WO2017063880A1

WO2017063880A1 - Weld-free electrode plate for a battery cell

Info

Publication number: WO2017063880A1
Application number: PCT/EP2016/073066
Authority: WO
Inventors: Mark KOTIK; Robert Schoenherr
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2015-10-16
Filing date: 2016-09-28
Publication date: 2017-04-20
Anticipated expiration: 2018-04-16

Abstract

A battery cell includes a housing, and an electrode plate stack disposed in the housing. The stack includes positive electrode plates alternating with negative electrode plates and separated by separator plates. A positive electrode plate includes a positive folded portion defined between a first edge and a first fold line that extends parallel to the first edge, and the stack is arranged such that the positive folded portion of one positive electrode plate overlaps and contacts the positive folded portion of an adjacent positive electrode plate. A negative electrode plate includes a negative folded portion defined between a second edge and a second fold line that extends parallel to the second edge, and the stack is arranged such that the negative folded portion of one negative electrode plate overlaps and contacts the negative folded portion of an adjacent negative electrode plate.

Description

WELD-FREE ELECTRODE PLATE FOR A BATTERY CELL

BACKGROUND

1. Field of the Invention

[001] The present invention relates to a battery cell that includes a stacked arrangement of electrode plates, and a current collector disposed in the battery cell that forms an electrical connection with the electrode plates. The electrode plates have a folded edge and are stacked in a manner that facilitates a weld- free electrical connection with the current collector.

2. Description of the Related Art

[002] Battery packs provide power for various technologies ranging from portable electronics to renewable power systems and environmentally friendly vehicles. For example, hybrid electric vehicles (HEV) use a battery pack and an electric motor in conjunction with a combustion engine to increase fuel efficiency. Battery packs are formed of a plurality of battery modules, where each battery module includes several electrochemical cells. The cells are arranged in two or three dimensional arrays and are electrically connected in series or in parallel. Likewise, the battery modules within a battery pack are electrically connected in series or in parallel.

[003] Different cell types have emerged in order to deal with the space requirements of a very wide variety of installation situations, and the most common types used in automobiles are cylindrical cells, prismatic cells, and pouch cells. Regardless of cell type, each cell includes a cell housing and an electrode assembly disposed in the cell housing. The electrode assembly includes a series of stacked or rolled positive electrode plates that alternate with negative electrode plates and are separated by an intermediate separator plates. Each cell may include a first current collector that is electrically connected via welding to the positive electrode plates and joins the positive electrode plates to a positive cell terminal disposed outside the cell housing, and a second current collector that is electrically connected via welding to the negative electrode plates and joins the negative electrode plates to a negative cell terminal disposed outside the cell housing. Due to the large number of electrode plates that form the electrode assembly (on the order of tens or hundreds of plates) and the very small plate thickness (on the order of 0.1 mm), welding the plates to the current collector is a challenging and labor intensive process.

SUMMARY

[004] A pouch cell includes an electrode assembly that is sealed within a pouch-type, metal laminated film cell housing along with an electrolyte to form a power generation and storage unit. The electrode assembly includes a series of stacked positive electrode plates alternating with negative electrode plates and separated by an intermediate separator plates. Each positive and negative electrode plate includes an edge that is folded, and the folded portion of each plate provides an exposed (e.g., free of electrical insulation) area that provides an electrical contact surface. Certain electrode plates within the electrode stack (e.g., electrode plates having a common electric polarity) are arranged such that the folded edges overlap each other and contact each other. This arrangement results in a large conductive surface of interconnected electrode plates of a common electric polarity. In addition, the pouch cell includes current collectors in the form of an electrically conductive plate that forms an electrical connection with the folded portion of the electrode plates (e.g., the large conductive surface) via a weld- free pressure contact. In particular, each current collector is pressed against the folded portion of the electrode plates via a force that is internal or external to the cell. The force provides a pressure contact electrical connection between the current collector and the electrode plate folded portions. Current generated in the electrode assembly passes through the current collector to a terminal disposed on an outside of the cell.

[005] In some aspects, the electrode assembly is a "stacked" electrode assembly that includes a series of individual plates for example as formed in a stamping operation that are arranged in a stacked configuration. The stacked arrangement of plates includes folded positive electrode plates alternating with folded negative electrode plates and separated by intermediate insulating separator plates. The folded portions of the positive electrode plates are arranged together to overlap each other and contact each other on one side of the electrode assembly, and the folded portions of the negative electrode plates are arranged together to overlap each other and contact each other on a side of the electrode assembly opposed to the one side.

[006] In some aspects, the electrode assembly is a "jelly roll" electrode assembly that includes a stacked arrangement of an elongated positive electrode plate alternating with an elongated negative electrode plate and separated by intermediate insulating separator plates, where the stacked arrangement is rolled in the direction of elongation of the plates. The end-view shape of the resulting jelly roll electrode assembly may be circular, or may be elongated in a manner similar to that of a racetrack to include generally linear portions connected by rounded end portions. The linear portions of the positive electrode plates are folded and arranged together to overlap each other and contact each other on one side of the jelly roll, and the linear portions of the negative electrode plates are folded and arranged together to overlap each other and contact each other on a side of the jelly roll opposed to the one side. Advantageously, by providing the electrode assembly in a jelly roll configuration, manufacturing costs associated with precise alignment of hundreds of individual plates required in some stacked electrode assemblies can be avoided.

[007] In some aspects, the electrode assembly includes a stacked arrangement of several elongated jelly roll electrode assemblies in which the linear portions of the positive electrode plates are folded and arranged together to overlap each other and contact each other on one side of the jelly roll, and the linear portions of the negative electrode plates are folded and arranged together to overlap each other and contact each other on a side of the jelly roll opposed to the one side.

[008] Advantageously, regardless of whether the electrode assembly is a stack or jelly roll arrangement, by providing each of the electrode plates with folded edge, and arranging the folded electrode plates within the electrode stack such that the folded edges are arranged to overlap each other and contact each other, a weld-free electrical connection with a current collector is obtained and the cost to manufacture the cell is reduced.

[009] The cell including an electrode assembly in which the electrode plates of the electrode assembly having a common electrical polarity form weld-free electrical connection with a current collector permits formation of electrode stacks that are higher (e.g., include a greater number of layers of electrode plates) than some conventional electrode assemblies in which the electrode plates of the electrode assembly having a common electrical polarity include protruding tabs that are welded together. In such conventional electrode assemblies, the number of electrode plates, which corresponds to the number of tabs to be welded together, is limited by the available weld depth. By providing a cell in which the electrode plates having a common electrical polarity form weld-free electrical connection with a current collector, the height of the electrode stack is not limited, whereby the footprint of the cell can be reduced. This in turn allows the cells to be formed in a more efficient shape. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Fig. 1 a partially exploded perspective view of a battery pack including an array of pouch cells.

[0011] Fig. 2 is a perspective view of a pouch cell.

[0012] Fig. 3 is a schematic cross sectional view of the pouch cell of Fig. 2 as seen across line 3— 3 of Fig. 2.

[0013] Fig. 4 is a perspective view of an electrode plate pair including a positive electrode plate, a negative electrode plate, and separator plates alternating with the positive and negative electrode plates.

[0014] Fig. 5 is a perspective view of an isolated negative electrode plate including a negative folded portion.

[0015] Fig. 6 is a perspective view of one side of the electrode plate stack illustrating the positive folded portions of the positive electrode plates arranged in an overlapped configuration.

[0016] Fig. 7 is an exploded perspective view of the pouch cell of Fig. 2.

[0017] Fig. 8 is a perspective view of one side of the electrode plate stack illustrating the positive folded portions of the positive electrode plates arranged in an overlapped configuration and in electrical contact with the positive current collector, with the negative electrode plates and separator plates omitted.

[0018] Fig. 9 is a schematic end cross-sectional view of an alternative electrode assembly.

[0019] Fig. 10 is a schematic side cross sectional view of the electrode assembly of Fig. 10.

[0020] Fig. 1 1 is a perspective view of a stack of alternative electrode assemblies.

[0021] Fig. 12 is a perspective view of the stack of alternative electrode assemblies of Fig. 12 illustrating the positive current collector forming a weld-free electrical contact with the positive folded portions of the positive electrode plate.

DETAILED DESCRIPTION

[0022] Referring to Figs. 1 -3, a battery pack 1 used to provide electrical power includes electrochemical cells 20 that are electrically interconnected and stored in an organized manner within a battery pack housing 2. The battery pack housing 2 includes a container portion 3 and a detachable lid 4. The cells 20 are lithium-ion pouch cells that include an electrode assembly 60 (Fig. 3) that is sealed within a cell housing 21 along with an electrolyte to form a power generation and storage unit. In some embodiments, groups of cells 20 may be bundled together to form battery modules (not shown), which in turn are stored within the battery pack housing 2. However, in the illustrated embodiment, the cells 20 are not bundled into modules and instead are directly electrically connected to battery pack housing terminals 6, 7. Within the battery pack housing 2, the cells 20 are electrically connected in series or in parallel.

[0023] Each cell 20 includes a pouch-type cell housing 21 that is an assembly of two box shaped portions 36, 38 formed of a metal laminated film. The cell housing 21 has a rectangular shape. In the illustrated embodiment, the cell housing 21 is cube shaped, and includes six orthogonal surfaces. The surfaces include a first end 22, a second end 23 that is opposed to the first end 22, a first side 24, a second side 25 adjoining the first side 24, a third side 26 adjoining the second side 25 and being opposed to the first side 24, and a fourth side 27 adjoining the third side 26 and the first side 24, the fourth side 27 being opposed to the second side 25. Each of the first side 24, the second side 25, the third side 26 and the fourth side 27 extend between the first end 22 and the second end 23, and the six surfaces together define a sealed interior space occupied by the electrode assembly 60.

[0024] Referring to Figs. 3-6, the electrode assembly 60 disposed in the cell 20 includes a series of stacked individual positive electrode plates 61 alternating with individual negative electrode plates 62 and separated by an intermediate separator plates 30, 32. The series of stacked electrode plates 61 , 62 and separator plates 30, 32 will be referred to herein as the "plate stack" 64, and a stack axis 66 of the plate stack 64 extends through a center of the plate stack 64 in a direction parallel to the stacking direction. The electrode plates 60, 61 are very thin (e.g., having a thickness on the order of about 0.095 to 0.145 mm) compared to the overall cell thickness (e.g. having a thickness on the order of tens or hundreds of mm) and thus are illustrated schematically in Fig. 3.

[0025] During stacking, the positive electrode plates 61, the negative electrode plates 62 and the separator plates 30, 32 that form the electrode assembly 60 are arranged in a layered or stacked configuration in the stacking direction. In the stacked configuration, the separator plates 30, 32, are stacked along the stack axis 66 such that peripheral edges of all the separator plates 30, 32 of the stack 64 are aligned in a direction parallel to the direction of the stack axis 66. However, the positive and negative electrode plates 61 , 62 are partially offset in a direction (i.e., a length direction) transverse to the stack axis 66 relative to the respective separator plates 30, 32.

[0026] In particular, the positive electrode plates 61 are stacked along the stack axis 66 such that peripheral edges of the positive electrode plates 61 are aligned with each other in a direction parallel to the direction of the stack axis 66 but are partially offset relative to the separator plates 30, 32 in a first direction parallel to the length direction. The first direction is represented in Fig. 4 by arrow 34. Thus, one edge (i.e., the first edge 61a) of each of the positive electrode plates 61 extends beyond a corresponding edge 30a, 32a of the separator plates 30, 32 resulting in a positive "clear lane" 63 of exposed conductive material. The positive clear lane 63 is folded about a first fold line 67 so as to overlie a side of the electrode stack 64. The first fold line 67 is disposed in the positive clear lane 63. In addition, the first fold 67 line is parallel to, and spaced apart from, the first edge 61a so as to be located adjacent the edges 30a, 32a of the separator plates 30, 32. The positive clear lane 63 provides a positive folded portion that is used to form an electrical contact with a positive current collector 50, as discussed further below.

[0027] The negative electrode plates 62 are stacked along the stack axis 66 such that peripheral edges of the negative electrode plates 62 are aligned with each other in a direction parallel to the direction of the stack axis 66 but are partially offset relative to the separator plates 30, 32, in a second direction, where the second direction is parallel to the length direction and opposed to that of the first direction. The second direction is represented in Fig. 4 by arrow 35. Thus, one edge (i.e., a second edge 62b) of each of the negative electrode plates 62 extends beyond a corresponding edge 30b, 32b of the separator plates 30, 32 resulting in a negative "clear lane" 65 of exposed conductive material. The negative clear lane 65 is folded about a second fold line 69 so as to overlie an opposed side of the electrode plate stack 64 relative to that of the positive clear lane 63 (Fig. 5). The second fold line 69 is disposed in the negative clear lane 65. In addition, the second fold line 69 is parallel to, and spaced apart from, the second edge 62b so as to be located adjacent the edges 30b, 32b of the separator plates 30, 32. Thus, the negative clear lane 65 provides a negative folded portion that is used to form an electrical contact with a negative current collector 54, as discussed further below.

[0028] Referring to Fig. 6, the electrode plate stack 64 is arranged such that the positive folded portions 63 overlie one side of the electrode plate stack 64, and the negative folded portions overlie another side, for example, the opposed side, of the electrode plate stack 64. In addition, the positive folded portion 63 of one positive electrode plate 61 (i.e., positive electrode plate 61 (1)) overlaps and contacts the positive folded portion 63 of an adjacent positive electrode plate 61 (i.e., positive electrode plate 61 (2)). Similarly, the negative folded portion 65 of one negative electrode plate 62(1) overlaps and contacts the negative folded portion 65 of an adjacent negative electrode plate 62. The amount of overlap and contact depends on the dimensions of the respective positive and negative folding portions, as well as the spacing of electrode plates of common polarity along the stack axis 66. Depending on the dimensions of the positive and negative folded portions 63, 65, they may overlap the respective folded portions 63, 65 of additional near electrodes 61 (3), 61(4). The overlapping arrangement of the folded portions 63, 65 results in a large conductive surface of interconnected electrode plates of a common electric polarity on each side of the electrode plate stack 64, further facilitating an electrical connection with the current collectors 50, 54.

[0029] Referring to Fig. 7, in addition to the electrode assembly 60, each cell 20 may optionally include an elastic restraint 40 used to maintain the plates 60, 61 of the plate stack 64 in the above-described alignment and in the stacked configuration, and to apply a compressive force in a direction parallel to the stack axis 66. The restraint 40 has a first U-shaped end cap 41 and a second U-shaped end cap 42 that enclose opposed ends of the plate stack 64. In addition, the elastic restraint includes a pair of elastic bands 43, 43 joining the first end cap 41 to the second end cap 42.

[0030] Each cell 20 also includes a pair of current collectors 50, 54 that form a weld-free electrical connection with the plates 60, 61 of the plate stack 64. The first and second current collectors 50, 54 are each in the form of an electrically conductive plate having a first side 51 , a second side 52 opposed to the first side 51 , and a peripheral edge 53 that extends transversely between, and connects, the first side 51 to the second side 52. In the illustrated embodiment, the peripheral edge 53 defines a rectangular shape to correspond to the rectangular shape of a side of the electrode stack 64. Each current collector 50, 54 is disposed adjacent a side of the electrode stack 64 such that the second side 52 of each current collector 50, 54 faces the electrode stack 64, and the first side 51 of each current collector 50, 54 faces a side of the cell housing 21. In particular, the first current collector 50 is disposed adjacent the side of the electrode stack 64 corresponding to the positive folded portions 63, and the second current collector 54 is disposed on the opposed side of the electrode stack 64 so as to be adjacent the side of the electrode stack

64 corresponding to the negative folded portions 65.

[0031] Referring to Figs. 7 and 8, the first current collector 50 is disposed between the positive folded portions 63 and one side, e.g., the first side 24, of the cell housing 21. In addition, the second side 52 of the first current collector 50 directly contacts the positive folded portions 63 and forms an electrical connection with the positive folded portions 63. The first current collector 50 joins the positive electrode plates 61 to a positive cell terminal 80 disposed outside the cell housing 21.

[0032] Similarly, the second current collector 54 is disposed between the negative folded portions 65 and the opposed side, e.g., the third side 26, of the cell housing 21. In addition, the second side 52 of the second current collector 54 directly contacts the negative folded portions

65 and forms an electrical connection with the negative folded portions 65. The second current collector 54 joins the negative electrode plates 62 to a negative cell terminal 90 disposed outside the cell housing 21. Thus, the first and second current collectors 50, 54 form an electrical connection with the electrode plates 61 , 62 via a we Id- free contact.

[0033] In some embodiments, the direct contact between each current collector 50, 54 and the corresponding positive or negative folded portion 63, 65 is achieved and/or ensured by applying a force to each current collector 50, 52. For example, each current collector 50, 54 is pressed against the electrode stack via a force that is internal to the cell 20. The force, represented by an arrow in Fig 8, is directed perpendicular to the first face 51 and provides a pressure contact electrical connection between the current collector second side 52 and the corresponding positive or negative folded portion 63, 65. In some embodiments, the force that urges the current collector 50, 52 against the electrode stack 64 is achieved by providing an elastic member such as a wave spring 13 (Fig. 7) between one or both current collectors 50, 52 and the adjacent cell housing side 24, 26.

[0034] Each current collector 50, 54 allows passage of current generated in the electrode assembly 60 to pass through the current collector and out of the cell 20. To this end, each current collector 50, 54 is electrically connected to a terminal disposed on the outside of the cell housing 21. In particular, each current collector 50, 54 includes a terminal 80, 90 that protrudes from a portion of the current collector peripheral edge 53. The first terminal 80 protrudes from the peripheral edge 53 of the first current collector 50, while the second terminal 90 protrudes from the peripheral edge 53 of the second current collector 54. The first and second terminals 80, 90 protrude through the cell housing first end 22, and a seal (not shown) is provided along the cell housing 21 at the base of each of the first and second terminals 80, 90 to prevent leakage of electrolyte solution at this location. In the illustrated embodiments, each of the first and second terminals 80, 90 is folded over so as to overlie an outer surface of the cell housing (Fig. 2) and the corresponding current collector 50, 54 (Fig. 7).

[0035] Referring to Figs. 9 and 10, the cell 20 may include an alternative electrode assembly 160 having a jelly roll electrode configuration. In particular, the electrode assembly 160 includes an electrode pair 170 having a stacked arrangement of an elongated positive electrode plate 161 alternating with an elongated negative electrode plate 162 and separated by intermediate insulating separator plates (not shown), where the electrode pair 170 has been rolled in the direction of elongation of the plates to form a jelly roll electrode assembly. In the illustrated example, the electrode pair 170 has been rolled about a plate-shaped mandrel (not shown) to give the electrode assembly 160 an elongated configuration in which the positive electrode plates 161 and the negative electrode plates 162 include generally linear portions 172 connected at each end by rounded end portions 174.

[0036] The positive electrode plates 161, the negative electrode plates 162 and the separator plates are stacked in the offset manner described above with respect to Figs. 4-6 such that positive folded portions 163 corresponding to the linear portions 172 of the positive electrode plate 161 are formed on one end of the electrode assembly 160. The positive folded portions 163 are used to form an electrical contact with the positive current collector 50. In addition, negative folded portions 165 corresponding to linear portions 172 of the negative electrode plate 162 are formed on an opposed end of the electrode assembly 160. The negative folded portions 165 are used to form an electrical contact with the negative current collector 54.

[0037] Referring to Figs. 1 1 and 12, in some embodiments, several elongated, jelly roll electrode assemblies 160 may be stacked within the cell housing 21 , each electrode assembly having a positive folded portions 163 formed on one end of the electrode assembly 160 and negative folded portions 165 formed on an opposed end of the electrode assembly 160. In the illustrated embodiment, four electrode assemblies 160 (1), 160(2), 160(3), 160(4) are stacked along a stack axis 166 that extends in a direction perpendicular to the linear portions 172 of the electrode plates 161 , 162. The positive folded portions 163 of each jelly roll assembly 160 (1), 160(2), 160(3), 160(4) can be electrically connected via the first current collector 50 in a weld- free manner as described above. Similarly, the negative folded portions 165 of each jelly roll assembly 160 (1), 160(2), 160(3), 160(4) can be electrically connected via the second current collector 54 in a weld-free manner as described above. In some embodiments, an elastic element such as the wavy spring 13 may be used to apply a force to the first and second current collectors 50, 54 in such a way as to press the first and second current collectors 50, 54 against the corresponding folded portion 163, 165.

[0038] In the embodiments illustrated in Figs. 9-12, only the linear portions 172 of the positive and negative electrode plate 161, 162 are used to form the folded portions 163, 165. This is due at least in part to the relative stiffness of the material used to form the positive and/or negative electrode plates 161, 162 and/or the separator plates, whereby it may be difficult to appropriately fold the rounded portions 174. It is understood that the size and shape of the current collectors 50, 54 may be adapted to correspond to the shape and dimensions defined by the respective folded portions 163, 165 within the linear portion 172. It is also understood that other materials may be used to form the positive and negative electrode plates 161, 162 and/or the separator plates that may accommodate folding of both the linear and rounded portions 172, 174. In some alternative embodiments, the positive and negative electrode plates 161 , 162 and/or the separator plates may be trimmed or removed along the clear lanes in regions corresponding to the rounded portions 174 in order to provide a cleanly folded configuration of the positive and negative folded portions 163, 165 along the linear portions 172.

[0039] Although the electrode assembly 60 is described herein as being a "stacked" electrode assembly that includes a series of stacked plates 61, 62, and the electrode assembly 160 is described herein as a jelly roll assembly, the electrode assembly 60, 160 disposed in the cell 20 is not limited to these configurations. For example, in some embodiments, the electrode assembly 60, 160 may include a Z-fold assembly or other electrode arrangement.

[0040] In the cell housing 20 illustrated in Figs. 6-7, the direct contact between each current collector 50, 54 and the corresponding electrode plates 61 , 62 may be achieved and/or ensured by providing a force that is generated within each cell housing 21. However, the force that provides the direct contact between each current collector 50, 54 and the corresponding electrode plates 61, 62 is not limited to being generated internally to each cell 20. For example, the force that provides the direct contact between each current collector 50, 54 and the corresponding electrode plates 61, 62 may be generated externally with respect to the cell housing 20. [0041] Although the cell housing 21 is described herein as being a pouch cell housing formed of a metal laminated film, the cell housing 21 is not limited to this material or configuration. For example, the cell housing 21 may be formed of other materials and/or may be formed having a prismatic, cylindrical or other configuration.

[0042] Although the cell 20 has a cube-shaped cell housing 21, the cell housing 21 is not limited to a cube shape. For example, the cell housing 21 may be rectangular in shape. In another example, the cell housing 21 may have other polygonal shapes that permit close packing such as an eight surface structure having hexagonally arranged sides (not shown).

[0043] Moreover, the cells 20 are not limited to being a lithium-ion battery. For example, the cells 20 may be aluminum-ion, alkaline, nickel-cadmium, nickel metal hydride, or other type of cell.

[0044] Selective illustrative embodiments of the battery system including the cell are described above in some detail. It should be understood that only structures considered necessary for clarifying these devices have been described herein. Other conventional structures, and those of ancillary and auxiliary components of the battery system, are assumed to be known and understood by those skilled in the art. Moreover, while working examples of the battery system and battery cell have been described above, the battery system and/or battery cell are not limited to the working examples described above, but various design alterations may be carried out without departing from the devices as set forth in the claims.

Claims

What is claimed is,

1. A battery cell comprising

a cell housing, and

an electrode plate stack disposed in the housing, the electrode plate stack including positive electrode plates alternating with negative electrode plates and separated by intermediate separator plates,

wherein

at least one positive electrode plate includes a positive folded portion defined between a first edge of the positive electrode plate and a first fold line, where the first fold line is formed in the positive electrode plate and extends parallel to the first edge, and the electrode plate stack is arranged such that the positive folded portion of one positive electrode plate overlaps and contacts the positive folded portion of an adjacent positive electrode plate, and

at least one negative electrode plate includes a negative folded portion defined between a second edge of the negative electrode plate and a second fold line, where the second fold line is formed in the negative electrode plate and extends parallel to the second edge, and the electrode plate stack is arranged such that the negative folded portion of one negative electrode plate overlaps and contacts the negative folded portion of an adjacent negative electrode plate.

2. The battery cell of claim 1, wherein the positive folded portions are arranged together to overlap each other and contact each other on one side of the electrode plate stack, and the negative folded portions are arranged together to overlap each other and contact each other on a side of the electrode plate stack opposed to the one side.

3. The battery cell of claim 1 , wherein the electrode assembly includes a series of individual positive electrode plates alternating with individual negative electrode plates and separated by individual intermediate separator plates that are arranged in a stacked configuration.

4. The battery cell of claim 1 , wherein the electrode assembly includes an electrode pair including a stacked arrangement of an elongated positive electrode plate alternating with an elongated negative electrode plate and separated by intermediate insulating separator plates, where the electrode pair has been rolled in the direction of elongation of the plates to form a jelly roll electrode assembly.

5. The battery cell of claim 4, wherein positive electrode plates and the negative electrode plates of the jelly electrode assembly include generally linear portions connected at each end by rounded end portions,

the positive folded portion is formed along a linear portion of the corresponding positive electrode plate, and

the negative folded portion is formed along a linear portion of the corresponding negative electrode plate.

6. The battery cell of claim 4, wherein the electrode assembly includes a stacked arrangement of several jelly roll electrode assemblies.

7. The battery cell of claim 1 , comprising electrically conductive first current collector disposed in the cell housing between one side of the electrode plate stack and one side of the cell housing, the first current collector forming a weld- free electrical connection with one of the positive folded portion and the negative folded portion.

8. The battery cell of claim 7, comprising an electrically conductive second current collector disposed in the cell housing between another side of the electrode plate stack and another side of the cell housing, the second current collector forming a weld-free electrical connection with the other of the positive folded portion and the negative folded portion.

9. The battery cell of claim 7, wherein an elastic element is disposed in the cell housing between the first current collector and the first one of the sides of the cell housing, the elastic element providing a force that urges the first current collector into direct contact with the one of the positive electrode plates and the negative electrode plates.

10. The battery cell of claim 7, wherein an elastic element is disposed in adjacent an outer surface of the cell housing such that the first one of the sides of the cell housing is disposed between the elastic element and the first current collector, and the spring element provides a force that urges the first current collector into direct contact with the one of the positive folded portion and the negative folded portion.

11. A battery cell comprising

a cell housing, and

wherein

at least one plate of one of the positive electrode plates and the negative electrode plates includes a first folded portion defined between a first edge of the one of the positive electrode plates and the negative electrode plates and a first fold line, where the first fold line is formed in the one of the positive electrode plates and the negative electrode plates and extends parallel to the first edge, and

the electrode plate stack is arranged such that the first folded portion of one of the one of the positive electrode plates and the negative electrode plates overlaps and contacts the first folded portion of an adjacent one of the one of the positive electrode plates and the negative electrode plates

12. The battery cell of claim 1 1 , wherein

at least one plate of the other of the one of the positive electrode plates and the negative electrode plates includes a second folded portion defined between a second edge of the other of the one of the positive electrode plates and the negative electrode plates and a second fold line, where the second fold line is formed in the other of the one of the positive electrode plates and the negative electrode plates and extends parallel to the second edge, and

the electrode plate stack is arranged such that the second folded portion of one of the other of the one of the positive electrode plates and the negative electrode plates overlaps and contacts the second folded portion of an adjacent one of the other of the one of the positive electrode plates and the negative electrode plates.