4:00pm - 4:30pmInvited
3D Nanoporous Microsupercapacitor As On-Board Energy Storage Device
1Institut National de la Recherche Scientifique (INRS), Canada; 2Laboratory for Analysis and Architecture of Systems (LAAS), France
The development of embedded electronic systems and wireless sensor network technologies have led to an increasing need of miniaturized energy storage devices, such as micro-supercapacitors. RuO2-based pseudo-capacitive electrode has been considered as a promising candidate due to its low electrical resistivity, fast reaction rate with protons in aqueous electrolyte and high specific capacitance (up to 1300 F/g).
However, up to now, despite their excellent power performances, the reported specific capacitances of RuO2 based micro-supercapacitors fall short of being able to power a wireless sensor node or any microelectronic device, with typical areal capacitance ranging from 1 to 10 mF/cm2geometric. An attractive approach to increase this capacitance is to deposit RuO2 onto a nanostructured support of high surface area. Gold film has been elected as RuO2-based electrode’s substrate not only for its good electronic conductivity, but also for its excellent mechanical properties, enabling it to be amenable to microfabrication and shaping structure processes.
For this purpose, 3D nanoporous gold thin films were prepared. This was achieved by immersing a conductive substrate in a gold ions containing solution. At large negative potential, hydrogen evolution occurs simultaneously with electroplating of gold, creating a highly porous 3D gold structure via a process called “hydrogen bubble dynamic template”. Under the optimal deposition conditions, the gold specific surface area was found to be increased by a factor of 1000 compared to the geometrical surface area. RuO2 electrodeposition is then performed from an aqueous solution of ruthenium chloride hydrate on the porous substrate. Typical areal capacitance in the range of 3 F/cm2geometric were achieved, which is a factor of 1000 larger than previously obtained.
4:30pm - 5:00pmInvited
One-Dimensional Nanomaterials for Energy Storage
Wuhan University of Technology, China
One-dimensional nanomaterials can offer large surface area, facile strain relaxation upon cycling and efficient electron transport pathway to achieve high electrochemical performance. Hence, nanowires have attracted increasing interest in energy related fields. We designed the single nanowire electrochemical device for in situ probing the direct relationship between electrical transport, structure, and electrochemical properties of the single nanowire electrode to understand intrinsic reason of capacity fading. The results show that during the electrochemical reaction, conductivity of the nanowire electrode decreased, which limits the cycle life of the devices. Recently, we designed the general synthesis of complex nanotubes by gradient electrospinning, including Li3V2(PO4)3, Na0.7Fe0.7Mn0.3O2 and Co3O4 mesoporous nanotubes, which exhibit ultrastable electrochemical performance when used in lithium-ion batteries, sodium-ion batteries and supercapacitors, respectively. In addition, we have successfully fabricated a field-tuned hydrogen evolution reaction (HER) device with an individual MoS2 nanosheet to explore the impact of field effect on catalysis. We also constructed a new-type carbon coated K0.7Fe0.5Mn0.5O2 interconnected nanowires through a simply electrospinning method. The interconnected nanowires exhibit a discharge capacity of 101 mAh g-1 after 60 cycles, when measured as a cathode for K-ion batteries. Our work presented here can inspire new thought in constructing novel one-dimensional structures and accelerate the development of energy storage applications.
5:00pm - 5:30pmInvited
Nanocarbon-infused Metal Composites: A New Class of Covetic Materials for Energy Applications
Argonne National Laboratory, United States
Covetic materials, or simply covetics, are novel materials that have recently attracted increased research interest due to their potential for energy-saving applications. Covetics are metals that have been infused with nanophase carbon through a unique electrocharging process in which carbon is infused into the metal matrix by stirring a mixture of molten metal and carbon while applying a large electrical current (hundreds of amperes). The process can produce structures that seem thermodynamically unavailable via conventional processing methods but remain stable once established. Tenaciously bound to the metal, the nanocarbon particles increase the electrical and thermal conductivities and, in some cases, increase the strength at elevated temperatures. We measured ~15% increase in thermal conductivity and ~30% increase in electrical conductivity in covetic copper compared with the base copper metal from which the covetic was produced. In the case of covetic grey cast iron, we measured ~50% increase in thermal conductivity at 500°C compared to its parent grey iron sample. Covetics are commercially important because the covetic process is scalable to tonnage quantities with widespread implications for energy savings in thousands of potential applications, such as high-voltage electrical power transmission, electrical motors and generators, advanced heat exchangers, electrodes for batteries, fuel cells, supercapacitors, and for thermal management in micro- and power electronics. Covetics will be a game-changer for materials scientists and engineers who have long sought to combine metals with light-weight and high-conductivity carbon in their pursuit to improve materials performance. Examples of improvements in the properties of covetic copper, aluminum, and iron will be presented in this talk along with results from electron microscopy, X-ray imaging, and thermal analysis of the materials.
This work was supported by the U.S. Department of Energy, Energy Efficiency and Renewable Energy, Advanced Manufacturing Office.
5:30pm - 6:00pmInvited
Piezoelectric and Pyroelectric Composite Materials for Energy Harvesting and Storage
1Materials and Structures (MAST) Centre, University of Bath, United Kingdom; 2Warwick Manufacturing Group (WMG), University of Warwick, United Kingdom
This paper demonstrates the significant benefits of exploiting highly aligned porosity in piezoelectric and pyroelectric materials for improved energy harvesting performance. Porous lead zirconate (PZT) ceramics with aligned pore channels and varying fractions of porosity were manufactured in a water-based suspension using a unidirectional freezing method, termed ‘freeze casting’. The aligned porous PZT ceramics were characterized in detail for both piezoelectric and pyroelectric properties and their energy harvesting performance figures of merit were assessed parallel and perpendicular to the freezing direction. Due to the introduction of porosity into the ceramic microstrucutre, the permittivity of the porous freeze-cast PZT decreased significantly, compared to the dense PZT, and this was highly beneficial in achieving high piezoelectric and pyroelectric harvesting figures of merit. Experimental results were compared to parallel and series analytical models of the distribution of the material with good agreement. The porous PZT with porosity aligned parallel to the freezing direction exhibited the highest piezoelectric and pyroelectric response and this was a result of the enhanced interconnectivity of the ferroelectric material along the poling direction and reduced fraction of unpoled material that leads to a higher polarization. Using the materials characterisation and modelling data, a complete thermal energy harvesting system, composed of a parallel-aligned PZT harvester element and an AC/DC converter was constructed to successfully demonstrate the real-time operation of charging a storage capacitor. The results are of benefit for the design and manufacture of high performance porous pyroelectric and piezoelectric materials in devices for energy harvesting applications.
6:00pm - 6:15pmOral
Carbon-Metal Oxides Nanocomposites for Energy and Environmental Applications
Humboldt University of Berlin, Germany
The combination of different nanobuilding blocks in a single heterostructure can lead to materials with improved properties by selecting components with the desired characteristics for a specific application. Carbon-based nanomaterials demonstrated to be highly suitable as support for the elaboration of heterostructures. Atomic layer deposition proved to be a technique of choice for the coating of nanostructured carbon materials. These heterostructures find applications in various areas such as electronics, sensors and energy storage and conversion. Because the chemical inertness of the graphitic carbon inhibits the initiation of ALD film growth, numerous surface functionalization approaches have been investigated in order to provide the required nucleation sites. The different strategies employed for the ALD onto carbon nanotubes, graphene, graphite and other nanostructured carbon materials (e.g. carbon black, fibers) will be described. The peculiarity of ALD for tailoring the chemical, structural and morphological properties of the deposited material will be discussed.
Finally, in order to highlight the importance of this class of materials, possible applications in energy storage and conversion, catalysis and gas sensing devices are also reviewed.