Active material for batteries
A method of producing an active material for batteries comprising providing electrochemically active particles, optionally comminuting the electrochemically active particles, adding an organic carbon compound, optionally in a suitable organic solvent, and mixing, heating the mixture under protective gas to a temperature above the decomposition limit of the organic compound and below the decomposition temperature of the electrochemically active particles, active materials thus obtained and also corresponding applications and uses.
1. A method of producing an active material for batteries without using water, said method comprising the steps of:
a) adding an organic carbon compound to electrochemically active particles comprising Li 2 S, and mixing to form a mixture, and
b) heating the mixture under protective gas to a temperature above the decomposition limit of the organic carbon compound and below the decomposition temperature of the electrochemically active particles, whereby the organic carbon compound decomposes into carbon, which forms a homogeneous layer on the surface of the electrochemically active particles comprising Li 2 S, to form the active material.
2. The method as claimed in claim 1 , wherein the organic carbon compound comprises at least one member selected from the group consisting of sucrose and polyacrylonitrile.
3. The method as claimed in claim 1 , wherein the organic carbon compound comprises polyacrylonitrile, and the mixture further comprises an organic solvent for the organic carbon compound.
4. The method as claimed in claim 1 , wherein an organic solvent for the organic carbon compound is present in the mixture.
5. The method as claimed in claim 3 , wherein the solvent comprises N-methyl-2-pyrrolidone.
6. The method as claimed in claim 1 , wherein the mixture in step b) is heated to a temperature of up to 850° C.
7. The method as claimed in claim 6 , wherein the temperature is in the range from 550 to 750° C.
8. The method as claimed in claim 6 , wherein the temperature is maintained at said temperature for 2 to 5 hours.
9. A method as in claim 1 further comprising incorporating the active material into an electrode.
10. A method as in claim 1 further comprising incorporating the active material into a battery.
11. A method according to claim 9 , wherein said electrode comprises a cathode, and wherein said active material is present in a cathode.
12. A method according to claim 10 , wherein the battery is a lithium-metal or lithium-ion battery.
13. A method as in claim 1 further comprising
i) mixing the active material and at least one electronically conductive additive to form a materials mixture, and
ii) drying the materials mixture to obtain a cathode material.
14. An active material for batteries produced as in claim 1 , the active material comprising electrochemically active particles comprised of Li 2 S particles coated with a homogeneous carbon envelope, wherein the weight ratio of sulfur in Li 2 S to carbon in the homogeneous carbon envelope is in the range of about 9.2:1 to about 15:1.
15. An electrode containing the active material for batteries of claim 14 , wherein the electrode containing the active material has a specific capacity above about 600 mAh/g sulfur.
16. A method of producing an active material for batteries without using water, the method consisting of the steps of:
a) adding an organic carbon compound to electrochemically active Li 2 S particles, and mixing to form a mixture, and
b) heating the mixture under protective gas to a temperature above the decomposition limit of the organic carbon compound and below the decomposition temperature of the electrochemically active particles, whereby the organic carbon compound decomposes into carbon, which forms a homogeneous layer on the surface of the electrochemically active particles comprising Li 2 S, to form the active material.
17. A method as in claim 1 comprising, prior to adding the organic compound, comminuting the electrochemically active particles to an average particle size of less than about 2 μm, as measured using scanning electron microscopy.
18. A method as in claim 9 wherein the electrode containing the active material has a specific capacity above about 500 mAh/g sulfur.
19. A method as in claim 13 wherein at least one binder is included in step i).
20. The method as in claim 2 wherein the organic compound consists of sucrose or polyacrylonitrile.
21. The method as in claim 1 wherein the weight ratio of sulfur in Li 2 S to carbon in the organic compound is in the range of about 9.2:1 to about 15:1.
22. The method as in claim 1 wherein the active material has a weight ratio of sulfur in Li 2 S to carbon in the homogeneous carbon envelope in the range of about 9.2:1 to about 15:1.