Abstract: The large-scale integration of renewable energy places increasingly stringent demands on the safety, cost, service life, and operational reliability of stationary energy-storage technologies. Aqueous zinc-ion batteries are promising candidates because zinc is abundant and inexpensive, aqueous electrolytes are intrinsically nonflammable, and cell fabrication does not require strictly anhydrous and oxygen-free environments. Their practical development, however, remains constrained by cathode structural degradation, nonuniform zinc deposition, hydrogen evolution and corrosion, the limited electrochemical stability window of aqueous electrolytes, and the incomplete transfer of laboratory-scale material performance to practical cells. This review establishes a cross-scale analytical framework that links energy-storage mechanisms, key materials, practical full-cell conditions, ampere-hour-scale cells, and operational monitoring. Recent studies are classified according to cathode stabilization, zinc-anode interfacial regulation, electrolyte solvation and additive engineering, and separator-mediated ion-transport control. Representative practical cells are then compared using cathode areal loading and areal capacity, negative-to-positive capacity ratio, electrolyte-to-capacity ratio, zinc utilization, full-cell gravimetric and volumetric energy densities, cycle life, calendar aging, and cumulative capacity throughput. Long-term behavior is further organized into an operating-stress–failure-process–quantitative-indicator hierarchy that connects cycling, standby, temperature, and dynamic-power demands with zinc corrosion, gas evolution, dendrite growth, cathode dissolution, and impedance increase, as well as capacity retention, Coulombic efficiency, energy efficiency, and rest-capacity loss. This approach distinguishes genuine materials advances from performance gains produced by excess zinc, excess electrolyte, or low active-material loading. The synthesis shows that Zn2? insertion/extraction, H? participation, multicarrier co-storage, and dissolution–deposition reactions may coexist or dominate in different cathode systems. Consequently, voltage profiles alone cannot identify the actual capacity origin, and a combined evidence chain involving phase, valence state, mass, solution species, and local interfacial environment is required. Quantitative comparison further reveals a substantial scale-dependent performance gap. A representative cell delivers 119.8 W·h·kg?1 when calculated from active materials but only 33.6 W·h·kg?1 on a full-cell basis, corresponding to approximately 28% of the material-level value. Existing 1.0–2.7 A·h pouch cells generally achieve volumetric energy densities of 68–79.5 W·h·L?1, whereas their cycle lives under relatively practical material constraints are commonly limited to 120–390 cycles. Electrolyte coordination and interfacial regulation reduce the daily self-discharge rate of a pouch cell to 0.13% and retain 93% of its capacity after 900 cycles at 25 °C. Calendar-aging studies report 96.2% capacity retention after 1000 h of intermittent resting, while representative wide-temperature systems operate from ?60 to 80 °C. These isolated results nevertheless require validation under unified material and testing boundaries. For large-format cells, in situ pressure and pH sensors provide sensitivities of 137 nm·MPa?1 and 74.51 mV·pH?1, respectively, demonstrating feasible routes for detecting gas evolution and interfacial abnormalities. The main contribution of this review is therefore not a component-by-component catalogue, but an evidence-based connection between material regulation and usable cell-level energy, lifetime, and reliability. Future research should coordinate material and full-cell design, standardize coupled cycle- and calendar-aging protocols, and develop multiparameter monitoring for ampere-hour-scale cells and small series-connected modules. These measures are essential for determining whether aqueous zinc-ion batteries can progress from laboratory demonstrations to reliable stationary energy-storage deployment.