KR102079142B1 - An Electrochromic Device - Google Patents

Abstract

The present application relates to an electrochromic device and a method of manufacturing the same. The present application including a novel ion storage layer material provides an electrochromic device that is excellent in durability and thin film productivity, and has improved color change rate compared to the prior art.

Description

Electrochromic Device

The present application relates to an electrochromic device. In particular, the present application relates to an electrochromic device having improved color change efficiency and switching time.

Electrochromism refers to a phenomenon in which optical properties such as color or light transmittance of an electrochromic active material change depending on an electrochemical oxidation and reduction reaction. Electrochromic devices using such a phenomenon can be manufactured in a large area of the device at a low cost, and has a low power consumption, attracting attention in various fields such as smart windows, smart mirrors, electronic paper and the like.

1 is a cross-sectional view of a general electrochromic device. As shown in the drawing, the electrochromic device 100 includes a first electrode layer 110, an electrochromic layer 120 provided on the first electrode layer 110, an electrolyte layer 130 provided on the electrochromic layer, and the It may include an ion storage layer 140 provided on the electrolyte layer, and a second electrode layer 150 provided on the ion storage layer. Although not shown, a substrate formed from transparent glass or polymer resin may be further included on the outer surfaces of the electrodes 110 and 150.

In general, the electrochromic layer and / or the ion storage layer may include an inorganic material such as tungsten oxide (WOx) or lithium nickel oxide (LiNiOx) as an electrochromic material. Specifically, when a specific potential is applied to the electrode, electrolyte ions such as H ⁺ , or Li ⁺ , Na ⁺ move through the electrolyte layer between the electrochromic layer and the ion storage layer, and at the same time electrons are transferred through the external circuit. As it is injected into or disengaged from the electrochromic layer, oxidation / reduction reactions of the electrochromic material are alternately performed, and coloration or bleaching of the electrochromic layer or the ion storage layer is performed. As described above, since the change of the optical properties of the electrochromic device is premised on the movement of the ionic material, the color change takes a predetermined time, that is, a switching time, thereby improving the color change efficiency and reducing the color change time. Skill is required.

One object of the present application is to provide an electrochromic device having excellent discoloration efficiency and improved discoloration speed.

Another object of the present application is to provide an electrochromic device having a sufficient discoloring effect even with a thin film.

The above and other objects of the present application can be solved by the present application described in detail below.

The present application relates to an electrochromic device. The electrochromic device may include two electrode layers opposing each other, an electrochromic layer, an electrolyte layer, and an ion storage layer.

The electrode may refer to a configuration capable of supplying charge to the electrochromic layer. In one example, the electrode may be formed of any one or more of a transparent conductive oxide (TCO), a conductive polymer, silver nanowire (Ag Nanowire), or a metal mesh (Metal mesh). More specifically, ITO (Indium Tin Oxide), FTO (Fluor doped Tin Oxide), AZO (Aluminum doped Zinc Oxide), GZO (Galium doped Zinc Oxide), ATO (Antimony doped Tin Oxide), IZO (Indium doped Zinc Oxide) Niobium doped Titanium Oxide (NTO), ZnO, Oxide / Metal / Oxide (CTO), or CTO may be used as the electrode material, but is not limited thereto. In another example, the electrode layer may have a structure in which two or more electrode materials are stacked in a plurality of layers.

The method for forming the electrode layer is not particularly limited, and known methods can be used without limitation. For example, an electrode layer may be provided by forming an electrode material including transparent conductive oxide particles in a thin film form on a transparent glass substrate through a sputtering process. The electrode layer may have a thickness of 150 nm or more, 200 nm or more, or 300 nm or more within the range of 1 nm to 1 μm. The upper limit of the electrode layer thickness is not particularly limited, but for the purpose of low resistance, the electrode layer may have a thickness of 800 nm or less, 700 nm or less, or 500 nm or less.

In one example, the electrode layer may have a light transmittance in the range of 70% to 95% with respect to visible light. In the present application, the visible light may mean light having a wavelength in a range of about 350 nm to 750 nm, and more specifically, light having a wavelength of 550 nm.

The electrochromic layer may include an electrochromic material that changes color according to an electrical signal. Examples of electrochromic materials that can be used include conductive polymers, organic chromic materials, and / or inorganic chromic materials. The conductive polymer may be polypyrrole, polyaniline, polypyridine, polyindole, polycarbazole, or the like, and an organic discoloring material may be a material such as viologen, anthraquinone, phenocyazine, but is not limited thereto. no.

In one example, the electrochromic layer may include one or more oxides of oxides of Ti, Nb, Mo, Ta, W, V, Cr, Mn, Fe, Co, Ni, Rh, and Ir as an inorganic color change material. have. More specifically, TiO _{2 ,} Nb ₂ O ₅ , MoO ₃ , Ta ₂ O ₅ , WO ₃ , V ₂ O _{5 ,} CrO _{3 ,} Li _x CoO _{2 ,} NiOx, LiNiO _x , Rh ₂ O _3, IrO _2, etc. This may be an inorganic discoloration material that can be used, but is not limited thereto.

More specifically, the electrochromic layer may include nickel oxide. For example, NiOx or LiNiO _x may include a color change material. The lithium nickel oxide (LiNiO _x ) compound, for example, may be colored or decolorized through the following reaction. In the scheme below, M may be an electrolyte ion such as H ⁺ , Li ⁺ , or Na ⁺ .

[Scheme]

LiNiO ₂ (Color: Brown) + M ⁺ + e ^- ⇔ Li ₂ NiO ₂ (Discoloration: colorless)

In the above reaction, when the color change material included in the electrochromic layer is decolorized, the electrochromic device transmits incident light, and when colored, the optical characteristics of the electrochromic device may be changed while the amount of incident light is reduced. The coloring and decolorizing reactions may occur alternately depending on the polarity of the applied voltage, or the direction of current flow.

In one example, the electrochromic layer may have a transmittance of 20% to 40% for visible light when colored and a range of 45% to 80% for visible light when decolored.

In another example, the electrochromic layer may have a thickness of 300 nm or less, 200 nm or less, 150 nm or less, or 120 nm or less within the range of 10 nm to 400 nm. If the thickness is less than 10 nm, it is difficult to sufficiently react for discoloration. If the thickness exceeds 400 nm, the electrochromic device of the thin film may not be provided, and the transmittance of the device may be reduced. In the case of the present application, since the following ion storage layer materials are used, the discoloration efficiency is improved, and the discoloration of the electrochromic layer may be sufficiently performed even at a thickness of 150 nm or less, or 120 nm or less.

The ion storage layer may refer to a layer in which charge particles necessary for the redox reaction of the electrochromic layer may be inserted or desorbed, thereby participating in the discoloration reaction. In the prior art, in order to balance the charge between the electrochromic layer and the ion storage layer, complementary electrochromic materials were used for the electrochromic layer and the ion storage layer, respectively. For example, when the electrochromic layer includes an oxidative discoloration material such as lithium nickel oxide (LiNiO _x ), the ion storage layer includes a reducing discoloration material such as tungsten oxide (WO _x ). However, the electrochromic device having the above configuration has a disadvantage in that the color change efficiency is not good and the switching time is slow.

In consideration of the problems of the prior art, the electrochromic device according to the present application uses an ion storage layer containing conductive graphite. Conductive graphite having a unique structure and high strength thereby can prevent cracking of the ion storage layer. In addition, the layered structure of graphite provides a space in which electrolyte ions involved in electrochromic can be sufficiently inserted and desorbed. Furthermore, the conductive graphite not only has excellent thin film deposition property but also can sufficiently receive and store charge even at a thickness of 100 nm or less, thereby reducing switching time required between discoloration and discoloration of the device.

The conductive graphite may be graphite oxide. In one example, the graphite oxide may have a mass ratio of oxygen to carbon in a range of 0.001 ≦ O / C ≦ 0.5, or 0.005 ≦ O / C ≦ 0.3. Specifically, in the XPS analysis of the constituent element distribution of the graphite thin film, the content of the C element and O element may be slightly different depending on the measurement position, the entire graphite may be used to satisfy the above range. If the mass ratio is less than 0.005, the conductivity is somewhat improved, but the transmittance is lowered. If the mass ratio is greater than 0.3, the electrical conductivity is lowered, and the switching time may be hindered.

In one example, the ion storage layer of the present application may be formed in the thickness range of 10 nm to 150 nm, 100 nm or less, or 80 nm or less. When the thickness is less than 10 nm, the ion storage effect is not sufficient, and when the thickness exceeds 150 nm, the transparent ion storage layer of the thin film may not be provided and productivity may be reduced.

In another example, the refractive index of the ion storage layer with respect to visible light may be in the range of 1.0 to 3.0.

In one example, the ion storage layer formed by depositing graphite on the electrode can greatly reduce the internal resistance to ion migration. For example, in the case of the ion storage layer formed from conventional lithium nickel oxide, its internal resistance was in the range of 1M Ω / □ to 10M Ω / □, while in the ion storage layer formed by depositing graphite, the internal resistance was 100 Ω / It has a range of □ to 10,000 μs / □, which may contribute to shortening of discoloration time.

In addition, in one example, the ion storage layer may have a visible light transmittance of 65% to 75% range.

The electrolyte layer may include ions involved in the electrochromic reaction, such as lithium ions (Li ⁺ ). The kind of electrolyte included in the electrolyte layer is not particularly limited, and a liquid electrolyte, a gel-polymer electrolyte, or an inorganic solid electrolyte may be used.

In one example, when the electrolyte is a gel-polymer electrolyte, the electrolyte layer may include a cured product of a composition including a carbonate compound and a lithium compound. Since the carbonate compound has a high dielectric constant, the conductivity of ions provided by the lithium salt can be increased. For example, carbonate-based compounds such as propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethylmethyl carbonate (EMC) may be used, but are not limited thereto. Lithium compounds include LiF, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiClO ₃ , LiAsF ₆ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiNO ₃ , LiN (CN) ₂ , LiPF ₆ , Li (CF ₃ ) ₂ PF ₄ , Li (CF ₃ ) ₃ PF ₃ , Li (CF ₃ ) ₄ PF ₂ , Li (CF ₃ ) ₅ PF, Li (CF ₃ ) ₆ P, LiSO ₃ CF ₃ , LiSO ₃ C ₄ F ₉ , LiSO ₃ (CF ₂ ) ₇ CF ₃ , or LiN (SO ₂ CF ₃ ) ₂ , and the like, but are not limited thereto.

In another example, when the electrolyte is an inorganic solid electrolyte, the electrolyte layer may include a lithium phosphorus oxynitride called LIPON (Lithium Phosphorous Oxynitride), or for example, Ta ₂ O ₅ To oxides of transition metals It may include an electrolyte doped with lithium ions. Examples of the transition metal that may be used for the inorganic solid electrolyte include transition metals such as molybdenum (Mo), tantalum (Ta), zirconium (Zr), hafnium (Hf), and tungsten (W). In the case of the gel polymer, as the charge and discharge cycle is increased, bubbles are generated and durability thereof is decreased, whereas when the inorganic solid electrolyte is used, bubbles are not generated, thereby increasing durability and lifespan of the device.

The electrolyte layer may have a thickness in the range of 30 μm to 200 μm, and the transmittance to visible light may range from 70% to 95%.

The electrochromic device of the present application may further include a power source. For example, the power source may be electrically connected to the electrode layer through an external circuit. The apparatus or method for applying the voltage may be appropriately selected by those skilled in the art and is not particularly limited.

In one example, the power source may apply coloring and decolorization potentials of 4V or less with respect to the electrochromic device. In the case of the present application, only the electrochromic layer is colored or decolorized according to the applied voltage, and the ion storage layer may have a range of light transmittance without coloring and decolorizing. More specifically, when a coloring potential having a positive sign is applied in a size of 1.5 V to 2.5 V to a layer including LiNiO _x , that is, an electrode layer on which an electrochromic layer is directly stacked, lithium ions are desorbed and electrochromic. During the time when the layer is colored and the electrochromic layer is colored, the conductive graphite included in the ion storage layer may serve as an ion storage layer while maintaining transparency without discoloration. On the contrary, the electrochromic device may be discolored by applying a discoloration potential having a negative sign to a size of 3V to 4V to an electrode layer on which an electrochromic layer including lithium nickel oxide (LiNiO _x ) is directly stacked.

In another example of the present application, the present application relates to a method of manufacturing an electrochromic device. More specifically, the manufacturing method includes the steps of providing a lithium nickel oxide layer on one electrode layer; And providing a graphite layer having a mass ratio of oxygen and carbon on the other electrode layer having a range of 0.005 ≦ O / C ≦ 0.3. As described above, the lithium nickel oxide layer may be used as an electrochromic layer, and the graphite layer may be used as an ion storage layer. The configuration or other properties of the electrode layer, ion storage layer and electrochromic layer are the same as mentioned above.

The method of providing each said layer is not specifically limited, A well-known method can be used. For example, any one of deposition, spin coating, dip coating, screen printing, gravure coating, sol-gel, or slot die coating Each layer can be provided by. In the case of deposition, the deposition may be performed by physical vapor deposition (PVD) or chemical vapor deposition (CVD). Usable physical vapor deposition methods include sputtering, e-beam evaporation, thermal evaporation, laser molecular beam epitaxy (L-MBE) or pulsed laser deposition ( Pulsed Laser Deposition (PLD) and the like, and examples thereof include Chemical Chemical Vapor Deposition (Thermal Chemical Vapor Deposition), Plasma-Enhanced Chemical Vapor Deposition (PECVD), and Photo Chemical Vapor Deposition (Light). Chemical Vapor Deposition, Laser Chemical Vapor Deposition, Metal-Organic Chemical Vapor Deposition (MOCVD), or Hydride Vapor Phase Epitaxy (HVPE). May be, but is not limited thereto.

The manufacturing method of the present application may further include providing a solid electrolyte layer on one surface of the lithium nickel oxide layer or the graphite layer. The type of electrolyte that can be used for the electrolyte layer is the same as mentioned above.

The present application including a novel ion storage layer material can provide an electrochromic device that is not only excellent in thin film productivity but also improved in color change efficiency and color change rate.

1 is a schematic cross-sectional view of a general electrochromic device.

Hereinafter, the present application will be described in detail through examples. However, the protection scope of the present application is not limited by the examples described below.

Experimental example  1: Measurement of Optical and Driving Characteristics of Half-Cell

For the half-cell prepared as follows, the driving and optical characteristics of each cell were measured at 25 ° C. using potentiostat equipment (Princeton Applied Research, PMC-1000) and UV-vis spectrometer equipment (Solidspec 3700). . The half-cell was applied with a voltage of 2V as the coloring potential and the voltage of 4V as the discoloration potential. The size of each specimen used was consistent with 2.0 cm × 10 cm = 20 cm ² . The results are shown in Table 1 below.

Example

Preparation of Working Electrode: Electrochromic layer formed of lithium nickel oxide (LiNiOx) was deposited to 100 nm thickness by using a DC sputter method on the ITO electrode, which is a transparent conductive oxide, and a working electrode including the first electrode and the electrochromic layer. Was prepared.

Preparation of counter electrode: A formed ion storage layer including conductive graphite was deposited to a thickness of 50 nm on a ITO electrode, which is a transparent conductive oxide, by using a DC sputter method, and a working electrode including a second electrode and an ion storage layer was manufactured. It was.

Comparative example

Similar to the above embodiment, except that a 300 nm thick tungsten oxide (WOx) layer is used as the electrochromic layer and a 100 nm thick lithium nickel oxide (LiNiOx) layer is used as the ion storage layer. An electrochromic layer and an ion storage layer were prepared on the ITO electrode by using a DC sputter method.

Comparison of Optical and Driving Characteristics of Half-Cell Half-cell: working electrode containing an electrochromic layer Half-cell: counter electrode including ion storage layer Measure
Item TCO sheet resistance
(Ω / □) Charge
(mC) ΔT (%) Time (s)
Col. / Ble. TCO sheet resistance Charge
(mC) ΔT (%) Time (s)
Col. / Ble. Example 30 200 40 30/30 30 100 - - Comparative example 30 600 60 60/30 30 200 40 30/30 TCO sheet resistance: sheet resistance of ITO electrode
ΔT: Difference in transmittance during coloring and decolorization of each electrode
Time (s) Col. : Time taken for the electrode to switch from the decoloring state to the coloring state. It can be measured by the time required to have 80% transmittance relative to the transmittance of the fully colored state.
Time (s) Ble. : Time taken for the electrode to transition from the coloring state to the bleacing state. It can be measured by the time required to have a transmittance of 80% relative to the transmittance in a completely decolorized state.

As shown in Table 1, the ion storage layer included in the counter electrode of the present application, unlike the ion storage layer of the comparative example, it can be seen that there is no change in transmittance. This means that in the case of lithium nickel oxide included in the comparative example ion storage layer, coloring and decolorization occur according to the applied voltage, whereas the graphite included in the example ion storage layer does not occur coloring and decolorization.

Experimental example  2: Measurement of Optical and Driving Characteristics of Full-Cell

The working electrode and the counter electrode prepared in Examples and Comparative Examples, respectively, were bonded to _each other via a gel polymer electrolyte prepared from a mixture of PC (propylene carbonate) and LiClO ₄ to prepare an electrochromic device. For the manufactured electrochromic device, optical and driving characteristics were measured using the same apparatus as Experimental Example 1. The results are shown in Table 2 below.

Comparison of Optical and Driving Characteristics of Full-Cell Electrochromic Device (Full Cell) ΔT (%) Coloring Time (s) Bleaching Time (s) Charge amount (mC) Example 35 10 5 150 Comparative example 50 36 13 250 ΔT: Difference in transmittance during coloring and decolorization of the entire device
Bleaching Time (s): The time taken when the electrochromic layer bleaches in the colored state. It can be measured by the time required to have a transmittance of 80% relative to the transmittance in a completely decolorized state.
Coloring Time (s): The time taken when the electrochromic layer is colored in the bleacing state. It can be measured by the time required to have 80% transmittance relative to the transmittance of the fully colored state.

As shown in Table 2, it can be seen that the charge amount of the entire electrochromic device composed of the working electrode and the counter electrode is larger than that of the comparative example. However, in the case of the coloration efficiency (coloration efficiency = ΔT / charge amount), which can be represented by the change in transmittance with respect to the charge amount, it can be confirmed that the device of the embodiment is higher than that of the comparative device. Furthermore, it can be seen that the device of the embodiment has a switching time shortened by 50% or more compared with the comparative example.

Claims (19)

An electrochromic device comprising two oppositely disposed electrode layers, an electrochromic layer, an ion storage layer, and an electrolyte layer, wherein the electrochromic layer comprises lithium nickel oxide (LiNiOx), and the ion storage layer comprises conductive graphite. Is an electrochromic device,
The electrochromic device further includes a power source, the color potential of the electrochromic device is 1.5 V to 2.5 V in size with a positive sign, and the discoloration potential is 3 V to 4 V with a negative sign. Electrochromic device of size.
The electrochromic device of claim 1, wherein the conductive graphite is graphite oxide, and a mass ratio of oxygen and carbon is in a range of 0.005 ≦ O / C ≦ 0.3.
The electrochromic device of claim 2, wherein the ion storage layer has a resistance of 100 Ω / □ to 10,000 Ω / □.
The electrochromic device of claim 2, wherein the ion storage layer has a thickness in a range of 10 nm to 150 nm and a refractive index of visible light ranges from 1.0 to 3.0.
The electrochromic device of claim 2, wherein the ion storage layer has a transmittance of 65% to 75% of visible light.
The electrochromic device of claim 1, wherein the electrochromic layer has a thickness in the range of 10 nm to 300 nm.
The electrochromic device of claim 1, wherein the electrochromic layer has a transmittance of 20% to 40% for visible light when colored and 45% to 80% for visible light when decolored.
The electrochromic device of claim 1, wherein the electrolyte layer has a thickness of 30 μm to 200 μm and a light transmittance of visible light in a range of 70% to 95%.
The electrochromic device of claim 1, wherein the electrolyte layer comprises any one of a liquid electrolyte, a gel-polymer electrolyte, and an inorganic solid electrolyte.
The electrochromic device of claim 9, wherein the electrolyte is an inorganic solid electrolyte containing LiPON or Ta ₂ O ₅ .
The electrochromic device according to claim 9, wherein the electrolyte is a gel-polymer electrolyte formed from a cured product of a mixture containing a carbonate compound and a lithium compound.
The electrochromic device of claim 11, wherein the carbonate-based compound is selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethylmethyl carbonate (EMC).
The method of claim 11, wherein the lithium compound is LiF, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiClO ₃ , LiAsF ₆ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiNO ₃ , LiN (CN) ₂ , LiPF ₆ , Li (CF ₃ ) ₂ PF ₄ , Li (CF ₃ ) ₃ PF ₃ , Li (CF ₃ ) ₄ PF ₂ , Li (CF ₃ ) ₅ PF, Li (CF ₃ ) ₆ P, LiSO ₃ CF ₃ , LiSO ₃ An electrochromic device selected from C ₄ F ₉ , LiSO ₃ (CF ₂ ) ₇ CF ₃ , and LiN (SO ₂ CF ₃ ) ₂ .
The method of claim 1, wherein the electrode layer is formed of indium tin oxide (ITO), fluor doped tin oxide (FTO), aluminum doped zinc oxide (AZO), gallium doped zinc oxide (GZO), antimony doped tin oxide (ATO), or IZO (IZO). At least one transparent conductive compound (TCO) selected from the group consisting of Indium doped Zinc Oxide), Niobium doped Titanium Oxide (NTO), ZnO, Oxide / Metal / Oxide (OMO) and CTO; Conductive polymers; Silver nanowires; And electrochromic device comprising any one of a metal mesh (Metal mesh).
The electrochromic device of claim 14, wherein the electrode layer has a thickness in a range of 1 nm to 1 μm, and transmittance of visible light is in a range of 70% to 95%.
delete Providing a lithium nickel oxide (LiNiOx) layer on one electrode layer; And
On the other electrode layer is a method of manufacturing an electrochromic device comprising the step of providing a graphite layer having a mass ratio of oxygen and carbon in the range 0.005 ≤ O / C ≤ 0.3,
The electrochromic device further includes a power source, wherein the color potential of the electrochromic device is 1.5 V to 2.5 V in magnitude with a positive sign, and the color fading potential is 3 V to 4 V with a sign of negative. A method of manufacturing an electrochromic device of size.
The method of claim 17, wherein the lithium nickel oxide layer or graphite layer is deposited, spin coated, dip coated, screen printed, gravure coated, sol-gel, or slotted. A method for manufacturing an electrochromic device provided by any one of a die die.
19. The method of claim 18, further comprising providing a solid electrolyte layer on one surface of the lithium nickel oxide layer or the graphite layer, wherein the solid electrolyte layer includes a gel-polymer electrolyte or an inorganic solid electrolyte. Method for producing an electrochromic device.

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