Polypyrrole-Doped NH₄V₃O₈ with Oxygen Vacancies as High-Performance Cathode Material for Aqueous Zinc-Ion Batteries

The inherent slow diffusion dynamics of aqueous zinc-ion batteries (AZIBs) act as a significant hindrance to their universal utilization as energy storage systems, largely attributed to the scarcity of superior cathode materials. In this study, a novel method that amalgamates oxygen defect engineering and polymer intercalation, guided by theoretical computations, to confront this challenge, is introduced. This approach begins with density functional theory calculations, demonstrating that the shielding effect rendered by polypyrrole (PPy) between NH4V3O8 (NVO) layers, along with the cooperative influence of oxygen defects (O-d), optimizes the kinetic transport of Zn2+. Leveraging these theoretical outcomes, a two-step hydrothermal synthesis procedure is devised to fabricate PPy-intercalated NVO embedded with O-d (NVO-O-d@PPy). The empirical findings corroborate the theoretical predictions, showcasing that the NVO-O-d@PPy//Zn system manifests exceptional cycling stability. Specifically, the NVO-O-d@PPy electrode delivers an optimal reversible capacity, yielding 421 mAh g(-1) at a current density of 0.1 A g(-1). Remarkably, even at an elevated current density of 10 A g(-1), it sustains a capacity of 175.7 mAh g(-1), while maintaining a capacity retention of 99% over 1000 cycles. This research provides pivotal insights for the engineering of high-performing cathode materials for AZIBs, paving the way for their future advancements.