Method for detecting lithium precipitation in lithium battery

Abstract

The application provides a lithium battery lithium precipitation detection method, which comprises the following steps: charging a standard battery without lithium precipitation problem in a charging process, coupling a sinusoidal disturbance electric signal, obtaining a standard charging capacity of the standard battery and a standard battery capacity, and obtaining a reference curve; charging a test battery, coupling a sinusoidal disturbance frequency, obtaining different test charging capacities of the test battery in the charging process and a test battery capacity, and obtaining a test curve; comparing the test curve with the reference curve, when the test curve deviates from the reference curve, the charging capacity corresponding to the intersection point of the two before the test curve deviates from the reference curve is the charging capacity at which lithium precipitation occurs. The lithium battery lithium precipitation detection method has high detection efficiency and detection precision.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and in particular to a method for detecting lithium plating in lithium batteries. Background Technology

[0002] Lithium plating has always been a major concern regarding lithium-ion battery degradation and safety. It typically occurs during fast charging, low-temperature charging, and long-term cycling, impacting battery life and safety characteristics. Preventing lithium plating and quickly identifying batteries that have already undergone plating are key methods to effectively prevent further degradation and failure.

[0003] Detecting lithium plating is highly challenging, and reliable, in-situ, and real-time detection methods are crucial for developing fast and safe charging processes. Many factors influence lithium plating during actual testing, including temperature, charge rate, state of charge (SOC), battery design, electrolyte composition, negative electrode capacity, N / P ratio of the negative to positive electrode, and battery defects.

[0004] Existing technologies for detecting lithium plating include CT scans, ultrasonic testing, and hydrogen detection. These methods have relatively high detection limits, often only capturing reliable signals when significant amounts of lithium plating are present. At low levels of lithium plating, they are significantly affected by the surrounding environment and cannot be detected. Future methods for detecting lithium plating include using three electrodes to monitor the negative electrode potential, implanting pressure sensors within the battery, and implanting optical sensors. While these methods can detect lithium plating-related signals with relatively high sensitivity, they are invasive procedures that can impact battery safety and lifespan, making them unsuitable for practical applications. Summary of the Invention

[0005] In view of this, the present invention aims to propose a method for detecting lithium plating in batteries, so as to improve the efficiency and accuracy of lithium plating detection in lithium batteries.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] A method for detecting lithium plating in lithium batteries includes the following steps:

[0008] A standard battery without lithium plating issues is charged and coupled with a sinusoidal perturbation signal to obtain different standard charge amounts during the charging process, as well as the standard battery capacitance corresponding to each standard charge amount, and to obtain a baseline curve showing the relationship between the standard charge amount and the standard battery capacitance.

[0009] The test battery is charged and coupled with a sinusoidal perturbation electrical signal to obtain different test charge amounts during the charging process, as well as the test battery capacitance corresponding to each test charge amount, and to obtain a test curve showing the relationship between the test charge amount and the test battery capacitance.

[0010] The test curve is compared with the reference curve. When the test curve deviates from the reference curve, it indicates that lithium plating has occurred in the test battery.

[0011] Furthermore, the standard battery and the test battery are simultaneously charged using any one of the following charging methods: step voltage charging, variable current charging, or constant current charging.

[0012] Furthermore, when the standard battery and the test battery are charged simultaneously with a step voltage, the step voltage ΔU < 5mV.

[0013] Furthermore, when charging with the step voltage, after coupling the sinusoidal disturbance signal, the amplitude of the coupled disturbance voltage is 1mV~1V.

[0014] Furthermore, variable current charging is adopted, or the amplitude of the coupled disturbance current is 0.1mA~1A.

[0015] Furthermore, the charge level and battery capacitance of the standard battery and the test battery are obtained using the Mott-Schottky test, or the charge level and battery capacitance of the standard battery and the test battery are obtained by coupling the sinusoidal perturbation electrical signal with a charging device.

[0016] Furthermore, the frequency of the sinusoidal perturbation electrical signal is between 100 kHz and 1 mHz.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] The lithium battery lithium plating detection method of the present invention involves charging a standard battery and a test battery without lithium plating problems respectively, and coupling them with a sinusoidal perturbation electrical signal to obtain a reference curve of the charging amount and battery capacitance of the standard battery, and a test curve of the charging amount and battery capacitance of the test battery. By comparing the reference curve and the test curve, the charging amount corresponding to the intersection of the two curves before the test curve deviates from the reference curve can be determined to determine whether lithium plating has occurred in the lithium battery. This method can detect lithium batteries that fail the lithium plating test, and has high detection efficiency and accuracy, making it highly practical.

[0019] Furthermore, employing step voltage charging, variable current charging, or constant current charging facilitates lithium battery charging, resulting in higher testing accuracy. Determining the step voltage improves detection accuracy and facilitates implementation. Setting the charging voltage amplitude enhances the accuracy of lithium plating testing. Using Mott-Schottky testing to obtain charge amount and battery capacitance improves detection efficiency. The frequency range of the sinusoidal perturbation signal improves the detection accuracy after coupling. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0021] Figure 1 The standard curve is the standard curve of the standard battery described in the embodiments of the present invention;

[0022] Figure 2 The test curve of the test battery described in the embodiment of the present invention;

[0023] Figure 3 This is a comparison chart of the standard curve and the test curve described in the embodiments of the present invention;

[0024] Figure 4 This is a curve showing the relationship between the battery capacitance and the negative electrode potential of the test battery described in an embodiment of the present invention. Detailed Implementation

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0026] In the description of this invention, it should be noted that if terms such as "upper," "lower," "inner," or "back" appear, indicating orientation or positional relationship, these are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing the 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, and therefore should not be construed as a limitation of the invention. Furthermore, if terms such as "first" or "second" appear, they are also used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0027] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] This embodiment relates to a method for detecting lithium plating in lithium batteries. Generally, the method includes the following steps:

[0029] A standard battery exhibiting no lithium plating during charging is charged, and a sinusoidal perturbation signal is coupled to obtain different standard charge amounts during charging, along with the corresponding standard battery capacitances. A baseline curve showing the relationship between standard charge amount and standard battery capacitance is then generated. A test battery is charged, and a sinusoidal perturbation signal is coupled to obtain different test charge amounts during charging, along with the corresponding test battery capacitances. A test curve showing the relationship between test charge amount and test battery capacitance is then generated. The test curve is compared to the baseline curve; when the test curve deviates from the baseline curve, it indicates that lithium plating has occurred in the test battery.

[0030] It should be noted that in current battery materials, including but not limited to lithium iron phosphate, lithium manganese iron phosphate, ternary cathode materials, and graphite and silicon anode materials, the active material undergoes regular expansion or contraction during ion extraction and insertion. When the material expands or contracts, the contact area between the material and the electrolyte changes accordingly. Since the double-layer capacitance at the material-electrolyte interface is proportional to its contact area, the value of the double-layer capacitance changes accordingly when the contact area changes.

[0031] During normal battery cycling (without lithium plating), the area-dependent double-layer capacitance (Cp) of the positive electrode and the area-dependent double-layer capacitance (Cn) of the negative electrode remain constant with the state of charge (SoC). The capacitance related to the area of ​​the active material in the battery, i.e., the battery capacitance (Cf), is the result of the positive and negative electrode capacitances connected in series, and has the following relationship: 1 / C f =1 / Cp + 1 / Cn. Where Cf is the battery capacitance, Cp is the positive capacitance, and Cn is the negative capacitance. Additionally, the battery capacitance in the charging state also satisfies the following relationship: f _SoC (Cf)=f_ SoC ((Cp× Cn) / (Cp+Cn)) .

[0032] Lithium plating in lithium-ion batteries leads to the formation of lithium dendrites on the negative electrode surface, increasing the surface area and thus the negative electrode capacitance. Lithium plating does not affect the surface area of ​​the positive electrode active material, meaning the positive electrode capacitance Cp remains unchanged, but it does affect the negative electrode capacitance Cn. Therefore, lithium plating alters the battery capacitance Cf, changing the original functional relationship between Cf and the system of charge (SoC). Thus, by monitoring the change in battery capacitance Cf during charging and its relationship to a standard curve (without lithium plating), the lithium plating status of the battery during this charging process can be determined.

[0033] In this specific implementation, the standard battery and the test battery are simultaneously charged using any one of the following charging methods: step voltage charging, variable current charging, or constant current charging. As a preferred embodiment, the charge level and battery capacitance of the standard battery and the test battery are obtained using a Mott-Schottky test in an electrochemical workstation. This Mott-Schottky test integrates charging and sinusoidal perturbation coupling functions. By connecting the battery to the electrochemical workstation, the charge level and corresponding battery capacitance can be directly obtained, thus improving testing efficiency and facilitating deployment and implementation.

[0034] When performing the Mott-Schottky test, a constant voltage amplitude or constant current scan is performed, with the voltage scan range covering the normal or required voltage range of the battery. Alternatively, besides using the Mott-Schottky test in an electrochemical workstation, the charge quantity and corresponding battery capacitance can be obtained by coupling a sinusoidal perturbation signal to a charging device. Of course, obtaining the charge quantity and battery capacitance of both standard and test batteries using a charging device coupled with a sinusoidal perturbation signal is also feasible.

[0035] In this embodiment, the coupled sinusoidal disturbance electrical signal can be either a voltage signal or a current signal. The method of coupling the sinusoidal disturbance electrical signal during the charging process makes the detection process more realistic. The specific coupling method can be found in existing technologies and will not be elaborated upon here.

[0036] In practice, to improve detection accuracy and more precisely determine the amount of charge required for lithium plating, in this embodiment, when the standard battery and the test battery are simultaneously charged with a step voltage, the step voltage ΔU < 5mV. For example, the step voltage ΔU can be 1mV, 2mV, 3mV, 4mV, or 5mV, etc.

[0037] Furthermore, when using step voltage, variable current charging, or constant current charging, the amplitude of the charging voltage after coupling the sinusoidal disturbance signal as a voltage is 1mV to 1V. For example, the amplitude of the charging voltage can be 10mV, 50mV, 200mV, 500mV, or 800mV. When using variable current charging or constant current charging, the amplitude of the charging current after coupling the sinusoidal disturbance signal as a current is 0.1mA to 1A. For example, the amplitude of the charging current can be 10mA, 50mA, 200mA, 500mA, or 800mA.

[0038] In a preferred embodiment, the frequency of the sinusoidal perturbation signal is between 100 kHz and 1 mHz. Specifically, the frequency of the sinusoidal perturbation signal can be 200 kHz, 500 kHz, 800 kHz, or 1 mHz. In practice, the sinusoidal perturbation frequency is related to the type of battery system.

[0039] As an example of application, the standard curve of a lithium iron phosphate battery during charging at 0.33C (a rate at which lithium plating is not possible) is shown below. Figure 1 As shown in the figure, the standard spectrum in the figure is the baseline curve. Using step voltage charging, with a step voltage of 5mV, the battery's test curve during the charging process is as follows. Figure 2 As shown in the figure, the design curve is the same as the test curve. Comparing the test curve and the standard curve is as follows: Figure 3 As shown. Based on the basic theory of the invention, it is believed that at approximately 50% SoC, the Cf value of the test curve deviates from the standard curve, and the charging process is designed to begin lithium plating when the charge level is 50%.

[0040] In specific verification, a three-electrode method (the fabrication method of a three-electrode battery has been described in other patents) was used to test the negative electrode potential during the designed charging process, such as... Figure 4 As shown, the negative electrode potential is significantly lower than 0V when the charge is about 50%, indicating that lithium plating has occurred at the negative electrode. The detection method in this embodiment has good detection accuracy.

[0041] The lithium battery lithium plating detection method described in this embodiment charges a standard battery and a test battery without lithium plating issues separately, and couples them with a sinusoidal perturbation electrical signal to obtain a reference curve for the charging amount and battery capacitance of the standard battery, and a test curve for the charging amount and battery capacitance of the test battery. By comparing the reference curve and the test curve, when the test curve deviates from the reference curve, it can be determined that lithium plating has occurred in the lithium battery. This allows for the detection of lithium batteries that fail the lithium plating test, and the method has high detection efficiency and accuracy, making it highly practical. Furthermore, the charging amount corresponding to the intersection point of the test curve and the reference curve before the test curve deviates is the charging amount at which lithium plating occurs in the test battery. This lithium battery lithium plating detection method can not only determine whether lithium plating has occurred in a lithium battery, but also obtain the charging amount at which lithium plating occurs, demonstrating good usability.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for detecting lithium plating in lithium batteries, characterized in that: Includes the following steps: A standard battery without lithium plating issues is charged and coupled with a sinusoidal perturbation electrical signal to obtain different standard charge amounts during the charging process, as well as the standard battery capacitance corresponding to each standard charge amount, and to obtain a baseline curve of the relationship between the standard charge amount and the standard battery capacitance. The test battery is charged and coupled with a sinusoidal perturbation electrical signal to obtain different test charge amounts during the charging process, as well as the test battery capacitance corresponding to each test charge amount, and to obtain a test curve showing the relationship between the test charge amount and the test battery capacitance. The test curve is compared with the reference curve. When the test curve deviates from the reference curve, it indicates that lithium plating has occurred in the test battery.

2. The lithium battery lithium plating detection method according to claim 1, characterized in that: The standard battery and the test battery are simultaneously charged using any one of the following charging methods: step voltage charging, variable current charging, or constant current charging.

3. The lithium battery lithium plating detection method according to claim 2, characterized in that: When the standard battery and the test battery are charged simultaneously with a step voltage, the step voltage ΔU < 5mV.

4. The lithium battery lithium plating detection method according to claim 2, characterized in that: When charging with the step voltage, after coupling the sinusoidal disturbance signal, the amplitude of the coupled disturbance voltage is 1mV~1V.

5. The lithium battery lithium plating detection method according to claim 2, characterized in that: When using variable current charging or constant current charging, the amplitude of the coupled disturbance current after coupling the sinusoidal disturbance signal is 0.1mA~1A.

6. The lithium battery lithium plating detection method according to claim 1 or 2, characterized in that: The charge level and battery capacitance of the standard battery and the test battery were obtained using the Mott-Schottky test, or... The charge level and battery capacitance of the standard battery and the test battery are obtained by coupling the sinusoidal perturbation electrical signal using a charging device.

7. The lithium battery lithium plating detection method according to claim 1 or 2, characterized in that: The frequency of the sinusoidal perturbation signal is between 100 kHz and 1 mHz.

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