Cylindrical lithium ion battery winding core and cylindrical lithium ion battery

Abstract

The application discloses a winding core for a cylindrical lithium ion battery and the cylindrical lithium ion battery. The winding core before being curled comprises, in sequence from top to bottom, a positive electrode sheet, a first diaphragm and a negative electrode sheet. One end of the winding core is a winding starting end, and the other end is a winding ending end. The winding ending end of the negative electrode sheet away from the first diaphragm is provided with an empty foil winding area. The surface of the current collector of the empty foil winding area is not provided with a negative active layer containing a negative active material. According to the application, the empty foil winding area without an active material coating layer is arranged at the ending end of the winding core away from the first diaphragm. After the winding core is packaged, the current collector of the empty foil winding area can be in contact with the inner wall of the steel shell. With the high thermal conductivity of the metal current collector, an efficient heat dissipation path close to the steel shell is formed to improve heat management. In addition, the cost of the negative electrode slurry of the empty foil winding area is directly saved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more specifically, to a cylindrical lithium-ion battery core and a cylindrical lithium-ion battery. Background Technology

[0002] Lithium-ion batteries are used in applications requiring instantaneous high-power output, such as power tools and electric two-wheelers, where high-rate performance is crucial. These devices experience frequent fluctuations in operating conditions, necessitating rapid high-current charging and discharging. This places stringent demands on the battery's rate discharge capability, operational stability, and lifespan. Cylindrical lithium-ion batteries are typically assembled into a core by winding positive and negative electrodes and a separator, then encapsulated in a stainless steel casing. This compact and well-organized structure is suitable for the assembly needs of various small power devices. During high-rate charging and discharging, the internal electrochemical reaction rate accelerates significantly. Rapid ion migration and intense charge exchange generate substantial heat within the core. As the core's core operating area, its dense and relatively enclosed internal structure makes it prone to heat accumulation. The efficiency of heat conduction to the casing and dissipation directly impacts the battery's rate performance and cycle life. If internal heat cannot dissipate promptly, the battery's operating temperature will rise continuously, exacerbating internal side reactions, increasing battery polarization, and ultimately reducing the battery's rate output capability. Long-term heat accumulation can also continuously degrade the performance of electrode and separator materials, accelerate battery aging, significantly shorten battery cycle life, and in severe cases, affect battery safety. Therefore, efficient internal heat conduction and heat dissipation capabilities are the core key to the research and application of high-rate cylindrical lithium-ion batteries.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a cylindrical lithium-ion battery core and a cylindrical lithium-ion battery, and to solve the problem of how to improve the axial heat conduction efficiency of the cylindrical core and reduce the local temperature rise under high-rate conditions.

[0005] This invention is implemented as follows: In a first aspect, the present invention provides a cylindrical lithium-ion battery core, wherein the core comprises a positive electrode sheet, a first separator and a negative electrode sheet stacked sequentially before being wound, and one end of the core is a winding start end and the other end is a winding end end; The negative electrode sheet has an empty foil winding area at the winding end away from the first separator, and the current collector surface of the empty foil winding area is not provided with a negative electrode active layer containing negative electrode active material. The circumferential surface of the core is adhered with conductive finishing tape for fixing the core. The conductive finishing tape includes a substrate layer and an adhesive layer. The substrate layer and / or the adhesive layer contain conductive carbon black, and the mass percentage of the conductive carbon black in the layer is 2% to 10%. The thermal conductivity of the conductive finishing tape is 0.5 to 3.0 W / (m·K). The volume resistivity of the conductive finishing tape in the thickness direction is 10 to 80 Ω·cm.

[0006] In an optional embodiment, the direction from the starting end of the winding to the ending end is the length direction, and the direction perpendicular to the length direction is the width direction; along the width direction, the core includes a coated side and a blank foil side; the cylindrical lithium-ion battery core satisfies at least one of the following characteristics: A. The length dimension of the empty foil winding area is 55~60mm; B. The positive electrode sheet includes a positive current collector, a positive electrode coating area disposed on the coated side surface of the positive current collector, and a positive electrode empty foil area disposed on the empty foil side of the positive current collector; C. The negative electrode sheet includes a negative current collector and a first negative electrode coating area disposed on the negative current collector near the first diaphragm and a second negative electrode coating area disposed away from the first diaphragm. The first negative electrode coating area is located on the coating side of the first negative electrode empty foil area, and the second negative electrode coating area is located on the coating side of the second negative electrode empty foil area.

[0007] In an optional embodiment, the dimension of the positive electrode coating area in the length direction is equal to that of the positive electrode current collector; And / or, the ratio of the dimension of the positive electrode coating region in the length direction to its dimension in the width direction is 27~29:1; And / or, the dimension of the first negative electrode coating area in the length direction is equal to the length of the negative electrode current collector; And / or, the ratio of the dimension of the first negative electrode coating area in the length direction to its dimension in the width direction is 27~28:1; And / or, the end of the first negative electrode coating area extends 30-40 mm beyond the end of the positive electrode coating area; And / or, the ratio of the length dimension to the width dimension of the second negative electrode coating area is 26~27:1; And / or, an empty foil starting area is provided on the negative electrode current collector located at the starting end of the first negative electrode coating area, and the size of the empty foil starting area in the length direction is 55-60mm; And / or, the end of the positive electrode coating area extends 20-30 mm beyond the end of the second negative electrode coating area.

[0008] In an optional embodiment, the empty foil side of the first negative electrode coating area extends 6-11 mm beyond the positive electrode coating area; And / or, the empty foil side of the second negative electrode coating area extends 60-65 mm beyond the positive electrode coating area; In an optional embodiment, the ratio of the length dimension of the first diaphragm to its width dimension is 27~28:1; And / or, the end of the first diaphragm extends 40-120 mm beyond the first negative electrode coating area; And / or, a second diaphragm is provided on the side of the negative electrode sheet away from the first diaphragm, and the ratio of the dimension of the second diaphragm in the length direction to its dimension in the width direction is 27~29:1; And / or, a second diaphragm is provided on the side of the negative electrode sheet away from the first diaphragm, and the end of the second diaphragm extends 0~10mm beyond the end of the second negative electrode coating area.

[0009] In an optional embodiment, both the first diaphragm and the second diaphragm include a substrate and a ceramic coating disposed on the substrate, wherein the thickness of the substrate is 6-8 μm and the thickness of the ceramic coating is 1.5-2.5 μm; And / or, the porosity of the first diaphragm and the second diaphragm is independently 40% to 46%.

[0010] The present invention also provides a cylindrical lithium-ion battery, comprising a steel casing, an electrolyte encapsulated within the steel casing, and a winding core as described in any of the foregoing embodiments.

[0011] In an optional embodiment, the back side of the conductive finishing tape contacts the steel shell.

[0012] In an optional embodiment, the width of the conductive finishing tape is 8~20mm, and the ratio of its length to the outer perimeter of the core is 1.1~1.5. And / or, the thickness of the negative electrode sheet is 85~88μm, the thickness of the positive electrode sheet is 85~88μm, and the ratio of the thickness of the negative electrode sheet to the thickness of the positive electrode sheet is 0.99~1.01:1; And / or, the compaction density of the negative electrode sheet is 1.45~1.65 g / cm³, and the compaction density of the positive electrode sheet is 3.5~3.7 g / cm³; the ratio of the compaction density of the positive electrode sheet to the compaction density of the negative electrode sheet is 2.1~2.3:1.

[0013] In an optional embodiment, the negative electrode active material of the negative electrode sheet is a mixture of graphite and silicon-carbon composite material, wherein the graphite is one or both of artificial graphite and natural graphite, and the silicon-carbon is chemical vapor deposition silicon-carbon or biomass silicon-carbon, and the mass ratio of silicon-carbon in the negative electrode active material is 5% to 25%; And / or, the positive electrode active material in the positive electrode sheet is a ternary material.

[0014] The present invention has the following beneficial effects: This application provides an empty foil winding area without an active material coating at the end of the core away from the first diaphragm. After the core is packaged, the current collector in the empty foil winding area can contact the inner wall of the steel shell. The high thermal conductivity of the metal current collector forms an efficient heat dissipation path that is close to the steel shell to improve thermal management. In addition, it directly saves the cost of negative electrode paste in the empty foil winding area. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the core structure (before curling). Figure 2 This is a cross-sectional view of the core. Figure 3 This is a schematic diagram of the core structure (fixed with conductive finishing tape after being rolled up). Figure 4 This is a schematic diagram of the negative electrode.

[0017] Illustration: 100 - Positive electrode sheet; 200 - First separator; 300 - Negative electrode sheet; 310 - First negative electrode coating area; 320 - Second negative electrode coating area; 400 - Second separator; 500 - Conductive finishing tape. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0019] This invention provides a cylindrical lithium-ion battery core, such as... Figure 1-4As shown, the core includes a positive electrode 100, a first diaphragm 200 and a negative electrode 300 stacked in sequence before winding. One end of the core is the winding start end and the other end is the winding end end. The negative electrode sheet 300 has an empty foil winding area at the winding end on the side away from the first diaphragm 200, and the current collector surface of the empty foil winding area is not provided with a negative electrode active layer containing negative electrode active material. The circumferential surface of the core is adhered with conductive finishing tape 500 for fixing the core. The conductive finishing tape 500 includes a substrate layer and an adhesive layer. The substrate layer and / or the adhesive layer contain conductive carbon black. The mass percentage of the conductive carbon black in the layer is 2% to 10%, specifically 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%. The thermal conductivity of the conductive finishing tape 500 is 0.5 to 3.0 W / (m·K), specifically 0.5, 0.8, 1.0, 1.2, 1.5, 1.8, 2.0, 2.3, 2.5, 2.8, or 3.0 W / (m·K). The volume resistivity of the conductive finishing tape 500 in the thickness direction is 10 to 80 Ω·cm, specifically 10, 15, 20, 25, 30, 40, 50, 60, 70, or 80 Ω·cm.

[0020] This application provides an empty foil winding area without an active material coating at the end of the core away from the first diaphragm 200 (i.e., the outermost layer). After the core is packaged, the current collector in the empty foil winding area can contact the inner wall of the steel shell. The high thermal conductivity of the metal current collector forms an efficient heat dissipation path that is close to the steel shell to improve thermal management. In addition, it directly saves the cost of the negative electrode paste in the empty foil winding area.

[0021] Furthermore, traditional sealing tapes often use insulating polymer materials with extremely low thermal conductivity, severely hindering heat conduction from the core to the steel casing, becoming a heat dissipation bottleneck. This leads to excessive temperature rise in the battery under high-rate conditions, limiting further performance. Simultaneously, the insulating sealing tape makes the outermost ring of the negative electrode electrically insulated from the steel casing, leaving the steel casing potential in a suspended state. Under high-temperature storage conditions, electrochemical corrosion may occur on the inner wall of the steel casing, affecting battery reliability. In an optional embodiment, the conductive sealing tape 500 includes a substrate layer and an adhesive layer. The substrate layer and / or the adhesive layer contain conductive carbon black, with the conductive carbon black comprising 2% to 10% of the mass percentage of the layer. This gives the conductive sealing tape 500 both thermal and electrical conductivity, forming a thermal conduction path from the core to the steel casing, improving the core's heat dissipation effect, and effectively reducing battery temperature rise under high-rate conditions.

[0022] In alternative implementations, such as Figure 1As shown, the direction from the starting end of the winding to the ending end of the winding is the length direction, and the direction perpendicular to the length direction is the width direction; along the width direction, the core includes a coated side and an empty foil side.

[0023] In an optional embodiment, the empty foil winding area of ​​the cylindrical lithium-ion battery core has a length dimension of 55~60mm, specifically 55mm, 55.5mm, 56mm, 56.5mm, 57mm, 57.5mm, 58mm, 58.5mm, 59mm, 59.5mm or 60mm. When winding to the end, the copper foil has sufficient extension allowance, which avoids excessive tension causing edge wrinkles or tears, and provides a stable and continuous metal bonding surface to bond with the steel shell, ensuring the structural integrity of the heat conduction / electrical conduction path.

[0024] In an optional embodiment, the positive electrode 100 of the cylindrical lithium-ion battery core includes a positive current collector, a positive electrode coating area disposed on the coating side surface of the positive current collector, and a positive electrode empty foil area disposed on the empty foil side of the positive current collector.

[0025] In an optional embodiment, the negative electrode 300 of the cylindrical lithium-ion battery core includes a negative electrode current collector and a first negative electrode coating area 310 disposed near the first separator 200 and a second negative electrode coating area 320 disposed away from the first separator 200. The first negative electrode coating area 310 is located on the coating side of the first negative electrode empty foil area, and the second negative electrode coating area 320 is located on the coating side of the second negative electrode empty foil area.

[0026] In an optional embodiment, the dimension of the positive electrode coating area in the length direction is equal to that of the positive electrode current collector; In an optional embodiment, the ratio of the dimension of the positive electrode coating area in the length direction to the dimension in the width direction is 27 to 29:1, specifically 27:1, 27.2:1, 27.5:1, 27.8:1, 28:1, 28.2:1, 28.4:1, 28.6:1, 28.8:1 or 29:1.

[0027] In an optional embodiment, the dimension of the first negative electrode coating region 310 in the length direction is equal to the length of the negative electrode current collector; In an optional embodiment, the ratio of the length dimension to the width dimension of the first negative electrode coating area 310 is 27~28:1, specifically 27:1, 27.1:1, 27.2:1, 27.3:1, 27.5:1, 27.6:1, 27.7:1, 27.8:1, 27.9:1 or 28:1.

[0028] In an optional embodiment, the end of the first negative electrode coating area 310 extends 30-40 mm beyond the end of the positive electrode coating area, specifically 30 mm, 31 mm, 32 mm, 33 mm, 34 mm, 35 mm, 36 mm, 37 mm, 38 mm, 39 mm or 40 mm.

[0029] In an optional embodiment, the ratio of the length dimension to the width dimension of the second negative electrode coating area 320 is 26 to 27:1, specifically 26:1, 26.1:1, 26.2:1, 26.4:1, 26.5:1, 26.6:1, 26.7:1, 26.8:1, 26.9:1 or 27:1.

[0030] In an optional embodiment, an empty foil starting area is provided on the negative current collector located at the starting end of the first negative electrode coating area. The size of the empty foil starting area in the length direction is 55-60mm, specifically 55mm, 56mm, 57mm, 58mm, 59mm, or 60mm.

[0031] In an optional embodiment, the end of the positive electrode coating area extends 20-30 mm beyond the end of the second negative electrode coating area 320, specifically 20 mm, 21 mm, 22 mm, 23 mm, 24 mm, 25 mm, 26 mm, 27 mm, 28 mm, 29 mm or 30 mm.

[0032] In an optional embodiment, the empty foil side of the first negative electrode coating area 310 extends 6-11 mm beyond the positive electrode coating area, specifically 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, or 11 mm.

[0033] In an optional embodiment, the empty foil side of the second negative electrode coating area 320 extends 60-65 mm beyond the positive electrode coating area, specifically 60 mm, 61 mm, 62 mm, 63 mm, 64 mm, or 65 mm.

[0034] In an optional embodiment, the ratio of the length dimension of the first diaphragm 200 to its width dimension is 27 to 28:1, specifically 27:1, 27.1:1, 27.2:1, 27.3:1, 27.5:1, 27.6:1, 27.7:1, 27.8:1, 27.9:1 or 28:1.

[0035] In an optional embodiment, the end of the first diaphragm 200 extends beyond the first negative electrode coating area 310, specifically by 40mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, 110mm, or 120mm.

[0036] In an optional embodiment, a second diaphragm 400 is further provided on the side of the negative electrode 300 away from the first diaphragm 200. The ratio of the length dimension to the width dimension of the second diaphragm 400 is 27 to 29:1, specifically 27:1, 27.2:1, 27.5:1, 27.8:1, 28:1, 28.2:1, 28.4:1, 28.6:1, 28.8:1, or 29:1.

[0037] In an optional embodiment, a second diaphragm 400 is further provided on the side of the negative electrode 300 away from the first diaphragm 200. The end of the second diaphragm 400 extends 0-10 mm beyond the end of the second negative electrode coating area, specifically 0 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm or 10 mm.

[0038] In the core of this application, by defining the size of the empty foil winding area, the positive electrode coating area, the first negative electrode coating area 310 and the second negative electrode coating area 320, as well as the position of the end and the empty foil side, the mechanical stress on the outer edge of the core is effectively released during the winding process. This avoids the micro-cracks and active material shedding at the electrode edge caused by the total active material coating size of the positive and negative electrodes being completely uniform and the absence of an empty foil winding area. The main reason may be that the uniform stress at the edge of the core in this application reduces the local current density distortion during high-rate charging and discharging, and suppresses lithium plating. At the same time, the reasonable coating area size, end position, and empty foil side position ensure the continuity of current collection in the tab area and reduce the interface impedance, thereby maintaining a high coulombic efficiency and low Joule heat accumulation under high-rate operating conditions.

[0039] In an optional embodiment, both the first diaphragm 200 and the second diaphragm 400 include a substrate and a ceramic coating disposed on the substrate. The thickness of the substrate is 6-8 μm, specifically 6.0 μm, 6.2 μm, 6.5 μm, 6.8 μm, 7.0 μm, 7.2 μm, 7.5 μm, 7.8 μm, or 8.0 μm. The thickness of the ceramic coating is 1.5-2.5 μm, specifically 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, or 2.5 μm.

[0040] In an optional embodiment, the porosity of the first diaphragm 200 and the second diaphragm 400 is independently 40% to 46%, specifically 40%, 40.5%, 41%, 41.5%, 42%, 42.5%, 43%, 44%, 45% or 46%, which takes into account ion transport kinetics and mechanical support strength, maintains electrolyte wetting stability at high rates, suppresses concentration polarization, and avoids thermal shrinkage failure or aggravated side reactions due to excessive porosity.

[0041] The present invention also provides a cylindrical lithium-ion battery, comprising a steel casing, an electrolyte encapsulated within the steel casing, and a winding core as described in any of the foregoing embodiments.

[0042] In an optional embodiment, a conductive finishing tape 500 is adhered to the circumferential surface of the core, with the back side of the conductive finishing tape 500 contacting the steel shell. The contact between the back side of the conductive finishing tape 500 and the steel shell directly opens the axial heat conduction path from the outermost ring of the core to the shell, reconstructing the heat conduction channel that was originally blocked by the insulating tape into a low thermal resistance path, thereby improving the overall heat dissipation response speed.

[0043] In an optional embodiment, the width of the conductive finishing tape 500 is 8~20mm, specifically 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 18mm or 20mm; the ratio of its length to the outer perimeter of the core is 1.1~1.5, specifically 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45 or 1.5, to ensure the fixing effect on the core, prevent the core from loosening, and at the same time form a sufficient area of ​​continuous and gapless thermally conductive bridge to prevent local heat accumulation.

[0044] In an optional embodiment, the thickness of the negative electrode 300 is 85~88 μm, specifically 85 μm, 85.3 μm, 85.5 μm, 86 μm, 86.5 μm, 87 μm, 87.5 μm, or 88 μm. The thickness of the positive electrode 100 is 85~88 μm, specifically 85 μm, 85.3 μm, 85.5 μm, 86 μm, 86.5 μm, 87 μm, 87.5 μm, or 88 μm. The thickness ratio of the negative electrode 300 to the positive electrode 100 is 0.99 to 1.01:1, specifically 0.99:1, 0.992:1, 0.995:1, 0.998:1, 1:1, 1.002:1, 1.005:1, 1.008:1, and 1.01:1. This achieves uniform distribution of interlayer stress during winding, reduces shear misalignment and edge warping caused by thickness mismatch, and improves structural consistency during high-rate cycling.

[0045] In an optional embodiment, the compaction density of the negative electrode 300 is 1.45~1.65 g / cm³, specifically 1.45, 1.47, 1.5, 1.52, 1.55, 1.57, 1.6, 1.62, or 1.65 g / cm³. The compaction density of the positive electrode 100 is 3.5~3.7 g / cm³, specifically 3.5, 3.52, 3.55, 3.57, 3.6, 3.62, 3.65, 3.67, or 3.7 g / cm³. The ratio of the compaction density of the positive electrode 100 to the compaction density of the negative electrode 300 is 2.1 to 2.3:1, specifically 2.1:1, 2.12:1, 2.15:1, 2.17:1, 2.2:1, 2.22:1, 2.25:1, 2.27:1, and 2.3:1. This ensures the continuity of the electron pathway while retaining sufficient ion transport micropores, thus balancing rate capability and cycle performance.

[0046] In an optional embodiment, the negative electrode active material of the negative electrode sheet 300 is a mixture of graphite and silicon-carbon composite material, wherein the graphite is one or both of artificial graphite and natural graphite, and the silicon-carbon is chemical vapor deposition silicon-carbon or biomass silicon-carbon, and the mass ratio of silicon-carbon in the negative electrode active material is 5% to 25%, specifically 5%, 7%, 10%, 12%, 15%, 17%, 20%, 22%, and 25%. While improving capacity, the silicon volume effect buffers lithium intercalation stress, and in conjunction with the aforementioned structural design, alleviates active layer pulverization and interface debonding at high rates.

[0047] In an optional embodiment, the positive electrode active material in the positive electrode 100 is a ternary material. In an optional embodiment, the ternary material may contain doping elements. In an optional embodiment, the ternary material is LiNixCoyMnzMjO2, wherein the value of x ranges from 0.60 to 0.95, the value of y ranges from 0.01 to 0.10, the value of z ranges from 0.01 to 0.10, j = 1 - xyz, and M is selected from one or more of Al, Zr, Ti, Mg, Sr, Y, La, Ce, and V.

[0048] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0049] Example 1 This embodiment provides a method for preparing a cylindrical lithium-ion battery, specifically including the following steps: 1. Electrolyte preparation method: After thoroughly cleaning the beakers, graduated cylinders, glass rods, pipette tips, screw-cap bottles, and other glassware required for the experiment, place them in an 80℃ oven to dry for 3 hours. All dried equipment and the balance should then be transferred into the oven through the glove box transition chamber. The transition chamber must be evacuated 3-5 times (evacuated to below -0.08 MPa, then filled with argon gas) before being placed into the oven.

[0050] In an argon-atmospheric glove box (water and oxygen content both <0.1 ppm), ethylene carbonate (EC), dimethyl carbonate (DMC), and fluoroethylene carbonate (FEC) were mixed at a volume ratio of 3:6:1, followed by the addition of activated 4Å molecular sieves and drying for 48 hours. Subsequently, lithium hexafluorophosphate (LiPF6), which had been pre-dried under vacuum at 80°C for 24 hours in the glove box, was added to the monomer-containing mixed solvent and stirred for 30 minutes until completely dissolved, preparing a 1 M LiPF6 EC / DMC / FEC electrolyte. The resulting electrolyte was sealed and stored in the glove box for later use.

[0051] 2. Manufacturing method of negative electrode sheet 300: The negative electrode 300 provided in this embodiment includes a current collector and a negative electrode coating material coated on both sides of the current collector. The current collector used in the negative electrode 300 is copper foil, and the negative electrode coating material, calculated by mass percentage, includes 15.0% deposited silicon carbide, 81.0% graphite, 0.75% SWCNT, 0.75% Super P, 1.5% thickener sodium carboxymethyl cellulose (CMC), and 1.0% SBR. Thickener CMC was added to deionized water and stirred until completely dissolved to form a homogeneous adhesive solution. Conductive agents SWCNT and Super P were added sequentially to the adhesive solution and dispersed by high-speed stirring to ensure uniform dispersion. Active material graphite and deposited silicon carbon were added to the dispersion, and stirring continued. Finally, binder SBR was added, and an appropriate amount of deionized water was added to adjust the solid content of the system. Stirring continued until a homogeneous negative electrode slurry with good flowability and no agglomerated particles was formed. The negative electrode coating material was then intermittently coated onto both sides of the current collector (copper foil). After drying and rolling, negative electrode sheet 300 was prepared with a compaction density of 1.55 g / cm³. 3 The thickness is 86μm.

[0052] 3. Method for manufacturing 100 positive electrode plates: The positive electrode 100 provided in this embodiment includes a current collector and a positive electrode coating material coated on both sides of the current collector. By mass percentage, the positive electrode coating material includes: 96.0% ternary positive electrode material (LiNi0.9Co0). 05 Mn0. 05O2 (NCM9055), 2.0% conductive carbon black (Super P), 1.0% carbon nanotubes (CNTs), and 1.0% polyvinylidene fluoride (PVDF) binder.

[0053] Polyvinylidene fluoride (PVDF) was added to N-methylpyrrolidone (NMP) solvent and heated and stirred in a water bath at 50°C for 3 hours to prepare a PVDF adhesive solution with a solid content of 6.5 wt%, ensuring complete dissolution of PVDF. Conductive carbon black (Super P) and carbon nanotubes (CNTs) were added to the PVDF adhesive solution and dispersed by high-speed stirring to achieve uniform dispersion. Ternary cathode material (NCM9055) was added to the dispersion and stirring was continued for 3 hours. During this period, an appropriate amount of NMP could be added to adjust the slurry viscosity to 4000 mPa·s until a uniform cathode slurry without agglomerated particles was formed. The prepared cathode slurry was transferred to the surface of an aluminum foil current collector using a coating machine. The coated electrode was dried in a 110°C forced-air drying oven to completely remove residual solvent. The dried electrode was compacted by a roller press, with the compaction density controlled at 3.5 g / cm³ and the thickness at 85~88 μm, and then cut into the required sizes.

[0054] 4. Assembly of lithium-ion batteries: After the positive electrode 100 and negative electrode 300 are rolled and slit, they are wound together with the separator according to the predetermined process and then coated with finishing adhesive. The separator has a porosity of 42%. The finishing adhesive consists of PET substrate (7μm thick) + adhesive layer (2μm). The adhesive layer contains 5% superconducting carbon black, has a thermal conductivity of 1.2 W / (m·K), a volume resistivity of 40 Ω·cm, and a width of 10 mm.

[0055] A cylindrical battery core of specification 21700 was obtained. This core was welded and fixed to a current collector, and then welded again inside a metal casing. Subsequently, it underwent electrolyte injection, sealing, and formation processes. Finally, a cylindrical lithium-ion battery conforming to the 21700 standard (diameter 21.0 mm, length 70.0 mm) as described in Example 1 was obtained.

[0056] The cylindrical lithium-ion battery core prepared in this embodiment includes a positive electrode 100, a first separator 200, a negative electrode 300, and a second separator 400 stacked in sequence. The negative electrode 300 has a blank foil winding area at the winding end away from the first separator 200. The blank foil winding area has a length dimension of 57.5 mm. The dimension of the positive electrode coating area in the length direction is equal to that of the positive electrode current collector, and the ratio of the dimension of the positive electrode coating area in the length direction to its dimension in the width direction is 28:1. The first negative electrode coating area 310 has a length dimension equal to the length of the negative electrode current collector, and the ratio of its length dimension to its width dimension is 27.5:1. The end of the first negative electrode coating area 310 extends 35mm beyond the end of the positive electrode coating area. The empty foil side of the first negative electrode coating area 310 extends 8.5mm beyond the positive electrode coating area. The ratio of the length dimension to the width dimension of the second negative electrode coating area 320 is 26.5:1. The starting end of the winding of the negative electrode sheet is provided with an empty foil starting area, the length dimension of which is 57.5 mm. The ending end of the positive electrode coating area extends 25 mm beyond the ending end of the second negative electrode coating area 320, and the empty foil side of the second negative electrode coating area 320 extends 62.5 mm beyond the positive electrode coating area. The ratio of the length dimension of the first diaphragm 200 to its width dimension is 27.5:1, and the end of the first diaphragm 200 extends beyond the first negative electrode coating area by 310-80 mm. The ratio of the length dimension of the second diaphragm 400 to its width dimension is 28:1, and the end of the second diaphragm 400 extends 0 mm beyond the end of the second negative electrode coating area.

[0057] The core is covered with conductive finishing tape 500, and the back of the conductive finishing tape 500 is connected to the steel shell. The width of the conductive finishing tape 500 is 14mm and the ratio of its length to the outer perimeter of the core is 1.3. Example 2 The difference between this embodiment and Embodiment 1 is that the porosity of the diaphragm is 44%, while the rest are the same as in Embodiment 1.

[0058] Example 3 The difference between this embodiment and Embodiment 1 is that the porosity of the diaphragm is 46%, while the rest are the same as in Embodiment 1.

[0059] Example 4 The difference between this embodiment and Embodiment 1 is that the thermal conductivity of the carbon black-containing finishing adhesive is 1.5 W / (m·K), while the rest are the same as in Embodiment 1.

[0060] Example 5 The difference between this embodiment and Embodiment 1 is that the thermal conductivity of the carbon black-containing finishing adhesive is 2.0 W / (m·K), while the rest are the same as in Embodiment 1.

[0061] Example 6 The difference between this embodiment and Embodiment 1 is that the compaction density of the positive electrode sheet 100 is 3.6 g / cm³. 3Everything else is the same as in Example 1.

[0062] Example 7 The difference between this embodiment and Embodiment 1 is that the compaction density of the positive electrode sheet 100 is 3.7 g / cm³. 3 Everything else is the same as in Example 1.

[0063] Example 8 The difference between this embodiment and Embodiment 1 is that the compaction density of the negative electrode sheet 300 is 1.6 g / cm³. 3 Everything else is the same as in Example 1.

[0064] Example 9 The difference between this embodiment and Embodiment 1 is that the compaction density of the negative electrode sheet 300 is 1.65 g / cm³. 3 Everything else is the same as in Example 1.

[0065] Comparative Example 1 The difference between this comparative example and Example 1 is that the porosity of the diaphragm is 30%, while the rest are the same as in Example 1.

[0066] Comparative Example 2 The difference between this comparative example and Example 1 is that thermally conductive carbon black is not added to the finishing adhesive; otherwise, they are the same as in Example 1.

[0067] Comparative Example 3 The difference between this comparative example and Example 1 is that the compaction density of the negative electrode is 1.75 g / cm³. 3 The positive electrode compaction density is 3.90 g / cm³. 3 Everything else is the same as in Example 1.

[0068] Comparative Example 4 The difference between this comparative example and Example 1 is that the negative electrode sheet 300 does not have an empty foil winding area at the winding end away from the first separator 200, that is, the second negative electrode coating area 320 at the winding end is flush with the negative electrode current collector.

[0069] The performance of the batteries prepared in the above embodiments and comparative examples was tested, and the specific test methods are as follows.

[0070] 1. The test method for 8C charging rate performance includes the following steps: The lithium battery was discharged to 2.5V and placed in a 25℃ constant temperature chamber for 6 hours, and then tested according to the following steps: (1) Charge the capacitor to 4.2V under constant current and constant voltage conditions at 0.5 C, with a cutoff current of 0.05 C, and let it stand for 30 min; (2) Discharge at constant current to 2.5V under 0.2C conditions and let stand for 30 minutes. The capacity of constant current discharge to 2.5V is Q0 (constant capacity step); calculate the rate using Q0. (3) Under constant current and constant voltage charging at 1C to 4.2V, with a cutoff current of 0.1C, the capacity meter at which the constant current charging to 4.2V is Q. 1充 The highest temperature of the temperature sensing wire during charging is denoted as T. 1充 ; (4) Discharge at a constant current of 0.2 C until the cutoff voltage is 2.5 V, and let stand for 30 min; (5) Under constant current and constant voltage conditions of 8C, charge to 4.2V, cut-off current is 0.8C, and the capacity of constant current charging to 4.2V is Q8; the highest temperature of the temperature sensing wire during charging is recorded as T8; The calculation method for the charging capacity retention rate of a lithium battery at 25℃ is: Q8 / Q 1充 ×100%. The temperature rise at charging rate is T8-T. 1充 .

[0071] 2. Test method for 5C charging rate performance: Take three brand new batteries, discharge the lithium batteries to 2.5V and place them in a 25℃ constant temperature chamber for 6 hours, and then test them according to the following steps: (1) Charge the capacitor to 4.2V under constant current and constant voltage conditions at 0.5 C, with a cutoff current of 0.05 C, and let it stand for 30 min; (2) Discharge at constant current to 2.5V under 0.2C conditions and let stand for 30 minutes. The capacity of constant current discharge to 2.5V is Q0 (constant capacity step); calculate the rate using Q0. (3) Charge to 4.2V under constant current and constant voltage conditions at 1C, with a cutoff current of 0.1C; (4) The capacitance meter that can be discharged at a constant current of 1 C to a cutoff of 2.5 V is Q. 1放 After standing for 30 minutes, the highest temperature of the temperature sensing wire during charging is recorded as T. 1放 ; (5) Then charge it to 4.2V under constant current and constant voltage conditions at 1C, with a cutoff current of 0.1C; (6) The capacity meter that is discharged under constant current at 5 C to 2.5V cutoff is Q5, and after standing for 30 minutes, the highest temperature of the temperature sensing wire during charging is recorded as T5. The calculation method for the charging capacity retention rate of a lithium battery at 25℃ is: Q5 / Q 1放 ×100%. The temperature rise at charging rate is T5-T. 1放 .

[0072] 3. Room temperature cycling performance test method: Place the battery in a 25°C constant temperature chamber for 6 hours and test it according to the following steps: (1) First round of constant current and constant voltage charging: Charge at a constant current of 0.5C to 4.2V, then switch to constant voltage charging until the current drops to 0.05C.

[0073] (2) Let it stand for 30 minutes after charging is complete.

[0074] (3) Perform constant current discharge, and discharge to 2.5V at a rate of 0.2C.

[0075] (4) Cyclic charge and discharge process: Charge at a constant current rate of 2C to 4.2V. Let stand for 30 minutes again. Discharge at a constant current rate of 5C to 2.5V.

[0076] (5) Repeat the above charging and discharging process for a total of 300 cycles.

[0077] Statistical analysis of the battery discharge capacity Q1 and Q after 1 cycle and 300 cycles. 300 Calculate the battery capacity retention rate: Q 300 / Q1×100%.

[0078] 4. Place the battery in a 45℃ constant temperature chamber for 6 hours and test its high temperature cycling performance at a constant temperature of 60℃ according to the normal temperature cycling performance test method.

[0079] 5. Short-circuit safety performance test method: Place the lithium-ion battery in a constant temperature chamber at 25℃ for 6 hours; then conduct the test according to the following steps: Under a charging rate of 0.2C, constant current charging is performed until 4.2V is reached, then constant voltage charging is performed until the current drops to 0.02C, and the sample is left to stand for 30 minutes. Connect the positive and negative terminals of the lithium-ion battery with a wire, ensuring that the external resistance is the preset resistance; The preset resistances include 5mΩ, 10mΩ, 15mΩ and 20mΩ; here, different lithium-ion batteries are used for testing with different preset resistances.

[0080] After the test is completed, observe the battery for 1 hour to see if it catches fire or explodes.

[0081] Here, three parallel lithium-ion battery samples were tested respectively.

[0082] During the test, the battery temperature was monitored. The test was terminated when the battery temperature dropped to 80% of the peak temperature rise or when the short circuit time reached 6 hours. 6. Test method for thermal abuse safety performance: Place the battery in a 25°C constant temperature chamber for 6 hours and test it according to the following steps: (1) Constant current and constant voltage charging: Charge at a constant current of 0.2C to 4.2V, then switch to constant voltage charging until the current drops to 0.02C.

[0083] (2) The ambient temperature of the test chamber is increased at a rate of 5℃ / min. When the temperature inside the chamber reaches 140℃, it is kept constant for 1 hour. The battery should not catch fire or explode.

[0084] (3) Test 3 parallel samples.

[0085] 7. Test method for thermal overcharge safety performance: The battery was placed in a 25°C constant temperature chamber for 6 hours for insulation and then tested according to the following steps: (1) Constant current and constant voltage charging: Charge at a constant current of 0.2C to 4.2V, then switch to constant voltage charging until the current drops to 0.02C.

[0086] (2) Let it stand for 30 minutes after charging is complete.

[0087] (3) Connect the positive and negative terminals of the battery with a wire and charge it to 6.0V at a constant current of 3C. After charging to 6.0V, continue charging at a constant voltage for 1 hour. The battery should not catch fire or explode.

[0088] (4) Test 3 parallel samples.

[0089] The test results of the battery samples in the above embodiments and comparative examples are shown in Table 1.

[0090] Table 1

[0091] As can be seen from the test data in Table 1, the embodiments of the present invention are significantly superior to the comparative examples in terms of high-rate charging capacity retention, charge-discharge temperature rise, room temperature / high temperature cycle life, and short-circuit / thermal abuse safety. The specific analysis is as follows: 1. The impact of ultra-wide positive and negative electrode edges and asymmetric winding structure on polarization suppression and thermal management In Examples 1-9, the negative electrode 300 adopts an asymmetrical design where the side closest to the first separator 200 is the same length as the copper foil, and the side furthest from the first separator 200 has a reserved empty foil winding area. Furthermore, the long / short side of the negative electrode maintains a specific ultra-wide margin with the positive electrode. This structure effectively releases the mechanical stress on the outer edge of the winding core during winding, avoiding the micro-cracks and active material shedding at the electrode edge caused by traditional symmetrical winding (such as Comparative Example 4). Table 1 shows that the 8C charging capacity retention rate (88.4%~92.0%) of Examples 1-9 is 5.9~9.5 percentage points higher than that of Comparative Example 4 (82.5%), and the temperature rise is reduced by approximately 3~5℃. The mechanism is that edge stress homogenization reduces local current density distortion during high-rate charging and discharging, suppressing lithium plating; simultaneously, the reasonable ultra-wide margin ensures the continuity of current collection in the tab region, reducing interface impedance, thereby maintaining high coulombic efficiency and low Joule heat accumulation under high-rate operating conditions.

[0092] 2. The balance mechanism between membrane porosity and ionic conductivity and interfacial stability The comparison of Examples 1-3 shows that the membrane performance is optimal when the porosity is in the range of 40%-46%. Comparative Example 1 (porosity 30%) only maintained 84.6% of its 8C charging capacity, with a temperature rise of 48.7℃. This is because excessively low porosity leads to insufficient electrolyte wetting, increased tortuosity of the lithium-ion diffusion path, and severe concentration and ohmic polarization under high current (8C), resulting in a large amount of electrical energy being converted into heat. Example 1 (42%) achieves the best balance between ion transport channels and membrane mechanical strength, with sufficient electrolyte ionic conductivity, effectively supporting rapid lithium-ion insertion / extraction at high rates. Although the increased porosity in Examples 2 / 3 (44% / 46%) slightly improved ion diffusion, excessively high porosity weakened the membrane support and may increase the number of active sites for side reactions. Therefore, the capacity retention and cycle stability showed a slight decreasing trend (89.2% / 88.4%), confirming that 40%~46% is the optimal process condition that balances ion transport and interface stability.

[0093] 3. The 500mm thermal conductivity of the conductive finishing tape actively dissipates heat buildup. The comparison between Examples 1, 4, and 5 and Comparative Example 2 verifies the effectiveness of the thermally conductive structure. Comparative Example 2, without the addition of thermally conductive carbon black, experienced a temperature rise of 52.4°C during 8C charging, and ignition / thermal runaway occurred during external short circuit tests (10 / 15 / 20 mΩ) and thermal abuse tests. In contrast, Example 1 (thermal conductivity 1.2 W / (m·K)) saw a temperature rise of only 43.5°C, while Examples 4 / 5 (1.5 / 2.0 W / (m·K)) further reduced the temperature rise to 41.5°C / 40.2°C. The mechanism is as follows: in traditional cylindrical battery cells, heat is primarily conducted slowly through the sidewalls, easily leading to localized hot spots at high rates. This invention constructs a low thermal resistance axial heat dissipation network consisting of the core tab area, the tail tape, and the steel shell by attaching a conductive carbon black-containing tape to the outermost ring of the negative electrode and extending it to the inner wall of the steel shell. After the thermal conductivity is increased to 2.0 W / (m·K), the Joule heat generated by the core is quickly conducted to the shell and dissipated into the environment, which significantly reduces the risk of thermal decomposition of the SEI film and the probability of thermal runaway. This is directly reflected in the fact that all safety tests passed and the cycle capacity retention rate increased by 3~5% in Table 1.

[0094] 4. Synergistic optimization of electrode thickness ratio and compaction density The comparison between Examples 6-9 and Comparative Example 3 reveals the contributions of the thickness ratio (0.99-1.01:1) and compaction density (1.45-1.65 g / cm³ for the negative electrode and 3.5-3.7 g / cm³ for the positive electrode). Comparative Example 3 used excessively high compaction density (1.75 g / cm³ for the negative electrode and 3.90 g / cm³ for the positive electrode), leading to pore structure collapse, decreased electrolyte wetting rate, an 8C capacity retention of only 83.4%, and thermal runaway caused by a 15 mΩ short circuit. This invention achieves precise control of battery capacity and balanced winding stress by controlling the compaction density and matching a near 1:1 electrode thickness ratio. Appropriate compaction density ensures the continuity of the electronic conductive network while retaining sufficient micropores for rapid lithium-ion migration; consistent thickness avoids shear misalignment during winding, further improving the capacity retention (94.5%-95.1%) after 300 high-rate cycles.

[0095] 5. Summary Table 1 shows that the overall data of this invention is a comprehensive result of the edge stress relief structure, high porosity ion channels, axial heat conduction network, and matched compaction density. Under the synergistic effect of these four factors, the battery temperature rise is reduced by 5-12°C under 8C fast charging conditions, and the capacity retention rate is improved by 6-9 percentage points. Furthermore, it has passed all short-circuit, thermal abuse, and overcharge safety tests, breaking through the technical bottlenecks of traditional cylindrical lithium-ion batteries in high-rate fast charging, long cycle life, and intrinsic safety. This application demonstrates good operability and batch consistency in engineering preparation and can be widely applied in power tools, drones, high-performance energy storage, and lightweight electric power applications with stringent requirements for fast charging and high safety, possessing significant industrial application value and market competitiveness.

[0096] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A cylindrical lithium-ion battery core, characterized in that, Before the core is rolled up, it includes a positive electrode sheet, a first diaphragm and a negative electrode sheet stacked in sequence. One end of the core is the starting end of the winding and the other end is the ending end of the winding. The negative electrode sheet has an empty foil winding area at the winding end away from the first separator, and the current collector surface of the empty foil winding area is not provided with a negative electrode active layer containing negative electrode active material. The circumferential surface of the core is adhered with conductive finishing tape for fixing the core. The conductive finishing tape includes a substrate layer and an adhesive layer. The substrate layer and / or the adhesive layer contain conductive carbon black, and the mass percentage of the conductive carbon black in the layer is 2% to 10%. The thermal conductivity of the conductive finishing tape is 0.5 to 3.0 W / (m·K). The volume resistivity of the conductive finishing tape in the thickness direction is 10 to 80 Ω·cm.

2. The cylindrical lithium-ion battery core according to claim 1, characterized in that, The direction from the starting end to the ending end of the winding is the length direction, and the direction perpendicular to the length direction is the width direction; along the width direction, the core includes a coated side and a blank foil side; the cylindrical lithium-ion battery core satisfies at least one of the following characteristics: A. The length dimension of the empty foil winding area is 55~60mm; B. The positive electrode sheet includes a positive current collector, a positive electrode coating area disposed on the coated side surface of the positive current collector, and a positive electrode empty foil area disposed on the empty foil side of the positive current collector; C. The negative electrode sheet includes a negative current collector and a first negative electrode coating area disposed on the negative current collector near the first diaphragm and a second negative electrode coating area disposed away from the first diaphragm. The first negative electrode coating area is located on the coating side of the first negative electrode empty foil area, and the second negative electrode coating area is located on the coating side of the second negative electrode empty foil area.

3. The cylindrical lithium-ion battery core according to claim 2, characterized in that, The dimension of the positive electrode coating area in the length direction is equal to that of the positive electrode current collector; And / or, the ratio of the dimension of the positive electrode coating region in the length direction to its dimension in the width direction is 27~29:1; And / or, the dimension of the first negative electrode coating area in the length direction is equal to the length of the negative electrode current collector; And / or, the ratio of the dimension of the first negative electrode coating area in the length direction to its dimension in the width direction is 27~28:1; And / or, the end of the first negative electrode coating area extends 30-40 mm beyond the end of the positive electrode coating area; And / or, the ratio of the length dimension to the width dimension of the second negative electrode coating area is 26~27:1; And / or, an empty foil starting area is provided on the negative electrode current collector located at the starting end of the first negative electrode coating area, and the size of the empty foil starting area in the length direction is 55-60mm; And / or, the end of the positive electrode coating area extends 20-30 mm beyond the end of the second negative electrode coating area.

4. The cylindrical lithium-ion battery core according to claim 2, characterized in that, The empty foil side of the first negative electrode coating area extends 6-11 mm beyond the positive electrode coating area; And / or, the empty foil side of the second negative electrode coating area extends 60-65 mm beyond the positive electrode coating area.

5. The cylindrical lithium-ion battery core according to claim 2, characterized in that, The ratio of the length dimension of the first diaphragm to its width dimension is 27~28:1; And / or, the end of the first diaphragm extends 40-120 mm beyond the first negative electrode coating area; And / or, a second diaphragm is provided on the side of the negative electrode sheet away from the first diaphragm, and the ratio of the dimension of the second diaphragm in the length direction to its dimension in the width direction is 27~29:1; And / or, a second diaphragm is provided on the side of the negative electrode sheet away from the first diaphragm, and the end of the second diaphragm extends 0~10mm beyond the end of the second negative electrode coating area.

6. The cylindrical lithium-ion battery core according to claim 5, characterized in that, Both the first and second diaphragms include a substrate and a ceramic coating disposed on the substrate, wherein the thickness of the substrate is 6-8 μm and the thickness of the ceramic coating is 1.5-2.5 μm; And / or, the porosity of the first diaphragm and the second diaphragm is independently 40% to 46%.

7. A cylindrical lithium-ion battery, characterized in that, It includes a steel shell and an electrolyte encapsulated within the steel shell, and the core according to any one of claims 1-6.

8. The cylindrical lithium-ion battery according to claim 7, characterized in that, The back side of the conductive finishing tape is in contact with the steel shell.

9. The cylindrical lithium-ion battery according to claim 8, characterized in that, The conductive finishing tape has a width of 8-20mm and a length-to-circumference ratio of 1.1-1.

5. And / or, the thickness of the negative electrode sheet is 85~88μm, the thickness of the positive electrode sheet is 85~88μm, and the ratio of the thickness of the negative electrode sheet to the thickness of the positive electrode sheet is 0.99~1.01:1; And / or, the compaction density of the negative electrode sheet is 1.45~1.65 g / cm³, and the compaction density of the positive electrode sheet is 3.5~3.7 g / cm³; the ratio of the compaction density of the positive electrode sheet to the compaction density of the negative electrode sheet is 2.1~2.3:

1.

10. The cylindrical lithium-ion battery according to claim 7, characterized in that, The negative electrode active material of the negative electrode sheet is a mixture of graphite and silicon-carbon composite material, wherein the graphite is one or both of artificial graphite and natural graphite, and the silicon-carbon is chemical vapor deposition silicon-carbon or biomass silicon-carbon, and the mass ratio of silicon-carbon in the negative electrode active material is 5% to 25%; And / or, the positive electrode active material in the positive electrode sheet is a ternary material.

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