Method and device for predicting voltage after completion of small-current charging during formation of secondary battery

Abstract

The present invention discloses a method and device for predicting the voltage after the end of small-current charging during the formation of a secondary battery, which relates to the field of battery testing. The method includes obtaining a plurality of battery cells after liquid injection is completed and high-temperature standing, and testing the voltage of the battery cells after high-temperature standing; based on the voltage of the battery cells after high-temperature standing, selecting the battery cells located within a preset voltage range; for the selected battery cells, testing the voltage after the end of small-current charging during the formation process to obtain the voltage of the battery cells after the end of small-current charging during the formation; based on the tested voltage of the battery cells after high-temperature standing and the voltage after the end of small-current charging during the formation, fitting a correlation curve between the voltage of the battery cells after high-temperature standing and the voltage after the end of small-current charging during the formation; and obtaining the voltage of the battery cell to be tested after the end of small-current charging during the formation according to the fitted correlation curve and the voltage of the battery cell to be tested after high-temperature standing. The present invention can effectively evaluate the performance of secondary batteries.

Description

Technical Field

[0001] The present invention relates to the field of battery testing, and particularly to a method and device for predicting the voltage after the end of small-current charging during the formation of a secondary battery. Background Art

[0002] For secondary batteries, such as lithium-ion batteries, they mainly work by the movement of lithium ions between the positive electrode and the negative electrode. During the charge and discharge process, lithium ions are inserted and extracted back and forth between the two electrodes: during charging, lithium ions are extracted from the positive electrode and inserted into the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state; during discharging, the opposite occurs.

[0003] Currently, the performance of secondary batteries is usually evaluated by some parameter indicators such as the formation end voltage, capacity, voltage, AC internal resistance, DC internal resistance, self-discharge, and constant current ratio. However, these evaluation indicators cannot fully characterize the battery quality problems during the production process of lithium batteries. Summary of the Invention

[0004] Aiming at the defects existing in the prior art, the purpose of the present invention is to provide a method and device for predicting the voltage after the end of small-current charging during the formation of a secondary battery, which can effectively evaluate the performance of the secondary battery.

[0005] To achieve the above purpose, the present invention provides a method for predicting the voltage after the end of small-current charging during the formation of a secondary battery, specifically including the following steps:

[0006] Obtain a plurality of battery cells that have completed liquid injection and have been statically placed at a high temperature, and test the voltage of the battery cells after high-temperature static placement;

[0007] Based on the voltage of the battery cells after high-temperature static placement, select the battery cells located within a preset voltage range. There are multiple preset voltage ranges, and a set number of battery cells are selected within each preset voltage range;

[0008] For the selected battery cells, test the voltage after the end of small-current charging during the formation process to obtain the voltage of the battery cells after the end of small-current charging during the formation;

[0009] Based on the tested voltage of the battery cells after high-temperature static placement and the voltage after the end of small-current charging during the formation, fit to obtain the correlation curve between the voltage of the battery cells after high-temperature static placement and the voltage after the end of small-current charging during the formation;

[0010] According to the fitted correlation curve and the voltage of the battery cell to be tested after high-temperature static placement, obtain the voltage of the battery cell to be tested after the end of small-current charging during the formation.

[0011] On the basis of the above technical solution, the high-temperature static placement is to statically place the battery cells after one-time liquid injection for 15 - 36 hours, and the ambient temperature of the battery cells is 45 ± 5°C.

[0012] Based on the above technical solution, for the voltage of the battery cell after high-temperature standing, the battery cells located within a preset voltage range are selected. The specific steps are as follows:

[0013] Define multiple preset voltage ranges, and the voltage ranges of each preset voltage range are different;

[0014] According to the preset voltage range where the voltage of the battery cell after high-temperature standing is located, a set number of battery cells are selected within each preset voltage range.

[0015] Based on the above technical solution, the correlation curve is a linear curve.

[0016] Based on the above technical solution, the expression relation of the correlation curve is:

[0017] V1 = KV0 + B, where V1 represents the voltage of the battery cell after the end of small-current charging during formation, V0 represents the voltage of the battery cell after high-temperature standing, and K and B represent the functional relationship between V1 and V0.

[0018] Based on the above technical solution, the value range of K is 0.05 to 0.15, the value range of B is 2.92 to 2.928, and the correlation coefficient R 2 of the correlation curve has a value of 0.7 to 0.98. R 2 represents the correlation between V1 and V0.

[0019] Based on the above technical solution, for the voltage of the battery cell after the end of small-current charging during formation, the current magnitude is 0.02C to 0.1C, and the charging time is 0.5 to 2.5h.

[0020] Based on the above technical solution, the secondary battery includes a lithium-ion battery, a polymer lithium-ion battery, a nickel-metal hydride battery, a nickel-cadmium battery, and a lead-acid battery.

[0021] A prediction device for the voltage of a secondary battery after the end of small-current charging during formation provided by the present invention includes:

[0022] A first test unit, which is used to obtain multiple battery cells that have completed liquid injection and undergone high-temperature standing, and test to obtain the voltage of the battery cells after high-temperature standing;

[0023] A selection unit, which is used to select the battery cells located within a preset voltage range based on the voltage of the battery cells after high-temperature standing. There are multiple preset voltage ranges, and a set number of battery cells are selected within each preset voltage range;

[0024] A second test unit, which is used to test the voltage after the end of small-current charging during the formation process for the selected battery cells to obtain the voltage of the battery cells after the end of small-current charging during formation;

[0025] A fitting unit, which is used to fit a correlation curve between the voltage of the battery cell after high-temperature static storage and the voltage after the end of small-current charging during formation based on the test results of the voltage of the battery cell after high-temperature static storage and the voltage after the end of small-current charging during formation;

[0026] A prediction unit, which is used to obtain the voltage after the end of small-current charging during formation of the battery cell to be tested according to the fitted correlation curve and the voltage of the battery cell to be tested after high-temperature static storage.

[0027] On the basis of the above technical solution, the correlation curve is a linear curve.

[0028] Compared with the prior art, the advantages of the present invention are as follows: By using the voltage of the battery cell after high-temperature static storage and the voltage after the end of small-current charging during formation, a correlation curve between the voltage of the battery cell after high-temperature static storage and the voltage after the end of small-current charging during formation is fitted. Then, according to the fitted correlation curve and the voltage of the battery cell to be tested after high-temperature static storage, the voltage after the end of small-current charging during formation of the battery cell to be tested can be obtained. The voltage after the end of small-current charging during formation of the secondary battery is characterized by the voltage of the secondary battery after high-temperature static storage, so as to characterize the degree of side reactions during the formation process of the secondary battery, and realize the effective evaluation of the performance of the secondary battery. Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application, 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 application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1 It is a flowchart of a method for predicting the voltage after the end of small-current charging during formation of a secondary battery in an embodiment of the present invention. Detailed Embodiments

[0031] An embodiment of the present invention provides a method for predicting the voltage after the end of small-current charging during formation of a secondary battery. By using the voltage of the battery cell after high-temperature static storage and the voltage after the end of small-current charging during formation, a correlation curve between the voltage of the battery cell after high-temperature static storage and the voltage after the end of small-current charging during formation is fitted. Then, according to the fitted correlation curve and the voltage of the battery cell to be tested after high-temperature static storage, the voltage after the end of small-current charging during formation of the battery cell to be tested can be obtained. The voltage after the end of small-current charging during formation of the secondary battery is characterized by the voltage of the secondary battery after high-temperature static storage, so as to characterize the degree of side reactions during the formation process of the secondary battery, and realize the effective evaluation of the performance of the secondary battery. Correspondingly, an embodiment of the present invention also provides a device for predicting the voltage after the end of small-current charging during formation of a secondary battery.

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are some, but not all, of the embodiments of this application.

[0033] See Figure 1 As shown, a method for predicting the voltage after the end of small-current charging during the formation of a secondary battery provided by an embodiment of the present invention specifically includes the following steps:

[0034] S1: Obtain a plurality of battery cells after the injection is completed and after high-temperature standing, and test the voltage of the battery cells after high-temperature standing;

[0035] That is, select a number of battery cells after the injection is completed and after high-temperature standing, and perform voltage tests on the selected battery cells to obtain the voltage of the battery cells after high-temperature standing.

[0036] In the embodiment of the present invention, high-temperature standing means that the battery cells after the first injection are left standing for 15 to 36 hours, and the ambient temperature of the battery cells is 45 ± 5°C.

[0037] S2: Based on the voltage of the battery cells after high-temperature standing, select the battery cells located within a preset voltage range. There are multiple preset voltage ranges, and the size of each preset voltage range increases in turn, and a set number of battery cells are selected within each preset voltage range; this step is specifically as follows:

[0038] S201: Define multiple preset voltage ranges, and the voltage ranges of each preset voltage range are different;

[0039] S202: According to the preset voltage range where the voltage of the battery cells after high-temperature standing is located, select a set number of battery cells within each preset voltage range.

[0040] In a possible implementation manner, the defined preset voltage ranges are less than 0.1V, 0.1 - 0.12V, 0.12 - 0.13V, 0.13 - 0.14V, 0.14 - 0.15V, 0.15 - 0.16V, 0.16 - 0.17V, 0.17 - 0.18V, and greater than 0.18V. The voltage of each battery cell after high-temperature standing is different. For the above voltage ranges, a set number of battery cells are selected within each voltage range. Specifically, the value range of each preset voltage range is flexibly determined according to actual working experience, covering as much as possible the possible voltage range of the battery cells after high-temperature standing, and the adjacent preset voltage ranges are kept continuous. At the same time, the number of battery cells selected within each voltage range is also flexibly determined according to actual working experience, as long as the number of battery cells selected within each voltage range is the same.

[0041] S3: For the selected battery cells, during the formation process, measure the voltage after the end of small-current charging to obtain the voltage of the battery cells after the end of small-current charging during formation.

[0042] For multiple selected battery cells, measure the voltage after the end of small-current charging for each battery cell during the formation process to obtain the voltage of each battery cell after the end of small-current charging during formation.

[0043] In the embodiments of the present invention, for the voltage of the battery cells after the end of small-current charging during formation, where the current magnitude is 0.02C to 0.1C and the charging time is 0.5 to 2.5 h.

[0044] S4: Based on the voltage of the battery cells after high-temperature standing and the voltage of the battery cells after the end of small-current charging during formation obtained by measurement, fit to obtain the correlation curve between the voltage of the battery cells after high-temperature standing and the voltage of the battery cells after the end of small-current charging during formation.

[0045] In the embodiments of the present invention, the correlation curve is a linear curve. The expression formula of the correlation curve is:

[0046] V1 = KV0 + B,

[0047] where V1 represents the voltage of the battery cells after the end of small-current charging during formation, V0 represents the voltage of the battery cells after high-temperature standing, and K and B represent the functional relationship between V1 and V0. The value range of K is 0.05 to 0.15, the value range of B is 2.92 to 2.928, and the correlation coefficient R 2 of the linear curve takes a value of 0.7 to 0.98, and R 2 represents the correlation between V1 and V0.

[0048] It should be noted that the "voltage after the end of small-current charging during formation" is not the "formation end voltage". The voltage of the battery cells after the end of small-current charging during formation can more directly characterize the degree of side reactions during the formation process of the secondary battery. The focus of the present invention is before formation, and the voltage of the battery cells after the end of small-current charging during formation (after formation) can be characterized by the voltage of the battery cells after high-temperature standing, so as to predict the degree of side reactions during the formation process of the battery.

[0049] S5: According to the obtained correlation curve and the voltage of the battery cells to be tested after high-temperature standing, obtain the voltage of the battery cells to be tested after the end of small-current charging during formation. Based on the voltage of the battery cells after the end of small-current charging during formation, characterize the degree of side reactions during the formation process of the secondary battery. The secondary battery includes lithium-ion batteries, polymer lithium-ion batteries, nickel-metal hydride batteries, nickel-cadmium batteries, and lead-acid batteries.

[0050] For example, for a lithium-ion battery, during the initial stage of formation, a series of side reactions occur during the current charging process. The occurrence of these side reactions consumes a part of the electric charge, resulting in a decrease in the voltage of the lithium battery after the end of the small-current charging. Therefore, the voltage of the lithium battery after the end of the small-current charging during the formation process can characterize the degree of side reactions. In the present invention, the voltage of the lithium-ion battery after high-temperature standing after liquid injection can predict the voltage of the lithium battery after the end of the small-current charging during formation. Therefore, it can be considered that the voltage of the lithium battery after high-temperature standing can characterize the magnitude of the side reactions during the small-current charging process of the lithium battery formation.

[0051] The following specifically describes the method for predicting the voltage at the end of the small-current charging of the secondary battery according to the embodiments of the present invention with reference to specific examples.

[0052] Example 1

[0053] (1) Take 100 battery cells that have been standing for 25 h at 45°C after the first liquid injection.

[0054] (2) Measure the voltage of the battery cells after high-temperature standing.

[0055] (3) Select the battery cells within the preset voltage range, and select 5 battery cells within each preset voltage range; specifically, select 5 battery cells within the range less than 0.1 V, 5 battery cells within the range of 0.1 - 0.12 V, 5 battery cells within the range of 0.12 - 0.13 V, 5 battery cells within the range of 0.13 - 0.14 V, 5 battery cells within the range of 0.14 - 0.15 V, 5 battery cells within the range of 0.15 - 0.16 V, 5 battery cells within the range of 0.16 - 0.17 V, 10 battery cells within the range of 0.17 - 0.18 V, and 5 battery cells within the range greater than 0.18 V.

[0056] (4) For the selected battery cells, measure the voltage at the end of the small-current charging during the formation process (the charging current of the battery is 0.05 C and the charging time is 1 h) to obtain the voltage at the end of the small-current charging of the battery cells during the formation.

[0057] (5) Fit the correlation curve between the voltage of the battery cells after high-temperature standing and the voltage at the end of the small-current charging during the formation, that is, V1 = 0.0891V0 + 2.9274, R 2 = 0.8927.

[0058] Example 2

[0059] (1) Take 100 battery cells that have been standing for 25 h at 45°C after the first liquid injection.

[0060] (2) Measure the voltage of the battery cells after high-temperature standing.

[0061] (3) Select the battery cells within the preset voltage range, with 5 cells selected within each preset voltage range. Specifically, 5 cells are selected within the range less than 0.1V, 5 cells are selected within the range of 0.1 - 0.12V, 5 cells are selected within the range of 0.12 - 0.13V, 5 cells are selected within the range of 0.13 - 0.14V, 5 cells are selected within the range of 0.14 - 0.15V, 5 cells are selected within the range of 0.15 - 0.16V, 5 cells are selected within the range of 0.16 - 0.17V, 10 cells are selected within the range of 0.17 - 0.18V, and 5 cells are selected within the range greater than 0.18V.

[0062] (4) For the selected battery cells, during the formation process, test the voltage after the small - current charging ends (the charging current of the rechargeable battery is 0.02C and the charging time is 2.5h) to obtain the voltage of the battery cell after the small - current charging ends during formation.

[0063] (5) Fit the correlation curve between the voltage of the battery cell after high - temperature standing and the voltage after the small - current charging ends during formation, that is, V1 = 0.136V0 + 2.9203, R 2 = 0.95.

[0064] The present invention can characterize the voltage of the secondary battery after the small - current charging ends during formation by testing the voltage of the secondary battery after high - temperature standing, thereby characterizing the degree of side reactions during the formation process of the secondary battery, and providing a guarantee for the quality in the production process of the secondary battery.

[0065] A prediction device for the voltage of a secondary battery after the small - current charging ends during formation provided by an embodiment of the present invention includes a first test unit, a selection unit, a second test unit, a fitting unit, and a prediction unit.

[0066] The first test unit is used to obtain a plurality of battery cells that have completed liquid injection and have undergone high - temperature standing, and test to obtain the voltage of the battery cells after high - temperature standing; the selection unit is used to select the battery cells within the preset voltage range based on the voltage of the battery cells after high - temperature standing. There are multiple preset voltage ranges, and a set number of battery cells are selected within each preset voltage range; the second test unit is used to, for the selected battery cells, test the voltage after the small - current charging ends during the formation process to obtain the voltage of the battery cells after the small - current charging ends during formation; the fitting unit is used to fit the correlation curve between the voltage of the battery cells after high - temperature standing and the voltage after the small - current charging ends during formation based on the tested voltage of the battery cells after high - temperature standing and the voltage after the small - current charging ends during formation; the prediction unit is used to obtain the voltage of the battery cell to be tested after the small - current charging ends during formation according to the fitted correlation curve and the voltage of the battery cell to be tested after high - temperature standing.

[0067] In the embodiment of the present invention, the correlation curve is a linear curve. The expression formula of the correlation curve is:

[0068] V1 = KV0 + B, where V1 represents the voltage after the end of the formation small current charging of the battery cell, V0 represents the voltage after the high-temperature static storage of the battery cell, and K and B represent the functional relationship between V1 and V0.

[0069] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features claimed herein.

[0070] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, and the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing device generate means for implementing the specified functions in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

Claims

1. A method for predicting the voltage after the end of small-current charging during the formation of a secondary battery, characterized in that, Specifically, it includes the following steps: Obtain multiple cells after liquid injection is completed and high-temperature standing, and test to obtain the voltage of the cells after high-temperature standing; Based on the voltage of the cells after high-temperature standing, select the cells located within a preset voltage range. There are multiple preset voltage ranges, and a set number of cells are selected within each preset voltage range; For the selected cells, test the voltage after the end of small-current charging during the formation process to obtain the voltage of the cells after the end of small-current charging during formation; Based on the voltage of the cells after high-temperature standing and the voltage after the end of small-current charging during formation obtained by testing, fit to obtain the correlation curve between the voltage of the cells after high-temperature standing and the voltage after the end of small-current charging during formation; According to the fitted correlation curve and the voltage of the cell to be tested after high-temperature standing, obtain the voltage of the cell to be tested after the end of small-current charging during formation, so as to characterize the degree of side reaction during the formation process of the secondary battery; Wherein, the voltage after the end of small-current charging during formation is the voltage of the cell after the end of small-current charging during the formation process; Wherein, the high-temperature standing is to stand the cells after primary liquid injection for 15 to 36 hours, and the ambient temperature of the cells is 45 ± 5°C; 2. The method for predicting the voltage after the small current charging of formation of a secondary battery according to claim 1, wherein The specific steps for selecting the cells located within the preset voltage range based on the voltage of the cells after high-temperature standing are as follows: Define multiple preset voltage ranges, and the voltage ranges of each preset voltage range are different; According to the preset voltage range where the voltage of the cells after high-temperature standing is located, select a set number of cells within each preset voltage range; 3. The method for predicting the voltage after the end of small current charging during the formation of a secondary battery according to claim 1, wherein: The correlation curve is a linear curve; 4. The prediction method for the voltage after the end of small-current charging during the formation of a secondary battery according to claim 3, characterized in that, The expression formula of the correlation curve is: V1 = KV0 + B, Wherein, V1 represents the voltage of the cell after the end of small-current charging during formation, V0 represents the voltage of the cell after high-temperature standing, and K and B represent the functional relationship between V1 and V0; 5. The prediction method for the voltage after the end of small current charging during the formation of a secondary battery according to claim 4, wherein: The value range of K is 0.05 to 0.15, the value range of B is 2.92 to 2.928, and the correlation coefficient R of the correlation curve 2 has a value of 0.7 to 0.98, and R 2 represents the correlation between V1 and V0.

6. The method for predicting the voltage after the end of small current charging during the formation of a secondary battery according to claim 1, wherein: For the voltage of the cell after the end of small-current charging during formation, wherein the current magnitude is 0.02C to 0.1C, and the charging time is 0.5 to 2.5 hours; 7. The prediction method for the voltage after the end of small-current charging during the formation of a secondary battery according to claim 1, characterized in that, The secondary battery includes a lithium-ion battery, a polymer lithium-ion battery, a nickel-metal hydride battery, a nickel-cadmium battery, and a lead-acid battery; 8. A prediction device for the voltage after the end of small-current charging during the formation of a secondary battery, characterized in that, It includes: The first test unit is used to obtain multiple cells after liquid injection is completed and high-temperature standing, and test to obtain the voltage of the cells after high-temperature standing; The selection unit is used to select the cells located within the preset voltage range based on the voltage of the cells after high-temperature standing. There are multiple preset voltage ranges, and a set number of cells are selected within each preset voltage range; The second test unit is used to test the voltage after the end of small-current charging during the formation process for the selected cells to obtain the voltage of the cells after the end of small-current charging during formation; The fitting unit is used to fit the correlation curve between the voltage of the cells after high-temperature standing and the voltage after the end of small-current charging during formation based on the voltage of the cells after high-temperature standing and the voltage after the end of small-current charging during formation obtained by testing; The prediction unit is used to obtain the voltage of the cell to be tested after the end of small-current charging during formation according to the fitted correlation curve and the voltage of the cell to be tested after high-temperature standing, so as to characterize the degree of side reaction during the formation process of the secondary battery; Among them, the voltage after the end of the small-current charging during formation is the voltage of the battery cell after the end of the small-current charging during formation. Among them, the high-temperature standing means that the battery cell after the first liquid injection is left standing for 15 to 36 hours, and the ambient temperature of the battery cell is 45 ± 5 °C.

9. The prediction device for the voltage after the end of small-current charging during the formation of a secondary battery according to claim 8, wherein: The correlation curve is a linear curve.

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