Na-ion batteries get closer to replacing Li-ion batteries

Na-ion batteries get closer to replacing Li-ion batteries
Credit: ACS
(—As lithium resources continue to decline worldwide, the next generation of portable electronics will most likely be powered by something other than Li-ion batteries. One potential candidate is the sodium-ion (Na-ion) battery, which stands out because sodium is cheaper, non-toxic, and more abundant than lithium.

Currently, one of Na-ion's largest drawbacks is that the batteries take a long time to charge and discharge, and a slow discharge rate does not supply enough power density for high-power applications. In general, there is a tradeoff between the charge/discharge rate and capacity, so that attempts to increase the charge/discharge rate have resulted in severely reduced capacity.

Now in a new study published in the Journal of the American Chemical Society, researchers led by Yong Lei, a professor at the Technical University of Ilmenau in Germany, have achieved a significant improvement in this area. The researchers demonstrated a Na-ion battery that exhibits charge/discharge rate and capacity values that are among the highest achieved for both organic Na-ion and Li-ion batteries. The large improvement may help pave the way toward the integration of Na-ion batteries in portable and wearable electronics.

To achieve this improvement, the researchers had to consider some of the fundamental properties of sodium. Sodium and lithium have a similar tendency to lose electrons—as measured by their electrochemical potential—which makes them good anode materials. However, sodium ions are nearly 25% larger than lithium ions. The larger size makes it more difficult for sodium ions to be inserted into the crystal structure of the electrodes, where the chemical reactions take place. As a result, the ions can't move as fast, which lies at the root of the slow charge/discharge problem. Tied in with this problem, the charge transport and stability of the materials also need to be improved.

Although the researchers could not decrease the size of the sodium ions, they could improve the efficiency with which the sodium ions are inserted into the electrodes. To do this, the researchers used a molecular design strategy based on extending the electrode material's π-conjugated system, which basically involves manipulating the way that these molecules bond with each other. Physically, this strategy results in a terrace morphology, consisting of multiple, widely spaced layers that form a faster route for the to move through. The extended π-conjugated system also improves the charge transport and stabilizes the charged/discharged states so that they can better tolerate the fast insertion/extraction of Na ions.

In terms of battery performance, this change results in significant improvements. As always, there is still a tradeoff between charge/discharge rates and capacity. But the new Na-ion batteries can operate at a current density (a measure of the charge/discharge rate) that is 1000 times higher (10 A/g vs. 10 mA/g) than most previously reported organic Na-ion batteries while retaining a much higher capacity (72 mAh/g).

At an intermediate current density (1 A/g), the new battery delivers an impressive reversible capacity of 160 mAh/g, which is one of the highest values reported for both organic Na-ion and Li-ion batteries to date. The battery also exhibits good capacity retention (70% retention after 400 cycles).

"In this work, we focused on the molecular design for improving performance and addressing the current challenge of fast-charge and -discharge in organic Na-ion batteries," Lei told "Through reasonable molecular design strategy, we demonstrated that the extension of the π-conjugated system is an efficient way to improve the high rate performance, leading to much enhanced capacity and cyclability. We also think our work provides a good attempt to expand the search of new electrode materials from the traditional inorganic to organic materials, and might arouse further attention regarding this area."

Building on this research, the scientists plan to further improve the batteries using the molecular design strategy and other innovative methods.

"We will be continuously focusing on organic Na-ion batteries," Lei said. "As mentioned in our paper, there are only a few reports on organic Na-ion batteries. Therefore, there is still a long way to go for organic Na-ion batteries. Future goals include: 1) improve the capacity and cyclability of the cathodes and anodes; 2) enhance the rate performance of the cathodes and anodes; 3) adjust the electrochemical potential to achieve suitable output voltage of full cells; and 4) develop environmentally friendly and low-cost materials."

Explore further

Sodium-ion battery cathode has highest energy density to date

More information: Chengliang Wang, et al. "Extended π-Conjugated System for Fast-Charge and -Discharge Sodium-Ion Batteries." Journal of the American Chemical Society. DOI: 10.1021/jacs.5b00336

© 2015

Citation: Na-ion batteries get closer to replacing Li-ion batteries (2015, March 3) retrieved 17 June 2019 from
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

Feedback to editors

User comments

Mar 03, 2015
United, American, Air France and Delta Airlines no longer accept bulk packages of rechargeable lithium batteries for shipment by air due to the risk of fire.

Mar 03, 2015
I wonder if Musks $5B Li-ion battery factory can accomodate developments like this.

Mar 03, 2015
It's great we have so much R&D taking place in battery chemistry. I disagree that we need to be so concerned about the Lithium resources. Even if every car in the world became an EV with the amount of Lithium as in a Model S, with currently known resources, we would still have plenty more. I believe the key to ensure long-term sustainability of Lithium based batteries is to ensure that the metal gets maximally recycled. Unlike fossil fuels, Lithium doesn't burn up inside the batteries. But if Na-Ion can beat Li-Ion then that's only wonderful. But always remember that most news from research labs about battery technology have one sole purpose: secure additional funding. And in the efforts of getting funding for energy related projects, you can find a lot of deception out there. It's a high stake area of R&D and groundbreaking research can get lots of money. Telling the positive side and avoiding the negative is common practice.

Mar 03, 2015
Interesting, no discussion on discarding batteries, re-cycling, etc.

I think good technology but concerned with safety and environment.

Mar 03, 2015
But if Na-Ion can beat Li-Ion then that's only wonderful.

I don't see it as one beating the other. Each will have their uses. Even slow charge/discharge batteries can be immensely useful if they are dirt cheap (e.g. as stabilizing batteries for the grid and as intermediate energy storage)

Interesting, no discussion on discarding batteries,

Sodium is environmentally benign. But as with all batteries a recycling scheme is certainly a good idea

Mar 03, 2015
The electrodes sound complex and delicate to manufacture. The cost would still likely remain quite high even if the raw materials themselves are cheap.

Mar 03, 2015
"and more abundant than lithium." A bit of an understatement, yes?

The only thing that frustrates me about this report is that I have read so very many reports of new science revolutionizing batteries, but I have seen little real change in the last decade.

Mar 03, 2015
MIT freshman to news gathering rookie: We may, may, may possibly be able to turn horse manure into a battery that could possibly be .0001% better than other batteries;
I was at lunch with my prof and some big thinkers when the idea was discussed.
News gathering rookie: Great! I think I have my headline: Horse poop battery that will kill Li-ion just around the corner!!!!

Mar 03, 2015
Increased use of lithium means that we could run short on processed lithium - if - we don't' mine and process more lithium.

Thing is, we are opening more lithium mines. Tesla/Panasonic will be getting the lithium for their gigafactory from a newly opened mine in Nevada.

At 20 mg lithium per kg of Earth's crust, lithium is the 25th most abundant element. Nickel and lead have about the same abundance. There are approximately 39 million tonnes of accessible lithium in the Earth's crust.

The Nissan Leaf contains 4 kg of lithium. Assume we use 3x as much for each EV in the future. 39 million tonnes = 3,250,000,000 EVs.

At some point we start recycling. And if we're still using lithium further down the road there are approximately 208,652,550,000 tonnes of lithium in seawater.

Mar 04, 2015

We are running out of LITHIUM !!! Won't someone please, PLEASE, kick me in the balls !

What? What does hyperbole mean?

It means you should be afraid.

Mar 04, 2015
By the time they get lithium production up: Lithium could be old news.
Hopefully they will get Magnesium based batteries (solid metal anodes, no self shorting dendrites) sorted soon.

Mar 05, 2015
Re: Elon Musk is the biggest con man since Bernie Madoff. His expertise is bilking naive state legislatures out of subsidies and tax breaks. Solar City in California. Nevada kicked in $1.4B for the estimated $5B "Giga" Lithium ion battery factory, east of Reno. The greatest advocate for the battery factory is Lance Gillman, owner of the Mustang Ranch brothel, just up the road. With all the construction workers, business at the Ranch will be booming. You can't make this stuff up.

Mar 06, 2015
The "real world" use of most batteries is going to be for storage of electricity generated at solar and wind facilities, and for electric cars. To make any of these uses inexpensive requires high capacity and charge/discharge rates and very high capacity retention. For electric cars we will need all of the above plus high efficiency for achieving reasonable weights of vehicles. For electric vehicles to be really practical and sell well, batteries need to be at least five times as efficient as Tesla stuff.

We have a long way to go to get to these numbers, and I wonder when we become asymptotic to the laws of chemistry and physics??

Mar 06, 2015
Grid storage can tolerate lower capacity batteries than can EVs. Lower capacity means more weight/volume per kWh stored. Since grid batteries will be parked on lower value real estate size and weight becomes less important.

We've got some really impressive grid storage batteries that seem to be making their way to the grid.

The batteries in the Tesla S are adequate for almost all of us to move off petroleum. All most people need is a 200 mile range EV that can be recharged to 80% full in less than 30 minutes. With a 200 mile range one can drive 500+ miles in a day and arrive almost as soon as driving an ICEV.

For EV batteries, it's cost. Get battery cost down to the point at which EVs are about the same price as same-model ICEVs and we move to EVs.

Over time battery capacity will almost certainly improve. IIRC lithium-ion batteries are now about 10% of theoretical capacity.

Mar 09, 2015
@foolspoo - Good link.
Musk realizes the potential dangers of AI, but he also realizes the potential benefits so instead of fighting AI he puts his own money where his mouth is to steer AI in a beneficial direction.

Whoever gave your comment a 1 must not have realized that your first line was sarcastic.

Mar 09, 2015
Lithium seems to be more commonly found than many imagine.

The Tesla/Panasonic is obtaining its lithium from a newly discovered mine in Nevada.

Western Lithium claims the Humboldt County site's deposits represent the fifth-largest lithium resource in the world. The Nevada Governor's Office of Economic Development says the state's overall lithium portfolio is even bigger.
"Nevada is lithium rich — second only to the size of deposits found in Chile," said Steve Hill, executive director of the Governor's Office of Economic Development.


A big find was recently announced in Wyoming. The find could contain as much as 118 million tons of lithium. That would be enough for 59 billion Nissan Leafs. (If I didn't experience a math failure.)

(Had to remove the link due to character count.)

Mar 09, 2015
@Bob_W: Let's check the math... According to Nissan, a Leaf's 24 kWh battery pack uses about 4 kg of lithium. A metric ton is 1000 kg, so that's 250 Leafs per metric ton. If the 118 million tons is metric tones that would be 118/4 =29.5 billion Leafs, so you have a factor of two error somewhere.

But the 118 appears not to b right for the recent Wyoming find: "In a best-case scenario, the Rock Springs Uplift could harbor up to 18 million tons of lithium".
(see http://missoulian...3f4.html )

18 million is a lot less than 118 million, and it is probably 2000-lb tones which are about 10% smaller than tonnes, but it is still a LOT of lithium.
That would still be enough for 4 billion Nissan Leafs, so you got the spirit of the find right.

Mar 09, 2015
The spirit is willing, the pencil weak....

Four billion here, a few more billion in Nevada, there's the mine we used to use in North Carolina, the lithium from geothermal brine at the Salton Sea. Canada Lithium Corp. started shipping from their plant in 2013.

North America is good for a while. We could build a few generation of 100% lithium-ion cars before needing to recycle.

Argentina, Australia, Bolivia, Brazil, Canada, China, Portugal and Zimbabwe have roughly 13,000,000 metric tons of lithium that can be extracted.


There are apparently large lithium deposits in Afghanistan. Lord knows those people could use an income source.

Mar 09, 2015
I obviously screwed something up. Looking back at my notes I find "1 18 million tons". A space between the two 1s. That seems to be where the extra 100 million snuck in.

Thanks for the catch.

Mar 10, 2015
No problem - thanks for pointing out the Wyoming find!

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more