Sodium-ion battery semi-solid reference electrode for vehicle and preparation method thereof

Abstract

The application discloses a kind of sodium ion battery semi-solid reference electrode for vehicle and preparation method thereof, belong to electrode material technical field, specifically related to N-isopropyl acrylamide, acryloyloxy ethyl trimethylsilane and crosslinking agent N,N'-methylene bisacrylamide under the action of initiator, polyacryl compound is prepared, then polyacryl compound and polymer monomer, initiator are added in sodium ion liquid electrolyte, and polymeric precursor liquid is prepared, then reference electrode is prepared by the method of the application;Polyacryl compound is made of N-isopropyl acrylamide and acryloyloxy ethyl trimethylsilane.The sodium ion battery semi-solid reference electrode for vehicle prepared by the application has high potential stability, long stable time, is easy to replace, and avoids the problem of sodium dendrite.

Description

Semi-solid reference electrode for sodium-ion batteries in vehicles and its preparation method Technical Field

[0001] This invention belongs to the field of electrode material technology, specifically relating to a semi-solid reference electrode for sodium-ion batteries used in vehicles and its preparation method. Background Technology

[0002] Sodium-ion batteries have attracted much attention due to their high safety and low cost, and can be widely used in energy storage and power applications. In sodium-ion battery research, electrode potential is a crucial parameter. By measuring the potential change of a single electrode, detailed information about the internal reaction of the battery can be obtained, which is particularly important for failure mode analysis of sodium-ion batteries at the end of their lifespan. Currently, sodium-ion battery systems often use three-electrode batteries, which add a reference electrode between the positive and negative electrodes to achieve single-electrode potential acquisition. However, this three-electrode battery is manufactured in normal production processes, and therefore cannot be used to analyze truly failed sodium-ion batteries.

[0003] The fabrication process of three-electrode batteries is cumbersome. A common method for treating the reference electrode is sodium plating, which involves plating the metal electrode with sodium at a constant current of 0.01-1 mA for 20-30 minutes. While this method allows for precise monitoring of the positive and negative electrode voltages, after multiple cycles, as sodium is consumed, voltage monitoring becomes inaccurate, rendering the reference electrode meaningless. Extending the sodium plating time can lead to problems such as sodium dendrite formation. Therefore, developing a reference electrode that is easy to fabricate, provides reliable test data, and allows for timely analysis of failed batteries is of great significance. Summary of the Invention

[0004] The purpose of this invention is to provide a semi-solid reference electrode for vehicle sodium-ion batteries that is highly stable, easy to replace, and avoids problems such as sodium dendrite formation, as well as its preparation method.

[0005] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0006] A semi-solid reference electrode for a vehicle sodium-ion battery includes: a sodium sheet supported by a metal material, and a gel electrolyte layer covering the sodium sheet; the gel electrolyte layer contains a polymer material, which has polymer fragments of trimethylpropane ethoxytriacrylate, N-isopropylacrylamide, and acryloyloxyethoxytrimethylsilane. This invention prepares a polypropylene-based compound through preliminary polymerization of N-isopropylacrylamide and acryloyloxyethoxytrimethylsilane, and then polymerizes it with trimethylpropane ethoxytriacrylate to form a gel structure of a macromolecular polymer. The polymerization of the polypropylene-based compound and trimethylpropane ethoxytriacrylate is carried out in a sodium-ion liquid electrolyte under photo-initiated polymerization. Under the action of the polymer fragments of trimethylpropane ethoxytriacrylate, N-isopropylacrylamide, and acryloyloxyethoxytrimethylsilane, a reference electrode with stable potential and long stabilization time is prepared and successfully applied to practical detection. In this invention, the initial polymerization of the polypropylene-based compound has a significant impact. The time cannot be too long or too short. If the initial polymerization time is too short, the polymerization fragments of N-isopropylacrylamide and acryloyloxyethoxytrimethylsilane with good structures cannot be obtained. If the initial polymerization time is too long, the polymerization degree of N-isopropylacrylamide and acryloyloxyethoxytrimethylsilane will be too high. After co-polymerization with trimethylpropane ethoxytriacrylate, both will lead to a decrease in the performance of the reference electrode.

[0007] Preferably, the metal material is a steel needle or a copper needle.

[0008] Preferably, the gel electrolyte layer contains NaPF6; or, the gel electrolyte layer contains an initiator; or, the gel electrolyte layer contains 2-hydroxy-2-methylpropanone.

[0009] Preferably, the polymer fragments of N-isopropylacrylamide and acryloyloxyethoxytrimethylsilane in the polymer material have a cross-linked structure.

[0010] This invention discloses a method for preparing a semi-solid reference electrode for a sodium-ion battery in vehicles, comprising: preparing a polypropylene-based compound by reacting N-isopropylacrylamide and acryloyloxyethoxytrimethylsilane with a crosslinking agent and an initiator; adding the polypropylene-based compound, polymer monomer, and photoinitiator to a sodium-ion liquid electrolyte to prepare a polymerization precursor solution; applying the polymerization precursor solution to a sodium sheet supported by a metal material, and then photocuring to prepare a semi-solid reference electrode for a sodium-ion battery in vehicles.

[0011] Preferably, the crosslinking agent is N,N'-methylenebisacrylamide; or, the initiator is APS; or, the photoinitiator is 2-hydroxy-2-methylpropanone; or, the sodium ion liquid electrolyte contains NaPF6; or, the polymer monomer is trimethylpropane ethoxytriacrylate.

[0012] Preferably, the amount of acryloyloxyethoxytrimethylsilane used is 4-16 wt% of N-isopropylacrylamide; or, the amount of crosslinking agent used is 1-4 wt% of N-isopropylacrylamide; or, the amount of initiator used is 2-8 wt% of N-isopropylacrylamide.

[0013] Preferably, the ultraviolet light wavelength range used in the photocuring is less than 395nm; or, the photocuring time is 20-60s.

[0014] Preferably, in the preparation of the polypropylene-based compound, N-isopropylacrylamide and acryloyloxyethoxytrimethylsilane are added to deionized water, followed by the addition of N,N'-methylenebisacrylamide and sodium dodecyl sulfate. Under a nitrogen atmosphere, an initiator is added to carry out a polymerization reaction for 0.5-3 hours to obtain the polypropylene-based compound.

[0015] More preferably, in the preparation of the polypropylene-based compound, the amount of N-isopropylacrylamide used is 1-3 wt% of deionized water.

[0016] More preferably, in the preparation of the polypropylene-based compound, the amount of acryloyloxyethoxytrimethylsilane used is 4-16 wt% of N-isopropylacrylamide.

[0017] More preferably, in the preparation of the polypropylene-based compound, the amount of N,N'-methylenebisacrylamide used is 1-4 wt% of N-isopropylacrylamide.

[0018] More preferably, in the preparation of the polypropylene-based compound, the amount of sodium dodecyl sulfate used is 2-10 wt% of N-isopropylacrylamide.

[0019] More preferably, in the preparation of the polypropylene-based compound, the initiator is APS, and the amount of initiator used is 2-8 wt% of N-isopropylacrylamide.

[0020] Preferably, in the preparation of the semi-solid reference electrode for sodium-ion batteries, polymer monomers, polypropylene-based compounds, and photoinitiators are added to sodium-ion liquid electrolyte and mixed evenly to obtain a polymerization precursor solution; a steel needle is inserted into a sodium sheet, and then the polymerization precursor solution is dropped onto the surface of the sodium sheet. Under the action of ultraviolet light, the gel electrolyte layer is photopolymerized in situ to obtain the sodium-ion battery reference electrode.

[0021] More preferably, in the preparation of the semi-solid reference electrode for sodium-ion batteries, the sodium-ion liquid electrolyte is prepared by dissolving NaPF6 in a solvent, and the content of NaPF6 in the sodium-ion liquid electrolyte is 20-50 wt%.

[0022] More preferably, in the preparation of the semi-solid reference electrode for sodium-ion batteries, the polymer monomer is trimethylpropane ethoxytriacrylate, and the amount of trimethylpropane ethoxytriacrylate used is 200-500 wt% of the sodium-ion liquid electrolyte.

[0023] More preferably, in the preparation of the semi-solid reference electrode for sodium-ion batteries, the amount of polypropylene-based compound used is 10-40 wt% of trimethylpropane ethoxytriacrylate.

[0024] More preferably, in the preparation of the semi-solid reference electrode for sodium-ion batteries, the photoinitiator is 2-hydroxy-2-methylpropanone, and the amount of 2-hydroxy-2-methylpropanone used is 0.1-0.5 wt% of trimethylpropane ethoxytriacrylate.

[0025] More preferably, in the preparation of the semi-solid reference electrode for sodium-ion batteries, the sodium sheet is the same as that used in coin cells; the steel needle has a diameter of 0.5-2 mm, the middle is cured with AB glue, and high-temperature tape is attached near the tip of the needle to avoid contact with the positive and negative electrode plates of the battery, which could lead to a short circuit; the ultraviolet light wavelength range should be less than 395 nm, and the ultraviolet light curing time is 20-60 s.

[0026] Preferably, a polyether compound can be added during the preparation of the semi-solid reference electrode for sodium-ion batteries. In the process of preparing the semi-solid reference electrode for sodium-ion batteries, this invention can also add a polyether compound made of tripentaerythritol and polyvinyl alcohol, which improves the performance of the reference electrode.

[0027] More preferably, in the preparation of the polyether, tripentaerythritol is added to a DMSO solution and stirred at 20-40°C for 0.5-3 hours. Then, polyvinyl alcohol and concentrated sulfuric acid are added and stirred at 110-150°C for 3-9 hours. After the reaction is completed, the polyether is freeze-dried to obtain the polyether.

[0028] More preferably, in the preparation of the polyether compound, the DMSO solution is prepared by mixing DMSO and deionized water, and the DMSO solution contains 30-50 wt% deionized water.

[0029] More preferably, in the preparation of the polyether, the amount of tripentaerythritol used is 2-5 wt% of the DMSO solution.

[0030] More preferably, in the preparation of the polyether compound, the amount of polyvinyl alcohol used is 200-400 wt% of tripentaerythritol.

[0031] More preferably, in the preparation of the polyether compound, the concentrated sulfuric acid is undiluted sulfuric acid, and the amount of concentrated sulfuric acid used is 2-6 wt% of tripentaerythritol.

[0032] This invention discloses the application of a semi-solid reference electrode for sodium-ion batteries in vehicle performance testing.

[0033] This invention utilizes a method involving the preparation of a polypropylene-based compound by initiating N-isopropylacrylamide, acryloyloxyethoxytrimethylsilane, and the crosslinking agent N,N'-methylenebisacrylamide. The polypropylene-based compound, polymer monomers, and initiator are then added to a sodium-ion liquid electrolyte to prepare a polymerization precursor solution. A reference electrode is then prepared using this method. The polypropylene-based compound, composed of N-isopropylacrylamide and acryloyloxyethoxytrimethylsilane, offers the following advantages: high stability of the reference electrode potential, long stabilization time, ease of replacement, and avoidance of sodium dendrite formation problems. Therefore, this invention provides a semi-solid-state reference electrode for vehicle sodium-ion batteries that offers high stability, ease of replacement, and avoidance of sodium dendrite formation issues, along with its preparation method. Attached Figure Description

[0034] Figure 1 is a schematic diagram of the reference electrode;

[0035] Figure 2 shows the infrared spectrum;

[0036] Figure 3 shows the stability of the reference electrode;

[0037] Figure 4 shows the charge-discharge voltage-time curves of the sodium-ion battery before the reference electrode was packaged.

[0038] Figure 5 shows the charge-discharge voltage-time curves of the sodium-ion battery after the reference electrode is packaged.

[0039] Figure 6 shows the potential curve of the positive electrode of a sodium-ion battery.

[0040] Figure 7 shows the potential stabilization time.

[0041] The reference numerals in the attached diagram are as follows: 1 represents a steel needle or other metal needle; 2 represents a curing adhesive; 3 represents a high-temperature tape; 4 represents a sodium sheet; and 5 represents a gel electrolyte. Detailed Implementation

[0042] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings:

[0043] In the context of this application, the reference electrode in some descriptions refers to a semi-solid-state reference electrode for sodium-ion batteries used in vehicles. The specific meaning is determined by the content of the paragraph in which it appears.

[0044] In this invention, the solvent for the sodium ion liquid electrolyte is at least one of PC, DMC, and DEC, and DMC is used unless otherwise specified.

[0045] Example 1: A method for preparing a semi-solid reference electrode for a sodium-ion battery in a vehicle.

[0046] Preparation of polypropylene-based compounds: N-isopropylacrylamide and acryloyloxyethoxytrimethylsilane were added to deionized water, followed by N,N'-methylenebisacrylamide and sodium dodecyl sulfate. The polymerization reaction was carried out at 80°C under a nitrogen atmosphere with an initiator for 1 hour to obtain the polypropylene-based compound. The amount of deionized water used was 100 g, N-isopropylacrylamide was 2 g, acryloyloxyethoxytrimethylsilane was 0.2 g, N,N'-methylenebisacrylamide was 0.04 g, sodium dodecyl sulfate was 0.1 g, and APS was used as the initiator at a rate of 0.1 g.

[0047] The preparation of the semi-solid reference electrode for a sodium-ion battery, as shown in Figure 1, involves adding polymer monomers, a polypropylene-based compound, and a photoinitiator to a sodium-ion liquid electrolyte and mixing them thoroughly to obtain a polymerization precursor solution. A steel needle is inserted into a sodium sheet, and the polymerization precursor solution is then dropped onto the surface of the sodium sheet. Under ultraviolet light, the electrolyte layer is photopolymerized in situ to obtain the sodium-ion battery reference electrode. The sodium-ion liquid electrolyte is prepared by dissolving NaPF6 in a solvent, with a NaPF6 content of 35 wt% and a sodium-ion liquid electrolyte usage of 100 g. The polymer monomer is trimethylpropane ethoxytriacrylate, with a usage of 300 g. The polypropylene-based compound is used in a 100 g solution. The photoinitiator is 2-hydroxy-2-methylpropanone, with a usage of 0.9 g. The sodium sheet is the sodium sheet used in button cells; the steel needle is 1mm in diameter, and the middle is cured with AB glue. High-temperature tape is attached near the needle tip to avoid contact with the positive and negative electrodes of the battery, which could cause a short circuit; the ultraviolet light wavelength range should be less than 395nm, and the ultraviolet light curing time is 30s.

[0048] Example 2: A method for preparing a semi-solid reference electrode for a sodium-ion battery in a vehicle.

[0049] The difference between this embodiment and Example 1 lies in the preparation of the polypropylene-based compound.

[0050] Preparation of polypropylene-based compounds: N-isopropylacrylamide and acryloyloxyethoxytrimethylsilane were added to deionized water, followed by N,N'-methylenebisacrylamide and sodium dodecyl sulfate. The polymerization reaction was carried out at 80°C under a nitrogen atmosphere with an initiator for 2 hours to obtain the polypropylene-based compounds. The amount of deionized water used was 100 g, N-isopropylacrylamide was 2 g, acryloyloxyethoxytrimethylsilane was 0.2 g, N,N'-methylenebisacrylamide was 0.04 g, sodium dodecyl sulfate was 0.1 g, and APS was used as the initiator at a rate of 0.1 g.

[0051] Example 3: A method for preparing a semi-solid reference electrode for a sodium-ion battery in a vehicle.

[0052] The difference between this embodiment and Embodiment 1 lies in the preparation of the semi-solid reference electrode for the sodium-ion battery.

[0053] Preparation of a semi-solid reference electrode for sodium-ion batteries: Polymer monomers, polypropylene-based compounds, and photoinitiators are added to a sodium-ion liquid electrolyte and mixed uniformly to obtain a polymerization precursor solution. A steel needle is inserted into a sodium sheet, and then the polymerization precursor solution is dropped onto the surface of the sodium sheet. Under ultraviolet light, the electrolyte layer is photopolymerized in situ to obtain the sodium-ion battery reference electrode. The sodium-ion liquid electrolyte is prepared by dissolving NaPF6 in a solvent, with a NaPF6 content of 35 wt% and a sodium-ion liquid electrolyte usage of 100 g. The polymer monomer is trimethylpropane ethoxytriacrylate, with a usage of 300 g. The polypropylene-based compound is used in 50 g of the sample. The photoinitiator is 2-hydroxy-2-methylpropanone, with a usage of 0.9 g. The sodium sheet is the sodium sheet used in button cells; the steel needle is 1mm in diameter, and the middle is cured with AB glue. High-temperature tape is attached near the needle tip to avoid contact with the positive and negative electrodes of the battery, which could cause a short circuit; the ultraviolet light wavelength range should be less than 395nm, and the ultraviolet light curing time is 30s.

[0054] Example 4: A method for preparing a semi-solid reference electrode for a sodium-ion battery in a vehicle.

[0055] The difference between this embodiment and Embodiment 1 lies in the preparation of the semi-solid reference electrode for the sodium-ion battery.

[0056] Preparation of the polyether compound: Tripentaerythritol was added to a DMSO solution and stirred at 30°C for 2 hours. Then, polyvinyl alcohol and concentrated sulfuric acid were added, and the mixture was stirred at 130°C for 6 hours. After the reaction was complete, the mixture was freeze-dried to obtain the polyether compound. The DMSO solution was prepared by mixing DMSO and deionized water, containing 40 wt% deionized water. The amount of DMSO solution used was 100 g, the amount of tripentaerythritol used was 4 g, the amount of polyvinyl alcohol used was 12 g, and the amount of concentrated sulfuric acid used was 0.16 g (undiluted).

[0057] Preparation of a semi-solid reference electrode for sodium-ion batteries: Polymer monomers, polypropylene-based compounds, polyether compounds, and photoinitiators are added to a sodium-ion liquid electrolyte and mixed evenly to obtain a polymerization precursor solution. A steel needle is inserted into a sodium sheet, and then the polymerization precursor solution is dropped onto the surface of the sodium sheet. Under ultraviolet light, the electrolyte layer is photopolymerized in situ to obtain the sodium-ion battery reference electrode. The sodium-ion liquid electrolyte is prepared by dissolving NaPF6 in a solvent. The content of NaPF6 in the sodium-ion liquid electrolyte is 35wt%, and the amount of sodium-ion liquid electrolyte used is 100g. The polymer monomer is trimethylpropane ethoxytriacrylate, and the amount of trimethylpropane ethoxytriacrylate used is 300g. The amount of polypropylene-based compound used is 100g, the amount of polyether compound used is 50g, and the photoinitiator is 2-hydroxy-2-methylpropanone, and the amount of 2-hydroxy-2-methylpropanone used is 0.9g. The sodium sheet is the sodium sheet used in button cells; the steel needle is 1mm in diameter, and the middle is cured with AB glue. High-temperature tape is attached near the needle tip to avoid contact with the positive and negative electrodes of the battery, which could cause a short circuit; the ultraviolet light wavelength range should be less than 395nm, and the ultraviolet light curing time is 30s.

[0058] Example 5: A method for preparing a semi-solid reference electrode for a sodium-ion battery in a vehicle.

[0059] The difference between this embodiment and Embodiment 2 lies in the preparation of the semi-solid reference electrode for the sodium-ion battery.

[0060] Preparation of the polyether compound: Tripentaerythritol was added to a DMSO solution and stirred at 30°C for 2 hours. Then, polyvinyl alcohol and concentrated sulfuric acid were added, and the mixture was stirred at 130°C for 6 hours. After the reaction was complete, the mixture was freeze-dried to obtain the polyether compound. The DMSO solution was prepared by mixing DMSO and deionized water, containing 40 wt% deionized water. The amount of DMSO solution used was 100 g, the amount of tripentaerythritol used was 4 g, the amount of polyvinyl alcohol used was 12 g, and the amount of concentrated sulfuric acid used was 0.16 g (undiluted).

[0061] Preparation of a semi-solid reference electrode for sodium-ion batteries: Polymer monomers, polypropylene-based compounds, polyether compounds, and photoinitiators are added to a sodium-ion liquid electrolyte and mixed evenly to obtain a polymerization precursor solution. A steel needle is inserted into a sodium sheet, and then the polymerization precursor solution is dropped onto the surface of the sodium sheet. Under ultraviolet light, the electrolyte layer is photopolymerized in situ to obtain the sodium-ion battery reference electrode. The sodium-ion liquid electrolyte is prepared by dissolving NaPF6 in a solvent. The content of NaPF6 in the sodium-ion liquid electrolyte is 35wt%, and the amount of sodium-ion liquid electrolyte used is 100g. The polymer monomer is trimethylpropane ethoxytriacrylate, and the amount of trimethylpropane ethoxytriacrylate used is 300g. The amount of polypropylene-based compound used is 100g, the amount of polyether compound used is 50g, and the photoinitiator is 2-hydroxy-2-methylpropanone, and the amount of 2-hydroxy-2-methylpropanone used is 0.9g. The sodium sheet is the sodium sheet used in button cells; the steel needle is 1mm in diameter, and the middle is cured with AB glue. High-temperature tape is attached near the needle tip to avoid contact with the positive and negative electrodes of the battery, which could cause a short circuit; the ultraviolet light wavelength range should be less than 395nm, and the ultraviolet light curing time is 30s.

[0062] Example 6: A method for preparing a semi-solid reference electrode for a sodium-ion battery in a vehicle.

[0063] The difference between this embodiment and Embodiment 3 lies in the preparation of the semi-solid reference electrode for the sodium-ion battery.

[0064] Preparation of the polyether compound: Tripentaerythritol was added to a DMSO solution and stirred at 30°C for 2 hours. Then, polyvinyl alcohol and concentrated sulfuric acid were added, and the mixture was stirred at 130°C for 6 hours. After the reaction was complete, the mixture was freeze-dried to obtain the polyether compound. The DMSO solution was prepared by mixing DMSO and deionized water, containing 40 wt% deionized water. The amount of DMSO solution used was 100 g, the amount of tripentaerythritol used was 4 g, the amount of polyvinyl alcohol used was 12 g, and the amount of concentrated sulfuric acid used was 0.16 g (undiluted).

[0065] Preparation of a semi-solid reference electrode for sodium-ion batteries: Polymer monomers, polypropylene-based compounds, polyether compounds, and photoinitiators are added to a sodium-ion liquid electrolyte and mixed evenly to obtain a polymerization precursor solution. A steel needle is inserted into a sodium sheet, and then the polymerization precursor solution is dropped onto the surface of the sodium sheet. Under ultraviolet light, the electrolyte layer is photopolymerized in situ to obtain the sodium-ion battery reference electrode. The sodium-ion liquid electrolyte is prepared by dissolving NaPF6 in a solvent, with a NaPF6 content of 35 wt% and a sodium-ion liquid electrolyte usage of 100 g. The polymer monomer is trimethylpropane ethoxytriacrylate, with a usage of 300 g. The polypropylene-based compound and the polyether compound are both used in a 50 g manner. The photoinitiator is 2-hydroxy-2-methylpropanone, with a usage of 0.9 g. The sodium sheet is the sodium sheet used in button cells; the steel needle is 1mm in diameter, and the middle is cured with AB glue. High-temperature tape is attached near the needle tip to avoid contact with the positive and negative electrodes of the battery, which could cause a short circuit; the ultraviolet light wavelength range should be less than 395nm, and the ultraviolet light curing time is 30s.

[0066] Comparative Example 1: A method for preparing a semi-solid reference electrode for a sodium-ion battery in a vehicle.

[0067] The difference between this comparative example and Example 1 lies in the preparation of the polypropylene-based compound.

[0068] Preparation of polypropylene-based compounds: N-isopropylacrylamide and acryloyloxyethoxytrimethylsilane were added to deionized water, followed by N,N'-methylenebisacrylamide and sodium dodecyl sulfate. Under a nitrogen atmosphere, polymerization was carried out at 80°C with an initiator for 15 minutes to obtain the polypropylene-based compound. The amount of deionized water used was 100 g, N-isopropylacrylamide was 2 g, acryloyloxyethoxytrimethylsilane was 0.2 g, N,N'-methylenebisacrylamide was 0.04 g, sodium dodecyl sulfate was 0.1 g, and APS was used as the initiator at a rate of 0.1 g.

[0069] Comparative Example 2: A method for preparing a semi-solid reference electrode for a sodium-ion battery in a vehicle.

[0070] The difference between this comparative example and Example 1 lies in the preparation of the polypropylene-based compound.

[0071] Preparation of polypropylene-based compounds: N-isopropylacrylamide and acryloyloxyethoxytrimethylsilane were added to deionized water, followed by N,N'-methylenebisacrylamide and sodium dodecyl sulfate. The polymerization reaction was carried out at 80°C under a nitrogen atmosphere with an initiator for 3.5 h to obtain the polypropylene-based compounds. The amount of deionized water used was 100 g, N-isopropylacrylamide was 2 g, acryloyloxyethoxytrimethylsilane was 0.2 g, N,N'-methylenebisacrylamide was 0.04 g, sodium dodecyl sulfate was 0.1 g, and APS was used as the initiator at a rate of 0.1 g.

[0072] Comparative Example 3: A method for preparing a semi-solid reference electrode for a sodium-ion battery in a vehicle.

[0073] The difference between this comparative example and Example 1 lies in the preparation of the semi-solid reference electrode for the sodium-ion battery.

[0074] Preparation of a semi-solid reference electrode for sodium-ion batteries: Polymer monomers and photoinitiators are added to a sodium-ion liquid electrolyte and mixed evenly to obtain a polymerization precursor solution. A steel needle is inserted into a sodium sheet, and then the polymerization precursor solution is dropped onto the surface of the sodium sheet. Under ultraviolet light, the electrolyte layer is photopolymerized in situ to obtain the sodium-ion battery reference electrode. The sodium-ion liquid electrolyte is prepared by dissolving NaPF6 in a solvent. The content of NaPF6 in the sodium-ion liquid electrolyte is 35wt%, and the amount of sodium-ion liquid electrolyte used is 100g. The polymer monomer is trimethylpropane ethoxytriacrylate, and the amount of trimethylpropane ethoxytriacrylate used is 300g. The photoinitiator is 2-hydroxy-2-methylpropanone, and the amount of 2-hydroxy-2-methylpropanone used is 0.9g. The sodium sheet is the sodium sheet used in button cells; the steel needle is 1mm in diameter, and the middle is cured with AB glue. High-temperature tape is attached near the needle tip to avoid contact with the positive and negative electrodes of the battery, which could cause a short circuit; the ultraviolet light wavelength range should be less than 395nm, and the ultraviolet light curing time is 30s.

[0075] Experimental example:

[0076] The polypropylene-based compound prepared in Example 1 was characterized by infrared spectroscopy, and the results are shown in Figure 2. Specifically, the infrared spectroscopy results were obtained at 2800-3000 cm⁻¹. -1 The infrared absorption peaks between these two groups are those of methyl and methylene groups, with a peak at 1642 cm⁻¹. -1 The infrared absorption peak for the carbonyl group is at 1538 cm⁻¹. -1 The infrared absorption peak of nitrogen and hydrogen in amide is located at 1158 cm⁻¹. -1 The infrared absorption peak for carbon, oxygen, and carbon is located at 1082 cm⁻¹. -1 The infrared absorption peak at this point represents the silicon-oxygen bond.

[0077] In this invention, under the protection of inert argon gas, the following operations were performed in a glove box: a semi-solid reference electrode, prepared using a sodium metal sheet as the counter electrode, was used as the working electrode. The electrode potential was tested in a sodium ion electrolyte, and the test results are shown in Figure 3. The test results show that the reference electrode potential fluctuates little, remaining between 40-42 mV, indicating a very stable electrode potential. The reference electrode used in the above test was prepared by the method of Example 1.

[0078] This invention, under the protection of inert argon gas, involves the following operations performed in a glove box: a reference electrode is placed inside a pouch sodium-ion battery. The positive electrode of the pouch sodium-ion battery is sodium nickel iron manganese oxide, and the negative electrode is hard carbon. The electrode is then brought into contact with the positive electrode, negative electrode, or separator, and sealed using foam cotton, epoxy resin board, and dovetail clips to obtain a pouch sodium-ion battery containing a reference electrode. Charge-discharge tests are performed on the sodium-ion battery before the reference electrode is encapsulated; the voltage-time during the charge-discharge process is shown in Figure 4. Charge-discharge tests are also performed after encapsulation; the voltage-time during the charge-discharge process is shown in Figure 5. The charge-discharge curves before and after encapsulation of the reference electrode highly overlap, indicating that the effect of encapsulating the reference electrode on the battery is almost negligible. Simultaneously, electrode potential tests are performed using the positive electrode of the sodium-ion battery as the working electrode and the reference electrode as the counter electrode; the test results are shown in Figure 6. As can be seen from the figure, the electrode potential reflects the charge-discharge plateau of the positive electrode material, and the potential is stable and burr-free, indicating that this reference electrode can be successfully applied to the failure analysis of sodium-ion batteries. The reference electrode used in the above tests was prepared by the method of Example 1.

[0079] This invention tests the stability of reference electrodes prepared in various embodiments and comparative examples. The reference electrodes are placed in a simulated solution, and their relative potentials are measured using an A302-5 high-impedance digital voltmeter and a saturated calomel electrode. The salt bridge is saturated potassium chloride, and the temperature is 25°C. Measurements are taken daily, and the potentials and test dates are recorded. Stability analysis is performed, and the time it takes for the potential to stabilize is taken as the test result. The test results are shown in Figure 7, where S1 represents Example 1, S2 represents Example 2, S3 represents Example 3, S4 represents Example 4, S5 represents Example 5, and S6 represents Example 6. Example 6, D1 is Comparative Example 1, D2 is Comparative Example 2, and D3 is Comparative Example 3. In this invention, a polypropylene-based compound is prepared by reacting N-isopropylacrylamide, acryloyloxyethoxytrimethylsilane, and the crosslinking agent N,N'-methylenebisacrylamide with an initiator. The polypropylene-based compound, polymer monomers, and initiator are then added to a sodium ion liquid electrolyte to prepare a polymerization precursor solution. A reference electrode is then prepared using the method of this invention. In this invention, the degree of polymerization of the polypropylene-based compound cannot be too high; the polymerization time of the polypropylene-based compound needs to be controlled before application. In the preparation of the reference electrode, the reference electrode prepared by this invention exhibits high stability and a long stabilization time of its electrode potential. If the polymerization time of the polypropylene-based compound is too long or too short, the stability of the reference electrode prepared from it will decrease significantly. Only within a suitable polymerization time will the stability of the reference electrode prepared from it be greatly improved. Furthermore, when adding the polypropylene-based compound, polymer monomers, and initiator to a sodium ion liquid electrolyte to prepare a polymerization precursor solution, the higher the amount of polypropylene-based compound used, the higher the stability of the obtained reference electrode and the longer its electrode potential stabilization time. This invention further prepares a polyether from tripentaerythritol and polyvinyl alcohol, and then adds the polyether, polypropylene-based compound, polymer monomers, and initiator to a sodium ion liquid electrolyte to prepare a polymerization precursor solution. The reference electrode is then prepared using the method of this invention. The polypropylene-based compound and polymer monomers can be polymerized by an initiator to form a macromolecular polymer, which then interacts with the polyether to form a gel structure, thus forming the reference electrode. Under the action of the macromolecular polymer and the polyether, the stability of the reference electrode is improved, and its electrode potential stabilization time is increased.

[0080] The above embodiments are for illustrative purposes only and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all equivalent technical solutions also fall within the scope of this invention, and the patent protection scope of this invention should be defined by the claims.

Claims

1. A semi-solid reference electrode for a sodium-ion battery in a vehicle, comprising: The process involves a sodium sheet supported by a metal material and a gel electrolyte layer covering the sodium sheet. The gel electrolyte layer contains a polymer material having polymer fragments of trimethylpropane ethoxytriacrylate, N-isopropylacrylamide, and acryloyloxyethoxytrimethylsilane. The N-isopropylacrylamide and acryloyloxyethoxytrimethylsilane polymer fragments in the polymer material exhibit a cross-linked structure. In the preparation of a semi-solid-state reference electrode for a vehicle sodium-ion battery, N-isopropylacrylamide and acryloyloxyethoxytrimethylsilane are reacted with a cross-linking agent and an initiator to obtain a polypropylene-based compound. The polypropylene-based compound, polymer monomer, and photoinitiator are added to a sodium-ion liquid electrolyte to prepare a polymerization precursor solution. The polymerization precursor solution is applied to the sodium sheet supported by the metal material and then photocured to prepare a semi-solid-state reference electrode for a vehicle sodium-ion battery. The polymer monomer is trimethylpropane ethoxytriacrylate.

2. The semi-solid reference electrode for a vehicle sodium-ion battery according to claim 1, characterized in that: The metal material is a steel needle or a copper needle.

3. The semi-solid reference electrode for a vehicle sodium-ion battery according to claim 1, characterized in that: The gel electrolyte layer contains NaPF6; or, the gel electrolyte layer contains an initiator; or, the gel electrolyte layer contains 2-hydroxy-2-methylpropanone.

4. A method for preparing a semi-solid reference electrode for a sodium-ion battery in a vehicle, comprising: A polypropylene-based compound was prepared by reacting N-isopropylacrylamide and acryloyloxyethoxytrimethylsilane with a crosslinking agent and an initiator. The polypropylene-based compound, polymer monomer, and photoinitiator were added to a sodium ion liquid electrolyte to prepare a polymerization precursor solution. The polymerization precursor solution was applied to a sodium sheet supported by a metal material and then photocured to prepare a semi-solid reference electrode for a vehicle sodium ion battery. The polymer monomer was trimethylpropane ethoxytriacrylate.

5. The method for preparing a semi-solid reference electrode for a vehicle sodium-ion battery according to claim 4, characterized in that: The crosslinking agent is N,N'-methylenebisacrylamide; or, the initiator is APS; or, the photoinitiator is 2-hydroxy-2-methylpropanone; or, the sodium ion liquid electrolyte contains NaPF6.

6. The method for preparing a semi-solid reference electrode for a vehicle sodium-ion battery according to claim 4, characterized in that: The amount of acryloyloxyethoxytrimethylsilane used is 4-16 wt% of N-isopropylacrylamide; or, the amount of crosslinking agent used is 1-4 wt% of N-isopropylacrylamide; or, the amount of initiator used is 2-8 wt% of N-isopropylacrylamide.

7. The method for preparing a semi-solid reference electrode for a vehicle sodium-ion battery according to claim 4, characterized in that: The ultraviolet light wavelength range used in the photocuring is less than 395nm; or, the photocuring time is 20-60s.

8. The use of the semi-solid reference electrode for vehicle sodium-ion batteries as described in claim 1 in the performance testing of vehicle batteries.

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