Description:TECHNICAL FIELD
[001] The embodiments herein generally relate to secondary battery cells and more particularly, to a secondary cylindrical battery cell which has an electrode assembly and current collector plates which are designed to facilitate ease in assembling of the battery cell, and provide better electrolyte infiltration in the electrode assembly.
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 winded 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] Accurate and proper welding of the current collector plates with the tabs of the jelly roll is crucial to ensure electrical continuity within and outside the cell, structural integrity of the cell, and prevent potential points of failure. Inadequate welding can lead to high resistance connections, compromising the efficiency and safety of the battery. Proper alignment of the collector plates with the tabs, the electrode assembly, the casing, and the external connector parts is critical to achieve accurate and strong welding.
[005] After the collector plates are welded with the external connector parts of the cell assembly, 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 and the collector plate design. A densely interleaved pattern of the uncoated portion of the collector foils reduces electrolyte infiltration at the tabs of the jelly roll electrode assembly. Inadequate electrolyte infiltration can result in regions within the cell where the electrolyte does not reach, leading to increased internal resistance. Higher internal resistance can limit the rate at which ions can move within the cell, affecting both charging and discharging rates and overall energy efficiency of the battery cell.
[006] The existing secondary cylindrical cells fail to provide a robust solution wherein the electrolyte infiltration is optimized for a jelly roll assembly with integrated tabs. Furthermore, the cylindrical secondary cells of prior arts have collector plates which are designed to achieve high energy density by compromising on the sturdiness and strength of the current collector plates, thereby affecting the structural integrity and electrical connectivity of the cell. The existing cylindrical cells therefore, lack design optimization which ensures accurate welding of components of the cell assembly, high energy density with low resistance, and better electrolyte infiltration and distribution in the cell.
[007] Therefore, there is a need for a secondary cylindrical battery cell which obviates the aforementioned drawbacks.

OBJECTS
[008] The principal object of embodiments herein is to provide a secondary cylindrical battery cell which is easy to assemble and is designed to allow accurate welding of current collector plates with the electrode assembly of the cell.
[009] Another object of embodiments herein is to provide the secondary cylindrical battery cell which has a first current collector plate which allows better electrolyte infiltration into the electrode assembly, has sturdy structure without affecting the energy density of the cell, provides better connectivity, and accommodates height tolerance during assembling of the cell.
[0010] Another object of embodiments herein is to provide the secondary cylindrical battery cell which has a jelly roll type electrode assembly with electrode tab portions designed to allow better electrolyte infiltration, with locating features which are provided to guide and accommodate the current collector plates onto the tab portions.
[0011] Another object of embodiments herein is to provide a second current collector plate which is designed to be easily connected with the electrode assembly.
[0012] 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
[0013] 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:
[0014] Fig. 1 depicts an isometric view of a secondary cylindrical battery cell, according to embodiments as disclosed herein;
[0015] Fig. 2 depicts an exploded view of the secondary cylindrical battery cell, according to embodiments as disclosed herein;
[0016] Fig. 3A depicts an isometric view of an electrode assembly, according to embodiments as disclosed herein;
[0017] Fig 3B depicts a schematic diagram of a jelly roll type electrode assembly, according to embodiments disclosed herein;
[0018] Fig. 4 depicts an isometric view of a first current collector plate, according to embodiments as disclosed herein;
[0019] Fig. 5A depicts an isometric view of the first current collector plate and the electrode assembly, according to embodiments as disclosed herein;
[0020] Fig. 5B depicts another isometric view of the first current collector plate connected to the electrode assembly, according to embodiments as disclosed herein;
[0021] Fig. 6 depicts an isometric view of a second current collector plate, according to embodiments as disclosed herein;
[0022] Fig. 7A depicts an isometric view of the second current collector plate and the electrode assembly, according to embodiments as disclosed herein; and
[0023] Fig. 7B depicts another isometric view of the second current collector plate connected to the electrode assembly, according to embodiments as disclosed herein.
DETAILED DESCRIPTION
[0024] 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.
[0025] The embodiments herein achieve a cylindrical secondary battery cell which is easy to assemble and is designed to allow accurate welding of current collector plates with the electrode assembly of the cell. Further the embodiments herein achieve the secondary battery cell with an electrode assembly and current collector plates which facilitate better electrolyte infiltration. Referring now to the drawings Figs. 1 through 7B, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[0026] Fig. 1 and Fig. 2 respectively depict an isometric view and an exploded view of a secondary battery cell (100), according to embodiments as disclosed herein. The secondary battery cell (100) includes an electrode assembly (200), a first current collector plate (300), and a second current collector plate (400). For the purpose of this description and ease of understanding, the secondary battery cell (100) is explained herein with below reference to a cylindrical shaped battery cell having a jelly roll type electrode assembly. However, it is also within the scope of the invention to use/practice the components of the secondary battery cell (100) for any other type of secondary battery cell without otherwise deterring the intended function of the secondary battery cell (100) as can be deduced from the description and corresponding drawings. The electrode assembly (200) includes a first electrode tab portion (202), and a second electrode tab portion (204) disposed opposite to the first electrode tab portion (202). The first current collector plate (300) is adapted to be accommodated onto the first electrode tab portion (202) of the electrode assembly (200). The first current collector plate (300) is configured to be connected with a first electrode (not shown) of the electrode assembly (200) by welding the first current collector plate (300) with the first electrode tab portion (202). Therefore, the first current collector plate (300) provides electrical connectivity between the first electrode of the electrode assembly (200) and an outer terminal (not shown) of the secondary battery cell (100). The second current collector plate (400) is adapted to be accommodated onto the second electrode tab portion (204). The second current collector plate (400) is configured to provide electrical connectivity between a second electrode (not shown) of the electrode assembly (200) and an external circuit component (not shown). The second current collector plate (400) is connected to the second electrode through the second electrode tab portion (204). Further, each of the first electrode tab portion (202) and the second electrode tab portion (204) of the electrode assembly (200) has a corresponding locating feature (202F, 204F). The corresponding locating feature (202F, 204F) is adapted to guide the first current collector plate (300) onto the first electrode tab portion (202), and the second current collector plate (400) onto the second electrode tab portion (204). The locating feature (202F, 204F) provides ease in guiding and placing the respective current collector plates (300, 400) onto the respective electrode tab portions (202, 204) of the electrode assembly (200). This facilitates in ease of welding the current collector plates (300, 400) with the electrode assembly (200) by ensuring proper placement and alignment of the current collector plates (300, 400) with respect to the electrode assembly (200).
[0027] Fig. 3A depicts an isometric view of the electrode assembly (200), according to embodiments disclosed herein. Fig. 3B depicts a schematic diagram of the electrode assembly (200) in a form of jelly roll structure (2000), according to embodiments disclosed herein. The electrode assembly (200) includes a first electrode (2002), a second electrode (2202), and separator (2400) interposed therebetween, wherein the first electrode (2002), the second electrode (2202) and the separator (2400) are winded into a roll to form the jelly roll structure (2000). For the purpose of this description and ease of understanding, the first electrode (2002) is considered to be a positive electrode (cathode), and the second electrode (2202) is considered to be a negative electrode (anode). The first electrode (2002) includes an active electrode material coated on a conductive foil, and an uncoated portion (2004). A plurality of first electrode tabs (2006) are formed by fringing the uncoated portion (2004) of the first electrode (2002), such that when the first electrode (2002) is rolled into the jelly roll structure (2000), the plurality of first electrode tabs (2006) extend outside a first end (2008) of a longitudinal side (2000L) of the jelly roll structure (2000), thereby forming the first electrode tab portion (202) of the electrode assembly (200). Similarly, the second electrode (2202) includes another active material coated on another conductive foil, and a corresponding uncoated portion (2204). A plurality of second electrode tabs (2206) are formed by fringing the uncoated portion (2204) of the second electrode (2202), such that the plurality of second electrode tabs (2206) extend outside a second end (2208) of the longitudinal side (2000L) of the jelly roll structure (2000), thereby forming the second electrode tab portion (204) of the electrode assembly (200). As shown in Fig. 3A, a group of the plurality of first electrode tabs (2006) are crushed to form the locating feature (202F) on the first electrode tab portion (202), and a group of second electrode tabs (2206) are crushed to form the locating feature (204F) on the second electrode tab portion (204). In an embodiment, the group of the plurality of first electrode tabs (2006) and the group of the second electrode tabs (2206) are crushed/ folded along two perpendicular diameters of each of a first surface (2000F) and a second surface (2000S) of the jelly roll structure (2000) respectively. In another embodiment, a second group of the plurality of first electrode tabs (2006) positioned along and near a periphery of the first surface (2000F) are left unfolded such that the first electrode tab portion (202) accommodates the first current collector (300) and prevents displacement of the first current collector plate (300) after it has been placed on the first electrode tab portion (202). The pattern of the electrode tabs (2006, 2206) at the electrode tab portions (202, 204), wherein the first group of tabs are folded to form the locating feature (202F, 204F) and the other tabs are left unfolded, allows better electrolyte infiltration into the electrode assembly (200). The unfolded electrode tabs provide space for the electrolyte to reach the separator effectively, thereby enhancing performance of the cell.
[0028] Fig. 4 depicts an isometric view of the first current collector plate (300), according to embodiments disclosed herein. Fig. 5A depicts an isometric view of the first current collector plate (300) and the electrode assembly (200), and Fig. 5B depicts another isometric view of the first current collector plate (300) connected with the electrode assembly (200), according to embodiments disclosed herein. The first current collector plate (300) includes an outer section (302), an inner central section (304), and a plurality of connecting members (306). For the purpose of this description and ease of understanding, the outer section (302) is considered to have an annular profile, and the inner central section (304) is considered to be disc shaped. However, it is within the scope of this invention to have the outer section and the inner central section with any other structure, without otherwise deterring from the intended function of the first current collector plate, as can be deduced from the description and corresponding drawings. The outer section (302) defines the periphery of the first current collector plate (300), and is adapted to be placed in contact with the first electrode tab portion (202). In an embodiment, the outer section (302) is welded with the first electrode tab portion (202). The inner central section (304) is disposed centrally inwards of the outer section (302), and is positioned at a plane higher than a plane of the outer section (302), such that the inner central section (304) is positioned above the first electrode tab portion (202). In an embodiment, the inner central section (304) is positioned above an opening on the first surface (2000F) of the jelly roll structure (2000). Further, the plurality of connecting members (306) extend from the outer section (302) and connect the inner central section (304) with the outer section (302). The plurality of connecting members (306) are adapted to accommodate/ facilitate vertical displacement of the inner central section (304) with respect to the outer section (302). Each of the plurality connecting members (306) has a curvature, wherein the curvature provides elasticity to the connecting member (306), thereby facilitating vertical displacement of the inner central section (304) with respect to the outer section (302). In an embodiment, each of the plurality of connecting members (306) has a S shaped profile.
[0029] The electrode assembly (200), after the current collector plates (300, 400) have been connected with respective electrode tab portions (202, 204), is put in a casing (not shown) and an outer terminal (not shown) is connected with the inner central section (304) of the first current collector plate (300). The flexibility of the connecting members (306) provides the first current collector plate (300) to accommodate height tolerance between the electrode assembly (200) and the casing, thereby providing better connectivity between the electrode assembly (200) and the outer terminal. In an embodiment, each of said plurality of connecting members (306) has an elongated hole (306H) defined in a portion of said connecting member (306) disposed between the outer section (302) and the inner central section (304).
[0030] Further, in an embodiment, the outer section (302) of the first current collector plate (300) has a plurality of indentations (308) corresponding to intersection of the plurality of connecting members (306) and the outer section (302). As shown in Fig. 5A and Fig. 5B, the plurality of indentations (308) are adapted to be received by the corresponding locating feature (202F) provided on the first electrode tab portion (202), thereby guiding the first current collector plate (300) onto the first electrode tab portion (202) of the electrode assembly (200). Furthermore, the outer section (302) has a plurality of holes (310) defined in each of an area disposed between two consecutive indentations (308). The first current collector plate (300) is designed to be sturdy without affecting the energy density of the cell. The sturdiness of the first current collector plate (300) provides ease in handling during assembling of the cell (100), which further reduces the possibility of damage during assembling. Moreover, the plurality of holes (310) provided in the first current collector plate (300) facilitate electrolyte infiltration into the electrode assembly (200), thereby improving the performance of the cell (100).
[0031] Fig. 6 is an isometric view of the second current collector plate (400), according to embodiments disclosed herein. Fig. 7A is an isometric view of the second current collector plate (400) and the electrode assembly (200), and Fig. 7B is another isometric view of the second current collector plate (400) connected with the electrode assembly (200), according to embodiments disclosed herein. The second current collector plate (400) includes a projecting portion (404) extending from an inner surface (402) of the second current collector plate (400). For the purpose of this description and ease of understanding, the second current collector plate (400) is considered to be a disc. However, it is within the scope of this invention to have the second current collector plate (400) with any other construction, without otherwise deterring from the intended function of the second current collector plate (400), as can be deduced from the description and corresponding drawings. The projecting portion (404) of the second current collector plate (400) is received by the corresponding locating feature (204F) on the second electrode tab portion (204), thereby aligning the second current collector plate (400) with the second electrode tab portion (204). In an embodiment, the projecting portion (404) includes a plurality of projecting arms (404A) extending from a boundary of the second current collector plate (400) towards a center of the second current collector plate (400), wherein the plurality of projecting arms (404A) are positioned corresponding to the locating feature (204F). Further, the second current collector plate (400) includes a venting portion (406) positioned radially inwards of the projecting portion (404). A periphery (406P) of the venting portion (406) is depressed with respect to the inner surface (402) of the second current collector plate (400). The venting portion (406) is configured to detach from the second current collector plate (400) when a pressure in the secondary battery cell (100) exceeds a threshold value, allowing pressure built up in the cell (100) to be released outside the cell. In an embodiment, the venting portion (406) detaches from the second current collector plate (400) at a pressure of 20 bar.
[0032] The technical advantages of the secondary battery cell (100) are as follows. The locating feature provided on the electrode assembly, the indentations provided on the first current collector plate, and the projecting portion of the second current collector plate facilitates in accurate alignment of the current collector plates with the electrode assembly, thereby improving accuracy in welding of the current collector plates with the electrode assembly. Further, the tabs of the electrode assembly are folded in a pattern which allows better electrolyte infiltration through the tab portions of the electrode assembly, thereby improving the conductivity and performance of the cell. The construction of the first current collector plate provides sturdiness without affecting energy density of the cell. The first current collector plate further accommodates height tolerance during assembling of the electrode assembly with the casing, thereby ensuring better connectivity. The plurality of holes provided in the first current collector plate allow electrolyte to reach the electrode assembly. Furthermore, the second current collector plate has a venting portion which allows built up pressure to be released from the cell, thereby ensuring safety of the cell.
[0033] 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 battery cell (100), comprising:
an electrode assembly (200) comprising a first electrode tab portion (202), and a second electrode tab portion (204) disposed opposite to said first electrode tab portion (202); and
a first current collector plate (300) adapted to be accommodated onto said first electrode tab portion (202), wherein said first current collector plate (300) is electrically connected with a first electrode (2002) of said electrode assembly (200),
wherein,
said first current collector plate (300) comprises:
an outer section (302) defining a boundary of said first current collector plate (300), said outer section (302) adapted to be placed in contact with said first electrode tab portion (202);
an inner central section (304) disposed centrally inwards of said outer section (302) at a plane higher than a plane of said outer section (302) and positioned above said first electrode tab portion (202); and
a plurality of connecting members (306) extending from said outer section (302) and connecting said inner central section (304) with said outer section (302), wherein said plurality of connecting members (306) are adapted to facilitate vertical displacement of said inner central section (304) with respect to said outer section (302).
2. The battery cell (100) as claimed in claim 1, wherein said first electrode tab portion (202) has a locating feature (202F) which is adapted to guide said first current collector plate (300) onto said first electrode tab portion (202).

3. The secondary battery cell (100) as claimed in claim 1, wherein said secondary battery cell (100) comprises a second current collector plate (400) adapted to be accommodated onto said second electrode tab portion (204), wherein said second current collector plate (400) is electrically connected with a second electrode (2202) of said electrode assembly (200).
4. The secondary battery cell as claimed in claim 3, wherein, said second electrode tab portion (204) has a corresponding locating feature (204F) which is adapted to guide said second current collector plate (400) onto said second electrode tab portion (204).
5. The secondary battery cell (100) as claimed in claim 1, wherein said outer section (302) has a plurality of indentations (308) corresponding to intersection of said plurality of connecting members (306) and said outer section (302), wherein said plurality of indentations (308) are adapted to be received by said corresponding locating feature (202F) provided on said first electrode tab portion (202), thereby guiding said first current collector plate (300) onto said first electrode tab portion (202) of said electrode assembly (200).
6. The secondary battery cell (100) as claimed in claim 5, wherein said outer section (302) has a plurality of holes (310) defined in each of an area (312) disposed between two consecutive indentations (308).
7. The secondary battery cell (100) as claimed in claim 1, wherein said outer section (302) of said first current collector plate (300) is welded onto said first electrode tab portion (202) of said electrode assembly (200).
8. The secondary battery cell (100) as claimed in claim 1, wherein each of said plurality of connecting members (306) has an elongated hole (306H) defined in a portion of said connecting member (306) disposed between said outer section (302) and said inner central section (304).
9. The secondary battery cell (100) as claimed in claim 3, wherein the electrode assembly (200) has a jelly roll structure (2000), wherein a plurality of first electrode tabs (2006) formed by fringing an uncoated portion (2004) of the first electrode (2002) extend outside a first end (2008) of a longitudinal side (2000L) of the jelly roll structure (2000), forming said first electrode tab portion (202), and wherein a plurality of second electrode tabs (2206) formed by fringing an uncoated portion (2204) of the second electrode (2202) extend outside a second end (2208) of the longitudinal side (2000L) of the jelly roll structure (2000), forming said second electrode tab portion (204).
10. The secondary battery cell (100) as claimed in claim 9, wherein a group of said plurality of first electrode tabs (2006) and a group of second electrode tabs (2206) are folded/crushed to form said corresponding locating feature (202F, 204F) at the respective first electrode tab portion (202) and said second electrode tab portion (204).
11. The secondary battery cell (100) as claimed in claim 10, wherein the group of said plurality of first electrode tabs (2006) and the group of said second electrode tabs (2206) are crushed/ folded along two perpendicular diameters of each of a first surface (2000F) and a second surface (2000S) of the jelly roll structure (2000) respectively.
12. The secondary battery cell (100) as claimed in claim 11, wherein a second group of said plurality of first electrode tabs (2006) positioned along and near a periphery of the first surface (2000F) are kept unfolded, such that the first electrode tab portion (202) accommodates the first current collector plate (300) and prevents displacement of the first current collector plate (300) after said first current collector plate (300) has been placed on said first electrode tab portion (202).
13. The secondary battery cell (100) as claimed in claim 4, wherein said second current collector plate (400) has a projecting portion (404) extending from an inner surface (402) of the second current collector plate (400), wherein said projecting portion (404) is received by said corresponding locating feature (204F) defined on said second electrode tab portion (204), thereby guiding said second current collector plate (400) onto said second electrode tab portion (204).
14. The secondary battery cell (100) as claimed in claim 13, wherein said projecting portion (404) comprises a plurality of projecting arms (404A) extending from a boundary of the second current collector plate (400) towards a centre of said second current collector plate (400), wherein the plurality of projecting arms (404A) are positioned corresponding to said locating feature (204F) of said second electrode tab portion (204).
15. The secondary battery cell (100) as claimed in claim 13, wherein said second current collector plate (400) has a venting portion (406) positioned radially inwards of said projecting portion (404), wherein said venting portion (406) is configured to be detached from said second current collector plate (400) when a pressure inside said secondary battery cell (100) reaches a predetermined threshold value.
16. The secondary battery cell (100) as claimed in claim 15, wherein said venting portion (406) detaches from said second current collector plate (400) at a pressure of 20 bar.
17. The secondary battery cell (100) as claimed in claim 3, wherein the first electrode (2002) is a cathode, and the second electrode (2202) is an anode.