A winding type cylindrical lithium ion battery cell, a battery module, a battery pack, and an electrical device

Abstract

The application discloses a kind of winding type cylindrical lithium ion battery, battery module, battery pack and electrical equipment, belong to battery technical field.The winding type cylindrical lithium ion battery meets Ln-Lp is 35mm~100mm;Wn-Wp is 1.5mm~3.0mm, Ws-Wn is 1.5mm~4.0mm;Ks=(Ls-Ln) / Ln, Ks is 0.025~0.085, Kl=(Ln-Lp) / Lp, Kl is 0.020~0.060;Kw=(Wn-Wp) / 2, Kw is 0.75mm~1.50mm.The winding type cylindrical lithium ion battery can improve long tab 4Ah level cylindrical battery after high rate cycle, and the stability of roll head, roll tail and tab side edge is improved, the risk of local lithium precipitation, separator light transmission, ceramic layer shedding and center hole collapse is reduced, and the high rate cycle retention rate is improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to a wound cylindrical lithium-ion cell, a battery module, a battery pack, and an electrical device. Background Technology

[0002] Cylindrical lithium-ion cells are typically formed by winding positive electrode sheets, negative electrode sheets, and a separator. For high-rate cylindrical cells in the 4Ah range, increasing the unfolded length of the electrode sheets, increasing the active area, and reducing the current density per unit area are important approaches to improving rate cycling, rate temperature rise, and power output. However, when the positive and negative electrode sheets are significantly lengthened, problems such as local alignment deviations, separator pressure, insufficient wetting, and concentrated lithium-ion flux at the edges are more likely to occur at the beginning and end of the winding, the tab side, and the edge areas.

[0003] In existing designs, a slightly longer negative electrode length, a slightly wider negative electrode width, and a slightly wider separator width are generally considered standard safety margins. However, in scenarios involving long electrodes, low surface current, and high-rate cycling, an excessively small length difference can lead to insufficient coverage at the coiled edge, while an excessively large length difference can increase the risk of uneven winding and head collapse. An excessively small width difference can cause lithium-ion flux at the positive electrode edge to concentrate directly at the negative electrode edge, while an excessively large width difference can increase the ineffective negative electrode area, core stress, and electrolyte wetting burden. Furthermore, after high-rate cycling or low-temperature cycling, phenomena such as point-like lithium plating at the coiled head or tail, black spots on the negative electrode tab side, localized light transmission in the separator, ceramic layer detachment, reduced separator porosity, and central hole collapse may also be observed in long electrode systems.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a wound cylindrical lithium-ion cell, a battery module, a battery pack, and an electrical device to solve or improve the above-mentioned technical problems.

[0006] This invention can be implemented as follows: In a first aspect, the present invention provides a wound cylindrical lithium-ion battery cell, the wound cylindrical lithium-ion battery cell including a core, the core including a positive electrode sheet, a negative electrode sheet and a separator located between the positive electrode sheet and the negative electrode sheet; The positive electrode has a positive electrode material region unfolded length Lp and a positive electrode material region width Wp, the negative electrode has a negative electrode material region unfolded length Ln and a negative electrode material region width Wn, and the separator has a separator unfolded length Ls, separator width Ws and unfolded redundancy coefficient Ks corresponding to the negative electrode. Ln-Lp is 35mm~100mm; Wn-Wp is 1.5mm~3.0mm, and Ws-Wn is 1.5mm~4.0mm; Ks=(Ls-Ln) / Ln, Ks is 0.025~0.085; Kl=(Ln-Lp) / Lp, Kl is 0.020~0.060; Kw=(Wn-Wp) / 2, Kw is 0.75mm~1.50mm.

[0007] In an optional implementation, Lp is 1450mm~1900mm, and Ln is 1750mm~1860mm; preferably, Lp is 1700mm~1800mm, Ln-Lp is 40mm~80mm, and Kl is 0.025~0.050. And / or, Wp is 59.5mm~61.5mm, Wn is 61.5mm~63.5mm, Ws is 64.0mm~66.5mm, and Kw is 0.85mm~1.25mm; preferably, Ws-Wn is 2.0mm~3.2mm; And / or, Ls is 1835mm~1970mm, Ls-Ln is 50mm~130mm; preferably, Ks is 0.030~0.075.

[0008] In an optional implementation, the wound cylindrical lithium-ion cell also satisfies: Qp = C / (2Sp), where C is the discharge capacity of a wound cylindrical lithium-ion cell at 25℃ and 0.2C to 2.5V, in mAh; Sp is the geometric area of ​​a single side of the positive electrode, Sp = Lp × Wp / 100, where Lp and Wp are in mm, and Sp is in cm. 2 C ranges from 3800mAh to 4300mAh, and Qp is 1.75mAh / cm². 2 ~2.35mAh / cm 2 ; And / or, JI = I × 1000 / (2Sp), where I is in A, and JI is the double-sided equivalent discharge surface current density in mA / cm². 2 When I=50A, JI is 10mA / cm. 2 ~30mA / cm 2 .

[0009] In an optional embodiment, at the starting end of winding, the diaphragm forms a pre-wound section relative to the negative electrode sheet, the length of which is 8mm to 30mm; at the ending end of winding, the negative electrode sheet forms a tail-covering section relative to the positive electrode sheet, the length of which is 10mm to 40mm.

[0010] In an optional embodiment, the negative electrode sheet extends 0.8 mm to 1.5 mm beyond the width of the positive electrode sheet on the negative electrode tab side, and the separator extends 0.8 mm to 2.0 mm beyond the width of the negative electrode sheet on the negative electrode tab side.

[0011] In an optional embodiment, the wound cylindrical lithium-ion cell also has at least one of the following features: Feature 1: The porosity of the positive electrode is 24%~32%; Feature 2: The porosity of the negative electrode is 30%~38%; Feature 3: The electrolyte filling coefficient of the wound cylindrical lithium-ion cell is 3.1g / Ah~3.6g / Ah; Feature 4: In the negative electrode sheet, silicon-carbon materials account for 3% to 10% of the total mass of the negative electrode active materials; Feature 5: The N / P ratio of the negative electrode is 1.02~1.10, preferably 1.04~1.07.

[0012] In an optional embodiment, the wound cylindrical lithium-ion cell has at least one of the following features: Feature 6: Under a cycle regime of 25℃, 8A charging, 60A discharging, and 2.5V cutoff, the capacity retention rate of the wound cylindrical lithium-ion cell after 1000 cycles is no less than 80%. Feature 7: Under a cycle regime of 25℃, 14A charging, 50A discharging, and 2.5V cutoff, the capacity retention rate of the wound cylindrical lithium-ion cell after 1000 cycles is no less than 80%. Feature 8: The DC internal resistance of the wound cylindrical lithium-ion cell at 25℃ and 100% SOC is no greater than 8.0mΩ; Feature 9: When the wound cylindrical lithium-ion cell is discharged at a constant current of 40A, 50A and 60A to a cutoff of 2.5V at 25℃ and 100% SOC, the maximum temperature of the casing of the wound cylindrical lithium-ion cell is no higher than 60℃, 67℃ and 75℃, respectively.

[0013] Secondly, the present invention provides a battery module comprising a wound cylindrical lithium-ion cell according to any of the foregoing embodiments.

[0014] Thirdly, the present invention provides a battery pack comprising the battery module of the aforementioned embodiments.

[0015] Fourthly, the present invention provides an electrical device comprising a wound cylindrical lithium-ion cell according to any of the foregoing embodiments, a battery module according to the foregoing embodiments, or a battery pack according to the foregoing embodiments.

[0016] The beneficial effects of this invention include: This invention improves the stability of the beginning, end, and tab edges of a long-electrode 4Ah-class cylindrical cell after high-rate cycling by defining Ln-Lp, Wn-Wp, Ws-Wn, Ks, Kl, and Kw. This reduces the risks of local lithium plating, separator light transmission, ceramic layer detachment, and center hole collapse, and improves the high-rate cycle retention rate. Detailed Implementation

[0017] 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.

[0018] The following is a detailed description of the wound cylindrical lithium-ion cell, battery module, battery pack, and electrical equipment provided by this invention.

[0019] The present invention provides a wound cylindrical lithium-ion battery cell, which includes a core, an electrolyte, a housing, and a cap assembly.

[0020] The core includes a positive electrode sheet, a negative electrode sheet, and a separator located between the positive and negative electrode sheets, and is formed by winding the positive electrode sheet, the separator, and the negative electrode sheet. In some typical embodiments, the cell can be a 4Ah-class cylindrical lithium-ion cell.

[0021] The positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one side surface of the positive current collector. The positive current collector can be an aluminum current collector with a thickness of 10 μm to 14 μm. The positive active material layer can include a positive active material, a conductive agent, and a binder, and may further include a lithium-containing alkaline component. The positive active material can include a high-nickel layered lithium transition metal oxide, wherein the molar percentage of nickel in the high-nickel layered lithium transition metal oxide can be 80% to 93%. The conductive agent can include a carbon-based conductive agent, and the binder can include polyvinylidene fluoride, etc. The mass ratio of the positive active material, conductive agent, binder, and lithium-containing alkaline component can be (96.0~98.5%):(0.5~2.0):(0.8~2.0):1.0.

[0022] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side surface of the negative electrode current collector. The negative electrode current collector can be a copper current collector, and its thickness can be 4μm to 8μm. The negative electrode active material layer can include a negative electrode active material (such as artificial graphite, silicon carbide materials, etc.), a thickener (such as carboxymethyl cellulose, etc.), and a binder (such as styrene-butadiene rubber, etc.).

[0023] The membrane includes a polyolefin-based membrane and a ceramic coating disposed on at least one surface of the polyolefin-based membrane.

[0024] The electrolyte comprises a lithium salt, a non-aqueous organic solvent, and additives. The lithium salt may include lithium hexafluorophosphate, etc.; the non-aqueous organic solvent may include cyclic carbonates, chain carbonates, and low-viscosity co-solvents such as acetates; and the additives may include at least one of lithium difluorophosphate additives, fluorinated carbonate film-forming additives, sulfonate lactone additives, and boron-containing lithium salt additives. For example, the mass ratio of lithium salt, non-aqueous organic solvent, and additives, based on the total mass of the electrolyte, may be 12.5:85.0:2.5. The mass percentage of the low-viscosity co-solvent such as acetate in the non-aqueous organic solvent may be 0 wt% to 20 wt%. The mass percentage of lithium difluorophosphate additives in the additives may be 0.2 wt% to 1.5 wt%, and the mass percentage of fluorinated carbonate film-forming additives may be 0.5 wt% to 3.0 wt%.

[0025] In this invention, the positive electrode has a positive electrode material region unfolded length Lp and a positive electrode material region width Wp, the negative electrode has a negative electrode material region unfolded length Ln and a negative electrode material region width Wn, and the separator has a separator unfolded length Ls, a separator width Ws, and an unfolded redundancy coefficient Ks corresponding to the negative electrode. The length difference between the negative electrode and the positive electrode is denoted as Ln-Lp.

[0026] Ln-Lp is 35mm~100mm; Wn-Wp is 1.5mm~3.0mm, and Ws-Wn is 1.5mm~4.0mm; Ks=(Ls-Ln) / Ln, Ks is 0.025~0.085; Kl=(Ln-Lp) / Lp, Kl is 0.020~0.060; Kw=(Wn-Wp) / 2, Kw is 0.75mm~1.50mm.

[0027] It should be noted that when the core includes two diaphragms, Ls and Ks refer to the unfolded length and unfolded redundancy coefficient of any one diaphragm, respectively. That is, any one diaphragm satisfies the above conditions.

[0028] In some optional implementations, Ln-Lp can be 35mm, 40mm, 45mm, 50mm, 55mm, 60mm, 65mm, 70mm, 75mm, 80mm, 85mm, 90mm, 95mm, or 100mm, or other values ​​within the range of 35mm to 100mm. In some more typical implementations, Ln-Lp can be 40mm to 80mm.

[0029] Wherein, Lp can be 1450mm~1900mm, such as 1450mm, 1500mm, 1550mm, 1600mm, 1650mm, 1700mm, 1750mm, 1800mm, 1850mm or 1900mm, etc., or it can be other values ​​within the range of 1450mm~1900mm. Preferably, Lp is 1700mm~1800mm, and more preferably it is 1750mm~1800mm.

[0030] Ln can be 1750mm~1860mm, such as 1750mm, 1760mm, 1770mm, 1780mm, 1790mm, 1800mm, 1810mm, 1820mm, 1830mm, 1840mm, 1850mm or 1860mm, etc., or other values ​​within the range of 1750mm~1860mm, and further can be 1790mm~1860mm.

[0031] In some alternative implementations, Wn-Wp can be 1.5mm, 2.0mm, 2.5mm, or 3.0mm, or other values ​​within the range of 1.5mm to 3.0mm. In some more typical implementations, Wn-Wp can be 1.6mm to 2.8mm.

[0032] Ws-Wn can be 1.5mm, 2.0mm, 2.5mm, 3.0mm, 3.5mm, or 4.0mm, or other values ​​within the range of 1.5mm to 4.0mm. In some typical implementations, Ws-Wn can be 1.7mm to 3.5mm, and more specifically, 2.5mm to 3.5mm.

[0033] Wp can be 59.5mm to 61.5mm, such as 59.5mm, 60.0mm, 60.5mm, 61.0mm or 61.5mm, or other values ​​within the range of 59.5mm to 61.5mm.

[0034] Wn can be 61.5mm to 63.5mm, such as 61.5mm, 62.0mm, 62.5mm, 63.0mm, or 63.5mm, or other values ​​within the range of 61.5mm to 63.5mm. In some typical implementations, Wn can be 62.1mm to 63.3mm.

[0035] Ws can be 64.0mm to 66.5mm, such as 64.0mm, 64.5mm, 65.0mm, 65.5mm, 66.0mm or 66.5mm, or other values ​​within the range of 64.0mm to 66.5mm.

[0036] In some optional implementations, Ks can be 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06, 0.065, 0.07, 0.075, 0.08, or 0.085, or other values ​​within the range of 0.025 to 0.085. In some more typical implementations, Ks can be 0.030 to 0.075, and more specifically, 0.0331 to 0.0447.

[0037] Kl can be 0.020, 0.025, 0.030, 0.035, 0.040, 0.045, 0.050, 0.055, or 0.060, or other values ​​within the range of 0.020 to 0.060. In some typical implementations, Kl can be 0.0229 to 0.0457.

[0038] Kw can be 0.75mm, 0.8mm, 0.9mm, 1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, or 1.5mm, or other values ​​within the range of 0.75mm to 1.50mm. In some typical implementations, Kw can be 0.8mm to 1.40mm.

[0039] In some alternative implementations, Ls can be 1835mm to 1970mm, such as 1835mm, 1850mm, 1900mm, 1950mm, or 1970mm, or other values ​​within the range of 1835mm to 1970mm. In some more typical implementations, Ls can be 1870mm to 1940mm.

[0040] In some typical implementations, Ls-Ln is 50mm~130mm, and can be 60mm~80mm.

[0041] In some optional embodiments, Lp is 1700mm~1800mm, Ln is 1750mm~1860mm, and Ln-Lp is 40mm~80mm; Wp is approximately 60.5mm, Wn is 62.5mm, and Ws is 65mm. Under these conditions, the negative electrode sheet forms a coating of approximately 1.0mm on each side of the positive electrode sheet in the width direction, and the separator forms a coating of approximately 1.25mm on each side of the negative electrode sheet in the width direction.

[0042] In this invention, Ln-Lp is used to limit the end redundancy of the negative electrode relative to the positive electrode in the winding direction. When Ln-Lp is low, the positive electrode material area in the winding tail region is more likely to approach the termination edge of the negative electrode material area, and the local lithium-ion flux is concentrated at the edge of the negative electrode end. After cycling, this manifests as continuous lithium plating at the edge of the winding tail and light transmission through the separator. When Ln-Lp is high, the ineffective section at the tail of the negative electrode increases, the winding thickness and tension distribution are uneven, and the winding head is more prone to wrinkles and collapse of the central hole. Controlling Ln-Lp between 35mm and 100mm, especially 40mm to 80mm, can achieve a balance between end coating and winding stress, maintaining the capacity retention rate above 80% after 14A / 50A cycling.

[0043] Wn-Wp and Kw are used to limit the single-sided coating of the negative electrode onto the edge of the positive electrode. If Wn-Wp is too small, the electric field and liquid lithium-ion flux at the edge of the positive electrode can easily act directly on the edge of the negative electrode, making the tab side or non-tab side of the negative electrode a preferred site for lithium deposition, and further inducing light transmission at the edge of the separator. If Wn-Wp is too large, although it can increase edge coverage, it will introduce too much ineffective negative electrode area, increasing the lateral compressive stress and wetting path of the winding core, which is detrimental to cycle consistency. Controlling Wn-Wp to 1.5mm~3.0mm and keeping Kw at 0.75mm~1.50mm can balance edge coating, lithium deposition prevention, and winding volume utilization.

[0044] Ws-Wn is used to define the secondary edge protection of the separator relative to the negative electrode. When the separator width redundancy is insufficient, lateral alignment errors during the winding process, electrode edge burrs, and local thickness variations on the tab side will directly compress the separator edge area, leading to reduced separator porosity, increased light transmittance, or localized detachment of the ceramic layer. With an appropriately increased separator width redundancy, the separator can form a buffer zone on the outer side of the negative electrode edge, reducing the shearing and compression of the separator by the electrode edge and increasing the observable coverage allowance after the roll head and tail are unrolled. This invention controls Ws-Wn to 1.5mm~4.0mm, preferably 2.5mm~3.5mm, which helps reduce the risk of localized separator damage after high-rate cycling.

[0045] In some optional embodiments, the wound cylindrical lithium-ion cell also satisfies: Qp=C / (2Sp), where C is the discharge capacity of the wound cylindrical lithium-ion cell at 25°C and 0.2C to 2.5V, in mAh; Sp is the geometric area of ​​a single side of the positive electrode, Sp=Lp×Wp / 100, where Lp and Wp are both in mm, and Sp is in cm. 2 C ranges from 3800mAh to 4300mAh, and Qp is 1.75mAh / cm². 2 ~2.35mAh / cm 2 .

[0046] For example, C can be 3800mAh, 3900mAh, 4000mAh, 4100mAh, 4200mAh or 4300mAh, or other values ​​in the range of 3800mAh to 4300mAh.

[0047] For example, Qp can be 1.75 mAh / cm³. 2 1.80mAh / cm 2 1.85mAh / cm 2 1.90mAh / cm 2 1.95mAh / cm 2 2.00mAh / cm 2 2.05mAh / cm 2 2.10mAh / cm 2 2.15mAh / cm 2 2.20mAh / cm 2 2.25mAh / cm 2 2.30mAh / cm 2 Or 2.35mAh / cm 2 The value can also be 1.75 mAh / cm³. 2 ~2.35mAh / cm 2 Other values ​​within the range.

[0048] In some alternative implementations, the wound cylindrical lithium-ion cell also satisfies: JI = I × 1000 / (2Sp), where I is in A, and JI is the double-sided equivalent discharge surface current density in mA / cm². 2 When I=50A, JI is 10mA / cm. 2 ~30mA / cm 2 .

[0049] For example, JI can be 10mA / cm 2 15mA / cm 2 20mA / cm 2 25mA / cm 2 or 30mA / cm 2 etc., can also be 10mA / cm 2 ~30mA / cm 2 Other values ​​within the range.

[0050] In some optional embodiments, at the winding start end, the diaphragm forms a pre-wound section relative to the negative electrode sheet. The length of the pre-wound section can be 8mm to 30mm, such as 8mm, 10mm, 15mm, 20mm, 25mm, or 30mm, or other values ​​within the range of 8mm to 30mm. In some more typical embodiments, the length of the pre-wound section can be 8mm to 15mm.

[0051] At the winding tail end, the negative electrode sheet forms a rolled-tail covering section relative to the positive electrode sheet. The length of the rolled-tail covering section can be 10mm to 40mm, such as 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, or 40mm, or other values ​​within the range of 10mm to 40mm. In some typical embodiments, the length of the rolled-tail covering section can be 12mm to 30mm.

[0052] The tail-end covering section is used to handle the area most prone to relative displacement at the end of winding. If the tail-end covering is too short, the end of the positive electrode material area is prone to approaching the edge of the negative electrode material area during cyclic expansion and rebound. After local consumption of electrolyte, the edge polarization intensifies, manifesting as lithium plating on the side edge of the tail-end material area and detachment of the ceramic layer at the corresponding position of the separator. If the tail-end covering is too long, it increases the thickness accumulation at the tail end and the difficulty of fixing the termination adhesive, reducing the roundness of the outer ring of the core. This invention limits the tail-end covering section to 10mm~40mm, and in conjunction with Ls-Ln and Kl, it can ensure that the tail end has sufficient coverage without causing winding stress concentration due to excessive ineffective length.

[0053] In some optional embodiments, the width of the negative electrode sheet extending beyond the positive electrode sheet on one side relative to the negative electrode tab can be 0.8mm to 1.5mm, such as 0.8mm, 0.9mm, 1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, or 1.5mm, or other values ​​within the range of 0.8mm to 1.5mm. The width of the separator extending beyond the negative electrode sheet on one side relative to the negative electrode tab can be 0.8mm to 2.0mm, such as 0.8mm, 1.0mm, 1.2mm, 1.5mm, 1.8mm, or 2.0mm, or other values ​​within the range of 0.8mm to 2.0mm.

[0054] In some alternative implementations, the porosity of the positive electrode can be 24% to 32%, such as 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31% or 32%, or other values ​​within the range of 24% to 32%.

[0055] In some alternative implementations, the porosity of the negative electrode can be 30% to 38%, such as 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37% or 38%, or other values ​​within the range of 30% to 38%.

[0056] In some optional embodiments, the electrolyte filling coefficient of the wound cylindrical lithium-ion cell can be 3.1 g / Ah to 3.6 g / Ah, such as 3.1 g / Ah, 3.2 g / Ah, 3.3 g / Ah, 3.4 g / Ah, 3.5 g / Ah, and 3.6 g / Ah, or other values ​​within the range of 3.1 g / Ah to 3.6 g / Ah. In some more typical embodiments, the electrolyte filling coefficient of the wound cylindrical lithium-ion cell can be 3.35 g / Ah to 3.45 g / Ah.

[0057] The electrolyte injection coefficient affects the continuity of liquid phase transport in the long electrode core. Insufficient injection coefficient makes it difficult for the electrolyte to fully penetrate the microporous network between the beginning, middle, and end of the long electrode roll. Localized dry areas are more likely to form at the negative electrode edge and in the pressure zone of the separator, increasing lithium-ion migration resistance. After cycling, this manifests as increased ACR, higher temperature rise, and point-like lithium plating at multiple locations. Excessive injection, on the other hand, sacrifices energy density and increases the risk of high-temperature gas generation. This invention controls the electrolyte injection coefficient at 3.1 g / Ah to 3.6 g / Ah, and, combined with a porosity of 24% to 32% for the positive electrode and 30% to 38% for the negative electrode, improves the uniformity of wetting in the long core, allowing the width coverage and end redundancy structures to function effectively.

[0058] In some alternative embodiments, the silicon-carbon material in the negative electrode sheet can account for 3% to 10% of the total mass of the negative electrode active material, such as 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, or other values ​​within the range of 3% to 10%.

[0059] In some alternative embodiments, the N / P ratio of the negative electrode can be 1.02 to 1.10, such as 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, or 1.10, or other values ​​within the range of 1.02 to 1.10. In some more preferred embodiments, the N / P ratio of the negative electrode is 1.05 to 1.08.

[0060] The N / P ratio determines the negative electrode capacity redundancy and the negative electrode operating potential. When the N / P ratio is too low, even with geometrically defined negative electrode length and width coverage, localized high-rate charging may still result in excessively low negative electrode edge potentials, making the beginning, end, and tab sides sensitive areas for lithium plating. When the N / P ratio is too high, the negative electrode coating thickness or area redundancy increases, the liquid phase path becomes longer, and the winding pressure and wetting burden increase, which is also detrimental to rate cycling. This invention controls the N / P ratio to 1.02~1.10, preferably 1.05~1.08, and coordinates it with Qp, JI, and Kw to achieve a balance between capacity utilization, negative electrode safety redundancy, and long electrode wetting.

[0061] In some optional implementations, the capacity retention rate of the wound cylindrical lithium-ion cell after 1000 cycles under a cycle regime of 25°C, 8A charging, 60A discharging, and 2.5V cutoff is not less than 80%, such as 81.8% to 85.4%.

[0062] In some optional embodiments, the capacity retention rate of the wound cylindrical lithium-ion cell after 1000 cycles under a cycling regime of 25°C, 14A charging, 50A discharging, and 2.5V cutoff is not less than 80%, preferably not less than 82%, such as 84.5%~87.9%. Post-cycle disassembly shows that the beginning and end regions of the negative electrode do not form a continuous lithium plating band that runs through the full width of the negative electrode material area.

[0063] In some alternative implementations, the DC internal resistance of the wound cylindrical lithium-ion cell at 25°C and 100% SOC is no greater than 8.0 mΩ, such as 6.46 mΩ to 7.61 mΩ.

[0064] In some alternative implementations, when the wound cylindrical lithium-ion cell is discharged at a constant current of 40A, 50A and 60A to a cutoff of 2.5V at 25°C and 100% SOC, the maximum temperature of the casing of the wound cylindrical lithium-ion cell is no higher than 60°C, 67°C and 75°C, respectively.

[0065] In addition, the present invention also provides a battery module comprising the above-mentioned wound cylindrical lithium-ion cell.

[0066] In addition, the present invention also provides a battery pack comprising the above-described battery module.

[0067] In addition, the present invention also provides an electrical device comprising the above-described wound cylindrical lithium-ion cell, the above-described battery module, or the above-described battery pack.

[0068] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0069] The product parameters and performance results in this invention can be obtained according to the following unified testing method: (1) Cyclic test at 25℃ and 14A / 50A The cell under test was left to stand at 25±2℃ for 4 hours, then charged with a constant current of 14A to 4.2V, followed by constant voltage charging to the cutoff current of 0.2A, and then left to stand for 10 minutes. It was then discharged with a constant current of 50A to 2.5V and left to stand for 10 minutes, constituting one cycle. The discharge capacity of the first and Nth cycles was recorded, and the capacity retention rate was calculated according to Q. N Calculated as / Q1×100%, where Q1 is the discharge capacity in the first cycle, Q N The discharge capacity is the value for the Nth cycle; the cycle continues until 1000 cycles or the preset termination condition is met.

[0070] (2) Cyclic test at 25℃ and 8A / 60A The battery cell under test was left to stand at 25±2℃ for 4 hours, then charged with a constant current of 8A to 4.2V, followed by constant voltage charging to the cutoff current of 0.2A, and then left to stand for 10 minutes. It was then discharged with a constant current of 60A to 2.5V and left to stand for 10 minutes, completing one cycle. After 1000 cycles, press Q. 1000 / Q1×100% record capacity retention rate.

[0071] (3) DCR and rate rise test The battery cell was charged to 4.2V using a constant current and constant voltage method, with a cutoff current of 0.2A, and then allowed to rest for 60 minutes to reach 100% SOC. It was then discharged at a constant current of 10A for 10 seconds, and the voltage V0 before loading and the voltage V at 10 seconds after loading were recorded. 10 According to DCR=(V0-V 10 Calculate the DC internal resistance using 10A. After completing the DCR test, restore the cell to 100% SOC and let it stand for 60 minutes. Discharge to 2.5V with constant current at 40A, 50A and 60A respectively. Place thermocouples near 1 / 2 of the axial height of the casing and record the discharge process and the highest temperature within 300 seconds after the discharge ends.

[0072] (4) CT scan After the cycle was completed, the battery cell underwent X-ray CT scanning without being disassembled. The scan range covered the head, center hole, and tail areas of the core. Based on the CT images, the number of collapsed layers of the center hole was counted, and the eccentricity of the center hole, local collapse, and electrode wrinkling were recorded.

[0073] (5) Electrode dimensions: After completing the capacity, DCR and rate performance retest, discharge the cell at 0.2C to below 2.5V and let it stand for 2 hours. Disassemble the casing in an inert atmosphere with water and oxygen content of less than 1ppm, take out the core, and record the winding direction, beginning, middle, and end of the winding, the position of the tabs, and the diaphragm covering state. Unfold the positive and negative electrode sheets along the winding direction, separate the positive electrode sheet, negative electrode sheet and diaphragm, and use a steel ruler, image measuring instrument or automatic electrode length measuring device to measure the unfolded length Lp of the positive electrode material area, the unfolded length Ln of the negative electrode material area, and the unfolded length Ls of the diaphragm. Measure the width Wp of the positive electrode material area, the width Wn of the negative electrode material area and the width Ws of the diaphragm at at least three positions at the beginning, middle and end of the winding. Measure three times at each position and take the average value. Lp, Ln, Wp and Wn are based on the effective coating area of ​​the positive and negative active material layers, excluding the empty foil area, the tab welding area and the area without active material coverage. When two diaphragms are present, the unfolded length of each diaphragm is measured and Ks is calculated; the values ​​obtained for both diaphragms are judged within the same range. For samples with wavy edges or slight wrinkles, the projected length of the boundary of the continuous coating area is taken as the effective length.

[0074] The total width coverage of the negative electrode to the positive electrode is calculated by Wn-Wp, and the single-sided width coverage coefficient is calculated by Kw=(Wn-Wp) / 2; the total width redundancy of the diaphragm to the negative electrode is calculated by Ws-Wn.

[0075] (6) Positive electrode single-sided active area Sp: Lp and Wp are in mm, and calculated by the following formula: Sp = Lp × Wp / 100; the unit of Sp is cm. 2 .

[0076] Equivalent positive electrode areal capacity Qp: The cell capacity C is measured at 25℃ and 0.2C discharge to 2.5V, in mAh. Then, Qp is calculated using the formula: Qp = C / (2Sp); the coefficient 2 represents the active area on both sides of the double-coated positive electrode. The unit of Qp is mAh / cm². 2 .

[0077] Discharge surface current density JI: Under a specified discharge current I, calculate JI = I × 1000 / (2Sp), where I is in A, and JI is the equivalent discharge surface current density on both sides in mA / cm². 2 .

[0078] (7) Observation of lithium deposition at the edge of the electrode The negative electrode sheet was divided into three sections: beginning, middle, and end. Each section was further divided into tab side and non-tab side. Magnified images were taken of each observation area, and the number of point-like lithium deposits, the length of continuous lithium deposits, and the percentage of lithium deposited area were counted. If the lithium deposits penetrated along the width of the negative electrode material area, it was determined to be through-type lithium deposits; if the lithium deposits were only edge-like points or short segments, they were recorded as localized lithium deposits.

[0079] (8) Observation of diaphragm light transmission and damage Take diaphragm samples after circulation and observe them under backlight and transmitted light at the beginning, middle, and end of the roll. Perform SEM observation on the transmitted areas. If necessary, use EDS to detect the elemental composition of local particles. If there is a significant reduction in porosity, ceramic coating peeling, or a risk of connection between the base film and the ceramic coating in the transmitted areas, record it as local damage to the diaphragm.

[0080] (9) N / P ratio: Samples were taken from the disassembled positive and negative electrode sheets to obtain the reversible capacity q per unit area of ​​the positive electrode. p and the reversible capacity per unit area of ​​the negative electrode q n Coin cells can be prepared using powder or electrode samples disassembled from the same batch and tested at 0.1C. The reversible capacity of the positive and negative electrodes is calculated based on their effective active areas, using the following formula: N / P = Qn / Qp; where Qn is the reversible capacity of the negative electrode and Qp is the reversible capacity of the positive electrode. If the effective areas of the positive and negative electrodes are roughly corresponding, the ratio can also be calculated by converting the reversible capacity per unit area and the corresponding active area.

[0081] (10) Surface density, compaction density, and porosity: Samples of known area are punched from the head, middle, and tail of the positive and negative electrodes, respectively. The mass of the sample is weighed, and the mass of the current collector is weighed after removing the active material layer. The surface density of a single surface is calculated. The electrode thickness is measured using a micrometer or cross-sectional SEM. The compaction density is calculated by combining the coating mass and coating volume. Porosity can be calculated by converting the apparent volume of the electrode, the mass of the current collector, the coating mass, and the true density of each solid component. It can also be verified by mercury intrusion porosimetry, gas adsorption, or cross-sectional image methods.

[0082] (11) Material and electrolyte composition: The layered structure of the positive electrode material can be confirmed by XRD, and the proportions of elements such as Ni, Co, and Mn can be determined by ICP-OES; the artificial graphite and silicon-carbon materials of the negative electrode material can be confirmed by XRD, Raman, SEM / EDS and thermogravimetric analysis. The contribution of silicon-carbon materials can be verified by combining the capacity integral of the negative electrode coin cell curve and the distribution of Si elements. The electrolyte can be obtained by taking the residual liquid or electrode extract under an inert atmosphere, analyzing the organic solvent by GC-MS, and analyzing the lithium salt and additives by ion chromatography, nuclear magnetic resonance or ICP-MS. The liquid injection coefficient can be calculated from the liquid injection volume and capacity in the production sample; for disassembled samples, it can be estimated by the residual liquid volume, electrode liquid absorption rate and the weight of samples of the same specification.

[0083] Example 1 This embodiment provides a wound cylindrical lithium-ion battery cell, the preparation of which includes: S1: Preparation of positive electrode slurry.

[0084] With LiNi 0.9 Co 0.05 Mn 0.05O2 was used as the positive electrode active material. It was mixed with acetylene black, polyvinylidene fluoride and lithium carbonate in a mass ratio of 97:1:1:1 and N-methylpyrrolidone was used as the solvent to prepare a positive electrode slurry with a solid content of 72wt%.

[0085] S2: Prepare the positive electrode sheet.

[0086] The positive electrode slurry is coated on both sides of an aluminum current collector with a thickness of 12μm, and then dried, rolled and slit to obtain the positive electrode sheet.

[0087] The porosity of this positive electrode is 26%, and its areal density on one side is 10.57 mg / cm³. 2 The compacted density is 3.50 g / cm³. 3 The unfolded length Lp of the positive electrode material region is 1750mm, and the width Wp of the positive electrode material region is 60.5mm.

[0088] S3: Prepare negative electrode slurry.

[0089] Artificial graphite and silicon carbon materials were used as negative electrode active materials, with silicon carbon materials accounting for 6% of the total mass of negative electrode active materials. The negative electrode active materials, conductive carbon black, carboxymethyl cellulose and styrene-butadiene rubber were mixed in a mass ratio of 97:1:1:1 and deionized water was used as solvent to prepare a negative electrode slurry with a solid content of 46wt%.

[0090] S4: Prepare the negative electrode sheet.

[0091] The negative electrode slurry is coated on both sides of a copper current collector with a thickness of 6μm, and then dried, rolled and slit to obtain the negative electrode sheet.

[0092] The porosity of this negative electrode is 32%, and its areal density on one side is 5.2 mg / cm³. 2 The compacted density is 1.50 g / cm³. 3 The negative electrode material region has an unfolded length Ln of 1810 mm, a width Wn of 62.5 mm, and an N / P ratio of 1.05.

[0093] S5: Prepare the diaphragm.

[0094] Two separators are used, each composed of a polyolefin-based membrane and a ceramic coating. The unfolded length Ls of each separator is 1890 mm, the width Ws is 65.0 mm, and the thickness is 12 μm. The separators extend approximately 1.25 mm from each side of the negative electrode in the width direction.

[0095] S6: Winding.

[0096] During winding, the negative electrode sheet, separator, and positive electrode sheet are stacked sequentially, such that the negative electrode sheet is 60 mm longer than the positive electrode sheet in the length direction and extends approximately 1.0 mm on each side of the positive electrode sheet in the width direction. At the beginning of winding, the separator forms a 15 mm pre-wound section relative to the negative electrode sheet, and at the end of winding, it forms a 65 mm rear section with redundant separator material relative to the negative electrode sheet. At the end of winding, the negative electrode sheet forms an approximately 20 mm rear-wound covering section relative to the positive electrode sheet.

[0097] S7: Tabs and alignment control.

[0098] The positive electrode tab is positioned in the predetermined blank area of ​​the positive electrode sheet, and the negative electrode tab is positioned in the predetermined blank area of ​​the negative electrode sheet, such that the single-sided width coverage of the negative electrode tab side is 1.0 mm, and the single-sided extension of the separator relative to the negative electrode sheet on the negative electrode tab side is 1.25 mm. The winding tension is controlled at 1.2 N, and the alignment tolerance in the width direction of the positive and negative electrodes is controlled within ±0.30 mm, ensuring that the center hole remains round after winding.

[0099] S8: Assembly and injection.

[0100] The core is loaded into the cylindrical shell, completing the connection of the current collector components, grooving, electrolyte injection, sealing, formation, aging, and capacity testing. The electrolyte used, by total mass, includes 12.5 wt% lithium hexafluorophosphate, 20.0 wt% ethylene carbonate, 31.0 wt% methyl ethyl carbonate, 17.0 wt% diethyl carbonate, 17.0 wt% ethyl acetate, 0.5 wt% lithium difluorophosphate, 1.0 wt% fluoroethylene carbonate, 0.5 wt% 1,3-propanesulfonate lactone, and 0.5 wt% lithium difluorooxalate borate. The electrolyte injection rate is 3.35 g / Ah, corresponding to an injection volume of 13.75 g per 4.104Ah cell.

[0101] In this embodiment, Kl=0.0343, Kw=1.0mm, Ks=0.0442, and Sp=1058.75cm. 2 C=4104mAh, Qp=1.94mAh / cm 2 When I=50A, JI=23.6mA / cm 2 .

[0102] Example 2 The difference between this embodiment and Embodiment 1 is that the mass percentage of ethyl acetate in the electrolyte is reduced from 17 wt% to 10 wt%, and the mass percentage of lithium difluorophosphate is increased from 0.5 wt% to 1.0 wt%, so that the electrolyte composition is changed from the reference electrolyte to the first low-gas-producing electrolyte; the other conditions are the same as in Embodiment 1.

[0103] Example 3 The difference between this embodiment and Example 1 is that the mass percentage of ethyl acetate in the electrolyte is reduced from 17 wt% to 0 wt%, and the mass percentage of fluoroethylene carbonate is increased from 1.0 wt% to 2.0 wt%, so that the electrolyte composition is changed from the reference electrolyte to the second low-gas-producing electrolyte; the other conditions are the same as in Example 1.

[0104] Example 4 The difference between this embodiment and Embodiment 1 is that by adjusting the effective coating cutting length Ln of the negative electrode from 1810mm to 1790mm and adjusting the diaphragm cutting length Ls from 1890mm to 1870mm, Ln-Lp changes from 60mm to 40mm and Kl changes from 0.0343 to 0.0229; the other conditions are the same as in Embodiment 1.

[0105] Example 5 The difference between this embodiment and Embodiment 1 is that by adjusting the effective coating cutting length Ln of the negative electrode from 1810mm to 1830mm and adjusting the diaphragm cutting length Ls from 1890mm to 1910mm, Ln-Lp changes from 60mm to 80mm and Kl changes from 0.0343 to 0.0457; the other conditions are the same as in Embodiment 1.

[0106] Example 6 The difference between this embodiment and Embodiment 1 is that by adjusting the negative electrode slitting width Wn from 62.5mm to 62.1mm, Wn-Wp changes from 2.0mm to 1.6mm, and Kw changes from 1.0mm to 0.8mm; the other conditions are the same as in Embodiment 1.

[0107] Example 7 The difference between this embodiment and Embodiment 1 is that by adjusting the negative electrode slitting width Wn from 62.5mm to 63.3mm, Wn-Wp changes from 2.0mm to 2.8mm, and Kw changes from 1.0mm to 1.4mm; the other conditions are the same as in Embodiment 1.

[0108] Example 8 The difference between this embodiment and Embodiment 1 is that by adjusting the diaphragm cutting length Ls from 1890mm to 1870mm, Ls-Ln changes from 80mm to 60mm, and Ks changes from 0.0442 to 0.0331; the other conditions are the same as in Embodiment 1.

[0109] Example 9 The difference between this embodiment and Embodiment 1 is that the diaphragm cutting width Ws is adjusted from 65.0 mm to 66.0 mm, so that Ws-Wn changes from 2.5 mm to 3.5 mm; the other conditions are the same as in Embodiment 1.

[0110] Example 10 The difference between this embodiment and Embodiment 1 is that the pre-wound length of the diaphragm at the starting end of the winding is adjusted from 15mm to 8mm, and the wrapping section at the end of the winding is adjusted from 20mm to 12mm; the other conditions are the same as in Embodiment 1.

[0111] Example 11 The difference between this embodiment and Embodiment 1 is that the surface density of the negative electrode single side is adjusted from 5.2 mg / cm³. 2 Up to 5.35 mg / cm 2 The injection coefficient was adjusted from 3.35 g / Ah to 3.45 g / Ah, so that the N / P ratio changed from 1.05 to 1.08; the remaining conditions were the same as in Example 1.

[0112] Example 12 The difference between this embodiment and Embodiment 1 is that the effective coating length Lp of the positive electrode is adjusted from 1750mm to 1800mm, the effective coating length Ln of the negative electrode is adjusted from 1810mm to 1860mm, and the diaphragm cutting length Ls is adjusted from 1890mm to 1940mm, while Ln-Lp remains at 60mm; the other conditions are the same as in Embodiment 1.

[0113] Comparative Example 1 The difference between this comparative example and Example 1 is that the effective coating cutting length Ln of the negative electrode was adjusted from 1810mm to 1770mm, and the diaphragm cutting length Ls was adjusted from 1890mm to 1850mm, so that Ln-Lp changed from 60mm to 20mm and Kl changed from 0.0343 to 0.0114; the other conditions are the same as in Example 1.

[0114] Comparative Example 2 The difference between this comparative example and Example 1 is that the effective coating cutting length Ln of the negative electrode was adjusted from 1810mm to 1880mm, and the diaphragm cutting length Ls was adjusted from 1890mm to 1960mm, so that Ln-Lp changed from 60mm to 130mm and Kl changed from 0.0343 to 0.0743; the other conditions are the same as in Example 1.

[0115] Comparative Example 3 The difference between this comparative example and Example 1 is that the negative electrode slitting width Wn is adjusted from 62.5 mm to 61.1 mm, so that Wn-Wp changes from 2.0 mm to 0.6 mm, and Kw changes from 1.0 mm to 0.3 mm; the other conditions are the same as in Example 1.

[0116] Comparative Example 4 The difference between this comparative example and Example 1 is that the diaphragm cutting width Ws was adjusted from 65.0 mm to 63.0 mm, so that Ws-Wn changed from 2.5 mm to 0.5 mm; the other conditions are the same as in Example 1.

[0117] Comparative Example 5 The difference between this comparative example and Example 1 is that the tail-wrapping section is adjusted from 20mm to 3mm, and the redundant length of the diaphragm tail is adjusted from 65mm to 25mm simultaneously, so that the end of the negative electrode to the positive electrode in the tail-wrapping area is not fully covered; the other conditions are the same as in Example 1.

[0118] Comparative Example 6 The difference between this comparative example and Example 1 is that the injection volume was adjusted from 3.35 g / Ah to 2.60 g / Ah, so that the injection coefficient changed from 3.35 g / Ah to 2.60 g / Ah; the other conditions were the same as in Example 1.

[0119] Comparative Example 7 The difference between this comparative example and Example 1 is that the effective coating length Lp of the positive electrode was adjusted from 1750 mm to 1350 mm, the effective coating length Ln of the negative electrode was adjusted from 1810 mm to 1410 mm, and the diaphragm cutting length Ls was adjusted from 1890 mm to 1490 mm, and JI was adjusted from 23.6 mA / cm. 2 It becomes 30.6 mA / cm 2 The remaining conditions are the same as in Example 1.

[0120] Comparative Example 8 The difference between this comparative example and Example 1 is that the effective coating length Ln of the negative electrode was adjusted from 1810 mm to 1760 mm, the negative electrode slitting width Wn was adjusted from 62.5 mm to 61.0 mm, and the diaphragm width Ws was adjusted from 65.0 mm to 61.5 mm, so that Ln-Lp changed from 60 mm to 10 mm, Wn-Wp changed from 2.0 mm to 0.5 mm, and Ws-Wn changed from 2.5 mm to 0.5 mm; the other conditions were the same as in Example 1.

[0121] Some characteristics of the products prepared in Examples 1-12 and Comparative Examples 1-8 are shown in Tables 1 and 2, and the performance test results are shown in Tables 3 and 4.

[0122] Table 1. Some features of the embodiments

[0123] Table 2 Comparative features

[0124] Table 3 Test Results of Examples

[0125] Table 4 Comparative test results

[0126] Referring to Tables 1 to 4: (1) According to Examples 1, 4, 5, Comparative Example 1 and Comparative Example 2, when Ln-Lp is low, the positive electrode material area in the tail region is more likely to approach the termination edge of the negative electrode material area, and the local lithium-ion flux is concentrated at the edge of the negative electrode end. After cycling, this is manifested as continuous lithium plating at the tail edge and light transmission of the separator. When Ln-Lp is high, the ineffective section at the tail of the negative electrode increases, the winding thickness and tension distribution are uneven, and wrinkles and central hole collapse are easily generated at the head of the winding. Controlling Ln-Lp to 35mm~100mm, especially 40mm~80mm, can achieve a balance between end coating and winding stress, so that the capacity retention rate after 14A / 50A cycling is maintained above 85%.

[0127] (2) According to Examples 1, 6, 7 and Comparative Example 3, when Wn-Wp is too small, the electric field and liquid lithium-ion flux at the edge of the positive electrode can easily act directly on the edge of the negative electrode. The tab side or non-tab side of the negative electrode will become the preferred lithium plating site, and further induce light transmission at the edge of the separator. When Wn-Wp is too large, although it can increase edge coverage, it will introduce too much ineffective negative electrode area, which will increase the lateral compressive stress and wetting path of the core, which is not conducive to cycle consistency. Controlling Wn-Wp to 1.5mm~3.0mm (preferably 1.6mm~2.8mm) and keeping Kw at 0.75mm~1.50mm (preferably 0.8mm~1.40mm) can balance edge coverage, lithium plating prevention and winding volume utilization.

[0128] (3) As can be seen from Examples 1, 9 and Comparative Example 4, Ws-Wn is used to limit the secondary edge protection of the separator relative to the negative electrode. When the separator width redundancy is insufficient, the lateral alignment error during the winding process, the burrs on the electrode edge, and the local thickness changes on the tab side will directly compress the edge area of ​​the separator, resulting in reduced separator porosity, increased light transmittance, or local detachment of the ceramic layer. After the separator width redundancy is appropriately increased, the separator can form a buffer zone on the outside of the negative electrode edge, reducing the shearing and squeezing of the separator by the electrode edge, and increasing the observable coating allowance after the roll head and roll tail are unrolled. Therefore, controlling Ws-Wn to 1.5mm~4.0mm, preferably 2.5mm~3.5mm, is beneficial to reducing the risk of local damage to the separator after high-rate cycling.

[0129] (4) As can be seen from Examples 1, 10 and Comparative Example 5, the tail-end covering section is used to handle the area most prone to relative displacement when winding ends. When the tail-end covering is too short, the end of the positive electrode material area is prone to approach the edge of the negative electrode material area during the cyclic expansion and rebound process. After the electrolyte is locally consumed, the edge polarization is aggravated, which manifests as lithium plating on the side edge of the tail material area and the detachment of the ceramic layer at the corresponding position of the separator. If the tail-end covering is too long, it will increase the thickness accumulation of the tail and the difficulty of fixing the termination adhesive, which will reduce the roundness of the outer ring of the core. In this invention, the tail-end covering section is limited to 10mm~40mm (preferably 12mm~30mm), and is used in conjunction with Ls-Ln and Kl to ensure that the tail end has sufficient coverage without causing winding stress concentration due to excessive ineffective length.

[0130] (5) As can be seen from Examples 1, 11 and Comparative Example 6, the electrolyte injection coefficient affects the continuity of liquid phase transport in the long electrode core. When the electrolyte injection coefficient is insufficient, the electrolyte is difficult to fully enter the microporous network between the beginning, middle and end of the long electrode core. Local dry areas are more likely to form at the edge of the negative electrode and the pressure area of ​​the separator, increasing the resistance to lithium-ion migration. After cycling, this manifests as increased ACR, increased temperature rise and point-like lithium deposition at multiple locations. Excessive electrolyte injection will sacrifice energy density and increase the risk of high-temperature gas generation. Controlling the electrolyte injection coefficient at 3.1 g / Ah~3.6 g / Ah (preferably 3.35 g / Ah~3.45 g / Ah), and coordinating it with the porosity of the positive and negative electrodes, can improve the wettability of the long core, support the width coverage and end redundancy structure to function.

[0131] (6) As can be seen from Examples 1 and 11 and Comparative Examples 3 and 6, N / P determines the negative electrode capacity redundancy and the negative electrode operating potential. When N / P is too low, even if there is geometric coverage of the negative electrode length and width, local high-rate charging may still cause the negative electrode edge potential to be too low, and the beginning, end, and tab sides become lithium plating sensitive areas. When N / P is too high, the thickness or area redundancy of the negative electrode coating increases, the liquid phase path becomes longer, and the winding pressure and wetting burden increase, which is also not conducive to rate cycling. Controlling N / P at 1.02~1.10, preferably 1.05~1.08, and coordinating it with Qp, JI, and Kw, can achieve a balance between capacity utilization, negative electrode safety redundancy, and long electrode wetting.

[0132] In summary, by limiting Ln-Lp, Wn-Wp, Ls-Ln, and Ws-Wn, and further limiting Kw=(Wn-Wp) / 2, Kl=(Ln-Lp) / Lp, Ks=(Ls-Ln) / Ln, Sp=Lp×Wp / 100, Qp=C / (2Sp), and JI=I×1000 / (2Sp), that is, through the comprehensive balance of end redundancy, width coverage, diaphragm redundancy, and low surface current, this invention can improve the stability of the beginning, end, and tab edges of a long-electrode 4Ah-class cylindrical cell after high-rate cycling while reducing the current density per unit area. This reduces the risk of local lithium plating, diaphragm light transmission, ceramic layer detachment, and center hole collapse after high-rate cycling, and improves the high-rate cycling retention rate.

[0133] 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 wound cylindrical lithium-ion battery cell, characterized in that, The wound cylindrical lithium-ion battery cell includes a core, the core including a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet; The positive electrode has a positive electrode material region unfolding length Lp and a positive electrode material region width Wp, the negative electrode has a negative electrode material region unfolding length Ln and a negative electrode material region width Wn, and the separator has a separator unfolding length Ls, a separator width Ws, and an unfolding redundancy coefficient Ks corresponding to the negative electrode. Ln-Lp is 35mm~100mm; Wn-Wp is 1.5mm~3.0mm, and Ws-Wn is 1.5mm~4.0mm; Ks=(Ls-Ln) / Ln, Ks is 0.025~0.085; Kl=(Ln-Lp) / Lp, Kl is 0.020~0.060; Kw=(Wn-Wp) / 2, Kw is 0.75mm~1.50mm.

2. The wound cylindrical lithium-ion cell according to claim 1, characterized in that, Lp is 1450mm~1900mm, Ln is 1750mm~1860mm, preferably Lp is 1700mm~1800mm, Ln-Lp is 40mm~80mm, and Kl is 0.025~0.050; And / or, Wp is 59.5mm~61.5mm, Wn is 61.5mm~63.5mm, Ws is 64.0mm~66.5mm, Kw is 0.85mm~1.25mm, preferably, Ws-Wn is 2.0mm~3.2mm; And / or, Ls is 1835mm~1970mm, Ls-Ln is 50mm~130mm, preferably, Ks is 0.030~0.

075.

3. The wound cylindrical lithium-ion cell according to claim 1 or 2, characterized in that, The wound cylindrical lithium-ion cell also meets the following requirements: Qp = C / (2Sp), where C is the discharge capacity of a wound cylindrical lithium-ion cell at 25℃ and 0.2C to 2.5V, in mAh; Sp is the geometric area of ​​a single side of the positive electrode, Sp = Lp × Wp / 100, where Lp and Wp are in mm, and Sp is in cm. 2 C ranges from 3800mAh to 4300mAh, and Qp is 1.75mAh / cm². 2 ~2.35mAh / cm 2 ; And / or, JI = I × 1000 / (2Sp), where I is in A, and JI is the double-sided equivalent discharge surface current density in mA / cm². 2 When I=50A, JI is 10mA / cm. 2 ~30mA / cm 2 .

4. The wound cylindrical lithium-ion cell according to claim 1, characterized in that, At the starting end of winding, the diaphragm forms a pre-wound section relative to the negative electrode sheet, the length of which is 8mm to 30mm; at the ending end of winding, the negative electrode sheet forms a tail-covering section relative to the positive electrode sheet, the length of which is 10mm to 40mm.

5. The wound cylindrical lithium-ion cell according to claim 1, characterized in that, The negative electrode sheet extends 0.8 mm to 1.5 mm beyond the width of the positive electrode sheet on the negative electrode tab side, and the separator extends 0.8 mm to 2.0 mm beyond the width of the negative electrode sheet on the negative electrode tab side.

6. The wound cylindrical lithium-ion cell according to claim 1, characterized in that, The wound cylindrical lithium-ion battery cell also has at least one of the following characteristics: Feature 1: The porosity of the positive electrode is 24%~32%; Feature 2: The porosity of the negative electrode sheet is 30%~38%; Feature 3: The liquid injection coefficient of the wound cylindrical lithium-ion battery cell is 3.1g / Ah~3.6g / Ah; Feature 4: In the negative electrode sheet, silicon-carbon material accounts for 3% to 10% of the total mass of the negative electrode active material; Feature 5: The N / P ratio of the negative electrode is 1.02~1.10, preferably 1.04~1.

07.

7. The wound cylindrical lithium-ion cell according to claim 1, characterized in that, The wound cylindrical lithium-ion battery cell has at least one of the following characteristics: Feature 6: Under a cycle regime of 25°C, 8A charging, 60A discharging, and 2.5V cutoff, the capacity retention rate of the wound cylindrical lithium-ion cell after 1000 cycles is not less than 80%. Feature 7: Under a cycle regime of 25°C, 14A charging, 50A discharging, and 2.5V cutoff, the capacity retention rate of the wound cylindrical lithium-ion cell after 1000 cycles is not less than 80%. Feature 8: The DC internal resistance of the wound cylindrical lithium-ion cell at 25℃ and 100% SOC is no greater than 8.0mΩ; Feature 9: When the wound cylindrical lithium-ion cell is discharged at a constant current of 40A, 50A and 60A to a cutoff of 2.5V at 25℃ and 100% SOC, respectively, the maximum temperature of the casing of the wound cylindrical lithium-ion cell is no higher than 60℃, 67℃ and 75℃, respectively.

8. A battery module, characterized in that, Including the wound cylindrical lithium-ion cell as described in any one of claims 1 to 7.

9. A battery pack, characterized in that, Includes the battery module as described in claim 8.

10. An electrical appliance, characterized in that, Includes the wound cylindrical lithium-ion cell as described in any one of claims 1 to 7, the battery module as described in claim 8, or the battery pack as described in claim 9.

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