Vertically aligned carbon nanotube arrays as electrodes

Abstract

Embodiments of the present disclosure pertain to electrodes that include a plurality of vertically aligned carbon nanotubes and a metal associated with the vertically aligned carbon nanotubes. The vertically aligned carbon nanotubes may be in the form of a graphene-carbon nanotube hybrid material that includes a graphene film covalently linked to the vertically aligned carbon nanotubes. The metal may become reversibly associated with the carbon nanotubes in situ during electrode operation and lack any dendrites or mossy aggregates. The metal may be in the form of a non-dendritic or non-mossy coating on surfaces of the vertically aligned carbon nanotubes. The metal may also be infiltrated within bundles of the vertically aligned carbon nanotubes. Additional embodiments pertain to energy storage devices that contain the electrodes of the present disclosure. Further embodiments pertain to methods of forming said electrodes by applying a metal to a plurality of vertically aligned carbon nanotubes.

What is claimed is: 
     
         1 . (canceled) 
     
     
         2 . A method for reversibly storing lithium metal in electrodes of an energy-storage device, the method comprising:
 providing carbon nanotubes on a substrate, the carbon nanotubes forming a carbon-nanotube electrode;   inserting a metal into the carbon-nanotube electrode, the metal including at least one of Li, Na, K, Mg, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Sn, Sb, and Pb, to charge the energy-storage device; and   removing the inserted metal from the carbon-nanotube electrode to discharge the energy-storage device.   
     
     
         3 . The method of  claim 2 , wherein providing the carbon nanotubes on the substrate forms an ohmic contact between the carbon nanotubes and the substrate. 
     
     
         4 . The method of  claim 2 , wherein the substrate includes a graphene film, and wherein providing the carbon nanotubes on the substrate comprises growing the carbon nanotubes from the graphene film. 
     
     
         5 . The method of  claim 2 , wherein the metal consists essentially of lithium. 
     
     
         6 . The method of  claim 5 , wherein the carbon nanotubes and the lithium have a capacity greater than 339 mAh/g. 
     
     
         7 . The method of  claim 6 , wherein the carbon nanotubes and the lithium have a capacity greater than 1,857 mAh/g. 
     
     
         8 . The method of  claim 7 , wherein an amount of the metal inserted into the carbon-nanotube electrode is a function of a charge of the energy-storage device. 
     
     
         9 . The method of  claim 2 , wherein the carbon nanotubes extend vertically from the substrate. 
     
     
         10 . The method of  claim 2 , further comprising, while removing the inserted metal from the carbon nanotubes, moving the removed metal to a cathode. 
     
     
         11 . The method of  claim 10 , wherein the cathode comprises sulfur. 
     
     
         12 . An energy-storage device comprising:
 an anode having a metal inserted into a carbon-nanotube electrode, the metal of at least one of Li, Na, K, Mg, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Sn, Sb, and Pb;   an electrolyte in contact with the metal inserted into the carbon-nanotube electrode; and   a cathode in contact with the electrolyte opposite the anode.   
     
     
         13 . The energy-storage device of  claim 12 , further comprising a current collector in ohmic contact with the carbon-nanotube electrode. 
     
     
         14 . The energy-storage device of  claim 13 , the current collector including a substrate with a graphene film, wherein the carbon nanotubes extend from the graphene film. 
     
     
         15 . The energy-storage device of  claim 12 , the carbon-nanotube electrode including carbon nanotubes that extend vertically from a substrate. 
     
     
         16 . The energy-storage device of  claim 12 , wherein the metal inserted into the carbon-nanotube electrode consists essentially of lithium. 
     
     
         17 . The energy-storage device of  claim 16 , wherein an amount of the lithium is a function of a charge of the energy-storage device. 
     
     
         18 . The energy-storage device of  claim 12 , wherein the carbon-nanotube electrode includes at least one of monolayer graphene, few-layer graphene, double-layer graphene, triple-layer graphene, multi-layer graphene, graphene nanoribbons, graphene oxide, reduced graphene oxide, and graphite.