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PNNL team develops hybrid Mg-Li battery; excellent rate performance, safety and stability

Schematic illustration of the the hybrid Mg-Li battery designed in this work. This battery has a piece of Mg foil as the anode, Mo6S8 as the cathode, and the electrolyte contains both Mg2+ and Li+. Cheng et al. Click to enlarge.

Researchers at Pacific Northwest National Laboratory (PNNL) have devised hybrid batteries assembled with a magnesium (Mg) metal anode; a Li+ ion intercalation cathode (Mo6S8), and a dual-salt electrolyte containing Mg2+ and Li+ ions. The objective was to combine the advantages of lithium and magnesium electrochemistries.

In a paper in the RSC journal Chemical Communications, they reported that such hybrid batteries delivered strong rate performance (105 mAh g-1 at 15 C) and superior cycling stability (B5% capacity drop for 3000 cycles at 10 C), along with reasonable output voltages. The researchers suggested that the inherent safety and stability features of such devices make them very promising for many applications, especially for large-scale static energy storage.

Interest in rechargeable magnesium batteries has increased due to a number of factors. Magnesium is low-cost, safe and environmentally benign. When used as an anode, Mg has a low standard electrode potential and fast deposition/stripping kinetics with nearly 100% reversibility without formation of dendritic structures—the last being a major problem with a pure Li metal anode.

Magnesium also has a much higher theoretical energy density (gravimetric: 2205 mAh g-1, volumetric: 3832 mAh cm-3) compared with typical anode materials because of its divalent energy storage characteristics, the PNNL team noted.

Over the past few years, substantial progress in rechargeable Mg batteries has been demonstrated, but their practical application is still facing great challenges, largely due to limitations of cathode materials. … As an alternative to develop cathode materials for intercalating Mg2+ ions, here we desire to fabricate batteries by combining Mg and Li electrochemistry.

… It should be noted that a similar design has been discussed in a previous study [Yagi et al.], but it appears that prototypes fabricated in that work have some limitations (for example, low coulombic efficiency and short cyclic life), and therefore it is not evident that the design is indeed practical.

—Cheng et al.

(a) Typical cycling stability of hybrid cells tested at 10 C for 3000 cycles; (b) comparison of the charge–discharge profiles for the first cycle and the 3000th cycle, showing minimal changes upon repeated charge–discharge operations. Cheng et al. Click to enlarge.

Mo6S8 can undergo intercalation reactions with either Li+ or Mg2+ ions; reactions with Li+ ions have better kinetics. The PNNL team’s results showed that Li+ ion intercalation was the dominant reaction when both Mg2+ and Li+ ions were present; this is the fundamental basis for the design of Mg–Li hybrid batteries.

Electrochemical testing showed that the cell had a specific capacity of 126 mAh g-1 at 0.1 C—very close to the theoretical capacity of Mo6S8 (128.8 mAh g-1), calculated based on the mass of Mo6S8. The capacity had a slight decrease with increase of the C-rate, but was able to maintain 105 mAh g-1 at 15 C (83% retention).

The hybrid cell was very stable, with close to 100% coulombic efficiency for each cycle.

The results discussed above demonstrate that the hybrid cells designed here could combine the advantages of Mg and Li electrochemistry and have outstanding rate performance and cycling stability. Practically, however, the performance of hybrid cells will depend strongly on their assembly methods (in particular, active material loadings relative to amounts of electrolytes) due to their unique operating principle. In particular, the electrolyte should be able to supply sufficient Li+ ions for the cathode electrochemical reaction and intercalation kinetics, since the Mg–Li battery was assembled at the charged state.

… the hybrid batteries will have minimum requirements on the amount of electrolytes for optimal performance. The volume of electrolytes could be reduced by developing novel electrolytes, such as the solvent-in-salt type electrolyte developed recently for a Li–S battery. In principle, it is possible to adopt most Li cathode materials to develop Mg–Li hybrid battery. However, developing electrochemically stable Mg–Li dual salt electrolytes is an immediate technical hurdle, since most known Mg electrolytes have stable electrochemical windows less than 3 V. Research on developing new electrolytes to increase the voltage of hybrid batteries is underway.

—Cheng et al.


  • Yingwen Cheng, Yuyan Shao, Ji-Guang Zhang, Vincent L. Sprenkle, Jun Liu and Guosheng Li (2014) “High performance batteries based on hybrid magnesium and lithium chemistry,” Chem. Commun., 50, 9644-9646 doi: 10.1039/C4CC03620D

  • A. Yagi, T. Ichitsubo, Y. Shirai, S. Yanai, T. Doi, K. Murase and E. Matsubara (2014) “A concept of dual-salt polyvalent-metal storage battery ,” J. Mater. Chem. A 2, 1144–1149 doi: 10.1039/C3TA13668J



(B5% capacity drop for 3000 cycles at 10 C)



Yes, I always liked Babylon 5 too.

Wait, that was a tilde in the original....


"They delivered outstanding rate performance (83% capacity retention at 15 C) with superior safety and stability ([similar]5% fade for 3000 cycles)."!divAbstract


Off topic:

"The startup EP Tender intends to solve that problem. Not by developing a bigger or a better battery but by creating a range extender on a trailer."


Perhaps, at patent application, a prototype cell/battery should be required to be sent to national laboratories for immediate, comparative testing.

Around year 1900 EVs, battery energy density doubled in 25 years - then ICE ~stifled R&D. Around 1990, 2X battery density in <20 years, till GM/NMHD/EV crushing.

Even now, Republicans are at the door.

As hundreds of new batteries/announcements are never heard of again - so is support for battery research.


@SJC, one could also take a ~BMW I3 range extender(or a lighter Wankel) and hang the ~200 - 400 lb off a trailer hitch.


@SJC, one could also use/rent a heavier and cheaper genset with a supporting trailing wheel.

I once did a '180' from hundreds of extra pounds in the car trunk, throwing off driving dynamics, when dodging a deer.

But one could use the stability system or variant on the fifth wheel/camber and clip a rear view camera on for additional safety.

Royalty and trolling fees accepted.


"As hundreds of new batteries/announcements are never heard of again - so is support for battery research."

Make stuff up much?

Please list three authorized federally-funded battery research programs that have been terminated. Also please point out how the second ~$8B (with a B) tranche of ATVM spending (ALREADY authorized by Congress as an element of President Bush's FY09 Budget) does not represent actual spending.


Who said, "..federally-funded.."?

Google, "new battery breakthroughs".

Match the each of the over 9,600,000 results with their new marketed batteries and post the list..


@Herman, as for the Bush Hydrogen Initiative - Advanced Technology Vehicles Manufacturing (ATVM) -

..we certainty have a dozen years of hydrogen fuel cell cars crowding us off the roads - don't we?

And no doubt, ".. the second ~$8B (with a B) tranche of ATVM spending (ALREADY authorized by Congress as an element of President Bush's FY09 Budget).." IS GONE.


Ahhh... I get it. Anything was ever declared a "breakthrough" that didn't pan out, whether it was caused just a random act of poor, unrepeatable research in the first place, processes that are unscaleable or uneconomic, industrial methods that prove hazardous, unable to pass normal safety tests... is ALL the result of your political enemies' devious behavior? (You used the phrase "republicans are at the door", which should be GOOD since they passed the ATVM program in the first place right? I mean even Darrell Issa was a huge proponent of Aptera.)

Interesting. So ANYTHING that shows up in Google that isn't available in bulk on Alibaba has been secretly eliminated? And despite the fact that VERY bipartisan supported Federal funding (direct, loan guarantee, cost-sharing, University grants, IR&D tax credit, etc.) is by far the largest source of advanced battery research, that doesn't count?

OK. Look, first of all, your logic method is unbeatable: claim something is true, and then dare your opponent to disprove it. You will always win (in your own mind). I obviously have terrible, hideous garden gnomes because my tomato crop has been awful. Prove that they aren't there. Ha: I win, because you can't. Of course everyone who reads this knows it's foolish rhetoric. Ditto your argument.

Secondly, it's important to understand that conspiracy narcissism is not productive. It makes you think that anything that doesn't fit your personal model of how the world should work is not only flawed, but the result of global evil forces aligned against your superior intellect and moral compass. It can't possibly be any other reason, from grossly inflated expectations created by an uneducated "science" press to echo chambers of narrow interest groups. Nope: gotta be black hats.


Some like trailers, some don't. I would favor putting a range extender battery/fuel cell well in the back where the spare tire and fuel tank were. You can put in another 24 kWh of batteries or a 40 kW fuel cell after market. The fuel cell would include the tank that just plugs into the stock fuel line.


Well, if Republicans are "at the door', we stand a good chance as a nation to actually afford this technology that so many tax dollars have chased after.

And mind you, that unlike lithium, which has generated the same questionable scientific frissons as helium-3, magnesium is one of the few constituents of seawater that is actually profitable to extract. No need to beg China or a Latin American caudillo for the supply.


@Herman, many on this site have noted "battery breakthrough" articles with little/no follow up..
etc.. search just this site for over a thousand more.

As for politically, Republican oilman Bush crushed CARB laws and set EVs/batteries/charging infrastructure back a decade..

WITHOUT ONE marketed Hydrogen Initiative fuel cell car EVER. (PERIOD)


Had the last Iraq and Afghanistan futile wars been avoided, USA would already have national H2 and ultra quick charge networks together with cleaner electricity generation plants.

Let's hope that USA does get involved into a third costly Irak war.

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