CN111257782A - Lithium ion battery cycle life evaluation and prediction method - Google Patents
Lithium ion battery cycle life evaluation and prediction method Download PDFInfo
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- CN111257782A CN111257782A CN202010232568.1A CN202010232568A CN111257782A CN 111257782 A CN111257782 A CN 111257782A CN 202010232568 A CN202010232568 A CN 202010232568A CN 111257782 A CN111257782 A CN 111257782A
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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
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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]
- G01R31/382—Arrangements for monitoring battery or accumulator variables, e.g. SoC
- G01R31/3835—Arrangements for monitoring battery or accumulator variables, e.g. SoC involving only 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]
- G01R31/389—Measuring internal impedance, internal conductance or related variables
Abstract
The invention discloses an evaluation and prediction method for the cycle life of a lithium ion battery, which comprises the following steps: the method comprises the following steps: (1) according to the operation reliability theory, calculating the cycle number of the battery cycle life reaching the discharge end point; (2) measuring the limitation of the charge-discharge cycle state of the battery in a temperature environment based on the limitation indexes of the discharge capacity variance and the discharge capacity entropy; (3) in the aspect of battery charging and discharging test sequencing, a classification sequencing mode is adopted: in order to balance the requirements of calculation time and calculation precision, only batteries related to normal and abnormal batteries which reach a cyclic discharge end point in advance are searched for the cycle times of charge-discharge cycle cutoff of the batteries, the cycle times are sequenced, then the batteries with less cycle times are rapidly sequenced by using comprehensive restrictive indexes obtained by weighting of discharge capacity restrictive indexes, the cycle times characteristic extraction of the batteries is realized, the accurate evaluation and prediction of the cycle life is realized, and the test requirements of the cycle life of different batteries are met.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to an evaluation and prediction method for the cycle life of a lithium ion battery.
Background
Lithium ion batteries are widely used in mobile digital products, and recently, lithium ion batteries are also used as energy storage systems in electric vehicles. The service life is an important index for measuring the performance of the battery, the service life testing method widely used in the research, development, inspection and model selection processes of the lithium ion battery at present is to carry out cycle testing under a certain working condition, and the standard for testing the cycle life of the lithium ion battery at present generally refers to the regulations in two existing standards in China: according to the general specifications of the lithium ion storage battery for the QC/T743-2006 electric automobile and the QB/T2502-2000 lithium ion storage battery, a large amount of time is consumed in the test process.
In view of the above, chinese patent CN106124997A discloses a method for testing the high temperature life of a lithium iron phosphate battery, which comprises the steps of fully charging a finished lithium iron phosphate battery at a predetermined temperature with a small current, floating the battery at a predetermined temperature for a predetermined time after the battery is fully charged, discharging the battery at the predetermined temperature after the floating the battery is fully charged, and performing 1 cycle of the above steps, and after a plurality of cycles, obtaining 3 times of capacity at the predetermined temperature, comparing the capacity with 75% of the nominal capacity to determine whether the battery is qualified.
However, the method is only suitable for the lithium iron phosphate battery, the testing process is formed based on a statistical mode, and certain limits exist in testing accuracy and time consumption.
Disclosure of Invention
The invention provides a method for evaluating and predicting the cycle life of a lithium ion battery, which is used for quickly and accurately evaluating and predicting the cycle life of the battery by measuring the discharge capacity of the battery in a temperature environment by combining the open-circuit voltage and the internal resistance of the battery.
The invention can be realized by the following technical scheme:
the invention discloses an evaluation and prediction method for the cycle life of a lithium ion battery, which comprises the following steps:
(1) according to an operation reliability theory, considering the temperature environment of the battery, the open-circuit voltage and the internal resistance of the battery, and adopting an imputation degree statistical factor and a battery life reliability model for charging and discharging, thereby calculating the cycle number of the battery cycle life reaching the discharging end point;
(2) measuring the limitation of the charge-discharge cycle state of the battery in a temperature environment based on the limitation indexes of the discharge capacity variance and the discharge capacity entropy;
(3) in the aspect of battery charging and discharging test sequencing, a classification sequencing mode is adopted: in order to balance the requirements of calculation time and calculation precision, only batteries related to normal and abnormal batteries which reach the cyclic discharge end point in advance are searched for the cycle times of the charge-discharge cycle end of the batteries, the cycle times are sequenced, and then for the batteries with less cycle times, comprehensive restrictive indexes obtained by weighting the discharge capacity and the internal resistance restrictive indexes are used for rapid sequencing, so that the cycle time characteristic extraction of the batteries is realized.
Further, in the step (1), after comprehensively considering the temperature environment, the open-circuit voltage and the internal resistance of the battery, the reliability model of the battery is shown as follows:
further, in the step (2), the restrictive indexes include a battery charge-discharge cycle restrictive index based on the discharge capacity variance and a battery charge-discharge cycle restrictive index based on the discharge capacity entropy.
Further, in the battery charge-discharge cycle restrictive index based on the discharge capacity variance, the charge-discharge capacity variance of the battery charged and discharged normally under the temperature environment can be expressed as:
wherein n and ηi0The discharge capacity in the temperature environment and the discharge capacity of the battery at the ith time during normal charge and discharge are respectively,
after the battery reaches the cycle discharge end point k times, the discharge capacity variance of the temperature environment
Can be expressed as:
in the formula, ηk,iThe discharge capacity of the battery for i times after the battery reaches the cycle discharge end point for k times,
in summary, the limiting index of battery k with respect to the variance of charge/discharge capacity is defined as follows:
furthermore, in the battery charge-discharge cycle restrictive index based on the discharge capacity entropy, the discharge capacity entropy H of the battery in normal operation in a temperature environment is defined0As shown in the following formula:
in the formula, ηi0(or η)j0) The discharge capacity in the temperature environment and the discharge capacity of the battery at the i (or j) th time during normal charge and discharge are respectively,
after the battery reaches the cycle discharge end point k times, the entropy H of the discharge capacity of the battery in the temperature environmentkThe definition is shown as the following formula:
in the formula, ηk,i(or η)k,j) The discharge capacity of the battery for i (or j) times is obtained after the battery reaches the cycle discharge end point for k times;
the limiting index of the battery k based on the charge and discharge capacity entropy is defined as shown in the following formula:
similarly, the following formula of the normalized index can be obtained, and the normalized index based on the charge/discharge capacity entropy is shown as the following formula.
In the formula (I), the compound is shown in the specification,
further, the end point of the cycle life discharge was set to 80% of the first discharge capacity, the internal resistance was the internal resistance in the fully charged state of the battery, and the open-circuit voltage was the voltage of the battery after the fully charged state had been left to stand stably.
The method for evaluating and predicting the cycle life of the lithium ion battery has the following beneficial technical effects:
by adopting the method, the battery cycle life under the temperature environment charge-discharge cycle state can be calculated by combining the open-circuit voltage and the internal resistance of the battery, the weak influence factors of the battery cycle life can be effectively extracted, the battery cycle life can be accurately predicted and evaluated, the accuracy is high, the time consumption is short, and the requirements of the prediction and evaluation of the cycle life of different lithium ion battery types are met.
Detailed Description
In order to make the technical solution of the present invention better understood by those skilled in the art, the following detailed description is provided for the product of the present invention with reference to the examples.
The invention discloses an evaluation and prediction method for the cycle life of a lithium ion battery, which comprises the following steps:
(1) according to an operation reliability theory, considering the temperature environment of the battery, the open-circuit voltage and the internal resistance of the battery, and adopting an imputation degree statistical factor and a battery life reliability model for charging and discharging, thereby calculating the cycle number of the battery cycle life reaching the discharging end point;
(2) measuring the limitation of the charge-discharge cycle state of the battery in a temperature environment based on the limitation indexes of the discharge capacity variance and the discharge capacity entropy;
(3) in the aspect of battery charging and discharging test sequencing, a classification sequencing mode is adopted: in order to balance the requirements of calculation time and calculation precision, only batteries related to normal and abnormal batteries which reach the cyclic discharge end point in advance are searched for the cycle times of the charge-discharge cycle end of the batteries, the cycle times are sequenced, and then for the batteries with less cycle times, comprehensive restrictive indexes obtained by weighting the discharge capacity and the internal resistance restrictive indexes are used for rapid sequencing, so that the cycle time characteristic extraction of the batteries is realized.
Further, in the step (1), after comprehensively considering the temperature environment, the open-circuit voltage and the internal resistance of the battery, the reliability model of the battery is shown as follows:
further, in the step (2), the restrictive indexes include a battery charge-discharge cycle restrictive index based on the discharge capacity variance and a battery charge-discharge cycle restrictive index based on the discharge capacity entropy.
Further, in the battery charge-discharge cycle restrictive index based on the discharge capacity variance, the charge-discharge capacity variance of the battery charged and discharged normally under the temperature environment can be expressed as:
wherein n and ηi0The discharge capacity in the temperature environment and the discharge capacity of the battery at the ith time during normal charge and discharge are respectively,
after the battery reaches the cycle discharge end point k times, the discharge capacity variance of the temperature environment
Can be expressed as:
in the formula, ηk,iThe discharge capacity of the battery for i times after the battery reaches the cycle discharge end point for k times,
in summary, the limiting index of battery k with respect to the variance of charge/discharge capacity is defined as follows:
furthermore, in the battery charge-discharge cycle restrictive index based on the discharge capacity entropy, the discharge capacity entropy H of the battery in normal operation in a temperature environment is defined0As shown in the following formula:
in the formula, ηi0(or η)j0) The discharge capacity in the temperature environment and the discharge capacity of the battery at the i (or j) th time during normal charge and discharge are respectively,
after the battery reaches the cycle discharge end point k times, the entropy H of the discharge capacity of the battery in the temperature environmentkThe definition is shown as the following formula:
in the formula, ηk,i(or η)k,j) The discharge capacity of the battery for i (or j) times is obtained after the battery reaches the cycle discharge end point for k times;
the limiting index of the battery k based on the charge and discharge capacity entropy is defined as shown in the following formula:
similarly, the following formula of the normalized index can be obtained, and the normalized index based on the charge/discharge capacity entropy is shown as the following formula.
In the formula (I), the compound is shown in the specification,
further, the end point of the cycle life discharge was set to 80% of the first discharge capacity, the internal resistance was the internal resistance in the fully charged state of the battery, and the open-circuit voltage was the voltage of the battery after the fully charged state had been left to stand stably.
The foregoing is merely a preferred embodiment of the invention and is not intended to limit the invention in any manner; as will be readily apparent to those skilled in the art from the disclosure herein, the present invention may be practiced without these specific details; however, those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiments as a basis for designing or modifying other structures for carrying out the same purposes of the present invention; meanwhile, any changes, modifications, and evolutions of the equivalent changes of the above embodiments according to the actual techniques of the present invention are still within the protection scope of the technical solution of the present invention.
Claims (6)
1. A method for evaluating and predicting the cycle life of a lithium ion battery is characterized by comprising the following steps:
(1) according to an operation reliability theory, considering the temperature environment of the battery, the open-circuit voltage and the internal resistance of the battery, and adopting an imputation degree statistical factor and a battery life reliability model for charging and discharging, thereby calculating the cycle number of the battery cycle life reaching the discharging end point;
(2) measuring the limitation of the charge-discharge cycle state of the battery in a temperature environment based on the limitation indexes of the discharge capacity variance and the discharge capacity entropy;
(3) in the aspect of battery charging and discharging test sequencing, a classification sequencing mode is adopted: in order to balance the requirements of calculation time and calculation precision, only batteries related to normal and abnormal batteries which reach the cyclic discharge end point in advance are searched for the cycle times of the charge-discharge cycle end of the batteries, the cycle times are sequenced, and then for the batteries with less cycle times, comprehensive restrictive indexes obtained by weighting the discharge capacity and the internal resistance restrictive indexes are used for rapid sequencing, so that the cycle time characteristic extraction of the batteries is realized.
2. The method for evaluating and predicting the cycle life of a lithium ion battery according to claim 1, wherein: in the step (1), after comprehensively considering the temperature environment, the open-circuit voltage and the internal resistance of the battery, the reliability model of the battery is shown as follows:
3. the method for evaluating and predicting the cycle life of a lithium ion battery according to claim 2, wherein: in the step (2), the restrictive indexes include a battery charge-discharge cycle restrictive index based on the discharge capacity variance and a battery charge-discharge cycle restrictive index based on the discharge capacity entropy.
4. The method for evaluating and predicting the cycle life of a lithium ion battery according to claim 3, wherein: in the charge-discharge cycle restrictive index of the battery based on the discharge capacity variance, the charge-discharge capacity variance of the battery charged and discharged normally in a temperature environment can be expressed as follows:
wherein n and ηi0The discharge capacity in the temperature environment and the discharge capacity of the battery at the ith time during normal charge and discharge are respectively,
after the battery reaches the cycle discharge end point k times, the discharge capacity variance of the temperature environment
Can be expressed as:
in the formula, ηk,iThe discharge capacity of the battery for i times after the battery reaches the cycle discharge end point for k times,
in summary, the limiting index of battery k with respect to the variance of charge/discharge capacity is defined as follows:
5. the method for evaluating and predicting the cycle life of a lithium ion battery according to claim 3, wherein: in the charge-discharge cycle restrictive index of the battery based on the discharge capacity entropy, the discharge capacity entropy H of the battery in normal operation in a temperature environment is defined0As shown in the following formula:
in the formula, ηi0(or η)j0) The discharge capacity in the temperature environment and the discharge capacity of the battery at the i (or j) th time during normal charge and discharge are respectively,
after the battery reaches the cycle discharge end point k times, the entropy H of the discharge capacity of the battery in the temperature environmentkThe definition is shown as the following formula:
in the formula, ηk,i(or η)k,j) The discharge capacity of the battery for i (or j) times is obtained after the battery reaches the cycle discharge end point for k times;
the limiting index of the battery k based on the charge and discharge capacity entropy is defined as shown in the following formula:
similarly, the following formula of the normalized index can be obtained, and the normalized index based on the charge/discharge capacity entropy is shown as the following formula.
In the formula (I), the compound is shown in the specification,
6. the method for evaluating and predicting the cycle life of a lithium ion battery according to claim 3, wherein: the end point of the cycle life discharge was set to 80% of the first discharge capacity, the internal resistance was the internal resistance in the fully charged state of the battery, and the open circuit voltage was the voltage of the battery after the fully charged state had been left to stand stably.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113275271A (en) * | 2021-05-18 | 2021-08-20 | 上海电气国轩新能源科技有限公司 | Sorting method of lithium battery |
| CN113761716A (en) * | 2021-08-12 | 2021-12-07 | 惠州市豪鹏科技有限公司 | Lithium ion battery cycle life prediction method and application thereof |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113275271A (en) * | 2021-05-18 | 2021-08-20 | 上海电气国轩新能源科技有限公司 | Sorting method of lithium battery |
| CN113761716A (en) * | 2021-08-12 | 2021-12-07 | 惠州市豪鹏科技有限公司 | Lithium ion battery cycle life prediction method and application thereof |
| CN113761716B (en) * | 2021-08-12 | 2024-02-02 | 惠州市豪鹏科技有限公司 | Lithium ion battery cycle life prediction method and application thereof |
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