Researchers from the Korea Advanced Institute of Science and Technology (Kaist) in Daejeon, South Korea have developed a fabrication technique for high-performance flexible batteries called the universal transfer method.
To make a 10-µm thick flexible battery, researchers deposit battery materials onto a brittle mica substrate and then use sticky tape to peel the mica substrate away layer by layer. After around 10 minutes of peeling, the remaining layers are transferred onto a flexible polymer sheet and covered with another flexible polymer sheet. The result is a flexible Li-ion battery that can be made with the addition of an electrode material. Researchers use lithium cobalt oxide as the cathode material and traditional lithium for the anode material.
The battery can be bent with a high curvature angle because its active parts are stationed in a mechanically neutral space within the film. The battery maintains between 88.2 and 98.4% of its original capacity depending on the degree of bending deformation. It has a charging voltage of 4.2 V and charging capacity of 106 μAh/cm2. After about 100 charge-discharge cycles, the battery loses some of its capacity.
The universal transfer method could be used to make other flexible devices, such as thin-film nanogenerators, thin-film transistors, and thermoelectric devices. Researchers hope to replace the sticky tape with lasers to speed up production time and test 3D stacking.
More information: http://pubs.acs.org/doi/abs/10.1021/nl302254v