Smart Energy Storage: W₁₈O₄₉ NW/Ti₃C₂T_x Composite‐Enabled All Solid State Flexible Electrochromic Supercapacitors

AbstractDeveloping a highly efficient electrochromic energy storage device with sufficient color fluctuation and significant electrochemical performance is highly desirable for practical energy‐saving applications. Here, to achieve a highly stable material with a large electrochemical storage capacity, a W18O49 NW/Ti3C2Tx composite has been fabricated and deposited on a pre‐assembled Ag and W18O49 NW conductive network by Langmuir–Blodgett technique. The resulting hybrid electrode composed of 15 layers of W18O49 NW/Ti3C2Tx composite exhibits an areal capacitance of 125 mF cm−2, with a fast and reversible switching response. An optical modulation of 98.2% can be maintained at a current density of 5 mA cm−2. Using this electrode, a bifunctional symmetric electrochromic supercapacitor device having an energy density of 10.26 µWh cm−2 and a power density of 0.605 mW cm−2 is fabricated, with high capacity retention and full columbic efficiency over 4000 charge‐discharge cycles. Meanwhile, the device displays remarkable electrochromic characteristics, including fast switching time (5 s for coloring and 7 s for bleaching), and a significant coloration efficiency of 116 cm2 C−1 with good optical modulation stability. In addition, the device exhibits significant mechanical flexibility and fast switching while being stable over 100 bending cycles, which is promising for real‐world applications.