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Silicon rally: EnerG2’s new silicon battery anode material

It seems that every time the hottest new smartphone or tablet comes out, one of the biggest points of contention among users is its battery life. The demands put on the batteries run them down faster than users would like, and the OEMs can’t simply increase the batteries’ size while still hitting their targets for device size, weight and cost. It’s a small version of the same problem electric vehicles have with their batteries. Once you spot the new gadgets making big leaps in battery performance, it’ll be time to get excited about EV batteries as well. That should signify that after countless early-stage announcements of advanced battery technology, the ball is finally rolling. 

We’ve seen it many times: A small startup company has promising battery intellectual property, receives funding, develops its technology, scales up to production readiness, and then seeks customers in the consumer electronics space with the idea of eventually (hopefully) moving into EVs. Such is the case for Seattle company EnerG2, which launched in 2003 with some material science IP from co-founder and CTO Dr. Aaron Feaver, who was working on a PhD from the University of Washington. 

After several years of focusing on gas-storage technologies, EnerG2 switched focus about six years ago to its Carbon Technology Platform – advanced carbon materials for lead-acid batteries and ultracapacitors. During that period, the company raised about $24 million in venture capital, and in 2009, it received a $21.3 million DOE Recovery Act grant, which covered 75% of the cost of building a 73,000-square-foot manufacturing facility in Albany, Oregon. That plant opened in early 2012 and can now produce tens of tons of carbon materials a month, depending on demand. 

In January, with its infrastructure in place, EnerG2 announced its greatest breakthrough yet: an anode material for lithium-ion batteries that blends carbon and silicon, is meant to replace commonly used graphite materials, and supposedly offers five times better battery cycle life and higher energy density than other silicon anodes. 


The taming of silicon

It’s been a little more than a year since EnerG2’s manufacturing facility went online, producing its hard carbons for Li-ion anodes. According to the company, it’s the only plant in the world of its kind – dedicated to commercial-scale nano-engineered carbons for high-performance energy storage. Dr. Feaver told Charged that EnerG2’s hard carbon anode material already presented significant advantages in capacity, power, efficiency and cycle life over the graphite anode materials typically found in Li-ion batteries. However, compositing their hard carbon with silicon was the logical next step. 

“Hard carbon – and especially graphite – have really hit their maximum capacity,” he said. “Most manufacturers are capable of getting very close to the theoretical maximum amount of lithium that graphite can store.”

Feaver said that silicon can store about 10 times more lithium by weight than graphite can. However, while silicon appeals greatly to anode developers, it comes with a caveat as well. “Silicon undergoes a very large volume change when it takes on all that lithium,” said Feaver, “so it has a tendency to expand and contract as you charge and discharge the battery. Gradually it pulverizes itself inside the battery, and your electrode fails eventually… or rapidly in plenty of cases.”

EnerG2’s breakthrough has been to incorporate silicon into its hard carbon. “The powerful chemistry approach we use to produce these materials can incorporate silicon into the material before we carbonize it,” Feaver said. “It’s a very interesting approach unique to EnerG2. It’s given us the ability to tailor the amount of silicon and to use different silicons as a starting point. We’ve seen really fantastic cycle life on batteries with our new carbon-silicon anode material. Pretty much across the board we see a very large improvement in cycle stability.”

Because the new material was developed as part of EnerG2’s Carbon Technology Platform, the company was able to upgrade its factory relatively quickly to produce the carbon-silicon solution at scale. 

“Our competitors are still working in the lab,” said Rick Luebbe, EnerG2 co-founder and CEO. “Meanwhile, we’re able to work rapidly at large scale, because this new product is a drop-in for our existing plant. US manufacturing as a whole will benefit from our breakthrough.” 


The search for a source 

While EnerG2 is capable of mass-producing its carbon-silicon nano-composite, it still has the task of choosing the best silicon source for production. Different silicon sources provide varying results and at varying costs.  

“Whether it’s a really good silicon or a mediocre silicon material on its own, across the board we see a phenomenal improvement in cycle stability and cycle life by taking that silicon and incorporating it into our carbon,” Feaver said. “We don’t see any degradation in capacity in most cases, and in plenty of cases we actually see an improvement in capacity.” He added that they’re seeing cycle life of five to ten times what they would get with the silicon on its own. 

Luebbe said that their process is “silicon-source-agnostic,” but that the company is looking to establish a definitive source. “We are still evaluating the best silicon sources,” he said, “so anybody who thinks they have a really good fundamental silicon product, we are interested in testing it. But the process is scaled, and we can make the composite now.”

In testing silicon sources, EnerG2 seeks the sweet spot between the best performance and the best price. Luebbe has seen a huge range in silicon prices, from $10/kg on the low end to as much as thousands of dollars per kilogram. 

“You can have great performance, but if it’s not cost-effective, it’s not going to get adopted,” Luebbe said. “One of our objectives from the beginning was to keep the cost of our hard-carbon technology in the same range as current hard carbons employed in vehicle batteries. We’ve been able to do that. So ideally we want to find a silicon source that boosts the performance without raising the price.”


CE to EV

Soon EnerG2 will be sending samples of its carbon-silicon composite anode material to prospective customers in the consumer electronics (CE) world. While Luebbe said he wants EnerG2 to eventually serve the “cross-section of the battery space,” including EVs, the practical move is to go after CE applications first. 

“They qualify much more quickly and get to commercial revenues faster than EV batteries will,” Luebbe said. “[CE] is a great place to get approval points, get some market traction and start developing products.”

Luebbe said that it’s too early to tell how long it might be before EnerG2’s new anode material finds its way into EV battery packs, but he thinks they’re pretty close to being in the “strike zone” for EVs. Part of the process will depend on how good their final silicon source turns out to be.  

“We’re definitely in the strike zone for consumer electronics applications,” Feaver added. “I think that’s going to go extremely well. Any situation you put it in does depend on the silicon, the battery architecture you put the material into, and all kinds of nitty-gritty details associated with building a battery. But the results we’re seeing are very exciting for both consumer electronics and automotive.”


This article originally appeared in Charged Issue 12 – FEB 2014

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