, LiCF3SO3, LiC(CnF2n+iSO2)3, lithium imides such as LiN(CnF2n+iSO2)2, where n is an integer in the range from 1 to 20, LiN(SO2F)2, Li2SiFe, LiSbFe, LiAICU and salts of the general formula (CnF2n+iSO2)tYLi, where m is defined as follows: t = 1 , when Y is selected from among oxygen and sulfur, t = 2, when Y is selected from among nitrogen and phosphorus, and t = 3, when Y is selected from among carbon and silicon.

[0118] Preferred electrolyte salts are selected from among LiC(CF3SO2)3, LiN(CF3SO2)2, LiPFe, LiBF4, l_iCIO4, with particular preference being given to LiPFe and LiN(CF3SO2)2.

[0119] In an embodiment of the present invention, batteries according to the invention comprise one or more separators by means of which the electrodes are mechanically separated. Suitable separators are polymer films, in particular porous polymer films, which are unreactive toward metallic lithium. Particularly suitable materials for separators are polyolefins, in particular film-forming porous polyethylene and film-forming porous polypropylene.

[0120] Separators composed of polyolefin, in particular polyethylene or polypropylene, can have a porosity in the range from 35 to 45%. Suitable pore diameters are, for example, in the range from 30 to 500 nm.

[0121] In another embodiment of the present invention, separators can be selected from among PET nonwovens filled with inorganic particles. Such separators can have porosities in the range from 40 to 55%. Suitable pore diameters are, for example, in the range from 80 to 750 nm. Batteries according to the invention further comprise a housing which can have any shape, for example cuboidal or the shape of a cylindrical disk or a cylindrical can. In one variant, a metal foil configured as a pouch is used as housing.

[0122] Batteries according to the invention display a good discharge behavior, for example at low temperatures (zero °C or below, for example down to -10°C or even less), a very good discharge and cycling behavior.

[0123] Batteries according to the invention can comprise two or more electrochemical cells that combined with one another, for example can be connected in series or connected in parallel. Connection in series is preferred. In batteries according to the present invention, at least one of the electrochemical cells contains at least one cathode according to the invention. Preferably, in electrochemical cells according to the present invention, the majority of the electrochemical cells contains a cathode according to the present invention. Even more preferably, in batteries according to the present invention all the electrochemical cells contain cathodes according to the present invention.

[0124] The present invention further provides for the use of batteries according to the invention in appliances, in particular in mobile appliances. Examples of mobile appliances are vehicles, for example automobiles, bicycles, aircraft or water vehicles such as boats or ships. Other examples of mobile appliances are those which move manually, for example computers, especially laptops, telephones or electric hand tools, for example in the building sector, especially drills, battery-powered screwdrivers or battery-powered staplers.

[0125] The present invention is further illustrated by the following working examples.

[0126] Average particle diameters (D50) of secondary particles were determined by LASER scattering and refer to the volume-based average. Percentages and ppm are % by weight or ppm by weight, as the case may be, unless specifically noted otherwise.

[0127] The numbers of particles referring to the variables A, B, B70and B50were determined as follows: The bulk Li / TM ratio A was determined using the elemental analysis technique ICP-OES. The particle Li / TM ratio B was determined by LA-ICP-MS (laser ablation inductively coupled plasma mass spectrometry). For this measurement at least 15 secondary particles were ablated and the corresponding Li / TM ratio was determined per secondary particle. The values were normalized according to the bulk Li / TM ratio A. Afterwards, frequency distributions were obtained and it was determined how many percent of secondary particles have a particle Li / TM ratio B in the range of W2 = (A - 0.1) to (A + 0.1) and how many percent of secondary particles have a particle Li / TM ration B in the range of W1 = (A - 0.05) to (A + 0.05).

[0128] I. Manufacture of cathode active materials

[0129] 1.1 Manufacture of polycrystalline cathode active materials

[0130] Step (a.1): A hydroxide of TM was provided. TM was 91 mol-% Ni, and each 4.5 mol-% of Co and Mn. It was made by co-precipitation from an aqueous solution comprising the respective sulfates with NaOH in the presence of ammonia. The average diameter (D50) was 13.8 pm. The span, (D90 - D10) / D50 was 0.30.

[0131] In a box-type furnace, 4 kg hydroxide of TM were heated to 440°C for two hours under an oxy- gen-rich atmosphere, N2 / O2 = 1 :1 by volume. An oxide of TM was obtained.

[0132] Step (b.1): commercially available LiOH H2O was de-watered in in a box-type furnace at 300 °C for five hours. Water-free LiOH, C-LiOH-4, was obtained. The D50 was 440 pm, D99 was 1200 pm as determined by using laser scattering and a dry dispersion unit.

[0133] Step (c.1): In a mass colloider mill, Supermasscolloider a Series, Masuko Sangyo Co., LTD, three samples of LiOH were made from LiOH-4, by changing the gap size between the rotating blades, see Table 1. Residence time was below 5 seconds.

[0134] Table 1: Parameter of various LiOH samples.

[0135] PSD: shape of particle size distribution

[0136] Step (d.1) through (d.3) and C-(d.4):

[0137] An amount of 400 g oxide from (a.1) were mixed with 143.4 LiOH from step (c.1), 2.5 g AI(OH)3and 2 g ZrO2, yielding 536.9 of mixed powder (premix). Subsequently, the premix was filled in ceramic crucibles (150 mm 150 mm ■ 50 mm with bottom thickness of 8 mm) to a level of 10 mm below the rim of the crucible. Step (e.1) through (e.3) and C-(e.4): Step (e.1) through (e.3) and C-(e.4): Mixtures from steps (d.1) through (d.3) and C-(d.4) were calcined in a box-type furnace at 765°C for 8 hours under an atmosphere of O2 (heating rate of 2°C / min and gas flow of 2250L / h) and then allowed to cool naturally. Base cathode active materials were obtained, see Table 2.

[0138] Post-treatment: steps (f.1) and (g.1), general protocol exemplified on B-CAM.1

[0139] Step (f.1): An amount of 300 g B-CAM.1 was mixed with 150 g of de-ionized water and stirred for 5 minutes. The water was removed by filtration, and the resultant filter cake was dried in a vacuum oven for 12 hours at 120°C under N2. A dried filter cake was obtained.

[0140] Step (g.1): 344.9 g of dried filter cake were mixed with 2.0 g H3BO3 in a roller mill for 40 min. The resultant mixture was heated in a box-type furnace at 300°C for 5.5 hours under O2(heating rate of 3°C / min and gas flow of 2250 L / h) and then allowed to cool naturally. Inventive CAM.1 was obtained. For CAM.2 etc., the protocol was followed but with LiOH-2 instead. The properties of CAM.1 , CAM.2, CAM.3 and comparative C-CAM.4 are summarized in Table 2.

[0141] Table 2: Properties of inventive and comparative cathode active materials

[0142] Crystallite size was determined by XRD

[0143] It was observed that LiOH sources LiOH-1 to LiOH-3 led to comparable crystallite sizes and BET values, while the untreated C-LiOH-4 led to C-CAM.4 with significantly smaller crystallite size and higher BET surface area. Figure 3a and b show exemplary SEM images of CAM.2 and C-CAM.4. It can be seen that CAM.2 shows cathode active material with secondary particles which are agglomerates of smaller primary particles without indication of insufficiently lithiated particles, while C-CAM.4 shows secondary particles which keep partly the appearance of the TM oxide, an indication of Li loss during calcination. This is further emphasized by the values of bulk Li / TM ratio A and particle Li / TM ration B. It is observed that C-CAM.4 has a much lower bulk Li / TM ratio A compared to CAM.1 - CAM.3. 1.2 Manufacture of single-crystalline cathode active materials

[0144] 1.2.1 Manufacture of inventive cathode active material CAM.5

[0145] Step (a.5): A hydroxide of TM was provided. TM was 92 mol-% Ni, 3 mol-% Co and 5 mol-% Mn. It was made by co-precipitation from an aqueous solution comprising the respective sulfates with NaOH in the presence of ammonia. The average diameter (D50) was 3.6 pm. The span, (D90 - D10) / D50 was 0.5.

[0146] In a box-type furnace, 4 kg hydroxide of TM were heated to 425°C for four hours under an air atmosphere, N2 / O2 = 8:2 by volume. An oxide of TM was obtained.

[0147] Steps (b.1) and (c.1) were repeated.

[0148] Step (d.5) through (d.7) and C-(d.8):

[0149] An amount of 400 g oxide from (a.5) were mixed with 131.15 g LiOH from step (c.1), yielding 531 .15 g of mixed powder (premix). Subsequently, the premix was filled in ceramic crucibles (150 mm 150 mm ■ 50 mm with bottom thickness of 8 mm) to a level of 20 mm below the rim of the crucible.

[0150] Step (e.5) through (e.7) and C-(e.8): Mixtures from steps (d.5) through (d.7) and C-(d.8) were calcined in a box-type furnace at 840°C for 12 hours under an atmosphere of O2 (heating rate of 2°C / min and gas flow of 2250L / h) and then allowed to cool naturally. Base cathode active materials B-CAM.5 through C-B-CAM.8 were obtained. Before further processing, the base cathode active materials were deagglomerated to target D50 value ~ 5pm using a laboratory crusher.

[0151] Post-treatment: step (f.5), general protocol exemplified on B-CAM.5

[0152] Step (f.5): An amount of 150 g B-CAM.5 was mixed with 2.92 g Co(OH)2, 0.12 g AI2O3 and 0.18g TiC>2, corresponding to 2 mol-% Co, 0.0015 mol-% Al and 0.0015 mol-% Ti. The resultant mixture was heated in a box-type furnace at 700°C for 2 hours under O2 (heating rate of 3°C / min and gas flow of 2250 L / h) and then allowed to cool naturally. Inventive CAM.5 was obtained.

[0153] The properties of CAM.5, CAM.6, CAM.7 and comparative material C-CAM.8 are summarized in Table 3. It is observed that C-CAM.4 shows a larger BET surface area and a smaller D50 value compared to the inventive materials CAM.5, CAM.6 and CAM.7, while the amount of total extractable Li was similar for all samples. Moreover, it can be seen that C-CAM.8 shows a significantly smaller crystallite size compared to CAM.5, CAM.6 and CAM.7.

[0154] Table 3: Properties of inventive and comparative cathode active materials

[0155] Crystallite size was determined by XRD

[0156] Top view SEM imaging was performed on CAM.5, CAM.6, CAM.7 and comparative material C- CAM.8 and the results are shown in Figures 4 a to d. While the inventive materials CAM.5, CAM.6 and CAM.7 display the typical morphology of monolithic (“single crystalline”) cathode active materials with the majority of particles having a size of more than 1 pm, C-CAM.8 still shows secondary particle agglomerates composed of smaller primary particles besides the monolithic particles. This is further illustrated by the result of automated SEM image analysis shown in Figure 5. It shows that C-CAM.8 has much smaller particle sizes (equivalent diameter from SEM image segmentation) compared to the inventive materials. This is in good agreement with the larger BET surface area and smaller crystallite size values displayed in Table 3. It may be derived that the untreated C-LiOH-4 leads to worse lithiation during the calcination process and thus hampered particle growth.

[0157] II. Testing of Cathode Active Material

[0158] 11.1 Electrode manufacture, general procedure

[0159] 11.1.1 Cathode Manufacture

[0160] Positive electrode: PVDF binder (Solef® 5130) was dissolved in NMP (Merck) to produce a

[0161] 7.5 wt.% solution. For electrode preparation, binder solution (3 wt.%), graphite (SFG6L, 2 wt.%), and carbon black (Super C65, 1 wt.-%) were suspended in NMP. After mixing using a planetary centrifugal mixer (ARE-250, Thinky Corp.; Japan), either any of inventive CAM.1 to CAM.3 or any of inventive CAM.5 to CAM.7(94 wt.%) or a comparative C-CAM.4 or C-CAM.8 was added and the suspension was mixed again to obtain a lump-free slurry. The solid content of the slurry was adjusted to 65%. The slurry was coated onto Al foil using a KTF-S roll-to-roll coater (Mathis AG). Prior to use, all electrodes were calendared. The thickness of cathode material was 70 pm, corresponding to 15 mg / cm2. All electrodes were dried at 105°C for 7 hours before battery assembly.

[0162] 11.1.2: Electrolyte Manufacture

[0163] A base electrolyte composition was prepared containing 12.7 wt% of LiPFe, 26.2 wt% of ethylene carbonate (EC), and 61 .1 wt% of ethyl methyl carbonate (EMC) (EL base 1), based on the total weight of EL base 1. To this base electrolyte formulation 2wt.% of vinylene carbonate (VC) was added (EL base 2).

[0164] 11.2 Test cell Manufacture - coin-type half cells

[0165] Coin-type half cells (20 mm in diameter and 3.2 mm in thickness) comprising a cathode prepared as described under 11.1.1 and lithium metal as working and counter electrode, respectively, were assembled and sealed in an Ar-filled glove box. In addition, the cathode and anode and a separator were superposed in order of cathode / / separator / / Li foil to produce a half coin cell. Thereafter, 0.15 mL of the EL base 1 which is described above (III.2) were introduced into the coin cell.

[0166] 11.3 Evaluation of cell performance

[0167] Evaluation of coin half-cell performance: The initial performance, C-rate performance and cycling performance were measured as follows: Coin half cells according to 11.3 were tested in a voltage range between 4.3 V to 3.0 V at room temperature. For the initial cycles, the initial charging was conducted in the CC-CV mode, i.e. , a constant current (CC) of 0.1 C was applied until reaching 4.3 V, followed by the CV step until the current dropped to 0.01 C. After 10 min resting time, discharging was carried out at constant current of 0.1 C up to 3.0 V. For the cycling test, the constant current was chosen to be 1C until 113 cycles were reached and discharge capacity retention was calculated by comparing the initial 1C discharge capacity and the 1C discharge capacity at the end of the cycle test. The results are summarized in Table 4. Table 4: Electrochemical performance of inventive and comparative cathode active materials n.d.: not determined

[0168] It is observed that C-CAM.4 has a lower 1stdischarge capacity and worse capacity retention compared to CAM.1 - CAM.3. Moreover, C-CAM.8 shows lower 1stdischarge capacity yet comparable capacity retention compared to CAM.5 - CAM.7.

[0169] Brief Description of the Figures:

[0170] Figure 1: particle size distribution of LiOH-1 to C-LiOH-4

[0171] Figure 2 a: Particle Li / TM ratio in CAM.2

[0172] Figure 2 b: Particle Li / TM ratio in C-CAM.4

[0173] Figure 3 a: SEM image of secondary particles of CAM.2 without insufficiently lithiated particles.

[0174] Figure 3 b: SEM image of secondary particles of C-CAM.4 with insufficiently lithiated particle (left).

[0175] Figures 4 a to 4 d: SEM images of CAM.5, CAM.6, CAM.7 and C-CAM.8

[0176] Figure 5: Automated SEM image analysis based on the particles shown in Figures 4 a - d.

Claims

Patent Claims:

1. Process for making a cathode active material, wherein the process comprises the following steps:(a) Providing an (oxy)hydroxide or oxide of TM wherein TM is a combination of metals according to general formula (I)(NiaCObMnc)i-dM1d (I) with a being in the range of from 0.8 to 0.99, b being in the range of from 0.005 to 0.195, c being in the range of from 0.005 to 0.195, and d being in the range of from zero to 0.1 , or a being in the range of from 0.3 to 0.4, b being zero or in the range of from 0.01 to 0.05, c being in the range of from 0.55 to 0.7, and d being in the range of from zero to 0.1 ,M1is selected from Al, Mg, Ti, Zr, Nb, Ta, Y, Ce, and W, and a + b + c = 1 ,(b) Providing LiOH with an average particle diameter (D50) in the range of from 200 pm to 1 mm,(c) Processing LiOH from step (b) in a mass colloider mill, thus generating LiOH with a bimodal or multimodal particle size distribution,(d) Mixing (oxy)hydroxide or oxide of TM from step (a) and LiOH from step (c) in a molar ratio of Li to TM in the range of from 1.0 : 1.0 to 1.40 to 1.0, with or without addition of at least one (oxy) hydroxide or oxide of Al, Mg, Ce, Ti, Zr, Nb, Ta, W, or Y,(e) Treating the mixture resulting from step (d) at a temperature in the range of from 650 to 950°C, thereby obtaining a cathode active material.

2. Process according to claim 1 wherein such mass colloider mill is operated with an average residence time of the LiOH in the range of from 0.5 to 10 seconds.

3. Process according claims 1 or 2 wherein LiOH generated in step (c) has an average particle diameter (D50) in the range of from 200 to 300 pm and a local maximum in the particle size distribution in the range of from 30 to 90 pm and another local maximum in the range of from 300 to 700 pm, determined by LASER scattering and referring to the average volume value.

4. Process according to any of the preceding claims wherein said process comprises at least one additional step selected from coating steps and water washing steps.

5. Process according to any of the preceding claims wherein the (oxy)hydroxide or oxide of TM as provided in step (a) has a span of the particle diameter distribution in the range of from 0.15 to 0.33, wherein said span is defined as (D90 - D10) / D50, wherein D10, D50 and D90 are the respective percentiles and refer to the volume.

6. Cathode active material of the general formula Lii+xTMi.xO2 wherein x is in the range of from - 0.01 to 1 .40 and TM is a combination of metals according to general formula (I)(NiaCobMnc)i-dM1d (I) with a being in the range of from 0.8 to 0.99, b being in the range of from 0.005 to 0.195, c being in the range of from 0.005 to 0.195, and d being in the range of from zero to 0.1 , or a being in the range of from 0.3 to 0.4, b being zero or in the range of from 0.01 to 0.05, c being in the range of from 0.55 to 0.7, and d being in the range of from zero to 0.1 ,M1is selected from Al, Mg, Ti, Zr, Nb, Ta, Y, Ce, and W, and a + b + c = 1 , and wherein said cathode active material is composed of secondary particles that are agglomerates of primary particles and said cathode active material has a crystallite size in the range of from 50 to 300 nm as determined by X-ray diffraction,and wherein said cathode active material has a bulk Li / TM molar ratio A measured with ICP-OES, with TM as the sum of Ni, Co and Mn, and each secondary particle has a particle Li / TM molar ratio B measured with LA-ICP-MS, and at least 70% of the secondary particles have a particle Li / TM ratio B70in the range of from (A - 0.1) to (A + 0.1) and at least 50% of the secondary particles have a particle Li / TM ratio B50in the range of from (A - 0.05) to (A + 0.05), wherein the cathode active material may be coated with an oxide of Al or W or B.

7. Cathode active material according to claim 6 wherein the primary particles are platelet shaped, determined by SEM image analysis.

8. Cathode active material of the general formula Lii+xTMi.xO2 wherein x is in the range of from - 0.01 to 1 .40 and TM is a combination of metals according to general formula (I)(NiaCobMnc)i-dM1d (I) with a being in the range of from 0.8 to 0.99, b being in the range of from 0.005 to 0.195, c being in the range of from 0.005 to 0.195, and d being in the range of from zero to 0.1 , wherein said cathode active material is composed of monoliths, wherein the cathode active material is coated with an oxide of Al or W or B or Co.

9. Cathode active material according to any of the claims 6 to 8 having an average diameter (D50) in the range of from 3 to 15 pm.

10. Cathode active material according to any of the claims 6 to 9 having a span of the particle diameter distribution of the secondary particles in the range of from 0.20 to 1.00, wherein said span is defined as (D90 - D10) / D50, wherein D10, D50 and D90 are the respective percentiles and refer to the volume.

11. Cathode active material according to any of the claims 6 to 10 showing no indications for insufficiently lithiated particles are visible, determined by SEM image analysis.

12. Electrode containing(A) at least one electrode active material according to any of claims 6 to 11 ,(B) carbon in electrically conductive form and (C) a binder.

13. Secondary battery containing(1) at least one electrode according to claim 12,(2) at least one anode, and (3) an electrolyte.

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