Cylindrical battery, battery pack and electronic device

Abstract

Disclosed in the present application are a cylindrical battery, a battery pack and an electronic device. The cylindrical battery comprises a casing, a cover, an electrode assembly and a current-collecting disk, wherein the cover and the casing form an accommodating space by means of enclosing; the electrode assembly is arranged in the accommodating space; and in the axial direction of the cylindrical battery, the current-collecting disk is arranged between the electrode assembly and the bottom of the casing and is connected to the electrode assembly, and the current-collecting disk has a welding region. In the axial direction of the cylindrical battery, the bottom of the casing comprises a protrusion that protrudes towards the current-collecting disk, the protrusion being welded to the welding region, and the bottom comprises a first portion, a second portion and a third portion, which are connected to one another, the second portion being arranged around the first portion to form the protrusion, and the third portion being arranged around the second portion. In the axial direction of the cylindrical battery, the projection of the protrusion is located within the projection of the current-collecting disk, and the thickness of the first portion is less than the thickness of the third portion. A welding effect between the bottom and the current-collecting disk can be improved, thereby reducing the disconnection between the bottom and the current-collecting disk, improving the connection strength between the bottom and the current-collecting disk, and reducing the welding resistance.

Description

cylindrical batteries, battery packs and electronic devices Technical Field

[0001] This application relates to the field of battery technology, and in particular to a cylindrical battery, a battery pack, and an electronic device. Background Technology

[0002] Cylindrical batteries have advantages such as high automation, low cost and good consistency. As people's living standards improve, the power requirements for cylindrical batteries are also increasing, requiring cylindrical batteries to provide a higher charge and discharge output rate.

[0003] In cylindrical solar cells, laser penetration welding is typically performed at the bottom of the cell casing to electrically connect the bottom of the casing to the internal current collector. However, laser welding from the bottom of the casing is unpredictable and can easily result in poor welding quality, weak welds, and a potential break in the electrical connection between the bottom of the casing and the current collector.

[0004] Summary of the Invention

[0005] This application aims to provide a cylindrical battery, battery pack, and electronic device, with the goal of improving the welding effect between the bottom of the casing and the current collector.

[0006] In order to solve its technical problems, the embodiments of this application adopt the following technical solutions:

[0007] In a first aspect, this application proposes a cylindrical battery, including a casing, a cover, an electrode assembly, and a current collector. The cover and casing enclose a receiving space, and the electrode assembly is disposed within the receiving space. Along the axial direction of the cylindrical battery, the current collector is disposed between the electrode assembly and the bottom of the casing and connects to the electrode assembly. The current collector has a welding area. Along the axial direction of the cylindrical battery, the bottom of the casing includes a protrusion facing the current collector, the protrusion being welded to the welding area. The bottom includes a first part, a second part, and a third part interconnected, the second part surrounding the first part to form the protrusion, and the third part surrounding the second part. Along the axial direction of the cylindrical battery, the projection of the protrusion lies within the projection of the current collector, and the thickness of the first part is less than the thickness of the third part.

[0008] In the above technical solution, the first part, which serves as the welding point to the current collector, is thinner, allowing for easier laser penetration. This results in a tighter bond during laser-through welding, improving welding precision and reducing the risk of breakage between the bottom and the current collector. During laser-through welding, the protrusion formed by the first and second parts melts and fuses with the welding area of ​​the current collector instantly. The thinner first part facilitates full fusion, thus increasing welding strength. Simultaneously, the easier full fusion of the first part reduces minute gaps between the welding interfaces, lowering contact resistance and improving the charge / discharge rate of the cylindrical battery. Furthermore, it facilitates more uniform welding, reducing resistance inhomogeneity and making the welding resistance more stable under different operating conditions. Additionally, the third part is thicker, resulting in higher overall strength. Its surrounding arrangement allows it to bear stress preferentially, protecting the first part and improving the impact resistance of the cylindrical battery.

[0009] In some preferred embodiments, the projection of the welding area along the axial direction of the cylindrical battery lies within the projection of the first portion. This allows the welding area to be located within the plane of the protrusion, enabling better control of the welding position and depth, which is beneficial for improving welding accuracy, weld consistency, and reliability.

[0010] In some preferred embodiments, within the receiving space, a first portion includes a first surface opposite to the current collector, and a third portion includes a third surface opposite to the current collector. Along the axial direction of the cylindrical battery, the first surface extends beyond the third surface. This facilitates the first surface of the first portion fully supporting the current collector, improving the fit between the first surface and the current collector, thereby improving the welding effect and reducing the contact resistance between the protrusion and the current collector.

[0011] In some preferred embodiments, the distance between the first and third surfaces along the axial direction of the cylindrical battery is L, where 0.05mm ≤ L ≤ 0.5mm. This can improve the energy density of the cylindrical battery while increasing the fit between the protrusion and the current collector, thereby improving the welding effect and reducing the contact resistance between the protrusion and the current collector.

[0012] In some preferred embodiments, 0.05mm≤L≤0.3mm can further improve the energy density of the cylindrical cell while improving the welding effect and reducing contact resistance.

[0013] In some preferred embodiments, the second part includes a second surface located within the receiving space. The second surface is arc-shaped and has a radius of R, where L≤R≤3L. This allows the protrusion to fit more closely to the collector plate, effectively disperses stress, and reduces the resistance at the bottom.

[0014] In some preferred embodiments, the flatness of the first surface is T1, and the flatness of the third surface is T3, satisfying that T1≤T3 and T1≤0.005mm. Processing the first surface makes it smoother, which facilitates a better fit between the first surface and the collector plate, reducing the occurrence of incomplete solder joints. Furthermore, limiting T1 to 0.005mm further improves the welding accuracy between the protrusion and the collector plate.

[0015] In some preferred embodiments, along the axial direction of the cylindrical battery, the thickness of the first part is D1, and the thickness of the current collector is D2, satisfying: 0.8D2≤D1≤1.2D2, which can improve the welding effect and reduce the welding resistance while increasing the strength of the bottom of the casing.

[0016] In some preferred embodiments, satisfying 0.4mm≤D1≤0.6mm can further improve the welding effect and give the bottom of the shell higher strength, reducing deformation and tearing at the bottom.

[0017] In some preferred embodiments, the protrusion abuts against the welding area, which can provide pre-pressure between the protrusion and the manifold, significantly reducing the gap between the protrusion and the welding area, so that the protrusion and the welding area fit together fully, improving welding accuracy and reducing contact resistance.

[0018] In some preferred embodiments, along the axial direction of the cylindrical battery, the outer surface of the bottom has a first recess that is recessed towards the current collector, and the first recess is opposite to the convex portion. The first recess positions the welding area of ​​the current collector, and laser penetration welding can be performed directly in the first recess to ensure that the convex portion and the welding area of ​​the current collector are welded accordingly. Furthermore, by providing the first recess on the outer surface of the bottom to form a thinner first portion, it is easier to cold press the casing, thereby improving the production efficiency of the cylindrical battery.

[0019] In some preferred embodiments, located outside the receiving space, the first portion includes a fourth surface facing away from the manifold, the second portion includes a fifth surface facing away from the manifold, and the third portion includes a sixth surface facing away from the manifold. The fourth and fifth surfaces together form a first recess. The included angle between the fifth and fourth surfaces is α1, where 135°≤α1≤150°. This facilitates stress dispersion and reduces the risk of bottom breakage and tearing of the shell. Furthermore, the smoother transition between the fifth and fourth surfaces reduces resistance to metal flow during cold extrusion, making the forming process smoother and improving production efficiency.

[0020] Optionally, the included angle between the fifth and sixth surfaces is α2, where 135°≤α2≤150°.

[0021] In some preferred embodiments, the fourth and sixth surfaces are arranged parallel to each other, which facilitates the welding of the protrusion to the manifold welding area. Furthermore, the parallel arrangement allows the inner bottom wall of the first recess to uniformly withstand pressure from internal electrode components, etc.

[0022] In some preferred embodiments, the first portion is welded to the welding area to form a weld line. The cylindrical battery also includes a seal that is connected to the outer surface of the bottom and is at least partially located within a first recess. Along the axial direction of the cylindrical battery, the seal covers the weld line. The positioning of the first recess facilitates the installation of the seal, and the seal helps protect the welding area, reducing its erosion by external moisture. Furthermore, filling the first recess with the seal provides support and reinforcement, strengthening the bottom of the casing and reducing the risk of deformation when subjected to external impacts or pressure.

[0023] In some preferred embodiments, a liquid injection hole is provided at the bottom, extending through the first part along the axial direction of the cylindrical battery. A sealant covers and seals the liquid injection hole. By sealing the welding wires with the sealant, the liquid injection hole can be sealed simultaneously, improving the production efficiency of the cylindrical battery.

[0024] In some preferred embodiments, along the axial direction of the cylindrical battery, the fourth surface has a second recess recessed towards the current collector. This second recess is configured to open when the gas pressure within the containment space reaches a first threshold, thus connecting the containment space to the outside. Providing the second recess in the thinner first portion makes the portion of the first portion located in the second recess thinner. When the gas pressure in the casing reaches the first threshold, the second recess can be forced open, forming a gas transmission channel connecting the outside to the inside of the casing, reducing the risk of explosion of the cylindrical battery.

[0025] In some preferred embodiments, the cylindrical battery further includes a seal that is connected to the outer surface of the bottom and is at least partially located within the first recess. Along the axial direction of the cylindrical battery, the seal covers a second recess to reduce the accumulation of external dust and impurities within the second recess, thus protecting the second recess and ensuring normal operation of the cylindrical battery. Furthermore, the seal can seal the bottom of the casing.

[0026] In some preferred embodiments, the thickness of the third part along the axial direction of the cylindrical battery is D3, 1.6mm≤D3≤2.0mm, which makes the bottom of the casing have better strength, and the third part is arranged around the first part, so the third part can bear the force first and can protect the first part.

[0027] Secondly, this application proposes a battery pack including a cylindrical battery as described in any of the embodiments of the first aspect above.

[0028] Thirdly, this application proposes an electronic device comprising a cylindrical battery as described in any of the embodiments of the first aspect above; or comprising a battery pack as described in any of the embodiments of the second aspect above.

[0029] Additional aspects and advantages of the embodiments of this application will be described, shown, or illustrated in part by way of implementation of the embodiments of this application in the following description. Attached Figure Description

[0030] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0031] Figure 1 is a schematic diagram of the structure of a cylindrical battery according to some embodiments of this application;

[0032] Figure 2 is an explosion diagram of a cylindrical battery according to some embodiments of this application;

[0033] Figure 3 is a partial cross-sectional view of a cylindrical battery according to some embodiments of this application;

[0034] Figure 4 is a schematic diagram of the structure of the shell and cover of some embodiments of this application;

[0035] Figure 5 is a schematic diagram of the winding structure of the electrode assembly in some embodiments of this application;

[0036] Figure 6 is a magnified view of part A in Figure 3;

[0037] Figure 7 is a schematic diagram of the installation of electrode assembly, current collector and bottom in some embodiments of this application;

[0038] Figure 8 is a schematic diagram of the installation of electrode assembly, current collector and bottom in some embodiments of this application;

[0039] Figure 9 is a magnified view of part B in Figure 8;

[0040] Figure 10 is a schematic diagram of the installation of the seal and the bottom according to another embodiment of this application.

[0041] Explanation of reference numerals in the attached figures:

[0042] 100. Cylindrical battery;

[0043] 10. Shell; 11. Bottom; 11a. Protrusion; 11b. First Recess; 11c. Second Recess; 111. First Part; 1111. First Surface; 1112. Fourth Surface; 112. Second Part; 1121. Second Surface; 1122. Fifth Surface; 113. Third Part; 1131. Third Surface; 1132. Sixth Surface; 12. Main Body; 13. Opening; 14. Receiving Space; 115. Injection Hole;

[0044] 20. Electrode assembly; 21. Positive electrode plate; 22. Negative electrode plate; 23. Separator; 24. Central hole;

[0045] 30. Cover; 31. Plate; 32. Pole post;

[0046] 40. Manifold; 41. Welding area; 42. Through hole;

[0047] 50. Welding wire; 60. Seals;

[0048] X, axial direction. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0050] In this application, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0051] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0052] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0053] The technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0054] In a first aspect, this application proposes a cylindrical battery 100. Referring to Figures 1 to 3, the cylindrical battery 100 includes a housing 10, an electrode assembly 20, a cover 30, and a current collector 40. The cover 30 and the housing 10 enclose a receiving space 14, the electrode assembly 20 is disposed within the receiving space 14, and the current collector 40 is disposed between the electrode assembly 20 and the bottom 11 of the housing 10, and the current collector 40 is electrically connected to the electrode assembly 20 and the bottom 11 of the housing 10.

[0055] The housing 10 can be made of conductive metal materials such as aluminum, aluminum alloy, steel, stainless steel, nickel, copper, or magnesium alloy. This allows the housing 10 to lead out a certain polarity of the cylindrical battery 100, for example, the housing 10 itself can be used as the positive or negative electrode of the cylindrical battery 100. The housing 10 is used to house the electrode assembly 20 and the electrolyte (not shown in the figure). The electrolyte wets the electrode assembly 20 inside the housing 10, thereby causing an electrochemical reaction. Referring to Figures 3 and 4, the housing 10 can be cylindrical (e.g., circular, prismatic, elliptical, etc.). The housing 10 includes a main body 12 and a bottom 11. Along the axial direction X of the cylindrical battery 100, the bottom 11 and the main body 12 are arranged sequentially. An opening 13 can be provided at the end of the main body 12 opposite to the bottom 11. The electrode assembly 20 can be placed inside the housing 10 through the opening 13. The housing 10 can be sealed by covering the opening 13 with the cover 30.

[0056] In the embodiments of this application, the shell 10 may have a single opening, that is, the bottom 11 and the main body 12 are integrally formed. For example, the main body 12 and the bottom 11 are integrally formed by directly extruding metal material using a cold extrusion forming process. During the cold extrusion process, the metal material is subjected to triaxial compressive stress, which can improve the utilization rate of the metal material and improve the overall strength of the shell 10.

[0057] Furthermore, the integrated bottom 11 design, without additional seams or connection points, facilitates better sealing and can withstand greater external pressure and impact. For example, during transportation and storage, the cylindrical battery 100 may be subjected to external forces such as compression and collision, and the integrated bottom 11 design can effectively reduce the risk of deformation or even breakage of the casing 10. Simultaneously, the integrated bottom 11 design reduces the number of steps and complexity in the manufacturing process. Compared to multi-opening or split casings 10, the single-opening structure can reduce welding and splicing processes during production, improving production efficiency and reducing production costs. In other embodiments, the main body 12 of the casing 10 and the bottom 11 are connected separately; that is, the main body 12 is a hollow frame, and the bottom 11 is another cover, which are then connected together by welding or adhesive. In this case, the positive and negative terminals of the cylindrical battery 100 can be led out through the upper and lower covers respectively.

[0058] Referring to Figure 5, the electrode assembly 20 includes a positive electrode 21, a separator 23, and a negative electrode 22. The separator 23, positive electrode 21, separator 23, and negative electrode 22 are sequentially stacked and wound to form a columnar wound electrode assembly 20. The wound battery assembly 20 has a central hole 24, through which electrolyte can enter and then wet the positive electrode 21 and negative electrode 22 from the interior of the electrode assembly 20. Referring further to Figure 3, the electrode assembly 20 is adapted to the housing 10 and is housed within the housing 10.

[0059] Optionally, the positive electrode 21 of the electrode assembly 20 is electrically connected to the cover 30 so that the positive electrode of the cylindrical battery 100 is led out from the cover 30, and the negative electrode 22 of the electrode assembly 20 is electrically connected to the bottom 11 of the housing 10 so that the negative electrode of the cylindrical battery 100 is led out from the bottom 11 of the housing 10.

[0060] For example, the negative electrode 22 of the electrode assembly 20 may have a negative electrode empty foil area (not shown in the figure) without an active material layer, or the negative electrode 22 may be connected to multiple negative electrode tabs (not shown in the figure). The negative electrode empty foil area or the negative electrode tabs may face the bottom 11. By flattening the negative electrode empty foil area or the multiple negative electrode tabs to form a negative electrode flat surface, through-welding can be used to directly connect the bottom 11 to the negative electrode flat surface, thereby leading out the negative electrode through the bottom 11. The positive electrode of the electrode assembly 20 can be similarly configured. By flattening the positive electrode empty foil area (not shown in the figure) or the multiple positive electrode tabs (not shown in the figure) of the positive electrode 21 to form a positive electrode flat surface, the cover 30 can be electrically connected to the positive electrode flat surface, thereby leading out the positive electrode through the cover 30. In some other embodiments, the cover 30 may also lead out the negative electrode, while the bottom 11 of the housing 10 leads out the positive electrode.

[0061] Referring to Figures 2 and 4, after the electrode assembly 20 is placed inside the housing 10, the cover 30 can be directly connected to the opening 13 of the housing 10 to close the opening 13, thereby allowing the housing 10 and the cover 30 to together enclose and form the receiving space 14. The cover 30 can be made of a material similar to the housing 10, such as aluminum, aluminum alloy, steel, stainless steel, nickel, copper, or magnesium alloy, to improve the sealing performance and connection strength between the cover 30 and the housing 10.

[0062] In some implementations, the cover 30 includes a terminal post 32 and a plate 31. The terminal post 32 is disposed on the plate 31 and is electrically connected to the positive electrode tab or positive electrode mating plane through the terminal post 32, thereby leading out the positive electrode through the terminal post 32. The cover 30 and the housing 10, or the terminal post 32 and the housing 10, or the terminal post 32 and the plate 31, can be insulated and sealed, providing sealing performance while insulating the positive and negative electrodes of the cylindrical battery 100.

[0063] Referring to Figure 3, the current collector 40 is disposed inside the housing 10. Along the axial direction X of the cylindrical battery 100, the current collector 40 is electrically connected between the electrode assembly 20 and the bottom 11 of the housing 10. For example, the two sides of the current collector 40 are electrically connected to the electrode assembly 20 and the bottom 11 of the housing 10 respectively by welding. In some embodiments, the housing 10 may include another current collector (not shown in the figure), through which the positive electrode plane of the electrode assembly 20 is electrically connected to the cover 30 or the electrode post 32.

[0064] The current collector 40 effectively collects the current generated inside the cylindrical battery 100 and conducts it evenly and efficiently to the external circuit, ensuring stable and smooth current output and improving the performance and efficiency of the cylindrical battery 100. For example, in high-discharge-rate applications, the current collector 40 can quickly collect and transmit a large amount of current to meet the high-rate charging and discharging requirements of the cylindrical battery 100. Furthermore, the current collector 40 reduces the transmission resistance of current within the cylindrical battery 100, reducing energy loss. The current collector 40 can be made of highly conductive materials, such as copper or aluminum, which effectively reduces resistance. Additionally, the current collector 40 provides mechanical support for the electrode assembly 20, increasing the overall structural strength and stability of the cylindrical battery 100. When the cylindrical battery 100 is subjected to external forces such as vibration and impact, the current collector 40 reduces deformation and damage to the electrode assembly 20. Simultaneously, the current collector 40 provides a more convenient connection point, making the connection between the electrode assembly 20 and the bottom 11 of the housing 10 simpler and more reliable.

[0065] Referring to Figures 6 and 7, along the axial direction X of the cylindrical battery 100, the bottom 11 of the housing 10 includes a protrusion 11a protruding towards the current collector 40. For example, the protrusion 11a can be formed directly on the bottom 11 of the housing 10 using the aforementioned cold extrusion process. The current collector 40 has a welding area 41, and the protrusion 11a faces the welding area 41. The welding area 41 and the protrusion 11a can be welded together by through-welding. The protrusion 11a provides support for the current collector 40, resulting in more thorough and tighter contact with it. This improves the welding accuracy between the bottom 11 and the current collector 40, increases the welding area, and reduces welding resistance. It also facilitates smoother current conduction between the bottom 11 and the current collector 40, reducing energy loss. Furthermore, the protrusion 11a provides a gap space between the current collector 40 and the bottom 11 or between the electrode assembly 20 and the bottom 11, which facilitates the electrolyte to enter the electrode assembly 20 more smoothly through the current collector 40, which is beneficial to improving the charge and discharge rate of the cylindrical battery 100.

[0066] The bottom 11 includes a first portion 111, a second portion 112 (the portion between the two dashed lines in Figure 4), and a third portion 113 that are interconnected. The second portion 112 surrounds the first portion 111 to form a protrusion 11a, and the third portion 113 surrounds the second portion 112. Along the axial direction X of the cylindrical battery 100, the projection of the protrusion 11a lies within the projection of the current collector 40, which facilitates the protrusion 11a as a whole supporting the current collector 40, thereby enabling a more sufficient and tighter contact between the protrusion 11a and the current collector 40. Furthermore, along the axial direction X of the cylindrical battery 100, the thickness of the first portion 111 is less than the thickness of the third portion 113.

[0067] The first part 111, which serves as the welding point to the current collector 40, is thinner, allowing for easier laser penetration. This results in a tighter bond during laser-guided welding, improving welding precision and reducing the likelihood of separation between the bottom 11 and the current collector 40. During laser-guided welding, the protrusion 11a formed by the first part 111 and the second part 112 melts and fuses instantly with the welding area 41 of the current collector 40. The thinner first part 111 facilitates full fusion, thus increasing welding strength. For example, during the use of the cylindrical battery 100, the weld at the bottom 11 needs to withstand internal pressure and external stress; higher welding strength ensures the structural integrity and safety of the cylindrical battery 100.

[0068] Meanwhile, because the first part 111 is easier to fuse fully, the tiny gaps between the weld interfaces can be reduced, thereby lowering the contact resistance and improving the charge / discharge rate of the cylindrical battery 100. Furthermore, more uniform welding is achieved, reducing resistance non-uniformity and making the weld resistance more stable under different operating conditions. This improves the performance reliability of the cylindrical battery 100; for example, during temperature changes, vibration, or long-term use, stable weld resistance ensures that the output voltage and current of the cylindrical battery 100 remain at a relatively constant level.

[0069] In addition, the third part 113 is thicker and has higher overall strength. The third part 113 is arranged around the first part 111, so that the third part 113 can bear the force first and protect the first part 111, thereby improving the impact resistance of the cylindrical battery 100.

[0070] In some embodiments, referring to Figures 6 and 7, along the axial direction X of the cylindrical battery 100, the projection of the welding area 41 lies within the projection of the first portion 111, which allows the welding area 41 to be located within the plane of the protrusion 11a. In the embodiments of this application, confining the welding area 41 within this plane allows for better control of the welding position and welding depth, which is beneficial for improving welding accuracy and enhancing the consistency and reliability of the weld.

[0071] Referring to Figures 7 and 8, within the receiving space 14, the first portion 111 includes a first surface 1111 opposite to the current collector 40, and the third portion 113 includes a third surface 1131 opposite to the current collector 40. Along the axial direction X of the cylindrical battery 100, the first surface 1111 extends beyond the third surface 1131. This allows the first surface 1111 of the first portion 111 to fully support the current collector 40, improving the fit between the first surface 1111 and the current collector 40, thereby improving the welding effect and reducing the contact resistance between the protrusion 11a and the current collector 40. Simultaneously, because the first surface 1111 extends beyond the third surface 1131, a gap space can be formed between the third surface 1131 and the current collector 40, or between the third surface 1131 and the electrode assembly 20. This facilitates smoother entry of the electrolyte into the electrode assembly 20 through the current collector 40, further improving the charge / discharge rate of the cylindrical battery 100.

[0072] In some embodiments, the flatness of the first surface 1111 is T1, and the flatness of the third surface 1131 is T3, satisfying T1≤T3. By processing the first surface 1111, the first surface 1111 becomes flatter, which facilitates a better fit between the first surface 1111 and the collector plate 40, reducing the occurrence of incomplete solder joints. Furthermore, limiting T1 to ≤0.005mm further improves the welding accuracy between the protrusion 11a and the collector plate 40.

[0073] In some other embodiments, referring to FIG8, along the axial direction X of the cylindrical battery 100, the distance between the first surface 1111 and the third surface 1131 is L, 0.05mm≤L≤0.5mm. If the distance between the first surface 1111 and the third surface 1131 is too large, it occupies too much space, affecting the energy density of the cylindrical battery 100; if the distance is too small, the protrusion 11a may have difficulty supporting the current collector 40, resulting in insufficient contact between the protrusion 11a and the current collector 40. In the embodiments of this application, limiting 0.05mm≤L≤0.5mm can improve the energy density of the cylindrical battery 100 while simultaneously improving the contact degree between the protrusion 11a and the current collector 40, thereby improving the welding effect and reducing the contact resistance between the protrusion 11a and the current collector 40. Furthermore, limiting 0.05mm≤L≤0.5mm can also reduce the amount of material used in the housing 10 and reduce the processing difficulty of the housing 10, thereby reducing production costs.

[0074] Furthermore, limiting the thickness to 0.05mm≤L≤0.3mm can improve the welding effect and reduce contact resistance while further increasing the energy density of the cylindrical cell 100.

[0075] In some embodiments, referring to Figures 7 to 9, the second portion 112 includes a second surface 1121 located within the receiving space 14, and the second surface 1121 is arc-shaped. By setting the second surface 1121 to be arc-shaped, an arc transition is achieved between the protrusion 11a and the third portion 113, allowing the protrusion 11a to fit more closely with the current collector 40, resulting in a more uniform stress distribution. When the cylindrical battery 100 is subjected to external impact, vibration, or internal pressure changes, the arc transition can effectively disperse stress, reducing the risk of damage or tearing of the casing 10. Furthermore, the arc transition can reduce the phenomenon of current concentration at the connection between the protrusion 11a and the third portion 113, facilitating a more uniform current distribution at the bottom 11 of the casing 10, which helps to reduce resistance and improve the charge / discharge rate of the cylindrical battery 100. In addition, in this application, the radius of the second surface 1121 is R, and L≤R≤3L is defined, which allows the protrusion 11a to fit more closely with the current collector 40, fully dispersing stress and reducing the resistance of the bottom 11. Wherein, the radius R of the second surface 1121 is the radius of the second surface 1121 in this application, or the radius of the fitted circle on which the second surface 1121 is located.

[0076] In some embodiments, along the axial direction X of the cylindrical battery 100, the thickness of the first portion 111 is D1, and the thickness of the current collector 40 is D2, satisfying: 0.8D2≤D1≤1.2D2. If the first portion 111 is too thick, the laser needs to penetrate a thicker material to complete the welding, which requires higher laser power. If the power of the laser equipment is insufficient to penetrate the excessively thick area, it may lead to insufficient welding, resulting in defects such as incomplete penetration and porosity, which not only reduces the welding strength but also increases the welding resistance. If the first portion 111 is too thin, it is difficult to provide sufficient welding strength. During the use of the cylindrical battery 100, the weld may be subjected to various external forces, which may easily lead to the weld breaking, affecting the performance and safety of the cylindrical battery 100. In this application, limiting 0.8D2≤D1≤1.2D2 can improve the welding effect and reduce the welding resistance while increasing the strength of the bottom 11 of the casing 10. Here, the thickness D2 of the current collector 40 refers to the thickness of the portion of the current collector 40 including the welding area 41.

[0077] Furthermore, 0.4mm≤D1≤0.6mm can further improve the welding effect and make the bottom 11 of the shell 10 have higher strength, reducing the deformation and tearing of the bottom 11.

[0078] Optionally, in some embodiments, the thickness of the third part 113 along the axial direction X of the cylindrical battery 100 is D3, 1.6mm≤D3≤2.0mm, so that the bottom 11 of the housing 10 has better strength, and the third part 113 is arranged around the first part 111, so the third part 113 can bear the force first and can protect the first part 111.

[0079] In some embodiments, the protrusion 11a abuts against the welding area 41, which can provide pre-pressure between the protrusion 11a and the collector plate 40, thereby significantly reducing the gap between the protrusion 11a and the welding area 41, so that the protrusion 11a and the welding area 41 fit together fully, improving welding accuracy and reducing contact resistance.

[0080] In some embodiments, referring to Figures 7 and 10, along the axial direction X of the cylindrical battery 100, the outer surface of the bottom 11 is provided with a first recess 11b recessed toward the current collector 40, and the first recess 11b is disposed opposite to the protrusion 11a. When laser penetration welding is performed on the bottom 11 and the current collector 40, the first recess 11b is provided to position the welding area 41 of the current collector 40, and laser penetration welding can be performed directly on the first recess 11b to make the protrusion 11a correspond to the welding area 41 of the current collector 40 for welding. Furthermore, by providing the first recess 11b on the outer surface of the bottom 11 to form a thinner first portion 111, it is easier to cold press the casing 10, which can improve the production efficiency of the cylindrical battery 100.

[0081] In some embodiments, referring further to FIG6, outside the receiving space 14, a first portion 111 includes a fourth surface 1112 facing away from the manifold 40, a second portion 112 includes a fifth surface 1122 facing away from the manifold 40, and a third portion 113 includes a sixth surface 1132 facing away from the manifold 40. The fourth surface 1112 and the fifth surface 1122 enclose and form a first recess 11b. The included angle between the fifth surface 1122 and the fourth surface 1112 is α1, 135°≤α1≤150°, which means that the fifth surface 1122 is inclined relative to the fourth surface 1112, which facilitates stress dispersion and reduces the risk of breakage and tearing of the bottom 11 of the housing 10. Furthermore, the shape of the inclined transition between the fifth surface 1122 and the fourth surface 1112 is smoother, which can reduce the resistance to the flow of metal material during cold extrusion forming, making the forming process smoother and improving production efficiency.

[0082] Based on the same inventive concept, the included angle between the fifth surface 1122 and the sixth surface 1132 is α2, where 135°≤α2≤150°. This means that the fifth surface 1122 is inclined relative to the sixth surface 1132, which facilitates stress dispersion and reduces the risk of breakage and tearing of the bottom 11 of the shell 10. Furthermore, the transition shape between the fifth surface 1122 and the sixth surface 1132 is smoother, which reduces the resistance to metal flow during cold extrusion forming, making the forming process smoother and improving production efficiency.

[0083] Optionally, the fourth surface 1112 and the sixth surface 1132 are arranged parallel to each other, which is beneficial for welding the protrusion 11a to the welding area 41 of the manifold 40. Furthermore, the parallel arrangement allows the inner bottom wall of the first recess 11b to uniformly bear the pressure from the internal electrode assembly 20, etc. Simultaneously, the parallel arrangement simplifies mold design and processing; for example, in cold extrusion forming processes, parallel structures facilitate high-precision manufacturing. It should be noted that in the embodiments of this application, parallel arrangement is considered acceptable within a certain error range, for example, within a 5° error range.

[0084] In some embodiments, referring to FIG10, the first portion 111 is welded to the welding area 41 to form a weld line 50. The cylindrical battery 100 also includes a seal 60, which is connected to the outer surface of the bottom 11 and is at least partially located within the first recess 11b. Along the axial direction X of the cylindrical battery 100, the seal 60 covers the weld line 50. The positioning of the first recess 11b facilitates the positioning and installation of the seal 60, and the arrangement of the seal 60 helps protect the welding area and reduces the corrosion of the welding area by external moisture. In addition, by filling the first recess 11b with the seal 60, it can provide support and reinforcement, strengthen the bottom 11 of the housing 10, and reduce the risk of deformation of the housing 10 when subjected to external impact or compression. Combined with the above 135°≤α1≤150°, it is beneficial to reduce the gap between the seal 60 and the inner walls of the first recess 11b, thereby improving the sealing effect.

[0085] In some embodiments, the bottom 11 is provided with an injection hole 115. Along the axial direction X of the cylindrical battery 100, the injection hole 115 penetrates the first portion 111, so that the injection hole 115 communicates with the receiving space 14, and the injection hole 115 at least partially overlaps with the through hole 42 opened on the current collector 40 and the central hole 24 of the electrode assembly 20. During injection, the electrolyte can directly enter the through hole 42 of the current collector 40 and the central hole 24 of the electrode assembly 20 through the injection hole 115, which allows the electrolyte to wet the electrode sheet from the inside of the electrode assembly 20, improving the wetting efficiency.

[0086] The sealing element 60 covers and seals the injection hole 115. The first part 111 is relatively thin, making it easier to machine the injection hole 115. Combined with the aforementioned first recess 11b and protrusion 11a, the injection equipment can more accurately position the injection hole 115 during production, improving injection efficiency. Furthermore, since the injection hole 115 is located within the first recess 11b, it can be sealed simultaneously with the sealing element 60 covering the welding line 50, thereby improving the production efficiency of the cylindrical battery 100. The sealing element 60 can be made of sealing pins or rubber stoppers, which can reinforce the strength of the bottom 11 of the casing 10 while sealing the injection hole 115.

[0087] Referring to Figure 10, along the axial direction X of the cylindrical battery 100, the fourth surface 1112 is provided with a second recess 11c that is recessed towards the current collector 40. The second recess 11c is configured to disconnect when the gas pressure in the receiving space 14 reaches a first threshold, thereby connecting the receiving space 14 to the outside. For example, when the cylindrical battery 100 experiences a short circuit or thermal runaway, a large amount of gas will be generated inside the cylindrical battery 100. If the gas is not discharged in time, it may cause the cylindrical battery 100 to explode. In the embodiments of this application, by providing the second recess 11c on the fourth surface 1112 of the bottom 11 of the housing 10, that is, by providing the second recess 11c on the first part 111 with a smaller thickness, the portion of the first part 111 located in the second recess 11c can be made thinner. When the gas pressure value of the housing 10 reaches the first threshold, the second recess 11c can be forced open, forming a gas transmission channel connecting the outside and the inside of the housing 10, thereby reducing the explosion risk of the cylindrical battery 100.

[0088] In some embodiments, the seal 60 is connected to the outer surface of the bottom 11, and the seal 60 is at least partially located within the first recess 11b. Along the axial direction X of the cylindrical battery 100, the seal 60 covers the second recess 11c to reduce the accumulation of external dust and impurities within the second recess 11c, thus protecting the second recess 11c and ensuring the normal operation of the cylindrical battery 100. Furthermore, the seal 60 can seal the bottom 12 of the housing, and the welding of the protrusion 11a to the current collector 40 only needs to achieve the function of electrical connection, which can effectively reduce the risk of battery leakage.

[0089] Secondly, this application also proposes a battery pack including a cylindrical battery 100 as described in any of the embodiments of the first aspect above. The battery pack can be configured with multiple cylindrical batteries 100 connected in series or in parallel, thereby improving the charge and discharge rate.

[0090] Thirdly, this application also proposes an electronic device, including a cylindrical battery 100 as described in any embodiment of the first aspect above, or a battery pack as described in any embodiment of the second aspect above. The electronic device in this application is not particularly limited and can be any electronic device known in the prior art. For example, electronic devices include, but are not limited to, Bluetooth headsets, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0091] Experiment 1: Preparation of Lithium-ion Batteries

[0092] Example 1

[0093] <Preparation of the positive electrode>:

[0094] The positive electrode active material is lithium iron phosphate, the positive electrode conductive agent is acetylene black, and the positive electrode binder is polyvinylidene fluoride (PVDF, with a weight average molecular weight of 5×10⁻⁶). 5 The materials were mixed at a mass ratio of 94:3:3, with N-methylpyrrolidone (NMP) added as a solvent to prepare a positive electrode slurry with a solid content of 75 wt%. The slurry was then stirred uniformly under vacuum. An 8 μm thick aluminum foil was used as the positive electrode current collector. The positive electrode slurry was uniformly coated onto one surface of the foil, leaving an uncoated area. The foil was dried at 110°C to obtain a positive electrode sheet with a single-sided coating of the positive electrode active material layer. The above steps were then repeated on the other surface of the same aluminum foil to obtain a positive electrode sheet with a double-sided coating of the positive electrode active material layer. The coating weight of the positive electrode sheet was 25 mg / cm³. 2 .

[0095] <Preparation of Negative Electrode Sheets>

[0096] Graphite powder (negative electrode active material), conductive carbon black (Super P) (conductive agent), and styrene-butadiene rubber (SBR) (binder) were mixed in a weight ratio of 97.5:1:1.5. Deionized water was then added as a solvent to prepare a negative electrode slurry with a solid content of 50 wt%, and the mixture was stirred evenly. A 6 μm thick copper foil was used as the negative electrode current collector. The negative electrode slurry was uniformly coated onto one surface of the copper foil, leaving an uncoated area. The foil was dried at 90°C to obtain a single-sided negative electrode sheet. This completes the single-sided coating of the negative electrode sheet. The same steps were then repeated on the other surface of the negative electrode sheet to obtain a double-sided coated negative electrode sheet. The coating weight of the negative electrode sheet was 6.5 mg / cm³. 2 .

[0097] <Preparation of the separating membrane>

[0098] A porous polyethylene (PE) film with a thickness of 7 μm was used as the separator.

[0099] <Electrolyte Preparation>

[0100] In a dry argon atmosphere, ethylene carbonate, methyl ethyl carbonate and diethyl carbonate were mixed in a mass ratio of 30:50:20 to obtain an organic solution. Then, lithium hexafluorophosphate was added to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0101] <Shell Preparation>

[0102] A single-opening aluminum cylindrical shell was fabricated using a cold extrusion process. The shell's bottom comprises a first part, a second part, and a third part arranged circumferentially. The first and second parts are recessed inwards to form a first concave portion on the outer surface of the bottom and a convex portion within the shell. The first part has a thickness D1 of 0.3 mm, the third part has a thickness D3 of 1.6 mm, and the convex portion has a protrusion height L of 0.1 mm.

[0103] <Preparation of Lithium-ion Batteries>

[0104] The prepared separator, positive electrode sheet, separator, and negative electrode sheet are stacked in sequence and wound to form an electrode assembly. The electrode assembly is then hot-pressed (pressure 5 MPa, temperature 65°C, holding time 10 s). Each empty positive electrode foil area is flattened to form a flat positive electrode surface, and each empty negative electrode foil area is flattened to form a flat negative electrode surface, with the central hole exposed on each flat surface. A negative electrode current collector with a thickness D2 of 0.5 mm is welded to the flat negative electrode surface of the electrode assembly, and the positive electrode current collector is welded to the flat positive electrode surface. The assembly is placed in a cylindrical shell, and the other side of the positive electrode current collector is welded to the cover, sealing the shell with the cover. Laser penetration welding is used at the bottom of the shell to weld the bottom of the shell to the negative electrode current collector. After removing moisture at 80°C, electrolyte is injected, the assembly is sealed, and a heat-shrink film is fitted.

[0105] The relevant parameters in Examples 2 to 19 and Comparative Example 1 are shown in Table 1 below.

[0106] Drop test method: The lithium-ion battery was pretreated at 25°C and left to stand at room temperature for 60 minutes. Then, the lithium-ion battery was placed in a fixture and dropped freely from a height of 1m above the ground using a drop device in the following order: head-bottom-cylindrical surface-head horn-tail horn (angle: 45±15°), repeated 10 times. After the drop test, the battery was left to stand at room temperature for 24 hours. The lithium-ion battery was then disassembled to observe the degree of detachment between the bottom and the current collector. A broken bottom or a disconnection between the bottom and the current collector was considered a drop failure. 50 lithium-ion batteries were tested in each example and comparative example. The number of lithium-ion batteries that failed the test was X, and the failure rate was X / 50.

[0107] Table 1

[0108] According to Table 1 above, and in conjunction with Examples 1 to 19 and Comparative Example 1, it can be seen that when the thickness of the first part is less than the thickness of the third part, the drop failure rate of the lithium-ion battery can be reduced. This is because the first part, as the location for welding to the current collector, is thinner, allowing the laser to penetrate more easily. During laser penetration welding, a tighter bond can be formed, improving welding precision and reducing the risk of breakage between the bottom and the current collector. During laser penetration welding, the protrusion formed by the first and second parts melts and fuses with the welding area of ​​the current collector instantly. The thinner first part is more likely to achieve sufficient fusion, thereby increasing welding strength and reducing the risk of drop failure of the lithium-ion battery.

[0109] In Examples 1 to 5, the drop failure rates of Examples 2 to 4 are lower than those of Examples 1 and 5. In Example 1, the first part may be thinner and weaker, potentially leading to tearing and disconnection of the electrical connection between the bottom and the current collector. In Example 5, the first part is thicker, which may hinder laser penetration or melting, affecting the welding effect. In Examples 2 to 4, the first part has a moderate thickness, allowing for laser penetration and providing higher strength, thus reducing the risk of drop failure in lithium-ion batteries. Therefore, in the embodiments of this application, the thickness D1 of the first part is preferably 0.4 mm ≤ D1 ≤ 0.6 mm.

[0110] In Examples 6 to 9, the drop failure rates of Examples 7 and 8 are lower than those of Examples 6 and 9. In Example 6, the thickness of the third part is relatively small, which may lead to insufficient overall strength of the casing, making it difficult for the third part to effectively protect the first part. During drop tests, the first part may also break. In Example 9, the thickness of the third part is relatively large, affecting the energy density of the lithium-ion battery. Furthermore, the larger thickness results in greater kinetic energy during a drop, which may cause significant movement of the electrode assembly within the casing and could also lead to the electrical connection between the third part and the current collector being broken. In conjunction with Examples 7, 8, and 3, in the embodiments of this application, the thickness D3 of the third part is preferably 1.6 mm ≤ D3 ≤ 2 mm.

[0111] In Examples 10 to 19, the drop failure rates of Examples 11 to 18 are lower than those of Examples 10 and 19. In Example 10, the protrusion height of the convex part is too small, which may make it difficult to fully support the collector plate, resulting in insufficient contact force between the convex part and the collector plate, potentially causing welding gaps and affecting the welding strength between the bottom and the collector plate. In Example 19, the protrusion height is too large, which may lead to poor stress distribution, and excessive height may result in weak convex part strength, thus affecting the welding strength. In Examples 11 to 18, the drop failure rate is relatively small. Therefore, in the embodiments of this application, the protrusion height L of the convex part (i.e., the axial distance between the first surface and the third surface) can be selected as 0.05mm ≤ L ≤ 0.5mm.

[0112] In Examples 11 to 15, the drop failure rate is lower and the impact on the energy density of the lithium-ion battery is smaller. In the embodiments of this application, the protrusion height L of the protrusion is preferably 0.05mm≤L≤0.3mm.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them; under the concept of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of this application as described above, which are not provided in detail for the sake of brevity; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A cylindrical battery, characterized in that, include: case; A cover, the cover and the shell enclosing and forming an accommodating space; An electrode assembly is disposed within the accommodating space; A current collector, along the axial direction of the cylindrical battery, is disposed between the electrode assembly and the bottom of the housing and connects the electrode assembly; the current collector has a welding area. Along the axial direction of the cylindrical battery, the bottom of the housing includes a protrusion protruding toward the current collector, the protrusion being welded to the welding area, and the bottom including a first part, a second part, and a third part connected to each other, the second part being disposed around the first part to form the protrusion, and the third part being disposed around the second part; Along the axial direction of the cylindrical battery, the projection of the protrusion lies within the projection of the current collector, and the thickness of the first portion is less than the thickness of the third portion.

2. The cylindrical battery according to claim 1, characterized in that, Along the axial direction of the cylindrical battery, the projection of the welding area lies within the projection of the first portion.

3. The cylindrical battery according to claim 1 or 2, characterized in that, Located within the accommodating space, the first portion includes a first surface opposite to the current collector, and the third portion includes a third surface opposite to the current collector. Along the axial direction of the cylindrical battery, the first surface extends beyond the third surface.

4. The cylindrical battery according to claim 3, characterized in that, Along the axial direction of the cylindrical battery, the distance between the first surface and the third surface is L, where 0.05mm ≤ L ≤ 0.5mm.

5. The cylindrical battery according to claim 4, characterized in that, 0.05mm≤L≤0.3mm.

6. The cylindrical battery according to claim 4 or 5, characterized in that, The second part includes a second surface located within the receiving space, the second surface being arc-shaped and having a radius of R, where L≤R≤3L.

7. The cylindrical battery according to any one of claims 3 to 6, characterized in that, The flatness of the first surface is T1, and the flatness of the third surface is T3, satisfying that: T1≤T3, and T1≤0.005mm.

8. The cylindrical battery according to any one of claims 1 to 7, characterized in that, Along the axial direction of the cylindrical battery, the thickness of the first part is D1, and the thickness of the current collector is D2, satisfying: 0.8D2≤D1≤1.2D2.

9. The cylindrical battery according to claim 8, characterized in that, It satisfies: 0.4mm≤D1≤0.6mm.

10. The cylindrical battery according to any one of claims 1 to 9, characterized in that, The protrusion abuts against the welding area.

11. The cylindrical battery according to any one of claims 1 to 10, characterized in that, Along the axial direction of the cylindrical battery, the outer surface of the bottom is provided with a first recess that is recessed toward the current collector, and the first recess is opposite to the protrusion.

12. The cylindrical battery according to claim 11, characterized in that, Located outside the receiving space, the first part includes a fourth surface facing away from the collecting plate, the second part includes a fifth surface facing away from the collecting plate, and the third part includes a sixth surface facing away from the collecting plate. The fourth surface and the fifth surface together form the first recess. The angle between the fifth surface and the fourth surface is α1, 135°≤α1≤150°; and / or, the angle between the fifth surface and the sixth surface is α2, 135°≤α2≤150°.

13. The cylindrical battery according to claim 12, characterized in that, The fourth surface is arranged parallel to the sixth surface.

14. The cylindrical battery according to any one of claims 11 to 13, characterized in that, The first part is welded to the welding area to form a weld line; The cylindrical battery includes a seal that is connected to the outer surface of the bottom, and the seal is at least partially located within the first recess. Along the axial direction of the cylindrical battery, the seal covers the bonding wire.

15. The cylindrical battery according to claim 14, characterized in that, The bottom is provided with a liquid injection hole, which extends through the first part along the axial direction of the cylindrical battery, and the sealing element covers and seals the liquid injection hole.

16. The cylindrical battery according to any one of claims 11 to 15, characterized in that, Along the axial direction of the cylindrical battery, the fourth surface is provided with a second recess that is recessed toward the current collector. The second recess is configured to disconnect when the air pressure in the containment space reaches a first threshold, thereby connecting the containment space to the outside.

17. The cylindrical battery according to claim 16, characterized in that, The cylindrical battery also includes a seal that is connected to the outer surface of the bottom and is at least partially located within the first recess; Along the axial direction of the cylindrical battery, the seal covers the second recess.

18. The cylindrical battery according to any one of claims 1 to 17, characterized in that, Along the axial direction of the cylindrical battery, the thickness of the third part is D3, where 1.6mm ≤ D3 ≤ 2.0mm.

19. A battery pack, characterized in that, Including the cylindrical battery as described in any one of claims 1 to 18.

20. An electronic device, characterized in that, The electronic device comprises a cylindrical battery as described in any one of claims 1 to 18; or, the electronic device comprises a battery pack as described in claim 19.

Images