Shanghai University of Science and Technology: New materials of niobium and tungsten oxide make electrochromic devices more efficient and environmentally friendly

2022-06-09 0 By

Electrochromic devices can present color changes during charging and discharging, which brings some interesting applications.If the electrochromic device is used in intelligent Windows, the incoming light and heat can be dynamically adjusted. When the Windows are colored, the incoming light and heat can be reduced, and the energy consumption of air conditioning and refrigeration can be reduced.When the Windows are faded, they allow light and heat to enter, reducing air conditioning heating energy consumption.This is of great significance to energy conservation and emission reduction of buildings.Electrically induced discoloration devices are usually made of transparent conductive layer – electrically induced discoloration layer – ionic conduction layer – ion storage layer – the five layers of transparent conductive layer structure, which electrically induced discoloration layer as the core component of the entire device, electrically induced discoloration layer in the process of charging and discharging or REDOX can occur between coloring and faded states color shift.Traditional electrochromic materials, such as WO3 and NiO, exhibit long response time, low optical modulation and poor cyclic stability.In order to improve the performance of electrochromism, many strategies have been used, but it is still difficult to meet the needs of people.Recently, a new electrochromic material, Nb18W16O93, has been successfully prepared by sol-gel method using lithium ion battery electrode materials.The material is orthogonal phase and has a stable THREE-DIMENSIONAL network structure in which lithium ions can be inserted and removed quickly and stably.Compared with common electrochromic materials WO3 and NiO, Nb18W16O93 has a larger vacancy size, which facilitates the insertion and removal of lithium ions. The electrochromic device finally assembled by Nb18W16O93 exhibits a faster response time, with a coloring time of 4.7 seconds and a fading time of 4.0 seconds.At the same time, because it can accommodate a large number of lithium ions, it presents a large optical modulation.In addition, the material structure changes very little in the process of lithium ion insertion and removal, showing excellent electrochemical stability, and after 8000 cycles, the optical modulation is close to 80% relative to the first cycle.If the electrochromic material is compared to a shopping mall, the ions that migrate during the electrochromic process are compared to the people entering and leaving the shopping mall, and the sites of ion migration are compared to many doors of the shopping mall, then compared to WO3 and NiO and other traditional materials, Nb18W16O93 has a larger door, which allows people to enter and exit more quickly and is not easy to generate congestion.And the mall is large and solid, a large number of people in and out of the mall will not damage the structural stability.Figure: Nb18W16O93 device assembly, application and optical photo schematic.This work provides an effective solution for the design of electrochromic materials with fast response time and good cyclic stability, and provides a new choice for the development of electrochromic smart Windows, anti-vertigo rearview mirrors and other new electrochromic devices.The results were recently published in ACS Nano under the title “Niobium tungsten OXIDES for Electrochromic Devices with long-term stability”.Wu Cong, PhD candidate of the class of 2020, was the first author, and Professors Liu Wei and Yu Yi were the co-corresponding authors, with The University of Science and Technology of Shanghai as the first completion unit.Source: Shanghai university of science and technology thesis links: https://pubs.acs.org/doi/abs/10.1021/acsnano.1c09234