A new battery-like energy-storing device is also tough enough to provide protection and mechanical support. The device could lead to extra power stored in structures such as phone cases, electric vehicle frames and ship hulls.
That would mean EVs that drive longer between charges, powered partly by the material they are built from. “This can extend the operational time of electronic systems, like in submersibles for ocean explorations or in consumer electronics—imagine longer operating time for airpods,” says Tina Ng, a materials science and engineering professor at the University of California San Diego.
The device that Ng and her colleagues reported in the journal Science Advances is a supercapacitor. Much like batteries, supercapacitors are energy-storing devices with two electrodes and an electrolyte. The two devices complement each other, because batteries can deliver energy for a long time, while supercapacitors provide quick bursts of power for things like acceleration.
Both types of devices hold a limited amount of charge, though. So researchers have been trying to find ways to integrate batteries and supercapacitors into building materials for low-cost technologies to store energy.
Carbon fibers are a promising material for this because they are strong and durable, and they can also conduct electricity. Carbon fiber laminates are commonly used to make boat hulls already, so adding energy storage capacity to them was a logical step, Ng says.
Past efforts to make carbon fiber electrodes have resulted in damaged fibers, which compromises strength. The UCSD team carefully picked materials and a design that enhanced electrical performance and strength. They coated a fabric woven from carbon fibers with a mix of a conductive plastic and a carbon nanomaterial. The coated fabrics served as electrodes.
Then the researchers made a solid electrolyte by blending a strong epoxy resin with another conductive plastic. They designed the electrolyte so that it is more conductive in the areas near the electrodes and has more epoxy resin in the middle. This strikes the right balance between conductivity and strength.
As a demonstration, the team built a mini solar-powered boat with the supercapacitor. They molded the supercapacitor to form the boat’s hull, and connected to it a small motor and a solar cell. When the put the boat on water in the sunlight, the solar cell charged the supercapacitor, which in turn powered the boat’s motor and propelled it across the water.
“There is still a ways to go especially on the manufacturing challenge,” says Ng, but the large boat demonstration proves that the idea works.
Source: Lulu Yao et al. Structural pseudocapacitors with reinforced interfaces to increase multifunctional efficiency, Sci. Adv. 2023.