Toward the end of President Obama’s time in office, the US Department of Energy (DOE) launched a “Battery500 Consortium.” The goal is in the name: reaching 500 Wh/kg battery energy density with lithium-metal battery cells, a target which was reportedly triple the battery energy density at the time. (Notably, though, an update from the consortium indicates that when the program actually started in 2017, energy density was at 300 Wh/kg.)
Additionally, the goal was to go from 10 cycles to 1,000 cycles (100% battery discharges).
A quote from the launch: “The Battery500 Consortium aims to triple the specific energy (to 500 Wh/kg) relative to today’s battery technology while achieving 1,000 electric vehicles cycles. This will result in a significantly smaller, lighter weight, less expensive battery pack (below $100/kWh) and more affordable EVs.”
The Battery500 crew recently updated us on its progress, telling us that a Li-metal pouch cell has gotten to 350 Wh/kg and 350 cycles. How? “Specifically, they developed new electrolytes with enhanced stability against Li-metal, optimized the use of thick cathodes against a thin lithium foil, and applied cell-stack pressure to extend cycling life.”
Stable Cycling of 350 Wh/kg Li/NMC622 Pouch Cell. Courtesy US DOE.
Can Battery500 reach its target? Apparently, the conclusion is yes. “Recent research on even thicker cathodes and more stable electrolytes shows a path to a 500 Wh/kg cell. Current focuses include increasing rate capability and extending cycle life.”
Getting a little bit into the overarching technical matters and the impetus of the program from the DOE, here’s a summary: “Lithium-ion (Li-ion) batteries have found wide-spread use in electric vehicles (EV) and grid-scale energy storage. This adoption is partially in response to the dramatic decrease in EV battery costs over the past ten years, from over $1000 per kilowatt-hour (kWh) to under $200/kWh. Increasing cell energy is one way to decrease cost even further, as a higher specific energy value will result in fewer materials needed for the same total battery energy. But it is difficult to increase the energy density beyond that of today’s cells, which are approximately 220 watt hours per kilogram (Wh/kg) using graphite anodes. Li-metal anodes deliver almost 10 times the storage capacity of graphite anodes, thus enabling much higher cell energies. However, Li-metal anodes suffer from poor cycle life (typically 10 cycles or less, compared to the 1000 cycle EV battery requirement).”
Consortium partners include:
- Brookhaven National Laboratory
- Idaho National Laboratory
- SLAC National Accelerator Laboratory
- Pacific Northwest National Laboratory (PNNL)
- Binghamton University (State University of New York)
- University of California, San Diego
- University of Texas at Austin
- University of Washington
- Stanford University
Additionally, the 2019 Nobel Prize in Chemistry winners for their work on Li-ion batteries, John Goodenough and Stanley Whittingham, are on the research team.
Perhaps we can get Elon Musk’s opinion of the 350 Wh/kg achievement and 500 Wh/kg target at Tesla’s coming Battery Day.
But probably not.
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