Cylindrical lithium-ion battery and electric device using the same

Abstract

This application proposes a cylindrical lithium-ion battery and an electrical device. The cylindrical lithium-ion battery includes a casing, a core placed inside the casing and electrically connected to the casing at its bottom end, and a cap correspondingly placed on the top of the core. A current collector is also provided at the top of the core for electrical connection to the cap. The current collector includes a straight portion, a bent portion, and a main body portion connected in sequence. The straight portion is electrically connected to the cap, and the main body portion is electrically connected to the electrode end face at the top of the core. The AC internal resistance of the battery from the bent portion to the cap is set as a first internal resistance R1, and the AC internal resistance of the battery from the bent portion to the bottom of the casing is set as a second internal resistance R2. The first internal resistance R1 and the second internal resistance R2 satisfy: 70% ≤ R2 / (R1+R2) ≤ 95%. By proportionally allocating R1 and R2, the overall internal resistance of the lithium battery is reduced while retaining the short-circuit protection function of the current collector, achieving a balance between the low internal resistance performance and the short-circuit protection performance of the tabs, thus improving the safety of the cylindrical lithium-ion battery.

Description

Technical Field

[0001] This application relates to the field of electrical device technology, and in particular to a cylindrical lithium-ion battery and an electrical device. Background Technology

[0002] The internal resistance of cylindrical lithium-ion batteries is a crucial factor affecting battery performance and charge / discharge efficiency, and is also an important parameter for evaluating battery life. To achieve higher power applications, cylindrical lithium-ion batteries require lower internal resistance. Recent advancements in cylindrical lithium-ion batteries have significantly reduced internal resistance through a full-tab design, thereby reducing the frequency of temperature cutoff triggered by overheating during high-current discharge or charging, minimizing energy loss within the cell, and improving fast charging and discharging performance.

[0003] The internal resistance of a cylindrical lithium-ion battery mainly consists of two parts: the internal resistance of structural components and the internal resistance of the core. The internal resistance of structural components includes the cap, positive and negative current collectors, and steel casing; the internal resistance of the core includes the positive and negative electrode tabs, positive and negative electrode plates, positive and negative electrode active materials, and separator. Among them, the internal resistance of the positive current collector is not only related to the heat generation at the battery head, but also affects the battery's short-circuit protection performance; while the overall internal resistance of the core affects the battery's fast charging and fast discharging dynamics. Summary of the Invention

[0004] To address the aforementioned issues, this invention optimizes the internal resistance of different parts of the battery, significantly improving the battery's performance in high-rate charge and discharge applications and greatly enhancing the short-circuit protection performance of the positive electrode current collector. The first aspect of this application provides a cylindrical lithium-ion battery, including a housing, a core disposed inside the housing and electrically connected to the housing at its bottom end, and a cap correspondingly disposed on the top end of the core. The housing is filled with electrolyte to wet the core. The top end of the core is also provided with a current collector for electrical connection to the cap. The current collector includes a main body, a first bent portion, a straight portion, and a second bent portion connected in sequence. The main body is electrically connected to the top end of the core, and the second bent portion is electrically connected to the cap. The AC internal resistance of the battery from the first bent portion to the cap is set as a first internal resistance R1, and the AC internal resistance of the battery from the first bent portion to the bottom end of the housing is set as a second internal resistance R2. The first internal resistance R1 and the second internal resistance R2 satisfy: 70% ≤ R2 / (R1+R2) ≤ 95%. Using the junction of the first bend of the current collector and the main body as the dividing line, the battery's internal resistance is divided into a first internal resistance R1 from the first bend to the cap and a second internal resistance R2 from the first bend to the bottom of the casing. R1 and R2 are further proportionally allocated so that 70% ≤ R2 / (R1+R2) ≤ 95%. This reduces the overall internal resistance of the lithium battery (i.e., the sum of R1 and R2) while controlling the proportion of R2, and also preserves the short-circuit protection function of the current collector, achieving a balance between low internal resistance performance and tab short-circuit protection performance, thus improving the safety of the cylindrical lithium-ion battery. Preferably, the first internal resistance R1 and the second internal resistance R2 satisfy: 72% ≤ R2 / (R1+R2) ≤ 85%.

[0005] In some alternative embodiments, the core is formed by winding together a stacked positive electrode sheet, a separator, and a negative electrode sheet, and the core is wrapped with an insulating material layer to electrically insulate it from the casing. By wrapping the core with an insulating material layer, metal shavings from the battery manufacturing process are prevented from adhering to the core and causing a short circuit, thus improving the safety of cylindrical lithium-ion batteries. Simultaneously, the battery's charge retention capacity is enhanced, and battery performance and lifespan are optimized.

[0006] In some optional embodiments, the insulating material layer includes a first tape wound around the middle section of the outer wall of the core. The first tape adheres to the side of the core with its inner end and is wound turn by turn. When the core is assembled into the housing, the outermost layer of the first tape abuts against the inner wall of the housing, thereby fixing the core and the housing radially relative to each other. By providing a first tape in the middle section of the outer wall of the core, the outer wall of the core is insulated, and the outermost layer of the first tape abuts against the inner wall of the housing to radially fix the core and the housing, thereby enhancing the stability of the battery structure.

[0007] In some optional embodiments, the width of the first tape is 50%-99% of the axial height of the core. If the width of the first tape is less than 50% of the core height, the core will not be well fixed; if the width of the first tape is greater than 99% of the core height, the first tape will be too close to the electrodes at both ends of the core, and the adhesive on the adhesive side of the first tape may corrode the positive and negative electrode tabs. Setting the width of the first tape to 50%-99% of the core height can eliminate the corresponding safety hazards.

[0008] In some optional embodiments, the insulating material layer further includes a third tape wrapped around the core near both ends, extending along the side of the core and covering a portion of its top or bottom end face. By wrapping the third tape around the core near both ends, the third tape correspondingly covers a portion of the electrode facets at both ends of the core, preventing scratching against the inner wall of the housing during core installation and thus avoiding damage to the electrode facets, while preserving the conductivity at both ends of the core.

[0009] In some optional embodiments, the insulating material layer further includes a second tape, which is wound around the side of the core that is not covered by the first and third tapes. The second tape is connected to or partially overlaps with the first and third tapes. The second tape fills in the portions not covered by the first and third tapes, achieving complete insulation of the outer surface of the core and eliminating the risk of short circuits with the housing.

[0010] In some optional embodiments, the cylindrical lithium-ion battery further includes a fourth tape covering the innermost starting end of the positive electrode sheet located in the winding core. The fourth tape insulates the starting end of the positive electrode sheet and prevents displacement of the positive electrode sheet during winding, which could prevent the negative electrode sheet from wrapping around the positive electrode sheet axially in the winding core. This would lead to lithium plating on the portion of the positive electrode sheet coated with positive active material that extends beyond the portion of the negative electrode sheet coated with negative active material, ultimately affecting the battery's performance and safety. Preferably, the fourth tape adheres the starting end of the positive electrode sheet to the separator, further preventing displacement of the positive electrode sheet during battery use and improving the utilization rate of energy storage and release of the positive active material.

[0011] In some optional embodiments, the cylindrical lithium-ion battery further includes a fifth tape covering the outermost end of the positive electrode sheet located in the winding core. This fifth tape insulates the outermost end of the positive electrode sheet, preventing displacement during winding that could prevent the negative electrode sheet from properly wrapping the positive electrode sheet axially in the winding core. Furthermore, the portion of the positive electrode sheet coated with the positive active material that extends beyond the region of the negative electrode sheet coated with the negative active material may undergo lithium plating, ultimately affecting battery performance and safety. Preferably, the fifth tape adheres the outermost end of the positive electrode sheet to the separator, further preventing displacement of the positive electrode sheet during battery use and improving the utilization rate of energy storage and release of the positive active material.

[0012] In some optional embodiments, the insulating material layer, the fourth tape, and the fifth tape can all be one or more of the following: expandable tape, PET tape, PI tape, and polyurethane tape. Expandable tape, PET tape, PI tape, and polyurethane tape all possess good insulating properties.

[0013] In some alternative embodiments, the expanding tape includes a substrate and an adhesive layer on the surface of the substrate, wherein the substrate includes one or more of the following: synthetic resin (polyethylene PE, polyvinyl chloride PVC, polypropylene PP, polystyrene PS, polymethyl methacrylate PMMA, phenolic resin, polyether), and the adhesive layer includes polyacrylate.

[0014] In some optional embodiments, the positive electrode includes a positive electrode active material, a binder, and a conductive agent. The positive electrode active material is a nickel-based lithium-intercalated transition metal oxide material or a combination of a nickel-based lithium-intercalated transition metal oxide material and a lithium iron phosphate material. The nickel-based transition metal oxide material further includes one or more of cobalt, manganese, and aluminum, and the proportion of nickel atoms in the positive electrode active material to the total number of transition metal atoms is greater than or equal to 75%. By controlling the proportion of nickel atoms in the positive electrode active material to the total number of transition metal atoms, good electronic conductivity and ion diffusion are achieved, reducing the internal resistance of the positive electrode and increasing the energy density during battery charging and discharging, thus enabling high-rate charging and discharging.

[0015] In some optional embodiments, the negative electrode sheet includes a negative electrode active material, a binder, and a conductive agent. The negative electrode active material includes silicon-based materials or a combination of silicon-based materials and carbon-based materials, and the mass percentage of silicon-based materials in the negative electrode active material is 2%-30%. By controlling the mass percentage of silicon-based materials in the negative electrode active material, on the one hand, the silicon-based material can load and store more lithium ions, reduce the areal density and thickness of the negative electrode sheet, thereby reducing the internal resistance of the negative electrode sheet, increasing the energy density during battery charging and discharging, and achieving high-rate charging and discharging; on the other hand, controlling the silicon-based material content can suppress the volume expansion caused by the alloying of silicon-based materials with lithium, ensuring the stability of the negative electrode active material. The theoretical specific capacity of silicon-based materials (approximately 4200 mAh / g) is much higher than that of traditional graphite materials (372 mAh / g). Therefore, increasing the content of silicon-based materials can significantly improve the energy density of batteries. However, silicon-based materials undergo significant volume expansion when alloyed with lithium, which may compromise the structural stability of the battery. Therefore, it is necessary to control the content of silicon-based materials to account for 2%-30% of the mass of the negative electrode active material, so as to improve the energy density of the battery while ensuring the stability of the battery structure.

[0016] In some optional embodiments, the casing is further filled with an electrolyte comprising a solvent, a lithium salt, and additives. The solvent comprises one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; the additives comprise one or more of vinylene carbonate, methyl formate, ethyl acetate, and propyl propionate; and the lithium salt comprises one or more of lithium difluorophosphate, lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethyl)sulfonyl)imide. Using this combination of reagents as the electrolyte efficiently transports ions and improves the battery's charge and discharge efficiency.

[0017] In some optional embodiments, the area on the outer wall of the core covered by the insulating material layer is further provided with a QR code for associating the cylindrical lithium-ion battery's identification information. By setting a QR code on the insulating material layer to bind the battery's identity, the manufacturing information of the current battery's core and the insulating material layer can be obtained, facilitating quality control traceability.

[0018] A second aspect of this application provides an electrical device comprising a cylindrical lithium-ion battery as described in any of the preceding claims. Due to the advantages of cylindrical lithium-ion batteries as described above, the electrical device provided by this application has lower internal resistance and safer performance. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of a cylindrical lithium-ion battery according to an embodiment of this application;

[0021] Figure 2 This is an assembly schematic diagram of a cylindrical lithium-ion battery according to an embodiment of this application;

[0022] Figure 3 This is a front view of the current collector of a cylindrical lithium-ion battery according to an embodiment of this application;

[0023] Figure 4 This is a side view of a cylindrical lithium-ion battery according to an embodiment of this application, after the winding core and current collector are assembled.

[0024] Figure 5 This is a front view of the positive electrode sheet of a cylindrical lithium-ion battery according to an embodiment of this application after it has been unfolded, along with the fourth and fifth adhesive tapes.

[0025] Figure 6 This is a three-dimensional structural diagram of the core of a cylindrical lithium-ion battery according to an embodiment of this application;

[0026] Figure 7 This is a partial cross-sectional schematic diagram of the core of a cylindrical lithium-ion battery according to an embodiment of this application.

[0027] Reference numerals: 1-shell, 2-core, 3-cap, 4-current collector, 41-main body, 42-first bend, 43-straight section, 44-second bend, 21-positive electrode, 23-diaphragm, 25-negative electrode, 27-insulating material layer, 270-first tape, 272-second tape, 274-third tape, 276-fourth tape, 278-fifth tape, 210-starting end, 212-ending end. Detailed Implementation

[0028] The embodiments of this implementation are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this implementation, and should not be construed as limiting this implementation.

[0029] In the description of this embodiment, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this embodiment and simplifying the description, and 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. Therefore, they should not be construed as limitations on this embodiment.

[0030] In the description of this embodiment, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0031] In the description of this embodiment, unless otherwise explicitly limited, terms such as setting, installing, and connecting should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this embodiment in conjunction with the specific content of the technical solution.

[0032] Please refer to Figures 1-3 , Figure 1 This invention illustrates a schematic diagram of the structure of a cylindrical lithium-ion battery according to an embodiment of the present application. Figure 2 This diagram illustrates the assembled structure of a cylindrical lithium-ion battery according to one embodiment of this application. Figure 3 A schematic diagram of the current collector 4 is shown. The current collector 4 includes a main body 41, a first bent portion 42, a straight portion 43, and a second bent portion 44 connected in sequence. The current collector 4 has its main body 41 attached to the electrode end face at the top of the core 2, while the first bent portion 42 is bent accordingly to guide the straight portion 43 to extend toward the cap 3. Finally, the second bent portion 44 connected to the end of the straight portion 43 abuts against the cap 3 to form the external electrode of the cylindrical lithium-ion battery. Figure 1The diagram also shows the AC internal resistance of the battery from the bend 43 to the cap 3 as a first internal resistance R1, and the AC internal resistance of the battery from the bend 43 to the bottom of the casing 1 as a second internal resistance R2. The first internal resistance R1 and the second internal resistance R2 are set to satisfy: 70% ≤ R2 / (R1+R2) ≤ 95%. This reduces the overall internal resistance of the lithium battery (i.e., the sum of R1 and R2) while controlling the proportion of R2, thus preserving the short-circuit protection function of the current collector 4. This achieves a balance between the battery's low internal resistance performance and the tab's short-circuit protection performance, improving the safety of the cylindrical lithium-ion battery. Preferably, the first internal resistance R1 and the second internal resistance R2 satisfy: 72% ≤ R2 / (R1+R2) ≤ 85%. Preferably, when the first internal resistance R1 and the second internal resistance R2 satisfy R2 / (R1+R2)=80.4%, the experimentally obtained rate discharge retention rate is as high as 96.50%, the rate charge retention rate is 83.20%, the rate cycle retention rate is 72.70%, and the short circuit test pass rate is 100%.

[0033] In practice, reducing the overall internal resistance of cylindrical lithium-ion batteries can be achieved by optimizing the materials of the casing 1, the structure and / or materials of the cap 3, the materials and / or structures of the positive / negative electrode 25, the materials and / or structures of the separator, the composition and content of the binder, the composition and content of the conductive agent, the materials and usage ratio of the insulating material layer, and the formulation of the electrolyte solvent and additives.

[0034] In some alternative embodiments, a face pad is provided at one end of the battery metal casing, and a plastic sleeve is provided on the outside of the battery metal casing. The plastic sleeve can fix the position of the face pad to prevent external short circuits of the battery.

[0035] In some optional embodiments, the positive electrode 21 includes a positive electrode active material, a binder, and a conductive agent. The positive electrode active material is a nickel-based lithium-intercalated transition metal oxide material or a combination of a nickel-based lithium-intercalated transition metal oxide material and a lithium iron phosphate material. The metal element in the nickel-based transition metal oxide material further includes one or more of cobalt, manganese, and aluminum, and the proportion of nickel atoms in the positive electrode active material is greater than or equal to 75% of the total number of metal atoms. By controlling the proportion of nickel atoms in the positive electrode active material, the electron conductivity and ion diffusion are good, reducing the internal resistance of the positive electrode 21, increasing the energy density during battery charging and discharging, and achieving high-rate charging and discharging. The nickel-based lithium-intercalated transition metal oxide material can be one or more of lithium nickel cobalt manganese oxide, lithium nickel cobalt manganese aluminum oxide, lithium nickel cobalt aluminum oxide, and lithium nickel manganese oxide, and the lithium iron phosphate material can be lithium iron phosphate and / or lithium manganese iron phosphate.

[0036] In some optional embodiments, the negative electrode 25 includes a negative electrode active material, a binder, and a conductive agent. The negative electrode active material includes silicon-based materials and carbon-based materials, with the silicon-based material accounting for 2%-30% of the total mass. By controlling the mass percentage of silicon-based materials in the negative electrode active material, on the one hand, the silicon-based material can load and store more lithium ions, reduce the internal resistance of the negative electrode 25, and improve the energy density during battery charging and discharging, achieving high-rate charging and discharging; on the other hand, controlling the silicon content can suppress the volume expansion caused by the alloying of silicon-based materials with lithium, ensuring the stability of the negative electrode active material. The theoretical specific capacity of silicon-based materials (approximately 4200 mAh / g) is much higher than that of traditional graphite materials (372 mAh / g). Therefore, increasing the silicon-based material content can significantly improve the energy density of the battery. However, silicon-based materials undergo significant volume expansion when alloyed with lithium, which may compromise the structural stability of the battery. Therefore, it is necessary to control the silicon-based material content to be 2%-30% of the total mass of the negative electrode active material to both improve the energy density of the battery and ensure the stability of the battery structure.

[0037] The silicon-based material can be one or more of elemental silicon, silicon oxide, pre-lithiated silicon oxide, pre-magnesiated silicon oxide, and silicon / carbon composite materials. Typically, silicon-based materials are also carbon-coated to improve the interfacial stability and conductivity of the silicon-based material by coating the surface of the silicon-based material with amorphous carbon and / or carbon nanotubes. This improves the integrity of the SEI film (Solid Electrolyte Interface, a passivation layer formed on the surface of the electrode material during the first charge and discharge of a lithium-ion battery), reduces the possibility of deposited metal being reduced on its surface and forming dendrites, and improves the cycle and safety performance of the battery cell.

[0038] Carbon-based materials can be one or more of artificial graphite, natural graphite, hard carbon, and soft carbon, or a mixture thereof. Artificial graphite refers to graphite materials manufactured through artificial synthesis methods, such as high-temperature and high-pressure treatment of carbon materials (e.g., graphite ore, coke) or chemical synthesis. It exhibits strong consistency in morphology and particle size distribution, and its structure can take various forms, such as blocky, fibrous, or powdery forms. Natural graphite refers to graphite formed naturally in the world, mainly existing in the form of graphite schist, graphite gneiss, graphite-bearing schist, and metamorphic shale. Hard carbon refers to carbon that is difficult to graphitize; it is usually obtained from the thermal decomposition of polymers, such as resin carbon, pyrolytic carbon from organic polymers, and carbon black. Soft carbon refers to carbon that is easily graphitized, that is, amorphous carbon that can be graphitized at temperatures above 2500℃. Common soft carbons include petroleum coke, needle coke, carbon fibers, and carbon microspheres.

[0039] In some optional embodiments, the casing 1 is further filled with an electrolyte comprising a solvent, a lithium salt, and additives. The solvent comprises one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. The additives comprise one or more of vinylene carbonate, methyl formate, ethyl acetate, and propyl propionate. The lithium salt comprises one or more of lithium difluorophosphate, lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide. Using this combination of reagents as the electrolyte efficiently transports ions and improves the battery's charge and discharge efficiency.

[0040] In some alternative implementations, see [link to implementation details]. Figure 4 , Figure 6 and Figure 7 The core 2 is formed by winding together a positive electrode sheet 21, a separator 23, and a negative electrode sheet 25 in a stacked configuration. An insulating material layer 27 is wrapped around the core 2 to electrically insulate it from the casing 1. By wrapping the core 2 with the insulating material layer 27, metal shavings from the battery manufacturing process are prevented from adhering to the core 2, thus avoiding short circuits and improving the safety of the cylindrical lithium-ion battery. Simultaneously, the battery's charge retention capacity is enhanced, optimizing battery performance and lifespan.

[0041] Furthermore, the ratio of the first internal resistance R1 to the second internal resistance R2 can be achieved by adjusting the resistance value of R1. Specifically, to increase the first internal resistance R1, the length of the straight portion 43 of the current collector 4 can be extended, or the cross-sectional area of ​​the first bent portion 42 can be reduced; to decrease the first internal resistance R1, the straight portion 43 of the current collector 4 can be shortened, or the cross-sectional area of ​​the first bent portion 42 can be increased. The implementation methods are relatively simple and have good controllability.

[0042] To further improve the safety performance of cylindrical lithium-ion batteries, in some optional implementation methods, see [link to relevant documentation]. Figure 4The outer surface of the core 2 is also covered with an insulating material layer 27. The insulating material layer 27 includes a first adhesive tape 270 located in the middle section of the outer wall of the core 2. The innermost layer of the first adhesive tape 270 adheres to the side of the core 2, while the outermost layer abuts against the inner wall of the housing 1, thereby radially fixing the core 2 and the housing 1. By setting the first adhesive tape 270 in the middle section of the outer wall of the core 2, the first adhesive tape 270 wraps around the core 2 for insulation, and at the same time abuts against the inner wall of the housing 1 to radially fix the core 2 and the housing 1, thereby enhancing the stability of the battery structure. In specific implementation, the first tape 270 is preferably an expandable tape. The base material of the expandable tape is a synthetic resin material, and the coating is polyacrylate. It is used to achieve good insulation performance and utilize the expandable properties of the expandable tape. Therefore, it is not necessary to wrap it too thickly on the outer side of the core 2, so as to avoid interference with the inner wall of the shell 1 and affect the assembly of the core 2. After the core 2 is assembled, the expandable tape absorbs the electrolyte in the shell 1 and / or expands adaptively with the heat generated by the charging and discharging of the battery. At this time, the outermost layer of the expandable tape is pressed against the inner wall of the shell 1 to radially fix the core 2. At the same time, the expandable tape also has a buffering function, which is used to absorb the stress on the shell 1 caused by the expansion of the core 2 due to charging and discharging, effectively enhancing the stability of the battery structure and ensuring the charging and discharging performance of the battery.

[0043] In some alternative implementations, see [link to implementation details]. Figure 4 The width of the first tape 270 is 50%-99% of the axial height of the core 2. If the width of the first tape 270 is less than 50% of the height of the core 2, the fixing effect of the core 2 will be poor; if the width of the first tape 270 is greater than 99% of the height of the core 2, the first tape 270 will be too close to the tabs at both ends of the core 2. After absorbing the electrolyte, the first tape 270 will deform and may corrode the tabs of the core 2. Setting the width of the first tape 270 to 50%-99% of the height of the core 2 can eliminate the corresponding safety hazards.

[0044] In some alternative implementations, see [link to implementation details]. Figure 4The insulating material layer 27 further includes a third adhesive tape 274, which is wound around the core 2 near both ends and extends axially along the side of the core 2, covering part of its top and bottom end faces. By wrapping the third adhesive tape 274 around the core 2 near both ends, the third adhesive tape 274 covers part of the end faces of the electrode faces at both ends of the core 2, especially the outer edge of the current collector 4 relative to the inner wall of the housing 1. This prevents the core 2 from rubbing against the inner wall of the housing 1 during installation or from coming into contact with the inner wall of the housing 1 after assembly, thus improving battery safety. Meanwhile, the parts of the electrode faces at both ends of the core 2 not covered by the third adhesive tape 274 retain conductivity. It is understood that when the electrode faces of the core 2 are welded with corresponding current collectors 4, the third adhesive tape 274 should also cover the periphery of the current collector 4, so that the current collector 4 is insulated from the metal housing 1, further improving battery safety.

[0045] In the specific implementation process, the third tape 274 extends axially along the side of the core 2 until the corresponding end face, and then extends radially from the periphery of the corresponding end face towards the center by a predetermined distance. This is to specifically insulate and protect the outer edge of the electrode face of the casing 1, which is prone to impact, and reduce the risk of short circuit between the core 2 and the casing 1. The third tape 274 is preferably PI tape. PI tape is a film-type tape that is resistant to high temperature, chemical corrosion and has high insulation performance. It is easy to apply and cover the end face of the core 2. It has good compatibility with other processes in battery assembly and manufacturing and does not interfere with the normal production process of the battery. The third tape 274 also uses a high-performance PI film as the substrate and coats it with a special adhesive that is resistant to lithium battery electrolyte to cover the side and part of the end face of the core 2 to adapt to the harsh environment inside the battery.

[0046] In some alternative implementations, see [link to implementation details]. Figure 4 The insulating material layer 27 further includes a second adhesive tape 272, which is wound around the side of the core 2 to the portion not covered by the first adhesive tape 270 and the third adhesive tape 274. The second adhesive tape 272 is connected to or partially overlaps with the first adhesive tape 270 and the third adhesive tape 274. The second adhesive tape 272 is used to fill the portion not covered by the first adhesive tape 270 and the third adhesive tape 274, achieving complete insulation of the outer side of the core 2 and eliminating the risk of short circuit with the casing 1. In specific implementation, the second adhesive tape 272 is preferably PET tape to prevent electrolyte from seeping towards the ends of the core 2, maintaining the integrity of the internal structure of the battery.

[0047] In some alternative implementations, see [link to implementation details]. Figure 5The cylindrical lithium-ion battery further includes a fourth tape 276 and a fifth tape 278. The fourth tape 276 covers the starting end 210 of the positive electrode 21 located on the innermost side of the core 2, and the fifth tape 278 covers the ending end 212 of the positive electrode 21 located on the outermost side of the core 2. The fourth tape 276 and the fifth tape 278 cover the starting end 210 and the ending end 212 of the positive electrode 21, respectively, to insulate the starting end 210 and the ending end 212 of the positive electrode 21. This prevents the positive electrode 21 from shifting during the winding process and becoming misaligned with the negative electrode 25 in the axial direction. As a result, the area of ​​the positive electrode 21 coated with the positive active material protrudes in the axial direction relative to the area of ​​the negative electrode 25 coated with the negative active material. The negative electrode 25 cannot cover the positive electrode 21. During actual charging and discharging, the axially protruding part of the area of ​​the positive electrode 21 coated with the positive active material relative to the area of ​​the negative electrode 25 coated with the negative active material will produce local lithium plating, which will affect the electrochemical performance of the positive electrode 21 and ultimately affect the charging and discharging performance and safety of the battery. In the specific implementation process, the fourth tape 276 should cover the positive electrode active material coating area and / or ceramic layer coating area on the positive electrode sheet 21, and the fifth tape 278 should cover a portion of both the positive electrode sheet 21 and the separator 23.

[0048] In some optional embodiments, the area on the outer wall of the core 2 covered by the insulating material layer 27 is further provided with a QR code for associating with the identity information of the cylindrical lithium-ion battery. By setting a QR code on the insulating material layer 27, the battery identity is bound, and the manufacturing information of the current battery's core 2 and the insulating material layer 27 is obtained, facilitating quality control traceability. In specific implementations, the number of QR codes can be one or more, and they can be set on the outer wall of the core 2 by spraying or etching. The shape of the QR code can be square, circular, or irregular, and its area can be 1-200 mm². 2 The identification information of a cylindrical lithium-ion battery can include information about the core 2 and the insulating material layer 27, making it convenient to trace the tape information of each area on the core 2.

[0049] A second aspect of this application provides an electrical device comprising a cylindrical lithium-ion battery as described in any of the preceding claims. Due to the advantages of cylindrical lithium-ion batteries as described above, the electrical device provided by this application has lower internal resistance and safer performance.

[0050] It should be noted that the bottom end of the core mentioned in this application is electrically connected to the shell. This electrical connection includes both direct and indirect electrical connections. Direct electrical connection refers to the end face of the bottom end of the core being directly welded to the bottom wall of the shell. Indirect electrical connection refers to the connection between the core and the bottom wall of the shell by setting a current collector or adapter plate.

[0051] One method for preparing the cylindrical lithium-ion battery of the present invention is as follows:

[0052] (1) Making core 2: The positive electrode 21, the separator 23 and the negative electrode 25 are stacked in sequence. The fourth tape 276 is attached to the starting end 210 of the positive electrode 21 for winding and covers part of the positive active material coating area on the positive electrode 21 and part of the separator. The fifth tape 278 is attached to the outermost ending end 212 of the positive electrode 21 after winding and extends to the separator 23. The positive electrode 21, the separator 23 and the negative electrode 25 are wound from the starting end 210 to form core 2.

[0053] (2) Core insulation: The first tape 270 is wound around the middle section of the side of the core 2 using a winding machine. The first tape 270 extends circumferentially along the side of the core 2 and completely covers the side of the core 2 at least once. The third tape 274 is wound around the core 2 near its two ends. The third tape 274 is wound circumferentially and spirally extended on the shaft to the electrode end faces at both ends of the core 2, and extends radially a predetermined distance along the outer edge of the electrode end faces. The second tape 272 is used to cover the exposed area of ​​the side of the core 2 until the side of the core 2 is completely wrapped with insulating material.

[0054] (3) Preparation of electrolyte: Dissolve the fully dried lithium salt in an organic solvent to prepare an electrolyte;

[0055] (2) Assembly: First, weld the bottom end of the core 2 to the adapter piece, then put the core 2 into the housing, then weld the adapter piece to the housing 1, and weld the top end of the core 2 to the main body 41 of the current collector 4. After injecting electrolyte, weld the cap 3 to the second bent part 44 of the current collector 4 to seal the housing 1, thus obtaining a cylindrical lithium-ion battery.

[0056] The testing methods for the first internal resistance R1 and the second internal resistance R2 in this invention are as follows:

[0057] After removing the cap 3 of the cylindrical lithium-ion battery (without damaging the current collector 4), use a multimeter to test the AC internal resistance of the battery between the first bend 42 of the current collector 4 and the cap 3 as the first internal resistance R1, and test the AC internal resistance of the battery between the first bend 42 of the current collector 4 and the bottom of the casing 1 as the second internal resistance R2. Record the values ​​of the first internal resistance R1 and the second internal resistance R2.

[0058] The present invention will be further explained below with reference to Examples 1-14 and Comparative Examples 1-4.

[0059] Example 1:

[0060]

[0061]

[0062] Example 2:

[0063]

[0064] Example 3:

[0065]

[0066]

[0067] Comparative Example 1:

[0068]

[0069] Comparative Example 2:

[0070]

[0071]

[0072] Example 4:

[0073]

[0074] Example 5:

[0075]

[0076]

[0077] Comparative Example 3:

[0078]

[0079] Comparative Example 4:

[0080]

[0081] Example 6:

[0082]

[0083]

[0084] Example 7:

[0085]

[0086] Example 8:

[0087]

[0088]

[0089] Example 9:

[0090]

[0091] Example 10:

[0092]

[0093]

[0094] Example 11:

[0095]

[0096] Example 12:

[0097]

[0098]

[0099] Example 13:

[0100]

[0101] Example 14:

[0102]

[0103] Examples 1-14 and Comparative Examples 1-4 were subjected to 10C rate discharge retention rate test, 3C rate charge retention rate test, 10C rate cycle retention rate test, and short-circuit safety test, respectively.

[0104] The test method for 10C rate discharge retention rate is as follows:

[0105] Take a cylindrical lithium-ion battery prepared according to any of the above embodiments, place it in a constant temperature chamber at 25°C for more than 4 hours, and test it according to the following steps:

[0106] S1: Discharge the battery at a constant current of 0.1C until it reaches 2.5V cutoff, and let it stand for 10 minutes;

[0107] S2: Charge the battery at a constant current of 0.2C until it reaches 4.2V (cutoff), and then charge it at a constant voltage until it reaches 0.05C (cutoff), and let it stand for 10 minutes.

[0108] S3: Discharge the battery at a constant current of 0.2C until it is cut off at 2.5V, and let it stand for 10 minutes. Then read the battery capacity value C0 at this time.

[0109] S4: Charge the battery at a constant current of 0.2C until it reaches 4.2V (cutoff), and then charge it at a constant voltage until it reaches 0.05C (cutoff), and let it stand for 10 minutes.

[0110] S5: Discharge the battery at a constant current of 10C until it reaches 2.5V cutoff, and let it stand for 10 minutes. Then read the battery capacity value C3 at this time.

[0111] S6: The capacity retention rate at a 10C discharge rate is calculated as: (C3 / C0)*100%

[0112] The 3C rate charging retention rate test method is as follows:

[0113] Take a cylindrical lithium-ion battery prepared according to any of the above embodiments, place it in a constant temperature chamber at 25°C for more than 4 hours, and test it according to the following steps:

[0114] S1: Discharge the battery at a constant current of 0.1C until it reaches 2.5V cutoff, and let it stand for 10 minutes;

[0115] S2: Charge the battery at a constant current of 0.2C until it reaches 4.2V (cutoff), and then charge it at a constant voltage until it reaches 0.05C (cutoff), and let it stand for 10 minutes.

[0116] S3: Discharge the battery at a constant current of 0.2C until it reaches 2.5V cutoff, and let it stand for 10 minutes;

[0117] S4: Charge the battery at a constant current of 3C until it reaches 4.2V (cutoff), and then charge it at a constant voltage until it reaches 0.05C (cutoff), and let it stand for 10 minutes.

[0118] S5: Read the charging capacity value C1 of the constant current charging section in S4, and the total charging capacity C2 after constant voltage charging.

[0119] S6: The performance of high-rate charging can be expressed by the constant current and constant voltage ratio. The capacity retention rate of 3C high-rate charging is calculated to be: (C1 / C2)*100%.

[0120] The test method for 10C rate cycle retention is as follows:

[0121] Take a cylindrical lithium-ion battery prepared according to any of the above embodiments, place it in a constant temperature chamber at 25°C for more than 4 hours, and test it according to the following steps:

[0122] S1: Discharge the battery at a constant current of 0.1C until it reaches 2.5V cutoff, and let it stand for 10 minutes;

[0123] S2: Charge the battery at a constant current of 0.2C until it reaches 4.2V (cutoff), and then charge it at a constant voltage until it reaches 0.05C (cutoff), and let it stand for 10 minutes.

[0124] S3: Discharge the battery at a constant current of 0.2C until it reaches 2.5V cutoff, and let it stand for 10 minutes;

[0125] S4: Charge the battery at a constant current of 3C to 4.2V, and then charge at a constant voltage to 0.05C to cut off, and let it stand for 10 minutes;

[0126] S5: Discharge the battery at a constant current of 10C until it reaches 2.5V cutoff, and let it stand for 10 minutes. Then read the capacity value C1 at this time.

[0127] S6: Repeat steps S4 and S5 above, looping 600 times;

[0128] S7: Read the discharge capacity of the battery at 10C constant current to 2.5V for the 600th discharge cycle as C600. The cycle performance of a single battery can be obtained by comparing the discharge capacity of the battery at 10C constant current to 2.5V for the 600th discharge cycle with C600 and the discharge capacity of the battery at 10C constant current to 2.5V for the first discharge cycle with C1. The rate cycle capacity retention rate is calculated as: (C600 / C1)*100%.

[0129] The short-circuit safety test method is as follows:

[0130] Take a cylindrical lithium-ion battery prepared according to any of the above embodiments, place it in a constant temperature chamber at 25°C for more than 4 hours, and test it according to the following steps:

[0131] S1: Discharge the battery at a constant current of 0.1C until it reaches 2.5V cutoff, and let it stand for 10 minutes;

[0132] S2: Charge the battery at a constant current of 0.2C until it reaches 4.2V (cutoff), and then charge it at a constant voltage until it reaches 0.05C (cutoff), and let it stand for 10 minutes.

[0133] S3: Discharge the battery at a constant current of 0.2C until it reaches 2.5V cutoff, and let it stand for 10 minutes;

[0134] S4: Charge the battery at a constant current of 0.2C until it reaches 4.2V (cutoff), and then charge it at a constant voltage until it reaches 0.05C (cutoff), and let it stand for 10 minutes.

[0135] S5: Use a 20mΩ resistor to short-circuit the positive and negative terminals of the battery and record the battery voltage and temperature;

[0136] S6: If there is no fire throughout the process and the battery's outer surface temperature is below 150°C, the test is considered passed; otherwise, it is considered failed.

[0137] S7: The percentage of batteries that pass the parallel test is called the pass rate.

[0138] Using Example 1 as the blank group, Examples 2-3 and Comparative Examples 1-2 are variable experimental groups concerning the proportion of the second internal resistance R2; Examples 4-5 and Comparative Examples 3-4 are variable experimental groups concerning the proportion of the width of the first tape 270 in the axial height direction of the core 2; Examples 6-8 are variable experimental groups concerning the types of insulating material layer 27, fourth tape 276, and fifth tape 278; Examples 9-12 are variable experimental groups concerning the types of positive / negative electrode active materials; Examples 13-14 are variable experimental groups concerning the position and size of the QR code. Specific comparison results are shown in Tables 1-5.

[0139] Table 1:

[0140]

[0141] As shown in Table 1, when the proportion of the second internal resistance R2 is less than 70% or greater than 95%, the rate charge / discharge and cycle performance decrease significantly. When the proportion of the second internal resistance R2 exceeds 95%, the first internal resistance R1 is too small, and the current collector 4 generates heat too slowly when the battery is short-circuited. The first bent part 42 and the straight part 43 of the current collector 4 cannot melt in time, resulting in the complete failure of the battery's short-circuit protection function. When the proportion of the second internal resistance R2 is less than 70%, the current collector 4 generates heat too quickly, which easily disrupts the battery's temperature rise balance, leading to frequent temperature cutoff triggers and affecting the battery's fast charge and discharge performance.

[0142] Table 2:

[0143]

[0144] As can be seen from Table 2, when the width of the first tape 270 accounts for less than 50% or more than 99% of the axial height of the core 2, the short-circuit test pass rate, rate discharge and cycle performance decrease significantly. Moreover, when the width of the first tape 270 accounts for more than 99%, the first tape 270 is prone to corroding the conductive sheets, current collectors and other metal parts of the positive / negative electrodes of the core 2, which seriously affects the safety performance of the battery.

[0145] Table 3:

[0146]

[0147] As can be seen from Table 3, when the first tape 270 is a non-expanding tape, which does not have a certain deformation in the thickness direction, the rate cycle performance drops significantly. This is mainly because tapes such as PET and PI cannot expand adaptably during the continuous charging and discharging of the battery, which leads to deformation and displacement of the core 2 during use, resulting in poor stability of the battery structure and compromised safety.

[0148] Table 4:

[0149]

[0150] As shown in Table 4, when lithium nickel cobalt aluminum oxide with a nickel molar content of 88% is used as the positive electrode active material, the rate charge-discharge performance is better, while when lithium nickel cobalt manganese aluminum oxide with a nickel molar content of 88% is used, the rate cycle performance is better. When the silicon content in the negative electrode active material is 5%, the rate charge-discharge performance and cycle performance are relatively better. However, increasing the silicon content will lead to a decrease in battery safety. This may be because the silicon-lithium combination will cause the negative electrode sheet 25 to expand, resulting in instability in the battery structure. Adding hard carbon will lead to a deterioration in rate cycle performance.

[0151] Table 5:

[0152]

[0153] As can be seen from Table 5, the location and size of the QR code will not affect the performance of the battery. However, in practical applications, the QR code can play a significant role in quality control and traceability. Therefore, it is safe to engrave the QR code on the battery core 2 during the production process.

[0154] The cylindrical lithium-ion battery of this application embodiment can achieve a 10C rate discharge retention rate of 83-97%, a 3C rate charge retention rate of 62-85%, and a 10C rate cycle retention rate of 60-90%.

[0155] In the description of this specification, references to the terms "some embodiments," "an embodiment," or similar descriptions mean that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment or example. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0156] Although embodiments of this implementation have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this implementation, the scope of which is defined by the claims and their equivalents.

Claims

1. A cylindrical lithium-ion battery, comprising a casing, a core disposed within the casing and electrically connected at its bottom end to the casing, and a cap correspondingly disposed on the top end of the core, wherein the core is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet arranged in sequence, the casing is filled with an electrolyte to wet the core, the cylindrical lithium-ion battery is a full-tab cylindrical lithium-ion battery, and the top end of the core is further provided with a current collector electrically connected to the cap, the overall internal resistance of the cylindrical lithium-ion battery is R1+R2, and the current collector includes a main body portion, a first bent portion, a straight portion, and a second bent portion connected in sequence, the main body portion... The body is welded to the top of the core, and the second bend is electrically connected to the cap. The AC internal resistance of the battery between the first bend and the cap is set as the first internal resistance R1, and the AC internal resistance of the battery between the first bend and the bottom of the casing is set as the second internal resistance R2. The first internal resistance R1 and the second internal resistance R2 satisfy: 72% ≤ R2 / (R1+R2) ≤ 85%. An insulating material layer is wrapped around the core to electrically insulate it from the casing. The insulating material layer includes a first tape wound around the middle section of the outer wall of the core, with its inner end adhered to the core. The outermost layer of the first tape is wound around the outer wall of the housing, and when the core is assembled into the housing, the outermost first tape abuts against the inner wall of the housing to fix the core and the housing radially relative to each other; the width of the first tape accounts for 50%-99% of the axial height of the core; the insulating material layer also includes a third tape, which is wound around the core near one or both ends, and extends along the side of the core and covers part of its top and / or bottom end faces; the insulating material layer also includes a second tape, which is wound around the side of the core and not covered by the outer wall. The cylindrical lithium-ion battery includes a fourth tape covering the innermost starting end of the positive electrode sheet located on the core, and a fifth tape covering the outermost ending end of the positive electrode sheet located on the core. The cylindrical lithium-ion battery retains 83-97% of its discharge rate at 10C, 62-85% at 3C, and 60-90% at 10C cycle rate.

2. The cylindrical lithium-ion battery according to claim 1, characterized in that, The insulating material layer, the fourth tape, and the fifth tape can all be one or more of the following: expandable tape, PET tape, PI tape, and polyurethane tape.

3. The cylindrical lithium-ion battery according to claim 1, characterized in that, The positive electrode sheet includes a positive electrode active material, a binder, and a conductive agent. The positive electrode active material is a nickel-based lithium-intercalated transition metal oxide material or a combination of a nickel-based lithium-intercalated transition metal oxide material and a lithium iron phosphate material. The metal element in the nickel-based lithium-intercalated transition metal oxide material also includes one or more of cobalt, manganese, and aluminum, and the proportion of nickel atoms in the positive electrode active material to the total number of transition metal atoms is greater than or equal to 75%.

4. The cylindrical lithium-ion battery according to claim 1, characterized in that, The negative electrode sheet includes a negative electrode active material, a binder, and a conductive agent. The negative electrode active material includes silicon-based materials and carbon-based materials, and the mass percentage of silicon-based materials in the negative electrode active material is 2%-30%.

5. The cylindrical lithium-ion battery according to claim 1, characterized in that, The electrolyte comprises a solvent, a lithium salt, and additives. The solvent comprises one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. The additives comprise one or more of vinylene carbonate, methyl formate, ethyl acetate, and propyl propionate. The lithium salt comprises one or more of lithium difluorophosphate, lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethyl)sulfonylimide.

6. The cylindrical lithium-ion battery according to claim 1, characterized in that, The outer wall of the winding core, where the insulating material layer is covered, also has a QR code for associating with the identity information of the cylindrical lithium-ion battery.

7. An electrical device, characterized in that, Including the cylindrical lithium-ion battery according to any one of claims 1-6.

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