Lithium Batteries for Hybrid-Electric Vehicles
A long-standing focus of EETD electrochemical research has been to support the development of high-performance rechargeable batteries for electric vehicles. This has proved to be an extremely challenging task because of the need to simultaneously meet multiple battery performance requirements: high energy (watt-hours per unit battery mass or volume), high power (watts per unit battery mass or volume), long life (10 years and hundreds of deep charge-discharge cycles), low cost (measured in dollars per unit battery capacity), resistance to abuse and operating temperature extremes, perfect safety, and minimal environmental impact. Despite years of intensive worldwide R&D, no battery can meet all of these goals.
A compromise of sorts is the hybrid-electric vehicle (HEV). The HEV is a centerpiece of the Partnership for a New Generation of Vehicles (PNGV), a multi-agency government program aimed at introducing automobiles with three times the fuel economy of our present-day fleet. In a hybrid vehicle, a battery, a combustion engine (or a fuel cell), or both are used to drive an electric motor. The advantages of this configuration include the use of a smaller battery (compared to an all-electric vehicle) and a smaller combustion engine (compared to a conventional vehicle). The system can be designed so the combustion engine operates at a nearly constant speed, which greatly reduces its exhaust emissions and increases the overall vehicle fuel economy. The battery provides power for vehicle acceleration and absorbs the energy released during vehicle deceleration (regenerative braking). Prototype HEVs not only achieve more than 60 miles per gallon of gasoline, but also meet ultra-low vehicle emission requirements. The battery, however, must be designed to deliver very high power and undergo hundreds of thousands of shallow charge-discharge cycles. This is basically a new type of battery, and little is known about how it behaves under such use conditions.
The PNGV has contracts with three battery companies to develop high-power batteries for HEVs, and the U.S. Department of Energy has recently formed a new R&D program to support the PNGV contractor efforts. The basic chemistry chosen by the PNGV and its contractors is the lithium-ion system. This system uses a lithium-carbon negative electrode, an organic electrolyte, and a mixed metal-oxide positive electrode (typically nickel and cobalt oxides). Lawrence Berkeley National Laboratory (Berkeley Lab), Argonne National Laboratory (ANL), Sandia National Laboratory (SNL), Idaho National Engineering Laboratory (INEEL), and Brookhaven National Laboratory (BNL) participate in this new cooperative effort, which is called the Advanced Technology Development (ATD) Program. A unique feature of the ATD Program is the design and manufacture of special high-power lithium-ion battery cells, which are tested under strict protocols at INEEL, SNL, and ANL and then sent to Berkeley Lab and BNL for detailed diagnostic examinations (some cells are retained at ANL and SNL for related diagnostic tests). The program participants meet on a regular basis to discuss testing and diagnostic results. This represents a significant advance in cooperative R&D among national laboratories, at least in the electrochemical area. It also exemplifies the role national labs can play in supporting technology innovation in the private sector.
The primary Berkeley Lab role is to carry out diagnostic studies to determine cell component chemical, structural, and morphological changes that lead to battery performance degradation and failure as the batteries are aged, cycled, or abused. Berkeley Lab's diagnostic results will guide the development of improved cell chemistries and complement the results obtained at the other national laboratories. Berkeley Lab is using Raman spectroscopy, infrared spectroscopy (performed at Berkeley Lab's Advanced Light Source), atomic force microscopy, impedance measurements, gas chromatography, and other analytic tools to characterize electrodes and electrolytes taken from cells that have been cycled at other national laboratories. Our data are being compiled with related information obtained at the other participating laboratories on an ATD Program web site and are being made available to the PNGV managers and contractors.
EETD researchers participating in this program are Thomas Adler, Elton Cairns, John Kerr, Fanping Kong, Robert Kostecki, Frank McLarnon, Steve Sloop, and Kathryn Striebel, as well as Materials Science Division researchers Phil Ross and Sherry Zhang.
For more information, contact:
- Frank McLarnon
- (510) 486-4636; fax (510) 486-4260
Frank McLarnon's Research Groups' web page.
This research is supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Transportation Technologies, Office of Advanced Automotive Technologies of the U.S. Department of Energy.