Method for filling battery cells with electrolyte and related filling device

Abstract

A method and a device (2) for filling electrochemical cells (1) particularly of the prismatic type with electrolyte, wherein vacuum is created in the internal volume of the case of the cell before injecting the liquid electrolyte and the subsequent injection is such as to force an elastic deformation of at least one side wall (11a-11b) of the case away from the electrode assembly (12) contained in the case, due to the filling, with the complete dose of the electrolyte, of the interspace (13a-13b) between the at least one side wall (11a-11b) and the electrode assembly (12). The filling hole (14) is then plugged after the injection and the elastic return of the side walls previously deformed by the injection occurs during the step of wetting the electrode assembly (12), preferably in a buffer station (300).

Description

[0001] METHOD FOR FILLING BATTERY CELLS WITH ELECTROLYTE AND RELATED FILLING DEVICE

[0002] The present invention relates to a method for filling cells of batteries, in particular lithium-ion batteries, with electrolyte, and to a related filling device. The cells are preferably prismatic.

[0003] In the field of battery cell filling, a predetermined production speed may be required of the filling station in order to be able to insert the station in a production line operating at that speed.

[0004] However, it is not always possible to achieve certain particularly high production speeds, for example on the order of tens or hundreds of cells per minute, in cases where the actual time for filling the cell with the necessary volume of fluid is significantly greater than the time theoretically required to meet the production speed required of the filling station.

[0005] For example, this difference between actual filling time and theoretical time required is observed in the filling of prismatic cells with fluid electrolyte. These cells in fact contain an electrode assembly (comprising anode sheets, cathode sheets, and separators), whose pores must be uniformly filled with the electrolyte solution in a step known as “wetting” or “impregnation.”

[0006] With this intrinsic limitation on the filling speed, considerable filling time is currently required (for example, about half an hour for prismatic cells measuring 110x285x30 mmA3 with a dose of electrolyte solution of about 333 grams), where “filling” is understood to mean the combination resulting from the injection of the electrolyte into the cell and the wetting of the electrode assembly.

[0007] Filling is usually carried out by placing the cells in a vacuum bell, which is then pressurized to inject the electrolyte into the respective cell. Since injection would be faster than wetting, the required dose of electrolyte cannot be injected in one shot and it is necessary to repeat the application of vacuum and pressurization in the cell environment. These repetitions also serve to evacuate the gas that forms inside the case.

[0008] If the cell production line requires a filling speed of N containers per minute, a filling station of the line should provide for a number of filling taps equal to N * t, where “t” is the time required to fill a single container expressed in minutes. For example, in order to fill 10 cells per minute when filling with electrolyte takes 30 minutes per cell, 300 taps would be required.

[0009] Clearly, such a solution requires a considerable utilization of space, as well as such high costs and complexity that in practice it is not possible to provide high-speed filling stations.

[0010] The aim of the present invention is to provide a method and a device for filling cells, in particular electrochemical cells and preferably prismatic cells, which are capable of improving the background art in one or more of the abovementioned aspects.

[0011] Within the scope of this aim, an object of the invention is to fill cells for batteries, in particular lithium-ion batteries, at a high rate, in particular on the order of tens or hundreds of containers per minute, despite the fact that the time required to fill the individual cell is long, in particular on the order of tens of minutes (for example between 10 and 45 minutes).

[0012] Furthermore, an object of the present invention is to overcome the drawbacks of the background art in a manner that is alternative to any existing solutions.

[0013] Not least object of the invention is to provide a filling method and device that are highly reliable, relatively easy to provide and at competitive costs.

[0014] This aim, as well as these and other objects that will become more apparent hereinafter, are achieved by a filling method according to claim 1 , optionally provided with one or more of the characteristics of the dependent claims. The aim and objects are also achieved by a filling device according to claim 11 , preferably provided with one or more of the characteristics of the dependent claims.

[0015] In a method for filling at least one battery cell with electrolyte according to an embodiment of the invention, the cell comprises a substantially closed metallic box-like case having preferably a parallelepiped shape, said case comprising an internal volume occupied by an electrode assembly so as to leave interspaces between said electrode assembly and side walls of said case, said case comprising a hole adapted to allow an injection of a fluid electrolyte into said internal volume, said method comprising the steps of:

[0016] - injection of a predetermined dose of said electrolyte into said internal volume through said hole;

[0017] - wetting of said electrode assembly with said dose of electrolyte; said method being characterized in that:

[0018] - said injection step is preceded by a step of creating a vacuum in said internal volume of the case; and in that said method comprises the steps of:

[0019] - in said injection step, elastic deformation of at least one of said side walls of said case away from said electrode assembly due to filling, with said electrolyte, of the interspace between said at least one side wall and the electrode assembly;

[0020] - closure of said hole at the end of the injection step;

[0021] - springback of said at least one side wall toward said electrode assembly during the wetting step.

[0022] In a device for filling at least one battery cell with electrolyte according to an embodiment of the invention, the filling device comprises:

[0023] - a nozzle which can be coupled in a gas-tight manner to a filling hole of at least one cell;

[0024] - a common channel, which leads into said nozzle;

[0025] - volumetric dispensing means, for feeding a predetermined dose of fluid electrolyte to said nozzle, said volumetric dispensing means being in fluid communication with said common channel;

[0026] - vacuum creation means, which are in fluid communication with said common channel to perform air or gas suction through said nozzle.

[0027] Further characteristics and advantages of the invention will become more apparent from the description of a preferred, but not exclusive, embodiment illustrated by way of non-limiting example in the accompanying drawings, wherein:

[0028] Figure 1 is a view of a prismatic cell that can be used in a method according to the invention;

[0029] Figure 2 is a view of a filling device according to the invention, coupled to the prismatic cell of Figure 1;

[0030] Figure 3 is a plan view from above of the assembly of Figure 2;

[0031] Figure 4 is a sectional view of the assembly of the preceding figure, taken along the plane IV-IV;

[0032] Figure 5 is a sectional view of the assembly of the preceding figure, taken along the plane V-V;

[0033] Figure 6 corresponds to Figure 5 at the end of the injection of the predetermined dose of fluid electrolyte;

[0034] Figure 7 is a sectional view of the cell of Figure 6 during the step of wetting the electrode assembly;

[0035] Figure 8 is a sectional view of the cell, taken along the plane V-V at the end of the wetting step;

[0036] Figure 9 is a diagram of a portion of a cell or battery production line dedicated to filling with fluid electrolyte;

[0037] Figure 10 is a diagram showing a method according to the invention.

[0038] With reference to the cited figures, a method according to the invention performs the filling, with a fluid electrolyte, of a prismatic cell for batteries, in particular electrochemical or secondary batteries, such as for example lithium-ion batteries. The fluid electrolyte is preferably an electrolyte solution in the liquid state, in particular a liquid phase containing a non-aqueous liquid solvent and an ionizable substance, for example a salt that is dissociable in the solvent.

[0039] Although the description that follows refers to the filling of a single prismatic cell, the invention also extends to the filling of a plurality of prismatic cells at a time, for example arranged laterally adjacent in a straight line or arranged around a circular arc, for example in the case of a carouseltype filling station.

[0040] In the embodiment shown in Figure 9, the filling station 200 is arranged along a conveyance line 101 to receive a group of prismatic cells 1 to be filled simultaneously.

[0041] A prismatic cell 1 usable in the invention is per se of a known type and comprises a substantially closed box-like case 11 , in particular having substantially the shape of a parallelepiped. The box-like case 11 is preferably metallic.

[0042] The case 11 is made of sheet metal, is substantially rigid and may be made of aluminum. The case 11 can be obtained by drawing a sheet of metal, for example aluminum. The thickness of the aluminum sheet and, consequently, of the side walls of the case 11 correspondingly obtained from it is preferably less than 3 mm, more preferably less than 1 mm, for example comprised between 0.5 mm and 0.9 mm.

[0043] The case 11 comprises substantially rectangular side walls and is closed in an upward region by a cover 15. Two of these side walls, designated by 12a- 12b, are mutually opposite and preferably have a greater size than the other side walls. Said side walls 12a-12b are elastically deformable, as explained hereinafter.

[0044] The prismatic cell 1 also comprises an electrode assembly 12, which is manufactured separately and inserted inside the case 11 (in a previous station of the battery production line) before it is finally closed with the cover 15.

[0045] The electrode assembly 12 may be configured according to any per se known structure. For example, the electrode assembly 12 may have a so- called “jelly roll” structure (in which the cathode sheets and anode sheets are rolled together with separator sheets, so that the separators are interposed between the cathodes and the anodes) or a so-called “stacked” structure (in which a plurality of cathodes and anodes having a predetermined size are stacked sequentially with separators interposed) or a so-called “Z-folded” structure (in which a single separator sheet is fed along a zigzag path, while the cathodes and anodes are inserted alternately at each fold).

[0046] The cover 15 comprises poles 15a- 15b connected to respective anode and cathode terminals of the electrode assembly 12. The cover also comprises a safety vent 15c (per se known) suitable for discharging the gases that form inside the prismatic cell 1 in the event of overpressure. This safety vent 15c can be retained by an external abutment block during the fluid electrolyte injection step.

[0047] The electrode assembly 12 occupies the internal volume of the case 11, i.e. of the prismatic cell 1, leaving interspaces 13a- 13b between the electrode assembly 12 and the side walls of the case 11.

[0048] In particular, the interspaces 13a- 13b are formed between at least one of the side walls 11 a- 11b (preferably the side walls having a greater extension than the others) and the respective directly adjacent face of the electrode assembly 12. In the preferred embodiment shown, the interspaces 13 a- 13b are located at both of the largest faces of the electrode assembly 12.

[0049] The case 11 also comprises a filling hole 14 adapted to allow the injection of the fluid electrolyte into the internal volume of the case 11.

[0050] Said hole 14, of the through type, may have a diameter of a few millimeters (for example, less than 4 mm) and is preferably provided in the cover 15, for example between one of the poles 15a-15b and the safety vent 15c.

[0051] A device 2 for filling the prismatic cell 1 with the electrolyte necessary to wet the electrodes, according to the invention, is shown in Figure 2.

[0052] Said filling device 2 comprises a body 20 which is coupled to a support having a base 28. The base 28 can be engaged with the prismatic cell 1 to be filled and, for example, can have a substantially U-like shape that is complementary to the lateral contour formed by three adjacent side walls of the case 11 of the cell 1. The base 28 can thus form a stroke limiting abutment adapted to align and center the prismatic cell 1 with respect to the filling device 2.

[0053] The body 20 can be coupled slidingly to two guiding posts 26-27 fixed to the base 28 so as to translate in a direction substantially perpendicular to the base 28, i.e., vertically.

[0054] The filling device 2 comprises a nozzle 24, for example integrated in the body 20. The nozzle 24 is adapted to be coupled in a gas-tight manner to the filling hole 14 of the prismatic cell 1. For this purpose, the nozzle 24 preferably comprises a front sealing gasket 25, arranged so as to be pressed by the nozzle 24 against a surface of the cover 15 all around the filling hole 14.

[0055] The filling device 2 also comprises a common channel 23, which leads out at the nozzle 24. Said common channel 23 is advantageously straight and has a substantially constant diameter up to the rim of the nozzle 24.

[0056] The diametrical extension of the common channel 23 is advantageously sufficient to accommodate a cylindrical pin 3 so that the pin 3 can slide inside the common channel 23 and exit from the nozzle 24 following a pressure applied to the pin 3 by a plugging member 29. The plugging member 29 is operatively associated with the common channel 23 and configured to displace the pin 3 within the common channel 23 between a first position in which the vacuum creation device 21 and the dispensing device 22 are allowed to fluidically communicate with the nozzle 24, and a second position in which the pin 3 exits the nozzle 24 in order to be plugged into the filling hole 14 of the case 11 enclosing the electrode assembly 12. In particular, the plugging member is connected to the common channel on the opposite side with respect to the nozzle 24.

[0057] The plugging member 29 comprises an applicator (not shown) which is associated with said common channel 23 and is adapted to cause the pin 3 to pass through the common channel 23 to make it exit from the nozzle 24. For example, the applicator may comprise an air jet source or a push rod that can be inserted into the common channel 23.

[0058] The filling device 2 comprises a vacuum creation device 21, which is preferably fixed to the body 20 and in fluid communication with the common channel 23 to draw air or gas through the nozzle 24 exclusively from inside the case 11.

[0059] The vacuum creation device 21 comprises a second valve 214 which can be actuated by a port 212 (for example by means of a pneumatic valve) and is connected by virtue of an intake channel 210 between the common channel 23 and a vacuum pump 215. The vacuum pump 215 is connected to a suction outlet 213 of the vacuum creation device 21. Moreover, a filter 211 is preferably provided.

[0060] Through the vacuum creation device 21, the filling device can draw air or gas from the nozzle 24, which, being coupled in a gas-tight manner to the hole 14 of the prismatic cell 1, allows to create a vacuum inside the prismatic cell 1 prior to the subsequent step of injecting the fluid electrolyte.

[0061] To perform this injection, the filling device 2 comprises a (volumetric) dispensing device 22 which is preferably fixed to the body 20 and is in fluid communication with the common channel 23 to supply a predetermined dose of the fluid electrolyte (originating from a tank 226) through the nozzle 24 in a dispensing time that is independent of the duration of the wetting step required to completely impregnate the electrode assembly 12 with the electrolyte. The predetermined dose corresponds to a predetermined quantity of fluid electrolyte, i.e., a predetermined weight (for example, 333 grams), required to provide the final electrochemical cell 1. In particular, the predetermined dose consists of a quantity of electrolyte adequate to completely wet the electrode assembly (12).

[0062] The volumetric dispensing device 22 comprises a first valve 224, which can be actuated by an inlet 222 (for example, by a pneumatic valve) and is connected, by means of a dispensing channel 220, between the common channel 23 and a volumetric (or positive-displacement) pump 225. The volumetric pump 225 is connected to a delivery inlet 223 of the volumetric dispensing device 22. The predetermined dose of fluid electrolyte pushed by the volumetric pump 225 into the inlet 223 may come from a tank 226 communicating with the volumetric pump 225.

[0063] The volumetric dispensing device 22 may, moreover, comprise a filter 221.

[0064] By virtue of the volumetric pump 225, the predetermined dose of fluid electrolyte is injected into the prismatic cell 1 through the nozzle 24, regardless of any obstacles that the fluid electrolyte may encounter in the internal volume of the case 11. Therefore, the predetermined dose of fluid electrolyte will occupy the spaces it can within the case 11 and, given the slow penetrability of the electrode assembly 12, will necessarily deform at least some of the side walls, in particular the ones 11 a- 11b with greatest extension. These side walls therefore bulge. According to the invention, said bulging of the side walls is not prevented in any way from outside the cell 1.

[0065] Said side walls 1 la-1 lb are designed so as to maintain their deformation within the elastic domain; said deformation increases the volume of the interspaces 13- 13b so that said interspaces substantially contain the entire dose of fluid electrolyte required by the cell 1, in particular for the complete impregnation of the electrode assembly necessary for the normal operation of the final cell 1 after its production. For example, the volume of each interspace 13 a- 13b in the “domed” deformed shape is adapted to contain substantially half of the predetermined dose of fluid electrolyte.

[0066] To this end, the walls 11 a- 11b that must necessarily deform to allow rapid injection according to the invention, do not have to be retained or contained in any way, as is the case instead in the background art in order to avoid indeed said deformation. Instead, in the invention, the deformation is intentional and designed and is then allowed to return to normal in all the time necessary to complete the step of completely wetting the electrode assembly 12 with the fluid electrolyte accumulated in the interspaces.

[0067] The advantage is that once the predetermined dose of fluid electrolyte has been injected in the few seconds necessary for dispensing, the prismatic cell can be immediately closed with the pin 3 and removed from the filling station 200, in order to carry out the wetting step, at least in part or completely, in a buffer station 300. The “inflated” prismatic cells coming from the filling station 200 arrive and accumulate in the buffer station 300, which can be of the FIFO (First In - First Out) type.

[0068] The dispensing time, which coincides with the transfer time of a complete dose of fluid electrolyte from the filling device 2 to the internal volume of the case 11, can therefore have a low value as desired, limited only by the characteristics of the volumetric dispensing device 22, for example by the flow rate and / or power of the volumetric pump 225. In this way, the duration of the dispensing (and therefore the permanence of the prismatic cell in the filling station 200) can be chosen on the basis of the speed of the production line of cells or batteries in which the filling station 200 with the filling devices 2 according to the invention is to be inserted.

[0069] The predetermined dispensing time may be one or more (for example, two) orders of magnitude less than the duration of the wetting step, i.e., than the time required by the electrode assembly to finalize the prismatic cell. Preferably, the predetermined dispensing time is at least 100 times shorter than the duration of the wetting step. For example, in a prismatic cell measuring approximately 110x285x30 cubic millimeters, in which it is necessary to transfer a dose of 333 grams of lithium-ion electrolyte solution, the duration of the wetting step would be approximately 30 minutes. With the invention, the 333 -gram dose can be completely injected into the internal volume of cell 1 in approximately 10 seconds.

[0070] The operation of the invention is as follows.

[0071] In a cell or battery production line, after the production of the case 11 and of the electrode assembly 12, the latter is inserted in the case 11 and the cover 15 is fixed to the case 11 so that the terminals of the electrode assembly correspond to or are electrically connected to the poles 15a- 15b of the cell 1.

[0072] Since the production line operates in an ultra-dry environment, the hole 14 of the cell 1 is temporarily closed by a temporary pin, which may be the pin 3.

[0073] During conveyance, for example on the line 101, in step 401 the cells 1 are fed to the filling station 200 with the fluid electrolyte, which comprises one or more of the filling devices 2 operating in parallel. The cells engage the base 28 of the respective filling device 2.

[0074] The filling station 200 may include a dry chamber of the minimum size necessary to contain the cell 1 or group of cells 1 to be filled and the associated filling devices 2. In the dry chamber, which may measure only a few cubic decimeters in size, an ultra-dry environment is created in the time necessary to remove the temporary pin that might be present in the hole 14 and engage the nozzle 24 of the filling device 2 on said hole 14. Alternatively, the filling station 200 may comprise a vacuum chamber suitable for containing the cell 1, or the group of cells 1 to be filled, and the corresponding filling devices 2 during the dispensing step.

[0075] After removal of the temporary pin, if any, which can be done with pliers, in step 402 the body 20 of the filling device 2 descends towards the cell until the nozzle 24 is coupled in a gas-tight manner to the hole 14 of the cell 1. Optionally, the temporary pin can be removed by suction through the common channel 23 after said coupling of the nozzle 24 with the hole 14. In the latter case, the temporary pin can be temporarily retained in the common channel 23 and coincides with the pin 3.

[0076] In any case, the pin 3, if already present in the common channel 23, must be located upstream of the region where the intake channel 210 and delivery channel 220 connect to the common channel 23.

[0077] In step 403, the valve 214 of the vacuum creation device 21 is opened and the vacuum pump 215 is activated to draw the air contained in the internal volume of the cell 1 through the common channel 23 (which is engaged with the hole 14) and the intake channel 210. In this step 403, the valve 224 of the volumetric dispensing device 22 is closed.

[0078] Subsequently, in step 404, the valve 414 is closed and the valve 424 is opened to start the injection of the fluid electrolyte into the cell 1, through the dispensing channel 220, the common channel 23 and the hole 14. The injection of the entire dose of electrolyte into the internal volume of the cell 1 takes place in a predetermined time of a few seconds or in any case much shorter than the duration of the wetting step of the electrode assembly, i.e. shorter than the time needed for wetting the electrode assembly with the injected dose of electrolyte.

[0079] The volumetric pump 225 continues to push the electrolyte into the cell 1 until the entire dose has been transferred, and this causes the side walls 11 a- 11b to deform elastically away from the electrode assembly 12, since the electrolyte feed rate is much greater than the impregnation rate of the electrode assembly 12 and the electrolyte is forced to accumulate in the interspaces 13a- 13b between the electrode assembly and the side walls of the case 11.

[0080] Then, in step 405, the valve 224 is closed and the applicator 3 of the pin is activated, said pin being then pushed into hole 14 through the common channel 23 engaged with the hole 14. Thus, the closure of hole 14 takes place after the electrolyte injection step and before the at least one interspace 13a- 13b returns to its original dimension, which occurs during the wetting step.

[0081] Then, after the plugging step, the common channel 23 is disengaged from the filling hole 14. The cell 1 thus deformed and plugged leaves the filling station 200 and is fed to a buffer station 300 (step 406). This station can be of the FIFO (first in, first out) type and may be an accumulation table (of a per se known type). The wetting step accordingly occurs outside of the dry chamber used for the injection and plugging steps, i.e. no dry chamber is needed to carry out the wetting step.

[0082] In step 407, while the deformed and plugged cells remain in the FIFO buffer station 300, the electrolyte continues to impregnate the electrode assembly 12, gradually emptying the interspaces 13a-13b and gradually releasing the pressure the electrolyte exerted from the inside on the walls 11 a- 11b. The walls thus elastically return to the undeformed configuration (i.e., closer to the electrode assembly 12) that they had before the injection step, having undergone a deformation that is deliberately limited to the elastic range.

[0083] By virtue of the separation, in two distinct stations, of the injection and wetting steps, it is possible to continue operating the cell production line at high speed without limiting it with the time necessary for the complete wetting of the electrode groups contained in the cells 1. The limitation of the line speed is given solely by the transfer speed of the entire predetermined dose of fluid electrolyte inside the case 11 which, as mentioned, can be reduced to a few seconds by utilizing the elastic deformability of the metal sheet that constitutes the case 11.

[0084] Since the entire dose of electrolyte is transferred in a single step, it is not necessary to repeat the filling cycle or to dispense partial amounts of electrolyte, as is instead the case in the background art. Moreover, by filling an internal volume in which a vacuum has been created and in which deformation of the side walls of the cell casing is allowed, the formation of air bubbles is avoided.

[0085] In practice it has been found that the invention achieves the intended aim and objects.

[0086] The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims; all the details may furthermore be replaced with other technically equivalent elements.

[0087] In practice, the materials and the contingent shapes and dimensions may be any according to the requirements and the state of the art.

[0088] The disclosures in Italian Patent Application No. 102024000015070 from which this application claims priority are incorporated herein by reference.

[0089] Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

CLAIMS1. A method for filling at least one battery cell (1) with electrolyte, wherein the cell (1) comprises a substantially closed box-like case (11) having preferably a parallelepiped shape, said case (11) comprising an internal volume occupied by an electrode assembly (12) leaving interspaces (13a-13b) between said electrode assembly and side walls (1 la-1 lb) of said case (11), said case (11) comprising a hole (14) adapted to allow an injection of a fluid electrolyte into said internal volume, said method comprising the steps of:- creation of a vacuum in said internal volume of the case (11);- injection of a predetermined dose of said electrolyte into said internal volume through said hole (14) causing an elastic deformation of at least one of said side walls (1 la-1 lb) of said case, so as to increase the interspace (13a-13b) between said at least one side wall (1 la-1 lb) and the electrode assembly (12);- wetting of said electrode assembly (12) with said dose of electrolyte injected into the internal volume; said method being characterized by further comprising the step of:- closure of said hole (14) after the injection step and before the interspace (13a- 13b) returns to its original dimension which occurs during the wetting step.

2. The method according to claim 1, wherein said injection and closure steps occur in a filling station (200) and said wetting step occurs at least in part in a buffer station (300) in which the at least one cell (1) that has been injected with the respective dose of electrolyte is accumulated.

3. The method according to claim 1 or 2, wherein the injection of the predetermined dose of electrolyte into said internal volume takes a predetermined time which is shorter than the time needed for wetting the electrode assembly (12) with the injected predetermined dose of electrolyte, and lasts for a time preferably at least one order of magnitude less than thetime needed by said wetting step.

4. The method according to one or more of the preceding claims, wherein said at least one side wall is one of the two mutually opposite rectangular side walls (1 la-1 lb) of said case (11) that have a greater extension than each of the other two opposite side walls of the case (11).

5. The method according to the preceding claim, wherein, during said injection step, both of said side walls having a greater extension undergo an elastic deformation.

6. The method according to one or more of the preceding claims, wherein said injection step is performed by a volumetric dispensing device (22).

7. The method according to one or more of the preceding claims, wherein said closure step comprises plugging a pin (3) into said hole (14), said pin (3) being slidingly accommodated into a common channel (23) communicating with a filling device (2) used for the vacuum creation and injection steps, said common channel (23) being engaged with the hole (14) during the steps of creation of the vacuum, injection of the predetermined dose and closing of the hole (14).

8. The method according to the preceding claim, wherein after the plugging step, said common channel (23) is disengaged from the filling hole (14).

9. The method according to one or more of the preceding claims, wherein said injection and closure steps occur within a dedicated dry chamber while said wetting step occurs outside said dedicated dry chamber.

10. The method according to one or more of the preceding claims, wherein said predetermined dose of electrolyte consists of a quantity of electrolyte adequate to completely wet the electrode assembly (12).

11. A filling device for filling at least one battery cell (1) with electrolyte, said filling device comprising:- a nozzle (24) which can be coupled in a gas-tight manner to a fillinghole (14) of a case (11) enclosing an electrode assembly (12);- a common channel (23) which leads into said nozzle (24);- a dispensing device (22) for feeding a predetermined dose of fluid electrolyte through said nozzle (24), said dispensing device (22) being in fluid communication with said common channel (23);- a vacuum creation device (21) for creating vacuum through said nozzle (24), said vacuum creation device (21) being in fluid communication with said common channel (23), said filling device being characterized by further comprising a plugging member (29) operatively associated with said common channel (23) and configured to displace a pin (3) within said common channel (23) between a first position in which said vacuum creation (21) and dispensing (22) devices are allowed to fluidically communicate with said nozzle (24), and a second position in which it exits said nozzle (24) in order to be plugged into the filling hole (14) of the case (11) enclosing the electrode assembly (12).

12. The filling device according to the preceding claim, wherein said volumetric dispensing device (22) comprises a volumetric pump (225) and a first valve (224) connected between said common channel (23) and the volumetric pump (225).

13. The filling device according to claim 11 or 12, wherein said vacuum creation device (21) comprises a vacuum pump (215) and a second valve (214) connected between said common channel (23) and the vacuum pump (215).

14. A filling line for filling battery cells (1) with electrolyte, said filling line comprising a filling station (200) comprising at least one filling device (2) according to any of the claims 11 - 13 and a buffer station (300) configured to accumulate the plugged cases (11).

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