Method and apparatus for winding electrode foils and one or more separator tapes together for the production of electrochemical cells

Abstract

Method for winding electrode foils and one or more separator strips together for making electrochemical cells, the method comprising: making a first length (25) of a first electrode foil (21) wound on a first accumulation device (32) rotatable around its own rotation axis (V2); making a first length (26) of a second electrode 5 foil (23) on a second accumulation device (37) rotatable around its own rotation axis (V3); simultaneously winding the first length (25) of first electrode foil (21) from the first accumulation device (32), the first length (26) of second electrode foil (23) from the second accumulation device (37) and a first strip-shaped separator (22) from a first separator reel (15), and winding the first length (25) of 0 first electrode foil (21), the first length (26) of second electrode foil (23) and the first strip-shaped separator (22) on a mandrel (41). A relative winding apparatus is also described.

Description

[0001] Method and apparatus for winding electrode foils and one or more separator tapes together for the production of electrochemical cells

[0002] DESCRIPTION

[0003] The present invention refers to a winding method and to an apparatus for winding electrode foils and one or more separators together.

[0004] The present invention is particularly usable in a process for making electrochemical cells, for example secondary electrochemical cells, comprising electrodes separated from each other by a dielectric separator, typically a stripshaped separator.

[0005] One type of electrochemical cells, called jelly roll or Sw / ss roll, provides that a strip-shaped separator is interposed between two electrode foils, in particular an anode and a cathode, and that the multilayer made of separator and electrode foils is wound to form an electrochemical cell of cylindrical or almost cylindrical shape. Two separators can be used: an internal separator between anode and cathode and an external separator in contact with one of the two electrodes.

[0006] Typically, in order to make this type of electrochemical cells, winding apparatuses are used which provide a winding mandrel rotatable around its own longitudinal axis. Free ends of the first electrode foil, of the separator and of the second electrode foil are associated with the winding mandrel which is placed in rotation around its own longitudinal axis causing the winding of the electrode foils and of the separator between them.

[0007] In the Applicant's experience, in order to feed the materials to the winding mandrel, the foils and the strip-shaped separator are unwound from respective feeding reels, wound in the winding mandrel, at which each material is cut to be separated from the respective feeding reel. The winding mandrel is driven in rotation making the jelly roll type winding of the electrode foils and separators. Often, the winding mandrel is mounted on a rotatable forming station for finishing the product and unloading it.

[0008] In some types of automatic winding machines, the aforementioned operations are carried out by stopping the winding at the step of introducing and of cutting each material from the respective feeding roller.

[0009] In the Applicant's experience, in other types of machines the separator and the electrode foils are unwound continuously from the respective feeding reels and the winding is carried out without stopping the product, but by reducing the winding speed of the mandrel in preparation for the step of cutting the materials from the respective feeding reels. In particular, the Applicant has noted that, once the materials of the jelly roll assembly have been constrained to the winding mandrel, the latter is rotated at a predetermined and relatively fast winding speed. In preparation for the cutting of the material, the rotation speed is reduced in order to carry out the cutting operations with the required accuracy and precision.

[0010] The Applicant has also observed that the increasingly stringent quality specifications of the assembly both in relation to the length of the materials that make up the layers of the assembly and to the dimensional tolerances for the alignments between the layers actually require relatively significant speed reductions with a consequent increase in the production cycle time of the assembly. In order to avoid tugging in the material, it is also often preferable that the reduction in rotation speed is gradual, which condition can lead to a further increase in cycle time.

[0011] In the Applicant's experience, in some production processes, in order to ensure a better electrical insulation between anode and cathode, it is preferable that the cutting of each electrode is carried out before having finished the winding that makes the jelly roll so that the last wound layers consist only of separator material. Cutting the electrode foils from the respective feeding roller before cutting the separator strip or strips and thus before finishing the winding of the materials requires variations in winding speed (deceleration before cutting and acceleration after cutting) for each material. This, in addition to affecting the cycle time, makes the production process and its control and supervision complex.

[0012] The Applicant has perceived that if it were possible to decouple the continuous feeding of the electrode foils from the winding mandrel, it would be possible to simplify the management of the operations and therefore speed up the production process of the electrochemical cells.

[0013] The Applicant has understood that the provision of at least one temporary accumulation device on which a length of electrode foil cut from a feeding reel is wound allows to eliminate the need to stop or slow down the winding speed of the electrode foil in the winding mandrel and to improve the efficiency of the production cycle simplifying the step of making the wound multilayer and its control.

[0014] The present invention concerns, in a first aspect thereof, a method for winding electrode foils and one or more separator strips together for making electrochemical cells.

[0015] Preferably, the method comprises making a first length of a first electrode foil wound on a first accumulation device rotatable around its own rotation axis. Preferably, the method comprises making a first length of a second electrode foil on a second accumulation device rotatable around its own rotation axis.

[0016] Preferably, the method comprises simultaneously unwinding the first length of first electrode foil from the first accumulation device, the first length of second electrode foil from the second accumulation device, and a first strip-shaped separator from a first separator reel.

[0017] Preferably, the method comprises winding the first length of first electrode foil, the first length of second electrode foil and the first strip-shaped separator on a winding mandrel.

[0018] The present invention concerns, in a second aspect thereof, a winding apparatus for winding electrode foils and one or more separators together for making electrochemical cells.

[0019] Preferably, the winding apparatus comprises a first unwinding roller configured to house a first electrode reel of a first electrode foil and a first accumulation device rotatable around its own rotation axis and configured to receive a first length of first electrode foil from the first unwinding roller.

[0020] Preferably, the apparatus comprises a second unwinding roller configured to house a second electrode reel of a second electrode foil and a second accumulation device rotatable around its own rotation axis configured to receive a first length of second electrode foil from the second unwinding roller.

[0021] Preferably, the apparatus comprises a third unwinding roller configured to house a first separator reel of a first strip-shaped separator.

[0022] Preferably, the apparatus comprises a winding mandrel configured to receive the first length of first electrode foil from the first accumulation device, the first length of second electrode foil from the second accumulation device, and the first stripshaped separator from the first separator reel.

[0023] By “strip-shaped element” is meant an electrode foil or a strip-shaped separator. By “electrode foil” is meant a strip or foil having a dimension (i.e. length) much larger than two additional dimensions, wherein a first dimension of such two additional dimensions is much larger than a second dimension of such two additional dimensions. The electrode foil can be a monolithic strip (or foil) or a strip formed by a plurality of layers joined together made of identical material or different materials, possibly coated at least in part with an active material for electrodes. The electrode foil also has characteristics that allow some bending during its use.

[0024] By “strip-shaped separator” is meant a strip having a dimension that is much larger than two further dimensions, wherein a first dimension of such two further dimensions is much larger than a second dimension of such two further dimensions. The strip can be monolithic or formed by a plurality of layers joined together made of identical material or different materials. The separator strip is made of or coated with dielectric material. The strip-shaped separator also has characteristics such as to allow some bending during its use.

[0025] The term “adhesive”, in particular referred to an adhesive tape, refers to the ability of a body to attach to a surface on which it is applied, for example by means of an adhesive provided on the body.

[0026] The expression “upstream” means, unless otherwise specified, a position which, along a direction of forming of the jelly-roll winding or with respect to a direction of unwinding of a strip-shaped element, is placed towards the respective feeding reel and / or away from the forming station. The expression “downstream” means, unless otherwise specified, a position which, along a direction of forming of the jelly-roll winding or with respect to a direction of unwinding of a strip-shaped element, is placed away from the respective strip-shaped element feeding reel and / or towards the forming station.

[0027] Preferably, there is defined an assembly forming direction which extends from the unwinding of the first and second electrode foil from the respective feeding reels to the production of a jelly roll type winding.

[0028] Preferably, simultaneously unwinding the first length of first electrode foil, the first length of second electrode foil from the second accumulation device and the first strip-shaped separator comprises unwinding the first strip-shaped separator directly from the first separator reel. In particular, the first strip-shaped separator is unwound from the first separator reel to be directly transferred to the winding mandrel.

[0029] Preferably, the method comprises continuously feeding the first electrode foil to a plurality of first accumulation devices at distinct time instants separated by respective time intervals, wherein each accumulation device of the first accumulation devices is rotatable around its own rotation axis.

[0030] Preferably, continuously feeding the first electrode foil comprises winding a respective portion of first electrode foil on a respective accumulation device of the first accumulation devices, the plurality of portions of first electrode foil defining a plurality of lengths of first electrode foil which comprises the first length of first electrode foil.

[0031] Preferably, subsequently to winding a respective portion of first electrode foil on a respective accumulation device of the plurality of first accumulation devices, the method comprises cutting the first electrode foil upstream of the respective first accumulation device.

[0032] Preferably, the method comprises continuously feeding the second electrode foil to a plurality of second accumulation devices at distinct time instants separated by respective time intervals, wherein each accumulation device of the second accumulation devices is rotatable around its own rotation axis.

[0033] Preferably, continuously feeding the second electrode foil comprises winding a respective portion of second electrode foil on a respective accumulation device of the second accumulation devices, the plurality of portions of second electrode foil defining a plurality of lengths of second electrode foil which comprises the first length of second electrode foil.

[0034] Preferably, subsequently to winding a respective portion of second electrode foil on a respective accumulation device of the plurality of second accumulation devices, the method comprises cutting the second electrode foil upstream of the respective accumulation device.

[0035] Preferably, continuously feeding the first electrode foil comprises unwinding a first electrode foil from a first electrode reel.

[0036] Preferably, continuously feeding the second electrode foil comprises unwinding a second electrode foil from a second electrode reel.

[0037] Preferably, the first accumulation devices of the plurality of first accumulation devices are arranged in sequence along a first advancement path and are movable along the first advancement path.

[0038] Preferably, the plurality of first accumulation devices are arranged along the first advancement path at a distance from each other.

[0039] Preferably, the second accumulation devices of the plurality of second accumulation devices are arranged in sequence along a second advancement path and are movable along said second advancement path.

[0040] Preferably, the plurality of second accumulation devices are arranged along the second advancement path at a distance from each other.

[0041] Preferably, along the first advancement path there is arranged a respective first loading position at which each accumulation device of the first accumulation devices receives a respective length of first electrode foil.

[0042] Preferably, at the first loading position a respective first accumulation device is aligned with the first unwinding roller to receive the first electrode foil.

[0043] Preferably, along the second advancement path there is arranged a respective second loading position at which each accumulation device of the second accumulation devices receives a respective length of second electrode foil.

[0044] Preferably, at the second loading position a respective second accumulation device is aligned with the second unwinding roller to receive the second electrode foil.

[0045] Preferably, the first advancement path comprises a first unloading position arranged downstream of the first loading position in the advancement direction. At the first unloading position the length of the first electrode foil is unwound from the first accumulation device of the first accumulation devices.

[0046] Preferably, the second advancement path comprises a second unloading position arranged downstream of the second loading position in the advancement direction. At the second unloading position the length of the second electrode foil is unwound from the second accumulation device of the second accumulation devices.

[0047] Preferably, the method and the apparatus is for making a winding which further comprises a second strip-shaped separator.

[0048] Preferably, simultaneously unwinding further comprises unwinding a second strip-shaped separator from a second separator reel simultaneously with the first length of first electrode foil, the first length of second electrode foil and the first strip-shaped separator, and winding the first lengths of first and second electrode foil and the first strip-shaped separator comprises winding the second stripshaped separator on the winding mandrel simultaneously with the first lengths of first and second electrode foil and the first strip-shaped separator.

[0049] Preferably, simultaneously unwinding comprises unwinding the second stripshaped separator directly from the second separator reel.

[0050] In particular, the second strip-shaped separator is unwound from the second separator reel to be directly transferred to the winding mandrel.

[0051] Preferably, the first accumulation device is arranged between the first unwinding roller and the winding mandrel.

[0052] Preferably, the plurality of first accumulation devices is arranged downstream of the first unwinding roller and upstream of the unwinding mandrel.

[0053] Preferably, the second accumulation device is arranged between the second unwinding roller and the winding mandrel.

[0054] Preferably, the plurality of second accumulation devices is arranged downstream of the second unwinding roller and upstream of the winding mandrel.

[0055] Preferably, each accumulation device of the first accumulation devices is positioned in the first loading position at distinct instants separated by respective time intervals.

[0056] Preferably, each accumulation device of the first accumulation devices advances from the first loading position to the first unloading position so as to position each accumulation device in the first loading position at distinct times and separated by respective time intervals.

[0057] Preferably, the first accumulation devices move between successive positions of a first plurality of positions along the first advancement path, the first plurality of positions comprising the first loading position and the first unloading position.

[0058] Preferably, the first unwinding path of a length of the first electrode foil extends from the first unloading position to the winding position of the winding mandrel.

[0059] Preferably, the second electrode foil is unwound from the second electrode reel and is wound on a plurality of second accumulation devices at distinct time instants and separated by respective time intervals in which each accumulation device of the plurality is rotatable around its own rotation axis.

[0060] Preferably, each accumulation device of the second accumulation devices advances from the second loading position to the second unloading position so as to position each accumulation device in the second loading position at distinct times and separated by respective time intervals.

[0061] Preferably, the second accumulation devices move between successive positions of a second plurality of positions along the second advancement path, the second plurality of positions comprising the second loading position and the second unloading position.

[0062] Preferably, the second unwinding path of a length of the second electrode foil extends from the second unloading position to the winding position of the winding mandrel.

[0063] Preferably, the movement of the first accumulation devices along the first advancement path is intermittent linear. In one embodiment, each first accumulation device advances by a first stretch of path in a first time interval, remains stationary in a second time interval subsequent to the first time interval, and then repeats the sequence of advancing in the first time interval and stopping in the second time interval.

[0064] Preferably, the movement of the second accumulation devices along the second advancement path is intermittent linear. In one embodiment, each second accumulation device advances by a second stretch of path in a third time interval, remains stationary in a fourth time interval subsequent to the third time interval, and then repeats the sequence of advancing in the third time interval and stopping in the fourth time interval.

[0065] Preferably, the intermittent linear motion of the plurality of second accumulation devices is synchronous with the intermittent linear motion of the plurality of first accumulation devices. Further characteristics and advantages of the present invention will become clearer from the following detailed description of a preferred embodiment thereof, with reference to the appended drawings and provided by way of indicative and non-limiting example, in which: figure 1 is a schematic top view of a winding apparatus for winding electrode foils and one or more separators together for making an assembly for the production of electrochemical cells, in accordance with an embodiment; figure 2 schematically illustrates an example of arrangement of the plurality of first accumulation devices in the first intermediate conveyor at a time instant during the winding and unwinding process; figure 2a is a top view of an accumulation device of the plurality of first accumulation devices in which some parts of it are indicated; figure 3 schematically illustrates an example of arrangement of the plurality of second accumulation devices in the second intermediate conveyor at a time instant during the winding and unwinding process; figure 3a is a top view of an accumulation device of the second accumulation devices in which some parts of it are indicated; figure 4 is a schematic top view of the forming station of the apparatus of figure 1 , in which further details are shown, and figure 4a is a schematic top view of a winding mandrel according to an embodiment. figure 5 shows the forming station of figure 4 which is rotated in a successive position along the third advancement path.

[0066] The representations in the accompanying figures do not necessarily have to be understood in scale and do not necessarily respect the proportions between the various parts. In the figures, the same or similar elements of different embodiments will be indicated by the same reference numerals.

[0067] Figure 1 schematically illustrates an apparatus 10 for winding electrode foils and one or more separators together for making an assembly for the production of electrochemical cells.

[0068] The winding apparatus 10 comprises a plurality of unwinding rollers 1 -4 for feeding strip-shaped elements, wherein each unwinding roller is configured to house a respective strip-shaped element reel. Each of the strip-shaped elements is intended to form an anode, a cathode or a separator of dielectric material.

[0069] The anode and the cathode are formed starting from a respective electrode foil wound in a reel.

[0070] Typically, the electrode foils are composed of different materials. The foils comprise a thin metal layer, for example of copper or aluminium, which is coated on one side or both sides with an electrochemically active material. In other examples, the electrode foils may comprise a polymeric binder, a conductive additive, and an electrochemically active material. The main function of the polymeric binder is to retain the active material together with the conductive additive.

[0071] The separators are typically strip-shaped elements consisting of an insulating material, for example an electrically insulating polymeric membrane and are referred to in the present description and claims as strip-shaped separators.

[0072] Preferably, each strip-shaped element is fed by a respective reel continuously, in the form of continuous strips or foils.

[0073] In figure 1 , a first unwinding roller 1 is configured to support and unwind a first reel 14 of a first electrode foil 21 , below indicated with first electrode reel 14. A second unwinding roller 2 is configured to support and unwind a second reel 16 of a second electrode foil 23, below indicated with second electrode reel 16.

[0074] A third unwinding roller 3 is configured to support and unwind a first reel 15 of a first strip-shaped separator 22, below indicated with first separator reel 15.

[0075] The first and second unwinding roller 1 , 2 are arranged at a feeding station 11 summarily indicated in figure 1 with a dashed line.

[0076] The winding apparatus 10 further comprises a fourth unwinding roller 4 configured to support and unwind a second reel 17 of a second strip-shaped separator 24, below indicated with second separator reel 17.

[0077] The winding apparatus 10 further comprises a winding mandrel or winder mandrel 41 which is rotatable around its own forming axis V1 (figure 4a) and is placed at a forming station 13 indicated summarily with a dashed line. The winding mandrel 41 has the function of winding together the strip-shaped elements which make an assembly, in particular a jelly roll type winding.

[0078] The forming station 13 is placed downstream of the feeding station 11 with respect to a forming direction PD of the jelly roll type winding.

[0079] In the forming direction PD, an intermediate station 12 is placed between the feeding station 11 and the forming station 13.

[0080] The third unwinding roller 3 of the first strip-shaped separator 22 is arranged between the first and the second unwinding roller in a direction transverse to the direction of forming of the jelly-roll winding. The fourth unwinding roller of the second strip-shaped separator is arranged below the second unwinding roller of the second electrode foil with respect to a direction perpendicular to the forming direction. However, in further embodiments not illustrated in the figures, the third unwinding roller 3 can be arranged upstream or downstream of the intermediate station 12. More in general, the third unwinding roller 3 is arranged upstream of the forming station 13. Similarly, the fourth unwinding roller 4 is arranged upstream or downstream of the intermediate station 12. More in general, the fourth unwinding roller 4 is arranged upstream of the forming station 13.

[0081] At the intermediate station 12, there is placed a first accumulation device 32 rotatable around its own winding axis V2 and configured to receive and to wind a length 25 (figure 2a) of the first electrode foil 21 from the first electrode reel 14. The first accumulation device 32 is arranged to receive the first electrode foil 21 unwound along a first feeding direction F1 and wind the same around the winding axis V2. Along the first feeding direction F1 of the first electrode foil and upstream of the first accumulation device 32 there is provided a first cutting device 27a configured to cut the first electrode foil 21 from the first electrode reel 14 so as to make a length 25 (indicated in figure 2a) of the first electrode foil wound on the first accumulation device 32.

[0082] The first cutting device 27a is arranged upstream of the first accumulation device 32.

[0083] At the intermediate station 12, there is placed a second accumulation device 37 rotatable around its own winding axis V3 and configured to receive and wind a first length 26 (figure 3a) of the second electrode foil 23 from the second electrode foil reel 16.

[0084] The second accumulation device 37 is arranged to receive the second electrode foil 23 unwound along a second feeding direction F2 and wind the same around the winding axis V3. Along the feeding direction F2 of the second electrode foil and upstream of the second accumulation device 37 there is provided a second cutting device 27b configured to cut the second electrode foil 23 from the second electrode reel 16 so as to make a length of the second electrode foil 26 wound on the second accumulation device 37.

[0085] The second cutting device 27b is arranged upstream of the second accumulation device 37.

[0086] The cutting devices 27a and 27b may be a cutter or a rotating blade which are configured to cut an electrode foil.

[0087] The first accumulation device 32 and the second accumulation device 37 are arranged at the intermediate station 12 and spaced apart from each other in a direction perpendicular with respect to the forming direction PD.

[0088] In the embodiments illustrated in the figures, the apparatus 10 comprises a plurality of first accumulation devices 32 placed at the intermediate station 12. The plurality of first accumulation devices 32 comprises the first accumulation device. Each accumulation device of the first accumulation devices 32 comprises an accumulation roller 31 rotatable around a winding pin 28 coinciding with the winding axis V2. The accumulation roller 31 comprises an outer surface (not indicated) configured to receive thereon a length 25 of the first electrode foil 21 (figure 2a).

[0089] Each accumulation device 32 of the plurality of first accumulation devices is rotatable in two opposite directions: a first direction for winding the first electrode foil 21 and a second direction for unwinding a portion of the first electrode foil.

[0090] In the embodiment illustrated in figure 1 , the first unwinding roller 1 and the second unwinding roller 2 are arranged with respect to each other along a direction transverse with respect to the forming direction PD.

[0091] The winding apparatus 10 comprises a plurality of second accumulation devices 37 placed at the intermediate station 12. The plurality of second accumulation devices 37 comprises the second accumulation device. Each accumulation device of the second accumulation devices 37 comprises an accumulation roller 39 rotatable around a winding pin 29 coinciding with the winding axis V3. The accumulation roller 39 comprises an outer surface (not indicated) configured to receive thereon a length of electrode foil (figure 3a).

[0092] Each accumulation device of the plurality of second accumulation devices is rotatable in two opposite directions: a first direction for winding the second electrode foil 23 and a second direction for unwinding a portion of the second electrode foil.

[0093] The first and second accumulation devices 32, 37 may have a same structure.

[0094] The first accumulation devices 32 of the plurality are arranged in sequence and at a distance from each other along a first advancement path 33 and movable along said first advancement path.

[0095] The plurality of first accumulation devices 32 is arranged on a first intermediate conveyor 30. The first intermediate conveyor 30 comprises a first support structure 64 which is configured to rotate about its own first transfer axis T1 , the rotation defining the first advancement path 33. The first accumulation devices 32 of the plurality are mounted rotatably around their winding axis V2 on the first support structure 64 in such a way that each accumulation device 32 can rotate simultaneously about its own winding axis V2 and around the transfer axis T1 of the first support structure 64 along the first advancement path 33.

[0096] The first transfer axis T 1 is parallel to the winding axes V2 of the first accumulation devices 32.

[0097] The winding axes V2 are motorized to impart the rotation of the respective first accumulation devices 32. The rotation of the first support structure 64 along the first advancement path 33 is driven by an electric motor (not shown).

[0098] The step of cutting a length of the first electrode foil 25 by means of the cutting device 27a is typically preceded by one step of introducing the material to a first accumulation device 32 by means of a first material introduction group 61 (Fig. 1 ), known per se and not depicted in detail. The first introduction group 61 is arranged upstream of the cutting device 27a and is configured to hold in position and / or translate a free end (not shown in the figures) of the first electrode foil 21 and insert said end at the accumulation roller 31 , for example in a gripping clamp provided in the accumulation roller (not shown in the figures).

[0099] In a preferred embodiment, the first intermediate conveyor 30 is a horizontal conveyor.

[0100] Preferably the first support structure 64 is disc-shaped, in particular it is a transfer wheel.

[0101] The first support structure has an outer edge 64a (Fig. 2). In the example of the figures, the first accumulation devices 32 are arranged, at a distance from each other, at the outer edge 64a of the first support structure 64.

[0102] The first advancement path 33 is substantially circular.

[0103] The first advancement path 33 comprises a first loading position A1 at which a first accumulation device 32 is positioned to receive and to wind a length 25 of the first electrode foil 21 .

[0104] The first support structure 64 rotates around its own transfer axis T 1 to bring into alignment, one after the other, each first accumulation device 32, when arranged in the first loading position A1 , with the feeding direction F1 . In particular, at the first loading position A1 , the first accumulation device 32 is configured to receive the first electrode foil 21 from the first electrode reel 14. For example, the free end of the first electrode foil 21 (not shown) is inserted into the first accumulation device 32 placed in the loading position A1 by means of the first material introduction group 61 . Subsequently to the introduction of the first electrode foil 21 , the accumulation device 32 rotates around its own winding axis V2 to wind a portion of first electrode foil 21 around the winding pin 28. Once the winding is finished, the portion is cut off from the first electrode reel 14 by means of the cutting device 27a so as to form a length 25 of the first electrode foil 21 .

[0105] The accumulation device 32 of the first accumulation devices which has received the length 25 of the first electrode foil 21 proceeds along the first advancement path 33. The first advancement path 33 comprises a first unloading position A2 arranged downstream with respect of the first loading position A1. At the first unloading position A2, the length of the first electrode foil 25 wound on an accumulation device 32 of the plurality of first accumulation devices is unwound from the latter and wound on the winding mandrel 41 .

[0106] Preferably, the winding of the length 25 of the first electrode foil on the winding mandrel 41 is simultaneous with its unwinding from the first accumulation device 32.

[0107] The length 25 of the first electrode foil 21 is unwound at the first unloading position A2 along a first unwinding path U1 which extends from the position A2 to the winding mandrel 41 arranged on the forming station 40. In particular, during winding, the winding mandrel 41 is arranged at a winding position C1 of the forming station 40.

[0108] Figure 2 schematically illustrates an example of arrangement of the plurality of first accumulation devices 32 in the first intermediate conveyor 30 at a time instant during the process of loading and unloading the length 25 to / from the accumulation devices. Each accumulation device 32a to 32f is arranged at a position of a first plurality of positions (in the non-limiting example six positions for respective first accumulation devices). The first accumulation devices 32a-32f move between successive positions of the first plurality of positions. The first plurality of positions comprises the first loading position A1 and the first unloading position A2.

[0109] A first accumulation device 32a of the first accumulation devices 32 is placed at the first loading position A1 . At this position, the winding of a first electrode foil 21 is carried out on the first accumulation device 32a to form a length 25 of the first electrode foil. During winding, the first accumulation device 32a rotates around its own rotation axis V2.

[0110] A second and a third accumulation device 32b and 32c of the first accumulation devices 32 have wound a respective length 25, i.e. they are a successive step with respect to the accumulation device 32a in which the winding of the length 25 has been completed. The second and a third accumulation device 32b and 32c which house the length 25 advance along the first advancement path 33 towards the first unloading position A2.

[0111] A fourth accumulation device 32d of the first accumulation devices 32 is arranged at the first unloading position A2. The length of the first electrode foil 25 wound on the fourth accumulation device 32d is unwound from the accumulation roller 31 and simultaneously wound on the winding mandrel 41 . Along the first unwinding path U1 , there is arranged a second material introduction group 67 (Fig. 1 ) which is configured to insert a free end of the length 25 into the winding mandrel 41 . The second material introduction group 67 can be configured to hold in position and / or translate the free end of the length for the purpose of inserting it into the winding mandrel 41 .

[0112] A fifth and a sixth accumulation device 32e and 32f of the first accumulation devices 32 are devoid of the electrode foil winding (since already unwound on the winding mandrel 41 ) and advance along the first advancement path 33 to position themselves, in sequence with respect to each other in the first loading position A1 and receive respective lengths 25 of first electrode foil 21 .

[0113] The plurality of first accumulation devices 32 advance intermittently along the first advancement path 33. Specifically, each accumulation device 32 advances by a stretch of path in a first time interval, remains stationary in a second time interval subsequent to the first time interval, and then repeats the sequence of advancing in the first time interval and stopping in the second time interval. Preferably, the time interval in which each accumulation device 33 remains stationary is selected so as to allow the winding of a length 25 of the first electrode foil 21 at the first loading position A1.

[0114] In one embodiment, the unwinding of a length 25 from the first unloading position A2 takes place simultaneously with the winding of a length at the first loading position. In particular, the winding speed of the length is substantially equal to the unwinding speed of the length at the position A2.

[0115] The second accumulation devices 37 of the plurality are arranged in sequence and at a distance from each other along a second advancement path 38 and movable along said second advancement path.

[0116] The plurality of second accumulation devices 37 is arranged on a second intermediate conveyor 35. The second intermediate conveyor 35 comprises a second support structure 65 which is configured to rotate about its own second transfer axis T2 along the second advancement path 38. The second accumulation devices 37 of the plurality are mounted rotatably around their winding axis V3 on the second support structure 65 (figure 3a) in such a way that each second accumulation device 37 can rotate simultaneously around its own winding axis V3 and around the transfer axis T2 of the second support structure 65.

[0117] The second transfer axis T2 is parallel to the winding axes V3 of the second accumulation devices 37.

[0118] In a preferred embodiment, the winding axes V3 are motorized to impart the rotation of the respective second accumulation devices 37. The rotation of the second support structure 65 along the second advancement path 38 is driven by an electric motor (not shown).

[0119] The step of cutting a length 26 (indicated in figure 3a) of the second electrode foil 23 by means of the cutting device 27b is typically preceded by one step of introducing the material to a second accumulation device 37 by means of a third material introduction group 62, known per se and not depicted in detail. The third introduction group 62 is arranged upstream of the cutting device 27b and is configured to hold in position and / or translate a free end (not indicated in the figures) of the second electrode foil 23 and insert said end at the accumulation roller 29 of the accumulation device 37, for example in a gripping clamp provided in the accumulation roller (not shown).

[0120] In a preferred embodiment, the second intermediate conveyor 35 is a horizontal conveyor.

[0121] Preferably the second support structure 65 is disc-shaped, in particular it is a transfer wheel.

[0122] The second support structure 65 has an outer edge 65a (Fig. 3).

[0123] In the example of the figures, the second accumulation devices 37 are arranged, at a distance from each other, at the outer edge 65a of the second support structure 65.

[0124] The second advancement path 38 is substantially circular.

[0125] The second advancement path 38 comprises a second loading position B1 at which a second accumulation device 37 is positioned to receive and to wind a length 26 of the second electrode foil 23.

[0126] The second support structure 65 rotates around its own transfer axis T2 to bring into alignment, one after the other, each second accumulation device 37, when arranged in the second loading position B1 , with the feeding direction F2. In particular, at the second loading position B1 , the second accumulation device 37 is configured to receive the second electrode foil 23 from the second electrode reel 16. For example, the free end of the second electrode foil 23 is inserted into the second accumulation device 37 placed in the second loading position B1 by means of the third material introduction group 62.

[0127] Subsequently to the introduction of the second electrode foil 23, the accumulation device 37 rotates around its winding axis V3 to wind a portion of the second electrode foil 23 around the winding pin 29 (figure 3a). Once the winding is finished, the portion is cut off from the second electrode reel 16 by means of the cutting device 27b so as to form a length 26 of the second electrode foil 23.

[0128] The accumulation device of the second accumulation devices 37 which has received the length of the second electrode foil 26 proceeds along the second advancement path 38.

[0129] The second advancement path 38 comprises a second unloading position B2 arranged downstream with respect of the second loading position B1. At the second unloading position B2, the length 26 of the second electrode foil 23 wound on an accumulation device 37 of the plurality of second accumulation devices is unwound from the latter and wound on the winding mandrel 41 .

[0130] Preferably, the winding of the length 26 of the second electrode foil 23 at the position B1 on the winding mandrel 41 is simultaneous with its unwinding from the first accumulation device 37.

[0131] In one embodiment, the duration of a winding of a length 25 at the position A1 is approximately equal to the duration of a winding of a length 26 of the second electrode foil from the accumulation device 37 at the position B1. Similarly, the duration of the unwinding of a length 25 at the position A2 is approximately equal to the duration of an unwinding of a length 26 of the second electrode foil from the accumulation device 37 at the position B2.

[0132] The length 26 of the second electrode foil 23 is unwound at the second unloading position B2 along a second unwinding path U2 which extends from the position B2 to a winding position C1 of the winding mandrel 41 .

[0133] The length 26 of the second electrode foil 23 is unwound at the second unloading position B2 along a second unwinding path U2.

[0134] The plurality of second accumulation devices 37 advance intermittently along the second advancement path 38. Specifically, each accumulation device 37 advances by a stretch of path in a third time interval, remains stationary in a fourth time interval subsequent to the third time interval, and then repeats the sequence of advancing in the third time interval and stopping in the fourth time interval. Preferably, the time interval in which each accumulation device 37 remains stationary is selected so as to allow the winding of a length 29 of the second electrode foil 23 at the second loading position B1 .

[0135] In one embodiment, the stopping and advancing times of the second accumulation devices 37 are substantially equal to the stopping and advancing times of the first accumulation devices 32, so as to simplify the synchronization between the winding and unwinding operations in the first accumulation devices 32 with those of the second accumulation devices 37.

[0136] In the example of the figures, each of the first and second intermediate conveyor comprises six accumulation devices. Of course, this number is not limiting and is to be understood as purely exemplary. Figure 3 schematically illustrates an example of arrangement of the plurality of second accumulation devices 37 in the second intermediate conveyor 35 at a time instant during the process of loading and unloading the length 26 from the accumulation devices 37. Each accumulation device 37a to 37f is arranged at a position of a second plurality of positions which comprises the second loading position B1 and the second unloading position B2. The second accumulation devices 37a-37f move between successive positions of the second plurality of positions.

[0137] A first accumulation device 37a of the second accumulation devices 37 is placed at the second loading position B1. At this position, the winding of a second electrode foil 23 is carried out on the accumulation device 37a to form a length 26 of the second electrode foil 23. During winding, the first accumulation device 37a rotates around its own rotation axis V3 (figure 3a).

[0138] A second and a third accumulation device 37b and 37c of the second accumulation devices 37 have wound a respective length 26, i.e. they are at a successive step with respect to the accumulation device 37a in which the winding of the length 26 has been completed. The second and a third accumulation device 37b and 37c which house the length 26 advance along the second advancement path 38 towards the second unloading position B2.

[0139] A fourth accumulation device 37d of the second accumulation devices 37 is arranged at the second unloading position B2. The length of the second electrode foil 26 wound on the fourth accumulation device 37d is unwound from the accumulation roller 39 and simultaneously wound on the winding mandrel 41 . Along the second unwinding path U2, there is arranged a fourth material introduction group 68 which is configured to insert a free end of the length 26 into the winding mandrel 41. The fourth material introduction group 68 can be configured to hold in position and / or translate the free end of the length for the purpose of inserting it into the winding mandrel 41 .

[0140] A fifth and a sixth accumulation device 37e, 37f of the second accumulation devices 37 are devoid of the electrode foil winding and advance along the second advancement path 38 to position themselves, in sequence with respect to each other in the second loading position B1 and receive respective second electrode foil lengths 26.

[0141] Preferably the first intermediate conveyor 30 and the second intermediate conveyor 35 are arranged alignment with respect to each other in a direction transverse, preferably substantially perpendicular, to the forming direction PD. Preferably, the first and second support structure 64, 65 are aligned with each other along a direction perpendicular with respect to the forming direction PD.

[0142] In a preferred embodiment, both the first intermediate conveyor 30 and the second intermediate conveyor 35, in particular the first and second support structure 65, 66, rotate at a same speed.

[0143] In particular, the intermittent linear motion of the plurality of first accumulation devices is synchronous with the intermittent linear motion of the plurality of second accumulation devices.

[0144] The loading and unloading positions of the electrode material discussed above indicate a position of the advancement paths with respect to a fixed external point, for example the unwinding roller of the first or second electrode reel.

[0145] The winding mandrel 41 has the function of winding the strip-shaped elements together, i.e. a length of the first electrode foil 25, the first strip-shaped separator 22 and a length of the second electrode foil 26 and making a jelly-roll type winding.

[0146] Figure 4 shows more in detail the forming station 40, wherein the winding mandrel 41 is arranged on the forming station 40 at the winding position C1 .

[0147] The winding mandrel 41 winds together a length of the first electrode foil 25, a first strip-shaped separator 22, a length of the second electrode foil 26 and a second strip-shaped separator 24.

[0148] The winding mandrel 41 is rotatable around a forming axis V1 (indicated in figure 4a). The rotation of the winding mandrel 41 around the forming axis V1 is actuated by an electric motor (not illustrated).

[0149] The winding mandrel 41 comprises two half-parts 43a and 43b which can be moved towards and away from each other to allow the free end of a strip-shaped element, in particular an electrode foil or a strip-shaped separator, to be inserted between the two half-parts 43a and 43b by moving the two half-parts apart and to retain the strip-shaped element between them by bringing the two half-parts closer together.

[0150] Once the free ends of each strip-shaped element that will form the jelly-roll assembly have been inserted, the winding mandrel 41 carries out the winding of the electrode foils and separators.

[0151] The winding mandrel 41 is movable along a third advancement path 45 which comprises the winding position C1 at which the winding mandrel 41 is configured to receive and to wind a length of the first electrode foil 25, the first strip-shaped separator 22, a length of the second electrode foil 26 and possibly the second strip-shaped separator 24.

[0152] The winding of the strip-shaped elements on the winding mandrel 41 is simultaneous, where simultaneity means without surpluses in the length of a stripshaped element with respect to the other strip-shaped elements of the winding required by the production specifications. For example, in the production processes it is often preferable that the last wound layers consist only of separator material to ensure good electrical insulation of the winding.

[0153] The winding mandrel 41 is mounted on a third conveyor 40 which comprises a third support structure 66. The third support structure 66 is configured to rotate around its own third transfer axis T3, the rotation defining the third advancement path 45.

[0154] The rotation of the third support structure 66 along the third advancement path 45 is driven by an electric motor (not shown).

[0155] The first strip-shaped separator 22 is wound from the first separator reel 15 along a first separator unwinding path U3. The first separator unwinding path U3 extends from the third unwinding roller 3 to the winding mandrel 41. Therefore, the first strip-shaped separator 22 is transferred from the third unwinding roller 3 directly to the winding mandrel 41 .

[0156] In the embodiment of figure 1 , the first separator unwinding path U3 extends, at the intermediate station 12, between the first intermediate conveyor 30 and the second intermediate conveyor 35.

[0157] For the introduction of the first strip-shaped separator 22, its free end is inserted into the winding mandrel 41 .

[0158] The first unwinding path U1 of a length 25 of the first electrode foil extends from the first unloading position A2 to the winding mandrel 41 , in particular to the winding position C1 of the winding mandrel 41 .

[0159] The second unwinding path U2 of a length 26 of the second electrode foil 23 extends from the second unloading position B2 to the winding mandrel 41 , in particular to the winding position C1 of the winding mandrel 41 .

[0160] The second strip-shaped separator 24 is unwound from the second separator reel 17 along a second separator unwinding path U4. The second separator unwinding path U4 extends from the fourth unwinding roller 4 to the winding mandrel 41 arranged on the forming station 13. Therefore, the second stripshaped separator 24 is transferred from the fourth unwinding roller 4 directly to the winding mandrel 41 .

[0161] For the introduction of the second strip-shaped separator 24, its free end is inserted into the winding mandrel 41 .

[0162] In the embodiment of figure 1 , the second separator unwinding path U4 extends below the second intermediate conveyor 35. At the winding position C1 (figure 4), the unwinding directions U1 -U4 are arranged such that the first strip-shaped separator is arranged between the length 25 of the first electrode foil 21 and the length 26 of the second electrode foil 23 and the second strip-shaped separator 24 is arranged externally to the length 26 of the second electrode foil.

[0163] Once the winding of the strip-shaped elements 25, 22, 26 and 23 on the winding mandrel 41 at the position C1 has been completed, the winding mandrel proceeds along the third advancement path 45 to a cutting position C2 shown in Fig. 5. At the cutting position C2, the first and second strip-shaped separator 22 and 24 are cut by a respective third cutting device 56 along a cutting direction 57. For example, the third device 56 comprises a knife which cuts off along its cutting stroke simultaneously the first and the second strip-shaped separator.

[0164] During the movement of the winding mandrel 41 from the winding position C1 to the cutting position C2, and the first and second strip-shaped separator 22, 24 modify the unwinding direction U1 , U4 and in general the extension of the respective advancement paths. In order to accompany the relative unwinding of the separator strips from the respective reel, there is provided a first buffer device 54 for controlling the unwinding of the first separator strip 22 along the first advancement path U1 and a second buffer device 55 for controlling the unwinding of the second separator strip 24 along the fourth advancement path U4. The first and second buffer device 54 and 55, known per se, partially or entirely retain and release an excess length of the respective strip-shaped separator so as to adapt the length of the advancement path.

[0165] Subsequently to the cutting of the first and second separator 22 and 24, the winding mandrel 41 moves from the cutting position C2 to a finishing position C3 along the advancement path 45 at which an assembly or winding 49 of the jellyroll type is completed (step of the mandrel 41 not illustrated in the figures). In particular, at the finishing position C3, a patch of adhesive tape (not indicated) is applied on an end portion of the second strip-shaped separator 24 wound at an external position on the mandrel 41. To this end, there is provided an adhesive tape feeder 50 which comprises a reel 51 of adhesive tape 53 and a blade 52 configured to cut off a patch of adhesive tape 53. In particular, the patch of adhesive tape (mandrel step 41 not shown) is partially superimposed on the free end of the second strip-shaped separator 24 so as to close the winding and make the assembly more stable during its transfer to successive processing stations. The assembly thus formed proceeds along the third advancement path 45 from the completion position C3 to an unloading position C4 and transferred to successive processing stations, as schematically indicated with an arrow 60 (step of the mandrel 41 not illustrated in the figures).

[0166] In the example illustrated in figures 4 and 5, the forming station 40 comprises three winding mandrels, the winding mandrel 41 described above, a second winding mandrel 42 and a third winding mandrel 43. In figure 4 the second winding mandrel 42 is provided with a winding 49 and is arranged in the finishing position C3 for closing the winding by means of a patch of adhesive tape (not indicated) by means of the adhesive tape feeder 50. In figure 4 the third winding mandrel 43 is empty.

[0167] In the step subsequent to the advancement of the winding mandrels by one step between the subsequent positions C1 -C4 (figure 5), the first winding mandrel 41 has moved into the cutting position, the second winding mandrel is in the unloading position C4 and the third winding mandrel 43 is in the position C1. In the position C1 , the third winding mandrel 43 is ready to receive the lengths of the first and second electrode and the strip-shaped separators to form a new winding.

[0168] The person skilled in the art will recognize that it is possible to combine the various characteristics of the embodiments described above to obtain further embodiments, all falling within the scope of the present invention as defined by the subsequent claims.

Claims

CLAIMS1 . Method for winding electrode foils and one or more separator tapes together for the production of electrochemical cells, the method comprising:- making a first length (25) of a first electrode foil (21 ) wound on a first accumulation device (32) rotatable around its own rotation axis (V2);- making a first length (26) of a second electrode foil (23) on a second accumulation device (37) rotatable around its own rotation axis (V3);- simultaneously unwinding the first length (25) of first electrode foil (21 ) from the first accumulation device (32), the first length (26) of second electrode foil (23) from the second accumulation device (37) and a first strip-shaped separator (22) from a first separator reel (15), and- winding the first length (25) of first electrode foil (21 ), the first length (26) of second electrode foil (23) and the first strip-shaped separator (22) on a winding mandrel (41 ).

2. Method of claim 1 , wherein simultaneously unwinding comprises unwinding the first strip-shaped separator (22) directly from the first separator reel (15).

3. Method according to claim 1 or 2, which comprises continuously feeding the first electrode foil (21 ) to a plurality of first accumulation devices (32) at distinct time instants separated by respective time intervals, wherein each accumulation device of the first accumulation devices (32) is rotatable around its own rotation axis (V2) and continuously feeding comprises winding a respective portion of first electrode foil (21 ) on a respective accumulation device of the first accumulation devices, the plurality of portions of first electrode foil (21 ) defining a plurality of lengths (25) of first electrode foil (21 ) which comprises the first length of first electrode foil.

4. Method according to claim 3, which comprises, subsequently to winding a respective portion of first electrode foil (21 ) on a respective accumulation device of the plurality of first accumulation devices (32), cutting the first electrode foil (21 ) upstream of the respective first accumulation device (32).

5. Method according to claim 3 or 4, which comprises continuously feeding the second electrode foil (23) to a plurality of second accumulation devices (37) at distinct time instants separated by respective timeintervals, wherein each accumulation device of the second accumulation devices (37) is rotatable around its own rotation axis (V3), and continuously feeding comprises winding a respective portion of second electrode foil (23) on a respective accumulation device of the second accumulation devices (37), the plurality of portions of second electrode foil (23) defining a plurality of lengths (26) of second electrode foil (23) which comprises the first length of second electrode foil.

6. Method according to claim 5, which comprises, subsequently to winding a respective portion of second electrode foil (23) on a respective accumulation device of the plurality of second accumulation devices (37), cutting the second electrode foil (23) upstream of the respective accumulation device (37).

7. Method according to claim 5 or 6, wherein continuously feeding the first electrode foil (21 ) comprises unwinding a first electrode foil (21 ) from a first electrode reel (14) and continuously feeding the second electrode foil (23) comprises unwinding a second electrode foil (23) from a second electrode reel (16).

8. Method according to one of claims 5 to 7, wherein the plurality of first accumulation devices (32) are arranged in sequence along a first advancement path (33) and movable along said first advancement path (33) and the plurality of second accumulation devices (37) are arranged in sequence along a second advancement path (38) and movable along said second advancement path (38), along the first advancement path (33) there is arranged a respective first loading position (A1 ) at which each accumulation device of the first accumulation devices (32) receives a respective length (25) of first electrode foil (21 ) and wherein along the second advancement path (38) there is arranged a respective second loading position (B1 ) at which each accumulation device of the second accumulation devices (37) receives a respective length (26) of second electrode foil (23).

9. Method according to one of the preceding claims, wherein simultaneously unwinding further comprises unwinding a second strip-shaped separator (24) from a second separator reel (17) simultaneously with the first length (25) of first electrode foil (21 ), the first length (26) of second electrode foil (23) and the first strip-shaped separator (22), and whereinwinding the first lengths (25, 26) of first and second electrode foil (21 , 23) and the first strip-shaped separator (22) comprises winding the second strip-shaped separator (24) on the winding mandrel (41 ) simultaneously the first lengths (25, 26) of first and second electrode foils (21 , 23) and the first strip-shaped separator (22).

10. Method according to claim 9, wherein simultaneously unwinding comprises unwinding the second strip-shaped separator (24) directly from the second separator reel (4).

11. Winding apparatus (10) for winding electrode foils and one or more separators together for making electrochemical cells, the apparatus comprising:- a first unwinding roller (1 ) configured to house a first electrode reel (14) of a first electrode foil (21 );- a first accumulation device (32) rotatable around its own rotation axis (V2) configured to receive a first length (25) of first electrode foil (21 ) from the first unwinding roller (1 );- a second unwinding roller (2) configured to house a second electrode reel (16) of a second electrode foil (23);- a second accumulation device (37) rotatable around its own rotation axis (V3) configured to receive a first length (26) of second electrode foil (23) from the second unwinding roller (16);- a third unwinding roller (3) configured to house a first separator reel (15) of a first strip-shaped separator (22), and- a winding mandrel (41 ) configured to receive the first length (25) of first electrode foil (21 ) from the first accumulation device (32), the first length (26) of second electrode foil (23) from the second accumulation device (37) and the first stripshaped separator (22) from the first separator reel (16).

12. Winding apparatus according to claim 11 , wherein the winding mandrel (41 ) is configured to receive the first strip-shaped separator (22) directly from the first separator reel (15).

13. Winding apparatus according to claim 11 or 12, the first accumulation device (32) is arranged between the first unwinding roller (1 ) and the winding mandrel (41 ) and the second accumulation device (37) is arranged between the second unwinding roller (16) and the winding mandrel (41 ).

14. Winding apparatus according to a claim from 11 to 13, which comprises a plurality of first accumulation devices (32) arranged in sequence along a first advancement path (33) and movable along said first advancement path (33), wherein each first accumulation device is rotatable around its own rotation axis(V2) and along the first advancement path (33) there is arranged a first loading position (A1 ) at which a respective first accumulation device (32) is aligned with the first unwinding roller (1 ) to receive the first electrode foil (21 ).

15. Winding apparatus according to a claim from 11 to 14, wherein a plurality of second accumulation devices (37) arranged in sequence along a second advancement path (38) and movable along said second advancement path (38), wherein each second accumulation device (37) is rotatable around its own rotation axis (V3), wherein along the second advancement path (38) there is arranged a second loading position (B1 ) at which a respective second accumulation device (37) is aligned with the second unwinding roller (2) to receive the second electrode foil (23).

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