Battery thermal risk grading evaluation method

Abstract

The invention discloses a battery thermal risk grading evaluation method, and relates to the field of battery risk evaluation. Carrying out adiabatic thermal runaway test on the target battery to obtain characteristic temperatures in the thermal runaway process of the battery, including a self-exothermic initial temperature, a thermal runaway initial temperature and a thermal runaway highest temperature, meanwhile, obtaining thermal runaway characteristic temperatures of different battery types in the existing database, and extracting medians of the thermal runaway characteristic temperatures; and calculating the score of each thermal runaway characteristic temperature through the median of each thermal runaway characteristic temperature, and finally averaging the scores of the three thermal runaway characteristic temperatures to obtain a comprehensive score of the thermal risk of the target battery, and dividing the thermal risk grade according to the comprehensive score of the thermal risk. In addition, the method is suitable for thermal risk grading evaluation of secondary batteries such as lithium ion batteries, sodium ion batteries and lithium metal batteries, and has universality.

Description

Technical Field

[0001] The invention belongs to the field of battery hazard assessment, and in particular relates to a battery thermal hazard classification assessment method. Background Art

[0002] Secondary batteries such as lithium-ion batteries are developing rapidly, expanding from consumer electronics to new energy vehicles and electrochemical energy storage. Frequent fire safety accidents caused by battery thermal runaway have greatly hindered the large-scale application of batteries. However, there is currently a lack of battery thermal hazard grading evaluation methods, making it difficult to classify battery thermal hazard levels.

[0003] Research institutions at home and abroad have mainly specified test methods for key performance and technical indicators such as basic performance and safety performance for lithium-ion batteries for energy storage. Research on battery thermal hazard evaluation is relatively limited, and most of them use qualitative thermal hazard evaluation methods such as radar charts. The factors covered are still not comprehensive, and no thermal hazard level classification is performed. Therefore, in response to the above shortcomings, this method obtains the battery thermal runaway characteristic temperature through the classic adiabatic accelerated calorimetry experiment, obtains the target battery thermal hazard comprehensive score by comparing the thermal runaway characteristic temperature with the existing battery thermal runaway database, and divides the hazard level according to the thermal hazard comprehensive score, so as to evaluate the thermal hazard of the battery. Summary of the invention

[0004] The present invention proposes a battery thermal hazard grading evaluation method, which performs an adiabatic thermal runaway test on a target battery to obtain characteristic temperatures in the battery thermal runaway process, including the self-heating starting temperature, the thermal runaway starting temperature and the thermal runaway maximum temperature. At the same time, the thermal runaway characteristic temperatures of different battery types in an existing database are obtained, and the median of each thermal runaway characteristic temperature is extracted. The score of each thermal runaway characteristic temperature is calculated according to the median of each thermal runaway characteristic temperature. Finally, the scores of the three thermal runaway characteristic temperatures are averaged to obtain a comprehensive thermal hazard score of the target battery, and the hazard level is divided according to the comprehensive thermal hazard score.

[0005] The technical solution adopted by the present invention is: A battery thermal hazard classification evaluation method comprises the following steps: Step 1: For the target battery that needs to be evaluated for thermal hazard classification, fully charge the battery using a constant current and constant voltage charging method; Step 2, placing the charged battery in an adiabatic accelerating calorimeter to conduct a thermal runaway experiment, and obtaining the thermal runaway characteristic temperature during the thermal runaway process; Step 3, obtaining the thermal runaway characteristic temperatures of different battery types in the existing battery adiabatic thermal runaway database, and calculating the median of each thermal runaway characteristic temperature; Step 4: Calculate the scores corresponding to the thermal runaway characteristic temperatures of the target battery by using the thermal runaway characteristic temperature of the target battery and the thermal runaway characteristic temperatures of the batteries in the database; Step 5: Take the average value of the scores corresponding to each thermal runaway characteristic temperature as the comprehensive thermal hazard score of the target battery, and divide the hazard level according to the comprehensive thermal hazard score.

[0006] In the above technical solution, in step one, the target battery is a commercial cylindrical battery, a square battery, a soft-pack battery, or a homemade cylindrical, square and soft-pack battery.

[0007] In the above technical solution, in step 2 and step 3, the thermal runaway characteristic temperatures are the self-exothermic starting temperature, the thermal runaway starting temperature and the thermal runaway maximum temperature.

[0008] In the above technical solution, in step three, the existing battery adiabatic thermal runaway database includes but is not limited to battery material system, battery type, battery capacity, energy density, self-heating starting temperature, thermal runaway starting temperature and thermal runaway maximum temperature.

[0009] In the above technical solution, in step three, the existing battery adiabatic thermal runaway database is collected and obtained from publicly published literature.

[0010] In the above technical solution, in step four, the target battery self-heating starting temperature score is obtained by the ratio of the target battery self-heating starting temperature to the median of the battery self-heating starting temperature in the database; the target battery thermal runaway starting temperature score is obtained by the ratio of the target battery thermal runaway starting temperature to the median of the battery thermal runaway starting temperature in the database; the target battery thermal runaway maximum temperature score is obtained by the ratio of the battery thermal runaway maximum temperature in the database to the median of the target battery thermal runaway maximum temperature.

[0011] In the above technical solution, in step five, the comprehensive thermal hazard score is divided into four intervals, less than 1.0, 1.0-1.2, 1.2-1.4, and greater than 1.4. The hazard level is divided into four levels, of which Level I is extremely dangerous, Level II is moderately dangerous, Level III is slightly dangerous, and Level IV is relatively safe. The correspondence between the hazard level and the comprehensive thermal hazard score is: a comprehensive thermal hazard score less than 1.0 corresponds to Level I, a comprehensive thermal hazard score in the range of 1.0-1.2 corresponds to Level II, a comprehensive thermal hazard score in the range of 1.2-1.4 corresponds to Level III, and a comprehensive thermal hazard score greater than 1.4 corresponds to Level IV.

[0012] The advantages of the present invention compared with the prior art are: 1. The present invention proposes a battery thermal hazard classification evaluation method and divides the hazard levels, which can realize the thermal hazard evaluation and classification of the target battery; 2. The thermal hazard assessment method of the present invention only performs adiabatic accelerated calorimetry test on the battery, which is simple and easy to implement and has universal applicability; 3. The thermal hazard level classification in the present invention is combined with the existing battery thermal runaway database and has high credibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a thermal hazard classification evaluation step of the present invention; Figure 2 The temperature and voltage curves during the thermal runaway process of the sodium ion battery in the embodiment of the present invention; Figure 3 The temperature and voltage curves of the lithium iron phosphate battery during thermal runaway in an embodiment of the present invention; Figure 4 The temperature and voltage curves of the ternary NCM523 battery during thermal runaway in an embodiment of the present invention; Figure 5 This is the thermal hazard classification of each battery in the battery adiabatic thermal runaway database in an embodiment of the present invention. DETAILED DESCRIPTION

[0014] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and carefully in combination with preferred embodiments below, but the protection scope of the present invention is not limited to the following specific embodiments.

[0015] Example Taking the currently commercially available 102Ah square lithium iron phosphate battery, 114Ah square ternary nickel cobalt manganese oxide lithium ion battery, and 70Ah square sodium ion battery as examples, the present invention is described in full and detail. The method is not limited to such batteries, but is applicable to all commercial and self-made secondary batteries. Figure 1 As shown in the figure, the method is mainly divided into the following six parts: (1) the target battery is fully charged; (2) the target battery is placed in an adiabatic accelerating calorimeter to obtain the battery thermal runaway temperature curve; (3) the thermal runaway characteristic temperature of the battery during thermal runaway is extracted, including the self-heating starting temperature, the thermal runaway starting temperature and the thermal runaway maximum temperature; (4) the thermal runaway characteristic temperatures of different battery types in the existing battery adiabatic thermal runaway database are obtained, and the median of each characteristic temperature is calculated; (5) the score corresponding to each thermal runaway characteristic temperature of the target battery is calculated by the thermal runaway characteristic temperature of the target battery and the thermal runaway characteristic temperature of the battery in the database; (6) the average score corresponding to each thermal runaway characteristic temperature is calculated as the comprehensive thermal hazard score of the target battery, and the hazard level is divided according to the comprehensive thermal hazard score.

[0016] 1. The battery is fully charged using a constant current and constant voltage method as follows: The basic parameters of the three batteries are shown in Table 1. The batteries are fully charged by constant current and constant voltage charging at the current and voltage recommended by the manufacturer, and the three batteries are charged to 100%.

[0017] Table 1 Basic parameters of three batteries

[0018] 2. The battery is subjected to thermal runaway test in an adiabatic accelerating calorimeter as follows: 1) Place the battery in an adiabatic accelerating calorimeter (ARC) and simultaneously connect it to a cycler; 2) The battery is quickly heated from room temperature to the experimental starting temperature of 50°C, and then the battery temperature is increased in steps, with each temperature increase step being 5°C; after the sample temperature reaches the set temperature step and stabilizes, wait for 45 minutes to detect whether the battery releases heat. If the system detects that the battery's heating rate (dT / dt) is ≥0.02°C / min, it is considered that the battery self-heating reaction has occurred. After that, the calorimeter tracks the battery temperature change and creates adiabatic conditions until the sample has thermal runaway. The experimental stop temperature is 300°C. The experimental setting parameters are shown in Table 2.

[0019] Table 2 ARC test parameters

[0020] 3) Use high temperature tape to place the thermocouple at the center point of the front side of the battery; 4) Open the adiabatic calorimeter furnace cover and fix the battery sample with the thermocouple arranged in the calorimeter cavity. Place all data cables in the cable trough and fix them with high-temperature tape, and connect the thermocouple and heater of the calorimeter.

[0021] 5) Close the calorimeter furnace cover, set the experimental parameters on the operating software according to Table 2, and after confirming that they are correct, start ARC to start the experiment.

[0022] Specifically, the temperature and voltage curves of the sodium ion battery during thermal runaway in the embodiment of the present invention are shown in the attached specification. Figure 2 The temperature and voltage curves of the lithium iron phosphate battery during thermal runaway in the embodiment of the present invention are shown in the attached specification. Figure 3 The temperature and voltage curves of the ternary NCM523 battery during thermal runaway in the embodiment of the present invention are shown in the attached manual. Figure 4 .

[0023] 3. Extract the thermal runaway characteristic temperature during the battery thermal runaway process, including the self-heating start temperature, thermal runaway start temperature and thermal runaway maximum temperature.

[0024] Specifically, the self-heating starting temperature is determined by the ARC system. When the temperature rise rate is higher than 0.02°C / min, the battery begins to enter the adiabatic state, which is abbreviated as ; Specifically, the thermal runaway starting temperature is determined by the temperature rise rate being higher than 1°C / min, which is abbreviated as .

[0025] Specifically, the maximum thermal runaway temperature is the highest temperature of the battery in the thermal runaway curve, abbreviated as .

[0026] Specifically, the thermal runaway characteristic temperatures of the three batteries are shown in Table 3.

[0027] Table 3 Thermal runaway characteristic temperatures of three batteries

[0028] 4. Obtain the thermal runaway characteristic temperatures of different battery types in the existing battery adiabatic thermal runaway database, and calculate the median of each characteristic temperature; Specifically, by collecting and arranging existing literature, a total of 38 groups of battery adiabatic thermal runaway parameters included in this embodiment were collected to form a battery adiabatic thermal runaway database, as shown in Table 4.

[0029] Table 4 Existing battery adiabatic thermal runaway database

[0030]

[0031] Specifically, by calculating the existing battery adiabatic thermal runaway database, the median values ​​of the three battery thermal runaway characteristic temperatures are obtained as follows: The median temperature of the self-heating start ( ): 90.65℃; Median thermal runaway starting temperature ( ): 172.4℃; Median of maximum temperature of thermal runaway ( ):623℃.

[0032] 5. Calculate the scores corresponding to each thermal runaway characteristic temperature of the target battery by using the thermal runaway characteristic temperature of the target battery and the thermal runaway characteristic temperature of the battery in the database; Specifically, the scores of the three thermal runaway characteristic temperatures are calculated as shown in equations (1)-(3):

[0033]

[0034]

[0035] in is the score for the self-exothermic onset temperature, is the thermal runaway onset temperature score, Score the maximum temperature for thermal runaway; is the target battery self-heating starting temperature in this embodiment, is the target battery thermal runaway starting temperature, is the maximum temperature of thermal runaway of the target battery.

[0036] in is the score for the self-exothermic onset temperature, is the thermal runaway onset temperature score, Score the maximum temperature for thermal runaway; is the target battery self-heating starting temperature in this embodiment, is the target battery thermal runaway starting temperature, is the maximum temperature of thermal runaway of the target battery.

[0037] Specifically, the thermal runaway characteristic temperature scores of the three batteries in this embodiment are shown in Table 5.

[0038] Table 5 Thermal runaway characteristic temperature scores of the three batteries in this embodiment

[0039] 6. Calculate the average score corresponding to each thermal runaway characteristic temperature as the target battery thermal hazard comprehensive score, and divide the hazard level according to the thermal hazard comprehensive score.

[0040] Specifically, the target battery thermal hazard comprehensive score Calculation see formula (4)

[0041] Specifically, the comprehensive scores of thermal hazard of the three batteries in this embodiment are calculated to be: 1.17 points for sodium-ion battery, 1.28 points for lithium iron phosphate battery, and 0.99 points for ternary NCM523 battery.

[0042] Specifically, the danger level is divided into four levels, among which Level I is extremely dangerous, Level II is serious dangerous, Level III is moderate dangerous, and Level IV is mild dangerous.

[0043] Specifically, the correspondence between the hazard level and the comprehensive thermal hazard score is: a comprehensive thermal hazard score less than 1.0 corresponds to Level I, a comprehensive thermal hazard score in the range of 1.0 to 1.2 corresponds to Level II, a comprehensive thermal hazard score in the range of 1.2 to 1.4 corresponds to Level III, and a comprehensive thermal hazard score greater than 1.4 corresponds to Level IV.

[0044] Specifically, the hazard levels of the three batteries in this embodiment are: sodium ion battery level II, lithium iron phosphate battery level III, and ternary NCM523 battery level I.

[0045] Specifically, the thermal hazard classification of each battery in the existing adiabatic thermal runaway database is shown in the Appendix of the Instructions. Figure 5 It can be found that most high-nickel ternary batteries (NCM622 and NCM811) are at level I, most NCM523 and NCM111 batteries are at level II, sodium-ion batteries are at the boundary of level II, most lithium iron phosphate batteries are at level III, and only a small number of lithium iron phosphate batteries are at level IV.

[0046] The present invention does not elaborate on some of the common technologies of those skilled in the art. The above-described embodiments are only descriptions of preferred implementations of the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementations described. Without departing from the design spirit of the present invention, various modifications and improvements made by ordinary technicians in this field to the technical solution of the present invention should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A battery thermal hazard classification evaluation method, characterized in that: The following steps are involved: Step 1: For the target battery that needs to be evaluated for thermal hazard classification, fully charge the battery using a constant current and constant voltage charging method; Step 2, placing the charged battery in an adiabatic accelerating calorimeter to conduct a thermal runaway experiment, and obtaining the thermal runaway characteristic temperature during the thermal runaway process; Step 3, obtaining the thermal runaway characteristic temperatures of different battery types in the existing battery adiabatic thermal runaway database, and calculating the median of each thermal runaway characteristic temperature; Step 4: Calculate the scores corresponding to the thermal runaway characteristic temperatures of the target battery by using the thermal runaway characteristic temperature of the target battery and the thermal runaway characteristic temperatures of the batteries in the database; Step 5: Take the average value of the scores corresponding to each thermal runaway characteristic temperature as the comprehensive thermal hazard score of the target battery, and divide the hazard level according to the comprehensive thermal hazard score.

2. A battery thermal hazard classification evaluation method according to claim 1, characterized in that: The target battery in step 1 is a commercial cylindrical battery, a square battery, a soft-pack battery, or a homemade cylindrical, square and soft-pack battery.

3. A battery thermal hazard classification evaluation method according to claim 1, characterized in that: The thermal runaway characteristic temperatures in step 2 and step 3 are the self-exothermic starting temperature, the thermal runaway starting temperature and the thermal runaway maximum temperature.

4. A battery thermal hazard classification evaluation method according to claim 1, characterized in that: The existing battery adiabatic thermal runaway database in step three includes battery material system, battery type, battery capacity, energy density, self-heating starting temperature, thermal runaway starting temperature and thermal runaway maximum temperature.

5. A battery thermal hazard classification evaluation method according to claim 1, characterized in that: The existing battery adiabatic thermal runaway database in step three is collected and obtained from publicly published literature.

6. A battery thermal hazard classification evaluation method according to claim 1, characterized in that: In step 4, the target battery self-heating starting temperature score is obtained by the ratio of the target battery self-heating starting temperature to the median of the battery self-heating starting temperature in the database; the target battery thermal runaway starting temperature score in step 4 is obtained by the ratio of the target battery thermal runaway starting temperature to the median of the battery thermal runaway starting temperature in the database; the target battery self-heating runaway maximum temperature score in step 4 is obtained by the ratio of the battery thermal runaway maximum temperature in the database to the median of the target battery thermal runaway maximum temperature.

7. A battery thermal hazard classification evaluation method according to claim 1, characterized in that: The comprehensive thermal hazard score in step five can be divided into four intervals: less than 1.0, 1.0-1.2, 1.2-1.4, and greater than 1.

4.

8. A battery thermal hazard classification evaluation method according to claim 1, characterized in that: The danger level in step five is divided into four levels, among which level I is extremely dangerous, level II is serious dangerous, level III is moderate dangerous, and level IV is mild dangerous.

9. A battery thermal hazard classification evaluation method according to claim 1, characterized in that: The correspondence between the hazard level and the comprehensive thermal hazard score in step five is: a comprehensive thermal hazard score less than 1.0 corresponds to Level I, a comprehensive thermal hazard score in the range of 1.0 to 1.2 corresponds to Level II, a comprehensive thermal hazard score in the range of 1.2 to 1.4 corresponds to Level III, and a comprehensive thermal hazard score greater than 1.4 corresponds to Level IV.

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