A method for determining the safety boundary of arc induced by battery thermal runaway ejection

Abstract

The present invention provides a method for determining the safety boundary of an arc induced by jetting due to thermal runaway of a battery, which belongs to the field of battery safety technology. The method for determining the safety boundary of an arc induced by jetting due to thermal runaway of a battery comprises building an experimental platform for an arc induced by jetting due to thermal runaway of a battery; setting an operating range, conducting an arc induced by jetting due to thermal runaway of a battery, and obtaining critical conditions; calculating the arc ignition critical electric field strength based on an electric field strength calculation formula, converting the electric field strength into a voltage-electrode spacing relationship to obtain a safety boundary; adjusting the electrode placement height, and repeating the above steps to obtain the safety boundary of an arc induced by jetting due to thermal runaway of a battery at different electrode heights. The present invention provides a method for determining the safety boundary of an arc induced by jetting due to thermal runaway of a battery, which can solve the problem that the evaluation of electrical safety and the confirmation of the danger of arc induced during thermal runaway not only involve high-risk operations under high-temperature and high-pressure conditions, but also consume a lot of manpower and material resources.

Description

Technical Field

[0001] The present invention belongs to the field of battery safety technology, and in particular relates to a method for determining the safety boundary of an arc induced by ejection during thermal runaway of a battery. Background Art

[0002] Lithium-ion batteries have been widely used in electric vehicles, electrochemical energy storage, and other fields. In actual applications, due to problems such as electrical heating abuse, lithium-ion batteries may experience thermal runaway, accompanied by violent gas and solid ejection processes. Studies have shown that the ejected particles generated during the thermal runaway ejection process of ternary lithium-ion batteries can reduce the environmental breakdown voltage, causing arcing to occur or even occur multiple times. As a common electrical fault, arcing can persist at a voltage of 30V and the core temperature can instantly exceed 2000°C. The battery pack has many electrical connection points and usually has voltage conditions that can trigger arcing. If an arc fault is triggered by solid ejection during the battery thermal runaway process, it may further aggravate the thermal runaway process and pose a thermal threat to the normal batteries in the battery pack, making its hazards more urgent.

[0003] Currently, there is little research on arcing caused by thermal runaway ejection in lithium-ion batteries. Existing battery safety standards and test methods usually focus on basic battery performance indicators (such as capacity, charging rate, cycle life, etc.), while the assessment of electrical safety during thermal runaway and the dangers of arcing have not received sufficient attention and research. Testing each operating condition through experimental methods requires a lot of manpower and material resources, and also involves high-risk operations under high temperature and high pressure conditions. Therefore, without relying on complex experiments, there is still a lack of a simple and effective method to determine the safe voltage and electrical distance for the breakdown arc caused by thermal runaway ejection in batteries. Summary of the Invention

[0004] In view of this, the present invention provides a method for determining the safety boundary of an arc caused by battery thermal runaway jetting, which can solve the problem that the evaluation of electrical safety in the thermal runaway process and the confirmation of the danger caused by the arc not only involve high-risk operations under high temperature and high pressure conditions, but also consume a lot of manpower and material resources.

[0005] The present invention is achieved in that:

[0006] The present invention provides a method for determining the safety margin of an arc triggered by ejection during thermal runaway of a battery, which includes the following specific steps:

[0007] S10: Build an experimental platform for battery thermal runaway ejection-induced arcing;

[0008] S20: Setting an operating range, conducting a battery thermal runaway ejection arc experiment in the battery thermal runaway ejection arc experiment platform, and obtaining critical conditions;

[0009] S30: Based on the electric field strength calculation formula, the critical electric field strength for arc initiation is calculated and converted into a voltage-electrode spacing relationship to obtain a safety margin;

[0010] S40: Adjust the electrode placement height, and repeat the above steps to obtain the safety margin of arc induced by battery thermal runaway ejection at different electrode heights.

[0011] On the basis of the above technical solution, the method for determining the safety boundary of a battery thermal runaway ejection-induced arc of the present invention can be further improved as follows:

[0012] The specific steps of building a battery thermal runaway ejection arc experimental platform include:

[0013] The first step is to connect the various components of the battery thermal runaway arc simulation experimental platform accordingly;

[0014] In the second step, the metal electrodes used to initiate the arc are arranged opposite each other above the battery exhaust valve, fixed with a clamp and connected to the power supply line.

[0015] Furthermore, the electrical signal acquisition in the battery thermal runaway ejection-induced arc experimental platform adopts a high-frequency acquisition device with communication and data storage functions.

[0016] Furthermore, the specific steps of setting the operating range and conducting a battery thermal runaway jet arc experiment in the battery thermal runaway jet arc experiment platform to obtain critical conditions include:

[0017] The first step is to set the voltage and electrode spacing research range based on the actual battery pack voltage and electrical component spacing data, and trigger battery thermal runaway through heating or overcharging;

[0018] The second step is to analyze the electrical signal data of the battery injection process obtained by the high-frequency acquisition equipment, and combine the instantaneous change rate of the voltage and current signals and the time window average to determine whether an arc has occurred;

[0019] In the third step, the above steps are repeated to obtain the arc occurrence conditions at different voltages and electrode spacings, and to extract the critical conditions for arc initiation.

[0020] Furthermore, the instantaneous change rate thresholds of the voltage and current signals are obtained through experimental measurements.

[0021] Furthermore, the time window is set to 1-2 times of the sampling interval.

[0022] Furthermore, the specific steps of calculating the arc-starting critical electric field strength based on the electric field strength calculation formula, converting it into a voltage-electrode spacing relationship, and obtaining the safety margin include:

[0023] The first step is to establish a theoretical model of arc induced by battery ejecta and analyze the boundary conditions of electric field intensity;

[0024] In the second step, based on the electric field strength calculation formula and boundary conditions, combined with the critical arcing conditions, the voltage-electrode spacing relationship is obtained to obtain the safety margin.

[0025] Furthermore, in the step of arranging the metal electrodes for initiating the arc opposite to each other above the battery exhaust valve, fixing them with a clamp and connecting them to the power supply circuit:

[0026] The metal electrode is made of copper or tungsten with a high melting point, and the fixture is a rigid fixture provided with insulation isolation to prevent errors caused by violent battery ejection, such as electrode shaking or falling off.

[0027] Furthermore, referring to the actual battery pack voltage and electrical component spacing data, setting the voltage and electrode spacing research range, and triggering battery thermal runaway by heating or overcharging include the following specific steps:

[0028] The experimental working condition starts from the lower limit of the electrode spacing setting, and adopts the dichotomy method to test from the upper limit of the set voltage, so as to efficiently approach the most stringent arcing critical condition and avoid the omission of working conditions that affects the accuracy of the safety boundary result.

[0029] Furthermore, the specific steps of establishing a theoretical model of arc induced by battery ejecta include:

[0030] Combined with the arc phenomenon and arc signal changes recorded in the experiment, it was observed that the arc had obvious stage characteristics of occurrence (voltage dropped from the baseline value) - persistence (voltage remained unchanged or changed slightly) - disappearance (voltage rose to the baseline value). It was assumed that the high-speed ejecta that triggered the arc was a uniform particle cluster passing through the middle of the electrode electric field. A theoretical model of battery ejecta-induced arc was established based on the high-speed ejecta that triggered the arc, and the boundary conditions of the electric field intensity during the displacement process of the particle cluster-induced arc were obtained.

[0031] Compared with the prior art, the method for determining the safety margin of arc triggered by battery thermal runaway ejection provided by the present invention has the following beneficial effects:

[0032] (1) The critical arcing conditions were obtained by conducting experiments on arc induced by ejection during battery thermal runaway. The boundary conditions were obtained based on the theoretical model of arc induced by ejection. Then, the voltage-electrode spacing relationship was obtained by calculating the electric field strength, and the safety boundary of arc induced by ejection during battery thermal runaway was obtained, filling the gap in the field method.

[0033] (2) This method effectively reduces the cost of battery thermal runaway experimental testing, and the safety margin obtained can provide a reference for the electrical safety design of the battery pack, such as the setting of electrical gaps at different voltage levels within the battery system. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0035] Figure 1 An operational flow chart of a method for determining a safety margin of an arc induced by a battery thermal runaway ejection;

[0036] Figure 2 Schematic diagram of an experimental setup for determining the safety margin of arc induced by ejection during thermal runaway of a battery.

[0037] Figure 3 Experimental data and theoretical model of arc induced by ejecta from battery thermal runaway, which is a method for determining the safety margin of arc induced by ejecta from battery thermal runaway;

[0038] Figure 4 This is a diagram showing the safety margin results when the electrode height is 3 cm, according to an embodiment of a method for determining the safety margin of an arc triggered by ejection during thermal runaway of a battery.

[0039] Figure 5 This is a diagram showing the safety margin results when the electrode height is 4 cm, according to an embodiment of a method for determining the safety margin of an arc triggered by ejection during thermal runaway of a battery.

[0040] Figure 6 This is a diagram showing the safety margin results when the electrode height is 5 cm, according to an embodiment of a method for determining the safety margin of an arc triggered by ejection during thermal runaway of a battery.

[0041] Figure 7 This is the relationship between the arc starting critical voltage and the electrode gap when the electrode height is 3, 4, and 5 cm. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0043] like Figure 1 FIG. 1 shows a first embodiment of a method for determining a safety margin of an arc triggered by ejection during thermal runaway of a battery provided by the present invention. In this embodiment, the method includes the following specific steps:

[0044] S10: Build an experimental platform for battery thermal runaway ejection-induced arcing;

[0045] S20: Set the operating range and conduct a battery thermal runaway jet arc experiment in the battery thermal runaway jet arc experiment platform to obtain critical conditions;

[0046] S30: Based on the electric field strength calculation formula, the critical electric field strength for arc initiation is calculated and converted into a voltage-electrode spacing relationship to obtain a safety margin;

[0047] S40: Adjust the electrode placement height, and repeat the above steps to obtain the safety margin of arc induced by battery thermal runaway ejection at different electrode heights.

[0048] Among them, in the above technical solution, the specific steps of building a battery thermal runaway ejection-induced arc experimental platform include:

[0049] The first step is to connect the various components of the battery thermal runaway arc simulation experimental platform accordingly;

[0050] In the second step, the metal electrodes used to initiate the arc are arranged opposite each other above the battery exhaust valve, fixed with a clamp and connected to the power supply line.

[0051] Furthermore, in the above technical solution, the electrical signal acquisition in the battery thermal runaway ejection-induced arc experimental platform adopts a high-frequency acquisition device (above 10kHz) with communication and data storage functions, such as an oscilloscope, a high-frequency probe, etc.

[0052] Furthermore, in the above technical solution, the operating range is set, and a battery thermal runaway jet arc experiment is carried out in a battery thermal runaway jet arc experiment platform. The specific steps for obtaining critical conditions include:

[0053] The first step is to set the voltage and electrode spacing research range based on the actual battery pack voltage and electrical component spacing data, and trigger battery thermal runaway through heating or overcharging;

[0054] The second step is to analyze the electrical signal data of the battery injection process obtained by the high-frequency acquisition equipment, and combine the instantaneous change rate of the voltage and current signals and the time window average to determine whether an arc has occurred;

[0055] In the third step, the above steps are repeated to obtain the arc occurrence conditions at different voltages and electrode spacings, and to extract the critical conditions for arc initiation.

[0056] Furthermore, in the above technical solution, the threshold values ​​of the instantaneous rate of change of the voltage and current signals are obtained by experimental measurement.

[0057] Furthermore, in the above technical solution, the time window is set to 1-2 times the sampling interval.

[0058] Among them, when the instantaneous change rate of the current or voltage signal or the average value in the time window meets the following conditions, it is determined that a breakdown arc event has occurred (either the instantaneous change rate or the average value conditions are met); otherwise, it is determined that there is no arc or abnormal interference:

[0059]

[0060] is the instantaneous rate of change of voltage; is the instantaneous rate of change of current; U 平均 is the average value of voltage; U 基准 is the reference value of voltage;

[0061] Furthermore, in the above technical solution, based on the electric field strength calculation formula, the critical electric field strength for arc initiation is calculated and converted into a voltage-electrode spacing relationship to obtain the safety margin. The specific steps include:

[0062] The first step is to establish a theoretical model of arc induced by battery ejecta and analyze the boundary conditions of electric field intensity;

[0063] In the second step, based on the electric field strength calculation formula and boundary conditions, combined with the critical arcing conditions, the voltage-electrode spacing relationship is obtained to obtain the safety margin.

[0064] Furthermore, in the above technical solution, in the step of arranging the metal electrodes for initiating the arc opposite to each other above the battery exhaust valve, fixing them with a clamp and connecting them to the power supply circuit:

[0065] The metal electrode is made of high-melting-point copper or tungsten, and the fixture is a rigid fixture with insulation isolation to prevent errors caused by violent battery ejection, such as electrode shaking or falling off.

[0066] Furthermore, in the above technical solution, referring to the actual battery pack voltage and electrical component spacing data, the voltage and electrode spacing research range is set, and the specific steps of triggering battery thermal runaway by heating or overcharging include:

[0067] The experimental working condition starts from the lower limit of the electrode spacing setting, and the binary method is used to test from the set voltage upper limit to efficiently approach the most stringent arcing critical conditions and avoid the omission of working conditions that affect the accuracy of the safety boundary results.

[0068] Furthermore, in the above technical solution, the specific steps of establishing a theoretical model of arc induced by battery ejecta include:

[0069] Combined with the arc phenomenon and arc signal changes recorded in the experiment, it was observed that the arc had obvious stage characteristics of occurrence (voltage dropped from the baseline value) - persistence (voltage remained unchanged or changed slightly) - disappearance (voltage rose to the baseline value). It was assumed that the high-speed ejecta that triggered the arc was a uniform particle cluster passing through the middle of the electrode electric field. A theoretical model of battery ejecta-induced arc was established based on the high-speed ejecta that triggered the arc, and the boundary conditions of the electric field intensity during the displacement process of the particle cluster-induced arc were obtained.

[0070]

[0071] Where E is the electric field strength, E c is the critical arcing field strength;

[0072] The voltage-electrode spacing relationship is obtained based on the critical electric field strength and boundary conditions, including the following steps:

[0073] Calculate the maximum electric field strength E between the positive and negative electrodes max , since the electric field intensity is the largest at the midpoint of the vertical midline, x is taken as 0, and the formula is as follows:

[0074]

[0075] For the electric field strength E that can generate an arc d ,satisfy:

[0076] E d ≥E c >E n ;

[0077] Among them, E n is the electric field strength under critical working conditions where no arc is generated;

[0078] Since the voltage U is proportional to the charge Q:

[0079] Q∝U;

[0080] Combining the above formulas, we can obtain the voltage condition for the battery ejecta to trigger an arc:

[0081]

[0082] Among them, U n , L n are the voltage and electrode distance under the critical working condition where no arc is generated, respectively.

[0083] According to the voltage condition of the arc triggered by the battery ejection, the safe voltage under different electrode spacing and the safe spacing under different voltage conditions can be obtained.

[0084] Among them, the safety boundaries of different electrode heights can be used for the height layout of battery pack top plates, electrical and metal components, etc., to guide the electrical safety protection design of the battery system.

[0085] like Figure 1-4 FIG. 2 shows a second embodiment of a method for determining a safety margin of an arc triggered by ejection during thermal runaway of a battery provided by the present invention. In this embodiment, the method includes the following specific steps:

[0086] S10: Build an experimental platform for battery thermal runaway ejection-induced arcing;

[0087] S20: Set the operating range and conduct a battery thermal runaway jet arc experiment in the battery thermal runaway jet arc experiment platform to obtain critical conditions;

[0088] S30: Based on the electric field strength calculation formula, the critical electric field strength for arc initiation is calculated and converted into a voltage-electrode spacing relationship to obtain a safety margin;

[0089] S40: Adjust the electrode placement height, and repeat the above steps to obtain the safety margin of arc induced by battery thermal runaway ejection at different electrode heights.

[0090] Among them, in the above technical solution, the specific steps of building a battery thermal runaway ejection-induced arc experimental platform include:

[0091] The first step is to connect the various components of the battery thermal runaway arc simulation experimental platform accordingly;

[0092] In the second step, the metal electrodes used to initiate the arc are arranged opposite each other above the battery exhaust valve. In this embodiment, the electrodes are arranged 3 cm above the exhaust valve; they are fixed with a clamp and connected to the power supply circuit.

[0093] Furthermore, in the above technical solution, the electrical signal acquisition in the battery thermal runaway ejection-induced arc experimental platform uses a high-frequency acquisition device (above 10kHz) with communication and data storage functions, such as an oscilloscope, a high-frequency probe, etc. In this embodiment, a 12.5kHz sampling frequency oscilloscope is used to collect arc signals, and a 400V / 20A DC regulated power supply is used to provide voltage conditions. At the same time, a resistor is connected in series to enhance the circuit load capacity.

[0094] Furthermore, in the above technical solution, the operating range is set, and a battery thermal runaway jet arc experiment is carried out in a battery thermal runaway jet arc experiment platform. The specific steps for obtaining critical conditions include:

[0095] The first step is to set the voltage and electrode spacing research range, starting from the lower limit of the electrode spacing, and experimentally test different voltages using a dichotomy method. In this embodiment, the voltage is set to 100V-400V, the electrode spacing is 3mm-7mm, and the tests are carried out sequentially starting from the 3mm and 400V working conditions; the battery thermal runaway is triggered by heating.

[0096] The second step is to analyze the electrical signal data of the battery injection process obtained by the high-frequency acquisition equipment, and combine the instantaneous change rate of the voltage and current signals and the time window average to determine whether an arc has occurred;

[0097] Among them, when the instantaneous change rate of the current or voltage signal or the average value in the time window meets the following conditions, it is determined that a breakdown arc event has occurred (either the instantaneous change rate or the average value conditions are met); otherwise, it is determined that there is no arc or abnormal interference:

[0098]

[0099] is the instantaneous rate of change of voltage; is the instantaneous rate of change of current; U 平均 is the average value of voltage; U 基准 is the reference value of voltage;

[0100] In this embodiment, the average value time window is twice the sampling interval, that is, 0.16 ms.

[0101] The arc occurrence conditions obtained through experiments in this embodiment are shown in Table 1.

[0102] Table 1: Arc occurrence conditions obtained through experiments

[0103]

[0104] The third step is to repeat the above steps to obtain arc occurrence conditions at different voltages and electrode spacings, and extract the critical conditions for arc initiation. In this embodiment, Table 1 shows that the critical conditions for arc initiation are between 200V / 7mm and 400V / 7mm.

[0105] Furthermore, in the above technical solution, based on the electric field strength calculation formula, the critical electric field strength for arc initiation is calculated and converted into a voltage-electrode spacing relationship to obtain the safety margin. The specific steps include:

[0106] The first step is to establish a theoretical model of arc induced by battery ejecta and analyze the boundary conditions of electric field intensity;

[0107] In the second step, based on the electric field strength calculation formula and boundary conditions, combined with the critical arcing conditions, the voltage-electrode spacing relationship is obtained to obtain the safety margin.

[0108] Furthermore, in the above technical solution, in the step of arranging the metal electrodes for initiating the arc opposite to each other above the battery exhaust valve, fixing them with a clamp and connecting them to the power supply circuit:

[0109] The metal electrode is made of high-melting-point copper or tungsten, and the fixture is a rigid fixture with insulation isolation to prevent errors caused by violent battery ejection, such as electrode shaking or falling off.

[0110] Furthermore, in the above technical solution, the specific steps of establishing a theoretical model of arc induced by battery ejecta include:

[0111] Combined with the arc phenomenon and arc signal changes recorded in the experiment, it is observed that the arc has obvious stage characteristics of occurrence (voltage drops from the baseline value) - persistence (voltage remains unchanged or changes slightly) - disappearance (voltage rises to the baseline value). Assuming that the high-speed ejecta that triggers the arc are uniform particle clusters passing through the middle of the electrode electric field, a theoretical model of battery ejecta-induced arc is established based on the high-speed ejecta that triggers the arc, as shown in the following example: Figure 3 As shown in Figure 3, the boundary conditions of the electric field intensity during the arc displacement process induced by the particle cluster are obtained.

[0112]

[0113] Where E is the electric field strength, E c is the critical arcing field strength;

[0114] The voltage-electrode spacing relationship is obtained based on the critical electric field strength and boundary conditions, including the following steps:

[0115] Calculate the maximum electric field strength E between the positive and negative electrodes max , since the electric field intensity is the largest at the midpoint of the vertical midline, x is taken as 0, and the formula is as follows:

[0116]

[0117] For the electric field strength E that can generate an arc d ,satisfy:

[0118] E d ≥E c >E n ;

[0119] Among them, E n is the electric field strength under critical working conditions where no arc is generated;

[0120] Since the voltage U is proportional to the charge Q:

[0121] Q∝U;

[0122] Combining the above formulas, we can obtain the voltage condition for the battery ejecta to trigger an arc:

[0123]

[0124] Among them, U n 、L n are the voltage and electrode distance under the critical working condition where no arc is generated, respectively.

[0125] According to the voltage condition of the battery ejecta initiating arc, the voltage-electrode spacing safety margin of the arc induced by the thermal runaway ejecta 3 cm above the battery is obtained, such as Figure 4 The figure shows the voltage safety margin information for different electrode spacings and the change in electrical clearance under different voltage conditions. For example, when the voltage is 400V, the electrical safety clearance 3cm above the battery cannot be less than 9.9mm.

[0126] like Figure 5 FIG. 3 shows a third embodiment of a method for determining a safety margin of an arc triggered by ejection during thermal runaway of a battery provided by the present invention. In this embodiment, the method includes the following specific steps:

[0127] S10: Build an experimental platform for battery thermal runaway ejection-induced arcing;

[0128] S20: Set the operating range and conduct a battery thermal runaway jet arc experiment in the battery thermal runaway jet arc experiment platform to obtain critical conditions;

[0129] S30: Based on the electric field strength calculation formula, the critical electric field strength for arc initiation is calculated and converted into a voltage-electrode spacing relationship to obtain a safety margin;

[0130] S40: Adjust the electrode placement height, and repeat the above steps to obtain the safety margin of arc induced by battery thermal runaway ejection at different electrode heights.

[0131] Among them, in the above technical solution, the specific steps of building a battery thermal runaway ejection-induced arc experimental platform include:

[0132] The first step is to connect the various components of the battery thermal runaway arc simulation experimental platform accordingly;

[0133] In the second step, the metal electrodes used to initiate the arc are arranged opposite each other above the battery exhaust valve. In this embodiment, the electrodes are arranged 4 cm above the exhaust valve; they are fixed with a clamp and connected to the power supply circuit.

[0134] Furthermore, in the above technical solution, the electrical signal acquisition in the battery thermal runaway ejection-induced arc experimental platform uses a high-frequency acquisition device (above 10kHz) with communication and data storage functions, such as an oscilloscope, a high-frequency probe, etc. In this embodiment, a 12.5kHz sampling frequency oscilloscope is used to collect arc signals, and a 400V / 20A DC regulated power supply is used to provide voltage conditions. At the same time, a resistor is connected in series to enhance the circuit load capacity.

[0135] Furthermore, in the above technical solution, the operating range is set, and a battery thermal runaway jet arc experiment is carried out in a battery thermal runaway jet arc experiment platform. The specific steps for obtaining critical conditions include:

[0136] The first step is to set the voltage and electrode spacing research range, starting from the lower limit of the electrode spacing, and experimentally test different voltages using a dichotomy method. In this embodiment, the voltage is set to 100V-400V, the electrode spacing is 3mm-7mm, and the tests are carried out sequentially starting from the 3mm and 400V working conditions; the battery thermal runaway is triggered by heating.

[0137] The second step is to analyze the electrical signal data of the battery injection process obtained by the high-frequency acquisition equipment, and combine the instantaneous change rate of the voltage and current signals and the time window average to determine whether an arc has occurred;

[0138] Among them, when the instantaneous change rate of the current or voltage signal or the average value in the time window meets the following conditions, it is determined that a breakdown arc event has occurred (either the instantaneous change rate or the average value conditions are met); otherwise, it is determined that there is no arc or abnormal interference:

[0139]

[0140] is the instantaneous rate of change of voltage; is the instantaneous rate of change of current; U 平均 is the average value of voltage; U 基准 is the reference value of voltage;

[0141] In this embodiment, the average value time window is twice the sampling interval, that is, 0.16 ms.

[0142] The arc occurrence conditions obtained through experiments in this embodiment are shown in Table 2.

[0143] Table 2: Arc occurrence conditions obtained through experiments

[0144]

[0145] In the third step, the above steps are repeated to obtain the arc occurrence conditions at different voltages and electrode spacings, and to extract the critical conditions for arc initiation.

[0146] Furthermore, in the above technical solution, based on the electric field strength calculation formula, the critical electric field strength for arc initiation is calculated and converted into a voltage-electrode spacing relationship to obtain the safety margin. The specific steps include:

[0147] The first step is to establish a theoretical model of arc induced by battery ejecta and analyze the boundary conditions of electric field intensity;

[0148] In the second step, based on the electric field strength calculation formula and boundary conditions, combined with the critical arcing conditions, the voltage-electrode spacing relationship is obtained to obtain the safety margin.

[0149] Furthermore, in the above technical solution, in the step of arranging the metal electrodes for initiating the arc opposite to each other above the battery exhaust valve, fixing them with a clamp and connecting them to the power supply circuit:

[0150] The metal electrode is made of high-melting-point copper or tungsten, and the fixture is a rigid fixture with insulation isolation to prevent errors caused by violent battery ejection, such as electrode shaking or falling off.

[0151] Furthermore, in the above technical solution, the specific steps of establishing a theoretical model of arc induced by battery ejecta include:

[0152] Combined with the arc phenomenon and arc signal changes recorded in the experiment, it is observed that the arc has obvious stage characteristics of occurrence (voltage drops from the baseline value) - persistence (voltage remains unchanged or changes slightly) - disappearance (voltage rises to the baseline value). Assuming that the high-speed ejecta that triggers the arc are uniform particle clusters passing through the middle of the electrode electric field, a theoretical model of battery ejecta-induced arc is established based on the high-speed ejecta that triggers the arc, as shown in the following example: Figure 3 As shown in Figure 3, the boundary conditions of the electric field intensity during the arc displacement process induced by the particle cluster are obtained.

[0153]

[0154] Where E is the electric field strength, E c is the critical arcing field strength;

[0155] The voltage-electrode spacing relationship is obtained based on the critical electric field strength and boundary conditions, including the following steps:

[0156] Calculate the maximum electric field strength E between the positive and negative electrodes max , since the electric field intensity is the largest at the midpoint of the vertical midline, x is taken as 0, and the formula is as follows:

[0157]

[0158] For the electric field strength E that can generate an arc d ,satisfy:

[0159] E d ≥Ec >E n ;

[0160] Among them, E n is the electric field strength under critical working conditions where no arc is generated;

[0161] Since the voltage U is proportional to the charge Q:

[0162] Q∝U;

[0163] Combining the above formulas, we can obtain the voltage condition for the battery ejecta to trigger an arc:

[0164]

[0165] Among them, U n , L n are the voltage and electrode distance under the critical working condition where no arc is generated, respectively.

[0166] According to the voltage condition of the battery ejecta initiating arc, the voltage-electrode spacing safety margin of the arc induced by the thermal runaway ejecta 4 cm above the battery is obtained, such as Figure 5 The figure shows the voltage safety margin information for different electrode spacings and the changes in electrical clearance under different voltage conditions. For example, when the voltage is 800V, the electrical safety clearance 4cm above the battery cannot be less than 10mm.

[0167] like Figure 6 FIG. 4 shows a fourth embodiment of a method for determining a safety margin of an arc triggered by ejection in a battery due to thermal runaway provided by the present invention. In this embodiment, the following specific steps are included:

[0168] S10: Build an experimental platform for battery thermal runaway ejection-induced arcing;

[0169] S20: Set the operating range and conduct a battery thermal runaway jet arc experiment in the battery thermal runaway jet arc experiment platform to obtain critical conditions;

[0170] S30: Based on the electric field strength calculation formula, the critical electric field strength for arc initiation is calculated and converted into a voltage-electrode spacing relationship to obtain a safety margin;

[0171] S40: Adjust the electrode placement height, and repeat the above steps to obtain the safety margin of arc induced by battery thermal runaway ejection at different electrode heights.

[0172] Among them, in the above technical solution, the specific steps of building a battery thermal runaway ejection-induced arc experimental platform include:

[0173] The first step is to connect the various components of the battery thermal runaway arc simulation experimental platform accordingly;

[0174] In the second step, the metal electrodes used to initiate the arc are arranged opposite each other above the battery exhaust valve. In this embodiment, the electrodes are arranged 5 cm above the exhaust valve; they are fixed with a clamp and connected to the power supply circuit.

[0175] Furthermore, in the above technical solution, the electrical signal acquisition in the battery thermal runaway ejection-induced arc experimental platform uses a high-frequency acquisition device (above 10kHz) with communication and data storage functions, such as an oscilloscope, a high-frequency probe, etc. In this embodiment, a 12.5kHz sampling frequency oscilloscope is used to collect arc signals, and a 400V / 20A DC regulated power supply is used to provide voltage conditions. At the same time, a resistor is connected in series to enhance the circuit load capacity.

[0176] Furthermore, in the above technical solution, the operating range is set, and a battery thermal runaway jet arc experiment is carried out in a battery thermal runaway jet arc experiment platform. The specific steps for obtaining critical conditions include:

[0177] The first step is to set the voltage and electrode spacing research range, starting from the lower limit of the electrode spacing, and experimentally test different voltages using a dichotomy method. In this embodiment, the voltage is set to 100V-400V, the electrode spacing is 3mm-7mm, and the tests are carried out sequentially starting from the 3mm and 400V working conditions; the battery thermal runaway is triggered by heating.

[0178] The second step is to analyze the electrical signal data of the battery injection process obtained by the high-frequency acquisition equipment, and combine the instantaneous change rate of the voltage and current signals and the time window average to determine whether an arc has occurred;

[0179] Among them, when the instantaneous change rate of the current or voltage signal or the average value in the time window meets the following conditions, it is determined that a breakdown arc event has occurred (either the instantaneous change rate or the average value conditions are met); otherwise, it is determined that there is no arc or abnormal interference:

[0180]

[0181] is the instantaneous rate of change of voltage; is the instantaneous rate of change of current; U 平均 is the average value of voltage; U 基准 is the reference value of voltage;

[0182] In this embodiment, the average value time window is twice the sampling interval, that is, 0.16 ms.

[0183] The arc occurrence conditions obtained through experiments in this embodiment are shown in Table 3.

[0184] Table 3: Arc occurrence conditions obtained through experiments

[0185]

[0186] In the third step, the above steps are repeated to obtain the arc occurrence conditions at different voltages and electrode spacings, and to extract the critical conditions for arc initiation.

[0187] Furthermore, in the above technical solution, based on the electric field strength calculation formula, the critical electric field strength for arc initiation is calculated and converted into a voltage-electrode spacing relationship to obtain the safety margin. The specific steps include:

[0188] The first step is to establish a theoretical model of arc induced by battery ejecta and analyze the boundary conditions of electric field intensity;

[0189] In the second step, based on the electric field strength calculation formula and boundary conditions, combined with the critical arcing conditions, the voltage-electrode spacing relationship is obtained to obtain the safety margin.

[0190] Furthermore, in the above technical solution, in the step of arranging the metal electrodes for initiating the arc opposite to each other above the battery exhaust valve, fixing them with a clamp and connecting them to the power supply circuit:

[0191] The metal electrode is made of high-melting-point copper or tungsten, and the fixture is a rigid fixture with insulation isolation to prevent errors caused by violent battery ejection, such as electrode shaking or falling off.

[0192] Furthermore, in the above technical solution, the specific steps of establishing a theoretical model of arc induced by battery ejecta include:

[0193] Combined with the arc phenomenon and arc signal changes recorded in the experiment, it is observed that the arc has obvious stage characteristics of occurrence (voltage drops from the baseline value) - persistence (voltage remains unchanged or changes slightly) - disappearance (voltage rises to the baseline value). Assuming that the high-speed ejecta that triggers the arc are uniform particle clusters passing through the middle of the electrode electric field, a theoretical model of battery ejecta-induced arc is established based on the high-speed ejecta that triggers the arc, as shown in the following example: Figure 3 As shown in Figure 3, the boundary conditions of the electric field intensity during the arc displacement process induced by the particle cluster are obtained.

[0194]

[0195] Where E is the electric field strength, E c is the critical arcing field strength;

[0196] The voltage-electrode spacing relationship is obtained based on the critical electric field strength and boundary conditions, including the following steps:

[0197] Calculate the maximum electric field strength E between the positive and negative electrodes max , since the electric field intensity is the largest at the midpoint of the vertical midline, x is taken as 0, and the formula is as follows:

[0198]

[0199] For the electric field strength E that can generate an arc d ,satisfy:

[0200] E d ≥E c >E n ;

[0201] Among them, E n is the electric field strength under critical working conditions where no arc is generated;

[0202] Since the voltage U is proportional to the charge Q:

[0203] Q∝U;

[0204] Combining the above formulas, we can obtain the voltage condition for the battery ejecta to trigger an arc:

[0205]

[0206] Among them, U n 、L n are the voltage and electrode distance under the critical working condition where no arc is generated, respectively.

[0207] According to the voltage condition of the battery ejecta initiating arc, the voltage-electrode spacing safety margin of the arc induced by the thermal runaway ejecta 5 cm above the battery is obtained, such as Figure 6 The figure shows the voltage safety margin information for different electrode spacings and the change in electrical clearance under different voltage conditions. For example, when the voltage is 1500V, the electrical safety clearance 5cm above the battery cannot be less than 11.6mm.

[0208] like Figure 7 As shown, it is the fifth embodiment of the method for determining the safety boundary of the arc triggered by the ejection of a battery due to thermal runaway provided by the present invention. In this embodiment, combined with the safety boundary relationship formula under different electrode heights obtained in the early stage, a relationship diagram between the arc starting critical voltage and the electrode gap is drawn when the electrode height is 3, 4, and 5 cm.

[0209] When the external voltage remains unchanged, the higher the electrode height, the smaller the electrode gap required to trigger an arc caused by battery thermal runaway jets; when the electrode gap remains unchanged, the higher the electrode height, the higher the required external voltage. This is because the battery particle jet is in an inverted cone shape, and the farther away from the safety valve, the lower the concentration of the jet particles, and therefore the more stringent the requirements for forming a breakdown arc. According to the calculation results, it can be seen that when the voltage and electrode gap conditions are determined, the critical value of the electrode height can also be determined accordingly from the figure. Therefore, this method can be used for the height layout of the battery pack top plate, electrical and metal components, etc., to guide the design of electrical safety protection for the battery system.

[0210] Specifically, the principle of the present invention is: when in use, a battery thermal runaway jet-induced arc experimental platform is built; the operating range is set, and a battery thermal runaway jet-induced arc experiment is carried out in the battery thermal runaway jet-induced arc experimental platform to obtain critical conditions; based on the electric field strength calculation formula, the critical electric field strength for arc initiation is calculated, and converted into a voltage-electrode spacing relationship to obtain a safety margin; the electrode placement height is adjusted, and the above steps are repeated to obtain the safety margin of the battery thermal runaway jet-induced arc at different electrode heights.

Claims

1. A method for determining the safety margin of arc induced by battery thermal runaway ejection, characterized in that: The specific steps include: S10: Build an experimental platform for battery thermal runaway ejection-induced arcing; S20: Setting an operating range, conducting a battery thermal runaway ejection arc experiment in the battery thermal runaway ejection arc experiment platform, and obtaining critical conditions; S30: Based on the electric field strength calculation formula, the critical electric field strength for arc initiation is calculated and converted into a voltage-electrode spacing relationship to obtain a safety margin; S40: Adjust the electrode placement height, and repeat the above steps to obtain the safety margin of arc initiation caused by battery thermal runaway ejection at different electrode heights; The specific steps of setting the operating condition range, conducting a battery thermal runaway jet arc experiment in the battery thermal runaway jet arc experiment platform, and obtaining critical conditions include: The first step is to set the voltage and electrode spacing research range based on the actual battery pack voltage and electrical component spacing data, and trigger battery thermal runaway through heating or overcharging; The second step is to analyze the electrical signal data of the battery injection process obtained by the high-frequency acquisition equipment, and combine the instantaneous change rate of the voltage and current signals and the time window average to determine whether an arc has occurred; In the third step, the above steps are repeated to obtain the arc occurrence conditions at different voltages and electrode spacings, and to extract the critical conditions for arc initiation. The specific steps of calculating the arc-starting critical electric field strength based on the electric field strength calculation formula, converting it into a voltage-electrode spacing relationship, and obtaining the safety margin include: The first step is to establish a theoretical model of arc induced by battery ejecta and analyze the boundary conditions of electric field intensity; In the second step, based on the electric field strength calculation formula and boundary conditions, combined with the critical arcing conditions, the voltage-electrode spacing relationship is obtained to obtain the safety margin: ； Among them, U n 、L n are the voltage and electrode distance under critical working conditions without arc generation, respectively; is the voltage, is the electrode spacing.

2. The method for determining the safety margin of arc triggered by battery thermal runaway ejection according to claim 1, characterized in that: The specific steps of building a battery thermal runaway ejection arc experimental platform include: The first step is to connect the various components of the battery thermal runaway arc simulation experimental platform accordingly; In the second step, the metal electrodes used to initiate the arc are arranged opposite each other above the battery exhaust valve, fixed with a clamp and connected to the power supply line.

3. The method for determining the safety margin of arc triggered by ejection during battery thermal runaway according to claim 2, characterized in that: The electrical signal acquisition in the battery thermal runaway ejection-induced arc experimental platform adopts a high-frequency acquisition device with communication and data storage functions.

4. The method for determining the safety margin of arc triggered by ejection during battery thermal runaway according to claim 3, characterized in that: The instantaneous change rate thresholds of voltage and current signals are obtained through experimental measurements.

5. The method for determining the safety margin of arc triggered by ejection during battery thermal runaway according to claim 4, characterized in that: The time window is set to 1-2 times the sampling interval.

6. The method for determining the safety margin of arc triggered by ejection during battery thermal runaway according to claim 5, characterized in that: In the step of arranging the metal electrodes for initiating the arc opposite to each other above the battery exhaust valve, fixing them with a clamp and connecting them to the power supply circuit: The metal electrode is made of copper or tungsten with a high melting point, and the fixture is a rigid fixture provided with insulation isolation to prevent errors caused by the electrode shaking or falling off due to violent ejection of the battery.

7. The method for determining the safety margin of arc triggered by ejection during battery thermal runaway according to claim 6, characterized in that: The specific steps of setting the voltage and electrode spacing research range by referring to the actual battery pack voltage and electrical component spacing data and triggering battery thermal runaway by heating or overcharging include: The experimental working condition starts from the lower limit of the electrode spacing setting, and the binary method is used to test from the set voltage upper limit to efficiently approach the most stringent arcing critical conditions and avoid the omission of working conditions that affect the accuracy of the safety boundary results.

8. The method for determining the safety margin of arc triggered by ejection during battery thermal runaway according to claim 7, characterized in that: The specific steps of establishing a theoretical model of battery ejecta-induced arcing include: Combined with the arc phenomena and arc signal changes recorded in the experiment, it was observed that the arc had obvious occurrence-persistence-disappearance stage characteristics. It was assumed that the high-speed ejecta that triggered the arc was a uniform particle cluster passing through the middle of the electrode electric field. A theoretical model of battery ejecta-induced arc was established based on the high-speed ejecta that triggered the arc, and the boundary conditions of the electric field intensity during the displacement process of the particle cluster-induced arc were obtained.

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