A full-tab cylindrical lithium ion battery and a preparation method thereof

Abstract

The application provides a full-tab cylindrical lithium ion battery and a preparation method thereof. The full-tab cylindrical lithium ion battery comprises a positive electrode tab and a negative electrode tab. The positive electrode tab comprises a positive electrode current collector and a positive electrode active material layer located on at least one side surface of the positive electrode current collector. The single surface density A1 of the positive electrode active material layer is 13.2-14.0 mg / cm2, the positive electrode compaction density P1 is 3.52-3.65 g / cm3, and the effective length L1 of the positive electrode tab in the winding direction is 1500-1600 mm. The product of the ratio of A1 to 13.5 mg / cm2, the ratio of P1 to 3.55 g / cm3 and the ratio of 1600 mm to L1 is denoted as the tab high load factor Fp, and Fp is 0.98-1.08. Through the coupling control of A1, P1 and L1, the 40A discharge end-stage polarization increase caused by the mismatch of the positive electrode load, the compaction state and the tab length is avoided. Through the structure window limitation of Fp, the discharge heat level is matched with the winding core radial heat dissipation path, and the temperature peak after calibration under different heat dissipation conditions is reduced.

Description

Technical Field

[0001] This application relates to the field of energy storage equipment technology, such as a fully tabbed cylindrical lithium-ion battery and its preparation method. Background Technology

[0002] Currently, all-tab cylindrical lithium-ion batteries (such as the 21700 all-tab cylindrical lithium-ion battery) are widely used in high-rate discharge scenarios. To address the discharge polarization and heat generation issues under 40A-level high-rate discharge, positive electrode design typically employs two approaches: one is to reduce the areal density of the positive electrode active material layer and extend the electrode length to reduce local current density, thereby reducing discharge polarization, but this increases the winding path length of the core and sacrifices volumetric energy density; the other is to increase the areal density and compaction density of the positive electrode active material layer to improve capacity, but this easily leads to increased polarization at the end of the 40A discharge and a delayed increase in casing temperature. It is evident that in related technologies, increasing load capacity, reducing discharge polarization, and suppressing casing temperature rise are mutually restrictive, and temperature rise evaluation lacks a comparable standard across heat dissipation fixtures. How to balance low discharge polarization and low casing temperature rise under high-load structures, and to make temperature rise evaluations comparable, remains a technical problem to be solved. Summary of the Invention

[0003] To provide a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. This summary is not intended as a general commentary, nor is it intended to identify key / important components or describe the scope of protection of these embodiments, but rather as a prelude to the detailed description that follows.

[0004] This specification provides an embodiment of a cylindrical lithium-ion battery with multiple tabs and a method for its preparation. Through the coupling control of A1, P1 and L1, the polarization increase at the end of the 40A discharge is avoided due to the positive electrode load, compaction state and electrode length mismatch.

[0005] Firstly, this specification provides a fully tabbed cylindrical lithium-ion battery, comprising a positive electrode and a negative electrode. The positive electrode sheet includes a positive current collector and a positive active material layer located on at least one side surface of the positive current collector; The areal density A1 of the positive electrode active material layer is 13.2-14.0 mg / cm², the positive electrode compaction density P1 is 3.52-3.65 g / cm³, and the effective length L1 of the positive electrode sheet in the winding direction is 1500-1600 mm. The product of the ratio of A1 to 13.5 mg / cm², the ratio of P1 to 3.55 g / cm³, and the ratio of 1600 mm to L1 is denoted as the high loading factor Fp of the electrode sheet, Fp = (A1 / 13.5) × (P1 / 3.55) × (1600 / L1), and Fp is 0.98-1.08. Extending L1 can reduce the local in-plane current density but increase the number of winding layers, which increases the radial thermal resistance of heat conduction to the shell. Increasing A1 and P1 can compress the electrode sheet thickness and shorten the lithium ion diffusion path, but it will aggravate the porosity and Joule thermal density. The Fp window essentially limits the coupling ratio of the three components, enabling the in-plane current distribution and the radial thermal resistance network to achieve dynamic equilibrium.

[0006] The all-tab cylindrical lithium-ion battery meets the following requirements during the test of discharging from a state of charge (SOC) of 50% to a lower cutoff voltage of 2.5V at a constant current of 40A under 25℃ environment: discharge polarization value η≤0.225V, heat dissipation calibration temperature T1≤65.0℃, and electrothermal coupling temperature rise index K1≤190℃ / V. Wherein, the heat dissipation calibration temperature T1 represents the temperature calculated when a full-tab cylindrical lithium-ion battery is discharged from a state of charge (SOC) of 50% to a lower cutoff voltage of 2.5V at a constant current of 40A under an environment of 25℃; the electrothermal coupling temperature rise index K1 represents the ratio of the heat dissipation calibration temperature rise ΔT1 to the discharge polarization value η.

[0007] Secondly, this specification also provides a method for preparing a fully tabbed cylindrical lithium-ion battery, comprising the following steps: A positive electrode active material, a conductive agent, and a binder are mixed in a solvent to obtain a positive electrode slurry. The positive electrode slurry is coated onto the surface of a positive electrode current collector, and then dried, rolled, and die-cut to achieve a single-sided areal density A1 of 13.2-14.0 mg / cm², a positive electrode compaction density P1 of 3.52-3.65 g / cm³, and an effective length L1 of the positive electrode sheet in the winding direction of 1500-1600 mm. The product of the ratio of A1 to 13.5 mg / cm², the ratio of P1 to 3.55 g / cm³, and the ratio of 1600 mm to L1 is 0.98-1.08. A negative electrode active material, conductive agent, binder and thickener are mixed in a solvent to obtain a negative electrode slurry. The negative electrode slurry is coated on the surface of the negative electrode current collector, and then dried, rolled and die-cut to obtain a negative electrode sheet. The obtained positive electrode sheet, separator, and negative electrode sheet are wound to form a core. The positive electrode empty foil area is flattened / folded to form a positive electrode tab layer. The positive electrode tab layer is welded to the positive electrode current collector. The negative electrode empty foil area is flattened / folded to form a negative electrode tab layer. The negative electrode tab layer is welded to the negative electrode current collector. The core is then placed into a cylindrical shell. The negative electrode current collector is welded to the shell, and the positive electrode current collector is welded to a cap. The separator includes a polyolefin base film and a ceramic coating. The ceramic coating is disposed on the surface of the polyolefin base film facing the negative electrode sheet. Electrolyte is injected into the cylindrical shell, and after sealing, it undergoes formation, aging, and capacity testing to obtain the full-tab cylindrical lithium-ion battery. The fully tabbed cylindrical lithium-ion battery and its preparation method proposed in this specification have at least the following technical advantages: First, by controlling the coupling of A1, P1 and L1, the polarization increase at the end of the 40A discharge is avoided due to the positive load, compaction state and electrode length mismatch.

[0008] Second, by limiting the Fp structure window, the level of heat generated by the discharge is matched with the radial heat dissipation path of the core, thereby reducing the temperature peak after calibration under different heat dissipation conditions.

[0009] Third, by constraining the relationship between the heat dissipation calibration temperature rise and the discharge polarization value through the K1 index, we can avoid one-sided optimization that results in uncontrolled temperature rise by simply reducing polarization or excessive polarization by simply controlling temperature.

[0010] Fourth, by optimizing the configuration of high-nickel single-crystal / polycrystalline cathode, silicon-containing anode, ceramic-coated separator facing the anode side, and current collector thickness ratio, the stability and consistency of the above-mentioned electrothermal coupling performance window can be further improved.

[0011] The above general description and the description below are exemplary and illustrative only and are not intended to limit this application. Attached Figure Description

[0012] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations and drawings do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are shown as similar elements. The drawings are not to be scaled. And wherein: Figure 1 This is a schematic diagram of the structure of a cylindrical lithium-ion battery with all tabs provided in the embodiments of this specification.

[0013] Figure 2 This is a cross-sectional view of a cylindrical lithium-ion battery with all tabs provided in the embodiments of this specification.

[0014] Figure 3 This is a schematic diagram of a fully tabbed cylindrical lithium-ion battery core provided in the embodiments of this specification.

[0015] Figure 4 This is a schematic diagram of the positive electrode sheet of a cylindrical lithium-ion battery core with all tabs provided in the embodiments of this specification.

[0016] Figure 5 This is a schematic diagram of the negative electrode sheet of a cylindrical lithium-ion battery core with all tabs provided in the embodiments of this specification.

[0017] Figure 6 This is a flowchart illustrating a method for preparing a fully tabbed cylindrical lithium-ion battery according to an embodiment of this specification. Detailed Implementation

[0018] To provide a more detailed understanding of the features and technical content of the embodiments of this specification, the implementation of the embodiments is described in detail below with reference to the accompanying drawings. The accompanying drawings are for illustrative purposes only and are not intended to limit the embodiments of this specification. In the following technical description, for ease of explanation, several details are used to provide a full understanding of the disclosed embodiments. However, one or more embodiments may still be implemented without these details. In other cases, well-known structures and devices may be simplified in their depiction to simplify the drawings.

[0019] The terms "first," "second," etc., in the description, claims, and accompanying drawings of the embodiments herein are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of the present specification described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0020] In the embodiments of this specification, the terms "upper," "lower," "inner," "middle," "outer," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily used to better describe the embodiments of this specification and their implementations, and are not intended to limit the indicated devices, elements, or components to having a specific orientation, or to construct and operate in a specific orientation. Furthermore, some of the above terms may be used to indicate other meanings besides orientation or positional relationship; for example, the term "upper" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in the embodiments of this specification according to the specific circumstances.

[0021] Furthermore, the terms "set up," "connect," and "fix" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this specification according to the specific circumstances.

[0022] Unless otherwise stated, the term "multiple" means two or more.

[0023] In the embodiments described in this specification, the character " / " indicates that the objects before and after it are in an "or" relationship. For example, A / B means: A or B.

[0024] The term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or A and B.

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of this specification can be combined with each other.

[0026] All-tab cylindrical lithium-ion batteries, such as the 21700 all-tab cylindrical lithium-ion battery, are widely used in high-rate discharge scenarios. Under high-rate discharge conditions of 40A, discharge polarization, battery heat generation, and casing temperature rise become important factors affecting battery performance.

[0027] For high-rate discharge, there are generally two approaches to positive electrode design in related technologies. One approach is to reduce the areal density of the positive electrode active material layer and extend the length of the positive electrode to reduce the local current density on the electrode, thereby reducing discharge polarization. However, while reducing the local current density, this approach increases the winding path length of the core and may sacrifice the volumetric energy density of the battery. The other approach is to increase the capacity by improving the areal density and compaction density of the positive electrode active material layer. However, under high-rate discharge conditions, this approach is prone to leading to increased polarization at the end of the discharge and causing a delayed increase in the casing temperature.

[0028] Furthermore, in the evaluation of temperature rise during high-rate discharge, when different heat dissipation fixtures or heat dissipation conditions are used for temperature measurement, the temperature data measured by the same battery lack comparability, making it difficult to stably compare the temperature rise evaluation results between different samples.

[0029] Therefore, how to simultaneously achieve low discharge polarization and low casing temperature rise under high load conditions, and establish a comparable temperature rise evaluation caliber, is a technical problem to be solved in this field. To address the above problem by balancing low discharge polarization and low casing temperature rise under high load conditions, in some embodiments, such as... Figures 1 to 5 As shown in the figure, this specification provides a full-tab cylindrical lithium-ion battery. The full-tab cylindrical lithium-ion battery includes a cylindrical shell, a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode. The positive electrode, the separator, and the negative electrode are wound together to form a core, which is housed in the cylindrical shell. The full-tab cylindrical lithium-ion battery also includes an electrolyte that wets the positive electrode, the negative electrode, and the separator.

[0030] The positive electrode sheet includes a positive current collector and a positive active material layer located on at least one side of the surface of the positive current collector. The single-sided areal density A1 of the positive active material layer is 13.2-14.0 mg / cm², the positive electrode compaction density P1 is 3.52-3.65 g / cm³, and the effective length L1 of the positive electrode sheet in the winding direction is 1500-1600 mm.

[0031] In some embodiments, the single-sided dry film thickness of the positive electrode active material layer is 37-40 μm, and the single-sided dry film thickness of the negative electrode active material layer is 35-38 μm; the single-sided dry film thickness does not include the current collector thickness. The single-sided dry film thickness of the positive electrode active material layer, together with A1 and P1, defines the thickness and compaction state of the positive electrode active material layer; if the positive electrode active material layer is too thick, the lithium-ion diffusion path increases, and the concentration polarization at the end of the discharge stage is prone to increase; if the positive electrode active material layer is too thin, it is difficult to maintain the capacity design under high load structure. Limiting the single-sided dry film thickness of the negative electrode active material layer to 35-38 μm is beneficial for balancing capacity, electrode thickness, and core space occupation in silicon-containing negative electrode systems.

[0032] The product of the ratios of A1 to 13.5 mg / cm², P1 to 3.55 g / cm³, and 1600 mm to L1 is denoted as the electrode high loading factor Fp, where: Fp=(A1 / 13.5)×(P1 / 3.55)×(1600 / L1).

[0033] The Fp value is 0.98-1.08. Fp is a dimensionless number, and its physical meaning is: using a reference short electrode high-load structure composed of A1=13.5mg / cm², P1=3.55g / cm³, and L1=1600mm as a reference, it characterizes the normalized coupling of the positive electrode surface density, compaction density, and electrode length. Extending L1 can reduce the in-plane local current density but increases the number of winding layers, thus increasing the radial thermal resistance for heat conduction to the shell; increasing A1 and P1 can compress the electrode thickness and shorten the lithium-ion diffusion path, but it will exacerbate the porosity and Joule thermal density. The Fp window essentially limits the coupling ratio of the three, achieving a dynamic balance between the in-plane current distribution and the radial thermal resistance network.

[0034] The aforementioned A1, P1, L1, and Fp structural windows constitute the structural anchor points of this specification. Based on this, the positive electrode active material system, negative electrode active material system, separator structure, and current collector thickness configuration can be used as further synergistic implementation methods to improve the stability of the all-tab cylindrical lithium-ion battery in meeting the low polarization and low temperature rise performance indicators under 40A high-rate discharge.

[0035] In a test conducted at 25°C, the all-tab cylindrical lithium-ion battery, starting from a state of charge (SOC) of 50% and discharging at a constant current of 40A to a lower cutoff voltage of 2.5V, satisfies the following requirements: discharge polarization value η ≤ 0.225V, heat dissipation calibration temperature T1 ≤ 65.0°C, and electrothermal coupling temperature rise index K1 ≤ 190°C / V. In other words, this specification does not aim solely at reducing discharge polarization, lowering temperature, or optimizing a single performance characteristic. Instead, it uses the A1, P1, L1, and Fp structural windows as a basis to ensure that the all-tab cylindrical lithium-ion battery simultaneously meets the combined performance constraints of η, T1, and K1 under a high-rate discharge of 40A.

[0036] Its working principle is as follows: the single-sided areal density A1, the positive electrode compaction density P1, and the single-sided dry film thickness together determine the lithium loading per unit area, the thickness of the active material layer, and the tortuosity of the channels, thereby affecting the electrolyte wetting and the diffusion path of lithium ions in the electrode thickness direction; the effective length L1 of the positive electrode sheet determines the winding path length of the positive electrode sheet in the cylindrical battery and the local current density during high-rate discharge. When A1, P1, and L1 fall into the window of 0.98-1.08 after Fp normalization, the ion transport resistance, the ohmic heat generated during the discharge process, and the path of heat dissipation from the core to the cylindrical shell along the radial direction are in a mutually matched state, thereby enabling the all-tab cylindrical lithium-ion battery to simultaneously satisfy η≤0.225V, T1≤65.0℃, and K1≤190℃ / V in the 40A discharge test. If Fp deviates from the above window, for example, if L1 is too long and Fp is below 0.98, there may be a problem of low discharge polarization but high temperature rise per unit polarization; or if A1 or P1 is too high and Fp exceeds 1.08, the active material layer is too thick or the pore structure is compressed, which can easily lead to increased polarization at the end of the discharge and increased local heat source density.

[0037] The heat dissipation calibration temperature T1 is the temperature calculated under the aforementioned 40A constant current discharge test conditions. In some embodiments, T1 can be calculated based on the measured peak housing temperature T40 and the normalized cooling rate k using the formula T1 = T40 + βk × (k - k0). In other words, T1 is not simply the directly measured highest housing temperature, but a calibration temperature used to reduce the influence of differences in different heat dissipation fixtures or heat dissipation environments. The electrothermal coupling temperature rise index K1 represents the ratio of the heat dissipation calibration temperature rise ΔT1 to the discharge polarization value η, i.e., K1 = ΔT1 / η, used to characterize the heat dissipation calibration temperature rise corresponding to a unit discharge polarization.

[0038] The aforementioned η, T1, and K1 are constraints associated with the A1, P1, and L1 / Fp structural windows. Only when all three performance indicators mentioned above are simultaneously satisfied within the high-load structural window of the positive electrode sheet can the electrothermal coupling performance state described in this specification be constituted.

[0039] The discharge polarization value η is used to represent: under 25℃ conditions, the battery is discharged from its state of charge (SOC) of 50% to the lower cutoff voltage of 2.5V at a constant current of 40A, calculated as η = OCV(SOC=10%) - V40A(SOC=10%). Where OCV(SOC) is the open-circuit voltage-state of charge relationship obtained from the 0.05C quasi-static charge-discharge curve of the same model battery at 25℃, and OCV(SOC=10%) is the open-circuit voltage at SOC=10%; V40A(SOC) is the terminal voltage-state of charge relationship during the 40A constant current discharge process, and V40A(SOC=10%) is the terminal voltage at SOC=10% during the 40A constant current discharge process. SOC is converted using the discharge capacity obtained by the same model battery under 0.05C constant current discharge to 2.5V at 25℃ as a 100% benchmark.

[0040] This manual uses the voltage difference at SOC=10% to characterize discharge polarization. The engineering reasons are as follows: First, SOC=10% corresponds to the end of the discharge stage, where the polarization contributions of both the positive and negative electrodes are close to their maximum. Second, the slope of the OCV curve is relatively large at this SOC, and the voltage plateau changes significantly, making it easy to distinguish. Third, the terminal voltage at SOC=10% has not yet dropped to the cutoff voltage of 2.5V, which facilitates comparison and retesting between different samples.

[0041] The initial temperature T0 and the peak discharge temperature T40 are used to indicate that the temperature measuring point on the cylindrical sidewall is located at an axial position of 1 / 2 ± 2 mm of the axial height H of the cylindrical shell, and is at least 30° away from the shell weld, the heat-affected zone of the electrode tab welding, or areas with abnormal shell structure in the circumferential direction. When the battery is a 21700 cylindrical battery, the temperature measuring point can be located at an axial position 35 ± 2 mm from the end face of the positive electrode top cover. T0 is the temperature of the measuring point at the instant of the start of 40A constant current discharge, in °C; T40 is the highest value of the temperature curve T(t) of the measuring point within 300 s from the start of 40A discharge to the end of discharge, i.e., T40 = max[T(t)], in °C.

[0042] The physical basis for introducing the "within 300s after discharge" observation window is that during high-rate discharge, the main heat source is located inside the core. The heat from the core is conducted radially to the surface of the shell with a thermal lag of tens of seconds to several minutes. The peak temperature of the shell surface often occurs shortly after the discharge ends, rather than at the moment the discharge ends.

[0043] The normalized cooling rate k is used to represent the following: After discharge, the battery enters a monotonic cooling phase after a short thermal hysteresis period. A monotonic cooling range is selected from T40 to T0 + 0.5 × (T40 - T0). The normalized cooling rate k is obtained by fitting the first-order thermal equilibrium exponential decay model T(t) - Tamb = A·exp(-k·t); where Tamb is the ambient temperature, A is the fitting amplitude, t is in min, and k is in min. - ¹. The fitting interval should contain at least 5 time data points, and the fitting correlation coefficient R² should not be less than 0.98. k reflects the first-order rate of decay of the battery surface temperature to ambient temperature.

[0044] The heat dissipation calibration temperature T1 represents the temperature calculated based on T40 and k when a full-tab cylindrical lithium-ion battery is discharged from a state of charge (SOC) of 50% to the lower cutoff voltage of 2.5V at a constant current of 40A under 25℃ conditions. Specifically, T1 = T40 + βk × (k - k0), where βk = 140℃·min is the heat dissipation correction factor, and k0 = 0.155min. - ¹ represents the baseline cooling rate. Under the small perturbation assumption (|k-k0|) Under k0), the peak surface temperature of the battery is approximately linearly related to the normalized cooling rate. βk can be understood as the temperature correction magnitude per unit deviation of the cooling rate from the baseline value within the 40A discharge power range defined in this specification. By calibrating T40 using βk and k0, a more suitable T1 for comparison between different samples can be obtained. In some embodiments, the baseline test conditions are: ambient temperature 25±1℃, no active airflow, battery placed horizontally, and the distance between the battery and adjacent objects ≥50mm.

[0045] In one implementation, ΔT1 can be calculated using the following formula: ΔT1=(T40 T0)+βk×(k k0). Among them, T40 T0 represents the measured temperature rise during the 40A constant current discharge test, βk×(k k0) represents the heat dissipation correction term determined based on the deviation between the normalized cooling rate k and the reference cooling rate k0. This heat dissipation calibration temperature rise represents the temperature rise after calibration for different heat dissipation conditions during a 40A constant current discharge test.

[0046] Electrothermal coupling temperature rise index K1: K1 is the ratio of the heat dissipation calibration temperature rise ΔT1 to the discharge polarization value η, i.e., K1=ΔT1 / η. K1 is a positive real number with the dimension of ℃ / V, used to characterize the heat dissipation calibration temperature rise corresponding to a unit discharge polarization; the lower K1, the lower the temperature rise of the battery under the same discharge polarization.

[0047] Under the aforementioned high-load structure window of the positive electrode, the chemical system and particle size distribution of the positive electrode active material will affect the structural stability and the degree of interfacial side reactions under high-rate discharge.

[0048] In some embodiments, the positive electrode active material layer includes a positive electrode active material, wherein the positive electrode active material is LiNi. x Co y Mn z M j O2, where 0.88≤x≤0.95, 0.01≤y≤0.1, 0.01≤z≤0.1, 0≤j≤0.10, and x+y+z+j=1. When j=0, the positive electrode active material is LiNi. x Co y Mn z O2, such as LiNi 0.9 Co 0.05 Mn 0.05 O2; when j is greater than 0, M can be selected from one or more of Al, Zr, Ti, Mg, Sr, Y, La, Ce, and V.

[0049] In some embodiments, the positive electrode active material includes single-crystal particles and polycrystalline particles, wherein the mass ratio of polycrystalline particles to single-crystal particles is 7.5:2.5 to 8.8:1.2, preferably 7.8:2.2 to 8.5:1.5.

[0050] Single-crystal particles are dense, single grains, which helps reduce grain boundary side reactions and microcracks under high current. Polycrystalline particles are secondary spherical particles formed by the agglomeration of multiple primary grains, which facilitates particle size distribution and compaction with single-crystal particles. When the proportion of polycrystalline particles is too high, i.e., the mass ratio of polycrystalline particles to single-crystal particles is less than 7.5:2.5, the number of grain boundaries and crack paths within the secondary particles increases, and the risk of interfacial impedance growth increases. Therefore, the mass ratio of polycrystalline particles to single-crystal particles is limited to 7.5:2.5 to 8.8:1.2.

[0051] In some embodiments, the single-crystal particles have a D50 of 2.5-5.5 μm and a BET specific surface area of ​​0.25-0.80 m² / g; the polycrystalline particles have a D50 of 8-14 μm and a BET specific surface area of ​​0.20-0.70 m² / g. For example, the single-crystal particles have a D50 of approximately 4 μm and a BET specific surface area of ​​approximately 0.45 m² / g, while the polycrystalline particles have a D50 of approximately 11 μm and a BET specific surface area of ​​approximately 0.35 m² / g.

[0052] In some preferred embodiments, the D50 of the single-crystal particles is 3-5 μm, and the D50 of the polycrystalline particles is 9-13 μm. This narrower particle size range is beneficial for maintaining the gradation and filling state between the polycrystalline and single-crystal particles within a preferred structural window with a high electrode loading factor Fp of 1.00-1.06.

[0053] In some embodiments, the all-tab cylindrical lithium-ion battery further includes a negative electrode sheet. The negative electrode sheet includes a negative current collector and a negative active material layer located on at least one side of the negative current collector; the negative active material layer includes a negative active material, which includes graphite material and silicon-containing negative electrode material; the mass percentage of silicon element is 4.0%-15% based on the total mass of the negative active material, preferably 5.0%-7.5%.

[0054] Silicon-containing anode materials have a higher specific capacity than graphite. Appropriate introduction of silicon can improve the specific capacity of the anode active material, thereby maintaining a lower areal density and thickness of the anode active material layer, reducing the thickness of the core and the lithium-ion diffusion distance. If the silicon mass percentage is too low, below 4.0%, it is difficult to support the capacity design of high-rate batteries; if the silicon mass percentage is too high, above 8.5%, the stress caused by silicon lithium intercalation expansion and the risk of repeated SEI film rupture increase, and the interface impedance growth intensifies.

[0055] In some embodiments, the silicon-containing anode material is a SiC composite material, which is a silicon-carbon composite anode material. The SiC composite material accounts for 10%-18% of the total mass of the anode active material, preferably 12%-16%. In some embodiments, the specific capacity of the anode active material after disassembly is 500-520 mAh / g, the anode compaction density PDn is 1.55-1.65 g / cm³, and the single-sided areal density ADn of the anode active material layer is 5.7-6.1 mg / cm². The graphite material can be artificial graphite.

[0056] In some embodiments, the single-sided dry film thickness of the negative electrode active material layer is 35-38 μm. For example, when the single-sided areal density ADn of the negative electrode active material layer is 5.84 mg / cm² and the negative electrode compaction density PDn is 1.60 g / cm³, the single-sided dry film thickness of the negative electrode active material layer is approximately 36.5 μm.

[0057] In some embodiments, the all-tab cylindrical lithium-ion battery further includes a separator. The separator comprises a polyolefin-based film and a ceramic coating. The polyolefin-based film has a thickness of 8-10 μm, and the ceramic coating has a thickness of 2-4 μm. The ceramic coating is disposed at least on the surface of the polyolefin-based film facing the negative electrode. In a specific embodiment, the ceramic coating is disposed on one surface of the polyolefin-based film and faces the negative electrode during winding.

[0058] When the ceramic coating is positioned towards the negative electrode, it can form an inorganic heat-resistant support interface on the side of the separator facing the negative electrode, improving the dimensional stability of the separator under winding structures and 40A high-rate discharge temperature rise conditions. While an excessively thin polyolefin-based film can shorten some ion transport distance, it lacks sufficient thermal shrinkage margin and heat resistance barrier. Therefore, the thickness of the polyolefin-based film is limited to 8-10 μm, and the thickness of the ceramic coating is limited to 2-4 μm. In some embodiments, the polyolefin-based film is a polyethylene-based film; the ceramic coating comprises boehmite. In other embodiments, the ceramic coating comprises α-Al₂O₃.

[0059] In some embodiments, α-Al₂O₃ and boehmite are both insulating and heat-resistant ceramic particles; α-Al₂O₃ does not contain structural hydroxyl groups, and its thermal decomposition initiation temperature is higher than that of boehmite. While maintaining the ceramic coating thickness and orientation towards the negative electrode, the α-Al₂O₃ coating can also achieve a discharge performance close to that of the boehmite coating, around 40A.

[0060] In some embodiments, the positive current collector is an aluminum foil with a thickness of 10-14 μm, and the negative current collector is a copper foil with a thickness of 5-7 μm, with the ratio of the aluminum foil thickness to the copper foil thickness being 1.7-2.4. The aluminum and copper foils of these thicknesses can form a relatively stable current collection path and heat dissipation path. If the aluminum foil is too thin, the positive current collection impedance will increase; if the copper foil is too thick, the heat capacity and space occupation of the winding core will increase, which is detrimental to capacity utilization under the high-load structure of the short electrode. Therefore, limiting the aluminum foil to copper foil thickness ratio to 1.7-2.4 ensures that the positive and negative current collection impedances, mechanical support, and winding core space occupation are matched.

[0061] In some embodiments, the all-tab cylindrical lithium-ion battery is 21700A with a rated capacity of 4.5-5.5Ah. The tabs of the positive electrode are distributed along the length of the positive electrode and electrically connected to the positive current collector or positive conductive connection structure. The tabs of the negative electrode are distributed along the length of the negative electrode and electrically connected to the negative current collector or negative conductive connection structure. The all-tab structure reduces the current-collecting path impedance during high-current discharge and, in conjunction with the high-load structure window of the positive electrode, supports low polarization and low temperature rise performance under 40A high-rate discharge conditions.

[0062] In some embodiments, the high loading factor Fp of the electrode is 1.00-1.06. Within this factor range, the synergy between the positive electrode areal density, compaction density, and electrode length is higher, and the matching between ion transport resistance, ohmic heat generation, and radial heat dissipation path is more adequate, resulting in higher robustness of electrothermal coupling performance.

[0063] In some embodiments, the effective length L1 of the positive electrode sheet in the winding direction is 1540-1585 mm; the effective length Ln of the negative electrode sheet in the winding direction is 1550-1645 mm, and Ln-L1 is 40-80 mm, preferably 50-60 mm. The effective length Ln of the negative electrode sheet is slightly larger than the effective length L1 of the positive electrode sheet, which ensures sufficient coverage and alignment of the negative electrode with the positive electrode in the winding direction; if Ln-L1 is too small, the coverage margin is insufficient; if Ln-L1 is too large, it increases the space occupied by the winding core. In some embodiments, the all-tab cylindrical lithium-ion battery satisfies at least one of the following conditions: The positive electrode sheet includes a positive electrode slurry area and a positive electrode empty foil area. The area of ​​the positive electrode empty foil area / the area of ​​the positive electrode sheet is between 4% and 11%. If the area of ​​the positive electrode empty foil area is higher than the upper limit, the energy density of the battery will be too low. If the area of ​​the positive electrode empty foil area is lower than the lower limit, the flattening process of the full electrode tab will be affected.

[0064] The area of ​​the insulating coating region of the positive electrode sheet should be between 2% and 7% of the area of ​​the positive electrode sheet. If the area of ​​the insulating coating region is too small, the effect of preventing metal burrs and insulating the positive and negative electrodes will be reduced. If the area of ​​the insulating coating region is too large, it will result in a lengthy process and wasted costs.

[0065] The negative electrode sheet includes a negative electrode slurry area and a negative electrode empty foil area. The area of ​​the negative electrode empty foil area / the area of ​​the negative electrode sheet is between 3% and 10%. If the area of ​​the negative electrode empty foil area is higher than the upper limit, the energy density of the battery will be too low. If the area of ​​the negative electrode empty foil area is lower than the lower limit, the flattening process of the full tab will be affected.

[0066] The full-tab cylindrical lithium-ion battery is model 21700 or 21650, with a standard capacity between 5-6.5Ah.

[0067] In some embodiments, when the all-tab cylindrical lithium-ion battery is discharged at a constant current of 40A, the discharge polarization value η is 0.213-0.225V, the heat dissipation calibration temperature T1 is 63.9-64.6℃, and the electrothermal coupling temperature rise index K1 is 173-185℃ / V. These three indicators should be understood as being satisfied simultaneously within the A1, P1, and L1 / Fp structural window, that is, η, T1, and K1 must all fall within the above ranges to constitute the preferred solution; if only one indicator falls within the above range, but the structural parameters or other performance indicators deviate from the ranges defined in this specification, it does not constitute a complete fulfillment of the preferred solution.

[0068] See Figure 6 The aforementioned all-tab cylindrical lithium-ion battery can be obtained by the following preparation method. In some embodiments, the preparation method includes the following steps.

[0069] Step 100: Apply LiNi as the positive electrode active material x Co y Mnz M j O2 is mixed with conductive agent and binder in solvent to obtain positive electrode slurry. The positive electrode slurry is coated on the surface of positive electrode current collector, and then dried, rolled and die-cut to make the single-sided areal density A1 of 13.2-14.0 mg / cm², the positive electrode compaction density P1 of 3.52-3.65 g / cm³, and the effective length L1 of the positive electrode sheet in the winding direction of 1500-1600 mm. The product of the ratio of A1 to 13.5 mg / cm², the ratio of P1 to 3.55 g / cm³, and the ratio of 1600 mm to L1 is 0.98-1.08. Where 0.88≤x≤0.95, 0.01≤y≤0.1, 0.01≤z≤0.1, 0≤j≤0.10, and x+y+z+j=1.

[0070] In some embodiments, the molar percentage of Ni in the positive electrode active material is not less than 90 mol%, based on the total molar percentage of transition metals. The positive electrode active material comprises single-crystal particles and polycrystalline particles with a mass ratio of 7.5:2.5 to 8.8:1.2.

[0071] Step 102: Mix the negative electrode active material, conductive agent, binder and thickener in a solvent to obtain a negative electrode slurry. Coat the negative electrode slurry onto the surface of the negative electrode current collector. After drying, rolling and die cutting, the single-sided dry film thickness of the negative electrode active material layer is 35-38μm to obtain the negative electrode sheet.

[0072] In some embodiments, graphite materials and SiC composite materials are mixed at a silicon element mass ratio of 4.0%-8.5% as the negative electrode active material.

[0073] The SiC composite material accounts for 10%-18% of the total mass of the negative electrode active material, preferably 12%-16%.

[0074] Step 104: The obtained positive electrode sheet, separator, and negative electrode sheet are wound to form a core. The positive electrode empty foil area is flattened / cut and stacked to form a positive electrode tab layer. The positive electrode tab layer is welded to the positive electrode current collector. The negative electrode empty foil area is flattened / cut and stacked to form a negative electrode tab layer. The negative electrode tab layer is welded to the negative electrode current collector. The core is then placed into a cylindrical shell. The negative electrode current collector is welded to the shell, and the positive electrode current collector is welded to the cap. The separator includes a polyolefin base film and a ceramic coating. The ceramic coating is disposed on the surface of the polyolefin base film facing the negative electrode sheet.

[0075] Step 106: Inject electrolyte into the cylindrical shell, seal it, and then perform formation, aging, and capacity testing to obtain a full-tab cylindrical lithium-ion battery.

[0076] The above steps complete the fabrication of the all-tab cylindrical lithium-ion battery described in this specification. After completing the fabrication of the all-tab cylindrical lithium-ion battery, the following steps can be performed to test the performance of the fabricated all-tab cylindrical lithium-ion battery: The prepared all-tab cylindrical lithium-ion battery was subjected to a 40A constant current discharge test according to the following test procedure to obtain η, T0, T40, and k. T1 was calculated as T1=T40+βk×(k-k0), and ΔT1=(T40) / (βk×(k-k0)). T0)+βk×(k K1 is calculated using the formula k0) and K1 = ΔT1 / η. Where βk = 140℃·min, k0 = 0.155min. - ¹.

[0077] An example of the specific process parameters and raw material ratios for the above preparation method can be found in the following embodiments.

[0078] Example 1 This embodiment uses the preparation of a 21700a battery as an example to illustrate the all-tab cylindrical lithium-ion battery and its preparation method described in this specification. This embodiment is only used to illustrate a preferred implementation described in this specification and should not be construed as limiting the scope of protection of this specification.

[0079] The positive electrode active material is a layered high-nickel lithium transition metal oxide (LiNi). x Co y Mn z M j O2. This positive electrode active material is composed of single-crystal particles and polycrystalline particles. The single-crystal particles have a D50 of approximately 4 μm and a BET specific surface area of ​​approximately 0.45 m² / g; the polycrystalline particles have a D50 of approximately 11 μm and a BET specific surface area of ​​approximately 0.35 m² / g. The mass ratio of polycrystalline particles to single-crystal particles is 8:2.

[0080] In the positive electrode slurry, the mass ratio of positive electrode active material, conductive agent, and binder is approximately 97.2:1.6:1.5. The conductive agent includes acetylene black and single-walled carbon nanotubes, the binder is polyvinylidene fluoride, and the solvent is N-methylpyrrolidone. After mixing, dispersing, and degassing the above raw materials, the positive electrode slurry is obtained.

[0081] The positive electrode slurry was coated onto both sides of an aluminum foil with a thickness of 12 μm. After drying, rolling, and die-cutting, the positive electrode sheet was obtained. The single-sided areal density A1 of the obtained positive electrode active material layer was 13.57 mg / cm², the positive electrode compaction density P1 was 3.57 g / cm³, the single-sided dry film thickness of the positive electrode active material layer was approximately 38.0 μm, and the effective length L1 of the positive electrode sheet in the winding direction was 1563 mm. Therefore, the following calculations were made: Fp=(13.57 / 13.5)×(3.57 / 3.55)×(1600 / 1563)≈1.035.

[0082] Therefore, in this embodiment, A1, P1, the single-sided dry film thickness of the positive electrode active material layer, L1, and Fp are all within the window defined in this specification.

[0083] The negative electrode active material includes artificial graphite and SiC composite material, with the SiC composite material being a silicon-carbon composite negative electrode material. The SiC composite material contains approximately 45 wt% silicon, accounting for approximately 14.3 wt% of the total mass of the negative electrode active material, corresponding to a silicon content of approximately 6.4 wt% based on the total mass of the negative electrode active material. The negative electrode active material, conductive agent, binder, and thickener are mixed in deionized water to obtain a negative electrode slurry. This slurry is coated onto both sides of a 6 μm thick copper foil, and after drying, rolling, and die-cutting, a negative electrode sheet is obtained. The single-sided areal density of the obtained negative electrode active material layer is approximately 5.84 mg / cm², the negative electrode compaction density is approximately 1.60 g / cm³, the single-sided dry film thickness of the negative electrode active material layer is approximately 36.5 μm, and the effective length Ln of the negative electrode sheet in the winding direction is 1614 mm, with Ln-L1 being 51 mm.

[0084] The separator is a composite separator made of polyethylene-based membrane and ceramic coating. The polyethylene-based membrane is 9 μm thick, and the ceramic coating is a boehmite ceramic coating with a thickness of 3 μm. During winding, the ceramic coating is positioned so that it faces the negative electrode plate.

[0085] The positive electrode, separator, and negative electrode are wound in the order of "positive electrode - separator - negative electrode - separator" to form a core. After winding, the core is placed in a 21700 cylindrical shell, and the core is subjected to full tab folding and laser welding, so that the positive electrode tab is led out from the top of the core and connected to the positive conductive connection structure, and the negative electrode tab is led out from the bottom of the core and connected to the negative conductive connection structure. Then, electrolyte is injected into the cylindrical shell, sealed, and subjected to formation, aging, and capacity testing to obtain the full tab cylindrical lithium-ion battery S1 of this embodiment. In this embodiment, the electrolyte is a mixed solvent of 1.1 mol / L LiPF6 dissolved in EC:EMC:DEC=3:5:2 (volume ratio), with 1.0 wt% FEC and 1.5 wt% PS added, and the electrolyte injection volume of a single battery is approximately 5.5 g. After capacity testing, the rated capacity of battery S1 is 5 Ah.

[0086] Tests showed that when battery S1 was discharged from 50% SOC to 2.5V at a constant current of 40A at 25℃, T0 was 25.0℃, η was 0.218V, T40 was 64.52℃, and k was 0.1529min. -¹, T1 is 64.23℃, and K1 is 180.0℃ / V. Therefore, battery S1 simultaneously satisfies η≤0.225V, T1≤65.0℃, and K1≤190℃ / V.

[0087] Example 2-15 Examples 2-15 are based on Example 1 with a single variable adjusted, while the other raw materials, process steps and test conditions are the same as in Example 1.

[0088] The difference between Example 2 and Example 1 is that the areal density A1 of the positive electrode active material layer is adjusted to 13.20 mg / cm², P1 is kept at 3.57 g / cm³, the dry film thickness of the positive electrode active material layer is approximately 37.0 μm, and L1 is kept at 1563 mm. The resulting battery S2 has an η of 0.215 V, a T1 of 64.01 °C, and a K1 of 181.4 °C / V.

[0089] The difference between Example 3 and Example 1 is that the areal density A1 of the positive electrode active material layer is adjusted to 14.00 mg / cm², P1 is kept at 3.57 g / cm³, the dry film thickness of the positive electrode active material layer is approximately 39.2 μm, and L1 is kept at 1563 mm. The resulting battery S3 has an η of 0.222 V, a T1 of 64.51 °C, and a K1 of 178.0 °C / V.

[0090] The difference between Example 4 and Example 1 is that the positive electrode compaction density P1 is adjusted to 3.52 g / cm³, A1 is kept at 13.57 mg / cm², the single-sided dry film thickness of the positive electrode active material layer is approximately 38.6 μm, and L1 is kept at 1563 mm. The resulting battery S4 has an η of 0.214 V, a T1 of 64.11 °C, and a K1 of 182.8 °C / V.

[0091] The difference between Example 5 and Example 1 is that the positive electrode compaction density P1 is adjusted to 3.65 g / cm³, A1 is kept at 13.57 mg / cm², the single-sided dry film thickness of the positive electrode active material layer is approximately 37.2 μm, and L1 is kept at 1563 mm. The resulting battery S5 has an η of 0.223 V, a T1 of 64.56 °C, and a K1 of 177.4 °C / V.

[0092] The difference between Example 6 and Example 1 is that the effective length L1 of the positive electrode sheet in the winding direction is adjusted to 1500 mm, and the effective length Ln of the negative electrode sheet in the winding direction is adjusted to 1554 mm, with Ln-L1 being 54 mm. The single-sided dry film thickness of the positive electrode active material layer is approximately 38.0 μm. The resulting battery S6 has an Fp of approximately 1.078, η of 0.224 V, T1 of 63.93 °C, and K1 of 173.8 °C / V.

[0093] The difference between Example 7 and Example 1 is that the effective length L1 of the positive electrode sheet in the winding direction is adjusted to 1600 mm, and the effective length Ln of the negative electrode sheet in the winding direction is adjusted to 1640 mm, with Ln-L1 being 40 mm. The single-sided dry film thickness of the positive electrode active material layer is approximately 38.0 μm. The resulting battery S7 has an Fp of approximately 1.011, η of 0.216 V, T1 of 64.53 °C, and K1 of 183.0 °C / V.

[0094] The difference between Example 8 and Example 1 is that the mass ratio of polycrystalline particles to single-crystal particles in the positive electrode active material is adjusted to 7.5:2.5. The resulting battery S8 has an η of 0.216V, a T1 of 64.46℃, and a K1 of 182.7℃ / V.

[0095] The difference between Example 9 and Example 1 is that the mass ratio of polycrystalline particles to single-crystal particles in the positive electrode active material is adjusted to 8.8:1.2. The resulting battery S9 has an η of 0.224V, a T1 of 64.01℃, and a K1 of 174.2℃ / V.

[0096] The difference between Example 10 and Example 1 is that the proportion of SiC composite material in the negative electrode active material is adjusted to 10.0 wt%, and the mass proportion of silicon element in the corresponding negative electrode active material is adjusted to 4.5 wt%. The resulting battery S10 has an η of 0.220 V, a T1 of 64.21 °C, and a K1 of 178.2 °C / V.

[0097] The difference between Example 11 and Example 1 is that the proportion of SiC composite material in the negative electrode active material is adjusted to 18.0 wt%, and the mass proportion of silicon element in the corresponding negative electrode active material is adjusted to 8.1 wt%. The resulting battery S11 has an η of 0.221 V, a T1 of 64.56 °C, and a K1 of 179.0 °C / V.

[0098] The difference between Example 12 and Example 1 is that the separator uses an 8μm polyolefin-based membrane and a 2μm boehmite ceramic coating, with the ceramic coating facing the negative electrode. The resulting battery S12 has an η of 0.216V, a T1 of 64.51℃, and a K1 of 182.9℃ / V.

[0099] The difference between Example 13 and Example 1 is that boehmite in the separator ceramic coating was replaced with α-Al₂O₃, while maintaining the coating thickness of 3 μm and the orientation of the coating towards the negative electrode. α-Al₂O₃ and boehmite are both insulating and heat-resistant ceramic particles; however, α-Al₂O₃ does not contain structural hydroxyl groups, and its thermal decomposition initiation temperature is higher than that of boehmite. The resulting battery S13 had an η of 0.218 V, a T1 of 64.36 °C, and a K1 of 180.6 °C / V. This result indicates that, while maintaining the ceramic coating thickness and orientation towards the negative electrode, the α-Al₂O₃ coating can also achieve a discharge performance close to that of the boehmite coating, around 40 A.

[0100] The difference between Example 14 and Example 1 is that the negative electrode current collector uses a copper foil with a thickness of 7 μm, while the positive electrode current collector still uses an aluminum foil with a thickness of 12 μm. The ratio of the aluminum foil thickness to the copper foil thickness is approximately 1.71. The resulting battery S14 has an η of 0.216 V, a T1 of 64.35 °C, and a K1 of 182.2 °C / V.

[0101] The difference between Example 15 and Example 1 is that the positive electrode current collector uses an aluminum foil with a thickness of 14 μm, while the negative electrode current collector still uses a copper foil with a thickness of 6 μm. The ratio of the aluminum foil thickness to the copper foil thickness is approximately 2.33. The resulting battery S15 has an η of 0.220 V, a T1 of 64.21 °C, and a K1 of 178.2 °C / V.

[0102] The following sections will continue to introduce comparative examples that serve as embodiments 1-15 above: Comparative Example 1 represents a low areal density route with a long electrode. Its A1 is 12.70 mg / cm², P1 is 3.50 g / cm³, the single-sided dry film thickness of the positive electrode active material layer is approximately 36.3 μm, L1 is 1686 mm, the mass ratio of polycrystalline particles to single-crystalline particles is 7:3, the silicon content in the negative electrode active material is 3.6 wt%, the separator uses a 7 μm polyolefin-based film and a 2 μm ceramic coating with the ceramic coating facing the positive electrode, the positive current collector is a 14 μm thick aluminum foil, and the negative current collector is an 8 μm thick copper foil. The Fp of this comparative example is approximately 0.880, which is lower than the 0.98 specified in this specification. The resulting battery has an η of 0.209 V for C1, a T1 of 66.03 °C, and a K1 of 196.3 °C / V. The results indicate that while reducing the positive electrode surface density and extending the electrode length can reduce discharge polarization, they cannot simultaneously meet the requirements of heat dissipation calibration temperature and electrothermal coupling temperature rise index.

[0103] The difference between Comparative Example 2 and Example 1 is that the mass ratio of polycrystalline particles to monocrystalline particles was adjusted to 7:3, which is lower than the 7.5:2.5 specified in this specification. The resulting battery C2 had an η of 0.213V, a T1 of 65.03℃, and a K1 of 187.9℃ / V. This result indicates that when the proportion of monocrystalline particles is too low, although the polarization value is low, the heat dissipation calibration temperature exceeds the value specified in this specification.

[0104] The difference between Comparative Example 3 and Example 1 is that the separator uses a 7μm polyolefin-based film and a 2μm ceramic coating, with the ceramic coating facing the positive electrode. The resulting battery C3 has an η of 0.211V, a T1 of 65.50℃, and a K1 of 191.9℃ / V. This result indicates that when the separator thickness is insufficient and the ceramic coating faces the positive electrode, it is difficult to meet the thermal stability and electrothermal coupling constraints of this specification.

[0105] The difference between Comparative Example 4 and Example 1 is that A1 was adjusted to 14.50 mg / cm², exceeding the upper limit of 14.0 mg / cm² specified in this specification; P1 was maintained at 3.57 g / cm³, corresponding to a single-sided dry film thickness of approximately 40.6 μm for the positive electrode active material layer, exceeding the 37-40 μm range specified in this specification; the corresponding Fp was approximately 1.106, exceeding the upper limit of 1.08 specified in this specification. The resulting battery C4 had an η of 0.236 V, a T1 of 66.81 °C, and a K1 of 177.2 °C / V. This result indicates that even if K1 is at a low level, as long as A1, the single-sided dry film thickness of the positive electrode active material layer, and Fp deviate from the structural window specified in this specification, the requirements for discharge polarization value and heat dissipation calibration temperature cannot be simultaneously met.

[0106] The difference between Comparative Example 5 and Example 1 is that P1 was adjusted to 3.70 g / cm³, exceeding the upper limit of 3.65 g / cm³ specified in this specification; A1 remained at 13.57 mg / cm², corresponding to a single-sided dry film thickness of approximately 36.7 μm for the positive electrode active material layer, lower than the lower limit of 37 μm specified in this specification. The resulting battery C5 had an η of 0.230 V, a T1 of 66.21 °C, and a K1 of 179.2 °C / V. This result indicates that although the Fp of Comparative Example 5 is 1.072, falling within the range of 0.98-1.08, the collapse of the pore structure and a sharp increase in ion diffusion resistance due to P1 exceeding the intrinsic compaction limit of the material caused η and T1 to exceed the limits simultaneously. This result confirms that a single structural parameter or a broad Fp window is insufficient to solve the electrothermal coupling problem; the specific ranges of A1 / P1 / L1 and the combined constraints of η / T1 / K1 specified in this specification are necessary and synergistic.

[0107] The difference between Comparative Example 6 and Example 1 is that L1 was adjusted to 1710 mm, exceeding the upper limit of 1600 mm specified in this specification; the corresponding Fp is approximately 0.946, lower than the lower limit of 0.98 specified in this specification. The resulting battery C6 has an η of 0.210 V, a T1 of 65.17 °C, and a K1 of 191.3 °C / V. This result indicates that when the electrode length is too long, although the discharge polarization is lower, the temperature rise per unit polarization is too high, and it still cannot meet the electrothermal coupling temperature rise index requirement of this specification.

[0108] Table 1 below lists the main structural parameters and 40A discharge performance test results of Examples S1-S15 and Comparative Examples C1-C6.

[0109] Table 1

[0110] In Table 1, S1, S2, ..., S15 represent Examples 1, 2, ..., 15, respectively; C1, C2, ..., C6 represent Comparative Examples 1, 2, ..., 6, respectively. "9+3" indicates a 9μm polyolefin film superimposed with a 3μm ceramic coating, and "8+2" indicates an 8μm polyolefin film superimposed with a 2μm ceramic coating; "facing negative" indicates the ceramic coating faces the negative electrode, and "facing positive" indicates the ceramic coating faces the positive electrode. The ceramic coating in Example 13 was α-Al2O3, while the ceramic coatings in the other examples were boehmite.

[0111] The following test methods were used to test the all-tab cylindrical lithium-ion battery prepared according to the above preparation method: 1. Electrode geometric parameter testing The battery under test was pre-discharged to below 2.5V and left to stand at 25℃ for 12 hours. The battery was then disassembled in a dry environment with a dew point not higher than -40℃, and the positive and negative electrode plates were unfolded.

[0112] The effective length L1 of the positive electrode and the effective length Ln of the negative electrode are the effective lengths of the active material coating areas of the corresponding electrodes along the winding direction, which can be measured by a steel ruler, an image measuring instrument, or a continuous dimension scanning device.

[0113] The single-sided surface density A1 is the ratio of the mass of the dry film on one side of the positive electrode active material layer to the corresponding area. During testing, a sample of a fixed area is taken from the middle of the positive electrode sheet, the total mass of the electrode sheet is weighed, the mass of the positive electrode current collector is weighed after removing the active material layer, and the difference between the two is used to calculate the double-sided surface density of the active material, which is then divided by 2 to obtain the single-sided surface density A1.

[0114] The positive electrode compaction density P1 is the ratio of the one-sided areal density A1 of the positive electrode active material layer to the one-sided dry film thickness. The one-sided dry film thickness of the positive electrode active material layer does not include the thickness of the positive electrode current collector and can be measured using a micrometer or cross-sectional scanning electron microscope. The one-sided dry film thickness of the negative electrode active material layer and the negative electrode compaction density PDn can be measured and calculated in the same way.

[0115] 2. Discharge polarization value η test Establish a 0.05C quasi-static OCV-SOC curve using at least three batteries of the same model. During testing, charge the batteries at 0.05C constant current and constant voltage to 4.2V at 25℃, with a constant voltage cutoff current of 0.005C. After resting for 5 hours, discharge them at 0.05C constant current to 2.5V. Use this 0.05C discharge capacity as the 100% capacity reference to obtain the OCV (SOC) curve. The OCV (SOC) curve can be the average curve of at least three batteries of the same model.

[0116] Take another battery to be tested, charge it at 25℃ with a constant current and constant voltage of 1C to 4.2V, with a cutoff current of 0.05C, and let it stand for 1 hour; then discharge it with a constant current of 1C to 50% of the SOC calculated based on the 0.05C discharge capacity, and let it stand for 30 minutes; then discharge it with a constant current of 40A to 2.5V, and record the terminal voltage V40A (SOC) during the 40A discharge process. η is calculated according to the following formula: eta=OCV(SOC=10%)-V40A(SOC=10%).

[0117] 3. Tests for T0, T40, k, T1, ΔT1, and K1 The temperature measuring point on the cylindrical sidewall is located at 1 / 2 ± 2 mm of the axial height H of the cylindrical shell, and is at least 30° away from the shell weld, the heat-affected zone of the electrode tab welding, or areas with abnormal shell structure in the circumferential direction. When the battery is a 21700 cylindrical battery, the temperature measuring point can be located at an axial position 35 ± 2 mm from the end face of the positive electrode top cover.

[0118] Under conditions of ambient temperature 25±1℃, no active airflow, horizontal battery placement, and a distance of at least 50mm between the battery and adjacent objects, attach a T-type thermocouple to the temperature measurement point. The diameter of the T-type thermocouple can be 0.5mm, and the accuracy can be ±0.5℃. T0 is the temperature at the measurement point at the start of a 40A constant current discharge. T40 is the highest value of the temperature curve T(t) at the measurement point within 300s from the start of the 40A discharge to the end of the discharge.

[0119] After the battery temperature reaches T40, a monotonic cooling interval from T40 to T0 + 0.5 × (T40 - T0) is selected. The normalized cooling rate k is obtained by fitting T(t) - Tamb = A·exp(-k·t), where t is in min and k is in min. - ¹. The fitting interval should include at least 5 time data points, and the fitting correlation coefficient R² should not be less than 0.98.

[0120] The heat dissipation calibration temperature T1 is calculated using the following formula: T1 = T40 + βk × (k - k0).

[0121] Where βk is 140℃·min and k0 is 0.155min. - ¹. Therefore, T1 represents the temperature calculated after heat dissipation correction when a fully tabbed cylindrical lithium-ion battery is discharged from its state of charge (SOC) of 50% to the lower cutoff voltage of 2.5V at a constant current of 40A at 25℃. Under the small perturbation assumption (|k-k0| Under k0), the peak surface temperature of the battery is approximately linearly related to the normalized cooling rate. βk can be understood as the temperature correction range per unit deviation of the cooling rate from the reference value within the 40A discharge power range defined in this specification.

[0122] The electrothermal coupling temperature rise index K1 is calculated using the following formula: K1=ΔT1 / η.

[0123] Therefore, K1 represents the ratio of the heat dissipation calibration temperature rise ΔT1 to the discharge polarization value η.

[0124] 4. Material and structural characterization determination The molar ratio of transition metal elements in the positive electrode active material can be determined by ICP-OES, and the molar percentage of each element can be calculated based on the sum of the molar numbers of Ni, Co, Mn and doping elements.

[0125] The mass ratio of polycrystalline to monocrystalline particles in the positive electrode active material can be determined by combining scanning electron microscopy (SEM) image statistics, laser particle size distribution bimodal fitting, and cross-sectional morphology. Monocrystalline particles are dense, single crystals, while polycrystalline particles are secondary particles formed by the aggregation of multiple primary crystals. In some testing methods, at least 10 fields of view are collected during SEM image statistics, and at least 1000 particles are counted. If necessary, the particle morphology, cross-sectional grain boundary characteristics, and laser particle size bimodal distribution can be combined to distinguish between polycrystalline particles and monocrystalline secondary particles.

[0126] The mass percentage of silicon in the negative electrode active material is determined by ICP-OES based on the total mass of the negative electrode active material, and can be cross-confirmed by thermogravimetric analysis, energy dispersive spectroscopy, or Raman spectroscopy.

[0127] The thickness of the membrane base and the ceramic coating can be measured under an optical microscope or scanning electron microscope after liquid nitrogen cryosectioning. The orientation of the membrane ceramic coating can be confirmed by disassembling and recording the contact surfaces between the membrane and the positive and negative electrodes, combined with the surface distribution of ceramic elements.

[0128] The composition of ceramic coatings can be determined by X-ray diffraction or infrared spectroscopy. For example, boehmite has characteristic peaks associated with hydroxyl groups, while α-Al₂O₃ does not.

[0129] As shown in Table 1, Examples S1-S15 all simultaneously satisfy η≤0.225V, T1≤65.0℃, and K1≤190℃ / V. Comparative Examples C1-C6 deviate from the above requirements in at least one of the following: discharge polarization value, heat dissipation calibration temperature, or electrothermal coupling temperature rise index. This result indicates that the technical effect of this specification comes from the synergistic matching between the single-sided areal density A1 of the positive electrode active material layer, the positive electrode compaction density P1, the single-sided dry film thickness of the positive electrode active material layer, the effective length L1 of the positive electrode sheet, and the Fp structural window. In specific embodiments, the stability of the above electrothermal coupling performance can be further improved by the positive electrode particle gradation, silicon-containing negative electrode, the orientation of the separator ceramic coating, and the current collector thickness ratio.

[0130] Specifically, Examples S2-S3 show that when A1 is in the range of 13.2-14.0 mg / cm², the battery can simultaneously meet the requirements of low discharge polarization and low heat dissipation calibration temperature; Comparative Example C4 shows that when A1 increases to 14.50 mg / cm², the single-sided dry film thickness of the positive electrode active material layer reaches about 40.6 μm, Fp exceeds 1.08, and η and T1 both exceed the ranges specified in this specification.

[0131] Examples S4-S5 show that when P1 is in the range of 3.52-3.65 g / cm³, the battery can maintain low discharge polarization and temperature rise; Comparative Example C5 shows that when P1 increases to 3.70 g / cm³, the single-sided dry film thickness of the positive electrode active material layer decreases to about 36.7 μm, and both η and T1 exceed the ranges specified in this specification.

[0132] Examples S6-S7 show that when L1 is 1500-1600mm and Fp is in the range of 0.98-1.08, the battery can meet the comprehensive electrothermal constraints of 40A high-rate discharge; Comparative Example C6 shows that when L1 is too long and Fp is below 0.98, although η is low, K1 exceeds 190℃ / V, and cannot be considered as having qualified comprehensive performance.

[0133] Examples S8-S9 show that when the mass ratio of polycrystalline particles to monocrystalline particles is in the range of 7.5:2.5 to 8.8:1.2, it can maintain low polarization and low temperature rise together with the Fp structure window; Comparative Example C2 shows that when the proportion of monocrystalline particles is too low, T1 exceeds 65.0°C.

[0134] Examples S10-S11 show that when the mass percentage of silicon element is in the range of 4.0%-8.5% based on the total mass of the negative electrode active material, it is possible to balance the negative electrode capacity, electrode thickness and high-rate discharge stability.

[0135] Example S12 shows that the membrane structure of an 8-10 μm polyolefin-based membrane and a 2-4 μm ceramic coating can support the performance targets of this specification; Comparative Example C3 shows that when the membrane thickness is insufficient and the ceramic coating is oriented towards the positive electrode, both T1 and K1 deviate from the requirements of this specification. Example S13 shows that, while maintaining the ceramic coating thickness and orientation towards the negative electrode, the α-Al2O3 coating can also achieve a discharge performance of 40A similar to that of the boehmite coating.

[0136] Examples S14-S15 demonstrate that the combination of 10-14μm aluminum foil and 5-7μm copper foil, with the aluminum foil thickness to copper foil thickness ratio within the range of 1.7-2.4, is beneficial for maintaining a match between current collector impedance, mechanical support, and core space occupancy under a short electrode high-load structure. Comparative Example C1 is a comprehensive baseline comparative example for a long electrode low areal density route. While this comparative example exhibits lower η under lower positive electrode areal density, longer effective positive electrode length, and related structural configurations, T1 and K1 fail to simultaneously meet the requirements defined in this specification. Given that this comparative example deviates from multiple structural parameters such as A1, P1, L1, Fp, and current collector thickness, it is primarily used to illustrate that this comprehensive baseline route cannot achieve the combined electrothermal constraints of this specification, and is not considered an independent attribution basis for any single variable. The influence of the effective positive electrode length L1 and the Fp window is mainly explained in conjunction with Examples S6, S7, and Comparative Example C6.

[0137] It should be noted that the preferred ranges for η, T1, and K1 should be simultaneously satisfied within the structural windows of A1, P1, L1, and Fp specified in this specification. If a single indicator falls within the above ranges while the structural window or other performance indicators deviate, it does not constitute a preferred embodiment. For example, although Comparative Example C4 has a K1 of 177.2℃ / V, its A1 is 14.50 mg / cm², its single-sided dry film thickness of the positive electrode active material layer is approximately 40.6 μm, and its Fp is approximately 1.106. Furthermore, η and T1 both exceed the limits specified in this specification, therefore it does not constitute a complete fit of the preferred embodiment. Similarly, although Comparative Example C5 has a K1 of 179.2℃ / V, its P1, single-sided dry film thickness of the positive electrode active material layer, η, and T1 all deviate from the requirements specified in this specification, and therefore it does not constitute a complete fit of the preferred embodiment.

[0138] In summary, Examples S1-S15 cover representative boundary points, near-boundary points, and preferred points for key variables such as A1, P1, single-sided dry film thickness of the positive electrode active material layer, L1, single-crystal / polycrystalline mass ratio, silicon content, separator structure, ceramic composition, and current collector thickness ratio. All examples maintain η≤0.225V, T1≤65.0℃, and K1≤190℃ / V under 40A discharge conditions. Comparative Example C1 illustrates that the baseline route with a long electrode and low areal density cannot simultaneously meet the combined electrothermal constraints of this specification; Comparative Examples C2-C6 respectively demonstrate that exceeding the single-crystal / polycrystalline ratio limit, using a thin separator with incorrect ceramic layer orientation, exceeding the upper limit for A1, P1, and L1, will respectively compromise at least one key performance indicator. Therefore, the parameter combinations defined in this specification can simultaneously suppress polarization at the end of discharge and the temperature rise during heat dissipation calibration, providing a repeatable technical effect.

[0139] In some embodiments, this specification also provides a battery module including a plurality of all-tab cylindrical lithium-ion batteries of any of the foregoing embodiments.

[0140] In some embodiments, this specification also provides a battery pack including at least one of the aforementioned battery modules. This application does not specifically limit the structure of the battery module and battery pack other than the all-tab cylindrical lithium-ion battery. The improvement of this application focuses on the all-tab cylindrical lithium-ion battery having the aforementioned A1, P1, L1 / Fp structural windows and the combined constraint of a 40A discharge performance.

[0141] In summary, the all-tab cylindrical lithium-ion battery and its preparation method proposed in this specification have at least the following technical advantages: First, by controlling the coupling of A1, P1 and L1, the polarization increase at the end of the 40A discharge is avoided due to the positive load, compaction state and electrode length mismatch.

[0142] Second, by limiting the Fp structure window, the level of heat generated by the discharge is matched with the radial heat dissipation path of the core, thereby reducing the temperature peak after calibration under different heat dissipation conditions.

[0143] Third, by constraining the relationship between the heat dissipation calibration temperature rise and the discharge polarization value through the K1 index, we can avoid one-sided optimization that results in uncontrolled temperature rise by simply reducing polarization or excessive polarization by simply controlling temperature.

[0144] Fourth, by optimizing the configuration of high-nickel single-crystal / polycrystalline positive electrode, silicon-containing negative electrode, ceramic-coated separator facing the negative electrode side, and current collector thickness ratio, the stability and consistency of the above-mentioned electrothermal coupling performance window can be further improved.

[0145] The foregoing description and accompanying drawings fully illustrate embodiments of this specification to enable those skilled in the art to practice them. Other embodiments may include structural and other changes. The embodiments represent only possible variations. Individual components and functions are optional unless explicitly required, and the order of operation may vary. Parts and features of some embodiments may be included or substituted for parts and features of other embodiments. The embodiments of this specification are not limited to the structures described above and shown in the accompanying drawings, and various modifications and changes may be made without departing from their scope. The scope of this specification is limited only by the appended claims.

Claims

1. A cylindrical lithium-ion battery with multiple tabs, comprising a positive electrode and a negative electrode, characterized in that: The positive electrode sheet includes a positive current collector and a positive active material layer located on at least one side surface of the positive current collector; The single-sided areal density A1 of the positive electrode active material layer is 13.2-14.0 mg / cm², the positive electrode compaction density P1 is 3.52-3.65 g / cm³, and the effective length L1 of the positive electrode sheet in the winding direction is 1500-1600 mm. The product of the ratio of A1 to 13.5 mg / cm², the ratio of P1 to 3.55 g / cm³, and the ratio of 1600 mm to L1 is denoted as the high loading factor Fp of the electrode sheet, Fp = (A1 / 13.5) × (P1 / 3.55) × (1600 / L1), and Fp is 0.98-1.

08. The all-tab cylindrical lithium-ion battery meets the following requirements during the test of discharging from a state of charge (SOC) of 50% to a lower cutoff voltage of 2.5V at a constant current of 40A under 25℃ environment: discharge polarization value η≤0.225V, heat dissipation calibration temperature T1≤65.0℃, and electrothermal coupling temperature rise index K1≤190℃ / V. Wherein, the heat dissipation calibration temperature T1 represents the temperature calculated when a full-tab cylindrical lithium-ion battery is discharged from a state of charge (SOC) of 50% to a lower cutoff voltage of 2.5V at a constant current of 40A under an environment of 25℃; the electrothermal coupling temperature rise index K1 represents the ratio of the heat dissipation calibration temperature rise ΔT1 to the discharge polarization value η.

2. The all-tab cylindrical lithium-ion battery according to claim 1, characterized in that: The positive electrode active material layer includes a positive electrode active material, which is LiNi. x Co y Mn z M j O2, where 0.88≤x≤0.95, 0.01≤y≤0.1, 0.01≤z≤0.1, 0≤j≤0.10, x+y+z+j=1; when j is greater than 0, M is selected from one or more of Al, Zr, Ti, Mg, Sr, Y, La, Ce, and V.

3. The all-tab cylindrical lithium-ion battery according to claim 1, characterized in that: The positive electrode active material layer includes a positive electrode active material, which includes single crystal particles and polycrystalline particles, and the mass ratio of the polycrystalline particles to the single crystal particles is from 7.5:2.5 to 8.8:1.

2.

4. The all-tab cylindrical lithium-ion battery according to claim 1, characterized in that: The negative electrode sheet includes a negative current collector and a negative active material layer located on at least one side of the surface of the negative current collector; the negative active material layer includes a negative active material, which includes graphite material and silicon-containing negative electrode material; the mass percentage of silicon element is 4.0%-15% based on the total mass of the negative active material.

5. The all-tab cylindrical lithium-ion battery according to claim 4, characterized in that: It also includes a separator; the positive electrode, the separator, and the negative electrode are wound together to form a core; The separator comprises a polyolefin-based membrane and a ceramic coating. The polyolefin-based membrane has a thickness of 8-10 μm, and the ceramic coating has a thickness of 2-4 μm. The ceramic coating is disposed on the surface of the polyolefin-based membrane facing the negative electrode sheet.

6. The all-tab cylindrical lithium-ion battery according to claim 4, characterized in that: The positive current collector is an aluminum foil with a thickness of 10-14 μm, and the negative current collector is a copper foil with a thickness of 5-7 μm, wherein the ratio of the thickness of the aluminum foil to the thickness of the copper foil is 1.7-2.

4.

7. The all-tab cylindrical lithium-ion battery according to claim 1, characterized in that: The high loading factor Fp of the electrode is 1.00-1.

06.

8. The all-tab cylindrical lithium-ion battery according to claim 1, characterized in that: When the all-tab cylindrical lithium-ion battery is discharged at a constant current of 40A, the discharge polarization value η is 0.213-0.225V, the heat dissipation calibration temperature T1 is 63.9-64.6℃, and the electrothermal coupling temperature rise index K1 is 173-185℃ / V.

9. The all-tab cylindrical lithium-ion battery according to claim 5, characterized in that: The effective length L1 of the positive electrode sheet in the winding direction is 1540-1585mm; the effective length Ln of the negative electrode sheet in the winding direction is 1550-1645mm, and Ln-L1 is 40-80mm.

10. The all-tab cylindrical lithium-ion battery according to claim 1, characterized in that: It satisfies at least one of the following conditions: The positive electrode sheet includes a positive electrode slurry region and a positive electrode empty foil region, wherein the area of ​​the positive electrode empty foil region / the area of ​​the positive electrode sheet is between 4% and 11%. The area of ​​the insulating coating region of the positive electrode sheet / the area of ​​the positive electrode sheet is between 2% and 7%; The negative electrode sheet includes a negative electrode slurry region and a negative electrode empty foil region, wherein the area of ​​the negative electrode empty foil region / the area of ​​the negative electrode sheet is between 3% and 10%. The full-tab cylindrical lithium-ion battery is either a 21700 battery or a 21650 battery, with a standard capacity between 5 and 6.5 Ah.

11. A method for preparing a cylindrical lithium-ion battery with all tabs as described in any one of claims 1-10, characterized in that: Includes the following steps: A positive electrode active material, a conductive agent, and a binder are mixed in a solvent to obtain a positive electrode slurry. The positive electrode slurry is coated onto the surface of a positive electrode current collector, and then dried, rolled, and die-cut to achieve a single-sided areal density A1 of 13.2-14.0 mg / cm², a positive electrode compaction density P1 of 3.52-3.65 g / cm³, and an effective length L1 of the positive electrode sheet in the winding direction of 1500-1600 mm. The product of the ratio of A1 to 13.5 mg / cm², the ratio of P1 to 3.55 g / cm³, and the ratio of 1600 mm to L1 is 0.98-1.

08. A negative electrode active material, conductive agent, binder and thickener are mixed in a solvent to obtain a negative electrode slurry. The negative electrode slurry is coated on the surface of the negative electrode current collector, and then dried, rolled and die-cut to obtain a negative electrode sheet. The obtained positive electrode sheet, separator, and negative electrode sheet are wound to form a core. The positive electrode empty foil area is flattened / folded to form a positive electrode tab layer. The positive electrode tab layer is welded to the positive electrode current collector. The negative electrode empty foil area is flattened / folded to form a negative electrode tab layer. The negative electrode tab layer is welded to the negative electrode current collector. The core is then placed into a cylindrical shell. The negative electrode current collector is welded to the shell, and the positive electrode current collector is welded to a cap. The separator includes a polyolefin base film and a ceramic coating. The ceramic coating is disposed on the surface of the polyolefin base film facing the negative electrode sheet. Electrolyte is injected into the cylindrical shell, and after sealing, it undergoes formation, aging, and capacity testing to obtain the full-tab cylindrical lithium-ion battery.

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