Free Standing
Reduced Graphene Oxide Film Cathodes
for Lithium Ion Batteries
- Publication date
- Publisher
Abstract
We
report the fabrication and electrochemical activity of free-standing
reduced graphene oxide (RGO) films as cathode materials for lithium
ion batteries. The conducting additive and binder-free RGO electrodes
with different oxygen contents were assembled by a simple vacuum filtration
process from aqueous RGO colloids prepared with the aid of cationic
surfactants. The gravimetric capacity of RGO film cathodes showed
clear dependence on the oxygen contents controlled by the thermal
reduction process. The capacity increased with the increase of the
amount of oxygen functional groups, indicating that the main lithium
capturing mechanism of RGO cathodes is Li<sup>+</sup> ion interaction
with the surface oxygen functionalities. The hydroxyl groups (C–OH)
as well as carbon–oxygen double bonds have been identified
as the lithiation-active species. The RGO cathodes achieved excellent
rate capability due to the fast surface Faradaic reaction, suggesting
that self-supported RGO films are promising cathodes for high power
application. The graphene oxide (GO)/RGO composite films showed inferior
performance to those of RGO only. The poor electronic conductivity
of GO might result in inefficient utilization of redox active oxygen
functional groups despite the higher oxygen content and higher theoretical
capacity of GO/RGO composite films. Further optimization on the amount
of oxygen functional groups for higher capacity and better electronic
conductivity would lead to the development of RGO based high energy-high
power cathodes