Understanding the Anomalous Capacity of Li/Li[Ni[sub x]Li[sub (1/3−2x/3)]Mn[sub (2/3−x/3)]]O[sub 2] Cells Using In Situ X-Ray Diffraction and Electrochemical Studies

The electrochemical behavior of cells for 1/4, 1/3, 5/12, and 1/2 is reported. is derived from or by substitution of and by while maintaining all the remaining Mn atoms in the oxidation state. Conventional wisdom suggests that lithium can be removed from these materials only until both the Ni and Mn oxidation states reach giving a charge capacity of We show that cells give smooth reversible voltage profiles reaching about 4.45 V when Li atoms per formula unit are removed, as expected. If the cells are charged to higher voltages, surprisingly, they exhibit a long plateau of length approximately equal to in the range between 4.5 and 4.7 V. Subsequent to this plateau, the materials can reversibly cycle over 225…

• DU
  Dalhousie University
• NS
  Natural Sciences and Engineering Research Council of Canada