A Biomimetic Alveoli-in-Lung-Structured Electrode: Robustly Anchored Tungsten Oxide Quantum Dot on Ti₃C₂ MXene for Multifunctional Sodium-Ion-Based Electrochromic Devices

Sodium-ion-based electrochromic device (SECD) has been identified as an appealing cost-effective alternative of lithium-based counterparts, only if it can address the challenges in association with the inadequate electrochromic performance. In this regard, the quantized strategy is a particularly promising approach owing to the large surface-to-volume ratio and high reaction activity. However, quantum dots inevitably suffer from volume changes and undesired aggregation during electrochemical cycling. Herein, bioinspired from the robust connection of alveoli in lung, we propose a stable electrode, where WO₃ quantum dots (WQDs) are robustly anchored on Ti₃C₂ MXene through the strong chemical bonds of W-O-Ti. Theoretical results reveal the fundamental mechanism of the volume changes within WQDs and the dynamic diffusion process of sodium ions. The WQD@MXene electrodes exhibit a nearly twofold enhancement in cycling performance (1000 vs 500 cycles), coloration speed (3.2 vs 6.0 s), and areal capacity (87.5 vs 43.9 mAh m⁻² at 0.1 mA cm⁻²), compared to those of the pristine WQD electrode. As a proof-of-concept demonstration, a smart house system integrated with SECDs demonstrates a “3-in-1” device, enabling a combination of energy-saving, energy storage, and display functionalities. The present work significantly advances the versatile applications of cost-effective electrochromic electronics in interdisciplinary.