Graphene is beginning to show its potential in the battery field with the development of a lithium-ion based battery with a graphene ink anode demonstrating a 25% improvement in energy density over conventional Li-ion cells.
Graphene anode battery
The graphene anode battery was developed by a team of researchers in Italy led by Vittorio Pellegrini, director of the Graphene Labs at the Italian Institute of Technology in Genoa.
In the July issue of the publication Nano Letters, the researchers demonstrate an optimal battery performance with specific capacity 165mAh/g, energy density 190Wh/kg and stable operation for over 80 charge-discharge cycles. The components of the battery are low-cost and potentially scalable, they state.
The graphene ink, which is incorporated in the anode, is a spreadable liquid containing a suspension of graphene nanoflakes. Graphene inks are a particularly exciting area of research, because of their low cost, ease of use and scalability.
Graphene is a two-dimensional material based on single atom-thick layers of carbon, with the carbon atoms arranged in a honeycomb-like lattice. The material is both transparent and flexible, and in addition to being 100 times stronger than steel, it conducts electricity and heat with great efficiency.
Recognizing the potential of graphene, the European Commission in October 2013 established the Graphene Flagship research initiative with a budget of over €1 billion to take graphene from the labs to society within 10 years. [Engerati-Graphene-The Turning Point for Energy Storage?]
Besides the graphene anode battery, other developments highlighted in the Graphene Flagship’s first year review include a technique to produce large quantities of flawless graphene with a kitchen blender-type tool and a graphene-based flexible display with potential for applications such as tablets.
Graphene in energy
The Graphene Flagship’s Energy work package is responsible for assessing the interest of graphine in daily life energy applications. The focus is on specific functions in applications including photovoltaics, energy storage, fuel cells and hydrogen storage.
At the recent Graphene Connect – Energy Applications workshop, Etienne Quesnel, a senior materials scientist at France’s Atomic Energy and Alternative Energies Commission (CEA), who leads the Flagship’s Energy work package, commented on key application areas for graphene in the sector.
Among these graphene has potential in lowering device production costs and as a replacement for indium tin oxide in photovoltaics. ITO is a brittle compound, which means it cannot be used in flexible solar cells. Indium is also relatively scarce. Graphene also has the potential for replacing costly platinum in dye-sensitised solar cells. It may also have potential to develop new materials, such as graphene-quantum dot composites, that better absorb sunlight.
Supercapacitors can also benefit from the use of graphene. High energy and power densities result from electrodes made of materials with high specific surface areas and conductivities, which makes graphene a most suitable material for this purpose. One particularly interesting type of graphene comes in the form of petals grown perpendicularly to substrates over large surface areas, with which it is possible to achieve specific capacitances in excess of 1,200F/g and current densities of up to 100A/g.
Fuel cells can also benefit from graphene. The key here is in reducing if not removing the need for the platinum, which is used as a catalyst in the process. One option is to use graphene to build a tuneable catalyst support, which promotes better platinum adhesion and dispersion. Another strategy is to use an entirely metal-free cathode, with doped graphene as the catalyst.
Graphene in devices by 2020
In an interview prior to the event Quesnel said he was convinced that graphene and more generally 2D materials would be used in energy devices at the 2020 horizon.
“The question is to know precisely for which kind of market. Shall we stay at the level of various niche markets? Or shall we manage to identify THE application that will push towards massive production of graphene material?”