WO2025078192A1

WO2025078192A1 - Method of making a precursor for a cathode active material

Info

Publication number: WO2025078192A1
Application number: PCT/EP2024/077465
Authority: WO
Inventors: Rafael Benjamin BERK; Joop Enno FRERICHS; Fabian Seeler; Maike WIRTZ; Thorsten BEIERLING; Kathrin Michel; Michael Krumm
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2023-10-09
Filing date: 2024-09-30
Publication date: 2025-04-17
Anticipated expiration: 2026-04-09

Abstract

The present invention is directed towards a process for making a particulate (oxy)hydroxide or oxide of TM wherein TM comprises nickel and one transition metal selected from Co and Mn and, optionally, at least one further metal selected from Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, and wherein said process comprises the steps of: (a) Providing an aqueous solution (a) containing water-soluble salts of Ni and lithium and of at least one transition metal selected from Co and Mn, and, optionally, at least one further metal selected from Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, and an aqueous solution (P) containing sodium or potassium hydroxide and, optionally, an aqueous solution (y) containing ammonia, wherein the amount of lithium is in the range of from 0.01 to 2.5 mol-% with respect to TM, (a) combining a solution (a) and a solution (|3) and, if applicable, a solution (y) at a pH value in the range of from 10.0 to 12.7 in one or more sub-steps, thereby creating solid particles of a hydroxide containing nickel, said solid particles being slurried, (b) removing the particulate (oxy)hydroxide of TM by a solid/liquid separation method, followed by drying.

Description

Method of Making a Precursor for a Cathode Active Material

The present invention is directed towards a process for making a particulate (oxy)hydroxide or oxide of TM wherein TM comprises nickel and one transition metal selected from Co and Mn and, optionally, at least one further metal selected from Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, and wherein said process comprises the steps of:

(a) Providing an aqueous solution (a) containing water-soluble salts of Ni and lithium and of at least one transition metal selected from Co and Mn, and, optionally, at least one further metal selected from Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, and an aqueous solution (P) containing sodium or potassium hydroxide and, optionally, an aqueous solution (y) containing ammonia, wherein the amount of lithium is in the range of from 0.01 to 2.5 mol-% with respect to TM,

(b) combining a solution (a) and a solution (0) and, if applicable, a solution (y) at a pH value in the range of from 10.0 to 13.5, preferably 10.0 to 12.7 in one or more sub-steps, thereby creating solid particles of a hydroxide containing nickel, said solid particles being slurried,

(c) removing the particulate (oxy)hydroxide of TM by a solid/liquid separation method, followed by drying.

In addition, the present invention is directed towards certain precursors.

Lithiated transition metal oxides are currently 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.

In a typical 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, for example oxyhydroxides. The precursor is then mixed with a source of lithium such as, but not limited to LIOH, IJ2O or IJ2CO3 and calcined (fired) at high temperatures. Lithium source(s) 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 1000 °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.

To a major extent, properties of the precursor translate into properties of the respective cathode active material to a certain extent, such as particle size distribution, content of the respective transition metals, crystallographic defects and more. It is therefore possible to influence the properties of cathode active materials by steering the properties of the precursor.

Some traces of elements may have surprising influence on the manufacture or the performance of cathode active material.

It was therefore an objective to overcome the disadvantages indicated above and to provide a precursor that overcomes said disadvantage. It was further an objective to provide a process by which precursors may be made that overcome the disadvantages mentioned above. It was further an objective to provide a use of such precursors.

It has been found that crystallographic defects such as lithium-nickel scrambling may negatively affect the mobility of the lithium ions during charging and discharge of an electrode, thus reducing the capacity and charging properties. By lithium-nickel scrambling, nickel ions are located in lithium crystallographic sites and vice versa. Lithium-nickel scrambling may also be termed lithium-nickel disorder or lithium-nickel displacements. Such displacements are believed to hamper the diffusion of lithium during charging and discharging.

Accordingly, the process as defined at the outset was found, hereinafter also defined as inventive process. The inventive process comprises step (a), step (b) and step (c), hereinafter in brief also referred to as (a), (b) and (c). Steps (a), (b) and (c) are performed consecutively or - if the inventive process is carried out as continuous process - they may be performed simultaneously. Further steps may be performed in the course of the inventive process as well. Steps (a), (b) and (c) and further - optional - steps are described in more detail below.

It has been found that some amounts of lithium in the precursor lead to a cathode active material with an improved cycling behavior.

The inventive process is a process for making a particulate (oxy) hydroxide or oxide of TM. Said particulate (oxy)hydroxide then serves as a precursor for cathode active materials, and it may therefore also be referred to as precursor. In one embodiment of the present invention, the resultant precursor is comprised of secondary particles that are agglomerates of primary particles.

In one embodiment of the present invention the specific surface (BET) of the resultant precursor is in the range of from 1 to 70 m²/g, determined by nitrogen adsorption, for example in accordance with to DIN-ISO 9277:2003-05. The outgassing temperature is 120°C.

The precursor is an (oxy)hydroxide of TM wherein TM comprises Ni and lithium and at least one metal selected from Co and Mn, and, optionally, at least one further element selected from Ti, Zr, Ca, Si, Mo, W, Al, Mg, Nb, and Ta, preferably a combination of Al, W, Mg and Nb or a combination of Ti, Zr, Al and Mg. The amount of lithium is in the range of from 0.01 to 2.5 mol-% with respect to TM, preferably 0.05 to 1.5 mol-%.

In one embodiment of the present invention, TM is a combination of metals according to general formula (I)

(Ni_aCObMn_c)i.dMd (I) wherein a is in the range of from 0.6 to 0.95, preferably from 0.8 to 0.94, b is in the range of from 0.025 to 0.2, preferably from 0.025 to 0.15, c is in the range of from zero to 0.2, preferably from zero to 0.15, and d is in the range of from zero to 0.1 , preferably 0.02 to 0.05,

M is selected from Mg, Al, Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, preferably selected from Al, Mg, Nb, W, Ti, and Zr, more preferably a combination of Mg and Al or a combination of Al, Mg, W and Nb or a combination of Mg and Al or a combination of Al, Mg, Ti and Zr, and a + b + c = 1.

In each case, TM may contain traces of further metal ions other than the above, for example traces of ubiquitous metals such as sodium, calcium, iron, 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. Precursors as used herein are particulate materials. In one embodiment of the present invention, precursors have an average particle diameter D50 in the range of from 3 to 20 pm, preferably from 4 to 16 pm. The average particle diameter may be determined, e. g., by light scattering or LASER diffraction or electroacoustic spectroscopy. The particles are composed of primary particles, in particular they are agglomerates of primary particles, and the above particle diameter refers to the secondary particle diameter. Although (D50) is - strictly speaking - the median value rather than an average diameter both expressions are used interchangeably.

In one embodiment of the present invention, the span of the particle diameter distribution of precursors is in the range of from 0.2 to 2.0, preferably from 0.25 to 0.35 or from 0.6 to 1.5. The span is defined as [(D90) - (D10)]/(D50), with the values of (D90), (D50) and (D10) being the respective percentiles determined by dynamic light scattering or by X-ray diffraction.

Said particles of precursors may have an irregular shape but in a preferred embodiment, said particulate material has a regular shape, for example spheroidal or even spherical. The aspect ratio may be in the range of from 1 and 10, preferably from 1 to 3 and even more preferably from 1 to 1.5. The aspect ratio is defined as the ratio of width to length or specifically the particle diameter in the longest dimension versus the particle diameter in the shortest dimension. Perfectly spherical particles have an aspect ratio of 1.

Step (a) includes providing at least one aqueous solution (a) containing water-soluble salts of Ni and lithium and of at least one transition metal selected from Co and Mn, and of a water-soluble compound of at least one further element selected from Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, and an aqueous solution (P) containing sodium or potassium hydroxide and, optionally, an aqueous solution (y) containing a complexing agent, for example ammonia.

The term water-soluble salts of cobalt and nickel or manganese or lithium or of metals other than nickel and cobalt and manganese and lithium refers to salts that exhibit a solubility in distilled water at 25°C of 25 g/l or more, the amount of salt being determined under omission of crystal water and of water stemming from aquo complexes. Water-soluble salts of nickel and cobalt and manganese may preferably be the respective water-soluble salts of Ni²⁺ and Co²⁺ and Mn²⁺. Examples of water-soluble salts of nickel and cobalt and lithium are the sulfates, the nitrates, the acetates and the halides, especially chlorides. Preferred are nitrates and sulfates, of which the sulfates of nickel and cobalt and nitrate and sulfate of lithium are more preferred. Even more preferred are the sulfates of nickel, cobalt and lithium. In one embodiment of the present invention, lithium is added involuntarily as an impurity of nickel or cobalt obtained from work-up of spent lithium-ion batteries or off-spec batteries or off- spec battery materials.

In step (a), the amount of lithium is in the range of from 0.01 to 2.5 mol-% with respect to TM, preferably 0.5 to 1 .5 mol-%. It is observed that in the course of the inventive process, not all lithium present in step (a) is incorporated into the precursor.

The term “water-soluble compounds of aluminum” then refers to compounds like Al2(SO4)3, AI(NO₃)3, KAI(SO4)2, NaAIC>2 and NaAI(OH)4. Depending on the choice of water-soluble compound of aluminum, the pH value of aqueous solution (a) may be in the range of from 1 to 3 or above 13.

Examples of suitable compounds of Mg are MgSO4, Mg(NO₃)2, magnesium acetate and MgCfe, with MgSC>4 being preferred.

Examples of suitable compounds of Ca are Ca(NO3)2, calcium acetate and CaCfe,

Examples of Suitable compounds of Si are sodium metasilicate, sodium orthosilicate, and silicic acid.

Examples of suitable compounds of Ti are Ti(SO4)2, TIOSO4, TIO(NO3)2, Ti(NO3)4, with Ti(SO4)2 being preferred.

Examples of suitable compounds of Zr are zirconium acetate, Zr(SO4)2, ZrOSCk, ZrO(NO3)2, Zr(NO3)4, with Zr(SC>4)2 being preferred.

Examples of suitable compounds of Nb are (NH4)Nb(C2O4)3 and (NH4)NbO(C2O4)2. Examples of suitable compounds of Mo are MoOs, Na2MoC>4, and (NH4)2MoO4.

Examples of suitable compounds of W are WO3, WO3 ■ H₂O, Na₂WO4, ammonium tungstate and tungstic acid.

Solution (a) may have a pH value in the range of from 2 to 6. In embodiments wherein higher pH values are desired, ammonia may be added to solution (a). However, it is preferred to not add ammonia to solution (a). In case it is intended to provide a solution containing NaAIO2 and NaAI(OH)4 it is preferred to provide at least two aqueous solutions, one containing nickel and at least one of cobalt and manganese and, optionally, at least one of Ti , Zr, Mo, W, Mg, Nb, and Ta, and another aqueous solution containing NaAICfe or NaAI(OH)4.

The concentration of nickel and other constituents of TM, as the case may be, can be selected within wide ranges. Preferably, the respective total metal concentration is selected to be within a range of 1 to 1.8 mol of the metal/kg of solution, more preferably 1.3 to 1.7 mol of the metal/kg of solution.

In addition, in step (a) an aqueous solution of sodium or potassium hydroxide is provided, hereinafter also referred to as solution (P). Examples are potassium hydroxide and a combination of sodium and potassium hydroxide, and even more preferred is sodium hydroxide.

In one embodiment of the present invention, solution (P) mainly contains sodium or potassium hydroxide and some amount of carbonate, e.g., 0.1 to 2 % by weight, referring to the respective amount of sodium or potassium hydroxide, added deliberately or by aging of the solution (P) or the respective alkali metal hydroxide.

Solution (3) may have a concentration of hydroxide in the range from 0.1 to 12 mol/l, preferably 6 to 10 mol/l.

The pH value of solution (P) is preferably 13 or higher, for example 14.5.

Solution (y) contains a complexing agent. Examples of complexing agents are ammonia and organic acids or their alkali or ammonium salts wherein said organic acid bears at least two functional groups per molecule and at least one of the functional groups is a carboxylate group.

Examples of organic acids that bear two identical functional groups are adipic acid, oxalic acid, succinic acid and glutaric acid. An example of organic acids that bears three identical functional groups is citric acid.

In one embodiment of the present invention, said organic acid is selected from malic acid, tartaric acid, citric acid, and glycine.

In one embodiment of the present invention, the concentration of complexing agent(s) in solution (y) is in the range of froml to 30 % by weight. In embodiments wherein the complexing agent is selected from ammonia its concentration is preferably in the range of from 10 to 30 % by weight. In embodiments wherein the complexing agent(s) is or are selected from organic acids or their alkali or ammonium salts wherein said organic acid bears at least two functional groups per molecule and at least one of the functional groups is a carboxylate group, the concentration of said complexing agent in solution (y) may be in the range of from 0.2 to 10% by weight.

More preferred complexing agent is ammonia.

Step (b) includes combining a solution (a) and a solution (0) and, if applicable, a solution (y) at a pH value in the range of from 10.0 to 13.5, preferably 10.0 to 12.7 in one or more sub-steps, thereby creating solid particles of a hydroxide containing nickel, said solid particles being slurried. Preferably, step (b) is performed in two sub-steps wherein the pH value of the second substep is lower than in the first sub-step, for example by 0.5 to 2.0 units. In the context of the present invention, pH values are determined at 23°C.

Step (b) may be carried out in a stirred tank reactor or in a cascade of at least two stirred tank reactors.

Step (b) may be carried out in one or more sub-steps. Such sub-steps may be distinguished by at least one of pH value, temperature, composition of solution (a), stirring speed, residence time, or atmosphere.

In one embodiment of the present invention, step (b) is performed under an inert atmosphere, for example nitrogen or a rare gas such as argon. Oxygen-depleted air, for example with up to 2% by weight of O2, is feasible as well, especially when TM does not contain manganese. Due to the strong alkalinity of solution (0), CO2 is not a suitable inert atmosphere.

In step (b), solution (a) and solution (P) and - if applicable - solution (y) are combined, under precipitation of a hydroxide.

The continuous phase of step (b) is also referred to as “mother liquor”. Said mother liquor contains salt formed from the counterions of the metals of TM as well as alkali metal ions from the base in solution (P), for example Na2SC>4. The mother liquor may further contain some lithium.

In one embodiment of the present invention, step (b) is performed at a temperature in the range of from 40 to 70°C. Step (b) may be performed one stirred tank reactor or in a cascade of at least two stirred tank reactors that are each equipped with an overflow system. Preferably, the stirred tank reactor(s) is or are equipped with a solid-liquid separation device through which mother liquor is removed. Examples of sold-liquid separation units are clarifiers such as lamella clarifiers and filtration devices such as filter presses, hydrocyclones, and filters such as at least one candle filter. With the use of one or more of such solid-liquid separation devices, slurries with a solids content of up to 1200 g/l may be obtained.

The percentage of mother liquor withdrawn in steps (b) and (c) may be in the range of from 200 to 1 ,200 g/l, preferably 800 to 1,200 g/l. However, despite the withdrawal of mother liquor, the slurry is still well stirrable.

Step (b) includes combining solution(s) (a) and solution (P) and, if applicable, solution (y), in a continuous reactor, thereby creating solid particles of a hydroxide of TM. Said solid particles are slurried.

In one embodiment of the present invention, the particles resulting from step (b) have an average diameter in the range of from 2 to 10 pm, preferably 2 to 5 pm.

In step (b), the pH value of the liquid phase of the slurry is in the range of from 12.5 to 14.0. The pH value is determined at 23°C in the liquid phase.

In one embodiment of the present invention, the average hydraulic residence time of the slurry in step (b) is in the range of from 30 minutes to 16 hours, preferably in the range from 1 to 12 hours, more preferred in the range of 2 to 8 hours.

In one embodiment of the present invention, step (b) is performed at a temperature in the range from 10 to 85°C, preferably at temperatures in the range from 20 to 70°C.

In one embodiment of the present invention, step (b) is performed at constant pressure, for example at ambient pressure. In other embodiments, step (b) is performed at elevated pressure, for example up to 50 bar.

In one embodiment of the present invention, mother liquor is removed from the continuous reactor during step (b). The mother liquor contains water and sodium sulfate. In one embodiment of the present invention, step (b) is performed in two sub-steps, (b1) and (b2). Sub-step (b1) is performed at a pH value higher than (b2), for example 12.0 to 12.7 versus 10.0 to less than 12.0 but in any way distinguished by at least 0.5 units. In sub-step (b1), essentially particles of hydroxide are formed and in sub-step (b2), such particles of hydroxide are grown.

Step (c) includes removing the particulate (oxy)hydroxide of TM by a solid-liquid separation method, followed by drying. The solid-liquid separation of step (c) is thus also referred to as solid-liquid separation step.

In such a solid-liquid step (c), the particles from step (b) are separated from the liquid phase by a solid-liquid separation method, preferably by filtration or in a centrifuge. The liquid phase may also be termed mother liquor. Filtration may be performed, e.g., on a belt filter or in a filter press.

In order to remove mother liquor, it is preferred to wash the filter cake, for example with water or with alkali metal hydroxide or alkali metal carbonate solution.

Filtration may be supported by suction or by pressure.

The solid-liquid separation step (c) may be performed at any temperature at which water is in the liquid state, for example 5 to 95°C, preferred is 20 to 60°C.

Step (c) includes drying the solid material. Step (c) includes a thermal treatment of the solid, for example in a drying oven, in a rotary kiln or in a flash calciner.

By performing the solid-liquid separation part of step (c), a solid material is obtained which is a particulate (oxy)hydroxide of TM. Said material usually has a high water content, for example 1 to 30% by weight, and may be dried, e.g. at air, at a temperature in the range of from 80 to 150°C, or at reduced pressure (“in vacuo”), to a moisture content in the range of from 100 to 5,000 ppm, ppm being ppm by weight. The water content may be determined by drying in vacuo at a temperature of 100°C until the weight is remaining unchanged. The moisture content may be determined by Karl-Fischer titration.

The duration of drying may be in the range of from 30 minutes to 12 hours. In one embodiment of step (c), the wet solid material (filter cake) is introduced into a rotary kiln by a chute or a vibrating chute, by a spiral conveyor or a screw conveyor, preferably by a screw conveyor with a single screw or multiple screws.

In one embodiment of the present invention, step (c) is followed by a thermal treatment at a temperature in the range of from 250 to 500°C in the absence of a source of lithium as step (d). Such thermal treatment may be performed under an atmosphere of nitrogen, of air or of oxygen or of oxygen-enriched air. Such thermal treatment may be performed in a rotary kiln or in a moving bed or fixed bed or in a fluidized bed. In such embodiments, an oxide of TM is obtained.

In the context of the present invention, the term “in the absence of a source of lithium” means that a stoichiometric amount or even excess amounts of lithium compound are not added in said step. More precisely, it means that less than one mol-% of lithium with respect to TM are present in said thermal treatment step. It is difficult to completely avoid the presence of lithium but deliberately adding a compound such as lithium hydroxide or lithium carbonate is avoided.

In one embodiment of the present invention, said thermal treatment has a duration in the range of from 30 minutes to 6 hours.

The liquid phase obtained from step (c) may contain substances that should not be wasted or transferred to a sewage plant, e.g., lithium compounds. In one embodiment of the present invention, liquid medium obtained from the solid-liquid separation step (c) is worked up in a separate step (d), for example by an electrolysis in order to crystallize lithium hydroxide, for example by precipitation.

A further aspect of the present invention refers to particulate (oxy)hydroxides or oxides of TM, hereinafter also referred to as inventive (oxy)hydroxides or inventive precursors. Inventive precursors are advantageously made according to the inventive process.

Inventive precursors are (oxy)hydroxides of or oxides TM wherein TM comprises nickel and 0.01 to 0.1 mol- %Li, referring to TM, and at least one transition metal selected from Co and Mn and at, optionally, at least one further element selected from Ti, Zr, Ca, Si, Mo, W, Al, Mg, Nb, and Ta. Preferably, TM is a combination according to formula (I), vide supra.

Inventive precursors as (oxy)hydroxides or oxides may have a sulfate content in the range of from 0.2 to 1.5% by weight, determined by catalytic S-combustion. The sulfate is preferably uniformly dispersed over the diameter of the precursor particles. Inventive precursors have an average particle diameter (D50) in the range of from 3 to 20 pm, preferably 5 to 15 pm and more preferably 6 to 12 pm, determined by dynamic light scattering.

In one embodiment of the present invention, inventive precursors are selected from oxyhydroxides and oxides with an average oxidation state of TM in the range of from + 2.1 to + 2.6, determined by iodometric titration.

In one embodiment of the present invention, inventive precursors are comprised of secondary particles comprising asymmetric plate-like shaped primary particles that have a thickness of 20 to 200 nm and a length of 50 to 500 nm.

In one embodiment of the present invention, the primary particles are essentially radially aligned. The portion of radially aligned primary particles may be determined, e.g., by SEM (Scanning Electron Microscopy) of a cross-section of at least arbitrarily selected 5 secondary particles.

“Essentially radially alignment” does not require a perfect radial orientation but includes that in an SEM analysis, a deviation to a perfectly radial orientation is at most 5 degrees.

Inventive precursors as oxides of TM have a moisture content in the range of from 100 to 10,000 ppm by weight, preferably 250 to 8,000 ppm and more preferably 300 to 5,000 ppm. The moisture content may be determined by Karl-Fischer-titration.

Inventive precursors as (oxy)hydroxides and inventive oxides are preferably obtained according to the inventive process. Inventive precursors are excellent starting materials for cathode active materials which are suitable for producing batteries with a high volumetric energy density due to the low content of inactive impurities and an excellent cycling stability due to mitigation of parasitic side reactions of impurities inside the electrochemical cell. An undesired lithium consumption during calcination can be avoided.

By the inventive process, precursors are made that solve the objectives as outlined above.

A further aspect of the present invention is related to the use of inventive precursors for making cathode active materials, for example for lithium-ion batteries. A further aspect of the present invention is a process of making a cathode active material for a lithium-ion battery by using an inventive precursor, hereinafter also referred to as inventive calcination. Such inventive calcina- tion may be performed by mixing with a source of lithium, e.g., LiOH or IJ2O2 or IJ2CO3, followed by calcination, for example at a temperature in the range of from 600 to 1000°C. Especially in embodiments wherein TM of inventive (oxy)hydroxides corresponds to formula (I), said calcination 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 (II), said calcination may be performed in air atmosphere.

Examples of suitable set-ups for said calcination are rotary kilns, roller hearth kilns, and pusher kilns.

By performing a calcination in the above way, the essentially radial alignment of primary particles is - e.g., to at least 80%, preferably to at least 90% - retained, and cathode active materials with excellent capacity retention are obtained.

Specifically, the inventive calcination comprises the step of mixing an inventive precursor - as (oxy)hydroxide or oxide - with a source of lithium and, optionally, with an oxide or (oxy)hydroxide of at least one of Nb, Al, Ti or Zr, and thermally treating the resultant mixture at a temperature in the range of from 650 to 1000°C in one or more steps.

In one embodiment of the present invention, the mixing has a duration of 10 minutes to 2 hours.

Mixing of precursor, source of lithium compound and, if applicable, oxide or hydroxide of aluminum or Zr or Ti or Nb or Ta may be performed all in one or in sub-steps, for example by first mixing source of lithium compound and said oxide or hydroxide of aluminum and then combining such mixture with the precursor, or by first mixing precursor and source of lithium and then adding said oxide or hydroxide of aluminum, or by first mixing said oxide or hydroxide of aluminum and precursor and then adding source of lithium. It is preferred to first mix precursor and source of lithium compound and to then add said oxide or hydroxide of aluminum.

Although it is possible to add an organic solvent, for example glycerol or glycol, or water in for the mixing it is preferred to perform such mixing in the dry state, that is without addition of water or of an organic solvent.

Then, said mixture is subjected to heat treatment at a temperature in the range of from 650 to 1000°C, preferably 650 to 850°C. In one embodiment of the present invention, the mixture of precursor and source of lithium and compound of Al and, optionally, solvent(s), is heated to 700 to 1000 °C with a heating rate of 0.1 to 10 °C/min.

In one embodiment of the present invention, the temperature is ramped up before reaching the desired temperature of from 700 to 1000°C, preferably 750 to 900°C. For example, first the mixture of precursor and source of lithium and oxide or hydroxide of Al 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 it is raised to 650°C up to 1000°C, preferably 650 to 850°C.

In embodiments wherein for mixing at least one solvent has been used, as part of the thermal treatment, such solvent(s) are removed, for example by filtration, evaporation or distilling of such solvent(s). Preferred are evaporation and distillation.

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 and split tube furnaces are feasible as well.

In one embodiment of the present invention, the inventive calcination is performed in an oxy- gen-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 in the inventive calcination 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.

In one embodiment of the present invention, the inventive calcination 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. In one embodiment of the present invention, the inventive calcination 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.

After thermal treatment, 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.

By performing the inventive calcination process, cathode active materials with excellent properties are available through a straightforward process. Preferably, the electrode active materials so obtained have a specific surface (BET) in the range of from 0.1 to 0.8 m²/g, determined according to DIN-ISO 9277:2003-05.

A further aspect of the present invention is related to precursors, hereinafter also referred to as inventive precursors. Inventive precursors are particulate (oxy)hydroxides or oxides of TM wherein TM comprises nickel and one transition metal selected from Co and Mn and, optionally, at least one further metal selected from Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, wherein said particles of (oxy)hydroxide or oxide are in the form of spherical secondary particles that are composed of primary particles that mainly have a platelet shape and wherein said (oxy)hydroxide or oxide has a lithium content in the range of from 0.01 to 2.5 mol-%, corresponding to TM, and wherein said lithium is enriched at the outer surface of the secondary particles of said (oxy)hydroxide or oxide.

(Ni_aCObMn_c)i.dMd (I) wherein a is in the range of from 0.6 to 0.95, preferably from 0.8 to 0.94, b is in the range of from 0.025 to 0.2, preferably from 0.025 to 0.15, c is in the range of from zero to 0.2, preferably from zero to 0.15, and d is in the range of from zero to 0.1 , preferably 0.02 to 0.05, M is selected from Mg, Al, Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, preferably selected from Al, Mg, Nb, W, Ti, and Zr, more preferably a combination of Mg and Al or a combination of Al, Mg, W and Nb or a combination of Mg and Al or a combination of Al, Mg, Ti and Zr. a + b + c = 1.

In one embodiment of the present invention, in an XRD diffractogram, the integral breadth at the angle of 0 20 = 20.11 +0.5° divided by the intensity of the peaks at angle 20 = 8.86+0.5° and 20 = 15.08+0.5° from MoKal X-Ray diffraction is in the range from 0.01 to 0.2. X-ray Diffraction data were collected using a laboratory diffractometer (D8 Discover, Bruker AXS GmbH). The instrument was set up with a Molybdenum X-ray tube. The characteristic K-alpha radiation (A = 0.71 A) was monochromatized using a bent Germanium Johansson type primary monochromator. Data were collected in the Bragg-Brentano reflection geometry between 5-50o of 20, with 0.02o and 3 s/step. A LYNXEYE area detector was utilized to collect the scattered X-ray signal. (oxy)hydroxide samples were ground using an IKA tube-mill and an MT40.100 disposable grinding chamber. The resulting powder was placed in a sample holder and flattened using a glass plate.

In the context of the present invention, the term “mainly have a platelet shape” means that at least 90% of the primary particles have a platelet shape, as detected by SEM imaging. Platelet means that the thickness is 20% or less of both the length and the breadth of such primary particles.

Another aspect of the present invention is a process for making a cathode active material comprising the steps of mixing an inventive precursor with a source of lithium, e.g., LIOH or LI2O2 or i2CO3, followed by a thermal treatment at a temperature in the range of from 675 to 1000°C.

Especially in embodiments wherein TM of inventive (oxy)hydroxides corresponds to formula (I), said calcination 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 (II), said calcination may be performed in air atmosphere.

Examples of suitable set-ups for said calcination are rotary kilns, roller hearth kilns, and pusher kilns. By performing a calcination in the above way, the essentially radial alignment of primary particles is - e.g., to at least 80%, preferably to at least 90% - retained, and cathode active materials with excellent capacity retention are obtained.

Specifically, the inventive calcination comprises the step of mixing an inventive precursor - as (oxy)hydroxide or oxide - with a source of lithium and, optionally, with an oxide or (oxy)hydroxide of at least one of Nb, Ta, Al, Ti or Zr, and thermally treating the resultant mixture at a temperature in the range of from 650 to 1000°C in one or more steps.

Mixing of precursor, source of lithium compound and oxide or hydroxide of aluminum or Zr or Ti or Nb or Ta may be performed all in one or in sub-steps, for example by first mixing source of lithium compound and said oxide or hydroxide of aluminum and then combining such mixture with the precursor, or by first mixing precursor and source of lithium and then adding said oxide or hydroxide of aluminum, or by first mixing said oxide or hydroxide of aluminum and precursor and then adding source of lithium. It is preferred to first mix precursor and source of lithium compound and to then add said oxide or hydroxide of aluminum.

Then, said mixture is subjected to heat treatment at a temperature in the range of from 650 to 1000°C, preferably 650 to 850°C.

In one embodiment of the present invention, the mixture of precursor and source of lithium and oxide or hydroxide of aluminum or Zr or Ti or Nb or Ta and, optionally, solvent(s), is heated to 700 to 1000 °C with a heating rate of 0.1 to 10 °C/min.

In one embodiment of the present invention, the temperature is ramped up before reaching the desired temperature of from 700 to 1000°C, preferably 750 to 900°C. For example, first the mixture of precursor and source of lithium and oxide or hydroxide of Al 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 it is raised to 650°C up to 1000°C, preferably 650 to 850°C. In embodiments wherein for mixing at least one solvent has been used, as part of the thermal treatment, such solvent(s) are removed, for example by filtration, evaporation or distilling of such solvent(s). Preferred are evaporation and distillation.

In one embodiment of the present invention, the inventive calcination 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.

In one embodiment of the present invention, the inventive calcination 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.

A further aspect of the present invention is related to particulate cathode active materials, hereinafter also referred to as inventive cathode active material. Inventive cathode active materials have the general formula Lii_+xTMi.xO2 wherein TM comprises nickel and one transition metal selected from Co and Mn and, optionally, at least one further metal selected from Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, and wherein x is in the range of from zero to 0.05, wherein an average particle diameter (D50) in the range of from 2 to 15 pm. In addition, inventive cathode active materials have a residual lithium carbonate content in the range of from 0.03 to 0.15% by weight, determined by titration, and a lattice parameter a in the range of from 2.8736 to 2.8743 as determined by X-Ray diffraction and Rietveld refinement.

The titration may be performed, for example, by for example by soaking inventive cathode active material with water, followed by titration with 0.1 M aqueous HCI. One titration point corresponds to the sum of hydroxide and carbonate protonation, the second corresponds to the protonation of bicarbonate.

In one embodiment of the present invention, inventive cathode active materials display a nickellithium scrambling in the range of from 0.1 to 0.9 mol-%. The term “lithium-nickel scrambling” refers to crystallographic defects, with nickel ions being located in lithium ion crystallographic sites and vice versa. The percentages are referring to the total nickel content and may be determined by X-ray diffraction analysis and Rietveld refinement.

In one embodiment of the present invention, inventive cathode active materials are in the form of spherical secondary particles that are composed of primary particles that mainly have a platelet shape.

In an alternative embodiment of the present invention, inventive cathode active materials are monoliths. In such embodiments, the particles have an irregular shape, and primary particles like in the above embodiment are not well distinguishable.

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 mate- rial according to the present invention are hereinafter also referred to as inventive cathodes or cathodes according to the present invention.

Specifically, inventive cathodes contain

(A) at least one inventive cathode active material,

(B) carbon in electrically conductive form,

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

(D) a current collector.

In a preferred embodiment, inventive cathodes contain

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

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

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

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.

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.

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.

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-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 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.

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, divinyl benzene, especially 1,3-divinylbenzene, 1 ,2- diphenylethylene and a-methylstyrene.

Another preferred binder (C) is polybutadiene.

Other suitable binders (C) are selected from polyethylene oxide (PEO), cellulose, carboxymethylcellulose, 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.

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.

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 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).

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.

Embodiments of inventive cathodes have been described above in detail.

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

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.

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 according to the general formulae (II) and (III)

where R¹, R² and R³ 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 tertbutyl, with R² and R³ preferably not both being tert-butyl. In particularly preferred embodiments, R¹ is methyl and R² and R³ are each hydrogen, or R¹, R² and R³ 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 (C) further comprises at least one electrolyte salt. Suitable electrolyte salts are, in particular, lithium salts. Examples of suitable lithium salts are LiPFe, LiBF₄, UCIO4, LiAsF₆, IJCF3SO3, LiC(C_nF2n+i 802)3, lithium imides such as LiN(C_nF2n+iSO2)2, where n is an integer in the range from 1 to 20, LiN(SO2F)2, IJ2S i Fe, LiSbFe, LiAl Cl₄ and salts of the general formula (C_nF2n+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, IJCIO4, with particular preference being given to LiPFe and LiN(CF3SO2)2.

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.

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. 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.

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.

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.

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.

The present invention is further illustrated by working examples.

General remarks:

In order to determine the amount of lithium-containing residual compounds in form of LIOH and LI2CO3 in inventive cathode active materials, acid titration was performed. For this purpose, 2 g of cathode active material were mixed with 10 g of deionized H2O and stirred for 20 min in a glovebox under N2 atmosphere. Then, the cathode active material/H2O suspension was filtered using a syringe filter and the filtrate was titrated using an automatic titrator (Titrando 808, Deutsche Metrohm GmbH & Co. KG) and 0.1 M HCI as a standard solution (analytical grade, Bernd Kraft GmbH). The change of the pH value was monitored using a glass electrode (Metrohm). LiOH and LI2CO3 were distinguished by the two distinct equivalent points in the titration curve. The first equivalent point thereby corresponds to the protonation of the hydroxide and carbonate ions, whereas the second equivalent point equals the protonation of the hydrogen carbonate ions, thus making the differentiation of the two salt concentrations possible. Based on this the respective weight fractions of LiOH and LI2CO3 were calculated.

I. Synthesis of inventive cathode active materials and their precursors

1.1 Precursor synthesis

1.1.1 Manufacture of lithium containing solutions (a.1) and (a.2)

Nickel sulfate “NISO4 solution 1” was manufactured as follows:

Discharged end-of-life lithium-ion batteries were shredded, crushed, and milled until a black mass was obtained. The current collectors were removed from the black mass by sieving, and metallic iron was separated off by using magnetic separation. The resulting black mass was subjected to an acid leaching with concentrated sulfuric acid and SO2 at a pH value of below 2.0 until all metal oxides were dissolved. By adjusting the pH-value of the resulting solution to 3, the remaining iron, aluminum and copper impurities were depleted by precipitation and subsequent filtration. For further purification of the metal solution, other metal impurities were separated by precipitation of the respective metal fraction by stepwise increasing the pH-value to 5.0. Manganese and cobalt were recovered as aqueous solutions of the respective sulfates by organic solvent extraction using kerosine as solvent and di-(2-ethylhexyl) phosphoric acid as extractant at pH 5.5 and pH 6.0, respectively, while lithium remained in solution This resulted in 96 g/l Ni and 150 g/l LI2SO4 in the NISO4 solution, which is referred as NISO4 solution 1.

Nickel sulfate/NISO4 solution 2 was manufactured as follows:

Discharged end-of-life lithium-ion batteries were shredded, crushed, and milled until a black mass was obtained. The current collectors were removed from the black mass by sieving, and metallic iron was separated off by using magnetic separation. The resulting black mass was mixed with a nickel containing beneficiated mixed metal hydroxide ore and subjected to an acid leaching with concentrated sulfuric acid and a reducing agent at a pH value of below 2.0 until all metal oxides were dissolved. By adjusting the pH-value of the resulting solution to 3, the remaining iron, aluminum and copper impurities were depleted by precipitation and subsequent filtration. For further purification of the metal solution, other metal impurities were separated by precipitation of the respective metal fraction by stepwise increasing the pH-value. The valuable manganese and cobalt were recovered as aqueous sulfates by organic solvent extraction with kerosine as solvent and di-(2-ethylhexyl) phosphoric acid as extractant, while lithium remained in solution This resulted in 96 g/l Ni and 75 g/l IJ2SO4 in the NiSCk solution, which is referred as NISO4 solution 2.

1.1.2 Step (a)

The following aqueous solutions were provided, step (a.1):

Solution (a.1): NiSCk solution 1 as synthesized above, commercially available COSO4 and MnSC>4 (both battery grade) dissolved in deionized water (molar ratio 91 :4.5:4.5, total transition metal concentration: 1.45 mol/kg)

Solution (a.2): NiSCk solution 2 as synthesized above, commercially available COSO4 and MnSC>4 (both battery grade) dissolved in deionized water (molar ratio 91 :4.5:4.5, total transition metal concentration: 1.45 mol/kg)

Solution (a.3): Commercially available NISO4, COSO4 and MnSO4 (all three as battery grade) dissolved in deionized water (molar ratio 91 :4.5:4.5, total transition metal concentration: 1.45 mol/kg)

Solution (p.1): 25wt% NaOH dissolved in deionized water

Solution (y.1): 25wt% ammonia in deionized water

1.1.3 Synthesis of an inventive precursor P-CAM.1

A 3.0 I stirred vessel equipped with baffles and a cross-arm stirrer, and three dosing tubes, one for an aqueous solution (a.1), one for solution (0.1) and one for solution (y.1), was charged with 2.5 I of deionized water and the temperature of the vessel was set to 45°C. The feed for the metal sulfate solution was separated from both other tubes by 8 cm each, while the tube for ammonia was separated by 2.5 cm from the tube for the NaOH solution. All tubes had an outer diameter of 6 mm, an inner diameter of 2 mm and were located in the vessel so that the corresponding outlet was approximately 5 cm below the liquid level. The vessel had a constant nitrogen overflow during all reactions.

Step (b.1-1): The stirrer element was operated at 1100 rpm. Aqueous solution (a.1), (0.1) and (y.1) were simultaneously introduced into the vessel through the corresponding tubes. The molar ratio between ammonia and transition metal was adjusted to 0.25. Initially, the sum of volume flows was set to adjust the residence time to 10.0 hours. The flow rate of solution (0.1 ) was adjusted by a pH regulation circuit to keep the pH value in the stirred vessel at a constant value of 12.5 for 1 min of reaction time and thereafter was lowered to 11.4 for the remaining time of the precipitation reaction.

Step (b.1-2): After 16 h of reaction time, the particle growth was ceased by stopping the feed dosing. The slurry obtained was collected and had an average particle diameter (D50) of 3.3 pm and (D90-D10)/D50 of 0.8. A fraction of the slurry was transferred into another 3.0 I stirred tank reactor, which was equipped as described above. The slurry inside the reactor was combined with a solution (0.1) and (y.1) at pH-value of 11.4, and an ammonia concentration of 0.5 wt%. The temperature Inside the vessel was set to 55 °C, the stirrer element was operated at 950 rpm and the aqueous solution (a.1), (0.1) and (y.1) were simultaneously introduced into the vessel through the corresponding tubes and the particles were grown until a particle diameter of

14.4 pm was reached.

Step (c.1): The resulting slurry was filtered, washed with deionized water and an aqueous solution of sodium hydroxide (1kg of 25 wt% aqueous sodium hydroxide solution per kg of solid hydroxide and dried at 120 °C for 12 hours to obtain the inventive precursor P-CAM.1. P-CAM.1 had an average particle diameter (D50) of 13.7 pm, a value of (D90-D10)/D50 of 0.37, a BET surface of 14.4 m²/g, and a lithium-content of 200 ppm.

1.1.4 Synthesis of an inventive precursor P-CAM.2

The above protocol was repeated but aqueous solution (a.2) was used in step (b), hereinafter (b.2-1) and (b.2-2).

Step (b.2-2): After 17 h of reaction time in step (b.2-2), the particle growth was ceased by stopping the feed dosing. The slurry obtained was collected and had an average particle diameter (D50) of 3.9 pm and (D90-D10)/D50 of 1.1. The remaining steps were as described as above.

Step (c.2): The resulting slurry was filtered, washed with deionized water and an aqueous solution of sodium hydroxide (1kg of 25 wt% aqueous sodium hydroxide solution per kg of solid hydroxide and dried at 120 °C for 12 hours to obtain the inventive precursor P-CAM.2. P-CAM.2 had an average particle diameter (D50) of 12.0 pm, a value of (D90-D10)/D50 of 0.33, a BET surface of 16.0 m²/g, and a lithium-content of 140 ppm. 1.1.5: Synthesis of a comparative precursor C-P-CAM.3

The above protocol was repeated but aqueous solution (a.3) was used in step (b), hereinafter (b.3-1) and (b.3-2) .

Step (b.3): After 21 h of reaction time, the particle growth was ceased by stopping the feed dosing. The slurry obtained was collected and had an average particle diameter (D50) of 4.6 pm and (D90-D10)/D50 of 0.7. The remaining steps were as described as above.

Step (c.3): The resulting slurry was filtered, washed with deionized water and an aqueous solution of sodium hydroxide (1kg of 25 wt% aqueous sodium hydroxide solution per kg of solid hydroxide and dried at 120 °C for 12 hours to obtain the comparative precursor C-P-CAM.3. C-P- CAM.3 had an average particle diameter (D50) of 13.9 pm, a value of (D90-D10)/D50 of 0.34, a BET surface of 15.2 m²/g.

1.2 Manufacture of inventive and comparative cathode material: calcination and posttreatments of inventive precursor

Approximately 45 g of inventive P-CAM.1 was heated in a Linn oven for 2 hours at 450 °C under flowing air, and then mixed with LiOH monohydrate (molar ratio Li/metal=1.04), 277 mg AI(OH)3 and 231 mg ZrO₂ for 15 minutes in a grinding mill. A saggar was charged with the resultant mixture and transferred into a Linn oven. The temperature was raised at rate of 2 C/min to 765 °C under flowing oxygen and then held constant at 765 °C for 8 hours and subsequently allowed to naturally cool under flowing oxygen. The resultant powder was then deagglomerated in a grinding mill and sieved. After de-agglomeration, the powder had an average particle diameter (D50) of 13.6 pm and a span of 0.37.

30 g powder is then added to 15 ml deionized water stirred for 2 minutes and then immediately filtered on a Buchner funnel to remove water. The wet filter cake is then dried under an N₂ atmosphere with reduced pressure at 120 °C for 10 hours.

The resultant powder is then dry coated with boric acid by mixing 30 g powder, mixing media and 30 mg boric acid for 40 minutes at low speed on a roller mill. A saggar is charged with the dried powder and heat treated in Linn oven. The Linn oven is heated to 300 °C for 2 hours under oxygen atmosphere and allowed to cool naturally. Inventive CAM.1 is obtained. The protocol was repeated for the manufacturing of inventive CAM.2 from the inventive P- CAM.2 and the comparative C-CAM.3 from the comparative C-P-CAM.3. A comparison of the physical properties of the inventive and comparative cathode active materials is given in table 1. The X-ray diffraction pattern of the inventive CAM.1 using Mo-Ka radiation is given Figure 1 .

II. T esting of Cathode Active Material

11.1 Cathode manufacture

Positive electrode: PVDF binder (polyvinylidene difluoride, Solef® 5130) was dissolved in NMP (Merck) to produce a 7.5 wt.% solution. For electrode preparation, binder solution (2.5 wt.%), and carbon black (Li 400, 2.5 wt.-%) were suspended in NMP. After mixing using a planetary centrifugal mixer (ARE-250, Thinky Corp., Japan), either inventive CAM.2 or C-CAM.1 (95 wt.%) was added and the suspension was stirred again to obtain a lump-free slurry. The solids 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 85 pm, corresponding to 21 mg/cm². All electrodes were dried at 120°C for 7 hours before battery assembly.

11.2 Electrolyte Manufacture

A base electrolyte composition was prepared containing 12.0 wt% of LIPFe, 44.0 wt% of ethylene carbonate (EC), and 44.0 wt% of di-ethyl I carbonate (DMC) (EL base 1), based on the total weight of EL base 1 .

11.3 Test cell Manufacture - coin type half cells

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, 0.095 mL of the EL base 1 which is described above (III.2) were introduced into the coin cell. 11.4 Evaluation of 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 2.7 V at room temperature. For the initial cycles, the initial lithiation was conducted in the CC-CV mode, i.e., a constant current (CC) of 0.04 C was applied until reaching 4.3V, followed by the CV step until the current dropped to 0.01 C. After 10 min resting time, reductive lithiation was carried out at constant current of 0.04 C up to 27 V. For the C-rate test charge and discharge rates were adjusted accordingly. For the cycling test, the constant current was chosen to be 0.33 C until 56 cycles were reached.

A comparison of the electrochemical performances of the inventive and comparative cathode active materials is given in table 1.

Table 1: Lithium/nickel scrambling in mole-%, residual lithium carbonate, a-lattice parameter, charge capacity (CH), discharge capacity (DC) and coulombic efficiency (CE) of inventive cathode active materials CAM.1 and CAM.2 as well as comparative cathode active material C- CAM.3.

Claims

Patent Claims

1. Process for making a particulate (oxy)hydroxide or oxide of TM wherein TM comprises nickel and one transition metal selected from Co and Mn and, optionally, at least one further metal selected from Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, and wherein said process comprises the steps of:

(a) Providing an aqueous solution (a) containing water-soluble salts of Ni and lithium and of at least one transition metal selected from Co and Mn, and, optionally, at least one further metal selected from Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, and an aqueous solution ( ) containing sodium hydroxide or potassium hydroxide and, optionally, an aqueous solution (y) containing ammonia, wherein the amount of lithium is in the range of from 0.01 to 2.5 mol-% with respect to TM,

(b) combining a solution (a) and a solution (P) and, if applicable, a solution (y) at a pH value in the range of from 10.0 to 13.5 in one or more sub-steps, thereby creating solid particles of a hydroxide containing nickel, said solid particles being slurried,

(c) removing the particulate (oxy)hydroxide of TM by a solid-liquid separation method, followed by drying, and, optionally,

(d) a thermal treatment at a temperature in the range of from 250 to 500°C in the absence of a source of lithium.

2. Process according to claim 1 wherein the particulate mixed transition metal precursor is selected from hydroxidesoxyhydroxides and oxides of TM wherein TM is a combination of metals according to general formula (I)

(Ni_aCObMn_c)i.dMd (I) with a being in the range of from 0.6 to 0.95, b being in the range of from 0.025 to 0.2, c being in the range of from zero to 0.2, and d being in the range of from zero to 0.1,

M is selected from Mg, Al, Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, a + b + c = 1.

3. Process according to claim 1 or 2 wherein at least the water-soluble nickel salt is made by recycling of lithium-ion batteries.

4. Process according to any of the preceding claims wherein step (b) is performed as two sub-steps, performed at different pH values.

5. Process according to any of the preceding claims wherein the temperature in step (b) is in the range of from 40 to 70°C.

6. Process according to any of the preceding claims wherein lithium is removed from the liquid medium obtained from the solid-liquid separation step (c) by an electrolysis step (d).

7. Process of making an oxide precursor, said process comprising the steps (a) to (c) according to claims 1 to 6 followed by a thermal treatment at a temperature in the range of from 250 to 500°C in the absence of a source of lithium.

8. Particulate (oxy)hydroxide or oxide of TM wherein TM comprises nickel and one transition metal selected from Co and Mn and, optionally, at least one further metal selected from Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, wherein said particles of (oxy)hydroxide or oxide are in the form of spherical secondary particles that are composed of primary particles that mainly have a platelet shape and wherein said (oxy)hydroxide or oxide has a lithium content in the range of from 0.001 to 0.1 mol-%, corresponding to TM, and wherein said lithium is enriched at the outer surface of the secondary particles of said (oxy)hydroxide or oxide.

9. Particulate (oxy)hydroxide or oxide according to claim 8 wherein TM is a combination of metals according to general formula (I)

M is selected from Mg, Al, Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, a + b + c = 1.

10. Process for making a cathode active material comprising the steps of mixing a particulate (oxy)hydroxide or oxide of TM according to any of the claims 8 to 9 with a source of lithium followed by a thermal treatment at a temperature in the range of from 675 to 1000°C.

11. Particulate cathode active materials with the general formula Lii_+xTMi.xO2 wherein TM comprises nickel and one transition metal selected from Co and Mn and, optionally, at least one further metal selected from Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, and wherein x is in the range of from zero to 0.05, wherein said particles of cathode active materials have an average particle diameter (D50) in the range of from 2 to 15 pm, and wherein said cathode active materials have a residual lithium carbonate content in the range of from 0.03 to 0.15% by weight, determined by titration, and a lattice parameter a in the range of from 2.8736 to 2.8743 as determined by X-Ray diffraction and Rietveld refinement.

12. Particulate cathode active materials according to claim 11 wherein TM is a combination of metals according to general formula (I)

M is selected from Mg, Al, Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, a + b + c = 1.

13. Particulate cathode active materials according to claim 11 or 12 having a nickel-lithium scrambling in the range of from 0.1 to 0.9 mol-%.

14. Cathode containing

(A) at least one particulate cathode active material according to any of claims 11 to 13,

(B) carbon in electrically conductive form, and

(C) a binder material.