Recent Progress in Flexible Fibrous Batteries

Soft Fiber Electronics Based on Semiconducting Polymer

Fibers, originating from nature and mastered by human, have woven their way throughout the entire history of human civilization. Recent developments in semiconducting polymer materials have further endowed fibers and textiles with various electronic functions, which are attractive in applications such as information interfacing, personalized medicine, and clean energy. Owing to their ability to be easily integrated into daily life, soft fiber electronics based on semiconducting polymers have gained popularity recently for wearable and implantable applications. Herein, we present a review of the previous and current progress in semiconducting polymer-based fiber electronics, particularly focusing on smart-wearable and implantable areas. First, we provide a brief overview of semiconducting polymers from the viewpoint of materials based on the basic concepts and functionality requirements of different devices. Then we analyze the existing applications and associated devices such as information interfaces, healthcare and medicine, and energy conversion and storage. The working principle and performance of semiconducting polymer-based fiber devices are summarized. Furthermore, we focus on the fabrication techniques of fiber devices. Based on the continuous fabrication of one-dimensional fiber and yarn, we introduce two- and three-dimensional fabric fabricating methods. Finally, we review challenges and relevant perspectives and potential solutions to address the related problems.

Material Choice and Structure Design of Flexible Battery Electrode

With the development of flexible electronics, the demand for flexibility is gradually put forward for its energy supply device, i.e., battery, to fit complex curved surfaces with good fatigue resistance and safety. As an important component of flexible batteries, flexible electrodes play a key role in the energy density, power density, and mechanical flexibility of batteries. Their large-scale commercial applications depend on the fulfillment of the commercial requirements and the fabrication methods of electrode materials. In this paper, the deformable electrode materials and structural design for flexible batteries are summarized, with the purpose of flexibility. The advantages and disadvantages of the application of various flexible materials (carbon nanotubes, graphene, MXene, carbon fiber/carbon fiber cloth, and conducting polymers) and flexible structures (buckling structure, helical structure, and kirigami structure) in flexible battery electrodes are discussed. In addition, the application scenarios of flexible batteries and the main challenges and future development of flexible electrode fabrication are also discussed, providing general guidance for the research of high-performance flexible electrodes.

Co3O4 Nanoneedle Array Grown on Carbon Fiber Paper for Air Cathodes towards Flexible and Rechargeable Zn-Air Batteries

An economical and efficient method is developed for preparing flexible cathodes. In this work, a dense mesoporous Co₃O₄ layer was first hydrothermally grown in situ on the surface of chopped carbon fibers (CFs), and then carbon fiber paper (Co₃O₄/CP) was prepared by a wet papermaking process as a flexible zinc-air battery (ZAB). The high-performance air cathode utilizes the high specific surface area of a single chopped carbon fiber, which is conducive to the deposition and adhesion of the Co₃O₄ layer. Through the wet papermaking process, Co₃O₄/CP has ultra-thin, high mechanical stability and excellent electrical conductivity. In addition, the assembled ZAB exhibits relatively excellent electrochemical performance, with a continuous cycle of more than 180 times at a current density of 2 mA·cm⁻². The zinc-air battery can maintain a close fit and work stably and efficiently even under high bending conditions. This process of combining single carbon fibers to prepare ultra-thin, high-density, high-conductivity carbon fiber paper through a papermaking process has huge application potential in the field of flexible wearables.