Mechanically robust and transparent supercapacitors with electrochromic properties using a lithium chloride–doped polymer membrane electrolyte and optimized tungsten oxide-based electrodes

The simultaneous realization of mechanical flexibility, optical transparency, and electrochemical stability remains a critical challenge for next-generation wearable electronics. Herein, we demonstrate a mechanically robust transparent supercapacitor with electrochromic capability based on an optimized WO₃/ITO/PET heterostructure coupled with a LiCl-doped PVDF-co-HFP membrane electrolyte. By precisely tuning the active WO₃ layer thickness to 300 nm on ITO/PET substrates, the electrode architecture effectively buffers mechanical strain while ensuring homogeneous ion transport, yielding a high areal capacitance of 42 mF cm −2 at 0.1 mA cm −2 . When assembled into a symmetric device, the solid-state system operates within a wide potential window of ±2.5 V and exhibits extraordinary mechanical endurance, retaining 94% of its initial capacitance after 20,000 bending cycles ( r = 3 mm), significantly outperforming conventional gel-based counterparts. These results establish the optimized WO₃/ITO/PET architecture as a promising, highly durable platform for transparent and deformable energy storage systems.