Patent Publication Number: US-2022216502-A1

Title: Method and apparatus for producing an electrode stack

Description:
The invention relates to a method and to an apparatus for producing an electrode stack from monocells for a lithium-ion battery. 
     Such a lithium-ion battery has at least one battery cell in which is accommodated an electrode stack with a number of sheet-like cathodes (cathode sheets, cathode films) and sheet-like anodes (anode sheets, anode films), wherein the cathodes and the anodes are stacked on top of each other, for example, and wherein a separator is arranged between each of the cathodes and the anodes. 
     The electrode stack with anodes and cathodes stacked on top of each other is produced, for example, by means of so-called single-sheet stacking. Typically, the individual anodes and the cathodes are moved by means of a gripper system (gripping system). A gripper of this gripper system picks up each electrode, i.e. the each anode or cathode, conveys it while holding it to a stacking location, and deposits the electrode there. However, such gripper systems are comparatively slow. As a result, the manufacturing process of such an electrode stack is disadvantageously comparatively time-consuming. 
     The invention is based on the object of specifying a particularly suitable method, and also an apparatus, for producing an electrode stack for a lithium-ion battery. In particular, a production of the electrode stack that is as time-saving as possible can be realized by means of the method and/or by means of the apparatus. 
     With regard to the method, the stated object is achieved according to the invention by the features of claim  1  and, with regard to the apparatus, by the features of claim  4 . Advantageous further developments and designs are the subject matter of the dependent claims. The statements relating to the apparatus also apply analogously to the method, and vice versa. 
     In the method for producing an electrode stack from monocells for a lithium-ion battery (Li-ion battery), in a first step the monocells are conveyed into receptacles of a stacking wheel which is driven or can be driven in a rotary manner. The receptacles are also referred to as compartments or pockets, and the stacking wheel is also referred to as a conveyor wheel. The stacking wheel preferably rotates at a constant rotational speed. 
     A monocell is formed by means of a (single) anode and a (single) cathode, a separator (a separator film) being arranged between the anode and the cathode. Furthermore, a further separator is arranged on the side of the cathode facing away from the anode. The anode, the cathode and the separators are preferably joined to each other, in particular by means of lamination. 
     Appropriately, only a single monocell is accommodated in each of the receptacles. The monocells are in particular conveyed into the receptacles in such a way that the anodes and the cathodes of the monocells are arranged alternately in a circumferential direction (direction of rotation) of the stacking wheel. 
     The anodes and the cathodes of the monocell are collectively referred to as electrodes. These are designed in particular with the shape of a leaf. The electrodes therefore have a comparatively small extension in one spatial direction; in other words, the electrodes are flat. The electrodes are also referred to as electrode sheets, and the anodes and the cathodes as anode sheets and cathode sheets, respectively. The anodes and the cathodes expediently each have an electrical contact, also referred to as a tab, which is formed by means of a (cell conductor) current conductor of the given electrode. In particular, the contact of the anode is arranged on an (end-)face of the monocell that is arranged parallel and opposite to the (end-)face of the monocell on which the contact of the cathode is arranged. 
     In a second step, the monocells accommodated in the receptacles, that is to say the monocells conveyed into the receptacles, are conveyed to a stacking compartment by means of the rotation of the stacking wheel. As such, the monocells are guided to the stacking compartment by means of the stacking wheel. 
     In a third step, the monocells are held in the region of the stacking compartment, in particular by means of one or by means of two, preferably fixed, stripper arms. Due to the rotation of the stacking wheel, the monocells are guided out of their respective receptacles and into the stacking compartment. In other words, the monocells are held (supported) against the rotation of the stacking wheel by means of the stripper arm or by means of the stripper arms, such that each receptacle is displaced relative to the assigned monocell due to the rotation of the stacking wheel, and the monocell is accordingly transferred from the given receptacle into the stacking compartment. The monocells are stacked in the stacking compartment. 
     In particular, due to the rotation of the stacking wheel, an airflow is generated which supports the transfer of the monocells from each receptacle into the stacking compartment. In particular, as a result of this, the monocells are compelled into the stacking compartment. 
     In a fourth step, the stacked monocells are pressed against each other in the stacking compartment to form the electrode stack. The monocells pressed against each other are then expediently fixed, in particular wrapped, by means of a separator tape. 
     Compared to an unguided lowering of the monocells solely due to gravity, the conveying of the monocells into the stacking compartment by means of the stacking wheel takes place comparatively quickly. Furthermore, a comparatively precise and defined positioning of the monocells on top of each other is realized by means of the stacking wheel. Furthermore, the monocells are transferred to the stacking compartment by means of the stacking wheel without a gripper, i.e. without the use of a gripper or a gripping device. Because of this, the alternating stacking of the monocells advantageously takes place comparatively quickly, that is to say in a time-saving manner, in particular in comparison to the production of the electrode stack mentioned at the beginning by means of a gripping device. Thus, a process rate of the production of the electrode stack is advantageously increased—in other words, throughput is increased. 
     According to an advantageous development, in the course of the first step, at least two of the monocells are simultaneously conveyed into the corresponding receptacles of the stacking wheel. In particular, a conveyor device for conveying the monocells into the receptacles of the stacking wheel has at least two conveyor belts for the monocells. 
     A period of time which is necessary for the insertion of the monocells into the stacking wheel is advantageously comparatively short and, as a result, the production of the electrode stack is comparatively time-saving. 
     According to an expedient embodiment of the method, the conveying speed of the monocells into the respective receptacles of the stacking wheel is adjusted in such a way that the monocells, before they are stopped by the stripper arm, are decelerated to a standstill due to friction relative to the respective receptacles. In other words, a relative speed of the monocells for the each of the receptacles is then equal to zero. The conveying speed is expediently as high as possible. In this way, the monocells are prevented from hitting the ends of the receptacles in the region of the axis of rotation, and the associated risk of damage to the cathodes or the anodes of the monocells is avoided. 
     The electrode stack produced according to the method is provided in particular for a lithium-ion battery, preferably for a (traction) battery of an electrically driven motor vehicle. 
     The apparatus is configured and suitable for producing an electrode stack from monocells for a lithium-ion battery, for example for a (traction) battery of an electrically powered motor vehicle. In particular, the electrode stack is produced by means of the apparatus according to any of the variants of the method set out above. 
     The apparatus has a stacking wheel which can be driven to rotate about an axis of rotation, and which has receptacles for the monocells which are inserted on the circumference, and the receptacles extending in the axial direction, that is to say in a direction parallel to the axis of rotation. In other words, the stacking wheel has arms (blades) extending outward, that is to say away from the axis of rotation, by means of which the receptacles are formed. The receptacles expediently extend outward against the intended direction of rotation of the stacking wheel. In this way, the receptacles are inclined against a radial direction with respect to the axis of rotation. 
     According to a first variant of the apparatus, the stacking wheel furthermore has on the circumferential side thereof a recess passage extending in its circumferential direction. The recess therefore spans a plane perpendicular to the axis of rotation. The recess extends through the receptacles. In other words, the recess penetrates (passes through) the receptacles. As such, the arms are not continuous in the axial direction. A stripper arm can be inserted, preferably itself stationary, into the recess as a stop for the monocells accommodated in the receptacles when the stacking wheel rotates, such that, due to the rotation of the stacking wheel, each of the monocells is held so it cannot rotate together with the stacking wheel, and is transferred from the given receptacle into a stacking compartment. The recess is suitably designed in such a way that a distance between the stripper arm and the axis of rotation is less than the end of the receptacles closest to the axis of rotation. 
     In summary, the stripper arm protrudes into a recess of the stacking wheel that is continuous in the circumferential direction, and is therefore at least partially arranged in the recess. The recess therefore spans a plane perpendicular to the axis of rotation. With respect to the receptacle, the stripper arm consequently moves through the receptacle in the course of the rotation of the stacking wheel. The stripper arm serves as a stop or as a support for the monocells entrained by the rotation of the stacking wheel. 
     According to a second variant of the apparatus, it has two stripper arms, one of which is arranged in front of, and the other of which is arranged behind, the stacking wheel with respect to the axial direction. In other words, the two stripper arms flank the stacking wheel on both sides with respect to the axial direction. The stacking wheel in this case has a smaller extension in the axial direction than the monocells being conveyed or to be conveyed by means of the same. As such, the conveyed monocells protrude in the axial direction from the receptacles beyond the stacking wheel, such that the stripper arms form a stop for the monocells accommodated in the receptacles when the stacking wheel rotates. As a result, the monocells are transferred from the respective receptacles into the stacking compartments due to the rotation of the stacking wheel, 
     In both variants of the apparatus, the monocells are restacked, in alignment with each other, in the stacking compartment in the course of their transfer from the respective receptacles, in particular by means of the stripper arm acting as a stop or by means of the stripper arms acting as stops. The stacking compartment expediently also has a slide. This enables the monocells to be aligned with each other with improved accuracy. The monocells are preferably oriented in alignment with each other along their entire circumference. For this purpose, the slide can be moved toward a wall of the stacking compartment opposite it, or toward the stripper arm. Furthermore, the stacking compartment has a compression unit for generating a pressing force, in particular oriented perpendicular to a bottom of the stacking compartment, on the monocells stacked in the stacking compartment and aligned with each other. 
     Furthermore, the apparatus has a conveying device for conveying the monocells into the receptacles of the stacking wheel. 
     In the first variant of the apparatus, the receptacles suitably each have a wall at the end, with respect to a direction parallel to the axis of rotation—that is to say, a lateral wall. This prevents an undefined displacement of the monocells in one direction along the axis of rotation. The direction along the axis of rotation is also referred to here and below as the axial direction. 
     According to an advantageous embodiment of both variants of the apparatus, the receptacles are arc-shaped, preferably spiral-shaped, in a plane perpendicular to the axis of rotation. As such, the receptacles in this plane have a spiral or arcuate cross-section. In this case, a curvature of the arcuate receptacle increases from the circumferential side toward the axis of rotation—that is to say, it becomes greater as the radial distance from the axis of rotation becomes smaller. Because of this, a frictional force between the receptacles and the monocells conveyed into them increases from the circumferential side to the axis of rotation, that is to say inward, such that the monocells are increasingly decelerated. Thus, the monocells are reliably decelerated to a standstill relative to the receptacle in a timely manner before the monocells are stopped by the stripper arm or by the stripper arms. 
     According to an advantageous embodiment of the apparatus, the conveyor device has at least two first conveyor belts for conveying the monocells into the corresponding receptacles. As already shown in the context of the method, it is thus possible to convey at least two of the monocells into the corresponding receptacles of the stacking wheel at the same time. 
     At correspondingly high conveying speeds of the monocells by means of the first conveyor belt, the monocells can be lifted by the ambient air, such that the monocells are undesirably lifted off the conveyor belt and move in an uncontrolled manner. To avoid this, a second conveyor belt oriented in parallel is provided for each of the first conveyor belts, according to an expedient embodiment of the apparatus. The second conveyor belts each have opposite directions of rotation to the assigned first conveyor belt. The monocells are clamped between the corresponding first conveyor belt and the corresponding second conveyor belt. The monocells are therefore held in a direction perpendicular to the conveyor belt surfaces of each of the associated first and second conveyor belts. This prevents uncontrolled movement of the monocells during their conveyance into the receptacles of the stacking wheel. 
     According to an advantageous development of the apparatus, the first conveyor belts and/or the second conveyor belts project into the recess of the stacking wheel or, in the case of the second variant of the apparatus, into a circumferentially arranged and continuous recess of the stacking wheel in its circumferential direction, such that the monocells are conveyed tangentially into the receptacle. In other words, the ends of the first and/or the second conveyor belts, with respect to the conveying direction of the monocells, are arranged inside the recess of the stacking wheel. The first and/or the second conveyor belts are thus arranged between the blades of the stacking wheel with respect to the axial direction. In this way, the monocells are guided for a comparatively long time by means of the conveyor belts, and/or a comparatively high conveying speed of the monocells into the corresponding receptacles is made possible, and, as a result, a time-saving production of the electrode stack is made possible. The first and second conveyor belts expediently have a smaller extension than the monocells in a direction which is perpendicular to the conveying direction and in the planes spanned by the conveyor belt surfaces of the conveyor belts, or by the monocells. In other words, the monocells protrude beyond the conveyor belts in the transverse direction of the conveyor belt. 
     According to a suitable embodiment of the apparatus, the stacking compartment used for removing the electrode stack, in particular together with the compression unit, can be moved away from the stacking wheel and/or tilted about a tilting axis parallel to the axis of rotation. 
     According to a suitable embodiment, the slide and/or the stripper arm of the apparatus according to the first variant has a (contacting) recess to electrically contact the anodes and the cathodes of the monocells. Depending on the intended configuration of the monocell, the electrical contacts of its anode and its cathode are arranged on the same side or, alternatively, on opposite sides. If the electrical contacts of the anodes and the cathodes are to be arranged on the same side of the electrode stack, the slide or the stripper arm then has the contacting recess. If the anodes and the cathodes are to be arranged on opposite sides of the monocell and corresponding to the electrode stack, the electrical contacts of the anodes are arranged at the front with regard to their conveying direction in the given receptacle of the stacking wheel, and the electrical contacts for the cathodes are arranged at the rear with regard to their conveying direction, or vice versa. Both the slide and the stripper each have a recess for the electrical contacts. 
     Due to the contacting recesses, damage to the electrical contacts when the anodes and the cathodes are oriented in alignment with each other, or during the process of transferring the anodes and the cathodes from the receptacle, is advantageously avoided, or the risk of this is at least reduced. 
    
    
     
       Embodiments of the invention are explained in more detail below with reference to the drawings, wherein: 
         FIG. 1  schematically shows a first variant of an apparatus for producing an electrode stack, having a stacking wheel that can be driven to rotate about an axis of rotation, with receptacles for monocells, wherein a stripper arm is inserted into a circumferentially continuous recess of the stacking wheel, and by means of this the monocells can be transferred from the receptacles into a stacking compartment, 
         FIG. 2 a    schematically shows the first variant of the apparatus in a side view, viewed perpendicular to the axis of rotation, 
         FIG. 2 b    schematically shows the first variant of the apparatus in a plan view, 
         FIG. 3 a    shows a second variant of the apparatus in a side view, viewed perpendicular to the axis of rotation of its rotationally driven stacking wheel, wherein a stripper arm is arranged in front of the stacking wheel, and another stripper arm is arranged and behind the stacking wheel with respect to a direction parallel to the axis of rotation, and these serve as a stop for the monocells conveyed by means of the receptacles of the stacking wheel, 
         FIG. 3 b    schematically shows the second variant of the apparatus in a plan view, 
         FIG. 4  shows a method sequence for producing the electrode stack, in a flowchart, and 
         FIG. 5  shows one of the monocells, the monocell being formed from anodes and cathodes. 
     
    
    
     Corresponding parts and dimensions are always provided with the same reference signs in all figures. 
     In  FIG. 1  and  FIGS. 2 a  and 2 s   , a first variant of an apparatus  2  is shown, which is used to produce an electrode stack  4  from monocells  5 . One of the monocells is shown in  FIG. 5 . The monocell  5  is formed from an anode  6  and a cathode  8 , a separator  9  being arranged between the anode  6  and the cathode  8 . Furthermore, a further separator  9  is arranged on the side of the cathode  8  facing away from the anode  6 . The anode  6 , the cathode  8 , and the separators  9  are joined to each other by means of lamination. The anodes  6  and the cathodes  8  are sheet-shaped. Furthermore, the anodes  6  and the cathodes  8  each have an electrical contact  10 , the same also being referred to as a tab. For the purpose of improved clarity, the monocell  5  is shown in simplified form in  FIGS. 1 to 3   b.    
     The electrode stack  4  is intended for a lithium-ion battery (not shown in further detail), for example for a (traction) battery of an electrically powered motor vehicle. The apparatus  2  has a stacking wheel  12  which can be driven to rotate about an axis of rotation D. 
     The stacking wheel  12  has receptacles  14  for the monocell  5  formed on the circumference thereof and extending in the axial direction A, that is to say along the axis of rotation D. The receptacles  14  are formed by means of arms  16 , which are also referred to as blades, which extend from the region of the axis of rotation D to the circumferential side of the stacking wheel  12 —that is to say, outward. The arms  16 , and thus also the receptacles  14 , are designed in a spiral shape in a plane perpendicular to the axis of rotation D. The receptacles  14  therefore have a spiral cross-section in this plane. In this case, a curvature of the arcuate receptacle increases from the circumferential side toward the axis of rotation D—that is to say, as the radial distance from the axis of rotation D becomes smaller. Furthermore, the receptacles  14  extend outward opposite the direction of rotation of the stacking wheel  12  represented by a corresponding arrow about the axis of rotation D. 
     The stacking wheel  12  has a wall  18  at each end with respect to the axial direction A, which wall delimits the receptacles  14 . In this case, the front wall  18  in the viewing direction is not shown in  FIG. 1  for the purpose of visibility. The wall  18  prevents an undefined displacement of the monocells  5  in a direction along the axis of rotation D during the rotation of the stacking wheel  12 , and during the process of the monocells  5  being received in the receptacles  14 . 
     As can be seen in particular in  FIGS. 2 a  and 2 b   , the stacking wheel  12  has a circumferential recess  20  which is continuous in the circumferential direction of the stacking wheel  12 . The recess  20  thus extends in a plane perpendicular to the axis of rotation D. The recess  20  also has an extension opposite the radial direction R to the axis of rotation D, which is greater than the extension of the receptacles  14  in this direction. The arms  16  are therefore not continuous in the axial direction A. 
     A stripper arm  22  is arranged in the recess  20 . The section of the stripper arm  22  which is arranged within the recess  20  is shown with dashed lines in  FIG. 1 . The stripper arm  22  serves as a stop for the monocells  5  accommodated in the receptacles  14 . Upon the rotation of the stacking wheel  12 , the monocells  5  arranged in the receptacles  14  are displaced relative to the stripper arm  22 , such that they are held against further conveyance by means of the stacking wheel  12 . Due to the further rotation of the stacking wheel  12 , each of the monocells  5  are transferred from the respective receptacles  14  into a stacking compartment  24  arranged in the region of the stripper arm  22 . 
     The stacking compartment  24  has a slide  26  for orienting the monocells  5  in alignment with each other. For this purpose, it is able to move in the direction of the stripper arm  22 . This movement is shown in  FIG. 1  by means of a double arrow. Furthermore, the stacking compartment  24  has a compression unit  28  for generating a pressing force on the monocells  5  stacked in the stacking compartment  24  and aligned with each other. For this purpose, the compression unit  28  can be pivoted through the recess  20 . The electrode stack  4  is formed by orienting the monocells  5  in alignment with each other and pressing them together. 
     According to a variant of the stacking compartment  24 , not shown, the compression unit  28  is adjustable in the axial direction A, such that the compression unit  28  cannot be pivoted through the recess  20 , but can be moved between the stacking wheel  12  and a bottom  29  of the stacking compartment  24 . 
     The stacking compartment  24  can also be tilted, together with the compression unit  28  and with the stripper arm  22 , about a tilting axis K oriented parallel to the axis of rotation D, such that the electrode stack  4  can be removed from the stacking compartment and transported away by means of a conveyor belt  30 . By means of the conveyor belt  30 , the electrode stack  4 , that is to say the monocells  5  pressed against each other, can be transported for further production of the battery, or to a magazine or a storage. 
     In  FIG. 1 , the apparatus  2  is shown, with a viewing direction along the axis of rotation D; and in  FIGS. 2 a  and 2 b   , it is shown with a viewing direction perpendicular to the axis of rotation D and parallel or perpendicular to the bottom of the stacking compartment  29 . The stripper arm  22  is shown in simplified form in  FIGS. 2 a  and 2 b    for the purpose of improved clarity. 
     As can be seen in particular in  FIG. 2 b   , the slide  26  and the stripper arm  22  each have a contacting recess  32  for the electrical contacts  10  of the anodes  6  and the cathodes  8  of the monocells  5 . 
     Furthermore, the apparatus  2  has a conveying device  34  for conveying the monocells  5  into the receptacles  14  of the stacking wheel  12 . The conveying device  34  has two first conveyor belts  36 , by means of which two of the monocells  5  can be conveyed into the receptacles  14  of the stacking wheel  12  at the same time. Furthermore, each of the first conveyor belts  36  is assigned a second conveyor belt  38 , wherein each conveyor belt  38  is arranged parallel to the first conveyor belt  36  it is assigned to. Each of the conveyor belt surfaces  40  of the second conveyor belts  38  has an opposite direction of rotation to the conveyor belt surface  40  of the assigned first conveyor belt  36 . The first conveyor belts  36  and the assigned second conveyor belts  38  are each spaced apart from each other in such a way that the monocells  5  are clamped between the first conveyor belt  36  and the corresponding second conveyor belt  38  when they are conveyed. 
     The first conveyor belts  36  protrude partially into the recess  20  of the stacking wheel  12 , such that the monocells are conveyed tangentially into the receptacle  14 . Those portions of the conveyor belts  36  and  38  which protrude into the recess  20  are shown in dashed lines. 
     As can be seen in particular in  FIG. 2 a   , the first conveyor belts  36  and the second conveyor belts  38  have a smaller extension than the monocells  5  in a direction which runs perpendicular to the conveying direction and in the planes spanned by their conveyor belt surfaces  40 . In other words, the monocells  5  protrude beyond the conveyor belts  38  in the transverse direction of the conveyor belt. 
     A second variant of the apparatus  2  is shown in  FIGS. 3 a  and 3 b   . With the exception of what is discussed below, the explanations given above apply analogously to the second variant, and are not shown in further detail here. 
     The apparatus  2  has two stripper arms  22  which are arranged in the axial direction A on both sides of the stacking wheel  12 . In other words, one of the two stripper arms is arranged with respect to the axial direction A in front of the stacking wheel  12 , and the other stripper arm  22  is arranged behind it. The stacking wheel  12  in this case has a smaller extension in the axial direction A, such that the monocells  5  accommodated in the receptacles  14  protrude in the axial direction A on both sides beyond the stacking wheel  12 . When the stacking wheel  12  rotates, the two stripper arms  22  form a stop for the monocells  5  accommodated in the receptacles  14 . The monocells  5  are consequently supported against further conveyance due to the rotation of the stacking wheel  12 , and are transferred from the given receptacle  14  into the stacking compartment  24 . 
     In comparison to the first variant, the stacking wheel  12  does not have a wall  18  which closes off the receptacles  14  at the ends with respect to the axial direction A. 
     The stripper arms  22  still have no contacting recess  32  for the electrical contacts  10  of the anodes or the cathodes. Rather, the electrical contacts  10  are arranged between the arms  16  of the stacking wheel. 
     The flow diagram shown in  FIG. 4  illustrates a method for producing an electrode stack  4  from the monocells  5 . An apparatus  2  according to  FIGS. 1 and 2  is preferably used for this purpose. 
     In a first step I, the monocells  5  are conveyed into the receptacles  14  of the stacking wheel  12 , which is driven to rotate—in particular continuously. In the process, at least two of the monocells  5  are conveyed into the given receptacle  14  of the stacking wheel  12  at the same time. For this purpose, the apparatus  2 , as set out above, has two first conveyor belts  36 . 
     In this case, only a single monocell is received in each of the receptacles  14 , the receptacles  14  being formed in such a way that the anodes  6  and the cathodes  8  of the monocells  5  are arranged alternately in the circumferential direction (direction of rotation) of the stacking wheel  12 . 
     The electrical contacts  10  of the anodes  6  and the cathodes  8  of the monocells  5  are arranged at the front and rear with respect to their conveying direction into the given receptacle  14  of the stacking wheel  12 . In this way, the electrical contacts  10  of the anodes  6  and the cathodes  8  are arranged on opposite sides of the electrode stack  4 . 
     In a second step II, the monocells  5  accommodated in the receptacles  14  are conveyed to a stacking compartment  24  by means of a rotation of the stacking wheel  12 . 
     In a third step III of the method, the monocells  5  are held in the region of the stacking compartment  24  by means of the stripper arm  22  or by means of the stripper arms  22 . As such, the monocells  5  are held (supported) against the rotation of the stacking wheel  12  by means of the stripper arm  22  or by means of the stripper arms  22 , such that the given receptacle  14  is displaced relative to the associated monocell  5  due to the rotation of the stacking wheel  12 , and the monocell  5  is accordingly transferred out of the given receptacle  14  into the stacking compartment  24 . The monocells are alternately stacked in the stacking compartment  24 . 
     Furthermore, the conveying speed of the monocells  5  into each of the receptacles  14  of the stacking wheel  12  is adjusted in such a way that the monocells  5 , before they are stopped by the stripper arm  22  or the stripper arms  22 , are decelerated to a standstill relative to the given receptacle, due to friction between the monocells  5  and the given receptacle  14 . The conveying speed is adjusted as a function of the shape of the receptacles  14 . Due to the spiral shape of the receptacles  14 , a frictional force between each receptacle  14  and the monocell  5  becomes greater toward the end (at the axis of rotation) of the receptacle  14  facing the axis of rotation D. 
     In a fourth step IV, the stacked monocells  5  in the stacking compartment  24  are aligned with each other by means of the slide  26 , and are pressed against each other by means of the compression unit  28 , forming the electrode stack  4 . For this purpose, the compression unit  28  acts with a pressing force on the monocells  5  stacked in the stacking compartment  24  and aligned with each other. 
     The invention is not limited to the embodiment described above. Rather, other variants of the invention can also be derived therefrom by a person skilled in the art without departing from the subject matter of the invention. In particular, all of the individual features described in connection with the embodiments can also be combined with each other in other ways without departing from the subject matter of the invention. 
     LIST OF REFERENCE SIGNS 
     
         
         
           
               2  apparatus 
               4  electrode stack 
               5  monocell 
               6  anode 
               8  cathode 
               9  separator 
               10  electrical contact of the electrode 
               12  stacking wheel 
               14  receptacle 
               16  arm 
               18  wall 
               20  recess 
               22  stripper arm 
               24  stacking compartment 
               26  slide 
               28  compression unit 
               29  bottom of the stacking compartment 
               30  conveyor belt 
               32  contacting recess 
               34  conveying direction 
               36  first conveyor belt 
               38  second conveyor belt 
               40  conveyor belt surface 
             I conveying the monocells into the receptacles of the stacking wheel 
             II conveying the monocells to the stacking compartment by means of the stacking wheel 
             III transferring the monocells from the receptacle into the stacking compartment 
             IV pressing the monocells against each other 
             A axial direction 
             D axis of rotation 
             K tilting axis