Noticed only when they become “flat”, electrical batteries are essential to the functioning of so much that we now regard as indispensable from mobile phones to motor vehicles, but are they as good as they could be? With ever increasing emphasis on sustainability and environmental impact, the answer has to be “No”. Although first studied almost 100 years ago lithium-ion batteries are relative newcomers in the commercial field. Importantly they offer an appreciably higher electrical energy storage density than other existing rechargeable batteries (0.46 MJ kg-1 vs 0.36 MJ kg-1 for the recently introduced NiZn batteries, for example) and this could be enhanced if more lithium could be stored in the anode. It has been established that the presence of tin or silicon significantly increases the amount of lithium that can be stored, but with present anodes the movement of larger amounts of lithium into and out of the anode during charging and discharging leads to such large volume changes that the anode breaks up.
Derek Fray and Carsten Schwandt in the Department of Materials Science and Metallurgy at the University of Cambridge, have developed a novel method of making tin-filled carbon nanotubes and nanoparticles from graphite at much lower cost and 2500 times faster than the present (rather slow) methods and have shown that this material can store significant amounts of lithium with minimal change in volume. The same process can also be used to make silicon filled nanotubes and nanoparticles, which could lead to an even greater increase in battery performance.
To develop this work further Cambridge teamed up with Morgan AM&T in a project in which Morgan AM&T will perfect the graphite and the Cambridge team will optimise the process for producing tin-filled nanotubes and nanoparticles. The project team will then scale-up the process in order to supply materials for use in lithium-ion batteries and other applications.