A decrease in impedance of monolithic activated carbon cloth electrodes at increased charge density

Textiles have emerged as a potential material class for robots that can be worn as regular garments in various forms and arrangements. Despite tremendous progress, textile-based actuation or energy-storage systems are in need of higher performance, more sustainable, safer, and abundant materials. Carbon is an excellent candidate for flexible electrodes, yet most available electrodes suffer from carbon-to-carbon charge transfer losses. Activated carbon cloth (ACC) is a promising electron-to-ion transducer material that combines high specific surface area and monolithic structure that offers the possibility to transfer electrons within a continuous structure of even a meter scale without carbon-to-carbon contacts. This contrasts with composite electrodes (CEs) that experience repulsion of like charges upon charging, in turn rendering a charged composite electrode less conductive due to an increased distance for electron tunneling. Moreover, as the formation of an electrical double-layer at the electrode surface increases the local charge density, the impedance is expected to decrease. In CEs, this increase is obscured by interparticle contacts, but can be significant in ACCs due to its monolithic structure. The monolithic nature of ACC thus results in unique electrical characteristics: upon injecting more charge to an electroactive laminate with ACC electrodes, the system becomes increasingly conductive. This work investigates the in-situ impedance of an ACC electrode whilst charging intermittently. Favorable impedance behavior makes ACC an attractive electrode material for wearable technologies and medical devices.