Synthesis and use of hollow carbon spheres for electric double-layer capacitors

Supercapacitors have become an important energy storage device. Based on their energy storage mechanism, supercapacitors are generally categorized into pseudocapacitors and electric double-layer capacitors (EDLCs). Nowadays, carbon materials are used as the electrodes in commercial EDLCs. Hollow carbon spheres (HCSs) have attracted extensive attention for use as the electrode materials of EDLCs because of their large specific surface area, high electrical conductivity, excellent electrochemical stability and high mechanical strength. Progress on the preparation of HCSs is reviewed, including the hard and soft templating methods, template-free methods and the modified Stöber method. Their electrochemical performance as the electrode materials of EDLCs and the effect of their specific surface area, pore size and doped foreign atoms on their electrochemical performance are summarized, which gives insight into their low-cost preparation and high-performance for use in supercapacitors.