Fully‐Printed Flexible Aqueous Rechargeable Sodium‐Ion Batteries

Abstract The flexible aqueous rechargeable sodium‐ion batteries (ARSIBs) are a promising portable energy storage system that can meet the flexibility and safety requirements of wearable electronic devices. However, it faces huge challenges in mechanical stability and facile manufacturing processes. Herein, the first fully‐printed flexible ARSIBs with appealing mechanical performance by screen‐printing technique is prepared, which utilizes Na₃V₂(PO₄)₂F₃/C (NVPF/C) as the cathode and 2% nitrogenous carbon‐loaded Na₃MnTi(PO₄)₃/C (NMTP/C/NC) as the anode. In particular, the organic co‐solvent ethylene glycol (EG) is cleverly added to 17 m (mol kg⁻¹) NaClO₄ electrolyte to prepare a 17 m NaClO₄‐EG mixed electrolyte. This mixed electrolyte can withstand low temperatures of −20 °C in practical applications. Encouragingly, the fully‐printed flexible ARSIBs (NMTP/C/NC//NVPF/C) exhibit a discharge capacity of 40.1 mAh g⁻¹, an energy density of 40.1 Wh kg⁻¹, and outstanding cycle performance. Moreover, these batteries with various shapes can be used as an energy wristband for an electronic watch in the bending states. The fully‐printed flexible ARSIBs in this work are expected to shed light on the development of energy for wearable electronics.