Patent Application
20250141069
The present invention relates to a method to produce an energy storage battery, that is, more generally, to an energy storage device.
The meaning of “to produce a battery” also refers to the assembly thereof. The present invention finds advantageous application to the production of a lithium-ion cylindrical battery, to which the following description will explicitly refer without thereby losing generality.
Commercial lithium-ion batteries are assembled in three different geometries: cylindrical, prismatic and bag-like.
The cylindrical batteries are formed by a cylindrical metal container with inside a single electrochemical cell of the “jelly-roll” or “Swiss-roll” type, formed by an anode, separator and cathode which are wound together around a central pin.
In particular, the cylindrical container is at first open on one side (i.e. it has the shape of a cup having a first end which is closed and a second end which is open) to allow the insertion of the wound electrochemical cell and of the electrolyte that impregnates the wound electrochemical cell; once the formation of the battery has been completed (i.e. once all the components have been arranged inside the cylindrical container), the open end of the cylindrical container is closed making a sealed closure.
In particular, in order to close the open end of a cylindrical container, a circular lid (possibly coupled to an annular gasket) is used which is connected to the cylindrical container, deforming against the lid an upper rim of the cylindrical container itself.
Before inserting the electrochemical cell inside the cylindrical container, at the two opposite ends of the electrochemical cell two electrical collectors are coupled (which in the particular case of the cylindrical batteries are disc-shaped) at the cathode (in which an electrical collector made of aluminium is used) and at the anode (in which an electrical collector made of copper is used). Each electrical collector is pressed against the corresponding end of the electrochemical cell and is welded to connection lamellae of the conductive strips (made of aluminium and copper) which, wound together (with the interposition of insulating separators), constitute the electrochemical cell. The one first wall of the cylindrical container has centrally a through hole which is engaged by a rivet (also called rivet) made of aluminium having a head that is arranged on the outside of the cylindrical container and constitutes the positive pole of the cylindrical battery. In particular, the rivet is inserted through the through hole of the first wall of the cylindrical container with the interposition of a series of plastic gaskets that isolate the rivet from the cylindrical container and then the headless end of the rivet is bucked (i.e. plastically deformed) to form a counter-head.
When the electrochemical cell provided with the two electrical collectors is inserted inside the cylindrical container, the electrical cathode collector (made of aluminium) is pressed against the counter-head of the rivet (previously coupled to the first wall of the cylindrical container) and then welded to the counter-head of the rivet in order to make a stable connection of great extension (the greater the contact area, the lower the electrical resistance at the contact area).
Typically, the weld between the cathodic electrical collector and the counter-head of the rivet is made by using the central hole (with reduced dimensions) of the electrochemical cell to apply heat to the cathodic electrical collector and therefore melt the metal (aluminium) locally; in fact, generally it is not possible to apply heat in the zone between the cathodic electrical collector and the counter-head of the rivet passing from the first wall of the cylindrical container as, by doing so, the plastic gaskets that isolate the rivet from the cylindrical container would be damaged due to excess heating.
The Applicant has felt the need to provide a method to produce an energy storage battery that permits to operate at a high production speed (measured as batteries produced per unit time) while at the same time guaranteeing the achievement of a high-quality end product.
The Applicant has first of all observed that the geometric proportions between a conventional electrochemical cell and the relative central hole make it uneasy to perform the weld through the central hole itself, especially at high production speeds. In particular, it is complex to apply heat for example to the bottom of this hole (i.e. at the cathodic electrical collector that is located at the end of the central hole of the electrochemical cell); as a result, the welding operation requires high precision and is particularly slow, hence it requires a very long execution time and does not allow operating at a high production speed (measured as cylindrical batteries produced per unit time).
The Applicant has also observed that any metal splashes generated during welding, (which by cooling down form small metal debris), remain trapped inside the hole of the jelly roll, or in any case inside the battery, being therefore able to “contaminate” the electrochemical cell, giving rise to small local short circuits, which over time can impair the performance thereof or even cause it to degrade prematurely.
The Applicant has finally observed that the conventional weld through the hole of the jelly roll is difficult to inspect once it has been performed, making the subsequent quality controls difficult, or very slow, both on the line and on the finished product.
The Applicant has therefore understood that an access, even temporary, from the outside of the container of the battery during welding allows to eliminate the presence of metal debris from the inside of the container, also facilitates the insertion of the welding head at high speed which does not find obstacles in its path, and it therefore allows operating at high speed while maintaining the quality of the end product.
The Applicant has also noted that said access from the outside to the conductor(s) to be welded can also be guaranteed without necessarily exposing/making visible from the outside the conductor(s) to be welded, by using the so-called “transparent” weld.
In other words, the conductor to be welded, although not visible from the outside, is advantageously accessible from the outside to receive the heat/energy necessary for its welding, which can therefore be delivered from the outside of the container.
Thus, in accordance with the present invention there is provided a method to produce a battery for energy storage, comprising:
Preferably, the access comprises a first through hole made in the first wall.
Preferably, the access comprises a second hole made in the outer body and arranged at least partially aligned with the first hole when the outer body is arranged on the outer surface of the first wall; and the weld is made at the second hole.
Preferably, the weld is made from the outside of the container through the second hole and operating from the opposite side of the first wall relative to the electrochemical cell.
Preferably, the weld is at least partially arranged inside the second hole.
Preferably, the second hole is coaxial to the first hole when the outer body is arranged on the outer surface of the first wall.
In embodiments, the second hole of the outer body is a through hole.
In embodiments, the second hole of the outer body is blind and constitutes a recess into which a protrusion of the electrical collector is inserted.
In embodiments, the electrical collector comprises a protrusion which is inserted into the first hole of the first wall and into the second hole of the outer body, and the weld is made between the outer body and the protrusion of the electrical collector.
In embodiments, after having inserted the protrusion into the second hole, an outer surface of the protrusion is coplanar to an outer surface of the outer body.
In embodiments, an outer surface of the protrusion, after having inserted the protrusion into the second hole, at first projects from an outer surface of the outer body; the second central hole of the outer body has an outer flaring; and the method further comprises the step of at least partially bucking the outer surface of the protrusion against the outer body so as to make the outer surface of the protrusion coplanar to the outer surface of the outer body.
In embodiments, a rivet is provided which engages the first hole of the first wall and comprises a head which is arranged on the outside of the container and constitutes the outer body, and a counter-head, which is arranged inside the container.
In embodiments, the rivet has, at first, only the head, whereas the counter-head is obtained after having inserted the rivet through the first hole of the first wall by bucking the rivet against an inner surface of the first wall.
Preferably, the outer body only consists of a connection element completely arranged on the outside of the container.
Preferably, the protrusion of the electrical collector is surrounded, at the base, by a fixing element having the function of compressing an insulating gasket against an inner surface of the first wall.
In embodiments, the electrical collector has no protrusion and the weld is made inside the second hole of the outer body.
Preferably, the method comprises the further steps of:
In embodiments, the weld is made from the outside of the container through the outer body, passing through the outer body from side to side, and operating from the opposite side of the electrochemical cell relative to the first wall.
The appended claims describe embodiments of the present invention forming an integral part thereof.
It is also clear that the product obtained by the method according to the present invention, in the embodiment that provides for a weld operated “in transparency”, will show this type of weld among its characteristics.
The present invention will now be described with reference to the enclosed drawings, showing some non-limiting embodiments thereof, wherein:
In
The container 3 has a side wall 6 cylindrical in shape, a first end 7 which is closed since the beginning by a first wall 8 (that is, by a lower part) which is seamlessly connected to the side wall 6, and a second end 9 which is opposite to the first end 7, is at first open to permit the insertion of the electrochemical cell 2 into the container 3 and is subsequently closed and sealed. In particular, at the second end 9 of the container 3 a lid 10 is arranged (which in the case of the cylindrical battery is circular) which closes the second end 9 (i.e. it constitutes an upper base of the container 3).
Before inserting the electrochemical cell 2 inside the container 3, at the two opposite ends of the electrochemical cell 2 two electrical collectors 11 and 12 are coupled (which in the specific case of the cylindrical battery are disc-shaped) at the cathode (in which an electrical aluminium collector 11 is used) and at the anode (in which an electrical copper collector 12 is used). Each terminal collector 11 or 12 constitutes an electrical collector (cathodic for the electrical collector 11 made of aluminium and anodic for the electrical collector 12 made of copper) which collects the electric currents that are generated inside the electrochemical cell 2 in order to permit to such electric currents to circulate on the outside of the electrochemical cell 2. Each terminal collector 11 or 12 is pressed against the corresponding end of the electrochemical cell 2 and is welded to connection lamellae of the conductive strips (made of aluminium and copper) which, wound together (with the interposition of insulating separators) constitute the electrochemical cell 2.
The battery 1 comprises a negative electrical pole 13 which is arranged at the second end 9 and is made in the lid 10 and a positive electrical pole 14 which is arranged (with adequate electrical insulation as will be described below) at the first wall 8.
In general, according to the present invention, the collector 11 is placed in communication with the outside of the container 3 by means of at least one access 15, 22, 26.
As illustrated in
In particular, the rivet 16 is inserted through the hole 15 of the first wall 8 of the container 3 with the interposition of a series of plastic insulating gaskets 18, 19 and 20 that isolate the rivet 16 from the container 3 (in particular from the first wall 8 of the container 3) and then the headless end of the rivet 16 is bucked (i.e. plastically deformed) to form a counter-head 21. In other words, the rivet 16 engages the through hole 15 of the first wall 8 of the container 3 and comprises: a head 17 which is arranged on the outside of the first wall 8 of the container 3 and constitutes the positive electrical pole 14 of the battery 1; and a counter-head 21 which is arranged inside the first wall 8 of the container 3 and is therefore facing the cathodic electrical collector 11.
The insulating gasket 18 has a cylindrical shape and internally lines the through hole 15 of the first wall 8 of the container 3, so as to isolate the rivet 16 from the walls of the hole 15.
The insulating gasket 19 has a disc shape and is interposed between the head 17 of the rivet 16 and the first wall 8 of the container 3 in order to isolate the rivet 16 from the outer surface of the first wall 8.
The insulating gasket 20 has a disc shape and is interposed between the counter-head 21 of the rivet 16 and the first wall 8 of the container 3 in order to isolate the rivet 16 from the inner surface of the first wall 8. In other words, the two insulating gaskets 19 and 20 are arranged on the opposite sides of the first wall 8 of the container 3.
The rivet 16 has centrally the hole 22 which in the illustrated example is a through hole and is cylindrical in shape and which passes through the rivet 16 from side to side, and the electrical collector 11 has a protrusion 23 (which in the illustrated example is arranged centrally and is cylindrical in shape) which rises cantilevered from the electrical collector 11; the hole 22 of the rivet 16 is engaged by the protrusion 23 of the electrical collector 11. Furthermore, the hole 22 is arranged at least partially aligned (and preferably coaxial) with the hole 15 when the head 17 is arranged on the outer surface of the first wall 8. In general, the protrusion fits into the access 15, 22, 25. In this case, the access also comprises the hole 22.
The hole 22 could also be a non-through hole and therefore constitute a recess (seat, cavity, housing). That is, the rivet 16 could as an alternative to the through hole 22 comprise a non-through hole 22 which constitutes a recess (as illustrated in
Preferably, the hole 22 of the rivet 16 houses the protrusion 23 of the electrical collector 11 with a reduced clearance, i.e. minimum clearance (a certain clearance is certainly necessary to allow the protrusion 23 of the electrical collector 11 to be fitted into the hole 22 of the rivet 16, but such clearance must be small in order to make it easier to subsequently realize the joining between the protrusion 23 and the hole 22). Between the rivet 16 and the protrusion 23 of the electrical collector 11 there is a preferably annular weld 24 (i.e. forming a closed ring as illustrated in
The term weld generally refers to the result of the jointing/joining/fixing of elements together, regardless of the technique with which the operation takes place. For example, the jointing/joining/fixing can be by heat and/or mechanical pressure and/or vibrations; or it can result from a crimping or riveting of the parts to be joined. In embodiments, the weld can be a melting between elements (with or without filler material), for example a laser weld (to which reference will be made below by way of example only), an ultrasonic weld.
With reference to
As illustrated in
As illustrated in
As illustrated in
As illustrated in
Subsequently, as illustrated in
It is important to note that the weld 24 (which in this case is annular) can be made from the outside of the container 3 and therefore without any kind of obstacle; consequently, the execution of the weld 24 can be completed quickly while still ensuring the achievement of a high overall quality.
In essence, with the method according to the invention, the electrical collector 11 is (at least temporarily) placed in communication with the outside of the container (through the hole 15) and the weld 24 can thus be made from the outside of the container 3.
In the embodiment illustrated in
According to a different embodiment illustrated in
In this case, the access comprises the hole 26.
Between the connection element 25 and the protrusion 23 of the electrical collector 11 there is a weld 24 which makes both a stable mechanical connection between the connection element 25 and the protrusion 23 of the electrical collector 11 and a low-resistance electrical connection between the connection element 25 and the protrusion 23 of the electrical collector 11. In this embodiment, the positive electrical pole 14 of the battery 1 consists of the connection element 25 that replaces the head 17 of the rivet 16.
In the embodiment illustrated in
In the embodiment illustrated in
According to the alternative embodiment illustrated in
In the embodiments illustrated in
According to a different embodiment illustrated in
In this circumstance, the weld 24 is made from the outside of the container 3 in “transparency”, that is, through the outer connection body 25, and operating from the opposite side of the electrochemical cell 2 relative to the wall 8. This weld 24 is made from the outside in “transparency” since the heat necessary to melt the metal of the upper part of the protrusion 23 of the electrical collector 11 is not supplied directly to the protrusion 23 of the electrical collector 11 but passes through the connection element 25 (which is sufficiently thin) to reach the upper part of the protrusion 23 of the electrical collector 11.
The thickness of the connection element 25 is preferably comprised between 0.2 mm and 0.6 mm.
The weld 24 is preferably operated with a laser.
According to a different embodiment illustrated in
In other words, as illustrated in
In the embodiment illustrated in
Preferably, in both cases the thickness is comprised between 0.2 mm and 0.6 mm.
Similarly, as illustrated in
As highlighted above, in the embodiments illustrated in
In the embodiments illustrated in the accompanying figures, the battery 1 has a cylindrical shape and therefore consequently at least a part of the components of the battery 1 (e.g., the electrochemical cell 2 and the container 3) have a cylindrical shape (or in any case a shape with cylindrical symmetry); according to other embodiments not illustrated, the battery 1 has a shape other than the cylindrical shape (e.g., a parallelepiped shape) and therefore at least a part of the components of the battery 1 (e.g., the electrochemical cell 2 and the container 3) have a shape other than the cylindrical shape (e.g., a parallelepiped shape). That is, the electrochemical cell 2 and the container 3 could have a prismatic shape with a circular base (and therefore be cylindrical-shaped) or they could have a prismatic shape with a rectangular or square base (and therefore be parallelepipeds).
The head 17 which is arranged on the outside of the container 3 (i.e. on the outside of the first wall 8 of the container 3) and constitutes the positive electrical pole 14 of the battery 1 may have a cylindrical shape (as illustrated in the accompanying figures) or also a shape other than the cylindrical shape (for example a parallelepiped shape).
In a further embodiment not illustrated, access to the electrical collector 11 to be welded takes place exclusively through the container 3 without affecting the outer body 17, 25. In this embodiment, the first wall 8 of the container 3 comprises the hole 15 for inserting the rivet 16 and a further through hole through which a protrusion 23 of the electrical collector 11 is inserted; the weld 24 is made (from the outside) between the head 17 and the protrusion 23 of the electrical collector 11.
The energy storage battery in accordance with the previous embodiment therefore comprises: an electrochemical cell 2; an electrical collector 11 which is coupled to one end of the electrochemical cell 2; a container 3 which has a first wall 8 having a first through hole 15 and houses, on the inside, the electrochemical cell 2 so that the electrical collector 11 is arranged close to the first wall 8; a rivet 16 inserted into the first hole 15; and a further through hole on the first wall 8 of the container 3 through which a protrusion 23 of the electrical collector 11 is inserted, wherein a weld 24 is made between the head 17 of the rivet 16 and the protrusion 23 of the electrical collector 11.
The embodiments described herein may be combined with each other without departing from the scope of protection of the present invention.
The production method and the battery 1 described above have numerous advantages.
Firstly, the production method and the battery 1 described above make it possible to operate at a high production speed (i.e. with a high number of cylindrical containers 3 produced in the unit of time) thanks to the fact that the annular weld 24 is made on the outside of the container 3 and therefore without any spatial constraint on the dimension and on the movement of the welding tools. This is possible by placing in (at least temporary) communication the electrical collector 11 with the outside of the container 3 (through the hole 15 and/or the hole 22/26) in order to be able to perform the weld 24 from the outside of the container 3.
Furthermore, the production method and the battery 1 described above make it possible to guarantee the achievement of a high quality of the end product (i.e. a reduced defectiveness); this result is obtained thanks to the fact that the weld 24 is not made inside the (i.e. from the inside of) the container 3, but is made outside the (i.e. from the outside of) the container 3; in this way, any metal debris that accidentally form while making the weld 24 do not enter inside the container 3 but remain on the outside of the container 3 and therefore cannot pollute the cylindrical electrochemical cell 2. In other words, while making the annular weld 24, splashes of molten metal can originate which, by cooling down, form small metal debris; however such small debris cannot enter the container 3 as the weld 24 is made outside the container 3. The absence of any metal debris generated by the weld 24 inside the container 3 permits to substantially reduce the defectiveness of the electrochemical cell 2, since these small metal debris, if any, could give rise to small local short circuits that over time can cause a premature degradation of the electrochemical cell 2.
Furthermore, the thickness of the electrical collector 11 can be limited (i.e. the thickness of the electrical collector 11 may not be increased) to the advantage of the reduction of the height of the battery 1 as the electrical collector 11 does not have to withstand the breakthrough that may occur while making the weld 24, because the weld 24 (in the embodiment illustrated in
The fact that the rivet 16 has the through hole 22 (or alternatively that the connection element 25 has the through hole 26) simplifies (speeds up) the insertion of the electrochemical cell 2 into the container 3, in that as the electrochemical cell 2 enters the container 3 the air present at the bottom of the container 3 that is compressed by the advancement of the electrochemical cell 2 can more effectively be vented through the through hole 22 of the rivet 16 rather than be vented through the hole 5 of the electrochemical cell 2 (as would necessarily be the case in the absence of the through hole 22 of the rivet 16).
Finally, the production method and the battery 1 described above are simple and inexpensive to implement as they do not require complex mechanical machining or the use of particular (non-standard) materials.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102022000001838 | Feb 2022 | IT | national |
| 102022000001841 | Feb 2022 | IT | national |
| 102022000001844 | Feb 2022 | IT | national |
| 102022000001847 | Feb 2022 | IT | national |
| 102022000010673 | May 2022 | IT | national |
This application is a U.S. National Stage Application of International Application No. PCT/IB2022/062605, filed Dec. 21, 2022, which claims the benefit of and priority to Italian Patent Application No. 102022000001838, filed Feb. 3, 2022, Italian Patent Application No. 102022000001841, filed Feb. 3, 2022, Italian Patent Application No. 102022000001844, filed Feb. 3, 2022, Italian Patent Application No. 102022000001847, filed Feb. 3, 2022, and Italian Patent Application No. 102022000010673, filed May 23, 2022 the disclosure of each is incorporated herein by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2022/062605 | 12/21/2022 | WO |
