Inerting process for electrochemical accumulator

Abstract

A method for inerting an electrochemical accumulator cell (1) comprising a casing (4) containing active zones and a dead volume, this method comprising the following steps: – forming an inerting channel (5) in the casing (4) by drilling through the casing (4) opposite the dead volume; – introducing an injection cannula (8) into the inerting channel (5), the tip of the injection cannula (8) opening into the dead volume; – injecting a predetermined volume of an inerting liquid through the injection cannula (8). Figure for the abstract: Fig. 6

Description

Title of the invention: Inerting process for electrochemical accumulator. Technical field

[0001] The invention relates to the field of electrochemical accumulators and more particularly to inerting processes enabling in particular the recycling of electrochemical accumulators.

[0002] Electrochemical batteries allow for the storage of electrical energy and are increasingly common, particularly in widespread applications involving high power, such as electric vehicle propulsion. The recycling of electrochemical batteries is a crucial operation for a sector destined to become increasingly important. Electrochemical battery inerting processes are necessary to completely discharge an electrochemical battery, regardless of its initial state of charge, even if this is unknown. These inerting processes are essential to guarantee the safety and operational reliability required before any dismantling of an electrochemical battery for recycling purposes. PREVIOUS ART

[0003] Inerting processes and systems are currently known in the context of recycling certain electrochemical batteries. For example, processes targeting lithium-ion batteries subject the battery to an inerting medium.

[0004] These processes require large quantities of this inerting medium with frequent renewal, as it becomes contaminated during the inerting of an accumulator. Description of the invention

[0005] The invention aims to improve prior art inerting processes for electrochemical accumulators.

[0006] To this end, the invention relates to a method for inerting an electrochemical accumulator cell which comprises a casing containing active zones and a dead volume, this method comprising the following steps: - formation of an inerting duct in the envelope by drilling the envelope opposite the dead volume; - introduction of an injection cannula into the inerting duct, the end of the injection cannula opening into the dead volume; - injection through the injection cannula of a predetermined volume of an inerting liquid.

[0007] According to another object, the invention relates to an inerting system for an electrochemical accumulator cell comprising an envelope containing active zones and a dead volume, this system comprising: - a drilling device adapted to form in the casing an inerting conduit communicating with the dead volume; - an injection cannula adapted to be inserted into the inerting duct and to open into the dead volume; - an injection device via the injection cannula for an inerting liquid.

[0008] The dead volume of the electrochemical accumulator cell is defined as an empty internal volume of the cell, which is outside the active areas consisting of the electrodes and the electrolyte.

[0009] The method according to the invention guarantees the inerting of an electrochemical accumulator cell, that is to say, the neutralization of any electrochemical reaction within it, which corresponds to a complete discharge of the cell. The inerting is carried out simply and quickly, with a high level of safety.

[0010] An inert electrochemical accumulator cell, devoid of stored energy, can thus be disassembled, crushed, or undergo any other suitable recycling process. The invention is particularly advantageous for the recycling of large, high-power accumulator batteries, operations which are becoming increasingly essential with the widespread adoption of these batteries and current and future regulations.

[0011] Indeed, when an electrochemical storage battery, for example an electric vehicle battery made of lithium-ion cells, is received at a recycling center, its state of charge is not necessarily known in advance, and its cells may potentially contain a significant amount of energy. The invention enables recycling without needing to know the battery's state of charge, and therefore without having to carry out physicochemical measurements, electrical measurements, or consult the BMS (Battery Management System) devices possibly associated with the battery. Recycling operations can begin safely with the certainty of working on electrochemical storage cells that do not contain energy.

[0012] The invention requires only drilling a conduit and injecting a limited volume of inerting fluid, specific to each cell. These operations are carried out in a short time, which makes it possible to inert large quantities of electrochemical accumulator cells with small quantities of inerting fluid.

[0013] Furthermore, for cells where a safety cut-off device has been triggered, for example a CID (for "Current Interrupt Device"), the Externally accessible terminals of the cell are no longer both connected to the two potentials. The invention also makes it possible to inert such cells, which can no longer be discharged through their external terminals.

[0014] The electrochemical accumulator cell inerting process according to the invention may include the following additional features, alone or in combination:

[0015] - the predetermined volume of an inerting liquid is a volume substantially equal to dead volume of the electrochemical accumulator cell;

[0016] - the casing includes a vent, and the step of forming an inerting duct is achieved by drilling the vent;

[0017] - the electrochemical accumulator cell is cylindrical in shape and the volume the death consists of a central shaft delimited by the active zones, and the step of forming an inerting conduit is carried out by drilling the envelope in the longitudinal axis of the central shaft;

[0018] - the electrochemical accumulator cell comprises coils, and the step of formation of an inerting conduit is achieved by drilling the casing in an inter-coil area;

[0019] - the electrochemical accumulator cell comprises a flattened coil, and the step the formation of an inerting conduit is achieved by drilling the envelope along the longitudinal axis of the coil, opposite an area which is located in the heart of the coil, and which is adjacent to the active areas of greatest radius of curvature;

[0020] - the step of forming an inerting duct and the step of introducing a cannula injections into the inerting conduit are carried out simultaneously by a perforating injection cannula;

[0021] - the step of forming an inerting conduit is carried out by drilling the casing and an inerting spacer located inside the casing and included in the dead volume;

[0022] - the method includes a preliminary step of cell identification electrochemical accumulator and determination: of a drilling zone on the envelope, this drilling zone being located opposite the dead volume; and of a volume of inerting liquid to be injected;

[0023] - the process includes an additional step of controlling the temperature of the electrochemical accumulator cell after the injection stage;

[0024] - the process includes an end-of-inerting alert step when the temperature of the electrochemical accumulator cell falls below a predetermined threshold;

[0025] - the electrochemical accumulator cell includes a management device thermal, and the process includes a step of controlling the temperature of the electrochemical accumulator cell, and of controlling the thermal management device to maintain the temperature of the electrochemical accumulator cell below a maximum temperature;

[0026] The electrochemical accumulator cell inerting system according to the invention may include the following additional features, alone or in combination:

[0027] - the drilling device and the injection cannula are both formed of a cannula piercing injection;

[0028] - the system includes a means for identifying the battery cell electrochemical and a means of correspondence between the identified electrochemical accumulator cell and: a drilling area in the casing; and a volume of inerting liquid to be injected;

[0029] - the system includes an inerting support comprising a distribution conduit inerting fluid connected to the injection cannula which is fixed to the inerting support, and a location for the electrochemical accumulator cell arranged so that, when the electrochemical accumulator cell is inserted into the location, the injection cannula opens into the dead volume. PRESENTATION OF THE FIGURES

[0030] Other features and advantages of the invention will become apparent from the following non-limiting description, with reference to the accompanying drawings in which:

[0031] - [Fig.1] schematically illustrates an electrochemical accumulator cell;

[0032] - [Fig.2] illustrates a first step of the process according to the invention;

[0033] - [Fig.3] illustrates a second step of the process according to the invention;

[0034] - [Fig.4] illustrates a third step of the process according to the invention;

[0035] - [Fig.5] is a graph illustrating the inerting of a battery cell;

[0036] - Figure 6 illustrates the application of the method according to the invention to a cell of a particular accumulator;

[0037] - Figure 7 illustrates another example of an electrochemical accumulator cell adapted to undergo the inerting process according to the invention;

[0038] - [Fig.8] is a schematic cross-sectional view of the battery cell electrochemical of the [Fig.7];

[0039] - Figure 9 illustrates the application of the inerting process to the battery cell electrochemical of figures 7 and 8;

[0040] - Figures [Fig. 10] and [Fig. 11] illustrate the application of the inerting process to another type of electrochemical battery cell;

[0041] - Figure 12 illustrates another example of an electrochemical accumulator cell adapted to benefit from the inerting process;

[0042] - the [Fig. 13] illustrates an inerting support;

[0043] - [Fig.14] illustrates the implementation of the inerting support of [Fig.13].

[0044] Similar and common elements in the various embodiments bear the same reference numbers to the figures. DETAILED DESCRIPTION

[0045] Fig. 1 schematically illustrates in cross-section a cell 1 of an electrochemical accumulator. This illustrative example is a cylindrical accumulator cell of lithium-ion chemistry.

[0046] The cell 1 comprises a sealed casing 4 containing active zones 2 which are conventionally made of an alternating winding of electrodes and electrolyte. Inside the casing 4, the cell 1 also comprises a dead volume 6 consisting of empty spaces outside these active zones 2. In this example of a cylindrical cell, this dead volume 6 includes, in particular, a central shaft 3 which is delimited by the winding of electrodes and electrolyte.

[0047] In the context of the present invention, the electrochemical accumulator cell 1 is, for example, received at a recycling center for dismantling in order to recover its constituent elements, in particular the metals it contains, and to dispose of the polluting elements in a compliant manner. The electrochemical accumulator cell 1 potentially has an unknown charge upon its receipt at the recycling center.

[0048] The electrochemical accumulator cell 1 will first be inert in order to release the energy it contains, to bring its voltage back to zero, and thus allow its safe disassembly.

[0049] A first step of the inerting process is illustrated in [Fig. 2]. The electrochemical accumulator cell 1 is first drilled through its casing 4 (an operation schematically represented by the drill bit 7). The resulting hole forms an inerting channel 5 in the thickness of the casing 4, this inerting channel connecting the outside of the cell to its inside.

[0050] The inerting channel 5 is made opposite the dead volume 6 of the cell 1. In the illustrated example, relating to a cylindrical cell 1, the inerting channel 5 is made in the center of one of the end faces of the cell 1, along the longitudinal axis of the central shaft 3.

[0051] The diameter of the drill bit 7 is chosen so that the drilling does not cause damage in the active areas 2, so as not to cause interference with the active areas 2 (and therefore with the potential charge) of the cell 1. The drill bit 7 in this example has a diameter smaller than the diameter of the central shaft 3.

[0052] The next step in the inerting process, illustrated in [Fig. 3], consists of introducing an injection cannula 8 into the inerting conduit 5 so that the end of this injection cannula 8 opens into the dead volume 6 of cell 1, that is to say in this example into the central shaft 3.

[0053] The injection cannula 8 is connected to an injection device 9, schematically represented by a syringe in the figures. In a manual implementation of the process according to the invention, in the case of small-scale recycling of electrochemical battery cells, this injection device 9 can effectively be a syringe operated by a person. Alternatively, in more automated recycling centers with higher throughput, the injection device 9 may consist of any suitable injection means, such as: pumps, pressure-controlled tanks with an injector, or any other means of injecting a controlled quantity of liquid through the injection cannula 8.

[0054] Optionally, the injection device 9 can be equipped with a liquid pressure measurement system, which makes it possible to identify the end of the dead volume filling. This can compensate, during the application of the process, for any uncertainty in the predetermined volume of liquid to be injected.

[0055] The injection device 9 is charged with an inerting liquid 10 adapted to inert the cell 1 when this liquid comes into contact with the active areas 2.

[0056] In the present example, the inerting liquid 10 can be deionized water, optionally loaded with salts or conductive particles to optimize inerting. Metallic particles, carbon fillers, or microfibers can be used to constitute such a filler. For example, such a filler can advantageously consist of conductive carbon black mixed with a solvent such as dimethyl carbonate.

[0057] The relevant characteristic for choosing a suitable inerting liquid 10 is its electrical conductivity, which must be non-zero but sufficiently low so as not to induce thermal runaway of the cell during inerting. The inerting liquid 10 preferably has an electrical conductivity between 10 and 500 mS / cm.

[0058] The next step of the inerting process is illustrated in [Fig. 4]. In this step, the injection device 9 injects a predetermined quantity of inerting fluid 10 into the electrochemical accumulator cell 1. The injected inerting fluid 10 spreads through the dead volume 6 and then comes into contact with the active areas 2. The inerting fluid brings the anodic and cathodic layers into a controlled short circuit (by the choice of inerting fluid), thus initiating the inerting process.

[0059] The process according to the invention can be implemented by an inerting system, automated or not, which comprises: - a drilling device 7 adapted to create an inerting conduit 5 in the casing; - an injection cannula 8 adapted to be inserted into the inerting conduit 5; - an injection device 9 via the injection cannula 5 of an inerting liquid 10.

[0060] The electrochemical accumulator cell 1 is preferably identified beforehand (by means of an identification which may include external identification of cell type and size, or even identification by marked reference, by QR Code, etc.), so that: - a drilling zone can be defined as being positioned opposite the dead volume, so that the drilling step effectively leads to an inerting conduit 5 opening into the dead volume of cell 1; - the predetermined volume of inerting liquid 10 to be injected can be defined, this volume corresponding to a volume adapted to sufficiently fill the dead volumes so that the inerting liquid 10 comes into contact with all the active zones 2.

[0061] The correspondence between, on the one hand, the identified cell 1 and, on the other hand, the drilling area as well as the volume of inerting liquid to be injected, can be achieved by any appropriate means of correspondence, for example by a correspondence table or a local or remote database.

[0062] In the illustrated example [Fig.4], given the internal geometry of cell 1 in this example, the predetermined volume of injected inerting fluid 10 is substantially equal to the dead volume of cell 1, which here encompasses the central shaft 3 and an adjacent transverse volume 11. This injected volume allows the inerting fluid 10 to be in contact with an edge of all the layers of the active zones 2. The inerting fluid 10 can thus create limited electrical conduction between the different stacked layers of the active zones 2, given the electrical conductivity characteristics of the inerting fluid 10.

[0063] Figure 5 is a graphic illustrating an example of concrete implementation of the process according to the invention. The graph in [Fig.5] was obtained following measurements taken during the inerting of a lithium-ion cell of type 18650, very common in industry, with deionized water as the inerting liquid.

[0064] The graph in [Fig. 5] shows the evolution over time in seconds (on the x-axis) of: - the voltage across the terminals of the inertial cell (first curve 12 and abscissas on the left of the graph, in V); - the temperature of the inert cell (second curve 13 and abscissas to the right of the graph, in °C).

[0065] Under the initial conditions, at 0 s, the cell temperature is approximately 20 °C and the voltage across its terminals is 4.2 V (voltage of a fully charged 18650 cell). In this implementation, the cell is received for recycling with a 100% charge level, which corresponds to the most critical case.

[0066] Following the step of drilling the inerting conduit 5, the step of injecting a predetermined volume of inerting liquid through the injection cannula takes place at time t=0.

[0067] The graph shows that around time t=25,000 s, the voltage of cell 1 drops significantly, in parallel with a controlled heating of the cell, allowing the energy it contains to be dissipated. This heating reaches a peak at approximately 130°C, before falling back to the initial temperature.

[0068] After a time Tov corresponding to approximately 8.8 hours, cell 1 reaches a voltage of 0 V. The cell temperature is then in its falling phase. From time t=35,000 s, cell 1 returns to ambient temperature and is completely discharged.

[0069] The inerting of the cell took place by means of a heating which, in this example, reached 130°C at peak, which is a completely acceptable temperature, without risk of thermal runaway, and which also corresponds to a point in time where the cell is already largely discharged.

[0070] Dismantling and recycling operations can then take place safely.

[0071] Optionally, the inerting process may include an additional step for monitoring the temperature of the electrochemical battery cell after the inerting liquid injection step. Furthermore, the process may include an end-of-inerting alert step when the battery cell temperature falls below a predetermined threshold. In the example illustrated [Fig. 5], this threshold could be 40°C, which corresponds to an acceptable temperature for the safe handling of cell 1 and to a complete discharge of the battery.

[0072] Fig. 6 also illustrates the test relating to the graph of Fig. 5, and represents the step of injecting inerting liquid into the inerting conduit 5 of the cell 18650. Since these cells are cylindrical, the point chosen here to carry out the step of drilling the inerting conduit 5 is the center of the disk constituting one of the end faces of the cell 1.

[0073] Fig. 6 therefore illustrates the inerting channel 5, made in the middle of one face of the cell 1, and the injection device 9 with the injection cannula 8 in place to carry out the injection into the dead volume 6 of the cell 1, and more precisely into the central shaft around which the electrode and electrolyte windings are made (as in the example of Figures 1 to 4).

[0074] Figure 7 illustrates another example of an electrochemical battery cell for the application of the process according to the invention. In this example, cell 1 is a prismatic cell, and more specifically a stacked-electrode lithium-ion battery cell of the "stack" type.

[0075] Figure 8 schematically illustrates the classic structure of such a cell 1 electrochemical accumulator in which the active areas 2 consist of a stack of electrodes and layers of electrolyte, the electrodes being connected to two connection terminals 14.

[0076] These cells 1 are prismatic and their casing 4 is provided with a vent 15 forming a safety valve adapted to open when the internal pressure of the cell 1 exceeds a pressure threshold. In this example, the vent 15 is located on the upper face, at the level of the central area between the two connection terminals 14.

[0077] This prismatic cell 1 can also benefit from the inerting process by means of a drilling operation of the inerting conduit which can be carried out in any portion of the envelope 4, as long as this portion opens into the dead volume 6.

[0078] In the present example, the drilling step is carried out in the vent 15. By drilling in the vent 15, the inerting conduit 5 will open into the dead volume 6.

[0079] Figure 9 illustrates the step of introducing the injection cannula 8 into this conduit inerting 5, which was carried out by drilling the vent 15. The next step then consists of injecting the inerting liquid 10 into the dead volume 6 which is opposite the vent 15.

[0080] As before, the injected volume of inerting liquid 10 will be chosen to sufficiently fill the dead volume 6 of the cell 1 until it comes into contact with the entire stack constituting the active zones 2.

[0081] Figure 10 illustrates another example of an electrochemical accumulator cell 1 which can benefit from the inerting process according to the invention. Cell 1 of [Fig. 10] is a prismatic cell made up of four coils 16, in this example. Such prismatic electrochemical accumulator cells are made from a juxtaposition of flattened coils contained within the casing 4. These cells 1 are common in high-power and high-energy-density applications, such as batteries for electric vehicles, which will be recycled on a large scale in the future.

[0082] The method preferably includes a preliminary step of identifying the electrochemical accumulator cell 1 followed by a step of determining, based on this identification, a drilling zone opposite the dead volume 6 of the cell 1. This identified drilling zone will ensure a drilling of the envelope 4 which will open into this dead volume 6.

[0083] Figure 10 illustrates the operation of drilling the inerting conduit 5. In this example, The identified drilling area is a central area, between the two pairs of coils 16. In this example, cell 1 has previously been identified as a prismatic cell with four coils 16, and the chosen drilling area is located at the geometric center of one of the faces of the cell (the bottom face in the view of [Fig. 10]) to be located opposite an inter-coil space.

[0084] In the example of [Fig. 10], the drilling operation is performed directly by the injection cannula 8. The injection cannula 8 is therefore a piercing injection cannula, which has a tapered end adapted for piercing the casing 4, and is made of a material suitable for such drilling. For example, for a casing made of a polymer, the injection cannula 8 is made of steel with sufficient hardness for drilling through the corresponding thickness of that polymer.

[0085] When the drilling operation with the injection cannula 8 is completed, the injection cannula 8 is already in place in the inerting conduit 5 and the inerting liquid injection step can take place.

[0086] Figure 11 illustrates a variant of the inerting process in which the electrochemical accumulator cell 1 includes an inerting spacer 17 formed by an insert piece located inside the casing 4, which defines a safe drilling volume. The drilling tool (whether a drill bit 7, a perforating injection nozzle 8, or any other element suitable for drilling the casing 4) can perform the drilling and form the inerting channel 5 with the guarantee that this operation will not damage any active element inside the casing 4.

[0087] The inerting spacer 17 is porous or has through-holes, so that a conduit bored in the material of the inerting spacer 17 will be in fluidic communication with the outside of the inerting spacer 17, i.e. here with the dead volume 6 of the cell 1 (the inerting spacer 17 is in fact placed in the dead volume of the cell, or creates a dead volume itself by its presence and the empty spaces it contains).

[0088] Thus, after drilling the envelope 4 and then the inerting spacer 17, and the formation of the inerting conduit 5 within this inerting spacer 17, the operation of injecting the inerting liquid 10 into the inerting conduit 5 leads to an injection of this inerting liquid 10 into the dead volume 6, via the inerting spacer 17 included in the dead volume.

[0089] As an alternative to the drawings, the inerting spacer 17 can also occupy the entire dead space of the cell 1, the inerting spacer then constituting this dead volume.

[0090] An external marking on the casing 4 may optionally be provided to identify the position of the inerting spacer 17. Alternatively, the simple identification of the accumulator cell 1 can allow the location of the inerting spacer 17 to be determined.

[0091] Figure 12 illustrates another example of an electrochemical accumulator cell 1 on which the inerting process is implemented. This is a cell 1 consisting of also of a flattened reel 16. The [Fig.12] is a cross-sectional view of cell 1, schematically illustrating the winding layers of reel 16. The drilling step of such a cell 1 is here carried out along its longitudinal direction, i.e. along an axis perpendicular to the plane of the [Fig. 12].

[0092] Such a cell 1 may advantageously have zones 18 particularly suited to the drilling step (the zones 18 are identified by hatching in [Fig. 12]). These zones 18 are located in the core of the coil 16, adjacent to the windings with the largest radii of curvature, that is, on either side of the space enclosed by the most central winding of the coil 16. These zones 18 are well situated opposite the dead volume in the case of such a cell 1 consisting of a coil 16. The cell is then drilled along its longitudinal axis in one of these zones 18.

[0093] Alternatively, these zones 18 can also be provided with inerting spacers 17 which then secure the drilling step, in the same way as in the embodiment of [Fig. 11].

[0094] Figures 13 and 14 illustrate another embodiment of the inerting process in which the step of drilling a cell 1 of an electrochemical accumulator, to form the inerting conduit 5, is carried out by inserting the cell 1 onto an inerting support 19.

[0095] Figure 13 illustrates the inerting support 19 alone. The inerting support 19 comprises a distribution conduit 20 supplied with inerting fluid 10 by means (not shown) such as a pump associated with a regulator of the injected volume. The distribution conduit 20 is connected to one or more injection cannulas 8 (three in the illustrated example). The injection cannulas 8 are here perforating cannulas, as in the embodiment of Figure 10, formed by rigid punches adapted not only to inject the inerting fluid 10, but also to perforate the shell 4 of the cells 1.

[0096] To carry out the drilling step of a cell 1, the cell 1 is inserted on the inerting support 19, at a delimited location 21 and the injection cannula 8 pierces the envelope 4 of the cell 1, under the effect of the cell 1's own weight and possibly supplemented by the application of a driving force.

[0097] Fig. 14 illustrates the inerting support 19 on which three cells 1 have been placed, and which have therefore each undergone the step of drilling an inerting conduit 5 with their placement on the inerting support 19.

[0098] In this embodiment, the cells 1 may or may not include inerting spacers 17 as described above. In the illustrated example, one of the cells 1 includes an inerting spacer 17 as described above, and the other two cells do not.

[0099] The inerting support 19 is adapted to the cells 1 to be inerted, which is the case, for example, during the serial recycling of identical cells that have been previously identified. The inerting support 19 is thus calibrated with the locations 21, each intended to position the corresponding cell 1 so that the desired drilling area on the cell 1 is aligned with an injection cannula 8 when the cell is placed on the inerting support 19.

[0100] When a cell 1 is introduced into its location 21, the perforating injection cannula 8 pierces the envelope 4 in the chosen drilling area, which is opposite the dead volume 6 of the cell.

[0101] The placement of a cell 1 in its location 21 simultaneously performs the step of drilling the envelope 4 to create the injection channel 5, and the operation of introducing the injection cannula 8. The step of injecting the inerting liquid 17 can then take place through the distribution channel 20.

[0102] Furthermore, optionally, the method according to the invention can take advantage of the thermal management device possibly associated with cell 1. Indeed, some batteries have a thermal management device adapted to cool the battery and controlled by the battery management system (BMS). If these means are operational upon receipt of an electrochemical accumulator cell at a recycling center, the inerting process can include steps for implementing this thermal management device. The inerting device can include a step for monitoring the temperature of cell 1 and controlling the thermal management device to maintain the temperature of cell 1 below a maximum temperature.

[0103] Variations in the embodiment of the inerting process can be implemented. For example, the step of drilling an inerting conduit can be carried out by any means allowing the envelope 4 to be pierced at the desired location (drill bit, piercing injection cannula, punch, etc.).

[0104] The predetermined volume of injected inerting fluid 10 can be a volume substantially equal to the total dead volume of the cell 1. Alternatively, depending on the type of cell 1, this predetermined volume can be less than the dead volume of the cell 1, if such a volume of inerting fluid is able to come into contact with all the active areas 2 of the cell 1.

Claims

Demands

1. A method for inerting an electrochemical accumulator cell (1) comprising a casing (4) containing active zones (2) and a dead volume (6), and an inerting spacer (17) disposed inside the casing (4) and included in the dead volume (6), characterized in that it comprises the following steps: - formation of an inerting channel (5) in the casing (4) by drilling the casing (4) opposite the dead volume (6), and drilling the inerting spacer (17); - introduction of an injection cannula (8) into the inerting channel (5), the end of the injection cannula (8) opening into the dead volume (6); - injection by the injection cannula (8) of a predetermined volume of an inerting liquid (10), via the inerting spacer (17).

2. Inerting method according to claim 1, characterized in that the predetermined volume of an inerting liquid (10) is a volume substantially equal to the dead volume (6) of the electrochemical accumulator cell (1).

3. Inerting method according to any one of the preceding claims, the envelope (4) comprising a vent (15), characterized in that the step of forming an inerting conduit (5) is carried out by drilling the vent (15).

4. Inerting method according to any one of claims 1 or 2, the electrochemical accumulator cell (1) being cylindrical in shape and the dead volume (6) comprising a central barrel (3) delimited by the active zones (2), characterized in that the step of forming an inerting conduit (5) is carried out by drilling the envelope (4) in the longitudinal axis of the central barrel (3).

5. Inerting method according to any one of claims 1 or 2, the electrochemical accumulator cell (1) comprising coils (16), characterized in that the step of forming an inerting conduit (5) is carried out by drilling the envelope (4) in an inter-coil area.

6. A method for inerting according to claim 1 or 2, the electrochemical accumulator cell (1) comprising a flattened coil (16), characterized in that the conduit formation step inerting (5) is carried out by drilling the envelope (4) along the longitudinal axis of the coil (16), opposite a zone (18) which is located in the heart of the coil (16), and which is adjacent to the active zones (2) of greater radius of curvature.

7. Inerting method according to any one of the preceding claims, characterized in that the step of forming an inerting conduit (5) and the step of introducing an injection cannula (8) into the inerting conduit (5) are carried out simultaneously by a perforating injection cannula (8).

8. Inerting method according to any one of the preceding claims, characterized in that it comprises a preliminary step of identifying the electrochemical accumulator cell (1) and determining: a drilling zone on the envelope (4), this drilling zone being located opposite the dead volume (6); and a volume of inerting liquid (10) to be injected.

9. Inerting method according to any one of the preceding claims, characterized in that it comprises an additional step of controlling the temperature of the electrochemical accumulator cell (1) after the injection step.

10. Method according to claim 9, characterized in that it includes an end-of-inerting alert step when the temperature of the electrochemical accumulator cell (1) falls below a predetermined threshold.

11. A method according to any one of the preceding claims, the electrochemical accumulator cell (1) comprising a thermal management device, characterized in that the method comprises a step of controlling the temperature of the electrochemical accumulator cell (1), and of controlling the thermal management device to maintain the temperature of the electrochemical accumulator cell (1) below a maximum temperature.

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