Abstract
This Viewpoint clarifies the correlation between capacitance and pore size in electrical double-layer capacitors (EDLCs, also known assupercapacitors or ultracapacitors), which is of high practical importance for the design of advanced carbon electrode materials. Two extreme cases are obvious: excessively large pores, accompanied by large pore volumes and limited specific surface area, will lead to a lowenergy storage capacity, whereas very small pores will limit the ion access due to steric effects, in addition to imposing obstacles to ion transport