A Flexible Solid-State Aqueous Zinc Hybrid Battery with Flat and High-Voltage Discharge Plateau

The migration of zinc-ion batteries from alkaline electrolyte to neutral or mild acidic electrolyte promotes research into their flexible applications. However, discharge voltage of many reported zinc-ion batteries is far from satisfactory. On one hand, the battery voltage is substantially restricted by the narrow voltage window of aqueous electrolytes. On the other hand, many batteries yield a low-voltage discharge plateau or show no plateau but capacitor-like sloping discharge profiles. This impacts the battery's practicability for flexible electronics where stable and consistent high energy is needed. Herein, an aqueous zinc hybrid battery based on a highly concentrated dual-ion electrolyte and a hierarchically structured lithium-ion-intercalative LiVPO₄F cathode is developed. This hybrid battery delivers a flat and high-voltage discharge plateau of nearly 1.9 V, ranking among the highest reported values for all aqueous zinc-based batteries. The resultant high energy density of 235.6 Wh kg^-1 at a power density of 320.8 W kg^-1 also outperforms most reported zinc-based batteries. A designed solid-state and long-lasting hydrogel electrolyte is subsequently applied in the fabrication of a flexible battery, which can be integrated into various flexible devices as powerful energy supply. The idea of designing such a hybrid battery offers a new strategy for developing high-voltage and high-energy aqueous energy storage systems.