Electrode including nanostructures for rechargeable cells

Abstract

A lithium ion battery electrode includes silicon nanowires used for insertion of lithium ions and including a conductivity enhancement, the nanowires growth-rooted to the conductive substrate.

What is claimed is: 
     
         1 . A lithium ion battery electrode comprising:
 a conductive substrate; and   silicon containing nanowires substrate-rooted to the conductive substrate,
 the silicon containing nanowires having variable cross-sectional dimensions along the length of the silicon containing nanowires and having tapered profiles with wider ends and narrower ends, 
 wherein the wider ends are substrate-rooted to the conductive substrates to provide conductive attachment and mechanical support to the silicon containing nanowires with respect to the conductive substrate. 
   
     
     
         2 . The electrode of  claim 1 , wherein the silicon containing nanowires further comprise a silicide. 
     
     
         3 . The electrode of  claim 1 , wherein the silicon containing nanowires further comprise a carbide. 
     
     
         4 . The electrode of  claim 1 , wherein the silicon containing nanowires each comprise a silicide core and a silicon shell. 
     
     
         5 . The electrode of  claim 1 , wherein the conductive substrate comprises nickel. 
     
     
         6 . The electrode of  claim 1 , wherein the conductive substrate is provided in the form of a structure selected from the group consisting of a mesh, a perforated sheet, a foam, and a felt. 
     
     
         7 . The electrode of  claim 1 , the silicon containing nanowires comprise substrate-rooted cores and a layer of an electrochemically active material coating the substrate-rooted cores. 
     
     
         8 . The electrode of  claim 7 , wherein the electrochemically active material comprises a material selected from the group of consisting silicon, tin, and germanium. 
     
     
         9 . The electrode of  claim 8 , wherein the substrate-rooted cores comprise a silicide, and wherein the electrochemically active material consists essentially of silicon. 
     
     
         10 . The electrode of  claim 1 , further comprising a shell coating the silicon containing nanowires. 
     
     
         11 . The electrode of  claim 10 , wherein the shell comprising a carbon-containing material. 
     
     
         12 . The electrode of  claim 1 , wherein the silicon containing nanowires each contains a narrow neck located between a substrate-rooted end and a free end of the silicon containing nanowires. 
     
     
         13 . The electrode of  claim 1 , wherein the silicon containing nanowires have an average aspect ratio of at least about ten. 
     
     
         14 . The electrode of  claim 1 , wherein the silicon containing nanowires have an average cross-sectional dimension of between about 1 nanometer and 10 microns on average. 
     
     
         15 . The electrode of  claim 1 , wherein the silicon containing nanowires form a layer over the conductive substrate, the layer having porosity of less than about 75 percent. 
     
     
         16 . The electrode of  claim 1 , wherein the silicon containing nanowires have an average length of at least about 100 micrometers. 
     
     
         17 . The electrode of  claim 1 , wherein the silicon containing nanowires consist essentially of silicon. 
     
     
         18 . The electrode of  claim 1 , wherein the average cross-sectional dimension of the wider ends is below the silicon fracture. 
     
     
         19 . The electrode of  claim 1 , wherein the silicon containing nanowires are growth-rooted to the substrate. 
     
     
         20 . A lithium ion battery comprising:
 a negative electrode comprising a conductive substrate and silicon containing nanowires substrate-rooted to the conductive substrate,
 the silicon containing nanowires having variable cross-sectional dimensions along the length of the silicon containing nanowires and having tapered profiles with wider ends and narrower ends, 
 wherein the wider ends are substrate-rooted to the conductive substrates to provide conductive attachment and mechanical support to the silicon containing nanowires with respect to the conductive substrate.