SE2250503A1

SE2250503A1 - A current collecting plate and a cylindrical secondary cell

Info

Publication number: SE2250503A1
Application number: SE2250503A
Authority: SE
Inventors: Kenya Shatani; Tetsuya Makino
Original assignee: Northvolt Ab
Priority date: 2022-04-26
Filing date: 2022-04-26
Publication date: 2023-09-18
Also published as: WO2023208906A1

Abstract

This disclosure presents a current collecting plate (1) for a cylindrical secondary cell (100) comprising an external terminal (110, 115) and an electrode roll (120) comprising a conductive sheet (125, 127), the current collecting plate (1) being configured to be arranged in direct electrical contact with the conductive sheet (125, 127) and comprising electrolyte flow holes (2) for allowing an electrolyte to flow through the current collecting plate (1), the electrolyte flow holes (2) being elongate with their respective axis of elongation (3) oriented essentially towards the center of the current collecting plate (1). Further a cylindrical secondary cell (100) comprising such a current collecting plate (1) is presented.

Description

A CURRENT COLLECTING PLATE AND A CYLINDRICAL SECONDARY CELL TECHNICAL FIELD The present disclosure generally pertains to cylindrical secondary cells and components thereof. In particular, the disclosure relates to a current collecting plate and to a cylindrical secondary cell comprising such a current collecting plate. BACKGROUND In addressing climate change, there is an increasing demand for rechargeable batteries, e.g. to enable electrif1cation of transportation and to supplement renewable energy. Currently, lithium-ion batteries are becoming increasingly popular. They represent a type of rechargeable battery in which lithium ions move from the negative electrode to the positive electrode during discharge and back when charging.

As the demand for rechargeable batteries increases, more and more focus is being placed on production speed. To achieve an effective production and also highly reliable rechargeable batteries, the design of the batteries as well as their manufacturing process can be optimized.

A rechargeable battery, often referred to as a secondary battery, typically comprises one or more secondary cells electrically connected to each other. SUMMARY It is in view of the above considerations and others that the embodiments of the present invention have been made. The present disclosure aims at providing highly reliable secondary cells that are efficient in manufacture. The number of components is to be reduced and the assembly thereof is to be simplif1ed.

According to a first aspect of the present disclosure a current collecting plate for a cylindrical secondary cell is provided. The cylindrical secondary cell comprises an extemal terminal and an electrode roll comprising a conductive sheet. The current collecting plate is configured to be arranged in direct electrical contact with the conductive sheet and comprises electrolyte ﬂow holes for allowing an electrolyte to ﬂow through the current collecting plate. The electrolyte ﬂow holes being elongate with their respective axis of elongation oriented essentially towards the center of the current collecting plate.

The above electrolyte ﬂow holes may allow a relatively large through-flow area through the current collecting plate, while there is a remaining area for other functions of the current collecting plate. A relatively large through-ﬂow area may be benef1cial for the ﬂow of, typically liquid, electrolyte during manufacture. A relatively large through-flow area may in addition be beneficial for through-ﬂow of electrolyte in the event of failure of the cylindrical secondary cell. The remaining area may for example be used for attaching the current collecting plate to the conductive sheet, e. g. by welding such as laser welding.

The current collecting plate may be conf1gured to be arranged in direct electrical contact with the extemal terminal, such that the extemal terminal and the conductive sheet are efficiently and reliably contacted to one another. In this disclosure, direct electrical contact means direct electrical and physical contact. The current collecting plate may be one single component electrically coupled between the conductive sheet and the extemal terminal. In other words, the current collecting plate may be the only component electrically coupled between the conductive sheet and the extemal terminal. Thereby, the number of components of the cylindrical secondary cell is kept low, and its manufacture involves few steps. The current collecting plate may have the general shape of a circular disc.

The current collecting plate may comprise an outer, e.g. annular, contact region that is adapted to be arranged in direct electrical contact with the conductive sheet. The current collecting plate may comprise an inner, e.g. circular, contact region that is adapted to be arranged in direct electrical contact with the extemal terminal. In such a case, the extemal terminal may be formed by a rivet.

Altematively, the current collecting plate may comprise an outer, e.g. annular, contact region that is adapted to be arranged in direct electrical contact with the extemal terminal. In such a case, the extemal terminal may be formed by a cylindrical enclosure, or can, of the cylindrical secondary cell. The outer contact region may be formed by an outer edge of the current collecting plate. The edge may comprise a ﬂange that forms the outer edge. The outer contact region may be adapted to be arranged in direct electrical contact with a longitudinal side wall of the cylindrical enclosure. The current collecting plate may comprise an inner, e. g. annular, contact region that is adapted to be arranged in direct electrical contact With the conductive sheet.

In both above described examples, the inner and outer contact regions may be radially separated. There may be no overlap of the inner and outer contact regions.

According to a second aspect of the present disclosure a cylindrical secondary cell is provided. The cylindrical secondary cell comprises a cylindrical enclosure comprising a first enclosure end and a second enclosure end, an electrode roll comprising ﬁrst and second conductive sheets comprising electrode coatings, the electrode roll being arranged in the cylindrical enclosure. The cylindrical secondary cell further comprises a first extemal terminal arranged on the first enclosure end and electrically connected to the first conductive sheet, a second extemal terminal arranged on the first enclosure end and electrically connected to the second conductive sheet via the cylindrical enclosure, and a current collecting plate as described in the present disclosure. The current collecting plate may be arranged in direct electrical contact With the first or the second extemal terminal. BRIEF DESCRIPTION OF THE DRAWINGS The embodiments disclosed herein are illustrated by Way of example, and by not by Way of limitation, in the figures of the accompanying draWings. Like reference numerals refer to corresponding parts throughout the drawings, in Which Figure l is a plan view of a current collecting plate, Figure 2 is a plan view of an altemative current collecting plate, Figure 3 is a partly cross-sectional side view of a first end of a cylindrical secondary cell, and Figure 4 is a partly cross-sectional side view of a second end of a cylindrical secondary cell.

DETAILED DESCRIPTION Embodiments of the present disclosure Will now be described more fully hereinafter. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by Way of example so that this disclosure Will be thorough and complete, and Will fully convey the scope of the invention to those persons skilled in the art. 3 Figures 1 and 2 show two examples of current collecting plates 1 according to the present disclosure. The current collecting plates 1 are configured to be used in a cylindrical secondary cell 100 as the one illustrated in figure 3 and 4. Figures 3 and 4 may show the first (here: upper) and second (here: lower) ends of one and the same cylindrical secondary cell 100. However, it is to be noted that the current collecting plates 1 of figures 1 and 2 may be applied in a cylindrical secondary cell 100 that has the upper design shown in figure 3 but another design than the lower design shown in figure 4, and Vice versa.

Referring to figures 3 and 4, the cylindrical secondary cell 100 comprises a cylindrical enclosure 130 comprising a first (here: upper) enclosure end 130a and a second (here: lower) enclosure end 130b, an electrode roll 120 comprising first and second conductive sheets 125, 127 comprising electrode coatings, the electrode roll 120 being arranged in the cylindrical enclosure 130, a first external terrninal 110 arranged on the first enclosure end 130a and electrically connected to the first conductive sheet 125, a second external terrninal 1 15 arranged on the first enclosure end 130a and electrically connected to the second conductive sheet 127 via the cylindrical enclosure 130, and a current collecting plate 1.

As is shown in figure 3, the current collecting plate 1 may comprise a recessed portion. The recessed portion may accommodate the first external terrninal 110 here shown as a rivet. As is shown in figure 4, the current collecting plate 1 may comprise an outer ﬂange, or bent rim, for improved (e. g. welded) contact to the inner longitudinal side wall of the cylindrical enclosure 130. The ﬂange may increases the contact area.

The current collecting plate 1 is thus conf1gured to be arranged in direct electrical contact (e.g. by welding) with the conductive sheet 125; 127 and may further be configured to be arranged in direct electrical contact with the extemal terrninal 110, 115.

The current collecting plate 1 comprises electrolyte ﬂow holes 2 for allowing an electrolyte to ﬂow through the current collecting plate 1, the electrolyte ﬂow holes 2 being elongate with their respective axis of elongation 3 oriented essentially towards the center of the current collecting plate 1.

As is illustrated, the electrolyte ﬂow holes 2 may be arranged in a pattem on the current collecting plate 1, which pattem allows welding the current collecting plate 1 to the conductive sheet 125, 127 by a plurality of weld lines 50 arranged between the electrolyte ﬂow holes 2, the weld lines 50 being provided to attach the current collecting plate 1 to the conductive sheet 4 125, 127. As is shown, the weld lines 50 may be straight. Even though not illustrated, there may be three adjacent weld lines arranged between each of the electrolyte ﬂow holes 2. The three adjacent weld lines 50 may be parallel to one another. Thus, in figure 1 there may be in total 6 times 3 equals 18 weld lines (only 6 illustrated). In figure 2 there may be 3 times 3 equals 9 weld lines (only 3 illustrated).

Three adj acent weld lines may be beneficial for electrically contacting and attaching the current collecting plate 1 to the conductive sheet 125, 127, e.g. by welding such as laser welding as disclosed herein. The application of three adj acent weld lines may allow the use of a relatively thin current collecting plate 1. Three adjacent weld lines may provide a rigid connection between the current collecting plate 1 and the conductive sheet 125, 127, and may hinder the current collecting plate 1 from bending and also hinder the layers of conductive sheets 125, 127 of the electrode roll 120 from moving in relation to one another. It is to be apprehended that the herein described application of three adj acent weld lines may be used also in cylindrical secondary cells of other designs than the one shown herein, and together with other current collecting plates.

As is illustrated, the pattem allows arranging the weld lines 50 essentially towards the center of the current collecting plate 1. As is shown in figures 1 and 2, the weld lines 50 extent from the outer perimeter of the current collecting plate 1 towards its center.

The current collecting plate 1 may comprise a center electrolyte ﬂow hole 4 and electrolyte ﬂow holes 2 uniforrnly distributed around the center electrolyte ﬂow hole 4, see figures 1 and 2.

Figure 1 discloses a possible real implementation of the electrolyte ﬂow holes 2. Thus, the numbers and relative sizes of the electrolyte ﬂow holes 2 of figure 1 may correspond to a realized product.

The area of each electrolyte ﬂow hole 2 may be approximately 3 percent of the of the area of the current collecting plate 1, a suitable range being is 2 to 6 percent. It is believed that if three electrolyte ﬂow holes 2 are implemented (figure 3), the area of each one of the electrolyte ﬂow holes 2 may be larger than what is illustrated herein.

The total area of the electrolyte ﬂow holes may be approximately 18 percent of the area of the current collecting plate 1, a suitable range being 6 to 22 percent, or 15 to 20 percent.

The current collecting plate 1 may comprise at least three electrolyte ﬂow holes 2, such as exactly three electrolyte ﬂow holes 2 as is shown in figure 2.

The current collecting plate 1 may comprise at least six electrolyte ﬂow holes 2, such as exactly six electrolyte flow holes 2 as is shown in figure 1.

The current collecting plate 1 of figure 1 comprises six electrolyte ﬂow holes 2, wherein area of the electrolyte ﬂow holes is 15 to 22 percent of the area of the current collecting plate 1.

As is illustrated, the current collecting plate 1 may comprise a center electrolyte ﬂow hole 4. The area of the center electrolyte ﬂow hole 4 may be approximately 3 percent of the area of the current collecting plate 1, a suitable range being 2 to 5 percent.

In figure 2, the current collecting plate 1 comprises six electrolyte ﬂow holes 2 and a center electrolyte ﬂow hole 4. The area of the electrolyte ﬂow holes 2, 4 amounts to approximately 22 percent of the area of the current collecting plate 1, a suitable range being is 17 to 28 percent.

As is shown, the each electrolyte ﬂow hole 2 may have the general shape of a triangle or a trapezoid. Altematively, the each electrolyte ﬂow hole 2 is of an oblong shape.

In the present disclosure, the electrolyte ﬂow holes 2 being elongate means that the length of the holes exceeds the width of the holes, as seen in a plan view (figure 1 or 2). In other words, the holes are not circular or square.

Figures 3 and 4 disclose a number of exemplary features that are not of particular importance to the present disclosure that relates to the current collecting plate 1. For example, the first enclosure end 130a may be formed in one piece with the cylindrical enclosure 130 (as illustrated in figure 3) and the second enclosure end 130b may be formed by a separate second enclosure end lid.

The present cylindrical secondary cell 100 is of a type that has both a positive terminal 110 and a negative terminal 115 at one and the same end (the top end in figure 3) of the cylindrical secondary cell. The first enclosure end 130a comprises a central terminal through-hole for the positive terminal 110 (in this case in the form of a rivet). The negative terminal 115 is electrically connected to the cylindrical enclosure 130. More precisely, the negative terminal 115 is formed by the top surface of the cylindrical enclosure that surrounds the terminal 6 through-hole. Thus, the entire cylindrical enclosure (apart from the positive terminal at the top end) may be the negative terminal.

A cylindrical secondary cell having both terrninals at one end may bring advantages as regards electrically connecting the cell to a load. Conductors electrically connecting the terrninals to the load may be positioned on the same end, the terminal end, of the cell. The opposite end, the electrolyte-filling end, of the cell may be dedicated to electrolyte filling and gas venting. In the present disclosure, the electrolyte filling end is not described in detail. An overpressure may be generated within the cell during operation, in particular upon malfunction of the cell or of the load connected to the cell. Such malfunction may require a release of gas and/or electrolyte out of the cell, and it may be advantageous to direct the released gas and/or electrolyte away from the conductors.

For example, a number of cells may be positioned at a low position in an electric vehicle. The cells may be arranged with the terminal ends directed upwards and the electrolyte-filling ends directed downwards. Upon malfunction, for example resulting from a faulty electric vehicle charger or a faulty cell, a release of gas and/or electrolyte from the electrolyte-filling end(s) will be advantageously directed downwards towards the ground beneath the vehicle.

The electrode roll 120 comprises a first and a second conductive sheet 125, 127 and separating means (not shown). The separating means may also be terrned separator. The conductive sheets and the separating means are rolled to form a circular cylindrical roll defining a central channel (shown in figures 3 and 4). The sheets are coated with electrode coatings and on assembly of the cell the cylindrical enclosure is filled with an electrolyte. The electrolyte may ﬂow through the central channel. The coatings on the conductive sheets act as cathode and anode, respectively. The cathode, anode and electrolyte provide electrochemical energy storage. This principle is known per se, and the electrode roll is commonly referred to as a j ellyroll.

The sheets of the electrode roll are axially offset in relation to one another, and each comprises an end section that is not coated with electrode coating. In figure 3, only the first end of the electrode roll is shown, and at this end the first conductive sheet 125 protrudes axially from the electrode roll. At the opposite end, figure 4, of the electrode roll 3 the second conductive sheet 127 protrudes axially.

In figures 3 and 4, the upper end of the first conductive sheet 125 is not coated with electrode coating. Similarly, the lower end of the second conductive sheet 127 is not coated with 7 electrode coating. In this way, the respective ends of the electrode roll may be efficiently electrically connected to a respective assigned terminal 110, 115 of the cylindrical secondary 100. This design is known per se and commonly referred to as a tabless cell.

As is illustrated in figures 3 and 4, the cylindrical secondary cell l comprises the current collecting plate 1 that is arranged at the upper end of the electrode roll 120 (and, similarly, optionally, at the lower end of the electrode roll 120). The current collecting plate 1 may be in direct electrical contact with the first conductive sheet, more precisely with the non-coated end section of the first conductive sheet. The cylindrical secondary cell 1 may be attached, for example welded, for example laser welded, to the first conductive sheet.

The cylindrical secondary cell 100 further comprises an extemal terminal 110. In the embodiments of the present disclosure, the terminal is rotational symmetric around its longitudinal center axis (not illustrated). The terminal 110 extends through the first enclosure end l30a and has an outer, or first, end (e. g. factory head of rivet) and an inner, or second, end (e. g. shop head of rivet). As is shown, the terminal 110 may be in direct electrical contact with the current collecting plate 1. More precisely, the inner end (e.g. shop head) of the terminal may be in direct electrical contact (e.g. welded) with the current collecting plate.

As is shown in figure 3, there may be electrically isolating means surrounding at least a portion of the terminal 110. In the embodiment of figure 3, the terminal 110 has the shape of a rivet with a head portion, or so-called factory rivet head, and a shaft portion, or rivet shaft. As is illustrated, the electrically isolating means surrounds the rivet shaft. The electrically isolating means may be referred to as a rivet gasket.

The rivet shaft extends through the through-hole in the first enclosure end 130a and is electrically isolated from the through-hole by the electrically isolating means.

During manufacture of the cylindrical secondary cell 100, the rivet 110 is riveted, thus plastically deforrned, such that a portion of the rivet shaft is expanded radially, see figure 3. The rivet shaft is thus deforrned to form a so-called shop rivet head. The shop rivet head hinders the rivet 110 (that may be referred to as a terminal rivet) from being pulled out of the through- hole in the first enclosure end l30a.

A recessed current collecting plate 1 facilities the use of a rivet as a terminal 110. The shop head will occupy some space within the cell 100, which space may be provided by the recessed 8 current collecting plate. The rivet shop head and the inner contact region may be positioned Within the central channel of the electrode roll 120.

The current collecting plate 1 may have inner and outer contact regions that are positioned in the same plane. Thus, the current collecting plate 1 may have the forrn of a circular and ﬂat disc.

Modifications and other variants of the described embodiments Will come to mind to ones skilled in the art having benefit of the teachings presented in the foregoing description and associated drawings. Therefore, it is to be understood that the embodiments are not limited to the specific example embodiments described in this disclosure and that modifications and other variants are intended to be included Within the scope of this disclosure.

Furthermore, although speciﬁc terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. Therefore, persons skilled in the art Would recognize numerous variations to the described embodiments that Would still fall Within the scope of the appended claims. As used herein, the terms "comprise/comprises" or "include/includes" do not exclude the presence of other elements or steps. Furthermore, although individual features may be included in different claims (or embodiments), these may possibly advantageously be combined, and the inclusion of different claims (or embodiments) does not imply that a certain combination of features is not feasible and/or advantageous. In addition, singular references do not exclude a plurality. Finally, reference numerals in the claims are provided merely as a clarifying example and should not be construed as limiting the scope of the claims in any Way.

Claims

1.A current collecting plate (1) for a cylindrical secondary cell (100) coniprising an external terminal (110, 115) and an electrode roll (120) coniprising a conductive sheet (125, 127), the current collecting plate (1) being conf1gured to be arranged in direct electrical contact with the conductiVe sheet (125, 127) and coniprising - electrolyte ﬂow holes (2) for allowing an electrolyte to ﬂow through the current collecting plate (1), the electrolyte ﬂow holes (2) being elongate with their respective axis of elongation (3) oriented essentially towards the center of the current collecting plate (1).

2.The current collecting plate (1) of claini 1, wherein the electrolyte ﬂow holes (2) are arranged in a pattern on the current collecting plate (1), which pattern allows welding the current collecting plate (1) to the conductiVe sheet (125, 127) by a plurality of, optionally straight, weld lines (50) arranged between the electrolyte flow holes (2), the weld lines (5 0) being provided to attach the current collecting plate (1) to the conductive sheet (125, 127).

3.The current collecting plate (1) of claini 2, wherein the pattern allows arranging the weld lines (50) essentially towards the center of the current collecting plate (1).

4.The current collecting plate (1) of clain1 3 coniprising a center electrolyte ﬂow hole (4) and electrolyte ﬂow holes (2) uniforrnly distributed around the center electrolyte ﬂow hole (4).

5.The current collecting plate (1) of any preceding clain1, wherein the area of each electrolyte ﬂow hole (2) is 2 to 6 percent of the area of the current collecting plate (1).

6.The current collecting plate (1) of any preceding clain1, wherein the total area of the electrolyte ﬂow holes is 6 to 22 percent of the area of the current collecting plate (1).

7.The current collecting plate (1) of any preceding claini coniprising at least three electrolyte ﬂow holes (2).

8.The current collecting plate (1) of any preceding claini coniprising at least six electrolyte ﬂoW holes (2).

9.The current collecting plate (1) of any preceding claini coniprising six electrolyte ﬂoW holes (2), Wherein total area of the electrolyte ﬂoW holes is 15 to 22 percent of the area of the current collecting plate (1).

10.The current collecting plate (1) of any preceding claini coniprising six electrolyte ﬂoW holes (2) and a center electrolyte ﬂoW hole (4).

11.The current collecting plate (1) of claini 10, Wherein the area of the six electrolyte ﬂoW holes (2) and the center electrolyte ﬂow hole (4) is 17 to 28 percent of the area of the current collecting plate (1).

12.The current collecting plate (1) of any preceding claini, Wherein the electrolyte ﬂoW holes (2) have the general shape of a triangle or a trapezoid.

13.A cylindrical secondary cell (100) coniprising - a cylindrical enclosure (130) coniprising a first enclosure end (130a) and a second enclosure end (130b), - an electrode roll (120) coniprising first and second conductive sheets (125, 127) coniprising electrode coatings, the electrode roll (120) being arranged in the cylindrical enclosure (13 0), - a first external terrninal (110) arranged on the first enclosure end (130a) and electrically connected to the first conductive sheet (125), - a second external terrninal (115) arranged on the first enclosure end (130a) and electrically connected to the second conductive sheet (127) via the cylindrical enclosure (130), and - a current collecting plate (1) according to any preceding claini.

14.The cylindrical secondary cell (100) of claini 13, Wherein the first external terrninal (110) is a rivet.

15. The cylindrical secondary ce11 (100) of c1ain1 13 or 14, Wherein the second external terminal (115) is formed by the ﬁrst enclosure end (130a) of the cylindrical enclosure (130).