Optimisation of performance through electrode formulation in conversion materials for lithium ion batteries: Co3O4 as a case example

A systematic formulation study has been performed on Co3O4 based composite electrodes. The influence of diverse parameters has been studied such as: calendaring pressure applied, composition of the composite electrode, nature of the carbon additives (carbon super P, carbon nanofibers and carbon nanotubes) and the size of the active material particles. The influence of electrochemical parameters (lower cut-off voltage, initial C rate, and rate changes or open circuit potential steps during cycling) was also ascertained. These results are discussed in the perspective of the specific issues associated with materials reacting through conversion reactions (first cycle coulombic inefficiency, voltage hysteresis and capacity fade). Finally, basing on electrochemical impedance spectroscopy measurements and systematic record of the IR drop term of the cells upon cycling, a mechanism to account for the generally observed capacity fade on these materials is proposed. (C) 2012 Elsevier B.V. All rights reserved.