From The Mobilist Inbox This Week
Show-stopper for lithium-metal, Tesla safety, battery mania
Each Wednesday, The Mobilist highlights reader articles on Medium, comments, and updates.
The first item has been corrected to show that the total loss is about 25%, and 2%-3% in the first 24 hours. (h/t Matt Lacey)
‘Not so fast’ for lithium metal anodes: A surprising new paper in Nature Energy suggests that many of the most promising current lithium-metal batteries may have a fatal defect. The paper, authored by nine researchers at Stanford led by Yi Cui, a prominent materials scientist, says that when lithium metal is at rest, it loses 2%-3% of its capacity the first 24 hours, and eventually about 25%. In battery parlance, its “calendar life” is shortened while it is just sitting around. If that is the case, lithium metal batteries — regarded as a Holy Grail technology for affordable next-generation electric vehicles — might not be deployable. “It’s a possible show-stopper,” said Venkat Viswanathan, a professor of mechanical engineering at Carnegie Mellon.
A little less than a decade ago, a much-sought high voltage version of NMC, the workhorse lithium-ion formulation, turned out to have its own fatal flaw: Its voltage faded on every cycle, making it commercially unusable and disappointing customers like General Motors. But how did the high-voltage NMC ever get to GM with this flaw? It turned out that no one had bothered to check the voltage.
It appears to be the same with lithium-metal. Everyone has seemed laser-focused on other metrics and simply have not checked the material’s calendar life, Viswanathan said. In the case of voltage fade, the U.S. Department of Energy ordered much of the federally funded battery community to halt everything and try to fix it. Viswanathan said the same sort of action may be necessary with the apparent lithium-metal problem.
The Nature Energy paper looked specifically at lithium-metal batteries using liquid electrolyte. Qichao Hu, CEO of SES, a lithium-metal startup, told me that what the paper is pointing out, however, seems to affect only liquid-electrolyte batteries using ether-based solvents. “It depends on the solvent chemical structure,” Hu said. He said the problem also affects solid-state lithium-metal batteries.
Cui did not respond to an email. Neither did QuantumScape, a leading lithium-metal anode startup, in which Volkswagen is the top investor.
The safety of Teslas: Much is being reported on safety concerns surrounding Tesla. In this piece on the Medium platform, Mobilist reader Taylor Ford looks at various aspects of the safety of the new Plaid Tesla S.
An explosion of battery media: The elevated mania around EVs has triggered a gusher of quality blogs, newsletters, podcasts and YouTube channels concentrating on batteries. The newest to this party is Cellsiders, a weekly podcast diving deep into chemistry, metals and market forces. It comes on top of Intercalation Station, an authoritative newsletter. There also are The Limiting Factor and Battery Bulletin, must-watch YouTube channels. There is a blog called BatteryBits. Every week, battery professionals from around the world are meeting to chat about the field in the Battery Brunch. Finally, Venkat Srinivasan, a leading battery scientist at Argonne National Laboratory, says he wants to resurrect his much-read former blog, This Week in Batteries. This is not an exhaustive list. Tell us about your own outlet in the comments section below.