A single battery sorting method suitable for high rate lithium ion battery production

Abstract

The application discloses a single battery sorting method for high-multiplying lithium ion battery production. The single battery to be sorted is first charged at a constant current to a preset cut-off voltage, and a charging polarization voltage AV1 is recorded after a period of storage. Then, the single battery to be sorted is discharged at a constant current for the first time, and a first discharging polarization voltage AV2 is recorded after a period of storage. Then, the single battery to be sorted is discharged at a constant current for the second time, and a second discharging polarization voltage AV3 is recorded after a period of storage. The single battery to be sorted is sorted through a clustering algorithm according to the charging polarization voltage AV1, the first discharging polarization voltage AV2 and the second discharging polarization voltage AV3. The sum of the electric quantity of the twice constant current discharging is equal to 1 / 2 of the nominal capacity of the single battery to be sorted, and the polarization characteristics of the single battery can be obtained only through half charging and half discharging, the test time is short, and the energy consumption is low.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery, in particular to a single battery sorting method suitable for high-rate lithium ion battery production. BACKGROUND

[0002] The lithium ion battery pack is composed of a large number of single batteries through series and parallel combination, and the performance of the battery pack is affected by the "bucket effect", that is, the performance of the battery pack is determined by the worst single battery in the battery pack. Due to the inconsistency of raw materials in actual production process, the fluctuation of production process and environmental factors, etc., the capacity, internal resistance and other parameters of the same type of battery produced in the same batch show differences, that is, inconsistency. Therefore, before the battery combination, the single battery is sorted and combined, and the single batteries with different parameters such as discharge capacity, internal resistance, voltage and self-discharge rate within a certain range are sorted out, and then combined in series and parallel.

[0003] Only by static parameter sorting cannot reflect the dynamic characteristics of the battery pack in the working process, especially the high-rate lithium ion battery, the consistency of the dynamic characteristics of the single battery has greater influence on the performance of the battery pack, and a small polarization increase during the discharge of the high-rate lithium ion battery can cause a large drop in the discharge voltage, resulting in the deterioration of the working characteristics and discharge capacity of the battery pack. Therefore, for high-rate lithium ion battery, the difference of the dynamic characteristics of the single battery must be considered, and the single battery needs to be further sorted according to the dynamic parameters.

[0004] And the acquisition of dynamic parameters needs full charging and full discharging of the single battery, even multiple cycles of full charging and full discharging, which has high energy consumption, complex data processing and low sorting efficiency. SUMMARY

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

[0006] The single battery sorting method suitable for high-rate lithium ion battery production provided by the present application comprises:

[0007] Charging the single battery to be sorted 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, the voltage V2 after the first leaving is recorded;

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

[0010] discharge the first time the to-be-sorted single battery after the first rest with a discharge current I2, and record the voltage V3 after the first discharge;

[0011] After the to-be-sorted single battery is rested for a second preset time, record the voltage V4 after the second rest;

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

[0013] Discharge the to-be-sorted single battery after the first discharge with a discharge current I3, and record the voltage V5 after the second discharge;

[0014] After the to-be-sorted single battery is rested for a third preset time, record the voltage V6 after the third rest;

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

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

[0017] Wherein, the first discharge capacity is less than 1 / 2 of the nominal capacity of the to-be-sorted single battery, the sum of the second discharge capacity and the first discharge capacity is equal to 1 / 2 of the nominal capacity of the to-be-sorted single battery, and a plurality of parallel single batteries form a battery pack.

[0018] Further, the charge current I1 is 1 / n of the battery pack charging current, the discharge current I2 is 1 / n of the battery pack working current, and the discharge current I3 is 1 / n of the battery pack maximum discharge current; Wherein, n is the number of parallel single batteries in the battery pack.

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

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

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

[0022] Calculate the average value ΔV 1a and the mean square error ΔV 1s, calculate the average value AV of the first discharge polarization voltage AV2 2a and mean square deviation AV 2s , calculate the average value AV of the second discharge polarization voltage AV3 3a and mean square deviation AV 3s ;

[0023] The single battery satisfying the preset sorting condition is reserved, and the single battery not satisfying the preset sorting condition is screened out to complete the sorting;

[0024] The preset sorting condition comprises:

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

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

[0027] The AV' a is the average value of the polarization voltage of the remaining single battery after the last time of screening out the single battery when the value of AV a / AV s is greater than the first threshold value.

[0028] Further, the discharge time t2 of the second discharge is calculated by the following formula:

[0029]

[0030] The C is the nominal capacity of the single battery.

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

[0032] (1) The present application utilizes the charging polarization voltage AV1, the first discharge polarization voltage AV2 and the second discharge polarization voltage AV3 to sort the dynamic parameters of the single battery to be sorted, without the need of full charging and full discharging test on the single battery, the single battery in the half-electric state is fully charged, and then the single battery to be sorted is discharged twice at a constant current, the sum of the two constant current discharges is equal to 1 / 2 of the nominal capacity of the single battery to be sorted, and the polarization characteristics of the single battery can be obtained only by half-charging and half-discharging, the test time is short, and the energy consumption is low.

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

[0034] It should be understood that the description in the Summary of the Invention is not intended to limit the key or essential features of the embodiments of the present invention, nor is it intended to restrict the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

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

[0036] Figure 1 This is a flowchart of the sorting method in this application; Detailed Implementation

[0037] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0038] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

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

[0040] S1: n parallel individual cells can form a battery pack. Select n cells that have been sorted by static parameters as individual cells to be sorted. Charge the individual cells to be sorted with a constant current I1 to the preset cutoff voltage V1. Wherein, the charging current I1 is 1 / n of the battery pack charging current.

[0041] S2: After charging is complete, the individual cells to be sorted are left to rest for 5-60 minutes, and the voltage V2 after the first rest is recorded.

[0042] S3: Calculate and record the difference between the preset cutoff voltage V1 and voltage V2, and determine the charging polarization voltage ΔV1, where the charging polarization voltage ΔV1 = V1 - V2;

[0043] S4: Perform a first constant current discharge on the single cell to be sorted after the first rest with the discharge current I2, and record the voltage V3 after the first discharge. The discharge current I2 is 1 / n of the battery pack operating current, and the amount of discharge in the first discharge is less than 1 / 2 of the nominal capacity of the single cell to be sorted.

[0044] S5: Let the single cell to be sorted after one discharge rest for 5-60 minutes, and record the voltage V4 after the second rest.

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

[0046] S7: Perform a first constant current discharge on the single cell to be sorted after the first rest with the discharge current I2, and record the voltage V3 after the first discharge. The discharge current I3 is 1 / n of the maximum discharge current of the battery pack, and the sum of the discharge capacity of the second discharge and the discharge capacity of the first discharge is equal to 1 / 2 of the nominal capacity of the single cell to be sorted.

[0047] S8: After the second discharge of a single cell is completed, let it rest for 5-60 minutes and record the voltage V6 after the third rest.

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

[0049] S10: Using the charging polarization voltage ΔV1, the first discharge polarization voltage ΔV2, and the second discharge polarization voltage ΔV3 as references, the individual cells to be sorted are sorted using a clustering algorithm. In this embodiment, the average value-mean square error clustering algorithm is used for sorting.

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

[0051] S101: First calculate the average value ΔV of multiple charging polarization voltages ΔV1. 1a and mean square error Δa 1s If ΔV 1a / ΔV 1s When the value is greater than the first threshold, filter out |ΔV1-ΔV 1a Calculate the average value ΔV' of the remaining individual cells corresponding to the maximum value of |. 1a and mean square error ΔV' 1s until ΔV'1a / ΔV' 1s If the value is less than the first threshold, proceed to the next step;

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

[0053] S103: Calculate the average value ΔV of the remaining individual cells ΔV2. 2a and mean square error ΔV 2s If ΔV 2a / ΔV 2s When the value is greater than the first threshold, filter out |ΔV2-ΔV 2a Calculate the average value ΔV' of the remaining cells corresponding to the maximum value of |. 2a and mean square error ΔV' 2s until ΔV' 2a / ΔV' 2s If the value is less than the first threshold, proceed to the next step;

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

[0055] S105: Calculate the average value ΔV3 of the remaining individual cells after screening. 3a and mean square error ΔV 3s If ΔV 3a / ΔV 3s When the value is greater than the first threshold, filter out |Δs3-ΔV 3a Calculate the average value ΔV' of the remaining individual cells corresponding to the maximum value of |. 3a and mean square error ΔV' 3s until ΔV' 3a / ΔV' 3s If the value is less than the first threshold, proceed to the next step;

[0056] S106:ΔV' 3a / ΔV' 3s When the value is less than the first threshold, calculate |ΔV3-ΔV' 3a|ΔV 3a the value of |ΔV3-ΔV 3a |ΔV 3a If the value of |ΔV3-ΔV

[0057] The embodiment of the application will be described below in combination with a specific example.

[0058] The 10 18650 type 2.2 Ah ternary lithium ion batteries are sorted in this embodiment, 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 10.8 V, a nominal capacity of 4.4 Ah, a design charging current of 2.2 A, a discharge working current of 4.4 A, and a maximum discharge current of 22 A. According to the actual working parameters of the battery pack, the charging current I1 for the polarization test of the battery to be sorted by the application is calculated as 2.2 A / 2 = 1.1 A, the I2 discharge current is 4.4 A / 2 = 2.2 A, and the I3 discharge current is 22 A / 2 = 11 A.

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

[0060] The specific sorting steps are as follows:

[0061] S1: The single battery is charged with a current of I1 = 1.1 A, and the charging cutoff voltage is the charging upper limit voltage V1 = 4.2 V of the single battery.

[0062] S2: After the charging is completed, the single battery voltage V2 is recorded after 30 min.

[0063] S3: The difference ΔV1 between V1 and V2 is calculated, and the results are shown in Table 1.

[0064] S4: The single battery is discharged with a current of I2 = 2.2 A, and the discharge time t1 = 20 min, and the single battery instantaneous voltage V3 at the end of discharge is recorded.

[0065] S5: After 30 min, the single battery voltage V4 is recorded.

[0066] S6: The difference ΔV2 between V4 and V3 is calculated, and the results are shown in Table 1.

[0067] S7: Perform constant current discharge on the above single cell with I3 = 11A for a discharge time t2 = 2min, and record the instantaneous voltage V5 of the single cell at the end of the discharge; where...

[0068]

[0069] S8: After resting for 30 minutes, record the voltage V6 of the individual battery.

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

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

[0072]

[0073] S10: Sorting batteries using a clustering algorithm.

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

[0075] 1) As shown in Tables 2 and 3, calculate the average value ΔV of the individual cells to be sorted, ΔV1. 1a =114.4 and the root 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 For the 7th battery with the highest value, recalculate the average value ΔV' of the remaining batteries ΔV1. 1a =113.2 and the root mean square error ΔV' 1s =2.1489, then ΔV' 1s / ΔV' 1a =0.0189>ε 11 Then filter out |ΔV1-ΔV' 1a The 9th battery with the highest value is used to recalculate the average value ΔV1 of the remaining batteries. 1a =112.5 and the root 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)]]> | 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 AV' 1a ]]> 113.2

[0081] 2) As shown in Table 4, taking the second preset threshold ε 12 = 0.015, calculating |ΔV1- ΔV" 1a 1 / ΔV" 1a , all batteries |ΔV1- ΔV" 1a | / ΔV" 1a are less than 8 12 , i.e. all batteries meet the sorting condition, entering step 3);

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

[0083]

[0084]

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

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

[0087] Battery serial number AV2 (mV) | 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 AV 2a ]] 147

[0088] 4) As shown in Table 6, taking the second preset threshold ε 22 = 0.015, calculating |ΔV2- ΔV 2a | / ΔV 2a , all batteries |ΔV2- ΔV 2a | / ΔV 2a are less than ε 22 , i.e. all batteries meet the sorting condition, entering step 5);

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

[0090] Battery serial number AV2 (mV) | 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 AV 2a ]] 147

[0091] 5) As shown in Tables 7 and 8, calculate the average value ΔV of the above 8 individual cells. 3a =566.9 and the root 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 For the 5th battery with the highest value, recalculate the average value ΔV′ of the remaining batteries ΔV3. 3a =561.9 and the root 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 AV3 (mV) | 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 AV 3a ]]> 566.9

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

[0095] Battery serial number AV3 (mV) | 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 AV' 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 As shown in Table 9, for all batteries |ΔV3-ΔV′ 3a | / ΔV′ 3a All less than ε 32 This means that all batteries meet the sorting criteria and the sorting process is complete.

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

[0098]

[0099]

[0100] Seven individual cells that meet the sorting criteria are selected from ten individual cells to be sorted, thus completing the sorting of individual cells.

[0101] In the description of the application, the terms "one embodiment", "some embodiments", "an embodiment", "one specific embodiment", "some specific embodiments", and the like, can mean the same or similar thing, i.e., one or more embodiments or examples. By way of illustration, all of the above terms, i.e., "one embodiment", "some embodiments", "an embodiment", "one specific embodiment", "some specific embodiments", and the like, can mean one implementation so that there can be a variety of embodiments or examples. Also, the terms "first", "second", "third", etc., can be used herein to describe various embodiments or examples and do not need to have an implied meaning such as "the best", "better", "optimal", "best", etc.

[0102] The above description is only preferred embodiments of the present application and is not intended to limit the present application. The present application can be variously changed and modified by those skilled in the art. Any modification, equivalent replacement, improvement, etc., made within the spirit and principle of the present application should be included in the scope of the present application.

Claims

1. A method for sorting single cells in high-rate lithium-ion battery production, characterized by, Comprising: with a charging current The single cells to be sorted are charged with a constant current to a preset cut-off voltage ; The first voltage after the first preset time is recorded ; According to a preset cutoff voltage and voltage Determining a charging polarization voltage ; with a discharge current performing a first constant current discharge on the to-be-sorted single battery after the first resting, and recording the voltage after the first discharge ; The voltage after the second time of standing is recorded ; According to the voltage and the voltage determining the first discharge polarization voltage ; with a discharge current The unsorted single battery after the first discharge is discharged with a constant current, and the voltage after the second discharge is recorded ; The third time of resting after the voltage is recorded ; According to the voltage and the voltage determining the second discharge polarization voltage ; According to the charging polarization voltage , the first discharging polarization voltage , and the second discharging polarization voltage , the monomer battery to be sorted is sorted; wherein the first discharge amount is less than 1 / 2 of the nominal capacity of the single battery to be sorted, the second discharge amount and the first discharge amount together equal 1 / 2 of the nominal capacity of the single battery to be sorted, and the plurality of parallel single batteries form a battery pack; the charging current 1 / n of the battery pack charging current, the discharging current 1 / n of the battery pack operating current, the discharging current 1 / n of the battery pack maximum discharging current; wherein n is the number of parallel single cells in the battery pack.

2. The high rate lithium-ion battery production cell sorting method of claim 1, wherein, the charging polarization voltage , the first discharging polarization voltage , the second discharging polarization voltage .

3. The method of claim 1, wherein the method is used for sorting cells produced in high-rate lithium-ion battery production, and wherein the method is characterized by: According to the charging polarization voltage , the first discharging polarization voltage , and the second discharging polarization voltage , the sorting of the to-be-sorted single battery includes: acquiring the charge polarization voltage of each of the to-be-sorted monomer batteries in the battery pack the first discharge polarization voltage and the second discharge polarization voltage ; Calculate the charging polarization voltage average and mean square deviation Calculate the polarization voltage of the first discharge electrode. average and mean square deviation Calculate the polarization voltage of the second discharge electrode. average and mean square deviation ; retaining the single batteries that meet the preset sorting condition and screening out the single batteries that do not meet the preset sorting condition to complete the sorting; wherein the preset sorting condition comprises: In when the value of the first threshold is greater than the value of the second threshold, the single battery corresponding to the maximum value in the values of the second threshold is screened out when the value of the first threshold is greater than the value of the second threshold, the single battery corresponding to the maximum value in the values of the second threshold In the value of the remaining monomer battery is less than a first threshold value or the value of the remaining monomer battery is less than a first threshold value, if the value of the remaining monomer battery is less than a second threshold value, the monomer battery corresponding to the value is retained, otherwise the monomer battery corresponding to the value is screened out; in, In order to be in When the value is greater than the first threshold, it is the average value of the polarization voltage of the remaining individual cells after the last screening of individual cells; wherein i = 1, 2, 3.

4. The method of claim 1, wherein the method is used for sorting cells produced in high-rate lithium-ion battery production. Also comprising: The discharge time of the second discharge is calculated using the following formula : ； wherein C is the nominal capacity of the single battery.

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