A method for calibrating a lithium battery activation machine

Abstract

The application discloses a kind of lithium battery activation machine's verification method, including obtaining the first activation capacity of the battery tested by test platform and the capacity recovery rate of the batch of battery calculated in advance and calculating the theoretical capacity of the measured battery after storing at room temperature for a predetermined time;The measured battery is activated again, and the actual capacity of the measured battery is obtained under a plurality of preset compensation current values using the test platform after storing at room temperature for a predetermined time;Compare the capacity difference of theoretical capacity and actual capacity, obtain the best compensation current value, and use the best compensation current value to compensate the current of the test platform.The application solves the problem of battery capacity test error caused by the error of activation platform in the prior art, reduces the measurement error caused by the error of the platform itself, can accurately verify the platform, greatly reduces the measurement error of the platform itself, so that the capacity test of subsequent battery is more accurate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium battery capacity test, in particular to a kind of lithium battery activation machine's verification method. BACKGROUND

[0002] Battery is widely used in various fields such as electronic products with its high energy density, long service life, high safety and other excellent performance. In the traditional manufacturing of secondary lithium ion battery, after liquid injection is completed, a small current is used to charge the secondary lithium ion battery, so as to activate the battery to form SEI film and complete gas production, which is called formation in the industry. Thereafter, the process of capacity screening of the formed battery is called capacity grading. However, the formation and capacity grading of steel shell battery are generally combined into one, which is called activation. The charging and discharging process of the battery is basically as follows: first, a constant current is used to charge the secondary lithium ion battery, then a constant voltage is used for charging, and then the battery with full charging capacity is discharged at a constant current after standing. Each charging and discharging needs to set safety control points (the maximum safe voltage and current range value allowed by the battery). After the activation, high temperature aging and normal temperature aging of the steel shell battery, the capacity loss is large. The performance of the newly manufactured battery is not stable during the first activation, and the error of the activation machine and other comprehensive factors cause certain error in the capacity test. SUMMARY

[0003] The present application aims to overcome the shortcomings of the prior art, and provides a kind of lithium battery activation machine's verification method, solve the problem of certain error in battery capacity test caused by the error of activation machine in the prior art.

[0004] To achieve the above-mentioned purpose, the present application is realized by using the following technical scheme:

[0005] The present application provides a kind of lithium battery activation machine's verification method, comprising:

[0006] obtain the first activation capacity of the measured battery tested by the test machine and the capacity recovery rate of the batch of batteries calculated in advance;

[0007] According to the first activation capacity of the measured battery and the capacity recovery rate of the batch of batteries calculated in advance, the theoretical capacity of the measured battery after normal temperature storage for a predetermined time is calculated;

[0008] After normal temperature storage for a predetermined time, the measured battery is activated again, and the actual capacity of the measured battery is obtained by using the test machine under a plurality of predetermined compensation current values;

[0009] Compare the capacity difference between the theoretical capacity and the actual capacity of the measured battery, obtain the best compensation current value, and use the best compensation current value to compensate the current of the test machine.

[0010] Further, the pre-calculated capacity recovery rate of the batch of batteries includes:

[0011] Obtaining the first activation capacity of the battery in the same batch as the measured battery tested by a precision machine;

[0012] After storing at room temperature for a predetermined time, reactivating the battery in the same batch as the measured battery, and obtaining the actual capacity of the battery in the same batch as the measured battery tested by a precision machine;

[0013] According to the first activation capacity and the actual capacity of the battery in the same batch as the measured battery, the capacity recovery rate of the batch of batteries is obtained.

[0014] Further, the formula for calculating the capacity recovery rate is: capacity recovery rate = actual capacity / first activation capacity*100%.

[0015] Further, the measured battery is a lithium battery stored at room temperature for a predetermined time, and the lithium battery is a secondary lithium-ion button full battery with a positive electrode of a ternary material 622 system and a negative electrode of a silicon-oxygen system.

[0016] Further, the formula for calculating the theoretical capacity is: theoretical capacity = first activation capacity*capacity recovery rate.

[0017] Further, the comparison of the capacity difference between the theoretical capacity and the actual capacity of the measured battery to obtain the optimal compensation current value includes: comparing the absolute value of the capacity difference to obtain the compensation current value when the absolute value of the capacity difference is the smallest, and the compensation current value is the optimal compensation current value.

[0018] Further, the reactivation of the measured battery includes first constant current discharge and then constant current and constant voltage charging, and the alternating cycle test of constant current discharge and constant current and constant voltage charging.

[0019] Further, the reactivation of the measured battery includes calculating various data of the measured battery during the activation process, including constant current and constant voltage charging time, constant current charging time, constant current charging ratio, charging voltage difference, charging capacity, discharging voltage difference, constant current discharging time, and discharging capacity.

[0020] Further, the range of the compensation current value is 0-1mA.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] The application provides a verification method of a lithium battery activation machine, which comprises the following steps: calculating the theoretical capacity of a measured battery after a preset time of normal temperature storage according to the first activation capacity of the measured battery and the capacity recovery rate of the batch of batteries calculated in advance; reactivating the measured battery after the preset time of normal temperature storage, and obtaining the actual capacity of the measured battery tested by a test machine under a plurality of preset compensation current values; comparing the capacity difference between the theoretical capacity and the actual capacity of the measured battery tested by the test machine under the plurality of preset compensation current values, obtaining the optimal compensation current value, and performing current compensation on the test machine by using the optimal compensation current value. The current compensation method is used for reducing the measurement error caused by the error of the machine itself, the machine can be accurately verified, the measurement error of the machine itself is greatly reduced, and the capacity test of subsequent batteries is more accurate. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a whole flowchart of the verification method of the lithium battery activation machine provided by the first embodiment of the application. DETAILED DESCRIPTION

[0024] The technical scheme of the application will be described in detail below with reference to the drawings and specific embodiments. It should be understood that the specific features in the embodiments and the specific features in the embodiments are detailed descriptions of the technical scheme of the application, and are not limitations of the technical scheme of the application. In the case of no conflict, the technical features in the embodiments and the embodiments can be combined with each other.

[0025] In this paper, the term "and / or" is only used to describe the association relationship of the associated objects, which means that there are three kinds of relationships, for example, A and / or B, which means that there are three kinds of situations, that is, A exists alone, A and B exist together, and B exists alone. In addition, the character " / " in this paper generally represents that the associated objects before and after it are in an "or" relationship.

[0026] Embodiment one:

[0027] Figure 1 is a flowchart of the verification method of the lithium battery activation machine provided by the first embodiment of the application.

[0028] The measured battery used in this embodiment is a self-made battery, which is a secondary lithium ion button full battery with a positive electrode of ternary 622 material and a negative electrode of silicon-oxygen system. The battery is a normal temperature storage battery. The charge and discharge current of the battery is 0.5C, the voltage range is 2800-4350mV, and the termination current of the constant current and constant voltage charging is 3.75mA.

[0029] Referring to Figure 1 , the method of this embodiment specifically comprises the following steps:

[0030] Step one: Obtain the first activation capacity of the measured battery tested by the test platform;

[0031] The test platform used in this embodiment is manufactured by Huizhou Deshengsheng Technology Co., Ltd., with current accuracy ± (0.1% RD + 0.1% FS), current range of 0.001A-0.2A during charging, current range of 0.001A-0.2A during discharging, and resolution of 1mA. The first activation capacities of 5 measured batteries activated by the test platform are 78.7mAh, 78.6mAh, 78.7mAh, 78.4mAh and 78.6mAh respectively. The first activation capacity of the measured battery tested by the test platform is the average of the first activation capacities of the 5 measured batteries, which is 78.6mAh.

[0032] Step two: Calculate the capacity recovery rate of the batch of batteries;

[0033] The process of calculating the capacity recovery rate of the batch of batteries includes:

[0034] Select 3 batteries of the same batch as the measured battery, test the first activation capacity of each battery using the laboratory precision platform, and then activate again after storing at room temperature for a predetermined time using the process in Table 1. Test the actual capacity of the 3 batteries of the same batch as the measured battery using the precision platform. The precision platform used is produced by Wuhan Lande Technology Co., Ltd. The predetermined time for storing the measured battery at room temperature is 8 months.

[0035] According to the first activation capacity and the actual capacity of each of the 3 batteries of the same batch as the measured battery, calculate the average of the first activation capacity and the average of the actual capacity of the 3 batteries. Take the average of the first activation capacity of the 3 batteries as the first activation capacity, and take the average of the actual capacity of the 3 batteries as the actual capacity. Calculate the capacity recovery rate of the batch of batteries from the first activation capacity and the actual capacity. The formula for calculating the capacity recovery rate is: capacity recovery rate = actual capacity / first activation capacity*100%.

[0036] From the measurement data in Table 1, the first activation capacity of the 3 batteries measured by the test platform is 79.43mAh, and the actual capacity tested after storing at room temperature for 8 months is 75.06mAh. From this, the value of the capacity recovery rate can be calculated: capacity recovery rate = actual capacity (mAh) / first activation capacity (mAh) * 100% = 75.06 / 79.43*100% = 94.49%. Therefore, the capacity recovery rate of this batch of batteries is 94.49%.

[0037] Table 1

[0038] Cell number Actual test capacity after 8 months (mAh) Initial activation capacity (mAh) Capacity recovery rate 26260100718 75.12 79.5 94.49％ 26260101236 74.72 79.4 94.11％ 26260100669 75.34 79.4 94.89％ Mean 75.06 79.43 94.49％

[0039] Step three: calculate the theoretical capacity of the measured battery after the preset time of normal temperature storage according to the first activation capacity of the measured battery and the pre-calculated capacity recovery rate of the batch of batteries;

[0040] The formula for calculating the theoretical capacity is: theoretical capacity (mAh) = first activation capacity (mAh) * capacity recovery rate.

[0041] In step one, the average of the first activation capacity of the five batteries activated by the test machine in this embodiment is 78.6 mAh, so the first activation capacity of the measured battery is 78.6 mAh. According to the formula for calculating the theoretical capacity, the theoretical capacities of the five batteries after 8 months of normal temperature storage are 74.36 mAh, 74.27 mAh, 74.36 mAh, 74.08 mAh and 74.27 mAh, with an average of 74.27 mAh. Therefore, the theoretical capacity of the measured battery is 74.27 mAh.

[0042] Step four: after the preset time of normal temperature storage, activate the measured battery again to obtain the actual capacity of the measured battery tested by the test machine under a preset number of compensation current values;

[0043] The reactivation of the measured battery includes reactivating the measured battery after 8 months of normal temperature storage, and the activation process is as shown in Table 2.

[0044] Table 2

[0045]

[0046] In this table, 1C = 75 mA, 0.5C = 37.5 mA, 0.05C = 3.7 mA, and the five batteries used are all 50% state-of-charge batteries, so constant current discharge is required before constant current and constant voltage charging during the activation process, and alternating cycle tests of constant current discharge and constant current and constant voltage charging are performed.

[0047] The compensation current is set to 0-1 mA, and the compensation current value is set by the set calibration coefficient and the theoretical capacity of the battery, i.e. compensation current value = theoretical capacity * calibration coefficient. The theoretical capacity of the measured battery in this embodiment is 75 mAh, and the calibration coefficients are 0%, 0.67%, 1.07% and 1.33% respectively, so the compensation current values are 0 mA, 0.5 mA, 0.8 mA and 1 mA respectively, i.e. the collection currents used are 5 mA, 4.5 mA, 4.2 mA and 4 mA respectively.

[0048] The 5 measured batteries were activated using 0 mA, 0.5 mA, 0.8 mA and 1 mA compensation currents respectively according to the activation process in Table 2. During the activation process, various data of the measured batteries were measured and calculated, including constant current constant voltage charging time, constant current charging time, constant current charging ratio, charging voltage difference, charging capacity, discharging voltage difference, constant current discharging time and discharging capacity. The measured data are shown in Table 3, Table 4, Table 5 and Table 6 respectively. Table 3 is the various data measured and calculated during the activation process of the 5 measured batteries using 0 mA compensation current, Table 4 is the various data measured and calculated during the activation process of the 5 measured batteries using 0.5 mA compensation current, Table 5 is the various data measured and calculated during the activation process of the 5 measured batteries using 0.8 mA compensation current, and Table 6 is the various data measured and calculated during the activation process of the 5 measured batteries using 1 mA compensation current.

[0049] From the table, for 0 mA, 0.5 mA, 0.8 mA and 1 mA compensation currents, the constant current constant voltage charging time is 128.26 min, 129.14 min, 131.20 min and 138.66 min respectively, the constant current charging ratio is 83.06%, 84.63%, 83.45% and 78.16% respectively, the constant current constant voltage charging time of the first three is basically close, the constant current charging ratio is also basically close, the constant current constant voltage charging time using 1 mA compensation current is longer, the constant current charging ratio is smaller, i.e. the constant voltage segment charging time is longer, so the charging capacity is larger than the first three, about 74.54 mAh; the constant current discharging time of the first three is also basically close, the discharging capacity of 1 mA compensation current is also larger than the first three, about 74.88 mAh.

[0050] Table 3

[0051]

[0052]

[0053] Table 4

[0054]

[0055] Table 5

[0056]

[0057] Table 6

[0058]

[0059]

[0060] The average of the data measured by activating the five measured batteries under the compensation currents of 0 mA, 0.5 mA, 0.8 mA and 1 mA is shown in Table 7. As shown in the table, the average of the actual capacities of the five measured batteries measured under the compensation currents of 0 mA, 0.5 mA, 0.8 mA and 1 mA is 71.18 mAh, 72.3 mAh, 73.16 mAh and 74.88 mAh respectively.

[0061] Table 7

[0062]

[0063] Step five: comparing the capacity difference between the theoretical capacity and the actual capacity of the measured battery after storing for a predetermined time at room temperature, obtaining the optimal compensation current value, and using the optimal compensation current value to compensate the current of the test machine.

[0064] From the above data, the capacity difference between the theoretical capacity and the actual capacity of the measured battery under the compensation currents of 0 mA, 0.5 mA, 0.8 mA and 1 mA is obtained, as shown in Table 8. The average of the capacity difference of the five measured batteries is taken as the capacity difference of the measured battery, which is 3.09 mAh, 1.97 mAh, 1.11 mAh and -0.61 mAh respectively.

[0065] The absolute value of the capacity difference is compared to obtain the compensation current value when the absolute value of the capacity difference is the smallest. The smaller the absolute value of the capacity difference, the closer the test capacity of the machine, the more accurate the compensation current used, and the smaller the error of the machine itself. Therefore, the compensation current value is the optimal compensation current value. In this embodiment, the optimal compensation current value obtained is the compensation current of 1 mA. Using this compensation current to compensate the current of the test machine can accurately calibrate the machine, greatly reduce the measurement error of the machine itself, and accurately calibrate the test machine, so that the capacity test of the subsequent battery is more accurate.

[0066] Table 8

[0067]

[0068] It should be noted that the newly made battery needs to be charged with a small current when performing the first activation, so as to activate the battery to form an SEI film (solid electrolyte interface film). The formation of the SEI film is relatively slow, and the performance of the battery itself is not very stable, and the error of the activation machine and other comprehensive factors will cause a certain error in the capacity test. The accuracy of the capacity test is not high, and the error of the activation machine itself always exists and cannot be eliminated. The battery stored for a long time at room temperature has good stability, which eliminates the measurement error caused by the instability of the battery, and the error of the activation machine itself becomes the main error. Therefore, the battery stored for a long time at room temperature can be reactivated to verify the precision error of the activation machine.

[0069] The embodiment provides a verification method of a lithium battery activation machine. The theoretical capacity of a measured battery after storage at room temperature for a preset time is calculated according to the first activation capacity of the measured battery and the capacity recovery rate of the batch of batteries calculated in advance. After storage at room temperature for a preset time, the measured battery is activated again, and the actual capacity of the measured battery under a preset number of compensation current values is obtained by using a test machine. The capacity difference between the theoretical capacity and the actual capacity of the measured battery under a preset number of compensation current values is compared, the best compensation current value is obtained, and the test machine is compensated by using the best compensation current value. By using the long-time room-temperature storage battery and the current compensation method, the measurement error caused by the error of the machine itself can be reduced, the machine can be accurately verified, the measurement error of the machine itself can be greatly reduced, and the capacity test of the subsequent battery is more accurate.

[0070] The above only describes the preferred embodiments of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should be considered as the protection scope of the present application.

Claims

1. A method for verifying a lithium battery activation machine, characterized in that, The application relates to a method for calculating the best compensation current value of a lithium battery. The method comprises the following steps: calculating the theoretical capacity of the measured battery after normal-temperature storage for a preset time according to the first activation capacity of the measured battery and the capacity recovery rate of the batch of batteries; activating the measured battery again, and obtaining the actual capacity of the measured battery under a preset number of compensation current values by using a test platform; comparing the capacity difference between the theoretical capacity and the actual capacity of the measured battery, obtaining the best compensation current value, and using the best compensation current value to compensate the current of the test platform; The calculation process of the capacity recovery rate of the batch of batteries comprises the following steps: obtaining the first activation capacity of the battery of the same batch as the measured battery by using a precision test platform; activating the battery of the same batch as the measured battery again, and obtaining the actual capacity of the battery of the same batch as the measured battery by using the precision test platform; obtaining the capacity recovery rate of the batch of batteries according to the first activation capacity and the actual capacity of the battery of the same batch as the measured battery; The comparison of the capacity difference between the theoretical capacity and the actual capacity of the measured battery to obtain the best compensation current value comprises the following steps: comparing the absolute value of the capacity difference to obtain the compensation current value when the absolute value of the capacity difference is the smallest, and the compensation current value is the best compensation current value.

2. The verification method of a lithium battery activation machine according to claim 1, characterized in that, The calculation formula of the capacity recovery rate is: capacity recovery rate = actual capacity / first activation capacity*100%.

3. The method of claim 1, wherein the method further comprises: The measured battery is a lithium battery after normal-temperature storage for a preset time, and the lithium battery is a secondary lithium ion button full battery with a positive electrode of a ternary material 622 system and a negative electrode of a silicon-oxygen system.

4. The method of claim 1, wherein the activation of the lithium battery is verified by a user. The calculation formula of the theoretical capacity is: theoretical capacity = first activation capacity*capacity recovery rate.

5. The method of claim 1, wherein the method further comprises: The activation of the measured battery comprises the following steps: first, discharging the measured battery by constant current, then charging the measured battery by constant current and constant voltage, and alternately testing the constant current discharging and the constant current and constant voltage charging.

6. The method of claim 1, wherein the method further comprises: The activation of the measured battery comprises the following steps: calculating various data of the measured battery during the activation process, and the various data comprise constant current and constant voltage charging time, constant current charging time, constant current charging proportion, charging voltage difference, charging capacity, discharging voltage difference, constant current discharging time and discharging capacity.

7. The method of claim 1, wherein the method further comprises: The range of the compensation current value is 0-1 mA.

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