CN113578792B - Lithium ion battery self-discharge screening method and device and storage medium - Google Patents
Lithium ion battery self-discharge screening method and device and storage medium Download PDFInfo
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- 238000012216 screening Methods 0.000 title claims abstract description 59
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 56
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 56
- 238000000034 method Methods 0.000 title claims abstract description 37
- 238000003860 storage Methods 0.000 title claims abstract description 21
- 239000006185 dispersion Substances 0.000 claims abstract description 40
- 230000002159 abnormal effect Effects 0.000 claims abstract description 21
- 238000004364 calculation method Methods 0.000 claims description 30
- 238000009826 distribution Methods 0.000 claims description 10
- 238000001514 detection method Methods 0.000 claims description 9
- 238000004590 computer program Methods 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 abstract description 10
- 230000008569 process Effects 0.000 abstract description 4
- 238000012545 processing Methods 0.000 abstract description 2
- 238000012360 testing method Methods 0.000 description 8
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 229910052744 lithium Inorganic materials 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 239000000428 dust Substances 0.000 description 2
- 238000009472 formulation Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- KFDQGLPGKXUTMZ-UHFFFAOYSA-N [Mn].[Co].[Ni] Chemical compound [Mn].[Co].[Ni] KFDQGLPGKXUTMZ-UHFFFAOYSA-N 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 239000007771 core particle Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000002923 metal particle Substances 0.000 description 1
- -1 nickel-cobalt-manganese-aluminum Chemical compound 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
- B07C—POSTAL SORTING; SORTING INDIVIDUAL ARTICLES, OR BULK MATERIAL FIT TO BE SORTED PIECE-MEAL, e.g. BY PICKING
- B07C5/00—Sorting according to a characteristic or feature of the articles or material being sorted, e.g. by control effected by devices which detect or measure such characteristic or feature; Sorting by manually actuated devices, e.g. switches
- B07C5/34—Sorting according to other particular properties
- B07C5/344—Sorting according to other particular properties according to electric or electromagnetic properties
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
- B07C—POSTAL SORTING; SORTING INDIVIDUAL ARTICLES, OR BULK MATERIAL FIT TO BE SORTED PIECE-MEAL, e.g. BY PICKING
- B07C5/00—Sorting according to a characteristic or feature of the articles or material being sorted, e.g. by control effected by devices which detect or measure such characteristic or feature; Sorting by manually actuated devices, e.g. switches
- B07C5/36—Sorting apparatus characterised by the means used for distribution
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/48—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
- H01M10/482—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte for several batteries or cells simultaneously or sequentially
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
- B07C—POSTAL SORTING; SORTING INDIVIDUAL ARTICLES, OR BULK MATERIAL FIT TO BE SORTED PIECE-MEAL, e.g. BY PICKING
- B07C2301/00—Sorting according to destination
- B07C2301/0008—Electronic Devices, e.g. keyboard, displays
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
The invention provides a lithium ion battery self-discharge screening method, a lithium ion battery self-discharge screening device and a storage medium, wherein the method comprises the following steps: calculating a cell K value of the lithium ion battery to be detected; dividing the electric core of the lithium ion battery to be detected into m clusters, each cluster comprises n electric cores, and calculating the dispersion d of each electric core in each cluster ij ；d ij Representing the dispersion of the jth battery cell of the ith cluster, wherein i is more than 0 and less than or equal to m, and j is more than 0 and less than or equal to n; satisfies the condition d ij First reference value and/or K ij The battery cell with the reference value greater than the second reference value is an abnormal self-discharge battery cell, K ij And expressing the K value of the jth battery cell in the ith cluster. The invention can reduce the influence of abnormal processing procedure and capacity grading temperature in the capacity grading process on the self-discharge of the battery cell, and can effectively avoid the condition that the K value specification line is not suitable for deviation when the production line is abnormal. The sieve leakage of the abnormal self-discharge electric core can be effectively avoided.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a lithium ion battery self-discharge screening method, a lithium ion battery self-discharge screening device and a storage medium.
Background
The lithium ion battery has the advantages of high specific energy, long cycle life, greenness, no pollution and the like, and is widely applied to consumer electronics and new energy automobiles. In the production and manufacturing process of the battery core of the lithium ion battery, the battery core is usually subjected to self-discharge screening after the capacity grading is finished, so that the purpose is to screen out unqualified battery cores. And the self-discharge screening is completed by testing the K value of the battery cell. The K value is a physical quantity for describing the self-discharge rate of the battery cell, the K value is a project which must be tested by lithium battery cell manufacturing enterprises before shipment, and the test of the K value has the following meanings:
(1) Screening out a micro short circuit cell: dust may be introduced in the production process of the battery core, or metal particles may be generated in the welding process, and dust is also carried by the pole piece, the diaphragm, and the like, which may cause micro short circuit in the battery core. If the micro short circuit cell cannot be detected in time, the diaphragm can be punctured to form a short circuit in the subsequent use process of the cell, so that the thermal runaway of the cell is caused, and safety accidents are caused. For a micro-short circuit cell, the cell cannot be screened out through capacity grading and once OCV (Open circuit voltage) measurement, self-discharge screening must be introduced, and whether the micro-short circuit condition exists in the cell is judged by calculating the reduction rate of the storage voltage of the cell.
(2) Screening of cell consistency: the K value is a quantitative description of the cell voltage drop rate, and the calculation method is that the open circuit voltage difference of the two tests is divided by the time interval of the two voltage tests. If the K value is too large, it indicates that the cell storage voltage drops too fast, and if the self-discharged large cell is delivered to a customer, the voltage consistency of the self-discharged large cell will be worse and bigger with the lapse of time. According to the cask principle, if the module is constituteed with normal electric core from the unusual electric core of discharging, each electric core is from the nonconformity of discharging can lead to lithium cell group life-span to reduce, appears the capacity and attenuates rapidly to influence the use of electric core.
The current industry-common K value screening method comprises the following steps: after capacity separation, the cell → the storage is performed for a period of time t1 → the test voltage OCV1 → the storage is performed for a period of time t2 → the test voltage OCV2, and the ratio of the difference between the OCV1 and the OCV2 to the two storage time differences is the K value, that is, the K value = Δ OCV/Δ t = (OCV 1-OCV 2)/(t 2-t 1). And calculating the average voltage drop value and the standard deviation of the same group of battery cells, and screening qualified batteries according to the average voltage drop value and the standard deviation data.
The self-discharge screening method has the following defects:
(1) Influence K value specification formulation: currently, a general K value specification method is to set a specification line according to a mean value (+ n σ) according to a K value distribution range of a battery cell, where n is usually in a range of 2 to 6. In the actual production process of the battery cell, the OCV during storage of the battery cell is greatly influenced by the temperature of the storage workshop and the storage time. When the production line is abnormal, the OCV is in an overtime state, and according to the K value calculation mode, the longer the storage time is, the smaller the K value of the battery cell is, so that the K value specification line is deviated, and the condition that the original specification is not suitable to be formulated is caused.
(2) The possibility of electric core screen leakage caused by abnormal self-discharge exists: the K value is not only influenced by the manufacturing procedure of a production line, but also influenced by the temperature of a grading workshop, the K values of the cells all present different distributions in different grading time of the same grading cabinet and in the same grading time of the same column of grading cabinets, and the self-discharge abnormal cells can possibly flow out to a client side to cause customer complaints according to the condition that screen leakage often occurs according to the conventional K value screening method.
Disclosure of Invention
The invention aims to provide a lithium ion battery self-discharge screening method, a lithium ion battery self-discharge screening device and a storage medium, which can solve the problems of influencing K value specification formulation and possible abnormal battery cell screen leakage in the prior art.
The purpose of the invention is realized by the following technical scheme:
in a first aspect, the present invention provides a lithium ion battery self-discharge screening method, including the following steps:
calculating a cell K value of the lithium ion battery to be detected;
dividing the electric core of the lithium ion battery to be detected into m clusters, each cluster comprises n electric cores, and calculating the dispersion d of each electric core in each cluster ij ；d ij Representing the dispersion of the jth battery cell of the ith cluster, wherein i is more than 0 and less than or equal to m, and j is more than 0 and less than or equal to n;
satisfies the condition d ij First reference value and/or K ij The battery cell with the reference value greater than the second reference value is an abnormal self-discharge battery cell, K ij And expressing the K value of the jth battery cell in the ith cluster.
Further, before calculating the cell K value of the lithium ion battery to be detected, the method further comprises the step of grading the capacity of the detected lithium ion battery.
Further, the method for determining the first reference value comprises: taking a plurality of battery cores, and calculating the K value of each battery core to obtain the distribution range of the K values of all the battery cores; calculating the average value of the K values of all the battery cores; dividing all the battery cells into a plurality of regions according to different ranges of the K values of the battery cells; disassembling the electric cores in different intervals, reversely deducing whether the electric core in the interval is the electric core with the bad K value according to whether the disassembled electric core is abnormal or not, calculating the ratio of the K value of the electric core with the bad K value to the average value of the K value, and setting the minimum value of the ratio as a first reference value.
Further, the value range of the second reference value is as follows: and u-y sigma is less than or equal to a second reference value less than or equal to u + y sigma, wherein u represents the K value mean value of all the cells to be detected, sigma represents the standard deviation of all the cells to be detected, and y is a constant.
Further, the calculation formula of the cell K value is as follows:
t1 represents a first time period of standing after the battery cell is charged to a certain SOC, and OCV1 represents the open-circuit voltage of the battery cell tested when the first time period expires; t2 represents a second time period during which the cell is left standing after being charged to a certain SOC, and OCV2 represents the open circuit voltage of the cell tested when the second time period expires.
Further, calculating the dispersion d of the cells in each cluster ij The method comprises the following steps:
calculating the K value mean value a of the ith cluster battery cell i And standard deviation σ i ；
Reject K ij Third reference value, or K ij Calculating the K value mean value a of the residual cells in the cells with the reference value < fourth i '; wherein the third reference value is greater than the fourth reference value;
calculating the K value K of a single battery cell in the ith cluster ij And the K value mean value a i The ratio of' is the dispersion of the cells.
Further, the K value mean value a i The calculation formula of (2) is as follows:
K i1 、K i2 、K i3 ……K in and respectively representing the K values of n cells of the ith cluster.
Further, the standard deviation σ i The calculation formula of (2) is as follows:
in a second aspect, the present invention provides a lithium ion battery self-discharge screening apparatus configured to perform the above lithium ion battery self-discharge screening method, including:
the first calculation module is used for calculating the K value of the battery cell of the lithium ion battery to be detected;
the storage module is used for storing a plurality of different screening standards;
a second calculating module, configured to calculate the dispersion d of a single cell in each cluster of cells respectively ij (ii) a Wherein d is ij Representing the dispersion of the jth battery cell in the ith cluster;
a screening module for judging K value of the cell ij Whether the cell dispersion d is larger than a first reference value or not and the cell dispersion ij Whether the reference value is larger than a second reference value; wherein K ij Representing the K value of the jth battery cell in the ith cluster;
a first judgment module for judging the K value K of the battery cell when the screening module ij First reference value and/or cell dispersion d ij When the reference value is larger than the second reference value, the battery cell is judged to be a self-discharge abnormal battery cell;
a second judging module for judging the K value of the cell K when the screening module ij Not more than a first reference value and cell dispersion d ij And when the value is less than or equal to the second reference value, judging the battery cell to be a normal battery cell.
Further, the first calculating module includes a timing unit, an open circuit voltage detecting unit, and a first calculating unit, wherein:
the timing unit is used for starting timing after the battery cell of the lithium ion battery to be detected is charged to the set SOC, stopping timing after a set first time period t1, and detecting and recording the open-circuit voltage OCV1 of the battery cell by the open-circuit voltage detection unit; the timing unit continues timing, timing is stopped after a set second time period t2, and the open-circuit voltage detection unit detects and records the open-circuit voltage OCV2 of the battery cell;
the first calculation unit calculates a difference between the open-circuit voltage OCV1 and the open-circuit voltage OCV2 and a difference between the second period t2 and the first period t 1.
Further, the second computing module includes:
a second calculation unit for calculating each clusterAverage value a of battery cell i ；
A third calculating unit for calculating the standard deviation sigma of each cluster of cells i ；
A comparison unit for comparing the K value K of a single cell in each cluster ij Comparing the reference values with a third reference value and a fourth reference value respectively;
a rejecting unit rejecting K according to the comparison result of the comparing unit ij Third reference value, or K ij The battery cell with the fourth reference value;
a fourth calculating unit, configured to calculate an average value a of K values of remaining battery cells after each cluster of battery cells is removed by the removing unit i ’；
A fifth calculating unit, configured to calculate a K value K of a single cell in each cluster ij And the K value mean value a i ' to obtain the dispersion of the cells.
Further, the screening module comprises:
a first judging unit for judging the cell dispersion d ij Whether the reference value is larger than the first reference value;
a second judgment unit for judging the K value K of the battery cell ij Whether or not it is greater than the second reference value.
Further, the lithium ion battery self-discharge screening device further comprises an output module, which is used for outputting the judgment results of the first judgment module and the second judgment module.
In a third aspect, the present invention provides a storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the lithium ion battery self-discharge screening method is implemented.
The lithium ion battery self-discharge screening method provided by the invention combines the distribution rule of the K values of the battery cells of the lithium ion battery, takes n battery cells in a tray for producing the battery cells of the lithium ion battery as a cluster, and simultaneously combines the integral distribution of the K values to carry out self-discharge screening, so that the influence of abnormal processing procedures and capacity separation temperature in the capacity separation process on the self-discharge of the battery cells can be reduced, and the condition that a K value specification line is not suitable for deviation when a production line is abnormal can be effectively avoided. In addition, the invention sets two reference values for self-discharge screening, and when the two reference values are simultaneously met, the battery is a normal battery, otherwise, the battery is judged to be abnormal in self-discharge. The method can effectively avoid the screen leakage of the self-discharge abnormal cell.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a flow chart of a lithium ion battery self-discharge screening method of the present invention;
FIG. 2 is a diagram illustrating the calculation of the dispersion d of the cells in each cluster according to the present invention ij A flow chart of (1);
fig. 3 is a block diagram of a lithium ion battery self-discharge screening device according to the present invention.
Detailed Description
The embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.
The embodiments of the present disclosure are described below with specific examples, and other advantages and effects of the present disclosure will be readily apparent to those skilled in the art from the disclosure in the specification. It is to be understood that the embodiments described are only a few embodiments of the present disclosure, and not all embodiments. The disclosure may be embodied or carried out in various other specific embodiments, and various modifications and changes may be made in the details within the description without departing from the spirit of the disclosure. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict. All other embodiments, which can be derived by a person skilled in the art from the embodiments disclosed herein without making any creative effort, shall fall within the protection scope of the present disclosure.
The invention discloses a lithium ion battery self-discharge screening method, which comprises the following steps:
s1, calculating a cell K value of the lithium ion battery to be detected.
Further, calculating the cell K value of the lithium ion battery to be detected includes:
charging the battery cell to be detected to a set SOC (State of Charge), starting timing, testing the open-circuit voltage OCV1 of the battery cell after the battery cell is kept still for a first time period t1, continuing timing, and testing the open-circuit voltage OCV2 of the battery cell after the battery cell is kept still for a second time period t 2. And the ratio of the difference value of the OCV1 and the OCV2 to the standing time difference is the K value.
The calculation of the value of K is formulated as:
t1 represents a first time period during which the battery cell is left standing after being charged to a certain SOC, and OCV1 represents an open circuit voltage measured when the first time period expires. t2 represents a second time period during which the cell is left to stand after being charged to a certain SOC, and OCV2 represents an open circuit voltage measured when the second time period expires.
SOC, state of Charge, refers to the State of Charge of the battery. That is, the battery is charged at a certain rate, and the ratio of the charged amount to the rated capacity is called SOC. Preferably, the value range of the SOC in the application is 1% -90%.
Further, before step S1, a step of capacity grading is further included.
The capacity grading of the lithium ion battery is completed by a formation and capacity grading cabinet, and the function of the formation and capacity grading cabinet is actually like a charger, but the formation and capacity grading cabinet can charge and discharge a large number of batteries simultaneously. When the capacity of the battery is divided, the data of each detection point is obtained through computer management, so that the data of the capacity, the internal resistance and the like of the battery are analyzed, the quality grade of the battery is determined, and the process is the capacity division.
The battery cell is one of a lithium iron phosphate battery cell, a nickel-cobalt-manganese ternary battery cell and a nickel-cobalt-manganese-aluminum battery cell.
S2, dividing the battery cell to be detected intom clusters, each cluster comprises n electric cores, and the dispersion d of the electric cores in each cluster is calculated ij 。
One tray can be used as a cluster to divide all lithium battery cells to be detected into m clusters. d is a radical of ij And (3) representing the dispersion of the jth cell of the ith cluster, wherein i is more than 0 and less than or equal to m, and j is more than 0 and less than or equal to n. Preferably, n ranges from 10 to 500.
Further, calculating the dispersion d of the cells in each cluster ij The method comprises the following steps:
step S201, calculating the K value mean value a of the ith cluster battery cell i And standard deviation σ i 。
The K value of each cell is calculated in step S1, and after the cells are clustered according to the tray, the K value of the jth cell in the ith cluster is recorded as K ij J is more than 0 and less than or equal to n. The K values of n electric cores of the ith cluster are respectively K i1 、K i2 、K i3 ……K in . The sum of the K values of all the electric cores of the ith cluster is divided by the number n of the electric cores to obtain the K value mean value a of the electric core of the ith cluster i . Is formulated as:
standard deviation sigma i The calculation formula of (2) is as follows:
step S202, removing K ij Third reference value, or K ij Calculating the K value mean value a of the residual cells in the cells with the reference value < fourth i '. The third reference value is greater than the fourth reference value.
Wherein the third reference value = a i +c*σ i Fourth reference value = a i -c*σ i . Mean value a i ' and mean a i The calculation method is the same, and is not described herein. Where c is a constant, preferably 6.
Step S203, calculating K value K of single electric core in the ith cluster ij And the K value mean value a i The ratio of' is the dispersion of the cells.
The dispersion is formulated as:
d i1 ＝K i1 /a i ’，d i2 ＝K i2 /a i ’，d i3 ＝K i3 /a i ’，d in ＝K in /a i ’。
step S3, satisfying the condition d ij First reference value e and/or K ij And the battery cell with the second reference value f is the self-discharge abnormal battery cell.
The first reference value e and the second reference value f are preset values.
The first reference value e may be set according to actual conditions. The setting of the first reference value e will be described below by way of example, but the setting of the first reference value e is not limited to this manner, and the present invention is not limited thereto. And taking a plurality of battery cores, and calculating the K values of the battery cores to obtain the distribution range of the K values between 0.10 and 0.40. And calculating the average value of the K values of the battery cells to be 0.15. The battery cell is divided into different sections, namely, the battery cell is divided into the following sections according to the K value of the battery cell in different ranges: 0.15-0.16, 0.16-0.17, 0.17-0.18, 0.18-0.20, 0.20-0.23, etc. Disassembling the electric cores in different intervals, reversely deducing whether the electric core in the interval is the electric core with the bad K value according to whether the disassembled electric core is abnormal or not, calculating the ratio of the K value of the electric core with the bad K value to the average value of the K value, and setting the minimum value of the ratio as a first reference value e.
Preferably, e is in the range of 0.5 to 10.
The range of the second reference value f is determined according to the K value distribution of all the cells. And setting the range of the second reference value f as u-y sigma is less than or equal to f and less than or equal to u + y sigma by calculating the K value mean value u and the standard deviation sigma of all the electric cores to be detected.
y is a constant and has a value ranging from 1 to 6. Preferably, y has a value of 3. Then the preferred ranges for f are: u-3 sigma is less than or equal to f is less than or equal to u +3 sigma.
The invention also provides a lithium ion battery self-discharge screening device, which comprises:
the first calculation module is used for calculating the K value of the electric core of the lithium ion battery to be detected.
A second calculating module, configured to calculate the dispersion d of a single cell in each cluster of cells respectively ij 。
And the storage module is used for storing a plurality of different screening standards.
The screening criterion comprises a first reference value e and a second reference value f which are preset.
A screening module for judging K value K of the battery cell ij Whether the cell dispersion d is larger than a first reference value or not and the cell dispersion ij Whether the reference value is larger than a second reference value; wherein K ij And representing the K value of the jth cell in the ith cluster.
A first judgment module for judging the K value K of the battery cell when the screening module ij First reference value and/or cell dispersion d ij And if the second reference value is larger than the first reference value, judging that the battery cell is a self-discharge abnormal battery cell.
A second judging module for judging the K value of the cell K when the screening module ij Not more than a first reference value and cell dispersion d ij And when the second reference value is less than or equal to the second reference value, judging that the battery cell is a normal battery cell.
Preferably, the lithium ion battery self-discharge screening device further comprises an output unit for outputting the judgment results of the first judgment module and the second judgment module.
Further, the first calculation module comprises a timing unit, an open-circuit voltage detection unit and a first calculation unit, wherein the timing unit is used for starting timing after the battery cell of the lithium ion battery to be detected is charged to the set SOC, timing is stopped after a set first time period t1, the open-circuit voltage detection unit detects and records the open-circuit voltage OCV1 of the battery cell, timing is continued by the timing unit, timing is stopped after a set second time period t2, and the open-circuit voltage detection unit detects and records the open-circuit voltage OCV2 of the battery cell. A first calculation unit for calculating a difference between the open-circuit voltages OCV1 and OCV2 and a difference between the second period t2 and the first period t 1.
Further, the setting of the first reference value e stored in the storage unit may be performed according to actual conditions. The setting of the first reference value e will be described below by way of example, but the setting of the first reference value e is not limited to this manner, and the present invention is not limited thereto. And taking a plurality of battery cores, and calculating the K values of the battery cores to obtain the distribution range of the K values between 0.10 and 0.40. And calculating the average value of the K values of the battery cells to be 0.15. The battery cell is partitioned, namely, the battery cell is divided into different intervals, such as the following intervals, according to the K value of the battery cell in different ranges: 0.15-0.16, 0.16-0.17, 0.17-0.18, 0.18-0.20, 0.20-0.23, etc. Disassembling the electric cores in different intervals, reversely deducing whether the electric core in the interval is the electric core with the bad K value according to whether the disassembled electric core is abnormal or not, calculating the ratio of the K value of the electric core with the bad K value to the average value of the K value, and setting the minimum value of the ratio as a first reference value e. The range of the second reference value f is determined according to the K value distribution of all the cells. And setting the range of the second reference value f as u-y sigma is less than or equal to f and less than or equal to u + y sigma by calculating the mean value u and the standard deviation sigma of the K values of all the cells to be detected. y is a constant with a value ranging from 1 to 6. Preferably, y has a value of 3. Then the preferred range of f is: u-3 sigma is less than or equal to f is less than or equal to u +3 sigma.
Further, the second calculation module comprises a second calculation unit, a third calculation unit, a comparison unit, a rejection unit, a fourth calculation unit and a fifth calculation unit, wherein:
a second calculating unit for calculating the average value a of each cluster of battery cells i . i represents the ith cluster.
a i Is expressed as:
k values of n cells of the ith cluster are respectively expressed as K i1 、K i2 、K i3 ……K in 。
A third calculating unit for calculating the standard deviation sigma of each cluster of cells i 。
Standard deviation sigma i The calculation formula of (c) is:
K ij and expressing the K value of the jth battery cell in the ith cluster.
A comparison unit for comparing the K value K of the single battery cell in each cluster ij And comparing with the third reference value and the fourth reference value respectively. Calculating a third reference value and a fourth reference value according to the mean value and the standard deviation of the K values of the single battery cells in each cluster, wherein the third reference value = a i +6*σ i Fourth reference value = a i -6*σ i . The coefficient 6 may be adjusted according to actual needs, and is not necessarily 6.
A rejecting unit rejecting K according to the comparison result of the comparing unit ij Third reference value, or K ij < cells of the fourth reference value.
A fourth calculating unit, configured to calculate an average value a of K values of remaining battery cells after each cluster of battery cells is removed by the removing unit i ’。
A fifth calculating unit, configured to calculate a K value K of a single cell in each cluster ij And the K value mean value a i ' to obtain the dispersion of the cells.
Further, the screening module 3 includes a first judging unit and a second judging unit, wherein:
a first judging unit for judging the dispersion d of the cell to be detected ij Whether or not it is greater than the first reference value e.
A second judging unit for judging the K value of the cell to be detected ij Whether or not it is greater than the second reference value f.
The invention also provides a storage medium, on which a computer program is stored, and the computer program is executed by a processor to realize the lithium ion battery self-discharge screening method.
In the present invention, unless otherwise expressly stated or limited, the first feature may be "on" the second feature in direct contact with the second feature, or the first and second features may be in indirect contact via an intermediate. "plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the present invention, unless otherwise explicitly stated or limited, the terms "mounted," "connected," "fixed," and the like are to be construed broadly, e.g., as being permanently connected, detachably connected, or integral; may be mechanically coupled, may be electrically coupled or may be in communication with each other; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
The above description is for the purpose of illustrating embodiments of the invention and is not intended to limit the invention, and it will be apparent to those skilled in the art that any modification, equivalent replacement, or improvement made without departing from the spirit and principle of the invention shall fall within the protection scope of the invention.
Claims (11)
1. A lithium ion battery self-discharge screening method is characterized by comprising the following steps:
calculating a cell K value of the lithium ion battery to be detected;
dividing the electric core of the lithium ion battery to be detected into m clusters, each cluster comprises n electric cores, and calculating the dispersion d of each electric core in each cluster ij ；d ij The dispersion of the jth battery cell of the ith cluster is represented, i is more than 0 and less than or equal to m, and j is more than 0 and less than or equal to n;
satisfy the condition electric core K value K ij Not less than a first reference value and cell dispersion d ij When the second reference value is less than or equal to the first reference value, the battery cell is judged to be a normal battery cell, K ij Representing the K value of the jth cell in the ith cluster;
the method for determining the first reference value comprises the following steps: taking a plurality of battery cores, and calculating the K value of each battery core to obtain the distribution range of the K values of all the battery cores; calculating the average value of the K values of all the battery cores; dividing all the battery cells into a plurality of regions according to different ranges of the K values of the battery cells; disassembling the electric cores in different sections, reversely deducing whether the electric core in the section is a bad electric core with a K value according to whether the disassembled electric core is abnormal or not, calculating the ratio of the K value of the bad electric core with the K value to the average value of the K value, and setting the value with the minimum ratio as a first reference value;
the value range of the second reference value is as follows: u-y sigma is less than or equal to a second reference value less than or equal to u + y sigma, wherein u represents the K value mean value of all the cells to be detected, sigma represents the standard deviation of all the cells to be detected, and y is a constant;
calculating the dispersion d of the battery cell in each cluster ij The method comprises the following steps:
calculating the K value mean value a of the ith cluster battery cell i And standard deviation σ i ；
Removing the cells with Kij larger than a third reference value or Kij smaller than a fourth reference value, and calculating the K value mean value a of the residual cells i ’ (ii) a Wherein the third reference value is greater than the fourth reference value; the third reference value = ai + c σ i, and the fourth reference value = ai-c σ i;
calculating the K value K of a single electric core in the ith cluster ij And the K value mean value a i ’ The ratio of (a) to (b) is the dispersion of the cell.
2. The lithium ion battery self-discharge screening method according to claim 1, further comprising a step of grading the detected lithium ion battery before calculating the cell K value of the lithium ion battery to be detected.
3. The lithium ion battery self-discharge screening method according to claim 1 or 2, wherein the calculation formula of the cell K value is:
t1 represents a first time period of standing after the battery cell is charged to a certain SOC, and OCV1 represents an open-circuit voltage of the battery cell measured when the first time period expires; t2 represents a second time period during which the cell is left standing after being charged to a certain SOC, and OCV2 represents the open circuit voltage of the cell tested when the second time period expires.
4. Root of herbaceous plantThe lithium ion battery self-discharge screening method of claim 1, wherein the K value mean a i The calculation formula of (2) is as follows:
K i1 、K i2 、K i3 ……K in and respectively representing the K values of n cells of the ith cluster.
5. The lithium ion battery self-discharge screening method of claim 1, wherein the standard deviation σ is i The calculation formula of (2) is as follows:
6. a lithium ion battery self-discharge screening apparatus configured to perform the lithium ion battery self-discharge screening method of any one of claims 1 to 5, comprising:
the first calculation module is used for calculating the K value of the battery cell of the lithium ion battery to be detected;
a second calculating module, configured to calculate the dispersion d of a single cell in each cluster of cells respectively ij (ii) a Wherein d is ij Representing the dispersion of the jth battery cell in the ith cluster;
the storage module is used for storing a plurality of different screening standards;
a screening module for judging K value K of the battery cell ij Whether the cell dispersion d is larger than a first reference value or not and the cell dispersion ij Whether the reference value is larger than a second reference value; wherein K ij Representing the K value of the jth battery cell in the ith cluster;
a first judgment module for judging the K value K of the battery cell when the screening module ij First reference value and/or cell dispersion d ij When the reference value is larger than the second reference value, the battery cell is judged to be a self-discharge abnormal battery cell;
a second judging module for judging the K value of the cell K when the screening module ij Less than or equal to the first reference value and electricityCore dispersion d ij And when the second reference value is less than or equal to the second reference value, judging that the battery cell is a normal battery cell.
7. The lithium ion battery self-discharge screening device of claim 6, wherein the first calculation module comprises a timing unit, an open circuit voltage detection unit, and a first calculation unit, wherein:
the timing unit is used for starting timing after the battery cell of the lithium ion battery to be detected is charged to the set SOC, stopping timing after a set first time period t1, and detecting and recording the open-circuit voltage OCV1 of the battery cell by the open-circuit voltage detection unit; the timing unit continues timing, timing is stopped after a set second time period t2, and the open-circuit voltage detection unit detects and records the open-circuit voltage OCV2 of the battery cell;
the first calculation unit calculates a difference between the open-circuit voltage OCV1 and the open-circuit voltage OCV2 and a difference between the second period t2 and the first period t 1.
8. The lithium ion battery self-discharge screening apparatus according to claim 6, wherein the second calculation module comprises:
a second calculating unit for calculating the average value a of each cluster of battery cells i ；
A third calculating unit for calculating the standard deviation sigma of each cluster of cells i ；
A comparison unit for comparing the K value K of a single cell in each cluster ij Comparing the reference values with a third reference value and a fourth reference value respectively;
a rejecting unit rejecting K according to the comparison result of the comparing unit ij Third reference value, or K ij The battery cell with the fourth reference value;
a fourth calculating unit, configured to calculate an average value a of K values of remaining battery cells after each cluster of battery cells is removed by the removing unit i ’ ；
A fifth calculating unit, configured to calculate a K value K of a single cell in each cluster ij And the K value mean value a i ’ And obtaining the dispersion of the battery cell.
9. The lithium ion battery self-discharge screening apparatus of claim 6, wherein the screening module comprises:
a first judgment unit for judging the cell dispersion d ij Whether the reference value is greater than the first reference value;
a second judgment unit for judging the K value K of the battery cell ij Whether or not it is greater than the second reference value.
10. The lithium ion battery self-discharge screening device according to any one of claims 6 to 9, further comprising an output module configured to output the determination results of the first determination module and the second determination module.
11. A storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the lithium ion battery self-discharge screening method of any one of claims 1 to 5.
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| CN114460470A (en) * | 2022-01-26 | 2022-05-10 | 上海玫克生智能科技有限公司 | Battery pack state analysis method and system based on voltage and terminal |
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