Rechargeable Na-O2 batteries have received a great deal of attention as an alternative to current lithium-ion batteries, mainly due to their potential to provide higher energy densities. Na–O2 batteries are still in an early stage of development, with several challenges that need to be addressed, including limiting kinetics at the air cathode. In this regard, the use of suitable cathode materials is a point of major concern as they are responsible for achieving efficient deposition/redissolution of the solid discharge products formed during battery cycling.

Carbon materials have been widely used as air cathodes due to their low cost, high surface area, chemical and mechanical stability, high electrical conductivity, well-developed porosity and intrinsic catalytic activity towards ORR/OER. In particular, graphene has gained attention due to its superior electrical conductivity and highly accessible 2D area. The real integration of graphene as electrode material in energy storage devices, however, requires the development of sustainable and scalable approaches for its production and processing.

In this talk, graphene aerogels prepared by the graphite oxide route and the electrochemical exfoliation of graphite will be discussed. First, graphene aerogels with different pore sizes obtained by the graphite oxide route revealed a trade-off between pore texture and battery performance. This route, however, is not environmentally friendly and involves multiple steps, including a reduction step to tune the sheet conductivity. As an alternative, we have used a simpler, faster and more eco-friendly route to access high-quality graphene by electrochemical exfoliation of graphite, resorting to natural nucleotides as both exfoliating electrolytes and colloidal stabilizers. An aerogel prepared from this graphene suspension delivered a large discharge capacity and longer cycle life than those cathodes prepared by the graphene oxide route. The origin of such good performance is attributed to the participation of the nucleotide molecules in key chemical processes taking place at the battery cathode, including oxygen electrocatalysis and nucleation of the discharge products.The present work highlights not only the interest on this electrochemical method over more traditional routes when it comes to manufacturing graphene, but also the direct potential benefits of the resulting graphene in novel electrochemical energy storage technologies.

REFERENCES

M. Enterría, C. Botas, J.L. Gómez-Urbano, B. Acebedo, J.M. López del Amo, D. Carriazo, T. Rojo, N. Ortiz-Vitoriano, Journal of Materials Chemistry A, 42 (2018) 20778.

M. Enterría, J.L. Gómez‐Urbano, J.M. Munuera, S. Villar‐Rodil, D. Carriazo, J.I. Paredes, N. Ortiz‐Vitoriano, Small, 17 (2021) 2005034.