Experiments with graphene in next-generation batteries are highlighting the important role that this material will have in future energy storage solutions.
The domination of lithium-based batteries on the portable energy market continues, due to the low cost and natural abundance of elemental lithium, coupled with the material’s good energy density properties. Rising energy demands pushed forward by our mobile communication devices, electric vehicles, unmanned aerial vehicles and other portable technologies are putting a strain on lithium-ion battery performance and driving research into novel battery solutions.
New materials for electrodes are a very active research direction, due to the pivotal role of electrodes in battery performance. Increasing demands on charge/discharge power consumption and stability requirements have prompted researchers to engineer new composite materials that can stand the test of power-hungry mobile users.
Earlier, researchers experimented with graphene-boron composites, graphene with nanopores, and graphene-vanadium oxide mixtures as electrode materials for modern lithium-ion batteries. The replacement of standard graphite electrodes with these materials yielded 10x faster charging, 10x larger energy storage, charging in 20 seconds, and excellent cycling stability. It was concluded that there are three most promising strategies for enhancing lithium-ion batteries with graphene and other 2D materials. The first of these strategies is hybridization, when graphene or other conductive nanostructures are hybridized with other 2D materials, improving their conductivity and cycling stability. The second strategy is edge and surface functionalization, whereby adatoms of other materials are attached to 2D materials to tune their properties such as electronic structure, surface chemical reactivity, and interlayer spacing. The final strategy is to control the 2D material nanoparticle morphology, such as for example introducing nanopores or controlling thickness and lateral dimensions, which can significantly impact electrochemical performance or increase the surface-to-volume ratio. Research in this direction continues, as scientists find new ways to synthesize 2D materials for use in electrodes, resulting in more durable and long lasting Li-Ion batteries.
Lithium-ion technology can only go so far, and the search is on for viable replacement technologies that will satisfy the demand of the ever-growing mobile power demand. Graphene oxide (GO) in particular has arisen as a candidate cathode material for future lithium-sulfur (Li-S) batteries. Li-S is widely regarded as a most promising successor for today’s lithium-ion batteries. GO-based cathodes for these experimental batteries have shown to increase discharge capacity retention by 50% and improve cycle stability by up to 86%, more than any other type of cathode. Recent results show that graphene-based cathodes support a very high reversible capacity (1160 mAh/g). In these GO/sulfur composites, graphene plays a significant role in improving the electronic conductivity of sulfur, inhibiting the shuttle effect of soluble polysulfides that causes cathode cracking in traditional cathodes.
Finally, researchers are looking beyond lithium, to experimental solutions such as aluminum-ion batteries, which hold potential to deliver enormous capacity and high current capability, while being friendlier to the environment than lithium-based technology. These batteries also contain graphene electrodes. Although the capacity achieved in the first instance is modest, a full charge-discharge cycle takes less than three minutes.
Development in recent years has shown without a doubt that graphene can be a true enabling technology for novel portable energy solutions, with graphene-based electrode materials now being regarded as the cutting edge in battery components.