Sodium Solid-State Electrolytes for Superior Ionic Conductivity

Composite solid electrolytes are central to the advancement of sodium-based energy storage technologies, yet challenges in interfacial contact and mechanical reliability persist. In this study, NASICON-containing polyethylene oxide (PEO)-based composite electrolytes were fabricated with varying EO:Na ratios and NASICON contents. The optimized composition, with an EO:Na ratio of 15:1 and 25 wt% NASICON, achieved an ionic conductivity of 5 10 S cm at 30 degrees C. A custom-designed compression and temperature-controlled test rig was developed specifically for this study to evaluate the mechanical response of the electrolyte under repeated compressive loading. Ionic conductivity measurements under low pressure (60 kPa) revealed a baseline value of 5.74 10 S cm. After two compressive cycles at 825 kPa, the conductivity increased to 6.81 10 S cm at room temperature, corresponding to an 18.6% enhancement due to improved interfacial contact. However, a third compression cycle induced interfacial deterioration and mechanical damage, resulting in conductivity loss. This structural degradation-manifested by local delamination and tearing-was confirmed through scanning electron microscopy (SEM) imaging. These findings demonstrate that controlled mechanical conditioning enhances transport properties up to a critical threshold, beyond which irreversible damage limits performance. The methodology presented offers insights into mechanical-electrochemical coupling in composite solid electrolyte systems.