Preparation and electrochemical properties of Zn-doped LiNi0.8Co0.2O2

Zn-doped LiZnyNi0.8-yCo0.2O2 (0.0000 less than or equal to y less than or equal to 0.0100) compositions were synthesized by a conventional solid-state method. The products were characterized by XRD, galvanostatic cycling, cyclic voltammetry, electrochemical impedance spectroscopy and thermal analysis. For the LiZn0.0025Ni0.7975Co0.2O2 system cycled between 3.0 and 4.2 V, the discharge capacities in the 1st and 100th cycles were 170 and 138 mAh/g with charge retention of 81%. The corresponding values for the undoped material were 158 and 97 mAh/g, with charge retention of 61.4%. The improved electrochemical properties of the doped system were attributed to the structural stability derived from incorporating the size-invariant Zn2+ ions. The Zn-doped system also showed improved capacity and cyclability when the cycling was performed in a voltage wider window (2.5-4.4 V) and at a higher temperature (55 degreesC). The structural and electrochemical properties of the doped and undoped materials were correlated. (C) 2002 Elsevier Science B.V. All rights reserved.