Discharge method and installation for an electrochemical energy storage cell.

Abstract

Method and installation for discharging an electrochemical energy storage cell. The cell comprises a stack housed within a cell envelope. The stack comprises, successively in a stacking direction, at least one first electrode, one separator, and one second electrode. The method comprises forming (S1) a hole through the envelope to provide access to a zone of the stack, and discharging (S2) the cell by applying pressure to the zone without reaching the separator to reduce the stack thickness in order to transform chemical energy stored in the cell into thermal energy. The stack thickness is defined according to the stacking direction. Figure for the abstract: Fig. 5

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 the preferred means of storing energy in chemical form and releasing a portion of it to powered electrical systems. 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, in addition, ionic conduction between them to allow the movement of lithium ions 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 terminals. These terminals are used to electrically connect a battery to the external electrical circuit. These electrical conduction elements are also called current collectors or "tabs."

[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 for example, lithium-ion battery technologies Lithium-ion batteries offer the advantage of higher energy and power density. However, one of their drawbacks is safety. 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 such cases, smoke, flames, and even explosions can result. The safety of lithium-ion batteries is a fundamental aspect that influences their entire lifecycle.

[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] There are different processes for inerting accumulators.

[0007] One can cite, for example, abusive testing techniques for Lithium-ion batteries, such as the perforation 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 (creation An uncontrolled short circuit of low impedance within the battery systematically leads to its thermal runaway. This solution therefore does not allow for the recovery of the battery and its components intact.

[0008] 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 rendering an isolated cell inert within a system without risking damage to it, nor do they allow for the complete recovery of the materials for analysis or material recovery (for recycling, for example).

[0009] 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.

[0010] We can also cite patent applications CN215644580U and KR102404943B1, which disclose methods for perforating the battery in a controlled environment and, for example, allowing a conductive solution to enter in order to generate an internal short circuit. However, these solutions have the drawback of requiring an environment containing the conductive solution. The need to, for example, immerse a battery in a solution to discharge it makes these methods unusable for discharging a battery within a battery system before its dismantling. Furthermore, this type of process involves a conductive solution, often aqueous, which degrades the electrochemical and electrical constituents of the battery. Since the conductive solution is subsequently contaminated, it must also be treated as toxic waste.Therefore, these techniques do not allow the battery components to be recovered in their entirety, for example for recycling.

[0011] 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 or surrounding accumulators, with a view to recovering them safely by an operator.

[0012] 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

[0013] According to one aspect of the invention, a method for discharging an electrochemical energy storage cell is proposed, the cell comprising a stack housed in within a cell envelope, the stack comprising successively, in a stacking direction, at least a first electrode, a separator and a second electrode, the process comprising forming a hole opening through the envelope so as to form an access to an area of ​​the stack.

[0014] The method includes discharging the cell by applying pressure to the area without reaching the separator so as to reduce the thickness of the stack in order to transform chemical energy stored in the cell into thermal energy, the thickness of the stack being defined according to the stacking direction.

[0015] 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 electrode from a cell connection terminal. This process allows, through the formation of the through-hole and the pressure exerted on the stack area, for discharging a cell without degrading its components.The process also differs from standard cell perforation tests, known as "nail tests," because these tests do not prevent thermal runaway or interrupt discharge if the cell temperature becomes too high due to irreversible plastic deformation of the metal casing and internal components of the battery. Furthermore, implementing a cell electrode perforation and compression process requires expertise in the following areas: - the mechanical design of precision instruments; - the control and command of rotating electrical machines; - industrial computer programming of microcontrollers or of automata; - the architecture and geometry of lithium technology batteries, as well as their protection systems; - the physics of lithium-ion batteries; and - electrical and thermal metrology.

[0016] These points may be known to different experts in their specific fields, but interdisciplinarity makes it complex for the indicated experts to arrive at the process as defined above.

[0017] 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 an envelope of the cell, the stack comprising successively, in a stacking direction, at least a first electrode, a separator and a second electrode, the installation comprising a drill configured to form a through hole through the envelope so as to form access to an area of ​​the stack.

[0018] The installation includes a device configured to unload the cell by maintaining pressure on the area without reaching the separator so as to reduce the thickness of the stack in order to transform chemical energy stored in the cell into thermal energy, the thickness of the stack being defined according to the stacking direction. BRIEF DESCRIPTION OF THE FIGURES

[0019] 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:

[0020] [Fig.1]

[0021] [Fig.2] Figures 1 and 2 schematically represent the main stages of a method for discharging a chemical energy storage cell;

[0022] [Fig.3] [Fig.3] schematically represents an embodiment of a discharge installation for a chemical energy storage cell;

[0023] [Fig.4] [Fig.4] schematically represents another embodiment of a installation for discharging a chemical energy storage cell;

[0024] [Fig.5] [Fig.5] represents a flowchart of the main steps of an implementation method of a discharge process of a chemical energy storage cell;

[0025] [Fig.6] [Fig.6] represents a flowchart of the main steps of another method of implementing a process for discharging a chemical energy storage cell;

[0026] [Fig.7] [Fig.7] represents a flowchart of the main steps of another method of implementing a discharge process for a chemical energy storage cell;

[0027] [Fig.8] [Fig.8] represents a temperature curve of the envelope of a chemical energy storage cell as a function of time during the discharge process according to the invention; and

[0028] [Fig. 9] [Fig. 9] schematically represents one embodiment of a drill bit.

[0029] The drawings are given by way of example and are not limiting of the invention. They are schematic representations of principle intended to facilitate understanding of the invention and are not necessarily to scale with practical applications. DETAILED DESCRIPTION

[0030] 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.

[0031] According to one example, the discharge involves introducing a device through the through-hole formed in the casing, the device exerting pressure on the area while being kept at a distance from the separator, the distance being defined according to the stacking direction. This ensures that the separator is not damaged by an accidental perforation that could be caused by the device.

[0032] According to one example, the device comprises a longitudinal element extending along a longitudinal axis, and the discharge comprises supporting the longitudinal element on the area by moving the longitudinal element in translation along the stacking direction. Thus, it provides a simple method to be implemented.

[0033] According to one example, the stack is housed inside the envelope and the formation of the through hole is achieved by releasing the material extracted from the envelope to the outside of the envelope.

[0034] According to one example, the formation of the through hole is carried out using a drill animated in rotation and translation during the formation of the through hole.

[0035] According to one example, the device used is the stationary drill bit rotating during discharge. Advantageously, this limits the number of tools needed to discharge a cell, further simplifying the discharge process.

[0036] According to one example, the formation of the through hole comprises perforating the casing with the drill bit, determining the end point of the perforation corresponding to the creation of the through hole, and stopping the perforation. Such a method avoids prolonged movement of the drill bit by preventing it from penetrating the stack and, at the very least, from damaging at least one of the stack's electrodes.

[0037] According to one example, the process includes, before the formation of the through hole, determining an initial position in which the drill bit is in contact with the casing.

[0038] According to one example, the perforation of the envelope includes a translational movement of the drill in the direction of the stacking, and a determination of a stroke of the drill relative to the initial position, the determination of the end of perforation being carried out when the stroke of the drill is equal to a thickness of the envelope, the thickness of the envelope being defined according to the direction of stacking.

[0039] According to one example, the method comprises a measurement of a potential difference between the envelope and the drill bit, and in which, before determining the position Initially, the potential difference is not 0 Volts, and the determination of the initial position is carried out when the potential difference is equal to 0 Volts.

[0040] According to one example, the determination of the end of perforation is carried out when the potential difference is different from 0 Volts.

[0041] According to one example, the perforation of the casing includes rotating the drill bit using a motor, determining the motor's power consumption, and determining when the perforation is complete. This determination occurs when the motor's power consumption is less than or equal to a predetermined threshold. The motor that drives the rotating drill bit can be used to determine the end of the perforation, thus avoiding the need for additional measuring sensors.

[0042] According to one example, the perforation of the casing includes measuring the casing temperature, and the perforation completion is determined when the casing temperature is greater than or equal to a temperature threshold. Advantageously, it can be determined that the drill bit has begun to bear on the stacking area when heat dissipation begins. This ensures that the through hole has been properly created.

[0043] According to one example, the drill bit has a longitudinally extending body, a head located at one end of the drill bit body, the drill bit 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 drill bit head into contact with the casing during which the potential difference is equal to 0 volts, and the determination of the end of perforation being carried out 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 perforation, in particular an electrical contact between the drill bit and the cell casing to measure a potential difference, which simplifies the process.

[0044] According to one example, stopping the perforation of the casing includes stopping the rotation of the drill bit. This prevents damage to an electrode in the event of contact between the drill bit and the electrode.

[0045] According to one example, the discharge includes a temperature measurement of the envelope, and pressure is maintained on the area as long as the envelope temperature is strictly below a temperature threshold. Advantageously, the thermal energy generated by the cell is regulated by regulating the pressure on the stacked area. Such a method prevents irreversible thermal runaway of the cell, which could lead to the destruction of the electrodes and the separator.

[0046] According to one example, the discharge includes a measurement of the envelope temperature, and in which the pressure on the area is applied when the temperature the envelope temperature is within a temperature range, and the support is stopped when the envelope temperature is outside the temperature range.

[0047] Figures 1 and 2 illustrate the main stages of a discharge process for an electrochemical energy storage cell 2, referred to as a chemical energy storage cell 2. Generally, a cell 2 comprises a stack 3 housed within a cell 2 casing 4. In other words, the stack 3 is housed inside the casing 4. The stack comprises, successively along a stacking direction Z, at least a first electrode 5, a separator 7, and a second electrode 6. The cell 2 may be of lithium-based technology, such as lithium-ion, or of sodium-ion or potassium-ion, or other technologies. Preferably, the cell 2 is of the lithium-ion type. The casing 4 may be rigid, comprising, for example, grades of aluminum or steel, and cylindrical or prismatic in shape. According to another example, envelope 4 can be flexible, for example having the shape of a sachet.Flexible means a casing capable of deforming under its own weight. The first electrode 5 can be an anode, generally made of a copper strip coated with a carbonaceous material, typically graphite. The second electrode 6 can be a cathode, generally made of an aluminum strip coated with lithium-based metal oxides. One of the lithium-based metal oxide pairs used to constitute the cathode can be LiNiMnyCoZO2.

[0048] 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, for example, comprise polypropylene (PP) or polyethylene (PE). This electrical insulation and ionic conduction functionality is achieved by creating pores of controlled diameters (a manufacturing 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, the electrolyte also being called an ionically conductive medium. Alternatively, the separator 7 providing the ionic conduction functionality may be a solid electrolyte.

[0049] In general, the method comprises forming SI a hole 8 within the shell 4 and a discharge S2 of the cell 2. In particular, the formed hole 8 is a through hole through the shell 4 so as to provide access to a zone 9 of the stack 3. More specifically, the discharge S2 is carried out by exerting a pressure Fl on the zone 9 without reaching the separator 7. Advantageously, the pressure Fl is exerted so as to reduce a thickness El of the stack 3 in order to to transform chemical energy stored in cell 2 into thermal energy. The support Fl corresponds to a force exerted on the stack 3, preferably exerted along the stacking direction Z. The thickness El of the stack 3 is defined along the stacking direction Z. The support Fl corresponds to a pressure exerted on the electrodes 5, 6 and the separators 7 of the stack 3. The support Fl causes a deformation of at least the first electrode 5 and at least the separator 7. The deformation is defined by a reduction in the thickness El of the stack 3.

[0050] More specifically, the deformation causes an elongation, along a direction B perpendicular to the stacking direction Z, of the electrodes 5, 6 and the separator 7. This elongation then leads to an internal short-circuit fault that transforms the stored energy into thermal energy. The energy transformation results in the discharge of the cell 2. Thus, the cell can be discharged, at least partially, without reaching the separator 7. Such a process avoids severely damaging the separator 7. That is to say, the separator 7 is not destroyed, punctured, or torn. In other words, the discharge process includes a pressure Fl exerted at a distance from the separator 7, after a localized perforation (or drilling) of the casing 4, by compressing the electrodes 5, 6 and the separator 7. In particular, the formation SI allows access to at least one electrode 5 of the stack 3.

[0051] 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. 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 30 and 500 micrometers.

[0052] The separation distance creates a volume, called dead volume, located between the stack 3 and the casing 4. In general, the cells 2 have the smallest possible dead volume to increase energy density. The separation distance is usually less than 0.5 millimeters. 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 on any of its four lateral faces. For this type of cell, the separation distance can reach 2 mm on some of the faces. 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, the formation SI of the hole 8 is carried out at a point on the length of the cell 2, perpendicular to this face so that the drill 20 is perpendicular to the planes of the electrodes 5, 6.

[0053] 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 "spool." Generally, the location of the hole 8 is selected to maximize the probability of it being located perpendicular to the electrode windings 5, 6. Preferably, the hole 8 is made in the center of the cell 2 to promote heat dissipation. The ends of the cell 2 are areas to be avoided for two main reasons. The first reason is that at the ends, the probability of drilling into a dead volume of the cell without allowing access to area 9 of the stack 3 is high. The second reason is that compression at the edge of the spool would risk displacing only (without compressing) the electrodes 5, 6, making the process less efficient or ineffective.

[0054] For example, the discharge S2 includes the introduction of a support device 10 through the open hole 8. The device 10 is configured to exert the support Fl on the zone 9. The device 10 is preferably made from an electrically insulating material, or provides electrical insulation between the zone 9 and the casing 4. In particular, the support Fl is achieved by maintaining the device 10 at a distance from the separator 7. The distance is defined according to the stacking direction Z. In other words, the device 10 is not in mechanical contact with the separator 7. There is therefore no risk of damaging the separator 7 through an accidental perforation that could lead to thermal runaway of the cell 2.For example, the device 10 includes a longitudinal element 11 extending along a longitudinal axis AL. The discharge S2 includes a support of the longitudinal element 11 on the area 9 by moving the longitudinal element 11 in translation along the stacking direction Z.

[0055] Figure 5 shows an embodiment of the discharge process. The process may include an initial step 10 in which the cell 2 is placed on a support 30, as illustrated in Figures 3 and 4. Then, before the discharge step S2, the hole 8 formation step SI is performed. The formation SI consists of generating a localized opening at a point in the shell 4 so as to make the area 9 of the stack 3 accessible. Advantageously, the formation SI of the through hole 8 is carried out by clearing the material extracted from the shell 4 to the outside of the shell 4. Thus, the material extracted from the shell 4 is prevented from being projected inside the shell 4, and a significant short circuit and a Irreversible thermal runaway. For example, zone 9 corresponds to the first electrode 5. Generally, zone 9 includes elements of the stack 3 located between the separator 7 and the through hole 8. For example, zone 9 includes the first or second electrode 5, 6. Zone 9 may also include an insulating coating in contact with at least one of the first and second electrodes 5, 6. For example, the SI formation of the through hole 8 is carried out using a drill bit 20 animated in rotation and translation. Generally, the drill bit 20 is configured to form the hole 8. For example, the drill bit 20 has a body 21 extending longitudinally along a longitudinal axis A2. To create the through hole 8, the drill bit 20 is animated in rotation about its longitudinal axis A2, and in translation along the stack axis Z in the direction of the stack 3.The formation SI of the through hole 8 may include a perforation S3 of the envelope 4 using the drill bit 20. Advantageously, the formation S1 includes a determination of the end of the perforation DI corresponding to the creation of the through hole 8 and a stopping of the perforation D2. For example, the stopping of the perforation D2 includes a rotational stop of the drill bit 20. Thus, perforation of the cell 2, and more particularly the separator 7, is avoided. Furthermore, such a perforation S3 does not damage the electrodes 5, 6 located closest to the envelope 4. Preferably, the perforation S3 is stopped before the perforation S3 damages the first electrode 5 located closest to the envelope 4, i.e., before it pierces or tears it.

[0056] In particular, the support device 10 has a lower plasticity than the materials of the electrodes 5, 6 and the separator 7, so that the applied pressure Fl causes their deformation. 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 of less than 4 mm is suitable to reduce the torque required for forming SI of the hole 8 and thus reduce heating. The drill bit 2 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 A2 without excessive imbalance or wobble.The motor M generating the rotation can be an electric motor capable of reaching a suitable rotational speed for the formation SI of hole 8, such as a DC machine, a synchronous machine, an asynchronous machine or other rotating device that can be interrupted remotely.

[0057] Generally, the discharge S2 includes a compression S21 of the separator 7. The compression S21 includes a support Fl on the area 9 using the support device 10 passing through the through hole 8. The support Fl may correspond to a compression force. In other words, the discharge S2 includes compression of the electrodes 5, 6, and in particular of the separator 7, localized in area 9 via the through-hole 8. Advantageously, the discharge S2 includes regulation S22 of the support Fl according to a measurement of a parameter representative of the energy transformation. The regulation S22 may include compression S21 of the separator 7 without causing thermal runaway of cell 2. For example, the regulation S22 is carried out until a complete discharge S23 of cell 2 is obtained. Preferably, the diameter of the support device 10 is strictly smaller than the diameter of the through-hole 8.

[0058] According to one embodiment of the discharge process, the discharge S2 includes a temperature measurement of the envelope 4. For example, the temperature measurement of the envelope 4 can be carried out by placing a temperature sensor 31 on the envelope 4, as illustrated in [Fig. 3]. Preferably, the temperature sensor 31 is placed as close as possible to the hole 8. The sensor 31 can be a temperature probe, such as a type k thermocouple, or a resistive one, such as a negative temperature coefficient (NTC) material. Then, the pressure Fl on the area 9 is maintained as long as the temperature of the envelope 4 is strictly below a temperature threshold. The temperature threshold can correspond to a maximum discharge power of the cell 2 so as not to cause damage to the cell 2, for example, not to cause thermal runaway.For example, the temperature threshold could be a difference of 20°C between the temperature of envelope 4 and an ambient temperature.

[0059] Furthermore, by acting on the compression force Fl, that is, by maintaining, increasing, reducing, or stopping the pressure Fl, the discharge of cell 2 can be maintained, increased, reduced, or stopped due to the reversibility of the deformation of electrodes 5 and 6 and of the separator 7 induced by FL. For example, if the temperature threshold is reached, the discharge can be stopped and a certain time can be waited until the temperature of the casing 4 is again less than or equal to the temperature threshold. Moreover, the waiting time depends on the discharge power, the heat dissipation power, and the amount of energy contained in cell 2. The waiting time can be several minutes or several hours.

[0060] For example, the Fl support on zone 9 is maintained as long as the temperature of the envelope 4 is strictly below the temperature threshold. Alternatively, the Fl support on zone 9 is activated when the temperature of the envelope 4 is within a temperature range, and the Fl support is deactivated when the temperature of the envelope 4 is outside the temperature range. For example, the temperature range includes a lower bound corresponding to the ambient temperature, and an upper limit corresponding to ambient temperature plus 20°C.

[0061] Thus, to increase the compression force Fl, the translation of the drill 20 can be extended in the direction of the stack 3, it is also said that the drill 20 is advanced. To decrease the compression force Fl, the drill 20 is translated in the opposite direction to the stack 3, it is also said that the drill 20 is recoiled.

[0062] To prevent thermal runaway of cell 2, the formation SI of hole 8 includes determining the end of perforation Dl. Furthermore, the determination of the end of perforation Dl can be carried out in different ways. For example, the perforation of the envelope S3 includes determining 13 an initial position in which the drill bit 20 is in contact with the envelope 4.

[0063] For example, the method may include measuring a potential difference between the casing 4 and the drill bit 20. In this case, when the drill bit 20 is not in contact with the casing 4, the potential difference is not 0 volts. This is also referred to as measuring a noise signal or a "floating" potential. Then, the initial position is determined when the drill bit 20 comes into contact with the casing 4, and in this case, a potential difference of 0 volts is measured.

[0064] Alternatively, the initial position can be determined by measuring the electrical resistance between the drill bit 20 and the casing 4 during the movement of the drill bit 20. Thus, when the drill bit 20 is not in contact with the casing 4, a resistance other than 0 ohms is measured, i.e., an infinite resistance. Then, when the drill bit 20 touches the casing 4, a resistance of zero is measured.

[0065] Then, the SI formation includes a translational movement of the drill 20 in the direction of the stack 3. For example, the drill 20 is moved translationally along the stack direction 3. The SI formation then includes determining a stroke of the drill 20 relative to the initial position, and the perforation end-determination D1 is performed when the drill stroke equals the thickness of the envelope E2. The thickness of the envelope E2 is defined along the stack direction Z. The thickness of the envelope E2 can be known in advance by the operator and can be set to a discharge device 100 of a cell 2.

[0066] According to another embodiment of the perforation end determination Dl, the perforation of the envelope S3 includes rotating the drill bit 20 using a motor M, as illustrated in Figures 3 and 4. Then, the formation SI includes determining the electrical consumption of the motor M, and the perforation end determination Dl is performed when the motor's electrical consumption is less than or equal to an electrical consumption threshold, by example the electrical consumption of motor M before the first contact of drill 20 with the casing.

[0067] According to another embodiment of the perforation end determination Dl, the perforation of the envelope S3 includes a measurement of the temperature of the envelope 4. The measurement of the temperature of the envelope 4 can be carried out using the temperature sensor 31 used to regulate the support Fl on the area 9. Then, the perforation end determination Dl is carried out when the temperature of the envelope 4 is greater than or equal to a temperature threshold.

[0068] Figure 4 shows another method of determining the end of perforation Dl. According to this alternative method, the perforation of the casing S3 involves measuring a potential difference between the casing 4 and the drill bit 20, and the end of perforation Dl is determined when the potential difference is not 0 volts, i.e., when a noise signal is measured. To measure the potential difference, the drill bit 20 can be electrically coupled to a voltage measuring circuit 200. The measuring circuit 200 is electrically coupled to the casing 4 by a first connection 201, and to the drill bit 20 by a second connection 202. The second connection 202 can be a rotating electrical connector attached to the drill bit 20 or to the 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 the casing 4 of the cell 2. 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. 9]. 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 facilitate perforation of the envelope 4.Advantageously, the grooves are configured so that the material extracted from the shell 4 during perforation S3 is projected outwards from the shell 4. In other words, the grooves allow the evacuation of chips from the material of the shell 4 to the outside of the shell 4. Furthermore, the head 22 has a cross-section of a second diameter Dy strictly larger than the first diameter Dx. The first and second diameters Dx, Dy are defined along an axis B perpendicular to the longitudinal axis A2 of the drill 20.

[0069] The perforation of the envelope S3 includes bringing the head 22 into contact with the envelope 4 during which the potential difference is equal to 0 Volts. Then, the perforation end determination DI is performed when the head 22 is no longer in contact with the envelope 4 and when the potential difference is not 0 Volts.

[0070] The determination of the end of perforation DI may include an initial step where the electrical circuit between the drill bit 20 and the casing 4 is opened. The potential between the two is said to be "floating" and represents a parasitic random value.

[0071] Then, the drill bit 20 is moved translationally in the direction of the stack 3 until it comes into contact with the casing 4. At this point of contact, the electrical circuit is closed, 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. Next, the perforation step S3 of the casing 4 is performed by rotating the drill bit 20 while maintaining its translational movement along the stacking direction Z and towards the stack 3. When the perforation is complete, the through hole 8 is made, and the head 22 of the drill bit 20 passes through the hole 8. In this case, 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 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 is no longer in contact with the casing 4. Similarly, a resistance measurement between the drill bit and the casing allows us to determine contact with the casing, with a resistance measurement of zero, as well as the end of drilling, with a resistance measurement of infinite. Advantageously, such a drill bit 20 ensures electrical insulation between the drill bit 20 and the casing 4 when the head 22 of the drill bit 20 comes into contact with a cathode. Indeed, the casing 4 of cylindrical accumulators, for example, is in approximately 90% of cases electrically connected to the anode.Since drill bit 20 is conductive, it is highly advantageous to electrically isolate it from the casing 4. When the drill bit 22 touches an electrode 5 or 6, which could be the cathode 6, for example, it would cause a short circuit, as with the nail test. In other words, when the drill bit 22 is in contact with zone 9, the drill bit 20 is no longer in contact with the casing 4, and the drill bit 20 is electrically isolated from the casing 4. Therefore, the perforation step S3 and then the discharge step S2 can be performed using the same drill bit 20, thus saving on tools and accelerating the discharge process. According to another variant, a non-conductive device 10, different from the conductive drill 20 used for the drilling step S3, can be used to perform the pressure Fl on the electrodes 5, 6, i.e. to perform the discharge step S2.

[0072] After the formation step SI, the unloading step S2 is performed. For example, the formation step SI is performed using the drill bit 20, and the unloading step S2 is performed with a support device 10 separate from the drill bit 20. Alternatively, during unloading S2, the device 10 used to exert the support Fl is the drill bit 20, held fixed in rotation and movable in translation along the stacking axis Z. According to this alternative, it is avoided to have to use two separate pieces of equipment to perform the formation S1 of the hole 8 and the unloading S2.

[0073] To implement the discharge process, a discharge installation 100 for a cell 2 can be used. The installation 100 is illustrated in Figures 3 and 4. The discharge installation 100 includes the support 30 adapted to receive a cell 2. The installation 100 further includes a drill 101 configured to form the through hole 8. The drill 101 includes the motor M coupled to the drill 20 and configured to rotate the drill 20 about the longitudinal axis A2 of the drill 20. The installation 100 also includes a stepper motor configured to move the drill 20 in translation along the stacking direction Z. The installation 100 includes the support device 10 configured to discharge the cell 2 by maintaining the support Fl on the area 9 without reaching the separator 7 so as to reduce the thickness El of the stack 3 in order to transform a chemical energy stored in the cell is converted into thermal energy.

[0074] 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 A3 parallel to the stacking direction Z. The rotation of the worm gear is controlled by an electric motor that allows the number of rotations to be controlled. The electric machine can be a stepper motor, for example a variable reluctance motor, or a permanent magnet motor, or both.

[0075] 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.

[0076] For example, the installation 100 may include a control unit 103 configured to control the drill 101 and the translational movements of the plate 104. In addition, the control unit 103 is configured to receive the values ​​of The temperature of the envelope 4 is measured by the temperature sensor 31, via a connection 105. The control unit 103 is also configured to measure the potential differences between the drill 20 and the envelope 4. The control unit 103 can be a computer equipped with appropriate interface cards. The installation 100 may include means for converting electrical energy to convert a voltage from the electrical network into a voltage suitable for the drill 101, its motor M, actuators for moving the table 104 and the control unit 103. The installation 100 may further include a programmable logic controller or a microcontroller board for supplying power to the actuators of the table 104, supplying power to the motor M, receiving the temperature values ​​of the casing 4 measured by the temperature sensor 31 and the potential difference between the casing 4 and the drill bit 20 and then communicating them to the control unit 103.

[0077] Figure 6 shows a method of implementing the discharge process. installation assistance 100.

[0078] The initial step 10 includes positioning the cell 2 on the mechanical support 30. Then, the method includes rotating the drill 20. For example, the control unit 103, a microcontroller board or an external power supply controlled by remote operators, actuates the motor M to rotate the drill 20.

[0079] The control unit 103 receives, from remote operators or automatically, the instruction to advance the drill bit 12. 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.

[0080] This action is repeated until the drill bit 20 comes into contact with the shell 4 of cell 2. The method may include determining 13 when the drill bit 20 has come into contact with the shell 4. For example, determining 13 may be done using a potential measurement between the drill bit and the shell 4, a limit switch, an ultrasonic measurement, or a contact or position sensor. It is also possible to count the number of steps taken by the electric machine and deduce the number of steps required to reach the shell 4 of cell 2.

[0081] Once this determination 13 has been carried out, the formation SI of the hole 8 is performed. The formation SI includes the perforation S3 of the envelope 4 of the cell 2. The perforation step S3 can be carried out jointly with the perforation end determination step DI. In order to perforate the envelope 4 of the cell 2 without damaging the electrodes 5, 6 located behind the envelope 4, the advancement of the platform 104 is stopped as soon as the envelope 4 is perforated.

[0082] The determination of the end of perforation DI 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 µm. The thickness E2 may be known to the operators or stored in memory in the control unit 103.

[0083] Alternatively, the determination of the end of perforation DI comprises the following steps. A determination of the temperature variation of the envelope 4 is performed. Indeed, the passage of the drill bit 20 through a wall of the envelope 4 and the first contact with the first electrode 5 produces a rise in the temperature of the envelope 4. By detecting this temperature rise, it is possible to obtain the information indicating the end of perforation of the envelope 4 of cell 2.

[0084] Alternatively, determining the end of drilling DI 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 DI. Indeed, when the drill bit 20 begins drilling S3, the torque of the motor M increases, and therefore, the current consumed increases. Once drilling S3 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.

[0085] Once the envelope 4 of cell 2 is pierced, the method may include a step of stopping the rotation of the drill D2. The stopping of D2 may be effected, for example, by opening a relay controlled by the control unit 103.

[0086] Once the drill bit 20 has stopped D2, the discharge step S2 is carried out. Figure 7 illustrates one implementation of the discharge S2. For example, the discharge S2 includes controlling the advance of the drill bit 20 according to a parameter representative of the energy transformation, preferably the temperature of the casing 4. For example, during the discharge S2, an ambient temperature S0 is measured to serve as a reference with a measurement S221 of the temperature of the casing 4. The measurement S0 can also be the measurement of the casing temperature before the start of the perforation step S3. The advance of the plate 104 is controlled until the initiation of the discharge process is determined. For example, the drill bit 20 advances incrementally until the electrodes 5, 6 and the separator 7 are sufficiently deformed to initiate the discharge.At this point, the discharge energy is completely converted into thermal energy, raising the temperature of cell 2, and more specifically the temperature of the casing 4. This temperature rise, measured by the temperature sensor 31, indicates that the advance of the drill 20 must be stopped, by performing the stop step S222 of the drill 20 translation. For example, the advance is stopped for a determined time during which the discharge of cell 2 occurs. A minimum temperature rise indicates. the start of the discharge process. The minimum temperature may vary depending on the sensitivity and uncertainty of the temperature sensor 31 and the type of cell 2. A minimum rise of 5°C relative to ambient temperature can be an example of a temperature threshold.

[0087] Furthermore, due to the plasticity of the stack 3, stopping its compression causes it to return to its initial shape, and consequently, to stop the discharge completely. Moreover, the discharge power is linked to the pressure exerted on the stack. It is therefore possible for the waiting step S222 to be replaced by a control cycle for the support of the drill 20 on the stack 3 as a function of the temperature of the cell 2. One way to ensure the control cycle is, for example, the use of an on / off type control or a Proportional-Integral-Derivative type controller. The controller includes parameters configured according to the sensors 31, the actuators of the plate 104, and the type of cell 2 used. The temperature setpoint of the controller can be the temperature threshold. Preferably, the temperature setting is a safety temperature for the discharged accumulator.

[0088] Cell 2 can be considered to be discharged when its temperature reaches ambient temperature. In this case, during a retraction step 14, illustrated in [Fig. 6], the drill 20 is retracted, for example to its initial position, so that cell 2 can be removed from the support 30.

[0089] Figure 8 shows a curve of the temperature of the envelope 4 of a cell 2 as a function of time during the discharge process. The example illustrated in Figure 8 corresponds to a discharge process carried out on an intact (i.e., unabused) lithium-ion battery, having a cathode 6 made of aluminum coated with a mixture of nickel, manganese and cobalt (NMC), and an anode made of copper coated with graphite and silicon, cylindrical in the 18650 format of 3 Ah. In [Fig.8], the following steps are shown: a perforation S3 of the envelope 4, a rotation stop D2 of the drill 20, a compression S21 of the stack 3. The discharge power being insufficient (as evidenced by the temperature drop of the cell), the process includes an increase AC of the compression force applied to the stack 3. Following the step of increasing AC, the cell 2 discharges and the temperature of the envelope 4 increases.Then, when cell 2 is considered discharged, drill bit 20 is moved back 14, and the temperature of cell 2 decreases.

[0090] The discharge method and installation as defined above can be used for various applications. For example, an application may include a 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 daily in A research laboratory can be used to study, for example, the influence of certain parameters (aging, temperature, rapid charging) on ​​electrode materials. These batteries sometimes have safety devices that trigger, making it impossible to perform a safety analysis of the battery(ies). One application might involve remote discharge without battery degradation, for 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 described above can then be used in the battery pack to discharge the degraded cells before, for example, removing them from the battery system for replacement.Another application could involve the remote, non-degrading discharge of batteries for recycling. Current recycling methods mostly 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 envelope (4), the stack (3) having successively, along a stacking direction (Z), at least a first electrode (5), a separator (7) and a second electrode (6), the method comprising forming (S1) a through hole (8) through the envelope (4) so ​​as to form an access to a zone (9) of the stack (3), characterized in that the method comprises discharging (S2) the cell by exerting pressure (F1) on the zone (9) without reaching the separator (7) so as to reduce a thickness of the stack (El) in order to transform chemical energy stored in the cell into thermal energy, the thickness of the stack (El) being defined along the stacking direction (Z).

2. A method according to the preceding claim, wherein the discharge (S2) comprises an introduction of a device (10) through the through hole (8) formed through the envelope, the device (10) exerting pressure (Fl) on the area (9) while being kept at a distance from the separator (7), the distance being defined according to the stacking direction (Z).

3. A method according to the preceding claim, wherein the device (10) comprises a longitudinal element (11) extending along a longitudinal axis (Al), and the discharge (S2) comprises a support (Fl) of the longitudinal element (11) on the area (9) by moving the longitudinal element (11) in translation along the stacking direction (Z).

4. A method according to any one of the preceding claims, wherein the stack (3) is housed inside the envelope (4) and the formation (SI) of the through hole (8) is effected by a release of the material extracted from the envelope (4) to the outside of the envelope (4).

5. A method according to any one of claims 2 to 4, wherein the formation (SI) of the through hole (8) is carried out using a drill (20) animated in rotation and translation during the formation (SI) of the through hole (8).

6. Method according to the preceding claim, wherein the device (10) used is the drill (20) which is stationary in rotation during the discharge (S2).

7. A method according to any one of claims 5 or 6, wherein the formation (SI) of the through hole (8) comprises a perforation of the envelope (S3) using the drill (20), a determination of the end of perforation (Dl) corresponding to the creation of the through hole (8) and a stopping of the perforation.

8. Method according to the preceding claim, comprising, before the formation (SI) of the through hole (8), a determination of an initial position in which the drill (20) is in contact with the envelope (4).

9. A method according to the preceding claim, wherein the perforation of the envelope (S3) comprises a translational displacement of the drill (20) in the direction of the stack (3), and a determination of a stroke of the drill (20) relative to the initial position, the determination of the end of perforation (Dl) being carried out when the stroke of the drill (20) is equal to a thickness of the envelope (E2), the thickness of the envelope (E2) being defined according to the stacking direction (Z).

10. A method according to any one of claims 8 to 9, comprising a measurement of a potential difference between the envelope (4) and the drill (20), and wherein, before the determination of the initial position, the potential difference is not 0 Volts, and the determination of the initial position is carried out when the potential difference is equal to 0 Volts.

11. A method according to any one of claims 7 to 10, wherein the perforation of the envelope (S3) comprises rotating the drill (20) using a motor (M), determining the electrical consumption of the motor (M), and determining the end of perforation (Dl) is carried out when the electrical consumption of the motor (M) is less than or equal to an electrical consumption threshold.

12. A method according to any one of claims 7 to 11, wherein the perforation of the envelope (S3) includes a measurement of an envelope temperature, and the determination of the end of perforation (Dl) is carried out when the envelope temperature is greater than or equal to a temperature threshold.

13. Method according to claim 10, wherein the determination of the end of perforation (Dl) is carried out when the potential difference is different from 0 Volt.

14. A method according to the preceding claim, wherein the drill (20) has a body (21) extending longitudinally, a head (22) located at one end of the body (21) of the drill (20), the body (21) of the drill (20) having a constant cross-section of a first diameter (Dx), the head (22) having a cross-section of a second diameter (Dy) strictly greater than the first diameter (Dx), the perforation of the casing (S3) comprising bringing the head (22) into contact with the casing (4) during which the potential difference is equal to 0 Volts, and the determination of the end of perforation (Dl) being carried out when the head (22) is no longer in contact with the casing (4) and when the potential difference is not equal to 0 Volts.

15. A method according to any one of claims 7 to 14, wherein the stop of the perforation of the envelope (S3) includes a stop in rotation of the drill (20).

16. A method according to any one of the preceding claims, wherein the discharge (S2) includes a measurement of a temperature of the envelope, and wherein the support (Fl) on the area (9) is maintained as long as the temperature of the envelope is strictly below a temperature threshold.

17. A method according to any one of claims 1 to 15, wherein the discharge (S2) includes a measurement of a temperature of the envelope, and wherein the pressure (Fl) on the area (9) is made when the temperature of the envelope is within a temperature range, and the pressure (Fl) is stopped when the temperature of the envelope is outside the temperature range.

18. Discharge installation for an electrochemical energy storage cell, comprising a support (30) adapted to receive 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), the installation comprising a drill (101) configured to form a through hole (8) through the envelope (4) so ​​as to form access to a zone (9) of the stack (3), characterized in that the installation comprises a device (10) configured to discharge the cell by maintaining a support (Fl) on the area (9) without reaching the separator (7) so as to reduce a thickness of the stack (El) in order to transform a chemical energy stored in the cell into a thermal energy, the thickness of the stack (El) being defined according to the stacking direction (Z).

Images