WO2018010922A1

WO2018010922A1 - Dilatometer for electrode stacks

Info

Publication number: WO2018010922A1
Application number: PCT/EP2017/065179
Authority: WO
Inventors: Daniel Sauerteig; Christoph Schlund
Original assignee: Robert Bosch Gmbh
Priority date: 2016-07-11
Filing date: 2017-06-21
Publication date: 2018-01-18
Also published as: DE102016212556A1

Abstract

The invention relates to a dilatometer (1) for detecting the tendency of an electrode stack (12) to expand while charging the electrode stack (12). The dilatometer comprises a support unit (10) with a support (11) for receiving the electrode stack (12) and two contact elements via which the electrode stack (12) can be electrically charged when a first outer surface of the electrode stack (12) lies on the support (11). The dilatometer (1) further comprises a force transmission unit (20) with a force transmission element (21) which is provided for constantly contacting a second outer surface of the electrode stack (12) by means of a first end while the electrode stack (12) is being charged and allowing a free expansion of the electrode stack (12) and/or exerting a first force acting against the free expansion onto the electrode stack (12). The dilatometer (1) further comprises a measuring unit (14, 26) which is designed to measure a movement of the force transmission element (21) and/or the first force while the electrode stack (12) is being charged.

Description

Description title

Dilatometer for electrode stacks

The present invention relates to a dilatometer for detecting an expansion tendency of the electrode stack occurring when charging an electrode stack.

State of the art

When charging or discharging secondary batteries (accumulators) take place or aging reactions of, for example, lithium atoms instead, which lead to the expansion or contraction of electrodes of existing in such secondary batteries battery cells. A change in volume of the electrodes caused by expansion or contraction is dependent on a chemistry and a porosity of the electrodes as well as on an active material portion used in the electrodes. With an incorporation of active atoms in the electrodes, such as lithium atoms, there is an expansion or expansion of the electrodes. With a removal of active atoms from the electrodes, such as lithium atoms, there is a contraction of the electrodes. Consequently, a thickness of each of the electrodes, and hence a thickness of the corresponding battery cell, is dependent on a state of charge of this battery cell. In addition, aging effects also lead to an expansion of the electrodes.

The volume change of the electrodes described above must be in the corresponding battery cells or battery modules

or battery systems are taken into account or compensated by a mechanical counterforce. As with newly developed Battery cells, battery modules and battery systems are volumetric

Energy density plays an essential role, a compensation of the expansion of the corresponding electrodes must be done in a small space. In mechanically stiff battery modules, which have a counterforce on the

exercise appropriate battery cells, develops over the life of such battery modules, a pressure increase, which can accelerate aging of these battery cells.

DE 103 1 1 487 B3 describes an arrangement with two electrodes and an electrolyte. The two electrodes are each at least partially of the

Electrolytes wetted. The two electrodes comprise a first electrode and a second electrode. The first electrode is formed of porous, nanoscale, electrically conductive material. The second electrode serves as

Counter electrode. Furthermore, the arrangement comprises two contacts which are each connected to a different one of the two electrodes and between which an electrical voltage for charging the two electrodes can be applied. If the two electrodes are electrically charged by an electrical voltage applied between the two contacts, the nanoporous material of the first electrode expands or contracts. The first electrode is further between a fixed support and a first end of a

Positioning element arranged such that the first electrode, the carrier and the positioning element over two opposite

Outside surfaces contacted. The positioning member has a second end connected to an inductive displacement sensor. By means of the displacement sensor can occur during charging of the two electrodes expansion or

Contraction of the first electrode to be measured.

DISCLOSURE OF THE INVENTION According to the invention, a dilatometer is provided for detecting an electrode stack which is formed when a battery cell, in particular, is being charged

provided expansion efforts of the electrode stack. The dilatometer comprises a carrier unit with a carrier for receiving the electrode stack. The dilatometer further comprises two contact elements, via which an electrical charging of the electrode stack can take place when the Electrode stack rests with a substantially perpendicular to a first direction oriented first outer surface on the support. The dilatometer further comprises a power transmission unit with a

Power transmission element. The force transmission element is provided to contact a substantially perpendicular to the first direction oriented second outer surface of the electrode stack by means of a first end during charging of the electrode stack and to allow taking place along the first direction free expansion of the electrode stack. Alternatively or additionally, the force transmission element is provided to always contact the second outer surface of the electrode stack by means of the first end during charging of the electrode stack and one of the free expansion

to exert counteracting first force on the electrode stack. The

Dilatometer further comprises a measuring unit, which is for detecting the

Expansionsbestrebens of the electrode stack is formed during the

Charging the electrode stack to measure a movement of the force transmission element and / or the first force.

The dependent claims show preferred developments of the invention.

In the dilatometer described above, the power transmission element is provided so that when charging the electrode stack the

Power transmission element, the second outer surface of the electrode stack always contacted by means of its first end. This means that when charging the electrode stack, the power transmission element and the second

Outside surface of the electrode stack can only move together as a unit. This also means that an occurring during charging of the electrode stack due to its expansion tendency movement of the second

The outer surface of the electrode stack is the same as when charging the

Electrode stack occurring movement of the power transmission element is. This also means that an expansion of the electrode stack occurring during the charging of the electrode stack along the first direction can be determined on the basis of the movement of the force transmission element measured by the measuring unit. An increase in the charge occurring when charging the electrode stack

Charge state of the electrode stack thus leads to an increase of the distance traveled by the second outer surface of the electrode stack along the first direction path. Consequently, the expansion of the electrode stack along the first direction is dependent on the state of charge of the electrode

Electrode stack. In other words, the expansion of the electrode stack along the first direction is a charge state dependent expansion.

In a case where the force transmitting member allows the free expansion of the electrode stack, the movement measured by the measuring unit is a measure of the free expansion of the electrode stack. In a further case in which the force transmission element exerts the first force on the electrode stack, the movement measured by the measuring unit is a measure of an expansion of the electrode stack which is slowed down by the first force. Here it must be taken into account that the measuring unit both the movement of the

Force transmission element and the first force can measure. This means that measuring results of the measuring unit can also be used to determine an influence of the first force on the expansion of the electrode stack. In a case where an amount of the first force is constant, a constant mechanical counterforce represented by the first force is applied to the electrode stack. In such a case, based on measurement results of the measuring unit, the expansion of the electrode stack as a function of the constant mechanical counterforce examined and thus a

Volumetric work of the electrode stack can be determined. In another case, the first force during different measuring operations may have different amounts of force, so that the charging of the electrode stack may take place under different mechanical pressure conditions. In such a case, based on measurement results of the measuring unit, the

Expansion of the electrode stack for the different mechanical pressure conditions are determined.

In summary, this means that, on the basis of measurement results of the measuring unit, information about the Expansionsbesteben occurring during charging of the electrode stack or expansion behavior of the Electrode stack can be obtained. Such information is very valuable, especially when the electrode stack is a battery cell intended for incorporation in battery modules or systems. This information can be used to optimize a design of electrodes to be used in the electrode stack for mechanical stress so as to minimize expansion of the electrode stack. Such a minimization of the expansion of the

Electrode stack then leads to an optimization of one of the

Electrode stack deliverable electrical power.

Preferably, for generating the first force, a mechanical tension of the force transmission element by an external system, such as by pneumatic or hydraulic piston done. The advantage here is that no component must be provided in a corresponding dilatometer, by means of which the first force can be generated.

According to a first preferred development of the invention, the measuring unit comprises a displacement sensor. The displacement sensor is designed to charge one of a second end of the electrode when charging the electrode stack

To measure force transmission element along the first direction path and to determine therefrom along the first direction expansion of the electrode stack. The first end and the second end of the power transmission element are rigidly connected together. As a result, the path traveled by the second end of the power transmission member along the first direction is equal to one of the first end of the first end

Power transmission element along the first direction traveled path and thus also equal to the along the first direction expansion of the electrode stack. In this way it is avoided that a taking place during charging of the electrode stack mechanical contacting of the

Electrode stack is adversely affected by the first end of the power transmission element by a corresponding path measurement.

According to a second preferred development of the invention, the measuring unit comprises a force sensor arranged in the carrier unit. Of the

Force sensor is provided to a the first end of the Power transmission element facing away from the outer surface of the carrier

to contact, in particular to contact punctually. The force sensor is further provided to measure the first force during charging of the electrode stack. It should be noted that when charging the

Electrode stack, the force transmission element always contacted the resting on the carrier electrode stack by means of its first end. It should also be noted that when charging the electrode stack and the force sensor always contacted the carrier. Thereby, the first force from the force transmission element is applied to the electrode stack, of which

Electrode stack on the carrier and further from the carrier to the

Force sensor exerted. This means that the first force acts unadulterated on the force sensor, so that, by means of the force sensor arranged in this way, a very accurate measurement of the first force can be carried out. A selective contacting of the outer surface of the carrier by the force sensor allows a punctual resting of the carrier on the force sensor. This ensures a full-surface

Support of the force transmission element on the electrode stack and consequently also on an inner surface of the carrier contacting the electrode stack. The full - surface edition takes place via a at the first end of the

Power transmission element extending first outer surface of the

Power transmission element. In other words, is a corresponding

Dilatometer whose force sensor contacts the outer surface of the carrier selectively, self-locking.

According to a third preferred embodiment of the invention, the power transmission unit comprises an elastic element and a bracing element.

The bracing element is provided to generate a force leading to a mechanical strain of the force transmission element contraction of the elastic element for generating the first force. In this way it is achieved that the mechanical tension of the

Power transmission element and thus the first force can be generated by means of such incorporated in a corresponding dilatometer components, without the need for an external system must be used.

According to a fourth preferred embodiment of the invention is a

Elastic modulus of the elastic element selected so that when charging the electrode stack of the force transmission element on the

Electrode stack exerted first force is less than a second force. In this case, the second force is exerted during charging of the electrode stack due to a growing internal pressure of the electrode stack from the electrode stack to the force transmission element. This achieves in a simple manner that when charging the electrode stack, a movement of the second outer surface of the electrode stack is not completely slowed down by the first force. Consequently, when charging the electrode stack a

Expansion or expansion of the electrode stack along the first direction under the action of the first force take place.

According to a fifth preferred embodiment of the invention, the elastic element is a spring. Preferably, a spring travel of the spring occurring along the first direction during the contraction of the spring is greater by a predefined factor or at least an order of magnitude than an expansion of the electrode stack along the first direction during charging of the electrode stack. The predefined factor has, for example, a value of 10 ³ , 10 ⁴ or 10 ⁵ . In this way it is ensured that a change in the amount of the first force resulting from a due to the expansion of the

Electrode stack occurring changing a length of the spring arises is negligible. It should be noted that the length of the spring extends along the first direction. Here, the first force represents a constant mechanical counteracting force counteracting the expansion of the electrode stack. In other words, when charging the electrode stack, preferably a constant mechanical counterforce is exerted on the electrode stack, which causes an expansion or expansion of the electrode stack

Electrode stack along the first direction allows.

According to a sixth preferred embodiment of the invention is a

Elastic modulus of the elastic member selected so that when charging the electrode stack that of the force transmission element on the

Electrode stack exerted first force compensates for a second force. The second force is applied to the force transmitting member due to a growing internal pressure of the electrode stack from the electrode stack. In this way it is achieved that during charging of the electrode stack, a movement of the second outer surface of the electrode stack and thus an expansion or expansion of the electrode stack along the first direction are substantially prevented. It should be noted that when charging the electrode stack an expansion - related increase of the

Internal pressure of the electrode stack takes place, which is due to an expansion

Increase in an amount of the second force leads. The increase of the internal pressure and thus the amount of the second force is dependent on mechanical properties of electrodes installed in the electrode stack. Since the first force compensates for the second force when the electrode stack is charged, an increase in the magnitude of the first force also occurs when the electrode stack is charged.

Here, the first force represents one of the expansion of the electrode stack

In other words, during charging of the electrode stack, a variable mechanical counterforce is exerted on the electrode stack, which substantially prevents the expansion of the electrode stack occurring along the first direction. Thus, when charging the electrode stack, a path traveled by the second outer surface of the electrode stack along the first direction is greatly restricted and thereby defined. According to a seventh preferred embodiment of the invention, the elastic

Element a sleeve of solid material, in particular a metal sleeve. This achieves in a simple manner that when charging the

Electrode stack a variable mechanical counterforce on the

Electrode stack is applied, which substantially prevents expansion of the electrode stack along the first direction.

According to an eighth preferred embodiment of the invention, the elastic element surrounds the force transmission element. In this case, the elastic element on each two the force transmission element enclosing open end regions. The contracted by means of the bracing element elastic

Element presses with a first of its two open end portions against a side facing away from the first end of the force transmission element side of a first end portion of the force-transmitting element. The first end of the

Power transmission element comprises the first end of the

Power transmission element. The contracted by means of the bracing element elastic member presses with a second of the two open end portions against the bracing element. By the arrangement described above, in which the elastic element surrounds the force transmission element, a mechanical tension is made possible in a simple manner and in addition also achieves a reduction of a dimensioning of the force transmission unit along a second direction oriented perpendicular to the first direction.

According to a ninth preferred embodiment of the invention, the power transmission unit comprises a first housing which the

Power transmission element and the elastic element encloses. In this case, the first housing has an open end area. The open end portion of the first housing encloses the power transmission element. The

Clamping element is a first screw-threaded element and has a continuous along its screw-in cavity. The

Bracing element may further in the open end of the first

Housing be inserted. This can be done so that the first

screwable element surrounds the force transmission element and generates the contraction of the elastic element by screwing into the open end of the first housing. As a result, the mechanical tension of the elastic element and consequently also the first force can be generated in a simple manner by screwing in the first screw-in element.

According to a tenth preferred embodiment of the invention, the power transmission unit comprises a rotation-preventing element, which is designed to co-rotate the power transmission element during

Screw in the first screw-in element to prevent. In this way it is avoided that the second outer surface of the electrode stack is damaged by co-rotation of the power transmission element contacting them.

According to an eleventh preferred embodiment, the

Power transmission unit, a centering element, which is intended to center the enclosed by the first screw-threaded element force transmission element. In this way it is achieved that one, in particular of one Operator of the dilatometer caused misalignment of the power transmission element is prevented.

According to a twelfth preferred development of the invention, the carrier is designed in the form of a shell. In this way, a full-surface support of the electrode stack is made possible on an inner surface of the carrier. Alternatively or additionally, the force transmission element is designed in the form of a piston. Preferably, a first outer surface of the piston extending at its first end is larger than a second outer surface of the piston extending at a second end of the piston rigidly connected to the first end. In this way, one over the first outer surface of the

Piston successful full-scale support of the piston on the electrode stack allows.

According to a thirteenth preferred embodiment of the invention, the carrier unit and the power transmission unit for inserting the

Electrode stack on the carrier and for removing the electrode stack detachably connected to each other by the carrier. That way you can

Insert the electrode stack on the carrier and remove the

Electrode stack of the carrier uncomplicated and easily done.

According to a fourteenth preferred development of the invention, a previously described dilatometer comprises a second screw-in element and two holes associated therewith. The carrier unit and the

Power transmission unit each have one of the two holes. The carrier unit and the power transmission unit can be detachably connected to one another by screwing in the second screw-in element into the two bores positioned adjacent to one another. Thus, a detachable connection between the carrier unit and the power transmission unit is provided in a simple manner. Preferably, at least one further second screw-threaded element can be provided which is formed in the same way as the second screw-in element.

According to a fifteenth preferred embodiment of the invention, at least one of the holes in each case has an insulating layer. In this way it is achieved that no electrical connection between the carrier unit and the power transmission unit can be produced via the second screw-in element.

According to a sixteenth preferred embodiment of the invention, a previously described dilatometer comprises a between the carrier unit and the

Power transmission unit mounted insulating. In this way, a full-surface electrical insulation and thus a full-surface

Sealing of the carrier unit and the power transmission unit achieved.

Alternatively or additionally, a previously described dilatometer comprises a sealing element enclosing the carrier. Alternatively or additionally, a previously described dilatometer comprises a further sealing element enclosing the force transmission element. In this way, a reliability in charging the electrode stack is increased by a tightness with respect to a located in the electrode stack

Electrolyte ensured and penetration of contaminants, such as

Example of water from the air, is avoided. Preferably, at least one further sealing element can be provided, which is formed in the same way as a previously described sealing element. In a previously described dilatometer, the two contact elements preferably comprise a first contact element installed in the support and a second contact element installed in the force transmission element. The two contact elements are preferably designed in the form of plug sockets. In summary, a previously described dilatometer allows an on-site feasible measurement of a charge state-dependent expansion or expansion of an electrode stack, in particular in the form of a battery cell. According to some previously described

Further developments, it is possible to exert a constant mechanical counterforce on the electrode stack when charging the electrode stack.

According to other developments described above, it is possible to exert a variable mechanical counterforce on the electrode stack when charging the electrode stack. Thereby, the actual mounting state of electrodes to be used in such an electrode stack can be simulated and thereby optimized. Brief description of the drawings

Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings. The same reference numerals are used for the same components and parameters. each

Component and each parameter are each introduced once and each treated as already known at repetition, regardless of which drawing or on which embodiment, a respective corresponding part of the description in which the corresponding component or the corresponding parameter occurs repeatedly relates. In the drawings are:

Figure 1 is a sectional view of a first dilatometer according to a first embodiment of the invention;

Figure 2 is a sectional view of a second dilatometer according to a second embodiment of the invention; and

FIG. 3 shows a plurality of progressions measured by means of the first dilatometer for different mechanical pressure conditions, which shows a plurality of charge-state-dependent expansions of FIG

Specify electrode stacks as a function of time.

Embodiments of the invention

FIG. 1 shows a first dilatometer 1 according to a first embodiment of the invention. The first dilatometer 1 comprises a carrier unit 10 with a carrier in the form of a shell 1 1 for receiving a

Electrode stack 12. The electrode stack 12 is formed in the form of a battery cell. The first dilatometer 1 further comprises a

Power transmission unit 20 with a formed in the form of a piston 21 power transmission element. The first dilatometer 1 comprises two contact elements (not shown) in the form of plug sockets, via which an electrical contacting of electrodes (not shown) present in the electrode stack 12 can take place. Charging of the electrode stack 12 can take place via the two contact elements when the electrode stack 12 rests on the shell 1 1 with a first outer surface oriented essentially perpendicular to a first direction R1. The two contact elements comprise a built in the shell 1 1 first contact element and a built-in the piston 21 second

Contact element.

The electrodes of the electrode stack 12 comprise an anode and a cathode, are each coated on one side with active material and electrically insulated from one another by an ion-conducting separator. The electrode stack 12 further comprises an electrolyte. The electrode stack 12 is designed in particular in the form of a lithium-ion battery cell.

The piston 21 is provided to a substantially perpendicular to the first direction R1 oriented second outer surface of the electrode stack 12 by means of a located at a first end face over the entire surface

to contact. Thus, it is possible that during charging of the electrode stack 12, the piston 21 always contacted the second outer surface of the electrode stack 12 by means of its first end over the entire surface.

The power transmission unit 20 comprises a spring 22 in the form of a spring

formed elastic element and in the form of a first screwed

Element 23 trained bracing element. In this case, the spring 22 surrounds the piston 21st Furthermore, the first screw-in element 23 has a cavity extending along its screwing-in direction. The power transmission unit 20 further includes a first housing 24 which encloses the piston 21 and the spring 22. In this case, the first housing 24 has a piston 21 enclosing the open end region 25. The first screw-in element 23 can be inserted into the open end region 25 of the first housing 24 such that the first screw-in element 23 encloses the piston 21 and by screwing into the open end region 25 of the first housing 24 causes a contraction of the spring 22. Due to the contraction of the spring 22, a mechanical tension of the piston 21 is generated, so that the piston 21 presses against the electrode stack 12 with a first force resulting from the contraction of the spring 22.

Further, expansion of the electrode stack 12 occurring during charging of the electrode stack 12 along the first direction R1 is negligible with respect to a spring travel occurring upon contraction of the spring 22. As a result, by a change in the contraction of the spring 22nd

change in an amount of the first force is negligible. Consequently, the first force represents a constant and the expansion of the

Electrode stack 12 counteracting mechanical counterforce.

The power transmission unit 20 comprises a rotation-preventing element designed in the form of an axial needle bearing 27, which is provided to prevent co-rotation of the piston 21 when the first screw-in element 23 is screwed in. The axial needle bearing 27 is disposed between the spring 22 and the piston 21.

The power transmission unit 20 further comprises a centering element in the form of a centering ring 28, which is intended to center the piston 21 enclosed by the first screw-in element 23.

The first dilatometer 1 comprises a measuring unit which has a force sensor 14 arranged in the carrier unit 10, on which the bowl 1 1 rests punctually. The force sensor 14 is provided to measure the first force. Characterized in that the sound 1 1 rests selectively on the force sensor 14, a full-surface edition of the first end of the piston 21 extending end face of the piston 21 on the electrode stack 12 and consequently on an electrode stack 12 contacting inner surface of the shell 1 1 is ensured , Thus, the first dilatometer 1 is self-locking. This also achieves a full-surface mechanical contacting of the electrodes arranged in the electrode stack 12.

The measuring unit further comprises a displacement sensor 26 arranged in the force unit 20. The displacement sensor 26 is designed to charge the battery during charging Electrode stack 12 to measure one of a protruding from the open end portion 25 of the first housing 24 second end of the piston 21 along the first direction R1 path traveled. In this case, the second end of the piston 21 is rigidly connected to the electrode stack 12 contacting first end of the piston 21. Consequently, that of the second end of the

Piston 21 along the first direction R1 distance traveled equal to the expansion along the first direction R1 of the electrode stack 12. The displacement sensor 26 is for example a differential transformer displacement sensor (LVDT) or a capacitive displacement sensor.

The carrier unit 10 and the power transmission unit 20 are releasably connected to one another via a second screw-in element designed in the form of a screw 30. For this purpose, the carrier unit 10 and the

Power transmission unit 20 each one of two holes and are positioned by screwing the screw 30 in the two adjacent to each other

Holes detachably connectable to each other. To insert the electrode stack 12 on the shell 1 1, the power unit 20 together with their built-in parts 21, 22, 23, 24, 25, 26, 27, 28 are removed by loosening the screw 30. For electrical insulation of the carrier unit 10 and the power transmission unit 20, the bore of the power transmission unit 20 with a particular from

Polyethylene (PE) formed insulating layer 31 is provided. It can also be provided a further screw (not shown), which is formed in the same manner as the screw 30. The first dilatometer 1 further comprises an insulating element mounted between the carrier unit 10 and the power transmission unit 20 and formed in the form of a polyethylene ring 40. The carrier unit 10 and the

Power transmission unit 20 are electrically insulated and sealed via the polyethylene ring 40.

The first dilatometer 1 may also comprise a sealing element enclosing the shell 11 and formed in the form of a sealing ring 41. The first dilatometer 1 may further comprise a sealing element enclosing the piston 21 and formed in the form of a further sealing ring 42. The sealing rings 41, 42 can to ensure a tightness in the Electrode stack 12 located electrolytes and to prevent ingress of impurities, such as water from the air, are provided. These sealing rings 41, 42 are not necessary when the first dilatometer 1 is operated in a dry space or within a protective atmosphere, such as in a glovebox.

In a first variant of the first dilatometer 1, the spring 22 for mechanical tension of the piston 21 can be omitted. In this case, during the charging of the electrode stack 12, a free expansion of the electrode stack 12 along the first direction R1 can take place and be determined by means of the displacement sensor 26.

In a second variant of the first dilatometer, the spring 22 can be dispensed with for the mechanical tensioning of the piston 21 and the mechanical tensioning of the piston 21 can take place externally by means of pneumatic or hydraulic pistons.

FIG. 2 shows a second dilatometer 2 according to a second embodiment of the invention. The second dilatometer 2 differs from the first dilatometer 1 in that the spring 22 is replaced by a metal sleeve 102.

In the second embodiment, by screwing the first screw-in element 23 in the open end portion 25 of the first

Housing 24 causes a contraction of the metal sleeve 102. By the

Contraction of the metal sleeve 102, a mechanical strain of the piston 21 is generated so that the piston 21 presses with a resulting due to the contraction of the metal sleeve 102 first force against the electrode stack 12. A change in length of the metal sleeve 102 occurring during the contraction of the metal sleeve 102 along the first direction R1 is by several

Order of magnitude smaller than an expansion of the electrode stack 12, the charging of the electrode stack 12 in the absence of a mechanical

Distortion of the piston 21 along the first direction R1 would take place. For this reason, during charging of the electrode stack 12, a movement of the piston 21 contacting the second outer surface of the electrode stack 12 substantially prevented by the metal sleeve 102. In other words, during charging of the electrode stack 12, a path traveled by the second outer surface of the electrode stack 12 along the first direction R1 is greatly limited or defined by the very small change in length of the metal sleeve 102 occurring during the contraction of the metal sleeve 102.

That is, when charging the electrode stack 12, the first force must compensate for the second force exerted on the piston 21 from the electrode stack 12 due to a growing internal pressure of the electrode stack 12 to increase the expansion along the first direction R1

To prevent electrode stack 12 substantially. This also means that during the charging of the electrode stack 12 an expansion-induced increase in the amount of the first force takes place in order to compensate for the increasing internal pressure of the electrode stack 12. Consequently, here the first force represents a variable mechanical counterforce, which is measured by the force sensor 14. Thus, during the charging of the electrode stack 12, an expansion-related development of the first force acting on the electrode stack 12 can be measured by means of the force sensor 14.

In the second embodiment and in all of the above

Variants in which the spring 22 is omitted, the overall height of a corresponding dilatometer 2 can be reduced by approximately along the first direction R1 extending length of the spring 22, whereby a very compact construction of such a dilatometer 2 is made possible.

FIG. 3 shows a first course V1 of a charge state-dependent first expansion of a first lithium-ion battery cell as a function of time measured by means of the first dilatometer 1. The first expansion is measured during the first charging of the first battery cell. During the first charging of the first battery cell, the piston 21 exerts a first force on the first battery cell with such an amount that the first battery cell is exposed to a first mechanical pressure of 79 kPa. The first expansion is given on a first axis s in microns μηη. The time is given on a second axis t in hours h. FIG. 3 further shows a second curve V2 of a first voltage, which is shown as a function of time and bears against the first battery cell during the first charging of the first battery cell. The first voltage is given on a parallel to the first axis oriented third axis U in volts V. The first battery cell has a state of charge that changes between 0 and 1 during the first charging of the first battery cell.

FIG. 3 shows a third course V3 of a charge state-dependent second expansion of a second lithium-ion battery cell as a function of time measured by means of the first dilatometer 1. The first and the second battery cells are identical. The second expansion is measured during the first charging of the second battery cell. During the first charging of the second battery cell, the piston 21 exerts a first force on the second battery cell with an amount such that the second battery cell is exposed to a second mechanical pressure of almost 156 kPa, which is almost double the first pressure. The second expansion is also indicated on the first axis s in microns μηη.

FIG. 3 further shows a fourth curve V4 of a second voltage, which is shown as a function of time and bears against the second battery cell during the first charging of the second battery cell. The second voltage is also indicated on the third axis U in volts V. The second battery cell has a state of charge that changes between 0 and 1 during the first charging of the second battery cell.

It can be seen from FIG. 3 that for each state of charge assumed by the first battery cell and by the second battery cell, the first expansion of the first battery cell is greater than the second expansion of the second battery cell. In particular, the first expansion of the first battery cell taking place during the first pressure is greater by a factor of approximately 1.5 than the second expansion taking place during the second pressure when the first battery cell and the second battery cell each have a charge state of 1. This means that a large increase in a mechanical pressure applied to an electrically charged lithium-ion battery cell becomes a leads to significant reduction of a charge state-dependent expansion of this battery cell.

In addition to the above written disclosure is hereby further disclosure of the invention supplementary to the representation in Figures 1 to 3

Referenced.

Claims

claims

1 . Dilatometer (1; 2) for detecting a when charging a

in particular as a battery cell designed electrode stack (12) occurring expansion tendency of the electrode stack (12), comprising:

a support unit (10) having a support (11) for receiving the electrode stack (12);

two contact elements, via which an electrical charging of the

Electrode stack (12) can take place when the electrode stack (12) with a substantially perpendicular to a first direction (R1) oriented first outer surface rests on the support (1 1);

a power transmission unit (20) having a force transmission element (21) which is provided, when charging the electrode stack (12), a second outer surface of the electrode stack (12) oriented substantially perpendicularly to the first direction (R1) by means of a first

End always to contact and allow along the first direction (R1) taking place free expansion of the electrode stack (12) and / or exerting a free expansion counteracting first force on the electrode stack (12), and

- A measuring unit (14, 26) adapted to detect the expansion tendency of the electrode stack (12) to measure during charging of the electrode stack (12), a movement of the force transmission element (21) and / or the first force. 2. A dilatometer (1; 2) according to claim 1, wherein the measuring unit comprises a displacement sensor

(26) adapted to measure, during charging of the electrode stack (12), a path traveled by a second end of the force transmitting element (21) rigidly connected to the first end along the first direction (R1) and one thereof along the first Direction (R1) to determine expansion of the electrode stack (12). A dilatometer (1; 2) according to one of the preceding claims, wherein the measuring unit comprises a force sensor (14) arranged in the carrier unit (10), which is intended to be connected to the first end of the

To contact force transmission element (21) facing away from the outer surface of the carrier (1 1), in particular to contact selectively, and to measure the first force during charging of the electrode stack (12).

A dilatometer (1; 2) as claimed in any one of the preceding claims, wherein the power transmission unit (10) comprises an elastic member (22; 102) and a tension member (23), the tension member (23) being adapted to generate the first force to create a mechanical strain of the force transmission element (21) leading to contraction of the elastic element (22, 102).

A dilatometer (1) according to claim 4, wherein a modulus of elasticity of said elastic member (22) is selected such that when said electrode stack (12) is charged, said first force exerted on said electrode stack (12) by said force transmitting member (21) becomes smaller than that due to a increasing internal pressure of the electrode stack (12) of the electrode stack (12) on the force transmission element (21) is applied second force.

Dilatometer (1) according to one of claims 4 or 5, wherein the elastic element (22) in the form of a spring (22) is formed and wherein a occurring during the contraction spring travel of the spring (22) in particular by a predefined factor or at least one Magnitude is greater than one during charging of the electrode stack (12) taking place expansion of the electrode stack (12) along the first direction (R1).

A dilatometer (2) according to claim 4, wherein a modulus of elasticity of the elastic member (102) is selected such that when the electrode stack (12) is charged, the first force exerted on the electrode stack (12) by the force transmitting member (21) due to an increasing internal pressure of the electrode stack (12) from the electrode stack (12) to the

Power transmission element (21) applied compensated second force.

8. dilatometer (2) according to any one of claims 4 or 7, wherein the elastic element (102) in the form of a sleeve of solid material, in particular in the form of a metal sleeve (102) is formed.

A dilatometer (1; 2) according to any one of claims 4 to 8, wherein the elastic member (22; 102) encloses the force transmitting member (21) and two open ones respectively surrounding the force transmitting member (21)

End regions, wherein the means of the tensioning element (23) contracted elastic member (22; 102) with a first of its two open end portions against a first end of the

Power transmission member (21) facing away from a first end portion of the Kraftüberragungselements (21) and presses with a second of the two open end portions against the bracing member (23), wherein the first end portion of the force transmission element (21) comprises the first end of the force transmission element (21).

A dilatometer (1; 2) according to claim 9, wherein the power transmission unit (20) comprises a first housing (24) enclosing the force transmitting member (21) and the resilient member (22; 102) and having an open end portion (25) , wherein the open end region (25) of the first housing (24) surrounds the force transmission element (21), and wherein the bracing element (23) in the form of a first screw-in element (23) is formed with a continuous cavity along its screwing and thus in the open end portion (25) of the first housing (24) can be inserted, that the first screw-threaded element (23) surrounds the force transmission element (21) and by screwing into the open end portion (25) of the first housing (24) the contraction of the elastic element (22; 102).

1 1. A dilatometer (1; 2) according to claim 10, wherein the power transmission unit (20) comprises a rotation preventing member (27) adapted to prevent co-rotation of the power transmission member (21) when screwing the first screw-in member (23).

12. dilatometer (1; 2) according to any one of claims 10 or 11, wherein the

Power transmission unit (20) comprises a centering element (28) which is adapted to center the power transmission element (21) enclosed by the first screw-in element (23).

13. dilatometer (1; 2) according to any one of the preceding claims, wherein the carrier (1 1) in the form of a shell (1 1) is formed and / or the

Power transmission element (21) in the form of a piston (21) is formed.

14. dilatometer (1; 2) according to one of the preceding claims, wherein for inserting the electrode stack (12) on the carrier (1 1) and for removing the electrode stack (12) from the carrier (1 1) the carrier unit (10) and the power transmission unit (20) are releasably connected together.

15. Dilatometer (1; 2) according to claim 14, comprising a second screw-in element (30) and two holes associated therewith, wherein the

Carrier unit (10) and the power transmission unit (20) each have one of the two bores and can be connected to one another by screwing the second screw-in element (30) into the two bores positioned adjacent to one another.

16. A dilatometer (1; 2) according to claim 15, wherein at least one of the bores has an insulating layer (31).

17. Dilatometer (1; 2) according to one of the preceding claims, comprising an insulating element (40) mounted between the carrier unit (10) and the power transmission unit (20) and / or a carrier (11).

enclosing sealing element (41) and / or a

Power transmission element (21) enclosing further

Sealing element (42).