“Reversible” Energy Storage For Better, Cheaper, Non-Toxic Batteries
Lithium-ion technology dominates today’s energy storage market, but new alternatives are beginning to bubble up from research laboratories. In the latest development, a team of researchers at Pacific Northwest National Laboratories has unlocked the secret behind a reversible formula that could be used for low cost grid scale energy storage.
Re-Thinking An Energy Storage Formula
The new energy storage breakthrough is based on the familiar zinc-manganese formula. Researchers have been tinkering around with rechargeable zinc-manganese batteries for many years but they have gotten stuck on one problem: getting the manganese to stay on the positive electrode.
After only a few cycles manganese drifts off the electrode and settles into the electrolyte. Once that happens, the battery can hold only a fraction of its intended charge.
That may seem like a lost cause, but the allure of storing energy with relatively cheap, abundant, non-toxic materials is irresistible, so the PNNL team decided to give it another try.
The researchers started from scratch and built their own battery with the aim of finding out exactly why the manganese sloughs off. After subjecting it to chemical and structural analysis, they decided to rethink their entire approach.
The PNNL realized that they had been coming to the problem just like other researchers, with the idea that the zinc-manganese energy storage formula works like lithium-ion.
In a lithium-ion battery, lithium ions are simply passed back and forth between two electrodes. The new study revealed that when a zinc-manganese battery goes through charging cycles, it does something entirely different. The active materials in the battery undergo a reversible chemical reaction and create a new material, zinc hydroxyl sulfate.
A (Really) Rechargeable Non-Toxic Energy Storage Alternative
With that knowledge in hand, the PNNL team developed a strategy for slowing down the rate at which manganese could detach from the electrode:
…they added manganese ions to the electrolyte in a new test battery and put the revised battery through another round of tests. This time around, the test battery was able to reach a storage capacity of 285 milliAmpere-hours per gram of manganese oxide over 5,000 cycles, while retaining 92 percent of its initial storage capacity.
Sweet. Here’s the lowdown from the study, which you can find in the journal Nature Energy under the title “Reversible aqueous zinc/manganese oxide energy storage from conversion reactions:”
Here we demonstrate a highly reversible zinc/manganese oxide system in which optimal mild aqueous ZnSO4-based solution is used as the electrolyte, and nanofibres of a manganese oxide phase, α-MnO2, are used as the cathode. We show that a chemical conversion reaction mechanism between α-MnO2 and H+ is mainly responsible for the good performance of the system.
The team, which includes the University of Washington, also found that the zinc anode was highly stable.
Beyond Li-Ion
Lithium-ion is not going down without a fight, and researchers are still finding new ways to improve the technology.
However, the new PNNL energy storage solution could easily win on cost as well as energy density.
For now, the research team is focusing on grid scale energy storage for the new battery. It’s also possible that some variation of zinc-manganese could be used in EVs, or in gasmobiles as a replacement for conventional lead-acid batteries (as much as we love EV tech, the fact is that millions of gasmobiles — fossil and/or biofuel — will be with us for the foreseeable future).
The next steps for PNNL include digging deeper into the chain of reactions leading to the formation of zinc hydroxyl sulfate.
Meanwhile, work is rapidly progressing on systems for integrating renewable energy into the grid with the help of new energy storage solutions. That old trope about the unreliability of wind and solar power may have worked just a few years ago, but not today.
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Image (cropped): via PNNL.
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You can’t see the full paper without a subscription, but looking at the graphs it pretty odd. They show the additive decreases coulombic efficiency at the first cycles and then it settles down. With lithium the coulombic efficiency must be high or cell calendar life is compromised.
http://www.nature.com/article-assets/npg/nenergy/2016/nenergy201639/images_hires/w450/nenergy201639-f3.jpg
It looks that they have switched horses on the last graph; instead of blue = no additive, blue = right axis, red = left axis, both with additive. Makes sense, no problem with coulombic efficiency
Yes. Thats what confused me. It should be best coulombic efficiency for the better cell.
hey, Herb! thanks again for dropping in on the Berlin event!
and yeah, not the most intuitive design in these graphs.
Oh, those lovely voltamograms! – Not really for everyone to understand I do say as I remember the confused students back at the university….
The voltamgrams shows that the chemical reaction schemes are very different with and without addition. The voltamogram does not say how it works. You need a lot more different instrument to crack that problem.
I don’t like Ragone plots, either. I would rather deal with internal resistance. And give me a cycle life vs DoD chart, too.
I don’t mind staring at coulombic efficiency vs cycle life.
What about Alevo batteries. They have got $1.7 billion in private funding and say their batteries can be cycled 40,000 times!
I think the market is going to large enough for many many types of storage/batteries. Just look at all the options that were there before Li-ion and yet it found a market as it filled a much needed hole. Large grid/home storage is just getting started, the need for time shifting of solar and wind, frequency stabilization, large grid vs home back up vs short term grid peak demand, all will be addressed by several solutions.
40,000 cycles is massive compared to 5000 cycles of the Powerwall.
From Alevo’s battery capacity graph the 40,000 cycles is when its down to 20% of capacity not 80% Tesla uses.
I’ve been following battery claims for a number of years. I’m to the point at which I don’t believe anyone’s claims.
Even when something tests out in the lab it doesn’t necessarily make it to the real world. Look at Ambri and their liquid metal. They (apparently) got the battery to work in prototype form but couldn’t manufacture it.
I’ll take Alevo seriously when they’ve sold product on to other companies and those companies have used the batteries for awhile.
The Sadoway battery is very unconventional and runs at very high temperatures.
Alevo uses conventional LiFePo4 cells with a special electrolyte.
Alevo have got a contracts to supply 4MWh + 5MWh of storage.
http://www.utilitydive.com/news/alevo-partners-to-develop-10-mw-storage-project-in-texas/416560/
http://www.utilitydive.com/news/alevo-inks-deal-for-8-mw-storage-project-in-delaware/415932/
“..over 5,000 cycles, while retaining 92 percent of its initial storage capacity.”
Excellent
The American Chemical Society lists ZInc as a “Criticality Endangered Element”, not because it’s rare but because it’s widely used for corrosion control and cannot be recycled after it’s dissolved into the sea.
That sucks. They need to use alternatives like stainless steel or aluminium or chrome plating.
Interesting point.
Score one for Tina! This sounds like a real breakthrough in zinc based batteries.
“..over 5,000 cycles, while retaining 92 percent of its initial storage capacity.”, as sjc_1 has already pointed out.
Now, we’ll see if it makes it to market.
Good find, Tina. This hadn’t popped up on my usual feeds for various battery chemistries, yet.
The word “breakthrough” is used a bit too loosely in press releases nowadays. Only when the battery actually makes it to market and conquers a significant market share you can tell if there really was one specific breakthrough step during the whole R&D process.