Graphene: An ideal material for storing energy?
Graphene was the world’s first two-dimensional material. Stronger than steel, more conductive than copper, flexible and transparent, graphene’s properties have captured the imagination of many since its isolation in 2004.
Due to graphene’s diverse properties, it lends itself to a multitude of applications from composites and coatings, water filtration, sensors, electronics and biomedical applications.
Graphene has a very high surface area and has the highest theoretical electrical conductivity of any material, as such it would appear to be an ideal candidate for improving energy storage devices such as batteries and supercapacitors.
In order to exploit the many properties of graphene, The University of Manchester has invested in the new Graphene Engineering Innovation Centre (GEIC), a multi-million pound centre with a focus on scale-up towards industrial graphene applications. Projects within the GEIC are commercially led in partnership with academics.
Future Batteries are coming but where is the graphene?
There hasn’t been a significant breakthrough in battery performance in a long time, with the Lithium batteries (LiBs) which current electric vehicles use being discovered in the late 1970s. Improvements in LiBs that have been made since then have been more incremental and have been led by consortia such as that between Tesla Motors and Panasonic resulting in improvements of ~30% (in vehicle range) since the Tesla Roadster was released in 2008.
Graphene should be able to add to this story as it has a very high surface area and has the highest theoretical electrical conductivity of any material. As such it would appear to be an ideal candidate for improving energy storage devices such as batteries and supercapacitors. However despite some claims of early entry into the battery market (Skeleton, G-King), it is unclear as to where the advantages of graphene addition have been made and as yet market uptake has been limited at best.
The reason for slow market penetration could be due to lower cost/performance benefits because the obvious benefits of graphene addition have not been realised once scale-up from laboratory based processes are attempted. Commercial scale processes include laying down a wet film (containing graphene), drying and calendaring (squashing) the films into electrodes. This process begins to make the graphene behave more like its bulk derivative – graphite; reducing the expected performance impact and making the additional materials costs difficult to justify on a commercial basis.
Through access to the Energy facility in the GEIC, a host of formulation, process and engineering solutions can be brought into play, which better enable a graphene battery or supercapacitor to be made which make the grade. In fact a recent collaboration between the University and GEIC Tier 1 partner (First Graphene Ltd) has recently been started, which will look to scale up processes developed by Prof. Robert Dryfe and Prof. Ian Kinloch which will produce a form of graphene which will hope to overcome some of these issues through a project focussing on scale up of both the materials manufacture and production of supercapacitors to pouch cell scale.
Graphene could also be used to enable other promising battery technologies such as Silicon and Lithium Sulphur through encapsulation of unstable materials, improving the durability of these exciting technologies to a level that is acceptable to make them commercially viable and if successful allowing an electrified future to be easier to realise.
Graphene is just the first of many single layered two- dimensional materials. Some of these other materials have shown promising performance within energy storage devices. In particular recent work by groups led by Prof. Sarah Haigh and Dr Suelen Barg at the University have concentrated on the use of MXene materials, which are made from seemingly scalable processes. These groups have already fabricated working supercapacitor and batteries based on these materials here at UoM.
Other materials such as 2D Transition Metal Dichalogenides, Transition Metal Oxides and Transition Metal Hydrides also show a great deal of promise for use in advanced energy storage technologies and we could also see the uptake of these materials beginning within the next few years, fitting well within the roadmaps of ambitious programmes such as those of the Faraday Institute and Faraday Challenge.
Words by Dr Craig Dawson, Application Manager, Graphene Engineering Innovation Centre
Image by Peter Miller