Encapsulated sulfur cathodes for rechargeable lithium batteries

Abstract

A method of forming a sulfur-based cathode material includes: 1) providing a sulfur-based nanostructure; 2) coating the nanostructure with an encapsulating material to form a shell surrounding the nanostructure; and 3) removing a portion of the nanostructure through the shell to form a void within the shell, with a remaining portion of the nanostructure disposed within the shell.

1 - 12 . (canceled) 
     
     
         13 . A cathode, comprising:
 a plurality of hollow carbon nanofibers, wherein each nanofiber defines an internal volume; and   a sulfur-based material disposed within the internal volume.   
     
     
         14 . The cathode of  claim 13 , wherein the carbon nanofibers are aligned with one another along their long axes. 
     
     
         15 . The cathode of  claim 13 , wherein the sulfur-based material occupies less than 100% of the internal volume to define a void. 
     
     
         16 . The cathode of  claim 13 , wherein the sulfur-based material is present in a weight ratio from about 1:20 to about 20:1, relative to the hollow carbon nanofibers. 
     
     
         17 . The cathode of  claim 16 , wherein the sulfur-based material is present in a weight ratio from about 1:1 to about 10:1, relative to the hollow carbon nanofibers. 
     
     
         18 . The cathode of  claim 13 , wherein the hollow carbon nanofibers have an outer lateral dimension in the range of about 10 nm to about 5 μm. 
     
     
         19 . The cathode of  claim 18 , wherein the hollow carbon nanofibers have an outer lateral dimension of about 200 nm to about 300 nm. 
     
     
         20 . The cathode of  claim 13 , wherein the sulfur-based material, in a substantially de-lithiated state, occupies from about 10% to about 90% of the internal volume. 
     
     
         21 . The cathode of  claim 13 , wherein the hollow carbon nanofibers have a wall thickness of from about 5 nm to about 20 nm. 
     
     
         22 . The cathode of  claim 13 , wherein the hollow carbon nanofibers are hexagonally packed. 
     
     
         23 . The cathode of  claim 13 , wherein the hollow carbon nanofibers comprise carbon and a second material selected from the group consisting of: polymers; metals; metal oxides; metal nitrides; and metal sulfides. 
     
     
         24 . A battery, comprising:
 a cathode;   an anode; and   an electrolyte disposed between the cathode and the anode,   wherein the cathode comprises:
 a plurality of hollow carbon nanofibers, wherein each hollow carbon nanofiber defines an internal volume; and 
 a sulfur-based material disposed within the internal volume. 
   
     
     
         25 . The battery of  claim 24 , wherein a long axis of the hollow carbon nanofibers is aligned along a direction of current flow in the battery. 
     
     
         26 . The battery of  claim 24 , wherein the sulfur-based material occupies less than 100% of the internal volume to define a void. 
     
     
         27 . The battery of  claim 24 , wherein the cathode has a sulfur mass loading of about 0.1 mg/cm′ to about 10 mg/cm 2 . 
     
     
         28 . The battery of  claim 24 , wherein the hollow carbon nanofiber comprises carbon that is at least partially graphitized. 
     
     
         29 . The battery of  claim 24 , wherein the sulfur-based material is present in a weight ratio from about 1:20 to about 20:1, relative to the hollow carbon nanofibers. 
     
     
         30 . The battery of  claim 24 , wherein the sulfur-based material, in a substantially de-lithiated state, occupies from about 10% to about 90% of the internal volume. 
     
     
         31 . The battery of  claim 24 , wherein the hollow carbon nanofibers have a wall thickness of about 0.5 nm to about 100 nm. 
     
     
         32 . The battery of  claim 24 , wherein the hollow carbon nanofibers are hexagonally packed.