Dual-Band Electrochromic Optical Modulation Improved by a Precise Control of Lithium Content in Li_4+xTi₅O₁₂

Abstract

Dual-band electrochromic smart windows that can dynamically and independently control incident solar irradiation and visible light are envisioned as intelligent technology to reduce power consumption of buildings. However, there is still a great challenge to put the dual-band electrochromic technology into practice due to some limits in material systems and preparation techniques. Herein, a new electrochromic material of Li 4 Ti 5 O 12 is developed to implement the dual-band optical modulation behavior, which could be further improved by a precise control of the lithium content in the active material. It could separately modulate the light and heat based on regulation of the transmittance of visible and near-infrared light. This enables Li 4 Ti 5 O 12 to operate in three distinct modes of bright, cool, and dark, so as to meet various indoor needs. The optical transmittance contrast reaches over 60% at both visible-and near-infrared-light regions between different modes, and a large range of apparent temperature adjustments (7 °C) could be achieved. The prototype device based on dual-band electrochromic Li 4 Ti 5 O 12 is further developed into a smart window of a house model, which exhibits good optical and thermal modulation behaviors in response to a high-temperature environment. This work provides a new material system for achieving dual-band electrochromic optical modulation toward smart energy-saving window applications.

Design of Symmetric TiO2/LiI/TiO2 Electrochromic Devices for Gradient Shaded Smart Windows with Enhanced Switching and Cycling Properties

“…insertion and extraction. [8,9] Compared with organic EC materials, inorganic ones attract more interest in their application in smart windows due to their good environmental compatibility, operability, and stability. [10,11] In recent years, transition metal oxides such as WO 3−x , TiO 2−x , Nb 2 O 5−x , and their doped counterparts become candidates for commercialized smart windows.…”

Niobium and Fluorine Dually Doped Titanium Oxide Nanosheet Arrays for Selective Dual-Band Electrochromic Applications

“…Electrochromic (EC) materials are able to reversibly modulate their optical properties fundamentally through electrochemical redox reactions under applied bias voltages, which have shown great commercial potential in applications such as smart windows, low-energy displays, and energy-efficient glass. − While researchers pay more attention on the performance of EC materials in the visible (VIS) light region, there has been less research focus on EC property control in the near infrared (NIR) region which accounts for almost 50% of the total solar radiation. Thus, independent control of NIR and VIS light is desirable to efficiently and smartly utilize solar energy.…”

A highly transparent ion conducting film enabling a visual electrochromic battery

“…The EC materials used for constructing the EC battery mainly involve WO 3 , Li 4 Ti 5 O 12 , LiMn 2 O 4 , and conducting polypyrrole. [8][9][10][11] Compared with the capacitor-type EC material, the battery-type LTO demonstrates desirable features of high specific capacity and zero strain, and shows great potential in the application of EC batteries. For instance, Sato et al fabricated a novel EC battery by using Li 3 Fe 2 (PO 4 ) 3 and LTO thin-film electrodes via the molecular precursor method.…”