Challenges of "going nano": enhanced electrochemical performance of cobalt oxide nanoparticles by carbothermal reduction and in situ carbon coating.
The electrochemical performance of nano- and micron-sized Co(3)O(4) is investigated, highlighting the substantial influence of the specific surface area on the obtainable specific capacities as well as the cycling stability. In fact, Co(3)O(4) materials with a high surface area (i.e. a small particle size) show superior specific features, which are, however, accompanied by a rapid capacity fading, owing to the increased formation of an insulating polymeric surface film that results from transition-metal-catalyzed electrolyte decomposition. The simultaneous coating with carbon of Co(3)O(4) nanoparticles and in situ reduction of the Co(3)O(4) by a carbothermal route yields a CoO-Co-C nanocomposite. The formation of this material substantially enhances the long-term cycling stability and coulombic efficiency of the lithium-ion active material used. Although the metallic cobalt enhances the electronic conductivity within the electrode and remains electrochemically inactive (as revealed by in situ powder X-ray diffraction analysis), it might have a detrimental effect on the long-term cycling stability by catalytically inducing continuous electrolyte decomposition.
Institute of Physical Chemistry & MEET Battery Research Centre, University of Muenster, Corrensstr. 28/30 & 46, 48149 Muenster (Germany).
Dominic
D
Bresser
Elie
E
Paillard
Philip
P
Niehoff
Steffen
S
Krueger
Franziska
F
Mueller
Martin
M
Winter
Stefano
S
Passerini
carbon; coatings; cobalt oxide; lithium-ion batteries; nanoparticles