CN112526352B - SOH estimation method for retired lithium ion battery - Google Patents
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 73
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 73
- 238000000034 method Methods 0.000 title claims abstract description 47
- 238000002847 impedance measurement Methods 0.000 claims abstract description 23
- 238000001453 impedance spectrum Methods 0.000 claims description 41
- 238000012546 transfer Methods 0.000 claims description 16
- 230000014509 gene expression Effects 0.000 claims description 9
- 238000013178 mathematical model Methods 0.000 claims description 8
- 238000005259 measurement Methods 0.000 claims description 8
- 238000009792 diffusion process Methods 0.000 claims description 7
- 238000002474 experimental method Methods 0.000 claims description 7
- 238000012360 testing method Methods 0.000 claims description 6
- 239000007772 electrode material Substances 0.000 claims description 3
- 239000007787 solid Substances 0.000 claims description 3
- 238000005265 energy consumption Methods 0.000 abstract description 6
- 239000012071 phase Substances 0.000 description 24
- 230000008569 process Effects 0.000 description 6
- 238000007726 management method Methods 0.000 description 3
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
- 239000003990 capacitor Substances 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 230000036541 health Effects 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 239000011149 active material Substances 0.000 description 1
- 238000007600 charging Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000010281 constant-current constant-voltage charging Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 238000000157 electrochemical-induced impedance spectroscopy Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- 230000002687 intercalation Effects 0.000 description 1
- 238000012886 linear function Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
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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]
- G01R31/367—Software therefor, e.g. for battery testing using modelling or look-up tables
-
- 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
-
- 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
Abstract
The application discloses an SOH estimation method of a retired lithium ion battery, which comprises the following steps: primary impedance measurement is carried out to obtain a primary SOC estimated value SOC1 of the retired lithium ion battery; performing short-time constant-current discharge on the retired lithium ion battery to obtain a discharge quantity Q; obtaining a secondary SOC estimated value SOC2 of the retired lithium ion battery through secondary impedance measurement; obtaining an SOH estimated value of the retired lithium ion battery by using a formula SOH=Q/(SOC 1-SOC 2); the application has the advantages that: the method is suitable for SOH estimation of retired lithium ion batteries, and has the advantages of high SOH estimation speed and low energy consumption.
Description
Technical Field
The application relates to the technical field of lithium ion batteries, in particular to an SOH estimation method of a retired lithium ion battery.
Background
Lithium ion batteries have characteristics of high energy density, light weight, long cycle life, high power capacity, and the like, and therefore, in order to cope with dual pressures of environmental pollution and energy shortage, lithium ion power batteries are used as one of the commonly used vehicle-mounted energy sources for Electric Vehicles (EVs). In 2014, the commercial unit year of the electric vehicle, according to the average service life of the power battery of 4-6 years, the 'scrapping tide' of the power battery has come, and only the estimated scrapping quantity of the power battery in the present year in China can reach the scale of 17 ten thousand tons. At present, power batteries retired from electric automobiles or buses are mainly subjected to layer-by-layer disassembly, charge and discharge and long-time standing to screen out battery cores with good appearance, high safety and high consistency, and then are recombined for echelon utilization, such as UPS, communication base stations, field vehicles, wind-light power generation energy storage, street lamps and the like. The complete disassembly process of the battery cells not only requires a large amount of manpower and material resources, but also is unknown in the state of each battery cell, namely, in the state of SOC and SOH, when the battery pack is disassembled into a single battery cell because the existing Battery Management System (BMS) of the electric automobile cannot detect the temperature, voltage and current of each battery cell. Generally, the accurate residual capacity of the battery cell can be directly obtained through complete discharge after full charge for many times, but the complete discharge after full charge is not only more than ten hours, but also a large amount of electric energy is wasted. Therefore, on the basis of the prior art, the important problem of energy and time waste caused by long-time charge and discharge, standing and the like in the gradient utilization of the battery cell is urgent.
Chinese patent application No. CN201910625259.8 discloses a method for estimating SOH of power battery and electric vehicle, wherein the method for estimating SOH of power battery calculates available capacity Q 'of current power battery' 0 And available capacity Q at delivery 0 Taking the percentage as the state of health SOH of the power battery in the current state; the SOH of the power battery is estimated by adopting the available capacity of the power battery when leaving the factory and the accumulated electric quantity in the charging and discharging process, so that the residual service life of the power battery is more accurately reflected; in terms of estimated parameter measurement accuracy, the measurement errors of the available capacity in delivery and the accumulated electric quantity in the charge and discharge process are smaller than those of the existing power battery state of health SOH estimation method; the real-time on-line estimation of the SOH of the vehicle-mounted power battery can be realized, the accuracy is high, and the SOH of the power battery can be accurately and practically reflected. The power battery of the power battery checks the current available capacity through the battery management system, the retired lithium ion battery is disassembled and cannot use the battery management system to check the current capacity, so that the patent application is not suitable for SOH estimation of the retired lithium ion battery, and the patent application discharges to zero electric quantity with the discharge quantity of 1C, so that the SOH estimation speed is low and the energy consumption is large.
Disclosure of Invention
The application aims to solve the technical problems that the SOH estimation method of the battery in the prior art is not suitable for SOH estimation of the retired lithium ion battery, the SOH estimation speed is low and the energy consumption is high.
The application solves the technical problems by the following technical means: a SOH estimation method of a retired lithium ion battery, the method comprising:
primary impedance measurement is carried out to obtain a primary SOC estimated value SOC1 of the retired lithium ion battery;
performing short-time constant-current discharge on the retired lithium ion battery to obtain a discharge quantity Q;
obtaining a secondary SOC estimated value SOC2 of the retired lithium ion battery through secondary impedance measurement;
and obtaining the SOH estimated value of the retired lithium ion battery by using the formula SOH=Q/(SOC 1-SOC 2).
According to the application, the SOC values of the two measurements are obtained through the primary impedance measurement and the secondary impedance measurement, the discharge quantity Q is obtained through the short-time discharge, the SOC estimated by the two times and the discharge quantity Q are fully utilized to obtain the SOH estimated value, so that the SOH is rapidly and effectively predicted, the retired power battery is not required to be circularly charged and discharged for many times, the SOH of the battery can be predicted in a short time, and the method is suitable for SOH estimation of the retired lithium ion battery, and has the advantages of higher SOH estimation speed and lower energy consumption.
Further, the method for obtaining the primary SOC estimated value SOC1 of the retired lithium ion battery by primary impedance measurement comprises the following steps:
constructing an equivalent circuit model of the lithium ion battery based on electrochemical impedance spectrum;
performing SOC discharge and impedance measurement experiments at equal intervals at different temperatures;
determining a functional relation between specific parameters in the equivalent circuit model and the SOC at different temperatures, and establishing an offline model based on the functional relation between the specific parameters in the equivalent circuit model and the SOC at different temperatures;
and (5) carrying out SOC estimation on the retired power battery with unknown charge states at different temperatures by using an offline model.
Further, the construction of the equivalent circuit model of the lithium ion battery based on the electrochemical impedance spectrum comprises the following steps: and establishing an offline electrochemical equivalent circuit model of the lithium ion battery according to the characteristics of the electrochemical impedance spectrum curves of the lithium ion batteries which are tested in advance.
Still further, the equivalent circuit model includes an inductance L, an ohmic resistance Rs, a charge transfer internal resistance Rct, and a normal phase element, the normal phase element includes an electric double layer element Q1 and an electric double layer element Q2, the inductance L, the ohmic resistance Rs, and the electric double layer element Q1 are connected in series, the charge transfer internal resistance Rct is connected in series with the electric double layer element Q2, and the charge transfer internal resistance Rct is connected in parallel with the electric double layer element Q1 as a whole with the electric double layer element Q2.
Further, the inductance L represents a straight line portion of a high frequency region of the electrochemical impedance spectrum curve, the ohmic resistance Rs is at a point where the high frequency region and the middle frequency region of the electrochemical impedance spectrum curve are connected, the charge transfer internal resistance Rct is connected in parallel with the electric double layer element Q1 to represent a circular arc portion of the impedance spectrum of the middle frequency region of the electrochemical impedance spectrum curve, the electric double layer element Q2 represents a slope related to solid diffusion impedance of lithium ions in the electrode active material, the slope is 45 °, and the diffusion process is represented by weber impedance or the electric double layer element Q2.
Further, the expression of the electric double layer element Q2 isWherein Y is 0 Is a constant phase angle element parameter, and the dimension is omega -1 ·cm -2 ·s -n Taking the total positive value, j represents the sign of the imaginary part, ω represents the angular frequency, n represents the index of the normal phase element, and the value is 0<n<1；
The expression of the Weber impedance is Z W ＝σω -1/2 (1-j) wherein σ represents a weber impedance coefficient;
the phase angle expression isWherein (1)>Indicating the phase angle.
Further, each parameter in the equivalent circuit model is obtained by carrying out a least square method identification algorithm on electrochemical impedance spectrum curve data of the lithium ion battery.
Further, the performing of different temperature equidistant SOC discharge and impedance measurement experiments includes:
and (3) performing equal SOC discharge on a plurality of retired lithium ion power batteries at intervals of-5 ℃ to 35 ℃ at intervals of 5 ℃, standing for a first preset time every 5% of SOC discharged during the discharge, and performing electrochemical impedance spectrum measurement to obtain impedance spectrum data of equal SOC intervals at different temperatures.
Further, the determining the functional relationship between the specific parameter and the SOC in the equivalent circuit model at different temperatures, and establishing the offline model based on the functional relationship between the specific parameter and the SOC in the equivalent circuit model at different temperatures includes:
and fitting the impedance spectrum data of the equal SOC intervals at different temperatures to obtain parameter values of the constant phase element in the equivalent circuit model, and constructing a mathematical model by utilizing the functional relation between the parameter values of the constant phase element and the SOC at different temperatures, wherein the mathematical model is an offline model for estimating the SOC of the retired power battery.
Further, the SOC estimation of the retired power battery with unknown state of charge at different temperatures using an offline model includes:
and carrying out partial constant-current discharge on the retired power lithium battery with unknown SOC, standing for a second preset time, testing an electrochemical impedance spectrum curve, fitting the electrochemical impedance spectrum curve data to obtain a parameter value of a constant-phase element in an equivalent circuit model, and substituting the obtained parameter value of the constant-phase element into an offline model to obtain the predicted SOC.
The application has the advantages that: according to the application, the SOC values of the two measurements are obtained through the primary impedance measurement and the secondary impedance measurement, the discharge quantity Q is obtained through the short-time discharge, the SOC estimated by the two times and the discharge quantity Q are fully utilized to obtain the SOH estimated value, so that the SOH is rapidly and effectively predicted, the retired power battery is not required to be circularly charged and discharged for many times, the SOH of the battery can be predicted in a short time, and the method is suitable for SOH estimation of the retired lithium ion battery, and has the advantages of higher SOH estimation speed and lower energy consumption.
Drawings
Fig. 1 is a flowchart of an SOH estimation method for a retired lithium ion battery according to an embodiment of the present application;
fig. 2 is a flowchart of a method for obtaining an SOC estimation value in an SOH estimation method for a retired lithium ion battery according to an embodiment of the present application;
fig. 3 is a schematic diagram of an equivalent circuit model in an SOH estimation method of a retired lithium ion battery according to an embodiment of the present application;
fig. 4 is a schematic diagram of an electric double layer element Q2 changing with SOC at 25 ℃ in an equivalent circuit model of an SOH estimation method of a retired lithium ion battery according to an embodiment of the present application.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions in the embodiments of the present application will be clearly and completely described in the following in conjunction with the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
As shown in fig. 1, a SOH estimation method of a retired lithium ion battery includes:
step S1: primary impedance measurement is carried out to obtain a primary SOC estimated value SOC1 of the retired lithium ion battery;
step S2: performing short-time constant-current discharge on the retired lithium ion battery to obtain a discharge quantity Q;
step S3: obtaining a secondary SOC estimated value SOC2 of the retired lithium ion battery through secondary impedance measurement;
step S4: and obtaining the SOH estimated value of the retired lithium ion battery by using the formula SOH=Q/(SOC 1-SOC 2).
The methods for acquiring the SOC estimation value in step S1 and step S3 are the same, and the method for acquiring the SOC estimation value is described in detail below, as shown in fig. 2, and the method includes:
constructing an equivalent circuit model of the lithium ion battery based on electrochemical impedance spectrum;
performing SOC discharge and impedance measurement experiments at equal intervals at different temperatures;
determining a functional relation between specific parameters in the equivalent circuit model and the SOC at different temperatures, and establishing an offline model based on the functional relation between the specific parameters in the equivalent circuit model and the SOC at different temperatures;
and (5) carrying out SOC estimation on the retired power battery with unknown charge states at different temperatures by using an offline model.
The SOC estimation method of the present application is described in detail below by way of specific examples, and as shown in fig. 3, the construction of the equivalent circuit model of the lithium ion battery based on electrochemical impedance spectroscopy includes: and establishing an offline electrochemical equivalent circuit model of the lithium ion battery according to the characteristics of the electrochemical impedance spectrum curves of the lithium ion battery which are tested in advance, wherein the equivalent circuit model comprises an inductor, ohmic impedance (ohmic resistance can also be adopted), charge transfer impedance (internal resistance of charge transfer can also be adopted) and a normal phase element.
With continued reference to fig. 3, the present embodiment adopts a model of a first-order equivalent circuit LR (Q (RQ)) structure, and the equivalent circuit model includes an inductance L, an ohmic resistance Rs, a charge transfer internal resistance Rct, and a normal phase element, where the normal phase element includes an electric double layer element Q1 and an electric double layer element Q2, the inductance L, the ohmic resistance Rs, and the electric double layer element Q1 are connected in series, the charge transfer internal resistance Rct is connected in series with the electric double layer element Q2, and the charge transfer internal resistance Rct and the electric double layer element Q2 are connected in parallel with the electric double layer element Q1 as a whole.
Inductance L represents the straight line part of the high frequency region of the impedance spectrum curve and is mainly caused by the porosity, uneven surface, connection leads and the like of the electrode; ohmic resistance Rs is not equal to 0 at about the point where the high frequency region and the intermediate frequency region are connected, and this point functions in relation to the transport of lithium ions and electrons through electrolyte, porous separator, wire, active material particles, etc.; the parallel connection of the charge transfer internal resistance Rct with the electric double layer element Q1 represents a circular arc portion of the mid-band impedance spectrum, which is caused by the charge transfer impedance of li+ at the electrode-electrolyte interface, and is generally represented by a parallel circuit of the charge transfer internal resistance Rct and the electric double layer capacitance Cdl. However, since the arc part is a flattened semicircle in a general experiment, it is shown that the electric double layer capacitor is not a pure capacitor, so Cdl can be replaced by an electric double layer element Q1; the electric double layer element Q2 represents a slope of 45 ° in theory, which is related to the solid diffusion resistance of lithium ions in the electrode active material, and may deviate due to the influence of porous electrode diffusion and li+ intercalation capacitance in the solid phase. This diffusion process is generally represented by Warburg impedance Zw, but in order to improve the fitting accuracy of the equivalent circuit, an electric double layer element Q2 is used. The expressions of the electric double layer element and weber impedance are as follows:
the expression of the electric double layer element Q2 isWherein Y is 0 Is a constant phase angle element parameter, and the dimension is omega -1 ·cm -2 ·s -n Taking the total positive value, j represents the sign of the imaginary part, ω represents the angular frequency, n represents the index of the normal phase element, and the value is 0<n<1；
The expression of the Weber impedance is Z W ＝σω -1/2 (1-j) wherein σ represents a weber impedance coefficient;
the phase angle expression isWherein (1)>Indicating the phase angle.
As can be seen from the above formula, as long as n in the impedance expression of the constant phase angle element takes on a valueThe weber impedance can be expressed, however, the normal phase angle element can be used for better fitting the impedance spectrum instead of the weber impedance because the normal phase angle element is usually used for experiments to obtain the diagonal degree which is not the 45-degree inclined angle.
The parameters of the five circuit elements in the equivalent circuit model are obtained by carrying out a least square method identification algorithm on electrochemical impedance spectrum curve data of the lithium ion battery, the algorithm belongs to the prior art, the main improvement point of the application is not the algorithm, and the processing process of the algorithm is not repeated here.
After the equivalent circuit model is built, carrying out equal SOC discharge on a plurality of sections of retired lithium ion power batteries at the interval of-5 ℃ to 35 ℃ by utilizing a rapid detection system in a echelon manner through the built retired power batteries, standing for a first preset time every 5% of SOC discharged during the equal SOC discharge, and then carrying out electrochemical impedance spectrum measurement to obtain impedance spectrum data of equal SOC intervals at different temperatures.
And then, fitting the impedance spectrum data of the equal SOC intervals at different temperatures to obtain parameter values of the constant phase element in the equivalent circuit model, and constructing a mathematical model by utilizing the functional relation between the parameter values of the constant phase element and the SOC at different temperatures, wherein the mathematical model is an offline model for estimating the SOC of the retired power battery. Referring to fig. 4, the specific process of constructing the mathematical model is as follows: (1) Before electrochemical impedance spectrum measurement is implemented, placing a retired power battery sample to be measured in a high-low temperature test box for full standing, and then carrying out constant-current constant-voltage charging and constant-current discharging; (2) Performing constant-current discharge at equal 5% SOC intervals on the retired power battery by using the test result, wherein the constant-current discharge is completed by standing for one hour; (3) After standing, carrying out electrochemical impedance spectrum test on the retired power battery by using an electrochemical workstation to obtain an impedance spectrum curve with equal 5% SOC interval; (4) Processing the obtained impedance spectrum curve data, identifying all parameters in an equivalent circuit model LR (Q (RQ)) through a least square method, and drawing a 5% SOC interval change chart of an electric double-layer element Q2 and the like to obtain a corresponding relation; (5) According to the change relation of the electric double-layer element Q2 along with the SOC, a polynomial model is utilized to fit 5% -95% of SOC curves or a linear function is utilized to fit 65% -95% of SOC curves, so that a mathematical model for rapidly estimating the SOC can be obtained, and the fitting process is the prior art and is not repeated here.
And then, carrying out SOC estimation by using the offline model, wherein the SOC estimation method specifically comprises the following steps: and carrying out partial constant-current discharge on the retired power lithium battery with unknown SOC, standing for a second preset time, testing an electrochemical impedance spectrum curve, fitting the electrochemical impedance spectrum curve data to obtain a parameter value of a constant-phase element in an equivalent circuit model, and substituting the obtained parameter value of the constant-phase element into an offline model to obtain the predicted SOC.
After the primary SOC estimated value SOC1 of the retired lithium ion battery in primary impedance measurement is obtained by the method, short-time constant-current discharge is carried out on the retired lithium ion battery to obtain the discharge quantity Q, secondary impedance measurement is carried out after standing for one hour, the secondary SOC estimated value SOC2 is obtained by the same method, and then the SOH estimated value of the retired lithium ion battery is obtained by the formula SOH=Q/(SOC 1-SOC 2).
According to the SOH estimation method for the retired lithium ion battery, provided by the technical scheme, the SOC values measured twice are obtained through the primary impedance measurement and the secondary impedance measurement, the discharge quantity Q is obtained through short-time discharge, the SOC estimated twice and the discharge quantity Q are fully utilized to obtain the SOH estimated value, so that the SOH is rapidly and effectively predicted, repeated cyclic charge and discharge of the retired power battery are not needed, the SOH of the battery can be predicted in a short time, the SOH estimation method is suitable for SOH estimation of the retired lithium ion battery, the SOH estimation speed is high, and the energy consumption is low.
The above embodiments are only for illustrating the technical solution of the present application, and are not limiting; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims (6)
1. A method for SOH estimation of retired lithium ion batteries, the method comprising:
primary impedance measurement is carried out to obtain a primary SOC estimated value SOC1 of the retired lithium ion battery;
performing short-time constant-current discharge on the retired lithium ion battery to obtain a discharge quantity Q;
obtaining a secondary SOC estimated value SOC2 of the retired lithium ion battery through secondary impedance measurement;
obtaining an SOH estimated value of the retired lithium ion battery by using a formula SOH=Q/(SOC 1-SOC 2);
the method for acquiring the primary SOC estimated value SOC1 of the retired lithium ion battery by primary impedance measurement comprises the following steps:
constructing an equivalent circuit model of the lithium ion battery based on electrochemical impedance spectrum;
performing SOC discharge and impedance measurement experiments at equal intervals at different temperatures;
determining a functional relation between a specific parameter in the equivalent circuit model and the SOC at different temperatures, and establishing an offline model based on the functional relation between the specific parameter in the equivalent circuit model and the SOC at different temperatures, wherein the specific parameter is a parameter value of a constant-phase element;
performing SOC estimation on retired lithium ion batteries with unknown charge states at different temperatures by using an offline model to obtain a primary SOC estimation value SOC1;
the equivalent circuit model comprises an inductor L, an ohmic resistor Rs, a charge transfer internal resistance Rct and a normal phase element, wherein the normal phase element comprises an electric double-layer element Q1 and an electric double-layer element Q2, the inductor L, the ohmic resistor Rs and the electric double-layer element Q1 are connected in series, the charge transfer internal resistance Rct is connected in series with the electric double-layer element Q2, and the charge transfer internal resistance Rct and the electric double-layer element Q2 are integrally connected in parallel with the electric double-layer element Q1; the inductance L represents a straight line part of a high-frequency region of an electrochemical impedance spectrum curve, the ohmic resistance Rs is connected with the electric double-layer element Q1 in parallel at a point where the high-frequency region and the middle-frequency region of the electrochemical impedance spectrum curve are connected, the charge transfer internal resistance Rct represents an arc part of the impedance spectrum of the middle-frequency region of the electrochemical impedance spectrum curve, the electric double-layer element Q2 represents an oblique line related to solid diffusion impedance of lithium ions in an electrode active material, the slope is 45 degrees, and the diffusion process is represented by the electric double-layer element Q2; the expression of the electric double layer element Q2 isWherein Y is 0 Is a constant phase angle element parameter, and the dimension is omega -1 ·cm -2 ·s -n Taking the total positive value, j represents the sign of the imaginary part, ω represents the angular frequency, n represents the index of the normal phase element, and the value is 0<n<1。
2. The SOH estimation method of a retired lithium ion battery according to claim 1, wherein the constructing an electrochemical impedance spectrum based equivalent circuit model of the lithium ion battery comprises: and establishing an offline electrochemical equivalent circuit model of the lithium ion battery according to the characteristics of the electrochemical impedance spectrum curves of the lithium ion batteries which are tested in advance.
3. The SOH estimation method of retired lithium-ion battery according to claim 1, wherein each parameter in the equivalent circuit model is obtained by performing a least square method identification algorithm on electrochemical impedance spectrum curve data of the lithium-ion battery.
4. The SOH estimation method of a retired lithium-ion battery according to claim 1, wherein the performing of different temperature equidistant SOC discharge and impedance measurement experiments comprises:
and (3) performing equal SOC discharge on a plurality of retired lithium ion batteries at intervals of-5-35 ℃ at intervals of 5 ℃, standing for a first preset time every 5% of SOC discharged, and performing electrochemical impedance spectrum measurement to obtain impedance spectrum data of equal SOC intervals at different temperatures.
5. The SOH estimation method of a retired lithium ion battery according to claim 4, wherein determining the functional relationship between the specific parameter and the SOC in the equivalent circuit model at different temperatures, and establishing the offline model based on the functional relationship between the specific parameter and the SOC in the equivalent circuit model at different temperatures, comprises:
and fitting the impedance spectrum data of the equal SOC intervals at different temperatures to obtain parameter values of the constant phase element in the equivalent circuit model, and constructing a mathematical model by utilizing the functional relation between the parameter values of the constant phase element and the SOC at different temperatures, wherein the mathematical model is an offline model for estimating the SOC of the retired lithium ion battery.
6. The SOH estimation method of claim 5, wherein the SOC estimation of the retired lithium ion battery with unknown states of charge at different temperatures using an offline model to obtain a primary SOC estimation value SOC1 comprises:
and carrying out partial constant-current discharge on the retired lithium ion battery with unknown SOC, standing for a second preset time, testing an electrochemical impedance spectrum curve, fitting the electrochemical impedance spectrum curve data to obtain a parameter value of a constant-phase element in an equivalent circuit model, and substituting the obtained parameter value of the constant-phase element into an offline model to obtain the predicted SOC.
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| CN113614554A (en) * | 2021-06-17 | 2021-11-05 | 香港应用科技研究院有限公司 | State of health assessment of decommissioned lithium ion batteries and battery modules |
| CN113702845A (en) * | 2021-09-02 | 2021-11-26 | 重庆金康动力新能源有限公司 | Method and equipment for evaluating core parameters of retired lithium battery |
| CN114280479A (en) * | 2021-12-23 | 2022-04-05 | 中山大学·深圳 | Electrochemical impedance spectrum-based rapid sorting method for retired batteries |
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