Cylindrical battery and electric device

Abstract

This invention relates to the field of battery technology, specifically to a cylindrical battery and an electrical device. The disclosed cylindrical battery includes: a casing and a cell disposed within the casing. The cell includes a positive electrode, a separator, and a negative electrode, sequentially stacked. The positive electrode includes a positive current collector and a positive active coating disposed on one surface of the positive current collector in the thickness direction. The overall dimension of the casing in the height direction is H1 (mm); the length dimension of the positive electrode is L. p Unit: mm; A cylindrical battery under constant current discharge conditions of 25℃ and 40A satisfies: K T ≤1.8, and K V ≤1.00; K T =(T 40 -T0) / ρ p K V =100×ΔV 40 / ρ p ;ρ p ρ is the length density of the positive electrode. p =L p / H1 and ρ p ≠0, H1>0; This cylindrical battery achieves coordinated control of battery rate performance, thermal safety and structural design.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a cylindrical battery and an electrical device. Background Technology

[0002] In recent years, cylindrical lithium-ion batteries have achieved high capacity, high-rate discharge capability, and reliable thermal safety within a limited internal volume. To further develop cylindrical batteries, capacity can be maintained by adjusting the electrodes, such as increasing electrode length or optimizing the active material loading, based on the shortened casing height of the precursor. However, relying solely on absolute dimensional parameters is insufficient to accurately reflect the actual overall performance of the battery under a short-height structure, especially under high-current discharge conditions at around 40A. The matching relationship between electrode length and casing height has a significant impact on heat accumulation and concentration polarization within the cell. This can easily lead to problems such as increased temperature rise, increased polarization, or excessive compression of the casing space caused by improper length configuration.

[0003] Therefore, how to ensure that cylindrical batteries can meet the high capacity requirements while maintaining reasonable rate performance and thermal safety is an important research topic. Summary of the Invention

[0004] In view of this, the present invention aims to at least partially solve one of the technical problems in the related art. To this end, the present invention provides a cylindrical battery and an electrical device that can solve the problem that simply evaluating the electrode length or casing size cannot accurately reflect the rate response characteristics of the battery cell, enabling the battery to match the high-current discharge requirements while maintaining a reasonable temperature rise and polarization level, and achieving coordinated control of the rate performance, thermal safety, and structural design of short-high cylindrical batteries.

[0005] To solve the above-mentioned technical problems, the present invention is implemented as follows: According to one aspect of the present invention, a cylindrical battery is provided, comprising: a housing, and a cell disposed in the housing, the cell comprising a positive electrode, a separator and a negative electrode arranged in sequence; The positive electrode sheet includes a positive current collector and a positive active coating disposed on one side surface of the positive current collector in the thickness direction; The overall dimension of the housing in the height direction is H1, in mm; the length dimension of the positive electrode is L. p Unit: mm; The cylindrical battery satisfies the following condition under constant current discharge at 25℃ and 40A: K T ≤1.8, and K V ≤1.00; K T =(T 40 -T0) / ρp K V =100×ΔV 40 / ρ p ; Where, ρ p ρ is the length density of the positive electrode. p =L p / H1 and ρ p ≠0, H1>0; T0 is the temperature of the outer surface of the casing when the cylindrical battery starts discharging at a constant current of 40A, in °C; T 40 The highest temperature on the outer surface of the casing during a 40A constant current discharge process, in °C; ΔV 40 The difference between the average plateau voltage of the cylindrical battery in the 30%~70% discharge capacity range of the 1A constant current discharge curve and the average plateau voltage in the 30%~70% discharge capacity range of the 40A constant current discharge curve, in V.

[0006] In some of these implementations, 1.50 ≤ K T ≤1.70.

[0007] In some of these implementations, 0.78 ≤ K v ≤0.93.

[0008] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active coating disposed on one side surface of the negative electrode current collector in the thickness direction; The length of the negative electrode is L. n Unit: mm; the length density of the negative electrode is ρ n , 1.01≤ρ n / ρ p ≤1.08; where ρ n =L n / H1.

[0009] In some of these embodiments, the length dimension of the diaphragm is L. s Unit: mm; the length density of the diaphragm is ρ s , 1.04≤ρ s / ρ p ≤1.12, 1.02≤ρ s / ρ n ≤1.08.

[0010] In some of these implementations, 23.8 ≤ ρ p ≤26.1.

[0011] In some of these embodiments, the L p The value range is 1500mm~1700mm.

[0012] In some of these embodiments, the value of H1 ranges from 63.5 mm to 66.5 mm.

[0013] In some embodiments, the diameter of the housing is D, in mm; and H1 and D satisfy: 3.06 ≤ H1 / D ≤ 3.14.

[0014] In some of these implementations, 24.6 ≤ ρ n ≤26.8.

[0015] In some of these implementations, 26.0 ≤ ρ s ≤28.2.

[0016] In some of these embodiments, the L n The value range is 1560mm~1750mm.

[0017] In some of these embodiments, the L s The value range is 1680mm~1830mm.

[0018] In some of these embodiments, the value of D ranges from 20.6 mm to 21.5 mm.

[0019] In some of these embodiments, under discharge conditions of 25°C and 40A, with a constant current discharge capacity of 1A as a reference, the cylindrical battery shall at least satisfy one of features (1) to (2): (1) The capacity retention rate of the cylindrical battery is greater than or equal to 97.0%; (2) The energy retention rate of the cylindrical battery is greater than or equal to 91.0%, and the T 40 ≤66.5℃.

[0020] In some embodiments, under discharge conditions of 25°C and 0.2C, the discharge capacity of the cylindrical battery is 4.8Ah to 5.2Ah, and the discharge energy of the cylindrical battery is 17.8Wh to 18.3Wh.

[0021] In some of these embodiments, the cylindrical battery has a DC internal resistance (DCR) of 7.5 mΩ to 9.5 mΩ at 25°C and 100% SOC.

[0022] In some of these embodiments, under 25°C, 8A charge / 40A discharge cycle conditions, the capacity retention of the cylindrical battery after cycling is greater than or equal to 89.0%.

[0023] In some embodiments, the positive electrode active coating comprises a positive electrode active material, which comprises a layered high-nickel lithium transition metal oxide, wherein the molar content of nickel in the layered high-nickel lithium transition metal oxide is 88 mol% to 93 mol%.

[0024] In some embodiments, the shoulder height of the housing is H2, where 63.2 mm ≤ H2 ≤ 66.2 mm.

[0025] In some embodiments, the cell has a height dimension H5, where 60.8 mm ≤ H5 ≤ 63.8 mm.

[0026] In some of these implementations, 2.3mm ≤ H1-H5 ≤ 3.4mm.

[0027] According to another aspect of the present invention, the present invention also provides an electrical device comprising: a cylindrical battery as described in any of the above embodiments.

[0028] Implementing the technical solution of the present invention has at least the following beneficial effects: 1. The cylindrical battery of the present invention defines the total dimension H1 of the casing in the height direction and defines the positive electrode length density ρ. p =L p / H1 normalizes the effective reaction length of the positive electrode per unit casing height, converting absolute size into relative density coupled with height, providing a basis for evaluating short-height cells; simultaneously, it establishes a normalized response criterion for cylindrical batteries under 25℃, 40A constant current discharge conditions, i.e., setting a temperature rise normalization coefficient K. T =(T 40 -T0) / ρ p ≤1.80 and polarization normalization coefficient K V =100×ΔV 40 / ρ p ≤1.00, comparing the temperature rise and polarization behavior under a 40A high-current discharge with the positive electrode length density ρ p This binding creates a synergistic constraint window encompassing thermal, electrical, and structural aspects. This solves the problem that simply evaluating electrode length or casing size cannot accurately reflect the rate response characteristics of short, high-performance cells. It allows the battery to meet high-current discharge demands while maintaining reasonable temperature rise and polarization levels, achieving coordinated control over the rate performance, thermal safety, and structural design of short, high-performance cylindrical batteries.

[0029] 2. In a preferred embodiment of the present invention, by limiting the height and diameter range of the cylindrical battery casing, it is beneficial to balance the casing volume utilization rate, end assembly allowance and side wall heat dissipation area, and reduce the wetting and heat dissipation deterioration caused by excessive compression of the core after the height is shortened.

[0030] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0031] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0032] Figure 1 The diagram shown is a structural schematic of the cylindrical battery casing provided by the present invention.

[0033] Explanation of reference numerals in the attached figures: 10 - Shell.

[0034] The accompanying drawings have illustrated specific embodiments of the invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0035] The technical solution of the present invention and how the technical solution of the present invention solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0036] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0037] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0038] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0039] Currently, in high-energy-density cylindrical batteries, the overall height of the casing is limited to a shorter length. This reduced height directly compresses the space within the casing available to accommodate the core, which consists of a positive electrode, a negative electrode, and a separator layered and wound together. If capacity is maintained or increased by the areal density of the electrodes using conventional methods, the number of turns of the core will decrease accordingly. This leads to an increase in the current density per unit length of the electrode during charging and discharging, resulting in increased electrode polarization and concentrated ohmic heat. When the electrode length is not adapted to the allowable space of the casing, heat accumulation and polarization deterioration under high-current discharge become more severe.

[0040] Therefore, the researchers of this invention have found that for cylindrical batteries with limited casing height, simply measuring the absolute length of the positive or negative electrode, or focusing only on the external dimensions of the casing, is insufficient to accurately reflect the configuration of the electrochemical reaction pathways within the usable space. Absolute length cannot reflect the constraint relationship between casing height variations and electrode unfolding, thus lacking effective structural parameters to characterize the battery's ability to withstand high-current discharge. Furthermore, even if the electrode length meets manufacturing requirements, if a quantitative correlation cannot be established between the length parameter and the battery's thermal and electrochemical polarization behavior under high-current conditions, the actual performance of the cylindrical battery may still fall short of expectations. In short-height cylindrical batteries, multiple factors affect high-current discharge performance; the reduction in the overall casing height alters the upper limit of the axial space for electrode winding, while the diameter determines the allowable radial dimensions of the winding core. The positive electrode, as the main body providing active lithium ions, determines the area of ​​the reaction interface and the uniformity of current distribution through its effective unfolded length. The negative electrode needs to have sufficient length to receive the lithium ions extracted from the positive electrode to avoid lithium plating on the negative electrode surface. The separator needs to provide sufficient coverage redundancy at the beginning and end of the winding and along the axial direction to ensure the reliability of insulation between the positive and negative electrodes.

[0041] In view of the technical problems existing in the prior art, the present invention provides a cylindrical battery and an electrical device, wherein the total dimension H1 of the cylindrical battery casing in the height direction and the length dimension L of the positive electrode are defined by the following: p And introduce the length density ρ of the positive electrode. p The length of the positive electrode is normalized to the total height of the casing to measure the length of the available positive electrode reaction path per unit casing height. Based on this, a normalized response criterion is further established under constant current discharge conditions of 25℃ and 40A, including the temperature rise normalization coefficient K. T and polarization normalization coefficient K V The temperature change of the casing and the voltage difference of the discharge plateau during high-current discharge were correlated with the length density of the positive electrode, respectively; through K T ≤1.8 and K VThe constraint of ≤1.00 incorporates structural parameters and thermal and electrical performance responses into a unified evaluation window, thereby enabling the rate performance, thermal safety, and structural design of the battery to be determined collaboratively under the condition of limited casing height.

[0042] The specific technical solution of the present invention is as follows: Cylindrical battery In some embodiments of the present invention, a cylindrical battery is provided, comprising: a housing, and a cell disposed in the housing, the cell comprising a positive electrode, a separator and a negative electrode stacked sequentially.

[0043] The positive electrode includes a positive current collector and a positive active coating disposed on one surface of the positive current collector in the thickness direction; the overall dimension of the shell in the height direction is H1, in mm; the length dimension of the positive electrode is L. p , Unit: mm.

[0044] A cylindrical battery, under constant current discharge conditions of 25℃ and 40A, satisfies: K T ≤1.8, and K V ≤1.00; K T =(T 40 -T0) / ρ p K V =100×ΔV 40 / ρ p ; where ρ p ρ is the length density of the positive electrode. p =L p / H1 and ρ p ≠0, H1>0; T0 is the temperature of the outer surface of the cylindrical battery casing at the start of a 40A constant current discharge, in °C; T 40 The highest temperature on the outer surface of the casing during a 40A constant current discharge process, in °C; ΔV 40 The difference between the average plateau voltage of a cylindrical battery in the 30%~70% discharge capacity range of the 1A constant current discharge curve and the average plateau voltage in the 30%~70% discharge capacity range of the 40A constant current discharge curve, expressed in V.

[0045] As an example, see reference Figure 1A cylindrical battery includes a casing and a battery cell. The battery cell is housed within the casing, which may also contain an electrolyte, immersing the battery cell in the electrolyte. The specific composition of the electrolyte is not specifically limited in this invention. It is understood that the cylindrical battery also includes a cover plate assembly, such as a cover plate, plastic parts, seals, and adapter plates, which are also not specifically limited in this invention. The casing of the cylindrical battery is cylindrical and can be formed by rolling thin sheets of metal materials such as aluminum or aluminum alloys to create a cylindrical casing with a accommodating space. At least one end of the casing has an opening, which can be welded to the cover plate assembly to seal the battery cell, electrolyte, etc., within the accommodating space. The total dimension H1 of the casing in the height direction is [value missing], that is, the total height of the casing in the height direction, either parallel to the sidewalls of the casing or perpendicular to the radial direction of the cylindrical battery. The battery cell is a layered arrangement of a positive electrode sheet, a separator, and a negative electrode sheet. It can be formed by winding to create a core, i.e., a battery cell, or by stacking sheets, which is also not specifically limited in this invention. The positive electrode sheet includes a positive current collector and a positive active coating disposed along the thickness direction of the positive current collector. The positive active coating is a positive active material, including, but not limited to, lithium iron phosphate, ternary materials, and lithium manganese iron phosphate. The length dimension L of the positive electrode sheet is... p This refers to the total length of the positive electrode current collector, including the positive electrode active coating, within the positive electrode sheet. For example, it represents the length of the positive electrode sheet containing the positive electrode active coating after the winding core is unwound along the winding direction. It is understood that the material of the positive electrode current collector can be aluminum foil, aluminum alloy foil, etc.

[0046] Furthermore, the researchers of this invention discovered that: increasing the length L of the positive electrode plate p Correlate this to the total height H1 of the casing and introduce the positive electrode length density ρ. p This allows for the conversion of absolute dimensions into a relative density coupled with height, thus providing a normalized characterization of the effective reaction length of the positive electrode per unit casing height. Therefore, to ensure controlled temperature rise and polarization performance under high-current discharge, the cylindrical battery, under constant current discharge conditions of 25℃ and 40A, simultaneously satisfies two normalization conditions: K... T ≤1.80, and K V ≤1.00. Where, K T =(T 40 -T0) / ρ p , defined as the temperature rise normalization coefficient; K V =100×ΔV 40 / ρ p is defined as the polarization normalization coefficient. T0 is the temperature of the outer surface of the cylindrical battery casing at the start of a 40A constant current discharge, in °C; T 40 ΔV represents the highest temperature on the outer surface of the casing during a 40A constant current discharge process, expressed in °C. 40This is the difference between the average plateau voltage of the cylindrical battery in the 30%~70% discharge capacity range of the 1A constant current discharge curve and the average plateau voltage in the 30%~70% discharge capacity range of the 40A constant current discharge curve, expressed in volts (V). This difference is achieved using the two normalization coefficients K. T and K V The temperature rise and polarization behavior under a 40A high-current discharge are compared with the positive electrode length density ρ. p The binding forms a collaborative constraint window between the thermal, electrical, and structural elements. When K... T A value greater than 1.80 indicates an excessively high temperature rise per unit cathode length density, which may prevent the heat accumulation inside the battery from being effectively dispersed through a reasonable distribution of cathode length, potentially leading to thermal safety issues. When K... V When the value is greater than 1.00, the polarization per unit positive electrode length density may be too large, and the length of the positive electrode sheet may not be sufficient to carry the current load under a 40A discharge, leading to an increase in concentration polarization and ohmic polarization. Therefore, by using K... T and K V Within the above limits, the problem of not being able to accurately reflect the rate response characteristics of short and high-capacity cells by simply evaluating electrode length or casing size is solved, enabling the battery to match the demand for high-current discharge while maintaining reasonable temperature rise and polarization levels.

[0047] Understandably, the following method can be used for temperature rise and polarization testing under 40A constant current discharge conditions: The test environment temperature is controlled at 25±2℃. The battery is charged at a constant current of 0.2C to 4.2V, then charged at a constant voltage to 0.05C. After standing for 30 minutes, it is discharged at a constant current of 1A to 2.5V, and the 1A discharge curve is recorded. Another battery of the same model is fully charged in the same manner and left to stand for 30 minutes. Then, it is discharged at a constant current of 40A to 2.5V or to a casing temperature of 75℃, and the 40A discharge curve is recorded. Before the 40A discharge test, a K-type patch thermocouple is fixed at the axial height H1 / 2 of the casing sidewall, circumferentially avoiding the casing weld and the heat-affected zone of the electrode tab by 90°. The thermocouple reading at the start of the 40A discharge is T0, and the highest reading during the discharge process is T... 40 For the platform voltage difference ΔV 40 The calculation uses the average plateau voltage within the discharge capacity range of 30% to 70%. In the 1A discharge curve, the range of cumulative discharge capacity from 30% to 70% is determined, and the average voltage within this range is calculated and denoted as U(1A, 30-70). Similarly, in the 40A discharge curve, the range of cumulative discharge capacity from 30% to 70% is determined, and the average voltage within this range is calculated and denoted as U(40A, 30-70). Then ΔV 40 =U(1A, 30-70) - U(40A, 30-70). Based on the measured ρ p T 40T0 and ΔV 40 Calculate K respectively T =(T 40 -T0) / ρ p and K V =100×ΔV 40 / ρ p .

[0048] In some embodiments, 1.50 ≤ K T ≤1.70. For example, K T It can be any point value between any one of 1.50, 1.52, 1.55, 1.56, 1.58, 1.60, 1.62, 1.64, 1.65, 1.67, 1.69℃ or 1.70.

[0049] In some embodiments, 0.78 ≤ K v ≤0.93. For example, K V K can be any value from 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, or 0.93, or any value between any two of them. T and / or K v Within the above range, it can be ensured that the cylindrical battery has a lower temperature rise and polarization caused by the unit positive electrode length density under a high current discharge of 40A, resulting in higher battery energy efficiency and better thermal safety.

[0050] In some embodiments, the negative electrode includes a negative current collector and a negative active coating disposed on one surface of the negative current collector in the thickness direction; the length dimension of the negative electrode is L. n Unit: mm; Length density of the negative electrode is ρ n , 1.01≤ρ n / ρ p ≤1.08; where ρ n =L n / H1.

[0051] For example, the negative electrode current collector can be copper foil, copper alloy foil, etc., and a negative electrode active coating is formed on the thickness direction of the negative electrode current collector. The negative electrode active coating includes a negative electrode active material, which includes, but is not limited to, graphite, soft carbon, hard carbon, silicon-based materials, etc. The length dimension L of the negative electrode sheet is... n ρ represents the total length of the negative electrode current collector, including the negative electrode active coating, within the negative electrode sheet. For example, it represents the length of the negative electrode sheet containing the negative electrode active coating after the core is unwound along the winding direction. n / ρ pThe value can be any one of 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, or 1.08, or any value between any two. This allows for a better balance between negative electrode redundancy and space utilization. If the value is less than the above range, the length of the negative electrode is insufficient relative to the positive electrode. Under high current discharge, lithium ions extracted from the positive electrode may not be promptly absorbed on the negative electrode surface, resulting in an excessively low negative electrode potential and increasing the risk of lithium plating. If the value is greater than the above range, the length of the negative electrode is too long, occupying additional internal space and potentially compressing the cell's pores and heat dissipation channels, affecting the overall battery performance.

[0052] It is understandable that the length L of the positive electrode plate p The length Ln of the positive and negative electrode plates can be obtained by measuring after disassembling the battery. Specifically: after discharging the battery to 2.5V, disassemble it in a dry environment with a dew point no higher than -40℃, remove the cell, and unfold the positive electrode plate, negative electrode plate, and outer separator. The unfolded length L of the region on the positive electrode plate coated with the positive active material layer and participating in the electrochemical reaction is measured along the winding direction using a two-dimensional image measuring instrument. p Similarly, the unfolded length L of the region on the negative electrode sheet coated with the negative electrode active material layer and corresponding to the positive electrode reaction region is measured along the winding direction. n By measuring the total height H1 of the shell and according to ρ p =L p / H1 and ρ n =L n Calculate the length density of the positive electrode and the length density of the negative electrode, respectively, using / H1.

[0053] In some embodiments, the length dimension of the diaphragm is L. s Unit: mm; diaphragm length density is ρ s , 1.04≤ρ s / ρ p ≤1.12, 1.02≤ρ s / ρ n ≤1.08.

[0054] For example, the diaphragm length density ρ s =L s / H1, where L s ρ represents the total effective length of the separator, which is the length of the separator used for positive and negative electrode isolation and for covering the start and end ends of the winding after the cell is unwound. s / ρ p It can be any point value from 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, 1.11, or 1.12, or any value between any two of them. ρ s / ρ nIt can be any point value among 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, or 1.08, or any value between any two. ρ s / ρ p and ρ s / ρ n Within the above range, the diaphragm has sufficient coverage redundancy at the head, tail, and axial direction of the wound structure, reliably preventing short circuits at the edges between the positive and negative electrodes. If ρ s / ρ p and ρ s / ρ n If any of these parameters is less than the above range, the membrane coverage length may be insufficient, especially at the winding ends or electrode edges, posing a risk of direct contact between the positive and negative electrodes, thereby reducing battery safety and cycle stability. If ρ s / ρ p and ρ s / ρ n If any of these factors exceeds the above range, the separator length will be too long, thus occupying too much of the limited internal space and reducing the volumetric energy density of the battery.

[0055] In some embodiments, 23.8 ≤ ρ p ≤26.1. For example, ρ p It can be any value from 23.8, 24.0, 24.3, 24.6, 24.9, 25.1, 25.4, 25.7, 25.9, or 26.1, or any point value between any two. If it is less than the above range, the length of the positive electrode is too short relative to the height of the casing, and the reaction path per unit height is insufficient. During a high current discharge of 40A, the local current density increases, leading to an increase in the polarization voltage ΔV. 40 Temperature rise T 40 The increase of K T and K V It's easy to exceed the upper limit. If it exceeds the above range, the positive electrode sheet will be too long, compressing the pore space and electrolyte retention space inside the core, obstructing the radial heat dissipation channel, and also causing T... 40 Increase, although K V It may be lower, but the thermal safety margin decreases. Therefore, ρ p The value window not only takes into account the length of the electrode itself, but also couples it with the height of the shell, so as to balance the relationship between the electrochemical reaction area and the internal space occupation.

[0056] In some embodiments, L p The value range is 1500mm~1700mm. For example, L... pIt can be any point value between any one of 1500mm, 1520mm, 1540mm, 1560mm, 1580mm, 1600mm, 1620mm, 1640mm, 1660mm, 1680mm, 1686mm, 1690mm or 1700mm.

[0057] In some embodiments, the value of H1 ranges from 63.5mm to 66.5mm. For example, H1 can be any point value between any one or any two of 63.5mm, 63.8mm, 64.0mm, 64.3mm, 64.5mm, 64.7mm, 65.0mm, 65.1mm, 65.5mm, 65.8mm, 66.0mm, 66.2mm, or 66.5mm.

[0058] In some embodiments, the diameter of the housing is D (in mm); H1 and D satisfy: 3.06 ≤ H1 / D ≤ 3.14. Exemplarily, H1 / D can be any one of 3.06, 3.07, 3.08, 3.09, 3.10, 3.11, 3.12, 3.13, or 3.14, or any value between any two. This is beneficial for optimizing the aspect ratio of the housing, increasing the sidewall heat dissipation area, and improving the cell wetting effect, while also considering the internal space utilization, end assembly allowance, and sidewall heat dissipation capacity. When the housing height is shortened, if the aspect ratio is greater than the above range, the cell is excessively compressed axially, leading to poor electrolyte wetting and deterioration of the radial heat dissipation path; if the aspect ratio is less than the above range, the sidewall heat dissipation area is insufficient, which is also detrimental to thermal management under high current discharge.

[0059] In some embodiments, 24.6 ≤ ρ n ≤26.8. For example, ρ n It can be any point value among 24.6, 24.8, 25.0, 25.2, 25.4, 25.6, 25.8, 26.0, 26.2, 26.4, 26.6, or 26.8, or any point value between any two of them.

[0060] In some embodiments, 26.0 ≤ ρ s ≤28.2. For example, ρ s It can be any point value among 26.0, 26.2, 26.4, 26.6, 26.8, 27.0, 27.2, 27.4, 27.6, 27.8, 28.0, or 28.2, or any point value between any two of them.

[0061] In some embodiments, L n The value range is 1560mm~1750mm. For example, L... nIt can be any point value between any one of 1560mm, 1580mm, 1600mm, 1620mm, 1640mm, 1660mm, 1680mm, 1700mm, 1719mm, 1720mm, 1740mm or 1750mm.

[0062] In some embodiments, L s The value range is 1680mm~1830mm. For example, L... s It can be any point value between any one or any two of 1680mm, 1700mm, 1720mm, 1740mm, 1760mm, 1780mm, 1800mm, 1801mm, 1810mm, 1820mm or 1830mm.

[0063] In some embodiments, the value of D ranges from 20.6 mm to 21.5 mm. For example, D can be any point value between any one or any two of 20.6 mm, 20.7 mm, 20.8 mm, 20.9 mm, 21.0 mm, 21.1 mm, 21.2 mm, 21.3 mm, 21.4 mm, or 21.5 mm.

[0064] In some embodiments, under discharge conditions of 25°C and 40A, with a constant current discharge capacity of 1A as a reference, the cylindrical battery must satisfy at least one of the features (1) to (2): (1) The capacity retention rate of the cylindrical battery is greater than or equal to 97.0%; (2) The energy retention rate of the cylindrical battery is greater than or equal to 91.0%, and T 40 ≤66.5℃.

[0065] In some embodiments, under discharge conditions of 25°C and 0.2C, the discharge capacity of the cylindrical battery is 4.8Ah~5.2Ah, and the discharge energy of the cylindrical battery is 17.8Wh~18.3Wh.

[0066] For example, under 25°C and 0.2C discharge conditions, the discharge capacity of a cylindrical battery can be any value between 4.8Ah, 4.85Ah, 4.9Ah, 4.95Ah, 5.0Ah, 5.01Ah, 5.05Ah, 5.1Ah, 5.15Ah, or 5.2Ah. The discharge energy can be any value between 17.8Wh, 17.85Wh, 17.9Wh, 17.95Wh, 17.98Wh, 18.0Wh, 18.05Wh, 18.1Wh, 18.15Wh, 18.2Wh, 18.25Wh, or 18.3Wh. Under 25°C and 40A discharge conditions, with a 1A discharge capacity as a baseline, the battery's capacity retention rate is greater than or equal to 97.0%, its energy retention rate is greater than or equal to 91.0%, and the highest casing temperature T... 40 The temperature should not exceed 66.5℃. It's understandable that the capacity retention rate and energy retention rate are calculated as follows: After fully charging the battery at 0.2C and allowing it to stand, first discharge it at 1A to 2.5V, recording the 1A discharge capacity C1A and energy E1A; then, fully charge another battery of the same model under the same conditions, discharge it at 40A to 2.5V or until the casing reaches 75℃, recording the 40A discharge capacity C40 and energy E40. Then, the capacity retention rate RC40 = C40 / C1A × 100%, and the energy retention rate RE40 = E40 / E1A × 100%. If either the capacity retention rate or the energy retention rate is less than the above range, the battery's capacity or energy loss under a high current of 40A is too large, and the utilization rate of the positive electrode active material is limited by polarization and temperature rise, failing to meet the requirements of high-power applications. If T... 40 Above 66.5℃, the maximum temperature of the battery surface exceeds the safety window, increasing the risk of thermal management problems.

[0067] It is also understandable that the test method for 0.2C discharge capacity and energy can be achieved by charging at a constant current of 0.2C to 4.2V at 25±2℃, charging at a constant voltage to 0.05C cutoff, and letting it stand for 30 minutes; then discharging at a constant current of 0.2C to 2.5V, and recording the discharge capacity C0.2 and discharge energy E0.2. The discharge energy E0.2 is calculated by integrating E0.2=Σ[(Vi+Vi+1) / 2]×(Qi+1-Qi), where Vi and Vi+1 are the voltages of adjacent sampling points, and Qi and Qi+1 are the capacities of adjacent sampling points.

[0068] In some embodiments, the DC internal resistance (DCR) of the cylindrical battery is 7.5 mΩ to 9.5 mΩ at 25°C and 100% SOC.

[0069] For example, at 25°C and 100% SOC, the DCR of a cylindrical battery can be any value between 7.5mΩ, 7.8mΩ, 8.0mΩ, 8.2mΩ, 8.5mΩ, 8.8mΩ, 9.0mΩ, 9.1mΩ, 9.2mΩ, 9.3mΩ, 9.4mΩ, or 9.5mΩ. Understandably, the DCR can be tested by adjusting the battery to 100% SOC at 25±2°C and allowing it to rest for 60 minutes, applying a 25A discharge pulse for 10 seconds, and recording the voltage V0 before the pulse and the voltage V10 at the end of the 10 seconds. The DCR is then calculated as (V0-V10) / 25, converted to mΩ. If the DCR is greater than the above range, the voltage drop under high current discharge increases, and the energy efficiency decreases; if it is less than the above range, it may not be able to match the response of the positive electrode length density and rate capability.

[0070] In some embodiments, under 25°C, 8A charge / 40A discharge cycle conditions, the capacity retention rate of the cylindrical battery after cycling is greater than or equal to 89.0%.

[0071] For example, if the capacity retention rate of a cylindrical battery after cycling is within the above-mentioned range, it ensures that the battery not only has the ability to discharge high current instantaneously, but also has long-term operational reliability under harsh conditions. It can be understood that, under the conditions of 25℃, 8A charging / 40A discharging cycling, the capacity retention rate of a cylindrical battery after cycling is not less than 89.0%. The testing method involves charging at 25±2℃ with a constant current of 8A to 4.2V, then charging with a constant voltage to 0.25A (cutoff), and letting it rest for 10 minutes; then discharging with a constant current of 40A to 2.5V or the casing temperature to 75℃ (cutoff), and letting it rest for 10 minutes. This constitutes one cycle. The capacity retention rate CRn = Cn / C1 × 100%, where C1 is the discharge capacity of the first cycle and Cn is the discharge capacity of the nth cycle.

[0072] In some embodiments, the positive electrode active coating includes a positive electrode active material, which includes a layered high-nickel lithium transition metal oxide, wherein the molar content of nickel in the layered high-nickel lithium transition metal oxide is 88 mol% to 93 mol%.

[0073] For example, layered high-nickel lithium transition metal oxides include, but are not limited to, NMC811 (LiNi 0.8 Co 0.1 Mn 0.1 O2), NMC622, etc.; the nickel content can be any one of 88mol%, 89mol%, 90mol%, 91mol%, 92mol%, or 93mol%, or any value between any two. Using layered oxides with high nickel content can provide the battery with high reversible capacity and energy density, and can also enable rapid extraction of lithium ions under high current discharge.

[0074] In some embodiments, the shoulder height of the housing is H2, where 63.2 mm ≤ H2 ≤ 66.2 mm. For example, refer to... Figure 1 The shoulder height H2 of the shell can be any one of 63.2mm, 63.5mm, 63.8mm, 64.0mm, 64.3mm, 64.5mm, 64.8mm, 65.0mm, 65.2mm, 65.5mm, 65.8mm, 66.0mm or 66.2mm or any point value between any two.

[0075] In some embodiments, the dimension of the battery cell in the height direction is H5, where 60.8mm ≤ H5 ≤ 63.8mm. Exemplarily, the dimension H5 of the battery cell in the height direction can be any one of 60.8mm, 61.0mm, 61.3mm, 61.5mm, 61.8mm, 62.0mm, 62.3mm, 62.5mm, 62.8mm, 63.0mm, 63.3mm, 63.5mm, or 63.8mm, or any point value between any two of these values.

[0076] In some embodiments, 2.3mm ≤ H1-H5 ≤ 3.4mm. Exemplarily, H1-H5 can be any value between any one or any two of 2.3mm, 2.4mm, 2.5mm, 2.6mm, 2.7mm, 2.8mm, 2.9mm, 3.0mm, 3.1mm, 3.2mm, 3.3mm, or 3.4mm. This limitation allows for a reduction in the overall height of the housing, optimizing the welding space for the internal current collectors and the axial positioning of the battery cells.

[0077] [Electrical appliances] In some embodiments of the present invention, an electrical device is also provided, comprising: the cylindrical battery in any of the above embodiments.

[0078] Optionally, the electrical devices can be vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, power tools, energy storage devices, amusement equipment, elevators and lifting equipment, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, or electric airplane toys, etc.; power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc.; energy storage devices can be energy storage walls, base station energy storage, container energy storage, etc.; amusement equipment can be carousels, drop towers, etc. The aforementioned vehicles can be fuel-powered vehicles, natural gas vehicles, or new energy vehicles. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery is installed inside the vehicle, which can be located at the bottom, front, or rear of the vehicle. The battery can be used to power the vehicle; for example, the battery can serve as the vehicle's operating power source. The vehicle may also include a controller and a motor. The controller controls the battery's power supply to the motor, for example, to meet the vehicle's power needs during starting, navigation, and driving. The battery can serve not only as the vehicle's operating power source but also as its driving power source, replacing or partially replacing fuel or natural gas to provide propulsion.

[0079] It should also be noted that the battery of this application does not limit the specific material or type of electrolyte, and can use any components and types known in the art that can be used in batteries, as long as the purpose of this invention can be achieved.

[0080] The diaphragm used in this embodiment is a diaphragm used in the art. The diaphragm can be a polyolefin porous membrane such as a single-layer or multi-layer composite membrane of PP or PE, or a diaphragm with a functional coating such as ceramic or adhesive on its surface. No particular limitation is made here. All solvents and substances in this invention can be purchased commercially.

[0081] Since the battery provided in this embodiment of the invention adopts all the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be described in detail here.

[0082] The present application will be described in detail below with reference to the accompanying drawings and examples. However, the implementation and protection of the present invention are not limited thereto. The following embodiments are only some embodiments of the present application and are not intended to limit the present application.

[0083] Example 1 Example 1 is the optimal embodiment of a short-height cylindrical lithium-ion battery. The total height H1 of the cylindrical casing is 65.1 mm, the diameter D is 21.0 mm, the shoulder height H2 is 64.8 mm, and the bottom height H5 is 62.3 mm.

[0084] The positive electrode sheet is prepared as follows: The positive electrode active material is a layered high-nickel lithium transition metal oxide with a Ni content of approximately 90 mol%. By mass percentage, the solid components of the positive electrode slurry include 97.25% positive electrode active material, 1.50% conductive carbon black (SP), 0.10% carbon nanotube conductive agent (dry weight), and 1.15% PVDF (polyvinylidene fluoride) binder. PVDF is dissolved in NMP (N-methylpyrrolidone), the conductive agent is added for dispersion, and then the positive electrode active material is added in batches. After vacuum stirring and degassing, the positive electrode slurry is obtained. The positive electrode slurry is coated on both sides of an aluminum foil with a thickness of approximately 12 μm. After segmented drying, rolling, and slitting, the positive electrode sheet is obtained. The positive electrode coating surface density is reduced to 12.70 mg / cm². 2 The compaction density of the positive electrode was controlled to approximately 3.48 g / cm³. 3 The thickness of the positive electrode sheet was controlled to approximately 87 μm, allowing for increased winding length within the 21650 housing; the effective length L of the positive electrode... p It is 1686mm.

[0085] The negative electrode sheet is prepared as follows: The negative electrode active material uses artificial graphite and silicon carbon materials. By mass percentage, the solid components of the negative electrode slurry include 82.95% artificial graphite, 13.50% silicon carbon materials, 0.50% conductive carbon black SP, 0.25% carbon nanotube conductive agent (dry weight), 1.10% CMC (carboxymethyl cellulose) binder / thickener, and 1.70% SBR (styrene-butadiene rubber) binder. CMC is added to deionized water to prepare a glue solution, then the conductive agent, graphite, and silicon carbon materials are added and dispersed. Finally, SBR is added and stirred at low speed to remove bubbles. The negative electrode slurry is coated on both sides of a copper foil with a thickness of approximately 6 μm. After drying, rolling, and slitting, the negative electrode sheet is obtained. The negative electrode coating surface density is reduced to 5.45~5.48 mg / cm³. 2 The compaction density of the negative electrode was controlled to approximately 1.53 g / cm³. 3 The thickness of the negative electrode sheet after rolling is controlled to be approximately 83~84μm, ensuring the effective length L of the negative electrode. n Increased to 1719 mm, and maintains redundancy in negative electrode length density relative to positive electrode length density.

[0086] The diaphragm is a single-sided boehmite ceramic-coated polyolefin diaphragm with a base membrane thickness of approximately 9 μm and a ceramic layer thickness of approximately 3 μm. The effective total length of the diaphragm is L. s The diameter is 1801 mm. The positive electrode, separator, and negative electrode are wound into a core in the stacking order of "positive electrode-separator-negative electrode-separator". The number of winding turns is controlled to be about 25.5 turns and the winding tension is controlled to be 2.8 N. The core is then installed into a 21650 short and tall cylindrical shell. The current collector welding, shell insertion, liquid injection, sealing, formation, aging, and capacity testing are completed to obtain the battery cell of Example 1.

[0087] In Example 1, the surface density of the positive electrode coating was controlled to 12.70 mg / cm². 2 The surface density of the negative electrode coating reaches 5.45~5.48 mg / cm³. 2 And the winding lengths of the positive and negative electrodes were increased to 1686mm and 1719mm, respectively, so that ρ p Reaching 25.90, ρ n Reaching 26.41, ρ s The value reaches 27.67, and the thermal response and polarization response under 40A discharge conditions simultaneously satisfy K. T 1.56℃, K V It is 0.81. 40 The temperature is 65.47℃, and ΔV 40 It is 0.209V.

[0088] Example 2 The difference between Example 2 and Example 1 is that the positive electrode coating surface density is increased to 13.57 mg / cm². 2 Increase the compaction density of the positive electrode to 3.57 g / cm³. 3 Increase the surface density of the negative electrode coating to 5.84-6.00 mg / cm³. 2 Increase the compaction density of the negative electrode to 1.60 g / cm³. 3 Furthermore, the number of winding turns was reduced to approximately 24.0 turns, and the winding tension was increased to 3.0 N, resulting in a reduction in the effective length of the positive electrode from 1686 mm to 1563 mm, the effective length of the negative electrode from 1719 mm to 1614 mm, and the effective total length of the separator from 1801 mm to 1731 mm, thus reducing the ρ p The value changed from 25.90 to 24.01, ρ n The value changed from 26.41 to 24.79, ρ s The value changed from 27.67 to 26.59; all other conditions remained the same as in Example 1. The performance result was: T 40 The temperature is 64.50℃, and ΔV 40 0.218V, K T It is 1.65℃, K V It is 0.91.

[0089] Example 3 The difference between Example 3 and Example 1 is that the positive electrode coating surface density is increased to 14.10 mg / cm². 2 Increase the compaction density of the positive electrode roller to 3.62 g / cm³. 3 Increase the surface density of the negative electrode coating to 6.05 mg / cm³. 2 The number of winding turns was reduced to approximately 23.1 turns, and the winding tension was increased to 3.2 N, so that L p The diameter was changed from 1686mm to 1500mm, and the length of the L was also changed. nAdjusted from 1719mm to 1565mm, L s The diameter was adjusted from 1801 mm to 1695 mm; all other conditions remained the same as in Example 1. ρ p It is 23.04, ρ n It is 24.04, ρ s The value is 26.04. The performance result is: T 40 The temperature is 66.00℃, and ΔV 40 0.229V, K T It is 1.78℃, K V It is 0.99.

[0090] Example 4 The difference between Example 4 and Example 1 is that the positive electrode coating surface density is reduced to 12.60 mg / cm². 2 Increase the number of winding turns to approximately 26 turns and appropriately reduce the winding tension to 2.6N, so that L p The diameter was changed from 1686mm to 1700mm, and H1 was adjusted to 64.5mm and L... n Adjusted from 1719mm to 1740mm, L s The diameter was adjusted from 1801 mm to 1810 mm; all other conditions remained the same as in Example 1. ρ p It is 26.36, ρ n It is 26.98, ρ s The value is 28.06. The performance result is: T 40 The temperature is 66.30℃, and ΔV 40 0.221V, K T It is 1.57℃, K V It is 0.84.

[0091] Example 5 The difference between Example 5 and Example 1 is that the positive electrode coating surface density is increased to 13.10 mg / cm². 2 The compaction density of the positive electrode was controlled to be 3.53 g / cm³. 3 The surface density of the negative electrode coating was increased to 5.70 mg / cm³. 2 The number of winding turns was reduced to approximately 24.9 turns, and the winding tension was increased to 2.9 N, so that L p The diameter of the tube was changed from 1686mm to 1620mm. n The diameter of the tube was changed from 1719mm to 1645mm. s The diameter of the sample changed from 1801 mm to 1745 mm, and the ρ... n / ρ p It remained at approximately 1.02; all other conditions were the same as in Example 1. ρ p It is 24.88, ρ n It is 25.27, ρ sThe value is 26.80. The performance result is: T 40 The temperature is 65.80℃, and ΔV 40 0.222V, K T It is 1.64℃, K V It is 0.89.

[0092] Example 6 The difference between Example 6 and Example 1 is that the positive electrode coating surface density is increased to 13.25 mg / cm². 2 The compaction density of the positive electrode was controlled to be 3.55 g / cm³. 3 Reduce the surface density of the negative electrode coating to 5.43 mg / cm³. 2 Furthermore, the number of positive electrode winding turns was reduced to approximately 24.6 turns, while the negative electrode cutting length was maintained at a winding allowance corresponding to 1720mm, thus enabling L p The diameter of the tube was changed from 1686mm to 1600mm. n The diameter of the tube was changed from 1719mm to 1720mm. s The diameter of the sample changed from 1801 mm to 1731 mm, and the diameter of the sample changed from ρ to 1731 mm. n / ρ p The value was changed from 1.02 to 1.08; all other conditions remained the same as in Example 1. ρ p It is 24.58, ρ n It is 26.42 mm / mm, ρ s It is 26.59 mm / mm. The performance result is: T 40 The temperature is 65.50℃, and ΔV 40 0.214V, K T It is 1.65℃, K V It is 0.87.

[0093] Example 7 The difference between Example 7 and Example 1 is that: by reducing the pre-wound length of the diaphragm roll head from 25mm to 12mm, the roll tail wrapping length from 36mm to 20mm, and controlling the total cut length of the diaphragm to 1695mm, L s The thickness was reduced from 1801 mm to 1695 mm, while maintaining the positive electrode coating surface density of 12.70 mg / cm³. 2 The surface density of the negative electrode coating is 5.45~5.48 mg / cm³. 2 L p and L n The basic conditions remain unchanged; all other conditions are the same as in Example 1. s It is 26.04 mm / mm, ρ s / ρ p The value is 1.01. The performance result is: T 40 The temperature is 65.00℃, and ΔV 40 0.219V, K TIt is 1.54℃, K V It is 0.85.

[0094] Example 8 The difference between Example 8 and Example 1 is that: by increasing the pre-wound length of the diaphragm roll head from 25mm to 38mm and the wrapping length of the roll tail from 36mm to 52mm, and controlling the total cut length of the diaphragm to 1830mm, L s The thickness was reduced from 1801mm to 1830mm, while maintaining the positive electrode coating surface density of 12.70mg / cm³. 2 The surface density of the negative electrode coating is 5.45~5.48 mg / cm³. 2 The lengths of the positive and negative electrodes remain essentially unchanged; all other conditions are the same as in Example 1. ρ s It is 28.11 mm / mm, ρ s / ρ p The value is 1.09. The performance result is: T 40 The temperature is 65.60℃, and ΔV 40 0.216V, K T It is 1.57℃, K V It is 0.83.

[0095] Example 9 The difference between Example 9 and Example 1 is that the positive electrode coating surface density is increased to 13.95 mg / cm². 2 Increase the compaction density of the positive electrode to 3.60 g / cm³. 3 Increase the surface density of the negative electrode coating to 5.95 mg / cm³. 2 Furthermore, the number of winding turns was reduced to approximately 23.3 turns, and the winding tension was increased to 3.1 N, correspondingly shortening the negative electrode and separator, thus enabling L... p The diameter of the tube was changed from 1686mm to 1515mm, and the diameter of the tube was reduced to L. n The diameter of the tube was changed from 1719mm to 1580mm. s The diameter was changed from 1801 mm to 1700 mm; all other conditions remained the same as in Example 1. ρ p It is 23.27 mm / mm, ρ n It is 24.27 mm / mm, ρ s It is 26.11 mm / mm. The performance result is: T 40 The temperature is 66.70℃, and ΔV 40 0.225V, K T It is 1.79℃, K V It is 0.97.

[0096] Example 10 The difference between Example 10 and Example 1 is that the positive electrode coating surface density is increased to 14.05 mg / cm². 2The compaction density of the positive electrode was controlled to be 3.61 g / cm³. 3 The surface density of the negative electrode coating was controlled to be 5.90 mg / cm³. 2 The number of winding turns was reduced to approximately 23.1 turns, and the winding tension was increased to 3.2 N, so that L p The diameter of the tube was changed from 1686mm to 1505mm. n The diameter of the tube was changed from 1719mm to 1570mm. s The diameter was changed from 1801 mm to 1695 mm; all other conditions remained the same as in Example 1. ρ p It is 23.12 mm / mm, ρ n It is 24.12 mm / mm, ρ s It is 26.04 mm / mm. The performance result is: T 40 The temperature is 66.20℃, and ΔV 40 0.230V, K T It is 1.78℃, K V It is 0.99.

[0097] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the positive electrode coating surface density was increased to 14.35 mg / cm². 2 Increase the compaction density of the positive electrode to 3.65 g / cm³. 3 Increase the surface density of the negative electrode coating to 6.20 mg / cm³. 2 The number of winding turns was reduced to approximately 22.3 turns, and the winding tension was increased to 3.4 N, making L p The diameter of the tube was changed from 1686mm to 1450mm. n The diameter of the tube was changed from 1719mm to 1540mm. s The diameter was changed from 1801 mm to 1660 mm; all other conditions remained the same as in Example 1. ρ p It is 22.27, ρ n It is 23.66, ρ s The value is 25.50. The performance result is: T 40 The temperature is 67.20℃, and ΔV 40 0.235V, K T The temperature is 1.90℃, K V It is 1.06.

[0098] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the positive electrode coating surface density was excessively reduced to 12.20 mg / cm². 2 Reduce the surface density of the negative electrode coating to 5.25 mg / cm³. 2 The number of winding turns was increased to approximately 26.9 turns, and the winding tension was reduced to 2.4N, making L p The diameter of the tube was changed from 1686mm to 1750mm.n The diameter of the tube changed from 1719mm to 1810mm, and the diameter of the tube increased by 100mm. s The diameter was changed from 1801 mm to 1862 mm; all other conditions remained the same as in Example 1. ρ p It is 26.88 mm / mm, ρ n It is 27.80 mm / mm, ρ s It is 28.60 mm / mm. The performance result is: T 40 The temperature is 67.00℃, and ΔV 40 0.214V, K T It is 1.56℃, K V It is 0.80.

[0099] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the negative electrode slitting length is controlled to 1660 mm and the negative electrode coating surface density is increased to 5.65 mg / cm³. 2 The surface density of the positive electrode coating was adjusted to 12.75 mg / cm³. 2 The positive electrode cutting length is controlled at 1680mm, so that L n The length was changed from 1719mm to 1660mm, and the length of the L was also changed. p The change from 1686mm to 1680mm makes ρ n / ρ p The value was changed from 1.02 to 0.99; all other conditions remained the same as in Example 1. ρ p It is 25.81 mm / mm, ρ n It is 25.50 mm / mm. The performance result is: T 40 The temperature is 65.80℃, and ΔV 40 0.226V, K T It is 1.58℃, K V It is 0.88.

[0100] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the pre-wound length of the diaphragm roll head was reduced from 25mm to 5mm, the roll tail wrapping length was reduced from 36mm to 12mm, and the total cut length of the diaphragm was controlled to 1620mm, so that L s The diameter was changed from 1801mm to 1620mm, while maintaining the length L. p and Ln The basic conditions remain unchanged; all other conditions are the same as in Example 1. s It is 24.88 mm / mm. The performance result is: T 40 The temperature is 65.30℃, and ΔV 40 0.221V, K T It is 1.56℃, K V It is 0.85.

[0101] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that the positive electrode coating surface density was increased to 13.57 mg / cm². 2 Increase the surface density of the negative electrode coating to 5.84~6.00 mg / cm³. 2 The number of winding turns was reduced to approximately 24.0 turns, and the electrolyte injection coefficient was reduced from 3.15 g / Ah to 2.70 g / Ah, so that L p L n L s The diameters were shortened to 1563mm, 1614mm, and 1731mm, while the electrolyte wetting margin was reduced, resulting in T... 40 The temperature changed from 65.47℃ to 67.00℃, ΔV 40 The voltage was changed from 0.209V to 0.236V; all other conditions were the same as in Example 1. ρ p It is 24.01 mm / mm, ρn is 24.79 mm / mm, ρ s It is 26.59 mm / mm. The performance result is: K T It is 1.75℃, K V It is 0.98.

[0102] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is that: while retaining the 70mm cylindrical shell height and corresponding reference electrode design, the total height H1 of the cylindrical shell is changed from 65.1mm to 70.1mm, and the positive electrode coating surface density is set to 13.57mg / cm³. 2 The surface density of the negative electrode coating is set to 5.84~6.00 mg / cm³. 2 The number of winding turns is set to approximately 24.0 turns, and the winding tension is set to 3.0 N, so that L p L n L s The diameters are 1563 mm, 1614 mm, and 1731 mm, respectively; the remaining material systems are the same as in Example 1. ρ p It is 22.30 mm / mm, ρ n It is 23.02 mm / mm, ρ s It is 24.69 mm / mm. The performance result is: T 40 The temperature is 64.50℃, and ΔV 40 0.218V, K T It is 1.77℃, K V It is 0.98.

[0103] Performance testing 1. External dimensions and electrode length density test The batteries were left to stand at 25±2℃ for 2 hours. The total height H1, shoulder height H2, bottom height (core width) H5, and diameter D were measured using a 2D image measuring instrument. Each battery was measured 3 times and the average value was taken.

[0104] After discharging the battery to 2.5V, disassemble it in an environment with a dew point ≤-40℃, remove the core, and unfold the positive electrode, negative electrode, and outer separator. The length L of the positive electrode is measured using a 2D image measuring instrument. p Length L of the negative electrode n The total length L of the diaphragm s .

[0105] Calculate according to equations (1) to (3): ρ p =L p / H1——(1) ρ n =L n / H1——(2) ρ s =L s / H1——(3) 2. 0.2C Capacity, Energy, and Platform Testing At 25±2℃, charge at a constant current of 0.2C to 4.2V, then charge at a constant voltage to 0.05C and let stand for 30 minutes; then discharge at a constant current of 0.2C to 2.5V. The discharge capacity is C0.2, and the discharge energy E0.2 and plateau U0.2 are calculated according to equations (4) and (5): E0.2=Σ[(Vi+Vi+1) / 2]×(Qi+1-Qi) ——(4) U0.2=E0.2 / C0.2——(5) Where Vi and Vi+1 are the voltages of adjacent sampling points, and Qi and Qi+1 are the capacities of adjacent sampling points.

[0106] 3. 40A Rate Performance Test At 25±2℃, fully charge the battery at 0.2C and let it stand for 30 minutes. Then discharge it at 1A to 2.5V and record the C1A, E1A, and 1A discharge curves. Take another battery of the same model, fully charge it in the same way, let it stand for 30 minutes, and discharge it at a constant current of 40A to 2.5V or the temperature cutoff at 75℃. Record the C40, E40, and 40A discharge curves.

[0107] Calculate according to equations (6) and (7): RC40=C40 / C1A×100%——(6) RE40=E40 / E1A×100%——(7) 4. 40A Temperature Rise Response Test A K-type patch thermocouple was fixed at half the axial height H1 / 2 of the sidewall of the cylindrical housing, circumferentially avoiding the heat-affected zone of the housing weld and the electrode lugs by 90°. The test environment was 25±2℃. The temperature at the start of the 40A discharge was T0, and the highest temperature during the discharge to 2.5V or 75℃ cutoff was T. 40 Calculate according to formula (8): K T =(T 40 -T0) / ρ p —(8) 5. 40A Overpotential Response Test The average plateau voltage within the 30%-70% discharge capacity range is used for calculation. The average voltage within the range of 0.30C1A to 0.70C1A in the 1A discharge curve is taken as U(1A, 30-70); the average voltage within the range of 0.30C40 to 0.70C40 in the 40A discharge curve is taken as U(40A, 30-70). Calculate according to equations (9) and (10): ΔV 40 =U(1A,30-70)-U(40A,30-70)——(9) K V =100×ΔV 40 / ρ p —(10) 6. DCR Test At 25±2℃, the battery was adjusted to 100% SOC and allowed to stand for 60 minutes. A 25A, 10s discharge pulse was then applied. The voltage V0 before the pulse and the voltage V10 at the end of the 10s pulse were recorded. Calculate according to formula (11): DCR=(V0-V10) / 25——(11) The DCR unit is converted to mΩ.

[0108] 7. 8A / 40A Cyclic Test At 25±2℃, charge at a constant current of 8A to 4.2V, then maintain a constant voltage to 0.25A until cutoff, and let stand for 10 minutes; then discharge at a constant current of 40A to 2.5V or 75℃ until cutoff, and let stand for 10 minutes, which constitutes one cycle. The capacity retention rate is calculated according to formula (12): CRn=Cn / C1×100%——(12) Where C1 is the discharge capacity of the first cycle and Cn is the discharge capacity of the nth cycle.

[0109] The test results are shown in Table 1.

[0110] Table 1 As can be seen from Table 1, comparing Example 1, Example 3, Example 9 and Comparative Example 1, the positive electrode length density ρ p It cannot be lower than the window specified in this case. In Example 1, ρ p It is 25.90, T 40 The temperature is 65.47℃, and ΔV 40 0.209V, K T K is 1.56. V The value is 0.81; in Example 3, ρ p It dropped to 23.04, T 40 Rising to 66.00℃, ΔV 40 Rising to 0.229V, K T K is 1.78. V The value is 0.99; in Example 9, ρ p T is 23.27. 40 The temperature is 66.70℃, and ΔV 40 0.225V, K T K is 1.79. V It is 0.97. These three points illustrate that when ρ... p When the temperature is within the range of 23.0~26.5, the positive electrode's spread length can distribute the unit length current load under a 40A discharge, keeping the temperature rise response and polarization response within a controllable range. (Comparative Example 1, ρ...) p It dropped to 22.27, ρ n K dropped to 23.66 T Rising to 1.90, K V As the RC40 increases to 1.06, it decreases to 96.5%, indicating that insufficient cathode length density leads to increased local current density, enhanced concentration polarization, and concentrated heat load. Therefore, ρ p It is not an arbitrary length ratio, but a core structural window in short-high cells used to constrain the rate thermal / polarization response.

[0111] Comparing Examples 1, 4, 2, and 6, it is clear that the electrode length density cannot be increased independently of the short-height shell space. In Example 1, H1 is 65.1 mm, ρ p It is 25.90, ρ n K is 26.41. T K is 1.56. V It is 0.81; in Example 4, ρ p Increased to 26.36, ρ n Even when increased to 26.98, K can still be made T 1.57, K V The value is 0.84, indicating that appropriately increasing the length density in a short-height casing can reduce the current load per unit electrode length. In Comparative Example 2, ρ...p Further increased to 26.88, ρ n Increased to 27.80, although K V It is 0.80, but T 40 When the temperature rises to 67.00℃, RE40 drops to 90.8%, indicating that excessively high electrode length density compresses the core porosity, electrolyte retention space, and radial heat dissipation channels, leading to temperature rise degradation. In Comparative Example 6, H1 is 70.1 mm, ρ p Only 22.30, ρ n The value is 23.02. Even if the measured temperature of 40A is 64.50℃, it does not belong to the 21650 short-height structure, and cannot demonstrate the advantage of density per unit height after the height reduction. Therefore, ρ p and ρ n It must be evaluated together with H1.

[0112] Comparing Examples 5, 6, and 3, it can be seen that the negative electrode length density ρ n It cannot be evaluated independently of the positive electrode length density ρp. In Example 5, ρ... p It is 24.88, ρ n It is 25.27, ρ n / ρ p ΔV is 1.02. 40 0.222V, K V It is 0.89; in Example 6, ρ p It is 24.58, ρ n Increased to 26.42, ρ n / ρ p ΔV is 1.08. 40 Dropped to 0.214V, K V It is 0.87. Both of these indicate that when ρ n Relative to ρ p When appropriate redundancy is maintained, the negative electrode can absorb the lithium-ion flux released from the positive electrode, reducing the risk of negative electrode polarization and lithium plating under 40A discharge. In Comparative Example 3, ρ p Increased to 25.81, but ρ n Only 25.50, ρ n / ρ p The voltage drop decreased to 0.99, ΔV40 increased to 0.226V, DCR increased to 9.6mΩ, and the 8A / 40A cycle capacity retention decreased to 86.8%. Therefore, ρ n / ρ p It is not an arbitrary ratio, but a coordinated window that reflects the degree of matching between the negative electrode's receiving capacity and the positive electrode's unfolding length.

[0113] Comparing Examples 7, 8, and 4, it is clear that the membrane length density ρs should be evaluated together with the positive and negative electrode length densities. In Example 7, ρ... sIt is 26.04, ρ s / ρ p The value is 1.01, the DCR is 8.1 mΩ, and the capacity retention rate during 8A / 40A cycling is 89.5%; in Example 8, ρ s Increased to 28.11, ρ s / ρ p The Ω value was 1.09, the DCR was 8.2 mΩ, and the cycling capacity retention was 89.8%. Both indicate that an appropriate membrane length density provides redundancy in the head, tail, and axial directions, maintaining the continuity of the ion migration path. In Comparative Example 4, ρ... s It dropped to 24.88, below the window for this case, although the short-term T 40 65.30℃, K V The value was 0.85, but the cycle capacity retention dropped to 88.0%, indicating that insufficient diaphragm length density reduces coating and insulation redundancy. Therefore, ρ s It is not simply a parameter of diaphragm usage, but a structural parameter that reflects the stability of short- and high-strength core coating and rate cycling stability.

[0114] Comparing Example 1, Example 10, Comparative Example 1, and Comparative Example 5, it can be seen that K V This reflects the constraint effect of the length density window on the 40A polarization response. In Example 1, ρ p It is 25.90, ΔV 40 0.209V, K V The value is 0.81; in Example 10, ρ p Decreased to 23.12, ΔV 40 Rise to 0.230V, K V The value is 0.99, which is still within the upper limit of the claims. In Comparative Example 1, ρ... p It dropped to 22.27, ΔV 40 Rise to 0.235V, K V Rising to 1.06; in Comparative Example 5, ρ p Although the value is 24.01, due to the increased positive electrode surface density and reduced wetting margin, ΔV 40 As the voltage increased to 0.236V, the DCR increased to 10.0mΩ. These results indicate that K... V It is not a separate performance threshold, but a criterion obtained by normalizing the polarization degree of 40A to the positive electrode length density per unit height, which can exclude two types of avoidance schemes: "insufficient length density" and "length density is qualified but polarization is abnormal".

[0115] Comparing Examples 1, 9, 2, and 5, it can be seen that KT can reflect the matching relationship between length density and thermal response in short-height cells. In Example 1, KT is 1.56, and T... 40 The temperature was 65.47℃; in Example 9, ρ pApproaching the lower limit, T 40 Rising to 66.70℃, K T The value is 1.79, which is close to but does not exceed the upper limit. In Comparative Example 2, ρ... p Too high as 26.88, T 40 The temperature rose to 67.00℃, indicating that excessively increasing the electrode length would sacrifice heat dissipation and wetting space; in Comparative Example 5, ρ p It is 24.01 but T 40 The temperature rose to 67.00℃, indicating that merely meeting the length density requirements is insufficient to guarantee a satisfactory thermal response. Therefore, K T It is a normalized window used to simultaneously evaluate electrode length density, thermal intensity, and heat dissipation constraints of short and tall casing.

[0116] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0117] In the above embodiments, the descriptions of each embodiment have their own emphasis. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments. The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification.

[0118] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0119] It should be noted that the terms "and / or" or " / " used herein are merely descriptions of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The singular forms "a," "described," and "the" used in the embodiments of the invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0120] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0121] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A cylindrical battery, characterized in that, Includes: a housing, and a battery cell disposed in the housing, the battery cell comprising a positive electrode, a separator and a negative electrode arranged in sequence; The positive electrode sheet includes a positive current collector and a positive active coating disposed on one side surface of the positive current collector in the thickness direction; The overall dimension of the housing in the height direction is H1, in mm; the length dimension of the positive electrode is L. p Unit: mm; The cylindrical battery satisfies the following condition under constant current discharge at 25℃ and 40A: K T ≤1.8, and K V ≤1.00; K T =(T 40 -T0) / ρ p ,K V =100×ΔV 40 / ρ p ; Where, ρ p ρ is the length density of the positive electrode. p =L p / H1 and ρ p ≠0, H1>0; T0 is the temperature of the outer surface of the casing when the cylindrical battery starts discharging at a constant current of 40A, in °C; T 40 The highest temperature on the outer surface of the casing during a 40A constant current discharge process, in °C; ΔV 40 The difference between the average plateau voltage of the cylindrical battery in the 30%~70% discharge capacity range of the 1A constant current discharge curve and the average plateau voltage in the 30%~70% discharge capacity range of the 40A constant current discharge curve, in V.

2. The cylindrical battery according to claim 1, characterized in that, 1.50≤K T ≤1.70； And / or, 0.78≤K v ≤0.

93.

3. The cylindrical battery according to claim 1, characterized in that, The negative electrode sheet includes a negative electrode current collector and a negative electrode active coating disposed on one side surface of the negative electrode current collector in the thickness direction; The length of the negative electrode is L. n Unit: mm; the length density of the negative electrode is ρ n , 1.01≤ρ n / ρ p ≤1.08; Where, ρ n =L n / H1; And / or, the length dimension of the diaphragm is L s Unit: mm; the length density of the diaphragm is ρ s , 1.04≤ρ s / ρ p ≤1.12, 1.02≤ρ s / ρ n ≤1.

08.

4. The cylindrical battery according to claim 1, characterized in that, It also satisfies at least one of the features (1) to (4): (1) 23.8 ≤ ρ p ≤26.1; (2) The L p The value range is 1500mm~1700mm; (3) The value range of H1 is 63.5mm~66.5mm; (4) The diameter of the shell is D, in mm; H1 and D satisfy: 3.06≤H1 / D≤3.

14.

5. The cylindrical battery according to claim 3, characterized in that, 24.6≤ρ n ≤26.8; and / or, 26.0≤ρ s ≤28.

2.

6. The cylindrical battery according to claim 3, characterized in that, Satisfying at least one of features (1) to (3): (1) The L n The value range is 1560mm~1750mm; (2) The L s The value range is 1680mm~1830mm; (3) The value of D is in the range of 20.6mm~21.5mm.

7. The cylindrical battery according to any one of claims 1 to 6, characterized in that, Under discharge conditions of 25℃ and 40A, with a constant current discharge capacity of 1A as a reference, the cylindrical battery shall satisfy at least one of the following characteristics (1) to (2): (1) The capacity retention rate of the cylindrical battery is greater than or equal to 97.0%; (2) The energy retention rate of the cylindrical battery is greater than or equal to 91.0%, and the T 40 ≤66.5℃.

8. The cylindrical battery according to any one of claims 1 to 6, characterized in that, Under discharge conditions of 25℃ and 0.2C, the discharge capacity of the cylindrical battery is 4.8Ah~5.2Ah, and the discharge energy of the cylindrical battery is 17.8Wh~18.3Wh. And / or, at 25°C and 100% SOC, the DC internal resistance (DCR) of the cylindrical battery is 7.5 mΩ to 9.5 mΩ; And / or, under the conditions of 25°C, 8A charging / 40A discharging cycling, the capacity retention rate of the cylindrical battery after cycling is greater than or equal to 89.0%.

9. The cylindrical battery according to claim 1, characterized in that, The positive electrode active coating includes a positive electrode active material, which comprises a layered high-nickel lithium transition metal oxide, wherein the molar content of nickel in the layered high-nickel lithium transition metal oxide is 88 mol% to 93 mol%. And / or, the shoulder height of the housing is H2, 63.2mm≤H2≤66.2mm; And / or, the dimension of the battery cell in the height direction is H5, 60.8mm≤H5≤63.8mm; And / or, 2.3mm≤H1-H5≤3.4mm.

10. An electrical device, characterized in that, include: The cylindrical battery according to any one of claims 1 to 9.

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