WO2025074150A1 - Lid assembly for a battery cell having an improved sealing plug for sealing an electrolyte injection hole thereof - Google Patents

Abstract

There is described a lid assembly (1) for a battery cell comprising: a base plate (4) configured to be coupled with a casing (2) of the battery cell internally defining an inner compartment (3) thereof, for closing this latter; an electrolyte injection hole (12) defined by a through hole (12a) obtained in the base plate (4) and configured for allowing the injection of electrolytic material in the inner compartment (3); a closure assembly (8) for closing the injection hole (12) and including a sealing plug or pin (10) for engaging the through hole (12a) so as to seal the injection hole (12) in a fluid-tight manner; the sealing plug (10) comprises a plurality of bumps (14) protruding therefrom and cooperating in fluid-tight contact with the through hole (12a).

Description

LID ASSEMBLY FOR A BATTERY CELL HAVING AN IMPROVED SEALING

PLUG FOR SEALING AN ELECTROLYTE INJECTION HOLE THEREOF

TECHNICAL FIELD

The present invention relates to 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 a battery cell housing electrodes and electrolytic material .

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

BACKGROUND ART

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

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 .

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 , smartbands , etc .

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

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 .

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

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

A battery cell typically comprises a hollow casing, for example in the shape of a 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 .

The casing 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 .

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

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 .

The lid assembly essentially comprises :

- 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 ;

- 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 .

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 .

According to the known processes for manufacturing such battery cells , the inner compartment is filled with electrolytic material after having assembled the lid assembly to the casing, and in particular after having welded the base plate at the opening of the casing .

To this end, the lid assembly is provided with a small through hole , usually known as " inj ection hole" or "electrolyte inj ection hole" , obtained in the base plate .

The inj ection hole serves for the inj ection of the electrolytic material within the inner compartment .

Before nominal operation, the battery cell undergoes a formation process whereby it is charged and discharged several times . During this procedure the inj ection hole is closed temporarily with a plug .

After the formation process , the temporary plug is removed to release gases that built up during the formation and then the inner compartment is filled with the final amount of electrolyte .

Finally, the inner compartment of the battery cell is f luid-tightly closed by a closure assembly, which typically includes two components :

- a rubber sealing pin or plug; and

- a cover, which is typically defined by a small , shaped aluminum plate .

The sealing plug is fitted with interference engaging the inj ection hole , and then the inj ection hole cover is arranged into a dedicated recess obtained in the base plate above the inj ection hole , and welded thereto . The sealing plug has a sealing portion configured to cooperate in fluid-tight contact with an inner lateral wall of the through hole .

As the inj ection hole is typically round, the sealing portion usually has a cylindrical shape .

Hence , the sealing portion has a cylindrical outer lateral wall which f luid-tightly engage the inj ection hole with interference .

The Applicant has observed how the known sealing plugs are subj ect to local stresses during installation which may exceed the tensile strength of the material .

As a result , either the structure of the sealing plug itsel f is compromised, or a reaction force is established which biases the sealing plug to slide out from its seat in the through hole .

Due to the above , the sealing of the inj ection hole , and therefore of the inner compartment , may be partially or totally compromised during operation, at a particularly sensitive zone of the battery cell , since it can cause an undesired outflow of electrolytic material or an abrupt venting of gases that may have built up within the inner compartment of the battery cell during operation thereof .

DISCLOSURE OF INVENTION

It is therefore an obj ect of the present invention to provide 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 .

This obj ect is achieved by a lid assembly as claimed in claim 1 .

BRIEF DESCRIPTION OF THE DRAWINGS

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

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;

Figure 2 is a larger-scale , sectioned, exploded side view, with parts removed for clarity, of an inj ection hole area of the lid assembly of Figure 1 ; and

Figure 3 is a larger-scale , partially-sectioned side view, with parts removed for clarity, of the inj ection hole area of Figure 2 .

BEST MODE FOR CARRYING OUT THE INVENTION

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

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 . 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) .

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

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 .

Hence , the battery cell comprises casing 2 , with the electrodes , the separator and the electrolytic material , and lid assembly 1 .

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

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 .

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

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 .

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 ;

- an electrolyte inj ection hole 12 defined by a through hole 12a obtained in base plate 4 and configured for allowing the inj ection of the electrolytic material in inner compartment 3 ; and

- a closure assembly 8 for closing inj ection hole 12 .

In practice , inj ection hole 12 defines a pour opening through which the electrolytic material is to be inserted in inner compartment 3 once lid assembly 1 has been coupled to casing 2 , according to a manner known and not described in detail .

Closure assembly 8 includes at least a sealing plug or pin 10 for engaging through hole 12a so as to seal inj ection hole 12 in a fluid-tight manner .

Preferably, sealing plug 10 is made in an elastomeric material , such as EPDM rubber .

Alternatively, sealing plug 10 may be made of polypropylene .

Conveniently, closure assembly 8 further includes a cover 13 , for example a shaped metallic plate , for example made of aluminum .

During operation of the battery cell , sealing plug 10 is fitted with interference engaging through hole 12a, and then cover 13 is arranged into a dedicated recess 12b ( Figure 2 ) obtained in base plate 4 above inj ection hole 12 , and welded thereto .

As visible in Figure 1 , lid assembly 1 further comprises : 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 ;

- 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 ; and

- 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 .

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 .

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 4 , and having a central axis X .

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 .

For each terminal group, base plate 4 has a through hole 4a engaged by a pin 5b of 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 .

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 .

Expediently, the through hole 12a defining inj ection hole 12 is also obtained through stop frame 11 .

As already speci fied in the introductory portion of the description, it is desirable that inj ection hole 12 is firmly and ef fectively sealed in a fluid-tight manner throughout the entire li fespan of the battery cell .

In fact , an interruption of the fluid-tight sealing of inj ection hole 12 may lead to undesired leaks of electrolytic material and/or to entry of foreign agents ( dust , dirt ) into inner compartment 3 and/or to gas leaks or venting from inner compartment 3 .

It is speci fied that the expression " f luid-tight" is intended as comprising both liquid-tight and gas-tight .

According to the present invention, sealing plug 10 has a plurality of bumps 14 protruding therefrom and cooperating in fluid-tight contact with through hole 12a .

In detail , as schematically shown in Figure 3 , through hole 12a has an inner wall 15 delimiting inj ection hole 12 , and bumps 14 cooperate in fluid-tight contact with inner wall 15 .

It is stated that Figure 3 only schematically illustrates the interaction between sealing plug 10 and inner wall 15 , showing in particular undeformed bumps 14 . During normal operation, it is possible that bumps 14 are deformed when cooperating with inner wall 15 , due to the fact that sealing plug 10 engages through hole 12a with interference and no clearance .

As shown in Figures 2 and 3 , sealing plug 10 includes a sealing portion 16 and a support portion 17 protruding from sealing portion 16 .

In detail , sealing plug has a central longitudinal axis A. Support portion 17 axially extends from sealing portion 16 .

In greater detail , sealing portion 16 is the portion of sealing plug 10 which cooperates in contact with base plate 4 at through hole 12a .

That is , sealing portion 16 engages through hole 12a and cooperates in fluid-tight contact with inner wall 15 .

Support portion 17 is preferably arranged within inner compartment 3 , when sealing plug 10 is inserted into through hole 12a .

According to the invention, bumps 14 protrude from sealing portion 16 in direction of inner wall 15 and contacting inner wall 15 , so as to establish a fluid- tight sealing of inj ection hole 12 .

More speci fically, sealing portion 16 has an outer lateral sealing wall 18 facing inner wall 15 .

According to the invention, bumps 14 extend on sealing wall 18 and protrude therefrom in direction of inner wall 15 , thereby contacting in a fluid-tight manner inner wall 15 .

Preferably, bumps 14 radially protrude from sealing wall 18 , with respect to axis A.

The above configuration is illustrated in Figure 3 .

In practice , each bump 14 defines a sealing lip of sealing plug 10 , which sealing lip ensures a better fluid- tight sealing function of sealing plug 10 compared to the case in which sealing portion is devoid of any sealing lip ( for example , when the sealing portion is smooth) .

In fact , the Appl icant has observed that the presence of bumps 14 on sealing portion 16 , i . e . on the portion of sealing plug which engages through hole 12a and actively cooperates in contact with the inner wall 15 thereof , improves the coupling of sealing plug 10 with base plate 4 .

In particular, the Applicant has observed, by means of an extensive experimental campaign, that the local stresses which generate at the contact interface between sealing portion 16 and inner wall 15 are reduced .

More in particular, the stress distribution at the contact interface between sealing portion 16 and inner wall 15 is largely improved, and strongly reduces the establishing of a reaction force on the sealing plug 10 which ultimately largely decreases the risk of biasing the sealing plug 10 to disengage from the through hole 12a .

Due to the above , the risk that the fluid-tight sealing of inj ection hole 12 , and therefore of inner compartment 3 , in interrupted is strongly reduced, compared to the case in which no bump 14 is provided on sealing portion 16 .

Furthermore , the extensive experimental campaign conducted by the Applicant led to the conclusion that the li fespan of sealing plug 10 is increased, due to the improved stress distribution thereon .

Advantageously, sealing portion 16 comprises at least two ribs or ridges 14 protruding from sealing wall 18 , each ridge 14 defining one said bump and therefore cooperating in fluid-tight contact with inner wall 15 .

The presence of at least two ridges 14 improves the engaging stability of sealing plug 10 into through hole 12a, which ultimately further reduces the ris k of a disengaging thereof during operation . Such configuration also ensures that sealing plug 10 stays in place even in presence of rather strong vibrations .

Through hole 12a has a central axis B .

Conveniently, sealing plug 10 engages through hole 12a so that axes A and B are coaxial .

Accordingly, sealing wall 18 extends around axis A and each ridge 14 extends at least partially around axis A.

More speci fically, according to the preferred and non-limiting embodiment shown, sealing portion 16 has a substantially cylindrical shape , so that sealing wall 18 defines a substantially cylindrical lateral surface of sealing portion 16 and each ridge 14 extends circumferentially around axis A.

Accordingly, through hole 12a is preferably round .

More in particular, each ridge 14 extends entirely along a circumferential direction around axis A, so as to complete a circumference around axis A.

The Applicant observed that this configuration ensures a better sealing of inj ection hole 12 .

In one embodiment , each ridge 14 may have an interrupted conformation along the aforementioned circumferential direction . This configuration allows for material savings .

In one preferred embodiment , sealing portion 16 has at least one groove 19 obtained on sealing wall 18 .

Groove 19 defines the at least two ridges 14 , so that such ridges 14 are successively arranged on sealing wall 18 at opposite sides of groove 19 .

Preferably, groove 19 extends circumferentially around axis A. According to the preferred embodiment shown, sealing portion 16 has a plurality of said grooves 19 defining a set of ridges 14 alternating successively with grooves 19 on sealing wall 18 .

In other words , each groove 19 is axially interposed between two ridges 14 , as shown in Figure 3 .

In practice , a series of alternating ridges and valleys is defined on sealing wall 18 .

The Applicant observed that the presence of one or more grooves 19 contributes to further improve the stress distribution on sealing portion 16 .

Furthermore , such configuration provides for a more compact and sturdier and robust structure of sealing plug 10 , with respect to the case in which ridges 14 radially protrude from a smooth sealing wall 18 devoid of grooves 19 .

Preferably, sealing portion 16 axially engages through hole 12a in its entirety .

That is , sealing portion 16 is axially contained and completely radially surrounded by inner wall 15 .

In one embodiment , the axial si ze of sealing portion 16 is greater than the radius of the sealing portion 16 itsel f .

The Applicant has observed that such a geometric configuration represents the optimal in terms of structural robustness of sealing plug 10 , further improving the stress distribution thereon when engaging through hole 12a .

The advantages of lid assembly 1 , and of sealing plug 10 thereof , according to the present invention will be clear from the foregoing description .

In particular, thanks to the presence of bumps or ridges 14 improves the coupling of sealing plug 10 with base plate 4 , strongly reducing the risk of a disengagement of sealing plug 10 from through hole 12a .

Due to the above , the risk that the fluid-tight sealing of inj ection hole 12 , and therefore of inner compartment 3 , is interrupted is strongly reduced, compared to the case in which no bump 14 is provided on sealing portion 16 .

Furthermore , the li fespan of sealing plug 10 is increased, due to the better stres s distribution thereon .

Clearly, changes may be made to lid assembly 1 as described herein without , however, departing from the scope of protection as defined in the accompanying claims .

Claims

1.- Lid assembly (1) 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;

- an electrolyte injection hole (12) defined by a through hole (12a) obtained in the base plate (4) and configured for allowing the injection of electrolytic material in the inner compartment (3) ;

- a closure assembly (8) for closing the injection hole (12) and including a sealing plug or pin (10) for engaging the through hole (12a) so as to seal the injection hole (12) in a fluid-tight manner; wherein the sealing plug (10) comprises a plurality of bumps (14) protruding therefrom and cooperating in fluid-tight contact with the through hole (12a) .

2.- Lid assembly as claimed in claim 1, wherein the through hole (12a) has an inner wall (15) delimiting the injection hole (12) ; wherein the sealing plug (10) includes a sealing portion (16) engaging the through hole (12a) and cooperating in fluid-tight contact with said inner wall

(15) ; and wherein said bumps (14) protrude from the sealing portion (16) in direction of the inner wall (15) and contacting the inner wall (15) so as to establish a fluid- tight sealing of the injection hole (12) .

3.- Lid assembly as claimed in claim 2, wherein the sealing portion (16) has an outer lateral sealing wall (18) facing said inner wall (15) ; and wherein said bumps (14) extend on the sealing wall (18) and protrude therefrom in direction of the inner wall (15) .

4.- Lid assembly as claimed in any one of the foregoing claims, wherein each bump (14) defines a sealing lip of the sealing plug (10) .

5.- Lid assembly as claimed in claim 1 or 2, wherein the sealing portion (16) has an outer lateral sealing wall (18) facing said inner wall (15) ; and wherein the sealing portion (16) comprises at least two ribs or ridges (14) protruding from the sealing wall (18) , each ridge (14) defining one said bump and cooperating in fluid-tight contact with said inner wall (15) .

6.- Lid assembly as claimed in claim 5, wherein the through hole (12a) has a central axis (B) and the sealing plug (10) has a longitudinal axis (A) configured to be arranged coaxial with the central axis (B) when the sealing plug (10) engages the through hole (12a) ; wherein the sealing wall (18) extends around the longitudinal axis (A) and each ridge (14) extends at least partially around the longitudinal axis (A) .

7 Lid assembly as claimed in claim 6, wherein the sealing portion (16) has a substantially cylindrical shape, so that the sealing wall (18) defines a substantially cylindrical lateral surface of the sealing portion (1 ) ; and wherein each ridge (14) extends circumferentially around the longitudinal axis (A) .

8.- Lid assembly as claimed in any one of claims 5 to 7, wherein the sealing portion has at least one groove (19) obtained on said sealing wall (18) and defining the at least two ridges (14) successively arranged on the sealing wall (18) at opposite sides of the groove (19) .

9.- Lid assembly as claimed in claims 6 to 8, wherein the groove (19) extends circumferentially around the longitudinal axis (A) .

10.- Lid assembly as claimed in claim 8 or 9, wherein the sealing portion (16) has a plurality of said grooves (19) defining a set of said ridges (14) alternating successively with the grooves (19) on said sealing wall (18) .

11.- Lid assembly as claimed in claim 2, wherein the sealing plug (10) has a longitudinal axis (A) ; wherein the sealing portion (16) axially engages the through hole (12a) in its entirety, so that the sealing portion (16) is completely radially surrounded by the inner wall (15) ; and wherein the axial size of the sealing portion (16) is greater than half the radial size of the sealing plug (10) .

12.- Lid assembly as claimed in any one of the foregoing claims, and comprising:

- at least one current collector (5) electrically connectable to a respective electrode of the battery cell, for collecting electrical energy and transferring it from the inner compartment (3) outwards;

- at least one terminal (6) electrically coupled with the current collector (5) for receiving the electrical energy therefrom; wherein the terminal (6) and at least part of the collector (5) are arranged on opposite sides of the base plate (4) and are compressed towards one another and towards the base plate (4) .

13.- Sealing plug (10) for f luid-tightly sealing an electrolyte injection hole (12) of a base plate (4) of a lid assembly (1) configured for closing in a fluid-tight manner an inner compartment (3) of a battery cell, the sealing plug (10) comprising a plurality of bumps (14) protruding therefrom and cooperating in fluid-tight contact with the injection hole (12) .

14.- Sealing plug as claimed in claim 13, and including a sealing portion (16) configured for engaging the injection hole (12) and for cooperating in fluid- tight contact with an inner wall (15) delimiting the injection hole (12) ; wherein the bumps (14) extend on the sealing portion (16) and protrude therefrom for contacting the inner wall (15) .

15.- Sealing plug as claimed in claim 14, wherein the sealing portion (16) has an outer lateral sealing wall (18) configured to face said inner wall (15) ; wherein the sealing wall (18) has at least one groove (19) defining at least two successive ribs or ridges (14) arranged at opposite sides of the groove (19) , each ridge (14) defining one said bump.