A method for testing the pressure resistance of porous materials

Abstract

The present invention belongs to the technical field of measuring the pressure resistance of porous materials, and specifically relates to a method for testing the pressure resistance of porous materials. The present invention tests the specific surface area of ​​the porous material to obtain initial specific surface area data; places the porous material in a mold for pressing to obtain a pressed material sample; tests the specific surface area of ​​the pressed material sample to obtain pressed specific surface area data; obtains the relative change rate of the specific surface area of ​​the porous material according to Formula 1, and characterizes the pressure resistance of the porous material by the relative change rate of the specific surface area of ​​the porous material. The smaller the relative change rate of the specific surface area of ​​the porous material, the higher the pressure resistance of the porous material. The testing method provided by the present invention can quantitatively characterize the pressure resistance of porous materials, the detection method has high accuracy, and the operation is simple and fast, and is suitable for industrial applications.

Description

Technical Field

[0001] The invention belongs to the technical field of pressure resistance measurement, and particularly relates to a method for testing the pressure resistance of porous materials. Background Art

[0002] As people's requirements for battery energy density continue to increase, the existing graphite-based negative electrode system can no longer meet people's needs. Silicon-based negative electrode materials have many advantages, such as high capacity (4200mAh / g), abundant reserves, and low price, making them one of the most promising negative electrode materials. However, due to the huge volume change of silicon during the charging and discharging process, which leads to particle breakage, loss of electrical contact, and loss of active materials, silicon-based negative electrode materials have low initial efficiency and poor cycle performance, which greatly limits the practical application of silicon-based negative electrode materials.

[0003] Among the numerous silicon-carbon composite anode material preparation processes, those prepared by chemical vapor deposition (CVD) have attracted widespread attention due to their advantages, including high charge and discharge efficiency, good cycle stability, low equipment requirements, and suitability for industrial production. The core of this process is the storage of silicon within a porous carbon framework. Silicon is typically deposited on the inner surface of the porous carbon using CVD, providing an electronically conductive network for the silicon. The voids within the porous carbon also buffer the volume expansion of the silicon during lithium insertion, achieving good cycle stability.

[0004] However, since the silicon-carbon material prepared by chemical vapor deposition stores silicon through a porous carbon skeleton, the porous carbon has a hierarchical porous structure and its mechanical strength is poor, which makes it easy to crack and leak out the deposited silicon. On the one hand, the exposed silicon oxidizes and causes the electrode to heat up; on the other hand, it causes a decrease in capacity and initial efficiency, resulting in inaccurate battery capacity design and poor cycle performance.

[0005] Therefore, how to simply and quickly characterize the structural strength of porous carbon skeletons and silicon-carbon composites has become an urgent problem that needs to be solved by people in this field. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for testing the pressure resistance of porous materials. The testing method provided by the present invention characterizes the pressure resistance of porous materials by the relative change rate of the specific surface area of ​​the porous materials. The detection method has high accuracy, is simple and fast to operate, and is suitable for industrial application.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a method for testing the pressure resistance of a porous material, comprising the following steps:

[0009] Testing the specific surface area of ​​the porous material to obtain initial specific surface area data of the porous material;

[0010] placing the porous material in a mold and pressing it to obtain a pressed material sample;

[0011] Testing the specific surface area of ​​the compressed material sample to obtain compressed specific surface area data of the compressed material sample;

[0012] According to Formula 1, a relative change rate of the specific surface area of ​​the porous material is obtained from the initial specific surface area data of the porous material and the specific surface area data of the pressed material sample after pressing. The relative change rate of the specific surface area of ​​the porous material is used to characterize the pressure resistance of the porous material. The smaller the relative change rate of the specific surface area of ​​the porous material, the higher the pressure resistance of the porous material.

[0013]

[0014] Preferably, the porous material is a powder material, and the particle size range of the porous material is 50 3~60μm.

[0015] Preferably, the particle size range D of the porous material is 50 3 to 10 μm.

[0016] Preferably, the porous material is a porous electrode material.

[0017] Preferably, the porous electrode material includes activated carbon material, hard carbon material or silicon carbon material.

[0018] Preferably, the pressing pressure is 50 to 1500 MPa.

[0019] Preferably, the pressing pressure is 200-600 MPa.

[0020] Preferably, the holding time of the pressing is 10 to 120 seconds.

[0021] Preferably, the holding time of the pressing is 10 to 60 seconds.

[0022] Preferably, the number of the pressed material samples is ≥4, and the relative change rate of the specific surface area of ​​the porous material is the average value of multiple groups of relative change rates of the specific surface area obtained from multiple pressed material samples.

[0023] The present invention provides a method for testing the pressure resistance of a porous material, comprising the following steps: testing the specific surface area of ​​the porous material to obtain initial specific surface area data of the porous material; placing the porous material in a mold for pressing to obtain a pressed material sample; testing the specific surface area of ​​the pressed material sample to obtain pressed specific surface area data of the pressed material sample; obtaining a relative change rate of the specific surface area of ​​the porous material from the initial specific surface area data of the porous material and the pressed specific surface area data of the pressed material sample according to Formula 1, and characterizing the pressure resistance of the porous material by the relative change rate of the specific surface area of ​​the porous material. The smaller the relative change rate of the specific surface area of ​​the porous material, the higher the pressure resistance of the porous material. In the present invention, the pressing process involves particle crushing of the porous material, generation of new particles, and exposure of pores after the generation of the new particles, which will cause changes in the specific surface area of ​​the porous material; therefore, the present invention characterizes the pressure resistance of the porous material by the relative change rate of the specific surface area of ​​the porous material sample before and after pressing. The better the pressure resistance of the porous material, the fewer the number of cracks in the porous material and the smaller the degree of cracking. The smaller the change in the specific surface area of ​​the pressed material sample obtained after pressing, the smaller the relative change rate of the specific surface area of ​​the porous material. Therefore, the test method provided by the present invention can quantitatively characterize the pressure resistance of the porous material. The detection method has high accuracy, is simple and fast to operate, and is suitable for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a flowchart of the method for testing the pressure resistance of porous materials provided by the present invention. DETAILED DESCRIPTION

[0025] The present invention provides a method for testing the pressure resistance of a porous material, comprising the following steps:

[0026] Testing the specific surface area of ​​the porous material to obtain initial specific surface area data of the porous material;

[0027] placing the porous material in a mold and pressing it to obtain a pressed material sample;

[0028] Testing the specific surface area of ​​the compressed material sample to obtain compressed specific surface area data of the compressed material sample;

[0029] According to Formula 1, the relative change rate of the specific surface area of ​​the porous material is obtained from the initial specific surface area data of the porous material and the specific surface area data of the pressed material sample after pressing. The pressure resistance of the porous material is characterized by the relative change rate of the specific surface area of ​​the porous material. Under the same pressing operation conditions, the smaller the relative change rate of the specific surface area of ​​the porous material, the higher the pressure resistance of the porous material;

[0030]

[0031] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well known to those skilled in the art.

[0032] The present invention tests the specific surface area of ​​the porous material to obtain the initial specific surface area data of the porous material. In the present invention, the porous material is preferably a porous electrode material. The porous electrode material preferably includes an activated carbon material, a hard carbon material or a silicon-carbon material, and the silicon-carbon material is specifically a silicon-carbon negative electrode material. The porous material is preferably a powder material, and the particle size range of the porous material is D 50 Preferably, it is 3 to 60 μm, more preferably 3 to 10 μm. In the present invention, the specific surface area of ​​the porous material, ie, the initial specific surface area data, is preferably tested using a specific surface area tester. The present invention has no special requirements for the specific testing method of the initial specific surface area data.

[0033] The present invention places the porous material in a mold for pressing to obtain a pressed material sample. In the present invention, the pressing pressure is preferably 50 to 1500 MPa, more preferably 200 to 600 MPa. The holding time of the pressing is preferably 10 to 120 s, more preferably 10 to 60 s. In the present invention, the pressing is preferably tableting. In the present invention, the sample preparation preferably includes the following steps: placing the porous material in a mold, placing the mold in the center of a tablet press, applying uniform pressure until the set pressure is reached, holding the pressure for a fixed time, and recording the process pressure and holding time; after holding the pressure, release the pressure, remove the bottom of the mold, install a demolding tool, take the obtained pressed material sample out of the mold, and demold to obtain a pressed material sample. In the present invention, the number of pressed material samples is preferably ≥4, and specifically 4 groups in the embodiment.

[0034] After obtaining the compressed material sample, the present invention tests the specific surface area of ​​the compressed material sample to obtain compressed specific surface area data for the compressed material sample. In the present invention, the specific surface area of ​​the compressed material sample, i.e., the compressed specific surface area data, is preferably tested using a specific surface area tester. The present invention has no special requirements for the specific testing method for the compressed specific surface area data. When there are multiple groups of compressed material samples, the present invention preferably measures the specific surface area of ​​each group of compressed material samples separately to obtain compressed specific surface area data corresponding to each group of compressed materials.

[0035] After obtaining the initial specific surface area data of the porous material and the specific surface area data after compression of the pressed material sample, the present invention obtains the relative change rate of the specific surface area of ​​the porous material from the initial specific surface area data of the porous material and the specific surface area data after compression of the pressed material sample according to Formula 1. The relative change rate of the specific surface area of ​​the porous material is used to characterize the pressure resistance of the porous material. Under the same pressing operation conditions, the smaller the relative change rate of the specific surface area of ​​the porous material, the higher the pressure resistance of the porous material.

[0036]

[0037] In the present invention, the relative change rate of the specific surface area of ​​the porous material is the average value of multiple groups of relative change rates of the specific surface area obtained from multiple samples of the pressed material after removing abnormal data, that is, the average relative change rate of the specific surface area.

[0038] Compared with the prior art, the method for testing the pressure resistance of porous materials provided by the present invention has the following beneficial effects:

[0039] The tablet press and specific surface area tester of the present invention are mature equipment and there is no need to develop new equipment, thereby reducing testing costs.

[0040] The testing method provided by the present invention can quickly characterize the pressure resistance of a porous material by testing the relative change rate of the specific surface area of ​​the porous material before and after tableting. The better the pressure resistance of the porous material, the fewer the number of cracks, the smaller the degree of cracking, the smaller the change in specific surface area, and the relatively smaller the relative change rate of the specific surface area. Therefore, the testing method provided by the present invention can quantitatively characterize the pressure resistance of a porous material. The detection method has high accuracy, is simple and quick to operate, and is suitable for industrial application.

[0041] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0042] Example 1

[0043] according to Figure 1 The flow chart of the test method for the pressure resistance of porous materials provided in the test is used to test the porous electrode material. The specific test steps are as follows:

[0044] Step 1: Prepare a tablet press, a tableting mold, a tableting mold, a comparative table tester, and a porous electrode material to be tested; the porous electrode material in step 1 is a silicon-carbon material prepared by chemical vapor deposition, with a particle size of 7.63 μm, selected from Jiangxi Yijin New Energy Technology Co., Ltd.

[0045] Step 2: Use the surface area tester to test the silicon-carbon material to obtain the average initial specific surface area of ​​53.97m 2 / g.

[0046] Step 3: Place the silicon-carbon material to be tested into the mold, and place the mold in the center of the tablet press. Apply a uniform pressure of 600 MPa, hold the pressure for 60 seconds, and record the process pressure and holding time.

[0047] Step 4: Release the pressure, remove the mold bottom, install the stripping tool, remove the sample from the mold, and obtain the pressed material sample; repeat the above steps 4 times to obtain four groups of pressed material samples.

[0048] Step 5: The surface area of ​​the four groups of compressed material samples was tested by the surface area tester, and the surface area data of the four groups of compressed material samples were 100.89m 2 / g、99.59m 2 / g、100.54m 2 / g、99.87m 2 / g.

[0049] Step 6: According to formula 1, the relative change rates of the specific surface areas before and after tableting for the four groups of compressed material samples are calculated to be 86.94%, 84.53%, 86.29%, and 85.05%, respectively. The average value is taken to obtain the average relative change rate of the specific surface area of ​​the silicon-carbon material to be tested, which is 85.7%.

[0050] Example 2

[0051] The same method as in Example 1 was used, except that the applied pressure was set to 200 MPa, and the average specific surface area of ​​the material after pressing was 77.83 m 2 / g, 75.81m 2 / g、76.78m 2 / g、77.14m 2 / g, the relative change rates of specific surface area are 44.21%, 40.47%, 42.26% and 42.93% respectively. The average value is taken to obtain the average relative change rate of specific surface area of ​​the tested silicon-carbon material is 42.47%.

[0052] Example 3

[0053] The same operation as in Example 1 was carried out except that the applied pressure was set to 400 MPa, and the average specific surface area data of the pressed materials were 93.26 m 2 / g, 94.03m 2 / g, 93.36m 2 / g, 93.12m 2 / g, the relative changes in specific surface area were 72.80%, 74.23%, 72.98% and 72.54% respectively, and the average relative change in specific surface area was 73.14%.

[0054] It can be seen from the results of Examples 1 to 3 that: as the pressure increases, the specific surface area of ​​the pressed material samples obtained by silicon-carbon material sampling gradually increases, and the relative change rate of the average specific surface area is also greater, indicating that the relative change rate of the specific surface area of ​​the porous material reacts sensitively to the change of the sample preparation pressure. The test method provided by the present invention can quickly and accurately obtain the pressure resistance performance of the characterization material.

[0055] Example 4

[0056] The same method as in Example 1 was used for the operation, except that the holding time was set to 10s, and the average specific surface area data of the pressed materials were 65.87m 2 / g, 66.11m 2 / g, 66.02m 2 / g, 65.93m 2 / g, the relative changes in specific surface area were 22.05%, 22.49%, 22.33% and 22.16% respectively, and the average relative change in specific surface area was 22.26%.

[0057] Example 5

[0058] The same method as in Example 1 was used, except that the holding time was set to 30 s, and the average specific surface area of ​​the material after pressing was 88.16 m 2 / g,87.97m 2 / g、87.88m 2 / g、88.24m 2 / g, the relative changes in specific surface area were 63.35%, 63.00%, 62.83% and 63.50% respectively, and the average relative change in specific surface area was 63.17%.

[0059] Example 6

[0060] The same method as in Example 3 was used, except that the holding time was set to 90s, and the average specific surface area of ​​the material after pressing was 105.61m 2 / g,106.03m 2 / g, 105.21m 2 / g, 105.95m 2 / g, the relative changes in specific surface area were 95.68%, 96.46%, 94.94% and 96.31% respectively, and the average relative change in specific surface area was 95.85%.

[0061] In the present invention, since the porous silicon-carbon composite material particles crack and break after pressing (i.e., tableting), the particle size of the particles may decrease. Therefore, by testing the particle size change before and after tableting, the pressure resistance of the porous material can theoretically be characterized. The present invention thus conducts the following comparative example for verification.

[0062] Comparative Example 1

[0063] The same operation as in Example 1 was performed, except that: the particle size before and after tableting was tested, the initial particle size of the silicon-carbon material was Dv50: 7.63 μm, and the mass proportion of <2 μm was: 0.007%; the particle sizes of the materials after pressing were Dv50: 7.55 μm, and the mass proportion of <2 μm was: 0.01%; Dv50: 7.64, and the mass proportion of <2 μm was: 0.007%; Dv50: 7.59 μm, and the mass proportion of <2 μm was: 0.008%; Dv50: 7.61 mass, and the mass proportion of <2 μm was: 0.007%.

[0064] Comparative Example 2

[0065] The same operation as in Example 6 was performed, except that the particle size before and after tableting was tested. The particle size of the compressed material was Dv50: 7.58 μm, <2 μm mass proportion: 0.008%; Dv50: 7.62 μm, <2 μm mass proportion: 0.007%; Dv50: 7.60 μm, <2 μm mass proportion: 0.000%; Dv50: 7.65 μm, <2 μm mass proportion: 0.008%.

[0066] It can be seen from Comparative Examples 1 and 2 that, excluding the test measurement error, the particle size of the porous silicon-carbon composite material does not change before and after tableting. Therefore, measuring the change in the particle size of the porous material cannot characterize the pressure resistance of the porous material.

[0067] As can be seen from the above embodiments, the present invention provides a method for testing the pressure resistance of porous materials. The specific surface area of ​​the porous material before and after pressing is tested using a specific surface area tester, thereby obtaining the change in specific surface area of ​​the porous material before and after pressing. The relative change rate of the specific surface area is calculated according to Formula 1, and the pressure resistance of the porous material is characterized by the relative change rate of the specific surface area of ​​the porous material. The method for testing the pressure resistance of porous materials in the present invention can solve the problem that current detection methods cannot quantitatively characterize the pressure resistance of porous materials. By measuring the change in specific surface area before and after tableting, the pressure resistance of porous materials can be quantitatively understood. The method of the present invention is simple and quick.

[0068] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for testing the pressure resistance of porous materials, characterized in that: The following steps are involved: Testing the specific surface area of ​​the porous material to obtain initial specific surface area data of the porous material; The porous material is placed in a mold and pressed to obtain a pressed material sample, wherein the pressing pressure is 200 to 400 MPa and the holding time of the pressing is 60 to 120 seconds; Testing the specific surface area of ​​the compressed material sample to obtain compressed specific surface area data of the compressed material sample; The relative change rate of the specific surface area of ​​the porous material is obtained from the initial specific surface area data of the porous material and the specific surface area data of the pressed material sample according to Formula 1. The pressure resistance of the porous material is characterized by the relative change rate of the specific surface area of ​​the porous material. The smaller the relative change rate of the specific surface area of ​​the porous material, the higher the pressure resistance of the porous material. The number of the pressed material samples is 4, and the relative change rate of the specific surface area of ​​the porous material is the average value of multiple groups of relative change rates of specific surface areas obtained from multiple pressed material samples.

2. The testing method according to claim 1, wherein: The porous material is a powder material, and the particle size range of the porous material is D 50 3~60μm.

3. The testing method according to claim 2, wherein: The particle size range D of the porous material 50 3 to 10 μm.

4. The testing method according to any one of claims 1 to 3, characterized in that: The porous material is a porous electrode material.

5. The testing method according to claim 4, characterized in that: The porous electrode material includes activated carbon material, hard carbon material or silicon carbon material.

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