Structurally stable active material for battery electrodes
A process of producing active material for an electrode of an electrochemical cell includes providing lithium-intercalating carbon particles having an average particle size of 1 μm to 100 μm as component 1, providing silicon particles having an average particle size of 5 nm to 500 nm as component 2, providing a polymer or polymer precursor which can be pyrolyzed to form amorphous carbon and is selected from the group consisting of epoxy resin, polyurethane resin and polyester resin, as component 3, mixing components 1 to 3 in to a mixture and heat treating the mixture substantially in the absence of atmospheric oxygen at a temperature at which the pyrolyzable polymer or the pyrolyzable polymer precursor decomposes to form amorphous carbon.
1. A process of producing active material for an electrode of an electrochemical cell containing sodium carboxymethylcellulose comprising:
providing lithium-intercalating carbon particles having an average particle size of 1 μm to 100 μm as component 1,
providing silicon particles having an average particle size of 5 nm to 500 nm as component 2,
providing a polymer or polymer precursor which can be pyrolyzed to form amorphous carbon and is selected from the group consisting of, an epoxy resin based on bisphenol A and epichlorohydrin, polyurethane resin and polyester resin, as component 3,
mixing components 1 to 3 into a mixture such that component 3 comprises 20 to 80 wt % of the mixture, and
heat treating the mixture substantially in the absence of atmospheric oxygen at a temperature at which the pyrolyzable polymer or the pyrolyzable polymer precursor decomposes to form amorphous carbon.
2. The process as claimed in claim 1 , wherein the mixture comprises amorphous conductive carbon black as component 4.
3. The process as claimed in claim 1 , wherein:
a proportion of silicon particles in the mixture is 10% by weight to 50% by weight; and/or
a proportion of lithium-intercalating carbon particles in the mixture is 20% by weight to 80% by weight; and/or
a proportion of the amorphous conductive carbon black in the mixture is from 1% by weight to 20% by weight.
4. The process as claimed in claim 1 , wherein component 3 is initially provided as a solution in a solvent and the components 1 and/or 2 are dispersed in the solution.
5. The process as claimed in claim 1 , further comprising adding a hardener for the polymer or the polymer precursor to the mixture, after components 1 and/or 2 have been dispersed in the solution.
6. The process as claimed in claim 5 , wherein the solvent is removed before the heat treatment.
7. The process as claimed in claim 1 , wherein the mixture is heat treated at a temperature of 500° C. to 1200° C.
8. The process as claimed in claim 1 , wherein the heat treatment is carried out in a reducing atmosphere.
9. The process as claimed in claim 1 , wherein the cured mixture is pulverized before the heat treatment.
10. The process as claimed in claim 2 , wherein component 3 is initially provided as a solution in a solvent and the components 1, 2 and/or 4 are dispersed in the solution.
11. The process as claimed in claim 2 , further comprising adding a hardener for the polymer or the polymer precursor to the mixture, after components 1, 2 and/or 4 have been dispersed in the solution.
12. The process as claimed in claim 11 , wherein the solvent is removed before the heat treatment.