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We like to boast about how smart our mobile devices and computers have become but why are we still powering them with dumb batteries? Amy Prieto, a chemistry professor at Colorado State University, started a company that is created a three-dimensional battery with a core of copper foam. Although its still in the very beginning stages of development, this incredibly smart technology could lead to batteries that contain two times more energy and charge in five minutes flat.
Although modern rechargeable batteries make smartphones and GPS possible, theyre still extremely expensive, lose their charge in short order and come loaded with planet-killing toxins. Prieto thinks its inexcusable that while our devices have become more sophisticated, our batteries have remained virtually the same for over one hundred years.
The conventional battery surface is two-dimensional, which limits the direction and speed at which energy can flow. Prietos new design, being developed by the Prieto Battery Company in conjunction with CSU, adds a new dimension. Its just like a sponge, you could think about, Prieto told Marketplace.org. Then we paint all the inside spaces with the different materials that you need for the battery. So the ions can go in many different directions, but they dont have to go very far. So, thats what I mean by a three-dimensional battery.
The unique 3D architecture integrates nanowire or copper foam substrate, both of which will have higher power and energy densities than any traditional lithium-ion battery available. According to Prieto, the early stage prototype recharges in a few minutes, discharges slowly, and is manufactured using non-toxic chemicals (it uses citric acid instead of the kind that will burn your skin off).
While flexible and stretchable electronics have been on the rise, powering them with equally stretchy energy sources has been problematic. The new idea in Nature Communications uses small "islands" of energy-storing materials dotted on a stretchy polymer. The study also suggests the batteries can be recharged wirelessly. In a sense, the battery is a latecomer to the push toward flexible, stretchable electronics. A number of applications have been envisioned for flexible devices, from implantable health monitors to roll-up displays.
But consumer products that fit the bendy, stretchy description are still very few - in part, because there have been no equally stretchy, rechargeable power sources for them. "Batteries are particularly challenging because, unlike electronics, it's difficult to scale down their dimensions without significantly reducing performance," said senior author of the study John Rogers of the University of Illinois at Urbana-Champaign.
S for stretch "We have explored various methods, ranging from radio frequency energy harvesting to solar power," he told BBC News. In recent years, Prof Rogers worked with colleagues at Northwestern University, focusing on stretchy electronics of various sorts made using what they termed a "pop-up" architecture. The idea uses tiny, widely spaced tiny circuit elements embedded within a stretchy polymer and connected with wires that "popped up" as the polymer was stretched.
But batteries do not lend themselves to this idea; traditionally they are much larger than other circuit elements. They could be made from smaller elements wired together, but to create a small battery with sufficient power, the elements must be spaced more closely than those of the pop-up circuits. The team's new idea was to use "serpentine" connections - wires that loop back on themselves in a repeating S shape, with that string of loops itself looped into an S shape. Stretching out the polymer in which the tiny solar cells were embedded first stretches out the larger S; as it is stretched further, the smaller turns straighten - but do not become taut, even as the polymer was stretched to three times its normal size.
The team says the stretchy battery can be charged "inductively" - that is, wirelessly over a short distance. Prof Rogers said that the uses for such batteries and the stretchy circuits they power were myriad. "The most important applications will be those that involve devices integrated with the outside of the body, on the skin, for health, wellness and performance monitoring," he explained. However, the prototype batteries described in the paper were only run through 20 charge/discharge cycles, and Prof Rogers said that "additional development efforts to improve the lifetime will be required for commercialisation".
BBC News - Stretchy battery drawn to three times its size
