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Comment by jessaustin | Hacker News Reader

TFA is pretty thin on info. The "$500/kWh" goal seems to come from Musk's battery marketing rather than something inherent to this technology. And the technology itself isn't even hinted at. The description of "earlier versions" seems to imply a chemical reaction like regular batteries. However, speculating based on "liquid metal", maybe they've identified a metal with a melting point around ambient temp (or ambient temp of a sufficiently insulated vessel)? With high enough specific heat (typical for metals anyway), it could soak up energy by melting, and release it by freezing.

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Very thin:

    "Sadoway, who is also the John F. Elliott professor 
    of materials chemistry at Massachusetts Institute of 
    Technology, wouldn’t say what goes into liquid-metal 
    batteries."

Here's a description from an earlier article -- same idea with different materials:

    "After hitting upon the idea of the liquid-metal 
    battery, Sadoway searched for the perfect electrodes: 
    he ended up choosing magnesium and antimony because 
    they are cheap and separate naturally when in liquid 
    form, the lighter magnesium rising to the top. A 
    liquid-salt electrolyte rests between the magnesium 
    and antimony electrodes, creating a cell with three 
    layers."

http://www.technologyreview.com/featuredstory/511081/am

So it's a chemical battery where the electrodes are liquids. (FWIW: Magnesium melts at 650 °C).

It's a bit dated now, but in March 2012, Dr. Sadoway gave a TED talk about how these batteries work:

http://www.ted.com/talks/donald_sadoway_the_missing_link_to_...

A little bit more info and clarification here [1].

What I find so clever is that the containment is about as simple as a "hot bucket", hot enough to keep the anode, electrolyte and cathode always molten. The are materials chosen so that their different densities keep them separated physically in operation. No membranes, easy scalability.

[1] http://spectrum.ieee.org/energywise/energy/the-smarter-grid/...

The article doesn't have any specifics, but the group has been publishing in this area for a few years: http://sadoway.mit.edu/

It's an electrochemical cell - I know some people who've worked on the project and IIRC some of the main benefits are lower material cost / kWh and improved lifetime as the liquid metal "electrodes" don't degrade the same ways solid ones do.

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