High capacity positive electrodes for use in lithium-ion electrochemical cells and methods of making same

Abstract

Positive electrode for lithium-ion electrochemical cells are provided that have capacity retentions of greater than about 95% after 50 charge-discharge cycles when comparing the capacity after cycle 52 with the capacity after cycle 2 when cycled between 2.5 V and 4.7 V vs. Li/Li + at 30° C. Compositions useful in the provided positive electrodes can have the formula, Li 1+x (Ni a Mn b Co c ) 1−x O 2 , wherein 0.05≦x≦0.10, a+b+c=1, 0.6≦b/a≦1.1, c/(a+b)<0.25, and a, b, and c are all greater than zero. The process of making these positive electrodes includes firing the compositions at 850° C. to 925° C.

What is claimed is: 
     
         1 . A positive electrode for a lithium-ion electrochemical cell comprising a composition having the formula,
   Li 1+x (Ni a Mn b Co c ) 1−x O 2 ,   wherein 0.05≦x≦0.10, a+b+c=1, 0.6≦b/a≦1.1, c/(a+b)<0.25, and a, b, and c are all greater than zero,   wherein said composition has a capacity retention of greater than about 95% after 50 cycles when comparing the capacity after cycle 52 with the capacity after cycle 2 when cycled between 2.5 V and 4.7 V vs. Li/Li +  at 30° C.   
     
     
         2 . A positive electrode for a lithium-ion electrochemical cell according to  claim 1 , wherein 0.10≦c≦0.20. 
     
     
         3 . A positive electrode for a lithium-ion electrochemical cell according to  claim 2 , wherein b/a is about 1. 
     
     
         4 . A positive electrode for a lithium-ion electrochemical cell according to  claim 1 , wherein 0.05≦x≦0.07. 
     
     
         5 . A positive electrode for a lithium-ion electrochemical cell according to  claim 1 , wherein the composition has been prepared by heating to a temperature ranging from 850° C. to 925° C. 
     
     
         6 . A positive electrode for a lithium-ion electrochemical cell according to  claim 1 , wherein said composition has a capacity retention of greater than about 90% after 50 cycles after 50 cycles when comparing the capacity after cycle 52 with the capacity after cycle 2 when cycled between 2.5 V and 4.7 V vs. Li/Li+ at 50° C. 
     
     
         7 . A lithium-ion electrochemical cell comprising:
 an anode;   an electrolyte; and   a positive electrode according to  claim 1 .