Online detection method and device for lithium precipitation state of battery for energy storage, storage medium and computer program product

Abstract

The invention discloses an on-line detection method and device for a lithium precipitation state of a battery for energy storage, a storage medium and a computer program product. The on-line detection method for the lithium precipitation state of the battery for energy storage comprises the following steps: acquiring a change rule of expansion force of a ternary graphite system battery along with SOC in a multi-stage constant-current charging process, and obtaining a first curve; a dF / dSOC differential curve is obtained; on the premise of no lithium precipitation, the local maximum value appearing at the tail end of the first curve is a threshold V2, and the threshold V2 is used for online judging whether lithium precipitation of the battery begins or not. According to the on-line detection method and device for the lithium precipitation state of the battery for energy storage, the storage medium and the computer program product, the new thresholds V2 and V3 for lithium precipitation detection are provided, the lithium precipitation state of the battery can be judged on line, and irreversible lithium precipitation in the MCC charging process is effectively avoided; the method is applicable to single-stage MCC charging and multi-stage MCC charging, and is wide in application range and high in universality.

Description

Technical Field

[0001] The present invention relates to the technical field of battery testing, and particularly relates to an online detection method, device, storage medium and computer program product for the lithium plating state of a battery for energy storage. Background Art

[0002] Currently, lithium-ion batteries with graphite as the negative electrode have been widely used as energy storage sources for electric vehicles. However, compared with the refueling time of a few minutes for traditional vehicles, the charging time of electric vehicles usually takes dozens of minutes or even several hours, which leads to range anxiety. Therefore, improving the charging speed of electric vehicles is an urgent problem to be solved. The fundamental way to shorten the charging time is to increase the charging power of lithium batteries. However, existing commercial lithium-ion batteries are difficult to maintain their lifespan and safety at high charging powers. Therefore, how to maximize the shortening of the charging time while maintaining the performance of lithium-ion batteries without decline has attracted wide attention.

[0003] Lithium plating is the main failure mode of lithium batteries under fast charging conditions, which will directly damage battery safety, accelerate capacity decay and shorten service life. Lithium plating refers to the phenomenon that during the charging process, lithium ions cannot be normally intercalated into the graphite negative electrode, but are deposited on the graphite surface in the form of metallic lithium. For graphite, the working potential range can be as low as 65 - 200 mV vs. Li / Li+. When the battery is charged at a large current or high charging rate, it will cause severe polarization, excessive charge transfer overpotential and slow kinetics, resulting in the anode potential being lower than 0 V vs. Li / Li+, leading to the occurrence of lithium plating. Lithium plating will cause the growth of lithium dendrites, which may pierce the separator, causing an internal short circuit in the lithium battery, and may even cause fire and explosion in severe cases. In addition, the deposited lithium metal will consume the electrolyte and generate too much solid electrolyte interphase (SEI). In addition, some of the deposited lithium metal may lose its electrochemical contact with the anode, thus forming dead lithium. Both SEI and dead lithium will greatly reduce the available capacity of the lithium battery. Therefore, the key challenge is to prevent lithium plating while increasing the charging rate. In actual fast charging, due to the lack of an effective online detection method for lithium plating, a conservative charging rate is usually adopted. This makes the battery unable to fully utilize its charging potential, thus requiring a longer charging time. Developing a battery fast charging protocol is usually very challenging because many factors need to be considered, such as temperature, state of charge (SOC) of the battery and aging, to balance the charging time and the possibility of lithium plating. In fact, the inconsistency of battery operating conditions is very high. This inconsistency exists not only between different batteries in the same battery pack, but also between batteries in different vehicles. It is difficult to use a fixed charging protocol to solve the significant differences between batteries. This will lead to the occurrence of lithium plating and accelerate the battery aging rate, even if the charging protocol is carefully designed. The root cause of the problem is that the charging protocol is open-loop, which means it cannot adjust the charging rate according to the actual lithium plating state of the battery. Therefore, it is necessary to adjust the charging rate to an appropriate level in real time according to the actual lithium plating state. Summary of the Invention

[0004] Aiming at the problems in the prior art, the present invention discloses an online detection method, device, storage medium and computer program product for the lithium plating state of a battery, so as to solve the problem of the lack of an effective online detection method for lithium plating in the present situation, thereby being unable to prevent lithium plating.

[0005] The present invention is realized through the following technical solutions:

[0006] The present invention first provides an online detection method for the lithium plating state of a battery, including

[0007] Obtaining the change law of the swelling force during the multi-stage constant current charging process of a ternary graphite system battery and obtaining the first curve: the dF / dSOC differential curve;

[0008] On the premise of no lithium plating, the local maximum value that appears at the end of the first curve is the threshold value V2, and the threshold value V2 is used to online determine whether the battery starts to plate lithium.

[0009] As a further solution, the threshold value V2 can also be determined in advance by a small current when the single-stage MCC charging is completed.

[0010] As a further solution, the battery swelling force is affected by temperature, and the actual swelling force F of the battery = the total swelling force F 总 - the thermal expansion force ΔF q , the total swelling force can be directly obtained by the battery, and the calculation method of the thermal expansion force is as follows:

[0011] The thermal expansion thickness ΔL q is given by the following formula, where α bat is the thermal expansion coefficient of the battery, L bat is the initial thickness of the battery, T0 is the ambient temperature, and the formula for calculating the thermal expansion thickness is:

[0012]

[0013] The thermal expansion thickness is multiplied by the equivalent stiffness k of the battery e to obtain the thermal expansion force, and the formula for the thermal expansion force is given by the following formula:

[0014] ΔF q = k e ·ΔL q .

[0015] As a further solution, the first curve first decreases and then rises again during the charging process. When the value of dF / dSOC ≥ the threshold value V2 after the first curve rises again, it is determined that the battery starts to plate lithium.

[0016] As a further solution, after the battery plates lithium, the charging rate of the battery is reduced to the threshold value V3 when the value of dF / dSOC in the first curve is 0. When the first curve drops to the threshold value V3, it is determined that the battery stops plating lithium.

[0017] As a further solution, the multi-stage constant current charging process can be single-stage or multi-stage multi-stage constant current charging.

[0018] As a further solution, the swelling force of the battery in the first curve can be replaced by the battery swelling displacement, the battery surface deformation or the battery surface strain.

[0019] As a further solution, the swelling force of the battery can be replaced by the battery swelling displacement, the battery surface deformation or the battery surface strain.

[0020] The present invention also provides an on-line detection device for the lithium plating state of a battery, including a data acquisition module and a data analysis module,

[0021] A data acquisition module, configured to acquire the expansion force data and temperature data of the battery and transmit them to the data analysis module in real time;

[0022] A data analysis module, configured to analyze the data of the data acquisition module and fit the data.

[0023] As a further solution, the data analysis module includes a data processing unit and a display unit. The data processing unit fits and calculates the acquired data and transmits it to the display unit for display.

[0024] As a further solution, the display unit is a display screen.

[0025] As a further solution, the data acquisition module includes a pressure acquisition unit, a current acquisition unit, and a time acquisition unit. The pressure acquisition unit is configured to acquire the expansion force during the battery charging process in real time, the current acquisition unit is configured to acquire the current change during the battery charging process in real time, and the time acquisition unit is configured to acquire the charging time of the battery in real time.

[0026] As a further solution, the data processing unit calculates the acquired data and outputs the results of expansion force, dF / dSOC, impedance Z'1Hz, and temperature difference △T, and presents them through curves.

[0027] As a further solution, an on-line detection device for the lithium plating state of a battery further includes a charge and discharge module, which is configured to charge and discharge the battery and transmit the charge and discharge time and power data to the data analysis module in real time.

[0028] As a further solution, the data acquisition module is a pressure sensor installed on the surface of the battery for detecting the expansion force of the battery.

[0029] The present invention also provides a battery management system, which includes an on-line detection device for the lithium plating state of a battery for energy storage.

[0030] The present invention also provides a vehicle, which includes the battery management system applying the on-line detection device for the lithium plating state of a battery.

[0031] The present invention also provides an electronic device, which includes a processor and a memory storing programs or instructions; when the processor executes the programs or instructions, the on-line detection method for the lithium plating state of a battery is implemented.

[0032] The present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the on-line detection method for the lithium plating state of a battery is implemented.

[0033] The present invention also provides a computer program product, including a computer program which, when executed by a processor, implements the online detection method for the lithium plating state of the battery described above.

[0034] The features and beneficial effects of the present invention are as follows:

[0035] An online detection method for the lithium plating state of a battery for energy storage:

[0036] (1) For the online detection method for the lithium plating state of the battery for energy storage described in the present invention, new thresholds V2 and V3 for lithium plating detection are proposed, which can judge the lithium plating state of the battery online and effectively avoid irreversible lithium plating during the MCC charging process.

[0037] (2) In the online detection method for the lithium plating state of the battery for energy storage described in the present invention, the determined threshold V2 greatly improves the detection sensitivity compared with the threshold V1 of the prior art, and the threshold V2 can be determined by various methods.

[0038] (3) The determined threshold V3 in the online detection method for the lithium plating state of the battery for energy storage described in the present invention is convenient, simple and has strong versatility.

[0039] (4) The online detection method for the lithium plating state of the battery for energy storage described in the present invention is applicable to both single-stage MCC charging and multi-stage MCC charging, with a wide application range and strong versatility.

[0040] An online detection device for the lithium plating state of a battery for energy storage:

[0041] (1) The online detection device for the lithium plating state of the battery for energy storage of the present invention is applicable to the batteries on automobiles and electric vehicles, and can be integrated with their built-in systems; it can also be used for the separate detection of batteries in the laboratory, with a wide application range and stronger versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings without creative efforts based on these drawings.

[0043] Figure 1 is a flowchart of the online detection method for the lithium plating state of a battery for energy storage;

[0044] Figure 2 is the experimental result of single-stage MCC charging at 10°C and 20°C in the embodiment of the present invention;

[0045] Figure 3These are the experimental results of two-stage MCC charging at 10°C and 20°C described in the embodiments of the present invention;

[0046] Figure 4 These are the experimental results of three-stage MCC charging at 10°C and 20°C described in the embodiments of the present invention;

[0047] Figure 5 This is the schematic diagram of MCC charging described in the embodiments of the present invention. Detailed Embodiments

[0048] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below. Embodiments of the present invention are given, but the scope of the present invention is not limited thereby.

[0049] Glossary:

[0050] MCC: Multi-step Constant Current Charging, which is a charging method composed of single or multiple constant current (CC) stages, and the charging stops when the voltage reaches a clearly defined voltage value. MCC is often used in charging scenarios where lithium plating is likely to occur. Compared with the traditional constant current-constant voltage (CC-CV) charging method, it can better control the charging process, reduce the risk of battery polarization and lithium plating, and improve charging efficiency and battery safety.

[0051] Expansion force: The expansion force.

[0052] SOC: State of Charge, which represents the ratio of the remaining battery charge to the total battery capacity under certain conditions, usually expressed as a percentage. For example, an SOC of 50% means that the remaining battery charge is half of its total capacity.

[0053] dF / dSOC curve: Represents the rate of change of the expansion force (F) with respect to the state of charge (SOC).

[0054] C: The charging rate. A 1C charging rate means charging at a current equal to 1 times the battery capacity.

[0055] Z' 1Hz : The real part of the dynamic impedance at 1 Hz.

[0056] △T: The temperature difference during battery charging.

[0057] Li plating: Lithium plating.

[0058] Li plating indicator: The curve feature used to indicate lithium plating, literally translated as lithium plating indicator.

[0059] Maximum: The maximum value.

[0060] Local maximum: The local maximum value.

[0061] Current change position: The specific position or node where the current changes.

[0062] In the present invention, lithium plating is the main failure mode of lithium batteries under fast charging conditions, which will directly damage battery safety, accelerate capacity attenuation and shorten service life. Lithium plating refers to the phenomenon that during the charging process, lithium ions cannot be normally intercalated into the graphite negative electrode, but are deposited on the graphite surface in the form of metallic lithium. In actual fast charging, due to the lack of an effective on-line detection method for lithium plating, a conservative charging rate is usually adopted. This makes the battery unable to fully exert its charging potential, thus requiring a longer charging time. The start time or position of lithium plating can be determined by the dF / dSOC curve. The initial values of the dF / dSOC curves at different charging rates are basically the same. The first maximum value at the beginning of lithium plating is called V1. In previous research reports, V1 is usually used as the threshold for detecting lithium plating. Although using V1 as an indicator of lithium plating is usually effective, the value of V1 itself is relatively large, resulting in low sensitivity during detection.

[0063] The present invention proposes two lithium plating states, namely threshold V2 and threshold V3, based on the change rate of the battery expansion force with the state of charge, determines the diagnostic thresholds of threshold V2 and threshold V3, and gives an on-line detection method for the lithium plating state of a battery for energy storage based on this threshold.

[0064] An on-line detection method for the lithium plating state of a battery for energy storage, such as Figures 1 to 5 shown, obtains the change law of the expansion force with the SOC during the multi-stage constant current charging process of a ternary graphite system battery and obtains the first curve: the dF / dSOC differential curve; on the premise of no lithium plating, the local maximum value appearing at the end of the first curve is the threshold V2, and the threshold V2 is used to on-line judge whether the battery starts to plate lithium.

[0065] The multi-stage constant current charging process is a single-stage or multi-stage multi-stage constant current charging.

[0066] During each charging process, the change rate of the battery expansion force with the state of charge is data-fitted to obtain the first curve, that is, the dF / dSOC curve, and the impedance value of the battery charging process is data-fitted to obtain the second curve, that is, the Z' 1Hz curve.

[0067] When the battery is charged in single-stage or multi-stage MCC, when the charging rate is sufficient to cause lithium plating, the current changes at least once during the charging process, and lithium plating occurs in the previous stage of charging while not in the latter stage of charging, then the threshold V3 will appear. At this time, the first curve will first decline, rise again after reaching the first inflection point, and continue until the charging ends. The initial value of the first curve is set as the threshold V1. On the premise of no lithium plating, the local maximum value at the end of the first curve is defined as the threshold V2. When the value of the first curve ≥ the threshold V2, it is determined that lithium plating starts in the battery. After lithium plating occurs, the battery reduces the charging rate to a level where no lithium plating occurs, and the resulting 0 value is the threshold V3. Specifically: when the first curve remains above the threshold V2, it can be determined that lithium plating has occurred; after lithium plating occurs, the charging rate must be reduced until the first curve is below the threshold V3 to determine that no more lithium plating occurs.

[0068] The present invention provides a method for obtaining the threshold V2 when the battery plates lithium, which is achieved through the impedance Z'. 1Hz The specific implementation is as follows:

[0069] The method also obtains the impedance value of the battery during the charging process. When the battery is charged in MCC, the second curve regarding the impedance is obtained online, and the first curve and the second curve are analyzed to obtain the threshold V2.

[0070] Specifically, when the battery is charged in MCC, the expansion force, dF / dSOC, Z' 1Hz and △T of the battery are obtained online and are reflected through the corresponding curves. When the charging rate is sufficient to cause lithium plating, the dF / dSOC curve is above the threshold V2, and the accelerating downward inflection point that appears on the Z' 1Hz curve indicates that lithium plating has formed. The value of SOC% corresponding to this inflection point is the same as the value of SOC% corresponding to the threshold V2 on the dF / dSOC curve. Therefore, the threshold V2 can be obtained through the Z' 1Hz curve. When no lithium plating occurs at the end of charging, the corresponding threshold V2 is regarded as an indicator of the start of lithium plating formation.

[0071] As a specific example of the implementation of the present invention, the following detailed case is provided:

[0072] Since the ranges of the high and low values of the charging rates of different types of batteries are different, in this embodiment, the Funeng ternary lithium-ion battery is taken as an example. At this time, the intermediate value of the battery charging rate is 0.8C. When the battery charging rate is greater than 0.8C, it is defined as a high charging rate, and when the battery charging rate is less than or equal to 0.8C, it is defined as a low charging rate.

[0073] As Figure 2 shown, the battery charging rate at 10°C is 0.8C for detailed description:

[0074] When the SOC corresponding to the acceleration inflection point of the second curve is approximately 65%, the value 9 corresponding to this point on the first curve is the threshold V2. And the threshold V2 is located behind the inflection point on the first curve, further verifying the correctness of this value.

[0075] The present invention provides a method for obtaining the threshold V2 when the battery lithium plating occurs, which is as follows:

[0076] When the battery is charged by single MCC, the expansion force, dF / dSOC, and impedance Z' of the battery are obtained online 1Hz and △T, and are reflected through the corresponding curves. The dF / dSOC curve will initially decline. After reaching the first inflection point (the lowest point), it will rise again until the charging ends. At the end of the charging process, a local maximum value will appear at the end of the dF / dSOC curve, and this value is the threshold V2. As Figure 2 shown, the method based on Z' 1Hz also verifies this threshold on the curve.

[0077] As a specific example of the implementation of the present invention, the following detailed case is provided:

[0078] Since the ranges of the high and low values of the charging rates of different types of batteries are different, in this embodiment, the Funeng ternary lithium-ion battery is taken as an example. At this time, the intermediate value of the battery charging rate is 0.8C. When the battery charging rate is greater than 0.8C, it is defined as a high charging rate. When the battery charging rate is less than or equal to 0.8C, it is defined as a low charging rate.

[0079] The results of single-stage MCC charging are as Figure 2 shown. The experiment was carried out at ambient temperatures of 10°C and 20°C, and the charging rates varied from 0.4C to 2C. The selection of 10°C and 20°C is because they are the commonly used temperatures for fast charging. Among them, Figure a shows the experimental results at 10°C, and Figure b shows the experimental results at 20°C. a1)-b4) are the results of the expansion force, dF / dSOC, Z' 1Hz and △T respectively. The lithium plating start time can be determined by the dF / dSOC curve. As Figure 2 (a2) shown, for low charging rates, the dF / dSOC curve will initially decline and reach the lowest point when the SOC is approximately 35% (for different batteries, it may not necessarily reach the lowest point at 35%), and then start to rise again until the charging ends. The initial values of the dF / dSOC curves for different charging rates are basically the same, which is called the threshold V1. Compared with V1, V2 has higher sensitivity in lithium plating detection.

[0080] A detailed description is given with the battery charging rate of 0.8C at 20°C:

[0081] As Figure 2As shown in (b2), when the charging rate is 0.8C, a local maximum appears at the end of the charging process, and this value is very close to the threshold V2. As Figure 2 (a2) and Figure 2 (b2) show, this result is also confirmed at different temperatures. This characteristic provides great convenience for determining the threshold V2 under different working conditions. The threshold V2 can be calibrated by performing a charge at a low charging rate.

[0082] It should be noted that during this experiment, in order to obtain comprehensive data, high charging rates are also shown, and all data differences are maximally reflected. In fact, when the battery charging rate is between 0.4C and 0.8C, the local maximum that appears at the end of the charging process is also very close to the threshold V2, and the minor differences here can be ignored compared to the overall data.

[0083] As Figure 2 (a3) and Figure 2 (b3) show, the real part of the impedance at Z'1 Hz is also used to characterize lithium plating. The accelerating descending inflection point of the Z'1 Hz curve indicates that lithium plating has formed, which also verifies the correctness of this method indirectly through Method 1.

[0084] Although temperature has a significant impact on the occurrence of lithium plating, the temperature change does not affect the change pattern of the swelling force under lithium plating conditions. High charging rates and / or low temperatures will cause a significant increase in force. Subsequent experimental and simulation results show that compared with intercalation swelling and lithium plating swelling, the thermal expansion displacement and thermal expansion force of the battery are much smaller. Lithium plating can still be detected using V2. Since the thermal expansion effect can be calculated and excluded, the force-based method has significant advantages when dealing with large-capacity batteries.

[0085] The actual swelling force F of the battery = total swelling force F 总 - thermal expansion force ΔF q , the total swelling force can be directly obtained from the battery, and the calculation method of the thermal expansion force is as follows:

[0086] The thermal expansion thickness ΔL q is given by the following formula, where α bat is the thermal expansion coefficient of the battery, L bat is the initial thickness of the battery, T0 is the ambient temperature, and the formula for calculating the thermal expansion thickness is:

[0087]

[0088] The thermal expansion thickness is multiplied by the equivalent stiffness k of the battery e to obtain the thermal expansion force, and the thermal expansion force formula is given by the following formula:

[0089] ΔFq = k e ·ΔL q 。

[0090] Preferably, the threshold V2 can also be determined in advance by a small current when the single-stage MCC charging is completed.

[0091] The present invention also provides a method for obtaining the threshold V2 when the battery lithium plating occurs, which is as follows:

[0092] During two-stage MCC charging, the expansion force, dF / dSOC, and Z' of the detected battery are obtained online in real time 1Hz and △T, and are reflected by the corresponding curves. When the two charging stages are not sufficient to cause lithium plating, the maximum expansion force of the battery will not exceed the set maximum expansion force, and lithium plating will not occur; when the charging rate is sufficient to cause lithium plating, dF / dSOC is always higher than the threshold V2, and the local maximum value at the end of the corresponding dF / dSOC curve is regarded as an index for the formation of lithium plating start, and this value is the threshold V2.

[0093] As a specific example of the implementation of the present invention, the following detailed case is provided:

[0094] Since the ranges of the high and low values of the charging rates of different types of batteries are different, in this embodiment, a graphite soft-pack lithium-ion battery is taken as an example. At this time, the intermediate value of the battery charging rate is 0.6C. When the battery charging rate is greater than 0.6C, it is defined as a high charging rate, and when the battery charging rate is less than or equal to 0.6C, it is defined as a low charging rate. For the specific time period, please refer to Figure 3 。

[0095] The experimental results of two-stage MCC charging are as Figure 3 shown, where Figure a is the experimental result at 10°C, and Figure b is the experimental result at 20°C. Among them, a1)-b4) respectively represent the results of expansion force, dF / dSOC, Z' 1Hz and △T.

[0096] After lithium plating occurs, the charging rate decreases, and the dF / dSOC curve shows an obvious change according to the applied charging rate. As Figure 3 (b2) shows, at 20°C, the charging rate is maintained at 1.75C until the SOC is 50%. The expansion force increases rapidly. According to the threshold V2, it can be determined that lithium plating occurs at about SOC of 35%. When the charging rate is reduced to 1.5C, the value of dF / dSOC is still higher than V2, indicating that the lithium plating has not disappeared. The cross-validation with the method based on Z' 1Hz confirms that lithium plating is still occurring. When the charging rate is reduced to 1C, the value of dF / dSOC is always lower than V2, indicating that a charging rate of 1C will not cause lithium plating.

[0097] For two-stage MCC charging, the charging rate usually decreases during the subsequent charging process. When two charging stages are not sufficient to cause lithium plating, such as 0.6C-0.4C charging at 10 °C and 20 °C Figure 3 the maximum swelling forces shown in (a1) and (b1) do not exceed the set maximum swelling force. For two-stage MCC charging, lithium plating can also be determined by the threshold V2. When the charging rate is sufficient to cause lithium plating, dF / dSOC is always higher than the threshold V2, such as 0.6C-0.4C charging at 10 °C.

[0098] For three-stage MCC charging, the above conclusions still hold. As Figure 4 shown in (a1), at 10 °C, the charging method of 2.5C-1C-0.5C will cause serious lithium plating, resulting in a rapid increase in the swelling force of the battery.

[0099] Figure 4 The experimental results of three-stage MCC charging at 10 °C and 20 °C are shown. (a1)-(b4) represent the results of swelling force, dF / dSOC, Z'1Hz, and △T respectively. Figure 4 The corresponding dF / dSOC curve shown in (a2) can quickly determine lithium plating according to V2. Even when the charging rate is reduced to 1C, the swelling force does not decrease, and the corresponding dF / dSOC is still higher than V2, indicating that the rate reduction is not sufficient to prevent lithium plating. When the current is further reduced to 0.5C, the swelling force begins to decrease, and the corresponding dF / dSOC rapidly drops below V3, indicating that 0.5C is not sufficient to maintain lithium plating. When a low charging rate is adopted, such as 0.6C-0.4C-0.2C, both the swelling force and dF / dSOC meet the conditions to avoid lithium plating. As Figure 4 shown in (b1), even when a higher charging rate is adopted in the initial stage, when charging at a charging rate of 1.5C, as long as the charging rate is reduced to 1C and 0.5C before lithium plating occurs, lithium plating can be prevented. Note that at 20 °C, the combination of 1.5C-1C-0.5C MCC charging rates is significantly higher than the recommended charging rate. Through this force feedback-based method, the fast charging potential of the battery can be effectively utilized.

[0100] In the present invention, during the charging process of the battery, the impedance value and temperature value of the battery can also be obtained.

[0101] The present invention provides a specific method for obtaining the threshold V3 when the battery has lithium plating as follows:

[0102] When MCC charging, through the collected data, it shows that when the swelling force significantly decreases, the 0 value that appears at the end of the first curve is the threshold V3.

[0103] As a specific example of the implementation of the present invention, the following detailed case is provided:

[0104] As shown Figure 3 in the figure, the experimental results of two-stage MCC charging at 10 °C and 20 °C, where a1)-b4) represent the swelling force, dF / dSOC, Z' 1Hz and △T results respectively. When the current rate is reduced to 0.5C, as Figure 3 (b1) shows, it can be observed that the swelling force decreases significantly. This is due to the reinsertion of the precipitated lithium. The corresponding value of the dF / dSOC curve drops rapidly below the threshold V3.

[0105] According to experiments and simulations, as Figure 5 shown in the figure, during MCC charging, lithium precipitation will cause a significant increase in the swelling force, far exceeding the normal maximum swelling force. In addition, when the charging rate is reduced to a level where lithium precipitation no longer occurs, the swelling force will decrease significantly, which can be attributed to the reinsertion of the precipitated lithium into the graphite negative electrode. According to dF / dSOC, the state of lithium precipitation can be detected.

[0106] An on-line detection device for the state of lithium precipitation in a battery for energy storage, comprising a data acquisition module and a data analysis module. The data acquisition module is used to collect the swelling force data and temperature data of the battery and transmit them to the data analysis module in real time;

[0107] The data analysis module is used to analyze the data of the data acquisition module and fit the data.

[0108] In the present invention, the data analysis module includes a data processing unit and a display unit. The data processing unit fits and calculates the collected data and transmits it to the display unit for display.

[0109] The display unit is a display screen.

[0110] The data acquisition module includes a pressure acquisition unit, a current acquisition unit, and a time acquisition unit. The pressure acquisition unit is used to collect the swelling force during the battery charging process in real time. The current acquisition unit is used to collect the current change during the battery charging process in real time. The time acquisition unit is used to collect the charging time of the battery in real time.

[0111] Specifically, the data processing unit calculates the collected data and outputs the results of the swelling force, dF / dSOC, impedance Z'1Hz, and temperature difference △T, and presents them through curves.

[0112] An on-line detection device for the state of lithium precipitation in a battery for energy storage further includes a charge and discharge module. The charge and discharge module is used to charge and discharge the battery and transmit the charge and discharge time and power data to the data analysis module in real time.

[0113] In one or more embodiments, the data acquisition module is a pressure sensor installed on the surface of the battery for detecting the swelling force of the battery.

[0114] One embodiment provided by the present invention is as follows:

[0115] When the battery is a battery applied to an automobile, the data analysis module of the online detection device for the lithium deposition state of the energy storage battery can be integrated on the battery management system (BMS). The data acquisition module is a pressure sensor, which

[0116] The pressure sensor is installed on the outer surface of the battery to detect the expansion force of the battery. During the charging process of the battery, the pressure sensor transmits the collected data to the battery management system BMS. The control module simultaneously monitors data such as the charging time of the battery and the temperature of the battery, fits all the data, outputs the results regarding the expansion force, dF / dSOC, impedance Z'1Hz, and △T, and reflects them through curves. At the same time, it is displayed on the display screen of the automobile, facilitating the staff to understand the charging situation in real time.

[0117] Another embodiment provided by the present invention is as follows:

[0118] When the battery is a laboratory battery, the online detection device for the lithium deposition state of the energy storage battery includes a data acquisition module, a data analysis module, and a charge and discharge module. The charge and discharge module is used to charge and discharge the battery; the data acquisition module includes a pressure acquisition unit, a current acquisition unit, and a time acquisition unit. The pressure acquisition unit is used to collect the expansion force during the charging process of the battery in real time, the current acquisition unit is used to collect the current change during the charging process of the battery in real time, and the time acquisition unit is used to collect the charging time of the battery in real time. The data acquisition module transmits the collected data to the data processing unit in real time, and the data processing unit fits and calculates the collected data and transmits it to the display unit for display. This facilitates the experimenters to observe the experimental results in real time.

[0119] In one embodiment, the present invention also provides a battery management system, which includes an online detection device for the lithium deposition state of the energy storage battery.

[0120] In one embodiment, the present invention also provides a vehicle, which includes the above-mentioned battery management system.

[0121] In one embodiment, the present invention also provides an electronic device, which includes a processor and a memory storing programs or instructions; when the processor executes the programs or instructions, the online detection method for the lithium deposition state of the energy storage battery is implemented.

[0122] In one embodiment, the present invention also provides a machine-readable storage medium, on which programs or instructions are stored, and when the programs or instructions are executed by a processor, the online detection method for the lithium deposition state of the energy storage battery is implemented.

[0123] In one embodiment, the present invention further provides a computer program product. When the instructions in the computer program product are executed by a processor of an electronic device, the electronic device is caused to execute the online detection method for the lithium plating state of the battery for energy storage.

[0124] In the present invention, the battery expansion displacement can be used instead of the expansion force of the battery.

[0125] In summary, during the MCC charging process, the expansion caused by lithium plating increases rapidly. When the charging rate is insufficient to sustain lithium plating, the force decreases. The decrease in the expansion force is due to the reinsertion of lithium plating into the graphite negative electrode. The present invention can achieve real-time detection of online lithium plating by judging lithium plating through two thresholds, namely threshold V2 and threshold V3.

[0126] It should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An online detection method for the lithium plating state of a battery, characterized in that, Obtain the variation law of the swelling force of the ternary graphite system battery with the SOC during the multi-stage constant current charging process and obtain the first curve: the dF / dSOC differential curve; On the premise of no lithium plating, the local maximum value that appears at the end of the first curve is the threshold value V2, and the threshold value V2 is used to judge online whether the battery starts to plate lithium.

2. The online detection method for the lithium plating state of a battery according to claim 1, wherein The expansion force of the battery is affected by temperature. The actual expansion force F of the battery = total expansion force F 总 - thermal expansion force ΔF q , and the total expansion force can be directly obtained from the battery. The calculation method of the thermal expansion force is as follows: Thermal expansion thickness ΔL q is given by the following formula, where α bat is the thermal expansion coefficient of the battery, L bat is the initial thickness of the battery, and T0 is the ambient temperature. The formula for calculating the thermal expansion thickness is: The thermal expansion thickness is multiplied by the equivalent stiffness k of the battery e The thermal expansion force is obtained, and the thermal expansion force formula is given by the following formula: ΔF q = k e ·ΔL q .

3. The on-line detection method for the lithium plating state of a battery according to claim 1, characterized in that The first curve first decreases and then rises again during the charging process. When the value of dF / dSOC ≥ the threshold value V2 after the first curve rises again, it is determined that the battery starts to plate lithium.

4. The on-line detection method for the lithium plating state of a battery according to claim 1, characterized in that After the battery plates lithium, reduce the charging rate of the battery to the threshold value V3 when dF / dSOC in the first curve is 0. When the first curve drops to the threshold value V3, it is judged that the battery stops plating lithium.

5. The on-line detection method for the lithium plating state of a battery according to claim 3, characterized in that, The multi-stage constant current charging process is single-stage or multi-stage multi-stage constant current charging.

6. The on-line detection method for the lithium plating state of a battery according to claim 1, characterized in that, The swelling force of the battery in the first curve can be replaced by the battery swelling displacement, the battery surface deformation or the battery surface strain.

7. An on-line detection device for the lithium plating state of a battery, characterized in that, It includes a data acquisition module and a data analysis module, The data acquisition module is used to collect the total swelling force data and temperature data of the battery and transmit them to the data analysis module in real time; The data analysis module is used to analyze the data of the data acquisition module and fit the data.

8. The online detection device for the lithium plating state of the battery according to claim 7, wherein It also includes a charge and discharge module, which is used to charge and discharge the battery and transmit the time and current data of the charge and discharge to the data analysis module in real time.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method described in any one of claims 1 to 6.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the method described in any one of claims 1 to 6.

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