Abstract
Structural supercapacitors are promising candidates for future multifunctional energy storage components. Practical structural supercapacitors require electrolytes that simultaneously enable efficient ionic transport and mechanical load-bearing capability, a combination limited by the inherent trade-off between conductivity and stiffness in previous research. In this work, a single-phase polyethylene terephthalate (PET) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) solid polymer electrolyte (SPE) is developed using injection molding followed by post-fabrication solvent conditioning via humidity chamber and vaporized solvent dispersion system. This strategy decouples electrolyte fabrication from transport tuning while preserving structural integrity, thereby significantly mitigating the trade-off between electrochemical and mechanical properties. An optimized 0.8PET + 0.2LiTFSI (SPE:20) composition exhibits a flexural modulus of 3.93–4.0 GPa while maintaining a baseline ionic conductivity of 1.7–1.9 nS cm−1, establishing a mechanically robust reference state. Post-fabrication conditioning enables significant and tunable enhancements in ionic conductivity. Controlled hydration of 3 wt% increases ionic conductivity to 62.5 μS cm−1 while retaining stiffness. Organic solvent conditioning produces solvent-specific responses: acetonitrile and dimethylformamide achieve conductivities on the order of 10−7 S cm−1, while dimethyl sulfoxide results in minimal enhancement. These results demonstrate that post-fabrication solvent conditioning provides a practical design axis for tuning ionic conductivity in structurally rigid solid polymer electrolytes, advancing the development of multifunctional electrolytes for structural energy storage applications.
•Post-fabrication solvent conditioning tunes PET/LiTFSI SPE transport.•Hydration raises conductivity to 62.5 μS cm−1 in rigid electrolytes.•SPE:20 retains 4 GPa modulus while enabling transport tuning.•Organic vapors provide tunable electro-mechanical response.•Results establish a design map for structural supercapacitor electrolytes.