Effects of aluminum doping on the phase stability and electrochemical properties of LiCoO_2 and LiMnO_2

摘要

Aluminum is of interest as a consitutent for Li battery electrodes due to its low cost and low mass, and becasue ab initio calculations indicate that solid solution of LialO_2 with LiMO_2 (M chemical bounds transition metal) in the alpha -NaFeO_2 structure can increase intercalation voltage [1]. In this study, we investigated the effect of Al doping on LiCoO_2 and LiMnO_2. Single phase LiAl_yCo_(1-y)O_2 has been synthesized up to y chemical bounds 0.5 by firing homogeneous hydroxide precursor. A systematic increase in the open circuit voltage is observed with Al content. In LiAl_yMn_(1-y)O_2, the addition of LialO_2 stabilizes LiMnO_2 in the alpha -NaFeO_2 structure under conditions where neither endmember is stable in the structure. High resersible capacity was obtained over both a 4 V and 3 V plateau, indicating that the compond transforms to a spinel-related structure during cycling, but that the cooperative jahn-Teller distortion is suppressed.