Influence of LiF Additions on Li[Ni[sub x]Co[sub 1−2x]Mn[sub x]]O[sub 2] Materials

Abstract

Changing the synthesis conditions of layered stoichiometric LiMnO2LiMnO2 (O3 structure) induces differences in the charge/discharge capacity as a function of cycle number, during conversion of layered stoichiometric LiMnO2LiMnO2 to LiMn2O4LiMn2O4 spinel. Once a spinel phase has formed, such differences disappear, except for material synthesized by melt exchange. Differences in behavior between LiMnO2LiMnO2 and LixMnyO2LixMnyO2 are attributed to the former converting to spinel via a 2-phase reaction. A nanodomain structure forms on cycling LiMnO2,LiMnO2, but unlike nonstoichiometric LixMnyO2,LixMnyO2, or the nonstoichiometric doped materials, the domains show some evidence of growth on cycling. Ballmilling can improve the cyclability at low cycle numbers, hastening the conversion to spinel and attenuating somewhat the dip and rise in capacity in the early stages of cycling; however, ballmilling also induces greater fade at higher cycle numbers. © 2004 The Electrochemical Society. All rights reserved.