WO2015173114A1

WO2015173114A1 - Method for producing mixed oxide powder comprising lithium, lanthanum and zirconium

Info

Publication number: WO2015173114A1
Application number: PCT/EP2015/060068
Authority: WO
Inventors: Stipan Katusic; Peter Kress; Armin Wiegand; Tobias RENGER; Michael Hagemann
Original assignee: Evonik Degussa Gmbh
Priority date: 2014-05-16
Filing date: 2015-05-07
Publication date: 2015-11-19

Abstract

Method for producing a mixed oxide powder whose composition is Li_xLa₃Zr₂MyO_8.5+0.5x+z where 6.5 ≤ x ≤ 8, 0 ≤ y ≤ 0.5, z = 2y for M = Hf, Ga, Ge, Nb, Si, Sn, Sr, Ta and Ti, z = 1.5y for M = Al, Sc, V and Y, z = y for M = Ba, Ca, Mg and Zn, and for M= Al it holds that 6 ≤ x ≤ 7 und 0.2 ≤ y ≤ 0.5, wherein one or more solutions each comprising one or more compounds of lithium, lanthanum and zirconium and optionally metal compounds MX, in a concentration conforming to the stoichiometry, and in the form of fine droplets, are introduced into a flame, burning in a reaction chamber, that is formed by introducing into said reaction chamber an oxygen-containing gas and a combustion gas that forms water on reaction with oxygen and igniting it there, and thereafter the solid material is separated from matter in gas or vapour form.

Description

Process for the preparation of lithium, lanthanum and zirconium-containing mixed oxide powder

The invention relates to processes for preparing lithium, lanthanum and zirconium-containing mixed oxide powder, the mixed oxide powder itself and their use in lithium-ion batteries.

DE-A-102007030604 discloses a process for producing a mixed oxide powder containing lithium, lanthanum and zirconium by a solid phase reaction. The nitrates, carbonates and hydroxides of the metals are mixed in a first step, for example by means of a ball mill in 2-propanol. The resulting mixture is then heated to 400-1000 ° C for several hours in air over a period of 4-8 hours.

Subsequently, a grinding process is performed again. The reaction product is then pressed at uniaxial or isostatic pressure in fittings. These are then sintered for several hours at temperatures of 700-1200 ° C. You get one

Mixed oxide with garnet structure.

Further solid phase reactions for preparing lithium, lanthanum and zirconium-containing mixed oxides are disclosed in EP-A-2159867 or WO2010 / 090301.

In Solid State Ionics 185 (201 1) 42-46, a sol-gel process for producing lithium,

Lanthanum and zirconium containing mixed oxides disclosed in which one dissolves Li ₂ C0 ₃ and La ₂ 0 ₃ in HN0 ₃ and Zr (OC ₂ H ₅ ) ₄ in ethanol. Both solutions are mixed and subsequently mixed with citric acid and ethylene glycol. The solution is stirred for 3 hours at 323K and then the solvent is distilled off. The resulting gel is treated at 473K for 24 hours. The resulting powder is ground and calcined in air at temperatures of 923 to 1173K for 5 hours. A similar process is also disclosed in Solid State Ionics 183 (201 1) 48-53.

Lithium, lanthanum and zirconium-containing mixed oxides have hitherto been produced by classical, wet-chemical processes. These include sol-gel methods, precipitation methods and solid-phase reactions. Often these processes require several process steps, and the processes often leave much to be desired in terms of control and reproducibility of the reaction.

The object of the present invention was to provide a process which does not have the disadvantages mentioned and with which it is possible in a short time to produce relatively large amounts of lithium oxide, lanthanum and zirconium-containing mixed oxide powders. The object of the invention was in particular to produce mixed oxide powder with garnet structure.

The invention relates to a method for producing a mixed oxide powder of the composition Li _x La ₃ Zr ₂ M _y 08.5 + o, 5x + z with

6.5 <x <8, preferably 7 <x <7.5,

0 <y <0.5, preferably 0 <y <0.2

z = 2y for M = Hf, Ga, Ge, Nb, Si, Sn, Sr, Ta and Ti, z = 1.5y for M = Al, Sc, V and Y,

z = y for M = Ba, Ca, Mg and Zn, where

for M = AI it holds that 6 <x <7 and 0.2 <y <0.5,

in which a solution containing in each case one or more compounds of lithium, lanthanum and zirconium and optionally metal compounds MX in a concentration corresponding to stoichiometry and in the form of fine droplets is introduced into a flame burning in a reaction space, which is formed by reacting an oxygen containing gas and a in the reaction with oxygen forming water fuel gas into the reaction chamber and there ignites and subsequently separates the solid from vapor or gaseous substances.

The mixed oxide powder thus prepared is intended in the context of the present invention as

Mixed oxide powder A are called. Mixed oxide is the intimate mixing of all mixed oxide components to understand. It is therefore largely a mixture at the atomic level, not a physical mixture of oxides.

The mixed oxide powder prepared by the process of the present invention contains Li, La and Zr as essential metals and may further contain one or more metals M.

Usually, zirconium compounds contain up to 2% by weight of hafnium compounds

Contamination, so that the mixed oxide powder produced therefrom also contains hafnium. In the context of the present invention, this compulsory proportion of hafnium should not be considered as a mixed oxide component. An additionally introduced hafnium compound, on the other hand, should be regarded as a mixed oxide component.

Used solutions

In the method according to the invention, the solution or solutions are introduced into the reaction space in the form of fine droplets. The fine droplets preferably have an average droplet size of 1 to 120 μm, more preferably of 30 to 100 μm. One or more nozzles are usually used to generate the droplets.

The best results are obtained when the metal compounds are in solution. In order to achieve solubility and to achieve a suitable viscosity for sputtering the solution, the solution can be heated. In principle, all are soluble

Usable metal compounds that are oxidizable.

These may be inorganic metal compounds, such as nitrates, chlorides, bromides, or organic metal compounds, such as alkoxides or carboxylates. The alkoxides used may preferably be ethylates, n-propylates, isopropylates, n-butylates and / or tert-butylates. As carboxylates, those of acetic acid, propionic acid, butanoic acid, hexanoic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, octanoic acid, 2-ethyl Hexanoic acid, valeric acid, capric acid and / or lauric acid underlying

Connections are used.

2-ethylhexanoates or laurates can be used with particular advantage. The solution may contain one or more inorganic metal compounds, one or more organic metal compounds, or mixtures of inorganic and organic metal compounds.

Preferably, the nitrates of lithium, lanthanum, and zirconium and M are used.

The solvents may preferably be selected from the group consisting of water, C ₅ -C ₂ o alkanes, C ₁ -C 6 alkane carboxylic acids and / or C ₁ -C 6 alkanols. Particular preference may be given to using water or a mixture of water and an organic solvent.

As organic solvents, or as part of organic

Solvent mixtures, may preferably alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol or tert-butanol, diols such as ethanediol, pentanediol, 2-methyl-2,4-pentanediol, Ci-Ci2-carboxylic acids such as Acetic acid, propionic acid, butanoic acid, hexanoic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, octanoic acid, 2-ethylhexanoic acid, valeric acid, capric acid, lauric acid can be used. Furthermore, benzene, toluene, naphtha and / or gasoline can be used.

Preferably, aqueous solutions are used, wherein an aqueous solution is to be understood as a solution in which water is the main constituent of a

Solvent mixture is or in which only water is the solvent.

The concentration of the solutions used is not particularly limited. If only one solution is present, which contains all the mixed oxide components, the concentration is generally from 1 to 50% by weight, preferably from 3 to 30% by weight, very particularly preferably from 5 to 20% by weight, based in each case on the sum of oxides.

Used gases

As fuel gases that form water in the reaction with oxygen, hydrogen, methane, ethane, propane, butane and mixtures thereof can be used. Preference is given to using hydrogen.

The flame-forming, oxygen-containing gas is usually air.

The amount of oxygen is to be selected in the inventive method so that it is sufficient at least for complete conversion of the fuel gas and all metal compounds. It is usually advantageous to use an excess of oxygen. This excess is conveniently expressed as the ratio of existing Oxygen / combustion of the fuel gas necessary oxygen and referred to as lambda. Lambda is preferably 1.5 to 6.0, particularly preferably 2.0 to 4.0.

In addition, additional oxygen-containing gas can be introduced into the reaction space.

The solution is preferably introduced by means of a nebulizer gas into the reaction space. For example, nitrogen or air are suitable as nebulizer gases. If air is used, it will not be taken into account when calculating lambda.

A particular embodiment provides for ammonia and / or an ammonia-forming substance to be introduced into the reaction space. This can be done, for example, by adding an ammonia-forming substance, such as ammonium carbonate,

Ammonium bicarbonate or urea in which solution is introduced which is introduced into the flame. Another embodiment provides ammonia gas directly into the

Reaction space, preferably in the flame to bring. Yet another embodiment provides for mixing ammonia gas into the nebulizer gas.

The concentration of the ammonia gas is preferably 0.01 to 1 kg / Nm ³ Zerstäubergas, more preferably 0.05 to 0.3 kg / Nm ³ Zerstäubergas or 0.001 to 0.05 kg / Nm ³ (fuel gas + oxygen-containing gas) for the Case that the ammonia gas is introduced directly into the flame.

It has been shown that mixed oxide powder A can be produced by this measure, which have an improved sintering behavior in a subsequent step. At present it is assumed that with the addition of ammonia smaller particles are formed than without ammonia.

Furthermore, the average residence time of the reaction mixture in the reaction space is preferably 0.5-2.5 s, more preferably 0.5-1 s.

The average velocity in the reaction space is preferably 1-20 Nm / s, more preferably 3-10 Nm / s. The speed information is standardized speed. They are obtained by dividing the volume flow with the unit Nm ³ / h and the cross-sectional area.

Another object of the invention is a special mixed oxide powder A ^* , which can be prepared by the method according to the invention. This is a

Mixed oxide powder of composition Li _x La ₃ Zr ₂ M _y 08.5 + o, 5x + z with

6.5 <x <8, preferably 7 <x <7.5

0 <y <0.5, preferably 0 <y <0.2,

z = 2y for M = Hf, Ga, Ge, Nb, Si, Sn, Sr, Ta and Ti,

z = 1.5y for M = Al, Sc, V and Y, where for M = Al it holds that 6 <x <7 and 0.2 <y <0.5 z = y for M = Ba, Ca, Mg and Zn, which has a BET surface area of 3 to 20 m ² / g and a d ₅₀ value of less than or equal to 5 [im.

The BET surface area is determined according to DIN ISO 9277. The d ₅₀ value results from the cumulative volume distribution curve of the volume-averaged large distribution. This is determined in the usual way by laser diffraction. In the context of the present invention, a Cilas 1064 device from Cilas is used for this purpose. A d ₅₀ value is understood to mean that 50% of the mixed oxide particles A ^{* are} within the stated size range. A d ₅₀ value of 5 μm therefore means that 50% of the particle diameters are smaller than 5 μm. A d ₉₀ value of 8 μιη means that 90% of the particle diameters are smaller than 8 μιη. A d io value of 0.3 μιη means that 10% of the particle diameter is smaller than 0.3 μιη.

The d 50 value of the mixed oxide particles A according to the invention may preferably be from 1 to 15 μm, more preferably from 8 to 10 μm.

The d 10 value of the mixed oxide particles A according to the invention may preferably be from 3 to 25 μm, more preferably from 0.2 to 1 μm.

Another object of the invention is a method for producing a

Mischoxidpulvers B of the general composition Li _x La ₃ Zr ₂ M _y 0 _8i 5 ₊ o, 5x ₊ z with

6.5 <x <8, preferably 7 <x <7.5,

0 <y <0.5, preferably 0 <y <0.2,

z = 2y for M = Hf, Ga, Ge, Nb, Si, Sn, Sr, Ta and Ti

z = 1.5y for M = Al, Sc, V and Y, where for M = Al it holds that 6 <x <7 and 0.2 <y <0.5 z = y for M = Ba, Ca Mg , and Zn with

a) garnet crystal structure,

b) a BET surface area of <3 m ² / g, preferably <1 m ² / g and

c) at least 75%, preferably at least 90%, preferably at least 95%, of the theoretical solids density of cubic Li ₇ La ₃ Zr ₂ 0i ₂ ,, for M = Al and 6 <x <7 and 0.2 <y <0, 5 at least 95% of the theoretical density,

in which the obtainable by the process according to the invention mixed oxide A or the inventive mixed oxide A ^* at temperatures of 700 ° C to 1200 ° C over a period of 3 to 24 hours, preferably 6 to 12 hours, preferably while passing an inert gas such as Nitrogen or argon, thermally treated.

The same product is obtained by containing a solution containing one or more compounds of lithium, lanthanum and zirconium and optionally

Metal compounds MX in a concentration corresponding to the stoichiometry and in the form of fine droplets in a flame burning in a reaction chamber, which is formed by forming an oxygen-containing gas and in the reaction with oxygen

Introducing water-forming fuel gas into the reaction chamber and there ignites and subsequently separates the solid from vapor or gaseous substances and the solid at Temperatures of 700 ° C to 1200 ° C over a period of 3 to 24 hours, preferably 6 to 12 hours, preferably while passing an inert gas such as nitrogen or argon, thermally treated.

It is also possible to carry out the thermal treatment in a vacuum, for example at a pressure of <300 mbar. In this case, it may be provided to rinse the apparatus one or more times with an inert gas in order to minimize the proportion of oxygen. In a thermal treatment in a vacuum with a faster Kristallwachstun is expected.

The solids density is determined by gas pycnometry according to DIN 66137-2 (2004). For the determination, a Heliumpyknometer AccuPyc II 1340, Fa. Micromeritics ^® is suitable. The theoretical solids density of cubic Li ₇ La ₃ Zr ₂ 0i ₂ is 5.100 g / cm ³ .

The mixed oxide powders B produced in this way can have a tetragonal and / or cubic structure, and can easily be distinguished from the X-ray diffractograms. Usually, both structures are found, with the ratio of the teragonal / cubic being 5:95 to 95: 5.

Another object of the invention is the use of the invention

Mixed oxide powder or produced by the novel processes

Mixed oxide powder as a solid electrolyte in lithium ion batteries.

Examples

Example 1 :

Solution used: 5.91% by weight of lithium nitrate, 15.90% by weight of lanthanum nitrate, 10.41% by weight of zirconium nitrate, balance water. The concentration, based on the oxides Li ₂ 0, La ₂ 0 ₃ and Zr0 ₂ , is 10.28 wt .-%.

Mixed oxide powder A: 7000 g / h of the solution are atomized with a Zerstäubergas consisting of 15 Nm ³ / h of air and 1 kg ammonia gas / Nm ³ air by means of a two-fluid nozzle in a burning in a reaction chamber flame. The average droplet diameter is about 93 μιη. The flame is formed by the reaction of 1 1 Nm ³ / h of hydrogen, 70 Nm ³ / h of air. In addition, 20 Nm ³ / h of additional air, so-called secondary air, are brought into the reaction space. Lambda is 4.01. The average residence time in the reaction space is 0.71 s, the average velocity in the reaction space is 5.7 m / s. After cooling, the mixed oxide powder A is separated on a filter of gaseous substances.

The mixed oxide powder A has a composition Li ₇ La ₃ Zr ₂ 0i ₂ on. The BET surface area is 7.3 m ² / g. The d ₅₀ value is 2.28 μιη, the dio value 0.33 μιη and the d ₉₀ value 7.25 μιη. The X-ray diffractogram shows the reflexes of a tetragonal and a cubic

Garnet structure.

Mixed Oxide Powder B: In a rotary kiln, the mixed oxide powder A is thermally treated at a temperature of 800 ° C for a period of 8 hours. The mixed oxide powder B has a BET surface area of 2.3 m ² / g and a solids density of 4.872 g / cm ³ , corresponding to 95.5% of the theoretical solids density of cubic Li ₇ La ₃ Zr ₂ 0i ₂ -Das

X-ray diffractogram shows the reflexes of a tetragonal and a cubic

Garnet structure.

Examples 2 to 6 are carried out analogously. Starting materials, reaction conditions and the material properties of the resulting mixed oxide powders are shown in Tables 1 and 2

played.

The calculated composition of the mixed oxides from Examples 1 to 4 is Li ₇ La ₃ Zr ₂ O ₂ , that of the mixed oxide powder from Example 5

and the mixed oxide powder of Example 6

Used solutions

Solution 7: 5.21% by weight of lithium nitrate, 15.58% by weight of lanthanum nitrate, 10.30% by weight of zirconium nitrate,

1, 31 wt .-% aluminum nitrate, balance water. Concentration on the

Oxide Li ₆ , 3La 3 Zr ₂ Alo, 290i 2 is 10.13 wt .-%.

Solution 8: 4.93% by weight of lithium nitrate, 15.62% by weight of lanthanum nitrate, 10.32% by weight of zirconium nitrate,

1, 58 wt .-% aluminum nitrate, balance water. Concentration on the

Oxide Li _5i 95La3Zr2Alo, 350i2 is 10, 15 wt .-%.

Solution 9: 5.40% by weight of lithium nitrate, 15.68% by weight of lanthanum nitrate, 10.36% by weight of zirconium nitrate,

0.77 wt .-% aluminum nitrate, balance water. The concentration based on the oxide Li _6i 49La ₃ Zr2Alo, i70i2 is 10.17 wt .-%.

Solution 10: 5.21% by weight of lithium nitrate, 15.66% by weight of lanthanum nitrate, 10.35% by weight of zirconium nitrate,

1, 09 wt .-% aluminum nitrate, balance water. Concentration on the

Oxide Li ₆ , 27La3Zr ₂ Alo, 240i2 is 10.26 wt .-%.

Example 7:

Mixed oxide powder A: 8000 g / h of the solution 7 are atomized with a Zerstäubergas consisting of 15 Nm ³ / h of air and 0.05 kg ammonia gas / Nm ³ air by means of a two-fluid nozzle in a burning in a reaction chamber flame. The average droplet diameter is 91, 76 μιη. The flame is formed by the reaction of 12 Nm ³ / h of hydrogen, 70 Nm ³ / h of air and 20 NnrVh of secondary air. Lambda is 3.68. The average residence time in the reaction space is 0.69 s. the average velocity in the reaction space is 5.8 Nm / s. After cooling, the mixed oxide powder A is separated on a filter of gaseous substances.

The mixed oxide _powder A has a composition Li _6i 3La ₃ Zr2Alo, 290i2. The BET surface area is 3.7 m ² / g. The d ₅₀ value is 2.76 μιη, the d ₁₀ value 0.33 μιη and the d ₉₀ - value 7.30 μιη. Mixed oxide powder B:

In a rotary kiln, the mixed oxide powder A is thermally treated at a temperature of 1000 ° C over a period of 12 hours.

The mixed oxide _powder B has a composition Li _6i 3La ₃ Zr 2 Al 2 O, 290i 2 has a BET surface area of 0.30 m ² / g and a density of 4.881 g / cm ³ , corresponding to 95.7% of the theoretical density. The X-ray diffractogram shows the signals of a cubic garnet.

Examples 8 to 10 are carried out analogously. Starting materials, reaction conditions and the material properties of the resulting mixed oxide powders are reproduced in Tables 3 and 4.

Table 1: Mixed oxide A

1) v _R = avg. Speed in the reactor; 2) t _R = average residence time in the reactor; 3) k = cubic, t = tetragonal

Table 2: Mixed oxide B

1) M = muffle; D = rotary tube; 2) argon; 1001 / h; 3) 200 mbar Table 3: Mixed oxides A Li _x La ₃ Zr ₂ Al _y 08.5 ₊ o, 5x + i, 5y with 6 <x <7, 0.2 <y <0.5

1) med. Speed in the reactor; 2) average residence time in the reactor; 3) k = cubic a) Li _6i 3 La 3 _Zr 2 Al, 290 ₁₂ ; b)

Table 4: Mixed oxide B Li _x La ₃ Zr ₂ Al _y O _8i 5 ₊ o, 5x ₊ i, 5y with 6

Example 7a 7b 8a 8b 9a 9b

Oven temperature ° C 1000 800 1000 800 10.00 800

Tempering time h 12 6 12 6 12 6

BET surface area m ² / g 0.30 0.84 0.43 0.96 0.50 0.80

XRD phase k k K k k k

Solid density g / cm ³ 4,881 4,899 4,929 4,900 4,900 4,905

Solid density / Theor. % 95.7 96.0 96.6 96.07 96.07 96.17 Solid density

Claims

claims

A process for producing a composite oxide powder of the composition

Li _x La ₃ Zr ₂ M _y 08.5 ₊ o, 5x ₊ z with

6.5 <x <8,

0 <y <0.5,

z = 2y for M = Hf, Ga, Ge, Nb, Si, Sn, Sr, Ta and Ti

z = 1.5y for M = Al, Sc, V and Y,

z = y for M = Ba, Ca, Mg, and Zn, where

for M = Al it holds that 6 <x <7 and 0.2 <y <0.5,

in which one or more solutions containing in each case one or more compounds of lithium, lanthanum and zirconium and optionally

Metal compounds MX in a concentration corresponding to the stoichiometry and in the form of fine droplets in a burning in a reaction chamber flame, which is formed by introducing an oxygen-containing gas and in the reaction with oxygen water forming fuel gas into the reaction chamber and there ignites and subsequently separates the solid from vapor or gaseous substances.

2. The method according to claim 1, characterized in that

the mean droplet size is 1 to 120 μιη.

3. Process according to claims 1 or 2, characterized in that

the metal compounds of lithium, lanthanum, zirconium and M are used as nitrates.

4. Process according to claims 1 to 3, characterized in that

aqueous solutions are used.

5. Process according to claims 1 to 4, characterized in that

the concentration of the solution is 1 to 50% by weight, based on the sum of the oxides.

6. Process according to claims 1 to 5, characterized in that

Lambda, defined as the ratio of oxygen present from the air used / combustion of the fuel gas necessary oxygen, is 1, 5 to 6.0,

7. Process according to claims 1 to 6, characterized in that

Ammonia and / or an ammonia-forming substance in the reaction chamber brings.

8. The method according to claim 7, characterized in that

Ammonia gas in a concentration of 0.01 - 1 kg / Nm ³ nebulizer gas or

0.001-0.05 kg / Nm ³ (fuel gas + oxygen-containing gas) into the flame.

9. Process according to claims 1 to 8, characterized in that the mean residence time of the reaction mixture in the reaction space is 0.25 to 2.5 seconds.

10. The method according to claims 1 to 9, characterized in that

the average velocity in the reaction space is 1 - 20 Nm / s.

1 1. Mixed oxide powder of composition Li _x La ₃ Zr ₂ M _y 08.5 ₊ o, 5x + z with

6.5 <x <8, 0 <y <0.5;

z = 2y for M = Hf, Ga, Ge, Nb, Si, Sn, Sr, Ta and Ti

z = 1.5y for M = Al, Sc, V and Y, where for M = Al it holds that 6 <x <7 and 0.2 <y <0.5 z = y for M = Ba, Ca Mg, and Zn

characterized in that

it has a BET surface area of 3 to 20 m ² / g and a d ₅₀ value of less than or equal to 5 μm.

12. A process for producing a mixed oxide powder of the general Li _x La ₃ Zr ₂ M _y O _8i 5 ₊ o, 5x + z with 6.5 <x <8, 0 <y <0.5,

z = 2y for M = Hf, Ga, Ge, Nb, Si, Sn, Sr, Ta and Ti

z = 1.5y for M = Al, Sc, V and Y, where for M = Al it holds that 6 <x <7 and 0.2 <y <0.5 z = y for M = Ba, Ca, Mg, and Zn, with

a) garnet crystal structure,

b) a BET surface area of <3 m ² / g and

c) at least 75% of the theoretical solids density of cubic Li ₇ La ₃ Zr ₂ Oi ₂ , for M =

AI and 6 <x <7 and 0.2 <y <0.5 at least 95% of the theoretical density, characterized

that the mixed oxide obtainable by the process according to claims 1 to 10 or the mixed oxide according to claim 1 1 at temperatures of 700 to 1200 ° C over a period of 3 to 24 hours thermally treated.

13. A process for producing a composite oxide powder of the composition

Li _x La3Zr2M _y 08.5 + o, 5x + z

with 6.5 <x <8, 0 <y <0.5,

z = 2y for M = Hf, Ga, Ge, Nb, Si, Sn, Sr, Ta and Ti

z = 1.5y for M = Al, Sc, V and Y, where for M = Al it holds that 6 <x <7 and 0.2 <y <0.5, z = y for M = Ba, Ca, Mg, and Zn with

a) garnet crystal structure,

b) a BET surface area of <3 m ² / g and

c) at least 75% of the theoretical solids density of cubic Li ₇ La ₃ Zr ₂ 0i2 _, for M = Al and 6 <x <7 and 0.2 <y <0.5 at least 95% of the theoretical density, wherein a solution containing in each case one or more compounds of lithium, lanthanum and zirconium and optionally metal compounds M in one Concentration according to the stoichiometry and in the form of fine droplets in a burning in a reaction chamber flame, which is formed by introducing an oxygen-containing gas and an oxygen in the reaction with oxygen forming fuel gas into the reaction space and ignites there, and subsequently the solid from separates off steam or gaseous substances and

thermally treated at temperatures of 700 to 1200 ° C over a period of 3 to 24 hours.

14. Use of the mixed oxide powder according to claim 1 1 or the mixed oxide powder prepared by the process according to claims 12 or 13 as a solid electrolyte in lithium-ion batteries.