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Home > Nanotechnology Columns > UAlbany College of Nanoscale Science and Engineering > Advanced Energy Storage Devices

Manisha V. Rane-Fondacaro
CNSE Materials Scientist and Instructor
UAlbany College of Nanoscale Science and Engineering

Abstract:
The projected doubling of world energy consumption in the next fifty years will require certain measures to meet this demand. The ideal choice of energy provider needs to be reliable, efficient, and from a low emissions source such as wind, solar etc. The low carbon footprint of renewables is an added benefit, which makes them especially attractive during this era of environmental consciousness. Unfortunately, the intermittent nature of energy from these renewables is not suitable for the commercial and residential grid application, unless the power is delivered 24x7, with minimum fluctuation. This requires intervention of efficient electrical energy storage (EES) technology to make power generation from renewables practical.

August 26th, 2008

Advanced Energy Storage Devices

The projected doubling of world energy consumption in the next fifty years will require certain measures to meet this demand. The ideal choice of energy provider needs to be reliable, efficient, and from a low emissions source such as wind, solar etc. The low carbon footprint of renewables is an added benefit, which makes them especially attractive during this era of environmental consciousness. Unfortunately, the intermittent nature of energy from these renewables is not suitable for the commercial and residential grid application, unless the power is delivered 24x7, with minimum fluctuation. This requires intervention of efficient electrical energy storage (EES) technology to make power generation from renewables practical.

With soaring oil prices, and cost of gas overshooting the $4 a gallon mark, replacing gasoline-powered vehicles with hybrid electric vehicles, plug-in hybrids or all electric vehicles has become practical. The leading energy storage technologies are chemical energy storage devices as know as batteries, and electrochemical capacitors (EC), both based on electrochemistry. The battery generates energy by chemical reactions, where as electrochemical capacitors store energy directly as charge.

Greater improvement in performance of the current EES technology is required before its incorporation into transportation, commercial and residential application. For example, before we can replace the gasoline engine with all electric/ plug in hybrid vehicle, it would be imperative to enhance the performance- a very fast recharge time, and higher energy and power density. There are many gaps in fundamental understanding of atomic and molecular level processes, which determine their performance limitation of the energy storage devices, and their operation and failure mechanisms.

The progress to higher energy and power density especially for battery technology will push material to the edge of stability, and yet these materials must be rendered safe, stable and with reliable operation throughout their long life. A major challenge for chemical energy storage is developing the ability to store more energy while maintaining stable electrode-electrolyte interface. A structural transformation occurs during the charge-discharge cycle, accompanied by a volume change, which degrades the microstructure over time. The need to mitigate this volume and structural change accompanying charge-discharge cycle necessitates going to nanostructured and multifunctional materials, which have the potential of dramatically enhancing the energy density and power density. However, the advantage of exploiting nanoscale phenomena, requires the knowledge about interactions at interface of electrode-electrolyte, especially with respect to controlling charge transfer from electrode to electrolyte. Using the combined power of computational dynamics and in situ characterization diagnostics, can allow one to design novel multifunctional materials with desired physical and chemical properties that lead to enhanced performance.

Capacitor technology is capable of high power density, but lacks high energy density. As with batteries, the need for higher energy density requires new materials. Enhanced energy density of capacitor storage technology is possible by increasing the voltage window and conductivity, while maintaining the stability. A fundamental understanding of charge storage mechanism at the electrode-electrolyte interface, and charge transfer and transport mechanism is critical for designing materials of enhanced capabilities. Energy density can be enhanced using nanostructured electrodes with tailored pore size distribution, and high surface area architecture can potentially offer multiple charge storage at single site. High and reproducible charge storage, with rapid charge-discharge function is achievable by addition of surface functionalities. New computational and analytical tools can help with the design of new materials, and provide insights at the molecular level to establish physical and electrochemical criteria for attaining higher voltages and ionic conductivities with a wide stability range of electrochemical and thermal window.

Four crosscutting research directions critical for meeting the future technology demands in energy storage technology are identified as: advances in characterization; nanostructured materials; innovations in electrolytes; and, theory, modeling and simulation.

The information generated from the new generation of analytical tools such as in situ photon- and particle- based microscopic, spectroscopic, and scattering techniques capable of time resolution down to femtosecond; and spatial resolution spanning the atomic and mesoscopic scale are needed to meet the challenge developing future EES systems.

Transformational breakthroughs in key energy storage parameters of active materials, conductors, and inert additives can potentially enhance the properties of EES devices such as capacity, power, charge-discharge rates, and its lifetime. Synthetic control of materials architecture such as pore size, structure and composition, particle size and composition; and electrode structure down to nanoscale size, would enable development of multifunctional materials that are self-healing, self-regulating, impurity sequestering etc., which would enhance the EES performance.

Transporting ions/charges between the electrodes and electrolyte is a common theme of EES devices (battery and capacitors). An ideal electrolyte provides high ionic conductivity over a large temperature range, is chemically and electrochemically stable and safe. Operation at higher voltage leads to chemical interactions between the electrolyte and electrode, leading to undesirable phase formation, and hence degradation. There is poor understanding of the myriad interactions between ion-ion, ion-solvent, ion-electrode. Thus, the electrolyte is often the weakest link in the EES technology. Fundamental research will provide knowledge that will enable researchers to formulate high performance robust electrolytes capable of high energy and power density.

Fundamental understanding of charge transfer and transport processes required to understand the complex dynamics at the electrode-electrolyte interface. New capabilities are required to observe the dynamics of composition and structural variation during ion transportation at the interface and at regions away from interface.

In summary, incremental evolutionary improvement in the current technology will not allow us to meet the future energy storage needs. Revolutionary breakthroughs in EES technology are required to meet the energy security of this country, achievable only from fundamental research, which would enable us to understand the underlying processes involved in the EES, and develop novel EES concepts that incorporate revolutionary new materials and chemical processes.


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