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Sion Power Receives $800K DOE Grant to Enhance Lithium Sulfur Batteries

A lithium-sulfur cell. Source: Sion Power. Click to enlarge.

Sion Power Corporation has received a three-year, $800,000 research grant from the US Department of Energy (DOE) to support Sion’s ongoing work to develop a new class of electrolytes used in lithium sulfur (Li-S) batteries for electric vehicle (EV) applications. Sion Power will provide matching funds for this three-year effort.

The project objective is to increase performance of very-high-energy lithium metal anodes used in rechargeable battery systems. Sion Power will complete development of its unique electrolyte system employing multiple components. While improving lithium conductivity, one component will be optimized to enhance metallic lithium anode performance; another will enhance cathode functionality.

Ragone plot of current Sion Power cells and other chemistries. Sion believes that its current development work will push the specific energy to 550 Wh/kg. Source: Sion Power. Click to enlarge.

The multi-component electrolyte system will enable Sion Power to improve chemical stability leading to improved safety and abuse tolerance.

In May Sion Power and BASF SE signed a Joint Development Agreement (JDA) to accelerate the commercialization of Sion Power’s proprietary Li-S battery technology for the electric vehicle (EV) market and other high-energy applications. (Earlier post.)

Lithium-sulfur batteries. Lithium Sulfur batteries (LSBs) use a lithium metal anode and a soluble polysulfide cathode. Lithium ions are stripped from the anode during discharge and form lithium polysulfides in the cathode. Li2S in the cathode is the result of complete discharge. On recharge, the lithium ions are plated back onto the anode as the lithium polysulfides in the cathode move towards S8. High order Li-polysulfides (Li2S3 to Li2S8) are soluble in the electrolyte and migrate to the anode, scrubbing off any dendrite growth.

The theoretical specific energy of a lithium-sulfur battery chemistry is in excess of 2,500 Wh/kg with a theoretical energy density of 2,600 Wh/L.

Current status of Li-S development compared to USABC baselines. Source: Sion Power. Click to enlarge.

However, LSBs have a number of issues, including cycle life and operation at higher temperatures. Among the limiting mechanisms, according to Sion, are the rough lithium surface on the anode during cycling and Li/electrolyte depletion. Lithium roughness leads to generation of porous “mossy” Li deposits, absorption of electrolyte by porous deposits and premature Li anode disintegration. Li/electrolyte depletion leads to loss of the solvent necessary for proper functioning of the cathode. The products of these Li-solvent reactions also increase cell impedance and the rate of capacity fade.

Sion’s collaboration with BASF is pursuing solutions to those issues, including a proprietary anode design to reduce lithium roughness; development of structurally sable cathodes; and new materials for multi-functional membrane assemblies for the physical protection of lithium.

Sion Power’s Li-S technology already provides rechargeable cells with a specific energy of more than 350 Wh/kg, which is 50% greater than the currently commercially available rechargeable battery technologies.

The reduction of lithium surface roughness with new anode design, and better cathode structure demonstrate shows a substantially increased sulfur utilization to more than 1.45 Ah/g of specific capacity. With this improved specific capacity and reduced cell mass (resulting from the utilization of thin membrane protection) and, with improved cell design, Sion believes that the energy density of the Li-S cell can be increased from the present value of 350 Wh/kg to 550 Wh/kg.

The new approach is also resulting in a recharge time reduced to less than 3 hours, and a substantial cycle life increase. It is also eliminating the potential for thermal runaway, according to Sion.




Charge, Battery Charge!!! I'm a big fan of lithium Sulfur Chemistry, it has real potentially to dramatically reduced the size and increase the storage density of batteries to levels practical for cheap BEV, that and Zinc-Air are the long term practical batteries for BEV.


Good potential as far as energy density and power density are concerned.

Limited life cycle and long recharge times have to be improved for long range BEV applications.


Sulfer batteries are good for milt uses and such but they have horrid life cycles.

Henry Gibson

Waste of money in this case, but perhaps something new will be found. ..HG..

Henry Gibson

Sodium-Nickel-Chloride batteries have been tested in automobiles for over ten years now, and they have been tested and will be used in railway locomotives and mine trucks by General Electric who also intends to make them. These batteries are called ZEBRA batteries and are presently marketed and built by MES-DEA and have been used in truck and buses world wide. They must operate hot because both electrodes are liquid, one a salt the other a metal. The TH!NK car uses one as one of three battery options. They are also used in a submarine rescue vehicle.

The sodium-sulphur battery is similar and was invented first by Ford but is now marketed for power grid stabilization. Both types use the BASE, beta-alumina-solid-electrolye, that operates at high temperatures. Vacuum-Panel insulation is more than adequate for the Zebra battery so that it can run in very cold climates and very warm ones as well with only air cooling at any temperature. The battery must be kept hot inside, but if it cools off the charge is retained forever until heated again, but this means it must be heated to be kept active, but the energy loss is equivalent to that of other batteries. It is not a battery for only occasional use, so others are offered in the TH!NK for that type of use. The ZEBRA would be perfect for an extended electric range Prius that also retained its original battery because it would give about a hundred miles electric range but would operate still with an inactive ZEBRA that was left off charge for several days. The Prius battery and engine could also automatically keep the ZEBRA hot and charged whilst using the ZEBRA electrical energy to keep itself hot between engine runs if there were no grid connection. The high cycle life of the ZEBRA allows the ZEBRA battery to be a perfect V2G battery, which I suggested to CALCARS three or more years ago before it became a popular topic. The ZEBRA comes at a high price but only because of lack of mass production with thorough automation. The high cost of Nickel is not a major cost and iron already is substuted for part of it. When its power levels fail or too many cells fail the battery can still be used for grid support or UPS when removed from the vehicle.

Working cells can be obtained from end of vehicle life batteries and configured for grid support inside new insulation if too many cells have failed. The still working cells can also be used for emergency lights and power, as they have a long life at lower power demands in a stationary situation where no maintenance is required. ZEBRA cells fail mostly in a shorted condition which allows the remaining battery to continue operation until many cells fail in a long series chain.

NGK is making as many Sodium Sulphur batteries as it can but they should reconsider using them in vehicles, but at least they could be used as stationary batteries for rapid charging of electric vehicles whilst also functioning as grid support when no charging is being done.

A full electric car with long range is bad engineering for society, as the costs are still too high and will remain higher forever than liquid fueled vehicles. The pollution and CO2(not pollution) issues have known economical solutions.

The energy density of ordinary liquid fuels is about 45MJ/kg or about 12500 watt hours per kilogram, but to compare this with batteries the efficiency of the engine or fuel cell must be considered. Very large engines can reach an efficiency of 50 percent. An automobile engine generator could even get 40 percent, but for purposes of comparison 25 percent will be used. This gives liquid fuel an actual electrical energy density of over 3000 watt hours per kilogram which exceeds the theoretical lithium sulphur batter maximum and is nearly ten times the present value of 350.

The average trip of an automobile is short enough for low cost lead acid batteries to be used, and Firefly will make this even more attractive. EFFPOWER builds very high power bipolar lead-acid batteries for the acceleration demands, and CSIRO invented a lead battery with ultracap built in for a similar reason.

The reports about the TZERO, now missing from the WEBSITE, examined the careful design of range extenders by ACpropulsion first with lead batteries and then with lithium. They showed that full speed on all hills was possible on a cross country trip with a small range extender.

Lower horsepower range extenders are suitable for most car uses and may rarely be turned on for most trips, and this means that their efficiency is not very important. The average fuel consumption of your car can give you a good idea of the average horsepower you use from your present engine. Fifteen to twenty percent is a good range for average engine efficiency. At idle the efficiency is obviously zero.

The OPOC engine-generator is large enough at 13 pounds, for the engine only, for long distance trips even. Otherwise a range extender is needed only to stop the range anxiety of buyers and the related publicity. ..HG..


Molten salt based batteries have the draw back of needed to be kept hot and molten. LiS batteries cycle life is the issue being corrected here, if it is corrected LiS batteries will surely out compete most other li chemistry batteries in just a few years.


Interesting. They need a tenfold increase in cycle life. Spec energy theoretical claims 2500Wh/Kg.


To Henry Gibson

25% ICE efficiency - is't to high? 15% would be normal. 25% gas turbine efficiency for power genset.


One of the major problems with high temperature batteries has been seal corrosion. This is one reason why sodium sulfur batteries were dropped for transportation applications.

Robert (electricman) Weekley

I just want the battery pack designer to make me one that fits my old firefly - now electricfly - in the space of the old Gas Tank, 40 Litres / about 10 Gallons, and gives me about 100+ Kms Range! OK - 150 kms would be nice too, but 100 would for me for now - Pretty much covers 80%+ of my current needs!

Sure - if I could recharge it at Buffalo Airport while I am there for 4-5 days each flight I make - then - I sould need one that gets me about 250 kms or so - maybe 200 would do, but a bit of a margin is better!

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