PREPARATION OF NANOSTRUCTURED MIXED LITHIUM ZIRCONIUM OXIDES BY MEANS OF SPRAY PYROLYSIS

Abstract

The invention relates to a process for producing lithium zirconium mixed oxides by means of flame spray pyrolysis, mixed oxides obtainable by this process and their use in lithium ion batteries.

Claims

1. A method of producing a lithium zirconium mixed oxide by flame spray pyrolysis, the method comprising: spray pyrolyzing a solution of a metal precursor, comprising a metal carboxylate selected from the group consisting of a lithium carboxylate and a zirconium carboxylate, each metal carboxylate comprising a carboxylate comprising 5 to 20 carbon atoms, and a solvent comprising less than 5% by weight water.

2. The method of claim 1, wherein the spray flame pyrolysis comprises: atomizing the solution of a metal precursor using an atomizer gas to afford an aerosol, reacting the aerosol in a reaction space of a reactor with a flame obtained by ignition of a mixture of fuel gas and an oxygen-containing gas to obtain a reaction stream, cooling the reaction stream, and removing the lithium zirconium mixed oxide from the reaction stream.

3. The method of claim 1, wherein the lithium zirconium mixed oxide is a compound of a general formula Li.sub.aZrbO.sub.0.5a+2b, wherein 0.5≤a≤12, and 1.0≤b≤4.0.

4. The method of claim 1, wherein the lithium zirconium mixed oxide has a BET surface area of 0.1-100 m.sup.2/g.

5. The method of claim 1, wherein each carboxylate is, independently of each other, selected from the group consisting of linear, branched and cyclic pentanoate (C5), hexanoate (C6), heptanoate (C7), octanoate (C8), nonanoate (C9), decanoate (D10), undecanoate (C11), dodecanoate (C12), tridecanoate (C13), tetradecanoate (C14), pentadecanoate (C15), hexadecanoate (C16), heptadecanoate (C17), octadecanoate (C18), nonadecanoate (C19), and icosanoate (C20).

6. The method of claim 1, wherein the solvent is at least one selected from the group consisting of an alcohol, an ether, an ester, a carboxylic acid, and a halogenated hydrocarbon.

7. The method of claim 1, wherein the solution of a metal precursor further comprises a chelating agent selected from the group consisting of a diamine and 1,3-dicarbonyl compound.

8. The method of claim 1, wherein the lithium zirconium mixed oxide has a numerical mean particle diameter of d.sub.50=0.05 to 1 μm, as determined by static light scattering (SLS).

9. The method of claim 1, wherein the lithium zirconium mixed oxide has a tamped density of 20 to 1000 g/L.

10. The method of claim 1, further comprising thermally treating the lithium zirconium mixed oxide at a temperature of 500° C. to 1200° C.

11. A lithium zirconium mixed oxide, which is in the form of aggregated primary particles and has: a BET surface area of 15 to 50 m.sup.2/g, a numerical mean particle diameter of d.sub.50=0.05 to 1 μm, as determined by static light scattering (SLS), and a tamped density of 50 to 200 g/L.

12. A lithium zirconium mixed oxide, which is in the form of aggregated primary particles and has: a BET surface area of less than 20 m.sup.2/g, a numerical mean particle diameter of d.sub.50=1 to 50 μm, as determined by static light scattering (SLS), and a tamped density of 200 to 800 g/L.

13. A component material for a lithium battery, comprising the lithium zirconium mixed oxide of claim 11, the component material being at least one selected from the group consisting of an electrode coating, an electrode doping material, and an electrolyte additive.

14. A lithium ion battery comprising the lithium zirconium mixed oxide of claim 11.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0093] FIGS. 1A and 1B are TEM images of Li—Zr mixed oxide particles prepared as described in example 1.

[0094] FIG. 2 shows SEM-EDX mapping image of Zr (white) on LZO-coated NMC prepared using LZO prepared as described in example 1.

[0095] FIG. 3 shows SEM-EDX mapping image of Zr (white) on LZO-coated NMC prepared using LZO prepared as described in comparative example 1.

[0096] FIG. 4 shows the statistical analyses of the area distribution of Zr in the SEM-EDX mapping images of LZO-coated NMC prepared using LZO prepared as described in comparative example 1 and example 1.

[0097] FIG. 5 shows XRD patterns of the inventive Li—Zr mixed oxide (LZO) prepared as described in examples 1-3.

EXAMPLES

[0098] Commercial mixed lithium nickel manganese cobalt oxide powder NMC (7-1.5-1.5) (Type PLB-H7) with a BET surface area of 0.30-0.60 m.sup.2/g, a medium particle diameter d.sub.50=10.6±2 μm (determined by static laser scattering method), was supplied by Linyi Gelon LIB Co.

[0099] Commercial lithium zirconium oxide power LZO (type 2004PR) with a BET surface area of lower than 1 m.sup.2/g, a medium particle diameter d.sub.50=19.3±2 μm (determined by static laser scattering method), was supplied by Sigma Aldrich.

Comparative Example 1

[0100] (L-Zr Mixed Oxide from Aqueous Nitrate Precursors)

[0101] 8.54 kg of an aqueous solution containing 630 g of LiNO.sub.3 and 1733 g of Zr(NO.sub.3).sub.4 (metal content: 24 wt %) was prepared under intense stirring until al solid content was dissolved. This solution represents the theoretical composition of Li.sub.2ZrO.sub.3.

[0102] An aerosol was formed of 2.5 kg/h stream of this solution and 15 Nm.sup.3/h stream of air via a two-component nozzle and sprayed into a tubular reaction with a burning flame. The burning gases of the flame consist of 13 Nm.sup.3/h hydrogen and 75 Nm.sup.3/h of air. Additionally, 25 Nm.sup.3/h of secondary air was used. After the reactor the reaction gases were cooled down and filtered.

[0103] The particle properties are shown in Table 1.

Preparation of an NMC Powder Coated with Li—Zr Mixed Oxide of Comparative Example 1:

[0104] The NMC-powder (99 g) was mixed with 1.0 g (1 wt %) of the fumed powder of the comparative example 1 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 NMC) to homogeneously mix the two powders. Afterwards the mixing intensity was increased to 2000 rpm (specific electrical power: 800 W/kg NMC, 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 NMC particles by the fumed powder of the comparative example 1.

Comparative Example 2

[0105] (LU-Zr Mixed Oxide from Ethanolic Nitrate Precursors)

[0106] 8.32 kg of an ethanoic solution containing 450 g of LiNO.sub.3 and 1238 g of Zr(NO.sub.3).sub.4 (metal content: 24 wt %) was prepared under intense stirring until al solid content was dissolved. This solution represents the theoretical composition of Li.sub.2ZrO.sub.3.

[0107] An aerosol was formed of 2.5 kg/h stream of this solution and 15 Nm.sup.3/h stream of air via a two-component nozzle and sprayed into a tubular reaction with a burning flame. The burning gases of the flame consist of 6.8 Nm.sup.3/h hydrogen and 75 Nm.sup.3/h of air. Additionally, 25 Nm.sup.3/h of secondary air was used. After the reactor the reaction gases were cooled down and filtered.

[0108] The particle properties are shown in table 1.

Example 1

[0109] 7.94 kg of a solution containing 2725 g of a commercial solution (Borchers® Deca Lithium2), containing 2 wt % lithium in the form of lithium neodecanoate and 2984 g of a commercial solution (Octa Solingen Zirconium 12), containing 12 wt % Zr in the form of zirconium ethylhexanoate, and 2231 g 2-ethylhexanoic acid, were mixed, resulting in a clear solution. This solution represents the theoretical composition of Li.sub.2ZrO.sub.3.

[0110] An aerosol was formed of 2.5 kg/h stream of this solution and 15 Nm.sup.3/h stream of air via a two-component nozzle and sprayed into a tubular reaction with a burning flame. The burning gases of the flame consist of 4 Nm.sup.3/h hydrogen and 75 Nm.sup.3/h of air. Additionally, 25 Nm.sup.3/h secondary air was used. After the reactor the reaction gases were cooled down and filtered.

[0111] The particle properties are shown in table 1. The TEM images of the particles are shown in FIGS. 1A and 1B.

[0112] The XRD analysis (FIG. 5) showed, that the major phase of the product was still ZrO.sub.2 structure.

Example 2

(Calcined Li—Zr Mixed Oxide)

[0113] The mixed oxide obtained in example 1 was calcined at 700° C. for 6 h in a rotary kiln. The XRD analysis (FIG. 5) showed, that the major phase of the product was the tetragonal lithium zirconium oxide (Li.sub.4Zr.sub.3O) structure.

Example 3

(Calcined Li—Zr Mixed Oxide)

[0114] The mixed oxide obtained in example 1 was calcined at 750° C. for 6 h in a rotary kiln. The XRD analysis (FIG. 5) showed, that the major phase of the product was monoclinic lithium zirconium oxide (LiZrO.sub.3) and tetragonal lithium zirconium oxide (Li.sub.4Zr.sub.3O.sub.8) structure.

Preparation of an NMC Powder Coated with Li—Zr Mixed Oxide of Example 1:

[0115] The NMC-powder (99 g) was mixed with 1.0 g (1 wt %) of the fumed powder of the Example 1 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 NMC) to homogeneously mix the two powders. Afterwards the mixing intensity was increased to 2000 rpm (specific electrical power 800 W/kg NMC, 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 NMC particles by the fumed powder of the Example 1.

Analysis of Li.sub.2ZrO.sub.3-Dry Coated Mixed Lithium Transition Metal Oxides by SEM-EDX

[0116] FIG. 2 shows the SEM-EDX mapping of Zr (white) on Li.sub.2ZrO.sub.3 (LZO)-coated NMC prepared by using fumed nano LZO (Example 1), FIG. 3 shows the results of the analysis of NMC coated with fumed coarse LZO (Comparative Example 1). The axes of FIGS. 2 and 3 show: x axis=diameter of particles; the left y axis=volume in %, the right y axis=cumulative volume in %. NMC mixed oxide dry coated with fumed nano LZO (Example 1), shows a full and homogeneous coverage of al NMC particles with LZO (FIG. 2). No larger LZO agglomerates were detected, showing a good dispersibility of nanostructured fumed nano LZO. Additionally, no free unattached LZO-particles next to the NMC particles were found, indicating the strong adhesion between coating and the substrate (NMC). In contrast, FIG. 3 shows that only the fine LZO-particles of fumed coarse LZO are attached to the surface of NMC particles. The larger LZO-particles are non-dispersed and are therefore unattached, located next to the NMC particles. As a result, the NMC particles are not fully covered by zirconium oxide.

[0117] FIG. 4 shows the statistical analyses of FIG. 2 and FIG. 3. The area distribution of Zr (white) μm.sup.2 in the SEM-EDX mapping is further analyzed by box normal plot and showing a clear difference of the dispersibility of Zr (white) between Example 1 in FIG. 2 and Comparative Example 1 in FIG. 3.

Assembly & Characterizations of all-Solid-State Lithium Metal Batteries

[0118] Three sets of al-solid-state NMC_Li.sub.6SP.sub.5Cl_Li metal batteries that were assembled using fumed nano LZO (Example 1) and commercial LZO from Sigma Aldrich. Composite cathode using LZO coated NMC was prepared with the weight ratio of NMC:Li.sub.6SP.sub.5Cl:Carbon=60:35:5 as cathode. Li—In alloy is used as anode.

[0119] The initial impedance was analyzed by electrochemical impedance spectroscopy (EIS) and the results are shown in the table 2. Table 2 also show the initial coulombic efficiency of the al-solid-state batteries.

TABLE-US-00001 TABLE 1 Properties of the lithium-zirconium mixed oxides Tamped BET D10 D50 D90 density Example [m.sup.2/g] [μm] [μm] [μm] [g/L] Comparative 28 0.61 2.54 5.18 301 Example 1 Comparative 17 0.14 1.05 3.24 333 Example 2 Example 1 25 0.06 0.13 2.65 104 Example 2 13 0.06 0.086 2.60 350 Example 3 4.6 0.106 5.12 104 739

TABLE-US-00002 TABLE 2 Electrochemical analyses of all-solid-state batteries Initial coulombic Example Impedance [Ω] efficiency [%] Without coating 1237 62.55 Coating with Example 1 139 64.46 Coating with 164 63.46 commercial LZO