Process for Making an Electrode Active Material for Lithium Ion Batteries

The present invention relates to a process for making an electrode active material comprising the steps of

(a) treating a lithiated transition metal oxide comprising at least two different transition metals selected from nickel, cobalt and manganese with gaseous NH3,

(b) coating said lithiated transition metal oxide with carbon in electrically conductive form.

In addition, the present invention relates to core-shell particles, and to electrochemical cells and lithium-ion batteries.

Lithiated transition metal oxides with layered structures are currently being used as electrode materials for lithium-ion batteries. Extensive research and developmental work has been performed in the past years to improve properties like charge density, energy, but also other prop- erties like the reduced cycle life and capacity loss that may adversely affect the lifetime or applicability of a lithium-ion battery.

Improvement of at least one of the properties reduced cycle life and capacity loss is still a field of developmental work.

In a usual process for making cathode materials for lithium-ion batteries, first a so-called precursor is being formed by co-precipitating the transition metals as carbonates, oxides or preferably as hydroxides that may or may not be basic. The precursor is then mixed with a lithium salt such as, but not limited to LiOH, L12O, L1NO3 or - especially - L12CO3 - and calcined (fired) at high temperatures. Lithium salt(s) can be employed as hydrate(s) or in dehydrated form.

In US 7,488,465 a process is disclosed wherein a cathode active material, LiNio.1Coo.8Mno.1O2 is being manufactured by wet-milling N1CO3, MnCC"3, Co(OH)2 and L12CO3 in a two-step wet- milling process, followed by removal of the water and calcination. The disclosed process re- quires a lot of steps including a careful cleaning of the mill in order to avoid contamination of the next material to be manufactured.

Some authors suggest to make an after-treatment of lithiated transition metal oxides. For example, in US 2009/001 1335 discloses a method of treating lithiated transition metal oxides with aqueous mineral acids such as nitric acid. However, the process is tedious and requires complete removal of the water from the cathode active material. Furthermore, US 2009/001 1335 is silent about cycle-life of the resultant batteries.

It was therefore an objective to provide a method for making a battery with an improved cycle life and reduced capacity loss.

Accordingly, the process defined at the outset has been found, said process also being referred to as process according to the present invention or inventive process. The inventive process starts with a lithiated transition metal oxide, and it comprises two steps, hereinafter in brief also being referred to as step (a) or step (b), respectively. In the context of the present invention, step (a) may also be referred to as step (a) of the inventive process, and step (b) may also be referred to as step (b) of the inventive process. They are performed after another, step (a) being performed before step (b).

Lithiated transition metal oxides in the context of the present invention may have a spinel structure or preferably a layered structure. Lithiated transition metal oxide in the context of the pre- sent invention contains at least two different transition metals selected from nickel, cobalt and manganese. For example, lithiated transition metal oxide contains nickel and cobalt but no manganese, or manganese and cobalt but no nickel, or preferably nickel and manganese but no cobalt. Even more preferably, lithiated transition metal oxide contains nickel, cobalt and manganese.

The two transition metals selected from nickel, cobalt and manganese, hereinafter also being referred to as mandatory transition metals, are each present in lithiated transition metal oxide in at least 5 mole-%, referring to the total transition metal content. Preferably, such mandatory transition metals are each present in at least 10 mole-%.

In one embodiment of the present invention, the sum of contents of the mandatory transition metals in lithiated transition metal oxide is at least 65 mole-%, referring to the total transition metal content, preferably at least 50 mole-%. Many elements are ubiquitous. For example, sodium and iron are detectable in certain very small proportions in virtually all inorganic materials. In the context of the present invention, proportions of less than 0.05 mol-% of the cations of the respective lithiated transition metal oxide are disregarded. In one embodiment of the present invention, lithiated transition metal oxide may contain transition metals other than Ni and Mn. Examples of other transition metals are Fe, Co, Ti, V, Mo and Zn. In a preferred embodiment, lithiated transition metal oxide also contains Co.

In one embodiment of the present invention, lithiated transition metal oxides may contain one or more metal M. Examples of metal M are Al, Mg, Ca, Fe, Ti, V, Mo and Zn. Preferably, lithiated transition metal oxide contains only one metal M selected from Al, Mg, Ca, and Ti. Even more preferably, lithiated transition metal oxide contains only one metal M being Al.

In one embodiment of the present invention, the lithiated transition metal oxide is a compound according to general formula (I)

Lii _+x (NiaCObMn _c Md)i-x02 (I) wherein: x is in the range of from zero to 0.5, preferably from 0.02 to 0.42, even more preferably 0.07 to 0.2, a is in the range of from 0.2 to 0.8, preferably up to 0.4, b is in the range of from zero to 0.35, preferably from 0.1 to 0.2, c is in the range of from 0.2 to 0.7, preferably from 0.4 to 0.7, d is in the range of from zero to 0.2, preferably from 0.05 to 0.15 with a + b+ c+ d = 1

M being selected from one or more of Al, Mg, Ca, V, Mo, Ti, Fe and Zn, preferably only one metal M selected from Al, Mg, Ca, and Ti and even more preferably, M is Al. In one embodiment of the present invention, x is in the range of from 0.15 to 0.42.

In a preferred embodiment of the present invention, the inventive process is being carried out on a lithiated transition metal oxide with a lithium to total transition metal molar ratio including M in the range of from 1.0 to 1 .5.

Particularly preferred examples of compounds according to general formula (I) are

Lii+xi(Nio.4Coo.2Mno.4)i-xi02, with x1 being in the range of from 0.02 to 0.2. Other particularly preferred examples of compounds Lii.i ₇ (Nio.2iCoo.ii5Mno.675)o.8302. The following paragraphs refer to lithiated transition metal oxide before treatment according to step (a) of the inventive process.

In one embodiment of the present invention, the surface (BET) of lithiated transition metal oxide is in the range of from 0.2 to 12 m ² /g, preferably from 0.3 to 1 m ² /g. The surface (BET) can be determined by nitrogen absorption, for example according to DI N 66131 .

In one embodiment of the present invention, lithiated transition metal oxide is in the form of agglomerated primary particles of lithiated transition metal oxide. Such agglomerates are then referred to as secondary particles of lithiated transition metal oxide.

In one embodiment of the present invention, primary particles of lithiated transition metal oxide have an average diameter in the range from 1 to 2000 nm, preferably from 10 to 1000 nm, par- ticularly preferably from 50 to 500 nm. The average primary particle diameter can, for example, be determined by SEM or TEM, or by LASER scattering technologies, for example at a pressure in the range of from 0.5 to 3 bar. In one embodiment of the present invention, the particle diameter (D50) of secondary particles of lithiated transition metal oxide is in the range from 6 to 16 μηη, especially 7 to 9 μηη. The mean particle diameter (D50) in the context of the present invention refers to the median of the volume-based particle diameter, as can be determined, for example, by light scattering. According to step (a) of the inventive process, lithiated transition metal oxide is being treated with gaseous NH3. During such treatment, the respective lithiated transition metal oxide is in solid form.

In one embodiment of the present invention, step (a) is carried out at a temperature in the range of from 300 to 450°C, preferably from 350 to 400°C.

In one embodiment of the present invention, step (a) is carried out at a pressure in the range of from 0.5 to 10 bar, preferred is normal pressure. In step (a) of the inventive process, NH3 is being employed in gaseous form. The inventive process may be carried out in an atmosphere of pure NH3 or in an atmosphere that contains NH3 and at least one more gas other than NH3. For example, the inventive process may be carried out with NH3 diluted with air or nitrogen or a noble gas. Examples for such embodiments are 1 to 80% by volume - referring to normal pressure - NH3 in air, or 1 to 80 % by volume - referring to normal pressure - NH3 in nitrogen, or 1 to 80% by volume - referring to normal pressure - NH3 in argon.

In one embodiment of the present invention, the water content of the NH3 is in the range of from 1 to 100 ppm, preferably 5 to 50 ppm. In the context of the present invention, ppm with respect to water content refers to mass ppm. The water content can be determined, for example, by evaporation in the presence of 1 ,2-ethanediol direct Karl-Fischer titration of the residue, for example according to DIN 7105.

In one embodiment of the present invention, the step (a) is carried out over a time period in the range of from 10 minutes to 5 hours, preferably 30 minutes to 2 hours.

In one embodiment of the present invention, step (a) of the inventive process is repeated once or twice or even more frequently. In another embodiment of the present invention, step (a) of the inventive process is carried out only once.

In one embodiment of the present invention, step (a) of the inventive process is being carried out in a vessel selected from rotary furnaces, rotary hearth kilns, pendulum kilns, and muffle kilns. In lab scale experiments, a combination of a rotary kiln with subsequent quartz glass tube is preferred.

In one embodiment of step (a), lithiated transition metal oxide is being treated at a temperature in the range of from 350 to 450° in an ammonia-free environment before the inventive treatment with gaseous ammonia. In one embodiment of the present invention, lithiated transition metal oxide is being treated at a temperature in the range of from 350 to 450° in an ammonia-free environment after the inventive treatment with gaseous ammonia. Such pre- or after-treatment can be performed over a period of 5 minutes to 5 hours, preferably 10 minutes to two hours.

In a special embodiment of the present invention, step (a) of the inventive process is being carried out in a fixed bed reactor. The respective lithiated transition metal oxide is being put as a packing or bed on a permeable medium such as a sieve or network, such medium having a mesh size smaller than the particle diameter of the respective lithiated transition metal oxide, and a gas stream, e.g. NH3 or diluted with air or nitrogen or a noble gas, streams through such packing or bed without significantly moving the particles by such stream of gas.

In another special embodiment of the present invention, step (a) of the inventive process is being carried out in a fluidized bed reactor. The respective lithiated transition metal oxide is being put as a packing or bed on a permeable medium such as a sieve or network, such medium having a mesh size smaller than the particle diameter of the respective lithiated transition metal oxide, and a gas stream, e.g. NH3 or diluted with air or nitrogen or a noble gas, streams from bottom to top through such packing or bed under moving the particles by such stream of gas. Preferably, step (a) of the inventive process and especially the NH3 treatment step is being carried out in the absence of out a solvent. The term solvent in the context of the present invention refers to liquids that dissolve NH3 but not the respective lithiated transition metal oxide. Although a solvent such as NMP (N-methyl pyrrolidone) or NEP (N-ethyl pyrrolidone) may be applied it is advantageous to work in the absence of such solvent in order to ensure that NH3 is applied in the gaseous state.

After having carried out step (a) of the inventive process the solid product so obtained can be used without further purification, or it can be purified by washing the treated lithiated transition metal oxide with at least one solvent, or by removing traces of residual NH3 with air or an inert gas such as nitrogen or a noble gas. Such purification can be done during cooling down the treated lithiated transition metal oxide.

Another possible purification step can involve sieving. Such sieving can be performed in order to remove fines that may have formed during the inventive process, especially when performing the inventive process in a rotary furnace or in a rotary kiln or a fluidized bed. After having carried out step (a) of the process according to the present invention a treated lithiated transition metal oxide is being obtained, hereafter also being referred to as treated lithiated transition metal oxide. In many embodiments of the present invention neither film nor the like of nitride can be detected. However, upon performing an X-ray diffraction on an inventive treated lithiated transition metal oxide it can be found that the lattice constants have been increased, especially the c-axis may increase by 0.002 units. Without wishing to be bound by any theory it can be assumed that the overall chemical formula of lithiated transition metal oxide does not change as a result of step (a) of the inventive process but at least one of the crystal parameters does.

In step (b) of the inventive process, said treated lithiated transition metal oxide is coated with carbon in electrically conductive form. Preferably, said coating is a homogeneous coating.

In the context of the present invention, the term "coating" - and, in particular, the term "homogeneous coating" - are defined as making a layer of carbon on each secondary particle of a sample of lithiated transition metal oxide. When coating is performed, at least 95% (number) of all particles are coated, and in case of homogeneous coating, at least 98% of all particles are coated, each time determined by scanning electron microscopy (SEM). In case of homogeneous coating, no non-coated parts of a representative sample of particles may be detected by SEM. For coating, mills may be used, for example ball mills. In a preferred embodiment of the present invention, coating according to step (b) is effected in a jet-mill or in a high-shear mill. A jet mill is a mill in which particles are mixed or milled in a jet of gas, for example in an air gas. Milling and breaking of particles is effected by the energy introduced gas. The gas is usually introduced through a nozzle. A jet mill uses compressed gas, a high-shear mill does not.

In another embodiment of the present invention, step (b) may be performed by simultaneously generating compression and shear forces in a bed of a multitude of particles of treated lithiated transition metal oxide and carbon. The compression/shear stress so caused may be achieved by repeated compression of a powder bed in a centrifugal field, said powder bed essentially comprising treated lithiated transition metal oxide and carbon. The centrifugal force so exerted causes the powder bed to migrate to the inside wall of a so-called high-speed rotor. The highspeed rotor has as antagonist a stator that is stationary. Then, the powder bed is forced to pass through a gap. Such gaps may be 0.1 to 2 mm wide. In one embodiment of the present invention, step (b) has a duration in the range of from five minutes to three hours. Carbon may be selected from soot, active carbon, carbon nanotubes, graphene, and graphite. In a preferred embodiment of the present invention carbon in electrically conductive form is selected from graphite, acetylene black, and soot. In one embodiment of the present invention in step (b) the ratio of carbon to lithiated transition metal oxide is in the range of from 1 :19 to 1 :999, preferably from 1 :66 to 1 :199. In an even more preferred embodiment, in step (b) the ratio of carbon to lithiated transition metal oxide is in the range of from 1 :99 to 1 :150. Cathode active materials obtainable in accordance with the inventive process exhibit superior properties with respect to improved cycle life and reduced capacity loss. It is observed that inventive cathode active materials lead to reduced Mn dissolution on extended operation.

Another aspect of the present invention relates to core-shell particles, hereinafter also referred to as inventive core-shell particles, said core-shell particles containing

(a) a core containing a compound according to the general formula (I)

Lii _+x (NiaCObMn _c Md)i-x02 (I) wherein x is in the range of from zero to 0.2, a is in the range of from 0.2 to 0.8, preferably up to 0.4, b is in the range of from zero to 0.35, preferably from 0.1 to 0.2, c is in the range of from 0.2 to 0.7, preferably from 0.4 to 0.7, d is in the range of from zero to 0.2, preferably from 0.05 to 0.15,

with a + b+ c+ d = 1

M is selected from Al, Mg, Ca, V, Mo, Ti, Fe and Zn,

(β) and a shell containing carbon in electrically conductive form, wherein the shell is in the form of a homogeneous coating

and wherein the weight ratio of core (a) and shell (β) is in the range of from 99:1 to 150:1.

Inventive core-shell particles may be manufactured according to the inventive process. In one embodiment of the present invention, preferred examples of compounds according to general formula (I) are Lii _+x i(Nio.4Coo.2Mno.4)i-xi02, with x1 being in the range of from 0.02 to 0.2. A further particularly preferred example of compounds (I) is Lii.i ₇ (Nio.2iCoo.i i5Mno.675)o.8302. In one embodiment of the present invention, the surface (BET) of inventive core-shell particles is in the range of from 0.2 to 12 m ² /g, preferably from 0.3 to 1 m ² /g. The surface (BET) can be determined by nitrogen absorption, for example according to DIN 66131 .

In one embodiment of the present invention, the mean particle diameter (D50) of inventive core- shell particles is in the range from 4 to 20 μηη, especially 7 to 12 μηη. The mean particle diameter (D50) in the context of the present invention refers to the median of the volume-based particle diameter, as can be determined, for example, by light scattering.

In another embodiment of the present invention, lithiated transition metal oxides are selected from those of general formula Li(i _+g )[NihCOiAlj](i- _g )02. Typical values for g, h, i, and j are: g = 0 to

0.1 , h = 0.8 to 0.85, i = 0.15 to 0.20, and j = 0.02 to 0.03.

Inventive core-shell particles may in particular serve as electrode active materials for lithium ion batteries. Lithium ion batteries containing inventive core-shell particles exhibit an improved cy- cle life, especially an improved capacity loss upon repeated cycling compared to batteries containing the respective non-treated lithiated transition metal oxide.

Suitable electrode materials contain

(A) inventive core-shell particles, as described above,

(B) carbon in an electrically conductive state, and

(C) a binder.

Suitable electrodes contain carbon in electrically conductive modification, in brief also referred to as carbon (B). Carbon (B) may be solely present as shell (β) of inventive cathode active ma- terial. It is, however, possible to add more carbon (B) during manufacture of the respective inventive cathode.

In one embodiment of the present invention, the ratio of carbon (B) to inventive cathode active material is in the range of 1 to 15 % by weight, referring to component (b), preferably at least 2% by weight.

Suitable electrodes may comprise one or more further components. They can comprise a current collector, such as, but not limited to, an aluminum foil. They further comprise a binder (C). Suitable binders (C) are preferably selected from organic (co)polymers. Suitable (co)polymers,

1. e. homopolymers or copolymers, can be selected, for example, from (co)polymers obtainable by anionic, catalytic or free-radical (co)polymerization, especially from polyethylene, polyacrylo- nitrile, 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.

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 homopoly- ethylene, 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 oolefins 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. In the context of the present invention, polypropylene is not only understood to mean homopol- ypropylene, 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 oolefins such as butylene, 1 -hexene, 1 -octene, 1 -decene, 1 -dodecene and 1 -pentene. Polypropylene is preferably isotactic or essentially isotactic polypropylene.

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 omethylstyrene.

Another preferred binder (C) is polybutadiene.

Other suitable binders (C) are selected from polyethylene oxide (PEO), cellulose, carbox- ymethylcellulose, polyimides and polyvinyl alcohol.

In one embodiment of the present invention, binder (C) is selected from those (co)polymers which have an average molecular weight M _w in 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. Particularly preferably 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), tetrafluoroeth- ylene-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.

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.

Inventive electrodes may comprise 1 to 15% by weight of binder(s) (d), referring to the sum of component (a), component (b) and carbon (c).

A further aspect of the present invention is a battery, containing

(1 ) at least one cathode comprising an inventive cathode active material, carbon (B), and bind- er (C),

(2) at least one anode, and

(3) at least one electrolyte.

Embodiments of cathodes (1 ) have been described above in detail.

Anode (2) may contain at least one anode active material, such as carbon (graphite), ΤΊΟ2, lithium titanium oxide, silicon or tin. Anode (2) may additionally contain a current collector, for ex- ample a metal foil such as a copper foil.

Electrolyte (3) may comprise at least one non-aqueous solvent, at least one electrolyte salt and, optionally, additives. Nonaqueous solvents for electrolyte (3) 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.

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 M _w of suitable polyalkylene glycols and in particular suitable polyethylene glycols can be at least 400 g/mol. The molecular weight M _w of 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.

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.

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

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

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

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

Examples of suitable cyclic organic carbonates are compounds of the general formulae (II) and (III)

where R ¹ , R ² and R ³ can 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 tert- butyl, with R ² and R ³ preferably not both being tert-butyl. In particularly preferred embodiments, R ¹ is methyl and R ² and R ³ are each hydrogen, or R ¹ , R ² and R ³ are each hydrogen.

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

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.

Electrolyte (3) further comprises at least one electrolyte salt. Suitable electrolyte salts are, in particular, lithium salts. Examples of suitable lithium salts are LiPF6, LiBF ₄ , LiCI0 ₄ , LiAsF6, UCF3SO3, LiC(CnF2n+iS02)3, lithium imides such as LiN(C _n F2n+iS02)2, where n is an integer in the range from 1 to 20, LiN(S02F)2, Li2SiF6, LiSbF6, LiAICU and salts of the general formula

(CnF2n+iS02)tYLi, where t 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(CFsS02)3, LiN(CFsS02)2, LiPF6, LiBF ₄ , L1CIO4, with particular preference being given to LiPF6 and LiN(CFsS02)2. In an embodiment of the present invention, batteries according to the invention comprise one or more separators (4) by means of which the electrodes are mechanically separated. Suitable separators (4) are polymer films, in particular porous polymer films, which are unreactive toward metallic lithium. Particularly suitable materials for separators (4) are polyolefins, in particular film-forming porous polyethylene and film-forming porous polypropylene.

Separators (4) 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. In another embodiment of the present invention, separators (4) can be selected from among

PET nonwovens filled with inorganic particles. Such separators can have a porosity in the range from 40 to 55%. Suitable pore diameters are, for example, in the range from 80 to 750 nm.

Suitable batteries can further comprise a housing which can have any shape, for example cu- boidal or the shape of a cylindrical disk. In one variant, a metal foil configured as a pouch is used as housing.

Suitable batteries provide a very good discharge and cycling behavior, in particular with respect to the capacity loss. Suitable batteries 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 suitable batteries at least one of the electrochemical cells contains at least one electrode as described above. Preferably, in suitable electrochemical cells the majority of the electrochemical cells contain an electrode containing lithiated transition metal oxide treated according to the present invention. In even more suitable batteries according to the present invention all the electrochemical cells contain electrodes as described above. 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.

Working examples General:

Coating steps (b) were performed in a Nobilta™ Mixer, type NOB 130, high-shear mill commercially available from Hosokawa Alpine AG, Germany. The chamber volume was 1 .6 litres, the process volume was 0.5 I. The mixer was inertized with argon before begin of operation.

I. Manufacture of inventive cathode active materials, and of comparative materials

1.1 Treatment of lithiated transition metal oxide (1.1 )

A 0.5 litre quartz glass flask was charged with an amount of 50 g of lithiated transition metal oxide Lii.i7(Nio.23Coo.i2Mno.65)o.8302 (1.1 ). Using a rotary type furnace, the lithiated transition metal oxide (1.1 ) was heated up to 400 °C at a gradient rate of 3 °C/min and then subjected to a pre- treatment for 30 min under a N2 atmosphere with a flow rate fixed to 250 ml/min. the pressure was normal pressure. The rotating speed upon thermal treatment was 10 rounds per minute. After 30 min of pre-treating the gas atmosphere was switched from N2 to NH3. The pre-treated lithiated transition metal oxide (1.1 ) was then further thermally treated under NH3 gas atmosphere for 2 hours. Then the gas atmosphere was switched back to N2 again and the NH3 treated lithiated transition metal oxide was maintained at 400 °C for further 30 min. Then the rotary oven was switched off to cool down to 50 °C. The NH3 gas-treated lithiated transition metal oxide (1.1 a) was sieved (ca. 32 μηη sieve pore size) before electrochemical tests.

1.2 Coating of treated lithiated transition metal oxide (1.1 a), step (b.1 )

The mixer vessel of the high-shear mill was charged with an amount of 350 g of premixed powder consisting of transition metal oxide 331 .5 g (1.1 a) and 3.5 g graphite, commercially available as TIMREX KS-15 AD 172M. The mixer vessel was closed and flooded again with 0.05 bag argon gas. Then the rotor of the high-shear mill was started, the first minute at 1000 rpm, the second minute the rotation speed was set to 3000 rpm and for another 8 minutes. The whole mixing time was 10 min. The mixer vessel was jacketed and cooled with cooling water. The temperature of the material inside the mixer vessel was measured and was up to approx. 60°C. The power consumption of the motor varied as well depending on material and filling degree between 2 and 9 A.

Inventive core-shell particles (1.1 ab.) were obtained.

I.3 Coating of a non-treated lithiated transition metal oxide

Step (b.1 ) was basically repeated but with non-treated lithiated transition metal oxide (1.1 ) as starting material. Comparative core-shell particles C-(l.1 b) were obtained.

II. Manufacture of cathodes and batteries and of comparative cathodes and batteries 11.1 Manufacture of cathodes and batteries

Production of half cells:

To produce a cathode (A.1 ), the following ingredients are blended with one another:

84 g of treated lithiated transition metal oxide according to 1.1

7 g polyvinylidene difluoride, (d.1 ) ("PVdF"), commercially available as Kynar Flex ^® 2801 from Arkema Group,

6 g carbon black, (c.1 ), BET surface area of 62 m ² /g, commercially available as "Super C 65L" from Timcal,

3 g graphite, (c.2), commercially available as KS6 from Timcal.

While stirring, a sufficient amount of N-methylpyrrolidone (NMP) was added and the mixture was stirred with an Ultraturrax until a stiff, lump-free paste had been obtained. Cathodes were prepared as follows: On a 30 μηη thick aluminum foil the paste was applied with a 15 μηη doctor blade. The loading after drying was 2.0 mAh/cm ² . The loaded foil was dried overnight in a vacuum oven at 105°C. After cooling to room temperature in a hood disc-shaped cathodes were punched out of the foil. The cathode discs were then weighed and introduced into an argon glove box, where they are again vacuum-dried. Then, cells with the prepared discs were built.

Electrochemical testing was conducted in "TC1 " cells. The electrolyte (C.1 ) used was a 1 M solution of LiPF6 in ethyl methyl carbonate/ethylene carbonate (volume ratio 1 :1 ).

Separator (D.1 ): glass fiber. Anode (B.1 ): graphite. Potential range of the cell: 2.50 V - 4.525 V.

Inventive battery (BAT.1 ) was obtained. 11.2 Manufacture of cathodes and batteries according to the invention, and of comparative cathodes and batteries

For comparative purposes, the above experiment was repeated but inventive core-shell articles (1.1 ab) were replaced by the respective non-coated lithiated transition metal oxide C-(l.1 a), by the respective coated but non-ammonia treated core-shell particles C-(l.1 b), and by non-treated non-coated lithiated transition metal oxide C-(l.1 ).

The respective comparative batteries C-(BAT.2), C-(BAT.3) and C-(BAT.3) were obtained.

Testing of batteries

Batteries according to the invention and comparative batteries were each subjected to the fol- lowing cycling program: Potential range of the cell: 2.70 V to 4.2 V., 0.1 C (first and second cycles), 0.5 C (from the third cycle). 1 C = 150 mA-h/g. Temperature: 60 °C, ambient temperature, and 0°C.

Batteries according to the invention show an overall very good performance. For (BAT.1 ), discharge capacities at low C-rates such as at C/10, C/3 were increased in by 5 ~ 6 mA-h/g compared to C-(BAT.2). In addition, cycle stability of BAT.1 was significantly improved (6 % higher after 90 cycles in comparison with C-(BAT.2). Concerning BAT.1 , voltage fade as function of cycle number was also significantly mitigated, showing 24% less fading after 108 cycles than C- (BAT.2). The specific properties of batteries were determined according to Tables 1 and 2.

Table 1 : Overall capacity of inventive batteries and of comparative batteries at various C-rates

All capacities are in mA-h/g. DC: Discharge. CAM: Cathode active material

Table 2: Rate capabilities of inventive batteries and of comparative batteries at various C-rates

All capacities are in mA-h/g. DC: Discharge. CAM: Cathode active material

Rate capability 4C/0.1 C