A method and apparatus for determining the age of a battery

Abstract

The application discloses a battery aging degree determination method and device. A soft package battery is tested to obtain voltage-battery capacity V-Q data of the soft package battery. A button half battery is tested to obtain V-Q data of the button half battery. Based on the V-Q data of the soft package battery and the V-Q data of the button half battery, differential voltage analysis is performed on discharge characteristics of an aged soft package battery to obtain a model representing a loss degree of battery active material. An aging path parameter is obtained based on the model representing the loss degree of the battery active material. The aging path parameter represents a degradation degree of electrode material in percentage form. Based on the aging path parameter, a lithiumation state of the aged battery is determined. The application can accurately quantify the influence of active material loss on battery aging.

Description

Technical Field

[0001] This application relates to the field of electric drive and hybrid drive technology, specifically to a method and apparatus for determining the degree of battery aging. Background Technology

[0002] With the widespread application of lithium-ion batteries in electric vehicles and other fields, battery aging has become a key factor affecting their performance and lifespan. Battery aging is mainly manifested in the degradation of active materials and the gradual reduction of capacity. Currently, techniques such as voltage differential analysis and electrochemical impedance spectroscopy are commonly used to study battery aging, but a standardized method that can accurately quantify the impact of active material loss on battery aging is lacking. Summary of the Invention

[0003] This application provides a method and apparatus for determining the degree of battery aging, which can accurately quantify the impact of active material loss on battery aging. The technical solution is as follows.

[0004] In a first aspect, a method for determining the degree of battery aging is provided, the method comprising:

[0005] The pouch cell battery was tested to obtain its voltage-quantity (VQ) data.

[0006] The button cell was tested to obtain the VQ data of the button cell.

[0007] Based on the VQ data of the pouch cell and the VQ data of the coin cell, differential voltage analysis (DVA) is performed on the discharge characteristics of the aged pouch cell to obtain a model characterizing the degree of loss of battery active materials.

[0008] Aging path parameters are obtained based on the model characterizing the degree of loss of battery active materials, and the aging path parameters express the degree of degradation of electrode materials in percentage form.

[0009] Based on the aging path parameters, the lithiation state of the aged battery is determined.

[0010] In some embodiments, the differential voltage analysis of the discharge characteristics of the aged pouch cell based on the VQ data of the pouch cell and the VQ data of the coin cell half-cell, to obtain a model characterizing the degree of loss of battery active materials, includes:

[0011] Based on the VQ data of the pouch battery, the dV / dQ curve of the pouch battery is obtained. The dV / dQ curve of the pouch battery represents the voltage derivative with respect to capacity of the pouch battery.

[0012] Based on the VQ data of the button half-cell, the dV / dQ curve of the button half-cell is obtained. The dV / dQ curve of the button half-cell represents the derivative of the voltage with respect to the capacity of the button half-cell.

[0013] Based on the dV / dQ curves of the pouch cell and the dV / dQ curves of the coin cell, a model characterizing the degree of loss of battery active materials is determined.

[0014] In some embodiments, the formula for the model characterizing the degree of loss of battery active materials is as follows:

[0015]

[0016] in, 老化电池 The dV / dQ curve of a pouch cell characterizing calendar aging or cycle aging. 全新阳极 The dV / dQ curve characterizing a coin half-cell with a novel anode. 全新阴极 The dV / dQ curve characterizing a coin half-cell with a novel cathode, wherein the aging path parameters include a in the formula above. C a A b C and b A a C a represents the percentage of cathode active material remaining at the end of the lifespan of a pouch cell. A b represents the percentage of remaining anode active material at the end of the pouch cell's lifespan. C b represents the number of lithium ions stored in the cathode when the pouch cell is fully charged. A This indicates the number of lithium ions still needed for the remaining active anode of a pouch cell to reach full lithiation in a fully charged state.

[0017] In some implementations, the aging path parameters include a A a C and b A a A This indicates the percentage of remaining anode active material at the end of the lifespan of a pouch cell, a. C b represents the percentage of cathode active material remaining at the end of the pouch cell's lifespan. A This represents the number of lithium ions still needed for the remaining active anode of a pouch cell to reach full lithiation under full charge. The aging path parameters obtained based on the model characterizing the degree of loss of battery active materials include:

[0018] Based on the model characterizing the degree of loss of battery active materials, the dV / dQ curve of the pouch cell, and the dV / dQ curve of the coin cell, the aging path parameters are obtained using the following formula;

[0019]

[0020] b A = Capacity at the end of the pouch cell's life in the dV / dQ curve - Capacity at the end of the anode half-cell's life.

[0021] In some implementations, determining the lithiation state of the aged battery based on the aging path parameters includes:

[0022] Based on the capacity of the new anode half-cell, the capacity of the new pouch cell, and the aging path parameters, the lithium-ion loss of the anode half-cell is determined.

[0023] The lithiation state of the aged battery is determined based on the amount of lithium-ion loss in the anode half-cell.

[0024] In some embodiments, determining the lithiation state of the aged battery based on the lithium-ion loss of the anode half-cell includes:

[0025] Based on the capacity of the new pouch cell, the battery capacity measured by the aged cell, and the amount of lithium ion loss of the pouch cell, the number of irreversible lithium ions trapped in the aged anode is determined.

[0026] The lithiation state of an aged battery is determined based on the irreversible number of lithium ions, the capacity of a brand new pouch cell, the ratio of anode capacity to the total capacity of the pouch cell, and the percentage of degraded anode active material at the end of the pouch cell's life.

[0027] In some embodiments, after determining the lithium-ion loss of the anode half-cell based on the capacity of the new anode half-cell, the capacity of the new pouch cell, and the aging path parameters, the method further includes:

[0028] Based on the lithium-ion loss of the anode half-cell and the excess capacity of the anode, the translational capacity of the anode lithium half-cell is obtained, wherein the excess capacity of the anode is the difference between the maximum capacity of the anode-lithium half-cell and the maximum capacity of the new cathode-lithium half-cell.

[0029] The VQ data of the coin cell is calibrated by translation based on the translation capacity of the anode lithium half-cell.

[0030] Based on the VQ data of the button half-cell after translation calibration, the relationship between the full cell capacity loss, unused cathode capacity, and unused anode capacity of the button half-cell is determined.

[0031] In some embodiments, testing the pouch cell to obtain voltage-capacity (VQ) data includes:

[0032] Dynamic stress tests were conducted on the pouch cells in a 35°C hot chamber, and cyclic aging tests were performed at 100% depth of discharge. The capacity, resistance, and power changes of the cyclically aged pouch cells were monitored to obtain the discharge VQ curve of the cyclically aged pouch cells.

[0033] The pouch cell was subjected to calendar aging at 80% charge in a 45°C hot chamber, and the capacity, resistance and power changes of the calendar-aged pouch cell were monitored to obtain the discharge VQ curve of the calendar-aged pouch cell.

[0034] The testing of the button cell to obtain its VQ data includes:

[0035] The button cell was subjected to cyclic testing at room temperature, and the capacity, resistance and power changes of the cyclically aged button cell were monitored to obtain the discharge VQ curve of the cathode in the voltage range of 3 to 4.2V and the charging VQ curve of the anode in the voltage range of 5mV to 1.5V.

[0036] In some embodiments, the button half-cell is obtained by extracting electrode materials from brand-new pouch cells, calendar-aged pouch cells, and cycle-aged pouch cells, removing one side of the electrode material from the extracted electrode material using N-methylpyrrolidone, and then assembling the remaining electrode material with metallic lithium.

[0037] Secondly, a device for determining the degree of battery aging is provided, the device comprising:

[0038] The testing module is used to test the pouch cell to obtain the voltage-capacity (VQ) data of the pouch cell; and to test the coin cell to obtain the VQ data of the coin cell.

[0039] The analysis module is used to perform differential voltage analysis on the discharge characteristics of the aged pouch battery based on the VQ data of the pouch battery and the VQ data of the button half-cell, so as to obtain a model characterizing the degree of loss of battery active materials.

[0040] The determination module is used to obtain aging path parameters based on the model characterizing the degree of loss of battery active materials, wherein the aging path parameters express the degree of degradation of electrode materials in percentage form; and to determine the lithiation state of the aged battery based on the aging path parameters.

[0041] In some embodiments, the analysis module is used to obtain the dV / dQ curve of the pouch cell based on the VQ data of the pouch cell, the dV / dQ curve of the pouch cell representing the voltage derivative with respect to capacity of the pouch cell; to obtain the dV / dQ curve of the coin cell based on the VQ data of the coin cell, the dV / dQ curve of the coin cell representing the voltage derivative with respect to capacity of the coin cell; and to determine a model representing the degree of loss of battery active materials based on the dV / dQ curves of the pouch cell and the dV / dQ curves of the coin cell.

[0042] In some implementations, the aging path parameters include a A a C and b A a A This indicates the percentage of remaining anode active material at the end of the lifespan of a pouch cell, a. C b represents the percentage of cathode active material remaining at the end of the pouch cell's lifespan. A The analysis module, representing the number of lithium ions still missing from the remaining active anode of the pouch battery to reach full lithiation under full charge, is used to obtain aging path parameters using the following formula based on the model characterizing the degree of loss of battery active materials, the dV / dQ curve of the pouch battery, and the dV / dQ curve of the coin cell.

[0043]

[0044]

[0045] b A = Capacity at the end of the pouch cell's life in the dV / dQ curve - Capacity at the end of the anode half-cell's life.

[0046] In some implementations, the determining module is used to determine the lithium-ion loss of the anode half-cell based on the capacity of the new anode half-cell, the capacity of the new pouch cell, and the aging path parameters; and to determine the lithiation state of the aged cell based on the lithium-ion loss of the anode half-cell.

[0047] In some embodiments, the determining module is used to determine the number of irreversible lithium ions trapped in the aged anode based on the capacity of the new pouch battery, the battery capacity measured in the aged battery, and the amount of lithium ion loss in the pouch battery; and to determine the lithiation state of the aged battery based on the number of irreversible lithium ions, the capacity of the new pouch battery, the ratio of anode capacity to the total capacity of the pouch battery, and the percentage of degraded anode active material at the end of the pouch battery's life.

[0048] In some embodiments, the determining module is further configured to: obtain the translational capacity of the anode lithium half-cell based on the lithium-ion loss of the anode half-cell and the excess capacity of the anode, wherein the excess capacity of the anode is the difference between the maximum capacity of the anode-lithium half-cell and the maximum capacity of the new cathode-lithium half-cell; perform translational calibration on the VQ data of the button half-cell based on the translational capacity of the anode lithium half-cell; and determine the relationship between the complete battery capacity loss, unused cathode capacity, and unused anode capacity of the button half-cell based on the VQ data of the translated button half-cell after translational calibration.

[0049] In some embodiments, the test module is used to perform dynamic stress testing on the pouch cell in a 35°C hot chamber, cyclic aging testing at 100% depth of discharge, and monitor the capacity, resistance, and power changes of the cyclically aged pouch cell to obtain the discharge VQ curve of the cyclically aged pouch cell; to perform calendar aging on the pouch cell at 80% state of charge in a 45°C hot chamber, and monitor the capacity, resistance, and power changes of the calendar-aged pouch cell to obtain the discharge VQ curve of the calendar-aged pouch cell; and to perform cyclic testing on the coin cell at room temperature, and monitor the capacity, resistance, and power changes of the cyclically aged coin cell to obtain the discharge VQ curve of the coin cell cathode in the voltage range of 3–4.2V and the charging VQ curve of the anode in the voltage range of 5mV–1.5V.

[0050] In some embodiments, the button half-cell is obtained by extracting electrode materials from brand-new pouch cells, calendar-aged pouch cells, and cycle-aged pouch cells, removing one side of the electrode material from the extracted electrode material using N-methylpyrrolidone, and then assembling the remaining electrode material with metallic lithium.

[0051] Thirdly, a computer device is provided, comprising a processor coupled to a memory storing at least one computer program instruction, the at least one computer program instruction being loaded and executed by the processor to enable the computer device to implement the method provided by the first aspect or any alternative embodiment of the first aspect. Specific details of the computer device provided in the third aspect can be found in the first aspect or any alternative embodiment of the first aspect, and will not be repeated here.

[0052] Fourthly, a computer-readable storage medium is provided, which stores at least one instruction that, when executed on a computer, causes the computer to perform the method provided in the first aspect or any alternative method of the first aspect.

[0053] Fifthly, a computer program product is provided, the computer program product comprising one or more computer program instructions, which, when loaded and run by a computer, cause the computer to perform the method provided in the first aspect or any alternative method of the first aspect.

[0054] This application provides a method for quantitatively assessing battery aging based on the percentage loss of active materials. This method establishes a mathematical model of the degree of loss of battery active materials through differential voltage analysis and expresses the degree of degradation of electrode materials as a percentage, thereby quantifying the overall aging degree of the battery. This serves as an indicator to assist in evaluating the battery's health status and improve its application in electric vehicles. Attached Figure Description

[0055] Figure 1 This is a flowchart of a method for determining the degree of battery aging provided in an embodiment of this application;

[0056] Figure 2 This is a schematic diagram of a battery VQ curve provided in an embodiment of this application;

[0057] Figure 3 This application provides a battery dQ / dV vs. V curve diagram.

[0058] Figure 4 This is a schematic diagram of the correlation between an aged soft-pack battery and a brand-new semi-button battery provided in an embodiment of this application;

[0059] Figure 5 This is a schematic diagram of a device for determining the degree of battery aging provided in an embodiment of this application;

[0060] Figure 6 This is a schematic diagram of the structure of a computer device provided in an embodiment of this application. Detailed Implementation

[0061] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0062] Please refer to the attached document. Figure 1 , attached Figure 1 This is a flowchart illustrating a method for determining the degree of battery aging provided in an embodiment of this application. Figure 1 The method shown includes the following steps.

[0063] Step S110: Test the pouch cell to obtain the voltage-capacity VQ data of the pouch cell; test the coin cell to obtain the VQ data of the coin cell.

[0064] Testing pouch cells facilitates obtaining the overall voltage-capacity characteristics of the battery, including all electrodes. Testing coin cells facilitates separate testing of the voltage-capacity characteristics of the negative and positive electrodes.

[0065] First, pouch cell testing was conducted. To minimize the impact of battery expansion during aging, all pouch cells were compressed between two steel plates. Two cells underwent dynamic stress testing (DST) in a 35°C hot chamber, followed by cycle testing at 100% depth of discharge. The other cell was calendar-aged at 80% state of charge (SOC) in a 45°C hot chamber, with its capacity (Ah, 1C), resistance change, and 20s power change monitored. The discharge curves of the pouch cells were obtained, as shown in the attached figure. Figure 2 The dashed line in (b) indicates this. For example, the test environment for each battery during the pouch battery testing process is shown in Table 1 below.

[0066] Table 1

[0067] Battery Name temperature operate Capacity (1C) [Ah] New battery B1 N / A N / A <![CDATA[Q 0,全新B1 =15.09]]> Calendar aging battery B1 45℃ Maintain 80% SOC <![CDATA[Q 老化，日历B1 =12.20]]> Cyclic Aging Battery B2 35℃ 100% DST <![CDATA[Q 老化，循环B2 =9.10]]> Cyclic Aging Battery B1 35℃ 100% DST <![CDATA[Q 老化，循环B1 =8.81]]>

[0068] Next, button half-cell testing was conducted. Electrode materials were extracted from brand-new pouch cells, calendar-aged pouch cells, and cycle-aged pouch cells. One side of the extracted electrode material was removed using N-methylpyrrolidone, and the remaining electrode material was assembled with lithium metal to obtain button half-cells. Obtaining button half-cells by extracting electrode materials from pouch cells facilitates comparison of the effects of aging on the battery during testing.

[0069] Electrode loading (cathode and anode, in g / cm³) 2 The mass of the current collector was calculated by subtracting its mass from the total mass (assuming it is 100% active material). The button cell half-cell consists of a disc electrode, a new separator, a new electrolyte, and polished lithium metal foil. Cycling tests were conducted on the button cell at room temperature, and the discharge curves of the cathode in the voltage range of 3–4.2V at a C / 10 rate are shown in the attached figure. Figure 2 The charging VQ curves for the upper half of the middle section (a) and the anode in the voltage range of 5mV to 1.5V are shown in the attached figure. Figure 2 The lower half of (a). (In the appendix) Figure 2 In section (b), the anode curve needs to be shifted to the left by a specific value to reflect the correlation between coin cell and pouch cell measurements (these shift values ​​are derived from differential voltage analysis). In battery design, to prevent lithium deposition, the anode capacity is typically larger than the cathode capacity; the excess capacity Q of the anode can be obtained through data fitting methods. 过量阳极 That is, by subtracting the maximum capacity of a brand new cathode-lithium half-cell from the maximum capacity of the anode-lithium half-cell, for example, with Figure 2The example shown in (b) is relative to Figure 2 (a) In this regard, the novel anode-lithium half-cell curve shifted 0.22 Ah to the left to compensate for the excess capacity of the anode, Q 过量阳极 =0.22Ah.

[0070] Appendix Figure 2 (a) Discharge curve of the cathode coin cell (relative to lithium metal) between 4.2V and 3V (upper solid line); charging curve of the anode coin cell between 5mV and 1.5V (lower solid line). Figure 2 In comparison, (b) shows the discharge curve (dashed line) of a pouch cell; the curve for the anode half-cell has been shifted to the right by a specific value based on calculations. (Appendix) Figure 2 (c) Based on the appendix Figure 2 The changes in cathode and anode capacity in the full cell in (b).

[0071] Step S120: Perform dV / dQ differential voltage analysis (DVA) on the discharge characteristics of the aged pouch cell to obtain a model characterizing the degree of loss of the battery's active materials; obtain aging path parameters based on the model characterizing the degree of loss of the battery's active materials. The aging path parameters express the degree of degradation of the electrode materials in percentage form. By obtaining the aging path parameters, the path of active lithium loss is theoretically determined.

[0072] Existing VQ data can be converted into dQ / dV curves representing charge or discharge profiles, where peaks always correspond to changes in the relationship between (de)lithiation (i.e., capacity) and voltage. Peaks in the dQ / dV / V curve indicate phase equilibrium (i.e., capacity change with voltage), and dQ / dV is the derivative of capacity change Q with respect to voltage V. Peaks in the curve represent the maximum rate of capacity change with voltage within a certain voltage range, which typically indicates a phase transition or electrochemical reaction in the electrode material. Compared to the dQ / dV / V curve, the voltage-capacity derivative dV / dQ is better suited for understanding the relationship between half-cells and full cells, since the voltage of a full cell is defined as:

[0073] V Cell =V 阴极 -V 阳极 ;

[0074] (dV / dQ) Cell It can be expressed by the following formula, and the peak value in the dV / dQ curve of the full cell can be easily assigned to the peak values ​​of the cathode and anode in the coin half-cell:

[0075]

[0076] The dV / dQ curve of a full cell should correspond to the combined performance of the dV / dQ curves of the cathode and anode. If a graphite anode half-cell is only discharged (lithiated) to 80% of its full capacity and then fully charged, the entire curve will shift 20% to the left compared to the standard dV / dQ curve, with the peak position remaining essentially unchanged. Conversely, if the total mass of graphite is reduced to two-thirds of the reference value, both the peak position and the peak-to-peak position will change. Mathematically, the former curve can be derived from the x-value of the standard curve (e.g., in Li). x The curve for the latter can be obtained by subtracting 20% ​​of the full capacity from the x-value in C6, while the curve for the latter can be obtained by multiplying the x-value of the standard curve by 2 / 3, as shown in the appendix. Figure 3 (a). From a chemical perspective, the first case simulates the loss of active lithium ions when the active material is intact, while the second case simulates the loss of active material.

[0077] In battery design, the anode capacity is typically greater than the cathode capacity. To prevent lithium deposition, the anode's dV / dQ curve needs to shift to the left to compensate for the excess capacity and align it with the cathode's dV / dQ curve. This is because a brand-new anode will never reach full lithiation when cycling a brand-new full cell. This capacity shift manifests as a "slippage lithiation state" in the electrode material during battery cycling. The excess capacity of the anode can be obtained through data fitting methods.

[0078] The C / 10 discharge curves of pouch cells and half-cells are used to create dV / dQ versus Q curves, as shown in the attached figure. Figure 3 (b) The discharge curve typically contains approximately 300 data points. The dV / dQ curve is smoothed using a 5-point moving average. To compare the data for pouch cells with those for coin cells, the capacity of the coin cell needs to be normalized to the pouch cell capacity by multiplying by a scaling factor, i.e., -Q0×ΔV / ΔAh, where Q0 is the capacity (Ah) of a brand new pouch cell at a 1C rate, thus normalizing the half-cell voltage-capacity ratio to the pouch cell capacity.

[0079] Appendix Figure 3 In the diagram (a), the black line represents the standard complete lithiation and complete delithiation processes; the red line represents the complete lithiation and complete delithiation processes after 80% lithiation; and the blue line represents the complete lithiation and complete delithiation processes when the graphite mass is reduced to 2 / 3. (See attached diagram.) Figure 3 In (b), the black line represents the dV / dQ and Q curves extracted from the discharge process of a brand new pouch cell, the red line represents the dV / dQ and Q curves extracted from the charging process of the anode of a button half-cell, and the blue line represents the dV / dQ and Q curves extracted from the cathode discharge process (relative to lithium).

[0080] All these mathematical operations can be performed in Microsoft Excel or by developing a fitting tool to obtain the fitting results, thus yielding the dV / dQ curves of the correlation between aged pouch cells and brand-new semi-button cells, as shown in the attached figure. Figure 4 .

[0081] Appendix Figure 4 Figure (a) shows the correlation between the dV / dQ curves of the calendar-aged pouch cell B1 and its corresponding mathematically transformed novel cathode and anode coin half-cells, indicating that approximately 2.8 Ah of pouch cell capacity is used for various side reactions to grow the SEI layer. (Appendix) Figure 4 Figure (b) shows the correlation between the dV / dQ curves of the cycle-aged pouch cell B1 and its corresponding mathematically transformed novel cathode and anode coin half-cells. Only 88% and 85% of the active material remained at the cathode and anode, respectively. 3.9 Ah of active lithium ions were used to grow the SEI layer. Figure 4 Figure (c) shows the correlation between the dV / dQ curves of the cycle-aged pouch cell B2 and its corresponding mathematically transformed novel cathode and anode coin half-cells. The cathode and anode retain 85% and 83% of their active material, respectively, and have 3.5 Ah of active lithium ions available for SEI layer growth. Figure 4 The dQ / dV curve of the cycle-aged battery B2, as shown, has a significantly smaller area under the peak at 3.5V than that of the fresh battery, indicating anode loss. (See attached image.) Figure 4 Image (d) shows the cyclically aged anode B2 at full battery discharge, indicating that highly lithiated regions still exist and some lithium ions are trapped in the anode.

[0082] Through mathematical transformation, the following formula theoretically establishes the correlation between the dV / dQ curves of aged pouch cells and brand-new semi-button cells, quantifying the aging path. Subtraction ("left shift") of the curve signifies the loss of active lithium ions, while multiplication ("compression") signifies the loss of active material.

[0083]

[0084] Here, it is assumed that the differential value dV / dQ depends only on the active material and remains unchanged for different types of battery structures. The aging path parameters are as follows:

[0085] a C 1-a represents the percentage of cathode active material remaining at the end of the life of a pouch cell. C That is, the percentage of degraded cathodes.

[0086] a A 1-a represents the percentage of remaining anode active material at the end of the life of a pouch cell. A That is, the percentage of degraded anodes.

[0087] b C [Ah] represents the number of lithium ions stored in the cathode when the pouch cell is fully charged.

[0088] b A [Ah] represents the number of lithium ions that the remaining active anode of the pouch cell would still lack to reach a "fully lithiated state" under full charge (note that the interpretation of the parameter is based on the discharge process of a complete cell).

[0089] Appendix Figure 4 The original dV / dQ curves of the full pouch cell and the normalized dV / dQ curves of the half cell are shown. By analyzing the dV / dQ curves of the aged pouch cell, the remaining percentage of active material in the cathode and anode and the amount of lithium ions consumed during aging can be determined [Ah].

[0090] The remaining percentage of active material in the cathode is a. C and the remaining percentage of active material in the anode. A They are respectively:

[0091]

[0092] Then, due to the over-design of the anode capacity, it needs to be shifted (leftward by b). A The [Ah]) anode half-cell curve is used for standardization to ensure that its capacity is consistent with that of a pouch cell.

[0093] b A = Capacity at the end of the pouch cell's life in the dV / dQ curve - Capacity at the end of the anode half-cell's life;

[0094] For example, regarding calendar-aged batteries, see appendix. Figure 4 (a) The original dV / dQ curve of the new cathode needs to be multiplied by a. C To standardize to ~93%, the dV / dQ curve of the original brand new anode must be shifted to the left by b. A ~2.8Ah, to match the dV / dQ curve of calendar-aged batteries. 2.8Ah is almost equal to the capacity reduction (Q) measured in all-pouch batteries. 0,全新B1 -Q 日历老化B1 This result indicates that in calendar-aged cells, all the capacity loss (approximately 2.8 Ah) is used for various side reactions to grow the SEI layer. Using a similar strategy, aging path parameters for other cycle / calendar-aged cells can be obtained, as shown in the attached figure. Figure 4 (b) With only 88% and 85% of the active material remaining at the cathode and anode, respectively, 3.9 Ah of active lithium ions were used to grow the SEI layer. C ≈0.88,b C ≈0Ah,aA ≈0.85,b A ≈3.9Ah, with Figure 4 (c)a C ≈0.85,b C ≈0Ah,a A ≈0.83,b A ≈3.5Ah.

[0095] Step S130: Calculate the lithium-ion loss Q of the anode half-cell. loss,阳极半电池 .

[0096] The lithium-ion loss of a pouch cell can be converted into the lithium-ion loss of an anode half-cell using the following formula.

[0097]

[0098] Q 全新阳极 [mAh / cm^2] is the capacity of a brand new anode half-cell as measured at C / 10.

[0099] |b A |:[Ah] Lithium-ion loss in pouch cells caused by side reactions.

[0100] Q 全新电池 [Ah] is the capacity of a brand new pouch cell measured at C / 10.

[0101] For example:

[0102] Appendix Figure 4 (a): The amount of lithium-ion loss in the anode half-cell is

[0103] Appendix Figure 4 (b): The amount of lithium-ion loss in the anode half-cell is

[0104] Appendix Figure 4 (a): The amount of lithium-ion loss in the anode half-cell is

[0105] Step S140: Calculate the translational capacity ΔQ of the anode lithium half-cell in the VQ diagram. calibration .

[0106] In step S110, the anode curve needs to be shifted to the left by a specific value ΔQ. calibration To reflect the correlation between button half-cell measurements and pouch cell measurements:

[0107] ΔQ calibration =Q loss,阳极半电池 +Q 过量阳极;

[0108] For example, appendix Figure 2 (b):

[0109] New battery B1 anode half-cell: Curve shifted to the left by ΔQ calibration =0 + 0.22 = 0.22Ah.

[0110] Calendar aging B1 anode half-cell: Curve shifted to the left by ΔQ calibration =0.38+0.22=0.6Ah.

[0111] Cyclic aging of B2 anode half-cell: Curve shifted to the left by ΔQ calibration =0.52+0.22=0.74Ah.

[0112] Cyclic aging of B1 anode half-cell: Curve shifted to the left by ΔQ calibration =0.47 + 0.22 = 0.69 Ah.

[0113] The VQ curve, after translation calibration, can semi-quantitatively determine the relationship between the complete battery capacity loss, unused cathode capacity, and unused anode capacity of a button cell, as shown in the attached figure. Figure 2 (c) Since the coin cell is cycled under conditions of fresh electrolyte solution and unlimited lithium, the capacity loss obtained here represents only the loss of active material. The capacity loss of the cathode / anode material in the coin cell is compared with that in the pouch cell to determine the impact of active material degradation on calendar-aged or cycle-aged batteries.

[0114] Step S150: Determine the lithiation state of the aged battery.

[0115] Determine the lithiation state S of the degraded anode 阳极锂化 .

[0116] First, determine the number Q of irreversibly trapped lithium ions in the aging anode. 不可逆锂离子 :

[0117] Q 不可逆锂离子 =(Q0-Q 老化 )-|b A |;

[0118] Q0: New soft-pack battery capacity [Ah].

[0119] Q 老化 : Battery capacity [Ah] measured from an aged battery.

[0120] Calculate the lithiation state S of the degraded anode 阳极锂化 This refers to the lithium-ion state of an aged battery.

[0121]

[0122] r 阳极容量 The ratio of anode capacity to pouch cell capacity, here 1.1, with excess carbon used to ensure that its capacity limit is not reached at the end of charging, thus avoiding lithium deposition.

[0123] This embodiment enables rapid quantification of battery aging through precise electrochemical testing and model comparison. The method is simple to operate and, as an auxiliary evaluation tool, can be integrated with existing battery management systems (BMS) or other health monitoring tools. Subsequently, without disassembling the battery, external data obtained through electrochemical analysis (such as voltage, charge-discharge curves, etc.) can be matched with the mathematical aging model established in this embodiment to provide a quantitative assessment of the battery's aging level.

[0124] Figure 5 This is a schematic diagram of a battery aging determination device provided in an embodiment of this application. The device 500 includes:

[0125] Test module 510 is used to test pouch cells to obtain voltage-capacity VQ data of pouch cells; and to test button cells to obtain VQ data of button cells.

[0126] Analysis module 520 is used to perform differential voltage analysis on the discharge characteristics of aged pouch cells based on VQ data of pouch cells and VQ data of coin cells, so as to obtain a model characterizing the degree of loss of battery active materials.

[0127] The determination module 530 is used to obtain aging path parameters based on a model characterizing the degree of loss of battery active materials. The aging path parameters express the degree of degradation of electrode materials in percentage form. Based on the aging path parameters, the lithiation state of the aged battery is determined.

[0128] In some implementations, the analysis module 520 is used to obtain the dV / dQ curve of the pouch cell based on the VQ data of the pouch cell, the dV / dQ curve of the pouch cell representing the voltage derivative with respect to capacity of the pouch cell; to obtain the dV / dQ curve of the coin cell based on the VQ data of the coin cell, the dV / dQ curve of the coin cell representing the voltage derivative with respect to capacity of the coin cell; and to determine a model representing the degree of loss of battery active material based on the dV / dQ curves of the pouch cell and the dV / dQ curves of the coin cell.

[0129] In some implementations, the aging path parameters include a A a C and b A a A This indicates the percentage of remaining anode active material at the end of the lifespan of a pouch cell, a.C b represents the percentage of cathode active material remaining at the end of the pouch cell's lifespan. A The analysis module 520 represents the number of lithium ions that the remaining active anode of the pouch cell still lacks to reach full lithiation under full charge. It is used to obtain aging path parameters based on the model characterizing the degree of loss of battery active materials, the dV / dQ curve of the pouch cell, and the dV / dQ curve of the coin cell, using the following formula.

[0130]

[0131] b A = Capacity at the end of the pouch cell's life in the dV / dQ curve - Capacity at the end of the anode half-cell's life.

[0132] In some implementations, the determining module 530 is used to determine the lithium-ion loss of the anode half-cell based on the capacity of the new anode half-cell, the capacity of the new pouch cell, and aging path parameters; and to determine the lithiation state of the aged cell based on the lithium-ion loss of the anode half-cell.

[0133] In some implementations, the determining module 530 is used to determine the number of irreversible lithium ions trapped in the aged anode based on the capacity of the new pouch cell, the battery capacity measured in the aged cell, and the amount of lithium ion loss in the pouch cell; and to determine the lithiation state of the aged cell based on the number of irreversible lithium ions, the capacity of the new pouch cell, the ratio of anode capacity to the total capacity of the pouch cell, and the percentage of degraded anode active material at the end of the pouch cell's life.

[0134] In some embodiments, the determining module 530 is further configured to obtain the translational capacity of the anode lithium half-cell based on the lithium-ion loss of the anode half-cell and the excess capacity of the anode, wherein the excess capacity of the anode is the difference between the maximum capacity of the anode-lithium half-cell and the maximum capacity of the new cathode-lithium half-cell; perform translational calibration on the VQ data of the coin cell based on the translational capacity of the anode lithium half-cell; and determine the relationship between the full cell capacity loss, unused cathode capacity, and unused anode capacity of the coin cell based on the VQ data of the translated coin cell after translational calibration.

[0135] In some embodiments, the test module 510 is used to perform dynamic stress testing on the pouch cell in a 35°C hot chamber, cyclic aging testing at 100% depth of discharge, and monitor the capacity, resistance, and power changes of the cyclically aged pouch cell to obtain the discharge VQ curve of the cyclically aged pouch cell; to perform calendar aging on the pouch cell at 80% state of charge in a 45°C hot chamber, and monitor the capacity, resistance, and power changes of the calendar-aged pouch cell to obtain the discharge VQ curve of the calendar-aged pouch cell; and to perform cyclic testing on the coin cell at room temperature, and monitor the capacity, resistance, and power changes of the cyclically aged coin cell to obtain the discharge VQ curve of the coin cell cathode in the voltage range of 3 to 4.2V and the charging VQ curve of the anode in the voltage range of 5mV to 1.5V.

[0136] In some implementations, the button half-cell is obtained by extracting electrode materials from brand new pouch cells, calendar-aged pouch cells, and cycle-aged pouch cells, removing one side of the electrode material from the extracted electrode material using N-methylpyrrolidone, and then assembling the remaining electrode material with metallic lithium.

[0137] Figure 6 This is a schematic diagram of the structure of a computer device provided in an embodiment of this application. The computer device 600 includes: a processor 601, which is coupled to a memory 602. The memory 602 stores at least one computer program instruction, which is loaded and executed by the processor 601 to enable the computer device 600 to perform... Figure 1 The method provided in the embodiments.

[0138] In some embodiments, a computer-readable storage medium is also provided, storing at least one instruction that, when executed on a computer, causes the computer to perform the above-described... Figure 1 The method provided in the embodiments.

[0139] In some embodiments, a computer program product is also provided, comprising one or more computer program instructions that, when loaded and executed by a computer, cause the computer to perform the aforementioned... Figure 1 The method provided in the embodiments.

[0140] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0141] A references B, which means that A is the same as B or A is a simple variation of B.

[0142] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any combination thereof. When implemented in software, they can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., a solid-state drive (SSD)).

[0143] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method of determining the degree of aging of a battery, characterized by, The method includes: The pouch cell was tested to obtain the voltage-capacity VQ data of the pouch cell. The button cell was tested to obtain the VQ data of the button cell. Based on the VQ data of the pouch cell and the VQ data of the coin cell, differential voltage analysis is performed on the discharge characteristics of the aged pouch cell to obtain a model characterizing the degree of loss of battery active materials. Aging path parameters are obtained based on the model characterizing the degree of loss of battery active materials, and the aging path parameters express the degree of degradation of electrode materials in percentage form. Based on the aging path parameters, the lithiation state of the aged battery is determined.

2. The method of claim 1, wherein, The differential voltage analysis of the discharge characteristics of the aged pouch cell, based on the VQ data of the pouch cell and the coin cell, is performed to obtain a model characterizing the degree of loss of the battery's active materials, including: Based on the VQ data of the pouch battery, the dV / dQ curve of the pouch battery is obtained. The dV / dQ curve of the pouch battery represents the voltage derivative with respect to capacity of the pouch battery. Based on the VQ data of the button half-cell, the dV / dQ curve of the button half-cell is obtained. The dV / dQ curve of the button half-cell represents the derivative of the voltage with respect to the capacity of the button half-cell. Based on the dV / dQ curves of the pouch cell and the dV / dQ curves of the coin cell, a model characterizing the degree of loss of battery active materials is determined.

3. The method of claim 2, wherein, The formula for the model characterizing the degree of loss of battery active materials is as follows: in, 老化电池 The dV / dQ curve of a pouch cell characterizing calendar aging or cycle aging. 全新阳极 The dV / dQ curve characterizing a coin half-cell with a novel anode. 全新阴极 The dV / dQ curve characterizing a coin half-cell with a novel cathode, wherein the aging path parameters include a in the formula above. C a A b C and b A a C a represents the percentage of cathode active material remaining at the end of the lifespan of a pouch cell. A b represents the percentage of remaining anode active material at the end of the pouch cell's lifespan. C b represents the number of lithium ions stored in the cathode when the pouch cell is fully charged. A This indicates the number of lithium ions still needed for the remaining active anode of a pouch cell to reach full lithiation in a fully charged state.

4. The method of claim 1, wherein, The aging path parameters include a A a C and b A a A This indicates the percentage of remaining anode active material at the end of the lifespan of a pouch cell, a. C b represents the percentage of cathode active material remaining at the end of the pouch cell's lifespan. A This represents the number of lithium ions still needed for the remaining active anode of a pouch cell to reach full lithiation under full charge. The aging path parameters obtained based on the model characterizing the degree of loss of battery active materials include: Based on the model characterizing the degree of loss of battery active materials, the dV / dQ curve of the pouch cell and the dV / dQ curve of the coin cell, the aging path parameters are obtained using the following formula; b A = capacity at end of pouch battery life - capacity at end of anode half-cell life in dV / dQ curve.

5. The method of claim 1, wherein, Determining the lithiation state of the aged battery based on the aging path parameters includes: Based on the capacity of the new anode half-cell, the capacity of the new pouch cell, and the aging path parameters, the lithium-ion loss of the anode half-cell is determined. The lithiation state of the aged battery is determined based on the amount of lithium-ion loss in the anode half-cell.

6. The method of claim 5, wherein, Determining the lithiation state of the aged battery based on the lithium-ion loss of the anode half-cell includes: Based on the capacity of the new pouch cell, the battery capacity measured by the aged cell, and the amount of lithium ion loss of the pouch cell, the number of irreversible lithium ions trapped in the aged anode is determined. The lithiation state of an aged battery is determined based on the irreversible number of lithium ions, the capacity of a brand new pouch cell, the ratio of anode capacity to the total capacity of the pouch cell, and the percentage of degraded anode active material at the end of the pouch cell's life.

7. The method of claim 5, wherein, After determining the lithium-ion loss of the anode half-cell based on the capacity of the new anode half-cell, the capacity of the new pouch cell, and the aging path parameters, the method further includes: Based on the lithium-ion loss of the anode half-cell and the excess capacity of the anode, the translational capacity of the anode lithium half-cell is obtained, wherein the excess capacity of the anode is the difference between the maximum capacity of the anode-lithium half-cell and the maximum capacity of the new cathode-lithium half-cell. The VQ data of the coin cell is calibrated by translation based on the translation capacity of the anode lithium half-cell. Based on the VQ data of the button half-cell after translation calibration, the relationship between the full cell capacity loss, unused cathode capacity, and unused anode capacity of the button half-cell is determined.

8. The method of claim 1, wherein, The testing of the pouch cell to obtain its voltage-capacity (VQ) data includes: Dynamic stress tests were conducted on the pouch cells in a 35°C hot chamber, and cyclic aging tests were performed at 100% depth of discharge. The capacity, resistance, and power changes of the cyclically aged pouch cells were monitored to obtain the discharge VQ curve of the cyclically aged pouch cells. The pouch cell was subjected to calendar aging at 80% charge in a 45°C hot chamber, and the capacity, resistance and power changes of the calendar-aged pouch cell were monitored to obtain the discharge VQ curve of the calendar-aged pouch cell. The testing of the button cell to obtain its VQ data includes: The button cell was subjected to cyclic testing at room temperature, and the capacity, resistance and power changes of the cyclically aged button cell were monitored to obtain the discharge VQ curve of the cathode in the voltage range of 3 to 4.2V and the charging VQ curve of the anode in the voltage range of 5mV to 1.5V.

9. The method of claim 1, wherein, The button half-cell is obtained by extracting electrode materials from brand new pouch cells, calendar-aged pouch cells, and cycle-aged pouch cells, removing one side of the electrode material from the extracted electrode material using N-methylpyrrolidone, and then assembling the remaining electrode material with metallic lithium.

10. An apparatus for determining the degree of aging of a battery, characterized by The device includes: The testing module is used to test the pouch cell to obtain the voltage-capacity (VQ) data of the pouch cell; and to test the coin cell to obtain the VQ data of the coin cell. The analysis module is used to perform differential voltage analysis on the discharge characteristics of the aged pouch battery based on the VQ data of the pouch battery and the VQ data of the button half-cell, so as to obtain a model characterizing the degree of loss of battery active materials. The determination module is used to obtain aging path parameters based on the model characterizing the degree of loss of battery active materials, wherein the aging path parameters express the degree of degradation of electrode materials in percentage form; and to determine the lithiation state of the aged battery based on the aging path parameters.

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