Electrolyte formulations for electrochemical cells containing a silicon electrode

Abstract

Additives to electrolytes that enable the formation of comparatively more robust SEI films on silicon anodes. The SEI films in these embodiments are seen to be more robust in part because the batteries containing these materials have higher coulombic efficiency and longer cycle life than comparable batteries without such additives. The additives preferably contain a dicarbonate group or are an organo-metallic hydride.

1 . An electrochemical cell comprising:
 a cathode comprising an active cathode material capable of reversible intercalation of lithium ions;   a silicon alloy anode; and   a liquid electrolyte solution comprising a soluble additive and a lithium salt, wherein the additive is represented by the chemical structural formula (I):   
       
         
           
           
               
               
           
         
         where R 1  is selected from the group consisting of hydrogen, substituted and unsubstituted C 1 -C 20  alkyl groups, substituted and unsubstituted C 1 -C 20  alkenyl groups, substituted and unsubstituted C 1 -C 20  alkynyl groups, substituted and unsubstituted C 5 -C 20  aryl groups, hydride groups, halo groups, hydroxy groups, thio groups, alkyl groups, alkenyl groups, alkynyl groups, aryl groups, iminyl groups, alkoxy groups, alkenoxy groups, alkynoxy groups, aryloxy groups, carboxy groups, alkylcarbonyloxy groups, alkenylcarbonyloxy groups, alkynylcarbonyloxy groups, arylcarbonyloxy groups, alkylthio groups, alkenylthio groups, alkynylthio groups, arylthio groups, cyano groups, N-substituted amino groups, alkylcarbonylamino groups, N-substituted alkylcarbonylamino groups, alkenylcarbonylamino groups, N-substituted alkenyl carbonylamino groups, alkynylcarbonyl amino groups, N-substituted alkynylcarbonylamino groups, arylcarbonylamino groups, N-substituted arylcarbonylamino groups, boron-containing groups, aluminum-containing groups, silicon-containing groups, phosphorus-containing groups, and sulfur-containing groups. 
       
     
     
         2 . The electrochemical cell of  claim 1  wherein R 1  and R 2  each comprises an unsubstituted alkyl group. 
     
     
         3 . The electrochemical cell of  claim 1  wherein R 1  and R 2  each comprises an unsubstituted alkenyl group. 
     
     
         4 . The electrochemical cell of  claim 1  wherein R 1  and R 2  each comprises an unsubstituted aryl group. 
     
     
         5 . The electrochemical cell of  claim 1  wherein the additive comprises diallyl dicarbonate. 
     
     
         6 . The electrochemical cell of  claim 1  wherein the additive comprises dimethyl dicarbonate. 
     
     
         7 . The electrochemical cell of  claim 1  wherein the additive comprises diethyl dicarbonate. 
     
     
         8 . The electrochemical cell of  claim 1  wherein the additive comprises dibenzyl dicarbonate. 
     
     
         9 . The electrochemical cell of  claim 1 , further comprising a cathode having an active material represented by the chemical structural formula:
   LiNi x Mn y Co z O 2   (ii)
   where x+y+z=1.   
     
     
         10 . The electrochemical cell of  claim 1 , further comprising a cathode having an active material represented LiNi 0.33 Mn 0.33 Co 0.33 O 2 . 
     
     
         11 . The electrochemical cell of  claim 1  wherein the silicon alloy anode comprises greater than 50% graphite.