SOLID-STATE LITHIUM-ION CONDUCTOR MATERIALS, POWDER MADE OF SOLID-STATE ION CONDUCTOR MATERIALS, AND METHOD FOR PRODUCING SAME

Abstract

A powder with particulates of a lithium ion-conducting material has a conductivity of at least 10.sup.−5 S/cm. The powder has an inorganic carbon content (Total Inorganic Carbon Content (TIC)) of less than 0.4 wt % and/or an organic carbon content (Total Organic Carbon Content (TOC)) of less than 0.1 wt %. The particulates have a d50 particle size in a range from 0.05 μm to 10 μm. The particulates have a particle size distribution log (d90/d10) of less than 4.

Claims

1. A powder with particulates of a lithium ion-conducting material having a conductivity of at least 10.sup.−5 S/cm, wherein the powder has an inorganic carbon content (Total Inorganic Carbon Content (TIC)) of less than 0.4 wt % and/or an organic carbon content (Total Organic Carbon Content (TOC)) of less than 0.1 wt %, wherein particulates have a d50 particle size in a range from 0.05 μm to 10 μm, and wherein the particulates have a particle size distribution log (d90/d10) of less than 4.

2. The powder as claimed in claim 1, wherein the powder comprises Li.sub.2O, and wherein the inorganic carbon content (in wt %) is in a ratio to the Li.sub.2O content (in mol %) that is less than 80 ppm/mol % and/or the organic carbon content (in wt %) is in a ratio to the Li.sub.2O content (in mol %) that is less than 20 ppm/mol %.

3. The powder as claimed in claim 1, wherein the powder has a specific surface area of at least 0.05 m.sup.2/g.

4. The powder as claimed in claim 1, wherein the powder has a water content of at most 5 wt %.

5. The powder as claimed in claim 1, wherein the lithium ion-conducting material comprises an oxidic material.

6. The powder as claimed in claim 1, wherein the lithium ion-conducting material comprises lithium lanthanum zirconate (LLZO), NaSICon, garnet-like crystal phases and/or lithium aluminum titanium phosphate (LATP).

7. A lithium-ion conductor comprising: a powder with particulates of a lithium ion-conducting material having a conductivity of at least 10.sup.−5 S/cm, wherein the powder has an inorganic carbon content (Total Inorganic Carbon Content (TIC)) of less than 0.4 wt % and/or an organic carbon content (Total Organic Carbon Content (TOC)) of less than 0.1 wt %, wherein particulates have a d50 particle size in a range from 0.05 μm to 10 μm, and wherein the particulates have a particle size distribution log (d90/d10) of less than 4.

8. A method for lithium-ion conduction, the method comprising: a) providing a lithium-ion conductor comprising: a powder with particulates of a lithium ion-conducting material having a conductivity of at least 10-5 S/cm, wherein the powder has an inorganic carbon content (Total Inorganic Carbon Content (TIC)) of less than 0.4 wt % and/or an organic carbon content (Total Organic Carbon Content (TOC)) of less than 0.1 wt %, wherein particulates have a d50 particle size in a range from 0.05 μm to 10 μm, and wherein the particulates have a particle size distribution log (d90/d10) of less than 4, and b) inserting the lithium-ion conductor in a separator, an anode, a cathode, a primary battery and/or a secondary cell.

9. A method for producing a powder with particulates of a lithium ion-conducting material having a conductivity of at least 10.sup.−5 S/cm, wherein the powder has an inorganic carbon content (Total Inorganic Carbon Content (TIC)) of less than 0.4 wt % and/or an organic carbon content (Total Organic Carbon Content (TOC)) of less than 0.1 wt %, wherein particulates have a d50 particle size in a range from 0.05 μm to 10 μm, and wherein the particulates have a particle size distribution log (d90/d10) of less than 4a powder as claimed in claim 1, the method comprising: a) providing a crude product by means of a hot operation which comprises temperatures of at least 900° C., and b) comminuting the crude product with exclusion of CO.sub.2 sources and/or with exclusion of organic carbon sources.

10. The method as claimed in claim 9, wherein the hot operation is selected from the group consisting of (i) melt, (ii) reactive sintering, (iii) calcining of sol-gel precursors, and (iv) bottom-up synthesis in a pulsation reactor.

11. The method as claimed in claim 9, wherein b) comprises one or more of: b1) comminution by a hammer and chisel, b2) comminution by jaw crusher, ball mills and/or hammer mills, b3) comminution by ball, impact and/or planetary mills, b4) comminution by opposed-jet mills operated with process gases or steam, dry and/or wet ball mills, dry and/or wet agitator ball mills and/or by high-energy grinding in high-kinetic-energy rotor ball mills.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0096] FIG. 1 shows the results of the temperature-fractionated carbon phase analysis according to DIN 19539 of comparative example 7. The temperature profile employed in the analysis is represented as a solid line and is based on the right-hand y-axis. The TIC content is shown as a shaded area with dash outlining, and relates to the left-hand y-axis. The x-axis shows the time in seconds.

[0097] FIG. 2 shows the results of the temperature-fractionated carbon phase analysis according to DIN 19539 of the inventive working example 3. The temperature profile employed in the analysis is represented as a solid line and is based on the right-hand y-axis. The TIC content is shown as a shaded area with dash outlining, and relates to the left-hand y-axis. The x-axis shows the time in seconds.

[0098] FIG. 3 shows the results of the temperature-fractionated carbon phase analysis according to DIN 19539 of comparative example 9. The temperature profile employed in the analysis is represented as a solid line and is based on the right-hand y-axis. The TOC content is shown as a shaded area with dash outlining, and relates to the left-hand y-axis. The x-axis shows the time in seconds.

DETAILED DESCRIPTION OF THE DISCLOSURE

Working Examples of the Disclosure

[0099] 1 Carbonate-Free LLZO Powder Produced Via a Melting Operation Using Li.sub.2CO.sub.3 as Raw Material

[0100] Carbonate-free LLZO powder can be melted as described below using Li.sub.2CO.sub.3 as raw material: the crucible used is what is called a skull crucible, as described for instance in DE 199 39 782 C1. The skull technology uses a water-cooled crucible in which in the course of the melting a cooler protective layer is formed from the material to be melted. Accordingly no crucible material is dissolved during the melting procedure. The input of energy into the melt is realized by means of a radiofrequency incoupling via the surrounding induction coil into the liquid-melt material. A condition here is the sufficient conductivity of the melt, this being provided in the case of lithium garnet melts by the high lithium content. During the melting-in procedure, there is evaporation of lithium, which can easily be corrected by a lithium excess. For this purpose it is normal to operate with a slight lithium excess.

[0101] In the example the batch used comprised La.sub.2O.sub.3, Li.sub.2CO.sub.3, Nb.sub.2O.sub.5 and ZrO.sub.2, for the production of an Nb-doped lithium lanthanum zirconate having a nominal composition of Li.sub.7+xLa.sub.3Zr.sub.1.5Nb.sub.0.5O.sub.12. The raw materials were mixed in accordance with the composition and introduced into the skull crucible, which was open at the top. The batch had first to be preheated in order to attain a certain minimum conductivity. This was done using a burner heating system. When the coupling temperature was reached, the further heating and homogenization of the melt was achieved through radiofrequency incoupling via the induction coil. To improve the homogenization of the melts, stirring took place with a water-cooled stirrer. Following complete homogenization, direct samples were taken from the melt, while the rest of the melt was cooled more slowly by the switching-off of the radiofrequency. The material produced in this way may be converted in principle into a glass-ceramic material with garnet-like main crystal phase, either by direct solidification from the melt or by quenching followed by a temperature treatment (ceramicization).

[0102] Independently of the cooling, the samples taken directly from the melt showed spontaneous crystallization, and so there was no need for a downstream ceramicization treatment.

[0103] Comminution may be carried out for example as in one of examples 2 to 4.

[0104] 2. Carbonate- and Organic-Free LLZO Powder as Solid-State Lithium-Ion Conductor Produced by Wet Grinding in Water with Subsequent Freeze Drying and Temperature Treatment at 700° C. Under Reduced Pressure

[0105] 1 kg of coarsely fractionated lithium lanthanum zirconium oxide powder with a grain size <63 μm are dispersed in 2.33 L of water, as far as possible free from agglomerates, using a dissolver. The suspension is subsequently introduced into the initial-charge container of an agitator ball mill and is ground for 2.5 h using a grinding chamber with pin-type mill agitator, employing the multiple-passage mode. This grinding chamber is filled with grinding beads consisting of ZrO.sub.2 (fill level: 74%) which have a diameter of around 1 mm. Grinding is ended when 50% of the particulates present in the grinding slip have a diameter of approximately 0.78 μm, 90% have a diameter of around 1.63 μm and 99% have a diameter of around 2.71 μm. The particulate sizes are measured using the static light scattering method on a CILAS model 1064 particulate size measuring instrument. The measurement is carried out in water (refractive index: 1.33) as medium and evaluated according to the Mie method (Re=1.8, Im=0.8).

[0106] After the grinding, the grinding slip is subjected to drying in a freeze dryer. For this purpose it is first poured extensively into product trays intended for the purpose, and then frozen under reduced pressure at 0.5 to 1.0 bar and a temperature of −30° C. By subsequent successive heating of the product tray bases, the frozen water is removed from the solid slip residue gently by sublimation gradually, in a period of around 20 h. By means of the temperature-fractionated carbon phase analysis according to DIN 19539, the total of the TOC content and TIC content of the LLZO powder wet-ground in water is determined to be 0.4%, with the carbon detected consisting predominantly of inorganic carbon. The water content is determined to be 25%. The total carbon content in this case matches the sum of TOC content and TIC content, since there is no EC (elemental carbon) contribution.

[0107] In order to reduce the loading with water and particularly CO.sub.2, the LLZO powder, immediately after freeze drying, is introduced directly into a Nabertherm model N20/H oven, traversed by a flow of nitrogen gas, and is baked at 700° C. for 4 h.

[0108] After the baking, the LLZO powder is taken from the cooled oven, traversed by a flow of nitrogen gas, and is vacuum-packed directly into pouches consisting of metallized polyethylene.

[0109] With the aid of the temperature-fractionated carbon phase analysis according to DIN 19539, the TIC content of the LLZO powder wet-ground in water and baked, after freeze drying, under reduced pressure at 700° C. for 4 h is determined to be 0.09%, the water content to be 0.8%. The total carbon content in this case matches the TIC, since there are no TOC and EC contributions.

[0110] 3. Carbonate- and Organic-Free LLZO Powder as Solid-State Lithium-Ion Conductor Produced by Dry Grinding on an Opposed-Jet Mill Using Nitrogen as Process Gas

[0111] 5 kg of coarsely fractionated lithium lanthanum zirconium oxide powder with a grain size <1 mm are applied to an opposed-jet mill. The jet milling takes place through a ceramic die using nitrogen gas as grinding medium with a pressurization of 6 bar. With the downstream classifier, a powder fraction is obtained which, following further removal of fines in a cyclone, has a particulate size distribution with a d.sub.50=2.0 μm, d.sub.90=5.9 μm and d.sub.99=6.7 μm.

[0112] With the aid of the temperature-fractionated carbon phase analysis according to DIN 19539, the TIC content of the LLZO powder comminuted on the opposed-jet mill using nitrogen as process gas is determined to be 0.04%, the water content to be 0.4%. The total carbon content in this case too matches the TIC, since there are no TOC and EC contributions. The results of the determination of the TIC content are shown in FIG. 2.

[0113] 4. Carbonate- and Organic-Free LATP Powder as Solid-State Lithium-Ion Conductor Produced by Dry Grinding on a Ball Mill Using Nitrogen as Process Gas

[0114] For the comminution of lithium aluminum titanium phosphate in a ball milling operation, 160 g of the solid-state ion conductor material are charged together with 2.16 kg of cylindrical grinding media—Al.sub.2O.sub.3Cylpebs Ø=21 mm, H=21 mm—into a gastight 3.6 L polyethylene drum (Ø=198 mm, H=171 mm) and rotated on a roller bed (rotation frequency: 140 rpm) for 5 h at a rotational velocity of 1.45 m/s. The charging of the drum and the subsequent sample preparation are carried out under nitrogen gas atmosphere in a portable glovebox, in order to prevent the material becoming loaded with water and CO.sub.2 from the standard air atmosphere.

[0115] The grindstock was subsequently separated from the grinding media by sieving in a portable glovebox of brand Captair® Pyramid under nitrogen gas atmosphere with a humidity <2% and was vacuum-packed directly into pouches consisting of metallized polyethylene.

[0116] With the aid of the temperature-fractionated carbon phase analysis according to DIN 19539, the TIC content of the LLZO powder comminuted on the ball mill using nitrogen as process gas is determined to be 0.03%, the water content to be 0.1%. In this case as well, total carbon content and TIC are again identical. No TOC and EC contributions can be detected.

[0117] 5. Carbonate- and Organic-Free LLZO Powder as Solid-State Lithium-Ion Conductor Produced in a Pulsating Stream of Hot Gas Generated from an Oxyhydrogen Flame

[0118] 1.56 kg (4.7 mol) of zirconium carbonate hydrate were dissolved in at least 10.0 kg of 2.7 M nitric acid in a suitable reaction vessel. 3.83 kg (7 mol) of lanthanum carbonate hydrate were dissolved in 10 kg of 2.7 M nitric acid in a further reaction vessel. 1.33 kg (18 mol) of lithium carbonate and 0.22 kg (0.58 mol) of aluminum nitrate nonahydrate were dissolved in 5.0 kg of 2.7 M nitric acid in a third reaction vessel. Following complete dissolution of the components, the solutions were combined and the resultant reaction mixture was stirred at room temperature for 12 hours. By means of a peristaltic pump, the solution is conveyed into a pulsating stream of hot gas with a volume flow rate of 3 kg/h, where it is finely atomized via a 1.8 mm titanium nozzle into the reactor interior, where it is thermally treated. Generated in the combustion chamber for this purpose is an oscillating oxyhydrogen flame which has a slightly oxidizing character (ratio: H.sub.2/O.sub.2 volume flow=1.85/1). The temperature of the resonance tube is held at 825° C.

[0119] The predominantly amorphous, pulverulent intermediate generated in the pulsating stream of hot gas is introduced into a cuboidal alpha-alumina crucible, which is placed into a chamber kiln. In the kiln, the calcining material is brought to a temperature of 1050° C. in a CO.sub.2-free oxygen atmosphere for complete conversion into the desired crystalline LLZO phase.

[0120] By means of the temperature-fractionated carbon phase analysis according to DIN 19539, the TIC content of the LLZO powder produced in the pulsating stream of hot gas, the stream of hot gas being generated in turn using an oxyhydrogen flame, is determined to be 0.06%, the water content to be 0.9%. Here again, total carbon content and TIC content are identical.

[0121] 6. Carbonate-Free LLZO Powder as Solid-State Lithium-Ion Conductor Produced Via a Sol-Gel Reaction with Subsequent Calcining of the Resultant Intermediate Using CO.sub.2-Free Synthetic Air

[0122] To produce an aqueous sol-gel precursor, 22.9 g (0.047 mol) of zirconium acetylacetonate are dissolved in at least 100 mL (5.56 mol) of distilled water. In parallel with this, 24.0 g (0.07 mol) of lanthanum acetate sesquihydrate are dissolved in 100 mL (5.56 mol) of distilled water in a further reaction vessel. Furthermore, in a third reaction vessel, 18.4 g (0.18 mol) of lithium acetate dihydrate and 1.4 g (0.0058 mol) of aluminum chloride hexahydrate are dissolved in 50 mL (2.78 mol) of distilled water.

[0123] Finally all three of the stated solutions are combined and the resultant reaction mixture is stirred at room temperature for 12 hours.

[0124] The solvent is removed preferably with a rotary evaporator. The precursor can be concentrated rapidly at a water bath temperature of 90° C. with continuous pressure reduction.

[0125] To obtain a crystalline, ion-conducting powder, the intermediate obtained (precursor powder or resin) is calcined in a crucible in a radiation kiln. To obtain a cubic modification, temperatures in this case of at least 1000° C. and a hold time of more than 5 hours are advantageous. 1000° C. and 7 hours may be stated as optimum temperature-time conditions. During the calcining, all of the carbonate constituents which are introduced with the precursor compound and/or which form in the solution and also in the dried precursors and/or which form on an intermediate basis in the initial stage of the calcining are decomposed, owing to the action of the temperature. In order to ensure complete, residue-free combustion of the organic constituents present in the precursors, but at the same time to avoid the fully calcined material becoming reloaded with water and in particular CO.sub.2 from the atmosphere, the kiln is charged with CO.sub.2-free, synthetic air during the calcining.

[0126] By means of the temperature-fractionated carbon phase analysis according to DIN 19539, the TIC content of the LLZO powder produced via the sol-gel route and calcined using synthetic air is determined to be 0.08%, the water content to be 1.4%. Here again the following applies: total carbon content=TIC content.

[0127] Non-Inventive, Comparative Examples

[0128] Carbonate-Containing LLZO Powder as Solid-State Lithium-Ion Conductor Produced by Wet Grinding in Isopropanol with Subsequent Drying in a Rotary Evaporator and Temperature Treatment at 700° C. in Ambient Air

[0129] 1 kg of coarsely fractionated lithium lanthanum zirconium oxide powder with a grain size <63 μm are dispersed in 2.33 L of isopropanol, as far as possible free from agglomerates, using a dissolver. The suspension is subsequently introduced into the initial-charge container of an agitator ball mill and is ground for 2.5 h using a grinding chamber with pin-type mill agitator, employing the multiple-passage mode. This grinding chamber is filled with grinding beads consisting of ZrO.sub.2 (fill level: 74%) which have a diameter of around 1 mm. Grinding is ended when 50% of the particulates present in the grinding slip have a diameter of approximately 1.64 μm, 90% have a diameter of around 5.01 μm and 99% have a diameter of around 7.83 μm. The particulate sizes are measured using the static light scattering method on a CILAS model 1064 particulate size measuring instrument. The measurement is carried out in isopropanol (refractive index: 1.33) as medium and evaluated according to the Fraunhofer method.

[0130] After the grinding, the grinding slip is subjected to drying on a rotary evaporator. For this purpose it is first transferred into a 20 L round-bottom flask. The isopropanol is subsequently distilled off over a period of 10 to 15 h under reduced pressure, at pressures of 25 to 50 mbar, by rotating the flask, immersed into a heated water bath, with a rotation frequency, where the temperature of the water bath is 55 to 60° C.

[0131] The powder dried on the rotary evaporator is subsequently introduced into a Nabertherm model N20/H oven operated under ambient air, and is baked in an air atmosphere at 700° C. for 4 h, and after the temperature treatment is allowed to cool to room temperature.

[0132] By means of the temperature-fractionated carbon phase analysis according to DIN 19539, the TIC content of the LLZO powder, ground in isopropanol in an agitator ball mill and conditioned in air at 700° C. for 4 h, is determined to be 0.4%. In the course of the temperature treatment at 700° C. for 4 h, organic residues (TOC) bound on the particulate surfaces after the grinding are decomposed thermally into CO.sub.2 and water. By reaction with the solid-state ion conductor material, the CO.sub.2 is converted into carbonate and is detected as TIC in the carbon phase analysis. TOC and EC contributions are no longer detectable here. The results are shown in FIG. 1. The carbon here is liberated in relevant amounts only at temperatures above 800° C., meaning that it is what is called inorganic carbon which comes from a carbonate compound. The water content of the material is around 5%.

[0133] 8. Carbonate-Containing LLZO Powder as Solid-State Lithium-Ion Conductor Produced by Dry Grinding on an Opposed-Jet Mill Using Compressed Air as Process Gas

[0134] 5 kg of coarsely fractionated lithium lanthanum zirconium oxide powder with a grain size <1 mm are applied to an AFG100 opposed-jet mill module which is installed on a multi-process unit from Hosokawa-Alpine. The jet milling takes place through a ceramic die with 1.9 mm diameter using compressed air as grinding medium with a pressurization of 6 bar. With the downstream classifier, which rotates with a rotation frequency of 10 000 rpm, a powder fraction is obtained which, following further removal of fines in a cyclone, has a particulate size distribution with a d.sub.50=2.5 μm, d.sub.90=6.7 μm and d.sub.99=7.9 μm.

[0135] With the aid of the temperature-fractionated carbon phase analysis according to DIN 19539, the TIC content of the LLZO powder comminuted on the opposed-jet mill using compressed air as process gas is determined to be 0.83%, the water content to be 2.8%. Where grinding is carried out in the manner described, the CO.sub.2 from the air used as process gas reacts with the solid-state ion conductor material to form carbonate, and is detected again as TIC content in the downstream carbon phase analysis. In this case again, TOC and EC contributions are not detectable.

[0136] 9. LATP Powder, Carrying Organic Residues, as Solid-State Lithium-Ion Conductor Produced by Wet Grinding in Isopropanol with Subsequent Drying in a Rotary Evaporator

[0137] 1 kg of a lithium aluminum titanium phosphate powder, coarsely ground in a planetary mill, with a grain size <63 μm is dispersed in 2.33 L of isopropanol, as far as possible free from agglomerates, using a dissolver. The suspension is subsequently introduced into the initial-charge container of an agitator ball mill and is ground for 30 min using a grinding chamber with pin-type mill agitator, employing the multiple-passage mode. This grinding chamber is filled with grinding beads consisting of ZrO.sub.2 (fill level: 74%) which have a diameter of around 1 mm. Grinding is ended when 50% of the particulates present in the grinding slip have a diameter of approximately 1.03 μm, 90% have a diameter of around 2.44 μm and 99% have a diameter of around 3.78 μm. The particulate sizes are measured using the static light scattering method on a CILAS model 1064 particulate size measuring instrument. The measurement is carried out in water as medium and evaluated according to the Fraunhofer method.

[0138] After the grinding, the grinding slip is subjected to drying on a rotary evaporator. For this purpose it is first transferred into a 20 L round-bottom flask. The isopropanol is subsequently distilled off over a period of 10 to 15 h under reduced pressure, at pressures of 25 to 50 mbar, by rotating the flask, immersed into a heated water bath, with a rotation frequency, where the temperature of the water bath is 55 to 60° C.

[0139] By means of the temperature-fractionated carbon phase analysis according to DIN 19539, the TOC content of the LATP powder, milled in isopropanol in an agitator ball mill and dried on a rotary evaporator, is determined to be 0.14%. TIC and EC contributions are not detectable here, meaning that in this case the total carbon content is identical to the TOC content. The results are shown in FIG. 3. The water content of the material is around 0.7%.