Electrodeposition is an attractive tool for synthesizing energy storage materials - such as transition metal oxides (TMOs) - for batteries and capacitors. A key advantage of electrodeposition is that the material of interest is synthesized directly on a metal or carbon current collector promoting an intimate, low resistance contact between the deposited material and the current collector. But electrodeposition methods have limited reach if a soluble form of the metal ion does not exist. Li_xNb₂O₅ is one technologically important TMO that falls into this category.

The electrophoretic deposition (EPD) process we have developed produces nanoporous, phase pure T-Nb₂O₅ films 38 nm to 144 nm in thickness. These films exhibit unusually high specific capacities, C_sp (units: mAh/g). For example, films of 60 nm thickness produce C_sp = 420 mAh/g at 5 A/g and 220 mAh/g at 50 A/g which is to be compared with a theoretical Faradaic capacity of 202 mAh/g. T-Nb₂O₅ films also produce impressive energy and power with specific energy from 770 - 486 Wh/kg, and specific power in the range from 9-90 kW/kg. It is important to add here that the accuracy of all of these mass-normalized metrics is insured by directly measuring the mass of these films using quartz crystal microbalance (QCM) gravimetry. Our investigation of T-Nb₂O₅ is still in its early stages, but the exceptional performance seen for these EPD T-Nb₂O₅ films is very encouraging. Our hypothesis is that EPD provides a general method for the synthesis of energy storage materials with signicant advantages relative to competing methods, including the ability to impart a controllable porosity and the ability to facilitate the enhancement of mechanical and electrical properties via compositing.

In this presentation, I will discuss this EPD process and our recent investigations of the mechanisms of degradation operating in the T-Nb₂O₅ films prepared using this process. Gold@T-Nb₂O₅ core@shall nanowires can also be obtained by EPD and the properties of these systems for electrical energy storage will be compared with those of T-Nb₂O₅ films. Finally, the lithiation/potential-dependent electrical conductivity of solid (non core-shell) T-Nb₂O₅ nanowires prepared by has been measured for the first time, in-situ. These data, showing variations in electrical conductivity by three orders of magnitude with lithiation state, will also be discussed.