THE INFLUENCE OF DOPING ON THE OPERATION OF LITHIUM MANGANESE OXIDE SPINEL

LiMn2O4 and LiMn2-xCoxO4 (0.1 less than or equal to x less than or equ al to 0.4) samples were prepared by a precipitation technique followed by an appropriate heat treatment in the 600-800 degrees C temperature range, The spinel materials were characterized by powder X-ray diffra ction and electrochemical measurements. The differential capacity vers us voltage plots indicate that the presence of cobalt strongly influen ces the order/disorder phase transition of the inserted lithium ions i n the upper potential region of the spinel phase, This can be proven b y X-ray diffraction measurements of delithiated spinels, showing two c oexisting spinel phases in the undoped system whereas a single phase b ehavior in the cobalt-doped spinel system is observed. These materials show excellent capacity retention during extended cycling. (C) 1997 P ublished by Elsevier Science S.A.