<p>The expanding deployment of renewable energy systems requires electrochemical energy storage devices capable of stabilizing intermittent power fluctuations while simultaneously providing sustained energy output and rapid charge-discharge response. Although supercapacitors offer exceptional power density and long cycling stability, their relatively low energy density has limited widespread adoption in renewable energy-coupled applications. Addressing this challenge requires rational device engineering that simultaneously enhances charge-storage capacity and expands the operational voltage window, without compromising charge-transfer kinetics. Herein, we report a flexible solid-state asymmetric supercapacitor constructed using tungsten disulfide synthesized via a one-step hydrothermal route. The fabricated flexible device was systematically evaluated for electrochemical characteristics, rate capability, and mechanical resilience under flexible operating conditions. The optimized configuration achieves a stable 2&#xa0;V operating voltage window, delivering a device capacitance of 169.8&#xa0;F g^− 1, an energy density of 94.3 Wh kg^− 1, and a power density of 15,296&#xa0;W kg^− 1, while maintaining robust long-term cycling stability of 10,000 cycles. Importantly, beyond conventional laboratory potentiostatic evaluation, we demonstrate direct hydroelectric-driven charging and scalable voltage integration up to 11&#xa0;V through serial supercapacitor assembly. The device exhibits rapid charge acceptance and flow-dependent charging kinetics under hydrodynamic input, validating its capability to function as a renewable energy buffering unit. By bridging high-voltage solid-state architecture with renewable coupled validation, this work advances asymmetric supercapacitors from material level optimization toward deployable decentralized energy-storage systems.</p> Graphical Abstract <p></p>