A voltage compensation method for self-discharge test of lithium-ion batteries

Abstract

The present invention discloses a lithium-ion battery self-discharge test voltage compensation method, which belongs to the field of battery voltage compensation. A lithium-ion battery self-discharge test voltage compensation method includes the following steps: extracting cells to be capacity-separated from a production line and completing capacity separation; testing the open circuit voltage (OCV1) of the cells after capacity separation and passivation; testing the open circuit voltage (OCV2) of the cells after OCV1 test again; recording the voltage change of each cell after capacity separation; distinguishing the minimum reference time (b minutes) and the value (c); distinguishing the minimum reference time (d minutes) and the value (e); calculating f n and g n ; Calculate OCV1 补偿 and OCV2 补偿 ; Calculate the compensated K value; The present invention can make the self-discharge process parameter K value more accurate, and use the compensated K value to perform the off-line operation of the lithium-ion battery cell in the production process, thereby effectively improving the product quality of the lithium-ion battery and reducing the pressure of customer complaints.

Description

Technical Field

[0001] The present invention relates to the technical field of battery voltage compensation, and in particular to a voltage compensation method for self-discharge testing of a lithium-ion battery. Background Art

[0002] Self-discharge screening of lithium-ion batteries is a critical inspection step before cells come off the production line during the lithium battery manufacturing process. The effective formulation of self-discharge screening process standards can effectively screen out cells with abnormal self-discharge, which is crucial for improving product quality and reducing the pressure of customer complaints.

[0003] At present, the self-discharge screening process of mainstream battery factories is as follows: after the battery is divided into different capacities and has a certain SOC capacity, it is placed in the capacity division cabinet and left to stand for n hours. After the battery is passivated after n hours of standing, the open circuit voltage OCV1 is tested. The battery then enters the standing warehouse and begins to stand for a period of (Nn) hours. After (Nn) hours of standing, the open circuit voltage OCV2 is tested. The usual process parameter K value for self-discharge screening is (OCV2-OCV1) / (Nn). The standard for the self-discharge process parameter K value is finally determined based on multiple batches of K value data and related verification analysis.

[0004] In actual production, cells are grouped into pallets. The pallet's time of removal from the storage cabinet after separation is determined to be T1. After standing for n hours, the pallet's time of passivation is T2, where T2 - T1 = n hours. After the pallet's time of resting for (Nn) hours, the pallet's time of rest is T3, where T3 - T1 = N hours. Each batch of cells is simultaneously separated and unloaded from the storage cabinet, with hundreds or thousands of pallets distributed within. It's impossible to equip the production line with voltage testing equipment to detect OCV1 for each number of pallets. Measurements must be completed one pallet before the next. The queuing of pallets causes a delay of T2, ranging from a few minutes to several hours. This results in inconsistent passivation times. Battery voltage changes over time, decreasing more slowly over time. The voltage drop caused by inconsistent passivation times can affect the accuracy of K-value data. Similarly, a delay in T3 can cause the resting times of cells in different pallets to vary by minutes or even hours.

[0005] Based on the above background, the present invention proposes a voltage compensation method for lithium-ion battery self-discharge test to improve the accuracy of K value data. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems existing in the prior art and to propose a voltage compensation method for self-discharge testing of a lithium-ion battery.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A lithium-ion battery self-discharge test voltage compensation method comprises the following steps:

[0009] Step 1: Extract a cell to be capacity-separated from the production line and complete the capacity separation;

[0010] Step 2: After the battery is divided into different capacities, let it rest for n hours. After the battery is passivated after n hours of rest, test the open circuit voltage OCV1.

[0011] Step 3: After testing OCV1, let the battery rest for Nn hours. After Nn hours of rest, test the open circuit voltage OCV2.

[0012] Step 4: Record the voltage change of each battery after capacity division;

[0013] Step 5: The cells after capacity separation are taken as a pallet. The time when the cells in the pallet are separated and unloaded from the cabinet is T1. According to the passivation time n hours set by the production line, find the time T2 of the open circuit voltage OCV1 test recorded in the data. Then, according to the change of voltage over time after time T2, the minimum reference time b minutes that causes voltage change with time is effectively identified. Simultaneously determine the value c of voltage change every b minutes, and calculate the average value c of multiple values c. mean As the standard value of voltage change under the minimum reference time;

[0014] Step 6: Synchronously find the time T3 of the open circuit voltage OCV2 test recorded in the data. T3 is the time when the pallet battery cells enter the static warehouse and rest for Nn hours. According to the change of voltage with time after T3, effectively identify the minimum reference time d minutes that causes voltage change with time extension, and synchronously determine the value e of voltage change every d minutes, and calculate the average value e of multiple values e. mean As the standard value of voltage change under the minimum reference time;

[0015] Step 7: After the batteries in the capacity distribution cabinets of the production line batch have been idle for n hours, the voltage OCV1 of the first tray is measured. The test time is recorded as T21. The subsequent voltage test times of the second to nth trays are T22, T23, ... T2 n After the batteries in the capacity distribution cabinets of the production line batch have been stationary for N hours, the voltage OCV2 of the first tray is measured. Each battery cell outputs an OCV2 value. The test time is recorded as T31. The subsequent voltage test times of the second to nth trays are T32, T33, ... T3. n ;

[0016] Step 8: Calculate f n and g n ;f n =(T2 n-T11) / c;g n = (T3n-T31) / b;

[0017] Step 9: Compensate the voltage in units of pallets. If the compensation value of the same pallet is the same, then the OCV1 of the cells in different pallets after compensation will be 补偿 =OCV1+c mean ×f n ;OCV2 after compensation of different tray cells 补偿 =OCV2+e mean ×g n ;

[0018] Step 10: After compensation, K value = (OCV1 补偿 -OCV2 补偿 ) / (Nn).

[0019] Preferably, in step 1, the number of battery cells extracted is a≥5.

[0020] Preferably, in step 4, a voltage point is recorded every minute with a voltage accuracy of 0.01 mV, and the recording is continued for N+48 hours, which is sufficient to cover the time required for the entire self-discharge process setting.

[0021] Furthermore, in step five, b≥3 minutes, c≥0.01 mV; in step six, d≥3 minutes, e≥0.01 mV.

[0022] Furthermore, in step 5, T2-T1=n hours, n≥2; T3-T1=N hours, N≥24 hours.

[0023] Furthermore, in step 1, a battery cell is sampled, and the voltage change value of each battery cell under the minimum reference time b minutes is confirmed to be c1, c2, ... c a , c1, c2, ... c a The mean of mean ; Confirm the voltage change values e1, e2, ...e under the minimum reference time d minutes of each battery cell a , e1, e2, ...e a The mean of mean .

[0024] Preferably, in step eight, f n and g n All figures are rounded to the nearest integer.

[0025] Preferably, the process parameter K value of the common self-discharge screening is (OCV2-OCV1) / (Nn).

[0026] Preferably, the battery has an SOC capacity of 4%-8% after capacity division is completed.

[0027] Preferably, the battery after the OCV1 test in step 3 is placed in a static storage for rest.

[0028] Compared with the prior art, the present invention provides a lithium-ion battery self-discharge test voltage compensation method, which has the following beneficial effects:

[0029] 1. The voltage compensation method for lithium-ion battery self-discharge test is based on a pallet as the unit. The time when the pallet cells are unloaded is T1. According to the deactivation time n hours set by the production line, the time T2 of the open circuit voltage OCV1 test recorded in the data is found. The time T3 of the open circuit voltage OCV2 test recorded in the data is found synchronously. Then, f is calculated in sequence. n and g n , and then calculate OCV1 补偿 and OCV2 补偿 , thereby determining the compensated K value.

[0030] 2. The voltage compensation method for self-discharge test of lithium-ion battery, f n =(T2 n -T11) / c;g n = (T3n-T31) / b; OCV1 after compensation of different tray cells 补偿 =OCV1+c mean ×f n ;OCV2 after compensation of different tray cells 补偿 =OCV2+e mean ×g n ; After compensation, K value = (OCV1 补偿 -OCV2 补偿 ) / (Nn).

[0031] The parts not involved in the device are the same as the existing technology or can be implemented by using the existing technology. The present invention can make the self-discharge process parameter K value more accurate, and the compensated K value is used to perform the battery cell offline operation in the production process of the lithium-ion battery, thereby effectively improving the product quality of the lithium-ion battery and reducing the pressure of customer complaints. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0033] Example 1:

[0034] A voltage compensation method for self-discharge testing of a lithium-ion battery is operated using the following method.

[0035] The self-discharge screening process selected in this embodiment is as follows:

[0036] S1, after the battery capacity is divided, the SOC capacity is about 6%;

[0037] S2: After the battery is placed in the capacity distribution cabinet and left to stand for 4 hours, the open circuit voltage (OCV1) of the battery is tested after it is deactivated after 4 hours of standing.

[0038] S3, after the open circuit voltage OCV1 is tested, the battery enters the static storage and begins to rest for a period of 168 hours. After the static period is completed, the open circuit voltage OCV2 is tested. The usual process parameter K value for self-discharge screening is (OCV2-OCV1) / 168;

[0039] S4, the cells after capacity division are taken as a pallet. The time when the pallet cells are divided and unloaded from the cabinet is set as T1, and the time after they are passively placed for 4 hours is T2, so T2-T1=4 hours; the time when the pallet cells enter the static warehouse after 168 hours of static storage is T3, so T3-T1=172 hours.

[0040] Among them, OVC refers to open circuit voltage, that is, the terminal voltage of the battery in the open circuit state; the open circuit voltage of the battery is equal to the difference between the electrode potential of the positive electrode and the electrode potential of the negative electrode of the battery when the battery is disconnected (that is, when no current passes through the two poles).

[0041] Based on the above self-discharge screening process, a lithium-ion battery self-discharge test voltage compensation method is provided. The specific implementation steps are as follows:

[0042] First, eight cells to be capacity-separated are extracted from the production line and capacity-separated according to the process set on the production line.

[0043] Then, record the voltage change of each battery with the divided capacity, record one voltage point every 1 minute, with the voltage accurate to 0.01mV, and continue recording for 220 hours;

[0044] Next, find the time T2 of the OCV1 test recorded in the data of step 2. Based on the change in voltage over time after time T2, effectively identify the minimum reference time b = 20 minutes that causes the voltage change over time. Simultaneously determine the value c of the voltage change every 20 minutes. Generally, c ≥ 0.01mV. Simultaneously find the time T3 of the OCV2 test recorded in the data of step S2. Based on the change in voltage over time after time T3, effectively identify the minimum reference time d = 30 minutes that causes the voltage change over time. Simultaneously determine the value e of the voltage change every 30 minutes. Generally, e ≥ 0.01mV.

[0045] Since 8 cells were sampled, the five voltage change values c under the minimum reference time b = 20 minutes for each cell were determined, and the average value c of the five voltage change values c was used as the value. meanAs the standard value of voltage change under the minimum reference time of 20 minutes; then confirm the five voltage change values e of each battery cell under the minimum reference time d=30 minutes, and take the average value e of the five voltage change values e mean As the standard value of voltage change under the minimum reference time of 30 minutes;

[0046] In this step, the five voltage change values c measured are: 0.022mV, 0.019mV, 0.02mV, 0.022mV, and 0.22mV, and the average value c is obtained. mean =0.021mV; the five measured voltage change values e are: 0.019mV, 0.019mV, 0.022mV, 0.024mV, 0.021mV, and the average value of e is obtained. mean =0.021mV;

[0047] If there are 8 cells on the production line, each cell is loaded into a tray for capacity separation and OCV testing. According to the set production rhythm, each cell is tested for OCV1 or OCV2 every 10 minutes. According to the deactivation time set for the production line of 4 hours, after the batteries in the capacity separation cabinet have been idle for 4 hours, the voltage OCV1 is measured in sequence. The test time is recorded as T21, T22, T23...T2 10 After the batteries in the capacity distribution cabinets of the production line batch have been stationary for 172 hours, the voltage OCV2 is measured in sequence, and the test time is recorded as T31, T32, T33...T3 10 ;

[0048] f n =(T2 n -T11) / c,f n Round to the nearest integer;

[0049] g n =(T3 n -T31) / b,g n Round to the nearest integer;

[0050] Because f n and g n The integer is rounded off. Therefore, when the difference between T2 and T1 is small, f n and g n The size of tends to 0;

[0051] The compensation voltage is calculated based on the pallet. If the compensation value of the same pallet is the same, then the OCV1 of the cells in different pallets after compensation will be different. 补偿 =OCV1+c mean ×f n ; Then the OCV2 after compensation of different tray cells 补偿=OCV2+e mean ×g n ;

[0052] K value after compensation = (OCV1 补偿 -OCV2 补偿 ) / (168); By calculating the data of the compensated K value eight times, the K value calculated in this application is more accurate. The compensated K value is used to perform the off-line operation of the lithium-ion battery cell in the production process, thereby effectively improving the product quality of the lithium-ion battery and reducing the pressure of customer complaints.

[0053] Example 2:

[0054] A voltage compensation method for self-discharge testing of a lithium-ion battery is operated using the following method.

[0055] The self-discharge screening process selected in this embodiment is as follows:

[0056] S1, after the battery capacity is divided, the SOC capacity is about 6%;

[0057] S2: After the battery is placed in the capacity distribution cabinet and left to stand for 4 hours, the open circuit voltage (OCV1) of the battery is tested after it is deactivated after 4 hours of standing.

[0058] S3, after the open circuit voltage OCV1 is tested, the battery enters the static storage and begins to rest for a period of 168 hours. After the static period is completed, the open circuit voltage OCV2 is tested. The usual process parameter K value for self-discharge screening is (OCV2-OCV1) / 168;

[0059] S4, the cells after capacity division are taken as a pallet. The time when the pallet cells are divided and unloaded from the cabinet is set as T1, and the time after they are passively placed for 4 hours is T2, so T2-T1=4 hours; the time when the pallet cells enter the static warehouse after 168 hours of static storage is T3, so T3-T1=172 hours.

[0060] Among them, OVC refers to open circuit voltage, that is, the terminal voltage of the battery in the open circuit state; the open circuit voltage of the battery is equal to the difference between the electrode potential of the positive electrode and the electrode potential of the negative electrode of the battery when the battery is disconnected (that is, when no current passes through the two poles).

[0061] Based on the above self-discharge screening process, a lithium-ion battery self-discharge test voltage compensation method is provided. The specific implementation steps are as follows:

[0062] First, select 5 cells to be capacity-separated from the production line and complete the capacity separation according to the process set on the production line;

[0063] Then, record the voltage change of each battery with the divided capacity, record one voltage point every 1 minute, with the voltage accurate to 0.01mV, and continue recording for 220 hours;

[0064] Next, find the time T2 of the OCV1 test recorded in the data of step 2. Based on the change in voltage over time after time T2, effectively identify the minimum reference time b = 10 minutes that causes the voltage change over time. Simultaneously determine the value c of the voltage change every 10 minutes. Generally, c ≥ 0.01mV. Simultaneously find the time T3 of the OCV2 test recorded in the data of step S2. Based on the change in voltage over time after time T3, effectively identify the minimum reference time d = 15 minutes that causes the voltage change over time. Simultaneously determine the value e of the voltage change every 15 minutes. Generally, e ≥ 0.01mV.

[0065] Since 5 cells were sampled, the five voltage change values c of each cell under the minimum reference time b = 10 minutes were determined, and the average value c of the five voltage change values c was used as the value. mean As the standard value of voltage change under the minimum reference time of 10 minutes; then confirm the five voltage change values e of each battery cell under the minimum reference time d=15 minutes, and take the average value e of the five voltage change values e mean As the standard value of voltage change under the minimum reference time of 15 minutes;

[0066] In this step, the five voltage change values c measured are: 0.018mV, 0.018mV, 0.022mV, 0.022mV, 0.02mV, and 0.02mV, and the average value c is obtained. mean =0.02mV; the five measured voltage change values e are: 0.019mV, 0.019mV, 0.02mV, 0.021mV, 0.021mV, and the average value of e is obtained. mean =0.02mV;

[0067] If there are 10 battery cells on the production line, each battery cell is loaded into a tray for capacity separation and OCV testing. According to the set production rhythm, each battery cell is tested for OCV1 or OCV2 every 3 minutes. According to the deactivation time set for the production line of 4 hours, after the battery in the capacity separation cabinet reaches the static time of 4 hours, the voltage OCV1 is measured in sequence, and the test time is recorded as T21, T22, T23...T2 10 After the batteries in the capacity distribution cabinets of the production line batch have been stationary for 172 hours, the voltage OCV2 is measured in sequence, and the test time is recorded as T31, T32, T33...T3 10 ;

[0068] f n =(T2 n -T11) / c,f n Round to the nearest integer;

[0069] g n=(T3 n -T31) / b,g n Round to the nearest integer;

[0070] Because f n and g n The integer is rounded off. Therefore, when the difference between T2 and T1 is small, f n and g n The size of tends to 0;

[0071] The compensation voltage is calculated based on the pallet. If the compensation value of the same pallet is the same, then the OCV1 of the cells in different pallets after compensation will be different. 补偿 =OCV1+c mean ×f n ; Then the OCV2 after compensation of different tray cells 补偿 =OCV2+e mean ×g n ;

[0072] K value after compensation = (OCV1 补偿 -OCV2 补偿 ) / (168).

[0073] The specific data of K value after ten compensations are obtained by calculation, and the specific data are recorded in the following table:

[0074] Table 1: Data record table

[0075]

[0076] Therefore, it can be seen from the data in Table 1 that the K value calculated in this application is more accurate, thereby effectively improving product quality and alleviating customer complaint pressure.

[0077] Example 3:

[0078] A lithium-ion battery self-discharge test voltage compensation method comprises the following steps:

[0079] Step 1: Extract a number of cells to be capacity-separated from the production line and complete the capacity separation, where a=10;

[0080] Step 2: After the battery is divided into different capacities, let it rest for n hours. After the battery is passivated after n hours of rest, test the open circuit voltage OCV1, where n = 4.

[0081] Step 3: After testing OCV1, the battery is allowed to rest for Nn hours. After Nn hours of rest, the open circuit voltage OCV2 is tested, where Nn = 168 hours, or N = 172 hours.

[0082] Step 4: Record the voltage change of each battery after capacity division;

[0083] Step 5: The cells after capacity separation are taken as a pallet. The time when the cells in the pallet are separated and unloaded from the cabinet is T1. According to the passivation time n hours set by the production line, find the time T2 of the open circuit voltage OCV1 test recorded in the data. Then, according to the change of voltage over time after time T2, the minimum reference time b minutes that causes voltage change with time is effectively identified. Simultaneously determine the value c of voltage change every b minutes, and calculate the average value c of multiple values c. mean As the standard value of voltage change under the minimum reference time, where b = 5 minutes;

[0084] Step 6: Synchronously find the time T3 of the open circuit voltage OCV2 test recorded in the data. T3 is the time when the pallet battery cells enter the static warehouse and rest for Nn hours. According to the change of voltage with time after T3, effectively identify the minimum reference time d minutes that causes voltage change with time extension, and synchronously determine the value e of voltage change every d minutes, and calculate the average value e of multiple values e. mean As the standard value of voltage change under the minimum reference time, where d = 5 minutes;

[0085] Step 7: After the batteries in the capacity distribution cabinets of the production line batch have been idle for n hours, the voltage OCV1 of the first tray is measured. The test time is recorded as T21. The subsequent voltage test times of the second to nth trays are T22, T23, ... T2 n After the batteries in the capacity distribution cabinets of the production line batch have been stationary for N hours, the voltage OCV2 of the first tray is measured. Each battery cell outputs an OCV2 value. The test time is recorded as T31. The subsequent voltage test times of the second to nth trays are T32, T33, ... T3. n ;

[0086] Step 8: Calculate f n and g n ;f n =(T2 n -T11) / c;g n = (T3n-T31) / b, it should be noted that f n and g n The integer is rounded off. Therefore, when the difference between T2 and T1 is small, f n and g n The size of tends to 0;

[0087] Step 9: Compensate the voltage in units of pallets. If the compensation value of the same pallet is the same, then the OCV1 of the cells in different pallets after compensation will be 补偿 =OCV1+c mean ×f n;OCV2 after compensation of different tray cells 补偿 =OCV2+e mean ×g n ;

[0088] Step 10: After compensation, K value = (OCV1 补偿 -OCV2 补偿 ) / (Nn).

[0089] By calculating the K value after eight compensations, the self-discharge process parameter K value is made more accurate. The compensated K value is used to perform the cell off-line operation in the lithium-ion battery production process, thereby effectively improving the product quality of the lithium-ion battery and reducing the pressure of customer complaints.

[0090] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A lithium-ion battery self-discharge test voltage compensation method, characterized in that: The following steps are involved: Step 1: Extract a cell to be capacity-separated from the production line and complete the capacity separation; Step 2: After the battery is divided into different capacities, let it rest for n hours. After the battery is passivated after n hours of rest, test the open circuit voltage OCV1. Step 3: After testing OCV1, let the battery rest for Nn hours. After Nn hours of rest, test the open circuit voltage OCV2. Step 4: Record the voltage change of each battery after capacity division; Step 5: The cells after capacity separation are taken as a pallet. The time when the cells in the pallet are separated and unloaded from the cabinet is T1. According to the passivation time n hours set by the production line, find the time T2 of the open circuit voltage OCV1 test recorded in the data. Then, according to the change of voltage over time after time T2, the minimum reference time b minutes that causes voltage change with time is effectively identified. Simultaneously determine the value c of voltage change every b minutes, and calculate the average value c of multiple values c. mean As the standard value of voltage change under the minimum reference time; Step 6: Synchronously find the time T3 of the open circuit voltage OCV2 test recorded in the data. T3 is the time when the pallet battery cells enter the static warehouse and rest for Nn hours. According to the change of voltage with time after T3, effectively identify the minimum reference time d minutes that causes voltage change with time extension, and synchronously determine the value e of voltage change every d minutes, and calculate the average value e of multiple values e. mean As the standard value of voltage change under the minimum reference time; Step 7: After the batteries in the capacity distribution cabinets of the production line batch have been idle for n hours, the voltage OCV1 of the first tray is measured. The test time is recorded as T21. The subsequent voltage test times of the second to nth trays are T22, T23, ... T2 n After the batteries in the capacity distribution cabinets of the production line batch have been stationary for N hours, the voltage OCV2 of the first tray is measured. Each battery cell outputs an OCV2 value. The test time is recorded as T31. The subsequent voltage test times of the second to nth trays are T32, T33, ... T3. n ; Step 8: Calculate f n and g n ; Among them, f n =(T2 n -T11) / c;g n = (T3n-T31) / b; Step 9: Compensate the voltage in units of pallets. If the compensation value of the same pallet is the same, then the OCV1 of the cells in different pallets after compensation will be 补偿 =OCV1+c mean ×f n ;OCV2 after compensation of different tray cells 补偿 =OCV2+e mean ×g n ; Step 10: After compensation, K value = (OCV1 补偿 -OCV2 补偿 ) / (Nn); In step 5, T2-T1=n hours, n≥2; T3-T1=N hours, N≥24 hours.

2. A lithium-ion battery self-discharge test voltage compensation method according to claim 1, characterized in that: In step 1, the number of cells extracted is a≥5.

3. A lithium-ion battery self-discharge test voltage compensation method according to claim 1, characterized in that: In step 4, a voltage point is recorded every 1 minute with an accuracy of 0.01mV, and the recording is continued for N+48 hours, which is enough to cover the time required for the entire self-discharge process setting.

4. A lithium-ion battery self-discharge test voltage compensation method according to claim 3, characterized in that: In step 5, b ≥ 3 minutes, c ≥ 0.01 mV; in step 6, d ≥ 3 minutes, e ≥ 0.01 mV.

5. A lithium-ion battery self-discharge test voltage compensation method according to claim 4, characterized in that: In step 1, a battery cell is sampled and the voltage change values of each battery cell under the minimum reference time of b minutes are confirmed to be c1, c2, ... c a , c1, c2, ... c a The mean of mean ; Confirm the voltage change values e1, e2, ...e under the minimum reference time d minutes of each battery cell a , e1, e2, ...e a The mean of mean .

6. A lithium-ion battery self-discharge test voltage compensation method according to claim 1, characterized in that: In step eight, f n and g n All figures are rounded to the nearest integer.

7. A lithium-ion battery self-discharge test voltage compensation method according to claim 1, characterized in that: The usual process parameter K value for self-discharge screening is (OCV2-OCV1) / (Nn).

8. A lithium-ion battery self-discharge test voltage compensation method according to claim 1, characterized in that: After the battery capacity is divided, it has an SOC capacity of 4%-8%.

9. A lithium-ion battery self-discharge test voltage compensation method according to claim 1, characterized in that: After the OCV1 test in step 3, the battery is placed in a static storage for rest.

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