Prominent Electrochromism Achieved Using Aluminum Ion Insertion/Extraction in Amorphous WO₃ Films

Abstract

Although monovalent lithium has been successfully used as a coloring ion in electrochromic applications, it still faces the challenges of low safety, high cost, and limited reserves. Herein, we demonstrate that the amorphous WO3 films intercalated with Al3+ ions could exhibit desired wide optical modulation (∼63.0%) and high coloration efficiency (∼72.0 cm2 A–1, which is >100% higher than that with Li+ or Na+), benefiting from the three-electron redox properties of aluminum. Due to the strong electrostatic force and large atomic weight, the charge exchange processes for Al3+ ions are limited only to the near-surface region and consequently bring about enhanced electrochromic stability. Our findings provide in-depth insights into the nature of electrochromism and also open up a new route toward scalable electrochromic devices using sputtering techniques and earth-abundant materials.

Two-dimensional WO3 nanosheets for high-performance electrochromic supercapacitors

“…[21][22][23] To address these issues, Al 3+ ionbased electrolytes were selected instead for monovalent insertion ions due to a number of key advantages, such as their small ionic radius (0.53 Å), cost-effectiveness, environmental friendliness, high capacity (three-electron redox reactions), shallow embedding depth, and safety. [24][25][26] Therefore, Al 3+ ions were selected to be the insertion ions for WO 3 to guarantee comprehensive optical-electrochemical performances.…”

Rechargeable Zn2+/Al3+ dual-ion electrochromic device with long life time utilizing dimethyl sulfoxide (DMSO)-nanocluster modified hydrogel electrolytes

“…Most importantly, the trivalent Al 3+ intercalation into WO 3 electrodes allows for increased lifetime of the electrochromic WO 3 electrode due to the Al 3+ ions shallow insertion depth and the multivalent electron transfer process during Al 3+ -WO 3 intercalation. 26 While these ndings give insights into the mechanisms of intercalation itself, the applications are so far limited by the liquid nature of the electrolytes used.…”

Electrochromic Materials Based on Ions Insertion and Extraction

“…[ 117 ] If the charge density is high, M sites will have a high probability to contact electrons, obtaining high polaronic M sites on the same charge insertion level. [ 118 ] However, the practical application of monovalent ions‐based ECMs has various limitations, for example, the corrosiveness of H ions, the high cost of Li ions, and the large radius of Na ions, etc. In addition to monovalent ions, multivalent ions which have the advantages of low cost and small ionic radius are also promising ions.…”

“…Guo et al studied the impact of valency and ionic radius on the electrochromic performance of a‐WO 3 films in nonaqueous electrolytes containing Li + , Na + , and Al 3+ ( Figure a). [ 118 ] The corresponding transmittance degradation of electrolytes containing Li + in the bleached states was observed due to the charge accumulation of a‐WO 3 film during cycles. Due to the destruction of the ion diffusion channel by excessive lattice expansion, the transmittance decreases obviously in the films with a larger Na + radius.…”