Titanium dioxide (TiO2) by itself makes up a very low performance electrode, because the electrons move very slowly through it (can take years until you could fill a millimiter-thick TiO2 piece). When you reduce its thickness, though, TiO2 acts like a very good electrode – a 10 nm-thick piece of TiO2 can be filled with electrons in a few milliseconds, property that could be very useful for creating high-capacity batteries.
German and Chinese scientists, led by Fei-Fei Cao, et al, discovered that if they applied a thin coat of TiO2 on a carbon nanotube they can create coaxial nanocables, which can be formed into a crystalline solid. The newly-formed material has the useful property of transporting electrons very quickly and trapping lithium ions in a much better way than if used separately.
“On one hand, the CNT core provides sufficient electrons for the storage of lithium in the TiO2 sheath,” the researchers wrote in a study published in Chemistry of Materials. “On the other hand, the CNT itself can also store lithium whereby this storage kinetics is, in turn, improved by the presence of the nanoporous TiO2 – [which] enables rapid access of lithium-ions from the liquid electrolyte.”
Lithium-Ion batteries that use nanocable-based anodes already exist in prototype, but those new hybrid TiO2 and CNT discovery can improve their efficiency and lifetime – the nanocables showed almost no capacity loss after 100 charge-recharge cycles.
Supercapacitors could also benefit from the hybrid TiO2-CNT anode, and could also be used in electric/hybrid cars. TiO2 seems to be one of the most used materials in help of alternative energy – they also make up very good solar cells, after all.