Electrolyte leakage detection sensor and preparation method thereof

Abstract

The present invention discloses an electrolyte leakage detection sensor and its preparation method, relating to the field of sensor technology. Specifically, the electrolyte leakage detection sensor comprises a substrate layer, a COFs-loaded carbon paper layer, and a double-walled carbon nanotube-loaded carbon paper layer, laminated in sequence from bottom to top. The sensor not only has high detection sensitivity and excellent stability, enabling long-term, real-time monitoring of electrolyte leakage, but also has a simple structure, a compact size, and portability, enabling flexible use and significantly improving the safety of lithium-ion batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and in particular to an electrolyte leakage detection sensor and a preparation method thereof. Background Art

[0002] Lithium-ion batteries, as a new energy storage system, have become widely used in daily life. However, their safety issues have also attracted widespread attention. For example, the recent explosion of Samsung Galaxy Note 7 phones and the spontaneous combustion of Tesla Model S and NIO ES8 electric vehicles have cast a shadow over the commercial application of lithium-ion batteries. Currently, leakage of liquid lithium-ion battery electrolytes is considered an early sign of lithium-ion battery performance failure, which may subsequently threaten the safety of electric vehicles, electronic devices, and the people who use them. Conventional organic electrolytes are generally difficult to detect due to their volatility and redox neutrality. Therefore, real-time and effective detection of lithium-ion battery electrolyte leaks is urgently needed. Currently, inorganic semiconductor sensors are widely used, but they generally require high temperatures to achieve sensitive sensing, making them vulnerable to misjudgments and false alarms in complex environments, posing safety risks. Therefore, the development of new detection devices and methods for real-time monitoring of lithium-ion battery electrolyte leaks is of great significance.

[0003] In recent years, some means for detecting electrolyte leakage have emerged in the prior art, such as the Chinese patent document, application number CN201911269478.3, a method for quickly detecting leakage points of soft-pack lithium-ion batteries, which discloses the use of pH test paper to determine the leakage points on the surface of the lithium-ion battery, but it cannot detect the leakage of the electrolyte in the closed battery pack, and cannot monitor the leakage of the battery pack during use, thus posing a safety hazard; another example is the Chinese patent document, application number CN201911269478.3, an ion-conducting metal-organic framework thin film chemical sensor and preparation method, which discloses an ion-conducting metal-organic framework compound thin film chemical sensor, but it has the problems of complex preparation method and poor material stability; and the Chinese patent document, application number CN202010154633.3, a battery box electrolyte leakage detection device and electrolyte leakage detection method, which can detect the specific concentration of the electrolyte, but the detection device is complex and has poor flexibility in use. It can be seen from this that the existing electrolyte leakage detection device still has problems such as poor stability in use, complex structure, low detection sensitivity, and difficulty in achieving long-term real-time monitoring of electrolyte leakage. Summary of the Invention

[0004] 1. Technical problem to be solved by the invention

[0005] In response to the technical problems of existing electrolyte leakage detection devices such as poor stability, complex structure, low detection sensitivity, and difficulty in achieving long-term real-time monitoring of electrolyte leakage, the present invention provides an electrolyte leakage detection sensor and a preparation method thereof. It not only has high detection sensitivity and good stability, and can achieve long-term real-time monitoring of electrolyte leakage, but also has a simple structure, small size, and is easy to carry, which can be used flexibly.

[0006] 2. Technical solution

[0007] In order to solve the above problems, the technical solution provided by the present invention is:

[0008] An electrolyte leakage detection sensor comprises a substrate layer, a COFs-loaded carbon paper layer and a double-walled carbon nanotube-loaded carbon paper layer which are laminated in sequence from bottom to top.

[0009] Optionally, the substrate layer includes a silicon substrate and a conductive layer deposited on the surface of the silicon substrate.

[0010] Optionally, the silicon substrate has a thickness of 1-4 mm and a diameter of 1-3 cm; and the conductive layer has a thickness of 50-200 nm.

[0011] At the same time, the present application also provides a method for preparing the above-mentioned electrolyte leakage detection sensor, comprising the following steps:

[0012] S1. Preparation of COFs-loaded carbon paper layer: Mix raw material A, raw material B, a mixed solvent, and isoquinoline to obtain a mixed solution, add hydrophilic carbon paper, and heat to obtain COFs-loaded carbon paper;

[0013] S2. Preparation of a double-walled carbon nanotube-loaded carbon paper layer: coating a conductive adhesive layer on the surface of a hydrophobic carbon paper; pretreating the double-walled carbon nanotubes; adding the pretreated double-walled carbon nanotubes to an organic solvent, and ultrasonically dispersing them uniformly to obtain a suspension; dripping the suspension evenly onto the surface of the conductive adhesive layer, vacuum drying, and curing to obtain a double-walled carbon nanotube-loaded carbon paper layer;

[0014] S3, substrate layer preparation: depositing a conductive layer on the surface of the silicon substrate;

[0015] S4. Sequentially cover the COFs-loaded carbon paper layer prepared in step S1 and the double-walled carbon nanotube-loaded carbon paper layer prepared in step S2 on the surface of the substrate layer prepared in step S3, and press them to obtain an electrolyte leakage detection sensor.

[0016] Optionally, in step S1, the molar ratio of the raw material A to the raw material B is 2-4:1-2.5, the raw material A is (4-aminophenyl)amine or a dianhydride molecule, and the raw material B is 1,3,5-tris(4-aminophenyl)benzene; the mixed solvent is composed of a first solvent and mesitylene, and the volume ratio of the first solvent, the mesitylene and the isoquinoline is 0.5-1.5:0.5-1.0:0.5-2.5, the heating temperature is 150-200°C, and the heating time is 60-90min.

[0017] Optionally, the dianhydride molecule is any one of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, 2,2'-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane tetracarboxylic dianhydride, and 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane tetracarboxylic dianhydride; and the first solvent is any one of N-methyl-2-pyrrolidone, tetrahydrofuran, and dimethyl sulfoxide.

[0018] Optionally, in step S2, the process of pretreatment of double-walled carbon nanotubes is as follows: a. sintering the double-walled carbon nanotubes and cooling them to room temperature; b. adding the double-walled carbon nanotubes cooled in step a to a concentrated nitric acid solution, stirring evenly, placing them in a sealed high-pressure sterilizer for heating, cooling to room temperature, washing them with alcohol and water in sequence, and vacuum baking to obtain nitrogen-doped carbon nanotubes; c. washing the nitrogen-doped carbon nanotubes obtained in step b with alcohol and water in sequence, and vacuum drying them.

[0019] Optionally, in step a, the double-walled carbon nanotubes are sintered at 700-900°C in an inert atmosphere for 30-100 min at a heating rate of 5-10°C / min; in step b, the mass ratio of the double-walled carbon nanotubes to the concentrated nitric acid solution is 10-30:60-70, the heating temperature is 120-180°C, and the heating time is 8-12 h; in step c, the vacuum drying time is 6-10 h.

[0020] Optionally, in step S2, the thickness of the conductive adhesive layer is 0.5-1.5 μm, the ultrasonic dispersion time is 30-60 min, the vacuum drying temperature is 50-80° C., and the curing time is 1-3 h.

[0021] Optionally, in step S3, before depositing the conductive layer, the silicon substrate is further subjected to a de-impurity treatment; the thickness of the conductive layer is 50-200 nm, the conductive layer is a metal layer, and the material of the metal layer is any one of gold, silver, nickel or copper; in step S4, the pressing pressure is 10-30 standard atmospheres, the pressing temperature is 30-50°C, and the pressing time is 10-30S.

[0022] 3. Beneficial effects

[0023] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0024] (1) An electrolyte leakage detection sensor proposed in an embodiment of the present application has a simple structure. By setting a COFs-loaded carbon paper layer, the COFs material loaded on the carbon paper has better dispersion uniformity due to the characteristics of carbon paper such as high air permeability, high conductivity, corrosion resistance and light weight. COFs also has excellent three-dimensional porous structure, long-term stability and conductivity. Therefore, the combination of COFs and carbon paper enables the COFs-loaded carbon paper layer to have better conductivity and porosity, thereby improving the detection sensitivity. At the same time, by setting a double-walled carbon nanotube-loaded carbon paper layer, since the carbon paper surface is coated with a conductive adhesive layer, it can not only provide conductivity, but also provide a high contact area and excellent mechanical strength. At the same time, the pretreated double-walled carbon nanotubes not only achieve nitrogen doping to improve the conductivity of the carbon nanotubes, but also strengthen the surface functional groups such as hydroxyl and carboxyl groups, making it easier to adsorb with electrolyte solvents such as DMC, which can significantly improve the detection sensitivity. Therefore, when the substrate layer, the COFs-loaded carbon paper layer and the double-walled carbon nanotube-loaded carbon paper layer are sequentially pressed from bottom to top to form a sensor, when the sensor is working, once the electrolyte leaks, the double-walled carbon nanotube surface can be connected to the solvent DMC with a higher content in the electrolyte through hydrogen bonds due to the presence of hydroxyl groups. At the same time, COFs provides a three-dimensional porous structure and good electrical conductivity, which greatly increases the charge carriers between DMC and the double-walled carbon nanotubes, thereby improving the detection sensitivity. In addition, the carbon paper provides electrical conductivity, high contact area and excellent mechanical strength, thereby ensuring sufficient contact between the double-walled carbon nanotubes and COFs, further improving its electrical conductivity and detection sensitivity, and having long-term stability, it is suitable for long-term monitoring of electrolyte leakage. It can be seen from this that the sensor of the present application not only has high detection sensitivity and good stability, but also can realize long-term real-time monitoring of electrolyte leakage, and has a simple structure, a small size and is easy to carry, can realize flexibility of use, and significantly improves the safety of lithium-ion batteries.

[0025] (2) An electrolyte leakage detection sensor proposed in an embodiment of the present application can improve the conductivity of the substrate layer and thus improve the sensitivity by setting the structure of the substrate layer. At the same time, the setting of the thickness of the conductive layer can improve the detection sensitivity while ensuring low cost.

[0026] (3) The embodiment of the present application proposes a method for preparing an electrolyte leakage detection sensor. The sensor prepared by this method not only has high detection sensitivity and good stability, and can realize long-term real-time monitoring of electrolyte leakage, but also has a simple structure, a small size and is easy to carry, which can be used flexibly and significantly improve the safety of lithium-ion batteries.

[0027] (4) A preparation method of an electrolyte leakage detection sensor proposed in an embodiment of the present application, in the process of preparing the COFs-loaded carbon paper layer, the limitation of various parameters can obtain a COFs material with excellent porous structure and stability, and can improve the dispersion uniformity of the COFs material on the carbon paper surface, ensuring its long-term stability; at the same time, the limitation of the usage ratio between the first solvent, mesitylene and isoquinoline can make the entire mixed system have good viscosity, polarity and solubility, thereby ensuring the full dissolution and full reaction of each raw material, so that the formed COFs material is more stably deposited on the carbon paper surface, and a COFs-loaded carbon paper layer with excellent conductivity and good stability is obtained.

[0028] (5) The present invention proposes a method for preparing an electrolyte leakage detection sensor. In the preparation process of a double-walled carbon nanotube-loaded carbon paper layer, a conductive adhesive layer is coated on the surface of the hydrophobic carbon paper to improve the conductivity of the carbon paper. The thickness of the conductive adhesive layer is set to ensure that the carbon paper has high conductivity while ensuring the adhesion stability of the conductive adhesive layer on the carbon paper layer. At the same time, by pre-treating the double-walled carbon nanotubes and limiting the amount of concentrated nitric acid and double-walled carbon nanotubes, on the one hand, nitrogen doping is achieved as a nitrogen source to improve the conductivity of the carbon nanotubes, and on the other hand, surface functional groups such as hydroxyl and carboxyl groups are strengthened, making it easier to adsorb with electrolyte solvents such as DMC, thereby significantly improving the detection sensitivity. In addition, the limitation of the remaining parameters can obtain high-purity double-walled carbon nanotubes, improve the adsorption capacity and adsorption stability between the double-walled carbon nanotubes and the electrolyte solvent, thereby improving the detection sensitivity and improving the long-term monitoring of electrolyte leakage.

[0029] (6) The embodiment of the present application proposes a method for preparing an electrolyte leakage detection sensor, in which a conductive layer is deposited on the surface of a silicon substrate, thereby improving the conductivity of the silicon substrate and thereby improving the sensitivity. At the same time, before depositing the conductive layer, the silicon substrate is subjected to an impurity removal treatment, thereby improving the quality of the silicon substrate and preventing impurities from affecting its performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a structural schematic diagram of an electrolyte leakage detection sensor proposed in an embodiment of the present invention. DETAILED DESCRIPTION

[0031] To further understand the content of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0032] It should be noted that in this application, the model of hydrophilic carbon paper is TGP-H-060 or TGP-H-090; the model of hydrophobic carbon paper is TGP-H-060 or TGP-H-090; the model of double-walled carbon nanotube raw material is SUNANO, with a purity greater than 80%, a diameter less than 6nm, and a length of 5-18nm; and other reagent raw materials involved in this application can all be purchased from the market.

[0033] like Figure 1 As shown, the present application provides an electrolyte leakage detection sensor, comprising a substrate layer 3, a COFs-loaded carbon paper layer 2, and a double-walled carbon nanotube-loaded carbon paper layer 1, which are sequentially laminated from bottom to top. The sensor of this structure is simple. By arranging the COFs-loaded carbon paper layer, the COFs material loaded on the carbon paper has better dispersion uniformity due to the high air permeability, high conductivity, corrosion resistance, and light weight of the carbon paper. In addition, COFs has an excellent three-dimensional porous structure, long-term stability, and conductivity. Therefore, the COFs and the carbon paper have a good contact surface. The combination of the COFs and carbon paper layers makes the COFs-loaded carbon paper layer have better conductivity and porosity, thereby improving the detection sensitivity; at the same time, by setting up a double-walled carbon nanotube-loaded carbon paper layer, since the carbon paper surface is coated with a conductive adhesive layer, it can not only provide conductivity, but also provide a high contact area and excellent mechanical strength. At the same time, the pretreated double-walled carbon nanotubes not only achieve nitrogen doping to improve the conductivity of the carbon nanotubes, but also strengthen the surface functional groups such as hydroxyl and carboxyl, which are easier to adsorb with electrolyte solvents such as DMC, which can significantly improve the detection sensitivity. Therefore, when the substrate layer, the COFs-loaded carbon paper layer and the double-walled carbon nanotube-loaded carbon paper layer are sequentially pressed from bottom to top to form a sensor, when the sensor is working, once the electrolyte leaks, the double-walled carbon nanotube surface can be connected to the solvent DMC with a higher content in the electrolyte through hydrogen bonds due to the presence of hydroxyl groups. At the same time, COFs provides a three-dimensional porous structure and good electrical conductivity, which greatly increases the charge carriers between DMC and the double-walled carbon nanotubes, thereby improving the detection sensitivity. In addition, the carbon paper provides electrical conductivity, high contact area and excellent mechanical strength, thereby ensuring sufficient contact between the double-walled carbon nanotubes and COFs, further improving its electrical conductivity and detection sensitivity, and having long-term stability, it is suitable for long-term monitoring of electrolyte leakage. It can be seen from this that the sensor of the present application not only has high detection sensitivity and good stability, but also can realize long-term real-time monitoring of electrolyte leakage, and has a simple structure, a small size and is easy to carry, can realize flexibility of use, and significantly improves the safety of lithium-ion batteries.

[0034] The substrate layer includes a silicon substrate and a conductive layer deposited on the surface of the silicon substrate. This setting can improve the conductivity of the substrate layer and thus improve the sensitivity. The thickness of the silicon substrate is 1-4 mm and the diameter is 1-3 cm. The thickness of the conductive layer is 50-200 nm. The setting of the thickness of the conductive layer can improve the detection sensitivity while ensuring low cost.

[0035] At the same time, the present application also provides a method for preparing an electrolyte leakage detection sensor, comprising the following steps:

[0036] S1. Preparation of COFs-loaded carbon paper layer: Mix raw material A, raw material B, a mixed solvent and isoquinoline to obtain a mixed solution, add hydrophilic carbon paper, and heat to obtain COFs-loaded carbon paper; wherein the molar ratio of the raw material A to the raw material B is 2-4:1-2.5, the raw material A is (4-aminophenyl)amine or a dianhydride molecule, the raw material B is 1,3,5-tris(4-aminophenyl)benzene, and the dianhydride molecule is pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-dibenzophenone tetracarboxylic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, 2,2'-diphenyl ether tetracarboxylic dianhydride, Any one of [4-(3,4-dicarboxyphenoxy)phenyl]propane tetracarboxylic dianhydride and 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane tetracarboxylic dianhydride; the mixed solvent is composed of a first solvent and mesitylene, and the volume ratio of the first solvent, the mesitylene, and the isoquinoline is 0.5-1.5:0.5-1.0:0.5-2.5. This setting can make the entire mixed system have good viscosity, polarity, and solubility, thereby ensuring the full dissolution and reaction of each raw material, so that the formed COFs material is more stably deposited on the carbon paper surface, and a COFs-loaded carbon paper layer with excellent conductivity and good stability is obtained. The first solvent is one of N-methyl-2-pyrrolidone, tetrahydrofuran, and dimethyl sulfoxide, the heating temperature is 150-200°C, and the heating time is 60-90 minutes; in actual application, the mixed solvent is composed of N-methyl-2-pyrrolidone and mesitylene. By limiting the above parameters, COFs materials with excellent porous structure and stability can be obtained, and the dispersion uniformity of COFs materials on the carbon paper surface can be improved to ensure their long-term stability.

[0037] S2. Preparation of double-walled carbon nanotube-loaded carbon paper layer: A conductive adhesive layer is coated on the surface of the hydrophobic carbon paper, and the thickness of the conductive adhesive layer is 0.5-1.5 μm. The conductive adhesive layer material is one of silver conductive adhesive, copper conductive adhesive, carbon conductive adhesive, and nano-carbon tube conductive adhesive. The setting of the conductive adhesive layer can improve the conductive performance of the carbon paper. At the same time, the setting of the thickness of the conductive adhesive layer can ensure that the carbon paper has high conductivity while ensuring the bonding stability of the conductive adhesive layer on the carbon paper layer.

[0038] The double-walled carbon nanotubes are pretreated, and the pretreatment process is as follows: a. The double-walled carbon nanotubes are sintered at 700-900°C in an inert atmosphere at a heating rate of 5-10°C / min for 30-100 minutes, wherein the inert atmosphere can be an argon atmosphere, a nitrogen atmosphere or a carbon dioxide atmosphere, and naturally cooled to room temperature; b. The double-walled carbon nanotubes cooled in step a are added to a concentrated nitric acid solution, wherein the mass ratio of the double-walled carbon nanotubes to the concentrated nitric acid solution is 10-30:60-70, stirred evenly, placed in a sealed high-pressure sterilizer, heated at a temperature of 120-180°C for 8-12 hours, cooled to room temperature, washed with anhydrous ethanol and deionized water three times each, and vacuum-dried at 25-40°C to obtain nitrogen-doped carbon nanotubes; c. The nitrogen-doped carbon nanotubes obtained in step b are washed with anhydrous ethanol and deionized water three times each, and vacuum-dried at 35-45°C for 6-10 hours. By pre-treating the double-walled carbon nanotubes and limiting the amount of concentrated nitric acid and double-walled carbon nanotubes used, the method not only achieves nitrogen doping as a nitrogen source, improving the carbon nanotubes' conductivity, but also strengthens surface functional groups such as hydroxyl and carboxyl groups, making them more susceptible to adsorption to electrolyte solvents such as DMC, significantly enhancing detection sensitivity. Furthermore, by limiting other parameters, high-purity double-walled carbon nanotubes can be obtained, enhancing the adsorption capacity and stability between the double-walled carbon nanotubes and the electrolyte solvent, thereby increasing detection sensitivity and enhancing long-term monitoring of electrolyte leakage.

[0039] The pretreated double-walled carbon nanotubes are added to an organic solvent, anhydrous ethanol, and ultrasonically dispersed at room temperature for 30-60 minutes to obtain a suspension; the suspension is evenly dropped onto the surface of the conductive adhesive layer, vacuum dried at 50-80°C, and cured for 1-3 hours to obtain a double-walled carbon nanotube-loaded carbon paper layer.

[0040] S3. Preparation of substrate layer: A conductive layer is deposited on the surface of the silicon substrate. This setting can improve the conductivity of the substrate layer and thus improve the sensitivity. The thickness of the conductive layer is 50-200nm. This setting can improve the detection sensitivity while ensuring low cost. The conductive layer is a metal layer, and the material of the metal layer is any one of gold, silver, nickel or copper. Before depositing the conductive layer, the silicon substrate is also subjected to impurity removal treatment. The process is as follows: a silicon substrate with a thickness of 1-4mm and a diameter of 1-3cm is rinsed with a hydrofluoric acid solution with a mass fraction of 5-10% for 3-5 times, then rinsed with deionized water for 2-3 times, and dried at room temperature. This setting can improve the quality of the silicon substrate and prevent impurities from affecting its performance. In actual application, the deposition method is one of the gold spraying method (depositing gold elements) and the chemical plating method (nickel and silver).

[0041] S4. Sequentially cover the COFs-loaded carbon paper layer prepared in step S1 and the double-walled carbon nanotube-loaded carbon paper layer prepared in step S2 on the surface of the substrate layer prepared in step S3, and press at 30-50°C and 10-30 standard atmospheres for 10-30 seconds to obtain an electrolyte leakage detection sensor.

[0042] The present application provides an electrolyte leakage detection sensor, which requires a certain amount of direct current (200-1000 microamperes) to be applied during operation. When the electrolyte leaks, the double-walled carbon nanotubes have hydroxyl groups on their surface, which can be connected to the solvent DMC with a high content in the electrolyte through hydrogen bonds. COFs provide a three-dimensional porous structure and good electrical conductivity, resulting in a significant increase in the charge carriers between DMC and the double-walled carbon nanotubes. Carbon paper provides electrical conductivity, a high contact area and excellent mechanical strength to ensure sufficient contact between the carbon nanotubes and COFs. Finally, the difference R between the output current and the input current is recorded: where R = (I0-I) / I0*100%, where I0 is the input current and I is the output current. The larger the R value, the more obvious the output current change, and the more sensitive the sensor is to DMC.

[0043] Example 1

[0044] Preparation of COFs-loaded carbon paper layer: (4-aminophenyl)amine (TAPA) and 1,3,5-tris(4-aminophenyl)benzene (TAPB) were mixed with N-methyl-2-pyrrolidone (NMP), mesitylene and isoquinoline in a molar ratio of 3:2, wherein the volume ratio of N-methyl-2-pyrrolidone (NMP), mesitylene and isoquinoline was 1.1:0.7:1.6 to obtain a mixed solution, and a hydrophilic carbon paper (model TGP-H-060) was added. The mixture was heated to 180°C and maintained for 75 minutes to obtain COFs-loaded carbon paper.

[0045] Preparation of double-walled carbon nanotube-loaded carbon paper layer: A silver conductive adhesive layer with a thickness of 0.8 μm was coated on the surface of a hydrophobic carbon paper (model TGP-H-060); the double-walled carbon nanotubes were pretreated as follows: a. Double-walled carbon nanotube raw material (model SUNANO, purity greater than 80%, diameter less than 6 nm, length 5-18 nm) was sintered at 820°C in an argon atmosphere at a heating rate of 9°C / min for 50 min, and then naturally cooled to room temperature; b. The double-walled carbon nanotubes cooled in step a were added The double-walled carbon nanotubes are added into a concentrated nitric acid solution (mass fraction of concentrated nitric acid>60%), wherein the mass ratio of the double-walled carbon nanotubes to the concentrated nitric acid solution is 23:64, stirred evenly, placed in a sealed polytetrafluoroethylene-lined autoclave, heated at a temperature of 160°C for 9 hours, cooled to room temperature, washed with anhydrous ethanol and deionized water three times each, and vacuum-dried at 30°C to obtain nitrogen-doped carbon nanotubes; c. The nitrogen-doped carbon nanotubes obtained in step b are washed with anhydrous ethanol and deionized water three times each, and vacuum-dried at 40°C for 8 hours.

[0046] Next, the pretreated double-walled carbon nanotubes were added to an organic solvent, anhydrous ethanol, and ultrasonically dispersed at room temperature for 45 minutes to obtain a suspension. The suspension was evenly dropped onto the surface of the conductive adhesive layer, vacuum dried at 60°C, and cured for 2 hours to obtain a double-walled carbon nanotube-loaded carbon paper layer.

[0047] Preparation of the substrate layer: A silicon substrate with a thickness of 2 mm and a diameter of 2 cm was rinsed four times with a hydrofluoric acid solution with a mass fraction of 8%, then rinsed twice with deionized water, and dried at room temperature. A gold layer with a thickness of 100 nm was deposited on the surface of the silicon substrate by a gold spraying method to obtain the substrate layer.

[0048] Finally, the COFs-loaded carbon paper layer and the double-walled carbon nanotube-loaded carbon paper layer prepared above were sequentially covered on the surface of the substrate layer prepared above, and pressed at 35°C and 15 standard atmospheres for 15 seconds to obtain an electrolyte leakage detection sensor.

[0049] Example 2

[0050] Preparation of COFs-loaded carbon paper layer: (4-aminophenyl)amine (TAPA) and 1,3,5-tris(4-aminophenyl)benzene (TAPB) were mixed with N-methyl-2-pyrrolidone (NMP), mesitylene and isoquinoline in a molar ratio of 4:1, wherein the volume ratio of N-methyl-2-pyrrolidone (NMP), mesitylene and isoquinoline was 1.5:1.0:2.5 to obtain a mixed solution, and a hydrophilic carbon paper (model TGP-H-090) was added. The mixture was heated to 200°C and maintained for 90 minutes to obtain COFs-loaded carbon paper.

[0051] Preparation of double-walled carbon nanotube-loaded carbon paper layer: A silver conductive adhesive layer with a thickness of 1.5 μm was coated on the surface of a hydrophobic carbon paper (model TGP-H-090); the double-walled carbon nanotubes were pretreated as follows: a. Double-walled carbon nanotube raw material (model SUNANO, purity greater than 80%, diameter less than 6 nm, length 5-18 nm) was sintered at 900°C for 100 min at a heating rate of 10°C / min in an argon atmosphere, and then naturally cooled to room temperature; b. The double-walled carbon nanotubes cooled in step a were added to the to a concentrated nitric acid solution (mass fraction of concentrated nitric acid>60%), wherein the mass ratio of double-walled carbon nanotubes to concentrated nitric acid solution is 30:70, stirred evenly, placed in a sealed polytetrafluoroethylene-lined autoclave, heated at a temperature of 180°C for 12 hours, cooled to room temperature, washed with anhydrous ethanol and deionized water three times each, and vacuum-dried at 40°C to obtain nitrogen-doped carbon nanotubes; c. washing the nitrogen-doped carbon nanotubes obtained in step b with anhydrous ethanol and deionized water three times each, and vacuum-dried at 45°C for 10 hours.

[0052] Next, the pretreated double-walled carbon nanotubes were added to an organic solvent, anhydrous ethanol, and ultrasonically dispersed at room temperature for 60 minutes to obtain a suspension. The suspension was evenly dropped onto the surface of the conductive adhesive layer, vacuum dried at 80°C, and cured for 3 hours to obtain a double-walled carbon nanotube-loaded carbon paper layer.

[0053] Preparation of the substrate layer: A silicon substrate with a thickness of 4 mm and a diameter of 3 cm was rinsed 5 times with a 10% hydrofluoric acid solution, then rinsed 3 times with deionized water, and dried at room temperature. A silver layer with a thickness of 200 nm was deposited on the surface of the silicon substrate by chemical plating to obtain the substrate layer.

[0054] Finally, the COFs-loaded carbon paper layer and the double-walled carbon nanotube-loaded carbon paper layer prepared above are sequentially covered on the surface of the substrate layer prepared above, and pressed at 40°C and 30 standard atmospheres for 30 seconds to obtain an electrolyte leakage detection sensor.

[0055] Example 3

[0056] Preparation of COFs-loaded carbon paper layer: (4-aminophenyl)amine (TAPA) and 1,3,5-tris(4-aminophenyl)benzene (TAPB) were mixed with N-methyl-2-pyrrolidone (NMP), mesitylene and isoquinoline in a molar ratio of 2:1, wherein the volume ratio of N-methyl-2-pyrrolidone (NMP), mesitylene and isoquinoline was 0.5:0.5:0.5 to obtain a mixed solution, a hydrophilic carbon paper (model TGP-H-090) was added, and the mixture was heated to 150°C and maintained for 60 minutes to obtain COFs-loaded carbon paper.

[0057] Preparation of double-walled carbon nanotube-loaded carbon paper layer: A multi-directional carbon nanotube conductive adhesive layer with a thickness of 0.5 μm was coated on the surface of a hydrophobic carbon paper (model TGP-H-090); the double-walled carbon nanotubes were pretreated as follows: a. Double-walled carbon nanotube raw material (model SUNANO, purity greater than 80%, diameter less than 6 nm, length 5-18 nm) was sintered at 700°C for 30 min at a heating rate of 5°C / min in an argon atmosphere, and then naturally cooled to room temperature; b. The double-walled carbon nanotubes cooled in step a were Add to concentrated nitric acid solution (concentrated nitric acid mass fraction> 60%), wherein the mass ratio of double-walled carbon nanotubes to concentrated nitric acid solution is 10:60, stir evenly, place in a sealed polytetrafluoroethylene-lined autoclave, heat at a temperature of 120 ° C for 8 hours, cool to room temperature, wash with anhydrous ethanol and deionized water three times each, and vacuum bake at 25 ° C to obtain nitrogen-doped carbon nanotubes; c. Wash the nitrogen-doped carbon nanotubes obtained in step b with anhydrous ethanol and deionized water three times each, and vacuum dry at 35 ° C for 6 hours.

[0058] Next, the pretreated double-walled carbon nanotubes were added to an organic solvent, anhydrous ethanol, and ultrasonically dispersed at room temperature for 30 minutes to obtain a suspension. The suspension was evenly dropped onto the surface of the conductive adhesive layer, vacuum dried at 50°C, and cured for 1 hour to obtain a double-walled carbon nanotube-loaded carbon paper layer.

[0059] Preparation of the substrate layer: A silicon substrate with a thickness of 1 mm and a diameter of 1 cm was rinsed three times with a 5% hydrofluoric acid solution, then rinsed twice with deionized water, and dried at room temperature. A nickel layer with a thickness of 50 nm was deposited on the surface of the silicon substrate by chemical plating to obtain the substrate layer.

[0060] Finally, the COFs-loaded carbon paper layer and the double-walled carbon nanotube-loaded carbon paper layer prepared above are sequentially covered on the surface of the substrate layer prepared above, and pressed at 45°C and 10 standard atmospheres for 10 seconds to obtain an electrolyte leakage detection sensor.

[0061] Comparative Example 1

[0062] Compared with Example 1, in Comparative Example 1, the raw double-walled carbon nanotubes were not pretreated, and the other conditions were the same as those in Example 1.

[0063] Comparative Example 2

[0064] Compared with Example 1, in Comparative Example 2, double-walled carbon nanotubes were not loaded on the hydrophobic carbon paper, and the other conditions were the same as those in Example 1.

[0065] Comparative Example 3

[0066] Compared with Example 1, in Comparative Example 3, COFs material was not loaded on the hydrophilic carbon paper, and the other conditions were the same as those in Example 1.

[0067] Comparative Example 4

[0068] Compared with Example 1, in Comparative Example 4, the COFs material and double-walled carbon nanotubes were not loaded on the corresponding hydrophilic carbon paper and hydrophobic carbon paper, and the other conditions were the same as those in Example 1.

[0069] Comparative Example 5

[0070] Compared with Example 1, in Comparative Example 5, no conductive layer was deposited on the silicon substrate, and the other conditions were the same as those in Example 1.

[0071] Comparative Example 6

[0072] Compared with Example 1, in Comparative Example 6, the substrate layer was pressed at 35° C. and 15 standard atmospheres for 15 seconds, and the other conditions were the same as those in Example 1.

[0073] In order to verify the sensitivity of the sensors obtained in Examples 1-3 and Comparative Examples 1-6 to the electrolyte, the present application placed the sensors obtained in Examples 1-3 and Comparative Examples 1-6 in sealed chambers, respectively, and then introduced dimethyl carbonate DMC vapor into the sealed chamber, wherein DMC is the most commonly used solvent in lithium-ion battery electrolytes; then, a certain amount of direct current (600 μA) was introduced into the sensor, and the difference R between the output current and the input current was recorded. The difference R between the output current and the input current was detected when the volume of dimethyl carbonate DMC vapor was 50 μL, 100 μL, and 150 μL, respectively. The results are shown in Table 1.

[0074] Table 1. Comparison of DMC sensitivity of different sensors

[0075]

[0076] Table 2. Comparison of R value changes of different sensors at different times

[0077]

[0078] At the same time, in order to verify that the sensor of the present application has excellent long-term stability, the present application conducted a long-term stability test on the sensors obtained in Examples 1-3 and Comparative Examples 1-6. Specifically, the difference R between the output current and the input current of the sensors obtained in Example 1 and Comparative Examples 1-6 when continuously exposed to an inert atmosphere for 0, 1, 2, 3, 4, 5, and 6 months was detected, wherein the same amount of dimethyl carbonate DMC vapor was introduced and a direct current (600 μA) was introduced. At the same time, when testing the difference R of the above-mentioned sensors at different periods, each sensor was tested three times at different periods, and the R value of each period was finally averaged. The test results are shown in Table 2.

[0079] As shown in Table 1, compared to Comparative Examples 1-6, the difference R values ​​of the sensors prepared in Examples 1-3 varied significantly when the amount of dimethyl carbonate (DMC) vapor introduced was 50 μL, 100 μL, or 150 μL, significantly improving detection sensitivity. In particular, the comparison between Example 1 and Comparative Examples 2 and 4 demonstrates that the double-walled carbon nanotube-loaded carbon paper layer, due to the conductive adhesive coating on the carbon paper surface, not only provides electrical conductivity, but also provides a high contact area and excellent mechanical strength. Furthermore, the pretreated double-walled carbon nanotubes not only achieve nitrogen doping to enhance the carbon nanotubes' conductivity but also strengthen surface functional groups such as hydroxyl and carboxyl groups, making them more susceptible to adsorption by electrolyte solvents such as DMC, significantly improving detection sensitivity. Furthermore, the combination of COFs and carbon paper allows the COFs-loaded carbon paper layer to possess superior conductivity and porosity, thereby enhancing detection sensitivity. At the same time, combined with what is shown in Table 2, the difference R of the sensors prepared in Examples 1-3 remained almost unchanged after continuous exposure to air for 6 months, and the detection sensitivity did not decrease significantly. However, the difference R of the sensors prepared in Comparative Examples 1-6 measured at different time points varied greatly, and the detection sensitivity decreased significantly. This indicates that the sensors prepared in the present application have excellent long-term stability and are suitable for long-term monitoring of electrolyte leakage.

[0080] At the same time, combined with Example 1 and Comparative Examples 1-6, the main mechanism for improving the detection sensitivity of the sensor of the present application is: the pretreated carbon nanotubes on the carbon paper substrate have better detection sensitivity, and the COFs loaded on the carbon paper have excellent conductivity and porosity, which further improve the detection sensitivity. Finally, after adding a metal layer to the silicon substrate, the electronic conductivity can be significantly increased, the charge carrier transfer performance is improved, and the detection sensitivity is effectively improved.

[0081] It can be seen from this that the electrolyte leakage detection sensor prepared in the present application not only has excellent detection sensitivity, but also has good long-term stability.

[0082] The above is a schematic description of the present invention and its embodiments, which is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by this and, without departing from the purpose of the present invention, designs a structure and embodiment similar to this technical solution without inventiveness, they shall fall within the scope of protection of the present invention.

Claims

1. An electrolyte leakage detection sensor, characterized in that: The invention comprises a substrate layer, a COFs-loaded carbon paper layer, and a double-walled carbon nanotube-loaded carbon paper layer laminated in sequence from bottom to top; the substrate layer comprises a silicon substrate and a conductive layer deposited on the surface of the silicon substrate; and the preparation method of the electrolyte leakage detection sensor comprises the following steps: S1. Preparation of COFs-loaded carbon paper layer: Mix raw material A, raw material B, a mixed solvent, and isoquinoline to obtain a mixed solution, add hydrophilic carbon paper, and heat to obtain COFs-loaded carbon paper; the molar ratio of the raw material A to the raw material B is 2-4:1-2.5, the raw material A is (4-aminophenyl)amine or dianhydride molecule, and the raw material B is 1,3,5-tris(4-aminophenyl)benzene; S2. Preparation of double-walled carbon nanotube-loaded carbon paper layer: coating a conductive adhesive layer on the surface of hydrophobic carbon paper; pre-treating the double-walled carbon nanotubes; adding the pre-treated double-walled carbon nanotubes to an organic solvent, ultrasonically dispersing them evenly to obtain a suspension; dripping the suspension evenly onto the surface of the conductive adhesive layer, vacuum drying, and curing to obtain a double-walled carbon nanotube-loaded carbon paper layer; the process of pre-treating the double-walled carbon nanotubes is as follows: a. sintering the double-walled carbon nanotubes and cooling them to room temperature; b. adding the double-walled carbon nanotubes cooled in step a to a concentrated nitric acid solution, stirring evenly, placing them in a sealed high-pressure sterilizer to heat, cooling to room temperature, washing with alcohol, washing with water, and vacuum baking to obtain nitrogen-doped carbon nanotubes; c. washing the nitrogen-doped carbon nanotubes obtained in step b with alcohol, washing with water, and vacuum drying; S3, substrate layer preparation: depositing a conductive layer on the surface of the silicon substrate; S4. Cover the COFs-loaded carbon paper layer prepared in step S1 and the double-walled carbon nanotube-loaded carbon paper layer prepared in step S2 on the surface of the substrate layer prepared in step S3 in sequence, and press them to obtain an electrolyte leakage detection sensor; the pressing pressure is 10-30 standard atmospheres, the pressing temperature is 30-50°C, and the pressing time is 10-30S.

2. The electrolyte leakage detection sensor according to claim 1, characterized in that: The thickness of the silicon substrate is 1-4 mm, and the diameter is 1-3 cm; the thickness of the conductive layer is 50-200 nm.

3. The method for preparing an electrolyte leakage detection sensor according to claim 1, wherein: In step S1, the mixed solvent consists of a first solvent and mesitylene, the volume ratio of the first solvent, the mesitylene and the isoquinoline is 0.5-1.5:0.5-1.0:0.5-2.5, the heating temperature is 150-200° C., and the heating time is 60-90 min.

4. The method for preparing an electrolyte leakage detection sensor according to claim 3, wherein: The dianhydride molecule is any one of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, 2,2'-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane tetracarboxylic dianhydride, and 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane tetracarboxylic dianhydride; the first solvent is any one of N-methyl-2-pyrrolidone, tetrahydrofuran, and dimethyl sulfoxide.

5. The method for preparing an electrolyte leakage detection sensor according to claim 1, wherein: In step a, the double-walled carbon nanotubes are sintered at 700-900°C in an inert atmosphere for 30-100 minutes at a heating rate of 5-10°C / min; in step b, the mass ratio of the double-walled carbon nanotubes to the concentrated nitric acid solution is 10-30:60-70, the heating temperature is 120-180°C, and the heating time is 8-12 hours; in step c, the vacuum drying time is 6-10 hours.

6. The method for preparing an electrolyte leakage detection sensor according to claim 1, wherein: In step S2, the thickness of the conductive adhesive layer is 0.5-1.5 μm, the ultrasonic dispersion time is 30-60 min, the vacuum drying temperature is 50-80° C., and the curing time is 1-3 h.

7. The method for preparing an electrolyte leakage detection sensor according to claim 1, wherein: In step S3, before depositing the conductive layer, the silicon substrate is further subjected to a de-doping treatment; the thickness of the conductive layer is 50-200 nm, the conductive layer is a metal layer, and the material of the metal layer is any one of gold, silver, nickel or copper.

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