Lithium ion battery cycle test DCR growth evaluation method and system

Abstract

The invention provides a lithium ion battery cycle test DCR growth evaluation method and system, and the method comprises the steps: entering a cycle test step, adjusting the test temperature required by the cycle, confirming that a cell is adapted to the environment, standing the cell for a specific time, charging to the upper limit of a voltage test range, and standing for a period of time, discharging to the lower limit of the voltage test range, and performing a cycle test of a certain number of turns by the above steps; performing data extraction on a loop test result; calculating the discharge DCR and / or the charge DCR of the lithium ion battery; calculating a discharge DCR growth rate and / or a charge DCR growth rate; result analysis is carried out according to the DCR growth rate and the corresponding number of turns, and the continuous DCR growth rate change trend in the circulation process can be obtained. The technical problems that the DCR cannot be detected in the battery cell circulation process, the time cost and the test resource cost are high, and the error rate of test data is high are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery testing, and particularly to a method and system for evaluating the growth of DCR in lithium-ion battery cycle testing. Background Art

[0002] With the rapid development of human society, the wind power energy storage industry has great development potential, which promotes the research and development of lithium-ion batteries. At present, lithium-ion batteries have problems such as high cost, poor safety performance, and short cycle life. The direct current internal resistance (DCR) can reflect the service life and health status of the battery. Through the DCR results, we can judge the performance of the battery internal resistance consistency, the impedance value of the welding or connection end, and the battery discharge power, and can analyze whether the heat generation during the use of the battery affects the safety during use.

[0003] At present, most of the DCR tests involved in the lithium-ion cell cycle test are carried out separately before and after the cycle, or the cycle is paused after a fixed number of cycles, and after the DCR test is completed, the cycle test is resumed after the test is completed. The above solutions cannot detect the DCR during the cell cycle, cannot obtain the continuous change trend, and waste time and resources. There will be uncertainties during the test switching process, which will affect the test progress and increase the data error rate.

[0004] The existing invention patent application document "Method and Device for Calibrating Direct Current Internal Resistance during Lithium-Ion Battery Cycling" with the publication number CN113884883A. The existing method includes: obtaining the direct current internal resistance DCR1 of the first week cycle and the corresponding temperature value T1 of all experimental batteries tested at the same temperature, and the direct current internal resistance DCRN of the Nth week cycle and the corresponding temperature value TN; calculating the DCR growth rate and the temperature change value; performing curve fitting on the DCR growth rate and the temperature change value of all experimental batteries to obtain the relationship between the temperature change value and the DCR growth rate. The DCR decay during the cycle process in the foregoing prior art can only be tested at fixed intervals or before and after the cycle, and the amount of data is small. The DCR growth change trend will be affected by the DCR test frequency, but a high frequency will lead to a poor continuity of the cycle test.

[0005] In summary, the prior art has technical problems such as being unable to detect the DCR during the cell cycle, high time cost and test resource cost, and a high error rate of test data. Summary of the Invention

[0006] The technical problem to be solved by the present invention is: how to solve the technical problems in the prior art that the DCR cannot be detected during the cell cycle, the time cost and the test resource cost are high, and the error rate of the test data is high.

[0007] The present invention solves the above technical problems by adopting the following technical solutions: A method for evaluating the DCR growth during the cycle test of a lithium-ion battery includes:

[0008] S1. Enter the cycle test step, adjust the cycle test temperature, perform a static operation on the battery cell according to the preset static time, charge the battery cell to the upper limit of the preset voltage test range, complete the static operation, discharge the battery cell to the lower limit of the voltage test range, and perform a cycle test according to the preset number of cycles to obtain the cycle test results;

[0009] S2. Extract data from the cycle test results and calculate DCR-related data. Among them, the DCR-related data includes: discharge DCRn, charge DCR’n, discharge DCR growth rate, and charge DCR’ growth rate;

[0010] S3. Analyze the results according to the DCR growth rate and the corresponding number of cycles of the DCR growth rate to obtain the changing trend of the continuous DCR growth rate during the cycle process.

[0011] This calculation method does not affect the cycle continuity of the battery cell, better understands the DCR growth of the lithium-ion battery during the cycle process, quickly identifies the performance differences of the battery cells in the initial stage of the cycle, distinguishes the cycle performance advantages and disadvantages between DOE validations, saves the waiting time for the test results to be produced, and avoids possible problems that may occur during the switching between the cycle test and the DCR test, including but not limited to: process switching settings, equipment switching.

[0012] In a more specific technical solution, in S1, the cycle temperature range of the battery cell includes: [-20°C, 60°C]; specifically, operations of narrowing or widening can be performed according to the working temperature of the battery cell;

[0013] The charge and discharge voltage range includes: [1.8V, 4.5V]; specifically, operations of narrowing or widening the charge and discharge voltage range can be performed according to the specific situation of the battery cell during use or cycling;

[0014] The range of charge and discharge rates includes: [0.1C, 5C]; specifically, the charge and discharge rates can be adjusted according to the rates that the battery cell can withstand during use.

[0015] Specifically, the charging process involves complex phase transformation conversions of the positive and negative electrode materials, interfacial electrochemical reactions, polarization effects, and irreversible reactions. The charge and discharge systems are mainly related to the type of battery cell system and the corresponding test temperature. It is necessary to optimize the cycle charge and discharge steps on the premise of ensuring the safe cycling of the battery cell.

[0016] In a more specific technical solution, in S1, the preset standing time includes: [10 min, 180 min]; specifically, the standing time can comprehensively consider battery type, charge and discharge conditions, test temperature and incubator control ability, specified test scheme regulations, etc., select a suitable standing time, and dynamically adjust the given range.

[0017] In a more specific technical solution, in S1, it can be considered to follow 1I 1 (A) Discharge to the discharge end condition specified by the enterprise. After standing stably, follow I 1 (A) Constant current charge at a current of I until the charging end voltage specified by the enterprise is reached, then switch to constant voltage charging until the charging end current drops to 0.05I 1 (A) Stop charging when it reaches. I 1 is the 1-hour rate discharge current, and its value is equal to the 1-hour rate rated capacity. On the premise of ensuring the service life of the battery cell and the safety of the charge and discharge process, match the actual usage ability of the battery cell, and select a suitable charge and discharge mode according to factors such as the test temperature environment. This mode is not limited to the given charge and discharge mode.

[0018] In a more specific technical solution, in S1, before performing the cycle test, the battery cell is discharged at a constant current to the lower limit of the voltage test range.

[0019] In a more specific technical solution, S2 includes:

[0020] S21. Denote the end voltage of the standing step before the constant current discharge in the nth cycle of the cycle test as V1-n; the voltage recorded at the x s of the constant current discharge as V2-n; the current recorded at the x s of the constant current discharge as I1-n; the end voltage of the standing step before the constant current charge as V3-n; the voltage recorded at the y s of the constant current charge as V4-n; the current recorded at the y s of the constant current charge as I2-n;

[0021] S22. Calculate the discharge DCR and charge DCR of the lithium-ion battery;

[0022] S23. Calculate the growth rate of the discharge DCR and the growth rate of the charge DCR.

[0023] In a more specific technical solution, in S22, use the following logic to calculate the discharge DCR and charge DCR:

[0024] Discharge DCRn = (V1-n - V2-n) / I1-n;

[0025] Charge DCR’n = (V4-n - V3-n) / I2-n.

[0026] The present invention does not affect the progress and continuity of the cycle test, eliminates the need for test switching, saves test resources and time costs, and avoids uncertain factors such as cell transfer. It is applicable to various cycle formats and test temperatures, and is not affected by cell models, capacities, etc.

[0027] In a more specific technical solution, in S23, the following logic is used to calculate the discharge DCR growth rate and the charge DCR growth rate:

[0028] Discharge DCR growth rate = (DCRn - DCR1) / DCR1

[0029] Charge DCR' growth rate = (DCR'n - DCR'1) / DCR'1.

[0030] In a more specific technical solution, in S3, the preset voltage and current are for the same number of turns, and the corresponding number of turns of the DCR growth rate is obtained through processing.

[0031] During the cycle of the lithium-ion battery, the present invention analyzes and processes data, directly calculates the DCR results in each cycle, including discharge and / or charge, analyzes the change trend based on the DCR of each cycle, is used to judge the change of electrical performance during the cycle, provides data for the attenuation situation during the battery cycle and improving the cycle format, and gives early warning of abnormal cell conditions.

[0032] In a more specific technical solution, a DCR growth evaluation system for lithium-ion battery cycle testing includes:

[0033] A cycle test module for entering the cycle test steps, adjusting the cycle test temperature, performing a standing operation on the cell according to the preset standing time, charging the cell to the upper limit of the preset voltage test range, completing the standing operation, discharging the cell to the lower limit of the voltage test range, and performing a cycle test according to the preset number of turns to obtain the cycle test results;

[0034] A DCR data calculation module for extracting data from the cycle test results and calculating DCR-related data, where the DCR-related data includes: discharge DCRn, charge DCR'n, discharge DCR growth rate, and charge DCR' growth rate, and the DCR data calculation module is connected to the cycle test module;

[0035] A DCR growth rate continuous change trend prediction module for analyzing the results based on the DCR growth rate and the corresponding number of turns of the DCR growth rate to obtain the continuous DCR growth rate change trend during the cycle, and the DCR growth rate continuous change trend prediction module is connected to the DCR data calculation module.

[0036] The present invention has the following advantages compared with the prior art:

[0037] This calculation method does not affect the continuity of the battery cell cycle, enables a better understanding of the DCR growth of lithium-ion batteries during the cycle, quickly identifies the performance differences of battery cells at the beginning of the cycle, distinguishes the cycle performance advantages and disadvantages between DOE verifications, saves the waiting time for test results, and avoids possible problems during the switching between cycle tests and DCR tests, including but not limited to: process step switching settings and equipment switching.

[0038] The present invention does not affect the progress and continuity of cycle tests, eliminates the need for test switching, saves test resources and time costs, and avoids uncertain factors such as battery cell transfer. It is applicable to various cycle systems and test temperatures, and is not affected by battery cell models, capacities, etc.

[0039] During the cycle of lithium-ion batteries, the present invention analyzes and processes data, directly calculates the DCR results during each cycle, including discharge and / or charge, and analyzes the change trend based on the DCR of each cycle to determine the changes in electrical performance during the cycle, provides data for evaluating the attenuation during the battery cycle and improving the cycle system, and gives early warnings of abnormal battery cells.

[0040] The present invention solves the technical problems in the prior art, such as the inability to detect DCR during the battery cell cycle, high time cost and test resource cost, and high error rate of test data. Description of the Drawings

[0041] Figure 1 Schematic diagram of the basic steps of a method for evaluating the DCR growth of a lithium-ion battery cycle test in Embodiment 1 of the present invention;

[0042] Figure 2 Comparison chart of DCR growth rate results of different verification schemes for lithium-ion batteries of the same batch in Embodiment 2 of the present invention;

[0043] Figure 3 Comparison chart of DCR growth rate results of short-cycle discharge of lithium-ion batteries of different batches in Embodiment 2 of the present invention;

[0044] Figure 4 Curve chart of DCR growth rate of parallel samples of the same batch in Embodiment 2 of the present invention;

[0045] Figure 5 Curve chart of the corresponding cycle capacity retention rate of parallel samples of the same batch in Embodiment 2 of the present invention. Detailed Description of the Invention

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0047] Embodiment 1

[0048] As Figure 1 shown, a method for evaluating the DCR growth in the cycle test of a lithium-ion battery provided by the present invention includes the following basic steps:

[0049] S1. Enter the cycle test step, adjust the test temperature required for the cycle and confirm that the battery cell has adapted to the environment, let the battery cell stand for a specific time, charge it to the upper limit of the voltage test range, let it stand for a period of time, and discharge it to the lower limit of the voltage test range. The above steps are cycled a certain number of times for testing;

[0050] In this embodiment, the cycle temperature of the battery cell, the upper and lower limits of the charge and discharge voltages, and the charge and discharge rates are selected within the range that the lithium-ion battery can withstand;

[0051] In this embodiment, the standing time is determined according to the test environment control ability to ensure that the starting temperature of each cycle of charge and discharge is stable;

[0052] In this embodiment, the charge and discharge mode can be adjusted according to requirements;

[0053] In this embodiment, before the cycle test, the battery cell is first subjected to constant current discharge to the lower limit of the voltage test range;

[0054] S2. Extract data from the cycle test results and calculate DCR-related data;

[0055] In this embodiment, step S2 of data extraction and calculation of DCR-related data further includes the following specific steps:

[0056] S21. Denote the end voltage of the standing step before the nth cycle of constant current discharge during the cycle as V1-n;

[0057] S22. Denote the voltage recorded at the x s of the nth cycle of constant current discharge during the cycle as V2-n;

[0058] S23. Denote the current recorded at the x s of the nth cycle of constant current discharge during the cycle as I1-n;

[0059] S24. Denote the end voltage of the standing step before the nth cycle of constant current charge during the cycle as V3-n;

[0060] S25. Denote the voltage recorded at the y-th second of the constant-current charging in the n-th cycle of the cycling process as V4-n.

[0061] S26. Denote the current recorded at the y-th second of the constant-current charging in the n-th cycle of the cycling process as I2-n.

[0062] S26. Calculate the discharge DCR and / or charge DCR of the lithium-ion battery.

[0063] In this embodiment, the calculation formula for DCR-related data is as follows:

[0064] Discharge DCRn = (V1-n - V2-n) / I1-n;

[0065] Charge DCR’n = (V4-n - V3-n) / I2-n.

[0066] In this embodiment, the selection of time x and y is determined according to the minimum sampling unit of the cycling device. It is recommended to use 5s, 10s, 15s, etc. There is no strong correlation between x and y, and the same value can be selected.

[0067] S27. Calculate the discharge DCR growth rate and / or charge DCR growth rate. The calculation formula is as follows:

[0068] Discharge DCR growth rate = (DCRn - DCR1) / DCR1

[0069] Charge DCR’ growth rate = (DCR’n - DCR’1) / DCR’1

[0070] In this embodiment, record the voltages at the end of the rest steps before the constant-current discharges in the 1st, 2nd, 3rd,... cycles of the cycling process as V1-n in sequence;

[0071] Record the voltages of the data recorded at the 10th second of the constant-current discharges in the 1st, 2nd, 3rd,... cycles of the cycling process as V2-n in sequence;

[0072] Record the currents of the data recorded at the 10th second of the constant-current discharges in the 1st, 2nd, 3rd,... cycles of the cycling process as I1-n in sequence;

[0073] Calculate the discharge DCR of the lithium-ion battery and the corresponding growth rate.

[0074] As shown in Table 1, relevant data can be extracted to calculate the DCR values and growth rates corresponding to each cycle.

[0075] Number of circulation turns V1-n / V V2-n / V I1-n / A Discharge DCR / mΩ DCR growth rate 1 4.180 4.041 120.14 1.15 0.0％ 2 4.180 4.040 120.14 1.17 1.0％ 3 4.180 4.039 120.14 1.17 1.5％ 4 4.180 4.039 120.15 1.17 1.6％ 5 4.180 4.038 120.15 1.19 2.7％ 6 4.180 4.037 120.15 1.19 2.7％ 7 4.180 4.036 120.14 1.20 3.8％ 8 4.180 4.036 120.15 1.20 4.3％ 9 4.180 4.035 120.15 1.21 4.8％ 10 4.180 4.034 120.14 1.21 5.3％ 11 4.180 4.034 120.14 1.21 5.2％ 12 4.180 4.033 120.15 1.22 5.9％ 13 4.180 4.032 120.14 1.23 6.4％ 14 4.179 4.032 120.14 1.23 6.5％ 15 4.179 4.031 120.15 1.24 7.2％ 16 4.179 4.030 120.14 1.24 7.5％ 17 4.179 4.029 120.14 1.25 8.4％ 18 4.179 4.029 120.14 1.25 8.6％ 19 4.179 4.029 120.14 1.25 8.6％ 20 4.179 4.027 120.15 1.26 9.4％ …… …… …… …… …… ……

[0076] S3. Conduct result analysis based on the DCR growth rate and the corresponding cycle numbers, and the continuous DCR growth rate change trend during the cycling process can be obtained.

[0077] In this embodiment, during the calculation process, the voltage and current should ensure the same number of turns, so that the corresponding number of turns value can be obtained;

[0078] For the data record at the x-th second, it is only necessary to ensure that the value of x for intercepting the data is consistent. The minimum sampling unit multiple in the loop process is adopted, and 10s or 30s is recommended. When analyzing and comparing the data, the same description is selected for calculating the results.

[0079] According to this scheme, the DCR values corresponding to 100% SOC in the discharge part and / or 0% SOC in the charge part during the loop process and the corresponding DCR growth situation can be obtained quickly. Although the DCR of the full SOC cannot be monitored, the DCR growth changes corresponding to the high SOC in discharge / low SOC in charge points (characteristic SOC points) can be quickly analyzed, so as to quickly predict the loop of the battery cell and monitor for abnormalities.

[0080] In this embodiment, n corresponds to the number of loop turns n = 1, 2, 3, 4..., and the maximum value of n is determined according to the loop trend.

[0081] Embodiment 2

[0082] In this embodiment, the DCR during the loop process of the lithium-ion battery is tested; specifically, a constant current charge and discharge is carried out at a fixed rate of 1C, and the data recording interval during the loop process is 30s, which is recorded as the first scheme.

[0083] In this embodiment, the specific operations of the foregoing first scheme include:

[0084] Constant current discharge to the discharge cut-off voltage; stand still for 30 min; 1C constant current and constant voltage charge to the charge cut-off voltage, and the cut-off current is 0.05C; stand still for 30 min; 1C constant current discharge to the discharge cut-off voltage; loop steps 2 - 5 for 500 turns.

[0085] As a comparison scheme for verifying the foregoing first scheme, a total of two kinds are set, both of which are currently commonly used test schemes for obtaining the loop DCR value.

[0086] In this embodiment, a loop - DCR alternating test scheme is involved: a constant current charge and discharge loop is carried out at a fixed rate of 1C, and the 100% SOC DCR is tested once before the loop and every 100 cycles, which is recorded as the second scheme.

[0087] In this embodiment, the specific operations of the foregoing second scheme include:

[0088] DCR test. Specifically, the battery cell is charged at a constant current and constant voltage of 1C to the charge cut-off voltage, and the cut-off current is 0.05C; stand still for 30 min, and record V1; discharge at a constant current of 1C for 30s, and record V2; obtain the DCR and DCR growth rate results according to the calculation formula;

[0089] Cyclic operation. Specifically, constant current discharge to the discharge cut-off voltage; stand still for 30 min; constant current and constant voltage charge at 1C to the charge cut-off voltage, with the cut-off current being 0.05C; stand still for 30 min; constant current discharge at 1C to the discharge cut-off voltage; repeat steps 2 - 5 for 100 cycles; constant current discharge to the discharge cut-off voltage; the operation of standing still for 30 min is cycled and tested 5 times in total, and the total number of charge and discharge cycles is 500 cycles.

[0090] In this embodiment, a DCR test scheme before and after cycling is designed. Specifically, charge and discharge cycles are carried out at a fixed rate of 1C for 500 cycles, and DCR tests are only performed before the cycle and after 500 cycles are completed (for the specific test scheme, refer to the aforementioned second scheme. The DCR test scheme before and after cycling is denoted as Scheme Three).

[0091] In this embodiment, the above three schemes are all tested in an incubator at 25°C ± 2°C to ensure the stable operation of the incubator throughout the test process.

[0092] As Figures 2 to 5 shown, in this embodiment, the DCR growth rate results of the above three schemes are compared. All the above verifications are carried out using the same batch of battery cells, and parallel samples can be set. The charge and discharge rate can be changed according to the rate that the battery cells can adapt to, and the DCR pulse discharge rate needs to be modified accordingly. The discharge time can be adjusted according to requirements, and the cycle sampling time interval needs to be considered for convenient later data extraction. Figure 1 For the DCR growth rate situations obtained by the three schemes, the results obtained by the above three test schemes are close, but the result of Scheme Two is larger than the other two values. It is considered that multiple switching tests will have a certain impact on the test results. The DCR results measured by Scheme Three are less, and the DCR change trend during the test cannot be obtained.

[0093] The setting of the test scheme can verify that the result obtained by Scheme One is fast and reasonable. Scheme One can be used to obtain the DCR growth during the cycling of the battery cells and quickly judge whether there is an abnormality in the DCR during the cycling of the sample parts. Select samples with normal or excellent performance in the previous batches as the data benchmark to determine whether there is improvement or abnormality in the DCR of the subsequent sample parts. Figure 2For the DCR growth rate results of different batches, select the samples to be compared as the reference benchmark samples, and verify them according to the same cycling regime and data processing method. Compare the obtained results. The DCR growth rate result of test sample 1 shows a significant increase, indicating that there may be problems such as high heat generation and fast cycling decay in the battery cell. The DCR growth rate result of test sample 2 shows improvement, indicating that there is improvement in the DCR of this battery cell, but this is only the result obtained from a short number of cycling laps and further observation is still needed. The above conclusions show that using this DCR growth evaluation method can quickly screen out problem samples with fewer cycling laps, improve the verification efficiency and save test resources.

[0094] Results of three parallel samples in the same batch of samples for cycling verification, as Figure 3 、 4 shown, are the curves of DCR growth rate and capacity retention rate respectively. According to Figure 3 it can be seen that for sample 1, there is an obvious increase when the number of cycling laps is about 400, but Figure 4 the corresponding cycling capacity retention rate of sample 1 in only starts to significantly decay at 650 laps. This calculation method can predict the cycling trend in advance.

[0095] It can be understood that the test temperature, each time value, charge-discharge rate value, cycling times, etc. that appear in the embodiments of the present invention are only examples and should not bring any limitations to the execution of each step in the embodiments of the present invention. Those skilled in the art can adopt different values according to needs as long as the method of the present invention can be normally implemented.

[0096] The discharge DCR reflects the polarization and heat generation during the discharge process of the battery cell. During the cycling process, DCR is a long-term test of the battery cell, with a long test time and relatively more polarization accumulation and side reaction accumulation, so it can comprehensively reflect the health state of the electrode sheet, the ohmic internal resistance of the battery cell, polarization accumulation, side reaction accumulation, etc. By judging the growth of DCR, it can be determined whether the cycling performance deteriorates and the corresponding degree.

[0097] In summary, this calculation method does not affect the cycling continuity of the battery cell, can better understand the DCR growth situation of lithium-ion batteries during the cycling process, quickly identify the performance differences of battery cells at the initial stage of cycling, distinguish the cycling performance advantages and disadvantages between DOE verifications, save the waiting time for test results, and avoid possible problems that may occur during the switching between cycling tests and DCR tests, including but not limited to: process switching settings, equipment switching.

[0098] The present invention does not affect the cycling test progress and test continuity, does not require test switching, saves test resources and time costs, and avoids uncertain factors such as battery cell transfer. It is applicable to various cycling regimes and test temperatures and is not affected by battery cell models, capacities, etc.

[0099] During the cycle of the lithium-ion battery, the present invention analyzes and processes data, directly calculates the DCR results during each cycle, including discharging and / or charging, and analyzes the change trend based on the DCR of each cycle to determine the change in electrical performance during the cycle, provide data for the attenuation during the battery cycle and improving the cycle format, and early warning of abnormal cell conditions.

[0100] The present invention solves the technical problems existing in the prior art, such as the inability to detect DCR during the cell cycle, high time cost and test resource cost, and relatively high error rate of test data.

[0101] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for evaluating DCR growth in a lithium-ion battery cycle test, characterized in that: The method comprises: S1, enter the cycle test step, adjust the cycle test temperature, perform a static operation on the battery cell according to a preset static time, charge the battery cell to the upper limit of a preset voltage test range, complete the static operation, discharge the battery cell to the lower limit of the voltage test range, perform a cycle test according to a preset number of turns, and obtain a cycle test result; S2. Extract data from the cycle test results and calculate DCR-related data, wherein the DCR-related data includes: discharge DCRn, charge DCR'n, discharge DCR growth rate and charge DCR' growth rate; S3. Analyze the results based on the DCR growth rate and the corresponding number of cycles of the DCR growth rate to obtain the continuous DCR growth rate change trend of the cycle process.

2. A lithium-ion battery cycle test DCR growth evaluation method according to claim 1, characterized in that: In S1, the battery cell cycle temperature range includes: [-20°C, 60°C]; The charge and discharge voltage range includes: [1.8V, 4.5V]; The charge and discharge rates include: [0.1C, 5C].

3. A lithium-ion battery cycle test DCR growth evaluation method according to claim 1, characterized in that: In S1, the preset rest time is obtained and set according to the battery type, charging and discharging conditions, test temperature and temperature box control capability, and specified test scheme information.

4. A lithium-ion battery cycle test DCR growth evaluation method according to claim 1, characterized in that: In the S1, discharge at 1I1(A) to the discharge termination condition specified by the enterprise, and after standing still and stabilizing, charge at a constant current of I1(A) to a preset charge termination voltage, then switch to constant voltage charging, and stop charging when the charge termination current drops to 0.05I1(A); perform the actual use capacity matching operation of the battery cell, and select the charge and discharge standard parameters according to the test temperature.

5. A lithium-ion battery cycle test DCR growth evaluation method according to claim 1, characterized in that: In S1, before performing the cycle test, the battery cell is discharged at a constant current to a lower limit of a voltage test range.

6. A lithium-ion battery cycle test DCR growth evaluation method according to claim 1, characterized in that: The S2 includes: S21, in the cycle test, the voltage at the end of the rest step before the constant current discharge of the nth round is recorded as V1-n; the voltage recorded in the xsth data of the constant current discharge is recorded as V2-n; the current recorded in the xsth data of the constant current discharge is recorded as I1-n; the voltage at the end of the rest step before the constant current charge is recorded as V3-n; the voltage recorded in the ysth data of the constant current charge is recorded as V4-n; the current recorded in the ysth data of the constant current charge is recorded as I2-n; S22, calculating the discharge DCR and the charge DCR of the lithium-ion battery; S23, calculating the discharge DCR growth rate and the charge DCR growth rate.

7. A lithium-ion battery cycle test DCR growth evaluation method according to claim 6, characterized in that: In S22, the discharge DCR and the charge DCR are calculated using the following logic: Discharge DCRn = (V1-n-V2-n) / I1-n; Charging DCR'n = (V4-n-V3-n) / I2-n.

8. A lithium-ion battery cycle test DCR growth evaluation method according to claim 6, characterized in that: In S23, the discharge DCR growth rate and the charge DCR growth rate are calculated using the following logic: Discharge DCR growth rate = (DCRn-DCR1) / DCR1 Charging DCR' growth rate = (DCR'n-DCR'1) / DCR'1.

9. A lithium-ion battery cycle test DCR growth evaluation method according to claim 1, characterized in that: In S3, the voltage and current are preset to be the same number of turns, and the corresponding number of turns of the DCR growth rate is obtained by processing.

10. A lithium-ion battery cycle test DCR growth evaluation system, characterized in that: The system comprises: A cycle test module is used to enter a cycle test step, adjust a cycle test temperature, perform a static operation on the battery cell according to a preset static time, charge the battery cell to an upper limit of a preset voltage test range, complete the static operation, discharge the battery cell to a lower limit of a voltage test range, perform a cycle test according to a preset number of turns, and obtain a cycle test result; A DCR data calculation module, used to extract data from the cycle test results and calculate DCR related data, wherein the DCR related data includes: discharge DCRn, charge DCR'n, discharge DCR growth rate and charge DCR' growth rate, and the DCR data calculation module is connected to the cycle test module; The DCR growth rate continuous change trend prediction module is used to analyze the results according to the DCR growth rate and the corresponding number of cycles of the DCR growth rate to obtain the continuous DCR growth rate change trend of the cycle process. The DCR growth rate continuous change trend prediction module is connected to the DCR data calculation module.

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