A method for rapid characterization of rate performance of carbon anodes

Abstract

The present invention discloses a method for rapidly characterizing the rate performance of carbon anodes, belonging to the technical field of analytical detection. In this method, the first-order Raman spectrum of the carbon anode material is subjected to peak fitting to obtain defect structure information; the ratio (I D4 / I G ) of the area of the defect peak (D4 peak) to the area of the ideal graphite peak (G peak) is used to establish a fast charging standard curve for the rate performance of the carbon anode, which serves as the basis for detecting the unknown rate performance of the carbon anode. The method of the present invention establishes a standard curve based on statistically significant data, and has been reviewed and verified by the diffusion coefficient of hard carbon, and the detection result is more accurate, solving the problems of long evaluation period and complex operation process in the existing evaluation of carbon anode materials for fast charging alkali metal ion (lithium / sodium / potassium) batteries.

Description

Technical Field

[0001] The present invention belongs to the technical field of analytical detection, and particularly relates to a method for rapidly characterizing the rate performance of carbon anodes. Background Art

[0002] The electrochemical properties of alkali metal (lithium / sodium / potassium) ion batteries largely depend on the anode materials. As one of the most promising anode materials, carbon anode materials have the advantages of rich sources, low cost, environmental friendliness, high electronic conductivity, etc., and are the most commercially promising in lithium, sodium, and potassium ion batteries. Among them, disordered carbon materials, including soft carbon and hard carbon, etc., are the most commonly used carbon anode materials, which have large interlayer spacing, rich defect sites, and a large number of micropores, facilitating the adsorption and diffusion of alkali metal ions. It is reported in the research that the microstructure of carbon anodes significantly affects the alkali metal ion storage behavior, thus playing a decisive role in the reversible capacity. Some studies have found that the adsorption / desorption of ions at the edges and surface defects of materials is relatively easy to carry out, and rich defects and large interlayer spacing are beneficial to the improvement of rate performance. Raman spectroscopy is a powerful means to characterize the defect degree of carbon materials.

[0003] The basic electrochemical performance tests of carbon anode materials mainly include cycle performance tests and rate performance tests, and specific carbon anode life, capacity, working voltage, and capacity at different current densities can be obtained, but its characteristic is that the test period is relatively long. It should be noted that in the actual use process, it is necessary to develop a method that can quickly, simply, and accurately evaluate the rate performance of carbon-based anodes for sodium ion batteries to achieve the purpose of efficiently screening high-rate hard carbon anodes. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for rapidly characterizing the rate performance of carbon anodes, which solves the problems of long evaluation period and complex operation in the existing methods for evaluating carbon anode materials of alkali metal (lithium / sodium / potassium) batteries.

[0005] The present invention establishes a standard curve between the Raman spectrum of the carbon anode material and the rate performance as the basis for detecting the unknown rate performance of the carbon anode. It can quickly evaluate the rate performance of the carbon anode without undergoing a long-term rate performance test or collecting various structural parameters, and efficiently and quickly screen high-rate carbon anode materials.

[0006] The present invention first establishes a standard curve for the rate performance of carbon anodes, mainly including the following steps:

[0007] ① Perform rate performance tests on three or more carbon anodes with different defect degrees at high current density and low current density, obtain the ratio through the reversible specific capacity at relatively high current density and the reversible specific capacity at relatively low current density, and obtain the rate capacity retention rate of three or more carbon anodes with different defect degrees;

[0008] ② Perform Raman spectroscopy tests on the carbon negative electrode powders with 3 or more different degrees of defects in step ① to obtain Raman spectra, perform first-order Raman spectrum peak fitting, calculate the peak areas of the defect peak (D4 peak) and the ideal graphite peak (G peak) respectively, and record them as I D4 、I G respectively, and obtain the I D4 / I G ratio;

[0009] ③ Establish a standard curve, using the I D4 / I G value in step ② as the abscissa and the rate capacity retention rate obtained from the rate performance test in step ① as the ordinate to establish a rate standard curve;

[0010] Next is the rate performance test of the sample to be measured:

[0011] Perform Raman spectroscopy tests on the sample to be measured to obtain Raman spectra, perform peak fitting, and obtain the I D4 / I G value, and calculate the rate performance of the sample to be measured using the standard curve in step (1)③.

[0012] Preferably, the numerical ranges of the high current density and the low current density in step ① are 0.005 A g -1 -10 A g -1 .

[0013] Preferably, the numerical ranges of the high current density and the low current density in step ① are 20 mA g -1 -150 mA g -1 .

[0014] Preferably, the high current density in step ① is one of 60 mA g -1 , 90 mA g -1 , 150 mA g -1 , and the low current density is 20 mA g -1 .

[0015] Preferably, the carbon negative electrode is at least one of a hard carbon negative electrode, a soft carbon negative electrode, and a hard and soft carbon composite negative electrode.

[0016] Preferably, the hard carbon negative electrode is at least one of a biomass-based hard carbon, a resin-based hard carbon, and an asphalt-based hard carbon.

[0017] Preferably, the carbon negative electrode is applied to one of a lithium-ion battery, a sodium-ion battery, and a potassium-ion battery.

[0018] Preferably, the laser wavelength for Raman spectroscopy tests in step ② and the tests of the sample to be measured is one of 514 nm, 532 nm, and 633 nm.

[0019] Preferably, the Raman spectroscopy test mainly includes the following steps:

[0020] (1) The wavenumber range of the Raman spectroscopy used is 50 to 4000 cm -1 , and the laser power is 2 - 5 mW;

[0021] (2) Perform single-point scanning test, the number of scans includes but is not limited to 3 times, each sampling point is integrated 5 - 20 times, and the integration time is 5 - 20 s;

[0022] (3) Use origin data processing software for peak fitting, and the fitting function includes but is not limited to one of Gauss function, Gaussian function, Lorentz function, Voigt function, PsdVoigt1 function, PsdVoigt1 function;

[0023] (4) Obtain the peak areas of different peaks in the first-order Raman spectrum of the carbon negative electrode and perform calculations.

[0024] Preferably, the rate performance test mainly includes the following steps:

[0025] (1) Preparation of the electrode sheet:

[0026] Mix the carbon negative electrode sample with a conductive agent and a binder in a certain proportion, where the active material content shall not be less than 80%, after homogenization, coat it on a copper foil current collector with a certain thickness, and after vacuum drying at 60 - 100 °C for 4 - 12 h, cut it into small round pieces with a diameter of 12 mm, thus obtaining the electrode sheet, and the active material loading in the electrode sheet is 1.5 - 7 mg cm -2 ;

[0027] (2) Battery assembly and rate performance test:

[0028] In the glove box, use the carbon negative electrode sheet as the working electrode to assemble one of a half-cell, a full-cell, or a three-electrode cell. The battery is left standing for 6 - 48 h, and the electrochemical rate performance is carried out on the battery test system.

[0029] The beneficial effects of the present invention are as follows:

[0030] 1. This method is applicable to the rapid screening of carbon negative electrode materials for high-rate alkali metal ion (lithium / sodium / potassium) batteries. It can efficiently and accurately select the negative electrode materials according to the requirements of different application scenarios, with simple operation, rapid sampling, safety and reliability, low cost, and strong universality;

[0031] 2. The carbon negative electrode rate standard curve based on Raman spectroscopy in the present invention can obtain statistical data, making the established standard curve more accurate and improving the accuracy of detection. Description of the Drawings

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the accompanying drawings required in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0033] Figure 1 It is a relationship diagram between the diffusion coefficient and the rate performance in the platform region in Embodiment 1 of the present invention;

[0034] Figure 2 It is the Raman spectrum of the carbon negative electrode material in Embodiment 1 of the present invention;

[0035] Figure 3 It is the fitting diagram of the Raman spectrum of Sample 1 in Embodiment 1 of the present invention;

[0036] Figure 4 It is the I D4 / I G value (Raman laser wavelength is 532 nm) and the relationship diagram of the diffusion coefficient in the platform region;

[0037] Figure 5 It is the I D4 / I G value (Raman laser wavelength is 532 nm) and the standard curve diagram of the rate performance;

[0038] Figure 6 It is the Raman spectra with laser wavelengths of 532 nm and 633 nm in Embodiment 2 of the present invention.

[0039] Figure 7 It is the I D4 / I G value (Raman laser wavelength is 633 nm) and the relationship diagram of the rate performance;

[0040] Figure 8 It is the I D1 / I G value (Raman laser wavelength is 532 nm) and the relationship diagram of the rate performance in Comparative Example 2 of the present invention;

[0041] Figure 9 It is the I D2 / I G value (Raman laser wavelength is 532 nm) and the relationship diagram of the rate performance in Comparative Example 3 of the present invention;

[0042] Figure 10 It is the I D3 / I GRelationship diagram between value (Raman laser wavelength is 532 nm) and rate performance. Detailed implementation manners

[0043] To facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings of the specification and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0044] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. The preferred implementation methods and materials described herein are only for demonstration purposes. Without departing from the principle of the embodiments of the present invention, several improvements and modifications can be made, and these improvements and modifications are also regarded as the protection scope of the present invention.

[0045] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0046] Example 1

[0047] In this example, by performing Raman spectroscopy tests on the carbon negative electrode material and mathematical fitting, it can be used to predict the rate performance of the carbon negative electrode, which specifically includes the following steps:

[0048] I. Establish a standard curve for evaluating rate performance by Raman spectroscopy

[0049] 1. Preparation of electrode sheet and battery assembly:

[0050] (1) Preparation of electrode sheet:

[0051] Mix the carbon negative electrode sample, conductive carbon black, sodium carboxymethylcellulose, and styrene-butadiene rubber with a concentration of 48% in a mass ratio of 94%:1.5%:2.5%:2%, add an appropriate amount of deionized water, and stir evenly to prepare a slurry. Coat the slurry on a copper foil current collector with a certain thickness, and after vacuum drying at 80 °C for 12 h, cut it into small round pieces with a diameter of 12 mm to obtain the electrode sheet. The active material loading in the electrode sheet is 5 - 7 mg cm -2 ;

[0052] (2) Assembly of CR2032 button battery:

[0053] Place the carbon negative electrode sheet in the middle of the positive electrode shell in the glove box, with the active material side facing up, and drop 60 μL of electrolyte (1 mol L -1A solution of sodium hexafluorophosphate in ethylene carbonate / diethyl carbonate (with a solvent volume ratio of 1:1) was prepared. A glass fiber separator was placed, and then 60 μL of electrolyte was added dropwise. A sodium sheet, a spacer, a spring sheet, and a negative electrode case were placed in sequence. Finally, the battery components were pressed into a whole under a pressure of 10 GPa to complete the assembly of the battery;

[0054] 2. Rate performance test:

[0055] The battery assembled in Step 1 was allowed to stand for 8 h, and the rate performance test was carried out on a Neware battery test system or a Land battery test system to obtain the rate performance of the carbon negative electrode. The current densities were: 20 mA g -1 , 60 mA g -1 , 90 mA g -1 , 150 mA g -1 . By obtaining the ratio of the reversible specific capacity at high current densities (60 mA g -1 , 90 mA g -1 , 150 mA g -1 ) to the reversible specific capacity at low current density (20 mA g -1 ), the ratio was used as the rate capacity retention rate to describe the quality of the rate performance, and it was named according to the corresponding current density respectively. The results are shown in Table 1.

[0056] 3. Galvanostatic intermittent titration technique test:

[0057] The battery in Step 1 was studied by the galvanostatic intermittent titration technique to investigate the diffusion coefficient of Na + in the electrode. The pulsed current applied during the test was 10 mA g -1 , the pulse time was 15 min, and the relaxation time was 1 h. The diffusion coefficient in the plateau region (<0.1 V) of the electrochemical curve was calculated, and the results are shown in Table 1.

[0058] 4. Using the diffusion coefficient in the plateau region obtained in Step 3 as the abscissa and the rate capacity retention rate at a current density of 60 mA g -1 obtained in Step 2 as the ordinate, a linear relationship was established. The Pearson correlation coefficient was 0.81, indicating a high positive correlation between the rate performance and the diffusion coefficient in the plateau region. The results are shown in Table 3 and Figure 1 .

[0059] 5. Raman spectroscopy test with a laser wavelength of 532 nm:

[0060] (1) For the carbon negative electrode material, a multi-site detection method was adopted, and 3 point scans were taken. The wavenumber range of the Raman spectrum used was 850 to 2000 cm -1 , and the laser power was 2 mW;

[0061] (2) Perform single-point scanning tests, with the number of scans being 3 to 5 times, integrating 15 times at each sampling point, and the integration time being 3 s. The spectral results are as Figure 2 shown;

[0062] (3) Use origin data processing software to perform peak fitting on the D peak and G peak of the first-order Raman spectrum (in the wavenumber range of 850 to 2000 nm -1 ). The fitting function is the Voigt function, and 5 peaks are obtained. The results are as Figure 3 shown. From low to high Raman shift, they are the D4 peak at ~1200 cm -1 (stretching vibration of C-C / C═C double bonds in sp 2 -sp 3 hybrid structure or at the graphene terminal edge, A 1g symmetric), the D1 peak at ~1350 cm -1 (defect-induced graphite, A 1g symmetric), the D3 peak at ~1500 cm -1 (short-range sp 3 carbon in amorphous carbon), the G peak at ~1580 cm -1 (ideal graphite lattice, E 2g symmetric), and the D2 peak at ~1620 cm -1 (surface graphene layer of the graphite lattice, E 2g symmetric). Calculate the peak areas of the 5 peaks, and obtain the ratio of the D peak to the G peak area to get the corresponding defect degree information;

[0063] (4) Obtain the peak areas of different peaks in the first-order Raman spectrum of the carbon negative electrode, calculate the peak areas of the D4 peak and the G peak, and record them as I D4 , I G respectively. The ratio of I D4 / I G is shown in Table 2.

[0064] 6. Use the I D4 / I G value in step 5 as the abscissa and the diffusion coefficient in the plateau region in step 3 as the ordinate to establish a linear relationship. The Pearson correlation coefficient is 0.84, indicating a high positive correlation between the D4 peak and the diffusion coefficient in the plateau region. The results are shown in Table 3 and Figure 4 shown.

[0065] 7. Establish a standard curve for evaluating the rate performance of the carbon negative electrode using Raman spectroscopy:

[0066] Use the ratio of I D4 / I G in the Raman spectrum in step 5 as the abscissa and 60 mA g -1 , 90 mA g obtained from the rate test in step 2 as the ordinate...-1 、 150 mAg -1 The rate capacity retention rates at the current density are used as the ordinate respectively, and a rate standard curve based on the Raman spectrum with a laser wavelength of 532 is established. The results are shown in Table 4 and Figure 5 as follows.

[0067] II. Rate performance test of samples to be measured

[0068] 1. Perform Raman spectrum tests on samples A and B to be measured, fit and deconvolute the peaks, and obtain the I D4 / I G values of 0.38 and 0.46 respectively, as shown in Table 5;

[0069] 2. Using the Raman spectrum rate standard curve in Step 1, calculate that the rate capacity retention rates of sample A at 60 mAg -1 , 90 mAg -1 , 150 mAg -1 are 27.47%, 22.41%, and 18.45% respectively, and the rate capacity retention rates of sample B at 60 mAg -1 , 90 mAg -1 , 150 mA g -1 are 30.66%, 24.83%, and 20.56% respectively, as shown in Table 5.

[0070] Example 2

[0071] Since the larger the wavelength, the smaller the excitation energy of the laser and the larger the area of the D peak relative to the area of the G peak, the spectral comparison is as Figure 6 shown. Therefore, in this example, Raman spectra with a laser wavelength of 633 nm are used for testing, single-point scanning, 3 - 5 scanning times, 10 integrations at each sampling point, and the integration time is 10 s.

[0072] Use the same method as in Example 1 to characterize the Raman spectrum, fabricate the electrode sheet, assemble the button battery, and perform rate tests under the same conditions. Using the I D4 / I G value as the abscissa and the rate capacity retention rates at the current densities of 60 mAg -1 , 90 mA g -1 , 150 mA g -1 obtained from the rate test as the ordinate respectively, establish a linear relationship. The results are shown in Table 4 and Figure 7 as follows, indicating that the I D4 / I G value obtained from the Raman spectrum with a laser wavelength of 633 nm has a high positive correlation with the rate performance.

[0073] Comparative Example 1

[0074] In this comparative example, the test samples A and B were made into negative electrode sheets, assembled into button cells respectively, and the rate performance was tested. The test results showed that the rate capacity retention rates of sample A at 60 mA g -1 , 90 mA g -1 , and 150 mA g -1 were 27.19%, 21.86%, and 18.37% respectively, and the rate capacity retention rates of sample B at 60 mA g -1 , 90 mA g -1 , and 150 mA g -1 were 30.52%, 24.87%, and 20.33% respectively, as shown in Table 6.

[0075] Comparative Example 2

[0076] In this comparative example, the same method as in Example 1 was used to characterize the Raman spectrum, make the electrode sheet, assemble the button cell, and perform the electrochemical test under the same conditions. Using the peak area ratio of I D1 / I G as the abscissa and the rate capacity retention rate at a current density of 60 mA g -1 obtained from the rate test as the ordinate, a linear relationship was established, and the Pearson correlation coefficient was 0.56. The results are shown in Table 4 and Figure 8 .

[0077] Comparative Example 3

[0078] In this comparative example, the same method as in Example 1 was used to characterize the Raman spectrum, make the electrode sheet, assemble the button cell, and perform the electrochemical test under the same conditions. Using the peak area ratio of I D2 / I G as the abscissa and the rate capacity retention rate at a current density of 60 mA g -1 obtained from the rate test as the ordinate, a linear relationship was established, and the Pearson correlation coefficient was 0.50. The results are shown in Table 4 and Figure 9 .

[0079] Comparative Example 4

[0080] In this comparative example, the same method as in Example 1 was used to characterize the Raman spectrum, make the electrode sheet, assemble the button cell, and perform the electrochemical test under the same conditions. Using the peak area ratio of I D3 / I G as the abscissa and the rate capacity retention rate at a current density of 60 mA g -1 obtained from the rate test as the ordinate, a linear relationship was established, and the Pearson correlation coefficient was 0.64. The results are shown in Table 4 and Figure 10 .

[0081] Table 1 Rate performance and plateau region diffusion coefficient results of carbon negative electrode materials

[0082]

[0083] Table 2 I obtained by fitting the Raman spectra at different laser wavelengths D4 / I G value

[0084] <![CDATA[I D4 / I G (532nm)]]> <![CDATA[I D4 / I G (633nm)]]> Sample 1 0.39 1.05 Sample 2 0.44 1.27 Sample 3 0.32 0.99 Sample 4 0.32 0.92 Sample 5 0.21 0.55 Sample 6 0.58 1.44 Sample 7 0.45 1.01 Sample 8 0.31 0.93 Sample 9 0.44 1.31

[0085] Table 3 Correlation between diffusion coefficient and magnification, correlation between I D4 / I G value and diffusion coefficient

[0086] Pearson correlation coefficient Diffusion coefficient and rate 0.81 <![CDATA[I D4 / I G value and diffusion coefficient]]> 0.84

[0087] Table 4 I D4 / I G 、I D1 / I G 、I D2 / I G 、I D3 / I G values and their correlations with rate performance respectively

[0088]

[0089] Table 5 I of the sample to be measured D4 / I G value, rate performance obtained from the standard curve

[0090] <![CDATA[I D4 / I G > <![CDATA[60mA g -1 > <![CDATA[90mA g -1 > <![CDATA[150mA g -1 > Sample A 0.38 27.47％ 22.41％ 18.45％ Sample B 0.46 30.66％ 24.83％ 20.56％

[0091] Table 6 Rate performance obtained from the rate test of the sample to be measured

[0092] <![CDATA[60mA g -1 > <![CDATA[90mA g -1 > <![CDATA[150mAg -1 > Sample A 27.19％ 21.86％ 18.37％ Sample B 30.52％ 24.87％ 20.33％

[0093] In summary, it can be seen that in the present invention, by using the Raman spectrum I of the carbon negative electrode material D4 / I GA standard curve is established based on the value and rate performance as the basis for detecting the unknown rate performance of the carbon negative electrode. This method can quickly evaluate the rate performance of the carbon negative electrode without undergoing long-term rate performance tests and various microstructural characterizations with complex operations. Through Examples 1-2 and Comparative Examples 1-4, it can be found that the type and degree of the defect structure represented by the D4 peak in the Raman spectrum are positively correlated with the diffusion rate of sodium ions in the carbon negative electrode, and the magnitude of the diffusion coefficient affects the quality of the rate performance. Therefore, the rate performance of the carbon negative electrode can be quickly evaluated by obtaining the defect degree of the carbon negative electrode through Raman spectroscopy, and large-rate carbon negative electrodes can be screened efficiently, quickly, and accurately. At the same time, this method establishes a standard curve based on statistically significant data, showing the advantages of simple operation, rapid sampling, safety and reliability, low cost, accurate results, and strong universality, and is applicable to Raman with different laser wavelengths.

[0094] The above are only the preferred embodiments of the present invention and do not impose any form of limitation on the present invention. Therefore, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for rapidly characterizing the rate performance of a carbon negative electrode, characterized in that: The following steps are involved: (1) The establishment of the standard curve of carbon negative electrode rate performance mainly includes the following steps: ① Test the rate performance of three or more carbon negative electrodes with different defect degrees at high current density and low current density, obtain the ratio of the reversible specific capacity at relatively high current density and the reversible specific capacity at relatively low current density, and obtain the rate capacity retention rate of three or more carbon negative electrodes with different defect degrees; ② The three or more carbon anode powders with different defect levels in step ① are subjected to Raman spectroscopy test to obtain Raman spectra, and first-order Raman spectrum peak fitting is performed to calculate the peak areas of the defect peak D4 and the ideal graphite peak G, respectively, and are recorded as I D4 ,I G , and get I D4 / I G ratio; ③ Establish a standard curve, using I in step ② D4 / I G The value is the horizontal axis, and the rate capacity retention rate obtained from the rate performance test in step ① is used as the vertical axis to establish a rate standard curve; (2) Rate performance test of the sample to be tested The sample to be tested is subjected to Raman spectroscopy test to obtain the Raman spectrum, and the peaks are fitted to obtain I D4 / I G The value is calculated using the standard curve in step (1) ③ to calculate the rate performance of the sample to be tested.

2. A method for rapidly characterizing the rate performance of a carbon negative electrode according to claim 1, characterized in that: The numerical range of the high current density and the low current density is 0.005 A g -1 -10A g -1 .

3. A method for rapidly characterizing the rate performance of a carbon negative electrode according to claim 1, characterized in that: The high current density and low current density values ​​are in the range of 20 mA g -1 -150 mA g -1 .

4. A method for rapidly characterizing the rate performance of a carbon negative electrode according to claim 3, characterized in that: The high current density is 60 mA g -1 , 90 mA g -1 , 150 mA g -1 One of the three, with a low current density of 20 mA g -1 .

5. A method for rapidly characterizing the rate performance of a carbon negative electrode according to claim 1 or 2, characterized in that: The carbon negative electrode is at least one of a hard carbon negative electrode, a soft carbon negative electrode, and a soft and hard carbon composite negative electrode.

6. A method for rapidly characterizing the rate performance of a carbon negative electrode according to claim 5, characterized in that: The hard carbon negative electrode is at least one of biomass-based hard carbon, resin-based hard carbon, and asphalt-based hard carbon.

7. A method for rapidly characterizing the rate performance of a carbon negative electrode according to claim 1 or 2, characterized in that: The carbon negative electrode is applied to one of lithium ion batteries, sodium ion batteries and potassium ion batteries.

8. A method for rapidly characterizing the rate performance of a carbon negative electrode according to claim 1 or 2, characterized in that: The laser wavelength of the Raman spectrum test is one of 514 nm, 532 nm, and 633 nm.

9. A method for rapidly characterizing the rate performance of a carbon negative electrode according to claim 1 or 2, characterized in that: The Raman spectroscopy test mainly includes the following steps: (1) The Raman spectrum used ranges from 50 to 4000 cm -1 , laser power is 2~5 mW; (2) Perform a single-point scanning test, with the number of scans including but not limited to 3 times, integrating 5 to 20 times at each sampling point, and the integration time being 5 to 20 s; (3) Using origin data processing software to perform peak fitting, the fitting function includes but is not limited to one of Gauss function, Gaussian function, Lorentz function, Voigt function, PsdVoigt1 function, and PsdVoigt1 function; (4) Obtain the peak areas of different peaks in the first-order Raman spectrum of the carbon negative electrode and perform calculations.

10. A method for rapidly characterizing the rate performance of a carbon negative electrode according to any one of claims 1 or 2, characterized in that The rate performance test mainly includes the following steps: (1) Preparation of electrode sheets: The carbon negative electrode sample is mixed with a conductive agent and a binder in a certain proportion, wherein the active material content is not less than 80%. After homogenization, it is coated on a copper foil current collector with a certain thickness. After vacuum drying at 60-100 °C for 4-12 h, it is cut into small discs with a diameter of 12 mm to obtain an electrode sheet. The active material loading in the electrode sheet is 1.5-7 mg cm -2 ; (2) Battery assembly and rate performance testing: In a glove box, the carbon negative electrode sheet is used as the working electrode to assemble into a half-cell, a full cell, or a three-electrode cell. The cell is left to stand for 6 to 48 hours, and the electrochemical rate performance is tested on a battery testing system.

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