Cations-Pillared and Polyaniline-Encapsulated Vanadate Cathode for High-Performance Aqueous Zinc-Ion Batteries.

Layered vanadium-based oxides have emerged as highly promising candidates for aqueous zinc-ion batteries (AZIBs) due to their open-framework layer structure and high theoretical capacity among the diverse cathode materials investigated. However, the susceptibility to structural collapse during charge-discharge cycling severely hampers their advancement. Herein, we propose an effective strategy to enhance the cycling stability of vanadium oxides. Initially, the structural integrity of the host material is significantly reinforced by incorporating bi-cations Na+ and NH4 + as "pillars" between the V2O5 layers (NaNVO). Subsequently, surface coating with polyaniline (PA) is employed to further improve the conductivity of the active material. As anticipated, the assembled Zn//NaNVO@PA cell exhibits a remarkable discharge capacity of 492 mAh g-1 at 0.1 A g-1 and exceptional capacity retention up to 89.2 % after 1000 cycles at a current density of 5 A g-1. Moreover, a series of in-situ and ex-situ characterization techniques were utilized to investigate both Zn ions insertion/extraction storage mechanism and the contribution of polyaniline protonation process towards enhancing capacity.

Recent Progress on Phosphate Cathode Materials for Aqueous Zinc-Ion Batteries.

Rechargeable zinc-ion batteries (ZIBs) are attractive for large-scale energy storage due to their superiority in resources, safety, and environmental friendliness. However, the lack of suitable ZIBs cathode materials limits their practical applications. In consideration of the excellent electrochemical performance of phosphate materials in monovalent ion (Li+ , Na+ ) batteries, they were also employed as ZIBs cathode materials recently and performed well with high potential. But they also suffer from low capacity and poor conductivity, and the energy storage mechanism is not clear yet. This Review provides a state-of-the art overview on the developments of phosphate cathode materials in ZIBs, including NASICON-type phosphates, fluorophosphates, olivine-structured, layered-structured, and novel-structured phosphate materials mainly. This study presents the reaction mechanism and electrochemical performance of phosphate cathode materials in aqueous ZIBs, and future research directions are discussed, which are intended to provide guidance for exploring high-potential cathode materials for ZIBs.