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.