Originally Posted by Margery_Conner

Lithium-ion advancement improves safety and energy density

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Matsushita, which most people know better by its brand name, Panasonic, recently announced an advancement in lithium-ion cells that the company claims will make lithium-ion battery packs safer and slightly increase energy density, or the battery’s capacity for power.
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According to Rory Pynenburg, PhD, applications-engineering manager at lithium-battery-pack-design house Micro Power, battery manufacturers have been cramming more battery-active materials into the same cell dimensions. To achieve that task, they’ve had to compromise the thickness of the separator layer between the anode and cathode. The separators are polyolefin, typically a polyethylene with about 40% void volume. “The downside of using polyethylene is that, at about 93 to 98°C, the separator softens, and it can allow penetration by contaminants, leading to a short, says Pynenburg. “In pure polyethylene, it will start off with a pinhole penetration and then rapidly widen out, increasing the anode-to-cathode contact area, and you end up in a thermal-runaway situation.” In layman’s terms, this “situation” translates to a fire.
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According to Pynenburg, Panasonic’s improvement was the introduction of ceramic material, a metal oxide, that goes between the separator and the electrodes—the anode and cathode. “It’s shrouded in a bit of mystery as to whether [Panasonic is] coating it onto the electrodes or onto the separator,” he says. “But the metal oxide does greatly increases the thermal stability, so that if there is a penetration through the separator, it stops there, and you don’t get the thermal-runaway situation.” The polymeric separator is still present, but Panasonic has added a heat-resistant layer. . . .

Originally Posted by occ

Bob, I'm sure you've heard of Altair NanoSafe batteries, where they claimed they've already eliminated this problem by eliminating the separator.

http://www.altairnano.com/documents/...nder060920.pdf