Using a simple process, engineers have baked a cotton T-shirt into activated carbon, and by adding a thin conductive metal layer, they have created a stable, high performing super capacitor.
The engineers from the University of South Carolina envision using cotton for energy storage in flexible electronics, roll-up displays, and implanted medical devices.
One day, donning a T-shirt could mean you're also sporting a smart device charger. Engineers have successfully transformed cotton into a flexible, highly conductive component, which means it could charge devices.
"In the future, you can imagine our cell phones will be just like a piece of paper you can roll up. But we need to have a flexible energy device to integrate with flexible, stretchable motherboards," Discovery News quoted Xiaodong Li, who led the development with postdoc Lihong Bao, as saying.
Li knows how to be creative with cotton T-shirts. In 2010, he and his colleagues converted one into lightweight body armour by converting the fabric into boron carbide nanowires.
So when he began looking for a backbone to make a flexible energy storage device, he turned to a $5 cotton tee from Wal-Mart.
The engineers had to make the cotton highly conductive so they tried several "recipes", Li said.
He compared their experiments with trying to replicate a restaurant meal at home without having seen the chef's preparations. First they dipped the cotton in a sodium fluoride solution for an hour, took the wet material and dried it in a preheated oven for three hours. Then they heated it in a hotter furnace for an hour.
By the time it was done, the cotton had changed into activated carbon. Despite being baked, the charred-looking material could still be folded. From there, the engineers coated it with a nano-layer of the conductive metal manganese oxide for the last stage of building their energy storage device.
The device, called a super capacitor, is able to respond more quickly than a battery to power needs.
Lead researcher Xiaodong Li said his team knew that future body armour would need a flexible power source. And because the scientists work in South Carolina, which used to have a big cotton industry, they thought, "Why not use a cotton T-shirt as the energy device?"
Although others have used cotton in devices, Li said that to the best of his knowledge his research group is the first to activate a cotton T-shirt and build it into a super capacitor.
Their device's performance is on par with other carbon-based super capacitors, according to their testing. After 1,000 cycles it had 97.3 percent retention.
"This is a very simple low-cost process, and it's green," Li said.
In addition to starting with a renewable plant-based material, he and his research group estimate that using cotton directly from textile mills could be as much as 10 times cheaper than chemically processing coal or petroleum into activated carbon.
To take his concept to market, the process needs to be scaled up. Li said that for this next phase, he's looking for a potential industry partner. He's also reaching out to state government leaders about using this process to help revive local textile production.
The study has been published in the journal Advanced Materials (abstract).