Electrode material dynamics evaluation method

Abstract

The invention provides an electrode material dynamics evaluation method, and belongs to the technical field of secondary batteries. According to the evaluation method, through symmetric battery assembly, EIS testing, EIS fitting processing, DRT processing, dynamic characteristic peak identification, peak value integration and calculation and peak area comparison, judgment results of different dynamic processes are finally output, and the method can help discriminate and analyze changes of different dynamic processes. The problem that characteristic peaks in the dynamic process are overlapped and difficult to analyze in the current dynamic test is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of secondary batteries, and in particular relates to a method for evaluating the kinetics of electrode materials. Background Art

[0002] With the rapid development of the electric vehicle market, consumers have put forward higher requirements for the energy density of power batteries. Graphite, as the negative electrode material of traditional lithium-ion batteries, can no longer meet market demand due to its limited theoretical specific capacity. Silicon-based negative electrode materials have become a strong candidate for the new generation of negative electrode materials due to their high theoretical specific capacity.

[0003] The charging and discharging process of lithium-ion batteries involves multiple physical processes, including electronic conductivity, solid-phase diffusion of lithium ions in the material, electrochemical reaction of lithium ions at the solid-liquid interface, and liquid-phase mass transfer of lithium ions in the electrolyte. The kinetic characteristics of electrode materials have an important influence on the cycle performance and rate performance of symmetrical batteries. Impedance analysis based on electrochemical impedance spectroscopy (EIS) is one of the commonly used methods for evaluating the kinetics of electrode materials, which can quickly and non-invasively test the kinetic information of electrodes.

[0004] However, since the impedance spectra corresponding to the positive and negative electrodes in the full battery are in similar frequency bands, it is difficult to distinguish the kinetic states of the positive and negative electrodes based on EIS test analysis. Moreover, since the characteristic peaks of different kinetic parameters overlap and are difficult to distinguish, it is impossible to specifically separate the changes in a certain kinetic process during the charging and discharging process. Therefore, in reality, when faced with the situation where the EIS test shows that the electrode kinetics have deteriorated, it is impossible to distinguish which process has a problem. Summary of the invention

[0005] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, an embodiment of the present invention provides a method for evaluating the kinetics of an electrode material.

[0006] An embodiment of the present invention provides a method for evaluating electrode material kinetics, comprising the following steps:

[0007] Step 1. Symmetrical battery assembly, wherein the symmetric battery comprises a first symmetric battery and a second symmetric battery;

[0008] Step 2. Performing an AC impedance spectrum test on the symmetrical battery to obtain an AC impedance spectrum;

[0009] Step 3. Fitting the AC impedance spectrum based on an equivalent impedance model to obtain a Nyquist curve;

[0010] Step 4. performing relaxation time distribution processing on the Nyquist curve to obtain a relaxation time distribution curve;

[0011] Step 5. Perform kinetic characteristic peak interpretation based on the relaxation time distribution curve to obtain different kinetic characteristic peak identification results based on the relaxation time distribution;

[0012] Step 6. Perform peak integration and calculation on the kinetic characteristic peak in the relaxation time distribution curve, and output the kinetic interpretation result corresponding to the kinetic characteristic peak by comparing the calculation results of the kinetic characteristic peak at the same position between the first symmetric battery and the second symmetric battery.

[0013] The advantages and technical effects of the electrode material kinetics evaluation method of the embodiment of the present invention are as follows:

[0014] (1) The present invention is based on the AC impedance spectrum test and relaxation time distribution analysis of the symmetrical battery, eliminating the influence of the metal lithium electrode on the test results in the conventional half-cell test, and performing kinetic evaluation on different kinetic processes;

[0015] (2) Firstly, the AC impedance spectrum is fitted and then the relaxation time distribution is processed, which is conducive to obtaining clearer and more accurate data and eliminating some errors;

[0016] (3) Through AC impedance spectroscopy testing and corresponding relaxation time distribution analysis, the characteristic peaks of different kinetic processes can be found. Further, through area integration, calculation and comparison of the characteristic peaks, the changes in a specific kinetic process can be accurately evaluated.

[0017] In some embodiments, in step 1, the symmetrical battery is assembled in an environment where the water and oxygen contents are both less than 0.05 ppm, and then allowed to stand.

[0018] In some embodiments, the standing time in step 1 is more than 6 hours.

[0019] In some embodiments, in step 2, an AC impedance spectrum test is performed on the symmetrical battery in a constant temperature environment of 20-30° C., the test frequency is 100 kHz-100 MHz, and the disturbance voltage is 9-11 mV.

[0020] In some embodiments, step 4 specifically includes: inputting the real part Z′ and the inverse value of the imaginary part -Z″ in the Nyquist curve into a kinetic characteristic peak identification software based on relaxation time distribution, performing relaxation time distribution processing, and obtaining the relaxation time distribution curve.

[0021] In some embodiments, in step 6, outputting the kinetic interpretation results corresponding to the kinetic characteristic peaks specifically includes: analyzing the kinetic changes between different electrode materials, or analyzing the kinetic changes of the same target battery at different cycle stages or under different working environments.

[0022] In some embodiments, in step 6, when analyzing the kinetic changes between different electrode materials, the first symmetrical battery is a symmetrical battery assembled using the first electrode material, and the second symmetrical battery is a symmetrical battery assembled using the second electrode material; the characteristic peak of the SEI film process of the first symmetrical battery is integrated and calculated, and the corresponding integrated area is recorded as x 1 ; Integrate and calculate the characteristic peak of the SEI film process of the second symmetric battery, and the corresponding integral area is recorded as x 2 , calculate the ratio x 1 / x 2 ; if x 1 / x 2 If x is less than 1, it is judged that the SEI film process kinetics of the first electrode material is better; 1 / x 2 If it is greater than 1, it is judged that the SEI film process kinetics of the second electrode material is better.

[0023] In some embodiments, in step 6, when analyzing the kinetic changes between different electrode materials, the first symmetrical battery is a symmetrical battery assembled using the first electrode material, and the second symmetrical battery is a symmetrical battery assembled using the second electrode material; the characteristic peak of the charge transfer process of the first symmetrical battery is integrated and calculated, and the corresponding integrated area is recorded as y 1 ; Integrate and calculate the characteristic peak of the charge transfer process of the second symmetrical battery, and record the corresponding integrated area as y 2 , calculate the ratio y 1 / y 2 If y 1 / y 2 If y is less than 1, it is judged that the charge transfer process kinetics of the first electrode material is better; 1 / y 2 If it is greater than 1, it is judged that the charge transfer process kinetics of the second electrode material is better.

[0024] In some embodiments, in step 6, when analyzing the kinetic changes of the same target battery at different cycle stages, the first symmetrical battery is a symmetrical battery assembled after disassembling the target battery before the cycle, and the second symmetrical battery is a symmetrical battery assembled after disassembling the target battery after the cycle; the characteristic peaks of the SEI film process and the characteristic peaks of the charge transfer process of the first symmetrical battery are integrated and calculated, and the corresponding integral areas are recorded as x 1 and 1 ; The characteristic peaks of the SEI film process and the charge transfer process of the second symmetric battery are integrated and calculated, and the corresponding integral areas are recorded as x 2 and 2 ; Compare the ratio x 2 / x 1 and ratio y 2 / y 1 If x 2 / x 1 Greater than y 2 / y 1 , then it is judged that the SEI film process is the main reason for the performance degradation of the target battery; if x 2 / x 1 Less than y 2 / y 1 , it is judged that the charge transfer process is the main reason for the performance degradation of the target battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a logic flow chart of the electrode material kinetics evaluation method according to an embodiment of the present invention;

[0026] Figure 2 This is an AC impedance spectrum obtained by testing the first symmetrical battery of Example 1 of the present invention at 50% SOC and 25° C. ambient temperature;

[0027] Figure 3 This is an AC impedance spectrum obtained by testing the second symmetrical battery of Example 1 of the present invention at 50% SOC and 25° C. ambient temperature;

[0028] Figure 4 is the DRT curve of the first symmetrical battery of Example 1 of the present invention;

[0029] Figure 5 is the DRT curve of the second symmetrical battery of Example 1 of the present invention;

[0030] Figure 6 is a DRT curve of the first symmetrical battery of Example 2 of the present invention;

[0031] Figure 7 3 is the DRT curve of the second symmetrical battery of Example 2 of the present invention. DETAILED DESCRIPTION

[0032] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0033] The present invention provides a method for evaluating the kinetics of an electrode material. Figure 1 As shown, the following steps are included:

[0034] Step 1. Symmetrical battery assembly, wherein the symmetric battery comprises a first symmetric battery and a second symmetric battery;

[0035] Step 2. Performing an electrochemical impedance spectroscopy (EIS) test on the symmetrical battery to obtain an electrochemical impedance spectrum;

[0036] Step 3. Fitting the AC impedance spectrum based on an equivalent impedance model to obtain a Nyquist curve;

[0037] Step 4. performing a relaxation time distribution (DRT) process on the Nyquist curve to obtain a relaxation time distribution curve;

[0038] Step 5. Perform kinetic characteristic peak interpretation based on the relaxation time distribution curve to obtain different kinetic characteristic peak identification results based on the relaxation time distribution;

[0039] Step 6. By performing peak integration and calculation on the kinetic characteristic peak in the relaxation time distribution curve, and by comparing the calculation results of the kinetic characteristic peak at the same position between the first symmetric battery and the second symmetric battery, the kinetic interpretation result corresponding to the kinetic characteristic peak is output.

[0040] The evaluation method first assembles the battery, and then performs AC impedance spectrum tests respectively to obtain AC impedance diagrams, and then performs relaxation time distribution data processing and analysis for the fitting results of each set of AC impedance data, and extracts characteristic peak information under characteristic time parameters, and by comparing the differences in relaxation time distribution characteristic peaks between different batteries or electrode materials, the kinetic process of the electrode material is split and evaluated, and finally the determination results of different kinetic processes are output to help identify and analyze changes in different kinetic processes.

[0041] In the evaluation method of the embodiment of the present invention, a symmetrical battery is used instead of a full battery in step 1. Because the AC impedance spectra corresponding to the positive electrode and the negative electrode in the full battery are in a similar frequency band and difficult to distinguish, the subsequent test is performed using a symmetrical battery in the embodiment of the present invention to facilitate the distinction of the kinetic state of the positive electrode or the negative electrode.

[0042] It is understandable that if the purpose is to evaluate the kinetic state of different new electrode materials, the electrode materials can be directly assembled into a symmetrical battery. If the purpose is to evaluate the kinetic changes of the target battery at different cycle stages or under different working environments, the target battery needs to be disassembled, the positive electrode sheet or negative electrode sheet of the target battery needs to be cleaned, dried, and cut, and then the corresponding positive electrode sheet or negative electrode sheet needs to be assembled into a symmetrical battery.

[0043] In some embodiments, in step 1, the symmetrical battery is assembled in an environment where the water and oxygen contents are both less than 0.05 ppm, and then the battery is left to stand for a period of time before the EIS test in step 2 is performed, in order to prevent the electrode from reacting with water or oxygen in the air. Specifically, the symmetrical battery assembly can be performed in an anhydrous and oxygen-free glove box to control the water and oxygen content. The standing time is to allow the electrolyte to fully infiltrate the electrode and the diaphragm. Preferably, the standing time is more than 6 hours; more preferably, the standing time is 6-12 hours, for example, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, etc.

[0044] In some embodiments, in step 2, the symmetrical battery is subjected to an AC impedance spectrum test in a constant temperature environment of 20-30° C., such as 20° C., 22° C., 24° C., 26° C., 28° C., 30° C., etc., with a test frequency of 100 kHz-100 MHz and a disturbance voltage of 9-11 mV. The purpose of maintaining a constant temperature is to reduce the influence of temperature on the test results.

[0045] In the evaluation method of the embodiment of the present invention, the EIS fitting process in step 3 is to obtain clearer and more accurate data and eliminate some errors. If the DRT process is directly performed on the AC impedance spectrum without the fitting process, some test errors may be introduced.

[0046] In some embodiments, step 4 specifically includes: inputting the real part Z′ and the inverse value of the imaginary part -Z″ in the Nyquist curve into a kinetic characteristic peak identification software based on relaxation time distribution, performing relaxation time distribution processing, and obtaining the relaxation time distribution curve.

[0047] In the evaluation method of the embodiment of the present invention, step 6 integrates, calculates and compares the area of ​​the characteristic peaks instead of selecting the height of the peaks for calculation and comparison, because the area can more comprehensively and objectively represent the resistance of the kinetic process. In some embodiments, in step 6, outputting the kinetic interpretation results corresponding to the kinetic characteristic peaks specifically includes: analyzing the kinetic changes between different electrode materials, or analyzing the kinetic changes of the same target battery at different cycle stages or under different working environments.

[0048] In some embodiments, in step 6, when analyzing the kinetic changes between different electrode materials, the first symmetrical battery is a symmetrical battery assembled using the first electrode material, and the second symmetrical battery is a symmetrical battery assembled using the second electrode material; the characteristic peak of the SEI film process of the first symmetrical battery is integrated and calculated, and the corresponding integrated area is recorded as x 1 ; Integrate and calculate the characteristic peak of the SEI film process of the second symmetric battery, and the corresponding integral area is recorded as x 2 , calculate the ratio x1 / x 2 ; if x 1 / x 2 If x is less than 1, it is judged that the SEI film process kinetics of the first electrode material is better; 1 / x 2 If it is greater than 1, it is judged that the SEI film process kinetics of the second electrode material is better.

[0049] In some embodiments, in step 6, when analyzing the kinetic changes between different electrode materials, the first symmetrical battery is a symmetrical battery assembled using the first electrode material, and the second symmetrical battery is a symmetrical battery assembled using the second electrode material; the characteristic peak of the charge transfer process of the first symmetrical battery is integrated and calculated, and the corresponding integrated area is recorded as y 1 ; Integrate and calculate the characteristic peak of the charge transfer process of the second symmetrical battery, and record the corresponding integrated area as y 2 , calculate the ratio y 1 / y 2 If y 1 / y 2 If y is less than 1, it is judged that the charge transfer process kinetics of the first electrode material is better; 1 / y 2 If it is greater than 1, it is judged that the charge transfer process kinetics of the second electrode material is better.

[0050] In some embodiments, in step 6, when analyzing the kinetic changes of the same target battery at different cycle stages, the first symmetrical battery is a symmetrical battery assembled after disassembling the target battery before the cycle, and the second symmetrical battery is a symmetrical battery assembled after disassembling the target battery after the cycle; the characteristic peaks of the SEI film process and the characteristic peaks of the charge transfer process of the first symmetrical battery are integrated and calculated, and the corresponding integral areas are recorded as x 1 and 1 ; The characteristic peaks of the SEI film process and the charge transfer process of the second symmetric battery are integrated and calculated, and the corresponding integral areas are recorded as x 2 and 2 ; Compare the ratio x 2 / x 1 and ratio y 2 / y 1 If x 2 / x 1 Greater than y 2 / y 1 , then it is judged that the SEI film process is the main reason for the performance degradation of the target battery; if x 2 / x 1 Less than y 2 / y1 , it is judged that the charge transfer process is the main reason for the performance degradation of the target battery.

[0051] In some embodiments, in step 6, when analyzing the kinetic changes of the same target battery under different working environments, the first symmetrical battery is a symmetrical battery assembled after disassembling the target battery under the first working environment, and the second symmetrical battery is a symmetrical battery assembled after disassembling the target battery under the second working environment; the SEI film process characteristic peak, the charge transfer process characteristic peak and the contact impedance related characteristic peak of the first symmetrical battery are integrated and calculated, and the corresponding integrated areas are respectively recorded as x 1 ,y 1 and z 1 ; The characteristic peaks of the SEI film process, the characteristic peaks of the charge transfer process and the characteristic peaks related to the contact impedance of the second symmetric battery are integrated and calculated, and the corresponding integral areas are recorded as x 2 ,y 2 and z 2 ; Comparison ratio (x 2 -x 1 ) / x 1 and ratio (y 2 -y 1 ) / y 1 and (z 2 -z 1 ) / z 1 The size of the interval, if (x 2 -x 1 ) / x 1 Greater than (y 2 -y 1 ) / y 1 and (z 2 -z 1 ) / z 1 , it is judged that the SEI film process is the main reason for the performance degradation of the target battery; if (y 2 -y 1 ) / y 1 Greater than (x 2 -x 1 ) / x 1 and (z 2 -z 1 ) / z 1 , it is determined that the charge transfer process is the main cause of the target battery performance degradation; if (z 2 -z 1 ) / z 1 Greater than (x 2 -x 1 ) / x 1 and (y 2 -y 1) / y 1 , it is judged that the increase in contact impedance caused by electrolyte consumption is the main reason for the performance degradation of the target battery.

[0052] The present invention is described in detail below with reference to the embodiments and the accompanying drawings.

[0053] Example 1

[0054] A method for evaluating electrode material kinetics is used to analyze kinetic differences of electrodes coated with different materials, and specifically comprises the following steps:

[0055] Step 1. Symmetrical battery assembly

[0056] In a glove box with water and oxygen less than 0.05 ppm, the electrode plate coated with the first electrode material was cleaned with DMC solvent and vacuum dried for 24 hours. The vacuum dried plate was cut into a disc with a diameter of 12 mm, and assembled into a symmetrical battery in the order of plate, diaphragm, plate, gasket, and spring. A fixed amount of electrolyte was re-injected, and the assembly was allowed to stand for 10 hours to obtain the first symmetrical battery. The second electrode material was assembled into a second symmetrical battery in the same way.

[0057] Step 2. AC impedance spectroscopy test

[0058] The first symmetrical battery and the second symmetrical battery were kept at a constant ambient temperature of 25°C for 2 hours, the test frequency was 100kHz-100MHz, the disturbance voltage was 10mV, and the EIS graph of the first symmetrical battery and the EIS graph of the second symmetrical battery were obtained.

[0059] Step 3. EIS fitting process

[0060] Based on the equivalent impedance model, an EIS fitting process is performed on the EIS graph of the first symmetrical battery to obtain the Nyquist curve of the first symmetrical battery; based on the equivalent impedance model, an EIS fitting process is performed on the EIS graph of the second symmetrical battery to obtain the Nyquist curve of the second symmetrical battery.

[0061] Step 4. DRT processing

[0062] The Nyquist real part Z′ and the inverse value of the imaginary part Z″ in the EIS fitting processing results of the first symmetrical battery are input into the DRT-based kinetic characteristic peak identification software, and DRT processing is performed to obtain the DRT curve of the first symmetrical battery; the Nyquist real part Z′ and the inverse value of the imaginary part -Z″ in the EIS fitting processing results of the second symmetrical battery are input into the DRT-based kinetic characteristic peak identification software, and DRT processing is performed to obtain the DRT curve of the second symmetrical battery.

[0063] Step 5. Characteristic peak interpretation

[0064] Based on the DRT curve of the first symmetrical battery, the kinetic characteristic peaks are interpreted to obtain different kinetic characteristic peak identification results based on the relaxation time distribution of the first symmetrical battery; based on the DRT curve of the second symmetrical battery, the kinetic characteristic peaks are interpreted to obtain different kinetic characteristic peak identification results based on the relaxation time distribution of the second symmetrical battery;

[0065] Step 6. Integrate the characteristic peaks of different kinetic processes (characteristic peaks of the SEI film process and characteristic peaks of the charge transfer process) in the DRT curve of the first symmetric battery and the DRT curve of the second symmetric battery to obtain two groups of peak area values. By calculating the peak area ratio of the same kinetic process, the difference in kinetic performance of the two groups of materials can be determined.

[0066] Specifically, the characteristic peaks of the SEI film process and the charge transfer process of the first electrode material are integrated, and the corresponding integrated area is recorded as x 1 and 1 ; Integrate the characteristic peaks of the SEI film process and the charge transfer process of the second electrode material, and the corresponding integral area is recorded as x 2 and 2 Calculate the peak area ratio x of the SEI film process of different electrode materials 1 / x 2 , if x 1 / x 2 If x is less than 1, it is judged that the SEI film process kinetics of the first electrode material is better; 1 / x 2 If y is greater than 1, it is judged that the SEI film process kinetics of the second electrode material is better. Similarly, the peak area ratio y of the charge transfer process of the first electrode material and the second electrode material is calculated. 1 / y 2 , if y 1 / y 2 If y is less than 1, the charge transfer kinetics of the first electrode material is better; 1 / y 2 If it is greater than 1, the charge transfer kinetics of the second electrode material is better.

[0067] Example 2

[0068] A method for evaluating electrode material kinetics is used to analyze kinetic changes of a target battery under different cycle working conditions.

[0069] Step 1. Target battery disassembly and symmetrical battery assembly

[0070] In a glove box with water and oxygen less than 0.05ppm, the target battery before the cycle was disassembled, the electrode was taken out, the electrode was cleaned with DMC solvent, and vacuum dried for 24 hours. The vacuum dried electrode was cut into a 12mm diameter disc, and assembled into a symmetrical battery in the order of electrode, diaphragm, electrode, gasket, and spring. A fixed amount of electrolyte was re-injected, and the assembly was left to stand for 10 hours to obtain the first symmetrical battery. The target battery after 2 cycles was disassembled and assembled into the second symmetrical battery in the same way.

[0071] Step 2. AC impedance spectroscopy test

[0072] The first symmetrical battery and the second symmetrical battery were kept at an ambient temperature of 25° C. for 2 h, the test frequency was 100 kHz-100 MHz, the disturbance voltage was 10 mV, and the EIS graph of the first symmetrical battery and the EIS graph of the second symmetrical battery were obtained.

[0073] Step 3. EIS fitting process

[0074] Performing EIS fitting processing on the EIS graph of the first symmetrical battery based on the equivalent impedance model to obtain the Nyquist curve of the first symmetrical battery; performing EIS fitting processing on the EIS graph of the second symmetrical battery based on the equivalent impedance model to obtain the Nyquist curve of the second symmetrical battery;

[0075] Step 4. DRT processing

[0076] The Nyquist real part Z′ and the inverse value of the imaginary part Z″ in the EIS fitting processing results of the first symmetrical battery are input into the DRT-based kinetic characteristic peak identification software, and DRT processing is performed to obtain the DRT curve of the first symmetrical battery; the Nyquist real part Z′ and the inverse value of the imaginary part -Z″ in the EIS fitting processing results of the second symmetrical battery are input into the DRT-based kinetic characteristic peak identification software, and DRT processing is performed to obtain the DRT curve of the second symmetrical battery.

[0077] Step 5. Characteristic peak interpretation

[0078] Based on the DRT curve of the first symmetrical battery, the kinetic characteristic peaks are interpreted to obtain different kinetic characteristic peak identification results based on the relaxation time distribution of the first symmetrical battery; based on the DRT curve of the second symmetrical battery, the kinetic characteristic peaks are interpreted to obtain different kinetic characteristic peak identification results based on the relaxation time distribution of the second symmetrical battery;

[0079] Step 6. Integrate the characteristic peaks corresponding to different kinetic processes (characteristic peaks of the SEI membrane process and characteristic peaks of the charge transfer process) in the DRT curve of the first symmetric battery and the DRT curve of the second symmetric battery to obtain two sets of peak area values. By calculating the peak area ratio of the same kinetic process, the difference in the change of the kinetic process during the cycle process can be determined, which can help identify which process is the main kinetic problem that causes the deterioration of the cycle performance.

[0080] Specifically, the characteristic peaks of the SEI film process and the charge transfer process before the target battery cycle are integrated, and the corresponding integral area is recorded as x 1 and 1 ; Integrate the characteristic peaks of the SEI film process and the charge transfer process after the target battery cycle, and the corresponding integral area is recorded as x 2 and 2 Compare the peak area ratio x of the SEI film process before and after the cycle 2 / x 1 , and the peak area ratio of the charge transfer process before and after the cycle y 2 / y 1 The size between , can be used to determine which kinetic process is the main cause of performance degradation. 2 / x 1 Greater than y 2 / y 1 , then the SEI film process is judged to be the main cause of battery performance degradation; if x 2 / x 1 Less than y 2 / y 1 , it is judged that the charge transfer process is the main reason for the battery performance degradation.

[0081] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0082] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for evaluating electrode material kinetics, characterized in that: The following steps are involved: Step 1. Symmetrical battery assembly, wherein the symmetric battery comprises a first symmetric battery and a second symmetric battery; Step 2. Performing an AC impedance spectrum test on the symmetrical battery to obtain an AC impedance spectrum; Step 3. Fitting the AC impedance spectrum based on an equivalent impedance model to obtain a Nyquist curve; Step 4. performing relaxation time distribution processing on the Nyquist curve to obtain a relaxation time distribution curve; Step 5. Perform kinetic characteristic peak interpretation based on the relaxation time distribution curve to obtain different kinetic characteristic peak identification results based on the relaxation time distribution; Step 6. Perform peak integration and calculation on the kinetic characteristic peak in the relaxation time distribution curve, and output the kinetic interpretation result corresponding to the kinetic characteristic peak by comparing the calculation results of the kinetic characteristic peak at the same position between the first symmetric battery and the second symmetric battery.

2. The electrode material kinetics evaluation method according to claim 1, characterized in that: In step 1, the symmetrical battery is assembled in an environment where the water and oxygen contents are both less than 0.05 ppm, and then left to stand.

3. The electrode material kinetics evaluation method according to claim 2, characterized in that: The standing time in step 1 is more than 6 hours.

4. The electrode material kinetics evaluation method according to claim 1, characterized in that: In step 2, the symmetrical battery is subjected to an AC impedance spectrum test in a constant temperature environment of 20-30° C., the test frequency is 100 kHz-100 MHz, and the disturbance voltage is 9-11 mV.

5. The electrode material kinetics evaluation method according to claim 1, characterized in that: Step 4 specifically includes: inputting the real part Z′ and the inverse value of the imaginary part -Z″ in the Nyquist curve into the dynamic characteristic peak identification software based on relaxation time distribution, performing relaxation time distribution processing, and obtaining the relaxation time distribution curve.

6. The electrode material kinetics evaluation method according to claim 1, characterized in that: In step 6, outputting the kinetic interpretation result corresponding to the kinetic characteristic peak specifically includes: analyzing the kinetic changes between different electrode materials, or analyzing the kinetic changes of the same target battery at different cycle stages or under different working environments.

7. The electrode material kinetics evaluation method according to claim 6, characterized in that: In step 6, when analyzing the kinetic changes between different types of electrode materials, the first symmetrical battery is a symmetrical battery assembled with a first electrode material, and the second symmetrical battery is a symmetrical battery assembled with a second electrode material; the characteristic peak of the SEI film process of the first symmetrical battery is integrated and calculated, and the corresponding integrated area is recorded as x1; the characteristic peak of the SEI film process of the second symmetrical battery is integrated and calculated, and the corresponding integrated area is recorded as x2, and the ratio x1 / x2 is calculated; if x1 / x2 is less than 1, it is judged that the SEI film process kinetics of the first electrode material is better; if x1 / x2 is greater than 1, it is judged that the SEI film process kinetics of the second electrode material is better.

8. The electrode material kinetics evaluation method according to claim 6 or 7, characterized in that: In step 6, when analyzing the kinetic changes between different types of electrode materials, the first symmetrical battery is a symmetrical battery assembled with a first electrode material, and the second symmetrical battery is a symmetrical battery assembled with a second electrode material; the characteristic peak of the charge transfer process of the first symmetrical battery is integrated and calculated, and the corresponding integrated area is recorded as y1; the characteristic peak of the charge transfer process of the second symmetrical battery is integrated and calculated, and the corresponding integrated area is recorded as y2, and the ratio y1 / y2 is calculated; if y1 / y2 is less than 1, it is judged that the charge transfer process kinetics of the first electrode material is better; if y1 / y2 is greater than 1, it is judged that the charge transfer process kinetics of the second electrode material is better.

9. The electrode material kinetics evaluation method according to claim 6, characterized in that: In step 6, when analyzing the kinetic changes of the same target battery at different cycle stages, the first symmetrical battery is a symmetrical battery assembled after disassembling the target battery before the cycle, and the second symmetrical battery is a symmetrical battery assembled after disassembling the target battery after the cycle; the SEI film process characteristic peak and the charge transfer process characteristic peak of the first symmetrical battery are integrated and calculated, and the corresponding integrated areas are recorded as x1 and y1 respectively; the SEI film process characteristic peak and the charge transfer process characteristic peak of the second symmetrical battery are integrated and calculated, and the corresponding integrated areas are recorded as x2 and y2 respectively; compare the ratio x2 / x1 with the ratio y2 / y1, if x2 / x1 is greater than y2 / y1, it is judged that the SEI film process is the main reason for the performance degradation of the target battery; if x2 / x1 is less than y2 / y1, it is judged that the charge transfer process is the main reason for the performance degradation of the target battery.

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