Water-Induced Growth of a Highly Oriented Mesoporous Graphitic Carbon Nanospring for Fast Potassium-Ion Adsorption/Intercalation Storage.

A highly oriented mesoporous graphitic carbon nanospring (OGCS) with graphitic layers that are perpendicular to the axis is prepared by hydrothermal treatment of epoxy resin at 500 °C and annealing at 1400 °C. Water plays an important role in not only forming the graphitic carbon nanospring with a high [002] orientation and a large amount of active edge-plane sites, but also in the generation of the mesoporous structure, which facilitate fast K-ion adsorption and diffusion. In situ and ex situ measurements confirm that OGCS undergoes K-adsorption in mesopores and then K-intercalation in the graphite layer to form KC8 with a low discharge voltage. The spring-like nanostructure can expand one-dimensionally along the axial direction to accommodate the volume variation. The OGCS electrode thus shows a much better K-storage performance than that of unoriented graphitic carbon.