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].”
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.