Carbogel anode materials and method for their preperation
Carbogel anode materials and method for their preparation are disclosed. The described carbogels exhibit, at a temperature of 20° C., an electrical conductance of at least 0.5 S/cm and a reversible electrochemical capacity in relation to lithium of at least 350 mAh/g under a C/2 discharge current, enabling their use for preparation of anode materials, particularly those intended for preparation of lithium-ion cells.
1. A carbogel comprising at least 92% by wt. of carbon and exhibiting, at a temperature of 20° C., an electrical conductance of at least 0.5 S/cm and a reversible electrochemical capacity in relation to lithium of at least 350 mAh/g under a C/2 discharge current;
wherein the carbogel is prepared by a method comprising the steps of:
subjecting an aqueous suspension comprising 1-30% by wt. of a first starch composition consisting of rice starch in the amount of 75-99% by wt. and a second starch type in the amount of 1-25% by wt. to polycondensation at a temperature of 50-90° C.;
carrying out a solvent exchange using an aqueous solutions of an alcohol or a ketone with a concentration increasing from 10% to 99.8% to obtain an organic alcogel, and
subjecting the obtained organic alcogel to a pyrolysis process at a temperature of 300-2000° C. immediately following the solvent exchange step.
2. The carbogel according to claim 1 , wherein it exhibits a low roughness, vitreousness, lack of mesopores, and an ordered hierarchical lamellar structure.
3. A method for preparation of the carbogel according to claim 1 , wherein the method comprises the steps of:
subjecting an aqueous suspension comprising 1-30% by wt. of a starch composition consisting of rice starch in the amount of 75-99% by wt. and another starch type in the amount of 1-25% by wt. to polycondensation at a temperature of 50-90° C.;
carrying out a solvent exchange using an aqueous solutions of an alcohol or a ketone with a concentration increasing from 10% to 99.8%; and
subjecting the obtained organic alcogel to a pyrolysis process at a temperature of 300-2000° C. immediately following the solvent exchange step.
4. The carbogel according to claim 1 , wherein it has a structure obtained by the method defined in claim 3 .
5. The method according to claim 3 , wherein as the second starch type, starch selected from the group comprising: corn starch, potato starch, wheat starch, tapioca starch, and sago starch, is used.
6. The carbogel according to claim 1 , wherein it has a structure obtained by the method defined in claim 5 .
7. The method according to claim 3 , wherein as the alcohol, one selected from the group comprising: ethanol, methanol, and isopropanol, is used.
8. The carbogel according to claim 1 , wherein it has a structure obtained by the method defined in claim 7 .
9. The method according to claim 3 , wherein acetone is used as the ketone.
10. The carbogel according to claim 1 , wherein it has a structure obtained by the method defined in claim 9 .
11. The method according to claim 3 , wherein the pyrolysis is carried out under inert conditions.
12. The carbogel according to claim 1 , wherein it has a structure obtained by the method defined in claim 11 .
13. The method according to claim 11 , wherein the pyrolysis is carried out in an inert gas atmosphere, preferably selected from a group including: argon, nitrogen, and helium.
14. The carbogel according to claim 1 , wherein it has a structure obtained by the method defined in claim 13 .
15. The method according to claim 3 , wherein the pyrolysis is carried out under slightly reducing conditions.
16. The method according to claim 3 , wherein the pyrolysis is carried out in vacuo.
17. An anode material made from a carbogel for use in a lithium-ion cell, the carbogel comprising:
at least 92% by wt. of carbon; and
exhibiting, at a temperature of 20° C., an electrical conductance of at least 0.5 S/cm and a reversible electrochemical capacity in relation to lithium of at least 350 mAh/g under a C/2 discharge current; and wherein
the carbogel is prepared by a method comprising the steps of:
subjecting an aqueous suspension comprising 1-30% by wt. of a first starch composition consisting of rice starch in the amount of 75-99% by wt. and a second starch type in the amount of 1-25% by wt. to polycondensation at a temperature of 50-90° C.;
carrying out a solvent exchange using an aqueous solutions of an alcohol or a ketone with a concentration increasing from 10% to 99.8% to obtain an organic alcogel, and
subjecting the obtained organic alcogel to a pyrolysis process at a temperature of 300-2000° C. immediately following the solvent exchange step.
18. The anode material of claim 17 , wherein the carbogel exhibits a low roughness, vitreousness, lack of mesopores, and an ordered hierarchical lamellar structure.