Method of depositing silicon on carbon materials and forming an anode for use in lithium ion batteries

Abstract

A method of modifying the surface of carbon materials such as vapor grown carbon nanofibers is provided in which silicon is deposited on vapor grown carbon nanofibers using a chemical vapor deposition process. The resulting silicon-carbon alloy may be used as an anode in a rechargeable lithium ion battery.

What is claimed is: 
     
         1 . An anode for use in a lithium ion battery, said anode formed by:
 providing a carbon material selected from vapor grown carbon fibers, vapor grown carbon nanofibers, and PAN or pitch derived carbon fibers;   heating said carbon material at a temperature between about 100° C. to about 1200° C.;   flowing a silicon-containing precursor gas in contact with said carbon material for a time sufficient for said gas to decompose and form a coating on at least the surface of said carbon material; and   adding a binder to said silicon-coated carbon material.   
     
     
         2 . The anode of  claim 1  wherein said precursor gas comprises silane, a blend of silane and hydrogen, or a blend of silane and an inert gas. 
     
     
         3 . The anode of  claim 1  wherein said carbon material comprises vapor grown carbon nanofibers. 
     
     
         4 . The anode of  claim 3  wherein said vapor grown carbon nanofibers have been heated treated at a temperature above 700° C. 
     
     
         5 . The anode of  claim 1  wherein said silicon coating comprises crystalline silicon, amorphous silicon, or silicon compounds. 
     
     
         6 . The anode of  claim 1  wherein said carbon material further includes a carbide material selected from metal carbides, silicon carbides, and silicon oxides. 
     
     
         7 . The anode of  claim 1  wherein said carbon material further includes a carbon or graphite additive selected from single-walled carbon nanotubes, multi-walled carbon nanotubes, exfoliated graphite flakes, graphite platelets, graphene particles, carbon black, and mesocarbon microbeads. 
     
     
         8 . The anode of  claim 1  wherein said carbon material further includes a conductive additive comprising macroscopic vapor grown carbon nanofibers having a diameter of from about 500 nm to 10 micrometers. 
     
     
         9 . The anode of  claim 1  wherein said carbon material has a length of from about 1 to about 500 micrometers. 
     
     
         10 . The anode of  claim 1  wherein said carbon material is in the form of a composite or preform. 
     
     
         11 . The anode of  claim 1  wherein said silicon is coated onto said carbon material at a thickness of about 0.001 and 100 microns. 
     
     
         12 . The anode of  claim 1  wherein said silicon is coated onto said carbon material at a thickness of about 2 to 100 nm. 
     
     
         13 . The anode of  claim 1  wherein said silicon-coated carbon material has a graded interface. 
     
     
         14 . The anode of  claim 1  wherein said binder is selected from polyvinylidene difluoride, EPDM, and polystyrene. 
     
     
         15 . The anode of  claim 1  having an electrical conductivity of from about 0.01 to about 0.5 ohm/cm. 
     
     
         16 . The anode of  claim 1  having an irreversible capacity of from about 5% to 40% of total capacity. 
     
     
         17 . The anode of  claim 1  having a reversible capacity of at least 350 mAH/g. 
     
     
         18 . The anode of  claim 1  having a reversible capacity of at least 1000 mAH/g. 
     
     
         19 . The anode of  claim 1  having a thermal conductivity of at least 50 w/m-K up to 1000 w/m-K. 
     
     
         20 . A lithiated carbon-silicon alloy formed by providing a carbon material selected from vapor grown carbon fibers, vapor grown carbon nanofibers, PAN or pitch derived carbon fibers, graphite flakes, graphene platelets, and carbon nanotubes;
 heating said carbon material at a temperature between about 100° C. to about 1200° C.;   flowing a silicon-containing precursor gas in contact with said carbon material for a time sufficient for said gas to decompose and form a coating on at least the surface of said carbon material; and   depositing lithium on the silicon-coated carbon material by evaporation.