Early warning method for lithium battery thermal runaway early stage with vibration parameters as leading and coupling of multiple parameters

Abstract

The invention provides a lithium battery thermal runaway early-stage early-warning method with vibration parameters as a leading and coupling of various parameters, and the method comprises the following steps: S1, arranging related sensors, and monitoring the vibration, temperature and expansive force of a lithium battery; s2, performing a thermal runaway experiment on the lithium battery in the S1, monitoring historical data of the three key indexes, and obtaining related parameters of the lithium battery; s3, inputting the lithium battery vibration data in the S2 into a Transform model, predicting a predicted value at the next moment, and calculating predicted vibration RMS ', a vibration peak factor F' and a displacement difference D; s4, determining an alarm threshold value of the lithium battery of the model in combination with the relevant parameters of the lithium battery in the S2; and S5, comparing the data in the S3 with a set alarm threshold value, and judging a thermal runaway early warning level. According to the method, vibration parameters, temperature and expansive force can complement each other, and the lithium battery thermal runaway process is comprehensively monitored.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium battery thermal runaway, and particularly relates to a lithium battery thermal runaway early stage warning method dominated by vibration parameters and coupling multiple parameters. BACKGROUND

[0002] Lithium batteries are widely used in electric vehicles, energy storage power stations, consumer electronics and other fields as an efficient and portable energy storage device. However, the problem of lithium battery thermal runaway seriously threatens its safety in use and becomes a key factor restricting its further large-scale application.

[0003] When lithium battery thermal runaway occurs, a series of violent chemical reactions will occur inside the battery, causing the temperature to rise sharply, up to 800℃ or more, and releasing a large amount of flammable and toxic gases. These gases not only cause serious environmental pollution, but also may cause explosions and fires, posing a great threat to human life and property safety. Therefore, early warning of lithium battery thermal runaway is of great significance. Early warning can timely issue a warning when the battery thermal runaway has not developed to an uncontrollable stage, reminding users to take appropriate measures, thereby effectively avoiding the occurrence of safety accidents and reducing losses.

[0004] Currently, although the traditional lithium battery thermal runaway monitoring and warning method also uses multiple sensor data coupling, the coupling process generally does not use vibration sensor data due to external environmental interference factors. However, the battery thermal runaway stage is sensitive to vibration due to the internal stage reaction, which can reveal the changes inside the battery to a certain extent, and has correspondence and stage compared to traditional parameters. Therefore, coupling vibration data for thermal runaway warning can greatly improve the accuracy and reliability of the warning. SUMMARY

[0005] In order to solve the problems in the prior art, the application provides a lithium battery thermal runaway early stage warning method dominated by vibration parameters and coupling multiple parameters.

[0006] In order to achieve the above purpose, the application provides the following technical scheme:

[0007] A lithium battery thermal runaway early stage warning method dominated by vibration parameters and coupling multiple parameters, comprising the following steps:

[0008] S1: laying related sensors for monitoring three key indicators of lithium batteries; the three key indicators are vibration, temperature and swelling force;

[0009] S2: performing a thermal runaway experiment on the lithium battery in S1, monitoring historical data of three key indicators through the related sensors arranged in S1, and calculating to obtain the lithium battery related parameters; the lithium battery related parameters are: μ RMS , σ RMS , μ F , σ F , μ T and σ T ; μ RMS represents the vibration RMS mean value, σ RMS represents the vibration RMS standard deviation; μ F represents the vibration peak factor F mean value; σ F represents the vibration peak factor F standard deviation; μ T represents the temperature change slope mean value; σ T represents the temperature change slope standard deviation;

[0010] S3: inputting the vibration data of the lithium battery of the same type in S2 into the Transformer model, based on the Transformer model, setting the current time as t-1, predicting the next time prediction value of the lithium battery vibration data, and calculating the predicted vibration RMS', the vibration peak factor F' and the displacement difference D according to the predicted data;

[0011] S4: combining the lithium battery related parameters in S2 to determine the alarm threshold of the lithium battery of the same type;

[0012] S5: comparing the data in S3 with the set alarm threshold, and judging the thermal runaway early warning level according to the comparison result.

[0013] Further, step S3 includes the following steps:

[0014] S3.1: inputting the monitored vibration data into the Transformer model, and giving the next time prediction value by the trained Transformer model; setting the vibration data of the lithium battery as: W t-1 ={x1, x2, x3, …, x i , …, x t-2 , x t-1}, wherein x i represents the Y-axis displacement peak value at the i-th time point; after the Transformer model prediction, it is assumed that the prediction value at t time is x t ; then W' t ={x1, x2, x3, …, x i , …, x t-2 , x t-1 , x t};

[0015] S3.2: According to the predicted data, calculate the predicted vibration RMS', the vibration peak factor F' and the displacement difference D;

[0016] The formula of the predicted vibration RMS' is:

[0017]

[0018] In formula (1), n represents the number of data points in the prediction result W'; x t represents the i-th data value in the prediction result W'; i t

[0019] The formula of the vibration peak factor F' is:

[0020]

[0021] In formula (2), x max represents the maximum data value in the prediction result W'; t

[0022] The formula of the displacement difference D is:

[0023]

[0024] In formula (3), x t represents the predicted value of the vibration data at time t; x t-10 represents the predicted value of the vibration data at time t-10.

[0025] Further, step S4 includes the following steps:

[0026] S4.1: Vibration data threshold determination;

[0027] The vibration data threshold is set as: μ RMS +kσ RMS ; in the formula, k represents an adjustable coefficient, and the value range is between 1-3;

[0028] S4.2: Temperature data threshold determination;

[0029] The temperature data threshold is set as: μ T +mσ T ; in the formula, m represents an adjustable coefficient, and the value range is between 1-2;

[0030] S4.3: Vibration peak factor threshold determination;

[0031] The vibration peak factor threshold is set as: μ F +cσ F ; in the formula, c is an adjustable coefficient, and the value range is generally between 1-2. ​​​

[0032] Further, the following judgment criteria are included in step S5:

[0033] When RMS' > μ RMS +kσ RMS , and the duration reaches t1, a level I early warning is triggered; the meaning of level I early warning is that the battery thermal runaway alarm system judges that the battery is in an early abnormal stage, reminding relevant personnel to suspend the use of lithium batteries, check and eliminate potential risks;

[0034] When F' > μ F +cσ F , and the lithium battery temperature slope > μ T +mσ T , a level II early warning is triggered; the meaning of level II early warning is that the battery thermal runaway alarm system judges that the battery is gradually out of control, and immediately eliminates all heat sources and strengthens battery heat dissipation;

[0035] When RMS' > μ RMS +kσ RMS , the lithium battery temperature slope > μ T +mσ T , the displacement difference D > D thresh , and the expansion force slope is greater than the set threshold, a level III early warning is triggered; the meaning of level III early warning is that the battery thermal runaway alarm system judges that the lithium battery is close to opening the valve, which is extremely dangerous, and reminds relevant personnel to evacuate in time.

[0036] Further, in step S1, the vibration data is obtained by monitoring the vibration sensor fixed on the side of the lithium battery, the vibration measured direction is the lateral direction of the battery, and the peak value of the displacement of the battery along the Y axis is obtained; the temperature data is obtained by monitoring the thermocouple attached to the surface of the lithium battery; the expansion force data is obtained by monitoring the pressure sensor fixed on the mold of the lithium battery.

[0037] Further, in step S2, the lithium battery is a 314Ah lithium iron phosphate battery with a state of charge of 75%, and the numerical values of the lithium battery related parameters are: μ RMS = 0.0018 mm, σ RMS = 0.0007 mm, μ F = 1.0594, σ F = 0.0853, μ T = 0.0515℃ / s, σ T = 0.0427℃ / s.

[0038] Further, the relative difference between the predicted value and the actual value is calculated to determine whether the predicted value x t is reliable;

[0039] The formula of the relative difference is:

[0040]

[0041] In the formula, x r t represents the true value of the vibration data at time t (i.e., the peak value of Y-axis displacement) ; x t represents the predicted value of the vibration data at time t;

[0042] When Diff t is greater than 10%, it indicates that W' t The predicted value x t at time t is suspicious data, which is not reliable and is no longer used for subsequent thermal runaway early warning;

[0043] When Diff t is less than or equal to 10%, it is reliable, the displacement difference D is continued to be calculated, and is used for subsequent thermal runaway early warning.

[0044] The beneficial effects that can be achieved by using the above technical content are:

[0045] With the high sensitivity of the vibration parameter to the subtle changes in the lithium battery, abnormal signals can be quickly captured when the thermal runaway is in the early stage, such as the decomposition of the solid electrolyte interface film and the slight deformation of the electrode material. Through multi-parameter coupling (joint action) analysis, the problem of high false alarm rate and high false alarm rate of single parameter susceptible to environmental interference can be effectively overcome. In addition, the vibration parameter and the temperature, expansion force and other parameters are mutually complementary, which can comprehensively monitor the thermal-power-chemical multi-field coupling changes in the thermal runaway process of the lithium battery, provide rich information support for emergency decision-making, and help to take effective measures in time to reduce the risk of safety accidents caused by lithium battery thermal runaway. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is a flowchart of the method;

[0047] Figure 2 is a diagram of various data measured in the actual measurement of the method. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the present application will be described in detail below with reference to the drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0049] As Figure 1 shown, a lithium battery thermal runaway early stage early warning method dominated by vibration parameters and coupled with multiple parameters includes the following steps:

[0050] S1: Lay related sensors for monitoring three key indicators of lithium batteries;

[0051] Among them, the three key indicators are: vibration, temperature and expansion force.

[0052] The vibration data is obtained by monitoring the vibration sensor fixed on the side of the lithium battery. The measured direction of the vibration is perpendicular to the side of the battery pack. The vibration data is represented as the peak value of the Y-axis displacement. The Y-axis is explained as perpendicular to the side of the battery pack. The measured vibration data is input into the lithium battery management system BMS.

[0053] The temperature data is obtained by monitoring the thermocouple attached to the surface of the lithium battery. The measured temperature data is input into the lithium battery management system BMS.

[0054] The expansion force data is obtained by monitoring the pressure sensor fixed on the lithium battery mold. The lithium battery expands and presses the pressure sensor to generate expansion force data. The measured expansion force data is input into the lithium battery management system BMS.

[0055] S2: Perform thermal runaway experiment on the lithium battery in S1. Monitor the historical data of the three key indicators through the related sensors arranged in S1. Calculate the relevant parameters of the lithium battery.

[0056] Specifically, taking a 314Ah lithium iron phosphate battery with a state of charge of 75% as an example, a 1000W heating plate with the same size as the battery is used as a heating source to heat the lithium battery and cause it to undergo thermal runaway. The specific data obtained by statistics is shown in the following table.

[0057] Table 1 Relevant parameters of 314Ah lithium iron phosphate battery with state of charge of 75%

[0058]

[0059] Among them, the relevant parameters of the lithium battery obtained are: mean μ RMS = 0.0018mm, standard deviation σ RMS = 0.0007mm; mean μ F = 1.0594, standard deviation σ F = 0.0853, temperature change slope mean μ T = 0.0515℃ / s, temperature change slope standard deviation σ T = 0.0427℃ / s.

[0060] S3: Input the vibration data of the same type of lithium battery in S2 into the Transformer model. Based on the Transformer model, set the current time as t-1 time, predict the next time prediction value of the lithium battery vibration data, and calculate the predicted vibration RMS', vibration peak factor F' and displacement difference D according to the predicted data.

[0061] S3 specifically comprises the following steps:

[0062] S3.1: input the monitored vibration data into the Transformer model, and give the predicted value of the next time by the trained Transformer model.

[0063] Suppose the vibration data of the lithium battery is: W t-1 ={x1, x2, x3, …, x i , …, x t-2 , x t-1}, where x i represents the Y-axis displacement peak value at the i-th time point, and the Y-axis is perpendicular to the side surface of the battery pack. After the Transformer model prediction, suppose the predicted value at time t is x t .

[0064] For example, suppose the actual 10s vibration time series data is: W t-1 ={0.00158, 0.00157, 0.00153, 0.00155, 0.00159, 0.0015, 0.00154, 0.00162, 0.00162, 0.00164}, and the Transformer model prediction outputs the predicted value of the next time, i.e. x t =0.00170.

[0065] Then, the prediction result W t '={0.00158, 0.00157, 0.00153, 0.00155, 0.00159, 0.0015, 0.00154, 0.00162, 0.00162, 0.00164, 0.00170}, unit: mm.

[0066] S3.2: According to the predicted data, calculate the predicted vibration RMS', vibration peak factor F' and displacement difference D.

[0067] The formula of the predicted vibration RMS' is:

[0068]

[0069] In formula (1), n represents the number of data points in the prediction result W' t ; x i represents the i-th data value in the prediction result W' t .

[0070] The formula of the vibration peak factor F' is:

[0071]

[0072] In equation (2), x max The prediction result W' is represented by t The maximum data value in; for example: W' t The maximum value in the range {0.00158, 0.00157, 0.00153, 0.00155, 0.00159, 0.0015, 0.00154, 0.00162, 0.00162, 0.00164, 0.00170} is 0.00170.

[0073] Calculate the relative difference between the predicted value and the actual value, and determine the predicted value x. t Is it credible?

[0074] The formula for relative difference is:

[0075]

[0076] In the formula, x r ,t represents the true value of the vibration data (i.e., the peak value of the Y-axis displacement) at time t; x t This represents the predicted value of the vibration data at time t;

[0077] When Diff t When it is greater than 10%, it indicates that W' t The predicted value x at time t t This data is considered suspicious and unreliable; it will no longer be used for subsequent thermal runaway early warning.

[0078] When Diff t If the value is less than or equal to 10%, it is considered reliable, and the displacement difference D can be calculated further.

[0079] The formula for the displacement difference D is:

[0080]

[0081] In equation (3), x t x represents the predicted value of the vibration data at time t; t-10 This represents the predicted value of the vibration data at time t-10.

[0082] Vibration RMS, peak vibration factor F, and displacement difference D characterize vibration signals from three dimensions: energy accumulation, impact characteristics, and trend changes, respectively, and are strongly correlated with physical phenomena such as microstructural damage, stress release, and morphological abrupt changes during thermal runaway.

[0083] S4: Combine the relevant parameters of the lithium battery in S2 to determine the alarm threshold of this model of lithium battery.

[0084] S4 specifically includes the following steps:

[0085] S4.1: Vibration data threshold determination.

[0086] The vibration data threshold is set as: μ RMS +kσ RMS , wherein k represents an adjustable coefficient, and the value range is between 1-3.

[0087] S4.2: Temperature data threshold determination.

[0088] The temperature data threshold is set as: μ T +mσ T , wherein m represents an adjustable coefficient, and the value range is between 1-2.

[0089] S4.3: Vibration peak factor threshold determination.

[0090] The vibration peak factor threshold is set as: μ F +cσ F , wherein c is an adjustable coefficient, and the value range is generally between 1-2.

[0091] S5: Comparing the data in S3 with the set alarm threshold, and judging the thermal runaway early warning level according to the comparison result.

[0092] When the predicted vibration RMS' in S3> μ RMS +kσ RMS , and the duration reaches t1 (such as 10s), level I early warning is triggered; the meaning of level I early warning is that the battery thermal runaway alarm system judges that the battery is in an early abnormal stage, reminds the relevant personnel to suspend the use of lithium battery, checks and eliminates the potential risk;

[0093] When the vibration peak factor F'> μ F +cσ F , and the lithium battery temperature slope> μ T +mσ T , level II early warning is triggered; the meaning of level II early warning is that the battery thermal runaway alarm system judges that the battery is gradually out of control, and immediately eliminates all heat sources and strengthens the battery heat dissipation.

[0094] When the vibration peak factor F'> μ F +cσ F , the lithium battery temperature slope> μ T +mσ T , the displacement difference D> D thresh (set as 0.0002mm / 10s), and the expansion force slope exceeds 24N / s, it is considered as sharp rise, and level III early warning is triggered. The meaning of level III early warning is that the battery thermal runaway alarm system judges that the lithium battery is close to opening the valve, and the danger is extremely high, reminding the relevant personnel to evacuate in time.

[0095] Taking the 314Ah lithium iron phosphate battery with 75% state of charge in S2 as an example, the actual monitored data are shown below. Figure 2 ,from Figure 2 As can be seen, the warning time for Level I is 363s; for Level II it is 678s; and for Level III it is 916s. This solution can provide timely warnings before the opening time of the lithium battery valve, with a time difference of more than 2 minutes, which has a good warning effect and reduces the risk of thermal runaway caused by lithium battery.

[0096] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for early warning of thermal runaway in a lithium battery in a stage dominated by a vibration parameter and coupled with multiple parameters, characterized in that, Comprise the following steps: S1: lay the relevant sensor, for monitoring the three key indicators of lithium battery; Three key indicators are: vibration, temperature and expansion force; S2: performing a thermal runaway experiment on the lithium battery in S1, monitoring historical data of three key indicators through the related sensors arranged in S1, and calculating to obtain the lithium battery related parameters; the lithium battery related parameters are: μ RMS , σ RMS , μ F , σ F , μ T and σ T ; μ RMS represents the vibration RMS mean, σ RMS represents the vibration RMS standard deviation; μ F represents the vibration peak factor F mean; σ F represents the vibration peak factor F standard deviation; μ T represents the temperature change slope mean; σ T represents the temperature change slope standard deviation; S3: the same type lithium battery vibration data in S2 is input into the Transformer model, based on the Transformer model, set the current time as t-1 time, predict the next time prediction value of the lithium battery vibration data, and calculate the predicted vibration RMS', vibration peak factor F' and displacement difference D according to the predicted data; S4: combine the lithium battery related parameters in S2 to determine the alarm threshold of the lithium battery of this type; S5: compare the data in S3 with the set alarm threshold, and judge the thermal runaway early warning level according to the comparison result. 2.The early warning method of thermal runaway in the early stage of lithium battery with vibration parameters as the leading and multiple parameters coupling according to claim 1, characterized in that, Step S3 includes the following steps: S3.1: input the monitored vibration data into the Transformer model, and give the predicted value of the next moment by the trained Transformer model; set the vibration data of the lithium battery as: W t-1 = {x1, x2, x3, …, x i , …, x t-2 , x t-1}, wherein x i represents the Y-axis displacement peak value at the i-th time point, i.e. the vibration data, and the Y-axis is explained as perpendicular to the lateral direction of the battery pack; after the prediction by the Transformer model, it is assumed that the predicted value at t moment is x t ; then W' t = {x1, x2, x3, …, x i , …, x t-2 , x t-1 , x t}. S3.2: according to the predicted data, calculate the predicted vibration RMS', vibration peak factor F' and displacement difference D; The formula of predicted vibration RMS' is: In formula (1), n represents the number of data points in the prediction result W' t i t i-th data value in the prediction result W'​​ The formula of vibration peak factor F' is: In formula (2), x max represents the maximum data value in the prediction result W′ t ​ The formula of displacement difference D is: In formula (3), x t represents the predicted value of the vibration data at time t; x t-10 represents the predicted value of the vibration data at time t-10. 3.The early warning method of thermal runaway in the early stage of lithium battery with vibration parameters as the leading and multiple parameters coupling according to claim 2, characterized in that, Step S4 includes the following steps: S4.1: vibration data threshold determination; The vibration data threshold is set as μ RMS +kσ RMS ; wherein k represents an adjustable coefficient, and the value range of k is between 1 and 3. S4.2: temperature data threshold determination; The temperature data threshold is set as μ + mσ T + mσ T wherein m represents an adjustable coefficient, and the value range of m is between 1 and 2. S4.3: vibration peak factor threshold determination; The shock peak factor threshold is set as μ F + cσ F ; where c is an adjustable coefficient, generally in the range of 1-2.

4. The early warning method of thermal runaway in the early stage of lithium battery dominated by vibration parameters and coupled with multiple parameters according to claim 3, characterized in that, Step S5 includes the following judgment standards: when RMS' > μ RMS + kσ RMS , and the duration reaches t1, a level I early warning is triggered; the meaning of level I early warning is that the battery thermal runaway alarm system judges that the battery is in an early abnormal stage, reminds relevant personnel to suspend the use of lithium batteries, checks and eliminates potential risks; When F' > μ F + cσ F , and the lithium battery temperature slope > μ T + mσ T , trigger a level II early warning; The meaning of II level early warning is: the battery thermal runaway alarm system judges that the battery is gradually out of control, immediately eliminates all heat sources, and strengthens the battery heat dissipation; when RMS' > μ RMS +kσ RMS , the lithium battery temperature slope > μ T +mσ T , the displacement difference D > D thresh , and the expansion force slope is greater than a set threshold, a level III early warning is triggered; the meaning of the level III early warning is that the battery thermal runaway alarm system judges that the lithium battery is close to opening the valve, the danger is extremely high, and reminds the relevant personnel to evacuate in time.

5. The early warning method of thermal runaway in the early stage of lithium battery dominated by vibration parameters and coupled with multiple parameters according to claim 4, characterized in that, In step S1, the vibration data is obtained by monitoring the vibration sensor fixed on the side of the lithium battery, the measured direction of vibration is the lateral direction of the battery, and the peak value of the displacement along the Y axis of the battery is obtained; The temperature data is obtained by monitoring the thermocouple attached to the surface of the lithium battery; The expansion force data is obtained by monitoring the pressure sensor fixed on the mold of the lithium battery.

6. The early warning method of thermal runaway in the early stage of lithium battery dominated by vibration parameters and coupled with multiple parameters according to claim 5, characterized in that, The lithium battery in step S2 is a 314 Ah lithium iron phosphate battery at 75% state of charge. The values of the lithium battery related parameters are: μ RMS = 0.0018 mm, σ RMS = 0.0007 mm, μ F = 1.0594, σ F = 0.0853, μ T = 0.0515 °C / s, σ T = 0.0427 °C / s.

7. The early warning method for the early stage of lithium battery thermal runaway dominated by vibration parameters and coupled with multiple parameters according to claim 6, characterized in that, The predicted value is calculated with the actual value to calculate the relative difference, judge the predicted value x t Whether it is reliable; The formula of relative difference is: In the formula, x r t represents the true value of the vibration data (i.e. Y-axis displacement peak value) at time t; x t represents the predicted value of the vibration data at time t. When Diff t is greater than 10%, it indicates that W' t The predicted value x t at time t is suspicious data, which is not trusted and is no longer used for subsequent thermal runaway early warning. When Diff t is less than or equal to 10%, it is considered valid, and the displacement difference D is continued to be calculated and used for subsequent thermal runaway warning.

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