jueves, 25 de junio de 2015

Chemical Battery Can Recharge Itself With Light

Image: Musthafa Ottakam Thotiyl/IISER Pune
Batteries, by definition, convert chemical energy into electricity. Once you’ve sucked them dry, you have to reverse the process to convert electricity into chemical energy, and for that, you need a source of electricity. It’s not like it’s hard to do this, but it is certainly a minor annoyance that could do with a fix.

Researchers at the Indian Institute of Science Education and Research (IISER) in Pune, India, have skipped the annoying step by developing a battery that charges directly from light. We’re not talking about a battery with a solar panel on it: it’s a “photo battery” where the anode itself is made of titanium nitride and ambient light.

Under artificial light, this prototype battery has a capacity of 77.8 mAh/g. It’ll quite happily power a small fan or LED light for about 30 seconds, and then if you give it a break for 30 seconds while shining a light on it, it’ll be all charged up and good to go again. Over 100 cycles, the battery retained a bit over 70 percent of its discharge capacity, which at least suggests some potential for longevity and usefulness.

In addition to being charged directly by light, which is pretty awesome, this battery design offers other benefits, including “ 
  • a sustainable and economical anode material which will not be consumed as a part of the discharge reactions, and 
  • an anode material that is free from loss of active materials, irreversible structural deformations, spontaneous deinsertion reactions, and safety concerns commonly encountered in the state of the art anode materials in [aqueous rechargeable batteries].
Here we show a surrogate strategy for power production, wherein light is used to actuate a discharge chemistry in the cathode of an aqueous rechargeable battery (ARB). The proposed photo battery consists of a titanium nitride photoanode, promising cathode material iron(III) hexacyanoferrate(II) as the battery active species and Na2S2O8 as the chemical charging agent. The photo battery delivered negligible capacity in the dark and the capacity shot up to 77.8 mAh/g when artificially shined light, confirming that the battery chemistry is light driven. In the ambient light, the device retained 72% of its artificial light discharge capacity with a stable cycling for more than 100 cycles. Further, an unprecedented means for charging the battery rapidly is presented using Na2S2O8 and it revitalized the battery in 30 s without any external bias. This methodology of expending a photoanode extends to a battery that is free from dissolution of active materials, irreversible structural changes, spontaneous deinsertion reactions, and safety concerns commonly encountered in the state of the art anode materials in ARBs. Apart from bringing out a sustainable way for power production, this device opens up avenues for charging the battery in the likely events of electrical input unavailability, while solving the critcial issues of longer charging time and higher charging voltage. Source: http://pubs.acs.org/doi/full/10.1021/acs.jpcc.5b02871.
J. Phys. Chem. C, 2015, 119 (25), pp 14010–14016
DOI: 10.1021/acs.jpcc.5b02871
Publication Date (Web): May 27, 2015
Copyright © 2015 American Chemical Society

According to a press release from the American Chemical Society, “the researchers say their design is a promising first step toward a more sustainable and safer battery technology.” In other words, this is a thing that does cool stuff in a lab right now, but getting your hopes up for a light-powered battery in your cell phone might be premature by a decade or so. For now, the best you’ll be able to do is read the full paper here.

By Evan Ackerman
Posted 24 Jun 2015

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