"We have added a molecule spacer on one side of the graphene layer. When the layers are stacked together, the molecule creates larger space between graphene sheets and provides an interaction point, which leads to a significantly higher capacity," says researcher Jinhua Sun at the Department of Industrial and Materials Science at Chalmers and first author of the scientific paper, published in Science Advances.

Ten times the energy capacity of standard graphite

Typically, the capacity of sodium intercalation in standard graphite is about 35 milliampere hours per gram (mA h g-1). This is less than one tenth of the capacity for lithium-ion intercalation in graphite. With the novel graphene the specific capacity for sodium ions is 332 milliampere hours per gram. the energy capacity boost gets sodium batteries near the capacity of lithium in graphite. The results also showed full reversibility and high cycling stability.