Solid electrolyte, preparation method thereof and electrochromic device

Abstract

The invention provides a solid electrolyte, a preparation method thereof and an electrochromic device, and belongs to the technical field of electrochromic devices. Vanadium-based oxide is added as a catalyst, and a mixed solution of a cross-linking agent containing carbon-carbon double bonds, an electrolyte salt, an ionic liquid, a curing agent, a first solvent and a second solvent is thermally cured to prepare the solid electrolyte. The curing agent is at least one of an amine curing agent, an anhydride curing agent or a thiol curing agent. The solid electrolyte obtained by thermocuring has the characteristics of high transparency, good flexibility and high stripping force, can form a film with the thickness of less than 100 microns, and is suitable for preparing a flexible electrochromic device; the electrochromic device prepared from the solid electrolyte is relatively good in cyclic aging stability.

Description

Technical Field

[0001] The present invention relates to a solid electrolyte and a preparation method thereof, and an electrochromic device, belonging to the technical field of electrochromic devices. Background Art

[0002] Electrochromic devices use electrochromic materials that undergo a reversible color change through the application of voltage. The electrolyte layer in electrochromic devices acts as an ion conductor. Solid-state electrolytes offer improved processability and safety compared to liquid electrolytes. Common solid-state electrolyte curing methods include thermal curing and UV curing.

[0003] CN119376152A discloses an all-solid-state electrochromic device based on a quasi-solid electrolyte and its fabrication method. The all-solid-state electrochromic device comprises a first conductive substrate, a second conductive substrate, and a quasi-solid-state electrolyte sandwiched between the first and second conductive substrates. The quasi-solid-state electrolyte is assembled into an all-solid-state electrochromic device by in-situ curing of a quasi-solid-state electrolyte precursor solution disposed between the first and second conductive substrates. The quasi-solid-state electrolyte precursor comprises polyethylene oxide, a nano-inorganic filler, a crosslinker, a colorless photoinitiator, and an organic solution containing a lithium salt. The technical solution involves curing the electrolyte under ultraviolet light by adding the colorless photoinitiator.

[0004] CN118562064A discloses a photocurable polyurethane acrylate electrolyte for electrochromic application and a preparation method thereof, wherein the preparation steps are as follows: (1) adding polyether carbonate diol and diisocyanate to a solvent and mixing them uniformly, then adding dibutyltin dilaurate, and prepolymerizing them at 40-80°C and 200 r / min for 1.5-3 hours to obtain a mixed solution; (2) adding a hydroxy acrylate monomer to the mixed solution obtained in step (1), then adding a polymerization inhibitor, and reacting them at 40-65°C for 1-2 hours to obtain polyether carbonate polyurethane acrylate; (3) adding a lithium salt, an additive, an active diluent, and a photoinitiator to the polyether carbonate polyurethane acrylate obtained in step (2), stirring the reaction thoroughly for 0.5 hours to obtain a final product, which is then poured into a brown bottle and stored in the dark. This technical solution is to achieve the curing of the electrolyte under ultraviolet light by adding a photoinitiator.

[0005] Electrochromic devices typically consist of an ion storage layer, an electrolyte layer, and an electrochromic layer. The electrochromic layer contains polymers, whose structure and material properties may change when exposed to strong ultraviolet light, resulting in low contrast and failure after cyclic aging. Therefore, in order to minimize the impact of ultraviolet light on the charge storage layer and electrochromic layer, it is necessary to eliminate the effects of ultraviolet light on the device's performance. Summary of the Invention

[0006] To solve the above problems, the present invention provides a solid electrolyte and a preparation method thereof, and an electrochromic device. The solid electrolyte can be quickly solidified at a low curing temperature and has a good film-forming effect, and can be used to prepare electrochromic devices.

[0007] The present invention provides a solid electrolyte and a preparation method thereof, and an electrochromic device adopting the following technical solutions: In one aspect of the present invention, a solid electrolyte is provided, which is obtained by adding a vanadium-based oxide as a catalyst and thermally curing a mixture of a cross-linking agent containing a carbon-carbon double bond, an electrolyte salt, an ionic liquid, a curing agent, a first solvent, and a second solvent; the curing agent is at least one of an amine curing agent, an acid anhydride curing agent, or a thiol curing agent.

[0008] In the present invention, a crosslinker containing a carbon-carbon double bond reacts with a curing agent to produce a solid electrolyte skeleton structure. During the preparation of the solid electrolyte, the crosslinker containing a carbon-carbon double bond and at least one curing agent selected from an amine curing agent, an acid anhydride curing agent, or a thiol curing agent are added. The vanadium-based oxide provides vanadium ions that activate the carbon-carbon double bond, enhancing its electrophilicity. The amine, acid anhydride, and thiol groups in the curing agent react with the double bond, allowing the electrolyte to rapidly cure under heating in air.

[0009] Preferably, the vanadium-based oxide is selected from at least one of vanadium pentoxide, vanadium bis(pyridine-2-carboxylate)oxyvanadium.

[0010] Preferably, the electrolyte salt is a metal lithium salt, and the metal lithium salt is selected from at least one of LiBOB, LiFSI, LiTFSI, LiPF6, LiBF4, LiClO4 or LiCF3SO3.

[0011] Preferably, the ionic liquid is selected from at least one of pyridine, pyrrole, imidazole or piperidine ionic liquids.

[0012] Preferably, the ionic liquid is selected from at least one of N-methyl-N-ethylpyrrolidine bis(trifluoromethylsulfonyl)imide, N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide, 1-allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-vinyl-3-butylimidazolium bis(trifluoromethylsulfonyl)imide, N-hexyl-4-methylpyridine bis(trifluoromethylsulfonyl)imide, N-ethylpyridine bis(trifluoromethanesulfonyl)imide, N-butylpyridine trifluoromethanesulfonate, and N-hexyl-N-methylpiperidinium bis(trifluoromethanesulfonyl)imide.

[0013] Preferably, the cross-linking agent is selected from at least one of polyethylene glycol diacrylate, polyethylene glycol dimethacrylate or polypropylene glycol dimethacrylate.

[0014] Preferably, the amine curing agent is selected from at least one of polyamide, triethylenetetramine, tetraethylenepentamine or m-xylenediamine; the acid anhydride curing agent is selected from at least one of phthalic anhydride, methylcyclohexene tetracarboxylic dianhydride or methylcyclohexene tetracarboxylic dianhydride; the thiol curing agent is selected from at least one of ethylene glycol dimercaptoacetate, 1,4-butanediol di(3-mercaptopropionate) or trimethylolpropane tris(3-mercaptopropionate).

[0015] Preferably, the first solvent and the second solvent are solvents with a boiling point above 60°C.

[0016] Preferably, the first solvent is selected from at least one of isopropyl alcohol, sec-butyl alcohol, butanone, propylene glycol methyl ether acetate, propylene carbonate or diethyl carbonate; the second solvent is selected from at least one of isopropyl alcohol, sec-butyl alcohol, butanone, propylene glycol methyl ether acetate, propylene carbonate or diethyl carbonate; the first solvent and the second solvent are the same or different solvents.

[0017] Preferably, the solid electrolyte has a transparency of more than 80%.

[0018] Another aspect of the present invention provides a method for preparing a solid electrolyte, comprising the following preparation steps: Step 1): adding a cross-linking agent and an ionic liquid to a first solvent to obtain a mixed solution A; Step 2): adding an electrolyte salt to the second solvent to obtain a mixed solution B; Step 3): Mixing the mixed solution A obtained in step 1) with the mixed solution B obtained in step 2) to obtain a mixed solution C; Step 4): adding a curing agent and a vanadium-based oxide to the mixed solution C obtained in step 3) to obtain a mixed solution D; Step 5): coating the mixed solution D obtained in step 4) on a substrate to form a coating; Step 6): The coating obtained in step 5) is heated at 100-130° C. for 5-15 minutes to obtain a solid electrolyte.

[0019] Preferably, in step 1), a functional polymer is further added to the first solvent and mixed with a cross-linking agent and an ionic liquid to obtain a mixed solution A; the functional polymer is selected from at least one of polymethacrylate (PMMA), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), polyethylene oxide, polyethylene glycol diglycidyl ether, polyethylene glycol diacrylate or polyethylene terephthalate.

[0020] To achieve a balance between the film-forming performance, stripping force, and ion conductivity of the solid electrolyte, the crosslinker is preferably added in an amount of 20-40% of the total mass of the solid electrolyte, the curing agent in an amount of 2-15% of the total mass of the electrolyte, and the vanadium-based oxide in an amount of 0.01-0.5% of the total mass of the solid electrolyte. If the crosslinker, curing agent, and vanadium-based oxide addition levels are below this control range, film formation of the solid electrolyte will be impaired. If the crosslinker and curing agent addition levels are above this control range, the stripping force will be improved, but the final solid electrolyte ion composition will be reduced, affecting the final ion conductivity and, therefore, the performance of the device. If the vanadium-based oxide addition level is above this control range, the mixed solution D will directly solidify and will not form a film.

[0021] Preferably, the added amount of the functional polymer is 1-10% of the total mass of the solid electrolyte; the added amount of the ionic liquid is 2-20% of the total mass of the solid electrolyte; the added amount of the electrolyte salt is 10-40% of the total mass of the solid electrolyte; and the total added amount of the first solvent and the second solvent is 10-70% of the total mass of the solid electrolyte.

[0022] In another aspect of the present invention, an electrochromic device is provided, which comprises, in sequence: a first electrode, an electrochromic layer, a solid electrolyte layer composed of the above-mentioned solid electrolyte, a charge storage layer, and a second electrode.

[0023] Preferably, the charge storage layer contains vanadium-based oxide; vanadium pentoxide as the charge storage layer, combined with a solid electrolyte containing vanadium-based oxide, can further reduce the thermal curing temperature.

[0024] Compared with the existing technology, it has the following beneficial effects: The present invention uses vanadium-based oxide as a reaction catalyst. During the reaction, the vanadium-based oxide provides vanadium ions to activate the carbon-carbon double bonds in the cross-linking agent, thereby enhancing the electrophilicity of the carbon-carbon double bonds. The double bonds react with the amino groups, acid anhydrides or thiol groups in the curing agent, thereby achieving rapid thermal curing of the cross-linking agent containing double bonds and the curing agent in air, thereby avoiding the influence of UV curing on the material. The solid electrolyte obtained by thermal curing has high transparency (greater than 80%), good flexibility and high peeling strength, can form a thin film of less than 100μm, and is suitable for flexible electrochromic devices. The electrochromic device prepared with the solid electrolyte first continuously increases in capacity and then remains stable during 8000 cycles at room temperature, and has good cycle aging stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The coloring and fading capacity change curves of the electrochromic device prepared from the solid electrolyte obtained in Example 1 of the present invention; Figure 2 Coloration and fading capacity change curves of an electrochromic device prepared with the solid electrolyte obtained in Comparative Example 7 of the present invention. DETAILED DESCRIPTION

[0026] In order to make the present invention more clear and easy to understand, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] The present invention provides a solid electrolyte produced by thermally curing a mixture of a cross-linking agent containing carbon-carbon double bonds, an electrolyte salt, an ionic liquid, a curing agent, a first solvent, and a second solvent by adding a vanadium-based oxide as a catalyst; the curing agent is at least one of an amine curing agent, an acid anhydride curing agent, or a thiol curing agent. The present invention also provides an electrochromic device comprising, in order: a first electrode, an electrochromic layer, a solid electrolyte layer composed of the above-mentioned solid electrolyte, a charge storage layer, and a second electrode.

[0028] The present invention provides a method for preparing a solid electrolyte, comprising the following preparation steps: Step 1): adding a functional polymer, a cross-linking agent and an ionic liquid to a first solvent to obtain a mixed solution A; Step 2): adding an electrolyte salt to the second solvent to obtain a mixed solution B; Step 3): Mixing the mixed solution A obtained in step 1) with the mixed solution B obtained in step 2) to obtain a mixed solution C; Step 4): adding a curing agent and a vanadium-based oxide to the mixed solution C obtained in step 3) to obtain a mixed solution D; Step 5): Applying the mixed solution D obtained in step 4) on the substrate to form a coating; Step 6): The coating obtained in step 5) is heated at 100-130° C. for 5-15 minutes to obtain a solid electrolyte.

[0029] The added substances, addition amounts and process parameter control during the preparation of solid electrolytes are shown in Table 1-3.

[0030] Table 1 Additives in the process of preparing solid electrolytes in various embodiments of the present invention

[0031] Table 2 Amounts of additives added during the preparation of solid electrolytes in various embodiments of the present invention

[0032] Table 3 Process parameter control and performance of solid electrolytes prepared in various embodiments and comparative examples of the present invention

[0033] The cross-linking agents polyethylene glycol diacrylate are denoted as J1, polyethylene glycol dimethacrylate are denoted as J2, and polypropylene glycol dimethacrylate are denoted as J3.

[0034] The ionic liquid N-methyl-N-ethylpyrrolidine bis(trifluoromethylsulfonyl)imide is represented as L1, N-butyl-N-methylpyrrolidine bis(trifluoromethylsulfonyl)imide is represented as L2, 1-allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide is represented as L3, and 1-ethyl-3-methylimidazolium chloride is represented as L4.

[0035] Vanadium-based oxide vanadium pentoxide is represented as C1, vanadium diacetylacetonate is represented as C2, and bis(pyridine-2-carboxylate)vanadium oxide is represented as C3.

[0036] Examples 1-10 The solid electrolyte is prepared by adjusting the combination of additives (as shown in Table 1), the amount of each additive added (as shown in Table 2) and the process parameters (as shown in Table 3) during the preparation process.

[0037] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the added amount of the cross-linking agent is 10% of the total mass of the solid electrolyte.

[0038] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the amount of the cross-linking agent added is 45% of the total mass of the solid electrolyte.

[0039] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the added amount of the curing agent is 1% of the total mass of the solid electrolyte.

[0040] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the added amount of the curing agent is 20% of the total mass of the solid electrolyte.

[0041] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that the added amount of vanadium-based oxide is 0.005% of the total mass of the solid electrolyte.

[0042] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is that the added amount of vanadium-based oxide is 0.6 wt % of the total mass of the solid electrolyte.

[0043] Comparative Example 7 The difference between Comparative Example 7 and Example 1 is that: Step 4): Add curing agent and photoinitiator 1173 to mixed solution C to obtain mixed solution D; Step 5): Applying the obtained mixed solution D on the substrate to form a coating; Step 6): Irradiate the coating under a 365nm light source for 5 min to obtain a solid electrolyte.

[0044] The solid electrolytes obtained in the embodiments and comparative examples of the present invention were subjected to the following performance tests: (1) Transmittance: tested using a CM-5 desktop spectrophotometer; for solid electrolytes used in electrochromic devices, the higher the transmittance, the smaller the impact on the overall transmittance of the device.

[0045] (2) Membrane thickness: measured using an altimeter. Different solid electrolyte thicknesses are required to adapt to different electrochromic materials. The thickness of the solid electrolyte provided by the present invention is adjustable in the range of micrometers to millimeters.

[0046] (3) Peeling force: tested using a universal testing machine. The higher the peeling force, the greater the adhesion of the electrolyte layer, which is more beneficial for subsequent membrane processing.

[0047] As shown in Table 3, the prepared solid electrolyte has high transparency (greater than 80%), good flexibility and high peeling strength, and can form a thin film below 100 μm.

[0048] Comparative Examples 1, 3, 5, and 6 cannot form films because the added amounts of the crosslinking agent, curing agent, and vanadium-based oxide are not within the control range of the present invention.

[0049] In Comparative Examples 2 and 4, the amount of crosslinking agent and curing agent added is higher than the control range of the present invention, so the peeling force is improved, but the solid electrolyte ion component is reduced, the ion conductivity is poor, and the device performance is affected.

[0050] The present invention further prepares the solid electrolyte obtained in Example 1 and Comparative Example 7 into an electrochromic device, which comprises, in order: a first electrode, an electrochromic layer, a solid electrolyte layer composed of the above-mentioned solid electrolyte, a charge storage layer, and a second electrode; First electrode: tin-doped indium oxide (ITO); Second electrode: tin-doped indium oxide (ITO); Electrochromic layer: poly-3,4-ethylenedioxythiophene (PEDOT), disposed on the first electrode; Charge storage layer: vanadium pentoxide, deposited on the second electrode; Solid electrolyte layer: arranged between the electrochromic layer and the charge storage layer.

[0051] The prepared electrochromic device was subjected to the following performance tests: Coloring and fading capacity change curves: Testing was performed using Lanbo charging and discharging equipment. At room temperature, a certain charge and discharge voltage was applied to the device, causing it to switch between the colored and faded states. One cycle is one full cycle at room temperature. Capacity change during cycling reflects the change in charge during the device's operation, reflecting changes in device performance. Capacity decay typically indicates device performance degradation.

[0052] Figure 1 As shown, the solid electrolyte obtained by thermal curing in Example 1 was prepared into an electrochromic device. During 8000 cycles at room temperature, the capacity continued to increase and reached a plateau, and the device was activated during the room temperature cycle.

[0053] Figure 2 As shown, the solid electrolyte obtained by UV curing in Comparative Example 7 is prepared into an electrochromic device with room temperature cyclic coloration and fading capacity change curve. According to the data of 2500 cycles at room temperature, the device capacity is continuously attenuating, and the appearance of the device also has uneven color change.

[0054] The above results indicate that the solid electrolyte obtained by thermal curing provided by the present invention is more stable in terms of room temperature cyclic aging when used to prepare electrochromic devices.

[0055] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form or substance. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the present invention, and these improvements and supplements should also be regarded as the scope of protection of the present invention. Any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the spirit and scope of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A solid electrolyte, characterized in that The solid electrolyte is prepared by adding vanadium-based oxide as a catalyst and thermally curing a mixture of a cross-linking agent containing carbon-carbon double bonds, an electrolyte salt, an ionic liquid, a curing agent, a first solvent, and a second solvent; the curing agent is at least one of an amine curing agent, an acid anhydride curing agent, or a thiol curing agent.

2. The solid electrolyte according to claim 1, characterized in that The vanadium-based oxide is at least one selected from vanadium pentoxide, vanadium diacetylacetonate oxide, or bis(pyridine-2-carboxylate)vanadium oxide.

3. The solid electrolyte according to claim 1, characterized in that The electrolyte salt is a metal lithium salt, and the metal lithium salt is selected from at least one of LiBOB, LiFSI, LiTFSI, LiPF6, LiBF4, LiClO4 or LiCF3SO3.

4. The solid electrolyte according to claim 1, characterized in that The ionic liquid is selected from at least one of N-methyl-N-ethylpyrrolidine bis(trifluoromethanesulfonyl)imide, N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide, 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-vinyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide, N-hexyl-4-methylpyridine bis(trifluoromethanesulfonyl)imide, N-ethylpyridine bis(trifluoromethanesulfonyl)imide, N-butylpyridine trifluoromethanesulfonate, and N-hexyl-N-methylpiperidinium bis(trifluoromethanesulfonyl)imide.

5. The solid electrolyte according to claim 1, characterized in that The cross-linking agent is selected from at least one of polyethylene glycol diacrylate, polyethylene glycol dimethacrylate or polypropylene glycol dimethacrylate.

6. The solid electrolyte according to claim 1, characterized in that The amine curing agent is selected from at least one of polyamide, triethylenetetramine, tetraethylenepentamine or m-xylenediamine; the acid anhydride curing agent is selected from at least one of phthalic anhydride, methylcyclohexene tetracarboxylic dianhydride or methylcyclohexene tetracarboxylic dianhydride; the thiol curing agent is selected from at least one of ethylene glycol dimercaptoacetate, 1,4-butanediol di(3-mercaptopropionate) or trimethylolpropane tris(3-mercaptopropionate).

7. The solid electrolyte according to claim 1, characterized in that The first solvent is selected from at least one of isopropyl alcohol, sec-butyl alcohol, butanone, propylene glycol methyl ether acetate, propylene carbonate or diethyl carbonate; the second solvent is selected from at least one of isopropyl alcohol, sec-butyl alcohol, butanone, propylene glycol methyl ether acetate, propylene carbonate or diethyl carbonate; the first solvent and the second solvent are the same or different solvents.

8. The solid electrolyte according to claim 1, characterized in that The added amount of the cross-linking agent is 20-40% of the total mass of the solid electrolyte; the added amount of the curing agent is 2-15% of the total mass of the solid electrolyte; and the added amount of the vanadium-based oxide is 0.01-0.5% of the total mass of the solid electrolyte.

9. A method for preparing a solid electrolyte according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1): adding a cross-linking agent and an ionic liquid to a first solvent to obtain a mixed solution A; Step 2): adding an electrolyte salt to the second solvent to obtain a mixed solution B; Step 3): Mixing the mixed solution A obtained in step 1) with the mixed solution B obtained in step 2) to obtain a mixed solution C; Step 4): adding a curing agent and a vanadium-based oxide to the mixed solution C obtained in step 3) to obtain a mixed solution D; Step 5): coating the mixed solution D obtained in step 4) on a substrate to form a coating; Step 6): The coating obtained in step 5) is heated at 100-130° C. for 5-15 minutes to obtain a solid electrolyte.

10. The method for preparing a solid electrolyte according to claim 9, characterized in that: In step 1), a functional polymer is further added to the first solvent and mixed with a cross-linking agent and an ionic liquid to obtain a mixed solution A; the functional polymer is selected from at least one of polymethacrylate, polytetrafluoroethylene, polyvinylidene fluoride, poly(vinylidene fluoride-co-hexafluoropropylene), polyethylene oxide, polyethylene glycol diglycidyl ether, polyethylene glycol diacrylate, or polyethylene terephthalate.

11. The solid electrolyte according to claim 10, characterized in that The added amount of the functional polymer is 1-10% of the total mass of the solid electrolyte; the added amount of the ionic liquid is 2-20% of the total mass of the solid electrolyte; the added amount of the electrolyte salt is 10-40% of the total mass of the solid electrolyte; and the total added amount of the first solvent and the second solvent is 10-70% of the total mass of the solid electrolyte.

12. An electrochromic device, characterized in that: Including in order: A first electrode, an electrochromic layer, a solid electrolyte layer composed of the solid electrolyte according to any one of claims 1 to 8, a charge storage layer, and a second electrode.

13. The electrochromic device according to claim 12, characterized in that: The charge storage layer contains a vanadium-based oxide.

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