Quantitative evaluation method for action effect of lithium ion cell fire extinguishing agent

Abstract

The invention discloses a quantitative evaluation method for the action effect of a lithium ion cell fire extinguishing agent, which comprehensively evaluates the fire extinguishing effect, the cooling effect and the smoke toxicity inhibition effect of the fire extinguishing agent, and overcomes the defect that the overall performance of the fire extinguishing agent cannot be fully reflected under a single evaluation dimension in the existing method. Meanwhile, by introducing the weight of each index, the problem that evaluation of each dimension is independent and lack of association in a traditional method is solved; besides, by correcting the temperature when the fire extinguishing agent is sprayed, the objectivity and credibility of the evaluation result are enhanced, and it is ensured that the evaluation results under different experiment conditions have higher consistency and comparability.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion battery core fire extinguishing agents, and in particular to a method for quantitatively evaluating the effect of lithium ion battery core fire extinguishing agents. Background Art

[0002] China is the world's largest producer and consumer of lithium batteries. The mass production and application of lithium batteries provide a strong foundation and strategic support for my country's modernization. However, lithium batteries are prone to thermal runaway under conditions such as overcharging, overheating, and mechanical damage, leading to fire, explosion, and the production of large amounts of toxic smoke, posing a huge potential risk to public safety. Although certain progress has been made in the intrinsic safety design of batteries, it is still difficult to avoid the occurrence of thermal runaway. Therefore, developing an effective lithium-ion battery fire extinguishing method is one of the important measures to reduce the hazards of thermal runaway of lithium batteries and ensure public safety.

[0003] The existing lithium battery fire extinguishing methods focus on the development of fire extinguishing agents. Usually, under the same experimental conditions (such as battery cell specifications, thermal runaway triggering conditions, etc.), the fire extinguishing agent is sprayed during the open flame stage after the thermal runaway of the lithium battery. By evaluating the fire extinguishing and cooling effects of different fire extinguishing agents, the best fire extinguishing agent is screened out, and the inhibitory effect of the best fire extinguishing agent on the thermal runaway of the battery module is further studied.

[0004] However, the existing evaluation methods for the effect of lithium-ion battery fire extinguishing agents have the following shortcomings:

[0005] 1. Most existing evaluation methods are qualitative evaluations, lacking quantitative means, and it is difficult to clearly determine the relative advantages and disadvantages of various fire extinguishing agents. For example, although perfluorohexanone has a significant cooling effect, its decomposition products such as CO, CO2 and HF will increase system toxicity, thus bringing potential risks; liquid nitrogen has a fast initial cooling speed, but the low temperature maintenance effect is poor. Since different fire extinguishing agents have their own advantages and disadvantages, simple qualitative analysis is difficult to accurately compare their comprehensive effects.

[0006] 2. Single evaluation dimension. The existing evaluation method focuses on the isolated evaluation of fire extinguishing and cooling, and fails to cover the effect of fire extinguishing agents on suppressing or releasing toxic gases. In addition, the existing evaluation system lacks comprehensive consideration of the relationship between various evaluation dimensions, resulting in the inability to comprehensively evaluate the comprehensive performance of fire extinguishing agents.

[0007] 3. The existing evaluation methods do not fully consider the temperature correction when spraying the fire extinguishing agent. Due to factors such as the uneven distribution of active materials inside the lithium-ion battery cell, the temperature of its thermal runaway is uncontrollable. For experiments using temperature-sensitive automatic fire extinguishing devices to spray fire extinguishing agents, the impact of temperature differences at the injection point on the experimental results can be basically ignored. However, for experiments that require spraying fire extinguishing agents at specific temperature points or judging the injection time based on the rate of temperature change, it is usually necessary to manually monitor the temperature and manually open the valve, which requires a certain amount of reaction time. The temperature of the lithium-ion battery cell changes rapidly during thermal runaway, which will cause the temperature of the injection point to deviate from the set injection temperature, thereby affecting the accuracy of the results. Therefore, temperature correction during injection needs to be considered in the evaluation method. Summary of the invention

[0008] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for quantitatively evaluating the effect of a fire extinguishing agent for a lithium-ion battery. The method comprehensively evaluates the fire extinguishing effect, the cooling effect and the effect of inhibiting the toxicity of smoke of the fire extinguishing agent in three dimensions, thereby overcoming the defect that the existing method cannot fully reflect the overall performance of the fire extinguishing agent under a single evaluation dimension; at the same time, by introducing the weights of various indicators, the problem that the evaluation of each dimension is independent and lacks correlation in the traditional method is solved; in addition, by correcting the temperature when the fire extinguishing agent is sprayed, the objectivity and credibility of the evaluation results are enhanced, thereby ensuring that the evaluation results under different experimental conditions have higher consistency and comparability.

[0009] To achieve the above purpose, the technical solution provided by the present invention is:

[0010] A method for quantitatively evaluating the effect of a lithium-ion battery fire extinguishing agent, comprising:

[0011] Design a lithium-ion battery fire extinguishing experiment and collect data to obtain evaluation index parameters, which include multiple categories including injection temperature correction index parameters, fire extinguishing effect index parameters, cooling effect index parameters, and smoke toxicity suppression effect index parameters;

[0012] Calculate the values ​​of each evaluation index under various evaluation index parameters and normalize them;

[0013] Obtain the weight of each evaluation index under various evaluation index parameters;

[0014] Construct a model to evaluate the effect of fire extinguishing agents for lithium-ion batteries;

[0015] The normalized evaluation index value and the corresponding evaluation index weight are input into the lithium-ion battery cell fire extinguishing agent effect evaluation model to obtain the scores of the effects of different fire extinguishing agents on lithium-ion batteries;

[0016] The advantages and disadvantages of different fire extinguishing agents are arranged according to the scores of their effects on lithium-ion batteries.

[0017] Furthermore, the formula of the lithium-ion battery fire extinguishing agent effect evaluation model is as follows:

[0018]

[0019] Where, k is the correction coefficient; Q is the evaluation score, with a value range of [0, 100]; A is the injection temperature correction index; S is the comprehensive effect of the lithium-ion battery fire extinguishing agent;

[0020] The calculation formula of injection temperature correction index A is as follows:

[0021]

[0022] In the formula, c cell is the capacity of the lithium-ion battery; t i is the temperature when the fire extinguishing agent is sprayed; T i Thermal runaway temperature of lithium-ion battery cell;

[0023] The calculation formula for the comprehensive effect S of the lithium-ion battery fire extinguishing agent is as follows:

[0024] S=E+C+M

[0025] Wherein, E is the fire extinguishing effect index parameter, C is the cooling effect index parameter, and M is the smoke toxicity inhibition effect index parameter.

[0026] Furthermore, the fire extinguishing effect index parameter E includes a fire extinguishing time index e1 and a re-ignition situation index e2;

[0027] Calculate the fire extinguishing time index e1:

[0028] e1=t extinguish t start

[0029] Where, t extinguish The moment when the flame is completely extinguished; start The moment to start spraying fire extinguishing agent on the flame;

[0030] Calculate the re-ignition indicator e2:

[0031]

[0032] If the lithium-ion battery does not reignite within a set time after the open flame is extinguished, the value is 1; otherwise, the value is 0.

[0033] Furthermore, the cooling effect index parameter C includes a cooling rate index c1, a temperature recovery rate index c2, and a low temperature maintenance time index c3;

[0034] Calculate the cooling rate index c1:

[0035]

[0036] Where c1 is the cooling rate index, which refers to the average cooling rate during the injection of fire extinguishing agent; T end The temperature at which the spraying of the fire extinguishing agent stops; T start is the temperature when the fire extinguishing agent starts to be sprayed; t spary The time for spraying fire extinguishing agent;

[0037] Calculate the temperature recovery rate index c2:

[0038]

[0039] Wherein, the temperature recovery rate index c2 is the average temperature recovery rate of the temperature to the peak value after the spraying of the fire extinguishing agent is stopped, T re,peak It is the peak value of temperature rise after stopping spraying fire extinguishing agent; Δt re,peak-end It is the time interval from the cessation of spraying of fire extinguishing agent to the temperature returning to the peak value;

[0040] Calculate the low temperature maintenance time index c3:

[0041] c3=t 设定 -t end

[0042] In the formula, t 设定 Set as the moment when the temperature of the monitoring point exceeds the set temperature for the first time after the fire extinguishing agent is released, t end This is the moment to stop spraying the fire extinguishing agent.

[0043] Furthermore, the smoke toxicity suppression effect index parameter M includes the toxicity index m of the asphyxiating gas. FED 、Toxicity index of irritating gas m FEC , Toxicity index m when the asphyxiating gas reaches its peak after stopping the spraying of fire extinguishing agent FED(re,peak) , Toxicity index m when the irritating gas reaches its peak after stopping the spraying of the fire extinguishing agent FEC(re,peak) ;

[0044] Toxicity index of asphyxiating gas FED The calculation formula is as follows:

[0045]

[0046] Toxicity index of irritant gas m FEC The calculation formula is as follows:

[0047]

[0048] In the formula, m FED(start) It is the toxicity index of asphyxiating gas when the fire extinguishing agent is sprayed, m FED(end) It is the toxicity index of asphyxiating gas when the spraying of fire extinguishing agent is stopped, m FEC(start) It is the toxicity index of the irritating gas when the fire extinguishing agent is sprayed, m FEC(end) It is the toxicity index of the irritant gas when the spraying of the fire extinguishing agent is stopped;

[0049] The toxicity index m when the asphyxiating gas reaches its peak after the spraying of the fire extinguishing agent is stopped FED(re,peak) The calculation formula is as follows:

[0050]

[0051] Z A =[CO2] re,peak ×0.05

[0052] Where, [CO] re,peak , [CO2] re,peak They are the highest concentrations of CO and CO2 after stopping the spraying of fire extinguishing agent, μL / L; is the average volume concentration of O2; is the weighting factor of CO2 when respiration is stimulated by CO2; LC 50,CO It refers to the median lethal concentration of CO within a certain exposure time; Z A It is an acid poisoning factor;

[0053] Toxicity index m when the irritant gas reaches its peak after stopping the spraying of the fire extinguishing agent FEC(re,peak) It is equal to the sum of the values ​​obtained by dividing the critical concentration of each irritant gas involved by the value at which the irritant gas is expected to cause personal incapacitation.

[0054] Furthermore, the normalization process includes:

[0055] The evaluation indicators of the fire extinguishing effect index parameter E, the cooling effect index parameter C and the smoke toxicity suppression effect index parameter M are combined into an index data set; according to the attributes of the evaluation indicators, the index data set is divided into positive indicators and negative indicators; positive indicators refer to indicators with larger values ​​representing better effects; negative indicators refer to indicators with smaller values ​​representing better effects;

[0056] The calculation formula for normalization of positive indicators is as follows:

[0057]

[0058] The calculation formula for normalization of the reverse indicator is as follows:

[0059]

[0060] In the formula, G ij is the original value of the evaluation index of the j-th fire extinguishing agent under the i-th index, is the normalized value of the evaluation index of the j-th fire extinguishing agent under the i-th index; Max(G ij ) and Min(G ij ) are the maximum and minimum values ​​of the indicator in all samples respectively.

[0061] Furthermore, the weights of each evaluation index under the evaluation index parameters are obtained, including:

[0062] Calculate the proportion H of the jth fire extinguishing agent in the i-th indicator ij , i=1, 2, 3,…,n; j=1, 2, 3,…,m;

[0063]

[0064] Calculate the entropy value P under the i-th indicator i :

[0065]

[0066] In the formula, n is the number of evaluation indicators;

[0067] Calculate the weight ω of the i-th evaluation index i :

[0068]

[0069] Where m is the amount of fire extinguishing agent.

[0070] Furthermore, the normalized evaluation index value and the corresponding evaluation index weight are input into the lithium-ion battery cell fire extinguishing agent effect evaluation model to obtain the scores of the effects of different fire extinguishing agents on lithium-ion batteries. The process includes:

[0071] Calculate the fire extinguishing effect parameter E:

[0072]

[0073] In the formula, is the normalized value of the ith fire extinguishing effect index, e i Including e1, e2; is the weight of the i-th fire extinguishing effect index;

[0074] Calculate the cooling effect index parameter C:

[0075]

[0076] is the normalized value of the ith cooling effect evaluation index, c i Including c1, c2 and c3; ω ci is the weight of the i-th cooling effect evaluation index;

[0077] If the sprayed fire extinguishing agent can effectively suppress the generation of asphyxiating gas and irritating gas, the calculation formula of the smoke toxicity suppression index parameter M is:

[0078]

[0079] and are the normalized values ​​of the toxicity index values ​​of asphyxiating gases and irritating gases, respectively; ω mFED and ω mFEC are the weights of the toxicity evaluation indicators for asphyxiating gases and irritating gases, respectively;

[0080] If the sprayed fire extinguishing agent fails to effectively suppress the generation of asphyxiating gas and irritating gas, the calculation formula of the smoke toxicity suppression effect index parameter M is:

[0081]

[0082] In the formula, It is the normalized value of the toxicity index when the asphyxiating gas reaches its peak after the spraying of the fire extinguishing agent is stopped. It is the normalized value of the toxicity index when the irritant gas reaches the peak after the spraying of the fire extinguishing agent is stopped, ω mFED(re,peak) is the weight of the toxicity index when the asphyxiating gas reaches its peak after the spraying of the fire extinguishing agent is stopped, ω mFEC(re,peak) The weight of the toxicity index when the irritant gas reaches its peak value after the spraying of the fire extinguishing agent is stopped;

[0083] Based on the obtained fire extinguishing effect index parameter E, cooling effect index parameter C, and smoke toxicity suppression effect index parameter M, the comprehensive effect S of the lithium-ion battery fire extinguishing agent is calculated;

[0084] Then, the comprehensive effect S of the lithium-ion battery fire extinguishing agent is substituted into the formula of the lithium-ion battery fire extinguishing agent effect evaluation model to obtain the score of the effect of the fire extinguishing agent on the lithium-ion battery.

[0085] Compared with the prior art, the principles and advantages of this technical solution are as follows:

[0086] 1. Comprehensively evaluate the fire extinguishing effect, cooling effect and smoke toxicity inhibition effect of the fire extinguishing agent, so as to overcome the defect that the existing method cannot fully reflect the overall performance of the fire extinguishing agent under a single evaluation dimension.

[0087] 2. By introducing the weights of various indicators, the problem of independent evaluation and lack of correlation of various dimensions in traditional methods can be solved.

[0088] 3. By correcting the temperature when spraying the fire extinguishing agent, the objectivity and credibility of the evaluation results can be enhanced, ensuring that the evaluation results under different experimental conditions have higher consistency and comparability. BRIEF DESCRIPTION OF THE DRAWINGS

[0089] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the services required for use in the embodiments or the prior art descriptions are briefly introduced below. 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 creative work.

[0090] Figure 1 This is a principle flow chart of a method for quantitatively evaluating the effect of a lithium-ion battery fire extinguishing agent according to an embodiment of the present invention;

[0091] Figure 2 The temperature variation curve of each fire extinguishing agent in Experiment 1 (the time of spraying the fire extinguishing agent is taken as the 0 point);

[0092] Figure 3 This is the curve diagram of the change of CO, SO2 and NO2 gas concentration when spraying water in Experiment 1;

[0093] Figure 4 This is the curve of the change of O2 and CO2 gas concentration when spraying water in Experiment 1;

[0094] Figure 5 This is the temperature change curve of each fire extinguishing agent in Experiment 2 (the moment of spraying the fire extinguishing agent is taken as point 0). DETAILED DESCRIPTION

[0095] The present invention will be further described below in conjunction with specific embodiments:

[0096] like Figure 1 As shown, the method for quantitatively evaluating the effect of a lithium-ion battery fire extinguishing agent described in this embodiment includes the following steps:

[0097] S1. Design a lithium-ion battery fire extinguishing experiment and collect data to obtain evaluation index parameters, which include multiple categories including injection temperature correction index parameters, fire extinguishing effect index parameters, cooling effect index parameters, and smoke toxicity suppression effect index parameters;

[0098] Specifically, in this step, when designing the lithium-ion battery cell fire extinguishing experiment, select lithium-ion batteries of the same specifications, and change the type of fire extinguishing agent under the same conditions of fire extinguishing agent spraying height, fire extinguishing agent spraying time, etc., and induce thermal runaway of the lithium-ion battery cell by heating, overcharging or acupuncture. Once the lithium-ion battery cell has thermal runaway, immediately turn off the triggering device such as heating or overcharging, and spray the fire extinguishing agent at the preset spraying point.

[0099] During the experiment, the temperature and pressure changes are monitored by thermocouples and pressure sensors, and the temperature and pressure change data are recorded by Hioki data acquisition. The gas concentration changes generated by the experiment can be continuously detected at a fixed point or collected using a smoke exhaust pipe, and then analyzed using a flue gas analyzer, gas mass spectrometer or Fourier transform infrared spectrometer. In addition, the entire experimental process is recorded in real time by a camera. After the injection is completed, all monitoring equipment will be turned off after the temperature of the lithium-ion battery cell drops to 100°C.

[0100] Continuously collect real-time data from various monitoring devices to obtain evaluation index parameters; the evaluation index parameters include four categories: injection temperature correction index parameters, fire extinguishing effect index parameters, cooling effect index parameters, and smoke toxicity suppression effect index parameters;

[0101] Among them, the spray temperature correction index parameters include the thermal runaway temperature index of the lithium-ion battery cell and the temperature index when spraying the fire extinguishing agent. The thermal runaway temperature of the lithium-ion battery cell refers to the temperature when the lithium-ion battery cell undergoes thermal runaway. The judgment standard for thermal runaway refers to GB / T 36276-2018, that is, when the temperature monitoring point on the opposite side of the lithium-ion battery cell close to the heating device has a continuous heating rate of more than 1°C / s for three seconds, and the voltage drops by 25%, it is judged as thermal runaway.

[0102] The fire extinguishing effect index parameter E includes the fire extinguishing time index e1 and the re-ignition index e2. The fire extinguishing time index e1 refers to the time required from the start of spraying the fire extinguishing agent to the complete extinguishing of the flame, which is determined by the video recorded by the camera. The re-ignition index e2 refers to whether the lithium-ion battery cell re-ignites within 30 minutes after the open fire is extinguished.

[0103] The cooling effect index parameter C includes the cooling rate index c1, the temperature recovery rate index c2 and the low temperature maintenance time index c3. The low temperature maintenance time index c3 refers to the time period during which the temperature of the monitoring point is maintained below 150°C after the fire extinguishing agent is released according to CCCF / XFJJ-01.

[0104] The smoke toxicity suppression effect index parameter M includes the toxicity index m of the asphyxiating gas FED 、Toxicity index of irritating gas m FEC , Toxicity index m when the asphyxiating gas reaches its peak after stopping the spraying of fire extinguishing agent FED(re,peak), Toxicity index m when the irritating gas reaches its peak after stopping the spraying of the fire extinguishing agent FEC(re,peak) .

[0105] S2. Calculate the values ​​of each evaluation index under various evaluation index parameters and normalize them;

[0106] The specific process of calculating the values ​​of each evaluation index under various evaluation index parameters includes:

[0107] Calculate the fire extinguishing time index e1:

[0108] e1=t extinguish -t start

[0109] In the formula, t extinguish The moment when the flame is completely extinguished; start The moment to start spraying fire extinguishing agent on the flame;

[0110] Calculate the re-ignition indicator e2:

[0111]

[0112] If the lithium-ion battery does not reignite within 30 minutes after the open flame is extinguished, the value is 1; otherwise, the value is 0.

[0113] Calculate the cooling rate index c1:

[0114]

[0115] Where c1 is the cooling rate index, which refers to the average cooling rate during the injection of fire extinguishing agent; T end The temperature at which the spraying of the fire extinguishing agent stops; T start is the temperature when the fire extinguishing agent starts to be sprayed; t spary The time for spraying fire extinguishing agent;

[0116] Calculate the temperature recovery rate index c2:

[0117]

[0118] Wherein, the temperature recovery rate index c2 is the average temperature recovery rate of the temperature to the peak value after the spraying of the fire extinguishing agent is stopped, T re,peak It is the peak value of temperature rise after stopping spraying fire extinguishing agent; Δt re,peak-end It is the time interval from the cessation of spraying of fire extinguishing agent to the temperature returning to the peak value;

[0119] Calculate the low temperature maintenance time index c3:

[0120] c3=t 150℃ -t end

[0121] In the formula, t 150℃ Set as the moment when the temperature of the monitoring point exceeds the set temperature for the first time after the fire extinguishing agent is released, t end This is the moment to stop spraying the fire extinguishing agent.

[0122] Toxicity index of asphyxiating gas FED The calculation formula is as follows:

[0123]

[0124] Toxicity index of irritant gas m FEC The calculation formula is as follows:

[0125]

[0126] In the formula, m FED(start) It is the toxicity index of asphyxiating gas when the fire extinguishing agent is sprayed, m FED(end) It is the toxicity index of asphyxiating gas when the spraying of fire extinguishing agent is stopped, m FEC(start) It is the toxicity index of the irritating gas when the fire extinguishing agent is sprayed, m FEC(end) It is the toxicity index of the irritant gas when the spraying of the fire extinguishing agent is stopped;

[0127] Toxicity index of asphyxiating gas when starting to spray fire extinguishing agent m FED(start) The calculation formula is as follows:

[0128]

[0129] Z A(start) =[CO2] start ×0.05

[0130] Where, [CO] start , [CO2] start They are the concentrations of CO and CO2 when the fire extinguishing agent is sprayed, μL / L; [O2] start V is the volume concentration of O2 when the fire extinguishing agent is sprayed; CO2(start) It is the weighting factor of CO2 when CO2 stimulates breathing when the fire extinguishing agent is sprayed; LC 50,CO It refers to the median lethal concentration of CO within a certain exposure time; Z A(start) It is the acid poisoning factor when the fire extinguishing agent is first sprayed;

[0131] Toxicity index of asphyxiating gas when spraying of fire extinguishing agent is stopped m FED(end) The calculation formula is as follows:

[0132]

[0133] Z A(end)=[CO2] end ×0.05

[0134] Where, [CO] end , [CO2] end are the concentrations of CO and CO2 when the spraying of fire extinguishing agent is stopped, μL / L; [O2] end V is the volume concentration of O2 when the spraying of fire extinguishing agent is stopped; CO2(end) It is the weighting factor of CO2 when breathing is stimulated by CO2 when the spraying of fire extinguishing agent is stopped; LC 50,CO It refers to the median lethal concentration of CO within a certain exposure time; Z A(end) It is the acid poisoning factor when the spraying of fire extinguishing agent is stopped.

[0135] Toxicity index of irritating gas when spraying fire extinguishing agent FEC(start) It is equal to the sum of the values ​​obtained by dividing the critical concentration of each irritant gas at the beginning of the injection of the fire extinguishing agent by the critical concentration of each irritant gas that is expected to cause personal incapacity.

[0136] Toxicity index of irritating gas when spraying fire extinguishing agent is stopped m FEC(end) It is equal to the sum of the values ​​obtained by dividing the critical concentration of each irritant gas that is expected to cause personal incapacity when the spraying of the fire extinguishing agent is stopped by the irritant gas involved.

[0137] The toxicity index m when the asphyxiating gas reaches its peak after the spraying of the fire extinguishing agent is stopped FED(re,peak) The calculation formula is as follows:

[0138]

[0139] Z A =[CO2] re,peak ×0.05

[0140] Where, [CO] re,peak , [CO2] re,peak They are the highest concentrations of CO and CO2 after stopping the spraying of fire extinguishing agent, μL / L; is the average volume concentration of O2; is the weighting factor of CO2 when respiration is stimulated by CO2; LC 50,CO It refers to the median lethal concentration of CO within a certain exposure time; Z A It is an acid poisoning factor;

[0141] Toxicity index m when the irritant gas reaches its peak after stopping the spraying of the fire extinguishing agent FEC(re,peak) It is equal to the sum of the values ​​obtained by dividing the critical concentration of each irritant gas involved by the value at which the irritant gas is expected to cause personal incapacitation.

[0142] The normalization process includes:

[0143] The evaluation indicators of the fire extinguishing effect index parameter E, the cooling effect index parameter C and the smoke toxicity suppression effect index parameter M are combined into an index data set; according to the attributes of the evaluation indicators, the index data set is divided into positive indicators and negative indicators; positive indicators refer to indicators with larger values ​​representing better effects; negative indicators refer to indicators with smaller values ​​representing better effects;

[0144] The calculation formula for normalization of positive indicators is as follows:

[0145]

[0146] The calculation formula for normalization of the reverse indicator is as follows:

[0147]

[0148] In the formula, G ij is the original value of the evaluation index of the j-th fire extinguishing agent under the i-th index, is the normalized value of the evaluation index of the j-th fire extinguishing agent under the i-th index; Max(G ij ) and Min(G ij ) are the maximum and minimum values ​​of the indicator in all samples respectively.

[0149] S3. Obtain the weights of each evaluation index under various evaluation index parameters. The process is as follows:

[0150] Calculate the proportion H of the jth fire extinguishing agent in the i-th indicator ij , i=1, 2, 3,…,n; j=1, 2, 3,…,m;

[0151]

[0152] Calculate the entropy value P under the i-th indicator i :

[0153]

[0154] In the formula, n is the number of evaluation indicators;

[0155] Calculate the weight ω of the i-th evaluation index i :

[0156]

[0157] Where m is the amount of fire extinguishing agent.

[0158] S4. Construct a lithium-ion battery fire extinguishing agent effect evaluation model. The model formula is as follows:

[0159]

[0160] Where, k is the correction coefficient; Q is the evaluation score, with a value range of [0, 100]; A is the injection temperature correction index; S is the comprehensive effect of the lithium-ion battery fire extinguishing agent;

[0161] The calculation formula of injection temperature correction index A is as follows:

[0162]

[0163] In the formula, c cell is the capacity of the lithium-ion battery; t i is the temperature when the fire extinguishing agent is sprayed; T i Thermal runaway temperature of lithium-ion battery cell;

[0164] The calculation formula for the comprehensive effect S of the lithium-ion battery fire extinguishing agent is as follows:

[0165] S=E+C+M

[0166] Wherein, E is the fire extinguishing effect index parameter, C is the cooling effect index parameter, and M is the smoke toxicity inhibition effect index parameter.

[0167] S5, inputting the normalized evaluation index value and the corresponding evaluation index weight into the lithium-ion battery cell fire extinguishing agent effect evaluation model to obtain the scores of the effects of different fire extinguishing agents on lithium-ion batteries;

[0168] The process includes:

[0169] Calculate the fire extinguishing effect parameter E:

[0170]

[0171] In the formula, is the normalized value of the ith fire extinguishing effect index, e i Including e1, e2; is the weight of the i-th fire extinguishing effect index;

[0172] Calculate the cooling effect index parameter C:

[0173]

[0174] is the normalized value of the ith cooling effect evaluation index, c i Including c1, c2 and c3; ω ci is the weight of the i-th cooling effect evaluation index;

[0175] If the sprayed fire extinguishing agent can effectively suppress the generation of asphyxiating gas and irritating gas, the calculation formula of the smoke toxicity suppression index parameter M is:

[0176]

[0177] and are the normalized values ​​of the toxicity index values ​​of asphyxiating gases and irritating gases, respectively; ω mFED and ω mFEC are the weights of the toxicity evaluation indicators for asphyxiating gases and irritating gases, respectively;

[0178] If the sprayed fire extinguishing agent fails to effectively suppress the generation of asphyxiating gas and irritating gas, the calculation formula of the smoke toxicity suppression effect index parameter M is:

[0179]

[0180] In the formula, It is the normalized value of the toxicity index when the asphyxiating gas reaches its peak after the spraying of the fire extinguishing agent is stopped. It is the normalized value of the toxicity index when the irritant gas reaches the peak after the spraying of the fire extinguishing agent is stopped, ω mFED(re,peak) is the weight of the toxicity index when the asphyxiating gas reaches its peak after the spraying of the fire extinguishing agent is stopped, ω mFEC(re,peak) The weight of the toxicity index when the irritant gas reaches its peak value after the spraying of the fire extinguishing agent is stopped;

[0181] Based on the obtained fire extinguishing effect index parameter E, cooling effect index parameter C, and smoke toxicity suppression effect index parameter M, the comprehensive effect S of the lithium-ion battery fire extinguishing agent is calculated;

[0182] Then, the comprehensive effect S of the lithium-ion battery fire extinguishing agent is substituted into the formula of the lithium-ion battery fire extinguishing agent effect evaluation model to obtain the score of the effect of the fire extinguishing agent on the lithium-ion battery. The higher the evaluation score Q of the fire extinguishing agent, the more significant the effect of the fire extinguishing agent under the selected evaluation index; conversely, the lower the evaluation score Q of the fire extinguishing agent, the worse its effect.

[0183] S6. Arrange the order of advantages and disadvantages of different fire extinguishing agents according to the scores of their effects on lithium-ion batteries.

[0184] In order to prove the authenticity and effectiveness of the method described in this embodiment, two experiments are performed below:

[0185] Experiment 1:

[0186] The experimental object uses a 106Ah ternary lithium-ion battery cell, and the lithium-ion battery cell fire extinguishing test conditions are designed as shown in Table 1 below:

[0187] Table 1

[0188]

[0189] The experiment used heating to induce thermal runaway in lithium-ion batteries. There are two temperature monitoring points in the experiment: the first temperature monitoring point TC1 is located at the midpoint of the surface of the lithium-ion battery close to the heating device; the second temperature monitoring point TC2 is located at the midpoint between the safety valve and the positive electrode on the upper surface of the battery. The battery is judged whether thermal runaway has occurred based on the voltage change of the lithium-ion battery and the temperature change of TC1, and heating is stopped after the battery thermal runaway. The time point for spraying the fire extinguishing agent is set to TC2 ≥ 500°C. During the experiment, the Hioki data acquisition instrument was used to record the changes in temperature and pressure of the lithium-ion battery over time. At the same time, a camera was placed outside the laboratory to record the entire experimental process. In addition, a portable flue gas analyzer is used to monitor the concentration changes of CO, SO2, NO2, O2, and CO2 in real time, such as Figure 3 and Figure 4 shown.

[0190] S2. Calculate the values ​​of each evaluation index under various evaluation index parameters and normalize them;

[0191] Calculate the fire extinguishing time index e1:

[0192] e1=t extinguish -t start

[0193] In the formula, t extinguish The moment when the flame is completely extinguished; start The moment to start spraying fire extinguishing agent on the flame;

[0194] Calculate the re-ignition indicator e2:

[0195]

[0196] If the lithium-ion battery does not reignite within 30 minutes after the open flame is extinguished, the value is 1; otherwise, the value is 0.

[0197] Calculate the cooling rate index c1:

[0198]

[0199] Where c1 is the cooling rate index, which refers to the average cooling rate during the injection of fire extinguishing agent; T end The temperature at which the spraying of the fire extinguishing agent stops; T start is the temperature when the fire extinguishing agent starts to be sprayed; t spary The time for spraying fire extinguishing agent;

[0200] Calculate the temperature recovery rate index c2:

[0201]

[0202] Wherein, the temperature recovery rate index c2 is the average temperature recovery rate of the temperature to the peak value after the spraying of the fire extinguishing agent is stopped, T re,peak It is the peak value of temperature rise after stopping spraying fire extinguishing agent; Δt re,peak-end It is the time interval from the cessation of spraying of fire extinguishing agent to the temperature returning to the peak value;

[0203] Calculate the low temperature maintenance time index c3:

[0204] c3=t 150℃ -t end

[0205] In the formula, t 150℃ Set as the moment when the temperature of the monitoring point exceeds the set temperature for the first time after the fire extinguishing agent is released, t end The moment to stop spraying fire extinguishing agent;

[0206] The toxicity index m when the asphyxiating gas reaches its peak after the spraying of the fire extinguishing agent is stopped FED(re,peak) The calculation formula is as follows:

[0207]

[0208] Z A =[CO2] re,peak ×0.05

[0209] Where, [CO] re,peak , [CO2] re,peak They are the highest concentrations of CO and CO2 after stopping the spraying of fire extinguishing agent, μL / L; is the average volume concentration of O2; is the weighting factor of CO2 when respiration is stimulated by CO2; LC 50,CO It refers to the median lethal concentration of CO within a certain exposure time; Z A It is an acid poisoning factor;

[0210] Toxicity index m when the irritant gas reaches its peak after stopping the spraying of the fire extinguishing agent FEC(re,peak) The calculation formula is as follows:

[0211]

[0212] In the formula, and are the concentrations of the corresponding gases; and is the critical concentration of the corresponding gas that is expected to cause incapacitation of personnel; 150μL / L, 250μL / L.

[0213] In the above, the data values ​​directly obtained and the values ​​of each evaluation index under various evaluation index parameters obtained by calculation are shown in Table 2:

[0214] Table 2

[0215]

[0216]

[0217] S3. Obtain the weights of each evaluation index under various evaluation index parameters, and obtain the weight data shown in Table 3 below:

[0218] Table 3

[0219]

[0220] Since the lithium-ion battery does not re-ignite after the above-mentioned fire extinguishing agent is sprayed, the weight of the re-ignition index ω e2 is 0.

[0221] S4. Constructing a model for evaluating the effect of fire extinguishing agents for lithium-ion batteries;

[0222] S5. The normalized evaluation index values ​​and the corresponding evaluation index weights are input into the lithium-ion battery fire extinguishing agent effect evaluation model to obtain the scores of the effects of different fire extinguishing agents on lithium-ion batteries; it is calculated that the scores of the fire extinguishing agent effects of water, liquid nitrogen, and liquid nitrogen and perfluorohexanone sprayed simultaneously are 99.47, 25.84, and 61.55, respectively.

[0223] S6. Arrange the order of merit of different fire extinguishing agents according to the scores of their effects on lithium-ion batteries. Specifically: water 99.47 points, liquid nitrogen and perfluorohexanone 61.55 points, liquid nitrogen 25.84. This shows that under experimental conditions, water has the best fire extinguishing effect on lithium-ion batteries, followed by the compound fire extinguishing agent of liquid nitrogen and perfluorohexanone, while liquid nitrogen has the worst effect. It is worth noting that the compound score of liquid nitrogen and perfluorohexanone is higher than the effect of liquid nitrogen alone, indicating that the addition of perfluorohexanone enhances the fire extinguishing performance of liquid nitrogen to a certain extent.

[0224] Experiment 2:

[0225] The experimental object uses a 106Ah ternary lithium-ion battery cell, and the lithium-ion battery cell fire extinguishing test conditions are designed as shown in Table 4 below:

[0226] Table 4

[0227]

[0228] S2. Calculate the values ​​of each evaluation index under various evaluation index parameters and normalize them;

[0229] The data values ​​directly obtained in this step and the values ​​of various evaluation indicators under various evaluation indicator parameters calculated are shown in Table 5:

[0230] Table 5

[0231]

[0232] The normalized data are shown in Table 6 below:

[0233] Table 6

[0234]

[0235] S3. Obtain the weights of each evaluation index under various evaluation index parameters. The obtained weight data are shown in Table 7 below:

[0236] Table 7

[0237]

[0238] S4. Constructing a model for evaluating the effect of fire extinguishing agents for lithium-ion batteries;

[0239] S5, inputting the normalized evaluation index value and the corresponding evaluation index weight into the lithium-ion battery cell fire extinguishing agent effect evaluation model to obtain the scores of the effects of different fire extinguishing agents on lithium-ion batteries;

[0240] The calculated scores are shown in Table 8 below:

[0241] Table 8

[0242]

[0243] S6. Arrange the order of advantages and disadvantages of different fire extinguishing agents according to the scores of their effects on lithium-ion batteries.

[0244] The sorting results are:

[0245] Water: 99.47 points, a mixed fire extinguishing agent of perfluorohexanone and 2-BTP in a mass ratio of 1:1: 87.10 points, perfluorohexanone: 45.72 points, liquid nitrogen: 39.59 points, 2-BTP: 34.98 points, and a mixed fire extinguishing agent of perfluorohexanone and 2-BTP in a mass ratio of 9:1: 28.96 points.

[0246] After sorting, it can be seen that under the experimental conditions, if only the fire extinguishing effect and cooling effect are considered, the effect of water is the best, followed by the compound fire extinguishing agent of perfluorohexanone and 2-BTP at a mass ratio of 1:1, and the worst is the compound fire extinguishing agent of perfluorohexanone and 2-BTP at a mass ratio of 9:1. In addition, the effect of the fire extinguishing agent compounded with perfluorohexanone and 2-BTP at a mass ratio of 1:1 is better than the effect of spraying perfluorohexanone and 2-BTP separately.

[0247] The embodiments described above are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention. Therefore, all changes made according to the shape and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for quantitatively evaluating the effect of a lithium-ion battery fire extinguishing agent, characterized in that: include: Design a lithium-ion battery fire extinguishing experiment and collect data to obtain evaluation index parameters, which include multiple categories including injection temperature correction index parameters, fire extinguishing effect index parameters, cooling effect index parameters, and smoke toxicity suppression effect index parameters; Calculate the values ​​of each evaluation index under various evaluation index parameters and normalize them; Obtain the weight of each evaluation index under various evaluation index parameters; Construct a model to evaluate the effect of fire extinguishing agents for lithium-ion batteries; The normalized evaluation index value and the corresponding evaluation index weight are input into the lithium-ion battery cell fire extinguishing agent effect evaluation model to obtain the scores of the effects of different fire extinguishing agents on lithium-ion batteries; The advantages and disadvantages of different fire extinguishing agents are arranged according to the scores of their effects on lithium-ion batteries.

2. A method for quantitatively evaluating the effect of a lithium-ion battery fire extinguishing agent according to claim 1, characterized in that: The formula for the evaluation model of the effect of lithium-ion battery fire extinguishing agent is as follows: Where, k is the correction coefficient; Q is the evaluation score, with a value range of [0, 100]; A is the injection temperature correction index; S is the comprehensive effect of the lithium-ion battery fire extinguishing agent; The calculation formula of injection temperature correction index A is as follows: In the formula, c cell is the capacity of the lithium-ion battery; t i is the temperature when the fire extinguishing agent is sprayed; T i Thermal runaway temperature of lithium-ion battery cell; The calculation formula for the comprehensive effect S of the lithium-ion battery fire extinguishing agent is as follows: S=E+C+M Wherein, E is the fire extinguishing effect index parameter, C is the cooling effect index parameter, and M is the smoke toxicity inhibition effect index parameter.

3. A method for quantitatively evaluating the effect of a lithium-ion battery fire extinguishing agent according to claim 2, characterized in that: The fire extinguishing effect index parameter E includes the fire extinguishing time index e1 and the re-ignition situation index e2; Calculate the fire extinguishing time index e1: e1=t extinguish -t start In the formula, t extinguish The moment when the flame is completely extinguished; start The moment to start spraying fire extinguishing agent on the flame; Calculate the re-ignition indicator e2: If the lithium-ion battery does not reignite within a set time after the open flame is extinguished, the value is 1; otherwise, the value is 0.

4. A method for quantitatively evaluating the effect of a lithium-ion battery fire extinguishing agent according to claim 3, characterized in that: The cooling effect index parameter C includes the cooling rate index c1, the temperature recovery rate index c2 and the low temperature maintenance time index c3; Calculate the cooling rate index c1: In the formula, c1 is the cooling rate index, which refers to the average cooling rate during the injection of fire extinguishing agent; T end The temperature at which the spraying of the fire extinguishing agent stops; T start is the temperature when the fire extinguishing agent starts to be sprayed; t spary The time for spraying fire extinguishing agent; Calculate the temperature recovery rate index c2: Wherein, the temperature recovery rate index c2 is the average temperature recovery rate of the temperature to the peak value after the spraying of the fire extinguishing agent is stopped, T re,peak It is the peak value of temperature rise after stopping spraying fire extinguishing agent; Δt re,peak-end It is the time interval from the cessation of spraying of fire extinguishing agent to the temperature returning to the peak value; Calculate the low temperature maintenance time index c3: c3=t 设定 -t end Where, t 设定 is the moment when the temperature of the monitoring point exceeds the set temperature for the first time after the fire extinguishing agent is released, t end This is the moment to stop spraying the fire extinguishing agent.

5. A method for quantitatively evaluating the effect of a lithium-ion battery fire extinguishing agent according to claim 4, characterized in that: The smoke toxicity suppression effect index parameter M includes the toxicity index m of the asphyxiating gas FED 、Toxicity index of irritating gas m FEC , Toxicity index m when the asphyxiating gas reaches its peak after stopping the spraying of fire extinguishing agent FED(re,peak) , Toxicity index m when the irritating gas reaches its peak after stopping the spraying of the fire extinguishing agent FEC(re,peak) ; Toxicity index of asphyxiating gas FED The calculation formula is as follows: Toxicity index of irritant gas m FEC The calculation formula is as follows: In the formula, m FED(start) It is the toxicity index of asphyxiating gas when the fire extinguishing agent is sprayed, m FED(end) It is the toxicity index of asphyxiating gas when the spraying of fire extinguishing agent is stopped, m FEC(start) It is the toxicity index of the irritating gas when the fire extinguishing agent is sprayed, m FEC(end) It is the toxicity index of the irritant gas when the spraying of the fire extinguishing agent is stopped; The toxicity index m when the asphyxiating gas reaches its peak after the spraying of the fire extinguishing agent is stopped FED(re,peak) The calculation formula is as follows: With A =[CO2] re,peak ×0.05 Where, [CO] re,peak , [CO2] re,peak They are the highest concentrations of CO and CO2 after stopping the spraying of fire extinguishing agent, μL / L; is the average volume concentration of O2; is the weighting factor of CO2 when respiration is stimulated by CO2; LC 50,CO It refers to the median lethal concentration of CO within a certain exposure time; Z A It is an acid poisoning factor; Toxicity index m when the irritant gas reaches its peak after stopping the spraying of the fire extinguishing agent FEC(re,peak) It is equal to the sum of the values ​​obtained by dividing the critical concentration of each irritant gas involved by the value at which the irritant gas is expected to cause personal incapacitation.

6. A method for quantitatively evaluating the effect of a lithium-ion battery fire extinguishing agent according to claim 1, characterized in that: The normalization process includes: The evaluation indicators of the fire extinguishing effect index parameter E, the cooling effect index parameter C and the smoke toxicity suppression effect index parameter M are combined into an index data set; according to the attributes of the evaluation indicators, the index data set is divided into positive indicators and negative indicators; positive indicators refer to indicators with larger values ​​representing better effects; negative indicators refer to indicators with smaller values ​​representing better effects; The calculation formula for normalization of positive indicators is as follows: The calculation formula for normalization of the reverse indicator is as follows: In the formula, G ij is the original value of the evaluation index of the j-th fire extinguishing agent under the i-th index, is the normalized value of the evaluation index of the j-th fire extinguishing agent under the i-th index; Max(G ij ) and Min(G ij ) are the maximum and minimum values ​​of the indicator in all samples respectively.

7. A method for quantitatively evaluating the effect of a lithium-ion battery fire extinguishing agent according to claim 1, characterized in that: Obtain the weights of each evaluation index under the evaluation index parameters, including: Calculate the proportion H of the jth fire extinguishing agent in the i-th indicator ij ,i=1,2,3,…,n; j=1,2,3,…,m; Calculate the entropy value p under the i-th indicator i : In the formula, n is the number of evaluation indicators; Calculate the weight ω of the i-th evaluation index i : Where m is the amount of fire extinguishing agent.

8. A method for quantitatively evaluating the effect of a lithium-ion battery fire extinguishing agent according to claim 5, characterized in that: The normalized evaluation index value and the corresponding evaluation index weight are input into the lithium-ion battery cell fire extinguishing agent effect evaluation model to obtain the scores of the effects of different fire extinguishing agents on lithium-ion batteries. The process includes: Calculate the fire extinguishing effect parameter E: In the formula, is the normalized value of the ith fire extinguishing effect index, e i Including e1, e2; is the weight of the i-th fire extinguishing effect index; Calculate the cooling effect index parameter C: c i * is the normalized value of the ith cooling effect evaluation index, c i Including c1, c2 and c3; ω ci is the weight of the i-th cooling effect evaluation index; If the sprayed fire extinguishing agent can effectively suppress the generation of asphyxiating gas and irritating gas, the calculation formula of the smoke toxicity suppression index parameter M is: and are the normalized values ​​of the toxicity index values ​​of asphyxiating gases and irritating gases, respectively; ω mFED and ω mFEC are the weights of the toxicity evaluation indicators for asphyxiating gases and irritating gases, respectively; If the sprayed fire extinguishing agent fails to effectively suppress the generation of asphyxiating gas and irritating gas, the calculation formula of the smoke toxicity suppression effect index parameter M is: In the formula, It is the normalized value of the toxicity index when the asphyxiating gas reaches its peak after the spraying of the fire extinguishing agent is stopped. It is the normalized value of the toxicity index when the irritant gas reaches the peak after the spraying of the fire extinguishing agent is stopped, ω mFED(re,peak) is the weight of the toxicity index when the asphyxiating gas reaches its peak after the spraying of the fire extinguishing agent is stopped, ω mFEC(re,peak) The weight of the toxicity index when the irritant gas reaches its peak value after the spraying of the fire extinguishing agent is stopped; Based on the obtained fire extinguishing effect index parameter E, cooling effect index parameter C, and smoke toxicity suppression effect index parameter M, the comprehensive effect S of the lithium-ion battery fire extinguishing agent is calculated; Then, the comprehensive effect S of the lithium-ion battery fire extinguishing agent is substituted into the formula of the lithium-ion battery fire extinguishing agent effect evaluation model to obtain the score of the effect of the fire extinguishing agent on the lithium-ion battery.

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