High‐Toughness Hydrated Polymer Electrolytes for Advanced Structural Supercapacitors

Structural supercapacitors that simultaneously bear mechanical loads and store electrical energy have exciting potential for enhancing the efficiency of various mobile systems. However, a significant hurdle in developing practical structural supercapacitors is the inherent trade‐off between their mechanical properties and electrochemical capabilities, particularly within their electrolytes. This study demonstrates a tough polymer electrolyte with enhanced multifunctionality made through the controlled hydration of a solid polymer electrolyte with poly(lactic acid) (PLA) and lithium salts. Characterization via differential scanning calorimetry, X‐ray diffraction, and Fourier transform infrared spectroscopy confirms the consistent amorphous solid solution phase in varying salt concentrations, whether dried or hydrated. Electrochemical tests and tensile tests are performed to evaluate the ionic conductivity and mechanical properties of these electrolytes. The results indicate that the strategic incorporation of water in the polymer electrolyte significantly enhances the ionic conductivity while preserving its mechanical properties. A specific composition demonstrated a remarkable increase in ionic conductivity (3.11 µS cm−1) coupled with superior toughness (15.4 MJ m−3), significantly surpassing the base polymer. These findings open new horizons for integrating electrochemical functionality into structural polymers without compromising their mechanical properties. Additionally, the paper reports the successful fabrication and testing of structural supercapacitor prototypes combining carbon fibers with fabricated electrolytes, showcasing their potential for diverse applications.