Lithium-ion batteries seem to be everywhere these days. They power most of the electronic devices we carry around with us - cell phones, laptops, MP3 players, digital cameras and so on. They get their name from the lithium ion that moves from the anode to the cathode during discharge and from the cathode to the anode during recharging. Due to their good energy-to-weight ratios, lithium batteries are some of the most energetic rechargeable batteries available today.  

In terms of weight and size, batteries have become one of the limiting factors in the continuous process of developing smaller and higher performance electronic devices. This not only applies to consumer electronics. As with so many other nanotechnology research, the military is a strong driver behind battery R&D. All of the electronic gizmos of a modern soldier - night vision goggles, flashlights, laptops, radios, GPS, etc. - are powered by batteries. The backup batteries soldiers are required to carry generally add several kilograms to their basic load, and the logistics necessary to supply the troops with sufficient numbers of replacement batteries is costly.  
To meet the demand for batteries having higher energy density and improved cycle characteristics, researchers have been making tremendous efforts to develop new electrode materials or design new structures of electrode materials. For instance, metallic tin has recently been widely researched as one of the promising anode materials for the next generation of high energy density lithium-ion batteries. This new anode material has a high theoretical specific capacity but its practical application is limited by its poor cycling performance. The problem with increasing the performance of lithium batteries is that none of the existing electrode materials alone can deliver all the required performance characteristics including high capacity, higher operating voltage, and long cycle life. Consequently, researchers are trying to optimize available electrode materials by designing new composite structures, often at the nanoscale.  

Demonstrating the benefits of directed nanostructure-design of electrode materials, Chinese scientists have prepared tin nanoparticles encapsulated in elastic hollow carbon spheres. This tin-based nanocomposite exhibits a very high specific capacity, excellent cycling performance, and therefore shows great potential as anode materials in lithium-ion batteries.  
"Metallic tin is considered to be a very promising anode material for lithium batteries mainly for three reasons" Prof. Li-Jun Wan explains to Nanowerk. "Firstly, its theoretical specific capacity is much higher than that of conventional graphite. Secondly, the tin anode has higher operating voltage than graphite, so it is less reactive and the safety of batteries during rapid charge/discharge cycle could be improved. And thirdly, a significant advantage of metallic tin over graphite is that it does not encounter solvent intercalation – which causes irreversible charge losses – at all. Unfortunately, the biggest challenge for employing metallic tin as applicable active anode materials is that it is suffering from huge volume variation during the lithium insertion/extraction cycle, which leads to pulverization of the electrode and very rapid capacity decay."  

Wan, Director of the Institute of Chemistry at the Chinese Academy of Sciences