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Internally Funded Research Activities
Ongoing and completed efforts related to energy storage:
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- Materials Behavior Underlying the Electrochemical Performance of Advanced Batteries
This work undertakes two research thrusts aimed at developing underlying knowledge of basic materials behavior that governs lithium battery electrochemical performance and lifetime. Specific objectives include (1) dynamic characterization of the initial development of the solid-electrolyte interface in terms of morphology and molecular composition at a heretofore unattained level of resolution, thus demonstrating the ability to fundamentally relate these characteristics to energetics and kinetic factors, and (2) development of an understanding of the evolution of stress states and mechanical behavior of electrodes and the SEI in order to directly connect structure and materials processing routes to the factors that make major contributions to a lithium battery’s durability (lifetime) and safety.
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- Design of Evanescent-Wave Power Transfer for Parked and Moving Hybrid Electric Vehicles
As Hybrid Electric Vehicles (HEVs) become more prevalent, there is a need to transfer the power source from gasoline on the vehicle to electricity from the grid, thereby relieving requirements for onboard storage and reducing dependency on oil by using available power more efficiently. Traditional systems for trains and buses rely on physical contact to transfer electrical energy to vehicles in motion, which is not practical for vehicles of the future.
Theoretically, evanescent waves in loosely coupled transformer systems can provide the mechanism for this power transfer without physical contact over a significant fraction of a meter, eliminating the need for precision alignment of the vehicle and power source. Initial results from a Seed Money project currently under way have demonstrated efficiencies of around 30% in the laboratory, but simulations indicate that efficiencies greater than 90% are possible with proper tuning. The challenge and objective of this project is to efficiently accomplish this tuning to optimize the transfer of tens of kilowatts of power for very large currents at HEV voltages in the low MHz range.
This project will use analysis and simulations to design a loosely coupled evanescent wave bench-top power transfer system for laboratory evaluation. This experimental proof-of principle system will be used to determine the limits of today’s technology. The project object is to develop the technology necessary to design efficient power transfer to electric vehicles, first for a stationary charging system and then for a moving vehicle.
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- Computer Design and Predictive Simulation of High-Capacity, Cyclable, and Versatile Nanoporous Supercapacitors for Energy Storage Applications
We propose to develop multiscale computational tools to investigate and optimize key variables of supercapacitors based on nano-porous carbon materials. There is a projected doubling of world energy consumption within the next decades and a desperate need for low-emission sources of energy. However, the use of electricity generated from renewable sources requires efficient electrical energy storage. A particularly promising technology is carbon supercapacitors, which have higher power density than batteries and have higher energy density than conventional dielectric capacitors due to the large surface area provided by the nanometer-sized pores. The capacitance of a supercapacitor depends on complex phenomena occurring in the pores, the effective dielectric constant of the electrolyte, and the thickness of the double layer formed at the interface.
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Experimental measurements are hard to perform and difficult to interpret, especially at the nanoscale. Optimization of these key variables requires a fundamental understanding that can only be obtained through detailed scalable first-principles calculations combined with mesoscale and microscale simulation tools. As part of this proposal, we will further improve the scaling of our first-principles methods along with the heat (micro), mass (micro), and ionic (meso) transport codes. These types of simulations require computational resources that can only be provided by the ORNL National Center for Computational Sciences (NCCS). This work will uniquely position ORNL as the lead institution in the simulation of energy storage materials.
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- Understanding Interfacial Electrochemical Phenomena in Advanced Energy Storage Capacitors Using Spectroscopy and Modeling
Effective use of electricity generation from alternative energy sources is critically dependent on the development of cost-effective and efficient electrical energy storage systems. A thorough knowledge of electrode double-layer charging effects and alteration of the oxidation state of molecules bound in surface pores will result in improvements in the energy storage capacity of electrochemical capacitors. Currently the primary challenge to understanding electrochemical energy storage with supercapacitors resides in the mediating effects due to electrode pores and the transport of electrolyte ions into and out of these pores. This proposed effort will generate a quantitative assessment of ion transport, ultimately leading to tailored electrode materials that will permit improvements in energy storage. We will investigate unique mesoporous carbon materials with controlled pore characteristics as the electrode material for advanced capacitors. First, we will examine electrical double-layer charging to make gains in carbon electrode capacitance. Then, we will study an added pseudocapacitance effect for greater electrical energy storage. Our effort will also include modeling and simulation of transport dynamics to determine how ions diffuse into and out of mesoporous carbon, and establish how the interfacial pore structure mediates charging events in electric double layers. The studies will be conducted under the realistic (extreme) conditions that exist in energy storage capacitors. Our results will lead to improved materials and designs for electrical energy storage devices.
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- Laser-Enhanced, Nanoscale-Focused, Electron-Beam-Induced Processing
The directed assembly of nanoscale materials is essential for controlled nanofabrication. While standard lithographic techniques will continue to play an important role in nanofabrication, clearly the frontier of nanofabrication is the direct writing of nanoscale features with specified size, shape, location, orientation, and composition. Electron-Beam-Induced Deposition (EBID) is one such nanoscale, direct write approach that has been successfully employed to deposit a diverse host of materials and structures. While EBID makes it possible to synthesize three–dimensional nanoscale features on textured or complex surfaces, often the subsequent materials are amorphous or nanocrystalline. In addition, the final nanostructures are frequently contaminated with non-volatile by-products resulting from the electron dissociation reaction sequence. These contaminants compromise material quality and ultimately the nanoscale functionality. We propose to use photon irradiation during EBID to remove adsorbed reaction by-products from the growing deposit to achieve deposits of high-purity and controlled composition.
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- Novel Carbon Materials for Advanced Energy Storage – complete 2009
This project is focused on devising innovative materials technology for electrochemical capacitors, including nanostructured carbon for electrodes and alternative electrolytes. Electrochemical capacitors are high-power energy storage devices that have performance properties intermediate between conventional capacitors and batteries and are attractive for a wide variety of applications, both as stand-alone energy storage devices and as a complement to batteries in hybrid power systems. Currently, application of electrochemical capacitors is limited by cost and performance issues of electrode and electrolyte materials. Novel mesoporous carbon materials synthesized at ORNL exhibit large, accessible surface area and controllable pore size and thus present promise for exceptional energy-storage performance. Through the experimental synthesis, characterization, and performance testing conducted in this project, we expect to develop inexpensive materials that provide greater energy and power density than currently available systems and breakthrough frequency response. We aim to develop a unique capability for tunable production of electrode materials and matching electrolytes that can deliver performance characteristics targeted for specific applications. This project, which transitions an ORNL nanoscience discovery into an energy-related nanotechnology, will provide opportunities for long-term fundamental research as well as multiple opportunities for grid, vehicle, renewable energy, and military applications.
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- Development of Lightweight Lead-Acid Batteries – complete 2009
The low specific energy of lead-acid batteries has limited their use in electric and hybrid-electric vehicles, as well as in other mobile and portable applications where the weight of the battery is critical to meeting efficiency goals. Major factors controlling the specific energy of lead-acid batteries include the weight of the main components (grid/current collector, active materials, electrolyte, and container) and the efficient utilization of the active materials. The potential weight savings to be gained by replacing the lead alloys currently used as grid/current collectors with graphite (carbon) materials has been widely recognized. In addition to its relatively low density, graphite has the advantage of being chemically stable in sulfuric acid and is a good thermal and electrical conductor. The objective of this project was to develop technologies that can be used for the production of durable, lightweight lead-acid batteries by (1) reducing the weight of the grid/current collectors through the use of graphite fibers, (2) designing layers of active materials that increase material utilization, and (3) engineering the interface between the graphite fibers and the active material to ensure long-term durability.
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- Antiferroelectric Thin-Film Capacitors for Ultrafast High-Power Energy Storage – complete 2008
Advanced energy storage devices, such as batteries, inductors, and capacitors, for continuous or pulsed power are required for various technologies. Among these, capacitors offer the highest power density and thus are well suited to replace and supplement batteries in many power applications that require an extremely fast response time. However, the main drawback for high energy and power-density storage applications is that ferroelectrics exhibit properties that reduce the attainable energy density at the high operating fields. Therefore, we aim to develop new antiferroelectrics (AFEs) with high induced polarization and high dielectric strength. The goal is to understand and control the variation in fundamental physical properties by external constraints (e.g., chemical composition, ordering, strain, and orientation). Perovskite-based materials will be the main focus of this program, where we already have world-leading capabilities in thin-film synthesis and state-of-the-art density-functional calculations for addressing a key element of alternative-energy programs (i.e., energy storage).
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- Nanoparticle Phase Change Materials: The Nanoscale Science Basis for Gigajoule Energy Storage – complete 2008
The goal of this project is to advance fundamental understanding of solid-solid transformations and solid-fluid interactions in concentrated inorganic nanoparticle dispersions as the foundation for novel thermal-storage media. Inorganic Phase-Change Materials (PCM), stabilized by optimized carrier solutions that remain liquid at high temperature, can provide the unique properties promising a dramatic increase in thermal solar energy efficiency. Indirect evidence exists for phase stability reversals in relation to the bulk phase driven by large differences in surface energies. For small nanoparticles, the latent heats may reach and even exceed the enthalpy of freezing of water. Several questions need to be answered before the optimal nanosolid+liquid combination can be found, and its thermal properties can be tuned. Critical challenges include determination of the mechanism of solid-solid transformations at the nanoscale and the source of high heat effects, transition kinetics and reversibility over multiple cycles, and size stability of the nanophase in the liquid matrix.
Experimental and modeling studies of interactions between nanoparticles and carrier solutions will enable the rational design of novel high-performance thermal storage systems. The principal focus of this effort is to demonstrate the principle of using high-energy inorganic solid-solid transitions in stable nanoparticles for energy storage. Success in this research will enable more efficient utilization of solar thermal energy by providing a breakthrough pathway for thermal energy transfer and storage.
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- New LDRD cross cutting initiative “Solar Generation and Storage of Electrical Energy"
- Evaluation of proposals is under way – new starts soon to be announced
In light of the nation’s dependence on foreign oil, desire to generate and integrate renewable energy sources into our economy, and need to reduce greenhouse gas emissions, solar generation and storage of electrical energy are among the most strategic capabilities to be developed to meet our society’s needs for abundant, clean energy, a growing economy, and national security. Environmentally benign solar-energy-generation technologies coupled with electrical-energy storage technologies will create new opportunities to meet future energy requirements. However, today’s solar photovoltaic (PV) and electrical-energy storage (EES) technologies fall far short of market requirements for efficiency, cost, durability, and/or safety. Revolutionary improvements are required in basic and applied materials sciences, materials processing, and manufacturing to break through barriers and achieve the desired changes nessary to implement these technologies. Such transformative capabilities include (1) rechargeable batteries for all-electric vehicles with a 500-mile range and (2) commodity-grade, solar PV cells that are 50% efficient will enable net-zero energy residential neighborhoods.
Revolutionary technologies are needed to efficiently capture and convert solar energy over wide areas and at low cost for use in the residential and commercial sectors. Simultaneous optimization of efficiency, area, cost, and reliability will not only demand a fundamental understanding of the material science involved in photovoltaics but will also require careful characterization and process control to achieve large-scale performance on a flexible substrate. The research community has detailed these needs within the DOE report Basic Research Needs for Solar Energy Utilization, a Report of the Basic Energy Sciences Workshop on Solar Energy Utilization, April 18-21, 2005, as well as the DOE Solar Energy Technologies Program’s Multi Year Program Plan 2008-2012, April 15, 2008.
A similar theme holds true for electrical storage, as revolutionary technologies are needed to electrify transportation through cost-effective plug-in hybrid and all-electric vehicles, and to level the cyclic nature of intermittent renewable energy sources. These will include advanced electrical-energy storage technologies with high energy and power densities, long life, low cost, little or no maintenance, and a high degree of safety. Achieving these characteristics will require scientific and technological breakthroughs in new materials, designs, processes, and innovative scalable manufacturing technologies, for EES systems. The research community has detailed these needs within the DOE Report Basic Research Needs for Electrical Energy Storage, a Report of the Basic Energy Sciences Workshop on Electrical Energy Storage, April 2-4, 2007.
Achieving technological breakthroughs in (1) solar generation of electricity and (2) storage of electrical energy will have much in common. Both will require large, focused research efforts vertically integrated across materials phenomena, electro-chemistry and photo-electro-chemistry, materials processing, and fabrication. For both, we expect that significant progress will result from advances in neutron and x-ray scattering, in-situ characterization, and predictive modeling of complex, multi-component materials and systems over multiple length and timescales. This LDRD initiative will focus on developing cross-cutting research teams to apply ORNL’s capabilities in materials science and engineering, computational sciences, and neutron sciences to develop new, world-class capabilities in solar PV and electrical-storage systems. The scope and quality of the research capabilities developed for one will have significant implications for the strategic development of the other, and the leverage achieved in the evolution of ORNL’s capabilities will have large implications for ORNL’s competitiveness in attracting programmatic funding in growing “science-to-energy” programs.
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