Porosity analysis method and pore analysis device

Abstract

The present invention provides a pore analysis method and a pore analysis device, the method comprising a solid-liquid wetting angle adjustment step, a pressure application step and a porosity determination step. In the solid-liquid wetting angle adjustment step, a solid sample is immersed in a liquid medium, and the wetting angle between the liquid medium and the solid sample is increased by applying an external stimulus to the solid sample and / or the liquid medium, and the value of a parameter indicating the space occupied by the liquid medium is obtained as a first value L1 in a state where the external stimulus is applied. In the pressure application step, pressure is applied to the liquid medium in a state where the external stimulus is applied, and the value of the parameter is obtained as a second value L2 in a state where pressure is applied to the liquid medium. In the porosity determination step, the porosity of the solid sample is determined based on the volume V of the solid sample and the comparison result between the first value L1 and the second value L2.

Description

Technical Field

[0001] The invention relates to the field of pore analysis of solid samples, in particular to a pore analysis method and a pore analysis device. Background Art

[0002] Lithium-ion power batteries are now widely used as the main power source for new energy vehicles. Various technologies of lithium-ion power batteries have developed rapidly in recent years, and higher requirements have been placed on the fast charging capability of lithium-ion batteries. The porosity of solid electrodes, especially the porosity of solid negative electrodes, has received more and more attention as an important indicator for measuring the fast charging capability of lithium-ion power batteries. However, how to measure the porosity of solid electrodes has also become a difficult point. In the existing technology, mercury intrusion porosimetry (MIP) is mainly used to measure the porosity of solid negative electrodes.

[0003] However, the mercury injection method provided in the prior art has the problem of high cost of the equipment used and being restricted in some areas due to the toxicity of mercury. Summary of the invention

[0004] The present invention aims to provide a pore analysis method and a pore analysis device so as to at least solve or alleviate some of the problems existing in the prior art.

[0005] The first aspect of the present invention provides a pore analysis method, including a solid-liquid wetting angle adjustment step, a pressure application step and a porosity determination step. In the solid-liquid wetting angle adjustment step, a solid sample is immersed in a liquid medium, and the wetting angle between the liquid medium and the solid sample is increased by applying an external stimulus to the solid sample and / or the liquid medium, and the value of a parameter indicating the space occupied by the liquid medium is obtained as a first value L1 in a state where the external stimulus is applied. In the pressure application step, pressure is applied to the liquid medium in a state where the external stimulus is applied, and the value of a parameter indicating the space occupied by the liquid medium is obtained as a second value L2 in a state where pressure is applied to the liquid medium. In the porosity determination step, the porosity of the solid sample is determined based on the volume V of the solid sample and the comparison result between the first value L1 and the second value L2.

[0006] The parameter used to indicate the space occupied by the liquid medium refers to a parameter that describes the amount of space occupied by the liquid medium around the solid sample. For example, the parameter may be the volume or liquid level of the liquid medium. Thus, by obtaining the volume or liquid change caused by the liquid medium entering the pores of the solid sample after being pressurized, the pore volume of the solid sample can be indirectly obtained.

[0007] According to the pore analysis method provided by the present invention, by applying an external stimulus that can increase the wetting angle between the liquid medium and the solid sample to the solid sample and / or the liquid medium, the liquid medium is not easy to adsorb and wet the surface of the solid sample, or naturally enter the pores of the solid sample, so as to help avoid the parameter value error caused by the liquid medium adsorbing and wetting the surface of the solid sample or naturally entering the pores of the solid sample. In this way, the change of the parameter value from the first value L1 to the second value L2 is basically caused by the liquid medium entering the pores of the solid sample due to pressure. In other words, by comparing the first value L1 and the second value L2, the pore volume can be obtained more accurately, which is conducive to improving the detection accuracy of the porosity. In addition, through the solid-liquid wetting angle adjustment step, the selection of the liquid medium can be not limited to mercury, that is, the range of liquid media that can be selected can be broadened. In this way, when the liquid medium is selected as a non-mercury liquid, the equipment cost used for pore analysis can be reduced, and the above-mentioned pore analysis method can be implemented in more areas.

[0008] In the pore analysis method of the optional technical solution of the present invention, "applying external stimulation to the solid sample and / or the liquid medium" means applying a potential difference between the solid sample and the liquid medium.

[0009] According to the above preferred technical solution, the wetting angle between the solid sample and the liquid medium can be reliably adjusted by a relatively simple device. The method of applying a potential difference also has low environmental requirements, which is conducive to reducing the cost required for pore analysis. In addition, when the solid sample is a solid electrode, applying a potential difference is also a more easily operated method of applying external stimulation.

[0010] Preferably, the value of the potential difference applied between the solid sample and the liquid medium is greater than or equal to 0.2 volts and less than or equal to 15 volts.

[0011] In the pore analysis method of the optional technical solution of the present invention, the liquid medium is a non-polar liquid, and the solid sample has a non-polar solid surface.

[0012] According to the above preferred technical solution, the electrostatic repulsion force is dominant between the non-polar solid surface and the non-polar liquid, and the wetting angle increases after applying a potential difference between the solid sample and the liquid medium. Preferably, when no external stimulus is applied, the wetting angle between the liquid medium and the solid sample is greater than or equal to 60° and less than or equal to 90°. That is, the liquid medium exhibits hydrophobicity.

[0013] Preferably, when no external stimulus is applied, the wetting angle between the liquid medium and the solid sample is greater than or equal to 70° and less than or equal to 90°.

[0014] Optionally, the solid sample is a solid negative electrode, and the solid negative electrode includes a current collector and a graphite material layer coated on the current collector.

[0015] In the pore analysis method according to an optional technical solution of the present invention, the liquid medium contains conductive particles.

[0016] According to the above optional technical solution, by adding conductive particles, the conductivity of the liquid medium can be improved, which is beneficial to apply a potential difference between the solid sample and the liquid medium.

[0017] In the pore analysis method of an optional technical solution of the present invention, the liquid medium is an oily liquid containing conductive particles.

[0018] Optionally, the conductive particles are metal powder particles or carbon powder particles.

[0019] In the pore analysis method of an optional technical solution of the present invention, the liquid medium is an ether hydrophobic liquid.

[0020] The pore analysis method of the optional technical solution of the present invention also includes a solid sample volume determination step. Before the solid sample is placed in the liquid medium, the value of the parameter is obtained as the initial value L0, and the volume V of the solid sample is determined based on the comparison result of the first value L1 and the initial value L0.

[0021] According to the above preferred technical solution, before the solid sample is placed in the liquid medium, the value of the parameter used to indicate the space occupied by the liquid medium is the initial value L0. When the solid sample is immersed in the liquid medium and an external stimulus is applied, the value of the parameter becomes the first value L1. Since the first value L1 is a parameter value obtained when an external stimulus is applied, it is helpful to avoid the problem of the first value L1 being too small due to the liquid medium adsorbing and wetting the surface of the solid sample or naturally entering the pores of the solid sample. That is, by applying an external stimulus, the first value L1 is corrected, so that by comparing the first value L1 and the initial value L0, the displacement volume of the solid sample to the liquid medium can be obtained more accurately, and then the volume V of the solid sample can be obtained conveniently and accurately.

[0022] In the pore analysis method of the optional technical solution of the present invention, in the pressure applying step, a gradually increasing pressure is applied to the liquid medium, and multiple values ​​of the parameter are obtained, and the second value L2 is an extreme value among the multiple values.

[0023] According to the above preferred technical solution, by applying gradually increasing pressure to the liquid medium, it is helpful for the liquid medium to enter the pores of the solid sample, thereby facilitating the improvement of the detection accuracy of the porosity.

[0024] In the pore analysis method of the optional technical solution of the present invention, the parameter used to indicate the space occupied by the liquid medium is the liquid level of the liquid medium. In the pressure application step, gradually increasing pressure is applied to the liquid medium, and multiple values ​​of the liquid level are obtained, and the second value L2 is the minimum value among the multiple values.

[0025] A second aspect of the present invention provides a pore analysis device for determining the porosity of a solid sample, comprising a sample container for holding a liquid medium, a pressure applying device, and a potential difference applying device. The pressure applying device is connected to the sample container and is used to apply pressure to the liquid medium so that the liquid medium enters the pores of the solid sample. The potential difference applying device has two connection ends, which are electrically connected to the solid sample and the liquid medium, respectively, so as to apply a potential difference between the solid sample and the liquid medium.

[0026] According to the pore analysis device provided by the present invention, the range of liquid media that can be selected when determining the porosity of a solid sample is broadened.

[0027] In the pore analysis device of the optional technical solution of the present invention, the sample container has an opening, and the pressure applying device is a piston, which is installed in the opening and is configured to apply pressure to the liquid medium during the advancement of the piston.

[0028] According to the above preferred technical solution, since the pressure applying device is a piston, its structure is simple and it is convenient to apply gradually increasing pressure to the liquid medium, which is conducive to allowing the liquid medium to enter the pores of the solid sample and improve the accuracy of porosity detection.

[0029] The pore analysis device of the optional technical solution of the present invention further includes a liquid level indicator and a pressure indicator. The liquid level indicator is used to indicate the change of the space occupied by the liquid medium. The pressure indicator is used to indicate the change of the pressure applied by the pressure applying device to the liquid medium.

[0030] According to the above preferred technical solution, the liquid level of the liquid medium and the pressure applied to the liquid medium can be conveniently and accurately obtained, thereby improving the reliability of the process of determining the porosity of the solid sample.

[0031] In the pore analysis device of an optional technical solution of the present invention, the sample container is a columnar container.

[0032] According to the above preferred technical solution, since the sample container is a cylindrical container, its multiple transverse cross-sectional areas perpendicular to the gravity direction are the same, which facilitates calculation of the change in space occupied by the liquid medium according to the change in the liquid level of the liquid medium. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A flow chart of a pore analysis method according to an embodiment of the present invention is shown;

[0034] Figure 2 A schematic diagram showing a wetting angle between a liquid medium and a solid sample in a state where no external stimulus is applied in an embodiment of the present invention;

[0035] Figure 3 A schematic diagram showing a wetting angle between a liquid medium and a solid sample when an external stimulus is applied in an embodiment of the present invention;

[0036] Figure 4 A diagram showing the relationship between the pressure applied to the liquid medium and the liquid level of the liquid medium in an embodiment of the present invention;

[0037] Figure 5 A schematic diagram showing a sample container and a potential difference applying device according to an embodiment of the present invention;

[0038] Figure 6 A schematic diagram showing a liquid medium contained in a sample container according to an embodiment of the present invention;

[0039] Figure 7 A schematic diagram showing a solid sample of an embodiment of the present invention immersed in a liquid medium and electrically connected to a potential difference applying device;

[0040] Figure 8 A schematic diagram showing a pressure applying device according to an embodiment of the present invention applying pressure to a liquid medium;

[0041] Reference numerals: solid sample (solid negative electrode) 8 , liquid medium 9 , pore analysis device 100 , sample container 1 , opening 11 , liquid level indicator 12 , pressure applying device (piston) 2 , pressure indicator 21 , potential difference applying device 3 , connection terminal 31 . DETAILED DESCRIPTION

[0042] It should be noted that the working principle, characteristics and advantages of the pore analysis method and pore analysis device according to the present invention will be described below in an exemplary manner. However, it should be understood that all descriptions are given for illustrative purposes only and should not be construed as limiting the present invention in any way.

[0043] In addition, for any single technical feature described or implied in the embodiments mentioned in this document, or any single technical feature displayed or implied in the drawings, the present invention still allows any combination or deletion between these technical features (or their equivalents) without any technical obstacles, thereby obtaining more other embodiments of the present invention that may not be directly mentioned in this document.

[0044] <Pore Analysis Method>

[0045] This embodiment provides a pore analysis method, referring to Figure 1 The pore analysis method includes: a solid-liquid wetting angle adjustment step S1, a pressure application step S2 and a porosity determination step S3.

[0046] In the solid-liquid wetting angle adjustment step S1, the solid sample 8 is immersed in the liquid medium 9, and the wetting angle between the liquid medium 9 and the solid sample 8 is increased by applying an external stimulus to the solid sample 8 and / or the liquid medium 9, and the value of the parameter indicating the space occupied by the liquid medium 9 is obtained as a first value L1 in the state of applying the external stimulus. In the pressure application step S2, pressure is applied to the liquid medium 9 in the state of applying the external stimulus, and the value of the parameter is obtained as a second value L2 in the state of applying the pressure to the liquid medium 9. In the porosity determination step S3, the porosity of the solid sample 8 is determined based on the volume V of the solid sample 8 and the comparison result of the first value L1 and the second value L2.

[0047] Specifically, in the solid-liquid wetting angle adjustment step S1, the solid sample 8 is immersed in the liquid medium 9, and the wetting angle between the liquid medium 9 and the solid sample 8, that is, the angle between the liquid-solid interface and the tangent line of the droplet surface at the contact point between the liquid medium 9 and the solid sample 8, is as follows: Figure 2 As shown, it is θ1. The relatively small wetting angle θ1 indicates that the wetting degree of the liquid medium 9 on the surface of the solid sample 8 is high, that is, the droplets of the liquid medium 9 can spread more easily on the surface of the solid sample 8. In this way, without applying external pressure, the liquid medium 9 may adsorb and wet the surface of the solid sample 8, and the liquid medium 9 may also naturally enter the pores of the solid sample 8. In order to avoid the accuracy of porosity detection being affected by the adsorption and wetting of the surface of the solid sample 8 by the liquid medium 9, or by naturally entering the pores of the solid sample 8, an external stimulus that can increase the wetting angle between the liquid medium 9 and the solid sample 8 is applied to the solid sample 8 and / or the liquid medium 9. As a specific example, the method of applying the external stimulus is to apply a potential difference between the solid sample 8 and the liquid medium 9. Reference Figure 3 After applying a potential difference between the solid sample 8 and the liquid medium 9, the interfacial tension between the solid sample 8 and the liquid medium 9 is changed, so that the wetting angle between the liquid medium 9 and the solid sample 8 becomes θ2. The relatively large wetting angle θ2 indicates that the wetting degree of the liquid medium 9 on the surface of the solid sample 8 is low, that is, the droplets of the liquid medium 9 tend to maintain a spherical shape on the surface of the solid sample 8. In this way, in the state where no external pressure is applied, the liquid medium 9 will not easily adsorb and wet the surface of the solid sample 8, nor will it be easy to naturally enter the pores of the solid sample 8, which is conducive to obtaining a more accurate pore volume V' of the solid sample 8, and further conducive to improving the detection accuracy of the porosity.

[0048] In the solid-liquid wetting angle adjustment step S1, when the solid sample 8 is immersed in the liquid medium 9 and a potential difference is applied between the solid sample 8 and the liquid medium 9, the parameter indicating the space occupied by the liquid medium 9 is obtained as a first value L1. As a specific example, the parameter indicating the space occupied by the liquid medium 9 is the liquid level of the liquid medium 9, that is, the value of the liquid level of the liquid medium 9 obtained when a potential difference is applied between the solid sample 8 and the liquid medium 9 is the first value L1.

[0049] In the pressure applying step S2, a pressure is applied to the liquid medium 9 while a potential difference is applied between the solid sample 8 and the liquid medium 9, so that the liquid medium 9 is pressed and enters the pores of the solid sample 8. Figure 4 The applied pressure may be gradually increased. In the process of applying gradually increasing pressure to the liquid medium 9, a plurality of gradually decreasing values ​​of the liquid level of the liquid medium 9 may be continuously or intermittently obtained. In other words, as the pressure applied to the liquid medium 9 gradually increases, the liquid level of the liquid medium 9 gradually decreases. Figure 4 When the pressure applied to the liquid medium 9 continues to increase and there is no obvious change in the liquid level of the liquid medium 9, this indicates that the liquid medium 9 has filled all the pores of the solid sample 8 that it can enter. At this time, the value of the liquid level of the liquid medium 9 is the second value L2, that is, the minimum value of the liquid level of the liquid medium 9.

[0050] When a potential difference is applied between the solid sample 8 and the liquid medium 9, the liquid medium 9 basically does not adsorb or wet the surface of the solid sample 8, or enter the pores of the solid sample 8. At this time, the value of the liquid level of the liquid medium 9 is the first value L1. While maintaining the state of applying the potential difference, after applying pressure to the liquid medium 9, the liquid medium 9 enters the pores of the solid sample, and the value of the liquid level of the liquid medium 9 changes to the second value L2. In other words, the change of the value of the liquid level of the liquid medium 9 from the first value L1 to the second value L2 is caused by the liquid medium 9 entering the pores of the solid sample 8. In this way, by comparing the first value L1 and the second value L2, the pore volume V' of the solid sample 8 can be obtained. Based on the volume V of the solid sample 8 and the pore volume V' of the solid sample 8, the porosity of the solid sample 8 can be determined.

[0051] Since a potential difference is applied between the solid sample 8 and the liquid medium 9 when the first value L1 is obtained and during the process of applying pressure to the liquid medium 9, the wetting degree of the solid sample 8 by the liquid medium 9 is kept low. In this way, the liquid level of the liquid medium 9 will not change substantially due to the liquid medium 9 adsorbing and wetting the surface of the solid sample 8 or naturally entering the pores of the solid sample 8. In other words, the factors affecting the change in the liquid level of the liquid medium 9 are controlled, so that the change in the liquid level of the liquid medium 9 can reflect the amount of the liquid medium 9 that enters the pores of the solid sample 8 due to pressure, and further reflect the pore volume V' of the solid sample 8.

[0052] In short, by applying a potential difference between the solid sample 8 and / or the liquid medium 9, the liquid medium 9 is not easy to adsorb or wet the surface of the solid sample 8 or naturally enter the pores of the solid sample 8, which is conducive to obtaining a more accurate pore volume V' of the solid sample 8, and further conducive to improving the detection accuracy of the porosity. In addition, through the solid-liquid wetting angle adjustment step S1, the selection of the liquid medium 9 is not limited to mercury, that is, the range of liquid media 9 that can be selected can be broadened. In this way, when the liquid medium 9 is a non-mercury liquid, the equipment cost used for pore analysis can be reduced, and the pore analysis method in this embodiment can be implemented in more areas. It should be noted here that although the technical effect when the liquid medium 9 is a non-mercury liquid is specifically mentioned in this embodiment, the present invention is not limited to this. In some embodiments, mercury liquid can be selected as the liquid medium 9, and the solid-liquid wetting angle adjustment step S1 is implemented to improve the detection accuracy of the porosity.

[0053] Although in this embodiment, applying a potential difference between the solid sample 8 and the liquid medium 9 is used as an example to illustrate the method of applying external stimulation, the present invention is not limited thereto, and any external stimulation that can increase the wetting angle between the solid sample 8 and the liquid medium 9 is within the technical scope of the present invention. For example, in some embodiments, the method of applying external stimulation is to change the temperature of the solid sample 8 and / or the liquid medium 9. For another example, in some embodiments, the method of applying external stimulation is to apply light or a magnetic field to the solid sample 8 and / or the liquid medium 9.

[0054] It should be noted that there is an electrostatic attraction and an electrostatic repulsion between the solid sample 8 and the liquid medium 9. When the electrostatic repulsion is dominant between the solid sample 8 and the liquid medium 9, the wetting angle increases after a potential difference is applied between the solid sample 8 and the liquid medium 9. When the electrostatic attraction is dominant between the solid sample 8 and the liquid medium 9, the wetting angle decreases after a potential difference is applied between the solid sample 8 and the liquid medium 9. Therefore, those skilled in the art can select an appropriate liquid medium 9 according to the properties of the solid sample 8 to be tested, so as to achieve the purpose of increasing the wetting angle by applying a potential difference.

[0055] Although the liquid level of the liquid medium 9 is taken as an example in this embodiment to illustrate the parameters used to indicate the space occupied by the liquid medium 9, the present invention is not limited to this. As long as such parameters can be used to indicate the space occupied by the liquid medium 9, they are within the technical scope of the present invention.

[0056] Although the present embodiment takes the application of gradually increasing pressure as an example to illustrate the method of applying pressure to the liquid medium 9, the present invention is not limited to this. As long as the pressure application method can make the liquid medium 9 enter the pores of the solid sample 8, it is within the technical scope of the present invention.

[0057] In this embodiment, the volume V of the solid sample 8 is determined by detecting the displacement volume of the solid sample 8 to the liquid medium 9. Specifically, before the solid sample 8 is placed in the liquid medium 9, the value of the liquid level of the liquid medium 9 is obtained as the initial value L0. When the solid sample 8 is immersed in the liquid medium 9 and a potential difference is applied between the solid sample 8 and the liquid medium 9, the value of the liquid level of the liquid medium 9 is obtained as the first value L1. The value of the liquid level of the liquid medium 9 changes from the initial value L0 to the first value L1, which is caused by the solid sample 8 being immersed in the liquid medium 9. In this way, by comparing the initial value L0 and the first value L1, the volume V of the solid sample 8 can be determined. It should be noted here that the volume V of the solid sample 8 is the volume V of the solid sample 8 including the pore volume V' of the solid sample 8. Of course, in some embodiments, the volume V of the solid sample 8 can be detected and obtained by geometric measurement or laser scanning.

[0058] <Pore Analysis Device 100>

[0059] This embodiment provides a pore analysis device 100, referring to Figure 8 , including a sample container 1, a pressure applying device 2, a potential difference applying device 3, a liquid level indicating part 12 and a pressure indicating part 21.

[0060] The sample container 1 is used to hold the liquid medium 9. As a specific example, the sample container 1 is a cylindrical container so that the change in the space occupied by the liquid medium 9 can be calculated by the change in the liquid level of the liquid medium 9. The pressure applying device 2, as a specific example, is a piston 2, which is installed at the opening 11 of the sample container 1 and is configured to apply pressure to the liquid medium 9 during its advancement so that the liquid medium 9 enters the pores of the solid sample 8. The potential difference applying device 3 has a voltage source and two connecting ends 31, which are electrically connected to the solid sample 8 and the liquid medium 9 respectively, so as to apply a potential difference between the solid sample 8 and the liquid medium 9. The liquid level indicating part 12 is used to indicate the change in the space occupied by the liquid medium 9. Specifically, a float liquid level sensor, a capacitive liquid level sensor or an optical liquid level sensor can be selected as the liquid level indicating part 12. The pressure indicating part 21 is used to indicate the change in the pressure applied by the pressure applying device 2 to the liquid medium 9. Specifically, a mechanical pressure sensor or a digital pressure sensor can be selected as the pressure indicating part 21.

[0061] Although the structure of the pressure applying device 2, and the specific positions of the liquid level indicating part 12 and the pressure indicating part 21 are shown in the illustrated embodiment, this does not constitute a limitation of the present invention. Any structure that can apply pressure to the liquid medium 9 is within the technical scope of the pressure applying device 2 described in the present invention. Any component that can indicate the change of the space occupied by the liquid medium 9 is within the technical scope of the liquid level indicating part 12 described in the present invention. Similarly, any component that can indicate the change of the pressure applied by the pressure applying device 2 to the liquid medium 9 is within the technical scope of the pressure indicating part 21 described in the present invention.

[0062] The specific steps of the pore analysis method using the pore analysis device 100 described above will be introduced below.

[0063] refer to Figure 5 First, prepare a sample container 1 and build a potential difference applying device 3 inside it. Figure 6 , pour the liquid medium 9 into the sample container 1, and obtain the value of the liquid level of the liquid medium 9 as the initial value L0.

[0064] refer to Figure 7, put the solid sample 8 into the sample container 1 containing the liquid medium 9, and immerse the solid sample 8 in the liquid medium 9. Make the two connection ends 31 of the potential difference applying device 3 electrically connected to the solid sample 8 and the liquid medium 9 respectively, so as to apply a potential difference between the solid sample 8 and the liquid medium 9, so as to increase the wetting angle between the liquid medium 9 and the solid sample 8. Adjust the output of the potential difference applying device 3 until the wetting angle between the liquid medium 9 and the solid sample 8 is at or close to the maximum, that is, when the output of the potential difference applying device 3 reaches the preset value, the value of the liquid level of the liquid medium 9 is obtained as the first value L1. According to the initial value L0 and the first value L1, the volume V of the solid sample 8 can be calculated, that is, V=(L1-L0)×S, where S is the bottom area of ​​the sample container 1.

[0065] refer to Figure 8 , maintain the state of applying a potential difference between the solid sample 8 and the liquid medium 9, and continue to advance the piston 2 to apply a gradually increasing pressure to the liquid medium 9. When it is detected that the pressure applied to the liquid medium 9 continues to increase, and the liquid level of the liquid medium 9 does not basically change with the increase in pressure, the value of the liquid level of the liquid medium 9 is obtained as the second value L2. According to the first value L1 and the second value L2, the pore volume V' of the solid sample 8 can be calculated, that is, V'= (L1-L2) × S, where S is the bottom area of ​​the sample container 1. Furthermore, the porosity of the solid sample 8 can be calculated, that is, porosity = (V' / V) × 100%.

[0066] <Porosity Detection of Solid Negative Electrode>

[0067] This embodiment also provides a method for detecting the porosity of a solid negative electrode 8, that is, the solid negative electrode 8 is used as the solid sample 8 introduced above. The solid negative electrode 8 includes a current collector and a graphite material layer coated on the surface of the current collector. The graphite material layer can be coated on one side or both sides of the current collector as required.

[0068] The following will introduce a method for detecting the porosity of the solid negative electrode 8 using the pore analysis device 100 introduced above.

[0069] refer to Figure 5 First, prepare a sample container 1, and build a potential difference applying device 3 inside the sample container 1. The potential difference applying device 3 includes a voltage source and two connection terminals 31. Figure 6 , the liquid medium 9 is poured into the sample container 1 , and the value of the liquid level of the liquid medium 9 is obtained as the initial value L0 . At this time, the potential difference applying device 3 is immersed in the liquid medium 9 .

[0070] Here, the selection of the liquid medium 9 mainly considers the following aspects. First, the liquid medium 9 should exhibit non-polar characteristics, that is, it is a non-polar liquid. In this way, the electrostatic repulsion force is dominant between the liquid medium 9 and the solid negative electrode 8 (that is, the non-polar graphite material layer), and after a potential difference is applied between the two, the wetting angle increases. In addition, the liquid medium 9 should be able to conduct electricity, so that a potential difference can be applied between the solid negative electrode 8 and the liquid medium 9. In addition, the liquid medium 9 should have good hydrophobicity, that is, in the state where no potential difference is applied, the wetting angle between the liquid medium 9 and the solid negative electrode 8 is greater than or equal to 60° and less than or equal to 90°. Preferably, the wetting angle is greater than or equal to 70° and less than or equal to 90°. And the liquid medium 9 whose wetting angle is closer to 90° is considered to be a preferred liquid medium 9.

[0071] As a specific example, the liquid medium 9 is a conductive lubricating oil, that is, a lubricating oil to which metal powder or carbon powder is added. Lubricating oil is a non-polar solvent with good hydrophobicity. When no potential difference is applied, the wetting angle between it and the solid negative electrode 8 is about 72°. After adding metal powder particles or carbon powder particles to the lubricating oil, it is made conductive. As a specific example, the liquid medium 9 is cyclopentyl methyl ether. Cyclopentyl methyl ether exhibits non-polar properties, has certain conductivity, and has good hydrophobicity. When no potential difference is applied, the wetting angle between it and the solid negative electrode 8 is about 83°. Of course, there are many choices for the liquid medium 9, and those skilled in the art can comprehensively consider factors such as polarity, conductivity, and hydrophobicity to select the specific category of the liquid medium.

[0072] refer to Figure 7 , put the solid negative electrode 8 into the sample container 1 containing the liquid medium 9, and immerse the solid negative electrode 8 in the liquid medium 9. The two connecting ends 31 of the potential difference applying device 3 are respectively connected to the graphite material layer of the solid negative electrode 8 and the liquid medium 9, so as to apply a potential difference between the solid negative electrode 8 and the liquid medium 9, and increase the wetting angle between the liquid medium 9 and the solid negative electrode 8. Adjust the output of the potential difference applying device 3 until the wetting angle between the liquid medium 9 and the solid sample 8 is maximum or close to maximum, that is, when the output of the potential difference applying device 3 reaches a preset value, the value of the liquid level of the liquid medium 9 is obtained as the first value L1. According to the initial value L0 and the first value L1, the volume V of the solid sample 8 can be calculated, that is, V=(L1-L0)×S, where S is the bottom area of ​​the sample container 1.

[0073] The above preset value (the value of the potential difference applied between the solid negative electrode 8 and the liquid medium 9) can be confirmed by experiment. Specifically, a droplet of the liquid medium 9 can be dropped on the surface of the solid negative electrode 8, and then a varying potential difference can be applied, and the change in the wetting angle between the droplet and the solid negative electrode 8 can be observed and detected at the same time. When the wetting angle between the droplet and the solid negative electrode 8 is maximum or close to maximum, the value of the potential difference applied at this time is recorded as the preset value. Depending on the type of liquid medium 9, the preset value will also be different. Preferably, the preset value is greater than or equal to 0.2 volts and less than or equal to 15 volts.

[0074] refer to Figure 8 , maintain the state of applying a potential difference between the solid negative electrode 8 and the liquid medium 9, and continue to advance the piston 2 to apply a gradually increasing pressure to the liquid medium 9. When it is detected that the pressure applied to the liquid medium 9 continues to increase, and the liquid level of the liquid medium 9 does not basically decrease with the increase in pressure, the value of the liquid level of the liquid medium 9 is obtained as the second value L2. According to the first value L1 and the second value L2, the pore volume V' of the solid negative electrode 8 can be calculated, that is, V'= (L1-L2) × S, where S is the bottom area of ​​the sample container 1. Furthermore, the porosity of the solid negative electrode 8 can be calculated, that is, porosity = (V' / V) × 100%.

[0075] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A pore analysis method, characterized in that: The following steps are involved: a solid-liquid wetting angle adjustment step, immersing the solid sample in a non-mercury liquid medium, and increasing the wetting angle between the non-mercury liquid medium and the solid sample by applying an external stimulus to the solid sample and / or the non-mercury liquid medium, and obtaining a first value L1 of a parameter indicating a space occupied by the non-mercury liquid medium in a state where the external stimulus is applied; a pressure applying step of applying pressure to the non-mercury liquid medium in a state where the external stimulus is applied, and obtaining a value of a parameter indicating a space occupied by the non-mercury liquid medium as a second value L2 in a state where the pressure is applied to the non-mercury liquid medium; a porosity determining step of determining the porosity of the solid sample based on the volume V of the solid sample and a comparison result of the first value L1 and the second value L2, The non-mercury liquid medium is a non-polar liquid, and the solid sample has a non-polar solid surface.

2. The pore analysis method according to claim 1, characterized in that: Applying external stimulation to the solid sample and / or the non-mercury liquid medium is applying a potential difference between the solid sample and the non-mercury liquid medium.

3. The pore analysis method according to claim 2, characterized in that: The non-mercury liquid medium contains conductive particles.

4. The pore analysis method according to claim 2, characterized in that: The non-mercury liquid medium is an oily liquid containing conductive particles, or the non-mercury liquid medium is an ether hydrophobic liquid.

5. The pore analysis method according to claim 1, characterized in that: Also includes: The solid sample volume determination step is: before the solid sample is placed in the non-mercury liquid medium, the value of the parameter is obtained as an initial value L0, and the volume V of the solid sample is determined based on a comparison result between the first value L1 and the initial value L0.

6. The pore analysis method according to claim 1, characterized in that: In the pressure applying step, a gradually increasing pressure is applied to the non-mercury liquid medium, and a plurality of values ​​of the parameter are obtained, wherein the second value L2 is an extreme value among the plurality of values.

7. A pore analysis device, applied to the pore analysis method as claimed in any one of claims 1 to 6, characterized in that: include: Sample container, containing non-mercury liquid medium; a pressure applying device, connected to the sample container, for applying pressure to the non-mercury liquid medium so that the non-mercury liquid medium enters the pores of the solid sample; The potential difference applying device has two connection ends, and the two connection ends are electrically connected to the solid sample and the non-mercury liquid medium respectively, so as to apply a potential difference between the solid sample and the non-mercury liquid medium.

8. The pore analysis device according to claim 7, characterized in that: The sample container has an opening, The pressure applying device is a piston, which is mounted in the opening and is configured to apply pressure to the non-mercury liquid medium during its advancement.

9. The pore analysis device according to claim 7, characterized in that: Also includes: A liquid level indicator, used to indicate changes in the space occupied by the non-mercury liquid medium, The pressure indicating portion is used to indicate the change of the pressure applied by the pressure applying device to the non-mercury liquid medium.

10. The pore analysis device according to claim 7, characterized in that: The sample container is a columnar container.

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