Methods and systems for measuring the electronic conductivity of battery electrodes

Abstract

System (1) for measuring the electronic conductivity of a strip (2) of electrode moving between a first and a second rotating roller (3, 4), this system comprising: - an electronic conductivity measuring device (11); - a first rotating movable conductive contact element (12) connected to said device, this first conductive contact element incorporating a first circular distal edge intended to come into tangential contact with a first surface of the electrode strip; - a second rotating movable conductive contact element (13) connected to said measuring device, this second conductive contact element incorporating a second circular distal edge intended to come into tangential contact with the first surface when the first circular distal edge is in contact with said first surface so as to be able to apply a predefined electric current between the first and the second conductive contact element (12, 13). Figure for the abbreviation: Fig.1.

Description

Title of the invention: Methods and systems for measuring the electronic conductivity of battery electrodes

[0001] The present invention relates to methods and systems for monitoring the electrochemical performance of battery electrodes, and more particularly to methods and systems for measuring the electronic conductivity of such electrodes.

[0002] The electronic conductivity of an electrode represents its ability to allow the free movement of electrical charges between the active material and the current collector of this electrode. The higher this electrical conductivity, the greater the transfer of electrical charges during electrochemical reactions of the electrode. Various strategies aimed at improving this fundamental property of the electrode exist, such as the choice of electrode materials or the addition of a conductive agent or additive to the active material.

[0003] Once an electrode composition conferring a certain electronic conductivity is adopted, the latter is regularly checked on sample electrodes taken at the end of the production line or on pellets cut from them. For this, an electric current is applied between two points on the surface of the electrode in order to measure the evolution of the electric voltage between these two points as a function of time. The evolution of the voltage as a function of the applied electric current represents the electronic conductivity of the electrode. It is also known to measure this electronic conductivity by the “four points” method.

[0004] However, a major drawback of this control of the electronic conductivity is that sample electrodes do not allow precise and complete information to be given on the state of the electronic conductivity of each of the electrodes produced. Sample electrodes, however frequent they may be, are not necessarily representative of all the electrodes produced. The electronic conductivity is, in fact, subject to numerous factors such as a variable quality of the materials used, a variation in the content of the conductive additive, the quality of deposition of the active material on the current collector or, more generally, the slightest accidental or repetitive defect in any of the steps of the battery electrode manufacturing process (preparation of the active material, preparation of the current collector, deposition of the active material on the current collector, drying of the electrode, calendering and cutting of the electrode).An accidental or random deviation from the objective electronic conductivity can thus occur without being detected or detected too late. Furthermore, between the time when a sample electrode is taken and the time when it is found ex situ that this sample does not meet the quality criteria. imposed in terms of electronic conductivity (a point or mass defect), the manufacture of the product continues while the production carried out during this period is unusable. In other words, a control of sample electrodes does not allow for immediate corrective control, which results in a loss of the electrodes during production and, consequently, possible financial and environmental damage.

[0005] Another disadvantage is that the electronic conductivity control relates to finished electrodes so that an electronic conductivity defect is only confirmed at the stage of the finished electrode, in particular cut and adapted to the format of the battery for which they are intended. This approach does not make it possible to prevent mass defects and reduce the additional cost of manufacturing the electrodes.

[0006] An object of the present invention is to remedy the aforementioned drawbacks.

[0007] Another object of the present invention is to provide methods and systems for measuring the electronic conductivity of battery electrodes capable of preventing defects and, consequently, reducing the manufacturing cost of battery electrodes.

[0008] To this end, there is proposed, firstly, a system for measuring the electronic conductivity of a strip of electrode for a battery moving between a first and a second rotating roller, this system comprising - an electronic conductivity measuring device; - a first conductive contact element connected to said measuring device, this first conductive contact element incorporating a first circular distal edge intended to come into substantially tangential contact with a first surface of the electrode strip; - a second conductive contact element connected to said measuring device, this second conductive contact element incorporating a second circular distal edge intended to come into substantially tangential contact with the first surface when the first circular distal edge is in contact with said first surface so as to be able to apply a predefined electric current between the first conductive contact element and the second conductive contact element; - a support for the first contact conductive element and the second contact conductive element; - the first conductive contact element being mounted to rotate on said support so that, when the first circular distal edge comes into substantially tangential contact with said first surface of the electrode strip running between the first rotating roller and the second rotating roller, said first conductive contact element is driven in rotation; - the second conductive contact element being mounted to rotate on said support so that, when the second circular distal edge comes into contact with the second conductive contact element, the second conductive contact element is ... possibly tangential with said first surface of the electrode strip running between the first rotating roller and the second rotating roller, the second conductive contact element is driven in rotation.

[0009] Various additional features may be provided, alone or in combination: - the first circular distal edge and / or the second circular distal edge are rounded in shape; - the first conductive contact element and / or the second conductive contact element are spherical in shape and mounted in a ball joint on said support; - the distance between the first circular distal edge and the second circular distal edge is adjustable; - the measuring system further includes, a third conductive contact element incorporating a third circular distal edge intended to come into substantially tangential contact with said first surface when the first and second circular distal edges are in contact with said first surface; a fourth conductive contact element incorporating a fourth circular distal edge intended to come into substantially tangential contact with the first surface when the first, second and third circular distal edges are in contact with said first surface so as to be able to measure an electrical voltage between the third conductive contact element and the fourth conductive contact element, the third and fourth circular distal edges being arranged so as to come into contact with said first surface between the first and second circular distal edges substantially on the same straight line; the third conductive contact element being mounted rotatably on said support so that, when the third circular distal edge comes into substantially tangential contact with said first surface of the electrode strip running between the first rotating roller and the second rotating roller, the third conductive contact element is driven in rotation; the fourth conductive contact element being mounted rotatably on said support so that, when the fourth circular distal edge comes into substantially tangential contact with said first surface of the electrode strip running between the first rotating roller and the second rotating roller, the fourth conductive contact element is driven in rotation; - the electronic conductivity measuring device is configured to measuring an electronic conductivity between the first conductive contact element and the second conductive contact element; generate an alert message when the measured electronic conductivity is in outside a predefined interval; - the measuring system further comprises a means capable of locating an electronic conductivity defect.

[0010] Secondly, a method for measuring the electronic conductivity of a battery electrode strip is proposed, this method comprising: - a step of scrolling said electrode strip between a first rotating roller and a second rotating roller; - a step of measuring an electronic conductivity of the electrode strip by means of the measuring system presented above arranged between the first rotating roller and the second rotating roller.

[0011] In one embodiment, this method further comprises a step of cutting said electrode strip into a plurality of electrodes downstream of the measuring step relative to the direction of travel of this electrode strip.

[0012] Other characteristics and advantages of the invention will appear more clearly and concretely on reading the following description of embodiments, which is given with reference to the appended drawings in which:

[0013] Figure [Fig.l] schematically illustrates a system for measuring the electronic conductivity of an electrode strip according to various embodiments;

[0014] figure [Fig.2] schematically illustrates elements of the measuring system according to a first embodiment;

[0015] figure [Fig.3] schematically illustrates elements of the measuring system according to a second embodiment;

[0016] Figure [Fig.4] schematically illustrates a four-point electronic conductivity measuring system for an electrode strip according to various embodiments;

[0017] Figure [Fig.5] schematically illustrates steps of a method for measuring the electronic conductivity of an electrode strip according to various embodiments.

[0018] Referring to [Fig.l], there is shown a system 1 for measuring the electronic conductivity of an electrode strip 2 for a battery (or, more generally, for an electrochemical energy storage device) running between a first rotating roller 3 and a second rotating roller 4.

[0019] The electrode strip 2 is a continuous strip of metal coated with a layer of active material on at least one of its two opposite faces. In one embodiment, the electrode strip 2 is double-coated. In other words, each face of the metal strip is coated with active material.

[0020] The first and second rotating rollers 3, 4 are two unwinding, advancing or conveying rollers for the electrode strip 2, the axes of rotation of which are substantially parallel. As it travels between the first and second rotating rollers 3, 4, the electrode strip 2 is kept taut. The rotating rollers 3, 4 maintain, in fact, a certain tension on the electrode strip 2 so as to guarantee flatness of the electrode strip 2 as it moves. The first and second rollers 3, 4 are located upstream of an electrode cutting station. The measurement of the electronic conductivity of the electrode strip 2 can, therefore, be carried out online without interrupting the electrode manufacturing process.

[0021] The measuring system 1 comprises a device 11 (or an instrument) for measuring electronic conductivity to which are connected at least a first conductive contact element 12 and a second conductive contact element 13 intended to come into contact with a surface of the electrode strip 2. A plurality of pairs of conductive contact elements 12, 13 connected to the measuring device 11 can be envisaged. Advantageously, a plurality of pairs of conductive contact elements 12, 13 makes it possible to obtain a discretization of the measurement. Indeed, a defect is, most often, local, hence the interest in measuring, preferably, over the entire width of the electrode strip 2. Conductive contact elements 12, 13 are connected in pairs to the electronic conductivity measuring device 11.The electronic conductivity of the electrode strip 2 can be measured directly by the measuring device 11 or deduced from another measured physical quantity such as resistance and / or impedance.

[0022] Each of the conductive contact elements 12, 13 respectively comprises a circular distal edge 14, 15 (a tip or a contact end) intended to come into substantially tangential contact with a surface of the electrode strip 2. Each of the conductive contact elements 12, 13 ends with a spherical or circular edge to ensure substantially tangential contact with a surface of the moving electrode strip 2. This advantageously results in substantially point contact with the moving electrode strip 2. The circular geometry of the distal edges 14, 15 intended to come into contact with the electrode strip 2 advantageously makes it possible to avoid deterioration of the active material.

[0023] In order to apply a predefined electric current between the first conductive element 12 and the second conductive contact element 13, the first distal edge 14 and the second distal edge 15 are simultaneously brought into contact with the moving electrode strip 2. When in contact with the surface of the electrode strip 2, the conductive contact elements 12, 13 close an electronic conductivity measuring circuit. An electrical contact is established between the first and second conductive contact elements 12, 13 via the surface of the electrode strip 2. By measuring this current, the measuring device 11 determines the electronic conductivity of the target section of the surface of the electrode strip 2.

[0024] Each of the conductive contact elements 12, 13 is mounted to move in rotation on a support 16 of the electronic conductivity measuring system 1 so that this conductive contact element 12, 13 is rotated when its circular distal edge 14, 15 comes into substantially tangential contact with a surface of the electrode strip 2 running between the first and second rotating rollers 3, 4. By being free to rotate, the conductive contact element 12, 13 follows the movement of the electrode strip 2. This advantageously results in each of the conductive contact elements 12, 13 being in rolling contact with the surface of the electrode strip 2 so as not to damage the layer of active material. Rolling contact with the surface of the electrode strip 2 advantageously makes it possible to carry out a continuous and online measurement of its electronic conductivity while it runs between the two rotating rollers 3, 4. An in situ measurement of the electronic conductivity of the electrode strip 2 over its entire length before it is cut is thus possible.

[0025] In a first embodiment illustrated in [Fig. 2], the conductive contact elements 12, 13 are spherical in shape and mounted to rotate on the support 16. Thus, the conductive contact elements 12, 13 are mounted in a ball joint connection on the support 16. In a second embodiment illustrated in [Fig. 3], the conductive elements 12, 13 are in the form of a metal wheel mounted to rotate on the support 16. Thus, in the first and second embodiments, the circular distal edge 14, 15 of the conductive contact elements 12, 13 is rounded in shape.

[0026] Advantageously, the measuring system 1 comprises at least one actuator (not shown in the drawings). The actuator may be a jack, a telescopic arm or a robotic arm for example. The support 16 is arranged on the actuator so that the latter is able to move the conductive contact elements 12, 13 to the electrode strip 2. This actuator is able to move the conductive contact elements 12, 13 between a rest position in which these conductive contact elements 12, 13 are set back from the surface of the electrode strip 2 and a measuring position in which these conductive contact elements 12, 13 are in contact with the surface of the electrode strip 2.

[0027] In one embodiment, the distance between two distal contact edges 14, 15 is adjustable so as to be able to choose the position and the width of the target section of the surface of the electrode strip 2 for measuring the electronic conductivity. In one embodiment, this distance is strictly less than the width of the layer of active material.

[0028] In an embodiment illustrated by [Fig. 4], the electronic conductivity of the electrode strip 2 is measured according to the so-called “4-point” method (also called 4-wire). This method consists of bringing into contact four circular distal edges (or points) aligned on the surface of the electrode strip 2. Then, a current is applied between the two external points and a voltage is measured across the terminals of the two internal tips. The electronic conductivity is calculated from the measured voltage (e.g., according to the Waxman-Smits equation). In one embodiment, the four tips are placed aligned away from the edges of the active material layer of the electrode strip 2.

[0029] With reference to [Fig. 4], a third and a fourth conductive contact element 17, 18 incorporating, respectively, a third and a fourth circular distal edge 23, 24 may be provided for measuring the electronic conductivity according to the four-point measurement principle. The third circular distal edge 23 is intended to come into substantially tangential contact with the surface of the strip 2 of the electrode when the first and the second circular distal edge 14, 15 are in contact with this surface.The fourth circular distal edge 24 is intended to come into substantially tangential contact with the surface of the electrode strip 2 when the first, second and third circular distal edges 14, 15, 23 are in contact with this surface so as to be able to measure an electrical voltage between the third and fourth conductive contact element, the third and fourth circular distal edges being arranged so as to come into contact with the surface of the electrode strip between the first and second circular distal edges substantially on the same straight line.The third (respectively, the fourth) conductive contact element is rotatably mounted on the support 16 so that, when the third (respectively, the fourth) circular distal edge comes into substantially tangential contact with the surface of the electrode strip running between the first and second rotating roller, the third (respectively, the fourth) conductive contact element is rotated. The third conductive element 17 and the fourth conductive element 18 may be annular (metal wheel) or spherical in shape, like the first conductive element and the second conductive element.

[0030] In one embodiment, when the electrode strip 2 comprises a layer of active material on both sides, two measuring systems are arranged on either side of the electrode strip 2. These two measuring systems are preferably arranged opposite each other on either side of the electrode strip 2 to avoid any possible deformation of the latter.

[0031] The measuring device 11 records the electronic conductivity data associated with their position on the electrode strip, in a database and / or communicates them to a control unit of the measuring system 1. In one embodiment, the electronic conductivity measuring device 11 is configured to measure an electronic conductivity between two conductive contact elements 12, 13 and generate, when the measured electronic conductivity is outside a predefined interval, an alert message. Thus, when an anomaly is observed, a alert can be issued to the operator and / or to a control unit of the measuring system 1. This advantageously results in continuous, real-time automatic monitoring of the electronic conductivity of the electrode strip 2.

[0032] In order to be able to associate the measured electronic conductivity with a precise position of the moving electrode strip 2, the measuring system 1 further comprises a sensor configured to measure a moving distance of the electrode strip 2 or, more generally, a means capable of locating or identifying an electronic conductivity defect (for example, a physical marking of the laser type or any other equivalent technique). The measured electronic conductivity is associated with the measured moving distance and / or a time stamp. It is thus possible to locate the position of the electrode strip 2 at which an electronic conductivity outside a predefined interval has been measured.

[0033] Referring to [Fig. 5], a method for measuring the electronic conductivity of the electrode strip 2 comprises, as described above, a step 20 of running the electrode strip 2 between the first rotating roller and the second rotating roller 3, 4 and a step 21 of measuring this electronic conductivity by means of the measuring system 1 presented above arranged between the first and second rotating roller 3, 4.

[0034] In one embodiment, this measuring step occurs upstream of a step 22 of cutting the electrode strip 2 into a plurality of electrodes. In other words, the step 22 of cutting the electrode strip into a plurality of electrodes is downstream, relative to the direction of travel of this electrode strip, of the measuring step 21.

[0035] Advantageously, the embodiments presented above allow - to reduce the additional cost of manufacturing electrodes by detecting any possible defects in advance and, thus, preventing electrode ground defects; - increased quality control by continuously checking the conformity of the electronic conductivity of the electrode strip to the set objectives.

Claims

1. Claims Set of systems for measuring the electronic conductivity of a strip (2) of electrode for a battery running between a first and a second rotating roller (3, 4) and comprising a layer of active material on its two faces, this set integrating a first system (1) for measuring electronic conductivity comprising - a device (11) for measuring electronic conductivity; - a first conductive contact element (12) connected to said measuring device (11), this first conductive contact element (12) incorporating a first circular distal edge (14) intended to come into substantially tangential contact with a first surface of a first face of said two faces of the electrode strip (2); - a second conductive contact element (13) connected to said measuring device (11), this second conductive contact element (13) incorporating a second circular distal edge (15) intended to come into substantially tangential contact with the first surface when the first circular distal edge (14) is in contact with said first surface so as to be able to apply a predefined electric current between the first conductive contact element (12) and the second conductive contact element (13); - a support (16) for the first conductive contact element (12) and the second conductive contact element (13); - the first conductive contact element (12) being mounted to rotate on said support (16) so that, when the first circular distal edge (14) comes into substantially tangential contact with said first surface of the electrode strip (2) running between the first rotating roller (3) and the second rotating roller (4), said first conductive contact element (12) is driven in rotation; - the second conductive contact element (13) being mounted to rotate on said support (16) so that, when the second circular distal edge (15) comes into substantially tangential contact with said first surface of the electrode strip (2) running between the first rotating roller (3) and the second rotating roller (4), the second conductive contact element (13) is driven in rotation; said assembly further integrating a second electronic conductivity measurement system identical to said first electronic conductivity measurement system (1), the first system (1) and the second system being arranged opposite each other on either side of the electrode strip (2).

2. Set of systems according to the preceding claim, characterized in that the first circular distal edge (14) and / or the second circular distal edge (15) of the first system (1) are of rounded shape.

3. Set of systems according to claim 1 or 2, characterized in that the first conductive contact element (12) and / or the second conductive contact element (13) of the first system (1) are of spherical shape mounted in a ball joint connection on said support (16).

4. System assembly according to any one of the preceding claims, characterized in that the distance between the first circular distal edge (14) and the second circular distal edge (15) of the first system (1) is adjustable.

5. Set of systems according to any one of the preceding claims, characterized in that the first system (1) further comprises - a third conductive contact element (17) incorporating a third circular distal edge intended to come into substantially tangential contact with said first surface when the first and second circular distal edges (14, 15) are in contact with said first surface;- a fourth conductive contact element (18) incorporating a fourth circular distal edge intended to come into substantially tangential contact with the first surface when the first, second and third circular distal edges are in contact with said first surface so as to be able to measure an electrical voltage between the third conductive contact element (17) and the fourth conductive contact element (18), the third and fourth circular distal edges being arranged so as to come into contact with said first surface between the first and second circular distal edges substantially on the same straight line;- the third conductive contact element (17) being mounted rotatably on said support (16) so that, when the third circular distal edge comes into substantially tangential contact with said first surface of the electrode strip (2) running between the first rotating roller (3) and the second rotating roller (4), the third conductive contact element (17) is driven in rotation; - the fourth conductive contact element (18) being mounted rotatably on said support (16) so that, when the fourth edge; circular distal element comes into substantially tangential contact with said first surface of the electrode strip (2) running between the first rotating roller (3) and the second rotating roller (4), the fourth conductive contact element (18) is driven in rotation.

6. Set of systems according to any one of the preceding claims, characterized in that the electronic conductivity measuring device (11) of the first system (1) is configured to - measure an electronic conductivity between the first conductive contact element (12) and the second conductive contact element (13); - generate an alert message when the measured electronic conductivity is outside a predefined interval.

7. Set of systems according to any one of the preceding claims, characterized in that the first system (1) further comprises means capable of locating an electronic conductivity defect.

8. Method for measuring the electronic conductivity of a battery electrode strip (2) comprising a layer of active material on both sides, this method comprising: - a step (20) of running said electrode strip (2) between a first rotating roller (3) and a second rotating roller (4); - a step (21) of measuring an electronic conductivity of the electrode strip (2) by means of the set of measuring systems of any one of the preceding claims arranged between the first rotating roller (3) and the second rotating roller (4).

9. Method according to the preceding claim, characterized in that it further comprises a step (22) of cutting said electrode strip (2) into a plurality of electrodes downstream of the step (21) of measuring relative to the direction of travel of this electrode strip (2).

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