Method for measuring safety of sodium battery positive electrode material

Abstract

The invention discloses a method for measuring the safety of a sodium battery positive electrode material. The method comprises the following steps: 1, screening and preparing a material; 2, assembling the battery; step 3, carrying out ARC test; 4, determining the thermal runaway temperature and the highest temperature; and 5, data analysis and evaluation. By simulating thermal abuse conditions, such as rapid temperature rise, of the battery in actual use through an ARC test, safety assessment closer to actual application is provided, meanwhile, the dynamic monitoring capability can reflect the thermal behavior of the battery at a specific temperature in real time, the accuracy and effectiveness of assessment are ensured, and the safety of the battery is improved. A direct index is provided for thermal stability evaluation by accurately measuring heat flow change and determining the thermal runaway temperature TSD through an ARC test, the thermal runaway risk can be rapidly identified, detailed chemical information can be provided for material design and improvement, and the safety of the battery is enhanced.

Description

Technical Field

[0001] The invention relates to a method for measuring the safety of sodium battery positive electrode materials, belonging to the technical field of battery thickness measurement. Background Art

[0002] The cathode material of sodium-ion batteries is a key component of the battery, which determines the energy density, cycle life and safety of the battery. When processing sodium-ion batteries, the performance of the cathode material needs to be tested. TG-DSC is commonly used to measure thermal stability, but this method is carried out in a laboratory environment, and the conditions are different from actual use, and the results are not completely consistent. TG-DSC is a static test and cannot simulate thermal abuse in dynamic applications, such as charging and discharging, mechanical shock, etc., and TG-DSC only measures thermal stability and does not evaluate thermal runaway performance, such as internal temperature rise and thermal runaway propagation. Different experimental conditions also increase the uncertainty of test results. Summary of the invention

[0003] In view of the above-mentioned defects of the prior art, the present invention provides a method for measuring the safety of sodium battery positive electrode materials.

[0004] The technical solution of the present invention is as follows: A method for measuring the safety of sodium positive electrode materials comprises the following steps:

[0005] Step 1: Screen materials based on electrochemical performance and potential safety;

[0006] Step 2: Assemble the screened materials into batteries and assemble standard sodium iron phosphate batteries;

[0007] Step 3: Perform accelerated calorimetry test on the assembled battery and the standard sodium iron phosphate battery;

[0008] Step 4: Determine the thermal runaway temperature and maximum temperature of the battery under thermal abuse conditions based on the accelerated calorimetry test results;

[0009] Step 5: Evaluate the thermal safety performance of the material. If the battery thermal runaway temperature of the test material is higher than that of the standard sodium iron phosphate battery, and the maximum temperature is lower than that of the standard sodium iron phosphate battery, the positive electrode material is considered safe.

[0010] Furthermore, the step 1 includes using X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) to perform physical and chemical characterization on the candidate material and performing electrochemical testing to obtain cyclic voltammetry (CV) and charge-discharge curves.

[0011] Furthermore, the step 1 includes performing an XRD test, recording the position and intensity of the diffraction peak, analyzing the crystal structure, observing the microscopic morphology of the material using a SEM, and taking corresponding images, and analyzing the elemental composition of the material using EDS.

[0012] Furthermore, the step 1 of testing to obtain cyclic voltammetry (CV) and charge-discharge curves includes preparing electrodes for electrochemical testing, assembling candidate materials into a simple battery and then performing a CV test on an electrochemical workstation, setting different scan rates and potential ranges, recording and analyzing the CV curve, performing a charge-discharge test, recording the charge-discharge curve of the battery, and calculating its specific capacity and energy density.

[0013] Furthermore, the step 2 includes preparing the positive electrode material, negative electrode material, electrolyte and separator required for the battery; assembling the battery according to the battery design specification to ensure the sealing and reliability of the battery.

[0014] Furthermore, when assembling a standard sodium iron phosphate battery, 14.5 g of sodium iron phosphate positive electrode material, 5.7 g of negative electrode material, and 15 g of electrolyte are used to assemble a battery with a capacity of 1.3 Ah according to a filling factor of 11, and the screened positive electrode material is used to replace the sodium iron phosphate positive electrode material to make a battery with the same capacity of 1.3 Ah.

[0015] Furthermore, the step three includes preheating the accelerated calorimetry test system to a set starting temperature, and adjusting the heating rate of the accelerated calorimetry test system to a predetermined value. The heating rate is usually selected according to the test standard and the characteristics of the battery, calibrating the test system, and placing the battery assembled in step two and the standard sodium iron phosphate battery into the accelerated calorimetry test system for testing, and recording the heat flow, temperature, and pressure data of the battery.

[0016] Furthermore, the step 4 includes:

[0017] 4.1. Use thermal analysis software to plot the temperature and heat curves over time, analyze key characteristic points, calculate the total reaction heat, and evaluate the thermal behavior and heat release of the battery;

[0018] 4.2. Use the temperature-time curve to find the point where the battery temperature starts to rise abnormally quickly, that is, the starting thermal runaway temperature of the battery. Use the temperature-heat flow curve to find the point where the heat flow suddenly increases.

[0019] 4.3. Find the peak of temperature rise through the curve of temperature change over time. This temperature value is the maximum temperature of the battery.

[0020] Furthermore, the step five includes analyzing the thermal stability of the material under different conditions according to the thermal runaway temperature and the maximum temperature in combination with the test conditions, and evaluating the risk of thermal runaway and the internal structural damage that may be caused.

[0021] Compared with the prior art, the advantages of the technical solution provided by the present invention are:

[0022] 1. The present invention provides a safety assessment that is closer to actual application by simulating the thermal abuse conditions of the battery in actual use, such as rapid temperature rise, through the ARC test (accelerated calorimetry test). At the same time, its dynamic monitoring capability can reflect the thermal behavior of the battery at a specific temperature in real time, ensuring the accuracy and effectiveness of the assessment.

[0023] 2. The present invention provides a direct indicator for thermal stability assessment by accurately measuring heat flow changes and determining thermal runaway temperature TSD through ARC testing. This method can not only quickly identify thermal runaway risks, but also provide detailed chemical information for material design and improvement, thereby enhancing battery safety.

[0024] 3. The high efficiency of the ARC test in the present invention makes the research and development process faster and helps to quickly screen and evaluate new materials. In addition, the method is applicable to a variety of battery types and provides a flexible testing method, making the thermal stability evaluation more comprehensive and applicable. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The figure is a flow chart of a method for measuring the safety of a sodium battery cathode material according to an embodiment. DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading this description, various equivalent modifications to this description by those skilled in the art fall within the scope defined by the claims attached to this application.

[0027] like Figure 1 As shown, an embodiment of the present invention provides a method for measuring the safety of a sodium-based positive electrode material, and the method for measuring the safety of a sodium-based positive electrode material comprises the following steps:

[0028] Step 1: Material screening and preparation: Screening out materials with good electrochemical performance and potential safety from a large number of candidate materials. This step specifically includes the following parts:

[0029] 1.1: Physically and chemically characterize the candidate materials, including taking an appropriate amount of candidate material samples, performing XRD tests, recording the position and intensity of diffraction peaks, analyzing the crystal structure, observing the microscopic morphology of the materials using a scanning electron microscope (SEM), and taking corresponding images, and analyzing the elemental composition of the materials using energy dispersive spectroscopy (EDS) to ensure the purity and quality of the materials.

[0030] 1.2: Conduct electrochemical tests on the materials, prepare the electrodes for electrochemical tests, usually including working electrode, counter electrode and reference electrode, assemble the candidate materials into a simple battery and conduct cyclic voltammetry (CV) test on the electrochemical workstation, set different scan rates and potential ranges, record and analyze the CV curve, conduct charge and discharge tests, record the charge and discharge curve of the battery, calculate its key parameters such as specific capacity and energy density, and evaluate its electrochemical activity.

[0031] 1.3: Based on the results of physicochemical characterization and electrochemical testing, evaluate the electrochemical performance and potential safety of candidate materials, and select materials with excellent performance and good thermal stability for subsequent thermal stability testing and safety assessment.

[0032] At this point, from among the many candidate sodium battery positive electrode materials, through a series of physical and chemical characterizations and electrochemical tests, screening out materials with both good electrochemical properties and potential safety is crucial for subsequent safety assessment and battery performance optimization.

[0033] Step 2: Battery assembly: Assemble the selected materials into batteries for safety testing in practical applications, including:

[0034] 2.1: Prepare the positive electrode material, negative electrode material, electrolyte and separator required for the battery.

[0035] The positive electrode material needs to be ground to improve dispersion and contact. The negative electrode material should ensure that the purity and physical form meet the battery design requirements. The selection of electrolyte should be based on the battery design and the characteristics of the positive and negative electrode materials, and usually contains solvents, lithium salts or additives. The selection of separator materials is crucial, as its function is to isolate the positive and negative electrodes and allow ions to pass through to ensure battery conductivity.

[0036] 2.2: Assemble the battery according to the battery design specifications to ensure the sealing and reliability of the battery.

[0037] Battery manufacturing includes the preparation, drying and cutting of positive and negative electrodes. When assembling battery cells, it is necessary to place diaphragms and maintain spacing. After injecting an appropriate amount of electrolyte, the battery casing must be sealed to prevent leakage. After assembly is completed, pre-charge and discharge treatment is carried out to activate chemical reactions and improve performance. Safety checks such as appearance, leakage, and voltage are also performed to ensure that the battery is reliable and safe.

[0038] In order to conduct comparative analysis, a standard sodium iron phosphate battery manufacturing method was used to prepare a 4060F0 size soft-pack battery with a capacity of 1.3Ah. The specific manufacturing parameters are as follows: 14.5g of sodium iron phosphate positive electrode material, 5.7g of negative electrode material, and 15g of electrolyte according to a 11 injection coefficient. During the preparation process, the screened positive electrode material can replace the sodium iron phosphate positive electrode to make a battery with the same capacity of 1.3Ah for subsequent comparative testing;

[0039] Step 3: ARC test: Evaluate the thermal safety performance of the battery through accelerated calorimetry testing. Specifically include:

[0040] 3.1: Preheat the ARC test system to the set starting temperature and adjust the system's heating rate to a predetermined value. The heating rate is usually selected based on the test standard and the characteristics of the battery. Calibrate the test system to ensure the accuracy and reliability of data collection. Then place the assembled battery in the ARC test system to ensure good contact between the battery and the test system so that heat and temperature changes can be accurately measured. Close the test system's hatch and start testing. Test the batteries made of the selected materials and the standard sodium iron phosphate battery separately.

[0041] 3.2: Start the ARC test system and heat the battery at a predetermined heating rate.

[0042] During the test, the system automatically monitors and records the battery's heat flow, temperature changes, and pressure changes inside the battery, and continuously monitors the battery's response until the predetermined test termination conditions are reached.

[0043] 3.3: Record the test data, including the heat flow, temperature, pressure, etc. of the battery, and save it in the form of charts or data files.

[0044] The thermal safety performance of the battery is evaluated by simulating the thermal abuse conditions that the battery may encounter in actual use. This method can provide detailed information on the thermal stability of the battery in a shorter period of time, helping researchers understand the reaction of the battery under thermal abuse conditions, thereby optimizing material design and battery structure and improving battery safety.

[0045] Step 4: Determination of thermal runaway temperature and maximum temperature: Determine the thermal runaway temperature and maximum temperature of the battery under thermal abuse conditions. Specifically include:

[0046] 4.1: Collect and organize test data, use thermal analysis software to plot temperature and heat curves over time, analyze key characteristic points, calculate the total reaction heat, and evaluate the thermal behavior and heat release of the battery.

[0047] 4.2: Observe the temperature-time curve and find the point where the battery temperature starts to rise abnormally quickly, that is, the starting thermal runaway temperature of the battery. Further analyze the temperature-heat flow curve and find the point where the heat flow suddenly increases. Combining the temperature change rate and heat flow change, the starting temperature of the battery thermal runaway can be determined more accurately.

[0048] 4.3: Analyze the temperature-time curve and find the peak of the temperature rise. This temperature value is the maximum temperature of the battery. The maximum temperature usually corresponds to the temperature at which a violent reaction occurs inside the battery. This temperature point can reflect the maximum heat release of the battery during thermal runaway.

[0049] Through the above process, the thermal runaway temperature TSD and the maximum temperature of the battery under thermal abuse conditions can be determined. These temperature indicators are crucial for evaluating the thermal safety of the battery and predicting the thermal risks of the battery in practical applications. After determining these temperatures, the material design can be optimized accordingly to improve the safety of the battery.

[0050] Step 5: Data analysis and evaluation: Detailed analysis of the data obtained from the ARC test, including:

[0051] 5.1: Determine the thermal runaway temperature and thermal stability of the battery through the temperature-time curve, analyze the thermal stability of the material under different conditions based on the test conditions, and evaluate the risk of thermal runaway and the internal structure damage that may be caused.

[0052] 5.2: Based on the data analysis results, make suggestions for improving materials or battery design, including chemical or physical modification, optimizing heat dissipation structure, using high thermal conductivity materials, and improving packaging design, so as to improve the thermal stability and safety of the battery.

[0053] Evaluate the thermal safety performance of the material. In this step, add a safety comparison standard: if the battery thermal runaway temperature of the test material is higher than that of the standard sodium iron phosphate battery, and the maximum temperature is lower than that of the standard battery, then the positive electrode material is considered to have better safety. This standard helps to clearly distinguish and evaluate the safety performance of different positive electrode materials.

[0054] Through the present invention, firstly, materials with excellent electrochemical performance and safety potential are screened out; then these materials are assembled into batteries for testing; then the thermal safety of the battery is evaluated through ARC testing; the thermal runaway temperature and the maximum temperature of the battery under thermal abuse conditions are determined; finally, the test data are analyzed to evaluate the thermal safety performance of the material, which can more accurately evaluate the safety of sodium battery positive electrode materials in practical applications, provide a scientific basis for battery design and material selection, and in addition, not only the thermal stability of the material itself is considered, but also the thermal abuse that the battery may encounter in actual use, thereby providing a more comprehensive perspective for battery safety evaluation.

Claims

1. A method for measuring the safety of sodium positive electrode materials, characterized in that: The following steps are involved: Step 1: Screen materials based on electrochemical performance and potential safety; Step 2: Assemble the screened materials into batteries and assemble standard sodium iron phosphate batteries; Step 3: Perform accelerated calorimetry test on the assembled battery and the standard sodium iron phosphate battery; Step 4: Determine the thermal runaway temperature and maximum temperature of the battery under thermal abuse conditions based on the accelerated calorimetry test results; Step 5: Evaluate the thermal safety performance of the material. If the battery thermal runaway temperature of the test material is higher than that of the standard sodium iron phosphate battery, and the maximum temperature is lower than that of the standard sodium iron phosphate battery, the positive electrode material is considered safe.

2. The method for measuring the safety of sodium positive electrode materials according to claim 1, characterized in that: The step 1 includes using X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive spectroscopy (EDS) to perform physical and chemical characterization on the candidate material, and performing electrochemical testing to obtain cyclic voltammetry (CV) and charge-discharge curves.

3. The method for measuring the safety of sodium positive electrode materials according to claim 2, characterized in that: The step 1 includes performing an XRD test, recording the position and intensity of the diffraction peak, analyzing the crystal structure, observing the microscopic morphology of the material using a SEM, taking corresponding images, and analyzing the elemental composition of the material using EDS.

4. The method for measuring the safety of sodium positive electrode materials according to claim 2, characterized in that: The step 1 of testing to obtain cyclic voltammetry (CV) and charge-discharge curves includes preparing electrodes for electrochemical testing, assembling candidate materials into a simple battery and then performing a CV test on an electrochemical workstation, setting different scan rates and potential ranges, recording and analyzing the CV curve, performing a charge-discharge test, recording the charge-discharge curve of the battery, and calculating its specific capacity and energy density.

5. The method for measuring the safety of sodium positive electrode materials according to claim 1, characterized in that: The step 2 includes preparing the positive electrode material, negative electrode material, electrolyte and separator required for the battery; assembling the battery according to the battery design specification to ensure the sealing and reliability of the battery.

6. The method for measuring the safety of sodium positive electrode materials according to claim 5, characterized in that: When assembling a standard sodium iron phosphate battery, 14.5g of sodium iron phosphate positive electrode material, 5.7g of negative electrode material, and 15g of electrolyte are used to assemble a battery with a capacity of 1.3Ah according to an injection factor of 11. The screened positive electrode material is used to replace the sodium iron phosphate positive electrode material to make a battery with the same capacity of 1.3Ah.

7. The method for measuring the safety of sodium positive electrode materials according to claim 1, characterized in that: The step three includes preheating the accelerated calorimetry test system to a set starting temperature, and adjusting the heating rate of the accelerated calorimetry test system to a predetermined value. The heating rate is usually selected according to the test standard and the characteristics of the battery, calibrating the test system, and placing the battery assembled in step two and the standard sodium iron phosphate battery into the accelerated calorimetry test system for testing, and recording the heat flow, temperature, and pressure data of the battery.

8. The method for measuring the safety of sodium positive electrode materials according to claim 7, characterized in that: The fourth step comprises: 4.

1. Use thermal analysis software to plot the temperature and heat curves over time, analyze key characteristic points, calculate the total reaction heat, and evaluate the thermal behavior and heat release of the battery; 4.

2. Use the temperature-time curve to find the point where the battery temperature starts to rise abnormally quickly, that is, the starting thermal runaway temperature of the battery. Use the temperature-heat flow curve to find the point where the heat flow suddenly increases. 4.

3. Find the peak of temperature rise through the curve of temperature change over time. This temperature value is the maximum temperature of the battery.

9. The method for measuring the safety of sodium positive electrode materials according to claim 8, characterized in that: The step five includes analyzing the thermal stability of the material under different conditions based on the thermal runaway temperature and the maximum temperature in combination with the test conditions, and evaluating the risk of thermal runaway and the internal structural damage that may be caused.

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