Enhanced lithium ion intercalation properties of vanadium oxides

My research is focused on the development of high-rate Li-ion intercalation electrodes based on vanadium oxide for clean energy applications. The main accomplishments of this work are: (1) engineering the microstructure and the interlayer structure of vanadium oxide thin films, and (2) developing various vanadium oxide (based) nanostructures. Both methods result in significantly enhanced Li-ion intercalation properties in vanadium oxides. Part I focuses on thin films of vanadium oxides. Electrophoretic deposition (EPD) is utilized to prepare nanoporous thin films of anhydrous crystalline vanadium pentoxide, and the EPD film shows high capacity and sustainable cycling performance as a result of porosity. In the case of V2O5·nH 2O thin films, thermal annealing is used to control the water content and modify the interlayer spacing; V2O5·0.3H 2O film is found to have the optimal water content and exhibits the highest Li+-intercalation capacity and most sustainable cycling life, attributed to the reduced water content, the retained interlayer spacing and the dominant amorphous phase. Further, addition of silver nanowires to V2O5·nH2O has been found to improve the Li+-intercalation capacity by two times, due to the enhanced electrical conductivity, changes in crystallinity and lattice structure. The second part of the work concentrates on developing various vanadium oxide based nanostructures, including the nanorod, nanotube, and nanocable arrays of single-component oxide, complex oxide and composite oxides. We have prepared V2O5·nH2O nanotube array and the Ni-V 2O5·nH2O core-shell nanocable array. Both nanostructures demonstrate higher Li-ion intercalation capacity and better kinetics compared to the film electrode, due to the higher surface area and the shorter diffusion distance. The nanocable arrays shows the best performance among all; both energy density and power density of such nanocable-array electrodes are higher than the V2O5 film electrode by at least one order of magnitude. In addition, a capillary-enforced template-based method has been used to prepare V2O5-TiO2 composite nanorod arrays, InVO4 and InVO4/acetylacetone(acac) nanotube arrays. The addition of TiO2 to V2O5 and the addition of acetylacetone to InVO4 have demonstrated to greatly improve the Li+ intercalation capacity of V2O 5 and InVO4, respectively, as a result of change in crystallinity.