Extrusion-Based 3D-Printed Supercapacitors: Recent Progress and Challenges

Supercapacitors have been regarded as promising power supplies for future electronics due to their high power density, superior stability, easy integration, and safety. Extrusion-based three-dimensional printing technologies hold promise to satisfy the demands for integrated and flexible supercapacitors because of their highly versatile manufacturing process. In this review article, a comprehensive and timely review of these state-of-the-art technologies is presented. We start with a brief introduction of fundamental concepts of supercapacitors, including energy storage mechanisms and device structures. Then, the latest progress of extrusion-based three-dimensional printing technologies (e.g., fused deposition modeling, inkjet printing, and direct ink writing) along with their applications for manufacturing supercapacitors is summarized. The choice of printable materials (e.g., graphene, carbon nanotubes, metal oxides, and MXenes), printing process, and the resulted electrochemical performances of supercapacitors are especially emphasized. Finally, the development of extrusion-based three-dimensional printing supercapacitors is summarized, with existing challenges diagnosed, possible solutions proposed, and future outlooks forecasted. We hope this review can offer insights to further improve the performance of three-dimensional-printed supercapacitors for practical applications.