Towards implantable supercapacitors with high longevity

In the medical field, research on (bio-)electronic devices is a rapidly expanding area. These devices are becoming smaller, wirelessly connected, and independent of the electrical power grid. With the advent of implantable devices, power supply and energy storage have become crucial factors in recent advancements. This work focuses on the development of supercapacitor (SC) devices designed for medical energy storage applications, emphasizing long lifespan, reliability, and stability, alongside a cost-effective and straightforward manufacturing process. To meet the essential requirements of biocompatibility and high electrical conductivity, emphasis was given to the selection and study of materials such as MXenes, graphene, and polyaniline (PANI), all of which have demonstrated potential in bio-based applications. High-performance electrodes were fabricated by combining a highly conductive carbon felt substrate with the active components applied via a scalable doctor blade coating technique. Both symmetrical and asymmetrical SC devices incorporating various material combinations and aqueous electrolytes were evaluated, achieving peak areal capacitances of up to 400 mF/cm 2 . Under specific conditions, remarkable long-term stability was observed, even during the harsh “floating test”. Additionally, the biocompatibility of both the materials and the devices were demonstrated by cytotoxicity and genotoxicity testing according to ISO10993, OECD and ECVAM guidelines. • Symmetrical and asymmetrical supercaps based on 2D materials coated on carbon felt • Carbon felt used as current collector in pouch-cells with acidic electrolytes • Aqueous electrolyte containing PVA remarkably enhances the stability of devices. • All used materials showed excellent biocompatibility. • The devices are likely safe for potential in-vivo applications.