A method for characterizing the effect of the spacing between lithium-ion battery electrodes on polarization impedance

Abstract

The present invention proposes a method for characterizing the effect of the spacing between the pole pieces of a lithium-ion battery on the polarization impedance, comprising the following steps: S1, taking a plurality of groups of diaphragms, each group comprising two diaphragms, taking out a diaphragm from each group and attaching different layers of insulating tape on the taken diaphragms, and then assembling each group of diaphragms with the positive pole piece and the negative pole piece into a soft-pack laminated battery; S2, after each battery is formed, adjusting them to a predetermined SOC state for EIS testing; S3, analyzing the impedance spectrum and impedance value of each battery. The present invention increases the spacing between the positive and negative pole pieces of a lithium-ion battery by adhering diaphragms with different layers of insulating tape, simulates the increase in the spacing between the positive and negative pole pieces of a lithium-ion battery caused by factors such as gas production, and combines EIS characterization to analyze the effect of polarization caused by the increase in the spacing between the pole pieces on the battery impedance, which can better analyze the change in the polarization impedance of the battery caused by the increase in the spacing between the positive and negative pole pieces.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a method for characterizing the influence of the distance between pole pieces of a lithium ion battery on polarization impedance. Background Art

[0002] Since the commercialization of lithium-ion batteries, they have been used more and more widely in people's daily lives. The polarization size of lithium-ion batteries is an important parameter that affects the health of batteries. The generation of polarization will cause the battery to reach the cut-off condition prematurely during the charging and discharging process, reduce the battery capacity, and cause the battery cycle life to decay. Therefore, it is very important to study the changes in the polarization size of lithium-ion batteries. There are many factors that lead to increased battery polarization during the cycle of lithium-ion batteries. Among them, the weakening of the contact between the positive and negative pole pieces of the battery due to factors such as battery gas production is one of the reasons for the increase in battery polarization. However, there are currently few related solutions that can characterize and analyze the changes in battery polarization impedance caused by the increase in the distance between the positive and negative pole pieces of lithium-ion batteries. Summary of the invention

[0003] Based on the technical problems existing in the background technology, the present invention proposes a method for characterizing the influence of the spacing between pole pieces of a lithium-ion battery on the polarization impedance.

[0004] The present invention provides a method for characterizing the influence of the spacing between the pole pieces of a lithium-ion battery on the polarization impedance, comprising the following steps:

[0005] S1. Take several groups of separators, each group containing two separators, take out a separator from each group and attach different layers of insulating tape to the taken separators, and then assemble each group of separators with the positive electrode sheet and the negative electrode sheet into a soft-pack laminated battery;

[0006] S2, after each battery is formed, it is adjusted to a predetermined SOC state for EIS test;

[0007] S3. Analyze the impedance spectrum and impedance value of each battery.

[0008] Preferably, in step S1, in several batteries, the structural shape of the positive electrode sheet remains consistent and the structural shape of the negative electrode sheet also remains consistent; in each battery, the positive electrode sheet and the negative electrode sheet are both rectangular structures with a single layer of active material coated, and the active material on the positive electrode sheet and the negative electrode sheet is intermittently coated.

[0009] Preferably, in step S1, in each battery, the active material coating on the positive electrode sheet and the negative electrode sheet is located at the center of the positive electrode sheet and the negative electrode sheet, respectively.

[0010] Preferably, in step S1, in each battery, the coating position and shape of the active material on the positive electrode sheet are consistent with the coating position and shape of the active material on the negative electrode sheet.

[0011] Preferably, in step S1, in each battery, the ratio of the active material coating area on the positive electrode sheet to the positive electrode sheet area, and the ratio of the active material coating area on the negative electrode sheet to the negative electrode sheet area are both less than 0.2.

[0012] Preferably, in step S1, in each battery, the N / P range of the active material on the positive electrode sheet and the negative electrode sheet is 1-1.2.

[0013] Preferably, in step S1, in each battery, a through hole is provided at a position corresponding to the insulating tape and the active material coating on the positive electrode sheet.

[0014] Preferably, in step S1, the shape and size of the through hole on the insulating tape are respectively adapted to the shape and area of ​​the active material coating on the positive electrode sheet.

[0015] Preferably, in step S1, the number of layers of the insulating tape is 0-10 layers, and the thickness of the insulating tape is 50-60 μm.

[0016] Preferably, in step S2, several batteries are subjected to EIS test at the same SOC state.

[0017] The present invention proposes a method for characterizing the influence of the distance between the pole pieces of a lithium-ion battery on the polarization impedance. The method attaches different numbers of layers of insulating tape to a diaphragm and assembles the diaphragm into a battery to simulate a battery in which the distance between the pole pieces changes due to factors such as gas production, and then investigates the influence of the change on the polarization of the battery. The present invention controls the ratio of the area of ​​the active material coating on the pole piece to the area of ​​the pole piece to prevent the active material on the pole piece from being concave when the battery is assembled and affecting the distance between the pole pieces. The shape, area and position of the through holes on the active material coating on the positive and negative pole pieces and the insulating tape are controlled to ensure that when the lithium-ion battery is subjected to an EIS test, the variable is only the distance between the pole pieces, and when the battery is disturbed, lithium ions migrate only in the active area corresponding to the through holes on the insulating tape. The present invention increases the spacing between the positive and negative pole pieces of a lithium-ion battery by adhering a diaphragm with different numbers of layers of insulating tape, simulates the increase in the spacing between the positive and negative pole pieces of a lithium-ion battery caused by factors such as gas production, and combines EIS characterization to analyze the influence of polarization on battery impedance caused by the increase in the spacing between the pole pieces. The change in battery polarization impedance caused only by the increase in the spacing between the positive pole piece and the negative pole piece can be well analyzed, and has a good application prospect in the gas production failure analysis of lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A flow chart of a method for characterizing the influence of the spacing between pole pieces of a lithium-ion battery on polarization impedance proposed by the present invention;

[0019] Figure 2This is a schematic diagram of the structure of the soft-pack laminated battery proposed in the present invention;

[0020] Figure 3 The impedance spectra of the battery with different layers of insulating tape at 0% SOC in Example 1;

[0021] Figure 4 The impedance spectra of the battery with different numbers of insulating tape layers at 50% SOC in Example 2. DETAILED DESCRIPTION

[0022] Reference Figure 1 , Figure 2 The present invention proposes a method for characterizing the influence of the spacing between the pole pieces of a lithium-ion battery on the polarization impedance, comprising the following steps:

[0023] S1. Take several groups of diaphragms, each group containing two diaphragms, take out a diaphragm from each group and attach different layers of insulating tape on the taken diaphragms, and then assemble each group of diaphragms with the positive electrode sheet and the negative electrode sheet into a soft-pack laminated battery.

[0024] Specifically, in several batteries, the structure and shape of the positive electrode sheet remain consistent and the structure and shape of the negative electrode sheet also remain consistent. In each battery, the positive electrode sheet and the negative electrode sheet are rectangular structures with a single layer of active material coated, the active material on the positive electrode sheet and the negative electrode sheet is intermittently coated, and the active material coating on the positive electrode sheet and the negative electrode sheet is located in the center of the positive electrode sheet and the negative electrode sheet, respectively.

[0025] In each battery, the coating position and shape of the active material on the positive electrode sheet are consistent with the coating position and shape of the active material on the negative electrode sheet. The ratio of the coating area of ​​the active material on the positive electrode sheet to the positive electrode sheet area, and the coating area of ​​the active material on the negative electrode sheet to the negative electrode sheet area are both less than 0.2. The N / P range of the active material on the positive electrode sheet and the negative electrode sheet is 1-1.2.

[0026] In each battery, a through hole is provided at a position corresponding to the active material coating on the positive electrode sheet of the insulating tape, and the shape and size of the through hole on the insulating tape are respectively adapted to the shape and area of ​​the active material coating on the positive electrode sheet. The number of layers of the insulating tape is 0-10, and the thickness of the insulating tape is 50-60 μm.

[0027] S2. After each battery is charged, each battery is adjusted to the same SOC state for EIS test.

[0028] S3. Analyze the impedance spectrum and impedance value of each battery.

[0029] The technical solution of the present invention is described in detail below through specific embodiments.

[0030] Example 1

[0031] Take the EIS impedance of the soft-pack battery with 1 and 3 layers of insulating tape at 0% SOC as an example:

[0032] S1. Punching the intermittently single-layer coated positive and negative electrode sheets into rectangular electrode sheets;

[0033] S2. Take four separators and divide them into two groups. Take one separator from each group and attach one layer of insulating tape and three layers of insulating tape to the two separators respectively. Then assemble the two groups of separators with the positive electrode sheet and the negative electrode sheet respectively into a single-layer soft-package stacked full battery with N / P≈1.1.

[0034] S3, after the two batteries are charged, adjust them to 0% SOC state and perform EIS test;

[0035] S4. Analyze the impedance spectrum and impedance value of each battery:

[0036] Depend on Figure 3 It can be seen from the EIS impedance spectrum that with the increase in the number of insulating tape layers, that is, the increase in the spacing between the positive electrode pieces and the negative electrode pieces, the battery polarization impedance shows an increasing trend. Combined with the impedance value obtained by fitting (see Table 1 for specific data), it can be seen that the increase in the spacing between the electrode pieces will lead to an increase in the polarization impedance of the battery, and the electrochemical transfer impedance Rct is the most obvious.

[0037] Table 1

[0038]

[0039] Example 2

[0040] Take the EIS impedance of the soft-pack battery with 1 and 3 layers of insulating tape at 50% SOC as an example:

[0041] S1. Punching the intermittently single-layer coated positive and negative electrode sheets into rectangular electrode sheets;

[0042] S2. Take four separators and divide them into two groups. Take one separator from each group and attach one layer of insulating tape and three layers of insulating tape to the two separators respectively. Then assemble the two groups of separators with the positive electrode sheet and the negative electrode sheet respectively into a single-layer soft-package stacked full battery with N / P≈1.1.

[0043] S3, after the two batteries are charged, adjust them to 50% SOC state and perform EIS test;

[0044] S4. Analyze the impedance spectrum and impedance value of each battery:

[0045] Depend on Figure 4It can be seen from the EIS impedance spectrum that with the increase in the number of insulating tape layers, that is, the increase in the spacing between the positive electrode pieces and the negative electrode pieces, the battery polarization impedance shows an increasing trend. Combined with the impedance value obtained by fitting (see Table 2 for specific data), it can be seen that the increase in the spacing between the electrode pieces will lead to an increase in the polarization impedance of the battery, and the electrochemical transfer impedance Rct is the most obvious.

[0046] Table 2

[0047]

[0048] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for characterizing the effect of the spacing between lithium-ion battery pole pieces on polarization impedance, characterized in that: The following steps are involved: S1. Take several groups of separators, each group containing two separators, take out a separator from each group and attach different layers of insulating tape to the taken separators, and then assemble each group of separators with the positive electrode sheet and the negative electrode sheet into a soft-pack laminated battery; S2, after each battery is formed, it is adjusted to a predetermined SOC state for EIS test; S3. Analyze the impedance spectrum and impedance value of each battery.

2. The method for characterizing the influence of the distance between the pole pieces of a lithium-ion battery on the polarization impedance according to claim 1, characterized in that: In step S1, in several batteries, the structural shape of the positive electrode sheet remains consistent and the structural shape of the negative electrode sheet also remains consistent; in each battery, the positive electrode sheet and the negative electrode sheet are both rectangular structures with a single layer of active material coated, and the active material on the positive electrode sheet and the negative electrode sheet is intermittently coated.

3. The method for characterizing the influence of the distance between the pole pieces of a lithium-ion battery on the polarization impedance according to claim 2, characterized in that: In step S1 , in each battery, the active material coating on the positive electrode sheet and the negative electrode sheet is located at the center of the positive electrode sheet and the negative electrode sheet, respectively.

4. The method for characterizing the influence of the distance between the pole pieces of a lithium-ion battery on the polarization impedance according to claim 3, characterized in that: In step S1 , in each battery, the coating position and shape of the active material on the positive electrode sheet are consistent with the coating position and shape of the active material on the negative electrode sheet.

5. The method for characterizing the influence of the distance between the pole pieces of a lithium-ion battery on the polarization impedance according to claim 2, characterized in that: In step S1, in each battery, the ratio of the active material coating area on the positive electrode sheet to the positive electrode sheet area, and the ratio of the active material coating area on the negative electrode sheet to the negative electrode sheet area are both less than 0.

2.

6. The method for characterizing the influence of the distance between the pole pieces of a lithium-ion battery on the polarization impedance according to claim 2, characterized in that: In step S1, in each battery, the N / P range of the active material on the positive electrode sheet and the negative electrode sheet is 1-1.

2.

7. The method for characterizing the influence of the spacing between pole pieces of a lithium-ion battery on polarization impedance according to any one of claims 2 to 6, characterized in that: In step S1, in each battery, a through hole is opened at a position corresponding to the insulating tape and the active material coating on the positive electrode plate.

8. The method for characterizing the influence of the distance between the pole pieces of a lithium-ion battery on the polarization impedance according to claim 7, characterized in that: In step S1 , the shape and size of the through hole on the insulating tape are respectively adapted to the shape and size of the active material coating on the positive electrode sheet.

9. The method for characterizing the influence of the spacing between pole pieces of a lithium-ion battery on polarization impedance according to any one of claims 1 to 6, characterized in that: In step S1 , the number of layers of the insulating tape is 0-10, and the thickness of the insulating tape is 50-60 μm.

10. The method for characterizing the influence of the distance between pole pieces of a lithium-ion battery on polarization impedance according to any one of claims 1 to 6, characterized in that: In step S2, several batteries are subjected to EIS test at the same SOC state.

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