DE102015222804A1 - ENERGY STORAGE DEVICE, METHOD FOR OPERATING AN ENERGY STORAGE DEVICE, BATTERY MODULE AND VEHICLE - Google Patents

Abstract

The invention relates to an energy storage device having an electrochemical energy storage cell, for example a lithium-ion accumulator, which has at least one anode and at least one cathode, a reference electrode, which is integrated in the energy storage cell, an amplifying device, which is adapted to a potential difference between the Anode or cathode and the reference electrode to amplify, and a processing device which is adapted to determine based on the increased potential difference an operating condition, in particular a state of charge, the energy storage cell. The invention further relates to a method for operating such an energy storage device, a battery module with such energy storage devices and a vehicle with such a battery module.

Description

The invention relates to an energy storage device, a method for operating such an energy storage device, a battery module with such energy storage devices and a vehicle with such a battery module.

Batteries for storing electrical energy play an important role in almost every aspect of daily life, for example in watches, portable electrical appliances and in the field of wireless telecommunications. They are of central importance, in particular in the field of so-called electromobility, both in vehicles with pure electric drive and in vehicles with hybrid drive. Especially here it is of great importance to be able to accurately determine the operating state of the batteries, for example the state of charge or the service life.

To determine the operating state of the batteries, in particular the state of charge (SOC), various methods are used, for example, a simple comparison of a measured voltage with a known charge voltage curve, a direct measurement of the charge flow by integration of the already flowed or an adjustment of integrated current with computer-aided real-time calculations of the overvoltage potentials of a battery model occurring during operation. The accuracy of the determination of the operating state, in particular of the state of charge, is generally determined substantially by the measurement accuracy in the voltage or current measurement.

It is an object of the present invention to provide an energy storage cell, a method for operating such an energy storage cell, a battery module with such energy storage cells and a vehicle with such a battery module, which is particularly precise with respect to the determination of the operating state.

The energy storage device according to the invention comprises: an electrochemical energy storage cell having at least one anode and at least one cathode, a reference electrode, which is integrated in the energy storage cell, an amplifying device, which is designed to increase a potential difference between the anode or cathode and the reference electrode, and a processing device which is designed to determine an operating state of the energy storage cell based on the amplified potential difference.

The battery module according to the invention has two or more interconnected inventive energy storage devices.

An inventive vehicle, in particular a motor vehicle, has an electric drive or a hybrid drive and at least one energy storage device according to the invention and / or at least one battery module according to the invention.

A motor vehicle in the sense of the present invention is preferably a non-permanently track-guided land vehicle, in particular a road vehicle, for example a passenger car, lorry, bus or a motorcycle.

The method according to the invention for operating an energy storage device which has an electrochemical energy storage cell with at least one cathode and at least one anode and a reference electrode integrated in the energy storage cell has the following steps: amplification of a potential difference between anode or cathode and reference electrode by an amplification device and determination of an operating state the energy storage cell in a processing device based on the increased potential difference between the cathode or anode and reference electrode.

The invention is based on the approach, instead of measuring the voltage drop between the cathode and anode of the respective energy storage cell to tap a potential difference between the cathode or anode on the one hand and in the energy storage cell additionally integrated reference electrode on the other hand, and amplify it by an amplifying device. In this case, the amplification device has an amplification factor, which is preferably adjustable so that the potential differences between cathode or anode and reference electrode occurring or expected during operation of the energy storage cell are amplified in such a way that they greatly affect the dynamic range of a downstream evaluation electronics during operation of the cell or even completely exhausted. As a result, at a given dynamic range of the evaluation electronics, which is determined by the sampling or bit depth of the evaluation electronics, the accuracy, ie the resolution with which the amplified potential difference can be detected and further processed by the evaluation electronics, significantly increased. The amplified potential differences are thereby processed in the evaluation electronics with high resolution, so that the operating state, in particular the state of charge, the energy storage cell can be determined with very high precision.

The following example is intended to illustrate this: in lithium-ion cells, depending on the design, the cathode voltage with respect to the grounded anode typically decreases from 4.2 to 3 volts over the period of discharge, so that the essential for determining the state of charge Voltage change is 1.2 volts. The dynamic range of a connected to the electrodes of the cell evaluation electronics can not be fully exploited in the determination of the state of charge when considering the total potential difference between the cathode and anode due to the relatively high offset in the amount of 3 volts. On the other hand, the introduction of a reference electrode with a voltage of, for example, 3 volts with respect to the anode or ground reduces the range of measurement of the potential difference between the cathode and the reference electrode which changes during the discharge to approximately 1.2 volts. By means of a suitable or adapted amplification of the potential differences between the cathode and the reference electrode during operation, the dynamic range of the evaluation electronics can now be fully or at least largely utilized, whereby the resolution of the potential difference used in determining the state of charge is considerably improved for a given bit depth of the evaluation electronics , For example, if the bit depth of the evaluation electronics is 10 bits, then the potential difference between the cathode and the reference electrode of up to about 1.2 volts can be accurately processed after appropriate amplification with up to 1024 steps, resulting in a resolution of about 1.2 mV corresponds.

Overall, this significantly improves the determination of the operating state of energy storage devices and battery modules with such energy storage devices.

In a preferred embodiment of the invention, the energy storage device comprises an analog-to-digital converter, which is designed to convert the amplified potential difference into a corresponding digital output signal. Accordingly, the analog-to-digital converter downstream processing device, such as a suitably programmed microcontroller, is adapted to determine the operating state of the energy storage cell based on the digital output signal. In this way, the operating state can be determined particularly reliably from the increased potential difference.

In a further preferred embodiment, the analog-to-digital converter has an input voltage range and is designed to convert potential differences lying within the input voltage range into corresponding digital output signals. Accordingly, the amplification device is designed to amplify the potential differences between the anode or cathode and the reference electrode to be expected or occurring during operation of the energy storage cell in such a way that the amplified potential differences lie in a voltage range which covers a large part of the input voltage range of the analog-to-digital interface. Converter covers. The amplified potential differences preferably cover more than 70%, in particular more than 80% or more than 90%, of the input voltage range. The following example illustrates this: A occurring during discharge of the cell maximum potential difference between the cathode and the reference electrode is 1.2 V. This is in the amplification device z. B. amplified by a factor of 4 and is then a maximum of 4.8 V. An input voltage range of the analog-to-digital converter, for example, 5 V is thus exhausted by the maximum occurring increased potential difference during discharge up to 96%. For example, with a gain factor of 3.5, the input voltage range is depleted by up to 84%. This ensures that the potential differences required for determining the operating state of the energy storage cell are digitized at any time with the highest possible resolution and the smallest possible quantization error.

In a particularly preferred embodiment, the output of the analog-to-digital converter has a resolution that is at least two millivolts (2 mV). That is, the amplified potential difference is converted into a digital output signal in the form of an output voltage whose magnitude is given by an integer multiple of a factor that is two millivolts or less. With the aid of this accuracy of the digital output signal, the operating state of the energy storage cell can be determined by the processing device with particularly high precision.

In a further preferred embodiment, the input voltage range of the analog-to-digital converter is given by a voltage applied to the analog-to-digital converter reference voltage, in particular an operating voltage of the analog-to-digital converter. This reference voltage is preferably predetermined by a temporally constant as possible voltage source, whereby a constant dynamic range of the analog-to-digital converter is set accurately and the digitized output signal reproduces the voltage applied to the analog-to-digital converter, to be digitized potential difference as accurately as possible.

In a preferred embodiment, the voltage applied to the analog-to-digital converter reference voltage, in particular the operating voltage of the analog-to-digital converter, at least as large as during the operation of the energy storage cell maximum expected or occurring potential difference between the cathode and anode. Thus, the dynamic range of the analog-to-digital converter is sufficiently large, if necessary, to use the occurring during operation of the energy storage cell potential differences between the cathode and anode to determine the operating state of the energy storage cell.

In a further preferred embodiment, the voltage applied to the analog-to-digital converter reference voltage, in particular the operating voltage of the analog-to-digital converter, at least as large as the maximum expected during operation or occurring and amplified by the amplifying device potential difference between the cathode or anode and reference electrode. This ensures that the dynamic range of the analog-to-digital converter is sufficiently large in order to process the potential differences between cathode or anode and reference electrode occurring during operation of the energy storage cell and amplified by the amplifying device and to be able to determine the operating state of the energy storage cell ,

In a preferred embodiment, the energy storage device has a first switching device for switching between a first and a second circuit mode, wherein in the first circuit mode, the potential difference between cathode or anode and reference electrode amplified by the amplifying device is applied to the analog-to-digital converter, whereas in the second circuit mode Potential difference between the cathode and anode, without being amplified by the amplifying device, applied directly to the analog-to-digital converter. Thus, it can be decided variably and depending on the situation, which potential difference should be used to determine the operating state of the energy storage cell. In particular, the switching between the circuit modes allows a comparison between the operating state of the energy storage cell determined by processing the potential difference between cathode or anode and reference electrode and processing the potential difference between cathode and anode, thereby detecting errors and / or irregularities in the determination of the operating state of the energy storage cell and if necessary eliminated or corrected.

In a further preferred embodiment, a second switching device is provided for switching between a third and fourth circuit mode. In the third circuit mode, the potential difference between cathode and anode and reference electrode and in the fourth circuit mode, the potential difference between the reference electrode and cathode or anode is applied to the amplifying device, so that the potential differences applied to the amplifying means in the third and fourth circuit modes have opposite signs Amount after, however, are the same. As a result, potential differences between cathode or anode and reference electrode in the analog-to-digital converter can be digitized if the reference electrode potential lies between the potential limits of the cathode or anode, ie between the minimum and maximum cathode or anode potential. In this case, the potential difference to be determined is particularly small in magnitude and has two voltage ranges with different signs. With a correspondingly selected amplification factor, the potential differences in both voltage ranges from the analog-to-digital converter can therefore be digitized with a particularly high resolution while maintaining the dynamic range, thereby enabling a particularly accurate determination of the operating state.

Preferably, the reference electrode is selected so that the potential difference between anode or cathode and reference electrode is located approximately in the middle between maximum and minimum operating voltage of the cathode or anode. This case is particularly advantageous, since in this case the change occurring during the discharge of the potential difference to be measured in relation to the change in the potential difference between cathode and anode is divided into two approximately equal parts. By selecting a correspondingly higher amplification factor of the amplification device, the entire input voltage range of the analog-to-digital converter and thus also the total bit depth can be used for the change of the potential difference in each of the two parts, so that the resolution of the total change of the potential difference is effectively doubled , Thus, the best possible resolution of the digitized signal is achieved and achieved a correspondingly high reliability in the determination of the operating condition.

In a preferred embodiment, the electrochemical energy storage cell is designed as a lithium-ion accumulator. In this embodiment, the energy storage cell has a particularly high specific energy, with a precise determination of the operating state being particularly advantageous in order to avoid overcharging or overdischarge.

In a further preferred embodiment, the cathode contains lithium-nickel-manganese-cobalt oxide (Li (NiCoMn) O ₂ , NMC) and / or the Reference electrode Lithium iron phosphate (LiFePO ₄ , LFP), lithium manganese dioxide (LiMn ₂ O ₄ LMO) or lithium cobalt dioxide (LiCoO ₂ , LCO). As a result, an advantageous relative position of the operating voltages of the cathode and the reference electrode is achieved, in which the potential difference to be measured between the cathode and the reference electrode is smaller than the amount of the potential difference between the cathode and the anode. Due to the position of the reference electrode potential between the potential limits of the cathode, ie the maximum and minimum cathode voltage, the potential difference to be measured can be divided into two voltage ranges. If the amplification factor is selected accordingly, these two potential differences from the analog-to-digital converter can therefore be digitized with a particularly high resolution for a given dynamic range. Conversely, for a given or desired resolution, for example, 2 mV or less, a lower sampling or bit depth is required.

Other features, advantages and applications of the invention will become apparent from the following description taken in conjunction with the figures. Show it:

1 an example of an embodiment of the energy storage device according to the invention;

2 another example of an embodiment of the energy storage device according to the invention;

3 an example of the course of the cathode potential relative to the anode potential and the potential of the reference electrode; and

4 an example of an alternative embodiment of an energy storage device.

1 shows an example of a first embodiment of the energy storage device according to the invention 1 with an electrochemical energy storage cell 10 , For example, a lithium-ion battery. The energy storage cell 10 has a cathode 11 and an anode 12 on, which are shown only schematically in the example shown and in specific embodiments of the energy storage cell 10 may be arranged for example in the form of a stack or a roll.

In addition, a reference electrode 13 into the energy storage cell 10 integrated, for example by arranging the reference electrode 13 between cathode 11 and anode 12 or in the area of the cathode 11 or the anode 12 , It is also possible in principle, several reference electrodes in the energy storage cell 10 to integrate.

The potential differences between the electrodes 11 to 13 are tapped and a monitoring electronics 20 supplied, which is adapted to the operating state, in particular the state of charge, the energy storage cell 10 to determine. Through the interconnection of the monitoring electronics 20 with the energy storage cell 10 an intelligent cell (so-called "smart cell") is realized in which information about the operating state of the energy storage cell 10 determined and via a communication unit 30 in which z. B. a transmitter unit 31 is provided, can be forwarded to a display device, such as a display in a vehicle cockpit, and / or to a battery management system. Furthermore, the communication unit 30 a receiver unit 32 have, with the to the monitoring electronics 20 or to individual components of the monitoring electronics 20 addressed control commands can be received.

In the example shown, the anode is 12 the energy storage cell 10 on earth 21 placed and thus acts as a reference of the potentials in the energy storage cell 10 ,

The potentials of cathode 11 and reference electrode 13 lie in the example shown on the input channels of a gain unit 22 , For example, an operational amplifier to. The reinforcement unit 22 is designed to amplify the potential difference applied to the input channels with an amplification factor k and to output the correspondingly amplified potential difference.

The monitoring electronics 20 also has a first switching device in the illustrated embodiment 23 on, for example, a selection circuit ("multiplexer"), which between a first and a second circuit mode, preferably digitally by receiving a corresponding instruction by the receiving unit 32 , which can be switched and to which the output signal of the amplification unit 22 ie the amplified potential difference between the cathode 11 and reference electrode 13 , is forwarded. The output signal of the amplification unit 22 thus occupies a first supply line of the first switching device 23 whose signal in the first circuit mode as an output signal of the first switching device 23 is issued. In the in 1 In the case shown, the second circuit mode is shown in which on a second supply line of the first switching device 23 the unamplified operating voltage of the cathode 11 , So the cathode potential, is applied and as an output signal of the first switching device 23 is issued.

From the output signal of the first switching device 23 , in particular from the reinforcing device 22 increased potential difference between cathode 11 and reference electrode 13 in the case of the first circuit mode, the evaluation electronics of the operating state, in particular the state of charge, the energy storage cell 10 determined. In the evaluation electronics is an analog-to-digital converter 24 provided, which is designed to digitize applied analog voltage signals, in particular the amplified potential differences. The analog-to-digital converter has a predetermined sampling depth, which is also referred to as the bit depth and the number of bits used in the quantization of an analog, ie continuous voltage signal per sample (sample). The sampling depth thus determines in how many gradations a digital output signal obtained from the analog input signal can be represented. Typical sampling depths are 10, 11 or 12 bits.

The input voltage range of the analog-to-digital converter 24 , That is, the voltage range in which the applied voltage signal is reliably digitized by one of the analog-to-digital converter 24 applied reference voltage U _ref determined by a voltage source 25 provided. The reference voltage U _ref can in particular be the operating voltage of the analog-to-digital converter 24 be and is chosen in the example shown so that it is at least as high as that during operation of the energy storage cell 10 maximum or expected potential difference between cathode 11 and anode 12 , Alternatively or additionally, however, the reference voltage U _ref can also be selected such that it is the maximum that is expected or occurring during operation of the cell and in the amplification unit 23 increased potential difference between cathode 11 or anode 12 and reference electrode 13 equivalent. This ensures that at the analog-to-digital converter 24 applied voltage signal the input voltage range of the analog-to-digital converter 24 covers the majority and thus the dynamic range and the resolution of the analog-to-digital converter 24 be exploited in the best possible way. As a result, the digitized voltage signal, in particular the potential difference between the electrodes 10 to 13 , as the output signal of the analog-to-digital converter 24 very precise, especially with an accuracy of two millivolts or better, determinable.

The amplification factor k of the amplification device is preferably 22 so chosen, that of the first switching device 23 to the analog-to-digital converter 24 forwarded potential difference the input voltage range of the analog-to-digital converter 24 for the most part covers. Preferably, that is through the voltage source 25 provided reference or operating voltage greater than the potential difference between the cathode 11 and reference electrode 13 in that also in the first circuit mode of the first switching device 23 the default dynamic range of the analog-to-digital converter 24 is exploited as possible, whereby the digitized voltage signal as precise as possible, in particular with an accuracy of two millivolts or better, can be determined.

The following example is intended to illustrate this: If the reference or operating voltage z. B. 5 V, so are at an amplification of the potential difference between the cathode 11 and reference electrode 13 from Z. B. a maximum of 1.2 V by a factor of 4 in the first circuit mode of the switching device occurring during discharging amplified potential differences at a maximum of 4.8 V and thus within the given by the operating voltage input voltage range, so that these in the analog-to-digital converter 24 can be reliably digitized. In the second circuit mode, the non-amplified potential differences between cathode and anode at the analog-to-digital converter, which vary between about 4.2 V and 3 V when the cell is discharged, lie 24 On, so are these potential differences within the input voltage range and can also be reliably digitized.

The evaluation electronics have in addition to the analog-to-digital converter 24 , which receives the output signal of the first switching device 23 digitized, also a processing facility 26 on, for example, a suitably programmed microcontroller, which on the basis of the analog-to-digital converter 24 digitized voltage signal the operating state of the energy storage cell 10 determined. Corresponds to this digitized voltage signal of the potential difference between the cathode 11 and anode 12 , as in 1 by the position of the first switching device 23 shown in the second circuit mode, the operating state, for example, by comparing this potential difference with a voltage characteristic, so the potential profile of the cathode 11 or anode 12 depending on the state of charge of the energy storage cell 10 , be determined.

For energy storage cells with a flat course of this voltage characteristic changes in the by the monitoring electronics 20 determined potential differences relatively small, so that these may be from the analog-to-digital converter 24 can not be resolved with sufficient accuracy. A change to the first circuit mode of the first switching device 23 circumvents this problem by exemplifying the amplified by the gain factor k and the input voltage range of the analog-to-digital converter 24 guided potential difference between cathode 11 and reference electrode 13 through the analog-to-digital converter 21 is digitized, whereby its input voltage range is largely exhausted, the measuring voltage change but not by the minimum voltage of the cathode 11 opposite the anode 12 is superimposed. Accordingly, the interconnection can also be chosen so that the potential difference between the reference electrode and the anode is amplified and digitized. In any case, can be with this signal, the operating state of the energy storage cell 10 in the processing facility 26 determine with much increased precision.

2 shows an example of a second embodiment of the energy storage device according to the invention 1 with an energy storage cell 10 and a monitoring electronics 20 , for which, unless otherwise stated, the above explanations in connection with the in 1 apply as shown in the example.

The monitoring electronics 20 is up to a second switching device 27 identical to the one in 1 illustrated and described above first embodiment of the energy storage device according to the invention 1 , The second switching device 27 has a third and fourth circuit mode, allowing an adjustment of the monitoring electronics 20 to the sign of the potential difference between the cathode 11 and reference electrode 13 because of the analog-to-digital converter 25 usually only digitize positive potential differences. So lie in the in the 2 shown third circuit mode of the second switching device 27 the operating voltages of the cathode 11 on the first and the reference electrode 13 on the second input channel of the amplification device 22 , analogous to the first circuit mode of the first switching device 23 the in 1 shown first embodiment of the energy storage device 1 , In the fourth circuit mode of the second switching device 27 on the other hand, the occupancy of the input channels of the amplification device 22 reversed, ie the operating voltages of the cathode 11 or reference electrode 13 lie on the second or first input channel of the second switching device 27 , Thus, when switching the switching mode of the second switching device is reversed 27 the sign of the at the amplification device 22 adjacent and amplified by this potential difference. The advantage of this switching is related in the following description of the figures 3 explained.

3 shows an example of a cathode voltage characteristic 40 , which shows the potential E of an NCM cathode as a function of the state of charge of the energy storage cell 10 indicates. The reference electrode potential 41 , in the present case an electrode made of LFP, remains independent of the state of charge of the energy storage cell 10 constant and is shown as a dashed line at about 3.4 volts. The cathode voltage characteristic 40 is located during normal discharging or charging of the energy storage cell 10 consistently above the reference electrode potential 41 , The intersection of the cathode voltage characteristic 40 with the reference electrode potential 41 is generally not reached, as a rule, a deep discharge of the energy storage cell 10 should be avoided.

The potential difference to be digitized between cathode 11 and reference electrode 13 In this example, it moves between about 1.3 and 0.2V before being amplified by the gain k to a large extent the approximately 5V input voltage range of the analog-to-digital converter 24 , given by the maximum cathode voltage 42 , covers. For example, the gain factor could be k = 3.5 in this case. The superposition with a base voltage ("offset") of k · 0.2 V = 0.7 V, which is likewise amplified by the amplification factor k, therefore decreases in comparison to an offset of approximately 3.5 V, given by the minimum cathode potential 43 when measured against the potential of the anode 12 , significant, so that the amplified potential change from k * 1.3V = 4.5V to k * 0.2V = 0.7V the dynamic range of the analog-to-digital converter 24 much better exploited.

It is also possible to use a reference electrode 13 whose potential is the cathode voltage characteristic 40 in an area that cuts when operating the energy storage cell 10 is actually going through. With a reference electrode 13 For example, from LCO, the potential difference to be measured can be divided into two regions separated by the intersection of the LCO reference electrode potential 44 with the cathode voltage characteristic 40 , which can be divided, wherein the potential difference between cathode 11 and reference electrode 13 in the first area 45 positive, in the second area 46 is negative. If the measured potential difference disappears, the second switching device must be switched off 27 Therefore, be switched from the third to the fourth circuit mode, so that the analog-to-digital converter 24 supplied potential difference continues to have a positive sign.

As a result, the potential difference to be determined is reduced again, and an offset is now completely avoided. By a suitably chosen amplification factor k of the amplification device 22 the potential differences to be determined are amplified so that they are the input voltage range of the analog-to-digital converter 24 cover most of them and can thus be converted into a digital signal with the best possible resolution.

According to an alternative aspect of the invention, an energy storage device has the following components: an electrochemical energy storage cell with at least one anode and at least one cathode, a reference electrode which is integrated into the energy storage cell, and a processing device which is designed to operate on the basis of a potential difference between the anode and the anode Cathode and reference electrode to determine an operating state of the energy storage cell. This will be explained in more detail below with reference to an example.

4 shows an example of an embodiment of the energy storage device described above 2 according to an alternative aspect of the invention. Unless otherwise stated below, the above explanations apply in connection with 1 according to the example shown.

Unlike the in 1 illustrated embodiment, the monitoring electronics 20 in the present embodiment, no amplifying means for enhancing the potential differences between the cathode 11 and reference electrode 13 on. Instead of the potential difference between cathode 11 or anode 12 on the one hand and reference electrode 13 on the other hand, and thereby to the input voltage range of the analog-to-digital converter 24 In the present embodiment, the voltage to be adjusted by the voltage source 25 predefinable reference voltage U _ref , z. B. the operating voltage of the analog-to-digital converter 24 to which during the operation of the cell 10 expected or occurring maximum potential difference between cathode 11 or anode 12 and reference electrode 13 adjusted and thus ensures that the input voltage range of the analog-to-digital converter 24 by the unamplified potential difference between the cathode 11 or anode 12 and reference electrode 13 is largely covered. Preferably, the reference voltage U _{ref is} greater than that during operation of the energy storage cell 10 maximum expected or occurring potential difference between cathode 11 or anode 12 and reference electrode 13 , In this embodiment, in the energy storage device 2 advantageously be dispensed with a component, which is the structure of the monitoring electronics 20 simplified.

LIST OF REFERENCE NUMBERS

1

Energy storage device

2

Alternative energy storage device

10

Energy storage cell

11

cathode

12

anode

13

reference electrode

20

electronic monitoring system

21

Dimensions

22

reinforcing device

23

switching device

24

Analog to digital converter

25

Voltage source for reference voltage

26

processing unit

30

communication unit

31

transmitter unit

32

receiver unit

40

Cathode voltage characteristic

41

LFP reference electrode potential

42

maximum cathode potential

43

minimal cathode potential

44

LCO-reference electrode potential

45

first area

46

second area

U _ref

reference voltage

Claims (15)

Energy storage device ( 1 ) with - an electrochemical energy storage cell ( 10 ), which at least one anode ( 12 ) and at least one cathode ( 11 ), - a reference electrode ( 13 ), which in the energy storage cell ( 10 ), - an amplification device ( 22 ), which is adapted to a potential difference between the anode ( 12 ) or cathode ( 11 ) and the reference electrode ( 13 ), and - a processor ( 26 ), which is designed to use the increased potential difference an operating state of the energy storage cell ( 10 ) to investigate. Energy storage device ( 1 ) according to claim 1 with an analog-to-digital converter ( 24 ), which is designed to convert the amplified potential difference into a corresponding digital output signal, wherein the processing device ( 26 ) is adapted to the operating state of the energy storage cell ( 10 ) based on the digital output signal. Energy storage device ( 1 ) according to claim 2, wherein the analog-to-digital converter ( 24 ) has an input voltage range and is configured to convert potential differences lying within the input voltage range into corresponding digital output signals, and the amplification device ( 26 ) is adapted to, during operation of the energy storage cell ( 10 ) expected or occurring potential differences between the anode ( 12 ) or cathode ( 11 ) and the reference electrode ( 13 ) in such a way that the amplified potential differences lie in a voltage range which covers a large part of the input voltage range of the analog-to-digital converter ( 24 ) covers. Energy storage device ( 1 ) according to claim 2 or 3, the output signal of the analog-digital Converter ( 24 ) has a resolution which is at least 2 mV. Energy storage device ( 1 ) according to claim 3, wherein the input voltage range of the analog-to-digital converter ( 24 ) by one on the analog-to-digital converter ( 24 ) applied reference voltage (U _ref ), in particular an operating voltage of the analog-to-digital converter ( 24 ), given is. Energy storage device ( 1 ) according to claim 5, wherein the at the analog-to-digital converter ( 24 ) applied reference voltage (U _ref ), in particular the operating voltage of the analog-to-digital converter ( 24 ), at least as large as that during operation of the energy storage cell ( 10 ) maximum expected or occurring potential difference between cathode ( 11 ) and anode ( 12 ). Energy storage device ( 1 ) according to claim 5 or 6, wherein the at the analog-to-digital converter ( 24 ) applied reference voltage (U _ref ), in particular the operating voltage of the analog-to-digital converter ( 24 ), at least as large as that during operation of the energy storage cell ( 10 ) maximum expected or occurring increased potential difference between cathode ( 11 ) or anode ( 12 ) and reference electrode ( 13 ). Energy storage device ( 1 ) according to one of claims 2 to 7 with a first switching device ( 23 ) for switching between a first and a second circuit mode, wherein in the first circuit mode, the amplification means ( 22 ) increased potential difference between cathode ( 11 ) or anode ( 12 ) and reference electrode ( 13 ) on the analog-to-digital converter ( 24 ), whereas in the second circuit mode a potential difference between cathode ( 11 ) and anode ( 12 ), without the reinforcing device ( 22 ), directly at the analog-to-digital converter ( 24 ) is present. Energy storage device ( 1 ) according to one of the preceding claims with a second switching device ( 27 ) for switching between a third and fourth circuit mode, wherein in the third circuit mode the potential difference between cathode ( 11 ) or anode ( 12 ) and reference electrode ( 13 ) and in the fourth circuit mode the potential difference between the reference electrode ( 13 ) and cathode ( 11 ) or anode ( 12 ) at the reinforcement device ( 22 ), whereby the third and fourth circuit modes on the amplifying device ( 22 ) adjacent potential differences have opposite signs. Energy storage device ( 1 ) according to one of the preceding claims, wherein the reference electrode ( 13 ) is chosen so that the potential difference between anode ( 12 ) or cathode ( 11 ) and reference electrode ( 13 ) approximately in the middle between maximum and minimum operating voltage ( 45 . 46 ) of the anode ( 12 ) or cathode ( 11 ) lies. Energy storage device ( 1 ) according to one of the preceding claims, wherein the electrochemical energy storage cell ( 10 ) is designed as a lithium-ion battery. Energy storage device ( 1 ) according to claim 11, wherein the cathode ( 11 ) Lithium-nickel-manganese-cobalt oxide (Li (NiCoMn) O ₂ , NMC) and / or the reference electrode ( 13 ) Lithium iron phosphate (LiFePO ₄ , LFP), lithium manganese dioxide LiMn ₂ O ₄ (LMO) or lithium cobalt dioxide (LiCoO ₂ , LCO). Battery module with two or more interconnected energy storage devices ( 1 ) according to one of the preceding claims. Vehicle, in particular motor vehicle, with a hybrid or electric drive and at least one battery module according to the preceding claim Method for operating an energy storage device ( 1 ), which an electrochemical energy storage cell ( 10 ) with at least one cathode ( 11 ) and at least one anode ( 12 ) and one into the energy storage cell ( 10 ) integrated reference electrode ( 13 ), in which - a potential difference between cathode ( 11 ) or anode ( 12 ) and reference electrode ( 13 ) by an amplification device ( 22 ) and - based on the increased potential difference between the cathode ( 11 ) or anode ( 12 ) and reference electrode ( 13 ) an operating state of the energy storage cell ( 10 ) in a processing device ( 26 ) is determined.

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