Periodic Reporting for period 4 - STEM (Structural energy harvesting composite materials)
Reporting period: 2020-12-01 to 2021-05-31
This project deals with the fabrication and study of new materials that combine structural mechanical properties, with the ability to harvest energy from the environment. It bears close relation with current technological trends in transport, not just with respect to continuous efforts to the reduction of emissions, but for the emerging interest in multifunctional materials for de-centralised power management and in general in mechanically-augmented electronics.
The materials studied in the project consist of a strong, highly-conducting fabric of carbon nanotubes, which provides most of the mechanical reinforcement and charge collection. It is used as a scaffold to support a thin layer of an inorganic material that can convert external energy (e.g. light) into electrical energy.
Key for successful realization of both mechanical and energy-harvesting properties is the controlled assembly of the carbon and inorganic building blocks. We perform studies detailed studies on the structure of these hybrid materials, particularly on interfacial stress and charge transfer processes, and which help us identify routes for improvement in multifunctional properties.
The materials studied in the project consist of a strong, highly-conducting fabric of carbon nanotubes, which provides most of the mechanical reinforcement and charge collection. It is used as a scaffold to support a thin layer of an inorganic material that can convert external energy (e.g. light) into electrical energy.
Key for successful realization of both mechanical and energy-harvesting properties is the controlled assembly of the carbon and inorganic building blocks. We perform studies detailed studies on the structure of these hybrid materials, particularly on interfacial stress and charge transfer processes, and which help us identify routes for improvement in multifunctional properties.
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.
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.
A central idea of STEM was the development of electrodes distinct from traditional layered systems, and instead more analogous to a composite structure with interpenetrated phases that improve charge and stress transfer. This concept was successfully materialised as composite electrodes for energy conversion and storage. Furthermore, these materials were also employed for the assembly of structural power composites, combining both load-bearing and energy storage functions. The underlying scientific achievements enabling these activities is the development of synthetic methods for growth of active materials on nanocarbon fibres, the recurrent measurement of lower internal electrical resistance as an inherent feature9, and the demonstration of operation as devices26
A significant breakthrough in STEM is the establishment of a new universal method for the synthesis of nanostructured network materials via floating catalyst chemical vapour deposition. This is considered the most significant achievement of the project because of both its scientific and technological impact. Scientifically, it has opened a new route for the synthesis of organised inorganic 1D nanomaterials at ultra-fast rates and their direct assembly into high-performance solids. Technologically, assembling nanostructured Si as freestanding fabrics directly from suspension in the gas phase eliminates solvents, polymers and energy-intensive processing from the manufacture of Si nodes.
Another area of progress beyond the SoA has been the development of a model to describe the tensile mechanical properties of nanocarbon fibres, particulalry by separating the effects of alignment and chemical composition and drawing from work on macromolecular polymer fibres. The model and associated experimental methods provide a framework for accurate description of structure-property relations in complex nanostructured networks. This has helped produce CNT fibres with superior bulk properties to any synthetic fibre, while also enabling a descrition of other fibrillary solids suchas as membranes and electrodes.
A significant breakthrough in STEM is the establishment of a new universal method for the synthesis of nanostructured network materials via floating catalyst chemical vapour deposition. This is considered the most significant achievement of the project because of both its scientific and technological impact. Scientifically, it has opened a new route for the synthesis of organised inorganic 1D nanomaterials at ultra-fast rates and their direct assembly into high-performance solids. Technologically, assembling nanostructured Si as freestanding fabrics directly from suspension in the gas phase eliminates solvents, polymers and energy-intensive processing from the manufacture of Si nodes.
Another area of progress beyond the SoA has been the development of a model to describe the tensile mechanical properties of nanocarbon fibres, particulalry by separating the effects of alignment and chemical composition and drawing from work on macromolecular polymer fibres. The model and associated experimental methods provide a framework for accurate description of structure-property relations in complex nanostructured networks. This has helped produce CNT fibres with superior bulk properties to any synthetic fibre, while also enabling a descrition of other fibrillary solids suchas as membranes and electrodes.