Electrode useable in electrochemical cell and method of making same

Abstract

A method of making an electrode useable in an electrochemical cell, includes the steps of (a) providing an electrically conductive substrate; (b) forming nanostructured current collectors on the conductive substrate; and (c) attaching nanoparticles of a ternary orthosilicate composite to the nanostructured current collectors. The ternary orthosilicate composite includes Li 2 Mn x Fe y Co z SiO 4 , where x+y+z=1.

What is claimed is: 
     
         1 . A method of making an electrode useable in an electrochemical cell, comprising the steps of:
 (a) providing an electrically conductive substrate;   (b) forming nanostructured current collectors on the conductive substrate; and   (c) attaching nanoparticles of a ternary orthosilicate composite to the nanostructured current collectors.   
     
     
         2 . The method of  claim 1 , wherein the conductive substrate comprises a film formed of an electrically conductive material. 
     
     
         3 . The method of  claim 2 , wherein the film is flexible or rigid. 
     
     
         4 . The method of  claim 1 , wherein the nanostructured current collectors comprise conductive nanotubes/fibers. 
     
     
         5 . The method of  claim 4 , wherein the conductive nanotubes/fibers comprie carbon nanotubes (CNTs) or carbon fibers (CFs). 
     
     
         6 . The method of  claim 4 , wherein the forming step comprises growing the conductive nanotubes/fibers on the conductive substrate. 
     
     
         7 . The method of  claim 1 , wherein the ternary orthosilicate composite comprises Li 2 Mn x Fe y Co z SiO 4 . 
     
     
         8 . The method of  claim 7 , wherein x+y+z=1. 
     
     
         9 . The method of  claim 7 , wherein the ternary orthosilicate composite is synthesized by a hydrothermal process comprising:
 (a) mixing starting precursors of lithium hydroxide, SiO 2  particles, Fe(II) chloride tetrahydrate, manganese chloride, and cobalt chloride, in a predetermined composition ratio to form a mixture;   (b) sealing the mixture under an Ar environment and baking the sealed mixture at a predetermined temperature for a period of time to form Li 2 Mn x Fe y Co z SiO 4  compound;   (c) rinsing the Li 2 Mn x Fe y Co z SiO 4  compound with de-ionized (DI) water;   (d) drying rinsed Li 2 Mn x Fe y Co z SiO 4  compound in vacuum;   (e) ball-milling the dried Li 2 Mn x Fe y Co z SiO 4  compound into nanoparticles; and   (f) calcining the Li 2 Mn x Fe y Co z SiO 4  powder in an inert or reducing environment.   
     
     
         10 . The method of  claim 7 , wherein the ternary orthosilicate composite is synthesized by a Pechini process comprising:
 (a) dispersing lithium acetate dehydrate, SiO 2  particles, citric acid, and ethylene glycol at a first predetermined composition ratio in de-ionized (DI) water to form a first mixture, wherein the mixture is sonicated for a period of time;   (b) adding Fe(III) citrate, manganese acetate, and cobalt carbonate at a second predetermined composition ratio into the first mixture to form a second mixture;   (c) stirring and dwelling the second mixture to form a Li 2 Mn x Fe y Co z SiO 4  gel;   (d) drying the Li 2 Mn x Fe y Co z SiO 4  gel to form Li 2 Mn x Fe y Co z SiO 4  compound;   (e) grinding the Li 2 Mn x Fe y Co z SiO 4  powders into nanoparticles; and   (f) heat-treating the Li 2 Mn x Fe y Co z SiO 4  powders in an inert or reducing atmosphere.   
     
     
         11 . The method of  claim 7 , wherein the ternary orthosilicate compound is synthesized by a sol-gel process comprising the steps of:
 (a) dispersing lithium acetate, iron citrate, manganese acetate and cobalt carbonate at a first predetermined composition ratio in de-ionized (DI) water to form a first mixture;   (b) adding citric acid to the first mixture to form a second mixture,   (c) adding tetraethylorthosilicate (TEOS) and ethanol at a second predetermined composition ratio to form a third mixture;   (d) stirring and dwelling the third mixture at a reflux station to form a Li 2 Mn x Fe y Co z SiO 4  gel;   (e) drying the Li 2 Mn x Fe y Co z SiO 4  gel to form a Li 2 Mn x Fe y Co z SiO 4  compound;   (f) grinding the Li 2 Mn x Fe y Co z SiO 4  compound into nanoparticles; and   (g) calcining the Li 2 Mn x Fe y Co z SiO 4  powders in an inert or reducing environment.   
     
     
         12 . The method of  claim 1 , wherein the attaching step is performed by a dripping/wetting process comprising:
 (a) preparing a suspension of the nano-particles of the ternary orthosilicate composite in a liquid medium;   (b) dripping the suspension into the nanostructured current collectors in electrical contact with the conductive substrate; and   (c) drying the suspension to attach the nano-particles of the ternary orthosilicate composite onto the nanostructured current collectors.   
     
     
         13 . The method of  claim 12 , wherein the liquid medium comprises acetone, water or other liquid media. 
     
     
         14 . The method of  claim 1 , further comprising filling an electrolyte solution in spaces defined among the nanostructured current collectors and the nanoparticles of the active material.