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BASF and Sion Power to Collaborate on Lithium Sulfur Battery Technology; Targeting EV Market
15 May 2009
|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
Yuriy Mikhaylik (2006) Fundamental Chemistry of Sion Power Li/S Battery. IBA-HBC 2006
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