MIXED LITHIUM TRANSITION METAL OXIDE COATED WITH PYROGENICALLY PRODUCED ZIRCONIUM-CONTAINING OXIDES

Abstract

Process for producing a mixed lithium transition metal oxide usable as an active positive electrode material in lithium batteries, wherein i) a transition metal oxide, and/or a transition metal hydroxide and/or a transition metal oxyhydroxide and a pyrogenically produced zirconium dioxide and/or a pyrogenically produced mixed oxide comprising zirconium are subjected to dry mixing by means of an electric mixing unit to obtain a coated precursor compound, wherein the mixing unit has a specific electrical power of 0.05-1.5 kW per kg of the coated precursor compound; ii) the coated precursor compound is mixed with a lithium containing compound; and iii) the mixture of the coated precursor compound and the lithium containing compound is heated at a temperature between 500 and 1400° C. to obtain the mixed lithium transition metal oxide.

Claims

1. A process for producing a mixed lithium transition metal oxide usable as an active positive electrode material in lithium batteries, the process comprising: i) dry mixing a transition metal source which is at least one selected from the group consisting of a transition metal oxide, a transition metal hydroxide, and a transition metal oxyhydroxide, and a zirconium source which is at least one selected from the group consisting of a pyrogenically produced zirconium dioxide and a pyrogenically produced mixed oxide comprising zirconium to obtain a coated precursor compound, wherein the dry mixing is performed with an electric mixing unit having a specific electrical power of 0.05 to 1.5 kW per kg of the coated precursor compound; ii) mixing the coated precursor compound with a lithium containing compound to form a reaction mixture; and iii) heating the reaction mixture at a temperature of 500 to 1400° C. to obtain the mixed lithium transition metal oxide.

2. The process of claim 1, wherein: the transition metal is at least one selected from the group consisting of nickel, manganese, and cobalt.

3. The process of claim 1, wherein: a BET surface area of the zirconium source is 5 to 200 m.sup.2/g.

4. The process of claim 1, wherein: the zirconium source is in the form of aggregated primary particles having a numerical mean diameter of primary particles of 5 to 100 nm, as determined by transition electron microscopy (TEM).

5. The process of claim 1, wherein: a mean particle size d.sub.50 of particles of the zirconium source is 10 to 150 nm, as determined by static light scattering (SLS).

6. The process of claim 1, wherein: a span (d.sub.90−d.sub.10)/d.sub.50 of particles of the zirconium source is 0.4 to 1.2, as determined by static light scattering (SLS).

7. The process of claim 1, wherein: the mixed oxide comprising zirconium further comprises lithium and optionally comprises at least one of lanthanum and aluminium.

8. The process of claim 1, wherein: the transition metal hydroxide is a compound of a general formula M(OH).sub.2, wherein M is at least one transition metal selected from the group consisting of nickel, manganese, and cobalt, and said transition metal hydroxide is optionally doped with at least one compound selected from the group consisting of aluminium oxide, aluminium hydroxide, aluminium oxyhydroxide, zirconium oxide, zirconium hydroxide, and zirconium oxyhydroxide.

9. The process of claim 1, wherein: the transition metal oxyhydroxide is a compound of a general formula MOOH, wherein M is at least one transition metal selected from the group consisting of nickel, manganese, and cobalt, and said transition metal oxyhydroxide is optionally doped with at least one compound selected from the group consisting of aluminium oxide, aluminium hydroxide, aluminium oxyhydroxide, zirconium oxide, zirconium hydroxide, and zirconium oxyhydroxide.

10. The process of claim 1, wherein: the zirconium source is present in the coated precursor in an amount of 0.05% to 5% by weight, based on a total weight of coated precursor.

11. The process of claim 1, wherein: the mixed lithium transition metal oxide is at least one selected from the group consisting of a lithium-cobalt oxide, a lithium-manganese oxide, a lithium-nickel-cobalt oxide, a lithium-nickel-manganese-cobalt oxide, a lithium-nickel-cobalt-aluminium oxide, and a lithium-nickel-manganese oxide.

12. The process of claim 1, wherein: the lithium containing compound is at least one selected from the group consisting of a lithium oxide, a lithium hydroxide, a lithium alkoxide, and a lithium carbonate.

13. A mixed lithium transition metal oxide usable as an active positive electrode material in lithium batteries, comprising a pyrogenically produced zirconium dioxide and/or a pyrogenically produced mixed oxide comprising zirconium having a number average particle size d.sub.50 of 10 nm to 150 nm.

14. A coated precursor compound for a mixed lithium transition metal oxide, the coated precursor compound comprising a pyrogenically produced zirconium dioxide and/or a pyrogenically produced mixed oxide comprising zirconium having a number average particle size d.sub.50 of 10 nm to 150 nm present on a surface of the coated precursor.

15. An active positive electrode material for a lithium battery comprising the mixed lithium transition metal oxide of claim 13.

16. A lithium battery comprising the mixed lithium transition metal oxide of claim 13.

17. (canceled)

Description

EXAMPLES

[0096] Starting Materials

[0097] Fumed ZrO.sub.2 with a specific surface area (BET) of 40-60 m.sup.2/g, was produced by flame spray pyrolysis according to Example 1 of WO 2009053232 A1.

[0098] Commercial “nano ZrO.sub.2” powder (particle size 20-30 nm) with BET surface area of ≥5 m.sup.2/g, was supplied by ChemPUR Feinchemikalien and Forschungsbedarf GmbH

[0099] Commercial mixed lithium nickel manganese cobalt hydroxide powder Ni.sub.0.8Mn.sub.0.1Co.sub.0.1(OH).sub.2 with a BET surface area of 0.35-0.65 m.sup.2/g, a medium particle diameter d.sub.50=11.0±2 μm (determined by static laser scattering method), was supplied by Linyi Gelon LIB Co.

[0100] Particle Size Distribution of Different ZrO.sub.2 Types

[0101] The samples of a fumed ZrO.sub.2 or a commercial “nano ZrO.sub.2” powder (5 wt %) were dispersed in the solution of sodium pyrophosphate (0.5 g/L) in distilled water and treated at 25° C. for 1 minute in an external ultrasonic bath (160 W).

[0102] FIG. 1 shows the particle size distribution of the fumed ZrO.sub.2 and FIG. 2 shows the particle size distribution of the “nano ZrO.sub.2”, analyzed by static laser diffraction method (SLS) using laser diffraction particle size analyzer (HORIBA LA-950). For fumed ZrO.sub.2, a mono-modally and very narrow particle size distribution was detected (d.sub.10=0.06014 μm, d.sub.50=0.07751 μm, d.sub.90=0.11406 μm, span=(d.sub.90−d.sub.10)/d.sub.50=0.7), while a wide spread bimodal distribution was detected for “nano ZrO.sub.2” of ChemPUR, showing large non-dispersed particles (d.sub.10=0.10769 μm, d.sub.50=3.16297 μm, d.sub.90=5.80804 μm, span=(d.sub.90−d.sub.10)/d.sub.50=1.8).

Example 1

[0103] The Ni.sub.0.8Mn.sub.0.1Co.sub.0.1(OH).sub.2-powder (217.8 g) was mixed with 2.2 g (1.0 wt %) of the fumed ZrO.sub.2-powder in a high intensity laboratory mixer (Somakon mixer MP-GL with a 0.5 L mixing unit) at first for 1 min at 500 rpm (specific electrical power: 350 W/kg Ni.sub.0.8Mn.sub.0.1Co.sub.0.1(OH).sub.2) to homogeneously mix the two powders. Afterwards the mixing intensity was increased to 2000 rpm (specific electrical power: 800 W/kg Ni.sub.0.8Mn.sub.0.1Co.sub.0.1(OH).sub.2, tip-speed of the mixing tool in the mixing unit: 10 m/s) and the mixing was continued for 5 min to achieve the dry coating of the Ni.sub.0.8Mn.sub.0.1Co.sub.0.1(OH).sub.2 particles by ZrO.sub.2.

Comparative Example 1

[0104] The procedure of Example 1 was repeated exactly with the only difference, that “nano ZrO.sub.2” powder was used instead of fumed ZrO.sub.2.

[0105] Analysis of ZrO.sub.2-Coated Mixed Transition Metal Hydroxides by SEM-EDX

[0106] FIG. 3 shows the SEM-EDX mapping of Zr (white) on ZrO.sub.2-coated Ni.sub.0.8Mn.sub.0.1Co.sub.0.1(OH).sub.2 prepared by using fumed ZrO.sub.2 (Example 1), FIG. 4 shows the results of the analysis of Ni.sub.0.8Mn.sub.0.1Co.sub.0.1(OH).sub.2 coated with “nano ZrO.sub.2” (Comparative Example 1). The axes of FIGS. 3 and 4 show: x axis=diameter of particles; the left y axis=volume in %, the right y axis=cumulative volume in %. Ni.sub.0.8Mn.sub.0.1Co.sub.0.1(OH).sub.2 dry coated with fumed ZrO.sub.2, shows a full and homogeneous coverage of all Ni.sub.0.8Mn.sub.0.1Co.sub.0.1(OH).sub.2 particles with ZrO.sub.2. No larger ZrO.sub.2 agglomerates were detected, showing a good dispersibility of nanostructured fumed ZrO.sub.2. Additionally, no free unattached ZrO.sub.2-particles next to the Ni.sub.0.8Mn.sub.0.1Co.sub.0.1(OH).sub.2 particles were found, indicating the strong adhesion between coating and the substrate (Ni.sub.0.8Mn.sub.0.1Co.sub.0.1(OH).sub.2). In contrast, FIG. 5 shows that only the fine ZrO.sub.2-particles of “nano ZrO.sub.2” are attached to the surface of Ni.sub.0.8Mn.sub.0.1Co.sub.0.1(OH).sub.2 particles. The larger ZrO.sub.2-particles are non-dispersed and are therefore unattached, located next to the Ni.sub.0.8Mn.sub.0.1Co.sub.0.1(OH).sub.2 particles. As a result, the Ni.sub.0.8Mn.sub.0.1Co.sub.0.1(OH).sub.2 particles are not fully covered by zirconium oxide.

[0107] Preparation of Mixed Lithium Transition Metal Oxides

[0108] For the preparation of mixed lithium transition metal oxides (NMC), the undoped LiNi.sub.0.8Mn.sub.0.1Co.sub.0.1(OH).sub.2 was mixed with Li.sub.2CO.sub.3 with a molar ratio of 1:0.54. The mixture was preheated at 600° C. for 7 h and further annealed at 870° C. for 15 h to obtain the mixed lithium transition metal oxide.

[0109] The procedure was repeated exactly with the only difference, that “nano ZrO.sub.2”-doped and “fumed ZrO.sub.2”-doped LiNi.sub.0.8Mn.sub.0.1Co.sub.0.1(OH).sub.2 powders were used instead of the undoped LiNi.sub.0.8Mn.sub.0.1Co.sub.0.1(OH).sub.2.

[0110] Preparation of Electrodes

[0111] Electrodes for electrochemical measurements were prepared by blending 90 wt % NMC with 5 wt % of a polyvinylidene fluoride binder (PVDF 5130, manufacturer: Solef) and 5 wt % of a conductive carbon black (SUPER PLi, manufacturer: TIMCAL) under inert gas atmosphere. N-Methyl-2-pyrrolidone (NMP) was used as a solvent. The slurry was casted on aluminum foil and dried at 120° C. for 20 min on a heating plate under air. Afterwards, the electrode sheet was dried in a vacuum furnace at 120° C. for 2 h. Circular electrodes with a diameter of 12 mm were punched out of a larger piece and then flattened between 2 rollers with a pressure of 90 psi, and dried again in a vacuum furnace at 120° C. for 12 h to remove any residual water and NMP.

[0112] Assembly of Lithium Batteries

[0113] The lithium battery cells for the cycling tests were assembled as CR2032 type coin cells (MTI Corporation) in an argon-filled glovebox (GLOVEBOX SYSTEMTECHNIK GmbH). Lithium metal (ROCKWOOD LITHIUM GmbH) was used as the anode material. Celgard 2500 was used as the separator. 25 μL of a 1 M solution of LiPF.sub.6 in ethylene carbonate and ethyl methyl carbonate (50:50 wt/wt; SIGMA-ALDRICH) was used as an electrolyte. The cells were locked with a crimper (MTI).

[0114] Galvanostatic Cycling Tests

[0115] Galvanostatic cycle performance of the assembled lithium-ion batteries was measured at 25° C. using a MACCOR battery cycler at cut-off voltage of 3.0-4.3 V. The cell was cycled at 0.5 C/0.5 C for long term stability test. (0.5 C rate corresponds to current density of 0.7 mAh/cm.sup.2). For the calculation of the capacities and the specific currents, only the mass of the active material was considered.

[0116] The cycling performance of NMC 811 doped with fumed ZrO.sub.2 (Evonik) was compared with the NMC 811 doped with commercial “nano ZrO.sub.2” and as a reference with the undoped (pristine) NMC 811. It is clear from the results (FIG. 5), that the fumed ZrO.sub.2 doping improves the stability and cycle life of NMC significantly. The cell with NMC doped with “nano ZrO.sub.2” shows a significantly worse cycling performance.