A battery with variable electrostatic capacity is proposed as a new type battery with increased capacity. If the electrostatic capacity can be significantly changed by redox, then the capacity of a capacitor can be superimposed on the capacity of the battery. Calcination of a mixture of anthracene and sulfur was performed to prepare a sulfur composite material (ANS450) as a model material. Elemental analysis and Raman spectroscopy indicated that ANS450 has a structure in which anthracene frames combined with sulfur are linked together by dithiane structures. Although XPS analysis indicated that sulfur in ANS450 performed a one-electron reduction, ANS450 exhibited an extremely large capacity of 0.86Ahg−1, which was larger than the capacity estimated from the sulfur content. Cyclic voltammetry revealed that the electrostatic capacity of ANS450 was significantly changed by redox. This change in electrostatic capacity is considered to be the main factor for the increase in capacity, which validates the basic concept of a battery with variable electrostatic capacity.