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New Silicon Nanotube Anodes for Li-ion Batteries Hold Capacity and Efficiency Even After 200 Cycles

Rate capability (top) and cycle life performance (bottom) of the Si nanotubes anodes in pouch-type Li-ion cells between 2.75 and 4.3 V to 200 cycles. C rate for the cycle test was 1C. Credit, ACS, Park et al. 2009. Click to enlarge.

Researchers from South Korea and Stanford University, led by Dr. Jaephil Cho at Ulsan National Institute of Science & Technology (UNIST) and Dr. Yi Cui at Stanford, have developed another approach to silicon-based anodes for Li-ion batteries that show promise for capacity and efficiency retention over cycling.

Prepared by reductive decomposition of a silicon precursor in an alumina template and etching, the Si nanotubes show a very high reversible charge capacity of 3,247 mAh/g with Coulombic efficiency of 89%, and also demonstrate a superior capacity retention even at a 5C rate (=15 A/g). A Li-ion full cell consisting of a LiCoO2 cathode and Si nanotube anode demonstrated 10 times higher capacity than commercially available cells with graphite anodes even after 200 cycles.

A paper on the work was published online 11 September in the ACS journal Nano Letters. In addition to Drs. Cho and Cui, authors included Mi-Hee Park of UNIST; Min Gyu Kim of Pohang Accelerator Laboratory; Jaebum Joo of Hanyang University; and Kitae Kim, Jeyoung Kim and Soonho Ahn of Battery R&D, LG Chem, Ltd.

USABC Cycle Life Goals for EV and PHEV Batteries
  • EV: 1,000 cycles, 80% DoD
  • PHEV (CD mode): 5,000 cycles
  • PHEV (CS mode): 300,000 cycles
  • Silicon is a very promising material for use as an anode material in Li-ion batteries, due to its potential for increasing the capacity of the resulting cells. The obstacle researchers worldwide have been working to clear, however, is the rapid loss of reversible capacity upon cycling of the Si-anode batteries, which is associated with the large volume expansion of the Si anode. Researchers have tried a variety of approaches, some of them showing promise, including the use of Si nanowires and nanoporous silicon. Both Dr. Cho (earlier post) and Dr. Cui (earlier post) have published recent efforts in this area.

    When reacting with Li, Si is known to incorporate 4.4 Li atoms per Si atom. In Li-ion batteries, this results in the extremely high specific capacity of 4200 mAh/g, which is 10 times higher than the capacity of graphitic carbon (372 mAh/g). However, the 300% volume change upon lithium insertion commonly causes pulverization and thus a loss of electrical contact between Si and the current collector.

    —Park et al. 2009

    However, the researchers noted, even some of the promising approaches showing improved capacity still suffer loss of capacity and efficiency after cycling.

    In the current approach described in the Nano Letters paper, the researchers fabricated novel Si nanotube structures to increase the surface area accessible to the electrolyte, which allows the Li ions to intercalate at the interior and exterior of the nanotubes. In addition, they deposited a carbon coating on the surface of the nanotubes, which stabilized the Si-electrolyte interface and promoted stable SEI formation for long cycle life.

    This work was supported by the World Class University (WCU) program supported by National Research Foundation (NRF) and Ministry of Education, Science and Technology (MEST) of Korea.



    A ten-fold increase in energy density (from 100 Wh/Kg to 1000 Wh/Kg) may go from dream to reality by 2015 or there about.

    When that happens, BEVs e-range per charge may very well go from 100 Km to 1000 Km. Most people could drive around with a single charge every two or three weeks. BEV city buses, taxis, delivery trucks etc would quickly become common place.

    PHEV-100+ Km would be possible with a rather small lower cost battery pack making that option affordable.

    Intgeresting transition decade ahead.


    At 3.5 amps per gram and a cell voltage of about 3 volts, doesn't this translate into 10 kwh per kg? An efficient gasoline engine can produce about 4 to 5 kwh per kg of fuel. It sounds like this energy density well exceeds IC engines, with less battery weight than fuel weight, and much lower drivetrain weights.



    Don't get too excited, this kind of breakthrough will take a lot of time to make it through (if it does), 200 cycles is still not enough and producing nanotubes at industrial scale is still out of reach. 10 years is a very minimum for such an exotic material to emerge but 20 years is more realistic. Look a the silicon solar cells, they were invented in the 70s an only now they are not scaled in production to make a dent in our energy production.


    Why does new/modified battery manufacturing take so long?

    It seems that entire coal, sometimes nuclear, power plants are built and online before a 'breakthrough' electrode is switched into a car battery and improved performance is on sale to the public.



    A little dream does not hurt.

    May it be 5, 10 or 20 years, it will come, specially if enough resources are allocated to new improved battery technologies.


    hah, my friend last night was telling me abotu how they had just developed batteries that could hold 10 times the charge but I kind of dismissed it in my head, but it turns out he was right!

    Treehugger, I am more optimistic about this kind of thing coming to market sooner rather than later. The reason solar panels didn't progress fast was because oil was so cheap and the reigning government / industry was certainly in no way interested in helping it along.

    These batteries are a bit different because once the BEV firmly establishes itself, in about 5 years, then the race will be on to get better and better ones out, because that's what the consumer will demand. It will be another example of competitive markets forcing innovation, like Canon vs. Nikon, Iphone vs. Blackberry, these products progress at lightning speed, and the same will happen with BEV's when they hit market because there will be so much money at stake.


    Wow. This is a huge improvement in just a little over a year since Cui's last "breakthrough" (80% capacity after 20 charges I believe). Another 10x advance and oil is toast.

    BTW, with these energy densities for an electric drivetrain, it is very interesting what happens to necessary pack size and overall vehicle weight. Smaller motors, wheels, and brakes are needed to achieve the same levels of acceleration, handling, and braking


    Yep, that's about 10kw/h/kg. A 100kw/h battery pack would only weight 10kg/22lbs. Figure 50% loss for packaging and you are still looking at only 20kg/44lbs. 100kw/h should be good for 500 miles. Using the existing 200 charge cycle limit that means the battery would be good for 100,000 miles. Not bad.



    their result is a remarkable achievement but new material are notoriously long to developp for reasons that are too complex to be described here. As long as someone shows how to make nanotudes in volume this nice thing will stay a curiosity. There is no evidence to day that we can make nanotube in volume as far as I am aware of.


    Silicon photo cells were invented in the late 1950s not 1970s.


    Manufacture of nano particles on an industrial scale will most likely pose an extreme health hazard. As a matter of fact the safety hazards of most nano particles are just now being evaluated. Initial tests do not look promising. Nano particles may turn out to be the ultimate pollution.


    It will be very useful for miltary but if you look the charge capacity starts to nosedive rapidly at about 170 cycles.


    During 150 years of lead-acid and 15+ years of NiMH, Li-ion, etc battery production, it would seem they could at least be less expensive.

    Account Deleted

    Some people transpire the duty to qualified resume writers because they don't have the ability to compose a respectable resume that is the argument why you
    need to resume writing, but such guys like author don't do that. Thanks for the information. Really good information about Li-ion Batteries Hold Capacity and Efficiency Even After 200 Cycles.

    HealthyBreeze hard is it to grow silicon nanotubes?

    Most of the battery and capacitor technologies that want to use nano-scale features to dramatically increase surface area or overcome other materials limitations will require some serious manufacturing breakthroughs on nano-sized features to become financially viable.

    Where do we stand on that?


    The capacity of the anode "the Si nanotubes show a very high reversible charge capacity of 3,247 mAh/g" is not the whole story. In a typical Li-Ion cell with LiCoO2 cathode and carbon anode, the anode is only about 20% of the weight, including packaging and electrolyte. So if the anode capacity is increased by ten times, but the cathode is unchanged, the weight of a battery can't be reduced by more than 20%. This results in a battery with 125% the gravimetric capacity, not ten times.

    However, the researchers say that "A Li-ion full cell consisting of a LiCoO2 cathode and Si nanotube anode demonstrated 10 times higher capacity." I'd love to know how that works because the gravimetric capacity of LiCoO2 cathode is only 140 mAh/g. How did they get the cathode capacity to increase by more than 20 times? Carbon anodes are about 370 mAh/g.

    Looking at the chart, the capacity drops in a straight line until, at 200 cycles, there is a hint of a downward curve. This isn't enough to see what the capacity does after that. However, it's still about 12 times normal cell at 200 cycles, therefore maybe five times at 300 cycles. 200 cycles would be fine with me if the battery cost is ten times less than current batteries. Something like a 40 kg battery, with 300 mile range, charged once a week, might last about four years. Nanowire etching, according to Cui, is probably not very difficult, but clearly more expensive than simple carbon anodes.


    I love seeing things like this coming from places like Korea, China, S. Africa, etc. This is becoming a world wide race, and that's what will keep it moving. It will make it difficult to bottle it up.
    I remember when xray lithography for silicon seemed impossible. Si nanotubes will be commonplace once the industrial processes are established.


    HealthB... & danm

    Have a look at USA Patent number 7544626


    I love the "while stirring", sound like making tomato sauce. Ironic it's from China. Since when do they care about patents?


    I don't believe what the writer of this article says - "A Li-ion full cell consisting of a LiCoO2 cathode and Si nanotube anode demonstrated 10 times higher capacity than commercially available cells with graphite anodes even after 200 cycles."

    The paper and abstract of the researcher's paper are here -

    The abstract says something different - "Furthermore, the capacity in a Li-ion full cell consisting of a cathode of LiCoO2 and anode of Si nanotubes demonstrates a 10 times higher capacity than commercially available graphite even after 200 cycles."

    With better grammar, this should say "Furthermore, the capacity OF THE NANOWIRES, in a Li-ion full cell consisting of a cathode of LiCoO2 and anode of Si nanotubes, demonstrates a 10 times higher capacity than commercially available graphite ANODES even after 200 cycles."

    I'm not going to spend $30 to download a paper that was obviously misread not read at all by the GCC writer. Looks like he or she only read the abstract and rewrote it to create some exciting news.


    If you look at the chart, the vertical scale is labeled Cell Potential (Volts). The horizontal scale is labeled Capacity (mAh/g). This capacity is only for the Silicon nanotube anode, not for the whole cell. The cell's capacity is limited to that of the LiCoO2 cathode, which has a capacity of only 140 mAh/g.


    Well BLEEP!



    I suspect that you could contact the authors directly to get some of you answers. They will probably send you the paper.

    Jaephil Cho [email protected] and
    Yi Cui [email protected]



    Well, that has been the question since Cui first published; What about the cathode? Do we cut annode bulk by 4/5ths and increase cathode material by 4/5ths and end up with a battery with 1.8x the density?

    Do we try to apply nano features to the cathode to get some increase in capacity to heighten this ratio further?

    Anybody know what Cui says about it?



    I get a little tired of hearing about nanotubes, nanowires, nanohorns, and nanorods, since they can't seem to make it to the market. I'm sure Cui and his associates are great scientists and they know all about the cathode problem, but have to focus on their anode research, which is so much more meticulous than most of us can imagine. However, there are plenty of others trying to make better anodes. My favorite is the coaxial nanotubes being developed at Rice - It looks very promising to me, so we might have a real 40 kg, 500 km battery soon.

    Even a 10 times better Li-Ion battery would be difficult to compete with the EESTOR super-ultra capacitor - no chemistry, no temperature problems, charges super fast, lasts forever, tiny self-discharge rate, and cheap. But there's not much to read about them, so we have to talk about Li-Ion, Li-S, Li-Air, nanorods, etc.


    I meant there are plenty of others trying to make better CATHODES, which is what Ajayan's group at Rice are doing.

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