Energy storage devices

Abstract

A novel hybrid lithium-ion anode material based on coaxially coated Si shells on vertically aligned carbon nanofiber (CNF) arrays. The unique cup-stacking graphitic microstructure makes the bare vertically aligned CNF array an effective Li+ intercalation medium. Highly reversible Li′ intercalation and extraction were observed at high power rates. More importantly, the highly conductive and mechanically stable CNF core optionally supports a coaxially coated amorphous Si shell which has much higher theoretical specific capacity by forming fully lithiated alloy. Addition of surface effect dominant sites in close proximity to the intercalation medium results in a hybrid device that includes advantages of both batteries and capacitors.

What is claimed is: 
     
         1 . An electrode comprising:
 a conductive substrate;   a plurality of support structures held in proximity to the conductive substrate; and   a plurality of multi-layered nanoparticles dispersed with the plurality of support structures, wherein the multi-layered nanoparticles provide surface effect dominant sites to adsorb charge carriers via faradaic interactions or catalyze intercalation of the charge carriers, and the multi-layered nanoparticles comprise an inner core comprising Si, Co, Ni, Mn, Ta, Ru, Rb, Ti, Sn, V 2 O 2 , FeO, Cu or Fe, and an outer layer comprising graphene or graphite.   
     
     
         2 . The electrode of  claim 1 , wherein the inner core comprises silicon. 
     
     
         3 . The electrode of  claim 1 , wherein the plurality of nanoparticles have an average diameter of less than 1 μm. 
     
     
         4 . The electrode of  claim 1 , wherein the conductive substrate comprises one or more of Cu, Au, and Sn. 
     
     
         5 . The electrode of  claim 1 , wherein each of the plurality of support structures comprises at least one of a graphite and a carbonaceous material. 
     
     
         6 . The electrode of  claim 1 , wherein the plurality of support structures comprises a plurality of carbon nanotubes. 
     
     
         7 . The electrode of  claim 1 , wherein the plurality of support structures comprise a plurality of carbon particles. 
     
     
         8 . The electrode of  claim 1 , wherein the one or more charge carriers comprises lithium ions. 
     
     
         9 . The electrode of  claim 1 , wherein the plurality of nanoparticles is selected to donate electrons to the one or more charge carriers on a surface of each of the plurality of nanoparticles via faradic interactions.