Composite quasi-solid electrolyte with porous structure, electrochromic device and preparation method of composite quasi-solid electrolyte

Abstract

The invention discloses a composite quasi-solid electrolyte with a porous structure, an electrochromic device and a preparation method. The composite quasi-solid electrolyte with the porous structure comprises a semi-interpenetrating polymer network structure, cone salt and an organic solvent, wherein the semi-interpenetrating polymer network structure is jointly constructed by a polymer matrix and a polyvinylidene fluoride-hexafluoropropylene copolymer with a linear long-chain structure, and the cone salt and the organic solvent are distributed in the semi-interpenetrating polymer network structure. And the polymer matrix is at least any one of ethoxylated trimethyl propyl triacrylate, pentaerythritol triacrylate and 3 (propoxy) glycerol triacrylate. Compared with a traditional quasi-solid electrolyte, the ionic conductivity of the prepared porous structure composite quasi-solid electrolyte meets the requirement for application in an electrochromic device, the porous structure composite quasi-solid electrolyte has certain flexibility, the problem of poor contact between interfaces is solved, the interface compatibility of an electrode and the electrolyte is enhanced, the device preparation method is simple, and the preparation cost is low. And the material has long cycle stability.

Description

Technical Field

[0001] The present invention relates to an electrochromic device, in particular to a porous structure composite quasi-solid electrolyte and an electrochromic device and a preparation method, belonging to the technical field of electrochromism. Background Art

[0002] Electrochromic devices undergo reversible changes in optical properties under the action of external voltage, and have important application prospects in the fields of smart windows, smart camouflage, non-emissive displays, etc. Usually, the basic composition of the device includes a transparent conductive layer, an ion storage layer, an ion conduction layer (electrolyte layer) and an electrochromic layer. Among them, the electrolyte layer is particularly important. It not only plays the role of transmitting ions, but also isolates the upper and lower electrodes to prevent the device from short-circuiting and failing. From a physical point of view, electrolytes are divided into three categories, namely liquid electrolytes, all-solid electrolytes and quasi-solid electrolytes. Liquid electrolytes have extremely high ionic conductivity and can easily reach 10 -3 Order of magnitude, but when it is applied to devices, the problems of liquid volatility, difficulty in packaging, and easy leakage are difficult to overcome, which can easily lead to device failure. These factors greatly limit its practical application in electrochromic devices (ECD). Although all-solid-state electrolytes avoid the leakage problem and have certain mechanical strength, they still have defects such as low conductivity, complex manufacturing equipment, low product yield, and high cost. For example, a solvent-free polymethyl methacrylate (PMMA)-based solid polymer electrolyte (hereinafter referred to as SN-PMMA) with succinonitrile (SN) as a plasticizer was prepared by a blade coating method. The electrolyte exhibits excellent ionic conductivity under solvent-free conditions, reaching 0.58mS / cm. Based on this electrolyte, a solid-state electrochromic device (ECD) constructed in combination with a WO3 hot lamination process still maintains an optical modulation amplitude of 90.8% after 500 cycles, showing good cycle stability. In addition, the device has a high coloring efficiency (53.77cm 2 / C), and a faster fading / coloring response time of 23.8 seconds and 38.1 seconds, respectively. Although this solution has achieved certain results in improving ionic conductivity by introducing succinonitrile to replace traditional volatile organic solvents, its preparation process is relatively complicated, and poor interface contact during the lamination process may lead to prolonged response time and decreased cycle performance, thus limiting its promotion and use in practical applications. In addition, studies have used magnetron sputtering to prepare solid LiAlSiO4 electrolyte materials, but their room temperature ionic conductivity is low, only 10 -7 –10 -9S / cm, which seriously restricts the response speed and electrochemical performance of the device. Experiments show that the response time of the electrochromic device based on this electrolyte exceeds 20 seconds, and after 1000 cycles, its optical modulation ability is significantly attenuated, resulting in the overall performance being difficult to meet the requirements of fast response and high stability in practical applications. Although solid polymer electrolytes overcome the shortcomings of liquid electrolytes and have good mechanical properties, their high crystallinity and glass transition temperature result in a low conductivity at room temperature (10 -8 -10 -5 S / cm) is lower than the conductivity required in practical applications (10 -3 S / cm), which limits its application in ECD. In comparison, quasi-solid-state electrolytes avoid the problems existing in liquid electrolytes and solid electrolytes, while taking into account the mechanical properties of solid electrolytes and the high ionic conductivity of liquid electrolytes. They are electrolyte materials with application potential in electrochromic devices. For example, studies have used the silane coupling agent KH-560 to modify SiO2 to reduce the degree of agglomeration between inorganic particles, increase dispersibility and achieve grafting modification, thereby improving the ionic conductivity of quasi-solid-state electrolytes. However, this method has complex processes, cumbersome operations, and limited conductivity improvement effects. In addition, a study proposed a self-supporting electrolyte SSE based on a PHPA-PMMA skeleton structure, which was applied to an electrochromic device with an ITO / WO3 / SSE / NiO / ITO structure. The optical modulation of the device at 550nm was 41.2%, and the coloring efficiency was 87cm 2 ·C -1 , the optical modulation retention rate is 95% after 1000 cycles. However, the stability of the device during long-term cycling still needs to be improved. Summary of the Invention

[0003] The main purpose of the present invention is to provide a porous composite quasi-solid electrolyte to overcome the deficiencies in the prior art.

[0004] Another object of the present invention is to provide an electrochromic device and a method for preparing the same.

[0005] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0006] An embodiment of the present invention provides a porous structure composite quasi-solid-state electrolyte, which includes: a semi-interpenetrating polymer network structure jointly constructed by a polymer matrix and a polyvinylidene fluoride-hexafluoropropylene copolymer with a linear long-chain structure, and a lithium salt and an organic solvent distributed in the semi-interpenetrating polymer network structure, wherein the polyvinylidene fluoride-hexafluoropropylene copolymer penetrates the polymer matrix to form a three-dimensional network structure, and the polymer matrix is a polymer obtained by cross-linking reaction of any one or more combinations of ethoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, and 3(propoxy)propylene triacrylate.

[0007] The present invention also provides a method for preparing a porous composite quasi-solid electrolyte, comprising:

[0008] The lithium salt, the organic solvent, the polyvinylidene fluoride-hexafluoropropylene copolymer, the polymer monomer, and the initiator are uniformly mixed to form a quasi-solid electrolyte precursor solution;

[0009] The quasi-solid electrolyte precursor solution is irradiated under ultraviolet light to chemically cross-link the polymer monomers to form a three-dimensional network structure, thereby preparing a porous structure composite quasi-solid electrolyte.

[0010] The embodiment of the present invention further provides the use of the aforementioned porous structure composite quasi-solid electrolyte in the preparation of an electrochromic device.

[0011] Correspondingly, an embodiment of the present invention also provides an electrochromic device, comprising an ion storage layer, an electrolyte layer and an electrochromic layer plated on a conductive substrate in sequence, wherein the electrolyte layer is composed of the aforementioned porous structure composite quasi-solid electrolyte.

[0012] An embodiment of the present invention further provides a method for preparing an electrochromic device, comprising:

[0013] The lithium salt, the organic solvent, the polyvinylidene fluoride-hexafluoropropylene copolymer, the polymer monomer, and the initiator are uniformly mixed to form a quasi-solid electrolyte precursor solution;

[0014] A quasi-solid electrolyte precursor solution is applied to the surface of an ion storage layer disposed on a conductive substrate, and then an electrochromic layer disposed on the conductive substrate is placed on the ion storage layer, and then irradiated with ultraviolet light to produce an electrochromic device.

[0015] Compared with the prior art, the beneficial effects of the present invention include at least:

[0016] 1) Compared with traditional quasi-solid electrolytes, the porous composite quasi-solid electrolyte prepared by the present invention has an ionic conductivity that meets the requirements for application in electrochromic devices and has a certain degree of flexibility. The in-situ curing method achieves good compatibility between the electrolyte and the electrode interface. The device preparation method is simple and has long-term cycle stability.

[0017] 2) The preparation method provided by the present invention avoids complex polymer synthesis and modification processes, does not require the addition of inorganic fillers, avoids the agglomeration problem that exists when inorganic fillers are introduced, and adopts a solution blending method to prepare the quasi-solid electrolyte precursor solution, thereby reducing the complexity of the preparation process;

[0018] 3) The present invention adopts an in-situ integrated assembly process based on UV curing technology, which makes the assembly process of the electrochromic device simple and convenient, improves the problem of poor contact between interfaces, enhances the interfacial compatibility of the electrolytic electrolyte, and improves the cycle life of the electrochromic device. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 Schematic diagram of the process of preparing a porous composite quasi-solid electrolyte and an in-situ assembly electrochromic device according to Example 1 of the present invention;

[0021] Figure 2a 、 Figure 2b and Figure 2c They are respectively the Nyquist plots, ionic conductivity plots, and optical transmittance plots of quasi-solid electrolytes of polyvinylidene fluoride-hexafluoropropylene copolymers (PVDF-HFP) with different contents in a typical embodiment of the present invention;

[0022] Figure 3a 、 Figure 3b Surface morphology scanning electron microscope images of an electrolyte membrane without PVDF-HFP in a comparative example and an electrolyte membrane containing PVDF-HFP in a typical embodiment of the present invention, respectively;

[0023] Figure 4a CV curve of an electrochromic device at a scan rate of 100 mV / s in a typical embodiment of the present invention;

[0024] Figure 4bGraph showing the switching time and transmittance versus time under the conditions of wavelength λ=633nm and voltage ±1.4V in a typical embodiment of the present invention;

[0025] Figure 4c The UV-visible-infrared transmission spectra (320-1000 nm) of the WO3-NiO complementary ECD in a typical embodiment of the present invention in a faded state and in states of varying degrees of coloration;

[0026] Figure 4d Graph showing changes in optical density (ΔOD) and charge density (Q) at a wavelength of 633 nm in a typical embodiment of the present invention;

[0027] Figure 5a Figure 2 shows the in-situ transmission spectra of the ECD in a typical embodiment of the present invention in the wavelength range of 320 to 1000 nm and a voltage of ±1.4 V in the faded and stained states (initial and after 50,000 cycles).

[0028] Figure 5b In a typical embodiment of the present invention, the current density is 0.20 mA cm -2 The charge-discharge cycle performance diagram of the WO3–NiO complementary electrochromic device;

[0029] Figure 5c This is an ECD kinetic transmission spectrum diagram before and after 50,000 cycles of continuous long cycle testing (-1.4V / +1.4V, 20s per segment) in a typical embodiment of the present invention;

[0030] Figure 5d This is a physical digital photograph of a 25mm×25mm device in a typical embodiment of the present invention in its faded and colored states. DETAILED DESCRIPTION

[0031] In view of the problems of poor wettability of the electrolyte and electrode interface, large interface impedance, and poor compatibility in the existing technology, the inventors of this case innovatively introduced polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) as an additive for quasi-solid electrolytes, and prepared a new type of porous structure composite quasi-solid electrolyte for use in electrochromic devices. The electrochromic devices were assembled by in-situ UV curing. The preparation method is simple, and the device achieves fast response and long life.

[0032] The following further explains the technical solution, its implementation process, and principles. However, it should be understood that within the scope of the present invention, the above-mentioned technical features of the present invention and the technical features specifically described below (in the embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be described here one by one.

[0033] The following terms need to be explained:

[0034] Semi-interpenetrating polymer networks (SIPNs) are composite materials composed of two or more polymers, at least one of which forms a chemically cross-linked three-dimensional network, while the other polymer runs through the network in a linear or branched form without forming chemical cross-links. This structure combines the high strength and stability of the cross-linked network with the flexibility and processability of linear polymers, offering unique performance advantages.

[0035] Quasi-solid electrolytes are mixtures consisting of a polymer matrix, a solvent containing electrolyte salts, and additives. They incorporate an appropriate amount of liquid components into the polymer electrolyte. The liquid components act as a filler and are dispersed within the polymer network, forming a gel-like substance that possesses both the properties of a liquid electrolyte and a solid. This system contains the liquid components but lacks fluidity, yet possesses a defined geometry, strength, and elasticity. The ionic conductivity of quasi-solid electrolytes is significantly improved compared to that of pure polymer electrolytes, typically by two orders of magnitude.

[0036] Electrochromism: Electrochromism refers to the phenomenon that a material undergoes a reversible oxidation-reduction reaction under the action of an external electric field, resulting in a stable and reversible change in its optical properties (transmittance, reflectivity and absorptivity).

[0037] As one aspect of the technical solution of the present invention, a porous structure composite quasi-solid electrolyte involves a semi-interpenetrating polymer network structure constructed by a polymer matrix and a polyvinylidene fluoride-hexafluoropropylene copolymer with a linear long-chain structure, as well as a lithium salt and an organic solvent distributed in the semi-interpenetrating polymer network structure. The polyvinylidene fluoride-hexafluoropropylene copolymer penetrates the polymer matrix to form a three-dimensional network structure.

[0038] In some embodiments, the polymer matrix is a polymer obtained by cross-linking a combination of any one or more of ethoxylated trimethylolpropane triacrylate (ETPTA), pentaerythritol triacrylate, 3(propoxy)glycerol triacrylate, and the like.

[0039] In some more preferred embodiments, the polymer matrix is a polymer obtained by cross-linking ethoxylated trimethylolpropane triacrylate (ETPTA).

[0040] In some embodiments, the porous structure composite quasi-solid electrolyte includes a porous structure composite quasi-solid electrolyte membrane.

[0041] In some embodiments, the surface of the porous composite quasi-solid electrolyte membrane exhibits a loose and porous structure.

[0042] Furthermore, the porous composite quasi-solid electrolyte membrane has nanoscale pores with a pore size not exceeding 20 nm.

[0043] In some embodiments, the mass ratio of the polymer matrix to the polyvinylidene fluoride-hexafluoropropylene copolymer having a linear long-chain structure is 450:1 to 9:2.

[0044] In some embodiments, the content of the polymer matrix in the porous composite quasi-solid electrolyte is 10-45 wt%, the content of the polyvinylidene fluoride-hexafluoropropylene copolymer is 0.1-10 wt%, and the content of the lithium salt is 1-10 wt%.

[0045] In some preferred embodiments, the structural formula of the ethoxylated trimethylolpropane triacrylate (ETPTA) is as shown in formula (I):

[0046]

[0047]

[0048] Among them, a+b+c=3~20.

[0049] Furthermore, the sum of the total number of ethoxy groups a+b+c in the ethoxylated trimethylolpropane triacrylate (ETPTA) can be 3, 6, 9, 15, 20, and the like.

[0050] Furthermore, the number average molecular weight of the ethoxylated trimethylolpropane triacrylate is 428-1176.

[0051] In some preferred embodiments, the structural formula of the polyvinylidene fluoride-hexafluoropropylene copolymer is as shown in formula (II):

[0052]

[0053] Among them, x=214~963, y=321~642.

[0054] Polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) is a polymer with a linear long chain structure, has good thermal stability and high mechanical strength, can effectively prevent the deformation and rupture of the electrolyte during the cycle, thereby improving the cyclic stability of the device, and can reduce the crystallinity of the polymer matrix, expand the amorphous region, thereby promoting the dissociation of lithium salts, and increasing the number of free lithium ions. At the same time, the strong electronegative groups in its amorphous region can promote the migration of lithium ions and improve the transmission efficiency of lithium ions. The present invention introduces polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) as an additive for quasi-solid electrolyte, its good thermal stability and high mechanical strength, can effectively prevent the deformation and rupture of the electrolyte during the cycle, thereby improving the cyclic stability of the device.

[0055] In some preferred embodiments, the lithium salt may include any one or more combinations of lithium perchlorate (LiClO4), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(fluorosulfonyl)imide (LiFSI), etc., but is not limited thereto.

[0056] In some embodiments, the ionic conductivity of the porous composite quasi-solid electrolyte is 10 -5 ~10 - 3 S / cm, its ionic conductivity meets the requirements for application in electrochromic devices, and it has a certain flexibility. The in-situ curing method is used to achieve good compatibility between the electrolyte and the electrode interface.

[0057] In summary, the present invention uses a quasi-solid electrolyte composed of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and a polymer matrix to form a semi-interpenetrating polymer network. The electrolyte membrane has a loose and porous structure with a pore size in the nanometer range (<20nm), which improves the mechanical properties and ionic conductivity of the electrolyte.

[0058] As another aspect of the technical solution of the present invention, a method for preparing a porous composite quasi-solid electrolyte involves:

[0059] The lithium salt, the organic solvent, the polyvinylidene fluoride-hexafluoropropylene copolymer, the polymer monomer, and the initiator are uniformly mixed to form a quasi-solid electrolyte precursor solution;

[0060] The quasi-solid electrolyte precursor solution is irradiated under ultraviolet light to chemically cross-link the polymer monomers to form a three-dimensional network structure, thereby preparing a porous structure composite quasi-solid electrolyte.

[0061] In some embodiments, the lithium salt and polyvinylidene fluoride-hexafluoropropylene copolymer used in the present invention are as described above and will not be described in detail here.

[0062] In some embodiments, the polymer monomers used in the present invention may include any one or more combinations of ethoxylated trimethylolpropane triacrylate (ETPTA), pentaerythritol triacrylate, 3 (propoxy) glycerol triacrylate, etc., but are not limited thereto.

[0063] Furthermore, the polymer monomer is preferably ethoxylated trimethylolpropane triacrylate (ETPTA). ETPTA has three cross-linkable functional groups, exhibiting high gelation efficiency and cross-link density. Furthermore, ETPTA behaves like a low-viscosity liquid at room temperature, facilitating the preparation of quasi-solid-state electrolyte precursor solutions, making it an ideal functional monomer.

[0064] In some embodiments, the mass ratio of the polyvinylidene fluoride-hexafluoropropylene copolymer, the polymer monomer, the lithium salt and the initiator is 0.1-10:10-45:1-10:0.1-0.45.

[0065] In some embodiments, the organic solvent includes any one or a combination of two of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), etc., but is not limited thereto.

[0066] In some embodiments, the initiator can be 2-hydroxy-2-methylphenyl acetone, or any one or a combination of two or more colorless initiators such as 1-hydroxycycloethylphenyl acetone and azobisisobutyronitrile, but is not limited thereto.

[0067] In some preferred embodiments, the method for preparing the quasi-solid electrolyte precursor solution may include:

[0068] mixing polyvinylidene fluoride-hexafluoropropylene copolymer, lithium salt, and an organic solvent to form a mixed solution;

[0069] The mixed solution is stirred at 50-100° C. for 1-12 hours, and then a polymer monomer and an initiator are added, and the mixture is stirred for 0.2-1 hour in a light-proof condition to prepare the quasi-solid electrolyte precursor solution.

[0070] In some embodiments, the irradiation time is 1 to 30 minutes, and the wavelength of the ultraviolet light used is 240 to 380 nm.

[0071] In summary, compared with traditional quasi-solid-state electrolytes, the preparation method of the present invention avoids complex polymer synthesis and modification processes, does not require the addition of inorganic fillers, avoids the agglomeration problem caused by the introduction of inorganic fillers, and adopts a solution blending method to prepare a quasi-solid-state electrolyte precursor solution, thereby reducing the complexity of the preparation process.

[0072] As another aspect of the technical solution of the present invention, it also relates to a porous structure composite quasi-solid electrolyte prepared by the aforementioned preparation method.

[0073] As another aspect of the technical solution of the present invention, it also relates to the application of the aforementioned porous structure composite quasi-solid electrolyte in the preparation of electrochromic devices.

[0074] Furthermore, another aspect of the present invention relates to an electrochromic device, comprising an ion storage layer, an electrolyte layer and an electrochromic layer plated on a conductive substrate in sequence, wherein the electrolyte layer is composed of the aforementioned porous structure composite quasi-solid electrolyte.

[0075] Furthermore, the thickness of the electrolyte layer is 0.05 to 500 μm.

[0076] Furthermore, the material of the ion storage layer may be NiO, but is not limited thereto. For example, it may also be Prussian blue, PANI (polyaniline), etc.

[0077] Furthermore, the material of the electrochromic layer includes WO3, but is not limited thereto. For example, it may also be V2O5, PEDOT, etc.

[0078] As another aspect of the technical solution of the present invention, it also relates to a method for preparing the aforementioned electrochromic device, which comprises:

[0079] The lithium salt, the organic solvent, the polyvinylidene fluoride-hexafluoropropylene copolymer, the polymer monomer, and the initiator are uniformly mixed to form a quasi-solid electrolyte precursor solution;

[0080] A quasi-solid electrolyte precursor solution is applied, preferably dropped, on the surface of an ion storage layer disposed on a conductive substrate, and then an electrochromic layer disposed on the conductive substrate is placed on the ion storage layer, and then irradiated with ultraviolet light to obtain an electrochromic device.

[0081] In some embodiments, the irradiation time is 1 to 30 minutes, and the wavelength of the ultraviolet light used is 240 to 380 nm.

[0082] Furthermore, the present invention adopts an in-situ UV curing method to integrate the glass substrate / ITO / WO3 / quasi-solid electrolyte / NiO / ITO / glass substrate "laminated" electrochromic device, which solves the problems of poor wettability of the electrolyte and electrode interface, large interface impedance, and poor compatibility.

[0083] The technical solution of the present invention is further described in detail below in conjunction with several preferred embodiments and the accompanying drawings. Obviously, the embodiments described are only a part of the embodiments of the present invention, rather than all of the embodiments. It should be pointed out that the embodiments described below are intended to facilitate the understanding of the present invention and do not have any limiting effect on it. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0084] Example 1

[0085] like Figure 1 As shown, a quasi-solid electrolyte precursor solution was prepared by solution blending. First, 10.64g of LiClO4 powder was weighed using an analytical balance and placed in a beaker. Then, 100ml of N-methylpyrrolidone (NMP) was measured with a measuring cylinder and added to the beaker to dissolve the LiClO4 powder to obtain a 1mol / L LiClO4-NMP liquid electrolyte. Subsequently, 0.18g of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP, number average molecular weight of 110,000) was weighed using an analytical balance and placed in a brown reagent bottle. 9g of 1mol / L LiClO4-NMP liquid electrolyte was added to the reagent bottle, and the mixed solution was stirred in a water bath at 50°C for 2h. 2.82g of ethoxylated trimethylolpropane triacrylate (ETPTA) (wherein the number of ethoxy groups in ETPTA is a+b+c=15) and 0.028g of 2-hydroxy-2-methylphenylacetone were added to the reagent bottle. The mixed solution was then stirred for 0.5 h in the dark.

[0086] Device assembly: Place 150μm diameter height-limiting particles around the NiO / ITO / glass substrate, use a dropper to transfer the electrolyte precursor solution, add 2 to 3 drops of electrolyte precursor solution on the NiO film, then cover the glass substrate / ITO / WO3 on the NiO / ITO / glass substrate, and place it under ultraviolet light for 15 minutes to obtain an all-solid-state electrochromic device.

[0087] The content of PVDF-HFP in the porous composite quasi-solid electrolyte of the electrochromic device prepared in this example is 2 wt %.

[0088] Comparative Example 1

[0089] The difference between this comparative example and Example 1 is that no PVDF-HFP is added to the quasi-solid electrolyte precursor solution.

[0090] Example 2

[0091] The difference between this comparative example and Example 1 is that the content of PVDF-HFP in the porous composite quasi-solid electrolyte is 4 wt %.

[0092] Example 3

[0093] The difference between this comparative example and Example 1 is that the content of PVDF-HFP in the porous composite quasi-solid electrolyte is 6 wt %.

[0094] Example 4

[0095] The difference between this comparative example and Example 1 is that the content of PVDF-HFP in the porous composite quasi-solid electrolyte is 8 wt %.

[0096] Example 5

[0097] The difference between this comparative example and Example 1 is that the content of PVDF-HFP in the porous composite quasi-solid electrolyte is 10 wt %.

[0098] The inventors of this case also tested a series of quasi-solid electrolytes with different contents of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) prepared in Examples 1 to 5 and Comparative Example 1, and the results are as follows:

[0099] Figure 2a and Figure 2b The Nyquist plots and ionic conductivity diagrams of quasi-solid electrolytes with different contents of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) are shown. When the mass ratio of ETPTA and PVDF-HFP remains unchanged, the bulk resistance of the electrolyte gradually decreases as the content of PVDF-HFP increases, indicating that the addition of PVDF-HFP can improve the ionic conductivity of the quasi-solid electrolyte. The electrolyte is made into a sandwich structure (glass / quasi-solid electrolyte / glass), and its optical transmittance is measured in the wavelength range of 320 to 1000 nm. The optical transmittance curve is shown in Figure 2. Figure 2c All electrolyte samples exhibit excellent optical transparency (>80% @ 633nm), with transmittances in the visible and infrared spectra close to or even exceeding that of glass, demonstrating an anti-reflection effect.

[0100] Figure 3a The scanning electron microscope (SEM) image of the electrolyte membrane without PVDF-HFP prepared in Comparative Example 1 is shown. Figure 3aIt can be observed that the polymer matrix on the surface of the electrolyte membrane presents a tightly packed morphology. Figure 3b The SEM image of the PVDF-HFP electrolyte membrane prepared in Example 1 is presented. The surface thereof exhibits a loose and porous structural feature, and the pore distribution is relatively uniform. The pore size analysis of the SEM image of the electrolyte membrane containing PVDF-HFP was performed using ImageJ software. The results showed that the electrolyte membrane had nanoscale pores with a pore size of no more than 20 nm. The formation of this porous structure is attributed to the introduction of PVDF-HFP with a linear long-chain structure, which together with ETPTA constructs a semi-interpenetrating polymer network. The loose and porous structure is conducive to forming a good contact interface with the electrode surface, thereby improving the interfacial contact and ion conductivity. From the perspective of structural characteristics, it is further explained that the quasi-solid electrolyte with the addition of PVDF-HFP has more excellent performance.

[0101] Taking Example 1 as an example, the inventors of this case also conducted electrochemical and optical performance tests on the electrochromic device assembled with the quasi-solid electrolyte. Figure 4a The device's initial 300 cycles of cyclic voltammetry (CV) curves are shown, with a scan rate of 100 mV / s and a voltage range of -1.4 to +1.4 V. The envelope area of the CV curve increases slightly with increasing cycles, indicating activation of the device. The CV curves of the first and 300 cycles show no significant changes, indicating good electrochemical cycling stability. Figure 4b The in-situ transmittance spectrum and response time of the device in the voltage range of -1.4 to +1.4V and wavelength of 633nm are shown. It can be seen that the fading response time of the device is extremely fast (0.86s) and the coloring response time is 4.3s, showing an extremely short response time. Figure 4c As shown, the UV-visible-infrared transmission spectra (320-1000nm) of the WO3-NiO complementary ECD in the faded state and different degrees of coloring state. After applying different coloring voltages, the transmittance in the visible light band and near-infrared band decreased significantly, and the color of the device changed from light brown close to transparent to dark blue close to black. The transmittance can be freely controlled by adjusting the applied voltage. Figure 4d The graphs showing the changes in optical density (ΔOD) and charge density (Q) at a wavelength of 633 nm show that the coloring efficiency of the electrochromic device is as high as 104.94 cm 2 C -1 The possible reason is that the introduction of PVDF-HFP promotes the dissociation of ions, and the in-situ curing increases the compatibility between the electrolyte and the electrolytic interface, thereby improving the utilization of the charge.

[0102] Figure 5a-5cThese are the results of long-cycle performance tests conducted by the inventors of this case on electrochromic devices assembled using the porous structure composite quasi-solid electrolyte of the present invention. Figure 5a The in-situ transmission spectra of the ECD in the faded and colored states in the wavelength range of 320 to 1000 nm and at a voltage of ±1.4 V (initial and after 50,000 cycles) show that the optical modulation of the device reaches 51.69% (633 nm) after 50,000 cycles, which is 40.3% higher than the initial value. Figure 5d This is a digital photo of a 25mm x 25mm device in its faded and stained state. Figure 5b The current density is 0.20 mA cm -2 The charge-discharge cycle performance of the WO3-NiO complementary electrochromic device was demonstrated at a current density of 0.20 mA cm -2 Figure 60,000 cycles of capacitance retention. After 20,000 cycles of charge and discharge, the device still maintained a capacitance retention rate of 94.63% (dropping to 70.56% after 60,000 cycles), indicating that this electrochromic device has excellent long-cycle stability. It is worth noting that after the start of the cycling test, the device showed a capacitance retention rate greater than 100%, which may be due to the complete activation of the device interface and the increase in the effective specific surface area of the WO3 and NiO thin film electrodes. Figure 5c The ECD kinetic transmission spectrum before and after 50,000 continuous long-term cycle tests shows that the device's optical modulation capability increased from 30.37% at the beginning to 42.66% after 50,000 continuous step voltage cycle tests (-1.4V / +1.4V, 20s per segment). The in-situ optical modulation did not decay after 50,000 cycles, indicating that the device has excellent long-term cycle stability. This is attributed to the excellent stability of the porous composite quasi-solid electrolyte and its good compatibility with the electrode interface.

[0103] Example 6

[0104] This comparative example differs from Example 1 in that the polymer monomer in the porous composite quasi-solid-state electrolyte is replaced with pentaerythritol triacrylate. The polymer formed from pentaerythritol triacrylate used in this example typically has higher hardness but relatively lower flexibility. The polymer formed from ETPTA exhibits greater flexibility and stronger adhesion.

[0105] Example 7

[0106] This comparative example differs from Example 1 in that the polymer monomer in the porous composite quasi-solid electrolyte is replaced with 3-(propoxy)propylene glycol triacrylate. The 3-(propoxy)propylene glycol triacrylate used in this example exhibits high hardness while maintaining good flexibility. The polymer formed by ETPTA exhibits greater flexibility and improved adhesion.

[0107] Example 8

[0108] Compared with Example 1, the difference between this comparative example and Example 1 is that the number of ethoxy groups in the polymer monomer ethoxylated trimethylolpropane triacrylate (ETPTA) in the porous structure composite quasi-solid electrolyte is a+b+c=3, the crosslinking density is higher, and the electrolyte membrane is harder.

[0109] Example 9

[0110] Compared with Example 1, the difference between this comparative example and Example 1 is that the number of ethoxy groups in the polymer monomer ethoxylated trimethylolpropane triacrylate (ETPTA) in the porous structure composite quasi-solid electrolyte is a+b+c=20, the cross-linking density is smaller, and the electrolyte membrane has better flexibility.

[0111] Example 10

[0112] The quasi-solid electrolyte precursor solution was prepared by solution blending. First, 1.15g of LiClO4 powder was weighed on an analytical balance and placed in a beaker. Then, 100ml of N-methylpyrrolidone (NMP) was measured with a measuring cylinder and added to the beaker to dissolve the LiClO4 powder to obtain a LiClO4-NMP liquid electrolyte. Subsequently, 0.01g of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP, number average molecular weight of 110,000) was weighed on an analytical balance and placed in a brown reagent bottle. 9g of LiClO4-NMP liquid electrolyte was added to the reagent bottle, and the mixed solution was stirred in a water bath at 50°C for 1h. 1g of ethoxylated trimethylolpropane triacrylate (ETPTA) (where the number of ethoxy groups in ETPTA is a+b+c=15) and 0.01g of 2-hydroxy-2-methylphenylacetone were added to the reagent bottle. The mixed solution was then stirred for 0.2h in the dark.

[0113] Device assembly: Place 150μm diameter height-limiting particles around the NiO / ITO / glass substrate, use a dropper to transfer the electrolyte precursor solution, add 2 to 3 drops of electrolyte precursor solution on the NiO film, then cover the glass substrate / ITO / WO3 on the NiO / ITO / glass substrate, and place it under ultraviolet light for 1 minute to obtain an all-solid-state electrochromic device.

[0114] Example 11

[0115] The quasi-solid electrolyte precursor solution was prepared by solution blending. First, 29.54g of LiClO4 powder was weighed on an analytical balance and placed in a beaker. Then, 100ml of N-methylpyrrolidone (NMP) was measured with a measuring cylinder and added to the beaker to dissolve the LiClO4 powder to obtain a LiClO4-NMP liquid electrolyte. Subsequently, 2g of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP, number average molecular weight of 110,000) was weighed on an analytical balance and placed in a brown reagent bottle. 9g of LiClO4-NMP liquid electrolyte was added to the reagent bottle, and the mixed solution was stirred in a water bath at 100°C for 1h. 9g of ethoxylated trimethylolpropane triacrylate (ETPTA) (wherein the number of ethoxy groups in ETPTA is a+b+c=15) and 0.09g of 2-hydroxy-2-methylphenylacetone were added to the reagent bottle. The mixed solution was then stirred for 12h in the dark.

[0116] Device assembly: Place 150μm diameter height-limiting particles around the NiO / ITO / glass substrate, use a dropper to transfer the electrolyte precursor solution, add 2 to 3 drops of electrolyte precursor solution on the NiO film, then cover the glass substrate / ITO / WO3 on the NiO / ITO / glass substrate, and place it under ultraviolet light for 30 minutes to obtain an all-solid-state electrochromic device.

[0117] Comparative Example 2

[0118] This comparative example is basically the same as Example 1, except that the mass ratio of the polyvinylidene fluoride-hexafluoropropylene copolymer, the polymer monomer, the lithium salt and the initiator is 20:50:10:1.

[0119] After in-situ curing, the adhesion between the quasi-solid electrolyte membrane and the substrate will decrease, and the electrolyte membrane permeability will decrease; the ionic conductivity will decrease, and the ionic conductivity will be less than 10 -5 S / cm; if the amount of initiator is too much, the electrolyte membrane will turn yellow and affect the transmittance.

[0120] Comparative Example 3

[0121] This comparative example is basically the same as Example 1, except that the mass ratio of the polyvinylidene fluoride-hexafluoropropylene copolymer, polymer monomer, lithium salt, and initiator is 0.01:8:10:0.08. The electrolyte membrane cannot be formed after UV curing and has a certain fluidity.

[0122] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments using other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0123] It should be understood that the above are only some embodiments of the present invention. It should be pointed out that for ordinary technicians in this field, other variations and improvements can be made without departing from the creative concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A porous composite quasi-solid electrolyte, characterized in that: include: A semi-interpenetrating polymer network structure is constructed by a polymer matrix and a polyvinylidene fluoride-hexafluoropropylene copolymer having a linear long-chain structure, and a lithium salt and an organic solvent are distributed in the semi-interpenetrating polymer network structure. The polyvinylidene fluoride-hexafluoropropylene copolymer penetrates the polymer matrix to form a three-dimensional network structure. The polymer matrix is a polymer obtained by cross-linking a combination of any one or more of ethoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, and 3(propoxy)propylene triacrylate.

2. The porous composite quasi-solid electrolyte according to claim 1, characterized in that: The porous structure composite quasi-solid electrolyte comprises a porous structure composite quasi-solid electrolyte membrane; Preferably, the surface of the porous composite quasi-solid electrolyte membrane presents a loose and porous structure. Preferably, the porous composite quasi-solid electrolyte membrane has nanoscale pores with a pore size not exceeding 20 nm.

3. The porous composite quasi-solid electrolyte according to claim 1, characterized in that: The mass ratio of the polymer matrix to the polyvinylidene fluoride-hexafluoropropylene copolymer having a linear long chain structure is 450:1 to 9:2; And / or, the content of the polymer matrix in the porous composite quasi-solid electrolyte is 10-45 wt%, the content of the polyvinylidene fluoride-hexafluoropropylene copolymer is 0.1-10 wt%, and the content of the lithium salt is 1-10 wt%; And / or, the structural formula of the ethoxylated trimethylolpropane triacrylate is shown in formula (I): Where a+b+c=3-20; Preferably, the number average molecular weight of the ethoxylated trimethylolpropane triacrylate is 428 to 1176; And / or, the structural formula of the polyvinylidene fluoride-hexafluoropropylene copolymer is as shown in formula (II): Where, x = 214 to 963, y = 321 to 642; And / or, the lithium salt includes any one or more combinations of lithium perchlorate, lithium bis(trifluoromethylsulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium bis(fluorosulfonyl)imide.

4. The porous composite quasi-solid electrolyte according to claim 1, characterized in that: The ionic conductivity of the porous composite quasi-solid electrolyte is 10 -5 ~10 -3 S / cm.

5. The method for preparing a porous composite quasi-solid electrolyte according to any one of claims 1 to 4, characterized in that: include: The lithium salt, the organic solvent, the polyvinylidene fluoride-hexafluoropropylene copolymer, the polymer monomer, and the initiator are uniformly mixed to form a quasi-solid electrolyte precursor solution; The quasi-solid electrolyte precursor solution is irradiated under ultraviolet light to chemically cross-link the polymer monomers to form a three-dimensional network structure, thereby preparing a porous structure composite quasi-solid electrolyte.

6. The preparation method according to claim 5, characterized in that: The mass ratio of the polyvinylidene fluoride-hexafluoropropylene copolymer, the polymer monomer, the lithium salt and the initiator is 0.1-10:10-45:1-10:0.1-0.45; And / or, the polymer monomer includes any one or more combinations of ethoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, and 3(propoxy)glycerol triacrylate; preferably, the structural formula of the ethoxylated trimethylolpropane triacrylate is as shown in formula (I): Where a+b+c=3-20; And / or, the organic solvent includes any one of N-methylpyrrolidone and N,N-dimethylformamide or a combination of two thereof; And / or, the initiator includes any one of 2-hydroxy-2-methylphenyl acetone, 1-hydroxycycloethyl phenyl acetone, and azobisisobutyronitrile, or a combination of two or more thereof.

7. The preparation method according to claim 5, characterized in that include: mixing polyvinylidene fluoride-hexafluoropropylene copolymer, lithium salt, and an organic solvent to form a mixed solution; The mixed solution is stirred at 50-100° C. for 1-12 hours, and then a polymer monomer and an initiator are added, and the mixture is stirred for 0.2-1 hour in a dark environment to obtain the quasi-solid electrolyte precursor solution; And / or, the irradiation time is 1 to 30 minutes, and the wavelength of the ultraviolet light used is 240 to 380 nm.

8. Use of the porous composite quasi-solid electrolyte according to any one of claims 1 to 4 in the preparation of an electrochromic device.

9. An electrochromic device comprising an ion storage layer, an electrolyte layer, and an electrochromic layer, which are sequentially deposited on a conductive substrate, characterized in that: The electrolyte layer is composed of the porous composite quasi-solid electrolyte according to any one of claims 1 to 4; Preferably, the thickness of the electrolyte layer is 0.05 to 500 μm; Preferably, the material of the ion storage layer includes any one or more combinations of NiO, Prussian blue, and polyaniline; Preferably, the material of the electrochromic layer includes any one or more combinations of WO3, V2O5, and PEDOT.

10. The method for preparing the electrochromic device according to claim 9, characterized in that: include: The lithium salt, the organic solvent, the polyvinylidene fluoride-hexafluoropropylene copolymer, the polymer monomer, and the initiator are uniformly mixed to form a quasi-solid electrolyte precursor solution; Applying, preferably dropping, a quasi-solid electrolyte precursor solution onto the surface of an ion storage layer disposed on a conductive substrate, then placing an electrochromic layer disposed on the conductive substrate on the ion storage layer, and then irradiating the layer with ultraviolet light to produce an electrochromic device; Preferably, the irradiation time is 1 to 30 minutes, and the wavelength of the ultraviolet light used is 240 to 380 nm.

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