NEW LITHIUM RARE-EARTH HALIDES

Abstract

The present invention concerns new lithium rare earth halides that may be used as solid electrolytes or in electrochemical devices. The invention also refers to wet and dry processes for the synthesis of such lithium rare earth halides and lithium rare earth halides susceptible to be obtained by these processes.

Claims

1. A solid material according to general formula (I) as follows:
Li.sub.6-3x-4y RE.sub.xT.sub.yX.sub.6  (I) wherein: X is a halogen; 0<x+(4/3) y<2; 0≤y≤0.8; RE denotes two or more rare earth metals; the rare earth metals are different from each other; and T is Zr or Hf; with the proviso that when y=0 and RE denotes two rare earth metals then when one rare earth metal is Y, the other one is selected from the group consisting of Gd, Yb, Ho, Er, Dy, Ce, Tb and Nd.

2. The solid material according to claim 1 wherein the solid material is any one of the compounds of formulas (II) to (V) as follows:
Li.sub.6-3x-4y RE1.sub.a RE2.sub.bT.sub.yX.sub.6  (II) wherein a+b=x, with 0.05≤a≤0.95 and 0.0<b≤0.95; and when y=0 and RE1 is Y, RE2 is selected from the group consisting of Gd, Yb, Ho, Er, Dy, Ce, Tb and Nd;
Li.sub.6-3x-4y RE1.sub.a RE2.sub.b RE3.sub.cT.sub.yX.sub.6  (III) wherein a+b+c=x, with 0.05≤a≤0.95, 0.0<b≤0.95 and 0.0<c≤0.95 with 0.05≤b+c;
Li.sub.6-3x-4y RE1.sub.a RE2.sub.b RE3.sub.c RE4.sub.dT.sub.yX.sub.6  (IV) wherein a+b+c+d=x, with 0.05≤a≤0.95, 0.0<b≤0.95, 0.0<c≤0.95 and 0.0<d≤0.95 with 0.05<b+c+d;
Li.sub.6-3x-4y RE1.sub.a RE2.sub.b RE3.sub.c RE4.sub.d RE5.sub.cT.sub.yX.sub.6  (V) wherein a+b+c+d+e=x, with 0.05≤a≤0.95, 0.0<b≤0.95, 0.0<c≤0.95, 0.0<d≤0.95 and 0.0<e≤0.95, with 0.05≤b+c+d+e; and X is a halogen; 0<x+(4/3)y<2; 0≤y≤0.8; RE1 is selected from the group consisting of: Y, Yb, Ho, and Er; RE2 is selected from the group consisting of: Yb, Ho, Gd, Er, Sm, Dy, La, Nd, Ce, and Tb; RE3 is selected from the group consisting of: Ho, Gd, Er, Sm, Dy La, Nd, Ce, and Tb; RE4 is selected from the group consisting of: Er, Gd Sm, Dy La, Nd, Ce, and Tb; and RE5 is selected from the group consisting of: Gd Sm, Dy La, Nd, Ce, and Tb; where RE1, RE2, R3, R4 and RE5 are different; and T is Zr or Hf,

3. The solid material according to claim 1 wherein the mean ionic radius of RE exhibits an ionic radius value (in Å) lower than 0.938 Å.

4. (canceled)

5. (canceled)

6. The solid material according to claim 1 wherein y=0.

7. The solid material according to claim 1 wherein it is selected from the group consisting of Li.sub.3Y.sub.0.9Gd.sub.0.1Cl.sub.6; Li.sub.3Y.sub.0.3Er.sub.0.3Yb.sub.0.3Gd.sub.0.1Cl.sub.6, Li.sub.2.7Y.sub.1Gd.sub.0.1Cl.sub.6; Li.sub.3Y.sub.0.5Er.sub.0.5Cl.sub.6; Li.sub.3Y.sub.0.45Er.sub.0.45 Gd.sub.0.1 Cl.sub.6; and Li.sub.3Y.sub.0.45Er.sub.0.45La.sub.0.1Cl.sub.6.

8. The solid material according to claim 1 wherein it comprises a fraction consisting of glass phases.

9. The solid material according to claim 1 wherein it is in powder form with a distribution of particle diameters having a D50 comprised between 0.05 μm and 10 μm.

10. (canceled)

11. A process for the preparation of a solid material according to claim 1 comprising the steps of: a) obtaining a composition by admixing stoichiometric amounts of a lithium halide, at least two different rare-earth metal halides, in such halides the rare-earth metal are different from each other and optionally zirconium or hafnium halide, optionally in one or more solvents, under an inert atmosphere; b) applying a mechanical treatment to the composition obtained in step a) in order to obtain the solid material; and c) optionally removing at least a portion of the one or more solvents from the composition obtained on step b), so that to obtain the solid material.

12. A process for the preparation of a solid material according to general formula (I) as follows:
Li.sub.6-3x-4y RE.sub.xT.sub.yX.sub.6  (I) wherein: X is a halogen; 0<x+(4/3)y<2; 0≤y≤0.8; RE denotes one or more rare earth metals; the rare earth metals are different from each other; and T is Zr or Hf; said process comprising the steps of: a) obtaining a composition by admixing stoichiometric amounts of a lithium halide, at least one rare earth metal halide and optionally zirconium or hafnium halide, in one or more solvents, under an inert atmosphere; b) applying a mechanical treatment to the composition obtained in step a) in order to obtain the solid material; and c) removing at least a portion of the one or more solvents from the composition obtained on step b), so that to obtain the solid material.

13. The process according to claim 12 wherein the solid material is any one of the compounds of formulas (II) to (V) as follows:
Li.sub.6-3x-4y RE1.sub.a RE2.sub.bT.sub.yX.sub.6  (II) wherein a+b=x, with 0.05≤a≤0.95 and 0.0<b≤0.95;
Li.sub.6-3x-4y RE1.sub.a RE2.sub.b RE3.sub.cT.sub.yX.sub.6  (III) wherein a+b+c=x, with 0.05≤a≤0.95, 0.0<b≤0.95 and 0.0<c≤0.95 with 0.05≤b+c;
Li.sub.6-3x-4y RE1.sub.a RE2.sub.b RE3.sub.c RE4.sub.dT.sub.yX.sub.6  (IV) wherein a+b+c+d=x, with 0.05≤a≤0.95, 0.0<b≤0.95, 0.0<c≤0.95 and 0.0<d≤0.95 with 0.05≤b+c+d;
Li.sub.6-3x-4y RE1.sub.a RE2.sub.b RE3.sub.c RE4.sub.d RE5.sub.cT.sub.yX.sub.6  (V) wherein a+b+c+d+e=x, with 0.05≤a≤0.95, 0.0<b≤0.95, 0.0<c≤0.95, 0.0<d≤0.95 and 0.0<e≤0.95, with 0.05≤b+c+d+e; and wherein X is a halogen, 0<x+(4/3)y<2; 0≤y≤0.8; RE1 is selected from the group consisting of: Y, Yb, Ho, and Er; RE2 is selected from the group consisting of: Yb, Ho, Gd, Er, Sm, Dy, La, Nd, Ce, and Tb; RE3 is selected from the group consisting of: Ho, Gd, Er, Sm, Dy La, Nd, Ce, and Tb; RE4 is selected from the group consisting of: Er, Gd Sm, Dy La, Nd, Ce, and Tb; and RE5 is selected from the group consisting of: Gd Sm, Dy La, Nd, Ce, and Tb; where RE1, RE2, RE3, RE4 and RE5 are different; and T is Zr or Hf.

14. (canceled)

15. (canceled)

16. The process according to claim 11 wherein zirconium halide is ZrCl.sub.4.

17. The process according to claim 11 wherein the solvents are chosen in the group consisting of aliphatic hydrocarbons, and aromatic hydrocarbons.

18. (canceled)

19. A solid material susceptible to be obtained by the process according to claim 11.

20. A method comprising incorporating the solid material according to claim 1 into a solid electrolyte.

21. A solid electrolyte comprising at least a solid material according to claim 1.

22. An electrochemical device comprising at least a solid electrolyte comprising at least a solid material according to claim 1.

23. A solid state battery comprising at least a solid electrolyte comprising at least a solid material according to claim 1.

24. A vehicle comprising at least a solid state battery comprising at least a solid electrolyte comprising at least a solid material according to claim 1.

25. An electrode comprising at least: a metal substrate; directly adhered onto said metal substrate, at least one layer made of a composition comprising: (i) a solid material according to claim 1; (ii) at least one electro-active compound (EAC); (iii) optionally at least one lithium ion-conducting material (LiCM) other than the solid material of the invention; (iv) optionally at least one electro-conductive material (ECM); (v) optionally a lithium salt (LIS); and (vi) optionally at least one polymeric binding material (P).

26. A separator comprising at least: a solid material according to claim 1; optionally at least one polymeric binding material (P); optionally at least one metal salt, notably a lithium salt; and optionally at least one plasticizer.

Description

FIGURES

[0311] FIG. 1: powder XRD pattern of Li.sub.3YCl.sub.6 obtained by dry mechanochemistry in Example 1.

[0312] FIG. 2: powder XRD pattern of Li.sub.3GdCl.sub.6 obtained by dry mechanochemistry in Example 2.

[0313] FIG. 3: powder XRD pattern of Li.sub.3Y.sub.0.9Gd.sub.0.1Cl.sub.6 obtained by dry mechanochemistry in Example 3.

[0314] FIG. 4: powder XRD pattern of Li.sub.3Y.sub.0.3Er.sub.0.3Yb.sub.0.3Gd.sub.0.1Cl.sub.6 obtained by dry mechanochemistry in Example 4.

[0315] FIG. 5: powder XRD pattern of Li.sub.2.7YGd.sub.0.1Cl.sub.6 obtained by dry mechanochemistry in Example 5.

[0316] FIG. 6: powder XRD pattern of Li.sub.3(Y.sub.0.45Er.sub.0.45Gd.sub.0.1)Cl.sub.6 obtained by wet mechanochemistry in Example 6.

[0317] FIG. 7: powder XRD pattern of Li.sub.3YCl.sub.6 obtained by wet mechanochemistry in Example 8.

EXPERIMENTAL PART

[0318] The examples below serve to illustrate the invention, but have no limiting character.

[0319] X-Ray Diffraction

[0320] The XRD diffractograms of the powders were acquired on a XRD goniometer in the Bragg Brentano geometry, with a Cu X Ray tube (Cu Kalpha wavelength of 1.5406 Å). The setup may be used in different optical configurations, i.e. with variable or fixed divergence slits, or Soller slits. A filtering device on the primary side may also be used, like a monochromator or a Bragg Brentano HD optics from Panalytical. If variable divergence slits are used; the typical illuminated area is 10 mm×10 mm. The sample holder is loaded on a spinner; rotation speed is typically 60 rpm during the acquisition. Tube settings were operating at 40 kV/30 mA for variable slits acquisition and at 45 kV/40 mA for fixed slits acquisition with incident Bragg Brentano HD optics. Acquisition step was 0.017° per step. Angular range is typically 5° to 90° in two theta or larger. Total acquisition time was typically 30 min or longer. The powders are covered by a Kapton film to prevent reactions with air moisture.

[0321] Conductivity Measurements

[0322] The conductivity was acquired on pellets done using a uniaxial press operated at 500 MPa. Pelletizing was done using a lab scale uniaxial press in glovebox filled with moisture free Argon atmosphere. Two carbon paper foils (Papyex soft graphite N998 Ref: 496300120050000, 0.2 mm thick from Mersen) are used as current collector. The measurement is done in a swagelock cell closed using a manual spring. The impedance spectra are acquired on a Biologic VMP3 device and the control of temperature is ensured by a Binder climatic chamber. Duration of two hours is set to allow the temperature to be equilibrated between two measurements. Impedance spectroscopy is acquired in PEIS mode with an amplitude of 10 mV and a range of frequencies from 1 MHz to 1 kHz (25 points per decade and a mean of 50 measurements per frequency point). Electronic conductivities are acquired by imposing a potential difference of 1V during 2 minutes and measuring the resultant current to extract the electronic resistance of the pellet.

Example 1: Comparative—Li.SUB.3.YCl.SUB.6 .by Dry Mechanochemistry

[0323] The weighing of precursors and preparation of the sample was carried out in an Ar-filled glovebox with oxygen and moisture levels both below 1 ppm. In a typical experiment, a 30 mL glass vial is used to weight LiCl (≥99.9%, Sigma Aldrich, 1.98 g) and dry YCl.sub.3 (≥99%, Sigma Aldrich, 3.004 g) according to the target stoichiometry Li.sub.3YCl.sub.6. Precursors used here were powders having an average particle diameter comprised between 10 μm and 400 μm.

[0324] The sample has been poured in a 20 mL ZrO.sub.2 milling jar which contained 30 g of diameter 5 mm ZrO.sub.2 balls. The jar was equipped with a Viton seal and hermetically closed with Ar atmosphere inside the jar. The jar was removed from the glovebox and set inside a planetary ball-milling (Pulverisette 7 premium line, Fritsch). The mechanosynthesis has been carried out at 600 rpm during 10 min for 207 cycles with a 10 min rest period between each cycle.

[0325] After the end of the mechanosynthesis the jar was entered in the glovebox. The grey powder obtained has been recovered and the XRD was in accordance with the reported pattern of Li.sub.3YCl.sub.6 (orthorhombic phase). The white part of the powder was recovered separately and presented a large amount of precursors.

[0326] The transport properties of the grey powder have been measured after pelletizing:

[0327] Ionic conductivity measured at 20° C.: 0.16 mS/cm

[0328] Activation energy for lithium transport: 0.42 eV

[0329] Electronic conductivity at 20° C.: 3.17E-09 S/cm

Example 2: Comparative—Li.SUB.3.GdCl.SUB.6 .by Dry Mechanochemistry

[0330] The weighing of precursors and preparation of the sample was carried out in an Ar-filled glovebox with oxygen and moisture levels both below 1 ppm. In a typical experiment, a 30 mL glass vial has been used to weight LiCl (≥99.9%, Sigma Aldrich, 1.24 g) and dry GdCl.sub.3 (≥99%, Sigma Aldrich, 2.58 g) according to the target stoichiometry Li.sub.3GdCl.sub.6. The sample was poured in a 20 mL ZrO.sub.2 milling jar which contained 30 g of diameter 5 mm ZrO.sub.2 balls. The jar was equipped with a Viton seal and hermetically closed (Ar atmosphere inside the jar). The jar was removed from the glovebox and set inside a planetary ball-milling (Pulverisette 7 premium line, Fritsch). The mechanosynthesis was carried out at 600 rpm during 10 min for 155 cycles with a 10 min rest period between each cycle.

[0331] After the end of the mechanosynthesis the jar was entered in the glovebox. The grey powder obtained has been recovered and the XRD was in accordance with the reported pattern of LiGdCl.sub.4 and LiCl (tetragonal I41/a phase). The white part of the powder was recovered separately and presented a large amount of precursors (GdCl.sub.3 and LiCl).

[0332] The transport properties of the grey powder have been measured after pelletizing:

[0333] Ionic conductivity measured at 20° C.: 0.0009 mS/cm

[0334] Activation energy for lithium transport: 0.5 eV

[0335] Electronic conductivity at 20° C.: 2E-09 S/cm

Example 3: Li.SUB.3.Y.SUB.0.9.Gd.SUB.0.1.Cl.SUB.6 .by Dry Mechanochemistry

[0336] The weighing of precursors and preparation of the sample was carried out in an Ar-filled glovebox with oxygen and moisture levels both below 1 ppm. In a typical experiment, a 30 mL glass vial has been used to weight LiCl (>99.9%, Sigma Aldrich, 1.25 g), dry YCl.sub.3 (>99.9%, Sigma Aldrich, 1.72 g) and dry GdCl.sub.3 (>99%, Sigma Aldrich, 0.26 g) according to the target stoichiometry Li.sub.3Y.sub.0.9Gd.sub.0.1Cl.sub.6. The sample was poured in a 20 mL ZrO.sub.2 milling jar which contained 30 g of diameter 5 mm ZrO.sub.2 balls. The jar was equipped with a Viton seal and hermetically closed (Ar atmosphere inside the jar). The jar was removed from the glovebox and set inside a planetary ball-milling (Pulverisette 7 premium line, Fritsch). The mechanosynthesis was carried out at 600 rpm during 10 min for 155 cycles with a 10 min rest period between each cycle.

[0337] After the end of the mechanosynthesis the jar was entered in the glovebox. The grey powder obtained has been recovered and the XRD was in accordance with the reported pattern of the parent Li.sub.3YCl.sub.6. The white part of the powder was recovered separately and presented a large amount of precursors (YCl.sub.3 and LiCl).

[0338] The transport properties of the grey powder have been measured after pelletizing:

[0339] Ionic conductivity measured at 20° C.: 0.31 mS/cm

[0340] Activation energy for lithium transport: 0.37 eV

[0341] Electronic conductivity at 20° C.: 2.3E-9 S/cm

Example 4: Li.SUB.3.Y.SUB.0.3.Er.SUB.0.3.Yb.SUB.0.3.Gd.SUB.0.1.Cl.SUB.6 .by Dry Mechanochemistry

[0342] The weighing of precursors and preparation of the sample was carried out in an Ar-filled glovebox with oxygen and moisture levels both below 1 ppm. In a typical experiment, a 30 mL glass vial has been used to weight LiCl (≥99.9%, Sigma Aldrich, 1.13 g), dry YCl.sub.3 (≥99.9%, Sigma Aldrich, 1.92 g), dry ErCl.sub.3 (≥99.9%, Sigma Aldrich, 1.92 g),), dry YbCl.sub.3 (≥99.9%, Sigma Aldrich, 1.92 g) and dry GdCl.sub.3 (≥99%, Sigma Aldrich, 0.26 g) according to the target stoichiometry Li.sub.3Y.sub.0.3Er.sub.0.3Yb.sub.0.3Gd.sub.0.1Cl.sub.6. The sample was poured in a 20 mL ZrO.sub.2 milling jar which contained 30 g of diameter 5 mm ZrO.sub.2 balls. The jar was equipped with a Viton seal and hermetically closed (Ar atmosphere inside the jar). The jar was removed from the glovebox and set inside a planetary ball-milling (Pulverisette 7 premium line, Fritsch). The mechanosynthesis was carried out at 600 rpm during 10 min for 155 cycles with a 10 min rest period between each cycle.

[0343] After the end of the mechanosynthesis the jar was entered in the glovebox. The grey powder obtained has been recovered and the XRD was in accordance with the reported pattern of the parent Li.sub.3YCl.sub.6. The white part of the powder was recovered separately and presented a large amount of precursors (YCl.sub.3, ErCl.sub.3, YbCl.sub.3 and LiCl).

[0344] The transport properties of the grey powder have been measured after pelletizing:

[0345] Ionic conductivity measured at 20° C.: 0.20 mS/cm

[0346] Activation energy for lithium transport: 0.40 eV

[0347] Electronic conductivity at 20° C.: 2.2E-9 S/cm

Example 5: Li.SUB.2.7.YGd.SUB.0.1.Cl.SUB.6 .by Dry Mechanochemistry

[0348] The weighing of precursors and preparation of the sample was carried out in an Ar-filled glovebox with oxygen and moisture levels both below 1 ppm. In a typical experiment, a 30 mL glass vial has been used to weight LiCl (≥99.9%, Sigma Aldrich, 1.13 g), dry YCl.sub.3 (≥99.9%, Sigma Aldrich, 1.92 g) and dry GdCl.sub.3 (>99%, Sigma Aldrich, 0.26 g) according to the target stoichiometry Li.sub.2.7YGd.sub.0.1Cl.sub.6. The sample was poured in a 20 mL ZrO.sub.2 milling jar which contained 30 g of diameter 5 mm ZrO.sub.2 balls. The jar was equipped with a Viton seal and hermetically closed (Ar atmosphere inside the jar). The jar was removed from the glovebox and set inside a planetary ball-milling (Pulverisette 7 premium line, Fritsch). The mechanosynthesis was carried out at 600 rpm during 10 min for 155 cycles with a 10 min rest period between each cycle.

[0349] After the end of the mechanosynthesis the jar was entered in the glovebox. The grey powder obtained has been recovered and the XRD was in accordance with the reported pattern of the parent Li.sub.3YCl.sub.6. The white part of the powder was recovered separately and presented a large amount of precursors (YCl.sub.3 and LiCl).

[0350] The transport properties of the grey powder have been measured after pelletizing:

[0351] Ionic conductivity measured at 20° C.: 0.44 mS/cm

[0352] Activation energy for lithium transport: 0.37 eV

[0353] Electronic conductivity at 20° C.: 9E-10 S/cm

Example 6: Li.SUB.3.Y.SUB.0.45.Er.SUB.0.45.Gd.SUB.0.1.O.SUB.6 .by Wet Mechanochemistry

[0354] The weighing of precursors and preparation of the sample was carried out in an Ar-filled glovebox with oxygen and moisture levels both below 1 ppm. In a typical experiment, a 30 mL glass vial has been used to weight LiCl (≥99.9%, Sigma Aldrich, 3.78 g), dry YCl.sub.3 (≥99.9%, Sigma Aldrich, 2.64 g) dry ErCl.sub.3 (≥99.9%, Sigma Aldrich, 3.65 g) and dry GdCl.sub.3 (≥99%, Sigma Aldrich, 0.77 g) according to the target stoichiometry Li.sub.3Y.sub.0.45Er.sub.0.45Gd.sub.0.1Cl.sub.6. The sample was poured in a 45 mL ZrO.sub.2 milling jar which contains 30 g of diameter 5 mm ZrO.sub.2 balls. Then 10.65 g of p-xylene (≥99%, Sigma-Aldrich, anhydrous) was added in the jar. The jar was equipped with a Viton seal and hermetically closed (Ar atmosphere inside the jar). The jar was removed from the glovebox and set inside a planetary ball-milling (Pulverisette 7 premium line, Fritsch). The mechanosynthesis was carried out at 800 rpm during 165 cycles of 10 min with a 30 min rest period between each cycle. After the end of the mechanosynthesis the jar was entered in the glovebox. The product and the balls were set inside two 30 mL glass vials (without caps) placed themselves in a glass tube. The tube was closed, removed from the glovebox and set in a Glass Oven B-585 from Büchi. The sample was dried under vacuum for 2 h at room temperature to evaporate the p-xylene. The grey powder obtained has been recovered and the XRD was in accordance with the reported pattern of Li.sub.3YCl.sub.6.

[0355] The transport properties of the grey powder have been measured after pelletizing:

[0356] Ionic conductivity measured at 20° C.: 0.39 mS/cm

[0357] Activation energy for lithium transport: 0.35 eV

[0358] Electronic conductivity at 20° C.: 3E-9 S/cm

Example 7: Stability Measurements in Various Solvents

[0359] Stability was checked by weighting 100 mg of Li.sub.3YCl.sub.6 from example 1 into 2 g of the selected solvents for 7 days and filtered the solution. When a filter residue is present, it was dried with under vacuum at 25° C. to test the conductivity.

TABLE-US-00005 Product conductivity Solvent at 20° C. (mS/cm) Water No Acetonitrile Below 10.sup.−7 Ethanol No N-Methyl-2- No pyrrolidone Paraxylene 0.18 Perfluoropolyether 0.14 (Galden HT-135) Acetone No THF No

[0360] Filtrate was then analyzed by ICP-MS in case of paraxylene and less than 1 ppm of Y.sup.3+ and Li.sup.+ where found in the filtrate. Same was done on the starting agents LiCl and YCl.sub.3 and no solubility was found (less of 1 ppm of Y.sup.3+ and Li.sup.+ in the filtrate).

[0361] It appears that these compounds are stable (by XRD and conductivity) in xylene and fluorosolvents (Galden HT-135).

Example 8: Li.SUB.3.YCl.SUB.6 .by Wet Mechanochemistry

[0362] The weighing of precursors and preparation of the sample was carried out in an Ar-filled glovebox with oxygen and moisture levels both below 1 ppm. In a typical experiment, a 30 mL glass vial has been used to weight LiCl (≥99.9%, Sigma Aldrich, 2.45 g) and dry YCl.sub.3 (≥99%, Sigma Aldrich, 3.78 g) according to the target stoichiometry Li.sub.3YCl.sub.6. The sample was poured in a 45 mL ZrO.sub.2 milling jar which contained 30 g of diameter 5 mm ZrO.sub.2 balls. Then 6.05 g of p-xylene (≥99%, Sigma-Aldrich, anhydrous) was added in the jar.

[0363] The jar was equipped with a Viton seal and hermetically closed (Ar atmosphere inside the jar). The jar was removed from the glovebox and set inside a planetary ball-milling (Pulverisette 7 premium line, Fritsch). The mechanosynthesis was carried out at 800 rpm during 165 cycles of 10 min with a 30 min rest period between each cycle. After the end of the mechanosynthesis the jar was entered in the glovebox. The product and the balls were set inside two 30 mL glass vials (without caps) placed themselves in a glass tube. The tube was closed, removed from the glovebox and set in a Glass Oven B-585 from Büchi. The sample was dried under vacuum for 2 h at room temperature to evaporate the p-xylene. The grey powder obtained has been recovered and the XRD was in accordance with the reported pattern of Li.sub.3YCl.sub.6.

[0364] The transport properties of the grey powder have been measured after pelletizing:

[0365] Ionic conductivity measured at 20° C.: 0.14 mS/cm.

[0366] Activation energy for lithium transport: 0.38 eV

[0367] Electronic conductivity at 20° C.: 6E-10 S/cm

Example 9: Li.SUB.3.YCl.SUB.6 .with Water Mediated Synthesis

[0368] Li.sub.3YCl.sub.6 has been produced by using a method described to produce Li.sub.3InCl.sub.6 in water mediated synthesis (Angewandte Chemie, 131(46), 16579-16584).

[0369] In a typical experiment, a 50 mL glass beaker was used to weight LiCl (≥99.9%, Sigma Aldrich, 1.90 g), and a aqueous solution of YCl.sub.3 (≥99%, 13.5 g with a Dry equivalent content of YCl.sub.3 equal to 3.01 g) according to the target stoichiometry Li.sub.3YCl.sub.6.

[0370] The beaker was then placed into oven at 120° C. for water evaporation for 19 h. Final product was white glassy solid. This product was then vacuum dried at 120° C. during 4 h in Glass Oven B-585 from Büchi. XRD of this sample shown presence of LiCl, LiCl(H.sub.2O), YCl.sub.3 and YCl.sub.3.6H.sub.2O. There is no presence of an unknown phase, which can be attributed to a hydrated phase Li.sub.3YCl.sub.6, xH.sub.2O, contrary to reported Li.sub.3InCl.sub.6, xH.sub.2O).

[0371] The subsequent heating of the sample at 200° C. under vacuum (Glass Oven B-585 from Büchi) during 4 h lead to the formation of a mixture of LiCl and YCl.sub.3. There is no presence of Li.sub.3YCl.sub.6, contrary to reported Li.sub.3InCl.sub.6.

Example 10: Li.SUB.2.6.Zr.SUB.0.4.Y.SUB.0.54.Sm.SUB.0.06.Cl.SUB.5.82.Br.SUB.0.18 .by Wet Mechanochemistry

[0372] The weighting of precursors and preparation of the sample is carried out in an Ar-filled glovebox with oxygen and moisture levels both below 1 ppm. In a typical experiment, a 30 mL glass vial is used to weight LiCl (≥99.9%, Sigma Aldrich, 1.65 g), dry YCl.sub.3 ((≥99.9%, Sigma Aldrich, 1.59 g), dry ZrCl.sub.4 ((≥99.9%, Sigma Aldrich, 1.43 g) and dry SmBr.sub.3 (≥99%, Sigma Aldrich, 0.35 g) according to the target stoichiometry Li.sub.2.6Zr.sub.0.4Y.sub.0.54Sm.sub.0.06Cl.sub.5.82Br.sub.0.18.

[0373] The sample is poured in a 45 mL ZrO.sub.2 milling jar which contains 66 g of O 5 mm ZrO.sub.2 balls. Then 5.0 g of p-xylene (≥99%, Sigma-Aldrich, anhydrous) is added in the jar.

[0374] The jar is equipped with a Viton seal and hermetically closed (Ar atmosphere inside the jar). The jar is removed from the glovebox and set inside a planetary ball-milling (Pulverisette 7 premium line, Fritsch). The mechanosynthesis is carried out at 800 rpm during 165 cycles of 10 minutes with a 15 minutes rest period between each cycle.

[0375] After the end of the mechanosynthesis the jar is entered in the glovebox. The product and the balls are set inside two 30 mL glass vials (without caps) placed themselves in a glass tube. The tube is closed, removed from the glovebox and set in a Glass Oven B-585 from Büchi.

[0376] The sample is dried under vacuum at 110° C. for 5 h to evaporate the p-xylene. The powder obtained is recovered and the XRD is in accordance with the reported pattern of Li.sub.3YCl.sub.6

[0377] The ionic conductivity measured at 30° C. is 0.57 mS/cm with an activation energy of 0.35 eV.

TABLE-US-00006 TABLE 1 Conductivities at 20° C. and at lower temperature 20° C. 0° C. −20° C. Example 1 0.16 mS/cm 0.038 mS/cm 0.013 mS/cm (Li.sub.3YCl.sub.6 dry mechanochemistry) Example 9 0.14 mS/cm 0.046 mS/cm 0.016 mS/cm (Li.sub.3YCl.sub.6 wet mechanochemistry) Example 6 0.39 mS/cm  0.13 mS/cm  0.16 mS/cm (Li.sub.3Y.sub.0.45Er.sub.0.45Gd.sub.0.1Cl.sub.6 wet mechanochemistry)

[0378] The results compiled in Table 1, show that the solid lithium rare-earth halides obtained by the wet mechanochemistry process according to the invention have surprisingly improved ionic conductivities at low temperature compared to solid lithium rare-earth halides obtained by the dry mechanochemistry process (compare example 9 with example 1 at 0° C. and −20° C.).