Eco‐Friendly Flexible <scp>PVA</scp> / <scp>AC</scp> /Borax‐Based All‐In‐One Solid‐State Capacitor With Self‐Healing Capability

ABSTRACT This study introduces an all‐in‐one solid‐state capacitor (SSC) fabricated via green synthesis, integrating polyvinyl alcohol (PVA), borax, and activated carbon (AC) to form a flexible, self‐healing system. The All‐in‐One (AiO) design combines electrodes and electrolytes into a PVA/AC/borax composite matrix, eliminating liquid electrolytes and traditional separators, enhancing safety and flexibility. The SSC exhibited remarkable electrochemical performance, and cyclic voltammetry (CV) analysis demonstrated electric double‐layer capacitors (EDLCs) behavior. The CCD tests at 10 mV s −1 showed a maximum discharge capacitance of ~74 mF g −1 after 1000 cycles, with capacity retention exceeding 95% and coulombic efficiency above 98%. The calculated energy and power density at 10 mV s −1 were approximately 0.03 and 0.63 mW g −1 , respectively, reflecting the system's suitability for low‐power applications despite the trade‐off in capacitance due to the solid‐state design. FTIR and UV–Vis spectroscopy confirmed AC integration into the structure. The SSCs' flexibility and self‐healing, enabled by reversible diol‐borate bonds, allow them to repair damage within minutes upon rehydration. EIS revealed a high charge transfer resistance (300–400 kΩ), indicating limited ion mobility at higher scan rates. These findings indicate that the PVA/AC/borax SSC is promising for sustainable energy storage in low‐rate applications, with potential for high‐rate performance optimization.