Synergistic Effect and Electrochromic Mechanism of Nanoflake Li-doped NiO in LiOH Electrolyte

Inorganic metal oxide electrochromic materials have good application prospects for energy-saving windows in buildings and smart display applications.Therefore,the development of electrochromic films with good cycling stabilities,fast color-change response times,and high coloring efficiencies has attracted considerable attention.In this study,nanoflake Li-doped NiO electrochromic films were prepared using a hydrothermal method,and the films exhibited superior electrochromic performances in the LiOH electrolyte.Li^(+)ions doping increased the ion transmission rates of the NiO films,and effectively promoted the transportation of ions from the electrolyte into NiO films.Meanwhile,the nanoflake microstructure caused the NiO films to have larger specific surface areas,providing more active sites for electrochemical reactions.It was determined that the NiO-Li20%film exhibited an ultra-fast response in the LiOH electrolyte(coloring and bleaching times reached 3 and 1.5 s,respectively).Additionally,the coloration efficiency was 62.1 cm^(2)C^(−1),and good cycling stability was maintained beyond 1500 cycles.Finally,the simulation calculation results showed that Li doping weakened the adsorption strengths of the NiO films to OH^(−),which reduced the generation and decomposition of NiOOH and helped to improve the cycling stabilities of the films.Therefore,the research presented in this article provides a strategy for designing electrochromic materials in the future.

Correlation between lithium storage and diffusion properties and electrochromic characteristics of WO_3 thin films

As essential electrochromic（EC） materials are related to energy savings in fenestration technology,tungsten oxide（WO3） films have been intensively studied recently.In order to achieve better understanding of the mechanism of EC properties,and thus facilitate optimization of device performance,clarification of the correlation between cation storage and transfer properties and the coloration performance is needed.In this study,transparent polycrystalline and amorphous WO3 thin films were deposited on SnO2：F-coated glass substrates by the pulsed laser deposition technique.Investigation into optical transmittance in a wavelength range of 400-800 nm measured at a current density of 130 μA·cm-2 with the applied potential ranging from 3.2 to 2.2 V indicates that polycrystalline films have a larger optical modulation of ～ 30% at 600 nm and a larger coloration switch time of 95 s in the whole wavelength range compared with amorphous films（～ 24% and 50 s）.Meanwhile,under the same conditions,polycrystalline films show a larger lithium storage capacity corresponding to a Li/W ratio of 0.5,a smaller lithium diffusion coefficient（2×10-12cm2·s-1 for Li/W=0.24） compared with the amorphous ones,which have a Li/W ratio of 0.29 and a coefficient of ～2.5×10-11cm2·s-1 as Li/W=0.24.These results demonstrate that the large optical modulation relates to the large lithium storage capacity,and the fast coloration transition is associated with fast lithium diffusion.

Electrochemical Properties of Poly(ethylene oxide)(PEO) Doped TiO_2-PEO Films Prepared by Sol-gel Dip Coating Technique

PEO modified Ti02 -PEO organic-inorganic hybrid thin films were prepared via, sol-gel dipping process on glass substrate pre-coated with ITO. The preparation parameters were studied. Electrochemical and optical properties of the films were characterized by cyclic voltammetric response and visible transmittance. X-ray diffraction (XRD) was used to determined the crystalline structure of the gel. The results show the sols added with PEO have acceptable stable periods for practical use. The PEO modified optical transitivity of the hybrid films has heavy effects on the crystallization of TiO2 during structural evolution because of the interaction between PEO and Ti02 . PEO-TiO2 films have better electrochemical activity than the TiO2 equivalent behaved as higher Li + insertion/extraction current density and cyclic reversibility.

Colorless-to-colorful switching of electrochromic MXene by reversible ion insertion

Electrochromic(EC)materials that change color with voltage have been widely studied for use in dynamic windows.However,colorless-to-colorful switching with high contrast ratio is generically unattainable,especially for colorless-to-black electrochromic materials with an ultrahigh contrast ratio over the entire visible region.In this work,we developed Nb_(1.33)C MXene-based dynamic windows with colorless-to-black switching of up to 75%reversible change in transmittance from 300 to 1,500 nm.By exploring the electrochromic effects of different electrolytes through in situ optical changes and electrochemical quartz crystal microbalance(EQCM),it is found that electrochromic behavior is greatly influenced by the extent of reversible Li^(+)insertion/deinsertion between the two-dimensional Nb_(1.33)C MXene nanosheets.In addition,a colorless-to-black EC device based on Nb_(1.33)C with an overall integrated contrast ratio over 80%was successfully constructed by a solution-processable spin coating method.This work enables a simple route to fabricate MXene-based high-performance electrochromic smart windows,which is important for further expanding the application of MXenes to optoelectronic and photonic applications.

A single-molecule multicolor electrochromic device generated through medium engineering

Multicolor organic electrochromic materials are important for the generation of full-color devices.However,achieving multiple colors using a single-molecule material has proved challenging.In this study,a multicolor electrochromic prototype device is generated by integrating medium engineering/in situ‘electro base’/laminated electrode technologies with the simple flying fish-shaped methyl ketone TM1.This multicolor electrochromic(green,blue and magenta)device is durable and has a high coloration efficiency(350 cm^(2) C^(-1)),a fast switching time(50 ms)and superior reversibility.This study is a successful attempt to integrate solvatochromism and basochromism in an electronic display.This integration not only introduces a new avenue for color tuning,in addition to the structural design of the colorant,but will also inspire further developments in the tuning of many other properties by this medium engineering approach,such as conductance and the redox property,and thereby accelerate versatile applications in data recording,ultrathin flexible displays,and optical communication and sensing.