Biocarbon Cathode Materials with Heterocyclic Aromatic Rings Bonded to Sulfur
Described are sulfurized-carbon particles, and methods of making them, for use in cathodes of energy-storage devices. In the material that makes up the particles, those carbon atoms with the adjacent sulfur atoms are bonded to the adjacent sulfur atoms via carbon-sulfur bonds. The methods rely on readily available biological materials and sulfur. Biological materials, products of living cells, are made largely of organic macromolecules; namely, carbohydrates, lipids, proteins, and nucleic acids. In a cathode, most of the carbon and nitrogen atoms in the carbon-sulfur is incorporated into heterocyclic aromatic rings that strongly bind the sulfur and promote electrical conductivity.
1 . Sulfurized carbon comprising:
carbon atoms;
nitrogen atoms;
clustered heterocyclic aromatic rings incorporating most of the carbon atoms in the sulfurized carbon and most of the nitrogen atoms in the sulfurized carbon;
primary sulfur atoms, each primary sulfur atom adjacent to at least one of the carbon atoms, wherein most of the primary sulfur atoms are covalently bonded to at least one of the carbon atoms via a carbon-sulfur bond; and
secondary sulfur atoms, each secondary sulfur atom separated from each of the carbon atoms by at least one intervening atom.
2 . The sulfurized carbon of claim 1 , wherein the carbon comprises a biocarbon.
3 . The sulfurized carbon of claim 1 , wherein most of the heterocyclic aromatic rings include at least one of the nitrogen atoms.
4 . The sulfurized carbon of claim 1 , wherein the carbon atoms, the primary sulfur atoms, and the secondary sulfur atoms have a combined weight; and the primary sulfur atoms and the secondary sulfur atoms have a sulfur weight greater than 10 wt % of the combined weight.
5 . The sulfurized carbon of claim 1 , wherein the nitrogen atoms comprise between 1 wt % and 10 wt % of the sulfurized carbon.
6 . The sulfurized carbon of claim 1 , wherein most of the heterocyclic aromatic rings have a size between 2 nm and 20 nm.
7 . The sulfurized carbon of claim 1 , wherein the heterocyclic aromatic rings are covalently bonded to form particles.
8 . The sulfurized carbon of claim 7 , wherein a majority of the particles have a size between 0.5 μm and 30 μm.
9 . The sulfurized carbon of claim 1 , wherein the particles form agglomerates.
10 . The sulfurized carbon of claim 9 , wherein a majority of the agglomerates have a size between 2 μm and 60 μm.
11 . The sulfurized carbon of claim 1 , wherein the carbon atoms include carbon-14 atoms and carbon-12 atoms at a ratio of the carbon-14 atoms to the carbon-12 atoms of 1.25/10E12.
12 . The sulfurized carbon of claim 1 , wherein the primary sulfur atoms outnumber the secondary sulfur atoms.
13 . The sulfurized carbon of claim 12 , wherein a majority of the secondary sulfur atoms are covalently bonded to at least one of the primary sulfur atoms or secondary sulfur atoms via a sulfur-sulfur bond.
14 . The sulfurized carbon of claim 1 , wherein a portion of the carbon atoms are arranged in at least one of carbon nanotubes, graphene, graphene nanoribbon, graphene quantum dots, graphene oxide, and reduced graphene oxide.
15 . A method of making sulfurized biocarbon, the method comprising
heating at least one biological material with sulfur, each biological material comprising organic macromolecules, to a temperature of at least 300° C.;
wherein the biological material is sulfurized as it reacts with the sulfur, pyrolyzed and converted to the sulfurized biocarbon, and wherein the sulfurized biocarbon comprises:
carbon atoms;
nitrogen atoms;
heterocyclic aromatic rings incorporating most of the carbon atoms and most of the nitrogen atoms;
primary sulfur atoms adjacent the carbon atoms; and
secondary sulfur atoms separate from the carbon atoms by at least one intervening atom;
wherein a majority of the primary sulfur atoms are covalently bonded to the adjacent carbon atoms via carbon-sulfur bonds; and
wherein the primary sulfur atoms in combination with the secondary sulfur atoms are greater than 10% of the sulfurized biocarbon by weight.
16 . The method of claim 15 , wherein the aromatic rings incorporate most of the wherein the biological material consists predominantly of the organic macromolecules.
17 . The method of claim 15 , further comprising producing the at least one biological material before the heating by pre-heating a biological precursor with functional groups to a temperature below 300° C. to decompose at least one of its functional groups.
18 . An electrode comprising:
amorphous carbon-sulfur including:
carbon atoms, sulfur atoms, and nitrogen atoms;
wherein most of the carbon atoms and most of the nitrogen atoms are incorporated into heterocyclic aromatic rings; and
the sulfur atoms are bonded to the heterocyclic aromatic rings via carbon-sulfur chemical bonds.
19 . The electrode of claim 18 , wherein most of the heterocyclic aromatic rings include at least one of the nitrogen atoms.
20 . The electrode of claim 18 , further comprising a conductive framework of tangled nanofibers extending through the carbon-sulfur.
21 . The electrode of claim 18 , wherein the carbon atoms are primarily biocarbon.