Surface treatment of electrochemically active materials for rechargeable cells
Provided herein are methods for processing electrochemically active materials and resulting active material structures for use in rechargeable batteries. The resulting active materials structures include carbon containing coatings that partially or completely cover the surface of the active material structures. In a typical embodiment, the method includes providing a solution of carbon containing precursor in a solvent, dispersing electrochemically active material in the solution to form a mixture, removing the solvent from the mixture to form electrochemically active material coated with the carbon containing precursor, and heating the electrochemically active material coated with the carbon containing precursor in an inert atmosphere at a temperature sufficient to at least partially convert the carbon containing precursor into a carbon coating. Also provided are an electrochemically active material prepared according to the methods described herein, as well as an electrode and a rechargeable electrochemical cell, each containing such electrochemically active material.
1. A method for processing an electrochemically active material for use in a rechargeable cell, the method comprising:
providing a solution comprising a solvent and a carbon containing precursor;
dispersing the electrochemically active material in the solution to form a mixture wherein the electrochemically active material is lithium titanium oxide in particulate form prior to dispersing in solution;
removing the solvent from the mixture to form the electrochemically active material coated with the carbon containing precursor; and
heating the electrochemically active material coated with the carbon containing precursor in an inert atmosphere at a temperature less than 700° C. to at least partially convert the carbon containing precursor into a carbon coating.
2. The method of claim 1 , wherein the average particle size of the electrochemically active material is less than about 1 micrometer.
3. The method of claim 1 , wherein a weight ratio of carbon in the carbon containing precursor to the electrochemically active material in the mixture is insufficient to completely cover the electrochemically active material with the carbon coating.
4. The method of claim 1 , wherein the carbon containing precursor has a molecular weight of less than about 1000 g/mol.
5. The method of claim 1 , wherein the carbon containing precursor comprises a water-soluble polymer.
6. The method of claim 1 , wherein the carbon containing precursor comprises a carbohydrate.
7. The method of claim 6 , wherein the carbon containing precursor comprises one or more materials selected from the group consisting of sucrose, glucose, and fructose.
8. The method of claim 1 , wherein the carbon precursor is selected from the group consisting of fatty acids, glycerol esters, and poly-carboxylic acids.
9. The method of claim 1 , wherein the solution comprises one or more solvents selected from the group consisting of water, N-Methyl-2-pyrrolidone, acetone, ethanol, methanol, iso-propanol, and dimethylformamide.
10. The method of claim 1 , wherein removing the solvent from the mixture comprises drying at a pressure less than about 760 mmHg.
11. The method of claim 1 , wherein the inert atmosphere comprises one or more gases selected from the group consisting of nitrogen, argon, and carbon dioxide.
12. The method of claim 1 , further comprising mixing the coated electrochemically active material into a slurry comprising a binder and coating the slurry onto a conductive substrate.
13. The method of claim 12 , wherein the slurry is free of conductive additives.
14. The method of claim 1 , wherein a weight ratio of carbon in the carbon containing precursor to the electrochemically active material in the mixture is between about 0.1% and 10%.
15. The method of claim 1 , wherein a weight ratio of carbon in the carbon containing precursor to the electrochemically active material in the mixture is between about 0.5% and 5%.
16. The method of claim 1 , wherein a weight ratio of carbon in the carbon coating to the carbon in the carbon containing precursor is between about 50% and 99%.
17. The method of claim 1 , wherein the carbon containing precursor is partially carbonized during heating.
18. A method for processing an electrochemically active material for use in a rechargeable cell, the method comprising:
providing a solution comprising a solvent and a carbon containing precursor, wherein the solvent is water;
dispersing the electrochemically active material in the solution to form a mixture, wherein the electrochemically active material is lithium titanium oxide in particulate form prior to dispersing in solution;
removing the solvent from the mixture to form the electrochemically active material coated with the carbon containing precursor; and
heating the electrochemically active material coated with the carbon containing precursor in an inert atmosphere at a temperature less than 700° to at least partially convert the carbon containing precursor into a carbon coating.
19. The method of claim 18 , further comprising dispersing lithium titanium oxide in the solution with a weight ratio of 1:3.665 lithium titanium oxide: solution.
20. The method of claim 18 , wherein the inert atmosphere is 99.99% pure Argon gas.
21. A method for processing an electrochemically active material for use in a rechargeable cell, the method comprising:
providing a solution comprising a solvent and a carbon containing precursor, wherein the solvent is ethanol;
dispersing the electrochemically active material in the solution to form a mixture, wherein the electrochemically active material is lithium titanium oxide in particulate form prior to dispersing in solution;
removing the solvent from the mixture to form the electrochemically active material coated with the carbon containing precursor; and
heating the electrochemically active material coated with the carbon containing precursor in an inert atmosphere at a temperature less than 700° to at least partially convert the carbon containing precursor into a carbon coating.
22. The method of claim 21 , wherein the carbon containing precursor is butylated hydroxytoluene.
23. The method of claim 22 , further comprising adding butylated hydroxytoluene to the solution with a weight ratio of 1:55.38 BHT:Ethanol.
24. The method of claim 1 , wherein the solution has a viscosity of less than 100,000 cP.
25. The method of claim 1 , wherein the mixture has a viscosity of between about 1000 cP and 100,000 cP.