Planar Fully Stretchable Lithium-Ion Batteries Based on a Lamellar Conductive Elastomer

Stretchable Gas Barrier Films Using Liquid Metal toward a Highly Deformable Battery

Highly deformable batteries that are flexible and stretchable are important for the next-generation wearable devices. Several studies have focused on the stable operation and life span of batteries. On the other hand, there has been less focus on the packaging of highly deformable batteries. In wearable devices, solid-state or pouch lithium-ion batteries (LIBs) packaged in aluminum (Al)-laminated films, which protect against moisture and gas permeation, are used. Stretchable elastomer materials are used as the packaging films of highly deformable batteries; however, they are extremely permeable to gas and moisture. Therefore, a packaging film that provides high deformability along with gas and moisture barrier functionalities is required for the stable operation of highly deformable batteries used in ambient conditions. In this study, a stretchable packaging film with high gas barrier functionality is developed successfully by coating a thin layer of liquid metal onto a gold (Au)-deposited thermoplastic polyurethane film using the layer-by-layer method. The film exhibits excellent oxygen gas impermeability under mechanical strain and extremely low moisture permeability. It shows high impermeability along with high mechanical robustness. Using the proposed stretchable gas barrier film, a highly deformable LIB is assembled, which offers reliable operation in air. The operation of the highly deformable battery is analyzed by powering LEDs under mechanical deformations in ambient conditions. The proposed stretchable packaging film can potentially be used for the development of packaging films in advanced wearable electronic devices.

Bioinspired, Shape-Morphing Scale Battery for Untethered Soft Robots

Geometrically multifunctional structures inspired by nature can address the challenges in the development of soft robotics. A bioinspired structure based on origami and kirigami can significantly enhance the stretchability and reliability of soft robots. This study proposes a novel structure with individual, overlapping units, similar to snake scales that can be used to construct shape-morphing batteries for untethered soft robots. The structure is created by folding well-defined, two-dimensional patterns with cutouts. The folding lines mimic the hinge structure of snakeskin, enabling stable deformations without mechanical damage to rigid cells. The structure realizes multi-axial deformability and a zero Poisson's ratio without off-axis distortion to the loading axis. Moreover, to maximize areal density, the optimal cell shape is designed as a hexagon. The structure is applied to a stretchable Li-ion battery, constructed to form an arrangement of electrically interconnected, hexagonal pouch cells. In situ electrochemical characterization and numerical simulation confirm that the shape-morphing scale battery maintains its performance under dynamic deformation with a 90% stretching ratio and 10-mm-radius bending curve, guaranteeing a long-lasting charging/discharging cycle life during cyclic bending and stretching (exceeding 36,000 cycles). Finally, the shape-morphing energy storage device is applied to movable robots, mimicking crawling and slithering, to demonstrate excellent conformability and deformability.

Conductive electrodes of metallic-organic compound CH3CuS nanowires for all-solid-state flexible supercapacitors

Development of wearable electronics puts forward higher requirements for flexible energy storage devices. Lighter and thinner electrodes with high conductivity are one of the key factors to meet this demand. Herein, a conductive paper-based electrode, assembled from metallic-organic compound CH₃CuS nanowires prepared by a one-step thermal solution process, is reported. By using the conductive electrodes of CH₃CuS nanowires, the fabricated all-solid-state supercapacitor device delivers an excellent electrochemical performance: an areal capacitance of 90.5 μF cm^-2 at a current density of 0.5 mA cm^-2, an energy density of 5.2 μW h cm^-2, and 98% retention of initial capacitance after undergoing 10 000 cycles. In particular, the fabricated all-solid-state supercapacitor device can work normally under a bent state. The no-additive, cost-effective, and eco-friendly paper-based electrodes present a potential application prospect in the field of flexible energy storage devices.