Method for determining the interplanar spacing of hard carbon material 002

Abstract

This invention belongs to the field of X-ray material detection technology, specifically a method for determining the interplanar spacing of hard carbon material 002. Addressing the technical problems in existing technologies where the standards for determining the interplanar spacing of hard carbon material 002 are inconsistent, the measurements are inaccurate, and the repeatability of the test data is poor, hindering the research and preparation of hard carbon materials in the power battery field, this application provides a method for determining the interplanar spacing of hard carbon material 002. The method uses silicon powder to calibrate the 2θ peak angle of the X-ray diffractometer. The peak angle of the 111 crystal plane of silicon powder is 28.442°. A mixture of hard carbon material and silicon powder is used for detection, with a mass ratio of hard carbon material to silicon powder of 95:5 to 99:1. The obtained diffraction peaks have complete shapes, which is more conducive to the analysis software reading the peak angle of the diffuse scattering peak of hard carbon. Furthermore, through angle calibration with standard samples, the obtained data on the interplanar spacing of hard carbon material 002 has high accuracy and good repeatability, providing a favorable guarantee for guiding the development and application of power battery materials.

Description

Technical Field

[0001] This invention belongs to the field of X-ray material detection technology, specifically relating to a method for measuring the interplanar spacing of hard carbon material 002. Background Technology

[0002] Hard carbon refers to carbon that is difficult to graphitize. It is the result of the thermal decomposition of polymers. Common hard carbons include resin carbon, pyrolytic carbon from organic polymers, and carbon black. Hard carbon can be obtained by thermally decomposing cross-linked resins with special structures at around 1000℃. This type of carbon is also difficult to graphitize at high temperatures above 2500℃. Studies have found that hard carbon materials generally have high reversible specific capacity, typically 500-700 mAh. Low- or non-graphitized hard carbon is also a negative electrode material for power lithium-ion batteries. Hard carbon has a stable structure, long charge-discharge cycle life, and a carbon-lithium potential higher than 0.2V, resulting in better safety performance. It overcomes the high reactivity of graphitized carbon during the lithium-to-graphite reaction, which can lead to severe exothermic reversal and explosion risks if an internal short circuit occurs. Hard carbon also suffers from problems such as large variations in discharge voltage with capacity and lower initial charge-discharge efficiency compared to graphitized carbon. Research on the modification of hard carbon materials is one of the important ways to improve its suitability as a negative electrode material for lithium-ion batteries. Existing technologies have conducted extensive research on the preparation of hard carbon materials, making them more suitable for application in the battery field. For example, Chinese patent application publication number CN115332538A, filed on October 22, 2022, entitled "Hard Carbon Material and its Preparation Method, Electrochemical Device and Electronic Device," discloses a hard carbon material comprising a porous framework and at least one first element and zinc element located within the porous framework. The first element includes one or more of nitrogen, sulfur, boron, phosphorus, and selenium. The 002 peak, with a 2x diffraction peak around 21°, indicates that the hard carbon material has a large interplanar spacing, which is beneficial for lithium-ion transport between layers. When applied to electrochemical devices, this hard carbon material can significantly improve the energy density of the electrochemical device. The capacity of new energy batteries is a crucial indicator affecting their development. As a negative electrode material for sodium-ion batteries, the larger the 002 interplanar spacing of hard carbon materials, the higher the capacity of the sodium-ion battery. Therefore, how to measure the 002 interplanar spacing of hard carbon materials to guide the selection of negative electrode materials for sodium-ion batteries is a problem that needs to be solved.

[0003] In 1912, British physicists the Bragg family discovered the diffraction phenomenon caused by the interaction of monochromatic X-rays with crystals through experiments. Using this principle, they invented a method for determining the lattice constant (interplanar spacing) *d*, which can also be used to determine the wavelength *λ* of X-rays. The interplanar spacing and the wavelength of X-rays are roughly on the same order of magnitude. When a beam of monochromatic X-rays is irradiated into a crystal at a certain angle θ, interference occurs when the path difference between the X-rays and the light is an integer multiple of the wavelength *λ*: 2dsinθ = nλ, which is the famous Bragg formula. The derivation of the Bragg formula has certain conditions. To highlight the main challenge, reasonable simplifications were made: the sample crystal is pure, without impurity phase mosaicking, and without lattice distortion. The thermal vibrations of atoms at the lattice points are very small, meaning the lattice points can be considered stationary. In summary, there is currently no sufficiently accurate method to quantify the interplanar spacing of hard carbon material 002, therefore, solving the problem of finding a method for measuring the interplanar spacing of hard carbon material 002 is urgently needed. Summary of the Invention

[0004] 1. The technical problem the invention aims to solve.

[0005] To address the technical problems in the existing technology of inconsistent standards for measuring the interplanar spacing of hard carbon material 002, inaccurate measurement of the interplanar spacing of hard carbon material 002, and poor repeatability of test data, which hinders the research on the preparation of hard carbon materials in the field of power batteries, this application provides a method for measuring the interplanar spacing of hard carbon material 002. The method has high accuracy and good repeatability, providing a favorable guarantee for guiding the development and application of power battery materials.

[0006] 2. Technical Solution

[0007] To achieve the above objectives, the provided technical solution is as follows:

[0008] The present invention provides a method for determining the interplanar spacing of hard carbon material 002, comprising the following steps:

[0009] The 2θ peak angle of the X-ray diffractometer was calibrated using silicon powder; the peak angle of the 111 crystal plane of the silicon powder was 28.442°.

[0010] The test was performed using a mixture of hard carbon material and silicon powder, wherein the mass ratio of hard carbon material to silicon powder was 95:5 to 99:1; the 002 interplanar spacing of the hard carbon material was obtained.

[0011] Furthermore, the mass ratio of the hard carbon material to the silicon powder is 98:2.

[0012] Furthermore, the purity of the silicon powder is ≥99.99%.

[0013] Furthermore, it also includes the following steps:

[0014] The step of grinding and mixing the hard carbon material and silicon powder using a mortar and pestle to obtain the mixed powder; the particle size of the mixed powder is 10~40 μm.

[0015] Grinding samples is usually performed to reduce the influence of the "preferred orientation" of large-particle samples. However, grinding carries the risk of causing crystal form transformation (pressure crystallization) and reduced crystallinity, which can lead to varying degrees of "peak loss" or "peak intensity" changes.

[0016] Preferably, the mortar is an agate mortar.

[0017] Furthermore, the O02 interplanar spacing of the hard carbon material is calculated using Bragg's formula 2dsinθ002=nλ;

[0018] The peak angle of the 111 crystal plane of the silicon powder is θsi, the peak angle of the 002 crystal plane of the hard carbon material is θhard carbon material, and the actual peak angle of the hard carbon material is θ002 = 28.442° - θhard carbon material + θsi.

[0019] Further, three parallel test samples of the silicon powder mixture are prepared; the 002 interplanar spacing is the average value of the 002 interplanar spacing of the parallel test samples.

[0020] Furthermore, the weighing error of the parallel test samples is ≤0.001 g.

[0021] Furthermore, the glass slide used in the measurement was a glass slide, and the length, width and height of the sample preparation groove were 20×20×0.5 mm, respectively.

[0022] Furthermore, the measured parameters were: 2θ range of 10~35°, step size of 0.01°, and scanning speed of 5° / min.

[0023] Furthermore, the X-ray diffractometer is a Rigaku SmartLab 3Kw; the analysis software used is PDXL.

[0024] Preferably, the 2θ angle measurement range is -3 to 160°, the scanning speed is 0.02 to 100° / min, and the step size is 0.0001 to 12°. The measurement parameters are set to obtain complete and good peak shapes for hard carbon materials and silicon powder, and can be adjusted according to different instrument models.

[0025] 3. Beneficial effects

[0026] Compared with existing known technologies, the technical solution provided by this invention has the following beneficial effects:

[0027] The method for determining the 002 interplanar spacing of hard carbon material of the present invention includes a step of calibrating the 2θ peak angle of an X-ray diffractometer using silicon powder. The peak angle of the 111 crystal plane of silicon powder is 28.442°. A mixed powder of hard carbon material and silicon powder is used for detection, with a mass ratio of hard carbon material to silicon powder of 95:5 to 99:1. The obtained diffraction peaks have complete shapes, which is more conducive to the analysis software reading the peak angle of the diffuse scattering peak of hard carbon. Furthermore, by calibrating the angle of the standard sample, the peak angle of the 002 crystal plane of the hard carbon material can be obtained more accurately, making the obtained 002 interplanar spacing more precise. This provides a favorable guarantee for guiding the development and application of power battery materials and has an important impact on improving the capacity of sodium-ion batteries. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the process for determining the interplanar spacing of hard carbon material 002 in Example 1.

[0029] Figure 2 The graph shows the measured parameters of the hard carbon material in Example 1.

[0030] Figure 3 This is one of the parallel samples for analyzing the 002 interplanar spacing data of the hard carbon material in Example 1.

[0031] Figure 4 This is the second parallel sample for analyzing the 002 interplanar spacing data of the hard carbon material in Example 1.

[0032] Figure 5 The third figure is a parallel sample of the 002 interplanar spacing data analysis of the hard carbon material in Example 1.

[0033] Figure 6 This is a comparison graph showing the repeatability of the determination methods for the examples and comparative examples. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments.

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] The method for determining the interplanar spacing of hard carbon material 002 in this embodiment includes the following specific steps:

[0038] (1) Turn on the X-ray diffractometer and replace the optical path calibration accessories to perform optical path calibration.

[0039] (2) Use silicon powder with a peak angle of 28.442° on the 111 crystal plane to calibrate the 2θ peak angle of the X-ray diffractometer.

[0040] (3) Weigh the hard carbon material and silicon powder using an analytical balance at a ratio of 95:5 to 99:1. The purity of the silicon powder is ≥99.99%. The ratio used in this embodiment is 98:2.

[0041] (4) Use an agate mortar to grind and mix the hard carbon material and silicon powder to make the particle size 10~40 μm. The particle size used in this embodiment is 25 μm.

[0042] (5) Three parallel samples of a mixture of hard carbon material and silicon powder were prepared using XRD-specific glass slides.

[0043] (6) Using the testing software, set the test parameters 2θ range to 10~35°, step size to 0.01°, and scanning speed to 5° / min to obtain data for three parallel samples of hard carbon and silicon powder mixture.

[0044] (7) Using XRD analysis software to process the data of three parallel samples, the peak angles θ1, θ2, θ3 (i.e. θsi) of the 111 crystal plane of silicon powder and the peak angles θ4, θ5, θ6 (i.e. θ hard carbon material) of the 002 crystal plane of hard carbon material were obtained.

[0045] (8) The actual peak angles of hard carbon, θ7, θ8, and θ9 (i.e. θ002), were obtained by using the actual peak angles of the 111 crystal plane of Si, 28.442°-θ4+θ1, 28.442°-θ5+θ2, and 28.442°-θ6+θ3, respectively.

[0046] (9) Calculate the interplanar spacings D1, D2, and D3 of hard carbon according to the Bragg formula 2dsinθ=nλ.

[0047] (10) Calculate the average value D4 of D1, D2 and D3. D4 is the interplanar spacing of the D002 crystal plane of hard carbon material.

[0048] The interplanar spacing of the hard carbon material 002 measured in this embodiment is shown in Table 1. A total of 10 measurements were taken.

[0049] Table 1 Summary of interplanar spacing data of hard carbon material 002 measured in Example 1

[0050]

[0051] This method utilizes a 98:2 ratio to mix silicon powder with a purity of 99.99% or higher with hard carbon, stirring until homogeneous. XRD patterns of the mixture within the range of 10° to 35° are then obtained using parameters of 0.01° step size and 5° / min scan rate. This ratio and parameters ensure complete peak shape data for the 111 peak of silicon powder and the 002 peak of hard carbon, and facilitate the acquisition of the peak angle of the amorphous 002 peak of hard carbon. The accurate peak angle of the 002 crystal plane of hard carbon is calibrated using the theoretical and actual peak angles of the 111 crystal plane of silicon powder. Three parallel samples are measured three times, and the interplanar spacings D1, D2, and D3 of the 002 peak of hard carbon are calculated using the Bragg formula 2dsinθ=nλ. The average value D4 is taken as the interplanar spacing of the 002 crystal plane of the hard carbon material, yielding ideal results.

[0052] Example 2

[0053] The method for determining the interplanar spacing of the hard carbon material 002 in this embodiment is basically the same as in Example 1, except that the ratio of hard carbon material to silicon powder is 99:1 in this embodiment. The specific steps are as follows:

[0054] (1) Turn on the X-ray diffractometer and replace the optical path calibration accessories to perform optical path calibration.

[0055] (2) Use silicon powder with a peak angle of 28.442° on the 111 crystal plane to calibrate the 2θ peak angle of the X-ray diffractometer.

[0056] (3) Weigh the hard carbon material and silicon powder using an analytical balance at a ratio of 95:5 to 99:1. The ratio used in this embodiment is 99:1.

[0057] (4) Use an agate mortar to grind and mix the hard carbon material and silicon powder to make the particle size 10~40 μm. The particle size used in this embodiment is 25 μm.

[0058] (5) Three parallel samples of a mixture of hard carbon material and silicon powder were prepared using XRD-specific glass slides.

[0059] (6) Using the testing software, set the test parameters 2θ range to 10~35°, step size to 0.01°, and scanning speed to 5° / min to obtain data for three parallel samples of hard carbon and silicon powder mixture.

[0060] (7) Using XRD analysis software to process the data of three parallel samples, the peak angles θ1, θ2, θ3 (i.e. θsi) of the 111 crystal plane of silicon powder and the peak angles θ4, θ5, θ6 (i.e. θ hard carbon material) of the 002 crystal plane of hard carbon material were obtained.

[0061] (8) The actual peak angles of hard carbon, θ7, θ8, and θ9 (i.e. θ002), were obtained by using the actual peak angles of the 111 crystal plane of Si, 28.442°-θ4+θ1, 28.442°-θ5+θ2, and 28.442°-θ6+θ3, respectively.

[0062] (9) Calculate the interplanar spacings D1, D2, and D3 of hard carbon according to the Bragg formula 2dsinθ=nλ.

[0063] (10) Calculate the average value D4 of D1, D2 and D3. D4 is the interplanar spacing of the D002 crystal plane of hard carbon material.

[0064] The interplanar spacing of the hard carbon material 002 measured in this embodiment is shown in Table 2. A total of 10 measurements were performed.

[0065] Table 2 Summary of interplanar spacing data of hard carbon material 002 measured in Example 2

[0066]

[0067] Example 3

[0068] The method for determining the interplanar spacing of the hard carbon material 002 in this comparative example is basically the same as in Example 1, except that the ratio of hard carbon material to silicon powder is 95:5 in this example. The specific steps are as follows:

[0069] (1) Turn on the X-ray diffractometer and replace the optical path calibration accessories to perform optical path calibration.

[0070] (2) Use silicon powder with a peak angle of 28.442° on the 111 crystal plane to calibrate the 2θ peak angle of the X-ray diffractometer.

[0071] (3) Weigh the hard carbon material and silicon powder using an analytical balance at a ratio of 95:5.

[0072] (4) Use an agate mortar to grind and mix the hard carbon material and silicon powder to make the particle size 10~40 μm. The particle size used in this embodiment is 25 μm.

[0073] (5) Three parallel samples of a mixture of hard carbon material and silicon powder were prepared using XRD-specific glass slides.

[0074] (6) Using the testing software, set the test parameters 2θ range to 10~35°, step size to 0.01°, and scanning speed to 5° / min to obtain data for three parallel samples of hard carbon and silicon powder mixture.

[0075] (7) Using XRD analysis software to process the data of three parallel samples, the peak angles θ1, θ2, θ3 (i.e. θsi) of the 111 crystal plane of silicon powder and the peak angles θ4, θ5, θ6 (i.e. θ hard carbon material) of the 002 crystal plane of hard carbon material were obtained.

[0076] (8) The actual peak angles of hard carbon, θ7, θ8, and θ9 (i.e. θ002), were obtained by using the actual peak angles of the 111 crystal plane of Si, 28.442°-θ4+θ1, 28.442°-θ5+θ2, and 28.442°-θ6+θ3, respectively.

[0077] (9) Calculate the interplanar spacings D1, D2, and D3 of hard carbon according to the Bragg formula 2dsinθ=nλ.

[0078] (10) Calculate the average value D4 of D1, D2 and D3. D4 is the interplanar spacing of the D002 crystal plane of hard carbon material.

[0079] The interplanar spacing of the hard carbon material 002 measured in this embodiment is shown in Table 3. A total of 10 measurements were taken.

[0080] Table 3 Summary of interplanar spacing data of hard carbon material 002 measured in Example 3

[0081]

[0082] Comparative Example 1

[0083] The method for determining the interplanar spacing of the hard carbon material 002 in this comparative example is basically the same as in Example 1, except that the ratio of hard carbon material to silicon powder is 94:6 in this example. The specific steps are as follows:

[0084] Table 4 Summary of interplanar spacing data of hard carbon material 002 measured in Comparative Example 1

[0085]

[0086] (1) Turn on the X-ray diffractometer and replace the optical path calibration accessories to perform optical path calibration.

[0087] (2) Use silicon powder with a peak angle of 28.442° on the 111 crystal plane to calibrate the 2θ peak angle of the X-ray diffractometer.

[0088] (3) Weigh the hard carbon material and silicon powder using an analytical balance at a ratio of 94:6, wherein the purity of the silicon powder is ≥99.99%.

[0089] (4) Use an agate mortar to grind and mix the hard carbon material and silicon powder to make the particle size 10~40 μm. The particle size used in this embodiment is 25 μm.

[0090] (5) Three parallel samples of a mixture of hard carbon material and silicon powder were prepared using XRD-specific glass slides.

[0091] (6) Using the testing software, set the test parameters 2θ range to 10~35°, step size to 0.01°, and scanning speed to 5° / min to obtain data for three parallel samples of hard carbon and silicon powder mixture.

[0092] (7) Using XRD analysis software to process the data of three parallel samples, the peak angles θ1, θ2, θ3 (i.e. θsi) of the 111 crystal plane of silicon powder and the peak angles θ4, θ5, θ6 (i.e. θ hard carbon material) of the 002 crystal plane of hard carbon material were obtained.

[0093] (8) The actual peak angles of hard carbon, θ7, θ8, and θ9 (i.e. θ002), were obtained by using the actual peak angles of the 111 crystal plane of Si, 28.442°-θ4+θ1, 28.442°-θ5+θ2, and 28.442°-θ6+θ3, respectively.

[0094] (9) Calculate the interplanar spacings D1, D2, and D3 of hard carbon according to the Bragg formula 2dsinθ=nλ.

[0095] (10) Calculate the average value D4 of D1, D2 and D3. D4 is the interplanar spacing of the D002 crystal plane of hard carbon material.

[0096] The interplanar spacing of the hard carbon material 002 measured in this embodiment is shown in Table 1. A total of 10 measurements were taken.

[0097] The repeatability of the data obtained in Examples 1-3 is as follows: Figure 6 As shown, by Figure 6 It can be seen that the method used in the example test has better repeatability and the results obtained are more consistent with actual results.

Claims

1. A method for determining the interplanar spacing of hard carbon material 002, characterized in that: Includes the following steps: The 2θ peak angle of the X-ray diffractometer was calibrated using silicon powder; the peak angle of the 111 crystal plane of the silicon powder was 28.442°. The test was performed using a mixture of hard carbon material and silicon powder, wherein the mass ratio of hard carbon material to silicon powder was 95:5 to 99:

1. The actual peak angle of the 111 crystal plane of the silicon powder is θsi, and the peak angle of the 002 crystal plane of the hard carbon material is θhard carbon material. The actual peak angle of the 002 crystal plane of the hard carbon material is θ002 = 28.442° - θhard carbon material + θsi. The O02 interplanar spacing of the hard carbon material was calculated using Bragg's formula 2dsinθ002=nλ. The 002 interplanar spacing of the hard carbon material was obtained.

2. The method for determining the interplanar spacing of hard carbon material 002 according to claim 1, characterized in that: The mass ratio of the hard carbon material to the silicon powder is 98:

2.

3. The method for determining the interplanar spacing of hard carbon material 002 according to claim 2, characterized in that: The purity of the silicon powder is ≥99.99%.

4. The method for determining the interplanar spacing of hard carbon material 002 according to claim 3, characterized in that: It also includes the following steps: The step of grinding and mixing the hard carbon material and silicon powder using a mortar and pestle to obtain the mixed powder; the particle size of the mixed powder is 10~40 μm.

5. The method for determining the interplanar spacing of hard carbon material 002 according to claim 4, characterized in that: Three parallel test samples of the silicon powder mixture were prepared; the 002 interplanar spacing was the average value of the 002 interplanar spacing of the parallel test samples.

6. The method for determining the interplanar spacing of hard carbon material 002 according to claim 5, characterized in that: The weighing error of the parallel test samples is ≤0.001 g.

7. The method for determining the interplanar spacing of hard carbon material 002 according to claim 6, characterized in that: The glass slides used in the measurement were glass slides, and the length, width and height of the sample preparation groove were 20×20×0.5 mm.

8. The method for determining the interplanar spacing of hard carbon material 002 according to claim 7, characterized in that: The parameters measured were: 2θ range of 10~35°, step size of 0.01°, and scanning speed of 5° / min.

9. A method for determining the interplanar spacing of hard carbon material 002 according to any one of claims 1-8, characterized in that: The X-ray diffractometer used was a Rigaku SmartLab 3Kw; the analysis software used was PDXL.

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