Novel high-magnification cylindrical lithium battery

Abstract

The utility model relates to the technical field of batteries, in particular to a novel high-magnification cylindrical lithium battery, which is characterized in that the top of a shell is a positive electrode end, the bottom of the shell is a negative electrode end, the negative electrode end is provided with a welding mark, the welding mark is in an Archimedes spiral line shape, and the welding mode is laser welding. The width of the bonding wire is 0.2-0.3 mm, and the distance between the spiral lines is 1.0-1.5 times of the width of the bonding wire. According to the utility model, the shape distribution of the bonding wires is improved, so that the connection strength and the 360-degree tensile consistency of the battery cell are improved, and the 360-degree tensile capacity of the shell and the collector plate is enhanced.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, and in particular to a novel high-rate cylindrical lithium battery. Background Technology

[0002] In the current technology, the birth of lithium-ion batteries has brought them into modern life. After years of development, they have become a hot research field. They not only make mobile devices more convenient, but also drive the rapid development of the electric vehicle and power tool industries, profoundly impacting energy storage technology. The connection technology between battery current collectors is the core technology to ensure the safety of lithium batteries, playing a role in energy transmission and ensuring the structural strength of the cell, and occupying an important position in the battery assembly process.

[0003] The connections between current collectors in cylindrical lithium batteries mainly include the following: the casing and the negative current collector, the cap and the positive current collector, and the positive and negative current collectors and the cell tabs. The connection between the casing and the negative current collector typically uses laser welding. Conventional welding methods include spot welding and wire welding. While ensuring current carrying capacity, these methods have certain shortcomings in terms of connection strength and heat generation during overcurrent, especially under high-rate charge and discharge requirements. Under the intense vibration conditions of power tools, there are requirements for welding strength and reliability, and the welding area is related to the welding resistance. Utility Model Content

[0004] To address the shortcomings of existing cylindrical lithium batteries in terms of weld connection strength and overcurrent heating, this invention provides a weld structure for high-rate cylindrical lithium batteries that increases connection strength and improves overcurrent heating.

[0005] The technical solution adopted by this utility model to solve its technical problem is:

[0006] A novel high-rate cylindrical lithium battery includes a casing and a bare cell located within the casing. The top of the casing is the positive terminal, and the bottom of the casing is the negative terminal. The negative terminal has a solder mark, which is welded by laser welding. The solder mark is in the shape of an Archimedean spiral, with a solder line width of 0.2 to 0.3 mm and a spiral line spacing of 1.0 to 1.5 times the solder line width.

[0007] Furthermore, the diameter of the innermost spiral of the solder mark is 4 to 6 times the width of the solder line.

[0008] Furthermore, the solder embossing depth is 0.04–0.07 mm.

[0009] Furthermore, the solder penetration depth decreases in a stepwise manner from the outer ring to the inner ring.

[0010] Furthermore, the battery also includes a positive current collector, a bare cell, and a negative current collector. The bare cell is formed by winding the positive electrode sheet, separator, and negative electrode sheet together. The positive current collector is located at the top of the casing, and the negative current collector is located at the bottom of the casing.

[0011] Furthermore, the number of spiral turns is 2.5 to 3.5.

[0012] Furthermore, the weld pool depth between the outer casing and the negative electrode current collector is 0.34 mm to 0.37 mm.

[0013] Furthermore, the width of the weld between the outer casing and the negative electrode current collector is 0.2mm to 0.3mm.

[0014] Furthermore, the aspect ratio of the weld between the outer casing and the negative electrode current collector is 1.13 to 1.85.

[0015] Furthermore, the weld pool depth between the outer casing and the negative electrode current collector is 1 / 4 to 1 / 2 of the thickness of the end cap of the outer casing.

[0016] Furthermore, the ratio of the radius R of the termination point of the outer ring of the solder mark from the center point to the radius r of the starting point of the inner ring of the solder mark from the center point is 2.5 to 3.5.

[0017] Furthermore, the angle between the line connecting the termination point and the center point of the Archimedean spiral and the line connecting the starting point and the center point of the Archimedean spiral is between 0° and 180°, preferably between 165° and 180° or between 0° and 15°.

[0018] Furthermore, the ratio of the radius R of the termination point of the outer ring of the solder mark from the center point of the Archimedean spiral to the radius Rm of the negative end of the bottom of the battery casing is 0.15 to 0.25.

[0019] Furthermore, the distance between the center point of the Archimedes spiral and the center point of the bottom of the outer shell is 0 to 0.6 mm.

[0020] Beneficial effects:

[0021] (1) By improving the shape distribution of the welding wires, the connection strength of the battery cell and the tensile consistency of 360° are increased, and the tensile strength of the casing and the current collector is enhanced.

[0022] (2) On the other hand, the design of the number of welding coils, spacing and spiral diameter is conducive to the conduction of current, ensuring the overcurrent capacity and the heat dissipation uniformity during the overcurrent process, thus improving the heat dissipation during the conduction process and enhancing the safety of the battery.

[0023] (3) The design of different molten pool depths in the inner and outer rings ensures both welding strength and heat input during the welding process, keeping it under control without affecting the safety performance of the battery cell.

[0024] (4) The ratio of the radius of the termination point to the starting point of the solder mark is 2.5 to 3.5, the angle between the two and the line connecting them to the center point is 0° to 180°, and the ratio of the radius of the termination point of the outer ring of the solder mark from the center point of the Archimedes spiral to the radius of the bottom of the battery casing is 0.15 to 0.25. This setting can improve the welding quality, increase the stability of the connection between the current collector and the casing, and improve the ability to carry high-rate current. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the solder mark distribution;

[0027] Figure 2 This is a schematic diagram of the cross-section of a cylindrical lithium battery;

[0028] Figure 3 This is a schematic diagram of the winding of a bare battery cell;

[0029] Figure 4 This is a schematic diagram of the positive electrode structure;

[0030] Figure 5 This is a schematic diagram of the negative electrode.

[0031] Figure 6 Metallographic diagram of the molten pool between the outer shell and the manifold;

[0032] Figure 7 This is a schematic diagram of the solder joint of the negative electrode of the battery of the present invention.

[0033] 1. Positive terminal, 2. Negative terminal, 3. Solder mark, 4. Casing, 5. Positive current collector, 6. Bare cell, 61. Positive electrode sheet, 611. Positive electrode tab area, 612. Positive electrode coating area, 62. Separator, 63. Negative electrode sheet, 631. Negative electrode coating area, 632. Negative electrode tab area, 7. Negative current collector, R, radius of the solder mark termination point from the center point of the Archimedean spiral, r, radius of the solder mark start point from the center point of the Archimedean spiral, α, angle between the line connecting the termination point of the outer ring of the solder mark to the center point of the Archimedean spiral and the line connecting the start point of the inner ring of the solder mark to the center point of the Archimedean spiral, Rm, radius of the negative terminal at the bottom of the battery casing. Detailed Implementation

[0034] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present utility model or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the scope of protection of the present utility model.

[0035] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0036] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0037] In the description of this utility model, it should be understood that the directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this utility model. The directional terms "inner" and "outer" refer to the inner and outer contours of each component itself.

[0038] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0039] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this utility model.

[0040] like Figures 1-7 A soldering structure for a novel high-rate cylindrical lithium battery is disclosed. The top of the casing 4 is the positive terminal 1, and the bottom of the casing 4 is the negative terminal 2. The negative terminal 2 has a soldering mark 3 in the shape of an Archimedean spiral. The welding method is laser welding. The width of the solder line 3 is 0.2-0.3 mm, and the spacing between the spiral lines is 1.0-1.5 times the width of the solder line. This design ensures a certain current-carrying area while simultaneously guaranteeing uniform heat dissipation throughout the battery during current flow.

[0041] The innermost spiral diameter of solder mark 3 is 4 to 6 times the weld line width to ensure that heat dissipation does not accumulate in the innermost ring. The penetration depth of solder mark 3 is 0.04 to 0.07 mm. The relevant dimensional parameters of the solder mark are directly measured from the metallographic or CT images of the cylindrical lithium battery. The penetration depth of solder mark 3 decreases in a stepped manner from the outer ring to the inner ring. The number of spiral turns is 2.5 to 3.5 to ensure a certain welding strength, balancing tensile and torsional forces. Power is controlled in a time-sharing and spatial manner during the welding process. Specifically, as an example, [example follows]. Figure 1 During welding, the laser energy distribution is as follows: high energy in the first two half-circles, decreasing energy in the third and fourth half-circles, stable energy in the fifth half-circle, and decreasing energy again in the sixth half-circle. This energy design across the inner, middle, and outer rings ensures relatively uniform penetration depth. The decreasing energy design from the outside in guarantees penetration depth in each ring while maintaining a certain gradient.

[0042] To ensure welding quality and connection stability, and to improve the ability to carry high-rate current, the ratio of the radius R of the termination point of the weld to the radius r of the termination point of the weld to the center point is 2.5–3.5. The angle α between the line connecting the termination point to the center point of the Archimedean spiral and the line connecting the start point to the center point of the Archimedean spiral is 0°–180°. The ratio of the radius R of the termination point of the outer ring of the weld to the center point of the Archimedean spiral to the radius Rm of the bottom of the battery casing is 0.15–0.25. The weld start point refers to the innermost starting point of the weld, and the weld termination point refers to the outermost ending point of the weld. The distance between the center point of the Archimedean spiral and the center point of the bottom of the casing is 0–0.6 mm.

[0043] The battery also includes a positive current collector 5, a bare cell 6, and a negative current collector 7. The bare cell 6 is formed by winding a positive electrode sheet 61, a separator 62, and a negative electrode sheet 63 together. The positive current collector 5 is located at the top of the casing 4, and the negative current collector is located at the bottom of the casing 4. The positive electrode sheet 61 includes a positive current collector and a positive active material coating applied to at least one surface of the positive current collector. The negative electrode sheet 63 includes a negative current collector and a negative active material coating applied to at least one surface of the negative current collector. The positive current collector is made of aluminum foil with a thickness ranging from 8 to 15 μm, and the negative current collector is made of copper foil with a thickness ranging from 5 to 10 μm. The thickness of the current collector foil greatly helps to improve the energy density of lithium-ion batteries. As power tools place increasingly higher demands on the gravimetric and volumetric energy density of lithium-ion batteries, developing and adopting thinner current collectors is a common need for engineers. In addition to conventional copper or aluminum foil, a new type of current collector using polymer double-sided metallized layers has emerged. Lithium-ion batteries using this new current collector achieve a significantly higher gravimetric energy density and greatly improved battery safety. The single-sided coating thickness of the positive electrode active material ranges from 30 to 150 μm, while that of the negative electrode active material ranges from 40 to 180 μm. The coating thickness of the active material significantly impacts the electrochemical performance of lithium-ion batteries, primarily affecting battery capacity, rate performance, and voltage plateau. The active material coating also influences the utilization efficiency of the positive and negative electrode materials, thus affecting the overall battery capacity. When the coating is thicker, the contact area between the active material and the current collector is smaller, resulting in limited electron conduction paths, increased internal resistance, and negatively impacted rate performance. Conversely, a thinner coating increases the contact area, allowing for smoother electron conduction paths and improving rate performance. However, an excessively thick active material coating increases the diffusion path of lithium ions within the electrode sheet, negatively affecting rate performance. Therefore, this application limits the active material coating within the aforementioned range to optimize the electrochemical performance of the battery. Furthermore, the thickness of the active material coating also significantly impacts the cycle life of lithium-ion batteries. This is mainly reflected in two aspects: firstly, an appropriate coating thickness can mitigate volume changes in the active material during charging and discharging, reducing material breakage and pulverization, thereby extending the battery's cycle life. Secondly, an excessively thick coating increases internal stress in the active material, accelerating material breakage and pulverization, and shortening the battery's cycle life. In addition, an excessively thick coating can also lead to poor internal heat dissipation, increasing the risk of thermal runaway. Therefore, this application controls the thickness of the active material coating within a reasonable range, resulting in excellent cycle life for the lithium-ion battery. The thickness of the active material coating also significantly affects the safety performance of lithium-ion batteries. The impact of the active coating thickness on safety performance is mainly reflected in two aspects: thermal stability and mechanical stability.An appropriate coating thickness can improve the thermal stability of a battery and reduce the risk of thermal runaway. However, an excessively thick coating can lead to heat accumulation inside the battery, increasing the risk of thermal runaway. Furthermore, an excessively thick coating can increase mechanical stress inside the battery, reducing its mechanical stability and increasing the risk of battery rupture and leakage. Therefore, controlling the coating thickness appropriately in this application can improve the safety performance of the battery.

[0044] The structure of the positive electrode 61 is as follows: Figure 4 As shown, the upper part is the positive electrode tab area 611 (uncoated area), and the lower part is the positive electrode coated area 612. The area of ​​the positive electrode tab area 611 accounts for 86% to 99% of the area of ​​the positive electrode current collector. The area of ​​the positive electrode tab area 611 should not be too large, otherwise it will occupy too much of the area of ​​the positive electrode coated area and reduce the utilization rate of the electrode sheet. The area of ​​the positive electrode tab area 611 should not be too small, otherwise it will be difficult to control the positive electrode tab during the flattening or cutting process, and phenomena such as tab breakage and tab folding may occur. The structure of the negative electrode sheet 63 is as follows. Figure 4As shown, the upper part is the negative electrode coating area 631, and the lower part is the negative electrode tab area 632 (uncoated area). The area of ​​the negative electrode tab area 632 accounts for 87% to 99% of the area of ​​the negative electrode current collector. The area of ​​the negative electrode tab area 632 should not be too large, otherwise it will occupy too much area of ​​the negative electrode coating area 631, reducing the utilization rate of the electrode sheet; the area of ​​the negative electrode tab area 632 should not be too small, otherwise it will be difficult to control the negative electrode tab during the flattening or folding process, and phenomena such as tab breakage and tab folding may occur. The full tab design is an innovative tab structure. Its feature is that the entire surface of the electrode sheet is covered by tabs. Compared with the traditional single tab or multi-tab design, the full tab structure greatly reduces the electron transmission distance on the electrode sheet surface, improves electron transmission efficiency, and thus significantly improves the rate performance and charge / discharge efficiency of the battery. The full tab design also has the following advantages: First, it improves the rate performance of the battery. The full-tab design increases the contact area between the tabs and the electrolyte, reducing the electron transport path and thus lowering the battery's internal resistance, significantly improving its rate performance. This makes full-tab batteries perform exceptionally well in high-power devices such as electric vehicles, electric drones, electric cleaning tools (handheld vacuum cleaners, floor scrubbers), power tools (lawn mowers, milling and planing tools), electric golf carts, and electric two-wheelers. Secondly, it provides uniform current distribution. Because the tabs are evenly distributed across the entire electrode surface (usually one side of the positive or negative electrode is entirely used as a tab), the full-tab design effectively avoids current concentration, resulting in a more uniform current distribution during charging and discharging, reducing the internal temperature gradient, and improving battery safety and cycle life. Thirdly, it reduces battery temperature rise. Under high-rate charge and discharge conditions, due to its excellent conductivity, the full-tab battery can charge from 0% to 80% SOC in less than 10 minutes. The maximum discharge rate can reach 25C. Under high-rate charge and discharge conditions, the battery temperature rise is greatly reduced, preventing power tools from overheating and malfunctioning. Fourth, improve the battery's low-temperature charging and discharging capabilities. Because the battery has a full tab design, it has excellent self-heating properties, allowing it to charge and discharge smoothly even at low temperatures, thus preventing situations where the battery cannot be activated due to excessively low ambient temperatures.

[0045] The weld pool depth between the outer casing 4 and the negative electrode current collector 7 is 0.34 mm to 0.37 mm. As the weld pool depth between the outer casing 4 and the negative electrode current collector 7 increases, the connection strength between them increases. However, to avoid welding through the outer casing 4, its thickness also increases, which reduces battery space utilization and further reduces the battery's gravimetric energy density. Therefore, the weld pool depth between the outer casing 4 and the negative electrode current collector 7 needs to be controlled between 0.34 mm and 0.37 mm.

[0046] The width of the weld between the outer casing 4 and the negative current collector 7 is 0.2mm to 0.3mm. As the width of the weld between the outer casing 4 and the negative current collector 7 increases, the connection strength between the outer casing 4 and the negative current collector 7 increases, thereby improving the firmness of the connection between the battery current collector and the outer casing 4.

[0047] The aspect ratio of the weld between the outer casing 4 and the negative electrode current collector 7 is 1.13 to 1.85. The aspect ratio refers to the ratio of the weld pool depth to the weld width. As the aspect ratio of the weld between the outer casing 4 and the negative electrode current collector 7 increases, the connection strength between the outer casing 4 and the current collector increases.

[0048] The weld pool depth between the outer casing 4 and the current collector assembly is between 1 / 4 and 1 / 2 of the thickness of the end cap assembly of the outer casing 4. If the weld pool depth is too large compared to the thickness of the end cap assembly of the outer casing 4, the end cap assembly is prone to being welded through, resulting in poor battery sealing performance and even electrolyte leakage, thus affecting battery safety performance. If the weld pool depth is too small compared to the thickness of the end cap assembly of the outer casing 4, the welding strength between the outer casing 4 and the negative current collector 7 cannot be guaranteed, and even a false weld may occur, leading to dangers such as battery short circuit and fire.

[0049] The above are merely preferred embodiments of this utility model, but the scope of protection of this utility model is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this utility model, based on the technical solution and inventive concept of this utility model, should be included within the scope of protection of this utility model.

Claims

1. A novel high-rate cylindrical lithium battery, comprising a casing (4) and a bare cell located within the casing (4), characterized in that: The top of the outer shell (4) is the positive end (1), the bottom of the outer shell (4) is the negative end (2), the negative end (2) has a solder mark (3), the welding method is laser welding, the solder mark (3) is in the shape of an Archimedean spiral, the width of the solder mark is 0.2~0.3mm, and the spiral spacing is 1.0~1.5 times the width of the solder mark.

2. The novel high-rate cylindrical lithium battery according to claim 1, characterized in that: The diameter of the innermost spiral of the solder mark (3) is 4 to 6 times the width of the solder line.

3. The novel high-rate cylindrical lithium battery according to claim 1, characterized in that: The weld penetration depth of the weld mark (3) is 0.04~0.07mm.

4. The novel high-rate cylindrical lithium battery according to claim 1, characterized in that: The penetration depth of the solder mark (3) decreases in a stepwise manner from the outer ring to the inner ring.

5. The novel high-rate cylindrical lithium battery according to claim 1, characterized in that: The battery also includes a positive current collector (5), a bare cell (6) and a negative current collector (7). The bare cell (6) is formed by winding together a positive electrode sheet (61), a separator (62) and a negative electrode sheet (63). The positive current collector (5) is located at the top of the outer casing (4) and the negative current collector is located at the bottom of the outer casing (4).

6. The novel high-rate cylindrical lithium battery according to claim 1, characterized in that: The spiral has 2.5 to 3.5 turns.

7. The novel high-rate cylindrical lithium battery according to claim 5, characterized in that: The weld pool depth between the outer shell (4) and the negative electrode current collector (7) is 0.34mm~0.37mm.

8. The novel high-rate cylindrical lithium battery according to claim 5, characterized in that: The width of the weld between the outer shell (4) and the negative electrode current collector (7) is 0.2mm~0.3mm.

9. The novel high-rate cylindrical lithium battery according to claim 5, characterized in that: The depth-to-width ratio of the weld between the outer shell (4) and the negative electrode current collector (7) is 1.13~1.

85.

10. The novel high-rate cylindrical lithium battery according to claim 5, characterized in that: The weld depth between the battery casing (4) and the negative electrode current collector (7) is 1 / 4 to 1 / 2 of the thickness of the bottom of the casing (4).

11. The novel high-rate cylindrical lithium battery according to claim 1, characterized in that: The ratio of the radius R of the termination point of the solder mark from the center point of the Archimedean spiral to the radius r of the starting point of the solder mark from the center point is 2.5 to 3.

5.

12. The novel high-rate cylindrical lithium battery according to claim 1, characterized in that: The angle α between the line connecting the end point of the outer ring of the solder mark to the center point of the Archimedean spiral and the line connecting the beginning point of the inner ring of the solder mark to the center point of the Archimedean spiral is 0°~180°.

13. The novel high-rate cylindrical lithium battery according to claim 1, characterized in that: The ratio of the radius R of the termination point of the outer ring of the solder mark from the center point of the Archimedean spiral to the radius Rm of the bottom of the battery casing is 0.15~0.

25.

14. The novel high-rate cylindrical lithium battery according to claim 1, characterized in that: The distance between the center point of the bottom of the outer shell and the center point of the Archimedes spiral is 0~0.6mm.

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