Frontiers of Engineering Reports on Leading-Edge Engineering from the 2012 Symposium (2013) / Chapter Skim
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Keeping Up with Increasing Demands for Electrochemical Energy Storage--Jeff Sakamoto
Keeping Up with Increasing Demands for Electrochemical Energy Storage--Jeff Sakamoto
Pages 41-56
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From page 41... ...
Research in sophisticated and efficient power electronics, battery/cell telemetry, safety, thermal management, and schemes to recycle/reuse EV batteries can help to establish a solid foundation for the development and use of EVs. This article provides an overview of energy storage technology for vehicle electrification, highlights challenges, and discusses opportunities at the frontiers of battery research.
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From page 42... ...
If EVs can improve energy efficiency in the short term and the technology for non-fossil-fuel-based/renewable electrical power generation can be realized in the long term, the benefits to our country's current and future sustainability are clear. Assuming the latter, the following discussions focus on electrical energy storage, specifically batteries.
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FIGURE 1 Energy use in the United States in 2011.
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. Replacement of the ICE powertrain with an electric powertrain should not considerably add to the vehicle cost, and the cost of the battery pack should be less than $5,000.
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and the capacity to store lithium ions in the solid state, resulting in high specific energy and low cell volume (energy density) , respectively.
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46 FIGURE 4 Schematic of a lithium (Li) -ion cell: (A)
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These past and recent successes are impressive, but Li-ion battery packs still require considerable reductions in cost as well as increases in specific energy to extend vehicle range. The following section presents a materials perspective on opportunities in electrochemical energy storage and milestones whose achievement will address these issues.
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48 FIGURE 5 Li-ion batteries come in a variety of designs: (a) spiral wound cell, (b)
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Increasing the mass/volume fraction of active material is one strategy to improve specific energy. Making thicker, less porous electrodes is a popular approach to achieve this, but thicker and less porous active electrode layers impede the transport of ions in the electrolyte and thus reduce power (Buqa et al.
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From page 50... ...
of lithium can provide 26.8 Ah of electrical charge. Graphitic anodes have a theoretical specific capacity of 372 mAh/g, and silicon and tin have specific capacities of 4,009 and 960 mAh/g, respectively, making the interest in these anodes apparent.
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In a Li-S cell, elemental lithium and sulfur are the reactants, a nonaqueous electrolyte shuttles lithium ions between electrodes, and, because sulfur does not have sufficient electrical conductivity, a specific porous carbon (Ji et al.
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prevent pore and electrolyte interface occlusion when/if LiOH precipitates at higher depths of discharge. Although there are few examples of advanced prototypes, the projected specific energy for both Li-air variants is expected to be about 1,000 Wh/kg.
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Shown above, a prototypical LLZO membrane fabricated in the Sakamoto lab using unique powder synthesis and sintering technology. CONCLUSIONS There is a compelling need for advanced electrochemical energy storage to power the next generation of electric vehicles.
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Solving the lithium metal anode–electrolyte interface stability issue; developing novel catalyst/catalyst support cathodes; and creating stable, semipermeable solid electrolytes require further research and development if Li-air and Li-S technologies are to mature. The frontiers of electrochemical energy storage are exciting from multiple perspectives, and are likely to generate significant engineering research and development opportunities in the coming decades.
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2012. Stable cycling of double-walled silicon nanotube battery anodes through solid-electrolyte interphase control.
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