Method for evaluating storage performance of battery cell

Abstract

The invention provides a method for evaluating the storage performance of a battery cell. Specifically, the evaluation method comprises the following steps: acquiring the initial capacity of a battery cell; based on a preset storage method and a test method, storing the battery cell and testing the discharge capacity of at least one storage period; according to the initial capacity and the discharge capacity of any storage period, determining a battery cell capacity recovery rate of the corresponding storage period; the test method comprises an acceleration method, and the acceleration method comprises the following steps: continuously discharging for a first preset duration under a preset voltage; wherein the preset voltage is smaller than the minimum working voltage of the battery cell. According to the embodiment of the invention, the battery cell is controlled to continuously discharge for the first preset duration under the preset voltage, so that the capacity loss is accelerated, the capacity distinction degree in unit time is improved, the storage capacity recovery rate difference of different design battery cells is identified in a shorter time, and the iteration period is shortened.

Description

Technical Field

[0001] The present disclosure relates to the field of battery technology, and in particular to a method for evaluating storage performance of a battery cell. Background Art

[0002] Cycle life and calendar life are important indicators for evaluating the performance of lithium-ion batteries. Among them, the evaluation object of calendar life is the capacity decay of the battery during long-term storage. At present, the industry often uses the method of testing the high-temperature storage capacity recovery rate of the battery cell to measure the calendar life of the battery. The specific method is: first, after the battery is fully charged, it is placed at a certain temperature (such as 60°C, 85°C and other high temperatures) for a certain period of time (such as 15 days), and then the battery is cooled to room temperature. Use a current of 0.333C for three cycles of charge and discharge in the battery operating voltage range, and use the last discharge capacity as the storage recovery capacity. The ratio of the last discharge capacity to the initial capacity of the battery is the storage capacity recovery rate. The above process is usually regarded as a storage test cycle. Since electric vehicles have high requirements for calendar life, the storage performance test often requires multiple cycles of testing, with a total time of up to 1 to 2 years, which consumes a lot of time. Summary of the invention

[0003] In view of this, the purpose of the present disclosure is to provide a method for evaluating the storage performance of a battery cell.

[0004] Based on the above purpose, the present disclosure provides a method for evaluating the storage performance of a battery cell, comprising:

[0005] Get the initial capacity of the battery cell;

[0006] Based on a preset storage method and test method, storing the battery cell and testing the discharge capacity of at least one storage cycle;

[0007] According to the initial capacity and the discharge capacity of any storage cycle, the cell capacity recovery rate of the corresponding storage cycle is determined; wherein,

[0008] The testing method includes an acceleration method, which includes: continuously discharging for a first preset time period at a preset voltage; wherein the preset voltage is less than the minimum operating voltage of the battery cell.

[0009] In some embodiments, the storage method includes storing the battery cell at a preset temperature for a second preset time period after the battery cell is fully charged.

[0010] In some embodiments, the acceleration method further includes: discharging the battery cell from a fully charged state to a preset voltage in a constant current discharge manner.

[0011] In some embodiments, the difference between the minimum operating voltage and the preset voltage is ≥0.5V.

[0012] In some embodiments, the acceleration method is applied to at least one storage cycle and the acceleration method is executed at least once in the storage cycle.

[0013] In some embodiments, the acceleration method is executed no more than 5 times in any storage cycle.

[0014] In some embodiments, the testing method further comprises a detection method; the detection method comprises:

[0015] The battery cell is discharged from a fully charged state to a minimum operating voltage in a constant current discharge manner, and the discharge capacity of the battery cell is detected.

[0016] In some embodiments, the first preset time length is 5 to 30 minutes.

[0017] In some embodiments, the positive electrode material of the battery cell is a ternary positive electrode material; and the preset voltage is 2.0V to 2.3V.

[0018] In some embodiments, the testing method further includes a charging process; the charging process includes constant current charging and constant voltage charging.

[0019] From the above, it can be seen that the present disclosure provides a method for evaluating the storage performance of a battery cell, which controls the battery cell to discharge continuously for a first preset time at a preset voltage; wherein the preset voltage is less than the minimum operating voltage of the battery cell, thereby accelerating the capacity loss and improving the capacity differentiation per unit time, thereby accurately identifying the differences in storage capacity recovery rates of battery cells of different designs in a shorter time and shortening the iteration cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the present disclosure or related technologies, the drawings required for use in the embodiments or related technical descriptions are briefly introduced below. Obviously, the drawings described below are only embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 A schematic flow chart of a method for evaluating storage performance of a battery cell provided in an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0022] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0023] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present disclosure should be understood by people with ordinary skills in the field to which the present disclosure belongs. The "first", "second" and similar words used in the embodiments of the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. "Including" or "comprising" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0024] In order to facilitate understanding of the technical solutions of the present disclosure, some technical terms involved in the present disclosure are introduced below.

[0025] Calendar life refers to the service life of a battery when it is left unused.

[0026] Storage means that the battery is left motionless at a certain state of charge (SOC) and temperature.

[0027] Capacity calibration refers to determining the actual capacity of a battery under specific conditions through charge and discharge tests.

[0028] "C number" refers to the discharge rate of the battery, which indicates the ratio of the current intensity that the battery can release in a specific time to the battery capacity. Specifically, 1C means the current intensity when the battery is fully discharged in one hour, 2C means the current intensity when it is fully discharged in half an hour, and 0.5C means the current intensity when it is fully discharged in two hours. For example, for a battery with a capacity of 1200mAh, the current is 1200mA when discharged at 1C, and the current is 2400mA when discharged at 2C.

[0029] Constant current (CC) charging means that the current value is constant and the battery voltage rises.

[0030] Constant current discharge means that the current value is constant and the voltage decreases.

[0031] Constant current and constant voltage (CV) process: It includes two stages: constant current and constant voltage. First, the current is charged (discharged) at a constant level until the voltage reaches a certain cut-off voltage, and then the voltage is charged (discharged) at a constant level to a certain cut-off current.

[0032] The cell voltage range refers to the operating voltage range of a battery or battery pack, specifically the interval between the maximum voltage (corresponding to the maximum operating voltage) and the minimum voltage (corresponding to the minimum operating voltage) at which the cell can work normally. Outside the voltage range of the cell, the cell may not work properly, or even pose a safety hazard. For example, the cell voltage range for lithium-ion batteries can be 2.5V to 4.2V. When the cell voltage is lower than 2.5V, the battery enters a protection state to prevent over-discharge of the cell. When the cell voltage is higher than 4.2V, in order to protect the safety and life of the cell, a charging management system is generally used for charging control.

[0033] As mentioned in the background technology section, electric vehicles have high requirements for calendar life, and storage performance testing often requires multiple cycles of testing, with a total time of up to 1 to 2 years. In such a test process, by comparing the capacity recovery rates of battery cells with different designs, the advantages and disadvantages of different designs can be evaluated. However, the 1 to 2 years of testing time not only takes up a lot of resources but also greatly prolongs the product iteration cycle, resulting in a long development cycle.

[0034] In order to speed up product iteration and shorten the development cycle, it is urgent to develop more efficient evaluation methods for battery cell storage performance.

[0035] The inventors of the present disclosure have analyzed the relevant technologies and noticed that in the later stages of battery development, the short-term differences in storage performance of cells of different designs are usually small. For example, the capacity retention rate of the two solutions after one year of storage is 2%, which may be less than 0.2% when converted to one month according to the linear trend. Therefore, short-term data can basically not distinguish the advantages and disadvantages of the two solutions. In other words, if an improved solution that directly shortens the test cycle is adopted, it is impossible to effectively evaluate the performance of cells of different designs.

[0036] In view of this, the inventor changed his thinking and analyzed the battery attenuation mechanism during storage. It was found that during long-term storage, the capacity attenuation of the battery comes from active lithium loss, positive and negative electrode capacity loss and kinetic loss. Among the three losses, active lithium loss accounts for the main part of the battery capacity loss. Active lithium refers to the reversible lithium inventory in the battery. When the battery is in a discharged state, the active lithium is stored in the positive electrode of the battery. When the battery is in a charged state, the active lithium is stored in the negative electrode of the battery. Usually, the battery is stored with charge (in most cases, fully charged). In the storage state, the active lithium in the battery exists in the negative electrode in the form of lithiated graphite (LiC6). The potential of lithiated graphite is between 0.05 and 0.2V based on the ratio of Li+ / Li. It is in a strong reduction state and is very easy to react with the electrolyte (solvent, represented by Sol), resulting in oxidation of the lithiated graphite, that is, LiC6+xSol→Li1-xC6+xLiSol reaction, forming a solid electrolyte interface (Solid ElectrolyteInterface, referred to as SEI), where its main component is LiSol. Obviously, this reaction will lead to the loss of active lithium in the negative electrode, resulting in capacity decay. It can be seen that the storage capacity loss of the battery mainly comes from the side reactions of the negative electrode and the electrolyte, and the side reactions come from the solvent passing through the SEI and the reaction of LiC6, and its reaction rate depends on the integrity of the SEI. If the stability of the SEI during storage is reduced, the side reactions of the negative electrode and the electrolyte can be accelerated, thereby accelerating the difference in short-term internal capacity loss.

[0037] Based on the above analysis, the inventors of the present invention propose a method for evaluating the storage performance of a battery cell, by controlling the battery cell to discharge continuously for a first preset time at a preset voltage during the capacity calibration process after storage; wherein the preset voltage is lower than the minimum operating voltage of the battery cell, thereby causing the SEI to partially decompose at a high potential and reducing the SEI stability, thereby accelerating the capacity loss and improving the capacity differentiation per unit time, thereby accurately identifying the differences in storage capacity recovery rates of battery cells of different designs in a shorter time and shortening the iteration cycle.

[0038] Figure 1 A schematic diagram showing a flow chart of a method for evaluating the storage performance of a battery cell provided by an embodiment of the present disclosure is shown. Figure 1 As shown, the evaluation method includes:

[0039] S101: Obtaining the initial capacity of the battery cell.

[0040] The present disclosure uses a ternary lithium battery as an example to illustrate the initial capacity test method, wherein the standard voltage of the ternary lithium battery is 3.7V, the minimum discharge voltage is 2.8V, and the maximum charge voltage is 4.25V.

[0041] The test method includes a charging process and a first discharging process.

[0042] Exemplarily, the charging process may be: charging the battery cell at 25° C. and leaving it to stand for a certain period of time (e.g., 30 minutes). Optionally, the charging condition may be first charging at a constant current of 0.333C to 4.25V, and then charging at a constant voltage of 4.25V to 0.05C.

[0043] Exemplarily, the first discharge process may be: discharging the battery cell and leaving it to stand for a certain period of time (eg, 30 minutes). Optionally, the discharge condition may be 0.333C constant current discharge to 2.8V.

[0044] After cycling the above charging and discharging process three times, the discharge capacity of the battery cell is detected and recorded as C0.

[0045] It should be noted that the number of the above cycles can be set as needed, and the present disclosure does not limit this.

[0046] It should be noted that those skilled in the art may adjust the above-mentioned charging and discharging conditions according to different types of battery cells, and the present disclosure does not limit this.

[0047] S103: Based on a preset storage method and test method, the battery cell is stored and the discharge capacity of at least one storage cycle is tested.

[0048] In some embodiments, the storage method includes storing the battery cell at a preset temperature for a second preset time after the battery cell is fully charged. It should be noted that the method of fully charging the battery cell can refer to the charging condition of step S101, which will not be repeated.

[0049] Optionally, the preset temperature may be 55° C. to 90° C., such as 60° C., 85° C., etc. Here, by storing the battery cells in a thermostat, the temperature of the battery cells may be conveniently controlled to be in a preset temperature environment.

[0050] Optionally, the second preset time period may be 10 to 20 days, for example, 10 days, 15 days, or 20 days.

[0051] It should be noted that the above storage method can be performed once as a storage cycle. During the evaluation process, multiple storage cycles can be performed on the battery cell, such as 1, 2, 5, 10, 20, etc.

[0052] In some embodiments, the storage method further includes cooling the battery cell, and the cooling time may be 2 hours to 4 hours, for example, 2.5 hours, 3 hours, 3.5 hours, etc.

[0053] In some embodiments, the testing method includes an acceleration method and a detection method.

[0054] Furthermore, the acceleration method includes a charging process and a second discharging process, wherein the charging process is similar to S101 and will not be described in detail.

[0055] Exemplarily, the second discharging process includes:

[0056] Discharging the battery cell from a fully charged state to a preset voltage in a constant current discharge manner;

[0057] The battery is continuously discharged for a first preset time period at a preset voltage, wherein the preset voltage is less than a minimum operating voltage of the battery cell.

[0058] Furthermore, the difference between the minimum operating voltage and the preset voltage is ≥ 0.5 V. Such a voltage difference can ensure the rate of partial decomposition of SEI and reduce SEI stability, thereby accelerating capacity loss and improving capacity differentiation per unit time.

[0059] Taking ternary lithium battery as an example, the minimum working voltage is 2.8V, then the preset voltage can be 2.3V, 2.2V, 2.15V, 2.0V, etc. Optionally, the preset voltage is 2.0V to 2.3V. If it is lower than 2.0V, the stability of the battery cell electrode will be affected; if it is higher than 2.3V, the SEI decomposition degree is insufficient and the acceleration efficiency is poor.

[0060] Optionally, the first preset time is 5 to 30 minutes, such as 5 minutes, 10 minutes, 15 minutes, 20 minutes, 30 minutes, etc. If the first preset time is less than 5 minutes, the preset voltage does not act on the battery cell for a long time, and SEI is difficult to decompose; if the first preset time is longer than 30 minutes, SEI decomposition has reached a balanced state, and increasing the time is unlikely to produce better results. Optionally, the first preset time is 5 to 10 minutes.

[0061] It should be understood that the above acceleration method is applied to at least one storage cycle and the acceleration method is executed at least once in the storage cycle. In other words, in multiple storage cycles, the acceleration method can be executed in each storage cycle, or in selected storage cycles. When executing the acceleration method, the acceleration method can be executed once in one storage cycle, or the charging process and the second discharging process of the acceleration method can be executed cyclically (i.e., the acceleration method is executed multiple times).

[0062] Optionally, the acceleration method is executed no more than 5 times in any storage cycle, for example, 2 times, 3 times, etc. Here, if the execution times are within 5 times, SEI has a better degradation effect, and there is no need to continue to increase the execution times.

[0063] Taking ternary lithium batteries as an example, the acceleration method can be to charge the battery cell at 25°C and let it stand for a certain time (for example, 30 minutes). Optionally, the charging condition can be to first charge to 4.25V at a constant current of 0.333C, and then charge to 0.05C at a constant voltage of 4.25V. After standing, discharge the battery cell and let it stand for a certain time (for example, 30 minutes). Optionally, the discharge condition can be to discharge to 2.2V at a constant current of 0.333C, and then maintain a constant voltage discharge of 2.2V for 10 minutes.

[0064] In some embodiments, the detection method includes a charging process and a third discharging process. The charging process can refer to the charging process of S101; the third discharging process can be to discharge the battery cell from a fully charged state to a minimum operating voltage, such as 2.8V of a ternary lithium battery, in a constant current discharge manner. It should be noted that the third discharging process can refer to the first discharging process of S101 and will not be repeated.

[0065] It should be noted that those skilled in the art may choose to measure the discharge capacity of each storage cycle, or may choose to measure the discharge capacity of part of the storage cycle, and the measured discharge capacity is recorded as C n Here, n represents the number of storage cycles. For example, C1 represents the discharge capacity after one storage cycle; C5 represents the discharge capacity after five storage cycles.

[0066] If the storage cycle executes the acceleration method, the charging process and the third discharge process of the detection method can be executed after the acceleration method, and then the discharge capacity of the battery cell at this time can be detected. If the storage cycle does not execute the acceleration method, the charging process and the third discharge process of the detection method can be executed cyclically, for example, 3 times, and the discharge capacity of the battery cell can be detected for the last time. When a storage cycle is neither accelerated nor detected, it can directly enter the next storage cycle.

[0067] It should be noted that, during the evaluation process, each charging (discharging) process may be left to stand for a certain period of time, such as 30 minutes.

[0068] S105: Determine a cell capacity recovery rate for a corresponding storage cycle according to the initial capacity and the discharge capacity of any storage cycle.

[0069] For example, the cell capacity recovery rate C r =C n / C0×100%.

[0070] Example

[0071] Hereinafter, embodiments of the present disclosure are described. The embodiments described below are exemplary and are only used to explain the present disclosure, and should not be construed as limiting the present disclosure. If specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in the art or the product instructions are used. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially.

[0072] Evaluation object

[0073] Cell A: LiNi is used as the positive electrode material 0.9 Co 0.1 Mn 0.1 O2, artificial graphite is used as the negative electrode material, and the electrolyte composition is 1M LiPF6 dissolved in a solvent of EC:EMC=3:7 (mass ratio). Among them, EC is ethylene carbonate and EMC is ethyl methyl carbonate.

[0074] Cell B: The difference from cell A is that the electrolyte composition is 1M LiPF6 dissolved in a solvent with EC:EMC=3:7 (mass ratio), and then VC accounting for 2% of the total mass of the electrolyte is added as an additive. Among them, VC is vinylene carbonate.

[0075] Example 1

[0076] (1) Obtaining the initial capacity

[0077] Place the battery cell in a constant temperature box and adjust the temperature of the constant temperature box to 25℃. After standing for 30 minutes, charge it to 4.25V at a constant current of 0.333C. Charge it to a current of 0.05C at a constant voltage of 4.25V and stand for 30 minutes. Then, discharge it to 2.8V at a constant current of 0.333C (DC). The discharge capacitance at this time is recorded as C0.

[0078] (2) Store and detect the discharge capacity C of each storage cycle n

[0079] After step (1) the test is completed, let it stand for 30 minutes and then perform the following steps:

[0080] 2.1 Storage

[0081] Charge to 4.25V at a constant current of 0.333C, charge to a current of 0.05C at a constant voltage of 4.25V, adjust the incubator temperature to 60°C, store for 15 days, and cool for 3 hours;

[0082] 2.2 Acceleration

[0083] The temperature of the constant temperature box was adjusted to 25°C. After standing for 30 minutes, the battery was charged to 4.25V at a constant current of 0.333C, and then charged to a current of 0.05C at a constant voltage of 4.25V, and then stood for 30 minutes. Then, the battery was discharged (DC) to 2.2V at a constant current of 0.333C, and then discharged at a constant voltage of 2.2V for 10 minutes, and then stood for 30 minutes.

[0084] The charging and discharging steps in 2.2 were cycled twice.

[0085] 2.3 Detection

[0086] Charge to 4.25V at a constant current of 0.333C, charge to a current of 0.05C at a constant voltage of 4.25V, and let stand for 30 minutes; then, discharge (DC) to 2.8V at a constant current of 0.333C, and record the discharge capacitance at this time as C1.

[0087] Execute steps 2.1 to 2.3 three times in a cycle, and detect the discharge capacitors C2, C3, and C4 after 2, 3, and 4 cycles of storage.

[0088] (3) Determine the cell capacity recovery rate

[0089] The capacity recovery rate corresponding to each storage cycle is determined based on C0, C1, C2, C3 and C4, and the results are shown in Table 1.

[0090] Example 2

[0091] The difference between this embodiment and embodiment 1 is that in step 2.2, the battery is discharged at a constant current of 0.333C to 2.3V, and then discharged at a constant voltage of 2.3V for 5 minutes.

[0092] Example 3

[0093] The difference between this embodiment and embodiment 1 is that in step 2.2, the battery is discharged at a constant current of 0.333C to 2.2V, and then discharged at a constant voltage of 2.2V for 30min.

[0094] Comparative Example 1

[0095] The difference between this comparative example 1 and embodiment 1 is that after each storage, 2.2 is omitted, and the charging and discharging process of 2.3 is cycled four times. After the last discharge, the discharge capacitance is detected and recorded as C n ; and the number of storage cycles is different.

[0096] Table 1

[0097]

[0098] As can be seen from Table 1, compared with Comparative Example 1, using the evaluation method provided in the embodiment of the present disclosure, both battery cell A and battery cell B show a significant decrease in capacity recovery rate after the first storage cycle. For battery cell A, the capacity recovery rate after 4 storage cycles in Example 1 is close to the capacity recovery rate after 9 storage cycles in Comparative Example 1; for battery cell B, the capacity recovery rate after 4 storage cycles in Example 1 is close to the capacity recovery rate after 7 storage cycles in Comparative Example 1. It can be seen that using the battery cell storage performance evaluation method provided in the present disclosure, it is possible to discover the performance differences between battery cells using fewer cycle cycles, saving time for iterative research on battery cells.

[0099] It can be seen from Examples 1 and 2 that the shorter the first preset time and the higher the preset voltage, the longer the time (period) that the A and B battery cells show performance differences. Therefore, lowering the preset voltage and increasing the first preset time are conducive to discovering the difference in battery cell performance in fewer storage cycles; it can be seen from Examples 1 and 3 that the longer the first preset time, the shorter the time that the two battery cells show performance differences (i.e., the fewer the number of cycle periods), but the acceleration effect brought by 30 minutes is limited compared to 10 minutes, so the first preset time can complete the acceleration effect within 30 minutes.

[0100] In addition, by comparing the storage capacity recovery rate change trends of battery cells A and B in the embodiments of the present application with those in the comparative examples, it can be seen that the battery cell storage performance evaluation method provided by the present invention can reduce the impact of changes in the test process on the observed parameter change trends while accelerating the test, thereby obtaining more accurate test results.

[0101] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present disclosure (including the claims) is limited to these examples. Based on the concept of the present disclosure, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the embodiments of the present disclosure as described above, which are not provided in detail for the sake of simplicity.

[0102] In addition, to simplify the description and discussion, and in order not to make the embodiments of the present disclosure difficult to understand, the known power / ground connections to the integrated circuit (IC) chips and other components may or may not be shown in the provided figures. In addition, the device can be shown in the form of a block diagram to avoid making the embodiments of the present disclosure difficult to understand, and this also takes into account the fact that the details of the implementation of these block diagram devices are highly dependent on the platform on which the embodiments of the present disclosure will be implemented (that is, these details should be fully within the scope of understanding of those skilled in the art). Where specific details (e.g., circuits) are set forth to describe exemplary embodiments of the present disclosure, it is apparent to those skilled in the art that the embodiments of the present disclosure can be implemented without these specific details or with changes in these specific details. Therefore, these descriptions should be considered illustrative rather than restrictive.

[0103] Although the present disclosure has been described in conjunction with specific embodiments of the present disclosure, many replacements, modifications and variations of these embodiments will be apparent to those skilled in the art from the foregoing description. For example, other memory architectures (e.g., dynamic RAM (DRAM)) may use the embodiments discussed.

[0104] The embodiments of the present disclosure are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present disclosure should be included in the scope of protection of the present disclosure.

Claims

1. A method for evaluating the storage performance of a battery cell, characterized in that: include: Get the initial capacity of the battery cell; Based on a preset storage method and test method, storing the battery cell and testing the discharge capacity of at least one storage cycle; According to the initial capacity and the discharge capacity of any storage cycle, the cell capacity recovery rate of the corresponding storage cycle is determined; wherein, The testing method includes an acceleration method, which includes: continuously discharging for a first preset time period at a preset voltage; wherein the preset voltage is less than the minimum operating voltage of the battery cell.

2. The evaluation method according to claim 1, characterized in that: The storage method includes storing the battery cell at a preset temperature for a second preset time after the battery cell is fully charged.

3. The evaluation method according to claim 1, characterized in that: The acceleration method further includes: discharging the battery cell from a fully charged state to a preset voltage in a constant current discharge manner.

4. The evaluation method according to claim 1, characterized in that: The difference between the minimum operating voltage and the preset voltage is ≥0.5V.

5. The evaluation method according to claim 1, characterized in that: The acceleration method is applied to at least one storage cycle and the acceleration method is executed at least once in the storage cycle.

6. The evaluation method according to claim 5, characterized in that: The acceleration method is executed no more than 5 times in any storage cycle.

7. The evaluation method according to claim 1, characterized in that: The test method also includes a detection method; the detection method includes: The battery cell is discharged from a fully charged state to a minimum operating voltage in a constant current discharge manner, and the discharge capacity of the battery cell is detected.

8. The evaluation method according to claim 1, characterized in that: The first preset time length is 5 to 30 minutes.

9. The evaluation method according to claim 1, characterized in that: The positive electrode material of the battery cell is a ternary positive electrode material; the preset voltage is 2.0V to 2.3V.

10. The evaluation method according to claim 1, characterized in that: The testing method also includes a charging process; the charging process includes constant current charging and constant voltage charging.

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