Method and device for evaluating insulating property of battery insulating material

Abstract

The invention relates to the field of performance testing of insulating materials, in particular to a method and device for evaluating the insulating performance of a battery insulating material, and the method comprises the steps: making a to-be-tested battery insulating material into a test piece; the lower portion of the test piece is immersed in the electrolyte, standing and soaking are conducted for preset time at the preset environment temperature, and the preset environment temperature and the preset time are obtained based on a thermal runaway curve of the battery; calculating the size change rate, the weight change rate and the insulation resistance change rate of the test piece before and after soaking; and inputting the size change rate, the weight change rate and the insulation resistance change rate into an insulation performance evaluation model, and outputting to obtain an insulation performance evaluation value of the battery insulation material. The method is simple to operate, has low requirements on equipment, and can efficiently obtain an evaluation result of the insulating property of the battery insulating material.

Description

Technical Field

[0001] The invention relates to the field of performance testing of insulating materials, and in particular to a method and device for evaluating the insulating performance of a battery insulating material. Background Art

[0002] As the market share of new energy vehicles increases year by year, the safety performance of new energy vehicles has also been widely discussed. In the design process of power battery systems, the battery cell, as an energy storage device, needs to select suitable insulating materials to ensure its insulation performance with other metal parts. Otherwise, if the battery cell circuit interferes with other metal parts to form an unexpected circuit, the battery cell temperature will rise rapidly, thereby causing thermal runaway of the battery cell. Therefore, in the power battery system on the market, insulating sheet materials are often arranged on the top of the battery cell to isolate the battery cell from the upper cover to avoid short circuit arcing and fire.

[0003] After a lithium iron phosphate battery cell has thermal runaway, the electrolyte erupts in large quantities from the explosion-proof valve port, causing a double impact of heat and electrolyte corrosion on the top insulating sheet in a high-temperature environment. If the insulating sheet is corroded or melted through, the battery cell will lose its insulation protection. At the same time, the ejected material or molten material accumulates on the top of the battery cell, reducing the gap between the battery cell and the upper cover, which can easily cause arcing and eventually lead to a short circuit or even a fire.

[0004] In the related art, the physical quantity characteristic information in the impedance frequency spectrum of the insulating material obtained by AC impedance testing is used to reliably evaluate the aging temperature grade, temperature upper limit, and heat resistance grade of the insulating material. However, the AC impedance test involved in this method has high requirements for equipment and operation, and is not efficient and concise. Summary of the invention

[0005] The purpose of the present invention is to provide a method and device for evaluating the insulation performance of a battery insulation material, which is simple to operate, has low requirements on equipment, and can efficiently obtain evaluation results of the insulation performance of the battery insulation material.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a method for evaluating the insulation performance of a battery insulation material, comprising:

[0008] The battery insulation material to be tested is made into a test piece;

[0009] Immerse the lower part of the test piece in the electrolyte and allow it to stand and soak for a preset time at a preset ambient temperature, wherein the preset ambient temperature and the preset time are obtained based on the thermal runaway curve of the battery;

[0010] The size change rate, weight change rate and insulation resistance change rate of the specimen before and after immersion are calculated;

[0011] The size change rate, weight change rate and insulation resistance change rate are input into the insulation performance evaluation model, and the insulation performance evaluation value of the battery insulation material is output.

[0012] Furthermore, the insulation performance evaluation model is specifically: δ=a×θ+b×β+c×γ, wherein δ is the insulation performance evaluation value of the battery insulation material, θ is the dimensional change rate, a is the weight coefficient of the dimensional change rate, β is the weight change rate, b is the weight coefficient of the weight change rate, γ is the insulation resistance change rate, and c is the weight coefficient of the insulation resistance change rate.

[0013] Furthermore, the weight coefficient a of the dimensional change rate is equal to the weight coefficient b of the weight change rate;

[0014] Alternatively, the weight coefficient a of the dimensional change rate is equal to the weight coefficient c of the insulation resistance change rate;

[0015] Alternatively, the weight coefficient b of the weight change rate is equal to the weight coefficient c of the insulation resistance change rate;

[0016] Alternatively, the weight coefficient a of the dimensional change rate, the weight coefficient b of the weight change rate, and the weight coefficient c of the insulation resistance change rate are equal.

[0017] Furthermore, the specimen is a cuboid, and the calculation formula for the dimensional change rate is: Where θ is the dimensional change rate, L1 is the length of the specimen before immersion, and L2 is the length of the specimen after immersion.

[0018] Further, the calculation formula of the weight change rate is: Where β is the weight change rate, W1 is the weight of the specimen before immersion, and W2 is the weight of the specimen after immersion.

[0019] Furthermore, the calculation formula for the insulation resistance change rate is: Where γ is the insulation resistance change rate, R1 is the insulation resistance of the specimen before immersion, and R2 is the insulation resistance of the specimen after immersion.

[0020] Furthermore, the preset ambient temperature and the preset time are obtained based on the thermal runaway curve of the battery and specifically include: obtaining the thermal runaway curve of the battery, dividing the time axis of the thermal runaway curve into multiple time periods, obtaining the median temperature on the temperature curve corresponding to each time period, using the time length corresponding to the time period as the preset time, and using the median temperature as the preset ambient temperature.

[0021] Furthermore, the time lengths of the multiple time periods are equal.

[0022] Furthermore, the test piece is in the shape of a cuboid, and during immersion, a preset length area at the bottom of the test piece is vertically immersed in the electrolyte.

[0023] In a second aspect, the present invention provides an evaluation device for the insulation performance of a battery insulating material, which includes a testing module, a calculation module and an evaluation module, wherein the testing module is used to immerse the lower part of a test piece made of the battery insulating material to be tested into an electrolyte, and let it stand and soak for a preset time at a preset ambient temperature, wherein the preset ambient temperature and the preset time are obtained based on a thermal runaway curve of the battery; the calculation module is used to calculate the size change rate, weight change rate and insulation resistance change rate of the test piece before and after immersion; the evaluation module is used to input the size change rate, weight change rate and insulation resistance change rate into an insulation performance evaluation model, and output an insulation performance evaluation value of the battery insulating material.

[0024] The present invention has the following unexpected beneficial effects:

[0025] The present invention immerses the lower part of the test piece in the electrolyte and leaves it to soak for a preset time at a preset ambient temperature. The preset ambient temperature and preset time are obtained based on the thermal runaway curve of the battery, thereby accurately simulating the environmental conditions of the insulating material when the battery is in thermal runaway. The insulating performance of the insulating material is comprehensively evaluated by the size change rate, weight change rate and insulation resistance change rate of the test piece before and after immersion. On the one hand, the operation is simple, the equipment requirements are low, and the evaluation results can be obtained efficiently; on the other hand, the accuracy of the average result is guaranteed by limiting the immersion conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention.

[0027] Figure 1 A schematic flow chart of a method for evaluating the insulation performance of a battery insulation material according to the present invention is shown;

[0028] Figure 2 The temperature drop curve of a battery cell after thermal runaway is shown;

[0029] Figure 3 A schematic diagram showing the composition and structure of the device for evaluating the insulation performance of the battery insulation material of the present invention is shown. DETAILED DESCRIPTION

[0030] The following will describe the embodiments of the present invention with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention, not for limiting the scope of protection of the present invention.

[0031] In one embodiment, see Figure 1 As shown, the present invention provides a method for evaluating the insulation performance of a battery insulation material, which comprises:

[0032] The battery insulation material to be tested is made into a test piece, that is, the battery insulation material to be tested is made into a test piece according to a specified size and shape, so as to carry out a subsequent immersion test.

[0033] The lower part of the test piece is immersed in an electrolyte, which should be consistent or similar to the electrolyte in the actual battery to simulate the real battery environment. The test piece is then left to soak for a preset time at a preset ambient temperature, which is based on the thermal runaway curve of the battery to ensure that the test conditions can reflect the extreme conditions that may occur in the actual use of the battery.

[0034] The size change rate, weight change rate and insulation resistance change rate of the specimen before and after immersion were calculated.

[0035] The size change rate, weight change rate and insulation resistance change rate are input into the insulation performance evaluation model, and the insulation performance evaluation value of the battery insulation material is output.

[0036] On the one hand, the present invention determines the preset ambient temperature and time of immersion according to the battery thermal runaway curve, so that the test conditions can better simulate the extreme conditions that may occur in the actual use of the battery, thereby more accurately evaluating the performance of the insulating material under these conditions, which is of great significance for ensuring the safety of battery use.

[0037] On the other hand, the present invention adopts data of three different dimensions, namely, dimensional change rate, weight change rate and insulation resistance change rate, as the basis for evaluation, and conducts comprehensive analysis through the established insulation performance evaluation model, which can more comprehensively and objectively reflect the insulation performance of battery insulation materials and avoid the one-sidedness that may exist in single indicator evaluation.

[0038] In the process of developing new batteries, it is necessary to strictly screen and evaluate the performance of various selected insulating materials. The evaluation method described in the present invention can help researchers quickly and accurately understand the advantages and disadvantages of the insulating performance of different insulating materials under simulated actual working conditions, so as to select suitable insulating materials for the optimal design of battery devices. And when quality inspection is carried out after the battery device is completed, this evaluation method can also be used to conduct random inspections and evaluations on the insulating materials used in the battery to ensure that the insulating materials of the battery can continue to play a good insulating role in a stable manner during the use of the battery in the market, thereby reducing the safety hazards caused by poor insulation performance.

[0039] In a preferred embodiment, the insulation performance evaluation model is specifically: δ=a×θ+b×β+c×γ, wherein δ is the insulation performance evaluation value of the battery insulation material, and θ is the dimensional change rate, which indicates the percentage of dimensional change of the specimen before and after the immersion test. a is the weight coefficient of the dimensional change rate, which reflects the importance of dimensional change to the insulation performance evaluation. β is the weight change rate, which indicates the percentage of weight change of the specimen before and after the immersion test. b is the weight coefficient of the weight change rate, which reflects the importance of weight change to the insulation performance evaluation. γ is the insulation resistance change rate, which indicates the percentage of insulation resistance change of the specimen before and after the immersion test. c is the weight coefficient of the insulation resistance change rate, which reflects the importance of insulation resistance change to the insulation performance evaluation.

[0040] It should be noted that the determination of weight coefficients (a, b, c) is usually based on statistical analysis of experimental data, expert experience or industry standards. These coefficients should meet the following conditions: First, a+b+c=1, ensuring that the sum of all weight coefficients is 1, so that the insulation performance evaluation value is normalized to a reasonable range. Second, the weight coefficients should be adjusted according to different application scenarios and test requirements. For example, in some cases, the change in insulation resistance may be more important than the change in size and weight, so a higher weight coefficient should be given.

[0041] In a preferred embodiment, the weight coefficient a of the dimensional change rate is equal to the weight coefficient b of the weight change rate. This indicates that in the current test or application scenario, the effects of dimensional change and weight change on insulation performance are considered to be equally important. This is because both dimensional change rate and weight change rate are directly related to the physical stability and structural integrity of the material, and have a direct impact on insulation performance.

[0042] Alternatively, the weight coefficient a of the dimensional change rate is equal to the weight coefficient c of the insulation resistance change rate. In this case, the dimensional change and the insulation resistance change are considered to have equal influence on the insulation performance. This is mainly because the dimensional change can be directly related to the internal structure and porosity of the material, thus affecting its insulation performance; while the insulation resistance change is a key indicator to directly measure the insulation performance.

[0043] Alternatively, the weight coefficient b of the weight change rate is equal to the weight coefficient c of the insulation resistance change rate. This situation indicates that in the current test or application scenario, the liquid absorption (or quality stability) and insulation performance changes of the material are considered equally important. This is mainly because the liquid absorption of the material may affect the electrolyte distribution and ion conductivity inside it, thereby affecting the insulation performance.

[0044] Alternatively, the weight coefficient a of the dimensional change rate, the weight coefficient b of the weight change rate and the weight coefficient c of the insulation resistance change rate are equal. In this case, the data of all three dimensions are considered to have equal impact on the insulation performance. This is mainly because the test or application scenario requires a comprehensive assessment of the physical stability, quality stability and insulation performance of the material to ensure its reliability and safety under extreme conditions.

[0045] Preferably, the weight coefficient a of the size change rate, the weight coefficient b of the weight change rate and the weight coefficient c of the insulation resistance change rate are equal, and a+b+c=1.

[0046] In a preferred embodiment, the specimen is a cuboid, and the calculation formula for the dimensional change rate is: Where θ is the dimensional change rate, L1 is the length of the specimen before immersion, and L2 is the length of the specimen after immersion.

[0047] By limiting the shape of the specimen to a cuboid, it helps to maintain the stability and consistency of the specimen during the test, and the shape of the cuboid is also convenient for measuring and calculating the dimensional change rate.

[0048] The present invention can accurately calculate the dimensional change rate of the test piece by accurately measuring the length of the test piece before and after immersion, thereby evaluating the expansion or contraction of the material in the electrolyte. By adopting a rectangular test piece and standardized measurement steps, the repeatability of the test can be improved, making the test results between different batches or different laboratories comparable. The method is simple and easy to implement, suitable for the performance evaluation of various battery insulating materials, and provides strong support for the research and development, production and quality control of batteries.

[0049] In a preferred embodiment, the weight change rate is calculated as follows: Where β is the weight change rate, W1 is the weight of the specimen before immersion, and W2 is the weight of the specimen after immersion. Similar to the dimensional change rate, the weight change rate of the specimen can be accurately calculated using a standardized calculation formula and precise measurement tools, thus improving the accuracy of the assessment.

[0050] In a preferred embodiment, the calculation formula for the insulation resistance change rate is: In the formula, γ is the insulation resistance change rate, R1 is the insulation resistance of the specimen before immersion, and R2 is the insulation resistance of the specimen after immersion. Similar to the size change rate and weight change rate, the insulation resistance change rate of the specimen can be accurately calculated using standardized calculation formulas and precise measurement tools to improve the accuracy of the assessment.

[0051] In a preferred embodiment, the preset ambient temperature and the preset time are obtained based on the thermal runaway curve of the battery and specifically include:

[0052] Obtaining the thermal runaway curve of the battery is the basis for determining the preset parameters. The thermal runaway curve is usually obtained through experiments or simulations, reflecting the temperature changes of the battery under specific conditions.

[0053] The time axis of the thermal runaway curve is divided into multiple time periods of equal or unequal length. Each time period represents a specific time interval for subsequent median temperature calculation. For each time period, find the set of all temperature values ​​in the time period from the thermal runaway curve, and then calculate the median temperature of this set. The median temperature is a statistic that represents the central trend of the temperature in the time period.

[0054] The time length corresponding to the time period is used as the preset time, and the median temperature is used as the preset ambient temperature. This means that for each time period, a corresponding preset time and preset ambient temperature will be obtained. The calculated median temperature is used as the preset ambient temperature, indicating that the medium level of temperature in the time period is used as the preset ambient temperature.

[0055] In a preferred embodiment, see Figure 2 As shown, the lengths of multiple time periods are equal. This setting simplifies the analysis process and makes each time period consistent in time. At the same time, this also makes the determination of the preset time and the preset ambient temperature more standardized and unified.

[0056] In a preferred embodiment, the specimen is in the shape of a cuboid, and during immersion, a preset length region at the bottom of the specimen is vertically immersed in the electrolyte. The selection of the preset length is usually based on the purpose of the experiment, the properties of the electrolyte, and the characteristics of the specimen material. By adjusting the preset length, the influence of different immersion depths on the evaluation results can be studied.

[0057] The present invention ensures the consistency and repeatability of the test experiment by specifying the shape and immersion method of the test piece.

[0058] In one embodiment, the present invention provides a device for evaluating the insulation performance of a battery insulation material, see Figure 3As shown, the evaluation device 10 includes a test module 11, a calculation module 12 and an evaluation module 13. The test module 11 is used to immerse the lower part of the test piece made of the battery insulation material to be tested into the electrolyte, and let it stand for a preset time at a preset ambient temperature. The preset ambient temperature and preset time are obtained based on the thermal runaway curve of the battery. The calculation module 12 is used to calculate the size change rate, weight change rate and insulation resistance change rate of the test piece before and after immersion. The evaluation module 13 is used to input the size change rate, weight change rate and insulation resistance change rate into the insulation performance evaluation model, and output the insulation performance evaluation value of the battery insulation material.

[0059] The following is an analysis and explanation with reference to specific examples.

[0060] A method for evaluating the insulation performance of a battery insulation material, comprising:

[0061] The battery insulation material to be tested is made into a test piece. The battery insulation material to be tested includes polycarbonate (PC) with a thickness of 0.5mm, 0.4mm, 0.25mm, and 0.175mm, polypropylene (PP) with a thickness of 0.5mm and 0.25mm, polyimide (PI) with a thickness of 0.14mm and 0.05mm, expanded polypropylene (MPP) with a thickness of 1mm, and polyethylene terephthalate (PET) with a thickness of 0.05mm, for a total of 10 groups of insulation materials. The 10 groups of insulation materials are cut into a rectangular shape of 50mm×20mm. The electrolyte composition is selected to be 1M LiPF6+EC / DMC (1:1) v / v. Check the appearance integrity of the initial insulation sheet material, and measure its weight, thickness and insulation resistance. The measurement results are shown in Table 1.

[0062] Table 1 Thickness, length, weight and insulation resistance of each group of insulating materials before immersion

[0063] Sample No. Sample Information Thickness(mm) Length(mm) Weight(g) Insulation resistance(MΩ) S-1 PC 0.5 50 0.6033 >550 S-2 PC 0.4 50 0.5082 >550 S-3 PC 0.25 50 0.2651 >550 S-4 PC 0.175 50 0.2077 >550 S-5 PP 0.5 50 0.5519 >550 S-6 PP 0.25 50 0.2162 >550 S-7 PI 0.14 50 0.4969 >550 S-8 PI 0.05 50 0.3010 >550 S-9 MPP 1 50 0.3053 >550 S-10 PET 0.05 50 0.0720 >550

[0064] Pour the electrolyte into the container, and immerse the above 10 groups of insulating materials vertically into the electrolyte, so that the corresponding area of ​​30mm below the insulating material is completely immersed in the electrolyte, and the corresponding area of ​​20mm above the upper end does not contact the electrolyte, and fix the upper part of the insulating material with tape or clips to keep it vertical. Then seal the container and put it in an oven, and obtain the static temperature gradient and corresponding static time according to the temperature change fitting curve after thermal runaway of various battery cells. In this embodiment, the temperature gradient is as follows Figure 2 shown.

[0065] After the standing still was completed, 10 groups of insulating materials were taken out, and the size, weight and insulation resistance of each group of insulating sheets were measured. The results are shown in Table 2.

[0066] Table 2 Length, weight and insulation resistance of each group of insulating materials after immersion

[0067] Sample No. Length(mm) Weight(g) Insulation resistance(MΩ) S-1 50 0.6815 >550 S-2 50 0.5911 >550 S-3 49 0.3163 >550 S-4 46 0.2419 >550 S-5 50 0.5677 >550 S-6 50 0.2274 >550 S-7 50 0.4976 >550 S-8 50 0.3046 >550 S-9 48 0.5788 2.19 S-10 50 0.0746 >550

[0068] The size change rate, weight change rate and insulation resistance change rate of the specimen before and after immersion were calculated to evaluate the insulation performance of the insulation sheet after thermal runaway of the battery.

[0069] The calculation formula of the dimensional change rate is: Where θ is the dimensional change rate, L1 is the length of the specimen before immersion, and L2 is the length of the specimen after immersion.

[0070] The calculation formula of the weight change rate is: Where β is the weight change rate, W1 is the weight of the specimen before immersion, and W2 is the weight of the specimen after immersion.

[0071] The calculation formula of the insulation resistance change rate is: Where γ is the insulation resistance change rate, R1 is the insulation resistance of the specimen before immersion, and R2 is the insulation resistance of the specimen after immersion.

[0072] The size change rate, weight change rate and insulation resistance change rate are input into the insulation performance evaluation model, and the insulation performance evaluation value of the battery insulation material is output. The insulation performance evaluation model is specifically: δ = a × θ + b × β + c × γ, where δ is the insulation performance evaluation value of the battery insulation material, θ is the size change rate, a is the weight coefficient of the size change rate, β is the weight change rate, b is the weight coefficient of the weight change rate, γ is the insulation resistance change rate, and c is the weight coefficient of the insulation resistance change rate. The weight coefficient a = b = c = 1 / 3. The calculation results are shown in Table 3.

[0073] Table 3 Size change rate, weight change rate, insulation resistance change rate and insulation performance evaluation value of each group of insulation materials

[0074] Sample No. Dimensional change rate Weight change rate Insulation resistance change rate Insulation performance evaluation value S-1 0.0000％ 12.9620％ 0.0000％ 4.3207％ S-2 0.0000％ 16.3125％ 0.0000％ 5.4375％ S-3 2.0000％ 19.2380％ 0.0000％ 7.0793％ S-4 8.0000％ 16.4661％ 0.0000％ 8.1554％ S-5 0.0000％ 2.8628％ 0.0000％ 0.9543％ S-6 0.0000％ 5.1804％ 0.0000％ 1.7268％ S-7 0.0000％ 0.1409％ 0.0000％ 0.0470％ S-8 0.0000％ 1.1960％ 0.0000％ 0.3987％ S-9 4.0000％ 89.5840％ 99.6018％ 64.3953％ S-10 0.0000％ 3.6111％ 0.0000％ 1.2037％

[0075] By comparison, the insulation performance of PI materials in groups S-7 and S-8 is better after thermal runaway of the battery cell, while the insulation performance of MPP materials in group S-9 is the worst.

[0076] The above embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Any equivalent substitution or change made by a person skilled in the art based on the present invention is within the protection scope of the present invention.

Claims

1. A method for evaluating the insulation performance of a battery insulation material, characterized in that: include: The battery insulation material to be tested is made into a test piece; Immerse the lower part of the test piece in the electrolyte and allow it to stand and soak for a preset time at a preset ambient temperature, wherein the preset ambient temperature and the preset time are obtained based on the thermal runaway curve of the battery; The size change rate, weight change rate and insulation resistance change rate of the specimen before and after immersion are calculated; The size change rate, weight change rate and insulation resistance change rate are input into the insulation performance evaluation model, and the insulation performance evaluation value of the battery insulation material is output.

2. The method for evaluating the insulation performance of a battery insulation material according to claim 1, characterized in that: The insulation performance evaluation model is specifically: δ=a×θ+b×β+c×γ, where δ is the insulation performance evaluation value of the battery insulation material, θ is the dimensional change rate, a is the weight coefficient of the dimensional change rate, β is the weight change rate, b is the weight coefficient of the weight change rate, γ is the insulation resistance change rate, and c is the weight coefficient of the insulation resistance change rate.

3. The method for evaluating the insulation performance of a battery insulation material according to claim 2, characterized in that: The weight coefficient a of the dimensional change rate is equal to the weight coefficient b of the weight change rate; Alternatively, the weight coefficient a of the dimensional change rate is equal to the weight coefficient c of the insulation resistance change rate; Alternatively, the weight coefficient b of the weight change rate is equal to the weight coefficient c of the insulation resistance change rate; Alternatively, the weight coefficient a of the dimensional change rate, the weight coefficient b of the weight change rate, and the weight coefficient c of the insulation resistance change rate are equal.

4. The method for evaluating the insulation performance of a battery insulation material according to claim 1, characterized in that: The test piece is a cuboid, and the calculation formula of the dimensional change rate is: Where θ is the dimensional change rate, L1 is the length of the specimen before immersion, and L2 is the length of the specimen after immersion.

5. The method for evaluating the insulation performance of a battery insulation material according to claim 1, characterized in that: The calculation formula of the weight change rate is: Where β is the weight change rate, W1 is the weight of the specimen before immersion, and W2 is the weight of the specimen after immersion.

6. The method for evaluating the insulation performance of a battery insulation material according to claim 1, characterized in that: The calculation formula of the insulation resistance change rate is: Where γ is the insulation resistance change rate, R1 is the insulation resistance of the specimen before immersion, and R2 is the insulation resistance of the specimen after immersion.

7. The method for evaluating the insulation performance of a battery insulation material according to claim 1, characterized in that: The preset ambient temperature and preset time are obtained based on the thermal runaway curve of the battery, specifically including: obtaining the thermal runaway curve of the battery, dividing the time axis of the thermal runaway curve into multiple time periods, obtaining the median temperature on the temperature curve corresponding to each time period, using the time length corresponding to the time period as the preset time, and using the median temperature as the preset ambient temperature.

8. The method for evaluating the insulation performance of a battery insulation material according to claim 7, characterized in that: The time periods are of equal length.

9. The method for evaluating the insulation performance of a battery insulation material according to claim 1, characterized in that: The test piece is in the shape of a cuboid, and during immersion, a preset length area at the lower part of the test piece is vertically immersed in the electrolyte.

10. A device for evaluating the insulation performance of a battery insulation material, characterized in that: include: A test module, used to immerse the lower part of the test piece made of the battery insulation material to be tested into the electrolyte, and let it stand and soak for a preset time at a preset ambient temperature, wherein the preset ambient temperature and the preset time are obtained based on the thermal runaway curve of the battery; A calculation module is used to calculate the size change rate, weight change rate and insulation resistance change rate of the test piece before and after immersion; The evaluation module is used to input the size change rate, weight change rate and insulation resistance change rate into the insulation performance evaluation model, and output the insulation performance evaluation value of the battery insulation material.

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