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Externally Funded Research Activities
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Materials Characterization (Understanding Performance and Lifetime Limitations) |
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Characterization efforts at ORNL are focusing on elucidating life-limiting structural and compositional phenomena in operating batteries in order to propose new and advanced materials for the future. To this end, ORNL is developing in-situ characterization tools such as in-situ microscopy and in-situ fatigue testing.
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Scientist from the ORNL and colleagues at Vanderbilt University have developed a new nanoscale imaging technique for micrometer-thick specimens in liquid that can be used to image both whole cells in biological experiments and operating energy systems. The new technique – liquid STEM – uses a micro-fluidic device with electron transparent windows to enable the imaging of materials in liquid and will be utilized for in-situ microscopy of energy storage materials and battery cells. The fundamentals of the liquid STEM technique have been the basis for designing a specialized holder for the in-situ microscopy testing of micrometer-sized (miniaturized) batteries in the Hitachi HF-3300 high-resolution Scanning/Transmission Electron Microscope (S/TEM). For the in-situ battery testing and the concurrent live-time observation (and recording) of the Secondary Electrolyte Interface (SEI) formation (and other microstructural changes) during rapid charge-discharge events, the liquid flow cell will “contain” the liquid electrolyte as well as the battery anode and cathode materials (forming the miniature battery). Testing of the holder has recently started, and the study will require chip/window (which form flow cell) redesign and extensive baseline characterization of “known” battery materials and the correlation of the in-situ tests with actual laboratory testing of full-size batteries.
Funding:
- Office of Electricity, Department of Energy
- Laboratory Directed Research and Development Funds
Principal Investigator and Point of Contact:
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The objective of this effort is to establish in-situ characterization capabilities to investigate and characterize the fatigue behavior of electrode materials due to electrochemical cycling. In-situ X-ray diffraction stress analysis together with acoustic emission spectroscopy to characterize microscopic crack initiation, crack growth, fracture of grains and particles, and loosening of particles during cycling will be employed to establish the first-ever in-situ fatigue testing of electrode materials for lithium-ion batteries. This will result in a deeper understanding of the mechanical behavior of electrode materials being used in lithium-ion batteries. Analogies between traditional fatigue, which is mostly limited to deviatoric stress behavior from cyclic mechanical loading, and electrochemical battery cycling, which includes mostly hydrostatic stresses, will be drawn. These investigations will lead to the development of complex fatigue models for battery electrodes and ultimately, will guide development of advanced electrode materials that can withstand crack initiation and crack growth. As a result, acceptable stress and strain thresholds could be raised and lifetimes could be significantly extended, compared to state-of-the-art electrode materials. Researchers in the Materials Science and Technology Division and the High Temperature Materials Laboratory at ORNL will work closely together to establish the needed characterization tools and develop fatigue models based on newly accessible experimental data.
Funding:
- Vehicle Technologies Program, Energy Efficiency and Renewable Energy, Department of Energy
Principal investigator:
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- Focused-Ion-Beam Micromachined Electrodes for Determination of Intercalation-Induced Strains
For long cycle life, battery electrodes must maintain their structural integrity to ensure high capacity with minimum internal resistance. A common expectation is that repeated cycling causes the electrode particles to become fractured or pulverized, inactive, and isolated from the current collector. A few materials exhibit small volume changes, but many other attractive materials undergo fairly large volume changes to give high-energy densities. Unfortunately the information needed to accurately model and predict such structural changes is lacking.
The goal of this proposed work is fundamental. We do not propose to fabricate improved high-rate electrode materials or structures. Rather the aim is to gain an understanding of the fundamental mechanical stresses imposed by the lithium intercalation reaction and how these result in deterioration of the electrode structure with age. To accurately and unambiguously measure the transport kinetics and associated mechanical stresses, fabrication of model electrode-electrolyte structures will be required. Advanced and novel material processing and characterization capabilities at ORNL will be utilized in this endeavor. These samples will be cycled at University of Michigan to investigate their performance and any changes in architecture resulting from mechanical or kinetic loads.
Funding:
- Vehicle Technologies Program, Energy Efficiency and Renewable Energy, Department of Energy
Principal Investigators:
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Materials Processing (Advanced Low-Cost Processing, Process Control, and Scaling) |
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- Self-Assembled, Nanostructured Carbon for Energy Storage and Water Treatment
Collaboration with Honeywell Specialty Materials
This nanomanufacturing process development project consists of stage 3 research and development in nanoscale materials processing. The project is aimed at translating a unique approach for synthesis of self-assembled nanostructured carbon into industrially viable technologies for two important large-scale applications: electrochemical double-layer capacitors for electrical energy storage and capacitive deionization systems for water treatment and desalination.
These tailorable, nanostructured materials – described in US Patent Application 2006 057051, "Highly ordered porous carbon materials having well-defined nanostructures and method of synthesis" – are synthesized by self-assembly in solution, followed by heat treatment. The materials can be produced using scalable chemical and materials processing operations; therefore, there is an excellent opportunity exists for development of manufacturing processes for cost-effective production. Preliminary testing at ORNL has indicated positive results relevant to energy-related applications, including tunable pore size and structure in the range of 2 to 12 nm, high specific capacitance, excellent electrical conductivity, and high purity.
The project will overcome scale-up issues to develop reliable manufacturing processes to produce the nanostructured carbon materials. The project will be conducted in close collaboration with two industrial partners that are focused on commercialization of the technology. Approaches will be developed to produce materials in two forms – an unconsolidated form suitable for displacement of activated carbon in current capacitor production and a sheet form suitable for capacitive deionization applications. The work will be centered on overcoming issues that hinder the translation of the nanomaterial production process from laboratory scale to commercial production including optimization of process variables to achieve desired product properties; identification and mitigation of factors that lead to product variability; development of a process for the recycle of costly chemicals used as templates for structuring the carbon; adaptation of the process to employ inexpensive, renewable feedstocks; and developments of scalable manufacturing processes for industrial production of materials.
Successful development and commercial implementation of the proposed technology will have wide-ranging impact. The ultracapacitor implementation would have a cross-cutting application to a wide range of energy issues, including transportation (hybrid automobiles and buses, rail systems); electrical grid (stability, power quality, transmission and distribution equipment); and renewable energy (wind, solar). The technology can be applied to a variety of water treatment processes, including wastewater treatment, oil/gas-produced water treatment, and seawater desalination. The market for desalination systems is expected to increase as the global demand for clean water and energy increases and due to the potential impacts of global warming on water supplies.
Funding:
- Nanomanufacturing Initiative, Industrial Technologies Program, Energy Efficiency and Renewable Energy, Department of Energy
Prinicipal Investigator:
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Materials and Systems Simulations (Understanding Characterization Results and Guiding Next-Generation Systems) |
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- Systems level simulations under way. Updates soon to be posted.
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Prinicipal Investigators:
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New Concepts and Materials |
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- Li-S – Internal Seed Funding
This effort proposes to develop sulfur/carbon (S/C) nanocomposites and electrolyte additives for Li/S batteries that can be cycled over 200 deep discharge/charge cycles with a cathode capacity over 1100 mAh/g in anhydrous liquid electrolytes. The current state-of-the-art Li/S batteries with liquid electrolytes have cycle lives of less than 100 cycles with about 60% of the theoretical capacity of sulfur. A primary obstacle to extending the cycle life of Li/S batteries lies in the intrinsic polysulfide shuttle phenomenon, which leads to an irreversible deposition of Li2S at the anode, thereby leading to complete loss of capacity of the sulfur cathode. The preliminary results derived from the Seed Money project show that the combination of nanostructured S/C composites and electrolyte additives can significantly extend the cycle life and promote the capacity of Li/S batteries. The nanostructure of the cathode material and the novel battery chemistry conferred by the additives are essential to the improvement of Li/S batteries. Questions to be addressed by this effort are (1) how does the nanostructure of the S/C composites affect the cycling performance of Li/S batteries and (2) how do the electrolyte additives affect the Li/S chemistry?
Funding:
- Laboratory Directed Resaerch and Development, Seed Money Funds – continuation expects external funding
Principal investigator:
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- PHEV R&D High-Energy Materials
FreedomCAR goals for the short-term Hybrid-Electric Vehicles (HEV) have been met or exceeded in 8 out of 11 areas, those being discharge pulse power, regenerative pulse power, available energy, efficiency, cycle life, system weight, system volume, and self-discharge. Despite the tremendous success of this program, achievement of three more challenging goals still remain that must be met. These goals are attaining an operating temperature from -30°C to 52°C (less than 40% of the stated goal met), a lifetime of 15 years (less than 80% met), and a selling price less than $500/system at 100K/year (about 50% met). For intermediate-term Plug-in Hybrid-Electric Vehicles (PHEV) and the long-term all-Electric Vehicles (EV), accomplishment of these goals as well as need to overcome significant material-processing technological barriers must be met.
Approach: Based on the FY07 and FY08 Technology Assessment, ORNL has identified several materials-related issues and processing strategies to transform the materials and processing approach taken in battery manufacturing.
Funding:
- Vehicle Technologies Program, Energy Efficiency and Renewable Energy, Department of Energy
Principal Investigator:
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