Lithium peroxide test paper for discharge product of lithium-oxygen battery and preparation method thereof

Abstract

The application provides a lithium-oxygen battery discharge product lithium peroxide detection test paper and a preparation method thereof, and belongs to the technical field of lithium-oxygen batteries. The preparation method of the test paper comprises the following steps: mixing titanyl sulfate, concentrated sulfuric acid, water and an impregnation solvent to obtain an impregnation solution; uniformly loading the impregnation solution on the surface of a test paper substrate, and drying to obtain the test paper; the impregnation solvent is selected from acetone, anhydrous ethanol, N-methyl pyrrolidone, methylcyclohexane, isopropyl alcohol or cyclohexane. The test paper is prepared by using titanyl sulfate as a specific color developing active component, can have a specific color developing reaction with lithium peroxide, a lithium-oxygen battery discharge product, solves the technical problems that a traditional detection method relies on large and precise instruments, an operation process is complicated, a detection period is long, and in-situ detection cannot be realized on site. The accuracy and reliability of detection are effectively ensured, the test paper has a fast response speed, a color developing effect is intuitive, and specificity is strong.

Description

Technical Field

[0001] This invention relates to the field of lithium-oxygen battery technology, and in particular to a test paper for detecting lithium peroxide, a discharge product of lithium-oxygen batteries, and its preparation method. Background Technology

[0002] In recent years, global warming and the energy crisis have become increasingly severe, accelerating the transformation of the global energy structure towards low-carbon and clean energy. High-energy-density electrochemical energy storage technology has gradually become a research focus in the fields of energy materials and electrochemistry. Among various energy storage technologies, lithium-oxygen batteries, due to their theoretical energy density being far higher than that of traditional lithium-ion batteries, have promising application prospects in portable electronics, electric vehicles, and large-scale energy storage scenarios, and are considered a star technology in the future energy storage field.

[0003] As a core product in the discharge process of lithium-oxygen batteries, the amount of lithium peroxide (Li2O2) generated, its morphological characteristics, and decomposition properties are directly related to the discharge capacity, charge-discharge efficiency, and cycle stability of lithium-oxygen batteries. Detection of Li2O2 is an important foundation for in-depth research into the electrochemical reaction mechanism of lithium-oxygen batteries, improving battery performance, and optimizing electrode materials and electrolyte systems.

[0004] Currently, the detection and analysis of Li2O2, a discharge product of lithium-oxygen batteries, mainly relies on traditional characterization and analysis methods such as X-ray diffraction (XRD), titration analysis, scanning electron microscopy (SEM), and conventional electrochemical testing. These methods generally suffer from numerous drawbacks, including complex and cumbersome procedures, lengthy detection cycles, high instrument costs, and difficulty in achieving rapid in-situ detection. They are ill-suited to the practical application requirements of rapid, real-time Li2O2 detection in lithium-oxygen battery research and development. Currently, there is a lack of simple, portable test strip-like devices capable of rapidly detecting lithium peroxide (Li2O2), a discharge product of lithium-oxygen batteries. This, to some extent, restricts research into the mechanisms of lithium-oxygen batteries and also affects the optimization of their electrode materials. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a lithium peroxide test strip for detecting lithium-oxygen battery discharge products and its preparation method, aiming to solve the technical problems of existing lithium-oxygen battery discharge product detection methods being cumbersome to operate, having long detection cycles, high equipment costs, and being difficult to achieve rapid on-site detection.

[0006] To achieve the above objectives, the present invention provides the following technical solution: One of the technical solutions of this invention is a method for preparing a lithium peroxide test strip for detecting lithium oxide discharge products of lithium-oxygen batteries, comprising the following steps: Titanium oxysulfate is mixed with concentrated sulfuric acid, water and impregnation solvent to obtain an impregnation solution; The impregnation solution is uniformly loaded onto the surface of the test paper substrate and dried to obtain the test paper. Li2O2 standard was prepared by aqueous solution precipitation method. The Li2O2 standard was dispersed in anhydrous ethanol and used for colorimetric calibration of test paper. The impregnation solvent is selected from acetone, anhydrous ethanol, N-methylpyrrolidone, methylcyclohexane, isopropanol, or cyclohexane.

[0007] The second technical solution of the present invention is a test paper for detecting lithium peroxide, a discharge product of lithium-oxygen batteries, prepared by the above preparation method.

[0008] The third technical solution of the present invention is the application of the above-mentioned test strip in the detection of lithium peroxide, a discharge product of lithium-oxygen batteries.

[0009] The present invention discloses the following technical effects: This invention utilizes titanium oxysulfate as a specific colorimetric active component to prepare test strips, which can undergo a specific colorimetric reaction with lithium peroxide, a discharge product of lithium-oxygen batteries. This fundamentally solves the technical problems of traditional detection methods, such as reliance on large precision instruments, cumbersome operation procedures, long detection cycles, and difficulty in achieving on-site in-situ detection. Simultaneously, this invention provides a matching high-purity Li₂O₂ standard for calibrating the test strips, effectively ensuring the accuracy and reliability of the detection. The test strips exhibit fast response speed, intuitive colorimetric effects, and strong specificity, significantly improving the convenience and real-time performance of Li₂O₂ detection, a discharge product of lithium-oxygen batteries.

[0010] The test strip preparation process of this invention uses readily available and inexpensive raw materials, with mild reaction conditions in each step. It requires only simple operations such as impregnation and light-protected drying, eliminating the need for complex equipment and harsh preparation environments. The process exhibits excellent repeatability and stability, making it suitable for batch preparation and large-scale application. This test strip is portable, easy to store, and has a low barrier to entry, making it widely applicable in lithium-oxygen battery laboratory research and development, rapid on-site screening, and other scenarios. It provides an efficient and low-cost detection method for the study of lithium-oxygen battery electrochemical reaction mechanisms, performance evaluation, and system optimization, significantly promoting the basic research and application development of lithium-oxygen batteries. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a flowchart illustrating the synthesis process of preparing titanium oxysulfate powder using the hydrothermal method of this invention. Figure 2This is a flowchart illustrating the synthesis of high-purity Li2O2 standards prepared by the aqueous solution precipitation method of this invention. Figure 3 This is a flowchart illustrating the preparation process of the test paper for detecting lithium peroxide, a discharge product of lithium-oxygen batteries, according to the present invention. Figure 4 This is a comparison chart showing the selection of impregnation solvents during the preparation of the test paper of this invention; Figure 5 This is a comparative diagram showing the selection of the test strip substrate during the preparation of the test strip of this invention. Detailed Implementation

[0013] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0014] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0015] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0016] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0017] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0018] The first aspect of this invention provides a method for preparing a lithium peroxide test strip for detecting lithium oxide discharge products of lithium-oxygen batteries, comprising the following steps: Titanium oxysulfate is mixed with concentrated sulfuric acid, water and impregnation solvent to obtain an impregnation solution; The impregnation solution is uniformly loaded onto the surface of the test paper substrate and dried to obtain the test paper. Li2O2 standard was prepared by aqueous solution precipitation method. The Li2O2 standard was dispersed in anhydrous ethanol and used for colorimetric calibration of test paper. The impregnation solvent is selected from acetone, anhydrous ethanol, N-methylpyrrolidone, methylcyclohexane, isopropanol, or cyclohexane.

[0019] In a preferred embodiment of the present invention, the titanium oxysulfate is prepared by reacting titanium dioxide powder with concentrated sulfuric acid under hydrothermal conditions, followed by cooling and crystallization, washing, and drying to obtain the titanium oxysulfate.

[0020] More preferably, the mass-to-volume ratio of titanium dioxide to concentrated sulfuric acid is 4.0-7.0 g: 80-120 mL; the reaction temperature under hydrothermal conditions is 80-90 °C, and the reaction time is 60-120 min.

[0021] In this invention, the reaction is carried out under hydrothermal conditions in a fume hood. Concentrated sulfuric acid is added to a three-necked flask, heated in a water bath to 80-90°C, and preheated by stirring at low speed of 100-200 rpm for 10-20 minutes to obtain a preheated solution. Titanium dioxide powder is slowly added to the preheated solution in batches, and the reaction is continued at 80-90°C in a water bath for 60-120 minutes to obtain a translucent milky white solution. After naturally cooling to room temperature, white crystals precipitate out. After washing with deionized water and drying, white titanium oxysulfate powder is obtained.

[0022] Understandably, the hydrothermal method for synthesizing titanium oxysulfate is simple, uses readily available raw materials, and yields high-purity titanium oxysulfate crystals, providing a reliable active component for the specific colorimetric reaction of subsequent test strips. Controlling the reaction temperature and stirring speed ensures that titanium dioxide reacts fully with concentrated sulfuric acid to form a uniform titanium oxysulfate solution. Natural cooling crystallization is beneficial for obtaining titanium oxysulfate powder with complete crystal structure, thus improving its stability and colorimetric activity.

[0023] In a preferred embodiment of the present invention, the volume ratio of the concentrated sulfuric acid, water and impregnation solvent is (1.5-2):(8-10):(10-20), and the concentration of the concentrated sulfuric acid is 95%-98%.

[0024] In a preferred embodiment of the present invention, the ratio of titanium oxysulfate to impregnation solvent is 1.2-1.5g:10-20mL.

[0025] In this invention, the impregnation solution is prepared in a fume hood. The method of adding acid to water is used, where concentrated sulfuric acid is slowly added to water, and after vigorous stirring and cooling to room temperature, titanium oxysulfate powder is added and stirred until completely dissolved. Finally, the impregnation solvent is added and mixed evenly, and the titanium oxysulfate impregnation solution is prepared and used immediately.

[0026] Understandably, the addition of the impregnation solvent can effectively reduce the surface tension of the impregnation solution, improve its penetration and dispersion uniformity on the filter paper substrate, and ensure that titanium oxysulfate forms a uniform and stable colorimetric layer on the filter paper surface; the addition of concentrated sulfuric acid can adjust the acidity of the system, inhibit the hydrolysis of titanium oxysulfate, and maintain the Ti 4+ It exists in a stable form; the liquid is prepared and used immediately, which can avoid the hydrolysis and failure of active components due to long-term storage, and ensure the accuracy and sensitivity of the test strip.

[0027] In a preferred embodiment of the present invention, the test strip substrate is selected from one of qualitative filter paper, carbon cloth, PE diaphragm, glass fiber diaphragm, absorbent paper, and lint-free cloth. In the present invention, the thickness of the test strip substrate is preferably 0.10-0.30 mm.

[0028] In a preferred embodiment of the present invention, before uniformly loading the impregnation solution onto the surface of the test strip substrate, a pretreatment step is included; the pretreatment involves washing and drying the test strip substrate for later use. Specifically: first, the substrate material is cut into appropriate sizes, then washed 1-3 times with deionized water to remove surface paper scraps and soluble impurities. After washing, it is dried naturally or at a low temperature of 35-45℃ to complete the pretreatment.

[0029] Understandably, using qualitative filter paper or glass fiber membrane as a substrate provides good water absorption and mechanical strength, effectively loading the active component of titanium oxysulfate. Its chemical inertness also prevents side reactions with the detection system. Controlling the substrate thickness ensures uniform loading of the active component during impregnation, while facilitating the storage, portability, and actual testing of the test strip. Washing with deionized water removes soluble impurities, preventing interference with color development, and low-temperature drying prevents substrate deformation, ensuring its structural integrity.

[0030] In a preferred embodiment of the present invention, the method for uniformly loading the impregnation liquid onto the surface of the test paper substrate is as follows: immersing the test paper substrate in the impregnation liquid, or spraying the impregnation liquid uniformly onto the surface of the reagent substrate by spraying.

[0031] In this invention, the test strip substrate is immersed in the impregnation solution for 20-80 seconds. By controlling the impregnation time, this invention ensures that the titanium oxysulfate solution penetrates the substrate uniformly, avoiding uneven local concentrations.

[0032] It is understandable that impregnation can achieve uniform loading of titanium oxysulfate on the substrate surface, and the impregnation method is suitable for batch preparation. Controlling the impregnation time can adjust the loading of titanium oxysulfate on the substrate surface. Too high a loading can easily lead to uneven color development of the test paper, while too low a loading will affect the color development sensitivity. A reasonable loading can ensure the response speed and color development effect of the test paper to Li2O2.

[0033] In a preferred embodiment of the present invention, the drying process involves air drying under light-protected conditions or low-temperature drying under light-protected conditions. Low-temperature drying is performed at 35-55°C for 10-12 hours. After drying, the obtained test paper is cut into test strips and stored in a sealed container away from light. The present invention strictly avoids light during the drying process to prevent Ti... 4+ Photocatalytic decomposition occurs, affecting the detection performance of the test strip.

[0034] Understandably, Ti 4+ It has photocatalytic activity and is prone to decomposition under light conditions, generating titanium oxides with no color development activity. Therefore, the drying process must be strictly protected from light to ensure the activity of titanium oxysulfate. Low-temperature drying and natural air drying can avoid the decomposition of titanium oxysulfate or substrate deformation caused by high temperature, while ensuring uniform drying of the substrate, so that titanium oxysulfate is firmly attached to the substrate surface, forming a stable color development layer, improving the storage stability and detection reliability of the test strip.

[0035] This invention cuts the test reagent into test strips, facilitating operation and color comparison during actual testing. The strips are compact and portable; sealing them away from light prevents moisture absorption and damage. 4+ Photolysis and loss of active components ensure that the test strip has stable detection performance over a long period of time.

[0036] A second aspect of the present invention provides a test strip for detecting lithium peroxide, a discharge product of lithium-oxygen batteries, prepared by the above-described preparation method.

[0037] A third aspect of the present invention provides an application of the above-mentioned test strip in the detection of lithium peroxide, a discharge product of lithium-oxygen batteries.

[0038] In the detection of lithium peroxide, this invention uses an aqueous solution precipitation method to prepare Li2O2 standard, which is then dispersed in anhydrous ethanol for colorimetric calibration of test strips.

[0039] Specifically, the preparation of Li₂O₂ standard by aqueous solution precipitation is as follows: Using lithium hydroxide monohydrate and hydrogen peroxide solution as raw materials, 10-15g of lithium hydroxide monohydrate is added to 80-120mL of 25%-35% hydrogen peroxide solution, and the mixture is stirred vigorously for 30-90min. After the reaction is complete, a white Li₂O₂ precipitate is obtained. The precipitate is collected by filtration and placed in a vacuum drying oven at 70-80℃ for 10-12h to obtain high-purity Li₂O₂ standard. Subsequently, 5-10mg of Li₂O₂ standard is dissolved in 10-20mL of anhydrous ethanol and ultrasonically dispersed for 10-20min for use in color calibration of test strips.

[0040] Understandably, the aqueous solution precipitation method for preparing Li2O2 standards is simple, has mild reaction conditions, and uses readily available raw materials, yielding high-purity Li2O2 precipitates. Vacuum drying and treatment at 70-80℃ effectively remove residual moisture and hydrogen peroxide, preventing Li2O2 decomposition and ensuring the purity and stability of the standards. Dispersing the Li2O2 standards in anhydrous ethanol can simulate the sample state during actual testing, calibrating the colorimetric reaction of test strips and ensuring the accuracy and reliability of the test results.

[0041] This invention provides a lithium peroxide test strip for detecting lithium oxide, a discharge product of lithium-oxygen batteries. Using titanium oxysulfate as a specific colorimetric active component, it undergoes a specific colorimetric reaction with Li₂O₂, a discharge product of lithium-oxygen batteries. The reaction principle is as follows: Li₂O₂ reacts with titanium oxysulfate on the surface of the test strip to generate a titanium oxide complex with a characteristic color. Rapid qualitative detection of Li₂O₂ can be achieved based on this color reaction. On one hand, titanium oxysulfate, as a colorimetric active component, can effectively identify Li₂O₂ and produce a significant color change. On the other hand, by optimizing the formulation of the impregnation solution and the impregnation process parameters, a uniform and stable colorimetric layer of titanium oxysulfate is formed on the substrate surface, significantly improving the colorimetric sensitivity and detection reliability of the test strip. In the test strip preparation process, high-purity titanium oxysulfate crystals are synthesized using a hydrothermal method, and the impregnation solvent is introduced for impregnation of the test strip, ensuring uniform loading and firm adhesion of the active component on the substrate. Simultaneously, substrate pretreatment, light-protected drying, and sealed storage effectively inhibit the growth of TiO₂. 4+ The photocatalytic decomposition of the test strips prevents them from failing, ensuring long-term storage stability and consistent use. The Li₂O₂ standard prepared using the aqueous solution precipitation method is simple, high-purity, and provides a reliable reference for colorimetric calibration of the test strips, further ensuring the accuracy and repeatability of the test results. Simultaneously, the standardized and simple preparation process effectively avoids interference from impurities and batch variations, significantly improving the overall performance and practical value of the test strips. In particular, the prepared lithium peroxide test strip for lithium-oxygen battery discharge products achieves optimal colorimetric effects and detection performance through an optimized combination of acetone impregnation solvent and a glass fiber membrane substrate.

[0042] The test strip of this invention is portable and easy to use. It can undergo a specific colorimetric reaction with Li2O2, with fast color development speed and high specificity. By comparing with the standard color, the rapid qualitative determination of Li2O2 can be achieved.

[0043] It is understood that the core advantages of the lithium peroxide test paper for lithium-oxygen battery discharge products prepared by this invention are its high specificity, lack of complex equipment, and ability to effectively avoid interference from other impurities on the test results. At the same time, the preparation process is simple and low-cost, and it can be mass-produced, which greatly lowers the threshold for Li2O2 detection and is suitable for various scenarios such as laboratory research and development and rapid on-site detection.

[0044] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0045] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0046] In the following examples and comparative examples, the relevant operations for test strip color calibration and actual detection are as follows: Different amounts of high-purity Li₂O₂ standard are dissolved in anhydrous ethanol solution and dispersed by sonication for 10-20 min to obtain Li₂O₂ standard solutions of different concentrations (0.01-0.1 mol / L). The standard solutions are then added dropwise to the test strips prepared according to this invention, allowed to stand for 1-3 min, and the color development of the test strips is observed to calibrate whether the color development reaction of the test strips is normal. In actual detection, a sample of lithium-oxygen battery discharge products is taken, placed in anhydrous ethanol, dissolved by sonication or standing, and then added dropwise to the test strips. After standing for 1-3 min, the color change is observed. If the test strip changes from colorless to yellow, it is determined that the sample contains Li₂O₂. All reagents used are analytical grade, and the operating environment temperature is 20-25℃, the relative humidity is 40%-60%, and direct sunlight is avoided.

[0047] Comparative Example 1 The effect of different test strip substrates on the performance of lithium peroxide test strips: This comparative study investigated the effects of six different substrates—qualitative filter paper, carbon cloth, PE diaphragm, glass fiber diaphragm, absorbent paper, and cleanroom cloth—on the colorimetric effect, sensitivity, and stability of the test strips. Except for the substrate type, all other process parameters were kept consistent for the preparation of the test strips on each substrate. The specific preparation and testing methods are as follows: (1) Preparation of titanium oxysulfate powder The solution was synthesized using a hydrothermal method. 5.0 g of titanium dioxide powder and 100 mL of concentrated sulfuric acid were added to a three-necked flask and heated to 85 °C in a water bath in a fume hood. The mixture was preheated by stirring at 150 rpm for 15 min. Titanium dioxide powder was added slowly in batches, and the reaction was continued at 85 °C for 90 min to obtain a translucent milky white solution. After naturally cooling to room temperature, white crystals precipitated. After washing with deionized water and drying, white titanium oxysulfate powder was obtained.

[0048] (2) Preparation of titanium oxysulfate impregnation solution In a fume hood, using the acid-to-water method, 1.8 mL of concentrated sulfuric acid was slowly added to 9 mL of deionized water, stirred vigorously, and cooled to room temperature; 1.35 g of titanium oxysulfate powder was added and stirred until completely dissolved; finally, 15 mL of acetone was added as the impregnation solvent, mixed evenly, and the titanium oxysulfate impregnation solution was prepared and used immediately.

[0049] (3) Pretreatment of different substrates Qualitative filter paper, carbon cloth, PE diaphragm, glass fiber diaphragm, absorbent paper, and lint-free cloth were selected as test paper substrates, with the thickness of each substrate controlled at 0.20 mm. The six substrates were cut into the same size, washed twice with deionized water to remove surface impurities, and then placed in a 40℃ drying oven for 2 hours. After drying, they were taken out for use.

[0050] (4) Preparation of test strips with different substrates The six pretreated substrates were immersed in the titanium oxysulfate impregnation solution prepared in step (2) for 50 seconds to ensure uniform penetration of the impregnation solution into the substrate. After impregnation, all substrates were placed in a vacuum drying oven at 50°C and vacuum-dried at low temperature for 8 hours. After drying, all substrates were cut into standard test strips of 0.5 cm × 5 cm, placed in brown light-proof glass bottles, silica gel desiccant was added, sealed and stored in a cool and dry place to obtain lithium peroxide test strips with six different substrates.

[0051] (5) Preparation of Li2O2 standard The aqueous solution precipitation method was used. 12g of lithium hydroxide monohydrate was added to 100mL of 30% hydrogen peroxide solution and stirred vigorously for 120min to form a white Li2O2 precipitate. The precipitate was collected by filtration and placed in a vacuum drying oven at 80℃ for 12h to obtain a high-purity Li2O2 standard. 8mg of the Li2O2 standard was dissolved in 15mL of anhydrous ethanol and ultrasonically dispersed for 15min to prepare a Li2O2 standard calibration solution.

[0052] (6) Performance testing of test strips with different substrates The Li2O2 standard calibration solution prepared in step (5) was added dropwise to six different substrate test strips. After standing for 2 minutes, the color development speed, color development uniformity, and color depth of each test strip were observed and recorded under the conditions of 20-25℃, relative humidity 40%-60%, and protection from light. At the same time, each test strip was sealed and stored for 30 days, and the standard calibration solution was added again to test its storage stability.

[0053] result Qualitative filter paper and glass fiber membrane-based test strips showed the fastest color development, producing a distinct yellow color within 1 minute of standing, with a moderate shade. Glass fiber membrane-based test strips showed no significant color degradation after 30 days of storage, while qualitative filter paper-based test strips showed slight fading. Absorbent paper-based test strips showed relatively fast color development, but uneven absorption resulted in locally excessively dark colors. Carbon cloth-based test strips developed color slowly, producing only a pale yellow color after 2 minutes of standing, and the color of the carbon cloth itself interfered with the color observation. PE membrane-based test strips exhibited poor impregnation of the impregnating solution, resulting in uneven loading of the active components and no color development. Dust-free cloth-based test strips easily shed residue after color development, exhibited poor adhesion of the active components, and lost their color development ability after 10 days of storage.

[0054] Comparative Example 2 Effects of different impregnation solvents on the performance of lithium peroxide test paper This comparative study investigated the effects of six different impregnation solvents—acetone, anhydrous ethanol, N-methylpyrrolidone, methylcyclohexane, isopropanol, and cyclohexane—on the uniformity of active component loading, colorimetric sensitivity, and substrate compatibility of test strips. Except for the type of impregnation solvent, all other process parameters were kept consistent for the preparation of test strips using these solvents. The specific preparation and detection methods are as follows: (1) Preparation of titanium oxysulfate powder The preparation of white titanium oxysulfate powder was completely consistent with step (1) of Comparative Example 1.

[0055] (2) Preparation of titanium oxysulfate impregnation solutions with different impregnation solvents In a fume hood, using the acid-to-water method, 1.8 mL of concentrated sulfuric acid was slowly added to 9 mL of deionized water, and the mixture was stirred vigorously and cooled to room temperature. 1.35 g of titanium oxysulfate powder was added and stirred until completely dissolved. Subsequently, 15 mL of acetone, anhydrous ethanol, N-methylpyrrolidone, methylcyclohexane, isopropanol, and cyclohexane were added as impregnation solvents, and a separate impregnation solution was prepared for each solvent. The solutions were mixed thoroughly and used immediately to obtain six titanium oxysulfate impregnation solutions with different impregnation solvents.

[0056] (3) Pretreatment of test strip substrate Qualitative filter paper was selected as the uniform test paper base, with a thickness controlled at 0.20 mm. After being cut into the same size, it was washed twice with deionized water and dried at a low temperature in a 40℃ drying oven. After drying, it was taken out for use.

[0057] (4) Preparation of test strips with different impregnation solvents The pretreated qualitative test strip substrates were immersed in six different impregnation solvents containing titanium oxysulfate for 50 seconds each. After impregnation, all substrates were placed in a vacuum drying oven at 50°C and dried under vacuum for 8 hours. After drying, the substrates were cut into standard test strips of 0.5 cm × 5 cm, placed in brown light-proof glass bottles, desiccated with silica gel, sealed, and stored in a cool, dry place to obtain lithium peroxide test strips with six different impregnation solvents.

[0058] (5) Preparation of Li2O2 standard The process was completely consistent with step (5) of Comparative Example 1. High-purity Li2O2 standard was prepared and a standard calibration solution was prepared.

[0059] (6) Performance testing of test papers with different impregnation solvents The Li2O2 standard calibration solution was added dropwise to six test strips impregnated with different solvents. After standing for 2 minutes, the uniformity of the active component loading, the color development speed, and the clarity of the color development were observed and recorded under the conditions of 20-25℃, 40%-60% relative humidity and in the dark.

[0060] result When acetone and anhydrous ethanol are used as impregnation solvents, the active components are evenly loaded on the qualitative test paper substrate without local agglomeration. The test paper develops color quickly, showing a clear and uniform yellow color after standing for 1 minute, with high color clarity. Among them, the test paper prepared with acetone solvent has a slightly better color development effect than that prepared with anhydrous ethanol. The impregnation solution prepared with isopropanol solvent has good penetration and a moderate color development speed, showing a yellow color after standing for 1.5 minutes, but the color is slightly light. The impregnation solution prepared with N-methylpyrrolidone solvent has a higher viscosity, and the active components are prone to local accumulation, resulting in uneven color development. The impregnation solutions prepared with methylcyclohexane and cyclohexane solvents will make the qualitative test paper substrate brittle, and the test paper will be damaged and cannot be stored after drying, but the color development is uniform and the color is deep.

[0061] Example 1 Preparation and performance of lithium peroxide test paper with acetone as impregnation solvent and glass fiber membrane as substrate In this embodiment, acetone, which has the best performance in the comparative example, is used as the impregnation solvent and glass fiber membrane is used as the substrate. Lithium peroxide test paper is prepared according to the optimized process parameters, and its detection specificity, sensitivity and long-term storage stability for Li2O2 are tested.

[0062] (1) Preparation of titanium oxysulfate powder Using a hydrothermal method, 7.0 g of titanium dioxide powder and 120 mL of concentrated sulfuric acid were added to a three-necked flask and heated to 90 °C in a water bath in a fume hood. The mixture was preheated for 20 min with low-speed stirring at 200 rpm. Titanium dioxide powder was added slowly in batches, and the reaction was continued at 90 °C for 120 min to obtain a translucent milky white solution. After natural cooling to room temperature, white crystals precipitated. The solution was repeatedly washed with deionized water and dried to obtain high-purity titanium oxysulfate white powder.

[0063] (2) Preparation of titanium oxysulfate impregnation solution In the fume hood, the acid-water method was used. 2 mL of concentrated sulfuric acid was slowly added to 10 mL of deionized water, and the mixture was stirred vigorously and cooled to room temperature. 1.5 g of titanium oxysulfate powder was added and stirred until completely dissolved. Finally, 20 mL of acetone was added as the impregnation solvent, and the mixture was mixed evenly. The solution was prepared and used immediately to obtain the titanium oxysulfate impregnation solution.

[0064] (3) Pretreatment of glass fiber membrane substrate A 0.30mm thick glass fiber membrane was selected as the substrate, washed three times with deionized water to remove soluble impurities from the surface, and then placed in a 45℃ drying oven to dry at a low temperature to ensure that the substrate was dry and free of moisture before being taken out for use.

[0065] (4) Preparation of test strips The pretreated glass fiber membrane substrate was immersed in the impregnation solution of step (2) for 80 seconds to ensure that the impregnation solution fully and evenly penetrated the substrate. After impregnation, the substrate was placed in a vacuum drying oven at 50°C and vacuum dried at low temperature for 8 hours. After drying, it was precisely cut into standard test strips of 0.6 cm × 6 cm, placed in a brown light-proof glass bottle, silica gel desiccant was added, and after vacuum sealing, it was stored in a cool and dry place to obtain lithium peroxide test strips.

[0066] (5) Preparation of high-purity Li2O2 standard and preparation of calibration solution The aqueous solution precipitation method was used. 15g of lithium hydroxide monohydrate was added to 120mL of 35% hydrogen peroxide solution and stirred vigorously for 90min to generate a white Li2O2 precipitate. The precipitate was collected by filtration and dried in a vacuum drying oven at 80℃ for 12h to obtain a high-purity Li2O2 standard. 1mg, 3mg, 5mg, 8mg, and 10mg of Li2O2 standard were dissolved in 20mL of anhydrous ethanol and ultrasonically dispersed for 20min to prepare Li2O2 standard calibration solutions with concentrations of 0.01mol / L, 0.03mol / L, 0.05mol / L, 0.08mol / L, and 0.1mol / L, respectively, for use in colorimetric calibration and sensitivity testing of test strips.

[0067] The test strip in this embodiment shows a distinct yellow color after standing for 1 minute. The color intensity is moderate and there is no local aggregation, making it suitable for rapid detection of Li2O2.

[0068] Example 2 Preparation and performance of lithium peroxide test paper using anhydrous ethanol as impregnation solvent and qualitative filter paper as substrate This embodiment uses anhydrous ethanol, which has the second-best performance in the comparative example, as the impregnation solvent and qualitative filter paper as the substrate. Lithium peroxide test strips are prepared according to optimized process parameters, suitable for routine rapid testing scenarios in laboratories. Specific preparation and performance are as follows: (1) Preparation of titanium oxysulfate powder Using a hydrothermal method, 4.0 g of titanium dioxide powder and 80 mL of concentrated sulfuric acid were added to a three-necked flask and heated to 80 °C in a water bath in a fume hood. The mixture was preheated by stirring at 100 rpm for 10 min. Titanium dioxide powder was added slowly in batches, and the reaction was continued at 80 °C for 60 min to obtain a translucent milky white solution. After natural cooling to room temperature, white crystals precipitated. The solution was washed with deionized water and dried to obtain white titanium oxysulfate powder.

[0069] (2) Preparation of titanium oxysulfate impregnation solution In the fume hood, the acid-to-water method was used. 1.5 mL of concentrated sulfuric acid was slowly added to 8 mL of deionized water, and the mixture was stirred vigorously and cooled to room temperature. 1.2 g of titanium oxysulfate powder was added and stirred until completely dissolved. Finally, 10 mL of anhydrous ethanol was added as the impregnation solvent, and the mixture was mixed evenly. The solution was prepared and used immediately to obtain the titanium oxysulfate impregnation solution.

[0070] (3) Pretreatment of qualitative filter paper substrate A 0.30mm thick glass fiber membrane was selected as the substrate, washed three times with deionized water to remove soluble impurities from the surface, and then placed in a 45℃ drying oven to dry at a low temperature to ensure that the substrate was dry and free of moisture before being taken out for use.

[0071] (4) Preparation of test strips The pretreated glass fiber membrane substrate is immersed in the impregnation solution of step (2) for 80 seconds to ensure that the impregnation solution fully and evenly penetrates the substrate. After impregnation, the substrate is placed in a vacuum drying oven at 50°C and vacuum-dried at low temperature for 8 hours. After drying, it is precisely cut into standard test strips of 0.4 cm × 4 cm, placed in a brown light-proof glass bottle, silica gel desiccant is added, and after sealing, it is stored in a cool and dry place to obtain lithium peroxide test strips.

[0072] (5) Preparation of Li2O2 standard and preparation of calibration solution In complete consistency with step (5) of Example 1, prepare a series of Li2O2 standard calibration solutions of different concentrations.

[0073] The test strip in this embodiment shows a distinct yellow color after standing for 1 minute. The color intensity is moderate and there is no local aggregation, making it suitable for rapid detection of Li2O2.

[0074] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a lithium peroxide test strip for detecting lithium oxide discharge products of lithium-oxygen batteries, characterized in that, Includes the following steps: Titanium oxysulfate is mixed with concentrated sulfuric acid, water and impregnation solvent to obtain an impregnation solution; The impregnation solution is uniformly loaded onto the surface of the test paper substrate and dried to obtain the test paper. Li2O2 standard was prepared by aqueous solution precipitation method. The Li2O2 standard was dispersed in anhydrous ethanol and used for colorimetric calibration of test paper. The impregnation solvent is selected from acetone, anhydrous ethanol, N-methylpyrrolidone, methylcyclohexane, isopropanol, or cyclohexane.

2. The preparation method according to claim 1, characterized in that, The preparation method of the titanium oxysulfate is as follows: titanium dioxide powder is reacted with concentrated sulfuric acid under hydrothermal conditions, and the titanium oxysulfate is obtained after cooling and crystallization, washing and drying.

3. The preparation method according to claim 2, characterized in that, The mass-to-volume ratio of titanium dioxide to concentrated sulfuric acid is 4.0-7.0 g: 80-120 mL; the reaction temperature under hydrothermal conditions is 80-90 °C, and the reaction time is 60-120 min.

4. The preparation method according to claim 1, characterized in that, The ratio of titanium oxysulfate to impregnation solvent is 1.2-1.5g:10-20mL.

5. The preparation method according to claim 1, characterized in that, The method for uniformly loading the impregnation liquid onto the surface of the test paper substrate is as follows: immerse the test paper substrate in the impregnation liquid, or spray the impregnation liquid evenly onto the surface of the reagent substrate using a spraying method.

6. The preparation method according to claim 1, characterized in that, The test strip substrate is selected from one of the following: qualitative filter paper, carbon cloth, PE diaphragm, glass fiber diaphragm, absorbent paper, and dust-free cloth.

7. The method for preparing the lithium peroxide test strip for lithium-oxygen battery discharge products according to claim 1, characterized in that, The Li2O2 standard was prepared by aqueous solution precipitation method, including the following steps: using lithium hydroxide monohydrate and hydrogen peroxide solution as raw materials, stirring and reacting, filtering, and vacuum drying to obtain high-purity Li2O2 standard.

8. The lithium peroxide test paper for lithium-oxygen battery discharge products prepared by the preparation method according to any one of claims 1-7.

9. The application of the test strip as described in claim 8 in the detection of lithium peroxide, a discharge product of lithium-oxygen batteries.

Images