Using an origami-folding pattern similar to how maps are folded, they folded the paper into a stack of 25 layers, producing a compact, flexible battery that provides significant energy density – or the amount of energy stored in a given system or space per unit of volume of mass.
The above image illustrates the architecture of a foldable lithium-ion battery ASU engineers have constructed using paper coated with carbon nanotubes. They began with a porous, lint-free paper towel, coated it with polyvinylidene difluoride to improve adhesion of carbon nanotubes and then immersed the paper into a solution of carbon nanotubes. Powders of lithium titanate oxide and lithium cobalt oxide – standard lithium battery electrodes – are sandwiched between two sheets of the paper. Thin foils of copper and aluminum are placed above and below the sheets of paper to complete the battery.
The researchers have also developed a new process to incorporate a polymer binder onto the carbon nanotube-coated paper. The polymer binder improves adhesion of the structure’s active materials.
The achievements open up possibilities of using the origami technique to create new forms of paper-based energy storage devices, including batteries, light-emitting diodes, circuits and transistors, says Candace Chan, who led the research team.