Growing concerns about the reliability and safety of modern energy storage technologies have intensified efforts to redesign core material components and device structures. Conventional batteries and supercapacitors rely on liquid electrolytes and reactive alkali-metal chemistries, which can introduce safety risks during operation. To address these challenges, solid-state electrolytes (SSEs) have emerged as promising alternatives by eliminating volatile liquid phases from devices and modules. Recently, environmentally benign fabrication strategies using water as the processing medium have further expanded their appeal. In parallel, sodium-based SSEs have been highlighted due to the abundance and cost-advantage of sodium over lithium. This work demonstrates water-processable sodium-based polymer SSEs with pronounced ion-transport characteristics leading to high long-term cycling stability.