Next generation pseudocapacitor materials from sol–gel derived transition metal oxides

Capacitive energy storage is distinguished from other types of electrochemical energy storage by short charging times and the ability to deliver significantly more power than batteries. A key limitation to this technology is its low energy density and for this reason there is considerable interest in exploring pseudocapacitive charge storage mechanisms which offer the prospect of increasing energy density without compromising the power density of electrochemical capacitors. In this paper we review our recent work on using sol–gel synthesis methods to prepare nanostructured transition metal oxides which exhibit increased levels of pseudocapacitance and enhanced energy storage properties. Our work with TiO 2 nanoparticles and mesoporous films of TiO 2 and CeO 2 is highlighted as we use these studies to understand the role of crystallite size, nanoscale porosity and understanding the differences between pseudocapacitance and intercalation processes.