Electrochromic fabric and its preparation method

Abstract

The present invention provides an electrochromic fabric and a preparation method thereof. The conductive fabric is treated to make its surface rich in active functional groups; oxalic acid and sodium tungstate solution are mixed, hydrochloric acid is added to adjust the pH, and then n-butanol is added to obtain a precursor solution. The fabric is placed in the precursor solution for high-temperature reaction to obtain the electrochromic fabric. By pre-treating the fabric, the number of functional groups on the fabric surface is increased, and adjusting the pH enhances the binding force between WO3 and the fabric; n-butanol ensures the stable formation of tungsten trioxide, promotes the interaction between oxalic acid and the functional groups on the fabric surface, improves the interfacial interaction force between the WO3 crystal nucleus and the fabric, and at the same time affects the crystal nucleus growth direction, forming a nanorod-like or three-dimensional microsphere structure, and improving the electrochromic performance. Through the synergistic cooperation of each process and related parameters, the electrochromic fabric of the present invention has obvious color change, good cycle stability and high mechanical properties; and the process is simple, the cost is low, and it is suitable for industrial mass production.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochromic fabrics, and particularly to an electrochromic fabric and a preparation method thereof. Background Art

[0002] With the rapid development of the textile technology field, in addition to the traditional properties of fabrics, such as warmth retention, skin-friendliness, and comfort, people also have an increasing demand for specific functions of fabrics. Being able to change the color of clothes according to the changes in the surrounding environment has always been people's dream. Currently, the developed fabrics with color changes usually involve adding photosensitive, thermosensitive, humidity-sensitive and other color-changing materials to the fabrics and their fibers. However, the stimulating conditions such as light intensity, temperature, and humidity cannot be artificially controlled and are greatly affected by the external environment, which limits the color change effect and duration, and such methods are difficult to implement on textiles. However, the electrochromic phenomenon is the color change of fabrics caused by the change of current or electric field, which can achieve artificial control and stable color-changing performance.

[0003] The most typical inorganic electrochromic material is WO3, and its color-changing mechanism is caused by the insertion / extraction of ions or electrons. The invention patent (application number: CN202010467384.3) discloses a preparation method of a multi-dimensional WO3 composite electrochromic thin film. By using potassium oxalate and sodium tungstate to prepare a mixed solution, adjusting the pH value of the solution by adding dilute hydrochloric acid, preparing a reaction solution of one-dimensional WO3 nanorod precursors, and then using hydrothermal reaction and heat treatment to prepare a one-dimensional WO3 nanorod thin film on the surface of FTO conductive glass; then using sodium tungstate, dilute hydrochloric acid and ammonium oxalate to prepare a reaction solution of two-dimensional WO3 nanosheet precursors, and continuing to prepare two-dimensional WO3 nanosheets on the surface of FTO conductive glass loaded with one-dimensional WO3 nanorods by using hydrothermal reaction and heat treatment to obtain a multi-dimensional WO3 composite electrochromic thin film; however, this preparation method is complex, and FTO glass is used as the substrate to prepare the thin film material, and then the glass substrate and the thin film material are separated; however, compared with glass, fabrics have completely different structures, and there are high requirements for the integrity of the prepared electrochromic fabrics. The firmness between the color-changing layer and the fabric substrate is crucial for the subsequent application of the electrochromic fabrics; therefore, this solution cannot solve the technical problem of how to synthesize a stable and strongly bonded color-changing layer on the surface of a flexible conductive fabric.

[0004] In view of this, it is necessary to design an improved electrochromic fabric and a preparation method thereof to solve the above problems. Summary of the Invention

[0005] The object of the present invention is to provide an electrochromic fabric and a preparation method thereof. By mixing oxalic acid with sodium tungstate and adjusting the pH to improve the activity of functional groups on the fabric surface, tungsten trioxide with a special structure is obtained, which forms an interlaced structure with the fabric fibers, thereby improving the binding ability between the fabric and tungsten trioxide. At the same time, n-butanol is added to ensure the stable formation of tungsten trioxide. The electrochromic fabric has obvious color change and good cycle stability, and also has relatively high fabric mechanical properties.

[0006] To achieve the above-mentioned invention object, the present invention provides a preparation method of an electrochromic fabric, including the following steps:

[0007] S1. Perform decontamination treatment and hydrophilic treatment on the fabric to make the surface of the fabric have active functional groups; the fabric has conductivity.

[0008] S2. Add an oxalic acid solution to a sodium tungstate solution with a certain concentration, stir evenly to obtain a mixed solution; add hydrochloric acid to the mixed solution, adjust the pH to 1.2 - 2, and then add n-butanol and stir to obtain a precursor solution.

[0009] S3. Place the fabric treated in step S1 into the precursor solution in step S2 for high-temperature reaction, take out the fabric, wash it multiple times and dry it to obtain an electrochromic fabric.

[0010] As a further improvement of the present invention, in step S2, the concentration of the sodium tungstate solution is 0.01 - 0.04 mol / L, and the solvent is deionized water; the concentration of the oxalic acid solution is 0.2 - 0.5 mol / L.

[0011] As a further improvement of the present invention, the addition amount of n-butanol is 8% - 15% of the volume of the mixed solution.

[0012] As a further improvement of the present invention, the volume ratio of the sodium tungstate solution to the oxalic acid solution is 1:(0.08 - 0.2).

[0013] As a further improvement of the present invention, in step S2, the concentration of the hydrochloric acid is 2 - 3 mol / L; add the hydrochloric acid to the mixed solution and adjust the pH to 1.4 - 1.8.

[0014] As a further improvement of the present invention, in step S1, the method of hydrophilic treatment is: immerse the fabric after decontamination treatment in a hydrogen peroxide solution with a mass concentration of 40% - 60%, heat it to 80 - 100 °C, keep it warm for 2 - 5 h, and then alternately wash it multiple times with deionized water and ethanol and dry it to obtain a fabric with active functional groups on the surface.

[0015] As a further improvement of the present invention, in step S3, the temperature of the high-temperature reaction is 150 to 170 °C, and the time is 12 to 24 h.

[0016] As a further improvement of the present invention, in step S1, the decontamination treatment is to soak the fabric in an ethanol or acetone solution and perform ultrasonic treatment for 3 to 5 min; the fabric includes one or more of carbon cloth, conductive cloth, and silver-plated nylon cloth.

[0017] The present invention also provides an electrochromic fabric prepared by the preparation method of the electrochromic fabric described in any one of the above, including a conductive fabric substrate and an electrochromic layer loaded on the surface of the conductive fabric substrate. The electrochromic layer is a WO3 nanomaterial, and the WO3 nanomaterial is in a rod-like structure and / or a microspherical structure formed by stacking rod-like structures.

[0018] As a further improvement, the diameter of the rod-like structure is 50 to 500 nm, and the diameter of the microspherical structure is 3 to 5 μm; the coloring time of the electrochromic fabric is 1.5 to 3 s, and the bleaching time is 4 to 5 s.

[0019] The beneficial effects of the present invention are as follows:

[0020] 1. The present invention provides an electrochromic fabric and a preparation method thereof. By performing decontamination treatment and hydrophilic treatment on the conductive fabric, active functional groups are formed on the fabric surface; oxalic acid and sodium tungstate solution are mixed, hydrochloric acid is added thereto, the pH is adjusted to 1.2 to 2, and then n-butanol is added and stirred to obtain a precursor solution; finally, the fabric is placed in the precursor solution for high-temperature reaction, the fabric is taken out, washed multiple times and dried to obtain an electrochromic fabric. Tungsten trioxide is grown on the flexible fabric substrate of the present invention. The treatment method of the fabric is simple and the cost is low. At the same time, through the synergistic cooperation of each process and related parameters, tungsten trioxide grows uniformly on the fabric surface. The synthesis process of the electrochromic layer is simple, the cost of preparing the electrochromic fabric is low, the raw materials are easy to obtain, and it is suitable for industrial mass production.

[0021] 2. By adjusting the pH value in the precursor solution to 1.2 to 2, the present invention improves the activity of the functional groups on the fabric surface, enables tungsten trioxide to have better binding ability with the fabric during the formation process, and at the same time ensures that the electrochromic layer of tungsten trioxide is more uniform and stable; and in this pH environment, the Cl provided by hydrochloric acid -It can accelerate the regulation of the longitudinal growth of WO3 crystal nuclei to form nanorods. These nanorods are intertwined with fabric fibers to form an interlaced structure, which greatly improves the binding ability between WO3 and the fabric substrate, and further enhances the stability of the electrochromic layer of the electrochromic fabric. At the same time, the addition of n-butanol can play a role in immobilizing the WO3 crystal nuclei. N-butanol increases the interaction force between oxalic acid and the functional groups on the fabric surface, which is beneficial to the contact between the WO3 crystal nuclei and the fabric interface, and improves the interfacial interaction force between the WO3 crystal nuclei and the fabric, especially at the fabric weaving nodes. Meanwhile, it affects the growth direction of the crystal nuclei, causing them to grow along the one-dimensional direction to form a nanorod-like structure; these nanorod-like structures accumulate in the increased space at the nodes to form a three-dimensional stable microsphere structure, which is conducive to improving the electrochromic performance of the fabric.

[0022] 3. The n-butanol added in the present invention has the common characteristics of small molecule alcohols and macromolecule alcohols. It can dissolve some polar compounds but is insoluble in water. At the same time, using n-butanol can form an oil film on the surface of the solution, providing a closed environment for its reaction system, preventing side reactions of other impurities and gases, and being conducive to the smooth progress of the reaction. On the other hand, it reduces the loss of the solvent and can extract polar impurities in the precursor solution, ensuring that the obtained product is more stable without by-products.

[0023] 4. The present invention uses oxalic acid and sodium tungstate as raw materials. Oxalic acid can not only be used as an inducer to regulate the morphology of tungsten trioxide but also as a dispersant to make the WO3 crystal nuclei more easily dispersed on the fabric, enhancing the contact with the fabric, especially at the fabric weaving points, and enabling the WO3 crystal nuclei to grow on it to form a structure interlaced with the fabric. Moreover, the presence of oxalic acid can reduce the use of hydrochloric acid, avoiding damage to the mechanical properties of the fabric substrate caused by excessive hydrochloric acid and affecting the application of the prepared electrochromic fabric. The electrochromic fabric prepared by the present invention has obvious color change, good cycle stability, and also has relatively high fabric mechanical properties. Description of the Drawings

[0024] Figure 1 It is the micrograph of the electrochromic fabric prepared in Example 1.

[0025] Figure 2 It is the infrared absorption spectra of the WO3 electrochromic fabric prepared in Example 1 in the colored state and the bleached state.

[0026] Figure 3 It is the micrograph of the electrochromic fabric prepared in Example 2.

[0027] Figure 4 It is the micrograph of the electrochromic fabric prepared in Example 4.

[0028] Figure 5SEM images taken of the WO3 powder prepared in Comparative Example 1 are collected.

[0029] Figure 6 Cyclic voltammetry performance test curves of the electrochromic fabrics prepared in Examples 1 to 5.

[0030] Figure 7 Time-current curves of the electrochromic fabrics prepared in Examples 1 to 5. Detailed implementation manners

[0031] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Here, it should also be noted that in order to avoid obscuring the present invention due to unnecessary details, only the structures and / or processing steps closely related to the solution of the present invention are shown in the drawings, while other details less related to the present invention are omitted.

[0033] In addition, it should also be noted that the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0034] A method for preparing an electrochromic fabric, comprising the following steps:

[0035] S1. The fabric is subjected to decontamination treatment and hydrophilic treatment to make the fabric surface have active functional groups; the fabric used is a conductive fabric with conductivity;

[0036] Among them, the method of hydrophilic treatment is: the fabric after decontamination treatment is immersed in a hydrogen peroxide solution with a mass concentration of 40% - 60%, heated to 80 - 100 °C, kept warm for 2 - 5 h, and then alternately washed with deionized water and ethanol for multiple times and dried to obtain a fabric with active functional groups on the surface; treating the fabric with a hydrogen peroxide solution can not only activate the functional groups on the fabric surface, but its self-borne anions are easily attached to the surface of the fiber, increasing the number of active groups on the fabric surface, which is beneficial to the nucleation and growth of tungsten trioxide on the fabric surface subsequently;

[0037] S2. Oxalic acid solution is added to a sodium tungstate solution with a certain concentration, and stirred evenly to obtain a mixed solution; hydrochloric acid is added to the mixed solution to adjust the pH to 1.2 - 2, and then n-butanol is added and stirred to obtain a precursor solution;

[0038] By regulating the pH value in the precursor solution, the activity of the functional groups on the fabric surface is enhanced, enabling tungsten trioxide to have a better binding ability with the fabric during the formation process, while ensuring that the electrochromic layer of tungsten trioxide is more uniform and stable; and in this pH environment, the Cl provided by hydrochloric acid - can accelerate the regulation of the longitudinal growth of WO3 crystal nuclei to form nanorods. These nanorods are intertwined with the fabric fibers to form an interlaced structure, which greatly improves the binding ability between WO3 and the fabric substrate, and further enhances the stability of the electrochromic layer of the electrochromic fabric; meanwhile, the addition of n-butanol can play a role in immobilizing the WO3 crystal nuclei. N-butanol increases the interaction force between oxalic acid and the functional groups on the fabric surface, which is beneficial to improving the interfacial interaction force between the WO3 crystal nuclei and the fabric, especially at the fabric weaving nodes, and at the same time affects the growth direction of the crystal nuclei, causing them to grow along a one-dimensional direction to form a nanorod-like structure; these nanorod-like structures accumulate in the increased space at the nodes to form a three-dimensional stable microsphere structure, which is conducive to improving the subsequent electrochromic performance;

[0039] S3. Immerse the fabric treated in step S1 in the precursor solution of step S2 for high-temperature reaction. The temperature of the high-temperature reaction is 150 - 170 °C, and the time is 12 - 24 h. Take out the fabric, wash it multiple times and dry it to obtain the electrochromic fabric.

[0040] Specifically, the addition of n-butanol has the common characteristics of small-molecule alcohols and large-molecule alcohols, and can dissolve some polar compounds but is insoluble in water; therefore, using n-butanol can form an oil film on the surface of the solution, providing a closed environment for its reaction system, preventing side reactions of other impurities and gases, which is beneficial to the smooth progress of the reaction. On the other hand, it reduces the loss of the solvent and can extract the polar impurities in the precursor solution, ensuring that the obtained product is more stable without by-products.

[0041] Specifically, in step S2, the concentration of the sodium tungstate solution is 0.01 - 0.04 mol / L, and the solvent is deionized water; the concentration of the oxalic acid solution is 0.2 - 0.5 mol / L. The addition amount of n-butanol is 8% - 15% of the volume of the mixed solution. The volume ratio of the sodium tungstate solution to the oxalic acid solution is 1:(0.08 - 0.2). By limiting the concentrations of sodium tungstate and oxalic acid and their volume ratio, the two can better play a synergistic role during the formation of the electrochromic layer, which is beneficial to the growth of tungsten trioxide on the fabric surface.

[0042] Oxalic acid and sodium tungstate are used as raw materials. Oxalic acid can not only be used as an inducer to regulate the morphology of tungsten trioxide, but also as a dispersant to make the WO3 crystal nuclei more easily dispersed on the fabric, enhance the contact with the fabric, especially the fabric weaving points, and enable the WO3 crystal nuclei to grow on them, forming a structure intertwined with the fabric. Moreover, the presence of oxalic acid can also reduce the use of hydrochloric acid, avoiding damage to the mechanical properties of the fabric substrate caused by excessive hydrochloric acid and affecting the application of the prepared electrochromic fabric.

[0043] Specifically, the concentration of hydrochloric acid is 2 - 3 mol / L; hydrochloric acid is added to the mixed solution of oxalic acid and sodium tungstate to adjust the pH to 1.4 - 1.8. In this pH environment, the electrochromic fabric obtained has the best color-changing performance, good mechanical properties, and a more uniform and stable structure of the electrochromic material on the fabric surface.

[0044] In some specific embodiments, in step S1, the decontamination treatment is to soak the fabric in an ethanol or acetone solution and perform ultrasonic treatment for 3 - 5 minutes.

[0045] In some specific embodiments, the fabric includes one or more of carbon cloth, conductive cloth, and silver-plated nylon cloth.

[0046] In some specific embodiments, the reaction kettle for the high-temperature reaction is a stainless steel reaction kettle with a polytetrafluoroethylene reaction kettle liner.

[0047] In some specific embodiments, after the oxalic acid solution is added to the sodium tungstate solution, the stirring time is 3 - 5 minutes; after hydrochloric acid is added to the mixed solution of oxalic acid and sodium tungstate, the stirring time is 20 - 30 minutes, and the stirring time for continuously adding n-butanol is 15 minutes.

[0048] An electrochromic fabric prepared by the preparation method of an electrochromic fabric includes a conductive fabric substrate and an electrochromic layer loaded on the surface of the conductive fabric substrate. The electrochromic layer is a WO3 nanomaterial, and the WO3 nanomaterial is in a rod-like structure and / or a microsphere structure formed by stacking rod-like structures. Among them, the diameter of the rod-like structure is 50 - 500 nm, and the diameter of the microsphere structure is 3 - 5 μm; the coloring time of the electrochromic fabric is 1.5 - 3 s, and the bleaching time is 4 - 5 s.

[0049] In the present invention, tungsten trioxide is grown on a flexible fabric substrate. The treatment method of the fabric is simple and the cost is low. At the same time, through the synergistic cooperation of various process parameters, tungsten trioxide grows uniformly on the fabric surface. The synthesis process of the electrochromic layer is simple, the cost of preparing the electrochromic fabric is low, the raw materials are easily available, and it is suitable for industrial mass production. The prepared electrochromic fabric has obvious color change, good cycle stability, and also has high fabric mechanical properties.

[0050] Example 1

[0051] This embodiment provides an electrochromic fabric and a preparation method thereof, including the following steps:

[0052] S1. Immerse a 3×3 cm carbon cloth in an ethanol or acetone solution, perform ultrasonic treatment for 5 min, immerse the cleaned fabric in a hydrogen peroxide solution with a mass concentration of 40%, heat to 80 °C, keep warm for 3 h, alternately wash twice with deionized water and ethanol, and then put it in an oven at 60 °C for drying and storage for later use;

[0053] S2. Weigh 3.00 g of sodium tungstate powder and dissolve it in 50 mL of deionized water, stir for 5 min to obtain a 0.02 mol / L sodium tungstate solution; take 10 mL of oxalic acid with a concentration of 0.2 mol / L and add it to the sodium tungstate solution and stir for 5 min to obtain a mixed solution; add hydrochloric acid with a concentration of 3 mol / L to the mixed solution in a stirred dropwise manner, adjust the pH to 1.6, stir for 30 min, then add 5 mL of n-butanol solution, and continue to stir for 15 min to obtain a precursor solution;

[0054] S3. Vertically place the carbon cloth into a polytetrafluoroethylene inner liner and fix it, put it into a stainless steel autoclave for high-temperature reaction, the reaction temperature is 170 °C, the reaction time is 24 h, after the reaction is completed, the carbon cloth is alternately washed with deionized water and ethanol, and then dried in an oven at 60 °C for 12 h to obtain an electrochromic fabric.

[0055] Please refer to Figure 1 as shown, which is the microelectron microscope image of the electrochromic fabric prepared in Example 1. It can be seen from the figure that at this time, the morphology of WO3 on the surface of the carbon cloth fiber is composed of a nanorod-like structure and a microsphere-like structure formed by the stacking of nanorods; and the surface of the carbon cloth is a morphological structure tightly coated with tungsten trioxide nanomaterials, indicating that this embodiment successfully prepares a structurally compact and uniform electrochromic fabric with the carbon cloth as the substrate.

[0056] Please refer to Figure 2 as shown, which is the infrared absorption spectra of the WO3 electrochromic fabric prepared in Example 1 in the colored state and the bleached state. It can be seen from the figure that there is a maximum contrast at 868 nm. According to the coloring efficiency formula: where Tb is the transmittance in the bleached state, and Tc is the transmittance in the colored state; the coloring efficiency of the WO3 electrochromic fabric prepared in this embodiment is calculated to be 53.24 cm 2 / C.

[0057] Example 2

[0058] This embodiment provides an electrochromic fabric and a preparation method thereof. Compared with Example 1, the difference is that in step S2, the pH is adjusted to 1.4, and the rest is substantially the same as in Example 1, which will not be elaborated here.

[0059] Please refer to Figure 3 as shown, which is the micrograph of the electrochromic fabric prepared in Example 2. It can be seen from the figure that the morphology of WO3 on the surface of the carbon cloth fiber is composed of a nanorod-like structure and a microsphere structure formed by the stacking of nanorods; and the surface of the carbon cloth is a morphological structure tightly coated with tungsten trioxide nanomaterials.

[0060] Example 3

[0061] This example provides an electrochromic fabric and its preparation method. Compared with Example 1, the difference is that in step S2, the pH is adjusted to 1.2, and the rest is roughly the same as in Example 1, which will not be elaborated here.

[0062] Example 4

[0063] This example provides an electrochromic fabric and its preparation method. Compared with Example 1, the difference is that in step S2, the pH is adjusted to 1.8, and the rest is roughly the same as in Example 1, which will not be elaborated here.

[0064] Please refer to Figure 4 as shown, which is the micrograph of the electrochromic fabric prepared in Example 4. It can be seen from the figure that at this time, the morphology of WO3 is nanorods with a length of 3 - 5 μm and a diameter of 400 nm. It can be observed that the surface of the carbon cloth is a morphological structure tightly coated with tungsten trioxide nanorods, indicating that this example successfully prepared a tightly structured and uniform electrochromic fabric with the carbon cloth as the substrate.

[0065] Example 5

[0066] This example provides an electrochromic fabric and its preparation method. Compared with Example 1, the difference is that in step S2, the pH is adjusted to 2.0, and the rest is roughly the same as in Example 1, which will not be elaborated here.

[0067] Comparative Example 1

[0068] Comparative Example 1 provides an electrochromic fabric and its preparation method. Compared with Example 1, the difference is that in step S2, the pH is adjusted to 1.0, and the rest is roughly the same as in Example 1, which will not be elaborated here.

[0069] Please refer to Figure 5As shown, SEM images of the WO3 powder prepared in Comparative Example 1 were collected. Since the mixed solution in Comparative Example 1 was too acidic, which affected the hydroxyl activity on the surface of the carbon cloth after hydrophilic treatment, resulting in fewer WO3 particles attached to the carbon cloth fibers, and the electrochromic fabric could not be successfully prepared. Therefore, the synthesized WO3 powder was collected for SEM imaging. It can be seen from the figure that the WO3 at this time was in a cubic crystal phase, and the side length of the cube was about 300 nm. This structure also affected its combination with the carbon cloth.

[0070] Comparative Example 2

[0071] Comparative Example 2 provides an electrochromic fabric and a preparation method thereof. Compared with Example 1, the difference lies in that in step S2, the pH was adjusted to 2.2, and the rest was substantially the same as in Example 1, which will not be elaborated here.

[0072] In Comparative Example 2, since the acidity of the mixed solution was weak and the degree of acidification of sodium tungstate was low, the amount of WO3 obtained after the high-temperature reaction was small, and the growth of WO3 was faster in a weak acid environment, resulting in larger particle sizes, which also affected the combination of the electrochromic material and the fabric. Although an electrochromic fabric with a relatively thick electrochromic layer attached to the surface was prepared in Comparative Example 2, the adhesion of the electrochromic layer to the fabric was poor and it was easy to fall off, making it difficult to be applied in practice.

[0073] Please refer to Figure 6 As shown, it is the cyclic voltammetry performance test curve graph of the electrochromic fabrics prepared in Examples 1 to 5. It can be seen from the figure that the curve shows a reduction peak of tungsten trioxide at -0.3 V / -0.5 V and an oxidation peak at 0.3 V / 0.5 V, indicating that the color change of the electrochromic fabric is mainly caused by the change in the redox state of the electrochromic material. From pH = 1.2 to pH = 2.0, the maximum current values of the electrochromic fabric were all between 6 and 8 A, and the current value was the largest at 8.17 A when pH = 1.6, indicating that the electrochromic fabric obtained at this pH had the best cycling performance.

[0074] Please refer to Figure 7 As shown, it is the time-current curve graph of the electrochromic fabrics prepared in Examples 1 to 5. This curve shows the color change times of the WO3 electrochromic fabric in the reduced state and the oxidized state. When pH = 1.2 to pH = 1.6, the coloring time of the fabric was within 5 s, and the bleaching time was within 6 s, and the optimal values were reached at pH = 1.6 (the coloring time was 1.7 s and the bleaching time was 4.7 s), indicating that the electrochromic fabric prepared in this example had a relatively fast color switching rate. As the pH value continued to increase, both the coloring time and the bleaching time increased. This was attributed to the fact that as the pH value increased, the WO3 nanorods became nanosheets, reducing the H + embedding and detachment rates in the WO3 electrochromic layer.

[0075] The electrochromic fabrics prepared in Examples 1 to 5 and the fabrics treated in Comparative Examples 1 to 2 were tested for coloring efficiency and mechanical properties, and the results are shown in the following table.

[0076] Table 1 Comparison results of fabric properties of Examples 1 to 5 and Comparative Examples 1 to 2

[0077] <![CDATA[Coloring efficiency (cm 2 / C)]]> Breaking strength (N / 25mm) Elongation at break (%) Example 1 53.24 1610 1.7 Example 2 50.93 1613 1.7 Example 3 49.11 1607 1.6 Example 4 50.21 1609 1.7 Example 5 48.89 1611 1.6 Comparative Example 1 39.18 1542 1.5 Comparative Example 2 40.21 1576 1.5

[0078] As can be seen from Table 1, when the pH value of the system is between 1.2 and 2.0, the breaking strength and elongation at break of the fabric do not change significantly and remain at a relatively high level. When pH = 1.0, due to the too strong acidity of the solution, the fabric surface is eroded to a certain extent, resulting in the fabric being more prone to breakage; when pH = 2.2, the WO3 electrochromic layer grown on the fabric surface is relatively thick, which affects the flexibility of the fabric itself, so the mechanical properties also decrease. The structure and thickness of the WO3 electrochromic layer directly affect the coloring efficiency of the fabric. When pH = 1.6, WO3 is in a nanorod structure and the thickness is appropriate without changing the flexibility of the fabric itself, so its coloring efficiency is the highest. When the acidity is too strong or too low, it is not conducive to the growth of the WO3 electrochromic layer, and the coloring efficiency also decreases significantly.

[0079] Comparative Example 3

[0080] Comparative Example 3 provides an electrochromic fabric and its preparation method. Compared with Example 1, the difference is that in step S2, n-butanol is not added, and the rest is substantially the same as in Example 1, which will not be elaborated here.

[0081] Comparative Example 4

[0082] Comparative Example 4 provides an electrochromic fabric and its preparation method. Compared with Example 1, the difference is that in step S2, ethanol is used instead of n-butanol, and the rest is substantially the same as in Example 1, which will not be elaborated here.

[0083] Comparative Example 5

[0084] Comparative Example 5 provides an electrochromic fabric and its preparation method. Compared with Example 1, the difference is that in step S2, isopentanol is used instead of n-butanol, and the rest is substantially the same as in Example 1, which will not be elaborated here.

[0085] Comparative Example 6

[0086] Comparative Example 6 provides an electrochromic fabric and its preparation method. Compared with Example 1, the difference is that in step S2, sulfuric acid is used instead of hydrochloric acid to adjust the pH, and the rest is substantially the same as in Example 1, which will not be elaborated here.

[0087] Comparative Example 7

[0088] Comparative Example 7 provides an electrochromic fabric and a preparation method thereof. Compared with Example 1, the difference lies in that in step S1, oxalate is used instead of oxalic acid, and the rest is substantially the same as in Example 1, which will not be elaborated here.

[0089] Comparative Example 8

[0090] Comparative Example 8 provides an electrochromic fabric and a preparation method thereof. Compared with Example 1, the difference lies in that in step S1, citric acid is used instead of oxalic acid, and the rest is substantially the same as in Example 1, which will not be elaborated here.

[0091] The electrochromic fabrics prepared in Comparative Examples 3 to 8 were subjected to tests on coloring efficiency, cyclic voltammetry performance, time-current, and mechanical properties, and the results obtained are shown in Table 2.

[0092] Table 2 Comparison results of fabric properties of Example 1 and Comparative Examples 3 to 8

[0093]

[0094] As can be seen from Table 2, by adding different alcohols / acids to the sodium tungstate solution for regulation, the WO3 synthesized on the fabric surface has little effect on the breaking strength and elongation at break of the fabric. However, when n-butanol was not added or other alcohols were added in Comparative Examples 3 to 5, the coloring efficiency of the fabric decreased significantly, and the color switching time also increased. This is attributed to the fact that low-molecular alcohols and higher-molecular alcohols will affect the binding ability of the generated WO3 particles to the fabric and cannot achieve the promoting effect like n-butanol. In Comparative Example 6, the WO3 electrochromic fabric obtained by changing different acids to provide an acidic environment cannot achieve the effect of accelerating the regulation of the longitudinal growth of WO3 crystal nuclei to form nanorods, improving the binding ability of WO3 to the fabric substrate, and further improving the stability of the electrochromic layer of the electrochromic fabric; resulting in the coloring efficiency and color switching time of the electrochromic fabric in Comparative Example 6 being inferior to those of the fabric in hydrochloric acid and oxalic acid environments. In Comparative Example 7, oxalate was used instead of oxalic acid. Since the synthesized WO3 particles are larger and the thickness of the WO3 electrochromic layer on the fabric surface increases, although its maximum current value will increase to a certain extent, it limits the interpenetration of ions in the electrochromic layer and reduces the electrochromic performance of the fabric. In Comparative Example 8, citric acid was used instead of oxalic acid, and it is difficult to exert the synergistic effect of oxalic acid and sodium tungstate, and the coloring efficiency and color switching time of the obtained electrochromic fabric are lower than those in Example 1. - Accelerate the regulation of the longitudinal growth of WO3 crystal nuclei to form nanorods, improve the binding ability of WO3 to the fabric substrate, and further improve the stability of the electrochromic layer of the electrochromic fabric; resulting in the coloring efficiency and color switching time of the electrochromic fabric in Comparative Example 6 being inferior to those of the fabric in hydrochloric acid and oxalic acid environments. In Comparative Example 7, oxalate was used instead of oxalic acid. Since the synthesized WO3 particles are larger and the thickness of the WO3 electrochromic layer on the fabric surface increases, although its maximum current value will increase to a certain extent, it limits the interpenetration of ions in the electrochromic layer and reduces the electrochromic performance of the fabric. In Comparative Example 8, citric acid was used instead of oxalic acid, and it is difficult to exert the synergistic effect of oxalic acid and sodium tungstate, and the coloring efficiency and color switching time of the obtained electrochromic fabric are lower than those in Example 1.

[0095] In summary, the present invention provides an electrochromic fabric and a preparation method thereof. By performing decontamination treatment and hydrophilic treatment on the conductive fabric, active functional groups are formed on the fabric surface; oxalic acid is mixed with a sodium tungstate solution, hydrochloric acid is added thereto, the pH is adjusted to 1.2 - 2, and then n-butanol is added and stirred to obtain a precursor solution; finally, the fabric is placed in the precursor solution for a high-temperature reaction, the fabric is taken out, washed multiple times and dried to obtain the electrochromic fabric. By regulating the pH value in the precursor solution, the present invention improves the activity of the functional groups on the fabric surface, enables tungsten trioxide to have better binding ability with the fabric during the formation process, and at the same time ensures that the electrochromic layer of tungsten trioxide is more uniform and stable; and in this pH environment, the Cl provided by hydrochloric acid - can accelerate the regulation of the longitudinal growth of WO3 crystal nuclei to form nanorods, and these nanorods are intertwined with the fabric fibers to form an interlaced structure, which greatly improves the binding ability between WO3 and the fabric substrate, and further improves the stability of the electrochromic layer of the electrochromic fabric. In addition, due to the addition of water-insoluble n-butanol, it can play a role in immobilizing the WO3 crystal nuclei, improve the strong interaction between oxalic acid and the functional groups on the fabric surface, facilitate the contact between the WO3 crystal nuclei and the fabric interface, and improve the interfacial interaction between the WO3 crystal nuclei and the fabric, especially at the fabric weaving nodes, and at the same time affect the growth direction of the crystal nuclei, making them grow along a one-dimensional direction to form a nanorod-like structure; these nanorod-like structures accumulate in the increased space at the nodes to form a three-dimensional stable microsphere structure, which is beneficial to improving the subsequent electrochromic performance. The present invention grows tungsten trioxide on a flexible fabric substrate, and at the same time, through the synergistic cooperation of various processes and related parameters, tungsten trioxide grows uniformly on the fabric surface. The prepared electrochromic fabric has obvious color change, good cycle stability, and also has high fabric mechanical properties; the synthesis process of the electrochromic layer is simple, the cost of preparing the electrochromic fabric is low, the raw materials are easy to obtain, and it is suitable for industrial mass production.

[0096] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A preparation method of an electrochromic fabric, characterized in that It includes the following steps: S1. Perform decontamination treatment and hydrophilic treatment on the fabric to make the surface of the fabric have active functional groups; The fabric has conductivity; S2. Add an oxalic acid solution to a sodium tungstate solution with a certain concentration, and stir evenly to obtain a mixed solution; Add hydrochloric acid to the mixed solution, adjust the pH to 1.2 - 2, and then add n-butanol and stir to obtain a precursor solution; The concentration of the sodium tungstate solution is 0.01 - 0.04 mol / L, the solvent is deionized water, and the concentration of the oxalic acid solution is 0.2 - 0.5 mol / L; the addition amount of n-butanol is 8% - 15% of the volume of the mixed solution; S3. Immerse the fabric treated in step S1 in the precursor solution of step S2 for high-temperature reaction, take out the fabric, wash it multiple times and dry it to obtain an electrochromic fabric.

2. The preparation method of the electrochromic fabric according to claim 1, characterized in that, The volume ratio of the sodium tungstate solution to the oxalic acid solution is 1:(0.08 - 0.2).

3. The preparation method of the electrochromic fabric according to claim 1, characterized in that, In step S2, the concentration of the hydrochloric acid is 2 - 3 mol / L; add the hydrochloric acid to the mixed solution and adjust the pH to 1.4 - 1.

8.

4. The preparation method of the electrochromic fabric according to claim 1, characterized in that, In step S1, the method of hydrophilic treatment is: immerse the decontaminated fabric in a hydrogen peroxide solution with a mass concentration of 40% - 60%, heat it to 80 - 100°C, keep it warm for 2 - 5 h, and then alternately wash it multiple times with deionized water and ethanol and dry it to obtain a fabric with active functional groups on the surface.

5. The preparation method of the electrochromic fabric according to claim 1, characterized in that, In step S3, the temperature of the high-temperature reaction is 150 - 170°C, and the time is 12 - 24 h.

6. The preparation method of the electrochromic fabric according to claim 1, characterized in that, In step S1, the decontamination treatment is to soak the fabric in an ethanol or acetone solution and perform ultrasonic treatment for 3 - 5 min; the fabric includes one or more of carbon cloth, conductive cloth, and silver-plated nylon cloth.

7. An electrochromic fabric prepared by the method for preparing an electrochromic fabric according to any one of claims 1 to 6, characterized in that, It includes a conductive fabric substrate and an electrochromic layer loaded on the surface of the conductive fabric substrate. The electrochromic layer is a WO3 nanomaterial, and the WO3 nanomaterial is in a rod-like structure and / or a microsphere structure formed by stacking rod-like structures.

8. The electrochromic fabric according to claim 7, wherein The diameter of the rod-like structure is 50 - 500 nm, and the diameter of the microsphere structure is 3 - 5 μm; the coloring time of the electrochromic fabric is 1.5 - 3 s, and the bleaching time is 4 - 5 s.

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