Aluminum-ion-intercalation nickel oxide thin films for high-performance electrochromic energy storage devices

Abstract

Aluminum-ion electrochromic energy storage devices (EESDs) are one of the most promising alternatives to lithium-ion devices. Nevertheless, they face a substantial challenge in their successful application due to the difficulties in constructing a suitable anode electrochromic material for robustly hosting the trivalent Al³⁺ ions. Herein, a desired aluminum-ion-intercalation-based electrochromic energy storage device with a sandwich configuration of an ITO/WO₃/Al³⁺-based liquid electrolyte/NiO/ITO has been facilely constructed. Relying on the NiO/Al³⁺ interfacial merits that offer a highly nanoporous NiO host, the effective adsorption energy of Al³⁺ ions on the preferred NiO(111) plane, and the strong electrostatic interactions of aluminum trivalent cations on the NiO host, the EESDs can achieve a high performance with a large optical modulation of 50.4%, a high coloration efficiency of 102.2 cm² C⁻¹ and an enhanced long cycling stability (at least 10 000 cycles with only 10% decay). Impressively, the highly reversible EESDs visualized by their electrochromism can provide long-term power supply due to their high specific capacitance of 9.97 F g⁻¹. In addition, the electrochemical storage mechanism and Al³⁺ ion diffusion kinetics have been further clarified. The current work is expected to provide a new space for the construction of advanced multivalent and inert conductive ion electrolyte materials for bifunctional electrochromic energy storage devices.