Description:TECHNICAL FIELD
[001] The embodiments herein generally relate to secondary battery cells and more particularly, to a current collector plate for a secondary cylindrical battery cell which is designed to provide better contact with an electrode tab portion of the cell and ease in opening of a venting portion of the current collector.
BACKGROUND
[002] Generally, in large format cylindrical cells such at 4680, the safety components such as a current interrupt device (CID), and a positive temperature coefficient (PTC) current limiting device are excluded from the cell assembly to improve the overall energy density of the cell. In such cells, a venting portion is provided on a current collector as a primary safety feature. A typical large format cylindrical cell includes a positive electrode, a negative electrode, and a separator that are stacked together and wound to form a jelly roll having positive tabs on one end and negative tabs on the other end. The jelly roll is encased in a casing with a top lid and a current collector plate. The top lid includes a positive terminal that is connected to positive tabs, and the current collector plate includes a negative terminal connected to negative tabs. Additionally, the current collector plate includes a vent designed as a weakened portion. The vent is configured to open when the internal pressure of the casing exceeds a predetermined threshold.
[003] Traditionally, the venting portion of the current collector plate is positioned nearer to a core of the jelly roll or the center of the current collector plate to facilitate maximum connection between the negative tabs and the current collector plate. For instance, the diameter of the venting portion is typically situated close to one-fourth of the overall diameter of the current collector plate. However, it has been observed that the smaller diameter or area of the venting portion is inadequate to generate the necessary force for opening the vent when the internal pressure of the cell reaches a threshold value, thereby compromising the safety of the cell. Moreover, increasing the area of the venting portion to address the insufficiency of force results in a reduction of the contact area between the current collector plate and the negative electrode tab portions. Consequently, this diminishes the electrical connectivity of the cell while elevating the direct current internal resistance, thereby affecting the performance of the cell.
[004] Hence, there exists a necessity for an improvement in current collector plate that facilitates vent operation without compromising the connection between current collector plate and negative tabs for a secondary battery cell, and which alleviates the aforementioned drawbacks.
OBJECTS
[005] The principal object of embodiments herein is to provide a current collector plate for a secondary battery cell which provides improved venting in the cell and better contact with an electrode tab portion of the cell.
[006] Another object of embodiments herein is to provide the current collector plate for the secondary battery cell with a larger venting portion designed to open effectively when a pressure inside the cell reaches above a threshold pressure.
[007] Another object of embodiments herein is to provide a secondary battery cell with the current collector plate.
[008] Another object of embodiments herein is to provide a method for assembling the current collector plate in the secondary battery cell.
[009] 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
[0010] 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:
[0011] Fig. 1 depicts an exploded view of a secondary battery cell, according to embodiments as disclosed herein;
[0012] Fig. 2A depicts an isometric view of a current collector plate, according to embodiments as disclosed herein;
[0013] Fig. 2B depicts a sectional view of the current collector plate, according to embodiments as disclosed herein;
[0014] Fig. 2C depicts a front view of the current collector plate, according to embodiments as disclosed herein;
[0015] Fig. 2D depicts a side view of the current collector plate, according to embodiments as disclosed herein;
[0016] Fig. 3A depicts an exploded view of the current collector plate with an electrode assembly of the secondary battery cell, according to embodiments as disclosed herein;
[0017] Fig. 3B is an isometric view of the current collector plate with the electrode assembly, according to embodiments as disclosed herein;
[0018] Fig. 4 depicts a sectional view of the current collector plate connected with the electrode assembly, according to embodiments as disclosed herein; and
[0019] Fig 5 is flowchart depicting a method for assembling the current collector plate in a secondary battery cell, according to embodiments disclosed herein.
DETAILED DESCRIPTION
[0020] 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.
[0021] The embodiments herein achieve a current collector plate for a secondary battery cell which provides improved venting in the cell and better contact with an electrode tab portion of the cell. Further the embodiments herein achieve a secondary battery cell with the current collector plate. Furthermore, the embodiments herein achieve a method for assembling the current collector plate in the secondary battery cell. Referring now to the drawings Figs. 1 through 5, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[0022] Fig. 1 depicts an exploded view of a secondary battery cell (100), according to embodiments disclosed herein. The secondary battery cell (100) includes an electrode assembly (100A) having a first electrode tab portion (102) and a second electrode tab portion (106), a current collector plate/ anode disc (200), another current collector plate/ cathode disc (300), and a shell (108). 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 current collector plate (200) is adapted to be accommodated on any one of the first electrode tab portion (102) and the second electrode tab portion (106). In an embodiment, the current collector plate (200) is adapted to be accommodated onto the first electrode tab portion (102) of the electrode assembly (200). The first current collector plate (200) is configured to be connected with a first electrode (not shown) of the electrode assembly (100A) by welding the current collector plate (200) with the first electrode tab portion (102). In an embodiment, the first electrode tab portion (102) includes a plurality of tabs (not shown) folded towards a lateral face of the electrode assembly (100A). By welding the current collector plate (200) with the first electrode tab portion (102), the current collector plate (200) is connected with the plurality of tabs of the first electrode tab portion (102), whereby the current collector plate (200) facilitates in providing electrical connectivity between the first electrode of the electrode assembly (100A) and a component of an external circuit. In an embodiment, the first electrode of the electrode assembly (100A) is an anode, wherein the current collector plate (200) is adapted to facilitate connectivity with the anode of the secondary battery cell (100). In an embodiment, the current collector plate (200) is made of steel with a coating of Nickel.
[0023] Further, as shown in Fig. 1, the secondary battery cell (100) includes another current collector plate (300) which is configured to provide electrical connectivity between a second electrode (not shown) of the electrode assembly (100A) and the component of the external circuit. The other current collector plate (300) is connected to the second electrode through the second electrode tab portion (106). In an embodiment, the other current collector plate (300) is connected to a cathode of the electrode assembly (100A). Furthermore, the electrode assembly (100A) with the current collector plate (200) and another current collector plate (300) connected thereon, is adapted to be inserted into the shell (108) of the secondary battery cell (100). A circumference of the current collector plate (200) is connected to sides of the shell (108) of the battery cell (100), thereby connecting the shell (108) with the first electrode of the electrode assembly (100A). In an embodiment, the current collector plate (200) is connected to the sides of the shell (108) by welding. In another embodiment, the current collector plate (200) is connected to the shell (108) by crimping. In yet another embodiment, the current collector plate (200) is formed as a contiguous body from the sides of the shell (108). The secondary battery cell (100) further includes a terminal portion (112), and an isolating member (110). The isolating member (110) is inserted between the terminal portion (112) and the shell (108), and is adapted to electrically isolate the terminal portion (112) from the shell (108). The terminal portion (112) extends from an outside of the shell (108) to an inside of the shell (108), and is adapted to be connected with the other current collector/cathode disc (300). The terminal portion (112) is thereby adapted to facilitate electrical connectivity of the other current collector/ cathode disc (300) with the component of the external circuit.
[0024] Fig. 2A, Fig. 2B, Fig. 2C, and Fig. 2D, respectively depict an isometric view, a sectional view, a front view, and a side view of the current collector plate (200), according to embodiments as disclosed herein. current collector plate (200). The current collector plate (200) includes an outer portion (202), and an inner portion (204). The outer portion (202) is disposed at a first plane (P1), and the inner portion (204) is disposed concentrically inwards of the outer portion (202). The inner portion (204) is disposed at a second plane (P2) such that the second plane (P2) is spaced apart from the first plane (P1) by a vertically defined gap (G) (as shown in Fig. 2B). The inner portion (204) is connected with the outer portion (202) to form an integrated structure. Further, the inner portion (204) includes a venting portion (204V). An outer periphery (204P) of the inner portion (204) is connected with the inner periphery (202P) of the outer portion (202). In an embodiment, the inner portion (204) is connected with the outer portion (202) through the venting portion (204V). The venting portion (204V) is adapted to detach from the current collector plate (200) when a pressure inside the secondary battery cell (100) reaches above a threshold pressure, thereby detaching a portion of the inner portion (204) from the current collector plate (200). The detachment of the portion of the inner portion (204P) from the current collector plate (200) provides an opening in the current collector plate (200), allowing the pressure to be released out of the cell (100), thereby preventing the cell (100) from damage. The venting portion (204V) has a predetermined thickness which is adapted to allow the detachment venting portion (204V) from the inner portion (204). In an embodiment, a thickness of the current collector plate (200) is 0.4 to 0.6mm, and a thickness of the venting portion (204V) is 0.1 to 0.3mm. In an embodiment, the current collector plate (200) is a plate made by stamping process.
[0025] Fig. 3A and Fig. 3B respectively depict an exploded view and an isometric view of the current collector plate (200) connected with the electrode assembly (100A), according to embodiments as disclosed herein. Fig. 4 depicts a sectional view of the current collector plate (200) connected with the electrode assembly (100A) of the secondary battery cell (100), according to embodiments as disclosed herein. As shown in Fig. 4, the outer portion (202) is disposed at the first plane (P1) such that the outer portion (202) of the current collector plate (200) abuts the first electrode tab portion (102) when the current collector plate (200) is connected on the first electrode tab portion (102). Further, the inner portion (204) is disposed at a second plane (P2) such that the inner portion (204) is disposed at the gap (G) from the outer portion (202), when the current collector plate (200) is connected on the first electrode tab portion (102). In an embodiment, the current collector plate (200) is welded with the first electrode tab portion (102) from a core/center of the first electrode tab portion (102) up to a circumference of the first electrode tab portion (102). As the outer portion (202) of the current collector plate (200) abuts with the first electrode tab portion (202), a strong welding connection is achieved at the outer portion (202). Whereas, in the inner portion (204) which is disposed at the gap (G) from the outer portion (202), a weaker welding connection is achieved between the first electrode tab portion (102) and the inner portion (204). Therefore, by using same welding parameters for welding across a diameter of the current collector plate (200), different welding strengths are achieved, wherein the welding strength at the outer portion (202) is higher than the welding strength at the inner portion (204). The positioning of the outer portion (202) at the first plane (P1) and the inner portion (204) at the second plane (P2) allows using the same welding parameters to achieve different welding strengths across the diameter of the current collector plate (200). While, the welding connection across both the inner portion (204) and the outer portion (202) with the first electrode tab portion (102) of the electrode assembly (100) improves the electrical connectivity, the weak welding connection at the inner portion (204) along with the gap (G ) facilitates in providing contact with the plurality of tabs provided on the first electrode tab portion (102) while allowing the venting portion (204V) to detach from the first electrode tab portion (102) when the pressure inside the secondary battery cell (100) reaches the threshold pressure. In an embodiment, the threshold pressure ranges from 20 bar to 30 bar and the gap (G) is maintained at 0.1 to 0.25 mm.
[0026] Further, the inner portion (204) of the current collector plate (200) is designed to have a larger diameter, wherein a ratio of a diameter (204D) of the inner portion (204) (shown in Fig. 1) and a diameter (100D) of the secondary battery cell (100) (shown in Fig. 1) is at least 1:2. The larger diameter of the inner portion (204) along with the gap (G) allows pressure in the secondary battery cell (100) to be distributed more towards the inner portion (204), thereby providing the required thrust to open the venting portion (204V). In an embodiment, the diameter (100D) of the cell (100) is 46mm, and the diameter (204D) of the inner portion (204) is 24mm.Furthermore, the current collector plate (200) includes a central portion (206) defined concentrically inwards of the inner portion (204). The central portion (206) of the current collector plate (200) is adapted to be received into an opening (104) defined centrally along a height of the electrode assembly (100A). The central portion (206) of the current collector plate (200) defines an aperture (206A) which is adapted to facilitate entry of electrolyte into the electrode assembly (100A) of the secondary battery cell (100). Further, the aperture (206A) of the central portion (206) of the current collector plate (200) is adapted to receive a sealing member (114) (as shown in Fig. 1) of the secondary battery cell (100). The sealing member (114) is configured to seal the aperture (206A) of the central portion of the current collector to prevent the electrolyte egressing the electrode assembly (100A).
[0027] Fig. 5 is flowchart depicting a method (400) of assembling a current collector plate (200) in a secondary battery cell (100). The method (400), at step (502) includes placing the current collector plate (200) on the first electrode tab portion (102) of the electrode assembly (100A) of the secondary battery cell (100), wherein the outer portion (202) of the current collector plate (200) abuts with the first electrode tab portion (102), and the inner portion (204) is disposed at the gap (G) from the outer portion (202) of the current collector plate (200). Further, the method (400), at step (504) includes welding the outer portion (202) and the inner portion (204) of the current collector plate (200) with the first electrode tab portion (102) from a center of the first electrode tab portion (102) towards a circumference of the first electrode tab portion (102), wherein the strength of welding at the outer portion (202) of the current collector plate (200) is stronger than the strength of welding at the inner portion (204) of the current collector plate (200). Furthermore, at step (506), the method (400) includes, connecting the current collector plate (200) with a shell (108) of the secondary battery cell (100), wherein the current collector plate (200) is connected to the sides of the shell (108) by any one of welding, and crimping.
[0028] The technical advantages of the current collector plate (200), the secondary battery cell (100) with the current collector plate (200), and the method (400) for assembling the current collector plate in the secondary battery cell are as follows. Providing a larger venting portion provides effective opening of the venting portion by ensuring the pressure is distributed towards the venting portion, thereby providing the required thrust to open the venting portion when the pressure inside the secondary battery cell reaches the threshold pressure. Providing the outer portion and the inner portion at different planes allows to achieve different welding strengths across the diameter of the current collector plate without varying the welding parameter, wherein a weaker welding connection at the inner portion along with the gap provides electrical connectivity with the tabs of the electrode tab portion while ensuring ease in opening of the venting portion, and a strong welding connection at the outer portion facilitates strong and durable electrical connectivity with the tabs of the electrode tab portion. Achieves better electrical contact, reduces direct current internal resistance, and provides enhanced venting operation, without affecting the throughput of the manufacturing process.
[0029] 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 current collector plate (200) for a secondary battery cell (100), said current collector plate (200) comprising:
an outer portion (202) disposed at a first plane (P1); and
an inner portion (204) disposed concentrically inwards of said outer portion (202) at a second plane (P2), wherein said second plane (P2) is spaced apart from said first plane (P1) by a vertically defined gap (G),
wherein said current collector plate (200) is adapted to be connected on a first electrode tab portion (102) of an electrode assembly (100A) of said secondary battery cell (100), wherein each of said outer portion (202) and said inner portion (204) of said current collector plate (200) is connected with the first electrode tab portion (102) of said secondary battery cell (100).
2. The current collector plate (200) as claimed in claim 1, wherein a ratio of a diameter (204D) of said inner portion (204) and a diameter (100D) of said secondary battery cell (100) is at least 1:2.
3. The current collector plate (200) as claimed in claim 1, wherein said current collector plate (200) is adapted to be connected with the first electrode tab portion (102) by welding, wherein a strength of welding at said outer portion (202) is higher than a strength of welding at said inner portion (204).
4. The current collector plate (200), as claimed in claim 1, wherein said inner portion (204) includes a venting portion (204V), wherein said venting portion (204V) has a predetermined thickness adapted to allow detachment of a portion of said inner portion (204) from said current collector plate (200) when a pressure inside said secondary battery cell (100) reaches above a threshold pressure.
5. The current collector plate (200) as claimed in claim 4, wherein said threshold pressure ranges from 20 bar to 30 bar.
6. The current collector plate (200) as claimed in 1, wherein said current collector plate (200) includes a central portion (206) defined concentrically inwards of said inner portion (204), said central portion (206) adapted to be received in an opening (104) defined centrally along a height of the electrode assembly (100A), wherein said central portion (206) defines an aperture (206A) adapted to facilitate entry of electrolyte into the electrode assembly (100A) of said secondary battery cell (100).
7. The current collector plate (200) as claimed in claim 1, wherein said current collector plate (200) is a plate made by stamping process.
8. The current collector plate (200) as claimed in claim 1, wherein said current collector plate (200) is made of steel with a coating of Nickel.
9. The current collector plate (200) as claimed claim 1, wherein said current collector plate (200) has a thickness of 0.4 to 0.6mm, said venting portion (204V) has a thickness of 0.1 to 0.2mm, said diameter (204D) of said inner portion (204) is 24mm, and said diameter (100D) of said secondary battery cell (100) is 46mm.
10. A secondary battery cell (100) comprising:
an electrode assembly (100A) having a first electrode tab portion (102), and a second electrode tab portion (106);
a current collector plate (200) adapted to be connected with said first electrode tab portion (102) of said electrode assembly (100A),
wherein said current collector plate (200) comprises:
an outer portion (202) disposed at a first plane (P1); and
an inner portion (204) disposed concentrically inwards of said outer portion (202) at a second plane (P2), wherein said second plane is spaced apart from said first plane by a vertically defined gap (G),
wherein each of said outer portion (202) and said inner portion (204) of said current collector plate (200) is connected with the first electrode tab portion (102) of said secondary battery cell (100), and wherein
said current collector plate (200) is adapted to be connected with said first electrode tab portion (102) by welding, wherein a strength of welding at said outer portion (202) is higher than a strength of welding at said inner portion (204).
11. The secondary battery cell (100) as claimed in claim 10, wherein said inner portion (204) includes a venting portion (204V), wherein said venting portion (204V) has a predetermined thickness adapted to allow detachment of a portion of said inner portion (204) from said current collector plate (200) when a pressure inside said secondary battery cell (100) reaches above a threshold pressure, wherein said threshold pressure ranges from 20 bar to 30 bar.
12. The secondary battery cell (100) as claimed in claim 10, wherein a ratio of a diameter (204D) of said inner portion (204) and a diameter (100D) of said secondary battery cell (100) is at least 1:2, wherein said diameter (204D) of said inner portion (204) is 24mm, and said diameter (100D) of said secondary battery cell (100) is 46mm.
13. The secondary battery cell (100) as claimed in claim 10, wherein said current collector plate (200) is a plate made of steel with a coating of Nickel.
14. A method (400) for assembling a current collector plate (200) in a secondary battery cell (100), said method (400) comprising:
placing a current collector plate (200) on a first electrode tab portion (102) of an electrode assembly (100A) of said secondary battery cell (100), wherein an outer portion (202) of said current collector plate (200) is disposed at a first plane (P1), and an inner portion (204) of said current collector plate (200) disposed at a second plane (P2), wherein said second plane (P2) is spaced apart from said first plane (P1) by a vertically defined gap (G); and
welding each of said inner portion (204) and said outer portion (202) of said current collector plate (200) with the first electrode tab portion (102) from a center of said first electrode tab portion (102) up to a circumference of said first electrode tab portion (102), wherein said outer portion (202) abuts the first electrode tab portion (102) and said inner portion (204) is disposed at said gap (G) from said outer portion (202) when each of said outer portion (202) and said inner portion (204) of said current collector plate (200) is connected with the first electrode tab portion (102), and wherein a strength of welding at said outer portion (202) is stronger than strength of welding at said inner portion (204).
15. The method (400) as claimed in claim 14, wherein said method (400) includes connecting said current collector plate (200) with a shell (108) of said secondary battery cell (100), wherein said current collector plate (200) is connected to sides of said shell (108) by any one of welding, and crimping.