Ultra-thin metal shell secondary battery

Abstract

This invention belongs to the field of lithium-ion battery technology, specifically relating to an ultra-thin metal-cased secondary battery, comprising: a metal casing, a positive electrode post assembly, an electrode assembly, and a lower casing; the electrode assembly is formed using a stacking or winding process, and has a positive current collector and a negative current collector formed by welding uncoated current collectors; the metal casing consists of an upper cover and a lower casing, wherein at least one casing component forms a recessed structure inward into the battery at a position corresponding to the current collector; the positive electrode post assembly is installed within the recessed structure and insulated from the casing by an insulating seal, and its outer surface does not protrude from the outer surface of the casing component; the negative current collector is electrically connected to a connection area of ​​the upper cover or the lower casing, so that the casing in this area serves as the negative terminal of the battery or is conductive to the negative terminal. This invention, for the first time, compresses the total thickness of a metal-cased battery to below 2.5 mm, breaking through the thickness barrier that is difficult to overcome in existing technologies.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to an ultra-thin metal-cased secondary battery. Background Technology

[0002] As wearable devices, ultra-thin smart cards, and micro-medical devices evolve towards extreme thinness and lightness, stringent requirements are placed on the thickness of their built-in power supplies, requiring them to be less than 2.5mm or even 1mm. Existing lithium-ion batteries face different technical routes and structural bottlenecks in achieving ultra-thinness.

[0003] Currently, the mainstream battery packaging forms mainly include two categories: soft-pack batteries and metal-cased batteries.

[0004] Soft-pack batteries use aluminum-plastic film as the packaging material, which has advantages such as light weight, thinness, and flexible shape, and is currently the mainstream choice for achieving thinner batteries. However, when the battery thickness is compressed to an ultra-thin size of less than 2.5mm, soft-pack batteries face the following inherent defects: (1) The packaging space in the width direction is compressed: The side seal of traditional soft-pack batteries is usually attached to the side of the battery through a folding process to reduce the width occupation. However, in ultra-thin batteries, due to the small thickness, the side seal cannot be effectively folded and can only extend outward in a flat manner, resulting in insufficient effective packaging width. It is necessary to occupy additional space in the width direction of the battery, which compresses the filling width of the active material under a given width size; (2) The front edge of the packaging occupies space in the length direction: After the tab of the soft-pack battery is led out from the inside, it needs to be laid flat in the packaging film, forming a "front edge" packaging area of ​​about 3-5mm at one end of the battery. This part of the space cannot be filled with active material. Under ultra-thin size, the proportion of this ineffective area increases significantly, further reducing the volumetric energy density; (3) The mechanical strength is weak. The aluminum-plastic film has poor puncture resistance and extrusion resistance, and cannot effectively suppress thickness expansion, making it difficult to meet the requirements of high reliability application scenarios; (4) The packaging reliability depends on the heat sealing process. There is a risk of aging of the packaging layer and decreased air tightness during long-term use.

[0005] Metal-cased batteries (steel / aluminum casing) utilize a rigid enclosure, offering advantages such as high mechanical strength, reliable sealing, and excellent heat dissipation. However, the terminals of traditional metal-cased batteries typically extend from the end face or side wall along the battery's length, with the terminals and their sealing structure primarily occupying space along the battery's length or width. When the battery thickness needs to be compressed to below 2.5mm, the available space on the battery's end face or side wall becomes extremely limited, making it impossible to accommodate the diameter of the traditional terminals and the dimensions of the sealing structure.

[0006] To resolve the aforementioned contradictions, existing technologies have explored various approaches, but none have been able to provide a complete solution.

[0007] Patents such as CN108400385A, CN202373667U, and CN218101390U disclose technical solutions that improve space utilization at the electrode assembly level by embedding the tabs within the electrode contour through electrode slots, notch designs, or diaphragm windows. CN202373667U discloses creating slots on the side edge of the electrode, with the tabs located within the slots and only connected to the current collector at the bottom. CN218101390U further discloses creating corresponding notches on the electrode and diaphragm, forming embedded substrate tabs in the empty foil area. However, these solutions only address the space optimization problem within the electrode assembly and do not address how to encapsulate such electrode assemblies within a rigid metal casing, nor do they resolve the fundamental contradiction of increased thickness caused by protruding electrode posts in metal-cased batteries.

[0008] For example, patent CN120784577A discloses a stepped shell structure, including a thicker first part and a thinner second part. The electrode assembly is located in the first part, and the tabs are connected to the second part by bending a metal component. This solution brings the tabs to the thinner area of ​​the shell, but the positive electrode post still protrudes from the shell surface. Its shortcomings are: the connection requires bending a metal component, increasing the number of parts and process complexity; the positive electrode post protrudes from the surface, occupying additional space in the thickness direction, making it impossible to achieve a flat, non-protruding design; and a "front edge" space needs to be reserved at one end of the battery for the electrode post connection structure, occupying space in the length direction. Patent CN111403822B discloses a lithium battery and its manufacturing method, where a first connector and a second connector are integrated on the sealing plate assembly. The tabs are first welded to the sealing plate assembly and then inserted into the shell as a whole, forming an expansion space between the connectors. This solution achieves exposed welding of the tabs before insertion into the shell, facilitating automated production. Its shortcomings are: the pole is located on the end face of the sealing plate assembly and protrudes from the surface of the housing, so it is also impossible to achieve a flat position without protrusion; the connector structure is complex and occupies the space inside the housing; and the direct conduction design between the negative pole and the housing is not achieved. Summary of the Invention

[0009] The purpose of this invention is to provide an ultra-thin metal-cased secondary battery, which solves the technical problems existing in the prior art.

[0010] To achieve the above objectives, the present invention provides the following technical solution: an ultra-thin metal-cased secondary battery, comprising: a metal casing, a positive electrode post assembly, an electrode assembly, and a lower casing; The electrode assembly is formed using a lamination or winding process, and has a positive current collector and a negative current collector formed by welding with an uncoated current collector. The metal housing consists of an upper cover and a lower shell, wherein at least one shell component forms a recessed structure inward into the battery at a position corresponding to the current collector. The positive electrode post assembly is installed in the recessed structure and insulated from the housing by an insulating seal, and its outer surface does not protrude from the outer surface of the shell component. The negative current collector is electrically connected to a connection area of ​​the upper cover or the lower shell, so that the housing in this area serves as the negative terminal of the battery or is conductive to the negative terminal. The total thickness of the battery is ≤2.5mm.

[0011] Preferably, the upper cover or lower shell has a process through hole that penetrates the shell at the projection position corresponding to the negative electrode current collector, and the process through hole is sealed by laser welding of a metal sealing component.

[0012] Preferably, the connection area between the negative electrode current collector and the upper or lower shell is directly connected by laser welding.

[0013] Preferably, the housing region connected to the negative electrode current collector is a plane or an inwardly recessed second portion.

[0014] Preferably, the positive current collector and the negative current collector are formed by ultrasonic welding or laser welding of the uncoated current collector areas of all positive or negative electrode plates in the electrode assembly.

[0015] Preferably, the electrode assembly is formed using a stacking process, and the positive current collector and the negative current collector are respectively formed by aligning and welding the uncoated current collector areas of multiple layers of positive or negative electrode sheets in the thickness direction.

[0016] Preferably, the electrode assembly is formed by a winding process, and the positive current collector and the negative current collector are respectively formed by welding together the uncoated current collector areas that are aligned after winding.

[0017] Preferably, the positive electrode assembly is installed in the recessed structure of the lower shell, and the negative electrode current collector is electrically connected to the lower shell.

[0018] Preferably, the positive electrode assembly is installed in the recessed structure of the upper cover, and the negative electrode current collector is electrically connected to the lower shell.

[0019] Preferably, the upper cover and the lower shell are formed into a fully sealed structure by continuous peripheral laser welding.

[0020] The beneficial effects of this invention are: First, it achieves ultra-thinness to the physical limit. Through the synergistic design of the concave shell and the flat electrode post, the positive electrode post assembly is completely embedded in the concave structure of the shell, with its outer surface flush with the shell surface, completely eliminating the thickness occupied by the protruding electrode post surface in traditional metal-cased batteries; the negative electrode current collector is directly welded to the shell for conductivity, eliminating the need for additional electrode posts. The total battery thickness depends only on the sum of the electrode assembly body thickness and the thickness of the two shell materials, and a stable mass production thickness of 0.4-2.5mm can be achieved, meeting the extreme requirements of ultra-thin electronic products for power supply thickness. In particular, this invention is the first to compress the total thickness of a metal-cased battery to below 2.5mm, breaking through the thickness barrier that is difficult to overcome in existing technologies.

[0021] Secondly, space utilization is maximized. The electrode assembly is completely embedded in the thickness direction, achieving zero footprint; the electrode connection is entirely within the battery's thickness plane in the length direction, eliminating the need for a "leading edge" space as required by existing technologies; and the all-metal casing in the width direction requires no additional encapsulation space. The combination of these three features allows for maximum active material filling within the same external dimensions, significantly improving volumetric energy density.

[0022] Secondly, high reliability. The all-metal casing provides puncture and crush resistance that aluminum-plastic film cannot match; the large-area welding between the current collector and the casing has mechanical strength and conductivity far exceeding that of traditional spot-welded tabs, and superior vibration and fatigue resistance; laser welding ensures long-term airtightness and avoids the risk of electrolyte leakage.

[0023] Finally, the process is highly feasible. The lamination / winding, ultrasonic welding, laser welding, and precision stamping processes used are all mature technologies; the integrated through-hole design cleverly solves the engineering challenges of internal welding and liquid injection in ultra-thin metal shells; the assembly process is optimized, and all connection processes can be automated, demonstrating good prospects for industrialization. Attached Figure Description

[0024] Figure 1 This is an explosion diagram of an ultra-thin metal-cased secondary battery according to an embodiment of the present invention; Figure 2 for Figure 1 The diagram shows a cross-sectional view of the ultra-thin metal-cased secondary battery along its thickness direction. Figure 3 for Figure 2 A partially enlarged schematic diagram of the through-hole area in the intermediate process (before welding). Figure 4 for Figure 2 A magnified view of a portion of the through-hole area in the middle process (after welding). Figure 5 This is a schematic diagram of the planar structure of the positive electrode sheet according to an embodiment of the present invention; Figure 6This is a schematic diagram of the negative electrode planar structure according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the diaphragm planar structure according to an embodiment of the present invention; Figure 8 This is a partially enlarged cross-sectional view along the width direction after the electrode and diaphragm are stacked. Figure 9 for Figure 8 A cross-sectional view along the AA direction; Figure 10 This is a three-dimensional structural diagram of an electrode assembly according to an embodiment of the present invention.

[0025] In the diagram: 100, top cover; 101, process through hole; 200, positive electrode post assembly; 201, positive electrode post body; 202, insulating seal; 300, electrode assembly; 301, positive electrode current collector; 302, negative electrode current collector; 303, electrode assembly body; 400, lower shell; 401, lower shell connection area; 402, lower shell concave structure; 500, metal sealing component; 600, negative electrode welding point; 601, positive electrode welding point; 602, sealing component welding seal; 801, positive electrode active material coating area; 802, positive electrode foil tab area; 803, negative electrode active material coating area; 804, negative electrode foil tab area; 805, diaphragm body; 806, first window; 807, second window; 808, first clearance area; 809, second clearance area. Detailed Implementation

[0026] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings and preferred embodiments. Example

[0027] This embodiment provides an ultra-thin metal-cased secondary battery, such as... Figures 1 to 10 As shown, the battery includes an electrode assembly 300, a metal casing consisting of an upper cover 100 and a lower casing 400, a positive electrode post assembly 200, and a metal sealing component 500.

[0028] The electrode assembly 300 is formed using a stacking process. The positive electrode uses an aluminum foil with a thickness of approximately 0.010 mm as the current collector. An uncoated area is reserved on one edge of the positive electrode as the positive electrode foil tab area 802, and the remaining area is coated with positive electrode active material to form the positive electrode active material coating area 801. The negative electrode uses a copper foil with a thickness of approximately 0.006 mm as the current collector. An uncoated area is reserved on one edge of the negative electrode as the negative electrode foil tab area 804, and the remaining area is coated with negative electrode active material to form the negative electrode active material coating area 803. The positive electrode foil tab area 802 and the negative electrode foil tab area 804 are located on opposite sides of the electrode.

[0029] The separator 805 has a first window 806 and a second window 807, corresponding to the positions of the positive electrode foil tab region 802 and the negative electrode foil tab region 804, respectively. A Z-type stacking machine is used to sequentially stack the positive electrode sheet, separator, and negative electrode sheet, with a stack of 6 pairs of electrodes. After stacking, the positive electrode foil tab regions 802 of the positive electrode sheet are exposed and aligned with each other at the first window 806 of the separator, and the negative electrode foil tab regions 804 of the negative electrode sheet are exposed and aligned with each other at the second window 807 of the separator. A first void region 808 (i.e., no negative electrode active material) is provided at the negative electrode sheet position corresponding to the positive electrode foil tab region 802, and a second void region 809 (i.e., no positive electrode active material) is provided at the positive electrode sheet position corresponding to the negative electrode foil tab region 804, to avoid the risk of short circuit.

[0030] A multi-layer positive electrode tab region 802 is welded together using ultrasonic welding to form an integrated positive electrode current collector 301, and a multi-layer negative electrode tab region 804 is welded together to form an integrated negative electrode current collector 302. Both the positive electrode current collector 301 and the negative electrode current collector 302 are metal blocks formed by stacking and welding multiple layers of foil tabs, and their thickness is less than the thickness of the electrode assembly body 303. In this embodiment, the thickness of the positive electrode current collector is approximately 0.2 mm, and the thickness of the negative electrode current collector is approximately 0.1 mm. The positive electrode current collector 301 and the negative electrode current collector 302 extend from both sides of the electrode assembly body 303, respectively.

[0031] The metal casing consists of an upper cover 100 and a lower shell 400, and is made of stainless steel, which has good ductility and weldability.

[0032] The bottom side of the lower casing 400 is precision stamped to form a recessed structure 402 that is recessed into the battery. The recess depth of the recessed structure 402 is approximately 0.4 mm. A positive electrode post assembly 200 is pre-installed in the recessed structure 402. The positive electrode post assembly 200 includes a positive electrode post body 201 and an insulating seal 202 surrounding its periphery. The insulating seal 202 is made of polypropylene (PP) material that is resistant to electrolytes and high temperatures. The positive electrode post body 201 is insulated and sealed to the lower casing 400 by the insulating seal 202, and the outer surface of the positive electrode post body 201 is flush with the outer surface of the lower casing 400, without any protrusion.

[0033] A connection area 401 is provided on the other side of the bottom of the lower shell 400. The connection area 401 is a planar structure and is used for electrical connection with the negative current collector 302.

[0034] The top cover 100 has a flat plate structure, and a process through hole 101 is provided at the projection position corresponding to the negative electrode current collector 302, which penetrates the shell. This process through hole 101 is used as a process channel for liquid injection and vacuuming in subsequent processes (in some alternatives, it can also serve as an internal welding channel).

[0035] When in use, first place the electrode assembly 300 into the lower shell 400, so that the positive current collector 301 is aligned with the inner welding surface of the positive electrode post assembly 200, and the negative current collector 302 is aligned with the connection area 401 of the lower shell 400.

[0036] First, laser welding (power 500-1000W, welding speed 30-70mm / s) is used to weld and fix the positive current collector 301 to the inner welding surface of the positive electrode post assembly 200, forming a positive electrode welding point 601. Then, laser welding (power 800-1200W, welding speed 30-60mm / s) is used to weld and fix the negative current collector 302 to the connection area 401 of the lower shell 400, forming a negative electrode welding point 600. Through the above welding, the positive current collector 301 sequentially achieves positive electrode lead-out through the positive electrode post assembly 200, and the negative current collector 302 is directly conductive through the lower shell 400, making the lower shell 400 the negative terminal of the battery.

[0037] After completing the internal welding, the upper cover 100 is placed on top. Continuous laser welding is used to seal the periphery of the upper cover 100 and the lower shell 400.

[0038] Electrolyte is injected into the housing through the process through-hole 101 of the top cover 100, and a vacuum process is performed to ensure that the electrolyte fully wets the electrode assembly 300. After the electrolyte injection is completed, the metal sealing component 500 is placed in the process through-hole 101, and the metal sealing component 500 is sealed and fixed to the top cover 100 by laser welding to form a fully sealed structure. The upper surface of the sealing component 500 is flush with the outer surface of the top cover 100. The material of the metal sealing component 500 is the same as that of the top cover 100, which is stainless steel, to ensure welding reliability.

[0039] Measurements show that the total thickness of the ultrathin metal-cased secondary battery prepared in this embodiment is approximately 1.8 mm, which meets the design requirement of a total thickness of ≤2.5 mm.

[0040] Example 2

[0041] This embodiment provides another ultra-thin metal-cased secondary battery, the main difference from embodiment 1 being that the electrode assembly is formed using a winding process.

[0042] The preparation of the positive and negative electrode sheets is basically the same as in Example 1, except that the positive electrode foil tab region 802 and the negative electrode foil tab region 804 are respectively disposed on both sides of the electrode sheet. The positive electrode sheet, separator, and negative electrode sheet are wound into an electrode assembly using a winding process. After winding, the uncoated current collector areas of the positive electrode sheet are aligned in the thickness direction to form a positive electrode foil tab stack, and the uncoated current collector areas of the negative electrode sheet are aligned in the thickness direction to form a negative electrode foil tab stack. The positive electrode foil tab stacks are welded together using ultrasonic welding to form the positive electrode current collector 301, and the negative electrode foil tab stacks are welded together to form the negative electrode current collector 302.

[0043] The subsequent steps, including casing structure, electrode assembly, internal welding, electrolyte filling and sealing, and peripheral encapsulation, are the same as in Example 1 and will not be repeated here. The total thickness of the battery prepared in this example is also approximately 1.8 mm, which meets the requirement of a total thickness ≤ 2.5 mm.

[0044] Example 3 This embodiment provides another type of ultra-thin metal-cased secondary battery, which differs from Embodiment 1 mainly in the installation position of the positive electrode post assembly 200 and the setting position of the process through hole 101.

[0045] In this embodiment, the positive electrode post assembly 200 is installed within the recessed structure of the upper cover 100. Specifically, the upper cover 100 has a recessed structure that extends inwards into the battery, and the positive electrode post assembly 200 is pre-installed within this recessed structure. The outer surface of the positive electrode post body 201 is flush with the outer surface of the upper cover 100. The bottom of the lower shell 400 has a connection area 401 for electrical connection with the negative electrode current collector 302. A process through-hole 101 is provided on the lower shell 400, corresponding to the projected position of the negative electrode current collector 302.

[0046] During assembly, the electrode assembly 300 is first placed into the lower shell 400, and the negative current collector 302 is welded to the connection area 401 of the lower shell 400 using laser welding. Then, the upper cover 100 with the positive electrode post assembly 200 is placed on top, and the positive current collector 301 is welded to the inner welding surface of the positive electrode post assembly 200 on the upper cover 100 using laser welding through the process through hole 101 on the lower shell 400. After welding, liquid is injected and vacuum is drawn through the process through hole 101. Finally, the process through hole 101 is sealed with a metal sealing part 500 using laser welding, and the periphery of the upper cover 100 and the lower shell 400 are laser welded together.

[0047] This embodiment also achieves a structure where the electrode post is flat and does not protrude, and the negative electrode is directly connected to the casing, with a total battery thickness of ≤2.5mm.

[0048] Based on the above embodiments, the present invention can also have a variety of alternative embodiments: Replacement of electrode position: The positive electrode assembly 200 can be installed on the lower shell 400 (as in Examples 1 and 2) or the upper cover 100 (as in Example 3), both of which can achieve the technical effect of the electrode being embedded and the outer surface not protruding.

[0049] Negative electrode connection alternative: The negative electrode current collector 302 can be connected to the lower shell 400 (as in embodiments 1-3) or the upper cover 100, as long as the connected shell component is electrically insulated from the shell component where the positive electrode post assembly 200 is located. The negative electrode connection area 401 can be either a plane (as in embodiments 1-3) or an inwardly recessed second portion.

[0050] Alternative methods for forming the manifold: The welding method for the manifold is not limited to ultrasonic welding. Laser welding or other fusion connection methods can also be used, as long as the multiple layers of uncoated manifold areas can be firmly connected into one piece.

[0051] Alternative locations for process holes: The process through-hole 101 can be located in the upper cover 100 (as in Examples 1 and 2) or the lower shell 400 (as in Example 3) according to process requirements, or it can be located in other positions as needed, as long as it facilitates internal welding and liquid injection operations. In some alternative solutions, if other liquid injection methods are used (such as all-dry encapsulation), the structure of the process through-hole 101 and the metal sealing component 500 can be omitted.

[0052] Shell material alternatives: The metal shell material is not limited to stainless steel; nickel-plated steel, aluminum alloy, and other metal materials with good ductility and weldability can also be selected. The positive electrode post body 201 can be made of a metal material that can be welded to the shell, such as aluminum or aluminum alloy. The insulating seal 202 can be made of polymer materials that are resistant to electrolytes and high temperatures, such as polyphenylene sulfide (PPS) and perfluoroalkoxy resin (PFA).

[0053] For those skilled in the art, various improvements and modifications can be made without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention.

Claims

1. A thin metal-cased secondary battery, characterized in that, include: Metal casing, positive electrode post assembly (200), electrode assembly (300) and lower casing (400); The electrode assembly (300) is formed by a lamination process or a winding process, and has a positive current collector (301) and a negative current collector (302) formed by welding with an uncoated current collector; the metal housing consists of an upper cover (100) and a lower housing (400), wherein at least one housing component forms a recessed structure (402) that is recessed into the battery at a position corresponding to the current collector; the positive electrode post assembly (200) is installed in the recessed structure (402) and is insulated from the housing by an insulating seal (202), and its outer surface does not protrude from the outer surface of the housing component; the negative current collector (302) is electrically connected to a connection area (401) of the upper cover (100) or the lower housing (400), so that the housing in this area serves as the negative terminal of the battery or is connected to the negative terminal; the total thickness of the battery is ≤2.5mm.

2. The ultra-thin metal-cased secondary battery according to claim 1, characterized in that, The upper cover (100) or lower shell (400) is provided with a process through hole (101) through the shell at the projection position corresponding to the negative current collector (302), and the process through hole (101) is sealed by laser welding of a metal plug (500).

3. The ultra-thin metal-cased secondary battery according to claim 1, characterized in that, The negative current collector (302) is directly connected to the upper cover (100) or lower shell (400) via laser welding in the connection area (401).

4. The ultra-thin metal-cased secondary battery according to claim 1, characterized in that, The housing region connected to the negative current collector (302) is a plane or an inwardly recessed second portion.

5. The ultra-thin metal-cased secondary battery according to claim 1, characterized in that, The positive current collector (301) and the negative current collector (302) are formed by ultrasonic welding or laser welding of the uncoated current collector areas of all positive or negative electrodes in the electrode assembly (300).

6. The ultra-thin metal-cased secondary battery according to claim 1, characterized in that, The electrode assembly (300) is formed by a stacking process. The positive current collector (301) and the negative current collector (302) are formed by aligning and welding the uncoated current collector areas of multiple positive or negative electrode sheets in the thickness direction.

7. The ultra-thin metal-cased secondary battery according to claim 1, characterized in that, The electrode assembly (300) is formed by a winding process, and the positive current collector (301) and the negative current collector (302) are respectively formed by welding the aligned uncoated current collector areas after winding.

8. The ultra-thin metal-cased secondary battery according to claim 1, characterized in that, The positive electrode post assembly (200) is installed in the concave structure (402) of the lower shell (400), and the negative electrode current collector (302) is electrically connected to the lower shell (400).

9. The ultra-thin metal-cased secondary battery according to claim 1, characterized in that, The positive electrode assembly (200) is installed in the recessed structure of the upper cover (100), and the negative electrode current collector (302) is electrically connected to the lower shell (400).

10. The ultra-thin metal-cased secondary battery according to claim 1, characterized in that, The upper cover (100) and the lower shell (400) are formed into a fully sealed structure by continuous peripheral laser welding.

Images