Method for rapidly detecting excessive deposited silicon in porous matrix on line

Abstract

The embodiment of the invention relates to a method for rapidly detecting excessive deposited silicon in a porous substrate on line. The method comprises the following steps: weighing a certain amount of porous matrix material, and measuring the powder resistance of the porous matrix material to obtain the resistivity rho 1; depositing silicon on the porous matrix material, weighing the porous matrix material with deposited silicon, and measuring powder resistance to obtain resistivity rho2; and determining whether the deposited silicon in the porous matrix is excessive or not according to the ratio of the resistivity rho2 to the resistivity rho1.

Description

Technical Field

[0001] The present invention relates to the technical field of material detection, and in particular, to a method for on-line rapid detection of excessive deposited silicon in a porous matrix. Background Art

[0002] In order to pursue lithium-ion power battery anode materials whose specific capacity, cycle performance, rate performance, etc. can basically meet the application requirements, silicon-carbon composite materials with various different structures have been designed and innovated. At present, porous materials with silicon deposited in pores are the focus of research. However, whether the deposition of silicon on the porous matrix is excessive affects the electrochemical performance of the material. Detecting whether the deposited silicon in the porous matrix is excessive is of great significance for evaluating whether the material is successfully prepared.

[0003] Currently, the commonly used detection methods include the following several kinds:

[0004] Chemical analysis method: Separate silicon from the matrix through a chemical reaction, and then measure the content of silicon by means such as titration or spectrophotometry. Although this method has high precision, it requires the use of chemical reagents, the operation is relatively cumbersome, and it will have a certain impact on the environment.

[0005] X-ray diffraction method: By measuring the intensity and angle of the X-ray diffraction peak of silicon in the matrix, the content of silicon can be deduced. This method has high precision and sensitivity, but it requires equipment such as an X-ray diffractometer, with high cost and certain operation difficulties.

[0006] Scanning electron microscope (SEM) method: By observing the morphology and composition distribution of the matrix surface, it can be preliminarily judged whether the content of silicon is excessive. This method is easy to operate, but can only provide qualitative results.

[0007] Raman spectroscopy method: By measuring the Raman spectrum of silicon in the matrix, the content of silicon can be determined. This method has high precision and sensitivity, but it requires equipment such as a Raman spectrometer, with high cost and certain operation difficulties.

[0008] Each of the above detection methods has its own advantages and disadvantages, but all have unsatisfactory drawbacks. At present, a detection method with good instantaneity, low cost, simple operation, and accurate measurement precision is needed. Summary of the Invention

[0009] The purpose of the present invention is to provide a method for on-line rapid detection of excessive deposited silicon in a porous matrix. The test process is simple and convenient, and the test results have good accuracy and reproducibility.

[0010] For this reason, an embodiment of the present invention provides a method for on-line rapid detection of excessive deposited silicon in a porous matrix, including:

[0011] Weigh a quantitative porous matrix material, measure the powder resistance of the porous matrix material, and obtain the resistivity ρ1;

[0012] Deposit silicon on the porous matrix material, weigh the porous matrix material with deposited silicon, measure the powder resistance, and obtain the resistivity ρ2;

[0013] Determine whether the deposited silicon in the porous matrix is excessive according to the ratio of the resistivity ρ2 to the resistivity ρ1.

[0014] Preferably, the method for measuring the powder resistance includes one of the four-probe method, the two-probe method, or the bridge method.

[0015] Preferably, the quantification is 0.5 - 2.5 g.

[0016] Preferably, the determination of whether the deposited silicon in the porous matrix is excessive according to the ratio of the resistivity ρ2 to the resistivity ρ1 specifically includes:

[0017] When the ratio of the resistivity ρ2 to the resistivity ρ1 is greater than the set value, the deposited silicon in the porous matrix is excessive;

[0018] When the ratio of the resistivity ρ2 to the resistivity ρ1 is not greater than the set value, the deposited silicon in the porous matrix is not excessive.

[0019] Preferably, the set value is 5.

[0020] Preferably, the method for measuring the powder resistance is specifically: under a certain pressure, detect the voltage on both sides of the sample by applying an excitation current to the material to be measured, obtain the overall resistance, and then convert the resistivity of the sample through the formed size of the sample.

[0021] Preferably, the certain pressure is 10 - 200 MPa.

[0022] Preferably, the certain pressure is 20 MPa.

[0023] Preferably, the porous matrix material is specifically a porous carbon matrix.

[0024] The method for on-line rapid detection of excessive deposited silicon in a porous matrix provided by the embodiments of the present invention has a simple and convenient test process and has good accuracy and reproducibility for test results. Description of the Drawings

[0025] Figure 1 It is a flowchart of the method for on-line rapid detection of excessive deposited silicon in a porous matrix provided by the embodiments of the present invention. Detailed Embodiments

[0026] The technical solutions of the present invention will be further described in detail below with reference to the drawings and embodiments.

[0027] An embodiment of the present invention provides a method for quickly and online detecting excessive deposited silicon in a porous matrix, which is used for quickly and online detecting whether the content of deposited silicon in the porous matrix is excessive. The main steps are as Figure 1 shown:

[0028] Step 110: Weigh a quantitative porous matrix material, measure the powder resistance of the porous matrix material, and obtain the resistivity ρ1;

[0029] Specifically, the method for measuring the powder resistance may include: one of the four-probe method, the two-probe method, or the bridge method.

[0030] Preferably, the two-probe method is adopted: under 10 - 200 MPa, by applying an excitation current to the material to be measured to detect the voltage on both the upper and lower sides of the sample, the overall resistance is obtained, and then the resistivity of the sample is obtained through conversion based on the formed size of the sample. Preferably, a pressure of 20 MPa is used for detection.

[0031] The quantitative material for measurement is 0.5 - 2.5 g, which is a small-sized powder sample.

[0032] The porous matrix material is specifically a porous carbon matrix.

[0033] Step 120: Deposit silicon on the porous matrix material, weigh the porous matrix material with deposited silicon, measure the powder resistance, and obtain the resistivity ρ2;

[0034] The measurement method is the same as above.

[0035] This step process can be carried out during the production and preparation process to achieve quick and online detection.

[0036] Step 130: Determine whether the deposited silicon in the porous matrix is excessive according to the ratio of the resistivity ρ2 to the resistivity ρ1.

[0037] When the ratio of the resistivity ρ2 to the resistivity ρ1 is greater than the set value, the deposited silicon in the porous matrix is excessive; when the ratio of the resistivity ρ2 to the resistivity ρ1 is not greater than the set value, the deposited silicon in the porous matrix is not excessive. Preferably, the set value is 5, that is, when ρ2 > 5ρ1, the deposited silicon in the porous matrix is excessive.

[0038] The original network structure of the porous carbon material itself has a low resistivity. After depositing silicon in and on the surface of the porous matrix, it will cause an increase in resistivity.

[0039] Appropriate deposition of silicon in the porous matrix used as the anode material of the battery can improve the material in terms of electrical properties, thermal properties, permeability, and mechanical properties. For example, appropriate deposition of silicon in the porous matrix can increase the hardness and strength of the porous matrix, improve its load-bearing capacity and wear resistance, while the porous structure can effectively disperse and absorb external stress, reduce stress concentration inside the material, and thus improve the overall performance of the material. The porous matrix deposited with silicon has good thermal conductivity and thermal stability, which can effectively improve the thermal performance of the material, making the material have good stability and durability in high-temperature environments.

[0040] However, if an excessive amount of silicon is deposited in the porous matrix, it will have the following effects on the battery performance:

[0041] Reduce the battery capacity: Since the deposition of silicon will occupy the proportion of the active material, resulting in a decrease in the active material, thus reducing the battery capacity;

[0042] Increase the internal resistance of the battery: The deposition of silicon will increase the internal resistance of the battery, making the charge-discharge performance of the battery worse and affecting the cycle life of the battery;

[0043] Reduce the stability of the battery: The deposition of excessive silicon will damage the structure of the battery, and the volume expansion effect is obvious, making the stability of the battery worse.

[0044] Therefore, it is necessary to control the appropriate deposition of silicon in the porous matrix to bring its advantages into play.

[0045] Through the method provided by the present invention, it is possible to quickly and simply detect whether the deposition of silicon in the porous matrix is excessive, and the accuracy and repeatability of the test results are very high.

[0046] In order to more clearly illustrate the purpose and advantages of the present invention, the present invention will be further elaborated below in conjunction with embodiments. In addition, the embodiments described in the present invention are only partial embodiments. All other embodiments obtained by those skilled in the art without creative efforts based on the embodiments described in the present invention belong to the protection scope of the present invention. Additionally, it should be understood that these embodiments are only for more detailed illustration and should not be construed as limiting the present invention in any form, that is, it is not intended to limit the protection scope of the present invention.

[0047] Example 1

[0048] Weigh 2 g of the porous carbon matrix and obtain the resistivity ρ1 through powder resistance; after depositing silicon on the porous matrix, weigh 2.2 g of the sample and measure the powder resistance to obtain the resistivity ρ2.

[0049] The specific measurement method is as follows:

[0050] Excitation current: 10 mA, probe spacing for applying the excitation current: 1 cm, sample size: 2 cm in length, 0.5 cm in width, 1.5 cm in thickness; voltage detection probe spacing on the upper and lower sides: 0.5 cm.

[0051] Place the powder sample to be tested in a pressure device of 20 MPa and keep the sample under a constant pressure. Apply an excitation current to the sample and measure the excitation current and the voltages on the upper and lower sides. Repeat the experiment, change the pressure value, and record the excitation current and the voltages on the upper and lower sides at each pressure. Overall resistance of the sample = (voltage on the upper side - voltage on the lower side) / excitation current; Resistivity = (4πkL) / (overall resistance × sample length × sample width × sample thickness), where k is a constant and L is the probe spacing.

[0052] The resistivity obtained from the test is recorded in Table 1.

[0053] Comparative Example 1

[0054] In this comparative example, all steps are the same as those in Example 1, and the only difference is that the deposition time for carbon deposition on the porous carbon matrix is 3 times that of Example 1. The specific test values are recorded in Table 1.

[0055] Use the materials prepared in Example 1 and Comparative Example 1 above as the anode material, weigh them according to a mass ratio of 92%: 2%: 3%: 3% with conductive carbon black, sodium carboxymethyl cellulose, and styrene-butadiene rubber, and uniformly mix them in an aqueous solvent using a beater. Coat the battery slurry on copper foil, dry it, and cut it into pieces to obtain the anode; Assemble a 1 Ah soft-pack battery with lithium cobaltate as the cathode. Specifically, use lithium cobaltate cathode material as the cathode active material, mix it with a conductive agent Super P and a binder polyvinylidene fluoride (PVDF) in a mass ratio of 90: 5: 5 to obtain the cathode slurry. Use an automatic coater to coat the cathode slurry on the current collector aluminum foil with a coating thickness of 100 μm, and obtain the cathode plate after drying. Stack and assemble the cathode case, cathode plate, separator, electrolyte, anode, gasket, spring piece, and anode case in sequence to obtain the battery. Among them, the separator uses a polypropylene (PP) base film, and the electrolyte uses a conventional lithium-ion electrolyte 1 mol L i PF6 @ ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) = 1: 1: 1. After assembly, cycle at 0.5C for 20 weeks and test the charging efficiency at 0 - 2V. The test results are recorded in Table 1.

[0056]

[0057] Table 1

[0058] As can be seen from Table 1, the powder resistance method provided by the present invention can quickly, effectively, and accurately detect whether the deposited silicon in the porous matrix is excessive.

[0059] Example 2

[0060] Weigh 2 g of the porous carbon matrix, measure the powder resistance in the same manner as in Example 1, and obtain a resistivity ρ1 = 1.31 Ω / cm. After depositing silicon in the same method as in Example 1, weigh 3 different groups of 2 g samples respectively, measure the powder resistance, and obtain resistivity ρ2 respectively. The specific values are recorded in Table 2 below.

[0061]

[0062] Table 2

[0063] It can be seen from Table 2 that the test results of the powder resistance method of the present invention have good reproducibility.

[0064] The detection of whether the silicon deposition in the porous matrix proposed by the present invention is excessive has good accuracy and reproducibility for the test results, improves the test efficiency, and is of great significance for improving the R & D efficiency and on-line rapid detection.

[0065] The specific embodiments described above further elaborate on the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An online rapid method for detecting excessive deposited silicon in a porous matrix, characterized in that, The method includes: Weigh a quantitative porous matrix material, measure the powder resistance of the porous matrix material, and obtain the resistivity ρ1; Deposit silicon on the porous matrix material, weigh the porous matrix material with deposited silicon, measure the powder resistance, and obtain the resistivity ρ2; Determine whether the deposited silicon in the porous matrix is excessive according to the ratio of the resistivity ρ2 to the resistivity ρ1.

2. The method according to claim 1, wherein The method for measuring the powder resistance includes one of the four-probe method, the two-probe method, or the bridge method.

3. The method according to claim 1, characterized in that, The quantification is 0.5 - 2.5 g.

4. The method according to claim 1, wherein The determination of whether the deposited silicon in the porous matrix is excessive according to the ratio of the resistivity ρ2 to the resistivity ρ1 specifically includes: When the ratio of the resistivity ρ2 to the resistivity ρ1 is greater than the set value, the deposited silicon in the porous matrix is excessive; When the ratio of the resistivity ρ2 to the resistivity ρ1 is not greater than the set value, the deposited silicon in the porous matrix is not excessive.

5. The method according to claim 1, characterized in that The set value is 5.

6. The method according to claim 1, characterized in that, The method for measuring the powder resistance is specifically: under a certain pressure, detect the voltages on the upper and lower sides of the sample by applying an excitation current to the material to be measured, obtain the overall resistance, and then convert the resistivity of the sample through the formed size of the sample.

7. The method according to claim 6, characterized in that, The certain pressure is 10 - 200 MPa.

8. The method according to claim 7, characterized in that, The certain pressure is 20 MPa.

9. The method according to claim 1, wherein The porous matrix material is specifically a porous carbon matrix.

Images