Core-shell structured nanoparticles for lithium-sulfur cells

Abstract

Described is a method of synthesizing a plurality of core-shell nanoparticles. The method includes forming shells around a plurality of lithium sulfide nanoparticles, wherein the shells conduct electrons and lithium ions.

What is claimed is: 
     
         1 . A method of synthesizing a plurality of core-shell nanoparticles comprising:
 providing a plurality of lithium sulfide nanoparticles; and   forming shells around the plurality of lithium sulfide nanoparticles, wherein the shells conduct electrons and lithium ions.   
     
     
         2 . The method of  claim 1 , further comprising synthesizing the plurality of lithium sulfide nanoparticles, the synthesizing comprising:
 dissolving or suspending a plurality of sulfur particles in an organic solvent to form a solution or suspension;   adding a lithium reducing agent to the solution to react with the plurality of sulfur particles and form precipitates comprising the plurality of lithium sulfide nanoparticles; and   separating the plurality of lithium sulfide nanoparticles from the solution.   
     
     
         3 . The method of  claim 1 , wherein the shells comprise carbon shells and forming the shells around the plurality of lithium sulfide nanoparticles comprises:
 performing chemical vapor deposition (CVD) of carbon onto the plurality of lithium sulfide nanoparticles based on heating the plurality of lithium sulfide nanoparticles in the presence of an oxygen free organic vapor.   
     
     
         4 . The method of  claim 3 , wherein the organic vapor comprises one of methane, ethylene or acetylene. 
     
     
         5 . The method of  claim 1 , wherein forming the shells around the plurality of lithium sulfide nanoparticles comprises:
 adding the plurality of lithium sulfide nanoparticles to a solution comprising a polar organic solvent and a polymer; and   evaporating the polar organic solvent, leaving behind a plurality of coated lithium sulfide nanoparticles having polymer shells formed thereon.   
     
     
         6 . The method of  claim 5 , wherein the polar organic solvent comprises toluene, the polymer comprises polyaniline, and the shells comprise polyaniline shells. 
     
     
         7 . The method of  claim 5 , further comprising:
 heating the plurality of core-shell nanoparticles to convert the polymer shells into carbon shells.   
     
     
         8 . The method of  claim 1 , wherein the shells comprise titanium disulfide shells and forming the shells around the plurality of lithium sulfide nanoparticles comprises reacting titanium tetrachloride onto the plurality of lithium sulfide nanoparticles. 
     
     
         9 . The method of  claim 1 , further comprising:
 creating a mixture comprising the plurality of core-shell nanoparticles, an organic solvent and a polymer binder; and   coating an electrical conductor with the mixture to form a positive electrode.   
     
     
         10 . The method of  claim 9 , further comprising:
 providing a negative electrode;   forming a cell of a lithium sulfur battery that comprises the positive electrode, the negative electrode and an electrolyte separating the positive electrode and the negative electrode, wherein the electrolyte comprises a lithium salt dissolved in an ionic liquid and a porous separator, the ionic liquid being absorbed into the porous separator; and   hermetically sealing the cell.   
     
     
         11 . The method of  claim 1 , wherein the shells comprise carbon. 
     
     
         12 . The method of  claim 1 , wherein the shells comprise polyaniline.