Methods and systems for drying electrodes for electric batteries

Abstract

The invention relates to a drying unit (10) for drying an electrode (1), comprising: • - a first chamber (2) for heating with infrared rays under vacuum, having a first inlet slot (21) and a first outlet slot (22) allowing the electrode to pass through the first heating chamber, this first heating chamber being intended to heat the passing electrode to a first target temperature; • - a second chamber (3) for heating by laser under vacuum, having a second inlet slot (31) and a second outlet slot (32) allowing the electrode to pass through the second heating chamber, the second inlet slot being opposite and contiguous to the first outlet slot, this second heating chamber (3) being intended to heat the passing electrode (1) to a second target temperature higher than the first target temperature.

Description

Methods and systems for drying electrodes for electric batteries

[0001] The present invention relates to methods and systems for drying electrodes for electric batteries, as well as to the electrodes thus dried.

[0002] Even the smallest amount of residual moisture in an electrode poses a critical problem in several respects, compromising the battery's energy efficiency, safety, and durability. Therefore, it is essential to eliminate all traces of moisture from the electrodes before battery assembly to prevent these risks.

[0003] For this purpose, the prior art exists for drying processes and systems that involve unwinding and then rewinding, or maintaining as is, a roll of electrode inside a vacuum heating chamber for a predetermined time. A cooling device is often provided at the outlet of this roller vacuum drying chamber to gradually stabilize the electrode temperature.

[0004] However, a drawback of known solutions lies in the specific challenges they cause, which may affect the quality and performance of the electrode.

[0005] Indeed, drying an electrode held in a roll results in uneven heat treatment due to a non-uniform distribution of heat within the roll. This inhomogeneity can lead to defects such as over-dried or under-dried areas, thus compromising the quality and integrity of the electrode.

[0006] As for unwinding and rewinding the electrode roll in the vacuum drying chamber, this often results in telescoping of the rewound electrode, meaning a misalignment of the electrode roll. This phenomenon not only disrupts the regularity of the process but also generates variations in the pressure exerted on the active material of the electrode. Consequently, these pressure fluctuations create irregularities in the structure and density of the electrode, which can alter its electrochemical performance and compromise its final quality.

[0007] Furthermore, the electrode path during unwinding and rewinding in a drying chamber is often very narrow and congested. A complex path can make electrode threading difficult, increasing the risk of placement defects such as kinks or misalignment. Moreover, this complexity makes accessing internal components for cleaning, maintenance, or repairs much more difficult and time-consuming, which can extend downtime, increase maintenance costs, and negatively impact productivity.

[0008] Another drawback of known solutions is that they require a relatively long changeover time. When it is necessary to switch from one production run to another (for example, by changing the type or size of the electrode), the changeover process generally takes considerable time. This is mainly due to the need to reconfigure the roller vacuum drying chamber to accommodate the new production specifications, which can lead to extended downtime and increased manufacturing costs.

[0009] One object of the present invention is to remedy the aforementioned drawbacks.

[0010] To this end, it is proposed, firstly, a drying unit for drying an electrode incorporating a metal foil of which at least one face is at least partially coated with an active material, this drying unit comprising - a first vacuum infrared heating chamber, having a first inlet slot and a first outlet slot allowing the electrode to pass through the first heating chamber, this first heating chamber being intended to heat the electrode as it passes between the first inlet slot and the first outlet slot to a first target temperature;- a second vacuum laser heating chamber, comprising a second inlet slot and a second outlet slot allowing the electrode to pass through the second heating chamber, the second inlet slot being opposite and contiguous to the first outlet slot or the second outlet slot being opposite and contiguous to the first inlet slot, this second heating chamber being intended to heat the electrode passing between the second inlet slot and the second outlet slot to a second target temperature higher than the first target temperature.;

[0011] Various additional features may be provided, alone or in combination: - the drying unit further includes a third vacuum infrared heating chamber, having a third inlet slot and a third outlet slot allowing the electrode to pass through the third heating chamber, the third inlet slot being opposite and contiguous to the second outlet slot, the second inlet slot being opposite and contiguous to the first outlet slot, this third heating chamber being intended to heat the electrode passing between the third inlet slot and the third outlet slot to a third target temperature lower than the second target temperature; - the second target temperature is between 100 and 160 degrees; - the first heating chamber and / or the third heating chamber include a plurality of rollers to guide and hold the electrode passing;- the second laser heating chamber includes a near-infrared laser source; - the power of the laser source is associated with a speed of electrode movement between the second inlet slot and the second outlet slot; - the drying unit further includes a first pair and a second pair of electrode tension rollers arranged on either side of the second laser heating chamber; - the drying unit further includes a first pair of tension rollers arranged upstream, with respect to the direction of electrode movement, of the first infrared heating chamber, a second pair of tension rollers arranged downstream, with respect to the direction of electrode movement, of the third infrared heating chamber;- the drying unit further comprises an electrode cooling chamber located at the outlet of the third vacuum infrared heating chamber, and a third pair of tension rollers located at the outlet of the cooling chamber; - the drying unit further comprises an air curtain generation device located at the first inlet slot, when the second inlet slot is opposite and contiguous to the first outlet slot, or at the first outlet slot, when the second outlet slot is opposite and contiguous to the first inlet slot.

[0012] Secondly, a drying process is proposed using the drying unit presented above for an electrode incorporating a metal foil, at least one face of which is at least partially coated with an active material. This process includes a step of passing the electrode through the first heating chamber and the second heating chamber of the drying unit, and a step of drying the electrode while passing through the first heating chamber and the second heating chamber.

[0013] The process described above also includes: - an electrode unwinding step carried out outside the drying unit, this unwinding step being prior to the drying step; - a winding step of the electrode dried by the drying unit, this winding step being carried out outside the drying unit.

[0014] Other features and advantages of the invention will become clearer and more concrete upon reading the following description of embodiments, which is made with reference to the accompanying drawings in which:

[0015] The figure schematically illustrates a drying unit for an electrode according to various embodiments;

[0016] The figure schematically illustrates the steps of an electrode drying process according to various embodiments.

[0017] With reference to the figure, a drying unit 10 is shown for drying an electrode 1 comprising a metal foil or strip of metal foil (for example, aluminum or copper) of which at least one face is at least partially coated with an active material. In one embodiment, each of the two opposite faces of the metal foil is partially coated with an active material.

[0018] The electrode 1 moves between an unwinder 11 and a rewinder 12 located on either side of the drying unit 10. In one embodiment, an unwinder roller 11 is positioned upstream of the drying unit 10, relative to the direction of movement of the electrode 1. This is followed by a rewinder roller 12, which picks up the electrode 1 after it has been processed by the drying unit 10. The electrode 1 is thus unwound at the entrance of the drying unit 10 and rewound at its exit.

[0019] The unwinder 11 and the winder 12 of electrode 1 are in normal atmosphere outside the drying unit 10. In other words, the unwinding and winding of electrode 1 take place under standard atmospheric pressure conditions, without requiring special conditions such as vacuum or pressurization.

[0020] The drying unit 10 comprises a first vacuum infrared heating chamber 2. This first heating chamber 2 has a first inlet slot 21 and a first outlet slot 22 allowing the electrode to pass through the first heating chamber 2. In one embodiment, the first inlet slot 21 and the first outlet slot 22 are provided in two opposite faces of the first heating chamber 2. The first heating chamber 2 is intended to heat the electrode 1 as it passes between the first inlet slot 21 and the first outlet slot 22 to a first target temperature.

[0021] The drying unit 10 further comprises a second vacuum laser heating chamber 3. This second heating chamber 3 has a second inlet slot 31 and a second outlet slot 32, allowing the electrode 1 to pass through the second heating chamber 3. In one embodiment, the second inlet slot 31 and the second outlet slot 32 are provided in two opposite faces of the second vacuum laser heating chamber 3.

[0022] The second vacuum laser heating chamber 3 is designed to heat the moving electrode 1 between the second inlet slit 31 and the second outlet slit 32 to a second target temperature higher than the first target temperature. To achieve this, at least one laser source 33, used as a heat source, is arranged to uniformly irradiate the moving electrode 1. In one embodiment, a first laser source 33 and a second laser source 33, or reflectors, can be used to heat both faces of the moving electrode 1 between the second inlet slit 31 and the second outlet slit 32.

[0023] In one embodiment, the second laser heating chamber 3 includes a near-infrared laser source 33. Such a laser source 33 is advantageously easy to install and inexpensive.

[0024] Advantageously, the adoption of vacuum laser heating of the moving electrode 1 in the second heating chamber 3 allows for homogeneous and precise heating. This uniformity prevents the formation of hot spots or underheated (or overheated) areas of the electrode 1, which can create deformations, including waviness during rewinding of the electrode by the winder 12, or even damage the active material coating. Furthermore, the use of a laser source 33 as the heat source allows for rigorous and precise control of heat and humidity. Dynamic, real-time adjustment of the laser source 33 advantageously allows for targeting and stabilizing the temperature across the entire surface of the moving electrode 1 at a predefined second target temperature.

[0025] In order to manage the temperature of the moving electrode1, the power of the laser source33 is, in one embodiment, associated with a speed of movement of the electrode1 between the second inlet slit31 and the second outlet slit32.

[0026] The second target temperature is preferably between 100 degrees and 160 degrees. This advantageously results in targeted laser drying.

[0027] In one embodiment, the second inlet slot 31 is opposite and contiguous with the first outlet slot 22. This arrangement of the first heating chamber 2 and the second heating chamber 3 advantageously allows for a progressive heat treatment of the electrode 1. Initially, the electrode 1 undergoes rough (or preliminary) drying in the first vacuum infrared heating chamber 2, aimed at removing as much moisture as possible from the moving electrode 1. Then, in the second vacuum laser heating chamber 3, a finer and more targeted drying (or finishing treatment) takes over to eliminate any remaining traces of moisture. In other words, the second vacuum laser heating chamber 3 refines the drying process of the moving electrode 1.Since the second target temperature is higher than the first, this advantageously allows for a controlled and gradual temperature rise, without risk to electrode1.

[0028] In another embodiment, the second outlet slot 32 is opposite and contiguous with the first inlet slot 21. Such an arrangement of the heating chambers 2, 3 advantageously allows for gradual cooling of the electrode 1. This reduces thermal stress and, consequently, preserves the structure of the electrode 1 and prevents chemical damage to the active material.

[0029] In one embodiment illustrated in Figure 1, the drying unit 10 further comprises a third vacuum infrared heating chamber 4. This third heating chamber 4 has a third inlet slot 41 and a third outlet slot 42, allowing the electrode 1 to pass through this third heating chamber 4. This third heating chamber 4 is intended to heat the electrode 1 as it passes between the third inlet slot 41 and the third outlet slot 42 to a third target temperature lower than the second target temperature. The third inlet slot 41 is opposite and contiguous with the second outlet slot 32. The second inlet slot 31 is opposite and contiguous with the first outlet slot 22. Infrared radiation drying is thus performed on either side of laser drying in the second vacuum laser heating chamber 3.This arrangement of the heating chambers 2 and 3 advantageously allows for a gradual increase, followed by a gradual decrease in the temperature of the electrode 1, thus eliminating any trace of moisture while preserving its internal structure and minimizing the risk of thermal stress. Of course, this arrangement is by no means limiting; an alternative configuration, with a single infrared heating chamber 2 and 4 located either upstream or downstream of the laser heating chamber 3 relative to the direction of travel of the electrode 1, can also be considered, as described above.

[0030] In one embodiment, the drying unit 10 further comprises an electrode cooling chamber 5 located at the outlet of the third vacuum infrared heating chamber 4 or, in its absence, at the outlet of the second vacuum laser heating chamber 3 to gradually stabilize the temperature of the electrode 1. The cooling chamber 5 is designed to lower the temperature of the electrode 1 to a predefined value (for example, by convection, conduction, or radiation), allowing for its safe rewinding. This advantageously results in gentle and controlled thermal management of the electrode 1's temperature during winding.

[0031] To maximize the length of the electrode 1's path in the first heating chamber 2, the third heating chamber 4, and / or the cooling chamber 5, while optimizing the available space, a plurality of rollers 6 can be provided within these chambers to guide and maintain the moving electrode 1. These rollers 6 are arranged to create a zigzag path, thus increasing the length of the electrode 1's path inside the heating or cooling chambers 2, 4, and 5. These rollers 6 increase the residence time of the moving electrode 1 in the heating or cooling chamber 2, 4, and 5, promoting more uniform and efficient thermal exposure.

[0032] Furthermore, to keep the electrode 1 taut as it moves through the drying unit 10, the unit may include a first pair and a second pair of tension rollers 7 for the electrode 1, positioned on either side of the second laser heating chamber 3. Driven by an electric motor, each pair of tension rollers 7 applies tension to the electrode 1, thus preventing sagging or creasing during its movement, particularly within the second laser heating chamber 3.

[0033] In one embodiment, the first pair of tension rollers 7 is arranged upstream, relative to the direction of travel of electrode 1, of the first infrared heating chamber 2, in particular upstream of the first inlet slot 21 or, more generally, at the inlet of the first infrared heating chamber 2. In another embodiment, the second pair of tension rollers 7 is arranged downstream, relative to the direction of travel of electrode 1, of the third infrared heating chamber 4, in particular downstream of the third outlet slot 42 or, more generally, at the outlet of the third infrared heating chamber 4. A third pair of tension rollers 7 may also be arranged at the outlet of the cooling chamber 5.These pairs of tension rollers 7 advantageously allow for the application of controlled tension to the electrode 1, thus ensuring smooth and consistent movement of the electrode through the drying unit 10. This tension effectively prevents any loosening or wrinkling of the electrode 1, particularly during its passage through the vacuum laser heating chamber 3, the vacuum infrared heating chambers 2 and 4, and / or the cooling chamber 5. This tensioning mechanism not only helps maintain the quality and uniformity of the heat treatment applied to the electrode 1, but it also reduces the risk of defects that could compromise its final properties.

[0034] To limit heat loss from the drying unit 10, an air curtain generator 8 (more commonly known as an "air cutter") is installed at its inlet and outlet. This device 8 advantageously creates a thermal barrier, reducing heat loss to the outside of the drying unit 10 and the intrusion of ambient air. This results in stable thermal control inside the drying unit 10, thus improving its energy efficiency and the uniformity of the drying of the electrode 1. In one embodiment, the air curtain generator 8 is located at the first inlet slot 21, when the second inlet slot 31 is opposite and adjacent to the first outlet slot 22, or at the first outlet slot 22, when the second outlet slot 32 is opposite and adjacent to the first inlet slot 21.When the drying unit 10 incorporates a cooling chamber 5 as illustrated by the, an air curtain generation device 8 is, in one embodiment, disposed at the outlet of the cooling chamber 5.

[0035] Referring to the figure, a process for drying electrode 1 using the drying unit 10 includes a step of unwinding electrode 11 using an unwinder 11. This unwinding step 21 is carried out outside the heating unit. The unwinder 11 is indeed located outside the heating unit 10. This process further includes a step of moving electrode 1 through the first heating chamber 2 and the second heating chamber 3 of the drying unit 10.

[0036] A drying step 23 of the electrode 1 as it passes through the first heating chamber 2 and the second heating chamber 3 is carried out by the drying unit 10. The unwinding step 21 precedes the drying step 23.

[0037] Once dried by the drying unit 10, the electrode 1 is re-wound (winding step 24) out of it by the winder 12, located at the outlet of the unit 10.

Claims

Drying unit (10) for drying an electrode (1) incorporating a metal foil of which at least one face is at least partially coated with an active material, this drying unit (10) comprising a first vacuum infrared heating chamber (2), having a first inlet slot (21) and a first outlet slot (22) allowing the electrode to pass through the first heating chamber (2), this first heating chamber (2) being intended to heat the electrode (1) passing between the first inlet slot (21) and the first outlet slot (22) to a first target temperature;- a second vacuum laser heating chamber (3), comprising a second inlet slit (31) and a second outlet slit (32) allowing the electrode to pass through the second heating chamber (3), the second inlet slit (31) being opposite and contiguous to the first outlet slit (22) or the second outlet slit (32) being opposite and contiguous to the first inlet slit (21), this second heating chamber (3) being intended to heat the electrode (1) passing between the second inlet slit (31) and the second outlet slit (32) to a second target temperature higher than the first target temperature.; Drying unit (10) according to the preceding claim, characterized in that it further comprises a third vacuum infrared heating chamber (4), having a third inlet slot (41) and a third outlet slot (42) allowing the electrode (1) to pass through the third heating chamber (4), the third inlet slot (41) being opposite and contiguous to the second outlet slot (32), the second inlet slot (31) being opposite and contiguous to the first outlet slot (22), this third heating chamber (4) being intended to heat the electrode (1) passing between the third inlet slot (41) and the third outlet slot (42) to a third target temperature lower than the second target temperature. Drying unit (10) according to any one of the preceding claims, characterized in that the second target temperature is between 100 and 160 degrees. Drying unit (10) according to any one of the preceding claims, characterized in that the first heating chamber (2) and / or the third heating chamber (4) comprise a plurality of rollers (6) to guide and hold the electrode (1) in motion. Drying unit (10) according to any one of the preceding claims, characterized in that the second laser heating chamber (3) comprises a near-infrared laser source. Drying unit (10) according to any one of the preceding claims, characterized in that the power of the laser source (33) is associated with a speed of movement of the electrode (1) between the second inlet slit (31) and the second outlet slit (32). Drying unit (10) according to any one of the preceding claims, characterized in that it further comprises a first pair and a second pair of tension rollers (7) of the electrode (1) arranged on either side of the second laser heating chamber (3). Drying unit (10) according to any one of claims 2 to 6, characterized in that it further comprises: - a first pair of tension rollers (7) arranged upstream, with respect to the direction of movement of the electrode (1), of the first infrared heating chamber (2), - a second pair of tension rollers (7) arranged downstream, with respect to the direction of movement of the electrode (1), of the third infrared heating chamber (4). Drying unit (10) according to the preceding claim, characterized in that it further comprises: - a cooling chamber (5) for the electrode (1) disposed at the outlet of the third vacuum infrared heating chamber (4); - a third pair of tension rollers (7) disposed at the outlet of the cooling chamber (5). Drying unit (10) according to any one of the preceding claims, characterized in that it further comprises a device (8) for generating an air curtain disposed at the first inlet slot, when the second inlet slot is opposite and contiguous to the first outlet slot, or at the first outlet slot, when the second outlet slot is opposite and contiguous to the first inlet slot. A drying method using the drying unit (10) of any one of the preceding claims of an electrode (1) incorporating a metal foil having at least one face at least partially coated with an active material, this method comprising a step of moving (22) the electrode through the first heating chamber (2) and the second heating chamber (3) of the drying unit (10), a step of drying (23) the electrode while moving through the first heating chamber and the second heating chamber (3). Drying method according to the preceding claim, characterized in that it further comprises an unwinding step (21) of the electrode (1) carried out outside the drying unit (10), this unwinding step (21) being prior to the drying step (23); a winding step (24) of the electrode (1) dried by the drying unit (10), this winding step (24) being carried out outside the drying unit (10).

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