Recent Progress and Prospect of Electrochromic Metal Oxides

Hongren Zhou

School of Petrochemical Engineering and Environment, Zhejiang Ocean University, Zhoushan, Zhejiang

316022, China

Keywords: Metal Oxides, Electrochromism, Smart Window, Flexible Electronics, Energy Storage.

Abstract: Electrochromic metal oxide materials, which have high optical contrast and high environmental stability, are

widely used in smart Windows, capacitors and other fields. Compared with organic polymer materials, metal

oxide materials have higher stability and better optical performance, making them suitable for long-life

devices. This paper systematically reviews the latest research progress of metal oxide electrochromic

materials, with a focus on their applications in smart Windows, high-resolution displays, flexible electronics,

and energy storage. Metal oxides (such as WO₃, NiO) have become the core of research due to their excellent

optical modulation capabilities (up to 75% ΔT), high environmental stability (78% performance after 3500

cycles), and diverse preparation processes (sol-gel, lithography). Nanostructure design (MXene/WO₃

microcavities) and photoelectro-synergistic self-healing technology significantly improved response speed

(coloring time <1 second) and device lifetime (no decay after 1000 cycles). In the future, challenges such as

large-scale fabrication, cost reduction, extreme environment stability and multi-functional integration need to

be overcome to promote their commercial application in smart buildings and wearable devices.

1 INTRODUCTION

Electrochromic materials have become a research

hotspot in recent years due to their broad application

prospects in smart Windows, energy-saving displays,

flexible electronics, and other fields. Traditional

electrochromic materials are divided into two major

categories: organic and inorganic. Inorganic metal

oxides (such as WO₃, NiO, IrO₂, etc.) have become

the mainstream research direction due to their

excellent optical modulation ability, environmental

stability, and diverse and flexible preparation

processes.

Unlike the traditional preparation process, Gu et

al. (2025) developed direct lithography technology to

achieve high-resolution patterning of WOₓ

nanoparticles, which gave them the characteristics of

fast response, high coloring efficiency, and good

cycling stability. In addition, Ren (2023) synthesized

Nb18W16O93 bimetallic oxides by the sol-

hydrothermal method and prepared thin films by the

spraying method, and studied the effect of electrolyte

cations on the electrochromic properties of the

material, achieving extremely high optical

https://orcid.org/0009-0006-0643-6827

modulation range and cycling stability. In the study

of microcavity structures, Wang et al. (2024)

developed the synergism of electrochromism and

rapid deformation through the study of Fabry- Perot

microcavity structures of MXene/WO bilayer films,

and achieved the results of a maximum bending

Angle of 95°, a response time of 10 seconds and 1000

cycle stability.

Although many studies have made progress in

preparation methods and performance optimization,

there are still many challenges in the display field,

environmental stability, and the preparation process.

Therefore, this paper aims to review the latest

research progress of electrochromic metal oxide

materials, clarify their advantages in optical

modulation, environmental stability, and preparation

process, and provide references for innovative

applications for researchers in related fields. In

addition, expectations are presented for its

development trends and the commercial application

of related devices.

Zhou, H.

Recent Progress and Prospect of Electrochromic Metal Oxides.

DOI: 10.5220/0013827400004708

Paper published under CC license (CC BY-NC-ND 4.0)

In Proceedings of the 2nd International Conference on Innovations in Applied Mathematics, Physics, and Astronomy (IAMPA 2025), pages 451-456

ISBN: 978-989-758-774-0

451

2 ADVANTAGES OF METAL

OXIDE MATERIALS IN

ELECTROCHROMISM

2.1 Excellent Optical Modulation

Ability and Color Diversity

In the field of electrochromism, metal oxide materials

refer to a class of materials whose optical properties

(such as color, transparency, etc.) are reversibly

regulated under the action of an electric field. These

materials are mostly transition metal oxides or their

derivatives, such as WO₃, TiO₂, MoO₃, etc., which

have the characteristics of long-lasting color change,

good stability, and excellent optical memory.

Compared with traditional electrochromic

materials such as organic polymers, metal oxides

(such as WO₃, NiO, V₂O₅) can not only achieve

reversible optical changes through dual

implantation/deimplantation of ions and electrons,

but also have a wide spectral modulation range. In Jia

et al. (2023), for example, electrochromic devices

based on Nb: TiO

nanocrystals still achieved a

spectral modulation of more than 64% at 800-2000

nm, and spectral modulation in the visible light band

was also achievable at a high potential of 3-4 V.

Unlike traditional electrochromic materials, the

transmittance variation range of Prussian blue is

usually less than 50%, while tungsten oxide (WOₓ)

can be transformed from transparent to dark blue

under electrical stimulation, with an optical

modulation amplitude of up to 55.9% (Gu et al.,

2025). Bimetallic oxides (such as NiMn-LDH)

further expand the light modulation ability through

elemental synergies and achieve neutral tones (such

as brownish black and pale yellow) to avoid visual

fatigue caused by traditional blue tones (Feng, Ma, &

Wang, 2024). In addition, rare earth metal oxides

(e.g., Ce₄W₉O₃₃) can independently regulate visible

light and near-infrared light through surface

plasmonic resonance effects to accommodate

different environmental requirements (Guo et al.,

2024).

2.2 High Environmental Stability

Traditional electrochromic materials such as

polyaniline and polypyrrole are prone to structural

fracture or side reactions during repeated REDOX

processes, resulting in performance degradation. In

addition, humidity, temperature, and other factors can

accelerate the decomposition of the material. Metal

oxides, due to their inorganic properties, have

excellent chemical stability and durability. Doped

metal oxide nanocrystals, such as ITO and AZO, due

to their special chemical composition and structure,

can maintain good performance under environmental

factors such as air and humidity, and are not easily

oxidized or corroded. For example, tungsten oxide

nanoparticles were used in cyclic voltammetry (CV)

to produce electrochromic devices based on

photolithography WOx films. The results of

maintaining its electrochemical reduction and

reoxidation performance after 3,600 cycles are as

follows: The device underwent a complete coloring

and bleaching process during the cycle, and the

optical modulation performance was well maintained,

with a residual optical modulation limit of 22.4% and

a maintenance ratio of 78%, indicating good

environmental stability (Gu et al., 2025).

2.3 The Preparation Process Is Flexible

and Highly Compatible

Metal oxides have shown excellent process

advantages in the field of electrochromic materials.

Because of its strong structural controllability, it can

not only precisely control the microstructure through

the sol-gel method, but also achieve the growth of

specific morphology and obtain uniform films

through the hydrothermal method and sputtering

method, and flexibly adjust physical and chemical

properties according to different application

scenarios. Take WOₓ(0<x ≤ 3) nanoparticles as an

example. They have both excellent electrochromic

properties and good stability, and are favored in smart

Windows, roof sunroofs, and electronic shelf labels.

Especially in near-eye virtual/augmented reality

display scenarios, its ultra-high resolution and ideal

electrochromic performance are crucial to advancing

display technology. Gu et al. (2025) could adjust the

surface properties and chemical composition of WOₓ

NPs by selecting the appropriate photosensitive

additive (PAGs) and using the in-situ ligand exchange

mechanism triggered by ultraviolet radiation (UV).

This indicates that in practical applications, different

photosensitizers can be selected according to

different requirements, and thus the physicochemical

properties of WOₓ NPs can be flexibly adjusted.

Moreover, the direct lithography technology they

developed perfectly demonstrates metal oxide

preparation's flexibility, breaks traditional etching

processes' limitations, and achieves high-resolution

patterning with line widths less than 4μm. This

innovative preparation process not only gives full

play to the properties of metal oxides but also opens

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up a new path for the application of electrochromic

materials in fine display fields.

3 SMART WINDOWS

With the advancement of technology, the

environment is being overdrawn. Smart Windows can

effectively reduce building energy consumption by

intelligently adjusting the intensity of indoor and

outdoor light, thus maintaining the environment.

Electrochromic smart Windows, which have the

advantages of simple control and quick response

compared to other types of smart Windows, have

received extensive attention from researchers (Xie,

2024). Among them, Xie(2024) developed a tungsten

oxox-based smart window (WO₃) based on the

method of controlled sputtering to prepare WO₃ films

at different power levels and high-temperature

annealing of WO₃ films, resulting in O₃ films with an

average transmittance of over 75% in the visible light

range and a light modulation range of 60%-80%. The

response time was reduced to less than 3 seconds.

Combining the above advantages, these tungsten-

oxide-based smart Windows are suitable for buildings

in high latitudes and can significantly reduce light

source energy consumption. The Nb₁₈W₁₆O₉₃ device

through a layered structure. The sol-hydrothermal

synthesis and spray fabrication method was used to

obtain Nb₁₈W₁₆O₉₃ film with high optical modulation,

fast response, and excellent cycling stability in the

Zn²⁺ electrolyte system. This electrochromic metal

oxide can achieve uniform and reversible color

transition on large-area devices, which enhances their

cycle life. Similar prospects for surface

electrochromic metal oxide materials in smart

Windows. Not only that, for example, the global

brand Tesla's new Model S uses an electrochromic

sunroof that automatically adjusts according to light,

reducing the energy consumption of the in-car air

conditioning by about 30 percent. Compared with

traditional glass, smart Windows made of metal oxide

material can make more efficient use of solar energy,

reduce reliance on artificial lighting and HVAC

systems, and improve the energy efficiency of

buildings, all of which illustrate the promising future

of smart Windows.

4 HIGH RESOLUTION DISPLAY

WITH HIGH CONTRAST

Metal oxide materials also have significant

advantages over traditional electrochromic materials

in the display field. This is mainly reflected in high-

resolution displays and high contrast, etc. Peng et al.

(2025) achieved ultra-high resolution patterning of

WOₓ nanoparticles with line widths less than 4

microns through sol-gel synthesis, which is the

highest resolution among electrochromic materials

without electrochromic materials. The core technique

is to prepare ultra-high resolution electrochromic

patterns on tungsten oxide (WOₓ) nanoparticles by

direct lithography with in-situ light-induced ligand

exchange (Gu et al., 2025). Not only that, the

MXene/WO₃ Fabry-Perot microcavity developed by

Wang et al. (2025) enables multi-color display

through interference effect, allowing for continuous

regulation of WO₃ thickness variation (215-293 nm)

from yellow-green to purple to pink to blue, with

wide CIE color gamut coverage and RGB standard

coverage. And by multiple reflections of light of

specific wavelengths on the upper and lower surfaces

of the WO₃ layer and by changing the Angle of the

incident light, constructive and destructive

interferences are produced to generate specific

structural colors. This interference effect not only

enhances the contrast of the color but also ensures its

accuracy.

5 FLEXIBLE DESIGN

5.1 Flexible Substrate Development

Compared with traditional electrochromic materials,

transparent electrode materials such as ITO and FTO

have poor toughness and are prone to separation from

the substrate after bending, which limits the

development of flexible devices. Shen (2022)

selected Nafion as the polymer electrolyte, WO3 and

MXene composites as the electrochromic layer, and

PEDOT: PSS as the electrode material to prepare the

PEDOT: PSS electrode layer on the electrochromic

layer and the polymer electrolyte layer by roller

coating, and dried at 50°C for 1 hour. The

WO3/MXene films obtained under this condition

have a high specific capacitance, a large area of cyclic

voltammetry curve, strong charge storage and

intercalation and migration capabilities, and can

achieve wing vibration and color-changing effects

under low voltage stimulation. This new type of

flexible substrate not only improves the flexibility

and optical performance in the field of flexible design

Recent Progress and Prospect of Electrochromic Metal Oxides

453

of electrochromic materials, but also provides new

ideas and methods for the development of flexible

smart devices

5.2 Self-Healing Properties

The self-healing property of a flexible device refers

to the ability of its material to repair itself through

internal chemical or physical mechanisms after

physical damage (such as scratches, breaks), restoring

its original structure, conductivity, or function. Zhou

et al. (2025) prepared amorphous WO₃ (300 nm) on

ITO substrates by magnetron sputtering using the

electro-optical co-ion release technique and

conducted long-term cyclic voltammetry (CV) tests

on WO₃ in LiClO₄-PC electrolyte (2.0-4.0 V vs.

Li/Li⁺) for 1000 cycles. Their photoelectro-

synergistic technology (UV+ low bias) breaks down

damaged phases such as Li₂WO₄ through

photogenerated current, releases captured Li⁺, and

restores material properties. The technology is

applicable to a variety of oxides and complete

devices, with key parameters being wavelength (≤405

nm), power (≥100 μW/cm²), and bias (≥3.8 V). This

technology provides an efficient and safe solution for

extending the lifetime of electrochromic devices, as

well as a safe and efficient solution for achieving the

self-healing function of the devices, and an important

breakthrough for the durability and sustainability

development of flexible devices.

6 WEARABLE DEVICES

6.1 High Response, High Stability

Significant progress has been made in the study of

metal oxide electrochromism (EC) in wearable

devices. At present, response speed and cycling

stability can be enhanced through material

modification (such as nickel molybdate, vanadium

pentoxide composite carbon materials), with a

maximum light modulation retention rate of 99.4%

after 1500 cycles, and neutral tones and flexible

integration can be achieved (Ma et al., 2024). Metal

oxides not only have the advantages of low power

consumption and dynamic dimming, but also have

innovations in human-computer interaction,

enhancing the comfort and interactivity of wearable

devices by combining multi-color displays with

flexible substrates. Such technologies offer a more

energy-efficient and adaptable solution for the next

generation of smart wearables.

6.2 Real-Time Monitoring of Human

Health

The electrochromic material is formed by the

combination of polyaniline and rare earth oxides

(La2O3 and CeO2). Regarding whether it is possible

to conduct health monitoring by monitoring the

coloration of human body voltage changes in real

time to report the changes in internal potential of the

human body under different conditions. In Dai's

(2023) study, the f-La₂O₃/PANI composites

demonstrated faster response and better cycling

stability than pure PANI. The electrochromic

performance of the composite was optimal when the

lanthanum-amine ratio was 1:3.5, with a coloring

efficiency of 22.81 cm²·C⁻¹ and fading and coloring

response times of 1.29 seconds and 1.33 seconds,

respectively. At a wavelength of 570 nm, the film

reversibly changed between emerald green, dark

green, and reddish-brown, while the f-CeO₂/PANI

composite showed reversibly changing between

emerald green, dark green, and reddish-brown. These

composites all showed good color change and

electrochemical performance during the

electrochromic process. These properties give them

great potential for electrochromic applications in

human wearable devices.

7 SUPERCAPACITORS

7.1 Excellent Innovation in Electrode

Materials

As industrialization progresses, the problem of

energy consumption needs to be addressed.

Traditional fossil fuels cause greenhouse effects and

air pollution, and the development of clean energy is

an inevitable trend. Supercapacitors, with their high

power density and long cycle life, are an important

part of energy storage, especially widely used in new

energy equipment and defense equipment. Metal

oxides, due to their high theoretical specific capacity

and abundant natural resources, have attracted much

attention as electrode materials for supercapacitors.

Zhang Zhichao studied vanadium-cobalt bimetallic

oxide (VCoOₓ) by hydrothermal synthesis, and by

controlling variables such as reactant concentration,

reaction temperature, and time, samples of vanadium-

cobalt bimetallic oxide with different micromorphic

morphology were synthesized. These samples

demonstrated excellent capacitance performance and

cycling stability in electrochemical tests, and they

successfully synthesized novel star-shaped and

spheroidal Co3O4, expanding the variety of

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microstructure morphology of metal oxide materials

and providing a reference for the innovative design of

supercapacitor electrode materials (Zhang, 2024).

7.2 Fiber Supercapacitors

In recent years, the function of ECDs has expanded

from a single electrochromic function to energy

storage, resulting in electrochromic supercapacitors

(ECSs), devices that can not only alter their optical

properties but also store energy. WO₃/TiO₂ nanowire

fibers can be woven into fabrics that not only store

energy at a density of 15 Wh/kg, but also change color

with the state of charge. Keon-Woo Kim et al.

successfully fabricated mesoporous WO₃

electrochromic supercapacitors using polystyrene-

polyoxyethylene (PS19k-b-PEO6.5k) and WCl₆ as

raw materials through evaporation-induced self-

assembly (EISA) technology. It has fast color-

changing speed, high optical modulation, and

excellent energy storage performance (Kim et al.,

2020). As a result, metal oxide materials, due to their

diverse structures and compositions, exhibit high

specific surface area, excellent optical and

electrochemical performance, enabling rapid ion

transport and intercalation/deintercalation, and thus

have advantages such as fast response, high

capacitance, and good cycling stability in

electrochromic supercapacitors and supercapacitors.

It has driven the development of high-performance

energy storage and display-integrated devices.

8 CHALLENGES AND

EXPECTATIONS

Jia et al. (2023) mentioned that electrochromic metal

oxides are costly to produce on a large scale because

of their complex preparation process, which involves

high-precision equipment and expensive raw

materials. And even though they have more stable

properties compared to organic materials, their

stability in extreme conditions is still insufficient;

especially in extreme conditions such as high

temperature and high humidity, their performance

may still gradually decline. Jia et al. (2023) also

mentioned that integrating electrochromic functions

with other functions (such as energy storage, sensing)

into a single device requires addressing complex

issues such as material compatibility, structural

design, and performance optimization. Therefore,

achieving multi-functional integration is complex and

difficult. In Peng et al. 's (2025) study, metal oxide

materials (such as WO₃, etc.) still have performance

bottlenecks such as long response time, insufficient

cycling stability, and limited optical modulation

amplitude in high-resolution displays, which limit

their application potential in high-resolution dynamic

displays.

In future studies, green synthesis processes such

as hydrothermal and sol-gel, which are low-cost and

highly compatible, can be developed to reduce

material preparation costs and improve process

compatibility. And further explore new

heterojunctions and porous structure designs,

continue to design porous structures or

heterojunctions, such as the MXene/WO₃ microcavity

structure designed by Wang et al. (2025), and further

improve ion transport efficiency and optical contrast.

We can also deepen multifunctional integration

research to promote the integration of electrochromic

materials with energy storage, sensing, and self-

powered systems, and develop multifunctional

devices like electrochromic supercapacitors.

Electrochromic metal oxide materials have the

potential to achieve greater breakthroughs in green

energy and smart interaction through

interdisciplinary collaboration and technological

innovation.

9 CONCLUSIONS

This paper systematically reviews the core

advantages of metal oxide electrochromic materials

in optical control, environmental stability, and

preparation processes, and focuses on their innovative

applications in energy-saving Windows, high-

resolution displays, flexible electronics, and

multifunctional energy storage devices. The study

shows that through nanostructure design (such as

MXene/WO₃ Fabry-Perrot microcavities) and

lithography technology innovation (line width <4

μm), the optical modulation capabilities of metal

oxide materials in the visible and near-infrared bands

have been significantly enhanced (ΔT over 75%). It

also has ultrafast response (coloring time <1 second)

and long cycle life (>1000 times). In the field of

flexible devices, the combination of MXene-based

composites and self-healing technology (electro-

optical synergistic ion release) enables the

multifunctional integration of mechanical

deformation and color change, providing new ideas

for smart wearable devices. In addition, the

development of dual-function electrochromic

supercapacitors (such as WO₃/TiO₂ fibers) has

Recent Progress and Prospect of Electrochromic Metal Oxides

455

promoted the synergistic development of energy

storage and dynamic light regulation.

The development of electrochromic metal oxides

still faces problems such as complex preparation

processes, high costs, performance degradation in

extreme environments, difficulties in multi-

functional integration, long response times, and

insufficient cycling stability in high-resolution

displays. In the future, the development of green

synthesis processes, the design of new

heterojunctions and porous structures, and the

deepening of multifunctional integration research are

expected to enhance their performance and expand

their application areas. And cross-disciplinary

collaboration and technological innovation will drive

greater breakthroughs in electrochromic metal oxides

in green energy and smart interaction.

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