Sodium-ion cylindrical battery with continuous tabs and its preparation method

Abstract

This invention discloses a sodium-ion cylindrical battery with continuous tabs and its preparation method. The positive and negative tabs are laser-divided to remove some of the tabs, allowing for winding and forming 20-30 layers of continuous annular tabs at the center of the core radius. This ensures high-rate overcurrent capability. Compared to the multi-tab solutions used in existing technologies, the continuous tabs offer higher strength and are less prone to tearing or breakage that could cause short circuits or poor contact. After forming the core, a support frame structure placed inside the core, along with positive and negative electrode cover assemblies with annular current collectors, completes the welding of the current collector to the core tabs. This design offers advantages such as simple structure, convenient processing, higher structural reliability, and stronger overcurrent capacity. It solves the technical problems of existing designs failing to achieve the high-power characteristics of sodium-ion battery systems and posing certain safety risks.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a method for preparing a sodium-ion cylindrical battery with continuous tabs. Background Technology

[0002] The bottleneck of current carrying capacity in cylindrical batteries is generally the number of tabs on the core and the welding area between the core and the current collector on the end cap. In order to improve the current carrying capacity of cylindrical batteries, the industry has proposed a full tab flattening process, but this process has the following problems:

[0003] (1) The blank foil of the electrode is relatively narrow, usually ≤10mm. After being flattened, the foil material that is kneaded into the electrode assembly is prone to increase the interface gap of the active material coating area. During the use of the battery, lithium plating of the negative electrode is caused by the interface inconsistency, which poses a serious safety hazard. Although this problem can be alleviated by increasing the width of the blank foil of the electrode, it will increase the cost of the foil material and reduce the energy density of the battery.

[0004] (2) The flattening process uses mechanical or ultrasonic methods to forcibly bend and compact the foil, which can easily generate metal shavings, leading to serious safety hazards in the battery.

[0005] (3) The flattening process often makes it difficult to ensure the tight fit of the end face electrode. That is, the foil material that is flattened on the end face is unevenly distributed in the direction from the center outward, and there may be some large gaps, which may cause the laser to break through the foil material, resulting in poor welding, or even melting the diaphragm in the core, causing a short circuit.

[0006] (4) The flattening process aims to form a tight fit between the end face plates of the battery cell, which hinders the electrolyte from reaching the positive and negative electrode active material areas through the end face of the battery cell. In order to achieve a good electrolyte wetting effect and electrochemical reaction interface, a longer injection and wetting time is often required.

[0007] To mitigate the problems and risks associated with kneading, the industry has implemented corresponding optimizations, including replacing all tabs with multi-tabs, optimizing the kneading interface, and using multi-tab combination kneading technology. However, the following issues still exist:

[0008] Chinese patent application CN 112928401 A discloses a multi-tab cylindrical lithium-ion battery. It employs several sets of positive tabs that pass sequentially through the first positive tab through-hole and the second positive tab through-hole before being welded to a positive current collector. The extension stalk of the positive current collector is bent and then welded to the battery cover. The negative electrode is handled similarly to the positive electrode. This method increases the battery's current carrying capacity to meet high-rate charge and discharge requirements. However, because the die-cut tabs are small, they are prone to deformation, bending, or even tearing during the winding and welding process, leading to poor contact or internal short circuits after welding.

[0009] Chinese patent application CN 113540400 B discloses a large-size cylindrical lithium-ion secondary battery and its positive and negative electrode sheets. By filling the gaps between the positive and negative electrode sheets at both ends of the electrode assembly with metal, the method overcomes the problem of the foil material being rolled into the electrode assembly during the flattening process causing localized arching of the electrode coating area. This results in a smooth end face, facilitating subsequent current collector welding, improving yield, and ensuring that the positive and negative electrode sheets are not damaged before and after welding, thus improving the overall performance of the battery. However, because a binder is needed to ensure the adhesion between the metal powder and the foil, this leads to differences in welding characteristics between the foil area and the metal powder area, potentially causing welding defects.

[0010] Publication No. CN 113488746 A discloses a manufacturing process and a multi-tab battery cell. The process involves laser die-cutting all tabs to form multiple tabs. The laser die-cutting lines are a set of mutually parallel inclined straight lines, and the individual tabs are parallelogram-shaped. These are then wound to form the battery cell, and finally, the multi-tabs are flattened. Due to their parallelogram-shaped individual tabs, the flattening process reduces the outward turning of the electrode sheets and the generation of metal shavings, and also reduces the gap between the flattened electrode sheets, increasing the stability of welding to the busbar. However, this method still uses multi-tab flattening technology. The flattened surface is generally composed of the inner and outer loops of the core tabs after bending and stacking, making it more difficult to form a tight and flat core end face. The end face welding quality is highly random and unstable, and the risk of the tabs being torn during manufacturing cannot be avoided.

[0011] Therefore, how to propose a new technical solution to overcome the shortcomings of existing technologies is a problem that we urgently need to solve. Summary of the Invention

[0012] To address the shortcomings of the aforementioned technologies, this invention provides a method for preparing a sodium-ion cylindrical battery with continuous tabs. This method has advantages such as simple structure, convenient processing, higher structural reliability, and stronger overcurrent capacity. It can solve the technical problems that existing designs cannot achieve the high power characteristics of sodium-ion battery systems and pose certain safety risks.

[0013] To achieve the above objectives, the present invention provides a sodium-ion cylindrical battery with continuous tabs, comprising a hollow cylindrical shell, a winding core disposed inside the shell, and a support frame; the winding core consists of an electrode sheet and tabs, the tabs being located at both ends of the electrode sheet, including a positive tab and a negative tab; the length of the tabs is less than the length of the electrode sheet and is located in the middle of the electrode sheet; both the upper and lower ends of the shell are provided with cover plate assemblies; a current collector is provided between the cover plate assembly and the shell, the edge of the current collector abutting against the tabs and being welded and fixedly connected; the support frame is located between the winding cores, including a guide portion and a fitting portion, one end of the guide portion being fixedly connected to the fitting portion, and the other end extending into the interior of the winding core, the outer edge of the fitting portion contacting the tabs.

[0014] Preferably, the cover plate assembly includes a cover plate and an electrode post. The cover plate has a through hole adapted to the electrode post. The electrode post is installed in the through hole, and the lower end of the electrode post is connected to the electrode tab through a connector.

[0015] Preferably, the support frame is made of insulating material, and the thickness of the fitting portion is the same as the height of the electrode tab.

[0016] Preferably, the collector plate is provided with through holes, and multiple through holes are provided and evenly distributed on the surface of the collector plate; the outer edge of the collector plate extends downward to form a rim portion, and the rim portion is in contact with the electrode tab.

[0017] This invention also discloses a method for preparing a sodium-ion cylindrical battery with continuous tabs, comprising the following steps:

[0018] S1: The electrode sheet is cut off at the beginning and end of the electrode sheet by laser die cutting to form the positive electrode and the negative electrode.

[0019] S2: The laser-cut positive and negative electrode tabs and the diaphragm are wound together to form a core with a hollow structure, and the core has 20-30 layers of continuous annular electrode tabs.

[0020] S3: The support frame is placed inside the hollow structure of the core, and the circular current collector and the support frame work together to completely cover the tab.

[0021] S4: Weld the edge of the collector plate to the electrode tab to fix them together.

[0022] Preferably, in step S1, before laser die-cutting, a tab R angle is reserved, which is 0.3-0.5 times the tab height; during the laser die-cutting process, the cutting length of the tab foil area is 40%-60% of the tab length.

[0023] Preferably, in step S3, the length of the guide portion in the support frame is 20%-100% of the core height; and the diameter is 90%-97% of the hollow hole diameter of the core.

[0024] Preferably, in step S4, after the collector plate and support frame are assembled, laser welding is used to weld the side wall of the collector plate to the multi-layer electrode tabs. The welding path is along the circumference direction and adopts one of continuous welding, spot welding or short-segment welding.

[0025] The beneficial effects of this invention are as follows: Compared with the prior art, this invention uses laser die-cutting of the positive and negative electrode tabs to remove part of the tabs, so that after winding, 20 to 30 layers of continuous annular tabs can be formed in the middle of the core radius, ensuring the requirement of high-rate overcurrent. At the same time, compared with the multi-tab solution used in the prior art, the continuous tabs have higher strength and are less likely to tear and break, causing battery short circuits or poor contact. After the core is formed, a support frame structure placed inside the core, along with a positive electrode cover assembly and a negative electrode cover assembly with an annular current collector, completes the welding of the current collector to the core tabs. The welding contact surface is a flat and regular multi-layered tab and annular metal current collector. Compared with the all-tab solution used in the prior art, this avoids battery short circuits caused by metal shavings or residues due to the flattening process. Compared with the irregular gaps between the flattened electrode sheets, the present invention has higher welding stability and welding quality, and is less likely to cause weld burn-through, effectively reducing the occurrence of safety issues. Regarding the problem of long electrolyte injection and immersion time after flattening, the present invention significantly reduces the obstruction of the core end face, which can accelerate the rate of electrolyte immersion in the positive and negative electrode sheets, effectively improving the production efficiency of cylindrical batteries. Attached Figure Description

[0026] Figure 1 This is a diagram of the unfolded core of the present invention;

[0027] Figure 2 This is a cross-sectional view of the cylindrical battery of the present invention;

[0028] Figure 3 This is a top view schematic diagram of the battery of the present invention;

[0029] Figure 4 This is a schematic diagram of the structural installation of the present invention;

[0030] Figure 5 This is a schematic diagram of the support frame structure of the present invention;

[0031] Figure 6 This is a flowchart of the steps of the present invention;

[0032] Figure 7 This is a schematic diagram illustrating the operation of the present invention;

[0033] Figure 8 This is a schematic diagram comparing the internal resistance of batteries;

[0034] Figure 9 This is a schematic diagram of battery cycle performance.

[0035] The symbols for the main components are explained below:

[0036] 1. Electrode 2. Electrode tab 3. Support frame 4. Housing 5. Center hole 6. Current collector 7. Cover plate 8. Electrode post

[0037] 9. Connector 31. Guide part 32. Fitting part. Detailed Implementation

[0038] To more clearly illustrate the present invention, the invention will be further described below with reference to the accompanying drawings. Of course, the scope of protection of the present invention is not limited thereto, without requiring creative effort.

[0039] Please see Figures 1-5 This invention discloses a sodium-ion cylindrical battery with continuous tabs, comprising a hollow cylindrical shell 4, a winding core placed inside the shell, and a support frame 3; the winding core consists of an electrode sheet 1 and tabs 2, the tabs 2 being located at both ends of the electrode sheet 1, including a positive tab and a negative tab; the length of the tabs 2 is less than the length of the electrode sheet 1 and is located in the middle of the electrode sheet 1; both the upper and lower ends of the shell 4 are provided with cover plate assemblies; a current collector 6 is provided between the cover plate assembly and the shell, the edge of the current collector 6 abutting against the tabs 2 and being welded and fixedly connected; the support frame 3 is located between the winding cores, including a guide part 31 and a fitting part 32, one end of the guide part 31 being fixedly connected to the fitting part 32, and the other end extending into the central hole 5 inside the winding core, the outer edge of the fitting part 32 contacting the tabs 2. In this embodiment, the entire core is first protected by a housing, and a support frame is provided to cooperate with the current collector to clamp and fix the tabs from both the inside and outside. This avoids bending of the tabs and makes the welding process simpler and easier to operate. Of course, in order to further improve the wetting speed and effect of the electrolyte, the support frame can be hollow. During welding, the hollow part can be fixed by inserting a fixing pin, which causes the end face of the support frame to expand and push the tabs to fit tightly against the current collector, thus improving the welding quality.

[0040] The cover plate assembly includes a cover plate 7 and an electrode post 8. The cover plate 7 has a through hole that matches the electrode post 8. The electrode post 8 is installed in the through hole, and the lower end of the electrode post is connected to the electrode lug 2 through a connector 9. The support frame 3 is made of insulating material, and the thickness of the fitting part is the same as the height of the electrode lug. The collector plate 6 has multiple through holes that are evenly distributed on the surface of the collector plate. The outer edge of the collector plate extends downward to form a edging part that fits against the electrode lug. In this embodiment, a cover plate assembly is provided to seal the entire housing and fix the current collector, support frame, etc., to prevent displacement. The transfer of battery power is achieved through the electrode posts. Since the support frame is immersed in electrolyte for a long time, it needs to be made of materials with good insulation properties, such as PET (polyethylene terephthalate), PE (polyethylene), or PTFE (polytetrafluoroethylene). The through holes on the current collector can effectively reduce the overall weight and further improve the wetting speed and effect of the electrolyte. In practice, the number and size of the holes can be adjusted according to the size of the current collector. Generally, the number can be selected as 2-20, and the hole size can be 5%-50% of the diameter of the current collector. More importantly, the current collector is provided with an edge banding part, which can effectively fit and accommodate the electrode tabs from the outside. Combined with the welding process, the connection between the current collector and the electrode tabs is more stable.

[0041] Please see Figures 6-7 The present invention also discloses a method for preparing a sodium-ion cylindrical battery with continuous tabs, comprising the following steps:

[0042] S1: The electrode sheet is laser-cut to remove the tab foil areas at the beginning and end, forming positive and negative tabs; S2: The laser-cut positive and negative tabs are wound with a diaphragm to form a core with a hollow structure, and the core has 20-30 layers of continuous annular tabs; S3: A support frame is placed inside the hollow structure of the core, and the tabs are completely covered by the cooperation of the circular current collector and the support frame; S4: The edge of the current collector is welded to the tabs to fix them together.

[0043] More specifically, for laser-die-cut electrode tab length, 40%-60% of the electrode sheet length is generally selected to ensure that the thickness of the multi-layer tabs after winding is moderate. Too short a tab length has limited improvement on current carrying capacity, while too long a tab length will cause inconvenience in assembly and processing. Furthermore, a radius (R-angle) needs to be reserved for the tabs in laser die-cutting to improve their strength. The R-angle is generally designed to match the tab height, typically being 0.3-0.5 times the tab height, i.e., a tab height of 6mm-2mm. If the diameter is 0mm, then the radius (R) is 2mm-10mm. For the support frame, the height and diameter of the part extending into the center hole of the core (i.e., the guide part) can be adjusted according to the core parameters to meet the fixing of the bonding part in the support frame. Its height is generally 20%-100% of the core height, and its diameter is generally 90%-97% of the core center hole. The size of the bonding part can be designed according to different electrode tab fits and welding methods. Its height is consistent with the electrode tab height, and its diameter is 90%-99% of the inner circle electrode tab.

[0044] Regarding the fit between the support frame and the core, it can be inserted into the center holes on the positive and negative sides of the core after winding; alternatively, the support frame can directly replace the center pin of the original winding machine at the initial stage of winding, allowing the electrode sheet to be wound directly on the support frame in the center hole. For the current collector, its diameter is generally 101%-105% of the diameter of the outer ring of the core's electrode tab, its height generally exceeds the electrode tab by 0.5mm-1mm, and its thickness is generally 2mm-5mm, so as to better fit with the electrode tab and meet the subsequent welding requirements. After the current collector and the core with the support frame are assembled, laser welding is used to weld the side wall of the current collector to the multi-layer electrode tab. The welding path is generally along the circumference direction and can be continuous welding, spot welding, or short-segment welding.

[0045] Example 1

[0046] This embodiment uses the 32140 large-size cylindrical sodium-ion battery of the Prussian white system as the model cell, and its manufacturing process is as follows:

[0047] Electrode manufacturing: Positive electrode homogenization → positive electrode continuous coating → positive electrode rolling → positive electrode slitting → positive electrode tab die cutting; negative electrode is the same as positive electrode;

[0048] Core manufacturing: positive and negative electrode sheets and diaphragm are wound → support frame is inserted into the center of the core;

[0049] Welding and assembly: Welding of the positive current collector of the core → Bending of the positive end cap → Welding of the positive end cap to the shell; The negative end is the same as the positive end;

[0050] Formation testing: Liquid injection → Sealing → Formation → Settling → Volume separation → Storage.

[0051] The height of the positive electrode is 124mm, of which the positive electrode material area is 114mm, the tab empty foil area is 10mm, the electrode length is 2100mm, the tab length after laser die-cutting is 1100mm, the R angle is 3mm, and the tab is located in the middle of the electrode length. The negative electrode is the same as the positive electrode.

[0052] After winding, the number of tab layers is 28 turns. PP material support frames are inserted into the center of the core on both the positive and negative sides. In the radial direction, they are basically in contact with the inner tab, with a gap of less than 1mm and a height exceeding the tab by 0.5mm. Then, the current collector of the end cap assembly is assembled with the support frame and the tab. At this time, the current collector can be supported by the support frame in the height direction to avoid crushing the tab and causing deformation of the tab. The outer wall of the current collector is basically in contact with the outer tab in the radial direction, with a gap of less than 1mm.

[0053] The assembled core, support frame, and end cap assembly are suspended and horizontally fixed. The outer wall of the collector plate is clamped using an arc-shaped welding fixture, so that the extruded electrode tabs are tightly attached to the support frame to achieve a flat and regular welding contact surface. By rotating the welding laser head, two continuous welding paths are completed along the circumference of the outer wall of the collector plate. After welding, the surface weld marks are clear and bright, with a width of 2mm and a length of 75% of the outer edge of the collector plate. The welding tensile force can reach more than 15N. Through disassembly and observation, the weld marks can penetrate directly to the innermost electrode tab. The weld marks are clear and the quality is reliable.

[0054] After the positive and negative collectors are welded, the end caps on both sides are welded and sealed to the shell. After liquid injection, settling, formation and capacity testing, the product is put into storage.

[0055] Example 2:

[0056] Based on Example 1, a support frame with a hollow structure and a collector plate with a central hole structure are adopted. Before welding the collector plate to the electrode, a circular fixing pin is inserted into the hollow structure of the support frame, causing the end face of the support frame with the central hole to expand, so as to achieve a tight fit between the electrode and the inner wall of the collector plate. Laser welding can then be performed. After welding is completed, the cylindrical fixing pin is removed.

[0057] Example 3:

[0058] Based on Example 1, a manifold with a porous structure is adopted, which can significantly improve the injection time and the immersion time after injection after welding, with the injection time being <5min.

[0059] Please see Figure 8 and Figure 9After testing the three embodiments, it was found that, in terms of internal resistance, the internal resistance of the cylindrical battery using the present invention was significantly reduced, and the dispersion of the measurement results was also significantly improved; in terms of long-term reliability, due to the reduction of internal resistance, the overcurrent temperature rise of high current was effectively controlled, and the long-term cycle life was improved to a certain extent.

[0060] The advantages of this invention are:

[0061] 1) This invention adopts a continuous electrode tab in conjunction with a positive electrode cover plate assembly and a negative electrode cover plate assembly with a circular annular current collector to complete the welding of the current collector to the core electrode tab. The welding contact surface is flat and regular, and there are no risks such as the introduction of metal chips and foreign objects in the flattening process and poor welding that seriously affect battery safety, as well as manufacturing problems such as long electrolyte wetting time. Compared with this invention, it has the advantages of simple structure, convenient processing, higher structural reliability, and stronger current carrying capacity.

[0062] 2) This invention uses continuous tabs, and the length dimension can reach more than half of the core length. Compared with the multi-tab technology route, continuous tabs are less likely to cause problems such as tab deformation, bending or even tearing during the manufacturing process such as winding and welding, which greatly reduces the risk of poor contact or internal short circuit in the battery after welding.

[0063] 3) This invention uses continuous tabs, which have a large tolerance redundancy in the manufacturing process. Compared with the multi-tab technology route, there is no need to consider the problem of the tabs being misaligned in the core and unable to match the current collector, and it also has higher processing efficiency.

[0064] 4) The current collector used in this invention can be perforated, which greatly reduces the obstruction of the end face of the core and can accelerate the rate of electrolyte wetting of the positive and negative electrode sheets, effectively improving the production efficiency of cylindrical batteries.

[0065] The above-disclosed embodiments are merely a few specific examples of the present invention, but the present invention is not limited thereto. Any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A sodium-ion cylindrical battery having continuous tabs, characterized by, The application relates to a battery with a hollow cylindrical shell, a winding core arranged in the shell and a supporting frame; the winding core is composed of a pole piece and pole tabs, the pole tabs are located at two ends of the pole piece, the pole tabs comprise positive pole tabs and negative pole tabs, the length of the pole tabs is smaller than the length of the pole piece and the pole tabs are located at the middle position of the pole piece, upper and lower ends of the shell are provided with cover plate assemblies, a current collector is arranged between the cover plate assemblies and the shell, the edge of the current collector is in abutment with the pole tabs and is fixedly connected through welding, the supporting frame is located between the winding core and comprises a guide part and a fitting part, one end of the guide part is fixedly connected with the fitting part and the other end of the guide part penetrates into the winding core, the outer edge of the fitting part is in contact with the pole tabs. The supporting frame is made of insulating material, the thickness of the fitting part is the same as the height of the pole tabs, and the supporting frame adopts a hollow structure.

2. The sodium-ion cylindrical battery with continuous tab according to claim 1, wherein, The cover plate assembly comprises a cover plate and a pole, the cover plate is provided with a through hole matched with the pole, the pole is arranged in the through hole, and the lower end of the pole is connected with the pole tab through a connecting piece.

3. The sodium-ion cylindrical battery with continuous tab according to claim 1, wherein, The current collector is provided with through holes, the through holes are arranged in multiple numbers and are uniformly distributed on the surface of the current collector, the outer edge of the current collector extends downward to form a wrapping part, and the wrapping part is in abutment with the pole tab.

4. A method of manufacturing a sodium-ion cylindrical battery having continuous tabs, characterized by, The application further discloses a manufacturing method of the battery. S1: the pole tabs are cut to remove the pole tab foil areas at the first and tail parts of the pole tabs through laser die cutting to form positive pole tabs and negative pole tabs; S2: the positive and negative pole tabs subjected to laser die cutting are wound with a diaphragm to form a winding core with a hollow structure, and the winding core position has 20-30 layers of continuous annular pole tabs; S3: the supporting frame is arranged in the hollow structure of the winding core, the current collector and the supporting frame are matched with each other in a circular structure to completely wrap the pole tabs; S4: the wrapping part of the current collector is welded with the pole tab to fix the two parts; The supporting frame comprises the guide part and the fitting part, one end of the guide part is fixedly connected with the fitting part and the other end of the guide part penetrates into the winding core, the outer edge of the fitting part is in contact with the pole tab, the supporting frame is made of insulating material, the thickness of the fitting part is the same as the height of the pole tab, and the supporting frame adopts a hollow structure.

5. The method of claim 4 for the preparation of sodium-ion cylindrical batteries with continuous tabs, characterized by, In step S1, an R angle of the pole tab is reserved before laser die cutting, the R angle of the pole tab is 0.3-0.5 times the height of the pole tab, and the cutting length of the pole tab foil area is 40%-60% of the length of the pole tab during laser die cutting.

6. The method of claim 4 for the preparation of sodium-ion cylindrical batteries with continuous tabs, characterized by, In step S3, the length of the guide part of the supporting frame is 20%-100% of the height of the winding core and the diameter is 90%-97% of the diameter of the hollow hole of the winding core.

7. The method of claim 4 for the preparation of sodium-ion cylindrical batteries with continuous tabs, characterized by, In step S4, after the current collector and the supporting frame are assembled, laser welding is used to realize welding of the side wall of the current collector and the multiple pole tabs, the welding path is along the circumferential direction, and one of continuous welding, spot welding and short segment welding is adopted.

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