A detection method and device for testing the crosstalk characteristics of lithium batteries

Abstract

The present invention provides a detection method and device for testing the crosstalk characteristics of lithium batteries, belonging to the field of lithium battery detection. The method includes the following steps: assembling two button-type half-cells with the positive and negative electrode materials respectively, and assembling a full cell with the same positive and negative electrode materials; electrically connecting the electrode cases of the metal lithium foil counter electrodes of the two button-type half-cells and performing the first charge and discharge test; performing charge and discharge tests on the full cell with the same charge and discharge test parameters to eliminate the overpotential of the two button-type half-cells; evaluating the crosstalk degree of the lithium battery based on the test data of the full cell and the two button-type half-cells. By reverse series connection operation, the crosstalk between the electrodes in the lithium battery is isolated and its crosstalk characteristics are tested. This method not only improves the detection efficiency, but also can effectively deepen people's understanding of the crosstalk characteristics and provide a scientific basis for quality control in the battery production process.

Description

Technical Field

[0001] The present invention belongs to the field of lithium battery detection, and particularly relates to a detection method and device for testing the crosstalk characteristics of lithium batteries. Background Art

[0002] As a key technology in the current energy storage field, lithium batteries are widely used in electric vehicles, consumer electronics, and energy storage devices. However, with the improvement of battery energy density and the complexity of usage scenarios, the crosstalk phenomenon inside lithium batteries has gradually become one of the important issues affecting their performance and safety. So-called crosstalk means that transition metals or reaction-generated gases in the positive and negative electrodes pass through the battery separator and enter another electrode, having an adverse impact on the normal operation of the battery. This phenomenon gradually appears during the long-term electrochemical reaction process, posing a serious threat to battery life, performance, and safety.

[0003] During the operation of lithium batteries, the positive and negative electrode materials often generate unstable metal ions or by-products due to electrochemical reactions. These substances migrate through the separator to the opposite electrode, causing adverse reactions in the electrode materials. For example, the dissolution and migration of transition metals in the positive electrode can cause side reactions in the negative electrode, resulting in uneven growth of the solid electrolyte interface (SEI) film, thereby affecting the cycle life and capacity retention ability of the battery. At the same time, the generation and transmembrane transport of gases will also affect the pressure balance inside the battery, increasing safety risks such as explosion and fire.

[0004] The existence of the crosstalk phenomenon not only causes the electrochemical balance of the battery to be destroyed, resulting in rapid capacity decay, but also increases the internal resistance of the battery, reduces the charge and discharge efficiency, and may even cause catastrophic consequences such as thermal runaway in severe cases. Therefore, how to effectively suppress the crosstalk problem between the positive and negative electrodes has become an important topic in the research of lithium battery technology.

[0005] Although there are currently some technical means to reduce crosstalk, such as optimizing the stability of electrode materials or improving the selectivity of the separator, there are still many challenges to completely solve this problem. Currently, the industry's understanding of the crosstalk characteristics of lithium batteries is not deep enough, and most crosstalk detection methods have high requirements for equipment and cannot meet the needs of rapid and simple detection. Summary of the Invention

[0006] To solve the above problems, the present invention provides a detection method and device for testing the crosstalk characteristics of lithium batteries. By reverse series operation, the crosstalk between the electrode plates in the lithium battery is isolated, and its crosstalk characteristics are tested. This method not only improves the detection efficiency but also effectively deepens people's understanding of the crosstalk characteristics, providing a scientific basis for quality control in the battery production process.

[0007] To achieve the above object, the technical solutions adopted by the present invention are as follows:

[0008] On the one hand, the present invention provides a detection method for testing the crosstalk characteristics of a lithium battery, including the following steps: assembling two button-type half-cells with positive and negative electrode materials respectively, and assembling a full cell with the same positive and negative electrode materials; electrically connecting the electrode cases of the metal lithium sheet counter electrodes of the two button-type half-cells and performing the first charge and discharge test; performing charge and discharge tests on the full cell with the same charge and discharge test parameters to eliminate the overpotential of the two button-type half-cells; evaluating the crosstalk degree of the lithium battery based on the test data of the full cell and the two button-type half-cells.

[0009] Further, the positive electrode of the button battery case is used as the substrate of the metal lithium sheet counter electrode for both button-type half-cells.

[0010] Further, the positive electrode cases of the two button-type half-cells are electrically connected.

[0011] Further, eliminating the overpotential of the two button-type half-cells includes: performing the first charge and discharge test on the two button-type half-cells to obtain the first specific capacity-voltage curve; performing the first charge and discharge test on the full cell to obtain the second specific capacity-voltage curve; obtaining the overpotential by subtracting the first specific capacity-voltage curve from the second specific capacity-voltage curve.

[0012] Further, before performing the first charge and discharge test, the full cell and the two button-type half-cells are left to stand for at least 8 h or more.

[0013] Further, the charge and discharge test is as follows: charging at a constant current to a preset voltage, then performing constant voltage charging, the cut-off rate is half of the constant current value, after standing for 2 - 30 min, discharging at a constant current with the preset voltage, and collecting the specific capacity-voltage curve during the first charge and discharge.

[0014] Further, the Coulomb efficiency of the two button-type half-cells and the full cell is calculated through the specific capacity-voltage curve of the first charge and discharge; the crosstalk degree of the lithium battery is evaluated based on the difference or ratio of the Coulomb efficiencies of the two button-type half-cells and the full cell.

[0015] Further, when the difference between the Coulomb efficiencies of the two button-type half-cells and the full cell is less than 1% of the Coulomb efficiency of the two button-type half-cells, it is determined that no crosstalk has occurred; or, when the ratio of the Coulomb efficiencies of the two button-type half-cells and the full cell is less than 1.01, it is determined that no crosstalk has occurred.

[0016] On the other hand, the present invention provides a detection device for testing the crosstalk characteristics of lithium batteries, including: a charge-discharge test device for performing the first charge-discharge test on two button half-cells and a full cell to obtain the specific capacity-voltage curve of the first charge-discharge; the electrode housings of the metal lithium sheet counter electrodes of the two button half-cells are electrically connected, and the two button half-cells are respectively assembled with positive and negative electrode materials; the full cell is assembled with the positive and negative electrode materials; a data processing module that calculates the overpotential based on the specific capacity-voltage curves of the two button half-cells and the full cell, corrects the specific capacity-voltage curves of the two button half-cells based on the overpotential, and calculates the Coulomb efficiency through the corrected specific capacity-voltage curves of the two button half-cells and the specific capacity-voltage curve of the full cell; a crosstalk discrimination module that evaluates the crosstalk degree of the lithium battery based on the difference or ratio of the Coulomb efficiencies of the two button half-cells and the full cell.

[0017] Further, when the difference in Coulomb efficiency between the two button half-cells and the full cell is less than 1% of the Coulomb efficiency of the two button half-cells, it is determined that no crosstalk has occurred; or, when the ratio of the Coulomb efficiencies of the two button half-cells and the full cell is less than 1.01, it is determined that no crosstalk has occurred.

[0018] The beneficial effects brought by the technical solutions provided in the embodiments of the present invention include:

[0019] The technical solution proposed by the present invention ingeniously isolates the crosstalk between the electrode sheets through reverse series operation, greatly simplifying the detection process. This method not only improves the detection efficiency and shortens the experimental time, but also makes the detection results more accurate by eliminating the influence of overpotential. Its core lies in the reverse series of button half-cells, and through charge-discharge tests, the crosstalk characteristics of lithium batteries are clearly evaluated. This innovative means not only deepens the understanding of the crosstalk phenomenon of lithium batteries, but also provides a more scientific basis for quality control in battery production, with broad application prospects. Description of the Drawings

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0021] Figure 1 It is a schematic diagram of the series structure of the full cell and two button half-cells provided by the embodiment of the present invention;

[0022] Figure 2The first-cycle specific capacity-voltage curve and the corresponding first Coulombic efficiency obtained from the charge-discharge test of Example 1 of the present invention;

[0023] Figure 3 The first-cycle specific capacity-voltage curve and the corresponding first Coulombic efficiency obtained from the charge-discharge test of Example 2 of the present invention;

[0024] Figure 4 The first-cycle specific capacity-voltage curve and the corresponding first Coulombic efficiency obtained from the charge-discharge test of Example 3 of the present invention. Detailed implementation manners

[0025] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] The embodiment of the present invention provides a detection method for testing the crosstalk characteristics of a lithium battery, including the following steps:

[0027] S1 Assemble two button-type half-cells using the positive and negative electrode materials respectively, and assemble a full cell using the same positive and negative electrode materials;

[0028] S2 After electrically connecting the electrode cases of the lithium metal foil counter electrodes of the two button-type half-cells, perform the first charge-discharge test;

[0029] S3 Perform charge-discharge tests on the full cell using the same charge-discharge test parameters to eliminate the overpotentials of the two button-type half-cells;

[0030] S4 Evaluate the crosstalk degree of the lithium battery based on the test data of the full cell and the two button-type half-cells.

[0031] The technical solution proposed by the present invention ingeniously isolates the crosstalk between the electrode sheets through reverse series connection operation, greatly simplifying the detection process. This method not only improves the detection efficiency and shortens the experimental time, but also makes the detection results more accurate by eliminating the influence of overpotential. Its core lies in using the reverse series connection of button-type half-cells and clearly evaluating the crosstalk characteristics of lithium batteries through charge-discharge tests. This innovative means not only deepens the understanding of the crosstalk phenomenon of lithium batteries, but also provides a more scientific basis for quality control in battery production, with broad application prospects.

[0032] It should be noted that the button-type half-cell structure is a well-known structure, including a positive electrode housing, a negative electrode housing, and a pair of lithium metal electrodes, a separator, an electrode sheet, and an electrolyte disposed within the positive electrode housing and the negative electrode housing. The pair of lithium metal electrodes is electrically connected to the positive electrode housing or the negative electrode housing. In the embodiments of the present invention, the positive electrode material and the negative electrode material to be studied are respectively encapsulated with the pair of lithium metal electrodes to form a button-type half-cell for studying the crosstalk characteristics; the separator, the positive and negative electrodes use the same materials as those in actual production. To verify the accuracy of the technical solution proposed in this application, in the embodiments of the present invention, the separator uses a Celgard separator, the battery case uses CR2025, the positive electrode material uses lithium-rich manganese-based (LRMO), and the negative electrode material uses graphite (Graphite) and silicon monoxide (SiO). The electrode prepared from the lithium iron phosphate material does not generate crosstalk and is used as a standard; while the lithium-rich manganese-based material generates crosstalk. It should be noted that the positive and negative electrode materials, the separator, and the battery case used in the present invention are all commercially available products, and battery cases of other specifications can be used. The above selections do not affect the inventive points proposed in this application.

[0033] As Figure 1 shown, a normal battery, i.e., a full battery, is formed by sequentially arranging a positive electrode, a separator, and a negative electrode, filled with an electrolyte and covered with a battery case. For the reverse series isolation method of this application, as shown in the right figure, by setting two button-type half-cells, in one button-type half-cell, the positive electrode material, the separator, and the pair of lithium metal electrodes are sequentially arranged, filled with an electrolyte and covered with a battery case; in the other button-type half-cell, the negative electrode material, the separator, and the pair of lithium metal electrodes are sequentially arranged, filled with an electrolyte and covered with a battery case. It should be noted that the button-type battery case includes a positive electrode case and a negative electrode case. The pair of lithium metal electrodes in the two button-type half-cells can be electrically connected to the positive electrode case or the negative electrode case. Preferably, the positive electrode of the button-type battery case in this application is used as the base of the pair of lithium metal electrodes. The positive electrode cases of the two button-type half-cells are electrically connected. Specifically, the positive electrode cases of the two button-type half-cells can be directly abutted, which is convenient for assembly.

[0034] Eliminating the overpotential of the two button-type half-cells includes: performing a first charge-discharge test on the two button-type half-cells to obtain a first specific capacity-voltage curve; performing a first charge-discharge test on the full battery to obtain a second specific capacity-voltage curve; and obtaining the overpotential by subtracting the first specific capacity-voltage curve from the second specific capacity-voltage curve.

[0035] Preferably, before performing the first charge-discharge test, the full battery and the two button-type half-cells are left to stand for at least 8 hours or more.

[0036] The charge-discharge test is as follows: constant current charging is carried out until a preset voltage is reached, followed by constant voltage charging. The cut-off rate is half of the constant current value. After standing for 2 - 30 min, constant current discharging is carried out at the preset voltage, and the specific capacity-voltage curve during the first charge-discharge is collected. The preset voltage is a voltage common to lithium batteries made of different materials, such as 2.0 - 4.8 V for lithium-rich manganese-based, 2.5 - 4.3 V or 2.5 - 4.5 V for high-nickel ternary, and 3 - 4.5 V for lithium cobaltate. The preset voltage is common knowledge. In the embodiments of the present invention, the constant current is preferably 0.1C - 0.2C.

[0037] Through the specific capacity-voltage curve of the first charge-discharge, the Coulomb efficiency of the two coin-type half-cells and the full cell is calculated; based on the difference or ratio of the Coulomb efficiencies of the two coin-type half-cells and the full cell, the crosstalk degree of the lithium battery is evaluated. When the difference between the Coulomb efficiencies of the two coin-type half-cells and the full cell is less than 1% of the Coulomb efficiency of the two coin-type half-cells, it is determined that no crosstalk has occurred; or, when the ratio of the Coulomb efficiencies of the two coin-type half-cells and the full cell is less than 1.01, it is determined that no crosstalk has occurred.

[0038] The embodiments of the present invention also provide a detection device for testing the crosstalk characteristics of lithium batteries, including:

[0039] A charge-discharge test device, which is used to perform the first charge-discharge test on two coin-type half-cells and a full cell to obtain the specific capacity-voltage curve of the first charge-discharge; the electrode housings of the metal lithium foil counter electrodes of the two coin-type half-cells are electrically connected, and the two coin-type half-cells are respectively assembled with positive and negative electrode materials; the full cell is assembled with the positive and negative electrode materials; a data processing module, which calculates the overpotential based on the specific capacity-voltage curves of the two coin-type half-cells and the full cell, corrects the specific capacity-voltage curve of the two coin-type half-cells based on the overpotential, and calculates the Coulomb efficiency through the corrected specific capacity-voltage curves of the two coin-type half-cells and the specific capacity-voltage curve of the full cell; a crosstalk discrimination module, which evaluates the crosstalk degree of the lithium battery based on the difference or ratio of the Coulomb efficiencies of the two coin-type half-cells and the full cell.

[0040] When the difference between the Coulomb efficiencies of the two coin-type half-cells and the full cell is less than 1% of the Coulomb efficiency of the two coin-type half-cells, it is determined that no crosstalk has occurred; or, when the ratio of the Coulomb efficiencies of the two coin-type half-cells and the full cell is less than 1.01, it is determined that no crosstalk has occurred.

[0041] To better illustrate the implementation manners of the present invention, the present invention will be further described in detail through specific embodiments below.

[0042] Embodiment 1

[0043] An embodiment of the present invention provides a detection method for testing the crosstalk characteristics of a lithium battery, including:

[0044] S1 Assemble two button-type half-cells using positive and negative electrode materials respectively, and assemble a full cell using the same positive and negative electrode materials.

[0045] Cut commercial lithium-rich manganese-based electrode sheets and graphite electrode sheets into circular pieces with a diameter of 12 mm, and transfer them to a glove box filled with an argon atmosphere. Prepare a circular metal lithium piece with a diameter of 14 mm, as well as corresponding CR2025 battery cases, Celgard diaphragms, and electrolytes. Package two button-type half-cells in the order of positive electrode case, metal lithium piece, diaphragm, electrode sheet, and negative electrode case, where the electrode sheets in the two button-type half-cells are graphite electrode sheets and lithium-rich manganese-based electrode sheets respectively.

[0046] Similarly, in a glove box filled with an argon atmosphere, use the same materials to package a third button cell in the order of positive electrode case, lithium-rich manganese-based electrode sheet, diaphragm, graphite electrode sheet, and negative electrode case.

[0047] S2 After electrically connecting the electrode cases of the metal lithium sheets of the two button-type half-cells to the counter electrodes, perform the first charge and discharge test, and perform the charge and discharge test on the full cell using the same charge and discharge test parameters to eliminate the overpotential of the two button-type half-cells.

[0048] Connect the two button-type half-cells in reverse series, with the positive electrode cases partially overlapping and contacting each other. Use the lithium-rich manganese-based as the positive electrode and graphite as the negative electrode, and clamp them on the alligator clips of a Neware charge and discharge tester to form a system for isolating crosstalk between electrodes; for the third button cell, also use the lithium-rich manganese-based as the positive electrode and graphite as the negative electrode, and clamp it on the alligator clips of the Neware charge and discharge tester to form a system with crosstalk between electrodes.

[0049] After leaving it for 8 hours until the voltage is stable, both systems are charged at a constant current of 0.1C to 4.8V, then charged at a constant voltage, with a cut-off rate of 0.05C, and left to stand for 2 minutes. Subsequently, discharge at a constant current of 0.1C. Subtract the specific capacity-voltage curves of the two systems through software to obtain the specific value of the overpotential, and adjust the cut-off voltage according to this value so that the voltage windows after subtracting or adding this overpotential are the same. The obtained first-cycle specific capacity-voltage curve is as Figure 2 shown.

[0050] S3 Evaluate the crosstalk degree of the lithium battery based on the test data of the full cell and the two button-type half-cells.

[0051] The Coulomb efficiency of the two button-type half-cells is 75.8%, and the Coulomb efficiency of the full cell is 66.3%. The difference between the two is 9.5%. 9.5% / 75.8% = 12.5%, indicating crosstalk occurs.

[0052] Or, 75.8% / 66.3% = 1.14, and crosstalk occurs.

[0053] Example 2

[0054] An embodiment of the present invention provides a detection method for testing the crosstalk characteristics of a lithium battery. Different from Example 1, in this embodiment, a commercial lithium iron phosphate electrode is used as the positive electrode, and the same graphite electrode as in Example 1 is used as the negative electrode.

[0055] After eliminating the overpotential, the first-cycle specific capacity-voltage curve obtained is as Figure 3 shown.

[0056] Based on the test data of the full battery and the two button-type half-cells, the crosstalk degree of the lithium battery is evaluated.

[0057] The Coulombic efficiency of the two button-type half-cells is 80.5%, and the Coulombic efficiency of the full battery is 80.2%. The difference between the two is 0.3%. 0.3% / 80.5% = 0.3%, and no crosstalk occurs.

[0058] Or, 80.5% / 80.2% = 1.004, and no crosstalk occurs.

[0059] Example 3

[0060] An embodiment of the present invention provides a detection method for testing the crosstalk characteristics of a lithium battery. Different from Example 1, in this embodiment, the same lithium-rich manganese-based electrode as in Example 1 is used as the positive electrode, and a silicon monoxide electrode is used as the negative electrode.

[0061] After eliminating the overpotential, the first-cycle specific capacity-voltage curve obtained is as Figure 4 shown.

[0062] Based on the test data of the full battery and the two button-type half-cells, the crosstalk degree of the lithium battery is evaluated.

[0063] The Coulombic efficiency of the two button-type half-cells is 70.2%, and the Coulombic efficiency of the full battery is 56.3%. The difference between the two is 13.9%. 13.9% / 70.2% = 19.8%, and crosstalk occurs.

[0064] Or, 70.2% / 56.3% = 1.247, and crosstalk occurs.

[0065] It can be seen from Examples 1-3 that the detection method proposed in the embodiments of the present invention can accurately detect the crosstalk situation and the degree of crosstalk of different battery electrodes, quantify the crosstalk to guide the R & D process; and the detection method of this application is fast and effective, which can improve the R & D efficiency.

[0066] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A detection method for testing the crosstalk characteristics of lithium batteries, characterized in that, It includes the following steps: Assemble two button-type half-cells using the positive and negative electrode materials respectively, and assemble a full cell using the same positive and negative electrode materials; After the electrode cases of the metal lithium foil counter electrodes of the two button-type half-cells are electrically connected, perform the first charge-discharge test; Perform charge-discharge tests on the full cell using the same charge-discharge test parameters to eliminate the overpotential of the two button-type half-cells; Evaluate the crosstalk degree of the lithium battery based on the test data of the full cell and the two button-type half-cells; Eliminating the overpotential of the two button-type half-cells includes: Perform the first charge-discharge test on the two button-type half-cells to obtain the first specific capacity-voltage curve; Perform the first charge-discharge test on the full cell to obtain the second specific capacity-voltage curve; Obtain the overpotential by subtracting the first specific capacity-voltage curve from the second specific capacity-voltage curve; The charge-discharge test is: charge at a constant current to a preset voltage, then perform constant voltage charging, the cut-off rate is half of the constant current value, after standing for 2 - 30 min, discharge at a constant current with the preset voltage, and collect the specific capacity-voltage curve during the first charge-discharge; Based on the overpotential, correct the specific capacity-voltage curves of the two button-type half-cells, and calculate the Coulomb efficiency through the corrected specific capacity-voltage curves of the two button-type half-cells and the specific capacity-voltage curve of the full cell; Evaluate the crosstalk degree of the lithium battery based on the difference or ratio of the Coulomb efficiencies of the two button-type half-cells and the full cell.

2. The detection method according to claim 1, wherein Both of the button-type half-cells use the positive electrode of the button battery case as the base of the metal lithium foil counter electrode.

3. The detection method according to claim 2, wherein Electrically connect the positive electrode cases of the two button-type half-cells.

4. The detection method according to claim 1, wherein Before performing the first charge-discharge test, leave the full cell and the two button-type half-cells for at least 8 h or more.

5. The detection method according to claim 1, wherein When the difference in Coulomb efficiency between the two button-type half-cells and the full cell is less than 1% of the Coulomb efficiency of the two button-type half-cells, it is determined that no crosstalk has occurred; Or, when the ratio of the Coulomb efficiencies of the two button-type half-cells and the full cell is less than 1.01, it is determined that no crosstalk has occurred.

6. A detection device for testing the crosstalk characteristics of a lithium battery, characterized in that, It includes: A charge-discharge test device, which is used to perform the first charge-discharge test on two button-type half-cells and a full cell to obtain the specific capacity-voltage curve of the first charge-discharge; the electrode cases of the metal lithium foil counter electrodes of the two button-type half-cells are electrically connected, and the two button-type half-cells are respectively assembled with positive and negative electrode materials; the full cell is assembled with the positive and negative electrode materials; A data processing module, which calculates the overpotential based on the specific capacity-voltage curves of the two button-type half-cells and the full cell, corrects the specific capacity-voltage curves of the two button-type half-cells based on the overpotential, and calculates the Coulomb efficiency through the corrected specific capacity-voltage curves of the two button-type half-cells and the specific capacity-voltage curve of the full cell; A crosstalk discrimination module, which evaluates the crosstalk degree of the lithium battery based on the difference or ratio of the Coulomb efficiencies of the two button-type half-cells and the full cell.

7. The detection device according to claim 6, wherein when the difference in the Coulomb efficiencies of the two button-type half-cells and the full cell is less than 1% of the Coulomb efficiency of the two button-type half-cells, it is determined that no crosstalk has occurred; or, when the ratio of the Coulomb efficiencies of the two button-type half-cells and the full cell is less than 1.01, it is determined that no crosstalk has occurred.

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