Method for judging gas production condition of sodium ion battery and detection system

Abstract

The invention relates to the technical field of sodium ion batteries, and discloses a method for judging the gas production condition of sodium ion batteries and a detection system, and the method comprises the steps: charging a plurality of sodium ion batteries to the same upper limit voltage, standing, and testing to obtain the open-circuit voltage V0 of the plurality of sodium ion batteries, the maximum value in the open-circuit voltage V0 of the plurality of sodium ion batteries is recorded as Vmax; discharging the plurality of sodium-ion batteries to a lower limit voltage, standing, and calculating the charge-discharge coulombic efficiency of the sodium-ion batteries; and on the basis that the voltage difference value delta V between the open-circuit voltage V0 and the Vmax is greater than or equal to 8mV and the charge-discharge coulombic efficiency of the sodium-ion battery is less than 95%, judging that the sodium-ion battery produces gas. The method is non-destructive detection, is simple to operate, and can accurately judge the gas production state of the sodium ion battery.

Description

Technical Field

[0001] The present application relates to the technical field of sodium ion batteries, and in particular to a method and a detection system for determining the gas production of a sodium ion battery. Background Art

[0002] As the country pays more and more attention to energy security and environmental pollution prevention and control, batteries have been widely used in the fields of consumer goods, new energy power and energy storage. The existing large-scale chemical energy storage batteries are mainly lithium-ion batteries, but their large-scale application is limited due to their high production costs and limited lithium mineral resources. The working principle of sodium-ion batteries is similar to that of lithium-ion batteries, and they are also secondary batteries. Compared with lithium-ion batteries, sodium-ion batteries have good high and low temperature performance, low cost, and a wide range of sodium metal sources. They are expected to become an important supplement to the future large-scale energy storage market of lithium-ion batteries, and provide strong support for the layout and application of large-scale storage facilities such as wind power storage and smart grids, and the development of new energy transportation. Summary of the invention

[0003] In the first aspect of the present application, the present application proposes a method for judging the gas production of a sodium ion battery, comprising: charging a plurality of sodium ion batteries to the same upper limit voltage, and after standing, testing to obtain the open circuit voltage V0 of the plurality of the sodium ion batteries, wherein the maximum value of the open circuit voltage V0 of the plurality of the sodium ion batteries is recorded as V max ; Discharge the multiple sodium ion batteries to the lower limit voltage, and after standing, calculate the charge and discharge coulomb efficiency of the sodium ion batteries; Based on the open circuit voltage V0 and the V max If the voltage difference |ΔV| between the two is ≥8mV and the charge and discharge coulomb efficiency of the sodium ion battery is less than 95%, it is determined that the sodium ion battery produces gas.

[0004] The method for judging the gas production of sodium ion batteries proposed in this application detects the key performance values ​​of multiple sodium ion battery charge and discharge cycle processes, compares the voltage of multiple sodium ion battery samples in parallel, calculates the pressure difference and the charge and discharge coulomb efficiency, and thus judges the gas production state of the multiple sodium ion batteries tested based on the two criteria of voltage difference and charge and discharge coulomb efficiency. This method is a non-destructive test with simple operation and can more accurately judge the gas production state of the sodium ion battery.

[0005] In some embodiments, the multiple sodium ion batteries are charged with constant current first and constant voltage second at a preset charging rate, and the preset charging rate is 0.02C-10C. Therefore, charging the battery with constant current first and constant voltage second at the preset charging rate is conducive to maintaining a relatively consistent charging process for the multiple sodium ion batteries, so that the sodium ion batteries reach the upper limit voltage more accurately, and reduce the error and uncertainty of the test results. The aforementioned charging rate range is suitable for testing sodium ion batteries of different types and different working state requirements, and is suitable for testing a wide range of sodium ion batteries.

[0006] In some embodiments, the plurality of sodium ion batteries are subjected to constant current discharge at a preset discharge rate. Thus, constant current discharge at a preset discharge rate is conducive to better evaluating the performance of the sodium ion battery and improving the accuracy and repeatability of the test.

[0007] In some embodiments, the preset charging rate is 4C-5C. When charging at the preset charging rate, if gas production changes occur, the open circuit voltage and charge and discharge coulomb efficiency of the sodium ion battery can reflect the conditions of the internal materials and structures of the sodium ion battery. Therefore, the method proposed in the present application has a high sensitivity in judging whether the sodium ion battery produces gas.

[0008] In some embodiments, the preset discharge rate is 0.02C-10C. Therefore, the aforementioned discharge rate range is suitable for testing sodium ion batteries of different types and different working state requirements, and is applicable to a wider range of sodium ion batteries.

[0009] In some embodiments, the standing time is 1 hour to 2 hours. Within the aforementioned standing time range, it is beneficial for the sodium ion battery to regain a relatively stable state, making the measured value more accurate.

[0010] In some embodiments, calculating the charge and discharge coulombic efficiency of the sodium ion battery includes: charging a plurality of sodium ion batteries to the same upper limit voltage, and calculating the charge capacity of the plurality of sodium ion batteries; discharging the plurality of sodium ion batteries to a terminal voltage, and calculating the discharge capacity of the plurality of sodium ion batteries; and calculating the charge and discharge coulombic efficiency of the plurality of sodium ion batteries based on the charge capacity of the sodium ion battery and the discharge capacity of the sodium ion battery.

[0011] The charge and discharge coulomb efficiency obtained by the above method can determine the gas production state of the sodium ion battery after each charge and discharge cycle. Feedback on the health status of the sodium ion battery and timely alert of related risks are helpful to reduce the occurrence of risks such as thermal runaway of the battery.

[0012] In some embodiments, the number of the plurality of sodium ion batteries is 2 to 40. The number of the plurality of sodium ion batteries within the aforementioned range is conducive to adapting to the test requirements under which different numbers of sodium ion batteries work together, reminding of the risk of gas production, and reducing the risk of thermal runaway.

[0013] In some embodiments, the temperature of the plurality of sodium ion batteries is detected, thereby enabling monitoring and prevention of potential safety hazards during the entire operation of the sodium ion batteries.

[0014] In a second aspect of the present application, the present application proposes a detection system for determining the gas production situation of a sodium ion battery, the detection system comprising: a charging and discharging device, which charges and / or discharges the sodium ion battery; a gas production test module, the gas production judgment module determines the gas production situation of the sodium ion battery according to the method for determining the gas production situation of the sodium ion battery proposed in the present application.

[0015] The detection system for determining the gas production of sodium-ion batteries proposed in this application can work together with other battery cycle detection systems. When detecting battery performance, the gas production of sodium-ion batteries can be detected to reduce the risk of thermal runaway of sodium-ion batteries, while protecting the safety of related facilities and personnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0017] Figure 1 This is a flow chart of a method for determining the gas production condition of a sodium ion battery in one embodiment of the present application;

[0018] Figure 2 The sodium ion battery that produces gas at a charging rate of 4C in Example 1 of the present application;

[0019] Figure 3 This is the sodium ion battery that produces gas when the charging rate is 5C in Example 2 of the present application. DETAILED DESCRIPTION

[0020] The embodiments of the present application are described in detail below. Examples of the embodiments are shown in the drawings, but unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of actually identical structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0021] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field to which this application belongs; the terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application; unless otherwise specified, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the embodiments of this application).

[0022] The terms "including" and "having" in the specification and claims of the present application and any modifications thereof are open expressions, that is, including the contents specified in the present application but not excluding other contents.

[0023] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range.

[0024] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0025] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0026] With the rapid development of the new energy industry, the energy density of batteries is getting higher and higher, and extreme design (high group margin, thick coating design, etc.) has become the current trend. Although the above measures can significantly improve the use capacity and service life of sodium-ion batteries, sodium-ion batteries are prone to electrolyte oxidation decomposition and rupture and recombination of solid electrolyte interface membranes (SEI) during long cycles, which leads to performance degradation of sodium-ion batteries during use, which can also lead to battery failure and even serious safety hazards. Therefore, it is necessary to monitor the gas production state of sodium-ion batteries throughout their life cycle and evaluate the safety performance of the batteries. The test method for gas production of sodium-ion batteries proposed in this application is a non-destructive test. By analyzing the performance data of sodium-ion batteries, the gas production state of sodium-ion batteries can be monitored. This method is not limited by the working environment and physical distance of the battery. There is no need for special sampling tests or close observation of the state of sodium-ion batteries. Remote operation and analysis can be achieved. It is easy to operate and has high practicality.

[0027] In a first aspect of the present application, the present application proposes a method for determining the gas production condition of a sodium ion battery.

[0028] The method for judging the gas production of sodium ion batteries proposed in this application is referred to Figure 1 ,include:

[0029] S100: charging a plurality of sodium ion batteries to the same upper limit voltage, and after standing, testing to obtain the open circuit voltages V0 of the plurality of sodium ion batteries, wherein the maximum value of the open circuit voltages V0 of the plurality of sodium ion batteries is recorded as V max

[0030] When charging multiple sodium-ion batteries, charging will cause polarization inside the sodium-ion batteries, including electrochemical polarization and concentration polarization. If the electrolyte, such as the carbonate electrolyte solvent, decomposes during the charging process, it will release gases such as hydrogen (H2) and carbon dioxide (CO2). In addition, the solvents and additives in the electrolyte form an SEI layer on the electrode surface. The unevenness or instability of the SEI layer may lead to more side reactions that aggravate the irreversible consumption of sodium ions, accompanied by the release of gas. Therefore, the chemical changes in the substances inside the sodium-ion battery will cause changes in the electrochemical potential of the electrode, the properties of the electrolyte, etc., thereby causing changes in the open circuit voltage of the sodium-ion battery. During the standing period, the SEI layer may further form or change, affecting the voltage and stability of the battery. After standing for a certain period of time, the ion concentration distribution and electrochemical state inside the sodium-ion battery gradually stabilize, and then testing the open circuit voltage V0 is conducive to obtaining a more accurate test value. The maximum value V of the open circuit voltage in multiple sodium-ion batteries that have undergone the same charging process is calculated. max Marking is performed to identify the changes in the open circuit voltage of different sodium-ion batteries.

[0031] S200: Discharging the plurality of sodium ion batteries to a lower voltage limit, and after standing still, calculating the charge and discharge coulomb efficiency of the sodium ion batteries

[0032] During the discharge process of a sodium-ion battery, the sodium ions that were embedded in the negative electrode during charging are released from the positive electrode and return to the positive electrode, causing the lattice structure of the positive electrode active material to expand and contract. Among them, the structure of the positive electrode active material is restored due to the embedding of sodium ions, but this recovery is not completely reversible. If a chemical reaction that causes gas production does occur inside the sodium-ion battery, it will have a significant impact on the structure of the electrode material and the electrolyte, resulting in a significant difference between the charging capacitance measured during the charging process and the discharge capacitance measured during the discharge process. Therefore, the charge and discharge coulomb efficiency of the sodium-ion battery is calculated after discharging to the lower limit voltage. The charge and discharge coulomb efficiency can be used to analyze whether the change in open circuit voltage is caused by an irreversible chemical reaction, thereby improving the accuracy of judging the gas production condition.

[0033] S300: Based on the open circuit voltage V0 and the V maxThe voltage difference between |ΔV|≥8mV and the charge and discharge coulomb efficiency of the sodium ion battery is less than 95%, and the sodium ion battery is judged to produce gas.

[0034] Based on the joint judgment of the voltage difference |ΔV| of the open circuit voltage transformation and the charge and discharge coulomb efficiency, the irreversible chemical changes that cause gas production inside the sodium ion battery can be correctly identified.

[0035] The method for judging the gas production of sodium-ion batteries proposed in this application performs a charge and discharge cycle on multiple sodium-ion batteries, compares the voltages of multiple sodium-ion batteries in parallel, and calculates the voltage difference and the charge and discharge coulomb efficiency. The voltage difference and the charge and discharge coulomb efficiency reflect the degree of change of the internal material of the sodium-ion battery. The relevant characteristic values ​​exceeding the threshold indicate irreversible destructive changes in the internal materials and structures of the sodium-ion battery, and also indirectly explain the gas production of the ion battery. Therefore, the gas production status of multiple sodium-ion batteries tested can be judged based on the two standards of voltage difference |ΔV|≥8mV and charge and discharge coulomb efficiency less than 95%. This method is a non-destructive test with simple operation and can more accurately judge the gas production status of sodium-ion batteries. It is suitable for both quality inspection of sodium-ion batteries before leaving the factory and health inspection of sodium-ion batteries in service.

[0036] In some embodiments, the multiple sodium ion batteries are charged with constant current first and then constant voltage at a preset charging rate, and the preset charging rate is 0.02C-10C.

[0037] By charging a plurality of sodium ion batteries in the aforementioned manner and controlling the current and voltage changes during the charging process, it is advantageous to more accurately control the charging rate of the sodium ion batteries, maintain a high charging efficiency, achieve a relatively stable charging capacitance level, and reduce the damage caused to the sodium ion batteries by the charging process. At the same time, the controlled charging process is advantageous to improve the repeatability of the test and the comparability between the multiple data obtained by testing a plurality of sodium ion batteries. Thus, charging the battery with constant current first and then constant voltage at a preset charging rate is advantageous to maintain a relatively consistent charging process for a plurality of sodium ion batteries, so that the sodium ion batteries reach the upper limit voltage more accurately, and reduce the error and uncertainty of the test results.

[0038] As an example, the preset charging rates are 0.02C, 0.05C, 0.1C, C / 3, 0.5C, 1C, 2C, 3C, 4C, 5C, and 10C.

[0039] In some embodiments, the plurality of sodium ion batteries are discharged at a constant current at a preset discharge rate.

[0040] Discharging multiple sodium ion batteries in the aforementioned manner, and controlling the discharge current during the discharge process, makes the discharge conditions of each sodium ion battery the same during each test, which is conducive to controlling the discharge rate of the sodium ion battery, so that the changes caused by the current during the discharge process of multiple sodium ion batteries are relatively consistent, which is conducive to achieving a relatively stable discharge capacitance. At the same time, the controlled discharge process is conducive to reducing test errors and uncertainties. Therefore, constant current discharge at a preset discharge rate is conducive to better evaluating the performance of the sodium ion battery and improving the accuracy and repeatability of the test.

[0041] In some embodiments, the preset charging rate is 4C-5C.

[0042] When charging at the aforementioned preset charging rate, the charging rate is high, and more serious crosstalk may occur between the positive and negative electrodes inside the battery. The crosstalk may cause the water and impurities inside the battery to be reduced to produce hydrogen, or the protons released by the oxidation of soluble substances to be reduced to gases such as H2. After the gas production change occurs, the open circuit voltage and charge and discharge coulomb efficiency of the sodium ion battery can reflect the condition of the internal materials and structures of the sodium ion battery. The method proposed in this application has a high sensitivity for judging whether the sodium ion battery produces gas.

[0043] In some embodiments, the preset discharge rate is 0.02C-10C. The method for judging the gas production of a sodium ion battery proposed in the present application is based on the changes after the charging and discharging process of the sodium ion battery to judge the gas production state of the sodium ion battery, which can be applied to a wider range of discharge rates. Therefore, the aforementioned preset discharge rate range can test sodium ion batteries of different types and different working state requirements, and is applicable to a wider range of sodium ion batteries.

[0044] As an example, the preset discharge rates are 0.02C, 0.05C, 0.1C, C / 3, 0.5C, 1C, 2C, 3C, 4C, 5C, and 10C.

[0045] In some embodiments, the standing time is 1h-2h. The sodium ion battery is charged or discharged, and polarization occurs inside the sodium ion battery during the charging and discharging process, including electrochemical polarization and concentration polarization. These polarization phenomena can cause the open circuit voltage of the battery to change, thereby affecting the difference between the full-charge voltage and the static voltage. As the standing time increases, the ion concentration distribution and electrochemical state inside the battery gradually become uniform. Within the aforementioned standing time range, it is beneficial for the sodium ion battery to regain a relatively stable state, making the measured value more accurate.

[0046] In some embodiments, calculating the charge and discharge coulombic efficiency of the sodium ion battery includes: charging a plurality of sodium ion batteries to the same upper limit voltage, and calculating the charge capacity of the plurality of sodium ion batteries; discharging the plurality of sodium ion batteries to a terminal voltage, and calculating the discharge capacity of the plurality of sodium ion batteries; and calculating the charge and discharge coulombic efficiency of the plurality of sodium ion batteries based on the charge capacity of the sodium ion battery and the discharge capacity of the sodium ion battery.

[0047] The charge and discharge coulomb efficiency obtained by the above method can determine the gas production state of the sodium ion battery after each charge and discharge cycle. Feedback on the health status of the sodium ion battery and timely alert of related risks are helpful to reduce the occurrence of risks such as thermal runaway of the battery.

[0048] In some embodiments, the number of the plurality of sodium-ion batteries is 2-40. The number of the plurality of sodium-ion batteries is within the aforementioned range. By using the method for determining the gas production of sodium-ion batteries proposed in the present application, information on whether a specific sodium-ion battery among the plurality of sodium-ion batteries produces gas can be specifically known through data analysis, and the sodium-ion battery producing gas can be accurately located. This is conducive to adapting to the test requirements under which different numbers of sodium-ion batteries work together, reminding of the risk of gas production, and reducing the risk of thermal runaway.

[0049] In some embodiments, temperature detection is performed on the plurality of sodium ion batteries.

[0050] The sodium ions in sodium ion batteries have higher chemical activity than the lithium ions in lithium ion batteries. During the charging and discharging process of sodium ion batteries, the sodium ions and electrons inside the battery move in coordination, and the heat released by the chemical reaction of gas production can directly cause further thermal runaway. Therefore, through temperature detection, the method for judging the gas production of sodium ion batteries proposed in this application can be further supplemented by the characteristic that the judgment must be made after the charging and / or discharging process is completed. In this way, it is possible to monitor and prevent safety hazards throughout the entire operation process of sodium ion batteries.

[0051] In a second aspect of the present application, the present application proposes a detection system for determining the gas production situation of a sodium ion battery, the detection system comprising: a charging and discharging device, which charges and / or discharges the sodium ion battery; a gas production test module, the gas production judgment module determines the gas production situation of the sodium ion battery according to the method for determining the gas production situation of the sodium ion battery proposed in the present application.

[0052] The detection system for judging the gas production of sodium-ion batteries proposed in this application can work together with other battery cycle detection systems. When testing battery performance, the gas production of sodium-ion batteries can be detected to reduce the risk of thermal runaway of sodium-ion batteries, while protecting the safety of related facilities and personnel. The detection system is suitable for testing and controlling the quality of sodium-ion battery products by sodium-ion manufacturers, and is also suitable for related inspections of sodium-ion batteries in service.

[0053] The scheme of the present application is described below by specific examples. It should be noted that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If no specific technology or conditions are specified in the examples, the technology or conditions described in the literature in this area or the product instructions are used. The reagents or instruments used are not specified by the manufacturer, and are all conventional products that can be obtained commercially.

[0054] Example 1

[0055] S1: Connect the sodium ion battery to be tested to the charging and discharging system, with a total of 24 parallel samples;

[0056] S2: Under the condition of preset charging rate of 4C, the sodium ion battery is charged with constant current and constant voltage to the upper limit voltage of the battery, and then left to stand for 1 hour. It is then discharged with constant current at the preset discharge rate of 1C to the terminal voltage of the battery, and left to stand for 1 hour. During the test, the voltage and temperature of the battery are monitored and recorded in real time.

[0057] S3: Based on the open circuit voltage V0 and the V max If the voltage difference |ΔV| between the two is ≥8mV and the charge and discharge coulomb efficiency of the sodium ion battery is less than 95%, it is determined that the sodium ion battery produces gas.

[0058] The test data of Example 1 is shown in Table 1.

[0059] Table 1

[0060]

[0061]

[0062] As shown in Table 1, when the charging rate is 4C, the voltage difference between the voltage V0 after standing for 1h after charging and the maximum voltage Vmax in the test parallel sample |ΔV|≥8mV, and the charge and discharge coulomb efficiency is less than 95%, the reference Figure 2 , the sodium ion battery can be observed to produce gas from the outside, indicating that this method correctly indicates the sodium ion battery that produces gas.

[0063] Example 2

[0064] Embodiment 2 is the same as Embodiment 1, except that the preset charging rate is 5C.

[0065] The test data of Example 2 is shown in Table 2.

[0066] Table 2

[0067] Battery ID |ΔV| / mV Coulomb efficiency / % Whether to produce gas 1# 15.843 85.91 yes 2# 8.231 96.75 no 3# 0.43 96.23 no 4# 0.472 96.25 no 5# 2.325 97.56 no 6# 0 99.03 no 7# 12.787 84.88 yes 8# 8.871 92.66 yes 9# 12.425 84.01 yes 10# 14.467 79.36 yes 11# 2.287 99.68 no 12# 3.056 99.84 no 13# 6.353 99.43 no 14# 6.008 99.45 no 15# 57.159 90.9 yes 16# 42.221 90.57 yes 17# 57.494 90.43 yes 18# 26.448 93.55 yes 19# 54.03 77.4 yes 20# 51.747 77.06 yes 21# 7.499 94.93 no 22# 11.162 88.42 yes 23# 7.674 94.5 no 24# 5.349 98.33 no

[0068] It can be seen from Table 2 that when the charging rate is 5C, the voltage difference between the voltage V0 after standing for 1h after charging and the maximum voltage Vmax in the test parallel sample |ΔV|≥8mV, and the charge and discharge coulomb efficiency is less than 95%, the reference Figure 3 , correctly indicating the occurrence of gassing in sodium-ion batteries. When only the voltage difference |ΔV|≥8mV or the charge and discharge coulomb efficiency is less than 95%, the sodium-ion battery does not produce gas.

[0069] In the description of the present application, "A and / or B" may include the case of A alone, the case of B alone, or any of the cases of A and B, where A and B are only used for examples and may be any technical feature connected by "and / or" in the present application.

[0070] In the present application, the writing order of each step does not mean a strict execution order and does not constitute any limitation on the implementation process. The specific execution order of each step should be determined by its function and possible internal logic. If there is no special explanation, all steps of the present application can be performed in sequence or randomly, preferably in sequence. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed in sequence, or may include steps (b) and (a) performed in sequence. For example, the method may also include step (c), indicating that step (c) can be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0071] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for determining the gas production of a sodium ion battery, characterized in that: include: A plurality of sodium ion batteries are charged to the same upper limit voltage, and after standing, the open circuit voltages V0 of the plurality of sodium ion batteries are measured and obtained, wherein the maximum value of the open circuit voltages V0 of the plurality of sodium ion batteries is recorded as V max ; Discharging the plurality of sodium ion batteries to a lower limit voltage, and after standing still, calculating the charge and discharge coulomb efficiency of the sodium ion batteries; Based on the open circuit voltage V0 and the V max If the voltage difference |ΔV| between the two is ≥8mV and the charge and discharge coulomb efficiency of the sodium ion battery is less than 95%, it is determined that the sodium ion battery produces gas.

2. The method according to claim 1, characterized in that The multiple sodium ion batteries are charged at a preset charging rate by first constant current and then constant voltage, and the preset charging rate is 0.02C-10C.

3. The method according to claim 1, characterized in that: The multiple sodium ion batteries are discharged at a constant current at a preset discharge rate.

4. The method according to claim 2, characterized in that: The preset charging rate is 4C-5C.

5. The method according to claim 3, characterized in that: The preset discharge rate is 0.02C-10C.

6. The method according to any one of claims 1 to 5, characterized in that: The standing time is 1h-2h.

7. The method according to any one of claims 1 to 5, characterized in that: Calculating the charge and discharge coulombic efficiency of the sodium ion battery includes: Charging a plurality of sodium ion batteries to the same upper limit voltage, and calculating the charging capacity of the plurality of sodium ion batteries; Discharging the plurality of sodium ion batteries to a terminal voltage, and calculating the discharge capacity of the plurality of sodium ion batteries, Based on the charging capacity of the sodium ion battery and the discharging capacity of the sodium ion battery, the charging and discharging coulombic efficiencies of the plurality of sodium ion batteries are calculated.

8. The method according to any one of claims 1 to 5, characterized in that: The number of the multiple sodium ion batteries is 2-40.

9. The method according to any one of claims 1 to 5, characterized in that: Temperature detection is performed on the plurality of sodium ion batteries.

10. A detection system for judging the gas production of a sodium ion battery, characterized in that: The detection system comprises: A charging and discharging device, wherein the charging and discharging device charges and / or discharges the sodium ion battery; A gas production test module, wherein the gas production judgment module judges the gas production condition of the sodium ion battery according to the method for judging the gas production condition of the sodium ion battery according to any one of claims 1 to 9.

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