UAlbany NanoCollege licenses silicon/silicide chemistry and branched nanostructure for advanced Li-ion batteries to spin-out
06 October 2012
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| BESS Technologies anode performance, capacity vs. cycle number. Source: BESS Tech. Click to enlarge. |
The College of Nanoscale Science and Engineering (CNSE) of the University at Albany in New York has licensed a silicon/silicide nanostructured anode technology developed there for Li-ion batteries to spin-out company BESS Technologies. The agreement enables BESS to begin to commercialize and to scale-up the technology.
BESS (Battery Energy Storage Systems) Technologies is a component design and engineering firm started by a group of CNSE graduate students in 2010. The CEO and co-founder is Dr. Fernando Gómez-Baquero, a nanoengineer and economist with more than 10 years experience in nanotechnology research and in launching nanotechnology startups. Issac Lund, the CTO, is one of the co-inventors on the technology patent.
The technology represents another approach to enabling the use of silicon-based anode materials to enable a significant increase in battery capacities; the graphite used in the anodes of many current Li-ion batteries has a capacity of around 372 mAh g-1, while silicon theoretically offers a capacity of more than 4,000 mAh g-1. However, silicon undergoes major expansion during the insertion of Li ions, and the stress causes the silicon to degrade over time, resulting in poor lifetime and degrading battery capacity. Numerous research groups are exploring ways to counteract that property to enable a commercially viable silicon anode material. (Earlier post.)
Working at CNSE’s Albany NanoTech Complex, the BESS team developed an innovative process to build branched nanostructures which offer significantly increased energy storage capacity, faster charging rates, and a longer lifetime. The branched, flexible nanowires relieve the stress of lithium ion insertion. These structures offer several advantages, the researchers claim:
The surface area of the branched nanostructures is increased significantly over that of thin film or non-branched nanostructures of the same footprint.
The flexibility of these nanostructures mitigates the problems with stressing due to their ability to flex. This allows for the required expansion area needed for lithium insertion and silicon expansion.
Each branch of the nanostructure is connected to a trunk structure and each trunk is well-connected to the substrate electrically and mechanically. The branched nature of the nanostructures of the invention allows for a higher anode density, thus requiring less area for same charging capacity.
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| An illustration of the branched nanostructure from the patent document. Click to enlarge. |
The core of the nanostructure is a resistive semiconducting material and the shell is a lower-resistance current collecting material; the current transfer occurs in the shell, not in the core. This nanostructure is then coated with an electroactive or electrically conductive coating that acts as the capacitive material. The anode technology does not require the use of carbon or any type of binder, unlike some other silicon anode technologies under development.
Incorporation of catalyst particles into nanostructures changes the electrical and/or chemical characteristics of the outside shell. As an example, the conductivity of a nickel silicided nanostructure can be adjusted by changing growth parameters to make the silicided region thicker. An additional surface coating may also be utilized to change the nanostructures’ properties.
The BESS Tech team has submitted a paper with more details regarding the technology to the Journal of Power Sources, according to Gómez-Baquero, who says that BESS is now consistently obtaining around 1,200 mAh g-1 with very stable behavior that goes beyond 500 cycles. The JPS paper will describe some half cells that were tested beyond 1,000 cycles. The team has charged at 5C-10C without damaging the anode.
BESS is not a materials company, Gómez-Baquero emphasizes. The company designs components such as the anode, tweaking the manufacturing “recipe”—i.e., controlling the process parameters—to improve their performance. The company is are working to make several “recipes” based on the same nanoengineering core knowledge he said.
We license designs (recipes) to manufacturers. Some manufacturers prefer to use their own equipment to manufacture, in which case we help them lay out production plans. Other manufacturers prefer to receive a fully manufactured anode, in which case we seek the help of a foundry (outsourced manufacturer). We are currently working with two companies in NY State that want to pursue this foundry model.
—Dr. Gómez-Baquero
In addition to the licensing agreement, BESS will have continued access to the cleanrooms, laboratories and tooling at CNSE, providing further stability as the company grows.
CNSE has already assisted BESS in obtaining more than $800,000 in funding through technology programs offered by the New York State Energy Research and Development Authority (NYSERDA) and the National Science Foundation’s (NSF) Partnerships for Innovation program.
The UAlbany CNSE is dedicated to education, research, development and deployment in the emerging disciplines of nanoscience, nanoengineering, nanobioscience and nanoeconomics.
I don't see how an anode material that destroys 50% of the lithium in the cell during the first 100 cycles could ever be commercially viable. The anode is the smallest part of the cell, so it's very important to differentiate between anode capacity and the corresponding cell capacity as it fades over time.
Commercial graphite anodes retain 94% of their capacity after 100 cycles. So cell capacity might fade from 100 units to 94 units. For this new silicon/silicide anode, capacity might start high at 115 units, but it would fade quickly to 63 units. 94 versus 63 - that's the relevant comparison.
1,000 mAh/g versus 350 mAh/g is not a fair comparison. Unless this anode material can be tailored so it's lithium loss (capacity fade) is minimized.
Posted by: David Snydacker | 06 October 2012 at 07:10 AM
If this anode material can maintain twice the graphite capacity over 500 cycles, it sounds useful.
Isn't the cathode is the present bottleneck and does this material work there as well?
Posted by: kelly | 06 October 2012 at 08:50 AM
David S,
I'm not understanding your point. Unless I'm misreading the graph, they do have ~1,000 mAh/g for over 500 cycles. Why would this not be the relevant comparison? Sure, it would be nice if it stayed up closer to 2,000 mAh/g where is starts for it's first cycle (at least eyeballing the chart) but as long as it levels off and stays at the 1,000 range...why is that bad?
Posted by: DaveD | 06 October 2012 at 09:04 AM
If this high performance anode can be mass produced at lower cost than existing limited performance counterparts, future EV batteries could, in principle, offer much better e-range with less weight, improved duration and performance.
If so, it could become what the electrified vehicle industry has been waiting for to become competitive and progressively replace our inefficient ICEVs?
Let's hope that it will be improved and produced locally.
Posted by: HarveyD | 06 October 2012 at 09:05 AM
Dave D,
Cell energy density (not anode energy density) is the ultimate measure of performance. Cell energy density is calculated by adding up the size of the anode, the size of the cathode, and the size of all other inactive components in the cell. The cathode is the largest part of the cell, and the anode is relatively small. Even if you reduce the size of the anode by 75%, you've only reduced the size of your cell by 15%.
Ok. Now here's the really bad news. In a working cell, lithium shuttles back-and-forth between the anode and the cathode. When the anode loses capacity, lithium dies and cannot shuttle back to the cathode. The whole cell loses capacity. So if your anode capacity fades by half, the whole cell capacity fades by half. Essentially, your anode dies and takes your cathode down with it. That extra 15% cell capacity from a smaller anode isn't worth a thing if your anode is going to eat up all the lithium from the cathode.
Hope that makes things more clear.
Best,
Dave S
Posted by: David Snydacker | 06 October 2012 at 06:42 PM
1,000 mAh/g for 500 cycles is really great. This only gives more respectability to Envia Systems 400 Wh/kg battery, which also uses Carbon Silicon composite. Envia's battery uses the cheap 250 mAh/g cathode developed by Argone Labs. The 200 mile range BEV is within reach.
http://www.greencarcongress.com/2012/02/envia-20120227.html
General Moters is excited too.
http://www.greencarcongress.com/2012/08/envia-20120810.html
It's true that the cathode has less capacity than the anode, but going from graphite to Silicon anode is a major improvement. Envia's anode also fades in the first few cycles. I don't buy the trapped Li argument. Do you have any references for it Dave?
Posted by: Zhukova | 07 October 2012 at 07:25 PM
Knowing nothing but throwing my hat into the ring anyway ... is it trapped or wasted lithium?
If the later then build the cell with the initial anode capacity (mAh) twice as large as that of the cathode so that after the 50% fade there is still enough anode capacity. No wasted lithium.
Posted by: DavidJ | 08 October 2012 at 04:29 AM
Dave S,
I was simply assuming what Dave J was suggesting....too damn many of us Dave's running around! :-)
I assumed that they knew that the anode would lose it's initial capacity quickly and therefore "right size" it for to optimize the overall cells capacity for charges 5 through 500+.
Yes, this would be a waste of lithium and make the cell slightly larger/heavier. But lithium is not very expensive relative to the rest of the cell and as you point out the anode is a small portion of the overall cell weight so it won't much affect the entire cell size.
Posted by: DaveD | 08 October 2012 at 06:29 AM
I tend to fall in the same camp with Zhukova and Bob Wallace. I believe both of them comment many times that a ~200 mile EV with decent charging infrastructure and some improvements in charge time will be more than sufficient to kick EVs into high gear.
Would a 300 mile or 400 mile range be better? Yes. But could 99% of the population be fine with a 200 mile range and a 10 minute charge time on those few occasions when it was really needed? Yes.
Posted by: DaveD | 08 October 2012 at 06:33 AM
Silicon anodes are probably the future. But as I said before, they need to offer stable capacity, not just high capacity. Check out this picture of the Solid-Electrolyte Interphase (SEI), these are lithium-rich phases that form in the anode: http://www.cse.anl.gov/cees/index.html Electrolyte additives can help form a stable SEI, but much of that lithium comes from the cathode and corresponds to reduced capacity for the full cell.
I'd bet that in five years, we'll have Li-Si/Li-S or Li-Si/Li-Mn-M-O batteries so that a Tesla Model S with the same size battery will go 450 miles. Nissan Leaf will go 150 miles and charge in 15 minutes.
Posted by: David Snydacker | 08 October 2012 at 07:14 AM
I think we've allowed "acceptable" standards to be set too high. As several of us are now saying 200 mile range with <20 minute 90%/95% charging would be acceptable to almost all car owners. Not many of us drive more than 200 miles per day very often. We'd trade a bit of charging inconvenience a few days a year for massive fuel savings all day a year.
(Those that need high range more frequently might be better served by PHEVs.)
The other part of "acceptable" we might have set too high is battery life.
Let's play with the Envia specs, tested and projected. Envia has a high capacity battery that has been tested and has held capacity for ">450 cycles". They expect to get cost to $160/kWh.
So, let's say you put their battery in a 200 mile range EV. 450 cycles should get you 90,000 miles before your range falls to 160 miles.
A new 60kWh battery (200 miles * 0.3kWh/mile) would cost $9,600.
At that point you have a choice.
Replace the battery and drive the car another 90k, gas savings will more than pay for the new battery. Pay for it in five years or less.
Or sell it on to someone who can easily get by with less range. As a second car a used EV with >100 mile range would be an excellent vehicle for many. Or a first car for people who aren't making a lot of money and need a way to get to work/shopping/school.
Some day, EVs with 1,000 mile ranges and selling for $19.95. Those are not the sorts of guidelines we should be using. What needs to happen to make EVs break through is "adequate range" and "adequate battery life".
If you crank through the numbers EVs are already cheaper to purchase and operate over their lifetimes than ICEVs. Without subsidies.
Posted by: Bob Wallace | 08 October 2012 at 09:27 AM
DaveS may be right about the trapped Li as described in this paper on the second page.
http://nanotube.skku.ac.kr/data/paper/Highly%20Interconnected_Hung%20T.%20Nguyen.pdf.
This trapping is caused by pulverization, where the Si particle is filled with Li ions, which causes it to expand, crack, and eventually turn into powder. The main thing in pulverization is that the silicon is detatched from the conductor surface and the Li is trapped in the inactive silicone. This effect occurs in nanowires described in the paper.
However, the reason for capacity fading in the UAlbany anode is not given in this article. So how does DaveS know the Li is being trapped, or if pulvarization is the cause? I don't know what he means by "wasted", unless he means that the Li is unavailable because it can't be conducted out of the inactive Si particles.
It may be caused by something else, which doesn't lead to trapped Li ions. In any case, Envia Systems is already marketing and sampling their 400 Wh/kg battery. A big 200 kg Envia battery might give 80 kWh of energy. At 3 miles per KWh, you might get 240 miles. Envia/GM 400 Wh/kg and $180/kwh means a much cheaper and smaller battery for typical daily charge, around town driving in a BEV.
Posted by: Zhukova | 08 October 2012 at 10:49 AM
China's battery producers will probably buy both Envia and this new start up company and mass produce both by 2014/2015?
Posted by: HarveyD | 12 October 2012 at 09:49 AM