Stretchable Li-Ion Battery Using Origami Scale Structure for Untethered Soft Robots

In recent years, technology of soft robotics has emerged as an important issue for the robot industry. Compared to conventional industrial metallic robots in controlled environments, soft robots are highly expandable in responding to non-standardized environments. Due to these characteristics, it is expected to be used not only in daily life, but also in specific applications such as treatment of disease and disaster relief. The development of a structure that is free to deformation with energy source is also essential to improve the technology. The integration of flexible structure and energy supply is very important to reduce the waste of space and weight of soft robots for versatility and portability. However, there are many difficulties due to the absence of batteries with high reliability under deformation. In this study, we propose a novel geometric structure for stretchable devices, created by folding well-defined two-dimensional patterns with cutouts to produce an extremely stretchable structure with superior reliability and bi-axial deformability. The structure is designed to mimic the hinge of a snakeskin so that its unit cells do not interfere with each mutual movement enabling stable deformations without mechanical damage. In addition, to maximize areal density and stretchability, the optimal shape of unit is determined. The unit-based geometric structure is applied to a stretchable Li-ion battery and constructed of hexagonal pouch cells and parallelogram interconnections. In situ electrochemical characterization confirms that the performance of the battery is maintained under dynamic deformation with a stretching ratio of 90% and a 10-mm-radius bending curvature, guaranteeing a long-lasting cycle life. Finally, the geometrically designed structure-based battery is applied to movable robots, crawling and slithering, with dynamic bi-axial deformations and can be pivotal role in the development of flexible electronics including human-friendly wearable electronics and soft robots.