Description:TECHNICAL FIELD
[001] The embodiments herein generally relate to cylindrical secondary battery cells with tabs integrated with the electrode assembly and more particularly, to a secondary battery cell with a jelly roll electrode assembly having tabs designed to allow faster electrolyte wetting of the cell, and facilitate connection with a current collector disc with minimal impact on the electrode assembly during welding.
BACKGROUND
[002] Generally, secondary cylindrical battery cells have metal tabs welded to electrodes of the jelly roll electrode assembly. The tabs are typically metal strips welded to the intermittent part of electrodes to allow current to flow from the electrodes to connectors located on the outside of the battery cell. In some of such traditional designs, the current travels all the way along the jelly roll and passes to the outer circuit through the tabs. The ohmic resistance of the tabs may cause power loss thereby contributing to the rise of the cell temperature and acting as a limiting factor to the current carrying capacity of the cell. Further, the welding of the tabs with the jelly roll makes it non-continuous and might cause some manufacturing defects like loose welding of the tabs, leading to short circuits.
[003] To overcome the drawbacks associated with the conventional tabs which are separately attached to the jelly roll, cylindrical cells with tabs integrated with the jelly roll electrode assembly have been designed. A portion of the collector foil of the electrodes which is not coated with active material, act as tabs for the jelly roll electrode assembly. Once the electrode assembly is wound into a jelly roll, the uncoated portion of the collector foils are folded to form the tabs. A positive current collector plate and a negative current collector plate is welded to the positive tab and the negative tab respectively. Thereafter, the electrode assembly is put into a casing that is pre-assembled with a rivet on a top side. The positive current collector plate is welded to the rivet and the negative current collector plate is welded to the side wall of the casing to close the casing.
[004] Conventionally, the tabs are folded perpendicular to an axis of the jelly roll in an interleaved pattern, or are crushed onto a face of the jelly roll. The current collector plates are then welded with the folded or crushed tabs of the respective electrodes. To ensure proper connectivity between the current collector plate and tabs, the welding is done vertically, i.e., a laser penetrates through a top surface of the current collector plate into the electrode assembly, connecting the tabs with the current collector plate. However, welding the current collector plate vertically from top with the tabs, may cause joining of the positive and negative electrodes along with the separator due to inaccurate penetration of the laser, resulting in short-circuiting within the cell. Such errors in welding may be detected during hi-potential testing of the cell at the manufacturing stage, wherein the cell may be rejected or discarded on failing to pass the hi-potential test. Therefore, an error is welding may result in wastage, reducing throughput of the manufacturing process.
[005] After the collector plates are welded with the external connector parts of the cell assembly, an electrolyte is introduced in the cell assembly through an opening provided in a bottom lid of the casing. The infiltration of the electrolyte in the electrode assembly is affected by the pattern of the tabs. A densely interleaved pattern or crushing of the uncoated portion of the collector foil reduces electrolyte infiltration at the tabs of the jelly roll electrode assembly. Further, such dense folding or non-uniform crushing of the tabs also increases the time taken for wetting the electrode assembly with the electrolyte, thereby increasing the manufacturing time.
[006] Therefore, there exists a need for a secondary cylindrical battery cell which obviates the aforementioned drawbacks.
OBJECTS
[007] The principal object of embodiments herein is to provide a secondary cylindrical battery cell with a jelly roll electrode assembly configured to have a tab portion which optimizes electrolyte infiltration in the electrode assembly, and has minimal impact during welding of the current collector disc with the electrode assembly.
[008] Another object of embodiments herein is to provide the secondary cylindrical battery cell which is configured to facilitate connection of the current collector disc with the electrode assembly by allowing welding of a plurality of tabs of the tab portion with sides of the current collector disc, thereby eliminating the possibility of joining electrodes of the electrode assembly during welding.
[009] Another object of embodiments herein is to provide the secondary cylindrical battery cell with the tab portion having the plurality of tabs which are provided near a circumference of the electrode assembly, wherein the tab portion is configured to minimize error in welding, while achieving required internal resistance in the battery cell.
[0010] Another object of embodiments herein is to provide a method for assembling the secondary cylindrical battery cell.
[0011] These and other objects of embodiments herein will be better appreciated and understood when considered in conjunction with following description and accompanying drawings. It should be understood, however, that the following descriptions, while indicating embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
BRIEF DESCRIPTION OF DRAWINGS
[0012] The embodiments are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[0013] Fig. 1 depicts an exploded view of a secondary cylindrical battery cell, according to embodiments as disclosed herein;
[0014] Fig. 2 depicts a perspective view of the secondary cylindrical battery cell, according to embodiments as disclosed herein;
[0015] Fig. 3 depicts a perspective view of an electrode assembly of the secondary cylindrical battery cell, according to embodiments as disclosed herein;
[0016] Fig. 4 depicts a schematic view of the electrode assembly, according to embodiments as disclosed herein;
[0017] Fig. 5 depicts a top view of the electrode assembly, according to embodiments as disclosed herein;
[0018] Fig. 6 depicts a magnified view of the electrode assembly, according to embodiments as disclosed herein;
[0019] Fig. 7 depicts a schematic view of a positive electrode of the electrode assembly, according to embodiments as disclosed herein;
[0020] Fig. 8A depicts an exploded view of the electrode assembly with a current collector disc, according to embodiments as disclosed herein;
[0021] Fig. 8B depicts a perspective view of the electrode assembly with the current collector disc, according to embodiments as disclosed herein;
[0022] Fig. 8C depicts a top view of the electrode assembly with the current collector disc, according to embodiments as disclosed herein;
[0023] Fig. 9 depicts a sectional view of the electrode assembly with a current collector disc, according to embodiments as disclosed herein;
[0024] Fig. 10A depicts a close sectional view of the electrode assembly with the current collector disc, according to embodiments as disclosed herein;
[0025] Fig. 10B depicts a magnified sectional view of the electrode assembly with the current collector disc, according to embodiments as disclosed herein; and
[0026] Fig. 11 is a flowchart depicting a method for assembling the secondary cylindrical battery cell, according to embodiments as disclosed herein.
DETAILED DESCRIPTION
[0027] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0028] The embodiments herein achieve a secondary cylindrical battery cell with a jelly roll electrode assembly which is configured to optimize electrolyte infiltration in the electrode assembly, and minimize wastage due to errors in welding a current collector disc with the electrode assembly. Further, embodiments herein achieve a method for assembling the secondary cylindrical battery cell. Referring now to the drawings Figs. 1 through 11, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[0029] Fig. 1 depicts an exploded view of a secondary cylindrical battery cell (100), according to embodiments as disclosed herein. The secondary cylindrical battery cell (100) includes, an electrode assembly (200) having a jelly roll structure, at least one current collector disc (102, 104) adapted to be connected with the electrode assembly (200), a casing (106) configured to receive the electrode assembly (200) with the at least one current collector disc (102, 104), at least one collector disc isolator (108) adapted to isolate the current collector disc (102) from an electrode of the electrode assembly (200), and at least one connecting member (110) adapted to facilitate connection of the current collector disc (102) with an external circuit component. For the purpose of this description and ease of understanding, the secondary cylindrical battery cell (100) is explained herein with below reference to the electrode assembly (200) having a jelly roll structure. However, it is also within the scope of the invention to use/practice the components of the secondary cylindrical battery cell (100) for any other type of electrode assembly (200), without otherwise deterring the intended function of the secondary cylindrical battery cell (100) as can be deduced from the description and corresponding drawings.
[0030] Fig. 3 is a perspective view of the electrode assembly (200) of the secondary cylindrical battery cell (100), according to embodiments, as disclosed herein. Fig. 4 is a schematic view of the electrode assembly (200), according to embodiments, as disclosed herein. The electrode assembly (200) includes a positive electrode (202), a negative electrode (204), and a separator (206) inserted between the positive electrode (202) and the negative electrode (204). The positive electrode (202), the negative electrode (204), and the separator (206) are rolled together, forming the jelly roll structure (300). The jelly roll structure (300) includes a first face (302) and a second face (312) disposed at corresponding ends of a longitudinal axis of the jelly roll structure (300). For the purpose of this description and ease of understanding, the first face (302) of the jelly roll structure (300) is considered to correspond to the positive electrode (202) of the electrode assembly (200). However, it is within the scope of this invention to have the first face (302) of the jelly roll structure (300) correspond to the negative electrode (204) of the electrode assembly (200).
[0031] Fig. 5 depicts top view of the electrode assembly (200), according to embodiments as disclosed herein. Fig. 6 depict a magnified view of the electrode assembly (200), according to embodiments as disclosed herein. The first face (302) of the jelly roll structure (300) has an inner portion (304) formed around a center (300C) of the jelly roll structure (300), and an outer portion (306) disposed concentrically outwards of the inner portion (304). In an embodiment, the positive electrode (202) includes a sheet of positive current collector. Fig. 7 depicts a schematic view of the positive electrode (202) of the electrode assembly, according to embodiments as disclosed herein. A portion of the positive current collector is coated with a positive active material, leaving another portion of the positive current collector uncoated. The portion of the positive current collector coated with the positive active material forms a coated portion (202A) of the positive electrode (202), and the other portion of the positive current collector forms the uncoated portion (202B) of the positive electrode (202). The uncoated portion (202B) functions as tabs of the positive electrode (202), providing electrical connectivity between the current collector disc (102) and the coated portion (202A) of the positive electrode (202). The uncoated portion (202B) extends vertically from/along a longitudinal edge (202AL) of the coated portion (202A) for a pre-determined length (L), such that when said positive electrode (202) is rolled to form the jelly roll structure (300), the uncoated portion (202B) is rolled to form the outer portion (306) and a section of the coated portion (202A) is rolled to form the inner portion (304). In an embodiment, the inner portion (304) is formed by rolling a part of the positive electrode (202) including the coated portion (202A) and a section of the uncoated portion (202B). In an embodiment, a length (L’) of the positive electrode (202) ranges from 4000 mm to 3500 mm, and the pre-determined length (L) of said uncoated portion (306) ranges from 1300 mm to 1800 mm, wherein an internal resistance of the battery cell varies from 12 m? to 9 m?. In an embodiment, the length (L’) of the positive electrode (202) is 3588mm, and the pre-determined length (L) of the uncoated portion (202B) is 1700 mm, wherein the internal resistance of the battery cell (100) is 9.6 m?. Further, in an embodiment, a width of the coated portion (202A) is 67mm, and a width of the uncoated portion (202B) is 7mm. The inner portion (304) is adapted to be formed in plane of the first face (302) of the jelly roll structure (300), and the outer portion (306) includes a plurality of tabs (306T) which are adapted to extend perpendicularly from the first face (302) of the jelly roll structure (300). Further, the plurality of tabs (306T) of the outer portion (306) are arranged concentrically from a circumference (300A) of the jelly roll structure (300) towards a center (300C) of said jelly roll structure (300), and up to an outer periphery of the inner portion (304) (as shown in Fig. 6). By providing the plurality of tabs (306T) near the circumference (300A) of the jelly roll structure (300), and the absence of plurality of tabs near the core (200C) of the electrode assembly (200), time required for wetting the electrode assembly (200) with an electrolyte is reduced. The inner portion (304) of the first face (302) of the jelly roll structure (300) provides better flow path for the electrolyte, increasing the penetration of the electrolyte in the electrode assembly (200). In an embodiment, the time required for wetting the electrode assembly (200) of the battery cell (100) with 30 shots of electrolyte, i.e. approximately 28ml to 30ml of electrolyte, ranges from 8 min to 15 min. In an embodiment, a ratio of surface area covered by the inner portion (304) to surface area covered by the outer portion (306) ranges from 1:1 to 9:1. In an embodiment, the ratio of surface areas cover by the inner portion (304) and the outer portion (306) is 7:3.
[0032] Figs. 8A, 8B, 8C, and 9 respectively depict an exploded view, a perspective view, a top view, and a sectional view of the electrode assembly (200) with the current collector disc (102), according to embodiments as disclosed herein. The at least one current collector disc (102) of the secondary cylindrical battery cell (100) is adapted to be received onto the inner portion (304) of the first face (302) of the jelly roll structure (300), such that the outer portion (306) is disposed external to the current collector disc (102), surrounding an outer periphery (102P) of the current collector disc (102). In an embodiment, the current collector disc (102) includes a wall defined on the outer periphery (102P), wherein the wall is adapted to abut the outer portion (306) of the first face (302) of the jelly roll structure (300), when the current collector disc (102) is received onto the inner portion (304). Figs. 10A and 10B respectively depict a close and magnified sectional view of the electrode assembly (200) with the current collector disc (102), according to embodiments as disclosed herein. In an embodiment, the current collector disc (102) is adapted to be connected with the positive electrode (202) by connecting the outer portion (306) with sides of the current collector disc (102), along the outer periphery (102P) of the current collector disc (102). The wall defined on the outer periphery (102P) of the current collector disc (102) allows the plurality of tabs (306T) of the outer portion (306T) to be connected with sides of the current collector disc (102). In an embodiment, the plurality of tabs (306T) are welded with sides of the current collector disc (102), along the outer periphery (102P) of the current collector disc (102). However, it is within the scope of this invention to connect the current collector disc (102) with the outer portion (306) through any other means such as, but not limited to, crimping, and adhesive bonding. In an embodiment, the plurality of tabs (306T) are partially folded towards the outer periphery (102P) of the current collector disc (102) when the outer portion (306) is connected with the current collector disc (102). By connecting the plurality of tabs (306T) with sides of the current collector disc (102), the risk of damaging the electrodes (202, 204) and separator (206) of the electrode assembly (200) is minimized. This reduces the percentage of wastage of the battery cell (100) during the manufacturing process. The throughput of the manufacturing process increases by reducing the possibility of the battery cell (100) failing to meet criteria during a hi-potential testing.
[0033] Fig. 11 is a flowchart depicting a method (400) for assembling the secondary cylindrical battery cell (100), according to embodiments as disclosed herein. The method (400) includes, at step (402), forming the positive electrode (202) with the coated portion (202A) extending along the length (L’) of the positive electrode (202), and the uncoated portion (202B) extending vertically from the longitudinal edge (202AL) of the coated portion (202A) for the pre-determined length (L). In an embodiment, the step (402) includes, forming the sheet of the positive current collector (202C), coating a portion of the positive current collector (202C) with the positive active material, thereby forming the coated portion (202A) of the positive electrode (202), and leaving the longitudinally extending portion of the positive current collector (202C) uncoated, and removing a part of uncoated positive current collector (202C) up to a pre-defined length, thereby forming the uncoated portion (202B) of the positive electrode (202). Further, at step (404), the method (404) includes, rolling the positive electrode (202), the negative electrode (204), and the separator (206) placed between the positive electrode (202) and the negative electrode (204), to form the jelly roll structure (300). Furthermore, the method (400) includes, at step (406), forming, by the uncoated portion (202B) of the positive electrode (202), the outer portion (306) having the plurality of tabs (306T) extending perpendicularly from the first face (302) of the jelly roll structure (300), and forming by a section of the positive electrode (202), the inner portion (304) disposed concentrically inwards of the outer portion (306), in plane of the first face (302) of the jelly roll structure (300). In an embodiment, at step (406), the method includes, forming, by a section of the coated portion (202A) of the positive electrode (202), the inner portion (304) of the first face (302) of the jelly roll structure (300). At step (408), the method (400) includes, placing the current collector disc (102) on the inner portion (304) of the first face (302) of the jelly roll structure (300). The method (400), at step (410) includes, connecting the current collector disc (102) with the outer portion (306). In an embodiment, at step (410), the method (400) includes welding the plurality of tabs (306T) of the outer portion (306) with sides of the current collector disc (102), along the outer periphery (102P) of the current collector disc (102). In an embodiment, the step (410) includes partially folding the plurality of tabs (306T) towards the outer periphery (102P) of the current collector disc (102). Additionally, the method (400), at step (412) includes connecting a second current collector disc (104) with the electrode assembly (200). At step (414), the method (400) includes filling an electrolyte into the electrode assembly (200), wherein the time for wetting the electrode assembly (200) by 30 shots of the electrolyte including about 28ml to 30ml of the electrolyte, ranges from 8 min to 15 min. Moreover, the method (400), at step (416) includes, sealing by a sealing cap (111), the secondary cylindrical battery cell after filling of electrolyte.
[0034] The technical advantages of the secondary cylindrical battery cell (100) and the method (400) for assembling the secondary cylindrical battery cell (100) are as follows. Reduction in time required for wetting the electrode assembly with the electrolyte, thereby reducing the manufacturing time. Better electrolyte infiltration due to increased flow paths available due to absence of tabs near the core of the electrode assembly. Improved efficiency in connecting the current collector disc with the tabs by facilitating welding the current collector with the tabs from sides. Reduction in wastage at manufacturing stage by eliminating damaging of electrodes and separator during welding, thereby increasing throughput of the manufacturing process.
[0035] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modifications within the spirit and scope of the embodiments as described herein.
, Claims:We claim:
1. A secondary cylindrical battery cell (100) comprising:
an electrode assembly (200) comprising a positive electrode (202), a negative electrode (204), and a separator (206) inserted therebetween, rolled together to form a jelly roll structure (300) having a first face (302) and a second face (312) disposed at corresponding ends of a longitudinal axis of said jelly roll structure (300),
wherein said first face (302) of said jelly roll structure (300) has an inner portion (304), and an outer portion (306) disposed concentrically outwards of said inner portion (304), wherein said outer portion (306) comprises a plurality of tabs (306T) extending perpendicularly from said first face (302); and
at least one current collector disc (102), wherein said current collector disc (102) is adapted to be received onto said inner portion (304) of said first face (302) of said jelly roll structure (300),
wherein said outer portion (306) is disposed external to said current collector disc (102), and adapted to be connected with said outer periphery (102P) of said current collector disc (102).
2. The battery cell (100) as claimed in claim 1, wherein said outer periphery (102P) of said current collector disc (102) comprises a wall adapted to abut against said outer portion (306) of said first face (302) of said jelly roll structure (300), when said current collector disc (102) is received onto said inner portion (304).
3. The battery cell (100) as claimed in claim 1, wherein, said inner portion (304) comprises a section of coated portion (202A) of said positive electrode (202), and said outer portion (306) comprises an uncoated portion (202B) of said positive electrode (202).

4. The battery cell (100) as claimed in claim 3, wherein said uncoated portion (202B) extends vertically from a longitudinal edge (202AL) of said coated portion for a pre-determined length (L) such that when said positive electrode (202) is rolled to form the jelly roll structure (300), said uncoated portion (202B) is rolled to form said outer portion (306) which is disposed concentrically outwards of said inner portion (304).
5. The battery cell (100) as claimed in claim 1, wherein said plurality of tabs (306T) of said outer portion (306) are arranged concentrically from a circumference (300A) of said jelly roll structure (300) towards a center (300C) of said jelly roll structure (300), and up to an outer periphery of said inner portion (304).
6. The battery cell (100) as claimed in claim 2, wherein said current collector disc (102) is adapted to be connected with said positive electrode (202) by connecting said plurality of tabs (306T) of said outer portion (306) with sides of said current collector disc (102), along said outer periphery (102P) of said current collector disc (102).
7. The battery cell (100) as claimed in claim 6, wherein said plurality of tabs (306T) are welded with sides of said current collector disc (102), along said outer periphery (102P) of said current collector disc (102).
8. The battery cell (100) as claimed in claim 4, wherein a length (L’) of said positive electrode (202) ranges from 4000 mm to 3500 mm, and wherein said pre-determined length (L) of said uncoated portion (306) ranges from 1300 mm to 1800 mm.
9. The battery cell (100) as claimed in claim 6, wherein said plurality of tabs (306T) are partially folded towards said outer periphery (102P) of said current collector disc (102) when said outer portion (306) is connected with said current collector disc (102).

10. The battery cell as claimed in claim 1, wherein a ratio of surface area covered by said inner portion (304) and surface area covered by said outer portion (306) varies between 1:1 to 9:1.
11. A method (400) for assembling a secondary cylindrical battery cell (100), said method (400) comprising:
forming a positive electrode (202) with a coated portion (202A) extending along a length (L’) of said positive electrode (202), and an uncoated portion (202B) extending vertically from a longitudinal edge (202AL) of said coated portion (202A) for a pre-determined length (L);
rolling said positive electrode (202), a negative electrode (204), and a separator (206) placed between said positive electrode (202) and said negative electrode (204), to form a jelly roll structure (300); and
forming, by said uncoated portion (202B) of said positive electrode (202), an outer portion (306) having a plurality of tabs (306T) extending perpendicularly from a first face (302) of said jelly roll structure (300), and forming by a section of said positive electrode (202), an inner portion (304) disposed concentrically inwards of said outer portion (306), and in plane of said first face (302) of said jelly roll structure (300).
12. The method (400) as claimed in claim 11, wherein said method (400) comprises:
placing a current collector disc (102) on said inner portion (304) of said first face (302) of said jelly roll structure (300);
abutting by a wall defined on an outer periphery (102P) of said current collector disc (102), said outer portion (306) of said first face (302) of said jelly roll structure (300); and
connecting from sides, said current collector disc (102) with said outer portion (306), along said outer periphery of said current collector disc (102).

13. The method (400) as claimed in claim 12, wherein said connecting said current collector disc (102) with said outer portion (306) comprises welding said plurality of tabs (306T) of said outer portion (306) with sides of said current collector disc (102), along said outer periphery (102P) of said current collector disc (102).
14. The method (400) as claimed in claim 11, wherein said forming said positive electrode (202) comprises:
forming a sheet of a positive current collector (202C);
coating a portion of said positive current collector (202C) with a positive active material, thereby forming said coated portion (202A) of said positive electrode (202), and leaving a longitudinally extending portion of said positive current collector (202C) uncoated; and
removing a part of uncoated positive current collector (202C) up to a pre-defined length, thereby forming said uncoated portion (202B) of said positive electrode (202),
wherein a section of said coated portion (202A) of said positive electrode (202) is adapted to be rolled to form said inner portion (304) of said first face (302) of said jelly roll structure (300).
15. The method (400) as claimed in claim 12, wherein said connecting said outer portion (306) with said current collector disc (102) comprises partially folding said plurality of tabs (306T) towards said outer periphery (102P) of said current collector disc (102).
16. The method (400) as claimed in claim 11, wherein said method (400) comprises:
connecting a second current collector disc (104) with said electrode assembly (200); and
filling an electrolyte into said electrode assembly (200), wherein a time for wetting said electrode assembly (200) by a pre-determined quantity of said electrolyte ranging from 28 ml to 30 ml, ranges from 8 min to 12 min.