Lithium ion battery lithium precipitation quantitative grading evaluation method based on electrochemical simplified model
By simulating lithium plating in batteries using a simplified electrochemical model, calculating the amount of lithium plating and establishing correlations, the problem of quantitative grading and evaluation of lithium plating in lithium-ion batteries is solved. This enables safe management and real-time evaluation of batteries and is suitable for practical applications of lithium-ion batteries.
Patent Information
- Application Number
- CN202511391913.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-26
- Publication Date
- 2026-02-06
AI Technical Summary
Existing technologies struggle to accurately establish the relationship between lithium plating index and degree of lithium plating in lithium-ion batteries, and lack quantitative grading and evaluation methods for lithium plating under complex operating conditions, which affects the cycle life and safety status of batteries.
By employing a simplified electrochemical model and simulating the voltage curves of the battery under different temperatures and operating conditions, the lithium plating situation and trigger current boundary value are determined. The amount of reversible and irreversible lithium plating is calculated, and the correlation between the degree of lithium plating and the capacity decay rate is established to achieve graded evaluation.
It enables precise quantification and grading assessment of the degree of lithium plating in batteries, provides a clear basis for battery safety management, supports real-time adjustment of charging strategies and safety warnings, and is suitable for the actual operation of lithium-ion batteries.
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Figure CN121483408A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of fault diagnosis of lithium-ion power batteries, and more particularly to a fault diagnosis method for lithium-ion power batteries. Background Technology
[0002] In recent years, lithium-ion batteries have been considered an effective way to reduce environmental pollution and energy consumption. However, low-temperature charging or high-rate charging increases the risk of lithium plating and accelerates battery capacity degradation. Lithium dendrites formed during battery cycling, and even internal short circuits caused by lithium dendrites piercing the separator, can significantly impact the battery's cycle life and safety. Achieving in-situ rapid detection and quantitative grading assessment of lithium plating in lithium-ion batteries is one of the key technologies for the safe and efficient operation of lithium-ion batteries.
[0003] Currently, various methods exist for accurately identifying lithium plating in lithium-ion batteries and enabling real-time charging strategy control. However, establishing the relationship between lithium plating indicators and the degree of lithium plating, and characterizing the amount of lithium plating in batteries through measurable quantities, remain significant technical challenges in the battery field. Research on the quantitative grading and evaluation of lithium plating in batteries under complex operating conditions is relatively scarce. Summary of the Invention
[0004] This invention provides a method for quantitative grading and evaluation of lithium plating in lithium-ion batteries based on a simplified electrochemical model, comprising the following steps: Step 1: Simulate the voltage curves of the battery under different temperatures and operating conditions using a simplified electrochemical-lithium plating model to determine the lithium plating status and the boundary value of the lithium plating trigger current. Step 2: Calculate the reversible lithium plating amount, irreversible lithium plating amount, and total lithium plating amount of the battery to quantify the degree of lithium plating in the battery; Step 3: Using the boundary value of the lithium plating trigger current determined in Step 1 as the initial condition of the model, simulate the change in the amount of lithium plating and the capacity decay rate during the battery cycling process, establish the correlation between the degree of lithium plating and the capacity decay rate, and determine the grading index and its value of the degree of lithium plating in lithium-ion batteries. Step 4: Utilize simplified electrochemical models and lithium plating models to dynamically simulate and calculate the amount of irreversible lithium plating during battery operation. Combine this with the battery capacity decay rate to achieve a graded evaluation of battery lithium plating.
[0005] Furthermore, in step one, the battery operating environment temperature is any value within the range of -10℃ to 50℃, and the battery charge / discharge rate is any value within the range of 1 / 5C to 1.5C.
[0006] Furthermore, in step one, it is determined whether lithium plating has occurred in the battery by at least one of the following methods: simulating the battery anode potential curve, calculating the differential voltage curve, the capacity increment curve, or the relaxation voltage curve.
[0007] Furthermore, in step two, the reversible lithium plating capacity is determined by the capacity value corresponding to the lowest point of the trough in the battery differential voltage curve, the irreversible lithium plating capacity is determined by the battery capacity calibration difference or theoretical calculation, and the total lithium plating amount and lithium plating reversibility factor are calculated by summing the reversible and irreversible lithium plating capacities.
[0008] Furthermore, the simplified electrochemical model and lithium plating model include electrode reaction kinetic equations, lithium-ion diffusion equations, and lithium plating side reaction equations, used to simulate the electrochemical behavior of the battery under low temperature or high rate conditions.
[0009] Furthermore, in step three, the grading indicators include the cumulative amount of irreversible lithium plating and the capacity decay rate, and the degree of lithium plating is divided into four levels: slight, moderate, severe, and failure based on the correlation.
[0010] Furthermore, the mild lithium plating level corresponds to an irreversible lithium plating accumulation of less than 5% of the battery capacity and a capacity decay rate of less than 1.1% / cycle; the moderate lithium plating level corresponds to an irreversible lithium plating accumulation between 5% and 10% of the battery capacity and a capacity decay rate of less than 1.3% / cycle; the severe lithium plating level corresponds to an irreversible lithium plating accumulation between 10% and 15% of the battery capacity and a capacity decay rate of less than 1.6% / cycle; and the failure level corresponds to an irreversible lithium plating accumulation exceeding 15% of the battery capacity and a capacity decay rate of not less than 1.6% / cycle.
[0011] Furthermore, in step four, the dynamic simulation calculation is based on real-time battery operating data, including voltage, current and temperature, and the model predicts the cumulative trend of irreversible lithium plating.
[0012] Furthermore, the method is applicable to any one of cobalt-free lithium-ion batteries, ternary lithium-ion batteries, or lithium iron phosphate batteries.
[0013] Furthermore, the method also includes integrating the graded evaluation results into the battery management system for real-time adjustment of charging strategies or triggering safety warnings.
[0014] The present invention has the following technical effects: 1. This invention is based on a simplified electrochemical-lithium plating model, which can quickly simulate the voltage curve of the battery under different temperatures and charge / discharge rates, accurately determine the lithium plating status of the battery and the boundary value of the lithium plating trigger current, and lay a reliable foundation for subsequent lithium plating quantification and classification evaluation.
[0015] 2. By calculating the amount of reversible lithium plating, irreversible lithium plating, and total lithium plating, the degree of lithium plating in the battery is quantified. Compared with the traditional single-dimensional lithium plating diagnosis method, it can reflect the lithium plating state of the battery more comprehensively and accurately.
[0016] 3. A correlation was established between the degree of lithium plating in batteries and the capacity decay rate. The grading indicators and numerical ranges of the degree of lithium plating were clarified, enabling a graded assessment of battery lithium plating and providing a clear and operable basis for battery safety management.
[0017] 4. The simplified electrochemical-lithium plating model, while ensuring computational accuracy, has a high simulation speed and can meet the needs of real-time evaluation during actual battery operation. It can be widely used in scenarios such as lithium-ion power batteries for electric vehicles, and has good practicality and promotion value. Attached Figure Description
[0018] Figure 1 This is a flowchart of the method of the present invention; Figure 2 Simulated terminal voltage curves of the battery at different charging rates at -5℃; Figure 3 Anode potential curves of the battery at different charging rates at -5℃; Figure 4 Differential voltage curves of the battery after charging at different rates at -5℃ and then discharging. Figure 5 The curves show the changes in irreversible lithium deposition and capacity decay rate during battery cycling. Detailed Implementation
[0019] To make the objectives, advantages, and features of the present invention more apparent, the following description is provided in conjunction with the appendix. Figure 1-5 The present invention will be further described in detail below with reference to specific embodiments.
[0020] This invention verifies its correctness by conducting charging experiments with three cobalt-free batteries at different temperatures and rates using three different batteries. The experimental equipment used includes: Fujian Xingyun charge-discharge testing equipment, Bell BTT-544C high and low temperature chamber, and Jinke multi-channel temperature acquisition equipment. Detailed testing procedures are outlined below. Figure 1 As shown. This embodiment does not constitute a limitation of the present invention.
[0021] Step 1: Use a simplified electrochemical-lithium plating model to simulate the voltage curves of the battery under different temperatures and operating conditions to determine the lithium plating status of the battery and the boundary value of the lithium plating trigger current. This invention utilizes a simplified electrochemical-lithium plating model to simulate the battery terminal voltage curves of a cobalt-free battery under different charging rates at -5℃, and compares these curves with experimental values to confirm the accuracy of the simulated terminal voltage curves. Figure 2 As shown. From Figure 2As can be seen, the simulation accuracy of the simplified model is significantly improved after introducing the lithium plating reaction, with the maximum RMSE of the terminal voltage within 30mV. This result shows that the simplified electrochemical-lithium plating model can accurately describe the electrochemical behavior of the battery under low temperature conditions, especially the voltage change characteristics near the lithium plating trigger boundary.
[0022] Furthermore, to verify the accuracy of the model in detecting lithium plating in the battery, the potential distribution at the interface between the negative electrode and the separator was simulated (e.g., Figure 3 (as shown) and the calculated differential voltage curve of the battery during the discharge process (as shown) Figure 4 As shown in the figure, the lithium plating behavior of the battery under different charging rates and the boundary value of the lithium plating trigger current were determined. Simulation results show that at charging rates of 0.75C and 1C, the negative electrode potential drops below 0V during charging, which is highly consistent with the thermodynamic criterion for lithium plating triggering. A significant trough appears in the differential voltage curve, a feature corresponding to the voltage plateau caused by the lithium re-intercalation process. This indicates that the simplified electrochemical-lithium plating model can accurately predict the lithium plating trigger boundary of the battery. The critical lithium plating current of the battery can be determined to be 0.75C using the anolyte potential curve and the differential voltage curve.
[0023] Step 2: Calculate the reversible lithium plating, irreversible lithium plating, and total lithium plating amount of the battery to quantify the degree of lithium plating in the battery; This invention determines the reversible lithium plating capacity of a battery by identifying the capacity corresponding to the lowest point of the trough in the differential voltage curve during battery discharge, and determines the irreversible lithium plating capacity by identifying the battery capacity calibration difference, or by theoretically calculating the irreversible lithium plating capacity. The total amount of lithium plating and the lithium plating reversibility factor are calculated by summing the reversible and irreversible lithium plating capacities. Table 1 shows the proportion of reversible lithium plating and the corresponding lithium plating reversibility factor results.
[0024] Table 1. Percentage of reversible lithium plating ; ; ; The error in the proportion of irreversible lithium plating capacity to total lithium plating calculated by this invention can be controlled within 8%.
[0025] Step 3: Using the boundary value of the lithium plating trigger current determined in Step 1 as the initial condition of the model, simulate the change in lithium plating amount and capacity decay rate during the battery cycling process, establish the correlation between the degree of lithium plating and the capacity decay rate, and determine the lithium plating degree classification index and its value for lithium-ion batteries. This invention uses the boundary value of the lithium plating trigger current determined in step one as the initial condition for a simplified electrochemical-lithium plating model to simulate the battery's tolerance under cycle conditions and quantify the relationship between the amount of irreversible lithium plating and the capacity decay rate. Figure 5 The changes in the amount of irreversible lithium plating generated by the lithium plating side reaction and the battery capacity decay rate with the increase of the number of cycles are given.
[0026] Battery capacity loss generally increases with the number of cycles, reaching 53.3 mAh in the last cycle. This rapid increase in lithium deposition indicates that the more metallic lithium accumulates on the surface of graphite particles, the greater the risk of lithium dendrite formation. To establish a quantitative assessment method for the degree of lithium plating, this invention comprehensively considers two key parameters: the amount of irreversible lithium plating accumulation and the capacity decay rate, using these as a safety boundary for lithium plating.
[0027] Step 4: Combine the battery capacity decay rate to achieve graded evaluation of battery lithium plating.
[0028] Given that the irreversible lithium plating accumulated during cycling in a low-temperature, high-rate environment reaches 500mAh, accounting for 16% of the battery capacity, this invention uses 15% irreversible lithium plating accumulation and its corresponding capacity decay rate of 1.6% as the boundary for battery failure. Based on the value of the accumulated irreversible lithium plating, the battery is classified into three levels: Level 1 is slight lithium plating, with an irreversible lithium plating accumulation of less than 5% and a capacity decay rate of less than 1.1%; Level 2 is moderate lithium plating, with an irreversible lithium plating accumulation between 5% and 10% and a capacity decay rate of less than 1.1%; and Level 3 is severe lithium plating, with an irreversible lithium plating accumulation between 10% and 15% and a capacity decay rate of less than 1.6%, as shown in Table 2.
[0029] Table 2 Grading Criteria for Lithium Plating Degree at Low Temperatures ;
[0030] This invention, based on a simplified electrochemical-lithium plating model, can rapidly simulate lithium plating conditions and amounts under different battery operating conditions, and achieve automatic grading and evaluation of battery lithium plating during operation. Compared with existing diagnostic technologies, this invention can achieve quantitative grading and evaluation of lithium plating in lithium-ion batteries, and is more precise and accurate than single-dimensional lithium plating diagnostic methods.
[0031] The above embodiments are for illustrative purposes only and are not intended to limit the scope of this invention. Those skilled in the art can make various changes and modifications without departing from the essence and scope of this invention. Therefore, all equivalent technical solutions also fall within the scope of this invention, and the patent protection scope of this invention should be defined by the claims. Content not described in detail in this specification is prior art known to those skilled in the art.
Claims
1. A quantitative grading and evaluation method for lithium-ion battery lithium plating based on a simplified electrochemical model, characterized in that, Includes the following steps: Step 1: Simulate the voltage curves of the battery under different temperatures and operating conditions using a simplified electrochemical-lithium plating model to determine the lithium plating status and the boundary value of the lithium plating trigger current. Step 2: Calculate the reversible lithium plating amount, irreversible lithium plating amount, and total lithium plating amount of the battery to quantify the degree of lithium plating in the battery; Step 3: Using the boundary value of the lithium plating trigger current determined in Step 1 as the initial condition of the model, simulate the change in the amount of lithium plating and the capacity decay rate during the battery cycling process, establish the correlation between the degree of lithium plating and the capacity decay rate, and determine the grading index and its value of the degree of lithium plating in lithium-ion batteries. Step 4: Utilize simplified electrochemical models and lithium plating models to dynamically simulate and calculate the amount of irreversible lithium plating during battery operation. Combine this with the battery capacity decay rate to achieve a graded evaluation of battery lithium plating.
2. The method as described in claim 1, characterized in that, In step one, the battery operating environment temperature is any value within the range of -10℃ to 50℃, and the battery charge / discharge rate is any value within the range of 1 / 5C to 1.5C.
3. The method as described in claim 1, characterized in that, In step one, it is determined whether lithium plating has occurred in the battery by using at least one of the following methods: simulating the battery anode potential curve, calculating the differential voltage curve, the capacity increment curve, or the relaxation voltage curve.
4. The method as described in claim 1, characterized in that, In step two, the reversible lithium plating capacity is determined by the capacity value corresponding to the lowest point of the trough in the battery differential voltage curve, the irreversible lithium plating capacity is determined by the battery capacity calibration difference or theoretical calculation, and the total amount of lithium plating and the lithium plating reversibility factor are calculated by summing the reversible and irreversible lithium plating capacities.
5. The method as described in claim 1, characterized in that, The simplified electrochemical model and lithium plating model include electrode reaction kinetic equations, lithium-ion diffusion equations, and lithium plating side reaction equations, which are used to simulate the electrochemical behavior of batteries under low temperature or high rate conditions.
6. The method as described in claim 1, characterized in that, In step three, the grading indicators include the cumulative amount of irreversible lithium plating and the capacity decay rate, and the degree of lithium plating is divided into four levels: slight, moderate, severe, and failure based on the correlation.
7. The method as described in claim 6, characterized in that, The "slight" lithium plating level corresponds to an irreversible lithium plating accumulation of less than 5% of the battery capacity and a capacity decay rate of less than 1.1% per cycle; the "medium" lithium plating level corresponds to an irreversible lithium plating accumulation between 5% and 10% of the battery capacity and a capacity decay rate of less than 1.3% per cycle; the "severe" lithium plating level corresponds to an irreversible lithium plating accumulation between 10% and 15% of the battery capacity and a capacity decay rate of less than 1.6% per cycle; and the "failure" level corresponds to an irreversible lithium plating accumulation exceeding 15% of the battery capacity and a capacity decay rate of not less than 1.6% per cycle.
8. The method as described in claim 1, characterized in that, In step four, the dynamic simulation calculation is based on real-time battery operating data, including voltage, current and temperature, and the model predicts the cumulative trend of irreversible lithium plating.
9. The method as described in claim 1, characterized in that, The method is applicable to any one of cobalt-free lithium-ion batteries, ternary lithium-ion batteries, or lithium iron phosphate batteries.
10. The method as described in claim 1, characterized in that, The method also includes integrating the graded evaluation results into the battery management system for real-time adjustment of charging strategies or triggering safety warnings.