Aug 6, 2009
Nanotubular morphology upgrades lithium-ion storage
Rechargeable lithium ion batteries are now the de facto mobile power source with approximately 50% of the market share. High energy density and long cycle life have been the most recognizable features of this battery type. Yet improvements in battery performance are still needed to meet the increasingly demanding specifications of today's portable devices.
The performance of a lithium-ion battery is dependent on the active materials used in its electrodes. Tin-based anodes are a high-capacity alternative to the carbonaceous anodes in use today. In theory, they can store up to 2.6 times the charge of a carbon anode. However, the impressive capacity of tin for lithium storage is undermined by poor cyclability.
As reported recently in Nanotechnology, researchers from Shanghai University, China, and the National University of Singapore have fabricated one-dimensional SnO2 nanomaterials with hollow or semi-hollow interiors (SnO2 nanotubes or SnO2 nanotube-nanorod hybrids) with a cycle life that is higher than that of SnO2 nanomaterials without a hollow interior (nanorods or nanoparticles).
The typical characteristics associated with a hollow one-dimensional material such as ample free volume, fast lithium diffusion kinetics and shorter distance of travel for both lithium ions and electrons are thought to be more accommodating to the volume excursion in repetitive lithium insertion and extraction reactions, which is the bane of cycle life.
Another aspect is the group's new and facile templated synthesis method, which allows the morphology of the one-dimensional SnO2 nanostructures to be continuously tuned from nanotubes to nanorods. The transition from nanotubes to nanorods via a SnO2 nanotube-nanorod hybrid intermediate was observed for the first time.
About the author
The work is performed at Shanghai University, China, and the National University of Singapore. It is supported by the National Natural Science Foundation of China. Prof. Yong Wang is head of the Department of Chemical Engineering, Shanghai University. He holds a PhD from the National University of Singapore, and an MS and a BS (Tianjin University) in chemical engineering. He was a researcher of the Singapore-Massachusetts Institute of Technology Alliances. Prof. Jim Yang Lee is head of the Department of Chemical and Molecular Engineering at the National University of Singapore.