Mesoporous Supercapacitor Films
Using polymer templating, a variety of inorganic materials can be formed into porous frameworks, with high surface areas for increased capacitance
One new material type that utilizes this method is mesoporous frameworks made from sintered nanocrystals. Isolated nanocrystals (<10 nm diameter) have extremely high surface areas, resulting in an enhancement of their capacitance due to an increased contribution of pseudocapacitance (redox reactions leading to an ion pair adsorbed to a surface). However, the kinetics of nanocrystal films are sluggish due to poor ion transport to the interior of the film. Our sintered TiO2 frameworks maintain this pseudocapacitive enhancement which is not present in dense mesoporous frameworks that are formed using molecular precursers. In addition, the kinetics of ion transport are improved due to the interconnected pores of the frameworks. Sintering nanocrystals into mesoporous framworks allows for materials with the advantages of both: extremely high surface area of packed nanocrystals, and interconnected openness of mesoporous materials.
These architectures can also be used to allow for hybrid battery-supercapacitor materials to be feasible. While dense ceramics such as CeO2 cannot intercolate ions into its bulk due to a lack of ion-conductivity, a sintered mesoporous framework of CeO2 was shown to intercolate lithium at the surface, adding to the pseudocapacitance and double layer capacitance effects that the TiO2 sintered frameworks are capable of. This allows for an enhancement of the energy density of mesoporous supercapacitors by using a battery-like charge-storage mechanism.