CN110806545B - Method for rapidly detecting cycle life of lithium battery - Google Patents
Method for rapidly detecting cycle life of lithium battery Download PDFInfo
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- CN110806545B CN110806545B CN201911113322.6A CN201911113322A CN110806545B CN 110806545 B CN110806545 B CN 110806545B CN 201911113322 A CN201911113322 A CN 201911113322A CN 110806545 B CN110806545 B CN 110806545B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/385—Arrangements for measuring battery or accumulator variables
- G01R31/387—Determining ampere-hour charge capacity or SoC
- G01R31/388—Determining ampere-hour charge capacity or SoC involving voltage measurements
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/378—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC] specially adapted for the type of battery or accumulator
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/389—Measuring internal impedance, internal conductance or related variables
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/392—Determining battery ageing or deterioration, e.g. state of health
Abstract
The invention discloses a method for rapidly detecting the cycle life of a lithium battery, which comprises the following steps: acquiring a capacity retention percentage reference value of a batch of lithium batteries to be detected after each charge-discharge cycle; randomly extracting a grading cabinet on the lithium battery to be tested for charge-discharge circulation, calculating the percentage of the actual capacity value and the initial capacity value after the lithium battery is circulated, and obtaining the (N) value1、N2 N3……Nn) Percent actual capacity retention of cycle; comparing the actual capacity retention percentage of the lithium battery after N times of circulation with the reference value of the capacity retention percentage of the lithium battery after N times of circulation, judging that the cycle life of the lithium battery is unqualified when the actual capacity retention percentage is smaller than the reference value, and continuously and repeatedly circulating to obtain the actual capacity retention percentage value to compare when the actual capacity retention percentage value is larger than the reference value until the cycle number reaches the preset number (50 times is recommended and N is used for 50 times)50Indicating) and then judging whether the cycle life of the batch of lithium batteries is qualified or not. The invention shortens the test time of the conventional lithium battery cycle life test and estimates whether the life of the lithium battery is qualified in advance.
Description
Technical Field
The invention relates to the technical field of lithium battery/lithium battery pack detection, in particular to a method for rapidly detecting the cycle life of a lithium battery.
Background
At present, the lithium battery charge-discharge cycle life test is specified in the recommended national standard or enterprise product specification, the capacity of the lithium ion lithium battery needs to be compared and judged after the charge-discharge cycle is carried out for about 400 times to determine whether the cycle life is qualified, if the charge-discharge cycle test is carried out for 300 times and 400 times according to the test requirement, the time of more than two months is generally needed, the test time is long, the customer requirement cannot be met for the production delivery cycle of a lithium battery packaging plant, and meanwhile, more test equipment of an enterprise can be occupied and other tests cannot be carried out.
Therefore, the prior art has yet to be developed.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a method for rapidly detecting the cycle life of a lithium battery, and aims to shorten the test time of the existing lithium battery charge-discharge cycle life test and estimate in advance whether the lithium battery meets the cycle life requirement.
In order to realize the purpose, the invention adopts the following technical scheme:
a lithium battery cycle life rapid detection method comprises the following steps:
s10, acquiring a reference value: acquiring a capacity retention percentage reference value of a batch of lithium batteries to be detected after each charge-discharge cycle;
s20, sampling: randomly extracting 3PCS lithium batteries from the batch of lithium batteries;
s30, obtaining actual capacity retention percentage: carrying out charge and discharge cycles on the sampled lithium battery on a grading cabinet, recording the actual capacity value of the lithium battery after each charge and discharge cycle is completed, calculating the percentage of the actual capacity value and the initial capacity value of the lithium battery, and obtaining the actual capacity retention percentage of the lithium battery after the charge and discharge cycle;
s40, compare: and comparing the actual capacity retention percentage of the lithium battery after N times of charge and discharge cycles with the capacity retention percentage reference value of the lithium battery after N times of charge and discharge cycles, judging that the charge and discharge cycle life of the batch of lithium batteries is unqualified when the actual capacity retention percentage is smaller than the reference value, continuing the charge and discharge cycles to obtain the actual capacity retention percentage when the actual capacity retention percentage is larger than the reference value, and comparing the actual capacity retention percentage with the capacity retention percentage reference value of the corresponding times until the cycle times reach the preset times.
The step S40 is performed in a manner that comparison is performed after each charge-discharge cycle is completed, specifically:
and comparing the actual capacity retention percentage of the lithium battery after each charge-discharge cycle with the charge-discharge cycle capacity retention percentage reference value of the lithium battery, judging that the charge-discharge cycle life of the batch of lithium batteries is unqualified when the actual capacity retention percentage is smaller than the reference value, continuing the charge-discharge cycle to obtain the actual capacity retention percentage when the actual capacity retention percentage is larger than the reference value, and comparing the actual capacity retention percentage with the capacity retention percentage reference value of the corresponding times until the cycle times reach the preset times.
The step S40 is performed after the intermittent charge-discharge cycle is completed, and specifically includes:
step S30 is repeated to initiate cycle N1Calculating the actual capacity retention percentage of the lithium battery after the charge-discharge cycle every 5 times at the beginning, and adding the lithium battery N5、N10、N15……NnComparing the actual capacity retention percentage after the secondary charge-discharge cycle with the reference value of the capacity retention percentage corresponding to the times of the lithium batteries, judging that the charge-discharge cycle life of the batch of lithium batteries is unqualified if the actual capacity retention percentage is smaller than the reference value, and continuing the step until the preset cycle times N are reached if the actual capacity retention percentage is larger than the reference valuenAnd then the process is finished.
The method comprises the following steps of obtaining a capacity retention percentage reference value after each charge-discharge cycle of the lithium battery:
obtaining a charge-discharge cycle life specification in a specification for a lithium battery, the specification comprising: total number of charge and discharge cycles N of lithium batterynAfter the treatment, the capacity retention percentage is more than or equal to X%;
and (3) averagely calculating the capacity fading percentage after each charge-discharge cycle of the lithium battery: (1-X%) +/Nn＝P1％；
The percentage of capacity fade after the 2 nd charge-discharge cycle was calculated: p1％×N2＝P2%, i.e. P2% of 2 nd chargePercentage of capacity fade after discharge cycle, where N2＜Nn；
Calculate the percentage capacity retention reference after the 2 nd charge-discharge cycle: 100% -P2％；
Other times the capacity holds the percentage reference and so on.
Wherein, the lithium cell of random extraction needs the primary verification qualified, the primary verification includes: self-discharge, internal resistance and voltage detection.
Wherein, carry out the charge-discharge cycle of predetermineeing the number of times on the partial volume cabinet and include: the charging and discharging current provided during the charging and discharging circulation on the grading cabinet is 0.5C, the maximum value of the charging and discharging current cannot exceed the maximum charging/discharging current of the grading cabinet, and when the 0.5C current of the lithium battery to be tested in the circulation is greater than the maximum charging/discharging current of the grading cabinet, the charging and discharging circulation is carried out at 0.2C or 2A.
Wherein, carry out the charge-discharge cycle of predetermineeing the number of times on the partial volume cabinet still includes: the charge limiting voltage, the discharge cutoff voltage and the charge cutoff current provided during charge-discharge cycling on the grading cabinet all meet the requirement standards of the specification of the batch of lithium batteries.
When the lithium battery is charged and discharged in the capacity grading cabinet, the voltage or current change of the constant current source or the constant voltage source provided by the lithium battery is within the range of +/-1%.
Wherein, the ambient temperature of the lithium battery during the detection of the charge-discharge cycle life is within 23 +/-2 ℃.
And marking the unqualified label stuck to the lithium battery when the charge-discharge cycle life of the lithium battery is unqualified.
The method for rapidly detecting the charge-discharge cycle life of the lithium battery can rapidly judge whether a test sample is qualified or not by calculating the reference value of the capacity retention percentage of the lithium battery after each charge-discharge cycle, then recording and calculating the actual capacity retention percentage of each charge-discharge cycle in the actual charge-discharge cycle process, and continuously or intermittently comparing the actual capacity retention percentage of the lithium battery after a certain charge-discharge cycle with the reference value of the corresponding capacity retention percentage, thereby concluding whether the charge-discharge cycle life of the whole batch of lithium batteries is qualified or not. The actual capacity retention percentage of the lithium battery after each charge-discharge cycle is compared with a corresponding capacity retention percentage reference value, so that whether the attenuation value of the capacity of the lithium battery after each charge-discharge cycle is within a reasonable range can be accurately compared, whether the charge-discharge cycle life of the whole batch of lithium batteries is qualified can be inferred with fewer charge-discharge cycle times such as 30-50 times, and the judgment is not needed after the charge-discharge cycle is finished for 400 times of 300-fold charge-discharge cycles in the prior art, so that the test time is greatly shortened, the detection of the charge-discharge cycle life of the lithium battery can be quickly and efficiently finished, and meanwhile, the detection method is also suitable for detecting the charge-discharge cycle life of the lithium battery pack.
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, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
FIG. 1 is a schematic flow chart of a lithium battery cycle life rapid detection method according to a first embodiment of the present invention;
FIG. 2 is a schematic flow chart of the capacity retention percentage reference value acquisition of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. 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.
It should be noted that all the directional indicators (such as up, down, left, right, front, and rear … …) in the embodiment of the present invention are only used to explain the relative position relationship between the components, the movement situation, etc. in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indicator is changed accordingly.
In addition, the descriptions related to "first", "second", etc. in the present invention are only for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature.
Referring to fig. 1, an embodiment of the invention provides a method for rapidly detecting a charge-discharge cycle life of a lithium battery, including the following steps;
s10, acquiring a reference value: and acquiring a capacity retention percentage reference value of the lithium battery to be detected after each charge-discharge cycle. The capacity retention percentage reference value can be directly given in the technical specification of the batch of lithium batteries or can be obtained by calculating parameters in the specification.
S20, sampling: randomly extracting the 3PCS lithium battery from the batch of lithium batteries.
S30, obtaining actual capacity retention percentage: and carrying out charge and discharge circulation on the sampled lithium battery on a grading cabinet, recording the actual capacity value of the lithium battery after each charge and discharge circulation is completed, calculating the percentage of the actual capacity value and the initial capacity value of the lithium battery, and obtaining the actual capacity retention percentage of the lithium battery after the charge and discharge circulation. And multiplying the ratio of the actual capacity value of the lithium battery after the charge-discharge cycle to the initial capacity value of the lithium battery by 100% to obtain the capacity retention percentage of the lithium battery after the charge-discharge cycle.
If the actual capacity value after the 1 st charge-discharge cycle is 99.9mAh, and the initial capacity value of the lithium battery is 100mAh, the capacity retention percentage of the lithium battery after the 1 st charge-discharge cycle is 99.9%.
If the actual capacity value after the 5 th charge-discharge cycle is 99.7mAh, the recording is performed, and then the capacity retention percentage of the lithium battery after the 5 th charge-discharge cycle is 99.7% because the initial capacity value of the lithium battery is 100 mAh.
Preferably, the lithium battery that is randomly extracted needs to be qualified by initial inspection, the initial inspection includes: self-discharge, internal resistance and voltage detection. Thus, unqualified products can be screened out before the charge-discharge cycle detection.
Preferably, the embodiment of the present invention has the following control parameters when performing the charge and discharge cycles for the preset number of times on the capacity grading cabinet:
1) and when the 0.5C current of the lithium battery to be tested in a circulating mode is greater than the maximum charge/discharge current of the grading cabinet, the charge/discharge circulation is carried out by 0.2C or 2A.
2) The charge limiting voltage, the discharge cutoff voltage and the charge cutoff current provided during charge-discharge circulation on the grading cabinet all meet the requirement standards of the specification of the batch of lithium batteries.
For example, the charge limiting voltage is 4.2V, and the discharge cutoff voltage is 2.75V.
3) And the intermediate shelf time of each step in the charge-discharge cycle process is 10 minutes.
4) When the lithium battery is charged and discharged in the capacity grading cabinet, the voltage or current change of the constant current source or the constant voltage source provided by the lithium battery is within the range of +/-1%.
5) And the ambient temperature of the lithium battery is within 23 +/-2 ℃ during the detection of the charge-discharge cycle life.
Therefore, the accuracy and reliability of the detection of the charge-discharge cycle life of the batch of lithium batteries are ensured.
S40, compare: comparing the actual capacity retention percentage of the lithium battery after N times of charge-discharge cycles with the capacity retention percentage reference value of the lithium battery after N times of charge-discharge cycles, judging that the charge-discharge cycle life of the batch of lithium batteries is unqualified if the actual capacity retention percentage is less than the reference value, continuing the charge-discharge cycles to obtain the actual capacity retention percentage if the actual capacity retention percentage is more than the reference value, and comparing the actual capacity retention percentage with the capacity retention percentage reference value of the corresponding times until the cycle times reach the preset times (if N times are reached)n＝50) Back knotAnd (4) bundling.
Preferably, in the embodiment of the invention, N is more than or equal to 30 ≦ Nn≤50。
Suppose NnTaking 50 times, and assuming N in the actual charge-discharge cycle test process5And for the 5 th charge-discharge cycle, if the actual capacity retention percentage of the lithium battery after the 5 th charge-discharge cycle is 99.2%, and the capacity retention percentage reference value of the lithium battery after the 5 th charge-discharge cycle is 99.7%, namely the actual value is less than the reference value, the charge-discharge cycle life of the lithium battery is judged to be unqualified.
If the actual capacity retention percentage of the lithium battery after the 5 th charge-discharge cycle is 99.8 percent, and the capacity retention percentage reference value of the lithium battery after the 5 th charge-discharge cycle is 99.7 percent, namely the actual value is greater than the reference value, continuing the charge-discharge cycle, calculating the actual capacity retention percentage after each charge-discharge cycle, comparing the actual capacity retention percentage with the capacity retention percentage reference value after the charge-discharge cycle, judging that the cycle life of the lithium battery is unqualified if the actual capacity retention percentage is less than the reference value, stopping the cycle life test, repeating the charge-discharge cycle and the comparison if the actual capacity retention percentage is greater than the reference value, and repeating the cycle until the number of the charge-discharge cycle of the lithium battery reaches the preset number NnAnd stopping the test after 50 times, and deducing whether the cycle life of the whole batch of lithium batteries is qualified or not according to whether the sample is qualified or not.
In the embodiment of the invention, when the charge-discharge cycle life of the lithium battery is unqualified, the unqualified label stuck to the lithium battery is marked. Thus, unqualified products in the batch lithium batteries can be conveniently and rapidly identified. And meanwhile, for unqualified lithium batteries, an abnormal single is sent back to relevant units for evaluation treatment.
The comparison step of step S40 in the embodiment of the present invention may have two ways:
one of the comparison modes is to perform comparison after each charge-discharge cycle is completed, and specifically includes:
and comparing the actual capacity retention percentage of the lithium battery after each charge-discharge cycle with the charge-discharge cycle capacity retention percentage reference value of the lithium battery, judging that the charge-discharge cycle life of the batch of lithium batteries is unqualified when the actual capacity retention percentage is smaller than the reference value, continuing the charge-discharge cycle to obtain the actual capacity retention percentage when the actual capacity retention percentage is larger than the reference value, and comparing the actual capacity retention percentage with the capacity retention percentage reference value of the corresponding times until the cycle times reach the preset times.
The method is characterized in that the actual capacity retention percentage of the lithium battery after each charge-discharge cycle is compared with the capacity retention percentage reference value after the charge-discharge cycle, and the comparison mode is that the actual capacity retention percentage and the capacity retention percentage reference value after the charge-discharge cycle are continuously compared in the process before the preset number of cycles is finished.
The other comparison mode is to perform comparison after the intermittent charge-discharge cycle is completed, and specifically comprises the following steps:
step S30 is repeated to initiate cycle N1Calculating the actual capacity retention percentage of the lithium battery after the charge-discharge cycle every 5 times at the beginning, and adding the lithium battery N5、N10、N15……NnComparing the actual capacity retention percentage after the secondary charge-discharge cycle with the reference value of the capacity retention percentage corresponding to the times of the lithium batteries, judging that the charge-discharge cycle life of the batch of lithium batteries is unqualified if the actual capacity retention percentage is smaller than the reference value, and continuing the step until the preset cycle times N are reached if the actual capacity retention percentage is larger than the reference valuenAnd then the process is finished.
I.e. in NnComparisons during the next charge-discharge cycle, e.g. NnIf the number of the intervals is 5 times and 50 times, only the 1 st time (N) of the charge-discharge cycle of the lithium battery needs to be calculated1) 5 th (N)5) 10 th time (N)10) … th 50 (N)50) Comparing the actual capacity retention percentage with the reference value of the capacity retention percentage of the corresponding times, performing the first comparison between the actual capacity retention percentage of the lithium battery and the reference value of the capacity retention percentage of the corresponding times after the 5 th time of the charge-discharge cycle of the lithium battery, directly judging that the lithium battery is unqualified and terminating the continuous test if the actual capacity retention percentage is less than the reference value, performing the second comparison after the 10 th time of the charge-discharge cycle is continued if the actual capacity retention percentage is greater than the reference value, and repeating the steps for 15 times and 2 times… … times 0, 25 times, until 50 times are completed.
The number of the interval times can be determined according to the number of the circulation times per day, the comparison time is kept in the same time period as much as possible, the regularity is also comparable, and the number of the circulation times of two days can be used as the interval comparison time.
The mode can reduce comparison times to reduce workload and ensure the reliability of detection.
The invention relates to a method for rapidly detecting the charge-discharge cycle life of a lithium battery, which comprises the steps of calculating a volume retention percentage reference value of the lithium battery after each charge-discharge cycle, recording and calculating the volume retention percentage of each charge-discharge cycle in the actual charge-discharge cycle process, and comparing the volume retention percentage of the lithium battery after each charge-discharge cycle with a corresponding volume retention percentage reference value to accurately compare whether the volume retention percentage of the lithium battery after each charge-discharge cycle is in the reference value range, so that the volume retention percentage after continuous selection or interval selection cycle is compared with the reference percentage, and whether the charge-discharge cycle life of the whole batch of lithium batteries is qualified can be determined in fewer charge-discharge cycle times such as 30-50 times without judging after waiting for 300-400 charge-discharge cycles to be completed like the prior art, the test time is greatly shortened, and the rapid detection of the charge-discharge cycle life of the lithium battery can be rapidly and efficiently completed.
Fig. 2 is a flow of acquiring a capacity retention percentage reference value of the lithium battery after each charge and discharge cycle in step S10 according to the embodiment of the present invention, which includes the following steps:
s11, obtaining the specification of the charge-discharge cycle life in the specification of the lithium battery, wherein the specification comprises: total number of charge and discharge cycles N of lithium batterynAfter that time, the capacity retention percentage is more than or equal to X percent.
The specification of the charge-discharge cycle life is as follows: n is a radical ofnWhen X% is equal to 80% and 300 cycles, the capacity retention percentage is equal to or greater than 80% of the initial capacity.
S12, averagely calculating the charge and discharge of each lithium batteryPercent capacity fade after cycling: (1-X%) +/Nn＝P1％。
With the above specifications, the percentage capacity fade after each charge-discharge cycle: (1-80%)/300 ≈ 0.067%.
S13, calculating the percentage of capacity fade after the 2 nd charge-discharge cycle: p1％×N2＝P2%, i.e. P2% is the percentage of capacity fade after 2 nd charge-discharge cycle, where N2＜Nn。
Taking N as the above calculation2Percentage of capacity fade after 2 nd charge-discharge cycle: 0.067% × 2 ═ 0.134%.
S14, calculating the capacity retention percentage reference value after the 2 nd charge-discharge cycle: 100% -P2％。
Continuing with the above calculation, the capacity retention percentage reference value after the 2 nd charge-discharge cycle is: 100% -0.134% ═ 99.866%. Then in the actual test, Nth2When the number of the cycles is 2, the percentage of the actual capacity retention is more than 99.866% and less than 99.866% is not qualified.
S15, other times capacity retention percentage reference and so on.
Taking N as the above calculation50Percentage of capacity fade after 50 th charge-discharge cycle: 0.067% × 50 ═ 3.35%.
Continuing with the above calculation, the capacity retention percentage reference value after the 50 th charge-discharge cycle is: 100% -3.35% ═ 96.65%. Then in the actual test, Nth50When the number of the cycles is 50, the percentage of actual capacity retention is more than 96.65% and less than 96.65% is passed and less than 96.65% is failed.
As a specific example, the detection process of the lithium battery charge-discharge cycle life detection method of the invention is as follows:
1. calculating the capacity fading percentage after each charge-discharge cycle according to the capacity retention percentage at the end of life given by the specification of the lithium battery;
the method specifically comprises the following steps: respectively calculating the capacity fading percentage of 5 times, 10 times, 15 times, 20 times, 25 times, 30 times, 35 times, 40 times, 45 times and 50 times, and respectively subtracting the capacity fading percentage from the initial capacity 100% to obtain the capacity retention percentage reference value after each charge-discharge cycle;
2. using 0.5C charge-discharge circulation for a capacity grading cabinet on a lithium battery to be detected for the charge-discharge circulation life, recording the actual capacity of the interval times of each charge-discharge circulation, and calculating the percentage of the actual capacity to the initial capacity to obtain the actual capacity retention percentage;
3. and comparing the percentage of the actual capacity and the initial capacity at every 5 charge-discharge cycle intervals with the capacity retention percentage reference value after the corresponding charge-discharge cycle times, if the percentage is smaller than the reference value, the percentage is unqualified, and if the percentage is larger than the reference value, the steps are continuously circulated until the preset cycle times are 50 times. That is, the values of the percentage of capacity retention after 5 th, 10 th, 15 th, 20 th, 25 th, 30 th, 35 th, 40 th, 45 th and 50 th cycles and the reference value of the percentage of capacity retention were compared in this order.
The method for rapidly detecting the charge-discharge cycle life of the lithium battery can rapidly judge whether the cycle life of the sample battery is qualified or not by calculating the reference value of the capacity retention percentage after each charge-discharge cycle of the lithium battery, then recording and calculating the actual capacity retention percentage of each charge-discharge cycle in the actual charge-discharge cycle process, and continuously or intermittently comparing the actual capacity percentage after a certain charge-discharge cycle, such as 50 th time, with the reference value of the corresponding capacity retention percentage, thereby deducing whether the charge-discharge cycle life of the whole batch of lithium batteries is qualified or not. The cycle life detection method can accurately compare whether the capacity retention percentage of the lithium battery is within the reference value percentage range after each charge-discharge cycle, so that whether the charge-discharge cycle life of the whole batch of lithium ion lithium batteries is qualified can be determined by fewer charge-discharge cycle times such as 30-50 times, and judgment is not needed after the charge-discharge cycle is finished by waiting for 400 charge-discharge cycles of 300 times, thus greatly shortening the test time and improving the working efficiency.
The lithium battery charging and discharging cycle life detection method can rapidly detect and evaluate the charging and discharging cycle life of the lithium battery, whether the service life of the lithium ion lithium battery meets the requirement can be obtained within about 10 days, a large amount of time and test cost are saved, the cycle life of each batch of incoming materials can be tested, a plurality of lithium ion lithium batteries in each batch of service life are provided, the durability of the outgoing lithium batteries is ensured, and the customer satisfaction degree is improved.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (9)
1. A lithium battery cycle life rapid detection method is characterized by comprising the following steps:
s10, acquiring a reference value: acquiring a capacity retention percentage reference value of a batch of lithium batteries to be detected after each charge-discharge cycle;
s20, sampling: randomly extracting 3PCS lithium batteries from the batch of lithium batteries;
s30, obtaining actual capacity retention percentage: carrying out charge and discharge cycles on the sampled lithium battery on a grading cabinet, recording the actual capacity value of the lithium battery after each charge and discharge cycle is completed, calculating the percentage of the actual capacity value and the initial capacity value of the lithium battery, and obtaining the actual capacity retention percentage of the lithium battery after the charge and discharge cycle;
s40, compare: comparing the actual capacity retention percentage of the lithium battery after N times of charge and discharge cycles with the capacity retention percentage reference value of the lithium battery after N times of charge and discharge cycles, judging that the charge and discharge cycle life of the batch of lithium batteries is unqualified when the actual capacity retention percentage is smaller than the reference value, continuing the charge and discharge cycles to obtain the actual capacity retention percentage when the actual capacity retention percentage is larger than the reference value, and comparing the actual capacity retention percentage with the capacity retention percentage reference value of the corresponding times until the cycle times reach the preset times;
the step S40 is carried out in a comparison mode after the completion of each charge-discharge cycle or after the completion of every charge-discharge cycle;
the method for acquiring the capacity retention percentage reference value of the lithium battery after each charge-discharge cycle comprises the following steps:
obtaining a charge-discharge cycle life specification in a specification for a lithium battery, the specification comprising: total number of charge and discharge cycles N of lithium batterynAfter the treatment, the capacity retention percentage is more than or equal to X%;
and (3) averagely calculating the capacity fading percentage after each charge-discharge cycle of the lithium battery: (1-X%) +/Nn＝P1％；
The percentage of capacity fade after the 2 nd charge-discharge cycle was calculated: p1％×N2＝P2%, i.e. P2% is the percentage of capacity fade after 2 nd charge-discharge cycle, where N2＜Nn；
Calculate the percentage capacity retention reference after the 2 nd charge-discharge cycle: 100% -P2％；
Other times the capacity holds the percentage reference and so on.
2. The method for rapidly detecting the cycle life of a lithium battery as claimed in claim 1, wherein the step S40 is performed in a manner that the comparison is performed after each charge-discharge cycle is completed, specifically:
and comparing the actual capacity retention percentage of the lithium battery after each charge-discharge cycle with the charge-discharge cycle capacity retention percentage reference value of the lithium battery, judging that the charge-discharge cycle life of the batch of lithium batteries is unqualified when the actual capacity retention percentage is smaller than the reference value, continuing the charge-discharge cycle to obtain the actual capacity retention percentage when the actual capacity retention percentage is larger than the reference value, and comparing the actual capacity retention percentage with the capacity retention percentage reference value of the corresponding times until the cycle times reach the preset times.
3. The method for rapidly detecting the cycle life of the lithium battery as claimed in claim 1, wherein the step S40 is performed after the completion of the interval charge-discharge cycles, specifically:
repeating the stepsStep S30, with an initial cycle N1Calculating the actual capacity retention percentage of the lithium battery after the charge-discharge cycle every 5 times at the beginning, and adding the lithium battery N5、N10、N15……NnComparing the actual capacity retention percentage after the secondary charge-discharge cycle with the reference value of the capacity retention percentage corresponding to the times of the lithium batteries, judging that the charge-discharge cycle life of the batch of lithium batteries is unqualified if the actual capacity retention percentage is smaller than the reference value, and continuing the step until the preset cycle times N are reached if the actual capacity retention percentage is larger than the reference valuenAnd then the process is finished.
4. The method for rapidly detecting the cycle life of the lithium battery as claimed in claim 1, wherein the randomly extracted lithium battery sample is qualified by initial inspection, and the initial inspection comprises: self-discharge, internal resistance and voltage detection.
5. The method for rapidly detecting the cycle life of the lithium battery as claimed in claim 1, wherein the performing of the charge-discharge cycle on the capacity-divided cabinet for the preset number of times comprises:
the charging and discharging current provided during the charging and discharging circulation on the grading cabinet is 0.5C, the maximum value of the charging and discharging current cannot exceed the maximum charging/discharging current of the grading cabinet, and when the 0.5C current of the lithium battery to be tested in the circulation is greater than the maximum charging/discharging current of the grading cabinet, the charging and discharging circulation is carried out at 0.2C or 2A.
6. The method for rapidly detecting the cycle life of the lithium battery as claimed in claim 1, wherein the performing of the charge-discharge cycle on the capacity-divided cabinet for the preset number of times further comprises:
the charge limiting voltage, the discharge cutoff voltage and the charge cutoff current provided during charge-discharge cycling on the grading cabinet all meet the requirement standards of the specification of the batch of lithium batteries.
7. The method for rapidly detecting the cycle life of the lithium battery as claimed in claim 1, wherein the voltage or current variation of the constant current source or the constant voltage source provided by the lithium battery is within ± 1% when the lithium battery is charged and discharged in the capacity-divided cabinet.
8. The method for rapidly detecting the cycle life of the lithium battery as claimed in claim 1, wherein the ambient temperature of the lithium battery during the detection of the charge-discharge cycle life is within 23 ℃ ± 2 ℃.
9. The method for rapidly detecting the cycle life of the lithium battery as claimed in claim 1, wherein when the cycle life of the lithium battery is unqualified, a label which is unqualified is marked on the lithium battery.
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| CN111896879B (en) * | 2020-07-31 | 2023-06-06 | 北京石墨烯研究院 | Rapid detection method for bending life of flexible lithium ion battery |
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