Porosity measurement device and method

Abstract

The present application relates to the field of battery technology, and discloses a new porosity measurement device and method for improving the way of measuring the porosity of structural materials in batteries. The porosity measurement device includes: a liquid measuring container and an upper cover, the upper cover is provided with a cantilever for extending into the interior of the container, and a reading area is provided on the portion of the side wall of the container horizontally opposite to the cantilever. The porosity measurement device can improve the accuracy of the judgment of the liquid level reading, thereby improving the accuracy of the final porosity test results. In addition, the porosity obtained by testing with the porosity measurement device can more accurately reflect the effective pore volume and porosity of the electrode or diaphragm to be tested sample in the electrolyte environment.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a porosity measurement device and method. Background Art

[0002] The cycle performance and internal resistance characteristics of the battery are closely related to the amount of battery liquid injection, which is determined by the compaction density of the battery cell and the porosity of the pole piece and diaphragm. In the related technology, the methods used to test the porosity of the battery cell mainly include mercury injection method, hexadecane method and SEM imaging method. However, these current testing methods have their own defects and cannot accurately test the actual effective pore volume and porosity of lithium-ion batteries.

[0003] For example, the mercury injection method uses highly toxic mercury, which can cause serious harm to testers and the environment. In addition, the porosity measured by the mercury injection method includes invalid pores and cannot reflect the actual porosity of the lithium battery electrode or diaphragm. When the hexadecane method is used, hexadecane will adhere to the surface of the electrode and cannot be removed. In addition, the affinity of hexadecane and the electrolyte for the electrode is different. Changes in ambient temperature will also affect the volatilization rate of hexadecane, resulting in a larger porosity test result. The SEM imaging method uses an ion beam to continuously cut the sample, while imaging it under an electron beam, and then performs three-dimensional reconstruction and simulation calculations to obtain the porosity of the sample. The porosity obtained by this method cannot accurately reflect the actual porosity of the electrode or diaphragm in the electrolyte environment. Summary of the invention

[0004] The purpose of the present invention is to provide a new porosity measurement device and method, which are used to improve the way of measuring the porosity of internal structural materials of batteries.

[0005] In a first aspect, the present application provides a porosity measuring device, comprising: a liquid measuring container and an upper cover, wherein the upper cover is provided with a cantilever for extending into the interior of the container, and a reading area is provided on a portion of the side wall of the container horizontally opposite to the cantilever.

[0006] The porosity measurement device provided in this embodiment includes a liquid measurement container and an upper cover, and can perform a liquid volume displacement test to obtain the true volume of the sample to be tested, that is, the actual volume without pores, and then calculate the porosity of the sample to be tested by the true volume of the sample to be tested. This embodiment uses a liquid-immersed sample method to perform the test, which is closer to the actual situation of the electrode or diaphragm to be tested sample in an electrolyte environment. Therefore, the porosity measured in this way can more accurately reflect the effective pore volume and porosity of the electrode or diaphragm to be tested sample in an electrolyte environment.

[0007] In addition, the porosity measuring device is provided with an upper cover matching the container, the upper cover is provided with a cantilever for extending into the interior of the container, the reading area of ​​the container is opposite to the cantilever, the liquid level in the container must exceed the cantilever to measure the reading, that is, the cantilever must extend below the liquid level, and the liquid level is limited between the cantilever and the side wall of the container, so that the height of the liquid level changes greatly before and after the addition of the sample to be tested, and by increasing the height difference between the liquid levels before and after, the accuracy of the true volume of the sample to be tested finally calculated can be improved; moreover, the setting of the cantilever can avoid the large surface area of ​​the liquid surface, so that the concave liquid surface formed in the middle makes the judgment of the liquid level reaching the constant volume line when measuring the liquid inaccurate. In this embodiment, the liquid level is only in the narrow space between the cantilever and the side wall of the container, which is conducive to observing and comparing the liquid level and the scale line, and can improve the accuracy of the judgment of the liquid level reading, thereby improving the accuracy of the final test result.

[0008] In addition, the cantilever provided on the upper cover can also abut against the sample, so that the sample is completely immersed in the liquid, thereby avoiding inaccurate test results caused by the sample not being completely immersed in the liquid.

[0009] In a second aspect, the present application provides a porosity measurement method, the measurement method comprising the following steps:

[0010] Liquid is injected into the container, and an upper cover is placed on the container. The upper cover is provided with a cantilever for extending into the interior of the container, and a reading area is provided on a portion of the side wall of the container horizontally opposite to the cantilever. The cantilever of the upper cover extends below the liquid surface so that the liquid surface is in the reading area, and the scale corresponding to the liquid surface at this time is read, which is recorded as the first reading D1;

[0011] Add the sample to be tested into the container, cover the container with the upper cover, extend the cantilever of the upper cover below the liquid surface so that the liquid surface is in the reading area, read the scale corresponding to the liquid surface at this time, and record it as the second reading D2;

[0012] Calculate the true volume of the sample to be tested according to the first reading D1 and the second reading D2;

[0013] The porosity of the sample to be tested is calculated according to the true volume of the sample to be tested.

[0014] The porosity measurement method provided by the present application adopts a porosity measurement device for measurement. The porosity measurement device is provided with a container and an upper cover. The reading area of ​​the container is set at the part opposite to the cantilever of the upper cover, which can improve the height difference of the liquid level change before and after the addition of the sample to be tested, and improve the accuracy of the liquid level reading judgment, thereby improving the accuracy of the true volume of the sample to be tested finally calculated. In addition, the porosity measurement method provided by the present application uses the liquid volume displacement method to calculate the true volume and porosity of the sample to be tested, and tests are performed by infiltrating the sample with liquid, which is closer to the actual situation of the sample to be tested in the electrolyte environment. Therefore, the measured porosity can more accurately reflect the effective pore volume and porosity of the electrode or diaphragm to be tested in the electrolyte environment. The porosity measurement method of the present application does not require large instruments, has simple test tools, is simple to operate, can quickly and accurately measure the porosity of the material, improves the accuracy of the porosity test, and has a guiding role in battery design and process parameter optimization. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to better understand the present invention, reference may be made to the embodiments shown in the following drawings. The components in the drawings are not necessarily to scale, and some related components may be omitted in order to emphasize and clearly illustrate the technical features of the present disclosure. In addition, related elements or components may have different arrangements as known in the art.

[0016] Figure 1 A schematic structural diagram of a porosity measurement device provided by an embodiment of the present invention;

[0017] Figure 2 A schematic structural diagram of a porosity measurement device provided by another embodiment of the present invention;

[0018] Figure 3 A flow chart of a porosity measurement method provided in an embodiment of the present invention.

[0019] Reference numerals:

[0020] 1- container; 2- lid; 21- cantilever; 3- reading area; 4- sample. DETAILED DESCRIPTION

[0021] The following will be combined with the accompanying drawings in the exemplary embodiments of the present disclosure to clearly and completely describe the technical solutions in the exemplary embodiments of the present disclosure. The exemplary embodiments described herein are only for illustrative purposes and are not intended to limit the scope of protection of the present disclosure. Therefore, it should be understood that various modifications and changes can be made to the exemplary embodiments without departing from the scope of protection of the present disclosure.

[0022] In a first aspect, the present application provides a porosity measurement device, such as Figure 1 and Figure 2As shown, the porosity measuring device comprises: a liquid measuring container 1 and an upper cover 2, wherein the upper cover 2 is provided with a cantilever 21 for extending into the interior of the container 1, and a reading area 3 is provided on a portion of the side wall of the container 1 horizontally opposite to the cantilever 21.

[0023] The porosity measuring device provided in this embodiment includes a liquid measuring container 1 and an upper cover 2, and can perform a liquid volume displacement test to obtain the true volume of the sample 4 to be tested, that is, the actual volume without pores, and then calculate the porosity of the sample 4 to be tested by the true volume of the sample 4 to be tested. This embodiment uses a liquid-immersed sample method to perform the test, which is closer to the actual situation of the sample 4 to be tested in an electrolyte environment. Therefore, the porosity measured in this way can more accurately reflect the effective pore volume and porosity of the electrode or diaphragm sample 4 to be tested in the electrolyte environment.

[0024] Specifically, the porosity measuring device is provided with an upper cover 2 matched with the container 1, and the upper cover 2 is provided with a cantilever 21 for extending into the interior of the container 1, and the reading area 3 of the container 1 is opposite to the cantilever 21. The liquid level in the container 1 must exceed the cantilever 21 to measure the reading, that is, the cantilever 21 must extend below the liquid level, and the liquid level is limited between the cantilever 21 and the side wall of the container 1. In this way, the height of the liquid level changes greatly before and after the addition of the sample 4 to be tested. By increasing the height difference between the front and rear liquid levels, the accuracy of the true volume of the sample 4 to be tested that is finally calculated can be improved; moreover, the setting of the cantilever 21 can avoid the surface area of ​​the liquid surface being large, so that the concave liquid surface formed in the middle makes the judgment that the liquid level reaches the constant volume line when measuring the liquid inaccurate. In this embodiment, the liquid level is only in the narrow space between the cantilever 21 and the side wall of the container 1, which is conducive to observing and comparing the liquid level and the scale line, and can improve the accuracy of the judgment of the liquid level reading, thereby improving the accuracy of the final test result.

[0025] In addition, the cantilever 21 provided on the upper cover 2 can also be pressed against the sample 4, so that the sample 4 is completely immersed in the liquid, thereby avoiding inaccurate test results caused by the sample 4 not being completely immersed in the liquid; for example, when a diaphragm is used as the sample 4, due to the extension and curling of the diaphragm, part of the diaphragm may extend to the liquid surface when the diaphragm is placed in the container, or due to the high density of the liquid, part of the sample 4 may float on the liquid surface. In these cases, when the upper cover 2 is placed on the container 1, the sample 4 can be completely immersed in the liquid through the pressure of the cantilever 21.

[0026] In addition, the design of the upper cover 2 can also prevent the liquid from volatilizing, affecting the accuracy of the test and polluting the environment.

[0027] Specifically, the porosity measurement device of the present embodiment is particularly suitable for measuring test samples with larger volumes. For test samples with larger volumes, if an ordinary volumetric flask is used for testing, since the volume of the body and neck of the volumetric flask are both larger, the change in the liquid level after adding the sample is small, and the determination of whether the concave liquid surface of the liquid reaches the constant volume line when measuring the liquid is not accurate enough, all of which will affect the final measurement and calculation results. The porosity measurement device provided by the present embodiment can effectively improve these problems and improve the accuracy of the porosity measurement and calculation results.

[0028] In some embodiments, Figure 1 and Figure 2 As shown, the horizontal cross-section of the accommodating space of the container 1 and the horizontal cross-section of the cantilever 21 are of the same shape, and both are regular shapes. In this way, it is easy to measure and calculate the cross-sections of the two, and calculate the liquid volume change based on the cross-sections of the two, which is conducive to the subsequent calculation of the true volume of the sample 4 to be tested according to the liquid volume replacement method.

[0029] For example, Figure 1 As shown, the container 1 and the cantilever 21 are both cylindrical structures, and the horizontal cross-section of the accommodating space of the container 1 and the horizontal cross-section of the cantilever 21 are both circular; or Figure 2 As shown, the container 1 and the cantilever 21 are both polygonal column structures, and the horizontal cross-section of the accommodating space of the container 1 and the horizontal cross-section of the cantilever 21 are both polygonal, such as rectangular or square.

[0030] Exemplarily, the axis lines of the container 1 and the cantilever 21 coincide with each other, which can ensure the uniformity and stability of the liquid level and facilitate observation and reading.

[0031] In some embodiments, Figure 1 and Figure 2 As shown, there is a set spacing between the side of the cantilever 21 and the side wall of the container 1, and the set spacing ranges from 1mm to 5mm, for example, specifically 1mm, 2mm, 3mm, 4mm, and 5mm. The liquid level is only within the very small set spacing, which can make the uniformity of the liquid level height better and improve the accuracy of the liquid level reading. In addition, a very small set spacing is set between the side of the cantilever 21 and the side wall of the container 1, which can make the height of the liquid level change greatly before and after the addition of the sample 4 to be tested, thereby improving the accuracy of the final test result.

[0032] Of course, in the technical solution of the present application, the distance between the side of the cantilever 21 and the side wall of the container 1 is not limited to the above range. During the actual test operation, the shape and volume of the container 1, the shape and length of the cantilever 21, and the volume of the sample to be tested are comprehensively considered. The above distance can also be set to be greater than 5 mm, for example, 1 cm or even several cm.

[0033] In some embodiments, the ratio of the horizontal cross-sectional area of ​​the cantilever 21 to the horizontal cross-sectional area of ​​the accommodation space of the container 1 is greater than 0.8. The liquid level before and after the addition of the sample 4 to be tested is between the cantilever 21 and the side wall of the container 1. By setting the horizontal cross-sectional area of ​​the cantilever 21 larger, the height change of the liquid level before and after the addition of the sample 4 to be tested can be larger, thereby improving the accuracy of the final test result.

[0034] In some embodiments, the upper cover 2 can be engaged with the container 1, or it can just be placed on the opening of the container 1. If it is just placed on the opening of the container 1, the density of the cantilever 21 is greater than the density of the liquid to ensure that the cantilever 21 can extend into the liquid and will not float.

[0035] In some embodiments, the scale of the reading area 3 on the container 1 may be a length unit for calibrating the liquid level; or, the scale of the reading area 3 may be a volume unit for directly reading the change in liquid level volume.

[0036] In a second aspect, based on the porosity measuring device provided in the present application, the present application also provides a porosity measuring method, wherein the porosity measuring device as described above is used for measurement. Figure 3 As shown, the measuring method specifically comprises the following steps:

[0037] Step 101, inject liquid into the container, cover the container with an upper cover, extend the cantilever of the upper cover below the liquid level so that the liquid level is in the reading area, read the scale corresponding to the liquid level at this time, and record it as the first reading D1;

[0038] Step 102, add the sample to be tested into the container, cover the container with the upper cover, extend the cantilever of the upper cover below the liquid surface so that the liquid surface is in the reading area, read the scale corresponding to the liquid surface at this time, and record it as the second reading D2;

[0039] Step 103, calculating the true volume of the sample to be tested according to the first reading D1 and the second reading D2;

[0040] Step 104: Calculate the porosity of the sample to be tested according to the true volume of the sample to be tested.

[0041] The porosity measurement method provided in the present application adopts a porosity measuring device for measurement. The porosity measuring device is provided with a container and an upper cover. The reading area of ​​the container is arranged at the part opposite to the cantilever of the upper cover, which can improve the height difference of the liquid level change before and after the addition of the sample to be tested, and improve the accuracy of the liquid level reading judgment, thereby improving the accuracy of the true volume of the sample to be tested obtained by the final calculation.

[0042] In addition, the porosity measurement method provided in the present application utilizes liquid volume displacement to calculate the true volume and porosity of the sample to be tested, and tests are performed by infiltrating the sample with liquid, which is closer to the actual situation of the sample to be tested in the electrolyte environment. Therefore, the measured porosity can more accurately reflect the effective pore volume and porosity of the electrode or diaphragm to be tested sample in the electrolyte environment.

[0043] The porosity measurement method of the present application does not require large instruments, has simple test tools and is easy to operate. It can quickly and accurately measure the porosity of materials, improve the accuracy of porosity testing, and has a guiding role in battery design and process parameter optimization.

[0044] In some embodiments, the porosity measurement method of this embodiment further includes the following steps:

[0045] Before step 103, the mass m0 of the container, the mass m2 of the sample to be tested, the mass m1 of the container when the liquid is injected into the container until the liquid level reaches a first reading, the mass m3 of the container when the liquid level reaches a second reading after the sample to be tested is added, and the density ρ of the liquid are measured respectively.

[0046] Further, the volume V1 of the liquid in the container at the first reading and the volume V2 of the liquid in the container at the second reading are calculated respectively according to the following formulas;

[0047]

[0048]

[0049] Specifically, the density ρ of the liquid can be measured by a densitometer; the mass m1 is the total mass of the container and the liquid in the container when the liquid level is at the first reading, which can be obtained by placing the container directly on an electronic scale for weighing after adding the liquid to the container, and the operation is simple; the mass m2 is the total mass of the container, the liquid level in the container and the sample to be tested when the liquid level is at the second reading. Similarly, after adding the sample to be tested to the container, the container can be placed on an electronic scale for weighing, and the operation is simple.

[0050] Step 103, the true volume of the sample to be tested is calculated according to the first reading D1 and the second reading D2, specifically, the true volume V of the sample to be tested is calculated using the following formula:

[0051] V=V1-V2+ΔV

[0052] ΔV=(S2-S1)(D2-D1)

[0053] Wherein, S2 is the horizontal cross-sectional area of ​​the container's accommodation space, S1 is the horizontal cross-sectional area of ​​the cantilever, and D2 and D1 are length units.

[0054] In some embodiments, in step 102, after adding the sample to be tested into the container and before taking the second reading D2, the following step is further included: draining part of the liquid so that the liquid level is within the effective reading area.

[0055] Since the upper cover must be placed on the container when reading, the cantilever of the upper cover extends below the liquid level, which will cause the height of the liquid level to change greatly or even cause the liquid to overflow from the container, so that the liquid level is not within the reading area; and after the sample to be tested is added, the liquid level has risen to some extent, and the above situation is likely to occur if the cantilever is extended below the liquid level at this time. Therefore, in this embodiment, after the sample to be tested is added, part of the liquid is first discharged, and then the upper cover is covered to take the reading, which can avoid the liquid level being too high or the liquid overflowing after the upper cover is covered, and can make the liquid level within the effective reading area, so that the accuracy of the second reading can be guaranteed and the feasibility of the test operation can be improved.

[0056] For example, after adding the sample to be tested, the container can be left to stand for a certain period of time to allow the liquid to fully soak the sample to be tested, for example, it can be left to stand for about 1 hour, and then the excess liquid is drained and the upper cover is closed. When the liquid level is stable, the scale at which the liquid level is located is read to obtain a second reading. Alternatively, after adding the sample to be tested, the upper cover can be directly closed and then left to stand until the liquid level is stable.

[0057] The porosity measurement method and its calculation formula V=V1-V2+ΔV in the above embodiment of the present application can be effectively applied to the situation of the present embodiment. In the present embodiment, the discharge of part of the liquid will cause the mass and volume of the liquid in the container to change at the first reading and the second reading, but the above test method and calculation formula do not depend on parameters such as the volume and / or mass of the liquid before and after, so the change of the parameter will not affect the calculation result of the true volume of the sample to be tested in the present application.

[0058] In other embodiments, the mass and volume of the liquid in the container do not change during the first reading and the second reading, that is, there is no liquid overflow or active liquid discharge. At this time, the testing method of the present application can also directly use ΔV as the true volume V of the sample to be tested, that is, at this time, the true volume of the sample can also be directly obtained by V=(S2-S1)(D2-D1).

[0059] In some embodiments, the mass of the sample to be tested is not less than 4% of the sum of the mass of the liquid in the container and the sample to be tested at the second reading. The greater the mass and volume of the sample to be tested, the higher the test accuracy. The setting of the mass of the sample to be tested in this embodiment can improve the accuracy of the test result.

[0060] In some embodiments, the porosity of the sample to be tested is calculated according to the true volume of the sample to be tested, specifically, the porosity of the sample to be tested is calculated using the following formula:

[0061]

[0062] Wherein, P is the porosity of the sample to be tested, and V0 is the total pore volume of the sample to be tested.

[0063] In some embodiments, before step 102, that is, before adding the sample to be tested into the container, the following steps are further included: drying the sample to be tested in a vacuum drying oven for no less than 12 hours. In this way, the test accuracy can be effectively improved, thereby improving the accuracy of the calculation results.

[0064] Specifically, the porosity measurement device and porosity testing method provided in this embodiment are suitable for porosity testing of materials in the new energy field, such as porosity testing of battery core materials.

[0065] In some embodiments, the total volume of the sample to be tested including pores can be calculated according to a volume formula; taking the sample to be tested as a cell separator as an example, the volume of the separator can be calculated by multiplying the length, width and thickness. Of course, the measurement method of the total volume of the sample to be tested including pores is not limited to this, and can be selected according to actual conditions.

[0066] In some embodiments, the porosity measurement device and porosity testing method provided by the present application are used to test the porosity of a battery material, and the sample to be tested may be a pole piece, a diaphragm battery, or a battery as a whole. Specifically, the larger the sample to be tested, the higher the test accuracy.

[0067] Exemplarily, the liquid used for measurement may be at least one of an electrolyte, a main component of an electrolyte, or a solvent of an electrolyte. For example, the liquid may be dimethyl carbonate (DMC), which is a main component of a lithium ion electrolyte.

[0068] In this embodiment, the test is performed using the electrolyte actually used in the battery, the main component of the electrolyte, or the solvent of the electrolyte, which is closer to the actual situation of the sample to be tested in the electrolyte environment. Therefore, the measured porosity can more accurately reflect the effective pore volume and porosity of the electrode or diaphragm sample to be tested in the electrolyte environment.

[0069] Below, taking the diaphragm as a sample to be tested as an example, the measurement method of the present embodiment is described by way of example:

[0070] First, add electrolyte into the container, calibrate the electrolyte level at a certain scale in the reading area, read the electrolyte level scale at this time to obtain a first reading D1, and weigh the container to obtain the mass m1.

[0071] Then, place the diaphragm sample to be tested into a test container filled with electrolyte, let it stand for a certain period of time, wait for the electrolyte to fully soak the diaphragm, drain the excess electrolyte until the liquid level is stable in the reading area, read the liquid level scale of the electrolyte at this time to obtain the second reading D2, and weigh the container to obtain the mass m3.

[0072] Substitute D1, D2, m1, and m3 into the following formula to calculate the true volume of the diaphragm sample to be tested:

[0073]

[0074] Substitute the true volume V of the membrane sample to be tested into the following formula to obtain the porosity of the membrane sample to be tested:

[0075]

[0076] Exemplarily, the pole piece includes a coating layer and a foil. For example, the coating layer of the negative pole piece is composed of graphite, and the coating layer of the positive pole piece is composed of ternary. For the pole piece, its foil part is assumed to be a non-porous material by default, and the porosity of its coating layer generally needs to be calculated separately; at this time, the true volume of the pole piece can be calculated by liquid volume replacement, and then the volume of the pole piece foil is subtracted from the true volume of the pole piece to obtain the true volume of the coating layer, and finally the porosity of the coating layer is calculated based on the true volume of the coating layer and the total pore volume of the coating layer. Specifically, the volume of the foil can also be calculated by multiplying the length, width and thickness.

[0077] Similarly, for battery cells, it is often necessary to test the total porosity of the diaphragm and electrode coating in the battery cell. At this time, the volume of the foil in the electrode can be subtracted from the true volume of the battery cell to obtain the true volume of the coating and diaphragm. Finally, the total porosity of the coating and diaphragm can be calculated based on their true volumes and the total pore volume of the two.

[0078] In addition, the inventors also compared and analyzed the test results of the porosity test method of the embodiment of the present application with the hexadecane test method in the related art, and specifically used the porosity test method of the present embodiment and the hexadecane test method to test the porosity of the diaphragm, wherein the liquid used in the porosity test method of the present embodiment is dimethyl carbonate (DMC). It is known that the factory value of the porosity of the diaphragm sample to be tested is 40%, and the test results of the two test methods are shown in Table 1 below. As shown in Table 1, compared with the hexadecane test method, the test results obtained by the porosity test method of the embodiment of the present application are obviously closer to the actual porosity of the sample, and the test accuracy of the porosity test method of the embodiment of the present application is obviously higher, and the results are more accurate. Therefore, according to the porosity test method of the embodiment of the present application, the porosity of the pole piece and the diaphragm, as well as the compaction density of the battery cell, can be more accurately reflected, and the amount of battery injection, as well as the important performance of the battery such as cycle performance and internal resistance characteristics can be more accurately known.

[0079] Table 1

[0080] Sample (diaphragm) Hexadecane method (porosity / %) Method of this embodiment (porosity / %) 1 48.66 41.55 2 49.28 42.73 3 48.57 42.42 average value 48.84 42.23

[0081] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the inventions disclosed herein. The present disclosure is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the present disclosure and include common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The specification and example embodiments are to be considered exemplary only, and the true scope and spirit of the present disclosure are indicated by the appended claims.

[0082] It should be understood that the present disclosure is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from its scope. The scope of protection of the present disclosure is limited only by the appended claims.

Claims

1. A porosity measuring device, characterized in that: include: A liquid measuring container and an upper cover, wherein the upper cover is provided with a cantilever for extending into the interior of the container, and a reading area is provided on a portion of the side wall of the container horizontally opposite to the cantilever; the liquid level in the container is located between the cantilever and the side wall of the container; There is a set distance between the side of the cantilever and the side wall of the container; The horizontal cross-section of the accommodation space of the container and the horizontal cross-section of the cantilever are of the same shape, and both are regular shapes; The ratio of the horizontal cross-sectional area of ​​the cantilever to the horizontal cross-sectional area of ​​the accommodating space of the container is greater than 0.

8.

2. The porosity measuring device according to claim 1, characterized in that: The set spacing range is between 1mm and 5mm.

3. A porosity measurement method, characterized in that: Applicable to the porosity measuring device according to claim 1 or 2; the porosity measuring method comprises the following steps: Liquid is injected into the container, and an upper cover is placed on the container. The upper cover is provided with a cantilever for extending into the interior of the container, and a reading area is provided on a portion of the side wall of the container horizontally opposite to the cantilever. The cantilever of the upper cover extends below the liquid surface so that the liquid surface is in the reading area, and the scale corresponding to the liquid surface at this time is read, which is recorded as the first reading D1; Add the sample to be tested into the container, cover the container with the upper cover, extend the cantilever of the upper cover below the liquid surface so that the liquid surface is in the reading area, read the scale corresponding to the liquid surface at this time, and record it as the second reading D2; Calculate the true volume of the sample to be tested according to the first reading D1 and the second reading D2; Calculating the porosity of the sample to be tested according to the true volume of the sample to be tested; The true volume of the sample to be tested is calculated according to the first reading D1 and the second reading D2, specifically, the true volume V of the sample to be tested is calculated using the following formula: V=V1-V2+ΔV ΔV=(S2-S1)(D2-D1) Among them, V1 is the volume of the liquid in the container at the first reading, V2 is the volume of the liquid in the container at the second reading, S2 is the horizontal cross-sectional area of ​​the container's accommodating space, S1 is the horizontal cross-sectional area of ​​the cantilever, and D2 and D1 are length units.

4. The porosity measurement method according to claim 3, characterized in that: The following steps are also included: Respectively measure the mass m0 of the container, the mass m2 of the sample to be tested, the mass m1 of the container when the liquid is injected into the container until the liquid level reaches a first reading, the mass m3 of the container when the liquid level reaches a second reading after the sample to be tested is added, and the density ρ of the liquid; The volume V1 of the liquid in the container at the first reading and the volume V2 of the liquid in the container at the second reading are calculated according to the following formulas:

5. The porosity measurement method according to claim 4, characterized in that: After adding the sample to be tested into the container and before taking the second reading D2, the following steps are also included: Drain some of the liquid so that the liquid level is within the effective reading area.

6. The porosity measurement method according to claim 4, characterized in that: The mass of the sample to be tested is not less than 4% of the sum of the mass of the liquid in the container and the sample to be tested at the time of the second reading.

7. The porosity measurement method according to claim 3, characterized in that: The porosity of the sample to be tested is calculated according to the true volume of the sample to be tested, specifically, the porosity of the sample to be tested is calculated using the following formula: Wherein, P is the porosity of the sample to be tested, and V0 is the total pore volume of the sample to be tested.

8. The porosity measurement method according to claim 3, characterized in that: Before adding the sample to be tested into the container, the following steps are also included: The sample to be tested is placed in a vacuum drying oven for drying for no less than 12 hours.

9. The porosity measurement method according to claim 3, characterized in that: The sample to be tested is a battery cell, a battery cell separator or a pole piece.

10. The porosity measurement method according to claim 3, characterized in that: The liquid is one of an electrolyte, a main component of an electrolyte, or a solvent of an electrolyte.

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