A method for constructing an equivalent three - electrode system of a lithium - ion battery

Abstract

The present invention relates to a method for constructing an equivalent three - electrode system of a lithium - ion battery. The method comprises the following steps: S1. Obtain the DC impedance value R between the positive electrode of the battery and the battery housing respectively P and the DC impedance value R between the negative electrode of the battery and the battery housing N ; S2. Select a metal material identical to the battery housing as the equivalent reference electrode; S3. Select a resistor with a resistance value of R P to connect the positive electrode of the battery and the equivalent reference electrode, and select a resistor with a resistance value of R N to connect the negative electrode of the battery and the equivalent reference electrode, thus completing the construction of the equivalent three - electrode system. Compared with the prior art, the present invention has the advantages of not requiring modification of the battery, being easy to implement, and having high measurement accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a method for constructing an equivalent three-electrode system of a lithium-ion battery. Background Art

[0002] Lithium-ion batteries are widely used due to their excellent characteristics such as high energy density, high output voltage, low self-discharge rate, long service life, no memory effect, and environmental friendliness. In order to better study the performance of the positive and negative electrodes of the battery, a reference electrode is often introduced and used as a standard to measure the potential of the positive electrode or the negative electrode with respect to the reference electrode respectively.

[0003] The existing three-electrode battery uses metallic lithium as the reference electrode, and the reference electrode coexists with the positive and negative electrodes inside the battery. This three-electrode battery not only has a complex preparation process and requires changing the structure of the battery, but also cannot be used for production and is limited to evaluating the performance of the battery system. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for constructing an equivalent three-electrode system of a lithium-ion battery to overcome the defects of the existing technologies described above.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A method for constructing an equivalent three-electrode system of a lithium-ion battery, the method comprising the following steps:

[0007] S1. Obtain the DC impedance values R P between the positive electrode of the battery and the battery housing and the DC impedance value R N between the negative electrode of the battery and the battery housing respectively;

[0008] S2. Select a metal material identical to the battery housing as the equivalent reference electrode;

[0009] S3. Select a resistor with a resistance value of R P to connect the positive electrode of the battery and the equivalent reference electrode, and select a resistor with a resistance value of R N to connect the negative electrode of the battery and the equivalent reference electrode to complete the construction of the equivalent three-electrode system.

[0010] Preferably, step S1 specifically includes:

[0011] S11. Measure the AC impedance spectra between the positive electrode of the battery and the battery housing and between the negative electrode of the battery and the battery housing respectively;

[0012] S12. Obtain the DC impedance value R P between the positive electrode of the battery and the battery housing according to the AC impedance spectrum;

[0013] S13. Obtain the DC impedance value R between the battery negative electrode and the battery case according to the AC impedance spectrum between the battery negative electrode and the battery case N .

[0014] Preferably, in step S11: when measuring the AC impedance spectrum between the battery positive electrode and the battery case, connect the electrochemical workstation sampling positive electrode to the battery positive electrode, and connect the electrochemical workstation sampling negative electrode to the battery case; when measuring the AC impedance spectrum between the battery negative electrode and the battery case, connect the electrochemical workstation sampling positive electrode to the battery case, and connect the electrochemical workstation sampling negative electrode to the battery negative electrode.

[0015] Preferably, the DC impedance value R between the battery positive electrode and the battery case in step S12 P is the real-axis intercept of the AC impedance spectrum between the battery positive electrode and the battery case.

[0016] Preferably, the DC impedance value R between the battery negative electrode and the battery case in step S13 N is the real-axis intercept of the AC impedance spectrum between the battery negative electrode and the battery case.

[0017] Preferably, the equivalent reference electrode is arranged outside the battery.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] By obtaining the DC impedance value between the battery positive electrode and the battery case and the DC impedance value between the battery negative electrode and the battery case, the present invention further constructs an equivalent reference electrode outside the battery, and finally forms an equivalent three-electrode system, without the need to modify the battery, and is simple to implement, with high precision, and is convenient for subsequent research on the performance of the positive and negative electrodes of the battery. Description of the Drawings

[0020] Figure 1 is a flowchart of a method for constructing an equivalent three-electrode system of a lithium-ion battery according to the present invention;

[0021] Figure 2 is a schematic diagram of a method for calculating the DC impedance value between the battery positive electrode and the battery case and between the battery negative electrode and the battery case according to the present invention;

[0022] Figure 3 is a schematic diagram of the connection mode of the equivalent reference electrode of the lithium-ion battery according to the present invention. Detailed Embodiments

[0023] The present invention will be described in detail below with reference to the drawings and specific embodiments. Note that the following description of the embodiments is only illustrative in nature, and the present invention is not intended to limit the objects or uses to which it is applicable, and the present invention is not limited to the following embodiments.

[0024] Embodiment

[0025] As Figure 1 shown, this embodiment provides a method for constructing an equivalent three - electrode system of a lithium - ion battery, and the method includes the following steps:

[0026] S1. Obtain the DC impedance value R between the battery positive electrode and the battery housing P and the DC impedance value R between the battery negative electrode and the battery housing N , specifically:

[0027] Step S1 specifically includes:

[0028] S11. Measure the AC impedance spectra between the battery positive electrode and the battery housing, and between the battery negative electrode and the battery housing respectively;

[0029] S12. Obtain the DC impedance value R between the battery positive electrode and the battery housing according to the AC impedance spectrum between the battery positive electrode and the battery housing P ;

[0030] S13. Obtain the DC impedance value R between the battery negative electrode and the battery housing according to the AC impedance spectrum between the battery negative electrode and the battery housing N .

[0031] The theoretical basis of the present invention is to construct an equivalent three - electrode system based on the relative potential relationship between the positive and negative electrodes of the battery and the battery housing. Therefore, the surface of the housing of the lithium - ion battery cannot be directly connected to the positive or negative electrode. Otherwise, the housing and the positive or negative electrode are always at the same potential, and the AC impedance spectrum between the positive and negative electrodes and the equivalent reference electrode cannot be measured. Therefore, when measuring the AC impedance spectrum between the battery positive electrode and the battery housing, connect the sampling positive electrode of the electrochemical workstation to the battery positive electrode, and connect the sampling negative electrode of the electrochemical workstation to the battery housing; when measuring the AC impedance spectrum between the battery negative electrode and the battery housing, connect the sampling positive electrode of the electrochemical workstation to the battery housing, and connect the sampling negative electrode of the electrochemical workstation to the battery negative electrode.

[0032] The method for calculating the DC impedance values R between the positive electrode and the housing and between the negative electrode and the housing according to the obtained impedance spectra P and R N is as Figure 2 shown. In the AC impedance spectrum, the real - axis intercept of the curve represents the DC impedance value of the lithium - ion battery. Therefore, the DC impedance value R between the battery positive electrode and the battery housing can be obtained by calculating the real - axis intercept of the AC impedance spectrum curve between the battery positive electrode and the battery housing P , correspondingly, the DC impedance value R between the battery negative electrode and the battery housing can be obtained by calculating the real - axis intercept of the AC impedance spectrum curve between the battery negative electrode and the battery housing N .

[0033] S2. Select a metal material identical to the battery case as the equivalent reference electrode;

[0034] S3. Construct a three - electrode system, specifically:

[0035] S31. Select a resistor with a resistance value of R P and connect the positive electrode of the battery to the equivalent reference electrode;

[0036] S32. Select a resistor with a resistance value of R N and connect the negative electrode of the battery to the equivalent reference electrode.

[0037] Among them, the equivalent reference electrode, the resistor with a resistance value of R P and the resistor with a resistance value of R N are all arranged outside the battery. The connection schematic diagram is as shown in Figure 3 shown.

[0038] The present invention obtains the DC impedance value between the positive electrode of the battery and the battery case and the DC impedance value between the negative electrode of the battery and the battery case, and then constructs an equivalent reference electrode outside the battery, finally forming an equivalent three - electrode system, without the need to modify the battery, and is simple to implement and has high precision. Through the equivalent reference electrode, the potential relationship between the positive electrode of the battery and the equivalent reference electrode and the potential relationship between the negative electrode of the battery and the equivalent reference electrode can be established, so as to study the performance of the positive and negative electrodes of the battery.

[0039] The above - mentioned embodiments are only examples and do not represent the limitation of the scope of the present invention. These embodiments can also be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the technical idea of the present invention.

Claims

1. A method for constructing an equivalent three - electrode system of a lithium - ion battery, characterized in that, the method comprises the following steps: S1. Obtain the DC impedance value R between the battery positive electrode and the battery housing respectively P and the DC impedance value R between the battery negative electrode and the battery housing N ; S2. Select a metal material identical to the battery housing as the equivalent reference electrode; S3. Select a resistor with a resistance value of R P and connect it between the positive electrode of the battery and the equivalent reference electrode. Select a resistor with a resistance value of R N and connect it between the negative electrode of the battery and the equivalent reference electrode to complete the construction of the equivalent three-electrode system; Step S1 specifically includes: S11. Measure the AC impedance spectra between the battery positive electrode and the battery housing, and between the battery negative electrode and the battery housing respectively; S12. Obtain the DC impedance value R between the battery positive electrode and the battery case according to the AC impedance spectrum between the battery positive electrode and the battery case P ; S13. Obtain the DC impedance value R between the battery negative electrode and the battery housing according to the AC impedance spectrum between the battery negative electrode and the battery housing N ; In step S11: When measuring the AC impedance spectrum between the battery positive electrode and the battery housing, connect the sampling positive electrode of the electrochemical workstation to the battery positive electrode, and connect the sampling negative electrode of the electrochemical workstation to the battery housing; when measuring the AC impedance spectrum between the battery negative electrode and the battery housing, connect the sampling positive electrode of the electrochemical workstation to the battery housing, and connect the sampling negative electrode of the electrochemical workstation to the battery negative electrode; The DC impedance value R between the positive electrode of the battery and the battery housing in step S12 P is the real-axis intercept of the AC impedance spectrum between the positive electrode of the battery and the battery housing; The DC impedance value R between the negative electrode of the battery and the battery case in step S13 N is the real-axis intercept of the AC impedance spectrum between the negative electrode of the battery and the battery case; The said equivalent reference electrode is arranged outside the battery.

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