Sumitomo Electric Industries of Japan has developed a rechargeable molten-salt battery that promises to cost about 10% as much as lithium ion batteries.  Sumitomo Electric working with researchers at Kyoto University has developed a sodium material that melts at only 57º C, just 134º F.  This is news.

With about double the energy density of a typical lithium ion battery Sumitomo’s new battery would power an electric vehicle travel twice as far as a lithium ion battery of the same weight.  The company aims to commercialize the molten-salt battery around 2015 and market it as an alternative to lithium ion batteries used in automobiles, buses, trucks, forklifts, and homes.

Sumitomo Electric spokesman Yoichiro Horiba says the company will work on safety issues over the next year and try to lower the battery’s running temperature.  The firm is not yet in talks with automakers.

Sodium Sulfur Basic Configuration. Click image to go to the Fullwiki page.

The new battery uses sodium-containing substances melted at a high temperature.  Molten salt technology has been around for decades, but current technology molten-salt batteries require keeping the electrolyte in a liquid state at a temperature at or higher than 300º C or 572º F.  As you can expect, that temp drop is going to have an intense impact.  Keeping a mass warm to 134º F vs. 572º F is a huge thermal demand reduction.

Sumitomo also expects the energy volume required to be halved as well.  Cutting the weight and size by half would allow engineers to reduce the space taken up by batteries. For electric vehicles this will be significant savings.  For example the Tesla carries along 900 lbs of lithium-ion batteries.  The counter point will be what is needed to keep the batteries warm enough – but that’s where the giant temperature drop requirement comes in.

Sumitomo is also asserting their molten-salt batteries also have high heat and impact resistance and are said to be less susceptible to igniting than lithium ion batteries.

The economics are so encouraging because sodium is much cheaper than lithium and its in abundant supply. Reporting has it the new battery is expected to be priced at about $240 per kilowatt-hour – about 10% as much as domestic Japanese lithium ion batteries and one-fifth as much as comparable Chinese products.

But will it work?  The news is just news so far, no press release from either Sumitomo or Kyoto University.  The technology is likely real and in the laboratory for now.  Yet for this to escape and have a spokesman answer about it puts a firmament under the news reports.  Dropping that temp for maintaining the battery and doubling the energy density is major news.

Lets keep an eye on this.  Sumitomo and Kyoto University might well pull that operating temperature down further.  Getting to an operating temp below what would scald flesh changes the dynamic once and operating at comfortable ambient or room temperature would change the dynamic even more.

It sure sounds good.  But there is one question of concern.  If the battery does cool below the molten state and solidifies, what are the consequences?  Can it be warmed up to regular service?  These are important question in this writer’s view.


2 Comments so far

  1. rick blazecka on March 8, 2011 3:09 PM

    I’m sorry, but 10% of Chinese produced Lion batteries sounds totally unrealistic. I can buy Chinese LiPo batteries at $700/kw. 10% of that would be $70/kw. So where do you get the $240/kw figure? That’s a HUGE difference! Please check your figures before publishing.

  2. snu on March 14, 2011 5:57 AM

    “$240 per kilowatt-hour – about 10% as much as domestic *Japanese* lithium ion batteries.”

    Chinese batteries are obviously cheaper than Japanese.

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