PROGRAM AREA OVERVIEW

17. TECHNOLOGIES RELATED TO ENERGY STORAGE FOR ELECTRIC AND HYBRID VEHICLES

The commercial use of electric and hybrid electric vehicle technologies, including fuel cell vehicles, has been limited by a variety of technical barriers. In conjunction with the Office of Basic Energy Sciences, the Office of Energy Efficiency and Renewable Energy is interested in identifying and developing innovative concepts for advanced technologies for energy storage devices (batteries and electrochemical capacitors) that will improve the performance, extend the life, and significantly reduce the cost of the vehicles.

Battery-powered electric vehicles (EVs) require energy storage devices with high specific energy, and hybrid electric vehicles (HEVs) require devices that can deliver high power pulses. Advanced hybrids may require devices that both store significant energy and can deliver high power pulses. All of these devices must be able to accept high power recharging pulses from regenerative braking. For high specific energy systems, the near term goals are to develop cells that provide at least 150 Watt-hours/kg (Wh/kg), 230 Wh/l, 300 W/kg, and 460 W/l (with long term goals that exceed these targets); have a life of 1000 cycles at 80 percent depth of discharge; and have a calendar life of at least 10 years. For high power applications, the goal is to develop cells that provide peak power of 1000 W/kg or greater, have a cycle life of at least 300,000 shallow cycles, and have a calendar life of 15 years. For all systems, materials to be utilized should be plentiful, have low cost (< $10/kg), be environmentally benign, and be easily recycled. Evaluation of the technology with regard to the above criteria should be performed in accordance with applicable U.S. Advanced Battery Consortium test procedures or Society of Automotive Engineers recommended practices (see references that follow).

Grant applications must show how proposed innovations would result in significant advances in performance and cost reduction over state-of-the-art technologies. Grant applications are sought only in the following subtopics:

a. Improved Electrolytes for Electrochemical Capacitors—The most common electrochemical capacitors, also known as “super” or “ultra” capacitors, use an aqueous or organic electrolyte solution. For vehicular applications, the higher cell voltages available with an organic electrolyte are attractive. Most organic electrolytes are based on acetonitrile. This solvent allows the preparation of electrolytes that have acceptable conductivity and function over a wide range of temperatures. Unfortunately, the solvent is quite flammable and under some circumstances can decompose to yield cyanide. Therefore, grant applications are sought to address the flammability and potential toxicity issues associated with acetonitrile. Replacement materials that result in reduced performance relative to the state-of-the-art (in areas such as power capability, energy stored, operating temperature, useful life, or cost) are not of interest. All proposals must provide a clear discussion based upon available data and theory to support an assertion that the materials to be developed will be improvements. Grant applications must include a demonstration of the materials’ performance in laboratory cells by the end of Phase I and in capacitors suitable for use in a vehicle by the end of Phase II.

b. Technology to Improve the Performance of Lithium-Ion Cells at Low Temperatures—Lithium-ion cells and batteries discharged or charged at low temperatures (between -10 and - 20 degrees Celsius) exhibit poor performance relative to performance at room temperature. Power capability is significantly reduced on discharge, and lithium plating on the negative electrode can occur upon charge. The loss of power below -10 Celsius is much more severe than would be predicted from the conductivity vs. temperature relationships for conventional Li-Ion electrolyte systems. Studies of cells being cycled at low temperatures indicate that the impedance increase is interfacial in nature and fairly evenly distributed between the positive and negative electrodes. Grant applications are sought for technology to address these concerns. Approaches that result in significantly reduced performance relative to the state-of-the-art (in areas such as room temperature performance, cycle life, calendar life, or cost) are not of interest. Grant applications must provide a clear discussion, based upon available data and theory, to support the assertion that the research will result in improved performance. The technologies being developed must be demonstrated in full electrochemical cells of at least 0.2 Ampere hour in size by the end of Phase I and in cells of at least 1.0 Ampere hour by the end of Phase II.

c. Technologies to Improve the Tolerance of Lithium-Ion Cells and Batteries to Thermal Runaway Provoked by Abusive Discharge or Overcharge—High energy and high power lithium-ion cells and batteries may be subject to inadvertent, abusive discharge or overcharge if the battery’s control mechanism fails. For this subtopic, an abusive discharge is one that results in a cell going into thermal runaway sufficient to result in cell failures such as venting and/or fire. Depending upon the failure mode, cells may experience charging voltages that exceed the design specification by as little as 100 millivolts or by many volts. Even low levels of overcharge have been shown to make a cell more susceptible to thermal runaway. More extreme overcharge can produce rapid events such as venting with smoke and flames. Grant applications are sought to develop novel methods of improving the tolerance of lithium-ion cells to abusive discharge and/or overcharge. Grant applications may focus on changes in one or more of a cell’s basic components (cell hardware, anode, electrolyte, separator, and cathode), or on materials added to a “standard” cell. Any standard, commercially available lithium-ion cell, suitable for vehicular use, may be used as the basis for the changes/improvements. (Note: some commercially available cells are not suitable for vehicular use because they contain costly components, operate only at low rates, have relatively limited cycle or calendar lives, etc.) Investigators that do not have access to specific information about the components of commercially available cells may use the specifications published by the Advanced Technology Development Program for its Generation 1 and Generation 2 cells as a starting point (see references 3 and 4).

Grant applications must be for novel research and development as defined in the introductory sections of this solicitation, provide a theoretical basis for the research, address the probable cost of using the technology in vehicular batteries, and address the impact of the technology on other performance parameters such as calendar life, power capability, and energy density – technologies that adversely affect these parameters are not likely to be adopted. Improvements must be demonstrated in cells of at least 0.2 Ampere-hour in size in Phase I and in cells of at least 1.0 Ampere hour in Phase II.

d. Methods for Rapidly Predicting the Calendar Life of Lithium-Ion Cells and Batteries—Lithium-ion cells and batteries proposed for vehicular use must meet goals related to both cycle life and calendar life. As described in the references, end-of-life is defined when an EV battery’s capacity, as measured according to the procedures described in the EV Test Manual (reference 1), drops below 80% of its original capacity. For an HEV battery, the most common failure is the inability to provide the minimum power and energy for pulse cycles as described in the HEV battery test manuals. Cycle life can be experimentally evaluated within relatively short periods of time, typically less than one year. Quickly assessing calendar life, when the desired life is more than ten years, is much more difficult. Grant applications are sought to develop novel methods of rapidly assessing the calendar life of state-of-the-art lithium-ion cells. The ideal method would result in a reliable prediction within twelve to eighteen months. All grant applications must provide a clear discussion, based upon available data and theory, to support the assertion that the research is viable. Phase I efforts must include development of the basic approach and its preliminary evaluation on a commercially available cell. By the end of Phase II, the approach must be refined and demonstrated using at least two different types of commercial cells. The deliverables under Phase II shall include a general, procedural manual that describes how one can assess the calendar life of lithium-ion cells other than those used to develop and demonstrate the approach.

References:

Please note: Paper copies of those references not available in the open literature or from NTIS may be obtained by addressing a request to Mr. Irwin Weinstock, Senior Engineer, Sentech, Inc., 7475 Wisconsin Avenue, Suite 9000, Bethesda, MD 20814. Where available, locations of the documents on the Internet are given.

1. Links to the following manuals are all available at: http://ev.inel.gov/battery. These documents provide a good general basis for understanding the performance requirements for electric and hybrid electric vehicle energy storage devices.
· FreedomCAR 42V Battery Test Manual
· FreedomCAR Battery Test Manual for Power Assist Hybrid Electric Vehicles
· PNGV Battery Test Manual, Revision 3
· Electric Vehicle Capacitor Test Procedures
· USABC Electric Vehicle Battery Test Procedure Manual, Revision 2

2. The internet site for the Batteries for Advanced Transportation Technologies (BATT) program at http://berc.lbl.gov/BATT/BATT.html includes quarterly and annual reports. This program addresses many long-term issues related to lithium batteries, including new materials and basic issues related to abuse tolerance.

References 3, 4, and 5 discuss issues related to more mature, high power, lithium-ion batteries. They include information about cell chemistries that have proven to be useful model systems for these applications along with discussions of issues related to abuse tolerance and cell life. Advanced Technology Development (High-Power Battery): 2001 Annual Progress Report, U.S. DOE, Office of Advanced Automotive Technologies, February 2002. (Full text available at: http://www.eere.energy.gov/vehiclesandfuels/resources/fcvt_publications.shtml. Scroll down to 2001, and select “Advanced Technology Development …”.)

3. “Applied Research”, in the 2002 Annual Progress Report, U.S. DOE, Office of Advanced Automotive Technologies, May 2003. (Full text available at: http://www.eere.energy.gov/vehiclesandfuels/resources/fcvt_publications.shtml. Scroll down to 2002, select “Energy Storage Research and Development,” and go to Chapter III, “Applied Research”.)

4. “Applied Research”, in the 2003 Annual Progress Report, U.S. DOE, Office of Advanced Automotive Technologies, May 2004. (Full text available at: http://www.eere.energy.gov/vehiclesandfuels/resources/fcvt_publications.shtml. Scroll down to 2003, select “Energy Storage Research and Development,” and go to Chapter III, “Applied Research”.)

5. Information about requirements for vehicular batteries, separators for lithium-ion batteries, and abuse testing can all be found at the USABC section of the USCAR internet site. Go to http://www.USCAR.org; click on “Teams”; scroll down and click on “United States Advanced Battery Consortium (USABC)”. This site provides a second source for many of the documents found at reference 1.

6. The abuse test procedures, developed for FreedomCAR by Sandia National Laboratories may be accessed directly at: http://www.uscar.org/consortia&teams/USABC/SAND99-0497%20USABC%20Safety%20Manual.pdf

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