Method and device for accurately obtaining battery cell charging strategy based on pressure correction
By using dynamic electrochemical impedance spectroscopy and preload adjustment, a fast-charging window model for lithium-ion battery cells was established, which solved the problem of high lithium plating risk during fast charging of lithium-ion batteries and achieved battery safety and life extension.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-21
- Publication Date
- 2026-03-13
AI Technical Summary
Existing technologies for fast charging lithium-ion batteries suffer from problems such as complex three-electrode systems, insufficient consideration of pressure factors, and lack of correlation with full life cycle performance, resulting in high lithium plating risk and accelerated battery degradation.
The critical state of charge (SOC) of the battery cell during constant current charging was obtained by dynamic electrochemical impedance spectroscopy. Combined with the charging rate under different preload forces, a pressure-corrected fast charging window model for the battery cell was established, and the charging strategy was dynamically adjusted to reduce the risk of lithium plating.
This method significantly reduces the risk of lithium plating during high-current charging of lithium-ion batteries, extends battery cycle life, improves battery safety and adaptability, and is simple and low-cost.
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Figure CN121662998A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of battery technology, and in particular to a method and apparatus for accurately obtaining cell charging strategies based on pressure correction. Background Technology
[0002] Lithium-ion batteries are widely used in electric vehicles and energy storage systems due to their high energy density and long cycle life. As users' demands for charging speed continue to increase, fast charging technology has become crucial in alleviating "range anxiety." However, the problem of lithium plating on the negative electrode during high-current charging severely restricts the charging efficiency and safety of batteries. Lithium plating not only leads to capacity decay but can also cause safety accidents such as internal short circuits and thermal runaway. Therefore, developing methods that can accurately identify lithium plating boundaries and formulate safe and efficient charging strategies accordingly has become a research hotspot in the current battery technology field.
[0003] In existing technologies, studies have used segmented fast-charging cycles to screen for optimal fast-charging strategies, which can reduce the risk of lithium plating on the negative electrode surface during high-current charging to some extent. However, this method still relies on the complex construction and experimental operation of a three-electrode system, resulting in limitations such as high cost and long cycle time. Furthermore, optimization methods based on mathematical models of internal battery processes have also been applied in fast-charging design. These methods reduce reliance on physical sensors but fail to systematically consider the impact of mechanical stress on the cells under actual packaging and usage conditions. In reality, batteries are placed in a fixed space, and the cells within the battery are tightly fitted together. During battery charging, a certain amount of pressure is generated between the cells. Under different pressure conditions, the interfacial contact state, ion transport kinetics, and critical conditions for lithium plating within the cells all change significantly. Ignoring the dynamic effects of pressure and its coupling mechanism with the aging process will reduce the applicability of optimization strategies in actual battery modules and may even accelerate battery performance degradation.
[0004] In summary, although existing technologies have made some progress in lithium plating monitoring and fast charging strategies, there are still problems such as the complexity of the three-electrode system, insufficient consideration of stress factors, and lack of correlation with the performance throughout the entire life cycle.
[0005] Therefore, developing a method for obtaining battery cell charging strategies that is easy to operate, cost-effective, can comprehensively consider the effects of electrochemical and mechanical stress, and is applicable to the entire life cycle of the battery cell is of great significance for improving the safety and adaptability of the battery fast charging process and extending the battery cell's lifespan. Summary of the Invention
[0006] Therefore, it is necessary to provide a method and apparatus for accurately obtaining cell charging strategies based on pressure correction to address the aforementioned technical problems in the existing technology. This method dynamically adjusts the charging strategy according to changes in cell pressure, significantly reducing the risk of lithium plating on the surface of the negative electrode during high-current charging of lithium-ion batteries, slowing down battery degradation, and extending the cycle life of the battery.
[0007] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A method for accurately obtaining cell charging strategies based on pressure correction includes the following steps: S1. The critical SOC value at which the lithium plating reaction begins during constant current charging of the battery cell is obtained by dynamic electrochemical impedance spectroscopy. S2. Change the magnitude of the constant current during dynamic electrochemical impedance spectroscopy testing to obtain the lithium-free safe charging range of the cell under different charging rates without preload, i.e., the safe fast charging window of the cell. S3. Apply different preload forces to the battery cell to obtain a safe fast charging window where lithium plating does not occur under different preload forces; S4. Establish a pressure-corrected fast charging window model for battery cells based on the relationship between pressure, charging rate, and critical SOC value. S5. Based on the pressure-corrected fast charging window model of the battery cell obtained in step S4, obtain a battery cell charging strategy applicable to different pressure states throughout the entire life cycle of the battery cell.
[0008] In this invention, the term "full life cycle" refers to the entire usage process of a lithium-ion battery cell from its initial healthy state (e.g., SOH of 100%) to its end-of-life state (e.g., SOH decaying to 70% or 80%). It should be noted that the specific value of the end-of-life state can be defined according to different cell systems or application requirements, and the methods and models described in this invention are applicable to any stress state during this process.
[0009] Preferably, the method further includes step S6, verifying the cell charging strategy obtained in step S5.
[0010] More preferably, the verification of the cell charging strategy obtained in step S5 in step S6 specifically involves: verifying the cycle life of the cell using the cell charging strategy obtained in step S5.
[0011] Preferably, step S1 includes the following steps: S11. Obtain the charge transfer characteristic impedance of the battery cell across the entire SOC range during constant current charging by dynamic electrochemical impedance spectroscopy. S12. Based on the abnormal decrease in the charge transfer characteristic impedance value in the high SOC range, it is determined that the cell has undergone lithium plating reaction. The SOC value corresponding to the inflection point where the charge transfer characteristic impedance value first shows a significant decrease is determined as the critical SOC value at which the lithium plating reaction begins at that rate. The critical SOC value at which the lithium plating reaction begins in the entire SOC range of the cell during constant current charging is obtained.
[0012] Preferably, in step S2, the charging rate is between 0.1C and 3.5C.
[0013] Preferably, in step S3, the preload applied to the battery cell is between 0 and 1 MPa.
[0014] Preferably, step S5 specifically involves: inputting the real-time measured pressure value of the battery cell into the pressure-corrected fast charging window model of the battery cell, and having the model output the corresponding optimal charging strategy.
[0015] Accordingly, the present invention also provides an apparatus for implementing the method for accurately obtaining cell charging strategies based on pressure correction as described above, comprising: The monitoring unit is configured to obtain the critical SOC value at which the lithium plating reaction begins in the entire SOC range of the cell during constant current charging by using dynamic electrochemical impedance spectroscopy, and to obtain the lithium-free safe charging range of the cell under different charging rates by changing the magnitude of the constant current charging current during dynamic electrochemical impedance spectroscopy testing, i.e., the safe fast charging window of the cell. The force application unit is used to apply preload and is configured to apply different preloads to the battery cell to obtain a safe fast charging window where lithium plating does not occur in the battery cell under different preloads. The cell testing unit is configured to test the cell and obtain the measured pressure value of the cell. The calculation and analysis unit is configured to establish a pressure-corrected fast charging window model for the battery cell based on the relationship between pressure, charging rate, and critical SOC value, and to obtain the battery cell charging strategy based on the measured pressure value throughout the battery cell's life cycle.
[0016] Preferably, the monitoring unit is an electrochemical impedance spectroscopy instrument.
[0017] Preferably, the calculation and analysis unit is also configured to build a model based on the internal pressure change data throughout the entire life cycle of the battery cell in order to obtain the battery cell charging strategy in real time.
[0018] Due to the adoption of the above technical solutions, the present invention has the following advantages compared with the prior art: 1. The present invention provides a method for accurately obtaining cell charging strategies based on pressure correction. The charging strategy is dynamically adjusted according to changes in cell pressure, which significantly reduces the risk of lithium plating on the surface of the negative electrode during high-current charging of lithium-ion batteries, slows down battery degradation, and extends the cycle life of the battery. 2. The method of the present invention is simple, low-cost, and highly flexible. It can accurately obtain the charging strategy of the battery cell for different battery cell systems and structures, and meets the requirements of common conventional material systems and battery cell structures. It has stronger universality. Attached Figure Description
[0019] Figure 1 This is the electrochemical impedance spectroscopy at 50% SOC in an embodiment of the present invention; Figure 2 This is a charge transfer characteristic impedance diagram of the entire SOC range during 0.5 C constant current charging according to an embodiment of the present invention; Figure 3 This is a charge transfer characteristic impedance diagram of the entire SOC range under different charging rates in an embodiment of the present invention; Figure 4 This is a fast charging window diagram of the battery cell under different charging rates without preload according to an embodiment of the present invention; Figure 5 This is a fast charging window diagram of the battery cell under different preload forces according to an embodiment of the present invention; Figure 6 This is a diagram of the fast charging window pressure correction model according to an embodiment of the present invention; Figure 7 This is a fast charging cycle verification diagram at 25°C according to an embodiment of the present invention. Detailed Implementation
[0020] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.
[0021] Unless otherwise defined, 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 invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
[0022] Existing technologies have made some progress in lithium plating monitoring and fast charging strategies, but there are still problems such as the complexity of the three-electrode system, insufficient consideration of pressure factors, and lack of correlation with the performance throughout the entire life cycle.
[0023] Therefore, developing a method for obtaining battery cell charging strategies that is easy to operate, cost-effective, can comprehensively consider the effects of electrochemical and mechanical stress, and is applicable to the entire life cycle of the battery cell is of great significance for improving the safety and adaptability of the battery fast charging process and extending the battery cell's lifespan.
[0024] Based on this, the present invention provides a method and apparatus for accurately obtaining a battery cell charging strategy based on pressure correction. A method for accurately obtaining a battery cell charging strategy based on pressure correction includes the following steps: S1. The critical SOC value at which the lithium plating reaction begins during constant current charging of the battery cell is obtained by dynamic electrochemical impedance spectroscopy. S2. Change the magnitude of the constant current charging during dynamic electrochemical impedance spectroscopy testing to obtain the lithium-free safe charging SOC range of the cell under different charging rates without preload, i.e., the safe fast charging window of the cell. S3. Apply different preload forces to the battery cell to obtain a safe fast charging window where lithium plating does not occur under different preload forces; S4. Establish a pressure-corrected fast charging window model for battery cells based on the relationship between pressure, charging rate, and critical SOC value. S5. Based on the pressure-corrected fast charging window model of the battery cell obtained in step S4, obtain a battery cell charging strategy applicable to different pressure states throughout the entire life cycle of the battery cell.
[0025] In a specific embodiment, step S5 specifically involves: inputting the real-time measured pressure value of the battery cell into the pressure-corrected fast charging window model of the battery cell, and having the model output the corresponding optimal charging strategy.
[0026] In a preferred embodiment of the present invention, the "full life cycle" of the battery cell can be understood as starting from its state of health (SOH) of 100% until the SOH decays to approximately 70%. Those skilled in the art will understand that the definition of the end of the life cycle may differ slightly for battery cells with different systems or design requirements. Any adjustments based on the concept of this invention should fall within the protection scope of this invention.
[0027] This invention dynamically adjusts the charging strategy based on changes in cell pressure, significantly reducing the risk of lithium plating on the surface of the negative electrode during high-current charging of lithium-ion batteries, slowing down battery degradation, and extending battery cycle life.
[0028] In a specific embodiment, the method further includes step S6, verifying the cell charging strategy obtained in step S5.
[0029] In a specific embodiment, the verification of the cell charging strategy obtained in step S5 in step S6 specifically involves verifying the cycle life of the cell using the cell charging strategy obtained in step S5.
[0030] In a specific embodiment, step S1 includes the following steps: S11. Obtain the charge transfer characteristic impedance (Rct) of the cell across the entire SOC range during constant current charging by dynamic electrochemical impedance spectroscopy (EIS). S12. Determine whether the cell has undergone lithium plating reaction based on the abnormal decrease in the charge transfer characteristic impedance value in the high SOC range. Determine the SOC value corresponding to the inflection point where the charge transfer characteristic impedance value first shows a significant decrease as the critical SOC value at which the lithium plating reaction begins at that rate. Obtain the critical SOC value at which the lithium plating reaction begins in the entire SOC range of the cell during constant current charging.
[0031] When lithium plating occurs during the charging process of a battery cell in the high SOC range, the Rct value decreases. The SOC corresponding to the decrease in Rct is the lithium plating SOC at that charging rate, i.e., the critical SOC. If no lithium plating occurs during the charging process, the Rct value in the high SOC range remains unchanged or increases.
[0032] In a specific embodiment, in step S2, the charging rate is between 0.1C and 3.5C. Specifically, C can be equal to 0.2, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, etc. This charging rate is only the charging rate / current magnitude adopted in the embodiment of the present invention and is not intended to limit the present invention. It can be adjusted according to actual needs.
[0033] In a specific embodiment, in step S3, the preload applied to the battery cell is between 0 and 1 MPa. Specifically, the preload applied to the battery cell can be 0 MPa, 0.1 MPa, 0.2 MPa, 0.4 MPa, 0.6 MPa, or 0.8 MPa.
[0034] The present invention also provides an apparatus for implementing the method for accurately obtaining cell charging strategies based on pressure correction as described above, comprising: The monitoring unit is configured to obtain the critical SOC value at which the lithium plating reaction begins in the entire SOC range of the cell during constant current charging by using dynamic electrochemical impedance spectroscopy, and to change the magnitude of the constant current charging current during dynamic electrochemical impedance spectroscopy testing to obtain the lithium-free safe charging range of the cell under different charging rates without preload, i.e., the safe fast charging window of the cell. The force application unit is used to apply preload and is configured to apply different preloads to the battery cell to obtain a safe fast charging window where lithium plating does not occur in the battery cell under different preloads. The cell testing unit is configured to test the cell and obtain the measured pressure value of the cell. It should be noted that the method of this invention does not limit the specific means of obtaining the measured pressure value. Any technical solution that can directly or indirectly obtain, estimate, or calculate the equivalent pressure on the battery cell, whether it is directly measured by a pressure sensor or indirectly obtained by monitoring other physical quantities (such as deformation displacement, acoustic characteristics, internal resistance, etc.) that have a definite correlation with pressure and converting them through a model, should be considered to fall within the protection scope of this invention, as long as it is ultimately applied to the pressure-corrected fast charging strategy described in this invention.
[0035] The calculation and analysis unit is configured to establish a pressure-corrected fast charging window model for the battery cell based on the relationship between pressure, charging rate, and critical SOC value, and to obtain the battery cell charging strategy based on the measured pressure value throughout the battery cell's life cycle.
[0036] In one specific embodiment, the monitoring unit is an electrochemical impedance spectroscopy instrument.
[0037] In a specific embodiment, the computational analysis unit is also configured to build a model based on the internal pressure change data throughout the entire life cycle of the battery cell in order to obtain the battery cell charging strategy in real time.
[0038] It should be noted that, unless otherwise specified, in the embodiments of the method and apparatus of this invention, all tests in steps S1 to S3, including dynamic electrochemical impedance spectroscopy testing and the acquisition of safety windows under different charging rates and preload forces, are performed in a constant temperature environment (e.g., 25±2℃). This constant temperature condition ensures that the electrochemical reaction kinetics and ion transport rate inside the battery cell are stable. The pressure correction model established on this basis has higher accuracy and reliability. Those skilled in the art will understand that, based on the model obtained under the constant temperature conditions of this standard, temperature variables can be further introduced to construct a more complex multi-dimensional fast charging window model to adapt to application scenarios under different thermal management conditions.
[0039] It is understood that the methods and apparatus described in this invention are not limited to specific battery chemistry systems. Any lithium-ion battery whose internal pressure or volume changes during charging and discharging can have its charging strategy optimized using the methods disclosed in this invention, and therefore is applicable to this invention.
[0040] The following is in conjunction with the appendix Figure 1 To be continued Figure 7 Specific embodiments of the present invention will be described in detail below.
[0041] This invention takes NCM cells as an example. NCM cells refer to lithium-ion battery cells that use lithium nickel cobalt manganese oxide as the positive electrode material.
[0042] This embodiment of the method for accurately obtaining the cell charging strategy based on pressure correction includes the following steps: S1. Obtain the Rct value of the battery cell across the entire SOC range during constant current charging at 0.5C without preload pressure through dynamic EIS testing (1~10 Hz frequency). The value of Rct is as follows: Figure 1 As shown.
[0043] By detecting the Rct inflection point under different SOCs, the accurate value of Rct-SOC can be obtained, such as... Figure 2 As shown, the Rct value first decreases during the charging process of the cell in the high SOC range (approximately 75% SOC in this example). This indicates that a lithium plating reaction has occurred. Therefore, the SOC value (75%) corresponding to the decrease in Rct is the lithium plating SOC value at 0.5C, which is the critical SOC value.
[0044] S2. Change the constant current during dynamic EIS testing to obtain the maximum SOC value of the cell without lithium plating under different charging rates (C=0.5, 1, 1.5, 2, 2.5, and 3) without preload. Figure 3 As shown, the SOC value corresponding to the occurrence of lithium plating decreases with increasing rate of increase.
[0045] Will be Figure 3 The lithium plating SOC values obtained at different charging rates were plotted to obtain a safe fast charging window diagram of the battery cell under different charging rates without preload (0 MPa), as shown below. Figure 4 As shown.
[0046] S3. Apply different preload forces (0 MPa, 0.1 MPa, 0.2 MPa, 0.4 MPa) to the battery cell to obtain the SOC range where lithium plating does not occur under different preload forces, i.e., the safe fast charging window. Figure 5 As shown.
[0047] S4. Based on the relationship between pressure, charging rate, and critical SOC value, establish a three-dimensional model of the battery cell's fast charging window after pressure correction, such as... Figure 6 As shown.
[0048] S5. Based on this model, the battery cell charging strategy can be obtained and its fast charging method can be determined by the measured pressure values under different pressure states throughout the battery cell's life cycle.
[0049] S6. Verify the cell charging strategy obtained in step S5. For the NCM cell in this embodiment, the measured pressure value at the end of its life cycle, i.e. the end of aging, at 25°C is about 0.2 MPa. The charging strategy at 0.2 MPa (as shown on the right side of Table 1) is used as the experimental group, and the charging strategy at 0 MPa (as shown on the left side of Table 1) is used as the control group. The cycle life is verified respectively.
[0050] Table 1. Charging rates of NCM cells at different SOC ranges. The results are as follows Figure 7 As shown in the figure, the capacity retention rate of the control group and the experimental group is related to the number of cycles. The verification results show that the fast charging cycle life of the battery cell is significantly improved after adopting the pressure-corrected charging strategy. Under the experimental conditions, its cycle life (based on a capacity retention rate of 90%) is about 50% higher than that of the uncorrected strategy.
[0051] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0052] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.
Claims
1. A method for accurately obtaining cell charging strategies based on pressure correction, characterized in that, Includes the following steps: S1. The critical SOC value at which the lithium plating reaction begins during constant current charging of the battery cell is obtained by dynamic electrochemical impedance spectroscopy. S2. Change the magnitude of the constant current during dynamic electrochemical impedance spectroscopy testing to obtain the lithium-free safe charging range of the cell under different charging rates without preload, i.e., the safe fast charging window of the cell. S3. Apply different preload forces to the battery cell to obtain a safe fast charging window where lithium plating does not occur under different preload forces; S4. Establish a pressure-corrected fast charging window model for battery cells based on the relationship between pressure, charging rate, and critical SOC value. S5. Based on the pressure-corrected fast charging window model of the battery cell obtained in step S4, obtain a battery cell charging strategy applicable to different pressure states throughout the entire life cycle of the battery cell.
2. The method for accurately obtaining cell charging strategies based on pressure correction according to claim 1, characterized in that, It also includes step S6, verifying the cell charging strategy obtained in step S5.
3. The method for accurately obtaining cell charging strategies based on pressure correction according to claim 2, characterized in that, The verification of the cell charging strategy obtained in step S5 in step S6 specifically involves verifying the cycle life of the cell using the cell charging strategy obtained in step S5.
4. The method for accurately obtaining cell charging strategies based on pressure correction according to claim 1, characterized in that, Step S1 includes the following steps: S11. Obtain the charge transfer characteristic impedance of the battery cell across the entire SOC range during constant current charging by dynamic electrochemical impedance spectroscopy. S12. Based on the abnormal decrease in the charge transfer characteristic impedance value in the high SOC range, it is determined that the cell has undergone lithium plating reaction. The SOC value corresponding to the inflection point where the charge transfer characteristic impedance value first shows a significant decrease is determined as the critical SOC value at which the lithium plating reaction begins at that rate. The critical SOC value at which the lithium plating reaction begins in the entire SOC range of the cell during constant current charging is obtained.
5. The method for accurately obtaining cell charging strategies based on pressure correction according to claim 1, characterized in that, In step S2, the charging rate is between 0.1C and 3.5C.
6. The method for accurately obtaining cell charging strategies based on pressure correction according to claim 1, characterized in that, In step S3, the preload applied to the battery cell is between 0 and 1 MPa.
7. The method according to claim 1, characterized in that, Step S5 specifically involves inputting the real-time measured pressure value of the battery cell into the pressure-corrected fast charging window model of the battery cell, and having the model output the corresponding optimal charging strategy.
8. An apparatus for implementing the method of accurately acquiring cell charging strategy based on pressure correction as described in any one of claims 1 to 7, characterized in that, include: The monitoring unit is configured to obtain the critical SOC value at which the lithium plating reaction begins in the entire SOC range of the cell during constant current charging by using dynamic electrochemical impedance spectroscopy, and to obtain the lithium-free safe charging range of the cell under different charging rates by changing the magnitude of the constant current charging current during dynamic electrochemical impedance spectroscopy testing, i.e., the safe fast charging window of the cell. The force application unit is used to apply preload and is configured to apply different preloads to the battery cell to obtain a safe fast charging window where lithium plating does not occur in the battery cell under different preloads. The cell testing unit is configured to test the cell and obtain the measured pressure value of the cell. The calculation and analysis unit is configured to establish a pressure-corrected fast charging window model for the battery cell based on the relationship between pressure, charging rate, and critical SOC value, and to obtain the battery cell charging strategy based on the measured pressure value throughout the battery cell's life cycle.
9. The apparatus according to claim 8, characterized in that, The monitoring unit is an electrochemical impedance spectroscopy instrument.
10. The apparatus according to claim 8, characterized in that, The computational analysis unit is also configured to build a model based on the internal pressure change data throughout the entire life cycle of the battery cell, so as to obtain the battery cell charging strategy in real time.