One of the major types of rechargeable batteries is currently lithium-ion batteries. Found in laptops and phones, the length of time their power lasts dictates most of our lives, and plenty of time and research has gone into figuring out how to extend this time period. For a long time, graphite was used on the anode of the cells, but in recent years silicon has been looked into as a potential replacement. At ten times the gravimetric energy density, it’s also far more abundant than graphite (must be all those pencils), so would be a cheaper, more efficient alternative.
However, silicon turned out to not be the hero we needed as it was found to undergo volume expansion, causing the silicon to degrade over many charges. This expansion causes the atoms to agglomerate or stick together, and so reduces charging/discharging efficiency. This is why our phones don’t keep their power for as long after a lot of charges, and also take longer to fully charge. Don’t panic though, as recent research may have found a solution.
“This is why our phones don’t keep their power for as long after a lot of charges”
Ever since the landmark research performed on graphene by Konstantin Novoselov and Andre Geim, which secured them the 2010 Nobel prize, graphene has been the subject of fervent research and development. It’s best described a single atomic layer of graphite (colloquially known as the ‘original G’), with carbon atoms arranged in a hexagonal structure. Graphene forms three bonds with neighbouring atoms, which leaves a spare electron above the layer providing interesting electronic properties. Not only this, but the carbon bonds themselves are very strong, making graphene applications broad and relatively cheap.
Using graphene, Dr Melanie Loveridge, a senior research fellow in WMG, has come up with an innovative solution to the issue with lithium-ion batteries. Published in Nature Scientific Reports on 23 January, (Phase-related Impedance Studies on Silicon–Few Layer Graphene (FLG) Composite Electrode System), her most recent paper describes how chemically modified graphene can be used in tandem with silicon to resolve the issues with straight silicon. FLG refers to few-layerr graphene’, several layers of the atomically thin graphene which are separate and can be manipulated.
“Graphene has been the subject of fervent research and development”
Loveridge spoke on the issue, explaining how the FLG flakes “increased the resilience and tensile properties of the material greatly reducing the damage caused by the physical expansion of the silicon.” They do this by acting as ‘girders’ between the silicon atoms during their agglomeration that occurs during charge/discharge, hence preserving the degree of separation between the silicon particles. The layer, made up of 60% micro silicon particles, 16% FLG and sodium/polyacrylic acid and 10% carbon additives, was tested over 100 charge/discharge cycles.
With this research now in place, Loveridge and team have already begun building on their work in a major European project, spearheaded by Varta Micro-innovations, with partners such as Cambridge University and the Italian Institute of Technology. This all forms a part of an initiative known as the Graphene Flagship, and with a budget of €1 billion, it aims to bring together academic and industrial research teams generating economic growth, new jobs and new opportunities.
“Loveridge and team have already begun building on their work in a major European project”
With the reported influence of this most recent development having the potential to double the life of rechargeable lithium-ion batteries like those found in our phones, I think it’s safe to say they’ve definitely gotten my attention.