Tunable Intracrystal Cavity in Tungsten Bronze‐Like Bimetallic Oxides for Electrochromic Energy Storage

Abstract

Designing materials with appropriate crystal and electronic structures to enhance ionic and electronic transport simultaneously are highly desirable for both electrochromic and electrochemical energy storage devices. It remains a great challenge to simultaneously meet these requirements. Here, a Nb18W16O93 nanomaterial is successfully synthesized with superstructure motifs and uniform self‐supported electrochromic films are prepared on a transparent conductive substrate. The results show that the films can effectively accommodate lithium ions and facilitate intercalation–deintercalation on transparent fluorine‐doped tin oxide (FTO) substrates at high current density. Mechanistic insights into the excellent electrochromic and rechargeable energy storage properties are provided by density functional theory (DFT) calculations. Specifically, the Nb18W16O93 film displays a large optical modulation (up to 93% at 633 nm and 89% at 1200 nm), high coloration efficiency (105.6 cm2 C−1), high energy storage capacity (151.4 mAh g−1 at 2 A g−1), excellent rate capability, and long‐term electrochemical stability (6000 cycles). As a demonstration of its application, an energy storage indicator is illustrated and a complementary electrochromic energy storage smart window is fabricated based on the Nb18W16O93 film. The results demonstrate that the Nb18W16O93 nanomaterial has a promising application in the field of high‐performance electrochromic and energy storage devices.

Emerging Electrochromic Materials and Devices for Future Displays

“…In fact, this is favorable evidence for using composite materials to improve performance, as discussed above. As reported in this paper, the authors synthesized Nb 18 W 16 O 93 nanomaterials through a sol-hydrothermal method. The as-prepared nanomaterials (film) further overcame the limitation of EC performance.…”

“…Another classic example of EC nanomaterials is the preparation of nanostructured tungsten-bronze-like Nb 18 W 16 O 93 , as reported by Guofa Cai, Pooi S. Lee and coauthors . As we know, WO 3 and Nb 2 O 5 are two typical inorganic EC materials, and their response rates are limited by ion diffusion within the crystal structures.…”

“…Inset: photographs of the Nb 18 W 16 O 93 film in these two states. Reproduced from ref . Copyright 2021 Wiley-VCH GmbH.…”

“…Another classic example of EC nanomaterials is the preparation of nanostructured tungsten-bronze-like Nb 18 W 16 O 93 , as reported by Guofa Cai, Pooi S. Lee and coauthors. 237 As we know, WO 3 and Nb 2 O 5 are two typical inorganic EC materials, and their response rates are limited by ion diffusion within the crystal structures. However, in 2018, Clare P. Grey et al found that even if the active particles reached micron sizes, niobium tungsten oxides (Nb 16 W 5 O 55 and Nb 18 W 16 O 93 ) still exhibited fast ion-diffusion kinetics due to their appropriate crystal structures.…”

Understanding the Role of Charge Storage Mechanisms in the Electrochromic Switching Kinetics of Metal Oxide Nanocrystals

“…Nanocrystals of transition metal oxides were synthesized and applied as electrochromic layers to mitigate the influence of Li + intercalation by minimizing diffusion path length. [7][8][9][10][11][12] In this regard, electrochromic coloration mechanisms can differ from the Li + intercalation typically operating in bulk transition metal oxides, with other mechanisms such as capacitive charging and surface redox becoming dominant in some cases. 4,[13][14] Alternatively, plasmonic metal oxide nanocrystals were synthesized with the ability to modulate their transmittance spectrum by capacitive charging only, which circumvents the slow ion diffusion rate in bulk transition metal oxides.…”