A sweet approach to battery materials manufacturing

Researchers in the Departments of Materials Science & Engineering and Chemical & Biological Engineering have been developing a novel approach to the production of battery materials, using biotemplating.

The benefits of renewable energy sources are widely recognised, from reduced reliance on fossil fuels to lower carbon emissions. But uncertainty still remains around the stability of energy sources such solar, wind and wave. Consistency of these sources cannot easily be predicted, so there is greater requirement for the development of efficient, large-scale stationary energy storage systems to allow the decoupling of supply and demand.

Many energy storage systems found in everyday life are based on lithium-ion (Li-ion) batteries. These have high power densities, and are suitable for small-scale and portable devices. However, the scarcity of lithium (amongst other factors) makes these batteries unsuitable for large-scale industrial and commercial energy storage applications. Researchers are therefore investigating alternative materials which are more suitable for larger scale facilities, for example energy storage for renewable sources on the National Grid, and batteries used in electric vehicles.

One option is the use of sodium-ion (Na-ion) batteries, or NIBs. Sodium is much more abundant than lithium and is much safer to work with.

Researchers in the Departments of Materials Science & Engineering and Chemical & Biological Engineering at the University of Sheffield have been using a novel approach to synthesise the oxide materials used in the cathodes of such batteries.

Biotemplating involves mixing the necessary metal ions with a naturally occuring polymer such as sugar, and water to produce a solution. The solution is then heated at around 80°C to get the metal ions to form a composite with the sugar molecules. This process prevents the metal ions from sticking to each other, giving a more even distribution. When heated to higher temperatures, the sugar burns away to leave the cathode material. In this work the temperatures used were around 550 °C, where usually they are in the region of 1,000°C, and so this new work may help to save energy during manufacture.

On top of this, it was found that the particle sizes within the materials were much finer, which leads to significantly better battery properties.

Scanning electron microscope images of battery cathode materials
SEM images of trial materials processed using biotemplating, compared to those produced by solid state synthesis.
Experimental data showing the properties of Biotemplated cathode materials compared to solid state cathodes
Specific discharge capacities versus cycle number for solid state and biotemplated cathode materials.

Dr Rebecca Boston, of the Department of Materials Science and Engineering, observed, ‘By using this novel approach to cathode production, we’ve discovered a significantly less energy-intensive way of producing battery materials, which compare very favourably with the electrical properties of batteries made using traditional methods’.

This process is still in development, but the possibility of these materials being used in commercial applications look promising.

Further details of this research can be found here.