3D-printed twisted yarn-type Li-ion battery towards smart fabrics

Flexible batteries have gained significant attention in recent years, owing to their huge demand for portable wearable electronics and smart fabrics. However, conventional Li-ion batteries (LIBs) have limited device adaptability because of their planar architecture. To address this issue, the LIBs are shrunk to a one-dimensional fiber shape, which provides the freedom and flexibility needed for their integration with wearable electronics and smart fabrics. Herein, we demonstrate a method to fabricate twisted yarn-type (TYT) LIBs by a direct ink writing-based three-dimensional printing technology, using natural graphite and LiNi0.6Co0.2Mn0.2O2 as anode and cathode active materials, respectively, along with vapor-grown carbon fibers as an integrated conductive matrix. The printed electrode fibers are twisted together to create anode and cathode yarns, which are then assembled together to obtain a prototype TYT LIB device. The fabricated device performs significantly better in terms of both electrochemical performance and flexibility. The proposed method thus enables the direct integration of batteries into commercial fabrics either in the form of individual electrodes or full devices, which opens up a new route for developing next-generation energy storage devices for smart fabrics.