New batteries for EV’s use “rust” for power storage

Renaissance of the Iron–Air Battery

Jülich researchers show charging and discharging reactions during operation with nanometre precision

Jülich, 3 November 2017 – Iron–air batteries promise a considerably higher energy density than present-day lithium-ion batteries. In addition, their main constituent – iron – is an abundant and therefore cheap material. Scientists from Forschungszentrum Jülich are among the driving forces in the renewed research into this concept, which was discovered in the 1970s. Together with American Oak Ridge National Laboratory (ORNL), they successfully observed with nanometre precision how deposits form at the iron electrode during operation. A deeper understanding of the charging and discharging reactions is viewed as the key for the further development of this type of rechargeable battery to market maturity. The results were published in the renowned journal Nano Energy.

 

For reasons including insurmountable technical difficulties, research into metal–air batteries was abandoned in the 1980s for a long time. The past few years, however, have seen a rapid increase in research interest. Iron–air batteries draw their energy from a reaction of iron with oxygen. In this process, the iron oxidizes almost exactly as it would during the rusting process. The oxygen required for the reaction can be drawn from the surrounding air so that it does not need to be stored in the battery. These material savings are the reason for the high energy densities achieved by metal–air batteries.

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Gravimetric and volumetric energy densities of various metal–air battery systems in comparison with Li-ion batteries and conventional gasoline  Copyright: Forschungszentrum Jülich / H. Weinrich


Iron–air batteries are predicted to have theoretical energy densities of more than 1,200 Wh/kg. By comparison, present-day lithium-ion batteries come in at about 600 Wh/kg, and even less (350 Wh/kg) if the weight of the cell casing is taken into account. Lithium–air batteries, which are technically considerably more difficult and complicated to realize, can have energy densities of up to 11,400 Wh/kg. When it comes to volumetric energy density, iron–air batteries perform even better: at 9,700 Wh/l, it is almost five times as high as that of today’s lithium-ion batteries (2,000 Wh/l). Even lithium–air batteries have “only” 6,000 Wh/l. Iron–air batteries are thus particularly interesting for a multitude of mobile applications in which space requirements play a large role.

“We consciously concentrate on research into battery types made of materials that are abundant in the Earth’s crust and produced in large quantities,” explains institute head Prof. Rüdiger-A. Eichel. “Supply shortages are thus not to be expected. The concept is also associated with a cost advantage, which can be directly applied to the battery, particularly for large-scale applications such as stationary devices for the stabilization of the electricity grid or electromobility.”

Difficult conditions for analysis

The insights obtained by the Jülich researchers create a new basis for improving the properties of the battery in a targeted manner. Using in situ electrochemical atomic force microscopes at the Center for Nanophase Materials Sciences at Oak Ridge National Laboratory, they were able to observe how deposits of iron hydroxide particles (Fe(OH)2) form at the iron electrode under conditions similar to those prevalent during charging and discharging.

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Changes to the electrode surface over the course of four charging/discharging (redox) cycles Copyright: Forschungszentrum Jülich / H. Weinrich


“The high pH of 13.7 alone represents a borderline condition for the instrument,” explains Henning Weinrich from Jülich’s Institute of Energy and Climate Research (IEK-9). “We were the first at Oak Ridge to successfully conduct such an experiment under realistic conditions,” says Weinrich, who stayed in the USA for three months especially for the measurements.

Deposits increase capacity

The deposits do not decrease the power of the battery. On the contrary, since the nanoporous layer increases the active surface area of the electrode, it contributes to a small increase in capacity after each charging and discharging cycle. Thanks to the investigations, the researchers have for the first time obtained a complete picture of this layer growth. “It was previously assumed that the deposition is reversed during charging. But this is obviously not the case,” explains Dr. Hermann Tempel from Jülich’s Institute of Energy and Climate Research (IEK-9). Furthermore, a direct link was verified for the first time between the layer formation at the electrode surface and the electrochemical reactions.

There is, however, still a long way to go until market maturity. Although isolated electrodes made of iron can be operated without major power losses for several thousand cycles in laboratory experiments, complete iron–air batteries, which use an air electrode as the opposite pole, have only lasted 20 to 30 cycles so far.

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Schematic of the measuring method: the tip of the in situ electrochemical atomic force microscope scans the surface of the iron electrode. Laser-beam deflection reveals spatial irregularities, which can be compared to each other over the course of several cycles.  Copyright: Forschungszentrum Jülich / H. Weinrich

Original publication:

Understanding the nanoscale redox-behavior of iron-anodes for rechargeable iron-air batteries Henning Weinrich, Jérémy Come, Hermann Tempel, Hans Kungl, Rüdiger-A. Eichel, Nina Balke Nano Energy 41 (available online 10 October 2017), DOI: 10.1016/j.nanoen.2017.10.023

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56 thoughts on “New batteries for EV’s use “rust” for power storage

    • Help please. If deposits do not affect power, If rusting leads to a small increase in capacity, why do the batteries only last 20 to 30 cycles?

    • TH, I have worked in energy storage since the mid 1990’s. Even have several issued seminal materials patents. The 20-30 cycles here is not only fundamental, it is inherent in all metal /metal oxide (air) batteries. Same problems in lithium, zinc, iron…only the rate of deterioration changes due to chemical reaction kinetics. Short explanation, cannot avoid dendrite shorts. And no known nanotech stuff solves that problem. And I know a fair bit about nanotech. See, for example, the discussion of Fiskars Nanotech ‘batteries’ (actually, already experimentally proven LiC) at guest post Vehicular Decarbonization last November over at Climate Etc.

      • What are your thoughts about battery technologies that are most likely to solve some of the problems with Lithium-ion batteries? Are there any emerging battery technologies that you believe are worth watching? In Aust. recently there have been many discussions about the large South Australian battery system, but I can’t see lithium-ion batteries solving the conflicting requirements of a high discharge rate and long battery life.

      • Rud. If you have time, can you answer a naive question? A couple of years ago, I got out my cocktail napkin and consulted the all-knowing Google. In a couple of hours, I determined that batteries that allow solar and wind to actually power a modern society might be 30 years away (2045) … Give or take a lot. Because I used a model (which I didn’t write down and probably can’t reproduce), this is SCIENCE and therefore trumps reality. But I am curious if it is at all close to what might actually come about.

        BTW, The biggest problem I encountered, isn’t battery technology per se. It’s the apparent need for a (site specific?) Probability Distribution Function that describes how long the wind can not blow and the sun not shine at a given generation site.

      • Yes atmospheric humidity is a killer for zinc-air batteries. You can’t seal them, and you can’t leave them unsealed. So how are you going to take a shower while wearing a pacemaker ??

        G

    • Hmm.
      Iron and Air.
      Both common.

      If the purity requirements are limiting – it’s a no-go.

      If not – and I have no idea whether that is correct – surely swapping out every week [or so] would cure that.

      As noted, iron and air are not preciously rare.

      Auto

    • I don’t know about Iron-air batteries or rechargables; but I do know of a 3V 85mAhr Lithium ion one use button cell (20 mm) being replaced by a 1.3 V 1400 mAhr ZINC-AIR battery. In fact I’m working on a product that uses such a battery.
      Can’t say the change doesn’t create more problems than it solves. Not a lot of useful electronics can operate from a 1.3 V battery with an end of life of 0.9V. Well EOL is really more like 1.15-.2V,so at 0.9V you have time to put your head between your knees to kiss your a*** goodbye.

      Also, nobody makes ….. LOW …. power boost switching regulators, so to get say 2.7 to 3 or 4 volts to operate electronics, you have to use devices intended for supplying 250mA at 5.0 volts, and if you are looking for 5 mA at 3.0 Volts, you can get 15-20% efficiency from these chips. Really useful product developments.

      It’s not that you can’t design such low power circuits; but none of the regular semi-conductor industry houses offer anything that is really low power and still efficient.

      Yes I can design it myself, so of course I know it’s possible.

      G

    • I bought my last Chevrolet in 1986. It started to rust within 4 weeks. I actually kept the damn thing for 9 years. It was the last Chevy I ever owned. I am now a Happy Honda Driver.

    • So if your dead battery can’t crank the motor, just hook your jumper cables on to the rusty rocker panel.

      On the more serious side, big, cheap iron batteries would make wind and solar more viable. Not cheaper, but less intermittent.

    • Rusty panels are easy, I’ve owned a Vega and a Jeep. Just carry a gallon or two of Ospho (re: Ospho.com) with a paint brush in the trunk. Each night when you park just look for any new red spots and paint ’em. They’ll be gone in the morning :<)

      • Painting inside rocker panels and frame box rails … ? It’s not the rust you can readily see that’s the problem. Ask Toyota.

      • I just waited until it reached the surface where I could see it then hit it with the Ospho. Didn’t care about the holes, just stopped ’em from growing bigger. :<)

  1. This is valuable and worthwhile research. Eventually, we will need a wide array of energy strategies as fossil fuels become scarcer. In Canada, a field was just brought on line off the East coast that was discovered in 1980. It is a big deal. It is expected to produce 800 million barrels of crude over its life. That translates into less than 10 days of world oil consumption!

      • Or our children’s, or my 17 month old grandchild’s life. The one thing we learned in the last 15 years is that “Peak Oil” is nonsense.

      • Peak oil is not a problem. There will always be enough to fill the demand. The demand will be sharply curtailed as prices increase due to scarcity.

      • Keep dreaming.

        Oil runs out in 50 years

        Coal in 90

        Uranium in 200

        That is from the Oil, Coal and Uranium Industry numbers

  2. I thought iron oxidation causes expansion of the material. How extensive is the oxidation? Would this cause a volumetric issue with casings, or pressures?

    • Same problem as with PbA, partly solved with exotic alloys and carbon impregnations. But not the so far insolvable metal air battery idea, no matter the metal. Darned air does not impede dendrites.

      • IIRC early iron air batteries had a problem with self-discharge happening over a few days.
        And if memory serves me right there was a problem of the evolution of hydrogen (gas?) during charging (and self-discharge?).

    • according to the info presented the iron changes to Fe(OH)2, the Fe-O-O-. Apparently is doesn’t get to plain old FeO at pH 13.7. That is rather extreme. The layers formed appear to a few nanometers thick, plus they have to allow for access of the air.
      Dendrites can form in a number of different types of batteries that depend on metallic cathode. Apparently the extended metal crystals are the lowest energy form for deposition on the cathode. Something that sticks up makes a better target for electrons.

    • according to the info presented the iron changes to Fe(OH)2, the Fe-O-O-. Apparently is doesn’t get to plain old FeO at pH 13.7. That is rather extreme. The layers formed appear to a few nanometers thick, plus they have to allow for access of the air.
      Dendrites can form in a number of different types of batteries that depend on metallic cathode. Apparently the extended metal crystals are the lowest energy form for deposition on the cathode. Something that sticks up makes a better target for electrons.

  3. Do I recollect correctly that iron to iron..oxide conversion leads to large volumetric expansion ….. such as in corrosion in reinforcement spalling..off concrete at extremly high pressure?
    If I am right, how is this going to be accommodated in a rechargeable battery format?
    I wd enjoy commentary from Chemists out there!

  4. Not a chemist. Just an energy storage ‘expert’. You point out one of seversl problems why this electrochemistry has never been seriously explored for commercialization.

  5. So if they can make this work then all humanity can stop producing carbon dioxide that our Food needs and instead consume oxygen on a massive industrial scale. Gee how could that not be good!

    • We already consume O2 on a massive industrial scale by burning fossil fuels. It’s a renewable resource as long as there’s CO2 and H2O which can be converted back into O2 by photosynthesis. The long term problem we will have once fossil fuels get prohibitively expensive is running out of atmospheric CO2 to replenish otherwise sequestered O2. Note that combustion doesn’t sequester O2, but converts it into CO2 which biology reconverts back into O2.

  6. Oxidation is not typically a reversible reaction, hence this is not a battery. Do you people write these articles and post on here without any simple knowledge about chemistry, physics, thermodynamics, heat transfer, etc.???

  7. I have never seen a ferrous metal, fully oxidized (Rusted), regenerate back to a non-oxidised state, to be then oxidised again, and then regenerated again. Am I reading this wrong even for 30, in a lab, cycles?

    Oxygen is nasty. It’s responsible for creating all the iron ore we have. Oh, and water too!

    Move on, nothing to see here apart from…rust.

  8. Without pretending to know much at all about battery technology, I read something about a zinc-based technology recently: https://spectrum.ieee.org/energywise/transportation/advanced-cars/zincbased-batteries-can-provide-more-energy-safety-than-liion.

    Apparently the problem with zinc has been its tendency to grow dendrites inside the battery, causing short circuits. A way around this has been found according to the article cited. Comments, anyone?

    BTW, a matter of terminology. Strictly speaking, we should use the term voltaic cell technology. Battery is just a collective noun, as in a battery of voltaic cells, or an artillery battery. But then I guess it would get shortened to cell technology, and people would start thinking we were discussing DNA and related topics.

    • “Comments, anyone?”
      See comments re Toshiba’s Lithium Titanate technology above and London to a brick they’re trading off one or more of the 3 imperatives of range(capacity)/charge time/longevity but not to worry the technology that resolves all 3 by marvellous multiples is just around the corner. All the plant food doomsdayers have to do is legislate for EVs and those recalcitrant capitalists will simply come to the party with the goods they’ve been sitting on.

  9. Mind you, you’d reckon it’s any day now Big Oil will roll out that engine that runs on water they’ve been sitting on all these years in order to screw us all over at the bowser.

      • Well I don’t know if my car even has a carburetor but if it does, it is at least a 50 MPG one.

        I know because I have actually made round trips beyond the range of ANY Tesla and beat 50 MPG for the complete trip. Including incidental local driving at the mid trip destination. Did it just last week , on a 400 km round trip, plus maybe 25km of local stop and go errands.

        G

      • I should hasten to add that my 50 MPG trip was in the laser leveled central valley of California, but I did have to get over the Si valley hills to the CV.

        G

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