A Silicon Valley battery company determined to revolutionise the world of lithium-ion batteries forever has successfully completed its latest round of funding, it announced on Monday. Founded in 2008 as a Stanford Univeristy spinout, Amprius has been perfecting a new type of silicon-based lithium-ion battery pack which could not only pave the way to gadgets that last longer between charges, but also plug-in cars that could go hundreds of miles between recharges.
At the heart of Amprius’ battery technology is an anode made of silicon, instead of the carbon traditionally used for anode material in lithium-ion batteries. Much higher in its potential energy density than carbon — due to its surface structure — building electrodes from silicon has always been viewed as a holy grail of battery chemistry. Because of the way that silicon expands under lithium-ion insertion however, making silicon-based lithium-ion batteries that can withstand the repeated abuse of thousands of charge and discharge cycles has historically been a challenge.
Amprius says it has the solution. By turning silicon into ultra-thin nanowires using chemical vapour deposition, it is able to produce silicon nanowire electrodes that are not only capable of storing a large amount of energy but also strong enough to withstand the stresses and strains of repeated charge/discharge cycles.
As we’ve explained before, silicon-based lithium-ion batteries have the potential to more than double the energy density of today’s consumer-grade lithium-ion cells, both for consumer electronics devices and for plug-in cars.
But how much better is better? Tesla’s prized Model S sedan, the current gold-standard in electric vehicle technology, features a lithium-ion battery pack made of Panasonic cylindrical cells with an energy density of around 240 watt-hours per kilo. Most other electric cars on the market today use battery packs with an energy density of between 150 and 200 watt-hours per kilo.
Amprius says its third generation silicon nanowire technology has the potential to increase the battery energy density of lithium-ion cells from its industry best-figure of 450 watt-hours per litre to more than 800 watt-hours per litre. In an automotive application, that equates to more than 500 watt-hours per kilo. We think without any use of mathematics, you can appreciate the difference that would have on EV battery technology.
It’s no wonder then that Amprius’s latest round of funding brings its total funding to date to more than $55 million, not counting an undisclosed A series funding round. With backing from firms like Kleiner Perkins, Trident Capital, VantagePoint, and the U.S. department of Energy (via a DoE $5 million DoE energy grant specifically focused on EV battery technology) Amprius is certainly one of the darlings of the rapidly expanding lithium-ion battery industry.
As anyone who has followed the ups and downs of the lithium-ion battery industry will tell you however, having great technology in a laboratory environment doesn’t necessarily equate to success. For Amprius to truly succeed, it not only needs to scale cell manufacture to an appropriate industrial level — something that can be a real challenge when working with nano technology — but it also needs to prove the battery’s longevity and suitability for plug-in vehicle applications.
In other words, we’re still a ways from silicon-based lithium-ion cells transforming plug-in cars from vehicles capable of ranges between 100 and 200 miles per charge to ones capable of travelling further per charge than a gasoline car between fill-ups. But with more than one battery manufacturer — and more than one automaker — chasing this particular solution to making EVs go further, we think it’s inevitable we’ll see silicon lithium-ion technology in EVs in the mid to long-term future.