CN114243132B - Method for testing aging time of lithium ion battery - Google Patents

Method for testing aging time of lithium ion battery Download PDF

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CN114243132B
CN114243132B CN202111290897.2A CN202111290897A CN114243132B CN 114243132 B CN114243132 B CN 114243132B CN 202111290897 A CN202111290897 A CN 202111290897A CN 114243132 B CN114243132 B CN 114243132B
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battery
aging time
test
impedance
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CN114243132A (en
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郭密
陈述林
万里鹏
王珍珍
徐鲲
曾素琼
兰水静
李姝�
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Dongguan Zhenhua New Energy Technology Co ltd
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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
    • H01M10/44—Methods for charging or discharging
    • H01M10/446—Initial charging measures
    • 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
    • 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
    • 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

Abstract

The invention relates to the technical field of lithium ion battery materials, and discloses a method for testing the aging time of a lithium ion battery. The invention provides a method for testing the aging time of a lithium ion battery, which determines the optimal temperature and time relation of battery core aging by designing the battery core aging temperature, greatly shortens the battery production period, quickly determines the optimal aging temperature and the aging time of the battery core of a certain material, creates the optimal economic benefit for battery manufacturers, introduces an alternating current impedance test timing sampling process, and increases the first charge-discharge efficiency test to determine the influence of the aging temperature on the battery performance, so as to conveniently determine the optimal aging temperature on the premise of keeping the battery quality and realize the shortest battery production period.

Description

Method for testing aging time of lithium ion battery
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a method for testing the aging time of a lithium ion battery.
Background
Since the commercial production of the lithium ion battery in the 90 s of the 20 th century, the lithium ion battery has the advantages of higher energy density, no pollution, no memory effect, long cycle life and the like, is an ideal power supply for portable electronic products such as mobile phones, notebook computers, cameras and the like, and is also a power source for future electric tools (military power supply equipment), so a series of researches on the lithium ion battery have become hot spots of researches in the battery world in recent years.
The aging is a key process in the manufacturing process of the lithium ion battery, and the necessity of aging lies in that the electrolyte is made to fully soak the pole piece # so that the electrolyte required by lithium ion migration is filled between particles of the anode and cathode materials. The selection of the aging condition determines the infiltration degree of the electrolyte, and further determines the first efficiency, constant current time ratio and the like of charge and discharge of the electrolyte. Therefore, the research on the aging condition of the lithium ion battery is crucial to the optimization of the production process of the lithium ion battery and the improvement of the electrochemical performance of the lithium ion battery.
In the prior art, many lithium ion battery companies employ the following two test methods: after aging, disassembling the battery, and observing whether the internal pole piece is completely soaked; and (4) pre-charging and supplementing electricity, and observing the first efficiency of charge and discharge and the retention rate of discharge capacity after circulation. Both methods can only roughly judge whether the battery is well aged or not, can not quantify and are long in time.
At present, a method for standing and aging a battery cell, testing the alternating current impedance value of the battery cell in different standing time periods, and determining the aging time through the stabilization time of the alternating current impedance value is also developed, but the aging time in actual production is greatly influenced by the aging temperature, and the production cycle of the lithium ion battery can be greatly improved by adjusting the aging time. In addition, the aging time is determined only by the stabilization time of the alternating current impedance, so that the quality control of a battery product cannot be strictly controlled, and the aging effect of the battery can be more accurately judged by combining with parameters such as the first charge-discharge efficiency or the initial capacity of the lithium ion battery.
Disclosure of Invention
The invention aims to provide a method for testing the aging time of a lithium ion battery, which tests the aging time of a battery cell by setting a constant temperature test, determines the influence of different temperatures on the aging time of the battery cell by changing the set temperature, determines the optimal aging temperature, and determines the aging time by combining alternating current impedance and first charge-discharge efficiency.
The method is realized by extracting a plurality of battery cores which are subjected to a liquid injection sealing procedure in one batch for aging time test, wherein the aging time test comprises an alternating current impedance stability test and a first charge-discharge efficiency test, and comprises the following specific steps of:
s1: taking a plurality of battery cells which are just injected with liquid and sealed, pre-charging the battery cells for a certain capacity at a current of 0.05C, activating the battery cells in the process, and partially decomposing electrolyte on the surface of an electrode to form an SEI film;
s2: placing the pre-charged battery cores in a constant-temperature test chamber, setting the room temperature of the constant-temperature test chamber as a target value, wherein the temperature has obvious influence on the diffusion and infiltration of the electrolyte, the step is used for determining the optimal aging temperature, and connecting all the battery cores with an alternating current impedance tester;
s3: setting AC impedance test parameters and spectrum acquisition interval time, and realizing the timing spectrum acquisition of AC impedance by software setting to avoid repeated setting and starting processes;
s4: carrying out curve fitting on the alternating current impedance spectrogram by using software, and calculating the slope of a diffusion region, wherein the diffusion region of the alternating current impedance spectrogram is not a regular straight line and needs to be fitted;
s5: taking the aged cell, carrying out constant current charge-discharge test on the cell by using a current of 0.1C, and calculating the first charge-discharge efficiency;
s6: and (3) data is collated, the alternating current impedance test result is drawn into a relation graph of impedance slope and aging time, and the first charge-discharge efficiency test result is drawn into a relation graph of first charge-discharge efficiency and aging time.
Further, the first charge-discharge efficiency test is performed after the alternating-current impedance stability test, the alternating-current impedance test does not affect the charge-discharge test, and the cell impedance values before and after the charge-discharge test are different, so that the test sequence must be determined.
Further, in S1, the precharging step is performed using a Land 2001C type charge and discharge tester.
Further, in S1, the certain capacity is 2% to 10% of the designed capacity of the battery cell, and the capacity portion of the battery cell in the pre-charging process is the capacity of the electrolyte to decompose and form an SEI film, which is a non-reversible capacity.
Further, in S2, the temperature of the constant-temperature test chamber is set to be 25-40 ℃, and the aging process is not favorable when the aging temperature is too high or too low.
Further, in S3, the specific parameters of the ac impedance test are that the frequency range is 10Hz to 100kHz, and the time interval of sampling the spectrum is 6 hours.
Further, in S2-S3, the ac impedance test is completed using a shanghai chen electrochemical workstation, model CHI 1000C.
Further, in S4, the fitting of the ac impedance spectrogram is performed by Z-view software.
Further, in S5, the constant current charge and discharge step is performed using a Land 2001C type charge and discharge tester.
Further, in S1 and S5, the 0.05C current magnitude is a current value at which the cell is charged to 100% of the design capacity in 20 hours, and the 0.1C current magnitude is a current value at which the cell is charged to 100% of the design capacity in 10 hours.
Mechanism of testing
The process of infiltrating the battery core with the electrolyte is actually a process of naturally diffusing the electrolyte in the battery core, the temperature is high, the viscosity of the electrolyte is reduced, the fluidity is increased, the infiltration process is accelerated, the aging time is shortened, and the period of battery preparation is greatly shortened; however, too high temperature causes decomposition of the electrolyte, increases the internal resistance of the battery, and deteriorates the overall performance of the battery.
In addition, the aging time is shortened by adjusting the aging temperature, so that the production efficiency of the battery can be greatly improved, but the problem of electrolyte decomposition caused by high temperature cannot be judged by the alternating current impedance of the battery core, so that the battery core needs to be subjected to constant current charge-discharge test, whether the battery core aging is finished or not is judged by the first charge-discharge efficiency, whether the aging temperature affects the performance of the battery or not is judged, the polarization of the battery is in a linear relation with the internal temperature of the battery (the lower the temperature is, the larger the polarization is, the lower the charge capacity is, and when the temperature is too high, the electrolyte lithium salt starts to decompose, so that less lithium ions can be utilized and the first charge capacity is also lower.
Compared with the prior art, the method for testing the aging time of the lithium ion battery provided by the invention has the following beneficial effects:
1. the invention provides a test method for the aging time of a lithium ion battery, which determines the relationship between the optimal temperature and the time for aging the battery core by designing the aging temperature of the battery core, greatly shortens the production period of the battery, and can quickly determine the optimal aging temperature and the aging time of the battery core of a certain material by designing the aging temperature of the battery core, wherein different battery materials are influenced by the size and the physical and chemical properties of the battery core material, the wettability of electrolyte on the battery materials is different, and the aging temperature endured by the battery core is also different.
2. Furthermore, the test method introduces an alternating current impedance test timing spectrum collection process, can avoid inconvenience caused by repeated parameter setting in the process of collecting the spectrum for multiple times, and in addition, the influence of the aging temperature on the battery performance is determined by adding the first charge-discharge efficiency test so as to conveniently determine the optimal aging temperature on the premise of keeping the battery quality and realize the shortest production period of the battery.
Drawings
FIG. 1 is a graph showing temperature control fluctuation in a constant temperature test at an aging temperature of 25 ℃ according to the present invention;
FIG. 2 is a graph showing the variation of the slope of the AC impedance with aging time at an aging temperature of 25 ℃ according to the present invention;
FIG. 3 is a graph showing the first charge-discharge efficiency as a function of aging time at an aging temperature of 25 ℃ according to the present invention;
FIG. 4 is a graph showing temperature control fluctuation in a constant temperature test at an aging temperature of 30 ℃ according to the present invention;
FIG. 5 is a graph of the slope of the AC impedance as a function of aging time at an aging temperature of 30 ℃ in accordance with the present invention;
FIG. 6 is a graph showing the first charge-discharge efficiency of the present invention as a function of aging time at an aging temperature of 30 ℃;
FIG. 7 is a graph showing temperature control fluctuation in a constant temperature test at an aging temperature of 35 ℃ according to the present invention;
FIG. 8 is a graph of the slope of the AC impedance as a function of aging time at an aging temperature of 35 ℃ in accordance with the present invention;
FIG. 9 is a graph showing the first charge-discharge efficiency as a function of aging time at an aging temperature of 35 ℃ in accordance with the present invention;
FIG. 10 is a temperature control fluctuation curve diagram of a constant temperature test at an aging temperature of 40 ℃ according to the present invention;
FIG. 11 is a graph of the slope of the AC impedance as a function of aging time at an aging temperature of 40 ℃ in accordance with the present invention;
FIG. 12 is a graph showing the first charge-discharge efficiency according to the aging time at an aging temperature of 40 ℃ according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
The following describes the implementation of the present invention in detail with reference to specific embodiments.
The same or similar reference numerals in the drawings of the present embodiment correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", etc., based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of the description, but it is not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed in a specific orientation and operate, and therefore the terms describing the positional relationship in the drawings are only used for illustrative purposes and are not to be construed as limiting the present patent, and it is possible for one of ordinary skill in the art to understand the specific meaning of the above terms according to the specific situation.
Example 1
Referring to fig. 1-3, a method for testing aging time of a lithium ion battery, which extracts 5 cells with the number of 1 from a batch to a liquid injection sealing process # -5 # And carrying out aging time test, wherein the aging time test comprises alternating current impedance stability test and first charge-discharge efficiency test, and comprises the following specific steps:
s1: taking a plurality of battery cores which are just injected with liquid and sealed, pre-charging the battery cores for a certain capacity at a current of 0.05C, activating the battery cores in the process, and partially decomposing electrolyte on the surface of an electrode to form an SEI film;
s2: placing the pre-charged battery cores in a constant-temperature test chamber, setting the room temperature of the constant-temperature test chamber as a target value, wherein the temperature has obvious influence on the diffusion and infiltration of the electrolyte, the step is used for determining the optimal aging temperature, and connecting all the battery cores with an alternating-current impedance tester;
s3: setting AC impedance test parameters and spectrum acquisition interval time, and realizing the timing spectrum acquisition of AC impedance by software setting to avoid repeated setting and starting processes;
s4: carrying out curve fitting on the alternating current impedance spectrogram by using software, and calculating the slope of a diffusion region, wherein the diffusion region of the alternating current impedance spectrogram is not a regular straight line and needs to be fitted;
s5: taking the aged battery cell, carrying out constant current charge-discharge test on the battery cell by using a current of 0.1C, and calculating the first charge-discharge efficiency;
s6: and (3) data is collated, the alternating current impedance test result is drawn into a relation graph of impedance slope and aging time, and the first charge-discharge efficiency test result is drawn into a relation graph of first charge-discharge efficiency and aging time.
In this embodiment, the first charge and discharge efficiency test is performed after the ac impedance stabilization test, the ac impedance test does not affect the charge and discharge test, and the cell impedance values before and after the charge and discharge test are different, so that the test sequence must be defined.
In this embodiment, in S1, the pre-charging step is performed by using a Land 2001C type charge/discharge tester, where a certain capacity is 2% of the designed capacity of the cell, and the capacity of the cell pre-charging process is partially the capacity of the electrolyte to decompose and form an SEI film, i.e., the irreversible capacity.
In the present embodiment, in S2, the temperature of the constant temperature test chamber is set to 25 ℃.
In this embodiment, in S3, the specific parameters of the ac impedance test are that the frequency range is 10Hz to 100kHz, and the time interval of sampling the spectrum is 6 hours.
In this example, the ac impedance test was performed using a shanghai shichen CHI 1000C electrochemical workstation in S2-S3.
In this embodiment, in S4, the fitting of the ac impedance spectrogram is performed by Z-view software.
In this example, in S5, the constant current charge and discharge step was performed using a Land 2001C type charge and discharge tester.
In this embodiment, in S1 and S5, the 0.05C current level is a current value at which the cell is charged to 100% of the design capacity in 20 hours, and the 0.1C current level is a current value at which the cell is charged to 100% of the design capacity in 10 hours.
Example 2
Referring to fig. 4-6, a method for testing aging time of a lithium ion battery extracts 5 cells with serial number of 1 from a batch to a liquid injection sealing process # -5 # And carrying out aging time test, wherein the aging time test comprises alternating current impedance stability test and first charge-discharge efficiency test, and the aging time test comprises the following specific steps:
s1: taking a plurality of battery cores which are just injected with liquid and sealed, pre-charging the battery cores for a certain capacity at a current of 0.05C, activating the battery cores in the process, and partially decomposing electrolyte on the surface of an electrode to form an SEI film;
s2: placing the pre-charged battery cores in a constant-temperature test chamber, setting the room temperature of the constant-temperature test chamber as a target value, wherein the temperature has obvious influence on the diffusion and infiltration of the electrolyte, the step is used for determining the optimal aging temperature, and connecting all the battery cores with an alternating-current impedance tester;
s3: setting alternating current impedance testing parameters and spectrum collection interval time, and realizing the timing spectrum collection of the alternating current impedance through software setting to avoid repeatedly setting a starting process;
s4: carrying out curve fitting on the alternating current impedance spectrogram by using software, and calculating the slope of a diffusion region, wherein the diffusion region of the alternating current impedance spectrogram is not a regular straight line and needs to be fitted;
s5: taking the aged battery cell, carrying out constant current charge-discharge test on the battery cell by using a current of 0.1C, and calculating the first charge-discharge efficiency;
s6: and (3) data is collated, the alternating current impedance test result is drawn into a relation graph of impedance slope and aging time, and the first charge-discharge efficiency test result is drawn into a relation graph of first charge-discharge efficiency and aging time.
In this embodiment, the first charge-discharge efficiency test is performed after the ac impedance stabilization test, the ac impedance test does not affect the charge-discharge test, and the cell impedance values before and after the charge-discharge test are different, and the test sequence must be determined.
In this embodiment, in S1, the pre-charging step is performed by using a Land 2001C type charge/discharge tester, and the predetermined capacity is 2% of the designed capacity of the cell, and the part of the capacity of the cell pre-charging process is the capacity of the electrolyte solution to decompose and form an SEI film, i.e., the irreversible capacity.
In the present embodiment, in S2, the temperature of the constant temperature test chamber is set to 30 ℃.
In this embodiment, in S3, the specific parameters of the ac impedance test are that the frequency range is 10Hz to 100kHz, and the sampling interval is 6 hours.
In this example, the ac impedance test was performed using a shanghai shichen CHI 1000C electrochemical workstation in S2-S3.
In this embodiment, in S4, the fitting of the ac impedance spectrogram is performed by Z-view software.
In this example, in S5, the constant current charge and discharge step was performed using a Land 2001C type charge and discharge tester.
In this embodiment, in S1 and S5, the 0.05C current level is a current value at which the cell is charged to 100% of the design capacity in 20 hours, and the 0.1C current level is a current value at which the cell is charged to 100% of the design capacity in 10 hours.
Example 3
Referring to fig. 7-9, a method for testing aging time of a lithium ion battery, which is to extract 5 cells with the number of 1 from a batch to a liquid injection sealing process # -5 # And carrying out aging time test, wherein the aging time test comprises alternating current impedance stability test and first charge-discharge efficiency test, and the aging time test comprises the following specific steps:
s1: taking a plurality of battery cores which are just injected with liquid and sealed, pre-charging the battery cores for a certain capacity at a current of 0.05C, activating the battery cores in the process, and partially decomposing electrolyte on the surface of an electrode to form an SEI film;
s2: placing the pre-charged battery cores in a constant-temperature test chamber, setting the room temperature of the constant-temperature test chamber as a target value, wherein the temperature has obvious influence on the diffusion and infiltration of the electrolyte, the step is used for determining the optimal aging temperature, and connecting all the battery cores with an alternating-current impedance tester;
s3: setting AC impedance test parameters and spectrum acquisition interval time, and realizing the timing spectrum acquisition of AC impedance by software setting to avoid repeated setting and starting processes;
s4: carrying out curve fitting on the alternating current impedance spectrogram by using software, and calculating the slope of a diffusion region, wherein the diffusion region of the alternating current impedance spectrogram is not a regular straight line and needs to be fitted;
s5: taking the aged cell, carrying out constant current charge-discharge test on the cell by using a current of 0.1C, and calculating the first charge-discharge efficiency;
s6: and (3) data is collated, the alternating current impedance test result is drawn into a relation graph of impedance slope and aging time, and the first charge-discharge efficiency test result is drawn into a relation graph of first charge-discharge efficiency and aging time.
In this embodiment, the first charge and discharge efficiency test is performed after the ac impedance stabilization test, the ac impedance test does not affect the charge and discharge test, and the cell impedance values before and after the charge and discharge test are different, so that the test sequence must be defined.
In this embodiment, in S1, the pre-charging step is performed by using a Land 2001C type charge/discharge tester, where a certain capacity is 2% of the designed capacity of the cell, and the capacity of the cell pre-charging process is partially the capacity of the electrolyte to decompose and form an SEI film, i.e., the irreversible capacity.
In the present embodiment, in S2, the temperature of the constant temperature test chamber is set to 35 ℃.
In this embodiment, in S3, the specific parameters of the ac impedance test are that the frequency range is 10Hz to 100kHz, and the sampling interval is 6 hours.
In this example, the ac impedance test was performed using a shanghai chen CHI 1000C type electrochemical workstation in S2-S3.
In this embodiment, in S4, the fitting of the ac impedance spectrogram is performed by Z-view software.
In this example, in S5, the constant current charge and discharge step was performed using a Land 2001C type charge and discharge tester.
In the present embodiment, in S1 and S5, the 0.05C current level is a current value at which the cell is charged to 100% of the design capacity in 20 hours, and the 0.1C current level is a current value at which the cell is charged to 100% of the design capacity in 10 hours.
Example 4
Referring to fig. 11-12, a method for testing aging time of a lithium ion battery, which extracts 5 cells, numbered 1, from a batch to a liquid injection sealing process # -5 # And carrying out aging time test, wherein the aging time test comprises alternating current impedance stability test and first charge-discharge efficiency test, and the aging time test comprises the following specific steps:
s1: taking a plurality of battery cores which are just injected with liquid and sealed, pre-charging the battery cores for a certain capacity at a current of 0.05C, activating the battery cores in the process, and partially decomposing electrolyte on the surface of an electrode to form an SEI film;
s2: placing the pre-charged battery cores in a constant-temperature test chamber, setting the room temperature of the constant-temperature test chamber as a target value, wherein the temperature has obvious influence on the diffusion and infiltration of the electrolyte, the step is used for determining the optimal aging temperature, and connecting all the battery cores with an alternating-current impedance tester;
s3: setting alternating current impedance testing parameters and spectrum collection interval time, and realizing the timing spectrum collection of the alternating current impedance through software setting to avoid repeatedly setting a starting process;
s4: carrying out curve fitting on the alternating current impedance spectrogram by using software, and calculating the slope of a diffusion region, wherein the diffusion region of the alternating current impedance spectrogram is not a regular straight line and needs to be fitted;
s5: taking the aged cell, carrying out constant current charge-discharge test on the cell by using a current of 0.1C, and calculating the first charge-discharge efficiency;
s6: and (3) data is collated, the alternating current impedance test result is drawn into a relation graph of impedance slope and aging time, and the first charge-discharge efficiency test result is drawn into a relation graph of first charge-discharge efficiency and aging time.
In this embodiment, the first charge-discharge efficiency test is performed after the ac impedance stabilization test, the ac impedance test does not affect the charge-discharge test, and the cell impedance values before and after the charge-discharge test are different, and the test sequence must be determined.
In this embodiment, in S1, the pre-charging step is performed by using a Land 2001C type charge/discharge tester, where a certain capacity is 2% of the designed capacity of the cell, and the capacity of the cell pre-charging process is partially the capacity of the electrolyte to decompose and form an SEI film, i.e., the irreversible capacity.
In the present embodiment, in S2, the temperature of the thermostatic test chamber is set to 40 ℃.
In this embodiment, in S3, the specific parameters of the ac impedance test are that the frequency range is 10Hz to 100kHz, and the sampling interval is 6 hours.
In this example, the ac impedance test was performed using a shanghai shichen CHI 1000C electrochemical workstation in S2-S3.
In this embodiment, in S4, the fitting of the ac impedance spectrogram is performed by Z-view software.
In this example, in S5, the constant current charge and discharge step was performed using a Land 2001C type charge and discharge tester.
In the present embodiment, in S1 and S5, the 0.05C current level is a current value at which the cell is charged to 100% of the design capacity in 20 hours, and the 0.1C current level is a current value at which the cell is charged to 100% of the design capacity in 10 hours.
Test examples
By comparing the AC impedance slope values at different aging temperatures and aging times, table 1 is obtained
TABLE 1
Figure BDA0003334733060000111
The AC impedance slope values in the table are the average of the measured values of the samples
By comparing the first charge-discharge efficiency at different aging temperatures and aging times, table 2 is obtained
TABLE 2
Figure BDA0003334733060000112
Figure BDA0003334733060000121
The results of the comparative examples show that the internal resistance of the battery is influenced to a certain extent when the temperature is too high or too low, the internal energy of liquid molecules is in direct relation with the internal temperature of the liquid, the higher the temperature is, the better the fluidity is, and on the contrary, the poorer the fluidity is, the poorer the effect of soaking the electrolyte is, and the internal resistance is higher; the first charge-discharge efficiency can reflect the quality of a formed film and can also reflect the proportion of lithium ions which can be reversibly charged and discharged, when the quality of the formed film is poor, the first charge-discharge efficiency is slightly high, the first charge-discharge efficiency basically keeps unchanged along with the rise of temperature, the deviation of a system is not large, the first efficiency is reduced, mainly caused by low first discharge capacity, the temperature of the aged battery is kept in the battery within a short time, the polarization of the battery is in a linear relation with the internal temperature, the lower temperature is, the higher polarization is, the lower charge capacity is, the electrolyte lithium salt starts to decompose when the temperature is too high, the available lithium ions are few, and the first charge capacity is also low.
In combination with the results of the examples, the aging temperature was 35 ℃ and the aging time was selected to be 24 hours, which is suitable, in order to optimize the process conditions and shorten the process time, refer to fig. 1 to 12, and example 3 is a preferred embodiment of the present invention.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (10)

1. A method for testing the aging time of a lithium ion battery is characterized in that a plurality of battery cores which are subjected to a liquid injection sealing procedure in one batch are extracted for aging time testing, the aging time testing comprises an alternating current impedance stability testing and a first charge-discharge efficiency testing, and the method comprises the following specific steps:
s1: taking a plurality of battery cores which are just injected with liquid and sealed, and pre-charging the battery cores for a certain capacity at the current of 0.05C;
s2: placing the pre-charged battery cores in a constant-temperature test chamber, setting the room temperature of the constant-temperature test chamber to different target values, and connecting all the battery cores with an alternating-current impedance tester;
s3: setting AC impedance test parameters and spectrum acquisition interval time;
s4: carrying out curve fitting on the alternating current impedance spectrogram by using software, and calculating the slope of the diffusion region;
s5: taking the aged battery cell, carrying out constant current charge-discharge test on the battery cell by using a current of 0.1C, and calculating the first charge-discharge efficiency;
s6: and (3) data is collated, alternating current impedance test results at different temperatures are drawn into a relation graph of impedance slope and aging time, first charge and discharge efficiency test results at different temperatures are drawn into a relation graph of first charge and discharge efficiency and aging time, and the optimal aging temperature and the optimal aging time are determined by analyzing the relation graphs in a combined manner.
2. The method for testing aging time of lithium ion batteries according to claim 1, wherein the first charge-discharge efficiency test is performed after the ac impedance stabilization test.
3. The method for testing aging time of lithium ion battery as claimed in claim 2, wherein in S1, the pre-charging step is performed by using a Land 2001C type charge and discharge tester.
4. The method for testing aging time of lithium ion batteries according to claim 3, wherein in S1, the certain capacity is 2% to 10% of the design capacity of the battery cell.
5. The method for testing aging time of a lithium ion battery according to claim 4, wherein in S2, the temperature of the constant temperature test chamber is set to 25 ℃ to 40 ℃.
6. The method for testing the aging time of the lithium ion battery as claimed in claim 5, wherein in S3, the specific parameters of the AC impedance test are that the frequency range is 10 Hz-100 kHz, and the time interval of sampling spectrum is 6 hours.
7. The method for testing aging time of lithium ion battery as claimed in claim 6, wherein in S2-S3, the AC impedance test is performed by using electrochemical workstation of Shanghai Chen-nationality CHI 1000C type.
8. The method for testing aging time of lithium ion battery according to claim 7, wherein in S4, the fitting of the AC impedance spectrum is performed by Z-view software.
9. The method for testing aging time of lithium ion battery of claim 8, wherein in S5, the step of constant current charging and discharging is performed by a Land 2001C type charging and discharging tester.
10. The method for testing aging time of a lithium ion battery as claimed in claim 9, wherein in S1 and S5, the 0.05C current is a current value at which the cell is charged to 100% of the design capacity in 20 hours, and the 0.1C current is a current value at which the cell is charged to 100% of the design capacity in 10 hours.
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