阅读说明：本技术 一种电压分辨原位电化学交流阻抗的测试方法 (Test method for voltage resolution in-situ electrochemical alternating-current impedance ) 是由 李世友 王鹏 赵冬妮 李春雷 崔孝玲 丁浩 李昭娟 东红 宋如 曾双威 芦红莉 于 2020-06-03 设计创作，主要内容包括：一种电压分辨原位电化学交流阻抗的测试方法,步骤(1)：将待测电化学体系通过引线接入三电极电化学测试系统；步骤(2)：以初始开路电压V<Sub>n</Sub>为S<Sub>n</Sub>步骤的基准电压；步骤(3)：在此基准电压的基础上,施加以m为振幅的正弦交变电压信号；步骤(4)：S<Sub>n</Sub>步骤结束后,存储该步骤响应信号数据；步骤(5)：通过程序控制将S<Sub>n+1</Sub>步的基准电压V<Sub>n+1</Sub>设定为V<Sub>n+m</Sub>或V<Sub>n-m</Sub>；步骤(6)重复步骤(3)至步骤(5),直至测试体系电位上升或下降至目标电位；步骤(7)：将测试结果叠加在一起,得到对应曲线的曲面变化图；步骤(8)：通过程序完成对每一次电化学交流阻抗测试结果的等效电路的拟合,得到对应电子元件参数。(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): applying a sinusoidal alternating voltage signal with m as amplitude on the basis of the reference voltage; 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.)

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 present voltage as V_nWherein 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+1Is 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.

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 10⁶Hz~10^-4Any 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 comprises but is not limited to realization 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+1Is set to V_n+ m or V_nThe method of-m comprises self-step setting and program control implementation through the test equipment, and also comprises injection of macros through a program interfaceScript, programming language implementation.

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, as well as its corresponding kinetic parameters.

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 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 present voltage as V_nWherein 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+1Is 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 electrode interface research and corresponding electrolyte and material research and development.

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 present voltage as V_n(where n is the serial number of the current electrochemical AC impedance test), and controlling the reference voltage V to be tested next time by a program_n+1Is 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;

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 10⁶Hz~10^-4Any 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 comprises the step (5) of realizing the program control to automatically test the reference voltage V of the next electrochemical alternating-current impedance test_n+1Is set to V_n+ m or V_nThe 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 present invention.