Stabilizing Water Molecules in Hydrogel Electrolytes Enables 2.8 V‐Class Purely Aqueous Zn–Li Hybrid Batteries

Abstract

ABSTRACT Currently, reported high‐voltage aqueous zinc batteries generally operate below 2.0 V. Achieving a discharge plateau/average operating voltage exceeding 2.0 V typically requires charging voltages above 2.5 V; however, the limited electrochemical stability of water molecules in has thus far prevented purely aqueous zinc batteries from reaching this threshold. Here, we report an extreme water‐confinement strategy that elevates the oxygen evolution potential of water in a poly(acrylamide‐co‐hydroxypropyl acrylate) hydrogel electrolyte to 2.85 V versus Zn/Zn 2+ , far beyond the theoretical value (∼1.58 V versus Zn/Zn 2+ ). This remarkable enhancement originates from the synergistic effects of strong cation–water coordination, TFSI − ‐induced water segregation, and extensive hydrogen bonding within the polymer network, which collectively suppress water activity. When coupled with a lithium nickel manganese oxide cathode, the hydrogel electrolyte enables a 2.8 V‐class Zn–Li hybrid battery that delivers a record‐breaking average operating voltage/discharge plateau of 2.35 V, far exceeding all previously reported purely aqueous zinc batteries. The battery further exhibits excellent mechanical robustness and directly powers a multifunctional wireless sensing monitoring of dynamic pressure, finger movement, muscle activity, speech, and full‐body motion. This work provides a viable pathway toward ultrahigh‐voltage aqueous zinc batteries for next‐generation wearable and intelligent electronic systems.