Sulfide-based solid electrolyte and preparation method thereof
A sulfide-based solid electrolyte contains a nickel (Ni) element and a halogen element. For example, a sulfide-based solid electrolyte can include, with respect to 100 parts by mole of a mixture of lithium sulfide (Li 2 S) and diphosphorus pentasulfide (P 2 S 5 ), 5 parts by mole to 20 parts by mole of nickel sulfide (Ni 3 S 2 ), and 5 parts by mole to 40 parts by mole of lithium halide.
1. A method of preparing a sulfide-based solid electrolyte, the method comprising:
preparing a starting material by adding 5 parts by mole to 20 parts by mole of nickel sulfide (Ni 3 S 2 ) and 5 parts by mole to 40 parts by mole of lithium halide with respect to 100 parts by mole of a mixture of lithium sulfide (Li 2 S) and diphosphorus pentasulfide (P 2 S 5 );
milling the starting material to obtain an amorphous material; and
heat-treating the amorphous material at a temperature range of 200° C. to 260° C. or 400° C. to 600° C., wherein a crystallized sulfide-based solid electrolyte is obtained after the heat-treating, wherein the heat-treated sulfide-based solid electrolyte has a cubic crystal structure that has diffraction peaks in an area of diffraction angles 2θ of 15.5±0.5°, 18±0.5°, 25.5±0.5°, 30±0.5°, 31.5±0.5°, 40±0.5°, 45.5±0.5°, 48±0.5°, 53±0.5°, 55±0.5°, 56.5±0.5° and 59.5±0.5° in an X-ray diffraction spectrum.
2. The method of claim 1 , wherein the mixture comprises
60 mole % to 90 mole % of the lithium sulfide; and
10 mole % to 40 mole % of diphosphorus pentasulfide.
3. The method of claim 1 , wherein the lithium halide is expressed by LiX, where X is Cl, Br or I.
4. The method of claim 1 , wherein the heat-treating is performed at 400° C. to 600° C.
5. The method of claim 1 , wherein, the heat-treating is performed at 200° C. to 260° C.
6. The method of claim 3 , wherein X is Cl.
7. The method of claim 3 , wherein X is Br.
8. The method of claim 3 , wherein X is I.
9. The method of claim 1 , wherein the method forms a sulfide-based solid electrolyte having a cubic crystal structure and comprising:
with respect to 100 parts by mole of a mixture of lithium sulfide (Li 2 S) and diphosphorus pentasulfide (P 2 S 5 );
5 parts by mole to 20 parts by mole of nickel sulfide (Ni 3 S 2 ); and
5 parts by mole to 40 parts by mole of lithium halide.
10. The method of claim 9 , wherein the mixture comprises
60 mole % to 90 mole % of the lithium sulfide; and
10 mole % to 40 mole % of diphosphorus pentasulfide.
11. The method of claim 9 , wherein the lithium halide is expressed by LiX, where X is Cl, Br or I.
12. The method of claim 9 , wherein a crystallization temperature of the sulfide-based solid electrolyte is 200° C. to 260° C.
13. The method of claim 9 , wherein a crystallization temperature of the sulfide-based solid electrolyte is 400° C. to 600° C.
14. The method of claim 9 , wherein the sulfide-based solid electrolyte has high ion conductivity in a wide crystallization temperature range.