Method for testing cycle performance of battery negative electrode material

Abstract

The invention discloses a method for testing the cycle performance of a battery negative electrode material, and the method comprises the steps: carrying out the activation pretreatment of a to-be-tested battery, so as to enable the battery to reach an initial stable state in which a charge-discharge cycle test can be carried out; charging and discharging the to-be-tested battery at a preset test current density until the number of cycles reaches a preset cycle termination period number, and in the charging and discharging cycle process, calculating the specific capacity retention ratio and the intrinsic current of the negative electrode material of the to-be-tested battery in the current charging and discharging period every first preset period to obtain the specific capacity retention ratio of the negative electrode material of the to-be-tested battery. Calculating the dynamic capacitance coupling attenuation coefficient of the negative electrode material in the current charging and discharging period based on the specific capacity retention ratio and the intrinsic current; and constructing a battery attenuation model based on the plurality of dynamic capacitance coupling attenuation coefficients obtained by calculation so as to evaluate the cycle performance of the negative electrode material of the to-be-tested battery. Based on the test method, the test efficiency of the negative electrode material is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of negative material cycle performance test, and particularly relates to a test method for cycle performance of battery negative material. BACKGROUND

[0002] At present, new energy storage batteries such as lithium ion batteries and sodium ion batteries have been widely used in the fields of automobile and aviation transportation power. The performance of the energy storage battery depends largely on the characteristics of its negative material. As a key component of the battery, the negative material directly determines the capacity, cycle life and rate performance of the battery. During the charging and discharging process of the battery, lithium ions (or sodium ions) are repeatedly embedded and extracted in the negative material, which is accompanied by the electrochemical reaction of the interface and the generation of by-products, which can easily lead to the destruction of the structure of the negative material. The broken interface will further react with the electrolyte to continuously form an unstable solid electrolyte interface film (SEI film), and even cause the separation between the active material and the current collector, thereby accelerating the decay of the reversible capacity of the battery.

[0003] In order to improve the electrochemical performance of the negative material, researchers usually improve it from the aspects of shape control and structure design, in order to enhance its structural stability, and then improve the cycle performance of the negative material. However, in the material research and development stage, the evaluation of the cycle performance of the negative material still depends on the full battery cycle test under constant rate for many weeks and long periods. This method has long test period and high time cost, which is not conducive to the improvement of research efficiency, and it is difficult to realize the independent and rapid characterization of the cycle performance of the single negative material. Therefore, it has become a technical problem to be solved in the field to establish a method for quickly and accurately evaluating the cycle stability of the negative material at the material level. SUMMARY

[0004] The purpose of the present application is to provide a test method for the cycle performance of battery negative material, which can accelerate the test efficiency of the cycle performance of the negative material.

[0005] To achieve the above purpose, the present application discloses a test method for the cycle performance of battery negative material, comprising: activating the to-be-tested battery for pretreatment, so that the battery reaches an initial stable state for charging and discharging cycle test; charging and discharging the to-be-tested battery at a preset test current density until the cycle number reaches a predetermined termination cycle period, and during the charging and discharging cycle process, every interval of the first predetermined period, the specific capacity retention rate and the intrinsic current of the negative material of the to-be-tested battery in the current charging and discharging period are calculated, and the dynamic capacity coupling attenuation coefficient of the negative material in the current charging and discharging period is calculated based on the specific capacity retention rate and the intrinsic current; A battery attenuation model is constructed based on the calculated several dynamic contact coupling attenuation coefficients, so as to evaluate the negative electrode material cycle performance of the battery to be tested.

[0006] Specifically, the step of the activation pretreatment comprises: The battery to be tested is placed under predetermined environmental conditions for a first preset duration; Based on the preset first current density and the second current density, the battery to be tested is subjected to at least one cycle of charge and discharge operation; The battery to be tested is again placed under the predetermined environmental conditions for a second preset duration.

[0007] Specifically, the step of calculating the specific capacity retention rate of the negative electrode material of the battery to be tested comprises: The initial specific capacity of the negative electrode material is calculated, which is the specific capacity calculated in the first charge and discharge cycle of the battery to be tested; Taking the initial specific capacity as a reference, the ratio of the specific capacity of the negative electrode material in the current cycle to the initial specific capacity is calculated every first predetermined period, to obtain the specific capacity retention rate of the current charge and discharge cycle.

[0008] Further, the specific capacity is the mass specific capacity of the negative electrode material.

[0009] Specifically, the step of calculating the intrinsic current of the negative electrode material of the battery to be tested comprises: Taking the second charge and discharge cycle as a starting point, the potential and resistance of the intrinsic electrode of the negative electrode material are tested every first predetermined period; Based on the potential and resistance of the intrinsic electrode, the intrinsic current of the negative electrode material in the current charge and discharge cycle is calculated.

[0010] Further, the step of calculating the intrinsic current of the negative electrode material of the battery to be tested comprises: In the current charge and discharge cycle, the battery to be tested is placed under a predetermined state of charge; The battery to be tested is placed under a predetermined state of charge; The potential and resistance of the negative electrode material of the battery to be tested are tested by an electrochemical workstation at a predetermined scan rate and a predetermined overpotential.

[0011] Specifically, the test method further comprises a preparation step of the battery to be tested, which comprises: An electrogel substrate is prepared, and a conductive agent and an active material are added to the electrogel substrate to obtain a negative electrode slurry; The negative electrode slurry is coated on a copper foil with a set thickness to form a negative electrode material tab with a specific thickness, and the negative electrode material tab is dried; The dried negative electrode material tab is cut and compacted to obtain a negative electrode material tab belt with a specific size and a compacted density; The negative electrode material tab belt is punched into a negative electrode material wafer and dried; In an inert gas-filled glove box, a bottom battery shell, a foam nickel, a lithium sheet, a separator, the negative electrode material wafer, and a top battery shell are sequentially stacked, and an electrolyte is added dropwise; The assembled battery is sealed using a sealing machine to obtain a battery to be tested.

[0012] Further, the specific steps of preparing the electrogel substrate and adding a conductive agent and an active material to the electrogel substrate to obtain the negative electrode slurry include: A predetermined weight of deionized water and a binder are mixed and stirred to obtain an electrogel substrate; The conductive agent is added to the electrogel substrate and high-speed stirring is performed, so that the conductive material in the conductive agent is fully dispersed and uniformly mixed in the electrogel substrate; The negative electrode active material is added to the electrogel substrate and stirred uniformly, thereby obtaining the negative electrode slurry.

[0013] Compared with the prior art, the test method for the cycle performance of the battery negative electrode material provided in the above technical solution constructs a test evaluation system from stabilization pretreatment, double-parameter synchronous monitoring to decoupling modeling, which can quickly and accurately evaluate the cycle performance of the negative electrode material. Specifically: (1) The test method ensures that all the batteries to be tested are in a uniform initial stable state through activation pretreatment, laying a foundation for subsequent evaluation.

[0014] (2) In the cycle test, the test method proposes a dynamic capacity coupling attenuation coefficient for quantifying the attenuation mechanism of the negative electrode material based on the specific capacity retention rate and the intrinsic current, the cycle performance of the negative electrode material is evaluated from the traditional end-point capacity judgment to the tracking of the full-cycle attenuation path of the negative electrode material by establishing a battery attenuation model varying with the cycle number, which enables the test to predict the quality of the negative electrode material early in the early stage of the charge and discharge cycle, greatly shortens the evaluation period, saves production cost, speeds up production and research and development, and provides direct theoretical basis for the modification direction of the negative electrode material, guides researchers to accurately optimize the structure or interface characteristics of the negative electrode material, and helps researchers to analyze and solve the problems of the battery negative electrode.

[0015] (3) The test method can be universally applied to different negative electrode materials, and can quickly realize the comparison of the cycle performance of different types of negative electrode materials. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the cycle performance of the battery negative electrode material in an embodiment of the present invention. Figure 1 .

[0017] Figure 2 This is a flowchart illustrating the cycle performance of the battery negative electrode material in an embodiment of the present invention. Figure 2 .

[0018] Figure 3 This is a flowchart illustrating the calculation of the specific capacity retention rate and intrinsic current of the battery negative electrode material in this embodiment of the invention.

[0019] Figure 4 This is a flowchart illustrating the preparation steps of the battery under test for the negative electrode material in an embodiment of the present invention.

[0020] Figure 5 This is a schematic diagram of the battery degradation curves of five negative electrode materials in an embodiment of the present invention. Detailed Implementation

[0021] To illustrate the technical content, structural features, objectives, and effects of this invention in detail, the following description, in conjunction with the embodiments and accompanying drawings, provides a comprehensive explanation. The embodiments described herein are merely illustrative of the technical solutions of this application and are therefore intended to be exemplary and should not be construed as limiting the scope of protection of this application.

[0022] This invention discloses a method for testing the cycle performance of battery anode materials, thereby accelerating the testing efficiency of battery anode materials' cycle performance. See also... Figure 1 As shown, the test method specifically includes the following steps: S1: Perform pre-activation treatment on the battery to be tested to bring it to an initial stable state suitable for charge-discharge cycle testing. In this embodiment, the battery to be tested is typically a brand-new battery that has just been manufactured.

[0023] S2: Perform charge-discharge cycles on the battery under test at a preset test current density. During the charge-discharge cycle, at each first predetermined interval, calculate the specific capacity retention rate and intrinsic current of the negative electrode material of the battery under test in the current charge-discharge cycle, and calculate the dynamic-capacitive coupling attenuation coefficient of the negative electrode material in the current charge-discharge cycle based on the specific capacity retention rate and intrinsic current.

[0024] In this embodiment, a charge-discharge cycle is defined as the discharge operation after the negative electrode material completes one charge. The specific capacity is the mass specific capacity of the negative electrode material. The specific capacity retention rate is the ratio of the specific capacity of the negative electrode material in the current charge-discharge cycle to the specific capacity of the negative electrode material in the first charge-discharge cycle, representing the degree of decay of the negative electrode material. The intrinsic current represents the intrinsic electrode activity density of the negative electrode material in the current charge-discharge cycle. The dynamic-capacitive coupling decay coefficient is the ratio of the intrinsic current to the specific capacity retention rate. The first predetermined cycle is preferably, but not limited to, 5 charge-discharge cycles. The preset test current density is preferably, but not limited to, 0.5C.

[0025] S3: Determine whether the number of cycles has reached the predetermined number of termination cycles. If yes, proceed to step S4; otherwise, return to step S2. In this embodiment, the number of termination cycles is preferably, but not limited to, 50 charge-discharge cycles.

[0026] S4: Based on several calculated dynamic-capacitive coupling attenuation coefficients, a battery attenuation model is constructed to evaluate the cycle performance of the negative electrode material of the battery under test.

[0027] During the testing of negative electrode materials, the damage to the interface of the negative electrode material intensifies with the increase of charge-discharge cycles. When the dynamic-capacitive coupling attenuation coefficient reaches a certain value, it can be considered that the negative electrode material has suffered severe irreversible damage, thus allowing for the assessment of the cycle performance of the negative electrode material. In this embodiment, the battery degradation model can be obtained by linearly fitting the specific capacity retention rate and the corresponding intrinsic current.

[0028] Compared with existing technologies, the testing method for anode materials proposed in this invention constructs a testing and evaluation system from stabilization pretreatment and dual-parameter synchronous monitoring to decoupled modeling, which can quickly and accurately evaluate the cycle performance of anode materials. Specifically: (1) This test method ensures that all the batteries under test are in a uniform initial stable state through activation pretreatment, which lays the foundation for subsequent evaluation.

[0029] (2) In the cycle test, this test method proposes a dynamic-capacitive coupling decay coefficient to quantify the decay mechanism of the negative electrode material based on two key parameters: specific capacity retention rate and intrinsic current. By establishing a battery decay model that varies with the number of cycles, this test method expands the evaluation dimension of the cycle performance of the negative electrode material from the traditional end-capacity judgment to the tracking of the full-cycle decay path of the negative electrode material. This allows the test to predict the quality of the negative electrode material in the early stages of charge-discharge cycles, significantly shortening the evaluation cycle, saving production costs, and accelerating production and R&D progress. Furthermore, it can provide a direct theoretical basis for the modification direction of the negative electrode material, guiding researchers to accurately optimize the structure or interface characteristics of the negative electrode material, and assisting R&D personnel in analyzing and solving battery negative electrode anomalies.

[0030] (3) This test method can be applied to different anode materials and quickly compare the cycling performance of different types of anode materials.

[0031] In summary, the testing method for anode materials provided by this invention not only provides clear theoretical guidance for material modification and accelerates the research and development process, but also has good universality. It can provide a reliable tool for the rapid screening and performance comparison of anode materials of different systems, effectively solving the problems of long cycle, high cost and unclear mechanism of traditional evaluation methods.

[0032] Specifically, see Figure 2 As shown, the pre-activation treatment steps specifically include: S11: Place the battery to be tested under predetermined environmental conditions and allow it to stand for a first preset duration. In this embodiment, the predetermined environmental conditions are a constant temperature and humidity environment, and the first preset duration is preferably, but not limited to, 8-10 hours. The purpose of standing under the predetermined environmental conditions is to allow the electrolyte inside the battery (especially a new battery) to fully and evenly penetrate into the pores of the internal separator and into every particle of the electrode material (including the negative electrode material), thereby forming a good ion pathway and allowing the temperature of the battery as a whole to reach equilibrium with the test environment, ensuring the consistency of subsequent tests.

[0033] S12: Perform at least one cycle of charge and discharge operation on the battery to be tested after it has been left to stand, based on the preset first current density and second current density respectively.

[0034] In this embodiment, the first current density is preferably, but not limited to, 0.1C, and the second current density is preferably, but not limited to, 0.2C. This step is the formation process of the new battery, specifically involving completing the first charge-discharge cycle of the battery based on a current density of 0.1C, and then completing another charge-discharge cycle based on a slightly higher current density of 0.2C. The purpose of this process is to form a stable and dense SEI film on the negative electrode material, and to enable ions in the negative electrode material to undergo normal reversible insertion and extraction reactions. Small current densities (0.1C, 0.2C) allow the SEI film to grow more uniformly, densely, and stably. Although the growth rate is slow, it is crucial for the long-term cycle life of the battery.

[0035] S13: Place the battery under test again under the predetermined environmental conditions and allow it to stand for a second preset duration. In this embodiment, the first preset duration is preferably, but not limited to, 3 minutes. After step S12 is completed, the battery undergoes charging and discharging, resulting in uneven ion concentration distribution and polarization, which leads to potential instability. Allowing it to stand again allows the ion concentration to redistribute evenly, restoring the potential to a stable open-circuit state.

[0036] Specifically, seeFigure 3 As shown, the calculation steps for the specific capacity retention rate of the negative electrode material of the battery under test and the calculation steps for the intrinsic current of the negative electrode material of the battery under test include: S21: Calculate the initial specific capacity of the negative electrode material. The initial specific capacity is the specific capacity of the negative electrode material of the battery under test calculated in the first charge-discharge cycle.

[0037] S22: Based on the initial specific capacity, calculate the ratio of the specific capacity of the negative electrode material in the current cycle to the initial specific capacity at each preset first predetermined period, so as to obtain the specific capacity retention rate in the current charge and discharge cycle.

[0038] S23: Starting from the second charge-discharge cycle, test the potential and resistance of the intrinsic electrode of the negative electrode material at intervals of the first predetermined cycle.

[0039] S24: Based on the intrinsic electrode potential and resistance, calculate the intrinsic current of the negative electrode material in the current charge / discharge cycle.

[0040] The calculation process for the specific capacity retention rate and intrinsic current is illustrated using a specific embodiment. Starting from the first charge-discharge cycle, this test method tests and records the initial specific capacity during the first charge-discharge cycle. Therefore, the specific capacity retention rate is calculated as follows: Subsequently, during the second charge-discharge cycle, the intrinsic electrode potential of the negative electrode material was tested. and resistance Thus, the intrinsic current can be calculated. The first dynamic capacitive attenuation coupling coefficient can then be calculated. Subsequently, during the fifth charge-discharge cycle, the current specific capacity was tested and recorded. Thus, the specific capacity retention rate can be calculated. The intrinsic electrode potential of the negative electrode material was tested during the sixth charge-discharge cycle. and resistance Thus, the dynamic-capacitive attenuation coupling coefficient can be calculated. The battery undergoes the above test process repeatedly until the 50th charge-discharge cycle, thereby obtaining several dynamic-capacitive degradation coupling coefficients. ,in The number of charging cycles, expressed as specific capacity retention rate The horizontal axis represents the dynamic-capacitive attenuation coupling coefficient. Using the vertical axis as the ordinate, the dynamic capacitance decay curve of the battery can be fitted, thus establishing a battery decay model. This embodiment utilizes the specific capacity retention rate of the negative electrode material... The dynamic-capacitive attenuation coupling coefficient corresponding to 80% The size of the material determines its cycling performance.

[0041] Furthermore, the method for testing the intrinsic electrode potential and resistance of the negative electrode material is as follows: during the current charge-discharge cycle, the battery under test is placed in a predetermined state of charge and left to stand until it reaches a stable state. Then, an electrochemical workstation is used to test the potential and resistance of the negative electrode material of the battery under test at a predetermined scan rate and a predetermined overpotential.

[0042] Specifically, this test method also includes a preparation step for the battery to be tested. This test method is to test the new battery prepared in the preparation step. See [link to relevant documentation]. Figure 4 As shown, the preparation steps include: S01: Prepare an electrolytic adhesive substrate and add conductive agents and active materials to the substrate to obtain a negative electrode slurry. The conductive agents used in preparing the negative electrode slurry include, but are not limited to, SP (conductive carbon black) and SFG-6 (flake graphite), and the active materials include, but are not limited to, graphite and other lithium-ion battery negative electrode materials.

[0043] S02: The negative electrode slurry is coated onto copper foil to a predetermined thickness to form a negative electrode material sheet with a specific thickness, and the negative electrode material sheet is then dried. In this embodiment, the coating speed of the coating machine is preferably, but not limited to, 26 cm / s to 38 cm / s; the coating thickness of the electrode sheet is, but not limited to, 100 μm to 280 μm; the drying temperature is preferably at least greater than 80°C, preferably 80 to 108°C; and the drying time is preferably, but not limited to, 3 h to 8 h.

[0044] S03: The dried negative electrode material sheets are cut and compacted to obtain negative electrode material sheet strips of specific dimensions and compaction densities. The width of the electrode sheet is preferably, but not limited to, 2.5 cm, and the compaction density is preferably, but not limited to, 1.51. ~1.55 .

[0045] S04: The negative electrode material strip is punched into negative electrode material discs and dried. The drying process is preferably carried out in a vacuum drying oven at 100°C for 2-4 hours.

[0046] S05: In a glove box filled with inert gas, stack the bottom battery casing, nickel foam, lithium sheet, separator, negative electrode material disc, and top battery casing in sequence, and add electrolyte. The electrolyte volume is preferably, but not limited to, 106~120ul.

[0047] S06: Seal the assembled battery using a sealing machine to obtain the battery to be tested. The radius of the battery is preferably, but not limited to, 5.0~8.0 mm.

[0048] Furthermore, see again Figure 4 As shown, step S01 can be further subdivided into: S011: Mix and stir a predetermined weight of deionized water and binder to obtain an electrolytic substrate. The binder used to prepare the negative electrode slurry includes, but is not limited to, L132.

[0049] S012: Add a conductive agent to the electro-adhesive substrate and stir at high speed to ensure that the conductive material in the conductive agent is fully dispersed and uniformly mixed in the electro-adhesive substrate.

[0050] S013: Add the negative electrode active material to the electrolytic substrate and stir evenly to obtain the negative electrode slurry.

[0051] In this embodiment, the preparation steps are as follows: First, 53.500g of deionized water is weighed, then 1.000g of L132 (binder) is added to the deionized water, and then the mixture is stirred at 1000-2000 rpm for 5-20 minutes using a high-speed dispersing stirrer to ensure that the binder is fully mixed in the deionized water. Next, 0.500g of SFG-6 (flake graphite) and 0.500g of SP (conductive carbon black) are added, and the mixture is stirred at 3000-5000 rpm for 25-40 minutes to obtain an electro-adhesive substrate with fully dispersed and uniformly mixed conductive materials. Subsequently, 7.000-9.000g of active material is added to the electro-adhesive substrate, and the mixture is stirred at 400-5500 rpm for 10-20 minutes. Then, the mixture is stirred at 2000-2500 rpm for 8-10 minutes using a rotary stirrer to obtain the negative electrode slurry for the battery.

[0052] The testing principle of this test method will be explained below with three specific embodiments and two specific comparative examples. The three embodiments and two comparative examples correspond to five different negative electrode materials, and the preparation methods, testing environments, and testing methods are the same for all five negative electrode materials. In this embodiment, the charge-discharge system is used to test the specific capacity of the negative electrode material at a 0.5C rate for different charge-discharge cycles. The specific capacity retention rate and dynamic capacitance decay coupling coefficient are tested and calculated every five charge-discharge cycles, and the test ends at the 50th charge-discharge cycle.

[0053] After testing and calculation, the battery degradation curve is plotted with the specific capacity retention rate corresponding to different charge and discharge cycles on the x-axis and the dynamic-capacitive degradation coupling coefficient of the negative electrode material on the y-axis. The battery degradation model formula is established, and the dynamic-capacitive degradation coupling coefficient value corresponding to 80% specific capacity retention rate is calculated. Finally, the cycle performance of the negative electrode material is judged by the magnitude of this value.

[0054] Example 1 (Negative Electrode Material No. 1):

[0055] Example 2 (Negative Electrode Material No. 2):

[0056] Example 3 (Negative Electrode Material No. 3):

[0057] Comparative Example 1 (No. 4 negative electrode material)

[0058] Comparative Example 2 (No. 5 negative electrode material)

[0059] Based on the specific capacity retention rate corresponding to different cycle periods as the x-axis and the dynamic-capacitive degradation coupling coefficient as the y-axis, a battery degradation model formula is established, and the battery degradation curve is plotted as follows: Figure 5 As shown.

[0060] from Figure 5 From this, we can conclude that: In Example 1, the dynamic-capacitive attenuation coupling coefficient corresponding to an 80% specific capacity retention rate for negative electrode material No. 1 is 359.548. .

[0061] In Example 2, the dynamic-capacitive attenuation coupling coefficient corresponding to an 80% specific capacity retention rate for the No. 2 negative electrode material is 267.808. .

[0062] In Example 3, the dynamic-capacitive attenuation coupling coefficient corresponding to an 80% specific capacity retention rate for the No. 3 negative electrode material is 266.216. .

[0063] In Comparative Example 1, the dynamic-capacitive attenuation coupling coefficient corresponding to an 80% specific capacity retention rate for anode material No. 4 is 179.08. .

[0064] In Comparative Example 2, the dynamic-capacitive attenuation coupling coefficient corresponding to an 80% specific capacity retention rate for anode material No. 5 is 56.07. .

[0065] Therefore, it can be seen that Example 1 has the largest dynamic-capacitive attenuation coupling coefficient and better cycle performance; followed by Example 2 with a dynamic-capacitive attenuation coupling coefficient of 267.808. The dynamic-capacitive attenuation coupling coefficient of Example 3 is smaller than that of Example 1, indicating that its cycling performance is inferior; the dynamic-capacitive attenuation coupling coefficient of Example 3 is approximately 266.216. This indicates that the cycle performance is worse than that of Examples 1 and 2; the dynamic capacitive attenuation coupling coefficient of Comparative Example 1 is approximately 179.08. The dynamic-capacitive attenuation coupling coefficient of Comparative Example 2 is approximately 56.07. The cycle performance is worse than that of Examples 1-3.

[0066] Therefore, the cycle performance can be obtained as follows: No. 1 negative electrode material > No. 2 negative electrode material > No. 3 negative electrode material > No. 4 negative electrode material > No. 5 negative electrode material.

[0067] By conducting the tests and calculations described above, the advantages and disadvantages of the cycle performance of the negative electrode materials can be compared.

[0068] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Although the embodiments have been described in the description and drawings of this application, this does not limit the scope of patent protection of this application. Any technical solutions resulting from equivalent structural or procedural substitutions or modifications made based on the essential concept of this application and utilizing the content described in the description and drawings of this application, as well as the direct or indirect application of the technical solutions of the above embodiments to other related technical fields, are all included within the scope of patent protection of this application.

Claims

1. A method for testing the cycle performance of a battery negative electrode material, characterized in that, include: The battery to be tested is activated and pretreated to bring it to an initial stable state suitable for charge-discharge cycle testing. The battery under test is charged and discharged at a preset test current density until the number of cycles reaches a predetermined number of termination cycles. During the charge and discharge cycle, at each first predetermined interval, the specific capacity retention rate and intrinsic current of the negative electrode material of the battery under test are calculated in the current charge and discharge cycle, and the dynamic-capacitive coupling attenuation coefficient of the negative electrode material in the current charge and discharge cycle is calculated based on the specific capacity retention rate and intrinsic current. A battery degradation model is constructed based on the calculated dynamic-capacitive coupling degradation coefficients to evaluate the cycle performance of the negative electrode material of the battery under test.

2. The method for testing the cycle performance of the battery negative electrode material according to claim 1, characterized in that, The pre-activation treatment step includes: The battery to be tested is placed under predetermined environmental conditions and left to stand for a duration of the first preset duration. Based on a preset first current density and a preset second current density, the battery under test after being left to stand is subjected to at least one cycle of charge and discharge operation. The battery to be tested is placed under the predetermined environmental conditions again and left to stand for a duration of the second preset duration.

3. The method for testing the cycle performance of the battery negative electrode material according to claim 1, characterized in that, The steps for calculating the specific capacity retention rate of the negative electrode material of the battery under test include: Calculate the initial specific capacity of the negative electrode material, which is the specific capacity of the negative electrode material of the battery under test calculated in the first charge-discharge cycle; Based on the initial specific capacity, at each preset first predetermined period, the ratio of the specific capacity of the negative electrode material in the current cycle to the initial specific capacity is calculated to obtain the specific capacity retention rate in the current charge-discharge cycle.

4. The method for testing the cycle performance of the battery negative electrode material according to claim 3, characterized in that, The specific capacity is the mass specific capacity of the negative electrode material.

5. The method for testing the cycle performance of the battery negative electrode material according to claim 1, characterized in that, The calculation steps for the intrinsic current of the negative electrode material of the battery under test include: Starting from the second charge-discharge cycle, the potential and resistance of the intrinsic electrode of the negative electrode material are tested at intervals of the first predetermined cycle. Based on the intrinsic electrode potential and resistance, the intrinsic current of the negative electrode material in the current charge-discharge cycle is calculated.

6. The method for testing the cycle performance of the battery negative electrode material according to claim 5, characterized in that, The calculation steps for the intrinsic current of the negative electrode material of the battery under test also include: During the current charge / discharge cycle, the battery under test is placed in a predetermined state of charge; Let the battery under test stand until it reaches a stable state; An electrochemical workstation was used to test the potential and resistance of the negative electrode material of the battery under test at a predetermined scan rate and a predetermined overpotential.

7. The method for testing the cycle performance of the battery negative electrode material according to claim 1, characterized in that, The testing method further includes a preparation step for the battery to be tested, the preparation step including: An electro-adhesive substrate is prepared, and a conductive agent and an active substance are added to the electro-adhesive substrate to obtain a negative electrode slurry; The negative electrode slurry is coated onto copper foil to a set thickness to form a negative electrode material sheet with a specific thickness, and the negative electrode material sheet is dried. The dried negative electrode material sheets are cut and compacted to obtain negative electrode material sheet strips of specific size and compaction density; The negative electrode material strip is punched into negative electrode material discs and then dried. In a glove box filled with inert gas, the bottom battery case, nickel foam, lithium sheet, separator, negative electrode material disc, and top battery case are stacked in sequence, and electrolyte is added. The assembled battery is sealed using a sealing machine to obtain the battery to be tested.

8. The method for testing the cycle performance of the battery negative electrode material according to claim 7, characterized in that, The specific steps for preparing the electro-adhesive substrate and adding conductive agents and active substances to the electro-adhesive substrate to obtain the negative electrode slurry include: Mix the predetermined weight of deionized water and adhesive to obtain an electro-adhesive base; A conductive agent is added to the electro-adhesive substrate and stirred at high speed to ensure that the conductive material in the conductive agent is fully dispersed and uniformly mixed in the electro-adhesive substrate; The negative electrode active material is added to the electrolytic substrate and stirred evenly to obtain the negative electrode slurry.

Images