CN111638257B - Test method for voltage resolution in-situ electrochemical alternating-current impedance - Google Patents
Test method for voltage resolution in-situ electrochemical alternating-current impedance Download PDFInfo
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- CN111638257B CN111638257B CN202010491882.1A CN202010491882A CN111638257B CN 111638257 B CN111638257 B CN 111638257B CN 202010491882 A CN202010491882 A CN 202010491882A CN 111638257 B CN111638257 B CN 111638257B
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Abstract
A test method of voltage resolution in-situ electrochemical alternating current impedance comprises the following steps of (1): connecting an electrochemical system to be tested into a three-electrode electrochemical test system through a lead; step (2): at an initial open circuit voltage V n Is S n The reference voltage of step (ii); and (3): on the basis of the reference voltage, a sinusoidal alternating voltage signal with the amplitude of m is applied; and (4): s n After the step is finished, storing the response signal data of the step; and (5): by program control will S n+1 Reference voltage V of step n+1 Is set to V n+m Or V n‑m (ii) a Step (6) repeating the steps (3) to (5) until the potential of the test system rises or falls to the target potential; and (7): superposing the test results together to obtain a curved surface change diagram of the corresponding curve; and (8): and (4) completing the fitting of the equivalent circuit of each electrochemical alternating-current impedance test result through a program to obtain the corresponding electronic element parameters.
Description
Technical Field
The invention relates to the field of electrochemical testing, in particular to a testing technology of voltage resolution in-situ electrochemical alternating-current impedance.
Background
Lithium ion battery electrolytes affect battery performance primarily by forming a solid phase interfacial film. Therefore, the research on the evolution of the kinetics and the interface structure of the electrolyte in the interface decomposition process is of great significance for exploring the mechanism of the electrolyte influencing the interface property and even searching for the high-performance electrolyte. The most intuitive method for exploring the properties of the interfacial film at present is to directly observe components, component distribution and structural change in the process of forming the interfacial film through in-situ element characterization, component characterization and microstructure characterization methods. However, the above characterization can only be performed in a specific reaction vessel, and has a certain difference from the electrode interface property under the actual battery working condition; meanwhile, the method can only be used for property characterization of micro-regions generally, and the statistical significance of the result is not strong; finally, the equipment required for these characterizations is expensive, making the relevant research unsuitable for large-scale generalization. The electrochemical alternating current impedance test can obtain corresponding electrode electrochemical reaction kinetic parameters according to the linear relation between electrochemical input signals and output signals, and meanwhile, the structure evolution of the interface film can be researched according to the relaxation time difference corresponding to different interface structures. However, the conventional electrochemical impedance ensures the stability of the interface during the test by standing for a long time or applying a constant voltage, but this destroys the original electrochemical environment, thereby deviating the characterization result from the objective fact under the actual working condition.
Disclosure of Invention
The invention aims to provide a method for testing voltage-resolved in-situ electrochemical alternating-current impedance.
The invention relates to a test method of voltage-resolved in-situ electrochemical alternating-current impedance, which comprises the following steps:
step (1): connecting an electrochemical system to be tested into a three-electrode electrochemical test system through a lead;
step (2): taking the initial open-circuit voltage as a reference voltage;
and (3): applying a sinusoidal alternating voltage signal with m as amplitude on the basis of the reference voltage; the amplitude will also be applied as a transition potential in electrochemical ac impedance testing;
and (4): performing an electrochemical ac impedance test at the reference voltage; after the test is finished, storing the response signal data of the step;
and (5): with the present voltage as V n Wherein n is the serial number of the current electrochemical AC impedance test, and the reference voltage V of the next test is controlled by a program n+1 Is set to V n + m or V n -m；
And (6): repeating the third step to the fifth step until the potential of the test system rises or falls to the target potential;
and (7): by superposing test results obtained under different voltages, a curve change diagram corresponding to a curve, namely an electrode electrochemical alternating current impedance evolution process, can be obtained;
and (8): the fitting of the equivalent circuit of each electrochemical alternating-current impedance test result is completed through a program, and corresponding electronic element parameters are obtained; and superposing the equivalent circuit fitting results under all potentials to obtain a dynamic change curve of each electronic element parameter along with the change of the voltage.
The invention has the following beneficial effects: the method provided by the invention can be completed only by common electrochemical testing equipment. Meanwhile, the result obtained by the invention can reflect the electrochemical alternating current impedance function change of an electrochemical system under a real test working condition, and provide real and reliable data for research of an electrode interface and research and development of corresponding electrolyte and materials.
Drawings
FIG. 1 is a schematic flow diagram of the process of the present invention, FIG. 2 is a schematic illustration of the principle of the process of the present invention, FIG. 3 is a Bode-phase diagram of the electrochemical impedance of example 1, and FIG. 4 is a Bode-phase diagram of the electrochemical impedance of example 2.
Detailed Description
As shown in fig. 1, the present invention is a method for testing voltage-resolved in-situ electrochemical ac impedance, comprising the following steps:
step (1): connecting an electrochemical system to be tested into a three-electrode electrochemical test system through a lead;
step (2): taking the initial open-circuit voltage as a reference voltage;
and (3): on the basis of this reference voltage, a sinusoidal alternating voltage signal with amplitude m is applied. The amplitude will also be applied as a transition potential in electrochemical ac impedance testing;
and (4): an electrochemical ac impedance test was performed at this reference voltage. After the test is finished, storing the response signal data of the step;
and (5): with the current voltage as V n (where n is the serial number of the current electrochemical AC impedance test), and the reference voltage V of the next test is controlled by a program n+1 Is set to V n + m or V n -m；
And (6): repeating the third step to the fifth step until the potential of the test system rises or falls to the target potential;
and (7): the test results obtained under different voltages are superposed together to obtain a curved surface change diagram of a corresponding curve, namely an electrochemical alternating current impedance evolution process of the electrode;
step eight: and (4) completing the fitting of the equivalent circuit of each electrochemical alternating-current impedance test result through a program to obtain the corresponding electronic element parameters. And superposing the equivalent circuit fitting results under all potentials to obtain a dynamic change curve of each electronic element parameter along with the change of the voltage.
The result obtained by the invention can provide detailed parameters under actual working conditions, such as electrode surface roughness and reaction strength of electrode material phase change process, for researching the electrode/electrolyte interface structure of an electrochemical system in the electrode reaction process and electrode reaction kinetics.
In the above test method, the amplitude m of the sinusoidal alternating voltage signal applied in step (3) is 1 to 20mV, and the frequency range includes 10 6 Hz~10 -4 Any frequency interval in Hz.
The above-mentioned testing method, in step (4), the method for implementing the storage of the corresponding signal includes manual storage and program control storage, wherein the program control storage process includes, but is not limited to, implementation by macro, script, and programming language.
The test method described above, in step (5), realizes the program control to automatically test the reference voltage V of the next electrochemical AC impedance test n+1 Is set to V n + m or V n The method of the-m comprises the steps of self-setting and program control realization through the test equipment, and also comprises the steps of injecting macros, scripts and program languages through a program interface.
In the above-mentioned test method, in the step (7), the test results include results obtained by directly plotting test data, such as Nyquist curve and lissajous diagram; also included are results obtained by processing test data such as the baud-phase angle curve, the baud-Z mode curve.
The test method as described above, wherein in step (8), the method of fitting the circuit comprises fitting using commercial software, and also comprises fitting by a self-compiling program; the parameters of fitting include intrinsic parameters of the electronic component, such as the R value of the resistance, the Q value and the n value of the constant phase angle component, and also include corresponding kinetic parameters, such as reaction rate constant, reaction order number, and transferred electron number.
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the invention.
Example 1:
the method is characterized in that a graphite/Li half-cell is used as a test system, liDFOB is used as electrolyte, EC and DEC are used as solvent systems, and a voltage resolution in-situ electrochemical alternating current impedance test method is adopted to represent the change of an interface structure, and comprises the following steps:
the method comprises the following steps: placing the graphite/lithium button half cell in a Faraday shielding box, and connecting the Faraday shielding box with an electrochemical workstation with an electrochemical alternating current impedance characterization function through a lead;
step two: after standing for 12 hours, the open-circuit voltage of the battery is stable;
step three: measuring a stable open circuit voltage as a reference voltage;
step four: automatically completing the writing of macro script by a program written by VB (visual basic), and completing the electrochemical alternating current impedance test once when the work station decreases 0.01V from the open-circuit voltage to 0.01V, wherein the test frequency range is 10 5 Hz~10 -1 ；
Step five: the automatic merging and drawing of the characterization data are realized through MATLAB scripts, and the result is shown in FIG. 3.
Example 2:
LiPF (lithium nickel manganese oxide)/lithium half cell serving as a test system 6 The method is characterized in that the method is an electrolyte, EC and DMC are solvent systems, and a voltage resolution in-situ electrochemical alternating current impedance test method is adopted to characterize the structural change of a material in a lithium intercalation and deintercalation process, and comprises the following steps:
the method comprises the following steps: placing the lithium nickel manganese oxide/lithium button half cell in a Faraday shielding box, and connecting the lithium nickel manganese oxide/lithium button half cell with an electrochemical workstation with an electrochemical alternating current impedance characterization function through a lead;
step two: after standing for 12 hours, the open-circuit voltage of the battery is stable;
step three: measuring a stable open circuit voltage as a reference voltage;
step four: automatically completing the writing of macro script by a program written by VB (visual basic), and completing the electrochemical alternating current impedance test once for every increment of 0.01V from the open-circuit voltage to 5.0V by the workstation, wherein the test frequency range is 10 5 Hz~10 -1 ；
Step five: the automatic merging and drawing of the characterization data are realized through MATLAB scripts, and the result is shown in FIG. 4.
Fig. 3 shows that the characterization by the method can clearly show that the surface of the graphite material starts to form a stable solid-state phase interface film at about 0.8V, and simultaneously, the characteristic of continuous change of ohmic impedance caused by the volume change of the graphite in the lithium intercalation process can be observed.
Fig. 4 shows the phase change of the lithium nickel manganese oxide material during the delithiation process and the change of the interface reaction kinetic parameters, which can be cleaned by the characterization of the method, in particular, the node voltage of the above change process can be clearly shown.
The foregoing description has described specific embodiments of the present invention. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.
Claims (6)
1. A test method for voltage-resolved in-situ electrochemical alternating-current impedance is characterized by comprising the following steps:
step (1): connecting an electrochemical system to be tested into a three-electrode electrochemical test system through a lead; step (2): taking the initial open-circuit voltage as a reference voltage;
and (3): applying a sinusoidal alternating voltage signal with m as amplitude on the basis of the reference voltage; the amplitude will also be applied as a transition potential in electrochemical ac impedance testing;
and (4): performing an electrochemical alternating current impedance test at the reference voltage; after the test is finished, storing the response signal data of the step;
and (5): with the current voltage as V n Wherein n is the serial number of the current electrochemical AC impedance test, and the reference voltage V of the next test is controlled by a program n+1 Is set to V n + m or V n -m; and (6): repeating the steps (3) to (5) until the potential of the test system rises or falls to the target potential;
and (7): by superposing test results obtained under different voltages, a curve change diagram corresponding to a curve, namely an electrode electrochemical alternating current impedance evolution process, can be obtained;
and (8): the fitting of the equivalent circuit of each electrochemical alternating-current impedance test result is completed through a program, and corresponding electronic element parameters are obtained; and superposing the equivalent circuit fitting results under all potentials to obtain a dynamic change curve of each electronic element parameter along with the change of the voltage.
2. The method for voltage-resolved in-situ electrochemical ac impedance testing of claim 1, wherein: the amplitude m of the sinusoidal alternating voltage signal applied in the step (3) is 1-20 mV, and the frequency range comprises 10 6 Hz～10 -4 Any frequency interval in Hz.
3. The method for voltage-resolved in-situ electrochemical ac impedance testing of claim 1, wherein: in the step (4), the method for realizing the corresponding signal storage comprises manual storage and program control storage, wherein the program control storage process includes but is not limited to be realized through macros, scripts and programming languages.
4. The method for voltage-resolved in-situ electrochemical ac impedance testing of claim 1, wherein: in the step (5), the reference voltage V for automatically testing the next electrochemical alternating-current impedance is controlled by a program n+1 Is set to V n + m or V n The method of the-m comprises the steps of self-setting and program control realization through the test equipment, and also comprises the steps of injecting macros, scripts and program languages through a program interface.
5. The method for voltage-resolved in-situ electrochemical ac impedance testing of claim 1, wherein: in step (7), the test results include results obtained by directly plotting the test data and results obtained by processing the test data.
6. The method for voltage-resolved in-situ electrochemical ac impedance testing of claim 1, wherein: in the step (8), the method for fitting the circuit comprises fitting by using commercial software, and also comprises fitting by a self-compiling program; the parameters of the fit include intrinsic parameters of the electronic component, and also include its corresponding kinetic parameters.
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| CN103487762A (en) * | 2013-09-30 | 2014-01-01 | 国家电网公司 | Screening method for lithium ion batteries |
| CN106897522A (en) * | 2017-02-27 | 2017-06-27 | 长安大学 | Multiple parametric circuit model and method based on lithium iron phosphate dynamic battery impedance spectrum |
| CN108957323A (en) * | 2017-05-18 | 2018-12-07 | 中信国安盟固利动力科技有限公司 | A kind of judgment method and device of cell health state |
| WO2019241291A1 (en) * | 2018-06-11 | 2019-12-19 | William Marsh Rice University | Systems and methods of detecting li dendrites |
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| US9177466B2 (en) * | 2011-01-20 | 2015-11-03 | Indiana University Research And Technology Corporation | Advanced battery early warning and monitoring system |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103487762A (en) * | 2013-09-30 | 2014-01-01 | 国家电网公司 | Screening method for lithium ion batteries |
| CN106897522A (en) * | 2017-02-27 | 2017-06-27 | 长安大学 | Multiple parametric circuit model and method based on lithium iron phosphate dynamic battery impedance spectrum |
| CN108957323A (en) * | 2017-05-18 | 2018-12-07 | 中信国安盟固利动力科技有限公司 | A kind of judgment method and device of cell health state |
| WO2019241291A1 (en) * | 2018-06-11 | 2019-12-19 | William Marsh Rice University | Systems and methods of detecting li dendrites |
Non-Patent Citations (1)
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