Scientists are exploring ways to store electricity in textiles. Photo: Shutterstock
It may not take too long before your jacket could charge your phone. A group of researchers in China have developed a kind of fiber that could store enough electricity to charge personal gadgets and wearable medical devices. In a study published in Nature last week, researchers with Fudan University in Shanghai said they managed to mass produce fiber batteries that hold 85.69 watt-hours of electricity per kilogram. In comparison, an iPhone 12 Pro Max, which weighs 228 grams, has a battery of about 14 watt-hours’ power capacity.
Scientists have demonstrated charging a smartphone wirelessly while wearing a shirt made with the fiber batteries.
As part of the wearable trend, smart clothes have attracted much commercial interest in recent years. The latest products include smart socks that track your foot-landing techniques, swimsuits that can remind you to put on sunscreen, and yoga pants that can sense when your pose needs adjusting. Most of the wearables are powered by conventional lithium-ion batteries, which are not usually foldable or waterproof. The latest study brings researchers closer to developing a commercially viable textile battery that could open up new possibilities for wearable devices. In the latest study, researchers made fiber-shaped lithium-ion batteries by winding an aluminium wire coated with lithium cobalt oxides – the positive electrode – together with a graphite-coated copper wire for the negative electrode. Special wrappings are applied between the two to prevent short circuiting. The scientists then discovered that as the fiber’s length increases, its internal resistance decreases, before leveling off. Based on the discovery, they designed an industrial process to produce fiber-batteries that were meters long and could be woven into textiles. The material retained 90.5 percent of its capacity after 500 rounds of charge-discharge, according to the study. The battery-textile worked well even as it was being folded, washed with water and punched through by a knife, researchers found.
In one experiment, a piece of the textile continued charging an iPad as a 1,300-kilogram car drove on top of it.
Peng Huisheng, who leads the research team, told Chinese news outlet Thepaper.cn that the fiber’s energy density, which measures the amount of energy a battery contains in proportion to its weight, still lags behind conventional batteries. But with sufficient funding and technical support, these types of materials could possibly enter commercial use in two to five years, Peng said. Zijian Zheng, a professor who studies wearable electronics with the Hong Kong Polytechnic University, said the lack of textile batteries had become a key shortcoming for wearable electronics. “You have to put your battery somewhere, with a cable linked to the device,” said Zheng, who is not associated with the study. “The advantage of the material published in this paper is that it looked like fiber, so it could be seamlessly integrated into your fabric structure.” Zheng said the authors of the new study demonstrated that it’s possible to make a fiber-shaped battery that’s hundreds of meters long, bringing the material a step closer to commercial applications. Researchers around the world are also working on other types of batteries that are foldable and washable like clothes. Zheng said his own research group had developed a kind of fabric battery that could store energy. In 2017, an international research group developed a stretchy yarn made of carbon nanotubes that generates electricity when being twisted or stretched. The technology could potentially allow people to power their fitness trackers with their own movements. Follow Viola Zhou on Twitter.