Electrical energy storage unit and method for manufacturing such a unit.

Abstract

Electrical energy storage unit and method of manufacturing such a unit. Electrical energy storage unit, comprising at least one lithium-ion cell (2) having two electrodes separated by an electrolyte configured to generate charge carriers, the unit comprising a package (3) enclosing said at least one cell (2), an optical sensor (4) and at least one optical fiber (5, 6), each optical fiber (5, 6) having a first end (7, 8) optically coupled to the optical sensor (4), the package (3) comprising a housing (10) in which the optical sensor (4) is housed, the unit comprising at least one end fitting (11, 12) located at a second end (13, 14) of said at least one optical fiber (5, 6) and the package (3) comprising at least one reservoir (15, 16) filled with an airtight material (20a, 20b), and said at least one end fitting (11, 12) includes an external part (23, 24) located outside the packaging (3).Figure for the abridged version: Fig.1.

Description

Title of the invention: Electrical energy storage unit and method for manufacturing such a unit. technical field

[0001] The present invention relates to electrical energy storage units, such as a battery, and more particularly a lithium-ion battery. PRIOR TECHNOLOGY

[0002] The field of lithium-ion batteries has experienced very strong development over the last ten years. Due to its high capacity, stability and durability, this electrical energy storage technology has been widely deployed for portable power tools, vehicles and stationary applications.

[0003] A lithium-ion battery comprises one or more cells, called lithium-ion cells. Each cell has two electrodes separated by an electrolyte configured to generate charge carriers, in particular lithium ions. A battery module is also called a battery module; a battery can comprise one or more modules. In order to increase the performance, safety, and durability of lithium-ion cells, it is necessary to better understand the internal parameters of the cells in operation. Indeed, in order to avoid stressing the cells, whether during charging or discharging, in hazardous areas, safety margins are used, in particular operating voltage ranges during charging and discharging. Another parameter that is monitored is temperature. During operation, the electrochemical processes within the cell generate heat.This heat must be efficiently dissipated by an external system. Therefore, when using lithium-ion batteries, it is advantageous to use an electronic control unit, generally called a BMS (Battery Management System), which limits the loads to optimize performance while ensuring battery safety and longevity. To do this, the system must be able to measure the parameters of the battery cells in real time. The battery is typically composed of several assembled cells, and the BMS must manage all of them.

[0004] To provide the BMS with control data, several measurements are taken on the cells or at the module level. Currently, the measurements taken are the external temperature of the cells, the voltage, and the current. However, this data is insufficient to obtain an accurate picture of the phenomena occurring inside the cell and does not allow for the anticipation of degradation and associated risks. These measurements are carried out by adding sensors to the cells (temperature, pressure, strain, acoustic sensors, etc.), but also inside the cells, by so-called internal sensors, in the heart of the electrolyte or on the electrodes.

[0005] Among these internal sensors, those based on optical fiber have shown their relevance and their ability to measure several internal parameters of the cells such as temperature, pressure, deformation, phase change of an electrode or even specific parameters of chemical decomposition reactions.

[0006] Several techniques using optical fibers for laboratory measurements can be cited, for example, evanescent wave techniques in transmission or reflection, or the use of thermoluminescent probes for internal temperature measurement, applications using Bragg grating fibers for measuring temperature, pressure, or chemical composition, as well as the use of optical fibers by Raman scattering. Optical fibers with plasmonic sensors can also be cited, allowing the measurement of the binding of a "ligand" to a "receptor" adsorbed on the surface of a metallic layer.

[0007] One example is European patent application EP3130029, which discloses a battery equipped with a plasmonic detection element. However, these techniques are suitable for laboratory measurements and are not easily applicable to batteries integrated into electrical devices.

[0008] We can also mention lithium-ion cells of the Swagelok® type (registered trademark), which are cells specifically designed for laboratory research. These cells include an optical sensor connected to an optical fiber that passes through a wall of the cell, inside a metal tube provided on the cell wall. However, the fiber exiting the tube remains fragile. All these types of connections are suitable for laboratory manipulations and do not guarantee the integrity of the optical fiber or its ease of implementation and handling for a battery designed to be used in an electrical device.

[0009] While optical fiber sensors have shown their effectiveness for measurement, they are complicated to implement, particularly for industrial use of cells and especially for use of batteries in situ, i.e. when they are embedded in various devices, such as smartphones, laptops or desktops, motor vehicles... Indeed, once the sensor is placed inside a cell, it is necessary to bring the optical fiber out in order to connect it to a measurement system, for example to the BMS.

[0010] Generally speaking, lithium-ion cells all have a hermetically sealed package that isolates the inside of the cells from the ambient air. Indeed, the The cells are assembled in an anhydrous room, and after activation, the active materials must not come into contact with air, otherwise they will degrade rapidly. The packaging can be flexible or rigid. Flexible packaging is defined as packaging that deforms under its own weight. Conversely, rigid packaging is defined as packaging that does not deform under its own weight. Currently, optical fibers are integrated into the cells by passing the optical fiber through the packaging. This makes the optical fibers relatively fragile, as the slightest stress on the optical fiber will cause degradation of the fiber core or even breakage. Furthermore, it is sometimes difficult to properly seal the cell without damaging the fiber. In addition, when a cell is instrumented with an optical fiber, the portion of the optical fiber protruding from the cell is often long and fragile.This makes it difficult to handle during the insertion of the optical fiber into the cell, but also during handling the cell after sealing and during its integration into an electrical device.

[0011] For example, in the case of a pouch cell, the cell is packaged in a pouch comprising a composite film made of two laminated polymers with an aluminum foil core. The pouch is generally flexible. This type of packaging is sealed by applying pressure from a heating element that melts the surface polymers, thus sealing the cell. This sealing technique is also called heat sealing. Passing the optical fiber through this point to access the cell core necessitates, firstly, the use of optical fibers with sufficient mechanical and thermal resistance to withstand the heat sealing process, and secondly, limiting the temperature and pressure to avoid damaging the optical fiber, which could lead to a suboptimal seal.

[0012] There are cased cells comprising a fiber optic sensor and a connector suitable for connection to a BMS external to the cell, either via an optical connection or radio waves. The connector is attached to the portion of the optical fiber that exits the casing; the connector is further bonded to the casing. However, the casing is sealed by heat sealing, which can damage the optical fiber.

[0013] Thus there is a difficulty in connecting a sensor, placed inside a cell, to the outside of the cell.

[0014] An object of the present invention is therefore to provide means to guarantee the integrity of an optical fiber connected to an optical sensor located within the packaging of an electrical energy storage unit.

[0015] 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

[0016] An electrical energy storage unit is proposed, comprising at least one lithium-ion type cell equipped with two electrodes separated by an electrolyte configured to generate charge carriers, the unit comprising a package enclosing said at least one cell, an optical sensor and at least one optical fiber, each optical fiber having a first end optically coupled to the optical sensor, the package comprising a housing within which the optical sensor is housed.

[0017] The unit comprises at least one end fitting located at a second end of said at least one optical fiber and the package comprises at least one reservoir communicating with the housing of the package through at least one orifice through said at least one optical fiber, said at least one reservoir being filled with an airtight material, and in that said at least one end fitting comprises an internal part encapsulated within the material filling said at least one reservoir and an external part located outside the package.

[0018] Thus, an electrical energy storage unit is provided equipped with an optical sensor coupled to an optical fiber which avoids damaging the optical fiber, during handling to place the optical sensor within the housing where the cells are located, and also during use of the unit in operation, in particular when the unit is embedded in mobile equipment.

[0019] According to another aspect, a method for manufacturing a unit as mentioned above is proposed, comprising: - a supply: • at least one lithium-ion type cell equipped with two electrodes separated by an electrolyte configured to generate charge carriers; • of an optical sensor; • at least one optical fiber, each optical fiber having a first end optically coupled to the optical sensor; and • of packaging comprising a housing within which said at least one cell is housed.

[0020] The process comprises: - an assembly of at least one end fitting at a second end of said at least one optical fiber; - a formation within the packaging of at least one reservoir communicating with the housing via at least one orifice; - the positioning of the optical sensor within the housing and of said at least one optical fiber passing through said at least one opening; and filling said at least one reservoir with an airtight material, such that said at least one nozzle comprises an internal part encapsulated within the material and an external part located outside the packaging. BRIEF DESCRIPTION OF THE FIGURES

[0021] 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:

[0022] [Fig.1] Fig.1 schematically represents a perspective view of an embodiment of an electrical energy storage unit;

[0023] [Fig.2] Fig.2 schematically represents a top cross-sectional view of another method of implementation of an electrical energy storage unit;

[0024] [Fig.3] Fig.3 schematically represents a top cross-sectional view of another method of implementation of an electrical energy storage unit;

[0025] [Fig.4]

[0026] [Fig. 5] Figures 4 and 5 schematically represent perspective views of a another embodiment of an electrical energy storage unit;

[0027]

[0028]

[0029]

[0030]

[0031] [Fig.6] [Fig.7] [Fig.8] [Fig.9] [Fig. 10]

[0032] [Fig. 11] Figures 6 to 11 schematically represent the main steps in implementing a manufacturing process for an electrical energy storage unit.

[0033] The drawings are given by way of example and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily at the scale of applications practices. DETAILED DESCRIPTION

[0034] 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.

[0035] According to one example, said at least one reservoir is a single reservoir filled with an airtight material, a first optical fiber connects the optical sensor to a The first end cap, and a second optical fiber connects the optical sensor to a second end cap, the first and second end caps respectively comprising two internal parts encapsulated within the material filling the single reservoir and two parts external components located outside the packaging. Such a unit is particularly suitable for optical sensors using an input and an output connected to the cells.

[0036] According to one example, the unit comprises first and second reservoirs filled respectively with first and second airtight materials, a first optical fiber connecting the optical sensor to a first end cap, and a second optical fiber connecting the optical sensor to a second end cap. The first and second end caps each comprise two internal parts encapsulated within the first and second materials filling the first and second reservoirs, respectively, and two external parts located outside the packaging. Such a unit allows optical fiber outputs to be placed on either side of the unit's packaging as required.

[0037] According to one example, the packaging is flexible so as to be deformable under its own weight. This is particularly suitable for units having "pouch cell" type cells.

[0038] Alternatively, the packaging can be rigid so as not to be deformed under the effect of its own weight.

[0039] According to one example, said at least one end piece has a cylindrical shape comprising a hollow into which the second end of said at least one optical fiber is inserted. Such an end piece is particularly simple to manufacture.

[0040] According to one example, said at least one tip comprises ceramic.

[0041] According to one example, said at least one tip is held at the second end of said at least one optical fiber using an adhesive comprising at least one epoxy polymer. This stiffens the second end of the optical fiber to improve its retention within the packaging.

[0042] According to another example, said at least one optical fiber is coated, at least in part, with a sheath extending between the first end of said at least one optical fiber and a part of said at least one optical fiber located within the housing of the packaging.

[0043] According to one example, the second end of said at least one optical fiber is encapsulated within said at least one end cap so that the second end does not protrude from said at least one end cap. This prevents any possible damage to the optical fiber.

[0044] According to one example, the unit comprises at least one adhesive retaining element located within the housing and in contact with said at least one optical fiber and an internal wall of the packaging delimiting the housing. This improves the retention of the optical fiber within the housing.

[0045] According to one example, the positioning includes placing at least one adhesive retaining element within the housing and in contact with said at least one optical fiber and an internal wall of the packaging delimiting the housing.

[0046] According to one example, the packaging comprises two flexible sheets so as to be deformable under the effect of their own weight, and the method comprises, before filling, sealing the flexible sheets around the housing and said at least one reservoir.

[0047] Figures 1 to 5 show an electrical energy storage unit 1 comprising at least one lithium-ion cell 2 configured to supply electrical power. Cell 2 may also be configured to store electrical energy. Generally, cell 2 comprises two electrodes separated by an electrolyte configured to generate charge carriers. Unit 1 may comprise several cells forming a module of unit 1. Unit 1 may also comprise several modules.

[0048] The unit 2 comprises a package 3 enclosing the cell(s) 2, an optical sensor 4, and at least one optical fiber 5, 6, each optical fiber 5, 6 having a first end 7, 8 optically coupled to the optical sensor. The package 3 includes a housing 10 in which the optical sensor 4 is housed. The package 3 may be flexible so as to be deformable under its own weight, as illustrated in Figures 1 to 3 and 5, 6. A flexible package 3 may comprise two hermetically sealed sheets 90, 91, for example by heat sealing, delimiting the housing 10 located between the two sheets 90, 91. Alternatively, the package 3 may be rigid so as not to be deformable under its own weight, as illustrated in [Fig. 5]. For example, a rigid package 3 may comprise a box 92 in which the housing 10 is formed. In other words, housing 10 is delimited by the walls of box 92.

[0049] More specifically, the unit 1 comprises at least one end piece 11, 12 located at a second end 13, 14 of each optical fiber 5, 6. An end piece 11, 12 allows an optical fiber 5, 6 to pass through the package 3. The end piece 11, 12 also facilitates the connection of the optical fiber 5, 6 to an electronic control unit 60 located outside the package 3, for example, a BMS. The end piece 11, 12 is further configured to be mechanically connected to a connector 70 connected to the electronic control unit 60, by a connection 71. The connection 71 may be another optical fiber, an electrical wire, or even radio waves. In general, connector 70 and connection 71 are suitable for transmitting information, such as measurement parameters or control data, between the optical sensor 4 and the electronic control unit 60. A ferrule 11, 12 prevents damage to an optical fiber 5, 6, particularly during the The handling and integration of optical fiber 5, 6 into the packaging 3. A ferrule 11, 12 ensures the integrity of optical fiber 5, 6 and the quality of the optical connection. Furthermore, a ferrule 11, 12 stiffens optical fiber 5, 6 to facilitate handling. A ferrule 11, 12 also decouples the insertion stress of optical fiber 5, 6 from its connection to connector 70.

[0050] The connector 70 may include a housing having a recess for inserting the external part 23, 24 of a ferrule 11, 12. For example, the connector 70 may include a screw for tightening the ferrule 11, 12 in the recess of the connector 70 in order to hold it fixed relative to the housing of the connector 70. Alternatively, the connector 70 may include a sleeve with a longitudinal groove for connecting a ferrule 11, 12 with the connection 71, for example another optical fiber external to the package 3. The sleeve is deformable and can be closed, reducing the groove to tighten the ferrule 11, 12 and the other optical fiber in order to hold them in contact.

[0051] For example, a tip 11, 12 has a cylindrical shape comprising a recess 30 into which the second end 13, 14 of an optical fiber 5, 6 is inserted. For example, a tip 11, 12 comprises ceramic. The ceramic makes the tip 11, 12 compatible with the internal environment of the cell 2. In other words, the ceramic is chemically and electrically inert. The ceramic may be alumina. Advantageously, a tip 11, 12 is made entirely of ceramic. For example, unit 1 may include a sheath 40, 41 surrounding each optical fiber 5, 6. An optical fiber 5, 6 may be surrounded, at least in part, by a sheath 40, 41 extending between the second end 13, 14 of the optical fiber 5, 6 and a portion of the optical fiber 5, 6 located within the housing 10 of the package 3. Generally, the second end 13, 14 of an optical fiber 5, 6 is fixedly mounted on a ferrule 11, 12.That is to say, the second end 13, 14 of an optical fiber 5, 6 is stationary relative to the end fitting 11, 12 on which it is mounted. An optical fiber 5, 6 is also said to have an optical fiber core enclosed in a sheath 40, 4L. The second end 13, 14 of an optical fiber 5, 6 is fixedly mounted on an end fitting 11, 12, either via the sheath 40, 41 placed in mechanical contact with the end fitting 11, 12, or directly so that the optical fiber core is in mechanical contact with the end fitting 11, 12. For example, an end fitting 11, 12 can be held to the second end 13, 14 of an optical fiber 5, 6 by means of an adhesive comprising at least one epoxy polymer. In particular, the epoxy polymer is compatible, in terms of adhesion, with optical fiber 5, 6, with electrolyte solvents and with the internal atmosphere of cell 2.

[0052] Advantageously, the second end 13, 14 of an optical fiber 5, 6 is encapsulated within a tip 11, 12 so that the second end 13, 14 does not does not extend beyond the end piece 11, 12. Advantageously, the second end 13, 14, which protrudes from the end piece 11, 12, is sanded so that it does not protrude outside the end piece 11, 12 and to have a surface compatible with the connector 70. Such a unit 1 does not have a portion of optical fiber 5, 6 located outside an end piece 11, 12 fixed to the package 3 and allows for easy connection to a measuring device located outside the package 3.

[0053] The package 3 further comprises at least one reservoir 15, 16 communicating with the housing 10 of the package 3 via at least one orifice 17, 18 through which an optical fiber 5, 6 passes. In particular, each reservoir 15, 16 is filled with an airtight material 20a, 20b. Each nozzle 11, 12 comprises an inner portion 21, 22 encapsulated within the material 20a, 20b filling the reservoir 15, 16, and an outer portion 23, 24 located outside the package 3.

[0054] In particular, when the package 3 is flexible, the package 3 is hermetically sealed by heat sealing. The heat sealing consists of sealing the sheets 90, 91 of the package along lines 100 to 102 shown as dashed lines in Figures 1 to 3 and 10, 11. A first line 100 represents the sealing of the cell(s) 2. The second and third lines 101, 102 represent the sealing of the first and second reservoirs 15, 16 respectively.

[0055] A reservoir 15, 16 encloses the inner part 21, 22 of a nozzle 11, 12, meaning that the inner part 21, 22 is entirely contained within the reservoir 15, 16. In other words, a reservoir 15, 16 does not completely encapsulate a nozzle 11, 12. A reservoir 15, 16 is further filled with an airtight material 20a, 20b, for example a resin, in order to fix a nozzle 11, 12 to the packaging 3. Two separate reservoirs 15 and 16 can be filled with the same material 20a or with two different materials 20a, 20b, each material 20a, 20b being airtight. A reservoir 15, 16 further allows the portion of the fiber between the orifice 17, 18 and a tip 11, 12 to be held in a rigid block. Thus, an external part 23, 24 of a tip 11, 12 protrudes outside the material 20a, 20b so that it can be connected, for example, to another optical fiber.Fiber 5, 6 is thus held rigidly inside unit 1 and cannot be subjected to twisting or bending, because it is embedded in the mass.

[0056] Furthermore, an end piece 11,12 allows the use of a connector 70 in order to be able to connect or disconnect the optical fiber 5, 6 at will.

[0057] Advantageously, the second end 13, 14 of an optical fiber 5, 6 can be placed very close to the optical sensor 4, which allows the use of a winding-free optical fiber 5, 6. That is to say, a fiber 5, 6 having a linear shape. In other words, an optical fiber 5, 6 can have a length less than or equal to a length of package 3, for example less than or equal to half the length of package 3.

[0058] Unit 1 may also include an adhesive retaining element 50, 51 located within the housing 10 and in contact with an optical fiber 5, 6 and an internal wall of the packaging 3 delimiting the housing 10.

[0059] In [Fig.2], an embodiment is shown in which the unit 1 comprises first and second reservoirs 15, 16 filled respectively with first and second airtight materials 20a, 20b, a first optical fiber 5 connecting the sensor 4 to a first tip 11, and a second optical fiber 6 connecting the sensor 4 to a second tip 12. The first and second tips 11, 12 comprise respectively two internal parts 21, 22 encapsulated respectively within the first and second materials 20a, 20b filling respectively the first and second reservoirs 15, 16 and two external parts 23, 24 located outside the packaging 3. In this case, two optical fibers 5, 6 have two outputs. Alternatively, the first and second optical fibers 5, 6 form a single optical fiber 5. That is to say, the first ends 7, 8 are optically coupled to each other and to the optical sensor 4.In this case, an optical fiber 5 also has two outputs. For example, two connectors 11, 12 are placed on two opposite sides of the package 3.

[0060] Figure 3 shows another embodiment in which the unit 1 comprises a reservoir 15 filled with an airtight material 20a, a first optical fiber 5 connecting the sensor 4 to a first end piece 11, and a second optical fiber 6 connecting the sensor 4 to a second end piece 12. The first and second end pieces 11, 12 comprise, respectively, two internal portions 21, 22 encapsulated within the material 20a filling the reservoir 15 and two external portions 23, 24 located outside the package 3. Alternatively, the first and second optical fibers 5, 6 form a single optical fiber 5. That is, the first ends 7, 8 are optically coupled to each other and to the optical sensor 4. In this case, an optical fiber 5 also has two outputs. Two end pieces can be placed on the same side of the package 3.

[0061] The embodiments illustrated in Figures 2 and 3 are particularly suitable for optical sensors 4 that require an input and output from a cell 2. For example, the sensors 4 can be equipped with probes along an optical fiber 5 (e.g., Bragg grating or Rayleigh scattering fibers) or with surface sensors 4 (evanescent wave fiber). For this type of sensor 4, it may be necessary to operate in transmittance mode; therefore, the optical fiber 5 must enter and exit at a different point in a cell 2. In this case, two ports 17, 18 are required for the passage of the optical fiber 5. The two other ends can therefore be prepared. 13, 14 of the optical fiber 5 in the manner described above, and insert the optical sensor 4 into the housing 10 in the same way as with two separate optical fibers 5, 6, but with two outputs.

[0062] Figures 4 and 5 show another embodiment of an electrical energy storage unit 1. In this embodiment, the unit 1 comprises a rigid package 3, such as a box 92 or a prismatic housing. Figure 4 illustrates an example of the insertion of an optical sensor 4 placed in a stack or winding of electrodes. The box 92 has an opening 17 allowing the optical fiber 5 to exit the housing 10. The internal part 21 of the tip 11 is then housed in a reservoir 15 formed on the box 92, or within a wall of the box 92. The reservoir 15 is then filled with the airtight material 20a to stiffen and seal the tip 11.

[0063] Figures 6 to 10 illustrate the main steps of a manufacturing process for an electrical energy storage unit 1.

[0064] Generally, the method involves inserting an optical fiber 5, 6 into a cell 2. The cell 2 may be new and unactivated, i.e., during manufacturing, or it may be complete and activated by opening the packaging 3. In the case of a new cell 2, the positive and negative electrodes, as well as the separator, are stacked or wound. However, in order to perform in situ measurements, the optical fiber 5, 6 must be placed at the core of the cell 2, either between the positive electrode and the separator, or between the negative electrode and the separator. Depending on the chosen position, this is done during either stacking (for a stacked cell) or winding (for a wound cell). Since optical fiber 5, 6 is generally quite long, it is delicate to handle the 5, 6 fiber, to insert it without damaging the 5, 6 fiber. All these operations are preferably carried out in an anhydrous room, for example using a glove box.Once the fiber 5, 6 is in place, it must be held securely before sealing. To do this, the fiber 5, 6 is secured with one or more adhesive retainers 50, 51, for example, pieces of tape. Then, once the adhesive retainer 50, 51 is in place and the cell 2 is fully wound, along with the soldering of the external connectors 80, 81, the cell 2 is filled with electrolyte, then vacuum-sealed before being sealed. During this operation, it is delicate to hold the optical fiber 5, 6 in place. Furthermore, the heat-sealing is performed on the fiber 5, 6. This operation is very delicate.

[0065] In particular, Figures 6 to 11 illustrate the main manufacturing steps of an electrical energy storage unit 1, and more specifically of a unit 1 having a flexible package 3. As illustrated in [Fig. 6], an optical fiber 5 is cut to a length corresponding to the position that the sensor 4 must have in the cell 2 and to the size of the cell 2 housed within its flexible package 3. Advantageously, a sheath 40 can encapsulate the core of the optical fiber 5. Then, as illustrated in [Fig. 7], an optional step is shown in which the sheath 40 is stripped to a length intended to be less than or equal to the distance between the first end 7 of the optical fiber 5 and the opening 17, 18 when the fiber is placed within the packaging 3. For example, if the sensor 4 is placed at the center of an electrode of the cell 2, the distance is equal to half the width of the electrode plus approximately half a centimeter. As illustrated in [Fig. 8], the optical fiber 5, 6 is made functional, that is, the optical sensor 4 is deposited at its first stripped end 7. The optical sensor 4 can be of different types (depending on the physical parameter to be measured). Next, as illustrated in [Fig.9], a tip 11 is inserted at the second end 13.The optical fiber 5 is attached to the tip 11 using an adhesive comprising an epoxy polymer, and then the second end 13 of the fiber 5 protruding from the tip 11 is cut and polished to provide an optical surface. Then, as illustrated in [Fig. 10], the sensor 4 is positioned within the housing 10, for example in contact with an element of a cell 2, and the tip 11 within the reservoir 15. Then, as illustrated in [Fig. 11], the reservoir 15 is filled with the material 20a. Advantageously, before the filling step, the packaging 3 can be heat-sealed.

[0066] The electrical energy storage unit described above ensures a reliable connection between an optical sensor and a measuring device located outside the unit's packaging. A comparison with a conventionally mounted optical sensor within the same unit showed that the connection quality was virtually identical. Thus, the use of a ferrule and connector does not degrade the optical signal and therefore does not affect the performance of the optical sensor. Such a unit maintains the optical transmission performance of an optical sensor while improving the robustness and simplicity of mounting the optical sensor within the packaging.

[0067] Another advantage is that, using the manufacturing process just described, it is possible to produce optical sensors in large quantities and simultaneously by depositing the active probe at the end of the optical fiber onto short samples. These sensors, prepared in this way, can be easily fitted with a specially adapted connector for attaching the sensor, which will subsequently be inserted into the cells. Handling these small objects offers advantages in terms of implementation and handling compared to a long optical fiber.

[0068] Such a unit could possibly be a fuel cell, for example a hydrogen fuel cell.

Claims

Demands

1. An electrical energy storage unit comprising at least one lithium-ion cell (2) having two electrodes separated by an electrolyte configured to generate charge carriers, the unit comprising a package (3) enclosing said at least one cell (2), an optical sensor (4), and at least one optical fiber (5, 6), each optical fiber (5, 6) having a first end (7, 8) optically coupled to the optical sensor (4), the package (3) comprising a housing (10) within which the optical sensor (4) is housed, characterized in that the unit comprises at least one end fitting (11, 12) located at a second end (13, 14) of said at least one optical fiber (5, 6), the at least one end fitting (11, 12) having a cylindrical shape comprising a recess (30) into which the second end (13, 14) of the optical fiber (5, 6) is inserted, and the package (3) includes at least one reservoir (15,16) communicating with the housing (10) of the packaging (3) via at least one opening (17, 18) through which said at least one optical fiber (5, 6) passes, said at least one reservoir (15, 16) being filled with an airtight material (20a, 20b), and in that said at least one nozzle (11, 12) comprises an internal part (21, 22) encapsulated within the material (20a, 20b) filling said at least one reservoir (15, 16) and an external part (23, 24) located outside the packaging (3).

2. Unit according to claim 1, wherein said at least one reservoir (15, 16) is a single reservoir (15) filled with an airtight material (20a), a first optical fiber (5) connecting the optical sensor (4) to a first tip (11), and a second optical fiber (6) connecting the optical sensor (4) to a second tip (12), the first and second tips (11, 12) respectively comprising two internal parts (21, 22) encapsulated within the material (20a) filling the single reservoir (15) and two external parts (23, 24) located outside the packaging (3).

3. Unit according to claim 1, comprising first and second reservoirs (15, 16) filled respectively with first and second airtight materials (20a, 20b), a first optical fiber (5) connecting the optical sensor (4) to a first end piece (11), and a second optical fiber (6) connecting the optical sensor (4) to a second nozzle (12), the first and second nozzles (11, 12) respectively comprising two internal parts (21, 22) encapsulated respectively within the first and second materials (20a, 20b) filling respectively the first and second reservoirs (15, 16) and two external parts (23, 24) located outside the packaging (3).

4. Unit according to any one of claims 1 to 3, wherein the packaging (3) is flexible so as to be deformable under its own weight.

5. Unit according to any one of claims 1 to 3, wherein the packaging (3) is rigid so as not to be deformable under the effect of its own weight.

6. Unit according to any one of claims 1 to 5, wherein said at least one tip (11, 12) comprises ceramic.

7. Unit according to any one of claims 1 to 6, wherein said at least one tip (11, 12) is held to the second end (13, 14) of said at least one optical fiber (5, 6) from an adhesive comprising at least one epoxy polymer.

8. Unit according to any one of claims 1 to 7, wherein said at least one optical fiber (5, 6) is coated, at least in part, with a sheath (40, 41) extending between the first end (7, 8) of said at least one optical fiber (5, 6) and a portion of said at least one optical fiber (5, 6) located within the housing (10) of the package (3).

9. Unit according to claim 8, wherein the second end (13, 14) of said at least one optical fiber (5, 6) is encapsulated within said at least one end piece (11, 12) such that the second end (13, 14) does not protrude from said at least one end piece (11, 12).

10. Unit according to any one of claims 1 to 9, comprising at least one adhesive retaining element (50, 51) located within the housing (10) and in contact with said at least one optical fiber (5, 6) and an internal wall of the packaging (3) delimiting the housing (10).

11. A method for manufacturing a storage unit according to any one of claims 1 to 10, comprising:

12. - a supply: • at least one lithium-ion type cell (2) equipped with two electrodes separated by an electrolyte configured to generate charge carriers; • of an optical sensor (4); • of at least one optical fiber (5, 6), each optical fiber (5, 6) having a first end (7, 8) optically coupled to the optical sensor (4); and • of a package comprising a housing (10) within which said at least one cell (2) is housed; characterized in that the process comprises: • an assembly of at least one end piece (11, 12) at a second end (13, 14) of said at least one optical fiber (5, 6), the at least one end piece (11, 12) having a cylindrical shape comprising a hollow (30) into which the second end (13, 14) of the optical fiber (5, 6) is inserted; • a formation within the packaging (3) of at least one reservoir (15, 16) communicating with the housing (10) via at least one orifice (17, 18); • a positioning of the optical sensor (4) within the housing (10) and of said at least one optical fiber (5, 6) passing through said at least one orifice (17, 18); and • filling said at least one reservoir (15, 16) with an airtight material (20a, 20b), such that said at least one nozzle (11, 12) comprises an inner part (21, 22) encapsulated within the material (20a, 20b) and an outer part (23, 24) located outside the packaging (3). Method according to claim 11, wherein the positioning includes placing at least one adhesive retaining element (50, 51) within the housing (10) and in contact with said at least one optical fiber (5, 6) and an internal wall of the packaging (3) delimiting the housing (10).

13. A method according to claim 11 or 12, wherein the packaging (3) comprises two flexible sheets (90, 91) so as to be deformable under the effect of their own weight, and the method comprises, before filling, a sealing of the flexible sheets (90, 91) around the housing (10) and said at least one reservoir (15, 16).

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