Characterizing Lithium Plating in Rechargeable Batteries

Abstract

The present invention discloses a method for characterizing a rechargeable battery (91-96) with a risk of lithium deposition, the method comprising: receiving (1001) an operating value (41) of a battery (91-96) as a time series, wherein the operating value of the battery comprises: a terminal voltage (U(t)) of the battery, a battery current (I(t)) of the battery; determining (1002) a modeled terminal voltage (USim(t)) using a battery model (400) based on the battery current (I(t)); comparing (1003) the modeled terminal voltage (USim(t)) with the terminal voltage (U(t)); and determining (1004, 1004a, 1004b) a lithium deposition state of the battery based on the comparison.

Description

Technical Field

[0001] Various examples of the present invention relate to methods for characterizing a rechargeable battery. Various examples of the present invention relate in particular to characterization techniques for determining a lithium deposition state of a battery. Background Art

[0002] Rechargeable batteries, such as power batteries for electric vehicles, have a limited lifespan. One factor that can affect the lifespan of a rechargeable battery is the so-called lithium plating that can occur in some rechargeable batteries.

[0003] Lithium deposition refers to the deposition of lithium in metallic form at the anode of a rechargeable battery. This metal deposition can have a negative impact on the performance of the rechargeable battery. Reversible lithium deposition and irreversible lithium deposition can be distinguished. Lithium deposition and laboratory studies on this are described in "Lithium Deposition Behavior in Lithium-ion Batteries" by Ratnakumar V. Bugga and Marshall C. Smart (ECS Trans. 2010, Vol. 25, No. 36, pp. 241-252, doi: 10.1149 / 1.3393860).

[0004] It is known to demonstrate lithium deposition under laboratory conditions by means of well-defined charging cycles or by post-analysis of battery cells using complex verification methods, such as electron microscopy. In-situ determination of lithium deposition is known only by much more complex methods, such as neutron diffraction methods. These verification methods are difficult to perform or even impossible during actual operation of the battery, for example during its daily use at the customer's site to supply energy to vehicles.

[0005] In addition to these physical measurements, there are also methods in which lithium deposition is demonstrated by means of a characteristic voltage plateau which occurs after the charging phase due to subsequent oxidation of the lithium.

[0006] Such voltage anomalies can be detected relatively easily during relaxation or constant current discharge. However, these plateaus disappear when the battery is discharged dynamically. Therefore, these measurements are only suitable to demonstrate lithium deposition in continuous operation, that is, in actual operation of a field cell of the battery. Summary of the invention

[0007] Therefore, there is a need for other feasible solutions to diagnose lithium deposition. In particular, there is a need for some feasible solutions to detect lithium deposition in practical applications with superimposed dynamics.

[0008] This object is achieved with the features of the independent claim. The features of the dependent claims define exemplary embodiments.

[0009] A method for characterizing a rechargeable battery with a risk of lithium plating is provided. The method includes: receiving an operating value of the battery, wherein the operating value of the battery includes: a terminal voltage of the battery and a battery current of the battery.

[0010] The operating values ​​can be received, for example, as a time series. Another alternative is to receive the operating values ​​as aggregated data. For example, a histogram can be used.

[0011] The method further comprises:

[0012] The modeled terminal voltage is determined using a battery model based on the battery current,

[0013] Compare the modeled terminal voltage to the terminal voltage,

[0014] The lithium plating state of the battery is determined based on the comparison.

[0015] The comparison may involve the instantaneous voltage value of the terminal voltage and the modeled terminal voltage. It is also possible that determining the modeled terminal voltage includes integrating the modeled terminal voltage within a specific range, thereby obtaining a modeled area. The modeled area can be compared with the area obtained by integrating the terminal voltage within a specific range. This means that the comparison may involve the integration of the voltage values. By comparing the modeled area with the area obtained by the operation of the battery, the lithium deposition state of the battery can be determined.

[0016] A time series may refer to a temporal sequence of data, which is determined, for example, by a series of measurements at different points in time. The temporal sequence may be continuous, but the temporal sequence may also be irregular.

[0017] The computer program or computer program product or a storage medium readable by a computer comprises a program code. Such a program code can be loaded and run by a processor. This causes the processor to perform a method for characterizing a rechargeable battery according to one of the methods. The method can be performed on the server side.

[0018] Furthermore, a system is provided, which comprises at least one device having a battery, wherein the device is configured to transmit operating values ​​to a server, wherein the operating values ​​include, for example, a terminal voltage of the battery as a time series and, for example, a battery current of the battery as a time series.

[0019] The system further comprises a server which is configured to receive operating values ​​of at least one device and thereby carry out the method described here.

[0020] At least one of the devices may be a vehicle.

[0021] Furthermore, a server is provided which is configured to receive operating values ​​of a battery, for example as a time series, and thus to carry out the method described here.

[0022] The features mentioned above and those explained below can be used not only in the respectively explicitly stated combination but also in other combinations or alone, without departing from the scope of protection of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Methods according to various embodiments are shown;

[0024] Figure 2 Systems according to various embodiments are shown;

[0025] Figure 3 An example of a battery powering a device is shown;

[0026] Figure 4 An example of a server is shown;

[0027] Figure 5 An example of a circuit including a rechargeable battery is shown;

[0028] Figure 6 An example of a time series of a battery current of a battery is shown;

[0029] Figure 7 Shows Figure 1 possible implementations of the method;

[0030] Figure 8 An equivalent circuit is shown which can be used to model a battery, wherein the model does not simulate lithium plating;

[0031] Fig. 9 An equivalent circuit of a battery is shown, which can be used to model the battery, wherein the model simulates lithium plating;

[0032] Fig.10 , Fig.11 and Fig.12 Examples of different voltage-charge curves are shown;

[0033] Fig.13 Shown in Figure 1 Possible method steps in a method. DETAILED DESCRIPTION

[0034] The above-mentioned characteristics, features and advantages of the present invention and the manner in which these characteristics, features and advantages are achieved will be more clearly and distinctly understood in conjunction with the following description of the embodiments explained in more detail with reference to the accompanying drawings.

[0035] Next, the present invention will be explained in more detail with reference to the accompanying drawings by means of preferred embodiments. In the accompanying drawings, the same reference numerals mark the same or similar elements. The accompanying drawings are schematic representations of different embodiments of the present invention. The elements shown in the accompanying drawings do not have to be shown in correct proportion. More precisely, the different elements shown in the accompanying drawings are reproduced so that those skilled in the art can understand their functions and general uses. The connections and couplings between the functional units and elements shown in the accompanying drawings can also be implemented as indirect connections or couplings. The connections or couplings can be implemented wired or wirelessly. The functional units can be implemented as hardware, software, or a combination of hardware and software.

[0036] Several techniques are described below in connection with characterization of rechargeable batteries. The techniques described herein can be used in connection with different types of rechargeable batteries where lithium plating may occur, such as in connection with lithium-ion based batteries, such as lithium-nickel-magnesium-cobalt oxide batteries or lithium-manganese oxide batteries.

[0037] The rechargeable batteries described here can be used in different fields of application. The batteries can be used, for example, in devices such as motor vehicles or drones or portable electronic devices such as mobile communication devices. It is also conceivable that the batteries described here are used in the form of static energy storage devices. The method described here can be performed on the server side. However, the method can also be performed alternatively or supplementally, for example partially by the device itself, for example by a battery management system of the device. In this case, all steps can be performed by the device. Some or all steps can alternatively be performed by a remote additional device, such as a server.

[0038] The determined lithium deposition state can be used in different ways and methods. For example, the result of the lithium deposition state can be used to adjust the operation of the battery. This can, for example, avoid excessive aging of the battery. Alternatively or additionally, the secondary use of the battery can also be determined based on the result of the lithium deposition state. For example, it can be determined whether the battery is still suitable for a specific use or must be withdrawn from circulation. Another possible use involves targeted maintenance and / or repair of the battery based on the lithium deposition state. For example, it is possible to maintain or replace these batteries that are predicted to have a deteriorated lithium deposition state, etc.

[0039] As a general rule, the technology described here for determining the lithium deposition state can be used at different levels: In a simple embodiment, the lithium deposition state is determined at the battery level, that is, the lithium deposition state can be determined horizontally across all battery blocks and battery cells. However, in other examples, the determination can also be done analytically for different battery blocks or even cells of individual battery blocks, for example for battery blocks connected in series and / or in parallel. Sometimes it is also possible to disassemble the battery and remove individual battery blocks, wherein other battery blocks can continue to be used. In this example, a separate determination is worth pursuing at the battery block level even in the preparation phase. This can also be achieved with the method and device described here.

[0040] The various examples described herein may be implemented at least partially on the server side. This means that at least a portion of the logic associated with the methods and devices described herein may be executed separately from the battery or the battery-operated device on a central server or multiple distributed servers (hereinafter also referred to as servers). In other words, the server may be a separate computer system. The server may also be distributed to different computer systems for operation, for example as so-called cloud computing.

[0041] For this purpose, a communication connection can be established between the server and one or more battery management systems of the battery. By implementing at least part of the logic on the server, particularly accurate and computationally intensive models and / or simulations can be used in conjunction with the lithium deposition state determination. This enables the state determination to be performed particularly accurately. It is also possible, for example, to collect data for all batteries and to evaluate the data in conjunction with a machine-learned model.

[0042] The different examples described here can perform the state determination based on the measured data of the battery during the use of the battery. This means that the lithium deposition state can be determined at a specific time point in the life cycle of the battery. The battery can also be in field use. In this case, in particular, the previous lithium deposition behavior of the battery can also be taken into account.

[0043] Figure 1 Methods according to various embodiments are shown.

[0044] The method can be used to characterize rechargeable batteries that may have a risk of lithium plating, for example, on the server side. Figure 1 The method can be, for example, Figure 2 Next, refer to Figure 2 However, in other examples, the method may also be performed without Figure 2 These examples should therefore not be construed as limiting.

[0045] The method comprises the following steps:

[0046] In 1001, operating values ​​41 of a battery, for example one of the batteries 91-96, are received as a time series. Here, the operating values ​​of the battery may include, for example, a terminal voltage of the battery and / or a battery current of the battery.

[0047] The terminal voltage and the battery current can be determined during a discharge process and / or a charge process of the battery. The terminal voltage and the battery current can also be determined by a combined charge and discharge process, for example, by a charge process and a discharge process. It is also possible to only partially perform the corresponding process, for example, a partial charge process.

[0048] The charging process can be, for example, the charging of the battery at an external power source, but the (partial) charging process can also be carried out by other energy supply processes, such as Figure 2 Energy recovery in vehicle 110 is performed.

[0049] In this case, the determination can be performed during use of the battery, ie, for example, when a vehicle with the battery is in use (sometimes also referred to as “field use”).

[0050] In 1002, a modeled terminal voltage USim(t) is determined using a model of the battery.

[0051] The battery model can be, for example, combined with Figure 8 and Fig. 9 The described model. In this case, the modeled terminal voltage can be determined based on the battery current I(t).

[0052] In 1003 , the modeled terminal voltage USim(t) is compared with the terminal voltage U(t).

[0053] The comparison may also include determining a voltage-charge curve based on the terminal voltage U(t) and the battery current I(t). Figures 10 to 12 and explained in more detail below.

[0054] The voltage-charge curve 200 can be used to compare the modeled terminal voltage with a selected range of the voltage-charge curve 200. The voltage-charge curve can be an example of the previously described summary data. A given voltage-charge curve is particularly unlikely to have a time correlation. For example, the modeled terminal voltage can be determined for a predetermined state of charge, for example a 90% state of charge. This can then be directly compared with the corresponding value of the determined voltage-charge curve 200. In other words, the modeling of the voltage-charge curve 200 can only be performed for a single point in some examples. In other examples, multiple points of the voltage-charge curve can also be determined and / or multiple points of the voltage-charge curve can be modeled.

[0055] The comparison may also include determining a modeled voltage-charge curve 300 based on the modeled terminal voltage (USim(t)) and the battery current.

[0056] The method may further include comparing the voltage-charge curve 200 to a modeled voltage-charge curve 300 .

[0057] These comparative variants may have the advantage that, for the comparison of the determined and modeled voltage-charge curves, techniques for characterizing lithium deposition may be used which presuppose the existence of voltage-charge curves, for example from laboratory measurements.

[0058] In 1003, alternatively, instead of comparing the voltage-charge curve 200 with the modeled voltage-charge curve 300, the difference between the two curves can also be calculated. The integration of the difference between the two curves produces a representative area. This area can then be compared with a reference area in order to determine the lithium deposition state in 1004. By taking into account this comparison of the integrated voltage values, a particularly high accuracy can be achieved, which, for example, compensates for fluctuations in short time periods.

[0059] Other comparison variants of the aggregated data can also be performed. For example, a histogram can also be determined from, for example, the charge state and the discharge state and compared with the simulated histogram. This can have the advantage that, for example, the amount of data to be detected by the device 100 can be reduced and / or the amount of data to be transmitted can be reduced. This can, for example, reduce the amount of data that must be transmitted via the communication connection 49. The corresponding statements also apply to the simulated data, and the results of the simulation can be stored, processed and transmitted with a smaller amount of data.

[0060] The comparison of the modeled terminal voltage to the terminal voltage can be based on a voltage offset value between the modeled terminal voltage and the terminal voltage. Fig.11 Provide explanation.

[0061] The modeled terminal voltage may additionally or alternatively be based on a voltage offset value. This is discussed below in conjunction with Fig.12 Provide explanation.

[0062] In 1004 , the lithium plating state of the battery is determined based on the comparison in 1003 .

[0063] The determination of the lithium deposition state can be quantified based on the width 810 of the plateau 800 of the voltage-charge curve, wherein the plateau 800 is determined based on the voltage offset value Uoff. Fig.11 and Fig.12 Shown in.

[0064] Figure 2 Systems according to various embodiments are shown.

[0065] exist Figure 2 System 80 is shown in the embodiment of FIG.

[0066] In one example, system 80 may include at least one vehicle, such as vehicle 110, which may include a battery, such as battery 95. However, other devices, such as Figure 2 The device 100 may also be an alternative or additional system component. The vehicle 110 may be configured to transmit operating values ​​to the server 81. The operating values ​​may include: a terminal voltage of a battery as a time series and / or a battery current of a battery as a time series. The server 81 may be configured to receive operating values ​​of at least one vehicle 110, for example via a communication connection 49, and thus to carry out at least one of the methods described here.

[0067] In a further example, which can be combined with the previous example but can also be implemented independently thereof, the server 81 is configured to receive the operating value 41 via a corresponding communication connection 49. The operating value 41 can in particular be a value used in the exemplary embodiment of the method described herein, for example in Figure 1 The running value in the method.

[0068] The server 81 may be, for example, Figure 4 and / or Figure 7 Server 81.

[0069] The operating value 41 can be provided by different batteries 91 to 96. The batteries can be installed in different devices. Battery 92 is installed in device 100, for example. Battery 95 is installed in vehicle 110.

[0070] exist Figure 2 It is also shown by way of example that the server 81 can send control data 42 to the batteries 91 to 96 via the communication connection 49. For example, it is possible that the control data 42 indicate one or more operating limits for the future operation of the respective battery 91 to 96. The control data can, for example, indicate one or more control parameters for the thermal management of the respective battery 91 to 96 and / or the charging management of the respective battery 91 to 96. By using the control data 42, the server 81 can also, in some embodiments, influence or control the operation of the batteries 91 to 96. In this case, for example, a specific state of lithium deposition can be used for Figure 1 In order to determine the control data 42 for the corresponding battery. It is thus possible to reduce or even avoid the continuation of lithium deposition, for example, in the following way, that is, the maximum permissible charging current is defined as a function of the temperature of the battery, for example.

[0071] Figure 3 An example of a battery powering a device is shown.

[0072] exist Figure 3 The schematic diagram is shown in Figure 2 Other possible components of the batteries 92 to 96 shown in FIG. The batteries 91 to 96 shown can be related to Figure 2 The battery 92 of the embodiment of the present invention. The batteries 91 to 96 can supply electrical energy to the device 69. The device 69 shown in the figure can be, for example, Figure 2 Device 100 or Figure 2 of vehicles 110.

[0073] The batteries 91 to 96 may include a plurality of battery blocks 63. Each battery block 63 typically includes a number of battery cells connected in parallel and / or in series. Electrical energy can be stored there. The behavior of the batteries 91-96 is controlled by a battery management system 61 or by a plurality of battery management systems. The battery management system 61 may be, for example, a so-called BMS or other control logic such as an on-board unit in the case of a vehicle. The battery management system 61 may be implemented, for example, by software on a processor. Alternatively or additionally, an application specific circuit (ASIC) or a field programmable gate array (FPGA) may be used, for example. The battery management system 61 may also be run at least partially in the cloud.

[0074] The batteries 91-96 can communicate with the battery management system 61, for example, by means of a bus system. The batteries 91-96 can also include a communication interface 62. The battery management system 61 can establish a communication connection 49 with the server 81 via the communication interface 62. The communication interface 62 can also be configured to transmit operating values ​​41 to the server 81. The communication interface 62 can also be configured to receive control data, such as Figure 2 In these examples, the battery management system 61 may be configured to adapt a control and / or regulation behavior based on the control data 42 .

[0075] When Figure 3 Although the battery management system 61 is shown separately from the batteries 91 to 96 in FIG. 1 , in other examples it is also possible for the battery management system 61 to be part of the batteries 91 to 96 . The corresponding description also applies to the communication interface 62 .

[0076] The battery management system 61 typically has access to one or more sensors in one or more battery blocks 63. In some examples, the battery management system 61 can additionally or alternatively access further sensor data. The sensors can, for example, measure the current and / or voltage in at least some of the battery cells. In this case, the voltage, which is sometimes also referred to as the open circuit voltage (OCV), can be determined both in idling operation, but also in load operation, which is sometimes also referred to as the terminal voltage. The sensors can alternatively or additionally also measure other variables in conjunction with at least some of the battery cells, such as temperature, volume, pressure, etc. The battery management system 61 can be configured to determine the current state variables for the corresponding battery 91 to 96 or, optionally, also for a separate battery block based on one or more such measured values ​​of the sensor. In some cases where there are further data, these data can also be transmitted to the communication interface 62 via the communication interface 62. Figure 2 of the server 81. This can, for example, enable Figure 1 The method can also be performed at other levels, for example at the level for each parallel-connected cell, for example after the terminal voltage for the parallel-connected cells has been jointly determined. Thus, for example, the lithium deposition state can be determined not only for the entire battery 91 to 96, but also for the lower layer of the battery 91 to 96.

[0077] Figure 4 An example of a server is shown.

[0078] exist Figure 4 The server 81 shown exemplarily in FIG. 8 includes a processor 51 and a memory 52. ​​The memory 52 may include volatile and / or non-volatile storage elements. In addition, the server 81 also includes a communication interface 53. The processor 51 can establish a communication connection 49 with each battery 91 to 96 and optionally also with the database 82 via the communication interface 53.

[0079] The program code may be stored in the memory 52 and loaded by the processor 51. The processor 51 may then execute the program code. The execution of the program code may cause the processor 51 to implement one or more methods as described in detail in conjunction with the various examples herein.

[0080] According to the invention, a computer program with a program code may be provided. When the computer program is run on a processor, for example on the processor 51, this may cause one of the methods described here to be performed.

[0081] As mentioned before, the server 81 may also be a logical unit and may be implemented as a virtual server or a cloud server, for example.

[0082] Figure 5 An example of a circuit including a rechargeable battery is shown.

[0083] exist Figure 5 A schematic equivalent circuit for circuit 101 is shown in FIG. 1 , which includes battery 95. Circuit 101 may be installed, for example, in Figure 2 In a vehicle 110 or other device, such as Figure 2 In the device 100.

[0084] In the example shown, the operating value 41 of the battery 95 is determined as a time series as described below. In other examples, other operating values ​​and / or alternative operating values ​​may be detected. The battery 95 may be, for example, Figure 1 A battery 95 is shown, which can be installed in the vehicle 110. However, other batteries are also possible. In the schematically shown example, the battery 95 is connected to an electrical consumer 103. The electrical consumer 103 can be, for example, the drive train of an electric vehicle. Not shown in the schematic diagram 101 is a control device, which regulates the load behavior of the electrical consumer 103. This can be a component of the electrical consumer 103 itself.

[0085] In response to the load behavior of the electrical consumer 103, the battery 95 supplies a current I(t). This current can be measured by a current measuring device 270. A terminal voltage U(t) is also present at the battery 95 as a function of the load behavior of the electrical consumer 103 and characteristics of the battery 95, such as the charge state and / or other state variables of the battery 95. This terminal voltage U(t) can be detected by a second measuring device 280.

[0086] The terminal voltage U(t) and the battery current I(t) can be measured by the measuring devices 270, 280 as a function of time at at least two different points in time. This allows the time series of these operating values ​​to be detected. This can be done, for example, by Figure 3 The battery management system 61 is completed, but other embodiments are also possible. The time series of the operating values ​​detected in this way can then be used, for example, Figure 2 The communication connection 49 is transmitted to Figure 2 In other embodiments, it is also possible that the operating values ​​are first partially stored and, for example, during maintenance work in a workshop, for example, when a connection with Figure 2 When a connection is established between the vehicle 110 or the diagnostic port of the device 100 Figure 2 The communication connection 49. In these cases, the time series can be stored, for example, by the battery management system 61, but there are other possibilities.

[0087] Figure 6 An example of a time series of a battery current of a battery is shown.

[0088] Figure 6 The battery current I(t) is shown, which is drawn from the battery, e.g. Figure 5 The battery 95 flows to, for example, Figure 5 The power consumption is 103. Figure 6 In the example shown in FIG. 7 , the battery current I(t) is positive. Phases of the relatively constant current requirement curve 721 alternate with phases of the current requirement curve 722 that vary greatly over time. A positive current means that the battery is being discharged. In other examples, the battery current I(t) can also be detected during battery charging, for example during a charging process or during other processes, such as energy recovery during vehicle operation. In these cases, the curve I(t) is positive. Figure 6 is negative under the convention. From the time series of the battery current I(t), the charge that has flowed can be determined, for example, by time integration. The charge that has flowed can then be used to determine the voltage-charge curve. This is discussed in the following in conjunction with Figure 10-12 Please explain.

[0089] But first with the help of Figure 7 A further possible approach to using the operating values ​​of the battery determined in this way as a time series is described.

[0090] Figure 7 Shows Figure 1 Possible implementations of the method.

[0091] Figure 7 A possible process that can be executed in the server 81 is shown to achieve Figure 1 The server 81 may be, for example, Figure 4 Server 81.

[0092] To perform one of the methods described herein, in 1001, the server 81 receives operating values ​​41 of a battery. The battery may be, for example, Figure 5 and / or Figure 6 The battery 95. As operating value 41, for example, the terminal voltage U(t) of the battery as a time series and the battery current I(t) of the battery as a time series can be provided.

[0093] The server 81 determines the modeled terminal voltage USim(t) based on the battery current I(t) with the aid of the model 400. In a further step, the modeled terminal voltage USim(t) is compared 1003 with the terminal voltage U(t). Based on the comparison 1003, the lithium deposition state of the battery is determined 1004. The lithium deposition state of the battery can be stored by the server 81 and / or provided to other applications, for example, in a Figure 1 The data base 82 of the battery or used in another process to provide control data 42 for the corresponding battery.

[0094] In some embodiments, control data 42 for a second battery may also be provided based on the lithium plating state determined for the first battery. If lithium plating occurs in the first battery during rapid charging at low operating temperatures, then control data 42 may be provided for other similar or identically constructed batteries, such as second batteries that may be installed in a similar series of vehicles as the first battery, which prevent lithium plating in these other batteries.

[0095] In some embodiments, lithium deposition state 1004 may also be used to determine state variable 900. State variable 900 may be considered in model 400 as shown in 901 .

[0096] In some embodiments, one or more state variables 900 of the battery can be provided to the server 81 in addition. The state variables 900 can be, for example, the temperature of the surroundings of the battery, the temperature of the battery, the state of charge, sometimes also referred to as the state of charge (SOC), the aging state of the battery, the event history of the battery and / or the current rate of the load of the battery. However, other state variables 900 are also possible. In this case, the current rate of the load of the battery can be the current of the battery called by the battery. The current can be normalized with the rated capacity of the battery.

[0097] The state variable 900 can be provided by another model, for example, determined based on the time series of the terminal voltage U(t) and / or the time series of the battery current I(t). Alternatively, the state variable can also be determined based on the measured state variable 902. For example, the temperature 902 can be measured directly in the battery cell and directly used as the state variable 900 after being transmitted to the server 81. In other examples, the local temperature of the battery can be modeled, for example, based on the measured external temperature 902 of the vehicle and the time series of the battery current I(t) and / or the terminal voltage U(t), for example, with the help of thermal simulation, and based on this, for example, the temperature of the battery cell as a function of time is provided as the state variable 900.

[0098] The temperature of the battery's surroundings can also be determined, for example, using weather data, for example based on a position measurement of the battery, for example based on a GPS measurement of the vehicle with the battery. These state variables 902 can therefore also be determined by the server 81 itself, for example by calling up a weather model for the GPS coordinates. The temperature of the battery can be detected by the battery management system, for example, by measurement, for example by measurement with a temperature sensor.

[0099] Model 400 may be associated with at least one state variable 900. At least one element of the model of the battery, for example a structural element, such as in Figure 8 and Fig. 9 As shown in , for example, the voltage source UOC and / or the RC element 420 can be dependent on at least one state variable.

[0100] Figure 8 and 9 An example of a battery model is shown.

[0101] Figure 8 An equivalent circuit 410 is shown that may be used to model the battery 95 , wherein the model does not simulate lithium deposition.

[0102] Fig. 9 Another equivalent circuit 411 of a battery is shown, which can be used to model the battery 95, wherein the model simulates lithium deposition.

[0103] The equivalent circuits 410 and 411 can be used to provide Figure 7 Model 400.

[0104] The equivalent circuits 410 and 411 each include a voltage source UOC and a resistor R0. In the illustrated examples of the equivalent circuits 410 and 411, at least one RC element is additionally present, for example, a plurality of RC elements 410 to 423. The at least one RC element may, for example, include a first RC element and a second RC element, wherein the at least one resistor and the first RC element and the second RC element may be connected in series with each other. The first RC element and the second RC element may additionally be connected in series with an ideal voltage source. Figure 8 and 9 In some embodiments not shown in FIG. 1 , no RC element is present.

[0105] exist Figure 8 and Fig. 9 In the example shown, each RC element 420 to 423 comprises a resistor and a capacitor connected in parallel with each other. Thus, the RC element 420 comprises a first resistor R1 and a first capacitor C1. The i-th RC element 421 comprises a resistor Ri and a capacitor Ci and the N-th RC element 422 comprises a resistor Rn and a capacitor Cn. By illustrating the points between the RC elements, a further RC element 423 may optionally be present.

[0106] By means of such equivalent circuits, such as the equivalent circuits 410 , 411 shown, but also by means of equivalent circuits which comprise fewer components than shown in the example or have additional further components, the time-dynamic load behavior of the battery 95 can be simulated.

[0107] The voltage source UOC may be an ideal voltage source. This may be parameterized, for example, as a function of the state of charge of the battery 95 .

[0108] In other examples, the UOC may have additional characteristics. These characteristics may be parameterized, for example, as state variables, such as Figure 7 The temperature dependence of the voltage source UOC can be parameterized, for example.

[0109] The equivalent circuits 410 and 411 shown may include additional elements in some examples. Thus, for example, additional characteristics of a battery can be simulated. In other examples, the equivalent circuits 410 and 411 do not include additional elements, or include fewer elements as described above. In one example, the equivalent circuit includes a resistor R0 and an ideal voltage source UOC.

[0110] A particularly efficient simulation can be achieved by means of an equivalent circuit with fewer components, which can be calculated with less effort and which can be sufficiently accurate for some tasks.

[0111] In some examples with at least one RC element, 10 RC elements are used, in some examples 8 RC elements are used, in some examples 6 RC elements are used, and in some examples 4 RC elements are used, but other numbers of RC elements are possible.

[0112] exist Fig. 9 In the equivalent circuit 411, there is another voltage source UPlating. Fig. 9 The equivalent circuit 411 can also be understood as being exemplary and can be combined with Figure 8 As illustrated include fewer or more elements than the examples shown.

[0113] The additional voltage source UPlating can be used to describe the voltage changes that occur due to the lithium deposition process by the model 411 .

[0114] The corresponding components of the equivalent circuits 410, 411 can be adjusted based on at least one state variable 900 of the battery. The i-th resistor Ri and the i-th capacitor Ci can change, for example, as a reaction to the temperature of the battery. This can be achieved technically, for example, with the aid of a lookup table. However, other methods can also be implemented, such as a functional description of the dimensioning of the capacitor Cn as a function of a state variable, such as the external air pressure.

[0115] Equivalent circuit, for example Figure 8 and Fig. 9 The equivalent circuits 410, 411 shown in FIG. 4 may additionally or alternatively include a hysteresis element. The hysteresis element may be configured to model the hysteresis behavior of the battery.

[0116] Individually, different models for modeling hysteresis behavior are known, such as zero-state and one-state hysteresis models, as described in Plett, GL, "Extended Kalman Filter for Battery Management Systems for LiPB-Based HEV Battery Packs", Power Sources 134 (2004), No. 2, pp. 252-261. Also known from Verbrugge et al., for example, are models described in Verbrugge, M., Tate, E., "Adaptive State of Charge Algorithm for Nickel Metal Hybrid Batteries Including Hysteresis", Power Sources 126 (2004), No. 1-2, pp. 236-249, and Verbrugge, M, "Adaptive, Multi-Parameter Battery State Estimator with Optimized Time Weighting Factors", Journal of Applied Electrochemistry 37 (2007), No. 5, pp. 605-616.

[0117] These models can be used, for example, in the form of additional elements in an equivalent circuit to design a model of battery 400 in such a way that, for example, the hysteresis behavior of the battery is modeled when switching from a charging process to a discharging process.

[0118] These or other hysteresis models can also be used in conjunction with the equivalent circuits described herein.

[0119] Fig.10 , Fig.11 and Fig.12 Examples of different voltage-charge curves are shown.

[0120] exist Fig.10 An exemplary voltage-charge curve 200 is shown in FIG. 2 . In the selected coordinate system, the charge in ampere-hours is plotted as the x-axis 220 and the voltage in volts is plotted as the y-axis 210. The voltage-charge curve 200 shown can be determined based on the terminal voltage U(t) and the battery current I(t). This is shown with points 250, 251, 252. The voltage-charge curve 200 can consist of a large number of such points. The y-coordinate of point 250 can be determined, for example, from the terminal voltage of the battery as a time series (t) for a given point in time T, where y can be equivalent to U(t=T). The x-coordinate of point 250 can be determined, for example, by time integration of the battery current of the battery as a time series I(t). The amount of charge flowing can be determined, for example, by integrating the battery current at a predetermined point in time T. Figure 6 The time integral of the curve shown is determined. Assumptions can be made here regarding the integration limits. For example, it can be assumed that at the time t=T0, the battery is fully charged and the amount of charge Q=0 ampere-hours flowing can be set. In other examples, the integration constant can be determined based on other models, for example for the charge state and / or the aging state. A lithium deposition state previously determined, for example in a previous charge / discharge cycle, can also be used to determine the integration constant.

[0121] Fig.10 The voltage-charge curve shown in FIG. 1 is an exemplary voltage-charge curve for a battery without lithium plating.

[0122] Fig.11 The voltage-charge curve 200 of a battery with lithium deposition is shown. This can be seen particularly clearly in the region 810, where a plateau can be seen in the voltage-charge diagram. The voltage-charge curve 200 can be compared with the modeled voltage-charge curve 300. In the example shown, the voltage-charge curve 200 has a voltage offset Uoff relative to the modeled voltage-charge curve 300. The voltage offset Uoff can indicate lithium deposition.

[0123] The determination of the lithiation state may be quantified based on the width 810 of the plateau 800 of the voltage-charge curve 200. The plateau 800 may additionally or alternatively be determined based on the voltage offset Uoff.

[0124] Contemplated mathematical functions may be used to characterize the platform 800, for example, including functions including the tanh function, although other functions are also possible.

[0125] The voltage offset Uoff can be between 50 mV and 150 mV, in particular between 80 mV and 120 mV.

[0126] The voltage offset can be the result of an electrochemical voltage sequence and is derived, for example, from different oxidation potentials of metallic or deintercalated materials. For example, it is known from Ratnakumar V.Bugga and Marshall C.Smart, "Lithium Deposition Behavior in Lithium-ion Batteries" (ECS Trans. 2010, Vol. 25, No. 36, pp. 241-252, doi: 10.1149 / 1.3393860), that the oxidation potential ratio for metallic lithium is about 100 mV higher during deintercalation. For these systems, a voltage offset Uoff of about 100 mV, for example 100 mV, can be selected. In other systems, the corresponding values ​​can be calculated.

[0127] The voltage offset Uoff can be used, for example, as a parameter of a tanh function.

[0128] The modeled voltage-charge curve 300 can be determined based on the modeled terminal voltage USim(t) and the battery current I(t). The presence of lithium deposition in the battery can then be determined by comparing the voltage-charge curve 200 with the modeled voltage-charge curve 300. The modeled voltage-charge curve 300 can be determined, for example, by means of Figure 8Because the modeled voltage-charge curve 300 does not take lithium plating into account, it can be inferred from the difference between the modeled voltage-charge curve 300 and the measured voltage-charge curve 200, for example, in region 800, that lithium plating has occurred in the battery. Fig.10 When the voltage-charge curve 200 is shown, the modeled voltage-charge curve 300 is similar to Fig.10 The measured voltage-charge curve 200 of 2 is consistent within the error range. Based on this, it can be determined in this case that there is no lithium deposition.

[0129] Fig.12 Shows Fig.11 The voltage-charge curve 200 of FIG. 2 is shown, but another modeled voltage-charge curve 301 is also shown. Fig.12 The modeled voltage-charge curve 301 shown in FIG. 3 may be based on, for example, a voltage-charge curve 301 that may include Fig. 9 The model of the equivalent circuit 411 is determined.

[0130] Because the equivalent circuit 411 has a voltage source UPlating, it is possible that the modeled voltage-charge curve 301 is also consistent with the trend change of the specific voltage-charge curve 200 in the region 800. In this case, it can be inferred that lithium deposition exists in the battery by the modeled voltage-charge curve 301 modeled for lithium deposition being consistent with the specific voltage-charge curve 200 within the range of error.

[0131] As combined Figures 10 to 12 The method for determining the voltage-charge curve as described also makes it possible to quantify the lithium deposition. This can be done, for example, by describing Fig.11 The width 810 occurs quantitatively.

[0132] Fig.13 Shown in Figure 1 Possible method steps in a method.

[0133] exist Fig.13 In a variant of , a comparison of USim(t) with U(t) takes place in 1003. This can be done, for example, in combination with Figures 10 to 12 This is done as described using a voltage-charge curve, but other approaches are also possible.

[0134] Based on the comparison 1003, it is now determined 1004a whether lithium deposition is present in the battery. If not, the algorithm ends. The information that lithium deposition is not present can be stored and / or transmitted.

[0135] If lithium precipitation exists, the algorithm may also be terminated, and the information that lithium precipitation exists may be stored and / or transmitted. In addition, lithium precipitation may be quantified as described above in 1004b. The quantification of lithium precipitation may also be stored and / or transmitted. The algorithm is then terminated.

[0136] The features of the above described embodiments and aspects of the invention can of course be combined with one another. In particular, the features can be used not only in the described combination, but also in other combinations or alone without departing from the scope of the invention.

[0137] For example, various previous techniques are described in conjunction with the determination of lithium deposition in a battery. These techniques can also be applied to individual blocks of batteries or battery cells or battery cell groups of batteries.

[0138] In addition, different technologies have been described before, in which operating values ​​as time series are received. But it is also usually possible to receive operating values ​​as summarized data, that is to say, for example, as operating values ​​of histograms. The process described before can also be implemented with these summarized data. For this reason, for example, the summarized data are also formed by the simulated parameters and the summarized simulated data are compared with the summarized measured data. The time series can be inferred again by the summarized data supplementarily or alternatively. For example, the time series can be reconstructed from the summarized data, for example, by determining the reference time series for the first group of reference equipment in the test cycle and / or in the field use and determining the summarized reference data derived from these time series. Then, for example, the summarized data can be found out for the second group of equipment and the reconstructed time series can be determined based on the reference time series by comparing the summarized data with the summarized reference data. The method described here can then be performed with the reconstructed time series. Other or modified practices are also feasible. These procedures can offer the advantage that only a small fraction of the devices, for example less than 1% of the vehicles, must be provided for detecting the time series and the individual battery states of the other vehicles in the series can then be inferred, for example based on the aggregated data called up at maintenance intervals.

Claims

1. A method for characterizing a rechargeable battery (91-96) with a risk of lithium plating, the method comprising: Receiving (1001) operating values ​​(41) of batteries (91-96) as a time series, wherein the operating values ​​of the batteries include: The terminal voltage of the battery is U(t), The battery current I(t) of the battery, determining (1002) a modeled terminal voltage USim(t) using a model (400) of a battery based on the battery current I(t), comparing (1003) the modeled terminal voltage USim(t) with the terminal voltage U(t) of the battery, determining a voltage-charge curve (200) based on the terminal voltage U(t) and the battery current I(t) of the battery, determining a modeled voltage-charge curve (300) based on the modeled terminal voltage USim(t) and the battery current, comparing the voltage-charge curve (200) to a modeled voltage-charge curve (300), and The lithium plating state of the battery is determined (1004, 1004a, 1004b) based on a comparison of the modeled terminal voltage with the terminal voltage of the battery.

2. The method according to claim 1, wherein: The comparison of the modeled terminal voltage with the terminal voltage of the battery is further based on a voltage offset Uoff between the modeled terminal voltage and the terminal voltage of the battery.

3. The method according to claim 2, wherein: The lithium deposition state is quantitatively determined based on the width (810) of the platform (800) of the voltage-charge curve, wherein the platform (800) is determined based on the voltage offset Uoff.

4. The method according to claim 2, wherein: The voltage offset Uoff is between 50 mV and 150 mV.

5. The method according to claim 1 or 2, wherein: The terminal voltage of the battery and the battery current during a discharge process and / or a charge process of the battery are determined.

6. The method according to claim 1 or 2, wherein: The battery model (400) includes the following elements (410, 411, 420-422, UOC): The equivalent circuit (410, 411) of the battery comprises at least one resistor R0 and an ideal voltage source UOC, And wherein the method further comprises: The dimensioning of at least one element (410, 411, 420-422, UOC) of a model of the battery is determined based on at least one state variable (900) of the battery.

7. The method according to claim 6, wherein: The battery model (400) further includes: at least one RC element (420, 421, 422) and / or At least one hysteresis element is configured to model a hysteresis behavior of the battery.

8. The method according to claim 1 or 2, wherein: At least one element of the model of the battery is dependent on at least one state variable.

9. The method according to claim 8, wherein: The at least one state parameter is selected from: The temperature of the battery's surroundings, The temperature of the battery, The charging state of the battery, i.e. the state of charge SoC, the aging state of the battery, The event history of the battery, The current rate at which the battery is loaded.

10. The method according to claim 1 or 2, wherein: The method further comprises: A configuration is provided for a battery management system based on the lithium deposition status of the battery.

11. The method according to claim 4, wherein: The voltage offset Uoff is between 80 mV and 120 mV.

12. A computer program with a program code which, when the program code is run on a processor, causes the method according to any one of claims 1 to 11 to be performed.

13. A system (80), comprising: At least one device (100) with a battery, wherein the device is configured to transmit operating values ​​to a server (81), wherein the operating values ​​include: the terminal voltage of the battery as a time series and the battery current of the battery as a time series, and A server (81) which is configured to receive operating values ​​of at least one device (100) and to carry out the method according to any one of claims 1 to 10.

14. A server, which is configured to receive operating values ​​(41) of a battery (91-96) as a time series and to carry out the method according to any one of claims 1 to 11.

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