Density-Tunable PEDOT:PSS Fibrous Sponges via Ice-Induced Self-Fusion for Soft and Stretchable Organic Batteries

In this study, we developed density-tunable fibrous PEDOT sponges for soft and stretchable organic batteries through freeze-induced self-fusion of PEDOT fibers. During freezing, ice crystal growth generates excluded-volume effects that promote fiber–fiber contact, while the accompanying local dehydration facilitates self-fusion through enhanced π–π stacking between PEDOT domains. The density of the resulting sponges can be readily controlled by varying the ratio of PEDOT fibers to water, thereby enabling systematic tuning of their electrical, mechanical, and electrochemical properties. By leveraging this density-dependent property control, the fibrous PEDOT sponges were employed as electrodes in an organic redox-diffusion battery. An optimal sponge density was identified to balance mechanical deformability and electrochemical performance, resulting in a stretchable energy-storage device with excellent electrochemical performance.