Characterization of  LT  ‐ Li x Co1 − y Ni y  O 2 Electrodes for Rechargeable Lithium Cells

LT ‐ LiCo 0.9 Ni 0.1 O 2 prepared at 400°C with a structure that is intermediate between an ideal lithiated spinel and a layered structure has been investigated as an electrode in rechargeable lithium cells; it delivers a voltage vs. pure lithium that is significantly lower than the voltage provided by its high‐temperature analogue, HT ‐ LiCo 0.9 Ni 0.1 O 2 , (synthesized at 900°C). The rechargeability of Li / LT ‐ LiCo 0.9 Ni 0.1 O 2 cells can be improved by leaching some lithium and a small amount of cobalt from LT ‐ LiCo 0.9 Ni 0.1 O 2 by acid treatment and loading the cells in a charged state. The improvement in electrochemical performance is attributed to the formation of a defect spinel phase Li 0.8 [ Co 1.6 Ni 0.2 ] O 4 in which the lithium ions adopt the tetrahedral A sites and the cobalt and nickel ions the B sites of an A [ B 2 ] O 4 spinel.