New lithium-oxygen battery greatly improves energy efficiency, longevity

New lithium-oxygen battery greatly improves energy efficiency, longevity
In a new concept for battery cathodes, nanometer-scale particles made of lithium and oxygen compounds (depicted in red and white) are embedded in a sponge-like lattice (yellow) of cobalt oxide, which keeps them stable. The researchers propose that the material could be packaged in batteries that are very similar to conventional sealed batteries yet provide much more energy for their weight. Credit: Courtesy of the researchers

Lithium-air batteries are considered highly promising technologies for electric cars and portable electronic devices because of their potential for delivering a high energy output in proportion to their weight. But such batteries have some pretty serious drawbacks: They waste much of the injected energy as heat and degrade relatively quickly. They also require expensive extra components to pump oxygen gas in and out, in an open-cell configuration that is very different from conventional sealed batteries.

But a new variation of the chemistry, which could be used in a conventional, fully sealed battery, promises similar theoretical performance as , while overcoming all of these drawbacks.

The concept, called a nanolithia cathode battery, is described in the journal Nature Energy in a paper by Ju Li, the Battelle Energy Alliance Professor of Nuclear Science and Engineering at MIT; postdoc Zhi Zhu; and five others at MIT, Argonne National Laboratory, and Peking University in China.

One of the shortcomings of lithium-air batteries, Li explains, is the mismatch between the voltages involved in charging and discharging the batteries. The batteries' output voltage is more than 1.2 volts lower than the voltage used to charge them, which represents a significant power loss incurred in each charging cycle. "You waste 30 percent of the electrical energy as heat in charging. ... It can actually burn if you charge it too fast," he says.

Staying solid

Conventional lithium-air batteries draw in oxygen from the outside air to drive a chemical reaction with the battery's lithium during the discharging cycle, and this oxygen is then released again to the atmosphere during the reverse reaction in the charging cycle.

In the new variant, the same kind of electrochemical reactions take place between lithium and oxygen during charging and discharging, but they take place without ever letting the oxygen revert to a gaseous form. Instead, the oxygen stays inside the solid and transforms directly between its three redox states, while bound in the form of three different solid chemical compounds, Li2O, Li2O2, and LiO2, which are mixed together in the form of a glass. This reduces the voltage loss by a factor of five, from 1.2 volts to 0.24 volts, so only 8 percent of the electrical energy is turned to heat. "This means faster charging for cars, as heat removal from the battery pack is less of a safety concern, as well as energy efficiency benefits," Li says.

This approach helps overcome another issue with lithium-air batteries: As the chemical reaction involved in charging and discharging converts oxygen between gaseous and solid forms, the material goes through huge volume changes that can disrupt electrical conduction paths in the structure, severely limiting its lifetime.

The secret to the new formulation is creating minuscule particles, at the nanometer scale (billionths of a meter), which contain both the lithium and the oxygen in the form of a glass, confined tightly within a matrix of cobalt oxide. The researchers refer to these particles as nanolithia. In this form, the transitions between LiO2, Li2O2, and Li2O can take place entirely inside the solid material, he says.

The nanolithia particles would normally be very unstable, so the researchers embedded them within the cobalt oxide matrix, a sponge-like material with pores just a few nanometers across. The matrix stabilizes the particles and also acts as a catalyst for their transformations.

Conventional lithium-air batteries, Li explains, are "really lithium-dry oxygen batteries, because they really can't handle moisture or carbon dioxide," so these have to be carefully scrubbed from the incoming air that feeds the batteries. "You need large auxiliary systems to remove the carbon dioxide and water, and it's very hard to do this." But the new battery, which never needs to draw in any outside air, circumvents this issue.

No overcharging

The new battery is also inherently protected from overcharging, the team says, because the chemical reaction in this case is naturally self-limiting—when overcharged, the reaction shifts to a different form that prevents further activity. "With a typical battery, if you overcharge it, it can cause irreversible structural damage or even explode," Li says. But with the nanolithia battery, "we have overcharged the battery for 15 days, to a hundred times its capacity, but there was no damage at all."

In cycling tests, a lab version of the new battery was put through 120 charging-discharging cycles, and showed less than a 2 percent loss of capacity, indicating that such batteries could have a long useful lifetime. And because such batteries could be installed and operated just like conventional solid lithium-ion batteries, without any of the auxiliary components needed for a lithium-air battery, they could be easily adapted to existing installations or conventional battery pack designs for cars, electronics, or even grid-scale power storage.

Because these "solid oxygen" cathodes are much lighter than conventional lithium-ion battery cathodes, the new design could store as much as double the amount of energy for a given cathode weight, the team says. And with further refinement of the design, Li says, the new batteries could ultimately double that capacity again.

All of this is accomplished without adding any expensive components or materials, according to Li. The carbonate they use as the liquid electrolyte in this battery "is the cheapest kind" of electrolyte, he says. And the component weighs less than 50 percent of the nanolithia component. Overall, the new battery system is "very scalable, cheap, and much safer" than lithium-air batteries, Li says.

The team expects to move from this lab-scale proof of concept to a practical prototype within about a year.


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More information: Zhi Zhu et al. Anion-redox nanolithia cathodes for Li-ion batteries, Nature Energy (2016). DOI: 10.1038/nenergy.2016.111
Journal information: Nature Energy

Citation: New lithium-oxygen battery greatly improves energy efficiency, longevity (2016, July 25) retrieved 22 May 2019 from https://phys.org/news/2016-07-lithium-oxygen-battery-greatly-energy-efficiency.html
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Jul 25, 2016
No it doesn't promise anything, because like all the hundreds of previous battery breakthroughs, we will yet again not see this materialize into a commercial product.

Jul 25, 2016
We do not always get instant gratification in life.

Jul 25, 2016
Looks like Cube Pizza...

Jul 25, 2016
Physorg needs a dashboard that indexes these techs where you can look at updates. Almost all the "breakthroughs" die when they try to get it into mass manufacture.

Jul 25, 2016
Physorg needs a dashboard that indexes these techs where you can look at updates. Almost all the "breakthroughs" die when they try to get it into mass manufacture.


Yep, like the way GitHub works for open-source software.

But these breakthroughs (which are more like 'increments') are neither software--they concern convoluted lab setups & expensive, abstruse equipment--nor open-source.

The problem is that academics are the lured by tenure to do research, publish it or perish! If this begets anything of practical promise, then researchers, often compelled by back-breaking loans, sell their brainchildren to commercial entities which, like most commercial entities, tend to struggle or completely flop, killing the breakthru in its cradle.

Jul 26, 2016
But these breakthroughs ... are neither software--they concern convoluted lab setups & expensive, abstruse equipment--nor open-source.

Complete BS. EVERYTHING you use right now was once a convoluted lab setup (I have in my posession a board with 3 transistors on it from my dad that cost the equivalent of 100k Euros today)...and yet: each of us has today more than a billion of the critters in their computers.

What you guys don't understand is that you never know in reasearch what will eventually pan out. You can't just decide to only do research that will easily go to market. If you think that's how science could work then you know nothing about it.

Even for those technologies that do reach the market: On physorg they report new papers. Which means first prototypes. These aren't even optimized. The entire engineering chain is missing and that takes years (sometimes decades).

This isn't the movies where you go from I have an idea to product in seconds.

Jul 27, 2016
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Jul 28, 2016
so only 8 percent of the electrical energy is turned to heat.


That's not "only". 8% efficiency loss means the battery has very low specific power because it simply overheats. Quick charging lithium batteries have efficiencies above 98%.

The 8% figure is pretty terrible - 1 Watt of heat for every 12.5W out.

Complete BS. EVERYTHING you use right now was once a convoluted lab setup


That's looking with 20/20 hindsight. The only way to get to the market is through the laboratory.

Most of them fail because they never manage to bring it out of the lab, because the process is too complex and costly or too unreliable, sometimes impossible to pull off in a mass-production setting.

Many fail to appreciate that Henry Ford didn't invent the production line, he invented -a- production line, and each new product has its own production line to be invented, and that's often much more difficult than coming up with the original invention.

Jul 28, 2016
To illustrate the point, the 1:12 ratio is terrible for quick charging because even a small EV battery like 24 kWh needs tremendous input power to charge rapidly. For 5 minutes it's 288 kW and with the efficiency loss it will be 313 kW which leaves 25 kW of heat in the battery.

And that's literally like lighting a fire inside the car. 25 kW is the power of a big cast iron stove used to heat houses, when it's stuffed full of wood and roaring with fire. You could pipe water into the battery compartment and steam would come out.

With a 98% efficient battery, the residual heat would be 6 kW which is still equivalent to a sauna stove. Way too hot to handle without an active cooling system.

For a larger battery of 85 kWh it would again be 21 kW - which is why the efficiency needs to be way higher for quick charging to actually happen, and why the existing "rapid" chargers leave you waiting for half an hour or more.


Jul 28, 2016
Eikka is right: Nobody will ever have an EV.

They do not work, and you will never even see one.

Jul 28, 2016
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Jul 28, 2016
Eikka is right: Nobody will ever have an EV.

They do not work, and you will never even see one.


That will be the case for battery electric vehicles - it's very unlikely they'll become popular enough because of the fundamental limitations of batteries and electric power transmission - but not electric vehicles in general. A FEV is basically all the good points of both ICE and EV.


Jul 30, 2016
This entire line of research is a waste. The future of rapid charge/discharge energy storage isn't batteries, it's capacitors.

Jul 30, 2016
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Jul 30, 2016
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