A simulation model establishment method for predicting charging performance of a safety battery

Abstract

The application belongs to the technical field of batteries, and particularly relates to a simulation model establishment method for predicting the charging performance of a safety battery cell, comprising the following steps: S1: providing a safety battery cell as the basis for modeling, wherein the safety battery cell comprises a positive electrode sheet, a negative electrode sheet and a separator; S2: drawing an equivalent long strip three-dimensional geometric model according to the parameters of the safety battery cell; 3: inputting the material properties of the main material to the long strip three-dimensional geometric model constructed in S2, creating empty material for the safety primer and inputting basic properties; S4: giving a physical field to the model battery cell and charging, and calculating the charging performance based on software; and S5: comparing the calculation result of S4 with the experimental test result of the entity battery cell, adjusting the parameters of the safety primer, and making the charging performance consistent with the experimental test result. The long strip three-dimensional geometric model with the safety primer established by the application can accurately predict the performance of the safety battery cell.

Description

Technical Field

[0001] This invention belongs to the technical field of batteries, specifically relating to a method for establishing a simulation model to predict the charging performance of a safe battery cell. Background Technology

[0002] Lithium-ion batteries are widely used due to their high energy density, good cycle performance, and lack of memory effect. To improve their safety, safe battery cells are gaining popularity. However, clients typically require an assessment of the charging performance of the safe battery cells before the project commences, including factors such as charging speed, charging temperature rise, and post-cycle charging temperature rise.

[0003] However, existing electrochemical simulation methods are only suitable for modeling and evaluating conventional battery cells. Since they cannot effectively define the physical field and material properties of the safety coating, they are not suitable for modeling and evaluating safety battery cells. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for establishing a simulation model to predict the charging performance of a safe battery cell. The method establishes a long strip three-dimensional geometric model with a safety primer, which solves the problem that the safety primer cannot be described in a physical field, thereby improving the accuracy of the predicted charging performance of the battery cell and the precision of the model.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for establishing a simulation model to predict the charging performance of a safe battery cell includes the following steps:

[0007] S1: Provide a safe battery cell as the basis for modeling. The safe battery cell includes a positive electrode, a negative electrode, and a separator. The positive electrode includes a positive current collector, a safety base coating, and a positive active material coating distributed sequentially along the thickness direction. The negative electrode includes a negative current collector and a negative active material coating distributed sequentially along the thickness direction.

[0008] S2. Draw an equivalent long strip three-dimensional geometric model based on the thickness, width and length of each structural layer of the safety battery cell;

[0009] S3. Input the material properties of the main material into the long strip three-dimensional geometric model constructed in S2, create an empty material for the safety primer, input the basic properties of the safety primer, and construct the model cell;

[0010] S4. The positive current collector, negative current collector, and safety base coating of the model cell are grouped into a whole. An electrode physical field is applied to the whole. A porous electrode physical field is applied to the positive active material coating and the negative active material coating of the model cell respectively. A separator physical field is applied to the separator of the model cell. The model cell is charged, and the charging performance is calculated based on software with an electrochemical simulation module.

[0011] S5. Compare the calculation results of S4 with the experimental test results of the actual battery cell, and adjust the parameters of the safety undercoating in the model battery cell so that the charging performance of the model battery cell matches the experimental test results of the actual battery cell.

[0012] Those skilled in the art should understand that the safety undercoat refers to a coating applied between the positive electrode active coating and the positive electrode current collector to improve safety (e.g., to prevent excessive heat generation from internal short circuits, to improve needle penetration rate, etc.).

[0013] As an improvement to the simulation model establishment method for predicting the charging performance of a safe battery cell described in this invention, in step S2, the basic properties of the safe undercoat include electrical conductivity.

[0014] As an improvement to the simulation model establishment method for predicting the charging performance of a safe battery cell described in this invention, the material properties of the main material include the solid volume fraction of the positive electrode active material, the solid volume fraction of the negative electrode active material, the particle radius of the positive electrode active material, the particle radius of the negative electrode active material, and the initial charging state of the battery cell. The solid volume fraction is the percentage of the volume of the active material in the electrode sheet to the total volume of the electrode sheet, and the initial charging state is the lithium ion concentration in the positive and negative electrode sheets at the start of charging.

[0015] As an improvement to the simulation model establishment method for predicting the charging performance of a safe battery cell described in this invention, the positive electrode and the negative electrode are respectively provided with a positive electrode tab and a negative electrode tab. When the model battery cell is charged, the charging current is applied to the end of the positive electrode tab, and the end of the negative electrode tab is grounded.

[0016] As an improvement to the simulation model establishment method for predicting the charging performance of a safe battery cell described in this invention, the calculation results are compared with the experimental test results of the actual battery cell by plotting a line graph of voltage versus time and a line graph of temperature versus time for the experimental test data and the simulation data.

[0017] As an improvement to the simulation model establishment method for predicting the charging performance of safe battery cells described in this invention, the charging performance includes charging speed.

[0018] As an improvement to the simulation model establishment method for predicting the charging performance of a safe battery cell described in this invention, the conformity criteria of step S5 include: the error between the simulation result of the charging speed and the experimental test result does not exceed 5%.

[0019] As an improvement to the simulation model establishment method for predicting the charging performance of safe battery cells described in this invention, the charging performance includes the charging temperature rise.

[0020] As an improvement to the simulation model establishment method for predicting the charging performance of safe battery cells described in this invention, the conformity standard of step S5 includes: the error between the simulation result of temperature rise and the experimental test result does not exceed 2℃.

[0021] As an improvement to the simulation model establishment method for predicting the charging performance of a safe battery cell described in this invention, the charging method for the model battery cell is as follows: based on the provided charging standard, a partial differential equation for the charging current is set, and the charging process of the battery cell is controlled by events.

[0022] Preferably, the partial differential equation is: CC_CH1×(I1-Icell)+CC_CH2×(I2-Icell)+CC_CH3×(I3-Icell)+CV_CH3×(E3-Ecell)=0; where I1, I2 and I3 are preset currents, E3 is a preset voltage, Icell is the battery charging current, Ecell is the battery voltage, and CC_CH1, CC_CH2, CC_CH3 and CV_CH3 are control symbols, which are either 0 or 1.

[0023] Preferably, the specific operation of event control is as follows: when the voltage reaches the target voltage, the corresponding control character is set to 1 and other control characters are set to 0. At this time, it is the constant current charging stage of the corresponding preset current until the next target voltage is reached.

[0024] The beneficial effects of this invention are as follows: The elongated three-dimensional geometric model with a safety primer established by this invention integrates the safety primer and the positive and negative current collectors into one and endows it with a physical field, solving the problem that the safety primer cannot be described in a physical field, improving the accuracy of the elongated three-dimensional geometric model, and thus improving the accuracy of predicting the charging performance of the safe battery cell; This method can obtain a highly accurate elongated three-dimensional geometric model by setting the physical field of the battery cell with the safety primer and adjusting the material parameters of the safety primer by comparing experimental results. Moreover, the entire process only needs to consider the material parameters of the safety primer, which greatly reduces the workload of adjusting parameters. At the same time, it restores the geometric structure of the safe battery cell, improves the accuracy of the elongated three-dimensional geometric model for predicting the charging performance of the safe battery cell, and thus obtains a highly accurate battery cell charging performance. Attached Figure Description

[0025] The features, advantages, and technical effects of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings.

[0026] Figure 1 This is a schematic diagram of the structure of a long strip three-dimensional geometric model magnified 2000 times in the thickness direction in this invention.

[0027] Figure 2 for Figure 1 The unfolded diagram at point A in the middle.

[0028] Figure 3 This is a simulated line graph comparing the charging speed of the safe battery cell in Example 1.

[0029] Figure 4 This is a comparison graph of the simulated temperature rise of the safe battery cell during charging in Example 1.

[0030] Figure 5 The graph shows the simulation results of the cell charging temperature rise after safe cell cycling in Example 1.

[0031] The reference numerals in the attached figures are explained as follows:

[0032] 1-Positive current collector; 2-Safety base coating; 3-Positive active material coating; 4-Separator; 5-Negative active material coating; 6-Negative current collector; 7-Positive electrode sheet; 71-Positive electrode tab; 8-Negative electrode sheet; 81-Negative electrode tab. Detailed Implementation

[0033] The specification and claims use certain terms to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The term "comprising" throughout the specification and claims is an open-ended term and should be interpreted as "comprising but not limited to." "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error. Furthermore, terms such as "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "horizontal", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0035] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0036] The following is in conjunction with the appendix Figures 1-5 The present invention will be further described in detail with reference to specific embodiments, but this is not intended to limit the present invention.

[0037] like Figure 1-2 As shown, a method for establishing a simulation model to predict the charging performance of a safe battery cell includes the following steps:

[0038] S1: Provide a safe battery cell as the basis for modeling. The safe battery cell includes a positive electrode 7, a negative electrode 8 and a separator 4. The positive electrode 7 includes a positive current collector 1, a safety base coating 2 and a positive active material coating 3 distributed sequentially along the thickness direction. The negative electrode 8 includes a negative current collector 6 and a negative active material coating 5 distributed sequentially along the thickness direction.

[0039] S2. Draw an equivalent long strip three-dimensional geometric model based on the thickness, width and length of each structural layer of the safety battery cell;

[0040] S3. Input the material properties of the main material into the long strip three-dimensional geometric model constructed in S2, create an empty material for the safety base coating 2, input the basic properties of the safety base coating 2, and construct the model cell.

[0041] S4. Combine the positive electrode current collector 1, the negative electrode current collector 6 and the safety base coating 2 into a whole, apply an electrode physical field to the whole, apply a porous electrode physical field to the positive electrode active material coating 3 and the negative electrode active material coating 5 respectively, apply a separator physical field to the separator 4, charge the model cell, and calculate the charging performance based on the software with the electrochemical simulation module.

[0042] S5. Compare the calculation results of S4 with the experimental test results of the actual battery cell, and adjust the parameters of the safety undercoat 2 in the model battery cell so that the charging performance of the model battery cell matches the experimental test results of the actual battery cell.

[0043] In this embodiment, the software used to perform calculations on the model is Siemens, but other software with electrochemical simulation modules can also be used; no specific requirements are specified.

[0044] In step S2, the basic properties of the safety base coating 2 include electrical conductivity. The material properties of the main material include the solid volume fraction of the positive electrode active material, the solid volume fraction of the negative electrode active material, the particle radius of the positive electrode active material, the particle radius of the negative electrode active material, and the initial charging state of the battery cell. The solid volume fraction is the percentage of the volume of the active material in the electrode sheet to the total volume of the electrode sheet. The initial charging state is the lithium ion concentration in the positive and negative electrodes at the beginning of charging. The above parameters mainly describe the dynamics and thermodynamic state of the positive and negative electrodes in the physical field, which is convenient for subsequent calculation and analysis.

[0045] Among them, the positive electrode 7 and the negative electrode 8 are respectively provided with positive electrode tab 71 and negative electrode tab 81. When charging the model cell, the charging current is applied to the end of the positive electrode tab 71 and the end of the negative electrode tab 81 is grounded.

[0046] The calculation in step S4 involves setting a partial differential equation for the charging current based on the provided charging standard. The charging process of the battery cell is controlled by events. The partial differential equation is set as CC_CH1×(I1-Icell)+CC_CH2×(I2-Icell)+CC_CH3×(I3-Icell)+CV_CH3×(E3-Ecell)=0; where I1, I2, and I3 are preset currents, E3 is a preset voltage, Icell is the battery charging current, Ecell is the battery voltage, and CC_CH1, CC_CH2, CC_CH3, and CV_CH3 are control symbols, which can be 0 or 1. When the voltage reaches the target voltage, the corresponding control symbol is set to 1, and the other control symbols are set to 0, indicating that constant current charging is in place for the corresponding stage.

[0047] In step S5, the calculation results are compared with the experimental test results of the actual battery cell by plotting line graphs of voltage versus time and temperature versus time for both measured and simulated data. Charging performance includes charging speed, with the error between the simulated and experimental results not exceeding 5%. Charging performance also includes charging temperature rise, with the error between the simulated and experimental results not exceeding 2℃. Within this range, the accuracy of the model can be guaranteed, improving the accuracy of predicting the charging performance of the safe battery cell. This method, through setting the elongated three-dimensional geometric model of the battery cell with the safety undercoating 2 in step S2 and correcting the model in step S5, can obtain a highly accurate elongated three-dimensional geometric model. Furthermore, the entire process only requires considering the material parameters of the safety undercoating 2, greatly reducing the workload of parameter adjustment. Simultaneously, it restores the geometric structure of the safe battery cell, improving the accuracy of the elongated three-dimensional geometric model predicting the charging performance of the safe battery cell, thus obtaining highly accurate battery cell charging performance data.

[0048] Example 1

[0049] like Figure 1-5As shown, the temperature rise of the safety battery cell 456693 after cycling under a 1.5C charging mode is simulated, including the following steps:

[0050] S1. Model the 456693 safety battery cell. The 456693 safety battery cell includes a positive electrode 7, a negative electrode 8, and a separator 4. The positive electrode 7 includes a positive current collector 1, a safety base coating 2, and a positive active material coating 3 distributed sequentially along the thickness direction. The negative electrode 8 includes a negative current collector 6 and a negative active material coating 5 distributed sequentially along the thickness direction. Draw an equivalent long strip three-dimensional geometric model based on the thickness, width, and length of each structural layer of the 456693 safety battery cell.

[0051] S2. Input the material properties of the main material into the long strip three-dimensional geometric model constructed in S1. Create an empty material for the safety base coating 2 and input the basic properties of the safety base coating 2. Among them, the basic property of the safety base coating 2 is the conductivity. The material properties of the main material are the solid volume fraction of the positive electrode active material, the solid volume fraction of the negative electrode active material, the particle radius of the positive electrode active material, the particle radius of the negative electrode active material, and the initial charging state of the cell. The solid volume fraction is the percentage of the volume of the active material in the electrode sheet to the total volume of the electrode sheet. The initial charging state is the lithium ion concentration in the positive and negative electrodes at the beginning of charging. The above parameters are mainly able to describe the dynamics and thermodynamic state of the positive and negative electrodes in the physical field, which is convenient for subsequent calculation and analysis.

[0052] S3. The positive current collector 1, negative current collector 6 and safety base coating 2 in the model cell are grouped into a whole. An electrode physical field is applied to this whole. A porous electrode physical field is applied to the positive active material coating 3 and the negative active material coating 5 of the model cell respectively. A separator physical field is applied to the separator 4 of the model cell. The model cell is charged. The positive electrode 7 and the negative electrode 8 are respectively provided with positive electrode tabs 71 and negative electrode tabs 81. When charging the model cell, the end of the negative electrode tab 81 is grounded and the charging current is applied to the end of the positive electrode tab 71. Then, the charging speed and charging temperature rise of the model cell are calculated using software with an electrochemical simulation module.

[0053] Specifically, the charging method for the model battery cell is as follows: Based on the provided charging standard, a partial differential equation for the charging current is set, and the charging process of the battery cell is controlled by events. The charging standard is: 1.5C constant current charging to 4.25V; 1.2C constant current charging to 4.45V; 0.8C constant current and constant voltage charging to 4.48V, with a cutoff rate of 0.19C. The partial differential equation for the charging current is CC_CH1×(I1-Icell)+CC_CH2×(I2-Icell)+CC_CH3×(I3-Icell)+CV_CH3×(E3-Ecell)=0; where I1, I2, and I3 are 1.5C, 1.2C, and 0.8C respectively, Icell is the battery charging current, E3 is 4.48V, and Ecell is the battery voltage. Voltage, CC_CH1, CC_CH2, CC_CH3, and CV_CH3 are all control characters; the event control process is as follows: first, CC_CH1 is set to 1, and other control characters are set to 0, at which point the charging current is constant at 1.5C; when charging reaches 4.25V, CC_CH2 is set to 1, and other control characters are set to 0, at which point the charging current is constant at 1.2C; when charging reaches 4.45V, CC_CH3 is set to 1, and other control characters are set to 0, at which point the charging current is constant at 0.8C; when charging reaches 4.48V, CV_CH3 is set to 1, and other control characters are set to 0, at which point the charging current is constant at 0.19C.

[0054] S4. Compare the simulation data calculated in S3 (i.e., the charging speed and temperature rise of the model cell) with the experimental test results of a fresh physical cell (i.e., a brand-new, uncycled cell), that is, plot a line graph of voltage versus time between the experimental test data and the simulation data (i.e.,...). Figure 3 ), and a line graph showing the relationship between temperature and time (i.e. Figure 4 The parameters of the safety undercoat in the model cell are adjusted to make the charging speed and temperature rise of the model cell consistent with the experimental test results of the actual cell. The standard for consistency is: the error between the charging speed of the model cell and the experimental test results of the actual cell does not exceed 5%, and the error between the temperature rise of the model cell and the experimental test results of the actual cell does not exceed 2℃.

[0055] S5. Using the corrected model, modify the cycling concentration to predict the temperature rise after cycling, and obtain the prediction results, such as... Figure 5 .

[0056] like Figure 3-5As shown in the figure, the established charging model for the safety cell can accurately predict its charging speed and temperature rise when it is fresh. Furthermore, based on the pattern of increasing internal resistance and temperature rise after cycling, it can be observed that the charging temperature rise of the cell after cycling is 1.9℃ higher than that of a fresh cell, which is consistent with actual trends. The charging simulation accuracy of the 456693 safety cell is good, and the predicted temperature rise after cycling conforms to the expected pattern, indicating high model accuracy.

[0057] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention are within the scope of protection of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A method for establishing a simulation model to predict the charging performance of a safe battery cell, characterized in that, Includes the following steps: S1. Provide a safety cell as the basis for modeling. The safety cell includes a positive electrode (7), a negative electrode (8) and a separator (4). The positive electrode (7) includes a positive current collector (1), a safety base coating (2) and a positive active material coating (3) distributed sequentially along the thickness direction. The negative electrode (8) includes a negative current collector (6) and a negative active material coating (5) distributed sequentially along the thickness direction. S2. Draw an equivalent long strip three-dimensional geometric model based on the thickness, width and length of each structural layer of the safety battery cell; S3. Input the material properties of the main material into the long strip three-dimensional geometric model constructed in S2, create an empty material for the safety base coating (2), input the basic properties of the safety base coating (2), and construct the model cell; S4. The positive current collector (1), negative current collector (6), and safety base coating (2) of the model battery cell are grouped into a whole. An electrode physical field is applied to the whole. A porous electrode physical field is applied to the positive active material coating (3) and the negative active material coating (5) of the model battery cell respectively. A separator physical field is applied to the separator (4) of the model battery cell. The model battery cell is charged. The charging performance is calculated based on software with an electrochemical simulation module. The charging method of the model battery cell is as follows: According to the provided charging system, a partial differential equation for the charging current is set. The partial differential equation is: CC_CH1×(I1-Icell)+CC_CH2×( I2-Icell)+CC_CH3×(I3-Icell)+CV_CH3×(E3-Ecell)=0, where I1, I2, and I3 are preset currents, E3 is a preset voltage, Icell is the battery charging current, Ecell is the battery voltage, and CC_CH1, CC_CH2, CC_CH3, and CV_CH3 are control symbols, which can be 0 or 1. The charging process of the battery cell is controlled by events. The specific operation of event control is as follows: when the voltage reaches the target voltage, the corresponding control symbol is set to 1, and the other control symbols are set to 0. At this time, it is the constant current charging stage of the corresponding preset current until the next target voltage is reached. S5. Compare the calculation results of S4 with the experimental test results of the actual battery cell, and adjust the parameters of the safety undercoating (2) in the model battery cell so that the charging performance of the model battery cell matches the experimental test results of the actual battery cell.

2. The simulation model establishment method for predicting the charging performance of a safe battery cell as described in claim 1, characterized in that, The basic properties of the safety primer (2) include electrical conductivity.

3. The method for establishing a simulation model to predict the charging performance of a safe battery cell as described in claim 1, characterized in that, The material properties of the main material include the solid volume fraction of the positive electrode active material, the solid volume fraction of the negative electrode active material, the particle radius of the positive electrode active material, the particle radius of the negative electrode active material, and the initial charging state of the battery cell. The solid volume fraction is the percentage of the volume of the active material in the electrode sheet to the total volume of the electrode sheet, and the initial charging state is the lithium ion concentration in the positive and negative electrode sheets at the start of charging.

4. The method for establishing a simulation model to predict the charging performance of a safe battery cell as described in claim 1, characterized in that, The positive electrode (7) and the negative electrode (8) are respectively provided with a positive electrode tab (71) and a negative electrode tab (81). When the model cell is charged, the charging current is applied to the end of the positive electrode tab (71) and the end of the negative electrode tab (81) is grounded.

5. The method for establishing a simulation model to predict the charging performance of a safe battery cell as described in claim 1, characterized in that, The calculation results are compared with the experimental test results of the actual battery cell by plotting the voltage versus time and temperature versus time graphs of the experimental test data and simulation data.

6. The method for establishing a simulation model to predict the charging performance of a safe battery cell as described in claim 1, characterized in that, The charging performance includes charging speed.

7. The method for establishing a simulation model to predict the charging performance of a safe battery cell as described in claim 6, characterized in that, The compliance criteria for step S5 include: the error between the simulation results and the experimental test results of the charging speed does not exceed 5%.

8. The method for establishing a simulation model to predict the charging performance of a safe battery cell as described in claim 1 or 6, characterized in that, The charging performance includes the charging temperature rise.

9. The method for establishing a simulation model to predict the charging performance of a safe battery cell as described in claim 8, characterized in that, The compliance criteria for step S5 include: the error between the simulation results and the experimental test results of the temperature rise does not exceed 2℃.

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