Batteries and electrochemical capacitors (ECs) represent the most widely used types of electrochemical energy storage devices. ECs are frequently overlooked as an energy storage technology despite the fact that these devices can deliver greater power, have much faster response times, and longer cycle life than batteries. Commercial technology uses carbon-based electrochemical capacitors in which energy storage by double layer processes leads to high power density, but low energy density. The interest in using pseudocapacitor-based materials for electrochemical capacitors is that the energy density associated with faradaic reactions is much greater, by at least an order of magnitude, than the electrical double layer capacitance of carbon electrodes. One key criterion is that fast faradaic reactions are required and for this reason oxide pseudocapacitors have largely been those materials which exhibit surface or near surface redox reactions. Our recent studies with Nb₂O₅ indicate that this material undergoes fast faradaic reactions through an intercalation pseudocapacitance mechanism in which lithium ion insertion occurs in the bulk of the material. The principal benefit realized from this mechanism is that high levels of charge storage are achieved within short periods of time because there are no limitations from solid-state diffusion. For example, Nb₂O₅ exhibits an energy density in excess of 100 mAh/g at a charging rate of 60C. While Nb₂O₅ may not be the optimum material for energy storage devices because of its potential range, it does provide a model system for addressing some of the outstanding issues regarding pseudocapacitive energy storage. We have identified certain characteristics associated with intercalation pseudocapacitance and expect that other oxide systems are also capable of achieving comparable levels of high rate energy storage.