Battery lithium precipitation detection method and system based on different scanning speeds, and electronic equipment

Abstract

The invention discloses a battery lithium precipitation detection method and system based on different scanning speeds and electronic equipment, and the method comprises the following steps: obtaining a plurality of charging voltages of a battery in a charging process, providing a scanning signal with a certain amplitude based on each charging voltage, and carrying out cyclic volt-ampere tests with different scanning speeds, a cyclic voltammetry curve is obtained; based on each charging voltage, carrying out linear fitting on response current corresponding to an intermediate voltage value of a scanning signal in a linear change range of a cyclic voltammetry curve and different scanning speeds to obtain an electric double-layer capacitance value; and based on the electric double layer capacitance values corresponding to the plurality of charging voltages respectively, judging whether lithium precipitation occurs in the battery or not. The detection method provided by the invention is simple and convenient to operate, accurate in detection result and suitable for batteries of various material systems, particularly has remarkable advantages in the aspect of improving the applicability and accuracy of detecting the lithium precipitation phenomenon, and can be widely applied to the field of battery quality detection.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical detection, and particularly to a method, system and electronic device for detecting lithium plating of a battery based on different scan rates. Background Art

[0002] With the wide application of lithium-ion batteries, their safety has become a key research direction. The phenomenon of lithium plating is one of the important factors leading to the decline of battery performance and potential safety hazards. Especially under high charging voltages, lithium metal is likely to deposit on the surface of the negative electrode, and then lithium dendrites are formed, increasing the safety risk of the battery.

[0003] In the prior art, the lithium plating detection based on the single-frequency impedance method (application number: 202111292878.3) applies a sinusoidal alternating current signal with a specific amplitude while the battery is being charged normally. However, the selection of the single-frequency of the sinusoidal alternating current scan signal has limitations for batteries with different material systems. This single frequency needs to avoid interference from the change of the positive electrode impedance so that the selected frequency is within the response frequency range of the negative electrode charge transfer impedance. Therefore, this method has high requirements for the selection of the characteristic frequency of the sinusoidal alternating current signal, with limited practicality and difficulty in achieving wide application.

[0004] In addition, another patent (application number: 202411093548.5) uses a triangular wave scan signal to test for lithium plating. The battery is charged at a constant current to different potentials, and then a low amplitude and high frequency are applied to obtain the peak response current of the battery during the triangular wave excitation process. The double-layer capacitance can be obtained by dividing the difference Δi between the peak response current and the fitted current value by twice the scan rate. The disadvantage of this method is that it can only test the lithium plating situation under low-rate overcharging conditions and is not suitable for the lithium plating detection of mass-produced battery cells. The reason is that this method requires charging at a low rate to slow down the electrochemical reaction rate so that the charging and discharging process of the double-layer capacitance can be more stably manifested, thus helping to detect whether the battery has lithium plating through the change of the double-layer capacitance.

[0005] Therefore, there is an urgent need for a new method to detect the lithium plating behavior. Summary of the Invention

[0006] The present invention provides a method, system and electronic device for detecting lithium plating of a battery based on different scan rates, aiming to efficiently and accurately detect the lithium plating phenomenon of lithium-ion batteries. This method is tested by cyclic voltammetry (CV) at different scan rates, and the double-layer capacitance is calculated using the linear relationship between the response current and the scan rate, and then it is determined whether the battery has lithium plating.

[0007] In one aspect of the present invention, a method for detecting lithium plating of a battery based on different scan rates is proposed. According to an embodiment of the present invention, the method includes the following steps:

[0008] (1) Obtain multiple charging voltages of the battery during charging. Based on each of the charging voltages, provide a scanning signal with a certain amplitude, and perform cyclic voltammetry tests at different scanning speeds to obtain cyclic voltammograms.

[0009] (2) Based on each of the charging voltages, perform a linear fitting of the response current corresponding to the intermediate voltage value of the scanning signal within the linearly varying range of the cyclic voltammogram and different scanning speeds to obtain the double-layer capacitance value.

[0010] (3) Based on the double-layer capacitance values corresponding to multiple charging voltages, determine whether lithium plating occurs in the battery.

[0011] The above solution determines whether lithium plating occurs in the battery based on the determined double-layer capacitance, without the need to measure impedance, measure the response frequency of impedance, and measure the triangular wave excitation frequency. Therefore, when performing lithium plating detection, it is not necessary to consider the current material system of the battery, and it is applicable to batteries with various different material systems. In the case of accurately detecting whether lithium plating occurs in the battery, the applicability is improved, and it can be well applied to the actual application conditions of lithium plating detection.

[0012] In addition, according to a method for detecting lithium plating in a battery based on different scanning speeds in the above embodiments of the present invention, the following additional technical features may also be provided:

[0013] In some embodiments of the present invention, in step (1), the method for obtaining multiple charging voltages of the battery during charging is as follows: charge the battery to different voltages according to a certain voltage step, time step, or charge state step, and then obtain multiple charging voltages. The design of this step can dynamically cover the key lithium plating stage: lithium plating usually occurs in the middle and late stages of charging (such as high SoC or high voltage range). Therefore, step-by-step sampling (voltage / time / SoC) can ensure that data covers the entire charging process and avoid missing key lithium plating points; in addition, the data volume and efficiency can be optimized. By reasonably setting the step, while reducing redundant data, the capture of lithium plating characteristics (sudden increase in double-layer capacitance) can be ensured.

[0014] In some embodiments of the present invention, in step (1), the battery is charged based on a constant current charging current. Charging with a constant current makes the polarization of the battery more regular with the change of time or capacity, which is convenient for data comparison and analysis of cyclic voltammetry tests. If constant voltage or pulse charging is used, the dynamic change of the current may cause the response of the double-layer capacitance to be unstable, increasing the interference factors for lithium plating judgment.

[0015] In some embodiments of the present invention, in step (1), the amplitude range of the scanning signal is 0 - 50 mV. Within this potential range, the electrochemical reaction is smaller than the double-layer charge and discharge process.

[0016] In some embodiments of the present invention, in step (1), the scanning rates at different sweep rates are 0.1 to 50 mV / s. Within this scanning rate range, the electrochemical reaction process is shorter than the double-layer charging and discharging process. The number of tests at different sweep rates is preferably greater than or equal to 3 times.

[0017] In some embodiments of the present invention, in step (2), the linear fitting results in a linear equation, and the slope of the linear equation is the double-layer capacitance value.

[0018] In the above solution, at each charging voltage, cyclic voltammetry tests are performed. A scanning signal with a certain amplitude is applied, and cyclic voltammetry tests at different sweep rates are carried out. During the cyclic voltammetry test at each sweep rate, a cyclic voltammetry curve of the response current varying with the scanning signal is generated. The response current value corresponding to the middle value of the scanning signal in the linear part of the curve change is taken. When cyclic voltammetry tests at different sweep rates are performed, multiple cyclic voltammetry test curves are generated. The response current values corresponding to the middle values of the scanning signals in the linear regions of these cyclic voltammetry test curves are all taken. Subsequently, the response current values are linearly fitted with different sweep rates, and the slope of the obtained linear fitting equation i c = C dl ·v is the double-layer capacitance value C dl at this charging voltage, where i c is the response current and v is the sweep rate.

[0019] In some embodiments of the present invention, in step (3), the change of the double-layer capacitance value with the charging voltage, charging time, or charging capacity at each charging voltage is analyzed to determine whether lithium plating occurs in the battery.

[0020] In some embodiments of the present invention, when the change of the double-layer capacitance value with the charging voltage, charging time, or charging capacity shows a sudden increase, it is determined that lithium plating has occurred in the battery. When lithium plating occurs, the deposition of metallic lithium on the negative electrode surface will significantly increase the surface area of the negative electrode, resulting in a sudden increase in the double-layer capacitance (C dl ). This change in the double-layer capacitance is in sharp contrast to the normal lithium insertion process (C dl showing a gentle change), which can be used as a reliable criterion for lithium plating determination. The sudden increase amplitude can be determined by comparing with the baseline, and at the same time, the lithium plating back-insertion peak of the open-circuit voltage curve is used for secondary verification.

[0021] On the other hand, the present invention proposes a battery lithium plating detection system based on different sweep rates. According to the embodiments of the present invention, the system includes:

[0022] A data extraction module, configured to obtain multiple charging voltages during the charging process of the battery, provide a scanning signal with a certain amplitude based on each charging voltage, and perform cyclic voltammetry tests at different sweep rates to obtain cyclic voltammetry curves;

[0023] The data analysis module linearly fits the response current corresponding to the intermediate voltage value of the signal scanned within the linearly varying range of the cyclic voltammetry curve and different scan rates based on each of the charging voltages to obtain the double-layer capacitance value;

[0024] The lithium deposition judgment module determines whether lithium deposition occurs in the battery based on the double-layer capacitance values corresponding to multiple charging voltages.

[0025] Plot the double-layer capacitance values obtained at each charging voltage against voltage / SOC / time. If the double-layer capacitance value suddenly increases at a certain voltage / SOC / moment, it indicates that lithium metal is deposited at this time, resulting in a sudden increase in the electrode surface area and ultimately an increase in the double-layer capacitance value obtained by the test.

[0026] In another aspect of the present invention, the present invention proposes an electronic device for detecting lithium deposition in a battery based on different scan rates. According to an embodiment of the present invention, it includes a storage medium and a processing module. The storage medium stores a computer program that can run in the processing module. When the processing module executes the computer program, it implements the steps of the method for detecting lithium deposition in a battery based on different scan rates. Through this step, real-time monitoring of lithium deposition during the charging process can be achieved. In the processing module, it also includes fitting of cyclic voltammetry data for different scan rates to ensure real-time display of the detection results. This electronic device can complete the full process from signal acquisition to lithium deposition determination locally without relying on cloud computing, meeting the low-latency requirements in the actual test process.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] (1) Simplified steps: The present invention only needs to obtain multiple charging voltage points during the battery charging process, and the double-layer capacitance value can be obtained through cyclic voltammetry tests at different scan rates and linear fitting, without the need for complex impedance frequency selection or low-rate overcharge conditions.

[0029] (2) Independent of the material system: By analyzing the linear response of the double-layer capacitance, the dependence on the impedance characteristics of the positive and negative electrode materials of the battery in the traditional method is avoided, and it is applicable to various battery systems such as ternary systems, lithium iron phosphate systems, and lithium manganese iron phosphate systems.

[0030] (3) Improved detection accuracy and reliability: By judging lithium deposition based on the change trend of the double-layer capacitance with charging voltage, time, or state of charge, and verifying with the open-circuit voltage curve, the credibility of the lithium deposition determination result is improved.

[0031] (4) Applicability to actual working conditions: The optimized selection of the scanning rate (0.1 - 50 mV / s) and signal amplitude (0 - 50 mV) enables the method to be directly used at the conventional charging rate without deliberately reducing the charging rate. Through the coordination of the data extraction, analysis, and judgment modules, it can be integrated into electronic devices to achieve real-time online monitoring. Description of the Drawings

[0032] Figure 1 is a schematic flow chart of a method for detecting lithium plating in a battery based on different scanning rates in Embodiment 1 of the present invention;

[0033] Figure 2 is a schematic diagram showing the relationship between the response current and the voltage of the scanning signal under different scanning rate conditions in Embodiment 1 of the present invention;

[0034] Figure 3 is a schematic diagram of the linear fitting relationship between the response current and the scanning rate at a certain charging voltage in Embodiment 1 of the present invention;

[0035] Figure 4 is a schematic diagram of the data of the double-layer capacitance changing with the charging time in Embodiment 1 of the present invention;

[0036] Figure 5 is a differential voltage curve graph of the battery during storage in Embodiment 1 of the present invention;

[0037] Figure 6 is a schematic diagram showing the relationship between the response current and the voltage of the scanning signal under different scanning rate conditions in Embodiment 2 of the present invention;

[0038] Figure 7 is a schematic diagram of the linear fitting relationship between the response current and the scanning rate at a certain charging voltage in Embodiment 2 of the present invention;

[0039] Figure 8 is a schematic diagram of the data of the double-layer capacitance changing with the charging SOC in Embodiment 2 of the present invention;

[0040] Figure 9 is a differential voltage curve graph of the battery during storage in Embodiment 2 of the present invention;

[0041] Figure 10 is a schematic diagram of the data of the double-layer capacitance changing with the charging voltage in Embodiment 3 of the present invention;

[0042] Figure 11 is a differential voltage curve graph of the battery during storage in Embodiment 3 of the present invention;

[0043] Figure 12 is a schematic diagram of a system for detecting lithium plating in a battery based on different scanning rates provided by the present invention. Detailed Embodiments

[0044] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following will further describe the specific technical solutions of this application in detail with reference to the accompanying drawings in the embodiments of this application. The following embodiments are used to illustrate this application but are not intended to limit the scope of this application.

[0045] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in this application are only for the purpose of describing the embodiments and are not intended to limit this application.

[0046] In the embodiments of this application, the battery involved may be a battery cell. The battery cell may be a secondary battery. The battery may also be a single physical module including one or more battery cells to provide a higher voltage and capacity. The battery cell may be a lithium-ion battery, a sodium-ion battery, etc., and the embodiments of this application are not limited thereto. The electrode system of the battery may include, but is not limited to, a three-electrode system battery and a two-electrode system.

[0047] Embodiment 1

[0048] As Figure 1 shown, a method for detecting lithium plating in a battery based on different scan rates includes the following steps:

[0049] (1) Obtain multiple charging voltages of the battery during the charging process. Based on each charging voltage, provide a scanning signal with a certain amplitude and perform cyclic voltammetry tests at different scan rates to obtain cyclic voltammograms.

[0050] In this embodiment, a 70 mAh lithium-ion battery is used, with a ternary material system as the positive electrode and a graphite system as the negative electrode. Cyclic voltammetry tests are performed in the voltage range of 2.8 V to 4.25 V. According to the time step of charging for 1 minute each, the charging current is 105 mA, and cyclic voltammetry tests are performed at different scan rates (0.1 mV / s, 0.2 mV / s, 0.3 mV / s, 0.4 mV / s, 0.5 mV / s). The voltage range of the scanning signal used is 50 mV. Record the relationship curve between the response current and the scanning signal voltage at each scan rate, as Figure 2 shown.

[0051] (2) Based on each charging voltage, perform linear fitting on the response current corresponding to the intermediate voltage value of the scanning signal within the linearly varying range of the cyclic voltammogram and different scan rates to obtain the double-layer capacitance value.

[0052] Take the response current corresponding to the intermediate voltage value (30 mV) of the scanning signal within the linear range of the cyclic voltammogram and the scan rate, and perform linear fitting on this response current and the scan rate. As shown in the appendix Figure 3 shown, obtain the linear fitting equation i c = Cdl ·v, where v is the slope of the equation, which is the value of the electric double layer capacitance C dl , where i c is the response current and v is the scanning rate. The values of the electric double layer capacitance in different charging stages are calculated respectively. The variation curve of the electric double layer capacitance with the charging time is as shown in Figure 4 shown.

[0053] (3) Based on the values of the electric double layer capacitance corresponding to multiple said charging voltages, it is determined whether lithium plating occurs in the battery.

[0054] As shown in Figure 4 , a significant increase in the electric double layer capacitance at the end of charging indicates that lithium plating has occurred in the battery. Figure 5 is the differential voltage curve of the battery during storage. It can be seen that there is an obvious peak of voltage mutation in the storage curve of the battery, and this peak is the peak of lithium plating back-insertion. Therefore, it can be proved that this method can determine whether lithium plating occurs in the battery.

[0055] Example 2

[0056] A method for detecting lithium plating in a battery based on different scanning rates, comprising the following steps:

[0057] (1) Obtain multiple charging voltages of the battery during the charging process. Based on each said charging voltage, provide a scanning signal with a certain amplitude and perform cyclic voltammetry tests at different scanning rates to obtain cyclic voltammograms;

[0058] In this example, a 1 Ah lithium-ion battery is used, with a positive electrode of a lithium iron phosphate material system and a negative electrode of a graphite system. Cyclic voltammetry tests are carried out in the voltage range of 2.5 V to 3.65 V. Constant current charging is carried out at a step size of 1% SOC according to the state of charge (SoC), with a charging current of 1.5 A. Cyclic voltammetry tests are carried out at different scanning rates (0.1 mV / s, 0.2 mV / s, 0.3 mV / s, 0.4 mV / s, 0.5 mV / s), and the voltage range of the scanning signal used is 50 mV. The relationship curve between the response current and the scanning signal voltage is recorded at each scanning rate, as shown in Figure 6 shown.

[0059] (2) Based on each said charging voltage, perform linear fitting on the response current corresponding to the intermediate voltage value of the scanning signal within the linearly varying range of the cyclic voltammogram and different scanning rates to obtain the value of the electric double layer capacitance;

[0060] Take the response current corresponding to the intermediate voltage value (30 mV) of the scanning signal within the linear range of the cyclic voltammogram and the scanning rate, and perform linear fitting on the response current and the scanning rate, as shown in Figure 7 shown, to obtain the linear fitting equation i c = C dl·v, the slope of this equation, which is the value of the electric double-layer capacitance C dl , where i c is the response current and v is the scan rate. Calculate the values of the electric double-layer capacitance at different charging stages respectively. The variation curve of the electric double-layer capacitance with the charging SOC is as Figure 8 shown.

[0061] (3) Based on the values of the electric double-layer capacitance corresponding to multiple said charging voltages, determine whether lithium plating occurs in the battery.

[0062] At the end of charging (at 90% SOC), the electric double-layer capacitance increases significantly, indicating that lithium plating occurs in the battery at this time. Figure 9 This is the differential voltage curve of the battery during storage. It can be seen that there is an obvious peak of voltage mutation in the storage curve of this battery, and this peak is the peak of lithium plating back-insertion. Therefore, it can be proved that using this method can determine that lithium plating occurs in the battery.

[0063] Example 3

[0064] A method for detecting lithium plating in a battery based on different scan rates, comprising the following steps:

[0065] (1) Obtain multiple charging voltages of the battery during the charging process. Based on each said charging voltage, provide a scanning signal with a certain amplitude and perform cyclic voltammetry tests at different scan rates to obtain cyclic voltammograms;

[0066] In this example, a 2 Ah lithium-ion battery is used, with a positive electrode of a lithium iron manganese phosphate material system and a negative electrode of a graphite system. Cyclic voltammetry tests are carried out in the voltage range of 3.0 V to 4.3 V. Constant current charging is carried out at intervals of 0.02 V in accordance with the voltage step, with a charging current of 3 A. Cyclic voltammetry tests at different scan rates (0.1 mV / s, 0.2 mV / s, 0.3 mV / s, 0.4 mV / s, 0.5 mV / s) are carried out, and the voltage range of the scanning signal used is 20 mV. Record the relationship curve between the response current and the scanning signal voltage at each scan rate.

[0067] (2) Based on each said charging voltage, perform linear fitting on the response current corresponding to the intermediate voltage value of the scanning signal within the linearly varying range of the cyclic voltammogram and different scan rates to obtain the value of the electric double-layer capacitance;

[0068] Take the response current corresponding to the intermediate voltage value of the scanning signal within the linear range of the cyclic voltammogram and the scan rate, and perform linear fitting on this response current and the scan rate. Calculate the values of the electric double-layer capacitance at different charging voltages respectively. The variation curve of the electric double-layer capacitance with the charging voltage is as Figure 10 shown.

[0069] (3) Based on the values of the electric double-layer capacitance corresponding to multiple said charging voltages, determine whether lithium plating occurs in the battery.

[0070] When the charging voltage is 3.9V, the electric double layer capacitance increases significantly, indicating that lithium plating occurs in the battery at this time. Figure 11 This is the differential voltage curve of the battery during storage. It can be seen that there is an obvious peak of voltage mutation in the storage curve of the battery, and this peak is the peak of lithium plating intercalation. Therefore, it can be proved that the method of the present invention can judge whether lithium plating occurs in the battery.

[0071] Example 4

[0072] As Figure 12 shown, a lithium plating detection system for batteries based on different scanning rates includes:

[0073] A data extraction module, configured to obtain multiple charging voltages of the battery during the charging process, based on each of the charging voltages, provide a scanning signal with a certain amplitude, and perform cyclic voltammetry tests at different scanning rates to obtain cyclic voltammograms;

[0074] A data analysis module, based on each of the charging voltages, linearly fits the response current corresponding to the intermediate voltage value of the scanning signal within the linear change range of the cyclic voltammogram with different scanning rates to obtain the electric double layer capacitance value;

[0075] A lithium plating judgment module, based on the electric double layer capacitance values respectively corresponding to multiple charging voltages, judges whether lithium plating occurs in the battery.

[0076] Example 5

[0077] A lithium plating detection electronic device for batteries based on different scanning rates includes a storage medium and a processing module. The storage medium stores a computer program that can run in the processing module. When the processing module executes the computer program, it implements the steps of the lithium plating detection method for batteries based on different scanning rates.

[0078] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for detecting lithium plating in a battery based on different scanning rates, characterized in that The method includes the following steps: (1) Obtain multiple charging voltages of the battery during charging. Based on each of the charging voltages, provide a scanning signal with a certain amplitude, and perform cyclic voltammetry tests at different scanning rates to obtain cyclic voltammograms; (2) Based on each of the charging voltages, linearly fit the response current corresponding to the intermediate voltage value of the scanning signal within the linearly varying range of the cyclic voltammogram with different scanning rates to obtain the double-layer capacitance value; (3) Based on the double-layer capacitance values corresponding to multiple charging voltages, determine whether lithium plating occurs in the battery.

2. The method for detecting lithium plating of a battery based on different scanning rates according to claim 1, wherein: In step (1), the method for obtaining multiple charging voltages of the battery during charging is as follows: charge the battery to different voltages according to a certain voltage step, time step, or charge state step, and then obtain multiple charging voltages.

3. A method for detecting lithium plating of a battery based on different scanning rates according to claim 1, characterized in that: In step (1), the battery is charged based on a constant current charging current.

4. A method for detecting lithium plating of a battery based on different scanning rates according to claim 1, characterized in that: In step (1), the amplitude range of the scanning signal is 0 - 50 mV.

5. A method for detecting lithium plating of a battery based on different scanning rates according to claim 1, characterized in that: In step (1), the scanning rates at different scanning speeds are 0.1 - 50 mV / s.

6. The battery lithium plating detection method based on different scanning rates according to claim 1, wherein: In step (2), the linear fitting results in a linear equation, and the slope of the linear equation is the double-layer capacitance value.

7. A method for detecting lithium plating of a battery based on different scanning rates according to claim 1, characterized in that: In step (3), analyze the variation of the double-layer capacitance value with the charging voltage, charging time, or charging capacity under each charging voltage to determine whether lithium plating occurs in the battery.

8. A method for detecting lithium plating of a battery based on different scanning rates according to claim 7, characterized in that: When the variation of the double-layer capacitance value with the charging voltage, charging time, or charging capacity shows a sudden increase, it is determined that lithium plating has occurred in the battery.

9. A lithium plating detection system for a battery based on different scanning rates, characterized in that, It includes: A data extraction module, configured to obtain multiple charging voltages of the battery during charging. Based on each of the charging voltages, provide a scanning signal with a certain amplitude, and perform cyclic voltammetry tests at different scanning rates to obtain cyclic voltammograms; A data analysis module, which linearly fits the response current corresponding to the intermediate voltage value of the scanning signal within the linearly varying range of the cyclic voltammogram with different scanning rates based on each of the charging voltages to obtain the double-layer capacitance value; A lithium plating determination module, which determines whether lithium plating occurs in the battery based on the double-layer capacitance values corresponding to multiple charging voltages.

10. An electronic device for detecting lithium plating in a battery based on different scanning rates, characterized in that: It includes a storage medium and a processing module. The storage medium stores a computer program that can run in the processing module. When the processing module executes the computer program, it implements the steps of the method for detecting lithium plating in a battery based on different scanning rates according to any one of claims 1 - 8.

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