A month ahead of its eagerly anticipated Battery Day event, Tesla CEO Elon Musk sparked speculation with hints of new battery tech that could drastically improve the energy density of current batteries used in EVs, allowing for much longer ranges with the same general exterior dimensions and perhaps a lighter weight—two of the main limiting factors in today’s EVs.
One clue to what the EV maker could have in store for a Sept. 22 reveal was shown on its own website announcing the event, leading some to speculate about a specific type of technology that Tesla and its research partners could be working on. The image on Tesla’s site displayed a background with a series of vertical filaments, prompting some to suggest Tesla could be researching silicon nanowire battery technology.
Elon Musk invited even more speculation on Monday this week, with a tweet suggesting batteries with far greater energy density were not too far on the horizon.
“400 Wh/kg *with* high cycle life, produced in volume (not just a lab) is not far. Probably 3 to 4 years,” Musk tweeted.
Wh/kg refers to watt-hours per kilogram, a common way of rating energy density in batteries, so 400 Wh/kg would represent a significant hike for energy density in a battery compared to the cells now used in several EVs, which sit above 230 Wh/kg.
A number of battery developers have been working on achieving energy densities in the neighborhood of 500 Wh/kg using different methods, but there is a difference between being able to do this in a lab and being able to produce them commercially for electric cars, especially when eventual consumer costs are considered.
It remains to be seen just what Tesla has in store for Sept. 22, but even by Musk’s own estimate 400 Wh/kg tech is not something we’ll see in an EV especially soon. And silicon nanowire filaments are just one of a few promising battery technologies making their way through the pipeline: Toyota promised a preview of solid-state battery tech at this year’s Olympic Games in Tokyo, games that have of course been postponed, ahead of a commercial rollout of long-awaited solid-state battery tech by the middle of the decade. Solid-state batteries had long been seen as the holy grail of battery composition, replacing the heavy soup of metals and chemicals in current lithium-ion cells with a solid polymer of sorts, (ideally) yielding a higher energy density and a much lighter battery weight.
EV battery technology has not seen a significant breakthrough for quite some time—progress has been incremental—while the biggest “gains” over the past five years have occurred in driving down the speed and cost of production, as well as in internal cooling.