NEW SOLID SULFIDE ELECTROLYTES

Abstract

The present invention concerns a method for producing a solid material according to general formula (I) as follows: Li.sub.6-.sub.x_.sub.2yCu.sub.xPS.sub.5_.sub.yX (I) wherein X is selected from the group consisting of: F, CI, I and Br; 0.005 ≤ x ≤ 5; and 0 ≤y ≤ 0.5.; comprising at least bringing at least lithium sulfide, phosphorous sulfide, halogen compound and a copper compound, optionally in one or more solvents. The invention also refers to said solid materials and their use as solid electrolytes notably for electrochemical devices.

Claims

1. A solid material according to general formula (I) as follows: ##STR00001## wherein: X is selected from the group consisting of F, Cl, I and Br; 0.005 ≤ x ≤ 5; and 0 ≤ y ≤ 0.5..

2. The solid material according to claim 1 wherein X is Cl.

3. The solid material according to claim 1 wherein 0.02 ≤ x ≤ 0.8.

4. The solid material according to claim 1 wherein the crystallization degree of the solid material is from 80% to 100%.

5. The solid material according to claim 1 wherein the solid material comprises at least peaks at position of: 15.65°+/- 0.5°, 25.53°+/-0.5°, 30.16°+/- 0.5°, and 31.52°+/- 0.5° (2θ) when analyzed by x-ray diffraction using CuKα radiation at 25° C.

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

7. A method for producing the solid material according to claim 1 comprising at least bringing at least lithium sulfide, phosphorous sulfide, halogen compound and a copper compound, optionally in one or more solvents.

8. A process for the preparation of a solid material according to claim 1 comprising at least the process steps of: a) obtaining a composition by admixing stoichiometric amounts of lithium sulfide, phosphorous sulfide, halogen compound and a copper compound, optionally in one or more solvents, under an inert atmosphere; b) applying a mechanical treatment to the composition obtained in step a); c) optionally removing at least a portion of the one or more solvents from the composition obtained on step b), so that to obtain a solid residue; d) heating the obtained residue obtained in step c) at a temperature in the range of from 100° C. to 700° C., under an inert atmosphere, thereby forming the solid material; and e) optionally treating the solid material obtained in step d) to the desired particle size distribution.

9. The process according to claim 8 wherein the copper compound is selected from the group consisting of CuS, Cu.sub.2S, Cu.sub.2-xS (wherein x is between 0 and 1 and CuCl.sub.2.

10. The process according to claim 8wherein the lithium sulfide is Li.sub.2S, the phosphorous sulfide is P.sub.2S.sub.5, the halogen compound is LiCl, and the copper compound is Cu.sub.2S.

11. The process according to claim 8 wherein the solvent is selected in the group consisting of alkanols; carbonates; acetates; ethers; organic nitriles; aliphatic hydrocarbons; and aromatic hydrocarbons.

12. The process according to claim 8 wherein in step b) the mechanical treatment is performed by wet or dry milling.

13. (canceled)

14. A process for the preparation of a solid material according to claim 1, said process comprising at least the process steps of: a′) obtaining a solution by admixing stoichiometric amounts of lithium compounds, sulfide compounds, phosphorous compounds, halogen compound and a copper compound, in one or more solvents, under an inert atmosphere; b′) removing at least a portion of the one or more solvents from the composition as obtained in step a′), so that to obtain a solid material; c′) optionally heating the solid material as obtained in step b′), at a temperature in the range of from 100° C. to 700° C., under an inert atmosphere; and d′) optionally treating the solid material obtained in step c′) to the desired particle size distribution.

15. (canceled)

16. (canceled)

17. A solid electrolyte comprising at least a solid material of formula (I) as follows: ##STR00002## wherein: X is selected from the group consisting of F, Cl, I and Br; 0.005 ≤ x ≤ 5; and 0 ≤ y ≤ 0.5..

18. An electrochemical device comprising at least the solid electrolyte of claim 17.

19. A solid state battery comprising at least the solid electrolyte of claim 17.

20. A vehicle comprising at least a solid state battery comprising at least the solid electrolyte of claim 17.

21. 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 of formula (I) as follows: ##STR00003## wherein: X is selected from the group consisting of F, Cl, I and Br; 0.005 ≤ x ≤ 5; and 0 ≤ y ≤ 0.5; (ii) at least one electro-active compound (EAC); (iii) optionally at least one lithium ion-conducting material (LiCM) other than the solid material of formula (I); (iv) optionally at least one electro-conductive material (ECM); (v) optionally a lithium salt (LIS); (vi) optionally at least one polymeric binding material (P).

22. A separator comprising at least: the solid material of claim 1 optionally at least one polymeric binding material (P); optionally at least one metal salt, notably a lithium salt; optionally at least one plasticizer.

Description

FIGURES

[0199] FIG. 1: powder XRD pattern of Li.sub.6-x-2yCu.sub.xPS.sub.5-yCl. Sample A : x=0; sample B : x=0.03; sample C : x=0.06; sample D : x=0.3; sample E : x=0.6; sample F : x=1.5.

[0200] FIG. 2: .sup.31P NMR data of Li.sub.6-x-2yCu.sub.xPS.sub.5-yCl with x=0.3 and y=0. Star symbol indicates the signature of PS.sub.4.sup.3- entities, Pentagon symbol indicates the signature of P.sub.2S.sub.7.sup.4- entities, and Hexagon symbol indicates the signature of PO.sub.4.sup.3- entities.

[0201] FIG. 3: .sup.7Li NMR data of Li.sub.6-x-2yCu.sub.xPS.sub.5-yCl with x=0.3 and y=0.

EXPERIMENTAL PART

[0202] The examples below serve to illustrate the invention, but have no limiting character.

X-Ray Diffraction

[0203] 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.

Conductivity & Electrochemical Impedance Spectroscopy (EIS)

[0204] The conductivity was acquired on pellets done using a uniaxial press operated at 500 MPa. The measurement is done under a loading of 40 MPa and two carbon paper foils are used as current collector in a pressure cell from MTI (BATTE-CELL-0067 EQ-PSC-15-P). 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.)

Solid-State NMR

[0205] Solid-State NMR spectra were recorded on a Bruker Avance 400 spectrometer equipped with a high-speed DVT4 probe. .sup.31P and .sup.6Li measurements were performed by magic-angle-spinning (MAS) at a speed of 10 kHz, in single-pulse mode with a relaxation time D1 depending on the experiment (see example below). .sup.7Li measurements were performed in the static, single-pulse mode with a relaxation time D1 = 120 s. Reference for .sup.31P NMR was 85% H.sub.3PO.sub.4, for .sup.6Li NMR a 5 mol L.sup.-1 aqueous LiCl solution.

Example 1: Synthesis

[0206] The weighing 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 Li.sub.2S (≥ 99.9 %, Albemarle), P.sub.2S.sub.5 (≥ 99%, Sigma Aldrich), LiCl (≥ 99%, Sigma Aldrich) and Cu.sub.2S (≥ 99.5%, Alfa Aesar) according to the target stoichiometry Li.sub.6-x-2yCu.sub.xPS.sub.5-yCl (0.015 ≤ x ≤ 1.5 and 0 ≤ y ≤ 0.25) (total mass of 8 g). For instance for a solid material Li.sub.5.94Cu.sub.0.06PS.sub.5Cl (x=0.06 and y=0) 3.34 g of Li.sub.2S, 3.27 g of P.sub.2S.sub.5, 1.25 g of LiCl and 0.14 g of Cu.sub.2S have been used. Precursors used here are powders having an average particle diameter comprised between 10 .Math.m and 400 .Math.m.

[0207] The glass vial is hermetically closed, removed from the glovebox and mixed with a Turbula mixer for 20 min. The glass vial is entered in the glovebox and the sample is poured in a 45 mL ZrO.sub.2 milling jar which contains 66.4 g of diameter ∅5 mm ZrO.sub.2 balls. Then 8 g of p-xylene (≥ 99%, Sigma-Aldrich, anhydrous) is added in the jar. The jar is equipped with a Viton seal and hermetically closed with Ar atmosphere inside the jar. The jar is removed from the glovebox and set inside a planetary ball-milling (Pluverisette 7 premium line, Fritsch). The mechanosynthesis is carried out at 800 rpm during 80 cycles of 15 min. Between each cycle the jar is naturally cooled for 30 min.

[0208] 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. The sample is dried under vacuum for 2 h at room temperature (25° C.) and subsequently heated to 110° C. for 5 h to evaporate the p-xylene. Thereafter, the tube is closed (vacuum inside) and entered in the glovebox. The powder is sieved and separated from the milling balls. The powder is set inside a 30 mL glass vial without caps placed itself in a glass tube. The tube is closed, removed from the glovebox and set in a Glass Oven B-585 from Büchi. The sample is heated under vacuum at 150° C. for 1 h, followed by 1 h at 280° C. and finally heated at 300° C. for 12 h. The tube is closed (vacuum inside) and entered in the glovebox. The sample is removed from the tube and stored for the further analyses.

Example 2 : Properties

[0209] Whatever the composition is in the selected range, the powder XRDs (FIG. 1) indicate the predominance of the argyrodite phase with a minute amount of Li.sub.2S when x ≤ 0.06. No copper containing impurities can be seen from powder XRDs, even for the higher copper content of the selected range (x = 1.5). The powder XRDs also show that the increase of copper content (x) decreases the amount of Li.sub.2S impurity.

[0210] Cell parameters were calculated using a Le Bail refinement, on kapton substrated diffractogram. This was done using Fullprof software.

TABLE-US-00002 X value Cell parameter x=0 9,857 Angstrom x=0.03 9,848 Angstrom x=0.06 9,848 Angstrom x=0.3 9,844 Angstrom x=0.6 9,831 Angstrom x=1.5 9,810 Angstrom

[0211] The .sup.31P NMR (FIG. 2) of the x = 0.3 sample corroborates the predominance of PS.sub.4.sup.3- species with a minute amount of P.sub.2S.sub.7.sup.4- and potentially a low amount of Li.sub.3PO.sub.4 impurity.

[0212] The .sup.7Li NMR (FIG. 3) of the x = 0.3 sample indicates the presence of a single Li environment, with a displacement close to 1.38 ppm, in very good agreement with the displacement of the Li.sub.6PS.sub.5Cl phase found in the literature.

[0213] The Electrochemical Impedance Spectroscopy measurements were carried out on 6 mm diameter pellets, densified under 500 MPa. The thickness of the pellet is close to 1 mm. The EIS measurements indicate that a small copper content increases the conductivity of the material. Thus, the samples with 0.03 ≤ x ≤ 0.06 benefit of a higher conductivity than the x = 0 sample. Furthermore, the activation energy of the samples with 0.03 ≤ x ≤ 0.06 remains below 0.40 eV between -20° C. and 60° C. For higher copper content (x ≥ 0.3) the conductivity decreases and the activation energy increases as expressed in the table below:

TABLE-US-00003 X value Li.sub.6-x-2yCu.sub.xPS.sub.5-yCl (%*) Li.sub.2S (%*) LiCl (%*) Conductivity at 30° C. (S cm.sup.-1) Ea (eV) x=0 94.5 4.4 1.1 2.06×10.sup.-3 0.37 x=0.03 96.8 3.2 0 2.83×10.sup.-3 0.37 x=0.06 96.3 nm 0 nm 0.40 x=0.3 100 0 0 nm nm %* corresponds to the portion of crystallized product among total crystalline phase as measured by peak areas Nm is non-measured