Making better batteries

Research focused on upscaling of energy-storage devices was presented by Dr Billy Wu and Professor Jason Riley in an IMSE Lunchtime Seminar last week.

The Institute for Molecular Science and Engineering (IMSE) co-ordinates a range of integrated activities to bring Imperial College London’s world class engineers, scientists, medics and business researchers together to collaborate on pressing global challenge problems.

The Lunchtime Seminar Series is a key part of these community-building endeavours. They provide the opportunity for Imperial staff and students to learn about different aspects of research projects that are ongoing in College, in a relaxed environment.

In the latest of these seminars, Dr Billy Wu (Dyson School of Design Engineering) and Professor Jason Riley (Department of Materials and Associate Director of IMSE) described some of their current research on the topic of upscaling energy-storage technologies.

These efforts are occurring within the modern ‘renewable revolution’, in particular the growing worldwide drive towards electric vehicles and the reduction of greenhouse gas emissions. For example, the UK government – as laid out in the Clean Growth Strategy – wants all new cars to be electric by 2030.

Dr Wu began his talk by explaining how the overarching problem of trying to make better batteries is a multiscale and multidisciplinary problem. He and his colleagues work across the interface of fundamental science and application-based engineering so that they are equipped to tackle the challenge from a range of perspectives.

The aim is to eventually develop high-power, high-energy batteries at a competitive cost, and some of the most important factors to consider in this work include:

the best chemistry (combination of materials) for a battery;
the availability and sustainability of necessary resources;
physical phenomena (i.e., how to best use the materials); and
how to scale-up laboratory-scale batteries to full-scale, usable cells for specific applications (e.g., electric cars).

Dr Wu’s group are currently working on a number of different ways to improve standard battery fabrication techniques. These conventional methods tend to involve many steps and have not really evolved in recent years. As such, there is plenty of room for optimisation.

In recently published work, led by Dr Xinhua Liu (Dyson School of Design Engineering), the method of ‘electrospinning’ was examined as a way to produce supercapacitor systems. Although the nanofiber structure devices exhibit high-power characteristics, the materials are inherently porous and thus have poor energy densities. In their current work, however, Dr Wu’s group is examining the possibility of coating electrospun carbon nanofibre frameworks with zinc materials to produce high-performance energy-storage devices.

The group is also investigating ways to improve the thermal management systems for battery cells. Such systems are an important – and expensive – part of full-scale cells. Their work will allow the degradation of cells, and their potential lifetimes, to be better understood.

In the second half of the Lunchtime Seminar, Professor Riley described a number of studies in which his group have examined how the microstructure of battery and capacitor materials can influence the performance – particularly the energy storage capacity – of devices.

For example, Professor Riley spoke about work on zinc-based metal-organic frameworks (MOFs) and phosphorous-doped graphene oxide. By precisely tuning the chemistry and internal structure of these materials, their energy storage capacities and stabilities can be substantially improved.

Going forward, Professor Riley’s team hopes to apply their methodologies to a range of other material systems and to thus improve their suitability for energy -storage technologies.”