Intercalation electrode based on ordered graphene planes
An intercalation electrode includes an electron current collector and graphene planes deposited normal to the surface of the current collector substrate. The graphene planes are deposited on the current collector substrate from a carbon-precursor gas using, for example, chemical vapor deposition. In an embodiment of an anode for a lithium-ion battery, the graphene planes are intercalated with lithium atoms. A lithium-ion battery may include this anode, a cathode, and a non-aqueous electrolyte. In repeated charging and discharging of the anode, lithium atoms and ions are readily transported between the graphene planes of the anode and the electrolyte.
1. A method of making a negative electrode that intercalates and deintercalates lithium during charging and discharging, respectively, for a lithium-ion electrochemical cell, the method comprising:
providing a metallic foil comprising an electrode surface region;
forming a ductile metallic layer onto the electrode surface region;
directly growing graphene planes onto the ductile metallic layer generally perpendicular to the electrode surface region and coextensive with the electrode surface region by chemical vapor deposition of a gas composition comprising carbon-precursor molecules, wherein an electrically insulating polymeric binder and conductive diluents are not included along with the graphene planes
heating the ductile metallic layer to above 950° C. after the graphene planes have been formed on the ductile metallic layer to flow and wet the ductile metallic layer around edges of the graphene planes;
cooling the ductile metallic layer to bond the edges of the graphene planes to the ductile metallic layer; and
intercalating lithium into the graphene planes.
2. A method as recited in claim 1 wherein the carbon-precursor molecules are at least one of CH 4 , C 2 H 2 , or C 3 H 6 , and wherein the chemical vapor deposition is conducted in a temperature range of 300° C. to 600° C.
3. A method as set forth in claim 1 wherein the metallic foil comprises one of copper, nickel, or stainless steel.
4. A method as recited in claim 1 wherein the ductile metallic layer comprises at least one of silver or gold or their alloys.
5. A method as recited in claim 1 wherein the ductile metallic layer has an initial thickness of about 10 nm to about 10 μm.
6. A method as recited in claim 3 wherein the metallic foil comprises copper, and further comprising depositing a transition metal catalyst over at least a portion of the electrode surface region prior to forming the graphene planes.
7. A method as recited in claim 6 wherein the transition metal catalyst comprises one of Fe, Ni, Co, Pt, or their alloys.
8. A method as recited in claim 6 further comprising:
forming a ductile metallic layer onto the electrode surface region of the copper foil before forming the graphene planes;
depositing the transition metal catalyst onto at least a portion of the ductile metallic layer;
forming the graphene planes onto the ductile metallic layer;
heating the ductile metallic layer to above 950° C. after the graphene planes have been formed on the ductile metallic layer to flow and wet the ductile metallic layer around edges of the graphene planes; and
cooling the ductile metallic layer to bond the edges of the graphene planes to the ductile metallic layer.
9. A method as recited in claim 6 wherein the transition metal catalyst is discontinuous.
10. A method as recited in claim 9 wherein the transition metal catalyst comprises islands of about 20 to 1000 nm across.
11. A method as recited in claim 3 wherein the current collector substrate comprises one of nickel or stainless steel that does not include a catalyst on the electrode surface region, and further comprising annealing the current collector substrate in hydrogen flow prior to forming the graphene planes.