Dimensional Engineering-Driven V/O Defect Modulation for Ultrahigh-Energy-Density Aqueous Zinc-Ion Batteries

Achieving high energy density in aqueous zinc-ion batteries (AZIBs) while simultaneously optimizing Zn²⁺ migration kinetics and redox activity remains a formidable challenge. Herein, a novel in situ strategy is developed using glutamic acid as a structural regulator during hydrothermal synthesis, enabling a dimensional transformation of ammonium vanadate and inducing a high density of V/O defects. This engineered structure, featuring abundant V/O defects and interlayer water, facilitates a significant increase in V⁴⁺ content, thereby enhancing redox kinetics and reaction reversibility. As a cathode material for AZIBs, the resulting defect-rich ammonium vanadate (denoted as V/O-NHVO) delivers a high specific capacity of 567.9 mAh g^-1 at 0.1 A g^-1, an energy density of 433 Wh kg^-1, and a peak power density of 3575 W kg^-1, along with excellent cycling stability-retaining 87.9% of its capacity over 2000 cycles. Moreover, the material exhibits promising performance in aqueous magnesium-ion batteries, demonstrating remarkable versatility. This work offers a compelling design paradigm for in situ structure and defect engineering toward high-performance cathode materials for aqueous multivalent-ion batteries.