Charging and discharging test method for accurately monitoring cycle life of lithium ion battery

A lithium-ion battery, charging and discharging testing technology, applied in the direction of measuring electricity, measuring electrical variables, measuring devices, etc., can solve problems that affect the accuracy of battery performance testing, Li+ can't come out, battery life impact, etc., to achieve an intuitive and effective healthy state , Novel method, accurate judgment effect

Inactive Publication Date: 2020-03-17
HEFEI GUOXUAN HIGH TECH POWER ENERGY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Different test methods will also affect battery life
The study found that as the cycle progresses, the polarization of the battery cell continues to increase, the voltage of the negative electrode is getting lower and lower, the voltage of the positive electrode is getting higher and higher, and the available capacity of the cycle is getting lower and lower; the increase in the polarization of the battery cell leads to Some Li+ cannot be extracted, and the effective lithium gradually decreases, which greatly reduces the test results of the battery cycle life and affects the accuracy of the battery performance test.

Method used

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  • Charging and discharging test method for accurately monitoring cycle life of lithium ion battery
  • Charging and discharging test method for accurately monitoring cycle life of lithium ion battery
  • Charging and discharging test method for accurately monitoring cycle life of lithium ion battery

Examples

Experimental program
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Effect test

Embodiment 1

[0033] Select two square lithium iron phosphate batteries with better consistency, one of which carries out 1C / 1C cycle according to the conventional charge and discharge method, and the other cycle according to the charge and discharge method provided in the present invention; other conditions such as current, The cut-off voltage, rest time, test cabinet and external environment are all consistent. Loop results like figure 2 as shown, figure 2 The depolarization-related data in the process has been omitted, and only the normal cycle data are selected for comparison. It can be seen that the predicted life according to the product of the Coulomb efficiency value per cycle is about 1000 weeks, while the measured life is 2000 weeks, and the predicted life only accounts for 50% of the measured life, indicating that cyclic polarization causes more lithium deposition on the negative electrode, and the cycle is effective Lithium becomes less, and more lithium is extracted from th...

Embodiment 2

[0035] Select two VDA ternary 622 batteries with better consistency, one of which carries out 1C / 1C cycle according to the conventional charge and discharge method, and the other cycle according to the charge and discharge method provided in the present invention; other conditions such as current, cut-off The voltage, resting time, test cabinet and external environment are all consistent. Loop results like image 3 as shown, image 3The depolarization-related data in the process has been omitted, and only the normal cycle data are selected for comparison. It can be seen that the predicted life according to the product of the Coulomb efficiency value per cycle is about 500 weeks, while the measured life is 930 weeks, and the predicted life only accounts for about 54% of the measured life, indicating that cyclic polarization still leads to more lithium deposition on the negative electrode , so that the circulating effective lithium becomes less, and more lithium needs to be ex...

Embodiment 3

[0037] Choose two soft-pack ternary Ni85 batteries with good consistency, wherein one carries out 1C / 1C cycle according to the conventional charge and discharge method, and the other cycle according to the charge and discharge method provided in the present invention; other conditions such as current, The cut-off voltage, rest time, test cabinet and external environment are all consistent. Loop results like Figure 4 as shown, Figure 4 In , the depolarization-related data in the process have been omitted, and only the normal cycle data are selected for comparison. It can be seen that the predicted life according to the product of the Coulomb efficiency value per circle is about 450 weeks, while the measured life is 900 weeks, and the predicted life only accounts for about 50% of the measured life, indicating that cyclic polarization still leads to more lithium deposition on the negative electrode , so that the circulating effective lithium becomes less, and more lithium nee...

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Abstract

The invention provides a charging and discharging test method for accurately monitoring the cycle life of a lithium ion battery. The method comprises steps that S1, the initial capacity C0 and direct-current internal resistance DCR0 of a battery core are acquired; S2, periodic charging and discharging of a battery are performed, each charging and discharging period includes a times of cyclic charging and discharging, during the first (a-1) times of charging and discharging, 1C/1C cyclic charging and discharging is performed; during the ath charging and discharging, after charging at 1C, discharging at 1C is performed to a cut-off voltage, then standing for a first time is performed, and then discharging at 0.1 C is performed to the cut-off voltage; standing for a first time is performed, and discharging to a cut-off voltage at 0.01 C is performed; S3, the current capacity Cn and the direct-current internal resistance DCRn of the battery core after k charging and discharging periods areperformed, and a is not smaller than 10k; and S4, whether the cycle life of the battery core is ended or not is determined according to the current capacity Cn and the direct-current internal resistance DCRn; if yes, the cycle life of the battery is recorded; and otherwise, the process returns to the S2. The method is advantaged in that the method can uniformly eliminate polarization accumulatedin the cycle, so more effective lithium is removed from a negative electrode to ensure the cycle, and the test result of the cycle life of the lithium ion battery is improved by more than 30%.

Description

technical field [0001] The invention relates to the technical field of lithium battery production, in particular to a charging and discharging test method for accurately monitoring the cycle life of a lithium ion battery. Background technique [0002] Due to the advantages of high reversibility, long cycle life, high energy density, no memory effect, and environmental friendliness, lithium-ion batteries have been widely used in various digital electronic devices, and also have broad applications in the fields of electric vehicles and energy storage power stations. application prospects. As an important part of new energy vehicles, the performance of the battery largely determines the overall performance of the vehicle. At the same time, the long cycle life of lithium-ion batteries is an important part of its comprehensive performance evaluation, which is related to important issues such as battery cell matching and cost. At the same time, there are many factors that affect...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R31/392G01R31/378
CPCG01R31/378G01R31/392
Inventor 段锐
Owner HEFEI GUOXUAN HIGH TECH POWER ENERGY
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