The general objective of this project was to develop structural materials based on CNT fibre/inorganic materials and polymer matrices, capable of harvesting energy. Technical progress focused on synthesis of new materials, studies on hybridisation, demonstration of efficient charge transfer and development of large composites with structural and energy-related functions. The majority of this work is captured in around 45 related scientific publications and 10 patent applications filed.
An overriding acitivty has been the development of methods to produce macroscopic ensembles of organised high aspect ratio nanostructures at high volume fractions (> 10%). One of the methods explored in detail was the synthesis of 1D nanomaterials through floating catalyst chemical vapour deposition and their direct assembly from the gas phase as continuous fibres/fabrics. Advances were made in applying this growth mode to produce continous high-performance fibres of carbon nanotubes, and in determining the key factors controlling their molecular composition and spatial organisation. Building on this work, the group demonstrated that this fabriction method is suitable to produce continuous fabrics of silicon nanowires. Effectively, this breakthrough has opened a new route to fabricate Si nanowire anodes, considered key for the next generation lithium-ion batteries, eliminating all sovents and mixing stage from the process. Current efforts are directed at industrialising this new manufacturing route.
Another block of activities has included the use of synthetic methods to grow inorganic nanostructured phases on porous CNT fabrics, ensuring that the distribution and volume fraction of the phases can be controlled. The project helped establish an electrochemical route to produce composite structures consisting of CNT fibres as both reinformcent and built-in current collectore, combined with a wide range of inorganic nanomaterials, including: TiO2, ZnO, MnO2, SiO2, Al2O3, Ta2O5, MoS2, CN, V2O5. Though extensive structural and (photo)electrochemical characterisation the project demonstrated close interaction at the interface and low charge transfer/transfor resistance, therefore leading to high efficiency energy storage and conversion processess.
In addition, methods were developed to produce large size laminate composites combining structural properties and energy management functions. This required addressing several manufacturing issues, such as the chemical compatibility of electrolytes and reinforcing polymer matrices, designing patterned structures for mechanical interconnection of lamina and developic CNT fibre current collectors to eliminate metalic conductors. Through coupled mechanical and electrochemical methods this strategy was shown to produce superior internal stress transfer and electrochemical durability than embedded devices, thus proving one of the initial hypotheses of STEM.
