A method for quantitatively evaluating the effect of a lithium ion battery cell fire extinguishing agent

Abstract

The application discloses a kind of lithium ion battery cell fire extinguishing agent effect quantitative evaluation method, from the fire extinguishing effect of fire extinguishing agent, cooling effect and the effect of inhibiting smoke toxicity three dimensions are comprehensively evaluated, overcome the defect that present method cannot fully reflect the overall performance of fire extinguishing agent under single evaluation dimension;At the same time, by introducing the weight of each index, solve the problem that each dimension evaluation is independent in traditional method, lack of correlation;In addition, by correcting the temperature when spraying fire extinguishing agent, to enhance the objectivity and reliability of evaluation result, ensure that the evaluation results under different experimental conditions have higher consistency and comparability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery fire extinguishing agents, and in particular to a method for quantitatively evaluating the effect of a lithium ion battery fire extinguishing agent. BACKGROUND

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

[0003] Existing lithium battery fire extinguishing methods focus on the development of fire extinguishing agents. Typically, under the same experimental conditions (such as battery size, thermal runaway triggering conditions, etc.), fire extinguishing agents are sprayed during the flaming stage after lithium battery thermal runaway. By evaluating the fire extinguishing and cooling effects of different fire extinguishing agents, the best fire extinguishing agent is selected, and further research is conducted on the inhibitory effect of the best fire extinguishing agent during battery module thermal runaway.

[0004] However, the existing evaluation method of the effect of lithium ion battery fire extinguishing agents has the following shortcomings:

[0005] 1. The existing evaluation method is mostly qualitative, lacking quantitative means, making it difficult to determine the relative advantages and disadvantages of each fire extinguishing agent. For example, perfluorohexanone has a significant cooling effect, but its decomposition products such as CO, CO2 and HF can increase the toxicity of the system, thereby posing potential risks. Liquid nitrogen has a fast initial cooling speed, but its low-temperature maintenance effect is poor. Since different fire extinguishing agents have their own advantages and disadvantages, simple qualitative analysis cannot accurately compare their comprehensive effects.

[0006] 2. Single evaluation dimension. The existing evaluation method focuses on isolated evaluation of fire extinguishing and cooling, and fails to cover the effect of fire extinguishing agents on inhibiting or releasing toxic gases. In addition, the existing evaluation system lacks comprehensive consideration of the relationship between each evaluation dimension, making it impossible to comprehensively evaluate the comprehensive performance of fire extinguishing agents.

[0007] 3. Existing evaluation methods do not fully consider the temperature correction when spraying fire extinguishing agents. Due to factors such as the uneven distribution of active materials inside lithium-ion batteries, the temperature of their thermal runaway is uncontrollable. For experiments using temperature-sensing 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 reaction time. The temperature of lithium-ion batteries 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 existing technology and provide a quantitative evaluation method for the effect of lithium-ion battery cell fire extinguishing agents. This method comprehensively evaluates the fire extinguishing effect, cooling effect and smoke toxicity inhibition effect of the fire extinguishing agent from three dimensions, overcoming the defect of the existing method that the overall performance of the fire extinguishing agent cannot be fully reflected under a single evaluation dimension; at the same time, by introducing the weight of each indicator, the problem of independent evaluation and lack of correlation of each dimension 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, ensuring that the evaluation results under different experimental conditions have higher consistency and comparability.

[0009] To achieve the above objectives, the technical solutions provided by the present invention are:

[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, including multiple categories such as spray 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 on lithium-ion battery cells;

[0015] The normalized evaluation index values ​​and corresponding evaluation index weights 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] According to the scores of the effects of different extinguishing agents on lithium ion cells, the extinguishing agents are ranked in order of quality.

[0017] Further, the formula of the lithium ion cell extinguishing agent effect evaluation model is as follows:

[0018]

[0019] In the formula, k is a correction coefficient; Q is the evaluation score, and the value range is [0, 100]; A is the injection temperature correction index; S is the lithium ion cell extinguishing agent comprehensive effect;

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

[0021]

[0022] In the formula, c cell is the capacity of the lithium ion cell; t i is the temperature when the extinguishing agent is injected; T i is the thermal runaway temperature of the lithium ion cell;

[0023] The calculation formula of the lithium ion cell extinguishing agent comprehensive effect S is as follows:

[0024] S=E+C+M

[0025] In the formula, E is the extinguishing effect index parameter, C is the cooling effect index parameter, and M is the smoke toxicity suppression effect index parameter.

[0026] Further, the extinguishing effect index parameter E includes the extinguishing time index e1 and the reignition condition index e2.

[0027] The extinguishing time index e1 is calculated as follows:

[0028] e1=t extinguish t start

[0029] In the formula, t extinguish is the time when the flame is completely extinguished; t start is the time when the extinguishing agent is injected to the flame;

[0030] The reignition condition index e2 is calculated as follows:

[0031]

[0032] If the lithium ion cell does not reignite within a set time after the open fire is extinguished, 1 is taken, otherwise 0 is taken.

[0033] Further, the cooling effect index parameter C includes the cooling rate index c1, the temperature rise rate index c2, and the low-temperature maintenance time index c3.

[0034] The cooling rate index c1 is calculated as follows:

[0035]

[0036] In the formula, c1 is the cooling rate index, which is the average cooling rate during the injection of the fire extinguishing agent; T end is the temperature at the time of stopping the injection of the fire extinguishing agent; T start is the temperature at the time of starting the injection of the fire extinguishing agent; t spary is the time of injecting the fire extinguishing agent;

[0037] The temperature rise rate index c2 is calculated as follows:

[0038]

[0039] In the formula, the temperature rise rate index c2 is the average temperature rise rate of the temperature rise to the peak value after stopping the injection of the fire extinguishing agent, T re,peak is the peak value of the temperature rise after stopping the injection of the fire extinguishing agent; Δt re,peak-end is the time interval from stopping the injection of the fire extinguishing agent to the temperature rise to the peak value;

[0040] The low-temperature maintenance time index c3 is calculated as follows:

[0041] c3 = t 设定 -t end

[0042] In the formula, t 设定 is set as the time when the temperature of the monitoring point exceeds the set temperature for the first time after the release of the fire extinguishing agent, t end is the time of stopping the injection of the fire extinguishing agent.

[0043] Further, the smoke toxicity suppression effect index parameter M includes the toxicity index m FED of the asphyxiating gas, the toxicity index m FEC of the stimulating gas, the toxicity index m FED(re,peak) of the asphyxiating gas at the time of reaching the peak value after stopping the injection of the fire extinguishing agent, and the toxicity index m FEC(re,peak) of the stimulating gas at the time of reaching the peak value after stopping the injection of the fire extinguishing agent.

[0044] The calculation formula of the toxicity index m FED of the asphyxiating gas is as follows:

[0045]

[0046] The calculation formula of the toxicity index m FEC of the stimulating gas is as follows:

[0047]

[0048] wherein m FED(start) is the toxicity index of the asphyxiating gas at the beginning of the injection of the extinguishing agent, m FED(end) is the toxicity index of the asphyxiating gas at the end of the injection of the extinguishing agent, m FEC(start) is the toxicity index of the irritating gas at the beginning of the injection of the extinguishing agent, m FEC(end) is the toxicity index of the irritating gas at the end of the injection of the extinguishing agent, m

[0049] is the toxicity index of the asphyxiating gas at the peak after the injection of the extinguishing agent has been stopped, m FED(re,peak) is calculated as follows:

[0050]

[0051] Z A = [CO2] re,peak x 0.05

[0052] wherein [CO] re,peak , [CO2] re,peak are the maximum concentrations of CO and CO2, respectively, in μL / L after the injection of the extinguishing agent has been stopped; is the average volume concentration of O2; is the weighting factor for CO2 when stimulating respiration; LC 50,CO is the concentration of CO that is lethal to 50% of the exposed population within a certain exposure time; Z A is the acidosis factor;

[0053] is the toxicity index of the irritating gas at the peak after the injection of the extinguishing agent has been stopped, m FEC(re,peak) is equal to the sum of the values obtained by dividing each of the irritating gases involved by the critical concentration of the respective irritating gas that is expected to cause incapacitation of the personnel.

[0054] Further, the normalization process comprises:

[0055] combining the individual evaluation criteria of the extinguishing effectiveness indicator parameter E, the cooling effectiveness indicator parameter C and the smoke toxicity suppression effectiveness indicator parameter M into an indicator data set; dividing the indicator data set into positive indicators and negative indicators depending on the properties of the evaluation criteria; a positive indicator is an indicator whose value increases the better the effectiveness; a negative indicator is an indicator whose value decreases the better the effectiveness;

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

[0057]

[0058] The calculation of the normalization of the negative indicators is as follows:

[0059]

[0060] G ij is the original value of the evaluation index of the jth fire extinguishing agent under the ith index, is the normalized value of the evaluation index of the jth fire extinguishing agent under the ith index; Max(G ij ) and Min(G ij ) are the maximum and minimum values of the index among all samples, respectively.

[0061] Further, the weight of each evaluation index under the evaluation index parameter is calculated, including:

[0062] The proportion H ij of the jth fire extinguishing agent in the ith index is calculated, i = 1, 2, 3, …, n; j = 1, 2, 3, …, m;

[0063]

[0064] The entropy value P i under the ith index is calculated:

[0065]

[0066] Wherein, n is the number of evaluation indexes;

[0067] The weight ω i of the ith evaluation index is calculated:

[0068]

[0069] Wherein, m is the number of fire extinguishing agents.

[0070] Further, the normalized evaluation index value and the corresponding evaluation index weight are input into the lithium ion cell fire extinguishing agent effect evaluation model to obtain the scores of different fire extinguishing agents on the lithium ion cell effect, the process including:

[0071] The fire extinguishing effect parameter E is calculated:

[0072]

[0073] Wherein, is the normalized value of the ith fire extinguishing effect index, e i including e1, e2; is the weight of the ith fire extinguishing effect index;

[0074] The cooling effect index parameter C is calculated:

[0075]

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

[0077] If the injection of the fire extinguishing agent can effectively inhibit the generation of the asphyxiating gas and the irritating gas, the calculation formula of the smoke toxicity inhibition effect index parameter M is:

[0078]

[0079] and are the normalized values of the toxicity index values of the asphyxiating gas and the irritating gas respectively; ω mFED and ω mFEC are the weights of the toxicity evaluation indexes of the asphyxiating gas and the irritating gas respectively;

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

[0081]

[0082] In the formula, is the normalized value of the toxicity index when the asphyxiating gas reaches the peak after stopping the injection of the fire extinguishing agent, is the normalized value of the toxicity index when the irritating gas reaches the peak after stopping the injection of the fire extinguishing agent, ω mFED(re,peak) is the weight of the toxicity index when the asphyxiating gas reaches the peak after stopping the injection of the fire extinguishing agent, ω mFEC(re,peak) is the weight of the toxicity index when the irritating gas reaches the peak after stopping the injection of the fire extinguishing agent;

[0083] The comprehensive effect S of the fire extinguishing agent on the lithium ion cell is calculated based on the obtained fire extinguishing effect index parameter E, the cooling effect index parameter C and the smoke toxicity inhibition effect index parameter M.

[0084] The comprehensive effect S of the fire extinguishing agent on the lithium ion cell is substituted into the formula of the lithium ion cell fire extinguishing agent effect evaluation model, so as to obtain the score of the effect of the fire extinguishing agent on the lithium ion cell.

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

[0086] 1. The comprehensive evaluation is performed from three dimensions of the fire extinguishing effect, the cooling effect and the 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 in a single evaluation dimension.

[0087] 2. By introducing the weight of each index, the problem of independent dimensions and lack of correlation in the traditional method is solved.

[0088] 3. By correcting the temperature when the fire extinguishing agent is sprayed, the objectivity and reliability of the evaluation results are enhanced, and the evaluation results under different experimental conditions have higher consistency and comparability. BRIEF DESCRIPTION OF DRAWINGS

[0089] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the services required in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0090] Figure 1 A principle flow chart of a lithium ion cell fire extinguishing agent effect quantitative evaluation method according to an embodiment of the present application;

[0091] Figure 2 A temperature change curve diagram of each fire extinguishing agent in experiment 1 (taking the time when the fire extinguishing agent is sprayed as 0 point);

[0092] Figure 3 A CO, SO2, NO2 gas concentration change curve diagram when water is sprayed in experiment 1;

[0093] Figure 4 A O2, CO2 gas concentration change curve diagram when water is sprayed in experiment 1;

[0094] Figure 5 A temperature change curve diagram of each fire extinguishing agent in experiment 2 (taking the time when the fire extinguishing agent is sprayed as 0 point). DETAILED DESCRIPTION

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

[0096] As shown in the figure, the lithium ion cell fire extinguishing agent effect quantitative evaluation method according to the present embodiment includes the following steps: Figure 1 S1, design a lithium ion cell fire extinguishing experiment and collect data, obtain evaluation index parameters, which include multiple categories such as spraying temperature correction index parameters, fire extinguishing effect index parameters, cooling effect index parameters, and smoke toxicity suppression effect index parameters.

[0097]

[0098] ​Specifically, in this step, when designing the lithium ion battery cell fire extinguishing experiment, lithium ion battery cells of the same specification are selected, the same extinguishing agent injection height, extinguishing agent injection time, and other conditions are selected, the type of extinguishing agent is changed, and the lithium ion battery cell is induced to thermal runaway by heating, overcharging, or needle pricking. Once the lithium ion battery cell experiences thermal runaway, the triggering device such as heating or overcharging is immediately turned off, and the extinguishing agent is sprayed at the preset injection 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 a daily data acquisition instrument. The concentration change of the gas generated in the experiment can be detected continuously at a fixed point or collected using a smoke exhaust pipe, and then analyzed using a smoke analyzer, a gas chromatograph, or a Fourier transform infrared spectrometer. In addition, the entire experimental process is recorded in real time by a video camera. After the injection is completed, all monitoring equipment is turned off after the temperature of the lithium ion battery cell drops to 100°C.

[0100] Real-time data is continuously collected from various monitoring equipment to obtain evaluation index parameters; the evaluation index parameters include four types of injection temperature correction index parameters, extinguishing effect index parameters, cooling effect index parameters, and smoke toxicity suppression effect index parameters;

[0101] The injection temperature correction index parameters include lithium ion battery cell thermal runaway temperature index and temperature index when the extinguishing agent is injected. The lithium ion battery cell thermal runaway temperature refers to the temperature of the lithium ion battery cell when it experiences thermal runaway. The determination standard for thermal runaway is referred to in GB / T 36276-2018, i.e., when the temperature monitoring point on the opposite side of the lithium ion battery cell close to the heating device has a continuous three-second temperature rise rate greater than 1°C / s and the voltage drops by 25%, it is determined to be thermal runaway.

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

[0103] The cooling effect index parameter C includes the cooling rate index c1, the temperature rise 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 extinguishing agent is released according to CCCF / XFJJ-01.

[0104] The smoke toxicity suppression effect index parameter M includes the toxicity index m FED of suffocating gas, the toxicity index m FEC of irritating gas, and the toxicity index m FED(re,peak) of suffocating gas when it reaches the peak after the injection of the extinguishing agent is stopped.m, the toxicity index of the irritating gas at the time when the irritating gas reaches the peak after stopping the injection of the fire extinguishing agent FEC(re,peak) .

[0105] S2, calculating the value of each evaluation index under each type of evaluation index parameter, and normalizing;

[0106] The specific process of calculating the value of each evaluation index under each type of evaluation index parameter includes:

[0107] Calculating the fire extinguishing time index e1:

[0108] e1=t extinguish -t start

[0109] In the formula, t extinguish is the time when the flame is completely extinguished; t start is the time when the fire extinguishing agent is started to be injected;

[0110] Calculating the reignition condition index e2:

[0111]

[0112] Taking 1 if there is no reignition of the lithium ion cell within 30 minutes after the open fire is extinguished, and taking 0 otherwise.

[0113] Calculating the cooling rate index c1:

[0114]

[0115] In the formula, c1 is the cooling rate index, which refers to the average cooling rate during the injection of the fire extinguishing agent; T end is the temperature when the injection of the fire extinguishing agent is stopped; T start is the temperature when the injection of the fire extinguishing agent is started; t spary is the time of injecting the fire extinguishing agent;

[0116] Calculating the temperature rising rate index c2:

[0117]

[0118] In the formula, the temperature rising rate index c2 is the average temperature rising rate when the temperature rises to the peak after stopping the injection of the fire extinguishing agent, T re,peak is the peak value of the temperature rising after stopping the injection of the fire extinguishing agent; Δt re,peak-end is the time interval from stopping the injection of the fire extinguishing agent to the temperature rising to the peak;

[0119] Calculating the low-temperature maintenance time index c3:

[0120] c3=t 150℃ -t end

[0121] where t 150℃ is the time when the temperature at the monitoring point first exceeds the set temperature after the fire extinguishing agent is released end is the time when the injection of the fire extinguishing agent is stopped.

[0122] the toxicity index m of the asphyxiating gas FED is calculated by the following formula:

[0123]

[0124] the toxicity index m of the irritating gas FEC is calculated by the following formula:

[0125]

[0126] where m FED(start) is the toxicity index m of the asphyxiating gas at the time when the injection of the fire extinguishing agent is started FED(end) is the toxicity index m of the asphyxiating gas at the time when the injection of the fire extinguishing agent is stopped FEC(start) is the toxicity index m of the irritating gas at the time when the injection of the fire extinguishing agent is started FEC(end) is the toxicity index m of the irritating gas at the time when the injection of the fire extinguishing agent is stopped

[0127] the toxicity index m of the asphyxiating gas at the time when the injection of the fire extinguishing agent is started FED(start) is calculated by the following formula:

[0128]

[0129] Z A(start) = [CO2] start x 0.05

[0130] where [CO] start , [CO2] start are the concentrations of CO and CO2, respectively, at the time when the injection of the fire extinguishing agent is started, μL / L; [O2] start is the volume concentration of O2 at the time when the injection of the fire extinguishing agent is started; V CO2(start) is the weighting factor of CO2 at the time when the injection of the fire extinguishing agent is started; LC 50,CO is the concentration of CO that is lethal to 50% of the exposed population in a certain exposure time; Z A(start) is the acidosis factor at the time when the injection of the fire extinguishing agent is started;

[0131] the toxicity index m of the asphyxiating gas at the time when the injection of the fire extinguishing agent is stopped FED(end) is calculated by the following formula:

[0132]

[0133] Z A(end)= [CO2] end x 0.05

[0134] wherein [CO] end , [CO2] end are the concentrations of CO, CO2, respectively, in μL / L at the time of stopping the injection of the fire extinguishing agent; [O2] end is the volume concentration of O2 at the time of stopping the injection of the fire extinguishing agent; V CO2(end) is the weighting factor of CO2 when CO2 stimulates respiration at the time of stopping the injection of the fire extinguishing agent; LC 50,CO is the median lethal concentration of CO within a certain exposure time; Z A(end) is the acidosis factor at the time of stopping the injection of the fire extinguishing agent.

[0135] Toxicity index m of the irritant gas at the time of starting the injection of the fire extinguishing agent FEC(start) is equal to the sum of the values obtained by dividing each of the irritant gases involved by the critical concentration of the respective irritant gas which is expected to cause incapacitation of the personnel.

[0136] Toxicity index m of the irritant gas at the time of stopping the injection of the fire extinguishing agent FEC(end) is equal to the sum of the values obtained by dividing each of the irritant gases involved by the critical concentration of the respective irritant gas which is expected to cause incapacitation of the personnel.

[0137] Toxicity index m of the asphyxiating gas at the time of reaching the peak after stopping the injection of the fire extinguishing agent FED(re,peak) is calculated according to the following formula:

[0138]

[0139] Z A = [CO2] re,peak x 0.05

[0140] wherein [CO] re,peak , [CO2] re,peak are the maximum concentrations of CO, CO2, respectively, in μL / L after stopping the injection of the fire extinguishing agent; is the average volume concentration of O2; is the weighting factor of CO2 when CO2 stimulates respiration; LC 50,CO is the median lethal concentration of CO within a certain exposure time; Z A is the acidosis factor;

[0141] Toxicity index m of the irritant gas at the time of reaching the peak after stopping the injection of the fire extinguishing agent FEC(re,peak) is equal to the sum of the values obtained by dividing each of the irritant gases involved by the critical concentration of the respective irritant gas which is expected to cause incapacitation of the personnel.

[0142] The normalization process includes:

[0143] Each evaluation index of the fire extinguishing effect index parameter E, the cooling effect index parameter C and the smoke toxicity suppression effect index parameter M is combined into an index data set; according to the attributes of the evaluation indexes, the index data set is divided into positive indexes and reverse indexes; the positive index is an index whose larger index value represents better effect; the reverse index is an index whose smaller index value represents better effect;

[0144] The calculation formula of the positive index normalization is as follows:

[0145]

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

[0147]

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

[0149] S3, the weight of each evaluation index under each type of evaluation index parameter is calculated, and the process is as follows:

[0150] The proportion H ij of the jth fire extinguishing agent in the ith index is calculated, i.e. i = 1, 2, 3, …, n; j = 1, 2, 3, …, m;

[0151]

[0152] The entropy value P i under the ith index is calculated:

[0153]

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

[0155] The weight ω i of the ith evaluation index is calculated:

[0156]

[0157] In the formula, m is the number of fire extinguishing agents.

[0158] S4, a lithium ion cell fire extinguishing agent effect evaluation model is constructed, and the formula of the model is as follows:

[0159]

[0160] In the formula, k is a correction coefficient; Q is an evaluation score, with a value range of [0, 100]; A is a jet temperature correction index; S is a comprehensive effect of the lithium ion cell fire extinguishing agent;

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

[0162]

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

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

[0165] S = E + C + M

[0166] In the formula, E is a fire extinguishing effect index parameter, C is a cooling effect index parameter, and M is a smoke toxicity suppression effect index parameter.

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

[0168] The process includes:

[0169] Calculate the fire extinguishing effect parameter E:

[0170]

[0171] In the formula, is the normalized value of the i th fire extinguishing effect index, e i including e1 and 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 i th 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 injection of fire extinguishing agent can effectively inhibit the generation of suffocating gas and irritating gas, the calculation formula of the smoke toxicity inhibition effect index parameter M is:

[0176]

[0177] and are the normalized values of the toxicity index values of the suffocating gas and the irritating gas respectively; ω mFED and ω mFEC are the weights of the toxicity evaluation indexes of the suffocating gas and the irritating gas respectively;

[0178] If the injection of fire extinguishing agent fails to effectively inhibit the generation of suffocating gas and irritating gas, the calculation formula of the smoke toxicity inhibition effect index parameter M is:

[0179]

[0180] wherein, is the normalized value of the toxicity index when the suffocating gas reaches the peak after stopping the injection of fire extinguishing agent, is the normalized value of the toxicity index when the irritating gas reaches the peak after stopping the injection of fire extinguishing agent, ω mFED(re,peak) is the weight of the toxicity index when the suffocating gas reaches the peak after stopping the injection of fire extinguishing agent, ω mFEC(re,peak) is the weight of the toxicity index when the irritating gas reaches the peak after stopping the injection of fire extinguishing agent;

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

[0182] The comprehensive action effect S of the lithium ion battery fire extinguishing agent is substituted into the formula of the lithium ion battery fire extinguishing agent action effect evaluation model, so as to obtain the score of the action 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 action effect of the fire extinguishing agent under the selected evaluation index; on the contrary, the lower the evaluation score Q of the fire extinguishing agent, the poorer the effect.

[0183] S6, the order of the advantages and disadvantages of different fire extinguishing agents is arranged according to the scores of the action effects of different fire extinguishing agents on the lithium ion battery.

[0184] In order to prove the authenticity and effectiveness of the method described in the embodiment, two experiments are carried out as follows:

[0185] Experiment 1:

[0186] The experimental object is a 106 Ah ternary lithium ion battery, and the design of the lithium ion battery fire extinguishing experiment conditions is shown in Table 1.

[0187] Table 1

[0188]

[0189] The experiment adopts a heating method to induce thermal runaway of the lithium ion cell. Two temperature monitoring points are set in the experiment: the first temperature monitoring point TC1 is located at the midpoint of the opposite surface of the lithium ion cell 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 cell. Whether the battery has thermal runaway is judged according to the voltage change of the lithium ion cell and the temperature change of TC1, and the heating is stopped after the thermal runaway of the battery. The time point of spraying the fire extinguishing agent is set as TC2≥500℃. During the experiment, the changes of the temperature and pressure of the lithium ion cell with time are recorded by a daily data acquisition instrument. At the same time, a camera is placed outside the laboratory to record the whole experiment process. In addition, a portable smoke analyzer is used to monitor the concentration changes of CO, SO2, NO2, O2 and CO2 in real time, as shown in Figure 3 and Figure 4

[0190] S2, calculate the value of each evaluation index under each type of evaluation index parameter, and normalize;

[0191] Calculate the fire extinguishing time index e1:

[0192] e1=t extinguish -t start

[0193] In the formula, t extinguish is the time when the flame is completely extinguished; t start is the time when the fire extinguishing agent is sprayed to the flame;

[0194] Calculate the rekindling condition index e2:

[0195]

[0196] Take 1 if the lithium ion cell does not rekindle within 30 minutes after the open fire is extinguished, otherwise take 0.

[0197] Calculate the cooling rate index c1:

[0198]

[0199] In the formula, c1 is the cooling rate index, which refers to the average cooling rate during the spraying of the fire extinguishing agent; T end is the temperature when the spraying of the fire extinguishing agent is stopped; T start is the temperature when the spraying of the fire extinguishing agent is started; t spary is the time of spraying the fire extinguishing agent;

[0200] ​The temperature rise rate index c2 is calculated:

[0201]

[0202] In the formula, the temperature rise rate index c2 is the average temperature rise rate of the temperature rise to the peak value after stopping the injection of the fire extinguishing agent, T re,peak is the peak value of the temperature rise after stopping the injection of the fire extinguishing agent; Δt re,peak-end is the time interval from stopping the injection of the fire extinguishing agent to the temperature rise to the peak value;

[0203] The low-temperature maintenance time index c3 is calculated:

[0204] c3 = t 150℃ -t end

[0205] In the formula, t 150℃ is set as the time when the temperature of the monitoring point exceeds the set temperature for the first time after the release of the fire extinguishing agent, t end is the time when the injection of the fire extinguishing agent is stopped;

[0206] The toxicity index m of the asphyxiating gas reaching the peak value after stopping the injection of the fire extinguishing agent is calculated as follows: FED(re,peak)

[0207]

[0208] Z A = [CO2] re,peak × 0.05

[0209] In the formula, [CO] re,peak , [CO2] re,peak are the highest concentrations of CO and CO2 respectively after stopping the injection of the fire extinguishing agent, μL / L; is the average volume concentration of O2; is the weighting factor of CO2 when stimulating respiration; LC 50,CO is the median lethal concentration of CO within a certain exposure time; Z A is the acid poisoning factor;

[0210] The toxicity index m of the stimulating gas reaching the peak value after stopping the injection of the fire extinguishing agent is calculated as follows: FEC(re,peak)

[0211]

[0212] In the formula, and are the concentrations of the corresponding gases; and are the critical concentrations of the corresponding gases that are expected to cause the loss of ability of personnel.​​ 150 μL / L, 250 μL / L.

[0213] Among the above, the data values directly obtained and the values of each evaluation index under each type of evaluation index parameter calculated are shown in Table 2:

[0214] Table 2

[0215]

[0216]

[0217] S3, the weight of each evaluation index under each type of evaluation index parameter is obtained, and the weight data shown in Table 3 is obtained:

[0218] Table 3

[0219]

[0220] Since the lithium ion cell does not exist after the above fire extinguishing agent is sprayed. Therefore, the weight ω of the rekindling condition index e2 is 0.

[0221] S4, constructing a lithium ion cell fire extinguishing agent effect evaluation model;

[0222] S5, inputting the normalized evaluation index value and the corresponding evaluation index weight into the lithium ion cell fire extinguishing agent effect evaluation model to obtain the scores of different fire extinguishing agents on the effect of lithium ion cells. Calculation shows that the scores of water, liquid nitrogen, and liquid nitrogen and perfluorohexone are 99.47, 25.84, and 61.55, respectively.

[0223] S6, arranging the order of different fire extinguishing agents according to the scores of different fire extinguishing agents on the effect of lithium ion cells. Specifically, water is 99.47 points, liquid nitrogen and perfluorohexone are 61.55 points, and liquid nitrogen is 25.84. This shows that under the experimental conditions, water has the best fire extinguishing effect on lithium ion batteries, followed by liquid nitrogen and perfluorohexone, and liquid nitrogen has the worst effect. It is worth noting that the score of liquid nitrogen and perfluorohexone is higher than that of liquid nitrogen alone, which shows that the addition of perfluorohexone enhances the fire extinguishing performance of liquid nitrogen to some extent.

[0224] Experiment 2:

[0225] The experimental object is a 106 Ah ternary lithium ion cell, and the design of the lithium ion cell fire extinguishing experiment conditions is shown in Table 4:

[0226] Table 4

[0227]

[0228] S2, calculate the value of each evaluation index under each type of evaluation index parameter, and normalize;

[0229] The data values obtained directly and the values of each evaluation index under each type of evaluation index parameter calculated are shown in Table 5:

[0230] Table 5

[0231]

[0232] The normalized data is shown in Table 6:

[0233] Table 6

[0234]

[0235] S3, obtain the weight of each evaluation index under each type of evaluation index parameter, and the weight data obtained is shown in Table 7:

[0236] Table 7

[0237]

[0238] S4, construct a lithium ion battery fire extinguishing agent effect evaluation model;

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

[0240] The calculated score is shown in Table 8:

[0241] Table 8

[0242]

[0243] S6, arrange the order of different fire extinguishing agents according to the score of the effect of different fire extinguishing agents on lithium ion batteries.

[0244] The sorting result is:

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

[0246] The sequencing shows that, under the experimental conditions, if only the extinguishing effect and the cooling effect are considered, the effect of water is the best, followed by the compound extinguishing agent with HFP and 2-BTP at a mass ratio of 1:1, and the compound extinguishing agent with HFP and 2-BTP at a mass ratio of 9:1 is the worst. In addition, the effect of the compound extinguishing agent with HFP and 2-BTP at a mass ratio of 1:1 is better than that of HFP or 2-BTP alone.

[0247] The above-mentioned embodiments are only the preferred embodiments of the present application, and are not intended to limit the scope of the present application. Any changes made according to the shape and principle of the present application should be covered within the scope of protection of the present application.

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, including multiple categories such as spray 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 on lithium-ion battery cells; The normalized evaluation index values ​​and corresponding evaluation index weights 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; Arrange the order of different fire extinguishing agents based on their effects on lithium-ion batteries; 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, ranging from [0 to 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: Where c cell is the capacity of the lithium-ion battery; t i T is the temperature when the fire extinguishing agent is sprayed; i is the thermal runaway temperature of the 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 Where, E is the fire extinguishing effect index parameter, C is the cooling effect index parameter, and M is the smoke toxicity suppression effect index parameter; The fire extinguishing effect index parameter E includes the fire extinguishing time index e1 and the re-ignition index e2; Calculate the fire extinguishing time index e1: e1=t extinguish -t start Where, t extinguish The moment when the flame is completely extinguished; start The moment to start spraying fire extinguishing agent on the flame; Calculate the resurgence indicator e2: If the lithium-ion battery does not reignite within the set time after the open fire is extinguished, the value is 1; otherwise, the value is 0; 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: 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 is stopped; 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 after the spraying of the fire extinguishing agent is stopped and the temperature rises to the peak value, T re,peak Δt is the peak value of temperature rise after stopping the spraying of fire extinguishing agent; re,peak-end It is the time interval from the cessation of spraying 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 t 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. end This is the moment to stop spraying the fire extinguishing agent.

2. The method for quantitatively evaluating the effect of a lithium-ion battery fire extinguishing agent according to claim 1, wherein: The smoke toxicity suppression effect index parameter M includes the toxicity index m of the asphyxiating gas FED 、Toxicity index of irritant 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 irritant gas reaches its peak after stopping the spraying of fire extinguishing agent FEC(re,peak) ; Toxicity index of asphyxiating gas m FED The calculation formula is as follows: Toxicity index of irritant gas m FEC The calculation formula is as follows: Where m FED(start) It is the toxicity index of asphyxiating gas when the fire extinguishing agent is sprayed, m FED(end) 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 irritant gas when the fire extinguishing agent is sprayed, m FEC(end) It is an indicator of the toxicity of the irritant gas when the spraying of the fire extinguishing agent is stopped; Toxicity index m when the asphyxiating gas reaches its peak after stopping the spraying of fire extinguishing agent 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; The toxicity index m when the irritant gas reaches its peak after the spraying of the fire extinguishing agent is stopped FEC(re,peak) It is equal to the sum of the values ​​obtained by dividing the critical concentration of each irritant gas by the value at which it is expected to cause personal incapacitation.

3. The method for quantitatively evaluating the effect of a lithium-ion battery fire extinguishing agent according to claim 1, wherein: 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 the normalized inverse indicator is as follows: Where 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.

4. The method for quantitatively evaluating the effect of a lithium-ion battery fire extinguishing agent according to claim 1, wherein: Obtain the weights of each evaluation index under the evaluation index parameters, including: Calculate the proportion H of the j-th fire extinguishing agent in the i-th indicator ij ,i=1,2,3,…,n; j=1,2,3,…,m; G ij is the original value of the evaluation index of the j-th fire extinguishing agent under the i-th index; Calculate the entropy value p under the i-th indicator i : Where 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.

5. The method for quantitatively evaluating the effect of a lithium-ion battery fire extinguishing agent according to claim 2, wherein: The normalized evaluation index values ​​and corresponding evaluation index weights 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: Where, is the normalized value of the i-th fire extinguishing effect index, e i Includes e1 and e2; is the weight of the i-th fire extinguishing effect index; n is the number of evaluation indicators; Calculate the cooling effect index parameter C: c i * is the normalized value of the i-th 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 effect 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 and irritating gases, the calculation formula for the smoke toxicity suppression effect parameter M is: Where, 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. is the normalized value of the toxicity index when the irritant gas reaches its 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 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; The comprehensive effect S of the lithium-ion battery fire extinguishing agent is then substituted into the formula of the lithium-ion battery fire extinguishing agent effect evaluation model to obtain the score of the fire extinguishing agent effect on the lithium-ion battery.

Images