Cylindrical cell for electric batteries

Abstract

An electrochemical cell (10) comprising: - a cylindrical stack comprising, in succession, a first electrode sheet, a first separator, a second electrode sheet, a second separator; - a cylindrical housing (2) accommodating the stack, this housing comprising a cover (3), a bottom (4) incorporating a through-hole (41), a lateral shell (5) connecting the cover to the bottom; - a metal rivet passing through the bottom through the through-hole; - a seal positioned between the metal rivet and the bottom; - the bottom comprising an annular rib (42) around the through-hole protruding from a first face of this bottom facing toward the outside of the housing such that the seal is compressed by the rivet against the annular rib.

Description

Cylindrical cell of electric batteries

[0001] The present invention relates to electrochemical cells of electric batteries, and more particularly cylindrical cells.

[0002] Cylindrical cells are manufactured by winding around a mandrel, a successive stack of at least: a positive electrode sheet or cathode; an insulating separator sheet; a negative electrode sheet or anode; an insulating separator sheet.

[0003] A cylindrical cell also includes a first and a second current collector, one connected to the anode and the other to the cathode. The cylindrical stack is inserted into a cylindrical casing for a sealed enclosure.

[0004] The cylindrical housing comprises a lid, a base opposite the lid, and a cylindrical side sleeve connecting the lid to the base. Initially, the lid is hermetically sealed to the sleeve, forming a container suitable for receiving the cylindrical stack. Once the cylindrical stack is placed inside this container and the first current collector is connected to the lid, thus forming the first terminal of the cylindrical cell, the base is secured to the cylindrical sleeve.

[0005] A through-hole is provided in the bottom, allowing the inside of the casing to be filled with electrolyte. Once the casing is filled with electrolyte, the through-hole is sealed with a metal blind rivet (also called a "pop rivet") which also acts as a second terminal for the cylindrical cell by connecting it to the second current collector. In addition to sealing the through-hole, this rivet acts as a negative or positive terminal for the cell, depending on whether the second current collector is connected to the anode or the cathode.

[0006] To electrically isolate this second terminal from the base it passes through and ensure a watertight seal of the opening, a flanged sealing gasket (rivet-shaped) is placed in the opening, so that the rivet deforms against this gasket. The second terminal of the cylindrical cell passes through the base via the opening and is secured there with the electrically insulating sealing gasket in between.

[0007] While this riveted sealing of the bottom opening is generally satisfactory, it can still be improved as it does not guarantee perfect protection against electrolyte leakage from the housing and / or against air ingress (especially when laden with moisture) under high-stress conditions. For example, a strict level of sealing of the bottom opening is increasingly required in the automotive industry.

[0008] An object of the present invention is therefore to improve the sealing of the closure of the opening for filling electrolyte in a cylindrical cell.

[0009] To this end, an electrochemical cell is proposed comprising: - a cylindrical stack successively comprising a first electrode sheet, a first separator, a second electrode sheet of opposite polarity to the first electrode sheet, a second separator; - a first current collector connected to the first electrode sheet; - a second current collector connected to the second electrode sheet; - a cylindrical case housing said cylindrical stack, this case comprising a metal lid, a base incorporating a through orifice, a lateral envelope connecting the lid to the base, the lid being connected to the first current collector; - a metal rivet passing through the base via the through orifice, this rivet being connected to the second current collector; - a sealing gasket interposed between the metal rivet and the base;- the base comprising an annular rib around the opening protruding from a first face of this base turned towards the outside of the housing so that the sealing gasket is compressed by the rivet against the annular rib.;

[0010] Various additional characteristics may be provided, alone or in combination: - the distance between the annular rib and the opening orifice, measured in a radial direction from the opening orifice, is between 1 and 4 times the thickness of the base; - the width of the annular rib measured in a radial direction from the opening orifice is between 0.2 and 0.8 times the thickness of the sealing gasket measured in a direction perpendicular to the base; - the width of the annular rib measured in a radial direction from the opening orifice is approximately equal to 0.5 times the thickness of the sealing gasket measured in a direction perpendicular to the base; - the height of the annular rib measured in a direction perpendicular to the base is between 0.1 and 5 millimeters;- the base comprises, on a second face opposite the first face, an annular groove around the opening so that the sealing gasket is compressed by the rivet against the annular groove; - the distance between the annular groove and the opening, measured in a radial direction from the opening, is between 1 and 4 times the thickness of the base; - the width of the annular groove measured in a radial direction from the opening is between 0.2 and 0.8 times the thickness of the sealing gasket measured in a direction perpendicular to the base; - the width of the annular groove measured in a radial direction from the opening is approximately equal to 0.5 times the thickness of the sealing gasket measured in a direction perpendicular to the base; - the depth of the annular groove measured in a direction perpendicular to the base is between 1 and 5 millimeters; - the annular groove is continuous;- The compression ratio of the sealing gasket is between 60% and 85%; - The annular rib is continuous.

[0011] 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:

[0012] The figure schematically illustrates elements of an electrochemical cell according to various embodiments;

[0013] The figure schematically illustrates an element of an electrochemical cell in longitudinal section according to various embodiments;

[0014] The figure schematically illustrates elements of an electrochemical cell in longitudinal section according to various embodiments.

[0015] Referring to the accompanying figures, an electrochemical cell is shown comprising a substantially cylindrical stack consisting successively of a first electrode sheet, a first separator, a second electrode sheet of opposite polarity to the first electrode sheet, and a second separator. In one embodiment, this cylindrical stack is obtained by winding an anode, a first separator, a cathode, and a second separator around a mandrel. A first current collector and a second current collector are connected to the first and second electrode sheets, respectively. These elements are not shown because they are known.

[0016] A cylindrical case 2 houses the cylindrical stack 1. This cylindrical case 2 has a metal lid 3, a base 4, and a lateral sleeve 5 connecting the lid 3 to the base 4. To highlight this base 4, the case 2 is shown vertically in Figure 1, with its base 4 facing upwards. In Figures 2 and 3, the base 4 of the case 2 is facing downwards.

[0017] The lateral casing 5 is assembled to the base 4 at one end and to the metal cover 3 at a second end, opposite the first. The metal cover 3 is connected to the first current collector, thus forming the first terminal of the electrochemical cell 10.

[0018] The base 4 incorporates a through-hole 41. This hole 41 is adapted for filling with electrolyte inside the housing 2. The base 4 includes an annular rib 42 around the through-hole 41. The annular rib 42 is preferably concentric with the through-hole 41. The annular rib 42 projects from a first face of the base 4 facing outwards from the housing 2.

[0019] As illustrated in Figure 42, the annular rib is a projection, elevation, protrusion, or, more generally, any local deformation in which a portion of the outward-facing face of the case extends above the surrounding level along an annular line around the opening 41. The annular rib is continuous, meaning it forms a single, unsegmented, closed structure—in other words, a complete ring.

[0020] Referring to the figure, a metal rivet 6 passes through the bottom 4 via the open hole 41, with a sealing gasket 7 interposed between them. The metal rivet 6 passes through the bottom 4 and is assembled with it by means of the sealing gasket 7. In one embodiment, the rivet 6 is made of a deformable alloy. The metal rivet 6 is, for example, a blind rivet.

[0021] The metal rivet 6 is connected to the second current collector, thus forming the second terminal of the electrochemical cell 10. By being interposed between the metal rivet 6 and the base 4, the sealing gasket 7 electrically isolates the rivet 6 from the base 4.

[0022] Advantageously, the annular rib 42 is positioned around the opening 41 so that the sealing gasket 7 is compressed by the rivet 6 against this annular rib 42. In other words, the sealing gasket 7 covers or extends over the annular rib 42, or the rib 42 is located within the bearing area of ​​the metal rivet 6. Thus, when the opening 41 is closed by riveting, the body of the rivet 6 compresses the sealing gasket 7 against the annular rib 42.

[0023] Advantageously, the annular rib 42 increases the contact area of ​​the base 4 with the sealing gasket 7. Furthermore, the annular rib 42 creates edges whose contact with the gasket 7 improves the seal. These edges promote more effective compression of the gasket 7 by the rivet 6 and create a barrier against leaks.

[0024] In one embodiment, the distance between the annular rib 42 and the opening 41, measured radially from the opening 41, is between 1 and 4 times the thickness of the bottom 4. This distance has the advantage, during the manufacturing of the bottom 4, of preventing breakage and, consequently, reducing scrap, thus improving the efficiency of the production process. Thanks to this configuration, the bottom 4 can be manufactured reliably, without risk of structural failure during production. Furthermore, this configuration helps ensure excellent mechanical strength of the bottom 4, both during riveting and over the long term under operating conditions. This not only ensures the durability of the bottom 4 component but also maintains the overall performance of the electrochemical cell 10.

[0025] Alternatively, or in combination, the width of the annular rib 42, measured radially from the opening 41, is between 0.2 and 0.8 times the thickness of the sealing gasket 7, or approximately 0.5 times the thickness of the sealing gasket 7 measured perpendicularly to the bottom 4. Such widths of the rib 42 advantageously prevent weakening or breaking (or rupturing) the sealing gasket 7 when applied tightly against this rib 42. These widths contribute to a better distribution of the mechanical stresses exerted on the sealing gasket 7, thus reducing the risk of failure while improving the sealing of this contact.

[0026] The height of the annular rib 42, measured in a direction perpendicular to the bottom 4, is preferably between 0.1 and 5 millimeters. Such rib heights advantageously prevent the weakening or rupture of the seal 7 applied closely against this rib 42. These heights not only minimize the risk of failure, such as cracking, crushing, or excessive deformation of the seal 7, thus allowing it to retain its functional properties, but they also improve the effectiveness and durability of the seal.

[0027] In an embodiment illustrated by Figures 2 and 3, the base 4 further comprises an annular groove 43 around the opening 41. More generally, this groove 43 is a channel, depression, or indentation formed around the opening 41, opening onto a second face of the base 4 opposite the first face. This second face is oriented towards the interior of the housing 2. The annular groove 43 is continuous, that is, it forms a single, unsegmented, and closed depression, in other words, a complete ring.

[0028] The annular groove 43 is arranged around the opening 41 so that the sealing gasket 7 is compressed by the rivet 6 against this annular groove 43. Advantageously, the presence of the annular groove 43 increases the contact surface of the base 4 with the sealing gasket 7 and thus improves the sealing of the opening 41.

[0029] The distance between the annular groove 43 and the open port 41, measured radially from the open port, is preferably between 1 and 4 times the thickness of the bottom 4. This distance has the advantage, during the manufacturing of the bottom 4, of preventing breakage and, consequently, reducing scrap, thus improving the efficiency of the production process. Thanks to this configuration, the bottom 4 can be manufactured reliably, without risk of structural failure during production. Furthermore, this configuration helps ensure excellent mechanical strength of the bottom 4, both during riveting and over the long term under operating conditions. This not only ensures the durability of the bottom 4 component but also maintains the overall performance of the electrochemical cell 10.

[0030] Alternatively, or in combination with other specifications, the width of the annular groove 43, measured radially from the opening 41, is preferably between 0.2 and 0.8 times the thickness of the sealing gasket 7, or substantially equal to 0.5 times the thickness of the sealing gasket 7 measured perpendicularly to the bottom 4. Such groove widths 43 advantageously prevent the weakening or breakage of the sealing gasket 7 when applied tightly against this groove 43. These widths contribute to a better distribution of the mechanical stresses exerted on the sealing gasket 7, thus reducing the risk of failure while improving the sealing of this contact.

[0031] The depth of the annular groove 43, measured in a direction perpendicular to the bottom 4, is preferably between 1 and 5 millimeters. Such groove depths advantageously prevent the weakening or breakage of the seal 7 applied closely against this groove 43. These depths not only minimize the risk of failure, such as cracking, crushing, or excessive deformation of the seal 7, thus allowing it to retain its functional properties, but they also improve the effectiveness and durability of the seal.

[0032] In one embodiment, the groove 43 and the rib 42 are advantageously formed simultaneously by stamping.

[0033] To ensure a tight fit against the annular rib 42 and / or the annular groove 43, the compression ratio of the sealing gasket 7 is preferably between 60% and 85%. An adequate compression ratio ensures optimal sealing. In one embodiment, the material of the sealing gasket 7 is a plastic material with high compressive and shear strength.

[0034] Advantageously, the raised elements 42, 43 provided around the orifice 41 opening into the bearing area of ​​the sealing gasket 7 ensure a watertight bearing of the rivet against the bottom 4. This makes it possible to close the orifice 41 in a sufficiently watertight and durable manner against any possible leakage of the electrolyte outside the housing 2 or an air intake inside it.

Claims

Electrochemical cell (10) comprising: - a cylindrical stack (1) successively comprising a first electrode sheet, a first separator, a second electrode sheet of opposite polarity to the first electrode sheet, a second separator; - a first current collector connected to the first electrode sheet; - a second current collector connected to the second electrode sheet; - a cylindrical housing (2) housing said cylindrical stack (1), this housing (2) comprising a metallic cover (3), a base (4) incorporating a through-hole (41), a lateral envelope (5) connecting the cover (3) to the base (4), the cover (3) being connected to the first current collector; - a metallic rivet (6) passing through the base (4) via the through-hole (41), this rivet (6) being connected to the second current collector; - a sealing gasket (7) interposed between the metallic rivet (6) and the base (4);the electrochemical cell (10) being characterized in that the base comprises an annular rib (42) around the opening orifice (41) projecting from a first face of this base turned towards the outside of the housing (2) so that the sealing gasket (7) is compressed by the rivet (6) against the annular rib (42). Electrochemical cell (10) according to the preceding claim, characterized in that the distance between the annular rib (42) and the opening orifice (41), measured in a radial direction of the opening orifice (41), is between 1 and 4 times the thickness of the bottom (4). Electrochemical cell (10) according to claim 1 or 2, characterized in that the width of the annular rib (42) measured in a radial direction of the opening orifice (41) is between 0.2 and 0.8 times the thickness of the sealing gasket (7) measured in a direction perpendicular to the bottom (4). Electrochemical cell (10) according to claim 1 or 2, characterized in that the width of the annular rib (42) measured in a radial direction of the opening orifice (41) is substantially equal to 0.5 times the thickness of the sealing gasket (7) measured in a direction perpendicular to the bottom (4). Electrochemical cell (10) according to any one of the preceding claims, characterized in that the height of the annular rib (42) measured in a direction perpendicular to the bottom (4) is between 0.1 and 5 millimeters. Electrochemical cell (10) according to any one of the preceding claims, characterized in that the base (4) comprises, on a second face opposite to the first face, an annular groove (43) around the opening orifice (41) so that the sealing gasket (7) is compressed by the rivet (6) against the annular groove (43). Electrochemical cell (10) according to the preceding claim, characterized in that the distance between the annular groove (43) and the opening orifice (41), measured in a radial direction of the opening orifice (41), is between 1 and 4 times the thickness of the bottom (4). Electrochemical cell (10) according to claim 6 or 7, characterized in that the width of the annular groove (43) measured in a radial direction of the opening orifice (41) is between 0.2 and 0.8 times the thickness of the sealing gasket (7) measured in a direction perpendicular to the bottom (4). Electrochemical cell (10) according to claim 6 or 7, characterized in that the width of the annular groove (43) measured in a radial direction of the opening orifice (41) is substantially equal to 0.5 times the thickness of the sealing gasket (7) measured in a direction perpendicular to the bottom (4). Electrochemical cell (10) according to any one of claims 6 to 9, characterized in that the depth of the annular groove (43) measured in a direction perpendicular to the bottom (4) is between 1 and 5 millimeters. Electrochemical cell (10) according to any one of claims 6 to 10, characterized in that the annular groove (43) is continuous. Electrochemical cell (10) according to any one of the preceding claims, characterized in that the compression ratio of the sealing joint (7) is between 60% and 85%. Electrochemical cell (10) according to any one of the preceding claims, characterized in that the annular rib (42) is continuous.

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