Electrochromic (EC) technology is increasingly recognized for its potential to improve energy efficiency, particularly through smart windows that modulate transparency to reduce reliance on artificial lighting and air conditioning. While EC devices generally require low external voltages to switch between colored and bleached states, further advancements are still needed to reduce energy consumption and achieve more efficient, sustainable performance. A promising solution lies in integrating EC materials with energy storage systems, offering a dual-purpose approach that enables light modulation and energy storage functionality. Numerous studies have explored zinc (Zn)-based EC energy storage devices, owing to their high theoretical specific capacity, environmental compatibility, and the abundance of zinc metal. However, the performance of Zn2+-based electrolytes is often constrained by large hydrated ion sizes and a limited electrochemical stability window. To address these limitations, this study focused on investigating water-in-bisalt (WiBS) electrolytes with varying Zn2+/Al3+ electrolyte composition to enhance both energy storage capability and EC functionality. Additionally, tungsten trioxide (WO3) was selected as the EC material due to its proven coloration efficiency, optical modulation, and cyclic stability. Deduced from the measurement, the 10 M Zn + 3 M Al electrolyte was identified as the optimal formulation, enabling the WO3 energy storage device to achieve an outstanding energy storage capacity of 146 mAh/m2, excellent optical contrast (80.5%), high coloration efficiency (35.3 cm2/C), and excellent cyclic stability of 75% after 1000 cycles. This research highlights the potential of advanced WiBS electrolytes in EC energy storage technologies, paving the way for applications in energy storage integrated smart windows and real-time energy indicators.
Tan et al. (Fri,) studied this question.