Surface Polymerization and Controlled Pyrolysis: Tailorable Synthesis of Bumpy Hollow Carbon Spheres for Energy Storage.

Architectural design of hollow carbon spheres (HCSs) plays a vital role in improving their performance and expanding applications. The tailorable synthesis of bumpy or asymmetric HCSs with a refined structure remains a challenge. Herein, bumpy HCSs (BHCSs) and bumpy concave HCSs (BCHCSs) have been engineered. The synthesis involves the formation of a core/shell precursor via the surface polymerization of pyrrole monomers on polystyrene nanoparticles, followed by the controlled pyrolysis process under different conditions. In comparison with HCSs, the concave hollow structure can reduce the excessive interior cavity and maintain prevalent merits of hollow structures; the bumpy shell can improve the surface area and number of active sites, thus improving the kinetics as energy storage devices. As a result, among BCHCSs, BHCSs, and HCSs, BCHCSs exhibit optimal electrochemical performance. The lithium-ion hybrid capacitors employing BCHCSs as an anode can deliver an energy density of 0.2182 kW h kg-1 at a power density of 0.2235 kW kg-1. Overall, this study provides an innovative design and strategy for constructing unique carbon nano-architectures for energy storage.