CN114260213A

CN114260213A - Screening method and system for lithium ion battery consistency

Info

Publication number: CN114260213A
Application number: CN202111616564.4A
Authority: CN
Inventors: 李洁辰
Original assignee: Shanghai Rox Intelligent Technology Co Ltd
Current assignee: Shanghai Rox Intelligent Technology Co Ltd
Priority date: 2021-12-27
Filing date: 2021-12-27
Publication date: 2022-04-01

Abstract

The invention provides a screening method and a system for lithium ion battery consistency, which comprises the following steps: primarily screening a preset number of single battery cells to obtain first single battery cells; performing high-temperature pulse test on the first monomer battery cell reaching the preset high-temperature pulse test temperature, and screening out a second monomer battery cell; performing high-temperature storage test on the second monomer battery cell at a preset high-temperature storage test temperature, and screening out a third monomer battery cell; carrying out a low-temperature charging test on the third monomer battery cell, and screening out a fourth monomer battery cell; and (5) carrying out a normal temperature performance recovery test on the fourth monomer battery cell, and screening out the monomer battery cells with consistency. The method is simple to operate, effectively shortens the screening period, and improves the screening efficiency and accuracy of the battery cell.

Description

Screening method and system for lithium ion battery consistency

Technical Field

The invention relates to the technical field of new energy batteries, in particular to a screening method and system for lithium ion battery consistency.

Background

With the rapid development of the electric automobile industry, the holding capacity of electric automobiles continues to increase. Lithium ion batteries have the advantages of high energy density, high power, high safety, long service life, and the like, and thus are becoming core energy components of electric vehicles. Due to the limitations of the capacity and power of the single battery cells, the power battery system of the electric automobile is often formed by combining dozens, hundreds or even thousands of lithium ion single battery cells in a series-parallel connection mode. The single battery cell has certain differences in voltage, capacity, internal resistance, service life, temperature influence, self-discharge rate and the like, and the use environments of the single batteries in the battery pack are not completely the same, so that the inconsistency of the single batteries is gradually amplified, the performance attenuation of the batteries is accelerated, the performance difference is continuously accumulated in the use process, and the premature failure of the battery pack is finally caused.

From the above, the uniformity of the single battery cells directly influences the performance of the battery pack, so that the service life and the use safety of the electric automobile are determined. Therefore, an effective method must be adopted to evaluate and screen the batteries before the batteries are used, so as to ensure high consistency of the grouped batteries. Meanwhile, when the battery system fails, the differential failure monomer can be rapidly and accurately distinguished from a plurality of battery cells, so that the service life of the power battery system is guaranteed, and the failure problem is searched and solved. The conventional cell screening and evaluation process is long in period, complex in procedure, low in screening efficiency and high in screening misjudgment rate.

Disclosure of Invention

In view of this, the present invention aims to provide a screening method and system for lithium ion battery consistency, which is simple in operation, effectively shortens the screening period, and improves the cell screening efficiency and accuracy.

In order to achieve the above purpose, the embodiment of the present invention adopts the following technical solutions:

in a first aspect, an embodiment of the present invention provides a method for screening consistency of lithium ion batteries, including: primarily screening a preset number of single battery cells to obtain first single battery cells; performing high-temperature pulse test on the first monomer battery cell reaching the preset high-temperature pulse test temperature, and screening out a second monomer battery cell; performing high-temperature storage test on the second monomer battery cell at a preset high-temperature storage test temperature, and screening out a third monomer battery cell; carrying out a low-temperature charging test on the third monomer battery cell, and screening out a fourth monomer battery cell; and (5) carrying out a normal temperature performance recovery test on the fourth monomer battery cell, and screening out the monomer battery cells with consistency.

In an embodiment, preliminarily screening a preset number of monomer electric cores to obtain a first monomer electric core, includes: acquiring a first voltage value and a first internal resistance value of each single battery cell;

calculating an average value of the first voltage values and an average value of the first internal resistance values which meet the first preset screening condition to obtain a first average voltage value and a first average internal resistance value; the first preset screening condition comprises a first preset voltage value screening range and a first preset internal resistance value screening range;

determining a first voltage interval according to the first average voltage value and the first preset voltage deviation value, and determining a first internal resistance interval according to the first average internal resistance value and the first preset internal resistance deviation value;

determining the monomer electric cores corresponding to the first voltage value and the first internal resistance value which meet the first voltage interval and the first internal resistance interval in the first voltage values and the first internal resistance values of the preset number of monomer electric cores as the first monomer electric cores.

In one embodiment, before performing a pulse test for a preset number of times on a first cell reaching a preset high-temperature pulse test temperature and screening out a second cell, the method further includes:

after each first monomer battery cell is subjected to one-time standard charging and discharging, and each first monomer battery cell is charged to a first preset charge state by first preset electric quantity, a first discharge capacity and a second internal resistance value are obtained.

In one embodiment, the high-temperature pulse test is performed on a first monomer battery cell which reaches a preset high-temperature pulse test temperature, and a second monomer battery cell is screened out, including:

carrying out charge-discharge cycle test on the first monomer battery cell reaching the preset high-temperature pulse test temperature for preset times by using second preset electric quantity, and obtaining a second discharge capacity and a third internal resistance value of the first monomer battery cell after test; wherein the range of the preset high-temperature pulse testing temperature is 40-55 ℃;

calculating a first capacity difference between the second discharge capacity and the first discharge capacity of each first monomer battery cell and a first internal resistance difference between the second internal resistance value and the third internal resistance value;

acquiring an average value and a corresponding variance of first capacity differences of each first monomer battery cell, and an average value and a corresponding variance of first internal resistance differences of each first monomer battery cell;

calculating the average value, the corresponding variance and a second preset voltage deviation value of the first capacity difference by adopting a preset interval algorithm to obtain a first capacity interval, and calculating the average value, the corresponding variance and the second preset internal resistance deviation value of the first internal resistance difference to obtain a second internal resistance interval;

and determining the first monomer battery cell corresponding to the second discharge capacity and the third internal resistance value which meet the first capacity interval and the second internal resistance interval in the second discharge capacity and the third internal resistance value of each first monomer battery cell as a second monomer battery cell.

In one embodiment, the method for performing a preset number of charge and discharge cycle tests on a first monomer battery cell reaching a preset high-temperature pulse test temperature with a second preset electric quantity includes:

charging the first monomer battery cell reaching the preset high-temperature pulse test temperature for a first preset time by second preset electric quantity or charging the first monomer battery cell to a first preset cut-off voltage;

after the second preset time, discharging the charged first monomer battery cell for a third preset time with a second preset electric quantity or to a second preset cut-off voltage;

and after the fourth preset time, performing charge-discharge cycle test on the first monomer battery cell for preset times.

In one embodiment, obtaining the second discharge capacity and the third internal resistance value of the first cell after the test includes:

performing capacity recovery calibration on the first monomer battery cell which is tested and reaches the preset temperature according to standard charging and discharging to obtain a second discharge capacity of the first monomer battery cell; wherein the preset temperature is lower than the preset high-temperature pulse testing temperature; the preset temperature range is 23-27 ℃;

and after the first monomer battery cell after the recovery capacity calibration is recharged to a full-charge state with a preset current and a preset voltage, acquiring a second voltage value and a third internal resistance value.

In one embodiment, at a preset high temperature storage test temperature, performing a high temperature storage test on the second cell, and screening out a third cell, includes:

after the second single battery cell in the full-power state is stored for a preset number of days at a preset high-temperature storage test temperature, a third voltage value and a fourth internal resistance value of the second single battery cell are obtained; wherein the range of the preset high-temperature storage test temperature is 40-55 ℃;

calculating a first voltage difference between a third voltage value and a second voltage value of each second single battery cell and a second internal resistance difference between a fourth internal resistance value and a third internal resistance value;

acquiring an average value and a corresponding variance of the first voltage differences of the second single battery cells and an average value and a corresponding variance of the second internal resistance differences of the first single battery cells;

calculating the average value, the corresponding variance and a third preset voltage deviation value of the first voltage difference by adopting a preset interval algorithm to obtain a second voltage interval, and calculating the average value, the corresponding variance and the third preset internal resistance deviation value of the second internal resistance difference to obtain a third internal resistance interval;

and determining a second monomer battery cell corresponding to a third voltage value and a fourth internal resistance value which meet a second voltage interval and a third internal resistance interval in the third voltage value and the fourth internal resistance value of each second monomer battery cell as a third monomer battery cell.

In one embodiment, performing a low-temperature charging test on the third cell to screen out a fourth cell includes:

discharging a third monomer battery cell at a preset temperature to a second preset cut-off voltage by using third preset electric quantity;

charging the discharged third monomer battery cell at the preset low-temperature charging test temperature to a fourth voltage value by using a fourth preset electric quantity; wherein the preset temperature is higher than the preset low-temperature charging test temperature; the range of the preset low-temperature charging test temperature is between 0 ℃ and 10 ℃;

after the charged third single battery cell is placed for a fifth preset time, acquiring a fifth voltage value of the third single battery cell;

calculating a second voltage difference between a fifth voltage value and a fourth voltage value of each third monomer battery cell, and acquiring an average value and a corresponding variance of the second voltage difference;

calculating the average value and the corresponding variance of the second voltage difference and a fourth preset voltage deviation value by adopting a preset interval algorithm to obtain a third voltage interval;

and determining a third monomer battery cell corresponding to a fifth voltage value which satisfies a third voltage interval in the fifth voltage values of the third monomer battery cells as a fourth monomer battery cell.

In an embodiment, carry out the normal atmospheric temperature performance recovery test to the fourth monomer electricity core, screen out the monomer electricity core that has the uniformity, include:

carrying out recovery capacity calibration and internal resistance test on a fourth single battery cell at a preset temperature to obtain the recovery capacity and a fifth internal resistance value of the fourth single battery cell;

calculating the average value of the recovery capacity and the average value of the fifth internal resistance value which meet the second preset screening condition to obtain the average value of the recovery capacity and the second average internal resistance value; the second preset screening condition comprises a recovery capacity screening range and a second preset internal resistance value screening range;

determining a recovery capacity interval according to the recovery capacity average value and the recovery capacity deviation value, and determining a fourth internal resistance interval according to the second average internal resistance value and a fourth preset internal resistance deviation value;

and determining the fourth monomer battery cell corresponding to the recovery capacity and the fifth internal resistance value which meet the recovery capacity interval and the fourth internal resistance interval in the recovery capacity and the fifth internal resistance value of each fourth monomer battery cell as the monomer battery cell with consistency.

In a second aspect, an embodiment of the present invention provides a screening system for lithium ion battery consistency, including:

the primary screening module is used for primarily screening a preset number of single battery cells to obtain first single battery cells;

the high-temperature pulse testing module is used for carrying out high-temperature pulse testing on the first monomer battery cell reaching the preset high-temperature pulse testing temperature and screening out a second monomer battery cell;

the high-temperature storage testing module is used for performing high-temperature storage testing on the second single battery cell at a preset high-temperature storage testing temperature and screening out a third single battery cell;

the low-temperature charging test module is used for carrying out a low-temperature charging test on the third single battery cell and screening out a fourth single battery cell;

and the normal temperature performance recovery testing module is used for performing normal temperature performance recovery testing on the fourth monomer battery cell and screening out the monomer battery cells with consistency.

The embodiment of the invention has the following beneficial effects:

according to the screening method and system for lithium ion battery consistency, provided by the embodiment of the invention, firstly, a preset number of single battery cells are preliminarily screened to obtain a first single battery cell; secondly, performing high-temperature pulse test on the first monomer battery cell reaching the preset high-temperature pulse test temperature, and screening out a second monomer battery cell; then, under the preset high-temperature storage test temperature, performing a high-temperature storage test on the second monomer battery cell, and screening out a third monomer battery cell; then, carrying out a low-temperature charging test on the third monomer battery cell, and screening out a fourth monomer battery cell; and finally, carrying out a normal temperature performance recovery test on the fourth monomer battery cell, and screening out the monomer battery cells with consistency. The method screens the single battery cell through preliminary screening, high-temperature pulse testing, high-temperature storage testing, low-temperature charging testing and normal-temperature performance recovery testing, is simple to operate and easy to realize, greatly shortens screening time and improves screening efficiency; meanwhile, the method dynamically considers the performance index change of the single battery cell under different conditions, adopts a high-temperature pulse test, a high-temperature storage test, a low-temperature charging test and a normal-temperature performance recovery test, fully compares the comprehensive differences of the battery cells, and effectively improves the screening accuracy of the battery cells.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

Fig. 1 is a flowchart of a screening method for lithium ion battery consistency according to an embodiment of the present invention;

fig. 2 is a flowchart of another screening method for lithium ion battery consistency according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of a screening system for lithium ion battery uniformity according to an embodiment of the present invention;

fig. 4 is a schematic structural diagram of an electronic device according to an embodiment of the present invention.

Detailed Description

To make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

At present, the conventional battery cell screening and evaluating process mainly comprises the steps of carrying out simple charge-discharge test on a battery cell, shelving the battery at normal temperature for more than 28 days after the battery cell is charged to a half-electric state, and screening according to the differences of the shelved voltage, internal resistance and capacity. In the process, complete charging and discharging are carried out for many times, the process is complex, the energy is consumed, and resources are occupied; half electric storage at normal temperature takes long time, and the difference change is little, and through the simple analysis of capacity, internal resistance, voltage after shelting simultaneously, can not reflect the actual difference of electric core correctly, and the screening efficiency is low simultaneously to the erroneous judgement rate height.

Based on this, the screening method and the screening system for lithium ion battery consistency provided by the embodiment of the invention are simple to operate, effectively shorten the screening period, and improve the battery cell screening efficiency and accuracy.

To facilitate understanding of the present embodiment, first, a method for screening consistency of lithium ion batteries disclosed in the embodiment of the present invention is described in detail, referring to a flowchart of a method for screening consistency of lithium ion batteries shown in fig. 1, which illustrates that the method mainly includes the following steps S101 to S105:

step S101: and preliminarily screening the preset number of monomer electric cores to obtain a first monomer electric core.

In specific application, a certain number of monomer battery cells can be randomly selected, the voltage and the internal resistance of each monomer battery cell are measured, preliminary screening is carried out according to the voltage and the internal resistance of the monomer battery cells, the monomer battery cells with obvious abnormality are screened out, namely, the voltage and the internal resistance are eliminated within a qualified range, and the rest monomer battery cells are used as first monomer battery cells.

Step S102: and carrying out high-temperature pulse test on the first monomer battery cell reaching the preset high-temperature pulse test temperature, and screening out a second monomer battery cell.

In specific application, the first monomer battery cell can be subjected to repeated high-rate and short-time (less than 30S) pulse charging and discharging tests at a preset high-temperature pulse test temperature, the first monomer battery cell is screened according to the capacity difference and the internal resistance difference of the first monomer battery cell before and after the high-temperature pulse test, the unqualified first monomer battery cell is removed, and the remaining first monomer battery cell is used as a second monomer battery cell.

Step S103: and under the preset high-temperature storage test temperature, performing high-temperature storage test on the second monomer battery cell, and screening out a third monomer battery cell.

In specific application, the second monomer cells which are subjected to the high-temperature pulse test and are in a full-state can be stored at a preset high-temperature storage test temperature, the second monomer cells are screened according to the internal resistance difference and the voltage difference before and after high-temperature storage, unqualified second monomer cells are removed, and the remaining second monomer cells are used as third monomer cells.

Step S104: and carrying out low-temperature charging test on the third monomer battery cell, and screening out a fourth monomer battery cell.

In specific application, the third monomer battery cell can be charged at a low temperature, the third monomer battery cells are screened according to the difference of charging voltages, the unqualified third monomer battery cells are removed, and the remaining third monomer battery cells are used as fourth monomer battery cells.

Step S105: and (5) carrying out a normal temperature performance recovery test on the fourth monomer battery cell, and screening out the monomer battery cells with consistency.

In specific application, the normal-temperature performance recovery test is carried out on the fourth monomer battery cell obtained through the high-low temperature test screening, the fourth monomer battery cell is screened according to the difference of recovery capacity and internal resistance, and unqualified fourth monomer battery cells are removed to obtain the monomer battery cells with consistency.

According to the screening method for the consistency of the lithium ion battery, provided by the embodiment of the invention, the single battery cells are screened through primary screening, a high-temperature pulse test, a high-temperature storage test, a low-temperature charging test and a normal-temperature performance recovery test, the operation is simple and easy to realize, the screening time is greatly shortened, and the screening efficiency is improved; meanwhile, the method dynamically considers the performance index change of the single battery cell under different conditions, adopts a high-temperature pulse test, a high-temperature storage test, a low-temperature charging test and a normal-temperature performance recovery test, fully compares the comprehensive differences of the battery cells, and effectively improves the screening accuracy of the battery cells.

In an embodiment, when a preset number of single cells are preliminarily screened to obtain a first single cell, the following methods may be adopted, including but not limited to the following steps, specifically including the following steps a1 to a 4:

step a 1: and acquiring a first voltage value and a first internal resistance value of each single battery cell.

In specific application, a certain number of single battery cells can be randomly selected, and the first voltage value V of each single battery cell is measured₁And a first internal resistance value R_AC1。

Step a 2: calculating an average value of the first voltage values and an average value of the first internal resistance values which meet the first preset screening condition to obtain a first average voltage value and a first average internal resistance value; the first preset screening condition includes a first preset voltage value screening range and a first preset internal resistance value screening range.

In specific application, the first preset voltage value screening range and the first preset internal resistance value screening range can be determined according to the type of the battery cell and application requirements, the first voltage value not in the first preset voltage value screening range and the first internal resistance value not in the first preset internal resistance value screening range are removed, namely, after the monomer battery cells with obviously low voltage and high internal resistance at the top end and the bottom end of the value are removed, the average value of the first voltage values of the residual monomer battery cells and the average value of the first internal resistance values are calculated, and the first average voltage value and the first average internal resistance value are obtained.

Step a 3: and determining a first voltage interval by using the first average voltage value and the first preset voltage deviation value, and determining a first internal resistance interval by using the first average internal resistance value and the first preset internal resistance deviation value.

In specific applications, the first preset voltage deviation value and the first preset internal resistance deviation value may be respectively determined according to specific battery cell types and application requirements, so as to obtain a first voltage interval X based on the first average voltage value and the first preset voltage deviation value₁±N₁%, wherein, X₁Is a first average voltage value, N₁% is a first preset voltage deviation value; obtaining a first internal resistance interval Y based on the first average internal resistance value and the first preset internal resistance deviation value₁±M₁%, wherein, Y₁Is a first average internal resistance value, M₁% is a first preset internal resistance deviation value.

Step a 4: determining the monomer electric cores corresponding to the first voltage value and the first internal resistance value which meet the first voltage interval and the first internal resistance interval in the first voltage values and the first internal resistance values of the preset number of monomer electric cores as the first monomer electric cores.

In a specific application, the first voltage interval X may be selected to be satisfied₁±N₁% and firstInternal resistance interval Y₁±M₁% of the first voltage value and the monomer cells corresponding to the first internal resistance value are used as the first monomer cells, namely qualified cells, and meanwhile, the monomer cells corresponding to the first voltage value and the first internal resistance value which do not meet the first voltage interval and the first internal resistance interval are removed, namely, the monomer cells in which the first voltage value and the first internal resistance value are lower than the lower limit and exceed the upper limit in the monomer cells are removed.

In an embodiment, a pulse test is performed on a first monomer battery cell reaching a preset high-temperature pulse test temperature for a preset number of times, and a second monomer battery cell is screened out, that is, a first monomer battery cell qualified in step S101 is subjected to pulse charging and discharging within a temperature range of 40 ℃ to 55 ℃, and specifically, the following steps b1 to b6 may be adopted, specifically, but not limited to:

step b 1: after each first monomer battery cell is subjected to one-time standard charging and discharging, and each first monomer battery cell is charged to a first preset charge state by first preset electric quantity, a first discharge capacity and a second internal resistance value are obtained.

The standard charging and discharging process of the battery is that the battery is firstly discharged to 1.0V/count at 0.2C, then charged for 16 hours at 0.1C, and placed to 1.0V/count at 0.2C after being left for 1 hour. In this embodiment, before the high-temperature pulse test, each first monomer battery cell is subjected to one-time standard charge and discharge, and then the first monomer battery cell is subjected to constant-current charging to a first preset charge state by using a first preset electric quantity, and a first discharge capacity C is recorded₁And a second internal resistance value R_AC2. The first preset electric quantity may be 0.5C-1C, and the first preset state of charge may be 50% SOC.

Step b 2: carrying out charge-discharge cycle test on the first monomer battery cell reaching the preset high-temperature pulse test temperature for preset times by using second preset electric quantity, and obtaining a second discharge capacity and a third internal resistance value of the first monomer battery cell after test; wherein the range of the preset high-temperature pulse testing temperature is 40-55 ℃.

In specific applications, each first cell charged to a first preset state of charge may be shelved until the first cell uniformly reaches a preset heightTesting the temperature (between 40 ℃ and 55 ℃) by the temperature pulse, and then performing charge-discharge cycle testing on the first monomer battery cell for preset times by using a second preset electric quantity, such as performing charge-discharge cycles for 100 times and 400 times; then, the tested first monomer battery cell is placed at room temperature until the first monomer battery cell uniformly reaches the room temperature, wherein the room temperature is 23-27 ℃, and then the second discharge capacity C of the tested first monomer battery cell is obtained₂And a third internal resistance value R_AC3。

Specifically, when the second discharge capacity and the third internal resistance value of the first battery cell after the test are obtained, the following methods may be adopted, including but not limited to:

firstly, performing recovery capacity calibration on a first monomer battery cell which is tested and reaches a preset temperature according to standard charging and discharging to obtain a second discharge capacity of the first monomer battery cell; wherein the preset temperature is lower than the preset high-temperature pulse testing temperature; the preset temperature range is 23-27 ℃.

In a specific application, the preset temperature may be room temperature, and the recovery capacity calibration refers to a capacity that can be output when the battery is left at a specified temperature for a specified time, is fully charged after being discharged, and is discharged again. In the embodiment of the invention, the tested first monomer battery cell can be placed at room temperature until the first monomer battery cell uniformly reaches the room temperature, and then the first monomer battery cell is subjected to recovery capacity calibration according to standard charging and discharging to obtain the second discharge capacity C of the first monomer battery cell₂And finally, obtaining the capacity output when the first single battery cell is completely charged after being discharged and is discharged again.

And then, after the first single battery cell after the recovery capacity calibration is recharged to a full-charge state with a preset current and a preset voltage, acquiring a second voltage value and a third internal resistance value.

In specific application, the first monomer battery cell with the calibrated recovery capacity is charged to a full-charge state at constant current and constant voltage, and a second voltage value V is recorded₂And a third internal resistance value R_AC3。

Further, when the first monomer battery cell reaching the preset high-temperature pulse test temperature is subjected to the charge-discharge cycle test for the preset number of times with the second preset electric quantity, the following methods may be adopted, including but not limited to:

firstly, charging the first monomer battery cell reaching the preset high-temperature pulse test temperature for a first preset time by second preset electric quantity or charging the first monomer battery cell to a first preset cut-off voltage.

Then, after a second preset time, discharging the charged first monomer battery cell for a third preset time by using a second preset electric quantity, or discharging to a second preset cut-off voltage;

and finally, after the fourth preset time, performing charge-discharge cycle test on the first monomer battery cell for preset times.

The second preset electric quantity may be a maximum continuous pulse current, and may be specifically determined according to the type and performance of the single battery cell; the first preset time can be between 10S and 30S, the second preset time can be between 5S and 30S, and the third preset time can be between 10S and 30S, wherein the first preset time and the third preset time can be the same or different; the first preset cut-off voltage and the second preset cut-off voltage may also be determined according to the type and performance of the individual electric core. In specific application, (1) charging a first monomer battery cell reaching a preset high-temperature pulse test temperature for 10S-30S in a constant current (maximum continuous pulse current) manner, or stopping charging until a first preset cut-off voltage is reached; (2) placing the charged first monomer battery cell for 5S-30S; (3) discharging for 10S-30S at constant current (maximum continuous pulse current), or discharging to a second preset cut-off voltage to stop discharging; (4) and laying the discharged first single battery cell for 5S-30S. And (5) circulating the steps (1) to (4) for 100-400 times to finish the charge-discharge cycle test of the first monomer battery cell.

Step b 3: and calculating a first capacity difference between the second discharge capacity and the first discharge capacity of each first monomer battery cell and a first internal resistance difference between the second internal resistance value and the third internal resistance value.

In specific application, the capacity difference and the internal resistance difference of each first monomer battery cell before and after the high-temperature pulse test, namely the first capacity difference delta C, are recorded₁＝C₂-C₁First internal resistance difference Δ R₁＝R_AC3-R_AC2。

Step b 4: and acquiring an average value and a corresponding variance of the first capacity difference of each first single battery cell and an average value and a corresponding variance of the first internal resistance difference of each first single battery cell.

Step b 5: and calculating the average value, the corresponding variance and a first preset capacity deviation value of the first capacity difference by adopting a preset interval algorithm to obtain a first capacity interval, and calculating the average value, the corresponding variance and a second preset internal resistance deviation value of the first internal resistance difference to obtain a second internal resistance interval.

In a specific application, the preset interval algorithm takes (mean ± variance × deviation value) as a qualified interval. Specifically, the first capacity interval is Z₁±K₁ΔS₁Wherein Z is₁Is the average value of the first capacity difference, Δ S₁Is the corresponding variance of the first capacity difference, K₁A first preset capacity deviation value; the second internal resistance interval is Y₂±M₂ΔS₂Wherein Y is₂Is the average value of the first internal resistance difference, Δ S₂Is the corresponding variance of the first internal resistance difference, M₂The second preset internal resistance deviation value is obtained.

Step b 6: and determining the first monomer battery cell corresponding to the second discharge capacity and the third internal resistance value which meet the first capacity interval and the second internal resistance interval in the second discharge capacity and the third internal resistance value of each first monomer battery cell as a second monomer battery cell.

In a particular application, the first capacity interval Z may be chosen to be satisfied₁±K₁ΔS₁And a second internal resistance interval Y₂±M₂ΔS₂The first monomer battery cell corresponding to the second discharge capacity and the third internal resistance value is used as a second monomer battery cell, namely a qualified battery cell, and meanwhile, the first monomer battery cell corresponding to the first voltage value and the first internal resistance value which do not meet the first capacity interval and the second internal resistance interval is removed, namely the first monomer battery cell in which the second discharge capacity and the third internal resistance value are lower than the lower limit and exceed the upper limit in the first monomer battery cell is removed.

In an embodiment, at a preset high-temperature storage test temperature, a high-temperature storage test is performed on the second cell, and a third cell is screened out, that is, the third cell is used to perform high-temperature storage on the qualified second cell in step S102, which may specifically adopt, but is not limited to, the following manners, specifically including the following steps c1 to c 5:

step c 1: after the second single battery cell in the full-power state is stored for a preset number of days at a preset high-temperature storage test temperature, a third voltage value and a fourth internal resistance value of the second single battery cell are obtained; wherein the range of the preset high-temperature storage test temperature is 40-55 ℃.

In specific application, the second monomer battery cell in the full-power state qualified in the high-temperature pulse test can be shelved for 2-4 days at a preset high-temperature storage test temperature (40 ℃ -55 ℃), and a third voltage value V of the shelved second monomer battery cell is recorded₃And a fourth internal resistance value R_AC4。

Step c 2: and calculating a first voltage difference between the third voltage value and the second voltage value of each second single battery cell and a second internal resistance difference between the fourth internal resistance value and the third internal resistance value.

Specifically, the first voltage difference Δ V is calculated₁＝V₃-V₂Second difference in internal resistance Δ R₂＝R_AC4-R_AC3。

Step c 3: and acquiring the average value and the corresponding variance of the first voltage difference of each second single battery cell and the average value and the corresponding variance of the second internal resistance difference of each first single battery cell.

In a specific application, before calculating the average value and the corresponding variance of the first voltage difference and the average value and the corresponding variance of the second internal resistance difference of each first single battery cell, the third voltage value V may be further calculated₃And a fourth internal resistance value R_AC4And eliminating second monomer battery cores with obviously low middle voltage (about 3% of lower limit) and obviously high internal resistance (about 3% of upper limit), wherein the percentage of the upper limit and the lower limit is determined according to the actual application requirement. And then calculating the average value and the corresponding variance of the first voltage differences of the second single battery cells after the abnormal battery cells are removed, and the average value and the corresponding variance of the second internal resistance differences of the first single battery cells.

Step c 4: and calculating the average value, the corresponding variance and a second preset voltage deviation value of the first voltage difference by adopting a preset interval algorithm to obtain a second voltage interval, and calculating the average value, the corresponding variance and a third preset internal resistance deviation value of the second internal resistance difference to obtain a third internal resistance interval.

In this manner, the preset interval algorithm is the same as the preset interval algorithm described above. Specifically, the second voltage interval is X₂±N₂ΔS₃Wherein X is₂Is the average value of the first voltage difference, Δ S₃Is the corresponding variance, N, of the first voltage difference₂A second preset voltage deviation value; the third internal resistance interval is Y₃±M₃ΔS₄Wherein Y is₃Is the average value of the second internal resistance difference, Δ S₄Is the corresponding variance of the second internal resistance difference, M₃And setting a third preset internal resistance deviation value.

Step c 5: and determining a second monomer battery cell corresponding to a third voltage value and a fourth internal resistance value which meet a second voltage interval and a third internal resistance interval in the third voltage value and the fourth internal resistance value of each second monomer battery cell as a third monomer battery cell.

In a specific application, the second voltage interval X may be selected to be satisfied₂±N₂ΔS₃And a third internal resistance interval Y₃±M₃ΔS₄The second single battery cell corresponding to the third voltage value and the fourth internal resistance value is used as a third single battery cell, namely a qualified battery cell, and meanwhile, the second voltage interval X which does not meet the second voltage interval is used₂±N₂ΔS₃And a third internal resistance interval Y₃±M₃ΔS₄The second single battery cell corresponding to the third voltage value and the fourth internal resistance value is removed, that is, the first single battery cell in which the third voltage value and the fourth internal resistance value are lower than the lower limit and exceed the upper limit in the second single battery cell is removed.

In an embodiment, the low-temperature charging test is performed on the third cell, and the fourth cell is screened out, that is, the qualified third cell in step S103 is subjected to the low-temperature charging test at a temperature range of 0 ℃ to 10 ℃, which may be performed in a manner including, but not limited to, the following steps d1 to d 6:

step d 1: and discharging the third monomer battery cell at the preset temperature to a second preset cut-off voltage by using a third preset electric quantity.

In the method, the preset temperature is room temperature, and is between 23 ℃ and 27 ℃ and higher than the preset low-temperature charging test temperature (between 0 ℃ and 10 ℃); the third preset electric quantity may be 0.5C-1C, and the specific discharge rate is based on the nominal discharge capacity of each battery cell. In specific application, the third monomer battery cell qualified in the high-temperature storage test is placed at room temperature for 2-24h to recover to normal temperature (the specific time is determined by the size, thickness and the like of the battery cell, and the whole battery recovers to normal temperature), then the battery is discharged to a second preset cut-off voltage at 0.5C-1C, and the discharged second monomer battery cell is placed for 10min-20 min.

Step d 2: charging the discharged third monomer battery cell at the preset low-temperature charging test temperature to a fourth voltage value by using a fourth preset electric quantity; wherein the preset temperature is higher than the preset low-temperature charging test temperature; the range of the preset low-temperature charging test temperature is between 0 ℃ and 10 ℃.

In this manner, the fourth preset electric quantity may be 0.5C-2C, and the specific charging rate is determined by the low-temperature charging capability of each battery cell. The third monomer battery cell discharged to the second preset cut-off voltage is placed for 4-24h at the preset low-temperature charging test temperature (between 0 ℃ and 10 ℃) (the specific time is determined by the size, the thickness and the like of the battery cell, and the whole battery reaches the environmental low temperature), and then the third monomer battery cell is charged to a fourth voltage value V at a constant current of 0.5C-2C₄。

Step d 3: and after the charged third monomer battery cell is placed for a fifth preset time, acquiring a fifth voltage value of the third monomer battery cell.

In this manner, the fifth preset time may be 5 to 10min, the third monomer electric core charged in the step d2 is placed for 5 to 10min, and a fifth voltage value V of the placed third monomer electric core is tested₅。

Step d 4: and calculating a second voltage difference between the fifth voltage value and the fourth voltage value of each third monomer battery cell, and acquiring an average value and a corresponding variance of the second voltage difference.

In particular, the meterCalculating a second voltage difference Δ V₂＝V₅-V₄And the mean value X of the second voltage difference₃And the corresponding variance Δ S₅。

Step d 5: and calculating the average value and the corresponding variance of the second voltage difference and a third preset voltage deviation value by adopting a preset interval algorithm to obtain a third voltage interval.

In this manner, the preset interval algorithm is the same as the preset interval algorithm described above. Specifically, the third voltage interval is X₃±N₃ΔS₅Wherein X is₃Is the average value of the second voltage difference, Δ S₅Is the corresponding variance, N, of the second voltage difference₃Is the third predetermined voltage offset value.

Step d 6: and determining a third monomer battery cell corresponding to a fifth voltage value which satisfies a third voltage interval in the fifth voltage values of the third monomer battery cells as a fourth monomer battery cell.

In a specific application, the third voltage interval X can be selected to be satisfied₃±N₃ΔS₅The third monomer battery cell corresponding to the fifth voltage value is taken as a fourth monomer battery cell, namely a qualified battery cell, and meanwhile, the third voltage interval X is not met₃±N₃ΔS₅The third monomer electric core corresponding to the fifth voltage value is removed, that is, the third monomer electric core in which the fifth voltage value is lower than the lower limit and exceeds the upper limit is removed.

In an embodiment, when the normal temperature performance recovery test is performed on the fourth single cell to screen out the single cells having consistency, the method may include, but is not limited to, the following steps, specifically including the following steps e1 to e 4:

step e 1: and carrying out recovery capacity calibration and internal resistance test on the fourth single battery cell at the preset temperature to obtain the recovery capacity and the fifth internal resistance value of the fourth single battery cell.

In this manner, the preset temperature is room temperature. In specific application, the fourth monomer voltage qualified in the step S104 is left to stand at room temperature for 2-24h to recover to the room temperature (the specific time is determined by the size and thickness of the battery core and the like, and the whole battery is recovered to the room temperature) Carrying out recovery capacity calibration and internal resistance test on the battery cell to obtain the recovery capacity C of the fourth single battery cell₃And a fifth internal resistance value R_AC5。

Step e 2: calculating the average value of the recovery capacity and the average value of the fifth internal resistance value which meet the second preset screening condition to obtain the average value of the recovery capacity and the second average internal resistance value; the second preset screening condition includes a recovery capacity screening range and a second preset internal resistance value screening range.

In a specific application, the recovery capacity screening range and the second preset internal resistance value screening range may be determined according to a specific battery cell type and an application requirement, respectively. And after the recovered capacity which is not in the recovered capacity screening range and the fifth internal resistance which is not in the second preset internal resistance screening range are removed, calculating the average recovered capacity value and the second average internal resistance value of the remaining fourth monomer battery cell.

Step e 3: and determining a recovery capacity interval according to the recovery capacity average value and the recovery capacity deviation value, and determining a fourth internal resistance interval according to the second average internal resistance value and a fourth preset internal resistance deviation value.

In specific application, the recovered capacity deviation value and the fourth preset internal resistance deviation value can be respectively determined according to specific battery cell types and application requirements, so that a recovered capacity interval Z is obtained based on the recovered capacity average value and the recovered capacity deviation value₂±K₂%, wherein, Z₂To restore the average value of capacity, K₂% is recovery capacity deviation value; obtaining a fourth internal resistance interval Y based on the second average internal resistance value and a fourth preset internal resistance deviation value₄±M₄%, wherein, Y₄Is the second average internal resistance value, M₄% is a fourth preset internal resistance deviation value.

Step e 4: and determining the fourth monomer battery cell corresponding to the recovery capacity and the fifth internal resistance value which meet the recovery capacity interval and the fourth internal resistance interval in the recovery capacity and the fifth internal resistance value of each fourth monomer battery cell as the monomer battery cell with consistency.

In a particular application, the interval Z satisfying the recovery capacity can be selected₂±K₂% and fourth internal resistance interval Y₄±M₄% of recovery capacity and the fourth monomer battery cell corresponding to the fifth internal resistance value are used as the monomer battery cells with consistency, namely qualified battery cells, and meanwhile, the recovery capacity interval Z is not met₂±K₂% and fourth internal resistance interval Y₄±M₄And removing the monomer battery cell corresponding to% of the recovery capacity and the fifth internal resistance value.

The method provided by the embodiment of the invention combines the change of each performance index of the battery cell under different application scenes, rapidly evaluates the dynamic difference of the parameters of the battery cell, effectively shortens the screening time, improves the screening efficiency and accuracy, and reduces the failure risk of the power battery system. Meanwhile, the method is simple to operate, high in practicability and convenient to produce, and a feasible method is provided for guaranteeing the consistency of the power system battery.

Further, the present invention also provides another method for screening consistency of lithium ion batteries, as shown in fig. 2, which mainly includes the following steps S201 to S205:

step S201: and (5) primarily screening voltage and internal resistance.

Specifically, a certain number of single battery cells are randomly selected, and the voltage and the AC internal resistance of the battery are tested. After removing the low voltage and high internal resistance cells with obvious top and bottom values, calculating the average value X of the voltages V1 of the residual single cells₁And average value Y of internal resistance of RAC1₁Selecting the qualified interval X₁±N₁% and Y₁±M₁% of the single battery cell, rejecting the battery cells with the voltage and the internal resistance lower than the lower limit and higher than the upper limit, and determining the N and M values respectively according to the specific battery cell type and the application requirement.

Step S202: and (5) high-temperature pulse testing.

Specifically, the qualified monomer battery cell in the step S201 is subjected to pulse charging and discharging at a temperature range of 40-55 ℃.

(1) After standard charging and discharging of the monomer battery cell, constant current charging is carried out to 50% SOC at 0.5C-1C, and the discharge capacity C is recorded₁And internal resistance R_AC2(ii) a (2) Laying the monomer battery cell until the battery cell uniformly reaches the testing temperature (namely 40-55 ℃); (3) for single cell constant current (maximum continuous pulse electricity)Flow) charging for 10-30S or stopping charging when the set cut-off voltage is reached; (4) laying aside for 5-30S; (5) and discharging the single battery cell for 10-30 seconds at constant current (maximum continuous pulse current) or reaching a set discharge cut-off voltage. (6) Laying aside for 5-30S; and (5) circulating the steps (3) to (6) for 400 weeks. (7) Laying the monomer cell until the cell is uniform to reach room temperature; (8) capacity recovery calibration according to standard charging and discharging₂Constant current and voltage recharging to full state V₂Measuring internal resistance R_AC3. Recording the standard capacity difference Δ C before and after the pulse test₁＝C₂-C₁And difference of internal resistance Δ R₁＝R_AC3-R_AC2Calculating Δ C₁Average value Z of₁And the corresponding variance Δ S₁And Δ R₁Average value Y of₂And the corresponding variance Δ S₂Is selected in a first capacity interval Z₁±K₁ΔS₁And a second internal resistance interval Y₂±M₂ΔS₂The single battery cells are removed, and the single battery cells which are lower than the lower limit and exceed the upper limit are removed.

Step S203: and (4) high-temperature storage testing.

Specifically, after the step S202 is finished, the single battery in the full charge state is placed at a high temperature (45-55 ℃) for 2-4 days, and the voltage V after the placement is recorded₃Internal resistance R_AC4. Rejection voltage V₃Internal resistance R_AC4The medium voltage is obviously lower (about 3% of lower limit) and the internal resistance is obviously higher (about 3% of upper limit), and the percentage of the upper limit and the lower limit is determined according to the practical application requirement. Calculating Δ V₁And Δ R₂，ΔV₁＝V₃-V₂、ΔR₂＝R_AC4-R_AC4After the apparent discrete values of the voltage difference and the internal resistance difference are eliminated, calculating delta V₁Average value of X₂And the corresponding variance Δ S₃And Δ R₂Average value Y of₃And the corresponding variance Δ S₄Selecting qualified interval in X₂±N₂ΔS₃And Y₃±M₃ΔS₄The single battery cells are removed, and the single battery cells which are lower than the lower limit and exceed the upper limit are removed.

Step S204: and (5) low-temperature charging test.

In particularAnd (3) standing the monomer battery cells screened in the step (S203) at room temperature (25 +/-2 ℃) for 4-24 hours to recover to the normal temperature (the specific time is determined by the size, the thickness and the like of the battery cells, the whole battery is subjected to normal temperature recovery, discharging to the specified discharge cut-off voltage by 0.5-1C (the discharge rate is determined by the nominal discharge capacity of each battery cell), and standing for 10-20 minutes. The battery is placed for 4-24h at 0-10 ℃ (the specific time is determined by the size and thickness of the battery cell, and the like, and the battery is subjected to low-temperature environment all the time), and the battery is charged at a constant current of 0.5C-2C (the charging multiplying power is determined by the low-temperature charging capacity of each battery cell) until the charging is cut to an upper limit voltage V₄Laying aside for 5-10min, testing voltage V at the end of laying aside₅Calculating Δ V₂＝V₅-V₄Eliminating the Δ V according to the same screening method as the aforementioned step S203₂The individual cells with larger differences.

Step S205: and (5) testing the normal temperature performance recovery.

Specifically, the monomer battery cells screened in step S204 are restored to room temperature (step S204), and then capacity restoration calibration and internal resistance test (performed according to national standards) are performed on the monomer battery cells, and the capacity restoration C of the monomer battery cells is recorded₃And internal resistance R_AC5And according to the same screening method in the step S201, the monomer cells with large differences in capacity and internal resistance are removed.

Considering that the low-temperature test can damage the battery cell and influence the performance of the battery cell, in order to improve the screening accuracy, the invention adopts the test sequence of high temperature, low temperature and normal temperature, thereby reducing the influence of the low-temperature test on the performance of the battery cell and ensuring the screening accuracy.

The screening method for lithium ion battery consistency provided by the embodiment of the invention is suitable for evaluating the consistency of the power batteries on all hybrid electric vehicles and pure electric vehicles, and has the following technical effects:

1. the working environment temperature of the lithium battery has certain influence on the internal resistance, the heat consumption rate, the discharge capacity, the cycle life and the consistency of the battery state. In general, lithium batteries are not sensitive to temperatures in the interval 0-40 ℃, however, capacity, internal resistance and lifetime are compromised once the temperature exceeds this interval for charging and discharging. The invention carries out a plurality of times of heavy current pulse tests on the battery under the high-temperature environment, amplifies the dynamic difference of the battery core through limit tests under the high temperature and improves the accuracy of battery screening.

2. The battery is placed in a full-electric state at high temperature, the higher the temperature is, the higher the SOC is, the larger the self-discharge of the battery is, the high-temperature full-electric state placing (namely, high-temperature storage testing) is adopted, and the self-discharge difference among the battery cores can be amplified, so that the self-discharge difference of the battery cores can be more accurately selected.

3. Through the low-temperature charging test, the difference of the battery cell can be inspected. From the electrochemical analysis, the ionic conductivity of the electrolyte at low temperature is reduced, the resistance of an SEI film and the resistance of electrochemical reaction are increased, so that ohmic polarization, concentration polarization and electrochemical polarization are increased at low temperature, and particularly the charging performance at low temperature is more difficult than that of low-temperature discharge and normal-temperature charge and discharge. Due to the fact that large polarization exists, voltage drop of the battery cell after charging at low temperature is more obvious than that of the battery cell at normal temperature, and the difference of the battery cell can be more accurately selected out than that of the battery cell at normal temperature through comparison of voltage drop differences.

4. After the early-stage high-low temperature charge-discharge dynamic screening, the normal-temperature performance recovery difference screening of the electric core is carried out, and the consistency of screening capacity is further improved from the capacity and internal resistance investigation.

5. The invention is completed only by simple test procedures, and has simple operation and easy realization. Meanwhile, compared with the conventional screening process, the evaluation time is greatly shortened, and the screening efficiency is improved. In addition, compared with the conventional static data screening, the method dynamically considers the performance index change under different conditions, fully compares the comprehensive differences of the battery cells, and effectively improves the screening accuracy of the battery cells.

For the screening method for the consistency of the lithium ion battery, an embodiment of the present invention further provides a screening system for the consistency of the lithium ion battery, referring to a schematic structural diagram of the screening system for the consistency of the lithium ion battery shown in fig. 3, which shows that the system mainly includes:

the preliminary screening module 301 is configured to perform preliminary screening on a preset number of monomer battery cells to obtain a first monomer battery cell.

And the high-temperature pulse testing module 302 is configured to perform a high-temperature pulse test on the first monomer electric core reaching a preset high-temperature pulse testing temperature, and screen out a second monomer electric core.

And the high-temperature storage testing module 303 is configured to perform a high-temperature storage test on the second monomer battery cell at a preset high-temperature storage testing temperature, and screen out a third monomer battery cell.

And the low-temperature charging test module 304 is configured to perform a low-temperature charging test on the third monomer electric core, and screen out a fourth monomer electric core.

And the normal temperature performance recovery testing module 305 is configured to perform a normal temperature performance recovery test on the fourth monomer electric core, and screen out monomer electric cores with consistency.

The screening system for lithium ion battery consistency provided by the embodiment of the invention screens the single battery cell through primary screening, high-temperature pulse testing, high-temperature storage testing, low-temperature charging testing and normal-temperature performance recovery testing, is simple and easy to operate and realize, greatly shortens screening time and improves screening efficiency; meanwhile, the method dynamically considers the performance index change of the single battery cell under different conditions, adopts a high-temperature pulse test, a high-temperature storage test, a low-temperature charging test and a normal-temperature performance recovery test, fully compares the comprehensive differences of the battery cells, and effectively improves the screening accuracy of the battery cells.

The system provided by the embodiment of the present invention has the same implementation principle and technical effect as the foregoing method embodiment, and for the sake of brief description, no mention is made in the system embodiment, and reference may be made to the corresponding contents in the foregoing method embodiment.

It should be noted that all the embodiments mentioned in the embodiments of the present invention are merely exemplary, and may be different from the embodiments in practical applications, and are not limited herein.

The embodiment of the invention also provides electronic equipment, which specifically comprises a processor and a storage device; the storage means has stored thereon a computer program which, when executed by the processor, performs the method of any of the above embodiments.

Fig. 4 is a schematic structural diagram of an electronic device 100 according to an embodiment of the present invention, where the electronic device 100 includes: a processor 40, a memory 41, a bus 42 and a communication interface 43, wherein the processor 40, the communication interface 43 and the memory 41 are connected through the bus 42; the processor 40 is arranged to execute executable modules, such as computer programs, stored in the memory 41.

The Memory 41 may include a high-speed Random Access Memory (RAM) and may also include a non-volatile Memory (non-volatile Memory), such as at least one disk Memory. The communication connection between the network element of the system and at least one other network element is realized through at least one communication interface 43 (which may be wired or wireless), and the internet, a wide area network, a local network, a metropolitan area network, etc. may be used.

The bus 42 may be an ISA bus, PCI bus, EISA bus, or the like. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, only one double-headed arrow is shown in FIG. 4, but that does not indicate only one bus or one type of bus.

The memory 41 is used for storing a program, the processor 40 executes the program after receiving an execution instruction, and the method executed by the apparatus defined by the flow process disclosed in any of the foregoing embodiments of the present invention may be applied to the processor 40, or implemented by the processor 40.

The processor 40 may be an integrated circuit chip having signal processing capabilities. In implementation, the steps of the above method may be performed by integrated logic circuits of hardware or instructions in the form of software in the processor 40. The Processor 40 may be a general-purpose Processor, and includes a Central Processing Unit (CPU), a Network Processor (NP), and the like; the device can also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field-Programmable Gate Array (FPGA), or other Programmable logic devices, discrete Gate or transistor logic devices, discrete hardware components. The various methods, steps and logic blocks disclosed in the embodiments of the present invention may be implemented or performed. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like. The steps of the method disclosed in connection with the embodiments of the present invention may be directly implemented by a hardware decoding processor, or implemented by a combination of hardware and software modules in the decoding processor. The software module may be located in ram, flash memory, rom, prom, or eprom, registers, etc. storage media as is well known in the art. The storage medium is located in a memory 41, and the processor 40 reads the information in the memory 41 and completes the steps of the method in combination with the hardware thereof.

The computer program product of the readable storage medium provided in the embodiment of the present invention includes a computer readable storage medium storing a program code, where instructions included in the program code may be used to execute the method described in the foregoing method embodiment, and specific implementation may refer to the foregoing method embodiment, which is not described herein again.

The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.

In the description of the present invention, it should be noted that the terms "first", "second", and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

Finally, it should be noted that: the above-mentioned embodiments are only specific embodiments of the present invention, which are used for illustrating the technical solutions of the present invention and not for limiting the same, and the protection scope of the present invention is not limited thereto, although the present invention is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: any person skilled in the art can modify or easily conceive the technical solutions described in the foregoing embodiments or equivalent substitutes for some technical features within the technical scope of the present disclosure; such modifications, changes or substitutions do not depart from the spirit and scope of the embodiments of the present invention, and they should be construed as being included therein. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A screening method for lithium ion battery consistency is characterized by comprising the following steps:

primarily screening a preset number of single battery cells to obtain first single battery cells;

performing high-temperature pulse test on the first monomer battery cell reaching a preset high-temperature pulse test temperature, and screening out a second monomer battery cell;

performing a high-temperature storage test on the second monomer battery cell at a preset high-temperature storage test temperature, and screening out a third monomer battery cell;

carrying out a low-temperature charging test on the third monomer battery cell, and screening out a fourth monomer battery cell;

and carrying out a normal temperature performance recovery test on the fourth monomer battery cell, and screening out the monomer battery cells with consistency.

2. The method of claim 1, wherein preliminarily screening a preset number of monomer cells to obtain a first monomer cell comprises:

acquiring a first voltage value and a first internal resistance value of each single battery cell;

determining a first voltage interval by using the first average voltage value and a first preset voltage deviation value, and determining a first internal resistance interval by using the first average internal resistance value and a first preset internal resistance deviation value;

and determining the single electric cores corresponding to the first voltage values and the first internal resistance values which meet the first voltage interval and the first internal resistance interval in the first voltage values and the first internal resistance values of the preset number of single electric cores as the first single electric cores.

3. The method of claim 1, wherein before performing the pulse test for a predetermined number of times on the first cell that reaches a predetermined high-temperature pulse test temperature and screening out a second cell, the method further comprises:

and after the first monomer battery cells are subjected to one-time standard charging and discharging and are charged to a first preset charge state by first preset electric quantity, acquiring a first discharge capacity and a second internal resistance value.

4. The method of claim 3, wherein the step of performing the high-temperature pulse test on the first cell reaching the preset high-temperature pulse test temperature to screen out a second cell comprises:

performing a charge-discharge cycle test on the first monomer battery cell reaching a preset high-temperature pulse test temperature for preset times by using a second preset electric quantity to obtain a second discharge capacity and a third internal resistance value of the first monomer battery cell after the test; wherein the range of the preset high-temperature pulse testing temperature is between 40 ℃ and 55 ℃;

calculating the average value, the corresponding variance and a first preset capacity deviation value of the first capacity difference by adopting a preset interval algorithm to obtain a first capacity interval, and calculating the average value, the corresponding variance and a second preset internal resistance deviation value of the first internal resistance difference to obtain a second internal resistance interval;

5. The method of claim 4, wherein performing a preset number of charge-discharge cycle tests on the first cell reaching a preset high-temperature pulse test temperature by using a second preset electric quantity comprises:

charging the first monomer battery cell reaching the preset high-temperature pulse test temperature for a first preset time by a second preset electric quantity or charging the first monomer battery cell to a first preset cut-off voltage;

after a second preset time, discharging the charged first monomer battery cell for a third preset time by using the second preset electric quantity, or discharging to a second preset cut-off voltage;

and after a fourth preset time, performing a charge-discharge cycle test on the first monomer battery cell for a preset number of times.

6. The method of claim 4, wherein obtaining the second discharge capacity and the third internal resistance value of the tested first cell comprises:

performing capacity recovery calibration on the first monomer battery cell which is tested and reaches a preset temperature according to standard charging and discharging to obtain a second discharge capacity of the first monomer battery cell; wherein the preset temperature is lower than the preset high-temperature pulse test temperature; the range of the preset temperature is 23-27 ℃;

7. The method of claim 6, wherein performing a high-temperature storage test on the second cell at a preset high-temperature storage test temperature to screen out a third cell comprises:

storing a second single battery cell in a full-charge state for a preset number of days at a preset high-temperature storage test temperature, and then acquiring a third voltage value and a fourth internal resistance value of the second single battery cell; wherein the range of the preset high-temperature storage test temperature is between 40 ℃ and 55 ℃;

calculating a first voltage difference between the third voltage value and the second voltage value of each second single battery cell, and a second internal resistance difference between the fourth internal resistance value and the third internal resistance value;

acquiring an average value and a corresponding variance of the first voltage differences of the second single battery cells, and an average value and a corresponding variance of the second internal resistance differences of the first single battery cells;

calculating the average value, the corresponding variance and a second preset voltage deviation value of the first voltage difference by adopting a preset interval algorithm to obtain a second voltage interval, and calculating the average value, the corresponding variance and a third preset internal resistance deviation value of the second internal resistance difference to obtain a third internal resistance interval;

and determining a second monomer battery cell corresponding to a third voltage value and a fourth internal resistance value which meet the second voltage interval and the third internal resistance interval in the third voltage value and the fourth internal resistance value of each second monomer battery cell as a third monomer battery cell.

8. The method of claim 1, wherein performing a low-temperature charging test on the third cell and screening out a fourth cell comprises:

charging the discharged third monomer battery cell at a preset low-temperature charging test temperature to a fourth voltage value by using a fourth preset electric quantity; wherein the preset temperature is higher than the preset low-temperature charging test temperature; the range of the preset low-temperature charging test temperature is between 0 ℃ and 10 ℃;

after the charged third monomer battery cell is placed for a fifth preset time, acquiring a fifth voltage value of the third monomer battery cell;

calculating a second voltage difference between the fifth voltage value and the fourth voltage value of each third monomer battery cell, and obtaining an average value and a corresponding variance of the second voltage differences;

calculating the average value and the corresponding variance of the second voltage difference and a third preset voltage deviation value by adopting a preset interval algorithm to obtain a third voltage interval;

and determining a third monomer battery cell corresponding to a fifth voltage value which satisfies the third voltage interval in the fifth voltage values of the third monomer battery cells as a fourth monomer battery cell.

9. The method of claim 1, wherein performing a normal temperature performance recovery test on the fourth cell to screen out a cell with consistency comprises:

performing recovery capacity calibration and internal resistance test on the fourth single battery cell at a preset temperature to obtain the recovery capacity and a fifth internal resistance value of the fourth single battery cell;

10. A screening system for lithium ion battery uniformity is characterized by comprising:

the high-temperature pulse testing module is used for performing high-temperature pulse testing on the first monomer battery cell reaching a preset high-temperature pulse testing temperature and screening out a second monomer battery cell;

the high-temperature storage testing module is used for performing high-temperature storage testing on the second monomer battery cell at a preset high-temperature storage testing temperature and screening out a third monomer battery cell;