Batteries graphene Li S energy storage

Published on December 29th, 2014 | by Tina Casey

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Graphene Could Kill Lithium-Ion Batteries

December 29th, 2014 by  

Don’t break out the widow’s weeds just yet, but it looks like momentum is building for energy storage to move past the lithium-ion phase and get into the more powerful territory of lithium-sulfur technology. In the latest development, a multinational research team has figured out how to overcome a major obstacle in the path of lithium-sulfur energy storage, by using graphene as a “bridge” between different components.

In theory, lithium sulfur (Li-S) batteries possess far greater energy density than the familiar lithium-ion (Li-ion), so breaking the technology out of the lab and into commercial development could have huge clean tech implications for EV battery range and energy storage for solar and wind sources, among other applications.

graphene Li S energy storage

Schematic of 3-D hierarchically structured graphene-sulfur/carbonZIF8-D composite ( by K.Xi/Cambridge via alphagalileo.org).

Lithium-Sulfur Energy Storage

Sulfur is super-cheap, which is mainly why researchers are interested in developing energy storage devices incorporating the material.

Sulfur also has some bonus attributes compared to conventional Li-ion battery technology, such as a high tolerance for overcharging, relatively light weight, and low toxicity.

However, sulfur opens up a can of worms. One problem is that in conventional Li-S batteries, the liquid electrolytes acts by dissolving the Li-S compound, which necessarily makes for a short-lived battery.

In other words, sulfur is brittle.

 

Last year, researchers at the Energy Department’s Oak Ridge National Laboratory came up with an answer for that based on a unique electrolyte and a new class of solid sulfur-based materials.

The University of Arizona has also been tinkering around with Li-S energy storage, and has come up with a process for converting waste sulfur from industrial processes into a lightweight, solid compound with potential use in EV batteries.

So, What’s Wrong With Lithium-Ion?

The latest development was published earlier this month by researchers from the University of Cambridge and the Bejing Institute of Technology, in the AIP journal APL Materials, where you can find it under the title, “Graphene-wrapped sulfur/metal organic framework-derived microporous carbon composite for lithium sulfur batteries.”

According to the research team, the established specific energy density of Li-ion batteries weighs in at 130-220 Wh kg – 1, which looks pretty good but not when you consider that at least in theory, Li-S batteries can get up into the 2,600 range.

As described in the paper, Li-ion batteries are typically hampered by the use of a graphite anode and a cobalt oxide cathode. In contrast, Li-S batteries use a pure lithium anode and a sulfur cathode (for those of you new to the topic, the anode and cathode are the two parts of the battery that collect and discharge the current, which is stored in the electrolyte).

The team points out that even though Li-S technology is still in the prototype state, samples are already developed that achieve an energy density in the 150-220 range.

The Graphene Solution For Sulfur

As for the sulfur degradation problem, here’s how the team sums it up:

…S is lost by dissolving in the solvent and further by shuttling away from the cathode and even more by reacting with the Li anode…The shuttle mechanism has been directly implicated as the cause for low S utilization following the initial discharge, which is exacerbated in subsequent charge-discharge cycle.

That’s not all. The team also identifies other obstacles stemming from the use of sulfur, including poor conductivity.

One promising solution is the use of porous carbon as a protective “host” for sulfur in the cathod, specifically carbonized metal-organic frameworks (MOFs).

The team took the MOF ball and ran with it, as explained by Cambridge’s Kai Xi:

Our carbon scaffold acts as a physical barrier to confine the active materials within its porous structure. This leads to improved cycling stability and high efficiency.

This is where graphene comes in. Typical MOFs have a relatively low capacity, and previous research has shown that a nice shot of graphene can overcome that obstacle.

The graphene energy storage solution, as described in the team’s press materials, consists of wrapping the sulfur-carbon unit in graphene sheets:

Fast charge-transfer kinetics are made possible by an interconnected graphene network with high electrical conductivity, according to the team. Their work shows that the composite structure of a porous scaffold with conductive connections is a promising electrode structure design for rechargeable batteries.

So, now what? The next step will be to develop new electrolytes and tweak the lithium “protection layers” for increased efficiency.

They better act fast. Just last year, researchers from the Lawrence Berkeley National Laboratory announced the development of a Li-S battery based on a new material they’re calling sulfur-graphene oxide.

They’ve already demonstrated a Li-S battery that has double the specific energy of Li-ion, and it exhibits minimal decay even after 1,500 charge-discharge cycles.

The Berkeley team is eyeballing the new technology to develop a low cost electric vehicle battery in the 300 mile range, so stay tuned.

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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.



  • omar

    This is the kind of news we want update on it. thanks

    • sal3

      Yes, and a lively, civil discussion is most refreshing and welcome.

  • Michael G

    So when do I get to hear Scotty asking for more di-Lithium crystals?

    As always, your article sent me on a tour to educate myself. I mean what are “widow weeds”? Wikipedia says “Widow’s Weeds is the first full-length album by the Norwegian Gothic metal band Tristania”. Thank you, Tina, for corrupting America’s youth with the subtext of black eye-makeup, leather wristbands, and disrespect for elders. Give it up, Tina! Marky-Mark has moved on.

    I also looked up energy densities. At:

    http://en.wikipedia.org/wiki/Energy_density

    I learned that Li-ion batteries (all batteries, actually) have a really, really low energy density – less than 2 MJ/Kg.

    Li-ion batteries = 0.4 to 0.9 MJ/kg
    Li batteries = 1.8 MJ/kg
    Coal = 24 MJ/kg
    Animal fat = 37 MJ/kg (liposuction fueled cars! Powering America into the 22nd century – “Extra order of fries – I’m going on a road trip.”)
    Gasoline = 44 MJ/kg
    Hydrogen = 142 MJ/kg (oops! How’d that get in there? Move along now – nothing to see here)
    Antimatter = 1.8 x 10^11 MJ/kg. Amazing what adding a little c^2 does to your engine.

    Antimatter is being produced as a by-product of the tiny blackholes created at CERN in Switzerland, possiby with a side order of anti-gravity. Cf.

    http://arxiv.org/vc/gr-qc/papers/0612/0612088v2.pdf

    I’d keep an eye on the Swiss patent offices, Tina, just in case you’re looking for another scoop.

    • Jan Veselý

      Comparing energy density of batteries and gasoline is a bit misleading. Much better would be propulsion system energy density.
      To compare gasoline,tank, transmission, engine, oil, transmission, alternator, exhaust system, pollution control devices, ………. and battery+BMS+small engine.

      • Michael G

        Completely agree – after all, what’s the energy density of a radiator?

        • I think a Radiator has a better Energy Density than an Exhaust system – since it is used to heat the car in cold weather, but the exhaust system is a dead system in terms of usable energy recovery!

          Now – if the exhaust system could be used for other forms of Energy Recovery, Cleaning it’s particulate matter via magnetic field generation and entrapment – maybe it would have some additional energy value, but not so much today!

          Maybe the Carbon particulates could be captured and removed from the air, and separated from the Nitrogen Oxides, etc., then maybe we could turn the car in to a manufacturing plant for carbon black production – the source for Graphene development! Wow – What a Dream(er I am)!

      • Burnerjack

        Good call!

    • Steve Grinwis

      You missed one, Lithium-Air batteries have a density on par with gasoline almost, with 40 MJ/kg.

      Also, with hydrogen, the issue isn’t weight. It is density. Hydrogen at 690 bar, and 15 C has an energy density of about 4.5 MJ / litre. Lithium ion batteries, it sits around 1-2.2 chemistry depending. Add in the 50% efficiency of fuel cells, and they work out to be a lot closer than you’d guess.

      • Bob_Wallace

        If lithium-air batteries have close to as much energy density as gasoline then they pack several times as much “kinetic energy”.

        Same amount energy going into the propulsion system, 20% efficiency in one case, 90% efficiency in the other.

        Batteries become equal to gasoline when they store about one fourth as much energy.

      • Michael G

        I did omit that. Thanks for the reminder. It seems to have great potential and the amount of research going on shows a lot of people are hoping for a breakthrough on its many issues. At the moment, labs are far away from realizing its potential.
        http://evobsession.com/lithium-air-batteries-take-step-forward/

        Wikipedia says Li-air wil probably produce as much energy at the wheel as petrol, after all the intermediate losses.

        http://en.wikipedia.org/wiki/Lithium%E2%80%93air_battery

        GreenCarReports has more:

        http://www.greencarreports.com/news/1091967_how-hard-is-lithium-air-battery-research-pretty-tough-actually

        One of the issues is how reactive it is. It is only element 3 in the periodic table so it’s outermost electron (one-and-only valence electron) is “desperately seeking a another electron” while it’s atomic structure “wants” to look like He. I recall my HS chem teacher putting a tiny sliver of Li in water in a test tube and it shot to the high ceiling instantly (if not sooner) with a loud noise leaving a black mark which stayed for the semester. Zn-air holds great potential as well and that might be safer and come to fruition earlier.

        Another issue favoring Zn is that there is 100X more Zn than Li around.
        http://en.wikipedia.org/wiki/Zinc%E2%80%93air_battery

        Certainly a fascinating area – thanks for motivating me to look it up.

        • Steve Grinwis

          Zinc-Air, Aluminum-Air… All of them very very interesting, for sure.

          I can see battery packs like that (which are typically primary cells, and not rechargable) being used at battery swap stations. You want to drive across the country? Swap in this battery pack that gives your car a 2500 km range, swap back in your regular li-ion pack when you’re done. The materials for the spent pack can then be recycled and made into a new pack. If they could work out the bugs, I think aluminum is already cost competitive for this purpose.

          It might not even actually be worth the trouble though, if Li-ion battery swap stations can be done cheaply and fast enough. Swapping in a charged battery pack good for 300 miles every couple of hours in a minute? Totally doable.

          • Shane 2

            Regarding Al-air, Phinergy say that they think that their Al-air cells with the Al being recycled via aluminum refinery will be competitive with gasoline. That means they hope it will be at some time in the future. I wouldn’t bet on it. However, these cells would easily give more than 1000 miles of range.

          • Steve Grinwis

            For long trips, it doesn’t have to be competitive. The idea that I pay $150 for a big Al-Air pack to take my family on a road trip, when I save more than that each and every month, is perfectly fine with me.

        • Mint

          You’re focusing on the wrong point in Steve’s post. Li-Air was just a side note.

          Volumetric density is what makes H2 no better than batteries. Long term, we’re looking at 1000 Wh/L for batteries, and it’s easy to make them any shape (e.g. a 3-inch thick floor pan, stuffed into dead space, etc).

          Mass is a minor issue when you’re talking about a 90% efficient drivetrain. 700 lbs of battery cells won’t even take 10% off of range/efficiency compared any other fuel system for a typical car.

          (As an aside, don’t forget that Toyota’s advanced H2 tank weighs 87kg to store 5kg of fuel)

    • Joseph Dubeau

      Tina wrote “Graphene Could Kill…”
      widow’s weeds – a black garment (dress) worn by a widow as a sign of mourning.

      Micheal, no harm came to any Lithium-Ion Batteries in the creation of this article.

    • Calamity_Jean

      “Widow’s weeds” in this context means exaggerated mourning clothes like Queen Victoria wore after Prince Albert died; black dress, black stockings, black gloves, black veil constantly covering her face — that sort of thing.

    • JamesWimberley

      I can see the press release: “Our patented antimatter/liquid hydrogen engine is ABSOLUTELY safe. The extension of the Zürichersee to cover the area formerly known as Zürich resulted, we admit, from an accident in our research lab due to human error that cannot possibly reoccur, and, besides, it’s prettier now”.

      If you like really exotic high-energy chemistry, try this yarn about rocket fuels from Charles Stross (link).

      • Michael G

        Thanks for the link. Fun story.

        The article I linked to on anti-matter had the interesting observation that there might be anti-gravity which would be repulsive to “regular” matter. So we could refill with little nano-black-holes spewing out positrons but held in place by repulsive anti-gravity.

        Would we have to pay to refuel by the femto-gram? “The new Chevy Volt gets 2,000,000 MPFg!”

        Is the opposite of anti-matter pro-matter? Do photons ever decide to go “pro”.

  • As usual Tina’s on it. Sulfur production is exceeding demand as more and more heavy sour crudes like oil sands are being produced. There are mountains of the stuff. Maybe li-s batteries will turn the Kochs green. Koch Sulfur Products, a subsidiary of Koch Carbon, a subsidiary of Koch Industries is one of the worlds biggest handlers of sulfur from oil and gas production and processing.
    http://www.kochcarbon.com/Businesses.aspx

    • Dragon

      Just what we need – more money to the Kochs so they can continue to drive us deeper into plutocracy. Whether they get their money from oil or renewables, they’ll still use it solely to better the lives of the ultra rich at the cost of everyone else. Unfortunately they’re so diversified at this point that nothing will bring down their empire short of a majority of people turning against them and anything they touch. http://www.boycottkochbrothers.com

      • Shane 2

        The USA, the best democracy Koch money can buy.

      • That said, distributed renewable power generation and storage are less capital and profit intensive than a network based on centralized power plants that need continual refueling.
        If one were to compare the ultimate destinations of the cash spent on energy by a household with solar cells and batteries, versus a household buying their electricity from a coal plant (over a few decades), the solar household would not only be spending less money, but a smaller fraction would be profit for big business.

      • Burnerjack

        So you would scuttle a huge energy storage solution because someone you don’t like is positioned to profit from its deployment? Really? This type of development could be potentially disruptive, ushering wide acceptance of EVs as well as distributed generation/storage but that huge positive should not occur because Koch Brothers are “too rich”? Maybe you need to expand your view.

        • Dragon

          I fully support the clean technology mentioned in this article and did not mean to suggest boycotting it in hopes of hurting the Kochs. If it’s the Kochs that supply it, or part of it, then not much can be done. We can still boycott their other industries. And I’m certainly not against Koch because they’re “too rich” but because they want to drive the rest of us into poverty for their wealth. They also want to remove worker safety regulations, repeal medicare, repeal usury laws, and on and on. The full egregious list is here: http://www.sanders.senate.gov/koch-brothers

    • Mint

      Sulfur is cheap, and always has been. Nobody is gonna get super rich by selling it to EV makers, including Koch Industries.

      • Tell the Kochs that. Sulfur and other waste products management is one of their biggest money makers. One of Koch’s biggest money makers is sinter and slag management for steel mills. Sulfur, like garbage, isn’t cheap since someone wants to get rid of it.

        • Mint

          Sinter and slag management isn’t profitable due to sulfur sales. They’re profitable due to the value of removing sulfur from steel.

          Going back to your garbage analogy, nobody is going to make money by selling garbage to someone that finds a small need for it. Anyone will sell it for peanuts. They’ll even pay to get rid of it.

          Same with sulfur. We’ll never make enough LiS batteries to cause a shortage of sulfur, and there will always be mountains of S sitting idle with little use, selling for peanuts.

          • I don’t think we’re communicating very well. I’m using the examples of waste management as a highly profitable business. Sinter and slag is steel by and waste products. It’s value is that a mill owner needs to get rid of it. Sulfur from oil and gas operations is a waste product, where processing and refining companies pay to get rid of it. The value isn’t to the generator, but the waste product manager.

            Same with garbage. Unless you live in the woods and throw your trash out the backdoor, garbage has value due to generators’ need to get rid of it. That’s why waste management is about a $500 billion per year global business.

            Koch makes a lot of money on providing by-product and waste management services to steel mills and oil and gas companies.

            Sulfur is plentiful, yes, but there’s value once refined. The value added would be sulfur refined to a purity acceptable for batteries. This refining would be a good business. Especially in a world needing batteries for power storage and transportation. As a matter of fact, Koch is getting heavy into the industrial water supply treatment and wastewater treatment business. And municipal.

            I’m confused why you’re confused.

          • Mint

            You keep bringing up irrelevant points.

            Sulfur is cheap and plentiful, and that’s all that matters. Maybe Koch will become very good at refining it for battery use, but there’s no reason at all to think they will have a monopoly on the process, and furthermore that has nothing to do with waste management. If EVs with Li-S based batteries take off, we’re gonna have battery gigafactories producing the cells, and if they’ll take raw material like this:

            http://www.alibaba.com/product-detail/high-purity-Sulfur-99-9-_1814574353.html?s=p

            $200-460 per tonne.

            LiS batteries are not going to provide significant business to Koch, because raw sulfur is just too cheap and plentiful from many suppliers. Sulfur used to make industrial sulfuric acid already dwarfs the distant future needs of 100M EVs/yr.

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