Inner wrinkled mesoporous hollow carbon spheres with nanopillars connected to double shells for excellent potassium storage

Carbon spheres are widely used in energy storage due to their adjustable particle size, controllable shape, and variable surface physical and chemical properties. However, there are still problems such as low specific surface area and unsatisfactory ion transport kinetics in K+ storage. Although increasing the specific surface area of the active material can increase the K+ storage sites, the contact area between the active material and the electrolyte also increases, aggravating the occurrence of side reactions and the consumption of the active materials. We developed an N-doped mesoporous hollow carbon sphere with a novel morphology-a smooth exterior and wrinkled interior structure with a carbon-supported pseudo-bilayer carbon structure (IW-MHCS). Its smooth outer structure sufficiently reduces the contact area with the electrolyte, and the wrinkled inner structure effectively increases the specific surface area. The obtained IW-MHCS exhibits superior rate performance (120.6 mAh g−1 at 5 A g−1) and sufficient capacity (202.7 mAh g−1 after 800 cycles at 1 A g−1) for K+ storage. This study provides a new insight into the structural design and morphological control of high-energy-storage carbon-based materials.