Electrochemical accumulator incorporating a current interruption device with high breaking capacity.

Abstract

Electrochemical accumulator incorporating a high-breaking-capacity current interruption device. The invention relates to a metal-ion electrochemical accumulator (A) with a current interruption device (11) integrated into the accumulator, which comprises a reservoir (14) filled with at least one endothermic and electrically insulating material. The device is pressure-controlled and has a high breaking capacity. Figure for the abstract: Fig. 12

Description

Title of the invention: Electrochemical accumulator integrating a current interruption device with high breaking capacity. technical field

[0001] The present invention relates to the field of electrochemical accumulators, and more particularly to metal-ion accumulators.

[0002] More particularly, the invention relates to improving the safety of electrochemical accumulator batteries.

[0003] The invention aims primarily to provide a current interruption safety device with improved breaking capacity that can be integrated into a metal-ion type electrochemical accumulator in particular to prevent its thermal runaway in order to limit the risks of propagation within a battery pack.

[0004] Although described with reference to a lithium-ion battery, the invention applies to any metal-ion electrochemical battery, that is to say, also sodium-ion, magnesium-ion, aluminum-ion, etc., or more generally to any electrochemical battery. The invention applies to any metal-ion battery chemistry, such as, for example, NMC / graphite, NCA / graphite, NMC / G-Si, LFP / graphite, and Na-ion with liquid electrolyte.

[0005] A battery according to the invention can be in an on-board or stationary module or battery pack. For example, the fields of electric and hybrid transportation and grid-connected storage systems can be considered within the scope of the invention. Previous technique

[0006] As schematically illustrated in figures 1 and 2, a lithium-ion battery or accumulator usually comprises at least one electrochemical cell consisting of an electrolyte constituent 1 between a positive electrode or cathode 2 and a negative electrode or anode 3, a current collector 4 connected to the cathode 2, a current collector 5 connected to the anode 3 and finally, a package 6 arranged to contain the electrochemical cell with sealing while being traversed by a part of the current collectors 4, 5.

[0007] The architecture of conventional lithium-ion batteries comprises an anode, a cathode, and an electrolyte. Several types of conventional architectural geometry are known:

[0008] - a cylindrical geometry as disclosed in the patent application US 2006 / 0121348,

[0009] - a rectangular prism geometry, called prismatic in the field of batteries, such that disclosed in US patents 7348098, US 7338733;

[0010] - a stacked geometry as disclosed in the US patent applications 2008 / 060189, US 2008 / 0057392, and US patent 7335448.

[0011] The electrolyte component 1 may be in solid, liquid, or gel form. In gel or liquid form, the component may include a separator made of polymer, ceramic, or microporous composite material impregnated with organic or ionic liquid electrolyte(s) that allows the movement of lithium ions from the cathode to the anode for charging and vice versa for discharging, thereby generating the current. The separator is commonly made of polypropylene (PP) or polyethylene (PE), or a multilayer of polymers. This functionality of the electrolyte-impregnated microporous separator is achieved by creating pores of controlled diameters (a so-called "wet process" or "dry process" manufacturing method) in the polymer material. The electrolyte is generally a mixture of organic solvents, for example, carbonates, to which a lithium salt, typically LiPF6, is added.

[0012] The positive electrode or cathode is made of Lithium cation insertion materials which are generally composite, such as lithium iron phosphate LiFePO4, lithium cobalt oxide LiCoO2, lithium manganese oxide, possibly substituted, LiMn2O4 or transition metal oxide, such as lamellar materials for example, a material based on LiNixMnyCozO2 with x+y+z = 1, such as LiNio.33Mno.33Coo.33O2, or a nickel cobalt aluminium oxide type material LiNixCoyAlzO2 with x+y+z = 1, such as LiNio.8Coo 1sA1o.05O2.

[0013] The negative electrode or anode is very often made of carbon, graphite, or LiTiOsO12 (titanate material), and may also be silicon-based, lithium-based, tin-based, or made from their alloys or silicon-based composites. This negative electrode, like the positive electrode, may also contain electronically conductive additives as well as polymer additives that give it mechanical properties and electrochemical performance suitable for the lithium-ion battery application or its manufacturing process.

[0014] The anode and cathode made of Lithium insertion material can be continuously deposited according to a conventional technique in the form of an active layer on a metallic sheet or strip constituting a current collector.

[0015] The current collector 4 connected to the positive electrode is generally made of aluminum.

[0016] The current collector 5 connected to the negative electrode is generally made of copper, nickel-plated copper or aluminum.

[0017] More specifically, aluminium is used for the common current collectors of positive and negative electrodes of Li4Ti5O12 titanate. Copper is rather for the negative electrodes of graphite (Cgr), silicon (Si) or silicon composite (Si-C).

[0018] Traditionally, a Li-ion battery or accumulator uses a pair of materials at the anode and cathode allowing it to operate at a voltage level, typically between 1.5 and 4.2 Volts.

[0019] The electrical terminals, or current collectors of the accumulator can also be implemented with functions related to the safety of the accumulator, by triggering the opening of the electrical circuit in the event of a fault in the accumulator.

[0020] A lithium-ion battery or accumulator can obviously comprise a plurality of electrochemical cells.

[0021] Depending on the type of application targeted, the aim is to produce either a thin and flexible lithium-ion battery or a rigid battery: the packaging is then either flexible or rigid and in the latter case constitutes a kind of casing.

[0022] Flexible packaging is usually made from a multilayer composite material, consisting of a stack of aluminum layers covered by one or more polymer film(s) laminated by bonding.

[0023] Rigid packaging is used when the applications are demanding where a long service life is required, for example with much higher pressures to withstand and a stricter level of sealing required, typically less than 108mbar.l / s, or in highly demanding environments such as the aeronautical or space sector.

[0024] Rigid packaging (cases) is usually made from a metallic material, typically an aluminum alloy or stainless steel or a rigid polymer such as acrylonitrile butadiene styrene (ABS).

[0025] The geometry of most rigid Li-ion battery packaging cases is cylindrical, since most electrochemical cells in batteries are wound in a cylindrical shape around a cylindrical core. Prismatic case shapes have also already been produced by winding around a flattened core.

[0026] One type of rigid cylindrical case, usually manufactured for a high-capacity Li-ion battery, is illustrated in [Fig.3].

[0027] Fig. 4 shows a longitudinal cross-sectional view of such a housing 6 with axisymmetric geometry around the central axis X, housing an elongated electrochemical beam F comprising a single electrochemical cell consisting of an anode 3 and a cathode 4 on either side of a separator 1 adapted to be impregnated with the electrolyte. Fig. 4 shows the resulting beam F, usually by winding around a central winding axis 10, inside the cylindrical case 6.

[0028] In [Fig.3], the housing 6 has a cylindrical side casing 7, a bottom 8 at one end, a cover 9 at the other end, the bottom 8 and the cover 9 being assembled to the casing 7. The cover 9 supports the current output poles or terminals 4, 5. One of the output terminals (poles), for example the negative terminal 5 is welded to the cover 9 while the other output terminal, for example the positive terminal 4, passes through the cover 9 with the interposition of a seal not shown which electrically isolates the positive terminal 4 from the cover.

[0029] The type of rigid housing widely manufactured also consists of a stamped cup and a lid, welded together around their periphery. In contrast, current collectors include a through-hole with a portion protruding from the top of the housing, forming a terminal also called the exposed battery pole.

[0030] A rigid prismatic-shaped case is also shown in [Fig.5].

[0031] A battery pack consists of a variable number of accumulators, which can reach several thousand, that are electrically connected in series and / or in parallel with each other and generally by connection bars, usually called busbars.

[0032] In the development and manufacture of lithium-ion batteries, for each profile / new demand, regardless of the market players, precise sizing is required (series / parallel electrical architectures, mechanical, thermal...) to optimally design a high-performance and safe battery pack.

[0033] In particular, the safety of lithium-ion batteries must be taken into consideration both at the level of a single battery, a module and a battery pack.

[0034] Indeed, when a lithium-ion battery is misused, whether 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 Li-ion batteries is therefore a fundamental aspect that influences their entire life cycle.

[0035] Various passive or active devices having a safety function can also be integrated at the level of a cell (accumulator), and / or a module and / or the battery pack to prevent problems when the battery is in so-called abusive operating conditions or in the event of a fault at the level of a cell.

[0036] A lithium electrochemical system, whether at the cell (battery), module, or pack level, produces exothermic reactions regardless of the cycling profile. Thus, at the scale of a single battery, in Depending on the chemistries involved, the optimal operation of lithium-ion batteries is limited within a certain temperature range.

[0037] An electrochemical accumulator must operate within a defined temperature range, typically generally below 70°C on its outer casing surface, otherwise its performance will be degraded, or it may even be physically degraded to the point of destruction.

[0038] Lithium iron-phosphate batteries, which generally have an operating range between -20°C and +60°C, can be cited as an example. Above 60°C, the materials and the electrolyte can undergo significant degradation, reducing the cell's performance. Above a so-called thermal runaway temperature, which can be between 70°C and 110°C, exothermic internal chemical reactions are initiated. When the battery is no longer able to dissipate sufficient heat, the cell temperature rises until it is destroyed; this phenomenon is commonly referred to as thermal runaway.

[0039] In other words, thermal runaway occurs in a cell (accumulator) when the energy released by the exothermic reactions occurring within it exceeds the capacity to dissipate it to the outside. This runaway can be followed by the generation of gas and an explosion and / or fire. For this thermal runaway phenomenon, refer to publication [1] and the protocol described therein. The so-called "self-heating" and "thermal runaway" temperatures are denoted T1 and T2 respectively in that publication.

[0040] The temperature Tl, typically 70°C, in [Fig.2] of the publication, is the temperature from which the accumulator heats up without an external source at a typical rate of 0.02 °C / min under adiabatic conditions.

[0041] The temperature T2, typically 150°C, in [Fig.2] of the publication, is the temperature from which the accumulator reaches a typical heating rate of 10°C / min under adiabatic conditions, which leads to the melting of the separator in the electrochemical bundle of the accumulator, to a short circuit and therefore to the collapse of the voltage.

[0042] By "thermal runaway", we can thus understand here and within the framework of the invention, a ratio between the value of the derivative of the heating temperature and that of the time at least equal to 0.02°C per min.

[0043] Also, maintaining a temperature below 70°C increases the lifespan of a battery, because the higher the operating temperature of a battery, the shorter its lifespan will be.

[0044] Furthermore, some battery chemistries require an operating temperature well above ambient temperature and consequently, it turns out It is necessary to regulate their temperature level by an initial preheating of the accumulators, or even by maintaining the accumulators at a permanent temperature.

[0045] At the level of a cell (battery), the various known internal protection devices are:

[0046] - a positive temperature coefficient (PTC) device (for "Polymeric Positive Temperature Coefficient"): currently, a large number of cylindrical batteries already on the market are equipped with this. Such a device takes the form of an electrically insulating polymer ring loaded with conductive particles. In case of overcharging, this polymer heats up, changes phase, expands, pushes the conductive particles apart, becomes more resistive and thus limits the flow of current;

[0047] - a current interruption device (CID): it interrupts the current if the gas pressure in the cell exceeds the specified limits;

[0048] - a circuit breaker (shutdown) device that prevents the generation high currents by melting one of the polymers of a multilayer separator which seals the pores of the separator;

[0049] - a vent consisting of a valve or a rupture disc, which opens when the internal pressure increases abruptly, and exceeds a predetermined critical pressure, in order to prevent the cell from exploding;

[0050] - a thermal fuse, currently implemented in high-capacity batteries capacity, which cuts off the current as soon as the temperature in the accumulator is too high.

[0051] These protective devices, also designated as cell (accumulator) safety devices, play a key role in mitigating the effects related to their thermal runaway.

[0052] Furthermore, battery manufacturers aim to constantly increase the energy of their batteries in order to improve their performance. Thus, the use of materials with high energy capacity but with a strongly exothermic behavior in the event of thermal runaway of a battery is becoming increasingly common: [2].

[0053] At the module or battery pack level, the BMS (Battery Management System) integrates a protection / safety function. Fuses may also be used.

[0054] These protections / safeties mentioned are effective with respect to the faults for which they are designed, but cannot protect the accumulators when the electrical fault, for example a short circuit due to a double insulation fault), appears upstream of them or when they are faulty.

[0055] Therefore, in order to protect batteries in low-power systems (typically delivering a few amperes) and low-voltage systems (typically from a few volts to a few tens of volts), battery manufacturers integrate the active or passive protection / safety devices mentioned above into the battery itself. Their general function is to disconnect the electrochemical core of the battery from its output terminals, and thus to electrically isolate it from a module or battery pack. These protection devices can protect the batteries during failures affecting a group of batteries, for example, the overcharging of one or more batteries or a short circuit in one or more batteries.

[0056] Among these safety devices, a CID (Cold Ignition Device) is integrated into the majority of existing small cylindrical Li-ion batteries, commonly 18 mm in diameter and 65 mm in length or 21 mm in diameter and 70 mm in length. Such a device, for example described in US patent 10770711B1, consists of two electrically conductive metal discs spot-welded together at their center to ensure electrical conductivity. The lower disc is perforated in several places to allow gases to pass through, and the upper disc is at the interface between the inside of the battery casing and the external environment.When gases are generated inside the battery, for example as a result of damage, and the pressure reaches approximately 10 bar inside the Li-ion cell of the battery casing, the upper disc deforms, tearing the weld with the lower disc which remains fixed, thereby interrupting the current.

[0057] In the case of a single accumulator supplying an electrical circuit, a CID device is a component triggered by internal pressure which interrupts the current below the voltage of the protected accumulator, i.e. 4.2 V maximum for accumulators with NMC cathode and graphite anode.

[0058] However, when assembled into modules or battery packs at higher voltages, for example 400 V or 800 V for automotive applications, with a large number of batteries connected in series, several dozen for example, the CID device must interrupt a current that can reach several thousand amperes under the branch voltage, which can be several hundred volts. However, CID manufacturers do not specify the breaking capacity of the CIDs, that is, the maximum current they can interrupt under the voltage imposed by the circuit. Typically, a breaking capacity is defined for several operating voltage levels within the permissible operating range of the device. If this is exceeded, an electric arc can be created, sustained, and lead to thermal runaway of the battery: [3].

[0059] Conventionally, CIDs such as the one described also perform a venting function. If the pressure continues to increase, the upper disc ruptures locally or completely, and the pressurized gases are released to prevent the accumulator from exploding.

[0060] In summary, existing CID devices and other safety features integrated into small batteries, particularly cylindrical ones, are currently unable to interrupt currents and voltages several orders of magnitude higher than the fault current and voltage level of a single battery. This is because their breaking capacity is too low, and is not specified by battery manufacturers.

[0061] In a technical field other than that of electrochemical accumulators, high breaking capacity electrical current interruption devices have been developed.

[0062] For a relay, the breaking capacity depends in particular on the opening distance of the electrical contacts: the larger the mechanical opening, the greater the relay's breaking capacity. However, the breaking capacity of relay electrical contacts in air at atmospheric pressure is relatively low. For example, the V23076A1001C133 1393277-4 relay from TE Connectivity requires a 0.5 mm opening to be specified at 12V and 30A repeating breaking capacity. This is especially true in direct current (DC) because there are no zero crossings of the current as in alternating current (AC). This zero crossing causes the total or partial extinction of the arc twice per period of alternating current. In fuses, an electrically conductive material melts, and an arc appears on either side of the area where the conductive material has melted.

[0063] To improve breaking capacity, the conventional solution is to place the relay contacts or the fusible material of the fuses in an environment unfavorable to the maintenance of an electric arc. For example, in the case of high-breaking-capacity fuses, the fusible element is placed in pure silica sand. Silica is a conventional solution for improving breaking capacity in the field of fuses because it is, on the one hand, an electrical insulator, and on the other hand, its melting upon contact with the arc is endothermic, which has the effect of cooling the arc and thus interrupting it. Finally, when the molten silica cools after contact with the arc, it transforms into fulgurite (amorphous silica), which is an electrical insulator and prevents the reignition of an electric arc. None of these solutions has yet been integrated into a metal-ion battery.

[0064] In this context, there is a need to further improve the breaking capacities of safety solutions for electrochemical accumulators, in particular metal-ion accumulators.

[0065] The aim of the invention is to meet at least part of this need. Description of the invention

[0066] To this end, the invention relates, in one of its aspects, to a metal-ion electrochemical accumulator (A) comprising:

[0067] - at least one electrochemical cell consisting of a cathode, an anode and of a separator impregnated with an electrolyte arranged between the cathode and the anode, the cell(s) defining an electrochemical beam;

[0068] - a housing arranged to contain the electrochemical beam in a hermetically sealed manner;

[0069] - two current output terminals, one of which, said first terminal, passes through a wall of the housing or closes it while being electrically isolated from it;

[0070] - a current interruption device comprising:

[0071] • a first electrically conductive part connected to one or the other of the anode(s) and cathode(s), fixedly mounted relative to the housing and electrically isolated from the current output terminals, configured to allow the passage of gases generated from the electrochemical beam,

[0072] • a second electrically conductive part, solid and mounted in such a way sealed within the housing, and comprising a first end portion connected to one of the output terminals and a second end portion extending from the first portion, and configured to occupy two possible positions, a first initial position in which it is electrically connected to the first electrically conductive part, and a second so-called deformed position in which it is away from the first electrically conductive part and without being electrically connected to it, the passage between the first position and the second position being effected under the pressure of gases generated from the electrochemical beam, the second end portion being welded directly or via an electrically conductive element at one or more points of contact to the first electrically conductive part, so as to form a circuit breaker during the passage between the first initial position and the deformed position,

[0073] • a longitudinal wall closed on itself internally defining a volume, the relative arrangement between the longitudinal wall, the second end portion of the second electrically conductive piece and the first electrically conductive piece being such that the volume is closed and defines a tank filled with at least one endothermic and electrically insulating material.

[0074] Advantageously, the passage from the first initial position to the deformed position of the second electrically conductive part opens the reservoir of endothermic and electrically insulating material by allowing the dispersion of said material.

[0075] According to one embodiment, the electrochemical beam is elongated along a longitudinal axis (X); the first terminal preferably comprising at least one through hole to allow gases to pass through.

[0076] According to another embodiment, the first electrically conductive part of the current interruption device is connected to one or the other of the anode(s) and the cathode(s) at a longitudinal end of the electrochemical beam, preferably of planar shape and preferably comprising at least one through hole to allow the passage of gases generated from the electrochemical beam.

[0077] Preferably, the circuit breaker is a fuse.

[0078] According to a first embodiment, the second end portion is the longitudinal wall welded directly at one or more points of contact to the first electrically conductive part.

[0079] According to a second embodiment, the longitudinal wall is made of electrically insulating material(s), the second end portion comprising at least one protrusion welded directly at one or more points of contact to the first electrically conductive part.

[0080] According to a third embodiment, the longitudinal wall is made of electrically insulating material(s), the second end portion comprising at least one protrusion welded directly at one or more points of contact to the first electrically conductive part.

[0081] According to a fourth embodiment, the metal-ion electrochemical accumulator comprises an electrically conductive element ensuring electrical contact between the first electrically conductive part and the second end portion of the second electrically conductive part, the longitudinal wall being made of electrically insulating material(s), the electrically conductive element having an electrical fuse function, configured to melt and break the contact in case of electrical overcurrent.

[0082] Advantageously, the electrically conductive element comprises at least one electrically conductive tab welded directly at one or more points of contact to the first electrically conductive part and to the second end portion, preferably flat.

[0083] The electrically conductive tab can advantageously be perforated with one or more through holes.

[0084] According to an advantageous embodiment, the first end part of the second electrically conductive part comprises a flat annular portion in planar support and welded to the first output terminal.

[0085] Advantageously, the endothermic and electrically insulating material is in granular form.

[0086] Preferably the endothermic and electrically insulating material being chosen from silica, KBF4, KMgCl3, NaKMgCl, KMgZnCl or a mixture thereof.

[0087] The accumulator can be generally cylindrical or prismatic in shape. It can be a standard 18650 Li-ion battery, and generally any of the following standard formats: 10440 / 14500 / 14650 / 16340 / 17335 / 17500 / 17670 / 18350 / 18490 / 18500 / 18650 / 18700 / 22650 / 25500 / 26650 / 32650.

[0088] According to an advantageous embodiment, in a cylindrical accumulator, the first electrically conductive part is a disk, the first end portion of the second electrically conductive part is a ring, the longitudinal wall is a hollow cylinder; the central axes of the disk, the ring and the hollow cylinder being coincident with the central axis (X).

[0089] The electrochemical beam can consist of a single electrochemical cell, obtained by winding or comprise a stack of elementary electrochemical cells each comprising a cathode, an anode, and an electrolyte-impregnated separator intercalated between the anode and the cathode.

[0090] The electrochemical beam according to the invention can be produced using a Z-folding technique. In such a process, the addition of the lower melting temperature separator zone requires stopping the folding itself before the last electrode layer in order to add said lower melting temperature zone to the lateral ends of the electrochemical cell stack.

[0091] According to an additional advantageous feature, the second electrically conductive part includes at least one thinned rupture zone intended to constitute a vent for the gases generated under overpressure in the accumulator.

[0092] Each accumulator can be a Li-ion accumulator in which:

[0093] - the negative electrode material(s) is chosen from the group comprising the graphite, lithium, titanate oxide Li4TiO5Oi2; The positive electrode material(s) is chosen from the group of intercalation / insertion compounds of the type LiM02 with M representing Co, Ni or Mn; LiM'2O4 with M' representing Ni or Mn; LiM''PO4 with M” representing Fe, Co, Mn or Ni.

[0094] Thus, the invention essentially consists of providing a current interruption device, to be integrated into the accumulator, pressure-controlled, and having a high breaking capacity.

[0095] Indeed, when metal-ion batteries are used outside their safety zone (thermal, electrical, or mechanical), one indicator of the onset of degradation of the electrochemical materials is the generation of gas. These generated gases, contained within the battery, increase its internal pressure. This Pressure is used to separate two electrically conductive parts in electrical contact, typically metal parts, at one of the output terminals of the accumulator, in order to interrupt the electrical circuit of the accumulator.

[0096] During normal operation of the battery, when these contact parts are used nominally, they are electrically connected, meaning that their electrical contact is effective and current flows. The electrical connection between these contact parts can be made by welding, for example, spot welding or laser welding. Making this electrical connection by welding minimizes contact resistance and therefore losses during nominal battery operation, and also allows the battery to be opened by breaking the weld in the event of internal overpressure.

[0097] Once the contact is open between these two parts, it is not necessary and should even be avoided for it to return to its initial state, since the accumulator is now degraded and unstable.

[0098] The implementation of these two electrical contact parts can be achieved, for example, by two metal parts arranged at one of the longitudinal ends of the accumulator. When the accumulator is cylindrical, these two parts can generally be in the form of discs.

[0099] One of the two contact pieces is perforated to allow the passage of gases generated by the accumulator. This perforated contact piece is connected by one or more contact points to a second concentric disk.

[0100] This second contact piece has its inner face subjected to the internal pressure of the accumulator and its outer face in contact with and subjected to the pressure of the ambient air. When the pressure difference between the inside of the accumulator and atmospheric pressure reaches a defined threshold, this second contact piece deforms, due to its plasticity, thereby breaking the contact point(s) between the two contact pieces. This action interrupts the current between the electrode to which the perforated contact piece is connected and the associated terminal of the accumulator.

[0101] It is at the point of the electrical contact breaking that an electric arc can form. In order to be able to interrupt this arc, the invention provides that the electrical contact area opening during the breaking is in contact with an electrically insulating endothermic material, previously stored in a reservoir delimited between the two contact parts, which absorbs the energy of the electric arc.

[0102] This fusible material is released over the entire tear-off area, thereby absorbing the energy of the electric arc. Advantageously, when the accumulator is in a position favoring the action of gravity, particularly vertically, the release of the fusible material, especially when in granular form, is facilitated.

[0103] The required quantity of fusible material depends on its physico-chemical nature and the desired performance, but for existing battery formats, the order of magnitude envisaged by the inventors is a few grams.

[0104] If the release of material by gravity is not possible, for example if the accumulator is in a position where the contact part which deforms is below the tank, the extinction of the arc is not as rapid, but still possible, because the electric arc will consume the material of the wall of the tank until it comes into contact with the fusible material for extinguishing the electric arc.

[0105] An advantageous example of a usable granular material is silica sand. Other endothermic materials during a phase change and electrical insulators can also be used.

[0106] Thus, thanks to the invention, the core of the electrochemical beam of a battery is preserved and thermal runaway is avoided.

[0107] The inventors have gone against existing solutions for the design of metal-ion batteries and the intended safety devices.

[0108] Indeed, electrical current interruption devices (ICDs) such as those integrated within a Li-ion battery have the initial objective of protecting a single battery, or a low voltage assembly of a few batteries in series, for example three for laptops, in order to protect against electrical faults, such as electrical overload or short circuit.

[0109] However, the person skilled in Li-ion batteries does not appear to have taken note of, and has not dealt with, the problems related to the breaking capacity of these protection devices integrated into the batteries.

[0110] One reason for this is the very rapid expansion of Li-ion technologies, initially designed for portable applications, typically camcorders in 1990 and then laptops, towards systems requiring increasingly powerful batteries, such as electric vehicles. Without having considered the problem, those skilled in the art therefore did not propose appropriate solutions, i.e., solutions enabling high breaking capacity.

[0111] Ultimately, the invention provides a battery that incorporates a current interruption device with improved breaking capacity compared to those of the prior art. This integrated device can interrupt currents and voltages several orders of magnitude higher than the fault current and voltage level of a single battery.

[0112] This can considerably increase the safety of a module or battery pack, comprising several accumulators, in particular in electrical series.

[0113] Industrial sectors where the invention may be of particular interest are those where the modules or battery packs require the series connection of a plurality of accumulators, typically twenty or more. Examples include the field of stationary energy storage, the aeronautical sector, and electric motor vehicles.

[0114] Other advantages and features of the invention will become clearer from the detailed description of examples of implementation of the invention given by way of illustration and not limitation with reference to the following figures. Brief description of the drawings

[0115] [Fig-1] [Fig. 1] is a schematic exploded perspective view showing the different elements of a lithium-ion battery.

[0116] [Fig.2] [Fig.2] is a front view showing a lithium-ion battery with its flexible packaging according to the state of the art.

[0117] [Fig.3] [Fig.3] is a perspective view of a lithium-ion battery according to state of the art with its rigid packaging consisting of a cylindrical case.

[0118] [Fig.4] [Fig.4] is a partial longitudinal sectional view of a state-of-the-art lithium-ion battery, showing the electrochemical bundle consisting of a single electrochemical cell wound on itself by winding in a cylindrical geometry inside the casing.

[0119] [Fig. 5] [Fig. 5] is a perspective view of a lithium-ion battery according to state of the art with its rigid packaging consisting of a prismatically shaped case.

[0120] [Fig.6] [Fig.6] is an isometric view of a first embodiment of current interruption device according to the invention, intended to be integrated into a cylindrical metal-ion battery.

[0121] [Fig.7] [Fig.7] is a perspective and longitudinal sectional view of the device according to [Fig.6].

[0122] [Fig.8] [Fig.8] is an isometric view of one of the electrical contact parts, under the shape of a perforated disc of the device according to figures 6 and 7.

[0123] [Fig.9] [Fig.9] is a side view of the other of the electrical contact parts of the device according to figures 6 and 7.

[0124] [Fig. 10] [Fig. 10] is a longitudinal sectional view of a current interruption device for a cylindrical metal-ion battery according to a second embodiment of the invention.

[0125] [Fig.11] [Fig.11] is an isometric view of the device according to [Fig.10].

[0126] [Fig. 12] [Fig. 12] is a schematic partial longitudinal sectional view of a lithium-ion battery incorporating a current interruption device according to the second mode of the invention.

[0127] [Fig. 13] [Fig. 13] is an isometric and longitudinal sectional view of a device current interruption for a cylindrical metal-ion battery according to a third mode of the invention.

[0128] [Fig. 14] [Fig. 14] is a longitudinal cross-sectional view of an interrupting device current for a cylindrical metal-ion battery according to a variant of the third mode of the invention.

[0129] [Fig. 15] [Fig. 15] is a schematic partial longitudinal sectional view of a lithium-ion battery incorporating a current interruption device according to the third mode of the invention. Detailed description

[0130] Figures 1 to 5 relate to different examples of Li-ion batteries, flexible packaging and battery cases, and a battery pack according to the prior art. These figures 1 to 5 have already been discussed in the preamble and are therefore not discussed further below.

[0131] For the sake of clarity, the same references designating the same elements according to the prior art and according to the invention are used for all figures 1 to 14.

[0132] Figures 6 to 8 illustrate a current interruption device 11 according to the invention, intended to be integrated within a cylindrical Li-ion battery. The electrically conductive parts 12, 13 of the device 11 can be manufactured using the same industrial tooling as that used to manufacture existing current interruption devices (CIDs).

[0133] The first electrically conductive metal part 12 is intended to be connected to one or the other of the anode(s) and the cathode(s) at a longitudinal end of the electrochemical beam of a flat-shaped accumulator.

[0134] As shown in [Fig. 8], this metal part 12 is an electrically conductive metal disc with a diameter smaller than that of the battery and a thickness that varies depending on the design and size of the battery. For example, the metal disc is made of a grade of aluminum, its diameter can be 12 mm for a battery with a diameter of 18 mm, and its thickness can be 0.5 mm.

[0135] This metal disc 12 includes a central portion 120 which is solid and is perforated, at the periphery of its central portion 120, with at least one through hole 121, 122 to allow the passage of gases generated from the electrochemical beam, in other words allowing the main faces of the disc to be in iso pressure, more particularly once the device is integrated within an accumulator.

[0136] The shape and number of perforations (through holes), 121, 122 depend in part on the surface area required for assembly with the other parts of the device 11, The desired volume of gas passing through and its distribution for bearing on the second electrically conductive part, or the desired mechanical strength of the disc, are all factors to consider. These openings in the disc can be created using various common machining methods, such as laser cutting. In the illustrated example, through holes 121 with an arc-shaped cross-section are regularly spaced at regular angular intervals in a first ring around the central portion, and circular holes 122 are also regularly spaced at regular angular intervals in a second ring around the first ring.

[0137] The device 11 includes a second solid electrically conductive part 13, which is intended to be mounted in a sealed manner in a battery case 6 while being electrically isolated from it.

[0138] As illustrated in [Fig.9], this second part 13 comprises a first end portion 130, in the form of a ring, intended to be connected to an output terminal of an accumulator and a second end portion 131, in the form of a hollow cylinder, in the extension of the first portion 130 by being connected by an intermediate portion 132, of frustoconical shape.

[0139] This hollow cylinder 131, together with the solid portion 120 of the disc 12, constitutes a material reservoir 14. This material reservoir can, for example, be produced by stamping a disc of conductive metal.

[0140] The ring portion 130 of the second part 13 has an outer diameter slightly smaller than that of the battery casing 6 and a thickness that varies depending on the desired mechanical strength. For example, this part 13 is made of a grade of aluminum; its diameter can be 16 mm for a battery with a diameter of 18 mm, and its thickness can be 0.5 mm.

[0141] The bottom of the cylindrical portion 131, delimiting the volume of the material reservoir 14, can advantageously be a thinned area of ​​mechanical weakness so as to constitute a vent for the gases of the accumulator. This area of ​​mechanical weakness is dimensioned and distributed according to the direction and flow rate desired during the release of the pressurized volume, for example when the internal pressure of the accumulator can reach 20 bar.

[0142] This cylindrical portion 131 of the second part 13 is directly welded to the first electrically conductive part 12, so as to form a circuit breaker. For this assembly between the cylinder 131 and the solid portion 120 of the disc 12, they can be positioned concentrically and then pressed against each other. Ultimately, the mechanical strength and the stability of the electrical contact can be achieved by welding, for example, through the reservoir to the disc 12. This weld S can be made at one or more points, or even along a continuous line, and in various ways, for example, by spot welding, laser welding, or ultrasonic welding.

[0143] Before the assembly of the two parts 12, 13, the reservoir 14 is filled with at least one endothermic and electrically insulating material. This endothermic material improves the breaking capacity when the current is interrupted by the device 11. For example, the material could be silica sand.

[0144] The operation of the device according to the invention 11 is as follows.

[0145] When the pressure inside the accumulator reaches a fixed pressure, for example 10 bar, part 13 deforms outwards from the accumulator. The weld between the material reservoir 14 and the disc 12 breaks / is torn away, thus interrupting the electrical contact between the two parts 12 and 13, which generates an electric arc in this area of ​​rupture / breakage.

[0146] The fusible endothermic material is then released over the entire tear-off area, absorbing the arc energy. The quantity of fusible material depends on the material used and the desired performance, but is on the order of a few grams. If the accumulator is positioned vertically with the reservoir facing downwards, then gravity will accelerate the release of the material. If gravity cannot act, then arc extinction is not as rapid, but still possible, because the electric arc will consume the material of the reservoir wall 14 until it comes into contact with the endothermic material intended for arc extinction.

[0147] One possible option that can be conferred to the device 11 according to the invention triggered by the internal pressure of the accumulator is to add a physical fuse function to provide protection against overcurrent or short-circuit current.

[0148] This fusible physical element plays a role in synergy with the action of the material endothermic to further facilitate the extinguishing of an electric arc within a battery.

[0149] Thus, these two elements provide electrical protection to the accumulator either in a situation of overload and / or overheating of the latter, where the dynamics allow the generation of gas and then the opening of the contact linked to the overpressure, or in a situation of short circuit or overcurrent where the physical phenomenon and the dynamics do not allow the generation of gas to deform the second part.

[0150] In this latter situation, a fusible element can be sized so as to melt when the current in the accumulator is greater than the maximum current it can admit.

[0151] This added functionality requires that the longitudinal wall delimiting the reservoir of fusible endothermic material 14 not be electrically conductive, since the fusible element also constitutes the overpressure release zone. Therefore, the activation of only one of the two functions must completely interrupt the current in the accumulator. For this purpose, the fusible reservoir can be made of at least one electrically insulating material, preferably resistant to high temperatures. This could be an electrically insulating polymer.

[0152] Two embodiments of this option are possible.

[0153] One of these two modes is illustrated in Figures 10 and 11. Part 13 comprises, as a second end portion 131, a protrusion, which can be formed by stamping. This protrusion 131, welded to the disc 12, is thinned to create a rupture zone corresponding to the electrical contact area with the disc 12. The fusible function is thus ensured by the very structure of part 12, by its thinned protrusion. In this way, the width of the contact area allows the current rating of the fusible function to be selected. As illustrated, the electrical contact area can be centered opposite a connection pad 123 formed on the other face of the disc 12 for electrical connection with an electrode of the electrochemical bundle of a battery.

[0154] A hollow, electrically insulating cylinder 15 is arranged around the protrusion 131 and thus delimits, together with the two parts 12, 13, the reservoir 14 filled with endothermic material.

[0155] An example of integrating the current interruption device 11, more specifically according to the mode of Figures 10, 11, within a cylindrical Li-ion battery A, is illustrated in [Fig. 12]. In this example, the positive output terminal 4 forms the cover of the battery case 6 of battery A and includes a vent hole 40 for the passage of ambient air.

[0156] The ring 130 is flat-mounted and welded to the output terminal 4 and these two components are held in the housing 6 by being mounted in a sealed manner in an electrically insulating annular seal 16.

[0157] The disk 12, immobile within the housing 6, is electrically connected to the cathode 2 of the electrochemical beam F by a current collector 17 in the form of a metal tab folded back on itself in contact, preferably by being welded to the connection pad 123 of the disk 12.

[0158] The alternative embodiment of the option with a physical fusible function is illustrated in Figures 13 and 14. Here, the fusible function is not constituted by the structure 131 of part 13, but by an electrically conductive fusible element 18 which is welded at its two longitudinal ends to each of the two parts 12 and 13. This separate element 18, which may be in the form of a folded tab, is dimensioned both to break away and interrupt the current in the event of overpressure in the accumulator, and to provide the fusible function in the event of overcurrent in the accumulator. This element 18 is arranged in the reservoir 14 to improve the current breaking capacity.

[0159] A variant of this fusible element 18 is illustrated in [Fig. 14]. The element 18 is perforated at one or more points 180. These perforations 180 both reduce the mechanical resistance and therefore the pull-out pressure of the element 18 and allow for a series connection of fuses within the single element 18. This increases the breaking capacity of the fuse by placing arcs in series. Since the voltage of the series arcs adds up, the current decays more rapidly.

[0160] An example of integration of the current interruption device 18, more specifically according to the mode of figures 13, 14, within a cylindrical accumulator A, of the Li-ion type, is illustrated in [Fig. 15].

[0161] The invention is not limited to the examples just described; in particular, features of the illustrated examples can be combined in unillustrated variants.

[0162] Other variants and improvements may be envisaged without departing from the scope of the invention.

[0163] The perforated electrical contact piece of a current interruption device according to the invention can be electrically connected equally well to a positive electrode (cathode), of the electrochemical beam or to a negative electrode (anode).

[0164] Any portion of the second electrically conductive part of the device may have at least one thinned area of ​​rupture to constitute a vent for the gases of the accumulator.

[0165] Although the illustrated examples relate to accumulators with cylindrical format casings, the invention applies to accumulators with prismatic format casings. List of cited references:

[0166] [1]: Xuning Feng, et al. « Key Characteristics for Thermal Runaway of Li-ion Batteries » Energy Procedia, 158 (2019) 4684-4689.

[0167] [2]: Xuning Feng, et al. « Thermal runaway mechanism of lithium-ion battery for electric vehicles: A review» Energy Storage Materials, Volume 10, January 2018, Pages 246-267.

[0168] [3]: J. Chauvin, D. Chatroux, L. Garnier, P. Azais and R. Vincent, “Key Points Regarding Electrical Safety in Small Cylindrical Li-ion Cell Assemblies During Overcharge or Partial Short-Circuit, ” PCIM Europe 2023; International Exhibition and Conférence for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, Nuremberg, Germany, 2023, pp. 1-8, doi: 10.30420 / 566091053.

Claims

1. Demands Electrochemical (A) metal-ion accumulator comprising: a. at least one electrochemical cell consisting of a cathode (2), an anode (3) and a separator (1) impregnated with an electrolyte arranged between the cathode (2) and the anode (3), the cell(s) defining an electrochemical beam; b. a housing (6) arranged to contain the electrochemical bundle in a hermetic manner; c. two current output terminals (4, 5), one of which, called the first terminal (4), passes through a wall of the housing (6) or closes it while being electrically isolated from it; d. a current interruption device (11) comprising: a first electrically conductive part (12) connected to one or the other of the anode(s) and the cathode(s), fixedly mounted relative to the housing and electrically isolated from the current output terminals, configured to allow the passage of gases generated from the electrochemical beam, a second electrically conductive part (13), solid and hermetically sealed in the housing, and comprising a first end portion connected to one of the output terminals and a second end portion in line with the first portion, and configured to occupy two possible positions, a first initial position in which it is electrically connected to the first electrically conductive part (12), and a second so-called deformed position in which it is away from the first electrically conductive part (12) and without being electrically connected to it, the passage between the first position and the second position being effected under the pressure of gases generated from the electrochemical beam, the second end portion being welded directly or via an electrically conductive element at one or more points of contact to the first electrically conductive part,so as to form a circuit breaker during the transition between the initial position and the deformed position, a longitudinal wall (131, 15) closed on itself internally defining a volume, the relative arrangement between the longitudinal wall, the second end portion of the second electrically conductive piece and the first electrically conductive piece being such that the volume is closed and defines a reservoir (14) filled with at least one endothermic and electrically insulating material.

2. Electrochemical accumulator (A) metal-ion according to claim 1, the passage from the first initial position to the deformed position of the second electrically conductive piece opens the reservoir of endothermic and electrically insulating material by allowing the dispersion of said material.

3. Electrochemical accumulator (A) metal-ion according to claim 1 or 2, a. the electrochemical beam (F) being elongated along a longitudinal axis (X); b. the first terminal (4) preferably comprising at least one through hole (40) to allow the passage of gases.

4. Metal-ion electrochemical accumulator (A) according to any one of claims 1 to 3, the first electrically conductive part (12) of the current interruption device (11) being connected to one or the other of the anode(s) and cathode(s) at a longitudinal end of the electrochemical beam, preferably planar in shape and preferably comprising at least one through hole (121, 122) to allow the passage of gases generated from the electrochemical beam.

5. Electrochemical (A) metal-ion accumulator according to any one of the preceding claims, the second end portion comprising the longitudinal wall welded directly at one or more points of contact to the first electrically conductive part.

6. Electrochemical (A) metal-ion accumulator according to any one of claims 1 to 4, the longitudinal wall being made of electrically insulating material(s), the second end portion comprising at least one protrusion welded directly at one or more points of contact to the first electrically conductive part.

7. Electrochemical (A) metal-ion accumulator according to any one of claims 1 to 4 comprising an electrically conductive element ensuring electrical contact between the first electrically conductive part and the second end portion of the second electrically conductive part, the longitudinal wall being made of electrically insulating material(s), the electrically conductive element having an electrical fuse function, adapted to melt and break the contact in case of electrical overcurrent.

8. Electrochemical accumulator (A) metal-ion according to claim 7 the electrically conductive element comprising at least one electrically conductive tab welded directly at one or more points of contact to the first electrically conductive part, and to the second end portion, preferably flat.

9. Accumulator according to claim 8, the electrically conductive tab being perforated with one or more through holes.

10. Accumulator according to any one of the preceding claims, the first end portion of the second electrically conductive part comprising a flat annular portion in planar support and welded to the first output terminal.

11. Accumulator according to any one of the preceding claims, the endothermic and electrically insulating material being in granular form.

12. Accumulator according to any one of the preceding claims, the endothermic and electrically insulating material being selected from silica, KBF4, KMgC13, NaKMgCl, KMgZnCl or a mixture thereof.

13. Accumulator according to any one of the preceding claims, the accumulator being generally cylindrical or prismatic in shape.

14. Accumulator according to claim 12, the accumulator being cylindrical in shape, the first electrically conductive part being a disc, the first end portion of the second electrically conductive part being a ring, the longitudinal wall being a hollow cylinder; the central axes of the disc, the ring and the hollow cylinder being coincident with the central axis (X).

15. Accumulator according to any one of the preceding claims, the second electrically conductive part comprising at least a thinned rupture zone intended to constitute a vent for gases generated under overpressure in the accumulator.

16. Accumulator according to any one of the preceding claims, constituting a Li-ion accumulator in which: - the anode material(s) is selected from the group comprising graphite, lithium, titanate oxide Li4TiO5Oi2; the cathode material(s) is selected from the group of intercalation / insertion compounds of the type LiMO2 with M representing Co, Ni or Mn; LiM'2O4 with M' representing Ni or Mn; LiM”PO4 with M'' representing Fe, Co, Mn or Ni.

Images