Method for rapidly detecting modification degree of lithium-rich lithium-iron phosphate

Abstract

The application provides a method for rapidly detecting the modification degree of lithium-rich lithium iron phosphate, and belongs to the technical field of lithium-rich lithium iron phosphate detection. The method creatively introduces a Raman test method into the lithium ion battery lithium supplementing / pre-lithiation field for the first time, and introduces the method into the detection of the modification degree of lithium-rich lithium iron phosphate, which has an important promoting effect on the detection of the modification degree of lithium-rich lithium iron phosphate and the detection of the air stability of lithium-rich lithium iron phosphate. The method is simple to operate, has high measurement precision, can assist in guiding the improvement of the stability of lithium-rich lithium iron phosphate, can reflect the modification condition of lithium-rich lithium iron phosphate in real time, fast and accurately, and the sample can be directly detected without treatment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium-rich lithium iron phosphate detection, and particularly relates to a method for rapidly detecting the metamorphic degree of lithium-rich lithium iron phosphate. BACKGROUND

[0002] Due to the rapid development of electric vehicles and electronic devices, the demand for high-energy-density lithium ion batteries is increasing. As one of the important measures to improve the energy density of batteries, lithium ion battery lithium supplement technology urgently needs to develop commercially available lithium supplement technology to compensate for the irreversible capacity loss during the initial and cycling processes. As a commercially available lithium supplement material, lithium-rich lithium iron phosphate represents a major advance in the field of lithium ion battery lithium supplement / pre-lithiation. Therefore, the research on the rapid and accurate detection method of lithium-rich lithium iron phosphate is of great significance for monitoring the purity of the material and formulating relevant industry standards.

[0003] Due to the poor air stability and easy metamorphism of lithium-rich lithium iron phosphate, the detection method of lithium-rich lithium iron phosphate material in the current research is usually X-ray diffraction technology (XRD), but when using this method for related detection, a large amount of sample is required, and the detection time is long. The material may have metamorphosed during the detection period, the operation is complex, and it is not suitable for the stability research of lithium-rich lithium iron phosphate material. Therefore, there is no unified and authoritative method and standard for the detection of lithium-rich lithium iron phosphate. Therefore, it is particularly important to provide a simple, rapid and sensitive method for detecting whether the lithium-rich lithium iron phosphate, a lithium supplement material for lithium ion batteries, is metamorphosed. SUMMARY

[0004] The application provides a method for rapidly detecting the metamorphic degree of lithium-rich lithium iron phosphate. The method creatively introduces the Raman test method into the detection of the metamorphic degree of lithium-rich lithium iron phosphate for the first time, and has simple detection operation, high measurement accuracy and direct sample detection without the need for processing.

[0005] In order to achieve the above purpose, the application provides a method for rapidly detecting the metamorphic degree of lithium-rich lithium iron phosphate. The positive electrode lithium supplement active material lithium-rich lithium iron phosphate Li5FeO4 is exposed to air for different times, and a laser Raman spectrometer is used for rapid detection. The metamorphic condition of lithium-rich lithium iron phosphate is obtained according to the peak position and peak strength of the Raman spectrum.

[0006] As a preferred, it specifically includes the following steps:

[0007] a. crushing the positive electrode lithium supplement active material lithium-rich lithium iron phosphate Li5FeO4 in a dry and stable environment;

[0008] b. crushing the impurity standard in the same environment as the lithium-rich lithium iron phosphate;

[0009] c. The crushed lithium-rich lithium-iron material is exposed to ambient air with a humidity of 10-30% for different time periods to perform air stability experiments, and then is placed on a glass slide with the crushed impurity standard, flattened, and placed in a laser Raman spectrometer to perform Raman testing, thereby obtaining the degree of metamorphism of the lithium-rich lithium-iron material.

[0010] Preferably, the crushing environment of the material is a glove box with a protective atmosphere of N2 / Ar or a dry room with a dew point of less than -30°.

[0011] The crushing method of the material is selected from any one of airflow crushing, ball milling, vacuum ball milling, mortar grinding, and mechanical crushing by a crusher.

[0012] Preferably, the impurity standard is lithium carbonate Li2CO3 and lithium hydroxide LiOH with a purity of analytical pure or above.

[0013] Preferably, the crushed lithium-rich lithium-iron material is exposed to ambient air for 0 hours, 2 hours, and 4 hours.

[0014] Preferably, the Raman testing specifically includes:

[0015] Raman testing is performed on lithium hydroxide, lithium carbonate, and lithium-rich lithium-iron material exposed to ambient air for 0 hours to obtain a standard curve.

[0016] Raman testing is performed on lithium-rich lithium-iron material exposed to ambient air for 2 hours and 4 hours, respectively, to obtain a test curve.

[0017] By analyzing the peak position and peak intensity of the Raman spectra of the standard curve and the test curve, the degree of metamorphism of the lithium-rich lithium-iron material is obtained.

[0018] Preferably, the Raman spectrum wave number range used in the Raman testing is 50 to 4000 cm -1 .

[0019] Preferably, the area of the face scan in the Raman testing is selected from any one of 3 μm*3 μm, 6 μm*6 μm, and 9 μm*9 μm; the number of points per row of the face scan is selected from any one of 10, 20, and 30; the number of rows of the face scan is selected from any one of 20 rows, 10 rows, and 30 rows; each sampling point is integrated for 3-40 times, and the integration time is 3-40 seconds.

[0020] Preferably, the area of the face scan in the Raman testing is 9 μm*9 μm, the number of points per row of the face scan is 30, the number of rows of the face scan is 30, each sampling point is integrated for 20 times, and the integration time is 20 seconds.

[0021] The application also provides a method for rapidly detecting the modification degree of lithium-rich lithium iron phosphate.

[0022] Compared with the prior art, the application has the advantages and positive effects that:

[0023] 1. The application creatively introduces the Raman test method into the lithium ion battery lithium supplementing / pre-lithiation field for the first time, and introduces the detection of the modification degree of lithium-rich lithium iron phosphate, which has an important promoting effect on the detection of the modification degree of lithium-rich lithium iron phosphate and the detection of the air stability of lithium-rich lithium iron phosphate.

[0024] 2. Compared with the existing detection method (such as XRD), the detection method provided by the application has the advantages of simple operation, less steps, less time and material consumption, and high measurement precision, and can assist in guiding the research on improving the stability of lithium-rich lithium iron phosphate, and can reflect the modification of lithium-rich lithium iron phosphate in real time, quickly and accurately.

[0025] 3. The method provided by the application has universality, and the sample can be directly detected without processing and can be batch detected. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The Raman spectrum of lithium-rich lithium iron phosphate exposed to air for 0 hours provided for the embodiment of the application;

[0027] Figure 2 The Raman spectrum of lithium carbonate Li2CO3 provided for the embodiment of the application;

[0028] Figure 3 The Raman spectrum of lithium hydroxide provided for the embodiment of the application;

[0029] Figure 4 The Raman spectrum of lithium-rich lithium iron phosphate exposed to air for 2 hours provided for the embodiment of the application;

[0030] Figure 5 The Raman spectrum of lithium-rich lithium iron phosphate exposed to air for 4 hours provided for the embodiment of the application;

[0031] Figure 6 The XRD spectrum of lithium-rich lithium iron phosphate exposed to air for 0 hours provided for the comparative example of the application;

[0032] Figure 7 The XRD spectrum of lithium carbonate provided for the comparative example of the application;

[0033] Figure 8 The XRD spectrum of lithium hydroxide provided for the comparative example of the application;

[0034] Figure 9XRD pattern of the lithium-rich lithium-iron oxide exposed to air for 2 hours provided for the comparative example of the present application;

[0035] Figure 10 XRD pattern of the lithium-rich lithium-iron oxide exposed to air for 4 hours provided for the comparative example of the present application. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0037] Embodiment 1

[0038] The lithium-rich lithium-iron oxide Li5FeO4 as the positive electrode lithium supplement active material was mechanically pulverized in a glove box with a protective atmosphere Ar for 30 minutes;

[0039] The impurity standard lithium carbonate Li2CO3 and lithium hydroxide LiOH were also mechanically pulverized in a glove box with a protective atmosphere Ar for 30 minutes;

[0040] The pulverized lithium-rich lithium-iron oxide material was exposed to air for 0 hours for air stability experiment, and then was placed on a glass slide together with the pulverized impurity standard lithium carbonate Li2CO3 and lithium hydroxide LiOH, and was flattened and placed in a Raman spectrometer for Raman test (Raman tests were performed on lithium hydroxide, lithium carbonate and the lithium-rich lithium-iron oxide exposed to air for 0 hours to obtain a standard curve; Raman tests were performed on the lithium-rich lithium-iron oxide materials exposed to air for 2 hours and 4 hours respectively to obtain test curves; the peak position and peak intensity of the Raman spectra of the standard curve and the test curves were analyzed) to obtain the deterioration degree of the lithium-rich lithium-iron oxide.

[0041] The Raman test was performed in a wave number range of 50 to 4000 cm -1 , the area of the area scan was 9 μm*9 μm, the number of points in each row of the area scan was 30, the number of rows of the area scan was 30, and each sampling point was integrated for 20 times with an integration time of 20 seconds. The Raman spectra of the lithium-rich lithium-iron oxide exposed to air for 0 hours, lithium carbonate Li2CO3 and lithium hydroxide are shown in Figures 1-3 .

[0042] Embodiment 2

[0043] The detection was performed according to the same operation as in Embodiment 1, except that the pulverized lithium-rich lithium-iron oxide material was exposed to air for 2 hours for air stability experiment. The Raman spectrum of the lithium-rich lithium-iron oxide exposed to air for 2 hours is shown inFigure 4

[0044] Example 3

[0045] The detection was carried out according to the same operation as in Example 1, except that the crushed lithium-rich lithium-iron-oxide material was exposed to the external air for 4h, to carry out the air stability experiment. The Raman spectrum of the lithium-rich lithium-iron-oxide exposed to the air for 4h is shown in Figure 5

[0046] Comparative Example 1

[0047] The detection of the modification degree of the lithium-rich lithium-iron-oxide was carried out using the traditional X-ray diffraction instrument technology (XRD).

[0048] The positive electrode lithium supplementing active material lithium-rich lithium-iron-oxide Li5FeO4 was mechanically crushed for 30 minutes in a glove box with a protective atmosphere Ar using a crusher;

[0049] The impurity standard lithium carbonate Li2CO3 and lithium hydroxide LiOH were also mechanically crushed for 30 minutes in a glove box with a protective atmosphere Ar using a crusher;

[0050] The crushed lithium-rich lithium-iron-oxide material was exposed to the external air for 0h (not exposed), to carry out the air stability experiment;

[0051] The circulating water was started, the transformer was started, the XRD instrument was started, and the instrument state was gradually increased to high voltage 40kV and current 40mA;

[0052] The sample preparation required a larger amount of sample, about 1-2g or so;

[0053] The fixed experimental parameters were set, the scanning range was 5°-85°, the scanning rate was 2° / min, and it took about 40 minutes to test one sample;

[0054] The XRD spectrum of the lithium-rich lithium-iron-oxide material exposed to the air for 0h was recorded, and compared with the standard spectrum of the lithium-rich lithium-iron-oxide material without exposure and the impurity standard. The Raman spectrum of the lithium-rich lithium-iron-oxide exposed to the air for 0h, the lithium carbonate Li2CO3 and the lithium hydroxide are shown in Figures 6-8

[0055] Comparative Example 2

[0056] The detection was carried out according to the same operation as in Comparative Example 1, except that the crushed lithium-rich lithium-iron-oxide material was exposed to the external air for 2h, to carry out the air stability experiment. The Raman spectrum of the lithium-rich lithium-iron-oxide exposed to the air for 2h is shown in Figure 9

[0057] Comparative Example 3

[0058] ​​​​The detection was performed according to the same operation as Comparative Example 1, except that the crushed lithium-rich lithium-iron-phosphate material was exposed to the external air for 4 h to perform the air stability experiment. The Raman spectrum of the lithium-rich lithium-iron-phosphate material exposed to the air for 4 h is shown in Figure 10

[0059] The Raman results of Examples 1-3 were summarized in Table 1 as follows:

[0060] Table 1 Raman results of Examples 1-3

[0061] 650 cm -1 peak intensity 1080 cm -1 Peak intensity 3550 cm -1 Peak intensity Lithium carbonate - 31634.1 - Lithium hydroxide - - 26882.4 Example 1 64325.4 - - Example 2 60765.7 11097.3 18572.7 Example 3 59174.3 14845.5 18761.1

[0062] The XRD results of Comparative Examples 1-3 were summarized in Table 2 as follows:

[0063] Table 2 XRD results of Comparative Examples 1-3

[0064] 21° peak intensity 23° peak intensity 31° peak intensity 32° peak intensity 33° peak intensity Lithium carbonate 11607.5 2510.7 16500 - - Lithium hydroxide - - - 29142.6 - Comparative Example 1 5108.6 5462.2 - 3576.5 5420.6 Comparative Example 2 4670.9 4822.4 - 3634.9 4358.9 Comparative Example 3 4738.2 - 3483.4 3711.2 4367.8

[0065] As can be seen from the comparison of Table 1 and Table 2, the XRD method is not sensitive enough to test the deterioration degree of the lithium-rich lithium-iron-phosphate, as shown in the results of Table 2, under the same air exposure condition, the XRD test results show that after exposure for 2 h (Comparative Example 2), compared with the impurity standard and exposure for 0 h (Comparative Example 1), only the peak intensity decreases, and no obvious impurity peak appears, but after exposure for 4 h (Comparative Example 3), obvious impurity peaks appear. However, the results of Table 1 show that under the same air exposure condition, the Raman test results show that after exposure for 2 h (Example 2), the characteristic peak intensity of the lithium-rich lithium-iron-phosphate decreases, but obvious impurity characteristic peaks of lithium hydroxide and lithium carbonate appear, and after exposure for 4 h (Example 3), the characteristic peak intensity of the lithium-rich lithium-iron-phosphate further decreases, and the peak intensity of the impurity characteristic peaks of lithium hydroxide and lithium carbonate further increases. It can be seen that the method provided by the present application has high sensitivity and reliability, and can effectively detect the deterioration degree of the lithium-rich lithium-iron-phosphate.​

Claims

1. A method for rapidly detecting the modification degree of lithium-rich lithium-iron phosphate, characterized in that, The positive electrode lithium supplement active material lithium-rich lithium iron oxide Li5FeO4 is exposed to air for different times, and is rapidly detected using a laser Raman spectrometer, and the metamorphic condition of the lithium-rich lithium iron oxide is obtained according to the peak position and peak strength of the Raman spectrum; specifically comprising: Raman testing is performed on lithium hydroxide, lithium carbonate and lithium-rich lithium iron oxide exposed to external air for 0 hours, and a standard curve is obtained; Raman testing is performed on lithium-rich lithium iron oxide materials exposed to external air for 2 hours and 4 hours respectively, and a test curve is obtained; The metamorphic degree of the lithium-rich lithium iron oxide is obtained by analyzing the peak position and peak strength of the Raman spectrum of the standard curve and the test curve.

2. The method of claim 1, wherein, Specifically comprising the following steps: a. The positive electrode lithium supplement active material lithium-rich lithium iron oxide Li5FeO4 is crushed in a dry and stable environment, and the crushing time is 20-90 minutes, and the particle size of the crushed material is 1-15 μm; b. The impurity standard is subjected to the same crushing operation in the same environment as the lithium-rich lithium iron oxide, and the crushing time is 20-90 minutes, and the particle size of the crushed material is 1-15 μm; c. The crushed lithium-rich lithium iron oxide material is exposed to air with an air humidity of 10-30% for different times for air stability experiments, and then the crushed impurity standard is placed on a glass slide, flattened and placed in a laser Raman spectrometer for Raman testing, and the metamorphic degree of the lithium-rich lithium iron oxide is obtained.

3. The method of claim 2, wherein, The crushing environment of the material is in a glove box with a protective atmosphere of N2 / Ar, or a dry room with a dew point of <-30°; The crushing method of the material is selected from any one of airflow crushing, ball milling, vacuum ball milling, mortar grinding and mechanical crushing of a crusher.

4. The method of claim 3, wherein, The crushing method of the material is mechanical crushing of a crusher.

5. The method according to claim 2, characterized in that, The impurity standard is lithium carbonate Li2CO3 and lithium hydroxide LiOH with a purity of analytical pure or above.

6. The method of claim 1, wherein, The Raman spectrum wave number range used in the Raman test is 50 to 4000 cm -1 .

7. The method of claim 1, wherein, The area of the face scan during Raman testing is selected from any one of 3 μm * 3 μm, 6 μm * 6 μm and 9 μm * 9 μm; the number of points per row of the face scan is selected from any one of 10, 20 and 30; the number of rows of the face scan is selected from any one of 20 rows, 10 rows and 30 rows; each sampling point is integrated for 3-40 times, and the integration time is 3-40 seconds.

8. The method of claim 7, wherein, The area of the face scan during Raman testing is 9 μm * 9 μm, the number of points per row of the face scan is 30, the number of rows of the face scan is 30, each sampling point is integrated for 20 times, and the integration time is 20 seconds.

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