Nanostructured Silicon Li-ion Batteries’ Capacity Figures Are In

Do the numbers really promise a game-changing technology for electric vehicles?

2 min read
Nanostructured Silicon Li-ion Batteries’ Capacity Figures Are In

Seven months ago I covered a small start-up called California Lithium Battery Inc. (CalBattery) that had entered into a Work for Others (WFO) agreement with Argonne National Laboratory (ANL) to develop and commercialize what they dubbed as the “GEN3” lithium-ion battery.

The GEN3 battery is largely based on ANL’s silicon-graphene battery anode process. Basically the ANL approach is to sandwich silicon between graphene sheets in the anode of the battery to allow more lithium atoms in the electrode.

This line of research was motivated by the hope of improving the charge life of Li-ion batteries. First, researchers showed that if you replaced the graphite of the anodes with silicon, the charge could be increased by a factor of ten.  There was one big drawback though. After a few charge-discharge cycles the silicon would crack and become inoperable from the expansion and contraction of the material. The solution seemed to be nanostructured silicon anodes that could last longer than the pure silicon variety, but just barely. 

The ANL silicon-graphene anode is supposed to overcome this problem and achieve comparable charge-discharge cycles of graphite, but with the charge significantly increased like you would achieve with pure silicon in the anode.

So, what’s been happening in the last seven months? Well, CalBattery has released a press announcement revealing the results of their last eight months of testing. According to the press release, the Li-ion batteries they have been testing have an energy density of 525WH/Kg and specific anode capacity of 1,250mAh/g. To offer a comparison, the company press release explains that Li-ion batteries currently on the market have an energy density of between 100-180WH/kg and a specific anode capacity of 325mAh/g.

“This equates to more than a 300% improvement in LIB (Li-ion battery) capacity and an estimated 70% reduction in lifetime cost for batteries used in consumer electronics, EVs, and grid-scale energy storage,” says CalBattery CEO Phil Roberts in the company press release.

Curiously, I didn’t see anything in the press release that talks about what numbers they were able to achieve in charge/discharge cycles with the material. And that really is the crux of the matter. Everyone has understood for the last few years that nanostructured silicon anodes have a high capacity. The problem is that it has only been slightly better than regular silicon when it comes to charge/discharge cycles.

Let’s look at Energy Secretary’s threshold numbers for making Li-ion battery-powered competitive to petrol-powered vehicles:

  • A rechargeable battery that can last for 5000 deep discharges
  • 6–7 x higher storage capacity (3.6 Mj/kg = 1000 Wh) at [a] 3x lower price

Well, we don’t know what the deep discharge figures are for this GEN3 battery. But improving the capacity 300% seems to be a little short of factor of 6 or 7. But as it was pointed out to me in the comments a 70% reduction in lifetime cost does seem to meet the criteria of a 3x lower price.

Maybe EVs don’t really need to be competitive with petrol-powered vehicles, and Secretary Chu’s figures are not pertinent, but if the dwindling sales of EVs are any indication, maybe those figures are relevant and EVs actually do need to be competitive with petrol-powered vehicles…for now.

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Two Startups Are Bringing Fiber to the Processor

Avicena’s blue microLEDs are the dark horse in a race with Ayar Labs’ laser-based system

5 min read
Diffuse blue light shines from a patterned surface through a ring. A blue cable leads away from it.

Avicena’s microLED chiplets could one day link all the CPUs in a computer cluster together.


If a CPU in Seoul sends a byte of data to a processor in Prague, the information covers most of the distance as light, zipping along with no resistance. But put both those processors on the same motherboard, and they’ll need to communicate over energy-sapping copper, which slow the communication speeds possible within computers. Two Silicon Valley startups, Avicena and Ayar Labs, are doing something about that longstanding limit. If they succeed in their attempts to finally bring optical fiber all the way to the processor, it might not just accelerate computing—it might also remake it.

Both companies are developing fiber-connected chiplets, small chips meant to share a high-bandwidth connection with CPUs and other data-hungry silicon in a shared package. They are each ramping up production in 2023, though it may be a couple of years before we see a computer on the market with either product.

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