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Fraunhofer researchers report significant extension to Li-S cycle life with silicon anodes and CNT-sulfur composite cathodes

Lithium-sulfur batteries are of great interest for electromobility applications, among others, due to their high specific energy and relatively low cost, but are challenged by significant capacity decay over cycling. (Earlier post.) Scientists at the Fraunhofer Institute for Material and Beam Technology IWS in Dresden, Germany say they have developed new cathode and anode designs for lithium-sulfur batteries that can increase the cycle life by a factor of seven.

According to Dr. Holger Althues, head of the Chemical Surface Technology group at IWS, by using the combination of silicon anode and composite carbon nanotube/sulfur cathode materials, the team has extended the cycle life of lithium-sulfur button cells from 200 cycles to 1,400 cycles.

The interplay between anode and cathode is the critical factor determining the performance and lifespan of a battery. In the lithium-sulfur model, the cathode is composed of elemental sulfur. However, sulfur also interacts with the liquid electrolyte, impairing the performance of batteries and, in the worst case, causes them to lose capacity entirely. The IWS researchers are using binder-free thick film sulfur cathodes based on a carbon structure with carbon nanotubes (CNT). The vertically aligned CNT are directly connected to the current collector.

Because the CNT electrode contains no polymer binder, the volume change of the active material (S8 ↔ Li2S) can be accommodated more easily, leading to better cycle stabilities. The sulfur mass fraction in the electrode can be as high as 90%.

In work reported in a paper in the Journal of Power Sources, the Fraunhofer teams found that the sulfur mass can be varied between 3 and 20 mg cm−2 electrode, leading to sulfur loads that are several times as high as in slurry electrodes. Reported achieved capacities for these extremely high sulfur loads are around 900 mAh g−1 sulfur of the total composite electrode mass at a current of 0.64 mA cm−2 electrode.

The anode of the team’s prototype is made from a silicon-carbon compound rather than the more common metallic lithium. This compound is significantly more stable, as it changes less during each charging process than metallic lithium. The more the structure of the anode changes, the more it interacts with the liquid electrolyte. This process causes the liquid to break down into gas and solids and the battery to dry out.

The energy density of a sulfur-silicon-lithium cell will be below the achievable values of a lithium-sulfur cell, the researchers note. Over the long term, the Fraunhofer team expects to reach a practical energy density of up to 600 Wh/kg. By comparison, the maximum energy density of the lithium-ion batteries currently in use is around 250 Wh/kg.

In the medium term, figures around the 500 Wh/kg mark are more realistic. In practical terms, this means you can drive twice as far with the same battery weight.

—Holger Althues

The work was part of the German joint project “AlkaSuSi-Alkalimetal sulfur and silicon” funded by German ministry BMBF.

The researchers are currently working on further optimizing the material and using it in larger battery models. They are also turning their attention to suitable manufacturing methods.


  • M. Hagen, S. Dörfler, P. Fanz, T. Berger, R. Speck, J. Tübke, H. Althues, M.J. Hoffmann, C. Scherr, S. Kaskel (2013) Development and costs calculation of lithium–sulfur cells with high sulfur load and binder free electrodes, Journal of Power Sources, Volume 224, Pages 260-268, doi: 10.1016/j.jpowsour.2012.10.004

  • M. Hagen, S. Dörfler, E.Q. González, H. Althues, J. Tübke, H. Föll (2012) High energy cells: Lithium-sulfur and lithium-sulfur-silicon. Honolulu PRiME 2012.

  • Arumugam Manthiram, Yongzhu Fu, and Yu-Sheng Su (2012) Challenges and Prospects of Lithium–Sulfur Batteries. Accounts of Chemical Research doi: 10.1021/ar300179v



An electrified vehicle (like a Tesla S-100+) equipped with a 600 Wh/Kg (100+ Kw) battery pack, good for 1400 cycles could go 840,000 Km on the same battery pack.

That would be good enough for 35 years @ 24,000 Km/year?


When an article says they already have achieved such high performance with low cost components - those batteries should be market sampled immediately.


In the medium term, figures around the 500 Wh/kg mark are more realistic. In practical terms, this means you can drive twice as far with the same battery weight.

A LEAF that can go 140 miles at 70 mph for the same weight, size and price would be good.


How cheaply can they mass produce carbon nanotubes?


Remember 2007 http://gm-volt.com/2007/12/21/gm-voltcom-interview-with-dr-cui-inventor-of-silicon-nanowire-lithium-ion-battery-breakthrough/ and

http://green.autoblog.com/2011/04/05/dbm-energy-record-breaking-kolibri-battery-passes-government-tests/ and


and all the other weekly battery crap for years and years?

It seems like so many of the same "many times better battery" promises from the same players.

Where the f**k are these batteries?


Fraunhofer is an R&D group in Germany, they are not GM nor IBM. They don't make batteries they look at ideas in the lab.

I know we would all like the 2X miracle battery breakthrough right now, but that is not likely. I would settle for it in the next 5 years, it might be lithium sulfide, but we will see.


It'll take a lot of button cells to power a tesla.


"..in 1979, John Goodenough and K Mizushima demonstrated a rechargeable cell ..(LiCoO2) as the positive electrode and lithium metal as the negative electrode" wiki

Sony started marketing Li-ion batteries in 1991 - 22 years ago - and Nissan leased Li-ion(bigger than button cells) battery EVs during the late 1990s.

Batteries have only three major components and NO moving parts. Rechargeable batteries have been mass produced since the 1860s.

The latest US taxpayer battery hub(5X density, 1/5 cost, <=5 yrs) alone proportionally should have released 34%(4 X 8.25%/month) better/cheaper batteries by last week.

Like the links noted since Cui, 2007 - where the f**k are these batteries?

Thomas Lankester

You seem to have answered your own question. 1979 rechargeable Li ion battery demonstrated, 1991 first mass production. Apply that to Cui, 2007 and new chemistry, doubled capacity Li ion batteries would be 'late' about 2019. So what's your beef?


@TL, these "breakthroughs" are often announced as produced completed working batteries of a decades marketed battery chemistry.

Taxes/consumers have been paying for '5X density, 1/5 cost, <=5 yrs' better batteries/research since long before Nov 2012.

The "dbm-energy-record-breaking-kolibri-battery.." broke a 370 mile EV range record back in 2010, besides being German government certified.

Where is it bought?

The "gm-backed-envia-claims-huge-advance.." stated it's US certified battery was from production lines in China 14 months ago.

Where is it?

The battery components only "breakthroughs" often state they are "drop in", which implies it's as hard to manufacture as a different color.

Where are they?

You don't know either.


I think making batteries is much harder than people realise, especially ones for motive applications.
You need to optimise the performance in terms of cost, weight, volume, energy, power, cycles, safety, thermal tolerance and expect them to work at near full performance for 10 years or so by writing a warranty.

There are many breakthroughs in one or two of those parameters, but to get a major improvement in one (say energy/weight) without spoiling one of the others is presumably quite difficult.

And that is why purchasable batteries hugely lag announced battery breakthroughs.


The batteries I linked were RUNNING YEARS AGO.

Typically, the latest battery announcement of "many times improvement" is from a alleged working battery measurements, even if just a button type.

Allow a month to enlarge anode, cathode, and electrolyte. Allow another month to place in pouch - not years and years and years.

That is like believing http://money.cnn.com/2004/01/06/pf/autos/detroit_gm_hybrids/



"A LEAF that can go 140 miles at 70 mph for the same weight, size and price would be good."

You assume a doubling of energy density. It gets even better. The LEAF uses cells that are not even close to 250 Wh/kg. It is more somewhere between 100-150 Wh/kg. A LEAF with this technology would do 250 miles for the same size and weight battery pack.


kelly seems to think government should handout magic wands so researchers need only one mighty swipe to transform their lab findings into cheap, fully working, guaranteed products.

Or you could start your own battery company and show 'em all how it's supposed to be done.

You should perhaps look into product development life cycles and the timescales involved to bring lab results to mass production. It is hard stuff, and consumers expect no less than a perfect product at a competitive price. Ever heard of lemon law or class action suits? Yup, those nasty things that can put you out of business or destroy your reputation if your product is less than perfect.

What you post here makes you look like an ignorant whiner.


I've done some griping here too, but the other folks are right...it takes time. And batteries for autos have to have 10 year shelf lives even if everything else (energy, power, price, safety, cycles, temperature, etc) works out. Stupid morons in CARB keep passing laws requiring a company to guarantee a battery for 10 years even though they don't do that to any regular cars for their power trains.

It's a little hard to test 10 year shelf life....without waiting a few years. I mean you can do things to help speed a simulation of 10 years, but in the end,nothing but time will guarantee it.


@Anne, DaveD,

The fact remains, I asked what happen to specific world record, certified batteries from YEARS ago and you have ABSOLUTELY NO answer.

The projected '2-4 years to commercialize' battery period has typically ENDED years ago on many of these "breakthroughs".

I'm saying, "Where's the many times better" batteries that decades of paid research and announcements reference and we are expected to believe.

The announced batteries could be in a box or a flashlight for placement in a e-bike, etc. and have a simple "30 day replacement" warranty - but it has to BE PUBLIC to show "many times better" EXISTS.

What you post here makes you look like an gullible non-whiner believing GM etc. http://money.cnn.com/2004/01/06/pf/autos/detroit_gm_hybrids/

I still ask what happen to specific world record, certified batteries from YEARS ago and you have ABSOLUTELY NO answer.


It takes time, but this is the chemistry that will make the real difference. Silicon-carbon and sulfur are not only high energy but low cost. Others are working on this one too, but this result if accurate, is impressive. I don't see why 5000 cycles isn't possible.


@Bk4, the time has been taken. My cited example batteries were, and if found, are government(US, Germany) certified.

The Li-S (~any EV) battery with ~200 miles/charge, 1000 charges w/80% remaining, and affordable will do.

An example from battery history. In 1994 GM got the Ovonics NiMH battery patent. GM released the Zero Emissions Lead-Acid battery EV1 in 1996.

Toyota had no EV and freaked.

But, in about six months, Panasonic had licensed the Ovonics NiMH patent, designed the EV-95 battery, and built the battery assembly line(commercialized).

Meanwhile, Toyota designed and built the RAV4 EV, which was running on US streets in June 1997.

I've seen these over ten year old RAV4 EVs still driving around Stanford University.

I didn't even mention the over 5 million Toyota hybrids and others also using various EV batteries.

Li-ion batteries have been researched, commercialized, and marketed for many decades.

The idea that it takes more decades to commercial another commercialized Li-ion version seems to be spread by the same corrupt, bailout stealing bankrupt that crushed and lied about EV batteries in the first place.


Different countries, different adaptation or work speed?

China built a 42 Km bridge in 26 months for $1.5B; we need 10 years and $7+B to build a 4 Km bridge.

China built 1600 Km of new subway lines last year; we need 20+ years to do the same at 4 to 5 times the cost.

China will build up to 100,000+ Km of new ultra high speed rails in about 5 years; we will need 100+ years and 5 to 10 times the cost if we ever do as much.

China built 39.5M 2-wheel electric vehicles last year (92.5+%) of the worldwide production; we will need another 20 to 40 years to produce as many.

The same may very well happen with EV batteries, e-buses, e-cars, e-trucks etc


@HarveyD, your statements note it's not a technical problem slowing a lot of progress.


they must have a shortage of lawyers, bureocrats and unions in China.. they could use a few to slow down things to a proper slow pace. Do you really want to live next to a nuke that they built in 4 years vs one of our nukes that took decades of careful review, protests and legal wranglings?


@Kit P, "The Chinese are building a CPR-1000 like hot cakes." means expect Chinese Chernobyl(s), like their high speed rail:


The Chinese government dictates/assumes/accepts millions of human deaths(People's Republic of China, Mao Zedong's regime (1949-1975): cultural revolution deaths: 40,000,000. http://necrometrics.com/20c5m.htm

Surviving Chinese couples can then have more than one child.

It is sad to have to explain to pro-nuclear power people that Western societies value individual life.

France has 75% of it's electricity from ~40-year-old nuke plants. Just their own report eariler:

"One reactor accident potentially costing 3 times the entire nation's GDP.."

was hidden, leaked, has them 'scared sh**less'.

Fukushima disaster cleanup is budgeted A TRILLION yen, before the inherent historic corrupt multi-times nuclear cost overruns.


Humanity can not afford ANY such costs or health risks - and past/present nuclear costs/deaths so far are ONLY PARTIAL - because there is NO solution to thousands of years of radioactive nuclear waste.

Like the dozens of times nuclear bomb earth life overkill we Americans paid to build, now pay to dismantle, so we can pay to build again - nuclear power is not necessary.

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