Current collector for a lid assembly of a prismatic cell battery and method for assembling such current collector

Abstract

There is described a current collector (5) for a terminal group of a lid assembly (1) configured to fluid-tightly close an inner compartment (3) of a battery cell, the current collector (5) being configured to be electrically connected to an electrode of the battery cell for collecting electrical energy therefrom and transferring the electrical energy to a terminal (6) of said terminal group, the current collector (5) comprising a base body (5a) and a pin member (5b) fixed to the base body (5a) and protruding from a main wall (5c) of the base body (5a); the base body (5a) includes a recess (10) obtained on the main wall (5c), and the pin member (5b) comprises a main portion (12) for electrically coupling with the terminal (6) and a coupling portion (13) which engages and occupies the recess (10) to determine a rigid coupling of the pin member (5b) with the base body (5a).

Description

[0001] CURRENT COLLECTOR FOR A LID ASSEMBLY OF A PRISMATIC CELL

[0002] BATTERY AND METHOD FOR ASSEMBLING SUCH CURRENT COLLECTOR

[0003] TECHNICAL FIELD

[0004] The present invention relates to a current collector for a terminal group of a lid assembly for a battery cell , in particular a lid assembly for closing and sealing in a fluid-tight manner an inner compartment of such battery cell housing electrodes and electrolytic material .

[0005] In detail , the present invention will refer, without however losing on generality, to a lid assembly for a prismatic battery cell .

[0006] The present invention also relates to a method for assembling such current collector .

[0007] BACKGROUND ART

[0008] Battery cells are known, which are used as electrical energy accumulators .

[0009] In particular, so-called primary batteries are known, which cannot be easily recharged and are therefore destined to single-use , and so-called secondary batteries are known, which can be repeatedly charged after each cycle of usage .

[0010] Single-cell batteries of the secondary type are known which are used for various portable small-si zed electronic devices , such as cellular phones , watches , smartwatches , smart bands , etc .

[0011] Also batteries which include a plurality of cells connected in series or in parallel are known, for example as used in the automotive industry .

[0012] The present invention will refer to a battery cell for the use in a battery of a hybrid or full-electric vehicle , without however losing generality .

[0013] Secondary battery cells can be manufactured as various types , such as cylindrical or prismatic cells .

[0014] The present invention will refer to prismatic battery cells , without however losing generality .

[0015] A battery cell typically comprises a hollow casing, for example in the shape of a hollow parallelepiped and usually made of metallic material , generally open on at least one side ( for example on the top ) and a lid assembly for closing the casing .

[0016] The casing internally defines an inner compartment of the cell and houses the cell electrodes ( cathode and anode ) , which are provided for example in the form of sheets , and a separator material electrically interposed between the electrodes .

[0017] Within the compartment , the electrodes and the separator are immersed in an electrolytic material , usually liquid or gelatinous .

[0018] The lid assembly is coupled to the casing at an opening thereof for closing the inner compartment in a fluid-tight manner, thereby maintaining electrodes and separator in place and preventing the outflow of the electrolytic material .

[0019] The lid assembly essentially comprises :

[0020] - a base plate , typically made of metallic material such as aluminum, arranged to match and engage the opening of the casing for the closing thereof ;

[0021] - one current collector for each electrode , which is electrically connected to the relative electrode and is configured to collect the electric energy from such electrode and feed it from the inner compartment towards the outside environment ; and a terminal for each electrode , which is electrically connected with the respective collector for receiving the electric energy therefrom, and which is configured for receiving a connector of a consumer device to be powered by the battery cell .

[0022] The terminal is arranged on an outer side of the base plate , so as to be connected to the consumer device , and the collector is arranged, at least partially, on an inner side of the base plate ( i . e . the side facing the inner compartment ) , so as to be connected with the respective electrode .

[0023] A typical lid as sembly also comprises an insulator member for each terminal , which is interposed between the relative terminal and the base plate for electrically insulating the terminal from the base plate .

[0024] Thanks to the presence of the insulator member, a direct electric connection between each terminal and the base plate , which would be dangerous and detrimental to the correct functioning of the battery cell , is avoided .

[0025] In light of the above , the lid assembly includes two terminal groups , each comprising one terminal , one collector, one insulator member .

[0026] During assembly of the battery cell , the components of each terminal group are stacked, compressed and welded together .

[0027] Typically, each current collector comprises a base body ( generally plate-shaped) and a pin member protruding ( orthogonally) form the base body .

[0028] The base body is placed in contact with the respective electrode , while the respective terminal is fitted to the pin member, which passes through a respective hole obtained in the base plate .

[0029] Each current collector is usually produced by rigidly coupling the pin member to the base body .

[0030] According to a common constructional implementation, the cathode terminal group ( i . e . the positive terminal group ) includes a current collector made entirely in aluminum .

[0031] Hence , the cathode current collector is usually produced by welding the aluminum pin member with the aluminum base body .

[0032] Due to known constructional constraints related to galvanic coupling, the anode terminal group ( i . e . the negative terminal group ) includes a current collector made of aluminum and copper .

[0033] For example , the pin member is made of aluminum and the base body is made of copper .

[0034] As it is well known, a normal welding between aluminum and copper is rather complicated and unstable , due to the natural welding incompatibility of these two materials . In fact , the phases produced by the two materials during the welding process are quite fragile , resulting in a weak welding seam subj ect to cracks and wear .

[0035] Hence , according to the known constructional solutions , the pin member and the base body of the anode current collectors are j oined together by means of friction welding, also known as FWR .

[0036] The Applicant has observed that the friction welding introduces some drawbacks and therefore the production of the anode current collector is still open to further improvements . In particular, the friction welding requires a further machining for removing the excess metal which results from the friction, thereby leading to increased production time and costs .

[0037] Moreover, the friction welding can be subj ect to imprecisions , also considering that the pin member is a rather small component .

[0038] DISCLOSURE OF INVENTION

[0039] It is therefore an obj ect of the present invention to provide a current collector for a terminal group of a lid assembly for a battery cell which is designed to overcome at least one of the above-mentioned drawbacks in a straightforward and low-cost manner .

[0040] This obj ect is achieved by a current collector as claimed in the appended independent claim 1 . Preferred embodiments of the present invention are laid down in the respective appended dependent claims .

[0041] It is a further obj ect of the present invention to provide a method for assembling a current collector for a terminal group of a lid assembly for a battery cell which is designed to overcome at least one of the above- mentioned drawbacks in a straightforward and low-cost manner .

[0042] This obj ect is achieved by a method for assembling a current collector as claimed in the appended independent claim 11 . Preferred embodiments of the present invention are laid down in the respective appended dependent claims .

[0043] BRIEF DESCRIPTION OF THE DRAWINGS

[0044] A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings , in which :

[0045] Figure 1 is a partially sectioned exploded view, with parts removed for clarity, of a lid assembly for a battery cell according to the present invention; and

[0046] Figures 2a to 2e show a current collector during distinct and successive assembling steps thereof .

[0047] BEST MODE FOR CARRYING OUT THE INVENTION

[0048] With reference to Figure 1 , number 1 indicates as a whole a lid assembly for a battery cell .

[0049] In particular, the battery cell comprises a hollow prismatic casing 2 which internally defines an inner compartment 3 with an opening 3a to access inner compartment 3 .

[0050] The battery cell further comprises electrodes ( cathode and anode , not shown) , which are housed in inner compartment 3 together with a separator material (not shown) . The electrodes and the separator are to be immersed, once the lid assembly 1 is finally assembled and coupled to casing 2 , in an electrolytic material (not shown) or electrolyte .

[0051] During assembly of the battery cell , the electrodes and the separator material are inserted into inner compartment 3 from opening 3a .

[0052] Accordingly, lid assembly 1 is configured to be coupled with casing 2 at opening 3a for f luid-tightly closing inner compartment 3 , as required during the normal use of the battery cell .

[0053] Hence , the battery cell comprises casing 2 , with the electrodes , the separator and the electrolytic material housed therein, and lid assembly 1 .

[0054] The present invention will refer to a prismatic battery cell , without however losing generality .

[0055] According to the embodiment shown, casing 2 has a parallelepiped shape . However, casing 2 may have any prismatic shape , such as cubic, triangular-based, etc .

[0056] In one embodiment , casing 2 may be cylindrical . Hence , in this case lid assembly may be round-shaped .

[0057] The present invention will refer to a battery cell for use in the automotive industry, for example in a battery module of a hybrid or full-electric vehicle , without however losing generality .

[0058] As shown in Figure 1 , lid assembly 1 essentially comprises : a base plate 4 , made of metallic material , preferably aluminum, configured to be coupled to casing 2 for closing opening 3a, namely arranged to match the shape of , and engage , opening 3a for closing inner compartment 3 ; at least one , and in particular two current collectors 5 each electrically connectable to the respective electrode of the battery cell for col lecting electrical energy therefrom and trans ferring it from inner compartment 3 outwards ; and

[0059] - at least one , and in particular two terminals 6 , each electrically coupled with one respective collector 5 for receiving the electrical energy therefrom, and each configured to receive a respective connector (not shown) of a consumer device (not shown) which is to be powered by the battery cell .

[0060] Each terminal 6 is configured to be electrically connected to one respective electrode , namely one terminal 6 is connectable with the anode and the other terminal 6 is connectable with the cathode .

[0061] In particular, the terminal 6 is arranged on an outer side of the base plate 4 , so as to be connected to the consumer device , and the collector 5 is arranged, at least partially, on an inner side of the base plate 4 ( i . e . the side facing the inner compartment ) , so as to be connected with the respective electrode .

[0062] Lid assembly 1 conveniently further comprise at least one , and in particular two insulator members 7 , each interposed between one respective terminal 6 and the base plate 4 for electrically insulating such terminal 6 from base plate 4 .

[0063] In detail , insulator members 7 are made of a plastic material , preferably rigid, which is electrically insulating .

[0064] Thanks to the presence of the insulator member 7 , a direct electric connection between each terminal 6 and the base plate 4 , which would be dangerous and detrimental to the correct functioning of the battery cell , is avoided .

[0065] In light of the above , lid assembly 1 comprises a pair of terminal groups , namely an anode terminal group and a cathode terminal group, each terminal group including one collector 5 , one terminal 6 and one insulator member 7 , and each having a central axis X .

[0066] For each terminal group, base plate 4 , terminal 6 , collector 5 and insulator member 7 are axially stacked relative to the respective axis X, with terminal 6 and part of collector 5 arranged on opposite ( axial ) sides of base plate 4 .

[0067] Each collector 5 comprises a base body 5a and a pin member 5b fixed to the base body 5a ( according to a manner better described below) and protruding from a main wall 5c of the base body 5a . According to the preferred embodiment shown, the base body 5a is plate-shaped .

[0068] For each terminal group, base plate 4 has a through hole 4a engaged by the pin member 5b of the respective collector 5 , which then protrudes on the opposite side of base plate 4 , in order to engage terminal 6 , thereby establishing the electrical connection between collector 5 and terminal 6 .

[0069] Conveniently, lid assembly 1 further comprises a stop frame 11 made of an electrically insulating material ( such as rigid plastic ) , the function of which is known per se and not described in detail .

[0070] As visible in Figure 1 , lid assembly may further comprise an electrolyte inj ection hole 12 obtained in base plate 4 and configured for allowing the inj ection of the electrolytic material in inner compartment 3 and / or a degassing during operation of the battery cell , according to a manner known and not described in detail .

[0071] In use , the inj ection hole 12 is sealed by a closure assembly 8 known per se and not described in detail .

[0072] Referring now to Figures 2a to 2e , for the sake of brevity reference will be made in the following to one single current collector 5 .

[0073] However, the structural and functional features described therefor are equally applicable to the other current collector 5 of lid assembly 1 .

[0074] In one embodiment , the pin member 5b is made of a first metallic material , preferably including aluminum, and the base body 5a is made of a second metallic material which is di f ferent from the first metallic material and, preferably includes copper .

[0075] Hence , as said in the introductory portion of the present disclosure , a normal welding between aluminum and copper is rather complicated and unstable , due to the natural welding incompatibility of these two materials .

[0076] According to an aspect of the present disclosure , the base body 5a includes a recess 10 obtained on the main wall 5c, and the pin member 5b comprises a main portion 12 for electrically coupling with the terminal 6 and a coupling portion 13 which engages and occupies the recess 10 to determine a rigid coupling of the pin member 5b with the base body 5a .

[0077] In detail , the recess 10 is defined by a blind slot or notch or cavity obtained in main wall 5c .

[0078] As visible in Figures 2a to 2c, pin member 5b has a central axis A and includes a first axial end 14 , at which the main portion 12 is located, and a second axial end 15 opposite the first axial end 14 and at which the coupling portion 13 is located .

[0079] According to a further aspect of the present disclosure, the current collector 5 is configured such that the coupling portion 13 is deformable once (and in particular only once) from:

[0080] - an initial undeformed configuration (Figures 2a- 2b) , whereby the coupling portion 13 defines, in a disassembled condition of the current collector 5 in which the pin member 5b is disjoined from the base body 5a, an overmaterial or extramaterial portion of the pin member 5b (i.e. an excess material portion) extending from the main portion 12, to

[0081] - a final deformed configuration (Figures 2d-2e) , whereby the coupling portion 13 engages and fills said recess 10 for defining an assembled condition of the current collector 5, in which the pin member 5b is rigidly joined to the base body 5a.

[0082] Conveniently, the coupling portion 13 completely fills the recess 20 for determining said rigid coupling.

[0083] In this way, a more stable connection between pin member 5b and base body 5a is established.

[0084] Advantageously, the coupling portion 13 has a size larger than the size of the main portion 12, relative to a direction transversal to axis A.

[0085] In particular, the coupling portion 13 has a radial size larger than the radial size of the main portion 12.

[0086] More in particular, coupling portion 13 has a peripheral edge 16 which is arranged in a position radially more external than the main portion 12 , relative to axis A.

[0087] In this way, coupling portion 13 can be easily processed from its initial configuration to its final configuration by a deforming device 17 ( for example a deforming bushing) without interfering with the main portion 12 , as better described below in relation to the method for assembling the current collector 5 according to the present invention .

[0088] More precisely, the coupling portion 13 has , in the undeformed condition thereof , a shape axially tapering from the second axial end 15 towards the first axial end 14 .

[0089] In detail , the coupling portion 13 has a frustum- conical shape , as visible in Figure 2a .

[0090] In greater detail , peripheral edge 16 is inclined with respect to axis A, in such initial undeformed condition .

[0091] This conformation of coupling portion 13 eases the deformation thereof , since the tapered shape def ines an invitation for the bushing 17 and improves the centering thereof relative to axis A.

[0092] Ultimately, this results in an increased precision and repeatability of the production process of the current collector 5 and in an increased quality thereof .

[0093] Preferably, the deformation of the coupling portion 13 from the initial undeformed condition to the final deformed condition is made by means of a cold-pressing process .

[0094] In particular, a crimping of coupling portion 13 is performed by means of bushing 17 .

[0095] More in particular, as schemati zed in Figures 2b to 2d, an axial downward movement o f bushing 17 determines a pressing and a deformation of coupling portion 13 into recess 10 , until coupling portion 13 completely fills recess 10 and is flush with main wall 5c .

[0096] Conveniently, in its final deformed configuration, coupling portion 13 is incorporated in the base body 5a and is flush with main wall 5c .

[0097] More precisely, the coupling portion 13 engages and fills recess 10 so that the peripheral edge 16 contacts a lateral delimiting wall 18 of recess 10 which is contiguous to main wall 5c and which laterally delimits recess 10 .

[0098] It is speci fied that in said initial undeformed configuration, and before starting of the deformation of the coupling portion 13 into the recess 10 , the coupling portion 13 is separated from the recess 10 .

[0099] That is , in said initial undeformed configuration, there is play between the peripheral edge 16 and the lateral delimiting wall 18 , i . e . the peripheral edge 16 and the lateral delimiting wall 18 are separated from one another .

[0100] According to a further aspect of the present disclosure , the coupling portion 13 is laser welded to the base body 5a at peripheral edge 16 .

[0101] In detail , the peripheral edge 16 is laser welded to the lateral delimiting wall 18 and / or to the main wall 5c .

[0102] In greater detail , the coupling portion 13 is laser welded to the base body 5a at a contact zone 19 defined between the peripheral edge 16 and the lateral delimiting wall 18 and / or the main wall 5c .

[0103] Such laser welding is performed by a known laser welding device 20 .

[0104] Since , as said, peripheral edge 16 is in a position radially more external than main portion 12 , the contact zone 19 is also arranged in a position radially more external than main portion 12 . This means that the accessibility for the laser welding device 20 is improved .

[0105] Moreover, the Applicant has observed that laser welding the pin member 5b according to the invention, which has a coupling portion 13 radially protruding from the main portion 12 , to the base body 5a results in a more stable connection between pin member 5b and base body 5a, with respect to the known cases in which the pin member only has the main portion and such main portion has to be welded or friction welded directly to the base body, which in turn has no recess . In such cases , in fact , the welding must be performed in a contact zone defined directly between the main portion and the main wall of the base body, which is quite less accessible than the contact zone 19 as described above . This ultimately leads to a rather weak welding, which is more prone and subj ect to cracks and failures during time .

[0106] Moreover, there is no need for performing a friction welding, which, as said, is subj ect to imprecisions and requires further machining of the component .

[0107] Such drawbacks are overcome by the configuration of the current collector 5 according to the present invention as described above .

[0108] In light of the above , the current collector 5 according to the invention includes a welding seam (not shown) defined by said laser welding at the contact zone 19 .

[0109] In one preferred embodiment , such welding seam extends discontinuously about axis A.

[0110] The Applicant has observed that such a discontinuous laser welding is suf ficient thanks to the presence of the coupling portion 13 cold-pressed into the recess 10 , and thanks to the radial outer position of the contact zone 19 .

[0111] In this way, energy can be saved, which results in reduced production costs and also reduced production time .

[0112] From the foregoing, and according to the present disclosure , an advantageous method for assembling a current collector 5 is provided .

[0113] Such method comprises the steps of : a ) providing a base body 5a with a recess 10 on a main wall 5c thereof ; b ) providing a pin member 5b having a central axis A and comprising a main portion 12 and a coupling portion 13 having a si ze larger than the si ze of the main portion 12 , relative to a direction transversal to the central axis A; c ) arranging the pin member 5b over the base body 5a in such a way that the coupling portion 13 is located over the recess 10 ; d) engaging the recess 10 with the coupling portion 13 ; e ) deforming the coupling portion 13 so that the coupling portion 13 fills the recess 10 , thereby determining a rigid coupling of the pin member 5b with the base body 5a .

[0114] As speci fied above , before the step e ) of deforming, the coupling portion 13 is separated and disengaged from the recess 10 .

[0115] In particular, the step e ) includes deforming the coupling portion 13 from an initial undeformed configuration, whereby it defines , in a disassembled condition of the current collector 5 in which the pin member 5b is disj oined from the base body 5a, an overmaterial portion of the pin member 5b extending from the main portion 12 , to a final deformed configuration, whereby it engages and fills said recess 10 for defining an assembled condition of the current collector 5 .

[0116] In particular, the step e ) of deforming includes deforming the coupling portion 13 until a peripheral edge 16 of the coupling portion 13 abuts against a lateral delimiting wall 18 of the recess 10 which is contiguous to main wall 5c and which laterally delimits the recess 10 , the peripheral edge 16 being arranged at a position radially more external than the main portion 12 , relatively to the central axis A.

[0117] As speci fied above , before the step e ) of deforming, the peripheral edge 16 is separated from the lateral delimiting wall 18 , i . e . there is play between the peripheral edge 16 is separated from the lateral delimiting wall 18 .

[0118] In one preferred embodiment , the step e ) of deforming includes cold-pressing the coupling portion 13 inside the recess 10 , preferably by means of a crimping bushing 17 .

[0119] By performing a cold deformation of the coupling portion 13 , energy can be saved, which ultimately leads to a cost ef fective and less polluting production process .

[0120] Preferably, the step e ) of deforming includes deforming the coupling portion 13 until the coupling portion completely fills the recess 10 and until the coupling portion 13 is flush with the main wall 5c .

[0121] Accordingly, in this case the recess 10 must be large enough at least to accommodate all the material forming the coupling portion 13 .

[0122] In this way, a compact configuration of current collector 5 and therefore of lid assembly 1 is maintained, notwithstanding the improvements in stability and durability thereof .

[0123] Advantageously, the method further comprises the step of : f ) laser welding the pin member 5b to the base body 5a at a contact zone 19 defined between the peripheral edge 16 and the lateral delimiting wall 18 and / or the main wall 5c .

[0124] In particular, the step f ) of laser welding includes laser welding the peripheral edge 16 to the lateral delimiting wall 18 and / or to the main wall 5c .

[0125] Such laser welding allows to obtain the advantages already listed above .

[0126] In light of the above , before the steps e ) of deforming and f ) of laser welding, the pin member 5b and the base body 5a define two distinct components which are separated from one another, whereas after such steps e ) and f ) the pin member 5b and the base body 5a are rigidly coupled to define one single component .

[0127] From the foregoing, it is clear that the present invention allows to implement a method for producing a battery cell , the method including the steps of : providing an hollow casing 2 with an inner compartment 3 ; inserting electrodes and electrolytic material within the inner compartment 3 ;

[0128] - assembling a current collector 5 by performing the method according to the above ;

[0129] - assembling a lid assembly 1 including the current collector 5 ; closing the casing 2 and sealing the inner compartment 3 by means of the lid assembly 1 .

[0130] The advantages of the current collector 5 and of the method for assembling a current collector 5 according to the present invention will be clear from the foregoing description .

[0131] In particular, thanks to the presence of the deformable coupling portion 13 and of the recess 10 , and thanks to the peculiar j oining of the pin member 5b with the base body 5a by means of such coupling portion 13 and recess 10 , it is possible to obtain a stable , repeatable , precise and strong j oining of the pin member 5b with the base body 5a, in an easy and cost-ef fective manner .

[0132] Furthermore , such configuration allows to perform the j oining between the pin member 5b and the base body 5a by laser welding at the contact zone 19 between these latter, which is stronger and more robust than the normal welding, especially considering that the pin member 5b and the base body 5a are made of di f ferent metallic materials ( aluminum and copper ) which are naturally incompatible from a welding point of view .

[0133] This ef fect is further enhanced by the fact that the contact zone 19 is located away from the j unction between the main portion 12 and the main wall 5c, as it is the case for the prior art configurations .

[0134] This last aspect also improves the accessibility of the contact zone 19 , which ultimately results in an improved overall quality of the assembling process of the current collector . Finally, a friction welding for j oining the pin member 5b and the base body 5a can be avoided .

[0135] Clearly, changes may be made to current collector 5 and to the method as described herein without , however, departing from the scope of protection as defined in the accompanying claims .

[0136] For example, the same configuration and method of assembling according to the present disclosure may be equally applied to the cathode current collector .

Claims

CLAIMS1.- Current collector (5) for a terminal group of a lid assembly (1) configured to f luid-tightly close an inner compartment (3) of a battery cell, the current collector (5) being configured to be electrically connected to an electrode of the battery cell for collecting electrical energy therefrom and transferring the electrical energy to a terminal (6) of said terminal group, the current collector (5) comprising a base body (5a) and a pin member (5b) fixed to the base body (5a) and protruding from a main wall (5c) of the base body (5a) ; wherein the base body (5a) includes a recess (10) obtained on the main wall (5c) , and the pin member (5b) comprises a main portion (12) for electrically coupling with the terminal (6) and a coupling portion (13) which engages and occupies the recess (10) to determine a rigid coupling of the pin member (5b) with the base body (5a) .2.- Current collector (5) as claimed in claim 1, wherein the current collector (5) is configured such that the coupling portion (13) is deformable once from an initial undeformed configuration, whereby it defines, in a disassembled condition of the current collector (5) in which the pin member (5b) is disjoined from the base body (5a) , an overmaterial portion of the pin member (5b)extending from the main portion (12) , to a final deformed configuration, whereby it engages and fills said recess (10) for defining an assembled condition of the current collector ( 5 ) .3.- Current collector as claimed in claim 1 or 2, wherein the coupling portion (13) completely fills said recess (10) for determining said rigid coupling.4.- Current collector as claimed in any one of the foregoing claims, wherein the pin member (5b) has a central axis (A) and includes a first axial end (14) , at which the main portion (12) is located, and a second axial end (15) opposite the first axial end (14) and at which the coupling portion (13) is located; and wherein the coupling portion (13) has a size larger than the size of the main portion (12) , relative to a direction transversal to said central axis (A) .5.- Current collector as claimed in claim 4, wherein the coupling portion (13) has, in an initial undeformed condition thereof, a shape axially tapering from the second axial end (15) towards the first axial end (14) .6.- Current collector as claimed in claim 4 or 5, wherein the coupling portion (13) has a peripheral edge (16) , the coupling portion (13) engaging and filling said recess (10) so that the peripheral edge (16) contacts a lateral delimiting wall (18) of said recess (10) which iscontiguous to said main wall (5c) and which laterally delimits said recess (10) , the peripheral edge (16) being arranged at a position radially more external than the main portion (12) , relatively to said central axis (A) ; and wherein the coupling portion (13) is laser welded to the base body (5a) at said peripheral edge (16) .7 Current collector as claimed in claim 6, wherein the coupling portion (13) is laser welded to the base body (5a) at a contact zone (19) defined between the peripheral edge (16) and said lateral delimiting wall (18) and / or said main wall (5c) , and wherein the current collector (5) includes a welding seam defined by said laser welding at said contact zone (19) , the welding seam extending discontinuously about said central axis (A) .8.- Current collector as claimed in any one of the foregoing claims, wherein the coupling portion (13) is incorporated in the base body (5a) and is flush with said main wall (5c) .9.- Current collector as claimed in any one of the foregoing claims, wherein the pin member (5b) is made of a first metallic material, preferably including aluminum, and the base body (5a) is made of a second metallic material, preferably including copper, which is different from the first metallic material.10.- Lid assembly for a battery cell, the lid assembly (1) being configured to f luid-tightly close an inner compartment (3) of the battery cell and comprising a base plate (4) configured to be coupled with a casing (2) of the battery cell internally defining the inner compartment (3) , for closing this latter, and a terminal group; the terminal group including:- at least one current collector (5) as claimed in any one of the foregoing claims and electrically connectable to a respective electrode of the battery cell, for collecting electrical energy and transferring it from the inner compartment (3) outwards; and- at least one terminal (6) electrically coupled with the current collector (5) for receiving the electrical energy therefrom.11.- Method for assembling a current collector (5) for a terminal group of a lid assembly (1) configured to f luid-tightly close an inner compartment (3) of a battery cell, the method comprising the steps of: a) providing a base body (5a) with a recess (10) on a main wall (5c) thereof; b) providing a pin member (5b) having a central axis (A) and comprising a main portion (12) and a coupling portion (13) having a size larger than the size of themain portion (12) , relative to a direction transversal to the central axis (A) ; c) arranging the pin member (5b) over the base body (5a) in such a way that the coupling portion (13) is located over the recess (10) ; d) engaging the recess (10) with the coupling portion (13) ; e) deforming the coupling portion (13) so that the coupling portion (13) fills the recess (10) , thereby determining a rigid coupling of the pin member (5b) with the base body (5a) .12.- Method as claimed in claim 11, wherein the step e) of deforming includes deforming the coupling portion (13) until a peripheral edge (16) of the coupling portion (13) abuts against a lateral delimiting wall (18) of said recess (10) which is contiguous to said main wall (5c) and which laterally delimits said recess (10) , the peripheral edge (16) being arranged at a position radially more external than the main portion (12) , relatively to said central axis (A) .13.- Method as claimed in claim 12, and further comprising the step of: f) laser welding the pin member (5b) to the base body (5a) at a contact zone (19) defined between the peripheral edge (16) and said lateral delimiting wall(18) and / or said main wall (5c) .14.- Method as claimed in any of the claims 11 to13, wherein the step e) of deforming includes coldpressing the coupling portion (13) inside the recess (10) .15.- Method as claimed in any of the claims 11 to14, wherein the step e) of deforming includes deforming the coupling portion (13) until the coupling portion (13) completely fills the recess (10) and until the coupling portion (13) is flush with said main wall (5c) .16.- Method for producing a battery cell, the method including the steps of: providing a hollow casing (2) with an inner compartment (3) ; inserting electrodes and electrolytic material within the inner compartment (3) ;- assembling a current collector (5) by performing the method according to any of the claims 11 to 15;- assembling a lid assembly (1) including the current collector ( 5 ) ; closing the casing (2) and sealing the inner compartment (3) by means of the lid assembly (1) .

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