1, University of California, Riverside, Riverside, California, United States
3, Princeton University, Princeton, New Jersey, United States
Amorphous carbons such as hard carbon are being developed as anode materials for next generation sodium ion batteries. These materials have a structure composed of nanoscale domains of twisted, rumpled, and vertically disordered graphene stacks. Compared to graphite anodes, the dilated morphology makes insertion of large sodium ions into the galleries between graphene layers more energetically favourable. However, there is a disparity between the average gallery spacing observed experimentally during Na intercalation and the ab initio predicted local dilation necessary for favourable intercalation. In this work sinusoidally rippled bilayer graphene is used as a model for amorphous hard carbon. Using this it is demonstrated that the rippled graphene morphology creates local regions with large d-spacing, and in these geometrically dilated regions Na storage is highly favorable.