Lithium-ion battery internal short circuit detection method and detection criterion setting and verification method

Abstract

The present application discloses a lithium-ion battery internal short circuit detection method and a detection criterion setting and verification method, including: setting a detection criterion threshold through a puncture short circuit experiment to realize the detection criterion threshold initialization; verifying whether the criterion can meet the detection requirements through a puncture short circuit experiment; setting a voltage safety threshold, a voltage sampling frequency, and a gas sampling frequency; real-time acquisition of voltage signals and gas signals during battery operation and recording the precipitation time and concentration change of the gas signal after precipitation; calculating the voltage change rate, the total VOC concentration, and the total CO concentration; substituting the real-time collected voltage value and the calculation result into the criterion to perform lithium-ion battery internal short circuit detection. The present invention has the potential for large-scale promotion and can provide a strong guarantee for the safe operation of lithium-ion batteries in the main application scenarios such as energy storage power stations and electric vehicles.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery safety, and relates to a lithium-ion battery internal short circuit detection method based on multi-signal fusion and a detection criterion setting and verification method. Background Art

[0002] Lithium-ion batteries have become the first choice for electrochemical energy storage power stations and electric vehicles due to their unique advantages such as high energy density and long service life. Driven by the ever-expanding application demand, the lithium-ion battery industry has developed rapidly, especially the continuous increase in single-cell energy density, the continuous reduction in cost, and the continuous increase in total shipments.

[0003] However, energy storage power stations and electric vehicles are in the ascendant, and the rapid growth in the use of lithium-ion batteries has revealed significant safety issues. Therefore, how to accurately detect internal short-circuit faults in lithium-ion batteries has become a primary issue to ensure the development of energy storage power stations and electric vehicles.

[0004] At present, there are some research results that can be used for internal short-circuit fault detection of batteries, but most of them only use voltage signals or only use temperature signals to realize fault detection, and there is a problem of low reliability of internal short-circuit detection. The reasons are as follows: For methods that only use voltage signals, voltage drops are often used as detection criteria, but internal short-circuit faults are not the only fault characteristics of voltage drops, that is, there is a sufficient but not necessary relationship between internal short-circuit faults and voltage drops. Methods that only use temperature signals also have the disadvantages of the above-mentioned voltage signal method, that is, low detection reliability. In addition, there is a certain hysteresis characteristic in the transmission of temperature. When used for internal short-circuit detection, this type of detection often has poor detection speed. Summary of the invention

[0005] In order to address the deficiencies in the prior art, the present application provides a lithium-ion battery internal short circuit detection method based on multi-signal fusion and a detection criterion setting and verification method, which have sufficient detection reliability.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A method for setting a detection criterion for an internal short circuit of a lithium-ion battery is provided. Through N puncture short circuit experiments, a detection criterion threshold based on multi-signal fusion is determined to initialize the detection criterion threshold. The method comprises the following steps:

[0008] Step 1: Use the puncture integrated machine to conduct an internal short-circuit test on the lithium-ion battery. During the experiment, the battery voltage signal and VOC, CO and C2H5F gas signals are collected in real time, and the precipitation time of the gas signal and the concentration change after precipitation are recorded;

[0009] Step 2: Calculate the voltage change rate, VOC and C2H5F precipitation time difference for each test based on the experimental data Time difference Total VOC concentration, CO and C2H5F precipitation time difference Time difference Total CO concentration inside;

[0010] Step 3: Filter the voltage change rate threshold, VOC total concentration threshold, and CO total concentration threshold from the calculation results of step 2 to initialize the detection criterion threshold.

[0011] The present invention further includes the following preferred embodiments:

[0012] Preferably, N≥1000.

[0013] Preferably, in step 1, the puncture machine uses a steel needle with a diameter of 6 mm, sets a puncture speed of 30 mm / s and a puncture stroke of 300 mm, uses a clamp to fix the battery in the center of the puncture machine, runs the puncture machine, punctures the battery, and pulls out the steel needle after it stays in the battery for 600 seconds.

[0014] Preferably, in step 1, the voltage sensor is directly connected to the positive and negative ears of the battery, and the gas sensor is connected to one end of the gas pipe, and the other end is close to the surface of the battery;

[0015] Preferably, the voltage signal is collected by a voltage sensor, the gas signal is collected by a gas sensor, and the precipitation time of the gas signal and the concentration change after precipitation are recorded.

[0016] Preferably, in step 2, the calculation formula of the voltage change rate DV is:

[0017]

[0018] In the formula, V represents the battery voltage, k represents the voltage sampling point number, and t represents the sampling interval. The calculation formula is:

[0019]

[0020] In the formula, f v is the voltage sampling frequency;

[0021] The calculation formula for the time difference between VOC and C2H5F precipitation is:

[0022]

[0023] In the formula, is the precipitation time of C2H5F, t VOC is the VOC precipitation time, which indicates the time corresponding to the gas concentration changing from zero to a certain value;

[0024] The calculation formula for the total VOC concentration is:

[0025]

[0026] In the formula, C VOC is the total VOC concentration, c VOC (k) is the VOC gas concentration at time k, n VOC yes The number of VOC sampling points within is calculated as follows:

[0027]

[0028] In the formula, f g is the gas sampling frequency;

[0029] Similarly, the calculation formula for the difference in precipitation time between CO and C2H5F and the total CO concentration is:

[0030]

[0031]

[0032] Where, t CO is the CO evolution time, C CO is the total CO concentration, c CO (k) is the CO gas concentration at time k, n CO yes The number of CO sampling points within is calculated as follows:

[0033]

[0034] Preferably, in step 3, the minimum voltage change rate, VOC total concentration and CO total concentration calculated values ​​in step 2 are screened and set as the voltage change rate threshold, VOC total concentration threshold and CO total concentration threshold to realize detection criterion threshold initialization.

[0035] The present invention also provides a lithium-ion battery internal short circuit detection criterion verification method, which verifies whether the criterion can meet the detection requirements through a puncture short circuit experiment. The detection criterion verification method includes the following steps:

[0036] Step 1: Set the voltage safety threshold, voltage sampling frequency, and gas sampling frequency, and use the above-mentioned detection criterion setting method to initialize the voltage change rate threshold, VOC total concentration threshold, and CO total concentration threshold;

[0037] Step 2: Use the puncture integrated machine to conduct an internal short-circuit test on the lithium-ion battery. During the experiment, the battery voltage signal and VOC, CO and C2H5F gas signals are collected in real time, and the precipitation time of the gas signal and the concentration change after precipitation are recorded;

[0038] Step 3: Calculate the voltage change rate, VOC and C2H5F precipitation time difference Time difference Total VOC concentration, CO and C2H5F precipitation time difference Time difference Total CO concentration inside;

[0039] Step 4: Based on the voltage criterion and the comprehensive criterion, compare the voltage value, the calculated value in step 3 and the threshold value corresponding to step 1, and verify whether the criterion can meet the detection requirements based on whether it can make a correct judgment on the internal short circuit of the lithium-ion battery.

[0040] The present invention also provides a method for detecting an internal short circuit of a lithium-ion battery, comprising:

[0041] Step 1: Set the voltage safety threshold, voltage sampling frequency, and gas sampling frequency, and respectively use the above-mentioned detection criterion setting method and detection criterion verification method to initialize and verify the voltage change rate threshold, VOC total concentration threshold, and CO total concentration threshold;

[0042] Step 2: Collect voltage signals and gas signals in real time during battery operation, and record the precipitation time of the gas signal and the concentration change after precipitation;

[0043] Step 3: Calculate the voltage change rate, VOC and C2H5F precipitation time difference Time difference Total VOC concentration, CO and C2H5F precipitation time difference Time difference Total CO concentration inside;

[0044] Step 4: Substitute the voltage value collected in real time into the voltage criterion. If the voltage criterion is met, the battery is abnormal and the process goes to step 5. If the voltage criterion is not met, the process goes back to step 2.

[0045] Step 5: Substitute the maximum voltage change rate, total VOC concentration, and total CO concentration obtained in step 3 into the comprehensive criterion. If the comprehensive criterion is met, an internal short circuit fault of the battery is output and an alarm signal is issued; if it is not met, other fault detection is prompted.

[0046] Preferably, the voltage safety threshold is set according to the inherent voltage range of the lithium-ion battery;

[0047] The voltage sampling frequency and the gas sampling frequency are set according to the sensor standard.

[0048] Preferably, the battery voltage safety threshold, the voltage change rate threshold, the VOC total concentration threshold, and the CO total concentration threshold are respectively recorded as R1, R2, R3, and R4;

[0049] In step 4, when the voltage value collected in real time is less than the battery voltage safety threshold, that is, it satisfies the voltage criterion of formula (9), it is considered that the battery is abnormal:

[0050] V<R1 (9).

[0051] Preferably, in step 5, the maximum value of the voltage change rate, the total VOC concentration, and the total CO concentration obtained in step 3 are compared with corresponding thresholds respectively. If they are all higher than the corresponding thresholds, that is, the comprehensive criteria of formulas (10) to (12) are satisfied, it is considered that an internal short circuit fault occurs in the battery, and an alarm signal is issued;

[0052] DV>R2 (10)

[0053] C VOC >R3 (11)

[0054] C CO >R4 (12).

[0055] Preferably, R1 is 2V, and the voltage sampling frequency and the gas sampling frequency are both 1 Hz.

[0056] Preferably, R2 is 0.5, R3 is 250 ppm, and R4 is 30 ppm.

[0057] Beneficial effects achieved by this application:

[0058] The present invention collects voltage signals and gas signals, proposes a detection criterion setting and verification method based on multi-signal fusion, and realizes high-reliability and high-accuracy detection of internal short-circuit faults in lithium-ion batteries. The method of the present invention has a simple principle, is easy to implement, does not require high computing costs, has the potential for large-scale promotion, and can provide a strong guarantee for the safe operation of major application scenarios of lithium-ion batteries such as energy storage power stations and electric vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 This is a scene diagram of an internal short circuit failure of a lithium-ion battery in a puncture integrated device;

[0060] Figure 2 It is a flow chart of a method for detecting an internal short circuit of a lithium-ion battery;

[0061] Figure 3 It is the voltage waveform of the lithium-ion battery during short circuit detection;

[0062] Figure 4 It is the voltage change rate diagram of lithium-ion battery during short circuit detection;

[0063] Figure 5 This is the graph of the changes in VOC and C2H5F concentrations of lithium-ion batteries during short-circuit detection;

[0064] Figure 6 This is a graph showing the changes in CO and C2H5F concentrations in a lithium-ion battery during short-circuit detection. DETAILED DESCRIPTION

[0065] The present application is further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present application.

[0066] The method for setting the detection criteria of the internal short circuit of the lithium-ion battery of the present invention determines the detection criteria threshold based on multi-signal fusion through N puncture short circuit experiments, and realizes the initialization of the detection criteria threshold. In the specific implementation, N≥1000;

[0067] The method specifically comprises the following steps:

[0068] Step 1: Use the puncture integrated machine to conduct an internal short-circuit experiment on the lithium-ion battery. During the experiment, the battery voltage signal and VOC (Volatile Organic Compounds), CO and C2H5F gas signals are collected in real time, and the precipitation time of the gas signal and the concentration change after precipitation are recorded;

[0069] That is, conduct a short circuit experiment and record the necessary signals, namely the voltage signal, the precipitation time of the three gas signals VOC, CO and C2H5F, and the concentration change after precipitation. Precipitation is from nothing to something. For example, under normal circumstances, the above three gases should all be 0ppm. As long as they are greater than 0ppm, it is precipitation.

[0070] When implementing it specifically, Figure 1 This is a scenario diagram of a lithium-ion battery internal short circuit fault in a puncture machine. The puncture machine uses a 6mm diameter steel needle and sets a puncture speed of 30mm / s and a puncture stroke of 300mm. Figure 1 (a) It can be seen that the lithium-ion battery is fixed in the center of the puncture machine body by a clamp. The voltage sensor is connected to the positive and negative ears of the battery to collect voltage signals in real time. At the same time, the gas tube is close to the surface of the battery to collect gas signals in real time. The gas signals include VOC, CO and C2H5F. Further, the puncture machine is operated to puncture the battery. The steel needle stays in the battery for 600 seconds and then is pulled out. Figure 1 (b)

[0071] Step 2: Calculate the voltage change rate, VOC and C2H5F precipitation time difference for each test based on the experimental data Time difference Total VOC concentration, CO and C2H5F precipitation time difference Time difference Total CO concentration inside;

[0072] Specifically, the calculation formula of the voltage change rate DV is:

[0073]

[0074] In the formula, V represents the battery voltage, k represents the voltage sampling point number, and t represents the sampling interval. The calculation formula is:

[0075]

[0076] In the formula, f v is the voltage sampling frequency;

[0077] The calculation formula for the time difference between VOC and C2H5F precipitation is:

[0078]

[0079] In the formula, is the time difference between VOC and C2H5F precipitation, is the precipitation time of C2H5F, t VOC is the VOC precipitation time, which indicates the time corresponding to the gas concentration changing from zero to a certain value;

[0080] The calculation formula for the total VOC concentration is:

[0081]

[0082] In the formula, C VOC is the total VOC concentration, c VOC (k) is the VOC gas concentration at time k, n VOC yes The number of VOC sampling points within is calculated as follows:

[0083]

[0084] In the formula, f g is the gas sampling frequency;

[0085] Similarly, the calculation formula for the difference in precipitation time between CO and C2H5F and the total CO concentration is:

[0086]

[0087]

[0088] Where, t CO is the CO evolution time, C CO is the total CO concentration, c CO (k) is the CO gas concentration at time k, n CO yes The number of CO sampling points within is calculated as follows:

[0089]

[0090] Step 3: Filter the voltage change rate threshold, VOC total concentration threshold, and CO total concentration threshold from the calculation results of step 2 to initialize the detection criterion threshold.

[0091] Specifically, the minimum voltage change rate, VOC total concentration and CO total concentration calculated values ​​in step 2 are screened and set as the voltage change rate threshold, VOC total concentration threshold and CO total concentration threshold to achieve detection criterion threshold initialization.

[0092] The lithium-ion battery internal short circuit detection criterion verification method of the present invention verifies whether the criterion can meet the detection requirements through a puncture short circuit experiment, that is, the effectiveness of the set detection criterion threshold is verified through a puncture short circuit experiment;

[0093] The detection criterion verification method comprises the following steps:

[0094] Step 1: Set the voltage safety threshold, voltage sampling frequency, and gas sampling frequency, and use the above-mentioned detection criterion setting method to initialize the voltage change rate threshold, VOC total concentration threshold, and CO total concentration threshold;

[0095] Step 2: Use the puncture integrated machine to conduct an internal short-circuit test on the lithium-ion battery. During the experiment, the battery voltage signal and VOC, CO and C2H5F gas signals are collected in real time, and the precipitation time of the gas signal and the concentration change after precipitation are recorded;

[0096] Step 3: Use the above formula to calculate the voltage change rate, VOC and C2H5F precipitation time difference Time difference Total VOC concentration, CO and C2H5F precipitation time difference Time difference Total CO concentration inside;

[0097] Step 4: Based on the voltage criterion and the comprehensive criterion, compare the voltage value, the calculated value in step 3 and the threshold value corresponding to step 1, and verify whether the criterion can meet the detection requirements based on whether it can make a correct judgment on the internal short circuit of the lithium-ion battery.

[0098] like Figure 2 As shown, the lithium ion battery internal short circuit detection method of the present invention comprises the following steps:

[0099] Step 1: Set the voltage safety threshold, voltage sampling frequency, and gas sampling frequency, and respectively use the above-mentioned detection criterion setting method and detection criterion threshold verification method to initialize and verify the voltage change rate threshold, VOC total concentration threshold, and CO total concentration threshold;

[0100] The reason why the threshold value is verified again by the short-circuit test after initialization is that the short circuit can only be triggered in this way in the laboratory environment, and for the battery that has been put into operation, it is impossible to short-circuit on site, so the validity of the setting of the detection criterion threshold value needs to be verified in advance. Based on this, for the battery that has been put into operation, it is only necessary to substitute the data threshold value obtained by the short-circuit test.

[0101] In specific implementation, the voltage safety threshold R1 is determined according to the inherent voltage range of the lithium-ion battery used. For the commonly used lithium iron phosphate battery, its lower limit cut-off voltage is 2V, that is, R1 is 2V;

[0102] The voltage change rate threshold R2, VOC total concentration threshold R3 and CO total concentration threshold R4 were determined after a large number of short-circuit experiments. Finally, R2 was set to 0.5, R3 was set to 250ppm, and R4 was set to 30ppm;

[0103] Voltage sampling frequency f v , gas sampling frequency f g is determined according to commercial sensor standards. In the specific embodiment of the present invention, f v and f g All are taken as 1Hz.

[0104] Step 2: Collect voltage signals and gas signals in real time during battery operation, and record the precipitation time of the gas signal and the concentration change after precipitation;

[0105] The time when the puncture machine starts running is recorded as 0s, and the time when the steel needle returns is recorded as 600s.

[0106] Figure 3 The voltage waveform of lithium-ion battery is shown in Figure 2. Figure 3 The battery voltage was maintained at 3.5V from 0 to 15s. At 15s, the voltage dropped to 1.5V instantly, and then recovered to 2.5V with strong fluctuations. From 15 to 127s, the voltage dropped to near 0V during the fluctuations. Figure 4 Given the voltage change rate of the lithium-ion battery, according to Figure 4 , around 15s, that is, in the short period of time after the voltage drops instantly, the voltage change rate fluctuates significantly. Figure 5 The VOC and C2H5F concentration changes of lithium-ion batteries are shown in Figure 2. Figure 5, the precipitation time of VOC and C2H5F is 8s and 60s respectively. At 8s, VOC precipitates first, and the concentration of VOC rises rapidly to around 100ppm from 8 to 60s. Then, the concentration of VOC increases rapidly at first, and then stabilizes after reaching the maximum value. Figure 6 This is the concentration change diagram of CO and C2H5F in lithium-ion batteries. Figure 6 The CO precipitation time is 15s, and then the concentration increases gradually, then increases rapidly, and finally stabilizes and gradually decays.

[0107] Step 3: Calculate the voltage change rate, VOC and C2H5F precipitation time difference Time difference Total VOC concentration, CO and C2H5F precipitation time difference Time difference Total CO concentration inside;

[0108] According to formulas (1) to (8), the maximum voltage change rate calculated in a short period of time after 15s is DV = 0.87, that is, when short-circuit detection is performed, the maximum voltage change rate calculated within a period of time is selected for judgment;

[0109] The difference in precipitation time between VOC and C2H5F is 52s, VOC The total concentration C VOC About 2500ppm, the precipitation time difference between CO and C2H5F For 45s, CO The total concentration C CO About 300ppm.

[0110] Step 4: Substitute the voltage value collected in real time into the voltage criterion. If the voltage criterion is met, the battery is abnormal and the process goes to step 5. If the voltage criterion is not met, the process goes back to step 2.

[0111] When the voltage value collected in real time is less than the battery voltage safety threshold, that is, it satisfies formula (9), it is considered that the battery is abnormal:

[0112] V<R1 (9)

[0113] Step 5: Substitute the maximum voltage change rate, total VOC concentration, and total CO concentration obtained in step 3 into the comprehensive criterion. If the comprehensive criterion is met, the output indicates that the battery has an internal short circuit fault and an alarm signal is issued; if it is not met, other fault detection is prompted, specifically:

[0114] The maximum value of the voltage change rate, the total VOC concentration, and the total CO concentration obtained in step 3 are compared with the corresponding thresholds. If they are all higher than the corresponding thresholds, that is, if equations (10) to (12) are satisfied, it is considered that the battery has an internal short circuit fault and an alarm signal is issued.

[0115] DV>R2 (10)

[0116] C VOC >R3 (11)

[0117] C CO >R4 (12).

[0118] Steps 4 and 5 are implemented as follows:

[0119] According to the initialization threshold results in step 1 of this embodiment, i.e., R1=2V, R2=0.5, R3=250ppm, R4=30ppm, and the real-time collected battery voltage, the voltage change rate obtained in step 3, the total VOC concentration and the total CO concentration, the following internal short circuit detection is implemented:

[0120] First, by Figure 3 It can be seen that the battery voltage suddenly drops to 1.2 V at 15 s, which is lower than 2 V. That is, equation (9) is satisfied, so it is considered that the battery is abnormal.

[0121] Secondly, within the short time when the battery is judged to be abnormal, the maximum rate of change of the battery voltage 0.87 is greater than 0.5, that is, equation (10) is satisfied. At the same time, within the time difference, 2500ppm is much greater than 25ppm and 300ppm is much greater than 30ppm, that is, equations (11) and (12) are satisfied at the same time.

[0122] Finally, it is reliably determined that the battery has a short circuit fault and an alarm is issued.

[0123] The applicant of the present invention has made a detailed explanation and description of the implementation examples of the present invention in conjunction with the drawings in the specification. However, those skilled in the art should understand that the above implementation examples are only preferred implementation schemes of the present invention, and the detailed description is only to help readers better understand the spirit of the present invention, but not to limit the scope of protection of the present invention. On the contrary, any improvements or modifications based on the inventive spirit of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for setting the detection criteria for internal short circuit of a lithium-ion battery, through N puncture short circuit experiments, determines the detection criteria threshold based on multi-signal fusion, and realizes the initialization of the detection criteria threshold, which is characterized by: The method comprises the following steps: Step 1: Use the puncture integrated machine to conduct an internal short-circuit test on the lithium-ion battery. During the experiment, the battery voltage signal and VOC, CO and C2H5F gas signals are collected in real time, and the precipitation time of the gas signal and the concentration change after precipitation are recorded; Step 2: Calculate the voltage change rate, VOC and C2H5F precipitation time difference Δt for each test based on the experimental data VOC-C2H5F , time difference Δt VOC-C2H5F Total VOC concentration, CO and C2H5F precipitation time difference Δt CO-C2H5F , time difference Δt CO-C2H5F Total CO concentration inside; Step 3: Filter the voltage change rate threshold, VOC total concentration threshold, and CO total concentration threshold from the calculation results of step 2 to initialize the detection criterion threshold.

2. The method for setting internal short circuit detection criteria of a lithium-ion battery according to claim 1, characterized in that: Said N≥1000.

3. The method for setting internal short circuit detection criteria of a lithium-ion battery according to claim 1, characterized in that: In step 1, the puncture machine uses a steel needle with a diameter of 6 mm, sets the puncture speed to 30 mm / s and the puncture stroke to 300 mm, uses a clamp to fix the battery in the center of the puncture machine, runs the puncture machine, punctures the battery, and the steel needle stays in the battery for 600 seconds before being pulled out.

4. The method for setting internal short circuit detection criteria of a lithium-ion battery according to claim 1, characterized in that: In step 1, the voltage signal is collected through the voltage sensor, the gas signal is collected through the gas sensor, and the precipitation time of the gas signal and the concentration change after precipitation are recorded.

5. The method for setting internal short circuit detection criteria of a lithium-ion battery according to claim 4, characterized in that: The voltage sensor is directly connected to the positive and negative ears of the battery, and the gas sensor is connected to one end of the gas pipe, and the other end is close to the surface of the battery.

6. The method for setting internal short circuit detection criteria of a lithium-ion battery according to claim 1, characterized in that: In step 2, the voltage change rate DV is calculated as: In the formula, V represents the battery voltage, k represents the voltage sampling point number, and t represents the sampling interval. The calculation formula is: In the formula, f v is the voltage sampling frequency; The calculation formula for the time difference between VOC and C2H5F precipitation is: In the formula, is the precipitation time of C2H5F, t VOC is the VOC precipitation time, which indicates the time corresponding to the gas concentration changing from zero to a certain value; The calculation formula for the total VOC concentration is: In the formula, C VOC is the total VOC concentration, c VOC (k) is the VOC gas concentration at time k, n VOC yes The number of VOC sampling points within is calculated as follows: In the formula, f g is the gas sampling frequency; Similarly, the calculation formula for the difference in precipitation time between CO and C2H5F and the total CO concentration is: Where, t CO is the CO evolution time, C CO is the total CO concentration, c CO (k) is the CO gas concentration at time k, n CO yes The number of CO sampling points within is calculated as follows:

7. The method for setting internal short circuit detection criteria of a lithium-ion battery according to claim 1, characterized in that: In step 3, the minimum voltage change rate, total VOC concentration and total CO concentration calculated values ​​in step 2 are screened and set as the voltage change rate threshold, the VOC total concentration threshold and the CO total concentration threshold to initialize the detection criterion threshold.

8. A method for verifying the criterion for detecting internal short circuit of a lithium-ion battery, which verifies whether the criterion can meet the detection requirements by a puncture short circuit test, and is characterized by: The detection criterion verification method comprises the following steps: Step 1: setting a voltage safety threshold, a voltage sampling frequency, and a gas sampling frequency, and initializing a voltage change rate threshold, a VOC total concentration threshold, and a CO total concentration threshold using the detection criterion setting method described in any one of claims 1 to 7; Step 2: Use the puncture integrated machine to conduct an internal short-circuit test on the lithium-ion battery. During the experiment, the battery voltage signal and VOC, CO and C2H5F gas signals are collected in real time, and the precipitation time of the gas signal and the concentration change after precipitation are recorded; Step 3: Calculate the voltage change rate, VOC and C2H5F precipitation time difference Δt VOC-C2H5F , time difference Δt VOC-C2H5F Total VOC concentration, CO and C2H5F precipitation time difference Δt CO-C2H5F , time difference Δt CO-C2H5F Total CO concentration inside; Step 4: Based on the voltage criterion and the comprehensive criterion, compare the voltage value, the calculated value in step 3 and the threshold value corresponding to step 1, and verify whether the criterion can meet the detection requirements based on whether it can make a correct judgment on the internal short circuit of the lithium-ion battery.

9. A method for detecting internal short circuit of a lithium-ion battery, characterized in that: The detection method comprises: Step 1: Set the voltage safety threshold, voltage sampling frequency, and gas sampling frequency, and respectively use the detection criterion setting method described in any one of claims 1 to 7 and the detection criterion verification method described in claim 8 to initialize and verify the voltage change rate threshold, VOC total concentration threshold, and CO total concentration threshold; Step 2: Collect voltage signals and gas signals in real time during battery operation, and record the precipitation time of the gas signal and the concentration change after precipitation; Step 3: Calculate the voltage change rate, VOC and C2H5F precipitation time difference Δt VOC-C2H5F , time difference Δt VOC-C2H5F Total VOC concentration, CO and C2H5F precipitation time difference Δt CO-C2H5F , time difference Δt CO-C2H5F Total CO concentration inside; Step 4: Substitute the voltage value collected in real time into the voltage criterion. If the voltage criterion is met, the battery is abnormal and the process goes to step 5. If the voltage criterion is not met, the process goes back to step 2. Step 5: Substitute the maximum voltage change rate, total VOC concentration, and total CO concentration obtained in step 3 into the comprehensive criterion. If the comprehensive criterion is met, an internal short circuit fault of the battery is output and an alarm signal is issued; if it is not met, other fault detection is prompted.

10. The method for detecting internal short circuit of a lithium-ion battery according to claim 9, characterized in that: The voltage safety threshold is set according to the inherent voltage range of the lithium-ion battery; The voltage sampling frequency and the gas sampling frequency are set according to the sensor standard.

11. The method for detecting internal short circuit of a lithium-ion battery according to claim 9, characterized in that: The battery voltage safety threshold, voltage change rate threshold, VOC total concentration threshold, and CO total concentration threshold are denoted as R1, R2, R3, and R4 respectively; In step 4, when the voltage value collected in real time is less than the battery voltage safety threshold, that is, it satisfies the voltage criterion of formula (9), it is considered that the battery is abnormal: V<R1 (9).

12. The method for detecting internal short circuit of a lithium-ion battery according to claim 11, characterized in that: In step 5, the maximum value of the voltage change rate, the total VOC concentration, and the total CO concentration obtained in step 3 are compared with the corresponding thresholds. If they are all higher than the corresponding thresholds, that is, the comprehensive criteria of equations (10) to (12) are satisfied, it is considered that the battery has an internal short circuit fault and an alarm signal is issued. DV>R2 (10) C VOC >R3 (11) C CO >R4 (12)。 13. The method for detecting internal short circuit of a lithium-ion battery according to claim 12, characterized in that: R1 is 2V, and the voltage sampling frequency and gas sampling frequency are both 1Hz.

14. The method for detecting internal short circuit of a lithium-ion battery according to claim 13, characterized in that: R2 is 0.5, R3 is 250ppm, and R4 is 30ppm.

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