CARBON NANOTUBE CARPET ON AND GROWN FROM COPPER
An anode for an electrochemical cell includes a base layer, predominantly of copper, and an interfacial layer from which extends a carpet of carbon nanotubes. The interfacial layer includes an alloy of the copper and a nanotube catalyst from which the nanotubes nucleate and grow. Lithium metal stored within and between the carbon nanotubes forms an active anode layer.
1 . An electrode comprising:
a base layer predominantly of copper at a first concentration;
an interfacial layer on the base layer, the interfacial layer including copper at a second concentration and a carbon-nanotube catalyst; and
carbon nanotubes extending from the interfacial layer.
2 . The electrode of claim 1 , wherein the interfacial layer comprises an alloy of the copper at the second concentration and iron.
3 . The electrode of claim 2 , wherein the carbon-nanotube catalyst includes precipitates of the iron.
4 . The electrode of claim 3 , wherein the carbon nanotubes extend from the precipitates of the iron.
5 . The electrode of claim 1 , wherein the second concentration is lower than the first concentration
6 . The electrode of claim 1 , the interfacial layer including a catalyst layer opposite the base layer.
7 . The electrode of claim 6 , wherein the catalyst layer is predominantly of a metal other than copper.
8 . The electrode of claim 7 , wherein the metal other than copper comprises iron.
9 . The electrode of claim 1 , wherein the interfacial layer is of a thickness between three and twenty nanometers.
10 . The electrode of claim 1 , the carbon nanotubes further comprising a second metal.
11 . The electrode of claim 10 , wherein the second metal comprises aluminum.
12 . The electrode of claim 10 , wherein the second metal is of a concentration in the carbon nanotubes that varies in proportion to a distance from the interfacial layer.
14 . The electrode of claim 1 , wherein the carbon-nanotube catalyst is of a metal with an interfacial concentration in the interfacial layer and a lower concentration in the base layer.
15 . The electrode of claim 1 , wherein the interfacial layer is in ohmic contact with the base layer.
16 . The electrode of claim 4 , wherein the interfacial layer is in ohmic contact with the carbon nanotubes.
17 . The electrode of claim 1 , wherein most of the carbon nanotubes are bonded to the interfacial layer by at least one metallic bond.
18 . The electrode of claim 1 , further comprising a substrate supporting the base layer opposite the interfacial layer.
19 . The electrode of claim 1 , wherein the copper includes a copper-oxide layer.
20 . The electrode of claim 1 , wherein the copper includes a copper surface comprising elements other than the copper constituting less than 20 wt. % of the copper surface.
21 . A method of forming nanotubes on an electrode comprising a base layer predominantly of copper, a catalyst layer of a nanotube catalyst on the base layer, and a protective layer over the catalyst layer, the method comprising:
exposing the protective layer to a nanotube source gas;
heating the electrode, the heating producing an interfacial layer on the base layer, the interfacial layer comprising an alloy of the copper and the nanotube catalyst; and
growing the nanotubes between the interfacial layer and the protective layer.
22 . The method of claim 21 , the nanotubes lifting the protective layer from the interfacial layer in consequence of the growing.
23 . The method of claim 21 , further comprising obtaining the electrode by forming the catalyst layer over the base layer and forming the protective layer over the catalyst layer.
24 . The method of claim 21 , wherein the catalyst layer comprises iron.
25 . The method of claim 21 , wherein the protective layer comprises an oxide of aluminum.
26 . The method of claim 21 , further comprising absorbing the protective layer into the nanotubes during the growing.
27 . The method of claim 21 , wherein the nanotubes are carbon nanotubes.