Cylindrical secondary batteries

Abstract

The present invention discloses a cylindrical secondary battery, which relates to the field of battery technology. It includes a winding core, a shell, a positive electrode assembly, and a negative electrode assembly. The winding core is arranged in the shell. The positive electrode assembly is arranged at the upper end of the shell and is welded to the positive electrode ear of the winding core. The negative electrode assembly is arranged at the lower end of the shell and is welded to the negative electrode ear of the winding core. The negative electrode assembly includes a negative electrode connecting piece, a negative electrode lower plastic, and a negative electrode substrate that are arranged closely together. The negative electrode lower plastic is spaced between the negative electrode connecting piece and the negative electrode substrate. The negative electrode connecting piece is located at the top and is welded to the negative electrode ear of the winding core. The negative electrode connecting piece passes through the negative electrode lower plastic to be welded to the negative electrode substrate, and the edge of the negative electrode substrate is welded to the bottom edge of the shell. In a cylindrical secondary battery of the present invention, the negative electrode assembly can directly limit the winding core to reduce the gap between the winding core and the negative electrode assembly, improve the internal space utilization of the battery, and further improve the energy density of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a cylindrical secondary battery. Background Art

[0002] The existing structural parts and cell assembly methods of steel shell cylindrical batteries are usually as follows:

[0003] ① Structural parts: The positive terminal adopts the grooving sealing process, and the negative terminal and the shell are integrated with the structure (steel shell 18650 / 21700 structure). On the negative side: after the negative electrode connecting piece is laser welded to the coil core, the negative electrode connecting piece is welded to the bottom of the shell by energy storage welding or bottom penetration welding; on the positive side: after the shell is grooved, the lead-out part of the positive electrode connecting piece is ultrasonically or laser welded to the positive electrode cover plate, and then the positive side cover plate is closed and riveted to seal.

[0004] ② Structural parts: The negative end adopts the groove sealing process, and the positive cover plate is riveted to the shell to form an integrated composite structure. On the positive side, the positive connecting piece and the positive electrode post are welded by torque welding or penetration welding from the top of the post. On the negative side, the negative connecting piece has a raised edge part. Laser welding can be used to weld the negative connecting piece to the inner wall of the shell, or penetration welding can be performed at the grooved part after groove rolling to weld the connecting piece to the inside of the shell, and the negative cover plate is assembled for riveting and sealing.

[0005] In the above two assembly methods, the end cover (positive end cover or negative end cover) is installed on the shell by adopting the rolling groove sealing process, wherein the rolling groove in the rolling groove sealing process refers to the annular limiting groove opened at the opening position of the shell, and the annular limiting groove is recessed toward the inside of the shell. The technicians can set the annular limiting groove at the end edge position of the battery cell to limit the battery cell so as to stably fix the battery cell in the shell.

[0006] However, due to the presence of the annular limiting groove (rolling groove), a cylindrical gap equivalent to the height of the annular limiting groove will inevitably appear between the end face of the battery cell and the corresponding end cover (positive end cover or negative end cover) installed using the rolling groove sealing process, resulting in the inability to fully utilize the internal space of the battery and the inability to further increase the battery energy density; moreover, the battery cell also needs to be connected to the corresponding pole through a bus, which further increases the cost of battery manufacturing materials. Summary of the Invention

[0007] The present invention provides a cylindrical secondary battery, in which the negative electrode connecting piece is directly welded to the negative electrode tab of the winding core and is also closely attached to the negative electrode substrate. The negative electrode assembly can directly limit the winding core to reduce the gap between the winding core and the negative electrode assembly, improve the internal space utilization of the battery, and further increase the energy density of the battery to solve the above-mentioned technical problems.

[0008] The technical solution of the present invention to solve the above problems is: to provide a cylindrical secondary battery, including a winding core, a shell, a positive electrode assembly, and a negative electrode assembly, the winding core is arranged in the shell, the positive electrode assembly is arranged at the upper end of the shell and is welded to the positive electrode ear of the winding core, and the negative electrode assembly is arranged at the lower end of the shell and is welded to the negative electrode ear of the winding core; the negative electrode assembly includes a negative electrode connecting piece, a negative electrode lower plastic, and a negative electrode substrate which are arranged closely to each other, and the negative electrode lower plastic is arranged between the negative electrode connecting piece and the negative electrode substrate, the negative electrode connecting piece is located at the top and is welded to the negative electrode ear of the winding core, and the negative electrode connecting piece passes through the negative electrode lower plastic to be welded to the negative electrode substrate, and the edge of the negative electrode substrate is welded to the bottom edge of the shell.

[0009] Furthermore, the negative electrode connecting sheet is provided with a plurality of structural holes.

[0010] Furthermore, a plurality of explosion-proof through holes are provided on the lower plastic of the negative electrode; at the same time, an explosion-proof notch is provided on the negative electrode substrate, and the explosion-proof notch is located directly below the explosion-proof through holes.

[0011] Furthermore, the negative electrode substrate includes a substrate body and an outer edge boss integrally provided at an edge position of the substrate body. The thickness of the substrate body is 0.01-0.05 mm, and the explosion-proof notch is provided on the substrate body.

[0012] Furthermore, a connecting through hole is provided at the center of the negative electrode lower plastic, and a negative electrode protrusion is correspondingly provided on the negative electrode connecting piece and passes through the connecting through hole to be connected to the negative electrode substrate.

[0013] Furthermore, a positioning groove is provided on the lower plastic of the negative electrode, and the connecting through hole is located in the positioning groove; a positioning piece adapted to the positioning groove is correspondingly provided on the negative electrode connecting piece, and the negative electrode protrusion is correspondingly provided on the positioning piece.

[0014] Furthermore, the positive electrode assembly includes a positive electrode post and a positive electrode connecting piece. A mounting through hole is opened at the upper end of the shell. The positive electrode post is plugged into the mounting through hole. The positive electrode connecting piece is arranged in the shell. The lower end surface of the positive electrode connecting piece is welded to the positive electrode ear of the winding core. A positive electrode protrusion is formed upward in the middle part of the positive electrode connecting piece for welding to the positive electrode post.

[0015] Furthermore, a corresponding accommodating groove for accommodating the positive electrode protrusion is provided at the lower end of the positive electrode column.

[0016] Furthermore, the side wall of the positive electrode column is provided with a step limiting surface for limiting the downward movement of the positive electrode column, and a positive electrode upper plastic is provided between the step limiting surface and the upper end wall of the shell; and also includes a positive electrode lower plastic provided between the upper end surface of the positive electrode connecting piece and the upper end wall of the shell.

[0017] Furthermore, it also includes a liquid injection through hole opened on the positive electrode column, and a sealing member arranged at the liquid injection through hole.

[0018] Furthermore, a plurality of structural holes are also provided on the positive electrode connecting sheet.

[0019] Furthermore, it also includes a sealing ring body arranged in the installation through hole and used to prevent liquid leakage.

[0020] Beneficial effects of the present invention:

[0021] 1. The negative electrode connecting piece is welded to the negative electrode tab of the winding core and is also tightly attached to the negative electrode substrate. At this time, the negative electrode substrate can press against the end face of the winding core through the negative electrode tab, thereby limiting the winding core in the shell; correspondingly, since the negative electrode substrate can directly limit the winding core, the negative electrode substrate and the shell can be directly welded, and the gap between the negative electrode substrate and the end face of the winding core is also basically close to zero, so as to effectively improve the internal space utilization of the battery and further improve the battery energy density.

[0022] 2. The negative electrode substrate adopts a variable wall structure with a thin middle and thick edges, and explosion-proof notches are also provided on the thin plate body (substrate body) of the negative electrode substrate, which can achieve multiple explosion-proof effects.

[0023] 3. The concave positive electrode column is connected to the convex positive electrode connecting piece, which not only saves internal space, but also reduces the weight of structural parts, saves space inside the battery, and improves the battery energy density.

[0024] Fourth, structural through holes are provided on both the positive electrode connecting sheet and the negative electrode connecting sheet, and the electrolyte can penetrate into the winding core through the structural through holes, which can help reduce the weight of the structural parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated into and constitute a part of the specification, illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the present invention. In the drawings, similar reference numerals are used to represent similar elements. The drawings described below are some embodiments of the present invention, but not all. It is clear that those skilled in the art can derive other drawings from these drawings without inventive effort.

[0026] Figure 1 Schematic cross-sectional view of the internal structure of the cylindrical secondary battery of this embodiment;

[0027] Figure 2 for Figure 1 A partial enlarged view of

[0028] Figure 3 for Figure 1 A partial enlarged view of B;

[0029] Figure 4 Schematic cross-sectional view of the structure of the positive electrode column of this embodiment;

[0030] Figure 5 1 is an exploded view and a cross-sectional schematic diagram of the structure of the negative electrode assembly of this embodiment;

[0031] Figure 6 Schematic diagram of the structure of the negative electrode connecting piece of this embodiment;

[0032] Figure 7 Schematic diagram of the cross-sectional structure of the negative electrode substrate of this embodiment;

[0033] 1-winding core, 2-shell, 3-positive electrode assembly, 31-positive electrode column, 311-accommodating groove, 312-step limiting surface, 32-positive electrode connecting piece, 321-positive electrode protrusion, 33-positive electrode upper plastic, 34-positive electrode lower plastic, 35-liquid injection hole, 36-seal, 37-sealing ring, 4-negative electrode assembly, 41-negative electrode connecting piece, 411-structural hole, 412-negative electrode protrusion, 413-positioning piece, 42-negative electrode lower plastic, 421-explosion-proof through hole, 422-connecting through hole, 423-positioning groove, 43-negative electrode substrate, 431-substrate body, 432-outer edge boss, 433-explosion-proof notch. DETAILED DESCRIPTION

[0034] In this specification, directional terms such as up, down, left, right, front, back, front, back, top, and bottom, which are mentioned or may be mentioned, are defined relative to the configurations shown in the accompanying drawings. The terms "inside" and "outside" refer to directions toward or away from the geometric center of a specific component, respectively. These are relative concepts and may vary depending on the location and usage of the component. Therefore, these or other directional terms should not be construed as restrictive.

[0035] See also Figures 1 to 7 A cylindrical secondary battery according to a specific embodiment of the present invention includes a winding core 1, a shell 2, a positive electrode assembly 3, and a negative electrode assembly 4. The shell 2 is a cylindrical pre-nickel-plated steel shell. The winding core 1 is a conventional cylindrical battery cell. The winding core 1 is arranged in the shell 2. The upper end of the shell 2 is provided with a mounting through hole. The positive electrode assembly 3 is correspondingly arranged at the mounting through hole at the upper end of the shell 2. The positive electrode assembly 3 is correspondingly welded to the positive electrode tab of the winding core 1. The lower end of the shell 2 is a circular opening, and the negative electrode assembly 4 is correspondingly welded and installed at the lower end of the shell 2.

[0036] Further, see Figure 3 and Figure 5The negative electrode assembly 4 includes a negative electrode connecting piece 41, a negative electrode lower plastic 42, and a negative electrode substrate 43 that are closely attached to each other. The negative electrode lower plastic 42 is spaced between the negative electrode connecting piece 41 and the negative electrode substrate 43. The negative electrode connecting piece 41 is located at the top and is welded to the negative electrode tab of the winding core 1. The negative electrode connecting piece 41 passes through the negative electrode lower plastic 42 to be welded to the negative electrode substrate 43, and the edge of the negative electrode substrate 43 is welded to the bottom edge of the shell 2.

[0037] Specifically, see Figure 5 、 6 7. The main body of the negative electrode connecting piece 41 is a circular plate, on which a plurality of structural holes 411 are evenly opened. The diameter of the structural holes 411 gradually increases from the center of the circular plate to the outside. This ensures the basic structural strength of the negative electrode connecting piece 41 while further reducing the weight of the negative electrode connecting piece 41 and facilitating the infiltration of the electrolyte.

[0038] A positioning piece 413 is also integrally provided on the edge of the negative electrode connecting piece 41. The positioning piece 413 is a rectangular plate, and a notch for positioning is provided at one diagonal position of the positioning piece 413. Correspondingly, a positioning groove 423 is provided on the negative electrode lower plastic 42. The positioning groove 423 is also rectangular, and a groove edge that adapts to the notch is provided at the corresponding diagonal position of the positioning groove 423. In addition, a negative electrode protrusion 412 is also integrally provided on the positioning piece 413, and a connecting through-hole 422 is provided at the center position of the negative electrode lower plastic 42. To this end, the technician can bend the positioning piece 413 toward the center of the circular plate so that the positioning piece 413 is tightly attached to the lower surface of the negative electrode connecting piece 41, and the negative electrode protrusion 412 is exactly at the center of the circular plate of the negative electrode connecting piece 41 and facing downward. The technician can correspondingly press the negative electrode connecting piece 41 downward against the negative electrode lower plastic 42 so that the positioning piece 413 just enters the positioning groove 423 downward, and further makes the negative electrode protrusion 412 extend into and pass through the connecting through hole 422 to be welded to the negative electrode substrate 43 under the negative electrode lower plastic 42; at this time, the technician controls the thickness of the negative electrode protrusion 412 to further make the negative electrode substrate 43 also tightly attached to the negative electrode lower plastic 42, and then directly welds the negative electrode substrate 43 to the lower end of the shell 2, so that the negative electrode assembly 4 can directly limit the lower end of the core 1 while connecting to the core 1, so as to further reduce the volume of the cavity in the shell 2 and improve the battery energy density.

[0039] Further, see Figure 5 and Figure 7Several explosion-proof holes 421 are evenly distributed around the circumference of the lower plastic material 42 of the negative electrode. Furthermore, arc-shaped explosion-proof notches 433 are provided on the corresponding lower surface of the negative electrode substrate 43, directly below the explosion-proof through-holes 421. Accordingly, when thermal runaway occurs in the cylindrical secondary battery of this embodiment, the gas within the housing 2 can flow from the explosion-proof through-holes 421 to the explosion-proof notches 433 on the negative electrode substrate 43, rapidly dislodging the negative electrode substrate 43 and opening the gas path to prevent battery explosion.

[0040] Moreover, in order to further improve the explosion-proof performance of the negative electrode substrate 43, the negative electrode substrate 43 includes a circular substrate body 431 and an annular outer edge boss 432 integrally arranged at the edge position of the substrate body 431. The thickness of the substrate body 431 is 0.01~0.05mm, the thickness of the outer edge boss 432 is 0.5~0.8mm, and the explosion-proof notch 433 is correspondingly arranged on the substrate body 431.

[0041] In addition, in this embodiment, after the negative electrode substrate 43 is welded to the shell 2, the negative electrode substrate 43 will be conductively connected to the shell 2. At this time, the upper end part of the shell 2 can serve as the negative electrode of the battery, so that the positive and negative electrodes of the battery are at the same end, thereby further reducing the manufacturing cost of the battery module.

[0042] For further information, see Figure 2 and Figure 4 The positive electrode assembly 3 includes a positive electrode post 31 and a positive electrode connecting piece 32. A mounting through hole is provided at the upper end of the shell 2. The positive electrode post 31 is inserted into the mounting through hole. The positive electrode connecting piece 32 is provided in the shell 2. The lower end surface of the positive electrode connecting piece 32 is welded to the positive electrode tab of the winding core 1. A positive electrode protrusion 321 for welding to the positive electrode post is formed upward in the middle part of the positive electrode connecting piece 32. A corresponding accommodating groove 311 for accommodating the positive electrode protrusion 321 is provided at the lower end of the positive electrode post 31.

[0043] Specifically, in this embodiment, the positive electrode column 31 is a cylinder, and the positive electrode column 31 can be inserted and installed in the installation through hole, and the end of the positive electrode column 31 with the accommodating groove 311 extends into the shell 2, and the positive connecting piece 32 is inserted upward into the accommodating groove 311 with the positive protrusion 321 and is welded to the positive electrode column 31.

[0044] It should be noted that in this embodiment, a step limiting surface 312 is provided on the outer wall of the positive electrode column 31 to limit the downward movement of the positive electrode column 31, and the diameter of the positive electrode connecting piece 32 is also larger than the mounting through hole; under normal circumstances, technicians can adjust the distance between the positive electrode connecting piece 32 and the step limiting surface 312 so that the step limiting surface 312 of the positive electrode column 31 and the positive electrode connecting piece 32 cooperate with each other to limit and fix the positive electrode column 31 at the mounting through hole, thereby ensuring the structural stability of the positive electrode of the battery.

[0045] However, in order to be able to set the positive and negative poles at the same end of the battery, when the positive electrode post 31 is inserted into the mounting through hole, a positive electrode upper plastic 33 is further arranged between the step limiting surface 312 of the positive electrode post 31 and the upper surface of the upper end shell wall of the shell 2, and a positive electrode lower plastic 34 is further arranged between the upper end surface of the positive connecting piece 32 and the lower surface of the upper end shell wall of the shell 2. The positive electrode upper plastic 33 and the positive electrode lower plastic 34 are both insulating materials. The positive electrode lower plastic 34 is clamped and fixed by being arranged between the positive connecting piece 32 and the upper end shell wall of the shell 2. The positive electrode lower plastic 34 is clamped and fixed by the step limiting surface 312 of the positive electrode post 31 and the upper end shell wall of the shell 2. The positive electrode lower plastic 34 and the positive electrode lower plastic 34 cooperate with each other to insulate and isolate the positive electrode post 31 from the shell 2 to prevent the battery from short-circuiting.

[0046] In addition, a second step surface is provided on the outer wall of the positive electrode column 31, and the second step surface is located below the step limit surface 312; when the positive electrode column 31 is installed in place, an annular cavity will be generated outside the position of the second step surface, and the upper end surface of the annular cavity extends to the upper end wall of the shell 2, the lower end extends to the upper end surface of the positive electrode connecting piece 32, and the outer side of the ring extends to the hole wall of the center hole of the positive lower plastic 34; at this time, the technicians also set a sealing ring body 37 in the annular cavity, so that the sealing ring body 37 is pressed in the annular cavity to seal the gap between the positive electrode column 31 and the installation through hole, so as to prevent the electrolyte injected into the shell 2 from leaking from the installation through hole.

[0047] Further, see Figure 2 and Figure 4 A liquid injection hole 35 is vertically opened at the center of the positive electrode column 31, and technicians can inject electrolyte into the shell 2 through the liquid injection hole 35; at the same time, a sealing member 36 with a size slightly larger than the liquid injection hole 35 is also provided in the liquid injection hole 35. After the liquid injection is completed, technicians can tighten the sealing member 36 into the liquid injection hole 35 to seal the liquid injection hole 35 to prevent leakage.

[0048] In addition, in order to facilitate the removal of the sealing member 36, a cover structure is provided on the upper end of the sealing member 36, and a countersunk hole for accommodating the cover structure is correspondingly provided on the upper end surface of the positive electrode column 31.

[0049] Any matters not mentioned above are applicable to the prior art.

[0050] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art will appreciate that modifications may be made to the technical solutions described in the above embodiments, or that some of the technical features may be replaced with equivalents; such modifications or replacements do not deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A cylindrical secondary battery, characterized in that: The invention comprises a winding core (1), a shell (2), a positive electrode assembly (3), and a negative electrode assembly (4), wherein the winding core (1) is arranged in the shell (2), the positive electrode assembly (3) is arranged at the upper end of the shell (2) and is welded to the positive electrode ear of the winding core (1), and the negative electrode assembly (4) is arranged at the lower end of the shell (2) and is welded to the negative electrode ear of the winding core (1); the negative electrode assembly (4) comprises a negative electrode connecting piece (41), a negative electrode lower plastic (42), and a negative electrode substrate (43) which are arranged closely to each other, the negative electrode lower plastic (42) is arranged between the negative electrode connecting piece (41) and the negative electrode substrate (43), the negative electrode connecting piece (41) is located at the top and is welded to the negative electrode ear of the winding core (1), the negative electrode connecting piece (41) passes through the negative electrode lower plastic (42) to be welded to the negative electrode substrate (43), and the edge of the negative electrode substrate (43) is welded to the bottom edge of the shell (2).

2. The cylindrical secondary battery according to claim 1, wherein The negative electrode connecting piece (41) is also provided with a plurality of structural holes (411).

3. The cylindrical secondary battery according to claim 1, wherein The negative electrode lower plastic (42) is also provided with a plurality of explosion-proof through holes (421); at the same time, the negative electrode substrate (43) is also provided with explosion-proof notches (433), and the explosion-proof notches (433) are also located directly below the explosion-proof through holes (421).

4. The cylindrical secondary battery according to claim 3, wherein: The negative electrode substrate (43) comprises a substrate body (431) and an outer edge boss (432) integrally arranged at an edge position of the substrate body (431); the thickness of the substrate body (431) is 0.01-0.05 mm, and the explosion-proof notch (433) is provided on the substrate body (431).

5. The cylindrical secondary battery according to claim 1, wherein A connecting through hole (422) is also provided at the center of the negative electrode lower plastic (42), and a negative electrode protrusion (412) is correspondingly provided on the negative electrode connecting piece (41) and passes through the connecting through hole (422) to connect to the negative electrode substrate (43).

6. The cylindrical secondary battery according to claim 5, wherein: The negative electrode lower plastic (42) is further provided with a positioning groove (423), and the connecting through hole (422) is located in the positioning groove (423); the negative electrode connecting piece (41) is correspondingly provided with a positioning piece (413) adapted to the positioning groove (423), and the negative electrode protrusion (412) is correspondingly provided on the positioning piece (413).

7. The cylindrical secondary battery according to claim 1, wherein: The positive electrode assembly (3) comprises a positive electrode column (31) and a positive electrode connecting piece (32). A mounting through hole is provided at the upper end of the shell (2). The positive electrode column (31) is plugged into the mounting through hole. The positive electrode connecting piece (32) is arranged in the shell (2). The lower end surface of the positive electrode connecting piece (32) is welded to the positive electrode tab of the winding core (1). A positive electrode protrusion (321) for welding to the positive electrode column is formed upward in the middle of the positive electrode connecting piece (32).

8. The cylindrical secondary battery according to claim 7, wherein: A corresponding accommodating groove (311) for accommodating the positive electrode protrusion (321) is provided at the lower end of the positive electrode column (31).

9. The cylindrical secondary battery according to claim 7, wherein: The side wall of the positive electrode column (31) is provided with a limiting step for limiting the downward movement of the positive electrode column (31), and a positive electrode upper plastic (33) is provided between the limiting step and the upper end wall of the shell (2); and also includes a positive electrode lower plastic (34) provided between the upper end surface of the positive electrode connecting piece (32) and the upper end wall of the shell (2).

10. The cylindrical secondary battery according to claim 7, wherein: It also includes a liquid injection through hole (35) provided on the positive electrode column (31), and a sealing member (36) provided at the liquid injection through hole (35).

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