Lithium-ion performance improved by nanotechnology?

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A new project aims to improve the capacity and safety of lithium-ion batteries, building on existing research which enabled a method for making carbon nanotubes and carbon nanoparticles that can be used in such batteries. The University of Cambridge is collaborating with industry on the project.

Nanotubes consist of atoms, arranged hexagonally and layered in sheets which are rolled up to form minute tubes, just a few atomic dimensions in diameter. However, they are expensive to produce and total worldwide production is currently only 1300tonnes per year. Professor Derek Fray, pictured, and Dr Carsten Schwandt of the Department of Materials Science & Metallurgy claim to have developed a method of producing nanotubes directly from graphite at a lower cost and at a rate 2500 times faster than current methods. This could pave the way for a wider use of nanotubes and, according to Prof Fray, the method can produce carbon nanoparticles that contain 'significant' amounts of tin. This, in turn, opens up new possibilities in the development of lithium-ion batteries, widely used in consumer electronics and expected to be used widely in next generation electric vehicles. Currently, lithium-ion batteries are the only energy storage medium that can meet the global demand for electric cars until 2050, but to support such widespread use, performance must be improved. The electrical current is carried by lithium ions and the energy capacity is limited by the amount of lithium that can be stored in the anode. However, the use of tin or silicon in anode materials significantly increases the amount of lithium stored in the anode, although the insertion and de-insertion of substantial quantities of lithium during charging and discharging is associated with very large volume changes in these materials. These volume changes cause the anode material to break up, so that the performance of the battery decreases after a small number of charge-discharge cycles. Currently, there is no satisfactory material containing tin or silicon that can be used within the anode of the batteries that does not change volume significantly as lithium is stored in it. Prof Fray believes that the tin filled carbon nanoparticles could provide the necessary performance enhancements in battery capacity. And there are plans to use the new process for the production of silicon filled particles which could enhance battery performance even further. "Using our method we can create a product that contains 80% carbon nanotubes or filled nanoparticles," said Prof Fray. "We have carried out experiments that show that our material can store significant amounts of lithium with minimal change in volume, and we believe that this material has the potential to greatly increase the capacity of lithium-ion batteries." The project is funded by the Technology Strategy Board and will be led by Morgan AM&T.