Modelling of sodium clusters in various conjugated carbonaceous structures
Hristo Rasheev, Veronika Petkova, Pavel Nikolov, Mariya Kalapsazova, Radostina Stoyanova, Alia Tadjer
Abstract: Sodium-ion batteries (SIBs) are emerging as a prospective alternative to lithium-ion batteries for many applications, including electric cars and stationary energy storage. Improving all components of SIBs is crucial for their future. Anode materials deserve special attention. A very promising candidate is the nongraphitizable carbon, also called hard carbon – a disordered form of carbon which does not turn into graphite even at very high temperatures. Important structural features of hard carbon are the presence of nano-sized graphitic domains, various defects, and multiple pores allowing the migration of ions larger than lithium. An important advantage of hard carbon, regarding its price and availability, is that it can be obtained by pyrolysis of organic wastes such as wood pulp, coffee grounds, walnut shells and others.
A peculiar feature of the insertion of Na in hard carbon is the substantial plateau capacity below 0.1 V (vs Na+/Na) observed in the chargedischarge curves. Some authors suggest that it is due to Na-intercalation into the graphitic domains; others ascribe it to Na-clusters formation in the micro-pores which we consider a more likely explanation and attempted to model and analyze. Fullerene fragments, nano-cones, and nanotubes were used as pore models. By means of DFT, the size-dependent stability of carbon-caged Na-clusters and the energetics of cluster growth in different carbonaceous fragments is discussed.
Acknowledgements: The study is supported by the Bulgarian Science Fund, project CARiM/VIHREN, КП-06-ДВ-6/2019 and project КП- 06-ПН-69/9, and by the Science fund of University of Sofia project 80-10-2/29.03.2024.
The authors from CARiM’s Research Team are bolded.
VIHREN-CARiM 2019 