A biocompatible, thin, wet-adhesive, and high-performance zinc-ion hybrid supercapacitor as an implantable power source for biomedical application

Functional bioelectronic implants necessitate energy storage modules as power sources in vivo. Existing energy storage implants grapple with balancing factors such as high performance, biosafety, mechanical properties matching soft tissues, and conformal adhesion. Herein, we report a thin, flexible, and wet-adhesive zinc-ion hybrid supercapacitor (ZHSC) as an implantable power source with high biocompatibility and superior performance. The thin implantable ZHSC (0.142 mm) comprises a MXene (Ti₃C₂T_x)-based cathode and a gel electrolyte-integrated Zn anode, with strongly connected interfaces, ensuring good mechanical flexibility and stable electrochemical performance. Specifically, the ZHSC exhibits an areal capacitance of 482.58 mF cm⁻² and an energy density of 7.37 mWh cm⁻³, surpassing majority of recently reported biocompatible energy storage devices. The ZHSC equipped with integrated electrolyte achieves an outstanding capacity retention rate of 96.4 % after 10000 cycles at 5 A g⁻¹, significantly superior to that of a device using a conventional separated electrolyte (75.6 %). The ZHSC also demonstrates excellent wet adhesion upon introduction of a silk protein encapsulation film, which can adhere firmly to curved and wet biological tissues/organs. Comprehensive in vitro and in vivo studies demonstrate that the ZHSC, with high biosafety, can provide stable power supply after implantation in rats. Importantly, the implantable ZHSC can degrade in vivo with no toxic produced substances during the degradation process. This work provides an example for the design and fabrication of biocompatible, thin, and wet-adhesive implantable energy storage devices with superior properties.