Lithium battery full-temperature-range DCR fitting test method and system based on multi-factor coupling

Abstract

The invention provides a lithium battery full-temperature-range DCR fitting test method and system based on multi-factor coupling, and relates to the technical field of lithium batteries, and the method comprises the steps: obtaining a to-be-tested lithium battery, carrying out the charge-discharge cycle under a set condition, and measuring the average discharge capacity as an initial capacity reference; the method comprises the following steps: carrying out multi-state-of-charge calibration on a lithium battery cell, adjusting the lithium battery cell to a set target SOC point, sequentially placing the lithium battery cell in different temperature environments to be stable, measuring the DCR value at each temperature, then carrying out cyclic aging on the lithium battery cell to different health states, and measuring the DCR values at each temperature and in different health states; based on the DCR values in different health states at different temperatures, utilizing an Arrhenius formula to fit the relation between the DCR values and the temperatures, introducing an SOC correction function and an SOH correction function, and constructing a three-dimensional DCR fitting model; and according to the fitting model, inputting the target temperature T, the SOC and the SOH, and outputting an estimated test DCR value.

Description

Technical Field

[0001] This disclosure relates to the field of lithium battery technology, specifically to a method and system for fitting and testing the full-temperature-range DCR of lithium batteries based on multi-factor coupling. Background Technology

[0002] The statements in this section are merely background information relating to this disclosure and do not necessarily constitute prior art.

[0003] Lithium-ion batteries, due to their high energy density, long cycle life, and low self-discharge rate, have become the preferred power source for electric vehicles, energy storage systems, and portable electronic devices. However, their performance and safety are highly dependent on the precise control of the Battery Management System (BMS). DC internal resistance (DCR), as one of the core parameters of lithium-ion batteries, directly affects the battery's power output capability, energy efficiency, temperature rise characteristics, and state of being. To comprehensively understand the behavioral characteristics of lithium-ion batteries under different operating conditions, DCR Maps have emerged, becoming a key database for BMS to achieve intelligent management. Without accurate DCR Maps, many advanced functions of the BMS (such as precise power limiting and SOH estimation) will be difficult to achieve or their accuracy will be significantly reduced. Lithium-ion battery DCR Maps are not only the cornerstone of BMS algorithms but also a core tool for achieving high-safety, long-life, and high-power battery systems. Therefore, improving the accuracy and speed of lithium-ion battery DCR testing is a primary choice. Especially within the full temperature range (e.g., -30°C to 60°C), changes in DCR are crucial to the accuracy of the Battery Management System (BMS).

[0004] Currently, the commonly used DCR testing methods mainly include: (1) pulse current method, which calculates DCR by measuring voltage drop through short-time high current discharge (such as 10s discharge pulse); (2) AC impedance method (EIS), which separates ohmic impedance and charge transfer impedance through spectrum analysis, but the equipment is complex and time-consuming; (3) HPPC (hybrid pulse power characteristic) test, which combines charge and discharge pulses to obtain DCR under different SOC, but requires multi-cycle testing. However, the above methods are all based on a single SOC point, only testing the DCR temperature change law under a certain fixed SOC, ignoring the nonlinear effect of SOC on DCR, and not considering the long-term effect of battery aging (SOH decay) on DCR. After battery aging, the internal resistance increases (such as DCR increasing by 20%~50% when SOH=80%), but the existing model still uses the new battery parameters and ignores dynamic temperature change conditions (such as cold start transient), resulting in inaccurate DCR prediction for dynamic scenarios (such as electric vehicle acceleration). Summary of the Invention

[0005] To address the aforementioned issues, this disclosure proposes a multi-factor coupled full-temperature-range DCR fitting test method and system for lithium batteries. By analyzing the coupled influence of SOC and SOH on DCR and conducting phased testing, a multi-factor coupled model is established to quantify the impact of SOC and SOH on the temperature change law of battery internal resistance, significantly improving the accuracy of full-temperature-range DCR prediction test.

[0006] According to some embodiments, the present disclosure adopts the following technical solutions: The multi-factor coupled full-temperature-range DCR fitting test method for lithium batteries includes: acquiring the lithium battery under test, performing charge-discharge cycles under set conditions, measuring the average discharge capacity, and using it as an initial capacity benchmark. The lithium battery cells were calibrated for multiple states of charge. The lithium battery cells were adjusted to the set target SOC point and then placed in different temperature environments for stabilization. The DCR value at each temperature was measured. The lithium battery cells were then cycled and aged to different health states, and the DCR value at each temperature and different health states was measured. Based on the DCR values ​​under different health states at various temperatures, the relationship between DCR values ​​and temperature is fitted using the Arrhenius formula. The SOC correction function and the SOH correction function are introduced to construct a three-dimensional DCR fitting model. Based on the fitted model, input the target temperature T, SOC, and SOH, and output the estimated test DCR value.

[0007] According to some embodiments, the present disclosure adopts the following technical solutions: A multi-factor coupled full-temperature-range DCR fitting test system for lithium batteries includes: The initialization module is used to acquire the lithium battery under test, perform charge-discharge cycles under set conditions, and measure the average discharge capacity as the initial capacity benchmark. The measurement module is used to perform multi-state-of-charge calibration on lithium battery cells. The lithium battery cells are adjusted to the set target SOC point, placed in different temperature environments for stabilization, and the DCR value at each temperature is measured. Then, the lithium battery cells are cycle-aged to different health states, and the DCR value at each temperature and different health states is measured. The fitting module is used to fit the relationship between DCR value and temperature based on DCR values ​​under different health states at various temperatures using the Arrhenius formula. It introduces the SOC correction function and the SOH correction function to construct a three-dimensional DCR fitting model. The prediction module is used to output the predicted test DCR value based on the fitted model, the input target temperature T, SOC and SOH.

[0008] According to some embodiments, the present disclosure adopts the following technical solutions: A computer program product includes a computer program that, when executed by a processor, implements the multi-factor coupled lithium battery full-temperature-range DCR fitting test method.

[0009] According to some embodiments, the present disclosure adopts the following technical solutions: A non-transitory computer-readable storage medium is provided for storing computer instructions, which, when executed by a processor, implement the aforementioned multi-factor coupled lithium battery full-temperature-range DCR fitting test method.

[0010] According to some embodiments, the present disclosure adopts the following technical solutions: An electronic device includes a processor, a memory, and a computer program; wherein the processor is connected to the memory, the computer program is stored in the memory, and when the electronic device is running, the processor executes the computer program stored in the memory to enable the electronic device to perform the aforementioned multi-factor coupled lithium battery full-temperature-range DCR fitting test method.

[0011] Compared with the prior art, the beneficial effects of this disclosure are as follows: The disclosed method for fitting DCR of lithium batteries across the entire temperature range based on multi-factor coupling models the degradation of SOC (20% / 50% / 80%) with SOH (State of Health) through multi-point SOC (20% / 50% / 80%) coupling. The SOC and SOH correction functions quantify the nonlinear effects, reducing the DCR prediction error rate from ±15% of the traditional method to within ±5%, thus greatly improving the accuracy of test prediction.

[0012] The disclosed method for full-temperature-range DCR fitting test of lithium batteries based on multi-factor coupling has a precise DCR-SOH three-dimensional fitting model that can dynamically adjust the BMS power limiting strategy to avoid over-discharge / overcharge of aging batteries and extend cycle life by about 20%, achieving high-precision and high-efficiency full-temperature-range DCR prediction.

[0013] The disclosed method for fitting the full-temperature-range DCR of lithium batteries based on multi-factor coupling solves the problems of long testing time and inaccuracy in DCR testing by testing the DCR at partial temperatures and fitting the full-temperature-range DCR based on the actual DCR. Attached Figure Description

[0014] The accompanying drawings, which form part of this disclosure, are used to provide a further understanding of this disclosure. The illustrative embodiments of this disclosure and their descriptions are used to explain this disclosure and do not constitute an undue limitation of this disclosure.

[0015] Figure 1 This is a flowchart of a multi-factor coupled lithium battery full-temperature-range DCR fitting test method according to an embodiment of the present disclosure. Detailed Implementation

[0016] The present disclosure will be further described below with reference to the accompanying drawings and embodiments.

[0017] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this disclosure. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0018] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this disclosure. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0019] Example 1 One embodiment of this disclosure provides a method for fitting and testing the full-temperature-range DCR of lithium batteries based on multi-factor coupling, the method steps of which include: Step 1: Obtain the lithium battery to be tested, perform charge-discharge cycles under set conditions, and measure the average discharge capacity as the initial capacity benchmark. Step 2: Perform multi-state-of-charge calibration on the lithium battery cells. Adjust the lithium battery cells to the set target SOC point, place them in different temperature environments for stabilization, measure the DCR value at each temperature, and then perform cycle aging on the lithium battery cells to different health states, measuring the DCR value at each temperature under different health states. Step 3: Based on the DCR values ​​under different health conditions at various temperatures, the relationship between DCR values ​​and temperature is fitted using the Arrhenius formula. The SOC correction function and the SOH correction function are introduced to construct a three-dimensional DCR fitting model. Step 4: Based on the fitted model, input the target temperature T, SOC and SOH, and output the estimated test DCR value.

[0020] As one embodiment, the multi-factor coupled lithium battery full-temperature-range DCR fitting test method disclosed herein analyzes the coupled influence of SOC and SOH on DCR, establishes a multi-factor coupled model through staged testing, quantifies the influence of SOC and SOH on the temperature change law of battery internal resistance, and significantly improves the accuracy of full-temperature-range DCR prediction test. The specific implementation method is as follows: Step 1: Obtain the lithium battery to be tested, perform charge-discharge cycles under set conditions, and measure the average discharge capacity as the initial capacity benchmark. Specifically, select cells from the same batch (N≥3, to ensure statistical significance), and perform at least 3 complete charge-discharge cycles (e.g., 0.5C constant current charge-discharge) at room temperature (25°C ± 2°C). Measure the average discharge capacity C0 as the initial capacity benchmark and record the initial SOH (typically, SOH = 100% for new batteries). The battery cell is calibrated for multiple states of charge (SOC). Key SOC points (such as 20%, 50%, and 80% SOC) are selected according to the application scenario to cover the nonlinear range. The open-circuit voltage (OCV) and SOC correspondence at the three SOC points of 20%, 50%, and 80% SOC are obtained.

[0021] Step 2: Adjust the lithium battery cell to the set target SOC point, place it in different temperature environments to stabilize it, measure the DCR value at each temperature, and then cycle the lithium battery cell to different health states, measuring the DCR value at each temperature under different health states. Specifically, based on the capacity C0, the test cell is charged to a specified SOC at room temperature, and the charged battery is placed in an environment at the required test temperature T1 to adapt, and its DCR value is tested.

[0022] The battery was adjusted from temperature T1 to room temperature environment for adaptation, and the battery was adjusted to the same SOC. After the battery was adjusted, it was placed in the environment at the temperature T2 to be tested, and the DCR value at temperature T2 was measured. The DCR value at temperature T3 was obtained in sequence.

[0023] For each SOC point (20%, 50%, 80%), repeat the following process: Place the battery cell at temperature T1 (e.g., -20°C) for 4 hours (to ensure temperature uniformity). Apply a short-time pulse current (e.g., 1C discharge for 10 seconds), record the voltage response, and calculate the DCR value. .

[0024] Increase the temperature to T2 (e.g., 0°C), T3 (e.g., 25°C)...Tn (e.g., 60°C), repeat the test, and output the DCR values ​​at different temperatures under different SOCs, as shown in Table 1.

[0025] Table 1. Temperature variation data of DCR under different SOCs (SOH=100%)

[0026] Furthermore, the same batch of cells is subjected to cyclic aging (such as 1C charge-discharge cycle at 25°C, and repeated calibration after every 50 cycles).

[0027] Record the data points when the capacity decays to SOH=90%, 80%, and 70% (or set the threshold according to actual needs); for each SOH stage (such as 90% and 80%), select a representative SOC point (50%) and repeat the full-temperature-range DCR test, as shown in Table 2.

[0028] Table 2. DCR at different SOH values ​​for each temperature point

[0029] Step 3: Based on the DCR values ​​under different health conditions at various temperatures, the relationship between DCR values ​​and temperature is fitted using the Arrhenius formula. The SOC correction function and the SOH correction function are introduced to construct a three-dimensional DCR fitting model. Specifically, based on the DCR values ​​under different health states at various temperatures, for each SOC and SOH combination, the InR~1 / T curve was plotted by fitting the relationship between the DCR value and temperature based on the Arrhenius formula to obtain the activation energy. Ea and pre-factor A The fitting process is as follows:

[0030] in, R DCR values ​​under different health conditions at various temperatures. T For temperature.

[0031] Furthermore, a SOC correction function is introduced. f (SOC), the SOC correction function f The form of (SOC) is:

[0032] in, a, b represents the fitting coefficient.

[0033] Furthermore, a SOH correction function is introduced. g (SOH), the SOH correction function g (SOH) is in the form of:

[0034] in, c This represents the aging coefficient.

[0035] Furthermore, by combining the Arrhenius formula with corrections to SOC and SOH, a three-dimensional DCR fitting model is constructed. The three-dimensional DCR fitting model is as follows:

[0036] in, f (SOC) is a quadratic polynomial function. g(SOH) is a linear or exponential decay function.

[0037] This disclosure uses a global nonlinear fitting (such as the Levenberg-Marquardt algorithm) to simultaneously optimize A , Ea , a , b , c .

[0038] Example 2 One embodiment of this disclosure provides a multi-factor coupled full-temperature-range DCR fitting test method for lithium batteries. Given a test cell, the specific implementation process is as follows: Step a: Select a test cell, perform three cycles of calibrating at room temperature (0.33°C), and achieve an average discharge capacity of 100Ah. Step b: Based on the measured capacity, adjust the charge of the test cell to 50% SOC at 25℃, and place the adjusted battery in an environment with the required test temperature of 25℃ for 6 hours to adapt. The DCR value R1 is 0.75 mΩ. Step c: Adjust the battery temperature from 25℃ to 25℃ for 6 hours to allow it to reach 50% SOC; after adjusting the battery, place it in an environment at the required test temperature of -20℃ for 6 hours and test its DCR value R2, which is 7.81 mΩ. Step d: Adjust the battery temperature from -20℃ to 25℃ for 6 hours to achieve 50% SOC; after adjusting the battery, place it in an environment at the required test temperature of -10℃ for 6 hours and test its DCR value R3, which is 4.10 mΩ. Step e: Adjust the battery from -10℃ to 25℃ for 6 hours to achieve 50% SOC; after adjusting the battery, place it in an environment at the required test temperature of 0℃ for 6 hours and test its DCR value R4, which is 2.40 mΩ. Step f: Adjust the battery temperature from 0℃ to 25℃ for 6 hours to achieve 50% SOC; place the adjusted battery in an environment at the required test temperature of 45℃ for 6 hours and test its DCR value R5, which is 0.31 mΩ. Step g: Based on the DCR values ​​under different health conditions at various temperatures, the relationship between DCR values ​​and temperature is fitted using the Arrhenius formula. The SOC correction function and the SOH correction function are introduced to construct a three-dimensional DCR fitting model. Step h: Based on the fitted model, input the target temperature T, SOC and SOH, and output the estimated test DCR value.

[0039] As one example, the SOC range in the example is 0%SOC to 100%SOC, and the temperature is -35℃ to 55℃. Under the same SOC, the DCR at two or more temperatures can be measured and fitted.

[0040] Example 3 One embodiment of this disclosure provides a multi-factor coupled lithium battery full-temperature-range DCR fitting test system, including: The initialization module is used to acquire the lithium battery under test, perform charge-discharge cycles under set conditions, and measure the average discharge capacity as the initial capacity benchmark. The measurement module is used to perform multi-state-of-charge calibration on lithium battery cells. The lithium battery cells are adjusted to the set target SOC point, placed in different temperature environments for stabilization, and the DCR value at each temperature is measured. Then, the lithium battery cells are cycle-aged to different health states, and the DCR value at each temperature and different health states is measured. The fitting module is used to fit the relationship between DCR value and temperature based on DCR values ​​under different health states at various temperatures using the Arrhenius formula. It introduces the SOC correction function and the SOH correction function to construct a three-dimensional DCR fitting model. The prediction module is used to output the predicted test DCR value based on the fitted model, the input target temperature T, SOC and SOH.

[0041] Example 4 One embodiment of this disclosure provides a computer program product, including a computer program that, when executed by a processor, implements the multi-factor coupled lithium battery full-temperature-range DCR fitting test method.

[0042] Example 5 One embodiment of this disclosure provides a non-transitory computer-readable storage medium for storing computer instructions. When these computer instructions are executed by a processor, they implement the multi-factor coupled lithium battery full-temperature-range DCR fitting test method.

[0043] Example 6 One embodiment of this disclosure provides an electronic device, including a processor, a memory, and a computer program; wherein the processor is connected to the memory, the computer program is stored in the memory, and when the electronic device is running, the processor executes the computer program stored in the memory to enable the electronic device to implement the multi-factor coupled lithium battery full-temperature range DCR fitting test method.

[0044] This disclosure is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this disclosure. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create a machine for implementing the flowchart illustrations and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0045] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0046] While the specific embodiments of this disclosure have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of this disclosure. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of this disclosure are still within the scope of protection of this disclosure.

Claims

1. A multi-factor coupled full-temperature-range DCR fitting test method for lithium batteries, characterized in that, include: Obtain the lithium battery to be tested, perform charge-discharge cycles under set conditions, and measure the average discharge capacity as the initial capacity benchmark. The lithium battery cells were calibrated for multiple states of charge. The lithium battery cells were adjusted to the set target SOC point and then placed in different temperature environments for stabilization. The DCR value at each temperature was measured. The lithium battery cells were then cycled and aged to different health states, and the DCR value at each temperature and different health states was measured. Based on the DCR values ​​under different health states at various temperatures, the relationship between DCR values ​​and temperature is fitted using the Arrhenius formula. The SOC correction function and the SOH correction function are introduced to construct a three-dimensional DCR fitting model. Based on the fitted model, input the target temperature T, SOC, and SOH, and output the estimated test DCR value.

2. The method for fitting and testing the full-temperature-range DCR of lithium batteries based on multi-factor coupling as described in claim 1, characterized in that, The lithium battery to be tested was selected and subjected to three charge-discharge cycles at room temperature (25°C ± 2°C) to determine the average discharge capacity, which was used as the initial capacity benchmark. The cell was calibrated with multiple states of charge (SOC) to obtain the relationship between the open circuit voltage (OCV) and the SOC at three SOC points: 20%, 50%, and 80%.

3. The method for fitting and testing the full-temperature-range DCR of lithium batteries based on multi-factor coupling as described in claim 1, characterized in that, Based on the DCR values ​​under different health states at various temperatures, for each SOC and SOH combination, the relationship between the DCR value and temperature was fitted using the Arrhenius formula to obtain the activation energy. Ea and pre-factor A The fitting process is as follows: in, R DCR values ​​under different health conditions at various temperatures. T For temperature.

4. The method for fitting and testing the full-temperature-range DCR of lithium batteries based on multi-factor coupling as described in claim 1, characterized in that, Introducing the SOC correction function f (SOC), the SOC correction function f The form of (SOC) is: in, a, b represents the fitting coefficient.

5. The method for fitting and testing the full-temperature-range DCR of lithium batteries based on multi-factor coupling as described in claim 1, characterized in that, Introducing the SOH correction function g (SOH), the SOH correction function g (SOH) is in the form of: in, c This represents the aging coefficient.

6. The method for fitting and testing the full-temperature-range DCR of lithium batteries based on multi-factor coupling as described in claim 1, characterized in that, Construct a three-dimensional DCR fitting model, wherein the three-dimensional DCR fitting model is as follows: in, f (SOC) is a quadratic polynomial function. g (SOH) is a linear or exponential decay function.

7. A multi-factor coupled lithium battery full-temperature-range DCR fitting test system, characterized in that, include: The initialization module is used to acquire the lithium battery under test, perform charge-discharge cycles under set conditions, and measure the average discharge capacity as the initial capacity benchmark. The measurement module is used to perform multi-state-of-charge calibration on lithium battery cells. The lithium battery cells are adjusted to the set target SOC point, placed in different temperature environments for stabilization, and the DCR value at each temperature is measured. Then, the lithium battery cells are cycle-aged to different health states, and the DCR value at each temperature and different health states is measured. The fitting module is used to fit the relationship between DCR value and temperature based on DCR values ​​under different health states at various temperatures using the Arrhenius formula. It introduces the SOC correction function and the SOH correction function to construct a three-dimensional DCR fitting model. The prediction module is used to output the predicted test DCR value based on the fitted model, the input target temperature T, SOC and SOH.

8. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the multi-factor coupled lithium battery full-temperature-range DCR fitting test method according to any one of claims 1-6.

9. A non-transitory computer-readable storage medium, characterized in that, The non-transitory computer-readable storage medium is used to store computer instructions, which, when executed by a processor, implement the multi-factor coupled lithium battery full-temperature-range DCR fitting test method as described in any one of claims 1-6.

10. An electronic device, characterized in that, include: The device includes a processor, a memory, and a computer program; wherein the processor is connected to the memory, the computer program is stored in the memory, and when the electronic device is running, the processor executes the computer program stored in the memory to enable the electronic device to perform the multi-factor coupled lithium battery full-temperature range DCR fitting test method as described in any one of claims 1-6.

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