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

Abstract

Process for making a cathode active material based on Li and TM wherein said process com- prises the following steps: (a) Providing a hydroxide TM(OH)2 or at least one oxide TMO or at least one oxyhydroxide of TM or a combination of at least two of the foregoing wherein TM contains at least 95 mol% Ni and, optionally, in total up to 5 mol-% of at least one metal selected from Ti, Zr, V, Co, Zn, Ba, Mn, or Mg, (b) mixing said hydroxide TM(OH)2 or oxide TMO or oxyhydroxide of TM with 1.10 to 1.75 equivalents of a source of lithium selected from lithium carbonate and lithium hydroxide, equivalents referring to molar amounts of lithium, (c) thermally treating the mixture obtained from step (b) at a temperature in the range of from 500 to 575°C under oxidizing conditions, thereby obtaining a lithium-rich oxide of TM, (d) thermally treating the lithium-rich oxide of TM from step (c) at a temperature of from 705 to 800°C, thereby obtaining lithium oxide and LITMO2, (e) removing lithium oxide by washing with an aqueous solution of LiOH, followed by drying and a thermal treatment.

Description

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

[0002] The present invention is directed towards a process for making a cathode active material based on Li and TM wherein said process comprises the following steps:

[0003] (a) Providing a hydroxide TM(OH)2 or at least one oxide TMO or at least one oxyhydroxide of TM or a combination of at least two of the foregoing wherein TM contains at least 95 mol% Ni and, optionally, in total up to 5 mol-% of at least one metal selected from Ti, Zr, Al, V, Co, Zn, Ba, Mn, or Mg,

[0004] (b) mixing said hydroxide TM(0H)2 or oxide TMO or oxyhydroxide of TM with 1 .10 to 1.75 equivalents of a source of lithium selected from lithium carbonate and lithium hydroxide, equivalents referring to molar amounts of lithium,

[0005] (c) thermally treating the mixture obtained from step (b) at a temperature in the range of from 500 to 575°C under oxidizing conditions, thereby obtaining a lithium-rich oxide of TM,

[0006] (d) thermally treating the lithium-rich oxide of TM from step (c) at a temperature of from 705 to 800°C, thereby obtaining lithium oxide and LITMO2,

[0007] (e) removing lithium oxide by washing with an aqueous solution of LiOH, followed by drying and a thermal treatment.

[0008] Lithium-ion secondary batteries are modern devices for storing energy. Many application fields have been and are contemplated, from small devices such as mobile phones and laptop computers through car batteries and other batteries for e-mobility. Various components of the batteries have a decisive role with respect to the performance of the battery such as the electrolyte, the electrode materials, and the separator. Particular attention has been paid to the cathode materials. Several materials have been suggested, such as lithium iron phosphates, lithium cobalt oxides, and lithium nickel cobalt manganese oxides. Although extensive research has been performed the solutions found so far still leave room for improvement.

[0009] Currently, a certain interest in so-called Ni-rich cathode active materials may be observed, for example cathode active materials that contain 95 mole-% or more of Ni, referring to the total transition metal content.

[0010] A particularly Ni-rich material is LiNiCh, sometimes abbreviated as LNO. However, LNO frequently suffers from various drawbacks that have lowered interest in its commercial use. The most important among these drawbacks is the difficile synthesis of stoichiometric LiNiO2 due to its tendency towards Li off-stoichiometry (Lii.zNii+zO2) and various instability problems of its de- lithiated state, which can be of (electro)chemical, mechanical or thermal nature. It was an objective of the present invention to provide a process for making Ni-rich cathode active materials with excellent electrochemical properties. It was also an objective to provide Ni- rich cathode active materials with excellent electrochemical properties.

[0011] It has been found that some of the problems of traditionally made LNO may be assigned to the nickel-lithium scrambling. Nickel-lithium scrambling is an expression that describes the location of lithium ions in nickel crystallographic sites and vice versa and is possible due to the similar sizes of the ions Li+and Ni2+.

[0012] Accordingly, the process defined at the outset has been found, hereinafter also referred to as “inventive process”. The inventive process comprises the following steps:

[0013] (a) Providing a hydroxide TM(OH)2 or at least one oxide TMO or at least one oxyhydroxide of TM or a combination of at least two of the foregoing wherein TM contains at least 95 mol% Ni and, optionally, in total up to 5 mol-% of at least one metal selected from Ti, Zr, Al, V, Co, Zn, Ba, Mn, or Mg,

[0014] (b) mixing said hydroxide TM(0H)2 or oxide TMO or oxyhydroxide of TM with 1.10 to 1.75 equivalents of a source of lithium selected from lithium carbonate and lithium hydroxide, equivalents referring to molar amounts of lithium,

[0015] (c) thermally treating the mixture obtained from step (b) at a temperature in the range of from 500 to 575°C under oxidizing conditions, thereby obtaining a lithium-rich oxide of TM,

[0016] (d) thermally treating the lithium-rich oxide of TM from step (c) at a temperature of from 705 to 800°C, thereby obtaining lithium oxide and LITMO2,

[0017] (e) removing lithium oxide by washing with an aqueous solution of LIOH, followed by drying and a thermal treatment.

[0018] The inventive process comprises four steps, (a), (b), (c), and (d), in the context of the present invention also referred to as step (a) and step (b) and step (c) and step (d), respectively. The four steps are preferably performed subsequently.

[0019] The inventive process starts off from a hydroxide TM(OH)2 or at least one oxide TMO or at least one oxyhydroxide of TM or a combination of at least two of the foregoing. In such hydroxide TM(OH)2 or at least one oxide TMO or oxyhydroxide of TM, TM contains at least 95 mol% Ni and, optionally, in total up to 5 mol-% of at least one metal selected from Ti, Zr, V, Co, Zn, Ba, or Mg. Preferably, TM contains at least 99.5 mol-% of Ni and, optionally, in total up to 0.5 mol-% of at least one metal selected from Ti, Zr, and Co, and only traces of V, Zn, Ba, and Mg. Even more preferably, TM is Ni. The amount and kind of metals such as Ti, Zr, Al, V, Co, Zn, Mn, Ba, or Mg may be determined inductively coupled plasma (“ICP”) and by synchrotron XRD.

[0020] TM(OH)2 or TMO or oxyhydroxide of TM provided in step (a) is preferably comprised of spherical particles, referring to particles that have a spherical shape. Spherical particles shall include not just those 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%.

[0021] In one embodiment of the present invention, TM(OH)2 or TMO or oxyhydroxide of TM provided in step (a) is comprised of secondary particles that are agglomerates of primary particles. Preferably, TM(OH)2 or TMO or oxyhydroxide of TM provided in step (a) is comprised of spherical secondary particles that are agglomerates of primary particles. Even more preferably, TM(OH)2 or TMO or oxyhydroxide of TM provided in step (a) is comprised of spherical secondary particles that are agglomerates of spherical primary particles or platelets.

[0022] In one embodiment of the present invention, TM(OH)2 or TMO or oxyhydroxide of TM provided in step (a) has an average particle diameter (D50) in the range of from 3 to 20 pm, preferably from 5 to 16 pm. The average particle diameter can be determined, e. g., 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.

[0023] Some elements are ubiquitous. In the context of the present invention, traces of ubiquitous metals such as sodium, calcium, iron or zinc, as impurities will not be taken into account in the description of the present invention. Traces in this context will mean amounts of 0.02 mol-% or less, referring to the total metal content of the starting material.

[0024] In embodiments wherein TM contains at least 95 mol% Ni and in total up to 5 mol-% of at least one metal selected from Ti, Zr, V, Co, Zn, Al, Ba, or Mn, Mg, said Ti, Zr, V, Co, Al, Zn, Ba, Mn or Mg or combinations of at least two of the foregoing may be homogeneously distributed within the particles of Ni(OH)2 or enriched at the surface, preference being giving to a homogeneous distribution. Preferably, TM is Ni.

[0025] TM(OH)2 as provided in step (a) may be manufactured by precipitation of Ni and - if applicable

[0026] - in total up to 5 mol-% of at least one metal selected from Ti, Zr, V, Co, Zn, Ba, Mn, or Mg with alkali metal hydroxide from an aqueous solution of nickel sulfate that contains, if desired, at least one compound of said metal(s) selected from Ti, Zr, Al, V, Co, Zn, Ba, Mn, or Mg, followed by filtration and drying.

[0027] TMO and oxyhydroxide of TM as provided in step (a) may be manufactured by heating TM(OH)2 and thus removing water.

[0028] Oxyhydroxide of TM is meant to include non -stoichiometric oxyhydroxides, with water bound chemically as hydroxide or with residual moisture content.

[0029] In step (b), said hydroxide TM(OH)2 or oxide TMO or oxyhydroxide of TM or combination provided in step (a) is mixed with 1 .10 to 1 .75 equivalents of a source of lithium selected from lithium carbonate and lithium hydroxide, equivalents referring to molar amounts of lithium. One equivalent of lithium hydroxide thus corresponds to 1 mole of lithium hydroxide or 0.5 mole of lithium carbonate. Preferably, said hydroxide TM(OH)2 or oxide TMO or oxyhydroxide of TM or combination provided in step (a) is mixed with 1 .4 to 1 .6 equivalents of a source of lithium.

[0030] In one embodiment of the present invention, a dopant is added in step (b), for example an oxide or oxyhydroxide or carbonate of Ti, Zr, V, Co, Zn, Ba, Mn, or Mg. The molar amount of such dopant does not exceed 1%, referring to TM. In other embodiments, no dopant is added in step (b). Preferred examples of dopants are TiO2, TiO2 aq, TiO(OH)2, Zr(OH)4, ZrO2, ZrOz-aq, V2O4, V2O5, CoO, CO(OH)2, CO3O4, CO2O3, Zn(OH)2, ZnO, AI2O3, for example Y-AI2O3, AIOOH, AI(OH)3, AhOs aq, BaCOs, ZnCOs, CoCOs, MnO2, Mn2Os, MnCOs, MgO, MgCOs or Mn(OH)2.

[0031] Step (b) may be performed by mixing hydroxide TM(OH)2 or TMO or oxyhydroxide of TM or combination with source of lithium and, optionally, with dopant(s) in a mixer, for example in a plough-share mixer or in a tumble mixer. For laboratory scale experiments, ball mills and roller mills may be applied as well.

[0032] Step (b) may be performed with the addition of water or of an organic solvent but it is preferred to not add any organic solvent or water in sub-step (b).

[0033] Preferred duration of step (b) is in the range of from one to 30 minutes.

[0034] In one embodiment of the present invention, step (b) is performed at normal pressure. It is possible to perform sub-step (b) under elevated pressure, for example at 10 mbar to 10 bar above normal pressure, or with suction, for example 50 to 250 mbar below normal pressure, preferably 100 to 200 mbar below normal pressure. It is preferred, though, to work at ambient pressure (one atmosphere).

[0035] A mixture is obtained from step (b).

[0036] It is possible to perform step (b) under heating but it is preferred to not perform additional heating in the course of step (b).

[0037] Step (c) includes thermally treating the mixture obtained from step (b) at a temperature in the range of from 500 to 575°C under oxidizing conditions, thereby obtaining a lithium-rich oxide of TM. Oxidizing conditions may be established by performing step (c) in the way that the oxygen partial pressure is increased. The step (c) can be performed under an atmosphere of oxygen or oxygen-enriched air, for example at volumetric ratio of oxygen : air of 5:1 to 10:1. Preferred is an atmosphere of pure oxygen.

[0038] In one embodiment of the present invention, step (c) is performed at a temperature in the range of from 500 to 575°C, preferably 525 to 565°C. The duration at said temperature may be in the range of from 6 to 24 hours. A heating rate in the range of from 1 to 10 °C / min is preferred.

[0039] A lithium-rich oxide of TM is obtained from step (c). The idealized formula is Li2 xTMi+xO3, with 0.09 < x < 0.33. Lithium-rich oxide from step (c) has a monoclinic C2 / m structure as derivable from X-ray diffraction.

[0040] In one embodiment of the present invention, step (c) is carried out 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 (c) under an atmosphere with a carbon dioxide content below detection limit for example with infrared lightbased optical methods.

[0041] The inventive process includes a subsequent step (d):

[0042] (d) thermally treating the lithium-rich oxide of TM from step (c) at a temperature of from 705 to 800°C, preferably 725 to 750°C, thereby obtaining lithium oxide and LITMO2, preferably in the presence of oxygen. Step (d) may be carried out in any type of oven, for example a roller hearth kiln, a pusher kiln, a rotary kiln, a pendulum kiln, or - for lab scale trials - in a muffle oven.

[0043] The temperature of 705 to 800°C, preferably 725 to 750°C, corresponds to the maximum temperature of step (d).

[0044] It is possible to subject the material obtained from step (c) directly to step (d). However, it is preferred to increase the temperature stepwise, or to ramp up the temperature. Said step-wise increase or ramping up may be performed under normal pressure or reduced pressure, for example 1 to 500 mbar.

[0045] Step (d) - at its maximum temperature - may be performed under normal pressure.

[0046] Step (d) is carried out under an oxygen-containing atmosphere, for example air, oxygen- enriched air or pure oxygen.

[0047] Preferably, both steps (c) and (d) are performed under an atmosphere of pure oxygen.

[0048] In one embodiment of the present invention, step (d) is carried out 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 (d) under an atmosphere with a carbon dioxide content below detection limit for example with infrared lightbased optical methods.

[0049] In one embodiment of the present invention, the duration of step (d) is in the range of from 5 to 24 hours, preferably 10 to 15 hours. Like in other steps, steps (c) and (e), the time for reaching the temperature of 705 to 800°C is not counted.

[0050] In one embodiment of the present invention, the lithium-rich oxide of TM is cooled down between steps (c) and (d), for example to ambient temperature. In other embodiments, the lithium- rich oxide from step (c) is directly heated to 705 to 800°C, preferably 725 to 750°C.

[0051] By performing step (d), lithium oxide and LiTMO2 is obtained. Said LiTMO2 has a rhombohedral R3-m structure, as detectable from X-ray diffraction. The lithium oxide is enriched at the surface of the LiTMO2. By exposure to ambient air, said lithium oxide may be converted at least partially to lithium carbonate and lithium hydroxide. In subsequent step (e), lithium oxide is removed by washing with an aqueous solution of LiOH, followed by drying and a thermal treatment. Said aqueous solution may have a LiOH concentration of 0.01 to 0.5 % by weight of lithium hydroxide and may be obtained by simply dissolving LiOH in water. Preferably, the water used for step (d) is de-ionized.

[0052] Washing may be performed by slurrying lithium oxide and LiTMO2 from step (d) in an aqueous solution of LiOH, or by placing lithium oxide and LiTMO2 from step (d) on a filter and rinsing it with said solution of LiOH.

[0053] It is observed that in the course of step (e), the pH value raises to at least 11 , for example 11 to 13. In embodiments wherein the pH value is in the range of from 11 to 11.5 at the beginning of step (e) it raises to more than 12 to up to 13.

[0054] It is preferred that the water hardness of said aqueous medium used in step (e) is at least partially removed, especially calcium. The use of desalinized water for making the aqueous solution of LiOH is preferred.

[0055] In one embodiment of the present invention, step (e) is performed at a temperature in the range of from 5 to 85°C, preferred are 10 to 60°C.

[0056] In one embodiment of the present invention, step (e) is performed at normal pressure. It is preferred, though, to perform step (e) under elevated pressure, for example at 10 mbar to 10 bar above normal pressure, or with suction, for example 50 to 250 mbar below normal pressure, preferably 100 to 200 mbar below normal pressure.

[0057] Step (e) may be performed, for example, in a vessel that can be easily discharged, for example due to its location above a filter device. Such vessel may be charged with starting material followed by introduction of aqueous medium. In another embodiment, such vessel is charged with aqueous medium followed by introduction of starting material. In another embodiment, starting material and aqueous medium are introduced simultaneously.

[0058] In one embodiment of the present invention, in step (e), the amounts of water and cathode active material have a weight ratio in the range of from 1 :5 to 5:1 , preferably from 2:1 to 1 :2.

[0059] Step (e) may be supported by mixing operations, for example shaking or in particular by stirring or shearing, see below. In one embodiment of the present invention, step (e) has a duration in the range of from 1 minute to 90 minutes, preferably 1 minute to less than 60 minutes. A duration of 5 minutes or more is possible in embodiments wherein in step (e), water treatment and water removal are performed overlapping or simultaneously.

[0060] In one embodiment of the present invention, treatment according to step (e) and removal of the aqueous medium are performed consecutively.

[0061] After or during the treatment with an aqueous medium in accordance to step (e), water may be removed by any type of filtration, for example on a band filter or in a filter press.

[0062] In one embodiment of the present invention, at the latest 5 minutes after commencement of step (e), the removal of aqueous medium is started. Such removal includes partially removing the water from treated particulate cathode active material, for example by way of a solid-liquid separation, for example by decanting or preferably by filtration. Said “partial removal” may also be referred to as partially separating off.

[0063] In one embodiment of the present invention, the slurry obtained in step (e) is discharged directly into a centrifuge, for example a decanter centrifuge or a filter centrifuge, or on a filter device, for example a suction filter or in a filter press or in a belt filter that is located preferably directly below the vessel in which step (e) is performed. Then, filtration is commenced.

[0064] In a particularly preferred embodiment of the present invention, steps (e) and the removal of the aqueous medium are performed in a filter press or in a filter device with stirrer, for example a pressure filter with stirrer or a suction filter with stirrer (German for example: “Ruhrfilter- nutsche”). At most 5 minutes after, preferably at most 3 minutes after - or even immediately after - having combined starting material and aqueous medium in accordance with step (e), removal of aqueous medium is commenced by starting the filtration. On laboratory scale, treatment with and removal of the aqueous medium may be performed on a Buchner funnel be supported by manual stirring.

[0065] In a preferred embodiment, step (e) is performed in a filter device, for example a stirred filter device that allows stirring of the slurry in the filter or of the filter cake.

[0066] In one embodiment of the present invention, the aqueous medium or water removal in accordance to step (e) has a duration in the range of from 1 minute to 1 hour. In one embodiment of the present invention, stirring in step (e) is performed with a rate in the range of from 1 to 100 revolutions per minute (“rpm”), preferred are 5 to 20 rpm. In other embodiments, it is 200 to 400 rpm.

[0067] Washing in step (e) may be performed once or several times, with fresh solution of LiOH.

[0068] In one embodiment of the present invention, filter media may be selected from ceramics, sintered glass, sintered metals, organic polymer films, non-wovens, and fabrics.

[0069] From the washing in step (e), a solid residue is obtained, preferably in the form of a wet filter cake. The moisture content of the solid residue and especially of the filter cake may be in the range of from 3 to 20 % by weight, preferably 4 to 9 % by weight.

[0070] After the washing in step (e), drying may be performed, for example under nitrogen or under reduced pressure (“in vacuo”) at 50 to 150°C, to obtain a free-flowing powder. Then, a thermal treatment is performed, for example at 250 to 750°C. Preferably the thermal treatment in step (e) is performed at a temperature in the range of from 450 to 750°C.

[0071] The thermal treatment in step (e) may have a duration in the range of from one hour to 12 hours.

[0072] In one embodiment of the present invention, the thermal treatment in step (e) is performed in a moving bed or fluidized bed. In other embodiments, the thermal treatment in step (e) is performed in a rotary kiln, in a roller hearth kiln or a pusher kiln. In laboratory scale, for example 1 to 5 g, muffle ovens are feasible as well.

[0073] In one embodiment of the present invention, step (e) is carried out 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.

[0074] The thermal treatment in step (e) is preferably performed at ambient pressure.

[0075] By performing the inventive process, a lithium-rich cathode active material is obtained with excellent electrochemical properties. It has a very low degree of lithium / nickel scrambling, On the other hand, no formation of NiO can be detected by XRD analysis. A further aspect of the present invention is a cathode active material, hereinafter also referred to as inventive cathode active material. It is advantageously synthesized according to the inventive process.

[0076] Inventive cathode active material is in particulate form and has the general formula Lii+xTMi-xO2, wherein

[0077] TM contains at least 95 mol% Ni and, optionally, up to 5 mol-% of at least one metal selected from Ti, Zr, V, Co, Zn, Al, Ba, Mn or Mg. Preferably, TM contains at least 99.5 mol-% of Ni and, optionally, in total up to 0.5 mol-% of at least one metal selected from Ti, Zr, Al, Mn and Co, and only traces or negligible amounts of V, Zn, Ba, and Ca. Even more preferably, TM is Ni.

[0078] -0.01 < x < +0.01.

[0079] In embodiments wherein TM contains at least 95 mol% Ni and in total up to 5 mol-% of at least one metal selected from Ti, Zr, V, Co, Al, Zn, Ba, Mn, or Mg, said Ti, Zr, Al, Mn, V, Co, Zn, Ba, or Mg or combinations of at least two of the foregoing may be homogeneously distributed within the particles of Ni(OH)2 or enriched at the surface, preference being giving to a homogeneous distribution

[0080] In one embodiment of the present invention inventive cathode active materials have an average particle diameter (D50) in the range of from 2 to 7 pm, preferably from 3 to 5 pm. The average particle diameter may be determined, e. g., by scanning electron microscopy (“SEM”), 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.

[0081] In one embodiment of the present invention inventive cathode active materials have a surface (BET) in the range of from 0.1 to 2.0 m2 / g, determined according to DIN-ISO 9277:2003-05.

[0082] In inventive cathode active materials, the nickel / lithium scrambling is below 1.5 mol-%, determined by X-ray diffraction analysis, and no NiO impurities are detectable by XRD analysis, combined with Rietveld refinement results indicating a ratio of lattice parameters a and c of c / a > 4.937. In one embodiment of the present invention, the nickel / lithium scrambling is at least 0.5 mol-%. A preferred upper limit of the ratio c / a is 4.943. The number of nickel / lithium scrambling refers to the percentage of Ni2+ions in the lithium crystallographic layer. In one embodiment of the present invention, inventive cathode active material has a content of extractable lithium in the range of from 0.1 to 0.6 % by weight, determined by titration, for ex- ample after soaking with 0.5 molar aqueous HCI, followed by titration with 0.5 M aqueous NaOH.

[0083] A further aspect of the present invention refers to electrodes comprising at least one cathode active material according to the present invention. They are particularly useful for lithium-ion batteries. Lithium-ion batteries comprising at least one electrode according to the present invention exhibit a good discharge behavior. Electrodes comprising at least one cathode active material according to the present invention are hereinafter also referred to as inventive cathodes or cathodes according to the present invention.

[0084] Specifically, inventive cathodes contain

[0085] (A) at least one inventive cathode active material,

[0086] (B) carbon in electrically conductive form,

[0087] (C) a binder material, also referred to as binders or binders (C), and, preferably,

[0088] (D) a current collector.

[0089] In a preferred embodiment, inventive cathodes contain

[0090] (A) 80 to 98 % by weight inventive cathode active material,

[0091] (B) 1 to 17 % by weight of carbon,

[0092] (C) 1 to 15 % by weight of binder material, percentages referring to the sum of (A), (B) and (C).

[0093] 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.

[0094] 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.

[0095] 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 )acry Ion itrile and 1 ,3-butadiene. Polypropylene is also suitable. Polyisoprene and polyacrylates are additionally suitable. Particular preference is given to polyacrylonitrile.

[0096] 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.

[0097] 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-Cio-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.

[0098] 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.

[0099] 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.

[0100] Another preferred binder (C) is polybutadiene.

[0101] Other suitable binders (C) are selected from polyethylene oxide (PEO), cellulose, carboxymethylcellulose, polyimides and polyvinyl alcohol.

[0102] 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. Binder (C) may be cross-linked or non-cross-linked (co)polymers.

[0103] 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.

[0104] 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.

[0105] Inventive cathodes may comprise 1 to 15% by weight of binder(s), referring to cathode active material. In other embodiments, inventive cathodes may comprise 0.1 up to less than 1% by weight of binder(s).

[0106] A further aspect of the present invention is a battery, containing at least one cathode comprising inventive cathode active material, carbon, and binder, at least one anode, and at least one electrolyte.

[0107] Embodiments of inventive cathodes have been described above in detail.

[0108] Said anode may contain at least one anode active material, such as carbon (graphite), TiO2, lithium titanium oxide, silicon or tin. Said anode may additionally contain a current collector, for example a metal foil such as a copper foil.

[0109] Said electrolyte may comprise at least one non-aqueous solvent, at least one electrolyte salt and, optionally, additives. 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.

[0110] 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.

[0111] The molecular weight Mwof suitable polyalkylene glycols and in particular suitable polyethylene glycols can be at least 400 g / mol.

[0112] 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.

[0113] 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.

[0114] Examples of suitable cyclic ethers are tetrahydrofuran and 1 ,4-dioxane.

[0115] Examples of suitable acyclic acetals are, for example, dimethoxymethane, diethoxymethane, 1 ,1 -dimethoxyethane and 1 ,1 -diethoxyethane.

[0116] Examples of suitable cyclic acetals are 1 ,3-dioxane and in particular 1 ,3-dioxolane.

[0117] Examples of suitable acyclic organic carbonates are dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate.

[0118] Examples of suitable cyclic organic carbonates are compounds according to the general formulae (II) and (III) 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.

[0119] In particularly preferred embodiments, R1is methyl and R2and R3are each hydrogen, or R1, R2and R3are each hydrogen.

[0120] Another preferred cyclic organic carbonate is vinylene carbonate, formula (IV).

[0121] 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.

[0122] Electrolyte (C) further comprises at least one electrolyte salt. Suitable electrolyte salts are, in particular, lithium salts. Examples of suitable lithium salts are LIPF6, LIBF4, LICIC , LIAsF6, IJCF3SO3, 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, LiAICk 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. Preferred electrolyte salts are selected from among LIC(CF3SO2)3, LIN(CF3SO2)2, LiPFe, IJBF4, LiCIC , with particular preference being given to LiPFe and LiN(CF3SO2)2-

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] The present invention is further illustrated by the following working examples.

[0131] I. Synthesis of Cathode Active Materials

[0132] Step (a.1 ): Synthesis of a precursor, P-CAM.1

[0133] The precipitation reaction was performed at 50°C under a nitrogen atmosphere using a continuous stirred tank reactor with a volume of 2.3 I. Then, the pH value of the solution was adjusted to 11 .70 using a 25% by weight aqueous solution of sodium hydroxide. An aqueous metal solution containing NiSO4, aqueous sodium hydroxide (25 wt. % NaOH) and aqueous ammonia solution (25 wt. % ammonia) were simultaneously introduced into the vessel. The molar ratio between ammonia and metal was adjusted to 0.7. The sum of volume flows was set to adjust the mean residence time to 3 hours. The flow rate of the NaOH was adjusted by a pH regulation circuit to keep the pH value in the vessel at a constant value of 11 .70. The apparatus was operated continuously keeping the liquid level in the vessel constant. Ni hydroxide was collected via free overflow from the vessel. The resulting slurry contained about 120 g / l Ni hydroxide with an average particle diameter (D50) of 4 pm, P-CAM.1 , which was recovered by filtration and drying at 120°C.

[0134] Step (b.1 ): Synthesis of lithium-rich nickel oxides, CAM.0-1

[0135] In a Kinematica mixer, 5 g of P-CAM.1 was mixed thoroughly with 1 .5 eq. 3.40 g IJOH H2O. A premix was obtained. The resultant mixture was then filled in an alumina crucible and heated in O2 flow with an exchange rate of 5 atm / h and heating rate of 3 K / min to 550°C and dwell time of 12 hours for two times with an intermittent mixing step in a mortar or Kinematica. The resultant lithium-rich nickel oxide CAM.0-1 was de-agglomerated in the Kinematica mixer or thoroughly ground in a mortar.

[0136] Further syntheses are summarized in Table 1 .

[0137] Step (c.1): Manufacture of the inventive material CAM.1

[0138] Step (c.1): Thermal decomposition of CAM.O

[0139] CAM.O from the step (b.1) was heated in O2 flow with an exchange rate of 5 atm / h and heating rate of 3 K / min to 725°C where it is then annealed for 12 hours. The resultant lithium oxide con- taining L1N1O2 was ground in a mortar or Kinematica mixer, and full conversion to hexagonal layered structure was confirmed by XRD. No impurity peak of NiO at 27.8° 2-theta (Mo K-a source) could be detected.

[0140] Step (d.1): Washing to remove residual lithium

[0141] 2 g of lithium oxide containing LiNiO2 from step (c.1 ) was mixed with aqueous LiOH solution (0.1 wt.%). After stirring for 10 min at 25°C stirring was discontinued and the sample left to separate. The remaining solid was washed with ethanol. The remaining ethanol was removed in vacuo. The resultant product, CAM.1 , was sieved with a 45 pm metal mesh prior to testing.

[0142] Step (e.1): Annealing

[0143] The solid residue from step (d.1 ) was heated in O2 flow with an exchange rate of 5 atm / h and heating rate of 3 K / min to 700°C where it is then annealed for 3 hours. The resultant product, CAM.1 was sieved with a 32 pm metal mesh prior to testing.

[0144] Table 1 : Syntheses of lithium-rich nickel oxides and inventive CAM

[0145] 1 : equivalents refer to Ni in Ni(OH)2

[0146] Step c-(b.1): Manufacture of comparative material, lithium nickel oxide, C-CAM.6

[0147] In a Kinematica mixer, 6 g of P-CAM.1 was mixed thoroughly with 1 .01 eq. of LiOH. A premix was obtained.

[0148] The resultant premix was then filled in an alumina crucible and heated in O2 flow with an exchange rate of 5 atm / h and heating rate of 3 K / min to 400°C and dwell time of 4 hours and a heating rate of 3K / min to 700°C and dwell time of 6 hours. The resultant lithium nickel oxide was de-agglomerated in the Kinematica mixer or thoroughly ground in a mortar.

[0149] Then, steps (c.1 ) to (e.1) were repeated mutatis mutandis. C-CAM.6 was obtained. II. Cathode and coin cell manufacture

[0150] 11.1 Cathode manufacture

[0151] General procedure:

[0152] The cathode slurries necessary for cathode preparation were prepared by first mixing a 7.5 wt. % binder solution of polyvinylidene difluoride (PVdF, Solef 5130, Solvay) in / V-methyl-2- pyrrolidone (NMP, > 99.5%, Merck KGaA) with conductive carbon black (Super C65, TIMCAL Ltd.) and NMP in a planetary centrifugal mixer (ARE-250, Thinky) for 3 min at 2000 rpm followed by 3 min at 400 rpm. After the first mixing, either CAM.1 or CAM.2 or CAM.3 was added to the slurry in an open mixing cup. The mixture was then stirred again for 3 min at 2000 rpm and 3 min at 500 rpm, yielding a homogenous deep black slurry. Using a motorized film applicator (Erichsen Coat Master 510), the slurry was immediately coated onto 0.03 mm thick aluminum foil using a blade film applicator with a slit height of 140 pm to achieve areal loadings of ~2- 12 mgcAM cm-2. The resulting tapes were dried at 120°C in vacuo for 12 hours.

[0153] 11.2 Coin cell manufacture

[0154] CR2032 coin cells were assembled in an argon-filled glovebox (H2O < 0.5 ppm and O2 < 0.5 ppm) and comprised a cathode (13 mm diameter), a GF / A glass microfiber separator (17 mm diameter; GE Healthcare Life Science, Whatman), a lithium metal anode (15 mm diameter), and 100 pl of electrolyte, consisting of 1.0 M LiPFe in 3:7 EC:EMC by weight.

[0155] Test protocol:

[0156] In general, for every experiment, at least three cells were successfully cycled and results are shown as the average of these cells. They were cycled with a battery testing system (MACCOR Inc.) at 25 °C.

[0157] The first five cycles involved galvanostatic cycling at 0.1 C rate in a voltage window between 2.8 and 4.3 V vs. Li+ / Li, followed by long-term cycling at 1C in the same voltage range. The results are summarized in Table 2.

[0158] Table 2: Specific discharge capacity and cycling behavior of inventive CAM and comparative CAM

Claims

Patent Claims1 . Process for making a cathode active material based on Li and TM wherein said process comprises the following steps:(a) Providing a hydroxide TM(OH)2 or at least one oxide TMO or at least one oxyhydroxide of TM or a combination of at least two of the foregoing wherein TM contains at least 95 mol% Ni and, optionally, in total up to 5 mol-% of at least one metal selected from Ti, Zr, V, Al, Co, Zn, Ba, Mn, or Mg,(b) mixing said hydroxide TM(OH)2 or oxide TMO or oxyhydroxide of TM with 1.10 to 1.75 equivalents of a source of lithium selected from lithium carbonate and lithium hydroxide, equivalents referring to molar amounts of lithium,(c) thermally treating the mixture obtained from step (b) at a temperature in the range of from 500 to 575°C under oxidizing conditions, thereby obtaining a lithium-rich oxide of TM,(d) thermally treating the lithium-rich oxide of TM from step (c) at a temperature of from 705 to 800°C, thereby obtaining lithium oxide and LITMO2,(e) removing lithium oxide by washing with an aqueous solution of LiOH, followed by drying and a thermal treatment.

2. Process according to claim 1 wherein the aqueous solution in step (e) has a concentration in the range of from 0.01 to 0.5 % by weight of lithium hydroxide.

3. Process according to claim 1 or 2 wherein steps (c) and (d) are performed under an atmosphere of oxygen.

4. Process according to any of claims 1 to 3 wherein TM is Ni.

5. Process according to any of the preceding claims wherein the thermal treatment in step (e) is performed at a temperature in the range of from 450 to 750°C.

6. Particulate cathode active material according to the general formula Lii+xTMi-xO2 wherein x is in the range of from -0.01 to +0.01 and TM is nickel or a combination of metals of which 95 mol-% or more is nickel and in total up to 5 mol-% of at least one metal selected from Ti, Zr, V, Co, Zn, Ba, Al, Mn, or Mg, wherein said material has an average particle diameter (D50) in the range of from 2 to 7 pm, determined by scanning electron microscopy, and the nickel / lithium scrambling is below 1.5 mol-%, determined by X-ray diffraction analysis, and no NIC impurities are detectable by XRD analysis.

7. Particulate cathode active material according to claim 6 wherein the cathode active material has a content of extractable lithium in the range of from 0.1 to 0.6 % by weight, determined by titration.

8. Particulate cathode active material according to claim 6 or 7 wherein its particles are composed of primary particles with an average diameter (D50) of from 400 nm to 2 pm.

9. Particulate cathode active material according to any of claims 6 to 8 wherein TM is nickel.

10. Particulate cathode active material according to any of claims 6 to 9 displaying a ratio of the lattice parameters c / a of more than 4.937.

11. Particulate cathode active material according to any of claims 6 to 9 displaying a ratio of the lattice parameters c / a of more than 4.937 and up to 4.943.

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

13. Cathode according to claim 12 containing(A) 80 to 98 % by weight cathode active material,(B) 1 to 17 % by weight of carbon,(C) 3 to 10 % by weight of binder material, percentages referring to the sum of (A), (B) and (C).

14. Electrochemical cell containing at least one cathode according to claim 12 or 13.

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