Single battery sorting method suitable for high-rate lithium ion battery production

Abstract

The invention discloses a single battery sorting method for high-magnification lithium ion battery production, which comprises the following steps of: firstly, carrying out constant-current charging on a single battery to be sorted to a preset cut-off voltage, and recording a charging polarization voltage delta V1 after standing for a period of time; carrying out first constant-current discharge on the to-be-sorted single batteries, and recording first discharge polarization voltage delta V2 after standing for a period of time; carrying out secondary constant-current discharge on the to-be-sorted single batteries, and recording secondary discharge polarization voltage delta V3 after standing for a period of time; and sorting the single batteries to be sorted through a clustering algorithm according to the charging polarization voltage delta V1, the first discharging polarization voltage delta V2 and the second discharging polarization voltage delta V3. The sum of the electric quantities of two times of constant-current discharging is equal to 1 / 2 of the nominal capacity of the single battery to be sorted, the polarization characteristics of the single battery can be obtained only through half charging and half discharging, the testing time is short, and the energy consumption is low.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a single cell sorting method suitable for the production of high-rate lithium-ion batteries. Background Art

[0002] Lithium-ion battery packs are composed of a large number of single cells connected in series and parallel. The performance of the battery pack is affected by the "barrel effect", that is, the performance of the battery pack is determined by the single cell with the worst quality in the battery pack. Due to the inconsistency of batches of raw materials, fluctuations in production processes and environmental factors in the actual production process, the capacity, internal resistance and other parameters of the same type of battery cells produced in the same batch show differences, that is, inconsistency. Once these differences exceed a certain range, they will have a significant impact on the performance of the battery pack. Therefore, before the battery is combined, the single cells must be sorted and grouped, and the single cells with differences in parameters such as discharge capacity, internal resistance, voltage, and self-discharge rate within a certain range must be sorted out, and then combined in series and parallel after grouping.

[0003] Static parameter sorting alone cannot reflect the dynamic characteristics of the battery pack during operation, especially for high-rate lithium-ion batteries, where the charge and discharge currents are large. The consistency of the dynamic characteristics of the single cell has a greater impact on the performance of the battery pack. When a high-rate lithium-ion battery is discharged, a small increase in polarization can cause a significant drop in the discharge voltage, leading to degradation of the battery pack's operating characteristics and discharge capacity. Therefore, for high-rate lithium-ion batteries, the differences in the dynamic characteristics of the single cells must be considered, and the single cells must be further sorted based on the dynamic parameters.

[0004] The acquisition of dynamic parameters requires full charging and discharging of the single battery, or even multiple cycles of full charging and discharging, which has high energy consumption, complex data processing and low sorting efficiency. Summary of the invention

[0005] In view of the above defects or deficiencies in the prior art, it is desired to provide a single cell sorting method suitable for high-rate lithium-ion battery production, which can obtain the dynamic parameters of the single cell by only half-charging and half-discharging the single cell, with short test time, high sorting efficiency and low energy consumption.

[0006] The present invention provides a single cell sorting method suitable for high-rate lithium-ion battery production, comprising:

[0007] The single battery to be sorted is charged with a charging current I1 to a preset cut-off voltage V1;

[0008] After the single battery to be sorted is left for a first preset time, a voltage V2 after the first leaving is recorded;

[0009] Determine the charging polarization voltage ΔV1 according to the preset cut-off voltage V1 and the voltage V2;

[0010] Performing a first constant current discharge on the single battery to be sorted after the first placement with a discharge current I2, and recording a voltage V3 after the first discharge;

[0011] After the single battery to be sorted is placed for a second preset time, a voltage V4 after the second placement is recorded;

[0012] Determine a first discharge polarization voltage ΔV2 according to the voltage V3 and the voltage V4;

[0013] Performing constant current discharge on the single battery to be sorted after the first discharge with a discharge current I3, and recording a voltage V5 after the second discharge;

[0014] After the single battery to be sorted is left for a third preset time, a voltage V6 after the third time of leaving is recorded;

[0015] Determine a second discharge polarization voltage ΔV3 according to the voltage V5 and the voltage V6;

[0016] Sorting the single cells to be sorted according to the charge polarization voltage ΔV1, the first discharge polarization voltage ΔV2 and the second discharge polarization voltage ΔV3;

[0017] The first discharge power is lower than 1 / 2 of the nominal capacity of the single cell to be sorted, the sum of the second discharge power and the first discharge power is equal to 1 / 2 of the nominal capacity of the single cell to be sorted, and multiple single cells connected in parallel form a battery pack.

[0018] Furthermore, the charging current I1 is 1 / n of the charging current of the battery pack, the discharging current I2 is 1 / n of the operating current of the battery pack, and the discharging current I3 is 1 / n of the maximum discharging current of the battery pack; wherein n is the number of single cells connected in parallel in the battery pack.

[0019] Furthermore, the charging polarization voltage ΔV1 = V1 - V2, the first discharge polarization voltage ΔV2 = V4 - V3, and the second discharge polarization voltage ΔV3 = V6 - V5.

[0020] Further, the single cells to be sorted are sorted according to the charge polarization voltage ΔV1, the first discharge polarization voltage ΔV2 and the second discharge polarization voltage ΔV3, including:

[0021] Obtaining the charge polarization voltage ΔV1, the first discharge polarization voltage ΔV2, and the second discharge polarization voltage ΔV3 of each single battery to be sorted in the battery pack;

[0022] Calculate the average value ΔV of the charging polarization voltage ΔV1 1a and mean square error ΔV 1s, calculate the average value ΔV of the first discharge polarization voltage ΔV2 2a and mean square error ΔV 2s , calculate the average value ΔV of the second discharge polarization voltage ΔV3 3a and mean square error ΔV 3s ;

[0023] Retaining the single cells that meet the preset sorting conditions, and screening out the single cells that do not meet the preset sorting conditions to complete the sorting;

[0024] Wherein, the preset sorting conditions include:

[0025] In ΔV a / ΔV s When the value of is greater than the first threshold, |ΔV-ΔV is screened out a The single cell corresponding to the maximum value of |;

[0026] In ΔV a / ΔV s The value is less than the first threshold or the ΔV of the remaining single battery a / ΔV s When the value of is less than the first threshold, if |ΔV-ΔV' a | / ΔV' a If the value of is less than the second threshold, the single battery corresponding to the value is retained, otherwise the single battery corresponding to the value is screened out;

[0027] Where, ΔV' a For ΔV a / ΔV s When the value of is greater than the first threshold, the average value of the polarization voltages of the remaining single cells after the single cell is screened out for the last time.

[0028] Furthermore, the discharge time t2 of the second discharge is calculated using the following formula:

[0029]

[0030] Where C is the nominal capacity of the single cell.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] (1) The present application utilizes the charge polarization voltage ΔV1, the first discharge polarization voltage ΔV2, and the second discharge polarization voltage ΔV3 to sort the dynamic parameters of the single cell to be sorted. There is no need to perform a full charge and full discharge test on the single cell. The single cell in a half-charged state is fully charged, and then the single cell to be sorted is subjected to two constant current discharges. The sum of the two constant current discharges is equal to 1 / 2 of the nominal capacity of the single cell to be sorted. The polarization characteristics of the single cell can be obtained by only half charging and half discharging. The test time is short and the energy consumption is low.

[0033] (2) After the single cells are sorted, the state of charge of the single cells is close to half-charged, and the battery pack does not need to be charged or discharged to adjust the voltage to meet the factory conditions.

[0034] It should be understood that the contents described in the summary of the invention are not intended to limit the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0036] Figure 1 A flow chart of the sorting method of the present application; DETAILED DESCRIPTION

[0037] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It should also be noted that, for ease of description, only the parts related to the invention are shown in the accompanying drawings.

[0038] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0039] Please refer to Figure 1 The embodiment of the present invention provides a single cell sorting method for high-rate lithium-ion battery production, comprising the following steps:

[0040] S1: n single cells connected in parallel can form a battery pack, and n cells that have been sorted by static parameters are selected as single cells to be sorted. The single cells to be sorted are charged with a constant current of I1 to a preset cut-off voltage V1, wherein the charging current I1 is 1 / n of the charging current of the battery pack;

[0041] S2: After charging, the single cell to be sorted is placed for 5-60 minutes, and the voltage V2 after the first placement is recorded;

[0042] S3: Calculate and record the difference between the preset cut-off voltage V1 and the voltage V2 to determine the charge polarization voltage ΔV1, where the charge polarization voltage ΔV1 = V1 - V2;

[0043] S4: performing a first constant current discharge on the single battery to be sorted after the first placement with a discharge current I2, and recording a voltage V3 after the first discharge, wherein the discharge current I2 is 1 / n of the working current of the battery pack, and the first discharge quantity is lower than 1 / 2 of the nominal capacity of the single battery to be sorted;

[0044] S5: placing the single battery to be sorted after the first discharge for 5-60 minutes, and recording the voltage V4 after the second placement;

[0045] S6: Calculate and record the difference between the voltage V3 and the voltage V4 to determine the first discharge polarization voltage ΔV2, wherein the first discharge polarization voltage ΔV2 = V4 - V3;

[0046] S7: performing a first constant current discharge on the single battery to be sorted after the first standby with a discharge current I2, and recording a voltage V3 after the first discharge, wherein the discharge current I3 is 1 / n of the maximum discharge current of the battery pack, and the sum of the second discharge power and the first discharge power is equal to 1 / 2 of the nominal capacity of the single battery to be sorted;

[0047] S8: Leave the single cell that has completed the second discharge for 5-60 minutes, and record the voltage V6 after the third leave-behind;

[0048] S9: Calculate and record the difference between the voltage V5 and the voltage V6 to determine the second discharge polarization voltage ΔV3, wherein the first discharge polarization voltage ΔV3 = V6 - V5;

[0049] S10: using the charge polarization voltage ΔV1, the first discharge polarization voltage ΔV2 and the second discharge polarization voltage ΔV3 as references, sorting the single cells to be sorted by a clustering algorithm. In this embodiment, the sorting is performed by a mean-mean square error clustering algorithm.

[0050] The specific sorting process of the mean-mean square error clustering algorithm is as follows:

[0051] S101: First calculate the average value ΔV of multiple groups of charging polarization voltages ΔV1 1a and mean square error Δa 1s , if ΔV 1a / ΔV 1s When the value of is greater than the first threshold, |ΔV1-ΔV 1a |The value of the single cell corresponding to the maximum value, calculate the average value ΔV' of the remaining single cells ΔV1 1a and mean square error ΔV' 1s , until ΔV'1a / ΔV' 1s The value is less than the first threshold value and proceeds to the next step;

[0052] S102: ΔV' 1a / ΔV' 1s When the value of is less than the first threshold, calculate |ΔV1-ΔV' 1a | / ΔV' 1a If |ΔV1-ΔV' 1a | / ΔV' 1a If the value of is less than the second threshold, the single cell corresponding to the value is retained, otherwise the single cell corresponding to the value is screened out, and the first screening is completed based on ΔV1;

[0053] S103: Calculate the average value ΔV of ΔV2 of the remaining single cells 2a and mean square error ΔV 2s , if ΔV 2a / ΔV 2s When the value of is greater than the first threshold, |ΔV2-ΔV 2a |The value of the single cell corresponding to the maximum value, calculate the average value ΔV' of the remaining single cells ΔV2 2a and mean square error ΔV' 2s , until ΔV' 2a / ΔV' 2s The value is less than the first threshold value and proceeds to the next step;

[0054] S104: ΔV' 2a / ΔV' 2s When the value of is less than the first threshold, calculate |ΔV2-ΔV' 2a | / ΔV' 2a If |ΔV2-ΔV' 2a | / ΔV' 2a If the value of is less than the second threshold, the single cell corresponding to the value is retained, otherwise the single cell corresponding to the value is screened out, and the second screening is completed based on ΔV2;

[0055] S105: Calculate the average value ΔV of ΔV3 of the remaining cells after screening 3a and mean square error ΔV 3s , if ΔV 3a / ΔV 3s When the value of is greater than the first threshold, |Δs3-ΔV is screened out 3a |The value of the single cell corresponding to the maximum value, calculate the average value ΔV' of the remaining single cells ΔV3 3a and mean square error ΔV' 3s , until ΔV' 3a / ΔV' 3s The value is less than the first threshold value and proceeds to the next step;

[0056] S106: ΔV' 3a / ΔV' 3s When the value of is less than the first threshold, calculate |ΔV3-ΔV' 3a| / ΔV' 3a If |ΔV3-ΔV' 3a | / ΔV' 3a If the value of is less than the second threshold, the single cell corresponding to the value is retained, otherwise the single cell corresponding to the value is screened out, and the third screening is completed based on ΔV3, and finally the single cell left by the screening is retained to complete the sorting.

[0057] The embodiment of the present application is described below with reference to a specific example.

[0058] In this embodiment, 10 18650 type 2.2Ah ternary lithium-ion batteries are sorted, and the sorted batteries are used to produce a lithium-ion battery pack with a combined structure of 3S2P. The above lithium-ion battery pack has a nominal voltage of 10.8V, a nominal capacity of 4.4Ah, a designed charging current of 2.2A, a discharge working current of 4.4A, and a maximum discharge current of 22A. According to the actual working parameters of the battery pack, it can be calculated that the charging current I1 when the present invention is used to perform charge and discharge polarization tests on the battery to be sorted is 2.2A / 2=1.1A, the discharge current I2 is 4.4A / 2=2.2A, and the discharge current I3 is 22A / 2=11A.

[0059] The above 10 18650 type single cells have been preliminarily sorted by the battery cell factory based on static parameters, and the results are as follows: capacity range 2210mAh-2230mAh, voltage range 3.650V-3.653V, internal resistance range 22mΩ-23mΩ.

[0060] The specific sorting steps are as follows:

[0061] S1: The single cell is charged with a constant current of I1 = 1.1A, and the charging cut-off voltage is the upper limit voltage of the single cell V1 = 4.2V;

[0062] S2: After charging, leave it for 30 minutes and record the single cell voltage V2;

[0063] S3: Calculate the difference ΔV1 between V1 and V2, and the result is shown in Table 1;

[0064] S4: Discharge the above single cell at a constant current of I2 = 2.2A for a discharge time of t1 = 20 min, and record the instantaneous voltage V3 of the single cell at the end of the discharge;

[0065] S5: After standing for 30 minutes, record the voltage V4 of the single cell;

[0066] S6: Calculate the difference ΔV2 between V4 and V3, and the result is shown in Table 1;

[0067] S7: Discharge the above single cell at a constant current of I3 = 11A, the discharge time t2 = 2min, and record the instantaneous voltage V5 of the single cell at the end of the discharge; wherein,

[0068]

[0069] S8: After standing for 30 minutes, record the single cell voltage V6;

[0070] S9: Calculate the difference ΔV3 between V6 and V5. The result is shown in Table 1:

[0071] Table 1 Polarization voltages of the batteries under test

[0072]

[0073] S10: sorting the batteries by clustering algorithm.

[0074] This example uses the mean-mean square error clustering algorithm to sort batteries:

[0075] 1) As shown in Table 2 and Table 3, calculate the average value ΔV of ΔV1 of the single battery to be sorted 1a =114.4 and mean square error ΔV 1s =4.0792, take the first preset threshold ε 11 =0.01, then ΔV 1s / ΔV 1a =0.0357>ε 11 . Screening out |ΔV1-ΔV 1a | The 7th battery with the largest value, recalculate the average value ΔV' of the remaining batteries ΔV1 1a =113.2 and mean square error ΔV' 1s =2.1489, then ΔV' 1s / ΔV' 1a =0.0189>ε 11 . Then remove |ΔV1-ΔV' 1a | The 9th battery with the largest value, recalculate the average value ΔV″ of the remaining batteries ΔV1 1a =112.5 and mean square error ΔV″ 1s =0.7071, then ΔV″ 1s / ΔV″ 1a =0.0063<ε 11 , proceed to step 2);

[0076] Table 2 | ΔV1-ΔV 1a |Calculation table

[0077]

[0078]

[0079] Table 3 | ΔV1-ΔV′ 1a |Calculation table

[0080] Battery serial number <![CDATA[|ΔV1(mV)]]> <![CDATA[|ΔV1-ΔV′ 1a |]]> 1 113 0.2 2 113 0.2 3 112 1.2 4 111 2.2 5 113 0.2 6 112 1.2 8 113 0.2 9 119 5.8 10 113 0.2 <![CDATA[ΔV′ 1a ]]> 113.2

[0081] 2) As shown in Table 4, take the second preset threshold ε 12 = 0.015, calculate |ΔV1-ΔV″ 1a 1 / ΔV″ 1a , all batteries |ΔV1-ΔV″ 1a | / ΔV″ 1a All less than 8 12 , that is, all batteries meet the sorting conditions, and go to step 3);

[0082] Table 4 | ΔV1-ΔV″ 1a | / ΔV″ 1a Calculation table

[0083]

[0084]

[0085] 3) As shown in Table 5, calculate the average value ΔV of ΔV1 of the above 8 remaining single cells: 2a =147 and mean square error ΔV 2s =2.7386, take the first preset threshold ε 12 =0.02, calculate ΔV 2s / ΔV 2a =0.0186<ε 12 , all the remaining 8 cells enter step 4);

[0086] Table 5 | ΔV2-ΔV 2a |Calculation table

[0087] Battery serial number <![CDATA[ΔV2(mV)]]> <![CDATA[|ΔV2-ΔV 2a |]]> 1 148 1 2 149 2 3 144 3 4 143 4 5 151 4 6 144 3 8 149 2 10 148 1 <![CDATA[ΔV 2a ]]> 147

[0088] 4) As shown in Table 6, take the second preset threshold ε 22 = 0.015, calculate |ΔV2-ΔV 2a | / ΔV 2a , all cells |ΔV2-ΔV 2a | / ΔV 2a Both are less than ε 22 , that is, all batteries meet the sorting conditions, and go to step 5);

[0089] Table 6 | ΔV2-ΔV 2a | / ΔV 2a Calculation table

[0090] Battery serial number <![CDATA[ΔV2(mV)]]> <![CDATA[|ΔV2-ΔV 2a | / ΔV 2a ]]> 1 148 0.006803 2 149 0.013605 3 144 0.02041 4 143 0.02721 5 151 0.027211 6 144 0.02041 8 149 0.013605 10 148 0.006803 <![CDATA[ΔV 2a ]]> 147

[0091] 5) As shown in Table 7 and Table 8, the average value ΔV of ΔV3 of the above 8 single cells is calculated. 3a =566.9 and mean square error ΔV 3s =12.4132, take the first preset threshold ε 31 =0.01, then ΔV 3s / ΔV 3a =0.0219>ε 31 . Screening out |ΔV3-ΔV 3a | The fifth battery with the largest value, recalculate the average value ΔV′ of the remaining batteries ΔV3 3a =561.9 and mean square error ΔV′ 3s =4.3239, then ΔV′ 3s / ΔV′ 3a =0.0077<ε 31 , proceed to step 6);

[0092] Table 7 | ΔV3-ΔV 3a |Calculation table

[0093] Battery serial number <![CDATA[ΔV3(mV)]]> <![CDATA[|ΔV3-ΔV 3a |]]> 1 560 6.9 2 561 5.9 3 568 1.1 4 555 11.9 5 602 35.1 6 568 1.1 8 561 5.9 10 560 6.9 <![CDATA[ΔV 3a ]]> 566.9

[0094] Table 8 | ΔV3-ΔV′ 3a |Calculation table

[0095] Battery serial number <![CDATA[ΔV3(mV)]]> <![CDATA[|ΔV3-ΔV′ 3a |]]> 1 560 1.9 2 561 0.9 3 568 6.1 4 555 6.9 6 568 6.1 8 561 0.9 10 560 1.9 <![CDATA[ΔV′ 3a ]]> 561.9

[0096] 6) As shown in Table 9, take the second preset threshold ε 32 = 0.015, calculate |ΔV3-ΔV′ 3a | / ΔV′ 3a , it can be seen from Table 9 that all batteries |ΔV3-ΔV′ 3a | / ΔV′ 3a Both are less than ε 32 , that is, all batteries meet the sorting conditions and the sorting is completed.

[0097] Table 9 | ΔV3-ΔV′ 3a | / ΔV′ 3a Calculation table

[0098]

[0099]

[0100] 7 single cells that meet the sorting conditions are sorted out from 10 single cells to be sorted, and the sorting of the single cells is completed.

[0101] In the description of this specification, the description of the terms "one embodiment", "some embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0102] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for sorting single cells in the production of high-rate lithium-ion batteries, characterized in that: include: The single battery to be sorted is charged with a charging current I1 to a preset cut-off voltage V1; After the single battery to be sorted is left for a first preset time, a voltage V2 after the first leaving is recorded; Determine the charging polarization voltage ΔV1 according to the preset cut-off voltage V1 and the voltage V2; Performing a first constant current discharge on the single battery to be sorted after the first placement with a discharge current I2, and recording a voltage V3 after the first discharge; After the single battery to be sorted is placed for a second preset time, a voltage V4 after the second placement is recorded; Determine a first discharge polarization voltage ΔV2 according to the voltage V3 and the voltage V4; Performing constant current discharge on the single battery to be sorted after the first discharge with a discharge current I3, and recording a voltage V5 after the second discharge; After the single battery to be sorted is left for a third preset time, a voltage V6 after the third time of leaving is recorded; Determine a second discharge polarization voltage ΔV3 according to the voltage V5 and the voltage V6; Sorting the single cells to be sorted according to the charge polarization voltage ΔV1, the first discharge polarization voltage ΔV2 and the second discharge polarization voltage ΔV3; The first discharge power is lower than 1 / 2 of the nominal capacity of the single cell to be sorted, the sum of the second discharge power and the first discharge power is equal to 1 / 2 of the nominal capacity of the single cell to be sorted, and multiple single cells connected in parallel form a battery pack.

2. The method for sorting single cells in the production of high-rate lithium-ion batteries according to claim 1, characterized in that: The charging current I1 is 1 / n of the charging current of the battery pack, the discharging current I2 is 1 / n of the working current of the battery pack, and the discharging current I3 is 1 / n of the maximum discharging current of the battery pack; wherein n is the number of single cells connected in parallel in the battery pack.

3. The method for sorting single cells in the production of high-rate lithium-ion batteries according to claim 1, characterized in that: The charging polarization voltage ΔV1 = V1 - V2, the first discharge polarization voltage ΔV2 = V4 - V3, and the second discharge polarization voltage ΔV3 = V6 - V5.

4. The method for sorting single cells in the production of high-rate lithium-ion batteries according to claim 1, characterized in that: The single cells to be sorted are sorted according to the charge polarization voltage ΔV1, the first discharge polarization voltage ΔV2 and the second discharge polarization voltage ΔV3, comprising: Obtaining the charge polarization voltage ΔV1, the first discharge polarization voltage ΔV2, and the second discharge polarization voltage ΔV3 of each single battery to be sorted in the battery pack; Calculate the average value ΔV of the charging polarization voltage ΔV1 1a and mean square error ΔV 1s , calculate the average value ΔV of the first discharge polarization voltage ΔV2 2a and mean square error ΔV 2s , calculate the average value ΔV of the second discharge polarization voltage ΔV3 3a and mean square error ΔV 3s ; Retaining the single cells that meet the preset sorting conditions, and screening out the single cells that do not meet the preset sorting conditions to complete the sorting; Wherein, the preset sorting conditions include: In ΔV a / ΔV s When the value of is greater than the first threshold, |ΔV-ΔV is screened out a The single cell corresponding to the maximum value of |; In ΔV a / ΔV s The value is less than the first threshold or the ΔV of the remaining single battery a / ΔV s When the value of is less than the first threshold, if |ΔV-ΔV' a | / ΔV' a If the value of is less than the second threshold, the single battery corresponding to the value is retained, otherwise the single battery corresponding to the value is screened out; Where, ΔV' a For ΔV a / ΔV s When the value of is greater than the first threshold, the average value of the polarization voltages of the remaining single cells after the single cell is screened out for the last time.

5. The method for sorting single cells in the production of high-rate lithium-ion batteries according to claim 1, characterized in that: Also includes: The discharge time t2 of the second discharge is calculated using the following formula: Where C is the nominal capacity of the single cell.

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