Coaxial nanostructure of PEDOT/MnO2/CNTs enabled flexible, solid-state, and miniature zinc-ion battery for wide electrochemical stability window and high energy-density toward bioelectronics applications

Emerging implantable bioelectronics for healthcare monitoring and biomedical therapy demand miniaturized energy storage devices. Among these devices, aqueous zinc-ion batteries have received much attention due to their outstanding safety, low cost, and environmental friendliness. However, they suffer from quick capacity fading, low energy density, and poor stability because of the manganese dissolution, sluggish electron transfer, structure instability, and narrow electrochemical stability window (ESW). Herein, coaxial PEDOT/MnO 2 /CNTs are synthesized and assembled for nanostructured cathodes while wide ESW ionogels are used as electrolytes, resulting in quasi-solid-state flexible zinc-ion batteries. The multilayer coaxial nanostructure of PEDOT/MnO 2 /CNTs overcomes the challenges of manganese dissolution, promotes electrical conductivity, and escalates ion diffusion, demonstrating high capacity (239.6 mAh/g at 1.0 A/g) and high stability (95% retention after 500 cycles compared to 56% retention for state-of-the-art). The ionic liquid-enabled ionogel electrolyte shows an ESW as high as 2.79 V compared to the current ESW of 1.81 V. The calculated energy density is 459.1 Wh/kg, around 3-fold higher than the state-of-the-art. Under different bending angles (0, 45, 90, 180°), the electrochemical performance is characterized, showing <6% performance loss. The in vitro cell test confirms excellent biocompatibility with almost 100% cell viability. Coaxial PEDOT/MnO 2 /CNTs electrode/ionogel-based miniature battery shows a high electrochemical stability window, large energy density, outstanding flexibility, and exceptional biocompatibility. • Synthesis of Coaxial nanostructure of PEDOT/MnO 2 /CNTs as an electrode of the soft battery • Multilayer core/shell structure electrodes prevent the capacity fading caused by the MnO2 dissolving in the electrolyte. • High electrochemical stability window of the soft battery • High Energy density of the soft battery • High flexibility with outstanding cycle bending from 0, 45, 90, 180° • Excellent biocompatibility