Contact unit and method for making an electrical contact

Abstract

A contact unit (10; 10') for making an electrical contact with a flat conductive part (B, M), for example a metallic film (M) of a pouch cell (P), comprises a first body (14; 34) and a second body (15; 35) mutually movable between an opening position and a closing position, and a plurality of conductive microspheres (8) filling the volume of a connection chamber (20) which is created in the closing position of the first and second bodies. The connection chamber houses an electrical connection terminal (21) and an end portion of the flat conductive part (B, M), the latter being retained between sealing and scraping surfaces (24, 25) of the first and second bodies. To bring the contact unit back to a rest condition, the flat conductive part (B, M) is extracted by means of a translation movement while the first and second bodies are in the closing position, before driving such first and second bodies towards the mutual opening position.

Description

[0001] “CONTACT UNIT AND METHOD FOR MAKING AN ELECTRICAL CONTACT”

[0002] Cross-Reference To Related Applications

[0003] This Patent Application claims priority from Italian Patent Application No. 102023000011826 filed on June 9, 2023, the entire disclosure of which is incorporated herein by reference.

[0004] Technical Field

[0005] The present invention relates to a contact unit utilized for carrying out an insulation checking on pouch cells and a method for the relative use for making an electrical contact.

[0006] Prior Art

[0007] In a pouch cell, a battery cell with relative electrodes is enclosed in a “pouch,” or shell made by means of a very thin metallic film coated, generally on both sides, with insulating material, for example with plastic films. The metallic film, for example an aluminum film, gives the shell consistency by creating a protective barrier and contributing to the thermal resistance of the cell.

[0008] The pouch generally consists of two half-shells joined together, for example by means of laser welding and cutting / trimming, so as to define a protruding edge which is configured as a flat part which comprises in such manner several layers, as shown in Figures 1 and 1A, in which the following is schematically illustrated: the pouch cell P, the battery cell C enclosed therein, the electrodes E of the latter, and the edge B; the latter, which is shown in an extremely schematic manner, with exaggerated thickness for an exemplifying purpose especially in the enlarged section of Figure 1A, comprises, for example, two pairs of plastic film I layers each enclosing a metallic film M.

[0009] In the event of an insulation loss between the cell enclosed in the pouch and the metallic film, for example following damage due to impacts or constructive defects, voltage variations, deformations of the cell up to the explosion thereof can occur.

[0010] The shell must electrically insulate what is contained inside with respect to the outside.

[0011] If the shell does not correctly implement the electrical insulation, and comes into contact with an electrical potential, the inside of the cell can be subject to a potential difference between the voltage applied to one of the poles or electrodes and the potential of the shell: if such potential difference is sufficiently high, the separator of the cell can undergo damage such to allow the two electrodes to short-circuit, even only locally. Such short-circuit condition can trigger a so-called thermal runaway condition, which can result in a fire or explosion of the cell. Therefore, to perform an insulation test on a pouch cell, it is necessary to establish a contact not only with one of the two electrodes, but also with the aluminum layer. The metallic film is very thin and, as mentioned, typically embedded between two layers of electrically insulating plastic material. The sole zone where the metallic film is exposed and potentially accessible is the outer edge of the cell, where the two half-shells are welded together and subsequently trimmed.

[0012] Figure 1 also shows, in a very schematic manner, a power supply and control unit 1 to which electrical conductors belong connecting it, through contact devices or units, to an electrode E in the pouch cell P and to the edge B where the metallic film M is accessible.

[0013] Known systems provide for the contact with the metallic film M by means of pins or pogo pins, but this solution has proven to be poorly reliable. In fact, the contact is substantially a point contact and consequently uncertain considering the extremely reduced thickness of the metallic film M; moreover, the force applied by the pin so that a sufficient physical contact is achieved, can easily deform the edge B and the metallic film M in an undue and damaging manner for the integrity of the cell P.

[0014] Far more reliable and effective solutions provide for the use of conductive sponges for making the contact with the metallic film.

[0015] A limitation found in the use of the conductive sponges consists in their progressive plastic deformation, a feature which limits operating life thereof.

[0016] Furthermore, in order to be reliable, the conductive sponges, must be of high quality with consequent non-negligible costs.

[0017] Patent US11187752B2 describes a test device for detecting possible leaks in the batteries utilized in the portable electronic devices; the test device comprises a chamber which is configured to contain a device to be tested and is provided with a conductive foam or a conductive liquid.

[0018] Description of the Invention

[0019] The object of the present invention is to obtain a contact unit particularly adapted for insulation checking of pouch cells which overcomes the problems of the known devices and results to be safe, reliable, and cost-effective.

[0020] A contact unit and a method for its use according to the appended claims achieve this object and allow other advantages.

[0021] Brief Description of the Drawings

[0022] The present invention will now be described with reference to the accompanying drawings, which illustrate some non-limiting example embodiments thereof, wherein:

[0023] • Figures 1 and 1A schematically depict a pouch cell of a known type object of insulation checking, which uses a contact unit according to the present invention;

[0024] • Figure 2 is a perspective view of a contact unit according to the invention;

[0025] • Figure 3 is a partial enlarged section of the contact unit of Figure 2 in a non-operative condition;

[0026] • Figure 4 is a partial enlarged section of the contact unit of Figure 2 in an operative condition; and

[0027] • Figure 5 is a partial section of a contact unit according to an alternative embodiment of the present invention, which is shown in a non-operative condition.

[0028] Preferred Embodiments of the Invention

[0029] Figures 2 to 4 show, in a quite schematic manner, a possible embodiment of a contact device or unit 10 according to the present invention, which comprises a plurality of conductive microspheres which defines a conductive “bath” or fluid in which the zone to be put into contact is immersed. The conductive microspheres have a diameter which is extremely small and in anyway very small with respect to the part to be controlled and, similar to what occurs with the conductive sponges, they adapt to the shape of such part to be contacted.

[0030] Two complementary elements, i.e. a first body or lower body 14 and a second body or upper body 15, are connected to a driving unit 11 , which causes a closing movement thereof, i.e. a mutual approach between lower body 14 and upper body 15, and an opening one, in mutual distancing, along a longitudinal direction of a driving axis A. The driving unit 11 comprises suitable mechanisms and control means, known per se and not illustrated nor described in detail, for causing in a manual or automated manner - for example, by means of a motor - the aforementioned movements.

[0031] The lower body 14 comprises a hollow part and comprises a piston 16, which can slide in the longitudinal direction, in particular, vertically, under the thrust of mechanical or pneumatic actuation means or of other type known per se, between a retracted position (Figure 3) and an advanced position, or operative position (Figure 4) defined by suitable mechanical strokes as is shown in the figures or in some other manner known per se, for example by the detection of given reached pressures. The actuation of the piston 16 can be subject to that of the driving unit 11 or be independent of it.

[0032] A niche, or lower half -chamber, 18 is present in the piston 16 and defines an at least partial housing for a plurality of conductive microspheres, indicated both individually and as a whole by reference numeral 8. The conductive microspheres 8 have, for example, a diameter of approximately 0.5 mm.

[0033] The upper body 15 defines an additional niche, or upper half-chamber, 17 aligned with the lower half-chamber 16 along the driving axis A. An electrical connection terminal 21 is present in the upper half-chamber 17 and is connected by means of electrical wires to a power supply and control unit 1 such as the one schematized in Figure 1 , in order to perform in a known manner the insulation checking, for example as described in a parallel Italian patent application filed on the same date and by the same Applicant of the present application.

[0034] Figures 3 and 4 also show a loading duct 13 in the upper body for introducing the plurality of microspheres 8 and a discharge duct 12 in the lower body, in particular obtained in the piston

[0035] 16, for evacuating or discharging the microspheres 8.

[0036] Before being used for carrying out the insulation checking on a pouch cell P, the contact unit 10 is in the rest condition shown in Figure 3, where the lower body 14 and upper body 15 are separated, in the opening position, by a gap S along the longitudinal direction. In particular, the gap S separates sealing and scraping facing surfaces 24 and 25 of the lower body 14 and the upper body 15. In order to carry out the checking, and in particular to make the electrical contact with the conductive element represented by the metallic film M, a flat conductive part

[0037] - which integrates such conductive element M and comprises the edge B of the pouch cell P of which the insulation is to be checked - is inserted in the gap S, and, by means of the driving unit 11 , the approaching between the lower body 14 and the upper body 15 is controlled up to the mutual closing position (Figure 4), in which the flat conductive part, in particular the edge B is retained, substantially compressed, between the respective sealing and scraping facing surfaces 24 and 25. The piston 16 housed in the lower element is actuated and displaced to the operative position towards the upper body 15, and the plurality of conductive microspheres 8 substantially fills the volume of a connection chamber 20 which is defined in the closing position and which is delimited partially by the niche or lower half-chamber 18, partially by the upper half-chamber

[0038] 17, and where an end portion of the flat conductive part, in particular of the edge B, is also located. The latter is immersed in the conductive “bath” or fluid defined by the conductive microspheres 8, thereby making the electrical connection between metallic film M, in contact with part of the conductive microspheres 8, and electrical connection terminal 21 .

[0039] The insulation test of the pouch cell P is then carried out, for example as described in the already mentioned parallel Italian application, after putting a second electrical contact into contact with one of the electrodes E (Figure 1 ) of the pouch cell P.

[0040] Once the test is performed, the contact unit 10 is brought back to the opening position which defines the rest condition of Figure 3 by following a procedure comprising these steps:

[0041] - the piston 16 is retracted and brought back to the retracted position; consequently, the end portion of the edge B emerges from the conductive fluid defined by the microspheres 8 and, by gravity, the microspheres 8 almost totally collect in the lower half-chamber 18 while all anyway remaining inside the lower body 14;

[0042] - the edge B of the pouch cell P is extracted while the lower body 14 and the upper body 15 are maintained in the mutual closing position, extracting said edge B by means of a mutual translation movement between the flat part, i.e. the cell P and the contact unit 10; consequently, any possible conductive microspheres 8 remained attached to zones of the edge B of the pouch cell P are retained inside the contact unit and flow together with the others inside the lower body 14; therefore, lower body 14 and upper body 15 also play the role of “scrapers” in this step, allowing the recovery of any possible microspheres 8 remained laying on or attached to the pouch cell P and thus avoiding that they may disperse in an uncontrolled manner into the external environment;

[0043] - by means of the driving unit 11 an opening movement is controlled between the lower body 14 and the upper body 15 for bringing the contact unit 10 in the rest condition of Figure 3.

[0044] The possibility of avoiding the dispersion of the conductive microspheres 8 in the area where the sealing test is performed, allowed by some features of the contact unit 10 and the described procedure, is of great importance. In fact, avoiding in a simple manner the dispersion of the conductive microspheres 8 and the consequent contamination of the test area or the pouch cell P allows preventing and avoiding undesired phenomena which are difficult to identify and control and the risk of accidental malfunctions which are difficult to predict. The described solution allows avoiding subsequent clean-up or “decontamination” operations which would result to be very time-consuming and expensive in order to be effective.

[0045] Therefore, the illustrated solution with the described “extraction” procedure results to be particularly effective.

[0046] The embodiment described so far, with the lower body 14 and the upper body 15 mutually movable along a longitudinal direction, which is substantially vertical, results to be particularly advantageous, exploiting in a simple manner the force of gravity for collecting the conductive microspheres 8.

[0047] Another advantage of the solution according to the invention is the possibility of simply, quickly and safely replacing the set or plurality of conductive microspheres 8 inside the contact unit 10. This can occur, for example, through the discharge duct 12 present in the cylinder 16 and schematically depicted in Figures 3 and 4. Contaminations can occur over time, due for example to room humidity, leading to the degradation of the microspheres 8, therefore the possibility of replacing them in a simple and effective manner minimizes maintenance expenses and thus reduces the costs thereof.

[0048] It should be noted that, unlike the conductive sponges which, in order to guarantee a reliable contact in an insulation test of a pouch cell must be of high quality and high cost, the solution with the conductive microspheres definitely results to be more cost-effective, as it is possible to use inexpensive microspheres available on the market without thereby compromising in anyway the reliability of the test.

[0049] Different embodiments of the contact device or unit fall within the scope of the invention. The mutually movable bodies with the half-chambers can, for example, be mutually movable along a horizontal direction or anyway a direction different from the vertical one. This does not allow exploiting the force of gravity for collecting the conductive microspheres 8 and provides for the presence of forced collection mechanisms (for example, by suction), resulting to be a little less advantageous than the one illustrated so far.

[0050] The two mutually movable bodies, for example the illustrated and described lower body 14 and upper body 15, can have a cylindrical, hemispherical or a more complex geometry depending on the contact needs of the pouch cell P being tested.

[0051] It is possible to implement a suitable shutter in the lower body 14 so as to facilitate the complete emptying of the conductive microspheres 8, under strictly controlled conditions, when the replacement is necessary.

[0052] A similar shutter can be provided in the upper body 15 for loading the microspheres, for example through the loading duct 13 schematically illustrated in Figures 3 and 4 under controlled conditions, so as to prevent the risk of contamination also during the maintenance of the contact unit 10.

[0053] The driving unit 11 has features which are known per se and can, for example, comprise a clamp, a hydraulic piston, an electric actuator, or any device adapted to implement the necessary driving.

[0054] Figure 5 schematically shows (in the rest condition only) a possible alternative embodiment of the present invention with a contact unit 10’ comprising a first body or lower body 34 with a niche or lower half-chamber 38, and a second body or upper body 35 with an additional niche or upper half-chamber 37 which, as for the embodiment of Figures 3 and 4, in the rest condition shown in figure, are separated by a gap S. In this alternative embodiment, the conductive microspheres 8 are introduced from above into the upper body 35 through a loading duct 33 present in the upper body 35 and extracted from the lower body 34 through a discharge duct 32. This embodiment provides for the presence of a movable tank 30 which collects the conductive microspheres 8 output from the discharge duct 32 and brings them to the input of the loading duct 31. The movable tank 30 is movable by means of mechanisms known per se and schematically indicated in Figure 5 by the arrow F; in particular, the arrow F also indicates the possible displacement of the movable tank 30 which can occur, for example, by means of a linear translation between two limit positions (one indicated by a solid line and one indicated by a dashed line). In particular, the movable tank is arranged at the exit of the discharge duct 32 to collect the plurality of conductive microspheres 8 output from the lower body 34 and displaces at the input of the loading duct 33 for introducing the plurality of conductive microspheres 8 through the upper body 35. In the embodiment of Figure 5, loading and discharging of the conductive microspheres 8 occur substantially by gravity in the closing position of the lower body 34 and upper body 35.

[0055] The sequence of the operations comprises, for example, the following steps:

[0056] - the pouch cell P is brought to test position and the relative edge B, i.e. the flat conductive part, is inserted in the gap S between the lower body 34 and upper body 35;

[0057] - the lower body 34 and upper body 35 are brought together, closing on the edge B and constituting the connection chamber 20 or test chamber delimited by the upper chamber 37 and lower chamber 38;

[0058] - a shutter 39 controlling the access to the inlet duct 31 is opened and the conductive microspheres 8 are inserted; the microspheres 8 flow into the test chamber by gravity. Once the conductive microspheres 8 flow out, the shutter 39 is closed.

[0059] - the sealing test of the pouch cell P is performed;

[0060] - a shutter 36 controlling the access to the exit duct 32 is opened, and the microspheres flow into the suitably positioned movable tank 36. Thereby, the end portion of the flat conductive part, in particular of the edge B, emerges from the conductive fluid defined by the plurality of microspheres 8;

[0061] - the edge B of the pouch cell P is extracted: as in the embodiment described in the foregoing, any possible microspheres 8 remained attached to edge B are “scraped” and collected;

[0062] - the shutter 36 closing the exit duct 32 is closed;

[0063] - the lower body 34 and the upper body 35 are separated, and the movable tank 30 which has collected the microspheres 8 is brought at the upper body 35 which is ready to pour the microspheres 8 into the test chamber through the loading duct 31 at the start of a subsequent test cycle which provides for the use of the contact unit 10’.

Claims

CLAIMS1. A contact unit (10; 10’) adapted to make an electrical contact with a flat conductive part (B, M), comprising a first body (14; 34) and a second body (15; 35) mutually movable between an opening position defining a rest condition of the contact unit (10; 10’) and a closing position, a plurality of conductive microspheres (8), at least a niche (18; 38) in one of said first body (14; 34) and second body (15; 35) adapted to house at least partially said plurality of conductive microspheres (8), an electrical connection terminal (21 ) connected to one of said first body (14; 34) and second body (15; 35) and electrically connected to a power supply and control unit (1 ), the first body (14; 34) and the second body (15; 35)- comprising sealing and scraping facing surfaces (24, 25) adapted to retain, between the first body (14; 34) and the second body (15; 35), in said closing position, the flat conductive part (B, M) to be put into contact, and- defining, in said closing position, a connection chamber (20) partially delimited by said niche (18; 38), in which the connection terminal (21 ) and an end portion of the flat conductive part (B, M) are housed, the plurality of conductive microspheres (8) substantially filling, in said closing position, the volume of said connection chamber (20) and defining a conductive fluid in which said connection terminal (21 ) and end portion of the flat conductive part (B, M) are immersed.

2. The contact unit (10; 10’) according to claim 1 , wherein the first body (14; 34) and the second body (15; 35) are a lower body (14; 34) and an upper body (15; 35) mutually movable along a vertical longitudinal direction.

3. The contact unit according to claim 2, wherein said lower body (14) comprises a hollow portion and a piston (16) adapted to vertically slide in the hollow portion between a retracted position and an operative position, the piston (16) having said niche (18) at the upper end.

4. The contact unit (10) according to claim 3, wherein said upper body (15) defines an additional niche (17), said niche (18) and additional niche (17) defining, in said closing position and at the advanced position of the piston (16), the connection chamber (20).

5. The contact unit (10; 10’) according to any one of the preceding claims, comprising a driving unit (11 ) to bring the first body (14; 34) and the second body (15; 35) from the opening position to the closing position, and vice versa.

6. The contact unit (10; 10’) according to claim 1 or claim 2, wherein the first body (14; 34) defines a loading duct (13, 33) and the second body (15; 35) defines a discharge duct (12, 32) forthe loading and the discharge of the plurality of conductive microspheres (8), respectively.

7. The contact unit (10’) according to claim 6, comprising a movable tank (30) adapted to be arranged at the exit of the discharge duct (32) to collect the plurality of conductive microspheres (8) output from the lower body (34), and to be displaced at the input of the loading duct (33) for inserting the plurality of conductive microspheres (8) through the upper body (35) substantially by gravity.

8. A method for making an electrical contact with a flat conductive part (B, M) by means of the contact unit (10, 10’) according to any one of the preceding claims, comprising the following steps: in the opening position, arranging the flat conductive part (B, M) in a gap (S) between said first body (14; 34) and second body (15; 35), controlling the approaching between the first body (14; 34) and second body (15; 35) up to the mutual closing position, retaining the flat conductive part (B, M) between the sealing and scraping facing surfaces (24, 25) of said first body (14; 34) and second body (15; 35), manufacturing the connection chamber (20) with the conductive fluid defined by the plurality of conductive microspheres (8) in which said electrical connection terminal (21 ) and end portion of the flat conductive part (B, M) are immersed.

9. The method for making an electrical contact with a flat conductive part (B, M) by means of the contact unit (10) according to claim 3 or claim 4, comprising the following steps: in the opening position, arranging the flat conductive part (B, M) in a gap (S) between said first body (14) and second body (15), controlling the approaching between the first body (14) and second body (15) up to the mutual closing position, retaining the flat conductive part (B, M) between the sealing and scraping facing surfaces (24, 25) of said first body (14) and second body (15), actuating the piston (16) to bring it to the operative position and manufacturing the connection chamber (20) with the conductive fluid defined by the plurality of conductive microspheres (8) in which said connection terminal (21) and end portion of the flat conductive part (B, M) are immersed.

10. The method according to claim 8 or 9, to bring the contact unit (10; 10’) back to the rest condition, comprising the following steps:- in the closing position between the first body (14; 34) and the second body (15; 35)- making the end portion of the flat conductive part (B, M) emerge from the conductivefluid defined by the plurality of conductive microspheres (8), and- extracting the flat conductive part (B, M) by means of a mutual translation movement between said flat conductive part (B, M) and the contact unit (10; 10’), and- controlling the distancing between the first body (14; 34) and second body (15; 35) up to the mutual opening position.

11. The method according to any one of claims 8 to 10, with a contact unit (10; 10’) according to claim 2, comprising the step of discharging the plurality of conductive microspheres (8) through a discharge duct (12; 32) in the lower body (14; 34) substantially by gravity.

12. A system for insulation checking of a pouch cell (P) having at least an electrode (E) and a shell comprising a metallic film (M), the system comprising a power supply and control unit (1) electrically connected to said at least one electrode (E) of the pouch cell (P) and the metallic film (M), and the contact unit (10; 10’) according to any one of claims 1 to 7 for electrically connecting the power supply and control unit (1 ) with the metallic film (M).

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