CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims priority from Italian patent applications no. 102020000028652 and 102020000028637 filed on November 26, 2020, the entire disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a welding method and to a welding device for welding to one another a plurality of layers of metal material at least partially overlapped.

In particular, the present invention is advantageously, but not exclusively, applied to the production of a power storage device, to which the following description will explicitly refer without thereby losing generality. Even more in particular, the present invention is advantageously, but not exclusively, applied to welding a plurality of layers of electrode tabs to one another and/or at least one electrode tab layer to at least one terminal metal layer and/or a support structure of a power storage device. BACKGROUND OF THE INVENTION

In the field of welding layers of metal material at least partially overlapped, especially in the case of welding metal foils, due to the delicateness of the material to be welded (particularly thin), heat welding systems without filler materials are mainly widespread, such as for example ultrasonic welding systems, where the heat is generated by the friction caused by the vibration with ultrasonic frequency of at least one of the elements to be welded, or laser welding, where the heat is generated by the huge energy provided by the laser beam and concentrated at a given focus.

In particular, in the field of the production of power storage devices, such as batteries or capacitors, where great precision and controlled conditions are required, the welding of the terminal electrode tabs of the electrode layers to one another and/or to possible terminal metal elements (having greater thickness) and/or to a support structure, made of metal as well, typically occurs by means of ultrasonic or laser welding systems.

Specifically, the known ultrasonic welding systems entail disposing the layers of metal material to be welded between an anvil and a sound wave emitter (also known as sonotrode) connected to a piezoelectric transducer, or to a converter, designed to convert an electronic ultrasound signal into a vibration which is then transferred (precisely by means of the sonotrode) to the zone to be welded. The energy created by the sound waves melts the layers of metal material to be welded, allowing the founding and thus the welding to one another of the layers of metal material. Laser welding, instead, entails the use of a welding device configured to emit and focus, by means of one or more lenses or mirror galvanometers, a laser beam on the plurality of layers of metal materials to be treated. The intensity, the speed of movement and the frequency of the emitted laser beam varies upon the varying of the material and/or of the thickness and/or of the layers to be treated.

Based on the foregoing, it is clear that the known ultrasonic or laser welding systems require complex welding devices, which have a large number of components and consequently a great bulk, high costs and require complex setting operations.

Furthermore, the maintenance of the abovementioned welding devices, especially in the case of ultrasonic welding (usually more reliable than laser welding or anyway capable of welding greater thicknesses), is particularly onerous, since the sonotrode has to be frequently replaced due to the great wear and, at each modification, the abovementioned complex setting operations have to be repeated.

One of the objects of the present invention is to provide an alternative welding method and device for welding to one another a plurality of layers of metal material at least partially overlapped, which at least partly overcome the abovementioned drawbacks ensuring, at the same time, a welding quality and reliability that stands comparison with the welding quality and reliability of the known welding systems.

SUMMARY

In accordance with the present invention, an assembling method and an assembling apparatus for assembling a power storage device are provided according to what is claimed in the appended independent claims, and preferably, in any one of the claims directly or indirectly dependent on the independent claims.

The claims describe preferred embodiments of the present invention forming integral part of the present description .

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the accompanying drawings, which illustrate several non limiting example embodiments thereof, wherein:

- Figures 1 and 2 schematically illustrate views in lateral section of a welding device, according to a first embodiment of the invention, in two different operating configurations, with several parts removed for clarity;

- Figures 3 and 4 schematically illustrate views in lateral section of a welding device according to a second embodiment of the invention in two different operating configurations;

- Figures 3a and 4a schematically illustrate views in lateral section of a welding device according to a third embodiment of the invention in two different operating configurations;

- Figures from 5 to 8 schematically illustrate lateral views of respective variants of a welding element 5 of the welding device of Figures 1 and 2, or of Figures 3 and 4, or of Figures 3a and 4a;

Figures 9, 10 and 11 schematically illustrate perspective views and on an enlarged scale of three different variants of the welding element 5 of the welding device of Figures 1 and 2, or of Figures 3 and 4, or of Figures 3a and 4a;

Figures 12 and 13 illustrate a schematic representation of subsequent steps of a welding method performed in accordance with the present invention;

- Figure 14 is an enlarged view of a part of Figure 13;

- Figures 15 and 16 illustrate two power storage devices wherein welds made by a device or by the method in accordance with the present invention are visible; and

Figure 17 schematically illustrates an apparatus comprising a device in accordance with the present invention and configured to perform the method in accordance with the present invention.

DETAILED DESCRIPTION

In the accompanying figures, reference numeral 1 indicates, as a whole, a welding device for welding to one another a plurality of layers 2 (Figures 12-17) of metal material at least partially overlapped.

Specifically, the welding device 1 is configured to weld together from 2 up to approximately 80 layers of metal material (preferably 2, or from 20 to 60, more precisely 40). In particular, the welding device 1 is configured to weld to one another a plurality of layers 2 of metal material at least partially overlapped.

Advantageously but not limitedly, at least one of the overlapped layers 2 of metal material to be welded has a configuration at least partially planar and has a (total) thickness ranging from approximately 5 pm to approximately 600 pm, even more in particular from approximately 50 pm to approximately 300 pm, more precisely from approximately 100 pm to approximately 200 pm. The reduced thickness ensures, in fact, a high deformation of the layer 2 of metal material, facilitating the welding thereof, as will be described below.

Specifically, advantageously but not necessarily, such layers 2 of metal material can each be made of aluminum, or copper, or gold, or brass or any combination or alloy thereof.

Advantageously but not necessarily, at least one of the layers 2 of metal material to be welded to one another is an electrode tab B.

It is further understood that the various layers 2 of the plurality of layers 2 of metal material to be welded (by means of the welding device 1 of the invention) can be made of different materials, for example one of the layers can be an electrode tab, whereas the other one can be a different metal element, for example a metal plate.

In the following description, explicit reference will be made, without thereby losing generality, to the use of such welding device 1 for the production of a power storage device 3 (as will be better explained below), in this case at least one of the layers 2 of metal material to be welded is an electrode tab B (Figures 15 and 16), i.e. the portion of electrode (generally copper for the cathode and aluminum or zinc for the anode) protruding from a stack so as to electrically interconnect to one another several layers of a same electrode (positive or negative).

With particular reference to Figures from 1 to 4a, the welding device 1 comprises a support portion 4 and a welding element 5, in particular a rod, which is coupled in a sliding (and removable) manner to the support portion 4 and has, at one end 6 thereof, at least one welding tip 7 designed to exert a welding action upon the plurality of layers 2 of metal material to be welded. Specifically, the welding element 5 is movable relative to the support portion 4 between at least a first position in a rest configuration I (see Figures 1 and 3) and a second position in an operating configuration 0 (see Figures 2, 4 and 4a).

Advantageously but not necessarily, in the configuration I, the welding element 5 is disposed so as to be in contact with the layers 2 of metal material to be welded. In particular, in the configuration I, the welding element 5 is disposed so as to lightly press (i.e. substantially without deforming them) the layers 2 of metal material. On the contrary, in the configuration 0, the welding element 5 is disposed so as to at least partially penetrate the volume initially occupied by the layers 2 of metal material to be welded.

Advantageously but not necessarily, the welding device 1 further comprises pushing means 8, which cooperate with the welding element 5 and can be operated, preferably by means of the application of a force from the outside, so as to transfer an impulsive force F onto the welding element 5 so as to cause the welding element 5 to move from the first position to the second position (i.e. from the configuration I to the configuration 0).

In the present disclosure, the expression "impulsive force" means a force that acts with a high module for a very short lapse of time, for example in the order of hundredths of a second, even more preferably of thousandths of a second. Advantageously but not limitedly, the impulsive force acts for a lapse of time ranging from 0.1ms to 200ms (in particular from 0.2 to 100 milliseconds, more in particular from 0.2 to 80 milliseconds).

Advantageously but not limitedly, the impulsive force F ranges from approximately 500 N to approximately 1400 N, in particular from approximately 650 N to approximately 800 N.

Advantageously but not necessarily, the impulsive force is generated by means of an impact between two elements of the welding device 1.

The welding device 1 is configured so that, while shifting from the rest configuration I to the operating configuration 0, the welding tip 7 exerts a welding action upon the plurality of layers 2 of metal material 2 at least partially overlapped such to weld together the layers 2 of metal material 1. In such manner, the layers 2 of metal material are (deeply) plastically deformed in a very short lapse of time; this operation, surprisingly, allows at least partially destroying (or at least generating cracks in) the thin layer of oxide generally present on the outside of the metal surfaces making the distance between the layers 2 of metal material similar to the parameters of the metal lattice of the element by which they are mainly formed, thus facilitating the creation of a strong bond. In particular, the impulsiveness of the welding force allows preventing the new forming of oxide on the deformed layers 2 of metal material, giving rise to the weld.

Advantageously but not necessarily, the welding action is a function of the impulsive force F; even more advantageously, welding action means the impact force that the welding tip 7, once subjected to the above-described impulsive force F (transferred by the pushing means 8), exerts upon the plurality of layers 2 of metal material.

According to some preferred but non-limiting embodiments, the welding device 1 comprises at least one welding tip 7, advantageously at least two welding tips 7, so as to exert, in use, such welding action upon the plurality of layers 2 of metal material.

Preferably but not necessarily, the welding device 1 (in particular the welding element 5) comprises at least four welding tips 7 disposed, for example, on two rows (as illustrated in Figures from 9 to 11), even more preferably six welding tips 7.

In some non-limiting cases such as the ones illustrated in Figure 9 or 10, each (or the) welding tip 7 has a polygonal cross section, for example square, or hexagonal. In other non-limiting cases, such as the one illustrated in Figure 11, each (or the) welding tip 7 has a closed curved section (a simple non-polygon section), for example circular or elliptical .

Advantageously but not necessarily, each (or the) welding tip 7 extends from the end 6 of the welding element 5 and has, on the opposite side relative to the welding element 5, a flat contact surface 9, which is designed to exert the welding action upon the plurality of layers 2 of metal material at least partially overlapped. In particular, the flat contact surface is disposed so as to be parallel to the plurality of layers 2 of metal material. More in particular, the flat contact surface is disposed so as to be perpendicular to the direction of the impulsive force F.

In particular, the welding action is exerted upon the overlapping zone, where the layers 2 overlap.

Advantageously but not limitedly, the flat contact surface 9 has an extension ranging from approximately 0.2 mm ² to approximately 5 mm ² (preferably between 0.4 mm ² and 3 mm ² ). Upon the increase of the flat contact surface 9, the impulsive force F being equal, the welding action (pressure) transmitted to the plurality of layers 2 of metal material varies (in particular decreases) in the area of a contact zone 10 (Figures 12 and 13) between the flat contact surface 9 of the (or of each) welding tip 7 and an outer surface of the overlapped plurality of layers 2 of metal material.

Therefore, by duly varying the welding device 1 or also by only modifying/replacing the welding element 5 (with the relative welding tip 7, and thus the flat contact surface 9) it is possible to obtain a different weld upon the varying of the thickness and/or of the number of the layers 2 of metal material (the impulsive force F also being equal).

Advantageously but not necessarily, when the impulsive force F or the shape of the flat contact surface 9 (or both) varies, it is possible to vary the welding action (pressure) acting upon the above-described contact zone 10 so as to ensure a correct (plastic) deformation of the various layers 2 of metal material, which will tend to press together and penetrate one another welding to one another (see in particular Figures 13 and 14). In particular, the welding action (pressure) is controlled by varying the welding element 5, more precisely, by varying the number, the shape and the size of the flat contact surface 9 of the welding tips 7.

Advantageously but not necessarily, and as illustrated in Figures from 5 to 8, the (or each) welding tip 7 has a trapezoidal (isosceles) cross section, delimited by a major base, in the area of the end 6, and by a minor base, in the area of the contact surface 9. In particular, the major base and the minor base are connected to one another by means of oblique sides, preferably alike. Between the oblique sides and the minor base, a welding angle is defined.

Advantageously but not necessarily, the welding angle has a width comprised between 95° and 175° (included). In particular, the welding angle has a width comprised between 110° and 160° (included). More in particular, the welding angle has a width comprised between 120° and 140° (included).

In some non-limiting cases, the minor base has a length greater than 2/3 of the major base. In other non-limiting cases, the minor base has a length smaller than 2/3 of the major base, in particular smaller than half of the major base, more precisely smaller than one third of the major base.

Advantageously but not necessarily, the (each) welding tip 7, perimetrically to the contact surface 9, comprises a corner E. In other words, the contact surface 9 is delimited by the corner E. In particular, the corner E is a sharp corner, i.e. an edge of rigid material with a radius of curvature (i.e. of beveling) less than 2.5 mm. More precisely, the radius beveling of the corner E is less than 1 mm, specifically less than 0.5 mm, preferably less than 0.2 mm or better 0.1 mm.

According to some non-limiting embodiments such as the ones illustrated in Figures 1 and 2, the welding device 1 comprises, more specifically the pushing means 8 of the welding device 1 comprise (in particular are composed of), a spring snapping mechanism 11 which can be operated, advantageously but not limitedly, from the outside, to exert the abovementioned impulsive force F upon the welding element 5. Specifically, in the embodiment illustrated in Figures 1 and 2, the support portion 4 comprises a seat 12 (specifically a recess) suitably dimensioned for receiving the spring snapping mechanism 11, and the spring snapping mechanism 11 is disposed in such seat 12 and is operatively connected to the welding element 5 so as to transmit, once activated, the above-described impulsive force F to such welding element 5.

The welding device 1, illustrated in Figures 1 and 2, further comprises a sleeve 13 which can slide moving closer or farther to the seat 12, along a direction parallel to a longitudinal axis X of the welding device 1, and is configured to operate the spring snapping mechanism 11, when moved (manually or automatically) closer to the seat 12.

Still with reference to the non-limiting embodiment illustrated in Figures 1 and 2, the welding device 1 also comprises a spring 14 having a given pre-load stretch, advantageously adjustable. In particular, such spring 14 is operatively connected to the sleeve 13 so as to counter the sliding of the sleeve 13 moving closer to the seat 12.

Specifically, such spring 14 is disposed inside the sleeve 13 so that the actuation of the spring snapping mechanism 11 is possible only overcoming the elastic action exerted upon the sleeve 13 by the spring 14.

Specifically, advantageously but not limitedly, the spring snapping mechanism 11 comprises: a triggering element 15 provided, at one end 16 thereof, with an abutment portion 17, and a further spring 18 which has a given pre-load stretch, advantageously adjustable and preferably less than the stretch of the spring 14, and is interposed in contact between the sliding sleeve 13 and the abutment portion 17 so that the sliding of the sleeve 13 towards the seat 12 causes the compression of the spring 18 and a consequent rotation of the triggering element 15, which, when at rest, is in a tilted position relative to a longitudinal axis X of the welding device 1.

In particular, in this manner, the triggering element 15 moves from an initial position tilted relative to the longitudinal axis X of the welding device 1 (see Figure 1) to a final position in which it is aligned with the longitudinal axis X of the device 1 (see Figure 2).

Advantageously but not limitedly, in such final position the triggering element 15, and in particular the abutment portion 17 of the triggering element 15, abuts against an end 19 of the welding element 5 (in particular opposite the end 6), when the spring 18 is compressed and the triggering element 15 is rotated, so as to be able to transfer onto said welding element 5 the impulsive force (impressed on said coupling element). In other words, the spring 18 is configured to align, during its compression, the triggering element 15 with the longitudinal axis X of the welding device 1. In particular, the spring 18 has a countersunk shape along the longitudinal axis X. More in particular, the spring 18 gets narrower while proceeding along the longitudinal axis X towards the welding element 5.

Advantageously, the triggering element 15 (illustrated in Figures 1 and 2) comprises a main body 20 from which the abutment portion 17 protrudes. In the initial tilted position (illustrated in Figure 1) the triggering element 15 is disposed tilted relative to the longitudinal axis X, the main body 20 is surrounded by the spring 18, which (spring 18) at least partially meets the abutment portion 17, so that the compression of the spring 18 determines the transfer of a thrust (generated by the spring 18) onto the abutment portion 17 such to cause the rotation of the triggering element 15 (clockwise, in Figure 1). In other words, the compression of the spring 18 determines the centering of the triggering element 15 relative to the spring 18 and the alignment of the triggering element 15 with the welding element 5.

Advantageously but not necessarily, the welding device 1 comprises an impact element 30 (illustrated in Figures 1, 2, 3a and 4a), which is configured to impress the impulsive force F on the welding element 5, in particular on the welding tip 7.

In the non-limiting embodiment of Figures 1 and 2, the sliding sleeve 13 internally has the impact element 30 which is operatively connected to the first spring 14, is configured to impress the impulsive force F (in particular, generated by the movement of the sleeve 13, once overcome the elastic action exerted by the spring 14 by means of the spring snapping mechanism 11) on the spring snapping mechanism 11, in particular on the welding element 5, and comprises a housing 21 which, advantageously but not limitedly, develops parallel to, in particular along, the longitudinal axis X, and is designed to receive a terminal section 31 of the triggering element 15, in particular a terminal section 31 of the main body 20 of the triggering element 15, when the spring 18 is compressed and the abutment portion 17 is in abutment against the end 19 of the triggering element 5. The housing 21 acts as guide for the triggering element 15 defining, at the same time, an end-of- stroke for the sliding when moving closer towards the seat 12 of the sliding sleeve 13.

Advantageously but not limitedly, the above-described impulsive force F is a function of the given pre-load stretch of the springs 14 and/or 18, therefore upon the varying of such pre-load stretch, the impulsive force transferred onto the welding element 5 varies and thus the welding action varies.

Advantageously but not necessarily, the impact element 30 comprises (at least) a stepped portion 32, which allows (as soon as the triggering element 15, rotating, overpasses the step) impulsively releasing the elastic energy generated by the compression of the springs 14 and/or 18 and impressing the impulsive force F towards the welding element 5, i.e. on the tip 7. In such manner, when a terminal section 31 of the triggering element 15 overcomes the stepped portion 32, due to the rotation impressed thereon by the spring 18, the impact element 30 springs towards the welding element 5 impressing thereon the impulsive force F. The springs 14 and 18 further act as return means 22 cooperating with the welding device 1, exerting a return action upon the welding element 5 so as to cause the shifting from the second position to the first position (i.e. from the operating configuration 0 to the rest configuration I), for example once completed the welding. In other words, according to some advantageous but non-limiting embodiments, the pushing means 8 coincide with the return means 22.

According to non-limiting alternative variants which are not illustrated, the welding device 1 comprises return means 22 (not coinciding with the pushing means 8) suitably configured (only) to exert a return action upon the welding element 5 so as to cause the shifting from the second position to the first position (i.e. from the operating configuration 0 to the rest configuration I).

Advantageously but not limitedly, the action exerted by the return means 22 is opposite relative to the (to the direction of the) impulsive force F which causes the moving of the welding element 5 from the first position to the second position (i.e. from the configuration I to the configuration 0).

Advantageously but not limitedly, the welding device 1, in particular the support portion 4, has a substantially cylindrical shape.

In particular, the welding element 5, the housing 21 and, in the final position (configuration 0) also the triggering element 15, are disposed in central position and are coaxial to the support portion 4, i.e. they extend along and symmetrically relative to the longitudinal axis X of the welding device 1.

Alternatively or additionally, according to some non limiting embodiments (such as the ones illustrated in Figures 3 and 4), the welding device 1 comprises external pushing means, for example an actuator 24 configured to exert the above-described impulsive force upon the welding element 5.

In particular, the actuator 24 is configured to move at least one between the welding element 5 and a different impact element 30 (for example a plate or the support element 4), so as to impress the impulsive force F on the welding element 5 and thus on the tip 7 and make the weld.

According to some non-limiting embodiments, the actuator 24 is operatively coupled (electrically or hydraulically) to an impact element 30 (Figures 3a and 4a) or to the welding element 5 (Figures 3 and 4), so as to exert the above-described impulsive force upon the welding element 5. In other words, the actuator 24 is configured to move the impact element 30 (Figures 3a and 4a) or directly the welding element 5 (Figures 3 and 4), so as to exert the above- described impulsive force upon the welding element 5 and thus upon the welding tip 7.

In some non-limiting cases, such as the one illustrated in Figures 3 and 4, the pushing means 8 of the welding device 1 comprise a hydraulic or electrohydraulic actuator 24, controlled by a control unit 28, for example a (monostable or bistable) solenoid valve, which controls the inlet and/or the outlet of a hydraulic fluid inside, for example, a cylinder.

In further non-limiting cases, such as the one illustrated in Figures 3a and 4a, the pushing means 8 of the welding device 1 comprise an electric actuator 24, commanded by a control unit 28, for example a motion controller or an industrial PC, which controls an electric motor 23, in particular a brushless motor. In such manner, it is possible to carry out a force control so as to be able to vary, based on the format (thickness and number) of the layers 2 of metal material to be welded, the impulsive force F. Alternatively or additionally, a position control could be carried out so as to vary the first and the second positions based on the format (thickness and number) of the layers 2 of metal material to be welded. In these non-limiting cases, the welding element 5 and the impact element 30 are configured to slide inside a guide 33, in particular substantially parallel to the longitudinal axis X. More precisely, the motor 23 commands the descent of the impact element 30, which hits the welding element 5, impressing thereon the impulsive force F. Advantageously but not necessarily, the (electric) actuator 24 can be operated for moving the welding element 5 or, alternatively, the support portion 4, or a different impact element 30, so as to impact the welding element 5, along a direction parallel to the longitudinal axis X of the welding device 1 and move it between the above-described first and second positions in such a time to allow the application of an impulsive welding action on the layers 2 of metal material.

Advantageously but not necessarily, the (external) pushing means 8 formed in such manner allow a reduction in the bulks of the welding device 1 (with respect to the embodiment that provides for the spring snapping mechanism 11) and allow adjusting with greater easiness and flexibility the intensity of the impulsive force F, and thus of the welding action to be exerted upon the layers 2 of metal material to be welded.

Advantageously but not limitedly, the actuator 24 can also be operated to exert the return action, therefore the return means 22 coincide with the pushing means 8 and comprise such (in particular, are composed of such) actuator 24.

Also in such non-limiting embodiments (Figures 3, 4, 3a and 4a), the welding device 1 comprises the support portion 4 and the welding element 5 (of the type described above) coupled in a sliding (and removable) manner to the support portion 4 and having, at one end 6 thereof, at least one welding tip 7, preferably a plurality of welding tips 7, (advantageously of the type described above) for exerting a welding action on the plurality of layers 2 of metal material to be welded.

Still with reference to Figures 3, 4, 3a and 4a, also in this case, advantageously but not limitedly, the welding device 1, in particular the support portion 4, has a substantially cylindrical shape and the welding element 5 is disposed in central position relative to the support portion 4 and is coaxial to the support portion 4, i.e. it extends along and symmetrically relative to the longitudinal axis X of the welding device 1.

According to another not illustrated variant of the welding device 1 (substantially analogous to the one of Figures 3 and 4 except by the type of pushing means 8), the pushing means 8 comprise an air piston which can be operated for inducing the shifting of the welding element 5 from the first position to the second position in such a time to allow the application of an impulsive welding action on the layers 2 of metal material to be welded. Also in this case, the air piston can also be operated for exerting the return action, therefore the return means 22 coincide with the pushing means 8 and comprise the (in particular, are composed of the) abovementioned hydraulic piston.

Advantageously but not necessarily, and as illustrated in the non-limiting embodiment of Figure 17, the welding device 1 comprises a contrast element 102, advantageously an anvil, configured to receive the plurality of layers 2 of metal material to be welded and counter the impulsive force F.

In some non-limiting advantageous cases, the contrast element 102 is fixed relative to an inertial system.

In other non-limiting cases, such contrast element 102 is movable and is configured to perform a movement that opposes the movement of the welding element 5.

In some non-limiting advantageous cases, such contrast element 102 is made of the same material of the (or of each) welding tip 7.

In other non-limiting cases, such contrast element 102 is made of a different material with respect to the (or to each) welding tip 7.

According to some non-limiting embodiments, such as the one illustrated in Figure 17, the contrast element 102 has a planar shape, in particular it is a plate.

According to other non-limiting embodiments which are not illustrated, the contrast element 102 has a curved shape or a shape corresponding to the shape of the welding tip 7.

Advantageously but not necessarily, the welding tip 7 (in particular the welding element 5) comprises portions manufactured, in particular it is totally manufactured, by means of sintering processes.

In particular, the welding tip 7 (in particular the welding element 5) comprises portions made, in particular it is totally made, of widia (i.e. cemented carbide, carboloy).

It is understood that the external force necessary for the actuation of the pushing means 8, also when the latter comprise the spring snapping mechanism 11, could also be exerted by actuation means of electric type (of known type and not further described or illustrated herein) which can be remotely controlled (in a known manner). This would allow, advantageously, the automatic actuation of the welding device 1 and would ease the use of such welding device 1 also inside continuous production plants and with different formats.

In some non-limiting cases, the welding tip 7 and the welding element 5 are made in one piece.

Alternatively or additionally, the welding tip 7 and/or the welding element 5 are manufactured by means of additive production techniques. In accordance with a second aspect of the present invention, a method for welding to one another a plurality of layers 2 of metal material at least partially overlapped is provided.

The method comprises the step of providing a plurality of layers 2 of metal material (advantageously of the type described above) at least partially overlapped and applying a welding action on an outer surface of such plurality of layers 2 of metal material at least partially overlapped.

Advantageously but not necessarily, the welding action is applied providing a welding device 1 comprising a welding element 5 which has, at one end 6 thereof, at least one welding tip 7 (advantageously but not limitedly of the type described above) which can be operated, following the application of an impulsive force, for shifting from a first position in a rest configuration I to a second position in an operating configuration 0, in which said welding tip 7 exerts said welding action proportional to said impulsive force upon said plurality of layers 2 of metal material at least partially overlapped so as to weld them together.

Specifically, advantageously the method comprises a step of positioning the welding device 1 (provided with the welding element 5 and comprising the welding tip 7) in contact with an outer surface 25 of the plurality of layers 2 of metal material in the area of an overlapping zone 40, where the layers 2 of metal material overlap (Figures 12 and 13). In particular, the portion of the overlapping zone 40 in contact with the welding tip 7 determines a welding zone. In other words, the welding device 1 is disposed relative to the layers 2 of metal material to be welded so that the welding tip 7 (or advantageously the plurality of welding tips 7) is (are) in contact with (in particular pressing without deforming) the outer surface 25 of the plurality of layers 2 of metal material at least partially overlapped to be welded.

Advantageously, the method further comprises a step of operating the welding device 1 by means of the application of an impulsive force F on said welding element 5 so as to cause the welding tip 7 to exert a welding action (at least partially deforming the layers 2 of metal material in the area of the contact zone 10), which is a function of the impulsive force F, so as to weld together the plurality of layers 2 of metal material. In other words, the method provides for applying a welding action of the type described above on the plurality of layers 2 of metal material to be welded, in particular (at least) on an outer surface 25 of the plurality of layers 2 of metal material, even more in particular in the area of the contact zone 10, in the area of which there is at least one partial overlapping of such layers 2 of metal material.

Advantageously but not necessarily, during the step of operating the welding device 1, the method provides for the application of an impulsive force F, by means of the pushing means 8 manufactured according to one of the variants described above, on said welding element 5 so that the welding tip 7 (even more advantageously as better explained above, the welding tips 7) transfers such impulsive force F onto the layers 2 of metal material to be welded, exerting a welding action, which is a function of the mentioned impulsive force F, upon the plurality of layers 2 of metal material at least partially overlapped so as to weld them together.

Advantageously but not limitedly, the step of exerting the welding action is performed by means of a welding device 1 of the type described above.

Advantageously but not necessarily, the step of operating the welding device 1 takes place by applying an external force (for example manually or as explained above by means of automatic actuation means) on the welding device 1 for operating the pushing means 8 of the welding device 1 so as to cause the welding element 5 to move from the first position to the second position (i.e. from the configuration I to the configuration 0).

According to a further aspect of the present invention, advantageously but not limitedly, a weld W, W' of a plurality of layers 2 of metal material at least partially overlapped is provided, made according to the method described above or by means of the welding device 1. Said weld W, W', comprises a plurality of layers 2 of metal material (advantageously such as the ones described above) at least partially overlapped which are welded (i.e. joined) together according to the method described above or by means of the welding device 1.

In the non-limiting embodiment of Figure 14, the detail of an overlapping zone 40 is illustrated, in which there is a weld W, W' made according to the method described above or by means of the welding device 1. In particular, such weld W, W' comprises a depression in the area of the contact zone 10.

Advantageously but not necessarily, the overall thickness of the layers 2 of metal material outside of the contact zone is greater than the overall thickness of the plastically deformed layers 2 of metal material in the area of the contact zone 10.

In the non-limiting embodiment of Figure 14, the layers 2 ¹ , 2 ¹¹ , 2 ¹¹¹ , 2 ^IV welded in the area of the contact zone 10 have a variable thickness, in particular decreasing from the more external layer 2 ^IV , i.e. the one in the area of the outer surface 25 of the layers 2.

According to a further aspect of the present invention, a power storage device 3 is provided.

Specifically but not exclusively, the invention can be applied for the production of power storage devices 3, such as for example lithium (ion or polymer) batteries (such as the one schematically illustrated in Figure 15) or capacitors (such as the one schematically illustrated in Figure 16).

In particular, a power storage device 3 comprises at least one power storage unit A (or a battery module A') (in particular, an electrochemical cell, in the case of lithium batteries, or a capacitive unit, in the case of capacitors) which in turn comprises at least two electrode (each provided with at least one terminal tab B) layers E (with opposite polarities) and at least two separator layers S, which at least partly face and are in contact with at least one of the at least two electrode layers E, of which at least one is interposed between the at least two electrodes.

Advantageously but not necessarily, the power storage device 3 comprises a weld according to what is described in the foregoing.

In some non-limiting cases, such as the one illustrated in Figure 15, the power storage unit A comprises a plurality of electrode layers E (in white - anode and cathode) and of separator layers S placed so as to be alternated with one another. In particular, each electrode E comprises at least one electrode tab B coming out of a main body of the unit A on the same side (as in Figure 15) or on opposite sides. More precisely, the unit A defines a stack composed so that all the tabs belonging to the same electrode (anode or cathode), are aligned and overlapped with one another so that they can be welded to one another.

Specifically, not limitedly, the electrode layers E are joined to one another by welding electrode tabs B, advantageously by applying the welding method for welding a plurality of layers 2 of metal material described above, and even more advantageously by using the welding device 1 described above.

In particular, the electrode tabs B are welded to one another by means of a weld W, also known as pre-weld.

Advantageously but not necessarily, the (at least one) electrode tab B is welded (also) to a terminal metal element T (that acts as positive or negative terminal electric pole of the unit A). In particular, the electrode tabs B are welded to the terminal metal element T by means of a weld W'.

Advantageously but not limitedly, also such weld is made by applying the welding method for welding a plurality of layers 2 of metal material described above, and even more advantageously by using the welding device 1 described above.

In other non-limiting cases, such as the one illustrated in Figure 16, the power storage unit A comprises a pair of electrode layers E (anode and cathode) and a pair of separator layers S placed so as to be alternated with one another. In particular, each electrode E comprises at least one electrode tab B coming out of a main body of the unit A, on the same side or on opposite sides (as in Figure 16). More precisely, the unit A defines a wound element.

Advantageously but not necessarily, the (at least one) electrode tab B is welded (also) to a terminal metal element T (that acts as positive or negative terminal electric pole of the unit A). In particular, the electrode tabs B are welded to the terminal metal element T by means of a weld

W'.

In some non-limiting cases, the terminal metal element T is a suitable metal bar. In other non-limiting cases, the terminal metal element T is obtained on a (metal) support structure 27 of the storage unit A (in particular of the capacitor) .

Advantageously but not limitedly, also such weld is made by applying the welding method for welding a plurality of layers 2 of metal material described above, and even more advantageously by using the welding device 1 described above.

According to a further aspect of the present invention, an assembling method for assembling a power storage device 3 is further provided, in particular a prismatic or cylindrical (more precisely a lithium ion) battery, or a capacitor.

Advantageously, as illustrated in the non-limiting embodiment of Figure 17, the assembling method comprises a feeding step, during which the abovementioned electrode layers E are fed (on a conveying plane P), each provided with a terminal tab B and the above-described separator layers S.

Advantageously, the method further comprises a placement step, during which such electrode layers E and separator layers S are disposed so as to at least partly face one another and be alternated with one another in order to form a power storage unit A.

In some non-limiting cases, the placement step entails stacking said electrode layers E and said separator layers S on top of one another alternated with one another. In fact, the apparatus 100 comprises a stacking device 101 configured to overlap, alternated with one another, the electrodes E and the separators S in order to form the power storage unit A (in particular a stack).

In other non-limiting cases, the placement step entails winding together, beside one another and alternated, said electrode layers E with said separator layers S (to form, for example, a cylindrical cell/battery or capacitor).

Advantageously but not necessarily, the method comprises a first joining step, during which at least one terminal tab B of the power storage unit A is joined (welded by means of the abovementioned weld W, W') to at least one further metal layer B (thus joining the terminal tabs B to one another in a so-called "pre-weld") or 31 (thus forming the battery module A' in Figure 17).

In particular, the first joining step entails an application sub-step, during which an impulsive welding action (i.e. a welding action according to what is described above by means of the application of an impulsive force F) is applied in the overlapping zone 40, where the terminal tab B and the further metal element B, 31 overlap, by means of a welding tip 7, which is operated following the application of an impulsive force F.

In some non-limiting cases, during the feeding step a plurality of electrode layers E is fed, each provided with a terminal tab B and a plurality of separator layers S. During the first joining step, in particular in the area of a station on the conveying plane P comprising a welding device 1, the terminal tabs B of said electrode layers E having a same polarity are welded to one another by means of said impulsive welding action (forming the weld W of Figure 17, mentioned above as "pre-weld").

Advantageously but not necessarily, in such cases, the method comprises a second joining step, during which the terminal tabs B welded to one another are in turn welded to a terminal metal element T by means of said further impulsive welding action (forming the weld W' of Figure 17).

In further (additional or alternative) non-limiting cases, the power storage unit A, or the battery module A', is joined (in particular, electrically connected, i.e. welded by means of the weld W') to the covering case 27. In particular, such first and second joining steps can be both or only one of the two can be performed by means of the welding method for welding a plurality of layers 2 of metal material described above, and even more advantageously by using the welding device 1 described above.

Specifically, advantageously but not necessarily, the first joining step and/or the second joining step entail an application sub-step, during which a welding action is applied according to the welding method for welding a plurality of layers 2 of metal material described above, and even more advantageously by using the welding device 1 described above.

With particular reference to Figure 15, according to some advantageous but non-limiting embodiments, the power storage device 3 is a lithium battery. In this case, advantageously but not limitedly, the power storage device 3 comprising a battery module (corresponding to the module A') which, in turn, comprises (in particular is composed of) an assembly of electrochemical cells (which form the storage unit A) each provided with two terminals B, in particular with two protruding terminal tabs B intended to form, in the power storage device 3, an electrical connection.

Each electrochemical cell can have, in particular, a flat shape. Each cell can comprise, in particular, at least one electrode E (for example an electrode sheet) and/or at least one separator S (for example a separator sheet, known per se and not further described herein) which at least partly overlap. The cell can comprise one or more separators and one or more electrodes. In particular, the cell can comprise two electrode layers E separated by at least one separator layer S. Each electrode layer E can comprise a cathode or an anode. In this case, advantageously, the cells are stacked on top of one another and the respective terminal tabs B are welded to one another (as schematically illustrated in Figure 15) by applying the welding method for welding a plurality of layers 2 of metal material described above, and even more advantageously by using the welding device 1 described above.

In other words, in this case, the abovementioned assembling method entails feeding a plurality of electrode layers E each provided with two terminal tabs B and a plurality of separator layers S, and the placement step entails placing them alternated with one another and stacked on top of one another in order to obtain a plurality of electrochemical cells (which form the unit A of Figure 17), which are then electrically connected to one another in assemblies, by welding the terminal tabs B to one another, by means of the welding method for welding a plurality of layers 2 of metal material described above, and even more advantageously by using the welding device 1 described above (forming the module A' of Figure 17).

According to a further aspect of the present invention, an assembling apparatus for assembling a power storage device 3 of this type, in particular a lithium battery, is proposed.

Advantageously, the assembling apparatus comprises: a frame; a feeding device configured to feed a plurality of electrochemical cells (advantageously made as described above), each provided with two respective terminal tabs B; a stacking device configured to stack the electrochemical cells on top of one another and a welding device 1, advantageously of the type described above, for welding the electrochemical cells to one another, in particular the terminal tabs B of the electrochemical cells to one another, so as to form at least one battery module A' (for example such as the one illustrated in Figure 15).

With particular reference to Figure 16, according to an alternative embodiment, the power storage device 3 is a capacitor .

In this case, advantageously but not limitedly, the battery module A' and the power storage unit A coincide and are composed of a capacitive unit comprising (in particular, composed of) an electrode layer E (cathode and/or anode) provided with two terminal tabs B, advantageously in the shape of a band of electrode material E, and a separator layer S, advantageously in the shape of a band of separator material S, wound beside one another, in particular alternated with one another, around a core (not visible in Figure 16) with an oblong shape, so that from said spiral the two terminal tabs B protrude, which are then joined to a support structure 27 (i.e. a covering case - can). Advantageously, the terminal tabs B can be welded to the support structure 27 by means of the welding method for welding a plurality of layers 2 of metal material described above, and even more advantageously by using the welding device 1 described above.

In this case, the assembling method for assembling a power storage device 3 described above, and more in particular the placement step of such method, entails a winding sub-step during which the band of electrode material E and the separator band S are wound beside one another, in particular alternated with one another, around the abovementioned core with an oblong shape, so that from said spiral the two terminal tabs B protrude, which are then joined to a support structure (as schematically shown in Figure 16).

According to a further aspect of the present invention, an assembling apparatus for assembling a power storage device 3 of this type, in particular a capacitor, is further provided. The assembling apparatus comprises: a first feeding device for feeding at least one electrode band E provided with two terminal tabs B; a second feeding device for feeding at least one separator band S; a winding device comprising a support element for supporting the abovementioned core with an oblong shape and at least one holding member, which can rotate around the support element and is configured to grab the electrode band E and the separator band S, which face one another and are in contact with one another, and to rotate around the support element so as to obtain a plurality of winding loops around the core with an oblong shape in order to generate a power storage unit A; a closing device configured to wrap said power storage unit A with the above-described support structure 27; and a welding device 1 disposed to weld the power storage unit A to the case; in particular, the terminal tabs B to the covering case 27 advantageously by means of the welding method for welding a plurality of layers 2 of metal material described above, and even more advantageously by using the welding device 1 described above.

The welding method and the welding device 1 described above have numerous advantages, among which the following are mentioned. The welding method and the welding device 1 for welding a plurality of layers 2 of metal material described above allow obtaining in a simple and quick manner an efficient cold weld between the layers 2 of metal material, which subjected to the welding action described above will tend to deform and penetrate one another (as schematically illustrated in Figure 14) firmly joining to one another.

Furthermore, the welding method and the welding device

1 described above have a much simpler embodiment and maintenance and they are much less expensive than the known welding devices and methods for welding a plurality of layers

2 of metal material.

The use of such welding method and of such welding device during the assembling of power storage devices 3, as explained above, allows reducing the manufacturing costs of the power storage devices, the performance being the same.

Advantageously but not necessarily, the power storage device 3 comprises at least one battery module A', provided with a support structure and with a plurality of electrochemical cells electrically connected to one another and to the support structure, each provided with an electrode layer E and a separator layer S at least partly facing and in contact with the electrode layer E and two terminal tabs B; in which the terminal tabs B are welded to the support structure by means of the method for welding a plurality of layers 2 of metal material described in the foregoing.