Engineering Interlayer Space of Vanadium Oxide by Pyridinesulfonic Acid-Assisted Intercalation of Polypyrrole Enables Enhanced Aqueous Zinc-Ion Storage.

By adjusting the structure of vanadium oxides, their electrochemical performances as cathode materials for aqueous rechargeable zinc-ion batteries (ARZIBs) can be improved effectively. Due to the layered structure and high specific capacity of V2O5, many guests (like metal ions and conducting polymers) intercalated and regulated the structure to enhance its electrochemical properties. Polypyrrole (PPy) has attracted people's attention due to its good conductive ability. However, the intercalation of PPy into a lamellar structure of hydrated V2O5 (VOH) has rarely been achieved as a cathode material for ARZIBs. Herein, we developed a pyridinesulfonic acid (PSA)-assisted approach to intercalate PPy into the interplanar spacing of VOH under acidic conditions, and the sample is denoted as VOH-PPy (PSA). The presence of protic acid can improve the electrical conductivity of the polymer and enhance the oxidation of VOH, making the polymerization of pyrrole easier. Furthermore, the nitrogen-containing groups in PSA can interact with vanadium to further expand the layer space of VOH, and the sulfonic groups can facilitate the polymerization of pyrrole. The addition of the PSA results in an ultralarge interlayer spacing of 15.8 Å. VOH-PPy (PSA) delivers an excellent specific capacity of up to 422 mAh·g-1 at 0.1 A·g-1 and a stable cycle performance of 165 mAh·g-1 after 5000 cycles at 10 A·g-1. This work not only realizes PPy expanding the lamellar structure of VOH but also provides feasibility for improving the electrochemical properties of VOH as a cathode material for ARZIBs by intercalating conductive polymers.