09 August 2013

New flexible micro-supercapacitor paves way for tiny electronics

Before the age of the smartphone, mobile phone manufacturers were locked in an arms race to see who could create a smaller, but still usable device. Smartphones came along, and now the arms race is more or less focused on how big a screen can be while still being accepted by consumers. During this arms race, the way to keep phones from being unwieldy is to make them thin. Researchers have created a new supercapacitor so small that if it were used in smartphones, could make the devices even thinner and lighter than they are now.

Normally, electrodes in supercapacitors are made from carbon or polymers that can conduct electricity with ease. Researchers at Leibniz Institute for Solid State and Materials Research in Dresden, led by Oliver G. Schmidt, turned away from the usual electrode materials and instead used manganese dioxide — an unconventional choice, because the material isn’t known for being adept at conducting electricity. However, the material is cheaper than the usual electrodes, and also not as harmful to the environment. So, in order to make manganese dioxide conductive, the team turned to something a supervillain might to do a captive hero: vaporize it with an electron beam.

Once the manganese was vaporized and Lex Luthor finally defeated Superman, the atoms in the vaporized gas reformed into thin, flexible strips. The strips were still as conductive as the non-gaseous manganese dioxide, so the team connected thin layers of gold to the films, increasing the conductivity. The team found that the new micro-supercapacitor was not only flexible enough to save some space and shrink down the size of mobile devices, but that it also stored more energy and provided more power per unit volume than its competing supercapacitors.

Though the manganese is cheaper than a carbon-based electrode, adding the thin gold strips — which are expensive — counteract the reduced cost. So, the team is currently working on a way to reduce the cost once again. This likely means the researchers will have to turn to a material other than gold sometime down the road, or they could perhaps conduct an aggressive takeover of the Cash4Gold business and accrue the needed gold that way.

In essence, the flexible supercapacitor works, but not for the team’s initial goals. The researchers aimed at creating the flexible supercapacitor with a high energy density, but at a low cost. Adding the gold to help achieve that high energy density, unfortunately, increased the cost beyond an acceptable amount. If there’s something to take from this experiment, though, it’s that the supercapacitor itself was a success, and bringing it to to the consumer market is more about cost now than anything else.

Research paper: DOI: 10.1039/C3EE41286E - ”On chip, all solid-state and flexible micro-supercapacitors with high performance based on MnOx/Au multilayers”


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