Discharge method and installation for an electrochemical energy storage cell.

Abstract

Method and installation for discharging an electrochemical energy storage cell. Method for discharging an electrochemical energy storage cell, the cell comprising: a stack (3) housed within a casing (4), the stack comprising a first electrode (5), a separator (7), a second electrode (6), and first and second electrical collectors (42, 43), the method comprising a perforation comprising the formation of at least one through hole (8) through the casing (4), a connection comprising contacting at least one electrically conductive device (10) with a first electrical collector (42, 43), and a discharge of the cell comprising a first electrical connection of said at least one electrically conductive device (10) with an electrical discharge system (45) and a second electrical connection of the electrical discharge system (45) with the second electrical collector (42, 43).so as to electrically couple in series the electrical discharge system (45) and the stack (3). Figure for the abstract: Fig. 3,

Description

Title of the invention: Method and installation for discharging an electrochemical energy storage cell. technical field

[0001] The present invention relates to the discharge of electrochemical energy storage cells, and more particularly to a lithium-ion type cell. STATE OF THE ART

[0002] Electrochemical accumulators are currently used to store energy in chemical form and to release some of the stored energy to power electrical devices. Electrochemical accumulators are also called "cells," and more generally, chemical energy storage cells. Accumulators can be lithium-ion based, or based on other lithium chemistries, such as lithium metal, or based on the intercalation of other ions, such as sodium-ion or potassium-ion chemistries within a battery system. Furthermore, accumulators comprise two electrodes and a separator placed between them. The separator's function is to provide electrical insulation between the electrodes and also to conduct ionic currents between them to ensure the movement of charges between the electrodes.Furthermore, an electrochemical system placed between the two electrodes may include a solid or liquid electrolyte to ensure ionic conduction. In addition, a battery includes a casing, also called a housing, which can be rigid (for cylindrical or rectangular batteries) or flexible, for example, in the form of a bag. This casing also ensures a watertight connection between the electrodes and an external electrical circuit. Electrical conduction elements are also integrated into batteries to ensure the electrical connection between the electrodes and the battery's external terminals, also known as power terminals. These external terminals are used to electrically connect the battery to the external electrical circuit.Electrical conduction devices are also called current collectors or "tabs" in English.

[0003] A battery generally comprises a series arrangement of these accumulators to obtain higher voltages, and a parallel arrangement to obtain greater capacities, and therefore greater stored energy. The combination of these accumulators in series to obtain higher voltages and in parallel to obtain greater capacities and therefore greater stored energy is called a battery.

[0004] Compared to other battery technologies, such as aqueous electrolyte technologies, lithium-ion batteries offer the advantage of higher energy and power density. However, one of the drawbacks of batteries using this technology is safety. Indeed, when a lithium-ion battery is misused—electrically, thermally, or mechanically—exothermic reactions can occur, leading in the worst-case scenario to thermal runaway. In this case, smoke, flames, and even an explosion can occur. The safety of lithium-ion batteries is a fundamental aspect that influences their entire life cycle.

[0005] Thermal runaway can be caused by a variety of factors, such as thermal, mechanical, or electrical abuse of one or more batteries. To protect batteries, manufacturers can integrate active or passive protection systems designed to disconnect one or both electrodes from their respective terminals. This electrically isolates the electrochemical core (i.e., the electrodes, electrolyte, and separator) of the cell from the battery system. Once one or more of these integrated cell protection systems has been triggered, the external terminals of the battery are no longer electrically connected to the electrodes inside the casing. These protection systems safeguard batteries during system-wide failures, such as the overcharging of one or more batteries, or a short circuit in one or more batteries.Once this protection is triggered, the battery system may become inoperative, operate at degraded performance, and enter an unstable safety state, with one or more cells being misused. Maintenance, aimed at removing the faulty cell(s) for replacement or system dismantling, is then necessary. However, once a cell is misused, its state is unstable and there is a risk of thermal runaway. It is therefore important to remove all the energy contained in the cell before working on it, until, for example, the voltage between its electrodes is zero or all the energy has been released thermally; the terminology in these two cases can be used for stabilization or inerting.But once one or more of their safety systems have been triggered, it is then impossible to discharge, or render inert, the damaged batteries by the external electrical circuit, the latter being disconnected from the electrodes.

[0006] For example, European patent application EP2866281 discloses an overload protection system comprising a deformable membrane controlled by the internal pressure of the cell and a fuse-type current collector connecting one of the electrodes to its terminal. When the cell is overloaded, the internal pressure increases due to the degradation of the species Chemicals. If the pressure reaches or exceeds a value set by the manufacturer (for example, five bar), the membrane deforms and connects the positive and negative terminals of the battery, thus short-circuiting it. In this situation, the current can reach several thousand amperes. This overcurrent triggers the fuse function integrated into the current collector. Due to the fuse function of the collector, the short circuit is interrupted after a time short enough not to damage the cell (a few milliseconds). The fusible current collector is therefore severed at one or more points, and the cell is said to be bypassed, which ensures the continuity of service of the branch and the system with one less battery. However, in this case, the battery can no longer be discharged through its external terminals due to the disconnection, but it may still be partially or fully charged, or even overcharged.

[0007] There are different battery discharge processes.

[0008] One can cite, for example, abusive testing techniques for lithium-ion batteries, such as the puncture test known as the "nail penetration test." This standardized test aims to puncture the battery with a standardized speed, force, and nail, and to study its reactions. However, this technique, due to the tearing of the metal casing, the tearing of the separator, and the electrical contact of the various components of the battery, systematically leads to thermal runaway. This method therefore does not allow for the recovery of the battery and its components intact, nor for the discharge of an abused battery that might be integrated into a battery pack with other, unabused batteries.

[0009] We can also cite Chinese patent applications CN109256598 and CN210187243, which disclose methods for destructively discharging the faulty battery or batteries. However, these methods are destructive and do not allow for the inertification of an isolated cell within a system or for the complete recovery of materials for analysis or material recovery (for recycling, for example).

[0010] For example, Chinese patent applications CN115275405 and CN114824543 disclose non-destructive methods for discharging batteries in liquid or paste-like substances with controlled electrical conductivity. However, these solutions are not applicable to batteries with activated internal protection, since the external terminals are no longer in contact with the battery's anode or cathode.

[0011] We may also cite patent documents CN215644580U and KR102404943B1, which disclose methods for perforating the accumulator in a controlled environment and, for example, allowing a conductive solution to enter. The aim is to generate an internal short circuit. However, these solutions have the disadvantage of requiring an environment containing the conductive solution. The need to, for example, immerse a battery in a solution to discharge it renders these methods unsuitable for discharging a battery within a battery system prior to its dismantling. Furthermore, this type of solution incorporates a conductive, often aqueous, solution that degrades the electrochemical and electrical components of the battery and, once exposed to the battery's chemical components, must be treated as toxic waste. Consequently, these techniques do not allow for the recovery of the battery components in their entirety, for example, for recycling purposes.

[0012] An object of the present invention is therefore to provide means for discharging an electrically isolated accumulator from a circuit, without destroying the elements of the accumulator, with a view to recovering them safely by an operator.

[0013] Another object is to be able to discharge a misused accumulator in which a protection system has disconnected one or two electrodes from the external terminals of the accumulator.

[0014] The other objects, features and advantages of the present invention will become apparent from an examination of the following description and accompanying drawings. It is understood that other advantages may be incorporated. SUMMARY

[0015] According to one aspect of the invention, a method for discharging an electrochemical energy storage cell is proposed, the cell comprising: - a stack housed within a cell envelope, the stack comprising successively, according to a stacking direction, at least a first electrode, a separator and a second electrode, and - the first and second electrical collectors coupled respectively to the first and second electrodes.

[0016] The process comprises: - a perforation comprising the formation of at least one through-hole through the casing so as to provide access to the first electrical collector. The method further comprises: - a connection comprising bringing at least one electrically conductive device into contact with said first electrical collector, via said at least one through hole. The method further comprises: - a cell discharge comprising a first electrical connection of said at least one electrically conductive device with a first terminal of an electrical discharge system and a second electrical connection of a second terminal of the discharge system electrical with the second electrical collector, so as to electrically couple in series the electrical discharge system and the stack.

[0017] Thus, the cell can be discharged at least partially without significantly damaging the separator. The cell can then be handled safely. Such a process can preserve the electrodes without destroying them. Advantageously, the electrodes can be recycled or the cell components analyzed to determine its performance. Furthermore, such a process is particularly suitable for discharging a cell equipped with a safety device that has been activated and has disconnected an electrical collector linking an electrode to an external terminal of the cell.

[0018] According to another aspect, a discharge installation for an electrochemical energy storage cell is proposed, comprising a support suitable for receiving a cell, the cell comprising a stack housed within a cell envelope, the stack comprising successively, according to a stacking direction, at least a first electrode, a separator and a second electrode.

[0019] The installation includes a perforator configured to form at least one through hole through the casing so as to form access to the first electrical collector, at least one electrically conductive device configured to be made in contact with said first electrical collector, via said at least one through hole, and an electrical discharge system comprising a first terminal electrically coupled to said at least one electrically conductive device, and a second terminal electrically coupled with the second electrical collector, so as to electrically couple in series the electrical discharge system and the stack to discharge the cell. BRIEF DESCRIPTION OF THE FIGURES

[0020] The aims, objects, features and advantages of the invention will become clearer from the detailed description of an embodiment thereof, which is illustrated by the following accompanying drawings in which:

[0021] [Fig.1] [Fig.1] represents a flowchart of the main steps of a discharge process of an electrochemical energy storage cell;

[0022] [Fig.2] [Fig.2] schematically represents one embodiment of a installation for discharging an electrochemical energy storage cell;

[0023] [Fig.3] [Fig.3] schematically represents a method of implementing a discharge stage of an electrochemical energy storage cell;

[0024] [Fig.4] [Fig.4] schematically represents another method of implementing a discharge stage of an electrochemical energy storage cell;

[0025] [Fig. 5] [Fig. 5] represents a flowchart of the main steps in a mode of implementation of a discharge process for an electrochemical energy storage cell;

[0026] [Fig.6] [Fig.6] represents a flowchart of the main steps of another mode implementation of a discharge process for an electrochemical energy storage cell;

[0027] [Fig.7] [Fig.7] schematically represents one embodiment of a drill bit;

[0028] [Fig.8] [Fig.8] represents a curve of the absolute displacement of an electrically conductive device engaged in the opening hole and a curve of the voltage measured between an electrically conductive device and the cell envelope as a function of time, the envelope being electrically connected to an electrode of the cell;

[0029] [Fig.9] [Fig.9] represents current and discharged capacitance curves of a cell as a function of time, and a voltage curve between the second electrode of the cell connected to the cell envelope and an electrically conductive device in contact with the first electrode through a hole opening as a function of time.

[0030] The drawings are given by way of example and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate understanding of the invention and are not necessarily to scale with practical applications. DETAILED DESCRIPTION

[0031] Before beginning a detailed review of embodiments and implementations of the invention, optional features which may possibly be used in association or alternatively are stated below.

[0032] According to one example, the cell further comprises first and second power terminals, the second power terminal being electrically coupled to the second electrode via the second electrical collector, and the second electrical connection comprises an electrical connection of the second terminal of the electrical discharge system with the second power terminal.

[0033] According to an alternative example, the perforation comprises forming a first through hole through at least one part of the casing to provide access to the first electrical collector, and forming a second through hole through at least one part of the casing to provide access to the second electrical collector. The connection comprises bringing a first electrically conductive device into contact with the first electrical collector via the first through hole and bringing a second device into contact with the first electrical collector. electrically conductive with the second electrical collector, via the second open hole. The discharge comprises a first electrical connection of the first electrically conductive device with the first terminal of the electrical discharge system and a second electrical connection of the second electrically conductive device with the second terminal of the electrical discharge system.

[0034] According to one example, the perforation includes forming said at least one through hole using a drill bit animated in rotation and translation during the formation of said at least one through hole.

[0035] According to one example, said at least one electrically conductive device is the drill bit, which is stationary while rotating during discharge. Advantageously, this limits the number of tools to be used to discharge a cell, thus further simplifying the discharge process.

[0036] According to one example, the method comprises, after the formation of said at least one through hole, maintaining the drill bit in rotation and translation, and after the connection, the method further comprises stopping the translation of the drill bit during discharge. Such a method makes it possible to perforate insulating elements, such as tapes or packaging of the electrochemical core, located between an electrical collector and the casing, so as to be able to pass through them to make contact between the electrically conductive device and the electrical collector.

[0037] According to one example, the method comprises, after the formation of at least one through hole, determining the end of the perforation corresponding to the creation of the through hole, stopping the rotation of the drill, and translating the drill to the connection. Such a method is suitable for cells without insulating elements between an electrical collector and the casing and makes it possible to avoid prolonged movement of the rotating drill and prevents the drill from penetrating the stack and at least from damaging at least one of the stack's electrodes. This avoids damaging an electrode in the event of contact between the drill and the electrode.

[0038] According to one example, the perforation includes determining an initial position in which the drill is in contact with the casing, a translational movement of the drill in the direction of one of the first and second electrical collectors, determining a stroke of the drill relative to the initial position, and determining the end of perforation is carried out when the stroke of the drill is equal to a predetermined value greater than or equal to a thickness of the casing, the thickness of the casing being defined according to the stacking direction.

[0039] According to one example, the method comprises a measurement of electrical resistance between the drill bit and the casing, and wherein, before determining the initial position, the electrical resistance is different from 0 Ohm, and the determination of the initial position is carried out when the electrical resistance is equal to 0 Ohm.

[0040] According to one example, the method includes a measurement of a potential difference between said at least one electrically conductive device and the second electrode, and the method includes a determination that the connection is made when the potential difference is distinct from a reference potential difference.

[0041] According to one example, the method includes a measurement of a potential difference between the second power terminal and said at least one electrically conductive device, and the method includes a determination that the connection is made when the potential difference is distinct from a reference potential difference.

[0042] According to one example, the second power terminal is electrically coupled to the envelope, the method comprising a measurement of a potential difference between the drill and the envelope, and the method comprises a determination that the connection is made when the potential difference is distinct from a reference potential difference.

[0043] According to one example, the potential difference measurement is carried out, after the perforation and before the connection, to determine the reference potential difference.

[0044] According to one example, the drill bit has an elongated body, a head located at one end of the elongated body, the elongated body having a constant cross-section of a first diameter, the head having a cross-section of a second diameter strictly larger than the first diameter, the perforation of the casing comprising bringing the head into contact with the casing during which the potential difference is equal to 0 Volts, and determining the end of the perforation when the head is no longer in contact with the casing and the potential difference is not 0 Volts. The drill bit is used to determine the end of the perforation, in particular an electrical contact between the drill bit and the cell casing to measure a potential difference, which simplifies the process.

[0045] According to one example, the connection comprises a first electrical connection of said at least one electrically conductive device with a first terminal of a measuring circuit and a second electrical connection of a second terminal of the measuring circuit with the second electrical collector, so as to determine at least one parameter representative of an operating state of the cell. Thus, the charge level of the cell can be known before discharging it.

[0046] It is specified that within the framework of the present invention, the expressions "A coupled to B", "A electrically coupled to B", "A connected to B", "A electrically connected to B", "A connected to B" or "A electrically connected to B" are synonymous with "A is electrically connected to B" and do not necessarily mean that there is no component between A and B. Thus, these expressions refer to an electrical connection between two elements, this connection may or may not be direct; this means that it is possible that between a first device A and a second device B that are electrically connected, linked, or coupled, a current flows in A, in B, and along the path connecting A to B, this path may or may not include other electrical equipment.

[0047] Conversely, in the context of the present invention, the term "electrically connected directly" or "directly connected" refers to a direct electrical connection between two elements. This means that between a first device A and a second device B that are electrically connected directly, no other equipment is present, other than an electrical connection or several electrical connections.

[0048] It is specified that in the context of the present invention, the term "electrically placed" or "electrically located" means a positioning of a device on a line in which a current flows.

[0049] Figure 2 shows a method of implementing a discharge process of an electrochemical energy storage cell 2, called a chemical energy storage cell 2. Generally, a cell 2 comprises a stack 3 housed within a cell 2 casing 4. The stack 3 consists, successively along a stacking direction Z, of at least a first electrode 5, a separator 7, and a second electrode 6. The cell 2 can be lithium-based, such as lithium metal, or sodium-ion or potassium-ion based. Preferably, the cell 2 is of the lithium-ion type. The casing 4 can be rigid and cylindrical or prismatic in shape. As another example, the casing 4 can be flexible, for example, having the shape of a pouch. Flexible is understood to mean a casing capable of deforming under its own weight. The first electrode 5 can be an anode, generally made of copper foil coated with a carbonaceous material.The second electrode 6 can be a cathode, usually made of an aluminum strip, coated with lithia metal oxides. One of the pairs of lithia metal oxides used to constitute the cathode can be LiNiXMnyCoZO2. Alternatively, the first electrode 5 can be a cathode and the second electrode can be an anode.

[0050] The separator 7 may comprise a polymer whose function is to provide electrical insulation between the cathode 6 and the anode 5 while ensuring ionic conduction between them. As a result, the cell 2 is not internally short-circuited, and ionic conduction ensures the movement of charges between the electrodes 5 and 6. The separator 7 may comprise polypropylene (PP) or polyethylene (PE). This Electrical insulation and ionic conduction functionality is achieved by creating pores of controlled diameters (a process known as "wet process" or "dry process") in the polymer material of the separator 7. Generally, the separator 7 is solid and porous to contain a liquid electrolyte, also called an ionic conduction medium. Alternatively, the separator 7 providing the ionic conduction functionality can be a solid electrolyte.

[0051] In addition, cell 2 includes two external terminals 40, 41, referred to as power terminals, configured to electrically couple cell 2 to an electrical device. For some cells, the second power terminal 41 is electrically coupled to the casing 4. The electrical device may be a current-consuming device, such as an electric motor, or a device for charging cell 2, such as an electric generator. Cell 2 also includes a first electrical collector 42 configured to electrically couple the first electrode 5 to the first power terminal 40 and a second electrical collector 43 configured to electrically couple the second electrode 6 to the second power terminal 41. The first and second electrical collectors 42, 43 are also called current collectors.An electrical collector 42, 43, electrically connecting an electrode 5, 6 to a power terminal 40, 41, is also said to be associated with the electrode 5, 6 and the power terminal 40, 41 that it connects. Furthermore, at least one electrical collector 42, 43 may be of the fusible type, also called a fusible collector. Advantageously, the first and second electrical collectors 42, 43 are of the fusible type. In this case, an overcurrent triggers the fusible function that is integrated into the fusible-type electrical collectors. In other words, the fusible-type electrical collector is thus severed at one or more points, and cell 2 is said to be broken, the electrical circuit being open between the electrode and the power terminal associated with the collector.

[0052] Figure 3 shows the case where the first fusible collector 42 is severed. Figure 4 shows the case where the first and second fusible collectors 42, 43 are severed. In particular, each severed electrical collector 42, 43 comprises a first part 44a remaining electrically coupled to its associated electrode 5, 6 and a second part 44b remaining electrically coupled to its associated power terminal 40, 41. Thus, when a fusible collector 42, 43 is severed, the first and second parts 44a, 44b are no longer electrically connected to each other. In this case, the cell 2 can no longer be discharged through its power terminals 40, 41 due to the disconnection.

[0053] In normal operation, each electrical collector 42, 43 electrically connects an electrode 5, 6 to a power terminal 40, 4L. When cell 2 is misused, Electrically, thermally, or mechanically, exothermic reactions can occur. When cell 2 includes at least one fusible collector 42, 43, and cell 2 is electrically damaged by an overcurrent or a short circuit, said at least one fusible collector 42, 43 is severed, and its first portion 44a remains electrically coupled to its associated electrode 5, 6. Furthermore, its first portion 44a is no longer electrically coupled to its associated power terminal 40, 41.

[0054] Figure 1 illustrates the main steps of a discharge method for the electrochemical energy storage cell 2. Generally, the method comprises a perforation S1, a connection S3, and a discharge S4.

[0055] The perforation SI includes the formation of at least one through hole 8, 9 through the envelope 4 so as to form an access to one of the first and second electrical collectors 42, 43. Advantageously, each through hole 8, 9 is formed as close as possible to the electrical contact between an electrical collector 42, 43 and its associated electrode 5, 6. Thus, when the electrical collector 42, 43 is a sectioned fusible collector, the through hole 8, 9 provides access to at least the first part 44a of the sectioned fusible collector 42, 43.

[0056] The perforation S1 comprises creating a localized opening at one or more locations in the envelope 4 of the cell 2 so as to make accessible an element of the internal electrical circuit of the cell 2 upstream of the protection that opens the circuit. Advantageously, the perforation S1 is made in such a way as not to damage the components or electrode layers located behind the envelope 4. The distance between the envelope 4 and the current collectors 42, 43 varies depending on the format and type of cell 2. In general, the order of magnitude of the distance varies from a few hundred micrometers to a few millimeters. If the perforation device damages the electrode layer(s) 5, 6 located behind the envelope 4, the resulting damage can, for example, lead to thermal runaway of the cell 2.To facilitate the drilling SI at the electrical collectors 42, 43, the position of the electrical collectors 42, 43 can be determined, for example by non-destructive techniques such as X-ray tomography, or by an envelope 4 displaying this information (for example: the drilling area and the depth before potential resumption) in the case of future cells 2 for which the discharge process would be planned.

[0057] The connection S3 includes contacting at least one electrically conductive device 10, 11 with the electrical collector 42, 43 made accessible through the through hole 8, 9. The accessible electrical collector 42, 43 is preferably located directly above the through hole 8, 9. The connection S3 includes introducing an electrically conductive device 10, 11 through the through hole 8, 9. In particular, the device 10, 11 is moved towards the electrical collector 42, 43 until contact is made.

[0058] The electrically conductive device 10, 11 enabling electrical contact preferably has a diameter smaller than the internal diameter of the through holes 8, 9. This ensures electrical insulation between the electrically conductive device 10, 11, intended to be connected to the potential of an electrode 5, 6, and the casing 4, when the latter is connected to the potential of the other electrode 6, 5. If the second external terminal 41 is still connected to the second electrode 6, the potential difference between the electrically conductive device 10 and the second external terminal 41 is equal to the inter-electrode potential difference 5, 6. Due to the restoration of the electrical circuit of cell 2, and therefore access to the inter-electrode potential 5, 6, the method potentially allows, at this stage, before initiating the discharge, for the diagnosis of cell 2 to be performed.Indeed, through potential measurement, several indicators measured passively or actively are accessible concerning cell 2, for example the state of charge or other parameters by impedance measurement for example.

[0059] The discharge S4 comprises a first electrical connection of the electrically conductive device 10, 11, in contact with the accessible electrical collector 42, 43, with a first terminal B1 of an electrical discharge system 45, and a second electrical connection of a second terminal B2 of the electrical discharge system 45 with the other electrical collector 43, 42, so as to electrically couple in series the electrical discharge system 45 and the stack 3. The first and second electrical connections allow the cell 2 to be discharged. Indeed, the discharge S4 closes the electrical circuit comprising the stack 3 and the electrical discharge system 45 connected in series, which results in the discharge of the cell 2. The electrical discharge system 45 may include a fixed resistive load or an electronic load including, for example, a discharge current regulator.

[0060] Furthermore, the discharge end S5 is reached when a measurement of a characteristic parameter of the cell 2 charge no longer shows any variation and returns to the initial or fixed values, for example. The most relevant parameter for this embodiment is the potential difference between electrodes 5 and 6, but other parameters can be used as a substitute or in addition, such as temperature or discharge current, for example.

[0061] In the case where cell 2 comprises a single fusible collector 42, as illustrated in [Fig. 3], the electrically conductive device 10 in contact with the fusible collector 42 is electrically connected to the first terminal B1 of the electrical discharge system 45, by means of a first electrical connection CL. Furthermore, one The second terminal B2 is electrically connected to the other electrical collector 43 via the second power terminal 41. In particular, the second power terminal 41 is electrically coupled to the second electrode 6 via the second electrical collector 43. The second power terminal 41 is electrically connected to the second terminal B2 of the load 45 via a second electrical connection C2. Furthermore, for some cells 2, the casing 4 may be electrically connected to the second power terminal 41. In this case, the casing 4 is electrically connected to the second terminal B2 of the load 45 via a connection not shown in [Fig. 3], for the sake of simplicity.

[0062] In the case where the cell 2 comprises two fusible collectors 42, 43 as illustrated in [Fig.4], a first electrically conductive device 10 in contact with a first fusible collector 42 is electrically connected to the first terminal B1 of the electrical discharge system 45, by the first electrical connection Cl. In addition, a second electrically conductive device 11 in contact with the second fusible collector 43 is electrically connected to the second terminal B2 of the electrical discharge system 45, by means of a third electrical connection C3.

[0063] For example, the cell 2 may include a casing 4 having a cylindrical shape, and the cell 2 is then called a cylindrical battery. The size of the cylindrical battery, referred to as "18650", may be 18 mm in diameter and 65 mm high, or referred to as "21700" for 21 mm in diameter and 70 mm high, or other formats. These batteries generally have a capacity between 1 and 6 Ah for Lithium-ion technologies, known as third-generation. Furthermore, the casing 4 may be located at a distance, called the separation distance, from the first electrode 5. The separation distance may vary depending on the type of cell 2. The separation distance is defined according to the stacking direction Z. For example, the separation distance may be between 100 micrometers and 1 mm. The separation distance creates a volume, called the dead volume, located between the stack 3 and the casing 4.In general, cells 2 have the smallest possible dead volume to increase energy density. The separation distance is usually less than 1 millimeter. The casing 4 can also be rigid and have a parallelepiped shape, and the cell 2 is called a parallelepiped cell. A parallelepiped cell can have a capacity greater than 50 Ah. The dimensions of a parallelepiped cell 2 can be, for example, 147 mm long, 29 mm wide, and 97 mm high. In this case, the cell 2 can be drilled approximately 6 mm from the first external terminal 40. Furthermore, for a parallelepiped cell, each electrode 5, 6 extends longitudinally in a plane, called the electrode plane, perpendicular to the stacking direction Z. Preferably, a through hole 8, 9 is formed. on one face of cell 2 at a point located at the right of an electrical collector 42, 43, perpendicular to this face.

[0064] For cylindrical cells 2, the electrodes 5, 6 are wound around a winding axis perpendicular to the stacking direction Z, and the stack is generally called a "coil". Generally, the location of the hole 8 is selected so as to maximize the probability of being located directly above an electrical collector 42, 43.

[0065] In general, the process may include an initial step S0 in which the cell 2 is placed on a support 30, as illustrated in [Fig. 2]. The perforation SI consists of generating a localized opening at a point in the envelope 4 so as to make an electrical collector 42, 43 accessible.

[0066] The formation of a through hole 8, 9 can be carried out using a drill bit 20 is animated in rotation and translation about a longitudinal axis Al of the drill bit 20. In particular, the drill bit 20 comprises a body 21 extending mainly along the longitudinal axis AL. Generally, the drill bit 20 is configured to form the through hole 8. For example, the drill bit 20 may have a hardness greater than or equal to that of the casing 4. For example, the drill bit 20 may be helical with a cylindrical shank. The drill bit 20 may be made of steel. The diameter of the drill bit 20 may be selected according to the size of the casing of the cell 2. For example, a drill bit with a diameter less than 4 mm is suitable to reduce the torque required for drilling SI and thus reduce heating. The drill bit 20 may be held by means of a chuck or other mechanical part so as to ensure its mechanical connection to an axial rotating element so that the drill bit 20 rotates about its longitudinal axis Al without excessive imbalance or wobble.A motor M generating the rotation can be an electric motor capable of reaching a suitable rotational speed for the perforation SI, such as a DC machine, a synchronous machine, an asynchronous machine, or other rotating device that can be remotely interrupted.

[0067] For example, the cell 2 may include insulating elements, such as tapes or packaging for the electrochemical core, located between an electrical collector 42, 43 and the casing 4. In this case, the method comprises, after the formation of said at least one through hole 8, 9, maintaining the drill 20 in rotation and translation so as to pierce the insulating elements and reach the electrical collector 42, 43. Then, when the connection S3 is made, the method comprises stopping the rotation and translation of the drill 20. Then the discharge S4 is carried out. In other words, the casing 4 is pierced and then the drill continues to advance and drill until the connection S3 is reached, that is to say, the contacting of at least one electrically conductive device 10, 11 with an electrical collector 42, 43.

[0068] Alternatively, the cell 2 may be devoid of insulating elements located between a collector 42, 43 and the casing 4. In this case, in order to avoid damaging the electrical collectors 42, 43, the method includes, before the connection S3, a determination of the end of the perforation S2, corresponding to the creation of the through hole 8, 9, and a rotational stop of the drill bit D3. Furthermore, the determination S2 prevents damage to the electrodes 5, 6 located closest to the casing 4 by avoiding piercing or tearing them.

[0069] Furthermore, the determination of the end of perforation S2 can be carried out in different ways. For example, the perforation SI includes determining an initial position in which the drill 20 is in contact with the casing 4, a translational movement of the drill 20 in the direction of one of the first and second electrical collectors 42, 43, determining a stroke of the drill 20 relative to the initial position, and the determination of the end of perforation S2 is carried out when the stroke of the drill 20 is equal to a predetermined value greater than or equal to a thickness El of the casing 4. The thickness El of the casing 4 is defined according to the stacking direction Z.

[0070] According to another example, the perforation SI includes rotating the drill DI 1 using the motor M, determining the electrical consumption of the motor M, and determining the end of perforation S2 is carried out when the electrical consumption of the motor M is less than or equal to an electrical consumption threshold. Advantageously, before performing the S4 discharge, a potential difference can be measured between the first electrically conductive device 10 and the second electrode 6 to perform diagnostics on cell 2. According to another advantage, this difference can be measured after the S1 perforation and before the S3 connection to determine a reference potential difference. The reference potential difference can also be determined before the S1 perforation step. Generally, the reference potential difference corresponds to a measurement taken when the circuit is open; that is, this reference potential difference corresponds to a floating potential. For example, the reference potential difference is considered to be less than 0.1 volts, and preferably, it is considered to be 0 volts.Then, the potential difference between the first electrically conductive device 10 and the second electrode 6 is measured to determine that connection S3 is made. The potential difference is equal to the potential difference between the first and second electrodes 5, 6. When the value of the potential difference between the first and second electrodes 5, 6 is unknown, connection S3 is considered made when the potential difference is distinct from the reference potential difference. By. A distinct potential difference means that the measured potential difference has a value different from the reference potential difference. For example, connection S3 is considered to be made when the difference is strictly greater than 0.1 Volt, preferably not equal to 0 Volt.

[0071] Figure 6 shows another embodiment of determining the end of perforation S2 and determining that connection S3 is made. According to this alternative embodiment, cell 2 comprises a single fusible collector 42, and the second power terminal 41 is coupled to the second electrode 6 via the second collector 43. In this case, perforation S1 includes measuring a potential difference S02 between the second power terminal 41 and the drill bit 20, and determining that connection S3 is made when the potential difference is distinct from the reference potential difference, for example, when the measured potential difference is not 0 volts, preferably equal to the potential difference between the first and second electrodes 5, 6.

[0072] To measure the potential difference, the drill bit 20 can be electrically coupled to a voltage measuring circuit 200. The measuring circuit 200 can be a voltmeter or a microcontroller. The measuring circuit 200 is further electrically coupled to the second power terminal 41 by a fourth electrical connection C4. Alternatively, when the second power terminal 41 is electrically connected to the housing 4, the measuring circuit 200 can be electrically coupled to the housing 4 by another electrical connection C7, as illustrated in [Fig. 2]. The voltage measuring circuit 200 is further electrically coupled to the drill bit 20 by a fifth electrical connection C5. The fifth electrical connection C5 can be a rotating electrical connector fixed to the drill bit 20 or a chuck mechanically connected to the drill bit 20 to rotate it.Preferably, the drill bit 20 and the chuck are made of electrically conductive materials and can conduct current. Thus, the drill bit 20 and the chuck allow the measuring circuit 200 to measure an electrical potential between the drill bit 20 and either the second power terminal 41 of the cell 2 or the housing 4. In this embodiment, the drill bit 20 includes a head 22 located at one end of the body 21 of the drill bit 20. One embodiment of the drill bit 20 is shown in [Fig. 7]. Advantageously, the body 21 of the drill bit 20 has at least one first portion 23 having a constant cross-section of a first diameter Dx. The first portion 23 is located between the head 22 and a second portion 24. The second portion 24 is configured to be coupled to the motor M. The second portion 24 may include a cross-section having a diameter different from or equal to the first diameter Dx.According to one advantage, the first part 23 includes grooves to evacuate the material extracted from the shell 4, in the form of chips, to the outside of the shell 4. Furthermore, the head 22 has a . section of a second diameter Dy strictly greater than the first diameter Dx. The first and second diameters Dx, Dy are defined along an axis B perpendicular to the longitudinal axis Al of the drill 20.

[0073] By using such a drill bit 20, the determination that the connection S3 is made can be improved. Preferably, the voltage SOI between the drill bit 20 and the second power terminal 41 is measured. Then, before the perforation SI, the drill bit 20 is positioned at a distance from the envelope 4, as illustrated in [Fig. 2]. In this case, the circuit between the second power terminal 41 and the drill bit 20 is open. The potential between the two is said to be "floating" and represents a parasitic random value. Then, the perforation SI of the envelope 4 is performed. The perforation SI involves bringing the head 22 of the drill bit 20 into contact with the envelope 4, during which the potential difference is equal to 0 volts if the second power terminal 41 is connected to the envelope 4, and remains different from 0 volts otherwise.Indeed, when the second power terminal 41 is connected to the casing 4, the electrical circuit is closed upon contact, and the potential difference between the drill bit 20 and the casing 4 is therefore 0V. In other words, this contact is determined by measuring a change in voltage value. Then, the perforation step SI of the casing 4 continues by rotating the drill bit 20 while maintaining its translational movement along the longitudinal axis Al and in the direction of an electrical collector 42, 43. When the perforation is complete, the through hole 8, 9 is made, and the head 22 of the drill bit 20 passes through the hole 8, 9.

[0074] The determination of the end of perforation S2 is carried out when the head 22 is no longer in contact with the casing 4 and when the potential difference is different from the reference potential difference, for example, different from 0 Volts. In this case, the head 22 has passed through the open hole 8, 9. That is to say, the head 22 is no longer in contact with the casing 4, and a "floating" potential, representing a random parasitic value, is again measured. Thus, thanks to the difference in diameter between the cross-sections of the head 22 and the first part 23 of the body 21 of the drill bit 20, it is ensured that the drill bit 20 is no longer in contact with the casing 4. Alternatively, an electrical resistance measurement can be carried out between the drill bit and the casing to detect the different stages of the process. In this case, an infinite resistance (i.e., a resistance other than 0 Ohm) is measured before the drill bit makes contact with the casing.The initial position of the drill bit in contact with the casing is detected when this resistance changes to zero, and then remains zero during drilling of the casing. At the end of drilling the casing, the resistance becomes infinite again.

[0075] Then, the drill bit 20 is moved until the drill bit 20 is in contact with the first collector 42, and it is determined that the connection S3 is made when the the potential difference between the second power terminal 41 and the drill 20, or between the envelope 4 and the drill 20 when the envelope 4 is coupled to the second power terminal 41, is distinct from the reference potential difference, for example when it reaches a value equal to the potential difference between the first and second electrodes 5, 6.

[0076] When cell 2 comprises two collectors 42, 43, as illustrated in [Fig. 4], the drilling end-determination S2 can be performed by measuring the potential difference between a drill bit 20 and the cell 2 casing. In this case, drilling end-determination S2 can be determined when the potential difference measurement changes from 0 volts to a value other than 0 volts, i.e., a floating potential. Drilling end-determination S2 can be performed by methods such as measuring the distance traveled by the drill bit 20 or by measuring the torque of the drilling motor, for example. Preferably, to determine that connection S3 is established, a potential measurement between the two drill bits 20 is used. Synchronized advance of the drill bits 20 prevents one of the drill bits 20 from damaging the accumulator by going too far.Preferably, the drills 20 begin their travel from the same distance from cell 2 and progress at the same speed if the cell is symmetrical, or staggered to compensate for the difference in distance to the collectors 42, 43 of cell 2 if it is not symmetrical. Preferably, both drills 20 touch the collectors 42, 43 at the same time. Indeed, if the difference is too great, one drill 20 may continue to progress and damage the electrodes 5, 6 before the other reaches the other collector 42, 43. Thus, connection S3 is made when the potential difference between the drills 20 is distinct from the reference potential difference. This is because, during connection S3, the potential difference between the drills 20 corresponds to the potential difference between the first and second electrodes 5, 6.

[0077] For example, to perform a diagnostic of the electrical state of cell 2 before discharge S4, connection S3 comprises a first electrical connection of at least one electrically conductive device 10, 11 with a first terminal B3 of the measuring circuit 200, via the fifth electrical connection C5, and a second electrical connection of a second terminal B4 of the measuring circuit 200 with the second electrical collector 43, so as to determine at least one parameter representative of an operating state of the cell. For example, the second terminal B4 of the measuring circuit 200 is connected with the second external terminal 41, via the fourth electrical connection C4, as illustrated in [Fig. 2]. Alternatively, the second terminal B4 of the measuring circuit 200 is connected with the second electrically conductive device 11, via a sixth electrical connection C6, as illustrated in [Fig. 4].Thus, one can. Measure the voltage across electrodes 5 and 6 of stack 3. This allows us to determine the charge level of cell 2 before discharging it. In other words, we can diagnose the cell's condition before discharging it.

[0078] During the discharge S4, an electrically conductive device 10, 11 other than the drill bit 20 can be used. Advantageously, as illustrated in [Fig.4], each electrically conductive device 10, 11 is a drill bit 20. To discharge the cell 2, the electrodes 5, 6 are electrically connected to the electrical discharge system 45.

[0079] When the discharge S4 is started, a discharge current and a voltage variation measured between the drill bit 20 and either the second power terminal 41, the cell 2 enclosure 4, or the second electrically conductive device 11, indicates that the longitudinal movement of the drill bit 20 must be stopped for a waiting period before the discharge. This waiting period depends on the discharge power and the amount of energy contained in cell 2. It can be several minutes or several hours.

[0080] Cell 2 can be considered discharged S5 when it reaches a charge level sufficiently low for the operators. The charge level of cell 2 can be estimated in several ways.

[0081] Alternatively, the voltage between electrodes 5 and 6 can be measured. Electrochemical batteries exhibit a variation in their open-circuit voltage depending on their state of charge. For example, for some lithium-ion batteries with a nickel manganese cobalt (NMC) cathode 6 and a carbon anode 5, the voltage can vary between 2.5 V (discharged) and 4.2 V (fully charged). The discharge current can also be measured. By measuring the discharge current over the entire discharge time S4, it is possible to determine the energy discharged from cell 2 and, therefore, knowing the initial capacity of the battery, to estimate its state of charge. A combination of the two methods mentioned above is also possible.

[0082] According to another advantage, during the discharge S4, using the electrical discharge system 45 electrically connected to the first and second electrodes 5, 6 of the cell 2, the voltage can be measured, using the measuring circuit 200, between the first and second electrodes 5, 6.

[0083] To implement the discharge process, a discharge unit 100 with a cell 2 can be used. The unit 100 is illustrated in [Fig. 2]. The discharge unit 100 includes the support 30 adapted to receive a cell 2. The unit 100 further includes a drill 101 configured to form the through holes 8, 9. The drill 101 includes the motor M coupled to the drill bit 20 and configured to rotate the drill bit 20 about the longitudinal axis Al of the drill bit 20. The unit 100 also includes a stepper motor configured to move the drill bit 20 in translation along the stacking direction Z. The installation 100 includes the electrically conductive devices 10, 11 configured to be made in contact with the first and second electrical collectors 42, 43, via the through holes 8, 9. The installation 100 further includes the electrical discharge system 45 allowing the cell 2 to be discharged.

[0084] To enable the "forward" and "reverse" movements of the drill bit 20, the drill 101, its connectors, the chuck, and the drill bit 20 are placed on a platform 102, allowing the drill bit 20 to be translated in a controllable manner, preferably with a forward or reverse accuracy of less than 1 mm per increment. An example embodiment is to place all the elements of the drill 101 on the platform 102, which has a helical connection constrained with a rotating axis. This function can be performed by a worm gear that drives a plate 104 mounted to move in translation on the platform 102, along a displacement axis A2 parallel to the longitudinal axis AL. The rotation of the worm gear is controlled by an electric motor that allows the number of rotations to be controlled. The electric motor can be a stepper motor, for example, a variable reluctance motor, a permanent magnet motor, or both.

[0085] The support 30 keeps the unloading cell 2 stationary relative to the ground. The support 30 can be configured to constrain the cell 2, in particular to ensure that the torque of the drill 101 does not cause movement of the cell 2.

[0086] For example, the installation 100 may include a control unit 103 configured to control the drill 101 and the translational movements of the table 104. The control unit 103 is also connected to the measuring circuit 200 to receive the measured voltages, such as the potential differences between the drill bit 20 and the casing 4, the potential differences between the drill bits 20, or between a drill bit 20 and the second power terminal 4L. The control unit 103 may be a computer equipped with appropriate actuator acquisition and management cards. The installation 100 may include means for converting electrical energy to convert a mains voltage into a voltage suitable for the drill 101, its motor M, actuators for moving the table 104, and the control unit 103.Installation 100 may also include a programmable logic controller or a microcontroller board to power the actuators of platform 104, and to communicate with the control unit 103.

[0087] Figure 5 shows a method of implementing the discharge process using the installation 100.

[0088] The initial step S0 comprises positioning the cell 2 on the mechanical support 30. Then, the process comprises rotating DI 1 of the drill bit 20. For example, the control unit 103, or an external power supply controlled by remote operators, actuates the motor M to rotate the drill bit 20.

[0089] The control unit 103 receives, from remote operators or automatically, the instruction to advance the drill bit D12. This can be done by actuating the electric machine located at the head of the worm gear in a clockwise direction. This action causes the plate 104, on which the drill bit 20 and its motor M are located, to advance.

[0090] This action is repeated until the drill bit 20 comes into contact with the shell 4 of cell 2. The method may include a determination D13 of the contact of the drill bit 20 with the shell 4. For example, the determination D13 may be carried out using a limit switch, or by ultrasonic measurement, or by a contact or position sensor. The determination D13 may also be carried out by measuring the potential between the drill bit 20 and the shell 4. It is also possible to count the number of steps taken by the electric machine and deduce from this the number of steps required to reach the shell 4 of cell 2.

[0091] Once this determination D13 is made, the perforation SL is performed. The perforation step SI can be carried out jointly with the perforation end determination step S2. Then, it is determined that the connection S3 is made. In order to perforate the envelope 4 of cell 2 without damaging the electrical collectors 42, 43 located behind the envelope 4, the advance of the platform 104 is stopped as soon as the connection S3 is made.

[0092] The determination of the end of perforation S2 may include the following steps. The platform 104 is advanced by the stepper motor by a distance equal to the thickness E2 of the envelope 4, for example 500 sq m. The thickness E2 may be known to the operators or stored in memory in the control unit 103.

[0093] Alternatively, determining the end of drilling S2 comprises the following steps. The current consumed by the motor M that rotates the drill bit 20 is measured. The current consumed by the motor M is related to the torque it applies. Thus, it is possible to use the current consumed to determine the end of drilling S2. Indeed, when the drill bit 20 begins drilling SI, the torque of the motor M increases, and therefore, the current consumed increases. Once drilling SI is completed, the mechanical resistance applied to the drill bit 20 decreases, and therefore the torque supplied by the motor M decreases, and thus the current consumed by the motor M decreases.

[0094] Once the envelope 4 of cell 2 is pierced, the method may include a step of stopping the rotation of the drill D3. The stopping of the rotation D3 of the drill 20 can be carried out, for example, by opening a relay controlled by the control unit 103.

[0095] Once the drill bit 20 has stopped rotating D3, the connection step S3 is performed via the measuring circuit 200. Preferably, when the cell 2 includes with insulating elements, the rotation and translation of drill bit 20 are maintained until connection S3 is reached. Then, when it is determined that connection S3 is made, the rotation and translation of drill bit 20 are stopped.

[0096] Then the S4 discharge can be carried out, via the electrical discharge system 45.

[0097] Cell 2 can be considered discharged S5 when the voltage measured across electrodes 5, 6 is less than or equal to a discharge threshold. The discharge threshold can be 0 volts. Then, during a retraction step S6, the drill bit 20 is retracted, for example to its initial position S7, so that cell 2 can be removed from the support 30.

[0098] Figure 8 shows a CIO displacement curve of a device Figure 8 shows the electrically conductive components 10 and 11, and a voltage curve C11 between the drill bit 20 and the envelope 4 of cell 2 as a function of time during the discharge process. The following steps are depicted: movement of the drill bit D12 to the connection S3, followed by discharge S4. When the drill bit 20 touches the envelope 4, at the determination step D13 of the contact between the drill bit 20 and the envelope 4, the potential between these two elements is zero. Once the envelope 4 is perforated by the drill bit 20, the potential becomes fluctuating (oscillations are present in the potential measurement). When the drill bit 20 comes into contact with the electrical collector 42 and 43, which is still connected to the electrode 5 and 6 inside cell 2, the potential measurement between electrodes 5 and 6 displays the voltage of cell 2.

[0099] Figure 9 shows a curve of the current C12 supplied by cell 2, that is, the current flowing between electrodes 5, 6 of cell 2 and the electrical discharge system over time. A curve of the discharged capacitance of cell C13 as a function of time and a curve of the voltage C14 between electrodes 5, 6 of cell 2 during the discharge process as a function of time are also shown. Connection S3 is shown, followed by discharge S4, during which the discharge current is approximately 4 A, the voltage decreases, and the discharged capacitance of the cell increases until cell 2 is discharged S5. In particular, the discharged capacitance C13 curve is obtained from the integrated current C12 curve over time. [Fig.[9] An optional discharge step S10 is also shown following a rest step (i.e., a cessation of discharge S4, for example by retracting the drill bit 20 so that it is no longer in contact with the collector 42, 43) or a disconnection of the electrical discharge system 45, in order to ensure that the cell 2 is discharged. Thus, a battery can be discharged using an electrical discharge system 45 without degradation of the battery materials.

[0100] The discharge method and installation as defined above can be used for various applications. For example, an application may include remote discharge without degradation of the battery, at least one of whose external terminals is no longer connected to its electrode, for the purpose of post-mortem analysis of the cell components. This type of analysis is performed routinely in research laboratories to study, for example, the influence of certain parameters (aging, temperature, rapid charging) on ​​electrode materials. These batteries sometimes have safety devices that are triggered, making safe analysis of the battery or batteries impossible. An application may include remote discharge without degradation of the battery for the maintenance or dismantling of battery systems.During their use in a battery system, one or more batteries may trigger their internal protection due to misuse or aging. In this case, the batteries are unusable in the system and potentially unstable. The process defined above can then be used in the battery system to discharge the degraded cells before, for example, removing them from the system for replacement. Another application could involve remote discharge of the batteries without damaging them for recycling. Current recycling methods generally involve electrical discharge or shredding of the battery to be recycled. The invention would allow for the safe disassembly of batteries without damaging the materials.

Claims

Demands

1. A method for discharging an electrochemical energy storage cell, the cell comprising: • a stack (3) housed within a cell casing (4), the stack comprising successively, in a stacking direction (Z), at least one first electrode (5), a separator (7) and a second electrode (6), and • first and second electrical collectors (42, 43) coupled respectively to the first and second electrodes (5, 6), characterized in that the method comprises: • a perforation (S1) comprising the formation of at least one through hole (8, 9) through the casing (4) so ​​as to form access to the first electrical collector (42), • a connection (S3) comprising contacting at least one electrically conductive device (10, 11) with said first electrical collector (42), via said at least one through hole (8, 9),and • a discharge (S4) of the cell comprising a first electrical connection of said at least one electrically conductive device (10, 11) with a first terminal of an electrical discharge system (45) and a second electrical connection of a second terminal of the electrical discharge system (45) with the second electrical collector (43), so as to electrically couple in series the electrical discharge system (45) and the stack (3).

2. A method according to the preceding claim, wherein the cell further comprises first and second power terminals (40, 41), the second power terminal (41) being electrically coupled to the second electrode (6) via the second electrical collector (43), and the second electrical connection comprises an electrical connection of the second terminal of the electrical discharge system (45) with the second power terminal (41).

3. A method according to claim 1, wherein the perforation (S1) comprises forming a first through hole (8) through at least one of the casing (4) so ​​as to form access to the first electrical collector (42), and forming a second through hole (9) through at least one of the casing (4) so ​​as to form access to the second electrical collector (43), the connection (S3) comprises making contact of a first electrically conductive device (10) with the first electrical collector (42), via the first through hole (8) and making contact of a second electrically conductive device (11) with the second electrical collector (43), via the second through hole (9),and the discharge (S4) comprises a first electrical connection of the first electrically conductive device (10) with the first terminal of the electrical discharge system (45) and a second electrical connection of the second electrically conductive device (11) with the second terminal of the electrical discharge system (45).

4. A method according to any one of claims 1 to 3, wherein the perforation (SI) comprises forming said at least one through hole (8, 9) using a drill (20) animated in rotation and translation during the formation of said at least one through hole (8, 9).

5. Method according to the preceding claim, wherein said at least one electrically conductive device (10, 11) is the drill bit (20), which is stationary in rotation during the discharge (S4).

6. Method according to the preceding claim, comprising, after the formation of said at least one through hole (8,9), holding the drill (20) animated in rotation and translation, and after the connection (S3), the method further comprises stopping the translation of the drill (20) during the discharge (S4).

7. A method according to any one of claims 5 or 6, comprising, after the formation of said at least one through hole (8,9), a determination of the end of the perforation (S2) corresponding to the creation of the through hole (8,9), a stop in rotation of the drill (20), and a translation of the drill (20) until the connection (S3).

8. A method according to the preceding claim, wherein the perforation (SI) comprises determining an initial position in which the drill (20) is in contact with the casing (4), a translational displacement of the drill (20) in the direction of one of the first and second electrical collectors (42, 43), determining a stroke of the drill relative to the initial position, and determining the end of perforation (S2) is carried out when the stroke of the drill (20) is equal to a predetermined value greater than or equal to a thickness (El) of the casing (4), the thickness (El) of the casing (4) being defined along the stacking direction (Z).

9. A method according to the preceding claim, comprising a measurement of an electrical resistance between the drill (20) and the envelope (4), and wherein, before the determination of the initial position, the electrical resistance is different from 0 Ohm, and the determination of the initial position is carried out when the electrical resistance is equal to 0 Ohm.

10. A method according to any one of the preceding claims, comprising a measurement of a potential difference between said at least one electrically conducting device (10, 11) and the second electrode (6), and the method comprises a determination that the connection (S3) is made when the potential difference is distinct from a reference potential difference.

11. A method according to any one of claims 4 to 9 in combination with claim 2, comprising a measurement of a potential difference between the second power terminal (41) and said at least one electrically conductive device (10, 11), and the method comprises a determination that the connection (S3) is made when the potential difference is distinct from a reference potential difference.

12. A method according to any one of claims 5 to 9 in combination with claim 2, wherein the second power terminal (41) is electrically coupled to the envelope (4), the method comprising a measurement of a potential difference between the drill (20) and the envelope (4), and the method comprises a determination that the connection (S3) is made when the potential difference is distinct from a reference potential difference.

13. A method according to any one of claims 10 to 12, wherein the potential difference measurement is carried out, after perforation (SI) and before connection (S3), to determine the reference potential difference.

14. A method according to claim 12, wherein the drill (20) has an elongated body, a head located at one end of the elongated body, the elongated body having a constant cross-section of a first diameter, the head having a cross-section of a second diameter strictly greater than the first diameter, the perforation (S1) comprising a contact of the head with the envelope (4) during which the potential difference is equal to 0 Volts, and a determination of the end of perforation (S2) when the head is no longer in contact with the envelope (4) and the potential difference is not equal to 0 Volts.

15. A method according to any one of the preceding claims, wherein the connection (S3) comprises a first electrical connection of said at least one electrically conductive device (10, 11) with a first terminal of a measuring circuit (200) and a second electrical connection of a second terminal of the measuring circuit (200) with the second electrical collector (43), so as to determine at least one parameter representative of an operating state of the cell.

16. Discharge installation for an electrochemical energy storage cell, comprising a support (30) suitable for receiving a cell, the cell comprising a stack (3) housed within a cell envelope (4), the stack (3) comprising successively, in a stacking direction (Z), at least a first electrode (5), a separator (7) and a second electrode (6), characterized in that the installation comprises a drill (101) configured to form at least one through hole (8, 9) through the envelope (4) so ​​as to form access to the first electrical collector (42), at least one electrically conductive device (10, 11) configured to be brought into contact with said first electrical collector (42), by means of said at least one through hole (8, 9), and an electrical discharge system (45) comprising a first terminal electrically coupled to said at least one electrically conductive device (10, 11),and a second terminal electrically coupled with the second electrical collector (43), so as to couple, electrically in series the electrical discharge system (45) and the stack (3) to discharge the cell.

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