Sodium-nickel battery performance evaluation method based on sodium flux stress test

Abstract

The present application belongs to the technical field of sodium nickel battery performance test, and particularly provides a sodium nickel battery performance evaluation method based on sodium flux stress test, comprising the following steps: S1, selecting a sodium nickel battery sample and performing formation pretreatment thereon, and simultaneously, regulating and controlling the test temperature to be constant at the working temperature of the sodium nickel battery; S2, performing graded variable power alternating charge-discharge test on the sodium nickel battery sample, and obtaining the electrical performance parameters of the sodium nickel battery sample capable of reflecting the sodium flux stress change; S3, performing large-current pulse discharge on the sodium nickel battery sample, and performing peak power test in cooperation with the multi-gradient SOC switching mode; S4, analyzing the parameters obtained in steps S2 and S3 to evaluate the performance of the sodium nickel battery; the present application simulates the high-temperature working environment of the sodium nickel battery, and adopts the composite stress test scene of first sodium nickel battery structure selection and then accurate calibration of full-condition peak power, thereby greatly improving the comprehensiveness and accuracy of the test evaluation.

Description

Technical Field

[0001] This invention belongs to the field of sodium-nickel battery performance testing technology, and particularly relates to a sodium-nickel battery performance evaluation method based on sodium flux stress testing. Background Technology

[0002] The sodium flow (sodium flux) characteristics of sodium-nickel batteries directly determine the battery's electrochemical performance and lifespan. Changes in the design structure or manufacturing process parameters, such as the wettability of the battery's thin gasket, the gasket gap, the ceramic tube powder formulation, and the steel shell sealing, will all alter the sodium flux and generate sodium flux stress, thereby affecting the battery's operational stability.

[0003] In the existing technology, there is a lack of standardized testing methods for sodium flux stress in sodium-nickel batteries, making it difficult to systematically verify the impact of battery structure or manufacturing process on the flow characteristics of liquid sodium. In addition, conventional tests do not match the actual operating temperature of sodium-nickel batteries at 260°C, and the test conditions are out of touch with real-world usage scenarios. Furthermore, existing tests lack clear quantitative evaluation indicators and can only record raw data, making it impossible to quickly determine whether the sodium flux stress performance of batteries after changes in design structure and manufacturing process is up to standard. This makes it difficult to meet the needs of industrial-scale batch testing and efficient screening in the R&D stage.

[0004] Therefore, there is an urgent need to develop a sodium flux stress testing method that fits the actual working conditions of sodium-nickel batteries, has a standardized process, and has clear judgment indicators, to fill the testing gap in this field and provide a scientific basis for the design optimization and process finalization of sodium-nickel batteries. Summary of the Invention

[0005] The purpose of this invention is to provide a sodium-nickel battery performance evaluation method based on sodium flux stress testing, which addresses the shortcomings of existing technologies.

[0006] This solution provides a method for evaluating the performance of sodium-nickel batteries based on sodium flux stress testing, including the following steps:

[0007] Step S1: Select a sodium-nickel battery sample and perform a formation pretreatment on it. At the same time, control the test temperature to be constant at the operating temperature of the sodium-nickel battery. The sodium-nickel battery sample is a sodium-nickel battery cell or a battery module. The battery module is composed of multiple sodium-nickel battery cells connected in series.

[0008] Step S2: Perform graded alternating charge-discharge tests on the sodium-nickel battery sample, constructing a low sodium flux steady-state condition and a high flux impact condition respectively, to achieve alternating sodium flux and bring the sodium flux stress inside the sodium-nickel battery sample to its peak value, and obtain the electrical performance parameters of the sodium-nickel battery sample that can reflect the change of sodium flux stress.

[0009] Step S3: The sodium-nickel battery sample processed in step S2 is subjected to high-current pulse discharge and peak power test using a multi-gradient SOC switching method.

[0010] Step S4: Analyze the parameters obtained in steps S2 and S3 above, and then evaluate the performance of the sodium-nickel battery.

[0011] As a preferred embodiment of this application: In step S1, the formation pretreatment method includes:

[0012] Step S11: Perform constant current charging at 16-24A until the voltage of the sodium-nickel battery cell rises to the rated charging voltage;

[0013] Step S12: Perform constant voltage charging at the rated charging voltage until the current is less than the termination current (the charging termination current during the constant voltage stage), and then stop charging.

[0014] As the preferred embodiment of this application:

[0015] In step S2, the specific steps for performing a graded variable power alternating charge-discharge test on the sodium-nickel battery sample include:

[0016] S21: Discharge at a constant current of 0.08C-0.12C until the cutoff voltage of the sodium-nickel battery cell is reached, then stop discharging.

[0017] S22: Charge at a constant power of 42-50W / Ni-N cell, with the charging current controlled at 18-22A. After the Ni-N cell voltage reaches the rated charging voltage (2.67V), switch to constant voltage charging until the charging current drops to the termination current, thus ending the charging process.

[0018] S23: Discharge the battery at a constant power of 120W-122W per sodium-nickel battery cell until the cutoff voltage of the sodium-nickel battery cell is reached, then stop discharging and let it stand for 10-15 minutes.

[0019] S24: Repeat the charging and discharging operations of steps S21 and S22 above 3-5 times, and obtain the electrical performance parameters of each sodium-nickel battery cell after discharge.

[0020] As the preferred embodiment of this application:

[0021] In steps S21 and S23,

[0022] When the sodium-nickel battery sample is a sodium-nickel battery cell, the cutoff voltage is 1.90-2.00V;

[0023] When the sodium-nickel battery sample is a battery module composed of multiple sodium-nickel battery cells connected in series, the cutoff voltage is the cutoff voltage of a single sodium-nickel battery cell multiplied by the total voltage of the number of cells connected in series, or the cutoff voltage is taken as the voltage of any sodium-nickel battery cell when it drops to 1.65-1.90V, and the discharge is terminated when either condition is met.

[0024] As the preferred embodiment of this application:

[0025] In step S3, the specific steps for performing a gradient SOC peak power test on the sodium-nickel battery sample processed in step S2 include:

[0026] S31: Discharge the sodium-nickel battery sample at a constant current of 0.08C-0.12C for 4-8 minutes to stabilize the internal state of the sample, so as to eliminate the static false voltage and balance the internal state of the cell.

[0027] S32: High-current short-time pulse discharge is adopted, and the voltage of the sodium-nickel battery cell is monitored in real time. When the voltage of the sodium-nickel battery cell drops to the pulse cutoff threshold, the pulse discharge is terminated. At the same time, the SOC peak power is obtained.

[0028] S33: Using a small current constant current discharge, the sodium-nickel battery is reduced from the current SOC to the next target SOC by quantitatively consuming power, thus realizing the test level gradient switching;

[0029] S34: Repeat steps S32 and S33 above until the voltage of the sodium-nickel battery cell drops to the cutoff voltage and discharge stops. At this point, the SOC peak power test of all gradients is completed.

[0030] As the preferred embodiment of this application:

[0031] In step S32, a constant current pulse discharge of 96-100A is used for 26-30s to calculate the instantaneous SOC peak power of the sodium-nickel battery cell based on the large current voltage drop.

[0032] Meanwhile, in step S33, the small current is 22-24A, and this constant small current is used for uniform discharge.

[0033] As the preferred embodiment of this application:

[0034] The electrical performance parameters include voltage parameters and capacity parameters;

[0035] In step S4, the voltage parameter, capacity parameter, and peak power parameter are used as evaluation indicators to determine the performance of the sodium-nickel battery cell.

[0036] As the preferred embodiment of this application:

[0037] Based on the determined performance of the sodium-nickel battery cell, it is possible to infer whether the structure and manufacturing process of the current sodium-nickel battery are qualified. Specific methods include:

[0038] The sodium-nickel battery samples include standard sodium-nickel battery cells for the test group prepared using a new structure or process, and standard sodium-nickel battery cells for the control group prepared using the original structure or process.

[0039] The evaluation indicators of the standard sodium-nickel battery cells in the test group are compared with those in the control group. If both meet the preset conditions, the cell is deemed qualified; otherwise, it is deemed unqualified.

[0040] As the preferred embodiment of this application:

[0041] In step S1, the operating temperature is 260-300℃, and the low-temperature shutdown protection temperature is set to 210-230℃.

[0042] As the preferred embodiment of this application:

[0043] The test was conducted in a temperature-controlled furnace, with a low-temperature shutdown protection temperature set.

[0044] Compared with existing technologies, the advantages of this solution are:

[0045] This scheme simulates the high-temperature operating environment of sodium-nickel batteries and employs a coupled mode of graded variable power alternating charge-discharge testing and multi-gradient SOC segmented high-current pulse peak power testing. It aims to reflect the performance of sodium-nickel batteries by testing changes in sodium flux stress. Specifically, the graded variable power alternating charge-discharge testing is used to construct low-sodium flux steady-state conditions and high-flux impact conditions, achieving alternating sodium flux and maximizing the sodium flux stress within the sodium-nickel battery. This precisely excites and screens batteries with defects such as weak interface bonding, weak gasket structures, and poor sealing reliability, completing the preliminary screening of battery structure. The multi-gradient SOC segmented high-current pulse peak power testing can accurately replicate the performance of sodium-nickel batteries. In actual operation, frequent instantaneous high-power impact conditions occur. At the same time, by switching smoothly in stages with a gradual SOC gradient, the solution covers the entire range of operating conditions from high SOC to low SOC, completely restoring the service working state of the sodium-nickel battery throughout its entire life cycle. It can be seen that this solution forms a composite stress test scenario for sodium-nickel batteries and can simulate the real service stress scenario of sodium-nickel batteries throughout their entire life cycle. The test accuracy and reliability are high. In addition, this solution adopts a test mode of first screening the advantages and disadvantages of sodium-nickel battery structures and then accurately calibrating the peak power of all operating conditions. This not only realizes the integrated evaluation of the structural reliability and peak electrical performance of sodium-nickel batteries, but also significantly improves the comprehensiveness and accuracy of the test evaluation. Attached Figure Description

[0046] Figure 1The flowchart of the sodium-nickel battery performance evaluation method based on sodium flux stress testing provided by the present invention is shown. Detailed Implementation

[0047] The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be emphasized that the following description is merely exemplary and not intended to limit the scope and application of the present invention.

[0048] This embodiment provides a method for evaluating the performance of sodium-nickel batteries based on sodium flux stress testing, such as... Figure 1 As shown, the specific steps include:

[0049] Step S1: Select a sodium-nickel battery sample and perform a formation pretreatment on it. At the same time, control the test temperature to be constant at the working temperature of the sodium-nickel battery. The sodium-nickel battery sample is a sodium-nickel battery cell or a battery module. The battery module is composed of multiple sodium-nickel battery cells connected in series. Preferably, the battery module is composed of 10 or 20 cells connected in series.

[0050] In this embodiment, the operating temperature is 206-300℃. Preferably, the entire test process is carried out in a temperature-controlled furnace, and the operating temperature is the temperature inside the temperature-controlled furnace after adjustment. To improve safety, a low-temperature shutdown protection temperature is also preferably provided, specifically 210-230℃.

[0051] In this embodiment, the sodium-nickel battery sample includes a test group of sodium-nickel battery cells prepared using a new structure or process, and a control group of sodium-nickel battery cells prepared using the original structure or process. Preferably, the sodium-nickel batteries in the test group and the control group use the same raw materials and production environment conditions.

[0052] The obtained sodium-nickel battery samples underwent a formation process to generate a metallic sodium anode, activate the positive and negative electrodes, stabilize the interface, and eliminate inherently defective cells. The specific formation process steps included:

[0053] Step S11: Perform constant current charging at 16-24A until the voltage of the sodium-nickel battery cell rises to the rated charging voltage.

[0054] This step is used to quickly replenish the sodium-nickel battery cells so that sodium ions migrate from the positive electrode to the negative electrode at a uniform speed and deposit liquid metallic sodium. In this embodiment, the charging current is preferably 20A to avoid initial sodium ion accumulation and sudden increase in ceramic lattice stress.

[0055] The rated charging voltage in this embodiment is 2.67V, which is also the nominal voltage of a fully charged sodium-nickel battery.

[0056] Step S12: Perform constant voltage charging at the rated charging voltage until the current is less than the termination current, then stop charging.

[0057] In this embodiment, the termination current is the charging termination current during the constant voltage stage, specifically 0.5A.

[0058] This step is used to lock the voltage when charging is completed quickly, slowly replenish the remaining capacity until the state of full charge (SOC=100%), and use a small current to cut off to ensure that the negative electrode metal sodium is fully filled and the sodium is evenly distributed. At the same time, it ensures that the sodium storage of each sodium-nickel battery cell tends to be consistent, so as to establish a consistent initial state for subsequent discharge tests.

[0059] Step S2: Perform graded alternating charge-discharge tests on the sodium-nickel battery sample, constructing a low sodium flux steady-state condition and a high flux impact condition respectively, to achieve alternating sodium flux and bring the sodium flux stress inside the sodium-nickel battery sample to its peak value, and obtain the electrical performance parameters of the sodium-nickel battery sample that can reflect the change of sodium flux stress. These electrical performance parameters are preferably the voltage and capacity of the sodium-nickel battery after discharge.

[0060] The specific steps for performing graded variable power alternating charge-discharge tests on sodium-nickel battery samples include:

[0061] S21: Discharge at a constant current of 0.08C-0.12C until the cutoff voltage of the sodium-nickel battery cell is reached and then discharge stops.

[0062] Preferably, a constant current discharge of 0.1C is used, which translates to a reference current of 4.6A, meaning a constant current discharge of 4.6A until the cutoff voltage. In this embodiment, when the nickel-sodium battery sample is a single nickel-sodium battery cell, the cutoff voltage is 1.90-2.00V, preferably 1.95V. This cutoff voltage is the rated discharge termination voltage of the nickel-sodium battery. When discharged to this voltage, most of the effective active sodium inside the battery cell has been consumed, ensuring the accuracy of the true rated capacity of the nickel-sodium battery cell. When the nickel-sodium battery sample is a battery module composed of multiple nickel-sodium battery cells connected in series, the cutoff voltage is the cutoff voltage of a single nickel-sodium battery cell multiplied by the total voltage of the number of cells connected in series (e.g., 1.95V*10), or the voltage of any nickel-sodium battery cell is reduced to 1.65-1.90V, preferably 1.65V (where 1.65V is the fault cutoff threshold of a nickel-sodium battery cell), as the cutoff voltage. Discharge is terminated when either condition is met. In other words, in either case, the voltage of the case that is reached first is used as the cutoff voltage. Furthermore, the reason why this embodiment uses 1.65-1.90V as the cutoff voltage for any sodium-nickel battery cell in the battery module is that the capacity, internal resistance, and sodium migration consistency of each sodium-nickel battery cell in series discharge are discrete. If discharged at 1.95V, some inferior battery cells will be forced to over-discharge (the internal resistance of defective battery cells is abnormally high, the sodium flux is disordered under the same discharge current, and the voltage drop rate is much faster than that of other good cells. Before the entire group has dropped to the total voltage of 19.5V, the defective battery cell rate will drop to the 1.65V fault threshold). Using 1.65V as the cutoff voltage of the battery module can stop the over-discharge operation in time and avoid damage to the battery module due to over-discharge. At the same time, it can also realize defect screening of battery molding to reflect the ion conduction capacity of ceramic tube, overall sodium flux level, sealing and vacuum performance, etc.

[0063] S22: Charge at a constant power of 42-50W / NiN battery cell, with the charging current controlled at 18-22A. After the NiN cell voltage reaches the rated charging voltage, switch to constant voltage charging until the charging current drops to the termination current, ending the charging process.

[0064] In this embodiment, the charging power of each sodium-nickel battery cell is locked between 42-50W, preferably 46W (it can be understood that when it is a battery module with 10 cells connected in series, the charging power is constant at 46W*10); when the sodium-nickel battery cell is charged with this constant power of 46W, the current rises slowly, sodium ions accumulate at a constant speed to the negative electrode metallic sodium, the sodium ion distribution is uniform, the sodium flux is stable and there is no local stress concentration, forming a steady state of sodium flux.

[0065] The purpose of limiting the charging current to 18-22A is to prevent the sudden increase in sodium flux and the abnormal stress caused by local sodium accumulation due to a sudden large current. In this embodiment, the specific charging current is preferably controlled at 20A to quickly replenish the sodium-nickel battery cells, so that sodium ions migrate from the positive electrode to the negative electrode at a uniform speed and deposit liquid metallic sodium. After the sodium-nickel cell voltage reaches the rated charging voltage (which is the constant voltage charging voltage, specifically 2.67V), it switches to constant voltage charging until the charging current drops to the termination current (which is the termination current of the constant voltage stage charging, specifically 0.5A), and the charging ends. This step is used to lock the voltage unchanged when the charging is completed quickly, slowly replenish the remaining capacity, and use a small current cutoff to ensure that the negative electrode metallic sodium is fully filled and the sodium distribution is uniform. At the same time, it ensures that the sodium storage of each sodium-nickel battery cell tends to be consistent, establishing a consistent initial state for subsequent high-power discharge.

[0066] S23: Discharge the sodium-nickel battery cell at a constant power of 120W-122W until the cutoff voltage of the sodium-nickel battery cell is reached, then stop discharging and let it stand for 10-15 minutes.

[0067] In this embodiment, similar to step S21, when the sodium-nickel battery sample is a single sodium-nickel battery cell, the cutoff voltage is 1.90-2.00V, preferably 1.95V; when the sodium-nickel battery sample is a battery module composed of multiple sodium-nickel battery cells connected in series, the cutoff voltage is the cutoff voltage of a single sodium-nickel battery cell multiplied by the total voltage of the number of cells connected in series (e.g., 1.95V*10), or the voltage of any sodium-nickel battery cell is reduced to 1.65-1.90V, preferably 1.65V, as the cutoff voltage, and discharge is terminated when either condition is met.

[0068] This step locks the charging power of each sodium-nickel battery cell between 120-122W, preferably 120W. It can be understood that when it is a battery module with 10 cells connected in series, the charging power is constant at 120W*10.

[0069] Using this 120W high-power charger to charge individual sodium-nickel battery cells can increase the instantaneous current within the cell, creating a high-flux impact condition that maximizes sodium flux stress. At this point, Na... + High-speed migration, intense liquid sodium flow, a sharp increase in local sodium flux, and a significant increase in sodium flux stress on ceramics directly expose problems such as local sodium deviation, stress distortion, and cell voltage drop caused by defects in the cell structure or manufacturing process. These problems can reflect defects in the wettability of the cell interface, the gap between the gaskets, and the local sodium flux, providing a preliminary basis for defect screening of battery cells.

[0070] In this embodiment, it is preferable to let it stand for 10 minutes to ensure that the sodium distribution inside the individual cell (also known as the battery cell) returns to static equilibrium after power is cut off.

[0071] S24: Repeat the charging and discharging operations of steps S21 and S22 above 3-5 times. After completion, let it stand for 5-10 minutes and obtain the electrical performance parameters of each sodium-nickel battery cell after discharge.

[0072] The purpose of repeating steps S21 and S22 is to verify the irreversible effects of high-power sodium flux stress on the battery cell capacity, sodium distribution, voltage, and stress. Each repetition acquires electrical performance parameters after discharge. It is understandable that electrical performance parameters after discharge are also acquired before high-power charging, i.e. after the first execution of steps S21 and S22, and these electrical performance parameters are used as the first round of baseline data. Finally, the acquired electrical performance parameters are compared with the first round of baseline data to reflect whether the interface wettability, gasket gap, and local sodium flux are abnormal. In other words, by quantifying the subtle abnormalities inside the cell into electrical performance parameters, the performance degradation caused by high-power sodium flux stress on the sodium-nickel battery cell is reflected.

[0073] In summary, the alternating charge-discharge test in this embodiment can fully stimulate the sodium flux stress inside the sodium-nickel battery, maximizing the amplification of subtle differences in battery manufacturing processes and assembly structures. These subtle differences can be intuitively quantified through changes in the electrical performance parameters (preferably capacity and voltage) of individual cells. This allows for precise stimulation and screening of defective batteries with weak interface bonding, weak gasket structures, and poor sealing reliability, thus completing the pre-screening of individual battery defects and preventing inferior battery cells from entering subsequent testing scenarios and application markets from the source.

[0074] Step S3: The sodium-nickel battery sample processed in step S2 is subjected to high-current pulse discharge and peak power test using a multi-gradient SOC switching method.

[0075] This step is used to accurately replicate the instantaneous high-power impact conditions that frequently occur in the actual operation of sodium-nickel batteries. At the same time, by smoothly switching the SOC gradient, it achieves full coverage of operating conditions from high SOC to low SOC, completely restoring the service working state of the battery throughout its entire life cycle. In conjunction with the alternating charge and discharge mode in step S2, it not only assesses the reliability of the battery's seals, gaskets, and interface structure through high-power alternating stress, but also accurately calibrates the peak output performance and ion migration stability under all operating conditions through gradient SOC segmented high-current pulse peak power testing. It can simultaneously complete the screening of battery structural advantages and disadvantages and the quantitative rating of electrochemical performance, greatly improving the comprehensiveness, accuracy, and scientific nature of sodium-nickel battery testing and evaluation.

[0076] This step specifically includes:

[0077] S31: Discharge the sodium-nickel battery sample at a constant current of 0.08C-0.12C for 4-8 minutes to achieve a steady state inside, in order to eliminate the static virtual voltage and ensure that the starting point of subsequent pulse tests is consistent.

[0078] In this embodiment, constant current discharge at 0.1C is preferred, which is equivalent to a reference current of 4.6A.

[0079] S32: Employs high-current short-time pulse discharge and monitors the voltage of individual sodium-nickel battery cells in real time. When the voltage of an individual sodium-nickel battery cell drops to the pulse cutoff threshold, the pulse discharge is terminated. At the same time, the SOC peak power is obtained.

[0080] This step uses a high current of 96-100A for short-time pulse discharge, preferably 98A, with a pulse duration of 28s; at the same time, the pulse cutoff threshold is preferably 1.7V; this is used to simulate the instantaneous high-power impact under the actual working conditions of sodium-nickel batteries, and to calculate the instantaneous peak output power of a single sodium-nickel battery cell by relying on the high current voltage drop, thereby reflecting the interface stability, gasket-ceramic tube contact state, and process adaptability under high sodium flux.

[0081] S33: Using a small current constant current discharge, the sodium-nickel battery is reduced from the current SOC to the next target SOC by quantitatively consuming power, thus realizing the gradient switching of the test level.

[0082] Since high-current discharge consumes almost no cell capacity, in order to reduce the SOC to the next target, it is necessary to achieve this through low-current constant-current discharge. In this embodiment, a low current of 22-24A is used, preferably 20A. Using this constant low current for uniform discharge avoids SOC jumps or runaway during high-current discharge, ensuring a precise gradient decrease in SOC. In this embodiment, the preferred SOC decrease step is 10%, for example, SOC is gradually reduced from 100%→90%→80%... until it reaches 10%.

[0083] S34: Repeat steps S32 and S33 above until the voltage of the sodium-nickel battery cell drops to the cutoff voltage and the discharge stops. At this point, the SOC peak power test for all gradients is completed.

[0084] In this embodiment, when the sodium-nickel battery sample is a single sodium-nickel battery cell, the cutoff voltage is 1.90-2.00V, preferably 1.95V; when the sodium-nickel battery sample is a battery module composed of multiple sodium-nickel battery cells connected in series, the cutoff voltage is the cutoff voltage of a single sodium-nickel battery cell multiplied by the total voltage of the number of cells connected in series (e.g., 1.95V*10).

[0085] Step S4: Analyze the parameters obtained in steps S2 and S3 above, and then evaluate the performance of the current sodium-nickel battery.

[0086] The electrical performance parameters include voltage parameters and capacity parameters;

[0087] In step S4, the parameters obtained in steps S2 and S3 are analyzed to determine the performance of the sodium-nickel battery cell.

[0088] In this embodiment, the electrical performance parameters include voltage parameters and capacity parameters; and the voltage parameters, capacity parameters, and peak power parameters are used as evaluation indicators to determine the performance of sodium-nickel battery cells.

[0089] Based on the assessed performance of individual sodium-nickel battery cells, it is possible to infer whether the current structure and manufacturing process of sodium-nickel batteries are up to standard. Specific methods include:

[0090] The sodium-nickel battery sample includes a test group of sodium-nickel battery cells prepared using a new structure or process, and a control group of sodium-nickel battery cells prepared using the original structure or process; then at least 3 sodium-nickel battery cells are selected from each group.

[0091] The three evaluation indicators of the three sodium-nickel battery cells in the test group are compared with the three evaluation indicators of the three sodium-nickel battery cells in the control group. If the results show:

[0092] (1) During the 120W discharge phase, the number of cells with a voltage below 1.7V in both the test group and the control group did not exceed 2;

[0093] (2) After 120W discharge, during 4.6A constant current discharge, the capacity of the test group was in the range of 21.8-22.5Ah, and the capacity of the control group was in the range of 22.0-22.6Ah, both within the preset range of 21-23Ah;

[0094] (3) The peak power of each sodium-nickel battery cell in the test group in each SOC range was consistent with that in the control group.

[0095] At this point, the test sample is deemed to meet all the criteria, and the structure and manufacturing process of the current sodium-nickel battery are deemed to be qualified under the sodium flux stress test. If any one of them is not met, it is deemed to be unqualified.

[0096] It should be noted that the qualified capacity range for 4.6A constant current discharge needs to be updated and determined based on the actual test results of the control group. That is, the qualified capacity range is preset based on the test structure of the control group.

[0097] In summary, this embodiment simulates the high-temperature operating environment of nickel-sodium batteries and employs a coupled mode of graded variable power alternating charge-discharge testing and multi-gradient SOC segmented high-current pulse peak power testing. The graded variable power alternating charge-discharge can maximize sodium flux stress through high-power discharge, thereby verifying the irreversible impact of high-power sodium flux stress on the capacity, sodium distribution, voltage, and stress of nickel-sodium battery cells, and achieving preliminary screening of defective nickel-sodium battery cells. In addition, the combined multi-gradient SOC segmented high-current pulse peak power testing can accurately replicate the instantaneous high-power impact conditions that frequently occur in the actual operation of nickel-sodium batteries, achieving full coverage of operating conditions from high SOC to low SOC, and completely restoring the service operating state of nickel-sodium batteries throughout their entire life cycle. Finally, the test data can not only determine the performance of current nickel-sodium batteries, but also verify the qualification of the current nickel-sodium battery structure or manufacturing process, providing data support and scientific basis for the optimization of nickel-sodium battery structure or manufacturing process.

[0098] As can be seen, this embodiment forms a sodium-nickel battery composite stress test scenario that first screens the advantages and disadvantages of sodium-nickel battery structures and then accurately calibrates the peak power under all operating conditions. At the same time, it also simulates the real service stress scenario of sodium-nickel batteries throughout their entire life cycle, which greatly improves the comprehensiveness and accuracy of the test evaluation and makes up for the shortcomings of the end plate in the prior art.

[0099] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics in the solutions is not described in detail here. It should be noted that those skilled in the art can make several improvements without departing from the present invention, and these should also be considered within the scope of protection of the present invention. These improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of the claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for evaluating the performance of sodium-nickel batteries based on sodium flux stress testing, characterized in that, Includes the following steps: Step S1: Select a sodium-nickel battery sample and perform a formation pretreatment on it. At the same time, control the test temperature to be constant at the operating temperature of the sodium-nickel battery. The sodium-nickel battery sample is a sodium-nickel battery cell or a battery module. The battery module is composed of multiple sodium-nickel battery cells connected in series. Step S2: Perform graded alternating charge-discharge tests on the sodium-nickel battery sample, constructing a low sodium flux steady-state condition and a high flux impact condition respectively, to achieve alternating sodium flux and bring the sodium flux stress inside the sodium-nickel battery sample to its peak value, and obtain the electrical performance parameters of the sodium-nickel battery sample that can reflect the change of sodium flux stress. Step S3: The sodium-nickel battery sample processed in step S2 is subjected to high-current pulse discharge and peak power test using a multi-gradient SOC switching method. Step S4: Analyze the parameters obtained in steps S2 and S3 above, and then evaluate the performance of the sodium-nickel battery.

2. The method for evaluating the performance of sodium-nickel batteries based on sodium flux stress testing according to claim 1, characterized in that: In step S1, the formation pretreatment method includes: Step S11: Perform constant current charging at 16-24A until the voltage of the sodium-nickel battery cell rises to the rated charging voltage; Step S12: Perform constant voltage charging at the rated charging voltage until the current is less than the termination current (the charging termination current during the constant voltage stage), and then stop charging.

3. The method for evaluating the performance of sodium-nickel batteries based on sodium flux stress testing according to claim 1, characterized in that: In step S2, the specific steps for performing a graded variable power alternating charge-discharge test on the sodium-nickel battery sample include: S21: Discharge at a constant current of 0.08C-0.12C until the cutoff voltage of the sodium-nickel battery cell is reached, then stop discharging. S22: Charge at a constant power of 42-50W / Ni-N cell, with the charging current controlled at 18-22A. After the Ni-N cell voltage reaches the rated charging voltage (2.67V), switch to constant voltage charging until the charging current drops to the termination current, thus ending the charging process. S23: Discharge the battery at a constant power of 120W-122W per sodium-nickel battery cell until the cutoff voltage of the sodium-nickel battery cell is reached, then stop discharging and let it stand for 10-15 minutes. S24: Repeat the charging and discharging operations of steps S21 and S22 above 3-5 times, and obtain the electrical performance parameters of each sodium-nickel battery cell after discharge.

4. The method for evaluating the performance of sodium-nickel batteries based on sodium flux stress testing according to claim 3, characterized in that: In steps S21 and S23, When the sodium-nickel battery sample is a sodium-nickel battery cell, the cutoff voltage is 1.90-2.00V; When the sodium-nickel battery sample is a battery module composed of multiple sodium-nickel battery cells connected in series, the cutoff voltage is the cutoff voltage of a single sodium-nickel battery cell multiplied by the total voltage of the number of cells connected in series, or the cutoff voltage is taken as the voltage of any sodium-nickel battery cell when it drops to 1.65-1.90V, and the discharge is terminated when either condition is met.

5. The method for evaluating the performance of sodium-nickel batteries based on sodium flux stress testing according to claim 1, characterized in that: In step S3, the specific steps for performing a gradient SOC peak power test on the sodium-nickel battery sample after step S2 include: S31: Discharge the sodium-nickel battery sample at a constant current of 0.08C-0.12C for 4-8 minutes to stabilize the internal state of the sample, so as to eliminate the static false voltage and balance the internal state of the cell. S32: High-current short-time pulse discharge is adopted, and the voltage of the sodium-nickel battery cell is monitored in real time. When the voltage of the sodium-nickel battery cell drops to the pulse cutoff threshold, the pulse discharge is terminated. At the same time, the SOC peak power is obtained. S33: Using a small current constant current discharge, the sodium-nickel battery is reduced from the current SOC to the next target SOC by quantitatively consuming power, thus realizing the test level gradient switching; S34: Repeat steps S32 and S33 above until the voltage of the sodium-nickel battery cell drops to the cutoff voltage and discharge stops. At this point, the SOC peak power test of all gradients is completed.

6. The method for evaluating the performance of sodium-nickel batteries based on sodium flux stress testing according to claim 5, characterized in that: In step S32, a constant current pulse discharge of 96-100A is used for 26-30s to calculate the instantaneous SOC peak power of the sodium-nickel battery cell based on the large current voltage drop. Meanwhile, in step S33, the small current is 22-24A, and this constant small current is used for uniform discharge.

7. The method for evaluating the performance of sodium-nickel batteries based on sodium flux stress testing according to claim 1, characterized in that: The electrical performance parameters include voltage parameters and capacity parameters; In step S4, the voltage parameter, capacity parameter, and peak power parameter are used as evaluation indicators to determine the performance of the sodium-nickel battery cell.

8. The method for evaluating the performance of sodium-nickel batteries based on sodium flux stress testing according to claim 7, characterized in that: Based on the determined performance of the sodium-nickel battery cell, it is possible to infer whether the structure and manufacturing process of the current sodium-nickel battery are qualified. Specific methods include: The sodium-nickel battery samples include standard sodium-nickel battery cells for the test group prepared using a new structure or process, and standard sodium-nickel battery cells for the control group prepared using the original structure or process. The evaluation indicators of the standard sodium-nickel battery cells in the test group are compared with those in the control group. If both meet the preset conditions, the cell is deemed qualified; otherwise, it is deemed unqualified.

9. The method for evaluating the performance of sodium-nickel batteries based on sodium flux stress testing according to claim 1, characterized in that: In step S1, the operating temperature is 260-300℃, and the low-temperature shutdown protection temperature is set to 210-230℃.

10. The method for evaluating the performance of sodium-nickel batteries based on sodium flux stress testing according to claim 1, characterized in that: The test was conducted in a temperature-controlled furnace, with a low-temperature shutdown protection temperature set.

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