SOC-temperature coupling-based ternary battery safety boundary design method, electronic device, and medium

Abstract

This application discloses a safety boundary design method, electronic device, and dielectric for ternary lithium batteries based on SOC-temperature coupling. The method may include: randomly selecting cells from a ternary lithium-ion battery system as experimental samples and preprocessing them; performing SOC calibration and verification on the preprocessed samples after 1 / 3C constant current-constant voltage charging / discharging to obtain verified data; conducting adiabatic tests at multiple initiation temperatures based on the verified data; extracting thermal runaway characteristic parameters, establishing a coupling relationship model, and fitting it to generate a safety boundary surface. This invention establishes a nonlinear coupling three-dimensional response surface between SOC and initiation temperature T0 through cell-level experiments, achieving a transition from a fixed threshold to a dynamic boundary. The aim is to identify the most dangerous range of "high SOC + medium-high temperature" at the cell level in advance, reducing the probability of thermal runaway in a single cell.

Description

Technical Field

[0001] This invention relates to the field of battery safety technology, and more specifically, to a safety boundary design method, electronic device, and medium for ternary batteries based on SOC-temperature coupling. Background Technology

[0002] Lithium-ion battery cathode materials have undergone technological iterations, from lithium iron phosphate to ternary materials, and from low-nickel to high-nickel materials. Around 2019, NCM811 (nickel-cobalt-manganese ratio of 8:1:1) began to be mass-produced and installed in vehicles, with an energy density of 250-280 Wh / kg, an improvement of about 30% compared to NCM523, becoming the mainstream choice for mid-to-high-end electric vehicles. However, the high nickel content brings significant degradation in thermal stability: the thermal runaway trigger temperature of NCM811 under full charge is about 130-140℃, which is 30-40℃ lower than the 165-175℃ of NCM523, and the cathode material begins to decompose and release oxygen at around 200℃, reacting violently with the electrolyte. This intrinsic property of the material presents a sharp contradiction with the actual usage scenarios of electric vehicles—the cell temperature can reach 60-70℃ under fast charging conditions, and the temperature after fast charging following high-speed driving in summer may exceed 50%. Users often tend to charge the battery to a higher SOC to obtain longer range, which falls right into the dangerous range of "high SOC + medium-high temperature". In existing technologies, the threshold setting is based on a single temperature variable, without considering the significant impact of SOC or the nonlinear effect of the temperature starting point.

[0003] Therefore, it is necessary to develop a safety boundary design method, electronic device, and dielectric for ternary batteries based on SOC-temperature coupling.

[0004] The information disclosed in the background section of this invention is intended only to enhance the understanding of the general background of this invention, and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] This invention proposes a safety boundary design method, electronic device, and dielectric for ternary batteries based on SOC-temperature coupling. It can establish a nonlinear coupling three-dimensional response surface between SOC (State of Charge) and initial temperature T0 through cell-level experiments, realizing the transition from a fixed threshold to a dynamic boundary. The aim is to identify the most dangerous range of "high SOC + medium and high temperature" in advance at the cell level and reduce the probability of thermal runaway in a single cell.

[0006] In a first aspect, embodiments of this disclosure provide a safety boundary design method for ternary batteries based on SOC-temperature coupling, including: Cells were randomly selected from ternary lithium-ion batteries as experimental samples and pre-processed. After preprocessing, the samples were subjected to 1 / 3C constant current-constant voltage charging / discharging, followed by SOC calibration and verification to obtain the verified data. Multiple initiation temperature adiabatic tests were conducted based on the validated data. Thermal runaway characteristic parameters are extracted, a coupling relationship model is established and fitted, and then a safe boundary surface is generated.

[0007] Preferably, the pretreatment includes formation and capacity separation, OCV-SOC curve calibration, and initial state zeroing.

[0008] Preferably, the multi-initial-temperature adiabatic test based on the verified data includes: Start by heating from room temperature to determine the initial calibration time, and then hold the temperature after reaching the target temperature to ensure uniform internal temperature of the cell. When the sample temperature is ≥150 ℃ or the pressure sensor detects a pressure rise of ≥0.5 MPa, the vacuum pump draws gas from the sample chamber into the sampling bag.

[0009] Preferably, the thermal runaway characteristic parameters include thermal runaway trigger temperature, temperature rise rate, self-exothermic initiation temperature, maximum temperature, and gas ejection rate.

[0010] Preferably, the coupling model is based on the thermal runaway trigger temperature and the state of charge (SOC) and target temperature. The coupling relationship.

[0011] Preferably, the coupling relationship is as follows: , In the formula, This is the temperature at which thermal runaway is triggered. The reference thermal runaway temperature; The SOC linear sensitivity coefficient; This is the coupling strength coefficient; This is the temperature decay coefficient.

[0012] Preferably, the Levenberg-Marquardt nonlinear least squares algorithm is used to fit the coupling relationship model.

[0013] Preferably, generating the safe boundary surface includes: Safe temperature: ; Maximum charging voltage: In the formula The function is the inverse of OCV-SOC, where ΔV is the safety increment considering polarization; Upper limit of operating temperature: ; Generate a discretized lookup table: SOC step size 5% (0–100%), T0 step size 5℃ (25–85℃), store each point. and .

[0014] Secondly, embodiments of this disclosure also provide an electronic device, the electronic device comprising: Memory, which stores executable instructions; A processor that executes the executable instructions in the memory to implement the aforementioned ternary battery safety boundary design method based on SOC-temperature coupling.

[0015] Thirdly, embodiments of this disclosure also provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the aforementioned ternary battery safety boundary design method based on SOC-temperature coupling.

[0016] Its beneficial effects are as follows: 1) Simultaneously quantifying SOC and temperature revealed that SOC is far more sensitive to thermal runaway than temperature. Therefore, the upper limit of the charging voltage in the high SOC range was reduced to decrease the probability of thermal runaway. 2) The upper temperature limit can be relaxed in low SOC and low temperature zones, shortening the vehicle's low-temperature fast charging time; 3) A single calibration at the cell level can cover the entire life cycle, eliminating the need for repeated large-sample explosion tests for each battery pack, thus reducing R&D costs; 4) Dynamic table lookup enables the BMS safety threshold to change in real time with the operating conditions, avoiding both excessive derating and blind over-limit, thereby improving energy utilization and extending cycle life.

[0017] The methods and apparatus of the present invention have other features and advantages that will be apparent from or will be set forth in detail in the accompanying drawings and following detailed description, which together serve to explain the particular principles of the invention. Attached Figure Description

[0018] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same parts.

[0019] Figure 1 A flowchart illustrating the steps of a ternary battery safety boundary design method based on SOC-temperature coupling according to an embodiment of the present invention is shown. Detailed Implementation

[0020] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0021] To facilitate understanding of the solutions and effects of the embodiments of the present invention, three specific application examples are given below. Those skilled in the art should understand that these examples are merely for the purpose of understanding the present invention, and any specific details therein are not intended to limit the present invention in any way.

[0022] Example 1

[0023] Figure 1 A flowchart illustrating the steps of a ternary battery safety boundary design method based on SOC-temperature coupling according to an embodiment of the present invention is shown.

[0024] like Figure 1 As shown, the ternary battery safety boundary design method based on SOC-temperature coupling includes: Step 101: Randomly select cells from the ternary lithium-ion battery system as experimental samples and perform preprocessing. Step 102: Perform SOC calibration and verification on the pre-processed sample after 1 / 3C constant current-constant voltage charging / discharging to obtain the verified data; Step 103: Perform multi-initial-temperature adiabatic testing based on the verified data; Step 104: Extract thermal runaway characteristic parameters, establish a coupling relationship model and fit it to generate a safe boundary surface.

[0025] In one example, preprocessing includes formation and capacity division, OCV-SOC curve calibration, and initial state zeroing.

[0026] In one example, multi-initial-temperature adiabatic testing based on validated data includes: Start by heating from room temperature to determine the initial calibration time, and then hold the temperature after reaching the target temperature to ensure uniform internal temperature of the cell. When the sample temperature is ≥150 ℃ or the pressure sensor detects a pressure rise of ≥0.5 MPa, the vacuum pump draws gas from the sample chamber into the sampling bag.

[0027] In one example, thermal runaway characteristic parameters include thermal runaway trigger temperature, rate of temperature rise, self-exothermic initiation temperature, maximum temperature, and gas ejection rate.

[0028] In one example, the coupling model is that the thermal runaway trigger temperature is related to the state of charge (SOC) and the target temperature. The coupling relationship.

[0029] In one example, the coupling relationship is as follows: , In the formula, This is the temperature at which thermal runaway is triggered. The reference thermal runaway temperature; The SOC linear sensitivity coefficient; This is the coupling strength coefficient; This is the temperature decay coefficient.

[0030] In one example, the Levenberg-Marquardt nonlinear least squares algorithm is used to fit the coupling relationship model.

[0031] In one example, generating a safe boundary surface includes: Safe temperature: ; Maximum charging voltage: In the formula The function is the inverse of OCV-SOC, where ΔV is the safety increment considering polarization; Upper limit of operating temperature: ; Generate a discretized lookup table: SOC step size 5% (0–100%), T0 step size 5℃ (25–85℃), store each point. and .

[0032] Specifically, cells were randomly selected from the same production batch of ternary lithium-ion batteries as experimental samples, according to the requirements of GB / T 36276-2018 "Lithium-ion Batteries for Power Storage". The samples needed to meet the following requirements: capacity deviation ≤ ±1.5%, internal resistance deviation ≤ ±3%, and initial state of charge ≤ 5%. The samples were grouped according to a full factorial experimental design (SOC and initial temperature T0). The selected samples underwent preprocessing: ① Formation and capacity testing: All samples were formed at 25 ℃ according to the standard process and subjected to 3 charge-discharge cycles at a 1 / 3C rate. The capacity of the 3rd discharge cycle was taken as the actual capacity. ② OCV-SOC curve calibration: At 25 ℃, charge and discharge with a small current of 1 / 20C, record the correspondence between open circuit voltage (OCV) and SOC, and establish a lookup table reference; ③ Initial state reset: Discharge to 2.5 V cutoff, let stand for 24 h, and ensure that the initial SOC is <5%.

[0033] After pretreatment, the samples were subjected to 1 / 3C constant current-constant voltage charging / discharging for SOC calibration and verification, and then allowed to stand at 25 ℃ for 2 h to eliminate polarization. 1. OCV Measurement: A high-precision voltmeter measures the terminal voltage; 2. SOC calibration: Compare the measured OCV with the OCV-SOC curve. If the deviation is >0.5%SOC, fine-tune the charge and discharge and repeat the resting process. 3. Final confirmation: After calibration, the SOC error is ≤ ±0.3%, and the actual SOC_actual is recorded as the experimental input.

[0034] Adiabatic testing with multiple initial temperatures was conducted based on the validated data. The temperature is increased from room temperature, with an initial calibration time of 300 min, then increased to the target T0℃. After reaching T0, the temperature is held for 30 min to ensure uniform internal temperature of the cell (cell-surface temperature difference ≤ ±0.5 ℃). The adjustment time is 20 min, the search time is 10 min, and the confirmation adiabatic calibration time is 10 min. The temperature increase for each segment is 5℃, dT / dt>0.02℃ / min, and the maximum search temperature is 300℃. When the sample temperature is ≥150℃ or the pressure sensor detects a pressure rise of ≥0.5 MPa, the vacuum pump extracts the gas from the sample chamber into the sampling bag for subsequent GC-MS analysis of characteristic gases such as H2, CO, CH4, and C2H4.

[0035] Thermal runaway characteristic parameters extracted from the raw data include: thermal runaway trigger temperature T. tr , temperature rise rate (dT / dt)max, self-exothermic onset temperature T onset Maximum temperature and gas ejection volume As shown in Table 1.

[0036] Table 1

[0037] The extraction results for each sample should meet the following conditions: The temperature should be within the range of 80–200 ℃, and the maximum temperature (dT / dt) should be within the range of 10–500 ℃ / min. Temperatures exceeding these ranges are considered abnormal. (This applies to parallel samples.) The standard deviation should be ≤3 °C; otherwise, outliers should be removed and additional experiments should be conducted. If the volume is less than 10 mL or the main component is N2 (air), it is considered a seal failure and the data is invalid.

[0038] Based on the effective experimental data, establish The coupling relationship with SOC and T0. Scatter plot analysis reveals: ①SOC effect: It decreases approximately linearly with increasing SOC, with a slope of approximately –0.4 ℃ / %SOC; ② Temperature effect: High temperature region (T0>60 ℃) The decline has slowed, exhibiting a "self-buffering" phenomenon; ③ Coupling effect: There is a nonlinear interaction between SOC and T0, and the temperature effect weakens at high SOC; Based on this, a nonlinear coupling model is proposed: , In the formula: This is the reference thermal runaway temperature (an extrapolated value at SOC=0, T0=0 ℃, which physically represents the theoretical limit at complete discharge and absolute zero). is the SOC linear sensitivity coefficient (°C / %SOC); The coupling strength coefficient (°C) reflects the intensity of the interaction between SOC and temperature. Temperature decay coefficient (°C) - ¹), characterizing the decay rate of the self-buffering effect in the high-temperature region.

[0039] The Levenberg-Marquardt nonlinear least squares algorithm was used to fit the coupling relationship model. Initial value estimation: obtained from linear regression ≈180, ≈0.4, ≈15, ≈0.02; Iterative optimization: Maximum 1000 iterations, convergence tolerance 10. -6 The optimal parameters are obtained as follows: = 185.6 ℃; = 0.42 ℃ / %SOC; = 15.3 ℃; = 0.018 ℃ - ¹; Goodness of fit: coefficient of determination R² = 0.968, root mean square error RMSE = 1.37 ℃.

[0040] Leave-one-out cross-validation (LOOCV): One sample is left out each time, and the remaining samples are used for training. The prediction is repeated for a total of [number] trials, resulting in a prediction error RMSE_CV = 1.89 ℃ < 3 ℃ (engineering requirement). Residual analysis: The residual histogram approximates a normal distribution with no systematic bias, confirming that the model is not underfitting. Extrapolation validation: Supplementary experiments were conducted with SOC = 10% (extrapolation) and T0 = 90 ℃ (extrapolation), and actual measurements were performed. The deviation from the predicted value is less than 5 °C, indicating that the model's extrapolation ability is acceptable.

[0041] Taking a 5% safety margin (according to SAE J2929-2021), generate the safety boundary surface: Safe temperature: ; Maximum charging voltage: In the formula The function is the inverse of OCV-SOC, where ΔV is the safety increment considering polarization; Upper limit of operating temperature: Take the smaller value between the safe temperature minus 10 ℃ and the material limit of 65 ℃; Generate a discretized lookup table: SOC step size 5% (0–100%), T0 step size 5℃ (25–85℃), totaling 21 × 13 = 273 grid points, each point storing... and .

[0042] Example 2

[0043] This disclosure provides an electronic device, comprising: a memory storing executable instructions; and a processor executing the executable instructions in the memory to implement the aforementioned ternary battery safety boundary design method based on SOC-temperature coupling.

[0044] An electronic device according to an embodiment of the present disclosure includes a memory and a processor.

[0045] This memory is used to store non-transitory computer-readable instructions. Specifically, the memory may include one or more computer program products, which may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may, for example, include random access memory (RAM) and / or cache memory. The non-volatile memory may, for example, include read-only memory (ROM), hard disk, flash memory, etc.

[0046] The processor may be a central processing unit (CPU) or other form of processing unit with data processing capabilities and / or instruction execution capabilities, and may control other components in the electronic device to perform desired functions. In one embodiment of this disclosure, the processor is used to execute computer-readable instructions stored in the memory.

[0047] Those skilled in the art will understand that, in order to solve the technical problem of how to achieve a good user experience, this embodiment may also include well-known structures such as communication buses and interfaces, and these well-known structures should also be included within the protection scope of this disclosure.

[0048] For a detailed description of this embodiment, please refer to the corresponding descriptions in the foregoing embodiments, which will not be repeated here.

[0049] Example 3

[0050] This disclosure provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the aforementioned ternary battery safety boundary design method based on SOC-temperature coupling.

[0051] A computer-readable storage medium according to embodiments of the present disclosure stores non-transitory computer-readable instructions. When these non-transitory computer-readable instructions are executed by a processor, all or part of the steps of the methods described in the foregoing embodiments of the present disclosure are performed.

[0052] The aforementioned computer-readable storage media include, but are not limited to: optical storage media (e.g., CD-ROM and DVD), magneto-optical storage media (e.g., MO), magnetic storage media (e.g., magnetic tape or portable hard drive), media with built-in rewritable non-volatile memory (e.g., memory card), and media with built-in ROM (e.g., ROM cartridge).

[0053] Those skilled in the art should understand that the above description of the embodiments of the present invention is only intended to illustrate the beneficial effects of the embodiments of the present invention, and is not intended to limit the embodiments of the present invention to any of the examples given.

[0054] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A safety boundary design method for ternary lithium batteries based on SOC-temperature coupling, characterized in that, include: Cells were randomly selected from ternary lithium-ion batteries as experimental samples and pre-processed. After preprocessing, the samples were subjected to 1 / 3C constant current-constant voltage charging / discharging, followed by SOC calibration and verification to obtain the verified data. Multiple initiation temperature adiabatic tests were conducted based on the validated data. Thermal runaway characteristic parameters are extracted, a coupling relationship model is established and fitted, and then a safe boundary surface is generated.

2. The ternary battery safety boundary design method based on SOC-temperature coupling according to claim 1, characterized in that, Preprocessing includes formation and capacity division, OCV-SOC curve calibration, and initial state zeroing.

3. The ternary battery safety boundary design method based on SOC-temperature coupling according to claim 1, characterized in that, The multi-initial-temperature adiabatic tests based on the validated data include: Start by heating from room temperature to determine the initial calibration time, and then hold the temperature after reaching the target temperature to ensure uniform internal temperature of the cell. When the sample temperature is ≥150 ℃ or the pressure sensor detects a pressure rise of ≥0.5 MPa, the vacuum pump draws gas from the sample chamber into the sampling bag.

4. The ternary battery safety boundary design method based on SOC-temperature coupling according to claim 1, characterized in that, Thermal runaway characteristic parameters include thermal runaway trigger temperature, temperature rise rate, self-exothermic initiation temperature, maximum temperature, and gas ejection rate.

5. The ternary battery safety boundary design method based on SOC-temperature coupling according to claim 4, characterized in that, The coupling model is based on the thermal runaway trigger temperature and the state of charge (SOC) and target temperature. The coupling relationship.

6. The ternary battery safety boundary design method based on SOC-temperature coupling according to claim 5, characterized in that, The coupling relationship is as follows: ， In the formula, This is the temperature at which thermal runaway is triggered. The reference thermal runaway temperature; The SOC linear sensitivity coefficient; This is the coupling strength coefficient; This is the temperature decay coefficient.

7. The ternary battery safety boundary design method based on SOC-temperature coupling according to claim 1, characterized in that, The Levenberg-Marquardt nonlinear least squares algorithm was used to fit the coupling relationship model.

8. The ternary battery safety boundary design method based on SOC-temperature coupling according to claim 6, characterized in that, Generating safe boundary surfaces includes: Safe temperature: ; Maximum charging voltage: In the formula The function is the inverse of OCV-SOC, where ΔV is the safety increment considering polarization; Upper limit of operating temperature: ; Generate a discretized lookup table: SOC step size 5%, T0 step size 5℃, store each point and .

9. An electronic device, characterized in that, The electronic device includes: Memory, which stores executable instructions; A processor that executes the executable instructions in the memory to implement the ternary battery safety boundary design method based on SOC-temperature coupling as described in any one of claims 1-8.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the ternary battery safety boundary design method based on SOC-temperature coupling as described in any one of claims 1-8.

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