Solid electrolyte for a lithium-ion electrochemical cell
The invention relates to a compound of the formula Li 7-x PS 6-x X x-z (BH 4 ) z , in which x is selected from the group comprising Cl, Br, I, F and CN, 0≤x≤2, 0≤z≤0.50. This compound can be used as a solid electrolyte of a lithium-ion electrochemical element.
1. A crystalline compound of formula Li 7-x PS 6-x X x-z (BH 4 ) z wherein:
X is selected from the group consisting of Cl, Br, I, F and CN
0<x≤2
0<z≤0.50.
2. The crystalline compound as claimed in claim 1 , wherein x=1.
3. The crystalline compound as claimed in claim 1 , wherein X is I or Cl.
4. The crystalline compound as claimed in claim 1 , where 0.1≤z≤0.35.
5. The crystalline compound as claimed in claim 1 , where 0.1≤z≤0.20.
6. The crystalline compound as claimed in claim 1 , where 0.15≤z≤0.20.
7. A process for preparing a crystalline compound as claimed in claim 1 , comprising the steps of:
a) providing a mixture comprising Li 2 S, P 2 S 5 , LiBH 4 and LiX wherein X is selected from the group consisting of Cl, Br, I, F and CN;
b) grinding the mixture for a period of at least 10 hours to allow the incorporation of LiBH 4 into the compound Li 7-x PS 6-x X x-z (BH 4 ) z .
8. The preparation process as claimed in claim 7 , wherein the grinding step b) is carried out for a period of at least 15 hours.
9. The preparation process as claimed in claim 8 , wherein the grinding step b) is carried out for a period of at least 20 hours.
10. An electrochemical cell comprising a solid electrolyte comprising the crystalline compound as claimed in claim 1 .
11. The electrochemical cell as claimed in claim 10 , wherein the solid electrolyte does not contain LiBH 4 .
12. The electrochemical cell as claimed in claim 10 , further comprising:
at least one negative electrode comprising an active material selected from the group consisting of carbon, tin, silicon, lithium and indium;
at least one positive electrode comprising an active material selected from the group consisting of lithiated transition metal oxides and sulfur compounds.
13. The electrochemical cell as claimed in claim 12 , wherein:
the active material of the negative electrode is selected from the group consisting of lithium and indium;
the active material of the positive electrode is selected from the group consisting of S, TiS 2 , TiS 3 , TiS 4 , NiS, NiS 2 , CuS, FeS 2 , Li 2 S, MoS 3 , polyacrylonitriles-sulfur, dithiooxamide and disulfur compounds.
14. A process for manufacturing a solid-electrolyte electrochemical cell, said process comprising the steps of:
a) preparing a mixture containing a positive electrochemically active material;
b) depositing on the mixture obtained in step a) a layer of the crystalline compound as claimed in claim 1 to form a solid electrolyte;
c) application of at least one layer of a mixture containing a negative electrochemically active material on a free side of the compound layer forming the solid electrolyte.
15. A method comprising the step of substituting a boron-containing anion for a halide ion in a crystalline compound of formula Li 7-x PS 6-x X x to obtain a crystalline compound of formula Li 7-x PS 6-x X x-z (BH4) z ,
where 0<z≤0.50,
where X is selected from the group consisting of Cl, Br, I, F and CN and 0<x≤2
in order to increase the ionic conductivity of this compound.