Silver nanowires/WO3 quantum dots electrode with enhanced vertical electric field gradient for Al3+/Li+ dual-functional electrochromic supercapacitor

Abstract

Dual-functional electrochromic supercapacitors (DECSs), which demonstrate the substantial potential for reversible changes in optical properties and energy storage capabilities, hold considerable promise for a wide range of applications in areas such as smart windows, displays, and wearable electronics. Nevertheless, challenges still exist in effectively optimizing their capacitance, ensuring cycling stability, and achieving cost-effective fabrication. Herein, this study explores an approach by integrating Al3+ and Li+ ions as hybrid electrolyte to enhance electrochemical activity. Utilizing WO3 quantum dots (WQDs) embedded within Ag nanowires (Ag NWs) grids offers a promising strategy to augment the vertical electric field gradient and prevent the self-agglomeration of WQDs. In addition, the integration of hybrid electrolyte comprising Al3+ and Li+ ions not only enhance electrochemical activity but also serves to mitigate the high-cost lithium sources. The resulting Ag NWs/WQDs electrode exhibits an impressive specific capacitance of 681.6 F g−1 at 0.25 mA cm−2 in Al3+/Li+ hybrid electrolyte, a notable 5-fold increase compared to the pristine WQDs electrode in Li+ electrolyte (139.3 F g−1). Simultaneously, this dual-function electrode demonstrates a large optical modulation (81.8 % at 700 nm), a fast switching-speed (tbleaching=7 s, tcoloring=5 s), and a long cycling life (maintaining 84.6 % of its original capacitance after 5000 cycles). Noteworthy insights from COMSOL simulations highlight the Ag NWs grid's "conductive bridge" function, which shows a positive attribution in optimizing the vertical electric field gradient. As a demonstration of proof-of-concept, a large-size flexible dual-functional electrochromic supercapacitor (DECS, 15 cm×10 cm) confirms energy-saving and storage dual-functionality device. Typically, the DECS-equipped inner room experiences a temperature 10°C lower than that of a room with a blank PET within 10 min, indicating the significant irradiation shielding. In addition, this device exhibits a remarkable specific capacitance of 9.25 mF cm−2 at 5 mV s−1, accompanied by an exceptional stability under simulated solar irradiation. The innovation of 0D/1D hierarchical structure of the electrodes together with the hybrid electrolyte not only reduce costs but also enhance the capacitance and cycle stability of DECSs, offering new insights for the development of next-generation flexible electronic wearables.