The scientists at the University of British Columbia have brought innovative and never heard of before technology to aid in the clothing sector. They have developed a battery that is both flexible and washable.
There have been other stretchable energy storage solutions designed to power wearable devices, from millimeter-scale batteries that stretch over the skin like a Band-Aid to fabric-like batteries that draw power from sweat. This time, the scientists have taken this concept to the next level and have made giant engineering advances to fill what they see as important gaps in the current technology.
“Wearable electronics are a big market and stretchable batteries are essential to their development,” says study author Dr. Ngoc Tan Nguyen. “However, up until now, stretchable batteries have not been washable. This is a critical addition if they are to withstand the demands of everyday use.”
They have incorporated innovation in the way the device is assembled. Instead of making a lithium-ion battery packed with hardened materials inside a rigid exterior, the team made us of zinc and magnesium oxide that has low cost and more safety. These materials were ground down into tiny pieces and embedded in a polymer to form ultra-thin and stretchable layers, with several of these stacked up and encased in the same polymer to seal up the finished product.
“We went with zinc-manganese because, for devices worn next to the skin, it’s a safer chemistry than lithium-ion batteries, which can produce toxic compounds when they break,” says Nguyen.
The battery that came as output is flexible and can be stretched to twice its normal length, has a specific capacity of 160 mAh g?1, and retains 75 percent of its capacity over 500 charge and discharge cycles. It has withstood 39 wash cycles so far.
“We put our prototypes through an actual laundry cycle in both home and commercial-grade washing machines,” says team member Bahar Iranpour. “They came out intact and functional and that’s how we know this battery is truly resilient.”
Scientists are now working to improve its power output and lifetime. Its cost will almost be the same as a standard rechargeable battery. The proposed use of the batteries is in watches and patches that measure vital signs, and in smart clothing that does much the same thing.
“The materials used are incredibly low-cost, so if this is made in large numbers, it will be cheap,” says electrical and computer engineering professor Dr. John Madden, who supervised the work. “Wearable devices need power. By creating a cell that is soft, stretchable, and washable, we are making wearable power comfortable and convenient.”
The research was published in the journal Advanced Energy Materials.