One-step hydrothermal synthesis of VO2@PPy nanorods as high-performance anode material for aqueous ammonium-ion batteries

Aqueous ammonium-ion batteries (AAIBs) have emerged as promising candidates for large-scale energy storage systems owing to their inherent safety, low cost, and favorable NH 4 + transport kinetics. However, the practical implementation of AAIBs is severely limited by the lack of high-performance anode materials with excellent rate capability and long-term cycling stability. In this work, a core-shell structured VO 2 @PPy nanorods was synthesized via a facile one-step hydrothermal method. The conductive PPy shell uniformly encapsulates VO 2 nanorods, forming a robust and continuous conductive network. The unique core-shell synergistic effect accelerates charge migration, buffers structural deformation during ion insertion/extraction, and facilitates dominant capacitive charge storage behavior. As a result, the VO 2 @PPy electrode delivers a high specific capacity of 192 mAh g −1 at 0.2 A g −1 , outstanding rate capability (107 mAh g −1 at 6 A g −1 ), and excellent cycling stability with 92% capacity retention after 5000 cycles. Moreover, the assembled VO 2 @PPy//MnO x full cell delivers a maximum energy density of 72 Wh kg −1 at a power density of 33 W kg −1 . This work presents a facile modification strategy for vanadium-based anode materials and provides a practical guidance for the rational design of high-performance electrode materials for advanced AAIBs.