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BASF and Sion Power to Collaborate on Lithium Sulfur Battery Technology; Targeting EV Market

Configuration of a Li-S cell. Click to enlarge.

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

The Sion Power / BASF collaboration targets the development of battery materials to improve Li-S battery life and to increase the energy density and thus extend driving range of future EVs beyond what is currently available with alternative rechargeable battery technologies. Li-S technology already offers significant energy density and weight advantages over those existing technologies.

Privately held Sion Power Corporation was established initially as Moltech Corporation in 1994, and holds more than 100 US and international patents on its technology.

Ragone plots for different rechargeable systems from a 2006 Sion paper. Click to enlarge.

The theoretical specific energy of a lithium-sulfur battery chemistry is in excess of 2,500 Wh/kg with a theoretical energy density greater than 2,600 Wh/L. Sion Power’s Li-S technology 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 company says that 600 Wh/kg in specific energy and 600 Wh/L in energy density are achievable in the near future.

This Li-S chemistry can be designed to deliver high energy, high power or a combination depending upon the requirements of the application. Sion Power cells have a voltage of 2.1 V. For higher voltages, the cells can be connected in series.

The anode and cathode of Li-S cells are thin materials substantially similar in thickness and tensile strength to those of lithium-ion. Standard lithium-ion winders can be used with little to no modifications, according to Sion. Prismatic and cylindrical form factors can be produced from the same anode and cathode raw materials.

Electrochemistry of the Li-S cell. Source: Sion. Click to enlarge.

Electrochemistry. At the negative electrode, lithium is dissolved into solution on discharge and plated out on charge. The sulfur chemistry is more complex in that a series of sulfur polymers are formed. Higher polymer states exemplified by Li2S8 are present at high states of charge, the charged form of the battery. Lower polymer states, exemplified by Li2S, are present at low states of charge, the discharged form of the battery.

Over the years, Sion Power has improved the sulfur utilization dramatically from about 46 to more than 90%.

We are excited to join Sion Power in advancing Li-S technology. It is clear that Sion’s technology offers high potential for significantly longer driving ranges over other technologies currently being considered for electric vehicles. We see a clear need for higher energy densities of the storage devices, and we will join forces with Sion to bring this technology to the market using innovative solutions. In combination with the lithium ion battery consortium ‘HE-Lion’ that we have formed recently [earlier post], we further strengthen our efforts to advance battery technology.

—Dr. Thomas Weber, CEO of BASF Future Business




This is excellent news.

SION (and Polyplus) have been investigating lithium-sulphur batteries for years with little commercial success. To date, their problem has been poor safety and cycle life.

With a huge company like BASF now on board, these two remaining hurdles can be addressed and we will soon have 500 Wh/kg (pack level) batteries for EVs.

That kind of energy density would enable a 200 kg battery containing 100 kWh of energy for 500 miles EV range.


Agreed. This is fantastic news.



I agree with you, it would be ideal for pure practical EVs. Let's wait for what E-P will say.

This is very good news for future PHEV-100+ and BEVs. High energy density (500+ Wh/Kg) and high power density is exactly what electrified vehicles have been waiting for. Can it be made to last at least 5000 cycles and at an affordable price?

Let's hope that BASF will supply the resources required to improved design and developement, establish automated mass production facilities and protect the 100+ related patents.

Patent holders are 100% responsible to legally defend their own patent rights. BASF has the resources to do that and copy cats know it.

(The same holds true for other patent holders for various lithium battery technologies, such as the Goodenough-UT-Hydro-Quebec version).


Why would you need 5,000 cycles? If the 200 kg battery gives 500 miles per charge cycle, that would be 2,500,000 miles! Your car (and probably your body)would fall apart first.

Like millions of people who use mass transit every day, I don't put many miles on my car - in my case only 3,000. So if a 150 kg battery gives me a 300 mile range, I would be perfectly happy. Charging about once a month, the battery would last about six or seven years. That's because these batteries only last about 80 cycles. People driving the average 12,000 miles per year would replace the battery every two years, or six years with the 500 kg Big Boy model.

They don't contain expensive cadmium and seem simple to manufacture. So, it seems like they would cost a lot less than Li-Ion.


I meant to say the batteries don't contain expensive cobalt or other heavy metals. Sulfer costs much less.


Before you get all perky remember lithium sulfur batteries have terrible lifespans currently. Unless they realy push the lifespan up a ton they will still be useless for evs.


If the lithium is fully reclaimable, and sulfur is cheap. Then light, powerful, short-lived batteries (with a relatively high core value)sounds like a great business opportunity. Obviously a battery that is replaced and remanufactured every five years is more profitable for the manufacturer than one that lasts 10 years. As long as the total cost is about the same for the consumer, as long as it is a savings over gasoline fill ups,and the upfront cost is less, then the product would be desirable for the consumer.


the Li S chemistry has been known for years, Duracell was making commercial Li-S batteries in the 80s. So given on one side the high potential of this chemistry and on the other side it poor industrial success I guess that the problems associated with this chemistry are not simple to solve. Sure S is a cheap abundant light and non toxic material, just like Si by the way. Still no Si or S battery available.

Now if BASF is ready to invest that's a good sign that they feel SION is in the right track, but who know if they will ever solve the 2 remaining problems.

On the other side it is true that if you can make batteries cheap enough they don't need to last for ever, so you can swap them every 5 years for example. But you need to be below 6000$ for the whole pack for this.


Life span of a battery is important in case you want to own the battery and purchase it for life. But maybe this requires different thinking, a few scenarios:

a) they own the battery and recharge it for you. So in that scenario you don't care about lifespan. Price of the battery is more important and of course how many millage.

b) If the lifespan is 3x times worse then current Li-Ion, but price would be 10x less who care about it, Li-Ion batteries only last 8 years anyway. so you just replace the battery with a new one. Just the same as bringing in your car for a maintenance checkup.


The accelerated commercialization effort with BASF seems the next step for SION, which has publicly presented detailed research results, produced prototype cells and practical batteries, and appears ready to market a commercial product for EVs. Their web site shows they will be planning a 426 lb 70kwh battery which will give a 3,400 lbToyota RAV4 a 226 mile range.

However, the average person drives only 33 miles a day. So they will be carrying a lot of dead weight. What SION and BASF need to do is make the batteries smaller and easy to install. A 30 lb 5 kwh battery could have a handle to carry it and plug it into a slot in the car's battery compartment. It should be as easy as attaching a cordless drill battery, purchased at at retail store. Two 5 kwh battery modules would give a 33 mile range. Seven for a 226 mile range.

SION says the batteries can be charged and discharged at a 3 C rate. 20 kwh of batteries would give 60 KW of power - about 80 HP. SION's batteries have a lifetime of about 300 cycles. At 20 miles per gallon, 33 miles per day, $3 per gallon, the yearly cost of gas is about $1,800. The Tesla is EPA rated for 33 miles on about $.70 of electricity (at $0.07/kwh). SION-BASF needs to get the cost down to below $200/kwh. In that case, a 20 kwh battery that lasts two years (cycled every two days) would cost about $4,000 for the batteries and $500 for electricity - $2,250 per year.

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